WO2019039993A1

WO2019039993A1 - Limb prosthesis and cooling device for cooling a residual limb

Info

Publication number: WO2019039993A1
Application number: PCT/SE2018/050853
Authority: WO
Inventors: Christian Ahlström; Felix ASPLUND; Joachim TOLSTOY
Original assignee: Chriah Ab
Priority date: 2017-08-25
Filing date: 2018-08-24
Publication date: 2019-02-28
Also published as: SE1751026A1

Abstract

The present disclosure relates to a limb prosthesis (200) for cooling a residual limb. The limb prosthesis (200) comprises a socket (202) for receiving the residual limb. A cooling element (204) is arranged in the socket. The limb prosthesis is configured to lead away excess heat from the cooling element via thermal coupling elements (206) to heat evacuating means (208) arranged at a first distance from the cooling element, along a longitudinal extension of the limb prosthesis. Heat is then evacuated radially from the heat evacuating means. The present disclosure also relates to corresponding cooling devices for cooling a residual limb received by a socket of a limb prosthesis.

Description

Limb prosthesis and cooling device for cooling a residual limb

TECHNICAL FIELD

The present disclosure relates to cooling of a limb prosthesis. In particular, the present disclosure proposes limb prostheses and cooling devices for cooling a residual limb.

BACKGROUND ART

A clear majority of amputees will at some point experience so-called phantom limb pain, which manifests as experiences of real pain seemingly originating from the missing limb. The phantom limb pain may diminish over time, but for some amputees, the phantom limb pain never goes away. Furthermore, phantom limb pains, e.g. in the form of jolts or sensations of electric chock, may be experienced by amputees not having suffered from phantom limb pains for an extended period of time. Phantom pains may significantly reduce the quality of life for the amputee and also constitute an obstacle to rehabilitative measures. Phantom sensations, i.e. sensations where an amputee experience feelings as if the missing limb is still there, are also very common. Although not painful, sensations such as the missing limb being too hot or too cold, or having an itch, may also significantly reduce the quality of life for the amputee.

Further issues in the life of amputees may arise from the use of limb prostheses. For instance, many removable limb prostheses attach by fitting a residual limb into a socket of the limb prosthesis. This often gives rise to problems associated with the interaction between the amputee and the limb prosthesis. For instance, the tight fit of the socket often leads to excessive sweating and irritation of the part of the residual limb inserted into the socket. Long periods of use or more physical exertion during use may cause swelling of the residual limb, which may cause inconvenience due to the restricted space of the socket. SUMMARY OF THE INVENTION

One object of the present disclosure is to provide a method which seeks to mitigate, alleviate, or eliminate one or more of the above-identified deficiencies in the art and disadvantages singly or in any combination and to provide a means for relieving a user from a state of pain or discomfort due to phantom limb pain, phantom sensations and/or interaction between a residual limb and a limb prosthesis.

In particular, the present disclosure relates to a limb prosthesis for cooling a residual limb. The limb prosthesis comprises a socket for receiving the residual limb. The limb prosthesis further comprises a cooling element arranged to be thermally coupled to a contact area of the socket intended to be in contact with a skin surface of the residual limb when received by the socket. The cooling element is arranged to cool the contact area to a desired temperature interval. The limb prosthesis also comprises heat evacuating means arranged to evacuate heat radially outwards from a longitudinal extension of the limb prosthesis. The heat evacuating means are arranged at a first distance along the longitudinal extension from the cooling element. The limb prosthesis additionally comprises thermal coupling elements having a thermal capacitance below a predetermined maximum thermal capacitance and/or a thermal conductivity above a predetermined minimum thermal conductivity. The thermal coupling elements are arranged to thermally couple the cooling element to the heat evacuating means. The limb prosthesis further comprises control circuitry arranged to control the cooling element. The limb prosthesis yet further comprises a battery arranged to provide power to the cooling element and the control circuitry. The disclosed limb prosthesis enables providing a cooling effect, which can reduce phantom pains and phantom sensations, e.g. with localized intensive cooling. The disclosed limb prosthesis further enables reduced swelling and irritation of the residual limb, e.g. with longer duration cooling of an intensity lower than when reducing phantom pains and phantom sensations. The disclosed limb prosthesis yet further enables reduced swelling in the residual limb.

According to some aspects, the cooling element comprises one or a plurality of Peltier elements. According to some further aspects, the cooling element comprises a plurality of Peltier elements. A Peltier element, also known as Peltier device, Peltier heat pump, solid state refrigerator or thermoelectric cooler, can be implemented in flat configurations. A Peltier element therefore enables a reduction in a lateral direction of the portable cooling device in a direction perpendicular to the contact area. In other words, the use of Peltier elements enables the prosthesis to essentially maintain its profile and maintain properties such as the socket being water tight, while simultaneously providing a cooling effect of the residual limb. A Peltier element also provides great flexibility in shape, thereby enabling a wide range of different conceivable contact areas. The flat profile of a Peltier element, with one side being cool and the opposite side being warm during use, enables heat to be effectively led away from the sealed environment defined by the socket. The plurality of cooling elements enables cooling over different areas without having to readjust the limb prosthesis with respect to a user. The plurality of cooling elements further enables cooling in different patterns, such as random contact areas, synchronized contact areas, or gradients, where a plurality of cooling elements are arranged to cool their respective contact areas to different temperatures with respect to each other. A plurality of cooling elements also enables striking a balance between cooling a large area and restricting the power necessary to cool the large area.

According to some aspects, the heat evacuating means comprises a heat sink. The heat sink is arranged to provide passive cooling of the limb prosthesis by transferring heat received from the cooling element via thermal coupling elements and dissipate the heat to air surrounding the limb prosthesis. According to some aspects, the heat evacuating means comprises a fan, wherein the control circuitry is further arranged to control the fan, and wherein the battery is further arranged to provide power to the fan. A fan is a means of active cooling, which enables time-varying heat transport. Active cooling such as a fan typically has a greater capacity to evacuate heat than passive heat evacuating means, which means that the total size and profile of the cooling mechanism of the limb prosthesis can be reduced with respect to heat evacuating means based solely on passive cooling. The size reduction typically also implies a corresponding weight reduction, which is of particular interest since the limb prosthesis is worn and moved around as the wearer moves. Furthermore, the fan relies on air as its cooling medium, thereby eliminating the need for bringing a dedicated cooling medium. According to some aspects, the battery is arranged at a second distance along the longitudinal extension from the cooling element, the second distance being greater than the first distance. The alignment achieved by distributing the cooling element, the heat evacuating means and the battery along the longitudinal extension of the limb prosthesis provides effective use of the available space provided by the prosthesis, without having to deform the profile of the prosthesis to such an extent as to hinder natural movement or risk undue interaction with the surroundings due to objects extending from the prosthesis. The longitudinal distribution of components further assists in effective heat dissipation, since a greater effective area becomes available for convective cooling. In other words, heat led away from the cooling element can be evacuated more effectively and distributed over a greater area, thereby preventing build-up of heat in a small region.

According to some aspects, the control circuitry is arranged adjacent to the battery. According to some aspects, comprising a casing arranged to house the control circuitry and the battery. By arranging the control circuitry adjacent to the battery, e.g. arranged opposite each other, the need for electric wiring can be reduced and advantage can be taken of central support structures, such as a titanium rod-structure, to fixate the control circuitry and the battery to reduce potential stress due to movement of the residual limb. By arranging the control circuitry adjacent to the battery, the volume taken up by the control circuitry and the battery can be fitted to, while still maintaining, the elongated shape of the limb prosthesis. By adding a casing arranged to house the control circuitry and the battery, both the control circuitry and the battery can be further protected from shock, e.g. due to walking and running in the case of leg limb prosthesis, and environmental factors such as moist and temperature. The casing may further facilitate easy replacement of batteries in examples using removable, and possibly rechargeable, batteries. According to some aspects, the limb prosthesis further comprises a casing arranged to house the heat evacuating means, the casing comprising a material having a thermal capacitance below a predetermined maximum thermal capacitance and/or a thermal conductivity above a predetermined minimum thermal conductivity, the casing being arranged to house the heat evacuating means and to enable evacuation of heat radially outwards from the longitudinal extension of the limb prosthesis. The casing embeds the heat evacuating means into the support structure of the limb prosthesis and protects the heat evacuating means from external forces. Furthermore, support structures having a thermal capacitance below a predetermined maximum thermal capacitance and/or a thermal conductivity above a predetermined minimum thermal conductivity provides assistance with passive cooling. The use of a casing provides a means which can be arranged to have a length to suit any prosthetic. Furthermore, the casing may be arranged to comprise a connection interface, thereby enabling standard connection for use with existing attachments.

The present disclosure also relates to a cooling device for cooling a residual limb received by a socket of a limb prosthesis. The cooling device comprises a cooling element arranged to be thermally coupled to a contact area of the socket intended to be in contact with a skin surface of the residual limb when received by the socket. The cooling element is arranged to cool the contact area to a desired temperature interval. The cooling device further comprises heat evacuating means arranged to, when the cooling device is arranged for cooling a residual limb received by a socket of a limb prosthesis, evacuate heat radially outwards from a longitudinal extension of the limb prosthesis and arranged at a first distance along the longitudinal extension from the cooling element. The cooling device also comprises thermal coupling elements having a thermal capacitance below a predetermined maximum thermal capacitance and/or a thermal conductivity above a predetermined minimum thermal conductivity and arranged to thermally couple the cooling element to the heat evacuating means. The cooling device additionally comprises a battery arranged to provide power to the cooling element. The cooling device yet further comprises control circuitry arranged to control the cooling element.

BRIEF DESCRIPTION OF THE DRAWINGS

Figure 1 illustrates a block diagram of limb prostheses according to the present disclosure;

Figure 2 illustrates a perspective view of embodiments of limb prostheses according to the present disclosure;

Figure 3 illustrates a block diagram of cooling devices for limb prostheses according to the present disclosure; and Figure 4 illustrates an exploded view of embodiments of cooling devices for limb prostheses according to the present disclosure.

DETAILED DESCRIPTION Figure 1 illustrates a block diagram of limb prostheses 100 according to the present disclosure. The limb prosthesis 100 is a limb prosthesis 100 for cooling a residual limb. The limb prosthesis 100 comprises a socket 102 for receiving the residual limb.

The limb prosthesis 100 further comprises a cooling element 104 arranged to be thermally coupled to a contact area of the socket intended to be in contact with a skin surface of the residual limb when received by the socket 102. The cooling element 104 is arranged to cool the contact area to a desired temperature interval. The desired temperature interval is preferably cool enough for a cooling effect to be appreciated by a user having the contact area in contact with the skin surface of the residual limb of the user and hot enough to avoid damage to the skin due to cold. The desired temperature interval is preferably five to twenty- five degrees centigrade, and even more preferably between ten to twenty degrees centigrade. Temperature intervals between five to fifteen degrees centigrade and fifteen to twenty-five degrees centigrade are also possible. The limb prosthesis is preferably arranged to ensure that the temperature at the contact area never drops below a lowest safety temperature. According to some further aspects, the temperature at the contact area is allowed to drop below the lowest safety temperature for a predetermined duration. The safety temperature thus safeguards against injury due to prolonged exposure to cold, while allowing temporary application of temperatures below the safety temperature. Since the desired cooling effect may differ between users, some aspects of the limb prosthesis are arranged to enable the user to select the desired temperature interval, as will be described further below. According to some aspects, the cooling element 104 comprises one or a plurality of Peltier elements 104a, 104b, 104c, 104d. According to some further aspects, the cooling element 104 comprises a plurality of Peltier elements 104a, 104b, 104c, 104d.

A Peltier element can be manufactured flat, with one side acting as or connecting thermally to the area arranged to be cooled by the Peltier element, i.e. a contact area, and thus minimizes the extension in a direction perpendicular to the contact area. A Peltier element thus enables a flat profile of the limb prosthesis to be maintained. This is very advantageous when arranging trying to maintain a limb prosthesis profile within a boundary corresponding to a full corresponding limb of the user. The flatness of the Peltier elements ensures that the limb prosthesis can be made to fit with the same range of everyday clothing as if no cooling element(s) were present. A Peltier element further enables a great freedom in the shape and dimension of the contact area. Peltier elements are typically inexpensive and have no moving parts, thereby eliminating noise, being extremely reliable and not requiring any maintenance. The current running through the Peltier element may be reversed, thereby switching the effect of the Peltier element from cooling the contact area to heating the contact area. This may be used in schemes where the cooling provided by the cooling element 104 is time- dependent, as will be described further below.

The limb prosthesis 100 also comprises heat evacuating means 108 arranged to evacuate heat radially outwards from a longitudinal extension of the limb prosthesis 100 and arranged at a first distance along the longitudinal extension from the cooling element 104.

The heat evacuating means 108 is arranged to prevent the limb prosthesis 100 from overheating. The heat evacuating means 108 may provide active cooling, passive cooling or a combination thereof.

According to some aspects, the heat evacuating means 108 comprises a heat sink 110. The heat sink provides passive cooling of the limb prosthesis 100 by transferring heat received from the cooling element via thermal coupling elements, as described further below, and dissipates the heat to air surrounding the limb prosthesis.

According to some aspects, the heat evacuating means 108 comprises a fan 112. The fan 112 is an example of active cooling. A fan has an advantage in that it uses air as it cooling medium, thereby eliminating the need to carry around cooling fluids, such as water, to cool the limb prosthesis.

According to some further aspects, the heat evacuating means 108 comprises a mesh grid 114 arranged to at least partially protect the fan. The mesh grid may be arranged to protect the fan from protruding objects or features of the limb prosthesis and/or objects external to the limb prosthesis 100.

The limb prosthesis 100 further comprises thermal coupling elements 106 having a thermal capacitance below a predetermined maximum thermal capacitance and/or a thermal conductivity above a predetermined minimum thermal conductivity and arranged to thermally couple the cooling element to the heat evacuating means. The thermal coupling elements 106 enable usage of the longitudinal extension of the limb prosthesis by distributing components needed for the cooling mechanism along the longitudinal extension. The profile of the limb prosthesis can thereby be kept within a boundary corresponding to a limb of an intended user of the limb prosthesis. For instance, in the case of a leg prosthesis, components extending radially from the extension of the leg prosthesis can be effectively avoided, i.e. kept within a desired leg profile, thereby eliminating problems associated with extending parts of the leg prosthesis getting caught in or interacting with the other leg of the user or the external environment during walk. Furthermore, the thermal coupling elements enables arranging the heat evacuating means at positions where they can be both better protected and operate more effectively than if they had been arranged at the socket. By keeping the thermal capacitance below a predetermined maximum thermal capacitance, unwanted heat build-up is avoided. By having the thermal conductivity above a predetermined minimum thermal conductivity, heat is led away from the cooling element to the heat evacuating means at a desired sufficiency. The thermal coupling elements may comprise a metal, e.g. copper. The thermal coupling elements preferably comprise a flexible region and/or a flexible material. The flexibility facilitates manufacturing as the flexibility may assist in fitting the thermal coupling elements to the shape of the socket of the limb prosthesis. The flexibility of the thermal coupling elements further enables the socket to maintain flexibility in regions overlapping with the thermal coupling elements. According to some aspects, the cooling element is embedded in the socket of the limb prosthesis. According to some aspects, the thermal coupling elements are at least partially embedded in the socket of the limb prosthesis.

According to some aspects, the limb prosthesis further comprises at least one temperature sensor 115 arranged to determine a temperature of the limb prosthesis. The temperature sensor 115 enables improved precision in determining the current cooling temperature of the cooling element. The temperature sensor further enables determining if the temperature in limb prosthesis rises above a highest allowable temperature threshold. This may be used to prevent overheating in case the ability of the heat evacuating means to evacuate heat is inhibited. A temperature sensor may further improve the power efficiency of the limb prosthesis, e.g. by avoiding unnecessary cooling by the cooling element 104 or unnecessary work by a power operated component, such as a fan 112, of the heat evacuating means 108.

The limb prosthesis 100 yet further comprises control circuitry 120 arranged to control the cooling element 104. The control circuitry 120 may comprise any suitable type of computation unit, e.g. a microprocessor, digital signal processor, DSP, field programmable gate array, FPGA, or application specific integrated circuit, ASIC, or any other form of circuitry. It should be appreciated that the control circuitry need not be provided as a single unit but may be provided as any number of units or circuitry. The control circuitry may also comprise a memory. According to some aspects, the memory may be arranged to store received or transmitted data and/or executable program instructions. The memory may be any suitable type of computer readable memory and may be of volatile and/or non-volatile type. According to some aspects, the memory is arranged to store a set of predetermined time-dependent cooling schemes. According to some further aspects, the control circuitry is further arranged to change at least one of the time-dependent cooling schemes based on user feedback. The user feedback may be provided directly via a user interface or a communications interface, as described further below, or be determined based on user behaviour, e.g. usage statistics. In other words, program settings may be changed adaptively based on user feedback. According to some aspects, the control circuitry 120 further comprises a timer. Also, the desired temperature interval may be time-dependent and the time- dependency is arranged to be controlled by the timer. By introducing time-dependence, different temperature application schemes are enabled. For example, the limb prosthesis may be arranged to apply cooling in a pulsed mode, e.g. cooling for a few seconds and then waiting for a few seconds, etc. For instance, the pulsed mode may comprise five seconds of cooling followed by five seconds of no cooling. The pulsed mode may comprise ten seconds of cooling followed by ten seconds of no cooling. The pulsed mode may comprise fifteen seconds of cooling followed by fifteen seconds of no cooling, and so on in five second increments. In a preferred example, the pulsed mode comprises thirty seconds of cooling followed thirty seconds of no cooling. In another preferred mode, the pulsed mode comprises sixty seconds of cooling followed sixty seconds of no cooling. The longer durations gives the user more time to sense the variations in temperature, potentially providing a greater contrast in the cooling experienced by the user. The durations of the cooling periods and/or the periods in between the cooling periods may be randomized. According to some aspects, a ramping scheme is applied. The time- dependence of the temperature may be coupled with other effects in between periods of cooling. For instance, in case the cooling element is a Peltier element, the current driving the Peltier element can be reversed back and forth. This will result in an alternating cooling and heating effect at the contact area. According to some aspects, the limb prosthesis further comprises a shocking element arranged to generate an electric discharge at the contact area. The limb prosthesis may then be arranged to provide an electric discharge, i.e. a shocking stimulus to a user, between the periods of cooling.

According to some aspects, the limb prosthesis further comprises a user interface 116 arranged to receive an input command and to control the control circuitry to set the desired temperature interval based on the input command. The user interface 116 preferably comprises an input and output interface. The input interface may be arranged to allow the user to set the desired temperature interval and/or program a time-dependent cooling scheme. According to some aspects, the limb prosthesis comprises a set of predetermined time-dependent cooling schemes, e.g. stored in the memory, and the input interface is arranged to enable the user to select a cooling scheme from the set of predetermined time- dependent cooling schemes. The output interface may comprise one or more light-emitting diodes, LEDs, arranged to indicate a selected cooling scheme. Such an output interface requires very little power and is a preferable option if the limb prosthesis is optimized for low power consumption. The output interface may also comprise a liquid crystal display, LCD, which can be arranged to display any type of 2D-information, e.g. text and numbers. According to some aspects, the limb prosthesis further comprises a communications interface 118 arranged to transmit data relating to usage of the limb prosthesis during a predetermined time period. The data relating to usage of the limb prosthesis may be obtained from e.g. a memory of the control circuitry or directly from the control circuitry and/or sensors of the limb prosthesis.

The data from the communications interface 118 enables external diagnostics of the limb prosthesis as such, as well as providing information relating to user statistics, which can be used to analyse user behaviour during the predetermined time period. According to some further aspects, the communications interface is further arranged to receive control signals and/or computer program code. In other words, the communications interface enables diagnostics and control of the limb prosthesis via an external device. The communications interface may be arranged to use any combination of wireless and wired transmission. For instance, according to some further aspects, the communications interface is arranged to communicate using Bluetooth. According to some aspects, the communications interface comprises a USB port and/or a micro USB port.

The limb prosthesis also comprises a battery 122 arranged to provide power to the cooling element 104 and the control circuitry 120.

According to some further aspects, the USB/micro USB ports may be used to charge the batteries of the limb prosthesis.

According to some aspects, the limb prosthesis comprises a plurality of batteries. With a plurality of batteries, the dimension of each battery can be reduced while still providing a predetermined total power. By reducing the dimension of each battery, the overall dimension of the limb prosthesis can be reduced. In particular, the limb prosthesis may be arranged having a more flat profile compared to using a single battery. The battery is preferably rechargeable.

According to some further aspects, if the heat evacuating means comprises a fan, the control circuitry 120 is further arranged to control the fan 112, and the battery 122 is further arranged to provide power to the fan 112.

According to some aspects, the battery 122 is arranged at a second distance along the longitudinal extension from the cooling element 104, the second distance being greater than the first distance. The arrangement of the battery at the second distance along the longitudinal extension further distribute the components of the cooling mechanism along the longitudinal extension, thereby utilizing the longitudinal direction of the limb prosthesis to be able to maintain the features of the limb prosthesis within a desired profile. By arranging the battery at the second distance further enables arranging the battery at a support structure, such as a titanium rod, thereby providing better stability and protection for the battery. Since the support structures are typically much narrower than a corresponding real limb, the placement of the battery at the second distance provides examples which make good use of available space.

According to some aspects, the control circuitry is arranged adjacent to the battery. According to some aspects, the limb prosthesis further comprises a casing arranged to house the control circuitry and the battery. By arranging the control circuitry adjacent to the battery, e.g. arranged opposite each other, the need for electric wiring can be reduced and advantage can be taken of central support structures, such as a titanium rod-structure, to fixate the control circuitry and the battery to reduce potential stress due to movement of the residual limb. By arranging the control circuitry adjacent to the battery, the volume taken up by the control circuitry and the battery can be fitted to, while still maintaining, the elongated shape of the limb prosthesis. By adding a casing arranged to house the control circuitry and the battery, both the control circuitry and the battery can be further protected from shock, e.g. due to walking and running in the case of leg limb prosthesis, and environmental factors such as moist and temperature. The casing may further facilitate easy replacement of batteries in examples using removable, and possibly rechargeable, batteries.

According to some aspects, the limb prosthesis further comprises a casing 124 arranged to house the heat evacuating means. The casing 124 comprises a material having a thermal capacitance below a predetermined maximum thermal capacitance and/or a thermal conductivity above a predetermined minimum thermal conductivity. The casing 124 is arranged to house the heat evacuating means and to enable evacuation of heat radially outwards from the longitudinal extension of the limb prosthesis. The casing embeds the heat evacuating means into the support structure of the limb prosthesis and protects the heat evacuating means from external forces. Furthermore, support structures having a thermal capacitance below a predetermined maximum thermal capacitance and/or a thermal conductivity above a predetermined minimum thermal conductivity provides assistance with passive cooling. The use of a casing provides a means which can be arranged to have a length to suit any prosthetic. Furthermore, the casing may be arranged to comprise a connection interface, thereby enabling standard connection for use with existing attachments.

Figure 2 illustrates a perspective view of embodiments of limb prostheses for cooling a residual limb according to the present disclosure.

The limb prosthesis 200 comprises a socket 202 for receiving the residual limb. The limb prosthesis in Fig. 2 is illustrated as a leg prosthesis, but the technical features and principles illustrated in relation to Fig. 2 applies to arm prostheses as well. The limb prosthesis 200 further comprises a cooling element arranged to be thermally coupled to a contact area of the socket intended to be in contact with a skin surface of the residual limb when received by the socket 202. The cooling element is arranged to cool the contact area to a desired temperature interval. The desired temperature interval is preferably cool enough for a cooling effect to be appreciated by a user having the contact area in contact with the skin surface of the residual limb of the user and hot enough to avoid damage to the skin due to cold. The desired temperature interval is preferably five to twenty-five degrees centigrade, and even more preferably between ten to twenty degrees centigrade. Temperature intervals between five to fifteen degrees centigrade and fifteen to twenty-five degrees centigrade are also possible. The limb prosthesis is preferably arranged to ensure that the temperature at the contact area never drops below a lowest safety temperature. According to some further aspects, the temperature at the contact area is allowed to drop below the lowest safety temperature for a predetermined duration. The safety temperature thus safeguards against injury due to prolonged exposure to cold, while allowing temporary application of temperatures below the safety temperature. Since the desired cooling effect may differ between users, some aspects of the limb prosthesis are arranged to enable the user to select the desired temperature interval, as will be described further below.

The cooling element 204 comprises a plurality of Peltier elements 204a, 204b, 204c. The flatness of the Peltier elements 204a, 204b, 204c enable the cooling element to maintain and follow the shape of the socket 202. According to some aspects, the Peltier elements 204a, 204b, 204c are embedded in the socket of the limb prosthesis.

The limb prosthesis 200 also comprises heat evacuating means 208 arranged to evacuate heat radially outwards from a longitudinal extension of the limb prosthesis 200 and arranged at a first distance along the longitudinal extension from the cooling element 204.

The heat evacuating means 208 is arranged to prevent the limb prosthesis 200 from overheating. The heat evacuating means 208 comprises a heat sink 210. The heat sink 210 provides passive cooling of the limb prosthesis 200 by transferring heat received from the Peltier elements 204a, 204b, 204c via thermal coupling elements 206 arranged to thermally couple the Peltier elements 204a, 204b, 204c to the heat evacuating means 208, and dissipates the heat to air surrounding the limb prosthesis.

The heat evacuating means 208 further comprises a fan 212.

The heat evacuating means 208 also comprises a mesh grid 214 arranged to at least partially protect the fan. The mesh grid may be arranged to protect the fan from protruding objects or features of the limb prosthesis and/or objects external to the limb prosthesis 200.

The heat sink 210 is preferably arranged to house the fan 212, e.g. by comprising a cavity arranged to receive the fan. In examples wherein the heat sink houses the fan in a cavity, the heat sink is further arranged to enable the fan to evacuate hot air to the surrounding air external to the limb prosthesis. The mesh grid 214 may be arranged to cover one or more openings of the heat sink, thereby securely enclosing and protecting the fan 212, while still allowing air to flow freely.

The limb prosthesis 200 further comprises thermal coupling elements 206 having a thermal capacitance below a predetermined maximum thermal capacitance and/or a thermal conductivity above a predetermined minimum thermal conductivity and arranged to thermally couple the cooling element to the heat evacuating means. In some examples, the thermal coupling elements may comprise channels arranged to conduct heat from a hot side of a Peltier element 204a, 204b, 204c to the heat sink 210. The coupling of each channel to the heat sink may be either direct or indirect, i.e. via another thermally conductive medium, such as a thermally conductive casing 224 partially enclosing the heat evacuating means 208. The channels thereby evacuate heat which would otherwise be trapped in the socket. The channels may comprise a metallic material, such as copper. The channels are preferably arranged to be flexible, which enables deformation of the socket without risking damage to the channels and facilitates manufacture of the limb prosthesis, since the flexible thermal coupling elements can be bent to match the shape of the socket. According to some aspects, the thermal coupling elements are embedded in the limb prosthesis. The thermal coupling elements can thereby be protected from an external environment by benefitting from material properties of the limb prosthesis, such as a water-proof socket.

According to some aspects, the limb prosthesis further comprises at least one temperature sensor arranged to determine a temperature of the limb prosthesis. The temperature sensor enables improved precision in determining the current cooling temperature of the cooling element. The temperature sensor further enables determining if the temperature in limb prosthesis rises above a highest allowable temperature threshold. This may be used to prevent overheating in case the ability of the heat evacuating means to evacuate heat is inhibited. A temperature sensor may further improve the power efficiency of the limb prosthesis, e.g. by avoiding unnecessary cooling by the cooling element or unnecessary work by the fan.

The limb prosthesis 200 yet further comprises control circuitry 220 arranged to control the Peltier elements 204a, 204b, 204c. The control circuitry 220 is further arranged to control the fan 212.

The control circuitry 220 may comprise any suitable type of computation unit, e.g. a microprocessor, digital signal processor, DSP, field programmable gate array, FPGA, or application specific integrated circuit, ASIC, or any other form of circuitry. It should be appreciated that the control circuitry need not be provided as a single unit but may be provided as any number of units or circuitry.

The control circuitry may also comprise a memory. According to some aspects, the memory may be arranged to store received or transmitted data and/or executable program instructions. The memory may be any suitable type of computer readable memory and may be of volatile and/or non-volatile type. According to some aspects, the memory is arranged to store a set of predetermined time-dependent cooling schemes. According to some further aspects, the control circuitry is further arranged to change at least one of the time-dependent cooling schemes based on user feedback. The user feedback may be provided directly via a user interface or a communications interface, as described further below, or be determined based on user behaviour, e.g. usage statistics. In other words, program settings may be changed adaptively based on user feedback.

According to some aspects, the control circuitry 220 further comprises a timer. Also, the desired temperature interval may be time-dependent and the time- dependency is arranged to be controlled by the timer. By introducing time-dependence, different temperature application schemes are enabled. For example, the limb prosthesis may be arranged to apply cooling in a pulsed mode, e.g. cooling for a few seconds and then waiting for a few seconds, etc. For instance, the pulsed mode may comprise five seconds of cooling followed by five seconds of no cooling. The pulsed mode may comprise ten seconds of cooling followed by ten seconds of no cooling. The pulsed mode may comprise fifteen seconds of cooling followed by fifteen seconds of no cooling, and so on in five second increments. In a preferred example, the pulsed mode comprises thirty seconds of cooling followed thirty seconds of no cooling. In another preferred mode, the pulsed mode comprises sixty seconds of cooling followed sixty seconds of no cooling. The longer durations gives the user more time to sense the variations in temperature, potentially providing a greater contrast in the cooling experienced by the user. The durations of the cooling periods and/or the periods in between the cooling periods may be randomized. According to some aspects, a ramping scheme is applied. The time- dependence of the temperature may be coupled with other effects in between periods of cooling. For instance, the current driving the Peltier elements can be reversed back and forth. This will result in an alternating cooling and heating effect at the contact area. According to some aspects, the limb prosthesis further comprises a shocking element arranged to generate an electric discharge at the contact area. The limb prosthesis may then be arranged to provide an electric discharge, i.e. a shocking stimulus to a user, between the periods of cooling.

According to some aspects, the limb prosthesis further comprises a user interface arranged to receive an input command and to control the control circuitry to set the desired temperature interval based on the input command. The user interface preferably comprises an input and output interface. The input interface may be arranged to allow the user to set the desired temperature interval and/or program a time-dependent cooling scheme. According to some aspects, the limb prosthesis comprises a set of predetermined time-dependent cooling schemes, e.g. stored in the memory, and the input interface is arranged to enable the user to select a cooling scheme from the set of predetermined time-dependent cooling schemes. The output interface may comprise one or more light-emitting diodes, LEDs, arranged to indicate a selected cooling scheme. Such an output interface requires very little power and is a preferable option if the limb prosthesis is optimized for low power consumption. The output interface may also comprise a liquid crystal display, LCD, which can be arranged to display any type of 2D-information, e.g. text and numbers.

According to some aspects, the limb prosthesis further comprises a communications interface arranged to transmit data relating to usage of the limb prosthesis during a predetermined time period. The data relating to usage of the limb prosthesis may be obtained from e.g. a memory of the control circuitry or directly from the control circuitry and/or sensors of the limb prosthesis.

The data from the communications interface enables external diagnostics of the limb prosthesis as such, as well as providing information relating to user statistics, which can be used to analyse user behaviour during the predetermined time period. According to some further aspects, the communications interface is further arranged to receive control signals and/or computer program code. In other words, the communications interface enables diagnostics and control of the limb prosthesis via an external device. The communications interface may be arranged to use any combination of wireless and wired transmission. For instance, according to some further aspects, the communications interface is arranged to communicate using Bluetooth. According to some aspects, the communications interface comprises a USB port and/or a micro USB port.

The limb prosthesis also comprises a battery 222 arranged to provide power to the Peltier elements 204a, 204b, 204c, the fan 212 and the control circuitry 220.

According to some aspects, the limb prosthesis comprises a plurality of batteries. With a plurality of batteries, the dimension of each battery can be reduced while still providing a predetermined total power. By reducing the dimension of each battery, the overall dimension of the limb prosthesis can be reduced. In particular, the limb prosthesis may be arranged having a more flat profile compared to using a single battery. The battery is preferably rechargeable. According to some aspects, the battery 222 is arranged at a second distance along the longitudinal extension from the cooling element 204, the second distance being greater than the first distance. The arrangement of the battery at the second distance along the longitudinal extension further distribute the components of the cooling mechanism along the longitudinal extension, thereby utilizing the longitudinal direction of the limb prosthesis to be able to maintain the features of the limb prosthesis within a desired profile. By arranging the battery at the second distance further enables arranging the battery at a support structure, such as a titanium rod, thereby providing better stability and protection for the battery. Since the support structures are typically much narrower than a corresponding real limb, the placement of the battery at the second distance provides examples which make good use of available space.

According to some aspects, the limb prosthesis further comprises a casing 224 arranged to house the heat evacuating means 208. The casing 224 comprises a material having a thermal capacitance below a predetermined maximum thermal capacitance and/or a thermal conductivity above a predetermined minimum thermal conductivity. The casing 224 is arranged to house the heat evacuating means and to enable evacuation of heat radially outwards from the longitudinal extension of the limb prosthesis. The casing embeds the heat evacuating means into the support structure of the limb prosthesis and protects the heat evacuating means from external forces. Furthermore, support structures having a thermal capacitance below a predetermined maximum thermal capacitance and/or a thermal conductivity above a predetermined minimum thermal conductivity provides assistance with passive cooling. The use of a casing provides a means which can be arranged to have a length to suit any prosthetic. Furthermore, the casing may be arranged to comprise a connection interface, thereby enabling standard connection for use with existing attachments.

Figure 3 illustrates a block diagram of cooling devices for cooling a residual limb received by a socket of a limb prosthesis. The cooling device 300 comprises a cooling element 304 arranged to be thermally coupled to a contact area of the socket intended to be in contact with a skin surface of the residual limb when received by the socket 302. The cooling element 304 is arranged to cool the contact area to a desired temperature interval. The desired temperature interval is preferably cool enough for a cooling effect to be appreciated by a user having the contact area in contact with the skin surface of the residual limb of the user and hot enough to avoid damage to the skin due to cold. The desired temperature interval is preferably five to twenty-five degrees centigrade, and even more preferably between ten to twenty degrees centigrade. Temperature intervals between five to fifteen degrees centigrade and fifteen to twenty-five degrees centigrade are also possible. The cooling device is preferably arranged to ensure that the temperature at the contact area never drops below a lowest safety temperature. According to some further aspects, the temperature at the contact area is allowed to drop below the lowest safety temperature for a predetermined duration. The safety temperature thus safeguards against injury due to prolonged exposure to cold, while allowing temporary application of temperatures below the safety temperature. Since the desired cooling effect may differ between users, some aspects of the cooling device are arranged to enable the user to select the desired temperature interval, as will be described further below.

According to some aspects, the cooling element 304 comprises one or a plurality of Peltier elements 304a, 304b, 304c, 304d. According to some further aspects, the cooling element 304 comprises a plurality of Peltier elements 304a, 304b, 304c, 304d.

A Peltier element can be manufactured flat, with one side acting as or connecting thermally to the area arranged to be cooled by the Peltier element, i.e. a contact area, and thus minimizes the extension in a direction perpendicular to the contact area. A Peltier element thus enables a flat profile of the limb prosthesis to be maintained. This is very advantageous when arranging trying to maintain a limb prosthesis profile within a boundary corresponding to a full corresponding limb of the user. The flatness of the Peltier elements ensures that a limb prosthesis at which the cooling device is to be arranged can be made to fit with the same range of everyday clothing as if no cooling element(s) were present. A Peltier element further enables a great freedom in the shape and dimension of the contact area. Peltier elements are typically inexpensive and have no moving parts, thereby eliminating noise, being extremely reliable and not requiring any maintenance. The current running through the Peltier element may be reversed, thereby switching the effect of the Peltier element from cooling the contact area to heating the contact area. This may be used in schemes where the cooling provided by the cooling element 304 is time-dependent, as will be described further below. The cooling device 300 further comprises heat evacuating means 308 arranged to, when the cooling device 300 is arranged for cooling a residual limb received by a socket of a limb prosthesis, evacuate heat radially outwards from a longitudinal extension of the limb prosthesis. The heat evacuating means 308 is arranged at a first distance along the longitudinal extension from the cooling element. The heat evacuating means 308 is thereby arranged to prevent the cooling device 300 and the limb prosthesis from overheating when heat is led away from the contact area. The heat evacuating means 308 may provide active cooling, passive cooling or a combination thereof.

According to some aspects, the heat evacuating means 308 comprises a heat sink 310. The heat sink provides passive cooling of the limb prosthesis 300 by transferring heat received from the cooling element via thermal coupling elements, as described further below, and dissipates the heat to air surrounding the limb prosthesis.

According to some aspects, the heat evacuating means 308 comprises a fan 312. The fan 312 is an example of active cooling. A fan has an advantage in that it uses air as it cooling medium, thereby eliminating the need to carry around cooling fluids, such as water, to cool the limb prosthesis.

According to some further aspects, the heat evacuating means 308 comprises a mesh grid 314 arranged to at least partially protect the fan. The mesh grid may be arranged to protect the fan from protruding objects or features of the limb prosthesis and/or objects external to the cooling device 300.

The cooling device 300 further comprises thermal coupling elements 306 having a thermal capacitance below a predetermined maximum thermal capacitance and/or a thermal conductivity above a predetermined minimum thermal conductivity and arranged to thermally couple the cooling element to the heat evacuating means. The thermal coupling elements 306 enable usage of the longitudinal extension of the limb prosthesis by distributing components needed for the cooling mechanism along the longitudinal extension. The profile of the limb prosthesis can thereby be kept within a boundary corresponding to a limb of an intended user of the limb prosthesis. For instance, in the case of a leg prosthesis, components extending radially from the extension of the leg prosthesis can be effectively avoided, i.e. kept within a desired leg profile, thereby eliminating problems associated with extending parts of the leg prosthesis getting caught in or interacting with the other leg of the user or the external environment during walk.

Furthermore, the thermal coupling elements enables arranging the heat evacuating means at positions where they can be both better protected and operate more effectively than if they had been arranged at the socket. By keeping the thermal capacitance below a predetermined maximum thermal capacitance, unwanted heat build-up is avoided. By having the thermal conductivity above a predetermined minimum thermal conductivity, heat is led away from the cooling element to the heat evacuating means at a desired sufficiency. The thermal coupling elements may comprise a metal, e.g. copper. The thermal coupling elements preferably comprise a flexible region and/or a flexible material. The flexibility facilitates manufacturing since the flexibility may assist in fitting the thermal coupling elements to the shape of the socket of the limb prosthesis. The flexibility of the thermal coupling elements further enables the socket to maintain flexibility in regions overlapping with the thermal coupling elements. According to some aspects, the cooling element is arranged to be embedded in the socket of the limb prosthesis. According to some aspects, the thermal coupling elements are arranged to be at least partially embedded in the socket of the limb prosthesis.

According to some aspects, the cooling device 300 further comprises at least one temperature sensor 315 arranged to determine a temperature of the limb prosthesis. The temperature sensor 315 enables improved precision in determining the current cooling temperature of the cooling element. The temperature sensor further enables determining if the temperature in limb prosthesis rises above a highest allowable temperature threshold. This may be used to prevent overheating in case the ability of the heat evacuating means to evacuate heat is inhibited. A temperature sensor may further improve the power efficiency of the cooling device, e.g. by avoiding unnecessary cooling by the cooling element 304 or unnecessary work by a power operated component, such as a fan 312, of the heat evacuating means 308.

The cooling device 300 yet further comprises control circuitry 320 arranged to control the cooling element 304.

The control circuitry 320 may comprise any suitable type of computation unit, e.g. a microprocessor, digital signal processor, DSP, field programmable gate array, FPGA, or application specific integrated circuit, ASIC, or any other form of circuitry. It should be appreciated that the control circuitry need not be provided as a single unit but may be provided as any number of units or circuitry.

According to some aspects, the control circuitry 320 further comprises a timer. Also, the desired temperature interval may be time-dependent and the time- dependency is arranged to be controlled by the timer. By introducing time-dependence, different temperature application schemes are enabled. For example, the limb prosthesis may be arranged to apply cooling in a pulsed mode, e.g. cooling for a few seconds and then waiting for a few seconds, etc. For instance, the pulsed mode may comprise five seconds of cooling followed by five seconds of no cooling. The pulsed mode may comprise ten seconds of cooling followed by ten seconds of no cooling. The pulsed mode may comprise fifteen seconds of cooling followed by fifteen seconds of no cooling, and so on in five second increments. In a preferred example, the pulsed mode comprises thirty seconds of cooling followed thirty seconds of no cooling. In another preferred mode, the pulsed mode comprises sixty seconds of cooling followed sixty seconds of no cooling. The longer durations gives the user more time to sense the variations in temperature, potentially providing a greater contrast in the cooling experienced by the user. The durations of the cooling periods and/or the periods in between the cooling periods may be randomized. According to some aspects, a ramping scheme is applied. The time- dependence of the temperature may be coupled with other effects in between periods of cooling. For instance, in case the cooling element is a Peltier element, the current driving the Peltier element can be reversed back and forth. This will result in an alternating cooling and heating effect at the contact area. According to some aspects, the cooling device further comprises a shocking element arranged to generate an electric discharge at the contact area. The cooling device may then be arranged to provide an electric discharge, i.e. a shocking stimulus to a user, between the periods of cooling. According to some aspects, the cooling device further comprises a user interface 316 arranged to receive an input command and to control the control circuitry to set the desired temperature interval based on the input command. The user interface 316 preferably comprises an input and output interface. The input interface may be arranged to allow the user to set the desired temperature interval and/or program a time-dependent cooling scheme. According to some aspects, the cooling device comprises a set of predetermined time-dependent cooling schemes, e.g. stored in the memory, and the input interface is arranged to enable the user to select a cooling scheme from the set of predetermined time- dependent cooling schemes. The output interface may comprise one or more light-emitting diodes, LEDs, arranged to indicate a selected cooling scheme. Such an output interface requires very little power and is a preferable option if the cooling device is optimized for low power consumption. The output interface may also comprise a liquid crystal display, LCD, which can be arranged to display any type of 2D-information, e.g. text and numbers.

According to some aspects, the cooling device further comprises a communications interface 318 arranged to transmit data relating to usage of the cooling device during a predetermined time period. The data relating to usage of the cooling device may be obtained from e.g. a memory of the control circuitry or directly from the control circuitry and/or sensors of the cooling device.

The data from the communications interface 318 enables external diagnostics of the cooling device as such, as well as providing information relating to user statistics, which can be used to analyse user behaviour during the predetermined time period. According to some further aspects, the communications interface is further arranged to receive control signals and/or computer program code. In other words, the communications interface enables diagnostics and control of the cooling device via an external device. The communications interface may be arranged to use any combination of wireless and wired transmission. For instance, according to some further aspects, the communications interface is arranged to communicate using Bluetooth. According to some aspects, the communications interface comprises a USB port and/or a micro USB port.

The cooling device also comprises a battery 322 arranged to provide power to the cooling element 304 and the control circuitry 320.

According to some further aspects, the USB/micro USB ports may be used to charge the batteries of the cooling device.

According to some aspects, the cooling device comprises a plurality of batteries. With a plurality of batteries, the dimension of each battery can be reduced while still providing a predetermined total power. By reducing the dimension of each battery, the overall dimension of the cooling device can be reduced. In particular, the cooling device may be arranged to have a more flat profile compared to using a single battery. The battery is preferably rechargeable.

According to some further aspects, if the heat evacuating means comprises a fan, the control circuitry 320 is further arranged to control the fan 312 and the battery 322 is further arranged to provide power to the fan 312.

According to some aspects, the battery 322 is arranged at a second distance along the longitudinal extension from the cooling element 304, the second distance being greater than the first distance. The arrangement of the battery at the second distance along the longitudinal extension further distribute the components of the cooling mechanism along the longitudinal extension, thereby utilizing the longitudinal direction of the limb prosthesis to be able to maintain the features of the limb prosthesis within a desired profile. By arranging the battery at the second distance further enables arranging the battery at a support structure of the limb prosthesis, such as a titanium rod, thereby providing better stability and protection for the battery. Since the support structures are typically much narrower than a corresponding real limb, the placement of the battery at the second distance provides examples which make good use of available space.

According to some aspects, the control circuitry is arranged adjacent to the battery. According to some aspects, the cooling device further comprises a casing arranged to house the control circuitry and the battery. By arranging the control circuitry adjacent to the battery, e.g. arranged opposite each other, the need for electric wiring can be reduced and advantage can be taken of central support structures, such as a titanium rod-structure, to fixate the control circuitry and the battery to reduce potential stress due to movement of the residual limb. By arranging the control circuitry adjacent to the battery, the volume taken up by the control circuitry and the battery can be fitted to, while still maintaining, the elongated shape of the limb prosthesis. By adding a casing arranged to house the control circuitry and the battery, both the control circuitry and the battery can be further protected from shock, e.g. due to walking and running in the case of leg limb prosthesis, and environmental factors such as moist and temperature. The casing may further facilitate easy replacement of batteries in examples using removable, and possibly rechargeable, batteries. According to some aspects, the cooling device further comprises a casing 324 arranged to house the heat evacuating means. The casing 324 comprises a material having a thermal capacitance below a predetermined maximum thermal capacitance and/or a thermal conductivity above a predetermined minimum thermal conductivity. The casing 324 is arranged to house the heat evacuating means and to enable evacuation of heat radially outwards from the longitudinal extension of the limb prosthesis. The casing enables embedding the heat evacuating means into the support structure of the limb prosthesis and protects the heat evacuating means from external forces. Furthermore, a thermal capacitance below a predetermined maximum thermal capacitance and/or a thermal conductivity above a predetermined minimum thermal conductivity provides assistance with passive cooling. The use of a casing provides a means which can be arranged to have a length to suit any prosthetic. Furthermore, the casing may be arranged to comprise a connection interface, thereby enabling a standard connection for use with existing attachments.

Figure 4 illustrates an exploded view of embodiments of cooling devices for cooling a residual limb received by a socket of a limb prosthesis. Dashed lines indicating components of the limb prosthesis have been included to facilitate understanding.

The cooling device 400 comprises a cooling element arranged to be thermally coupled to a contact area of the socket intended to be in contact with a skin surface of the residual limb when received by the socket. The cooling element is arranged to cool the contact area to a desired temperature interval.

The desired temperature interval is preferably cool enough for a cooling effect to be appreciated by a user having the contact area in contact with the skin surface of the residual limb of the user and hot enough to avoid damage to the skin due to cold. The desired temperature interval is preferably five to twenty-five degrees centigrade, and even more preferably between ten to twenty degrees centigrade. Temperature intervals between five to fifteen degrees centigrade and fifteen to twenty-five degrees centigrade are also possible. The limb prosthesis is preferably arranged to ensure that the temperature at the contact area never drops below a lowest safety temperature. According to some further aspects, the temperature at the contact area is allowed to drop below the lowest safety temperature for a predetermined duration. The safety temperature thus safeguards against injury due to prolonged exposure to cold, while allowing temporary application of temperatures below the safety temperature. Since the desired cooling effect may differ between users, some aspects of the cooling device are arranged to enable the user to select the desired temperature interval, as will be described further below. The cooling element comprises a plurality of Peltier elements 404a, 404b, 404c. The flatness of the Peltier elements 404a, 404b, 404c enable the cooling element to maintain and follow the shape of the socket. According to some aspects, the Peltier elements 404a, 404b, 404c are arranged to be embedded in the socket of the limb prosthesis.

The cooling device 400 also comprises heat evacuating means 408 arranged to, when the cooling device is arranged for cooling a residual limb received by a socket of a limb prosthesis, evacuate heat radially outwards from a longitudinal extension of the limb prosthesis. The heat evacuating means 408 is further arranged at a first distance dl along the longitudinal extension from the cooling element 404.

The heat evacuating means 408 is arranged to prevent the cooling device 400 and the limb prosthesis from overheating. The heat evacuating means 408 comprises a heat sink 410. The heat sink 410 is arranged to provide passive cooling of the limb prosthesis by transferring heat received from the Peltier elements 404a, 404b, 404c via thermal coupling elements 406 arranged to thermally couple the Peltier elements 404a, 404b, 404c to the heat evacuating means 408, and dissipate the heat to air surrounding the limb prosthesis. The heat evacuating means 408 further comprises a fan 412.

The heat evacuating means 408 also comprises a mesh grid 414 arranged to at least partially protect the fan. The mesh grid may be arranged to protect the fan from protruding objects or features of the limb prosthesis and/or objects external to the cooling device 400.

The heat sink 410 is preferably arranged to house the fan 412, e.g. by comprising a cavity arranged to receive the fan. In examples wherein the heat sink houses the fan in a cavity, the heat sink is further arranged to enable the fan to evacuate hot air to the surrounding air external to the limb prosthesis. The mesh grid 414 may be arranged to cover one or more openings of the heat sink, thereby securely enclosing and protecting the fan 412, while still allowing air to flow freely. The cooling device 400 further comprises thermal coupling elements 406 having a thermal capacitance below a predetermined maximum thermal capacitance and/or a thermal conductivity above a predetermined minimum thermal conductivity and arranged to thermally couple the cooling element to the heat evacuating means. In some examples, the thermal coupling elements may comprise channels arranged to conduct heat from a hot side of a Peltier element 404a, 404b, 404c to the heat sink 410. The coupling of each channel to the heat sink may be either direct or indirect, i.e. via another thermally conductive medium, such as a thermally conductive casing 424 partially enclosing the heat evacuating means 408. The channels are thereby arranged to evacuate heat which would otherwise be trapped in the socket. The channels may comprise a metallic material, such as copper. The channels are preferably arranged to be flexible, which enables deformation of the socket without risking damage to the channels and facilitates manufacture of the limb prosthesis, since the flexible thermal coupling elements can be bent to match the shape of the socket. According to some aspects, the thermal coupling elements are arranged to be embedded in the limb prosthesis. The thermal coupling elements can thereby be protected from an external environment by benefitting from material properties of the limb prosthesis, such as a water-proof socket.

According to some aspects, the cooling device further comprises at least one temperature sensor arranged to determine a temperature of the cooling device and/or limb prosthesis. The temperature sensor enables improved precision in determining the current cooling temperature of the cooling element. The temperature sensor further enables determining if the temperature in the limb prosthesis rises above a highest allowable temperature threshold. This may be used to prevent overheating in case the ability of the heat evacuating means to evacuate heat is inhibited. A temperature sensor may further improve the power efficiency of the limb prosthesis, e.g. by avoiding unnecessary cooling by the cooling element or unnecessary work by the fan.

The cooling device 400 yet further comprises control circuitry 420 arranged to control the Peltier elements 404a, 404b, 404c. The control circuitry 420 is further arranged to control the fan 412.

The control circuitry 420 may comprise any suitable type of computation unit, e.g. a microprocessor, digital signal processor, DSP, field programmable gate array, FPGA, or application specific integrated circuit, ASIC, or any other form of circuitry. It should be appreciated that the control circuitry need not be provided as a single unit but may be provided as any number of units or circuitry.

According to some aspects, the control circuitry 420 further comprises a timer. Also, the desired temperature interval may be time-dependent and the time- dependency is arranged to be controlled by the timer. By introducing time-dependence, different temperature application schemes are enabled. For example, the limb prosthesis may be arranged to apply cooling in a pulsed mode, e.g. cooling for a few seconds and then waiting for a few seconds, etc. For instance, the pulsed mode may comprise five seconds of cooling followed by five seconds of no cooling. The pulsed mode may comprise ten seconds of cooling followed by ten seconds of no cooling. The pulsed mode may comprise fifteen seconds of cooling followed by fifteen seconds of no cooling, and so on in five second increments. In a preferred example, the pulsed mode comprises thirty seconds of cooling followed thirty seconds of no cooling. In another preferred mode, the pulsed mode comprises sixty seconds of cooling followed sixty seconds of no cooling. The longer durations gives the user more time to sense the variations in temperature, potentially providing a greater contrast in the cooling experienced by the user. The durations of the cooling periods and/or the periods in between the cooling periods may be randomized. According to some aspects, a ramping scheme is applied. The time- dependence of the temperature may be coupled with other effects in between periods of cooling. For instance, the current driving the Peltier elements can be reversed back and forth. This will result in an alternating cooling and heating effect at the contact area. According to some aspects, the cooling device further comprises a shocking element arranged to generate an electric discharge at the contact area. The cooling device may then be arranged to provide an electric discharge, i.e. a shocking stimulus to a user, between the periods of cooling.

According to some aspects, the cooling device further comprises a user interface arranged to receive an input command and to control the control circuitry to set the desired temperature interval based on the input command. The user interface preferably comprises an input and output interface. The input interface may be arranged to allow the user to set the desired temperature interval and/or program a time-dependent cooling scheme. According to some aspects, the cooling device comprises a set of predetermined time-dependent cooling schemes, e.g. stored in the memory, and the input interface is arranged to enable the user to select a cooling scheme from the set of predetermined time-dependent cooling schemes. The output interface may comprise one or more light-emitting diodes, LEDs, arranged to indicate a selected cooling scheme. Such an output interface requires very little power and is a preferable option if the cooling device is optimized for low power consumption. The output interface may also comprise a liquid crystal display, LCD, which can be arranged to display any type of 2D-information, e.g. text and numbers.

According to some aspects, the cooling device further comprises a communications interface arranged to transmit data relating to usage of the cooling device during a predetermined time period. The data relating to usage of the cooling device may be obtained from e.g. a memory of the control circuitry or directly from the control circuitry and/or sensors of the limb prosthesis.

The data from the communications interface enables external diagnostics of the cooling device as such, as well as providing information relating to user statistics, which can be used to analyse user behaviour during the predetermined time period. According to some further aspects, the communications interface is further arranged to receive control signals and/or computer program code. In other words, the communications interface enables diagnostics and control of the cooling device via an external device. The communications interface may be arranged to use any combination of wireless and wired transmission. For instance, according to some further aspects, the communications interface is arranged to communicate using Bluetooth. According to some aspects, the communications interface comprises a USB port and/or a micro USB port.

The cooling device also comprises a battery 422 arranged to provide power to the Peltier elements 404a, 404b, 404c, the fan 412 and the control circuitry 420. According to some further aspects, the USB/micro USB ports may be used to charge the battery 422.

According to some aspects, the cooling device comprises a plurality of batteries. With a plurality of batteries, the dimension of each battery can be reduced while still providing a predetermined total power. By reducing the dimension of each battery, the overall dimension of the cooling device can be reduced. In particular, the cooling device may be arranged having a more flat profile compared to using a single battery. The battery is preferably rechargeable.

According to some aspects, the battery 422 is arranged at a second distance d2 along the longitudinal extension from the cooling element, the second distance d2 being greater than the first distance dl. The arrangement of the battery at the second distance along the longitudinal extension further distribute the components of the cooling mechanism along the longitudinal extension, thereby utilizing the longitudinal direction of the limb prosthesis to be able to maintain the features of the limb prosthesis within a desired profile. By arranging the battery at the second distance further enables arranging the battery at a support structure, such as a titanium rod, thereby providing better stability and protection for the battery. Since the support structures are typically much narrower than a corresponding real limb, the placement of the battery at the second distance provides examples which make good use of available space.

According to some aspects, the control circuitry is arranged adjacent to the battery. According to some aspects, the cooling device further comprises a casing arranged to house the control circuitry and the battery. By arranging the control circuitry adjacent to the battery, e.g. arranged opposite each other, the need for electric wiring can be reduced and advantage can be taken of central support structures, such as a titanium rod-structure, to fixate the control circuitry and the battery to reduce potential stress due to movement of the residual limb. By arranging the control circuitry adjacent to the battery, the volume taken up by the control circuitry and the battery can be fitted to, while still maintaining, the elongated shape of the limb prosthesis. By adding a casing arranged to house the control circuitry and the battery, both the control circuitry and the battery can be further protected from shock, e.g. due to walking and running in the case of leg limb prosthesis, and environmental factors such as moist and temperature. The casing may further facilitate easy replacement of batteries in examples using removable, and possibly rechargeable, batteries.

According to some aspects, the cooling device further comprises a casing 424 arranged to house the heat evacuating means 408. The casing 424 comprises a material having a thermal capacitance below a predetermined maximum thermal capacitance and/or a thermal conductivity above a predetermined minimum thermal conductivity. The casing 424 is arranged to house the heat evacuating means and to enable evacuation of heat radially outwards from the longitudinal extension of the limb prosthesis. The casing is arranged to embed the heat evacuating means into the support structure of the limb prosthesis and to protect the heat evacuating means from external forces. Furthermore, support structures having a thermal capacitance below a predetermined maximum thermal capacitance and/or a thermal conductivity above a predetermined minimum thermal conductivity provides assistance with passive cooling. The use of a casing provides a means which can be arranged to have a length to suit any prosthetic. Furthermore, the casing may be arranged to comprise a connection interface, thereby enabling standard connection for use with existing prosthetic attachments.

Claims

Limb prosthesis (100; 200) for cooling a residual limb, the limb prosthesis (100, 200) comprising

a socket (102; 202) for receiving the residual limb,

a cooling element (104) arranged to be thermally coupled to a contact area of the socket intended to be in contact with a skin surface of the residual limb when received by the socket (102; 202), the cooling element (104) being arranged to cool the contact area to a desired temperature interval,

heat evacuating means (108; 208) arranged to evacuate heat radially outwards from a longitudinal extension of the limb prosthesis and arranged at a first distance along the longitudinal extension from the cooling element,

thermal coupling elements (106; 206) having a thermal capacitance below a predetermined maximum thermal capacitance and/or a thermal conductivity above a predetermined minimum thermal conductivity and arranged to thermally couple the cooling element to the heat evacuating means,

control circuitry (120; 220) arranged to control the cooling element, and

a battery (122; 222) arranged to provide power to the cooling element and the control circuitry.

The limb prosthesis according to claim 1, wherein the cooling element comprises one or a plurality of Peltier elements (104a, 104b, 104c, 104d; 204a, 204b, 204c).

The limb prosthesis according to claim 1 or 2, wherein the heat evacuating means comprises a fan (112; 212), wherein the control circuitry is further arranged to control the fan, and wherein the battery is further arranged to provide power to the fan.

The limb prosthesis according to any of the preceding claims, wherein the battery (122; 222) is arranged at a second distance along the longitudinal extension from the cooling element, the second distance being greater than the first distance.

5. The limb prosthesis according to any of the preceding claims, wherein the control circuitry (120; 220) is arranged adjacent to the battery.

6. The limb prosthesis according to any of the preceding claims, further comprising a casing arranged to house the control circuitry and the battery.

7. The limb prosthesis according to any of the preceding claims, further comprising a casing (108; 208) arranged to house the heat evacuating means, the casing comprising a material having a thermal capacitance below a predetermined maximum thermal capacitance and/or a thermal conductivity above a predetermined minimum thermal conductivity, the casing being arranged to house the heat evacuating means and to enable evacuation of heat radially outwards from the longitudinal extension of the limb prosthesis.

8. A cooling device (300; 400) for cooling a residual limb received by a socket of a limb prosthesis, the cooling device comprising

a cooling element (304) arranged to be thermally coupled to a contact area of the socket intended to be in contact with a skin surface of the residual limb when received by the socket, the cooling element being arranged to cool the contact area to a desired temperature interval,

heat evacuating means (308; 408) arranged to, when the cooling device is arranged for cooling a residual limb received by a socket of a limb prosthesis, evacuate heat radially outwards from a longitudinal extension of the limb prosthesis and arranged at a first distance (dl) along the longitudinal extension from the cooling element, thermal coupling elements (306; 406) having a thermal capacitance below a predetermined maximum thermal capacitance and/or a thermal conductivity above a predetermined minimum thermal conductivity and arranged to thermally couple the cooling element to the heat evacuating means,

a battery (322; 422) arranged to provide power to the cooling device, and control circuitry (320; 420) arranged to control the cooling element.

9. The cooling device for cooling according to claim 8, wherein the cooling element comprises one or a plurality of Peltier elements (304a, 304b, 304c, 304d; 404a, 404b, 404c). 10. The cooling device according to claim 8 or 9, wherein the heat evacuating means comprises a fan (312; 412), wherein the control circuitry is further arranged to control the fan, and wherein the battery is further arranged to provide power to the fan.