WO2017208100A1

WO2017208100A1 - 3d-printed myoelectric hand prosthesis with improved thumb movement

Info

Publication number: WO2017208100A1
Application number: PCT/IB2017/052890
Authority: WO
Inventors: Jorge Alberto ROBLEDO RAMIREZ
Original assignee: Robledo Ramirez Jorge Alberto
Priority date: 2016-05-31
Filing date: 2017-05-17
Publication date: 2017-12-07

Abstract

The present invention relates to a 3D-printed myoelectric hand prosthesis with improved thumb movement, which comprises a plurality of mechanisms that provide independent movement to each finger and allow same to be fitted to any size of prosthesis, maintaining the strength and speed of the movements. Advantageously, the prosthesis of the present invention also allows the opposition of the thumb to the other fingers and the subterminolateral (key grip) opposition of the thumb, thereby providing a functionality closer to that of a human hand.

Description

ISOELECTRIC PROSTHETICS OF HAND OBTAINED BY 3D PRINTING WITH IMPROVED MOVEMENT OF THE THUMB

Technical Field of the Invention

The present invention relates to robotic prostheses for limb replacements, in particular with a myoelectric hand prosthesis manufactured by three-dimensional printing.

Background of the invention

A large number of people in the world lack at least one of their hands due to congenital conditions or trauma. Although there are currently robotic prostheses for limb replacement, which work with both electric power (for example myoelectric prostheses) and include mechanical devices, these are generally very expensive and have difficulty adjusting to any size. For example, the adjustment to the dimensions of the limbs of children is particularly difficult, since any modification in the dimensions of the prosthesis requires the change of the manufacturing mold. This limits access to a large number of patients to prosthetic aids that reduce the discomforts of amputations or congenital defects.

In recent years they have begun to develop cheaper alternatives to meet the demand for prostheses of different sizes, using three-dimensional printing technology (3D printing). Thanks to this type of printing, we have recently obtained prostheses tailored to cost less than traditional prostheses. Likewise, this printing system allows a much faster manufacturing of the prosthesis, allowing its design and production in a few days.

However, many times the size change in the prosthesis is not totally efficient because in general 3D printed prostheses use servo motors that are produced in standard sizes and therefore

i limit the possible dimensions of the prostheses. Likewise the reduction of the size entails a decrease in the strength and speed of the movements.

In addition to the above, prostheses made by 3D printing still do not completely mimic all possible movements of the fingers of the human hand.

There is therefore a need in the state of the art for an improved prosthesis that is of low production cost, can be tailored without reducing the strength and speed properties of finger movements and that provides a greater number of possible finger movements that are closer to the possibilities of a human hand.

Brief Description of the Invention

Advantageously, the present invention solves the problems of the state of the art by providing a hand-held myoelectric prosthesis obtained by 3D printing, which comprises a plurality of mechanisms that provide independent movement to each finger and allow to adjust to any size of prosthesis, maintaining the strength and speed of the movements. Additionally, advantageously, the prosthesis of the present invention allows both the opposition of the thumb to the other fingers and the subterminolateral opposition thereof (key grip), and therefore provides a functionality closer to that of a human hand.

Brief description of the figures

Figure 1 shows a front view of the myoelectric prosthesis of the present invention.

Figure 2 corresponds to a rear view of the myoelectric prosthesis of the present invention.

Figure 3 illustrates the detail of the engine operation and the pinion arrangement that allows the movement of each of the fingers. Figure 4 shows the preferred way of closing the fingers in the myoelectric prosthesis of the invention, taking the index finger as a model.

Figure 5 shows the preferred way in which hand opening occurs in the myoelectric prosthesis of the present invention, illustrated with the index finger.

Figures 6A and 6B illustrate the mechanism for performing thumb opposition in the myoelectric prosthesis of the invention.

Figures 7A and 7B show the preferred way of performing the thumb-to-bottom (key grip) opposition of the prosthesis of the present invention.

Figure 8 shows the preferred way of adjusting the motor and pinions to resize the prosthesis of the invention.

Figures 9A and 9B illustrate the preferred way of performing the size reduction of the prosthesis of the invention.

Detailed description of the invention

Within the state of the art, hand prostheses are required that can be made to the exact measure of the user's needs, maintaining the strength and speed of movements in any size and that provide finger movements more similar to one hand human

In this sense, the present invention solves the problems of the state of the art by providing a hand-held myoelectric prosthesis obtained by 3D printing, which allows a millimeter adjustment to the user's needs, has constant force and speed of movements regardless of the size of the prosthesis, and allows improved finger movements.

In this way, the present invention relates to a hand-held myoelectric prosthesis obtained by 3D printing that comprises a plurality of mechanisms for moving the fingers, which allows to adjust to any size of prosthesis. Said plurality of mechanisms provides independent movement of each finger and allows both the opposition of the thumb to the other fingers and their subterminolateral opposition (key grip), similar to how it is done in a human hand.

Preferably, the prosthesis of the invention has myoelectric sensors that are located in contact with the user's skin, and capture the signals produced by the muscles to convert them into a binary signal. Said binary signal is conducted to a microcontroller, which interprets it, sends a transformed signal to the controller circuit of the plurality of mechanisms for moving the fingers, and thanks to software translates this signal into movement of the prosthesis.

Preferably, the myoelectric prosthesis of the invention employs two myoelectric sensors located in the user's forearm that transmit the signals for the opening, closing and the different hand grips.

Figures 1 and 2 show a preferred embodiment of the prosthesis of the invention, each of the fingers moves independently thanks to a plurality of mechanisms that respectively operate the index, middle, ring and little fingers (1), (2 ), (3) and (4). On the other hand, preferably the thumb (9) has two mechanisms for its movement, a mechanism for flexion or extension (5) that achieves the opposition of the thumb to the other fingers and a mechanism for independent movement (6), that is, to obtain the subterminolateral opposition of the thumb. Each of the fingers comprises a lower phalanx (7) and an upper phalanx (8).

As shown in said Figures 1 and 2, the clamping parts (10) and (1 1) house the mechanisms for the movement of the fingers, which are fixed by means of screws (13) to the outer housing (12 ) which also houses the electronic part, forms the back of the hand and wrist and joins the contact cavity with the user.

As Figure 3 teaches, the plurality of mechanisms for the movement of the fingers of each of the fingers (1), (2), (3) and (4) comprises a motor (14), and an arrangement of pinions .

In a preferred embodiment the pinion arrangement of the plurality of mechanisms for moving the fingers of the myoelectric prosthesis of the invention It comprises a metal sprocket reduction mechanism (15) in which the motor (14) is embedded, and a first straight sprocket (16) which, when rotated, transmits the movement to one or more sprockets.

In this embodiment, the metal pinion reduction mechanism (15) converts the engine rotation speed, with low torque, into a movement with lower speed but greater torque. From this metal pinion reduction mechanism (15) there is an axis parallel to the motor shaft (14) where the first straight pinion (16) is connected.

In a preferred embodiment, the first straight pinion (16) is connected to a reducing pinion (17), which in turn moves a second straight pinion (18), attached to a cylinder (21). The Cylinder (21) holds a semi-rigid belt (19) of a pulley (20). The transmission of the movement to the upper phalanges (8) is obtained by means of the semi-rigid belt (19).

In a preferred embodiment of the invention the motor (14) is a direct current motor, more preferably a direct current metallic micro geared motor. Preferably, the motor (14) has a torque between 0.01 and 3 Kg / cm, more preferably between 0.05 and 2.5 Kg / cm.

Figure 4 shows the preferred way of closing each of the fingers of the myoelectric prosthesis of the invention, taking as an example the index finger. In this movement, the rotation of the motor (14) is transmitted by the reduction mechanism (15) to the first straight pinion (16), the reducing pinion (17), and the second straight pinion (18), and the semi-rigid belt (19 ) makes traction in the upper phalanx (8), which transmits the movement to the lower phalanx (7) to the point where the tip of the finger touches the palm of the hand, where the motor (14) stops.

On the other hand, as shown in Figure 5, preferably the myoelectric prosthesis of the invention generates the opening movement, by reversing the direction of rotation of the motor (14), which causes the semi-rigid belt (19) to perform traction on the upper phalanx (8) in the opposite direction, that is, upwards. The movement is transmitted to the lower phalanx (7) and continues until the finger is fully extended. As stated above, the myoelectric prosthesis of the present invention advantageously provides two independent movements of the thumb, controlled by two different mechanisms: a mechanism for flexion or extension (5) and a mechanism for independent movement (6), that is to say to obtain the subterminolateral opposition of the thumb. This advantageously makes the myoelectric prosthesis of the present invention provide movements closer to those possessed by a human hand.

Thus, preferably the opposition of the thumb to the other fingers is controlled by the flexion or extension mechanism (5) as evidenced in Figures 6A and 6B. In said mechanism for flexion or extension (5) the output of the motor (14) with a metal pinion reduction mechanism (15) a first straight pinion (16) is connected, which in turn is connected to a reduction pinion ( 17). On the other hand, this reducer pinion (17) is connected to an additional reducer pinion (22), which is connected to the second straight pinion (18). Said second straight pinion (18) is attached to a support (23) that is responsible for supporting the entire mechanism for independent movement (6), and the thumb (9). When the second straight pinion (18) moves, traction is made on the thumb (9) until it is in front of the other fingers. Similarly, the inversion of the rotation allows the movement of the thumb (9) in the opposite direction, returning it to its open palm position.

On the other hand, advantageously, the myoelectric prosthesis of the present invention also allows for the sub-lateral opposition of the thumb, the "key grip", as shown in Figures 7A and 7B. For this, the mechanism for independent movement (6) preferably comprises a motor (14), embedded in a metal pinion reduction mechanism (15), where the output of this motor is connected to a first straight pinion (16) , which is connected to a reduction pinion (17), which in turn is connected to a second straight pinion (18). This second straight pinion (18) is attached to a cylinder (21) that holds a semi-rigid belt (24), which is connected to the thumb (9). As in the case of opening and closing the other fingers, the mechanism for independent movement (6) moves the thumb (9) by the traction made by the semi-rigid belt (24). As a result of the foregoing, the myoelectric prosthesis that is the object of the present invention advantageously provides movements closer to those of a human hand, such as the thumb's sub-lateral opposition, with high precision, force and speed, regardless of the prosthesis size

Preferably, in the myoelectric prosthesis of the present invention, said force and speed of finger movements is adjusted by changing the torque value of the motor (14), and decreasing the diameters and number of teeth of the arrangement of pinions, for example of the first straight pinion (16), the reducing pinion (17) and the second straight pinion (18). In this way, regardless of the size of the prosthesis, the strength and speed of finger movements are kept constant.

Consequently, preferably the variation of the size of the myoelectric prosthesis of the invention is carried out by 3D printing of the clamping pieces (10) and (1 1) and the outer shell (12) in the desired dimensions, and the adjustment of the movement mechanisms of the fingers (1), (2), (3), (4), (5) and (6), varying the diameters of the first straight pinion (16), the reducing pinion (17) and the second straight pinion (18).

Example

Reduction of the size of the prosthesis.

In one embodiment of the invention the torque required to move the fingers is 0.49 Kg / cm.

A motor (14) with an output torque of 0.30 kg / cm is used and this is connected to the first straight pinion (16). Being directly on the motor shaft, the first straight pinion (16) retains the torque.

If said first straight pinion (16) has a diameter of 9.5mm and 24 teeth, when calculating the necessary output torque, it is obtained that it is possible to dispense with the reducing pinion (17) and connect the first straight pinion (16 ) to the second straight pinion (18), if the latter has a diameter of 17mm and 32 teeth. As illustrated in Figure 8, eliminating the gear pinion (17) results in a significant reduction in the length of the finger, and due to the torque ratio of the motor (14) and the diameters of the pinion arrangement connected to it, the torque to move the finger remains constant (0.49 Kg / cm). Similarly, when using a motor (14) with a different torque, it is possible to vary the diameter of the pinion arrangement to fit any size, maintaining the final torque needed to move the fingers.

As shown in Figures 9A and 9B, the variation of the size of the clamping pieces (10) and (1 1) and of the outer shell (1 2), allow to reduce or increase the size of the myoelectric prosthesis of the invention at convenience

Consequently, by varying the diameters and number of teeth of the pinion arrangement, that is, the first straight pinion (16), the reducing pinion (17) and the second straight pinion (18), and when changing the sizes of the pieces of clamping (10) and (1 1) and of the outer casing (12), prostheses of different sizes can be obtained, with pinpoint accuracy and, being the pieces obtained by 3D printing, the process is fast and inexpensive.

It is understood that the preferred embodiments of the invention disclosed herein are illustrative only and do not limit the scope of the invention only to these. The obvious variations for the person versed in the subject are also included within the scope of the invention.

Claims

1. A myoelectric hand prosthesis obtained by 3D printing characterized in that it comprises a plurality of mechanisms to move the fingers, where said plurality of mechanisms provides independent movement to each finger, allows adjustment to any size of prosthesis and produces both the opposition of the thumb to the other fingers as the subterminolateral opposition of the same.

2. The myoelectric prosthesis according to claim 1 further characterized in that the opposition of the thumb to the other fingers and the subterminolateral opposition of the thumb are produced by two different mechanisms.

3. The myoelectric prosthesis of any of the previous claims wherein a plurality of mechanisms for moving the fingers allows the torque necessary to move the fingers to be kept constant regardless of the size of the prosthesis.

4. The myoelectric prosthesis of any of the preceding claims wherein a plurality of mechanisms for moving the fingers (1), (2), (3), (4), (5) and (6) comprise a motor (14). ) and an arrangement of pine nuts.

5. The myoelectric prosthesis of claim 4, wherein the pinion arrangement of the plurality of mechanisms for moving the fingers (1), (2), (3), (4), (5) and (6) comprises a reduction mechanism of metal pinions (15) in which the motor (14) is embedded, and a first straight pinion (16) that transmits the movement to one or more pinions.

6. The myoelectric prosthesis of claim 5, wherein the first spur gear (16) is connected to a reduction pinion (17) which in turn moves a second spur gear (18), attached to a cylinder (21) that It holds a semi-rigid belt (19) from a pulley (20).

7. The myoelectric prosthesis of claim 5, wherein the first spur gear (16) connects to a reduction pinion (17) which in turn moves a second spur gear (18), and wherein the second spur gear ( 18) is attached to a cylinder (21) that supports a semi-rigid belt (24).

8. The myoelectric prosthesis of claim 5, wherein the first straight pinion (16) is connected to a reduction pinion (17) which is connected to an additional reduction pinion (22), which is connected to the second straight pinion (18). ) attached to a support (23).

9. The myoelectric prosthesis of any of the preceding claims wherein the size of the prosthesis can be varied by changing the dimensions of the fastening parts (10) and (1 1) and the outer casing (12), and adjusting the plurality of mechanisms of movement of the fingers (1), (2), (3), (4), (5) and (6), by varying the diameter of the pinion arrangement.

10. The myoelectric prosthesis according to any of the preceding claims, wherein the motor (14) is a direct current metallic micro-reduction motor.