WO1998055379A1

WO1998055379A1 - A conveyor and a method for operating a conveyor

Info

Publication number: WO1998055379A1
Application number: PCT/DK1998/000237
Authority: WO
Inventors: Anders Pedersen; Jakob Evald
Original assignee: Crisplant A/S
Priority date: 1997-06-04
Filing date: 1998-06-04
Publication date: 1998-12-10
Also published as: AU7640298A

Abstract

A conveyor for slidingly conveying and decelerating or accelerating items has a conveyor track having at least one track section (5) which comprises mutually transversely spaced first and second track section parts (6, 7) defining supporting surface parts (16, 17) having different frictional surface characteristics. Flexible sheet material (8) arranged between adjacent track section parts is provided so as to prevent items and foreign matter from becoming clamped or squeezed between adjacent track section parts. Displacement means for moving the first and second track section parts in relation to each other between item supporting and item non-supporting positions are provided, whereby the rate of movement of the items along the conveyor track may be controlled. A method for operating such a conveyor is disclosed.

Description

A CONVEYOR AND A METHOD FOR OPERATING A CONVEYOR

TECHNICAL FIELD

The present invention relates to a conveyor and a method for operating a conveyor.

More particularly, the invention relates to a conveyor of the type comprising a conveyor track defining an item supporting surface having means for controlling the rate of movement of items conveyed along the conveyor track. The conveyor according to the invention is in particular suited for conveying luggage at airports, railway stations etc., or for conveying postage packages and/or mail bags or for conveying fragile products at factories or at other relevant locations.

BACKGROUND OF THE INVENTION

In the prior art, conveyors having retarding means for retarding conveyed items are disclosed. The retarding means comprise obstacles which may be introduced in the conveying path of items. Examples of such conveyors are disclosed in EP-A 0 521 541, CA-A 1 315 714, US 4,130,193, DE 1 123 975 and DE 1 135 365.

EP-A 0 521 541 discloses a conveyor provided with an inclined conveyor track having a waved profile when seen in section. The bearing surface has peaks and valleys extending in the longitudinal direction of the conveyor track. In the valleys means are located which can be moved upwards from a position where the means lie in the valleys into a position in which the means proj ect above the peaks .

CA-A 1 315 714 discloses a device for decelerating rollable objects, the device comprising a number of recesses disposed along its raceway and a number of flexible conduits disposed in the recesses. The conduits are filled or partly filled with a fluid and extend partly above the rolling raceway. SUMMARY OF THE INVENTION

An object of the present invention is to provide a conveyor having a conveyor track which is capable of controlling the rate of movement of items conveyed along the conveyor track while preventing items and foreign matter from being clamped between moving parts of the conveyor. A further object of the present invention is to provide a conveyor of the aforementioned type which is robust and has a long life time and which is capable of conveying and controlling the rate of movement of items having varying shapes and sizes. A further object of the present invention is to provide a conveyor wherein the surfaces or at least parts thereof may be easily replaced in case of the surface being damaged by wear or in case of the need for the application of surfaces having different surface characteristics. It is a still further object of the present invention to provide a method of operating such a conveyor.

Thus, the present invention provides a conveyor for slidingly conveying items along a conveyor track defining an item supporting surface, said track having at least one track section which comprises

- mutually transversely spaced first and second track section parts defining supporting surface parts having different frictional surface characteristics,

- flexible sheet material being arranged between adjacent track section parts so as to prevent said items and foreign matter from becoming clamped between adjacent track section parts , and

- displacement means for moving said first and second track section parts in relation to each other between item supporting and item non-supporting positions, whereby the rate of movement of the items along the conveyor track may be controlled. With such a conveyor the rate of movement of items may be controlled due to different frictional surface characteristics of the supporting surfaces Thus, conveyed items may be accelerated due to gravity or decelerated, depending on the mutual positions of the first and second track section parts. With a conveyor according to the invention it is possible to effectively control the rate of movement of items conveyed along a conveyor section. A particular advantage of the conveyor is that no are obstacles introduced into the pathway of items and therefor no or nearly no impact, e.g., on fragile items, is caused on conveyed items. Furthermore, conveyed items and/or foreign matter are prevented from being clamped between displaceable parts of conveyor track sections. A further advantage of a conveyor according to the invention is that in case of heavy- items and/or items having sharp edges being conveyed therealong, there is no risk of the items damaging conduits or pipes being filled with a fluid which could cause damage on conveyed items .

The conveyed items may be of any type. A conveyor according to the present invention is in particular suited for luggage, postage packages , mail bags or other conveyable items . The conveyor may further be installed in factories or at process plants for conveying spare parts or final products.

A conveyor according to the invention is particularly suited for slidingly conveying items, e.g., in chutes wherein items are conveyed under the action of gravity or in substantially horizontal conveyor tracks wherein items are conveyed by one or more conveyor belts or by other conveying means. The conveyor track section comprised in the conveyor track is adapted to control the rate of movement of the items along the conveyor track. Since the first and second track parts having different frictional surface characteristics are mutually displaceable between item supporting positions and item non-supporting positions, the amount of frictional force applied to conveyed items may be adjusted, whereby a control of the rate of movement of the items is obtained. The conveyor track may be provided with a plurality of first and second track section parts. However, as an alternative, only one first and one second track section part may be provided. When a plurality of first and second track section parts is provided, the frictional characteristics of each of the track section parts may vary over its length and/or width. For example, for special deceleration/retarding applications of the conveyor track section it may be desired that the surfaces defined by the track section parts provide high friction forces on conveyed items at the beginning of a conveyor track section, i.e. at an upstream position in the conveyor track section, and low friction forces at the end of a conveyor track section, i.e. at a downstream position in the conveyor track section.

The first track section parts may define surfaces having all substantially identical frictional surface characteristics providing low friction forces on conveyed items, while the second track section parts may define surfaces having all substantially identical frictional surface characteristics providing high friction forces on conveyed items. Preferably, the first and second track section parts are arranged parallel to each other and extend in a direction substantially parallel to the longitudinal direction of the conveyor track section, the track section parts thus having a rectangular outline. However, alternatively, the track section parts may extend in a direction substantially perpendicular to the longitudinal direction of the conveyor track section. Further possible embodiments are embodiments wherein the first and second track section parts are arranged in a chessboard pattern.

The displacement means may comprise one or more pneumatic or hydraulic activators, electrically driven activators such as, e.g., spindle motors, magnetic/electromagnetic activators and/or any other suitable means for activating the mutual displacement between the first and second track section parts. For special applications of the invention, the displacement means may comprise one or more combustion devices . The displacement means may comprise one or more stationary parts, such as, e.g., one or more pneumatic cylinders, one or more hydraulic cylinders and/or stationary electro motor part(s) or stationary engine part(s), and one or more displaceable/moveable parts, such as, e.g., one or more hydraulically or pneumatically driven pistons, moving electro motor parts or displaceable engine parts. In case the displaceable parts comprise rotating parts, means for translating the rotating movement into a substantially linear displacement of the track section parts may further be comprised in the displacement means . The one or more displaceable parts may be displaceable/moveable in any direction in space. In case the displaceable/moveable parts cause a displacement in a moving direction which is not substantially parallel to the displacement direction of the track section parts, means for translating the displacement in the moving direction into a displacement of the track section parts in their displacement direction may be comprised in the displacement means and/or in the track section part. Particular embodiments of the invention relate to embodiments wherein the displaceable parts cause a displacement in a first direction which is substantially parallel to the displacement direction of the track section parts, and to embodiments wherein the displaceable parts cause a displacement in a second direction which is substantially perpendicular to the displacement direction of the track section parts. When the one or more displaceable partβ are displaceable in the second direction which is substantially perpendicular to the displacement direction, the displacement means further comprise means for translating the movement of said one or more displaceable parts in the second direction to a movement of at least some of the track section parts in the displacement direction.

The means for translating the displacement of the displacement means in a direction which is not substantially parallel to the displacement direction of the track section parts may comprise any suitable mechanical means, such as systems of rods and links, toothed wheels, wheels rolling on ramps and supporting the track section parts and/or associated parts, one or more members pivotally mounted at pivots and one or more rods connected eccentrically in relation to the pivots, and/or combinations thereof.

The displacement means may comprise one pneumatic or hydraulic activator. The displacement means may comprise four pneumatic or hydraulic activators. However, different numbers of pneumatic and/or hydraulic activators may be applied, such as, e.g., two, three, five, six or more, depending on the specific application of the conveyor and the load to be carried and/or lifted by the displacement means.

The displacement means may be adapted to selectively move the track section parts independently, or they may be adapted to move some of the track section parts independently and others simultaneously, or they may be adapted to move only some of the track section parts either independently or simultaneously.

A control system may be applied for controlling the mutual displacement of the tracks section parts. The control system may comprise processor means for processing data relevant to the control of the rate of movement of items . Such data may be variable data which are measured along the conveyor track, e.g., velocity and weight of conveyed items as well as predetermined data, such as, e.g., a prescribed velocity of items. Relevant measurement equipment, such as sensing means, e.g. photocells, cameras, weights and/or other equipment may be installed along the conveyor track and connected to the processor means of the control system. One or more photocells may be located upstream of the conveyor track section. The photocell or photocells may sense when an item is approaching the conveyor track section, and, if required, mutual displacement of the first and second track section part may be activated in order to control the rate of movement of the item.

Preferably, the flexible sheet material or flexible sheet is made from a rubber belt of the type commonly used for conveyor belts. However, it may be made from other materials such as wear resistant textiles, plastics materials or other materials. The flexible sheet should be resistant to wear. Due to the flexible sheet covering and closing gaps between the first and second track section parts and associated parts, it is prevented that conveyed items, as well as associated and foreign matter may be clamped between adjacent track section parts. Additionally and/or alternatively to the flexible sheet, other means fulfilling the same functions as the flexible sheet may be provided, such as, e.g., grids or meshes .

The at least one first track section part is preferably stationarily mounted and the at least one second track section part is preferably displaceably mounted, the displacement means being adapted to the second track section parts. Alternatively, the second track section parts may be stationarily mounted while the first track section parts may be displaceably mounted. A particular advantage of such configurations is that in situations wherein the control of the rate of movement of items is obtained by the surfaces defined either by first or the second track section parts solely, no displacement of the track section parts is required. A further advantage is that manufacturing and assembling of such configurations is easy and cheap.

Each of the first track section parts may be fixed to a corresponding stationary fixation part of the track section. The flexible sheet material may be positioned between the first track section parts and the corresponding fixation parts of the conveyor track section, while the first track section part may be fastened to the fixation part by fastening means. At least some of the fastening means may extend through the flexible sheet material . The fastening means preferably comprise screw or rivet connections. Preferably, each screw or rivet extends through the flexible sheet material, so as to obtain a secure and tight connection between the flexible sheet and the stationary parts of the conveyor track section. However, in other embodiments, the flexible sheet material may be fastened to the fixation members and the supporting members, respectively, by other means such as by gluing. Alternatively and/or additionally, magnetic materials may be incorporated in the flexible material , so that the flexible material may be connected to the fixation parts by magnetic means.

Each of the second track section parts preferably comprises a supporting member which in the item supporting position of the second track section part supports the flexible sheet material while stretching it. Thereby, the frictional properties of the flexible sheet may be at least partly exploited to a maximum degree, and obstacles due to bulges in the flexible sheet when not stretched are prevented.

Preferably, the supporting members are mounted on a connecting member extending across and below the conveyor track, the displacement means being connected to the connecting member. As mentioned above, the displacement means may comprise one or more pneumatic and/or hydraulic activators, electrical activators, magnetic/electromagnetic activators and/or combinations thereof. The connecting member is preferably rod-shaped with a cross section enabling it to withstand loads applied thereto when the second track section parts are in their item supporting position. The cross may, e.g., be U-shaped or I-shaped. Preferably, the connecting member is made from steel. However, it may be made from other materials, such as stainless steel, fiber materials, plastics materials or other materials.

In another aspect, the present invention relates to a method of operating a conveyor for slidingly conveying items along a conveyor track. The conveyor tracks define an item supporting surface and include at least one track section comprising mutually transversely spaced first and second track section parts. The first and second track section parts define supporting surface parts having different frictional surface characteristics. According to the invention, the method comprises :

- arranging flexible sheet material between adjacent track section parts so as to prevent said items and foreign matter from becoming clamped between and from passing downwardly between adjacent track section parts, and

- displacing said first and second track section parts in relation to each other between item supporting and item non- supporting positions, so as to control the rate of movement of the items along the conveyor track.

The method according to the invention is in particular suitable for operating a conveyor according to the invention but is not restricted thereto.

By displacing the first and second track section parts in relation to each other, preferably selectively, the amount of frictional forces caused to conveyed items and thereby the deceleration of items may be controlled. For example, when applied to a conveyor section of a chute wherein items are moved under the action of gravity, the method according to the invention may selectively cause items to be accelerated or decelerated, depending on whether the friction forces caused to a conveyed item exceeds the gravity force caused on that items or not . It should be understood that the method according to the invention also makes it possible to slow conveyed items down to a complete stop. The method may further be adapted to change the conveying direction of items in a controlled way. If the conveyor comprises a control system, the control of the rate of movement of conveyed items may be performed in an active way. Thus, the method may further comprise the steps of sensing variable data, such as velocity and/or weight of items. The method may be controlled by a control system which may optionally be connected to a main control system comprised in the conveyor. Thus, for example, the method may individually control the rate of movement of items.

In a method according to the invention, the conveyor track may comprise at least one first track section part being stationarily mounted and at least one second track section part being displaceably mounted, the mutual displacement between the first and second track section parts being provided by movement of the second track section parts. Obviously, the method also allows the first track section part or parts to be displaceably mounted and the second track section part or parts to be stationarily mounted.

The method may be adapted to perform the mutual displacement of the first and second track section parts while taking into account the different frictional surface characteristics of the surfaces defined by the first and second track section parts, so as to more accurately control the rate of movement of conveyed items .

In the method according to the invention, the conveyor track may comprise a plurality of first and second track section parts, the mutual displacement of the first and second track section parts being provided by simultaneous movement of a plurality of track section parts. This makes it possible to design and manufacture a conveyor to be operated by a method according to the invention in a cost efficient way, while providing a conveyor protecting items from damage. The mutual displacement of the first and second track section parts may alternatively be provided by individual movement of a plurality of track section parts. The supporting surface parts defined by the first track section parts may have surface characteristics providing a substantially lower frictional force on conveyed items than the surface characteristics of the supporting surface parts defined by the second track section parts, so as to provide substantially larger frictional forces on conveyed items when the second track section parts are in their item supporting position compared to the frictional forces provided on conveyed items when the second track section parts are in their item non-supporting position. The first track section part or parts may define surfaces having identical frictional surface characteristics or they may define surfaces having different frictional surface characteristics. The same applies to the second track section parts.

The method according to the invention may comprise the step of displacing the one or more displaceable parts in any direction in space, and, in case the displaceable parts are not being displaced in the displacement direction of the track section parts, translating the movement of the displaceable parts into a movement which is substantially parallel to the displacement direction of the track section parts , The method may comprise the step of moving the displaceable parts in a first direction which is substantially parallel to the displacement direction so as to displace the track section parts in relation to each other, or it may comprise the step of displacing the one or more displaceable parts in a second direction which is substantially perpendicular to the displacement direction.

When the one or more displaceable parts are displaceable in the second direction which is not substantially parallel to the displacement direction, the method may further comprise the step of translating the movement of the one or more displaceable parts to a movement of the track section parts in the displacement direction, so as to displace the track section parts in relation to each other. In order to obtain active control of the rate of movement of items, the method according to the invention may comprise arranging item sensing means in or adjacent to the conveyor upstream of said at least one track section. The method may thus comprise:

- sensing of items approaching the track section, and

- activating the mutual displacement of said first and second track section parts when one or more items are approaching the track section.

Other sensing means may be applied for sensing downstream items. Thus, it may be prevented that two items collide, e.g., when a downstream queue of accumulating items occurs.

The sensing means may be of any type. Preferred sensing means are photocells or cameras which may be connected to displacement means comprised in a conveyor track section.

Where in the present context, the term "upstream" is used, this term should be interpreted as any location along the conveyor track reached by a conveyed item before reaching a particular position, i.e. any position located prior to that particular position when seen in the conveying direction of items. Equivalently, where in the present context, the term "downstream" is used, this term should be interpreted as any location along the conveyor track reached by a conveyed item after having passed a particular position, i.e. any position located subsequent to that particular position when seen in the conveying direction of items.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will now be further described in connection with the appended drawing in which: Fig. 1 is an illustration of a conveyor installation comprising a conveyor according to the invention,

Fig. 2 is a cross sectional illustration of a conveyor track section in a first operating position, Fig. 3 shows the conveyor track section of Fig. 2 in a second operating position,

Fig. 4 is a cross sectional view in a first plane of a first embodiment of a conveyor track section comprised in a conveyor according to the invention, Fig. 5 is a top view of the conveyor track section of Fig. 4,

Fig. 6 is a cross sectional view in a second plane of the conveyor cross section of Figs . 4 and 5 ,

Fig. 7 is a cross sectional view in a first plane of a second embodiment of a conveyor track section comprised in a conveyor according to the invention,

Fig. 8 is a cross sectional view in a second plane of the conveyor track section of Fig. 7.

DETAILED DESCRIPTION OF THE DRAWINGS

Fig. 1 illustrates a conveyor system comprising a conveyor 1 according to the invention. The conveyor system may comprise conveyor wagons 2 for moving along track, the conveyor wagons 2 carrying items to be sorted and/or transported, such as, e.g., suit cases, mail bags, postage packages etc. The conveyor wagons 2 may be loaded with items at one or more loading stations arranged along the track, and items may be unloaded at one or more unloading station arranged along the track. The unloading stations may comprises a chute 4, wherein items are moved under the action of gravity. In the embodiment shown in Fig. 1, a conveyor track section 5 comprising mutually transversely spaced first and second track section parts 6 and 7 as shown in Figs. 2-5 is provided at a lower end of the chute 4 upstream of a straight portion 6 of the conveyor for controlling the movement of items along the conveyor track. The straight portion may comprise means for moving items, such as, e.g., a conveyor belt and/or rolls, or, alternatively or additionally, it may comprise only stationary parts.

Other means for carrying items may be provided, such as self- propelled wagons, electro trucks, trucks driven by combustion engines, chains of trucks of the above mentioned type or other means suitable for a given application of the conveyor.

Fig. 2 and 3 show cross sectional illustrations of a conveyor track section 5 comprised in a conveyor according to the invention. The conveyor track section 5 comprises a plurality of first and second track section parts 6 and 7, respectively, defining supporting surface parts 16 and 17, respectively, having different frictional surface characteristics. The first supporting surface parts 16 have frictional surface characteristics which provide a substantially lower frictional force on items moving along the conveyor track than the frictional force provided by the second supporting surface parts 17. The frictional characteristics of the second supporting surface parts 17 providing a high friction on conveyed items are obtained by a flexible sheet material, e.g., a rubber sheet 8 having a rough surface structure. The flexible sheet 8 is clamped between the first track section parts 6 and supporting stationary fixation parts 12 comprised in the conveyor track section 5 and extends over supporting members 9 adapted to the second track section parts for supporting the flexible sheet 8.

The supporting surface part 16 of the first track section part 6 is made from steel provided with a low- frictional coating resistant to wear, such as, e.g., Krautol 50-11 which may be diluted by a suitable diluent, such as Krautol PVC- diluent 10-26. In order to keep the frictional surface characteristics of the surface part 16 such that the friction provided is as low as possible irrespective of the amount of wear caused to the surface, the coating should be such that the surface remains smooth. The first track section part 6 may be made from a wide variety of materials including plastics, fiber materials, metals such as stainless steel, steel or others.

The flexible sheet 8 is preferably made from rubber sheet material being resistant to wear. This type of rubber sheet is commonly used, e.g., for conveyor belts.

Due to the different frictional surface characteristics of the supporting surface parts 16 and 17, the rate of movement of items along the conveyor track may be controlled, depending on the mutual position of the first and second track section parts. In the first position shown in Fig. 2, the second track section parts 7 are positioned in a retracted position in relation to the first track section parts 6, so that items conveyed along the conveyor track section 5 are supported by the first track section parts 6 providing a low frictional force on the items. In this case, the items are only decelerated to a negligible degree. In the second position shown in Fig. 3, the second track section parts 7 are positioned in a projecting position in relation to the first track section parts 6, so that items conveyed along the conveyor track section 5 are supported by the second track section parts 7 providing a high frictional force on the items.

In the configuration shown in Fig. 1, the conveyor track section 5 is positioned at the lower end of the chute 4 so as to decelerate items which are conveyed along the chute under the action of gravity. This kind of configuration is useful when the conveyed items comprise fragile goods, such as suitcases, mail bags. The configuration of Fig. 1 is a typical conveyor installation of an airport, railway station, mail distribution center or a factory.

The first track section parts 6 are stationary while the second track section parts 17 are displaceably mounted. The supporting members 9 adapted to the second track section parts 17 are connected to a connecting member 10 extending across the conveyor track section and being connected to pneumatic activators 11. In order to stabilize the conveyor track section 5, a connecting rod 14 connecting two side walls 15 of the conveyor track portion 5 is provided at the bottom portion of the conveyor track section.

The flexible sheet 8 extends unbrokenly across the first and second track section parts 6 and 7, respectively. Thus, gaps between the track section parts are closed, and items and foreign matter are prevented from becoming clamped between and from passing downwardly between adjacent track section parts .

Items are conveyed along and substantially parallel to the surface parts 16 and 17. However, in other embodiments (not shown) items may be conveyed across and substantially perpendicular the surface parts .

Fig. 4 is a cross sectional view along the line B-B in Fig. 6. The conveyor track section is shown in the second position, wherein supporting surfaces 17 of the second track section parts 7 project above the supporting surfaces 16 of the track section parts 6. The first position in which the supporting surfaces 17 of the second track section parts 7 is retracted in relation to the supporting surfaces 16 of the first track section parts 6 is shown in dashed outline in Fig. 4.

As shown in Fig. 4, holding members 19 are provided for positioning and fastening the flexible sheet 8 in relation to the supporting members 9. The flexible sheet 8 is fastened to each of the supporting members 9 by fastening means 29, extending through the holding members 19, the flexible sheet 8 and the supporting members 9. In a similar way the flexible sheet is clamped between the first track section parts 6 and the fixation parts 12 by fastening means 26. The fastening means preferably comprise screw or rivet connections. However, the flexible sheet material may alternatively be fastened to the fixation members and the supporting members, respectively, by other means such as by gluing.

Fig. 5 is a top view of a conveyor track section 5 suitable for use in a conveyor according to the invention. Preferably, items are conveyed in the longitudinal direction of the first and second track section parts 6 and 7, so as to prevent items from getting stuck between adjacent track section parts. However, the track section parts 6 and 7 may alternatively extend in a direction other than substantially parallel to the conveying direction of items, such as, e.g., in a direction substantially perpendicular to the conveying direction of items.

Fig. 6 is a cross sectional view along the line A-A in Fig. 4 of the conveyor track section illustrated in Figs. 2-5. The conveyor track section comprises a frame portion 25, preferably made from bent plate material made from steel. Each of the pneumatic activators 11 comprised in the displacement means for displacing the second track section parts 7 is held by a suspension member 21 fastened to stationary parts of the conveyor.

Figs. 7 and 8 illustrate a second embodiment of a conveyor track section comprised in a conveyor according to the invention. Fig. 7 is a cross sectional view along the line A- A in Fig. 8, and Fig. 8 is a cross sectional view along the line B-B in Fig. 7. In this embodiment, the displacement means comprise a pneumatic cylinder 31 having a displaceable piston 31a connected to a piston holding member 31b by a connecting rod 31c. As illustrated in Fig. 8, the pneumatic cylinder 31 and its piston 31a extend in a substantially horizontal plane. The cylinder 31 is connected to a stationary mounted support 34a.

In Figs. 7 and 8, the second track section parts 7 are positioned in a projecting position in relation to the first track section parts 6. The connecting member 10 is supported by four wheels 30 connected to the connecting member by wheel holding members 30a. The wheels 30 are supported by first and second ramps 32a and 32b interconnected by a beam or rod 33. When displacing the second track section parts 7 from their projecting position to their retracted position, the piston 31a is moved to the left in Fig. 8, the piston or part thereof being received in the cylinder 31. Thus, the first ramp 32a is pulled to the left in Fig. 8 thereby pushing the beam 33 and the second ramp 32b to the left. Due to gravity, the wheels 30 will roll along the ramps 32a and 32b thereby displacing the connecting member 10, the supporting members 9 and the second track section parts 7 downwards in a substantially vertical direction so as to bring the second track section parts 7 into their retracted position in relation to the first track section parts 6. When bringing the second track section parts 7 back into their projecting position in relation to the first track section parts 6, the piston 31a is moved to the right in Fig. 8. Thus, the first ramp 32a is pushed to the right in Fig. 8 thereby pulling the beam 33 and the second ramp 32b to the right. Thus the wheels 30 will roll upwards the ramps 32a and 32b, thereby displacing the connecting member 10, the supporting members 9 and the second track section parts 7 upwards so as to bring the second track section parts 7 into their projecting position in relation to the first track section parts 6.

As illustrated in Fig. 7, a flexible sheet 8a is provided so as to close the gaps between the first and second track section parts 6 and 7, thereby preventing items carried by the track section parts from being clamped between the track section parts.

The ramps 32a and 32b are supported by ramp supports 35 connected to the stationary fixation parts 12 by a connecting plate 36. The connecting plate 36 is fastened to the fixation parts 12 and to the ramp supports 35 by fastening means 37. During displacement of the ramps 32a and 32b, two intermediate supporting tracks 38, each of which is fastened to the two ramps 32a and 32b, slide along the ramp supports 35. The intermediate track 38 may be made from a material having surface characteristics providing relatively low frictional forces between the intermediate track 38 and the supports 35, such as, e.g., steel or plastics material, or it may be made from any material provided with a coating having such surface characteristics.

Although preferred embodiments of a conveyor according to the invention have been described, other embodiments are possible within the scope of the invention, including embodiments wherein the second track section parts are stationarily mounted and wherein the first track section parts are displaceably mounted, as well as embodiments wherein both the first and second track section parts are displaceably mounted.

Claims

1. A conveyor for slidingly conveying items along a conveyor track defining an item supporting surface, said track having at least one track section which comprises

- flexible sheet material arranged between adjacent track section parts so as to prevent said items and foreign matter from becoming clamped between adjacent track section parts, and

- displacement means for moving said first and second track section parts in a displacement direction in relation to each other between item supporting and item non- supporting positions, whereby the rate of movement of the items along the conveyor track may be controlled.

2. A conveyor according to claim 1, wherein the at least one first track section part is stationarily mounted and the at least one second track section part is displaceably mounted, the displacement means being adapted to the second track section parts.

3. A conveyor according to claim 1 or 2 , wherein the conveyor track section comprises a plurality of first and second track section parts.

4. A conveyor according to any of claims 1-3, wherein the displacement means comprise one or more pneumatic displacement means .

5. A conveyor according to any of claims 1-3, wherein the displacement means comprise one or more hydraulic displacement means.

6. A conveyor according to any of claims 1-5, wherein the displacement means comprise one or more stationary parts and one or more displaceable parts, said one or more displaceable parts being displaceable in a first direction which is substantially parallel to said displacement direction.

7. A conveyor according to any of claims 1-5, wherein the displacement means comprise one or more stationary parts and one or more displaceable parts, said one or more displaceable parts being displaceable in a second direction which is substantially perpendicular to said displacement direction, the displacement means further comprising means for translating the movement of said one or more displaceable parts in said second direction to a movement of said track section parts in said displacement direction.

8. A conveyor according to any of claims 2-7, wherein each of the first and second track section parts extends in a direction substantially parallel to the conveying direction of items.

9. A conveyor according to any of claims 2-7, wherein each of the first and second track section parts extends in a direction substantially perpendicular to the conveying direction of items.

10. A conveyor according to any of claims 1-9, wherein each of the first track section parts is fixed to a corresponding stationary fixation part of the conveyor track section, the flexible sheet material being positioned between the first track section parts and the corresponding fixation parts of the track section, the first track section part being fastened to the fixation part by fastening means, at least some of which extend through the flexible sheet material.

11. A conveyor according to any of the claims 1-10, wherein each of the second track section parts comprises a supporting member which in the item supporting position of the second track section part supports the flexible sheet material while stretching it.

12. A conveyor according to any of claims 3-10, wherein the supporting members are mounted on a connecting member extending across and below the conveyor track, the displacement means being connected to the connecting member.

13. A method of operating a conveyor for slidingly conveying items along a conveyor track defining an item supporting surface, said track including at least one track section comprising mutually transversely spaced first and second track section parts defining supporting surface parts having different frictional surface characteristics, said method comprising:

- displacing said first and second track section parts in a displacement direction in relation to each other between item supporting and item non-supporting positions, so as to control the rate of movement of the items along the conveyor track.

14. A method according to claim 13 , wherein the one or more first track section parts are stationarily mounted and wher╬▓in the one or more second track section parts are displaceably mounted, the mutual displacement between the first and second track section parts being provided by movement of the second track section parts .

15. A method according to claim 13 or 14, wherein the conveyor track comprises a plurality of the first and second track section parts, the mutual displacement of the first and second track section parts being provided by simultaneous movement of a plurality of track section parts.

16. A method according to any of claims 13-15, wherein the supporting surface parts defined by the first track section parts have surface characteristics providing a substantially lower frictional force on conveyed items than the surface characteristics of the supporting surface parts defined by the second track section parts, so as to provide substantially larger frictional forces on conveyed items when the second track section parts are in their item supporting position compared to the frictional forces provided on conveyed items when the second track section parts are in their item non- supporting position.

17. A method according to any of claims 13-16, wherein the displacement means comprise one or more stationary parts and one or more displaceable parts, the method comprising the step of displacing said one or more displaceable parts in a first direction which is substantially parallel to said displacement direction so as to displace the track section parts in relation to each other.

18. A method according to any of claims 13-16, wherein the displacement means comprise one or more stationary parts and one or more displaceable parts, the method comprising the step of displacing said one or more displaceable parts in a second direction which is substantially perpendicular to said displacement direction, the method further comprising the step_ of translating the movement of said one or more displaceable parts in said second direction to a movement of said track section parts in said displacement direction, so as to displace the track section parts in relation to each other.

19. A method according to any of claims 13-18, wherein item sensing means are comprised in the conveyor upstream of said at least one track section, the method comprising: - sensing of items approaching the track section, and