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Title:
A DEVICE AND A METHOD FOR THE POSITIONING OF ELEMENTS
Document Type and Number:
WIPO Patent Application WO/2006/098679
Kind Code:
A1
Abstract:
The invention relates to a device for positioning of elements, comprising a rotation device (10) arranged for rotation about an axis (A) in order to effect mutual relative rotation of elements (25), which rotation device (10) comprises a multiplicity of protruding drivers (12-15) resulting in the formation between the drivers (12-15) of a space (16, 17) for accommodating an element (25), so that during rotation the drivers (12-15) carry with them about the axis (A) an element (25) placed in the space (16, 17). The rotation device (10) is arranged for rotation between a first position and a second position disposed at an angle to the first position. The drivers (12-15) are arranged to form a first space (16) for alternately accommodating elements (25) in the first position of the rotation device (10), and a second space (17), disposed at an angle to the first space (16), for alternately accommodating elements (25) in the second position of the rotation device (10), whereby elements (25) can be rotated alternately in opposite directions. The invention also relates to a method for positioning of elements.

Inventors:
SVENSSON SVEN (SE)
SVENSSON FREDRIK (SE)
Application Number:
PCT/SE2006/000309
Publication Date:
September 21, 2006
Filing Date:
March 10, 2006
Export Citation:
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Assignee:
SVENSSONS VERKTYGSTEKNIK AB S (SE)
SVENSSON SVEN (SE)
SVENSSON FREDRIK (SE)
International Classes:
B65G47/244; B65G57/32; B25J15/00; B65G57/06; B65G61/00
Foreign References:
US3760928A1973-09-25
US5009305A1991-04-23
US5713453A1998-02-03
US4653628A1987-03-31
Attorney, Agent or Firm:
HANSSON THYRESSON PATENTBYRÅ AB (Malmö, SE)
Download PDF:
Claims:
CLAIMS
1. A device for positioning of elements, comprising a rotation device (10) arranged for rotation about an axis (A) in order to effect mutual relative rota tion of elements (25), which rotation device (10) comprises a plurality of protruding drivers (1215) resulting in the formation between the drivers (1215) of a space (16, 17) for accommodating an element (25), so that during rotation the drivers (1215) carry with them about the axis (A) an element (25) placed in the space (16, 17), c h a r a c t e r I s e d in that the rotation device (10) is arranged for rotation between a first position and a second position disposed at an angle to the first position, in that the drivers (1215) are so disposed as to form a first space (16) for alternately accommodating elements (25) in the first position of the rotation device (10), and a second space (17), disposed at an angle to the first space (16), for alternately accommodating elements (25) in the second position of the rotation device, whereby elements (25) can be rotated alternately in opposite directions, and in that the first and second spaces (16, 17) at least partly overlap one another, so that the axis (A) runs through the spaces (16, 17).
2. A device according to claim 1 , whereby the axis (A) runs through a centre point of each space (16, 17).
3. A device according to claims 1 or 2, whereby the spaces (16, 17) are disposed at an angle to one another corresponding to the angle between the first and second positions of the rotation device (10).
4. A device according to claim 3, whereby the spaces (16, 17) are disposed at an angle of 90 degrees to one another in order to rotate elements (25) alternately 90 degrees clockwise and 90 degrees anticlockwise, so that the elements (25) are positioned at a mutual angle of 180 degrees.
5. A device according to any one of the foregoing claims, whereby at least four drivers (1215) protrude parallel with the axis (A).
6. A device according to any one of the foregoing claims, whereby at least one driver (12) disposed between an inlet to the first space (16) and an inlet to the second space (17) is provided with a stop surface (20) to prevent any feeding of elements (25) towards the rotation device (10) during rotation.
7. A device according to claim 6, whereby at least the driver (12) disposed between the inlet to the first space (16) and the inlet to the second space (17) takes the form of a circle sector with the acute angle pointing to wards the axis (A).
8. A device according to any one of the foregoing claims, whereby the rotation device (10) is provided with rear stops (34) to the spaces (16, 17) in order to secure the position of the respective element (25) in the space (16, 17).
9. A device according to any one of the foregoing claims, whereby the drivers (1215) are each provided with a protruding lip (29) for supporting elements (25) in either of the spaces (16, 17).
10. A device according to any one of claims 18, whereby the rotation device (10) is disposed in an aperture (22) in a bench (21), which aperture (22) is provided with a contact surface (30) in which there is a recess (31) so disposed that each element (25) is supported by the contact surface (30) during rotation and falls through the recess (31) when the element has completed its rotation, and whereby lips (29) for subsequent support of elements are disposed at a distance from the contact surface (30) such that the rotation de vice (10) and the aperture (22) are clear for a subsequent second element (25) when the first element rests on the lips (29).
11. A device according to claim 9 or 10, whereby the rotation device (10) is provided with an arm (28) for pushing past the lips (29) an element (25) resting on the lips (29).
12. A device according to claim 11 , whereby the arm (28) is designed to push the respective elements (25) down at a velocity greater than the falling velocity of the elements (25).
13. A device according to any one of the foregoing claims, whereby the rotation device (10) is suspended for rotation of horizontally disposed elements (25).
14. A device according to any one of the foregoing claims, whereby the rotation device (10) is connected to a conveyor belt (24) for feeding of elements (25) in a row.
15. A device according to any one of the foregoing claims, whereby the rotation device (10) is connected to a table (26) for supporting a stack (27) of stacked elements (25).
16. A method for mutual relative rotation of elements (25) fed to a rotation device (10) which is arranged for rotation about an axis (A), characterised by the steps of a) introducing an element (25a) into a first space (16) in the rotation device (10) when the rotation device is in a first position, b) rotating the rotation device (10) from the first position to a second position in a first direction, while the rotation device (10) carries with it the element (25a) which is in the first space (16), c) in the second position of the rotation device (10), feeding out the element (25a) which is in the first space (16), d) in the second position of the rotation device (10), introducing a subsequent element (25b) into a second space (17) which is disposed in the rotation device (10) at an angle to the first space (16) and at least partly overlaps the first space (16), e) rotating the rotation device (10) from the second position to the first position in an opposite direction, while the rotation device (10) carries with it the element (25b) which is in the second space (17), so that the axis (A) runs through the spaces (16, 17), f) in the first position, feeding out the element (25b) which is in the second space (17), and g) repeating steps af in order to rotate elements (25) alternately in opposite directions.
17. A method according to claim 16, whereby elements (25) are fed to the rotation device (10) in a single row.
18. A method according to claim 16, whereby elements (25) are rotated through an angle corresponding to the angle between the first and second spaces (16, 17).
19. A method according to claim 16, whereby, during rotation, the feeding of elements (25) towards the rotation device (10) is prevented by a stop surface (20) of at least one driver (12) of the rotation device (10).
20. A method according to claim 16, whereby the respective elements (25), after rotation, are pushed down by an arm (28) towards, and become part of, a stack (27) of elements (25).
21. A method according to claim 16, whereby the position of each element (25) in the space (16, 17) is secured by a rear stop (34).
Description:
A DEVICE AND METHOD FOR POSITIONING OF ELEMENTS

FIELD OF THE INVENTION

The invention relates to a device and method for positioning of elements. More specifically, the present invention relates to a device and method for positioning of elements, whereby the device comprises a rotation device arranged for rotation about an axis in order to effect mutual relative rotation of elements, which rotation device is provided with a plurality of pro- truding drivers resulting in the formation of a space between the drivers which is adapted to accommodating an element, so that during rotation the drivers abut against and carry with them about the axis an element placed in the space.

Devices and methods of the type here referred to are applicable in connection with the positioning of various kinds of products for stacking or packing or in other contexts where mutual relative rotation of elements is required. Devices and methods of the type here referred to are often applicable in connection with the stacking of elements fed in a row, e.g. heat exchanger plates and the like, where the elements are positioned 180 degrees to one another by mutual relative rotation and are thereafter stacked to form heat exchanger units.

STATE OF THE ART

The state of the art comprises various different types of devices for positioning of elements. An example of such a type of device is an industrial robot for the stacking of heat exchanger plates. Such industrial robots are usually so designed that a first plate is placed on a hoist table or the like, after which a second plate following the first plate is rotated 180 degrees and placed on top of the first plate. Thus every second plate is rotated 180 de- grees during the stacking of the plates in order to create a heat exchanger unit comprising a plurality of such heat exchanger plates.

A major disadvantage of such state of the art devices is their low capacity due to their slowness, resulting in low cost-effectiveness and a more expensive product. There is therefore a need for a device and method for quicker and more effective positioning of elements in cases where mutual relative rotation is required.

A problem of such state of the art devices is that they are of complicated construction, resulting in low operational reliability and causing further cost-effectiveness problems.

SUMMARY OF THE INVENTION

An object of the present invention is to eliminate the abovementioned disadvantages and problems of the state of the art. The device and the method according to the invention result in rapid, effective and operationally reliable positioning of elements in a cost-effective manner. This is achieved by the invention being provided with the features indicated in the independent claims.

The present invention comprises a device for positioning of elements which itself comprises a rotation device arranged for rotation about an axis in order to effect mutual relative rotation of elements, which rotation device comprises a plurality of protruding drivers resulting in the formation of a space between the drivers which is adapted to accommodating an element, so that during rotation the drivers carry with them about the axis an element placed in the space, characterised in that the rotation device is arranged for rotation between a first position and a second position disposed at an angle to the first position, and that the drivers are so arranged as to form a first space for alternately accommodating elements in the first position of the rotation device, and a second space, disposed at an angle to the first space, for alternately accommodating elements in the second position of the rotation device, whereby elements can be rotated alternately in opposite directions. Since the rotation device comprises a first space and a second space for the accommodation of elements, which spaces alternately accommodate and rotate elements in opposite directions about the same axis of rotation,

the rotation device is never empty during the two-way rotation movement. For example, a first element in a row of said elements may be rotated clockwise from the first position to the second position in the first space. In the second position, the second space faces towards the next element in the row, whereby a subsequent second element is accommodated in the second space and is rotated anticlockwise in the return movement of the rotation device. It is thus possible, for example, for heat exchanger plates to be alternately rotated 90 degrees in an effective manner for stacking them at 180 degrees to one another. Elements are thus rotated alternately 90 degrees, clockwise and anticlockwise respectively, resulting in mutual relative rotation by 180 degrees. The angle between the first and second spaces may nevertheless be adapted to whatever angle is desired between elements fed in a single row.

The spaces may be disposed in one plane and may at least partly overlap one another so that the axis of rotation runs through the spaces. For example, the axis of rotation may run through a centre point of each space. The spaces are then disposed at an angle to one another which corresponds to the angle between the first position and second position of the rotation device. The rotation device may comprise any desired number of drivers for creating the spaces and carrying elements with them about the axis of rotation. According to one embodiment of the invention, the rotation device comprises four drivers. At least one of the drivers may be provided with a stop surface for preventing subsequent elements from entering the rotation device during the rotation movement of the rotation device. For example, at least the driver situated between the inlet to the first space and the inlet to the second space may take the form of a circle sector with its acute angle pointing towards the axis of rotation and with the rounded surface arranged to abut against a subsequent element in order to prevent access to the spaces during the rotation movement. There is thus no need to provide further stop devices or conveyor belts with intermittent patterns of movement for the feeding of elements, since the element feed stops automatically upon commencement of rotation and does not continue until the rotation ceases.

The rotation device may also be provided with a rear stop to prevent elements being fed too far into the rotation device and for securing their position in the space. Alternatively, the rotation device may be suspended in an aperture in a bench, whereby the bench on the inside of the aperture may constitute a rear stop.

According to an embodiment of the invention, the drivers are provided with a lip for supporting elements placed in either of the spaces. For example, the drivers may protrude vertically downwards from a carrier in the direction of the axis of rotation, whereby at least one lip of each driver protrudes horizontally across the direction of the axis of rotation. In cases where four drivers are used, each of them may be provided with two lips, one on each straight side of the circle sector-shaped drivers, so that there are four lips for each space when the spaces cross one another. The lips may be made of a flexible material so that elements resting on them can be pushed past the lips and down towards, for example, a table for stacking of elements. The lips may therefore be made stiff enough to support individual elements but soft enough to allow elements to be pushed past the lips by mechanical arms or the like. To achieve a stable stack of elements, the arms may be designed to push the respective elements down towards the stack after rotation of the elements. The arms may further be designed to push elements downwards at a greater velocity than their falling velocity, thereby preventing the risk of elements turning over on the way down to the table or stack.

The present invention also relates to a method for mutual relative rotation of elements fed to a rotation device which is arranged for rotation about an axis, characterised by the steps of a) introducing an element into a first space in the rotation device when the rotation device is in a first position, b) rotating the rotation device from the first position to a second position in a first direction, carrying with it the element which is in the first space, c) in the second position of the rotation device, feeding out the element which is in the first space,

d) in the second position of the rotation device, introducing a subsequent element into a second space disposed in the rotation device at an angle to the first space, e) rotating the rotation device from the second position to the first position in an opposite direction, carrying with it the element which is in the second space, f) in the first position, feeding out the element which is in the second space, and g) repeating steps a-f in order to rotate elements alternately in opposite di- rections.

Further features and advantages of the present invention are indicated by the description of embodiment examples below, the attached drawings and the dependent claims.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will now be described in more detail on the basis of embodiment examples with reference to the attached drawings, in which

Fig. 1 is a schematic perspective view of a rotation device according to an embodiment of the present invention, Fig. 2 is a schematic view from the underside of a rotation device according to the invention, showing the rotation device's first space and second space for accommodation of elements,

Fig. 3 is a schematic view from the underside of a rotation device according to an alternative embodiment of the " invention, Fig. 4 is a schematic sideview of the rotation device according to Fig. 3,

Figs. 5-11 are a series of drawings schematically depicting from above the rotary function of the device and a stop function of the rotation device according to the embodiment of it depicted in Figs. 1 and 2,

Fig. 12 is a schematic sideview partly in section, depicting a device for positioning of elements in a stack after rotation of the elements according to an embodiment of the invention,

Fig. 13 is a schematic sideview partly in section, depicting a device for positioning of elements according to a further embodiment of the invention in which the rotation device is connected to arms for pushing elements down to a stack, whereby an arm is depicted in an upper position,

Fig. 14 is a schematic view according to Fig. 13, depicting the arm in a lower position,

Fig. 15 is a schematic perspective view obliquely from above of a bench for cooperation with the rotation device according to an embodiment of the invention,

Fig. 16 is a schematic sideview partly in section, depicting the rotation device situated close to the bench according to Fig. 15, and

Fig. 17 is a schematic view from above of a rotation device according to an alternative embodiment of the invention, showing spaces with respective rear stops.

THE INVENTION

Fig. 1 and Fig. 2 illustrate schematically a rotation device 10 according to an embodiment of the present invention, arranged for rotation about an axis A. The rotation device 10 is designed to effect mutual relative positioning of elements by rotation, as described in more detail below. The rotation device 10 is thus designed to effect positioning of elements. The rotation device 10 may also be part of a device for positioning of elements or be connected to a further device for positioning of elements, such as a device for stacking of elements, as described in more detail below.

The rotation device 10 comprises a carrier 11 and drivers 12-15 pro- truding from the carrier 11 , whereby the carrier 11 is designed to support the drivers 12-15. The carrier 11 may for example take the form of a disc with a

shaft protruding from it for connection to a motor (not depicted). The drivers 12-15 protrude across a plane of the disc or across a planar portion of the carrier 11 , so that the drivers 12-15 protrude downwards when the rotation device 10 is suspended. The rotation device 10 may for example be made of metal, e.g. aluminium, or of plastic.

The drivers 12-15 form a first space 16 and a second space 17 between the drivers 12-15. The spaces 16, 17 are represented by broken lines in Fig. 2. The spaces 16, 17 extend in from a periphery of the rotation device 10 to the centre of the rotation device 10, through which centre the axis A runs. The spaces 16, 17 are disposed at an angle to one another. For example, the first space 16 may be disposed at an angle of 90 degrees to the second space 17. Alternatively, the first space 16 may be disposed at an angle of less than 90 degrees to the second space 17, depending on the desired mutual relative position of the elements. In the embodiment depicted, the respective spaces 16, 17 extend from the periphery of the rotation device 10 and across the carrier 11 to the periphery on the opposite side of the rotation device 10, whereby the first space 16 crosses the second space 17 and a centre point of the respective spaces 16, 17 coincides with the centre of the rotation device 10, through which cen- tre the axis A runs. Thus the first space 16 is disposed perpendicular to the second space 17 and in such a way that the middle portions of the spaces 16, 17 overlap one another. The spaces 16, 17 thus cross one another in such a way that a desired rotation point or centre point of the respective spaces 16, 17 coincides with the axis A. The spaces 16, 17 extend in the same plane.

In the embodiment depicted, the carrier 11 is provided with a first driver 12, a second driver 13, a third driver 14 and a fourth driver 15. The drivers 12-15 protrude vertically downwards from the carrier 11 when the rotation device 10 is suspended. The drivers 12-15 are disposed at mutual distances resulting in the formation of the spaces 16, 17, a first inlet to the first space 16 and a second inlet to the second space 17, whereby the first inlet is disposed at an angle to the second inlet corresponding to the spaces

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16, 17. The distance between adjacent drivers 12-15 corresponds substantially to the width of an element. The first inlet is bounded by the first and second drivers 12, 13 and the second inlet by the first and fourth drivers 12, 15. Each of the respective drivers 12-15 in the embodiment depicted in

Fig. 1 and Fig. 2 takes the form of a circle sector, i.e. with a first planar side 18, a second planar side 19 and a rounded side which constitutes a stop surface 20, whereby a acute angle opposite to the stop surface 20 points towards the centre of the rotation device 10, about which centre the rotation device 10 is arranged for rotation. The function of the stop surface 20 is described in more detail below. The respective first planar sides 18 of the drivers 12-15 delineate the first space 16, and the respective second planar sides 19 of the drivers 12-15 delineate the second space 17.

Fig. 3 and Fig. 4 depict the rotation device 10 according to an alterna- tive embodiment of the invention. The rotation device 10 comprises the carrier 11 and drivers 12-15, as described above with reference to Fig. 1 and Fig. 2, but with the difference that the drivers 12-15 are circular and only demarcate a width of the spaces 16, 17 at four points. Alternatively, a different number of drivers may be used, in which case they are disposed along the periphery of the spaces 16, 17. According to a further embodiment of the rotation device 10, the drivers are L-shaped or of some other configuration. Such versions lack, however, the stop surface 20 mentioned with reference to Fig. 1 and Fig. 2.

Fig. 5 shows the rotation device 10 connected to a bench 21. The bench 21 has running through it an aperture 22 whereby the rotation device 10 is suspended in aperture 22 by means of a yoke 23 and a portion of the carrier 11 which is depicted in section in Fig. 5. The bench 21 is connected to a conveyor belt 24 or a corresponding feed system, e.g. an air piston feed or the like, for feeding elements 25 to the rotation device 10. The bench 21 may be of any desired kind. The rotation device 10 may be connected directly to the conveyor belt 24. The rotation device 10 may for example be designed to receive elements 25 fed in a row.

Fig. 5 depicts the rotation device 10 in a first position where the first space 16 and the first inlet face towards incoming elements 25 so that a first element 25a can move forward and be accommodated in the first space 16. The rotation device 10 is thus designed to accommodate an element 25 be- tween the drivers 12-15, whereby the first space 16 is designed to accommodate an element 25, as depicted in Fig. 6. The element 25a may for example move forwards to a stop so that the element 25a cannot move further than a predetermined position. A stop is for example provided on the bench 21 or takes the form of the inside of the bench 21 in the aperture 22. Accord- ing to an embodiment of the invention, the aperture 22 thus corresponds substantially to the lower circumference of the rotation device 10.

Thereafter, the rotation device 10 is rotated clockwise, carrying with it the element 25a, as depicted in Fig. 7. During rotation, portions of the drivers abut against the element 25a to cause the element to move about the axis A. At the same time, the stop surface 20 stands in the way of a second element 25b following the first element 25a, with the result that the second element 25b is held in a position outside the rotation device 10 but in contact with the stop surface 20. The stop surface 20 may for example be designed to block the subsequent element 25b as soon as rotation commences, i.e. the stop surface 20 extends from the first inlet to the second inlet. Fig. 7 depicts the rotation device 10 at an angle of 45 degrees clockwise from the first position.

Fig. 8 shows the rotation device 10 having rotated further clockwise to a second position, carrying with it the first element 25a. In the second position, the first element 25a has completed its rotation and is removed from the rotation device 10. The second position of the rotation device 10 is disposed at an angle to the first position. For example, the angle between the first and second positions of the rotation device 10 may be 90 degrees. Alternatively, the angle between the first and second positions of the rotation device 10 may be less than 90 degrees. The first element 25a is removed, for exam- pie, via the aperture 22, by being released or pushed downwards through the aperture 22 to a hoist table for stacking, a further conveyor belt or the like.

In the second position, the second space 17 faces towards the second element 25b so that the second space 17 can accommodate the second element 25b. In the second position, the inlet to the second space, or the second inlet, thus faces towards the conveyor belt 24 and subsequent ele- ments 25 being fed in a row. In the second position, the feeding in of the second element 25b is initiated at the same time as the first element 25a is removed. The second element 25b moves into the second space 17 in the same way as the first element 25a moved into the first space 16. Fig. 9 depicts the rotation device 10 in the second position with the second element 25b placed inserted in the second space 17 for rotation from the second position to the first position.

Thereafter, rotation commences in the opposite direction, i.e. anticlockwise, as depicted in Fig. 10, where the stop surface 20 prevents a third element 25c from entering either of the spaces 16, 17 during the time when the second element 25b is being rotated. Rotation continues until the rotation device 10 has returned to its first position and the second element 25b has been rotated from the first position of the rotation device 10 to the latter's second position, as depicted in Fig. 11. After rotation of the second element 25b from the first position of the rotation device 10 to the latter's second posi- tion, the second element 25b is removed from the second space 17 while at the same time a subsequent element 25c moves into the first space 16. The rotation device 10 can thus be rotated between the first position and the second position in a reciprocating movement, whereby the first space 16 and the second space 17 alternately accommodate elements and rotate them in op- posite directions about the axis A.

Fig. 12 depicts a table 26 connected to the rotation device 10 and the conveyor belt 24, on which table 26 elements 25 can be stacked. The table 26 may for example take the form of a hoist table. Elements 25 are fed to the rotation device 10, as described above, are rotated alternately 90 degrees in opposite directions, are moved downwards after rotation and are placed in a stack 27 of elements 25 which are disposed at 180 degrees to one another. In the embodiment depicted, the elements 25 are thus stacked perpendicular to the direction in which they are fed to the rotation device 10. Stacking at a

mutual relative angle of 180 degrees is advantageous in the stacking of, for example, heat exchanger plates and other products where such stacking or mutual relative positioning is desired. Alternatively, the elements 25 may be positioned at some other mutual relative angle, as described above. Fig. 13 and Fig. 14 depict the rotation device 10 provided with at least one arm 28 for pushing an element 25 towards the stack 27 after rotation of the element 25. An arm 28 may for example be situated at the respective short side of an element 25 which has completed its rotation, and may run vertically parallel with the axis A in order to push the element 25 downwards. The arm 28 is designed to push each element 25 down in order to achieve a tightly packed stack 27. The arm 28 pushes each element 25 down at a velocity exceeding the latter's falling velocity in order to prevent platformlike elements, e.g. heat exchanger plates, from turning over on the way to the stack 27. When an element 25 is in either of the spaces 16, 17, it may rest, for example, on lips 29 of the rotation device 10. The lips 29 may for example protrude from the respective drivers 12-15 in order to support an element 25 which is in the space 16, 17. The lips 29 thus protrude horizontally when the drivers 12-15 protrude vertically from the carrier 11. According to one em- bodiment of the present invention, the lips 29 are provided with stiffness appropriate to supporting the element 25 and at the same time with flexibility so that the elements 25 can be pushed past the lips 29 by the arm 28 towards a stack 27 or a further conveyor belt or the like.

Fig. 15 depicts the bench 21 with the aperture 22 according to an al- ternative embodiment of the invention. The bench 21 is designed to cooperate with the rotation device 10, whereby the rotation device 10 works in the aperture, as depicted in Fig. 16. The aperture 22 in the bench 21 takes the form of a recess in the upper side of the bench 21 , so that a contact surface 30 is formed for abutment against an element 25 during rotation. The contact surface 30 has a recess 31 running through it in such a way that elements 25 which have completed their rotation can fall through the recess 31 after rotation and that elements 25 can be removed from the rotation device 10 and

the bench 21. The recess 31 is elongate, is designed to allow elongate elements 25 to pass through it and extends in a direction transverse to the feed- in direction of the elements 25. For example, the recess 31 may be substantially rectangular and extend across the aperture 22 to allow substantially rectangular elements 25 to pass through. For example, the aperture 22 may be circular, in which case the contact surfaces 30 take the form of circle segments.

In the embodiment depicted in Fig. 15, the aperture 22 is further provided with an inlet aperture 32 through which elements 25 can be fed. An element from the conveyor belt 24 thus moves through the inlet aperture 32 into the aperture 22 and into one of the spaces 16, 17 of the rotation device 10. During rotation of the element 25, its ends are supported by the contact surfaces 30 until the element 25 has been rotated to a desired angle, e.g. 90 degrees, at which the contact surfaces 30 no longer support the element 25 and the latter falls through the recess 31 in order to be accommodated by the lips 29 until it is pushed down to a stack 27 by the arms 28. The lips 29 are disposed at a distance from the contact surfaces 30 which corresponds to at least the thickness of an element 25, whereby a rotated element 25 drops to the lips 29 and leaves the aperture 22 and rotation device 10 free to accom- modate and rotate a subsequent element 25. Thus a subsequent element 25 can be accommodated in the rotation device 10 and rotation can commence after the previous element has dropped to the lips 29 but before said previous element is pushed down by the arms 28, thereby resulting in quicker stacking. The lips 29 are disposed at the short side of the recess 31 , as de- picted in Fig. 15, or at the long side of the recess, as depicted in Fig. 16. A funnel or the like may for example be disposed below the recess 31 to guide the elements 25 in a desired direction as they are pushed down towards the stack 27.

Fig. 17 depicts a rotation device 10 according to an alternative em- bodiment of the invention where the rotation device 10 is provided with a rear stop 34 to prevent elements 25 from being inserted too far in the respective spaces 16, 17. The rear stop 34 is thus designed to ensure that a desired rotation point of an element 25, e.g. a centre point, coincides with the axis A

when the element 25 is in the space 16, 17. Each space 16, 17 is provided with a rear stop 34, at an end opposite to the inlet to the space 16, 17. Thus a rear stop 34 of the first space 16 is disposed between the third driver 14 and the fourth driver 15, while a rear stop 34 of the second space 17 is disposed between the second driver 13 and the third driver 14. Alternatively, a rear stop may be disposed on a bench 21 or form part of the bench 21 in cases where such a bench 21 is used.