Manipulator Apparatus and Drive Elements Therefor

Technical Field

The present invention relates to a manipulator apparatus for the manipulation of materials. The present invention also relates to drive elements which are particularly although not exclusively suitable for use in the manipulator apparatus.

Background of the Invention and Prior Art

The present inventor has described in WO2004/018931 a novel construction of lampshades which requires panels to be secured to one another edge to edge while accurately controlling the overlap at the joints between panels. Unfortunately, these lampshades proved expensive to manufacture because of the high price of skilled manual labour, and to alleviate such problems it is desirable to simplify the handling of the panels so that they may be jointed more accurately by relatively unskilled operatives. The various elements of the present invention were conceived with such a problem in mind.

Summary of the Invention

The present invention has several different aspects. From first and second aspects two types of drive element are described, which are capable of driving an article in contact with the drive surfaces therewith in a plurality of directions or axes, in addition to backwards and forwards along the same direction or axis. Preferably the drive elements drive the article in orthogonal directions. In further aspects a manipulator is described which may make use of the drive elements, and moreover a machine for joining edges of sheets of material is described which may use the manipulator, but which has in itself several independent aspects, apparent from the appended claims.

From a first aspect, therefore, the present invention provides a drive element comprising a socket assembly having a ball rotatably mounted therein, the socket assembly comprising a plurality of drive rollers angularly disposed around the circumference of the ball and each arranged to drive the rotation of the ball about an

axis parallel to its own axis, the drive rollers being controllable whereby to control the rotation of the ball in a plurality of directions.

In embodiments of this aspect of invention, the drive assembly may be likened to a tracker ball operating in reverse. A tracker ball is frictionally moved by hand and its rotation about mutually orthogonal axes is detected by means of different sensor. By contrast, the ball in this type of drive element is preferably frictionally driven by two parallel pairs of driven rollers that are arranged such that the rollers of each pair are positioned on opposite sides of the ball, and each pair of rollers is positioned perpendicular to the other, such that each pair of rollers is able to rotate the ball about an axis formed by the contact points of the other pair with the ball thereby causing the ball to rotate about mutually orthogonal axes and it is used to advance a workpiece along mutually orthogonal directions.

From a second aspect the present invention also provides a drive element comprising: a toroidal element having a central axis extending through the centre of a hole in the centre of said toroidal element in a direction substantially perpendicular to the plane of said toroidal element and about which said toroidal element is rotatable, said toroidal element being further arranged to convolute about a substantially circular axis extending in the plane of the toroidal element through the centre of the toroidal element; and a convolution drive arranged to contact the outer surface of the toroidal element, and to cause said toroidal element at least to convolute.

In embodiments of the second aspect of the invention a wheel is provided having a drive element that is a tyre forming the toroidal element, comprising a plurality of individual rollers connected to one another by coupling elements, wherein both the rollers and coupling elements are rotatable about tangentially oriented axes and in meshing engagement with one another for rotation in unison. The tyre in this type of drive element is a convoluting tyre surrounding the wheel and is retained in position by recesses, provided in the wheel, in which the coupling elements are retained such that they rotate at a fixed position at the circumference of the wheel.

In the embodiments of the second type of drive assembly, gears are provided in the rollers and coupling elements which, at a desired angle of offset, mesh and cause the

rollers and coupling elements to rotate in unison about an axis that is tangential to the axis about which the tyre rotates such that movement of the workpiece in one direction is carried out by rotation of the wheel about its own axis whereas movement of the workpiece in the orthogonal direction is effected by rotating the rollers and coupling elements about an axis that is tangential to the axis about which the tyre rotates, to cause the tyre to convolute. This type of drive assembly offers the advantage of being able to operate closer to the edge of the sheet material than the first type of drive assembly.

The embodiments of the second type of drive assembly may be used as an infinitely variable mechanical gearbox in which the roller is provided with gear teeth that spiral about its barrel shaped length such that the plurality of connected rollers that comprise the tyre act as a single worm wheel, which is in meshed engagement with a worm gear that extends in the transverse direction to that of the axis about which the wheel rotates. In this design of the second type of drive assembly, rotation of the worm gear will result in rotation of the drive assembly about mutually orthogonal axes. This design of the second type of gearbox has the advantage that the majority of available torque introduces by the driven worm gear, acts to rotate the wheel about its own axis of rotation. Where the wheel is connected to a shaft that is part of a transmission system, it will rotate as fast as possible, dependent on the mass that it is moving, with any excess torque dispensed by way of the tyre convoluting, with the added feature that as the wheel gains rotational speed as a result of acceleration, the speed at which the tyre convolutes will decrease proportionately. This inverse relationship between the speed of rotation of the wheel and the speed at which its tyre convolutes enables it to provide smooth acceleration of the wheel.

A third aspect of the present invention provides a manipulator for advancing a workpiece in a plurality of directions, which comprises a drive assembly having a drive element, having an outer surface endlessly rotatable about at least mutually orthogonal axes, which frictionally engages the workpiece, the rotation of said drive element being controllable whereby to permit said workpiece to be advanced by said drive element in said plurality of directions. Here, the drive element is capable of driving an article in contact with the drive surfaces thereof in a plurality of directions

or axes, in addition to backwards and forwards along the same direction or axis. Preferably the drive elements drive the article in orthogonal directions.

In embodiments of the third aspect there is provided means for urging the workpiece into frictional contact with the drive element. The means for urging the workpiece into frictional contact with the drive element may be gravity. If the workpiece, for example, is a heavy box and the drive element is beneath the workpiece then gravity alone will suffice to provide the necessary frictional engagement between the workpiece and the drive element. If, on the other hand, the workpiece is a light sheet of material, or if the plane of the workpiece is not horizontal, then a clamping element may be employed to push the workpiece against the drive element.

It is in practice advantageous for a manipulator to use two separate drive elements to advance a workpiece as this will not only allow the workpiece to be moved in any desired direction but also enable it to be rotated about an vertical axis perpendicular to the plane of movement. Where two drive elements are provided, it is preferred to use a ball as one and a wheel with a convoluting tyre as the other, the two drive elements being staggered in the direction of movement of the workpiece.

Conveniently, each manipulator may incorporate a support surface for the sheet material which is inclined relative to the horizontal, the two support surfaces being inclined in opposite directions to form a trough.

In order to allow one edge to be positioned selectively either below or above the other edge, it is desirable for the support surfaces of the two manipulators to be adjustable in height relative to one another.

Any clamping surfaces used to urge the sheets of material against the drive elements needs to be held in place relative to the support surfaces but any physical connection between a clamping surface and a support surface will necessarily impede the advance of the sheets of the workpiece. In order to mitigate this problem, it is possible for the clamping surfaces to have an arrangement of rotatable bearing balls that are its only contact with the workpiece, and where the clamping surface is prevented from moving

in the planes of the support surfaces by magnetic attraction to the support surfaces acting through the workpiece.

The clamping surface may be part of a clamping element that is the housing of a workstation designed to treat a workpiece. The workpiece may be a sheet of material whereby the workstation may be designed to join together the edges of sheets of material and will typically have a work station at which the edges are bonded to one another and two separate manipulators for advancing the individual sheets through the workstation.

The clamping element may also be designed to house only part of a workstation, where other parts of the workstation may be housed within a manipulator such that the parts that comprise the workstation are contained within the clamping assembly and one or more manipulators. Such a workstation may be designed to sew together the edges of sheet material to produce garments and will typically have a bobbin that is contained within the clamping element interacting with a needle contained in a manipulator, whereby the needle pierces through the sheet material from the manipulator and into the clamping assembly where it presents a thread to a bobbin contained within the clamping assembly, and where the bobbin collects the thread and completes a stitch. The nature of the work station and the location of its parts is dependent upon the individual application.

Embodiments of the invention have application in conveyor and sorting systems and the like, where it enables the movement of objects in any direction, as well as in applications that generally require the conversion of rotational movement from a drive element into movement about mutually orthogonal axes.

Further aspects, features and advantages of the present invention will be apparent from the appended claims.

Brief Description of the Drawύifis

Further features and advantages of the present invention will become apparent from the following description of embodiments thereof, presented by way of example only,

and with reference to the accompanying drawings, wherein like reference numerals refer to like parts, and in which: -

Figure 1 is a schematic side view of a machine for joining the edges of two sheets of material; Figure 2 is a section in the plane II-II of Figure 1 showing only the manipulators;

Figure 3 is a section in the plane III-III of Figure 1 showing both the manipulators and the clamping assembly;

Figure 4 is a schematic plan view of a drive element comprising a single friction ball;

Figure 5 is a plan view of a drive element comprising a wheel having a plurality of rollers distributed about its circumference, each roller being rotatable about a tangentially oriented axis;

Figure 6 shows the internal view of one of two halves of the clam shell housing of the wheel shown in Figure 5 having recesses for retaining the drive rollers and their coupling elements; Figure 7 is a schematic representation of the drive rollers and coupling elements which form the tyre of the wheel shown in Figure 5;

Figure 8 is a partial exploded view showing the manner in which individual rollers and coupling elements of the wheel of Figure 5 are mechanically coupled for rotation in unison; Figure 9 is a view similar to that of Figure 7 showing an alternative second design of drive roller; and

Figure 10 is a view similar to that of Figure 9 illustrating a further design of drive roller.

Description of the Preferred Embodiments

A first type of drive element constituting a first embodiment of the present invention will now be described with reference to Figure 4. The drive element according to the first embodiment of the invention is preferably used within a manipulator apparatus of the type to be described later, but is not limited to such use and may also find application elsewhere, for example as a drive element in robotic or vehicular applications.

Figure 4 shows a drive element 22 according to the first embodiment of the invention, and comprising a ball 62. The ball 62 is rotatably located between bearing balls 66, and retained in a socket 64 in a manner analogous to the mounting of a trackball, such that a portion of the ball projects above the plane of the socket 64, as shown by reference 22 in Figure 3. The ball 62 is engaged about its circumference by two pairs of motor driven drive rollers 42 and 44. The rollers 42 rotate the ball 62 about an axis passing through the points of contact of the rollers 44 with the ball 62 and conversely the rollers 44 rotate it about an axis passing through the points of contact between the rollers 42 and the ball 62. The rollers 42 and 44 are thus positioned such that they do not interfere in any way with one another and each pair of rollers 42 and 44 can rotate the ball 62 substantially independently of the operation of the other pair of rollers. The rollers of each pair rotate in the same sense as one another, this being opposite to the sense of rotation of the ball 22.

To ensure that the rollers 42 and 44 do not interfere with each other, the rollers 42 are supported on parallel shafts 90 that are shorter in length than the distance between the parallel pair of shafts 92 that support rollers 44. Drive is transferred to the rollers 42 by means of bevel gears 94 that are fixed to each shaft 90 and are in meshed engagement with bevel gears 93 that are each fixed to a shaft 91, which extends vertically and perpendicular to shafts 90 and 92, below which they are situated.

To enable the unified rotation of the rollers 42, the pair of shafts 91, which are parallel and located such that both are closest to the same shaft 92, project through the under- surface of drive element 22 and are connected to one another by means of timing belt 109 that loops around two pulleys 107 that are each fixed to a shaft 91. Similarly the two shafts 92 project beyond one side of drive element 22 and are connected by a . timing belt 113 that loops around two pulleys 115 that are fixed each fixed to a shaft 92. Two motors may be connected, one to a shaft 90 and the other to one of the shafts 92 such that one motor provides drive to the pair of shafts 90 and the other motor to the shafts 92.

In use the ball 62 is rotatable in all directions, but is driven by the roller pairs 42 and 44 in respective orthogonal directions. That is, rotation of rollers 44 causes the ball to rotate about an axis running across the sheet of Figure 4, whereas rotation of rollers

42 causes the ball to rotate about an axis running up and down the sheet of Figure 4. The ball can be made to rotate in clockwise or counter-clockwise directions about other axes by simultaneously controlling the rotation of rollers 42 and 44, the resultant rotation of the ball being a resultant sum of the rotary motion applied by each pair of rollers. In this way, the ball 62 may be controlled to roll in any direction within the socket 64.

Variations may be made to the above described arrangement to provide further, although less preferable, embodiments. For example, in the arrangement above we described the rollers being arranged in pairs at opposite sides of the ball 62. However, in other embodiments the rollers need not be arranged in pairs, and only one roller may be provided on each orthogonal axis. That is only one of the rollers 44 is provided, and one of the rollers 42. In such a case the operation of the arrangement is the same as previously described, although less frictional force is applied to the ball to drive the ball.

Additionally, in other embodiments the rollers need not be provided on mutually orthogonal axes, but may instead be provided dispersed at angles around the socket at angles other than 90 degrees. For example, two, three, or more, rollers may be dispersed around the ball, and preferably although not exclusively equiangularly dispersed. Such rollers may be arranged in pairs on opposite sides of the ball as described previously, or may be singularly provided, as discussed above. Control of the ball to rotate in any direction can be obtained by controlling individually the rotation of the rollers, and the rotary motion applied to the ball by each roller. As with the previously described arrangements, the resultant rotary motion of the ball is dependent upon the resultant sum of the individual rotary motion applied by each roller. Whilst arranging the rollers in such a manner which is not mutually orthogonal complicates the control of the rollers to obtain a desired movement of the ball, by resolving the motion applied by each roller to the ball into its orthogonal directional components appropriate control of each roller to achieve a desired movement of the ball is readily obtainable.

A drive element 22 as described above may find application in a manipulator apparatus to be described, in which case the element 22 is fixed in position. A

workpiece to be manipulated is then placed on top of the drive element in contact with that portion of the ball 62 which projects above the plane of the socket 64. Rotation of the ball 62 by the rollers then causes the workpiece to be moved in the direction of rotation of the ball.

Alternatively, a drive element 22 as described above may be used as a vehicular drive element, for example in a toy or robot application. In this case the element 22 is fixed into the vehicle with the projecting part of the ball 62 in contact with the surface over which the vehicle is to be driven. Rotation of the ball by the rollers then causes the vehicle containing the drive element 22 to be driven over the surface.

A second type of drive element constituting a second embodiment of the invention will now be described with reference to Figures 5 to 10. The drive element according to the second embodiment of the invention may be used within a manipulator apparatus of the type to be described later, but is not limited to such use and may also find application elsewhere, for example as a transmission apparatus, and in particular as an infinitely variable transmission, as described later.

Generally, the second type of drive element according to the second embodiment comprises a toroidal element which is capable of rotation about its central axis, being the axis extending orthogonal to the major plane of the toroidal element through the centre of the hole of the element, as well as convoluting around a substantially circular axis running substantially circularly through the middle of the body of the toroid. That is, the toroidal element may convolute about the substantially circular axis such that those parts of the outer surface of the toroidal element which faced inwards into the hole of the torus are moved so as to face outwards from the outer surface of the toroidal element, and vice versa. Effectively, a convolution of the toroidal element is a movement of the toroidal element akin to turning the toroidal element inside out. The second type of drive element is further provided with a convolution drive means which causes the convolution of the toroidal element. The convolution drive means may be a further toroidal element arranged in contact with the first toroidal element such that rotation of the further toroidal element causes convolution of the first toroidal element and vice versa, or may alternatively be a gear

wheel, such as a helical gear, a spur gear or a worm gear. The variants of the second - type of drive element available will become apparent from the following descriptions.

A first variant of drive element according to the second embodiment is shown in Figure 5. Here the drive element comprises a wheel generally designated 24 and rotatable about an axis 52. The wheel 24 is formed of a clam shell construction having two housing halves 54, 56 secured to one another, the interior of each of these two housing halves 54 and 56 being as shown in Figure 6. A plurality of recesses 60 are evenly distributed around the circumference of the housing halves 54 and 56 to accommodate roller 72. The individual drive rollers 72 are coupled to one another (as shown in Figure 7) by spherical coupling elements 74, each of which is received into recesses 84 of adjacent rollers 72. The connected rollers 72 and coupling elements 74 together form an toroidal element 75 which is retained between the two housing halves 54 and 56 by virtue of the recesses 58 and can be convoluted.

As shown in Figures 5, 7, and 8, the coupling elements 74, which are retained by recesses 58 in the housing halves 54 and 56 are partially spherical with flat ends and are retained within the recesses 58 in such a manner as to allow them to rotate freely but remain at a fixed point on circumference of the secured housing halves 54 and 56. The drive rollers 72 housed in the recesses 60 do not make contact with recess 60 and are free to move so as to align themselves with the coupling elements 74.

The housing halves 54 and 56 and the recesses 58 and 60 are designed such that one side of each drive roller 52 projects beyond the circumference of the housing halves 54, 56, as shown in Fig. 5; it is the projecting outer surface of the drive rollers 72 which may engage, for example, with a material to be driven, and in particular when the drive element is being used in a manipulator application as will be described later. In other applications, for example where the drive element is being used as a transmission or torque conversion device, the projecting outer surface of the drive rollers need not contact any other element or material in use.

Each of the drive rollers 72, which is barrel shaped, has a part spherical recess 84 at each of its ends from the base of which there projects a truncated cone 86 having teeth on its conical surface. The truncated cone 86 is received within a conical depression

88 in the coupling elements 74 which is provided with teeth that mesh with the teeth on the truncated cone 86. The conical depression 88 is larger in diameter than the truncated cone 86 such that the meshing engagement between the teeth of the conical depression 88 and the truncated cone 86 only occurs when the coupling element 74 is rotated, within recess 84, such that its flat end is at a desired offset angle relative to the flat ends of roller 72 at which angle the coupling elements 74 and the rollers 72 all rotate in unison about tangentially oriented axes. The roller 72 is designed such that when a coupling element 74 is received into the recesses 84 of two adjacent rollers 72 such as to connect them, the spherical centres of the recesses 84 of the two rollers 72 is at a common point within coupling element 74.

Viewing the complete toroidal element 75 as it is shown in figure 7, its rotation about its centre will result in a sheet of material in contact with the surface of the wheel 24 being moved in the plane of Figure 7, whereas convolution of the toroidal element 75 by rotation of each of the drive rollers 72 along a respective axis tangential to the toroidal element will result in a sheet in contact with the perimeter of the wheel 24 being moved into and out of the plane of the drawing.

The design of the drive rollers 72 described above enables the wheel 24 to drive a sheet material in a direction horizontally across the plane of Figure 7 but there is no external drive to allow a motor to move a sheet into and out of the plane of Figure 7. If the material is pulled by some other means into and out of the plane of Figure 7, the drive rollers 72 can freewheel to accommodate such movement but they cannot in themselves bring about the movement. In order to cause the rollers 72 to rotate and the toroidal element to convolute, therefore, a drive element according to the second embodiment further includes a convolution drive means which causes, at least in part, the toroidal element to convolve. Several different variants of convolution drive are available, as described next.

A first such variant is shown in Figure 9. The toroidal element 177 shown in Figure 9 allows an external convolution drive to be coupled to the drive rollers so that the drive rollers can move a sheet of material in any desired direction in the plane of the sheet; that is, such that the toroidal element 177 can convolute.

More particularly the design of roller 72 may be used to alter the drive characteristics of wheel 24. The drive rollers 172 shown in Fig. 9 differ from the drive rollers 72 in that their external surface is provided with helical teeth 741 and at one point on the circumference of the tyre, they mesh with a helical gear 175 forming the convolution drive. With this design of roller 172 and convolution drive, rotation of gear 175 causes toroidal element 177 to rotate about an axis into and out of the plane of Fig. 9 i.e. its central axis, and at the same time convolute into and out of the plane of the drawing i.e. cause rollers 172 to rotate about respective tangential axes to the toroidal element. Control of the rotation about the central axis and the convolution of the rollers 172 is achieved by varying the rotational speeds of the whole toroidal element 177 and gear 175 relative to one another. In particular, if the toroidal element is prevented from rotating about the central axis then convolution may still occur.

A second variant which provides a different drive characteristic is provided by the rollers 182 shown in Fig. 10, which are similar to rollers 172 in that their external surfaces are provided with gear teeth, except that the gear teeth of rollers 182 spiral about their barrel shaped outer surfaces such that a toroidal element 81, comprised of connected rollers 182 and coupling elements 74, acts as a worm wheel in which the gear teeth of adjacent rollers 182 lead one into the other such that the connected plurality of rollers 182 act as a single worm wheel and present a continuous pitch at their point of meshing engagement with worm gear 179. With this design of roller 182, rotation of gear 179 will rotate the toroidal element 81 about its central axis into and out of Figure 11 and at the same time convolute element 81 by the rotation of each of the connected rollers 181 about respective tangential axes to the toroidal element along the plane of the surface of Figure 11, whereby each convolution increases the rotational speed of the toroidal element 81 about the central axis. A characteristic of a wheel 24 comprised of rollers 182 is that it will rotate at the maximum rate of acceleration that is supported by the torque provided by gear 179, and dispose of excess torque through slippage between gear 179 and rollers 182 and variations in the rate at which the toroidal elements 81 convolutes. As such, such an arrangement may find use not only as a drive element in a manipulator apparatus as described later, but also in torque conversion devices such as transmission systems, and particularly as an infinitely variable transmission system.

In either of the first or second variants noted above, the coupling elements 74 do not require modification so long as they are small enough not to contact helical gear 175 or worm gearl79.

A third variant of the drive element of the second embodiment is apparent from Figures 1 and 2. Here a first wheel 24 having a toroidal element 74 as shown in Figure 7 and described previously is provided mounted on a shaft which can control the rotation of the wheel. A second wheel 24 having a toroidal element 74 as shown in Figure 7 and described previously is also provided, respectively mounted on a second shaft which can control the rotation of the second wheel. The shafts are positioned such that the perimeters of the first and second wheels are in contact, but that the wheels are angularly disposed to one another. Preferably, and as shown in Figures 1 and 2, the wheels are angularly offset by 90 degrees, although a lesser or greater offset may be used. The angular offset is such as to ensure that rotation of the one of the wheels about its central axis causes the rollers 72 of the other wheel, to rotate, thus convoluting the other wheel.

With such an arrangement one of the wheels designated the drive wheel can be caused both to rotate in either direction by virtue of its shaft being rotated in either direction, thus causing a workpiece or material in contact with the wheel to be moved in first and second opposite directions, and also to convolute in either direction by virtue of the other wheel being rotated about its own shaft in either direction, thus causing the workpiece or material to be moved in orthogonal directions to the first and second directions. Within Figures 1 and 2, which illustrate such a drive element within a manipulator apparatus, the upper wheel is the designated drive wheel, the outer perimeter of which contacts a workpiece or material to be moved. The lower wheel is provided in contacting relationship to the upper wheel, and rotation of the lower wheel causes the upper wheel to convolute, which, in Figure 1, would cause movement of a workpiece into and out of the page. Movement of the workpiece across the page is caused by the upper wheel being rotated about its central axis by rotating the shaft upon which it is mounted.

Within the third variant of the drive element of the second embodiment, therefore, movement in orthogonal directions can be achieved by use of two toroidal elements

capable of rotation and convolution, with the toroidal elements being in contact with each other but angularly offset. With such an angular offset, rotation of one of the elements causes, at least partially, convolution of the other of the elements.

Both the first and second embodiments therefore provide drive elements which allow for movement of a driven element in a plurality of directions, and preferably orthogonal directions. Such drive elements may find application independently, for example as transmission devices or the like, but are particularly suitable for use in a manipulator apparatus according to a third embodiment of the invention, and described next.

More particularly, according to a third embodiment of the invention Figure 1 shows a machine for joining two sheets of material which comprises a base unit 10 and a clamping assembly 12. The base unit 10 incorporates two manipulators 103 and 105 arranged side-by-side one another as shown more clearly in the sections of Figures 2 and 3.

Each manipulator 103, 105 essentially comprises an inclined support surface 20 and two drive elements 22, 24, the respective drive surfaces of which project from the support surface 20 to engage the surface of a sheet of material to be advanced through a work station. The work station, generally designated 17 in Figure 3, is contained within the clamping assembly 12, and will not be described herein in any detail. It may for example include a conventional sewing mechanism or it may include a mechanism for coating the edges of sheet material with glue and bonding them chemically to one another.

One of the manipulators 105 incorporates a screw 26 to allow the height of its support surface 20 to be adjusted relative to the height of the other manipulator 103, so that the same base unit 10 can be used to overlap the edges of the sheets being joined (designated 30 and 32 in Figure 3) either from left to right or from right to left.

The drive elements 22 and 24 used to advance the sheets of material that are clamped between each of the two manipulators 103 and 105 and the clamping element 12 are of two different designs. More particularly, the drive element 22 is a drive element as

described previously in respect of the first embodiment, whereas the drive element 24 is a drive element as described previously in respect of the second embodiment. In particular, the drive element 24 is a drive element according to the third variant of the second embodiment, with two toroidal elements placed in contact but angularly disposed to each other.

The drive elements 22 and 24 are of the two different types because if, for example, the first type of drive element were the only one to be used to advance the sheets, the closest that these drive elements 22 could be arranged to the joint line between the two sheets of material would be determined by the size of each ball 62 and the diameter of the rollers 42 and 44. To avoid this limitation and enable a drive element to be positioned nearer to the edge of a sheet of material, it is therefore preferable also to use a drive element according to the second embodiment, in addition to the drive element according to the first embodiment.

The drive element 22 is arranged such that the drive portion of the ball 62 which extends above the plane of socket 64 extends above the plane of the support surface 20 so as to be able to contact a workpiece. Likewise, a portion of the outer perimeter of the upper wheel 24 of the second drive element also extends above the plane of the support surface, for the same reason. It can thus be seen that each of the manipulators 103 and 105 provided with the drive elements 22 and 24 can allow a sheet of material or other workpiece to be moved in any direction relative to the clamp 12 and furthermore the orientation of the sheet of material can be changed as desired, by suitable control of the drive elements 22 and 24.

The drive elements 22 and 24 in each manipulator are fixed to one another and supported on slides 97, shown in Fig. 3, which extend parallel to one another such that the drive elements 22 and 24 can be slide left to right within the plane of the drawing. A constant distance is maintained between the drive assemblies 22 and 24 in the two manipulators 103 and 105. This movability of the drive elements is to accommodate variations caused by the up and down movement of the support surfaces 20 of the manipulator 105, and if the two support surfaces 20 are fixed relative to one another then these slides are not required.

The clamping assembly 12 which is shown in Figs. 1 and 3 rests on the two manipulators 103 and 105. Its bottom surface is V-shaped and formed in two halves so that it automatically centres itself in the trough defined by the two support surfaces 20. The under surface of the clamping assembly 12 includes recesses at appropriate locations to receive the portions of drive elements 24 and ball 22 that project above support surfaces 20 of manipulators 103 and 105. Each such recess comprises an arrangement of balls that are freely journalled so as not to impede movement of the sheet material in any direction while still applying a downward force to maintain the fiϊctional engagement between the sheet material and the drive elements 22 and 24.

The clamping assembly 12 is restrained from moving left or right in the plane of Fig. 1 by magnets 102 within it that are fixed to its under surface. The magnets 102 are attracted to corresponding magnets 104 in each manipulator 103 and 105.

The clamping assembly simply 12 is therefore a free floating assembly which is centred on the manipulators on account of the V-shaped trough in which it rests and which is prevented from moving along the V-shaped trough by virtue of the attraction between the magnets 102 and 104, which act through the sheet material. By avoiding the need for external bars to prevent the movement of the clamping assembly 12, it is possible to avoid any restriction on the width or length of the sheet material that can be manipulated by the machine.

Fig. 3 shows the manipulator machine configured such that material to the right, in the plane of Fig. 3, overlaps material to the left. The machine can be configured such that material to the left of Fig. 3 overlaps material to the right by using the screw 26 to raise the support surface 20 of the manipulator 105. Dropping the height of the support surface 20 of the manipulator 105 will result in a movement of the clamping assembly 12 to the right, as viewed, and it is on account of this that the slides 97 are needed to permit the drive elements 22 and 24 to be moved so as to follow the movement of the clamping assembly 12.

The machine in Fig. 1 is designed to perform the jointing together of the edges of sheets of material. Therefore the clamping assembly 12 of Fig. I ₅ houses a workstation 17 that comprises a mechanism 106 for lifting the edge of sheet material

by means of a spring 108 fixed to a rotatable shaft and a rotatable wheel 110 that presses the overlapping sheet down onto the overlapped sheet thereby causing their glued edges to bond to one another.

A sensor 120, which is a camera that is part of a machine vision system inspects the sheet material below the clamping assembly 12, and provides data on the position, rate and direction of movement, and orientation of the sheet materials. The data provided by the sensor 120 is used to instruct the drive assemblies and thereby control the movement of the sheet material.

In further embodiments of the invention, manipulators may be provided with more than two drive elements, and in particular three or more. The drive elements in such embodiments are preferably arranged such that they lie in the same plane and may therefore each contact the workpiece when the workpiece is on the support surface. Manipulators with three or more drive elements may have particular use in sorting applications or the like, such as letter sorting.

Further modifications will be apparent to the skilled person to produce further embodiments which will fall within the scope of the appended claims.