Field of the Invention This invention relates to drive systems and, more particularly, to drive systems for use in elevation apparatus.

Background to the Invention There are many instances of drive systems configured to provide drive both along and about a drive axis, some of which employ rollers that rotate about axes that are skewed with respect to the drive axis. Examples are described in US Patent No's 3,603,653 and 4,726,242 but the described examples suffer from an inability to precisely control relative degrees of movement along and about the drive axis.

It is an object of this invention to provide a novel and useful alternative to that which is currently available.

Summary of the Invention

Accordingly, in one aspect, the invention provides a drive system mounted to engage over and drive with respect to a member of substantially constant cross-section having a member axis, said drive system having a first roller set and a second roller set, said roller sets being engageable with said member at locations spaced along said member axis; a first drive motor associated with said first roller set; a second drive motor associated with said second roller set, and a control facility configured to allow selective operation of said first and second drive motors to effect displacement of said drive system both along, and about, said member axis. Preferably rollers in at least one of said roller sets are provided with spiral drive surfaces. Preferably the axes of rotation of rollers in at least one of said roller sets are aligned at an angle to a plane passing through said member axis and through points of contact between said rollers and said members. Preferably the rollers of each roller set are contained within a swept area of constant axial length.

Preferably the rollers of each roller set are equally spaced about a periphery of said member.

Preferably each roller set includes at least three rollers.

Preferably said drive system further includes a chassis positioned between said roller sets. Preferably said control facility is configured to selectively operate said first drive motor and said second drive motor to rotate at the same speeds or at different speeds.

Preferably said control facility is configured to selectively operate said first drive motor and said second drive motor to rotate in the same directions or in opposite directions.

Preferably said contact surface is substantially round when viewed along said member axis.

Preferably said contact surface comprises the outer peripheral surface of a substantially round tube.

Preferably peripheral surfaces of rollers in each roller set are configured to compliment the cross-sectional shape of said contact surface. Preferably said member is fixed and said drive system is configured to move with respect to said member. In a second aspect the invention provides an elevator including the drive system as set forth above.

In a third aspect the invention provides a stairlift including the drive system as set forth above.

In a fourth aspect the invention provides a contrivance requiring displacement along and about an axis including the drive system as set forth above. Many variations in the way the present invention can be performed will present themselves to those skilled in the art. The description which follows is intended as an illustration only of one means of performing the invention and the lack of description of variants or equivalents should not be regarded as limiting. Subject to falling within the scope of the appended claims, wherever possible, a description of a specific element should be deemed to include any and all equivalents thereof whether in existence now or in the future.

Brief Description of the Drawings

The invention, and modifications thereof, will now be described with reference to the accompanying drawings in which:

Figure 1: shows a schematic plan view of an arrangement of rollers in contact with a member forming part of a drive system according to the invention;

Figure 2: shows the same components as in Figure 1 but viewed along

the axis of the member;

Figure 3 shows an isometric view of the components shown in Figures 1

& 2; Figure 4: shows an exploded isometric view of the components of Figures 1 to 3 being incorporated into a first roller set unit;

Figures 5A& 5B: show, assembled, the components of Figure 4 from a rig

perspective and a left-hand perspective, respectively;

Figure 6: shows an exploded isometric view of the assembly of Figure 5A

together with a drive unit for attachment thereto; Figures 7A&7B: show, assembled, the components of Figure 6 from a right-hand

perspective and a left-hand perspective, respectively;

Figure 8: shows an isometric view of two drive units mounted on a member and separated by a main body;

Figure 9: shows the drive units of Figure 8 assembled to the main body; and

Figures 10 to 12: show diagrammatic representations of three modes of operation of a drive system according to the invention.

Detailed Description of Working Embodiment

Referring firstly to Figures 1 to 3, the invention comprises a drive system in which a series of rollers 10 are driven along a member 11, or the positions of the rollers are held and the member 11 is displaced. As a further option the drive may combine the rollers being displaced in one mode and the member being displaced in another mode.

The crux of the invention is that, when viewed along a reference axis 12 extending through the contact points 13 between the rollers and the member, and through the member axis 14, the drive axes 15 of the rollers are arranged at acute angles a to the member axis 14. Thus, by controlling the directions and speeds of at least two spaced sets of rollers, displacement can be effected both along, and about the axis 12 of, the member 11 and this has significant advantages for applications that require or could benefit from, for example, lifting and rotation.

In the depicted example the member 11 comprises a tube of round or annular cross-section and the rollers 10 are of the diablo-type and thus have contact surfaces shaped to more fully accommodate the contour or contact surface of the tube. The angle a preferably lies in the range 5° to 85° and more preferably within the range 40° to 50°. It will further be noted that the number of rollers in each set is three, this being the preferred minimum number, the rollers in each set being equi- spaced around the periphery of the member 11, occupying an annulus of fixed axial length, and thus sweeping a surface part of the member 11 of length w as shown in Figure 1.

Turning now to Figs 4, 5A & 5B, each of the rollers 10 is rotatably mounted on a shaft 18, the ends 19 and 20 of which are held in bearing housings 21 and 22 forming part of, or attached to, base plate 23 and cover plate 24 respectively, the base plate 23 and cover plate 24 combining to provide a cradle for the three individual rollers 10. It will be noted that the bearing housings 21 and 22 are aligned on their respective members 23 and 24 so as to ensure that, when the base plate and cover plate are assembled together, the shafts 18 are aligned at the correct angles a relative to the axis 14.

Located between the base plate 23 and the cover plate 24, and parallel to but spaced from both, is a bearing plate 25 having a circular peripheral bearing surface 26. In the form shown, the bearing plate 25 is mounted on spigots 27 projecting from the face of base plate 23, the spigots continuing through the bearing plate 25 and providing mounts for the cover plate 24. Fixing screws 28 may be provided to fix the cover plate to the spigots.

The assembled components of Fig 4 are shown in Figs 5 A and 5B, in which the assembly shown in Fig 5 A is rotated through 180° in Fig 5B. It is appropriate to depict two assemblies in this manner as the drive system according to the invention includes at least two such assemblies mounted on shaft or member 11 as shown in Figs 8 & 9, the assembly of Fig 5A being first roller set 30 and the assembly of Fig 5B being second roller set 31. Each roller set may, in turn, be duplicated in a modular fashion to provide a unit having increased power or load capacity.

As can be seen most clearly in Fig 6, an annular support bracket 32 is provided about each bearing plate 25, the outer nearing surface 26 of the plate 25 locating in groove 33 which extends around the inner surface 34 of the bracket 32. To enable the bracket 32 to be fitted around the bearing plate, the same may be provided in two semi-circular sections 35A and 35B which are bolted together along joint lines 36. Mounted on each bracket 32 is a drive motor 37 on the output shaft of which is pinion 38. When the bracket is correctly located over the bearing plate the pinion 38 engages gear surface 39 provided about the periphery of base plate 23. This can be seen most clearly in Figs 7A & 7B.

The support brackets 32 of the respective roller sets are connected to a central body or chassis 40. In the form shown each bracket 32 includes spigots 41 projecting from the outer periphery at opposite ends of a diameter of the bracket. These spigots are aligned with bores 42 provided in pairs at each end of the chassis 40 and joining pins 43 engaged through both to form a pivotal connection between each roller set and the chassis 40, the axes of these pivots preferably passing through the member axis 14. It will be appreciated that this arrangement provides a single mode of rotation; more elaborate connections may be provided to allow three-dimension movement between the roller sets 30 & 31, and the chassis 40.

Whilst the embodiment depicted and described provides a mode of rotation for use on a curved member, for use on purely linear supports, the roller sets 31 and 32 may be located in fixed positions on opposite ends of a central chassis and the drive motors for roller each set, and the control facility, mounted in the chassis.

The assembly of all the described components into an effective drive unit is shown in Fig 9. The chassis 40 may carry batteries 45 to power the motors 37, and a control facility 46 to control the speeds and directions of the motors 37. In use, powering the motors 37 of both roller sets, in the same direction, causes the unit to displace linearly along the member 11. Driving both in one direction will ensure displacement in one direction. Reversing the drive directions of the motors effects linear displacement in the opposite direction. Driving the motors in opposite directions causes rotation of the unit about the member 11. Again the direction of rotation can be reversed by reversing the directions of rotation of the motors. By varying the speeds and directions of the motors, combinations of linear and rotational drive can be achieved.

While a drive system has been described in which two roller sets are employed, it will be appreciated that further roller sets could be coupled in series to increase the power of the system.

Referring now to Figure 10, a drive system according to the invention is shown

schematically at 50 mounted on a shaft 51. By locking the drive system 50 in position, the shaft 51 can be rotated in direction A and translated or displaced vertically in direction B. Alternatively, or in addition, the shaft 51 can be locked in position, allowing the drive system to rotate about the shaft in direction C.

A variation is shown in Figure 11 in which the shaft 51 is locked in position and the drive system 50 translates or displaces along the shaft in direction D and rotates about the shaft in direction E.

A yet further variation is shown in Figure 12 in which drive system 50 is mounted on shaft 51 the shaft 51, in turn, being mounted on spaced rails 52. A mass 53 is suspended from the drive system 50, the mass 53 being sufficient to maintain a vertical orientation of the drive system 50. On powering the drive system in a first mode, the drive system will translate or displace in a transverse direction as indicated by arrow F. By selectively reversing the motors in the drive system 50, because the orientation of the drive system is maintained by mass 53, the shaft 51 will be rotated relative to the drive system thus causing the shaft 51 to translate along the rails 52 in the direction of arrow G. If, at a desired position of the shaft 51 along the rails 52, the shaft is locked with respect to the rails, then the drive system 51 can rotate about the shaft 51 thus raising and lowering the mass in the direction of arrow H and effectively operating as a winch drum.

Suitable apparatus may be fixed to the chassis to achieve a particular objective. By way of example only, an elevator cabin could be mounted on the chassis so that elevator users could enter the elevator at a first orientation and depart the elevator at an alternative orientation, thus providing greater flexibility in the design of an elevator installation.

Similarly a stairlift could be configured with a drive system according to the invention in which the motors could be controlled to drive the stairlift carriage along the rail and, adjacent to the ends of the rail, the motors could be driven in opposite directions to provide a swivel action, thus obviating the need to incorporate a separate swivel mechanism in the chair.