VEHICLE DRIVE

Abstract: Apparatus for driving and steering an invalid chair, or other light wheeled vehicle, comprises a transverse drive transmission shaft (8) with end cones (9 and 10) which contact across the periphery respectively of each of a pair of road wheels (11 and 12). By transverse axial movement of the drive transmission shaft (8) the contact diameter of the cones (9, 10) can be varied and thus the relative speed of the road wheels (11, 12) controlled for differential steering.

Description: This invention relates to a vehicle drive which also provides for steering a light vehicle, especially an invalid chair but applicable also to passenger or light goods trolleys or carriers, for example on golf courses or in warehouses. Friction drive is known, for example in CH-A-649464 where independently speed-variable motors provide it combined with steering. The present invention does not require such motors. According to the invention, apparatus for driving and steering a wheeled vehicle comprising a pair of rotary friction-drives to be mounted in use to extend each respectively across the periphery of one of a pair of vehicle road wheels with means for holding the drives in frictional driving contact each with the periphery of its respective road wheel and transmitting drive thereto, characterised in that the drives are oppositely directed cones with means for simultaneously moving the cones axially in one direction or the other so as to control the cone diameter at which each respective cone contacts its road wheel and thus steer the vehicle by controlling the relative speed of the road wheels, means being provided permitting the cones to move so as to accommodate change in contact diameter of the cones on their respective wheels. In a preferred embodiment, the apparatus comprises a rotary drive transmission shaft, for driving and steering the vehicle with the friction-drive cones carried on each end of the transverse drive shaft, to bear on the periphery of and drive the respective road wheel, means for loading the transverse drive shaft to maintain frictional driving contact between the drive cones and road wheels, manual steering means for moving the transverse drive shaft axially so as to control the cone-diameter at which the respective drive cone contacts its wheel and thus vary differentially the drive ratios between the drive cones and their wheels, and means permitting the transverse drive shaft and/or the cones to accommodate change in contact diameter of the cones on their wheels. In a particularly advantageous construction, the apparatus is made as a unit or kit for attachment to an existing invalid chair which, with the addition of an electric motor and battery, can thus be converted into a powered chair. The apparatus will usually be designed for driving road wheels with pneumatic tyres or resilient solid tyres and tyre resilience can be utilised in maintaining driving contact of the cones. This enables the means for maintaining drive-contact to be simply a linkage whereby the cones can be moved into out of contact, the linkage passing a dead-centre, non-return, condition as the cones are pressed into contact with the tyres. To accommodate the effect on drive shaft alignment of change in contact diameter of the cones, their drive shaft or shafts may be journalled in a stirrup or cradle which rests in slotted brackets which permit the drive shaft or shafts to tilt and thus enable each cone to ride higher or lower across the periphery of its road wheel. The steering means may comprise a hand lever upstanding, convenient to a driver's hand, from the forward end of a steering shaft of linkage extending rearwardly towards a driven pair of rear road wheels. In an invalid chair, the steering column may extend along an armrest and conveniently house the electrical connections for motor control from a switch on the hand lever. From the rear end of the steering shaft a drop arm is connected by a ball-joint to a drag link ball-jointed to a steering arm fast on a drive-shaft stirrup or cradle. By turning the hand lever, left or right for instinctive steering, through a small angle, the cones are moved axially in the opposite sense to drive the outer wheel, for a left or right turn respectively, faster than the inner wheel and thus achieve differential speed steering. The invention is illustrated, by way of example, on the accompanying drawings, in which:- Fig. 1 is a plan of apparatus according to the invention for attachment to an existing invalid chair. Figs. 2 and 3 are fragmentary plan views showing the position of a driving cone on its road wheel for a full right turn and a full left turn respectively, Fig. 4 is a schematic view of a steering linkage, and Fig. 5 is a fragmentary and schematic view of a lever control for moving the drive shaft and cones into and from drive contact with the road wheels. The apparatus shown by Fig. 1 has a transverse carrier bar 1 with a pair of clamping arms 2 held on the ends of the bar by stub end fittings with hand nuts 3 so that the arms 2 can be clasped firmly on to rear frame members of an invalid chair but leaving the bar 1 free to pivot on its own axis. The bar 1 carries a pair of radial arm brackets 4 with slots in which rest slipper bearing pads 5 on a transverse stirrup bar 6 which is allowed to tilt by the pads 5 riding up or down in their slots and can also freely slide axially through and turn in the pads 5. At the ends of the stirrup bar 6, a pair of radial arms 7 carry bearings in which is journalled a transverse drive transmission shaft 8 on the ends of which are keyed fast a pair of driving cones 9 and 10 which taper oppositely outwardly each across the periphery of a respective road wheel 11 or 12. The cones have ribbed or roughened surfaces to promote driving grip against the wheel tyres. The shaft 8 is driven by a belt 13 and reduction driving and driven pulleys 14 and 15 from an electric motor 16 slung by a bearing bracket 17 from the stirrup bar 6 so as to move with that bar and maintain a constant relationship to the drive transmission shaft 8. To steer the chair, the drive transmission shaft 8 is moved axially, transversely between the wheels 11 and 12, in the opposite direction to that in which a turn is to be made. This results in the outer wheel in a turn being driven faster, by a larger contact diameter of the respective cone, than the inner wheel so that differential speed steering is achieved. Fig. 2 shows the extreme left position of the cone 9 on the wheel 11 for a full right-hand turn in which the wheel 11 is the outer wheel. Fig. 3 shows the extreme right position of the cone 9 on the wheel 11 for a full left-hand turn in which the wheel 11 is the inner wheel. Steering movement of the shaft 8 is obtained by axial movement of the stirrup bar and, just as an example, a suitable steering linkage is schematically shown by Fig. 4. At a suitable position on the stirrup bar 6, outside the range of sliding through the pads 5, a steering arm 18 is fixed to the bar 6 and has a ball-joint 19 to one end of a drag-link 20 of which the other end has a ball joint 21 to a drop arm 22 from the rear end of a steering shaft 23 in a steering column tube 24, extending along the arm rest of the chair, from a hand lever 25 upstanding conveniently to the occupants hand. By turning the hand lever 25 towards L or R (left or right) through a small angle, the steering shaft 23 is rotated to turn the drop arm 22 and thus move, in the opposite sense, the stirrup bar 6, towards R or L and therewith the drive shaft 8. The hand lever 25 may house an electrical switch control with an operating button 26. As a result of axial movement of the driving cones for steering, the change in contact diameter of the cones on the wheels tilts the drive shaft 8 and this is permitted by tilting of the stirrup bar 6 carried by the bearing pads 5 in the slotted brackets 4. For control of drive, the stirrup bar 6, with its arms 7, is rocked in the bearing pads 5 to press the cones on to the wheel tyres or move them away. Fig. 5 shows an example of a control lever arrangement for rocking the stirrup 6, 7. One of the radial arm brackets 4 is extended downwardly as a lever 27 to which is connected an articulated pull rod 28 from a hand lever 29 pivoted as a bell crank. Rearward movement (D) of the hand lever 29 pulls the rod 28 to rock the stirrup and thereby press the cones down on to the wheel tyres to engage the drive. At the end of this movement, the pivotal connection 30 of the hand lever and pull rod passes the dead-centre of the hand lever pivot 31 to relax the pull to an extent permitted by the resilient wheel tyres being indented by the cones and then recovering up to maintenance of resilient drive contact. Forward movement (R) of the hand lever 29 releases the drive. As a safety precaution, a hand brake lever 32 is arranged to cross the path of the drive hand lever 29 and has an abutment 33 which blocks drive-engaging movement of the lever 29 to D except when the brake lever 32 has been moved from its off position O to its brakes-on position B. A keeper roller 34 is carried by an arm 35 from the carrier bar 1 to prevent escape of the stirrup bar 6 from the brackets 4.

Claims: Apparatus for driving and steering a wheeled vehicle comprising a pair of rotary friction-drives to be mounted in use to extend each respectively across the periphery of one of a pair of vehicle road wheels with means for holding the drives in frictional driving contact each with the periphery of its respective road wheel and transmitting drive thereto, characterised in that the drives are oppositely directed cones (9, 10) with means (25, 23 etc, 6) for simultaneously moving the cones axially in one direction or the other so as to control the cone diameter at which each respective cone contacts its road wheel (11, 12) and thus steer the vehicle by controlling the relative speed of the road wheels, means (4, 5) being provided permitting the cones to move so as to accommodate change in contact diameter of the cones on their respective wheels. Apparatus according to claim 1, comprising a rotary drive transmission shaft (8), to extend transversely between the pair of road wheels (11, 12) of the vehicle, with the friction-drive cones (9, 10) carried on each end of the transverse drive shaft, to bear on the periphery of and drive the respective road wheel, means (27, 28, 29) for loading the transverse drive shaft to maintain frictional driving contact between the drive cones and road wheels, manual steering means (25, 23 etc, 6) for moving the transverse drive shaft axially so as to control the cone-diameter at which the respective drive cone contacts its wheel and thus vary differentially the drive ratios between the drive cones and their wheels, and means (4, 5, 6) permitting the transverse drive shaft and/or the cones to accommodate change in contact diameter of the cones on their wheels. Apparatus as claimed in claim 1 or 2, in which means for maintaining drive-contact is a linkage (27, 28, 29) whereby the cones can be moved into and out of contact with a resilient wheel tyre, the linkage being arranged to pass a dead-centre, non-return, condition through a position of greatest pressure as the cones are pressed into contact with the tyres. Apparatus according to any foregoing claim, in which, to accommodate the effect on drive shaft alignment of change in contact diameter of the cones, their drive shaft is journalled in a stirrup or cradle (6, 7) which rests in slotted brackets (4) which permit the drive shaft to tilt and thus enable each cone to ride higher or lower across the periphery of its road wheel. Apparatus according to any foregoing claim, in which steering means comprise a hand lever (25) to upstand in use, convenient to a driver's hand, from the forward end of a steering shaft (23) of linkage (23, 22, etc) extending rearwardly towards a driven pair of rear road wheels. Apparatus according to claim 5 and for a wheel chair with an arm rest along which the steering shaft extends. Apparatus according to claim 5 or 6, in which, from the rear end of the steering shaft (23) a drop arm (22) is connected to a drag link (20) connected to a steering arm (18) for moving the drive transmission shaft (8) in the opposite sense to the hand lever. Apparatus according to any foregoing claim mounted on a carrier for attachment as a kit or unit to an existing wheel chair.

Inventors: PARKER, HENRY
Applicants: AUTOKRAFT LIMITED
Application year: 1987
Main classification: A61G5
IPC codes: A61G5