KERB CLIMBING DEVICE

Abstract: A kerb climbing device 2 for a wheelchair having a pair of front castor wheels 4 of relatively small diameter comprises a guide arm 19 and a lifting arm 18 mounted centrally between the castor wheels 4 for pivotal movement about a horizontal axis HA extending between opposed side frame members 6. The guide arm 19 and lifting arm 18 extend forwardly of the castor wheels 4 in an operative position of the device 2 in which a jockey wheel 25 at the free end of the guide arm 19 is arranged for locating against a kerb and a rubber foot 24 at the free end of the lifting arm 18 is spaced above the jockey wheel 25. The lifting arm 18 is pivotal in response to engagement of the jockey wheel 25 with a kerb to lower the foot 24 onto the kerb and lift the castor wheels 4 of the ground thereby facilitating mounting of the kerb.

Description: The present invention relates to devices for use with wheelchairs having at least one ground engaging wheel of relatively small diameter to enable the wheelchair to mount raised obstacles in its path, for example kerbs, steps and the like. For convenience such devices will hereinafter be referred to as kerb climbing devices, it being understood that the term "kerb" embraces all kinds of raised obstacle which may be encountered in use of a wheelchair. A kerb climbing device for a wheelchair having a pair of castor wheels at the front and a pair of larger diameter wheels at the rear is known from UK Patent No.1,569,166 and UK Patent Application No.2,145,983-A, comprising a strut pivotally mounted on the wheelchair and carrying an arcuate ground engaging shoe at the free outer end. The strut is biassed by a spring to an operative position projecting forwardly of the castor wheels with the shoe raised clear of the ground for engagement with the upper front edge of a kerb to be mounted whereupon the strut is pivotal under the forward momentum of the wheelchair to lift the castor wheels off the ground onto the kerb. With this type of kerb climbing device, the shoe must have a considerable arcuate extent in order to cooperate with any one of a range of different kerb heights and this can give rise to problems both in fitting the device where the space available is restricted and in use where the upward pojection of the shoe presents a safety hazard. A further problem is that the point of contact between the shoe and the kerb lies on the longitudinal axis of the strut for one kerb height only and for all other kerb heights is offset so that the loads acting on the strut during lifting of the wheels generate forces tending to bend the strut. A kerb climbing device for a wheelchair having a pair of castor wheels at the front and a pair of larger diameter wheels at the rear is known from DE-A-3,039,611 comprising a pair of axially rigid divergent arms mounted for pivotal movement about a horizontal axis extending between opposed sides of the wheelchair. The arms extend forwardly of the castor wheels in an operative position of the device for locating a lower one of the arms against a kerb whereupon the device is pivotal for lowering the upper other of the arms onto the kerb to assist the castor wheels mount the kerb. According to the present invention we provide a kerb climbing device for a wheelchair having at least one ground engaging wheel of small diameter, the device comprising a lifting arm and a guide arm adapted to be mounted on the wheelchair for pivotal movement about a horizontal axis extending between opposed sides of the wheelchair, the lifting arm and guide arm being arranged to extend forwardly of the small diameter wheel in an operative position of the device with the lifting arm spaced above the guide arm, and the lifting arm being axially rigid and pivotal in response to location of a kerb by the guide arm for engagement with the kerb to lift the wheel off the ground characterised in that the guide arm is axially telescopic. The guide arm of the invented kerb climbing device is axially telescopic for adjusting automatically its length when located against a kerb for pivotal movement of the axially rigid lifting arm to lower the free end of the lifting arm onto the kerb. As a result, the device is automatically adjustable for a range of kerb heights and the axially ri gid lifting arm provides a strut of fixed length for withstanding the lifting loads. In this way, the point of contact between the free end of the lifting arm and the kerb is the same for all kerb heights so that the forces generated by the loads acting on the arm during lifting always act along the axial length of the arm and forces tending to bend the arm are substantially eliminated. Conveniently, means is provided for biassing the lifting arm and guide arm to the operative position. In this way, the lifting arm and guide arm are positively held in the operative position for locating the guide arm against a kerb and the biassing means permits pivotal movement of the lifting arm for lowering the free end of the lifting arm onto the kerb. Advantageously, the lifting arm and guide arm are connected to a pivot member comprising a shaft journalled for rotation about the horizontal axis in respective mounting brackets adapted for mounting on opposed sides of the wheelchair. In a preferred arrangement the lifting arm and guide arm comprise respective limbs of a member of generally V-shape in side elevation connected at the apex to the shaft for rotation therewith. The mounting brackets are preferably releasable for detachably mounting the device on the wheelchair and are preferably adjustable relative to each other for mounting the device on wheelchairs of different width. The lifting arm and guide arm are preferably pivotal between the operative position and an inoperative position in which the lifting arm and guide arm extend rearwardly of said small diameter wheel and are raised clear off the ground for use of the wheelchair on substantially flat surfaces for which the kerb climbing device is not required. Conveniently the biassing means for the lifting arm and guide arm comprises an over-centre spring linkage which biasses the lifting arm and guide arm to each of the operative and inoperative positions. As a result, the lifting arm and guide arm are automatically returned to the inoperative position in use of the device when the small diameter wheel of the wheelchair is lifted onto the kerb. Preferably the over-centre spring linkage adopts an equilibrium position in each of the operative and inoperative positions permitting limited resilient deflection of the device. In this way, obstructions and surface irregularities which the small diameter wheel can negotiate are accommodated without activating the device when in the operative position and larger obstructions or surface irregularities over which the wheelchair may pass are accommodated without risk of damage to the device when in the inoperative position. Advantageously, the lifting arm and guide arm are pivotal between the operative and inoperative positions by means of a manually operable lever positioned so as to be accessible to the occupant of the wheelchair for positioning the device as required. The lifting arm and guide arm are preferably constructed and arranged so that the free ends thereof lie in a common substantially horizontal plane in the inoperative position and a common substantially vertical plane in the operative position. Advantageously the lifting arm has a friction device such as a rubber foot at the free end to increase the frictional engagement between the lifting arm and the kerb to prevent the lifting arm slipping. The guide arm preferably has a jockey wheel at the free end to enable the guide arm to ride over minor surface irregularities and to assist in locating the guide arm against the kerb. According to a second aspect of the present invention we provide a wheelchair including first and second pairs of ground engaging wheels, the first pair being of small diameter, and a kerb climbing device according to the first aspect of the invention for assisting the first pair of wheels to mount a kerb. Advantageously means is provided for biassing the lifting arm and guide arm to the operative position. Preferably the lifting arm and guide arm are connected to a pivot member comprising a shaft journalled for rotation about the horizontal axis in respective mounting brackets secured to opposed sides of the wheelchair. The lifting arm and guide arm are preferably pivotal between the operative position and an inoperative position in which the lifting arm and guide arm extend rearwardly of the first pair of wheels, and the biassing means comprises an overcentre spring linkage biassing the lifting arm and guide arm to each of the operative and inoperative positions. The device extends between and is preferably detachably secured to opposed sides of the wheelchair by releasable mounting means which is preferably adjustable for mounting the device on wheelchairs of different width. Advantageously each of the second pair of wheels is powered by a respective electric motor. Each motor is preferably independently connected to one or more batteries through a control unit having a manually operable joystick for controlling forward, reverse and turning movement as well as the speed. Advantageously, each motor is pivotal to disengage the drive to facilitate manual pushing of the wheelchair. Alternatively or in addition to the electric drive, the second pair of wheels may be adapted for manual self-propulsion of the wheelchair. For example, each wheel may have a respective hand grip. The first pair of wheels is preferably at the front of the wheelchair with the second pair of wheels being at the rear. The first pair of wheels may comprise castor wheels and the second pair of wheels may comprise pneumatic tyres supported on a wheel rim. The invention will now be described in more detail by way of example only with reference to the accompanying drawings wherein:- FIGURE 1 is a side view of a wheelchair fitted with a kerb climbing device according to the present invention, the device being shown in the inoperative position; FIGURE 2 is a side view of the wheelchair showing the kerb climbing device in the operative position; FIGURES 3,4 and 5 are side views of the wheelchair showing different positions of the kerb climbing device during mounting of a kerb; FIGURE 6 is a side view showing the wheelchair mounted on the kerb; FIGURE 7 is a side view showing the wheelchair descending the kerb with the kerb climbing device in the operative position acting as a steady; and FIGURE 8 is an enlarged diagrammatic side view of part of the wheelchair showing the kerb climbing device in greater detail. In the following description of a wheelchair 1 fitted with a kerb climbing device 2 according to the present invention, the wheelchair 1 is of a known type generally comprising a frame 3 mounted on a pair of front castor wheels 4 of relatively small diameter and a pair of driven rear wheels 5. The frame 3 comprises a pair of similar laterally spaced side frame members 6 (one only shown) connected by hinge means (not shown) which enable the wheelchair 1 to be collapsed to a folded position in which the side frame members 3 lie alongside each other. Seat and back rest panels 7 and 8 respectively of flexible material such as canvas extend between the side frame members 6 and each side frame member 6 has detachable arm and foot rests 9 and 10 respectively. Each rear wheel 5 is driven by a respective electric motor 11 independently connected through a control unit 12 mounted on one of the side frame members 6 to a pair of re-chargeable batteries 13 supported beneath the seat panel 7 in respective removable containers 14 each attached to a respective side frame member 6. The control unit 12 has a manually operable joystick 15 which is movable forwards, backwards and sideways from a neutral centre position so that, by appropriate movement of the joystick 15, one or both motors 11 is energised to select forward, reverse and turning movement of the wheelchair 1 with the speed being controlled by the extent of displacement of the joystick 15 from the neutral position. In addition, each motor 11 is mounted for pivotal movement relative to the associated wheel 5 to enable the drive connection to be disengaged to facilitate manual pushing of the wheelchair 1 by an attendant using respective handgrips 16 (one only shown) provided by each side frame member 6. The kerb climbing device 2 extends between and is releasably secured to the side frame members 6 above the front castor wheels 4 by respective mounting brackets 17. The kerb climbing device 2 includes a lifting arm 18 and a guide arm 19 positioned centrally between the front castor wheels 4. As shown in greater detail in Figure 8, the lifting arm 18 and guide arm 19 comprise respective divergent limbs of a generally V-shaped member 20. The member 20 is connected at the apex to a pivot member comprising a transverse shaft 21 journalled adjacent each end in the mounting brackets 17 for rotation about a horizontal axis HA coaxial with the longitudinal axis of the shaft 21. One of the brackets 17 is axially slidable on the shaft 21 whereby the device 2 may be adapted for fitting to wheelchairs 1 having different widths between the side frame members 6. Secured to opposed ends of the shaft 21 outboard of the mounting brackets 17 are respective manually operable levers 22 accessible to the occupant of the wheelchair 1 for pivotting the device 2 about the horizontal axis HA through 90° between an inoperative or stored position shown in broken lines in Figure 8 and operative or ready position shown in full lines in Figure 8. The device 2 is resiliently biassed to each of the inoperative and operative positions by means of an overcentre compression spring linkage indicated generally by reference numeral 23 in Figure 8. The lifting arm 18 has a ground engaging rubber foot 24 at the free end and is axially rigid having a fixed length slightly less than the height of the pivot axis HA above a horizontal plane HP containing the lower peripheral surface of the castor wheels 4. In this way clearance is provided between the foot 24 and the ground for pivotal movement of the kerb climbing device 2 between the inoperative and operative positions. The guide arm 19 has a ground engaging jockey wheel 25 at the free end and is axially telescopic comprising an outer section 26 and an inner section 27 slidably received therein to adjust telescopically the length thereof. A compression spring 28 acting between the sections 26,27 biasses the guide arm 19 to an extended length greater than the height of the pivot axis PA above the plane HP and the inner section 27 is slidable into the outer section 26 against the biassing of the spring 28. In this way the length of the arm 19 is automatically shortened for pivotal movement of the kerb climbing device 2 between the inoperative and operative positions. In the inoperative position of the device 2 for use of the wheelchair 1 on substantially flat ground, both arms 18,19 extend rearwardly of the front castor wheels 4 with the rubber foot 24 and jockey wheel 25 raised clear off the ground. In this position, the spring loading of the overcentre linkage 23 enables the device 2 to deflect on striking any localised surface irregularity such as a brick or stone passing between the front castor wheels 4 so as to avoid damaging the device 2. In the operative position of the device 2 for assisting the wheelchair 1 to mount a kerb, both arms 18,19 extend forwardly of the front castor wheels 4 with the jockey wheel 25 adjacent to the ground for locating against a kerb of a height greater than that which the castor wheels 4 can mount and the rubber foot 24 spaced above the jockey wheel 25 for lifting the castor wheels 4 onto the kerb. In this position, the height of the foot 24 above the ground corresponds to the maximum height of kerb that can be mounted and the jockey wheel 25 is raised approximately ½″ above the horizontal plane so that the guide arm 19 assisted by the spring loading of the overcentre linkage 23 rides over any obstruction that can be mounted by the castor wheels 4 without assistance thereby ensuring that the device 2 is activated only when required. As shown, the foot 24 and jockey wheel 25 lie in substantially common horizontal and vertical planes in the inoperative and operative positions respectively. It will be understood, however, that this is not essential provided that, in the inoperative position, both are raised clear of the ground and that, in the operative position, the jockey wheel 25 is on or, more preferably, adjacent to the ground and the foot 24 is raised clear of the ground and the jockey wheel 25. The overcentre spring linkage 23 may be of any suitable construction but preferably comprises a piston slidably mounted in a cylinder and biassed to an extended equilibrium position by a compression spring. The free outer end of the piston is pivotally connected to the shaft 21 and the cylinder is pivotally connected to the fixed mounting bracket 17 by respective links for the overcentre movement. The axial length of the piston is adjustable on installation to set the height of the jockey wheel 25 above the ground in the operative position of the device 2 and the compression spring permits movement of the piston into and out of the cylinder from the extended equilibrium position for deflection of the device 2 in the operative and inoperative positions as above-described. The operation of the kerb climbing device 2 will now be described in more detail starting with Figure 1 where the device 2 is shown in the inoperative position in which both arms 18,19 extend rearwardly of the front castor wheels 4 between the battery containers 14 with the rubber foot 24 and jockey wheel 25 raised clear of the ground for use of the wheelchair 1 on substantially flat ground. For mounting a kerb 29 higher than that which the front castor wheels 4 can ride over, the device 2 is pivotted to the operative position shown in Figure 2 in which both arms 18,19 extend forwardly of the front castor wheels 4 between the footrests 10 with the jockey wheel 25 adjacent to the ground and the rubber foot 24 spaced above the jockey wheel 25. With the device 2 in the operative position, the wheelchair 1 is driven towards the kerb 29 causing the jockey wheel 25 to locate against the vertical front face of the kerb 29 with the rubber foot 24 spaced above the upper surface of the kerb 29 as shown in Figure 3. On continuing forward movement of the wheelchair 1, the jockey wheel 25 runs down into the corner between the kerb 29 and ground whereupon the guide arm 19 telescopes and pivots in the anticlockwise direction causing simultaneous pivotal movement of the lifting arm 18 in the same direction to lower the rubber foot 24 into engagement with the upper surface of the kerb 29 as shown in Figure 4. On continuing forward movement of the wheelchair 1, the lifting arm 18 is located by the frictional engagement between the foot 24 and the upper surface of the kerb 29 and pivots in the anticlockwise direction to lift the front castor wheels 4 of the ground as shown in Figure 5. In this way, the front castor wheels 4 are raised sufficiently to engage the upper surface of the kerb 29 under the forward momentum of the wheelchair 1. On continuing forward movement of the wheelchair, the kerb climbing device 2 is automatically returned to the inoperative position by the overcentre compression spring linkage 23 and the larger diameter rear wheels 5, driven by the respective motors 11, ride over the kerb 29 to complete mounting of the kerb 29 by the wheelchair 1 as shown in Figure 6. Referring now to Figure 7, the kerb climbing device 2 is shown in the operative position acting as a steady for the wheelchair 1 on descending the kerb 29 through the engagement of the jockey wheel 25 of the telescopic guide arm 19 with the ground during the descent of the kerb 29 by the front castor wheels 4. As will be appreciated from the foregoing description, by arranging for the guide arm to locate against the kerb and pivot the lifting arm to engage the upper surface of the kerb, the lifting arm is automatically adjusted for different kerb heights up to the maximum height determined by the height of the rubber foot above the ground in the operative position. In this way the point of contact between the lifting arm and the kerb is the same for all kerb heights so that the forces generated by the loads acting on the lifting arm during pivotal movement to lift the castor wheels always acts along the length of the arm. It will also be understood that the invented kerb climbing device is not limited to the particular embodiment above-described. For example, the device may comprise separate guide and lifting arms each mounted on the shaft and connected by link means for simultaneous pivotal movement. The link means may be adjustable to raise the lower the lifting arm relative to the guide arm in the operative position for adjusting the maximum height of kerb that can be negotiated by the device. The kerb climbing device may have one pair of lifting and guide arms positioned centrally between the front castor wheels as described or two pairs of lifting and guide arms may be provided, one for each castor wheel. Where two pairs are provided each pair may have its own shaft and operating lever or a common shaft and operating lever may be provided for both pairs. In addition the invented kerb climbing device may be used with different types of wheelchair. For example the wheelchair may be folding or non-folding. The small diameter wheels may be provided at the front or rear and may be castoring or non-castoring. The large diameter wheels may be driven by any suitable electric driving means and/or may be adapted for manual self-propulsion of the wheelchair, for example by the provision of annular hand grips.

Claims: 1. A kerb climbing device (2) for a wheelchair (1) having at least one ground engaging wheel (4) of small diameter, the device (2) comprising a lifting arm (18) and a guide arm (19) adapted to be mounted on the wheelchair (1) for pivotal movement about a horizontal axis (HA) extending between opposed sides of the wheelchair (1), the lifting arm (18) and guide arm (19) being arranged to extend forwardly of the small diameter wheel (4) in an operative position of the device (2) with the lifting arm (18) spaced above the guide arm (19), and the lifting arm (18) being axially rigid and pivotal in response to location of a kerb (29) by the guide arm (19) for engagement with the kerb (29) to lift the wheel (4) off the ground characterised in that the guide arm (19) is axially telescopic. 2. A kerb climbing device according to Claim 1 characterised in that the lifting arm (18) and guide arm (19) are connected to a pivot member comprising a shaft (21) journalled for rotation about the horizontal axis (HA) in respective mounting brackets (17) adapted for connection to opposed sides of the wheelchair (1). 3. A kerb climbing device according to Claim 2 characterised in that the mounting brackets (17) are releasable for detachably securing the device (2) to the wheelchair (1) and/or adjustable relative to each other for mounting the device (2) on wheelchairs (1) of different widths. 4. A kerb climbing device according to any one of the preceding Claims characterised in that means (23) is provided for biassing the lifting arm (18) and guide arm (19) to the operative position. 5. A kerb climbing device according to Claim 4 characterised in that a manually operable lever (22) is provided for pivotting the lifting arm (18) and guide arm (19) about the horizontal axis (HA) between the operative position and an inoperative position in which the lifting arm (18) and guide arm (19) extend rearwardly of the small diameter wheel (4), and the biassing means (23), for example an over-centre spring linkage, is operable to bias the lifting arm (18) and guide arm (19) to each of the operative and inoperative positions. 6. A kerb climbing device according to any one of the preceding Claims characterised in that a friction device (24) such as a rubber foot is provided at the free end of the lifting arm (18). 7. A kerb climbing device according to any one of the preceding Claims characterised in that a jockey wheel (25) is provided at the free end of the guide arm (19). 8. A wheelchair (1) including first and second pairs of ground engaging wheels (4,5), the first pair of wheels (4) being of small diameter, and a kerb climbing device (2) for assisting said first pair of wheel (4) to mount a kerb (29), the kerb climbing device (2) comprising an axially rigid lifting arm (18) and a guide arm (19) mounted for pivotal movement about a horizontal axis (HA) extending between opposed sides of the wheelchair (1) and arranged to extend forwardly of the first pair of wheels (4) in an operative position of the device (2) with the lifting arm (18) spaced above the guide arm (19) and pivotal in response to engagement of the guide arm (19) with a kerb (29) to engage the kerb (29) and lift the first pair of wheels (4) off the ground characterised in that the guide arm (19) is axially telescopic. 9. A wheelchair according to Claim 8 characterised in that the lifting arm (18) and guide arm (19) are mounted centrally between the first pair of wheels (4) and means (23) is provided for biassing the lifting arm (18) and guide arm (19) to the operative position. 10. A wheelchair according to Claim 8 or Claim 9 wherein the kerb climbing device (2) extends between and is detachably secured to opposed sides of the wheelchair (1) by releasable mounting means (17) and the mounting means (17) is preferably adjustable for mounting the device (2) on wheelchairs (1) of different width.

Inventors: SINGLETON, JOHN MICHAEL
Applicants: THE SPASTICS SOCIETY
Application year: 1988
Main classification: A61G5
IPC codes: A61G5