WO2012035341A1

WO2012035341A1 - Wheel assembly for a handcart

Info

Publication number: WO2012035341A1
Application number: PCT/GB2011/051725
Authority: WO
Inventors: Brian Milner
Original assignee: 13.17 Designs Limited
Priority date: 2010-09-15
Filing date: 2011-09-14
Publication date: 2012-03-22
Also published as: GB201015398D0; EP2616029A1

Abstract

The invention provides a light-weight mechanism that restricts rotation of a multi- wheel assembly by a ratchet and, when desired, lifts one of the ground-contacting wheels for manoeuvrability. An arm mountable on the handcart pivots from a disengaged position into an engaged position where the arm engages with the multi- wheel. A ratchet finger on the arm then restricts rotation of the multi- wheel (e.g. so that the multi- wheel can rotate backwards but not forwards, or vice versa). Further movement of the arm also lifts one of the ground-contacting wheels.

Description

WHEEL ASSEMBLY FOR A HANDCART

The present invention relates generally to a handcart, such as a trolley, wheelchair, sack truck, refuse cart or other carrying device. More specifically, the present invention concerns a wheel assembly for a handcart.

It is known to provide a multi- wheel assembly, such as a tri- wheel, to assist when moving a handcart over rough terrain, such as up or down stairs, kerbs and the like.

As one example, US-2931449 discloses a wheelchair with a tri- wheel arrangement. When travelling over a set of stairs, the tri-wheel assembly rotates to engage consecutive steps on the stairs.

Generally, the tri-wheel helps to give a smooth transition over a change in ground level, but the two ground-contacting wheels have a higher drag and reduced

manoeuvrability compared with one large wheel. US-2931449 therefore discloses raising one of the two ground-contacting wheels using an actuator assembly and an associated power supply, which however increases the weight and bulk of the wheelchair.

The tri-wheel also generally has a more complex braking system, so that braking is effected whichever of the wheels is contacting the ground. Hence, US-2931449 discloses a series of gears to apply a braking force. Disadvantageously, the gears and associated components increase the weight and bulk of the wheel chair.

The present invention provides a wheel assembly for a handcart, the wheel assembly comprising:

a multi-wheel unit having a plurality of wheels, and

a ratchet unit arranged in use to restrict rotation of the multi- wheel unit and to lift one of the wheels for manoeuvrability, in which the ratchet unit comprises a ratchet arm pivotally movable relative to the multi- wheel unit from a disengaged position into an engaged position where the ratchet arm engages with the multi- wheel unit to restrict rotation of the multi-wheel unit, and in which further movement of the arm also lifts the said wheel.

The multi-wheel unit comprises a support and a plurality of wheels. It can be preferred for the support to be generally star-shaped. It can be preferred for the number of arms of the star to be equal to the number of wheels on the multi-wheel unit, with a wheel mounted on the support at or towards the end of each of the arms of the star.

Optionally, the multi-wheel unit has a plurality of capture points. It will generally be preferred for the multi-wheel unit to include capture points which are each positioned to be engaged by the ratchet arm to lift a respective one of the wheels, especially with the number of capture points equal to the number of wheels. The ratchet arm can be used to engage any of the capture points. The ratchet arm can engage each of the capture points in turn to restrict rotation and to lift the wheel.

Optionally, the capture points can be disposed at or near an outer periphery of the multi-wheel unit. For example, capture points can be aligned with the axles of the wheels.

The multi- wheel unit will generally have a hub for mounting the unit on the frame of a handcart. Optionally, the capture points can be provided on a ring which is fixed to or alternatively formed integrally with the multi-wheel unit. The capture points can be provided on the internal surface of the ring, for example in the form of a series of recesses. For example, when the multi- wheel unit has three wheels, the ring can have three recesses formed in it. The ratchet arm can include a hook which can be deployed to engage with one of the recesses.

Optionally, the ratchet unit includes a ratchet finger pivotally mounted on the ratchet arm to move between an extended position disposed away from the ratchet arm to engage the respective capture point in one rotation direction, and a folded position that allows the capture point to rotate past the ratchet finger in the other rotation direction.

Optionally, the ratchet finger comprises a recess to hold securely one of the capture points.

Optionally, the ratchet arm includes a handle at or near one end for manual actuation of the ratchet unit.

The ratchet arm can be arranged to provide a mechanical advantage to assist the user when lifting one of the wheels off the ground.

Optionally, the ratchet unit includes a lock assembly to lock the ratchet arm in one or more positions.

Optionally, the lock assembly includes a sleeve which can be caused to slide along the ratchet arm using a lock handle disposed at or near the handle of the ratchet arm. Optionally, the wheel assembly includes a braking unit for braking the wheels of the multi- wheel assembly, the braking unit comprising a central hub arranged to co -rotate with each of the wheels of the multi-wheel unit, and a braking mechanism which brakes rotation of the central hub, thereby causing braking of each of the wheels.

Optionally, an outer periphery of each wheel engages the central hub to co-rotate by friction. Optionally, the wheels comprise a solid tyre cut into a gear that engages a corresponding gear on the central hub to co -rotate.

The invention also provides a handcart which includes the wheel assembly.

Examples of handcarts to which the invention is applicable include trolleys, wheelchairs, sack trucks and refuse containers such as bins mounted on wheels (particularly of the "wheelie-bin" type).

The invention also provides a handcart which comprises a load-bearing frame and a pair of multi-wheel units mounted on the frame, each of the multi-wheel units having a plurality of wheels and being mounted on the frame for rotation so that different wheels mounted on the unit can contact the ground, the handcart including a mechanism for causing the multi- wheel units to rotate relative to the frame, the mechanism including a lever arm which extends between at least one of the multi-wheel units and the frame, and a hook and recess arrangement with one of the hook and the recess provided on the multi- wheel unit, in which initial movement of the lever arm causes the other of the hook and the recess so that the hook engages with the recess and continued movement of the arm causes the multi- wheel unit to rotate relative to the frame so that no more than one wheel on the multi-wheel unit is in contact with the ground. The handcart can include one or more of the features of the wheel assembly which are referred to above.

Optionally, the hook and recess arrangement can operate as a ratchet. Optionally, the ratchet can allow rotation of the multi- wheel unit in one rotational direction.

Optionally, the lever arm pivots about an axis which is coaxial with the axis about which the multi- wheel unit rotates relative to the frame, and functions as a class 2 lever. A class 2 lever is one in which the load is applied at a point between the fulcrum and the applied effort.

Optionally, the lever arm is connected to a detent plate which defines a first position of the lever in which the hook and recess are not engaged and a second position of the lever in which the hook and recess are engaged and the multi- wheel unit is rotated relative to the frame so that no more than one wheel on the multi- wheel unit is in contact with the ground. The lever arm can include a sleeve which can slide along the arm to release a latch, allowing the lever arm to be moved between its first and second positions.

Optionally, the hook can be mounted to pivot between a deployed position in which it engages one of the recesses to restrict rotation of the multi- wheel assembly in at least one rotation direction, and a retracted position in which the hook does not engage the recesses. A keeper can be provided. The hook can engage the keeper when in the retracted position and so be held away from the recesses. In this way, the hook can be held in a position where it does not contact the recess or recesses, such as during rotation of the support in the forward or anti-counter clockwise direction (e.g. when descending a stair). The hook can be biased towards the retracted position or towards the deployed position. Preferably the hook is biased towards the deployed position. The lever arm can act on the hook, directly or indirectly, to cause it to move in the direction which is opposite to the direction in which the hook is biased. For example, when the assembly includes a keeper, the hook can be biased towards the deployed position and an arm can act on the hook to urge it away from the recess so as to engage the keeper.

It can be preferred that the number of hooks or recesses of the locking mechanism which are provided on the multi- wheel unit is equal to the number of wheels on the multi- wheel unit.

The invention also provides a wheel assembly for a handcart, the wheel assembly comprising:

a multi- wheel unit which comprises a support which can be mounted at its centre on the handcart, and a plurality of wheels mounted on the support for rotation relative to the support,

a brake unit comprising a body having a cylindrical cross-section, which is engaged by each of the wheels of the multi- wheel unit so that it rotates with the wheels relative to the support, and a brake device which can be actuated to engage the body so as to brake the body, and the wheels in contact with the body, against rotation relative to the support.

The invention also provides a handcart comprising a load-bearing frame and a pair of wheel assemblies mounted on the frame, each wheel assembly comprising: a multi- wheel unit which comprises a support mounted at its centre on the frame of the handcart, and a plurality of wheels mounted on the support for rotation relative to the support, and

Optionally, the brake unit body is a hollow cylindrical shell and the brake device includes at least one brake pad located within the shell which, when the brake is actuated, is displaced outwardly to engage the internal surface of the shell.

Optionally, the body has a textured external surface to promote factional engagement between the body and the wheels of the multi- wheel unit.

Optionally, the brake device can be mounted to a frame of the handcart. The brake device may be arranged so that it can be fixed relative to the frame and secured against rotation with the support. Optionally, the brake device can be directly or indirectly mounted to the frame.

Optionally, the brake unit is mounted to the support, and may be mounted on the support at its centre. The brake device may be fixed relative to the support.

The invention also provides a method of attaching a wheel assembly to a handcart, the method comprising:

attaching a multi-wheel unit having a plurality of wheels; and

providing a ratchet unit arranged in use to restrict rotation of the multi- wheel unit and to lift one of the wheels for manoeuvrability, the ratchet unit including a ratchet arm pivotally movable relative to the wheel assembly from a disengaged position into an engaged position where the ratchet arm engages with the multi- wheel unit to restrict rotation of the multi-wheel unit, and further movement of the arm also lifts the wheel.

Optionally, the method includes providing a brake unit where the wheels of the multi- wheel unit are arranged to co -rotate with a central hub and a braking mechanism brakes rotation of the central hub, thereby causing braking of each of the wheels.

In one example there is provided a light-weight mechanism that restricts rotation of a multi-wheel assembly by a ratchet and, when desired, lifts one of the ground-contacting wheels for manoeuvrability. An arm mountable on the handcart pivots from a disengaged position into an engaged position where the arm engages with the multi- wheel. A ratchet finger on the arm then restricts rotation of the multi- wheel (e.g. so that the multi- wheel can rotate backwards but not forwards, or vice versa). Further movement of the arm also lifts one of the ground-contacting wheels.

In one example there is provided a coordinated braking system for braking the multi- wheel assembly. The wheels each co -rotate with a central hub and the braking mechanism brakes rotation of the hub, thereby causing braking of each of the wheels. As one example, an outer periphery of each wheel engages the hub by friction, which is particularly suitable for pneumatic tyres. As another example, a solid tyre is formed as a gear and engages a corresponding gear on the hub. Advantageously, the braking system is simple, robust, reliable and light-weight.

Embodiments of the invention are described below by way of example with reference to the accompanying drawings in which:

Fig. 1 is a side view of a wheelchair;

Fig. 2 is a side view of a multi-wheel unit;

Fig. 3 is a side view of a ratchet unit;

Figs. 4 to 6 are side views showing movement of the wheel unit of Fig. 2 in use;

Fig. 7 is a side view showing a brake unit;

Fig. 8 is a side view of another wheelchair;

Fig. 9 is an enlarged side view of another multi-wheel unit;

Fig. 10 is an enlarged side view of a mechanism for causing the multi- wheel unit of Fig. 9 to rotate relative to a frame of the wheelchair;

Figs. 11 to 13 are side views showing movement of the wheel unit of Fig. 9 in use;

Figs. 14 and 15 are detailed perspective views of part of another multi- wheel unit, illustrated in different positions which show movement of the wheel unit in use;

Fig. 16 is a detailed exploded perspective view of another brake unit, shown incorporated into the multi- wheel unit of Figs. 14 and 15; and

Fig. 17 is an enlarged perspective view of the multi- wheel unit of Figs. 14 and 15, showing parts of the multi- wheel unit and the brake unit of Fig. 16 in more detail. Generally the invention is applicable to handcarts such as trolleys, wheelchairs, sack trucks, refuse carts such as wheel-mounted bins (particularly of the "wheelie-bin" type) and other load carrying devices and the techniques and principles discussed herein will find application in many specific embodiments. The following examples will be illustrated with reference to a wheelchair for ease of understanding and appreciation. Other applications of the invention may not employ all the features described herein.

Figure 1 is a side view of a wheelchair 100 as provided in an example embodiment. The wheelchair 100 includes a load bearing frame 200, and a wheel assembly 250. Here, the wheel assembly 250 includes a multi-wheel unit 300, a ratchet unit 400 and a brake unit 500, which will be discussed in detail below.

Advantageously, the example wheel assembly 250 can be mounted when manufacturing the wheelchair 100. Also, the wheel assembly 250 is readily retro-fitted to an existing wheelchair 100, and is quickly removed from the wheelchair 100, such as if the needs of a user should change. Thus, the wheelchair 100 is readily modified from having a single large rear wheel on each side to instead carrying the wheel assembly 250 described herein, and vice versa.

In use, the multi- wheel unit 300 is mounted for rotation about an axle 201 of the load bearing frame 200. Two of the wheels 310a, 310b may rest in ground contact on a level surface. Upon meeting a step change in the ground level, rotation of the multi- wheel 300 brings a third wheel 310c into contact to ease transition over the step.

Figure 2 is a side view showing the multi- wheel unit 300 in more detail, with the wheel 310c removed, for illustration purposes. Here the multi- wheel unit 300 includes a rotary support 330 which has a plurality of arms 331 arranged about a hub 332. In use the hub 332 is mounted to the axle 201 on the frame 200. Each arm 331 supports one of the wheels 310. In this example there are three wheels to form a tri- wheel, but different numbers of wheels can be used. The rotary support 330 may further include cut-outs 334 to reduce weight.

The wheels 310 are rotatably supported at or near the ends of the arms 331 by wheel axles 333. The wheel axles 333 may be removably attached to the rotary support 330, for instance by a threaded connection, or they may be permanently fixed to the rotary support 330, for instance by welding or brazing. Optionally, the wheels 310 may be positioned on the inner side, as shown, or on the outer side of the rotary support 330.

The rotary support 330 further includes a plurality of capture points 340 which in use engage with the ratchet unit 400. Here, the capture points 340 are conveniently positioned at or near the ends of each of the arms 331. These capture points 340 suitably protrude outwardly from the rotary support 330, such as generally perpendicularly. In this example the capture points 340 are each an exposed section of the wheel axle 333.

Advantageously, the capture points 340 are easy to manufacture and weight of the wheel unit 300 is reduced. However, in another example the capture points 340 may be separate from the wheel axles 333. In this instance the capture points 340 may be formed separately from the rotary support 330 so that they may be replaced during servicing.

The capture points 340 are located away from the axle 201 on the frame 200 by a distance. In this way the capture points 340 are able to restrict the rotation of the rotary support 330 about the axle 201 when engaged with the ratchet unit 400. In this example the capture points 340 are positioned at the ends of the arms 331, thus maximising the mechanical advantage about the axle 201. Consequently, a light-weight ratchet unit 400 can be used to engage the capture points 340. The number of capture points 340 may be increased or decreased to vary the restriction in the rotation of the rotary support 330.

The wheels 310 each comprise a tyre 312 mounted to a rim 313. The tyre 312 may be pneumatic or solid and the rim 313 may include cut-outs 314 to reduce weight. Optionally, the wheels 310 may be removably attached to the axles 333 so that the wheels 310 may be replaced during servicing. In this instance the wheel 310 may be held in place by a nut threaded onto the end of the axle 333.

Figure 3 is a side view showing the ratchet unit 400 in more detail. The ratchet unit 400 includes a ratchet arm 410 and a ratchet finger 420 for engaging the capture points 340. The arm 410 is rotatably mounted about an arm pivot 411. In this example, the arm pivot 411 comprises a cylindrical shaft which is connected to the frame 200. Suitably, the arm pivot 411 is carried by a linking plate 415 which couples to the frame 200 by two clamps 416, which allows the ratchet unit 400 to be mounted and demounted quickly and without substantial modification of the frame 200. In another example the arm pivot 411 is fixed directly to the frame 200, for instance by drilling a hole into the frame 200 and pressing or screwing the arm pivot 411 into the hole.

Figures 4 to 6 show movement of the wheel assembly 250 in use. Again, the wheel 310c has been removed, for illustration purposes. Firstly, Figure 4 shows the ratchet unit 400 resting in a disengaged position where the arm 410 lies clear of the wheel unit 300. In this position the ratchet unit 400 does not engage the capture points 340. Consequently, the rotary support 330 is able to rotate freely about the axle 201.

Figure 5 shows the ratchet unit 400 now moved to an engaged position wherein the ratchet arm 410, and more specifically the ratchet finger 420, engages each of the capture points 340 in turn and behaves as a pawl. Consequently, relative rotation of the wheel unit 300 about the axle 210 is restricted. In this example the wheel unit 300 may freely rotate backwards (clockwise or against the ordinary forward direction of travel), but the ratchet inhibits rotation forwards (anti-clockwise).

Figure 6 shows the ratchet unit 400 now in a lifting position which lifts one of the wheels 310 away from the ground. In this case the leading wheel 310a has been raised or inclined upwardly compared with the trailing wheel 310b. Hence, the trailing wheel 310b is ground contacting whilst the leading wheel 310a tends to remain clear of the ground surface. Consequently, the rolling resistance of the wheel assembly 250 is reduced.

Furthermore, it can be easier to manoeuvre the wheelchair (or other handcart) when the number of wheels which are in contact with the ground surface is reduced. It is anticipated that the primary or normal operating configuration of the wheelchair 100 will be that shown in Figure 6, where the wheel 310a has been raised, as this greatly improves manoeuvrability of the wheelchair. The wheel 310a would, however, require to be returned to the ground in order to descend stairs or the like.

Referring again Figure 3, the ratchet unit 400 will now be discussed in more detail. Here the ratchet arm 410 is elongate and extends lengthwise between a distal end and proximal end which are arranged on opposite sides of the arm pivot 411. The proximal end of the arm includes an arm handle 414 for actuating the arm 410. The distal end of the arm includes the ratchet finger 420 which is rotatably connected to the arm 410. In this example the arm 410 and ratchet finger 420 are connected via a ratchet finger pivot 421. The ratchet finger pivot 421 may comprise a fixture, such as a bolt, rivet or shaft and split pin, inserted through a hole in the ratchet finger 420 and arm 410.

The ratchet finger 420 may include a knuckle which is arranged to engage a stop on the arm 410. The knuckle engages with the stop to lock the ratchet finger 420 in an extended position. The ratchet finger 420 may however still rotate toward to the arm 410 into a folded position, thus allowing the capture point 340 of the wheel unit 300 to pass the ratchet. The ratchet finger 420 may be biased into the extended position by a torsion spring or other similar device.

The ratchet finger 420 suitably includes a capture surface 425 to arrest one of the capture points 340 during rotation of the wheel unit 300. Optionally, this capture surface 425 has a recess to hold securely the capture point 340. In this example the recess is concave in shape. The ratchet finger 420 may also include a disengaging surface 426 which easily passed by the capture points 340 during opposite rotation of the rotary support 330. The disengaging surface 426 is flat to allow the capture point 340 to slide along and in doing so temporarily press the ratchet finger 420 toward the folded position.

Notably, the distance between the arm pivot 411 and actuation handle 414 is greater than the distance between the arm pivot and the ratchet finger 420, giving a mechanical advantage such as when actuating the ratchet arm 410 to lift the leading wheel.

As shown in Figure 3, the ratchet unit 400 suitably includes a lock assembly 450, which allows the arm 410 to be retained in one or more positions. In this example, the arm 410 is retained in either the disengaged position (see Fig. 4) or the lifting position (see Fig. 6). Suitably, the arm 410 is configured to engage with corresponding lock positions which in this case are formed on the frame 200 such as by the linking plate 415. In this example, the lock assembly 450 has a sleeve 451 which is arranged to slide up and down the proximal end 413 of the arm 410. Arranged at one end of the sleeve 451 is a lock handle 452 which contains an internal spring (not shown). At the other end of the sleeve 451 is a boss 453. The lock handle 452 is used to slide the sleeve 451 along the arm 410. Conveniently, the lock handle 452 and the arm handle 414 are arranged so that they may both be actuated simultaneously by a single hand of a user. The boss includes a stop which is arranged to be inserted into a corresponding slot or recess 455 or 456 in the linking plate 415.

Consequently, the arm 410 can be locked in the engaged position by the engaged slot 455. The arm 410 can also be locked in the disengaged position by inserting into the disengaged slot 456. The sleeve 454 may be biased towards the arm pivot 411 by means of a spring or similar device.

Figure 7 is a side view showing the example brake unit 500 in more detail. The wheels 310 which are arranged to co -rotate with a central hub 530. In use the central hub 530 is rotatably mounted to the axle 201 of the frame. Advantageously by utilizing the wheels 310 as part of the braking unit 500 the weight and size of the brake unit 500 is reduced.

The wheels 310 each co -rotate with a central hub 530 and the braking mechanism brakes rotation of the hub 530, thereby causing braking of each of the wheels 310. As one example, an outer periphery of each wheel 310 engages the hub by friction, which is particularly suitable for pneumatic tyres. As another example, a solid tyre is cut or moulded into a gear surface 521 and engages a corresponding gear shape 531 around the hub 530. Advantageously, the braking system is simple, robust, reliable and light-weight.

The wheels 310 are braked by applying a braking force to the central hub 530. The braking force can be applied directly to the central hub 530 or via a further rotary member constrained to rotate with the central hub 530. In another example the braking force is applied directly to one of the wheels 310 or a further rotary member constrained to rotate with the wheel 310.

The braking force can be applied using a rim brake, drum brake, disc brake or other similar device. The calliper of the brake may be fixed to the frame 200 via a linking plate which is separate or integral to the linking plate 415 shown in Figure 3. Alternatively the calliper is fixed directly to the frame 200, for instance by clamping a bracket around the frame. The brake is actuated from an actuator 510, as shown in Figure 1. In this example, the brake actuator 510 is attached to handlebars 202 on the frame 200 to be easily accessible by a carer who stands behind the wheelchair. In another example, the brake actuator 510 is disposed on the frame 200 in a position which is convenient for a user in the wheelchair 100.

The multi-wheel unit 300, ratchet unit 400 and brake unit 500 are generally assembled from components made from light-weight, high-strength materials, such as alloys, plastics, resins or composites. Figure 8 is a side view of a wheelchair 1000 as provided in another example embodiment. Like components of the wheelchair 1000 shown in Figure 8 with the wheelchair 100 shown in Figures 1 to 7 share the same reference numerals, incremented by 1000.

As with the wheelchair 100, the wheelchair 1000 includes a load bearing frame 1200, and a wheel assembly 1250. The wheel assembly 1250 includes a multi-wheel unit 1300, a mechanism 1400 for causing the multi-wheel unit 1300 to rotate relative to the frame 1200, and a brake unit 1500. Only the substantive differences between the wheelchair 1000 and the wheelchair 100 of Figures 1 to 7 will be described in detail herein.

In this embodiment, the mechanism 1400 for causing the multi-wheel unit 1300 to rotate relative to the frame 1200 is of different structure and operation to that of the wheelchair 100. The mechanism is better shown in Figure 9, which is an enlarged side view of the multi- wheel unit 1300 (with a wheel 1310c removed, for illustration purposes), and Figure 10, which is a further enlarged and schematic side view of the mechanism 1400. Parts of the multi- wheel unit 1300 are shown in broken outline in Figure 10, for illustration purposes.

The wheelchair 1000 comprises two of the wheel assemblies 1250, one of which is shown in the Figures. The mechanism 1400 includes a lever arm 1410 which extends between at least one of the multi-wheel units 1300 and the frame 1200. In the illustrated embodiment, a separate such lever arm 1410 is provided for each multi-wheel unit 1300, although it will be understood that the multi- wheel units 1300 may be arranged so that a single such lever arm 1410 can be employed to cause both multi- wheel units to rotate relative to the frame 1200.

The mechanism 1400 also includes a hook and recess arrangement 1420, 1340 with one of the hook 1420 and the recess 1340 provided on the multi-wheel unit 1300. The recess 1340 or hook 1420 can be provided as a separate component coupled to a wheel support 1330 of the multi- wheel unit, or provided integrally with the support 1330. In the illustrated embodiment, the recess 1340 is provided in a separate ring 1342 which is coupled to the support 1330.

The lever arm 1410 is movable between two positions to rotate the support 1330 and raise one of the wheels 13 lOa-c off the ground. The lever arm 1410 is shown in Figures 9 and 10 in a first position, where both wheels 1310a, b are on the ground. Initial movement of the lever arm 1410 away from the Figure 9/10 position causes the hook 1420 to move to engage with one of the recesses 1340. Continued movement of the arm 1410 then causes the multi-wheel unit 1300 to rotate relative to the frame 1200, so that no more than one wheel 13 lOa-c on the multi- wheel unit 1300 is in contact with the ground.

In the illustrated embodiment, three recesses 1340 are provided and are in the ring 1342, and a single hook 1420 is provided and is on the lever arm 1410. It will be appreciated however that a number of hooks may alternatively be provided on the multi- wheel unit 1300 (such as on the ring 1342), and a recess on the lever arm. Also, any suitable number of hooks 1420 and recesses 1340 may be provided. Typically however the number of hooks 1420 or recesses 1340 of the locking mechanism which are provided on the multi- wheel unit 1300 is equal to the number of wheels 13 lOa-c on the multi- wheel unit.

The hook 1420 and recesses 1340 operate as a ratchet, which allows rotation of the multi- wheel unit 1300 in one rotational direction. The allowed rotation of the multi- wheel unit 1300 is backwards (clockwise or against the ordinary forward direction of travel), which corresponds to ascending a stair, kerb or the like. The ratchet thus inhibits rotation forwards (anti or counter-clockwise). The way in which this is achieved will now be described, with reference also to Figures 11 to 13, which are side views showing movement of the wheel unit 1300 in use.

The lever arm 1410 is connected to a detent plate 1415 which defines a first position of the lever arm in which the hook 1420 and a recess 1340 are not engaged (Figure 11), and a second position of the lever arm 1410 in which the hook 1420 and a recess 1340 are engaged (Figure 13). In the engaged position of the hook 1420 and the recess 1340, the multi- wheel unit 1300 has been rotated relative to the frame 1200 so that no more than one wheel 13 lOa-c on the multi- wheel unit is in contact with the ground.

The hook 1420 is mounted to pivot between a deployed position (Figure 13), in which it engages one of the recesses 1340 to restrict rotation of the multi- wheel assembly 1300 in at least one rotation direction, and a retracted position (Figure 11), in which the hook 1420 does not engage any of the recesses 1340. A keeper 1458 is provided and is mounted on the detent plate 1415. The hook 1420 can engage the keeper 1458 when in the retracted position and so be held away from the recesses 1340. The hook 1420 is biased towards the deployed position, typically by means of a suitable spring such as a compression or torsion spring, although other suitable means may be employed. Equally, the hook 1420 may be biased towards the retracted position, if desired. The keeper 1458 defines an inclined ramp 1468 which assists in the movement of the hook 1420 between its engaged and disengaged positions.

The lever arm 1410 acts on the hook, directly or indirectly, to cause it to move in the direction which is opposite to the direction in which the hook is biased. In the illustrated embodiment, the hook 1420 is biased towards the deployed position, and the lever arm 1410 acts on the hook to urge it away from the recess 1340, so as to engage the keeper 1458. The lever arm 1410 pivots about an axis which is coaxial with the axis about which the multi-wheel unit 1300 rotates relative to the frame 1200, and functions as a class two lever. A class two lever is one in which the load is applied at a point between the fulcrum and the applied effort. The lever arm includes a sleeve 1451 which can slide along the arm 1410 to release a lock assembly having a latch comprising a stop 1462 located in a slot, recess or channel 1455. This allows the lever arm 1410 to be moved between its first position (Figures 10 and 11) and its second position (Figure 13). The slot 1455 is shaped to define detents 1464 and 1466 for the stop 1462, to hold the lever 1410 in its first and second positions.

In use, and when it is desired to raise the wheel 1310b off the ground, the mechanism 1400 is operated as follows. A lock handle 1452 is raised to move the stop 1462 upwardly, to disengage the stop from the detent 1464. The lever arm 1410 is then pivoted in a clockwise direction about the axle 1201 using the handle 1414. Figure 12 shows the lever arm 1410 following release of the stop 1462 from the detent 1464, and after partial rotation of the lever arm, where the stop is located part-way along a length of the slot 1455. As the lever arm 1410 rotates from its first position, the hook 1420 is carried with the lever arm and so moves off the keeper 1458. Continued rotation of the lever arm 1410 causes the hook 1420 to travel down the inclined ramp 1468, under the biasing action of the spring, as shown in Figure 12. When the lever arm 1410 has moved sufficiently far that the hook 1420 is released from the keeper 1458, the hook moves radially outwardly to engage in one of the recesses 1340. As shown in the Figures, the recesses 1340 are circumferentially spaced around the ring 1342, and arranged such that a recess will be located in a position where it is ready to be engaged by the hook 1420 when it is released from the keeper 1458. This is the situation when the wheels 1310a, b and front steering wheels 1311 (one shown) of the wheelchair 1000 are in a common plane. It will be understood however that, depending upon a rotational position of the wheel support 1330 relative to the frame 1200, a recess 1340 may not be suitably positioned to receive the hook 1420. Such may occur if the lever arm 1410 is operated when the wheelchair 1000 is on uneven ground, or during ascent up stairs or a kerb, for example. In that event, the hook 1420 will run along an inside surface of the ring 1342 until such time as a recess 1340 presents itself for engagement. The biasing force imparted on the hook 1420 will then cause the hook to engage in the recess 1340.

Following engagement of the hook 1420 in a recess 1340, the lever arm 1410 is further rotated, to bring it to the position of Figure 13. This movement causes the wheel support 1330 to be rotated clockwise, lifting the frontmost wheel 1310b off the ground. The movement of the lever arm 1410 has now been completed, and the sprung lock handle 1452 can be released. The sleeve 1451 then acts to move the stop 1464 down into the slot detent 1466, which retains the wheel 1310b in the raised position.

The arrangement of the hook 1420 and the recesses 1340 therefore acts to hold the wheel assembly 1300 in the position of Figure 13 until such time as the lever arm 1410 is operated to return to the first position shown in Figure 11. Rotation of the support 1330 in the forward or anti/counter-clockwise direction is thus prevented by engagement of the hook 1420 in the respective recess 1340. However, rotation of the support 1330 in the reverse or clockwise direction is still possible. This enables the wheelchair 1000 to be moved up a stair, kerb or the like without requiring the lever arm 1410 to be operated to return the raised wheel 1310b to the ground. This is possible due to the shape of the recesses 1340 and the hook 1420. Specifically, each recess defines an inclined surface or ramp 1343 which faces a shaped outer surface 1421 of the hook 1420. When the support 1330 is rotated in the clockwise direction (such as during climbing of a stair or kerb), the ramp 1343 of the recess 1340 in which the hook 1420 is engaged comes into contact with the hook surface 1421. Continued rotation of the support 1330 causes the ramp 1343 to urge the hook 1420 against the biasing action towards its retracted position, so that the recess may pass the hook. The hook 1420 then runs along the internal surface of the ring 1342, engaging and disengaging each recess 1340 in turn (depending upon the number of rotations of the support 1330 which take place). When the climbing operation has been completed, the hook 1420 will reside in one of the recesses 1340, and so will prevent forward rotation of the support 1330 and thus retain one of the wheels 13 lOa-c in a raised position.

Turning now to Figures 14 and 15, there are shown detailed perspective views of part of another example embodiment of a multi-wheel unit 2300, illustrated in different positions which show movement of the wheel unit in use. Like components of the multi- wheel unit 2300 with the unit 300 shown in Figures 1 to 7, and with the unit 1300 shown in Figures 8 to 13, share the same reference numerals incremented by 2000 and 1000, respectively. The multi- wheel unit 2300 can be incorporated into the wheelchair 1000 shown in Figure 8 in place of the unit 1300, and will be described in relation to the wheelchair 1000. The multi- wheel unit 2300 is similar to the unit 1300, and only the substantive differences will be described herein.

The multi-wheel unit 2300 is shown in Figure 14 in a position corresponding to that of the unit 1300 shown in Figure 11, where two wheels are on the ground. The multi- wheel unit 2300 is operated to raise one of the wheels in the same manner as described in relation to Figures 8 to 13, and is shown in Figure 15 following completion of such movement.

In this embodiment, the multi-wheel unit 2300 comprises a rotary damper unit 2600 which is coupled to a support 2330 on which wheels (not shown) are mounted for rotation relative to the support. The damper unit 2600 is of a known type, and is arranged to provide a damping torque to control rotation of the support 2330 relative to the frame of the wheelchair 1000. The damper unit 2600 is typically arranged to control rotation in one rotational direction, and this will usually be the forward rotation direction, which corresponds to a descent down a stair, kerb or the like. In the drawings, this corresponds to an anti-clockwise (or counter-clockwise) rotation of the support 2330 relative to the frame of the wheelchair 1000, when viewed from the side as shown in Figure 8. This addresses a problem with prior handcarts, such as wheelchairs, having multi- wheel assemblies whereby such a descent can result in the wheel which is not in contact with the ground rotating at a velocity which causes the wheel to impact off the next lower stair or the ground. This can lead to discomfort for a user of the wheelchair, damage to components of the wheelchair (in particular the wheels or other components of the multi-wheel unit), the generation of undesired impact noise, and possible damage to the stairs.

The damper unit 2600 is arranged so that it does not provide a damping torque when the support 2330 of the multi-wheel unit 2300 is rotated in the opposite direction, that corresponds to climbing a stair, kerb or the like. In the drawings, this corresponds to a clockwise rotation of the support 2330 relative to the frame of the wheelchair 1000, when viewed from the side as shown in Figure 8. In this way, the damper unit 2600 does not restrict rotation of the support 2330 during ascent of a stair, kerb or the like, which would otherwise make the act of ascending more challenging. However, it will be understood that the damper unit 2600 may, if desired, be arranged to provide a damping torque for rotation of the support 2330 in the reverse or clockwise direction, or to provide a damping torque in both rotation directions, if desired.

The damper unit 2600 comprises a housing 2602 which is secured to the frame 1200 of the wheelchair 1000 by a mounting plate 2413. Alternatively the housing 2602 can be secured to a detent plate 2415 of the unit 2300, which is in-turn mounted to the frame 1200. The housing 2602 defines an internal chamber (not shown) in which a rotary member (also not shown) is mounted for rotation relative to the housing. The chamber contains a relatively viscous fluid, such as an oil, which is forced through an orifice or groove when the rotary member rotates, to thereby resist rotation of the rotary member. A shaft 2604 is coupled to the rotary member and extends out of the housing 2602. The shaft 2604 carries a spur gear 2606 at an end opposite the housing 2602. The damper unit 2600 also comprises a clutch mechanism (not shown) which functions in such a way that the rotary member is only caused to rotate, and thus to provide a damping torque, when the wheel support 2330 is rotated in one direction. Suitable rotary damper units are commercially available from many different sources. In these rotary damper units, the damping torque which is generated depends on the viscosity of the fluid and the configuration of the orifice.

Rotation of the wheel support 2330 may be damped using alternative damper units. For example, a damper unit comprising friction pads may be employed. The damper unit would typically employ a clutch so that the damping effect is only provided in one rotation direction.

Where the wheelchair 1000 is of a fixed (i.e. non- folding type), a single damper unit 2600 may be provided for controlling rotation of both of the multi- wheel units 2300 on the wheelchair. Typically however, and particularly on a folding wheelchair, a separate damping unit 2600 will be provided for each multi-wheel unit 2300. It will be understood that, where two such damper units 2600 are provided, each will be configured to permit rotation in the opposite rotational direction.

In this embodiment, the support 2330 of the multi-wheel unit 2300 comprises a gear ring 2342 which defines recesses 2340 of similar shape and orientation to the recesses 1340 of the multi- wheel unit 1300 shown in Figures 8 to 13. The gear ring 2342 is formed as a separate component which is coupled to the wheel support 2330, although may alternatively be formed integrally with the support. The gear ring 2342 has external spur gear teeth 2344, which mesh with teeth of the spur gear 2606 on the damper unit shaft 2604. In this way, rotation of the support 2330 is transferred to the damper unit by means of the meshed teeth on the gear ring 2342 and the damper spur gear 2606. Rotation of the gear ring 2342 in one direction causes a contra-rotation of the damper gear 2606, and thus of the damper shaft 2604.

As will be understood from the foregoing description, a rotation of the wheel support 2330 occurs when the wheelchair having the multi-wheel unit 2300 ascends or descends a set of stairs, kerb or the like. As discussed above, the damper unit 2600 generates a damping torque when the support 2330 is rotated in the forward direction, to control rotation of the support 2330, and thus the associated wheels, when descending stairs. The damping torque slows the rotation of the wheels and assists in addressing the problems associated with prior multi-wheel units, discussed above. A damping torque is not generated when the support 2330 is rotated in the opposite direction.

Turning now to Figure 16, there is shown a detailed exploded perspective view of another brake unit 2500, shown incorporated into the multi-wheel unit 2300 of Figs. 14 and 15. The brake unit may however be incorporated into the multi- wheel unit 1300 of the wheelchair 1000 shown in Figures 8 to 13, or indeed into the multi-wheel unit 300 of the wheelchair 100 of Figures 1 to 7. Like components of the brake unit 2500 and the brake unit 500 shown in Figures 1 to 7 share the same reference numerals, incremented by 2000. Only the substantial differences between the brake units 2500 and 500 will be described in detail. Reference will also be made to Figure 17, which is an enlarged perspective view of the multi-wheel unit 2300 of Figures 14 and 15, showing further parts of the multi-wheel unit and of the brake unit 2500 of Fig. 16.

The multi-wheel unit 2300 includes inner and outer bearing rings or plates 2344 and 2346 which support the brake shell 2530, and which are typically manufactured from a relatively low friction material. Suitable materials include plastics material, in particular plastics bearing materials such as NYLOTRON™, and other materials such as ceramics. As will be explained below, the bearing rings 2344 and 2346 are secured against rotation relative to the wheelchair frame 1200, and define respective bearing surfaces 2348 and 2350 which contact a body in the form of a hollow cylindrical brake shell 2530. The multi-wheel unit 2300 also includes an outer cap 2352 which has three legs 2354 that define recesses 2356a to c, each recess receiving a respective wheel of the multi-wheel unit, so that the wheels can contact the brake shell 2530. An outer lock plate 2357 is secured to the outer bearing ring 2346 through a central bore 2358 of the outer cap 2352.

The hollow cylindrical shell 2530 is engaged by each of the wheels of the multi- wheel unit 2300 so that it rotates with the wheels relative to the support 2330. The brake unit 2500 also comprises a brake device, indicated generally by reference numeral 2532, which can be actuated to engage the shell 2530 so as to brake the shell, and the wheels in contact with the shell, against rotation relative to the support 2330. The brake device 2532 includes at least one brake pad and, in the illustrated embodiment, includes two brake pads 2534a and 2534b. When the brake unit 2500 is actuated, the brake pads 2534a, b are displaced outwardly to engage an internal surface 2536 of the shell 2530.

A brake actuator 1510 (Figure 8) is mounted on the wheelchair 1000, and is coupled to the brake pads 2534a, b by means of a brake cable 2538, which is connected to a brake arm 2540 by a locking bolt 2542. The brake arm 2540 is secured to a brake pin 2544 which is pivotally mounted to a detent plate 2415, and which extends through an aperture 2345 in the inner bearing ring 2348. The brake pin 2544 is shaped to define an actuating element 2546 which is generally rectangular in cross-section, and which locates in an aperture 2548 defined between the brake pads 2534a, b. The brake pads 2534a, b are pivotally mounted to the inner bearing plate 2348 on a pivot pin 2549, for displacement to engage the brake shell 2530. Operation of the actuator 1510 rotates the brake arm 2540, thereby rotating the pin 2544 and causing the actuating element 2546 to rotate. This increases the width of the aperture 2548, and drives the brake pads 2534a, b apart to cause them to engage the brake shell 2530 and brake the wheels. The pin 2544 and brake pads 2534a, b are biased towards the positions of Figure 17 (typically by suitable torsion springs -not shown) so that, when the brake actuator 2510 is released, the brake pads disengage the brake shell 2530. A clamp 2551 mounted on the detent plate 2415 engages the brake cable 2538, to provide for adjustment of the brake operation.

The multi-wheel unit 2300 and brake unit 2500 are arranged as follows. The gear ring 2342 is secured to the support 2330, with a spacer 2358 located between the gear ring and the support. Where the gear ring 2342 is formed integrally with the support 2330, the spacer 2358 may be dispensed with. The inner bearing ring 2348 is mounted to the wheelchair frame 1200, and a pit pin 2359 having releasable locking members (not shown) extends from the outer lock plate 2357 and engages a female shaft or hub (also not shown) on the wheelchair. The pit pin 2359 enables the entire assembled wheel unit 2300 and brake unit 2500 to be mounted to and released from the wheelchair 1000 as a single assembly. The outer bearing ring 2346 is bolted to the inner bearing ring 2348 with the brake shell 2530 located between the rings. The outer end cap 2352 is secured through the support 2330 and spacer 2358 to the gear ring 2342, and is rotatable as a single assembly. The outer lock plate 2357 is secured to the outer bearing ring 2346 and thereby held against rotation with the outer end cap 2352. In this way, the brake pads 2534a, b are mounted within the brake shell 2530 on the inner bearing plate 2348 and secured against rotation with the support 2330.Although a few preferred embodiments have been shown and described, it will be appreciated by those skilled in the art that various changes and modifications might be made without departing from the scope of the invention, as defined in the appended claims.

Claims

CLAIMS:

1. A wheel assembly for a handcart, the wheel assembly comprising:

a multi-wheel unit having a plurality of wheels, and

2. The wheel assembly as claimed in claim 1 , in which the multi- wheel unit has a plurality of capture points, the number of capture points being equal to the number of wheels on the multi- wheel unit.

3. The wheel assembly as claimed in claim 2, in which capture points are disposed at or near an outer periphery of the multi-wheel unit.

4. The wheel assembly as claimed in claim 1 or claim 2, in which the capture points are provided on a ring which is fixed to the multi- wheel unit.

5. The wheel assembly as claimed in any one of claims 1 to 4, in which the ratchet unit further comprises a ratchet finger which is mounted so that it can be pivoted between an deployed position in which it engages one of the capture points to restrict rotation of the multi- wheel assembly in at least one rotation direction, and a retracted position in which the ratchet finger does not engage the capture points.

6. The wheel assembly as claimed in any preceding claim, in which the ratchet unit includes a lock assembly to lock the ratchet arm in one or more positions.

7. The wheel assembly as claimed in claim 6, in which the lock assembly includes a sleeve which can slide along the ratchet arm by the action of a lock handle disposed at or near the handle of the ratchet arm.

8. The wheel assembly as claimed in any preceding claim, which includes a braking unit for braking the wheels of the multi- wheel assembly, the braking unit comprising:

a central hub arranged to co-rotate with each of the wheels of the multi-wheel unit; a braking mechanism which brakes rotation of the central hub, thereby causing braking of each of the wheels.

9. The wheel assembly as claimed in claim 8, in which an outer periphery of each wheel engages the central hub to co -rotate by friction.

10. A handcart comprising the wheel assembly as claimed in any preceding claim.

11. The handcart as claimed in claim 10, in which the handcart is a wheelchair.

12. A handcart which comprises a load-bearing frame and a pair of multi-wheel units mounted on the frame, each of the multi-wheel units having a plurality of wheels and being mounted on the frame for rotation so that different wheels mounted on the unit can contact the ground, the handcart including a mechanism for causing the multi- wheel units to rotate relative to the frame, the mechanism including a lever arm which extends between at least one of the multi-wheel units and the frame, and a hook and recess arrangement with one of the hook and the recess provided on the multi-wheel unit, in which initial movement of the lever arm causes the other of the hook and the recess to move so that the hook engages with the recess and continued movement of the arm causes the multi- wheel unit to rotate relative to the frame so that no more than one wheel on the multi- wheel unit is in contact with the ground.

13. A handcart as claimed in claim 12, in which the number of hooks or recesses of the locking mechanism which are provided on the multi- wheel unit is equal to the number of wheels on the multi- wheel unit.

14. A handcart as claimed in claim 12, in which the hook and recess arrangement operates as a ratchet.

15. A handcart as claimed in claim 14, in which the ratchet allows rotation of the multi- wheel unit in one rotational direction.

16. A handcart as claimed in claim 12, in which the lever arm pivots about an axis which is coaxial with the axis about which the multi-wheel unit rotates relative to the frame, and functions as a class 2 lever.

17. A handcart as claimed in claim 12, in which the lever arm is connected to a detent plate which defines a first position of the lever in which the hook and recess are not engaged and a second position of the lever in which the hook and recess are engaged and the multi- wheel unit is rotated relative to the frame so that no more than one wheel on the multi- wheel unit is in contact with the ground.

18. A wheel assembly for a handcart, the wheel assembly comprising:

19. A wheel assembly as claimed in claim 18, in which the brake unit body is a hollow cylindrical shell and the brake device includes at least one brake pad located within the shell which, when the brake is actuated, is displaced outwardly to engage the internal surface of the shell.

20. A wheel assembly as claimed in claim 18, in which the body has a textured external surface to promote frictional engagement between the body and the wheels of the multi- wheel unit.