WO2023025683A1

WO2023025683A1 - Walker apparatus

Info

Publication number: WO2023025683A1
Application number: PCT/EP2022/073208
Authority: WO
Inventors: Oliver Bishop; Ben CHILDS; John Wakefield-Smith
Original assignee: The Crispa ( Richard Cahn) Charitable Trust
Priority date: 2021-08-27
Filing date: 2022-08-19
Publication date: 2023-03-02
Also published as: GB2610215A; GB202112277D0; GB2610215B

Abstract

A walker apparatus comprising a frame, a saddle, a handlebar and four wheels arranged in a front pair and a rear pair, the frame consisting of a single transverse cross member and four elongate arms, each arm being mounted at its proximal end to the cross member and having mounted at its distal end a stub axle of a wheel, so that in use two arms extend at a downward angle and forwardly from the cross member to hold the front pair of wheels spaced apart in a transverse direction, and two arms extend at a downward angle and rearwardly from the cross member to hold the rear pair of wheels spaced apart in a transverse direction, the saddle and handlebar being mounted by an adjustable mounting to the cross member so as in use to position the saddle: above and forwardly of the cross member; above and rearwardly of the stub axles of the front pair of wheels, and transversely between the elongate arms, the mounting being adjustable so as to enable the vertical height of the saddle, or of the saddle and the handlebar, above the cross member to be varied, in which there is no frame or other structure extending directly between each pair of wheels, and in which there is no structure extending directly between the elongate arms side-to-side apart from the cross member.

Description

Walker Apparatus

Fl ELD OF THE I NVENTI ON

The present invention relates to walker apparatus, that is apparatus which assists a person to walk.

BACKGROUND ART

Many people with physical restrictions use walker apparatus because they require additional support, or assistance in maintaining balance or stability, while walking. Most commonly the physical restrictions are age-related, but people with lower limb or back injuries, recent recipients of replacement hip or knee joints, or with other health conditions which adversely affect their mobility, can benefit from using walker apparatus, as an aid for moving around and/or for rehabilitation of such conditions.

One kind of walker apparatus is the well-known "Zimmer frame" (Zimmer is a trade mark of Zimmer, I nc., USA) , which is a lightweight frame with four waist high legs and horizontal handles at the top of the sides of the frame; a user walks with the frame surrounding their front and sides and their hands provide additional support by holding on to the handles. Early Zimmer frame walkers required the user to lift the entire frame and place it a short distance in front of the user, with the user then walking closer to the frame whilst using the handles for support, and then repeating the process. Having to pick the frame up and using it to support some bodyweight while walking forward could be difficult and/or tiring, particularly for people with limited arm strength, and so the simple early walkers were modified by adding wheels to the front two legs of the frame, removing the need to lift the whole frame for each movement; additional caster wheels or glides are often attached to the rear two legs, such as in US4384713 and JP-2004-105396. These types of walkers all necessitate a two-stage movement, of the frame followed by the user, which is inherently slower than walking ordinarily. They also require the user to support a significant part of their bodyweight using their arms, which is tiresome and frequently uncomfortable; they are also quite slow and difficult to manoeuvre, poor to use over rough surfaces or off road, and not very stable and easy to tip over.

Faced with these problems, and finding Zimmer-style walkers did not meet the requirements for a comfortable walking aid, Aina Wifalk of Sweden developed the four wheeled walker known as the rollator (the term rollator is a genericised trade mark) ; these usually have four large wheels (larger than in a Zimmer frame walker) which are mounted to a frame so that two wheels can caster, handlebars and a built-in bench seat - and often a shopping basket or shelf as well. Rollators can be used as a wheeled Zimmer frame walker, or the user can turn the rollator around and sit on the bench seat, using the handlebars as armrests. EP729737 and JP-H 10-33606 show typical rollators, the latter having a height adjustable saddle instead of the usual bench style seat. The larger wheels in a rollator enable the rollator to move more quickly than Zimmer-style walkers (so brakes are usually provided), the caster wheels make the rollator more manoeuvrable than Zimmer-style walkers, and the seat and handlebars are arranged such that the rollator can be used to move about by a person sitting on the bench seat. Most rollators are arranged so that when the user is walking the frame and the four wheels precede the person, as in a Zimmer-style walker, and so that when the user is sitting on the rollator the frame is reversed and the front, caster wheels are at the rear and the rollator is largely behind the user. I n the seated position, the user is supported as on a chair, so that if the user wants to "walk" while in that position the person must "scoot" his/her legs (i.e. bend them repeatedly at the knee joint) to propel the rollator forwards with the feet. This kind of "scooting" movement is slow and inefficient, and the user in this position adopts a rather unnatural posture which is tiring to the user, and which is not suitable for rehabilitation purposes. Rollators are, like wheeled Zimmer frames, not easy to use over broken ground, and still slow in moving forwards whether the user is standing or "scooting" while seated on the rollator. The design of rollators is such that when used for movement by a seated person parts of the frame and the wheels restrict the free movement of the user's legs and feet (and it is easy for the person's heels to clip a wheel or the frame). Finally, because a rollator seats the user as on a chair, the user's head and arms are at lower levels than they would be when standing: the first can lead to the user being talked down to and/or treated thoughtlessly, in a manner which can be patronising - in the manner of the "does he take sugar?" syndrome, where someone able-bodied asks the carer of a less-abled person about sugar instead of directly asking the less-abled person who is being offered a hot drink; the second means that the brakes (which are usually mounted to the handlebars) are comfortable to use in the standing position, but not so comfortable or easy to use in the seated position.

Whilst rollators can assist a user to move about, their design means that that they are not particularly useful in aiding a person to wa/k- there are many similar designs of apparatus which support a user and enable the user to move about, but in general these do not facilitate the user adopting a natural walking gait; examples of these types of device are disclosed in CN208021621 U which discloses a hobby horse cycle-type apparatus, FR2998537 which discloses a foot-propelled scooter with a saddle, and EP2844207 which discloses a tricycletype device with two front wheels and a saddle which operates in the same way as a hobby horse cycle. Such designs are not very stable (particularly the hobby horse and the scooter) or manoeuvrable in tight spaces, and in the case of the hobby horse and the tricycle too large to be suitable for use indoors.

GB2522187 discloses a four-wheeled walker apparatus which can be used in either a sitting or walking configuration. The user either sits on a seat or saddle between the four wheels, with the seat in a lower position, or stands and uses both the handlebars and the edge of the seat in a raised position. I n the seated configuration, the apparatus has similar drawbacks to the rollator-type walkers, whilst in the standing configuration the arrangement is such that only a small proportion of the user's weight is supported by the seat: a large proportion of the user's weight is supported by the user's arms, with the same disadvantages as with the Zimmer-type walkers described above. I n addition, the two A frames which constitute the two side frames of the device are joined together transversely by the seat and the rear bracing plank and, to provide the necessary structural rigidity, there are also bracing wires extending between the two frames; however, these bracing wires in use impede the user's gait in use. As can be seen in Figure 9 of GB2522187, when the apparatus is in its walking configuration, with the seat in the raised position, the user's rear leg almost contacts the rear bracing plank; it is unclear from GB2522187 exactly where the bracing wires are located, but Figure 9 suggests that, to have any structural effect, they must extend between the seat support column or the frame elements which support the larger front wheels, and such positioning would impede the user's legs, certainly cause the user's stride to be shortened and therefore be less natural than a normal gait. It is also unclear how the devise of GB2522187 can be adjusted so as to be usable in the seat raised, walking configuration. There is therefore a continuing need for a walker apparatus which can provide support and stability to a person whilst that person is able to adopt as natural a gait as possible; at the same time, the apparatus needs to be compact and manoeuvrable enough to be usable indoors, capable of outdoor and off road use and stable in such use, and easy to adapt to users of different heights.

SUMMARY OF THE I NVENTI ON

The present invention is predicated on assisting a user to walk in a normal, erect position and with a normal gait, whilst supporting a significant proportion of the user's weight and helping the user maintain balance throughout. This invention relates to a walker, which is designed to support a user within a frame so that the person's walking movement is generally the same as it would be without the walker present.

The present invention therefore provides walker apparatus comprising a frame, a saddle, and four wheels arranged in a front pair and a rear pair, the frame consisting of a single transverse cross member and four elongate arms, each arm being mounted at its proximal end to the cross member and having mounted at its distal end a stub axle of a wheel, so that in use two arms extend at a downward angle and forwardly from the cross member to hold the front pair of wheels spaced apart in a transverse direction, and two arms extend at a downward angle and rearwardly from the cross member to hold the rear pair of wheels spaced apart in a transverse direction, the saddle being mounted by an adjustable mounting to the cross member so as in use to position the saddle: above (or below) and forwardly of the cross member; above and rearwardly of the stub axles of the front pair of wheels, and transversely between the elongate arms, the mounting being adjustable so as to enable the vertical height of the saddle above the cross member to be varied, in which there is no frame or other structure extending directly between each pair of wheels, and in which there is no structure extending directly between the elongate arms side-to-side apart from the cross member. There may be a handlebar for supporting each of a user's hands, which may be mounted to the adjustable mounting with the saddle.

With such an arrangement, the apparatus is compact, lightweight and can allow the user to stand with the saddle supporting the pelvic girdle and thus all or at least a significant proportion of the user's weight (so that the handlebar does not have to support much of the user's weight, and the user does not have to support much weight through the arms), whilst the user is free to walk with a natural gait without the apparatus affecting the user's stride (this is aided by a narrow saddle) . Because there is no structure (i.e. no member which contributes substantially to the structural strength of the frame, in compression or tension) extending directly between the elongate arms, and in particular no such structure extending beneath the cross member, the entire region beneath the cross member and between the arms is essentially empty, allowing the user the maximum freedom of movement of the lower legs without impinging on any structural parts of the apparatus. I n addition, the apparatus is inherently stable because the user's weight bears down centrally on the frame and thence to the four spaced wheels, preferably so that the user's weight is spread equally between all four wheels, or equally transversely between each pair of wheels but biased toward the front wheels. The apparatus can if desired be used alternatively in the manner of a Zimmer-style walker, with the user not sitting on the saddle but using the apparatus for support through the hands/ arms alone. Unlike the known Zimmer frames, Rollators and walker apparatus of GB2522187 described above, embodiments in accordance with the invention do not utilise the handlebar for steering, instead the user steers the apparatus through the saddle, rather than through the handlebar. The turning moment begins at the users' feet and is transferred to the saddle through their legs. The handlebar is principally present for the stability of the user and to position brake levers rather than being used to induce the turn and steer the walker. This also leads to a beneficial reduction in weight at the top of the apparatus in use, which aids stability because the centre of gravity of the apparatus in use is therefore lower. When using the apparatus it is possible to walk forward, supported by the apparatus, and to turn right or left, without the user's hands being in contact with the handlebar at all. Steering in this way, from the feet, more naturally mimics real walking, and this helps strengthen and rehabilitate the muscles used when walking unaided. We prefer that the saddle be located above the cross member, but in some applications the elongate arms could be made longer so that the cross member is located higher (about the height of the middle of the user's back, for example) and the saddle is located below the cross member. This would make the apparatus heavier, but may give added stability. Therefore it should be understood that this invention encompasses arrangements in which the relative vertical positions of the saddle and the cross member could be construed differently, for example where the saddle is below (or level with) the cross member.

The anatomy of a human user may be defined by three orthogonal planes:

1. a sagittal (or longitudinal) plane which divides the body into right and left parts, and extends forwardly, rearwardly and vertically relative to the user,

2. a coronal (or frontal) plane that divides the body into front and rear parts, and extends to the left, the right and vertically relative to the user, and

3. a horizontal, axial or transverse plane which divides the body into top and bottom parts, and extends forwardly, rearwardly and to the left and the right relative to the user.

The terms "forward", "front", "back" and "rear" and like or related terms used herein should be interpreted in relation to the sagittal plane of the user of the walker, terms such as "left", "right", "transverse" and like or related terms used herein should be interpreted in relation to the coronal plane of the user of the walker, and terms such as "up", "down", "above", "below" and like or related terms used herein should be interpreted in relation to the horizontal plane of the user of the walker.

Suitably the diameters of the wheels, the lengths of the elongate arms and the configuration of the frame may be chosen such that, in use, the cross member is located above the ground at a height slightly higher than the popliteal height of the intended user. Popliteal height is the distance from the underside of the foot to the underside of the thigh at the knees for someone seated. This height greatly varies between ethnic groups. For British people, the median popliteal height is 440 millimetres for men and 400 mm for women, while Japanese men have a popliteal height of 400mm and women 360mm. So for British users a suitable cross member height would be 440 - 450 millimetres. We have found that, because in a normal walking gait the upper leg swings in an arc front to rear, while the lower leg swings though a slightly larger arc front to rear but from an axis at the knee, if the crossmember is above the user's popliteal height it is unlikely to impede either the larger swing of the lower leg or the smaller swing of the upper leg when the user adopts a normal walking gait. This makes apparatus in accordance with the invention capable of providing effective support without interfering with gait, so the apparatus is suitable for rehabilitation purposes (i.e. helping a user to walk normally) as well as assisting the frail or physically unstable. Also the frame and wheels (which in embodiments of the invention described herein account for a major proportion of the total weight of the apparatus) are all located below the user's popliteal height, which adds to the stability of the apparatus. Preferably there is also no structure extending between the elongate arms front-to-rear.

The front and/or rear arms may be adapted to be selectably variable in length. This allows the height of the cross member above the ground to be varied, to adjust to different popliteal heights of different users/groups of users.

The four wheels in use contact the ground at four distinct points of contact forming a quadrilateral shape, and the saddle in use is preferably located within the vertical extension of the quadrilateral shape, as is the upright user's centre of gravity. As described above, this provides stability for the user. Suitably, the quadrilateral shape is symmetrical about the central sagittal plane. This facilitates the design of the apparatus so as to ensure that it is as light as possible whilst still strong enough to support the intended user, or range of users, which makes the apparatus easy to use. The quadrilateral shape formed by the points of contact of the four wheels on level ground may be a rectangle, square or regular trapezium. The saddle may be located centrally between the front wheels, which maximises side-to-side stability.

Suitably the front pair of wheels may be of substantially larger diameter than the rear pair of wheels. This allows the apparatus to roll over kerbs, uneven pavements, bumps and potholes without being overly influenced or diverted in direction by them, and means the apparatus is suitable for rough ground or for off road use, as well as for use on smooth indoor floors or outdoor ground surfaces. The handlebar may be mounted to the saddle by an adjustable mounting, which allows the apparatus to be adapted for differently sized and/or shaped users, to adjust the vertical position of the handlebars relative to the saddle, to allow the handlebar to be folded when the apparatus is stored, and/or to support a backrest in different positions so that the apparatus is comfortable in use by different users of the apparatus when standing. The rear wheels may be castered, for improved steering and manoeuvrability, and as with the castered wheels in a rollator.

The front wheels are preferably positioned outside the elongate arms to which they are mounted. This arrangement has several advantages: the outside extremity of the device can be defined by the outer surface of the wheels, which allows the user to judge easily whether the walker is likely to brush up against a wall or other obstacle to the side; it ensures that if the walker is going to impact against something during forward movement it is the wheel which takes the first contact rather than a part of the frame (and, the wheel being pneumatic or of rubber or the like, this means that the wheel absorbs any such impact rather than the rigid frame) , and should the wheels become dirty in use through contact with the ground the wheels are distanced as far as possible from the user's legs so as to reduce the likelihood of dirt being transferred from the wheels to the user's legs or clothing.

The elongate arms mounting at least the rear pair of wheels may be foldable, the or each pair either independently or as an integral unit, about the cross member between open and folded configurations. This permits the apparatus to be reduced in size for storage when not in use. Additionally or alternatively the saddle and/or handlebar may be detachably mounted to the cross member. This allows the apparatus to be easily assembled for use and disassembled for storage; in disassembled form the apparatus takes up a small volume, and this may be decreased further if the wheels, particularly the larger front wheels, are detachable from the elongate arms; this is beneficial if the user wishes to travel by car and then be able use the apparatus to walk.

Conveniently, the saddle may be attached to the frame by way of an adjustable mounting adapted to releasably hold an elongate centre post at different positions along its length. Provided the centre post is oriented substantially vertically, this allows the saddle to be easily positioned vertically at a height above the ground approximate to the height of the pelvic girdle of a user of the apparatus when standing. It also permits the saddle height to be moved into position whilst the user is within the frame, and also for the saddle to be moved easily by the user to various heights so as to support different proportions of the user's weight - a user may require more or less weight to be supported comfortably according to circumstances, and as someone using the apparatus for rehabilitation purposes will require less assistance as the rehabilitation takes effect this can be accommodated and the saddle height adjusted quickly and easily. This arrangement eliminates the need to step off and on to the apparatus repeatedly to adjust it to the correct height. It also makes getting on and off easier. We have also found that there is a need to adjust the saddle height or angle slightly in use - lower when traveling up or downhill compared to when on the flat - and a vertically adjustable seat post as used in most bicycles is a suitable feature for this apparatus to be adjusted for this while in use.

I ndependently operable brakes may be provided on one or each wheel of the front pair of wheels. This improves the steering of the device, which can be advantageous if the user's leg strength is especially lacking in lateral directions, and/or if they have reduced strength in their lower limbs. The brakes can also be applied to help when travelling in a straight line on a camber.

I n the described embodiments of the invention a user mounts the device from the front, and this region remain open and unobstructed during use. This allows users to be free from obstructions when they are going about day-to-day tasks, such as picking up groceries from the supermarket shelf. The user's legs are also free which means a parent using the apparatus could kick a football to their child.

BRI EF DESCRI PTI ON OF THE DRAWI NGS

The invention will now be described by way of example and with reference to the accompanying drawings, in which;

Figure 1 is a perspective view of an embodiment of walker apparatus in accordance with the invention;

Figure 2 is a perspective view from another direction of the walker apparatus of Figure 1 ;

Figures 3a and 3b are side elevation views of the walker apparatus of Figure 1 in different states;

Figure 4 is a front view of the walker apparatus of Figure 1 ;

Figure 5 is a perspective view of the walker apparatus of Figure 1 with a backrest fitted; Figures 6a and 6b are schematic illustrations showing how the walker apparatus of Figure 1 may be used in two different ways, and

Figure 7 is a schematic perspective view showing the walker apparatus of Figure 1 disassembled.

DETAI LED DESCRI PTI ON OF THE EMBODI MENTS

Figure 1 shows a walker apparatus 2 (hereafter referred to as a "walker") in accordance with the invention. The walker 2 comprises a frame 4, a set of two handlebars 6, and four wheels, a large front pair 8a, 8b and a relatively smaller rear pair 10a, 10b. The frame 4 consists of four arms, a front pair of arms 12a, 12b and a rear pair of arms 14a, 14b, which are joined together through a cross member 16. The large front wheels 8a, 8b are mounted to stub axles (not shown) at the distal end of the front arms 12a, 12b so as to be directionally fixed but free to rotate independently, and the rear wheels 10a, 10b are mounted to the distal end of the rear arms 14a, 14b so as to rotate as a wheel and also in the manner of a caster about the vertical axis. A saddle 18 is mounted on a vertical pillar 20, which is mounted so as to be adjustable vertically to a cantilever arm 22 (shown more clearly in Figure 3b) extending forwardly from the crossmember 16. Also adjustably fitted to the pillar 20 is an angled rear arm 24 having at its distal end a rotatably adjustable fixing 26 to which the handlebar 6 is mounted and which allows the handlebar to be adjusted so that, preferably, each side of the handlebar is horizontal or comfortable for the user.. The handlebar 6 has two brake levers 28 one of which operates a brake (either a calliper type, or a drum or disc brake) acting by wire (or hydraulically) to brake one of the front pair of wheels 8a, 8b; the other brake lever operates a brake acting on the other of the front pair of wheels 8a, 8b similarly. The two brakes act individually on their respective wheel (i.e. right brake, right wheel, left brake left wheel). Squeezing the handle upwards creates a braking force until the handle is released. But the user can also push the handle down to lock the brake "on", as a handbrake. The handbrake can be released by unsnapping the brake lever. Each of the arms is selectably adjustable in length; this makes the walker 2 easily adjustable for use by people of very different heights. Turning to Figure 2, this shows the walker 2 from the rear. The proximal ends of the rear arms 14a, 14b are pivotally mounted to the internal crossmember 16, and are connected by a spar 30, which is primarily provided for non-structural purposes, such as to hang from or fix to accessories (such as a shopping basket, bags, etc.). The proximal ends of the front arms 12a, 12b are fixedly mounted to the internal crossmember 16 at the ends of the crossmember 16 and outside the mountings of the proximal ends of the rear arms 14a, 14b. Manual locks 32 lock the front and rear arms in the use position shown in Figures 1 and 2, and when unlocked they allow the front and rear arms to be moved into and locked in the closed position shown in Figure 7. I n the open position, the frame's construction supports the user's weight whilst keeping the area around their legs clear. This makes it easy to walk and manoeuvre without a user risking clipping their heels on any of the lower parts of the walker 2 while taking the user's weight.

We have found that the combination of front wheels of about 510mm diameter, rear wheels about 200mm diameter, and a cantilever arm 22 giving a seat post 20 position about 100 mm forward of the cross member 16 gives a good compromise between stability and manoeuvrability within a compact envelope overall. Also, the centre of the saddle 18 (usually coincident with the pillar 20) must be behind the axles of the front wheels 8a, 8b, and it should preferably be behind the rear edge of front wheel. The rear caster wheels can swivel 360 degrees and the front wheels can rotate independently which allows the device and its user to turn within a very small space. This makes the device highly manoeuvrable.

Figures 3a and 3b show the walker 2 with the saddle 18 and handlebars 6 at different heights. I n Figure 3a the saddle 18 and the rear arm 24 are in their lowest positions possible, while in Figure 3b the saddle 18 has been raised by way of the release/locking levers 33 which act on the pillar 20, and another lock lever (not shown) which allows the rear arm 24 to change position and be locked in position along the length of the pillar 20. The height and angle of the handlebars 6 can be adjusted through the adjustable fixing 26, and the saddle 18 can be raised up or down using underseat lever 34. These adjustment can easily be made while the user is standing astride the saddle. This arrangement allows the user to stand over the device and adjust the height of the saddle to perfectly suit their stand over height, it eliminates the need to step off and on repeatedly to adjust the device to the correct height, and it also makes getting on and off easier. I n the front view of Figure 4 it can be seen that the front arms 12a, 12b are straight, while the rear arms 14a, 14b are angled outwardly from their proximal ends to their distal ends (at the rear wheels 10a, 10b) . This allows the points of contact of each pair of wheels to be maximised for optimum stability, while ensuring that the rear wheels 10a, 10b sit within the front wheels 8a, 8b when the frame 4 is folded closed, as in Figure 7, and also accommodates the fixing of the proximal ends of the rear arms to the crossmember inside the proximal ends of the front arms. We have found that the maximum width of the walker at its widest point, the outer extremities of the front wheel stub axles on either side, can be as little as 684mm (which is important for fitting through internal doors, which are a minimum of 700mm wide under present building regulations) , whilst the horizontal front-to-back distance between the axles of the front and rear wheels can be as much as 540mm; the saddle height can be adjustable between a minimum height of 746mm and a maximum of 990mm. This all makes for a walker which is very compact yet stable in use.

I n Figure 5 a back rest 36 has been fitted to the fixing 26 shown in Figure 1 , 3a and 3b on the handlebars 6. Figures 6a and 6b illustrate how the walker 2 can be used by the user sitting on the saddle 18 (Figure 6a), or it can be used by a walking user in similar manner to a conventional rollator simply by reversing the walker 2 relative to the user (as in Figure 6b) . The brake levers 28 are designed so as to be easily operable with the user's hand in either orientation. I n the seated position of Figure 6a, the user is positioned in the centre of the walker with the rear wheels behind them and the front wheels out ahead and wider than their feet. This means the centre of gravity is well within the footprint of the device, making it very stable. Even if the user tries to tip the device over it is very difficult for them to do so which makes the device extremely stable, and very safe. Which is particularly important for a device intended to be used by elderly, injured, or disabled users. Figure 7 illustrates the walker disassembled into four main parts for carriage or storage, namely the two front wheels 8a, 8b, the frame 4 (shown in its folded configuration) with the rear wheels 10a, 10b still attached, and the handlebar/pillar/saddle assembly. Disassembly of the walker reduces the weight of the single heaviest part which a potentially weak or frail user might have to lift. Releasing the seat post clamp and separating the brake cable splitters allows the top half of the walker to be separated from the lower half. Depressing a button on the outside hub of the wheel releases the stub axle pin and allows the front wheels to be removed. Having described a specific embodiment in accordance with the invention it will of course be understood that many variations may be made to the above-described embodiment without departing from the scope of the present invention. For example, the front wheels could be driven, by electric motors in the wheel hubs for example. The rear wheels could be self-centering to encourage the device to travel straight when encountering uneven surfaces. The saddle may be removable/ replaceable saddle, so as to accommodate different pelvic shapes. There may be hooks for bags and/or detachable bags on the crossmember or on the front handlebars to carry shopping and the like. The saddle is preferably one which is narrow, so that it fits between a user's legs without forcing the thighs open and making the user walk with an unnatural gait, instead the narrow saddle allows the user to walk naturally; however, some users may benefit from (or find more comfortable) a wider saddle, more similar to a conventional bicycle seat/saddle. A seatbelt may be provided to give the user additional support; this may be used where the apparatus has a seat back fitted, for example. There may be an added mechanism which allows the saddle to be pivoted on its mounting; this may be by way of an underseat lever, alongside the lever 34 which is for adjusting the height of the saddle. The backrest shown in Figure 5 may have upper extensions so as to give support to a user's upper body under the armpits, or there may be crutch-style arms extending upwards from the crossmember for this purpose; such an arrangement would be helpful for a user with limited upper body strength. A footrest could be provided on or near the distal end of one or both front arms, so that a user with an injury or other impairment to a leg could rest the appropriate foot on the footrest and still use the apparatus for mobility using only the other leg; in order to keep the user's gait as near normal as possible, the footrest should be located as close to the ground as feasible. The drawings show a single, unitary handlebar, but it will be appreciated that there could be two separate handlebars mounted to the cross member, one for each of a user's arms; this would allow the handlebar heights to be separately adjustable. Embodiments of the invention have been described as having a saddle to support the user's pelvis, but it will be understood that any equivalent structure or element which provides adequate support to the user's pelvic girdle whilst allowing the user to walk normally (a sling, for example) could be used, and the word "saddle" should be construed accordingly. The invention has been described as having four wheels, however it should be understood that the rear pair of wheels could be replaced by a single rear caster wheel. Whilst this may have an adverse effect on the stability of the three-wheeled apparatus (if the user were to lose balance or lean backwards and to the side, for example), it would lead to a lighter weight apparatus; in this case, the apparatus might comprise a frame, a saddle, a handlebar for supporting each of a user's arms and at least three wheels arranged in a front pair and a rear wheel, the frame consisting of a single transverse cross member and at least three elongate arms, each arm being mounted at its proximal end to the cross member and having mounted at its distal end a stub axle of a wheel, so that in use two arms extend at a downward angle and forwardly from the cross member to hold the front pair of wheels spaced apart in a transverse direction, and at least one arm extends at a downward angle and rearwardly from the cross member to hold at least a rear wheel spaced from the front wheels in a longitudinal direction, the saddle and handlebar being mounted by an adjustable mounting to the cross member so as in use to position the saddle: above (or below) and forwardly of the cross member; above and rearwardly of the stub axles of the front pair of wheels, and transversely between the front pair of elongate arms, the mounting being adjustable so as to enable the vertical height of the saddle, or of the saddle and the handlebar, above the cross member to be varied, in which there is no frame or other structural member extending directly between the or each pair of wheels, and in which there is no structural element extending directly between the elongate arms side-to-side apart from the cross member. With such an arrangement, the preferred options set out above for the four-wheeled version would apply, where appropriate, to the three-wheeled version.

Where different variations or alternative arrangements are described above, it should be understood that embodiments of the invention may incorporate such variations and/or alternatives in any suitable combination.

Claims

CLAI MS

1. Walker apparatus comprising a frame, a saddle, and four wheels arranged in a front pair and a rear pair, the frame consisting of a single transverse cross member and four elongate arms, each arm being mounted at its proximal end to the cross member and having mounted at its distal end a stub axle of a wheel, so that in use two arms extend at a downward angle and forwardly from the cross member to hold the front pair of wheels spaced apart in a transverse direction, and two arms extend at a downward angle and rearwardly from the cross member to hold the rear pair of wheels spaced apart in a transverse direction, the saddle being mounted by an adjustable mounting to the cross member so as in use to position the saddle: i. above and forwardly of the cross member;

II. above and rearwardly of the stub axles of the front pair of wheels, and ill. transversely between the elongate arms, the mounting being adjustable so as to enable the vertical height of the saddle above the cross member to be varied, in which there is no frame or other structure extending directly between each pair of wheels, and in which there is no structure extending directly between the elongate arms side-to-side apart from the cross member.

2. Walker apparatus as claimed in Claim 1 , in which the four wheels in use contact the ground at four distinct points of contact forming a quadrilateral shape, and in which the saddle in use is located within the vertical extension of the quadrilateral shape.

3. Walker apparatus according to Claim 2, in which the quadrilateral shape is symmetrical about the central sagittal plane.

4. Walker apparatus according to Claim 1 , 2 or 3, in which the saddle is located centrally between the front wheels.

5. Walker apparatus according to any preceding claim in which the front pair of wheels are of larger diameter than the rear pair of wheels.

6. Walker apparatus according to any preceding claim, in which a handlebar is mounted to the saddle by an adjustable mounting. Walker apparatus according to any preceding claim, in which the front wheels are positioned outside the elongate arms to which they are mounted. Walker apparatus according to any preceding claim, in which the elongate arms mounting the rear pair of wheels are independently foldable about the cross member between open and folded configurations. Walker apparatus according to any preceding claim, in which the saddle is attached to the frame by way of an adjustable mounting adapted to releasably hold an elongate centre post at different positions along its length. Walker apparatus according to Claim 9, in which independently operable brakes are provided on each of the front pair of wheels. Walker apparatus according to any preceding claim, in which the rear wheels are caster wheels. Walker apparatus according to any preceding claim, in which the saddle and/or a handlebar is/are detachably mounted to the cross member. Walker apparatus according to any preceding claim, in which each of the front pair of wheels is detachably mounted to its elongate arm. Walker apparatus according to any preceding claim, in which the diameters of the wheels, the lengths of the elongate arms and the configuration of the frame are such that, in use, the cross member is located above the ground at a height slightly higher than the popliteal height of the intended user. Walker apparatus according to any preceding claim, in which the front and/or rear arms are adapted to be selectably variable in length.