MOBILE CHAIR

Abstract: A mobile chair is disclosed which utilises a narrow backbone frame structure having an upper portion (11) and a bifurcated lower portion (12) interconnected by an articulated hinge arrangement (14). The angle formed between the upper and lower portions may be maintained at the desired angle by a clamp member (13) connected to an offset axis of the hinge arrangement (14) and bolted to the upper portion (11). The frame comprises a seat support member (15) extending from and releasably attached to the hinge arrangement (14) at one end. The other end is supported by a front member (16) which is connected to the front wheel(s) (17). The rear wheels (19) are connected to the lower portion 12 by wheel mounts (18) which may be rotated to raise or lower the height of the lower portion (12) to cause a variation of the orientation of the seat fitted to the frame.

Description: TECHNICAL FIELD This invention relates to frames for mobile chairs such as pushchairs and wheelchairs. Pushchairs traditionally have small rear wheels and are designed to be manouvered by a person standing behind the chair, the chair is not designed to be manouvered by a person sitting in the chair except where motorised. Wheelchairs traditionally have large rear wheels which are arranged to be rotated by a person sitting in the chair. Wheelchairs are designed to be manouvered by either the person sitting in the chair or by someone standing behind the chair. RELATED BACKGROUND ART Mobile chairs are usually difficult to manouver because of their size and weight, additionally, the design of mobile chairs do not allow the feet of the person pushing the chair to be placed under the chair, thus requiring the person to push the chair with extended arms or to take small steps, either of which is uncomfortable to the pusher. The weight of the mobile chair affects its inertia and the force required to manouver the chair. Thus, the lighter the chair the easier it is to manouver and to start and stop. The frames of prior art mobile chairs are rigid and do not allow the seat fitted thereto to be individually tailored to suit the user. There is no provision for readily reclining seat of the chair or for changing the orientation of the seat with respect to the horizontal. GB1,447,949 (Orthokinetics) discloses a wheel chair which is particularly designed for children and which has been devised to simplify the process of moving a wheel chair bound person by automobile. One of the problems with the chair disclosed in this patent is its complexity of design, which increases manufacturing costs and increases the weight of the chair. Furthermore, the chair does not allow adjustment of the seat, nor does it enable a caregiver to place their feet under the chair. DE3,333,570 (Küschall) describes a wheel chair which does enable the caregiver to place their feet under the chair. The problem with this chair is that adjustment of the seat is not possible, and the size of various members makes the chair heavy and difficult to manoeuvre. DISCLOSURE OF THE INVENTION Accordingly, the present invention provides a frame for a mobile chair of the type having rear wheels and at least one front wheel, the frame being arranged to support a seat intermediate the rear and front wheels and to support handle grips for manoeuvring the chair, characterised in that the frame comprises: a substantially narrow backbone member arranged to support the handle grips at an upper portion thereof and having mounts for the securing rear wheels to a bifurcated lower portion thereof; a seat support member extending from the backbone member intermediate the upper and lower portions for supporting the seat thereon; and a front member extending downwardly from the seat support member to support the front end thereof, the front member having mounts at its lower end for connecting at least one front wheel thereto. Preferably, the backbone member is articulated so that the angle between the upper portion and the seat support member may be varied. Preferably, the articulated joint comprises a double hinge arrangement interconnecting the upper and lower portions and forming part of the lower portion wherein the upper portion of the backbone member is connected to a first hinge and a clamp member is connected to a second hinge offset from the first hinge whereby the relative angle between the upper and lower portions is maintained by securing the clamp member to the upper portion. Preferably, the seat support member is releasably connected to the lower portion of the backbone member in the region of the double hinge arrangement. Preferably, the rear wheel mounts are adjusted to vary the effective height of the lower portion of the backbone member. Preferably, the rear wheel mounts effect the height variation by rotation of the axles of the rear wheels about an offset axis. Preferably, the height variation causes approximately a 12° variation in the angle of the seat support member with respect to the horizontal. Preferably, the upper portion of the backbone member, the seat support member and the front member are formed from similar aluminium extrusions each having at least one slot arranged to receive heads of bolts for securing the clamp member, the handle grips, footrests and seat mounting means respectively to the frame. BRIEF DESCRIPTION OF THE DRAWINGS Notwithstanding any other forms that may fall within its scope, one preferred form of the invention will now be described, by way of example only, with reference to the accompanying drawings in which: Figure 1 is a side view of a mobile chair frame incorporating a hinge arrangement and rear wheel mounts according to the preferred embodiment; Figure 2 is a front view of the chair frame of Figure 1; Figure 3 is a view from above of the chair frame of Figure 1; Figure 4 is an enlarged view of the hinge arrangement of the preferred embodiment; Figure 5 and Figure 6 illustrate how the hinge is connected to the frame; Figure 7 illustrates a rear wheel mount in accordance with the embodiment shown in Figure 1; and Figure 8 illustrates a mounting block used to connect the seat and footrests to the frame. MODES FOR CARRYING OUT THE INVENTION As can be seen from Figures 1, 2 and 3, the mobile chair frame comprises a narrow backbone member 10 having an upper portion 11 and a bifurcated lower portion 12. A clamp member or lever 13 is shown connected to the upper portion at one end and its other end being connected to an articulated hinge arrangement 14 which forms part of the lower portion of the backbone frame. Extending from the hinge arrangement 14 is a seat support member 15. The distal end of the seat support member is supported by a front member 16 which is connected to a front wheel arrangement 17. The front wheel arrangement may incorporate a single wheel or two wheels as shown. The front wheel arrangement is castered allowing the mobile chair to be steered. The lower portion 12 of the backbone member is bifurcated to form a fork and in the preferred embodiment the backbone member is in the form of an inverted Y. The lower ends of the inverted Y are fitted with rear wheel mounts 18 to which rear wheels 19 are fitted. The rear wheel mounts 18 may be rotated so that the rear wheels are relocated to a new position 20 as shown in ghost form in Figure 1. The seat support member 15 is releasably connected to the backbone member 10 by a tongue and slot arrangement wherein a tongue (not shown) forms part of the seat support member and is arranged to fit within a groove or slot in the lower portion of the backbone member. The tongue is secured in the slot by means of a hand screw 21. The hinge 14, is depicted more clearly in Figure 4. As can be seen in that Figure, the hinge comprises a main body 25 which has a slot 26 passing therethrough. The slot 26 is arranged to receive the tongue from the seat support member. The top surface of the hinge body is arranged to abutt the seat support member 15. The hinge has two side arms 27 through which two sets of holes 28 are provided to support two axles 29 and 30. Axle 29 connects the upper portion to the hinge and axle 30 connects a clamp member 13 to the hinge. By this arrangement both the clamp member and the upper portion are freely pivotable about their respective axles. However, as the axles are offset when the clamp member 13 is fastened or secured to the upper portion a triangular body or truss is formed preventing rotation of either the upper portion 11 or clamp member 13 about their respective axle. The preferred embodiment utilises an aluminium extrusion containing two extruded slots 31 extending along one surface, each slot 31 being arranged to receive the head of a bolt. The clamp member 13 is secured to the upper portion 11 by means of two bolts 32 placed in respective slots and passing through respective holes in the clamp member, nuts are then placed on the bolts to securely fasten the two members together. To allow the upper portion to pivot, thus varying the angle between the upper portion and the lower portion, the two bolts 32 are loosened allowing the clamp member to slide along the undersurface of the upper portion at the same time the bolts 32 will slide within their respective slots 31. As the hinge 14 is securely attached to the lower portion and the seat support member 15 is securely attached to the hinge 14, the change in relative angle between the upper portion and lower portion also changes the relative angle between the upper portion 11 and the seat support member 15, therefore allowing a seat to be used on the mobile chair which has a back portion which is able to be moved with respect to the seat portion or indeed a seat which has a back portion and a seat portion formed as two separate items and mounted directly to the appropriate parts of the frame of the mobile chair. The seat support member 15 and the front member 16, are made of the same aluminium extrusion as the upper portion 11, the extruded slots providing means for securing the seat to the frame. A footrest may be similarly secured to the front member and because of the slot arrangement, its height may be readily adjusted. Handle grips for manouvering the chair are similarly fastened to the upper portion of the upper portion of the backbone member. Although the preferred embodiment uses twin slots, any other number of slots may be used including a single slot in the aluminium extrusion without departing from the spirit of the invention. Similarly, although two front wheels are shown, the front wheel arrangement may comprise a single wheel, the front wheel or wheels as the case may be, are, of course, pivotally attached to the front member so that the mobile chair may be steered. The rear wheels are attached to respective ends of the forked lower portion of the backbone member by respective wheel mounts 18. Each wheel mount, as more clearly shown in Figure 7, comprises main body 40 which is of substantially U-shaped cross section. Pivotally attached to the main body 40 and passing between its legs is an arm 41 which has a hole 42 through which the axle 43 of the wheel 19 is mounted. The arm 41 is pivotally connected to the mount body 40 at one end and arranged so that it may pivot between two positions such that in the first position the wheel axle 43 is in front of the pivotal axis and in the second position the wheel axle 43 is to the rear of the pivotal axis so that downward pressure on the wheel mount causes the arm 41 to bear against the mount body 40, thereby preventing downward forces from rotating the arm 41. Thus, it can be seen that regardless of the downward force exerted on the mobile chair, the rear wheels will not change from one orientation to the other. To change orientation it is necessary to lift the mobile chair so that no force is applied to the rear wheel about to be changed so that it can be rotated from one position to the other. This may be accomplished by either physically picking both wheels of the chair off the ground or simply by tipping the chair to one side so that one wheel becomes airborne which it may then be rotated to the other position. Placing that wheel back on the ground and tipping the chair in the other direction allows the other wheel to be similarly orientated. By such an arrangement, locking pins are not necessary, however, should the forward orientation not be sufficiently forward of the pivot axis, it may be desirable to incorporate a locking pin to prevent accidental change of orientation. Similarly, a locking pin with appropriate holes passing through the mount body or arm can be provided to allow additional orientations of the rear wheels to be maintained. The change in the location of the rear wheels allows the relative angle between the seats support member and the horizontal to be varied. By changing the rear wheel location the effective height of the lower portion 12 of the backbone member 10 is varied. As the height of the front member is kept constant the relative angle of the seat support member to the horizontal is varied. A similar result could be achieved by varying the height of the front member while maintaining the height of the lower portion constant. The arm 41 may also be used to mount a braking system for the rear wheels of the mobile chair. Mounting blocks 45 as illustrated in Figure 8 are connected to the slots 31 of the seat support member 15 by bolts. The mounting blocks 45 have holes 46 through which the bolts pass. Other holes 47 are provided in which the mounts for the seat are clamped by means of grub screws or set screws (not shown). Alternatively, the seat mounting frame may be bolted directly to the slots 31 of the seat support member 15. The slots 31 of the front member 16 similarly receive the bolts for the mounting blocks 45 used to mount the footrests, the use of the slots 31 allow the height of the footrests to be varied to suit the user. The use of the mounting blocks allows the footrests to be positioned spaced from the front member 16 again to suit the individual requirements of the user. The mounting blocks 45, upper portion 11, seat support member 15 and the front member 16, may be hollow alluminum alloy extrusions to reduce the weight of the frame while maintaining its strength. At the same time, providing a cost efficient method of manufacturing the frame. It should be realised that the mobile chair frame described may be used with either large wheels in a wheelchair configuration or small wheels as in a pushchair configuration. The difference between the two configurations requiring only a change in the length of the lower portion 12 of the backbone member.

Claims: A frame for a mobile chair of the type having rear wheels and at least one front wheel, the frame being arranged to support a seat intermediate the rear and front wheels and to support handle grips for manoeuvring the chair, characterised in that the frame comprises: a substantially narrow backbone member (10) arranged to support the handle grips at an upper portion thereof (11) and having mounts (18) for the securing rear wheels (19) to a bifurcated lower portion thereof (12); a seat support member (15) extending from the backbone member intermediate the upper and lower portions for supporting the seat thereon; and a front member (16) extending downwardly from the seat support member to support the front end thereof, the front member having mounts at its lower end for connecting at least one front wheel (17) thereto. A frame as defined in claim 1, further characterised in that the seat support member (15) is releasably connected to the lower portion (12) of the backbone member. A frame as defined in claim 1 or claim 2, further characterised in that the backbone member (10) is articulated so that the angle between the upper portion (11) of the backbone member and the seat support member (15) may be varied. A frame as defined in claim 3, further characterised in that the articulated joint comprises a double hinge arrangement (14) interconnecting the upper and lower portions and forming part of the lower portion (12) wherein the upper portion of the backbone member is connected to a first axle of the hinge (29) and a clamp member (13) is connected to a second axle of the hinge (30) offset from the first axle, whereby the relative angle between the upper and lower portions is maintained by securing the clamp member (13) to the upper portion (11). A frame as defined in any one of the preceding claims further characterised in that the rear wheel mounts (18) are adjustable to vary the effective height of the lower portion (12) of the backbone member. A frame as defined in claim 5, further characterised in that the rear wheel mounts (18) effect the height variation by rotation of the axle (43) of the rear wheels (14) about an offset axis. A frame as defined in claim 5, further characterised in that the height variation causes approximately a 12° variation in the angle of the seat support member (15) with respect to the horizontal. A frame as defined in any one of the preceding claim further characterised in that the upper portion (11) of the backbone member, the seat support member (15) and the front member (16) are formed from similar aluminium extrusions each having at least one slot (31) arranged to receive heads of bolts for securing the clamp member (13), the handle grips, footrests and seat mounting means respectively to the frame.

Inventors: LAND ANN LOUISE, OGLE CHRISTOPHER LEON, LAND, ANN LOUISE, OGLE, CHRISTOPHER LEON
Applicants: NORTHERN TERRITORY AUSTRALIA, LAND, ANN LOUISE, OGLE, CHRISTOPHER LEON, THE NORTHERN TERRITORY OF AUSTRALIA
Application year: 1988
Main classification: A61G5
IPC codes: A61G5, A47C31, G11C11, G11C5, B62B9, A47C7, A47C4