GB1582469A

GB1582469A - Wheel chairs

Info

Publication number: GB1582469A
Application number: GB29301/77A
Authority: GB
Original assignee: Individual
Current assignee: Individual
Priority date: 1976-07-15
Filing date: 1977-07-12
Publication date: 1981-01-07
Also published as: JPS5318145A; CA1112991A; SE402209B; AU2686477A; SE7608071L; FR2358130A1; DE2731952A1; AU515383B2

Description

(54) IMPROVEMENTS IN OR RELATING TO WHEEL CHAIRS (71) I, SVEN-OLOF BRATTGARD, a Swedish citizen of Storangsgatan 32, S-413 19 Goteborg, Sweden, do hereby declare the invention, for which I pray that a patent may be granted to me, and the method by which it is to be performed, to be particularly described in and by the following statement: The present invention relates to a wheel chair frame which when in use is movable on a base plane.

For a long time there has been a need to impove the stability of wheel chairs during tilting and steering, the designs of conventional wheel chairs often presenting steering difficulties and occasionally the operation thereof can give rise to accidents.

The cause of such accidents has been shown to be an uneven distribution of the load between the wheels against the foundation supporting them. The problem is especially evident in connection with movement on uneven ground, but also minor deviations from a plane foundation may unfavourably affect the steering stability especially in connection with wheel chairs provided with pivot wheels, which when the load is small, can swing out to a position transverse to the drive direction and give rise to considerable difficulties with respect to the control of the vehicle and may even result in the tilting over of the wheel chair.

It is an object of the invention to eliminate or minimise one or more of the disadvantages discussed above.

According to the present invention there is provided a wheel chair frame which when in use is movable on a base plane, the frame comprising a first wheel under-carriage provided with a shaft unit, a first pair of wheels rotatably carried on the shaft unit so as to be parallel to each other in a fixed axial position relative to the first wheel undercarriage, a second wheel undercarriage provided with a pair of shafts, a second pair of wheels each of which is rotatably carried on one of the said pair of shafts, means for supporting a seat unit connected to one of the wheel undercarriages, a first pivoting hinge between the first and second wheel undercarriages for pivoting movement about a pivot axis extending in a direction of the wheel chair frame approximately parallel to the base plane when the wheel chair frame is in its in use position, and the second wheel undercarriage having a pair of spaced apart pivoting hinges each pivotally carrying one of said pair of shafts and each pivoting hinge of the said pair of hinges having a pivot axis extending approximately perpendicular to the base plane when the wheel chair frame is in its use position. Preferably the first pivoting hinge is for limited pivoting movement about the said pivot axis to a predetermined maximal pivoting angle.

Generally the said first pivoting hinge will have a pivot axis extending in a longitudinal direction of the wheel chair frame when the wheel chair frame is in its in use position.

The said first pivoting hinge may extend in a substantially vertical plane through the wheel chair frame when the wheel chair frame is in its in tise position. Advantageously the pivot axis of each said pivoting hinge of the said pair of hinges deviates from the vertical by a predetermined slight angle when the wheel chair frame is in its in use position. If desired the said first pivoting hinge may exhibit a slight inclination relative to the normal rolling plane of the frame when the wheel chair frame is in its in use position.

In one expedient embodiment of the invention the said first pivoting hinge comprises two concentrically arranged pivotally journalled bearing sleeves each connected with one wheel of the said first pair of wheels, one sleeve passing into the other, the said sleeves being provided with limiting means, which comprise at least one slit provided in one bearing sleeve and at least one projection provided on the other bearing sleeve, said projection passing into said slit and co-operating with the margin of the slit to limit said pivoting movement and axial displacement between the bearing sleeves.

In another expedient embodiment of the invention the means for supporting the seat unit is mounted on one of the wheel undercarriages and the other wheel undercarriage is arranged with its bearing means displaced relatively to its plane, which extends symmetrically through the first pivoting hinge and in order to be mounted on the first mentioned wheel undercarriage in alternative pivoting postions. The two alternative pivoting positions are conveniently displaced by an arc of 1800.

The invention also provides a wheel chair including the wheel chair frame as defined in accordance with the invention.

By way of example preferred embodiments of the invention will now be described in detail, reference being made to the accompanying drawings, in which Figure 1 is a schematic side elevational view of a first embodiment of wheel chair frame and including a seat unit, Figure 2 is a plan view of the wheel chair frame illustrated in Figure 1, the seat unit being removed for the sake of clarity, Figure 3 is a partly broken view on an enlarged scale of a pivoting hinge forming part of the wheel chair frame of Figure 1, Figure 4 is a cross-sectional view through the pivoting hinge of Figure 3 along line IV IV, and schematically showing the function of the pivoting hinge, and Figure 5 is a side elevational view of a second embodiment of wheel chair frame.

The fundamental idea according to the present invention is based on the idea of providing an individual pivot hinge capacity between a front wheel undercarriage and a rear wheel undercarriage of a wheel chair frame by means of a pivoting hinge, which constitutes the connection between the wheel undercarriages. By this arrangement a more even distribution of the load between the wheels is obtained by a self alignment of the wheel undercarriages according to the contour of the foundation under constant control by the distribution of load.

When using pivot wheels in one wheel undercarriage, the even distribution of load between the wheels obtained by means of the invention permits the pivot shaft of the pivot wheels to be allowed to deviate from the vertical line by a suitably chosen caster angle, whereby expecially good stability of steering and tilting is obtained for the wheel chair frame according to the invention. On account of the caster angle a selfneutralization of the pivoting position in a sidewise direction of the wheels is obtained in a manner known per se. However, if such a wheel with caster angle receives too small a load, the wheel tends to swing, leading to its finally taking a position transversely of the direction, which drawback thus is eliminated or minimised by means of the wheel chair frame according to the invention.

According to a further development of the fundamental idea as per above an additional improvement of the characteristics of stability of the wheel chair frame is obtained by designing the shaft of the pivoting hinge with an inclination relative to the normal rolling plane of the wheels.

As is evident from the embodiment illustrated in Figures 1 and 2, the wheel chair frame is substantially built of two wheel undercarriages 1, 2, which are connected with each other by means of a pivoting hinge 3, which makes possible a pivoting of the wheel undercarriages relative to each other around a pivoting shaft 4, which in the embodiment illustrated in Figures 1 and 2 extends in a substantially horizontal direction, i.e. parallel to the normal rolling plane 5 of the wheel chair. One wheel undercarriage 1 exhibits a crosswise extending axle unit 6, from the ends of which pivot pins 7 project, on which two wheels 8 are pivotably journalled. A connection part 9 projects from the middle of the axle unit 6 and blends into the pivoting hinge 3.

The second wheel undercarriage 2 exhibits a cross strut 10, to the centre of which the pivoting hinge 3 is connected. From both the ends of the cross strut 10 two arms 11 extend, which at their extreme ends are provided with a pivoting hinge 12. In each one of the pivoting hinges is a pivot wheel 13 pivotably journalled by means of the upper end of a firk 14, the lower end of which is provided with a shaft 15, on which the pivot wheel is rotatably journalled. As is evident from Figure 1 the arms 11 exhibit an inclination relative to the pivoting shaft 4, whereby the pivot hinge 12 is displaced relative to said shaft. At the same time the pivoting hinge 3 is designed in such a manner that the wheel undercarriage 2 can be mounted in alternative ways with an arc of 1800 between them, resulting in the arms 11 being directed either downwards as in the example illustrated in Figure 1, or upwards, so that the pivot hinges 12 will be at different heights. In this manner one and the same wheel undercarriage of the wheel chair framing can be provided with different alternative wheel sizes, which has proven to be an important object to be desired.

A device 16 serving the purpose of supporting a seat unit 17 projects from one wheel undercarriage 1, more particularly its connection part 9. Said device comprises a tube 18 or the like provided with a locking device 19 for the locking of the seat unit in a preferably adjustable height position and pivoting postion. In the example illustrated the locking device quite simply comprises a locking pin, which extends through bores in the tube 18 and keeps a tube 20 projecting from the underside of the seat unit 17 and inserted into said tube 18 in the position set.

In addition to the seat 21 the seat unit 17 exhibits a back rest 22 and a foot rest 23.

The seat unit 17 at least for certain adaptations can be of a folding-up type, the back rest 22 being foldable downwards against the seat 21 and the foot rest 23 being foldable upwards against the underside of the seat.

The design of the pivoting hinge in the embodiment illustrated in Figures 1 and 2 is still more clearly evident from Figures 3 and 4. The pivoting hinge is provided with two bearing sleeves pivotably journalled relative to each other, one inner bearing sleeve 24 being inserted into an outer bearing sleeve 25. The inner bearing sleeve 24 is rigidly connected with the wheel undercarriage 2, more particularly at the centre point of the cross strut 10, while the outer bearing sleeve 25 is rigidly connected with the connecting part 9 of the wheel undercarriage. In order to make possible a dismantling of the framing, the outer bearing sleeve 25 is provided with an inner jointing sleeve 27, by means of which the pivoting hinge 3 is detachably connected with the connecting part 9 by means of screws 28.

The pivoting hinge 3 in the illustrated embodiment is provided with means for limiting the pivoting movement of the pivoting hinge up to a predetermined maximal pivoting angle 2v, as is evident from Figures 3 and 4. These limiting means according to the example comprise two slit shaped cuts in the outer bearing sleeve 25 and a locking pin 30, which extends through bores in the inner bearing sleeve 24, of such dimensions that the locking pin 30 rigidly connects with said sleeve 24 and penetrates into the slit shaped cuts. These cuts are given such dimensions that a locking of the pivoting hinge 3 is obtained in axial sense but permits a pivoting movement of the two bearing sleeves 24, 25 relative to each other within the predetermined maximal pivoting angle of 2v. The slit shaped cuts 29 exhibit edge portions 31, which cooperate with the locking pin 30, thereby limiting its movement.

From the embodiment of the wheel chair framing illustrated in Figure 5 it is evident that the pivoting hinge 3 can be designed with a pivoting shaft 4, which exhibits a suitably chosen angle of inclination u relative to the normal rolling plane of the wheel chair frame. According to the illustrated example an outer bearing sleeve 33 of the pivoting hinge 3 exhibits an angular shape and is provided with a sleeve portion 32 extending coaxially to the pivoting axis 4, in which sleeve portion 32 the inner bearing sleeve 24 penetrates analogous to the embodiment illustrated in Figure 3, and is further provided with a sleeve portion 34, which is parallel to the normal rolling plane 5.

Moreover the pivot wheels 13 have been designed with the pivoting axis of its pivoting hinges 35 deviating from the vertical line by a suitably chosen caster angle p, i.e. with an inclination forwards as measured in the normal direction of travel and located in a vertical plane extending through the wheel chair frame in its longitudinal direction. It is further evident that the seat unit can be mounted in a direction contrary to the one shown in Figures 1 and 2, the wheel undercarriage 2 with the pivot wheels serving as rear wheel undercarriage instead of front undercarriage.

By means of the wheel chair embodying the invention the two wheel undercarriages 1, 2 thus adapt themselves substantially independent of each other to the condition of the ground because of the function of the pivoting hinge 3. Thus the wheel undercarriages 1, 2 individually follow uneven contours of the foundation and maintain contact between said foundation and the wheels, whereby a wholly satisfactory distribution of load in cases of normal unevenness is obtained.However, the limiting means 29, 30, 31 of the pivoting hinge 3 ensure that the pivoting angle v between the two wheel undercarriages 1, 2 is limited to a maximal value, as otherwise unevenness of the foundation would bring about a deterioration of the stability, by way of example on account of a too strong displacement of the centre of gravity, and difficulties due to the fact that one wheel of one of the wheel undercarriages for example would have to be lifted over large size obstacles.

When such a large obstacle is present, one wheel undercarriage occupies the position indicated with a line of dots and dashes in Figure 4, whereby the locking pin 30 will abut against the edge portions 31 of the cuts 29, which thereby prevent a continued pivoting movement between the wheel undercarriages from taking place. This thus results in one wheel of one of the wheel undercarriages hanging in the air instead of for example completely sinking down in a deep depression in the ground.

As was mentioned in the beginning, a combination of good stability of steering and tilting is obtained by, in combination with the pivoting hinge 3, giving the pivoting hinge 35 of the pivot wheels 13 an inclination of a suitably chosen caster angle, whereby a self-neutralizing steering is obtained without risk of swinging effects, which otherwise arises also in connection with very small irregularities of the foundation.

The pivoting hinge eliminates or reduces such demands upon manufacturing tolerances for the wheel chair frame that an uneven distribution of the load on the wheels is not obtained.

The invention is not limited to the embodiments illustrated and described. For simplicity's sake the wheel chair frame illustrated in the embodiment of Figure 5 has been given an obliquely positioned pivoting hinge as well as a caster inclination of the pivot wheel and a reverse forward direction relative to the embodiment illustrated in Figure 1. However, it is within the scope of the invention to visualize that the wheel chair frame can be made with one or several of these characteristics. Moreover one and the same wheel chair frame can be designed with sizes of wheels, which completely depart from the proportions shown, all of the wheels by way of example having the same dimension and by way of example being provided with some form of driving means as an electric motor, friction force drive or the like.

WHAT I CLAIM IS: 1. A wheel chair frame which when in use is movable on a base plane, the frame comprising a first wheel undercarriage provided with a shaft unit, a first pair of wheels rotatably carried on the shaft unit so as to be parallel to each other in a fixed axial position relative to the first wheel undercarriage, a second wheel undercarriage provided with a pair of shafts, a second pair of wheels each of which is rotatably carried on one of the said pair of shafts, means for supporting a seat unit connected to one of the wheel undercarriages, a first pivoting hinge between the first and second wheel undercarriages for pivoting movement about a pivot axis extending in a direction of the wheel chair frame approximately parallel to the base plane when the wheel chair frame is in its in use position, and the second wheel undercarriage having a pair of spaced apart pivoting hinges each pivotally carrying one of said pair of shafts and each pivoting hinge of the said pair of hinges having a pivot axis extending approximately perpendicular to the base plane when the wheel chair frame is in its use position.

2. A wheel chair frame according to Claim 1, wherein the first pivoting hinge is for limited pivoting movement about the said pivot axis to a predetermined maximal pivoting angle.

3. A wheel chair frame according to Claim 1 or Claim 2. wherein the said first pivoting hinge has a pivot axis extending in a longitudinal direction of the wheel chair frame when the wheel chair frame is in its in use position.

4. A wheel chair frame according to any preceding claim, wherein the said first pivoting hinge extends in a substantially vertical plane through the wheel chair frame when the wheel chair frame is in its in use position.

5. A wheel chair frame according to any preceding claim, wherein the pivot axis of each said pivoting hinge of the said pair of hinges deviates from the vertical by a predetermined slight angle when the wheel chair frame is in its in use position.

6. A wheel chair frame according to any preceding claim, wherein the said first pivoting hinge exhibits a slight inclination relative to the normal rolling plane of the frame when the wheel chair frame is in its in use position.

7. A wheel chair frame according to any preceding claim, wherein the said first pivoting hinge comprises two concentrically arranged pivotally journalled bearing sleeves each connected with one wheel of the said first pair of wheels, one sleeve passing into the other, the said sleeves being provided with limiting means, which comprise at least one slit provided in one bearing sleeve and at least one projection provided on the other bearing sleeve, said projection passing into said slit and cooperating with the margin of the slit to limit said pivoting movement and axial displacement between the bearing sleeves.

8. A wheel chair frame according to any preceding claim, wherein the means for supporting the seat unit is mounted on one of the wheel undercarriages and wherein the other wheel undercarriage is arranged with its bearing means displaced relatively to its plane, which extends symmetrically through the first pivoting hinge and in order to be mounted on the first mentioned wheel undercarriage in alternative pivoting positions.

9. A wheel chair frame according to Claim 8, wherein the two alternative pivoting postitions are displaced by an arc of 1800.

10. A wheel chair frame substantially as herein described with reference to Figures 1 to 4 of Figure 5 of the accompanying drawings.

11. A wheel chair including the wheel chair frame as claimed in any preceding

Claims

claim.