GB1591577A

GB1591577A - Foldable frame for a wheel chair

Info

Publication number: GB1591577A
Application number: GB52564/77A
Authority: GB
Original assignee: Individual
Current assignee: Individual
Priority date: 1977-12-16
Filing date: 1977-12-16
Publication date: 1981-06-24

Description

(54) FOLDABLE FRAME FOR A WHEEL CHAIR (71) 1, 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 folding frame for a wheel chair.

It is possible with the present invention to provide a wheel chair framing, which by means of simple movements of the hand rapidly can be folded together to form a very compact unit and in spite thereof can exhibit a rigid and light design.

The present invention provides a foldable frame for a wheel chair, including a first and a second undercarriage, the first undercarriage comprising two supporting arms and two wheels, a respective one of said wheels being rotatably supported by each of said supporting arms, and the second undercarriage comprising one or two further supporting arms and one or two wheels respectively rotatably supported thereby, said first and second undercarriages being connected to each other through a central unit for support ing a seat unit, said supporting arms being pivotally connected to said central unit about pivot axes which extend transversely to the axis of rotation of the wheels and to a generally tangential plane common for all wheels, and pivotable between an unfolded position in which the two wheels of said first undercarriage form a pair of wheels having coinciding rotational axes and with the wheel or wheels of said second undercarriage axially displaced from said pair of wheels and a folded position in which the supporting arms of said first undercarriage with the wheels of said pair of wheels are pivoted inwardly closely together and the supporting arm or arms of said second wheel undercarriage with their wheel or wheels pivoted outwardly closely to the outside of said pair of wheels.

The invention will now be described in more detail, reference being made to the accompanying drawings, in which Fig. 1 is a partly broken view of one embodiment of a wheel chair frame as seen from above and in folded out condition, i.e. in its condition of use, Fig. 2 is a corresponding view of the wheel chair frame in a folded together condition, Fig. 3 shows the wheel chair frame from the side with the wheels schematically illustrated in a folded up as well as in a folded out condition and Fig. 4 is a schematic view of a somewhat modified embodiment of the wheel chair frame according to the invention and an example of a seat unit mounted on the frame.

The fundamental idea of the wheel chair frame according to the present invention is the bringing together of all the wheels of the frame. This can be brought about by designing the wheels of one wheel pair in such a manner that they are brought into a position close to each other and by the remaining wheels being pivoted into a position very close to the outside of said wheel pair. In this connection pivotable supporting arms are used, which support the wheels and radiate from a central unit, by means of which arrangement outer dimensions can be obtained which only slightly exceeds the diameter of the largest wheel and exhibits a' minimal width. Thereby, in addition to very simple movements of the hand being necessary, one obtains a surprisingly small power requirement because of the very practical design of the framing.

As is evident from the drawings, the wheel chair frame, illustrated by way of example, is provided with two undercarriages comprising four wheels 1, 2 and is built round a central unit 3, from which four supporting arms 4, 5, one for each one of the wheels, extend. The supporting arms are pivotally journalled in the central unit 3, which is provided with stop dogs 6, 7, 8 in order to limit their pivoting movement. In the illustrated example two of the wheels are considerably larger than the remaining two wheels, the supporting arms 4 belonging to one of the wheel pairs 1 extending in a direction towards its respective wheel axle 9. Both these wheel axles 9 are rigidly connected each one with a respective slewing bracket 10, which is pivotally journalled on the outer end of the corresponding supporting arm 4.Between the supporting arms 4 and their corresponding wheel pair 1 there is provided a locking strut 15, which comprises two parts 26, which are hinged by means of an articulation 16.

The strut is hinged at its extreme ends to the two slewing brackets 10 round a pivot pin 17, which is offset at a distance from the respective slewing bracket bearing of the corresponding supporting arm 4. Moreover the two parts of the strut are provided with stop dogs 18 in between them, which cooperate at the pivot pin 16. The position of said stop dogs 18 is chosen in such a manner in cooperation with the positions of the stop dogs 6 of the supporting arm 4 in the central unit 3 and with stop dogs 19 of the slewing brackets 10 as well as with the length of the strut 15 and the supporting arm and the distance between the pivot pin 17 and the bearing of the slewing brackets 10 in the supporting arms, that an overcenter lock is obtained in the position of use, i.e. the position illustrated in Fig. I.

The two supporting arms 5 belonging to the small wheel pair 2 diverge in angular form from each other and deflect in upwards direction at their outer end (see Fig. 3) which is provided with a bearing sleeve 11. In this sleeve a fork 13 for each one of the wheels is pivotally journalled on the wheel axle 12.

The central unit 3 comprises two relatively pivotable parts 3a, 3b, the two pairs of supporting arms 4, 5 being pivotally jour nalled each one in a respective part. The two parts 3a, 3b are relatively pivotably round an articluation 14, about an axis generally in a plane extending at right angles to the pivoting axes of the supporting arms 4, 5, whereby all the time a good simultaneous bearing against the foundation by all the four wheels 1, 2 even on rugged ground is obtained.

Moreover the deflection in a vertical direction of one pair 5 of the pairs of supporting arms makes a choice possible between two different sizes of wheels just by pivoting the two supporting arms 5 with their corresponding belonging part 3b of the central unit through one half of a revolution relative to the part 3a of the central unit.

At one part 3a of the central unit an upwards extending tubular column 27 is arranged, which is intended to support a seat unit 28, preferably in a detachable mounting, said unit being described more in detail with reference to figure 4.

In order to facilitate the folding together of the wheel chair frame as well as the resetting of the same into the condition of use, the frame in the example illustrated is provided with a synchronizing device 20, which is incorporated into the central unit 3. The synchronizing device 20 comprises a bar 21, which via the articulation 14 extends through the two parts 3a, 3b, of the central unit 3, said bar being axially displaceable and arranged by means of this movement to transmit the pivoting movement of one of the pairs of supporting arms 4 to the other pair of supporting arms 5.This is achieved by the bar 21 of the example illustrated at one of its ends being connected with one of the pairs of supporting arms 4 by means of offset slewing brackets 22, while the bar at its other end is provided with a rack 23, which is engaged by two gears 25, which are pivotally journalled around the pivot pin 24 of the supporting arms and rigidly connected each one with its supporting arm 5. The rack 23 is in the form of threadlike grooves without any pitch, which makes possible that the synchronizing device 20 functions irrespective of the pivoting position of the two parts 3a, 3b of the central unit 3 relative to each other.

The folding together of the wheel chair frame takes place in a very simple manner by releasing the locking device 15 in such a way that the strut 26 is folded outwards round its articulation 16, whereby the supporting arms 4 are pivoted towards each other and the two wheels I are brought together by a parallel displacement of them. By means of the slewing brackets 22 forming part of the synchronizing device 20 the pivoting movement of the supporting arms 4 is transformed into an axial displacement of the bar 21, which in its turn brings about a pivoting of the supporting arms 5 on account of the gears 25 engaging the rack 23.When the two supporting arms 4 have been brought together to a bearing against the stop dogs 8, the large wheels occupy a position parallel and close to each other, while the small wheels 2 on account of the angular shape and the pivoting direction of the supporting arms 5 are bearing against the outside of each one of the large wheels, as is evident from the figures 2 and 3. In a folded up condition, thus, the wheel chair frame occupies a very small width and a length that insignificantly exceeds the diameter of the large wheels. The folding out of the wheel chair frame into its condition of use takes place in a simple manner by pivoting out the two supporting arms 5 of the pair of small wheels and by straightening the strut 26 to the overcenter position.

The seat unit 28, which can be mounted on the wheel chair frame, and which is illustrated by means of an example in figure 4, is provided with a seat 29 with leg and foot supports 30, 31 and can be detachably mounted on the column 27, which makes it possible to place the seat unit in the desired direction with the large pair of wheels or the small pair of wheels in a front position.

Before folding up the frame the seat unit is thus first lifted off, and said unit can likewise be of the folding-up type.

In figure 4 also a somewhat modified arrangement of the journalling of the fork 13 of the small wheels 2 in the bearing sleeve 11 belonging thereto is shown. The sleeve 11 is deflected by a suitable chosen angle from the vertical line in direction towards the tangential point where the wheel 2 engages the ground. This inclination has turned out to give very favourable steering- and driving properties together with the individual capacity of pivoting of the two wheel pairs 1, 2, whereby the swinging tendency of so called pivot wheels of earlier known designs as well as their tendency to place themselves across the intended driving direction have been considerably reduced resulting in a reduction of the risks of accidents.

The invention is not limited to the example of embodiment described above and illustrated in the drawings. By way of example a synchronization between all the supporting arms 4, 5 is not necessary. The supporting arms 5 may instead be provided with some form of locking device, for example a strut extending between the supporting arms 5.

The embodiment of the wheel chair frame illustrated in the drawings can to advantage be equipped with such a strut in order to reduce the loading on the teeth of the synchronization device 20. It can moreover be imagined that the illustrated locking device 15 is of a completely different type, and also the supporting arms 4, 5 can likewise be of another design than the one shown. By way of example the seat unit to advantage can be designed in such a way that it is vertically adjustable suitably also when somebody is seated in the chair. It is not either necessary for the folding up principle according to the invention that the central unit 3 is divided up into two pivotable parts 3a, 3b.

WHAT I CLAIM IS: 1. A foldable frame for a wheel chair, including a first and a second undercarriage, the first undercarriage comprising two supporting arms and two wheels, a respective one of said wheels being rotatably supported by each of said supporting arms, and the second undercarriage comprising one or two further supporting arms and one or two wheels respectively rotatably supported thereby, said first and second undercarriages being connected to each other through a central unit for supporting a seat unit, said supporting arms being pivotally connected to said central unit about pivot axes which extend transversely to the axes of rotation of the wheels and to a generally tangential plane common for all wheels, and pivotable between an unfolded position in which the two wheels of said first undercarriage form a pair of wheels having coinciding rotational axes and with the wheel or wheels of said second undercarriage axially displaced from said pair of wheels and a folded position in which the supporting arms of said first undercarriage with the wheels of said pair of wheels are pivoted inwardly closely together and the supporting arm or arms of said second wheel undercarriage with their wheel or wheels pivoted outwardly closely to the outside of said pair of wheels.

2. A frame according to claim 1 wherein at least the first undercarriage has a link mechanism between said pair of wheels which is arranged to lock the supporting arms of the first undercarriage when in the unfolded position, and also to constrain the wheels of said pair in a substantially parallel relationship in the folded and in the unfolded positions.

3. A frame according to claim 2 wherein said link mechanism comprises a strut provided between said supporting arms, which strut can be folded and at its ends is hinged to said supporting arms via offset brackets in which the respective wheels are journalled, stop dogs being provided to limit the pivoting movements of the link mechanism and said two supporting arms, the locking provided by the link mechanism being overcentre locking.

4. A frame according to any one of the preceding claims wherein the movements of the supporting arms between the folded and unfolded positions are synchronized by means of a synchronizing device provided in the central unit.

5. A frame according to claim 4 wherein the synchronizing device comprises a bar connected to the supporting arms and arranged to be axially displaced by the pivoting of at least one of the supporting arms which axial displacement causes pivoting of the other supporting arms.

6. A frame according to claim 5 wherein the bar is connected at one end portion with the pair of supporting arms belonging to the first undercarriage by means of offset brackets and is provided at its other end portion with gear engaging means which the further supporting arm or supporting arms engage by means of pivotable gearing.

7. A frame according to claim 6 wherein the gear engaging means comprises thread likc grooves without pitch.

8. A frame according to any one of the preceding claims having a holder for a seat unit provided on the central unit comprising a column, on which the seat unit can be detachably mounted facing in a desired direction and can be adjusted to a desired height.

9. A frame according to any one of the preceding claims wherein the central unit comprises two main parts, of which one supports the supporting arms of the first undercarriage, while the other main part supports the supporting arm or arms of the second undercarriage, which main parts are

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. of the small wheels 2 in the bearing sleeve 11 belonging thereto is shown. The sleeve 11 is deflected by a suitable chosen angle from the vertical line in direction towards the tangential point where the wheel 2 engages the ground. This inclination has turned out to give very favourable steering- and driving properties together with the individual capacity of pivoting of the two wheel pairs 1, 2, whereby the swinging tendency of so called pivot wheels of earlier known designs as well as their tendency to place themselves across the intended driving direction have been considerably reduced resulting in a reduction of the risks of accidents. The invention is not limited to the example of embodiment described above and illustrated in the drawings. By way of example a synchronization between all the supporting arms 4, 5 is not necessary. The supporting arms 5 may instead be provided with some form of locking device, for example a strut extending between the supporting arms 5. The embodiment of the wheel chair frame illustrated in the drawings can to advantage be equipped with such a strut in order to reduce the loading on the teeth of the synchronization device 20. It can moreover be imagined that the illustrated locking device 15 is of a completely different type, and also the supporting arms 4, 5 can likewise be of another design than the one shown. By way of example the seat unit to advantage can be designed in such a way that it is vertically adjustable suitably also when somebody is seated in the chair. It is not either necessary for the folding up principle according to the invention that the central unit 3 is divided up into two pivotable parts 3a, 3b. WHAT I CLAIM IS:

1. A foldable frame for a wheel chair, including a first and a second undercarriage, the first undercarriage comprising two supporting arms and two wheels, a respective one of said wheels being rotatably supported by each of said supporting arms, and the second undercarriage comprising one or two further supporting arms and one or two wheels respectively rotatably supported thereby, said first and second undercarriages being connected to each other through a central unit for supporting a seat unit, said supporting arms being pivotally connected to said central unit about pivot axes which extend transversely to the axes of rotation of the wheels and to a generally tangential plane common for all wheels, and pivotable between an unfolded position in which the two wheels of said first undercarriage form a pair of wheels having coinciding rotational axes and with the wheel or wheels of said second undercarriage axially displaced from said pair of wheels and a folded position in which the supporting arms of said first undercarriage with the wheels of said pair of wheels are pivoted inwardly closely together and the supporting arm or arms of said second wheel undercarriage with their wheel or wheels pivoted outwardly closely to the outside of said pair of wheels.

journalled to each other about a pivoting axis which extends substantially along a line which is symmetrically placed relative to the undercarriages and parallel to said tangential plane common to all the wheels.

10. A frame according to claim 9 wherein the supporting arm or arms at least on one of the main parts are arranged in such a manner that the axes of the corresponding wheel or wheels are displaced from the general plane of the pivoting axis of the main parts in a direction substantially at right angles to said tangential plane, and wherein the main parts are pivotable through 180 relative to each other.

I I. A frame according to any one of the preceding claims wherein the wheel or wheels of one undercarriage can be pivoted sidewise about a pivoting axis which is deflected from the vertical by a chosen caster angle.

12. A frame for a wheel chair substantially as herein described with reference to and as shown in the accompanying drawings.

13. A wheel chair having a frame according to any one of the preceding claims.