CA1311676C

CA1311676C - Foldable wheelchair

Info

Publication number: CA1311676C
Application number: CA000603083A
Authority: CA
Inventors: Rainer Kuschall
Original assignee: Individual
Current assignee: Individual
Priority date: 1988-06-18
Filing date: 1989-06-16
Publication date: 1992-12-22
Anticipated expiration: 2009-12-22
Also published as: JP2950850B2; AU3596689A; EP0347492A1; ATE83645T1; JPH0246845A; DE3876984D1; EP0347492B1; CH678486C1; CH678486A5; ES2037796T3; NZ229592A; AU623401B2

Abstract

ABSTRACT OF THE DISCLOSURE:

A foldable wheelchair is provided with two lateral frames which are pivotally connected by means of two criss-crossed struts lying in a plane transverse to the driving direction. The struts are pivotally connected at their lower ends to each frame and at their upper ends support seat tubes extending parallel to the driving direction. The seat tubes in the unfolded condition of the chair are snapped into securing parts provided on the frames.
Additionally each strut is pivotally connected to the adjacent frame by means of a rotatable latch. The position of the pivot point of the latch and the length of the latches as well as the cross-section of the securing parts at their upper ends and the material of the arresting parts are so selected that the seat tubes are snapped into the securing parts with an elastic deformation of the parts.
The rotatable latches and the snap connections provide a firm coupling between the seat tubes and the frames so that the unfolded chair is quite stable.

Description

The present invention relates to a foldable wheelchair.
In particular, the present invention comprises a foldable wheelchair with two lateral frames which carry the drive and caster wheels and which are interconnected with one another by means of two criss-crossed struts lying in a plane transverse to the driving direction. The struts are interconnected at their crossing point and are pivotable like a scissors about their common pivot axis. The chair also has a seat and backrest~
Foldable wheelchairs of this type, so called cross-strut foldable wheel chairs, have been known for many years. The oldest wheelchairs of this type, which have been known for over 50 years (for example the system according to the patent of Everest and Jennings), consist of a rail- and guide- piece by means of which the seat tube and backrest are connected with the frame, and in front at the seat tube a guide tube which is telescopically retractable into the frame. It has already been proposed for the purpose of saving weight to provide cross-strut foldable wheelchairs without rail- and guide-pieces and without telescopic connections. However, these cross-strut foldable wheelchairs :: /
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1 3 1 1 676 1l have not been perfected since they develop too much free play with folding and unfolding of the wheelchairs, they had too little stability in the unfolded condition without tight , connections between the frame and the seat tubesr and in particular had less stability than the 50 year old construction of Everest and Jennings.
,1 In a well known wheelchair of the foregoing type (DE-PS 37 08 302) the seat is formed in such a ~anner that it 1 is not only shiftable bùt is also tiltable. For this purpose ,1 an expensive support body is provided which forms a seat wlth the seat body. So that the seat can be positioned ,, ordinarily, the carrier body has cutouts by which the struts consisting of tube sections pass through the frame. The seat ,1 is thereby formed so that it is adjustable in practically ,1 each folded or collapsed wheelchair since in principle it is , only necessary to select ~he cutouts and additionally the ~! I
1, hanger hoops provided for these so that they can cooperate with the struts and correspondingly the frame. Nothing is j disclosed in the German Patent D~-PS 37 08 3~2 of these 20~ , special features in this known wheelchair to assist such chairs in achleving simultaneously a saving in weight. Slnce with the known wheelchairs the seat can be fixed, after the I
desired position is achieved, in order assume a nonshiftable (fixed) position with respect to the support frame, it there-!

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-" 1 3 1 1 676 fore follows that the resulting fixing of the seat to the support frame by means of screws also serves to fix the wheelchair in its folded position. That is expensive because it requires screw type means for fi~ing the chair in the folded condition and besides it makes handling troublesome.
It is accord:ingly an object of the present invention to provide a foldable wheelchair of the foregoing type in which the criss-crossed struts are permitted to be firmly connected with the frame without free play in the unfolded condition in a simple manner and at the same time with a saving of weight so that the wheelchair is completely stable in its unfolded condition.
~ccording to the present invention there is provided a foldable wheelchair including two lateral frames which support the drive and caster wheels and which are connected to one another by means of two criss-crossed struts lying in a plane transverse to the driving direction, the struts being rotatably connected at a crossing point and movable in a scissors fashion about their axis of rotation, and a back rest and a seat, characterized in that the struts are pivotally connected at their lower ends to the frames and at their upper ends support seat tubes extending in the driving direction, the seat tubes being snapped into securing parts provided on the frames upon unfolding the wheelchair and each strut being pivotally connected above the intersecting point with the adjacent frame by means of a rotatable latch, the securing parts being elastically deform-able by the seat tubnes when the wheel chair is being unfolded.
According to the present invention there is also provided a foldable wheelchair comprising: two lateral frames each of which supports a drive and a caster wheel and which are connected to one another by means of two criss-crossed struts lying generally in a plane transverse to the driving direction, the struts being rotatably connected with .

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one another at a crossing point and movable in a scissors fashion about a common axis of rotation through the crossing point; a back rest and a seat, the respective struts being pivotally connected at their lower ends to the frames and at their upper ends supporting seat tubes extending in the driving direction, each strut also being pivotally connected above the crossing point with the adjacent frame by means of a rotatable latch to guide the rotational movement of the upper end of the strut and the supported seat tube into an unfolded position with respect to the adjacent Erame upon unfolding of the wheelchair, and securing parts disposed at forward and rearward positions of each frame remotely of the crossing point of the struts for snapping the seat tubes to the respective frames in the unfolded position of the chair.
The wheelchair according to the invention therefo~e consists of a special rotatable latch system and a special snap connection between the seat tube and the securing parts, the securing parts being fixed to the frame and permitting the establishment of a firm connection between the seat tube and the frame. The seat tubes which snap into the securing points produce a stable, very firm connection between the seat and the frame tubes. W~th such connections, practically all free play is eliminated.
Preferably the firm connection between the seat and frame tubes is produced by means of a specially calculated radial dimension of the seat tubP above the rotatable latch connecting point and, above all, a receiving piece precisely constructed for this radius as well as by the seat ra~ius and the material of the piece. The material selection permits the precisely correct elastic de~ormation of the receiving pieces in which the seat tubes then snap in an over-center movement at the securing points and by which ~: :

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, the especially stable and fixed conn~ction is established between seat and frame tubes.
A preferred embodimen-t of the invention is described below as an example withoug limitative manner with reference to the drawings.
Fig. 1 is a perspective view of a preferred embodiment of the wheelchair according to the invention.

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Fig. 2 is the wheelchair of Fig. 1 in a front view.
~ig. 3 is the wheelchair of Fig. 1 in a side view.
Fig. 4a-d is a series of four illustrations showing ' fro~ left to right the process of folding the wheelchair for the purpose of explaining ~he movements of the system consisting of the crossed struts and rotatable latches, and Fig. 5 is an enlarged illustration of a securing ~ part.
;, Eig. 1 shows in a perspective view a foldable wheelchair to lateral frames 10a, 10b each of which consists of steel t~bes and each of which is exhibieed in a rigidly formed construction. At the rear ends a gripping tube 12a ! 12b respectively extends upwardly from each frame. The frames 10a, 10b support drive wheels 14a, l~b and castered wheels 16a, 16b. Each frame 10a, 10b forms a rectangular i frame that is reinforced at the back end by means of a plate ¦
18a, 18b respectively. The plates 18a, 18b are provided with ~ apertures 20a, 20b respectively for securing the axle of the '~referenced drive wheels 14a, 14b at various positlons, for example, according to the body size of the wheelchair rider, -the desired seat slope and so forth. At the front the bent legs of the four sided frame extend at an angle and lead to the~oot rest 22 formed as a hoop, and which is pivotally ¦
~ ~ connected to the one frame 10b and is arrested by the other :: ~ ~: :
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fra~e 10a as wlll be understood from Figs. 1 and 2 without -further explanation.
The two frames 10a, 10b are interconnected by means ,' of two cris~-crossed struts 24a, 24b lying in a plane trans-S i verse to the driving directlon. The struts 24a, 2~b are rotatably interconnected at their crossing poin~ and are i' movable like a scissors about their axis of rotatlon 26 where the intersecting point lies. At the lower ends the struts 24a, 24b are pivotally connected to the frames l~b, 10a re-i spectively. At the upper ends the struts each support a seat ~, tube 28a, 28b respectively. The seat tubes 28a, 28b are rigidly connected with the stru~s 24a, 24b, for example by welding. The struts and the seat tubes are each made for exa~ple like the other out of steel tubing. The seat tubes 28a, 28b extend parallel to the driving direction, as ia I apparent from Figs. 1-3 wlthout further explanation. Two securing or arresting parts 30a,30b are attached to the upper ; horizontal arms of each rectangular frame. The two securing .;
j parts consist of elastically deformable receiving pieces into which the seat tubes 28a, 28b can be snapped. In the lllus- ¦
trated emboai~ent the securing parts are formed totally fro~ ¦
- elastically deformable recelving pieces. A further embodi-ment would consist of a socket which is connected with the frame tube and an elastically deformable receiving piece.

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Fig. S shows in an enlarged illustration a securing part formed as a receiving piece with through holes 31', 31'' which upon mounting the securing part mate with a correspond-1 ing through-hole in the frame, so that each securing part is S ; secured to the frame by means of screws.
The struts 24a, 24b at the lower ends each consist ', of a parallel pivoting tube 34a, 34b for the seat tube 28a, -28b respectively. Each pivoting tube is rotatably attached i ~o the respective frame 10a, 10b. The rotatable attachmen~
1~ ror each consists in the illustrated embodiment of block 36 or 37 which like the securing parts is fixed to the frame and ,' has a blind hole into which the pivotable tube end extends as is clear in Fig. 1 without further explanation. The pivotal tubes can likewise ba steel tubes, that is, connected with , the corresponding strut in the manner described for the seat tubes above. The wheelchair has webbing B1, B2 and B3 made of a textile material or the like which forms the seat back, the seat and correspondingly ~he lower leg support. In accordance with the illustration of Figs. 2-4 each strut 24a, ~i 24b is pivotally connected above the crossing point to the ¦
adjacent frame 10a or 10b respectively by means of a rotat-able la~ch 40a, 40b. The rotatable latches 40a, 40b are each ; rotatably fixed in a corresponding block 42a, 42b which on the one hand is rigidly connected to the referenced frame 10a ,, , :
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or correspondingly 10b, for example likewise by means of a through bolt in the same manner as the securing parts 30a, 30b. The fastening points of the blocks 42a, 42b to the ,I frames 10a, 10b can be seen clearly in Fig. 3. The position-S Ij ing of the pivoting points of the rotatable latches, that is,of the rotatable fastening points to the blocks ~2a, 42b and i to the struts 24a, 24b on the other hand, as well as the length of the rotatable latches are so selected that the seat ii tubes 28a, 28b with their movement along a particular radial ,~ sweep or arc from above toward the securing parts 30a, 30b ,~ fall into the receiving pieces. The radial sweep and the ,i individual phases o movement of the seat tubes are indicated ¦¦ in Fig. S with broken lines. The path of these movements il results in bringing the intersecting struts 24a, 24b into the ¦~ folded position according to the illustrations in Fig. 4a~d lll (from left to right).
¦~ Fig. 5 shows further that the transverse cross-i section of the receiving or arresting parts 30a, 30b corre-Il spond to the seat tubes, 28a, 28b, however, the cross-section ~ is so matched wlth an over-center movement of the seat tubes ,~ when opening so far upwardly that the seat tubes are arrested ~in the receiving pieces with a predetermined elastic ~' deformation of ~hese pieces. The elastic deformation is in-. .

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, dicated in the upper right-hand portion of Fig. S with the dashed lines of the arresting piece 30a.
Since the seat webbing B2 is captured on the seat " tubes 28a, 28b in ~he above-described wheelchair, the snap S connection between the seat tubes and the frames, 10a, 10b is additionally secured by the weight of the wheelchair driver.
i The webbing B2 is cut away in the region of the securing ! piece parts 30a, 30b (see Fig. 3) so that the snap connection ,, of the seat tubes 28a, 28b in the arresting parts is not hindered.

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Claims

1. A foldable wheelchair including two lateral frames which support the drive and caster wheels and which are connected to one another by means of two criss-crossed struts lying in a plane transverse to the driving direction, the struts being rotatably connected at a crossing point and movable in a scissors fashion about their axis of rotation, and a back rest and a seat, characterized in that the struts are pivotally connected at their lower ends to the frames and at their upper ends support seat tubes extending in the driving direction, the seat tubes being snapped into securing parts provided on the frames upon unfolding the wheelchair and each strut being pivotally connected above the intersecting point with the adjacent frame by means of a rotatable latch, the securing parts being elastically deform-able by the seat tubes when the wheel chair is being unfolded.

2. A foldable wheelchair comprising: two lateral frames each of which supports a drive and a caster wheel and which are connected to one another by means of two criss-crossed struts lying generally in a plane transverse to the driving direction, the struts being rotatably connected with one another at a crossing point and movable in a scissors fashion about a common axis of rotation through the crossing point; a back rest and a seat, the respective struts being pivotally connected at their lower ends to the frames and at their upper ends supporting seat tubes extending in the driving direction, each strut also being pivotally connected above the crossing point with the adjacent frame by means of a rotatable latch to guide the rotational movement of the upper end of the strut and the supported seat tube into an unfolded position with respect to the adjacent frame upon unfolding of the wheelchair, and securing parts disposed at forward and rearward positions of each frame remotely of the crossing point of the struts for snapping the seat tubes to the respective frames in the unfolded position of the chair.

3. A wheelchair according to claim 2, wherein the securing parts are secured to the frames and comprise receiving pieces elastically deformable to engage the seat tubes by means of a snap action.

4. A wheelchair according to claim 1, 2 or 3, wherein the position of the pivot points of the rotatable latch and the length of the rotatable latch are so selected that the seat tubes fall into the receiving pieces from above due to their movement toward the securing parts with a predetermined radial sweep.

5. A wheelchair according to claim 1, 2 or 3, wherein the cross-section of the receiving pieces corresponds to the seat tubes but is so matched with the over-eccentric movement of the seat tubes opening upwardly so far that the seat tubes are arrested in the receiving pieces with a predetermined elastic deformation of the pieces.

6. A wheelchair according to claim 1, 2 or 3, wherein the struts at the lower ends support respectively pivotal tubes extending parallel to the seat tubes, the pivotal tubes being secured rotatably to the corresponding frame.

7. A wheelchair according to claim 1, 2 or 3, wherein the seat back and seat are respectively formed from a webbing material and are stretched respectively between two gripping tubes of the frames and the two seat tubes.

8. A wheelchair according to claim 1, 2 or 3, wherein each frame is reinforced by means of a plate in which apertures are provided for securing the axles of the respective drive wheels at various positions.

9. A wheelchair according to claim 1, 2 or 3, wherein a foot rest is formed as a hoop and is pivotally connected to one frame and is arrested by the other frame.