|
(11) | EP 0 439 206 A1 |
| (12) | EUROPEAN PATENT APPLICATION |
|
|
|
|
|||||||||||||||||||||||||||
| (54) | Wheel chair |
| (57) The wheel chair of the invention is remarkable in the respect, that it incorporates
three or more link units between the lateral frames (R), each link unit comprising
two linking arms (1, 2) connected in a common junction point between the two lateral
frames. The junction point comprises two parallel lateral plates (3), between which
the linking arms (1,2) are swingably suspended in mutually displaced swinging planes.
In their unfolded position the two linking arms (1,2) intersect, the swing journal
of the first arm (1) forming a stop face for the second arm (2) and vice versa. The
linking arms (1,2) are provided with toothed wheel segments (11) in mesh. This mesh
or engagement of the teeth secures a synchronization of the movements of the two arms
(1,2) when the chair is folded or unfolded. By simultaneously establishig not-bendable
connections between the junction points, effective guidance in parallel of the two
lateral frames (R) is obtained, when the chair is folded. This guidance in parallel
is a prerequisite of the correct movement of the link mechanism, i.e. the link mechanism
should not be turning over or canting, when handling the chair, which would make the
link bearings jam. |
[0001] The invention relates to a collapsible or folding wheel chair, more precisely a wheel chair of the type mentioned in the preamble of claim 1.
[0002] When constructing wheel chairs of this type, a chair having as low a weight as possible, being sturdy and easy to operate is aimed at.
[0003] Besides great importance today is attached to the chair having an aesthetically attractive and simple design. In its folded position, the chair should take up as little room as possible, this feature among other things implying, that the two lateral frames must be foldable to a position, where the two frames are very close to each other. The folding and unfolding operations should take place quickly and easily, the operation of complicated releasing or locking mechanisms being not required, and the whole operation not implying unduly great display of force. Only when these conditions are fulfilled, the handicapped user of the wheel chair is able to perform the operation himself, when for instance the chair is to be brought with in a car or in other similar situations.
[0004] Wheel chairs are known, wherein the seat and the chair back are supported by a frame structure, primarily comprising two vertical lateral frames arranged in parallel and being connected the one with the other by jaw-tongs linking mechanisms being inserted between the frames beneath and behind the seat. The linking mechanisms permit a folding or collapsing of the chassis, during which folding the two vertical lateral frames are brought in close proximity to each other. See for instance DK patent application no. 147.508B, the specification.
[0005] The known wheel chairs of this type are characterized by the following common features: The linking mechanisms are sluggish (i.e., the friction in the links is high, and their guidance of the lateral frames is not accurate, especially are the individual linking mechanisms not mutually harmonized, so that the two lateral frames, when folding or unfolding the chair, may easily deviate from their essentially parallel relationship. This results in disadvantageous jamming effects in the links, making the whole folding operation even more difficult.
[0006] Another disadvantage of the known jaw-tong-type wheel chairs is that the linking mechanisms are often carrying locking mechanisms to be operated separately before the folding of the chair. In this way the whole operation of the chair becomes unnecessarily complicated to the handicapped user.
[0007] The object of the invention is to disclose a wheel chair of the aforementioned type being so constructed as to satisfy the above demands concerning low weight, the occupation of only little room in its folded position, high strength etc., besides being easily and handily foldable and unfoldable to the user of the wheel chair, so that the folding and unfolding is possible with only a minimum of physical strength being required, particularly using just a single grip. Still further, a simple and functional design is aimed at, and in its construction, the wheel chair is based on a modular system, permitting the manufacture of special wheel chair variants, as demanded by the users, on the basis of a number of common basic components.
[0008] The features aimed at are obtained by constructing the folding mechanism of the wheel chair as stated in the characterizing part of claim 1. The special presentation of the folding links, these links having a middle junction or centre point, at which two linking arms intersect in a mutually overlaid position, ensures an especially stable, self-locking engagement between these two arms in their uttermost unfolded position. This engagement is capable of transmitting great loads, as well vertically as sideways. Therefore, the folding link may be of a compact construction and of a low weight, i.e. a construction is achieved, which is optimal for the present purpose.
[0009] The tooth system between the two linking arms in each junction point leads to a coordination of the movements of the linking arms, so that the lateral frames as well are accurately guided forcibly, i.e. during the folding operation their mutual parallellity is preserved; the linking mechanisms having no tendency of canting or turning over.
[0010] The whole mechanical movement system is suitably supported by connecting the junction point fittings using appropriate means, so that all linking arms are moving synchronously, in a co-ordinated way. Given well functioning, frictionsless link bearings, for instance of the TeflonR type, the chair is capable of being folded or unfolded using only a single grip, e.g. at the lateral frames, and using only a minimum of force.
[0011] Making the two linking arms just passing across a dead-centre position before the establishment in the unfolded position of the chair of the self-locking engagement mentioned above, a self-locking, barring linking mechanism is ensured, which renders further locking mechanisms superfluous. The linking arms are suitably opened upwardly, so that the weight of the person sitting in the chair is enhancing the locking or barring effect.
[0012] In the embodiment of claims 3 and 4 an optimum link construction as regards weight and strength is achieved, and at the same time the link components are adapted to a rational production system of today. The linking arms may for instance be manufactured by extrusion of aluminium, and the wholly or partly toothed wheels at a CNC-controlled machining centre (CNC = Computer Numerical Construction). The aluminium linking arms are advantageously in a conventional way provided with weight reducing recesses in order to obtain an optimal relationship between weight and strength. Alternatively, the linking arm may be manufactured from a punched steel plate, the toothed wheel component being secured by pressing or welding.
[0013] Claim 5 discloses an especially suitable construction of the wheel chair according to the invention making use of the folding links. By this construction a chair of optimal strength is achieved, and at the same time the folding mechanism brings about a guidance completely in parallel of the lateral frames, when the chair is folded. Besides, according to claim 8, the wheel chair of the invention may be modular, so that different wheel chair variants are easily manufactured using only a limited number of basis elements. The different components forming part of the link mechanisms are easily fitted into a modular system. The lateral frames, the fittings for the driving wheels, the arm rests etc., are advantageously fitted into the modular system as well. Spastic wheel chair users frequently need reinforced variants of wheel chairs. According to the invention such reinforcement is achieved by inserting more than three link units between the lateral frames, this being possible owing to the modular construction..
[0014] In the following the invention is described in greater details, reference being had to the drawing, in which
fig. 1 is an exploded view of a link unit according to the invention;
fig. 2 a view of the link unit in its unfolded position;
fig. 3 a view of the link unit in its folded position;
fig. 4 a partially sectional view from above of the link unit;
fig. 5a a longitudinally sectional view of a toothed wheel component of the link unit;
fig. 5b an end view (top view) of the link unit;
fig. 6 a schematic view of a wheel chair chassis comprising four link units inserted between the two lateral frames of the chassis, and
fig. 7 a schematic vertically sectional view along the line A-A of fig. 6.
[0015] In the embodiment according to fig. 1-5, the link units of the wheel chair linking mechanism essentially comprise a first linking arm 1, a second linking arm 2, two lateral junction point plates 3, a first axle journal 4 belonging to the first linking arm, and a second axle journal 5 belonging to the second linking arm.
[0016] The two linking arms are placed between the two lateral plates in an overlaid position in mutually displaced swinging planes, these lateral plates in combination with the axle journals 4, 5 constituting the junction point fitting of the link unit. The axle journals are inserted transversely between the two lateral plates 3 in appropriate bores 4a, 5a.
[0017] Each linking arm 1,2 comprises an arm part 6 manufactured from an extruded aluminium profile. At its one end the arm carries a throughgoing bearing bore 7 to be employed in the linkage between the arm and the respective lateral frame R of the chair chassis (see fig. 2 and 3). At its opposite end, i.e. the junction point end, the arm carries a slotted bore 8 complete with tightening screw. At a certain distance from the bore 8, between the bore 8 and the opposite bearing bore 7 mentioned above, a semicircular depression is made in the arm. The importance of this is explained later on.
[0018] In the slotted bore 8, a toothed wheel element 11 is set up, this element being shown in fig. 5a and 5b. The element comprises a wheel section 12 with an oblong hub 13, 14 at each side. The hub 13 at the one side is intended for insertion in the slotted bore 8. The hub 14 at the other side constitutes a stopper for the complementary arm 2 and 1, respectively, when the link is completely unfolded (fig. 2). The toothed wheel element carries an axial perforation 15, into both ends of which a lining 16 of low friction type, for instance a TeflonR bearing bush, is pressed. The perforation with its bearing bushes together with the axle journal 4 and 5, respectively, constitutes the junction point swing bearing of the linking arm.
[0019] The wheel section 12 carries an external toothing 12a, extending around the whole periphery or being limited to an angular segment of the periphery. The pitch diameter of the toothing corresponds to the centre distance between the two junction point axes. The toothing wheels at the two arms 1, 2 are both in the same median plane between the two arms, and they are in mesh (see fig. 4). This mesh means a forced synchronization of the movements of the two arms, when the chair is folded.
[0020] As mentioned above, the arms 1, 2 are placed in an overlaid - i.e. intersecting - position between the two junction point lateral plates. The axle journal 5 for the first linking arms serves as a stop for the second arm and vice versa. In order to achieve a secure and stable locking engagement at the junction point between the two arms, when the link is unfolded, the above mentioned semicircular bearing depression 10 is made at the arm, for the abutment of the axle journal - strictly speaking the hub piece 14 at the complementary toothed wheel element.
[0021] The wheel chair of the invention is constructed as a modular system, a number of three or more of the above described linking mechanisms forming part of this modular system. In fig. 6 and 7 a special embodiment of the wheel chair is shown, wherein a total of four link units of the above described type are inserted between the two lateral frames R of the chassis.
[0022] The junction point lateral plates of the link units are transversely as well as vertically connected by a horizontal longitudinal connection profile 20 and prolonged junction point lateral plates 21, respectively, the latter being common to link units being mutually vertically placed. As far as possible, the connecting elements are not bendable ("bend-rigid"), so that all of the link units of the chair are forced to a synchronous movement. As a result of this, the parallelity of the two lateral frames R is preserved during the folding operation, whether or not the chair is acutated by a wry or distorted pull/pressure or is actuated unfavourably in another way. Every tendency of deviation from link unit parallelity and the consequent jamming of the link bearings is eliminated, and therefore the whole operation is effectable using only a minimum of force.
[0023] The invention is not limited to the embodiments of the drawings and to the above described embodiments. Other combinations of materials, other constructive embodiments and other ways of combining the link units between the two lateral frames of the chassis is possible within the scope of the invention.
- that the stiffening link connections, being inserted in a number of three or more link units, each comprises a first (1) and a second (2) linking arm, being assembled in a common middle junction point and being swingably connected to a lateral frame (R) each, so that the link connections, in a fashion being known as such, are foldable between an outstretched, stiffening position and a folded position, in which the lateral frames (R) are brought close to each other,
- that the said middle junction point comprises:
- two lateral plates (3) arranged in parallel, between which the two linking arms (1, 2) are suspended in a mutually displaced position, i.e. in displaced swinging planes,
- a first and a second axle journal (4, 5) being transversely inserted between the two lateral frames (3), having a certain distance to each other and being arranged symmetrically around the vertical centre plane of the chair, the first axle journal (4) constituting a swing bearing for the first linking arm (1) and the second axle journal (5) constituting a swing bearing for the second linking arm (2),
- that the first axle journal (4) is located opposite to the centre plane relative to that lateral frame (R), to which the first linking arm (1) is swingably connected, the second axle journal (5) analogously, so that the first and the second linking arm intersect at the junction point,
- that a toothed wheel or wheel segment (11) is connected to the first linking arm (1), either as an integrated part thereof or as an element secured to the arm, said wheel (11) being placed concentrically with the respective junction point swing axis and being in mesh with an analogously construed and toothed wheel segment at the other arm (2), the meshing causing a forced synchronization of the movements of the two linking arms, to guide them straightly and exactly during the folding and unfolding of the chair, and
- that the second axle journal (5) constitutes a stop face for the second linking arm (2), when the linking arms are completely unfolded, i.e. when the wheel chair is in the position for use.
- that each linking arm primarily comprises an oblong arm part (6), mainly of light-alloy metal, and a toothed wheel bearing element (11), mainly of steel, being pressed into or in other ways set up or fixed up in a corresponding bore (8) at the junction point end of the arm part,
- that the toothed wheel bearing element (11) for that purpose is constructed as a completely or partly toothed wheel, a hub extending to each side of the wheel, the hub piece (13) at the one side being intended to be set up at the said bore (8) of the arm part, and the hub piece (14) at the other side of the wheel serving as a stop face to the complementary linking arm (1, 2), and
- that the toothed wheel element carrying an axial perforation (15), linings (16) preferably being inserted therein, constitutes the junction point swing bearing of the linking arms, the axial length of this bearing corresponding to the distance between the two junction point lateral plates (3), so that the said swing support, as well as an axial guidance of the linking arm between the two lateral plates are obtained, as well as a stability as good as possible.
- that a total of three link units of the above described type are situated between the two lateral frames of the wheel chair, the first and the second unit being placed the one vertically over the other in the rear end of the chair, the third unit being placed approximately halfway between the front end and the rear end of the chair, at the same height as the uppermost link unit in the rear end,
- that the two rear link units are mutually connected, the junction point plates (21) being prolonged and in this fashion being common to the two link units, and
- that in the two uppermost link units, a horizontal connection profile (20) is inserted between the junction point plates, so that the junction point plates of the three link units are connected forming a continuous not-bendable unit.