LIFT, PREFERABLY FOR SEATS ON WHEELCHAIRS

Abstract: Due to their special construction, the known cantilever-type seat-lifts for wheelchairs require a strong actuator with a relatively great piston movement to bring about the necessary lifting height. The result is that the wheelchairs in which such lifts are incorporated become very space-demanding. There is disclosed a cantilever-type seat-lift which is characterized in that forces are applied to the respective cantilever arms (16, 32) via a transmission system comprising mutually connected push- and pull-rods (40, 42) which are connected to a moment rod (48) on a pivotally suspended, transversally-extending torsion axle (50) in the chassis (8), said axle (50) being driven by a motor-driven actuator (58) with a substantially horizontal field of action. There is hereby achieved a great range of variation for the lifting height, while at the same time a wheelchair provided with the new lift system occupies less space in comparison with the known wheelchair lift systems. A small building-in height for the chair lift is also achieved, whereby the starting level for the seat becomes lower and herewith more natural in relation to ordinary chair seats.

Description: Lift, preferably for seats on wheelchairs. The present invention concerns a lift, preferably for seats on wheelchairs for the elderly and the handicapped, and of the kind disclosed in the preamble to claim 1. An electrically-driven wheelchair provided with such a lift is known from US 5 046 571, where the height of the wheelchair seat is adjusted by the cantilever-lift by activation of the actuator, which displaces the second pair of cantilever arms which are mounted in a pivotally-displaceable manner on the chassis, whereby forces are transferred via the assembly point between said cantilever arms and the first pair of cantilever arms which are suspended in the upper frame in a pivotally-displaceable manner, whereby the first pair of cantilever arms are displaced and the height of the seat is changed depending on the direction in which the electrically-driven is displaced. At the front end, the wheelchair also comprises a hinged frame which supports a wheel- supported foot-rest, said frame being pivotally-suspended in the front end of the upper frame and to the actuator respectively, so that the foot-rest is displaced forwards by the lowering of the cantilever-lift. The raising and the lowering of the cantilever-lift is effected by a purely longitudinal displacement of the cantilevers arms which are pivotally- displaceable in the chassis, which results in a relatively great piston movement in order to bring about an adequate lifting height. Consequently, this results in a wheelchair construction which is relatively long and herewith very space-demanding, which is an inconvenience for the user. Mo- reover, the existence of the foot-rest will further increase the space requirement for the wheelchair. Furthermore, all of the forces which are transferred by the changing of the height of the lift by means of the actuator are transferred in the coupling points between the second and the first pair of cantilevers arms. The coupling points, and the surrounding areas, are thus exposed to very great stresses, which is indicated by the reinforcement of the first cantilever arm in the area around the coupling point, and the very great stres- ses unavoidably give rise to wear on the coupling point itself, which can therefore constitute a weak point in this lift construction. It is the object of the present invention to provide a lift of the kind disclosed in the preamble to claim 1, which at least has the same lifting height as the known lifts, while at the same time with a lift which is less space-consuming and has smaller building-in height than the known seat lifts, and at the same time that the above- mentioned weak points with the known lift are eliminated. With the invention, this object has been achieved with a lift of the kind disclosed where the respective cantilever arms are connected via mutually-connected push-rods and pull -rods by a pivot link connection to a first radially- projecting part, for example in the form of a torque bar, to a pivotally-mounted transversely-extending torsion shaft which further comprises a second radially-projecting part, for example in the form of a pressure-moment rod, the free end of which is connected by a swivel connection to a motor- driven actuator with a substantially horizontal field of ac- tion. With this construction, by connecting the respective cantilever arms to the pivotally-mounted torsion shaft it is achieved that the coupling point between the cantilever arms is not loaded to such a great degree, in that the forces for the raising/lowering of the lift are transferred directly to each of the cantilever arms, whereby at this point there does not arise any weakness in the construction. Moreover, a smaller building-in height for the lift is achieved, in that with the force transfer system consisting of the torsion shaft pivotally mounted in the chassis, the push-rods and pull-rods and the radially-projecting parts (the moment rods and pressure-moment rods) , there is achieved a system which in the lowest position of the lift is turned/folded together so that it does not project outside the chassis and the upper frame, and which during the raising "folds out" in height in such a manner that it is held within the limits of the chassis and the upper frame during the whole lifting procedure, up to and including the highest level for the lift. This is a very great advantage especially when the lift is used together with wheelchair seats, in that this characteristic considerably reduces the space required by the wheelchair in comparison with the known wheelchair. With the object of being able to reduce the power necessary from the actuator for the raising of the lift, i.e. upon initial lifting from the lowest position where the moment of resistance is greatest, the push-rod extending radially from the torsion shaft and connected to the actuator can with advantage project longer from the axis of rotation for the torsion shaft than the moment rod. There is hereby formed a power transmission system where the actuator connected to the longer arm exercises a very high moment on the moment rod in lifting from the lowest level where the moment of resistance is greatest. With the transmission system, there is also achieved a cantilever lift construction with a great variation between the lowest and the highest level of the lift, while at the same time only a relatively short piston movement is required for this purpose, which results in a short lift con- struction where none of the actuator parts extend outside the ends of the upper frame. There is thus provided a compact seat lift which together with a relatively great lift height occupies very little room in comparison with the wheelchair lift systems already known. A further advantage achieved with the smaller building-in height is that the starting level of the seat becomes lower and herewith more natural in comparison with ordinary chair seats. Moreover, a lower-placed seat during use of the wheelchair will always be advantageous as a consequence of the lower-lying centre of gravity, which reduces the risk of the wheelchair tipping over when used on sloping surfaces . From time to time there will be a need to be able to carry out a tilting of the lift's upper frame, i.e. in ca- ses where the lift is used together with seats on wheelchairs without the centre of gravity of the wheelchair being changed. This will be possible with the cantilever lift according to the present invention, in that the front end of the upper frame, to which the cantilever arms are pivotally connected, is pivotally suspended via arms to the upper frame, and that the same front end is connected via a hinge connection to a motor-driven actuator which is secured to the remaining part of the upper frame . A displacement brought about by the actuator will thus result in a circular displacement of the front end of the upper frame around the point at which the arms are suspended on the upper frame, during which movement the upper frame will be displaced vertically during a simultaneous ho- rizontal displacement of the remaining parts of the upper frame along the pivotally-displaceable bearings between the ends of the cantilever arms and the upper frame. This displacement will at the same time result in a raising and displacement in said directions of a seat secured to the upper frame. For example, a shortening movement of the actuator will result in a raising of the front end of the chair seat, which if this movement takes place alone will lead to a considerable and possibly dangerous displacement rearwards of the seat's centre of gravity as a consequence of a simultane- ous leaning backwards of the seat's back-rest. But since the seat is displaced forwards at the same time as the raising, compensation is thus made for the displacement of the centre of gravity, so that practically speaking the centre of gravi- ty is not displaced in the longitudinal direction of the chair. An above-mentioned displacement by the actuator will result in a lowering of the seat and at the same time a displacement backwards towards the initial position of the chair seat . In the following, the invention is explained in more detail with reference to the drawing, where fig. 1 is a side view of a wheelchair provided with a lift for the seat according to the invention, fig. 2 is a perspective side view of a lift accor- ding to the invention, fig. 3 is a perspective front view of the lift shown in fig. 2, fig. 4 is a perspective rear view of the lift shown in fig. 2, and fig. 5 is a view of the same seen from above. The lift 2 according to the invention can be envisaged for use under seats 4 on wheelchairs 6, for example of the type which is shown in fig. 1, and in the following an embodiment of the lift 2 according to the invention is de- scribed starting with the use of this together with a wheelchair 6, wherefore in the following the lift 2 is randomly called the lift 2 or the seat-lift 2. The seat-lift 2 is built up as a cantilever-lift, which is shown in figs. 2-5, and comprises a chassis frame 8 with a front end 10 and a rear end 12, where on the front end 10 a first set of cantilever arms 16 are suspended by means of pivot connections 14, the opposite ends of the arms 16 being suspended in a pivotally-displaceable manner by means of slide bearings 18 (cf. figs. 3 and 4) in U-profiled long sides 20 of an upper frame 22. The upper frame 22 comprises a front end 24, which via arms 26 is suspended in the long sides 20 by means of pi- vot connections 28. The front end 24 is also connected at pivot connections 34 with a second set of cantilever arms 32, which at pivot connections 34 are connected to the first set of cantilever arms 16, and the opposite ends of said second set of cantilever arms 32 are suspended in a pivotally- displaceable manner by means of slide bearings 36 in the U- profiled long sides 38 in the chassis frame 8. The cantilever arm sets 16, 32, respectively via rod connections 40, 42 and pivot-link connections 44, 46, are connected to a moment arm 48 at a common pivot link connecti- on 50. The moment arm 48 is suspended projecting radially on a transversally-extending torsion axle 52 which is pivotally suspended in the long sides 38 of the chassis frame 8, said axle 52 being connected via a further moment arm 54, which radially extends further than the arm 48 and is set at an an- gular-displaced manner in relation to this, and the pivot link connection 56, to the one end of a motor-driven actuator 58, the opposite end of which is pivotally mounted on the rear 12 of the chassis frame 8. As will appear from fig. 2, the motor-driven actua- tor 58 has a substantially horizontal field of action, the result being that the building-in height for the seat-lift according to the present invention becomes less. The advantages herewith are partly that the starting level for the chair seat becomes lower than on chair seats provided with the known seat-lifts, and partly that more room is provided under the seat for the placing of e.g. batteries for operation of the wheelchair, including lift systems etc. The seat lift 2 described above functions as follows, in that a procedure for raising the seat 4 is described: The actuator 58 is activated so that its push-rod 60 is displaced forwards towards the front end 10 of the chassis. This movement results in a turning of the torsion axle 52, and herewith also of the moment arm 48, which hereby describes a circular movement of the pivot connection 50 anticlockwise. This turning movement gives rise respectively to a pressure on the rod connection 40 and in traction on the rod connection 42, which respectively results in a forwards displacement of the slide bearings 18 in the end of the first set of cantilever arms 16 in the U-profiles 20 in the upper frame 22, and in a forwards displacement of the slide bea- rings 36 in the end of the second set of cantilever arms 32 in the U-profiles long sides 38 in the chassis frame 8. This displacement results in the raising of the upper frame 22 with the seat 4. A lowering of the seat is synonymous with an oppo- sitely-directed movement of the push-rod 60 on the motor- driven actuator 58, with a subsequently oppositely-directed displacement in relation to that described above. In the shown preferred example embodiment, the seat-lift is provided with a tilt function for the upper frame 22 and the seat 4 placed on the frame. The tilt function is provided by connecting the front end 24 of the upper frame 22 (which as described earlier is suspended via arms 26 in the long sides 20 by means of pivot connections 28) via a pivot connection 62 to a push/pull-rod 64 on a motor-driven actua- tor 66, suspended in a mainly U-shaped bracket 68 which in turn is secured on transverse stiffeners 70 secured to the upper frame 22.The tilt function is activated by a displacement of the push/pull rod 64 on a motor-driven actuator 66. In the following, a tilting procedure is described from the start position for the upper frame/the seat in a substantially horizontal position. When the upper frame/the seat 22, 4 is in the horizontal position, the actuator's push/pull rod 64 is in the outer position. With the tilting process, the pull-rod 64 is drawn rearwards, whereby the upper frame 22 is displaced forwards, sliding on the slide bearings 18, so that this is displaced in over the front end 24 during simultaneous raising, in that the arms 26 are turned in the pivot links 28, 30. The maximum achievable raising of the foremost part 25 of the upper frame (not the front end 24) is determined by the length of the arms 26. Here it is important to note that the raising of the foremost part of the frame 22 takes place at the same ti- me that this is displaced forwards, the result being that the centre of gravity for the lift 2 with seat 4 is not noticeably changed, even though the back-rest 5 of the wheelchair, which is also secured to the upper frame 22, leans backwards. With the invention there is thus provided a seat- lift which fulfils hitherto unfulfilled desires on the part of users of wheelchairs concerning a lower start position for the seat, and compensation for displacements in the centre of gravity when the seat is tilted. Moreover, the seat-lift according to the invention, with its relatively small building- in height, solves incompatible problems for the wheelchair manufacturers, i.e. the demand concerning a sufficiently great lift height for a seat-lift, in combination with a minimum space utilisation under the chair seat. The saving in space which is achieved in the use of the chair seat according to the present invention will thus be able to be used to increase the space available for batteries for operation of the wheelchair, which will increase the operation time between the battery charging periods. This will be of benefit to the users, provide more room for control units for the functions of the chair, also including the possibility of wheelchairs of a more smart design. In conclusion it must be mentioned that it will be obvious that the lift according to the invention, with changed dimensions, can be used for purposes other than that disclosed in the above-mentioned example embodiment. The lift could thus be used for raising and lowering together with fixed installations in offices and households, also in institutions, clinics, health centres etc.

Claims: C A I M S 1. Lift (2), preferably for seats on wheelchairs (6) for the elderly and handicapped, and of the kind which comprises a chassis (8) and an upper frame (22) supported by parallel pairs of cantilever arms (16, 32) , the respective ends of which are suspended in a pivotal and pivotally-displaceable manner in the chassis (8) and the upper frame (32) , and where the cantilever arms (16, 32) are coupled to an actuator (58) with a substantially horizontal field of action, c h a r a c t e r i z e d in that the respective cantilever arms (16, 32) are connected via push- and pull-rods (40, 42) to at least a first radially-protruding part (48) on a pivotally- suspended, transversally-extending torsion axle (52) in the chassis, said torsion axle further comprising a second radially-protruding part (54) which via a pivot connection (56) is connected to the actuator (58) . 2. Lift (2) according to claim 1, c h a r a c t e r i z e d in that the second part (54) protruding radially from the torsion axle (52) protrudes radially longer from the axis of rotation of the torsion axle than the first radially- protruding part (48) . 3. Lift (2) according to claim 1 or 2 , c h a r a c t e r i z e d in that the actuator (58) is connected to the second radially-protruding part (54) closest to its free end. 4. Lift (2) according to claim 2 or 3 c h a r a c t e r i z e d in that the push- and pull-rods (40, 42) are connected at a pivot link connection (50) to the first radially- protruding part (48) on the torsion axle (52) . 5. Lift (2) according to claim 4, c h a r a c t e r i z e d in that the push- and pull-rods (40, 42) are mutually connected in the pivot link connection (50) . 6. Lift (2) according to any of the claims 1-5, c h a r a c t e r i z e d in that the first and second radially- protruding parts (48, 54) on the torsion axle (52) consist respectively of a radially-protruding moment rod (48) and a pressure-moment rod (54) . 7. Seat-lift according to claim 6, c h a r a c t e r i z e d in that the pressure-moment rod (54) extends radially further than the moment rod (48) from the axis of rotation of the torsion axle 8. Lift (2) according to any of the claims 1-7, c h a r a c t e r i z e d in that the pair of parallel cantilever arms consist of a first cantilever arm (16) which is respectively pivotally suspended in a chassis (8) and pivotally suspended in a displaceable manner in the one end of an upper frame (22) , and a second cantilever arm (32) which is respectively pivotally suspended in the one end of the upper frame (22) and suspended in a pivotally-displaceable manner in the chassis (8) . 9. Lift (2) according to any of the claims 1-8, c h a r a c t e r i z e d in that the front end (24) of the upper frame (22) , to which the cantilever arms (32) are pivotally connected, is pivotally suspended via arms (22) in the upper frame (22) , and that the same front end is connected via a hinge connection (28) to a motor-driven actuator (66) which is secured to the remaining part of the upper frame (22) . 10. Lift (2) according to any of the foregoing claims 1-9, c h a r a c t e r i z e d in that the actuators (58, 66) comprise a displaceable piston (60) which is driven in the longitudinal direction of the actuator by an electric motor. AMENDED CLAIMS [received by the International Bureau on 28 February 2000 (28.02.00); original claims 1-10 replaced by new claims 1-8 ; (3 pages)] TITLE: Lift, preferably for seats on wheelchairs 1. Lift arrangement (2) of the cantilever-table type, preferably for wheelchairs, and comprising an under-chassis (8) and upper frame (22) supported on a cantilever frame with parallel pairs of cantilever arms (16, 32) , where the cantilever frame (16, 32) is arranged to be folded up under the influence of an actuator (58) with lying orientation, characterized in that below the X-axis (34) the cantilever arms (16, 32) are pivotally connected to the upper ends of a V-shaped toggle joint (40, 42, 50) , which toggle joint (50) is in lowering/raising connection with the actuator (58) through a transmission which converts the actuator movement to an up-and-down movement. 2. Lift arrangement (2) according to claim 1, characterized in that said transmission consists of a triangular structure which by a first pivot connection (52) at a lower corner is pivotally connected to the under-chassis (8) of the cantilever table, while by a second pivot connection (56) at an upper corner it is pivotally connected to the actuator (58) , and at its third corner is pivotally connected to the link (50) of the toggle joint for the swinging downwards and upwards of this by the swinging forwards and backwards of the upper corner (56) by the actuator. 3. Lift arrangement (2) according to claim 1 or 2 , characterized in that the triangular structure which constitutes the transmission comprises at least a V-formed beam extending from the first pivot connection (52) , where the first rod-shaped leg (54) lying uppermost is connected to the actuator (58) at the second pivot connection (56) , and where the second rod-shaped leg (48) lying below the first leg (54) is pivotally connected to the toggle joint (50) . 4. Lift arrangement (2) according to claim 3, characterized in that the rod-shaped legs (54, 48) extend radially from and are fixedly connected to a transversely- extending torsion axle (52) which is suspended in the first pivot connection (52) in the under-chassis (8) . 5. Lift arrangement (2) according to claim 4, characterized in that the first rod-shaped leg (54) lying uppermost extends radially from the axis of rotation of the torsion axis (52) for a longer distance than the second rod-shaped leg (48) . 6. Lift arrangement (2) according to any of the claims 1- 5, characterized in that each pair of parallel cantilever arms consists of a first cantilever arm (16) , which is respectively pivotally suspended in the under- chassis (8) and pivotally suspended in a displaceable manner in the one end of the upper frame (8) , and a second cantilever arm (32) which is respectively pivotally suspended in the one end of the upper frame (22) and pivotally suspended in a displaceable manner in the under-chassis (8) . 7. Lift arrangement according to any of the claims 1-6, characterized in that the front end (24) of the upper frame to which the cantilever arms (32) are pivotally connected by pivot connections (30) , is connected via arms (26) which are pivotally connected to the upper frame (22) by pivot connections (28) , and a pivot connection (62) on the front end (24) , to a second actuator (66) which lies in a substantially horizontal manner, said second actuator (66) being secured to the remaining part of the upper frame (22) by a hinge connection. 8. Lift arrangement (2) according to any of the foregoing claims, characterized in that the first actuator (58) and the second actuator (66) with substantially horizontal orientation comprises a displaceable piston (60) which is driven by an electric motor in the longitudinal direction of said actuators.

Inventors: BALLE HANS, BALLE, HANS
Applicants: BALLE HANS, HANS BALLE APS, BALLE, HANS
Application year: 1999
Main classification: A61G5
IPC codes: A61G5, B66F7