WO2008036018A1

WO2008036018A1 - Seat for a wheelchair and a method for varying the angle between a seat part and a backrest.

Info

Publication number: WO2008036018A1
Application number: PCT/SE2007/000817
Authority: WO
Inventors: Jan Astrom
Original assignee: Permobil Ab
Priority date: 2006-09-19
Filing date: 2007-09-18
Publication date: 2008-03-27

Abstract

A seat arrangement for a wheelchair, which arrangement comprises a seat part that is intended to support a user's bottom and a back rest part which is capable of rotation in relation to the seat part about a transverse axis of rotation, in order to permit adjustment of the angle between the seat part and the back rest part. In order to produce an advantageous movement for varying the angle between the back rest part and the seat part, the seat part (14, 114) is rotatably arranged about a first, transverse axis of rotation (A1, A101), the back rest part (15, 115) is rotationally arranged about a second transverse axis of rotation (A2, A102), the positions of the first and the second axis of rotation are fixed in relation to one another, and the first and the second axes of rotation are capable of being caused to rotate together about a common third transverse axis of rotation (A3, A103). The application also includes a method for varying the angle between a seat part and a backrest.

Description

SEAT FOR A WHEELCHAIR AND A METHOD FOR VARYING THE ANGLE BETWEEN A SEAT PART AND A BACKREST

Field of the invention

The invention relates to a seat arrangement for a wheelchair. The seat arrangement comprises a seat part that is intended to support a user's bottom and a back rest part that is capable of rotating about a transverse axis of rotation in order to permit adjustment of the angle between the seat part and the back rest part. The invention also relates to a wheelchair comprising a seat arrangement of this kind and to a method for varying the angle between a seat part arranged on a wheelchair and a back rest part.

Background and prior art

Modern wheelchairs, for example electric wheelchairs, often permit a range of different adjustments of the wheelchair seat. The seat can comprise, for example, a- normally horizontal part, on which the user's bottom rests, a back rest, two arm rests and two leg rests. Modern advanced wheelchairs can permit, for example, the separate adjustment of the height and inclination of the entire seat in relation to the chassis, the inclination of the leg rests in relation to the horizontal part and the inclination of the arm rests in relation to the back rest. It is often desirable to be able to perform such adjustments when the user is present on the seat. For this purpose, the wheelchairs can be equipped with electric drive units, such as motors and linear actuators which produce relative movements between the seat and ^■ the wheelchair chassis and between certain of the constituent parts of the seat. The electric drive units are usually controlled with the help of a control panel that can be positioned on one of the arm rests. In this way, even a seriously physically disabled user is able to adjust the seat unaided to the desired position when he or she is present in the seat . The back inclination, that is to say the inclination of the back rest m relation to the horizontal plane, is one parameter that it is important to be able to adjust. By adjusting the back inclination, it is possible to provide an ergonomically advantageous sitting position and to vary the sitting position m order to avoid prolonged static loading and, in so doing, to reduce the risk of pressure sores and other injuries. If the back inclination can be varied within a large angular range, it is also possible for the user to adopt a recumbent position. Previously disclosed wheelchair seats can thus be provided with a seat arrangement m which the back rest is pivotally arranged about a transverse horizontal axis m relation to the seat that is arranged on the lower end of the back rest. Rotation of the back rest about the transverse axis thus involves varying the angle of the back rest m relation to the normally horizontal seat part. In certain wheelchairs, the normally horizontal seat part can be arranged on a so-called seat tilt, which permits the normally horizontal seat part to be inclined or tipped m relation to the horizontal plane through its rotation about a transverse horizontal axis. The seat tilt in turn can be arranged on a seat lift, which is supported by the chassis and permits the vertical adjustment of the entire seat. Rotation of the back rest about the transverse axis can be achieved, for example, with the help of a linear actuator, one end of which is secured to the back rest and the other end of which is secured to the normally horizontal seat part .

EP 0 405 542 A2 discloses a wheelchair at which a back rest and a seat are mutually connected by means of a common horizontal shaft, about which the back rest and the seat are rotatable in relation to each other. At the wheelchair shown m EP 0 405 542 A2 , the distance between the back rest and the seat will increase when the angle them between increases. As will be explained more in detail below, this causes serious disadvantages .

Brief description of the invention One object of the invention is to provide an improved seat arrangement for wheelchairs. Another object is to provide a simple, ergonomic, functionally reliable and flexible seat arrangement with which the angle between a seat part that is intended to support the user's bottom and a back rest part can be adjusted in an advantageous manner.

These and other objects are achieved with a seat arrangement of the kind which is indicated in claim 1. The seat arrangement according to the invention is intended for a wheelchair and comprises a seat part, which is intended to support the bottom of a user and a back rest part which is rotatable in relation to the seat part, about a transverse axis of rotation, in order to permit adjustment of the angle between the seat part and the back rest part. The seat part is rotatably arranged about a first transverse axis of rotation and the back rest part is rotatably arranged about a second transverse axis of rotation. The position of the first axis of rotation is fixed in relation to the seat part and the position of the second axis of rotation is fixed in relation to the back rest part. The positions of the first and the second axes of rotation are also fixed in relation to one another, and together rotatable about a common third transverse axis of rotation.

The seat arrangement according to the invention thus permits the coordinated rotation of the seat part about the first axis of rotation, of the back rest part about the second axis of rotation, and of the first and the second axis of rotation about the third axis of rotation. At the same time the positions of the first and second axis of rotation are maintained in relation to each other and m relation to the seat part and the back rest part respectively. It is possible by this means to achieve an increase m the angle between the back rest part and the seat part while the distance between the lower part of the back rest part and the seat part is reduced. In a similar manner, it is possible to reduce the angle between the back rest part and the seat part and, at the same time, to increase the distance between the lower part of the back rest and the seat part.

In previously known seat arrangements, where the back rest is rotatable about a transverse axis that is arranged at the lower end of the back rest, the distance between all points on the back rest and the seat part arranged in front of the back rest will increase when the back rest is folded rearwards. Because of the anatomical configuration of the human body, an increase of this kind in the distance means that the lower part of the back will slide m the longitudinal direction relative to the lower part of the back rest. Such relative sliding of the user's back along the back rest is generally experienced as being uncomfortable and can be harmful, in particular for severely physically disabled persons, as it can give rise to or aggravate pressure sores and other skin or bodily injuries. With the seat arrangement according to the invention, m which the distance between the lower part of the back rest and the seat part is reduced when the back rest is folded rearwards, such relative movement between the user's back and the back rest can be reduced to a considerable degree or entirely eliminated. The same is also true when the back rest is folded up and the angle between the back rest part and the seat part is reduced, m conjunction with which the distance between the lower part of the back rest part and the seat part increases. With the seat arrangement according to the invention, m addition to producing an advantageous inclination of the back, it is also possible to produce other desirable movements. By retaining the angle of rotation of the seat part and the back rest part about the first and the second axis of rotation respectively, and by causing these axes of rotation to rotate about the third axis of rotation at the same time, it is possible, for example, to produce so-called tilting or inclination of the entire seat. The seat arrangement can also be used to facilitate getting up from a sitting position to a standing position by the user. This can be achieved, for example, by rotating both the seat part and the back rest part, from an upright sitting position for the back rest, so that the angle between them increases and, at the same time, by maintaining the rotational position of the first and the second axis of rotation about the third axis of rotation. Simultaneous lifting of the user's bottom and straightening of the back, the effect of which is to facilitate getting up to a significant degree, can be achieved m this way. The seat arrangement can also be used to adopt a so-called standing position, in which the seat part and the back rest part are arranged vertically m alignment with one another. This can be achieved by increasing the angle between the seat part and the back rest part, from an upright sitting position, and, at the same time, by causing the first and the second axis of rotation to rotate about the third axis of rotation m the opposite direction m relation to the direction of rotation for adopting a recumbent position.

The expression seat part is used here to denote a part of the seat of a wheelchair that is intended to support the bottom of a user. The seat part can incorporate or support a seat cushion or other structural elements, for example, such as frames, plates and the like intended to permit adjustment of the seat width and the seat length. The expression back rest part is similarly used to denote one part which, m itself, is capable of constituting the back rest of the wheelchair, or one which supports other constituent parts of the back rest .

The seat part and the back rest part are rotatably fixed to a carrier device, preferably on the first and the second transverse axis of rotation respectively. The carrier device can be configured as an angle element, for example, in which the first and the second axis of rotation are arranged respectively through a first and a second arm in. the angle element . The third axis of rotation is then appropriately arranged so that it extends through the angle element, for example at an angle knee where the first and the second arm are connected to one another.

Alternatively, the carrier device can be configured as an arc-shaped element that is capable of displacement m its longitudinal or circumferential direction relative to the wheelchair chassis. The first and the second axis of rotation are then preferably arranged on or m the vicinity of the respective ends of the arc- shaped element. Displacement of the arc-shaped element m its longitudinal direction thus produces rotation of the element, and with it the first and the second axis of rotation, about the centre of the arc, which m this case constitutes the third axis of rotation. Among other things, a well-balanced rotation about the third axis of rotation is achieved with this embodiment, m conjunction with which the force and the power required to drive this rotational movement are reduced.

The seat arrangement preferably comprises means for achieving coordinated rotation of the seat part, the back rest part and the carrier device respectively about the first, the second and the third transverse axis of rotation. This means can comprise, for example, a first, a second and a third electric drive unit that are mechanically connected respectively to the seat part, the back rest part and the carrier device and are electrically connected to a control unit m order to produce the coordinated rotations. Driving the three rotational movements m this way with separate drive units provides high flexibility in respect of which movement patterns and positions can be adopted by the seat part and the back rest part relative to one another and the chassis of the wheelchair.

Alternatively, the seat arrangement may comprise an electric drive unit that is mechanically connected to one or other of the seat part and the back rest part as well as a mechanical link mechanism which connects the seat part to the back rest part. A simple design is achieved m this way, m which the coordinated rotation of both the seat part and the back rest part can be driven with the one same drive unit .

The electric drive unit which drives the rotation of the seat part about the first axis of rotation preferably comprises a linear actuator that is fixed to the seat part and to the carrier device, preferably at or m the vicinity of the second axis of rotation. A reliable design that is favourable from the point of view of force distribution is achieved m this way.

In those cases m which the carrier device comprises an arc-shaped element, its rotation about the third axis of rotation is preferably driven by means of a gear arrangement m which the arc-shaped element exhibits gears arranged one after the other preferably on its inner surface m the circumferential direction. A gear which can be driven by an electric motor or manually by means of a handle, and which engages with the gears of the element, then drives the displacement movement of the element m its circumferential direction. The seat arrangement can, instead of having electrically driven drive units or in combination with these, comprise one or more manual drive units for the manual driving of one or more of the rotations of the seat part, the back rest part and the carrier device respectively about the first, second and third axis of rotation.

In order to obtain a stable and strong arrangement with the ability to withstand comparatively high loads, the seat arrangement preferably comprises two essentially identical carrier devices that are arranged side-by- side and are mutually connected by means of a first and a second transverse shaft, which defines respectively the first and the second transverse axis of rotation. The transverse shafts may be rotatably mounted in the carrier devices, in conjunction with which the seat part and the back rest part may be secured immovably to the respective shafts. Alternatively, the shafts may be immovably secured to the carrier devices, in conjunction with which the seat part and the back rest part are arranged rotatably about the respective shaft. It is naturally also possible for the shafts to be rotatably mounted on the carrier devices, at the same time as the seat part and the back rest part are rotatably attached to the respective shaft.

The invention also relates to a wheelchair comprising a seat arrangement of this kind and a method for varying the angle between a seat part and a back rest part. The wheelchair and the method are defined in Claims 13 and 14 below. Further objects and advantages of the seat arrangement and the wheelchair according to the invention can be appreciated from the following detailed description of embodiments and from the Patent Claims below. Brief description of the Figures

Illustrative embodiments of the invention are described below with reference to the Figures, in which:

Fig. 1 is a schematic side view of an electric wheelchair comprising a seat arrangement according to a first embodiment of the invention.

Fig. 2 is a schematic plan view from the front of an enlarged scale of the seat arrangement depicted in Fig. 1.

Figs. 3a and 3b are schematic side views of the seat arrangement depicted in Fig. 2, where Fig. 3a shows the back rest part in a folded-up sitting position, and Fig. 3b shows the back rest part in a folded-down position.

Figs. 4a and 4b are schematic side views, corresponding to those in Figs. 3a and 3b, of a second embodiment of the seat arrangement .

Figs. 5a and 5b are schematic side views from the opposite side of the embodiment depicted in Figs. 4a and 4b.

Figs. 6a and 6b are schematic perspective views of a third embodiment of the seat arrangement, in which the back rest part is shown folded up in Fig. 3a and folded down in Fig. 3b.

Detailed description of embodiments

The electric wheelchair that is depicted schematically in Fig. 1 comprises a wheelchair chassis 1 which is supported by front 2 and rear 3 wheels. The wheelchair chassis comprises a conventional seat lift 4 having a lower part 4a fixed to the chassis and an upper part 4b that is capable of displacement in the vertical sense. A seat arrangement 10 according to the invention is fixed to the upper moving part 4b of the seat lift. As can be appreciated most clearly from Figs. 2, 3a and 3b, the seat arrangement 10 comprises a stationary part 11, two carrier devices arranged laterally alongside one another, each of which consists of a generally L- shaped angle element 12, 13, a seat part 14 and a back rest part 15. In the embodiments illustrated in Figs. 1, 2, 3a and 3b, the back rest part comprises a frame part, to which other constituent parts (not shown here) of the back rest of the wheelchair seat are fixed.

The two angle elements 12, 13 comprise first 12a and second 12b legs or arms, which are connected at an angle knee on each angle element. A first shaft 16 extends between the two angle elements 12, 13 and is rotatably secured at the free end of the first arm 12a of the respective angle element 12, 13. This first shaft 16 thus defines a first transverse axis of rotation Al, about which the first shaft 16 is able to rotate in relation to the two angle elements 12, 13. The expression transverse is thus used here to denote a direction that is essentially perpendicular to the front-to-rear direction of the wheelchair seat and is essentially parallel to the seat plane. The first shaft 16 extends through the seat part 14 and is securely attached to it. The seat part 14 is thus able to rotate in relation to the angle elements 12, 13 about the first transverse axis of rotation Al.

A second shaft 17 extends between the two angle elements 12, 13 and is rotatably secured at the free end of the second arm 12b on the respective angle element 12, 13. This second shaft 17 thus defines a second transverse axis of rotation A2 , about which the second shaft 17 is able to rotate in relation to the two angle elements 12, 13. The second shaft 17 extends through the back rest part 15 and is securely attached to it. The back rest part 15 is thus able to rotate in relation to the angle elements 12, 13 about the second transverse axis of rotation A2.

A third shaft 18 extends between two projecting side flanges 11a, lib arranged on the stationary part 11 in the longitudinal direction and is rotatably secured to these side flanges. This third shaft thus defines a third transverse axis of rotation A3. The third shaft 18 extends through the respective angle knee of the two angle elements 12, 13 and is securely attached to these. The two angle elements 12, 13 are thus able to rotate together in relation to the stationary part 11 about the third transverse axis of rotation A3.

The seat arrangement is depicted in Fig. 3a after having adopted an upright sitting position. By increasing the angle between the back rest part 15 and the seat part 14, the back rest part can be folded rearwards relative to the seat part in order to adopt the recumbent position depicted in Fig. 3b, in which recumbent position the seat part 14 has retained its horizontal orientation. Increasing the angle between the back rest part 15 and the seat part 14 is achieved by the coordinated rotation of the seat part, the back rest part and the two angle elements 12, 13 about the first Al, the second A2 and the third A3 axis of rotation. The seat part 12 is driven in this way, causing it to rotate, according to Figs. 3a and 3b, in an anticlockwise direction about the axis of rotation Al, at the same time as the back rest part is driven causing it to rotate in a clockwise direction about the axis of rotation A2 , and the two angle elements are driven causing them to rotate in a clockwise direction about the axis of rotation A3. As can be appreciated clearly from the Figures, the distance between the lower section of the bcLCk rest part, which section is arranged below the second axis of rotation A2 , and the seat part will reduce as a result. The above-mentioned problems that are associated with previously disclosed wheelchair seats, m which the distance between the entire back rest and the seat part increases when the back rest is folded rearwards, are avoided m this way. In order to fold the back rest part 15 rearwards from the position shown in Fig. 3b into the position shown m Fig. 3a, the seat part 14, the back rest part 15 and the two angle elements 12, 13 are driven causing them to rotate m the opposite direction to that described above, m conjunction with which the distance between the lower section of the back rest part and the seat part increases once more.

In the embodiment described above, the rotation of the seat part 14, the back rest part 15 and the two angle elements 12, 13 is driven m each case by an electric, linear actuator (not shown here) . The actuators are connected electrically to a control unit, which can comprise a microprocessor and which coordinates the movement of the actuators m order to produce the rotations described above. The control unit may be configured appropriately to produce the back rest inclination described above when the user gives a single command, for example by pressing a button.

As can be appreciated from Figs. 3a and 3b, the vertical position of the seat part m relation to the stationary part 11 will be raised when the back rest part 15 is folded rearwards. If desired, such raising of the seat part can be reduced or entirely avoided by driving the seat lift 4, at the same time as the inclination movement of the seat arrangement described above, in such a way that its moving part 4b, to which the stationary part IL of the seat arrangement is fixed, is lowered m relation to the chassis 1. For this purpose, the seat lift is appropriately electrically connected to the control unit, so that the compensating lowering of the entire seating arrangement is also coordinated with the movements of the constituent parts of the seat arrangement. Depicted in Figs. 4a, 4b, 5a, 5b is another embodiment of the seat arrangement, in which a single, electric linear actuator is utilized in order to drive the rotation of both seat parts 14 about the first axis of rotation Al and the rotation of the back rest part 15 about the second axis of rotation A2. Figs. 4a and 4b depict the seat arrangement viewed from the left-hand side of the seat, and Figs. 5a and 5b depict the seat arrangement from the right-hand side. The actuator 21 is rotatably secured at a first end to the left-hand angle device 12 at or in the vicinity of the second shaft 17. The other end of the actuator, which is capable of linear displacement relative to the first end, is rotatably secured to the seat part 14 at a certain distance behind the first shaft 16. By driving the other end of the actuator in the direction of the first end, it is thus possible to cause the seat part to rotate in an anticlockwise direction (according to Figs. 4a, 4b) . When the other end of the actuator is driven in a direction away from the first end, the seat part is caused to rotate in a clockwise direction.

Figs. 5a and 5b illustrate how a mechanical link mechanism 30 is arranged on the right-hand side of the seat arrangement. The link mechanism 30 comprises a push rod 31 that is arranged on the back rest part 15 in such a way as to be capable of axial displacement. The axial displacement of the push rod parallel to the longitudinal direction of the back rest part 15 is guided by guide elements 32 that are fixed to the back rest part. One end of the push rod projecting from the lower end of the back rest part 15 is rotatably secured to a bracket 33, which is secured to the rear end of the seat part 14. When the seat part 14 is caused to rotate in a direction of rotation about the first axis of rotation Al by means of the actuator 21, the link mechanism 30 carries the back rest part 15 with it so that the latter is driven to rotate in the opposite direction about the second axis of rotation A2 , as can be appreciated from the Figures. In this embodiment, too, the rotation of the two angle elements 12, 13 can be driven by means of a separate, linear actuator or in some other way.

Figs, βa and 6b illustrate a further embodiment of the seat arrangement according to the invention. This seat arrangement 110 comprises a stationary part 111, a seat part 114, a back rest part 115 and a carrier element. This embodiment differs from the embodiments described above specifically in that the carrier device consists of an arc-shaped element 112. The arc-shaped element 112 is mounted by means of two lower rollers 140 and one upper roller 141 in such a way that it is capable of displacement on the stationary part 110. The lower 140 and the upper 141 roller are rotatably mounted on the stationary part. By causing the arc-shaped element 112 to be displaced in its longitudinal direction or in its circumferential direction, the element 112 will rotate about an axis of rotation A103 that is positioned at the centre of the circle that is defined by the arc and its imaginary prolongation, which centre is referred to here as the centre of the circular arc.

The seat part 114 is fixed to a first shaft 116, which is rotatably mounted on the front end of the arc-shaped element. The first shaft thus defines a first axis of rotation AlOl, about which the seat part is able to rotate relative to the arc-shaped element 112. The back rest part 115 is fixed to a second shaft 117, which is rotatably mounted on the rear end of the arc-shaped element. The second shaft 117 thus defines a second axis of rotation A102, about which the seat part is able to rotate relative to the arc-shaped element 112.

By causing the seat part 114, the back rest part 115 and the arc-shaped element to rotate respectively about the first AlOl, the second A102 and the third A103 axis of rotation, it is possible with this embodiment of the seat arrangement to produce a corresponding increase and reduction in the angle between the back rest part 115 and the seat part 114, as described above. As can be appreciated from Figs. 6a and 6b, the desired change in the distance between the lower section of the back rest part and the seat part is also achieved with this embodiment .

Driving of the rotation of the seat part 114 about the first axis of rotation AlOl and the rotation of the back rest part 115 about the second axis of rotation A102 can be achieved in a similar manner to that described above. Driving of the displacement of the arc-shaped element and thus its rotation about the third axis of rotation A103 is preferably achieved by means of a gear that is arranged on the upper roller 141 and is capable of being driven in both directions of rotation by an electric motor (not shown here) . The gear engages in gears that are arranged one after the other in the longitudinal direction or the circumferential direction of the surface of the arc- shaped element facing towards the centre of the arc. A well-balanced and easily-driven construction is obtained in this way, which permits the use of a comparatively small and low-output motor. In the embodiments depicted in Figs. 6a and 6b, the seat arrangement comprises only one carrier device in the form of an arc-shaped element. It will be appreciated, however, that the seat arrangement, as in the embodiments depicted in Figs. 1-5, preferably comprises two arc-shaped elements of essentially identical form, which are arranged each on its own side of the seat part and the back rest part and are joined together by means of the first and the second shaft.

Illustrative embodiments of the invention are described above. It will be appreciated that the invention is not restricted to these embodiments, but that it can be varied freely within the scope of the following Patent Claims. For example, the wheelchair on which the seat arrangement is arranged can be manual, instead of being electrically driven. Regardless of whether the wheelchair is electrically or manually driven, one or more of the drive units that are used to drive the rotation of the seat part, the back rest part and the carrier part can be manual . Such manual driving devices can incorporate linear driving devices, for example, consisting of two telescopically arranged tubes, of which the relative longitudinal displacement is achieved by means of an axial screw that is driven manually by means of a handle, a crank or the like. A rotating driving device for driving by means of the geared engagement of the displacement of the arc-shaped carrier devices in the circumferential direction can be driven manually in a similar fashion by a crank or a handle that is connected to a gear which, in a similar fashion to the motor -driven arrangement described above, drives the movement of the arc-shaped carrier device. Instead of using driving devices in order to provide one or more of the rotations of the seat part, the back rest part and the carrier device, it is also possible to produce these rotations simply by gripping the part concerned and rotating it by hand about the respective axis of rotation. Once the desired rotation position has been adopted, for example, manual locking devices can be used in order to lock the part in a releasable manner in the desired rotating position. Such manual locking devices can consist of telescopic tubes, for example, the different relative axial positions of which can be locked, for example, by means of a transverse pin passing through both tubes.

Claims

Patent Claims

1. Seat arrangement for a wheelchair, which 5 arrangement comprises a seat part that is intended to support a user's bottom and a back rest part which is capable of rotation in relation to the seat part about a transverse axis of rotation in order to permit adjustment of the angle between the seat part and the

KD back rest part, wherein the seat part (14, 114) is rotatably arranged about a first, transverse axis of rotation (Al, AlOl) and the back rest part (15, 115) is rotationally arranged about a second transverse axis of rotation (A2 , A102), characterized in that the

15 positions of the first and the second axis of rotation are fixed in relation to the seat part and the back rest part respectively and to one another, and in that the first and the second axes of rotation are capable of rotating together about a common third transverse

20 axis of rotation (A3, A103).

2. Seat arrangement according to Claim 1, in which the seat part (14, 114) and the back rest part (15, 115) , are rotatably fixed to a carrier device, at the

25 first (Al, AlOl) and the second (A2 , A102) transverse axis of rotation.

3. Seat arrangement according to Claim 2, in which the third transverse axis of rotation (A3) extends

30 through the carrier device.

4. Seat arrangement according to Claim 2, in which the carrier device consists of an arc-shaped element

(112) that is displaceable in the circumferential 35 direction in order to permit rotation of the element about the centre of its arc, which constitutes the third transverse axis of rotation (A103) .

5. Seat arrangement according to any of Claims 2-4, comprising means for achieving coordinated rotation of the seat part (14, 114), the back rest part (15, 115) and the carrier device respectively about the first (Al, AlOl), the second (A2 , A102) and the third (A3, A103) transverse axis of rotation.

6. Seat arrangement according to Claim 5, comprising a first, a second and a third electric drive unit that are mechanically connected respectively to the seat part, the back rest part and the carrier device and are electrically connected to a control unit in order to produce the coordinated rotations.

7. Seat arrangement according to Claim 5, comprising an electric drive unit that is mechanically connected to one or other of the seat part and the back rest part and a mechanical link mechanism which connects the seat part to the back rest part.

8. Seat arrangement according to Claim 7, in which the electric drive unit comprises a linear actuator (20) that is fixed to the carrier device and to the seat part (14) .

9. Seat arrangement according to Claims 5-8, in which the carrier device is arc-shaped and exhibits gears, which seat arrangement comprises a gear wheel driven by an electric motor, which gear wheel interacts with the gears of the carrier device in order to produce displacement of the carrier device in its circumferential direction and, thereby rotation of the carrier device about the third transverse axis of rotation .

10. Seat arrangement according to any of Claims 2-9, comprising at least one manually driven drive device in order to produce rotation of at least one of the seat parts, the back rest part and the carrier device respectively about the first, second and third axis of rotation.

11. Seat arrangement according to any of Claims 2-10, comprising locking devices for fixing at least one of the seat part, the back rest part and the carrier device m an adopted rotating position.

12. Seat arrangement according to any of Claims 2-11, comprising two essentially identical carrier devices that are arranged side-by-side and are mutually connected by means of a first and a second transverse shaft, which defines respectively the first and the second transverse axis of rotation.

13. Wheelchair comprising a seat arrangement according to one of Claims 1-12.

14. Method for varying the angle between a seat part arranged on a wheelchair, which seat part is intended to support a user's bottom and a back rest part, which is capable of rotation in relation to the seat part about a transverse axis of rotation, which method is characterized by rotating the seat part (14, 114) about a first, transverse axis of rotation (Al, AlOl) the position of which is fixed m relation to the seat part, by rotating the back rest part (15, 115) about a second transverse axis of rotation (A2 , A102) the position of which is fixed m relation to the back rest part and to the first axis of rotation, and by rotating the first and the second axis of rotation together about a common third transverse axis of rotation (A3, A103) .