WO1990011748A1

WO1990011748A1 - Bed

Info

Publication number: WO1990011748A1
Application number: PCT/SE1990/000156
Authority: WO
Inventors: Kenneth Leim
Original assignee: Mölnlycke AB
Priority date: 1989-03-30
Filing date: 1990-03-12
Publication date: 1990-10-18
Also published as: SE465250B; FI914593A0; SE8901122L; SE8901122D0; EP0465549A1

Abstract

A bed and/or chair arrangement comprises a stand (1) and an assembly forming support surfaces, which is divided into at least two members moveable with respect to each other, viz. a backrest (7) and an at least seat supporting member (8), said backrest being pivotally arranged about a substantially horizontal pivot axis (31) with respect to the stand, a power means (15) being arranged to generate a pivoting movement of the backrest (7) about said pivot axis between different inclination positions with respect to the stand. The pivot axis (31) of the backrest and that end of the at least seat supporting member which is closest to this are mutually displaceable in the longitudinal direction of the arrangement. A transmission device is arranged to cause the power means (15) to act between the backrest (7) and the at least seat supporting member so as to produce said mutual displacement, so that said pivot axis and end are displaced apart when the backrest is pivoted upwardly from a substantially horizontal position to a further risen position and towards each other upon pivoting in the opposite direction.

Description

Bed

FIELD OF THE INVENTION AND PRIOR ART

The present invention relates to a bed and/or chair arrangement comprising a stand and an assembly forming support surfaces, which is divided into at least two members movable with respect to each other, viz a backrest and an at least seat supporting member, said backrest being pivotally arranged about a substantially horizontal pivot axis with respect to the stand, a power means being arranged to generate a pivoting movement of the backrest about said pivot axis between different inclination positions with respect to the stand.

Arrangements or furniture of this type are primarily used as beds for disabled persons, but other fields of use could also be possible, for example as sun bath bed-chair. However, the field of use as a bed for disabled persons will mainly be described here, but this does however not constitute any kind of restriction of the scope of the invention.

Known furniture of this type have among others the disadvantage that the person resting in the piece of furniture tends to slide up and down the backrest when the backrest is pivoted upwardly and downwardly, respectively, and the clothes of this person will be pulled in various directions and cause the person discomfort. This is caused by the arrangement of the pivot axis of the backrest in a fixed position with respect to the at least seat supporting member, as a consequence of which the position of the hip-joint of the person resting in the piece of furniture considerably over said pivot axis means that the back of the person has a shorter distance to move than the backrest when the latter is pivoted upwardly and a longer distance than this when it is pivoted downwardly. Thus, for example a shirt on the person will be pulled upwardly along the back of the person on pivoting the backrest downwardly. Furthermore, a mattress lying on the assembly forming support surfaces will be pressed together and form bumps and irregularities on a pivo¬ ting of the backrest upwardly.

The present invention aims to remedy these inconveniences by an appropriate construction of an arrangement of the type de¬ scribed in the introduction.

SUMMARY OF THE INVENTION

This object is obtained according to the invention in that a bed and/or chair arrangement having the characteristics of the appended claim 1 is provided.

Thanks to the displaceability in the longitudinal direction of the arrangement between the pivot axis of the backrest and that end of the seat supporting member which is closest to this and the construction of the transmission device so as to cause a displacement of said pivot axis with respect to the at least seat supporting .,member when the backrest is pivoted upwardly and downwardly, the so called "shirt pulling effect" mentioned above can be counteracted and neutralized. A mattress lying on the assembly forming support surfaces will thereto upon pivo¬ ting of the backrest be able to lye loosely uneffected on this without any displacements with respect thereto or compressions forming folds and/or bumps. Further advantageous characteristics and advantages of the invention will appear from the other appended claims and the following description.

The characteristics of the appended claims 10 and 11 are particularly preferred, which characteristics make it possible to rapidly apply and remove different power means so as to produce desired movements of the members of the arrangement being parts of the assembly forming support surfaces.

BRIEF DESCRIPTION OF THE DRAWINGS

With reference to the appended drawings, a more specific description of preferred embodiments of the invention will follow hereinafter.

In the drawings:

Fig 1 is a simplified side view of a first embodiment of a bed according to the invention,

Fig 2 shows a portion of the bed according to Fig 1, which is longitudinally sectioned and enlarged.

Fig 3 is a perspective view obliquely from behind/below, which shows a part of the transmission device, parts of the bed being broken away,

Fig 4 is a side view similar to Fig 2 but with the backrest in a different inclination position, namely horizontal,

Fig 5 shows a longitudinally sectioned view of a bed according to the invention equipped with a power means,

Fig 6 shows a longitudinally sectioned view of an intermediate portion of a bed according to the invention equipped with three power means, and Fig 7 is a perspective view of an attachment member according to the invention for a moveable connection of the power means to the thigh supporting or calf supporting member of a bed according to the invention.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS OF THE INVENTION

A preferred embodiment of the arrangement according to the invention is shown in a side view in Fig 1 in the form of a bed for in particular disabled persons. For the sake of clarity some details having nothing to do with the invention have been omitted. For example the mattress, which is intended to lye on the assembly forming support surfaces, is not shown. The bed comprises a stand 1, which in its turn comprises legs 3 bearing on the ground by means of wheels 2 and a frame work 4 for supporting the other parts of the bed, such as the assembly forming support surfaces, power means and so on. The frame work 4 has a central box girder 5 extending in the longitudinal direction of the bed and a frame part 6 with outer dimensions substantially corresponding to the lying surface of the bed. The assembly forming support surfaces comprises a backrest 7 pivotally arranged about a substantially horizontal axis with respect to the stand, a seat supporting member 8 fixed with respect to the stand, a thigh supporting member 9 pivotally arranged with respect to the stand and a calf supporting member 10 pivotally arranged at the free end of the member 9. The members 8, 9 and 10 are pivotally interconnected by hinges 11 and 12, respectively, whereas the backrest 7 is arranged freely movable with respect to the seat supporting member 8. The members 7-10 being parts of the assembly forming support surfaces form a frame for receiving transverse laths not shown, which are interconnected by elastic rubber bands. These laths are intended to support a mattress. Accordingly, the only connection existing between the backrest 7 and the seat suppor¬ ting member 8 is the elastic rubber bands existing between adjacent laths in this region of the assembly forming support surfaces. The width of the assembly forming support surfaces is smaller than the one of the frame part 6, and therefore the end of the calf supporting member has been provided with a broader piece 13, which has rollers 14 for bearing upon the frame part 6 and thereby displaceably bearing the member 10 upon the latter. A portion of the foot end of the bed has been cut away in Fig 1 for space reasons.

Making reference to Figs 2-5 the possible movements or dis¬ placements of the members being parts of the assembly forming support surfaces and how these are produced will be described more in detail. A power means 15 of the type varying its length is at one of its ends pivotally connected to an attachment 16 fixed to the stand and at its other end pivotally connected to a second end 17 of a rigid first arm 18. The power means 15 comprises in this case an electric motor which is arranged to rotate the piston rod of a screw cylinder 20. A projection in the form of a rigid axle 22 extending substantially horizon¬ tally in the direction transverse to the bed is secured to the first end 21 of the first arm. The rigid axle 22 extends on both sides of the arm 18 and is at both ends rotatably received in square blocks 23, which each are displaceably received in a track 24 in opposed vertical walls 25 of the box girder 5. The box girder 5 has a mirror symmetry with respect to a longitu¬ dinal vertical plane passing through its centre, so that the two vertical walls 25 look identical (see especially Fig 3).

The rigid axle 22 is by means of bars 26 rigidly connected to cross beams 27, 28 of the backrest 7. This means that pivoting of the first arm 18 and thus the rigid axle 22 about the pivot axis passing through the centre of the blocks gives rise to a pivoting of the backrest between different inclination posi¬ tions. Such a pivoting can be achieved by shortening and prolongation of the screw cylinder 20, respectively.

A second rigid arm 29 is by a first end 30 rigidly connected to the first end 21 of the first arm, so that their common origin defines said pivot axis 31. A projection 33 extending substantially in parallel with the axle 22 is secured to the second end 32 of the second arm. The projection 33 extends on both sides of the second arm, and its extremities are in the position of the backrest shown in Fig 3 through rotatable rollers 33' received in tracks 34 in the vertical walls 25 of the box girder. The tracks 34 have in the front an opening 35 downwards and at the back an opening 36 upwards, which are so wide that the ends of the projection 33 may pass therethrough. The lower wall of the track 34 forms a shelf for the end in question of the projection 33, which at the opening 35 is continued forwardly by an arcuated shape 37. It has been found that a length of the shelf of about 70 mm is preferable, and this length will correspond to the maximum displacement of the pivot axis 31 with respect to the seat supporting member 8.

Finally, on both sides of the first and second arms made from one piece third arms 38 are at one of their ends secured to the rigid axle 22. At their other end the third arms have small projections 39, which are arranged to co-operate with arcuated guiding walls 40 on the vertical wall 25 in question.

Thanks to the parts just described constituting the transmis¬ sion device of the bed the power means 15 will produce the following motion pattern of the backrest 7: when the screw cylinder 20 in the horizontal position of the backrest (Fig 4) starts to contract itself a pivoting of the first arm 18, and by that of the backrest 7 rigidly connected thereto, about the pivot axis 31 formed by the axle 22 is obtained. During the initial pivoting of the backrest 7 upwards the extremities of the projection 33 move along the arcuated guiding walls 37 and hold the pivot axis 31 in a fixed position. When the extremi¬ ties of the second projection 33 pass through the opening 35, which happens when the backrest 7 has an inclination of 20°- 45°, preferably about 30°, with respect to the horizontal plane, continued contraction of the screw member 20 will lead to a displacement in Fig 4 to the right of the ends of the projection 33 in the tracks. Owing to this fact the blocks 23 inside the tracks 24 and the pivot axis 31 and by that the lower end of the backrest, which goes away from the seat supporting member 8, are also displaced. This displacement continues until the screw cylinder 20 has been shortened to such an extent that the ends of the projection 33 arrive to the opening 36, which preferably takes place after a displacement of about 70 mm, whereupon continued contraction of the screw cylinder will give rise to a continued pivoting of the backrest 7 upwards while the projection 33 goes out of the engagement with the track 34. During this continued pivoting of the backrest upwards a small projection 39 of the third arm will be displaced along and co-operate with the guiding walls 40 and by that assure that the pivot axis 31 remains in its second end position (the position in Fig 2). As the small projections 39 after completed displacement along the guiding walls 40 hit an upper stop wall 40', an unintentional pivoting of the backrest forwards further than to this position, preferably correspon¬ ding to the vertical position of the backrest, is also preven¬ ted.

Thus, a pattern of motion of the backrest is obtained, which avoids said shirt pulling effect thanks to that a pivoting of the backrest 7 upwards is associated with a displacement of the pivot axis of the backrest with respect to the stand and by that of the lower end of the backrest away from the seat supporting member 8. On the contrary, the lower end of the backrest is displaced towards the seat supporting member in connection with a pivoting of the backrest downwards to the position according to Fig 4.

Fig 5 illustrates how the power means 15 may influence the position of the thigh supporting member 9 and the calf suppor¬ ting member 10. A rigid link 41 is at its one end pivotally connected to the first arm 18 and at its other end pivotally connected to one arm 42 of a double armed lever 43 pivotally connected to one of the vertical walls of the box girder and by that to the stand. The second arm 44 of the double-armed lever pivotally receives a rigid piece 45, which in its turn, by means of a pivot pin, is pivotally connected to an attachment in the form of an ear 46 provided with a groove, secured to the thigh supporting member. The rigid link, the double-armed lever and the rigid piece as well as the attachment 46 are preferably two in number and arranged in a mirror symmetry relationship with respect to the central plane of the bed, so that the thigh supporting member is supported by a rigid piece on each verti¬ cal wall of the box girder.

A contraction of the screw cylinder 20 starting from the position according to Fig 4 will through the rigid links 41 lead to pivoting of the double-armed lever 43 counter-clockwise as seen in Fig 5, which leads to a pivoting of the rigid piece 45 while raising the thigh supporting member 8 and by that through the hinge 12 the calf supporting member 10, so that the latter slopes towards the foot end and is displaced by means of the rollers 14 on the frame part 6 of the stand. The bend of the knees of the person resting in the bed thus obtained in connection with pivoting of the backrest upwards then reduces the strain on the back and counteracts an unpleasant stretching of the back muscle, biceps femoris, of the thighs. When the backrest is pivoted downwardly the links 41 conversely produce a lowering of the hinge 12 between the members 9 and 10 and by that a stretching of the knee-joint of the person towards the position according to Fig 4.

In Fig 6 an embodiment variant with three power means is shown, the first of which not shown is designed and arranged in the same way as the power means 15 shown in for example Fig 2. It is possible to rapidly change from one of these embodiments to the other. This is achieved in the following way: starting from the embodiment shown in Fig 5 the rigid links 41 are removed, which are preferably secured by locking pins to the lever 43 and the first arm 18, respectively. Then the rigid piece 45 is pushed out of its engagement with the attachment 46. When this is done a first attachment member 47 is arranged on the under¬ side of the thigh supporting member and a second attachment member 48 is arranged on the underside of the calf supporting member. The two attachment members are designed in a similar way, and the second attachment member 48 is shown in Fig 7 in order to explain the fastening of the attachment members on the members 9 and 10. The attachment members has a plate 49, which at one end is terminated by a U-shaped piece 50. A flange 51 is protruding in right angle from the plate. This flange has a bore 52 for the passage of a locking pin. Furthermore, the attachment member has a pin 53. The attachment members are applied to the members 9 and 10, respectively, by pushing the U-shaped piece 50 onto a cross beam 54 of the member in ques¬ tion and pressing the pin 53 into locking engagement with an ear 46, 55, which is arranged on a cross beam 56 of the same member located closer to the foot end of the bed. In this way a quick locking of the attachment members 47 and 48 to the members 9 and 10 is obtained. The engagement of the pin 53 in the ear in question may if desired be supplemented by another locking pin or a similar means. When the two attachment members are brought into position a second power means 57 is by means of locking pins pivotally connected through its one end to an attachment 58 secured to the stand and its other end pivotally arranged on the flange 59 protruding downwardly of the first attachment member 47. Then a third power means 60 is pivotally connected by its one end to the flange 59 and its other end to the flange 51. The second and third power means are of the type varying its length and comprise preferably, like the first power means, an electric motor and a screw cylinder driven thereby. Advantageously, the piece 13 is now also removed from the foot end of the calf supporting member, so that the member 10 may freely pass downwardly between the lateral frame pieces of the frame part 6. In a short period of time and by a few simple movements of the hand and an embodiment with separately controlled movements of the members being parts of the assembly forming support surfaces has now been achieved. The first power means 15 will still cause the motion pattern defined above of the backrest when this is pivoted upwardly and downwardly. However, the pivoting of the thigh supporting member 9 about t hinge 11 is now controlled by actuating the second power means 57, while the pivoting of the calf supporting member 10 about the hinge 12 is effected by the third power means 60. Thus, if only the second power means 57 is actuated the angle between the members 9 and 10 will remain constant, in spite of the member 9 pivoting around the hinge 11. The third power means 60 then functions as a rigid link between the members 9 and 10. With a view to simplify the drawings the connections for the power supply of the power means and the wires to an operating board, which is preferably accessible to the person resting in the bed, has not been shown. In the state of the bed shown in Fig 5 it is only necessary to press one button for controlling the movement of the different members being parts of the assembly forming support surfaces. This may be advantageous to persons having difficulties in co-ordinating movements in their fingers or being scatter-brained. In the state according to Fig 6 the person has to push a separate button for controlling just one of the power means 15, 57 and 60. This has the advantage that the inclination of the members 7, 9 and 10 may be adjusted exactly according to the wishes of the user, but it requires at the same time a somewhat greater skill in operating the buttons of the board. The fact that the invention provides means for quick and easy change between the two states according to Fig 5 and 6, leads to the advantage that by one and the same bed the state suiting the person, usually the patient, resting in the bed on a given occasion may be provided, and accordingly a greater possibility to choose the function form as well as greater exploitation of the bed and thereby also saving of the number of beds, where they are found in greater institutions, such as nursing institutions, is obtained.

The invention is of course not restricted to the preferred embodiments thereof described above, but several possibilities to modify them will be apparent to a man with skill in the art without departing from the basic idea of the invention. For example, the stand of the arrangement could be designed in many different ways. The power means could be driven in other ways, for example be constituted of hydraulic pumps effecting hydraulic cylinders, but other types of power means, such as pneumatic ones, would also be possible.

Furthermore, it would be possible that the bars 26 connecting the rigid axle 22 with the backrest could be replaced by some kind of supporting member, which is secured to the axle 22 and on which the backrest rests only by means of the force of gravity.

The different guiding means and attachment members being parts of the piece of furniture according to the invention may of course be replaced by analogous ones, like a projection running in a track being provided with a track and the track is replaced by a projection in the form of a rib and so on.

The definition "rigidly connected to" in the claims comprises also cases in which the members in question are indirectly connected to each other. It is essential that they are not mutually movable.

In the first embodiment it would also be possible that the members 8, 9 and 10 of the assembly forming support surfaces consist of one single member fixed to the stand with respect to which the backrest is displaceable.

Finally, it would also be possible for the power means in the embodiment in Fig 5 to be arranged to act on another member in the transmission device than the first arm, for example on the double-armed lever, through which the long rigid link 41 then will transfer forces from the double-armed lever to the first arm instead of the reverse.

Claims

1. A bed and/or chair arrangement comprising a stand (1) and an assembly forming support surfaces, which is divided into at least two members movable with respect to each other, viz a backrest (7) and an at least seat supporting member (8) , said backrest being pivotally arranged about a substantially hori¬ zontal pivot axis (31) with respect to the stand, a power means (15) being arranged to generate a pivoting movement of the backrest (7) about said pivot axis between different inclina¬ tion positions with respect to the stand, c h a r a c t e r i z e d in that the pivot axis (31) of the backrest and that end of the at least seat supporting member which is closest to this are mutually displaceable in the longitudinal direction of the arrangement, and that a trans¬ mission device (17, 18, 21-40) is arranged to cause the power means (15) to act between the backrest (7) and the at least seat supporting member so as to produce said mutual displace¬ ment, so that said pivot axis and end are displaced apart when the backrest is pivoted upwardly from a substantially horizon¬ tal position to a further raised position and towards each other upon pivoting in the opposite direction.

2. An arrangement according to claim 1, c h a r a c t e ¬ r i z e d in that the at least seat supporting member com¬ prises a seat member (8) located closest to the backrest and fixed with respect to the stand (1), that the pivot axis (31) of the backrest is displaceable with respect to the seat member in the longitudinal direction of the arrangement, that the transmission device comprises a rigid first arm (18) rigidly connected to the backrest, a first end (21) of said arm being pivoted and displaceable while co-operating with guiding means (24) on the stand while defining the pivot axis of the back¬ rest, and that the power means is arranged to act upon the other end (17) of the arm so as to produce said pivoting and displacement of the backrest.

3. An arrangement according to claim 2, c h a r a c t e ¬ r i z e d in that the transmission assembly comprises a second rigid arm (29), a first end (30) of which is rigidly connected to the first end (21) of the first arm, so that their common origin defines said pivot axis (31), that this arm origin is connected to first guiding means (23) designed to co-operate with second guiding means (24) on the stand for arranging the arm origin displaceable and pivoted with respect to the stand, and that the second end (32) of the second arm is connected to third guiding means (33, 33') designed to co-operate with fourth guiding means (34, 37) on the stand so as to guide the movement of the guiding means of the arm origin with respect to the guiding means of the stand.

4. An arrangement according to claim 3, c h a r a c t e ¬ r i z e d in that the first guiding means comprises at least a first projection (22) rigidly connected to the arm origin, the longitudinal extension of said projection corresponding to the pivot axis of the backrest, that the extremity of the projec¬ tion is received in a substantially horizontal track (24) running in the longitudinal direction of the arrangement and displaceable in this between two end positions, that the third guiding means of the second arm comprises at least a second projection (33) extending substantially in parallel with the first projection (22), the extremity of the second projection being designed to co-operate with and be displaced along the fourth guiding means (34, 37) on the stand, so that the power means (15) is arranged to, in the substantially horizontal position of the backrest, affect the second end (21) of the first arm to cause pivoting of the first arm (18) and thus pivoting upwards of the backrest while keeping the first projection and by that the pivot axis in the first end position owing to the fact that the second projection is arranged to move along the fourth guiding means and retain the first projection in this position, that the fourth guiding means (34) are arranged to, after the backrest is pivoted upwards to an intermediate position, upon continued action of the power means on the first arm guide the second projection (33) substantially in the longitudinal direction of the arrangement away from the seat member (8) and by that give rise to a displacement of the first projection (22) and the pivot axis (31) of the backrest away from the seat member towards the second end position, and that the power means is arranged to, after the pivot axis has reached this end position, continue to pivot the backrest (7) upwardly by pivoting the first arm (18) while the second projection (33) leaves the guiding engagement with the fourth guiding means on 'the stand.

5. An arrangement according to claim 4, c h a r a c t e ¬ r i z e d in that a third arm (38) through its one end is rigidly connected to the two other arms on a level with said pivot axis, and that its other end (39) is arranged to, after the first projection (22) has reached the second end position, co-operate with arcuated guiding means (40) arranged on the stand so as to upon continued pivoting upwardly of the backrest guide the second end of the third arm along an arc of a circle with said pivot axis as center axis and prevent the extremity of the first projection to move back away from the second end position.

6. A bed and/or chair arrangement comprising a stand (1), an assembly forming support surfaces, which is divided into four members movable with respect to each other, viz a backrest (7) pivotally arranged with respect to the stand, a seat supporting member (8) fixed with respect to the stand, a thigh supporting member (9) pivotally arranged with respect to the stand and a calf supporting member (10) pivotally arranged at the free end of the latter, as well as a power apparatus arranged to, by means of a transmission device, produce the following motion pattern of the members being parts of the assembly forming support surfaces; a pivoting of the backrest (8) upwards from a substantially horizontal end position is accompanied of a pivo¬ ting of the thigh supporting member (9) upwards, so that the pivot centre (12) of the latter common to the calf supporting member is raised and the calf member slopes towards the foot end of the arrangement, and conversely, c h a r a c t e r i z e d in that the transmission device comprises a first arm (18) rigidly connected to the backrest (7) close to its pivot centre (31), a connecting member (43, 45) movably arranged between and connecting the stand and the thigh supporting member (9), and a rigid link (41) connecting the first arm (18) with said connecting member (43), that the free extremity of the calf supporting member (10) rests dis¬ placeable directly or indirectly on the stand, and that the power apparatus comprises one single power means (15) arranged to act between the stand and the transmission device formed by the arm, the link and the connecting member and produce said motion pattern of the assembly forming support surfaces.

7. An arrangement according to claim 6, c h a r a c t e ¬ r i z e d in that the power means (15) is arranged to act between the stand (1) and the first arm (18), and that the link (41) is loosenably arranged so as to enable separate pivoting of the backrest upwards and downwards without influencing the thigh supporting or the calf supporting members, as an alter¬ native to said motion pattern.

8. A bed and/or chair arrangement comprising a stand (1), an assembly forming support surfaces, which is divided into four members movable with respect to each other, viz a backrest (7) pivotally arranged with respect to the stand, a seat supporting member (8) fixed with respect to the stand, a thigh supporting member (9) pivotally arranged with respect to the stand and a calf supporting member (10) pivotally arranged at the free end of the latter, as well as a power apparatus arranged to produce the possible mutual movements of the members being parts of the assembly forming support surfaces, c h a r a c t e r i z e d in that the power apparatus comprises a first power means (15) arranged to act between the stand (1) and the backrest (7) in order to pivot the backrest with respect to the stand and a second power means (57) to act between the stand (1) and the thigh supporting member (9) so as to pivot this with respect to the stand and by that raise and lower the pivot centre (12) common to this member and the calf supporting member.

9. An arrangement according to claim 8, c h a r a c t e ¬ r i z e d in that the power apparatus further comprises a third power means (60) arranged to act between the thigh supporting member (9) and the calf supporting member (10) so as to change the angle therebetween.

10. An arrangement according to claim 8 or 9, c h a r a c ¬ t e r i z e d in that it comprises a first attachment member

(47) removably arranged on the thigh supporting member (9), said attachment member having means (50, 53) for holding it on the underside of the thigh supporting member, that these means comprise an U-shaped piece (50) grasping around a cross beam (54) of the thigh supporting member and arranged to receive said beam through the opening of the U and a quick-acting lock means (53) rigidly connected to this piece and arranged to, after snapping in, enter into engaging co-operation with a quick-acting lock means (46) arranged on the thigh supporting member (9) in the direction in which the opening of the U is directed and in the longitudinal direction of the arrangement at a distance from said cross beam (54), and together with the U-shaped piece secure the attachment member to the thigh supporting member, that the second power means (57) is of the type varying its length, and that the attachment member (47) comprises a flange (59) protruding downwardly to which one end of the second power means is adapted to be pivotally connected.

11. An arrangement according to claims 9 and 10, c h a r a c ¬ t e r i z e d in that it comprises a second attachment member

(48) removably arranged on the calf supporting member (10), said second attachment member having means (50, 53) for holding it on the underside of the calf supporting member, that these means comprise an U-shaped piece (50) grasping around a cross beam (54) of the calf supporting member and arranged to receive said beam through the opening of the U and a quick- acting lock means (53) rigidly connected to this piece and arranged to, after snapping in, enter into engaging co-opera¬ tion with a quick-acting lock means (53) arranged on the calf supporting member (10) in the direction in which the opening of the U is directed and in the longitudinal direction of the arrangement at a distance from said cross beam (54), and together with the U-shaped piece secure the attachment member to the calf supporting member, that the second attachment member (48) comprises a flange (51) protruding downwardly, that the third power means (60) is of the type varying its length, and that the third power means is arranged to, by means of one of its ends, be pivotally connected to the downwardly protru¬ ding flange (59) of the first attachment means and, by means of its other end, be pivotally connected to the downwardly pro¬ truding flange (51) of the second attachment member.

12. An arrangement according to claim 11, c h a r a c t e ¬ r i z e d in that at least the ends of the power means pivo¬ tally connected to the flange of the attachment members are connected by locking pins and thereby removably arranged.