GB2506665A

GB2506665A - A leg rest with a moving axis of rotation

Info

Publication number: GB2506665A
Application number: GB1217907.3A
Authority: GB
Inventors: Kah Ming Chan; Lee Humphries; David Smith
Original assignee: CAREFLEX Ltd
Current assignee: CAREFLEX Ltd
Priority date: 2012-10-05
Filing date: 2012-10-05
Publication date: 2014-04-09
Also published as: IE20130298A1; GB201217907D0

Abstract

A seat comprising a seat portion 15, a legrest portion 22 arranged to support an occupants calves and a linkage mechanism connecting the legrest 22 to the seat portion 14 wherein the linkage mechanism is arranged to rotate the legrest 22 about an axis of rotation 31 and wherein the axis of rotation 31 moves during movement of the legrest 22 such that the legrest 22 follows the inclination of the occupants calves. The mechanism may have a first set of components to move the axis or rotation 22 and a second set to adjust the inclination of the legrest 22. The device may employ guides or rails 34 and followers 37 to control movement. The legrest 22 may have a telescopic portion which extends when raised and a footrest which can be retracted behind the legrest 22. A frame may be independently tiltable on a base. An electric motor or gas strut may be used as an actuator.

Description

Seat with Raisable Lerest The present invention relates to a seat with a raisable legrest and is particularly applicable to a specialist posture management static seating system, as may be used by the elderly or disabled. The invention may have applications to other seating incorporating a legrest, both domestic and commercial and may for example be applicable to wheelchairs or other transportation seating, such as aircraft seating.

As the invention is particularly applicable to a specialist posture management static seating system, the invention will be descnbed in the context of such a seating system.

However, this does not limit the scope of the invention, which is defined by the attached claims.

A known type of posture management seating system, in this case a chair, is disclosed in Figures 1 and 2. The chair, indicated generally as I, comprises a base 2, a frame 3. a seat portion 4 and a legrest 5. The frame 3 may be tilted on the base 2 about pivot point 6 by means of actuator 7, which is commonly referred to as tilt in space (TIS).

The backrest, not shown, may be reclined in the frame 3 and the position of the base of the backrest adjusted forward or backwards in the frame 3, to shorten or lengthen the seat portion 4 that is available for an occupant to sit on. The legrest 5 is inclined by means of actuator S and the seat can be provided with different pairs of arms 9. each of a different width with each arm saddle shaped to sit on a respective side of the frame 3. Thus the width of the seat portion 4 available for the occupant to sit on can be adjusted by selecting appropriate pairs of arms.

An occupant of this type of chair will normally sit on it for many hours each day and may depend on a nurse or carer to assist them to get out of the chair, to adjust the chair or even to adjust their posture within the chair. It is for this reason that it is necessary that the chair has a number of independently adjustaNe components, for it is important that the occupant is colTectly supported to avoid any pressure points, which may lead to discomfort, a degradation of the body tissue or restricted circulation and the problems associated with this. It is also important to provide proper support to maintain an occupants posture. For

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example. undue leaning could result in a scholiotic profile, where the spine curves to maintain an upright head position.

Furtheimore, because an occupant is likely to be in the chair for long periods of time, it is important that each component is individually adjustable, so that the seating position of the occupant can both be tailored to the occupant and adjusted from time to time for an occupants comfort.

RefelTing now specifically to the egrest 5, with which the present invention is concerned, the legrest can be raised from a fully lowered position, shown in Figure 1, to the fully raised position, shown in Figure 2, to lift the occupants lower legs to provide a relaxing position. Leg devation is important because it encourages venous return and may reduce leg pain and swelling. Raising the eg above hip level for thirty minutes three or four times a day may allow swelling to subside and improve circulation.

The legrest 5, illustrated in Figure 1. is typical of chairs of this type and the legrest 5 is attached to frame 3 under the seat portion 4 at hinge, or pivot point 10. The pivot point is necessanly at a different location to the point 11 in the occupant's knee, about which the lower leg 12 of the occupant pivots. This has two consequences as can be seen from a comparison Figures 1 and 2. First, the lower leg 12 is not evenly supported, with more pressure being appfied in the region 13 than the region 14 as the lower leg is raised, causing pressure points. Secondly, the legrest 5 will be drawn upwards along the occupants calves, so that a point A on the legrest i, aligned with a point A' on the occupants lower leg 12 in Figure 1, will be displaced to the position shown in Figure 2, the points A and A' becoming several centimetres apart. In addition to this causing discomfort by causing the occupants clothing to become crumpled, it may also displace the body tissue on the occupants lower leg 12 which, if maintained in this position for a long period, could damage the body tissue or restrict circulation.

As can also be seen from a comparison of Figures 1 and 2, this known arrangement of legrest 5 results in the occupants foot extending a significantly greater distance past the end of the legrest when the legrest is in its raised position (Figure 2) than when in its lowered position (Figure 1). This again increases the pressure in the lower region 13 of the occupant's lower leg 12. This also makes it difficult to fit a footrest to the legrest 5. for if correctly fitted when the legrest is in its lowered position, as illustrated in Figure 1, then when the legrest 5 is raised to the position illustrated in Figure 2, the footrest will be in the wrong position, compressing the leg 12. This is problematic because a footrest is often desirable, as supporting the foot properly may assist the occupant in making some slight positional changes to their position and because it may also reduce the pressure between the occupants upper leg and the seat portion 4 of the seat I when the legrest 5 is in its lowered position.

It is an object of the present invention to provide a seat with an improved legrest.

Accordingly to the present invention there is provided a seat comprising: a seat portion for supporting an occupants buttocks; an elevating legrest having a generally planar support portion arranged to support the legs of the occupant in the region of the occupants calves; and a linkage mechanism connecting the legrest to the seat portion. wherein the linkage mechanism is arranged to support the legrest and rotate the legrest about a rotation axis when the legrest is raised to control the inclination of the legrest, the rotation axis being parallel to an axis passing through an occupants knees, about which the occupants lower legs rotate when their lower legs are raised by the legrest, characterised in that the linkage mechanism is arranged such that the legrest rotation axis is displaced rdative to the seat portion as the legrest is raised and the support portion is rotated about the legrest rotation axis as the legrest is raised so that the support portion generally follows the inclination of the back of the occupants lower legs in the region of their calves as the legrest is raised.

The present invention thus provides a linkage mechanism which can be arranged to keep a support portion of the legrest against the back of the occupants lower legs as the legrest is raised, by moving the axis about which the legrest rotates so that the support portion of the legrest can be both correctly positioned and correctly inclined in all positions of the legrest, from fully lowered to fully raised. This may enable the support portion of the legrest to be retained in contact along its length with the occupants lower leg, avoiding any pressure points occurring as the legrest is raised or lowered.

Preferably the linkage mechanism comprises a first set of components that control the position of the legrest rotation axis and a second set of components that control the inclination of the legrest. In this way the displacement of the rotation axis as the legrest is raised need not be a linear function of the rotation of the legrest about the rotation axis, thus any desired inclination of the legrest maybe achieved for any given displacement of the rotation axis from the seat portion of the seat.

Advantageously the first set of components comprise one or more extending members supporting the legrest relative to the seat portion to cause the legrest rotation axis, when the legrest is raised, to be displaced in a linear direction perpendicular to the rotation axis. If the extending member is to only move in a linear direction, it is relatively simple to provide a strong linkage mechanism to control the position of the axis of rotation of the legrest and to support the legrest at its axis of rotation.

It is also advantageous for the second set of components to include a guide and a follower to run in the guide, wherein one of the guide or follower is connected to the legrest and the other is fixed relative to the seat portion and wherein raising the legrest causes the follower to move along the guide and control the inclination of the legrest. This permits the guide to be shaped to provide the legrest with a desired inclination for any given displacement of the rotation axis. This arrangement also avoids the need for a separate actuator to control the inclination and ensures the inclination of the legrest is correct for the position to which the legrest has been raised. The guide may take the form of a slot or rail

for example.

The seat may comprise a frame to which the seat portion is attached and the legrest is attached by the linkage mechanism, the frame having side members and the linkage mechanism having two corresponding guides and followers, the guides may be in the form of slots formed in the side members of the frame with the followers being in the form of arms extending from the legrest.

Advantageously the linkage mechanism is arranged to move the support portion away from the seat portion as the legrest is raised such that the support portion substantially retains its position relative to an occupants lower legs in a lengthwise direction as the legrest is raised. hi this manner the support portion of the legrest does not move relative to the occupant's leg and thus will not drag the occupant's body tissue or clothing as the legrest is raised or lowered.

This maybe achieved if the legrest comprises an upper portion and a lower portion including the support portion for the occupant's legs, the upper and lower portions being arranged to extend telescopically and wherein the linkage mechanism comprises extension control components that control the extension of the legrest as the legrest is raised.

The seat may advantageously further comprise a footrest attached to the legrest such that the footrest moves with the support portion of the legrest. If the legrest remains correctly positioned against the back of lower legs of the occupant, as the legrest is raised.

then the foot rest will a'so be retained in the correct position, by being attached to the legrest and moving with the support portion of the legrest.

Preferably the footrest can be retracted behind the legrest without being detached. In this manner it can be retracted to enable the occupant to place his feet on the ground at the front edge of the seat, as is necessary for the occupant to raise themselves from the seat, without having to raise the legrest and an occupants legs first, in order to detach the footrest.

Preferably the position of the legrest is controlled independently of any other adjustment of the seat.

The seat may comprise a metal seat frame to which the linkage mechanism is attached, which metal frame supports the seat portion. The seat may also compnse a base unit to which the seat frame is pivotally supported to permit the frame, seat portion and legrest to tilt in space without any relative movement therebetween.

One embodiment of the present invention will now be described, by way of example only, with reference to the accompanying drawings, in which 111cc numerals are used throughout to indicate like parts and of which: Figure 1 depicts a lcnown chair with a legrest in a lowered position; Figure 2 depicts the chair of Figure 1 with the legrest in a raised position; Figure 3 is a perspective view of a base, seat frame, legrest and linkage mechanism of a seat in accordance with the present invention, with the egrest in a raised position; Figure 4 is a view similar to that of Figure 3 but with the legrest in a thwered position and showing some different components to Figure 3; Figure 5 is a side elevation of a chair in accordance with the present invention incorporating the base unit, seat frame, legrest and linkage mechanism illustrated in Figures 3 and 4. with some of the components of the linkage mechanism omitted for clarity and with the legrest in a fully lowered position; Figure 6 shows the chair of Figure 5 but with the legrest in a part raised position; Figure 7 shows the chair of Figures 5 and 6 but with the legrest in the fully raised position; Figures 8, 9 and 10 correspond to Figures 5, 6 and 7 but with alternative components of the linkage mechanism illustrated relative to those shown in Figures 5. 6 and 7; Figure II is a perspective view of the footrest shown in Figures 5 to 10 in a fully retracted position; Figure 12 shows the footrest of Figure 11 in a partially deployed position; Figure 13 shows the footrest of Figures 11 and 12 in a fully deployed position; Figure 14 shows the footrest of Figures 11 to 13 fully deployed and with the footrest extended; Figure 15 is an underneath view of the footrest of Figure 13, fully deployed but not extended; and Figure 16 is an underneath view of the footrest of Figure 14 fully deployed and extended.

Referring now to Figure 3, there is illustrated a chassis, indicated generally as 16, of a chair in accordance with the present invention, illustrated in Figures 5 to 10.

The chassis 16 comprises a wheeled sub-frame 17 to which seat frame 18 is pivotally connected by bolts 19. A mechanical actuator, not shown for clarity, acts between the sub-frame 17 and seat frame 18 so that it can be used to tilt the seat frame 18 and thus provide the chair with a tilt in space (TIS) capability, in a manner as commonly used and as previous'y described with references to Figures 1 and 2. The seat frame 18 comprises two side members I 8a and I Sb and two cross members I Sc and I 8d. The rear cross member 1 8c supports a mounting 20 for one end of a motorised actuator 21, as is more clearly shown in Figure 5.

The chassis includes the chassis of a legrest 22 of the chair 15. The chassis of the legrest comprises a proximal section 23 and a distal section 24 mounted on runners 25, so that distal section 24 can be telescopically extended from the proximal section 23.

In Figure 3, the legrest chassis 23, 24, 25 is shown in a raised position, with the distal section 24 fully extended from the proximal section 23.

The legrest chassis 23 to 25 is supported relative to the seat frame 18. by several components that shall hereinafter be collectively referred to as a linkage mechanism, indicated generally by the reference numeral 26.

The linkage mechanism 26 comprises three sets of components which respectively control the position of the legrest chassis 23 to 25 relative to the seat frame 18, the inclination of the legrest chassis 23 to 25 and the extension of the distal section 24 from the proximal section 23 of the legrest chassis.

The first set of components, which contr&s the position of the proximal section 23 of the legrest chassis, comprises two sets of quadruple rollers 27 and 28, only one (27) of which can be seen in Figure 3. Through each roller set 27 and 28 passes a respective support member 29, 30, each support member 2c.30 being arranged to roll in or out through the roflers at a fixed inchnation. Each support member 29, 30 is pivotaly connected at its distal end to the proximal section 23 of the legrest chassis such that the legrest chassis may pivot about an axis of rotation 31. The position of the axis of rotation 31 is thus controlled by actuator 21 acting between mounting 20, attached to the seat frame 18 and mounting 32 (which can just be seen in Figure 4) on the proximal section 23 of the legrest chassis. The mounting 32 lies approximately on the axis of rotation 31 and thus operation of the actuator 21 causes the axis 31 to be displaced away from or towards the seat frame 18 in a linear direction, determined by the roller sets 27 and 28 and respective support members 29 and 30.

A second set of components of the linkage mechanism 26 comprises slots 33 and 34 in respective seat frame side members I 8a and I 8b and associated arms 35 and 36. Each arm 35, 36 has a roller 37, 38 at one end engaged with a respective s'ot 33, 34 with its other end fixed to a respective side of the proximal section 23 of the legrest chassis.

Alternatively the slots could be in the foirn of any equivalent guide, for example rails.

This second set of components is more dearly seen in Figure 4, which illustrates the legrest chassis 23 to 25 in a fully lowered position and from which Figure some components, such as seat frame side member 18b, have been omitted for clarity. The inclination of the legrest chassis 23 to 25 is determined by the inclination of the arms 35, 36 which in turn is determined by the shape of the slots 33 and 34 and the position of the rollers 37, 38 in the slots 33, 34. Thus the inclination of the legrest chassis 23 to 25 is dependent on the position of the axis 31, as will be described in more detail later with reference to Figures 5 to 7.

The third set of components of the linkage mechanism shown in Figures 3 and 4 are components 39a to 39c and 40a to 40c which form respectively two three part linkages extending between the seat frame 18 and distal section 24 of the legrest chassis. These control the extension of the distal section 24 of the legrest chassis relative to the proximal section 23, which is described below with reference to Figures 8 to 10.

Although the motorised actuator 21 is a preferred way of controlling the position of the legrest chassis 23 to 25. because it enables the legrest 22 to be set to a fully lowered, fully raised or any intermediate position, this normally requires a power source to be carried by the chair, for example a battery (not shown), or the chair to be connected to a power source. If these are not desirable the motorised actuator 21 can be replaced by gas struts 41 and 42, shown in broken line in Figures 3 and 4. The gas struts 41 and 42 act on crossbar 43 extending between components 39a and 40a of three part linkages 39 and 40, described below, the gas struts 41 and 42 thus act via the respective three part Unkages 39 and 40 to raise the legrest chassis 23 to 25. When the legrest 22 is to be lowered it is forced down by a nurse or carer, recharging the struts.

Referring now to Figures 5 to 7, there is illustrated a chair 15 comprising the chassis 16 of Figures 3 and 4. from which linkage components 39a to 40c have been omitted for reasons of clarity. The chassis 16 supports a backrest 44 bolted to the rear of the seat frame side members 18a and 18b, shown in Figure 3. Chair arms 45 are mounted to respective seat frame side members 18a and 18b by means of pins (not shown) extending from the bottom of the arms 45 into sockets 46 on the seat frame side members I 8a and I 8b. A seat cushion 47 is secured on the seat frame 18 and a legrest cushion 48 is secured to the distal section 24 of the legrest chassis (not shown in Figure 5). Also attached to the distal section 24 of the legrest chassis is retractaNe footrest 49.

The footrest 49 includes a retraction mechanism which is descnbed below with reference to Figures 11 to 16. For reasons of clarity, the retraction mechanism of the footrest 49 has also been omitted from each of Figures 5 to 10, but it should be noted that the footrest shown in these figures can be retracted behind the egrest cushion 48, to enable the occupant of the chair to place their feet directly on the floor adjacent to the front edge of the legrest cushion 49, in order to assist them when getting out the chair 15.

In Figure 5, the legrest. indicated generally as 22, is shown in its fully lowered position with motorised actuator 21 fully retracted as indicated. In this position, the axis of rotation 31 of the legrest 22 is drawn back into the chair 15, the position of the axis of rotation 31 being determined by support members 29 and 30 running in respective roller sets 27 and 28. The legrest 22 is substantially vertical due to rollers 37 and 38 being at the uppermost end of respective slots 33 and 34, as shown.

In the position shown in Figure 5, the distal section 24 of the legrest chassis is fully retracted into the proximal section 23 of the legrest chassis, the extension of the distal section 24 relative to the proximal section 23 being controlled by separate components 39a to 40c of the linkage mechanism, omitted from Figures 5 to 7, but described below with reference to Figures 8 to 10.

As shown in Figure 5, when the chair 15 is correctly adjusted to accommodate an occupant and the legrest 22 is in the lowered position shown, the occupants upper leg 50 rests on seat cushion 47 with the point 11 of the occupants knee, about which the occupants lower leg 12 rotates, shghtly forward and above the front edge of the seat cushion 47. The lower leg 12 is supported by footrest 49 and also the legrest cushion 48. the surface of which is generally aligned with the occupant's lower leg 12 in the region of their calves.

RefelTing now to Figure 6. it is seen that on operation of the actuator 21, normally controlled by a nurse or carer for the occupant, the actuator 21 extends forcing the legrest 22 in the direction indicated by arrow 51, thus the axis of rotation 31 is displaced accordingly. This elevates the occupants lower leg 12. The inclination of the legrest 22 is controlled by rollers 37 and 38 moving along respective slots 33 and 34 so to cause legrest 22 to remain aligned with the occupants lower leg 12 as the lower leg 12 is raised, thus acting to ensure pressure is uniformly exerted on the lower leg 12 across the area of contact with the legrest 22.

The actuator 21 can be stopped in any position to provide a desired elevation for the lower leg 12. However, the actuator 21 may continue to be operated until the legrest 22 attains a fully extended position, as shown in Figure 7. Here the leg is fully elevated and the surface of the legrest seat cushion 47 is again correctly aligned with the back of the occupants lower leg 12, such as to maintain a uniform supporting pressure over the back of the occupants lower leg 12.

As mentioned above with reference to Figure 5, as the legrest 22 is raised a distal section of the legrest 24. to which the legrest cushion 47 is attached extends from the proximal section of the legrest chassis 23. This ensures that a point A on the legrest cushion 47, (see Figures 5 to 7), remains aligned with a point A' on the occupants lower leg 12. Thus raising or lowering the legrest 22 does not cause the occupants clothing or body tissue to be dragged, as may otherwise occur if the legrest cushion 47 moved relative to the lower leg 12 in a lengthwise direction. This also ensures that the footrest 49 remains in the correct position.

The extension of the distal section 24 of the legrest chassis is controlled by components 39a to 40c of the linkage mechanism, omitted from Figures 5 to 7 for clarity.

The operation of these components is described below with reference to Figures 8 to 10, from which those component of the linkage mechanism already described above, have been omitted for clarity.

Figures 8 to 10 only show components 40a to 40c. However, a corresponding set of components 39a to 39c is located on the other side of the chair 15. as can be seen from previous Figures 3 and 4 and these function in an identical manner to components 40a to 40c.

The components 40a to 40c form a three part linkage 40. The first component 40a is pivotally connected to the seat frame by pin 52, extending from the seat frame side member l8b. The other end of component 40a is pivotally connected to component 4Gb, with the midpoint of component 40a attached to crossbar 43, which extends to the midpoint of corresponding component 39a (not shown). The second component 40b is in turn pivotally connected to a pin 53 extending from bracket 54 attached to the proximal section 23 of the legrest chassis. The other end of component 4Gb is pivotally connected at point to the third component 40c. In turn, the third component 40c is pivotally connected at its other end to pin 56, extending from the distal section 24 of the egrest chassis.

As can be seen from Figures 8 to 10, when the legrest is raised from a fully lowered position, shown in Figure 8, to the fully raised position, shown in Figure 10, components

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40a to 40c (together with conesponding component 39a to 39c, not shown) cause the distal portion 24 of the legrest chassis to extend out from the proximal portion 23 on runners 25.

causing the legrest cushion 48, fixed to the distal section 24, to remain in a fixed position relative to the occupants lower leg 12 in a lengthwise direction.

The retractable footrest 49 of the chair 15, shown in Figures 5 to 10, will now be described in detail and with reference to Figures 11 to 16. The footrest, indicated generally as 49, comprises a footpate 57 having a recess 58 formed towards its front edge 69 and a support frame 59. The support frame 59 comprises an attachment tube 60, which is attached to the distal section 23 of the legrest chassis of the chair 15 of Figures 3 to 10. Attached to the bottom of the tube 60 is a crosspiece 61, supporting end plates 62 and 63. The bottom of end plates 62 and 63 in turn support respective machined blocks 64 and 65, shown most clearly in Figures 15 and 16.

Referring to Figure 15, a cross member 68 lies under footplate 57 toward the front edge 69. but footplate 57 is not attached to the cross member 68 and is free to slide over the cross member 68. Two rods 66 and 67 are attached to either end of the cross member 68.

such that they are spaced slightly apart from footplate 57. The rods 66 and 67 pass through drilled holes in machine block 64 and 65, (such they can slide there through) and are attached at their opposite ends to a rear cross member 70, most clearly seen in Figure 14.

As can be seen from Figures 14 and 15, rods 66, 67, front cross member 68 and rear cross member 70 form a square frame across which a cenni rod 71 extends, between rear cross member 70 and the front cross member 68. The central rod 71 has a machined block 72 mounted thereto which can slide along the rod. It is to this block 72, that the foot plate is attached by bolts 73.

The rear cross member 70 of frame 66, 67, 68, 70 is connected at fts ends to respective stub shafts 74 and 75. Stub shafts 74 and 75 have ends for receiving turned knobs 76 and 77. Turned knobs 76 and 77 are sprung loaded and machined such that, fixed to the ends of respective stub shafts 74 and 75, they retain the stub shafts in a selected one of three possible locations in apertures 78 in respective swing supports 79 and 80, but let the stub shafts 74. 75 rotate therein. The swing supports 79 and 80 are pivotally connected at their respective ends, opposite to apertures 78, to upper portions of end plates 62 and 63.

This arrangement permits the footplate 57 to adopt a fully retracted position, as shown in Figure 11, where rods 66 and 67 are fully retracted in the machined blocks 64 and so that front cross member 68 (not shown in Figure 11) abuts machined blocks 64 and 65. Thus the footplate, attached to central rod 71, is retracted behind the legrest with only the front edge 69 and the recess 58 protruding Mow the bottom edge of the legrest 22 (not shown). In this position the footrest will not obstruct an occupant placing his feet on the floor immediately in front of the fully lowered leg rest 22, when the occupant wishes to enter or exit the chair 15.

With reference to Figure 11, pulling the footplate 57. in the region of the recess 58, from under the legrest 22 (not shown) in the manner illustrated in Figures 12 and 13, until the rear cross member 70 comes into contact with the back of machined blocks 64 and 65, where the footplate adopts the position shown in Figurel3. Pulling the footplate 57 further forward causes the footplate 57 to slide over front cross member 68, but to be retained in place by machined block 72 sliding along the central rod 71, as most clearly seen in Figures and 16, until the machined block 72 abuts metal stop 81. Here magnets 82 and 83 (see figure 15) retain the machined block 72 in position against the stop 8, locking the footplate 57 in the fully extended position, as shown in Figures 14 and 16. This further forward extension of the footplate 57 enables the footplate to be less deep than would otherwise be necessary. assisting storage in the limited space available behind the foot rest.

To ensure the footplate 57 does not unintentionally slip from the retracted position shown in Figure 11, as can most clearly be seen from Figure 16, lugs 84 are provided on the front cross member 68 which lugs 84, when the footplate 57 is fully retracted to the position shown in Figure 11, engage with catches 85 fixed to a shaft 86. The shaft 86 extends between and is rotatable in the machined blocks 64 and 65. Catches 85 are biased to an engaged position with the lugs 84 by springs 87. To release footplate 57 from the position shown in Figure 11, a nurse or carer reaches under the footplate 57 to reach bar 88, shown in Figure 16, which is welded to the shaft 86. Pulling the bar 88 rotates the shaft 86 releasing catches 85 from lugs 84 permitting the footplate 57 to be pulled forward.

Similarly, to ensure the footplate 57 does not unintentionally slip back from its fully deployed position shown in Figures 12 to 16, especially when attached to a raised legrest 22, as shown in Figure 10 for example, an additional bar 89 is provided attached to the rear cross member 70. As can be most clearly seen from Figures 14 and 15. when the footplate 57 is in the fully deployed position. shown in these Figures. the bar 89 engages towards its ends with respective catches 85, thus locking the rear cross members 70 against machined blocks 64 and 65, retaining the footplate 87 in the fully deployed position, but letting it slide forward to a fully extended position along central rod 71. To release the footplate 57 a nurse or carer pulls the bar 88 to rotate the shaft 86. releasing catches 85, permitting the footplate 57 to be pushed back.

When the footrest 49 is mounted to the back of a legrest 22 of the seat 15, and deployed as illustrated in Figures 3 to 10, the footrest 49 will be maintained in the correct position relative to an occupants foot by the linkage mechanism 26, as previously explained. When the legrest 22 is fully retracted, as shown in Figures 5 and 8, it is desirable that the footrest 49 extend in a direction substantially perpendicular to the legrest, for when an occupant has his thwer legs 12 lowered, the foot may be comfortably maintained pointing in a direction substantially perpendicular to the direction in which the lower leg 12 extends. However, as the lower leg is elevated by the footrest 22, the tendons down the back of the lower leg will tighten. Thus when the occupants lower leg 12 is fully elevated to the position shown in Figures 7 and 10 it may be more comfortable for the occupant if the angle of the footpate 57 of the footrest 49 is adjusted. With reference to Figures 16, this can be achieved by pulling the turned knobs 56 and 57 and sliding the stub shafts 54 and 55 to one of the other two locations in apertures 58, this will cause the footplate 57 to adopt a less acute angle.

One embodiment of the present invention has been descnbed by way of example only, with reference to a specialist posture management static seat, or chair. However, this is only examp'e of an application where the invention may be employed and the invention is also applicable to other types of seats and seating. It will be realised that many modifications can be made to the arrangement depicted in the embodiment shown in the drawings without departing from the scope of the invention as defined by the appended claims. k this regard, the linkage mechanism 26 has been described as employing three distinctly identifiable sets of components. A first set for controlling the position of the legrest 22 so that the rotation axis 31 is moved in a linear direction only, a second set of components controlling rotation of the legrest about the axis of rotation and a third set of components for extending the legrest cushion away from the axis of rotation 31. These three sets of components permit the legrest cushion to raise an occupants legs whilst maintaining the cushion at the correct alignment to the leg and without dragging on the back of the leg. However, it will be realised that the components could be arranged in a different manner. For example. the components controlling the axis of rotation could be arranged so that the axis of rotation does not follow a linear path, thus the position of the axis of rotation could instead be controlled to not only cause the leg to be raised, but also to ensure that the axis of rotation was maintained in a fixed position relative to the lengthwise direction of the leg, therefore avoiding the need for a separate mechanism for controlling the extension of the legrest. Alternativdy, the first and second sets of components could be employed without the third set (the extension mechanism). This would permit the legrest to be correctly positioned and inclined, although the occupants calves may experience some dragging when the legrest is elevated. Such alternative arrangements are envisaged which are within the scope of the appended claims.

Claims

Claims 1. A seat comprising: a seat portion for supporting an occupants buttocks; an elevating legrest having a generally planar support portion alTanged to support the legs of the occupant in the region of the occupants calves; and a linkage mechanism connecting the legrest to the seat portion. wherein the linkage mechanism is arranged to support the legrest and rotate the legrest about a rotation axis when the egrest is raised to control the inclination of the legrest, the rotation axis being parallel to an axis passing through an occupants knees, about which the occupants lower legs rotate when their lower legs are raised by the legrest, characterised in that the linkage mechanism is arranged such that the legrest rotation axis is displaced relative to the seat portion as the legrest is raised and the support portion is rotated about the legrest rotation axis as the legrest is raised so that the support portion generally follows the inclination of the back of the occupants legs in the region of their calves as the legrest is raised.
2. A seat as claimed in Claim I, wherein the linkage mechanism comprises a first set of components that control the position of the legrest rotation axis and a second set of components that control the inclination of the legrest.
3. A seat as claimed in Claim 2, wherein the first set of components comprise one or more extending members supporting the legrest relative to the seat portion to cause the legrest rotation axis to be displaced in a linear direction perpendicular to the rotation axis when the egrest is raised.
4. A seat as claimed in Claims 2 or 3, wherein the second set of components include a guide and a follower to run in wherein one of the guide or follower is connected to the legrest and the other is fixed relative to the seat portion and wherein raising the legrest causes the follower to move along the guide and control the inclination of the legrest.
5. A seat as claimed in Claim 4, wherein the guide is shaped to permit the legrest to have a desired inclination at any point between a fully lowered position and a fully raised position.
6. A seat as claimed in Claim 5. further comprising a frame to which the seat portion is attached and the legrest is attached by the linkage mechanism, the frame having side members and the linkage mechanism having two guides and respective follower, the guides being in the form of slots formed in the side members of the frame and the foflowers being in the form of arms extending from the legrest.
7. A seat as claimed in any preceding claim, wherein the linkage mechanism is arranged to move the support portion away from the seat portion as the legrest is raised such that the support portion substantially retains its position relative to an occupants lower legs in a lengthwise direction as the legrest is raised.
8. A seat as claimed in Claim 7. wherein the legrest comprises an upper portion and a lower portion including the support portion for the occupants legs, the upper and lower portions being arranged to extend telescopically and wherein the linkage mechanism comprises extension control components that control the extension of the legrest as the legrest is raised.
9. A seat as claimed in Claim 7 or 8 comprising a footrest attached to the legrest such that the footrest moves with the support portion of the legrest.
10. A seat as claimed in any preceding claim comprising a footrest that can be retracted behind the legrest without being detached.
11. A seat as claimed in any preceding claim, wherein the position of the legrest is controlled independendy of any other adjustment of the seat.
12. A seat as claimed in any preceding claim, comprising a metal seat frame to which the linkage mechanism is attached, which metal frame supports the seat portion.
13. A seat as claimed in Claim 12. further comprising a base unit to which the seat frame is pivotally supported to permit the frame, seat portion and legrest to tilt in space without any relative movement therebetween.
14. A seat as claimed in Claim 12 or 13, comprising an actuator acting between the seat frame and the linkage mechanism or legrest to control raising and lowering of the legrest.
15. A seat as claimed in Claim 14, wherein the actuator is electric.
16. A seat as claimed in Claim 14, wherein the actuator is a gas strut.
17. A seat substantially as hereinbefore described with reference to one or more of figures 3 to 16 of the accompanying figures.