GB2087718A - Backrest assembly - Google Patents

Abstract

A backrest assembly, primarily for hospital beds, comprises an outer frame (10) having a pair of fixed upright rods (12), on which a mounting member (16) is slidable. A backrest (13) is pivoted (20) to the mounting member (16). The mounting member is normally releasably locked at any position along the rods, one hand only being required to release the locking means and simultaneously adjust the backrest. In figure 1, a pair of pivoted wedges (17) normally bear on the rods (12) and are releasable by a cam (21) which is rotated when a spring grip (25) is pressed towards an extensible strut (26), the strut being connected to the bottom of the backrest (13) to allow it simultaneously to be tilted. In Figure 2, the locking is carried out by a canting plate (29) acting on one of the rods (12) and tilted by a rotatable member (27) having an external thumb piece (28) and resiliently biassed (34) to a neutral position clear of the canting plate. The backrest has a hand-engagement portion (36) close to the thumb piece to enable simultaneous release and tilting using one hand. Both devices are operable from either side of the bed. <IMAGE>

Description

SPECIFICATION Backrest assembly This invention relates to a backrest assembly, primarily for hospital beds but possibly having other uses.

Hospital beds commonly have a backrest assem bly comprising a rigid head bow or frame on which a backrest is mounted for pivotal movement about a horizontal axis so as to enable the back of a patient in the bed to be supported at an angle determined by medical treatment or patient comfort. Since the foot of the backrest then rests on the mattress, the horizontal pivotal axis of the backrest is also arranged to move vertically in the plane of the head bow. Such a backrest assembly is herein referred to as being "of the type specified".

One typical arrangement uses a head bow having a pair of spaced parallel upright rods, a control box slidably mounted on the rods and selectively lockable at chosen positions along the rods, the backrest being horizontally pivoted to the control box.

To adjust the angle of the backrest while a patient occupies the bed, the patient must firstly be lifted away from the backrest and supported. The controls on the control box, which may comprise a pair of opposed plungers for example, are operated to cause the control box to unlock from the rods. Simul taneoussy, the backrest is grasped and swung to the new angle.

It will be appreciated that, if the patient requires support, one hand is being used to operate the controls and the other hand is being used to swing the backrest, and hence two people are required to adjust the backrest.

Futhermore, since the control box is slidable on two parallel rods, it must be moved parallel to the rods without being twisted relative to them, which could cause it to jam. It is desirable that the swinging and sliding movement is imparted to the backrest along the central upright axis of the backrest but there is no way of ensuring correct operation with the conventional arrangement.

it is an object of the invention to provide a backrest assembly of the type specified which overcomes or reduces some or all of the above mentioned disadvantages.

According to the invention there is provided a backrest assembly of the type specified wherein the head bow includes a pair of parallel generally upright rods; the backrest is pivotally mounted about an axis perpendicular to the rods on a mount ing member which is slidably mounted on the rods and is provided with locking means preventing such sliding movement, the locking means being selectively releasable by operating means; and the operating means is so positioned relative to the bac krest asto enable the locking means to be released and the backrest to be pivoted simultaneously, using one hand only.

The operating means may comprise a pair of elongate members adapted to be manually squeezed towards each other against a resilient bias, to release the locking means, at least one of the members being secured to the backrest to enable movement to be imparted thereto.

The other of the members may comprise a lever provided on a cam element forming part of the locking means.

The locking means may comprise a pair of spaced pivoted wedges, each being releasably biassed into wedging engagement with a respective one of said rods, the cam element acting on the wedges in a direction opposed to said bias, to release the wedges when the operating means are operated.

Said one member of the operating means may comprise a generally upright telescopic strut, pivotally secured by its upper end portion to the mounting member and pivotally secured by its lower end portion to a lower portion of the backrest.

Alternatively, the operating means may comprise a manually rotatable member pivotally mounted on the mounting member, rotation of which releases the locking means.

The manually rotatable member may be resiliently biased to a neutral position. It may be rotatable in one or in both senses of rotation.

The manually rotatable member may have abutment means adapted, on rotation of the member, to contact and tilt a canting plate locking member acting on one of said upright rods and forming part of said locking means.

When the canting plate is in its locked condition, one face thereof may abut a fixed abutment of the mounting member and the other face thereof, at a position on the side of said upright rod remote from the fixed abutment, may bear on a resilient abutanent.

The resilient abutment may comprise a coiled compression spring.

The tilting movement of the canting plate may be limited by the bottoming out of the coiled spring, wherebyovercentreing of the manually rotatable member is prevented.

The backrest may include a hand-engagement portion immediately adjacent the manually rotatable means to assist i rr in simultaneously releasing the lock- ing means and pivoting the backrest.

The manually rotatable means may include one or more leaf springs adapted to bear on part of the mounting means to provide the resilient bias tending to urge the manually rotatable means to a neutral position.

The manually rotatable means may comprise a moulding in a resilient plastics material, having one or more abutments and one or more integrally formed leaf springs.

The invention will now be described in more detail by way of example only, with reference to the accompanying drawings in which: FIGURE lisa front elevational view, partly broken away, of a backrest assembly embodying the invention; FIGURE 2 is a front elevational view of a backrest embodying the invention with a mounting means illustrated in section.

Referring to Figure 1 of the drawings, the backrest assembly comprises a fixed head bow or frame 10 which is rigid with the base of the bed. The head bow has an outer frame member 11 and at least a pair of rigid upright rods 12 which are parallel to each other and which lie in the general plane of the frame member 1 1.

The backrest assembly further comprises a backrest generally indicated at 13 which has a peripheral frame 14 of generally rectangular shape and a piurality of struts 15 which form a rest against which the patient's pillows can be placed.

The backrest 13 is slidably mounted on the upright rods 12 buy a mounting member 10 which is in the form of an elongate rectangular box having pairs of openings to receive the respective rods 12. Within the mounting member 16, which is shown broken away for clarity, a pair of pivoted wedges 17 are mounted. These are pivoted about respective pivot points 18 in the control box. Each wedge is provided with a strong leaf spring 78 which abuts against the wall of the mounting member 16 and tends to urge the pivoted wedge into firm wedging engagement with the associated rods 12. Thus, in normal use, the backrest 13 is held in a particular position by the wedging action of the wedges 17 on the rods 12.

The backrest 13 is pivoted to the mounting member about an axis generally indicated at 20 which extends at right angles to the rods 12 and which of course moves up and down with the movement of the mounting member along the rods.

Operating means are provided for releasing the locking means provided by the wedges 17 sothatthe backrest can be moved. A cam 21 is provided by a U-bracket which is pivoted at22 in the centre of the mounting member 16. The U-bracket cam 21 has 2 pair of studs 23 which are externally screw-threaded and are therefore adjustable in openings in the cam to set the positions of the studs 23 in accordance with the particular characteristics of the springs 19.

The studs 23 bear on portions of the pivoted wedges 17 as shown and it will be appreciated that, by rotat- ing the cam 21 about is pivotal axis 22, the studs will tend to force the pivoted wedges 17 in a direction opposed to the bias of the leaf springs 19, thereby releasing the wedges 17 from engagement with the rods 12. Such rotation of the cam therefore causes the locking means to be disengaged and permits the mounting member 16 to be slid up or down the upright rods 12 of the head bow.

The cam 21 has an extension leg 24 which projects downwardly through the base of the box-like mounting member. The leg 24 has a spring grip 25 secured to it, the other end of the spring grip being secured to a telescopic strut 26.

The telescopic strut is pivoted at its upper end to a rigid bracket on the mounting member 16. The lower end of the telescopic strut is pivotally secured to the peripheral frame 14 of the backrest 13.

In order to adjust the position of the backrest relative to the head bow, the spring grip 25 is manually squeezed towards the telescopic strut 26 so as to release the pivoted wedges 17 from the rods 12. At the same time, using the same hand, the telescopic strut is lifted or lowered and swung angularly relative to the pivotal axis 20 of the backrest, so as to move the backrest into the new chosen position. The spring grip 25 can then be released.

Thus, it is possible simultaneously to release the locking mechanism and move the backrest using one hand. It will be appreciated that either hand can be used to press the spring grip towards thetele- scopic strut. This means, that, for example if a nurse stands at the left side of a bed, and haste lift a patient away from the backrest, the nurse can use the right hand to support the patient away from the backrest, the nurse can use the right hand to support the patient and the left hand, adjacent the backrest assembly, to adjust .hue position of the backrest. It therefore becomes a one person operation to adjust the backrest although a relatively helpless patient may be occupying the bed.

Furthermore, since the two pivoted wedges 17 are operated simultaneously by the studs 23 on the cam 21, rotation of the cam 21 gives controlled and even movement of the two wedges 17. The sliding movement and swinging movement imparted to the backrest via the telescopic strut 26 is imparted substantially along the central upright axis of the backrest In combination, these features mean that there is a greatly reduced tendency for the backrest to jam because it has twisted relative to the parallel upright rods 12 during movement.

Various changes can be made within the scope of the invention, for example as regards the details of the cam operation or of the backrest construction. In particular, the use of a telescopic strut 26 could be avoided by using a backrest 13 constructed so that the axis of its pivotal movement 20 coincides with the pivotal axis of the telescopic strut relative to the mounting member.

Referring to Figure 2 of the drawings, there is shown a backrest of modified construction having a different form or operating means from that shown in Figure 1 of the drawings. However, where parts shown are similar, the same reference numerals are used.

The mounting member 16 in this case carried a manually rotatable member 27, part of which is mounted internally of the mounting member 16 and partofwhch is provided externally, in the form of a rotatable thumb piece shown in dotted outline at 28.

The inner and outer parts of the manually rotatable member are keyed together for rotation.

As with the embodiment described in Figure 1, the backrest 13 is pivotally mounted about an axis 20 to the mounting member 16 which is slidable on the parallel upright rods 12. The backrest is normally locked against sliding movement by a canting plate locking member 29 provided within the mounting member 16. The canting plate 29 has a clearance opening through which one of the rods 12 passes.

The plate is locked on the rods by being tilted slightly so that the borders of the opening bite onto the surface of the rod, in generally known manner.

The canting plate is normally held in the locked condition, that is tilted relative to a plane perpen dicular to the axis of the rod, by a pair of abutments.

One of these is a fixed abutment 30, which is formed in an end cap 31 of the mounting member, the end cap being a plastics moulding. The moulding is pref erably in a low friction plastics material so as to also to provide a bearing for a portion of the frame 14 of the backrest.

The other abutment against which the canting plate is normally located is a helically coiled compression spring 32. It will be appreciated that the canting or tiiting movement of the canting plate 29 can be regarded as a see-saw movement about an axis intersecting the axis of the rods 12 where it passes through the hole in the canting plate. The arrangement shown in the drawings prevents the mounting member 16 from being moved bodily either in the downward or in the upward sense relative to the rods 12 because the fixed abutment 30 tends to hold down the left-hand end of the plate, whereas the compression spring abutment 32 tends to hold upwardly the right-hand end of the plate. The plate is thus inclined upwardly considered from the left to the right-hand side of the rod.

In order to release the canting plate 29 from its locked condition on the rod, the manually rotatable member 27 is rotated. This rotation can take place in either sense since the manually rotatable member is symmetrical within the casing of the mounting member 16. Similarly, the thumb piece 28 is symmetrical so that it can be operated from either side of the bed.

Rotation of the manually rotatable member 27 causes tilting of the canting plate in a clock-wise sense away from the locked position, so as to release the mounting member 16 for sliding movement up or down the rods 12.

The part of the manually rotatable member which is housed inside the mounting member 16 comprises a body having a pair of abutments 33. Rotation of the member 27 brings one of the abutments into contact with the canting plate 29, depending on the sense of rotation.

The member 27 is also provided with a pair of integrally moulded leaf springs 34 which bear on the underside of the top plate of the mounting member 16 in normal use and which resiliently bias the rotatbale member 27 to a neutral position in which the abutments 33 are, as shown in the drawings, ciear of the upper surface of the canting plate 29. When the manually rotatable member is rotated in a particular direction, one of the leaf springs bears more strongly on the casing of the mounting member 16 while the other moves clear, thereby ensuring that a net resi lient force tends to return the member 27 to its neutral position.

Additionally, once one of the abutments 33 contacts the canting plate 29, further rotation takes place against the resilient biasing force of the compression spring 32, which is compressed downwardly, thereby releasing the canting plate with a smooth and controlled action.

In order to move the backrestto a new position, it is necessary not only to be able to release the locking engagement with the rods but also to pivot the backrest about the axis 20. This can be done using one hand only, using the slightly modified backrest shown in Figure 2. One of the straight struts 15 is replaced by a strut 35 having a hand-engagement portion 36 in the form of an inverted U-shape provided centrally of the strut 35. The hand-engagement portion 36 is very close to the mounting member 16 and a person holding the hand-engagement portion 36 can readily reach the thumb piece 28.

Since the arrangement is symmetrical considered from side-to-side of the backrest, it will be seen that operation of the backrest can be carried out from either side. Additionally, it can be carried out using the hand which is closest to the backrest. Thus, a nurse standing at the left-hand side of the backrest can use the left hand to adjust the backrestwhilstthe right hand supports a patient.

In order to prevent the possibility of the locking mechanism jamming in the unlocked condition, the manually rotatble member 27 is prevented from overcentreing by the presence of the spring 32 which bottoms out before the abutment 33 can reach its dead-centre position.

Although the arrangement shown uses only one canting plate, it would be possible to arrange a pair of canting plates acting on respective rods 12. Similarly, although the manually rotatable member shown can be rotated in either sense of rotation, it would be possible to allow it to rotate in one direction only.

Claims (18)

1. A backrest assembly of the type specified wherein the head bow includes a pair of parallel generally upright rods; the backrest is pivotally mounted about an axis perpendicularto the rods on a mounting member which is slidably mounted on the rods and is provided with locking means preventing such sliding movement, the locking means being selectively releasable by operating means; and the operating means is so positioned relative to the backrest as to enable the locking means to be released and the backrest to be pivoted simultaneously, using one hand only.

2. An assembly according to Claim 1 wherein the operating means comprises a pair of elongate mem- bers adapted to be manually squeezed towards each other against a resilient bias, to release the locking means, at least one of the members being secured to the backrest to enable movement to be imparted thereto.

3. An assembly according to Claim 2 wherein the other of the members comprises a lever provided on a cam element forming partofthe locking means.

4. An assembly according to Claim 3 wherein the locking means comprises a pair of spaced pivoted wedges, each being releasably biassed into wedging engagement with a respective one of said rods, the cam element acting on the wedges in a direction opposed to said bias, to release the wedges when the operating means are operated.

5. An assembly according to any one of Claims 2 to 4wherein said one member of the operating means comprises a generally upright telescopic strut, pivotally secured by its upper end portion to the mounting member and pivotally secured by its lower end portion to a lower portion of the backrest.

6. An assembly according to Claim 1 wherein the operating means comprises a manually rotatable member pivotally mounted on the mounting member, rotation of which releases the locking means.

7. An assembly according to Claim 6 wherein the manually rotatable member is resiliently biased to a neutral position.

8. An assembly according to Claim 6 or Claim 7 wherein the manually rotable member is rotable in both senses of rotation.

9. An assembly according to any one of Claims 6 to 8, wherein the manually rotatable member has an abutment means adapted, on rotation of the manually rotatable member, to contact and tilt a canting plate locking member acting on one of said upright rods and forming part of said locking means.

10. An assembly according to Claim 9 wherein, when the canting plate is in its locked condition, one face thereof abuts a fixed abutment of the mounting member and the other face thereof, at a position on the side of said upright rod remote from the fixed abutment, bears on a resilient abutment.

11. An assembly according to Claim 10 wherein the resilient abutment comprises a coiled compression spring.

12. An assembly according to Claim 11 wherein the tilting movement of the canting plate is limited by the bottoming out of the coiled spring, whereby overcentreing of the manually rotatable member is prevented.

13. An assembly according to any one of Claims 6 to 12 wherein the backrest includes a handengagement portion immediately adjacent the manually rotatable member to assist in simultaneously releasing the locking means and pivoting the backrest.

14. An assembly according to any one of Claims 6 to 13 wherein the manually rotatable member includes one or more leaf springs adapted to bear on part of tile mounting means to provide the resilient bias tending to urge the manually rotatable member to a neutral position.

15. An assembly according to Claim 14 wherein the manually rotatable member comprises a moulding in a resilient plastics material, having one or more abutments and one or more integrally formed leaf springs.

16. A backrest assembly substantially as hereinbefore described with reference to and as illustrated in Figure 1 of the accompanying drawings.

17. A back rest assembly substantially as herein before described with reference to and as illustrated in Figure 2 of the accompanying drawings.

18. Any novel feature or novel combination of features disclosed herein and/or shown in the accompanying drawings.