Improvements relating to beds

Abstract

 A hospital bed or trolley is of the radius arm type in which the base (10) the radius arms (14,16) and the platform (32) supporting the mattress form a generally parallelogram linkage, and the mechanical jack (30) of the canting plate type displaces a tie rod (22) connecting the radius arm to raise the mattress frame. One of the canting plates (70) wedge-locks the tie rod and has to be tilted to allow lowering of the mattress, and the invention provides a simple construction without any connection between the two pedals.

Description

[0001] This invention relates tc hospital beds and trolleys of the kind in which the platform to support the patient is mounted on a linkage from a base frame or chassis with a jack for extending the linkage so as to raise the platform.

[0002] One early proposal of this kind is contained in our prior Patent 1060120 where the linkage is an X franc and the jack is a hydraulic one. A much more recent proposal is contained in our application No. 2018221 where a mechanical jack is used to move pairs of radius arms, and the platform, base and radius arms together make u^p a kind of parallellogram linkage.

[0003] In beds of this kind the jack provides for elevation of the platform, and the platform is allowed to descend to a lower position under its own weight. Often a gas strut is used as a damper to restrict the rate of descent. Particularly in the case of the mechanical jack, elaborate provision is made for transferring the weight of the platform (and hence cf the patient) from one part of the linkage to the other at the end of a period of elevation, cr at the commencement of a period of descent, with the object of avoiding jerkiness and shocks which are transmitted to the patient.

[0004] The object of the invention is to provide an improved structure.

[0005] In accordance with the invention, a hospital bed or trolley has a platform carried on a pair of radius arms forming a generally parallellograrn linkage, a tic rod connected between the radius arms, the rod (or a ram connected to the radius arms) passing through a pair of canting plates of a mechanical jack, an elevating pedal on the end of one limb of a lever which extends generally parallel to said tie rod, a second limb of the lever extending transversely of the tie rod and being fixed tc a rocking crank, the crank being coupled tc an operating member connected tc one of said plates whereby pedal displacement cants the plate tc wedge on the rod (or rar) and axially displaces the same to elevate the platform, and the second of the plates being springloaded to a normal canting position in which it wedge-locks the rod (or ram) but allows the same to be drawn therethrough in the platform elevating direction, and a second like pedal for displacing the second plate to the non-canting non-wedge-locking position, characterised in that there is no connection between the two pedals and in that said second pedal is directly and permanently crank connected to a member for displacement of the second plate.

[0006] Comparing the invention with the structure in said prior application 2018221, it will be seen that considerable simplification is effected. A complete rod with its springloading abutments and like are omitted and the comparatively complicated linkages connecting the descent pedal to the second plate are also eliminated being replaced by the direct connection.

[0007] According to a feature of the invention, the platform is pivotally connected to one of the radius arms and is connected to the other of the radius arms by an adjustable length strut whereby the platform may be tilted relative to the base frame (known per se) and the base franc terminates as close as possible to the mechanism at the feet end of the latter so that maximum tilting of the platform in a foot down position is possible even at minimum elevations of the platform.

[0008] These and other features of the invention will be more clearly understood from the description of a presently preferred embodiment of the invention which is now given in conjunction with the accompanying drawings wherein:-

Figure 1 is a elevation of the bed,

Figure 2 is a plan view of the sane with the mattress supporting platform removed, and certain parts cut away for clarity;

Figure 3 is an elevation of the jack structure used in the bed of Figures 1 and 2 and

Figure 4 is a plan view of the same, Figures 3 and 4 being on a larger scale than Figures 1 and 2.

[0009] Turning now to Figure 1, the bed comprises a base frame 10 provided with a castor 12 at each corner and mounting a pair of radius arms 14 16 which are duplicated on opposite sides of the base frame and are journalled on the base frame. The radius arms have crank extensions 18 20 which are coupled by tie rods 22 only one of which is seen in these drawings. This may be effected by providing parallel shafts 24 26 each of which is coupled to the free ends of the corresponding cranks 18 or 20, these shafts 24 26 being interconnected by a single tie rod 22 which may be laterally offset from the centre line of the arrangement, as best seen in Figure 2. The tie rod may be connected to a gas strut or damper 28 and the opposite end of the same is fixed to the front of the base frame, as also seen in figure 2. The jack, which is particularly shown in Figures 3 and 4, comprises a ram 30 which is connected to the shaft 24 so that the action of the jack is to swing the shaft 24 anticlockwise during elevation of the bed platform 32.

[0010] The platform 32 is connected to the radius arms 14 and 16 by a pair of links 34 towards the foot end of the bed and by a pair of adjustable links 36 towards the head end of the bed. The former are connected tc the radius arms 14 and the latter to the radius arms 16. The adjustment, by extending the effective length of the links 36 tilts the foot end of the platform 32 downwardly (or vice versa), and it will be noted (particularly from Figure 2) that the base frame extends forwardly of the radius arms 18 by relatively small dimension so that maximum foot down tilt can be achieved even when the bed platform is at minimum elevation, and without the platform contacting the base frane in the area indicated by the arrow A of Figure 1.

[0011] The radius arms are journalled by diametrically split shell bearings clamped to the base frame by "U" bolts.

[0012] Turning now to the jack construction of Figures 2 and 4, this comprises a pair of side plates 40 which are connected together by transversely extending plates 42-46 which also form abutments as will be hereinafter explained. Additionally, the side plates 40 are connected by a carrier member 48 which is used to mount the jack in the base frame.

[0013] A first canting plate 50 abuts the jack member 42 and is urged by compression spring 52 trapped between it and the jack body member 44. This plate 50 is the one used to displace the ram 30 in the direction of the arrow B of Figure 3 and elevate the platform. Displacement is effected by tie rod 54 which is urged by spring 56 trapped between an abutment on the rod and a loose abutment plate 58, and the rod 54 is connected to crank 60 which is fast with the limb 62 cf the first pedal shaft. The pedal shaft is generally L-shaped with its second limb extending forwardly and approximately parallel to the ram 30, and the shaft is journalled in the plates 40 of the jack body. When the pedal 64 is depressed the crank is rocked anticlockwise, the tie rod 54 is displaced generally in the direction of the arrow B, the canting plate 50 tilts (because it is restrained in its lower end by the spring 52) the plate wedges on the ram 30, and the rod is displaced in the direction of arrow B. When the pedal is released, the springs return it and the tie rod 54 and plate 50 to the positions illustrated in Figures 1 and 3 respectively.

[0014] The ram 30 passes through a second and locking plate 70 which rocks on the abutment 46 and is urged to the illustrated position by spring 72 which is a compression spring abutting against the opposite side of the plate 42 to that abutted by the first plate 50. The spring 72 cants the second plate 70 into the locking position, but movement of the ram 30 in the direction of the arrow B is accompanied by slight movement of the plate against the spring 72 to allow the ram to be drawn through the plate. Any tendency towards reverse movement permits the spring to wedge the plate 70 on the ram and prevent reverse movement of the ram 30.

[0015] The second pedal 76 is connecteci to a corresponding pedal shaft likewise journalled and crank connected, but this time connected to rod 78 which is urged generally in the direction of arrow B by compression spring 80 trapped between abutment on the rod and the floating abutment 58. The free end of rod 78 carries a striker 82, here shown as an adjustable member, which, on depression of pedal 76 is generally axially displaced against the plate 7U to counter-cant the sar.e and overcome the spring 72 to allow the ram 30 to move in the direction opposite to that of arrow P.

[0016] It will he appreciated that because there is no interconnection between the rods 54 and 78 movement of either completely independently of the other is possible. This is a particularly simple jack mechanism which is economical to manufacture.

[0017] Nevertheless it has been found in experiments that the illustrated construction does not result in any jar to the platform when descent commences despite the absence of complicated provisions for transferring load from one pedal operated mechanism to the other.

Claims

1. A hospital bed or trolley having a platform 32 carried on a pair of radius arms 14, 16 forming a generally parallellogram linkage, a tie rod 22 connected between the radius arms, the rod (or a ram 30 connected to the radius arms) passing through a pair of canting plates 50, 58 of a mechanical jack, an elevating pedal 64 on the end of one limb of a lever which extends generally parallel to said tie rod, a second limb 62 of the lever extending transversely of the tie rod and being fixed to a rocking crank 60, the crank being coupled to an operating member 54 connected to one of said plates 50 whereby pedal displacement cants the plate to wedge on the rod (or ram) and axially displaces the sane to elevate the platform, and the second of the plates 70 being springloaded to a normal canting position in which it wedge-locks the rod (or ram) but allows the same to be drawn therethrough in the platform elevating direction, and a second like pedal 76 for displacing the second plate to the non-canting non-wedge-locking position, characterised in that there is no connection between the two pedals 64, 76 and in that said second pedal is directly and permanently crank connected to a member 78 for displacement of the second plate.

2. A hospital bed or trolley as claimed in Claim 1 wherein the platform 32 is pivotally connected to one of the radius arms 14, 34 and is connected to the other of the radius arms 16 by an adjustable length strut 36 whereby the platform may be tilted relative to the base frame (known per se) and the base frame 10 terminates as close as possible to the mechanism at the foot end of the latter so that maximum tilting of the platform in a foot down position is possible even at minimum elevations of the platform.

3. A hospital bed or trolley as claimed in Claim 1 or Claim 2 characterised in that the operating member 54 for displacing the canting plate which effects elevation of the platform 32 extends through a compression spring 56 which serves to return the pedal to the starting position after operation and release.

4. A hospital bed or trolley as claimed in Claim 3 wherein a loose abutment 58 forms a reaction member for said compression spring 56 and also for a like compression spring 80 operative to turn the second pedal to the starting position after operation and release.

Drawing