GB2033742A - Lockable swivel castor - Google Patents

Abstract

A lever mounted on the body 16, 18 of a castor can be pivoted to apply a brake pad 50 to a ground engagement wheel 12. Such pivoting of the lever 46 is effected by means of a slidable plunger 62 and a rotatable cam 66 mounted on a peg 22 by means of which the castor can be mounted on an article of furniture and with respect to which the body 16, 18 and wheel 12 can swivel. The lever 46 can also be pivoted to engage a pin 56 selectively with one of several bores 58 in the peg 22 and thereby lock the body and wheel against swivelling, and further to drive a tapered pin 44 so as to expand a split ring 38 mounted on the body into frictional engagement with the peg 22 and thereby brake swivelling movement of the castor. In one position of the lever 46, the pin 56 locks the castor against swivelling movement but both the wheel brake and the swivel brake are not applied. In a second position of the lever 46, the castor is not locked against swivelling by the pin 58 but both the wheel brake and the swivel brake are applied. <IMAGE>

Description

SPECIFICATION Lockable swivel castor This invention relates to lockable swivel castors, and more particularly is directed to the type of castor which can be locked against swivelling movement and in which a brake can be applied to a ground engagement wheel thereof. Such castors are generally used for hospital furniture, such as patients' beds, cabinets and trolleys.

According to the present invention, there is provided a castor comprising a body rotatably mounting a ground engagement wheel, mounting means whereby the castor can be mounted on an article, the body being capable of swivelling movement relative to the mounting means, a wheel brake actuable to lock the wheel against rotation relative to the body, and locking means actuable separately from the wheel brake to lock the body against swivelling movement relative to the mounting means.

The castor preferably also comprises an actuator movable between a first position in which the wheel brake is actuated and the locking means is de-actuated and a second position in which the wheel brake is deactuated and the locking means is actuated.

Desirably, the actuator is also movable into a third position intermediate the first and second positions in which both the wheel brake and the locking means are de-actuated.

Advantageously, the locking means is actuable to lock the body in at least one preselected angular position, relative to the mounting means.

The castor can also comprise a swivel brake actuable to brake swivelling movement of the body with respect to the mounting means, and which is conveniently actuated concomitantly with the wheel brake. In a preferred arrangement, the swivel brake comprises a split ring mounted on the body and radially expandable into frictional engagement with the mounting means.

An embodiment of the present invention will now be described, by way of example, with reference to the accompanying drawings, in which: Figure 1 is a longitudinal partial section through a castor in accordance with the present invention, showing a swivel lock of the castor actuated; Figure 2 is a similar view to Fig. 1, but showing a wheel brake and a swivel brake of the castor actuated; Figure 3 is a view in the direction of arrow A in Fig. 2 with a wheel of the castor omitted for clarity: Figure 4 is a section on the line IV-IV in Fig. 2; and Figure 5 is a partial section on the line V-V of Fig. 3.

The illustrated castor (referenced 10) comprises a body mounting a wheel 12, which has a resilient tyre 1 4 retained on the rim thereof, between two curved legs 16. The legs are preferably formed integral with the remainder of the castor body, which is in the form of a housing 1 8 of generally circular cross-section and which rotatably carries on a reduced diameter upper portion 20 thereof a retaining peg 22 (also of substantially circular cross-section) by means of which the castor is mounted on, for example, a trolley or an article of furniture. The housing 1 8 has an axially extending tubular member 24 secured thereto over which a tubular extension 26 of the peg 22 is slid.The peg 22 is retained axially of the tubular member 24 by means of a retaining member 28, such as a sleeve or nut, which is screwed onto a screw-threaded end portion of the member 24 and which abuts a shoulder 30 within the extension 26.

The peg 22 has a depending peripheral flange 32 whose radially inner face 34 lies opposite a radially outer face 36 of the housing upper portion 20. Between these two faces lies a split ring 38, as is best seen in Fig. 4, which serves as a brake for braking the swivel action of the castor. The split ring 38 has an enlarged width at the location of its split 40 and the opposing faces of the split 40 have formed therein respective grooves 42 to receive the head of an activating pin 44.

The operation of the swivel brake will be described in detail later.

The housing 1 8 also carries a brake activating lever 46 which is mounted on a substantially horizontal pivot pin 48. The lever 46 is biassed to rotate in an anti-clockwise direction as seen in the drawings by a torsion spring 47. At one side of the pivot the lever carries, preferably integrally therewith, a wheel brake pad 50, and at the other side of the pivot an extension 52 for driving the pin 44. The extension 52 is mounted to one side of the wheel 1 2 to avoid fouling the latter and is again preferably integral with the lever 46.

Where the brake pad 50 is not integral with the lever 46 its position thereon may be varied by means of a screw 51 abutting the pad 50 and mounted in a flange 53 at one end of the lever 46. The spring 47 retains the brake pad 50 against the adjusting screw 51.

The housing 1 8 also has a substantially vertical bore 54 in which is slidably located a pin 56. The latter cooperates with either of two blind bores 58 (only one of which is shown in the drawings) in the peg 22, angularly separated by 180 , to lock the wheel in a specific direction. Although two bores 58 are described, any suitable number may be provided at desired angular spacings. The pin 56 has a reduced diameter lower end portion 57 which carries a flange 59 intermediate its ends and against which flange a biassing spring 60 abuts. The spring urges the pin 56 towards engagement with one of the blind bores 58 and is opposed by the lever 46 which loosely engages and controls the operating axial position of the pin 56 by way of a surface 61 which abuts an upper surface of the flange 59.

From the above description, it will be appreciated that the lever 46 controls each of the brakes by virtue of its pivoted position. The lever 46 is in turn controlled by way of an operating plunger 62 which is slidably located within the tubular member 24 and whose lower end abuts against the lever 46 to one side of the pivot pin 48. The plunger 62 has on its upper end a preferably domed head 64, secured conveniently by means of a- pin 65, which abuts a cam 66 rotatably mounted in the extension 26. The cam 66 is rotatable to engage the domed head 64 selectively with one of three cam surfaces 68, 70 and 72, and is normally arranged to be operated by foot, but may instead be hand operated.

In the position shown in Fig. 1, the camsurface 68 engages the domed head 64 of the plunger 62 allowing the latter to be biassed to its uppermost axial position by the torsion spring 47 acting on the lever 46 is at an extreme anticlockwise position, raising the brake pad 50 clear of the wheel and lowering the pin 44 to allow the ring 38 to contract to its smaller diameter The pin 56, however, is allowed to rise to its highest position under the bias of the spring 47 so that when the housing 1 8 and peg 22 are relatively rotated to bring one of the blind bores 58 into alignment with the pin 56, the latter enters the bore and locks and the castor body and the wheel 1 2 in the preselected swivel position determined by the location of the bore 58.To disengage the pin 56 from the bore 58, the cam 66 is rotated to engage the domed head 64 with either of the cam surfaces 70, 72 thus depressing the plunger 62 and pivoting the lever 46 in a clockwise direction to lower the pin 56.

With the cam surface 70 engaged, the lever 46 has not rotated sufficiently to activate either the swivel brake or the wheel brake.

However, with the cam surface 72 engaged, as is shown in Fig. 2, the lever 46 has rotated clockwise sufficiently to urge the brake pad 50 against the tyre 14 to brake the wheel and to drive the pin 44 into the grooves 42 to expand the split ring 38 against the face 34 of the flange 32 and prevent relative rotation of the peg 22 relative to the housing 1 8.

Rotation of the ring 38 is prevented both by the presence of the pin 44 and a recess 74 accommodating the increased width of the ring at its split.

The pin 44 conveniently has a frustoconical head although any suitable shape may be employed. The initial position of the pin 44 can be adjusted by means of a screw 80 located in a screw-threaded bore in the lever extension 52. This enables the onset of swivel braking to be adjusted through a range of pivot positions of the lever 46.

Claims (23)

1. A castor comprising a body rotatably mounting a ground engagement wheel, mounting means whereby the castor can be mounted on an article, the body being capable of swivelling movement relative to the mounting means, a wheel brake actuable to lock the wheel against rotation relative to the body, and locking means actuable separately from the wheel brake to lock the body against swivelling movement relative to the mounting means.

2. A castor as claimed in claim 1, further comprising an actuator movable between a first position in which the wheel brake is actuated and the locking means is de-actuatedand a second position in which the wheel brake is de-actuated and the locking means is actuated.

3. A castor as claimed in claim 2, wherein the actuator is also movable into a third position intermediate the first and second positions in which both the wheel brake and the locking means are de-actuated.

4. A castor as claimed in claim 2 or 3, wherein the actuator includes a lever mounted for pivotal movement relative to the body and carrying a brake pad for engagement with the wheel, and the locking means includes a member movably carried by the body for selective engagement with one or more abutments on the mounting means, said member being moved relative to the body by pivotal movement of the lever.

5. A castor as claimed in claim 4, wherein the member is biassed towards engagement with said abutment or abutments but is normally held out of such engagement by the lever.

6. A castor as claimed in any of claims 2 to 5, wherein the actuator is biassed towards its second position.

7. A castor as claimed in any one of claims 2 to 6, wherein the mounting means includes a mounting member having an inter-nal bore, and the actuator includes a plunger slidably received in the bore and a cam engaged with an end of the plunger.

8. A castor as claimed in claim 7, wherein the cam is rotatably mounted on the mounting member and is foot-or hand-operable.

9. A castor as claimed in any preceding claim, wherein the locking means is actuable to lock the body in at least one preselected angular position relative to the mounting means.

10. A castor as claimed in claim 9, wherein the locking means includes a pin slidably mounted on the body for selective engagement with one or more recess in the mounting means.

11. A castor as claimed in any preceding claim, further comprising a swivel brake actuable to brake swivelling movement of the body with respect to the mounting means.

12. A castor as claimed in claim 1, wherein the swivel brake is arranged to be actuated concomitantly with the wheel brake.

1 3. A castor as claimed in claim 11 or 12, wherein the swivel brake includes a split ring mounted on one of the body and the mounting means and radially expandable or contractable into frictional engagement with the other of the body and the mounting means.

14. A castor as claimed in claim 13, wherein the split ring is mounted on the body and is radially expandable into frictional engagement with the mounting means.

1 5. A castor as claimed in claim 1 3 or 14, wherein the ring has a single split therein and is radially expanded and contracted by movement of a tapered member which engages opposing faces of said split.

1 6. A castor as claimed in claim 15, wherein the tapered member is movable parallel to the axis of the ring.

1 7. A castor as claimed in claim 1 5 or 16, wherein portions of the ring adjacent said split are enlarged and engage in a recess in the body to retain the ring against rotation relative to the latter.

18. A castor as claimed in claims 15, 1 6 or 17, wherein the tapered member is engaged by an actuator member which is movable relative to the body, the position of the tapered member relative to the actuator member being adjustable so that the onset of swivel braking can be adjusted through a range of positioning of the actuator member.

19. A castor as claimed in claim 18, wherein the position of the tapered member relative to the actuator member is adjustable by means of a screw in threaded engagement with the actuator member and abutting against the tapered member.

20. A castor as claimed in any preceding claim, wherein the wheel brake comprises a lever mounted for pivotal movement relative to the body and carrying a brake pad for engagement with the wheel.

21. A castor as claimed in claim 20, wherein the position of the brake pad on the lever is adjustable.

22. A castor as claimed in claim 21, wherein the brake pad is biassed into engagement with an adjustable stop on the lever.

23. A castor substantially as hereinbefore described with reference to the accompanying drawings.