GB2292072A - Castor assembly - Google Patents

Abstract

A castor comprising a castor wheel 10 which is freely rotatable about a generally horizontal axis afforded by a support member 11 which is itself swivelable about a generally upright axis, which is offset from said horizontal axis, the upright axis being defined by a head member 12 wherein restraint means are provided which is operative in at least one orientation of the support member relative to the head member. The restraint means may comprise a ball 33 or other detent element carried by the support member and biased by a spring means 34 into engagement with an annular surface 29 at the underside to the head member 12 and concentric with the swivel axis 13. The surface 29 is formed with a recess 30 so dimensioned as to receive the ball 33 and thereby provide resistance to swivelling movement of the wheel 10 from the preferred orientation, which resistance can be overcome by the application of torque to the support member relative to the head member about the swivel axis. The castor assembly may be supplied as a kit for conversion of conventional castor assemblies. <IMAGE>

Description

Title: Castor Assembly Description of Invention This invention relates to castors and is particularly but not exclusively concerned with a castor assembly suitable for fitting to shopping trolleys used in supermarkets or the like.

It is conventional practice for trolleys such as shopping trolleys and airport luggage trolleys to be provided with four castors, one at each corner of the trolley. Each castor may be of generally conventional construction comprising a castor wheel freely rotatable about an axis, which in use, is generally horizontal, the wheel being carried between a pair of support arms which are themselves freely swivelable about an axis which, in use is generally vertical, and which is offset from said horizontal axis. Each castor is thus freely rotatable and swivelable relative to the trolley and this total freedom of movement can lead to steering difficulties for the user especially when the trolley is loaded and is being wheeled transversely of a slope.Whilst such castors are usually swivel able through a full 3600, in some cases swivelling may be limited to a specific angular range.

It is an object of the present invention to provide a castor assembly which is restrainable in at least one orientation against swivelling and wherein such restraint does not interfere with the freedom of rotation of the castor wheel.

In accordance with the invention there is provided a castor assembly comprising: a castor wheel freely rotatably mounted on a support member, a head member relative to which the support member is swivelable about a swivel axis through a predetermined angular range of up to 360 , the axis of rotation of the wheel being offset from and perpendicular to the swivel axis, and releasable restraint means operable between an operative condition in which the support member is restrained against swivelling movement relative to the head member in at least one orientation of the support member relative to such head member, and an inoperative condition in which the support member is free to swivel relative to the head member said restraint means comprising a first element associated with said head member and a second element associated with said support member, and resilient means biasing said elements into engagement with one another over the entire angular range of swivelling, and into said operative condition when the support member and head member are in said at least one orientation, said elements being movable against their resilient bias out of their cooperative condition and into said inoperative condition under the application of a torque to the support member relative to the head member about the swivel axis.

Preferably said elements are moveable into said operative condition at a single orientation of the support member relative to the head member about the swivel axis. When a castor assembly in accordance with the invention is installed on a trolley, such single position would normally be that in which the wheel of the castor is in the "straight-ahead" position, with the axis of rotation of the wheel being disposed rearwardly of the swivel axis of the castor assembly having regard to the normal direction in which the trolley is wheeled.

One of said elements of the restraint means may comprise a surface of annular or part-annular form centred on the swivel axis, the other of said elements having a dimension circumferentially of the annular surface which is much less than the circumferential length of the surface so as to engage the latter over only a small part of its length.

Preferably, said other element has rolling engagement with said surface and comprises a roller or ball.

Said surface may comprise an in-use downwardly presented generally flat surface which is engaged by said other element, but where the other element comprises a ball, said surface may be formed with an annular groove in which the ball is located.

The (or each) orientation in which the swivelling of the castor is restrained may be defined by a recess in said surface so dimensioned as to enable said other element to enter said recess. The recess may be formed as an indentation in the surface, or as a gap.

In a preferred arrangement, said surface comprises said first element of the restraint means, namely that associated with the head member, and the surface may be formed on part of a cover element arranged at least partially to cover the head member and an associated bearing means by which the support member is swivelable relative thereto. Such a cover element conveniently is in the form of a dished annulus which fits over the head member.

The second element of the restraint means may be carried by a part of the support member facing the cover element, with a spring element engaging said second element to bias it towards said cover element. Said part of the support member may comprise a bridge portion extending between generally parallel support arms which carry the wheel, the second element being disposed in an aperture in the bridge portion with the spring element engaging the second element to bias it and also to prevent its escape from the bridge portion.

The cover element may be provided with sealing means which cooperates with a bearing means by which the support member is swivelable relative to the head member, to retain lubricant in and/or exclude dirt from the bearing means or a part thereof.

Conveniently the cover element is of a plastics material. It may be an injection moulding of such material. It may be configured to act as a buffer or shield, to help protect the ankle or lower leg of a user of a trolley equipped with a castor according to the invention from accidental contact with the castor assembly.

A castor assembly in accordance with the invention may be achieved by fitting to a conventional castor assembly (i.e. one not in accordance with the invention the first and second elements of the restraint means and the resilient biasing means. Thus in accordance with the second aspect of the invention there is provided a kit of parts for conversion of a castor assembly comprising a castor wheel freely rotatably mounted on a support member and a head member relative to which the support member is swivelable about a swivel axis, the axis of rotation of the wheel being offset from and perpendicular to the swivel axis; the kit of parts comprising: a first element of a restraint means, adapted to be fitted to said head member; a second element of the restraint means, adapted to be fitted to said support member; and resilient means arranged to bias said elements when fitted to their respective members into cooperation with one another to an operative condition in which the support member is restrained against swivelling movement relative to the head member, said elements being movable against their resilient bias out of their cooperation with one another to an inoperative condition wherein the support member is free to swivel relative to the head member, under the application of a torque to the support member relative to the head member about the swivel axis.

A trolley would normally be provided with castor assemblies according to the invention on two wheels only thereof, namely the rear wheels in the case of a trolley intended to be pushed by a user. When the rear wheels reach their "straight-ahead" orientation, the restraint means moves to its engaged position to retain such orientation of the wheels as the trolley is being wheeled. The trolley can then be wheeled transversely of a slope relatively easily. When the trolley is required to be manoeuvred in a confined space, however, the user of the trolley can push it sideways, and thereby, by virtue of the offset of the wheel axis from the swivel axis, apply sufficient torque to move the restraint means to its disengaged position and enable the rear wheels to swivel.

According to another aspect of the invention, there is provided a trolley, e.g. a shopping trolley, having at least one castor assembly according to the invention as above set forth. Preferably the trolley has two such castor assemblies, at the rear wheels thereof.

The invention will now be described by way of example with reference to the accompanying drawings, in which: FIGURE 1 is an elevation, partly in section, of a castor assembly in accordance with the present invention in a first position, FIGURE 2 is a view as Figure 1 but showing the castor assembly in a different position.

Referring firstly to Figure 1 of the drawings, the main components of a castor assembly according to the invention comprise a wheel 10, a support member 11, and a head member indicated generally at 12 relative to which the support member 1] and with it the wheel 10 are swivelable about a swivel axis 13 which in use is upwardly oriented. The support member 11 is of sheet metal and comprises two parallel or substantially parallel support arms 14, 15 joined at their upper ends by a bridge portion indicated generally at 16. The wheel 10 is carried by a bolt 17 extending between the two arms 14, 15, the wheel being rotatable about an axis 18 offset from the swivel axis 13.

The head member 12 comprises a central bush 19 with an aperture 20 extending therethrough, coaxially with the swivel axis 13, for receiving a fastener such as a bolt for securing the head member to a trolley. The bush 19 carries upper and lower bearing race members 21, 22 with a spacer 23 therebetween and a bearing race portion 24 of the bridge portion 16 lies between the bearing race members 21, 22 with interposed circular arrays of ball bearings 25, 26 respectively.

Thus the support member 11 and wheel carried thereby are swivelable relative to the head member 12 about the swivel axis 13 through a range of 3600.

However, it may be required in some cases to impose limits on the overall range of angular movement.

A cover element or shroud 27 of dished annular configuration fits on the bush 19 and extends over the upper bearing race 21. The element 27 has a rim 28 with a downwardly facing annular flat surface 29 having at one circumferential position a recess 3() formed as a part-spherical indentation as shown in Figure 2. Internally of the rim 28 a seal formation 31 is provided for engaging an annular surface of the portion 24 of the head member 16, to retain lubricant in/or exclude dirt from the region of the ball bearings 25.

The element 27 preferably is an injection moulding of a suitable plastics material.

A part of the bridge portion 16 facing the annular track 29 of the element 27 is provided with an aperture 32 in which there is movably received a ball 33. A leaf spring element 34 is attached to the bridge portion 16 and engages a ball 33 to spring bias it towards the surface 29. The spring 34 is clipped to a rearwardly extending flange portion 35 of the bridge portion 16 of the support member 11, the spring having a U-shaped portion 36 with a tag 37 engaging an aperture 38 in the portion 35 to retain the spring.

When the ball 33 aligns with the recess 30 in the rim 28 of the element 27, the spring biases the ball into engagement with such recess as shown in Figure 2. In this condition, the support member 11 is restrained from swivelling relative to the head member 12 about the swivel axis 13. Application of sufficient torque to the support member relative to the head member, however, causes the ball 33 to move out of the recess 30 against the biasing of the spring 34, whereafter swivelling is again possible.

It will be noted that the ball 33 is maintained in permanent engagement with the annular surface 29 so as to at all times to be protected from exposure to dust or rain etc., and also that at all angular orientations of the wheel 10 relative to the swivel axis 13, except that in which the ball 33 engages in the recess 30, there is no (or at least uniform) resistance to swivelling movement, and in particular no resistance has to be overcome to cause the ball to enter the recess.

Whilst the embodiment described above and illustrated in the accompanying drawings represents a preferred arrangement, it will be understood that numerous variations are possible.

For example, the ball may be replaced by a roller with its axis of rotation on a radius relative to the swivel axis. Whilst rolling contact with the track 29 is preferred, the ball 33 could be replaced by an element having sliding contact with the surface, e.g. a raised protuberance formed or provided on the leaf spring 34.

Whilst the surface 29 is flat, an annular groove could be formed therein to receive the ball 33 and provide further protection from exposure to dust etc.

Whilst it is convenient to provide the annular surface on the shroud 27 and the ball or other detent element on the support member 11, the converse arrangement would be possible.

Whilst the recess 30 is most conveniently formed as an indentation, it could alternatively be formed as a gap or interruption in the annular surface, and whilst only a single such recess would normally be provided, in some cases several such recesses may be provided at circumferentially spaced locations.

Apart from the provision of the element 27, ball 33 and spring 34, the castor assembly above described is generally conventional. Thus an existing castor may be converted to one in accordance with the invention by the addition of these components thereto.

The features disclosed in the foregoing description, or the accompanying drawings, expressed in their specific forms or in terms of a means for performing the disclosed function, or a method or process for attaining the disclosed result, as appropriate, may, separately or in any combination of such features, be utilised for realising the invention in diverse forms thereof.

Claims (21)

CLAIMS:

1. A castor assembly comprising: a castor wheel freely rotatably mounted on a support member, a head member relative to which the support member is swivelable about a swivel axis through a predetermined angular range of up to 3600, the axis of rotation of the wheel being offset from and perpendicular to the swivel axis, and releasable restraint means operable between an operative condition in which the support member is restrained against swivelling movement relative to the head member in at least one orientation of the support member relative to such head member, and an inoperative condition in which the support member is free to swivel relative to the head member said restraint means comprising a first element associated with said head member and a second element associated with said support member, and resilient means biasing said elements into engagement with one another over the entire angular range of swivelling, and into said operative condition when the support member and head member are in said at least one orientation, said elements being movable against their resilient bias out of their cooperative condition and into said inoperative condition under the application of a torque to the support member relative to the head member about the swivel axis.

2. A castor assembly according to Claim 1 wherein said elements are movable into said inoperative condition at a single orientation of the support member relative to the head member about the swivel axis.

3. A castor assembly according to Claim 1 or Claim 2 wherein one of said elements of the restraint means comprises a surface of annular or part-annular form centred on the swivel axis and the other of said elements has a dimension circumferentially of said annular surface which is much less than the circumferential length of the surface so as to engage the latter over only a small part of its length.

4. A castor assembly according to Claim 3 wherein said other element of the restraining means has rolling engagement with the surface.

5. A castor assembly according to Claim 4 wherein said other element comprises a roller.

6. A castor assembly according to Claim 4 wherein said other element comprises a ball.

7. A castor assembly according to any one of Claims 3 to 6 wherein the, or each, orientation in which swivelling of the castor is restrained is defined by the position of a recess in said surface and so dimensioned as to enable said other element of the restraining means to enter said recess.

8. A castor assembly according to Claim 7 wherein the recess is formed as an indentation in the surface.

9. A castor assembly according to Claim 7 wherein the recess is formed as gap in the surface.

10. A castor assembly according to any one of Claims 3 to 9 wherein said surface comprises said first element of the restraint means, associated with the head member.

11. A castor assembly according to Claim 10 wherein the surface is formed on part of a cover element arranged at least partially to cover the head member and an associated bearing means by which the support member is swivelable relative thereto.

12. A castor assembly according to Claim 10 or Claim 11 wherein said second element of the restraint means is carried by a part of the support member facing said cover element, with a spring element engaging said second element to bias it towards said cover element.

13. A castor assembly according to Claim 12 wherein said part of the support member comprises a bridge portion extending between generally parallel support arms which carry said wheel, the second element of the restraint means being disposed in an aperture in the bridge portion with the spring element engaging said second element to bias it and also prevents its escape from the bridge portion.

14. A castor assembly according to any one of Claims 10 to 13 wherein the cover element is provided with sealing means which cooperates with a bearing means by which the support member is swivelable relative to the head member, to retain lubricant in and/or exclude dirt from the bearing means or a part thereof.

15. A castor assembly according to any one of Claims 10 to 14 wherein the cover element is formed of a plastics material.

A A castor assembly according to Claim 15 wherein the cover element is configured to act as a buffer or shield. to help protect the ankle or lower leg of a user of a trolley equipped with a castor according to the invention from accidental contact with the castor assembly.

17. A kit of parts for conversion of a castor assembly comprising a castor wheel freely rotatably mounted on a support member and a head member relative to which the support member is swivelable about a swivel axis, the axis of rotation of the wheel being offset from and perpendicular to the swivel axis; the kit of parts comprising: a first element of a restraint means, adapted to be fitted to said head member; a second element of the restraint means, adapted to be fitted to said support member; and resilient means arranged to bias said elements when fitted to their respective members into cooperation with one another to an operative condition in which the support member is restrained against swivelling movement relative to the head member, said elements being movable against their resilient bias out of their cooperation with one another to an inoperative condition wherein the support member is free to swivel relative to the head member, under the application of a torque to the support member relative to the head member about the swivel axis.

18. A trolley having at least one castor assembly according to any one of Claims 1 to 16.

19. A trolley according to Claim 18 having two rear wheels which each comprise a castor assembly according to any one of Claims 1 to 16.

20. A castor assembly substantially as hereinbefore described with reference to and as shown in the accompanying drawings.

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