GB2153666A - Caster assembly - Google Patents

Abstract

A swivellable caster assembly for a supermarket trolley has an upper portion 10 in which a shaft 12 is rotatable. The shaft 12 is axially displaceable, to a limited extent, and is urged downwardly by a resilient element 40. Preferably this acts on a ball 38 which contacts an end of the shaft 12. A lower portion of the shaft 12 projects and bears an arcuate member (14) of resilient material on which wheel means (15) are journalled, offset from the shaft 12. The resilient element may be moulded from material such as rubber or may be a compression spring. <IMAGE>

Description

SPECIFICATION Caster assembly The present invention relates to a caster assembly, particularly but not exclusively for use on a supermarket trolley.

Conventionally, at least some of the casters of supermarket trolleys involve wheels which are journalled to caster portions which are pivotable about upright axes. It is usual for both sets of bearings to employ ball races. These have a large number of moving parts. The complex construction means that they tend to be expensive and/or unreliable. Furthermore, if it is desired to provide some suspension, this requires separate suspension means.

According to the present invention there is provided a swivellable caster assembly comprising: a first portion arranged to be mounted to an article; a shaft mounted in said first portion and projecting from it; and a second portion mounted on a projecting portion of said shaft and having ground engaging transport means; wherein the shaft is mounted in said first portion so as to be axially rotatable and axially displaceable, there being resilient means for urging displacement away from the first portion. Preferably the shaft has an axial end within the first portion, and this end abuts a rollable element, (e.g. a ball-bearing) which is resiliently urged against said axial end by said resilient means.

In the second portion, the ground engaging transport means may be spaced from the shaft, and resiliently displaceable relative thereto. This may be simply achieved by forming a body of the second portion of resilient material (e.g. moulded nylon or rubber).

Some embodiments of the invention will now be described in greater detail with reference to the accompanying drawings in which: Figure 1 is a vertical section through part of a first embodiment of the caster assembly according to the invention; Figure 2 is a vertical section through a second portion of the caster assembly of Fig. 1; and Figure 3 is a partial vertical section of a second embodiment.

The first embodiment of the caster assembly includes a first portion 10 for attachment to a trolley; a shaft 12; and a second portion 14 having ground engaging transport means such as one or more wheels 15.

A first portion 10 comprises a housing having an elongate cavity 16, open at the bottom. The housing may be formed of two like halves which are placed together to define the cavity 16. They may be locked together by means of pins passed through apertures 18. The cavity 16 has a narrow mouth portion 20; a bearing housing portion 22 terminated by an annular neck 24; a cylindrical chamber 26; and above this, an elongate narrower cylindrical chamber 28. A low friction bearing 30, preferably constituted by a tube of PTFE, is located in the bearing housing portion 22.

The shaft 12 is elongate and generally cylindrical. Slightly below its upper end there is an annular groove 32 in which a clip 34 is mounted. The clip 34 extends radially beyond the shaft 12. As can be seen from Fig. 1, the clip 34 serves to trap the shaft 12 in the cavity 16, with the clip within the chamber 26, since it is too large to pass beyond the neck 24. A bottom end portion 36 of the shaft 12 is adapted to be retained in the moulding constituting the second portion 14. Thus it may be, as shown, of larger diameter and with serrations or teeth. Above the shaft 12, within the elongate chamber 28 of the cavity 16, there is a ball-bearing 38 abutting the shaft 12. Above this there is a resilient element 40, preferably constituted by a suitably shaped injection moulded article of a suitable material, e.g. rubber or "hytrel".

The housing of the first portion 10 may be adapted so that it can easily be attached to the underside of the frame of a supermarket trolley. This adaptation is schematically shown in Fig. 1 by the U-shaped formations 42.

The second portion is approximately J-shaped. It is suitably injection moulded of a similar resilient material to the resilient element 40. It has a cavity 44 in which the end portion 36 of the shaft 12 is an interference fit. (The portion 14 could be moulded around the shaft 16.) Adjacent the end of the "J" there is an aperture in which a shaft bearing one or two wheels 15 will be journalled.

The caster assembly can be made entirely of plastics materials. It can be light and efficient to use. The compressible element 40 provides suspension, and further "springing" will be provided by the resilience of the second portion 14. The shaft 12 passes through the PTFE tube 30, which provides a very low-friction bearing which is virtually maintenance free. The top bearing employing the ball 38 (which may also be of PTFE) is also very simple and efficient. There are, of course, far fewer moving parts than in a conventional system using ball races.

Of course, much variation is possible. Some variants are shown in Fig. 3. This shows an upper portion of a shaft 112 partly received in a cavity 116. The cavity 116 has, near its mouth, a chamber 126, associated with a clip 34 mounted on the shaft 112 via an annular groove 132. Spaced above the chamber 126 are two mutually spaced bearing housing portions 122 and 123. Each contains a respective bearing element 130, which may be a portion of a PTFE tube like the tube 30 of the previous embodiment. Above the shaft 116 there is a ball 38 which is urged against the shaft 112 by means of a compression spring 140.

In other embodiments, the tube 30 or one or both of the tubes 122,123 could be replaced by one or more cylindrical roller bearings.

The cavity 16 or 116 may be provided by an insert, e.g. in the form of an injection moulded tube with a closed end. This could be mounted within a steel tube which formed at least part of the housing of the upper portion 10.

As will be apparent to the reader, the various features described above with reference to particu lar embodiments, and other features which can readily be devised, can be combined in numerous combinations.

In preferred embodiments, the housing is formed of two like halves which can be secured together around an element of a trolley, such as a horizontal rod, so as to clamp it. Thus for example each housing half may have a channel of semicircular section so as to define, in the assembled housing, a round bore in which a trolley element is engaged. Each half might have a plurality of channels so as to define a plurality of bores suitable for different types of trolley element.

Claims (11)

1. A swivellable caster assembly comprising: a first portion arranged to be mounted to an article; a shaft mounted in said first portion and projecting from it; and a second portion mounted on a projecting portion of said shaft and having ground engaging transport means; wherein the shaft is mounted in said first portion so as to be axially rotatable and axially displaceable, there being resilient means for urging displacement away from the first portion.

2. An assembly according to claim 1 including a rollable element within said first portion, wherein the shaft has an axial end within the first portion, and this end abuts said rollable element which is resiliently urged against said axial end by said resilient means.

3. An assembly according to claim 1 or claim 2 wherein the ground engaging transport means is spaced from the shaft, and resiliently displaceable relative thereto.

4. An assembly according to claim 3 wherein a body of the second portion is formed of resilient material to provide said resilient displaceability.

5. An assembly according to any preceding claim wherein the first portion provides an elongate cavity within which said shaft is mounted; said first portion having low friction internal surface means for contacting said shaft in said cavity.

6. An assembly according to claim 5 comprising at least one elongate annular bearing member of ptfe for providing said low friction surface means.

7. An assembly according to any preceding claim wherein one of the shaft and the first portion has means defining an annular projection and the other has an axially elongate annular cavity in which said projection is captive and axially displaceable.

8. An assembly according to any preceding claim wherein said first portion comprises two separable side portions having respective channels which together form an elongate cavity in which said shaft is mounted; the side portions each having at least one further channel for forming a through-opening for embracing an elongate portion of an article to which the assembly is to be mounted.

9. An assembly according to claim 8 wherein each side portion has a plurality of said further channels so that the first portion has a plurality of through openings.

10. A swivellable caster assembly substantially as any herein described with reference to and as illustrated in the accompanying drawings.

11. A supermarket-type trolley having a swivellable caster assembly according to any preceding claim.