GB2292776A - Castor fork - Google Patents

Abstract

A castor fork (1) which supports a wheel (2) is formed from two discrete parts (9, 10). Each part has a leg portion (3) and a body portion (5). The two parts are clamped together by means of screws or bolts (12, 13) and receive a bearing race (11) in which is mounted a support member (6) of an article to which the wheel is to be attached. The two parts may alternatively by secured by means of a sheath or cap. The castor fork thus constructed is stronger than known assemblies and can be assembled and dismantled more quickly and easily. <IMAGE>

Description

CASTOR FORK DESCRIPTION The present invention relates to a castor fork and particularly to a castor fork for containing a precision radial bearing or bearings for a swivel assembly.

Traditionally, castor forks are moulded from a thermoplastic material around a radial bearing race in the upper part and a wheel is fixed at the lower part between the two arms of the fork. This is an expensive process and the plastic material has limited strength.

Alternatively the castor fork is formed of pressed metal, the radial bearing race is pushed into a recess in the upper part of the fork and the edges of the recess are rolled over to hold it in place. The fork itself has more strength than a plastic fork but the rolled edges will only hold the bearing race in place up to certain loadings and this arrangement is too unreliable to use for heavy duty applications or those where safety is paramount (e.g.

wheelchairs). Sometimes tabs are added to a die casting and these are folded in to hold the bearing race in place.

However die cast material is brittle and breaks too easily so the known castor fork assemblies have a reputation for unreliability except at very low loads.

The present invention aims to provide an improved castor fork assembly which can be easily assembled, made from strong material in a cost effective manner and retain the bearing race efficiently and reliably for relatively high loads.

According to the present invention there is provided a castor fork comprising two discrete parts, each part having a leg portion and a body portion with a recess for receiving a radial bearing race, each of the two parts being formed of a die cast material and the two parts being connectable together to retain the radial bearing race in the co-joined recesses.

The two parts are most cost effectively formed of die cast metal but a glass filled plastic material may be used.

A bearing assembly formed using a castor fork according to the present invention can be made stronger than known assemblies, and can be assembled quickly and easily, particularly compared to traditional methods which require riveting and screwing operations. A particular advantage is the ease with which such a bearing assembly can be disassembled, for example if it is required to change the bearing. The two die cast parts of the fork may be clamped together or alternatively bolted or screwed or a retaining cap may be slotted over the body portions of the two parts.

By forming the fork in two discrete die cast parts, grooves or other indentations can be moulded into the inner surfaces; of the fork legs so as to hold items in place between the legs without the need to drill holes right through the legs: such drill holes are unsightly and in any case difficult to accurately position.

For a better understanding of the present invention, reference will be made by way of example to the accompanying drawings, in which: Figure 1 is a side elevation of a castor fork according to the invention in an assembled condition.

Figure 2 is a cross-section of the fork of Figure 1 on the line A-A.

Figure 3 is a cross-section of the fork of Figure 1 on the line B-B.

Figure 4 is a cross-section of one embodiment of a castor fork according to the invention.

Figure 5 is a part cross-section of a castor fork according to the invention illustrating an alternative form of assembly.

Figure 6 is a cross-section of an embodiment of the invention with two bearing races.

Figure 7 is a part cross-section of an alternative form of the embodiment of Figure 6.

in Figure 1 a castor fork i supports a wheel 2 between legs 3 on bolt 4 or rivet and 4 has an upper portion 5 In which a bearing and its race is retained and to which is attached a support member 6 of an article, e.g. a trolley or wheelchair to which the wheel 2 is to be attached in swivelable manner.

Figure 2 is a cross-section along line A-A of Figure 1 and shows the two leg parts 7 and 8 of the castor fork 1 supporting wheel 2 on bolt 4. The two parts 9 and 10 of the head 5 of the fork are clamped around bearing race 11 by means of screws or bolts 12 and 13 in drilled cooperating holes in the two parts.

Figure 3 is a cross-section on line B-B of Figure 1 and again like parts are indicated by like reference numbers.

In Figure 4 a side elevation cross-section is shown illustrating the bearing race 11 which provides a swivel joint with thewsupport member 6.

Figure 5 illustrates an alternative method of assembling the two castor fork parts wherein a sheath or cap 14 is slotted over the two head parts 9 and 10 to hold the bearing race 11 in place in the recess between the two parts.

Figure 6 is a side elevation cross-section view of a castor fork with two bearing races IlA and 1lB clamped between the two head parts.

Figure 7 also illustrates an arrangement with two bearing races but shows the alternative method of assembly using a sheath or cap 14 fitted over the head of the castor fork.

Of course many other alternatives are envisaged within the scope of the present invention. For example the two parts might be fastened by a clamping band. Spindles to support the wheel might be moulded or cast integrally with the castor fork parts to obviate the need for bolt or rivet 4 and the attendant drilling.

Claims (11)

CLAIMS:

1. A castor fork comprising two discrete parts, each part having a leg portion and a body portion with a recess for receiving a radial bearing race and the two parts being connectable together to retain the radial bearing race in the co-joined recesses.

2. A castor fork as claimed in claim 1, wherein each of the two parts is formed from die cast material.

3. A castor fork as claimed in claim 2, wherein the two parts are formed from die cast metal.

4. A castor fork as claimed in claim 1 or claim 2, wherein each of the two parts is formed from a plastics material.

5. A castor fork as claimed in claim 4, wherein each of the two parts is formed from a glass-filled plastics material.

6. A castor fork as claimed in any of the preceding claims, wherein the two parts of the fork are clamped together.

7. A castor fork as claimed in any of the preceding claims, wherein the two parts of the fork are bolted or screwed together.

8 A castor fork as claimed in any one of claims 1 to 5, further comprising a retaining cap located over the body portion of the two parts.

9. . A castor fork as claimed in any of the preceding claims, wherein each body portion comprises plurality of recesses for receiving a plurality of radial bearing races.

10. A castor fork as claimed in any of the preceding claims, further comprising a spindle integrally formed with one or both of the castor fork parts to support a castor wheel.

11. A castor fork substantially as herein described, with reference to, and as illustrated in, Figs. 1 to 4 or Figs.

to 4 as modified by Fig. 5, Fig. 6 or Fig. 7 of the accompanying drawings.