AU607483B2 - Ball castor - Google Patents

Description

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Form COMMONWEALTH OF AUSTR PATENTS ACT 1952 COMPLETE SPECIFICATION

(ORIGINAL)

FOR OFFICE USE Short Title: Int. Cl: 00 000 o ooo 000 o 0..o 0 0 00 0 0 0 0 0 0 0000 00 0 0 00 0000 0 .0 0000 o o Application Number: PI1440 Lodged: 14th April, 1987 Complete Specification-Lodged: Accepted: Lapsed: Published: Priority: This document contains the amendments made under Section 49 and is correct for rin Ling.

Related Art: TO BE COMPLETED BY APPLICANT Name of Applicant: Address of Applicant: Actual Inventor: Address for Service: KENNETH WILLIAM KENDRICK 24- AMelci'a Divr'e S48 Charles Hodge Avenue, North Mackay, Queensland 4740, AUSTRALIA Kenneth William Kendrick GRIFFITH HASSEL FRAZER 71 YORK STREET SYDNEY NSW 2000

AUSTRALIA

Complete Specification for the invention entitled: BALL CASTOR The following statement is a full description of this invention, including the best method of performing it known to me/us:- 1755A/ls -FC 7 ^P This invention relates to castors and in particular to light duty ball castors.

Ball castors in the past have comprised a spherical ball captured in a housing in a manner permitting a portion of the ball to be exposed for contact with a ground surface for rolling movement therealong. Between the ball and the housing is located a plurality of small bearing balls to allow the ball to freely rotate within the housing while allowing the housing to exert a loading force on the ball, caused by the weight of the object to which the castor is fitted. One problem associated with this arrangement is that the bearing balls tend to bind on one another and with use and wear the bearing balls do not fulfil their designed S function.

O0 0 0 0 15 oo o o 0 o 0 0 0 0 00 0 0 0 0 0 0 0oo 000 00 000 00 00 0 0 0000 0600 ooot oao o oooo oooo oa~ 0 0 00 a '1 004 The present invention however, provides a ball castor comprising: a housing; a spherical ball, captured within and protruding from the housing; means for retaining the ball within the housing; and a bearing surface within the housing in contact with the surface of the ball for transmitting a load force from the housing to the ball; wherein the bearing surface and the surface of the ball co-operate to provide point or ridge contact between the ball and the housing over substantially the entire half of the surface of the ball for the time being uppermost within the housing.

at Preferably, the bearing surface is in the form of 30 truncated spikes to reduce the actual area of contact with the ball.

Preferably, the bearing surface is made from a self-lubricating plastics material.

Preferably the retaining means is a sleeve placed around the housing to prevent enlargement of the opening through which the ball protrudes.

Notwithstanding any other forms that may fall within its scope, one preferred form of the invention will now be S described, by way of example only, with reference to the

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accompanying drawings in which:

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6 0S/EM -2- 6 Of 7-) 2. i~~ Figure 1 is an elevational view of a castor according to the preferred embodiment of the invention, Figure 2 is a view from below of the castor of Figure 1, and Figure 3 is an elevational view similar to Figure 1 in which the housing is shown in section viewed along section line X-X of Figure 2.

As can be seen from the figures, the preferred embodiment comprises a spherical ball 41, a housing 42 in which the ball is held captive and a sleeve 43. Between the ball 41 and the housing 42 is a contact or load bearing 00 0 surface 44 by which the load force applied to the housing is o o0 transmitted to the ball.

0 o o CO The housing 42 preferably is made from a plastics oo. 5 material. The housing encompasses more than half of the 0000oooo ball so that the ball is held captive in the housing. To 0 insert the ball into the housing the mouth of the ball opening is expanded by a slight pressure to allow the ball o oo00 to be inserted into the housing. The opening is made 0 20 suitably flexible to allow this expansion without damage to 0 00°° the housing. To prevent the mouth of the ball housing from being expanded to release the ball, the sleeve 43 is slid o over the housing to prevent the mouth of the housing being enlarged sufficiently to release the ball. The sleeve may 00oo 5 be made from a rigid plastics material. The sleeve which is I o o0 S0" a close tolerance fit over the housing may be glued in place o0 to prevent separation and to aid the mechanical strength and rigidity of the housing.

The bearing surface 44 is arranged to reduce the friction between the ball and the housing. Any surface which provides point or ridge contact may suffice, however, the preferred embodiment utilises truncated spikes or dimples. The low friction aspect is further enhanced by using a self-lubricating plastics material for the bearing surface 44.

6041S/ls -3- 1 'u, I~ The ball 41 may be stainless steel or a self-'.ubricated plastics material to aid the low friction contact between the ball and the housing.

The simple construction of the castor, involving only three separate items provides an easy to manufacture ball castor in which the possibility of malfunction is greatly reduced.

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Claims (5)

1. A ball castor comprising: a housing; a spherical ball, captured within and protruding from the housing; means for retaining the ball within the housing; and a bearing surface within the housing in contact with the surface of the ball for transmitting a load force from the housing to the ball; wherein the bearing surface and the surface of the ball co-operate to provide point or ridge contact between the ball and the housing over substantially the entire half of the surface of the ball for the time 0oo oo being uppermost within the housing. 00 0 0] o 0 Q o

2. A ball castor as defined in claim 1, wherein the 0 00 o bearing surface is in the form of truncated spikes. 0200 C

3. A ball castor as defined in claim 1 or claim 2, 0 "oo0 wherein the bearing surface is made from a self-lubricating plastics material. oooo

4. A ball castor as defined in any one of the 0 0o 0 preceding claims, wherein the retaining means is a sleeve o 0 26 placed around the housing to prevent enlargement of the o opening through which the ball protrudes. A

5. A ball castor substantially as hereinbefore described with reference to the accompanying drawings. S DATED this 27th day of November 1990 KENNETH WILLIAM KENDRICK By his Patent Attorneys GRIFFITH HACK CO. :S/EM