GB2306106A

GB2306106A - Castor wheel

Info

Publication number: GB2306106A
Application number: GB9521122A
Authority: GB
Inventors: Raymond Robert James Daniels
Original assignee: Guy Raymond Engineering Co Ltd
Current assignee: Guy Raymond Engineering Co Ltd
Priority date: 1995-10-16
Filing date: 1995-10-16
Publication date: 1997-04-30
Anticipated expiration: 2015-10-16
Also published as: GB2306106B; GB9521122D0

Abstract

A castor comprises a wheel 14 rotatably mounted to a body member 12. Seal means 82 engages relatively moveable surfaces e.g.30, 32 respectively of the wheel (or a member at least substantially fixed for rotation with the wheel) and the body member (or a member at least substantially fixed against rotation relative to the body member) such that free-running rotational movement of the wheel relative to the body member is retarded.

Description

CASTOR This invention relates to castors, and more particularly but not exclusively to castors comprising a wheel rotatably mounted to a body member by a spindle which extends from a spindle mount carried by the body member into a closed bore in a central boss of the wheel.

Such a castor is disclosed in our British Patent Specification 2171897A.

A problem with the above-mentioned castors is that they may be too free-running. This can result in a lack of controllability when an article to which the castors are mounted is manoeuvred using the castors and/or in undesired movement of the article on the castors when the article is intended to remain stationary.

An object of the invention is to mitigate or overcome the above-mentioned problem.

Accordingly, the invention provides a castor comprising a wheel rotatably mounted to a body member and retardation means engaging relatively movable surfaces respectively (i) of the wheel or a member at least substantially fixed for rotation with the wheel and (ii) the body member or a member at least substantially fixed against rotation relative to the body member, such that free-running rotational movement of the wheel relative to the body member is retarded.

The retardation means is preferably formed by a seal means.

Preferably, the wheel is rotatably mounted to the body member by a spindle which extends from a spindle mount carried by the body member into a closed bore in a central boss of the wheel, and shroud means shrouding the boss and/or spindle mount bridges the axial gap between the boss and the spindle mount.

Preferably, the shroud means is integral with the spindle mount and extends about an end portion of the boss from which the spindle emerges.

Preferably, the shroud means is formed by a counterbore in said spindle mount for receiving said boss end portion.

Preferably, the seal means is disposed in (i) a circumferentially extending recess in said shroud means located at the free end thereof and having respective radially inwardly and axially outwardly facing surfaces and (ii) a circumferentially extending step in said boss end portion, which step has surfaces respectively facing said surfaces of said recess.

Alternatively, the seal means may be disposed in (i) a circumferentially extending recess having a radially inwardly facing surface provided by said shroud means and an axially outwardly facing surface provided by said spindle mount and (ii) a circumferentially extending step in said boss end portion, which step has surfaces respectively facing said surfaces of said recess.

Alternatively, the seal means may be disposed in a circumferentially extending radially outwardly opening groove in said spindle and engage the radially inner surface of said bore in said boss.

Alternatively, the seal means may be disposed in (i) a circumferentially extending recess having a radially outwardly facing surface provided by said spindle and an axially outwardly facing surface provided by said spindle mount and (it) a circumferentially extending step in the bore of said boss at the open end thereof, which step has surfaces respectively facing said surfaces of said recess.

The seal means is preferably an annular seal of a synthetic rubber or other polymeric material.

The material may be neoprene or polyurethane.

Preferably, the seal means is an '0' ring seal.

The spindle mount may be integral with the body portion.

Preferably, grease is provided between the closed bore of the boss and the spindle, the shroud means extends the seepage path for such grease and said seal means is disposed in said seepage path of said grease such that said seal means prevents or hinders grease seepage and prevents or hinders ingress of dust and other debris along the seepage path.

In order that the invention may be better understood, various embodiments thereof, which are given by way of example only, will now be described with reference to the accompanying drawings, in which: Figures 1 to 3 are respectively side, front and top plan views of a twin wheel castor; Figure 4 is a cross-sectional view of one half of the same castor; Figure 5 is a cross-sectional view of one half of a modified castor; and Figures 6 and 7 are respective views similar to Figures 4 and 5 of two other castors.

Referring first to Figures 1 to 3, the illustrated castor generally comprises a body member 12 of a plastics material, for example a polyamide, or a metal, two plastics castor wheels 14 mounted to the body and a metal stem 16 extending from and rotatable in the body 12 for mounting the castor on a piece of furniture. The body 12 also includes a hood 18 which extends over the wheels.

Referring now to Figures 4 to 7, wherein similar features are given like reference numerals to avoid unnecessary description, one half of each castor is shown, each castor being symmetrical about its illustrated centre line. The two wheels 14 are rotatably mounted on respective end portions 19 of a spindle 20, which is mounted in a through-bore 22 of a spindle mount 24 of the body 12 so as to extend from the spindle mount on each side thereof and so as to be at least substantially fixed against rotation relative to the body 12. As illustrated, the spindle mount 24 is integral with the body and formed as a boss. Each wheel 14 is provided with a respective central boss 26 provided with a closed bore 27 into which the spindle end 19 extends.Each wheel is axially retained on its respective spindle end portion 19, by interengaging groove and rib means 28 of the spindle end portion and closed bore of the boss. As illustrated, these groove and rib means take the form disclosed in our aforementioned UK Patent 2171897. Specifically, each closed bore is formed with two radially inwardly projecting circumferentially extending annular ribs which are spaced along the bore and which are received in annular grooves in the spindle end portion.

Furthermore, the circumferentially extending annular ribs formed in the bore are provided with gaps in their circumferential extents for the reasons disclosed in the above-mentioned UK patent, which reasons include allowing grease deposited in the bore before the spindle is inserted to be spread evenly over the wall of the bore and complementary surfaces of the spindle during insertion of the spindle end portion into the bore.

The illustrated castors are each provided with a respective shroud means 29 associated with each wheel 14. The shroud means 29 is integral with the spindle mount 24 and extends about the end portion of the wheel boss 26 from which the spindle emerges. The shroud means is formed by a counterbore in the spindle mount 24 for receiving the wheel boss end portion.

The radially outer, or external, surface 30 of the wheel boss end portion and the radially inner, or internal, surface 32 of the shroud means 29 are each circular in cross-section to allow rotation of the wheel boss 26 relative to the shroud means 29.

Referring now to Figure 4, a circumferentially extending recess 80 is provided in the shroud means 29 located at the free end thereof and the wheel boss 26 is stepped to form a boss end portion of reduced outer diameter and define a circumferentially extending step 84. The recess 80 has respective radially inwardly and axially outwardly facing surfaces and the step 84 has surfaces respectively facing the surfaces of the recess 80. A seal means shown as an annular seal in the form of an 'O' ring 82 is disposed in the recess 80 and the step 84.

The arrangement of Figure 4 extends the seepage path for grease axially beyond the axial gap between the wheel boss 26 and spindle mount 24 over the wheel boss end portion between the surfaces 30 and 32 to the '0' ring seal 82 at the free end 34 of the shroud means 29. The '0' ring 82 is disposed in the seepage path and prevents or hinders grease seepage. The 'O' ring 82 also prevents or hinders ingress of dust and other debris along the seepage path.

Figure 5 shows a modified castor, having a circumferentially extending step 90 in the wheel boss end portion at the free end thereof and a circumferentially extending recess 93. The recess 93 has a radially inwardly facing surface provided by the surface 32 of the shroud means 29 and an axially outwardly facing surface 92 provided by the spindle mount 24. The step 90 has surfaces respectively facing the surfaces 32, 92 of the recess 93. The '0' ring 82 is disposed in the recess 93 and the step 90.

Figure 6 shows another modified castor, wherein the '0' ring 82 is disposed in a circumferentially extending radially outwardly opening groove 100 in the spindle 20 and engages the radially inner surface of the closed bore 27 in the wheel boss 26.

Figure 7 shows still another modified castor having a circumferentially extending step 112 in the closed bore 27 in the wheel boss 26 at the open end thereof and a circumferentially extending recess 115.

The recess 115 has a radially outwardly facing surface 114 provided by the spindle 20 an axially outwardly facing surface provided by the surface 92 of the spindle mount 24. The step 112 has surfaces respectively facing the surfaces of the recess 115.

The '0' ring 82 is disposed in the step 112 and the recess 115.

The '0' ring 82 may be of a synthetic rubber or other polymeric material, for example neoprene or polyurethane.

As will be apparent from the foregoing, retardation of the free-running rotational movement of the wheels 14 is provided by frictional engagement of the seal means 82 with relatively rotating surfaces of the castor. The resulting retardation provides improved controllability for an article to which a plurality of castors are mounted, particularly when the article is manoeuvred using the castors in contact with a hard floor surface, and/or prevents or hinders undesired movement of the article on the castors when the article is intended to remain stationary on such a surface.The '0' ring 82 also prevents or hinders the ingress of dust, fluff and other debris between the wheel boss 26 and adjacent surfaces of the spindle mount 24 and spindle 20, which can be a problem particularly, for example, with a castor wheel and/or body member made of electrically chargeable material such as synthetic plastics. The '0' ring 82 also prevents or hinders seepage of grease from the closed bore 27 along a seepage path between the wheel boss 26 and these adjacent surfaces. The '0' ring 82 thus prevents or hinders debris/grease contact and the consequent accumulation of debris into a mass by adhering to the grease, and mitigates the problem of such accumulated masses dropping to the floor to spoil the floor surface or interfering with the smooth running of the wheel boss end portion against the shroud means 29.

Provision of the seal means 82 is also advantageous in that it can allow greater tolerance in the amount of grease provided between the closed bore 27 of the central boss 26 of the wheel 14 and the spindle 20.

In another modified castor (not shown) the shroud means associated with each wheel is integral with the wheel boss and extends about an adjacent end portion of the spindle mount from which the spindle extends.

The shroud means is formed by a counterbore in the wheel boss for receiving an end portion of the spindle mount and seal means is provided between the shroud means and the spindle mount.

Although in each of the castors described above, the '0' ring 82 engages a surface of the wheel boss 26, this is not essential, and it will be understood that retardation is achieved provided that the seal means engages a surface of the wheel 14 or of a member which is fixed, or substantially fixed, for rotation with the wheel 14 and a surface of the body member 12 or a member which is fixed, or substantially fixed, against rotation relative to the body member 12. For example, a castor may be provided wherein the shroud means associated with each wheel comprises a tubular element formed separately from the wheel boss and spindle mount, respective end portions of the tubular element receiving an end portion of the wheel boss from which the spindle emerges and an end portion of the spindle mount from which the spindle extends. The tubular element may be a force fit on one of the wheel boss and the spindle mount, and the seal means may engage the tubular element and the other of the wheel boss and the spindle mount.

In all of the illustrated castors the spindle mount 24 is integral with the body member 12 of the castor, but it is to be understood that this is not essential since, for example, the spindle 24 mount may be carried by the body member 12 for relative movement thereto, as for example in an arrangement as disclosed in British Patent Specification 2195237.

Claims

CLAIMS:

1. A castor comprising a wheel rotatably mounted to a body member and seal means engaging relatively movable surfaces respectively ) of the wheel or a member at least substantially fixed fcr rotation with the wheel and (ii) the body member or a member at least substantially fixed against rotation relative to the body member, such that free-running rotational movement of the wheel relative to the body member is retarded.

2. A castor as claimed in claim 1, wherein the wheel is rotatably mounted to the body member by a spindle which extends from a spindle mount carried by the body member into a closed bore in a central boss of the wheel, and wherein shroud means shrouding the boss and/or spindle mount bridges the axial gap between the boss and the spindle mount.

3. A castor as claimed in claim 2, wherein the shroud means is integral with the spindle mount and extends about an end portion of the boss from which the spindle emerges.

4. A castor as claimed in claim 3, wherein said shroud means is formed by a counterbore in said spindle mount for receiving said boss end portion.

5. A castor as claimed in claim 3 or 4, wherein said seal means is disposed in (i) a circumferentially extending recess in said shroud means located at the free end thereof and having respective radially inwardly and axially outwardly facing surfaces and (ii) a circumferentially extending step in said boss end portion, which step has surfaces respectively facing said surfaces of said recess.

6. A castor as claimed in claim 3 or 4, wherein said seal means is disposed in (i) a circumferentially extending recess having a radially inwardly facing surface provided by said shroud means and an axially outwardly facing surface provided by said spindle mount and (ii) a circumferentially extending step in said boss end portion, which step has surfaces respectively facing said surfaces of said recess.

7. A castor as claimed in claim 3 or 4, wherein said seal means is disposed in a circumferentially extending radially outwardly opening groove in said spindle and engages the radially inner surface of said bore in said boss.

8. A castor as claimed in claim 3 or 4, wherein said seal means is disposed in (i) a circumferentially extending recess having a radially outwardly facing surface provided by said spindle and an axially outwardly facing surface provided by said spindle mount and (i) a circumferentially extending step in the bore of said boss at the open end thereof, which step has surfaces respectively facing said surfaces of said recess.

9. A castor as claimed in any one of the preceding claims, wherein said seal means is an annular seal of a synthetic rubber or other polymeric material.

10. A castor as claimed in claim 9, wherein said material is neoprene or polyurethane.

11. A castor as claimed in claims 9 or 10, wherein said seal means is an '0' ring seal.

12. A castor as claimed in any one of claims 2 to 11, wherein said spindle mount is integral with said body portion.

13. A castor as claimed in any one of claims 2 to 12, wherein grease is provided between the closed bore of the boss and the spindle and the shroud means extends the seepage path for such grease and wherein said seal means is disposed in said seepage path of said grease such that said seal means prevents or hinders grease seepage and prevents or hinders ingress of dust and other debris along the seepage path.

14. A castor substantially as hereinbefore described with reference to Figures 1 to 4 of the accompanying drawings, or those Figures as modified by Figure 5, 6 or 7 of the accompanying drawings.