GB2189557A

GB2189557A - Improvements in bearings for wheels

Info

Publication number: GB2189557A
Application number: GB08709529A
Authority: GB
Inventors: John Buik Butchart
Original assignee: EUROCASTORS Ltd
Current assignee: EUROCASTORS Ltd
Priority date: 1986-04-22
Filing date: 1987-04-22
Publication date: 1987-10-28
Also published as: GB8709529D0; GB8609763D0

Abstract

A trolley wheel has a hub and a cylindrical bearing 5 mutually rotatable within the hub. The outer surface of the bearing 5 is formed from a plurality of hollows 7 with interspaced raised portions 6 to provide a reduced contact surface and to provide pockets for ingressing dust. The hub and bearing 5 are formed respectively from a polyamide and an acetal copolymer so as to give a low coefficient of friction in use and reduce the need for bearing lubrication. <IMAGE>

Description

SPECIFICATION Improvements in wheels The present invention relates to a bearing for a wheel particularly for a trolley, such as, for example, a supermarket trolley or luggage trolley. Although the invention will be described as applied to a wheel for a supermarket or luggage trolley it is applicable also to wheels for other purposes.

Heretofore, such a wheel comprised a hub, into which was inserted an axial sleeve for reception of a friction reducing ball-bearing.

Washers held the whole assembly in place in the hub, and dust caps were applied to both faces of the hub to mask the washers and to reduce the ingress of dust into the ball-bearings. Dust further increases the friction between the bearing and the hub thereby decreasing the efficiency of the wheel. Although the dust caps have been partly successful, the proportion of dust still collecting presents a problem. Furthermore, consideration must be given to lubrication of the bearing and the cost of labour in assembly of the wheel.

It is an object of the present invention to obviate or mitigate the problems referred to.

According to one aspect of the invention there is provided a wheel having a hub and a bearing of substantially cylindrical shape located within said hub so as to provide for mutual rotation, an outer surface of said bearing being in contact with an inner surface of said hub and at least one of said surfaces being formed from a plurality of interspaced circumferentially arranged raised portions and hollows, said raised portions forming on interrupted bearing surface in use.

Preferably the raised portions and hollows extend continuously and axially of said bearing surface and preferably also the raised portions and hollows are are formed on the outer contact surface of the bearing.

In a second aspect of the invention there is provided a wheel having a hub and a bearing located within said hub so as to be mutuaily rotatable, the contacting surfaces of the hub and bearing being formed from an acetal copolymer or polyamide so as to give a low coefficient of friction therebetween.

Both aspects of the invention can be combined in the same embodiment. Therefore a wheel as described in the first aspect can be provided, with the hub and bearing formed of materials so as to give a low coefficient of friction.

Such materials are preferably an acetal copolymer and a polyamide advantageously nylon 6.

One embodiment of the invention will now be described by way of example only, with reference to the accompanying drawings, in which: Figure 1 shows a diamentral section of a wheel Figure 2 is a front view of the wheel of Fig.

1 Figure 3 shows an enlarged side view of a toothed bearing forming part of the wheel of Fig. 1 Figure 4 is a perspective view of the bearing of Fig. 3 Figure 5 is a plan view of the bearing of Fig. 3 Referring to the drawings, 1 denotes a tyre, covering an outer peripheral rim 2 of the wheel. A hub 4 is connected to the outer rim 2 by an integral webb 3. The hub 4 is moulded from a polyamide, for example nylon 6, and receives and is rotable about a bearing 5 (Figs. 3 to 5), moulded from an acetal copolymer. The bearing 5 has an axial hole 5a for receiving an axle (not shown) and has an outer surface 8 having a plurality of equispaced raised portions 6 and hollows 7 extending axially around the circumference of the bearing. The contact surface between the outer surface 8 of the bearing 5 and the inner surface 8a of the hub is therefore decreased.

In use any dust that enters the hub 4 collects in the hollows 7 of the bearing thereby mitagating the effect of friction between the hub 4 and bearing 5.

Because the hub 4 and bearing 5 are of different plastics, in combination the bearing 5 and hub 4 have a low coefficient of friction whereby the bearing 5 does not require lubrication.

Although acetal copolymer and polyamide have been found compatible in this respect any materials having a low coefficient of friction in combination and mechanical properties generally required for robust trolley wheels such as, for example, toughness, durability and impact resistance are also acceptable.

Dust caps (not illustrated) are applied in known manner to both end faces of the hub 4 to prevent or at least reduce the ingress of dust into the bearing 5.

The wheel and the bearing are easily assembled because all that is now necessary is to insert the bearing 5 axially into the hub 4, and then apply the dust caps (not shown) in known manner.

It will be appreciated that the 2 reduced contact surface could also be obtained by having the raised portions 6 and hollow formed on the inner surface 8a of the hub 4.

Furthermore the raised portion 6 need not be axially extending ribs, the criteria being that a reduced contact surface is obtained and hollows are provided for collection ingression dust.

1. A wheel having a hub and a bearing of substantially cylindrical shape located within said hub so as to provide for mutual rotation, an outer surface of said bearing being in con

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. SPECIFICATION Improvements in wheels The present invention relates to a bearing for a wheel particularly for a trolley, such as, for example, a supermarket trolley or luggage trolley. Although the invention will be described as applied to a wheel for a supermarket or luggage trolley it is applicable also to wheels for other purposes. Heretofore, such a wheel comprised a hub, into which was inserted an axial sleeve for reception of a friction reducing ball-bearing. Washers held the whole assembly in place in the hub, and dust caps were applied to both faces of the hub to mask the washers and to reduce the ingress of dust into the ball-bearings. Dust further increases the friction between the bearing and the hub thereby decreasing the efficiency of the wheel. Although the dust caps have been partly successful, the proportion of dust still collecting presents a problem. Furthermore, consideration must be given to lubrication of the bearing and the cost of labour in assembly of the wheel. It is an object of the present invention to obviate or mitigate the problems referred to. According to one aspect of the invention there is provided a wheel having a hub and a bearing of substantially cylindrical shape located within said hub so as to provide for mutual rotation, an outer surface of said bearing being in contact with an inner surface of said hub and at least one of said surfaces being formed from a plurality of interspaced circumferentially arranged raised portions and hollows, said raised portions forming on interrupted bearing surface in use. Preferably the raised portions and hollows extend continuously and axially of said bearing surface and preferably also the raised portions and hollows are are formed on the outer contact surface of the bearing. In a second aspect of the invention there is provided a wheel having a hub and a bearing located within said hub so as to be mutuaily rotatable, the contacting surfaces of the hub and bearing being formed from an acetal copolymer or polyamide so as to give a low coefficient of friction therebetween. Both aspects of the invention can be combined in the same embodiment. Therefore a wheel as described in the first aspect can be provided, with the hub and bearing formed of materials so as to give a low coefficient of friction. Such materials are preferably an acetal copolymer and a polyamide advantageously nylon 6. One embodiment of the invention will now be described by way of example only, with reference to the accompanying drawings, in which: Figure 1 shows a diamentral section of a wheel Figure 2 is a front view of the wheel of Fig. 1 Figure 3 shows an enlarged side view of a toothed bearing forming part of the wheel of Fig. 1 Figure 4 is a perspective view of the bearing of Fig. 3 Figure 5 is a plan view of the bearing of Fig. 3 Referring to the drawings, 1 denotes a tyre, covering an outer peripheral rim 2 of the wheel. A hub 4 is connected to the outer rim 2 by an integral webb 3. The hub 4 is moulded from a polyamide, for example nylon 6, and receives and is rotable about a bearing 5 (Figs. 3 to 5), moulded from an acetal copolymer. The bearing 5 has an axial hole 5a for receiving an axle (not shown) and has an outer surface 8 having a plurality of equispaced raised portions 6 and hollows 7 extending axially around the circumference of the bearing. The contact surface between the outer surface 8 of the bearing 5 and the inner surface 8a of the hub is therefore decreased. In use any dust that enters the hub 4 collects in the hollows 7 of the bearing thereby mitagating the effect of friction between the hub 4 and bearing 5. Because the hub 4 and bearing 5 are of different plastics, in combination the bearing 5 and hub 4 have a low coefficient of friction whereby the bearing 5 does not require lubrication. Although acetal copolymer and polyamide have been found compatible in this respect any materials having a low coefficient of friction in combination and mechanical properties generally required for robust trolley wheels such as, for example, toughness, durability and impact resistance are also acceptable. Dust caps (not illustrated) are applied in known manner to both end faces of the hub 4 to prevent or at least reduce the ingress of dust into the bearing 5. The wheel and the bearing are easily assembled because all that is now necessary is to insert the bearing 5 axially into the hub 4, and then apply the dust caps (not shown) in known manner. It will be appreciated that the 2 reduced contact surface could also be obtained by having the raised portions 6 and hollow formed on the inner surface 8a of the hub 4. Furthermore the raised portion 6 need not be axially extending ribs, the criteria being that a reduced contact surface is obtained and hollows are provided for collection ingression dust. CLAIMS

1. A wheel having a hub and a bearing of substantially cylindrical shape located within said hub so as to provide for mutual rotation, an outer surface of said bearing being in con tact with an inner surface of said hub and at least one of said surfaces being formed from a plurality of interspaced circumferentially arranged raised portions and hollows, said raised portions forming an interrupted bearing surface in use.

2. A wheel according to claim 1 wherein the raised portions and hollows extend continuously and axially of said bearing surface.

3. A wheel according to claim 1 or 2 wherein the raised portions and hollows are formed on the outer contact surface of the bearing.

4. A wheel according to claims 1 to 3 wherein the wheel is a trolley wheel.

5. A wheel according to any of the preceding claims where the hub and bearing are formed from materials selected to provide a low coefficient of friction thereby providing a bearing requiring no lubrication.

6. A wheel according to claim 5 wherein said materials are an acetal copolymer and a polyamide.

7. A wheel according to claim 6 wherein the hub is formed from the polyamide and the bearing from the acetal copolymer.

8. A wheel according to claims 6 or 7 wherein the polyamide is nylon 6.

9. A wheel substantially as described with reference to the drawings.

10. A bearing for a wheel comprising a substantially cylindrical body having an axial hole and an outer surface formed from a plurality of interspaced raised portions and hollows, said raised portions forming an interrupted bearing surface in use within the hub of a wheel.

11. A bearing according to claim 10 wherein the raised portions extend continuously and axially of said bearing surface.

12. A bearing substantially as described with reference to the accompanying drawings.

13. A wheel having a hub and a bearing located within said hub so as to be mutually rotatable, the contracting surfaces of the hub and bearing being formed from an acetal copolymer or polyamide so as to give a low coefficient of friction therebetween.

14. A wheel according to claim 13 wherein the hub is formed from the polyamide and the bearing from the acetal copolymer.

15. A wheel according to claim 13 or 14 wherein the polyamide is nylon 6.

16. A wheel substantially as described with reference to the accompanying drawings.