GB2257902A

GB2257902A - Castor wheel assembly

Info

Publication number: GB2257902A
Application number: GB9115873A
Authority: GB
Inventors: Frank Edwin Rattlidge
Original assignee: Individual
Current assignee: Individual
Priority date: 1991-07-23
Filing date: 1991-07-23
Publication date: 1993-01-27
Also published as: GB9115873D0

Abstract

A castor wheel assembly comprises one or more wheels 12 engageable by a snap fit to a wheel carrier 10. The wheel carrier 10 is formed integrally with a swivel post 14, for example by moulding of a plastics material. The carrier may comprise a pair of resiliently deformable arms 18 between which the wheel 12 is snap fitted to engage wheel bosses 42 in bearing surfaces provided by the inner peripheral surfaces of opposed aligned circular apertures in the carrier arms 18, but twin wheel arrangements are also disclosed. <IMAGE>

Description

Title: Castor Wheel Assembly This invention relates to a floor-engaging castor wheel assembly.

Floor-engaging castor wheel assemblies of many differing types are well known. For example, a typical conventional castor for domestic and commercial furniture requiring only local intermittent mobility comprises a steel housing to which a steel swivel pin is riveted. A plastics wheel is mounted for rotation on a steel axle itself riveted between opposed limbs of the housing. The swivel pin is engagable within a metal or plastics swivel socket which retains the swivel pin loosely with inefficient local and annular bearing contact.

Furniture or appliances which require regular mobility-are often fitted with two-wheel castor wheel assemblies. A typical conventional two-wheel castor comprises a central plastics housing providing two integral axially opposed bushes within each of which is engaged an integral boss of a plastics wheel. The housing includes a swivel socket within which is received one end of a steel swivel pin, the other end of the pin being mounted on the furniture or appliance.

It is an object of the present invention to provide a new or improved construction of floor-engaging castor wheel assembly.

In accordance with the broadest aspect of the invention there is provided a floor-engaging castor wheel assembly comprising a wheel carrier, one or more wheels rotatably mounted on said carrier, and swivel means comprising a swivel post provided on said wheel carrier coaxially engagable within a swivel socket whereby said wheel carrier may swivel relative to said socket wherein said wheel carrier and said swivel post are moulded integral with one another.

The said carrier and said swivel post are conveniently moulded of a plastics material. The or each wheel and the swivel socket are also conveniently moulded of a plastics material which may be the same material as that from which the carrier and swivel post are moulded. Such a plastics material may comprise reconstituted nylon.

In one embodiment of the invention the wheel carrier may comprise a pair of spaced apart carrier arms having aligned circular bearing surfaces with a said wheel received between said arms in rotatable bearing engagement with said bearing surfaces. Each of said bearing surfaces may comprise the peripheral surface of an aperture provided in a said carrier arm, said wheel being provided with opposed axially projecting bosses each of which is locatable in rotatable bearing engagement in a respective said aperture. Conveniently the diameter of each of said bearing surfaces is at least 40% of the outside diameter of the wheel.

Said spaced apart carrier arms conveniently provide resiliently deformable mounting means for the assembly of said wheel to the wheel carrier, said arms being resiliently deformable away from one another from a relaxed condition thereof to permit the passage of said wheel between said arms into the position at which the wheel is in bearing engagement with said bearing surfaces, the wheel being retained in said position by said arms when in their said relaxed condition.

In another embodiment of the invention the assembly may comprise a pair of said wheels rotatably mounted in coaxial relation with one another, said carrier comprising axially opposed bearing surfaces upon each of which a respective said wheel is located in rotatable bearing engagement therewith. A plurality of said bearing surfaces may be provided for each said wheel. Each of said axially opposed bearing surfaces may comprise a boss upon which a said wheel is rotatably located and there may be provided a central boss and one or more annular surfaces coaxial therewith, a said wheel being located in rotatable bearing engagement with said boss and the or each said annular surface.

Conveniently said boss is of tubular form. Each of said wheels is conveniently assembled to said wheel carrier by resiliently deformable mounting means deformable from a relaxed condition thereof to permit assembly of said wheels in the position at which each said wheel is located in rotatable bearing engagement with a said bearing surface, each wheel being retained in said position by the resilient mounting means when in its said relaxed condition. Said resiliently deformable means conveniently comprises co-operating resilient elements on each wheel and a part of said carrier. Each wheel conveniently includes one or more integral tubular bosses rotatably engaged with corresponding said bearing surfaces on the wheel carrier, at least one of said bosses on each wheel having a diameter which is at least 45% of the outside diameter of the wheel.

Said wheel carrier preferably includes a rigid arcuate surface engagable with the outer periphery of a said wheel in the event of overload deformation of the carrier and/or the wheel.

At least a part of the outer surface of the swivel post is conveniently of substantially constant radius cross sectional form and the swivel socket has an internal surface which is of substantially constant radius providing an arcuate bearing surface for said swivel post in said socket. The outer surface of the swivel post may comprise a cylindrical surface and the internal surface of the swivel socket may comprise a cylindrical surface whereby a cylindrical bearing surface is provided for said swivel post in said socket. Conveniently the swivel post is of tubular form and is adapted to receive a reinforcing pin therein. A thrust bearing surface may be provided integral with the wheel carrier and swivel post, said thrust bearing surface being engagable with a surface of the swivel socket when the swivel post is engaged therein.

Other features of the invention will become apparent from the following description given herein solely by way of example with reference to the accompanying drawings wherein: Figure 1 is an end elevation of a single wheel castor constructed in accordance with the invention; Figure 2 is a side cross sectional view of the castor of Figure 1 showing also a swivel socket within which the swivel post of the castor is engagable; Figure 3 is an end cross sectional view of the castor of Figure 1 with the wheel removed; Figure 4 is a side cross sectional view similar to that of Figure 2 but with the wheel removed and showing also a reinforcing pin inserted within the tubular swivel post; Figure 5 is an end elevation of a two-wheel castor constructed in accordance with the invention showing its swivel post engaged within a swivel socket;; Figure 6 is a side elevation of the castor shown in Figure 5 without the swivel socket; Figure 7 is a side elevation of one embodiment of a wheel carrier of a two-wheel castor of the type shown in Figures 5 and 6; Figure 8 is an end cross sectional view through the wheel carrier of Figure 7.

Figure 9 is an end cross sectional view showing one form of wheel rotatably mounted on the wheel carrier of Figures 7 and 8; Figure 10 is a view similar to that of Figure 9 but showing an alternative construction of wheel; Figure 11 is a side elevation of an alternative embodiment of wheel carrier of a two-wheel castor; Figure 12 is an end cross sectional view through the wheel carrier of Figure 11; and Figure 13 is an end cross sectional view similar to that of Figure 12 with wheels of the type shown in Figure 10 rotatably mounted thereon.

A first embodiment of the invention will now be described with reference to Figures 1 to 4 of the accompanying drawings which illustrate a single wheel castor of a type suitable for fitting to domestic and commercial furniture which requires only local intermittent mobility. The castor wheel assembly comprises a wheel carrier 10, a single wheel 12, a swivel post 14 and a swivel socket 16 attachable to the furniture or the like and in which the swivel post of the castor is engagable. The wheel carrier 10 and swivel post 14 are formed as an integral moulding of a synthetic plastics material such as for example reconstituted nylon and, similarly, the wheel 12 and the swivel socket 16 may also be moulded of the same synthetic plastics material.

The integral wheel carrier and swivel post comprises a pair of planar spaced apart carrier arms 18 each having a central circular aperture 20 therein with the two apertures 20 being aligned to receive co-operating parts of the wheel 12. The, in use, upper portions of the carrier arms 18 are connected together by a monolithic body portion 22 providing a rigid downwardly facing arcuate surface 24 disposed, in use, with a small clearance above the radially outermost surface of the wheel. Projecting upwardly from said body portion 22 there is provided the integral swivel post 14 in the form of a tubular cylindrical member of substantially constant radius in both interior and exterior cross section.The upper end of the swivel post 14 is provided with opposed axial slots 26 and an annular groove 28 whereby said upper end of the swivel post may be radially inwardly deformed for a snap fit into the upper end of the swivel socket 16.

As will be clearly seen from Figure 2, the swivel socket 16 is also of cylindrical form having a cylindrical internal wall of substantially constant radius.

The internal diameter of the swivel socket 16 is only minimally greater than the external diameter of the swivel post 14 whereby the swivel post may be received within the swivel socket with a snug fit to maintain engagement therewith over substantially the whole interior axial length of the swivel socket. The upper end of the socket 16 is provided with a radially inwardly extending rim 30 providing a central aperture 32 through which the radially inwardly deformable upper end of the swivel post may be engaged with a snap fit as mentioned above. The lower end of the swivel socket 16 is provided with a radially outwardly extending annular flange 34 which, when the swivel post is fully engaged within the swivel socket, provides a planar thrust bearing surface 36 in contact with a planar upper surface 38 of the wheel carrier body portion 22.

As mentioned above, each carrier arm 18 of the wheel carrier is provided with a circular aperture 20 and the internal peripheral surface 40 of each such aperture provides a bearing surface for the castor wheel 12. The wheel 12 comprises a wheel proper of substantially cylindrical form having a cylindrical floor engaging surface with axially opposed integral bearing bosses 42 projecting from either side thereof. The overall axial dimension of the wheel between the axially outer end faces of the bosses 42 is substantially equal to the axial distance between the axially outer faces of the carrier arms 18 and, to assemble the wheel to the carrier arms, it is necessary to press the wheel 12 upwardly between the arms 18 to cause them to separate axially and then spring back together as each wheel boss 42 enters a respective aperture 20 in a carrier arm.To facilitate this initial assembly of the wheel 12 to the wheel carrier 10 the lower ends of the axially opposed inner faces of the arms 18 are relieved as shown at 44 in Figures 3 and 4.

Thus, when the wheel 12 is assembled to the wheel carrier 10, the wheel bearings are provided by the outer circumferential surfaces of the wheel bosses 42 running against the inner peripheral surfaces 40 of the apertures 20 in the carrier arms. When fitted to a piece of furniture or the like, the swivel socket 16 is received within a preformed vertically disposed axial bore in a leg or the like of the article and the swivel post 14 is snap fitted into the swivel socket 16 so that, the swivel post 14, wheel carrier 10 and wheel 12 may swivel relative to the swivel socket 16. The swivel post 14, by virtue of its snug engineered fit within the swivel socket 16, will have efficient bearing contact with the socket over substantially its full axial length.Furthermore, an efficient thrust bearing for the assembly is provided between the lower surface 36 of the annular flange 34 on the socket 16 and the upper planar surface 38 of the wheel carrier body portion 22.

The aforesaid arcuate lower surface 24 of the body portion 22 is provided to act as an overload surface in the event that loading in excess of the specified load of the castor is applied to the castor wheel assembly to the extent that deformation of the wheel carrier 10 and/or the wheel 12 may occur. If such deformation occurs, said arcuate surface 24 may then bear on the outer peripheral surface of the wheel 12. Thus the castor wheel assembly will still be provided with a bearing surface even under overload which surface, by virtue of its circumferential extent, will spread the overload forces around the circumference of the wheel thereby mitigating against the possibility of permanent damage to any of the elements of the castor wheel assembly.Furthermore, by way of advantage over known single wheel castor assemblies, the actual bearing contact area of the wheel bosses 42 with the carrier arms 18 provides a large diameter circumferential bearing area as compared with the diameters of bearing area afforded by the simple small diameter axle mounting of conventional single castor wheels. For example, the diameter of each of the bearing surfaces 40 may be at least 40% of the outside diameter of the wheel 12.

Thus, in accordance with this first embodiment of the invention, there is provided a two-part castor wheel assembly comprising firstly a castor wheel and secondly an integral wheel carrier and swivel post. The wheel carrier arms 18 provide resiliently deformable mounting means whereby the wheel 12 may be assembled manually or automatically to the carrier arms by a simple "snap fit" operation. This ease of manufacture and assembly is significant in comparison with known single wheel castors of the type comprising a wheel mounted on a steel axle riveted between opposed metal limbs of a housing to which a swivel pin is riveted.

In a second embodiment of the invention there is provided a twowheel castor wheel assembly of the type which may be fitted to domestic, office or institutional furniture or appliances which require regular mobility. Such a two-wheel castor constructed in accordance with the invention is shown in Figures 4 to 13 of the accompanying drawings wherein the castor wheel assembly comprises a wheel carrier 10, a swivel post 14, a swivel socket 16 and a pair of coaxially arranged floor engaging wheels 12. The wheel carrier and swivel post are moulded integral with one another of a synthetic plastics material such as for example reconstituted nylon. The swivel socket 16 and each of the wheels 12 may also be moulded of the same synthetic plastics material as the wheel carrier 10 and its integral swivel post 14.

The wheel carrier 10 comprises an upper monolithic body portion 46 from which projects the substantially cylindrical swivel post 14 and which provides two axially spaced downwardly facing arcuate surfaces 48 for overload engagement respectively with each of the two wheels 12 of the castor wheel assembly as will be described below. The construction of swivel post 14 and swivel socket 16 and the manner in which the swivel post engages within the swivel socket are the same as described above with reference to the single wheel castor illustrated in Figures 1 to 4. Like reference numerals are given to like parts of the swivel post and swivel socket elements throughout the several views of the embodiments and such elements are not therefore described again in detail with reference to the embodiments of Figures 4 to 13.

The wheel carrier illustrated in Figures 7 and 8 comprises a central web portion 50 having a plurality of axially extending circumferentially arcuate wheel mounting elements 52 wherein each element is provided with an axially outer radially outwardly extending lip 54 for snap fitting of a respective wheel 12 thereon.

In the embodiment of Figures 7 to 10, the wheel carrier includes coaxial cylindrical bearing surfaces 56 provided as the radially inner surfaces of axially opposed integral annular rims 58 of the wheel carrier radially inwards of which are located the wheel mounting elements 52. One form of wheel 12 for use with such a wheel carrier is illustrated in Figure 9 wherein the wheel is of pot form having a radially outer floor-engaging peripheral surface 60 and an integral tubular boss 62 having cylindrical radially outer bearing surfaces 64 located radially inwardly of the outer surface 60 of the wheel.The boss 62 and the floor engaging surface 60 of the wheel are connected by an integral end face 66 and, extending radially inwardly of the radially inner surface of the central boss 62, there is provided an annular projection 68 for engaging with a snap fit over the lips 54 on the wheel mounting elements. When a wheel of the type shown in Figure 9 is snap fitted to each side of the wheel carrier of Figure 8, the load carrying bearing surface of the carrier comprises the, in use, upper part of the radially inner surface 56 of the annular rim 58 which bears upon the, in use, upper part of the radially outer surface 64 of the central boss 62.

An alternative form of wheel shown in Figure 10 is usable with the wheel carrier shown in Figure 8 and, as will be clearly seen from the drawings, each wheel of Figure 10 includes an additional annular flange 70 located intermediate the surfaces 60 and 64, said flange 70 being integral with the other elements of the wheel. In use, an additional bearing surface is thus provided between the lower part of the radially outer surface 72 of the wheel carrier rim 58 and the lower part of the radially inner surface 74 of the intermediate flange 70 of the wheel.

A further embodiment of wheel carrier is shown in Figures 11 to 13 of the drawings wherein, in Figure 13, a wheel of the type described and illustrated with respect to Figure 10 is mountable at each side of the carrier. As will be seen from a comparison of Figures 7 and 8 with Figures 11 and 12, the wheel carrier of Figures 11 and 12 differs only by the provision of an additional annular rim 76 integral with the remainder of the carrier and located radially outwardly of the rim 58.Thus, when a wheel of the type shown in Figure 10 is snap fitted to each side of the carrier of Figures 11 and 12, additional bearing surfaces are provided between the, in use, radially inner surface 78 of the rim 76 of the wheel carrier and the radially outer surface 80 of the intermediate flange 70 of the wheel at the upper part thereof and, additionally, between the radially outer surface 82 of the rim 58 of the wheel carrier and the radially inner surface 74 of the intermediate flange of the wheel at the lower part thereof.

In a similar manner to that described with reference to Figures 1 to 4 the downwardly facing circumferentially extending arcuate surfaces 48 of the wheel carrier body portion 46 provide rigid wheel engaging bearing surfaces engagable with the wheels 12 in the event of deformation of the wheel carrier and/or the wheels should they be inadvertently overloaded. Also in common with the advantage of the construction of the assembly of Figures 1 to 4, the various bearing surfaces provided between the various rims of the wheel carrier and the co-operating flange surfaces of the wheels are of substantial area in comparison with the bearing surface areas of conventional two-wheel castor assemblies.

In the embodiments described hereinbefore with reference to Figures 5 to 13 at least one of the tubular bosses on each wheel which engages the corresponding bearing surfaces on the wheel carrier is of a diameter which may advantageously be at least 45% of the outside diameter of the wheel.

In a similar manner to that described with reference to the embodiment of Figures 1 to 4, each wheel of the assembly of Figures 5 to 13 may be readily assembled by a "snap fit" to the wheel carrier by means of the resiliently deformable co-operating elements 52 and 54. A two-wheel castor is thus assembleable manually or automatically in a manner which will provide substantial economies of cost in comparison with known two-wheel castor assemblies.

In any of the embodiments described above a cylindrical metal or plastics reinforcing pin 84 (see Figure 4) may be located within the tubular swivel post. Also, although not illustrated in the drawings, the swivel post may have material relieved therefrom in those areas which are not exposed to in-use loading. For example, the upper part of the swivel post at its, in use trailing side may be relieved as may be the lower part of its, in use, leading side. By such relief, the upper part of the swivel post at its leading side and the lower part thereof at its leading side and the lower part thereof at its trailing side will be in arcuate bearing contact with the internal surface of the swivel socket at those positions of the swivel post which are subject to load during movement of items to which the castors are fitted.

It will be appreciated that castor wheel assemblies constructed in accordance with the invention may be of any appropriate size such as, for example, within the typical 40mm to 100mm outside diameter wheel sizes.

The features disclosed in the foregoing description, or the following claims, or the accompanying drawings, expressed in their specific forms or in terms of a means for performing the disclosed function, or a method or process for attaining the disclosed result, as appropriate, may, separately or in any combination of such features, be utilised for realising the invention in diverse forms thereof.

Claims

1. A floor-engaging castor wheel assembly comprising a wheel carrier, one or more wheels rotatably mounted on said carrier, and swivel means comprising a swivel post provided on said wheel carrier coaxially engagable within a swivel socket whereby said wheel carrier may swivel relative to said socket wherein said wheel carrier and said swivel post are moulded integral with one another.

2. An assembly as claimed in claim 1 wherein said carrier and said swivel post are moulded of a plastics material.

3. An assembly as claimed in either one of claims 1 or 2 wherein the or each said wheel is moulded of a plastics material.

4. An assembly as claimed in any one of claims 1 to 3 wherein the swivel socket is moulded of a plastics material.

5. An assembly as claimed in any one of the preceding claims wherein said swivel post is of tubular form and is adapted to receive a reinforcing pin therein.

6. An assembly as claimed in any one of the preceding claims including resiliently deformable mounting means permitting assembly of the or each wheel with the wheel carrier.

7. An assembly as claimed in any one of the preceding claims wherein said wheel carrier comprises a pair of spaced apart carrier arms having aligned circular bearing surfaces, a said wheel being received between said arms in rotatable bearing engagement with said bearing surfaces.

8. An assembly as claimed in claim 7 wherein each of said bearing surfaces comprises the peripheral surface of an aperture provided in a said carrier arm, said wheel being provided with opposed axially projecting bosses each of which is locatable in rotatable bearing engagement in a respective said aperture.

9. An assembly as claimed in either one of claims 7 or 8 wherein the diameter of each of said bearing surfaces is at least 40% of the outside diameter of the wheel.

10. An assembly as claimed in any one of claims 7 to 9 wherein said spaced apart carrier arms provide resiliently deformable mounting means for the assembly of said wheel to the wheel carrier, said arms being resiliently deformable away from one another from a relaxed condition thereof to permit the passage of said wheel between said arms into the position at which the wheel is in bearing engagement with said bearing surfaces, the wheel being retained in said position by said arms when in their said relaxed condition.

11. An assembly as claimed in any one of claims 1 to 6 comprising a pair of said wheels rotatably mounted in coaxial relation with one another, said carrier comprising axially opposed bearing surfaces upon each of which a respective said wheel is located in rotatable bearing engagement therewith.

12. An assembly as claimed in claim 11 wherein a plurality of said bearing surfaces are provided for each said wheel.

13. An assembly as claimed in either one of claims 11 or 12 wherein each of said axially opposed bearing surfaces comprises a boss upon which a said wheel is rotatably located.

14. An assembly as claimed in claim 13 wherein each of said axially opposed bearing surfaces comprises a central boss and an annular surface coaxial therewith, a said wheel being located in rotatable bearing engagement with said boss and said annular surface.

15. An assembly as claimed in either one of claims 13 or 14 wherein said boss is of tubular form.

16. An assembly as claimed in any one of claims 11 to 15 wherein each of said wheels is assembled to said wheel carrier by resiliently deformable mounting means deformable from a relaxed condition thereof to permit assembly of said wheels in the position at which each said wheel is located in rotatable bearing engagement with a said bearing surface, each wheel being retained in said position by the resilient mounting means when in its said relaxed condition.

17. An assembly as claimed in claim 16 wherein said resiliently deformable means comprises co-operating resilient elements on each wheel and a part of said carrier.

18. An assembly as claimed in any one of claims 11 to 17 wherein each said wheel includes one or more integral tubular bosses rotatably engaged with corresponding said bearing surfaces on the wheel carrier, at least one of said bosses on each wheel having a diameter which is at least 45% of the outside diameter of the wheel.

19. An assembly as claimed in any one of the preceding claims wherein said wheel carrier includes a rigid arcuate surface engagable with the outer periphery of a said wheel in the event of overload deformation of the carrier and/or the wheel.

20. An assembly as claimed in any one of the preceding claims wherein at least a part of the outer surface of the swivel post is of substantially constant radius cross sectional form and the swivel socket has an internal surface of substantially constant radius providing an arcuate bearing surface for said swivel post in said socket.

21. An assembly as claimed in any one of the preceding claims wherein the swivel post is of substantially constant radius cross sectional form and the swivel socket has an internal cylindrical surface of substantially constant radius providing a cylindrical bearing surface for said swivel post in said socket.

22. An assembly as claimed in any one of the preceding claims wherein there is provided a thrust bearing surface integral with the wheel carrier and swivel post, said thrust bearing surface being engagable with a surface of the swivel socket when the swivel post is engaged therein.

23. A floor-engaging castor wheel assembly constructed and arranged substantially as hereinbefore described with reference to Figures 1 to 4 of the accompanying drawings.

24. A floor-engaging castor wheel assembly constructed and arranged substantially as hereinbefore described with reference to Figures 5 to 13 of the accompanying drawings.

25. Any novel feature or novel combination of features described herein and/or in the accompanying drawings.