US3822437A

US3822437A - Castors

Info

Publication number: US3822437A
Application number: US00308937A
Authority: US
Inventors: S Screen
Original assignee: British Castors Ltd
Current assignee: British Castors Ltd
Priority date: 1972-11-24
Filing date: 1972-11-24
Publication date: 1974-07-09
Anticipated expiration: 1991-07-09

Abstract

In a castor having a body adapted to be mounted on an article of furniture and roller means mounted on the body for rotation relative thereto about a rolling axis, the roller means has mutually opposed disc portions which extend transversely of the rolling axis and a peripheral wall portion which is supported by the disc portions for engagement with a floor surface. The roller means comprises two wheel components which are connected together and each of which includes one of said disc portions. The wheel components include respective interfitting integral formations which locate one wheel component relative to the other.

Description

States aent 1 Screen 1 July 9-, 1974 [541 CASTORS 628,786 5/1957 Canada 16/46 1,114,244 2/1965 Great Britain 16/45 [75] Invent: Swim Screen 559,943 9/1956 Italy 16/18 A Stourbridge, England Primary Examiner-Bobby R. Gay Assistant Examiner-William E. Lyddane Attorney, Agent, or Firm-Holman & Stern [57] ABSTRACT In a castor having a body adapted to be mounted on an article of furniture and 'rollermeans mounted on the body for rotation relative thereto'about a rolling axis, the roller means has mutually opposed disc portions which extend transversely of the rolling axis and a peripheral wall portion which is, supported by the disc portions for engagement with a floor surface. The roller means comprises two wheel components which are connected together and each of which includes one of said disc portions. The wheel components include respective interfitting integral formations which locate one wheel component relative to the other.

'11 Claims, 17 Drawing Figures CASTORS SUMMARY OF, THE INVENTION The invention relates to castors of the kind having a body adapted to be mounted on an article of furniture or the like for pivoting movement relative to the article about a substantially upright pivot axis, and roller means mounted on the body for rotation relative thereto about a rolling axis which is transverse to the pivot axis, the roller means having mutually opposed disc portions which extend transversely of the rolling axis and a peripheral wall portion which is supported by the disc portions, faces radially outwardly from the rollwalls of the roller means but may be inset somewhat from the ends of the peripheral wall portion.

It is an object of the present invention to provide a castor of the kind referred to which can be assembled Y easily from a relatively small number of inexpensive prises two wheelcom'ponents which are connected together and each of which includes one of said disc portions, the wheel components including respective interfitting integral formations which locate one wheel component relative to the other. i

The interfitting formations may themselves locate one wheel component relative to the other against displacement in all directions. Alternatively, the'interfitting formations may provide location against relative displacement in some directions only, there being pro. vided a retaining element which cooperates with the wheel components to provide location'against relative displacement in the remaining direction or directions. In a further alternative the body may cooperate with the wheel components to locate them against displacement relative to each otherin the remaining direction or directions.

To enable the roller means to rotate relativeto the body about the rolling'axis, the roller means and body 2 projection so thatthey fit together with a snap fit, resilient distortion-being necessary as they are assembled together, but when assembly is complete the wheel components being free to rotate relative to each other. In this latter case location against relative movement of the wheel components longitudinally of the spigots would be provided by the cooperating recess and projection. X

As a further alternative relative displacement of the wheel components longitudinally of the spigots may be prevented by a retaining element so engaged with both wheel components as to prevent such displacement whilst permitting relative rotation. For example, the retaining element may be in the form of a plug having a shank which fits tightly within the inner spigot and an enlarged head which engageswith an axially presented face of the component which includes the outer spigot, this axially presented face lying radially outwardlyv of the inner spigot. The arrangement would be such that the head of the plugis able to slide relatively freelyover the axially presented face of the wheel component with I which it is engaged.

Instead of spigots which fit one inside the other, the wheel components maybe formed with respective integral spigots-which fit en'd-to-end and are formed adjacent their free ends with interfitting formations which locate the wheel components against relative movement along the rollingaxis. In this case the bearing surface of the roller means would be presented by the spigots collectively, and as the bearing surface of the body embraces both spigots, the body locates the wheel components against relative displacement in directions transverse to the rolling axis. 1

The interfitting formations at the free ends of the spigots may be a snap fit with each other. 7

Preferably the bearing surface of the body is presented by a sleeve portion which fits between the end wall portions of the roller meansso as to locate the latter against axial movement relative to the body. The body may further include a web portion which projects radially outwardly from the sleeve portion between the wheel components. This web portion may be formed have cooperating bearing surfaces which are concentrio with the rolling axis. Preferably the bearing surface of the body is an internal surface'and the bearing surface of the roller means is presented radially outwardly of the rolling axis of aspigot formed integrally with one wheel component or by spigots formed integrally with respective ones of the wheel components. 7

One wheel component may be freely rotatable about the rolling axis relative to the other wheel component.

The wheel components may be formed with respective spigots, at least one of these being hollow and the other spigot fitting inside said one spigot so that the wheel components are located against relative diswith a socket to receive a mounting member by means 45' of which the castor can be mounted on an article of furniture, the socket extending into the webportion to a position inside the peripheral wall portion of the roller means.

' Preferably the body is formed of a one-piece moulding of plastics material. Thusthe castor may consist of three components only, namely two wheel components and 'a body component, each of which is formed as an integral moulding. Furthermore, assembly of the castor may involve merely bringing the three components into their required positions relative to each other, in some cases this involving pressing the wheel components together so that they cooperate with a snap fit.

BRIEF DESCRIPTION OF THE DRAWINGS tion in cross-section in a vertical planewhich contains the rolling axis,

FIG. 2 shows a side view of a body of the castor shown in FIG. 1;

FIG. 3 shows a sectional view of the body in a horizontal plane which contains the rolling axis,

FIG. 4 shows a diametral sectional view of a firsttor shown in FIG. 7 in a horizontal plane which contains the rolling axis,

FIG. 9 showsa diametral sectional view of a first wheel component of the'castor shown in FIG. 7,

FIG. 10 shows a diametral sectional view of a second wheel component of the castor shown in FIG. 7,

FIG. 11 shows a view in side elevation of a third form of castor in accordance with the invention,

FIG. 12 shows the castor of FIG. 11 in cross-section in a vertical plane containing the rolling axis,

FIG. 13 is a side view of a fourth form of castor cordance with the invention,

FIG. 14 shows the castor of FIG. 13 in cross-section in a vertical plane containing the rolling axis,

FIG. 15 is a view in side elevation of a fifth form of castor in accordance with the invention,

FIG. 16 shows the castor of FIG. 15 in cross-section in acin a vertical plane which contains the rolling axis, and

FIG. 17 illustrates a modification of the castor of FIG. 16.

DETAILED DESCRIPTION upper rearward part of the generally annular portion 13 is enlarged radially as shown at 15 and a socket 16 is formed in this enlargement to receive a spindle (not shown) by means of which the body can be mounted on. an article of furniture. The socket l6 defines a pivot axis 17 which is upright when the castor is in use, and the body may be arranged to swivel freely on the spindle.

The spindle which is received in the socket 16 may be of conventional form and may be received within a socket formed in a leg of the article of furniture or the like, or alternatively provided with a mounting plate by means of which it can be attached to a downwardly facing surface of the article of furniture. Such spindle does not form part of the present invention and is therefore omitted from the accompanying drawings. The form of the socket 16 may be varied according to the form of the spindle with which the castor is intended to be used, but we prefer to provide a small projection on the wall of the socket as shown at 16a in FIG. 1. The spindle would then be formed with a circumferential groove to receive the projection when the spindle is inserted into the socket. Sufficient clearance would be provided between the projection and groove to permit the spindle to rotate freely relative to the body 10, but the projection would normally prevent axial movement of the spindle relative to the body. The spindle can be inserted into and withdrawn from the socket 16 by applying sufficient force in an axial direction, the body distorting resiliently during insertion or withdrawal to permit the projection 16a to pass into or from the groove of the spindle.

The castor further comprises roller means mounted on the body 10 for rotation relative thereto about a rolling axis 18 which is generally horizontal when the castor is in use. The rollervmeans comprises a pair of

wheel components

19 and 20. Each wheel component is also formed as a one-piece moulding of plastics material which may be the same as the material of which the body 10 is formed. The wheel components include respective

end wall portions

21, 22 which are of disc-like form, extending transversely of the rolling axis, and respective

peripheral wall portions

23, 24 facing radially outwardly from the rolling axis. I

The

peripheral wall portions

23 and 24 have an internal diameter slightly greater than the external diameter of the cylindrical flanges 14 of the body and overlap axially with these flanges. This axial overlap and the small clearance between the peripheral wall portions and the cylindrical flanges reduces the risk of dust, fibres from floor coverings and'other foreign matter entering the interior of the wheel components. Furthermore, the relatively large diameter of the peripheral wall portions and cylindrical flanges reduces the risk of fibres or threads being wrapped around the cylindrical flanges by the peripheral wall portions as the latter rotate. An accumulation of fibres or threads on the cylindrical flanges may interfere with free rotation of the wheel components on the body.

The outer surface of the generally annular portion 13 is substantially flush with the outer surface of the

peripheral wall portions

23 and 24 over the major part of these portions. However, at the underside of. the body 10 the generally annular portion 13 is cut away to provide a flat surface 25 which is spaced above the lowermost parts of the peripheral wall portions by a distance of approximately 0. 187 inches. With this arrangement, when the castor is used on a soft floor surface such as a carpet but is lightly loaded, the surface 25 will clear or will be in only light contact with the floor surface; whereas if the castor is heavily loaded the peripheral wall portions sink into the floor surface and the surface 25 acts as an additional load-bearing surface.

The enlargement 15 extends radially outwardly beyond the

peripheral wall portions

23 and 24. The socket 16 may be disposed entirely outside the peripheral wall portions, or it may extend to a position within these wall portions.

The

wheel components

19 and 20 are formed with other. In a case where relative rotation of the wheel components is not required, the spigot 26 could be a tight fit within the spigot 27.

The roller means further comprises a retaining element in the form of a plug 28 having a shank 29 which is a snap fit within the inner spigot 26. Approximately mid-way along the shank there is formed a slight radial projection and an annular groove 32 is formed in the internal face of the inner spigot 26 to receive this projection. As the shank 29 is inserted into the inner spigot, one or both of these is stressed elastically and such stress is at least partly relieved when the projection 31 is seated in the groove 32. Alternatively, the plug may be secured within the inner spigot by means of an adhesive or by welding. The plug 28 includes an enlarged head 30 which overlies an axially-presented face portion of the wheel component 20. This face portion lies radially outwardly of the inner spigot 26 and is preferably recessed relative to the outer face of the end wall portion 22 so that the outer face of the plug lies flush with the outer face of this end wall portion.

As shown in FIGS. 5 and 6 at 33 and 34 respectively, the plug 29 and spigot 26 may be formed with cooperating splines which prevent the possibility of rotation of the plug relative to the spigot. If relative rotation did occur during the working life of the castor, the projection 31 may become worn and the plug could be withdrawn from the spigot, thereby permitting the

wheel components

19 and 20 to become separated.

The plug 28 locates the wheel component 19 against movement relative to the wheel component 20 in a leftward direction as viewed inFIG. 1. Movement of the wheel component 19 rightward relative to the wheel component 20 as viewed in FIG. 1 is prevented by en-.

gagement of the outer spigot 27 with the internal face of the end wall portion 21. Relative displacement of the wheel components in directions transverse of therolling axis 18 is prevented by co-operation of the

interfitting spigots

26 and 27.

The

spigots

26 and 27 are disposed within the sleeve portion 11 of the body,.the radially outwardly presented face of the outer spigot 27 constituting a bearing surface of the roller means, and the inner surface of the sleeve portion 11 constituting a bearing surface of the body. There is sufficient clearance between these bearing surfaces to permit of rotation of the wheel components relative to the body. The sleeve portion 11 fits with a slight clearance between the

end wall portions

21 and 22 so that the wheel components are located against axial movement relative to the body; The wheel components are, however, freely rotatable relative to the body about the rolling axis 18.

- cient clearance with respect to the inwardly presented 7 certain parts thereof correspond to parts of the castor

peripheral wall portions

123, 124 similar to those of the wheel components described with reference to FIGS. 1, 4 and 5. The

wheel components

119 and 120 also have respective hollow spigots, 126, 127 which are coaxial with the

peripheral wall portions

123 and 124, but of smaller diameter than these peripheral wall portions. The

spigots

126 and 127 have the same diameter as each other and are each approximately one half the length of the sleeve portion 111 of the body so that they fit end-to-end. The radially outwardly presented surfaces of the

spigots

126 and 127 collectively constitute the bearing surface of the roller means and have suffisurface of the sleeve portion 1 11 to permit free rotation of the wheel components relative to the body. The sleeve portion of the body, however, locates the wheel components against movement relative to each other in directions transverse to the rolling axis 118.

The

wheel components

119 and 120 are located against relative movement along the rolling axis 118 by respective interfitting formations provided at the free ends of the

spigots

126 and 127. The free end of the spigot 126 is closed by a terminal wall 133 from the centre of which there projects in a direction along the rolling axis and towards the wheel component 120 a neck 134 which connects an enlarged head 135 with the terminal wall. An annular groove 136 is. thus defined between respective axially facing shoulders pres ented by thehead 135 and terminal wall 133. The free end of the head 135 is chamfered at 137.

At the free end of the spigot 120 there is provided a cylindrical extension 138 of the spigot, this extension being coaxial with the spigot but having a smaller wall thickness and external diameter. Thus in the unstressed state of the wheel component 120 there is an annular clearance space 139 between the sleeve portion 111 and the extension 138. At the free end of the extension 138 there is formed a radially inwardly projecting lip 140 which, as shown in FIG. 7, is received in the groove 136 when the wheel components are assembled together. Assembly of the castor shown in'FIG. 7 is effected by inserting the

spigots

126 and 127 into the sleeve'portion 111 of the body from opposite ends thereof and pressing the wheel components. 119 and 120 together. The lip 140 is thus caused to ride over the chamfer 137, thus stressing the wheel component 120 elastically. The extension 138 can be expanded radially into the clearance space 139. When the lip 140 enters the groove 136, the stress in the wheel component 120 is relieved. Thus the wheel components are secured together with a snap-fit.

Preferably there is sufficient clearance between the lip 140 and the surfaces bounding the groove 136 to permit free rotation of one wheel component relative I 140 to assist radial expansion of these parts as the wheel components are fitted together.

Preferably the body component 110 and the

wheel components

119, 120 are each formed as an integral moulding of plastics material, for example nylon. It will be noted that no further components, other than the spindle by means of which the castor would be mounted on an article of furniture, are required. Furthermore, assembly of the components is an extremely simple operation which can be performed at little cost.

Referring now to the castor shown in FIGS. 11 and 12, parts thereof which correspond to those of the castor shown in FIG. 1 are indicated by like reference numerals with the prefix 2, and the preceding description is deemed to apply, except for the differences hereinafter mentioned.

The castor shown in FIGS. 11 and 12, comprises a body 210 on which there is mounted roller means comprising

wheel components

219, 220 respectively. The wheel components each comprise

end wall portions

221, 222 respectively and

peripheral wall portions

223, 224 respectively. Furthermore, the wheel components comprise respective

integral spigots

226, 227 which interfit and locate the wheel components against relative movement. The spigot 227 is received within the spigot 226 and may be an interference fit therein. As shown in FIG. 12, one of the spigots, 226, is formed on that face which co-operates with the other spigot with a circumferential groove 241 which receives a circumferential rib 242, or a series of circumferentially spaced small projections, formed on the other spigot 227. Thus, one spigot may be a snap fit within the other. Additionally or alternatively, the spigots may be secured together by means of an adhesive or by welding. In order to ensure that relative rotation of the wheel components is prevented throughout the working life of the castor, particularly in cases where no adhesive, welding or like securement is employed, the spigots may be formed with cooperating splines. It will be appreciated that if relative rotation did occur the rib 242 may wear significantly during the working life of the castor so that there would be a risk of the wheel components becoming separated from each other.

The radially outwardly presented surface of the spigot 226 constitutes a bearing surface of the roller means which is embraced by a complementary bearing surface presented by a sleeve portion 211 of the body 210. The spigot 226 is a sliding fit within the sleeve portion so that the wheel components .12 and 13 can rotate together relative to the body about the rolling axis 218. The sleeve portion has an axial length such that it just fits within the

end wall portions

221 and 222, thereby establishing axial location of the roller means relative to the body.

The body 210 includes a web portion 212 which extends radially outwardly from the sleeve portion 211 between the

wheel components

219 and 220. The body further includes a cover 243 and a pillar 215, both of which are disposed entirely outside the

peripheral wall portions

223 and 224 of the roller means. The cover and pillar are connected with the sleeve portion by the web portion which extends through a gap 244 between the

peripheral wall portions

223 and 224. The part of the web portion which extends through this gap subtends at the rolling axis-218 an angle which is at least large enough to provide the required strength in the connection between the pillar 215 and the sleeve portion 211 of the body. There is sufficient clearance between the web portion 212 and the

peripheral wall portions

223, 224 at the gap 244 to avoid rubbing contact between these parts.

The cover 243 surrounds a part of the peripheral surface presented by each of the

wheel components

219 and 220, this part being an upper part when the castor is in position for use. Thus, the gap 244 is normally obscured from view when the castor is in use.

The pillar 215, which is formed integrally with the cover 243 and web 212, is formed with a socket 216 similar to the socket 16 of the castor shown in FIG. 1. Such socket provides for mounting of the castor by means of a spindle on an article of furniture for rotation relative thereto about a pivot axis 217.

Each of the three components of the castor shown in FIGS. 11 and 12, namely the body 210 and the

wheel components

219 and 220, is formed as an integral moulding of a plastics material, for example nylon. The components are assembled together by inserting the spigot 226 into the sleeve portion 211 and then inserting the spigot 227 into the spigot 226 and pressing the wheel components together to establish the snap fit.

Referring now to the castor shown in FIGS. 13 and 14, certain parts thereof which correspond to parts of the castor illustrated in FIGS. 11 and 12 are illustrated by like reference numerals with the prefix 3 substituted for the prefix 2 used in FIGS. 11 and 12, and the preceding description is deemed to apply to such parts except for the differences hereinafter mentioned.

The

wheel components

319, 320 of the castor shown in FIGS. 13 and 14 are similar to those of the castor shown in FIGS. 11 and 12, excepting that the

spigots

326 and 327 are somewhat longer to provide a somewhat wider gap 344 between the

peripheral wall portions

323 and 324. The spigots may be formed with cooperating splines as described with reference to FIGS. 11 and 12.

The body 310 includes a pillar 315, a part of which lies radially outwardly of the

peripheral wall portions

323 and 324, and a further part of which pillar lies radially inwardly of the peripheral wall portions and merges with the web portion 312 of the body. A socket 316 is formed in the pillar to receive a spindle or like mounting member for mounting the castor on an article of furniture. The socket 316 extends to a position radially inwardly of the peripheral wall portions of the wheel components.

The gap 344 is sufficiently wide to receive the pillar 315 without rubbing contact between the pillar and the

wheel components

319, 320. The pillar is connected with the sleeve portion 311 of the body by the web portion 312 and the latter may be formed at its radially outer extremity with a flange 314, which, together with the pillar 315, occupies and substantially fills the gap 344. The flange 314 may be flush with the outermost surface of the

peripheral wall portions

323 and 324 over a greater part of the circumference of the latter, but at that side of the body which is lowermost when the castor is in use, the flange 314 is situated somewhat nearer to the rolling axis 318 than are the peripheral wall portions in order to avoid contact between the body and a floor surface over which the castor rolls.

Referring now to the castor shown in FIGS. 15 and 16, this comprises a body 410 which may be formed from a single piece of metal rod and includes a spindle 411 on which there is mounted roller means for rotation relative to the body about a rolling axis 418.

The roller means comprises two

wheel components

419 and 420 which includes disc or end

wall portions

421, 422 respectively. These disc or end wall portions extend transversely of the rolling axis 418, and the wheel component 420 further comprises an integral peripheral wall portion which would normally be the only part of the castor to engage in pressure contact with a floor surface when the castor is in use. The peripheral wall portion shown is of cylindrical fonn and its axis coincides with the rolling axis 418.

The wheel component 419 is formed with an integral cylindrical portion 423, the axis of which is also coincident with the rolling axis 418. The outside diameter of this cylindrical portion 423 is substantially equal to the inside diameter of the peripheral wall portion 424. The cylindrical portion 423 and the peripheral wall portion 424 interfit as shown in FIG. 16 to locate the wheel components against relative movement in all directions. The cylindrical portion may be a force fit within the peripheral wall portion, and these portions may additionally be secured together by means of an adhesive or by welding.

Further, interfitting formations may be provided on the

wheel components

419 and 420 to further secure these components together, as shown in FIG. 16 these interfitting formations may comprise one or more spigots 412 which project from the end wall portion 421 of the component 419 towards the other component at positions offset from the rolling axis 418, and one or more complementary sockets 413 formed on the component 420 to receive these spigots The

wheel components

419 and 420 further include

boss portions

414 and 415 respectively which are formed with coaxial boresto receive the spindle 411. Each of the boss portions is concentric with the rolling axis 418 and projects from the end wall portion of its wheel component towards the other wheel component. However, the axial extent of these boss portions is such that when the wheel components are assembled gether there is a narrow gap between the respective free ends of the boss portions.

One end of the bore in the boss portion 414 is closed by the end wall portion 421, but the bore of the boss portion 415 is open at both ends to permit of insertion of the spindle 411 through the boss portion 415 into the boss portion 414. The wheel components are retained on the spindle by means of a star-lock or like locking washer 416 carried on the spindle and disposed within the gap between the free ends of the boss portions. If the spindle is passed through the boss portions into contact with the end wall portion 421, the locking washer prevents further axial movement of the spindle relative to the wheel components. There is a sufficient clearance between the adjacent ends of the boss portions to permit of rotation of the wheel components relative to the locking washer and the spindle. I

If required, the bore in the boss portion 414 also may be open at both ends, the spindle 411 being connected with the remainder of the body at each of its ends at po- I sitions outside the

end wall portions

421 and 422.

The body 410 includes a pin portion 417 integral with the spindle 411 and which is arranged to be received in and rotatably retained within a socket presented by an article of furniture or the like to which the castor is to be fitted. The pin portion 417 thus defines the pivot axis 4170 of the castor.

The

wheel components

419 and 420 are conveniently formed as one-piece mouldings from a plastic material such an ABS plastic. Alternatively, the wheel components could be formed of nylon or a like material, in

which case the wheel components could be adapted to cooperate with a snap fit.

Assembly of the castor shown in FIGS. 15 and 16 is conveniently carried out by passing the spindle 411 through the bore formed in the boss portion 415 and then through the locking washer 416 before assembling the wheel component 419 onto the component 420, which step completes assemblyof the castor. It will be noted that the end portion of the spindle between the washer 416 and the end wall portion 421 is free of shoulders perpendicular to the axis and facing towards the free end of the spindle, which shoulders would impede movement of the washer along the spindle.

Alternatively, the wheel components may be so formed as to define a cavity for containing the locking washer 416, and to locate the locking washer in a position in which it is substantially centred on the axis 418. With this arrangement, the wheel components and locking washer can be assembled together prior to insertion of the spindle 411 through the bores formed in the boss portions. Thus, assembled wheel components of various colours can be stored and mounted on bodies of selected colours or materials to provide specific combinations according to particular orders. Instead of a star-lock or like locking washer adapted to grip the radially presented surface of the spindle portion, a spring circlip may be provided,-in which case the spindle portion would be formed with a single circumferential groove to receive the circlip.

A modification of the castor shown in FIGS. 15 and 16 is illustrated in FIG. 17. In this modification, the

wheel components collectively define at their outer periphery an annular channel which in cross-section has the shape of a truncated triangle..This channel receives an attachment portion 425 of a tyre 426 which is formed of rubber, soft P.V.C. or like material. The attachment portion of the tyre has a shape complementary to that of the channel defined by the wheel components and a further portion of the tyre projects radially beyond the wheel components to engage with a floor surface when the castor is in use. Thus, in the modification of FIG. 17, the tyre 426 constitutes the peripheral wall portion hereinbefore mentioned.

The castors hereinbefore described which have wheel components secured together in such a manner as to prevent relative rotation are primarily intended for light duties, by which-we mean use where the maximum load which a single castor is required to bear is approximately 28 lbs. Where heavier loads are required to be borne, we prefer to employ one of the forms of castor wherein the wheel components present respective axially spaced peripheral wall portions for engagement with a floor surface, and relative rotation of the wheel components can take place when the castor rolls along a curved path.

In those cases where the body is formed as a plastics moulding, it is convenient to form the body and the two wheel components of the same material, especially nylon. The use of the same material for the body and wheel components is satisfactory in those castors which are subjected to intermittent use only and light duties as defined above. However, in the case of castors which are subjected to heavier loads or used continuously for prolonged periods, there is a risk that welding of the body to the wheel components will occur if the body and wheel components are formed of the same thermoplastic material. Accordingly, in the case of castors intended for heavier duties or continuous use over prolonged periods, we prefer to form the body of one material, for example an acetal resin, and the wheel components of a different material, for example nylon. The use of dissimilar plastics materials for those parts which present the cooperating bearing surfaces reduces the risk of welding at these surfaces.

In the case of castors intended for heavier duties a metal/plastics bearing may be preferred to a plastics/- plastics bearing. A metal/plastics bearing could be provided by introducing a metal sleeve inside the sleeve portion of a plastics body.- Alternatively, the body could be formed entirely of metal.

I claim:

1. A castor having two co-axial wheels having respective peripheral wall portions which are spaced apart axially and respective disc portions extending transversely of an axis of the wheels and supporting the peripheral wall portions, and a body whereof a portion lies between the wheels, wherein the wheels are mounted on said portion of the body and the wheels include respective interfitting formations which locate the wheels relative to each other. Y

2. The improvement according to claim 1 wherein said formations include means for locating one wheel against displacement relative to the other wheel in some directions only, and there is further provided a retaining element which cooperates with each of said wheels to provide location against relative displacement in the remaining direction.

3. The improvement according to claim 1 wherein the body cooperates with both of said wheels to provide location against movement of one wheel relative to to the other wheel in directions radially of the rolling axis.

4. The improvement according to claim 1 wherein one of said wheels is rotatable relative to the other of said wheel components about the rolling axis.

5. A castor according to claim 1 wherein said interfitting formations include spigots provided one on each wheel and said portion of the body includes a bearing opening within which said spigots are disposed.

6. A castor according to claim 5 wherein at least one of said spigots is hollow and the other of said spigots is received within said one spigot.

7. The improvements according to claim 5 wherein.

8. The improvement according to claim 5 wherein said spigots fit end-to-end and are formed adjacent to their free ends with interfitting formations which include means for locating the wheel components against relative movement along the rolling axis.

9. The improvement according to claim 5 wherein said body includes a sleeve portion which defines said bearing opening and fits between the disc portions of the wheels, whereby the sleeve portion of the body 10- cates the wheels against axial movement relative to the body.

10. In a castor having a body adapted to be mounted on an article of furniture or the like for pivoting movement relative to the article about a substantially upright pivot axis, and roller means mounted on the body for rotation relative thereto about a rolling axis which is transverse to the pivot axis,

the improvement wherein the roller means comprises two wheel components which are connected together by respective interfitting integral formation which locate one wheel component relative to the other, the wheel components each include a boss portion, these boss portions are formed with coaxial bores, the body includes a spindle which is received in said bores with a sliding fit, the spindle is formed with a single peripheral groove, and the wheel components are retained on the spindle by a locking washer means received in said groove, the locking washer means being disposed between the boss portions.

11. In a castor having a body adapted to be mounted on an article of furniture or the like for pivoting movement relative to the article about a substantially upright pivot axis, and roller means mounted on the body for rotation relative thereto about a rolling axis which is transverse to the pivot axis, the improvement wherein the roller means comprises two wheel components which are connected together and which include respective interfitting integral formations locating one wheel component relative to the other, the body includes a spindle which defines said rolling axis, one end of the spindle is free, the spindle is connected at its upper end with the remainder of the body, the wheel components include respective boss portions, each of said boss portions is formed with a bore in which the spindle is received with a sliding fit, a locking washer means is secured on the spindle at a position spaced from both ends thereof, the locking washer means is disposed between said boss portions to retain the wheel components on the spindle and the portion of the spindle between the locking washer means and the free end of the spindle is free of shoulders perpendicular to the rolling axis and facing towards the free end of the spindle.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3822437 Dated July 9, 1974 ve t r( Stafford Thomas Screen It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

[30] Foreign Priority Document Great Britain No. 54528/71 November 24, 1971 Great Britain No. 19998/72 April 29, 1972 Signed and sealed this 24th day of September 1974.

(SEAL) Attest:

MCCOY M. GIBSON-JR. c. MARSHALL DANN Commissioner of Patents Attesting Officer FORM PO-105O (10-69) g c 50 75425 U.$. GOVIINHZNY PRINTING OFFICE I In. 03ll-J3|.

Claims

1. A castor having two co-axial wheels having respective peripheral wall portions which are spaced apart axially and respective disc portions extending transversely of an axis of the wheels and supporting the peripheral wall portions, and a body whereof a portion lies between the wheels, wherein the wheels are mounted on said portion of the body and the wheels include respective interfitting formations which locate the wheels relative to each other.

7. The improvements according to claim 5 wherein at least one of said spigots is hollow and the other spigot fits inside said one spigot, and the spigots are formed with a co-operating recess and projection whereby they fit together with a snap-fit, the co-operating recess and projection providing location against relative movement of the wheels longitudinally of the spigots, and the spigots themselves providing location against relative movement of the wheels in directions transverse to the lengths of the spigots.

9. The improvement according to claim 5 wherein said body includes a sleeve portion which defines said bearing opening and fits between the disc portions of the wheels, whereby the sleeve portion of the body locates the wheels against axial movement relative to the body.

10. In a castor having a body adapted to be mounted on an article of furniture or the like for pivoting movement relative to the article about a substantially upright pivot axis, and roller means mounted on the body for rotation relative thereto about a rolling axis which is transverse to the pivot axis, the improvement wherein the roller means comprises two wheel components which are connected together by respective interfitting integral formation which locate one wheel component relative to the other, the wheel components each include a boss portion, these boss portions are formed with co-axial bores, the body includes a spindle which is received in said bores with a sliding fit, the spindle is formed with a single peripheral groove, and the wheel components are retained on the spindle by a locking washer means received in said groove, the locking washer means being disposed between the boss portions.