GB2133978A - Ball-shaped caster with two wheels - Google Patents

Abstract

A castor with two wheels and ball-shaped appearance has vertical wheels (11) placed on a common axle (7) fixed in a body (5), said axle having at each end an annular recess (16) co-operating with an annular bead in the wheel hub (14) for securing the wheels (11). In one embodiment, without a wheel guard, the body (5) has a cylindrical surface (9) in line with the treads (12) of the wheels (11). In another embodiment with a guard, the cylindrical surface (9) is omitted, and the body (5) instead is fitted with guideways co-operating with internal guides in the ball-shaped guard which also has an opening in the shape of a bushing fitting down over a tower-like projection (10) of a pivot pin bearing (8) which displacedly in respect of the wheel axle (7) is fitted into the body (5). In the described embodiments, the number of single components is brought, down to a minimum, and the castor can be assembled or dismantled without the use of tools. <IMAGE>

Description

SPECIFICATION Ball-shaped castor with two wheels This invention relates to a ball-shaped castor with two wheels. The castor is of the kind, where a wheel-bearing body has a bore, which is displaced in relation to the wheel axle and serves as a bearing for a pivot pin, which connects the castor to the piece of furniture.

Castors of the said kind are known in many different embodiments, including one, cf. for instance the French Patent Specification No.

1,497,845, where the castor has an outer design closely resembling a ball-shape. A substantial and greatly cost-increasing disadvantage of this known embodiment is that the wheels are obliquely placed in the castor, necessitating an oblique axle for each wheel, and that the body has to be wedge-shaped in a massive design in order to make possible a secure bearing of the axles, thus necessitating a large material consumption in the making of these castors. Further the said known castors do not have a guard over the treads and no easy possibility of furnishing such guard.

The object of the invention is to redress these disadvantages and to provide for a two-wheeled, ball-shaped castor of simple design, and where the number of individual components for making the castor has been reduced to a minimum.

With this object in view, the castor of the invention is characterized in that a through-going straight axle for the two wheels is fixed in the castor body, that the said axle has an annular recess near each end, said recess cooperating with a corresponding elastic bead in the hubs of the wheels, serving to retain the wheels on the axle, and that the wheels are designed as parts of ball shells turning into circular-cylindric treads with radial supporting ribs to the wheel hub.

In view of the fact that ball-shaped castors have been known for more than 1 5 years, it is surprising that no one before has observed the essential advantages of a design as described.

Of these advantages should be mentioned the common axle for the wheels, that by the upright wheels one avoids the pincing effect made by the oblique wheels in rolling, and especially that the castor is built from a minimum of individual components, since the two wheels are identical and also the axle and the pivot pin can be identical so that a castor without guard can be made from only three different parts, and for a castor with guard from only four different parts.

In a particularly advantageous embodiment, the castor of the invention has a wheel-bearing body shaped upwardly so as to be in line with the wheel treads, the pivot bearing, however, extending in a tower-like projection, the upper rim of which is in line with the top of the body, thus obtaining an almost perfect ball-shape, and a small height of construction, where the top of the castor almost touches the underside of the piece of furniture to which it is affixed.

By designing the castor of the invention so that the body at one end is limited by a bearing of cylindric shape for the pivot pin, whereas the other end is in a straight line parallel with the axis of the pivot pin, and by fitting both ends with guideways cooperating with corresponding guides on a guard in the form of a part of a ball shell with an opening corresponding to the tower-like projection of the pivot pin bearing, is obtained that the wheels are guarded from above over more than half their treads, and that the castor becomes more perfectly ball-shaped, only interrupted by the upward extending projection of the pivot pin bearing.

Preferably, only the wheel axle and the pivot pin are made from metal, the remaining parts being made from plastic.

In the following, the invention will be described more detailedly with reference to the embodiments of the castor shown on the accompanying drawings, where Fig. 1 is a perspective drawing of individual parts and illustrating how these are fitted together to a ball-shaped castor without guard, Fig. 2 is a corresponding drawing of individual parts for a castor with guard, and Fig. 3 is a perspective drawing of a guard for the castor of Fig. 2.

The castor of Fig. 1 has a body 5 of plastic moulded in one piece. The body has centrally a cylinderlike bushing 6, into which a fixed, metallic wheel axle 7 is pressed. Displaced in relation to the wheel axle, the body 5 has a bearing 8 for a pivot pin (not shown).

Upwards, the body 5 is limited by part of a cylindric surface 9, up through which the bearing 8 continues as a tower-like projection 10, the upper surface of which is in line with the top of the cylindric surface 9. The latter has the same outer diameter as the threads of two identical wheels 11, which are to be fitted on the axle 7.

The wheels 11 are also made from plastic with a narrow cylindrical tread 12 merging into an outer ball shell 13 with an internal hub 14 with radially extending, strengthening ribs 1 5.

At each end, the axle 7 has an annular groove 16 and correspondingly the hub 14 has internally a non-visible bead, which owing to a certain elasticity of the plastic can be compressed and, when the wheel is placed on the axle, can slide over the end of the latter till it reaches the groove 16, where it again expands, whereby the wheel is rotatably fixed on the axle 7.

The embodiment shown in Fig. 2 only differs from that in Fig. 1 in the shape of the body 5.

Here, the cylindric surface 9 is missing, and the body has at one end a guideway 18. In similar manner, the bearing 8 at the other end is provided with two guideways 1 9. The said guideways serve for fixing the guard 20 shown in Fig. 3, in that internally in the latter guides 21 and 22 are formed so as to fit into the guideways 1 8 and 1 9.

The guard 20 further has an opening 23 in the form of a bushing with an internal diameter equal to the outer diameter of the projection 1 0. Thus, when the axle 7 is in place and the wheels 11 are fitted onto the axle, the guard 20 can be pushed down over the body 5 and secured by interference fit.

Claims (4)

1. A ball-shaped castor with two wheels, and of the kind in which a wheel-bearing body has a bore, which is displaced in relation to the wheel axle and serves as a bearing for a pivot pin, which is to connect the castor to a piece of furniture, characterized in that a through-going straight axle (7) for the two wheels (11) is fixed in the castor body (5), that the said axle has an annular recess (16) near each end, said recess cooperating with a corresponding bead in the hub of the wheels, serving to retain the wheels on the axle, and that the wheels are designed as parts of ball shells (13), turning into circular-cylindric treads (12), and with radial supporting ribs (15) to the hub of the wheel.

2. A castor according to claim 1, in which the wheel-bearing body (5) upwards is designed so as to be on line with the wheel treads (12), whereas the pivot pin bearing extends upwards in a towerlike projection (10), the top of which is in line with the top of the body.

3. A castor according to any of claims 1 and 2, in which the body (5) at one end is limited by a cylinder-shaped bearing (8) for the pivot pin, whereas the other end is parallel to the pivot pin axis, and that at both ends guideways (18, 19) are provided to cooperate with corresponding internal guides (21, 22) on a wheelguard (20) of outer shape like part of a ball shell and having an opening (23) corresponding to the tower-like part of the pivot pin bearing (8).

4. A ball-shaped castor substantially as described herein with reference to the drawings.