GB2408198A

GB2408198A - Castor with angled axis of rotation

Info

Publication number: GB2408198A
Application number: GB0326989A
Authority: GB
Inventors: Adrian Robert Middleto Goodman; Jean Alice Goodman
Original assignee: Individual
Current assignee: Individual
Priority date: 2003-11-20
Filing date: 2003-11-20
Publication date: 2005-05-25
Also published as: GB0326989D0

Abstract

A castor that may be used on a shopping trolley has a substantially vertical axis (10) about which it may rotate. The castor has a wheel(12) with a circumferential rolling surface(14), the wheel mounted to the castor body so that the wheel can rotate about a rolling axis (23 fig 2). The rolling axis is tilted relative to the vertical swivel axis. The angle of tilt may be less than 90 degress and more than or equal to 10 degrees but is preferred to be between 10 and 30 degrees relative to the orientation of the swivel axis. The swivel axis and the rolling axis may be spaced apart (10, 23 fig 2). The castor wheel may be shaped as a truncated cone, the wheel may also have a bearing (16 fig 5) be mounted on an externally threaded stub axle(17) and may be held in place using a nut (20 , 21).

Description

24081 98

TROLLEY CASTOR

TECHNICAL FIELD OF THE INVENTION

This invention relates to a castor which is suitable for a trolley or similar article, particularly a shopping trolley.

BACKGROUND

It is well known that heavily loaded trolleys are often difficult to steer. Many attempts have been made to improve the steerability of shopping trolleys, but previous solutions have generally suffered from increased complexity and cost, and often, manoeuvrability may be impaired in an effort to provide greater steerability. For example, one known proposal is to bias the castors towards the straight-ahead position, but whilst this may increase steerability it tends to make it more difficult to manouevre the trolley in a tight space.

The present invention seeks to provide a new and inventive form of castor which is simple, inexpensive and effective in providing good steerability and manoeuverability.

SUMMARY OF THE INVENTION

The present invention provides a castor having: - a castor body provided with a swivel connection to rotate about a swivel axis which is substantially vertical in use; - a wheel having a circumferential rolling surface; and - a wheel mounting which connects the wheel to the castor body such that the wheel can rotate about a rolling axis; in which the rolling axis is tilted relative to the orientation of the swivel axis.

The angle of tilt of the rolling axis is preferably substantially less than 90 relative to the orientation of the swivel axis, and most preferably less than 45 . A tilt angle of between 10 and 30 achieves the best results.

As with a normal castor, the rolling axis will normally be spaced from the swivel axis.

The ground-contact surface of the wheel is preferably shaped as a truncated cone.

The wheel mounting preferably includes a bearing and a stub axle. The castor body may have an inclined lower face through which the stub axle is inserted. The castor body may have a body cavity with a bottom wall which provides said inclined lower face. The stub axle may be provided with an external screw-thread held by a retaining nut within the body cavity. The castor body preferably has a lateral opening for access to the retaining nut.

BRIEF DESCRIPTION OF THE DRAWINGS

The following description and the accompanying drawings referred to therein are included by way of non-limiting example in order to illustrate how the invention may be put into practice. In the drawings: Figure 1 is a rear view of a castor in accordance with the invention; Figures 2 and 3 are, respectively, right and left elevational views of the castor; Figure 4 is a front view of the castor; Figure 5 is an exploded view of the castor, partially sectioned, as viewed in Figure 4; and Figure 6 is a general view of a shopping trolley provided with a pair of such castors.

DETAILED DESCRIPTION OF THE DRAWINGS

Referring to Fig. 1, the castor 1 is intended for mounting on a trolley or similar article. Although this view is described as a rear elevation it will be appreciated that the castor may swivel to different positions in use, as will be described below.

The castor includes a castor body 2 which may be cast of metal or moulded of plastic for example. The body 2 has a top wall 3 with depending side walls 4 and 5 bridged at their lower ends by a bottom wall 6, which together define a body cavity 7. The front and rear of the castor (Fig.s 4 and 1 respectively) are preferably open to provide access to the body cavity. It can also be seen in Fig.s 2 and 3 that the top wall 3 is extended to the front of the castor body to provide support for a swivel mounting 8 which is offset in a forward direction from the bottom wall 6. This mounting 8 could take various forms. A simple form of swivel mounting could be an upstanding pivot pin which is fixed to the top wall 3 for reception is a socket on the trolley, but in this example the mounting incorporates a ball race contained within a housing 9 of inverted-pan shape. The housing is fixed to the trolley in use such that the castor body 2 may rotate freely about a vertical swivel axis 10.

Referring back to Fig.1, it will be seen that the side wall 5 extends below the side wall 4 so that the bottom wall 6 is inclined from side-toside at an angle of about 20 to horizontal. The castor includes a wheel 12 which is mounted in an inclined position such that a side face 13 of the wheel is disposed above the ground. A ground-contacting circumferential area 14 of the side face 13 is preferably in the form of a truncated cone to increase the potential support area in contact with the ground.

As can be seen in Fig. 5, the wheel contains another bearing assembly 16, such as a further ball race, by which the wheel can rotate freely about a stub axle 17. The bearing assembly 16 is held in place by a thrust washer 25 and a circlip 26. The stub axle is externally screw threaded and receives a washer 18 followed by a threaded locking nut 19. The stub axle is inserted through the bottom wall 6 and secured by a threaded retaining nut 20 within the body cavity 7. If desired, a split pin 21 may be inserted through the locking nut 19 and stub axle 17 as a safeguard against the locking nut working loose with rotation of the wheel 12.

From the foregoing it will now be understood that the axis of the stub axle 17, which forms the rolling axis 23 of the wheel 12, is inclined at an angle of 20 to vertical. Furthermore, as shown in Fig. 2, the rolling axis 23 is offset rearwardly from the vertical swivelling axis 10 of the castor (e.g. by about 25mm).

Fig. 6 shows a typical application of the castor. A shopping trolley 30 is provided with a pair of the castors 31 and 32 with a normal pair of castors 33 and 34 or non-swivelling wheels at the rear. Normally the castors will be handed such that opposing castors on opposite sides of the trolley have their rolling axes 35 and 36 tilted towards each other in an upward direction.

The trolley could have two pairs of castors in accordance with the invention, or the castors of the invention may be mounted at the rear with a pair of normal castors or non-swivelling wheels at the front.

The described arrangement whereby the point of ground contact of the wheel is offset from the front-rear axis of the castor provides greatly improved steerability and manoeuvrability compared with a normal castor having a substantially horizontal rolling axis. When the trolley stops following forward movement for example, it is easy to rotate the trolley to face in a different direction, requiring minimum physical effort. The trolley is also easy to stop, and will easily travel over uneven surfaces such as brick paving. The construction of the castor is very uncomplicated.

It will be appreciated that the features disclosed herein may be present in any feasible combination. Whilst the above description lays emphasis on those areas which, in combination, are believed to be new, protection is claimed for any inventive combination of the features disclosed herein.

Claims

1. A castor having: - a castor body provided with a swivel connection to rotate about a swivel axis which is substantially vertical in use; - a wheel having a circumferential rolling surface; and - a wheel mounting which connects the wheel to the castor body such that the wheel can rotate about a rolling axis; in which the rolling axis is tilted relative to the orientation of the swivel axis.

2. A castor according to Claim 1, in which the angle of tilt of the rolling axis is substantially less than 90 relative to the orientation of the swivel axis.

3. A castor according to Claim 2, in which the angle of tilt of the rolling axis is substantially less than 45 relative to the orientation of the swivel axis.

4. A castor according to Claim 3, in which the angle of tilt of the rolling axis is between 10 and 30 relative to the orientation of the swivel axis.

5. A castor according to any preceding claim, in which the rolling axis is spaced from the swivel axis.

6. A castor according to any preceding claim, in which the lowermost ground-contacting surface of the wheel is shaped as a truncated cone.

7. A castor according to any preceding claim, in which the wheel mounting includes a bearing and a stub axle.

8. A castor according to Claim 7, in which is the castor body has an inclined lower face through which the stub axle is inserted.

9. A castor according to Claim 8, in which the castor body may has a body cavity with a bottom wall which provides said inclined lower face.

10. A castor according to Claim 9, in which the stub axle is provided with an external screw-thread and is held by a retaining nut within the body cavity.

11. A castor according to Claim 10, in which the castor body has a lateral opening through which the retaining nut can be accessed.

12. A castor substantially as described with reference to the drawings.