WO1995008449A1

WO1995008449A1 - Castors

Info

Publication number: WO1995008449A1
Application number: PCT/GB1994/002071
Authority: WO
Inventors: David Banks-Fear; David John Johnson
Original assignee: Multicontrol Ltd.
Priority date: 1993-09-24
Filing date: 1994-09-23
Publication date: 1995-03-30
Also published as: AU7662994A; GB9319701D0

Abstract

A control mechanism (1) for a castor (3), comprising a spindle (17) for mounting between the castor (3) and a trolley or the like supported by the castor (3), a support (21) rotatably mounted on the spindle (17), means (25) for fixing the support (21) to the castor (3) so that, during use, the support (21) swings about the spindle (17) as the castor (3) changes direction, an enlarged bearing portion (29) provided on one side of the spindle (17) and resilient means (33) which act between the support (21) and the enlarged bearing portion (29) to urge the support (21), and hence the castor (3), into a first position B-B. A control mechanism (1) of this type not only helps to retain the wheel (5) of the castor (3) in a preferred orientation for forward movement, but is also able to retain the wheel (5) of the castor (3) in a position at substantially right angles to the forward position to enable safe sideways motion of a trolley mounted on the castor (3).

Description

CASTORS

This invention relates to castors, and in particular to a control mechanism for castor. The invention is particulary applicable to trolleys, especially supermarket trolleys.

Most supermarket trolleys are fitted with four castors, each castor comprising a wheel and a wheel support for connecting the wheel to the trolley. The wheel support is pivotable through 360° about a vertical pivot axis which lies substantially perpendicular to the horizontal axis of rotation of the wheel. The axis of rotation of the wheel is offset from the pivot axis so that the wheel automatically swivels around and trails along behind the pivot axis as the trolley is pushed along by the user. The castors allow the trolley to be pushed in any direction, and also allow the trolley to negotiate tight ends.

However, it is now well recognised that trolleys fitted with such castors present a serious safety hazard, and are the cause of thousands of accidents and injuries each year. Supermarket trolleys often do not naturally travel in a straight line even when they are new. The trolleys are particularly dangerous when they are heavily laden, since they can gather a considerable momentum when they are pushed along supermarket floors. The trolleys are also particularly dangerous on sloping surfaces, such as in car parks or on pavements, and can cause serious injuries if the user loses control when the trolley is allowed to run free down the slope. In view of the foregoing, the present invention aims to improve upon the known prior art castor arrangements and to provide an improved control mechanism for a castor which can be applied directly to many different types of castor already in use. The resulting castor and control mechanism allows for significantly improved control of a trolley mounted thereon.

Accordingly, the present invention provides a control mechanism for a castor, comprising a spindle for mounting between a castor and a trolley or the like supported by the castor, a support rotatably mounted on the spindle, means for fixing the support to the castor so that, during use, the support swings about the spindle as the castor changes direction, an enlarged bearing portion provided on one side of the spindle and resilient means which act between the support and the enlarged bearing portion to urge the support, and hence the castor, into a first position. As will be appreciated, the first position would normally be the position which corresponds to forward motion of the trolley supported on the castor.

The pressure applied by the resilient means on the bearing portion preferably increases as the support moves away from the first position. Hence, centering of the support, and thus the castor, about the first position is achieved.

The pressure preferably increases until the support has rotated an angle of about 65° about the spindle.

The support is preferably held in a substantially stable position when it has rotated an angle of approximately 90° about the spindle from the first position. More preferably, the support is held in a substantially stable position when it has rotated an angle of between 70° and 110°.about the spindle from the first position. As a result, sideways motion of a trolley mounted on the spindle can be readily effected without the trolley moving off in a wrong direction.

The support is preferably free to swing about the spindle when it makes an acute angle with the first position of more than approximately 120°. Thus, if the trolley mounted on the castor is to be dragged backwards, to approach a vehicle in a car park for example, the wheel of the castor will not snag but will simply trail at a position approximately 180° from the first position. Preferably a few degrees, say between 1 and 8 degrees, of slack or play are provided between the resilient means and the bearing portion on either side of the first position. In this way, if the trolley mounted on the castor is moved in a reverse direction, a "toe in" or "toe out" situation will arise, thus enabling the castor to "break out" from its first position into its position for reverse movement. The spindle preferably carries a locking collar to retain the support on the spindle.

The spindle is preferably formed with a bush for engagement with a castor, during use, and for supporting the enlarged bearing portion. The enlarged bearing portion may comprise a cam positioned adjacent the spindle. If so, the cam is preferably a D-shaped cam and the spindle is preferably cut away to receive the flat side of the D.

Alternatively, the enlarged bearing portion may comprise a plurality of rollers positioned adjacent the spindle.

The resilient means preferably grip the bearing portion from both sides when urging the support into its first position.

The resilient means preferably comprise a grip spring, but other suitable resilient means may alternatively be used.

If a grip spring is used, it preferably comprises a shaped strip of metal attached to the support.

The grip spring preferably includes splayed ends adjacent the spindle which engage the spindle or the bearing portion during use.

The means for fixing the support to the castor preferably comprises a bolt passing through the support and engaging the castor. If, however, the castor does not have a suitable part for receiving the bolt, a device may be attached to the support for engaging between the forks of the castor to lock the two components.

The present invention further provides a castor for a trolley or the like comprising a control mechanism as herein described. To enable the castor and control mechanism to be attached to a trolley leg or the like, a clamping bolt preferably extends from the castor through the spindle of the control mechanism. Finally, the present invention further provides a trolley incorporating one or more castor and control mechanism as herein described.

Specific embodiments of the present invention are now described, by way of example only, with reference to the accompanying drawings, in which:-

Figure 1 is a cross-sectional side view of a castor incorporating a control mechanism according to the present invention; Figure 2 is a plan view of the castor and control mechanism of Figure 1; and

Figure 3 shows the loading of the resilient means on the spindle and bearing portion (and hence the wheel of the castor) of the control mechanism of Figures 1 and 2. With reference to the drawings, the castor control mechanism l is shown mounted on a castor 3. The castor 3 is of well known form and includes a castor wheel 5 rotatably mounted via a horizontal axle 7 between the prongs of a fork 9, the fork 9 being rotatably mounted about a vertical axis to a castor hub 11. A series of bearing balls (not shown) are arranged between the fork 9 and the castor hub 11 to allow the fork 11 and hence the wheel 5 to rotate freely about the vertical axis, which is defined by a clamping bolt 13 passing through the fork 9 and castor hub 11 for engagement with a leg 15 of a trolley (not shown) .

The horizontal axis defined by the axle 7 is misaligned with the vertical axis defined by the clamping bolt 13 so that the wheel 5 of the castor 3 trails as the trolley is moved forwards. This castor arrangement is a standard design and well known.

The invention of this patent application relates primarily to the castor control mechanism 1. In this regard, the control mechanism 1 comprises a hollow spindle 17 mounted on the clamping bolt 13 such that a bush 19, formed integrally with the spindle 17, bears against the castor hub 11. A support beam 21 is mounted for free rotation about the spindle 17, as shown in Figure 1 of the drawings. A locking collar 23 is positioned on the spindle 17 to retain the support beam 21 in position on the spindle. The locking collar 23 is held in position on the spindle by means of a grub screw (not shown) which grips the spindle 17. The support beam 21 carries a locking bolt 25 which engages the fork 9 of the castor 3 to ensure that the beam 21 swings about the spindle 17 as the fork 9 swings about the clamping bolt 13, during use.

The spindle 17 has an enlarged diameter portion 27 directly below the support beam 21 against which the support beam 21 bears. One side of this enlarged diameter portion 27 is cut away to receive the flat side of a D-shaped cam 29. The cam 29, which may be formed of metal, ceramic or any other suitable material is fixed to the bush 19 by means of a grub screw or bolt 31. Thus, a camming surface is defined by the enlarged diameter portion 27 of the spindle 17 and the cam 29. The camming surface is almost egg- shaped in plan, as can be seen from Figure 2.

A grip spring 33, comprising a shaped strip of resilient metal, is mounted below the support beam 21 for bearing against the camming surface defined by the spindle 17 and the cam 29. The grip spring 33 is attached to the support beam 21 by means of a retaining bolt 35 and bears against guides 37 (as seen clearly in both Figures 1 and 2) during use. The grip spring 33 provides two splayed ends 39 which define curved surfaces 41 for engagement with the camming surface defined by the spindle 17 and the cam 29. The shapes of the grip spring 33 and the camming surface have been mathematically designed to provide the desired loading at particular angles of rotation of the support beam 21 about the spindle 17.

Although not specifically stated to date, it will be appreciated that the control mechanism 1 is formed as a self-contained unit which can be readily mounted on a castor of a supermarket trolley or the like simply by undoing the clamping bolt 13 to release the castor from the trolley leg 15, sliding the control mechanism 1 onto the clamping bolt 13, fixing the locking bolt 25 to the fork 9 and re- tightening the clamping bolt 13 to the trolley leg 15. The control mechanism is then ready for use.

Having described the components of the control mechanism, the control provided thereby will now be described in detail.

With reference to Figure 3 in particular, a first position, wherein the wheel 5 of the castor 3 points in the forward direction of the trolley, is shown as line A-A. The direction of the wheel 5 is, however, preferably centred (when the control mechanism is attached to the castor) about a rest position at an angle a of one or two degrees from the first position, such as shown by line B-B in Figure 3. In this way, "toe in" or "toe out" is provided which enables the castor to "break out" for reverse motion of the trolley. The grip spring 33 applies virtually no pressure on the camming surface of the spindle 17 and cam 29 when the wheel 5 (and hence support beam 21) moves by up to an angle of approximately 5° on either side of the rest position B-B. (This angle of essentially "free" movement is marked b in Figure 3.) As will be appreciated, this is preferable for smooth running of the castor 3 during motion of the trolley.

If sufficient pressure is applied to the wheel 5 during motion of the trolley, such that the wheel 5 swings about the clamping bolt 13 by more than 5° from the rest position B-B, loading is applied (cf. region c in Figure 3) by the grip spring 33 onto the camming surface of the spindle 17 and cam 29. This loading increases as the angle of swing of the wheel 5 increases. As a result, this loading assists in centering the wheel 5 about the rest position B-B to ensure smooth running of the castor 5. As shown in Figure 3, the load applied by the grip spring 33 increases constantly as wheel 5 swings from an angle of about 5° to an angle of about 65° about the clamping bolt 13. On reaching an angle of 65° (at which angle a load of approxia ately 9.1 kg (20 lbs) is being applied by the grip spring 33) , the curved surface 41 of the grip spring 33 bears against the mid point 43 of the curved surface of the D-shaped cam 29. As a result the wheel 5 is not urged in any direction because the force applied by the grip spring 33 passes directly through the centre of the spindle 17. There is, therefore, no rotational force acting about the spindle 17. Due to the shapes of the grip spring 33 and cam 29, no rotational force is applied about the spindle 17 if the wheel 5 is positioned at an angle of between approximately 65° and 110° from the rest position B-B, as defined by region d in Figure 3. Thus, the trolley can be readily moved sideways without the castor precessing about the clamping bolt 13 and causing the trolley to be uncontrollable. More importantly, the force acting between the grip spring 33 and the cam 29 helps to hold the castor 3 in a particular position for sideways movement of the trolley, thus making sideways movement a simple matter.

When the wheel 5 is positioned at an angle of more than approximately 120° from the rest position B-B, the cam 29 does not contact the grip spring 33 and the grip spring 33 simply straddles the enlarges diameter portion 27 of the spindle 17. In this position, no significant pressure is applied by the spring 33 on to the spindle 17 or cam 29, so that the castor is free to swing about the clamping bolt 13. This is desirable when the trolley is being moved backwards, since the wheel 5 is simply allowed to trail behind the trolley.

Although a control mechanism as herein described is particularly applicable for use on the rear wheels of a trolley, all four wheels of a trolley may beneficially have a control mechanism applied thereto. As will be appreciated, by using a control mechanism 1 in conjunction with the castors of a trolley, control of the trolley is greatly improved and safer use of the trolley can be obtained.

Although a specific embodiment of the invention has been described herein, modifications can be made to the mechanism without departing from the scope of the present invention. For example, the D-shaped cam 29 could be replaced by a series of rollers to achieve essentially the same function. Furthermore, by using rollers, reduced wear between the grip spring 33 and the cam may be achieved. If rollers are used, two small edge rollers and a large central roller could be attached directly to the bush 19 of the spindle 17. Other alternative arrangements will of course be appreciated by those skilled in the art.

Although the specific embodiment described herein is applicable to supermarket trolleys and the like, the control mechanism can of course be used in conjunction with other trolleys, such as hospital trolleys, airport trolleys, etc. In such instances, it may be preferable for the maximum load applied by the grip spring 33 to be larger than 201bs, possibly up to as much as 501bs or more.

As described above, the "toe in" of the wheel 5 may be set when the control mechanism is mounted on the castor 3 during installation. However, it will of course be appreciated by a man skilled in the art that the degree of "toe in" (or "toe out") may be defined by the shape of the cam 29, and thus set during manufacture of the control mechanism. As a result, installation of the mechanism may be simplified even further.

Claims

1. A control mechanism for a castor, comprising a spindle for mounting between a castor and a trolley or the like supported by the castor, a support rotatably mounted on the spindle, means for fixing the support to the castor so that, during use, the support swings about the spindle as the castor changes direction, an enlarged bearing portion provided on one side of the spindle and resilient means which act between the support and the enlarged bearing portion to urge the support, and hence the castor, into a first position.

2. A control mechanism as claimed in claim 1, wherein the pressure applied by the resilient means on the bearing portion increases as the support moves av.^*ay from the first position.

3. A control mechanism as claimed in claim 2, wherein the pressure increases until the support has rotated an angle of about 65° about the spindle from the first position.

4. A control mechanism as claimed in any preceding claim, wherein the support is held in a substantially stable position when it has rotated an angle of approximately 90° about the spindle from the first position.

5. A control mechanism as claimed in claim 4, wherein the support is held in a substantially stable position when it has rotated an angle of between about 70° and about 110° about the spindle from the first position.

6. A control mechanism as claimed in any preceding claim, wherein the support is free to swing about the spindle when it makes an acute angle with the first position of more than approximately 120°.

7. A control mechanism as claimed in any preceding claim. wherein a few degrees, say between 1 and 8 degrees, of play are provided between the resilient means and the bearing portion on either side of the first position.

8. A control mechanism as claimed in any preceding claim, wherein the spindle carries a locking collar to retain the support on the spindle.

9. A control mechanism as claimed in any preceding claim, wherein the spindle carries a bush for engagement with a castor, during use, and for supporting the enlarged bearing portion.

10. A control mechanism as claimed in any preceding claim, wherein the enlarged bearing portion comprises a cam positioned adjacent the spindle.

11. A control mechanism as claimed in claim 10, wherein the cam is D-shaped and the spindle is cut away to receive the flat side of the D.

12. A control mechanism as claimed in any one of claims 1 to 9, wherein the enlarged bearing portion comprises a plurality of rollers positioned adjacent the spindle.

13. A control mechanism as claimed in any preceding claim, wherein the resilient means grips the bearing portion from both sides when urging the support into the first position.

14. A control mechanism as claimed in any preceding claim, wherein the resilient means comprises a grip spring.

15. A control mechanism as claimed in claim 14, wherein the grip spring comprises a shaped strip of metal attached to the support.

16. A control mechanism as claimed in claim 14 or claim 15, wherein the grip spring has splayed ends adjacent the spindle which engage the spindle or the enlarged bearing portion during use.

17. A control mechanism as claimed in any preceding claim, wherein the means for fixing the support to the castor comprise a bolt passing through the support and engaging the castor.

18. A control mechanism for a castor substantially as hereinbefore described with reference to and as shown in the accompanying drawings.

19. A castor for a trolley or the like comprising a control mechanism as claimed in any preceding claim.

20. A castor as claimed in claim 19, wherein a clamping bolt extends from the castor through the spindle of the control mechanism for attachment to a trolley leg or the like.

21. A trolley comprising a castor and a control mechanism according to any preceding claim.