GB2290022A

GB2290022A - Lockable trolley castor

Info

Publication number: GB2290022A
Application number: GB9411316A
Authority: GB
Inventors: Thomas Barrow Dowling
Original assignee: Individual
Current assignee: Individual
Priority date: 1994-06-07
Filing date: 1994-06-07
Publication date: 1995-12-13
Anticipated expiration: 2014-06-07
Also published as: GB9411316D0; GB2290022B

Abstract

A device for engaging a castor wheel in a determined orientation with respect to a trolley equipped with the castor wheel, the device comprising: a wheel as such mounted for rotation in travel and casting with respect to the trolley about a castor axis; a pair of members 1, 10 adapted and arranged to co-operate to hold the wheel in the determined orientation, one 10 of the members being on the wheel and the other component 1 being on the trolley, and a speed controlled mechanism 16 for biasing the one member 10 to move towards the other member for engagement therewith when both the speed of rotation of the wheel exceeds a determined threshold and the wheel has cast about the castor axis to the determined orientation. In the embodiment, the speed sensitive device is a pump 16 actuated by a cam device 17, 19. It has a bleed valve 32 which determines the pressure and at the critical speed the pressure is enough to lift the blocking member 10, which is mounted at the end of a piston 27. When the speed reduces, the pressure decreases ad the member 10 is allowed to fall back. <IMAGE>

Description

TROLLEY The present invention relates to a device for engaging a castor wheel in a determined orientation, particularly though not exclusively a castor wheel of a trolley.

When loaded, trolleys having castor action wheels tend to follow their previous line of travel at corners due to inertia. Also on ground which is not flat they tend to move sideways in a downhill driection. In either case steering becomes difficult. This flaw is alleviated by the use of a wide handling bar at the rear with which the operator can exert a twisting, thus a straightening effect, or by crabbing the trolley across a slope at an angle to strike a balance. This problem is well known by visitors to supermarkets or airports, but applies also in hospitals, warehouses, places of work, and in any other place where castor action wheels are used, including babies' prams and push chairs.

In the case of supermarket, airport and railway station trolleys, for instance, it is a normal requirement that the trolleys be nested when not in use, as well as for returning them in convoy for re-use. When nested it is necessary for all the castors to be free to swivel, even when only two trolleys are nested, so that they can be manoeuvred into neat assemblies without shunting or the need to reverse them.

These trolleys are normally mounted on four wheels, although three wheel trolleys are sometimes used. In either case the same principles apply. The four wheel trolley will be assumed in this description.

The problem then is to provide the user with a trolley that is directionally stable when proceeding at and above a slow walking speed, yet is manoeuvrable at all speeds when nested, whilst still being totally manoeuvrable when at rest or almost at rest (such as when browsing in the aisles of a supermarket). It is essential that at very slow speed the trolley be unconstrained so that avoidance of other obstacles (for instance shoppers or passengers' luggage), is made easy, as indeed existing unconstrained trolleys manage well.

It is when cornering, particularly with a fully laden trolley, or whilst walking a trolley with one wheel running less freely than the others, and most noticeably on ground that is not level, that the problem of sideways movement presents itself.

US Patent 2,583,858, filed on December 10th 1949 by J K Kostolecki was taken out to solve the problem of directional stability. Kostolecki employs a spring biased ball engaging in a groove in the manner of a detent to bias a castor wheel to maintain a single direction until excess force disengages the detent and full castor action is permitted. The problems of manoeuvring nested trolleys and free movement in any direction at slow speeds were not addressed by him. My experiments indicate that either the detent action is too strong to be disengaged when necessary or it is too weak to be effective in providing a trolley with directional stability.

European Patent No. 0,370,716 B1, filed 20.11.89 by Herok RJK Ltd, inventor Paul Star France, describes an arrangement for holding a castor wheel in straight ahead position, but it can be restored to its normal castor action only by reversing of the direction of rotation. I regard this as a significant impediment to easy manoeuvrability of a convoy of nested trolleys.

In May 1994, at the Birmingham NEC 'The Great British Innovation and Inventions Fair' on the Safeway (supermarket) stand an invention was exposed that partially solved the problems described above, but only at the expense of introducing another problem. On the two front wheels of the trolley a knuckle engaged a cam and slot, essentially as described in Kostolecki's patent. The action is only engaged when the operator draws towards him a connected controlling bar mounted parallel with, and just in front of, the main bar or handle of the trolley. Thus the nesting problem was solved as was the free-manoeuvring from rest or slow speeds. I reject this approach, on the grounds that its use requires the co-operation of the shopper and is also quite unsuited to airport and railway trolleys in that they already mount an identical operating bar for brake release.

To manage one control, let alone two, in addition to the main handle is considered an unsatisfactory burden to the user.

Thus the present invention addresses the defined problems by using the speed of the trolley itself as the main control.

In accordance with my invention I provide a device for engaging a castor wheel in a determined orientation with respect to apparatus equipped with the castor wheel, the device comprising: a wheel as such mounted for rotation in travel and casting with respect to the apparatus about a castor axis; a pair of members adapted and arranged to co-operate to hold the wheel in the determined orientation, one of the members being on the wheel or a component which casts about the castor axis with the wheel and the other component being either on a component of the castor wheel which does not cast or on the apparatus; and a speed controlled mechanism for biasing one of the members to move towards the other member for engagement therewith when both the speed of rotation of the wheel exceeds a determined threshold and the wheel has cast about the castor axis to the determined orientation.

In use, once the speed has reached the determined threshold, the engagement occurs as soon as the wheel casts to its determined direction, whereby the trolley or other apparatus equipped with the wheel is given directional stability. When the speed drops below the threshold, the members disengage.

The determined speed threshold will be set to a suitably low speed according to the use of the device.

I envisage that the speed controlled mechanism may be a hydraulic mechanism, a centrifugal clutch, or an electromagnet clutch. However in the preferred embodiment, I provide a simply pneumatic mechanism. The mechanism may be double acting, that is arranged to withdraw the member moved by the mechanism when the speed drops. Alternatively, a spring return may be provided. Again in the preferred embodiment, I avoid the necessity for any forced return of the member other than gravity acting on it.

For this the movable member is arranged to be lifted essentially vertically with increased speed and mounted for casting with the wheel. The lifting may be along the castor axis or preferably radially from it. Alternatively, the movable member may be made to move horizontally (in the plane of the wheel) in and out of its operating position.

The other member can be a recess of any convenient shape, but it is preferably a slot. Normally it will have a cambered approach from both sides. Normally the slot will be arranged for engagement of the movable member in it when the wheel is cast for forwards motion of the apparatus.

In use, two castor wheels of a trolley may be equipped with the device. However I have found that fixing one wheel gives directional stability so single wheel operation will be assumed henceforth. For nesting trolleys, the device is conveniently fitted at the front.

In accordance with an important preferred feature of the invention, there are mechanisms to disengage the devices of both forward or rearward nested trolleys. Conveniently these include cooperating levers. In the preferred embodiment, the slot is mounted for essentially vertical movement. Two separate levers extend from the pivotably mounted slot and cam assembly on the trolley frame. A forward facing lever, mounted onto the said assembly, engages under a dedicated stub mounted on the trolley ahead to tip, lift and thus disengage the said slot when trolleys are nested. A rear facing lever mounted onto the same assembly rides up onto the frame of the trolley behind as it is being nested, again achieving disengagement. By these means all the wheels of two or more trolleys become disengaged when nested.

In this way the action is automatic; the shopper, traveller or user need not know there is a modification. He will simply find the trolley easier to use in practice.

However, as in all previous work, the engagement of the directional control requires the operator to so handle the trolley that the front operating wheel(s) align for forward travel.

Where the nesting of trolleys is not required in similar conveyances which find everyday use as baby prams and pushchairs, for general and specialist use in hospitals, as trolleys for the distribution, movement and storage of equipment, goods and merchandise in warehouses, factories, offices and shops, and which are found in supermarkets, garden centres, D-I-Y stores, airports, ferry terminals and docks and railway stations, the same directional stability problems exist and the directional element of the invention will still apply. In some cases a saving of manpower maybe achieved due to the improved handling of the vehicle, for example the movement of horizontal patients in hospitals.

To help understanding of the invention, a specific embodiment thereof will now be described with reference to the accompanying drawings, in which: Figure 1 shows the general arrangement, side elevation, of the preferred embodiment, Figures 2 and 2a show the rear elevation of one of the front wheels, Figure 3 shows the plan view, and Figure 4 shows the reciprocating pneumatic pump which operates the stud.

The latest trolley wheels in use are castors which have a fixed non-rotating centre section with effectively two wheels rotating around it and their use is illustrated throughout. In this latter case the majority of the relevant operating part of the invention can be sited in the centre section, thus making the invention neater in appearance.

The slot and cams 1, mounted on the trolley by bracket 2 and pivotted 3 to allow roughly vertical movement between limits 4 and 5, carry levers 6 and 7 extending forwards and backwards, to engage the trolley ahead (shown in broken line) to an engaging extension 8 and rearwards to the rear trolley frame 9, also in broken line. The lever mechanism shown diagramatically by solid line in Figure 1 illustrates the slot and cam assembly in the operative mode just clear of nesting.

Figure 2a shows the slot and cams in the tipped upwards to the inoperative position. This is the position effected when the trolley is nested, and is illustrated also by the broken line trolley on the right of Figure 1 The stud 10, mounted on the wheel assembly is shown solid in the slow or stopped position, 10 and is shown in broken line in the engaged or increased speed position 11.

The engagement of the stud in the slot 12, guided by the cams 13, is assisted by gravity. The geometry of the pivotably mounted levers-cum-slot-and-cams assembly is arranged so that there is a downward force on the cams and slot by gravity, assisted if required by additional weight 14 on lever 7. The castoring movement of the trolley wheel will bring the stud 11 to engage the face of the cam 13 as it approaches the ahead mode. The slot-and-cams assembly then rises against the force of gravity on the lever and slot-and-cams assembly as the wheel castors towards the ahead position until it reaches the peak of the cam, at which point a reverse cam assisting access to the slot takes effect.

The control of the stud 10/11, which is essentially vertical sided 15, but rounded at the top to assist the cam action with either approach to the slot 12, is by the pneumatic speed operated pump 16.

Referring to Figure 4, showing the air pump controlling the stud: in this drawing the air pump and stud are in line, but for instance if necessary for the reasons of siting components, the pump may be separated from the plunger operating the stud by a connecting air pipe. The plunger need not be on the centre line of the wheel and may be driven off the tyre, as opposed to the shaft, and could be mounted externally to the wheel; though for silence of operation, protection from dirt and accidental damage, as well as neatness, the internal mounting is preferred.As the speed increases the rotating drive 17 (which is spring 18 assisted to the return or down position), off the shaft 19 of the wheel itself rotates the pump operating cam 20 which drives piston 21, with non-return valve 22 closed at top of piston which forces air upwards inside cylinder 23 past a second and upper non-return valve 24 mounted on diaphram 25 into pressure chamber 26. On the return downward stroke of the piston non-return valve 22 opens permitting a recharging in-take of air into cylinder 23 while the upper non-return valve 24 closes, retaining pressure in the pressure chamber 26. The increase of pressure in pressure chamber 26 will, as trolley speed increases, force plunger 27 and stud 10 upwards to its operating height 11. When plunger 27 has risen to its full operating height limited by flange 28 the air will evacuate freely by way of the relieved cylinder wall 29.Thus the pump is relatively lightly loaded, except when raising the stud during the initial period of acceleration. To allow for slow traffic movement with the stud in the inoperative, or down, position the pressure chamber 26 wall is pierced providing relief bleed at its bottom, shown as relief bleed 30, thereby allowing controlled release of air, perhaps through a silencer chamber. This relief and the weight of the plunger and stud, together with the fit of the pump are the variables which control the cut-off point between free operation at slow speed and operation with directional stability at increased speed. Provision may be made for differing weights of ring 31 to be fitted to the base of the stud external to the trolley wheel assembly, to vary the cut-off speed of the control for differing conditions.In addition, or as an alternative, a fine adjusting screw 32 may be provided for relief bleed 30 It has been found that when operating on uneven ground one of the four wheels can leave the ground rendering the system momentarily out of action when the operating wheel contact is lost. This can be overcome in three ways if desired. One is to have both front wheels controlled.

Alternatively one can have one of the wheels sprung within small limits, so that in minor uneveness all wheels are permanently engaged. A third, preferred, approach is to allow sufficient travel of plunger 27 and stud 11 combined with the dampening effect of the dimensions of relief bleed 30 to bridge the time gap while the trolley wheel is off the ground.

The control of the stud 10,11 (which together with the arrangement of the levers 6,7, to disengage trolleys in front and behind when nesting) is the dominant part of this invention. This control can also be achieved by means other than those described above. In trials a centrifugal action has been successfully ulilised. Hydraulic pump action and electro-magnetic means are also available. Other means, such as air turbine for example, which convert a rotating force to power an essentially vertical or lateral movement can be employed. Essentially various alternative means will provide the power required to operate the stud function described above.

Claims

CLAIMS:

1. A device for engaging a castor wheel in a determined orientation with respect to apparatus equipped with the castor wheel, the device comprising: a wheel as such mounted for rotation in travel and casting with respect to the apparatus about a castor axis; a pair of members adapted and arranged to co-operate to hold the wheel in the determined orientation, one of the members being on the wheel or a component which casts about the castor axis with the wheel and the other component being either on a component of the castor wheel which does not cast or on the apparatus; and a speed controlled mechanism for biasing one of the members to move towards the other member for engagement therewith when both the speed of rotation of the wheel exceeds a determined threshold and the wheel has cast about the castor axis to the determined orientation; the arrangement being such that in use, once the speed of travel has reached the determined threshold, the engagement occurs as soon as the wheel casts to its determined direction, whereby the apparatus equipped with the wheel is given directional stability and when the speed drops below the threshold, the members disengage.

2. A device as claimed in claim 1, wherein the speed controlled mechanism is a hydraulic mechanism.

3. A device as claimed in claim 1, wherein the speed controlled mechanism is a centrifugal clutch.

4. A device as claimed in claim 1, wherein the speed controlled mechanism is an electromagnet clutch.

5. A device as claimed in claim 1, wherein the speed controlled mechanism is a pneumatic mechanism.

6. A device as claimed in any preceding claim wherein the speed control mechanism is double acting, that is arranged to withdraw the member moved by the mechanism when the speed drops.

7. A device as claimed in any one of claims 1 to 5, wherein the speed control mechanism is provided with a spring return.

8. A device as claimed in any one of claims 1 to 5, wherein the speed control mechanism is adapted and arranged for gravity return of the member.

9. A device as claimed in claim 8, wherein the movable member is arranged to be lifted essentially vertically with increased speed and mounted for casting with the wheel.

10. A device as claimed in claim 9, wherein the mechanism is arranged for lifting of the member along the castor axis or preferably radially from it.

11. A device as claimed in any preceding claim, wherein the the mechanism is adapted and arranged for the movable member to move substantially horizontally (in the plane of the wheel) in and out of its operating position.

12. A device as claimed in any preceding claim, wherein the other member comprises a recess, preferably a slot.

13. A device as claimed in claim 12, wherein the recess has a cambered approach from both sides.

14. A device as claimed in claim 12 or claim 13, wherein the recess is arranged for engagement of the movable member in it when the wheel is cast for forwards motion of the apparatus.

15. Apparatus equipped with a castor wheel and including a device as claimed in any preceding claim, wherein the device is fitted at the front of the apparatus for nesting thereof with like apparatus.

16. Apparatus as claimed in claim 15, including means for disengaging the devices of both forward or rearward nested apparatus.

17. Apparatus as claimed in claim 16, wherein the disengaging means includes co-operating levers.

18. Apparatus as claimed in claim 17, wherein the device is as claimed in claim 12, claim 13 or claim 14 and the recess is mounted for essentially vertical movement.

19. Apparatus as claimed in claim 18, wherein the recess has the cambered approach of claim 13, the apparatus including two separate levers extending from the recess which is pivotably mounted on a frame of the apparatus.

20. Apparatus as claimed in claim 19, including a dedicated stub mounted with the recess for engagement by a forwards facing one of the levers on the apparatus behind for tipping, lifting and thus disengaging the recess when apparatuses nested, and an adaption of the frame of the apparatus on which a rear facing lever mounted with the recess of an apparatus in front on which adaption this lever rides up for disengagement of this recess.

21. A device for engaging a castor wheel substantially as hereinbefore described with reference to the accompanying drawings.