GB2274979A - Trolley castor - Google Patents

Abstract

A trolley (10) has a chassis (14) mounted on wheels (16, 18), at least one of said wheels (18) being swivellable about a vertical axis for steering and at least one of said wheels (16) being swivellable about a vertical axis to a greater or lesser extent according to load in or on the trolley. <IMAGE>

Description

Title: Improvements in or relating to trolleys DESCRIPTION This invention concerns mprovements in cr relating to trolleys, especially four-wheeled trolleys, such as supermarket trolleys and hospital trolleys.

Basic four-wheeled trolleys are used in many situations including supermarkets, hospitals, airports, railway stations and in factories. Such trolleys generally comprise a chassis supported on four wheels generally one at each corner and a load carrying part mounted on the chassis, which may be, for example, a basket for a supermarket trolley or a flat bed for a hospital trolley. A handle is provided at the rear of the trolley for manoeuvering the trolley.

Generally all our wheels are arranged to swivel freely about a vertical axis to provide manoeuverability. However: such an arrangement presents problems in certain circumstances. In particular, if the trolley is travelling on a laterally sloping surface with respect to the fron-to-back axis of the trolley, the wheels tend to swivel to cause the trolley under gravity to travel down the slope, so that it is very difficult for the user to push the trolley in a straight line along the slope. The problem becomes more noticeable the more weight there is in or on the trolley.This presents particular problems where, for example, in the case of a supermarket trolley, a shopper wishes to transport goods from inside the supermarket, where the floor is level, to their vehicle in an adjacent car park where the ground is often sloping.

To alleviate this problem it has been proposed to replace one or a pair of swivellable wheels with a fixed wheel or wheels to inhibit unwanted sideways movement or the trolley, so that the trolley can be steered along a straight path even when it is sloping laterally In general it will be front wheels which are fixed as it is easier to steer with rear swivellable wheels due to the user being behind the centre of inertia of the trolley.

However, the use of non-swivellable wheels on a trolley presents a further problem as regards nestable trolleys, such as are used in supermarkets. These trolleys are usually nested one behind the other to be pushed back from say a car park to a collection point near the entrance of the supermarket either inside or outside thereof. A line of nested trolleys will, therefore, have pairs of non-sw vellable wheels distributed along its length, which will make the line of trolleys difficult to steer Further proposals have been made for front wheels of a trolley to be selectively swivellable and nonswivellable. To achieve that7 front wheels of the trolleys are arranged to be non-swivellable in normal use but are permitted to swivel about a vertical axis due to mechanical intervention of a nesting trolley.

However, the rearmost trolley of a line of nested trolleys will still have non-swivelling front wheels which may hinder movement of a line of trolleys and the mechanism required for this purpose adds to the cost of producing such trolleys and may be a hindrance to use of the trolley, if damaged.

An object of this invention is to provide an improved trolley.

According to this invention there is provided a trolley having a chassis mounted on wheels at least one of said wheels being swivellable about a vertical axis for steering and at least one of said wheels being swivellable about a vertical axis to a greater or lesser extent according to load in or on the trolley.

preferably the trolley has a pair of rear wheels which are independently swivellable each about its own vertical axis. The vertical axis is preferably offset relative to the rotational axis of the wheel.

Preferably the trolley has a pair of front wheels which are independently swivellable each about its own vertical axis when the trolley is unladen but as the load is increased, the extent to which the front wheels are swivellable reduces until at a desired load swivelling of the front wheels is prevented.

Each front wheel is preferably mounted at the end of a swivel shaft which is itself permitted to pivot about an axis transverse to the trolley. The extent of pivotal movement is preferably from the vertical rearwardly and is preferably against bias, such as provided by spring means Preferably stop means are provided to limited rearward pivotal movement Thus, as weight is added to the trolley7 swivel shafts of the front wheels will tend to pivot rearwards, which together with the offsetting of the swivel shafts to their wheels will inhibit swivelling of the rear wheels due to the progressive introduction of castor angle.

Thus, according to the invention as a trolley becomes laden, it will become increasingly easier to steer as the front wheels swivel less However, when the trolley is empty all front and rear wheels can swivel, which will enable a line of nested such trolleys to be moved relatively easily.

The means for biassing the swivel shafts to the vertical is preferably spring means. Such spring means may act between the swivel shaft and another part of the trolley Alternatively, the pivotal mountings of the swivel shafts may include spring means such as in the form of spring bushes.

In an alternative preferred embodiment the at least one wheel swivellable about a vertical axis to a greater or lesser extent of one trolley is only permitted to swivel when a second trolley is nested therewith. Preferably, the at least one wheel is mounted on a swivel shaft that is freely pivotable from a vertical position to an inclined position due to the weight of the trolley whether loaded or not and guide means of a second or nesting trolley are arranged to transfer the weight on said at least one wheel onto the second or nesting trolley. Preferably the front wheels of a trolley are on said pivotable shafts and said weight transfer is onto the rear wheels of the nesting trolley.

This invention will now be further described, by way of example only, with reference to the accompanying drawings, in which: Figure 1 shows a trolley in accordance with the invention; and Figure 2 shows schematically a trolley wheel of the trolley of Figure 1; Referring to the accompanying drawings, a trolley 10 typically a trolley of the type used in supermarkets, has a basket 12 mounted on a chassis 14.

The chassis 14 is supported on a pair of front wheels 16 and a pair of rear wheels 18 A handle 20 is provided at the rear of the trolley whereby it may be pushed, pulled and directed.

The rear wheels 18 are each mounted on vertical swivel shafts 22 for pivotal movement about the vertical shafts which are offset relative to the rotational axis of the wheel. Because of this arrangement, each wheel will tend to swivel so that its axis of rotation is rearward of the vertical swivel axis relative to the direction of travel of the trolley The front wheels 16 are mounted on swivel shafts 94 which are pivotable rearwards of the normal direction of travel of the trolley. Pivoting is restrained by spring bias means such as by spring bearings 26. Thus, inclination (angle ) of the vertical pivotal axis can alter in accordance with weight in the trolley. The more weight that is added to the trolley the further rearwards the front wheels move relative to their position when the trolley is unladen Stop means (not shown are provided to limit the rearward movement of the front wheels under load. The greater the inclination of the swivel axis to the vertical, the more difficult it is for the wheels to swivel. Thus, for a laden trolley, the rear wheels will remain free swivel for steering but the front wheels will be restrained from swiveling to improve manoeuverability. When the trolley is empty and, in particular, when nested in line with the trolleys the front wheels are also free to swivel so the line of trolleys may be manoeuvred relatively easily.

The invention has been described in relation to a shopping trolley but is equally applicable to any other load carrying trolley It will be appreciated that for a trolley which is intended to be pulled rather than pushed, it will be the front wheels which are free to swivel at all times, and the rear wheels which will be restrained from swiveling when the trolley is laden.

Claims (16)

1. A trolley having a chassis mounted on wheels, at least one of said wheels being swivellable about a vertical axis for steering and at least one of said wheels being swivellable about a vertical axis to a greater or lesser extent according to load in or on the trolley.

2. A trolley as claimed in claim 1, wherein the trolley has a pair of rear wheels which are independently swivellable each about its own vertical axis.

3. A trolley as claimed in claim 1 or 2, wherein the vertical swivel axis of the or each wheel is offset relative to the rotational axis of the wheel.

4. A trolley as claimed in claim 1, 2 or 3, having a pair of front wheels which are independently swivellable each about its own vertical axis when the trolley is unladen but as the load is increased, the extent to which the front wheels are swivellable reduces until at a desired load swivelling of the front wheel is prevented.

5. A trolley as claimed in any one of claims 1 to 4, wherein each front wheel is mounted at one end of a swivel shaft, which is itself pivotable about an axis transverse to the trolley.

6. A trolley as claimed in claim 5, wherein the extent of pivotal movement of a swivel shaft is from the vertical rearwardly.

7. A trolley as claimed in claim 5 or 6, wherein pivotal movement of a swivel shaft is against bias.

8. A trolley as claimed in claim 7, wherein bias is provided by spring means.

9. A trolley as claimed in any one of claims 5 to 8, wherein stop means is provided to limit rearward pivotal movement of a swivel shaft.

10. A trolley as claimed in claim 8 or 9, wherein the spring means acts between the swivel shaft and another part of the trolley.

11. A trolley as claimed in claim 8 or 9, wherein pivotal mountings of the swivel shafts include spring means.

12. A trolley as claimed in claim 11, wherein the pivotal mountings of the swivel shafts include spring bushes.

13. A trolley as claimed in claims 1, 2 or 3 wherein the at least one wheel swivellable about a vertical axis to a greater or lesser extent of one trolley is only permitted to swivel when a second trolley is nested therewith.

14. A trolley as claimed in claim 13, wherein the at least one wheel is mounted on a swivel shaft that is freely pivotable from a vertical position to an inclined position due to the weight of the trolley and guide means of a second trolley are arranged to transfer weight on said at least one wheel onto the second or nesting trolley.

15. A trolley as claimed in claim 14, wherein the front wheels of the trolley are on said pivotable shafts and said weight transfer is onto the rear wheels of the second or nesting trolley.

16. A trolley substantially as hereinbefore described with the reference to and as illustrated in the accompanying drawings.