WO1993025398A1

WO1993025398A1 - A guide wheel assembly for a trolley and a trolley equipped therewith

Info

Publication number: WO1993025398A1
Application number: PCT/GB1993/001241
Authority: WO
Inventors: Gerald E. Lloyd
Original assignee: Lloyd Gerald E
Priority date: 1992-06-10
Filing date: 1993-06-10
Publication date: 1993-12-23
Also published as: AU4254093A

Abstract

The invention provides a guide wheel assembly (22) and a trolley (T) equipped with such an assembly (22) to provide for straight line running of the trolley over sloping surfaces. The assembly (22) provides for the instinctive release of the straight running constraint by a user when faced with manoeuvring problems in a confined space. The constraint is automatically reapplied when the trolley (T) is being propelled on a straight line course (F) again.

Description

' l . 4

A GUIDE WHEEL ASSEMBLY FOR A TROLLEY AND A TROLLEY EQUIPPED THEREWITH

Technical field

This invention relates to a guide wheel assembly for a trolley and to a trolley equipped with such an assembly. It is particularly concerned with an assembly for a trolley of a general type provided in supermarkets, warehouses, airport termini for use by pedestrians wishing to transfer loads such as purchases, luggage or equipment from one location to another.

Background art

A typical trolley of this general type has a chassis which is supported by four wheels or castors. The wheel layout of the trolley is commonly two front and two rear wheels on a trapezoidal plan with the pair of wheels normally leading having a narrower track than the rear pair. At least one pair of wheels are mounted on offset trailing pivots so that in pushing the trolley forwardly the trailing pivots provide for their associated wheels to swing into a trailing position relative to the direction of movement. The trolley includes a raised basket provided with a handle to enable the trolley to be propelled by a user. The basket is disposed at a height comparable with or greater than the wheel track of the front or rear pair of wheels to provide for objects to be readily placed into and removed from the basket without a need for an excessive range of vertical movement by a user of average height. However this results in a raised centre of gravity for a loaded trolley which can lead to handling problems. In particular such a trolley is difficult to push across a sloping floor since the lateral displacement of the centre of gravity causes a resultant force to act resulting in the trolley tending to turn down the slope. Manoeuvring a trolley subject to this effect can be particularly trying for a user who is poorly co-ordinated, incapacitated or infirm.

Proposals have been made to provide for straight line running in such conditions. In European Patent 0 352 647 (Wanzl) there is described a stackable transport trolley with a pushing arrangement located at the rear and with a chassis which has at least one loading surface for piece goods and which is fitted with four castor wheels and at least one support castor, wherein at least one support castor is located between the castor wheels arranged on a support frame mounted so as to be liftable characterised in that the support frame is secured to the front end of the trolley and in that a lifting device is provided at the front, which lifting device is intended for lifting the support frame of a preceding trolley when two such trolleys are pushed one inside the other.

While this support castor arrangement does provide for straight running of the trolley on a level floor area it does not overcome a handling problem which arises when, for example, the trolley is laterally constrained by an obstruction and is not readily moved forwards. Such an event can arise in a supermarket when a trolley is pushed close alongside a cabinet to lie parallel to and in contact with it. To continue pusing the trolley forwardly is likely to result in at least cosmetic damage to the cabinet or or the trolley. Any attempt to angle the trolley relative to the cabinet (such as by pivoting the trolley about one corner in contact with the cabinet) is resisted by the guide wheel. Either the front or rear end of the trolley could be lifted to raise the opne pair of wheels and the guide wheel from the ground and the trolley pivoted to angle its longitudinal axis relative to the cabinet. The end is then lowered and then and thereafter the trolley can be pushed away. However to lift a trolley requires considerable strength and for this and other reasons the event is not readily dealt with especially in a stressful environment.

Proposals have been made to temporarily ameliorate the effect of straight line running. GB Application 2 222 362 (Herok-RJK) discloses a castor wheel assembly in which the castor axis is locked when the wheel is in the straight ahead position but unlocked in another position of motion, locking being caused by forward rotation of the wheel and released by backward rotation. A supermarket trolley or similar vehicle equipped with a pair of such castors at the front end and conventional castors at the rear can be steered under normal circumstances by the rear castors but readily adapted to four wheel steering in confined spaces by a slight reverse motion to unlock the front wheel castors action. While addressing the problem the practical embodiment of the proposal poses difficulties. Also to cause disengagement of the constraint when required the trolley needs to be drawn backwards and this is not necessarily an instinctive action.

Disclosure of invention

According to a first aspect of the present invention a guide wheel assembly, for attachment to a trolley, in the form of a trailing wheel mounted on a member providing for a horizontal axis of rotation of the wheel to be off-set from a vertical axis of rotation of the assembly is characterised by:

1 a member (29) for coupling the assembly (22) to a trolley (T) and serving to define a perimeter (29A) around the vertical axis (V), the perimeter (29A) including at a datum position a cut-out (30) bounded by limit profiles (30A, 30B); the cut out (30) lying closer to the vertical axis (V) than any other part of the periphery (29);

2 a trailing carrier (25) pivotably attached to the member (29) for rotation about the vertical axis (V) relative to the member (29);

3 a drag link (31) on which the guide wheel (21) is mounted to rotate about a lateral axis of rotation (28), the drag link (31) being pivotably attached to the trailing carrier (25) for rotation about the lateral axis (28); the drag link (31) being linked to the guide wheel (21) by a frictional device (38) providing for at least forward rotational motion of the wheel (21) about the lateral axis (28) to be transmitted to the drag link (31) to cause rotation of the drag link (31) about the lateral axis (28);

4 a stop (35) mounted on the drag link (31) comprising or including a low friction abutment (51, 52) whereby the stop(35) can roll or slide along the periphery (29A); motion of the drag link (31) caused by the frictional device (38), when the wheel (21) is rotating forwardly, serving to carry the stop (35) forwardly until the stop (35) is brought into initial contact with the perimeter (29A); and in the event that the initial contact is not in the cut-out (30) then any subsequent motion of the wheel (21) about the vertical axis (V) causes the stop (35) to slide or roll around the periphery (29A) until the stop (35) drops into the cut-out (30) and is held there by continuing forward rotation of the wheel (21) and laterally by the action of the limit profiles (30A, 30B) so as to maintain the carrier (25) and the plate (29) in a common alignment (F) and provide for the guide wheel (21) to resist any tendency to pivot about the vertical axis (V); and in the event the wheel (21) ceases to rotate in a forward direction (F) a relatively small lateral motion of the member (29) relative to the wheel (21) causes the stop 35 to be cammed out of the cut-out (30) by one or other limit profiles (30A, 30B) so releasing the drag link (31), and so the guide wheel (21), from constraint against rotation about the vertical axis (V).

According to a second aspect of the present invention there is provided a guide wheel guide wheel assembly according to the first apsect characterised by an arm (17) having an inboard end (18) for securing the assembly (22) to a trolley (T) and an outboard end (20) to which the member (29) is attached.

According to a third aspect of the present invention there is provided a trolley characterised in that it is equipped with an assembly (22) according to the first aspect.

According to a fourth aspect of the present invention there is provided a trolley trolley characterised in that it is equipped with an assembly according to the second aspect and the arm (17) serves to locate the guide wheel (21) intermediate the front and rear wheels (13, 15) for ground engaging rotation about the axis of rotation (28) of the wheel. Typically the arm (17) incorporates, or is located by, resilient biassing means serving to resiliently urge the guide wheel (21) downwardly into ground engagement in the common plane (P). In addition the trolley is equipped with a release (22) located on or by the trolley (T) such that on the trolley (T) being closely stacked with the similar trolley the release (L') on the similar trolley interacts with the assembly (22) to displace the stop (35) from its forward alignment and maintain it displaced therefrom. Accordig to a fifth aspect of the present invention the trolley of the third aspect is further chaacterised in that mounted forwardly of its end mounting (relative to the trolleys forward direction of travel) and the guide wheel trails relative to the arm. Alternatively the inboard end of the arm is mounted rearwardly of its end mounting (relative to the trolleys normal forward direction of travel) and the guide wheel leads relative to the arm.

The guide wheel assembly according to any aspect of the present invention provides for ready manoeuvring of a trolley so that when the trolley stops being propelled in a forward direction and is subjected to slight lateral displacement the wheel causes the drag link to be carried out of engagement with the carrier resulting in the release of the guide wheel from a first component configuration in which the wheel acts to inhibit motion of the trolley in anything other than a straight ahead direction to a second component configuration in which the guide wheel can pivot freely about the vertical axis to allow for the motion of the trolley in any direction. Once the motion of the trolley is restored to a forward direction the second component configuration is caused to change to the first configuration in which the wheel acts to inhibit motion of the trolley in anything other than a straight ahead direction.

Brief description of the drawings

An exemplary embodiment of the invention will now be described with reference to the accompanying drawings of a supermarket trolley and its component of which:

Figure 1 shows a side view of the trolley;

Figure 2 shows an end fitting, a part of Figure 1, in greater detail;

Figure 3 is a exploded perspective view of end fitting shown in Figure 2;

Figures 4 is a perspective view of the components of Figure 3 when assembled;

Figures 5 is a plan view of the components shown in Figure 4;

Figure 6 and 7 are plan views similar to that of Figure 5 saving that some of the components are shown in different relative positions; and

Figure 8 is a rear view of the assembly shown in Figure 4 seen in direction of arrow VIII. Mode for carrying out the invention

Figures 1 and 2 variously show a lower part of a chassis 11 of a super market trolley T supporting a basket 12. The normal forward direction of movement of the travel is in the direction F. The chassis has front wheels (typically wheel 13 mounted on a trailing castor 14) and rear wheels (typically wheel 15 mounted on a trailing castor 16).

The trolley T is equipped with a cantilevered trailing arm 17 has a leading end 18 which is secured to a front chassis member 19 of the trolley. The arm 17 has a trailing end 20 on which is mounted a guide wheel assembly 22 incorporating a guide wheel 21 which functions as will be described in more detail hereafter. The arm 17 tapers from the leading end 18 to the trailing end 20 and functions as a tapered leaf which is of shape and material providing that the trailing end 20 is resiliently biassed downwardly it can flex relative to its secured leading end 18 in a vertical plane about a horizontal axis X. The arm 17 is designed as to resist a twisting movement about longitudinal axis Y of the trolley and lateral motion in a horizontal plane transverse the axis Y. Many of the components shown in Figures 1 and 2 are of plastics material so providing for low unit production costs particular for large production runs. In this case the arm is shown in a trailing configuration. However it is envisaged that applications will arise where a leading arm configuaration will be more appropriate.

In normal usage with the chassis 11 travelling in the direction F the guide wheel 21 of assembly 22 is resiliently loaded by arm 17 into firm contact with the floor. The wheel 21 acts to resist any tendency on the part of the trolley to travel sideways. The contact point P between rubber tyre 24 of wheel 21 and the floor F is deliberately chosen to lie on or near vertical axis of rotation R of the trolley (similar to the vertical axis on which the centre of gravity of the loaded trolley lies) so that there is little or no reaction on turning the trolley about the axis R to move from the straight ahead path represented by arrow F. End fitting 22 is secured to trailing end 20 of the arm 17 by a nut N. Figures 3, 4 and 5 variously show the major components of the end fitting 22. In Figures 3 and 4 guide wheel 21 is omitted for the sake of clarity. Figures 5, 6 and 7 show the end fitting 22 with components in different relative positions.

Cap 29 is provided with a perimeter 29A incorporating a cut out 30 bounded by limiting profiles 30A, 30B. On assembly of the arm 17 on the chassis 11 the cap 29 is fixed to the arm 17 so that cut-out 30 permanently faces in the opposite direction to arrow F.

Carrier 25 is an inverted U-shaped member. Bore 26 provides for the pivotable attachment of the end fitting 22 to cap 29 so that the carrier 25 can readily rotate about vertical axis V except as will be discussed later. Bores 27 at the lower end of the carrier 25 serve to retain an axle for the guide wheel 21 so that the wheel 21 can rotate freely about axis 28. The carrier has in its upper rear end (Figure 5) a slot 40 with a front end 41 and a rear end 42.

Drag link 31 is pivotably mounted within carrier 25 by way of bores 32 at the lower end of the link 31 which are pivotable on axis 28' which is co-axial with axis 28 in the assembled end fitting. The link 31 is made up of side arms 33 and upper member 34. To ensure that the drag link 31 moves in conformity with rotation of the guide wheel 21 bosses 37 are located on the inside of each of the side arms 33 and each boss serves to anchor the inner end of a compression spring 37A which serves to drive a friction pad 38 into contact with side faces 39 of the wheel 21.

Stop 35 includes an abutment comprising a pair of ball bearings 51, 52 on pin 50.

The slot 40 in the carrier serves to slidably retain the stop 35 on a path P by way of bearing 52. The bearing 52 enables the stop 35 to roll freely along the sides of the slot 40 with little frictional restraint on the stop between a forward location established by end 41 of the slot 40, and a rearward location established by end 42 of the slot 40. The cut out 30 serves to retain the stop 35 by way of upper bearing 51 during normal forward motion of the trolley in the direction of the arrow F. As shown in Figures 5, 6 and 7 the horizontal depth D of the cutout 30 is greater than the radius but less than the diameter of the bearings 51, 52. The bearing 51 provides for the stop 35 to roll freely around the profile 29A and where necessary around the profiles 30A, 30B into cut-out 30 with little frictional restraint when the bearing 51 is enabled to do so. The profiles 30A, 30B are shaped so as to ensure retention of the stop 35 in cut out 30 when the wheel 21 is acting to urge the stop in the direction of the arrow F. However the profiles 30A, 30B provide for lateral release of the stop 35 from the cut out 30 when forward motion of the trolley is terminated and a slight lateral motion is applied to the trolley which results in the stop 35 being cammed out of engagement with the profile 30A/30B since it is no longer subject to a forward drive from motion of the wheel 21 acting on the stop 35 by way of the drag link 31.

Figures 3, 4 and 5 show a first operating position when the trolley 11 is still. In particular the bearing 52 of stop 35 is seated against the rear end 42 of the slot 40 and the bearing 51 is disengaged from cutout 30.

Figure 6 shows a second operating position when the carrier 25 is not aligned with the forward direction F of the trolley but has just been subjected to a forward push. _^As a consequence the stop 25 is carried forwardly by movement of the wheel 21 transmitted to the drag link 31 by way of pressure pads 38 so that bearing 51 of stop 25 rolls forwardly until bearing 51 strikes the perimeter 29A of cap 29.

Figure 7 shows the effect of continued forward motion of the trolley and the normal relative position of the components with the trolley in forward motion. To reach this position from the disposition shown in Figure 6 the bearing 51 having struck the perimeter 29' rolls around it, over the profile 30A into the cutout 30. The profile 30B stops further peripheral rolling by bearing 51. In this location with continued forward movement of the trolley 11 the stop 35 is maintained fixed in the cut-out 30 relative to the carrier by being prevented from lateral movement by the profiles 30A, 30B by the sustained motion of the guide wheel 21. In this alignment the carrier 25 is aligned with the direction of travel F of the chassis and the wheel 21 while rolling freely forward serves to prevent any lateral motion by the trolley. The stop 35 continues to be maintained in position for as long as ther wheel 21 rolls forwardly by the action of the drag link 31 under the influence of the friction pads 38 which are in permanent contact with side faces 39 of the wheel 21.

Two situations arise where this straight line constraint on the trolley could cause inconvenience. Firstly when it becomes necessary to manoeuvre the trolley T away from a closely juxtaposed lateral obstruction. Secondly when manoeuvring a closely stacked array of such trolleys. For both situations the end fitting 22 provides for the removal of the straight line control as will be described hereafter.

Taking the first situation when the trolley is close alongside an obstruction parallel to axis L. Without the availability of a dis-engaging arrangement provided by the present invention continuing to push the trolley forwardly would keep the guide wheel retained in its straight ahead position with frictional contact between the trolley and the obstruction. This would be likely to cause at least cosmetic damage to the obstruction and/or the trolley arising from such contact. A user of the trolley, especially one in a stressful situation such as a busy supermarket crowded with other trolley users, would not necessarily readily resolve the matter. A user could perhaps lift one or other end of the trolley and the guide wheel an empty trolley sideways to cause the trolley to be angled relative to the obstruction and so freely moved in a straight line away from it. However even for a strong user this would be impracticable with a loaded trolley and even with an empty trolley with a user who was weak or incapacitated.

One solution would be to draw the trolley back a trifle causing the drag link 31 to be displaced rearwardly (in the opposite direction to arrow A). As a result stop 35 would be disengaged from the cut out 30 to the relative position shown in Figure 4 whereupon the carrier 22, and so the guide wheel 21, can rotate about vertical axis V so freeing the trolley from the lateral constraint provided by the guide wheel when the stop 35 is in its forward position shown in Figure 7. However the present invention provides for a simpler disengagement action. All that is required when alongside the lateral obstruction is for the user to apply a slight lateral motion to the trolley in a direction away from the obstruction. No backward motion is needed. A slight lateral action has been found to be an almost instinctive action by an inexperienced user. As a result the bearing 51 strikes one or other of the limit profiles 30A, 30B which cause the stop 35 to be cammed out of engagement with the cut out 30 so releasing the constraint to lateral motion imposed by the guide wheel 21 when the trolley is in forward motion. The trolley can then be pushed forwardly and the guide wheel assembly operates to restore the restrained directional operation of the guide wheel with the component alignment shown in Figure 7.

The embodiment makes use of a stop abutment having a pair of roller bearings 51, 52 to provide a low friction arrangement. However the rather than using bearing to provide a low friction effect the abutment can be a contact surface formed from or coated with a slippery material such as PTFE.

The second situation arises in supermarket and other locations where large numbers of trolleys are involved. For these locations an individual trolley is designed so that it can be pushed into close engagement with a similar trolley to provide a stack whose overall length is considerably less than the product of the overall length of a single trolley and the number of trolleys in the stack. In such a close packed stack the conventional guide wheel of each of the trolleys, if allowed to continue in operation resisting lateral motion, would make it impossible to move the stack except in a straight line. However in close stacking trolleys according to the present invention the guide wheel is uncoupled from its constraint. This is achieved by providing on the underside of each trolley an outrigger X (Figure 2); and a latch L ri vetted to the outer extremity of trailing end 20. In stacking a second trolley with a trolley 11 outrigger X' (Figure 2) on the second trolley contacts latch K on trolley 11 positively displaces tongue K' on the latch L resulting in stop 35 being driven out of engagement with outline 30 in the carrier 22. This allows the carrier 22 and so guide wheel 21 to rotate freely about axis V so enabling a stack of such trolleys to be steered without constraint from any guide wheel on trolleys in the stack. There is a further benefit to be obtained from using a guide wheel 21 on a resilient arm whether leading or trailing. On level ground the four trolley wheels and the guide wheel lie on a common ground plane. The four outer wheels serve to sustain the weight of the trolley at a fixed level while the guide wheel is pressed into engagement with the ground regardless of the load carried by the trolley. If the trolley, especially when loaded, is driven over a curb the trolley temporarily ceases to be supported by one or more of the outer wheels consequently the trolley load ceases to be supported in a stable manner. If the guide wheel was rigidly supported or at least limited in the amount in which it could retract away from the common ground plane then a condition could arise where the trolley was supported by a pair of outer wheels and the guide wheel. This would especially be the case when the trolley cease to be supported on two wheels on the same side. Such support would not provide a stable configuration for the trolley which would consequently overbalance. However by making the arm supporting the guide wheel flexible the sudden removal of support described above result in a load suddenly being applied to the guide wheel would merely result in the arm flexing upwardly without providing a temporary fulcrum leading to instability. As a consequence the trolley would drop onto the one or two wheels previously temporarily out of contact with the ground so restoring support. Thus the guide wheel of the present invention would not lead to a worse instability situation than would exist with a four wheeled trolley.

The specific embodiment refers particularly to the use of the guide wheel device when mounted on the trolley by way of an arm. It is envisaged that one or more of the guide wheel assembly devices can be attached directly to a trolley in place of existing castors to provided for the provision of straight path as described but without the benefits of the arm including the resilient biassing and the ability of the guide wheel to retract under impulse loads. The device would operate in an identical way to that described that is to say for as long as the trolley was moving forwardly the guide wheels would resist any lateral movement of the trolley. On stopping the guide wheel effect is readily removed by the application of a small lateral movement to the trolley. Industrial applicability

The present invention provides a relatively simple device providing a substantial enhancement to trolley operation and safety. The device requires little maintenance. The device can be incorporated on a production line for new trolleys or readily be added as a fitment to existing trolleys. The device has been described in connection with a supermarket trolley. It is also applicable to a wide range of other trolley types such as those used for airport baggage, warehouse, building and do-it-yourself stores for the handling of bulky objects and other in many other applications.

Claims

1 A guide wheel assembly, for attachment to a trolley, in the form of a trailing wheel mounted on a member providing for a horizontal axis of rotation of the wheel to be off-set from a vertical axis of rotation of the assembly characterised by:

1 a member (29) for coupling the assembly (22) to a trolley (T) and serving to define a perimeter (29A) around the vertical axis (V), the perimeter (29A) including at a datum position (F) a cut-out (30) bounded by limit profiles (30A, 30B); the cut out (30) lying closer to the vertical axis (V) than any other part of the periphery (29);

4 a stop (35) mounted on the drag link (31) comprising or including a low friction abutment (51, 52) whereby the stop(35) can roll or slide along the periphery (29A); motion of the drag link (31) caused by the frictional device (38), when the wheel (21) is rotating forwardly, serving to carry the stop (35) forwardly until the stop (35) is brought into initial contact with the perimeter (29A); and in the event that the initial contact is not in the cutout then any subsequent motion of the wheel (21) about the vertical axis (V) causes the stop (35) to slide or roll around the periphery (29A) until the stop (35) drops into the cut-out (30) and is held there by continuing forward rotation of the wheel (21) and laterally by the action of the limit profiles (30A, 30B) so as to maintain the carrier (25) and the plate (29) in a common alignment (F) and provide for the guide wheel (21) to resist any tendency to pivot about the vertical axis (V); and in the event the wheel (21) ceases to rotate in a forward direction (F) a relatively small lateral motion of the member (29) relative to the wheel (21) causes the stop 35 to be cammed out of the cut-out (30) by one or other limit profiles (30A, 30B) so releasing the drag link (31), and so the guide wheel (21), from constraint against rotation about the vertical axis (V).

A guide wheel assembly as claimed in Claim 1 characterised by an arm (17) having an inboard end (18) for securing the assembly (22) to a trolley (T) and an outboard end (20) to which the member (29) is attached.

A trolley characterised in that it is equipped with an assembly (22) as claimed in Claim 1.

A trolley characterised in that it is equipped with an assembly as claimed in Claim 2 and that the arm (17) serves to locate the guide wheel (21) intermediate the front and rear wheels (13, 15) for ground engaging rotation about the axis of rotation (28) of the wheel.

A trolley as claimed in Claim 4 characterised in that the arm (17) incorporates, or is located by, resilient biassing means serving to resiliently urge the guide wheel (21) downwardly into ground engagement in the common plane (P).

A trolley as claimed in Claim 4 or Claim 5 characterised by a release (X) for the assembly (22) located on or by the trolley (T) such that on the trolley (T) being closely stacked with the similar trolley the release (L') on the similar trolley interacts with the assembly (22) to displace the stop (35) from its forward alignment and maintain it displaced therefrom.

A trolley as claimed in Claim 4, Claim 5 or Claim 6 characterised in that the inboard end (18) of the arm (17) is mounted forwardly of the rest of the assembly (22) (relative to the forward direction (F) of travel) and the guide wheel (21) trails relative to the arm (17).

A trolley as claimed in Claim 4, Claim 5 or Claim 6 characterised in that the inboard end (18) of the arm (17) is mounted rearwardly of the rest of the assembly (22) (relative to the forward direction (F) of travel) and the guide wheel (21) leads relative to the arm (17).