STEERING UNIT

Abstract: A steering unit (1) for a trolley (12) comprises a first member attached to the chassis (13) of the trolley (12) and a second member attached to a wheel (14) of the trolley (12) and locking means (7) and (5) which lock the second member, and so the wheel (14), in a predetermined position to allow the trolley (12) to be steered with ease.

Description: "Steering Unit" This invention relates to a steering unit. A number of factors are considered in the design of shopping trolleys such as: trolley width in relation to aisle width, trolley stacking ability, normal ergono ic considerations and overall manoeuvrability. Unfortunately, the vast majority of trolleys do not manoeuvre with the ease and accuracy required by users. Even a trolley which, when unladen, functions as the user requires can become extremely difficult to operate when heavily laden. This is a particular problem when a trolley is taken across even the shallowest of slopes, normally on the way to car parks, where any sideway movement of the trolley can build in momentum resulting, in some cases, in the user losing complete control of the trolley. According to the present invention there is provided a a steering unit for a trolley, comprising first and second members, said first member adapted to be fixed on the trolley, said second member attachable to a wheel of the trolley and connected to said first member for rotation with respect to said first member, and means provided to lock the two members in a predetermined position under load. Preferably, said second member is at least partially rotatable within said first member. Preferably, said predetermined position is determined by the two members being shaped to interlock in said predetermined position. Preferably, said first member comprises a hollow casing, attachable at one end to the trolley chassis and sealed at the other end to form a receptacle for the second member. Preferably, the casing is sealed with a releasable cap, the cap enabling access to the interior of the casing. Preferably, said second member comprises a longitudinal member spring-loaded to bear against the first member when under load. Preferably, the longitudinal member has a flange mounted upon it, said flange having grooves which are shaped to fit dogs provided on the receptacle, and so interlock the first and second members when engaged. The longitudinal member may be spring-loaded by a helical spring attached to the sealed end of the receptacle and bearing against the longitudinal member. Alternatively, the longitudinal member may be spring-loaded by a disc spring or a series of disc springs attached to the sealed end of the receptacle and bearing against the longitudinal member. Most preferably, the position of the second member, once interlocked with the first member, ensures that the wheel to which the second member is attached is directed to run in a forward direction. The trolley on which the steering unit is used may also have a shaped handle which extends across the rear of the trolley in a continuous curve and is positioned at an angle and distance that allows the standard stacking of such trolleys. Preferably, an external force of approximately ten pounds is sufficient to overcome the repulsive force of the spring and cause the locking mechanism to contact the locating barrel. An embodiment of the present invention will now be described, by way of example, with reference to the accompanying drawings in which:- Fig. 1 is a perspective view of a steering unit in accordance with the present invention, attached to a trolley wheel; Fig. 2 is a side view of the integral piston rod and locating barrel and the locking mechanism of the steering unit of Fig. 1; Fig. 3 is a side view of a unidirectional piston rod and locating barrel and the locking mechanism of the steering unit of Fig. 1; and Fig. 4 is a perspective view of a trolley with steering units of the present invention attached. A steering unit 1 comprises a first member in the form of a casing 2, releaεable cap 3, a second member provided as a longitudinal member in the form of a centrally mounted piston rod 4 housed within the casing 2, and locking means provided as a flange 5 with grooves 6, which may be interlocked with a collar 7 that has dogs 8 provided for this purpose. A repulsive force in direction A is generated by a spring 9 located at the top of the piston rod 4. The piston rod 4 is secured in position above the collar 7 by a locking pin 10. The collar 7 is fixed to the casing 2. A washer 11 is located above the locking pin 10, and the spring 9 acts between the washer 11 and the cap 3 attached to the top of the casing 2. The spring 9 is shown in Fig. 1 as a coil spring, but this may be replaced by a disc spring or stack of disc springs which can fulfil the same function but reduces the overall length. When in use, the casing 2 is bolted to the front of a shopping trolley 12 on its chassis 13, and a front wheel 14 of the trolley 12 is attached to a threaded section 15 at the base of the piston rod 4. The trolley wheel 14 will swivel as normal when the trolley 12 is empty. However, when the weight of the load in the trolley 12 overcomes a predetermined value the force produced by the load will exceed the repulsive force produced by the spring 9 and the chassis 13 of the trolley 12 will lower, thus lowering the collar 7 onto the flange 5. This can occur irrespective of the position of the wheel 14 and consequent position of the attached flange 5, but when the wheel 14 is located in the forward or backward direction, dogs 8 on the collar 7 and grooves 6 in the flange 5 will be aligned and mate, thus locking the flange 5 in position and locking the wheel 14 in a position to roll forwards or backwards. The symmetrical dog 8 and groove 6 arrangement illustrated in Fig. 2 enables the wheel 14 to be locked in a forward or a backward direction with respect to the trolley chassis 13, separated by 180°, whereas the asymmetric positioning of the dogs 8 and grooves 6 illustrated in Fig. 3 enables the wheel 14 to be locked only in the forward travel direction, with respect to the trolley chassis 13, where the majority of the wheel 14 is positioned behind the piston rod 4. Thus the trolley 12 will be compelled to move forward, under a user's direction, and will not move at a tangent under the laden trolley's own momentum, even when traversing very steep slopes. Two steering units 1 are shown attached to the chassis 13 of a trolley 12 in Fig. 4. The trolley 12 has a handle 16 which is a continuous curve. The distance to which the handle 16 extends from the body of the trolley is limited to a size suitable to allow stacking of such trolleys end-to-end in the usual linear fashion. When loaded, the weight of the trolley 12 bears upon the steering unit 1 and the wheels 14 swivel with the piston rod 4, until the grooves 6 engage the dogs 8 to fix the wheels 14 in a forward position. The locked wheel 14 will not deviate from the desired direction by more than one degree. However, should the user wish to release the locked wheel 14, this can be accomplished simply by raising the front of the trolley 12 or pressing down on the trolley handle 16 which is to the rear of the chassis 8, so that the front of the trolley 12 is raised slightly, thus separating the collar 7 and flange 5. Similarly, the wheels 14 unlock when the front of the laden trolley 12 is "snatched" sideways. The steering unit 1 may be manufactured in any suitable material such as metals or plastics or any combination of these as desired. The operating handle 16 of the trolley 12 with the steering unit 1 attached is curved to aid steering of the trolley and is more comfortable to use by being ergonomically suitable. Modifications and improvements may be incorporated without departing from the scope of the invention.

Claims: CLAIMS: 1. A steering unit for a trolley, comprising first and second members, said first member adapted to be fixed on the trolley, said second member attachable to a wheel of the trolley and connected to said first member for rotation with respect to said first member, and means provided to lock the two members in a predetermined position under load. 2. A steering unit for a trolley as claimed in Claim 1, wherein said second member is at least partially rotatable within said first member. 3. A steering unit for a trolley as claimed in Claims 1 or 2, wherein said predetermined position is determined by the two members being shaped to interlock in said predetermined position. 4. A steering unit for a trolley as claimed in any one of Claims 1 to 3, wherein said first member comprises a hollow casing, attachable at one end to the trolley chassis and sealed at the other end to form a receptacle for the second member. 5. A steering unit for a trolley as claimed in Claims 1 to 4, wherein said second member comprises a longitudinal member spring-loaded to bear against the first member when under load. 6. A steering unit for a trolley as claimed in Claim 5, wherein the longitudinal member has a flange mounted upon it, said flange having grooves which are shaped to fit dogs provided on the receptacle, and so interlock the first and second members when engaged. 7. A steering unit for a trolley as claimed in Claim 5, wherein the longitudinal member is spring-loaded by a helical spring attached to the sealed end of the receptacle and bearing against the longitudinal member. 8. A steering unit for a trolley as claimed in Claim 5, wherein the longitudinal member is spring-loaded by a disc spring attached to the sealed end of the receptacle and bearing against the longitudinal member. 9. A steering unit for a trolley as claimed in any one of Claims 4 to 8, wherein the casing is sealed by a releasable cap to provide access to the interior of the casing. 10. A steering unit for a trolley as claimed in any preceding Claim, wherein the position of the second member, once interlocked with the first member, ensures that the wheel to which the second member is attached is directed to run in a forward direction. 11. A trolley comprising a chassis and handle and front wheels each having a steering unit as defined in any preceding Claim. 12. A trolley as claimed in Claim 10, wherein the handle extends across the rear of the trolley in a continuous curve and is positioned at an angle and distance which allows the standard stacking of such trolleys.

Inventors: GRANTHAM JOHN, GRANTHAM, JOHN
Applicants: GRANTHAM JOHN, LOVIE MICHAEL ALEXANDER, GRANTHAM, JOHN, LOVIE, MICHAEL, ALEXANDER
Application year: 1990
Main classification: B60B33
IPC codes: B60B33, B62B3