Control wheel assembly for trolleys

A trolley control wheel assembly adapted to be fitted to a trolley having a longitudinal axis of travel includes (1) an array of castors; (2) a fixed wheel or wheels adapted to be positioned at or near the load center of the trolley or at or near the center of the array, and (3) a bias means and a damping means to provide controlled contact between the wheel or wheels and a surface on which the trolley is intended to travel. The bias means and the damping means may jointly comprise a gas strut.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS Referring to FIGS. 1 and 2 there is shown schematically a preferred control wheel assembly 10 made in accordance with the invention. The assembly 10 includes wheel means 11 (comprising a single wheel in FIG. 2 a and a pair of wheels, each able to rotate independently, in FIG. 2 b ) free to rotate only about rotational axis 12 , mounted by bracket 13 on to a telescopic member 14 comprising two square tubular sections 15 and 16 made such that section 15 is able to freely slide within section 16 . Mounted within the telescopic member 14 is a gas strut 17 attached to the tube sections 15 and 16 by attachment flanges 18 . The gas strut 17 provides damped bias to the telescopic movement between the tube sections 25 and 16 and thus to the wheel 11 . Mounting flange 19 is provided to permit attachment of the assembly to a trolley (not shown). The assembly may also include a lifting lug 20 , where the assembly is to be attached to a nestable trolley such as a shopping trolley to permit (as will be described later) the control wheel to be lifted to permit a single trolley or a group of nested trolleys to be easily manoeuvred in a direction lateral to the normally desired direction of travel. In the case of a trolley not designed to nest there may be provided a lever mechanism (not shown in detail) which can engage lifting lug 20 to raise the wheel 11 from contact with the floor or travel contact surface. The assembly may be readily fixed to a trolley to provide excellent control of the trolley in the longitudinal direction of the trolley, that is in the direction of travel of the control wheel, whilst still permitting the trolley to be manoeuvred sideways as required depending on the nature of the floor surface on which the trolley is situated. Referring to FIGS. 3 and 4 there is shown a trolley 30 including a control wheel assembly 10 as described in detail above in relation to FIGS. 1 and 2 . The trolley includes a frame 31 provided with shelves 32 and has a base 33 fitted with an array of four castors 34 fixed at or near the corners of the base 33 as is well known in the art. The control wheel assembly 10 is mounted at the centre of the array, equidistant from each of the castors 34 . The control wheel assembly 10 is attached to the base 33 by means of the mounting flange 19 . The control wheel assembly 10 controls the direction of travel of the trolley 30 over and above any influence of any one or more of the castors 34 . Referring to FIG. 5 there is shown an alternative construction of trolley 30 as shown in FIGS. 3 and 4 , wherein like numbers identify like parts, in which there are two separately mounted control wheel assemblies 10 a and 10 b attached to the base 33 of the trolley 30 . The dual control wheel assembly controls the direction of travel of the trolley 30 over and above the influence of any one or more of the castors 34 . Two control wheel assemblies such as have been described may be necessary if the trolley is carry heavy loads on slippery, polished or wet and/or inclined surfaces. Referring to FIGS. 6 and 7 there is shown a supermarket trolley 40 having a base frame 41 and a basket 42 with a handle 43 affixed thereto. The base frame includes posts 44 to connect the base frame 41 to the basket 42 . The base frame 41 is in plan view, best seen in FIG. 7 , of a “double J” form with one side frame section 41 a of the base frame 41 a mirror image of the other side frame section 41 b of the frame. The frame 41 is fitted with an array four castors 45 affixed at or near each corner of the baseframe as is well known in the art. The side frame sections frames 41 a and 41 b have a control wheel assembly 10 (as described in detail above with reference to FIGS. 1 and 2 ) affixed thereto by means of the mounting plate 19 near their ends 46 a and 46 b. The ends 46 a and 46 b of the side frame sections 41 a and 41 b on a trolley are turned down for reasons which will become apparent in the following. The control wheel assembly, as previously being biased downwards; controls the direction of travel of the trolley 30 over and above the influence of any one or more of the castors 34 . Referring to FIGS. 8 and 9 there is shown a number of shopping trolleys 40 ( 40 a, 40 b, 40 c, . . . ) which are as described in relation to FIG. 6 and 7 , and in which like numbers identify like parts. A group of trolleys 50 are nested together (as is the usual requirement for such trolleys) for compact storage and transport. Each of the trolleys includes, as described above in relation to FIGS. 6 and 7 , a control wheel assembly 10 . The ends 46 a and 46 b of the side frame sections 41 a and 41 b on the trolleys are turned to slope downwards to form a ramp configured so that the ramp on one trolley engages the lifting lug 20 on another trolley and raises the wheel of the control wheel assembly against the action of the bias means to lift the control wheel from engagement engage with the ground or travel surface. This allows the group of shopping trolleys to be moved as a whole without the hindrance of the control wheel assemblies of all of the trolleys in the group. The trolley of FIGS. 3 and 4 may preferably include a lever mechanism (not shown) to optionally engage a lifting flange to lift the wheel of the control wheel assembly from contact with the floor, ground (or other surface on which the trolley is to be used) so that the trolley can be readily moved sideways to enable the trolley to be parked in a confined space, for example. Whilst we have described preferred embodiments of the invention herein it will be realised by those skilled in the art that many variations may be made to the invention as particularly described without departing from the scope of the invention broadly disclosed. For example it will be appreciated that the control wheel assembly of the invention does not have to be positioned exactly at the centre of the array of castors. The control wheel assembly should, for ease and evenness of control, be laterally in the middle of the trolley. The position of the control wheel assembly longitudinally on the trolley is of lesser importance and may be determined by the load centre of the trolley or by the centre of the array of castors. Preferably the two points coincide although for purpose built assymetrical trolleys, this may not be the case. The control wheel is, as previously disclosed, “fixed” in that the wheel cannot rotate about a vertical axis as a castor is able. The wheel is able to rotate about it's normal horizontal rotational axis and is “fixed” to do so in the direction in which it is normally desired that the trolley proceed. In most cases in a trolley having a substantially rectangular base or castor array, the wheel is fixed and able to rotate in the longitudinal direction (as against the transverse direction) of the trolley and is at the centre of the array of castors.