Title of Invention

A CASTOR

Abstract

A castor for shopping and hospital trolleys which provides enhanced steering and manoeuvrability of the trolley, wherein a fork (13) of the castor is freely rotatable on a first bearing (15) with respect to a first member (16) connected to the fork (13), while the first member (16) is also freely rotatable on a second bearing (20) with respect to a second member (21) connected to the first member by a bolt (17). The second member may be connected to a frame or chassis (24) of a load bearing object such as a trolley. (FIG. - 1)

Full Text

A CASTOR This invention relates to castors. Many mobile devices such as shopping and hospital trolleys are manoeuvrable on four such castors, usually one at each corner, and such devices are notorious for their inability in certain circumstances to permit the trolley to be steered and manoeuvred easily, particularly when heavily loaded and when it is required to direct the trolley around corners. This difficulty arises largely through the inability of the castors to rotate freely about their upright axes. DE 19741742 and GB 1008550 disclose castors. The present invention defines an arrangement in which, inter alia, the central bolt or rivet is freely rotatable relative to the fork and the bearing assembly. Thus, there are at least three independent rotatable parts. In a preferred embodiment, there are four including the fork, the first member, the second member and the bolt, whilst in another embodiment there are three, the fork, the second member and the bolt. In DE 19741742 or GB 1008550, the central bolt is not rotatable and this applies to all hitherto known castors. The rotatable bolt is the key feature which provides enhanced manoeuvrability when compared with conventional castors. It is an object of the present invention to provide a castor with increased freedom of rotation about the upright axis in which it is mounted on the frame or chassis of the trolley. Typically, such castors are mounted on a thrust bearing which may be subject to contamination or wear such that the relatively movable parts of the bearing assembly tend to become stiff, or excessively loose thus to become misaligned. According to the present invention, there is provided a castor comprising a fork having a pair of lobes between which extends a transverse axle carrying at least one wheel rotatable thereon, and a connection member for connecting the castor to a frame or chassis of an object such as a trolley, the wheel and the connection member being connected together by at least one bolt or rivet and a bearing assembly; characterised in that the bolt or rivet is freely rotatable on the bearing assembly; in that the fork is freely rotatable relative to the bearing assembly; and in that the fork and the bolt or rivet, are independently rotatable relative to one another. Preferably, the fork is freely rotatable on a first bearing with respect to a first member connected to the fork, and the first member is freely rotatable on a second bearing with respect to a second member connected to the first member, the second member being adapted for connection to a frame or chassis of a load bearing object such as a trolley. Preferably, the first and second bearings are on aligned axes. The castor may comprise three or more roller or ball bearings. The first bearing may be a thrust bearing. The first bearing may be a journal bearing. The second bearing may be a journal bearing. The second member may be welded to the frame or chassis. The fork, first member and second member may be held in aligned assembly by a single central bolt or rivet. The first member may include a bearing axially aligned with the axis of rotation of said first member. The second member may comprise a pair of axially aligned bearings each axially aligned with the second member. The single central bolt or rivet may be independently rotatable with respect to the fork and the second member. Embodiments of the invention will now be described, by way of example only, with reference to the accompanying drawing, in which: Fig. 1 is a part-sectional elevation of a castor made in accordance with a first embodiment; and Fig. 2 is a similar view of a castor made in accordance with a second embodiment. Referring to Fig. 1, there is provided a castor wheel 10 mounted on a transverse axle 11 extending between a pair of lobes 12 of a fork generally indicated at 13. A cross plate 14 at the top of the fork is connected via a thrust bearing 15 having ball races 15a, 15b to a first upright member 16 by means of a bolt 17 the shaft of which extends upwardly through the entire bearing assembly to be secured by a self-locking nut 18. By the term "thrust bearing" is meant a bearing wherein, in use, a load applied thereto is borne by the balls or rollers thereof in an axial direction with respect to the bolt 17. Surrounding the shaft of the bolt 17 within the first upright member 16 is a first concentric ball or roller journal bearing 20 having inner and outer races 20a and 20b. Thus, the fork 13 is freely rotatable on the bearing 15 about the vertical axis of the bolt 17 with respect to the first upright member 16, and the latter is also freely rotatable on the bearing 20 about the axis of the bolt 17. By the term "journal bearing" is meant a bearing wherein, in use, a load applied thereto is borne by the balls or rollers thereof in a radial direction with respect to the bolt 17, with or without some axial bearing direction. Also mounted on the shaft of the bolt 17 above the first upright member 16 is a second upright member 21. This member is mounted on a pair of axially aligned ball or roller journal bearings 22 and 23 having, respectively inner and outer races 22a, 22b and 23a, 23b, such that the cylindrical wall of the second upright member 21 is freely rotatable on the bearings 22 and 23 with respect to the bolt 17, to the first upright member 16 and to the fork 13. Welded or otherwise attached to the cylindrical wall of the second upright member 21 is a frame member 24 of a trolley or other load bearing object. Grease seals 25 are provided on bearings 20, 22 and 23 and a dust cap (not shown) may be mounted on the top of the bearing assembly. It will therefore be seen that the fork 13, the first upright member 16 and the second upright member 21 are all freely rotatable relative to one another thus providing entirely free rotation of the castor with respect to the frame member 24. If required, the upright axes of rotation of the first upright member 16 and the second upright member 21 may be displaced by the interposition of a horizontal plate attached to one or other of the upright members and rotatable with respect to the other such upright member upon a thrust bearing or the like. Preferably, however, all axes of rotation are aligned thus ensuring complete freedom of rotary movement of the respective parts of the assembly. Referring to Fig. 2, the thrust bearing 15 of the aforementioned embodiment is omitted and replaced by a casing 30 fixed by welding to the top of the fork 31, and in which is located first and second journal bearings 32 and 33 having, respectively, inner and outer races 321, 32b and 33a, 33b. The head of a bolt 34 bears against the bottom surface of inner race 32a and the shank passes upwardly through the entire bearing assembly to be secured by a self-locking nut 35. Third and fourth bearings 36 and 37 located in a sleeve 38 replace the assembly of parts 22, 23 and 21 of Fig. 1. Spacers 39 support the inner races of the bearings within the assembly. In this embodiment, therefore, the fork 31 is freely rotatable on journal bearings 32 and 33 with respect to the bolt 34, as is sleeve 38 on journal bearings 36 and 37 with respect to bolt 34 and fork 31. Bolt 34 is similarly rotatable independently. Once again, a leg or frame member 40 of a trolley or other object may be attached by welding or other means, to the sleeve 38. A dust cap 41 may be fitted to the top of sleeve 38. In the embodiments of Figs. 1 and 2, the trolley or the like mounted on or connected to sleeve 21 or 38 is manoeuvrable on two or more bearings which interact in series to afford the castor entirely free rotational movement which does not rely on a single thrust bearing as typically found in conventional castors where movement can be inhibited by wear of the axial load-bearing races. Considerably improved stability and free manoeuvrability are afforded by a castor made in accordance with the invention. I CLAIM : 1. A castor comprising a fork (13) having a pair of lobes (12, 31) between which extend a transverse axle carrying at least one wheel (10) rotatable thereon, and a connection member (21, 38) for connecting the castor to a frame (24, 40) or chassis of an object such as a trolley, the wheel (10) and the connection member (21, 38) being connected together by at least one bolt or rivet (17, 34) and a bearing assembly (15, 20, 22, 23, 32, 33, 36, 37); characterised in that the bolt or rivet (17, 34) is freely rotatable on the bearing assembly; in that the fork (13) is freely rotatable relative to the bearing assembly; and in that the fork and the bolt or rivet, are independently rotatable relative to one another. 2. A castor as claimed in claim 2 wherein the fork (13) and the connection member (21, 38) are connected together by said at least one bolt or rivet (17, 34) and the bearing assembly, and wherein the fork, the connection member and the bolt or rivet are all independently rotatable. 3. A castor as claimed in claim 1 wherein the fork (13) is freely rotatable on a first bearing (15) with respect to a first member (16) connected to the fork; the first member (16) is freely rotatable on a second bearing (20) with respect to a second member (21) connected to the first member (16); the second member (21) being adapted for connection to a frame (24) or chassis of a load bearing object such as a trolley. 4. A castor as claimed in claim 3 wherein the first and second bearings are on aligned axes. 5. A castor as claimed in claim 1 wherein the bearing assembly has three or more roller or ball bearings. 6. A castor as claimed in claim 3 wherein the first bearing (15) is a thrust bearing. 7. A castor as claimed in claim 3 wherein the first bearing (32, 33) is a journal bearing. 8. A castor as claimed in claim 2 wherein the second bearing (20, 36, 37) is a journal bearing. 9. A castor as claimed in claim 3 wherein the second member (21) is welded to the frame or chassis. 10. A castor as claimed in claim 3 wherein the fork (13), the first member (16) and the second member (21) are held in aligned assembly by a single central bolt or rivet (17). 11. A castor as claimed in claim 3 wherein the first member (16) includes a rotational bearing (15a) axially aligned with the axis of rotation of said first member. 12. A castor as claimed in claim 3 wherein the second member (21) comprises a pair of axially aligned rotational bearings (22, 23), each being axially aligned with the second member. 13. A castor as claimed in claim 9 wherein the single central bolt or rivet (17, 34) is independently rotatable with respect to the fork (12, 31) and the second member (21,38). A castor for shopping and hospital trolleys which provides enhanced steering and manoeuvrability of the trolley, wherein a fork (13) of the castor is freely rotatable on a first bearing (15) with respect to a first member (16) is also freely rotatable on a second bearing (20) with respect to a second member (21) connected to the first member by a bolt (17). The second member may be connected to the frame or chassis (24) of a load bearing object such as a trolley.

Documents:

640-KOLNP-2005-CORRESPONDENCE.pdf

640-KOLNP-2005-FORM 27.pdf

640-kolnp-2005-granted-abstract.pdf

640-kolnp-2005-granted-claims.pdf

640-kolnp-2005-granted-correspondence.pdf

640-kolnp-2005-granted-description (complete).pdf

640-kolnp-2005-granted-drawings.pdf

640-kolnp-2005-granted-examination report.pdf

640-kolnp-2005-granted-form 1.pdf

640-kolnp-2005-granted-form 18.pdf

640-kolnp-2005-granted-form 3.pdf

640-kolnp-2005-granted-form 5.pdf

640-kolnp-2005-granted-gpa.pdf

640-kolnp-2005-granted-letter patent.pdf

640-kolnp-2005-granted-reply to examination report.pdf

640-kolnp-2005-granted-specification.pdf