AU765527B2

AU765527B2 - Friction plate

Info

Publication number: AU765527B2
Application number: AU32343/99A
Authority: AU
Inventors: John Cameron
Original assignee: Madad Pty Ltd
Current assignee: Madad Pty Ltd
Priority date: 1999-06-01
Filing date: 1999-06-01
Publication date: 2003-09-18
Anticipated expiration: 2019-06-01
Also published as: AU3234399A

Description

P/00/01i1 Regulation 3.2

AUSTRALIA

Patents Act 1990 4* .4 4 4 4. 4* 4. .4 4 4 44 4. 444 4.

4.

4 4

ORIGINAL

COMPLETE SPECIFICATION STANDARD PATENT Invention Title: "FRICTION PLATE" The following statement is a full description of this invention, including the best method of performing it known to us: THIS INVENTION relates to an accessory by which to attach a first member such as a castor on a leg, to a second member such as a furniture base. The invention finds particular application in the application of castors to beds.

It is known to fit castor wheels to beds, typically on short legs, usually fitted with a threaded rod, extended axially, for screwing into a fitting applied at the base of the bed. The top of a ~:castor leg is screwed hard up against the base of the bed. Friction between the top of the leg and the base of the bed acts to resist rotation that would undo the screwed connection. Over time the leg does rotate and the leg loosens.

::oooIt is known to fit a friction plate between the base of the bed and the top of the leg, with the intention of increasing the friction 0000 therebetween and better preventing unwanted rotation. It is known to provide the friction plate with a ratchet whose teeth catch, in use, on a castellated rim at the top of the leg. The friction plate acts to increase the surface area in contact with the base of the furniture and that way increases the degree of that friction therewith which resists rotation. Whilst this is an improvement, there is the need to apply the additional castellation to the top of the leg, and then each leg and respective friction plate are a complementary pair. The consequence of this is that separate friction plates need to be created for each differently dimensioned leg. The foregoing arises in the need for the castellation and the teeth of the ratchet to meet in order that the desired effect be achieved. A friction plate designed for interaction with one leg may not interact effectively with another differently configured leg. This increases the inventory of parts needed to be stocked by manufacturers, and provision of the castellation adds to those fabrication costs which are associated with the moulds by which to form the leg.

It is an object of the present invention to provide an improved friction plate, a friction plate which is operative across a .10 range of leg designs so as to effect a reduction in a parts inventory and/or to simplify the moulding of the leg which is to engage with the friction plate.

The invention achieves its object in provision of a friction plate by which to hold a first member, mounted to a second member in use, via a screw, against rotation of the first member relative to the second member comprising a plate-like means to be interposed between the first and second member; a hole provided in the platelike means; and a ratchet built on the plate-like member around the hole; the ratchet teeth dimensioned such as to engage, in use, with radially extended ribs in the top of the first member.

The friction plate of the invention is ideally one wherein the ratchet encircles the hole and is concentric therewith. The friction plate is ideally formed as a plastic moulding. The plate dimensions 4 are chosen to create adequate friction in use. The teeth of the ratchet are preferably regularly angularly spaced and configured with a valley therebetween in which to receive the rib. The hole of the friction plate is preferably provided in a tubular extension whose axis is generally perpendicular to the plane of the plate-like means and the ratchet teeth are ideally stood off the plate on a cylindrical flange.

The axial dimension of the extension is best sufficient to provide a degree of stability against twist when fitted over a threaded rod on .the top of the first member. The height of the flange that stands the 10 ratchet off the plate-like mneans is sufficient to reach into the top of the first member sufficient to engage with the radial ribs provided therein. The teeth of the ratchet on the flange are ideally configured with a valley floor therebetween in which the radial rib of a leg may nest in use.

In use of the invention the ratchet teeth ideally work with radially extended ribs in the top of a hollow leg so as to hold the leg against rotation by means of the increased contact with the base of the furniture which is generated by the friction plate. The friction plate is an interacting accessory which is interposed in use, to work with a screwed fitting against undesired rotation which might otherwise loosen it.

The invention will now be described with reference to a preferred embodiment as shown in the accompanying drawings in which:

V

FIG. 1 is a plan view of a friction plate in accordance with the invention; FIG. 2 is a section through the friction plate of FIG. 1; FIG. 3 is a side view of the friction plate which is seen in each of FIGS. 1 and 2; and FIG. 4 is a view of the top of the leg of a castor which may held in place by means of the invention.

In FIG. 1 is seen a friction plate 10 with a ratchet 11 ideally located around and preferably encircling a bore or hole 12 in a 10 substantially plate-like means or body. In this specification a ratchet is intended to include means fitted with a series of inclined teeth which are operative to enable sliding motion, in a first direction, of an element engaged therewith, the teeth being effective to resist movement of the element relative to the ratchet in a second opposed direction. The friction plate may be formed in a suitable plastic material by a process of moulding, as will be clear to those skilled in the art. The dimensions of the surface of the plate-like member which is in contact with the base of the second member are ideally chosen so as to create increased or adequate friction therebetween, in use. Ideally the ratchet teeth might regularly spaced and ideally they may be angularly spaced by 150. The spacing will be determined in the main with that feature of the first member they are to interact with. In practice the ribs of a standard form of castor leg are such that 150 is ideal.

6 In FIG. 2 is seen a central hole 12 with a generally tubular extension 13, axially aligned at right angles to the plate-like body of the friction plate. The ratchet teeth are stood off the surface of the plate-like body on a substantially cylindrical flange or rim The axial dimension or extent of the extension 13 might be determined so as to provide a degree of stability against twist when slid over the threaded rod on the top of the leg it works with. The extent of the flange may be set so as to reach into the top of the leg sufficient to engage with the radial ribs which are generally recessed therefrom.

In FIG. 3 is seen the teeth 16 of the ratchet, configured with a complementary valley 17 behind, in which the radial rib of a leg may nest in use.

In FIG. 4 is seen a typical castor on a supporting leg.

From the top of the leg 18 projects or extends a threaded rod 19, ideally projected from a central locating stem 21, extending through the hollow of leg 18, reinforced or supported therein by ribs 23. The ribs 23 may extend inwardly into the hollow of the leg from a point therein which is below or recessed from the leg top 22. This form of leg is well known. The teaching of the invention is that the ribs of such legs can be made use of as the means by which to engage with a friction plate so that the previously used castellation might be abandoned. The ratchet can work at a variety of points along the *IIIIIU.- Y~iln- I)tCI.IY~I~ .I .trrr;*r rY.i*rrr*;oluri*lr~.*.. i- i.;~*h.~x~ilr~niuini*_jc~.i~-~.ivni 7 radial extent of the rib so that a single friction plate can be used with a range of leg dimensions and the number of sizes which need to be stocked is reduced.

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Claims

2. A screwed member fixed by means of a screw and associated friction plate as claimed in claim 1 wherein the f irst member is formed with radially extended ribs in its top, the ratchet encircles the hole and is concentric therewith being axially extended to engage with the ribs.
3. A screwed member and friction plate as claimed in claim 2 wherein the teeth of the ratchet are regularly angularly spaced and configured with a valley therebetween in which to receive the rib. 9
4. A screwed member and friction plate as claimed in claim 2 wherein the hole is provided within a tubular extension whose axis is perpendicular to the plate-like member and the ratchet teeth are stood off the plate on a cylindrical flange. A screwed member and friction plate as claimed in claim 4 wherein the height of the flange over the plate-like member is ~:sufficient to reach into the top of the screwed member sufficient to engage with the radial ribs provided therein.
6. A screwed member and friction plate as claimed in claim wherein the teeth of the ratchet on the flange are configured with a valley floor therebetween in which the radial rib of a leg may nest in
7. A screwed member and friction plate as claimed in claim 2 wherein a castor depends from an end of the screwed member which is provided with a threaded rod projected from a second end from a central stem extending through a hollow therein and reinforced by ribs.
8. A screwed member and friction plate as claimed in claim 7 wherein the ribs are radial and are recessed from the second end of the first member.
9. A friction plate by which to hold a first member, mounted to a second member in use, via a screw, against rotation of the first member relative to the second member substantially as hereinbefore described with reference to the accompanying drawings. A screwed member and friction plate substantially as hereinbefore described with reference to the accompanying drawings. DATED this First day of June 1999. MADAD PTY LTD By their Patent Attorneys FISHER ADAMS KELLY ~l~jli~lPC-LUT i~C~T~h~: