GB2249949A - Bali castor - Google Patents

Abstract

A castor block for furniture is disclosed comprising a unitary plastic moulding and a ball (10). The ball (10) fits in a boss (14) extending from one side of the lateral plate (12) and on the other side a number of flanges (16, 18, 20) are provided for enabling the castor to be attached to the piece of furniture and increase the impact and load strength of the castor. The furniture castor is thus of a simple construction, moulded in one piece, is relatively inexpensive, yet provides the requisite strength and stiffness unlike castors known to date. <IMAGE>

Description

CASTOR BLOCK The present invention relates to a support block integral with a furniture castor.

Furniture castors provided on pieces of furniture are extremely well known in the art for enabling furniture to be slid across a floor. One type of castor well known in the art comprises a shaft to which a wheel is axially connected. The shaft passes through a hole in the wooden structure of the furniture. The main problem associated with these types of castors are that they are prone to impact damage and secondly excessive wear often occurs on the shaft hole causing the castor to become loose which may become irresplacably detached from the piece of furniture.

Castors provided at the corners of a piece of furniture are extremely labour intensive to manufacture, since wood blocks must be attached to the structure of the furniture. Typically, a furniture manufacturer producing 2000 suites per week would require 24,000 corner block castor assemblies per week. A standard corner block castor assemblies can be fitted to many different types of furniture. It has been proposed that a standard corner block castor assembly could be moulded or pressed from a material, such as plastic or metal, in order to eliminate the requirements for wood machine operatives to fit corner block castor assemblies.

Two examples of known plastic moulded castor assemblies are disclosed in U.S. Patent No. 2690584 and French Patent No. 904179. However, both of these castors, and others known in the art, are relatively complicated leading to an increase in manfacturing costs. Furthermore, both of these castors include a rotatable ball housed within a boss such that contact is maintained between the upper part of the ball and the internal surface of a boss. In order to minimise friction and increase the glidability of the castors, it is necessary to keep the uppermost portion of the ball out of contact with the rest of the caster assembly.

An aim of the present invention is to provide a castor block comprising a unitary plastic moulding which is relatively simple, with the minimal number of separate components, is inexpensive and reliable, yet affords sufficient impact resistance and strength to meet British Standard BS4875.

Accordingly there is provided a castor block comprising a unitary plastic moulding and a ball, wherein the moulding comprises a plate having a boss projecting on one face of the plate, the boss having a recess and an annulus for receiving the ball therebetween and for enabling at least part of the ball to project from the boss.

Features of the preferred embodiment are defined in the appended dependent claims.

By way of example only, a preferred embodiment of the present invention will now be described with reference to the accompanying drawings, of which: Figure 1 is a schematic plan view of the struture of a piece of furniture having a castor block according to the preferred embodiment disposed in one corner; Figure 2 is a schematic perspective view of the preferred embodiment; Figure 3 is a series of an upper plan view, side view, lower plan view and two cross-sections of the unitary plastic moulding shown in figure 2; and Figure 4 is an enlargement of section A-A of figure 3.

As shown figure 1, the structure of a piece of furniture comprises a pair of solid timber front and rear bars (2, 4) connected together by 15mm chipboard side panels (6). A castor block (8), of the preferred embodiment is designed to fit a perpendicular joint between the side panels (6) and bars (2, 4).

The castor block (8) comprises a unitary plastic moulding and a ball (10) as shown in figure 2 . The moulding comprises a plate (12) having a boss (14) extending from one face and from the other face a pair of perpendicularly disclosed flanges (16), a diagonal flange (18) between the two perpendicular disposed flanges (16) and an outer flange (20).

As shown in figures 3 and 4, the boss (14) is capable of receiving the ball (10). The ball is retained in the boss (14) by way of a lip (22).

The preferred embodiment comprises a lip disposed at 30 degrees to the vertical which enables the unitary plastic moulding to be easily removed from its manufacturing tool yet enables the ball (10) to be retained in a snap-fit manner.

The boss (14) also includes an angled ring or annulus (24).

The internal dimensions of the boss (14) enable the ball to fit snugly between lip (22) and annulus (24). It also enables the upper portion of ball (10) when in use not to be in contact with anything else.

The internal diameter of the annulus (24) is also critical so that the castor is capable of withstanding sufficient load yet strong enough to prevent the ball (10) from passing therethrough. The incompatible criteria of minimising friction yet providing sufficient support results in the annulus (24) having a relatively large inner diameter but also a relatively large depth.

The flanges on the unitary moulding provide two functions, they increase the strength of the castor and also enable the castor to be attached to the furniture structure. Side panels (6) are gripped by a compression force between the outer flange (20) and one of the perpendicular disposed flanges (16). The solid timber bars (2) and the side panel (6) are attached to respective perpendicularly disposed flanges (16). This provides a relatively rigid and strong attachment between the castor and the structure. The coupling is further increased by stapling the bar (2) or side panel (6) to the flanges. To improve fitting of the castor block on the structure, an undercut (26) is provided between the plate (12) and perpendicular flanges (16).

The outer flange (20) is preferably tapered to minimise any visual effects, since the material covering the piece of furniture passes over the outer flange (20) and is secured on the underside of plate (12).

Other types of attachment to the side panels (6) have been proposed. However, the outer flange (20) means that a single moulding can be used for the furniture castor unlike other types of attachment proposed. However, due to the presence of the outer flange (20), the moulding is then asymetric which means that two different mouldings are required for all of the corners of a piece of furniture.

Many features have been included in the castor in order to improve its impact and stiffness characteristics. For example, boss (14) is disposed on one face of the plate (12) directly opposite the space enclosed by the perpendicularly disposed flanges (16) and diagonal flange (18). Also, plate (12) extends beyond the flanges providing greater load support.

Diagonal flange (18) has a slightly thicker wall than the other flanges since it has been found that it is particularly important in providing adequate transverse strength. Preferably, the ball (10) is solid and along with the unitary plastics moulding is maufactured from polypropylene.

The aforegoing description has been given by way of example only and modifications may be made without departing from the scope of protection as claimed in the following claims.

Claims (10)

1. A castor block comprising a unitary plastic moulding and a ball, wherein the moulding comprises a plate having a boss projecting on one face of the plate, the boss having a recess and an annulus for receiving the ball therebetween and for enabling at least part of the ball to project from the boss.

2. A castor block as claimed in claim 1 in which the recess comprises a lip disposed at the free end of the boss and projecting therein.

3. A castor block as claimed in claim 1 or claim 2 further comprising at least two first flanges projecting from the other face of the plate.

4. A castor block as claimed in claim 3, in which said first flanges are disposed at right angels to each other.

5. A castor block as claimed in claim 4, further comprising a second flange disposed on the other face of said plate and coupled to both of the first flanges thereby forming a triangle.

6. A castor block as claimed in claim 5, in which said boss is disposed opposite to but within said triangle.

7. A castor block as claimed in any one of claims 3 to 6, further comprising a third flange disposed parallel to one of the first flanges for receiving a structural member of the piece of furniture therebetween.

8. A castor block as claimed in claim 7, in which said third flange is tapered.

9. A castor block as claimed in any one of the preceding claims in which said castor block is a corner castor.

10. A castor block substantially as hereinbefore described with reference to any one of figures 2 to 4.