GB2256249A

GB2256249A - Hollow door or cavity wall fixing

Info

Publication number: GB2256249A
Application number: GB9111828A
Authority: GB
Inventors: Robert John Lawrence
Original assignee: Individual
Current assignee: Individual
Priority date: 1991-06-01
Filing date: 1991-06-01
Publication date: 1992-12-02
Also published as: GB9111828D0

Abstract

A cavity wall fixing comprises a screw threaded shaft 10 and an elongate clamping member 12 connected to the screw threaded shaft and pivotable between an insertion position in which the axis of the clamping member 12 lies generally parallel to the shaft axis 10 and a retention position (Figure 3) in which the clamping member 12 lies transverse to the axis of the shaft 10. The clamping member 12 has an aperture through which the screw threaded shaft passes, and the lateral edges 18, 20 defining the aperture engage with the threads of the shaft when the member is in the retention position but not when the member is in the insertion position. The clamping member 12 is pivoted to the shaft 10 by means of a wire loop around the shaft 10 and extending through a hole in the clamping member 12. <IMAGE>

Description

Title Cavity Wall Fixing Field cf the invention The present invention relates to a fixing for enabling fixtures to be secured to a cavity wall.

Background of the invention The difficulty experienced in securing a fixture to a cavity wall is well known and various fixings are already available which provide a solution to the problem. The fixings have in common a clamping member which can pass through a hole in the wall and change its shape or attitude after entering the wall cavity to engage the cavity side of the wall and enable the fixture to be secured firmly by clamping the wall between the member and the fixture.

In one known fixing, a plastics plug for a screw is inserted in the hole and has a section designed to collapse within the cavity. On collapse, this section spreads radially to prevent the plug from being withdrawn from the hole and to act as a clamping member. A disadvantage of such a fixing is that it relies on a screw engaging in a plastics plug for its strength and this on certain occasions is insufficient to cope with the weight of the fixture.

In another known fixing, a bolt is threaded into a nut on which is pivoted a rigid elongate member. The elongate member can be aligned parallel to the bolt for insertion into a hole in the wall and on entering the cavity can swivel about the nut into a position parallel to the rear side of the wall and at right angles to the bolt. In this case, the hole in wall has to be significantly larger than the diameter of the bolt so that the nut and the elongate member can pass through it. Furthermore, the strength of the fixing relies on the pivot between the nut and the elongate member. If the elongate member should be deformed by the weight of the fixture, the nut can separate from the clamping member.

Still more complicated cavity wall fixings are known with two spring biased clamping members pivoted on a nut. The members can lie parallel to the bolt for insertion through a hole in the wall and automatically spring-apart on reaching the cavity. These fixings suffer from--the same problem as discussed above in that the strength of the fixing relies on the pivots between the nut and the pivoted clamping members and the hole for the fixing must be significantly larger that the bolt diameter.

Obiect of the invention The present invention seeks to provide a fixing having a screw threaded shaft and a clamping member pivotable relative to the shaft, which can be inserted through hole only slightly larger in diameter than the screw threaded shaft and in which the strength of the fixing does not depend on the pivot between the clamping member and the screw threaded shaft.

Summary of the invention According to the present invention, there is provided a cavity wall fixing comprising a screw threaded shaft and an elongate clamping member connected to the screw-threaded shaft and pivotable between an insertion position-in:Which the axis of the clamping member lies generally parallel to the shaft axis and a retention position'-i which the clamping member lies transverse to the axis f-fe shaft, wherein the clamping member has an aperture throüg Z hich the screw threaded shaft passes, and wherein the lateral edges defining the aperture engage with the threads of the shaft when the member is in the retention position but not when the member is in the insertion position.

In the fixing of the invention, the clamping member itself acts as the nut which engages the threaded shaft and its strength does not therefore depend on the pivoting connection between the shaft and the clamping member.

Furthermore, as the clamping member itself forms the nut engaging the threaded shaft, the outer diameter of the entire fixing need only be slightly larger than the diameter of the threaded shaft.

Preferred features of the invention Preferably, the clamping member is generally in the form of a tube with a transverse bore defining said aperture and an elongate cutaway portion in the tube wall extending from at least one end of the tube to the edge of the aperture. If two cutaway portions are provided, then they must be offset from one another to lie on opposite sides of the threaded shaft when the clamping member is in its insertion position.

Advantageously, the axis of the clamping member is slightly inclined to the plane normal to the shaft so that the contact pressure between the shaft and the edges of the aperture increases as the fixing is tightened.

The pivot is required only to guide the clamping to the correct position along the screw threaded shaft and once the fixing is tightened it serves no useful purpose. For this reason, it may be formed by one or two deformations in the tube wall engaging the threads or by a single loop of wire passing around the shaft and having one end passing through a hole in the side of the tube.

The clamping member may be formed from a tubular blank in which a bore is drilled and in which the cutaway is formed by milling or it may be formed from a flat sheet. In the latter case, the flat blank may be bent into a tube and seam welded or it may be deformed by-stamping to -be concave upwards on one side of the aperture and convex upwards on the other side of the aperture.

Brief description of the drawings The invention will now be described further, by way of example, with reference to the accompanying drawings, in which: Figure 1 shows a cavity wall fixing of the invention, Figure 2 is a partial side view of the fixing of Figure 1, and Figure 3 is a partial view of the fixing in its retention position.

The fixing in the drawings comprises a threaded shaft 10 and an elongate clamping member 12 which is loosely pivoted on it by means of a single turn of wire 22 of which at least one end is received in a hole bored in the clamping member 12. The loop of wire 22 ensures that as the shaft 10 is rotated, the clamping member 10 moves along the threaded shaft 10.

The threaded shaft 10 projects from the cavity wall when the fixing is in position and the wall is captured between the clamping member 12, which adopts the position shown in Figure 3 in the retention position of the fixing, and a washer 14 resting on a tightening-nut 16. A further washer 15 and lock nut 17 enable a fixture to be secured to the projecting end of the shaft 10. As an alternative, the threaded shaft 10 may be formed with a screw or bolt head.

To make the illustrated clamping member 12, a transverse bore is formed is drilled in a tube having an inner diameter only slightly larger that the outer diameter of the threaded shaft 10 and an elongate cutaway as wide as the threaded shaft is formed in the tube extending from the bore to the lower end of the clamping member as viewed in Figure 1. One such cutaway suffices to enable the clamping member to rotate when it reaches the end of the threaded shaft but the provision of two cutaways as illustrated is preferred as it allows the clamping member 12 to position in any position along the threaded shaft 10.

In use, a hole is drilled in the cavity wall and the clamping member is rotated manually to the position shown in Figure 1. The clamping member is inserted through the hole and on reaching the cavity, the shaft 10 is manipulated to cause the clamping member 12 to pivot slightly and prevent the threaded shaft 10 from being withdrawn from the hole. To this end, it is advantageous to ensure that the lengths of the clamping member on each side of the wire loop 22 are not of equal weight so that as the shaft 10 is rotated the clamping member tends to topple under its own weight into the position shown in Figure 3.

As the shaft 10 is turned using the nuts 16 and 17, the wire loop 22 advances up the thread. When the clamping member 12 reaches the rear face of the wall, it collides with the wall and this turns it counter-wise as viewed in Figure 3 until the edges 18 and 20 of the transverse bore formed in the clamping member 12 engage in the threads of the shaft 10.

At this point, the clamping member acts as a nut and it takes all the load on shaft as the latter continues to be tightened. When the nut 16 is tight, the wall is fully sandwiched between the washer 14 and the clamping member and all the tension in the shaft is taken by the engagement of the edges 18 and 18 with the threaded shaft, the wire loop 22 no longer serving any useful function.

As seen in Figure 3, the axis of the clamping member 12 is slightly inclined to the plane normal to the shaft 10 in the retention position so that the contact pressure between the shaft and the edges of the aperture increases as the fixing is tightened. This ensures a particularly strong connection which is effective even if the threaded is worn.

Unlike any other cavity wall fixing, it is possible to reuse a fixing of the invention. The shaft 10 is in this case unscrewed and pushed-in sufficiently for the clamping member 10 no longer to rest on the rear side of the wall. If the shaft thread is deformed at its end so that it cannot be withdrawn entirely from the wire loop 22, then when the clamping member reaches the end of the shaft 10 it will turn with the shaft and in one position it will naturally pivot into the aligned position shown in Figure 1 under the action of its own unbalanced weight. The fixing can therefore now be withdrawn from the wall without leaving behind the clamping member 12.

The clamping member may be formed from tubular metal stock or by bending an initially flat stamped blank. As a further possibility, the clamping member may moulded from a plastics material.

It will be clear that though termed a cavity wall fixing, the fixing of the invention is not restricted in its use to cavity walls and can be used in other circumstances such as in mounting fixtures on a hollow door.

Claims

1. A cavity wall fixing comprising a screw threaded shaft and an elongate clamping member connected to the screw threaded shaft and pivotable between an insertion position in which the axis of the clamping member lies generally parallel to the shaft axis and a retention position in which the clamping member lies transverse to the axis of the shaft, wherein the clamping member has an aperture through which the screw threaded shaft passes, and wherein the lateral edges defining the aperture engage with the threads of the shaft when the member is in the retention position but not when the member is in the insertion position.

2. A fixing as claimed in claim 1, wherein the clamping member is generally in the form of a tube with a transverse bore defining said aperture and an elongate cutaway portion in the tube wall extending from at least one end of the tube to the edge of the aperture.

3. A fixing as claimed in claim 2, wherein two cutaway portions are provided offset from one another to lie on opposite sides of the threaded shaft when the clamping member is in its insertion position.

4. A fixing as claimed in any preceding claim, wherein the axis of the clamping member is slightly inclined to the plane normal to the shaft so that the contact pressure between the shaft and the edges of the aperture increases as the fixing is tightened.

5. A fixing as claimed in any preceding claim, wherein the pivot between the shaft and the clamping member is formed by a single loop of wire passing around the shaft and having one end passing through a hole in the clamping member.

6. A cavity wall fixing constructed, arranged and adapted to operate substantially as herein described with reference to and as illustrated in the accompanying drawings.