GB2118378A

GB2118378A - Improvements in fixings

Info

Publication number: GB2118378A
Application number: GB08210583A
Authority: GB
Inventors: Colin Keith Ian Ratcliff
Original assignee: Allied Corp
Current assignee: Allied Corp
Priority date: 1982-04-08
Filing date: 1982-04-08
Publication date: 1983-10-26

Abstract

An internally screw-threaded bush 2 has a waisted portion 23 captively slidable in a slot 3 in a platform 13 having an entry extension 16 with a tapered constriction 19 through which the wasted portion of the socket can be introduced into the slot 3 by resilient spreading of the inlet portion 16. The fixing may be used to attach a cover bearing an electrical wiring accessory to a moulded plastics mounting box 9. <IMAGE>

Description

SPECIFICATION Improvements in fixings The present invention relates to improvements in fixings and more particularly but not exclusively to improvements in mounting boxes for electrical wiring accessories such as electrical sockets and switches and telephone outlets for example in the form of jack-sockets. Such accessories are commonly mounted on a cover plate for the mounting box, the box itself being either surface-mounted on a wall surface or "flush-mounted" in a recess cut into a wall with the rim of the box substantially flush with the wall surface. The mounting box includes two or more screw-threaded sockets to receive fixing screws which pass through holes in the cover plate and thereby enable the cover plate, carrying one or more wiring accessories, to be fastened in position over the box, with the fastening screws engaged in the screw-threaded sockets.The mounting box may also be used as a junction box, with a connector terminal block located in the mounting box which is then closed by a plain, blank cover plate. Commonly, such mounting boxes are formed from pressed sheet metal and one or more of the sockets may be slidably mounted to an adjacent wall or walls of the box to permit the final orientation of the cover plate to be adjusted prior to final tightening of the fastening screws. The assembly of such a slidable socket arrangement can involve additional components and forming operations such as riveting and/or bending after the components have been brought together.

Mounting boxes are also known in the form of plastics mouldings with the sockets formed as metal inserts which are moulded into the plastics moulding.

According to the present invention there is provided a mounting box for an electrical wiring accessory, which accessory is itself mounted on a cover plate for the box, the box comprising a unitary plastics moulding forming a base wall, peripheral side walls extending from the base wall, and at least one screw-threaded socket to receive a fixing screw for the cover plate, the socket being captively movable parallel to an adjacent said side wall, wherein the said movable socket has a waisted portion captively slidable in a slot in a portion of the moulding spaced from the base wall, and has abutment means spaced from the axis of its screw thread to abut said moulding to prevent rotation of said movable socket in said slot, and said slotforming portion of the moulding and said movable socket have cooperative conformations permitting introduction of said socket into captivity in said slot by resilient displacement of a wall which renders said socket captive.

Advantageously, the slot has a tapering entry extension, preferably at one end of the slot, for introduction of the waisted portion from an inlet to the extension, which inlet is wider than the waisted portion, through a resiliently deformable portion which is narrower than the waisted portion, into the slot. Preferably, the leading end of the waisted portion is chamfered to assist entry into the slot.

Advantageously, the abutment means on the movable socket comprises a face substantially parallel to the axis of the movable socket and closely adjacent an inner face of the adjacent side wall of the moulding.

Also according to the invention there is provided a fixing arrangement in a plastics moulding comprising at least one screw-threaded fixing element, said fixing element having a waisted portion captively slidable in a slot in said moulding, said fixing element further having abutment means spaced from the axis of the screw-thread of said fastening means to abut said moulding to prevent rotation of said fixing element in said slot, and said slot-forming portion of the moulding and said fastening element having cooperative conformations permitting introduction of said element into captivity in said slot by resilient displacement of a wall which renders said element captive.

With the arrangements described above, the or each movable socket can be readily formed by moulding and inserted into its slot by simple snapfitting operation without any subsequent forming of fixing operations.

An embodiment of the invention will now be described by way of example with reference to the accompanying drawings, in which Figure lisa front elevational view of a mounting box embodying the invention, Figure 2 is a vertical section on the line ll-ll of Figure 1, Figure 3 is a perspective view of a movable socket during its insertion into its slot, Figure 4 is a median cross-section of a movable socket in its slot, Figure 5 shows, in the left half, in elevation, and in the right half, in axial section, a movable socket, on the line V-V of Figure 4, Figure 6shows a detail, on an enlarged scale, as seen in the direction of the arrow VI in Figure 1, and Figure 7 is a cross-section on the line VII-VII of Figure 6.

The mounting box shown in Figures 1 to 5 comprises a plastics moulding 1 and a pair of screw-threaded movable sockets 2 forming screwthreaded fastening elements slidably mounted but captive in slots 3 in the moulding 1.

In use, the sockets receive screws which secure a square, bevelled plastics cover plate C over the box.

The cover plate C is here shown as a blank plate but may be formed with an appropriate aperture in which is mounted a wiring accessory such as a switch or outlet socket. Such arrangements are conventional and do not require further description.

The moulding 1 comprises a base wall 4 and side walls 5, 6,7 and 8 extending from the periphery of the base wall 4 to a rim 9. The moulding 1 is formed from ABS (CYCOLAC T Grade 25020) or unplasticised polyvinyl chloride, for example, in a two-part mould. As a result, the outer surfaces of the peripheral side walls conveniently taper inwards slightly in the direction from the base to the rim, thereby ensuring a degree of keying with surrounding plaster when the box is used as a plaster-depth mounting box. The base wall 4 is formed with weakened "knock-out" areas 10, preferably of elongated, slot form, to receive fixing screws. Further, larger "knock-out" areas 11 in the base wall 4 and 12 in the side wall are also selectively removable to permit entry of cables.

Each slot 3 is formed in a platform 13 which is joined to the base by upstanding wall portions 14 and 15 and also merges with the adjacent side wall (6 or 8). Each slot 3 is generally rectangular but is extended at one end by an extension 16 forming an entry to the slot from the end of the platform 13 opposite to the wall portion 15. The entry 16 has a first parallel-sided relatively wide portion 17, and a narrower parallel-sided portion 18 which leads into the slot 3 and is connected to the wider portion 17 by a tapering portion 19, thereby forming a pair of barbs or saw teeth.

The mounting box shown by way of example in the drawings is 63 mm square, the height of the side walls 5,6,7,8 above the base wall 4 is 19 mm and their thickness together with that of the base wall 4 is 2 mm. The thickness of the walls 13, 14 and 15may then be about 1.2 mm.

Each movable socket 2 has upper and lower flanges 21 and 22 which are connected by a central, waisted portion 23 of substantially square crosssection. The flanges 21 and 22 have flat abutment surfaces 24 which with the waisted portion 23 engaged in the slot 3, engage the adjacent side wall (6 or 8) to prevent rotation of the socket during insertion or removal of the screw.

The socket 2 is conveniently moulded from glassfilled nylon and its screw-threaded bore 25 may be formed by a subsequent tapping operation.

The process of installing the socket 2 in its slot 3 is shown in Figure 3. The waisted portion 23 is introduced into the wider, inlet portion 17 of the entry 16 and the socket 2 is then pushed home into the slot 3, the waisted portion 23 camming the sides of the tapered portion 19, and thus of the narrow portion 18, apart. To assist in this process, the leading corners of the waisted portion 23 are preferably chamfered at 26.

Where the mounting box is to be used with cover plates carrying accessories such as light switches which do not have earthing terminals for looping-in mandatory earth cables, the moulding 1 may include a mounting arrangement 31 (Figures 1,6 and 7) for securing an earthing terminal in the form of a brass block 41 formed with a bore 42 to receive one or more earthing wires and a screw 43 for securing these wires. Conveniently, this mounting arrangement consists of two upstanding clip arms 32 on the base wall 4, each arm 32 having a retaining lip 33 near its free end of sufficient size to retain the earthing block but sufficiently small to be resiliently removable from the mould after the moulding operation. The earth terminal block is prevented from sliding along the base wall 4 away from the side wall 5 by a projection 34 moulded integrally with the base wall 4.

Claims

1. A mounting box for an electrical wiring accessory, which accessory is itself mounted on a cover plate for the box, the box comprising a unitary plastics moulding forming a base wall, peripheral side walls extending from the base wall, and at least one screw-threaded socket to receive a fixing screw for the cover plate, the socket being captively movable parallel to an adjacent said side wall, wherein the said movable socket has a waisted portion captively slidable in a slot in a portion of the moulding spaced from the base wall, and has abutment means spaced from the axis of its screw thread to abut said moulding to prevent rotation of said movable socket in said slot, and said slotforming portion of the moulding and said movable socket have cooperative conformations permitting introduction of said socket into captivity in said slot by resilient displacement of a wall which renders said socket captive.

2. A mounting box according to claim 1, wherein the slot has a tapering entry extension, for introduction of the waisted portion from an inlet to the extension, which inlet is wider than the waisted portion, through a resiliently deformable portion which is narrower than the waisted portion, into the slot.

3. A mounting box according to claim 2, wherein the entry extension is at an end of the slot.

4. A mounting box according to any of claims 1 to 3, wherein the leading end of the waisted portion is chamfered to assist entry into the slot.

5. A mounting box according to any of the preceding claims, wherein the abutment means on the movable socket comprises a face substantially parallel to the axis of the movable socket and closely adjacent an inner face of the adjacent side wall of the moulding.

6. A fixing arrangement in a plastics moulding comprising at least one screw-threaded fixing element, said fixing element having a waisted portion captively slidable in a slot in said moulding, said fixing element further having abutment means spaced from the axis of the screw-thread of said fastening means to abut said moulding to prevent rotation of said fixing element in said slot, and said slot-forming portion of the moulding and said fastening element having cooperative conformations permitting introduction of said element into captivity in said slot by resilient displacement of a wall which renders said element captive.

7. A mounting box for an electrical wiring accessory, substantially as described with reference to the drawings.