GB2062354A - Electric accessory boxes and lugs therefor - Google Patents

Abstract

Electric accessory boxes 1 have lugs 8 to receive screws for attaching covers thereto, the lugs 8 being snap- fitted into position and capable of giving play to facilitate attachment of the cover. The lugs have hooked legs 9, 12 which snap fit in apertures 7 in the box with the hooks 12 engaging under crossbars 6. The crossbar 6 or the hooks 12 may be resilient, hooks 12 being formed on the legs 9 by stamping or bending or may comprise separate parts attached to the legs 9. <IMAGE>

Description

SPECIFICATION Accessory boxes and lugs therefor This invention relates to accessory boxes for electrical components such as switches.

Such boxes are commonly mounted on surfaces such as walls to contain various components and are provided on their sides or base with holes to receive cables passing from the outside to the inside of the box. When the box has been fitted in place and the components inside connected to the cables the box is normally closed with a cover. The cover may generally be screwed to the box by means of screws passing through the cover and engaging threaded members within the box.

Accessory boxes are commonly made by moulding thermoplastics materials such as polyvinyl chloride. However an internally threaded member to receive a screw passing through the cover generally has to be made of metal.

The present invention is intended to provide accessory boxes which may be easily and cheaply moulded from thermoplastic material provided with lugs to receive screws for screwing the cover to the box, the lugs being quickly and easily installed in the box either immediately after manufacture of the box or during installation of the box on site. It is desirable that the lugs, when installed, should have a considerable degree of play to allow quick and easy attachment of the cover as the lugs inside the box are not generally visible when the cover is mounted in place. On the other hand, the lugs should be mounted securely in the box so that they will not become detached during transport or during mounting of the box.

According to one aspect of the invention, there is provided an electric accessory box comprising an aperture and a lug to pass through the aperture, the lug comprising a stem, a cross-piece extending transversely from a top end of the stem and containing a threaded bore capable of receiving a screw to clamp a lid on to the box, the stem having a hook portion extending transversely to the stem remote from said top end to form an upwardly facing contact surface, the aperture being of width greater than the thickness of the stem and less than the maximum combined thickness of the stem and hook portion, a downwardly facing contact surface capable of abutting said upwardly facing surface of the hook portion being provided below the aperture, and at least one wall of the material surrounding the aperture and/or at leastpart of the lug being resilient so that the stem and hook portion may be pushed into the aperture until the upwardly facing contact surface snaps under the downwardly facing contact surface, abutment of said surfaces then preventing removal of the lug from the aperture.

Preferably the aperture is slot-shaped and the width of the stem in the longitudinal direction of the slot is less than that of the slot so that the lug has limited play in the aperture.

The hook portion may extend transversely to the stem in the same direction as the cross-piece.

The downwardly facing contact surface may comprise the lower edge of a bar member defining a side of the aperture and the threaded bore may be arranged so that a screw passing therethrough, extending below the cross-piece, can make contact witha surface of the bar member remote from the aperture so that the bar is clamped between the screw and the stem.

According to another aspect of the invention, there is provided a lug for use in such an accessory box comprising a stem and a cross-piece extending transversely from a top end of the stem and containing a threaded borecapableofreceiving a screw, the stem having a hook portion extending transversely to the stem remote from said top end to form an upwardly facing contact surface capable of abutting a downwardly facing contact surface of the box below an aperture thereof in which the lug may be inserted.

The upwardly facing surface of the hook portion may form a sharp edge to engage the downwardly facing surface. The lug may be formed of metal by a known extrusion technique or it may be formed by deformation of sheet metal. In the latter case the hook portion may be formed by folding an end of the stem upon itself or part of the stem may be deformed by punching to form the hook portion.

In one embodiment the hook portion is formed by a member engaging the stem of the lug and is resiliently deformable.

Embodiments of the invention will now be described by way of example with reference to the accompanying drawings in which: Figure 1 is a plan view of an accessory box provided with two apertures to receive lugs, a lug being mounted in one of the apertures, Figure 2 is a section along A-A of Figure 1, and Figures 3-10 show different designs of lug which may be used with the box of Figures 1 and 2: each of Figures 3-9 comprises orthogonal sections of a lug. Figures 10 and 11 show perspective views of a lug.

Referring to Figures 1 and 2, an accessory box comprises a horizontal bottom 1 and vertical walls 2, which may be provided with knock-out portions and holes to allow fixing of the box to a surface such as a wall. The box is provided with two apertures 3 to receive lugs to enable a lid to be screwed to the box by screws. The box including the apertures is moulded in one piece from a thermoplastics material such as polyvinyl chloride.

Each aperture is formed by an interior wall 4 which is of lesser height than the main wall 2 and encloses, with part of wall 2, a space 5 which is open downwardly (through the bottom of the box) and upwardly. Space 5 is partly blocked by a bar 6. Bar 6 and/or the adjacent part of wall 2 are sufficiently thin to be deformable elastically to a small extent in the respective directions indicated by arrows F. The bar 6 and the main wall 2 define between them a space 7 having a length, parallel to wall 2, greater than its width.

The box with these sockets may be made by simple moulding between male and female dies and no retractable cores are required.

The aperture is intended to receive a lug 8, which is shown in Figure 3. It is formed of hard brass or other metal or plastics material and comprises a stem 9 attached to a cross-piece 10 provided with a threaded bore 11 to receive a screw to a clamp a cover on the box. The bottom of stem 9 has a-hook portion 12 to engage the underside of the bar 6.

The dimensions of the lug and space 7 are such that when the lug is in the position shown in Figure 2 it cannot be removed without breaking the material of the box, the hook engaging the underside of the bar 6. However as the width of the lug, in the direction parallel to wall 2, is less than the length of space 7 the lug has a degree of play in this direction, facilitating alignment of the screw with the lug when the cover of the box is mounted in place.

The lug may be mounted in place by pushing its stem downwardly through the space 7, the bar 6 and/or wall 2 being sufficiently deformable to allow passage of its hooked end. When the lug is fully inserted the bar 6 springs back into its undeformed position so that the lug cannot be removed.

The hook portion 12 has an upstanding sharp edge 13 to engage the underside of the bar 6 so that the hook portion may engage the bar more securely. It will be understood from Figure 2 that, as the hook portion extends in the same direction as the cross-piece, when a screw is passed through the threaded bore the bar 6 is surrounded on all its sides by the stem, hook portion, crosspiece and screw. The bar may then be clamped securely by these members and, after passage of the screw, the lug is firmly fixed to the bar and cannot move.

The lug shown in Figure 3 may be made by extrusion of metal.

Figure 4 of the drawings shows an alternative design of hook which is similar to that of Figure 3, except that the stem is narrower than the crosspiece. This lug may be used in the same manner but the provision of a narrower stem allows greater degree of play in the aperture before insertion of the screw through the bore.

Alternatively, a wider bore to accommodate a wider screw may be provided for a stem of given dimensions.

The lug shown in Figure 5 is made by deformation of sheet metal and the hook portion of the stem is formed by folding the end of the stem 14 upon itself. The folded end 14 may then engage the lower surface of bar 6 in the same way as the hook portion 12 of the lug of Figure 3.

Figures 6 to 9 all show lugs of sheet metal in which the hook portion is formed by punching out a part of the stem. In the lugs of Figures 6, 7 and 8 it is a middle part 1 5 of the stem which is punched out to form a hook portion. In the lug of Figure 9 two side parts 16 are punched out to form a pair of hook portions, one on each side of an undeformed part of the stem. All the lugs of Figures 6 to 9 may be used with the accessory box of Figure 1 in the same way as the lug of Figure 3.

The lugs shown in Figures 3 to 9 are essentially rigid and intended to be inserted in an aperture of which at least one wall is resilient. The lug shown in Figure 10 is capable of being used with boxes made of rigid material and then it is the lug, not the box, which is resiliently deformed. The lug of Figures 10 and 11 is made in two parts, an upper part 17 and a lower part 18. Upper part 17 is rigid and comprises a cross-piece containing a threaded bore 20 and a stem 21. The lower part 1 8 is a sufficiently thin metal to be resilient and is generally U-shaped with an outstanding edge 22 providing a hook to engage the downwardly facing contact surface of the box.

Part 18 has an inwardly projecting tab 23 capable of entering a hole 24 in the stem 21. The parts are assembled together as shown in Figure 11, the tab 23 of the resilient part 18 snapping into the hole 24 to hold the parts firmly together.

When the composite lug is pushed into the aperture the edge 22 can bend inwards towards the stem 21 and then spring outwards below the contact surface of the box to hold the lug in place.

A resilient lug of this type can be used with a box of either rigid or resilient material.

In the above-described embodiments the bar 6 extends across the whole width of the space 5 but it may be replaced by other types of member which may extend over only part of this width.

This member may be of any design allowing the lower end of the lug to engage its underside by a hook or equivalent means.

Claims (20)

CLAIMS:

1. An electric accessory box comprising an aperture and a lug to pass through the aperture, the lug comprising a stem, a cross-piece extending transversely from a top end of the stem and containing a threaded bore capable of receiving a screw to clamp a lid on to the box, the stem having a hook portion extending transversely to the stem remote from said top end to form an upwardly facing contact surface, the aperture being of width greater than the thickness of the stem and less than the maximum combined thickness of the stem and hook portion, a downwardly facing contact surface capable of abutting said upwardly facing surface of the hook portion being provided below the aperture, and at least one wall of the material surrounding the aperture and/or at least part of the lug being resilient so that the stem and hook portion may be pushed into the aperture until the upwardly facing contact surface snaps under the downwardly facing contact surface, abutment of said surfaces then preventing removal of the lug from the aperture.

2. A box according to Claim 1, in which the aperture is slot-shaped and the width of the stem in the longitudinal direction of the slot is less than that of the slot so that the lug has limited play in the aperture.

3. A box according to Claim 1 or 2, in which the hook portion extends transversely to the stem in the same direction as the cross-piece.

4. A box according to Claim 3, in which the downwardly facing contact surface comprises the lower edge of a bar member defining a side of the aperture and the threaded bore is arranged so that a screw passed therethrough makes contact with a surface of the bar member remote from the aperture so that the bar is clamped between the screw and the stem.

5. A box according to any preceding claim, in which the upwardly facing surface of the hook portion forms a sharp edge to engage said downwardly facing surface.

6. A box according to any preceding claim, in which the lug is formed of extruded metal.

7. A box according to any one of Claims 1 to 5, in which the lug is formed by deformation of sheet metal.

8. A box according to Claim 7, in which the hook portion is formed by folding an end of the stem upon itself.

9. A box according to Claim 7, in which a part of the stem is deformed by punching to form the hook portion.

10. A box according to any one of Claims 1 to 7, in which the hook portion is formed by a member engaging the stem of the lug and is resiliently deformable.

11. An electric accessory box, substantially as hereinbefore described with reference to the accompanying drawings.

1 2. A lug for use in an accessory box according to any preceding claim, comprising a stem and a cross-piece extending transversely from a top end of the stem and containing a threaded bore capable of receiving a screw, the stem having a hook portion extending transversely to the stem remote from said top end to form an upwardly facing contact surface capable of abutting a downwardly facing contact surface of the box below an aperture thereof in which the lug may be inserted.

13. A lug according to claim 12, in which the hook portion extends transversely to the stem in the same direction as the cross-piece.

14. A lug according to Claim 12 or 13, in which the upwardly facing surface of the hook portion forms a sharp edge to engage said downwardly facing surface.

15. A lug according to Claim 12, 13, or 14 in which the lug is formed of extruded metal.

16. A lug according to Claim 12, 13 or 14 in which the lug is formed by deformation of sheet metal.

17. A lug according to Claim 16, in which the hook portion is formed by folding an end of the stem upon itself

18. A lug according to Claim 16, in which a part of the stem is deformed by punching to form the hook portion.

19. A lug according to any one of Claims 12 to 16, in which the hook portion is formed by a member engaging the stem of the lug and is resiliently deformable.

20. A lug for use in an accessory box, substantially as hereinbefore described with reference to the accompanying drawings.