GB2168205A - An improved junction box - Google Patents

Abstract

A junction box is made in two parts, comprising a mounting plate (11) having fixing holes for attachment of the plate (11) to a flat surface by means of fixing pins or screws housed in counter-bored recesses. A housing (23) is provided with bosses by means of which it can be secured to the mounting plate (11) by screws passing through passage (35,36) in the bosses. The housing has a rear wall and is entirely enclosed by a cover such that the interior of the housing is totally separate from the mounting plate thereby avoiding the possibility of thermal contact through the fixing screws with the interior of the housing and the body of the wall to which the junction box is fixed. Lips on the housing received in grooves in the plate may have snap-engaging detent means to retain the housing on the plate. <IMAGE>

Description

SPECIFICATION An improved junction box The present invention relates to an improved junction box, and particularly one suitable for surface mounting at a low level on a wall.

Recently, concern has been aroused from incidents resulting from condensation collecting on the metal fixings which are inserted into a wall to retain a surface-mounted junction box in position. This has resulted in two detrimental effects, the first of which is the unwanted corrosion of any ferrous metal components within the junction box, and the other is the possibility of a short circuit across the electrical connections within the junction box. This problem has been exacerbated with the increasing use being made of surface mounted junction boxes for telephones, particularly junction boxes incorporating plug-and-socket couplings. A primary cause of such condensation is the thermal transfer through the metal fixings from the interior of the wall to the interior of the junction box.The interior of the junction box is usually maintained at a temperature and humidity level concomitant with that in the room in which the junction box is located, whereas the temperature of the wall may be substantially below that of the room so that the moisture in the air in the room can condense on the exposed surfaces of the metal fixings. If the moisture content of the wall is excessively high for any reason, such as, for example, due to rising damp or the like, moisture can pass through the fixing holes, which are incompletely filled by the fixings, into the interior of the junction box and increase the humidity level inside it.This excess moisture is related, therefore, not to the low level of the junction box on the surface of the wall, but to the fact that it communicates, via the fixing holes, with the interior of the wall both in terms of thermal communication through the metal fixings and the physical passage of excess moisture within the wall.

The present invention seeks to provide a junction box in which the above indicated problems of existing junction boxes will be avoided and in which condensation due to temperature differences between the interior of a room and the body of a wall defining the room will not lead to condensation within the junction box.

According to one aspect of the present invention, therefore, a junction box for electrical connectors comprises a mounting attachable to a support surface by fixing screws or other fixing means, and the housing for the electrical connectors, the housing having coupling means for connecting it to the mounting in such a way that the fixing screws or other fixings attaching the mounting to the support surface do not extend into the interior of the housing or have any surface in communication with the interior of the housing.

Electrical connections within the housing can be made by passing an electrical lead through openings in the housing which are spaced from the location of the fixings by which the mounting is secured to a wall. The coupling between the housing and the mounting may incorporate screw or like fixing means with screws passing through bosses within the housing in such a way that the screws do not communicate with the interior of the housing, or form-engaging coupling means may be provided.

In the latter case, the mounting is conveniently a plate adapted to be screwed to a wall by fixing screws in suitably plugged holes in the wall, and the mounting plate has grooves or ridges along at least two parallel edges thereof whilst the housing of the junction box is provided with cooperating ridges or grooves respectively for form-engagement with the grooves or ridges in the mounting plate.

Other form-engaging coupling means may be provided, however, and the invention is not to be considered as limited by the form-engagement particularly described herein. For example, snap-engaging detent means may be provided to enable the housing to be pushed directly onto the mounting plate or pulled from it in a direction perpendicular to the plane of the plate. Form-engagement by grooves and ridges as discussed above, however, may be retained by snap-engaging detents which engage when the housing is moved onto the plate by a sliding movement parallel to the plane of the plate with the grooves and ridges interengaged, or suitable screw fixing retaining means may be provided, in which case suitable bosses as discussed above may be employed to maintain the screws out of communication with the interior of the housing.

One embodiment of the present invention will now be more particularly described, by way of example, with reference to the accompanying drawings, in which: Figure 1 is a front view of a mounting forming part of an embodiment of the present invention; Figure 2 is a side view of a mounting plate illustrated in Fig. 1 as seen in the direction of the arrow A of Fig. 1; Figure 3 is a plan view from above of the mounting plate illustrated in Fig. 1 as seen in the direction of the arrow B of Fig. 1; Figure 4 is a front view of a housing for attachment to the mounting plate illustrated in Figs. 1 to 3; Figure 5 is a side view seen in the direction of the arrow C of the housing illustrated in Fig. 4; Figure 6 is a plan view from above of the housing illustrated in Fig. 4, as seen in the direction of the arrow D of Fig. 4; and Figure 7 is a partly cut away perspective view of the junction box constituting an em bodiment of the present invention and described in Figs. 1 to 6, showing the two component parts in relative juxtaposition.

Referring first to Fig. 1 the moounting plate shown is generally rectangular and identified with the reference numeral 11. Two fixing holes 12,13 are provided for attachment of the plate 11 to a flat surface, and ;these fixing holes are suitably counterbored or countersunk at 12a and 13a as illustrated in Figs. 2 and 3.

Along two opposite edges 14,15 of the plate 11, there are two parallel grooves 16,17 defined by groove walls 18,19 in the case of the groove 16 and 20,21 in the case of the groove 17. The groove walls 18,20 which define the rear of the grooves 16,17 in relation to the plate 11 are higher than the walls 19,21 which define the front of the groove.

These walls 18,19,20,21 are in effect in the form of peripheral lips or flanges and rear flanges 18,20 are joined at one end by a transverse flange 22 which projects from the edge of the plate 11 extending at a right angle to those edges having the grooves 16,17. Although illustrated in Figs. 1 to 3 with the grooves 16,17 extending vertically and the flange 22 on the upper edge of the plate 11, there is no reason why the plate should not be fitted in an orthogonal or even inverted position providing space is sufficient to allow connection of the housing illustrated in Figs. 1 to 6 thereto in a manner which will be discussed below.

Referring now to Figs. 4 to 6, the housing illustrated is generally indicated with the reference numeral 23. This housing comprises a generally parallelepiped body having a square or rectangular front face 24 with a spaced parallel rear face 25 of approximately the same area and spanned, in the orientation illustrated in Figs. 4 to 6, by upper and lower walls 27, 28 respectively and left and right side walls 29,30 respectively. The left and right side walls 29,30 extend from the front wall 24 to a position beyond the rear wall 25 and each has a lip 31,32 respectively facing towards the opposite side wall and defining, with the wall from which it projects and the adjacent part of the rear face 25 a respective channel 33,34.

The distance by which the side walls 29,30 project beyond the rear wall 25 is marginally less than the thickness of the mounting plate 11, whilst the width of the channels 33,34 and the thickness of the lips 31 ,3 are such as to be a sliding fit into the flanges 19,21 and the grooves 16,17 respectively of the mounting plate 11. The upper wall 27 extends beyond the rear wall 25 by the same distance as the side walls 29,30 to form an overlapping flange 27a. The housing 23 can be interconnected with the mounting plate 11 by interengaging the lips 31,32 of the housing 23 into the grooves 17, respectively of the mounting plate 11 and causing relative sliding movement between the housing 23 and the mounting plate 11.

As illustrated in the drawings the housing 23 can be retained in position on the mounting plate 11 by means of screws passing through holes 35,36 which pass right through the housing from front to back and are surrounded by respective bosses 37, 38 projecting as ridges inwardly of the housing 23 from the side walls, 29, 30 respectively in such a way that the fixing screws passing through the holes 35, 36 and entering corresponding securing holes 39, 40 in the mounting plate 11 (which may contain suitable trapped nuts or may themselves be threaded) is completely out of communication with the interior of the housing 23. Alternatively, the housing and/or the mounting plate may be provided with snap engageable detents for cooperatively retaining the lips 31, 32 in the grooves 16, 17 once they have been slidably introduced therein.

As will be appreciated from a study of the drawings, the interior of the housing 23, identified with the reference numeral 41 is a completely closed volume entirely out of contact with the fixing screws passing through the holes 12, 13 in the mounting plate by means of which the junction box is secured to the wall, and out of contact with the fixing screws passing through the holes 35, 36 to retain the housing 23 and the mounting plate 11 together. Suitable apertures (not illustrated) in the side walls 29, 30 or the upper 27 or lower 28 wall in the junction box may be provided for the passage of electrical wires to the connectors (again not shown) within the volume 41 of the housing 23.The front wall 24 of the housing 23 is illustrated with an aperture 42 for receiving a jack plug of known design, although the junction box itself may be simply for the purpose of connecting the electrical leads passing through the holes (not shown) in the side, upper or lower walls and such jack plug connection may not be required or provided.

Suitable grommets or other means for ensuring air-tightness of the interior 41 may be provided in circumstances where the environment in which the junction box is to be fitted is one from which the interior 41 is intended to be isolated.

From the above description it will be seen that the previously described corrosion problems arising from communication between the fixing screws attaching the junction box to a wall and the interior of the junction box itself, have been entirely eliminated so that no communication takes place. The rear wall 25 constitutes a total and effective barrier to the transfer of moisture so that the interior of the junction box is entirely isolated from the wall.

Moreover, for maintenance purposes, the removal of the housing 23 from the mounting plate 11 is easy and quick and leaves the mounting plate 11 in position for rapid re placement of a new housing should mainte nance operations require such replacement.

Likewise, exchange of a junction box for one having a greater or smaller number of connectors or for one with or without the jack plug connection 42 can readily be made without removal of the mounting plate 11 from a wall.

If snap-engaging detent means are used to retain the housing 23 on the plate 11 this separation can simply be effected without requiring any tools except those necessary for removal of the electrical connections which can be readily effected by withdrawing the screws from the apertures 35, 36 enabling the front wall 24 to be removed.

Claims (11)

1. A junction box for electrical connectors comprising a mounting attachable to a support surface by fixing means, and a housing for the electrical connectors, the housing having coupling means for connecting it to the mounting in such a way that the fixing means by which the mounting is attachable to a support surface do not extend into the interior of the housing or have any surface in communication with the interior of the housing.

2. A junction box as claimed in Claim 1, in which the mounting is a plate adapted to be secured to a wall or other support surface by fixing screws or pins received in apertures in the mounting plate.

3. A junction box as claimed in Claim 2, in which the said apertures in the mounting plate have counter-bore or counter-sunk recesses communicating with the face of the plate which is remote from the wall when the plate is attached thereto, for receiving the heads of fixing means such that these, in use, do not protrude beyond the exposed face of the plate.

4. A junction box as claimed in any of Claims 1 to 3, in which the mounting plate has a groove along at least two parallel edges thereof for receiving cooperating inwardly directed flanges of the housing.

5. A junction box as claimed in Claim 4, in which the mounting plate has a groove along three parallel edges and the housing has inwardly directed flanges along three cooperating sides to be received in the grooves upon interconnection of the housing with the mounting plate.

6. A junction box as claimed in Claim 1, Claim 2 or Claim 3, in which the housing and the mounting plate are provided with means by which the housing can be snap-engaged onto the mounting.

7. A junction box as claimed in any preceding Claim, in which the housing is provided with bosses each having an end face which, when the housing is mounted on the said mounting, is in contact with the face of the mounting, to allow fixings to pass between the housing and the mounting without being exposed within the housing.

8. A junction box as claimed in any of Claims 1 to 3 or 7, in which the housing and the mounting are provided with co-operating form-engaging means in the form of grooves on one of the two--members and ridges of cooperating shape on the other.

9. A junction box as claimed in any preceding Claim, in which there provided electrical connectors within the said housing, carried on a front wall of the housing or on a partition wall separating the housing from the mounting plate in the assembled junction box.

10. A junction box as claimed in any preceding Claim, in which the electrical connectors are associated with or part of an electrical switch.

11. A junction box substantially as hereinbefore described with reference to, and as shown in, the accompanying drawings.