Box for electrical components

Boxes for electrical components are provided with elongate grooves (3, 26) to receive self-tapping or thread cutting screws for securing the components in the box. The grooves may extend above or below the bottom of the box.

BACKGROUND OF THE INVENTION 
Field of the Invention 
This invention relates to boxes intended to contain electrical circuit 
elements such as terminals, relays and lighting components. 
British Patent Specification No. 459,517 (Electric Supplies) dated July 8, 
1936, discloses a wall box for electrical switches and the like, in which 
an adaptor plate having four radially extending slots is secured parallel 
the base of the box, and the base is provided with corresponding channels 
under the slots. Anchor elements, such as internally-threaded nipples can 
be inserted in the slots with their heads accommodated in the channels 
such that they cannot be pulled out through the slots. The anchor elements 
can be positioned along the four orthogonal axes defined by the slots to 
provide fixing anchors for an electrical switch or the like to be secured 
in the wall box. Such a box requires an additional element, the adaptor 
plate which takes-up room within the box, has to be provided with some 
means of securing it in the box and can provide fixing means only over a 
restricted portion of the entire box surface. 
British Patent Specification No. 1,590,018 (Ritherdon) discloses a 
wall-mounted cabinet on the inner surface of the rear wall of which are 
provided perforated strip-like mounting members arranged in parallel, 
spaced relation to the rear wall. Sketched between the mounting members 
are one or more detachable, perforate mounting members or stringers. The 
mounting members form a "false back" to which components can be fixed. 
Again the cabinet requires additional components to provide the fixing 
means. 
SUMMARY OF THE INVENTION 
According to an aspect of the invention there is provided a box for 
electrical components of which an interior surface is provided with at 
least one elongate groove dimensioned to receive and engage self-tapping 
screws for securing electrical components within the box. The groove may 
be such that a screw may be engaged at substantially any point along the 
groove. 
The grooves may be positioned on the bottom of the box and may form a 
pattern extending over most of the area of the bottom so that screws may 
be inserted at a wide variety of locations in the box, allowing a high 
degree of flexibility in locating components therein. The grooves may be 
formed either by ridges extending above the bottom (i.e. extending into 
the box interior) or by channel portions extending below the bottom. In 
the latter case the walls of the box may extend below the bottom and the 
lower exterior surfaces of the channel portions may be substantially flush 
with the lower edges of the walls of the box. 
The grooves may be dimensioned so as to receive a standard self-tapping or 
thread cutting screw, such as a No. 6 screw in such a manner that the 
screw thread will bite the interior walls of the grooves and provide a 
screw fastening for components engaging the screw. The lower portion of 
the grooves may be parallel sided so that the lower portion is of uniform 
width but the upper edges of the grooves may be bevelled, providing an 
upper portion of increased width capable of receiving a larger screw, for 
example a No. 8 self-tapping or thread cutting screw. This arrangement 
allows more than one size of screw to be used. 
The box bottom may be provided with holes to receive screws for mounting 
the box on a wall or other support surface. 
One type of box may be closed with a lid attached to the body of the box by 
screws and a gasket may be provided between the lid and box body to render 
the box dust-resistant and moisture-resistant in order to protect 
components mounted inside. Wires may be run into the box through holes in 
the bottom or walls. The holes may be drilled or formed by pushing out 
knock-out portions of small thickness provided in the walls or bottom. 
Another type of box comprises two half-boxes of similar construction which 
are held together by screws with their respective upper edges abutting 
face-to-face: in this embodiment both half-boxes may be provided with 
grooves so that components can be mounted on either half. Wires can enter 
the box so formed by holes in the bottoms or walls of the half-boxes. 
Alternatively the abutting edges may be such that when the half-boxes are 
assembled together a gap between the edges is provided on part of the 
periphery of the boxes, the gap being wide enough to allow wires to pass 
through. The gap may be occupied by a pad of resilient material mounted on 
at least one of the edges to close the gap and render the box 
dust-resistant while allowing passage of wires through the gap while 
clamping the cables to prevent forced withdrawal. 
The boxes may be made by molding of polyvinylchloride, a polycarbonate or 
other plastic material.

DESCRIPTION OF PREFERRED EMBODIMENTS 
Referring to FIGS. 1 and 2 an open-topped box has walls 1 of height 54 mm 
and thickness 3.5 mm and a flat bottom 2 of thickness 3.5 mm, the lower 
surface of the bottom being raised above the lower edge of the wall by a 
distance of 8 mm. 
The bottom is provided with a plurality of slots 3 defined by channel 
portions 4 extending below the bottom, the lower surfaces of the channel 
portions being almost flush with the lower edges of the walls. The slots 
are of uniform width and are shown in cross-section in FIG. 3. The depth 
of each slot is 9.5 mm, the lower part of the slot is parallel-sided and 
of width 2.7 mm whereas the upper part of the slot has edges bevelled to 
15.degree. from the vertical. These slot dimensions allow a standard No. 6 
self-tapping or thread cutting screw 41 to be screwed into and securely 
held at any point along the slot. 
As shown in FIG. 1 the slots are arranged to extend in directions from the 
centre to the sides of the bottom in different directions so that they 
form a pattern extending over most of the area of the bottom. This 
arrangement allows a component to be secured to the bottom of the box at 
substantially any position by means of a screw inserted into the most 
convenient slot. 
The bottom of the box is provided with means for securing the box to a wall 
or the like. These means comprise well portions 5 extending below the 
lower surface of the bottom, as shown in FIG. 3, the lower surface of the 
well portions being flush with the bottom edge of the wall. The well 
portions, 4 in number, each have a hole 6 of 4.5 mm diameter to receive a 
No. 8 woodscrew 7 or 4 mm bolt by which the box may be attached to a wall. 
The screw or bolt may be provided with a skid washer and a seal washer in 
conventional manner. 
The box may be closed by a lid 8. In order to render the box dust-resistant 
after assembly the upper edge of wall 1 is provided with a shoulder 9 
extending around the whole periphery of the wall. The lid has a downwardly 
extending edge flange 10 to engage the upper edge of the wall and the 
engaging surface of the flange has an outer lip 11 to extend into the 
shoulder 9, an inner lip 12 of lesser depth than lip 11 and a gasket 13 of 
resilient material between the lips to abut the edge 14 of the wall. 
The lid is held against the wall of the box by threaded bolts 15 which 
extend through holes in the lid and engage threaded inserts 16 mounted in 
holes formed in pillars 17 projecting inwardly of the walls adjacent the 
corners of the box. A gasket seal 18 is provided around each bolt 15 and 
the bolt is provided with a skid washer and seal washer adjacent the head. 
Entry of dust to the box past the bolt is thus prevented. 
Wiring may be led into the box through holes provided in the sides or 
bottom. Such holes may be made by drilling or the box wall and/or bottom 
may comprise knock-out portions which are pressed out as required to 
provide the necessary openings. 
The box shown in FIGS. 4 and 5 comprises two identical half boxes which are 
joined together edge-to-edge to form a closed box. The bottom 23 of each 
half-box is 2.5 mm thick and has a lower surface 1.5 mm above the lower 
edge of the wall 24 of the half-box. The upper (inside) surface of the 
bottom 23 carries upstanding ridges 25 extending 4.5 mm above the inside 
surface forming grooves 26. The lower surface of the bottom 23 has ribs 27 
opposite the grooves extending beyond the bottom by 1 mm. The grooves have 
a depth of 7 mm and are parallel-sided at their lower part with a width of 
4 mm, the upper ends of the grooves being bevelled. These dimensions allow 
the grooves to securely engage a No. 6 self-tapping or thread cutting 
screw which may be inserted in and securely engage the groove sides at any 
point on the grooves. A component may thus be supported within the box in 
a wide choice of positions. 
The upper edge of the wall has an outwardly extending peripheral flange 28 
having holes 29 to receive bolts 21 to clamp the two half-boxes together. 
Holes 29 of the lower half-box shown in FIG. 4 have female threaded 
inserts to engage these bolts which are inserted through holes 29 of the 
upper half-box. On both of the shorter sides of the box the flange has an 
outer upstanding lip of which one has an internal shoulder 31 and the 
other an external shoulder 32. When two identical half-boxes are fitted 
together as shown in FIG. 5 the lip having an internal shoulder of one 
flange engages the lip having an external shoulder of the other flange so 
that the lips together provide a dust-resistant seal. 
When the half-boxes are clamped together in this way there is a gap about 3 
mm wide between respective flanges 28 on the longer sides of the box and 
to fill this gap each of the flanges on the longer sides is provided with 
a pad 50 of compressible resilient material such as a foam rubber, the pad 
being about 1.5 mm thick. The abutting pads of the respective half-boxes 
provide a seal but as the pad material is deformable wires may pass from 
the exterior to the interior of the box through the gap occupied by the 
pads, the abutting pads holding the wires in place. This feature allows 
wires to be passed into the box at any longitudinal position along either 
of its longer sides. 
The bottom of each half-box is also provided with circular upstanding 
ridges 33 defining circular holes 34 of similar width to grooves 26 to 
receive self-tapping screws; however, these holes are of greater depth (15 
mm) to receive longer screws as required. The bottom is also provided with 
knock-out portions 35 allowing screws to be passed through the bottom to 
mount the half-box on a wall or the like. 
Both the boxes described above may be made of a known plastic material such 
as polyvinylchloride or polycarbonate and may be formed to shape by 
molding. 
The boxes described are capable of containing a wide variety of electrical 
and electronic components and assemblies which are secured inside the 
boxes by screws engaging the grooves. The boxes have a neat appearance and 
are easily mounted in any location. The grooves are adapted to receive a 
standard No. 6 self-tapping or thread cutting screw but as they are 
slightly wider at the mouth they can also receive a wider No. 8 screw if 
required.