GB2137431A - Mounting terminals in lampholder: cable grip - Google Patents

Abstract

A lampholder has its contact terminals (4) located in bores (21) through the body (2). Transverse slots (not shown) open to the terminal receiving bores (21) and also to the upper side (23) of the body and receive terminal screws (5). The terminals (4) with their screws (5) are retained in position, firstly, by the engagement of the terminal screws (5) in the slots and, secondly, by a retaining plate (12) which closes the slots (24) and partly covers the ends of the terminal receiving bores (21). The retaining plate (12) includes legs (7) which are held in further bores in the body by friction. The retaining plate (12) includes a cable clamp (8, Figs. 2,3) which is partly received in the central opening of the lampholder cap (1), the cables being clamped between the clamp and the cap as the cap is threaded on to the body (2). Alternatively (Fig. 5), the cable clamp includes jaws (14) which grip the cable and may be clamped by the cap (1). <IMAGE>

Description

SPECIFICATION Lampholder This invention relates to a lampholder of the type having a body in which contact terminals are retained so as to protrude from a first side of the body for engagement with the contacts of a lamp.

For use, the electrical connections are passed through restricted openings from the second, oppo site, side of the body to the contact terminals and secured by terminal screws located in transverse slots in the body. Such a lampholderwill be referred to hereinafter as "a lampholder of the type described".

In known lampholders of the type described, each contact terminal is located in a blind bore in the body and is held in position by its terminal screw being located in the transverse slot. During assembly, the non-protruding end of the contact terminal is entered into the blind slot, and the terminal screw is introduced through the transverse slot and mated with a threaded hole in the terminal, the screw head then holding the contact terminal in position by its retention in the transverse slot.

The known lampholder suffers from the fact that the contact terminals and their terminal screws cannot be assembled together prior to introcuction to the body. As a consequence, automatic assembly of the lampholder is difficult, if not impossible.

One aspect of the present invention resides in a lampholder of the type described, in which the terminal receiving bores extend through the body, and which includes retaining means securable to the body to close the transverse slots and/or the terminal receiving bores at the second side of the body.

With that construction, the terminal screws may be fitted to the contact terminals before assembly of the lampholder and, during assembly, the contact terminals are dropped into the transverse slots from the second side of the body. After attachment of the retaining means, the contact terminals are held in position, in one direction by the screw heads, and, in the opposite direction, by the retaining means.

Thereby, automatic assembly of the lampholder is made possible.

Preferably, the retaining means comprises a plate overlying the second side of the body and having restricted openings for the passage of the electrical conductors. The plate may include a cable grip and be held in position by protruding pegs which are a push fit in corresponding holes in the body.

A second aspect of the invention resides in a lampholder of the type described comprising a lampholder cap attachable to the body, and a cable grip comprising a pair of normally spaced jaws attached to a plate securable on the body and projecting from the plate for engagement by the cap, the arrangement being such that the cable is retained between two jaws. If it is necessary to increase the grip, the cap can also be arranged to force the jaws towards one another to grip the cable therebetween.

The invention will be more readily understood by way of example from the following description of a lampholder in accordance therewith, and its method of assembly, reference being made to the accom panying drawings, in which Figure lisa plan view of the assembled lamphol der, with the cover removed, Figures 2 and 3 are respectively sections on the lines A-A and B-B of Figure 1, including the lamphol der cover, Figure 4 is a section illustrating the cable clamp, and Figures 5and 6 show a modified form of cable clamp.

The lampholder illustrated comprises a cap 1, a body 2, a lamp retaining liner 3, contact terminals 4 and a plate 12. The liner 3 is attached to the body 2 by rivets 6 and the cap 1 can be threaded on to the body 2 against a laterally extending rib 20 integral with the body 2.

The body 2 is generally circular in plan and has two parallel bores 21 for the reception of the contact terminals 4, the bores extending from a first side 22 of the body, from which the terminals 4 protrude and a second side 23 which in use is located within the cover 1. The plate 12 is formed with two integral pegs 7 carrying annular ribs 10; the pegs 7 can be received in counterbores 11 in the body 2, being then retained by the interference fit of the ribs 10 with the sides of the counterbores.

For the reception of terminal screws 5, body 2 has transverse slots 24 which extend from the edges of the body to the terminal-receiving bores 21 and open to the second side 23 of the body. The plate 12 is located in a recess 13 in the second side 23 of the body 2, and carries a cable grip 8, to be described hereinafter.

During assembly, the body 2 and liner3 are secured together by the rivets 6. The terminal screws 5 are threaded into holes in the contact terminals 4 which are then dropped into the bores 21 from the second side 23, i.e. in the direction of the arrow E of Figure 2, the protruding heads of the terminal screws 5 entering the transverse slots and coming to rest by engagement with the bottom of those slots. Next, the cord grip plate 12 is positioned, the pegs 7 being forced into the counterbores 11 and retained therein by the ribs 10. Plate 12 then closes the ends of the bores 21 and the adjacent parts of the transverse slots 24, thus preventing the terminals 22 moving in the upward direction as viewed in Figures 2 and 3.

As the heads of terminal screws 5 hold the contact terminals 4 against downward movement by their engagement with the slots 24, the contact terminals 4 are retained in position in the body 2.

Because the screws 5 can be attached to the terminals 4 before assembly of the lampholder, the automatic assembly of the lampholder is facilitated.

In the arrangement shown in Figures 1 to 4 of the drawings, the cord grip 8 is centrally disposed on the plate 12 and has a wedge section. As shown in Figure 4, during installation of the lampholder, the terminally split cable sheath 25 passed through the central opening 24 of the cap 1 is divided by the cord grip 8 and is trapped between that cord grip and the cap 1. The conductors themselves are passed through restricted openings 26 (Figure 2) in the plate 12, for attachment to the contact terminals 4 by the screws 5.

Figure 6 shows a modified form of cord grip plate, in which the cord grip consists of a pair af wedge jaws 14 flexibility attached to plate 12 and normally spaced apart. In use, the cable sheath 25 is passed between the wedges 14 and the conductor is secured to the contact terminals, as before. The dimensions can be arrranged so that, as the cap 1 is threaded on to the body 2, its engagement with the wedges 14 causes the latter to be driven together to grip wider ranges of cable size therebetween as shown in Figure 5. By the use of the cord grip of Figures 5 and 6, special preparation of the cable to split the cable sheath is unnecessary.

The cord grip may alternatively be of the known tortuous path type, in which the conductors are separately led round projections between the cable sheath and the terminals. In this case the plate 12 is formed integrally with a structure incorporating the projections forming the tortuous paths.

Preferably, the cap 1 and body 2 are made from thermoset material, while the cord grip plate 12 is thermoplastic.

Claims (9)

1. A lamphoider of the type described, in which the terminal receiving bores extend through the body, and which includes retaining means securable to the body to close the transverse slots and/or the terminal receiving bores at the second side of the body and thereby to prevent egress of contact terminals from the bores at the second side of the body.

2. A lampholder according to claim 1, in which the retaining means comprises a plate overlying at least a part of the second side of the body and having restricted openings to allow the passage of electrical conductors to terminals located in the terminal receiving bores.

3. A lampholder according to claim 2, in which the plate has integral pegs receivable with a push fit in corresponding holes in the body.

4. A lampholder according to any one of the preceding claims, in which the retaining means includes a cable grip.

5. A lampholder according to claim 4, in which the cable grip is a spigot projecting away from the body and receivable in part in the central opening of a cap threaded on to the body, the cables in use being gripped between the cap and the spigot.

6. A lampholder according to claim 4, in which the cable grip comprises a pair of wedge jaws carried by the retaining means to grip therebetween a cable sheath.

7. A lampholder according to claim 6, in which the jaws projectfrom the retaining means for engagement by a cap as the latter is threaded on to the body.

8. A lampholder of the type described having a lampholder cap attachable to the body and a cable grip comprising a pair of normally spaced apart jaws attached to a plate securabie on the body and projecting from the plate for engagement by the cap, the arrangement being such that, in use, attachment of the cap to the body urges the jaws towards one another.

9. A lampholder of the type described, substan- tially as herein described with reference to the accompanying drawings.