GRUNDY'S LAMP HOLDER.
We have recently described and illustrated several forms of incandescent lamp holders which have been more or less in general use, and we now furnish our readers with an illustrated description of an apparatus which we are informed is fitted in the Royal Courts of Justice.
Fig. 1 is the lamp holder as fitted at the Royal Courts.
Fig. 2 is the same adapted to screw into an ordinary gas or other tube.
Fig. 3 is the upper part of the holder, showing the electrical connections, which are identical in both cases. The insulating parts are different, in that, as the upper part of fig. 1 is fixed to its socket by a screw through the centre, there are two separate holes for the leads, while in fig. 2, as it has to be screwed into the pendant or bracket, both leads must come through one hole in the centre to prevent their being twisted.
A is a gun metal nozzle, which is in use in the original fittings at the Law Courts, and for which these holders were first designed; this nozzle terminates the pendant, tubular or flexible. If flexible, the space of the tube is occupied by a fibre, or other insulating plug, with two holes for the wires.
The leads pass through two holes in the part B, and are secured by the binding screws G, in fig. 3, thus ensuring a good contact between the leads and the parts, H, which extend up the sides of the part B as far as the groove, I. S is the screw which secures B to A. The plates, H, one on either side of B, now represent + and - of the circuit, and this part remains a portion of the electrolier or pendant.
Part C is movable, and consists of an insulating block with two metal arms, D, D, spread out in a fan shape, so as to partially encircle the neck of the lamp, and terminating at the other extremity in a collar made to fit the groove, I, in part B; the lamp is connected to these arms by the block, E, being pinched between the two parts of E, E, which are split, by means of the screws, F, F, thus ensuring a perfect contact and great rigidity in the lamp.
There is no danger of fusing either lamp lugs or holder contacts, as the lamp can be adjusted to the part C at leisure, and put up in one second when required. The lamp is first put up, and afterwards connected to the circuit by giving the part C a quarter of a turn, thus enabling the holder to be used as a switch wherever the lamp is within reach, and, when used for this purpose, a stop is added to prevent overturning the holder.
The whole of the contacts are in sight, and if used in a damp place, or anywhere where oxidization can take place, they are easily cleaned; in fact, the rubbing of the surfaces together in switching on and off will have a cleaning effect on the contacts.