"The incandescent lamps supplied by the Westinghouse company are made in four standard sizes, of 16, 25, 50 and 150 c. p. respectively. The greater number of lamps required are of course of the 16 c. p. grade, of which figure 14 is a correct representation in its natural size. The filament is of carbonized silk, a material which has been found to serve the purpose admirably when properly prepared and treated. The fittings of the 16 c. p. lamp are neat in design, ingenious in construction and arrangement, and extremely convenient and efficient in practical use. One of the terminals of the lamp is connected to the insulated brass tip shown in figure 14, and the other to the thimble or cup of sheet brass into which the neck of the lamp is inserted. The thimble is provided with a semi-circular circumferential groove at the end next the tip of the lamp for a purpose hereafter to be explained.
"Figure 15 is a full sized perspective view of the lamp socket and key, of which figure 16 is an elevation, the outer casing being shown in section. Figure 17 is a plan of the socket, the cap being removed, and figure 18 is a section in the plane of the line xx in figure 17. Figure 19 is a perspective view of the same. A perspective view of the socket showing the key and switch is given in figure 20. The various parts are supported upon a block of insulating material, A, upon one face of which is secured a cylindrical cap, B, having flexible resilient arms, b, adapted to grasp the semi-circular groove upon the lamp fitting, before referred to, when the lamp is
shoved into its socket. The opposite face of the block A, carries a metallic conducting bar, D, provided with a spring-jack device d1, d2, adapted to receive and grasp the central contact tip of the lamp. The contact-spring e is brought into electrical connection with another similar spring, e2, by means of a moving contact-piece, e, whenever it is desired to complete the circuit between the terminals B and D, for the purpose of lighting the lamp. The contact-piece e, is a
metallic pin extending through the pivoted plate K, but insulated therefrom.
The standard K1 to which the plate K is pivoted, is affixed to a crank axis, k, provided with a thumb piece k3. The plate k receives its motion through the intermediary of a spiral spring, s, attached at one end to the elbow of the crank axis, k, and at the other to an arm, s2, projecting from the plate k. When the crank-arm k is turned by the key, the end of the spring s is carried to one side or the other of the fulcrum of the plate k, and thus the tendency is to pull the latter suddenly in the corresponding direction the instant it is over the centre. This snap-movement effectually prevents the formation of an arc between the terminals when the circuit is broken. A tube R1, of insulating material surrounds the switch mechanism, and secures it against accidental electrical contact with the metallic case T. The cap is secured to the case by small set screws, o, o, which enter slots forming bayonet joints on each side of the cap, as seen in figure 15. It will be observed that the principle of the adjustable contact between the lamp and the socket in the Westinghouse lamp is precisely the same as that of the spring-jack device which has been so long in successful use in the telegraphic service, the simplicity and continued efficiency of which has been well established.
"Figure 21 shows a fitting designed to be attached to a reading or other portable lamp, and connected therewith by a flexible cord conductor. This is adapted to be inserted into any convenient socket from which a lamp has been removed, and will readily be understood without detailed explanation by referring to figure 22, which shows the same device with its component parts separated in order to more clearly exhibit its internal construction."
