Patent GB-194736-A (GB)
Title: Improvements in and relating to arc lamps
IPC: H05B31/00
Filed: 1921-09-14
Abstract: 194,736. Jackson, P. R., (Sperry Gyroscope Co.). Sept. 14, 1921. Arc lamps.-In a projector, Fig. 1, for motion pictures or the. like, the burning end of the positive electrode 34 is maintained in a fixed position in the optical axis by an electromagnet the circuit of which is completed by contact of the arc flame with an auxiliary electrode 152: the positive electrode may lie in or, as shown, at a small angle to the optical axis, the negative electrode being inclined to the positive and also to the optical axis. The positive electrode-holder 35 is rotatably mounted in a carriage 36 mounted on a threaded rod 26 connected by a universal joint 27 and an insulating coupling 29 with a square shaft 28 which may be turned to feed the electrode by a knob 43 or bv an electric motor 77 with which it its coupled by the action of the controlling electromagnet. Mounted parallel and similarly to the shaft 28, as shown in Fig. 13, are a shatt 32 adapted to rotate the electrode-holder 35 through gearing 39, 38, and a shaft 71 adapted to rotate a threaded rod 69 on which is mounted a carriage 68 connected by a link 67 with the negative electrode-holder. The gear for automatic actuation of the shafts 28, 33, 71 is mounted outside the lantern on a panel 86, Fig. 2. The motor 77 is connected by a flexible shaft and worm-wheel, not shown, with a wheel 89, gearing with a wheel 90 carrying an eccentric pin 91 engaging a forked lever 92, pivoted on a hub 93. Oscillation of the lever is communicated by a fork 96 and pin 97 to a carriage 98 on which are pivoted two pawls 100, 101. Secured to the armature of an electromagnet 114 controlled by the auxiliary electrode 152 is a resilient member 115 adapted to engage the pawl 100 when the armature is attracted and to raise it into engagement with a ratchet wheel 104 through the hub of which the square shaft 28 passes. The'shaft 71 is similarly brought into gear with the motor 77 by an electromagnet 109 controlled by an auxiliary electrode mounted above the negative arc electrode. The member 98 may be provided with a sloping stop 126 to ensure return of the armature of the electromagnet 109 at the end of each stroke. The wheel 89 is connected by an idler 133 with a wheel 94 carrying a pin 129 engaging a stop-pin 128 on a flange attached to the hub 93, in which the hub 32 it mounted; this provides for manual adustment of the shaft up to one revolution. The forward' end of the electrode 34 passes between a fixed hemi-cylindrical brush 46 and a brush 47 urged upwards by a spring-pressed lever 48, or by weighted lever. The auxiliary electrode 152 may be circular and rotatably mounted in a bracket 151 extending over the forward part. In a modification, the positive electrode-holder is provided with two auxiliary electrodes, the bridging of which by the arc flame completes a local circuit containing the electromagnet 114; in this case the negative electrode feed is controlled by a differential series-shunt electromagnet without the use of an auxiliary electrode. The arc is struck by pulling the rod 71 against the action of a spring 74; in a modification, the arc is struck by a solenoid of which a part of the rod 69 forms the core. The circuit of the motor 77 may contain a switch adapted to be closed by an electromagnet in series with the arc. The motor 77 may drive a fan 78 supplying air to a hollow frame 25 carrying the electrode-holders. The lantern 1 is provided with ventilation holes 147, 148 and a chimney 149; an opening 200 is provided for insertion of the positive electrode. Means are provided for tilting the frame 25 or adjusting it laterally. Connections. for operating several lamps in series, are described.