Patent GB-276655-A (GB)
Title: Improvements in or relating to electric lighting control mechanism
IPC: H05B37/02
Filed: 1927-08-11
Abstract: 276,655. Westinghouse Electric & Manufacturing Co., (Assignees of Masek, J. C.). Aug. 24, 1926, [Convention date]. Controlling consuming devices.-Electric light. ing-control mechanism, particularly for theatres, comprises a, cam-operated device for controlling the current in each circuit, a member driven at a predetermined speed and driving a follower through a yielding coupling, and restraining and releasing means such that the follower, which carries the cam, may be stopped in predetermined positions and subsequently released to overtake the driven member; the cam controls the position of the resistance controlling arm of a dimming resistance. Any number of such mechanisms may be interchangeably arranged in a switch board frame and simultaneously driven to cause predetermined variations in the lighting on each associated circuit, throughout the various scenes in a performance. Each mechanism comprises means for switching on and off at predetermined times. The circuits are susceptible, of manual control either singly or simultaneously. Fig. 1 shows an elementary circuit, controlling lamps 19 which are fed from a.c. supply mains 14 through reactances 15, 16 and a switch 23. The saturation of the reactances is controlled for dimming purposes by a coil 26 fed from d.c. mains 27 through a resistance 32 the position of the short circuiting arm 33 of which is controlled by a cam diagrammatically indicated at 65. This cam is driven through a spring. 41 from a driven member 34 also shown diagrammatically. The member 34 is driven at a predetermined rate by a motor 37 or a hand wheel 38 and carries pins 63, 64 controlling the switch 23 and pins 45, 46 controlling the restraining and releasing of the cam 65. These four pins are adjustable to predetermine the. lighting changes. Figs. 2 and 3 show the mechanism. The driven member 34 is mounted in a framework or drawer 82 which slides in guides 85 in the switchboard framing, carries contacts 90 detachably engaging fixed contacts 80 and is secured by screws 87 to the switchboard structure. Any unit may thus be replaced by another. The annular face 96 of the driven member 34 is divided circumferentially according to the number of scenes and between each " scene " sector is a " change " sector. The lighting circuit is switched on and off by pairs of members 63, 64 which may be set at any position within the arc of 18‹ allotted to the scene concerned by wheels 113 upon graduated screws 115 on the front plate 96. The members 63, 64 may lie in one of two different planes one including a pair of normally open switchblades 51, Fig. 13, and the other a pair of normally closed blades 49; the former pair is in the actuating circuit of the switch 23 and the latter in a retaining circuit therefor. The members 63, 64 may be placed in either plane by turning levers 121, 122 through 90‹. Since the driven member 34 turns at a steady speed the lamps in the circuit may thus be lit or extinguished at times predetermined by the setting of the wheels 113 and levers 121, 122. The cam 65 is constituted by telescopic links 132 carried by pillars 135 to which they are articulated at their ends. One, link covers each " scene " sector and one link each " change " sector. The pillars are mounted on screws 136 carried by the follower 39. The pillars 135 may be set by squared heads 138 to determine the maximum and minimum and also the rate of change of illumination of the circuit during a scene; indicators 139 are linked to, the pillars 135. The cam 65 is engaged by an arm 73 which carries a pin 154 engaging a cam groove in a drum 69. This engages a clutch member 67 splined to a shaft 66 and thus turns a shaft 126 geared to the last to determine the position of the resistance controlling arm 33 and the illumination intensity. To maintain the lighting of a circuit steady at any predetermined intensity arms 163, adjustably mounted on graduated screws 168, cause a clamp screw 42 to stop the follower 39 and the cam 65, the coupling spring 97 then extending. The follower is released and overtakes the driven member 34 when the screw 42 is operated reversely by arms 164 mounted also on the screws 168. A modified form of control comprises stop arms 193 and starting arms 195, Fig. 8, which project into the path of a stop plate 181 pivoted at 182 to a fixed bracket. The stop arms engage the edge of the stop plate and the starting arms a cam surface 201 whereby the stop plate is moved clear of the stop arm. The arms 193, 195 are slidably pivoted on, and engage graduated racks in the face of the follower 39 and driven members 34 respectively and may be set for operating at predetermined times. Manual control of anv selected circuit is obtained by an indicator handle 79 which, through a shaft 144 and fork 170, may be caused to rotate, the shaft 66 and resistance controlling arm 33 to give the degree of illumination indicated by a scale 173; the pointer 172 is adjustably mounted on the handle 79 to compensate for special characteristics of the individual circuit control. Before this handle can be effective a half-round shaft 76, which passes behind all the controls in a rank, must be turned' through 90‹ to free the member 67 from the drum 69. The shaft 76 may, in this position, be moved longitudinally, whereupon pins 81 turn all the members 67 in a rank, and operate simultaneously upon the controlling resistances of all the circuits affected. To enable any mechanism to be brought into register at a point corresponding to any desired scene the driving shaft 36 is carried in brackets 35 fixed to a shaft 223 which is operable to disengage the shaft 36 from all the driven drums. The speed of the follower drum 39 when overtaking the driven drum 34, i.e. the rate of change of illumination at such times may be adjusted to a predetermined value by a fan driven by gearing from the follower drum and having blades the pitch of which may be adjusted by an indicator (not shown) on the face of the drawer 82.