Patent GB-661083-A (GB)
Title: Improvements in electric lighting control apparatus
IPC: H05B37/02
Filed: 1947-05-28
Abstract: 661,083. Control systems for theatre &c. lighting. WILLIAMS, R. G. May 26, 1948 [May 28, 1947], No. 14226/47. Class 38 (iv). Relates to electric clutch-control arrangements in a stage lighting or like illumination control system in which means are provided for automatically clutching an element for moving the dimmer to an operating member, such as a shaft rotatable in one direction, and for automatically declutching the element when the operating member has moved the dimmer to a predetermined position. In the arrangement shown in Figs. 1-4, dimmers 1A-1D controlling separate lighting circuits are manually set by handles 14a-14d loosely pivoted to a shaft 6 and connected to the dimmers by links 4a-4d which move the dimmers through rack-and-pinion drives, such as 2a, 3a, Fig. 2. Each handle carries electromagnetic clutch windings 12b, 13b, Fig. 3, whereby the handle may be selectively coupled to either of two discs 6b, 7b which turn in opposite directions on rotation of the shaft 6. The energization of the clutches is determined by programme contact plates such as 15a, 16a, carried by a base 18 and co-operating with a spring-loaded contact, such as 26a, which is moved about a pivot 22a upon movement of the dimmer with which it is associated. The contact plates are separated by a gap 17a and are each connected to a different clutch winding so that one of the pair of windings is energized over contact 26a so long as the last engages either of the plates 15a, 16a. In consequence, rotation of shaft 6 will move the dimmer in such a direction as to cause contact 26a to move towards the gap 17a. On reaching the gap the contact opens the clutch energizing circuit and further rotation of the shaft is without effect on the dimmer. A pair of contact plates and associated dimmercontrolled contact is provided for each dimmer. Manual control of any dimmer may be obtained by pressing switch buttons 47a-47d on the handles 14a-14d to open the clutch winding circuits. The base 18 carries all the contact plates of the several dimmers and may be rocked laterally and longitudinally of the dimmer-controlled contacts to provide for different programmes. Instead of continuous contact plates, each pair may be divided laterally into a number of sections each comprising two cylindrical surfaces 53, 54, separated by a helical slot, as shown in Fig. 9. The surfaces are carried by a cone 59, the whole being capable of angular adjustment in bearings 57. Linkwork may be arranged between the pivot 22a and contact 26a to impart reciprocating, rather than oscillatory motion to the contact. In a modified arrangement, Fig. 14, the pair of contact plates and their co-operating moving contact are replaced by an assembly of cooperating contacts 93-95 which are moved bodily by the dimmer over a programme plate comprising surfaces 97, 98 at different levels are connected by an inclined surface 96. An insulating pin 90 carried by contact 93 bears on the surfaces and when on the inclined surface causes this contact to be clear of both the other contacts so that neither clutch winding is then energized and movement of the dimmer is arrested. A complete control apparatus utilizing this form of programme plate and including automatic means for laterally moving the programme plates in accordance with a pre-set lighting plot is described.