Patent GB-766970-A (GB)
Title: Improved installations or systems for motion picture projection
IPC: G03B21/00
Filed: 1955-02-28
Abstract: 766,970. Kinematograph apparatus. DOWLING, R. W. Feb. 28, 1955 '[March 16, 1954], No. 5876/55. Addition to 759,088. Class 97(1) In a system according to the main invention there is provided electrically-operated mechanism, responsive to the actuation of the projector, for feeding a control strip to bring markings thereon to operative positions to produce electrical signals for effecting the changes of size of projected pictures and un-masked screen area. As shown, Fi'g. 5, a control band R driven from the film feed mechanism through reduction, gear, or the film itself, carries a perforation which initiates each change in the projection conditions. A feeder 47 enters the perforation under the action of a spring 50 and closes contacts 44 to energize a solenoid 74 to actuate a feed claw 79, against a spring 82 to feed a strip or card 75 one step. Perforations are provided in the card at one or other of a number of lateral positions to permit, at particular stages of the feed of the strip 75, feelers 84 to rise and open normally-closed contacts 86 or close normally-open contacts 88. These contacts actuate relay systems controlling the operation of screen masking curtains or devices for changing the picture size or brightness. Thus Fig, 8 shows part of a system including two projectors and a screen having pairs of masking members at the vertical and horizontal margins connected respectively to two endless cables one of which is shown at 24 pasing round a pulley 26 on a shaft 27 so that rotation of the shaft produces equal and opposite movements of the members of one pair, the other pair being similarly operated. The shaft 27 is driven by a motor M3. Another motor M1 drives a shaft 31 carrying pulleys 30 driving members 19 through endless cables 17 in tubular guides 18. The members 19 form parts of the projector lens mounts and their rotation adjusts the focal lengths to vary the projected picture size as described in the parent Specification. Another motor may adjust the. brightness of the projection light source. In the arrangement shown the motors M1 and M3 are simultaneously operated to increase the picture size and the effective screen size by energization from a source 39 through contacts 56 of a relay 54, the coil of which is connected to a supply 55, when a feeler 84 moves to close a switch 88a. The relay has hold-on contacts 59 in series with a limit switch 61 and the motor may run until a projection 63 on the disc 63<SP>1</SP> on the shaft 31 opens this switch. A decrease of picture size is similarly produced when a feeler 84 moves to close the switch 88b and actuate a relay 57 to energize the motors to run in the opposite direction to that produced by the relay 54. The relay 57 has hold-on contacts 60 and is associated with a limit switch 62. Energization of either relay also energizes a coil 68 through contacts 66 to 67 to free a brake from a drum 92 on the shaft of the motor M1 and also frees a similar brake on the motor M3. The stopping of the motors M1 and M3 in whichever they are running is effected when a feeler 84 moves to open the switch 86 and de-energize a relay 70 the normally-open contacts of which are in series with the hold-on contacts of both relays. Similar relay systems may be used for controlling independently, in response to other feelers, motors operating other functions of the system or for initiating a change-over between projectors. The shape of the unmasked screen area may be different from that of the picture if the masks are covered with light absorbing material such as velvet.