Patent GB-202537-A (GB)
Title: Improved means for controlling the distribution of electric power to moving picture projecting machines
IPC: H05B31/00
Filed: 1922-09-20
Abstract: 202,537. Gard, E. G. Sept. 20, 1922. Electromagnetic switches; handles.-The lamps of two kinematograph projectors are so connected to an electric generator that both arcs may receive current of low amperage simultaneously for " burning in," and, by operation of a switch either of them may receive full amperage for projection while the other receives low amperage; the switch is also connected so that, when changing over from one projector to the other, operation of the switch, after the motor of the second projector has started through a temporary circuit, causes (1) the transference of the high amperage from one arc to the other without alteration of any reistance, (2) operation of the cut-off shutters, and (3) completion of the normal circuit of the second motor and breakage of the circuit of the first motor. Fig. 1 shows the connection for a hand-operated change-over switch; the motor 12, solenoid 20 for a cut-off shutter, and lamp 28 are provided in connection with one projector, and the corresponding features 12a, 20<a> and. 28<a> are provided in connection with the other projector. The switch has a hollow handle 3 provided with a head 6 containing push buttons 8, 8<a> by which a contact strip 5 may be pressed on to contacts 7, 7<a>. The switch blade 17 is now conducting and centrally pivoted; it carries a metal strip 16 engaging a contact segment 15 and contacts 18, 18<a>, and also metal portions 25, 25<a> engaging on one face contact segments 26, 26a respectively and on the other face short segments 22, 22a respectively and long segments 24, 24a respectively. When the switch is in the position shown low amperage current passes through leads 23, 23a to the segments 24, 24<a> and thence through the segments 26, 26a and wires 27, 27a to the lamps. When projection is to be commenced the button 8 is first depressed to engage the strip 5 and contact 7, and current then flows through a lead 1, and a wire 2 in the hollow handle to the strip 5, through a wire 9 connecting the contact 7 with a terminal 10, and thence through a wire 11 to the motor 12. The handle is then moved to the left so that a high amperage current from the lead 21 passes through the segments 22, 26 and wire 27 to the lamp 28, but, owing to the length of the segment 24<a>, this movement does not break the low amperage circuit to the lamp 28<a>. The movement also causes the segment 15 and the contact 18 to be connected by the strip 16 so that current passes through the circuit 14, 15, 16, 18, 19 to lift the cut-off shutter and drive the motor 12. The button 8 is now released to break the original motor circuit. When changing over to the second projector, the button 8<a> is depressed to start the motor 12<a> and the handle is smartly moved over to the right, thus completing circuits for the second projector corresponding to those previously made for the first projector and again closing the low amperage circuit for the lamp 28. Fig. 2 shows connections producing an automatic operation of the switch blade 17. A cross bar 3<a> replaces the handle 3 and is l'inked to solenoids 30, 30<a>. Contact segments 34, 34<a>, switch blades 32, 32<a> normally sprung away from the segments 34, 34<a> and terminals 39, 39<a> are also provided, the connections being shown. When projection is to be commenced the blade 32 is pressed into contact with the segment 34 to complete the motor circuit 14, 31, 32, 34, 12, 13. The blade is then moved along the segment and momentarily contacts with the terminal 39 to complete the circuit of solenoid 30 so that it draws down the arm 3<a> and completes circuits as previously described. When changing over the blade 32a is similarly moved. Isolating switches may be provided in the lamp circuits.