Switching device with time-delay control

摘要

611,816. Switching systems for consumption apparatus. PHILIPS LAMPS, Ltd. May 9, 1946, No. 14027. Convention date, Feb. 18, 1942. [Class 38 (iv)] [Also in Group XXXVII] A switching system, particularly for use with X-ray or welding equipment and for automatically ensuring the closure of one or more auxiliary circuits a predetermined time before the closure of a main circuit which is subsequently opened after the passage of either a predetermined quantity of energy or time, comprises a relay 21 for the main circuit 31, 32, controlled through a delay circuit by an auxiliary relay 1 having contacts controlling the auxiliary circuits, the energizing circuit of the last relay including contacts 29, 30 which are temporarily opened, to ensure de-energization of the auxiliary circuits, whenever the first relay is opened. The main circuit may be the high-tension supply circuit for an X-ray tube and the auxiliary circuits those for supplying heater current and current for rotating the anode. The delay circuit comprises a thyratron 15, the anode circuit of which includes the winding of relay 21 and which is energized from a pulsating D.C. source 20, the grid circuit including a timing condenser 9, associated resistor 11 and battery 10. Timing of the exposure is by a circuit 26-28 which deenergizes relay 21. To initiate an exposure, press-button switch 8 is operated, thereby energizing, over normally closed contacts 29, 30 of relay 21, the winding of relay 1 which, on picking up, holds in over contacts 5, closes the auxiliary circuits over contacts 3, 4 and removes a short-circuit from condenser 9 at contacts 6. The condenser voltage rises and eventually overcomes a hold-off bias 13 previously applied to a grid 14 of the thyratron which then conducts and energizes relay 21 from the pulsating source 20. Relay contacts 22, 23 in the main circuit, close and the tube is energized, auxiliary contacts 19 of this relay simultaneously opening to remove a short-circuit on the tuning condenser 26. The condenser voltage rises and eventually overcomes a " turn-on " voltage 17 on another grid 16 of the thyratron which then becomes non-conducting and de-energizes relay 21. A spring 25 returns the relay contacts to their initial positions, Fig. 2, to terminate the exposure, momentum, however, temporarily separating contact 29 from contact 30, which is carried by a pivoted arm, and so interrupting the holding circuit of the auxiliary relay which then drops out. In another construction, contact 29 is carried at the free end of a flexible strip fixed at the other and the armature of relay 21 is arranged to strike an extension of the arm carrying contact 30 to cause temporary separation of the contacts.