Patent GB-621464-A (GB)
Title: Control system for de-icer equipment
IPC: B64D15/20
Filed: 1944-10-02
Abstract: 621,464. De-icing equipment. BENDIX AVIATION CORPORATION. Oct. 2, 1944, No. 18841. Convention date, Aug. 11, 1943. [Class 4] [Also in Group XXXV] The inflatable de-icing shoes at the leading edges of the wings and other surfaces of an aircraft are automatically controlled so that the period of inflation of each unit is dependent upon the atmospheric pressure or altitude. The cycle of operations may also be initiated automatically by an ice formation detector. General arrangement,-In the form of apparatus illustrated, the valves of the inflatable shoes are operated by solenoids 65A, 65B ... 65J controlled by a step control relay 40, one arm 60 of which moves successively over contacts 62A, 62B ... 62Y to initiate inflation of the shoes, while the other arm 61 moves over contacts 63A, 63B ... 63Y to govern the period of inflation. The period is controlled by an electronic valve 18 which discharges through a condenser 79 and variable resistances 87, 87A ... 87E, the latter being controlled automatically by a barometric capsule 100D or by a manual adjusting member 94. Cycle of operations.-Upon closure of the main switch 5 the valve 18 operates, energizing an electromagnet 7, which controls switches 7A ... 7D, and charging a condenser 20. Closure of the contact 10 energizes an electro-magnet 39 of the step relay 40, moving a ratchetwheel 48 one step to cause the arms 60, 61 to engage the first contacts 62A, 63A respectively. Opening of the contact 12 results in the valve 18 being cut out, and the closing of contacts 8, 9 and charging of the condenser 79. The electromagnet 7 is deenergized when the discharge action of condenser 20 ceases, thereby opening contact 10 to de-energize the electromagnet 39, the ratchet-wheel 48 being retained in position by a latch arm 52. At the same time the contact 14 is closed to energize an electromagnet 34 and close a contact 37, thereby energizing the solenoid 65A to inflate the first pair of shoes. Upon the de-energization of the solenoid 7, the contacts 8, 9 open, terminating the charging of the condenser 79, and the contacts 11, 12, 13 close, to initiate the discharge of the condenser 79 through the control resistance 87. The potential falls, causing the valve 18 to strike, the solenoid 7 being energized to open contact 14, and the solenoid 34 is de-energized to open the contact 37 and break the circuit of the valve control solenoid 65A, to cause deflation of the shoes. The contact 10 is closed to operate the solenoid 39 to cause advance of the relay arms 60, 61 and closing of the contacts 62B, 63B, whereby the control solenoid 65B is operated to initiate inflation of the second set of shoes. The operation proceeds in this manner until the arms 60, 61 close the end contacts 62Y, 63Y, whereupon on the deenergization of the solenoid 7 the contact 10 is opened, de-energizing the solenoid 39, contact 14 is closed to energize the solenoid 34 and close contact 37, energizing the solenoid 29 and closing the contact 31, resulting in the energizing of a further solenoid 73 by which the arm 52 is withdrawn from the ratchet-wheel 48. A biassing spring 49 then returns the arms 60, 61 to the end contacts 62X, 63X. The contact 63X is connected by a conductor 101 to contacts 102, 104 and a variable resistance 103, the contact 104 being closed by a switch 111 operated by a solenoid 112 energized by an ice detector 114 as described in Specification 621,489 or U.S.A. Specification 2,159,186. When an arm 118 closes the contact 106, the cycle of operations may be initiated by a manually-operated switch 105 closing the contact 102. The period between the cycles may be varied by moving the arm 118 to close the contact 110, and adjusting the resistance 103 which serves as a leak for the condenser 79. With the arm 118 closing the contact 117, the switch 111 closes contact 104 when the solenoid 112 is operated by the ice detector 114, thus initiating the cycle of operations. The control system is shown as applied to a de-icing system of the type described in Specifications 439,284, 604,913 and 621,490.