Patent GB-641476-A (GB)
Title: Improvements in or relating to electric launching systems or catapults for airborne craft and control means therefor
IPC: B64F1/06
Filed: 1947-07-16
Abstract: 641,476. Electric railways. WESTINGHOUSE ELECTRIC INTERNATIONAL CO. July 16, 1947, No. 18908. Convention date, Jan. 28, 1943. [Class 104 (iii)] [Also in Groups XXXIII, and XXXV] An electric launching system or catapult for airborne craft comprises a reversible towing car which is driven on a track on the principle of a flattened out or developed induction motor, the system being controlled by a relatively stationary power switch for controlling a supply of polyphase energy in the requisite phase sequence, and associated control means for initiating and terminating a forward run in one phase sequence, with further control means responsive to the termination of the energization of the forward run for initiating a reverse phase sequence energization of the body. The part of the developed induction motor carried by the car may be either the primary or secondary winding, the complementary winding being located in a long shallow trough and providing a substantially flat surface level with that of the runway, the airgap between the two windings being relatively very small. As shown in Fig. 4, a polyphase primary member 17 carried by the car 7 comprises a laminated magnetizable core with slots to receive a winding 25, preferably 3- phase, extending substantially the whole length, being omitted from inclined ramps 21 at each end. Wheels 15 on the car run on track rails 16, and shoes are provided within housings 27 to co-operate with third rails 26 which may be of the slotted type, whereby 3-phase power is fed to the primary winding. The stationary secondary member 18 comprises a laminated magnetizable core 28 with a squirrel-cage winding which preferably comprises three portions having different resistances, the end portions 4, 6 being of higher resistance than the intermediate portion 5 upon which the car travels with considerable speed until the towline 8 to the aircraft is released, whereupon a rapid braking of the car is initiated. Control is effected by a 5-point switch 34, Fig. 5, with an " off " position and four operative positions S<1> 1 ... S4, of which S1 energizes a " ready " signal 35. Position S2 corresponds to " take off " and energizes a relay 80F. to close three contacts 36 and connect an 80 cycle 3-phase bus-bar 38 to bus-bars 37 connected to the track rails and third rails of the system, whereupon the towing car commences to pull the aircraft along. When the aircraft reaches a predetermined position on the runway 3 the car closes a track switch TS-400 which operates a relay TS1, thereby 'opening the circuit through contacts 40 and 44 and de-energizing relay 80F to re-open the bus-bar connections 36. At the same time a reversing-relay 80R is energized and closes the bus-bar connections 43 to energize the bus-bars 37 in a reverse phase sequence, thus causing the field of the primary winding to move in the return direction and braking the towing-car 7 strongly, tending to make it reverse its direction of movement. The car then decelerates rapidly while the aircraft moves on ahead, becomes unhooked from the tow rope, and is thus airborne. When the towing car comes to a stop, or just before, or just after (when it actually reverses) the operator advances the control switch 34 to the third position S3, thereby switching the power feed from the 80 cycle bus-bar 38 to a 16 cycle bus-bar 47 to obtain a slow return speed of the car back to its starting point. The control switch is advanced to position S4 as the car approaches the starting point, thereby de-energizing the 16 cycle reverse phase contactor 16R and energizing a 16 cycle forward contactor 16F to brake the car. As -the car comes to a stop the control switch is moved to the " off position. In a modification, Figs. 6 and 7 (not shown), the runway comprises the developed primary winding of a polyphase induction motor, and the towing car the developed secondary winding, the operation also being controlled by the system shown in Fig. 5.