Patent GB-876403-A (GB)
Title: Control system for automatic positioning of switches
IPC: H03J5/14
Filed: 1957-08-26
Abstract: 876,403. Electric selective signalling systems. CURTISS-WRIGHT CORPORATION. Aug. 26, 1957 [Aug. 28, 1956], No. 26914/57. Class 40 (1). Apparatus for positioning a controlled switchable member at one of a discrete number of positions corresponding to the position of a controlling switchable member comprises a potential source 109, Fig. 2, providing a pair of potentials balanced to ground a plurality of similar control circuits connected across the source so as to receive the potential pair at the common ends thereof, each control circuit comprising a plurality of interconnected impedances with at least a first and a second interior impedance junction point in each control circuit available for further circuit connections, the first and second impedance junction points of each control circuit being normally at balanced potentials with respect to the reference potential a first switch 103a actuated by the controlling member 100a for either connecting or disconnecting the first junction points of the control circuits with said reference potential for establishing different combinations of connections and disconnections with said reference potential in the several positions of the first switch, a second switch mechanically connected to the controlled member for normally connecting to the reference potential the second junction points of those control circuits whose first junction points are connected to said reference potential and normally disconnecting the remainder of such second junction points from said reference potential and means responsive to unbalance of potential as between the first and second junction points of at least one of said control circuits for sequentially positioning the second switch 103b to re-establish correspondence with the position of the first switch. In a selector tuning switch arrangement in which A, Fig. 2, is a master ground transmitter station and B, C, D (C, D identical to B) are slave receiver stations in aircraft or aircraft trainers, the selector contact wafer 103a of the master station can be moved automatically or manually through a series of eight positions and is designed to have projections of such differing circumferential extents that three selector lines 11, 12, 13 can be (a) all earthed (via 106a); (b) none earthed (if none contact any projection); (c) any two can be earthed; (d) any one can be earthed (or more generally 2<SP>N</SP> positions for N selector lines, so that any and every combination of selector lines can be earthed) and the three selector lines are connected through respective resistances 31b, 32b, 33b with one end of a transformer secondary 108 balanced with respect to earth (at 111) and through resistances 41, 42, 43 to respective diodes 71, 72, 73, and the identical rotating slave selector switch 103b is similarly connected to the other end 113 of the transformer secondary 108 via resistances 31b<SP>1</SP>, 32b<SP>1</SP>, 33b<SP>1</SP> and via resistances 41<SP>1</SP>, 42<SP>1</SP>, 43<SP>1</SP> to respective diodes 71, 72, 73 so that when slave selector switch 103b is in the same position as master selector switch 103a the circuit is balanced but if slave selector switch 103b differs in position from 103a due for example to a tuning movement of 103a to the next switch position, current passes through one or more the diodes 71, 72, 73 to develop by means of R-C circuit 116, 117, a biasing potential on the grid 118 of a triode 119 to cut it off so that relay coil 122 is deenergized, and armature 124 goes to position 124<SP>1</SP> so energizing " rotary solenoid " 128 which rotates shaft 104b to rotate slave selector switch 103b to the same position as that to which the master selector switch 103a has just been adjusted. The main advantage is that further slave stations can be added without interrupting operation of the already existing master and slave stations. It is stated that the invention is applicable to switchable apparatus in general such as mechanically, electromechanically or electronically switchable apparatus. The master and slave selector switches 101a, 103a, 101b, 103b can rotate in either direction, and tuning is effected by moving wiper 102 of selector switch wafer 101a ganged to selector switch 103a by motor shaft 104a. Selector switches 101a, 103a, 101b, 103b ... have the same number of switch positions, and 101a 103a; 101b, 103b . . . can in fact be on the same or opposite faces of a single disc. In the normally balanced circuits, R 31b  = R 31b 1, R 32 b = R 32b 1 ,  R 33b  = R 33b 1 ,  R 41 1 = R 41 , R 42 1 = R 42 , R 43 1 = R 43 , R 41  = R 42  = R 43 . R 41 , R 42 , R 43  are of the order of 100,000 ems while R 31b , R 32b , R 33b  are of relatively low resistance i.e. of the order of thousands of ohms. When 103b has been rotated by solenoid 128 to position (2), contact 12b is now grounded so the corresponding diode 72 is rendered non-conducting so that triode 119 is made conducting and armature 124 returns to 124<SP>1</SP> so -breaking the energizing circuit of solenoid 128. N can be 1, 2, 3 or any larger number e.g. if N = 5 there are 32 possible positions (2<SP>5</SP>). If the number of switch positions is not an exact power of 2, e.g. three, then the number N of contacts 11, 12, 13 is the same as in the case of the next higher power of 2. Thus for 2<SP>N</SP> + p positions there are N + 1 selector lines 11, 12, 13 where 1 #p#2<SP>N</SP>. Extra slave stations C, D .. can be added, the corresponding selector switches 101c, 103c; 101d, 103d. . . . aligning themselves automatically with 101a, 103a. Alternatively additional circuits similar to 125 can be added in slave station B, each motor similar to 128 driving a shaft 104c, 104d ... to bring selector switches 101c, 103c, 101d, 103d ... into the same positions as 101a, 103a. In a modification 105a can be stationary and selector contacts 11a, 12a, 13a rotatable. In another modification diodes 71, 72, 73 can be inverted and triode 119 normally biased to cut-off, in which case X instead of Y is connected to source V in solenoid circuit 125. A reversing switch can be provided to give bi-lateral operation of the solenoids such as 128, i.e. clockwise or anti-clockwise rotation, according to the direction of rotation at the master station. For " bi-lateral " operation, Fig. 4, the functions of master and slave stations are combined in a single station; in this case all rotations must be anti-clockwise. In Fig. 4, N = 2 so there are 4 selector switch positions in 103b and two external selector lines 11b, 12b. Manual rotation of knob 310 to select a new frequency as indicated by pointer 311 on a dial automatically actuates push-button switch 314, thus breaking the circuit 125 of solenoid 128. A circuit is thus made 125a-316-320-328<SP>1</SP>- relay coil 330- 332-334-125b so energizing relay coil 330. This causes 328 to go to 328<SP>1</SP> thereby enabling the solenoid 128 circuit to be held broken. The relay coil 330 has an additional energization circuit 125a - 323 - 324 - 3281 - 330 - 332 - 334-125b. The second armature 338 of relay 330 moves to 338<SP>1</SP> and breaks the solenoid circuit in a second place. A third armature 344 normalizes 328<SP>1</SP>, 338 to 328, 338; to do this it is connected to triode grid 350 to earth this grid, the triode 352 being normally cut off by a positive voltage applied to its cathode 354. When the relay coil 330 is energized 344 goes to 344<SP>1</SP> and the triode grid potential builds up to B + due to capacitor 370 charging through variable resistance 372. When the triode 352 thus becomes unblocked relay coil 366 is actuated thus breaking the circuit of relay coil 330 (as 332 goes to 332<SP>1</SP>) and so allowing 328, 344, 338 to normalize. Triode 352 is now cut off again so ending the preclusion cycle of solenoid 128. To prevent manual actuation of solenoid 128 during its preclusion cycle, relay 326 has a fourtharmature 372 to disconnect friction coupling 313. Solenoid 128 is connected through (optional) spur gears 379, 378, friction discs 376, 380 and 374 spur gears 304 and 306 (with optional idler pinion 305) to manually operable selector knob 310. Friction disc 376 can be smaller than friction disc 374 to effect a speed reduction of 376 as compared with 374. Solenoid 128 causes the correct resetting of 102b, 103b, as in Fig. 2. The shaft 381 has secured to each end thereof magnetic members 386, 388, disc member 380 being held against discs 374, 376 by a solenoid 394 having a core 392, the magnetic attraction being supplemented by one or more levers 402 having ball(s) 408 free to move in recesses in the free end(s) thereof to press against disc 386, the pressure being obtained by means of tension spring(s) 410. The lever(s) 402 may also be of magnetic material to reinforce the attractive force. When push button switch 314 is actuated so breaking the circuit of electromagnet 390, disc 386 is freed and electromagnet 418 is energized via Edc-372<SP>1</SP>-414; thus disc 388 is attracted towards electromagnet 418 to disengage disc 380 to a spacing limited by stops 422, 424. The disengaging movement may be reinforced by one or more magnetic levers 426 similar to 402 and similarly biased by tension springs 434. When relay coil 330 is de-energized electromagnet 418 de-energizes, electromagnet 390 re-energizes so disc 380 again engages discs 374, 376. Additional slave stations can be added. It is stated that since there is no true master station 114b can be tied to 107 instead of to 113. Disengagement of disc 380 as above described facilitates external positioning of 103b.