Patent GB-200211-A (GB)
Title: Improvements in or relating to telephone systems
IPC: H01H63/30
Filed: 1922-04-08
Abstract: 200,211. Conrad, H. S. April 8, 1922. Pneumatic actuation.-A quick-acting fluid motor operated by fluid pulsations is used to drive a hunting switch or to effect the intermittent opening and closure of an electrical circuit. The invention is described as applied to a hunting switch of the ratchet-and-pawl driven type. The driving pawl 5 is carried on a lever 4 mounted on a pivot 3 and connected to the movable portion of a quick-acting fluid motor 6 of the double-bellows or syphon kind, the supply of fluid to which is controlled by a valve 15 normally held open by a spring 18 fixed upon a pivoted member 17 provided with two substantially horizontal arms 22, 24. The arm 24 projects between two extensions 25, 26 on the pawl lever 4, which in its operative position turns the member 17 on its pivot to permit the air-pressure in the pipe 14 to close the valve 15, and in its relapsed position causes the spring 18 to depress the pin 19 and open the valve 15. The link 23 is held under compression between a notch in the end of the arm 22 and a notch in a spring 21, the link 23 and the arm 22 being arranged to be slightly out of alignment when the valve 15 is in both its open and closed positions. Bv this means the member 17 is prevented from assuming an intermediate position. In operation when the circuit of the starting magnet 7 is completed, manually or automatically, its armature 13 opens a check valve 10, thereby admitting air from the supply pipe 11 to a syphon motor 40, an extension 41 on which rises and permits a holding pawl 42 to engage the ratchet wheel 1, whilst the movement' of a collar 45 closes the springs 43, 44 and prepares circuit for a stopping magnet 34. Air is also admitted through the valve 15 to the driving motor 6 which raises the arm 4 and causes the pawl 5 to advance the wheel 1 and its attached wipers a step. In this movement the projection 26 strikes the arm 24 and moves the member 17 to its alternative position in which the pin 19 is freed and the valve 15 permitted to close under air-pressune. The motor 6 now relapses and the lever 4 moves back to its normal position the projection 25 striking the arm 24 and causing the spring 18 to open the valve 15 and again admit air to the driving motor 6, and rotate the wheel 1 another step. This alternate operation of the motor 6 and the valve 15 continues until the test wiper 30 engages an earthed contact 31 and a circuit is completed for the stopping magnet 34, the armature 36 of which is attracted. The end of the armature 36 is formed with a notch 37 which engages under the lever 4 and prevents it from falling back when air is cut off from the motor 6. The wipers are thus brought to rest on the terminals of an earthed line. The rate of operation may be controlled by suitable adjustment of the linkage between the motor and the valve. Release is effected on the de-energization of the starting magnet 7 which cuts off air from the motor 40, the relapse of which, aided by a spring 46, releases the holding pawl 42, and separates the springs 43, 44, thereby de-energizing the stopping magnet 34, which releases the pawl 5 and permits the wipers to return to their normal position, advance to a new position, or remain on the contacts last used. According to a modification, the circuit of the stopping magnet 34 may be opened over the test wiper to release the switch. A modification is also referred to in which the fluid supply is converted into pulsations by a valve intermittently opened by a continuously driven shaft.