Patent GB-161283-A (GB)
Title: Improvements in or relating to dial switches as used in automatic telephone or like systems
IPC: H04M1/34
Filed: 1920-01-07
Abstract: 161,283. Automatic Telephone Manufacturing Co., Ltd., Smith, S. R., and Savin, J., (Automatic Electric Co.). Jan. 7,1920. Impulse transmitters.-An impulse transmitter of the type in which impulses are sent on the return movement of a finger dial, is provided with a member which is moved at the commencement of the setting operation or during the setting operation, to prevent the generation of impulses until the finger has been removed and the movable member returned to normal under dashpotaction or under control of the same governor as regulates the generation of impulses. The invention also provides improved means for regulating the interval between successive series of impulses, the construction being such that a minimum interval is ensured when the next digit is a low one, such as 2 or 3, without, however, increasing the interval when the next digit is a high one, such as 8 or 9, in which case there is no danger of the next series of impulses commencing too soon. Figs. 1 and 2 show front and rear views of one construction in which the movable finger stop 6 effects the locking of the impulse-generating mechanism. The stop 6 is pivoted on the underside of the dial by means of an annular disc 9 rotatable on pips 8. The impulse-regulating governor-shaft 4 is traversed by a projecting pin 12, which engages the disc 9 except when the disc is in its normal position when the pin is opposite a slot 13. The finger, in setting-up the dial, carries round the stop 6 and with it the disc 9 until the former engages with the side of the guide plate 7. The pin 12 engages with the disc 9 and locks the impulse mechanism until the finger is removed and the stop 6 and disc 9 are returned to the normal position shown in Fig. 2, under the action of the spring 15. Fig. 4 shows a modification in which a fixed finger stop 17 is used. Shortly after the commencement of the setting movement, a dog 19 on the finger hold dial engages with the downturned edge of a spring 18 fixed on the disc 9, causing the disc to move against the spring 15 so that the slot 13 is no longer under the pin 12, Fig. 2. The spring 18 eventually engages with the end of slot 26, but the dog 19 is enabled to pass the spring and be carried round with the dial plate. As soon as the dog 19 passes the spring, the disc 9 is free to return to its normal position under the combined action of the spring 15 and a dashpot 21, thus ensuring a definite minimum interval between successive series of impulses. The dog 19 is so shaped as to pass the spring 18 readily on its return movement, and may be utilized to lock the impulse mechanism in its normal position to prevent further generation of impulses due to the inertia of the moving parts. In a third construction, Figs. 6 and 7, a finger-piece 30 is freely mounted on the shaft 29 and is limited in movement by stops 34, 35 secured to the rear plate 10. An arm 31 on the finger-piece 30 extends to the underside of the plate 10, and in its normal position spreads two contacts 36, 37. A ball 32 on the arm 31 has a freedom of movement in a radial direction which allows it to move in a channel between a guiding plate 33 and a ratchetwheel 28 moving with the dial plate 1. In setting the dial, before reaching the stop 35, the finger engages the finger-piece 30, moving with it the ball 32 and arm 31. The contacts 36, 37 close and short-circuit the interrupter springs 5, Fig. 2, thus rendering the impulse mechanism inoperative until the finger-piece 30 returns to normal. The ball 32 lies in a recess in the ratchet 28 and moves with it. In its movement the arm 31 engages with a pin 38 on the disc 9 and rotates the latter to lock the governor mechanism. When the finger is removed, the finger piece 30 is able to return a sufficient distance to restore the disc 9 and release the governor mechanism, the channels for this distance between the plate 33 and ratchet 28 being wide enough to permit passage of the ball 32. The dial plate 1 then begins to return, and the ball 32 being held by the ratchet at. a constricted part of the channel, returns the finger-piece 30 under the control of the governor. When the finger-piece 30 reaches its normal position, the extension 31 breaks the short circuit across the, interrupter springs and the ball 32 is pressed into the enlarged space allowed by the plate 33 at this position. Effective generation of impulses now commences and continues until the stop 27 on the dial plate 1 strikes against the finger-piece 30.