Patent GB-429871-A (GB)
Title: Improved relay mechanism applicable to deflecting instrument movements
IPC: G01K1/02
Filed: 1934-09-17
Abstract: 429,871. Mechanical relay and follow-up devices. SANDISON, A. G. S., Kelda, Baltasound, Shetland. Sept. 17, 1934, No. 26628. [Class 118 (ii)] To allow a recording pen or other device to follow the movement of an instrument pointer, a boom carried by the pointer is periodically clamped, a striker arm is moved into contact with the boom and the normally clamped recording pen is then released and moved into contact with the striker where it is re-clamped. A single measuring instrument can be connected successively to respond to a number of different quantities and different pens may be selectively released to record its own quantity. As shown in Fig. 1, a boom 1 carried by a measuring instrument is normally clamped by plates 5. As an arm 10 rotates, a striker arm 17 is driven by the friction between arm 12 and wheel 15 until the striker engages either the clamped boom or the stop 24 on the clamped recording arm 19. After further rotation the crank-pin 11 engages the curved surface 28 of a brake arm 25 and releases the recording arm 19. If the striker has stopped at the boom 1 the arm 19 swings towards the striker until stopped by it; if the striker engages the recording arm before meeting the boom, the arm 12 and wheel 15 are effective to carry both striker and recording arm forward until arrested by the clamped boom. When the crank pin 11 leaves the curved portion 28 of arm 25, the arm swings up to clamp the recording pen in its new position. Pin 13 now engages member 8 and first the arm 12 is rotated about pin 13 to release wheel 15 and allow striker arm 17 to restore and then, when arm 12 engages back stop 14, member 8 is forced to the right separating plates 5 by means of the pin and slot connections 7, 9 to allow the boom 1 to swing freely and take up a new position. In the arrangement shown in Figs. 5 and 6, a single instrument 40, 41 is connected in turn to two quantities 44A, 44B and two recording pens 20A, 20B are moved to give records 21A, 21B of the values of the two sources. The general operation is similar to that of the apparatus shown in Fig. 1, but the brake arms are operated through the cams 37A, 37B. When the crankpin 11 engages the end 58 of rod 54 the cams 37A, 37B are turned by pawl 52 to operate brake arms 25A, 25B and release arms 19A, 19B in turn so that each recording arm is effective at every other revolution of the arm 10. As cams 37A, 37B are turned the switch 49 is rotated so that pins 50A, 50B are in turn effective to connect thermo couples 44A, 44B to the instrument 40. Each time the striker arm 17 returns to normal, the stop pin 35 is swung over to engage in turn pins 36A, 36B and to be effective on pins 24A, 24B respectively. Consequently during one revolution of arm 10 the instrument 40 deflects boom 1 to a position controlled by couple 44A, cam 37A lifts brake arm 25A and recording arm 19A is set, whilst during the following revolution of arm 10 the couple 44B is connected to instrument 40 and cam 37B is effective, lifting brake arm 25B so that recording arm 19B takes up a new position. Specification 338,587, [Class 118 (ii)], is referred to.