Patent GB-647725-A (GB)
Title: Improvements in direct-reading recording meters
IPC: G01K1/02
Filed: 1947-08-05
Abstract: 647,725. Electric indicating systems. SYLVANIA ELECTRIC PRODUCTS, Inc. Aug. 5, 1947, No. 21275. Convention date, April 18, 1942. [Class 40 (i)] [Also in Group XX] In an automatic recording apparatus, a pointer rotatable in dependence on a variable operates follow-up contacts controlling a motor which moves a recording chart longitudinally relatively to a recording stylus movable in dependence on a second variable to trace a graph of the relationship of the variables. Fig. 1 shows a direct reading dilatometer in which a quartz specimen tube 13 is suspended from a spider 21 within a copper block 5 having a number of diametrically-arranged longitudinal channels 7 connected at the ends by headers 8 communicating with tubes 10, 11 for the circulation of a cooling fluid. The bottom of the tube is closed by a quartz disc having a central perforation 15, and the block is surrounded by a refractory tube 3 wound with a heating coil and enclosed in a heat-insulating jacket 4 within a stainless steel shell. An inlet pipe 12 in the copper block allows any desired atmosphere to be admitted to the specimen tube, and the heating and cooling of the furnace is regulated according to a predetermined law by a known heating cycle controller. The rod-shaped test specimen 1 is inserted through a window in the lower end of the quartz tube, and is contacted by the lower end of a tubular quartz rod 17 sliding in the outer tube 13 and wound with the wires of a thermocouple 18 whose hot junction is threaded into a transverse hole midway along the specimen. The upper end of the rod 17 bears on the plunger 21c of a standard dial displacement indicator 22 and the thermocouple is connected to control the recording arm 24 of a known automatic potentiometer temperature recorder. The displacement indicator pointer has a contact 25 moving between closely-spaced adjustable spring-loaded follow-up contacts 39, 40 (Fig. 7), rotated by and insulated from a shaft 30 driven through gearing by a reversible dynamically braked motor 57, which also drives the chart traversing drums of the recorder through a slipping clutch. On expansion of the specimen with rising temperature, contacts 25 and 40 close, and positively charge the starter electrode 73 of the cold cathode gas triode tube 70 from supply L through resistance 75, so that the tube ionizes and operates relay 62 which energizes one of the motor control windings so that the motor rotates the follow-up contacts until the control circuit is broken, and the motor stops after traversing the recording chart through a distance proportional to the specimen expansion, while the recording stylus moves perpendicularly through a distance dependent on the rise in temperature. On contraction of the specimen with falling temperature, contacts 25 and 39 close, tube 69 is ionized to operate relay 61, and the motor rotates the follow-up contacts and drives the chart in the opposite direction while the falling temperature is recorded perpendicularly until the contacts open and the motor stops. Thus the recorder graphs the expansion and contraction of the specimen as ordinates against temperature changes as abscissµ over the heating and cooling cycle to which it is subjected. The contact 25 may be replaced by a metal vane varying inductances or capacities in accordance with changes in the length of the specimen to operate a highfrequency relay circuit controlling the rotation of the motor.