GB787871A - Improvements in and relating to thermocouple temperature alarm systems - Google Patents

Abstract

787,871. Electric automatic temperature alarms. BOGUE ELECTRIC MANUFACTURING CO. Sept. 12, 1955, No. 26093/55. Class 118 (1). [Also in Group XXXIX] A temperature alarm system for the bearings of a machine comprises a thermocouple monitoring system having test thermocouples 11, Fig. 1, located at the bearings, and reference thermocouples 17 located within a container 18 the interior of which is maintained at a temperature of about 100‹ F. higher than the temperature of the test junctions 11 by a heater 19 regulated by a detector resistance 21, rheostat 23, and control device 20, in a known manner. Each test junction 11 I is connected via contacts 12, 14 and a reference junction 17 to input terminals 15 of a two-stage magnetic amplifier 16 (see Group XXXIX), and the system is supplied from an A.C. source 22 feeding a transformer 22a. Each switch 13 is actuated by a relay coil 24 and includes .contacts 25 connected to a cold jimetion thermocouple meter 26 so that when any one coil 24 is energized and its switch 13 operated the meter 26 may give a temperature reading of the respective test junction 11. The output 27, 27a of each amplifier 16 is supplied from its test junction 11 to a relay coil 28 operating a switch 29 which controls a warning light 33 and also a relay coil 37 holding off an audible alarm 34. The system also comprises the three position switches 36 each having a pair of fixed contacts 38, 39 selectively engageable by a movable contact 40, and a pair of contacts 41, 42 sequentially engageable by a contact 43. The switches 36 are connected to the relay operated switches 24, 29 and are interconnected as in Fig. 1 in which the system is shown operative. In operation a temperature alarm condition at a test junction 11 will cause the temperature differential between the test junction 11 and its reference junction 17 to decrease, thus decreasing the energy supply to the amplifier 16 thereby operating switch 29 to make contacts 30, 31., 30a, 32, to light a lamp 33 and deenergize coil 37 which is supplied through a contact 30 from terminals 46, 46a of a power supply 22a, the de-energizing of coil 37 causing the alarm 34 to operate. The switch arm 44 of the switch 36 is then moved to the "off" position in which the contact 40 is moved to touch 38 which re-closes the circuit to coil 37 to shut off alarm 34, but the lamp 33 remains lit until the temperature returns to normal when coil 28 will be re-energized to operate switch 29. When switch 29 operates the contacts 30, 31 will be opened which will de-energize coil 37 and operate the alarm 34 which indicates that the arm 44 of switch 36 should be returned to its "on" position to normalize the system. When a temperature reading on meter 26 is to be taken in respect of a selected test junction 11 the switch 36 is moved to the Fig. 5 position which energizes the coil 24 to make contacts 12 and 25 thus connecting the junction 11 to the meter 26. While the reading is being taken the amplifier 16 has no output and the coil 28 would be de-energized to sound the alarm were not contacts 41, 43 of switch 36 keeping the coil 37 energized. Open-circuit faults in the system de-energize the coil 37 and operate the alarm, and a rheostat 68 on each amplifier 16 permits the temperature alarm setting to be adjusted. The temperature of the container 18 may be checked by a hot junction connected to the meter 26 through a switch 70 operated by a relay coil 71 in circuit with a switch 72.