Patent GB-908995-A (GB)
Title: Condition monitoring device
IPC: G01K3/04
Filed: 1959-04-08
Abstract: 908,995. Temperature measurement. AVIEN Inc. April 8, 1959 [April 11, 1958], No. 11894/59. Class 40 (1). [Also in Group XIX] Apparatus for registering the periods of operation of a jet engine in several ranges of potentially dangerous high temperatures, the periods registered being over and above those considered safe for each range, comprises a commutator switch 45 producing signals indicative of the range in which the temperature lies, such signals causing time-delay relays 48 to energize elapsed time counters 50 after predetermined periods of operation within the respective ranges. A thermocouple 20 detects the temperature of the exhaust gas and a shaft 37 is caused to rotate through an angle corresponding thereto by a known self-balancing electrical system. The shaft 37 is coupled to a synchro-transmitter 38 and a repeater unit 40 rotates a pointer 41 over a dial face 44 on the instrument panel to indicate the temperature to the pilot. The shaft 37 is also coupled to a drum 45 with conducting segments 46a-46f corresponding to the several ranges of temperature to which voltage is supplied by brush 49 wiping a conducting ring 51. When the temperature approaches the lowest range, a segment 61 passes voltage over a wiper 62 to operate a relay 60 to set a constant speed motor 58 rotating shaft 56 which carries loosely the time-delay assemblies 48a-48e. As each temperature range (except the last) is reached the associated wiper 47a-47e passes a signal to an electromagnetic clutch to couple the respective cam 48a-48e to the shaft 56. Each cam is preset so that, after the appropriate safe period of operation within the range, the raised part 100 of the cam operates a switch 102a-102e to start the corresponding elapsed time counter 50a-50e. When the highest range is reached, a solenoid 165 is energized to operate a flag 52 on the dial 44 to warn the pilot. The flag 52 can be reset by closing switch 80 housed with the counters 50a-50e and accessible only to maintenance staff whereby potential damage due to overheating can be assessed. Conditions when starting up from cold are exceptional and temperatures even in the highest range can be tolerated for up to two seconds (the delay preset on relay 48e). The counters 50a-50e are cut out and the alarm 52 is inhibited for these two seconds by linking a switch 160 to the engine starting control so that when it is closed a solenoid 161 changes over gauged double-pole throw switches 162, 163, 164 and time-delay relay 48e is energized from wiper 47f when the highest range is reached so that if this high temperature lasts for two seconds the cam of 48e operates a switch 102f to operate the warning flag 52. The brushes 47a-47f are made circumferentially adjustable with respect to the drum 45 so that the ranges of temperature can be varied. The period of delay in each range can be preset by adjusting the initial stop 108, Fig. 9, to which cam 96 is restored by spring 94, whose tension can be adjusted. The presetting is done by rack and pinion 118, 122 operated through sealing bellows 124 by turning shaft 110. Instead of a thermocouple 20, optical or resistance temperaturesensitive devices may be used. Apart from monitoring temperature conditions in jet aircraft, the system may be applied to monitoring any condition, including temperature and pressure, which can be sub-divided into ranges and to effecting a control as the condition enters each range, in particular the system may be used for temperature control in chemical process automation.