Patent GB-756948-A (GB)
Title: Temperature control apparatus
IPC: G05D23/185
Filed: 1953-07-27
Abstract: 756,948. Fluid-pressure servomotor-control systems. GARRETT CORPORATION. July 27, 1953 [Aug. 13, 1952], No. 20819/53. Class 135. Apparatus for controlling the temperature in the supply duct 10 of an enclosure supplied with cool air by a conduit 12 and with hot air by a conduit 14 comprises pressureresponsive flow control means for the hot air conduit, a combined amplifier and pressure regulator 30 each part 31, 32 of which includes a valve controlled by a pressure-responsive element, an operating pressure duct for connecting the flow control means through the amplifier 32 to a source of air pressure, and temperature-responsive means 114 for controlling the amplifier. As shown in Fig. 1, the flow control means comprises an actuator 21 having a spring-loaded diaphragm 25 connected to a butterfly or other valve 16 in a conduit 14 supplying hot air at a relatively high pressure to a conduit 10 where it is mixed with relatively cool air from a conduit 12. The temperature responsive means 114 is arranged in the conduit 10 and is adapted to control the amplifier 32 of the combined pneumatic regulator and amplifier unit 30 so as to maintain a constant temperature in the conduit 10. The pneumatic regulator 31 of the unit 30 is connected to the upstream side of the valve 16 by a conduit 99 containing a filter 100 whilst the amplifier is connected to the actuator 21 by a conduit 98. The regulator 31 and the amplifier 32 are generally similar, each having a diaphragm loaded by an adjustable spring and controlling a piston valve mounted in a body part 33 common to both. Thus the diaphragm 43 of the regulator separates two chambers 45, 50, the chamber 50 being open to a low-pressure region such as the ambient atmosphere through an opening 58 and containing an adjustable loading spring 52. The two piston valves 91, 96 each have an enlarged head 89, 88 and are pressed against their respective diaphragms 43, 68 by springs 83, 85. The valves 91, 96 are mounted in ported plugs 120, 127 separated by a wall having a restricted orifice 107. The diaphragm loading springs 52, 77 are adjustable by screwed rods 48, 75 mounted in the end caps 46, 64 held in clamping engagement with the diaphragms 43, 68 by snap-rings 134, 135. The bore 90 in which the valve 91 operates has radial passages 99b, 103, and 104 off it leading to the conduit 99, the atmospheric, and a longitudinal passage 105 respectively. The passage 105 is connected to the chamber 45 through a restricted orifice 108, and to a similar passage 105a in the plug 127 through the restricted orifice 107. The bore 94 in which the valve 96 operates has radial passages 102a, 129 off it leading to the conduits 99, 98 respectively so that the valve 96 controls the supply of motive fluid to the actuator 21 in accordance with the movements of the diaphragm 68. The latter are controlled by a spring-loaded ball valve 159, Fig. 5, adapted to vent the chamber 69 to atmosphere through passages 110, 111. The valve 159 is arranged in a slidable member 160 connected to a relatively inexpansible rod 143 inside an expansible tube 140 having an enlarged head 145 mounted in a boss on the body part 33 and having a screwed plug 150 with a central passage 158 terminating at a seat for the ball valve 159. The head 145 and plug 150 have ports 168, 155 to connect the ball valve 159 to the passage 110. The valve 91 operates to maintain a constant pressure on the inlet side of the restricted orifice 107. In a modified arrangement, the chambers 50, 72 in the end caps are connected by a conduit and the vent 73 is dispensed with.