Patent GB-585412-A (GB)
Title: Improvements in or relating to heat interchangers
IPC: F01P7/16
Filed: 1944-06-14
Abstract: 585,412. Fluid-pressure servomotorcontrol systems. BROWN, C: A. June 14, 1944, No. 11410. [Class 135] The flow of coolant through a heat interchanger is controlled in accordance with variations in the pressure or temperature of the fluid being cooled or of the coolant by means of a servomotor control system comprising a pilot valve, a servomotor actuating a shutter or valve controlling the flow of coolant, and a follow-up device co-operating with the pilot valve. The invention is shown applied to an engine oil cooling system in which the coolant (air) is regulated according to the drop in the oil pressure across the interchanger. Oil is forced through the interchanger by an engine-driven scavenge pump and a tapping 118, Fig. 1, from the inlet leads through an aperture 89, Fig. 8, in a sleeve " follow-up " valve 83 into a chamber 106-in which.,it can act on the closed end of a piston valve 97. Oil flowing from the interchanger through a pipe 26 has access to the interior of valve 83 past a filter 117 and through apertures in a sleeve 112 and a slidable plug 111. The latter is adjustable in position by a screw 116-and it also forms an abutment for one end. of the loading spring 109 for the valve 97. Pressure oil is also tapped off from the inlet to the heat interchanger through a pipe 35, and valve 97 controls the flow of this oil through the followup valve 83 and passages 76, 77 to one side or the other of the servo-piston 8. The latter actuates a lever 13 secured to a shaft 11 which extends outside the casing 3 housing the pilot valve and servomotor, and the shaft is connected outside the casing to a rod 16 which actuates through a bell-crank 17 and connecting rod 19, the shutter controlling the flow of coolant. An extension of lever 13 is connected to the follow-up sleeve 83 so that the latter will be moved by the servo-piston to neutralize the movement of valve 97 as the coolant shutter is moved to its new position. Should the oil pressure-drop across the interchanger become excessive, the servo-piston may operate a valve to by-pass some of the oil. The pressure oil flowing through pipe 35 to the pilot valve passes first through an. over-riding rotary valvo 36, Fig. 3, so that, should the oil be below a minimum temperature, a spiral bi-metallic thermal element 55 situated in the outlet 26 will actuate the valve 36 either to cut-off the supply of oil to the pilot valve and-place both ends of the servo-cylinder in communication with each other so that the loading spring 9 in the servo-cylinder will force the piston to the position in which the shutter controlling the coolant fluid is closed, or the full oil pressure is allowed to reinforce spring 9 for the same purpose. One end of the thermal element 55 is connected to the stem of valve 36 and the other to an adjustable holder 56 which is locked in position by a lock-nut 58. A time lag in the speed of response of the servomotor is provided by an adjustable choke 122 in the oil pipe 119 or an adjustable choke 123 in the passage 77. Pipe 119 may be connected to a separate source of pressure oil. In another embodiment, a chamber 155, Fig. 9, filled with a fluid sensitive to temperature changes, is situated in the oil outlet or in the coolant fluid duct, and the chamber is connected to capsules 152 which can actuate the pilot valve 124. The temperature range of the capsules is varied by screwing in the cap 161 to which one end of the capsules is secured. Valve 124 is loaded by a spring 153 and is provided with passages 158 which allow the valve to be balanced. The follow-up sleeve 125 is moved in one direction by a rod 146 connected to an eccentric on the shaft 11 and in the opposite direction by a spring 144. In modifications of this last embodiment, the fluid may pass through the chamber 159 and act directly on the capsules, and the latter may be replaced by a bi-metallic coil. Valves 97 and 124 and follow-up sleeves 83, 125 may have a rotary instead of a longitudinal displacement.