Patent GB-1220961-A (GB)
Title: Automatic control for hydraulic systems
IPC: F16K17/20
Filed: 1968-03-01
Abstract: 1,220,961. Oil-cooling systems for aircraft &c. TEXTRON Inc. 1 March, 1968 [1 March, 1967], No. 10107/68. Heading F4U. [Also in Division F2) The power transmission of a helicopter or other vehicle, missile or stationary apparatus is cooled by lubricating oil which is circulated in a closed circuit by a pump and contains a flow control means responsive to a predetermined pressure imbalance between the input and output flows in the circuit between the transmission and cooling apparatus to allow the oil to by-pass the cooling apparatus in the event of damage or leakage. The flow control means comprises a by-pass valve 20, Fig. 2, having input ports from pump output line 21 and cooler line 18, and output ports connected to the cooler line 16 and transmission line 29, and the imbalance in momentum between the flows from the pump line 21 and cooler line 18 acts on opposed pistons in the valve to enable the oil to flow through a by-pass channel in the valve from the pump line 18 directly to the transmission. The momentum balance by-pass valve 20, Fig. 3, comprises a body 40 having bores at each end 43, 44 forming coaxial chambers 41 42 and coaxial chambers 45, 46 respectively A hollow cylindrical insert 50 is fixedly positioned in the chamber 41 by a pin 51 and has a bore with larger and smaller diameter sections 53, 54, the transition therebetween forming an annular valve seat 55 for the body 58 of a piston 56, the stem of which passes through the insert 50. The piston also includes an annular disc 60 having peripheral slots 61, Fig. 4, and a dished face 62. A hollow nozzle 70 slidably mounted on a holder 71 threaded on the body 40 closes the chamber 41 and section 43, seats the insert 50 in the chamber 41 and positions the flow of fluid from the nozzle against the face 62 by means of legs 73, 74 which .bear on the face 62 of the disc. The fluid flows from the pump inlet line 21 through a port 77 in the holder 71 into the nozzle 70. A by-pass channel in the body comprises bores 80, 81, 84 closed by caps, which bores respectively communicate with the section 53 in the insert 50, the chamber 42 and interconnect the bores 80, 81. The channel is normally closed by a slidable valve member 85 which is open at one end and which has ports 86 and a leak passage 87 leading to the chamber has ports 46 from which the transmission line 29 extends. A return piston 90 mounted in the chamber 45 has a shaft 91 which is secured to the end 88 of the valve member 85 and projects through a valve seat 93 in the chamber 45. A slidable nozzle 95 for oil from the cooler mounted on a holder 96 threaded on the body 40, is formed substantially as the nozzle 70 and has legs 100, 101 bearing on the face of the piston 90. The pressure of a helical spring 98 mounted between the holder 96 and piston 90 selects the threshold of the differential in momentums between the flows of oil from nozzles 70, 95 impinging on the pistons 56, 90 at which the valve will be actuated. In operation, when the momentum of the inlet stream exceeds the sum of forces represented by the pressure of spring 98 and momentum of the return stream, the valve system moves to the right and the valve member 85 is unseated to allow flow through the by-pass the pressure of which forces the end 88 of the valve member on to seat 93, and the piston 56 contacts seat 55 to prevent flow through the line 16 and all flow from the nozzle 70 passes through the by-pass into the valve member 85 and through ports 86 to transmission input line 29.