Patent GB-577837-A (GB)
Title: Improvements in or relating to pumps especially for fuel supply systems for internalcombustion engines
IPC: F02M59/00
Filed: 1943-08-06
Abstract: 577,837. Controlling. FREEMAN, A. G. Aug. 6, 1943, Nos. 12714/43, 14643/43, 20160/43 and 14247/44. [Class 7 (vi)] [Also in Groups XXVI and XXIX] In metering liquids to internal combustion engines the liquid is fed to a metering force control release valve disposed in a rotating housing and subjected to the centrifugal forces generated thereby. One form adapted for aircraft engines. comprises a housing 162, Fig. 8, enclosing diaphragms 183, 169, responsive respectively to boost pressure and exhaust back pressure, a temperature sensitive element 158 and a vane pump driven by a shaft 199, the pump consisting of a stator 225, Fig. 9, surrounding a rotor 230. Fuel supplied to an inlet 208 traverses a passage 209 to an annular chamber 207 adjacent the side plate 187 of the pump, the plate being apertured to convey the fuel to passages 228 in the rotor 230. The passages 228 are closed by spring pressed pawls 226 when the pawls are thrust inwards by a cam portion of the stator, but opened when the pawls rise, permitting pressure in a chamber 232 to force the fuel through passages 233 in the pawls past ball valves 229 into passages 231 leading to apertures 224 which open into chambers 221 formed in hollow portions of the driving shaft 199. The passages 231 also communicate through conduits 236 with a chamber 237 having in its wall nearest the driving shaft a ported pressure release valve 239 urged outwards against fuel pressure by centrifugal force and adapted as the speed increases to permit escape of a diminishing part of the fuel to a chamber 241 communicating with the annular chamber 207 on the inlet side of the pump. The mainstream of the fuel flows from the chamber 221 through a metering orifice 212, the passage shown in dotted lines, a chamber 213 and passages 210, 205, to a chamber 222 in communication with discharge nozzles each having a valve 350a, Fig. 10, controlled by a diaphragm 341, actuated by pressure of fuel entering the nozzles past a valve 350. The passage 131 connects the chamber 221 with a pre-set slow running nozzle 211, the needle 215 of which is surrounded by a sleeve 216, adapted to cut off the fuel supply to the valve when the throttle is opened. The main fuel metering orifice 212 is controlled by a valve 134 having a slotted end engaged through a pin 138 with one end of a lever 141 pivoted at its remote end to a slidable casing 159 carrying the heat sensitive element 158. The lever 141 adjacent this end is held by a spring pressed arm 147 against the end of a stem 163 passing through a chamber 219 exposed to exhaust back pressure and closed by the diaphragm 169 secured to the stem; the stem also carries the diaphragm 183 exposed at its remote side to a chamber 174 open to boost pressure through an orifice 175, the stem thus controlling the metering valve 134 through the lever 141 which is adjusted by the temperature sensitive element 158. One wall of the exhaust back pressure chamber 219 comprises a piston 149 connected to the throttle control lever, operative movement of which moves the piston outwards lowering the pressure in the chamber and operating the metering valve 134. A bleed 167 gradually restores the pressure in the chamber. Over part of the throttle range, the mixture strength is varied when a groove 179 in the stem 163 connects a passage 178 leading from the boost chamber 174 with a bleed 181 open to the atmosphere. In modifications the pump comprises a single vane sweeping over a series of crescent shaped hollows in the stator or is in two parts supplying different fuels to a common delivery outlet. In a modification temperature and exhaust back pressure controls are omitted. A metering jet 299, Fig. 14, is disposed in the rotary portion of the pump and controlled by boost pressure only, this pressure being communicated to a chamber 309 closed by a diaphragm 280 secured to the stem 314 of the metering valve 301. A slow running nozzle is arranged perpendicularly to the main nozzle and comprises a triangular needle 330 around which slides a piston 333 displaceable by the fuel pressure. An arm 288 on the needle valve permits manual or thermal adjustment of the valve. The period of opening of this valve may overlap that of the main valve 301.