Patent GB-729907-A (GB)
Title: Improvements in or relating to carburetters
IPC: F02M25/06
Filed: 1953-12-24
Abstract: 729,907. Spray carburetters. GENERAL MOTORS CORPORATION. Dec. 24, 1953 [Jan. 9, 1953], No. 35945/53. Class 7(3). Vapours drawn off from the crankcase are added to the mixture through two passages connected respectively to points upstream and downstream of the throttle, the flow through each of the passages being controlled by a valve. As shown, the carburetter comprises a float chamber 14, Fig. 1, main fuel jet 24, idling jet 112, mixture throttle 38, air choke valve 26 and a venturi 120. Fuel-feed. The fuel passes through a filter 48 into a passage 58 controlled by a valve 60 actuated by a float 64 pivoted at 68, the downward movement of the float being limited by a spring 72. Fuel jets. The jet 24 is held in position by a metering plug 76 formed with a passage 78 and has a part of reduced diameter to form an annular space 83 to which air is admitted via a passage in a calibrated plug 86, openings 90 connecting the space with the inside of the jet. A tube 94 extending through the nozzle 24 is connected to a passage 104 terminating in the jet 112 which is variable by means of a valve 114 ; air is supplied through a passage 108 in which is a calibrated plug 110. Throttle and choke valves. The valve 38 is carried by a pivot shaft 40 to which is secured a lever 132, Fig. 3, connected to a governor rod, a stop screw 138 on the lever engaging a stop 140 when the throttle is closed. A lever 142 loose on the shaft 40 has a lug 144 engaging a lug 134 on the lever 132 to close the throttle, the final closed position being determined by a stop screw 146 engaging a lug 148. The valve 26 is mounted on a pivot shaft 28 and has by-pass openings 30, Fig. 2, normally closed by a spring-pressed disc 32 raised off its seat by suction when the valve 26 is closed. A rod 150 attached to a block 158 fixed to an arm 160 on the shaft 28 is slidable within a block 152, and a second rod 162 is fixed to the block 158. A block 164 slidable on the rods 150, 162 has a yieldable connection with the block 152 consisting of a spring 172 engaging screws 168, 170 fixed to the blocks 152, 164. For starting, the block 164 is pulled to the right by a Bowden cable whereby the lever 142 is moved anticlockwise to move the throttle to the closed position and on further movement of the block it engages the block 158 to move the choke valve towards or to the closed position, as desired. Adding crankcase vapours. In Fig. 4 (not shown) a conduit from the crankcase is connected to a chamber having passages controlled by screw-operated conical valves, one passage communicating with the mixture passage through a hole in the venturi 120 and the other, smaller in size, joining the mixture passage downstream of the throttle. The amount of vapour added at each point varies with the suction which depends on the position of the throttle. In a modification, Fig. 5 (not shown), the two vapour passages are the same size and are controlled by spring-controlled suction-operated check valves which prevent reverse flow. In Fig. 2, control is partly by suction and partly mechanical. The conduit from the crankcase is connected at 222 to a chamber 220 having three outlets, 224, 226, 228, to the mixture passage. The outlet 224 enters the passage downstream of the throttle 38, 226 connects with 224 in the closed position of the throttle owing to the provision of a gear on the shaft 40, and 228 connects with a bevel-ended outlet tube 242 passing through the venturi and is controlled by a suction-operated valve 250.