GB760468A - Improvements in carburation devices of the overflow type for internal combustion engines - Google Patents

Abstract

760,468. Carburetters. SOLEX. Dec. 21, 1954 [Dec. 24, 1953]. No. 36932/54. Class 7 (3). In a carburetter of the overflow type in which fuel is sucked into the engine from an overflow chamber to which fuel is fed from a pump and where a fuel constant level is fixed by an overflow weir from which the excess of fuel drops into a low level chamber the carburetter being advantageously provided with distributing means for connecting the suction side of the pump either with the bottom of the low level chamber or with a fuel tank or with both according to the amount of fuel present in the low level chamber the top portion of the overflow chamber is connected exclusively with the top portion of the low level chamber which in turn is connected with the main air intake of the carburetter whereby on the one hand the same pressure exists in these two portions of the chambers and on the other hand the fuel vapours which are evolved under some conditions in the overflow chamber are conveyed toward the low level chamber instead of flowing directly to the main air intake of the carburetter as was the case when the top portion of the overflow chamber was in direct communication with the main air intake. Fuel is fed by a pump 7 into an overflow chamber 5 in which the fuel is maintained at a level N-N by means of an overflow tube 10 through which fuel' flows to a low level chamber 16 through a tube 18. A float operated valve 21, 22 is provided to connect the suction side of the pump either with the bottom of the low level chamber or with a fuel tank 19 or with both. The top portion of the overflow chamber is connected with the top portion of the low level chamber either by means of the tube 18 or by a separate tube. The tube 18 is of a section sufficient to be sure that even at the maximum fuel flow rate air can flow freely through the conduit 18. It is advantageous thermally to insulate the chamber 16 from the hot portions of the carburation device. For instance under the hood of an automobile vehicle chamber 16 can be located at a point where it is always suitably cooled down by air circulation. When the pump 7 ceases to feed fuel due to stopping of the engine the level in the chamber 5 drops due to the presence of a small orifice 27. This orifice might be replaced by a thin vertical slot or by a plurality of holes. When the engine is stopped when it is very hot vapour bubbles of fuel are formed in particular in the chamber 5. These vapour bubbles when flowing out carry fuel along with them. It has been found that the level N-N can be fixed sufficiently low to prevent this vapour bubble trouble while being sufficiently high to permit of starting the engine even if the pump 7 does not instantaneously feed fuel. An air filter may be provided on the intake 2.