Patent GB-417920-A (GB)
Title: Improvements in or relating to carburettors for internal combustion engines
IPC: F02M1/10
Filed: 1933-01-09
Abstract: 417,920. Spray carburetters. DELCOREMY CORPORATION, 2407, Columbus Avenue, Anderson, Indiana, U.S.A. Jan. 9, 1933, No. 773. Convention date, Jan. 8, 1932. [Class 7 (iii).] The air choke valve of a carburetter is, throughout its range of opening movement, controlled conjointly by suction operated means and by thermally sensitive means. Means are also provided to move the choke valve to a closed position upon sudden acceleration of the engine. One end of a bimetallic coil 19, Fig. 3, is connected to a rod 13 which operates an unbalanced air choke valve, and the other end is fixed to a shaft 18 mounted on a lever 21 which is normally held against a stop 23 by a spring 27, and is connected to a piston 32 operating in a cylinder 33. When the temperature is low and the engine is cranked, suction transmitted through a pipe 11, and through a narrow space formed between a rod 39, of "Invar" (Registered Trade Mark) or other material having a low coefficient of thermal expansion, and a cylinder 35 of brass or other material having a high coefficient of thermal expansion, opens a non-return valve 36 and raises the piston 32 slowly. The choke valve opens only when the flexibility of the coil 19 has been overcome. When the engine fires, the increased suction acting on the piston 32 forces the lever 21 against a stop 24 to open partly the valve. If the engine stops, the piston 32 is drawn downwards by the spring 27 as air gradually leaks past it or is admitted past a controllable leakage port. As the engine warms up, (1) the space between the cylinder 35 and the rod 39 increases and the suction is transmitted more quickly to the piston 32, and (2) the coil 19 opens the choke valve fully. If the engine is re-started when it is warm, the choke valve is held partly open by the coil 19, and it is opened fully by the suction acting on the piston when the engine starts. Suction is also transmitted through a passage 43 to the space beneath a spring-pressed piston 46, Fig. 4, in a cylinder 44, which is connected through a chamber 49, containing a non-return valve 50 opening to the atmosphere, to a second cylinder 54 which contains a piston 55 connected to the end of the coil secured to the rod 13. The suction draws the piston 46 downwards inducing air through the valve 50 and as the coil expands the piston 55 rises. If the throttle valve is opened suddenly, (1) the valve 36 closes, the piston 32 remaining unaffected and (2) the decrease in suction releases the piston 46 which forces air into the cylinder 54, depresses the piston 55 and closes the choke valve momentarily until the coil 19 returns the piston to its original position when the engine fires. The piston 55 may be drawn up suddenly in the cylinder 54 to move the choke valve to an open position. The cylinders 33, 35, 44, 54 are mounted in a casing 16 which is secured to the exhaust manifold. In a modified construction, the device 35-39 is mounted as a separate unit on the exhaust manifold and two suction connections are provided, one leading to the passage 43 and the other leading through the device 35-39 to the piston 32. In modifications, (1) the mechanism for closing the choke valve comprises a solenoid energized by the starting current and (2) a bellows type of thermally sensitive device is used.