Patent GB-803391-A (GB)
Title: Improvements in or relating to carburettor for internal combustion engines
IPC: F02M21/00
Filed: 1955-03-24
Abstract: 803,391. Carburetter devices; materials special for actuating. OFFICINE BOTTO MECCANICA DI PRECISIONE. March 24, 1955 [June 5, 1954; March 15, 1955], No. 8605/55. Classes 7(2) and 7(3) A carburetter device using liquefied gas fuels such as propane and butane or fairly volatile fuel such as various fuels included by the term petrol, comprises a collecting chamber 10 (which in some cases may be the fuel reservoir itself) to which fuel is supplied (or in which it is contained) at a superatmospheric pressure, the chamber having an outlet 16 at the top through which only the gas phase of the fuel is delivered and a second outlet 14 at the bottom through which the liquid phase is delivered, each outlet being connected to a separate pipe and the pipes terminating in the induction pipe 18 of the engine in separate jets, the delivery from the liquid jet being controlled by a pulsating valve 24 so operated through an electromagnet relay 28, 30 by the engine itself that the frequency of its cycle is proportionate to the engine speed and the relative durations of its opening and closing phases are varied in accordance with the engine speed and throttle opening and in particular so that when the engine is idling the duration of the opening phase of the valve is reduced to a minimum so that the liquid jet is substantially inoperative. The electromagnets 28, 30 are alternately excited by means of a rotary member comprising a cam assembly mounted on a rotary shaft 36 rotated by the engine and a cam follower 38 carrying an oscillating contact 40 which is caused to oscillate between contacts 42, 44 which are carried by a lever 54. The cams 46 of the cam assembly swing outwards under centrifugal force as the speed of the shaft 36 increases. The dwell of contact 40 on contact 42 increases as the speed of the shaft 36 increases. The follower 38 and the contact 40 are carried by a resilient blade 52. The lever 54 is connected by a linkage 60 to the throttle valve 20. A lever 58 connected as shown to a diaphragm acted on by the pressure in the induction pipe downstream of the throttle valve carries a pin 56 working in a slot of the lever 54 so that the position of the pin 56 is varied according to the pressure downstream of the throttle valve. Tube 68 is preferably heated to cause evaporation of liquid condensed from the gas owing to expansion of the latter through a pressure reducing valve 66. The needle valve 74 is actuated by the diaphragm shown which is acted upon by the pressure in the induction pipe downstream of the throttle valve 20. When insufficient suction is present, the valve 74 closes. If the suction is very low or nil the spring 84 causes the lever 80 to leave its fulcrum 82 and engage the stem of the valve 24 so as to close the latter. The pressure reducing valve 66 when using liquified gas fuel, may be set to reduce the pressure to approximately 0.5 atmosphere above atmospheric pressure. In the modification of Fig. 2 which is adapted for liquefied gas fuel, only the gas and liquid phases of the fuel are supplied directly from the fuel reservoir 90 which is under considerable pressure. The gas phase is taken from an outlet 92 via a pressure reducing valve 66 and a pipe 94 leading to the gas jet 78, Fig. 1, while the liquid phase is taken from an outlet 96 via a pipe 100 leading to the liquid jet 22, Fig. 1. Pipe 102 is connected through a selector cock 104 to the gas outlet pipe. Nested tubes 94, 100 act as a heat exchanger between the gas and liquid phases of the fuel.