Constant pressure carburettors

In a constant pressure carburettor for an internal combustion engine, said carburettor comprising a tubular wall defining a mixing chamber having an upstream end and a downstream end, a main throttle valve at said downstream end of said mixing chamber, a choke valve at said upstream end of said mixing chamber, means for opening and closing said choke valve in dependence upon the magnitude of air flow through said mixing chamber, fuel distributing means for supplying fuel on to said tubular wall in said mixing chamber, fuel metering means for controlling the supply of said fuel and means controlling said metering means in dependence upon the opening of said choke valve, an inner tube, means mounting said inner tube substantially concentrically within said tubular wall, means defining at least one duct between said tubular wall and said inner wall, said at least one duct extending in the direction of air flow through said mixing chamber and leading to said mixing chamber from a position upstream of said mixing chamber, said at least one duct having a flow cross-sectional area which is small compared with that of said inner tube, means defining a flow constricting profile at the upstream end of said at least one duct for constricting the flow through said at least one duct to produce a stable air flow therein, said fuel distributing means including means for discharging said fuel into said at least one duct downstream of said flow restricting profile, said choke valve being located in or adjacent the upstream end of said inner tube, said choke valve comprises a displaceable valve, said carburettor further comprising a diaphragm box, means connecting said diaphragm box to said mixing chamber, means mechanically connecting said diaphragm box to said choke valve, whereby the opening of said choke valve is adjusted in dependence upon the pressure in said mixing chamber, wherein the improvement comprises a partition wall in said mixing chamber, said partition wall extending in a direction of air flow through said mixing chamber and being operative substantially to prevent air flow transverse to said direction of air flow through said mixing chamber.

In a constant pressure carburettor for an internal combustion engine, said carburettor comprising a tubular wall defining a mixing chamber having an upstream end and a downstream end, a main throttle valve at said downstream end of said mixing chamber, a choke valve at said upstream end of said mixing chamber, means for opening and closing said choke valve in dependence upon the magnitude of air flow through said mixing chamber, fuel distributing means for supplying fuel on to said tubular wall in said mixing chamber, fuel metering means for controlling the supply of fuel, means controlling said metering means in dependence upon the opening of said choke valve, an inner tube, means mounting said inner tube substantially concentrically within said tubular wall, means defining at least one duct between said tubular wall and said inner tube, said at least one duct extending in the direction of air flow through said mixing chamber and leading to said mixing chamber from a position upstream of said mixing chamber, said at least one duct having a flow cross-sectional area which is small compared with that of said inner tube, means defining a flow constricting profile at the upstream end of said at least one duct for constricting the flow through said at least one duct to produce a stable air flow therein, said fuel distributing means including means for discharging said fuel into said at least one duct downstream of said flow restricting profile, and said choke valve being located in or adjacent the upstream end of said inner tube, wherein the improvement comprises that said fuel distributing means includes means defining an annular duct in said tubular wall, means defining inlets spaced around said tubular wall and communicating said annular duct and said at least one duct, and said carburettor further comprising means defining at least one auxiliary air duct and at least one fuel duct, said at least one auxiliary air duct and said at least one fuel duct leading substantially tangengtially into said annular duct, and said fuel metering means including a fuel nozzle in said fuel duct, a fuel metering element co-operating with said fuel nozzle and means connected to said choke valve for moving said fuel metering element relative to said fuel nozzle.

In a constant pressure carburettor for an internal combustion engine, said carburettor comprising a tubular wall defining a mixing chamber having an upstream end and a downstream end, a main throttle valve at said downstream end of said mixing chamber, a choke valve at said upstream end of said mixing chamber, means for opening and closing said choke valve in dependence upon the magnitude of air flow through said mixing chamber, fuel distributing means for supplying fuel on to said tubular wall in said mixing chamber, fuel metering means for controlling the supply of said fuel and means controlling said metering means in dependence upon the opening of said choke valve, an inner tube, means mounting said inner tube substantially concentrically within said tubular wall, means defining at least one duct between said tubular wall and said inner tube, said at least one duct extending in the direction of air flow through said mixing chamber and leading to said mixing chamber from a position upstream of said mixing chamber, said at least one duct having a flow cross-sectional area which is small compared to that of said inner tube, means defining a flow constricting profile at the upstream end of said at least one duct for constricting the flow through said at least one duct to produce a stable air flow therein, said fuel distributing means including means for discharging said fuel into said at least one duct downstream of said flow restricting profile, and said choke valve being located in or adjacent the upstream end of said inner tube, wherein the improvement comprises that said inner tube has a surface which, at least adjacent said fuel distributing means, is in contact with said tubular wall, and said inner tube has an external surface formed adjacent said fuel distributing means with channels which form the upstream end of said at least one duct.

In a constant pressure carburettor for an internal combustion engine, said carburettor comprising a tubular wall defining a mixing chamber having an upstream end and a downstream end, a main throttle valve at said downstream end of said mixing chamber, a choke valve at said upstream end of said mixing chamber, means for opening and closing said choke valve in dependence upon the magnitude of air flow through said mixing chamber, fuel distributing means for supplying fuel on to said tubular wall in said mixing chamber, fuel metering means for controlling the supply of said fuel and means controlling said metering means in dependence upon the opening of said choke valve, an inner tube, means mounting said inner tube substantially concentrically within said tubular wall, means defining at least one duct between said tubular wall and said inner tube, said at least one duct extending in the direction of air flow through said mixing chamber and leading to said mixing chamber from a position upstream of said mixing chamber, said at least one duct having a flow cross-sectional area which is small compared with that of said inner tube, means defining a flow constricting profile at the upstream end of said at least one duct for constricting the flow through said at least one duct to produce a stable air flow therein, said fuel distributing means including means for discharging said fuel into said at least one duct downstream of said flow restricting profile, and said choke valve being located in or adjacent the upstream end of said inner tube, means for heating said external peripheral surface of said inner tube, wherein the improvement comprises that said heating means includes an electrical resistance element on said external peripheral surface and means for heating said element during cold starting of an engine to which said carburettor is, in use, fitted.