Patent ID: 6354571
Filing Date: 2002-03-12
Classification: F02M,Y10S

Abstract:
A membrane carburetor for an internal combustion engine including an engine for a portable handheld work apparatus, the engine including a fuel tank, a fuel feed line connected to the tank and a fuel return line also connected to said tank, the membrane carburetor comprising:a carburetor housing defining an air-intake channel communicating with the engine and through which a stream of air flowing in an intake direction is drawn by suction when the engine is operating; said carburetor housing including a control chamber connected to said fuel-feed line and to said return line; a membrane arranged in said carburetor housing and mounted therein so as to delimit said control chamber; a valve assembly operatively connected to said membrane for clearing said fuel feed line in response to a deflection of said membrane in response to an underpressure in said control chamber; an intake passage for connecting said control chamber to said air-intake channel and for conducting fuel thereto; said intake channel including outlet means opening into said air-intake channel; a check valve mounted in said intake passage; a scavenging pump defining a first start-assist device and being connected in said fuel return line between said control chamber and said fuel tank; an injection pump defining a second start-assist device; said injection pump including: a cylinder and a displacer piston delimiting a pump chamber into which fuel can flow; an injection line connecting said pump chamber to said intake passage; said displacer piston being longitudinally movable in said cylinder through a piston stroke for pumping fuel in said pump chamber through said injection line, said outlet means and into said air-intake channel; said injection pump further including: a stop for limiting said piston stroke; and, an adjusting element having a shape changing in dependence upon temperature to determine the length of said piston stroke.