Abstract: A carburetor for an internal combustion engine of a hand-held working tool has a housing having an intake channel and a fuel-filled control chamber mounted in the housing. A fuel channel is connected to the control chamber and the intake channel. A control valve is mounted in the fuel channel and has a valve member. A control screw is mounted in the carburetor housing and acts on the valve member for adjusting it. A cap is fixedly mounted on the control screw and has a stop. A counter stop is mounted on the housing in a rotational path of the stop of the cap. A locking device for securing the cap relative to the housing is provided. The locking device has a locking member and counter locking members cooperating with the locking member for locking the cap in one of various preset positions relative to the housing.

Abstract: A diaphragm carburetor for an internal combustion engine has a carburetor housing having an intake channel with a venturi section. A plate valve is positioned in the intake channel. A fuel outlet valve is mounted in the venturi section. A fuel-filled control chamber is provided and delimited at one side by a diaphragm. A fuel supply channel is connected to the control chamber. A supply valve is mounted in the fuel supply channel and actuated by the diaphragm. A first fuel channel connects the control chamber and the fuel outlet valve. At least one fixed main throttle is mounted in the first fuel channel for fixedly determining a fuel flow cross-section to the fuel outlet valve. A lever is provided for actuating the valve plate. An adjustable stop cooperates with the lever. The flow cross-section of the intake air is adjusted by the stop to a desired air/fuel ratio and is changeable, in a limited range, in a direction of increasing the flow cross-section.

Abstract: A diaphragm carburetor for an internal combustion engine of a portable hand-held working tool has a housing with a control chamber. A suction channel extends through the housing and has a venturi section. An inlet valve is connected to the control chamber and supplies the control chamber with fuel. A main valve channel connects the control chamber to the venturi section of the suction channel. A check valve is positioned in the main valve channel adjacent to the control chamber and closes the main valve channel toward the control chamber. The main valve channel has a straight and elongate portion extending from the check valve into the venturi section and projecting into the suction channel.

Abstract: The invention is directed to a membrane carburetor which includes an intake channel having a throttle flap which is pivotally journalled. The carburetor also includes a control chamber from which fuel can be supplied to the intake channel. A valve is mounted in an ancillary channel and a corresponding adjustment of the throttle flap results in dependence upon the opening and closing position.

Abstract: A diaphragm carburetor for an internal combustion engine has a housing and a control chamber positioned in the housing and having a fuel inlet valve. A control diaphragm is positioned in the control chamber. A Venturi channel extends through the housing. At least one throttle valve is positioned in the Venturi channel. An idle valve and a main valve open into the Venturi channel and are connected with an idle valve channel, respectively, a main valve channel to the control chamber. A fuel pump is positioned in the housing. A fuel channel connects the fuel pump and the fuel inlet valve of the control chamber. A control lever that is actuated by the control diaphragm for controlling the fuel inlet valve is provided. The fuel inlet valve has a valve seat and a valve member with a sealing member cooperating with the valve seat for opening and closing the fuel inlet valve. The sealing element has a flat end face. The valve member is connected to the control lever.

Abstract: The invention relates to a membrane carburetor for an engine of a motor-driven chain saw. The membrane carburetor has a fuel-filled control chamber delimited by a control membrane. A throttle flap is mounted in an intake channel and a main nozzle opens into the intake channel upstream of the throttle flap. The main nozzle opening is connected to the control chamber via a fuel channel and a fixed nozzle limiting the inflowing fuel-mass flow. In order to make the mixture composition controllable, an air-supply channel opens into the fuel channel and a control valve is mounted in the air-supply channel. The control valve can be adjusted by a positioning device in dependence upon engine operating data. The positioning device is actuated by a control apparatus.

Abstract: The invention is directed to a carburetor for an internal combustion engine and includes an intake channel having a throttle flap mounted therein. Fuel passes from a fuel-filled control chamber via channels to main and idle nozzles through which the fuel enters the intake channel. The maximum permissible fuel quantity must be adjusted during a test run be means of an adjusting screw. This value can be changed by an operator. The maximum flow cross section for the fuel throughput is limited by at least one fixed throttle to which the main nozzle and the idle chamber are connected at the downstream end. In this way, strict exhaust-gas limit values are maintained. An adjustable throttle is provided with the aid of which the entire flow cross section can be reduced up to a pregiven minimum value. The carburetor described above is especially suitable for two-stroke engines of portable handheld work apparatus.

Abstract: The invention is directed to a membrane carburetor for an internal combustion engine such as a two-stroke engine having an intake for drawing the mixture in by suction. The membrane carburetor has a venturi section wherein the mixture is formed. A main nozzle opening opens forward of a throttle flap and an idle nozzle opening opens rearward of the throttle flap both viewed in flow direction. Both openings are connected via channels to a fuel-filled control chamber to which fuel flows via an inflow channel. An inlet valve is mounted in the inflow channel and has a valve body disposed opposite a valve seat fixed in the housing. The inlet valve is actuated in the opening direction via a control lever by a control membrane delimiting the control chamber.

Abstract: The invention is directed to a membrane fuel pump for a membrane carburetor of an internal combustion engine. The carburetor has a pressure controller and the engine has a crankcase wherein pressure fluctuates during the operation thereof. The membrane fuel pump includes a pump membrane mounted in a housing which partitions a space of the housing into a pump chamber for receiving fuel from a fuel supply connection and a drive chamber. The drive chamber is charged with the pressure of the crankcase. A pressure connection connects the pump chamber to the pressure controller of the membrane carburetor. A bypass channel connects the pressure connection to the fuel supply connection and a valve is interposed between the pressure connection and the bypass channel.

Abstract: The invention is directed to an adjustment safeguard for an adjusting screw rotatably held in a housing. The adjusting screw has a head which projects outside of the housing and a cap is mounted on the head of the adjusting screw so as to be accessible to an operator for imparting a rotational movement thereto. The cap has an appendage formed thereon and stops are provided which coact with the appendage to delimit the rotational range through which the adjusting screw can be rotated. A sleeve is disposed in surrounding relationship to the cap and is connected thereto. The cap is disposed almost entirely within the sleeve so that an operator cannot reach the cap for levering the latter off the adjusting screw without causing permanent visible damage to the safeguard. Accordingly, an effective tampering with the adjusting screw for obtaining a setting outside of the permitted adjusting range is effectively prevented since such a tampering will leave permanent visible damage.

Abstract: The invention relates to a carburetor for an internal combustion engine and especially for a portable small engine. The carburetor includes a carburetor housing defining an intake pipe and a control chamber which communicates with the intake pipe via intake channels. A fuel-feed line which is closable by an inlet valve opens into the control chamber. The inlet valve includes a valve seat formed in the fuel-feed line and a valve body mounted on a positioning lever which is connected to a membrane defining a wall of the control chamber. The positioning lever can be pivotally actuated to open the inlet valve to admit fuel into the control chamber. An actuating lever is pivotally mounted on the carburetor housing and can be pivoted from a rest position to an active position whereat the actuating lever applies a force against the membrane to displace the latter and pivotally actuate the positioning lever to immediately open the inlet valve when starting the engine.

Abstract: Disturbances can occur in handheld portable tools driven by internal combustion engines because the idle-nozzle system and the main-nozzle system influence each other. The carburetor of the invention prevents this disturbing influence and provides a control of the engine which is proportional to speed. The carburetor includes a control member which closes off the main nozzle during idle operation and the idle nozzle during operation under load in dependence upon the position of the throttle flap.

Abstract: The invention is directed to a handheld, portable tool such as a chain saw equipped with an internal combustion engine mounted in an engine housing. The engine has a carburetor defining an air-intake channel. A heating element is provided which is electrically connected to the generator of the chain saw and mounted on the carburetor in the region of the air-intake channel. The heating element has a positive temperature coefficient and a predetermined temperature region thereby preventing the carburetor housing and the throttle flap from heating to a temperature above a predetermined value. The heating element and the way it is mounted prevents icing at the carburetor in cold weather thereby enabling the engine to run uninterruptedly and uniformly especially when the engine idles.

Abstract: A carburetor for small motors has a housing with a carburetor bore wherein air and fuel are mixed to an air fuel mixture. The fuel enters the carburetor bore through fuel jets. A throttle valve is pivotally mounted in the carburetor bore by means of which the fuel-air mixture quantity is adjusted in dependence upon the operating condition of the engine. The throttle valve and the inner wall surface of the carburetor bore conjointly define an air gap in the idling position. An idling fuel outlet jet communicates with the carburetor bore in the region of this air gap and is connected to the control chamber containing the fuel. The idling fuel outlet jet together with a ventilation bore communicate with an emulsion chamber of the control compartment. Further, an idling control part is provided which is movable into the air gap whereby an outlet opening of the ventilation bore communicating with the emulsion chamber is passed over.

Abstract: A carburetor for internal combustion engines, especially for very small portable engines. The carburetor has a control chamber arranged in the carburetor in the fuel supply to the intake pipe. The control chamber is connected with the intake pipe via inlet passages, the rate or quantity of flow through which can be regulated, and is connected with fuel feed supplied by a fuel pump via an inlet valve, which is biased in the closed position. The inlet valve is opened by a control membrane which delimits the control chamber. The control membrane, on that side thereof remote from the control chamber, delimits an equalizing chamber along with a closure cover fastened to the carburetor housing. The equalizing chamber is constructed as a pressure chamber which can be selectively connected via a reversing or change-over valve with either the crankcase housing of the internal combustion engine, or with the atmosphere.

Abstract: A carburetor for an internal combustion engine in a power saw. The carburetor has at least one adjustment screw which is fastened and secured in a bore of a receiving part on the carburetor housing or on the internal combustion engine. A shim or clamping piece, which is secured against rotation, is arranged in a recess of the receiving part. The clamping piece receives the adjustment screw in a positive, locking manner. The clamping piece has projections with which the clamping piece is held locked in the recess of the receiving part.