Abstract: A pressure compensating valve is configured as a pressure control valve for a fuel tank. The valve body is operatively connected to a membrane via a two-arm valve lever so that, when there is an underpressure in a control chamber, which is bounded by the membrane, the membrane is displaced in the direction toward the lever. The lever is then pivoted and opens the valve for pressure compensating the fuel tank by allowing air to flow in.

Abstract: A diaphragm carburetor for a combustion engine having a manual starter has a housing and a control chamber arranged in the housing and filled with fuel. A suction channel is arranged in the housing and has a venturi section. A throttle flap is rotatably supported in the suction channel downstream of the venturi section in the flow direction of combustion air sucked into the suction channel. A main valve path connects a control chamber to the venturi section. An idle valve path connects the control chamber to the suction channel and opens into the suction channel at a location downstream of the throttle flap in the flow direction. A choke flap is rotatably supported in the suction channel and positioned upstream of the venturi section. The choke flap has identical cold start and warm start positions and allows a flow volume of combustion air into the suction channel sustaining engine operation after the engine has been started.

Abstract: A venting valve for a fuel tank of a working tool driven by an internal combustion engine has a pressure compensation channel connecting the fuel tank interior to the surrounding atmosphere. A valve seat and a diaphragm are provided for closing off the pressure compensation channel when the diaphragm is seated on the valve seat. The diaphragm is lifted off the valve seat to open the pressure compensation channel when vacuum is present in the fuel tank interior. The valve seat is located at a first side of the diaphragm facing away from the fuel tank interior. The diaphragm has a central opening arranged centrally relative to the valve seat. A support plate is positioned at a second side of the diaphragm facing the fuel tank interior. It covers the deflecting area of the diaphragm and supports the diaphragm. The support plate has a sealing bead positioned in alignment with the valve seat. The spring forces the support plate and the diaphragm against the valve seat.

Abstract: A closure arrangement of a container has fill socket with an inner thread and a closure cap with a cylindrical base body having an outer thread matching the inner thread of the fill socket of the container. The cylindrical base body has an annular flange adjacent to the outer thread. An annular seal, connected to one side of the annular flange facing the outer thread, is provided for sealingly resting on the rim of the fill socket when the closure cap is threaded into the fill socket. The outer thread has a resilient tongue extending in the circumferential direction of the cylindrical body and has a radial projection cooperating with the abutment of the matching inner thread. The radial projection, when the closure cap is threaded into the fill socket, catches in a catch position behind the abutment before a fully closed position of the closure cap in the fill socket is reached.

Abstract: The invention is directed to a spark plug connector which includes an electrically insulating housing having a spark plug receptacle. A contact element for electrically connecting to the connecting tip of the spark plug is mounted in the spark plug receptacle. The contact element can be displaced by the connection tip of the spark plug against a restoring spring force. The spark plug connector of the invention can be cost effectively manufactured and provides a reliable electrical insert connection. To make the spark plug connector, the housing is made of an elastic material and a clip spring, which is embedded in the housing material, is provided as a contact element. The legs of the clip spring have respective segments in a contact plane lying perpendicularly to the longitudinal axis of the receptacle. These segments are accessible for establishing a contact and delimit the smallest diameter of the spark plug receptacle.

Abstract: A tank closure for a fill opening of a fuel tank has a closing device extending axially through the fill opening of the fuel tank. The closing device includes a grip for actuating the closing device. The closing device also includes a first clamping member and a second clamping member movable axially toward one another. The first clamping member has a first clamping surface and the second clamping member has a second clamping surface. The first and second clamping surfaces face one another and define therebetween an annular chamber. The first and second clamping surfaces are positioned at an angle .alpha. to one another. The closing device also includes a radially elastically expandable sealing ring positioned in the annular chamber.

Abstract: The invention is directed to a pressure compensating valve for a fuel tank of a work apparatus such as a portable handheld work apparatus equipped with an internal combustion engine. The fuel tank has a tank wall and the pressure compensating valve includes a housing cap defining an inner space and is impermeable to air. A pressure compensating stub is provided on the tank wall and terminates within the housing cap. Pressure compensating apertures are formed in the tank wall to open into the stub and a valve is provided for controlling the apertures for venting and ventilating the fuel tank. A passage connects the inner space of the cap with the atmosphere. A finely porous filter element is fixedly held in the stub and the apertures open into the filter element. The housing cap is mounted on the filter element and is held on the filter element.

Abstract: A cutter has a drive motor and a drive shaft. A rotating cutting tool is connected to the drive shaft. A centrifugal clutch is connected between the drive motor and the drive shaft. A frictional brake having a brake drum and a brake element positioned on the brake drum to achieve a braking effect is provided. The frictional brake is connected to the drive shaft. A servo device, which includes a folding bellows, is connected to the frictional brake for releasing the brake element from the brake drum to cancel the braking effect. A switching device for activating the servo device is provided.

Abstract: The invention is directed to a tensioning arrangement for saw chains of motor-driven chain saws which include a device for longitudinally displacing the guide bar. The clamped guide bar is released so that the adjusting arrangement can be actuated for the longitudinal displacement of the guide bar. By rotating a disc having a spiral slot, a slide piece, which is coupled to the guide bar, is displaced in the longitudinal direction. Assembly is simplified and handling facilitated when the tension in the saw chain is adjusted. This is achieved by making the slide piece on the spiral disc so that it is not released therefrom but instead is held so as to be rotationally and longitudinally displaceable. The slide piece is fixedly connected to the guide bar by using appropriate attachment devices.

Abstract: An air filter for an internal combustion engine has a housing with an interior chamber. The housing has housing walls at least one of which is in the form of a filter element. One of the housing walls has a suction opening for connecting the air filter to a suction channel of the combustion engine, wherein combustion air flows through the filter element into the interior chamber and from the interior chamber through the suction opening into the combustion engine. Air flow resistance elements are arranged in the interior chamber upstream of the suction opening. The air flow resistance elements are arranged in a first and a second row. The first and second rows are spaced apart from one another in the direction of flow of the combustion air. The air flow resistance elements of the first row of the second row are spaced laterally from one another to form gaps therebetween. The air flow resistance elements of the first row are positioned so as to be substantially aligned with the gaps of the second row.

Abstract: The invention is directed to a tensioning arrangement for a saw chain of a motor-driven chain saw. The saw chain runs on a guide bar mounted on the motor housing of the chain saw. The tensioning arrangement includes a rotatable disc having a spirally-shaped guide slot in which a lug of a slide piece engages. The longitudinal displacement of the guide bar is provided by rotating the disc. The guide slot in the disc extends over a rotational angle of at least 270.degree.. A still lesser slope of the guide slot is provided with a rotational angle in the range of 360.degree. to 450.degree.. The tensioning arrangement is especially suitable for adjusting the guide bar in motor-driven chain saws thereby adjusting the tension in the saw chain.

Abstract: The invention is directed to an ignition circuit for an internal combustion engine in a portable handheld work apparatus wherein a work tool is driven via a clutch. The ignition circuit includes an ignition time point control which connects a spark plug via a switch to a voltage source in order to trigger an ignition spark. The spark plug is mounted in the combustion chamber of the engine. This connection takes place in dependence upon the crankshaft angle and the rpm of the engine. In order to prevent damage to the clutch because of a blocked work tool, a test value counter driven via a rpm gate circuit is provided. The test value counter increments its value in the pregiven rpm window of the gate circuit with each rotation of the crankshaft and the content of the test value counter is compared to a pregiven limit value by a comparator. The output of the comparator activates a rpm-reducing protective circuit and the output of the comparator indicates reaching or exceeding the limit value.

Abstract: The invention is directed to a fuel pump for an internal combustion engine such as a two-stroke engine in a portable handheld work apparatus such as a motor-driven chain saw or the like. A pump chamber is connected via a suction valve to a fuel feed and via a pressure valve to a pressure line. A pump membrane delimits the pump chamber and is driven by the fluctuating crankcase pressure of the engine which is present in the work chamber. Pump operation free of disturbances over a wide rpm range is attained with the suction valve to the pump chamber being configured essentially as a valve having the shape of a part circle, The pressure valve is disposed approximately at the center of the suction valve and delimits the pump chamber in the stroke direction of the pump membrane.

Abstract: The invention is directed to a circuit for providing a controlled voltage supply to a microprocessor in an ignition circuit of an internal combustion engine equipped with a spark plug. The circuit includes: a generator having an induction coil and magnetic device for generating an alternating voltage in the coil; a microprocessor for controlling the spark plug; the microprocessor having first and second connecting terminals and a capacitor connected across the terminals; a thyristor having a gate electrode is connected between the induction coil and the capacitor; and, a voltage limiter is connected to the gate electrode, The controlled voltage supply for the thyristor is ensured over the entire rpm range of the engine without noticeable energy losses.

Abstract: The invention is directed to an arrangement for assisting an operator to adjust a carburetor. The arrangement has a display for the setting of the carburetor of an internal combustion engine such as a two-stroke engine. An actual signal proportional to the carburetor setting is compared to desired limit values by means of a comparator and the display is switched in dependence upon the comparison result by a control unit into different operating states. The display assumes a first operating state below a minimum desired limit value and, between the minimum and maximum desired values, the display is switched into a second operating state. The arrangement for carburetor adjustment makes it possible for the operator to recognize whether the actual signal is above or below the window determined by the desired limit values. This is achieved in that, above the maximum desired limit value, the display is switched into a third operating state, for example, by driving the display intermittently.

Abstract: The invention is directed to a fuel-injection arrangement for a two-stroke engine in a portable handheld work apparatus such as a motor-driven chain saw or the like. Fuel is drawn by suction from a fuel tank by a fuel-feed pump and is made available at the suction connection of an injection pump. The injection pump has a pressure connection which is connected to an injection line through which the engine is supplied with fuel. A rapid start of a two-stroke engine provided with this fuel-injection arrangement is achieved by providing a bypass line which conducts fuel and bypasses the injection pump. A switchable flow valve is mounted in the bypass line. The bypass line opens directly into the intake channel conducting combustion air to the engine so that even without the pump action of the injection pump, adequate fuel is made available to the engine for starting the same.

Abstract: The invention directed to a portable handheld drilling apparatus for receiving and driving a drill which can encounter a drilling resistance during a drilling operation thereby causing the drilling apparatus to undergo an unwanted rotational movement.

Abstract: The invention is directed to a fuel-injection arrangement for a two-stroke engine in a motor-driven chain saw. An injection pump is mounted in a base housing with the injection pump including a pump piston axially displaceable in a pump cylinder. The pump piston delimits a pump chamber. The pump chamber is connected via a suction valve to a fuel tank. The fuel drawn by suction is pumped by the pump piston via a pressure valve, an injection line and an injection valve to the engine. For driving the pump piston, the latter is connected at one end to a membrane via a membrane plate. The membrane delimits a work chamber charged with fluctuating crankcase pressure. A simple assembly is provided by arranging the pump chamber, the suction valve and the pressure valve in a common valve housing which, in turn, is seated in the base housing of the injection pump in a seal-tight manner. The injection line is connected directly to the valve housing.

Abstract: The invention is directed to a pump for pumping a viscous fluid. The pump includes a stator body and a rotor body rotatably mounted in the stator body so as to be coaxial therewith. The stator body has a wall structure having a spiral slot formed therein which communicates with a suction connection formed in the stator body for conducting the viscous fluid to be pumped into the slot. A pressure connection is formed in the stator body for conducting the viscous fluid out of the slot. The suction connection and the pressure connection open into respective peripheral annular slots which are formed between a total of at least three sealing rings on the outer surface of the stator body. The channels for liquids provided in a housing can be disposed in any rotational position relative to the stator. This affords the advantage that the pump stator can be seated with any rotational position in a receiving cylinder of the housing.

Abstract: The invention relates to an operating-mode position selector arrangement for an internal combustion engine in a portable handheld tool such as a motor-driven chain saw. The engine includes an electrical ignition system and is supplied with a fuel mixture by a carburetor. In a start position of the operating-mode position selector, the position selector holds the choke flap and the throttle flap of the carburetor in pregiven start positions. In an operating position of the operating-mode position selector, the throttle flap is released for actuation via a throttle lever and the choke flap is fully opened. In a stop position of the operating-mode position selector, an electric contact is closed between a terminal of the electric ignition system and ground. The different positions of the operating-mode position selector are detected electrically.