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: 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 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 motor-driven chain saw having a drive motor which drives a saw chain via a sprocket with the saw chain running around the periphery of the cutter bar in a guide groove formed in this periphery. A brake device is provided to bring the saw chain to standstill which is actuated by a brake lever. In addition, the drive motor continuously drives a lubricating-oil pump which is mounted in a feed line between the supply tank and a outlet opening of the guide groove. The supply of lubricating oil is interrupted when the saw chain is brought to standstill. This is achieved by providing a blocking valve in the feed line which is closed during idle operation of the drive motor and is opened during load operation of the drive motor.

Abstract: The invention relates to a motor chain saw having a guide bar clamped between the housing and a clamping piece. The chain saw has a drive motor arranged in a housing and the drive motor drives a saw chain running on a guide bar. The guide bar is clamped to the housing at one end between the housing and a clamping piece with the clamping being transverse to the plane of the guide bar. For tensioning the saw chain, the guide bar is displaceable in the longitudinal direction thereof by means of a chain tensioning device when the clamping piece is loosened. If high forces act on the guide bar, then the latter slips toward the sprocket wheel in the longitudinal direction notwithstanding the fact that the guide bar is clamped to the housing. Accordingly, the saw chain must be again tensioned by means of the chain tensioning device.

Abstract: A two-stroke engine is disclosed which is controlled by a carburetor throttle valve and has a crankcase subjected to continuously alternating overpressure and underpressure. A pneumatic control member responsive to a signal dependent on the rotational speed of the engine is in pressure communication with the inner chamber of the crankcase via a valve. The output member of the pneumatic control member is connected with the throttle flap of the carburetor. The valve provided between the crankcase and the pneumatic control member is responsive to a signal for controlling the pressure in the pneumatic control member. This valve can be configured as a resonance control valve fixedly mounted to the housing of the engine.

Abstract: The invention is directed to a carburetor arrangement for an internal combustion engine of a working tool such as a portable hand-held chain saw, a cutoff machine or the like and includes a tank from which the fuel is conducted to the main nozzle of a carburetor via an inlet valve of the carburetor. A tank pressure blocking valve is mounted in the fuel feed line between the tank and the nozzle. The valve body of the blocking valve is pressed tightly against its valve seat in the direction of fuel flow and pressure drop when the engine is at standstill. During starting and running of the engine, the valve body is lifted from its seat by the underpressure condition caused by the engine and is moved in a direction opposite to an overpressure in the tank and against the flow of fuel.

Abstract: The invention is directed to a braking arrangement for a chain saw having a housing and a guide bar mounted on the housing for accommodating a saw chain thereon. The brake arrangement includes a brake drum operatively connected to the saw chain with a brake band disposed in surrounding relationship thereto. A brake member is connected to the brake band and moves between a ready position whereat the brake band is disposed in spaced relationship to the brake drum and a released position whereat the brake band is drawn tightly around the brake drum. A brake spring resiliently biases the brake member to cause the brake member to pull the brake band tightly about the brake drum when in the released position. A latch arrangement holds the brake member in the ready position against the force of the brake spring. A cam connected to the drive motor rotates through a predetermined path.

Abstract: The invention is directed to a control system for a two-stroke engine for limiting a control quantity thereof such as the rotational speed. For this purpose, a pressure line including a valve is connected to the crankcase and leads to a pneumatic controlling member which is responsive to a mechanical or electrical signal (vibrations or electric pulse from the ignition system). By means of suitable transmission means, the movement of the controlling member is transmitted to the carburetor throttle, for example.