Abstract: An automatic brake operating device to be used on a motor chain saw provided with a clutch drum around which there is a pretensioned brake band. By use of a spring and a toggle joint the band can be switched between a free position and a braking position. The toggle joint is operated between two corresponding positions by an inertia mass for releasing and a stirrup for resetting. The mass and the stirrup are individually movable and capable of triggering the brake independent of each other.

Abstract: An electronic circuit device for ignition pulses for an i.c. engine having a two- or three pole magnetic system generating positive and negative pulses. One of the pulses is used for ignition energy and the other for power supply of electronic equipment. As a reference point for ignition advance calculation is the peak of said power supplying pulses used. An oscillator (36) supplies a pulse frequency many times higher than the r.p.m. of the engine. A peak detector (14) and said oscillator are connected to a pulse counter (39) which after a predetermined number of pulses from the reference point releases a trigger pulse for the ignition energy. A logic unit (12) sets the counter on the predetermined number in dependence of the r.p.m. of the engine.

Abstract: An air filter in front of the intake opening of the carburetor has an elastic lower surface (20) with a bead (19) which is movable in the intake opening. The displacement is adjusted by means of a choke control (22) which at maximum deflection presses the whole bead into the intake opening.

Abstract: An ignition circuit according to the present invention has the properties of trigging, i.e. releasing the spark at a predetermined point behind the top of the primary voltage (the ignition generator voltage). During the ascending primary voltage the ignition switch (12) is conducting while a capacitor voltage (U.sub.K) is developed. When the primary voltage has passed its top value a potential difference to the capacitor voltage (U.sub.K) is created, which is used for the control of the switch to make it break. By the interruption of the primary current an ignition voltage is induced at duty r.p.m. in an ignition coil (11). At an extremely high r.p.m. the ignition is delayed behind the voltage top whereby the induced voltage will be too low for ignition. Too high an r.p.m. is thereby avoided.

Abstract: The bearings of the crankshaft of an internal combustion engine are surrounded by rings of a high temperature resistant polymer, the rings being pressed into bearing seats in the upper and lower portions of the crankcase, the rings being formed with extensions to completely separate the upper and lower portions of the crankcase. The rings enable the use of plastic materials for the lower crankcase, by insulating the lower portion of the crankcase from heat in the upper portion thereof.

Abstract: A motor-driven chain saw having a plurality of units including an engine-saw unit, a casing, a multiplicity of fuel tanks, and filter elements for fuel and lubricant. The filter-tank unit is provided with a top portion and a bottom portion which restricts spacings for a direct location of the filter elements. The filter-tank unit is provided with a fixed pipe system for the fuel and lubricant between the spacings and the auxiliary apparatus constituting a carburetor and lubricant pump.