Abstract: An internal combustion engine with a diaphragm carburetor which provides additional fuel injection in all starting and environmental conditions. The carburetor is provided with a fuel recirculation line which communicates at one end with the fuel feed line of the carburetor, and which communicates at the other end with the fuel tank. The recirculation line is also provided with a choke for flow resistance.

Abstract: A braking device for braking the saw chain of a portable motor-driven chain saw having a safety device which has a mass member, a locking lever being provided which is pivotably mounted on the hand guard lever and bears the mass member at its free, sprung end, co-operating by its other end with a control cam which bears against the brake lever and via which the braking operation of the rotating saw chain is controlled, in such a way that the braking operation of the rotating saw chain is automatically initiated, if an uncontrolled acceleration takes place, by the saw rolling down the timber trunk to be sawn at the moment when the saw becomes jammed, with the consequence that the resulting braking force counteracts the accelerating force, so that the recoil angle of the saw is reduced.

Abstract: The invention relates to an oil pump for hand rail chain saw machines in which a pump plunger has an annular groove at its end remote from the drive and which is connected via a duct to the pump oil pressure channel, so that the sucking in of secondary air, high wear and an undefined lubrication are avoided.

Abstract: The invention relates to a braking mechanism for braking the chain of a portable power chain saw when a hazardous state occurs. The operating lever rotatably mounted on the chain saw casing is in operative connection with a control lever acting on a brake band by means of a lever-like device. Thus, in the braking position the control lever is transferred into an angular position with a simultaneous position change of the two brake band articulation points. As a result, the brake band is applied to the brake drum, which ensures that the braking mechanisms act without any delay.

Abstract: The invention relates to a method and to a port-controlled two-stroke internal combustion engine in which the cross-sections of the intake and outlet are so constructed in the direction of the longitudinal axis of the cylinder that in the case of an upward or downward movement of the piston, the noise-generating intake and outlet pressure gradients and amplitudes are reduced by the gradual opening of the particular intake and outlet, the piston lower edge and intakes having special constructions.

Abstract: Apparatus for reducing intake noise is characterized in that the casing is provided with an air intake connection whose one end extends into the inner area of the casing and with a carburettor connection whose one end extends into the inner area of the casing and whose inlet faces the outlet of the air intake connection located in the inner area of the casing accompanied by the formation of a space having a width approximately corresponding to half the diameter of the connection which has the same diameter.