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 a composite crankshaft for a two-stroke engine for portable handheld work tools including chain saws, cutoff machines and the like. In composite crankshafts, a crank pin is connected to a crank web by a press fit wherein the inner diameter of the press-fit bore is expanded toward its axial end in order to reduce stress peaks. In this way, the press-fit surface has a radial spacing with respect to the center longitudinal axis of the press fit which changes. The press fit of the crankshaft of the invention is so configured that the radial distance of the press-fit surface changes in dependence upon the axial spacing to the axial center of the press fit according to an exponential function having the equation f(x)=a.multidot.e.sup.b.multidot.x wherein (a) and (b) are pregiven constants, (x) is the axial spacing and f(x) is the radial spacing.

Abstract: The guide bar for a motor-driven chain saw is provided for taking highest loading and is therefore made of solid material. For weight reduction, openings are provided in the guide bar which are closed off by cover plates that are flush with the flat sides of the guide bar. The cover plates are firmly joined to the base plate of the guide bar. By means of the hollow spaces inside the guide bar, a considerable weight reduction is attained, yet the stability of the guide bar is not substantially impaired as compared to a solid guide bar, since the hollow spaces are located in the zone that is neutral in terms of bending.