Piston with a rotatable piston top

Abstract

This invention relates to a two piece piston with a variable compression height, wherein a piston top part can be adjusted with respect to a piston bottom part along the longitudinal axis of the piston preferably by hydraulic devices and can be caused to perform a progressive rotating movement. This rotating movement is achieved by means of two thread sections of opposed pitch which, depending on the moving direction of the piston top part, alternately engage in corresponding counterthread sections on the piston bottom part. These threads and counterthreaded sections are multiple coarse pitch threads and are located on one side only as flanks disposed in the moving direction of the piston top part so that when the moving direction of the piston top part is reversed, a moving-apart of the engaged thread sections and counterthread sections occurs and the thread sections with an opposed pitch engage correspondingly on the flanks on the corresponding counterthread sections. In this case, either the thread sections assigned to the piston top part or the counterthread sections assigned to the piston bottom part are arranged offset with the respect to one another in the circumferential direction, by slightly less than the amount which corresponds to the rotation of the piston top part in the case of a certain stroke.

Dependencies are inferred from the claim text.