Abstract: A piston engine has at least one piston which is mounted to be movable in a cylinder in a linear manner towards a cylinder head and a deformable element extends around the piston between the piston and the cylinder.

Abstract: Apparatus for operating and controlling a free-piston Stirling engine with a displacement piston in a cylinder, said piston separating a hot cylinder space from a cold cylinder space, an annular space being formed between the cylinder and a sleeve section surrounding the cylinder, characterized in that the annular space extends right through from an annular gap in the region of the hot cylinder space to an annular gap in the region of the cold cylinder space, plates being inserted all the way along in the longitudinal direction into this annular space.

Abstract: A tracer head for a copy milling machine which is digitally controlled and causes a model to be scanned by a stylus mechanically mounted in the tracer head. The stylus is deflected both at right angles and tangentially to the surface of the model when the stylus contacts the model to produce scanning signals which are proportional to the deflections at right angles to the model surface and the deflections tangential to the model surface. These signals then are transmitted to a processor which processes, amplifies and subsequently feeds the processed and amplified scanning signals to servomotors of the machine to cut and shape a workpiece in such manner as to produce a copy of the model. The amount of spring pressure exerted on the stylus inside the head by the mechanical spring mounting when the stylus contacts the model is determined by establishing the pressure separately along each of the three mutually orthogonal x, y and z axes.