Drive for a machine comprising variable-stroke reciprocating pistons

A drive for a machine having variable-stroke reciprocating pistons, comprising:

• a shaft having an axis, said shaft being rotatably journalled in the machine;
• a plate, mounted on the shaft so that the plate cannot rotate with respect to the shaft around the shaft axis, said plate being mounted on the shaft so that the angle between the plate and the shaft axis can be varied, by pivoting the plate around a plate axis, and so that the plate is movable along the direction of the shaft axis;
• at least one piston comprising a piston rod having a piston rod head, said piston rod head having a side which faces the plate comprising a spherical surface;
• and
• means for slideably coupling the splerical surface of the piston rod head to the plate;
• CHARACTERIZED IN THAT
• the plate has a side which is remote from the piston rod, said side comprising a cam having a cam surface;
• the drive further comprises a structural member, rigidly coupled to the shaft, for supporting the cam via the cam surface;
• said cam has a cross section which passes through said cam surface and which is substantially at least a portion of a circle having an axis which is parallel to the plate axis, the axis of said circle passing through the center of curvature of said spherical surface of the piston rod head when the piston rod is situated opposite the cam.