Abstract: A mechanism comprising a piston-and-cylinder assembly including a piston housed in a cylinder is provided. The mechanism includes a pin member passing through the piston and a guide member having a guide recess accommodating an end of the pin member, the guide recess being so shaped and orientated in relation to the piston-and-cylinder assembly that a common axis exists between the guide recess and the piston-and-cylinder assembly. The guide member and the piston-and-cylinder assembly are mounted so as to be rotatable relative to each other about the common axis. The guide recess includes an inner periphery and an outer periphery, where the inner and outer peripheries include respective mid-portions where the periphery is narrowest lying between two end lobe portions, for guiding the pin member continuously in a path which includes two end lobe portions separated by a narrower mid-portion.

Abstract: A mechanism including a piston-and-cylinder assembly including a pin member passing through the piston and a guide member having a recess accommodating the end of the pin member, the guide member being rotated by reciprocating movement of the pistons.