Patent ID: 8584644

Claim:
An engine comprising: at least one cylinder having a piston defining a variable volume working chamber; wherein the cylinder is operable in any one of at least two modes, the first mode being where power is generated by burning fuel in the working chamber, and the second mode being where the cylinder acts to compress air admitted into the working chamber and to store the compressed air in an air tank; the engine further comprising: an intake manifold; a cam actuated intake valve for controlling flow of air into and out of the working chamber; an intake port in fluid communication with the intake valve and the intake manifold; a non-return valve situated in the intake port, so as to define an auxiliary chamber in the intake port between the intake valve and the non-return valve, the auxiliary chamber being in fluid communication with the air tank via a control valve; a selectively deployable stop situated to prevent full closure of the intake valve regardless of the position of the intake valve actuating cam when the stop is deployed, whereby the air compressed in the working chamber by the movement of the piston is admitted through the open intake valve into the auxiliary chamber; wherein the stop comprises an abutment that remains stationary throughout the engine cycle operation in the second mode.