748,295. Fluid-pressure engines; valve gear. MARPLES & SON, Ltd., R. M., and OLDFIELD, T. A. June 29, 1954 [June 29, 1953], No. 17892/53. Classes 122(2) and 122(3) [Also in Group XXIX] In a double-acting reciprocating motor in which a piston 1 is reciprocated in a cylinder by pressure fluid alternately admitted to and exhausted from the cylinder ends S<SP>2</SP>, S<SP>3</SP> by separate inlet and exhaust valves housed within the piston, the inlet valve comprises a member 20 movable in a chamber supplied with fluid pressure between two inwardly-facing hollow valve seats 21, 22 communicating with their respective cylinder ends S<SP>2</SP>, S<SP>3</SP> and the exhaust valve comprises a rod 28 having enlarged heads 29, 30 to alternately co-operate with seats 31, 32 formed by the junctures of an inner chamber 33, open to exhaust, and enlarged outer chambers 36, 37 having recesses 40, 41 therein which act as ports to connect the outer chambers 36. 37 with their respective cylinder ends S<SP>2</SP>, S<SP>3</SP> when the valve is open, the valve being reversed by extensions 38, 39 thereon which strike the cylinder ends 3, 4. The piston 1 is connected by a pin 11 to a piston rod 10 having a. first passage 16 open at one end to a chamber S<SP>1</SP> connected at 14 to a source of pressure fluid and communicating through ducts 25, 26 with spaces 23, 24 surrounding the seats 21. 22, and a second passage 17 communicating through a duct 34 with the chamber 33 ,and through/ports 18 with an exhaust chamber S<SP>4</SP>. In the position shown in Fig. 1 pressure fluid supplied to the space S<SP>3</SP> through passage 16 duct 26 and seat 22 holds the inlet and exhaust valves in position and forces the piston to the left, exhaust taking place from S<SP>2</SP> through recesses 40, chamber 33, passage 17 and ducts 34 and 18. Towards the end of the stroke the extension 38 contacts the cylinder end 3 and the piston overrides the exhaust valve until head 29 closes on seat 31 and S<SP>3</SP> is opened to exhaust via recesses 41. At the same time the pressure differential due to compression in S<SP>2</SP> and fall of pressure in S<SP>3</SP> moves the inlet valve 20 from seat 21 to seat 22 and fluid pressure enters S<SP>2</SP> to reverse the piston. At the other end of its stroke an identical cycle takes place and the piston is again reversed. In a modification ex- 'haust from the chamber 33 takes place through a radial duct in the piston to a recess in the outer periphery of the piston and from there is led to the exhaust chamber S<SP>1</SP> through further ducts in the piston and passage 17 and/or through passages in the cylinder wall and cylinder end 4. In a further modification, Figs. 10 and 11, the inlet valve 74 is a ball and pressure fluid is admitted to the spaces 77, 78 through an inlet 73 in the cylinder, groove 72 in the cylinder, ports 71 in the cylinder liner, to recesses 95, 96 in the piston sealed from the cylinder ends by piston rings 93, 94, and ducts 97, 98. Shoulders 99, 100 on the piston co-operate with ports 71 towards each end of the stroke to ensure that fluid is directed into the appropriate recess 95, 96. The enlarged heads 29 and 30 may both be formed integral with the rod 28, the seating for the heads being formed by the ends of a longitudinally split tube. Adjustable transverse screws or plugs may be fitted in the passages between the inlet valve chamber and the cylinder ends to allow the rate of flow of pressure fluid to the cylinder ends to be varied. The cylinder may reciprocate on the piston and several piston rods may be attached to the piston. The invention may be applied to a single-acting motor, the valve mechanism being arranged to communicate with one cylinder end only (the other being permanently open to exhaust) and the inlet valve being reversed mechanically; the return stroke being effected by means such as a spring-or gravity.