Abstract: A liquid metering injector assembly for injecting metered quantities of a first liquid into respective metered quantities of a second liquid comprising a metering cylinder, metering ports formed at either end of the metering cylinder; a metering piston displaceable in the metering cylinder; a valve unit having a valve inlet for coupling to a pressurized source of the first liquid; means for coupling the valve to a hydraulic pulse source; a valve outlet for coupling to a source of the second liquid; a pair of communication valve ports of said valve unit respectively communicating with the metering ports and selectively communicatable with the valve inlet and outlet and a displaceable spool valve of the valve unit responsive to the hydraulic pulses so as to be displaceable between two positions in which the respective communication of the valve unit communicating ports with the valve unit inlet and outlet are successively reversed.

Abstract: A hydraulic motor comprising a cylinder, a stepped piston reciprocatable in said cylinder and having relatively proportioned leading and trailing surfaces, the surfaces together with axially directed surfaces defining, with the cylinder walls, first, second and intermediate cylinder zones, which intermediate cylinder zone is sealed with respect the first zone, valve controlled inlet and outlet of said cylinder in communication with said first zone, a water inlet of said cylinder in communication with the intermediate zone, piston wall portions defining a cylindrical recess opening out into the second zone and passages serving to effect communication between the recess and the second and intermediate zones, a tubular spool valve rod, apertured adjacent one end thereof and formed adjacent an opposite end thereof with a pair of axially spaced apart flanges fitting slidingly into the cylindrical recess, the rod having formed thereon an outwardly directed abutment located intermediate the flanges and the one end o