Low flow meter for liquids

Claim 1

IN A FLOW METER FOR LIQUIDS, A CYLINDER HAVING EACH END CLOSED BY A CYLINDER HEAD, EACH CYLINDER HEAD INCLUDING A COAXIAL BORE, A VALVE ROD IN SAID CYLINDER AND EXTENDING BETWEEN SAID CYLINDER HEADS AND HAVING THE ENDS SLIDABLY RECEIVED IN SAID BORES FOR RECIPROCATION RELATIVE TO SAID CYLINDER, A PISTON HAVING A BORE RECEIVING SAID VALVE ROD AND MOVABLE IN SAID CYLINDER BETWEEN SAID HEADS AND RELATIVE TO SAID ROD, MEANS FOR LOCKING SAID VALVE ROD AT ITS EXTREMES OF TRAVEL, MEANS OPERABLE BY SAID PISTON TO MOVE SAID ROD IN THE DIRECTION OF PISTON TRAVEL AND RELEASE SAID LOCKING MEANS, ONE OF SAID CYLINDER HEADS HAVING AN INLET PORT AND AN OUTLET PORT, SAID VALVE ROD HAVING TWO FLUID PASSAGES ONE OF WHICH COMMUNICATES WITH SAID INLET PORT ON ONE END AND ON THE OTHER END WITH THE SPACE ON ONE SIDE OF SAID PISTON WHILE THE OTHER OF SAID PASSAGES COMMUNICATES WITH THE SPACE ON THE OPPOSITE SIDE OF SAID PISTON AND SAID OUTLET PORT WHEN SAID VALVE ROD IS IN ONE POSITION AND SAID FIRST NAMED PASSAGE COMMUNICATES WITH SAID OUTLET PORT AND SAID SECOND NAMED PASSAGE COMMUNICATES WITH SAID INLET PORT WHEN SAID VALVE ROD IS IN ANOTHER POSITION.