Fluid metering apparatus having drip prevention means

Claim 1

IN AN APPARATUS FOR CONTROLLING THE DISPENSING OF A SELECTED VOLUME OF A FLUID FROM A SOURCE OF THE FLUID UNDER PRESSURE TO A POINT OF DISTRIBUTION OF THE FLUID, THE COMBINATION COMPRISING: A HOLLOW CYLINDER HAVING AN INLET COMMUNICATING WITH SAID SOURCE, AN OUTLET COMMUNICATING WITH SAID POINT OF DISTRIBUTION, A FIRST PASSAGE CONNECTING SAID INLET AND SAID OUTLET, AND A SECOND PASSAGE COMMUNICATING WITH SAID FIRST PASSAGE BEYOND SAID INLET AND OF A GREATER CROSS SECTION THAN SAID FIRST PASSAGE; PLUNGER MEANS MOVABLE IN SAID FIRST PASSAGE BETWEEN AN OPEN POSITION IN WHICH SAID INLET IS OPEN FOR THE PASSAGE OF FLUID THERETHROUGH AND A CLOSED POSITION IN WHICH SAID PLUNGER MEANS OBSTRUCTS SAID FIRST PASSAGE TO HALT THE FLOW OF FLUID TO SAID OUTLET; PISTON MEANS MOVABLE IN SAID SECOND PASSAGE AND ADAPTED WHEN WITHDRAWN TO VACATE A VOLUME IN SAID CYLINDER GREATER THAN THAT DISPLACED BY MOVEMENT OF SAID PLUNGER MEANS TO SAID CLOSED POSITION WHEREBY A PARTIAL VACUUM IS CREATED TO DRAW FLUID INTO SAID CYLINDER THROUGH SAID OUTLET; AND ACTUATING MEANS ADAPTED WHEN ACTUATED TO MOVE SAID PLUNGER MEANS TO SAID CLOSED POSITION AND TO WITHDRAW SAID PISTON MEANS, WHEREBY THE DISPENSING OF FLUID IN EXCESS OF SAID SELECTED VOLUME IS PREVENTED.