Variable pressure pump for manometric metering device

Claim 1

IN A SMALL CAPACITY VACUUM PUMP OF THE FLUID COMPRESSION TYPE FOR USE IN APPLYING VACUUM TO A MANOMETRIC METERING DEVICE WHEREIN SAID PUMP INCLUDES A VESSEL FOR CONTAINING THE FLUID TO BE COMPRESSED, SAID VESSEL HAVING A CLEARANCE VOLUME AND ALSO COMMUNICATING WITH A HOLLOW PORTED BLOCK AND CHECK VALVE MEANS INCLUDED WITHIN THE BLOCK AT EACH PORT CONSTRUCTED AND ARRANGED ALTERNATIVELY TO OPEN AND TO CLOSE SERIALLY, AND A FIRST CONDUIT MEMBER COMMUNICATING WITH THE INTERIOR OF THE BLOCK AND LEADING TO SAID MANOMETRIC METERING DEVICE; THE IMPROVEMENT CONSISTING OF MEANS DEFINING A VOLUMETRIC EXTENSION OF THE CLEARANCE VOLUME OF SAID VESSEL COMPRISING, A SECOND CONDUIT MEMBER SECURED AT ONE END TO THE VESSEL AT THE VICINITY OF THE CLEARANCE VOLUME AND COMMUNICATING THERETO, AND ELONGATE TUBING MEMBER HAVING A FLEXIBLE PORTION CONNECTED WITH THE OTHER END OF SAID SECOND CONDUIT AND LEADING THEREFROM TO A LOCATION REMOTE FROM SAID VESSEL, MEANS FOR CLOSING THE OTHER END OF SAID TUBING AT SAID REMOTE LOCATION, AND, MEANS FOR REDUCING SELECTIVELY THE EFFECTIVE INTERNAL VOLUME OF SAID TUBING A PREDETERMINED AMOUNT TO VARY THE EFFECTIVE VOLUME OF SAID EXTENSION WITHIN DEFINED LIMITS THEREBY TO VARY THE COMPRESSION RATIO OF THE PUMP AND IN THAT MANNER, VARY THE PERCENTAGE VACUUM OUTPUT THEREOF DELIVERED TO THE MANOMETRIC METERING DEVICE.