Multi-stage displacement pump

Claim 1

IN A DISPLACEMENT PUMP ASSEMBLY FOR DEEP WELLS, A SERIES OF CONCENTRIC LIQUID DISPLACEMENT UNITS EACH COMPRISING A CYLINDRICAL HOUSING CLOSED AT ITS UPPER END BY A HEAD AND AT ITS LOWER END BY A BOTTOM CLOSURE, CENTRAL VERTICAL OPENINGS EXTENDING THROUGH RESPECTIVE HEADS AND BOTTOM CLOSURES, CONNECTING TUBES EXTENDING BETWEEN RESPECTIVE HOUSINGS AND SECURED AT OPPOSITE ENDS IN THE CENTRAL OPENINGS OF THE BOTTOM CLOSURE OF EACH HOUSING AND THE HEAD OF THE HOUSING NEXT BELOW, SUPPORTING SAID HOUSINGS IN VERTICALLY SPACED RELATION IN SAID WELL, EACH HOUSING HAVING AN INWARDLY SPACED, CONCENTRIC ANNULAR PARTITION FORMING THEREIN THE COMMON WALLS OF A LIQUID PASSAGEWAY AND A SURROUNDING LIQUID RESERVOIR, EACH PARTITION BEING CONNECTED AT ITS UPPER END INTO THE CENTRAL OPENING OF THE HEAD AND TERMINATING AT ITS LOWER END IN COMMUNICATION WITH THE RESERVOIR OF THE RESPECTIVE HOUSING, EACH LIQUID PASSAGEWAY COMMUNICATING THROUGH SAID HEAD WITH THE CONNECTING TUBE NEXT ABOVE, CHECK VALVES AT THE LOWER END OF EACH PARTITION CONTROLLING ENTRY OF LIQUID FROM SAID RESERVOIR INTO RESPECTIVE LIQUID PASSAGEWAYS, CHECK VALVES IN THE CENTRAL OPENING OF EACH HEAD CONTROLLING THE ENTRY OF LIQUID FROM EACH LIQUID PASSAGEWAY TO THE CONNECTING TUBE NEXT ABOVE, TUBULAR GAS CONDUCTING MEANS CONNECTED TO A SOURCE OF COMPRESSED GAS, EXTENDING THROUGH ALL OF SAID UNITS IN CONCENTRICALLY INWARDLY SPACED RELATION TO RESPECTIVE CONNECTING TUBES AND ANNULAR PARTITIONS, A