Deep well pump for viscous oil

Claim 1

A DEEP WELL PUMP ASSOCIATED, WHEN IN USE, WITH A PRODUCTION TUBING STRING AND A SUCKER ROD STRING, SAID PUMP COMPRISING: PUMP BARREL MEANS HAVING MEANS FOR CONNECTING THE UPPER END OF SAID BARREL MEANS TO THE LOWER END OF SAID TUBING STRING, THE MAXIMUM ID OF SAID BARREL MEANS BEING SUBSTANTIALLY LESS THAN THE ID OF SAID TUBING STRING; A STANDING VALVE PROVIDED AT THE LOWER END OF SAID BARREL MEANS AND CHECKING DOWNWARD FLOW THEREFROM; PUMP PLUNGER MEANS SLIDABLE WITHIN SAID BARREL MEANS AND HAVING MEANS TO CONNECT THE SAME TO THE LOWER END OF SAID SUCKER ROD STRING FOR LOWERING SAID PLUNGER MEANS THROUGH SAID TUBING STRING INTO SAID BARREL MEANS AND RECIPROCATING SAID PLUNGER MEANS IN SAID BARREL MEANS; AND A TRAVELLING VALVE PROVIDED ON SAID PLUNGER MEANS FOR CHECKING DOWNWARD FLOW THROUGH SAID PLUNGER MEANS, THERE BEING PORT MEANS AT AN INTERMEDIATE LOCATION IN SAID BARREL MEANS, SAID PORT MEANS COMMUNICATING BETWEEN THE INTERIOR OF SAID BARREL AND THE EXTERIOR THEREOF, UPPER AND LOWER PORTIONS OF SAID PLUNGER MEANS MAKING A SLIDING FIT WITH CORRESPONDING PORTIONS OF SAID BARREL MEANS DISPOSED RESPECTIVELY ABOVE AND BELOW SAID PORT MEANS THROUGHOUT THE VERTICAL PUMPING STROKES OF SAID PLUNGER THEREBY PREVENTING COMMUNICATION BETWEEN SAID PORT MEANS AND SAID STANDING VALVE AND COMMUNICATION BETWEEN SAID PORT MEANS AND THE LOWER END OF SAID TUBING STRING DURING THE NORMAL OPERATION OF SAID PUMP BUT EFFECTING THE AUTOMATIC DRAINING OF SAID TUBING STRING THROUGH SAID PORT MEANS WHEN SAID PLUNGER MEANS IS WITHDRAWN UPWARDLY FROM SAID BARREL MEANS.