Pump and valve assembly

Claim 1

A VALVE FOR CONTROLLING THE FLOW OF MATERIAL CONTAINING DISCRETE PARTICLES COMPRISING: A VALVE BODY HAVING A SEAT; A VALVE GATE RECIPROCALLY MOUNTED IN A CYLINDRICAL OPENING IN SAID BODY; SAID VALVE GATE COMPRISING A CORE OF RIGID MATERIAL HAVING A CYLINDRICAL PORTION AND A REDUCED NOSE PORTION AT ONE END THEREOF; A RESILIENT NOSE PLUG COVERING SAID NOSE PORTION AND SECURED THERETO; SAID NOSE PLUG COMPRISING A DOME-SHAPED END SURFACE CONNECTING WITH A CYLINDRICAL SURFACE SURROUNDING SAID NOSE PORTION, SAID CYLINDRICAL SURFACE HAVING THE SAME DIAMETER AS SAID CYLINDRICAL PORTION OF SAID CORE TO BE COEXTENSIVE THEREWITH; SAID CYLINDRICAL PORTION BEING IN FULL ENGAGEMENT WITH SAID CYLINDRICAL OPENING WHEN SAID VALVE IS CLOSED BY MOVING SAID NOSE PLUG AGAINST SAID SEAT AND HAVING A LENGTH GREATER THAN ITS DIAMETER TO PROVIDE SUFFICIENT BEARING AREA TO RESIST THE PRESSURE APPLIED TO SAID NOSE PLUG WHEN THE VALVE IS CLOSED; SAID NOSE PORTION EXTENDING INTO SAID NOSE PLUG BY A DISTANCE OF MORE THAN HALF THE LENGHT OF SAID NOSE PLUG AGAINST PRESSURE APPLIED THERETO WHEN IN SAID CLOSED POSITION; AND AN ANNULAR DAM EXTENDING OUTWARDLY FROM THE END OF SAID NOSE PORTION ADJACENT SAID CYLINDRICAL PORTION OF SAID CORE, SAID DAM COMPRISING AN ANNULAR WALL SEPARATED FROM SAID CYLINDRICAL PORTION BY A CYLINDRICAL GROOVE; THE DIAMETER OF SAID WALL BEING SMALLER THAN SAID CYLINDRICAL SURFACE OF SAID NOSE PLUG SO THAT SAID NOSE PLUG PASSES AROUND SAID WALL AND IS ANCHORED IN SAID GROOVE.