Reciprocating pumps

Claim 1

IN A HEAVY DUTY RECIPROCATING PUMP OF THE TYPE COMPRISING A RIGID FRAME, A FLUID END ASSEMBLY DEFINING A PLURALITY OF PUMP CHAMBERS, A PLURALITY OF DEVICES RIGIDLY SUPPORTED BY THE FRAME AND EACH DEFINING A CYLINDRICAL PASSAGE COMMUNICATING WITH A DIFFERENT ONE OF THE PUMP CHAMBERS, AND DRIVE MEANS INCLUDING A PLURALITY OF RECIPROCATORY MEMBERS EACH CONSTRAINED TO MOVE ALONG THE AXIS OF A DIFFERENT ONE OF THE CYLINDRICAL PASSAGES, THE COMBINATION OF A PLURALITY OF PLUNGER ASSEMBLIES EACH OPERATIVELY ARRANGED IN A DIFFERENT ONE OF CYLINDRICAL PASSAGES AND A EACH COMPRISING A TUBULAR PLUNGER A MANDREL HAVING A SHANK PORTION EXTENDING COAXIALLY WITH SAID PLUNGER, MEANS SECURING SAID MANDREL RIGIDLY TO SAID PLUNGER AT THE END OF SAID SHANK PORTION DISPOSED WITHIN SAID PLUNGER, AND MEANS CONNECTING THE OTHER END OF SAID MANDREL TO ONE OF THE RECIPROCATORY MEMBERS OF THE DRIVE MEANS; SAID SHANK PORTION HAVING A TRANSVERSE CROSS-SECTION WHICH IS SMALL AS COMPARED TO THE CROSS-SECTIONAL SIZE OF THE ONE OF THE RECIPROCATORY MEMBERS TO WHICH SAID MANDREL IS CONNECTED, WHEREBY SAID SHANK PORTION AFFORDS A LIMITED FLEXING ABILITY UNDER MISALIGMENTS AFFECTING THE RECIPROCATORY MOVEMENT OF SAID PLUNGER, SAID MEANS SECURING SAID MANDREL TO SAID PLUNGER INCLUDING AN ELEMENT WHICH IS INTERPOSED BETWEEN SAID SHANK PORTION AND SAID PLUNGER AND WHICH IS SUBSTANTIALLY WEAKER THAN SAID SHANK PORTION, SAID PLUNGER DEFINING A FREE ANNULAR SPACE ABOUT SAID SHANK PORTION TO ALLOW FLEXING OF SAID SHANK PORTION