Linear acting door closer

Claim 1

A HYDRAULIC DOOR CLOSER DEVICE COMPRISING A CYLINDER HAVING AN OPEN AND A CLOSED END A PISTON ROD HAVING AN OUTER END EXTENDING THROUGH THE OPEN END OF SAID CYLINDER AND MOUNTED FOR SLIDING MOVEMENT TOWARD AND AWAY FROM THE CLOSED END, CLOSER SPRING MEANS IN SAID CYLINDER URGIN SAID PISTON ROD TOWARD SAID CLOSED END, A THREADED PORTION ON THE INNER END OF SAID PISTON ROD, THE INNER END OF SAID ROD TERMINATING IN AN INWARDLY TAPERED PORTION, A LONGITUDINALLY EXTENDED GROOVE FORMED IN THE THREADED PORTION OF SAID ROD, THE CROSS-SECTIONAL AREA OF SAID GROOVE GROWING PROGRESSIVELY GREATER AT LONGITUDINALLY SPACED INCREMENTS OF SAID GROOVE, A PISTON HEAD ASSEMBLY MOUNTED ON THE THREADED PORTION OF SAID ROD, SAID ASSEMBLY INCLUDING A GASKET SUPPORT PORTION OF RESILIENT, DEFORMABLE PLASTIC HAVING A HIGH DEGREE OF PLASTIC MEMORY AND HAVING A CENTRALLY APERTURED HUB, THE LONGITUDINAL EXTENT OF SAID HUB BEING LESS THAN THE LENGTH OF SAID GROOVE, THE INNER SURFACE OF THE BORE DEFINING SAID APERTURE BEING DEFORMED BY SAID THREADED PORTION TO CONFORM TO THE CONFIGURATION OF SAID THREADED PORTION, THE DIAMETER OF AT LEAST PART OF SAID THREADED PORTION BEING GREATER THAN THE DIAMETER OF SAID APERTURE, THEREBY TO CAUSE INCREMENTS OF SAID HUB DEFINING SAID APERTURE TO FLOW INTO SAID GROOVE, AND ADJUSTMENT MEANS ROTATABLY MOUNTED IN THE CLOSED END OF SAID CYLINDER ENGAGED IN TORQUE TRANSMITTING RELATION TO SAID GASKET SUPPORT MEMBER WHEN SAID SUPPORT MEMBER IS DISPOSED ADJACENT SAID CLOSED END, ROTATION OF SAID ADJUSTMENT MEANS CAUSING A CONCOMITANT ROTATION OF SAID GASKET SUPPORT PORTION, THEREBY A SHIFT SAID SUPPORT PORTION AXIALLY ALONG SAID THREADED PORTION OF SAID ROD, WHEREBY SAID SUPPORT PORTION IS VARIABLY POSITIONED ALONG THE LENGTH OF SAID GROOVE, SAID GROOVE AND SAID INCREMENTS OF SAID HUB DEFINING A PASSAGE THROUGH SAID HEAD ASSEMBLY OF VARIABLE CROSS SECTIONAL AREA IN ACCORDANCE WITH THE ADJUSTED POSITION OF SAID SUPPORT PORTION ALONG SAID ROD.