Piston structure

Claim 1

A PISTON STRUCTURE FOR USE IN A HEATED COFFEE BREWING CYLINDER AND COMPRISING: A PISTON ROD, AN ANNULAR SEATING PLATE SECURED CENTRALLY NEAR AN EDN OF SAID ROD, A SEALING MEMBER IN THE SHAPE OF A SHALLOW CUP MADE OF A THIN FLUOROCARBON SYNTHETIC RESIN HAVING A FLARED NARROW SKIRT WITH AN OUTER RIM PORTION DISPOSED AT A PREDETERMINED GREATER DIAMETER THAN THE REMAINING PORTIONS THEREOF, SAID MEMBER HAVING A CENTRAL OPENING FITTING OVER SAID END OF THE ROD TO SEAT ON SAID PLATE; AN ANNULAR FILLER MEMBER OF FLEXIBLE MATERIAL SUCH AS RUBBER DIMESIONED TO FIT WITHIN SAID CUP OVER SAID END OF THE ROD, AND HAVING A BEVELED EDGE FLARING OUTWARDLY IN JUXTAPOSITION AGAINST SAID RIM PORTION OF THE CUP TO DISPOSE THE LATTER YIELDINGLY AT SAID GREATER DIAMETER, AND A CONCAVE HEADER WASHER FITTED UPON SAID ROD END, CONCAVE SIDE DOWM, ONTO SAID FILLER MEMBER WITH OUTER PERIPHERAL MARGINS BEARING DOWN UPON THE BEVELED EDGE OF THE FILLER MEMBER CLOSE TO THE MARGIN THEREOF AND SAID JUXTAPOSED CUP RIM, SO THAT ALL THREE OF SAID PERIPHERAL MARGINS ARE IN CLOSE JUXTAPOSITION, TOGETHER WITH RETAINING MEANS SECURING THE HEADER WASHER ON THE ROD AGAINST THE FILLER MEMBER UNDER TENSION TO YIELDINGLY MAINTAIN THE AFORESAID FLARE AND GREATER DIAMETER OF THE CUP RIM.