Patent ID: 7178451

Claim:
Piston for metering equipment with improved seal system, which includes sealing means constituted by a seal comprising an outer part ( 7 , 36 ) in contact with the wall ( 20 , 37 ) of the cylinder in which the piston moves and an inner part ( 14 , 33 ) made of a different material from the outer part, which said inner part presents a perimeter groove in which are inserted elastic means ( 18 , 34 ) that press on said outer part of the seal to keep it in contact with the cylinder wall, and further comprising: a cylindrical body ( 1 ) which presents an annular groove ( 3 ) at one end that defines an outer bead ( 4 ) and an inner bead ( 5 ); a cap ( 7 ), designed to be fitted over said annular body ( 1 ), which said cap presents an outer groove ( 11 ) at the base that defines an annular bead ( 10 ) having the same diameter as said inner annular bead ( 5 ) of cylindrical body ( 6 ), and an inner annular groove ( 12 ); an annular support ( 14 ) inserted into said groove ( 12 ) present in cap ( 7 ), which said annular support contains a perimeter groove ( 15 ) in which is inserted a spring-loaded element ( 18 ) that opens outwards, which said spring-loaded element acts on the side wall of said cap to press it against wall ( 20 ) of the cylinder in which the piston moves; a ring ( 21 ) which presents an inner groove ( 22 ) designed to fit round said annular bead ( 5 ) of said body and said annular bead ( 10 ) of said cap, to retain the assembly in position.