Patent ID: 7258060

Claim:
A piston and scraper assembly ( 26 , 26 ′) for a chromatography column, comprising a piston ( 5 ) and a scraper ( 25 ) wherein said piston ( 5 ) has a front, first face ( 7 ) a cylindrical portion ( 17 ), a second, rear face ( 15 ) and a through hole ( 11 ) connecting said first face ( 7 ) to said second face ( 15 ), and is provided with an annular groove ( 23 , 23 ′) of depth D 1 mm in the cylindrical portion ( 17 ), and wherein the scraper ( 25 ) is a ring, adapted to fit onto piston ( 5 ), having an L-shaped cross-section and having a complementary groove ( 39 ) of depth D2 mm in an inner face ( 37 ), characterised in that said annular groove ( 23 , 23 ′) is provided with a resilient sealing, locking and biasing means ( 45 ) which extends from said annular groove ( 23 , 23 ′) into said complementary groove ( 39 ) in order to retain said scraper ( 25 ) on said piston ( 5 ).