Patent ID: 8047977

Claim:
A process for producing a filter strand ( 31 ) comprising two or more filters ( 10 ) each including a first end filter element ( 12 , 24 , 26 ), a second inside filter element ( 14 ), a middle filter element ( 16 ) containing granular filter material ( 17 ) and located between the first and second filter elements, and an outside casing ( 20 ) surrounding all of the filter elements, the process comprising the steps of exerting force on the first end filter element ( 12 , 24 , 26 ) from outside the filter strand ( 31 ) in order to inwardly displace at least a portion of the first end filter element ( 12 , 24 , 26 ) relative to the casing ( 20 ) toward and against the middle filter element ( 16 ), to thereby compress the granular filter material ( 17 ) therein, and wherein each first end filter element ( 12 , 24 , 26 ) includes an outer ring ( 24 ) and an internal core ( 25 ), and wherein the internal core ( 25 ) is displaced inwardly against the granular filter material ( 17 ).