Patent ID: 7600793

Claim:
A twin-wall pipe, comprising a central longitudinal axis ( 18 ); a smooth-wall internal pipe ( 39 ′) which extends concentrically of the central longitudinal axis ( 18 ); a corrugated external pipe ( 37 ′), having elevations ( 38 ) each with an internal space and troughs ( 40 ) between the elevations ( 38 ), the troughs ( 40 ) and the internal pipe ( 39 ′) being welded together; a pipe socket ( 41 ) which is molded integrally with the internal pipe ( 39 ′) and the external pipe ( 37 ′); a transition portion ( 61 , 64 ) between the pipe socket ( 41 ) and an adjacent trough ( 40 ), the transition portion ( 61 , 64 ) having an inside between the external pipe ( 37 ′) and the internal pipe ( 39 ′); wherein said inside of the transition portion ( 61 , 64 ) is connected to the internal space of said adjacent elevation ( 38 ) by at least one overflow passage ( 59 , 63 ) which is formed in the external pipe ( 37 ′) and passes through said adjacent trough ( 40 ) between the transition portion ( 61 , 64 ) and the internal space of said adjacent elevation ( 38 ) in a direction of the central longitudinal axis.