Patent ID: 7735877

Claim:
A resin-tube connection structure comprising: a metallic pipe having a tip edge and at least a first and a second radially enlarged portion at a tip area, the first and second radially enlarged portion having a substantially equal outer diameter and being spaced from each other to form a circumferential groove with a bottom therebetween; the first radially enlarged portion having a first circumferential edge, being at a most tip side, gradually and linearly increasing in diameter from the tip edge backwards to the first circumferential edge and therefrom sharply reducing in diameter to the bottom of the groove; the second radially enlarged portion having a second circumferential edge, being at a back side of the first radially enlarged portion, sharply increasing in diameter from the bottom of the groove to the second circumferential edge and therefrom reducing in diameter backwardly; a seal ring being accommodated in the circumferential groove; and a resin tube being inserted by pressure over the metallic pipe until it passes beyond the second radially enlarged portion.