초록 ▼

A flexible double-walled plastic tubing product includes a helically wound support bead between inner and outer walls, and an helically wrapped electrical resistance heating conductor is disposed adjacent to the inner wall in good heat transfer relation to fluid flow within the tubing product. Fluid

A flexible double-walled plastic tubing product includes a helically wound support bead between inner and outer walls, and an helically wrapped electrical resistance heating conductor is disposed adjacent to the inner wall in good heat transfer relation to fluid flow within the tubing product. Fluid flow within the tubing product is insulated against heat loss to ambient by the helical support bead and a trapped "dead-air" space between the walls of the tubing product. Apparatus and method for making the tubing product are disclosed.

대표청구항 ▼

[ What is claimed is:] [1.] A method of making a double-walled flexible and collapse-resistant insulative plastic tubing having a substantially smooth bore provided by an inner one of two radially spaced apart integral walls trapping a dead-air space therebetween, and an integral helical support bea

[ What is claimed is:] [1.] A method of making a double-walled flexible and collapse-resistant insulative plastic tubing having a substantially smooth bore provided by an inner one of two radially spaced apart integral walls trapping a dead-air space therebetween, and an integral helical support bead disposed between the two walls so that the two integral walls and helical support bead are formed simultaneously and all have a common helix angle, said method comprising steps of:simultaneously providing an elongate thermoplastic first ribbon and an elongate thermoplastic second ribbon each having respective opposite marginal side edge portions;first, forming an elongate tubular body by winding said first ribbon on itself with opposite marginal side edge portions thereof overlapped and interbonding to form a helical lap joint;simultaneously providing a thermoplastic support bead;secondly, winding said support bead helically around and along said elongate tubular body atop said helical lap joint while heat-bonding said support bead to said elongate tubular body;thirdly, winding said second ribbon helically around and along said elongate tubular body while spanning from one wrap of said helical support bead to the next, while bowing radially outwardly, and while heat-bonding at overlapped opposite marginal side edge portions thereof itself and to said support bead; andcooling said tubing;whereby upon the tubing being bent, the flexibility of the tubing is improved by a radially outward bowing of the second ribbon at the inside of such bend.