Split die for extruding laminated tubing

Claim 2

A split extrusion die adapted to extrude laminated, seamless, plastic tubing in which separate tubular layers of said laminate are made of different plastic materials comprising outer and inner dies, said outer and inner dies terminating in separate outer and inner extrusion orifices which are concentrically arranged with respect to each other; said outer and inner dies being maintained in spaced relation with respect to each other by separator means interposed between said dies and defining therebetween a space gap, said separator means occupying at most only a minor portion of said space gap and contacting said dies at most at only a limited number of places thereby forming an insulating space between said outer and inner dies whereby a temperature gradient may be maintained between said dies, said split extrusion die having separate outer and inner die plastic feeding means; and said separator means comprising a hollow cylindrical body portion and lug means distributed on at least one surface of said hollow cylindrical body portion, said lug means serving to keep said outer and inner dies in spaced relation with respect to each other and providing a space gap therebetween.

Claim 3

A split extrusion die adapted to extrude laminated, seamless, plastic tubing in which separate tubular layers of said laminate are made of different plastic materials comprising outer and inner dies, said outer and inner dies terminating in separate outer and inner extrusion orifices which are concentrically arranged with respect to each other; said outer and inner dies being maintained in spaced relation with respect to each other by separator means interposed between said dies and defining therebetween a space gap, said separator means occupying at most only a minor portion of said space gap and contacting said dies at most at only a limited number of places thereby forming an insulating space between said outer and inner dies whereby a temperature gradient may be maintained between said dies, said split extrusion die having separate outer and inner die plastic feeding means, said separator means comprising a hollow cylindrical body portion and lug means distributed on at least one surface of said hollow cylindrical body portion, said lug means serving to keep said outer and inner dies in spaced relation with respect to each other and providing a space gap therebetween and comprising a plurality of lugs radially disposed at each end of said hollow cylindrical body portion.

Claim 4

A split extrusion die adapted to extrude laminated, seamless, plastic tubing in which separate tubular layers of said laminate are made of different plastic materials comprising outer and inner dies, said outer and inner dies terminating in separate outer and inner extrusion orifices which are concentrically arranged with respect to each other; said outer and inner dies being maintained in spaced relation with respect to each other by separator means interposed between said dies and defining therebetween a space gap, said separator means occupying at most only a minor portion of said space gap and contacting said dies at most at only a limited number of places thereby forming an insulating space between said outer and inner dies whereby a temperature gradient may be maintained between said dies, said split extrusion die having separate outer and inner die plastic feeding means, said separator means comprising a hollow cylindrical body portion and lug means distributed on at least one surface of said hollow cylindrical body portion, said lug means serving to keep said outer and inner dies in spaced relation with respect to each other and providing a space gap therebetween and comprising a plurality of lugs radially disposed at each end of said hollow cylindrical body portion.

Claim 5

A split die according to claim 1 including gas conduit means terminating in an orifice which is centrally disposed with respect to said inner annular extrusion orifice, said gas conduit means being disposed so as to introduce gas under pressure into the interior of a tubular layer issuing from said inner annular orifice during its extrusion, whereby the inner tubular layer is forced into contact with a tubular layer issuing from said outer annular orifice to insure the bonding of the tubular layers together to form said laminated tube.

Claim 6

A split die according to claim 3 including means for heating said inner and Outer dies to different temperatures.

Claim 7

A split die according to claim 3 including means for circulating coolant through said space gap under pressure.

Claim 8

A split die according to claim 3 including baffle means disposed in said inner die plastic material feeding means said baffle means momentarily serving to divide the stream of plastic material flowing in the inner die plastic material feeding means.