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US 7,001,547 B2Granted
Method and apparatus for joining sheet- or ribbon formed flows in a coextrusion process
OwnerOle-Bendt Rasmusseninventor
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OwnerOle-Bendt Rasmusseninventor
Estimating the term…
A method and apparatus are described for coextruding two materials A and B, in which B is extruded on A through a port (3), in which the separating wall between the flows of A and B is formed as a flap closure (4) adapted to act as a non-return valve for the flow of B into A, and further means are provided for extruding B through the port in pulses. The pulses may be effected by opening and closing the closure, by mechanical transmission means or by the effect of imposing pressure difference on the flap (4) by the flows of A and/or B. The pulsing means preferably involves rams (1). The invention is particularly suitable for extruding a low viscosity material B onto a higher viscosity material A, or for making sheets or pipes with alternating segments of differential flexibility, or for coextruding a flow of solid particles with a flow of liquid.
In a method of coextruding by means of a coextrusion die which comprises the steps of feeding under extrusion pressure a flow of an extrudable material A and at least one flow of an extrudable material B through separate passageways in said die which are separated by a separation wall, and at the end of said wall, delivering flow B through a laterally elongated delivery port to join with flow A to give a combined flow, and passing the combined flow through a common passageway and eventually out of said die in sheet- or ribbon-form, the improvement wherein the delivery of flow B through said port takes place in pulsating fashion with the flow pulses after emergence from said port being prevented from reentry into said port.
An extruder comprising a coextrusion die for coextruding a sheet- or ribbon-formed flow of an extrudable material A with at least one sheet or ribbon-formed flow of an extrudable material B said coextrusion die comprising separate passageways for the flows of A and B, said passageways being separated by a separation wall, extrusion feed means for advancing the flows A and B through their respective passageways, the passageway for flow B at the end of said wall terminating in an delivery port which is elongated in a direction transversely of the direction of flow therethrough, downstream of said delivery port a passageway common for both flows A & B wherein flow B after passage through said port joins to flow A to give a combined flow, said common passageway terminating in an exit through which the combined flows emerge from said die, pulsating flow control means for causing the advance of said flow B through said delivery port to take place in pulsating fashion, and reverse flow blocking means effective after the delivery of each flow A pulse through said delivery port to prevent reentry of such pulse into said port.
A circular coextrusion die for coextruding a sheet- or ribbon-formed flow of an extrudable material A with at least one sheet or ribbon-formed flow of an extrudable material B, said coextrusion die comprising separate annular passageways for the flows of A and B, a separation wall separating said passageways, the passageway for flow B at the end of said wall terminating in an annular delivery port into the A-flow passageway, and communicating with said A-flow annular passageway downstream of said delivery port an annular passageway common to both flows A & B wherein flow B after passage through said port joins to flow A to give a combined flow in said common passageway, said common passageway terminating in an annular exit opening through which the combined flow emerges from said die in tubular form, said separation wall having adjacent said delivery port at least an end portion thereof of generally planar form extending perpendicularly to the die axis, the planar end portion being adapted to flex from and to its plane to act as a flap closure for said delivery port and thereby to adjust its flexed position in response to a difference in flow pressure in the flows acting on its opposite sides.
Dependencies are inferred from the claim text.