Device for feeding an extrusion head for plastic material

Abstract

A device for feeding an extrusion head for plastic material includes a main extruder connected to a main die for extruding a continuous main flow of material, and an auxiliary feed mechanism associated with the main die and selectively controlled to cover the outer exit flow of the main die with a surface layer. The auxiliary feed mechanism continuously conducts two auxiliary flows, a first flow forming the surface layer and the second flow being mixed with the main flow. An invertor valve permits selective exchanging of the two auxiliary flows such that the second flow can cover the main flow and the first flow can be mixed with the main flow.

What is claimed is: 
     
       1. A device for forming a continuous elongated element of plastic material through extrusion, comprising: a main extruder for a continuous main flow of a first plastic material;   auxiliary feed means comprising two auxiliary flow exit orifices for continuously conducting auxiliary flows of a second and third plastic material, respectively, all of said first, second and third plastic materials forming said main and auxiliary flows having different constitutions;   a composite extrusion head having a die system, two auxiliary flow inlet orifices, a main flow inlet orifice, a mixing receptacle adjacent said main flow inlet orifice, an outlet orifice defined by an outlet die of said die system, and ducts within said composite extrusion head connecting each of said auxiliary flow inlet orifices to said outlet orifice through different routes, one of said routes connecting one of said auxiliary flow inlet orifices to said mixing receptacle through a helical channel in an outer peripheral portion of said composite extrusion head, the other one of said routes connecting the other one of said auxiliary flow inlet orifices with said outlet orifice through said die system to provide in said elongated element a continuous zone having in said element a predetermined location; and   inverter means connected to said exit orifices of said auxiliary feed means and said auxiliary flow inlet orifices of said composite extrusion head for exchanging the connections between said auxiliary flows exit and inlet orifices.   
     
     
       2. The device according to claim 1 .[.in which.]. .Iadd.wherein .Iaddend.one of the auxiliary flow inlet orifices of the composite extrusion head is connected to ducts forming an outer layer on the elongated element, and the other auxiliary-flow inlet orifice of the extrusion head is connected to means for mixing the auxiliary flow led through said other auxiliary flow inlet orifice with the main flow. 
     
     
       3. The device according to claim 2, .[.characterized in that.]. .Iadd.wherein .Iaddend.the extrusion head comprises a mixing cavity connected to a main inlet of the extrusion head connected in turn to the main extruder and to the other auxiliary-flow inlet orifice. 
     
     
       4. The device according to claim 1, .[.characterized in that.]. .Iadd.wherein .Iaddend.the auxiliary feed means comprise an auxiliary extruder having two screws housed in two cylinders contained in a single body. 
     
     
       5. The device according to claim 4, .[.characterized in that.]. .Iadd.wherein .Iaddend.the two screws of the auxiliary extruder are driven by a single motor through the intermediary of a single speed-reduction gear. 
     
     
       6. The device according to claim 4, .[.characterized in that.]. .Iadd.wherein .Iaddend.the two cylinders of the auxiliary extruder are each connected to a hopper for introducing plastic material, and in that each of .[.these.]. .Iadd.said .Iaddend.hoppers is provided with a colorant-metering apparatus. 
     
     
       7. The device according to claim 1, .[.characterized in that.]. .Iadd.wherein .Iaddend.the inverter means comprises a valve having two inlet ways and two outlet ways, and a valve needle rotatable between two active positions. 
     
     
       8. The device according to claim 7, .[.characterized in that.]. .Iadd.wherein .Iaddend.the valve needle is of cylindrical shape and has an axial passage connected to a radial inlet way and a radial outlet way, and an arcuate circumferential passage situated in a plane perpendicular to the axis of the valve needle, at the level of the radial inlet way, the radial inlet way and the ends of the circumferential passage defining three segments of a circle of 120° each on the circumference of the valve needle. 
     
     
       9. A device for continuous extrusion of an elongated element of plastic material comprising a composite extrusion head, a main extruder producing a main flow, auxiliary feed means including two exit orifices conducting two auxiliary flows, and control means permitting the extrusion head to be fed selectively so that one or the other of the said auxiliary flows forms a particular zone in the elongated element, the composite extrusion head further comprising two auxiliary-flow inlet orifices and a main-flow inlet orifice, respectively connected to the exit orifices and to the main extruder, and the control means comprising an inverter capable of exchanging the connections between the exit orifices of the auxiliary feed means and the said auxiliary-flow inlet orifices; wherein one of the auxiliary-flow inlet orifices of the extrusion head is connected to ducts forming an outer layer on the elongated element, the other auxiliary-flow inlet orifice of the extrusion head is connected to means for mixing the auxiliary flow led through this orifice with the main flow;   the extrusion head comprises a mixing cavity connected, on the one hand, to a main inlet of the extrusion head connected in turn to the main extruder and, on the other hand, to the said other auxiliary-flow inlet orifice; and   the inverter comprises a valve having two inlet ways and two outlet ways, and a cylindrical shape valve needle rotatable between two active positions, the valve needle having an axial passage connected to a radial inlet way and a radial outlet way, and an arcuate circumferential passage situated in a plane perpendicular to the axis of the valve needle, at the level of the said radial inlet way, the radial inlet way and the ends of the circumferential passage defining three segments of a circle of 120° each on the circumference of the valve needle.   
     
     
       10. The device according to claim 9, .[.characterized in that.]. .Iadd.wherein .Iaddend.the auxiliary feed means comprise an auxiliary extruder having two screws housed in two cylinders contained in a single body. 
     
     
       11. The device according to claim 10, .[.characterized in that.]. .Iadd.wherein .Iaddend.the two screws of the auxiliary extruder are driven by a single motor through the intermediary of a single .[.speedreduction grear.]. .Iadd.speed reduction gear.Iaddend.. 
     
     
       12. The device according to claim 10, .[.characterized in that.]. .Iadd.wherein .Iaddend.the two cylinders of the auxiliary extruder are each connected to a hopper for introducing plastic material, and in that each of .[.these.]. .Iadd.said .Iaddend.hoppers is provided with a .[.colorantmetering.]. .Iadd.colorant metering .Iaddend.apparatus. .Iadd. 
     
     
       13.  A device for forming a continuous elongated element of plastic material through extrusion, comprising: a main extruder for a continuous main flow of a first plastic material;   auxiliary feed means comprising two auxiliary flow exit orifices for continuously conducting auxiliary flows of a second and third plastic material, respectively, all of said first, second and third plastic materials forming said main and auxiliary flows having different constitutions;   a composite extrusion head having a die system, two auxiliary flow inlet orifices, a main flow inlet orifice, an outlet orifice defined by said die system, and ducts within said composite extrusion head connecting each of said auxiliary flow inlet orifices to said outlet orifice through different routes, one of said routes connecting one of said auxiliary flow inlet orifices to a channel in said composite extrusion head communicating with said main flow inlet orifice, the other one of said routes connecting the other one of said auxiliary flow inlet orifices with said outlet orifice through said die system to provide said elongated element with a continuous zone having a predetermined location; and   inverter means connected to said exit orifices of said auxiliary feed means and said auxiliary flow inlet orifices of said composite extrusion head for exchanging the connections between said auxiliary flows exit and inlet orifices. .Iaddend. .Iadd.14. The device according to claim 13, in which one of the auxiliary flow inlet orifices of the composite extrusion head connects to ducts forming an outer layer on the elongated element, and the other auxiliary flow inlet orifice of the extrusion head connects the auxiliary flow led through said other auxiliary flow inlet orifice with the main flow. .Iaddend. .Iadd.15. The device according to claim 13, wherein the inverter means comprises a valve having two inlet ways and two outlet ways, and is rotatable between two active positions. .Iaddend.   
     
     
        .Iadd.16.  The device according to claim 15, wherein the valve includes a valve needle of cylindrical shape and has an axial passage connected to a radial inlet way and a radial outlet way, and an arcuate circumferential passage situated in a plane perpendicular to the axis of the valve needle, at the level of the radial inlet way, the radial inlet way and the ends of the circumferential passage defining three segments of a circle of 120° each on the circumference of the valve needle. .Iaddend. .Iadd.17. A device for continuous extrusion of an elongated element of plastic material, comprising a composite extrusion head, a main extruder producing a main flow, auxiliary feed means including two exit orifices conducting two auxiliary flows, and control means permitting the extrusion head to be fed selectively so that one or the other of said auxiliary flows forms a particular zone in the elongated element, the composite extrusion head further comprising two auxiliary flow inlet orifices and a main flow inlet orifice, respectively connected to the exit orifices and the main extruder, and the control means comprising an inverter capable of exchanging the connections between the exit orifices of the auxiliary feed means and said auxiliary flow inlet orifices; wherein one of the auxiliary flow inlet orifices of the extrusion head is connected to ducts forming an outer layer on the elongated element, and the other auxiliary flow inlet orifice of the extrusion head connects the auxiliary flow led through the other auxiliary flow inlet orifice with the main flow; and   the inverter comprises a valve having two inlet ways and two outlet ways, and is rotatable between two active positions, said first active position directing a first flow of the auxiliary flows to the outer layer of the elongated element and a second flow of the auxiliary flows to the zone within the elongated element, and said second active position directing the first flow to the zone within the elongated element and the second   
     
     
        flow to the outer layer. .Iaddend. .Iadd.18.  A device for extruding a continuous elongated element of plastic materials having a core encompassed by at least one outer sheath, comprising: a main extruder for extruding a continuous main flow of a plastic material;   first auxiliary feed means for feeding a first continuous auxiliary flow of a first material, the first auxiliary feed means having a first exit orifice for continuously conducting said first auxiliary flow;   second auxiliary feed means for feeding a second continuous auxiliary flow of a second material, the second auxiliary feed means having a second exit orifice for continuously conducting said second auxiliary flow;   extruder means for extruding the elongated element comprised of said main flow and said first and second auxiliary flows, the extruder means having a first flow path for directing one material of said first and second materials to join with the main flow to form the core of the elongated element and a second flow path for directing the other material of said first and second materials to form the outer sheath of the elongated element to encompass the core; and   inverter means connected to the first and second exit orifices of the first and second auxiliary feed means and the first and second flow paths of the extruder means, for selectively exchanging connections between the first and second exit orifices and the first and second flow paths. .Iaddend. .Iadd.19. A device for extruding a continuous elongated element of plastic materials having a core encompassed by at least one outer sheath, comprising:   a main extruder for extruding a continuous main flow of a plastic material;   first auxiliary feed means for feeding a first continuous auxiliary flow of a first material, the first auxiliary feed means having a first exit orifice for continuously conducting said first auxiliary flow;   second auxiliary feed means for feeding a second continuous auxiliary flow of a second material, the second auxiliary feed means having a second exit orifice for continuously conducting said second auxiliary flow;   extruder means for extruding the elongated element comprised of said main flow and said first and second auxiliary flows, the extruder means having a first flow path for directing one material of said first and second materials to join with the main flow to form the core of the elongated element and a second flow path for directing the outer material of said first and second materials to form the outer sheath of the elongated element to encompass the core; and   inverter means connected to the first and second exit orifices of the first and second auxiliary feed means and the first and second flow paths of the extruder means, for selectively exchanging connections between the first and second exit orifices and the first and second flow paths and for selectively exchanging relative positions in the elongated element of the   
     
     
        first and second materials. .Iaddend. .Iadd.20.  A device for extruding a continuous elongated element of plastic materials having a core encompassed by at least one outer sheath, comprising: a main extruder for extruding a continuous main flow of a plastic material;   first auxiliary feed means for feeding a first continuous auxiliary flow of a first material, the first auxiliary feed means having a first exit orifice for continuously conducting said first auxiliary flow;   second auxiliary feed means for feeding a second continuous flow of a second material, the second auxiliary feed means having a second exit orifice for continuously conducting said second auxiliary flow;   extruder means for extruding the elongated element comprised of said main flow and said first and second auxiliary flows, the extruder means having a first flow path for directing one material of said first and second materials to join with the main flow to form the core of the elongated element and a second flow path for directing the outer material of said first and second materials to form the outer sheath of the elongated element to encompass the core;   inverter means connected to the first and second exit orifices of the first and second auxiliary feed means and the first and second flow paths of the extruder means, for selectively exchanging connections between the first and second exit orifices and the first and second flow paths and for selectively exchanging relative positions in the elongated element of the first and second materials without interruption of the first and second   
     
     
        continuous flows. .Iaddend. .Iadd.21.  A device for extruding a continuous elongated element of plastic materials having a core encompassed by at least one outer sheath, comprising: a main extruder for extruding a continuous main flow of a plastic material;   first auxiliary feed means for feeding a first continuous auxiliary flow of a first material, the first auxiliary feed means having a first exit orifice for continuously conducting said first auxiliary flow;   second auxiliary feed means for feeding a second continuous auxiliary flow of a second material, the second auxiliary feed means having a second exit orifice for continuously conducting said second auxiliary flow;   extruder means for extruding the elongated element comprised of said main flow and said first and second auxiliary flows, the extruder means having a first flow path for directing one material of said first and second materials to join with the main flow to form the core of the elongated element and a second flow path for directing the other material of said first and second materials to form the outer sheath of the elongated element to encompass the core; and   inverter means connected to the first and second exit orifices of the first and second auxiliary feed means and the first and second flow paths of the extruder means, for selectively exchanging connections between the first and second exit orifices and the first and second flow paths, the inverter means being circular in cross-section and defining two conduits through the inverter means for connecting the first and second exit orifices and the first and second flow paths. .Iaddend. .Iadd.22. A device for extruding a continuous elongated element of plastic materials having a core encompassed by at least one outer sheath, comprising:   a main extruder for extruding a continuous main flow of a plastic material;   first auxiliary feed means for feeding a first continuous auxiliary flow of a first material, the first auxiliary feed means having a first exit orifice for continuously conducting said first auxiliary flow;   second auxiliary feed means for feeding a second continuous auxiliary flow of a second material, the second auxiliary feed means having a second exit orifice for continuously conducting said second auxiliary flow;   extruder means for extruding the elongated element comprised of said main flow and said first and second auxiliary flows, the extruder means having a first flow path for directing one material of said first and second materials to join with the main flow to form the core of the elongated element and a second flow path for directing the other material of said first and second materials to form the outer sheath of the elongated element to encompass the core; and   inverter means connected to the first and second exit orifices of the first and second auxiliary feed means and the first and second flow paths of the extruder means, for selectively exchanging connections between the first and second exit orifices and the first and second flow paths, the inverter means being movable between first and second positions, said first position connecting the first exit orifice to the first flow path for conveying the first material to the core of the elongated element and connecting the second exit orifice to the second flow path for conveying the second material to the outer sheath of the elongated element, and said second position connecting the first exit orifice to the second flow path for conveying the first material to the outer sheath of the elongated element and connecting the second exit orifice to the first flow path for conveying the first material to the core of the elongated element.   
     
     
        .Iaddend. .Iadd.23.  A device for extruding a continuous elongated element of plastic materials having a core encompassed by at least one outer sheath, comprising: a main extruder for extruding a continuous main flow of a plastic material;   first auxiliary feed means for feeding a first continuous auxiliary flow of a first material, the first auxiliary feed means having a first exit orifice for continuously conducting said first auxiliary flow;   second auxiliary feed means for feeding a second continuous auxiliary flow of a second material, the second auxiliary feed means having a second exit orifice for continuously conducting said second auxiliary flow;   extruder means for extruding the elongated element comprised of said main flow and said first and second auxiliary flows, the extruder means having a first flow path for directing one material of said first and second materials to join with the main flow to form the core of the elongated element and a second flow path for directing the other material of said first and second materials to form the outer sheath of the elongated element to encompass the core; and   inverter means connected to the first and second exit orifices of the first and second auxiliary feed means and the first and second flow paths of the extruder means, for selectively exchanging connections between the first and second exit orifices and the first and second flow paths, the inverter means being circular in cross-section and defining two conduits through the inverter means, the conduits being movable between first and second positions, said first position connecting the first exit orifice to the first flow path for conveying the first material to the core of the elongated element and connecting the second orifice to the second flow path for conveying the second material to the outer sheath of the elongated element, and said second position connecting the first exit orifice to the second flow path for conveying the first material to the outer sheath of the elongated element and connecting the second exit orifice to the first flow path for conveying the first material to the core of the elongated element. .Iaddend. .Iadd.24. A device for extruding a continuous elongated element of plastic materials having a core encompassed by at least one outer sheath, comprising:   a main extruder for extruding a continuous main flow of a plastic material;   first auxiliary feed means for feeding a first continuous auxiliary flow of a first material, the first auxiliary feed means having a first exit orifice for continuously conducting said first auxiliary flow;   second auxiliary feed means for feeding a second continuous auxiliary flow of a second exit orifice for continuously conducting said second auxiliary flow;   extruder means for extruding the elongated element comprised of said main flow and said first and second auxiliary flows, the extruder means having a first flow path for directing one material of said first and second materials to join with the main flow to form the core of the elongated element and a second flow path for directing the other material of said first and second materials to form the outer sheath of the elongated element to encompass the core; and   inverter means connected to the first and second exit orifices of the first and second auxiliary feed means and the first and second flow paths of the extruder means, for selectively exchanging connections between the first and second exit orifices and the first and second flow paths to selectively exchange relative positions in the elongated element of the first and second materials, the inverter means being circular in cross-section and defining two conduits through the inverter means, at least one conduit extending about a periphery of the circular cross-section to extend partially circumferentially about the circular   
     
     
        cross-section. .Iaddend. .Iadd.25.  A device for extruding a continuous elongated element of plastic materials, comprising: a main extruder for extruding a continuous main flow of a plastic material;   first auxiliary feed means for feeding a first continuous auxiliary flow of a first material, the first auxiliary feed means having a first exit orifice for continuously conducting said first auxiliary flow;   second auxiliary feed means for feeding a second continuous auxiliary flow of a second material, the second auxiliary feed means having a second exit orifice for continuously conducting said second auxiliary flow;   extruder means for extruding the elongated element comprised of said main flow and said first and second auxiliary flows, the extruder means having a first flow path for burying one material of said first and second materials within the main flow and a second flow path for directing the other material of said first and second materials to from an overcoat for the elongated element, the overcoat encompassing the main flow and the one material; and   inverter means connected to the first and second exit orifices of the first and second feed means and the first and second flow paths of the extruder means, for selectively exchanging connections between the first and second exit orifices and the first and second flow paths so that the material that was previously the overcoat can be buried within the elongated element and the material that was previously buried within the elongated   
     
     
        element can be the overcoat. .Iaddend. .Iadd.26.  A device for extruding a continuous elongated element of plastic materials, comprising: a main extruder for extruding a continuous main flow of a plastic material;   first auxiliary feed means for feeding a first continuous auxiliary flow of a first material, the first auxiliary feed means having a first exit orifice for continuously conducting said first auxiliary flow;   second auxiliary feed means for feeding a second continuous auxiliary flow of a second material, the second auxiliary feed means having a second exit orifice for continuously conducting said second auxiliary flow;   extruder means for extruding the elongated element comprised of said main flow and said first and second auxiliary flows, the extruder means having a first flow path for burying one material of said first and second materials within the main flow and a second flow path for directing the other material of said first and second materials to form an overcoat for the elongated element, the overcoat encompassing the main flow and the one material; and   inverter means connected to the first and second exit orifices of the first and second feed means and the first and second flow paths of the extruder means, for selectively exchanging connections between the first and second exit orifices and the first and second flow paths, the inverter means being circular in cross-section and defining two conduits through the inverter means, the conduits being movable between first and second positions, said first position connecting the first exit orifice to the first flow path for burying the first material within the elongated element and connecting the second exit orifice to the second flow path for conveying the second material to be the overcoat of the elongated element, and said second position connecting the first exit orifice to the second flow path for conveying the first material to be the overcoat of the elongated element and connecting the second exit orifice to the first flow path for burying the second material in the elongated element, so that the material that was previously the overcoat can be buried within the elongated element and the material that was previously buried within the elongated element can be the overcoat..Iaddend.