Process and an apparatus for the extrusion of plastic pipes with composite walls
AssigneeSociete Generale de Canalisations Sogecan
InventorMarcel Doucet
Life of this patent
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Abstract
The invention relates to a process and an apparatus for manufacturing plastic pipes having a composite structure by extrusion. The material forming the inner and outer walls of the tube is introduced into a special heated and regulated distribution head and is separated into two distinct streams between which a filling material forming a first stream is injected. These three streams are brought together and placed in contact, thus forming a blank which is given its final dimensions by being passed into a conventional tool comprising a trefoil, die and mandrel, followed by a conformator. Application to the manufacture of large dimension tubes for the disposal and drainage of sewage and rainwater.
Claims8
In a process for the manufacture by coextrusion of plastic pipe having a composite structure formed of inner and outer walls of plastic material enclosing an intermediate layer of a filling material which is synthetic plastic or polymeric in nature and which adheres to said walls comprising introducing the material constituting said pipe walls in a heated and plastic state, separating the introduced plastic material into two distinct streams, injecting the filling material in a plastic state to between the separated streams of material constituting the inner and outer walls, bringing the three streams into a contacting relation with the stream of filling material sandwiched between the streams forming the inner and outer walls to form a composite having the final structure, the improvement comprising passing the sandwiched streams through a divergent passageway to form the sandwiched streams to a dimension greater than the final dimension of the product, separating the sandwiched streams into circumferentially separated streams, passing the separated sandwiched streams through a convergent passageway and die for rejoinder of said separated streams and to form a homogeneous pipe to final dimension.
An apparatus for the manufacture by coextrusion of plastic pipe having a composite structure formed of inner and outer walls of plastic material with a layer of filling material in between, comprising:
- (a) a heated and regulated distribution head,
- (b) a first extruder for introduction of the material constituting the inner and outer walls in a plastic state into said head,
- (c) a second extruder for introduction of a synthetic plastic or polymeric filling material into said distribution head,
- (d) means within said distribution head for separating the material introduced by the first extruder into two distinct streams,
- (e) means within said distribution head for guiding the filling material into a stream between said streams of wall material,
- (f) means for bringing the three streams together into contacting relation to form a continuous composite stream in the form of a sandwich with the filling material and wall material in their final arrangement,
- (g) a divergent passageway of conical shape in communication with the outlet of said distribution head wherein the sandwiched streams increase in dimension during passage therethrough,
- (h) a convergent passageway as a continuation of the divergent passageway,
- (i) a trefoil between said divergent and convergent passageways to separate the expanded sandwiched streams into circumferential segments before passage through the convergent passageway for rewelding the segments,
- (j) a heated and regulated tool downstream of said passageways and in communication therewith to give the sandwiched streams their final shape and dimension.
Dependencies are inferred from the claim text.