CA1174418A - Extrusion die with wiper means movable along die - Google Patents
Extrusion die with wiper means movable along dieInfo
- Publication number
- CA1174418A CA1174418A CA000372033A CA372033A CA1174418A CA 1174418 A CA1174418 A CA 1174418A CA 000372033 A CA000372033 A CA 000372033A CA 372033 A CA372033 A CA 372033A CA 1174418 A CA1174418 A CA 1174418A
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- Prior art keywords
- die
- plastic
- headpiece
- annulus
- annuli
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
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Abstract
Abstract: The present invention relates to an improvement in a die for extruding a hot plastic material from an exit port to an end of the die to form an annulus of plastic material. The improvement includes a cooled wiper member which is moveable across the end of the die to wipe off whatever annulus of plastic material is formed on the end of the die. 14
Description
L~
Back round of the Invention g Collapsible tubes are used, as dispensers for toothpaste and shampoo. They are often referred to as squeeze tubes. In forming a collapsible tube of this type, the body or sidewall is formed separately from the headpiece. The headpiece, generally, is molded to the formed sidewall portionO
The sidewall is often a multi~ply, collapsible sheet material having inner and outer plastic plies usually polyethylene, an interior metal foil ply, usually aluminum. The aluminum acts as a barrier to oxygen penetration and flavorant migration. The poly-ethylene protects the aluminum from the contents of the tube, provides a convenient printing surface and affects the feel of the tube to the end user. The aluminum and polyethylene are combined in amounts that pro~ide a desired collapsibility and avoidance of spring back. All of this is known in the art and will not be further discussed because the structure of the sidewall does not form a part of this invention except that the headpiece must be bondable to the sidewall.
The headpiece of the tube provides a number of functions. Because it forms one end of the collapsi~
ble tube, it must have structural integrity to prevent *
collapse in use. In addition, it must be formed of a material which, like the materials in the sidewall, prevents flavorant migration or deterioration of the contents. Further, the material of the headpiece has to be bonded to the plastic material of the sidewall and it must resist corrosion from the contents of the tube as well as avoid chemically reacting with the contents of the tube. As these functions cannot be provided by the same plastic material, the prior art has attempted to provide othex solutions. For example, a barrier member has been provided within the head-piece~ adjacent the contents of the tube. This pre-vents the migration or deterioration of the substances held within the tube. However, the cost of separate-ly forming and inserting this barrier member is high,so that its use is uneconomic. Further, there is a problem in holding the barrier member to the rest of the tube. -It is an object of the present invention to
Back round of the Invention g Collapsible tubes are used, as dispensers for toothpaste and shampoo. They are often referred to as squeeze tubes. In forming a collapsible tube of this type, the body or sidewall is formed separately from the headpiece. The headpiece, generally, is molded to the formed sidewall portionO
The sidewall is often a multi~ply, collapsible sheet material having inner and outer plastic plies usually polyethylene, an interior metal foil ply, usually aluminum. The aluminum acts as a barrier to oxygen penetration and flavorant migration. The poly-ethylene protects the aluminum from the contents of the tube, provides a convenient printing surface and affects the feel of the tube to the end user. The aluminum and polyethylene are combined in amounts that pro~ide a desired collapsibility and avoidance of spring back. All of this is known in the art and will not be further discussed because the structure of the sidewall does not form a part of this invention except that the headpiece must be bondable to the sidewall.
The headpiece of the tube provides a number of functions. Because it forms one end of the collapsi~
ble tube, it must have structural integrity to prevent *
collapse in use. In addition, it must be formed of a material which, like the materials in the sidewall, prevents flavorant migration or deterioration of the contents. Further, the material of the headpiece has to be bonded to the plastic material of the sidewall and it must resist corrosion from the contents of the tube as well as avoid chemically reacting with the contents of the tube. As these functions cannot be provided by the same plastic material, the prior art has attempted to provide othex solutions. For example, a barrier member has been provided within the head-piece~ adjacent the contents of the tube. This pre-vents the migration or deterioration of the substances held within the tube. However, the cost of separate-ly forming and inserting this barrier member is high,so that its use is uneconomic. Further, there is a problem in holding the barrier member to the rest of the tube. -It is an object of the present invention to
2~ provide a headpiece which provides both the structuralintegrity and the protection of the contents without the necessity for an additional insert.
It is further object of the present invention to pro~ide a method for forming a unitary headpiece of two plastic materials in an expeditious and effi-cient manner.
It is a still further ob~ect to provide an extrusion die for use in forming a unitary headpiece of two thermoplastio materials.
~'7~
~ 3 --Brief Descriptio_ In accordance with an aspect of the invention there is provided in a die for extruding a hot plastic material from an exit port at an end of the die to form an annulus of plastic material~ the improvement comprising a cooled wiper member movable ~e~ said end of said die to wipe off whatever annulus of plastic material is formed on said end of said die.
A unitary plastic headpiece for a collapsible squeeze tube has two plastic portions. One of the two plastics is compatible with bonding the headpiece to the plastic ply of the collapsible side wall of the squeeze tube. The other plastic is selected to prevent deterioration or migration of the substances contained within the collapsible tube. This dual-plastic unitary headpiece is achieved by extruding a first plastic annulus and a second plastic annulus, each of which have a torus type of shape, in succession, on top of one another from a single extruder die. This dual annulus structure is wiped from the die onto a lower mold piece which mold piece has a configuration that defines the inner surface of the headpiece to be formed. An upper mold piece defining the outer surface of the headpiece to be formed is brought into engagement with the lower mold piece to force the two annuli into the shape of the desired headpiece.
Concurrently, the sidewall is supported around the lower mold piece so that the upper edge of the sidewall comes into contact with the plastic annuli and is bonded thereto.
During this essentially transfer molding technique, the lower annulus becomes -an inner portion of the headpiece while the upper annulus becomes the outer portion of the headpiece. The upper annulus thus must be of a plastic material compatible with bonding to the plastic ply of the sidwall while the lower annulus must be of a plastic material compatible with the ingredients of the tube and tending to serve the functions of preventing deterioration or migration of the substances within the tube.
~.:
Variations in the xelative amounts of the plastics in the upper and lower annul.i can affect the extent to which, for example, the plastic forming the inner portioll of the headpiece can also be used to form or define a portion of the neck and threads of the headpiece.
'7~
Brief Description of the Drawings FIG. 1 is a view of the top portion of a col-lasible squeeze tube having a headpiece according to the present invention. FIG. 1 is in part an elevation view and in part a longitudinal sec~ional view of the headpiece.
FIG. 2 is a longitudinal sectional view of the extruder die employed to form the two annuli which are the starting points for molding the plastic head-piece of this invention, such as the headpiece shown in FIG. 1.
FIG. 3 is a schematic illustration of a first stage in the molding of the FIG. 1 headpiece. FIG. 3 illustrates the two annuli 28a/ 28b formed on the end of the extruder die and positioned immediately above the mold piece 34 employed to define the inner surface of the plastic headpiece.
FIG. 4 is a view similar to FIGo 3 showing the next stage in the operation in which a chilled wiper plate 32 has pushed the two annuli 28a, 28b off the die piece and dropped them onto the inner mold piece 34.
FIG. 5 shows the inner mold piece carrying the two plastic annuli indexed over to a position under and in alignment with the outer mold piece 36 which defines the outer surface of the headpiece to be molded.
FIG. 6 is a view similar to that of FIG. 5 showing the ouker mold piece 36 having engaged the inner mold piece 34 to define the mold cavity which forms the plastic headpiece from the two plastic annuli.
FIG. 7 through 10 show the progressive forming of the headpiece as the tube mold parts come together.
These four FIG~. are in simplified schematic form and illustrate the annuli in cross section, More specifi-cally, FIG. 7 illustrates the two plastic annuli in a condition correspond~ng to that of FIG. 4, ~IG. 8 illustrates the annult immediately after the inner mold par~ has contacted the two annuli. ~IG. 9 illustrates a furth.er staye in the molding where the two mold parts have partially come together, FIG, 10 illustrates the flnal stage of the molding when the two mold parts have completed their progression toward one another.
FIG. 11 is a cross sectional view showing a second embodiment of the headpiece in which substane tially less of the plastic B of the upper annulus 28b and substantially more of the plastic A of the lower annulus 28a is employed than is represented by the embodiment shown in TIGS. 7 through 10.
FIG. 12 illustrates a still further embodiment of this invention in whtch the amount of plastic B
employed in the upper annulus 28b and the amount of plastic A of the lower annulus 28a are intermediate between the amount~ employed to manufacture the head~
piece of FIG. 10 and FIG. 11, ~.~'7~L~
Description of the Preferred Emhodiments FIG. 1 illustrates a collapsible tube 20 having a cylindrical sidewall portion 22 and a plastic head-piece portion 24. The collapsible wall portion 22 is formed from one of the flexible web materials known in the art such as a multi-ply web having outer polyethylene plies and a center or interior aluminum ply . , The headpiece portion 24 has an inner plastic portion 24a and an outer plastic portion 24b. The two portions together form a unitary headpiece 24. The headpiece 24 is bonded to the wall 22 by plastic ad-hesion of the outer plastic 24b of the headpiece 24 to the inner plastic ply of the wall 22. That bonding is accomplished during molding of the headpiece.
The material of the outer plastic 24b is selected to be bondable with the inner plastic ply of the wall 22~ Most tube walls 22 presently employed in the art have outer and inner polyethylene plies.
Therefore, the outer plastic 24b of the headpiece 24 is preferably formed of polyethylene. However, should the composition of the inner plastic ply of the wall 22 be different, the outer plastic 24b of the head-piece can be varied accordingly.
The inner plastic 24a must be compatible with the contents of the tube and, in many cases, must act to prevent deterioration of those contents; for example, by preventing oxygen penetration. In cases where the inner plastic 24a must be hygroscopic, it can be formed of any of the standard polyamide mate-rials generally sold under the name nylon. Though nylon is particularly useful when it is important that the inner plastic 24a be hygroscopic, nylon has disadvantages. In particular, a hi~her temperature 749L~
is required to effect molding of the nylon so that, other factors being equal, greater cooli~g is also required after formation of the headpiece. Thus, slower processing is experienced employing nylon as the inner plastic 24aO
Other materials which can be employed in forming the inner plastic 24a are ionomers, such as those sold by DuPont under the trademark Surlyn. At present, polypropylene is the preferred material for tha inner plastic 24a for the combined reasons of cost, effecti~eness, and speed of manufacture.
The examples just given for the material of the inner plastic 24a, i.e., polypropylene, polyamide and ionomers, are the presently preferred types of mate-rials for the inner plastic 24a when the outer plastic24b is formed of polyethylene. If the composition of the outer plastic 24b is varied, the composition of the inner plastic may have to be varied, so as to be compatible with the material of the outer plastic, while still retaining the necessary properties for the inner plastic. -Because ~f the method of forming this head-piece, it is a unitary structure of plast.ic 24b com-patible with bonding to a plastic ply of the sidewall 22 and plastic 24a providing protection for the pro-duct contained in the tube. Thus it is not necessary to insert a barrier member into the headpiece to pro vide any additional properties.
FIGS. 2 and 3 show the die 26 for coextrusion of the two plastics into the composite extrusion which is then molded to form the headpiece 24. The plastic A, which forms the lower annulus 28a and thus the inner portion 24a of the headpiece, is fed to the die 26 through inlet 26a as indicated by the arrow in FIG. 2. The plastic B, which ~orms the upper annulus ~.~'7~
g 28b, and thus the outer layer 24b, is fed to the die 26 at inlet 26b, as indicated by the arrow in FIG. 2. The structure of the die 26, including mandrels, collars, etc., is known in the art and thus need not be more speci-fically illustrated or described.
The thermoplastic material A fed at inlet 26a follows a path in the die generally desiqnated ~y the ref-erence designation A to exit at the port designated 30u The thermoplastic material B enters the die at inlet 26b and follows the path B to exit at the port 30. The extru-sion sequence in the extrusion die 26 assures that the plastic A is extruded first so as to form a lower annulus 28a and that plastic B is extruded immediately thereafter to form the upper annulus 28b.
An a~ially movable water cooled wiper 32 in the form of an annulus around the outlet neck of the extrusion die 26 is used to wipe the plastic annuli 28a, 28b off the neck of the die 26. After the two plastic annuli 28a, 28b have been extruded from the outlet noz~le 30 of the extru-sion die 26, these two annuli 28a, 28b will be sitting on the lower end of the extrusion die 26. As soon as the two hot plastic annuli 2Ba and 28b have been formed, the water cooled wiper 32, is brought axially downward to wipe the two annuli off the end of the die and cause them to drop onto a lower mold piece 34, (see FIG. 4~.
The mold piece 34 is configured to define the inner surface of the headpiece to be molded and thus can be termed the inner mold piece. The sidewall 22 is held by light friction fit around the inner mold piece 34 and ex-tends upward into the area adjacent to where the hot plasticannuli fall to assure that contact will be made between the inner plastic ply of the sidewall 22 and the hot plas-tic of the annuli thereby causing the desired adhesion of headpiece to sidewall. The wiper 32 is water cooled to avoid having the hot plastic of the annuli stick to the wiper 32 during the wiping operation.
7~
After the annuli have dropped onto the inner mold piece 34 shown in FIG. 4, the inner mold piece 34 is indexed to a position under and in alignment with an upper mold piece 36 as shown in FIG. 5. The upper mold piece 36 has a surface configured to define the outer surface of the headpiece and thus can be called the outer mold piece.
This outer mold piece 36 includes a spring 38 loaded pin 40 that extends down into the cavity defined by the outer mold piece 360 After the two mold pieces 34 and 36 have been brought into the alignment shown in FIG. 5, they are brought together, as shown in FIG. ~, into engagement thereby de-fining a cavity in which the headpiece is molded. The pin 40 abuts against the upper edge of the inner mold piece 34 and is held tightly against the inner mold piece 34 by the spring 38 to assure that the plastic material being molded does not block the passage way 42 required through the head-piece 24.
As can be seen in FIG. 6, the mold cavity although primarily defined by the two major mold pieces 34 and 36 is also, in part, defined by the lower rim of the pin 40 and by the upper edge portion of the sidewall 22.
The mold is water cooled by water passages 44 to effect cooling and solidifying of the plastic materials A and B that form the molded head 24.
After formation of the headpiece in the mold as described, the tube now having a formed headpiece is moved to other positions for whatever finishing operations may be required.
FIGS. 7 through 10 illustrate in somewhat ideal-ized form the configuration of the plastic materials A and B during the process of molding the finished headpiece 24 from the composite annulus structure 28a, 28b. FIG. 7 illustrates the composite extrusion of plastics A and B
on their formation as they are dropped from the outlet end of die 26 onto the inner mold piece 34. As soon as these ~7~
hot, fluid plastic mate~ials A and B contact the surface of the inner ~old piece 34, they tend to assume the shape shown in FIG. 8. Upon further movement of the two mold parts 34 and 36 together, the plastics A and B form the configura-tion illustrated in FIG. 9 in which it can be seen that thelower annulus 28a has begun for form the inner plastic por-tion A and the upper annulus 28b has begun to form the outer plastic portion B. The completion of bringing together the two mold pieces 34 and 36 provides the end result as shown in FIG. 10; namely a headpiece 46 having integral plastic por-tions A and B.
The headpiece 46 shown in FIG. 10 differs from the headpiece 24 shown in ~IG. 1 in that the proportion of the two plastics A and B are different. More particularly, FIG.
10 represents a situation where there is relatively more of the plastic B than is the case in FIG. 1~
Further headpiece configurations 48 and 50 are shown in FIGS. 11 and 12 in which different amounts of the plastics A and B have been employed. The differences in the various headpieces shown herein 24, 46, 48 and S0 are not due to different methods of formation but are rather due to the relative amounts of plastic materials A and B employed for forming the upper and lower annuli 28b and 28a. Thus, for a configuration of a headpiece shown in FIG. 11, the annulus 28a has to be substantially thicker than the annulus 28b whereas in the configuration shown in FIG. 10, the relative sizes of the annuli 28a and 28b are much more similar.
It is important that the outer part of the shoulder portion of the headpiece be of the plastic B which is adapt-ed to bond to the plastic ply of the sidewall 22. Dependingupon the materials involved, their relative costs and the application, the neck portion of the headpiece may be formed solely o the inner plastic material A with no covering of the plastic material B.
~L~IL7~
The change in rela~ive amounts of the two plastics A and B can readily be accomplished by varying the shape of the die 26 or by increasing the pressure on the plastics fed at inlets 26a or 26b as appropriate, to vary the amount of plastic extruded at the exit port 30~
In each case, the peripheral lower edge portion of the headpiece is composed of the B plastic in order to bond to the plastic ply of the tube sidewall 22. In each case, the A plastic extends over the entire inner wall of the head-piece to assure that the entire headpiece is impermeable.
The composition extrusion 28a, 28b can be formedby first extruding one of the plastics A through the annular outlet 48a and annular exit port 30 as an annulus followed by extrusion of the second plastic B through the annular outlet 48b and exit port 30 as a second annulus. A slightly different die configuration would permit extrusion of the two annuli simultaneously. in any case, the composite dual annulus 28a, 28b is extruded on the tip 26t of the die 260
It is further object of the present invention to pro~ide a method for forming a unitary headpiece of two plastic materials in an expeditious and effi-cient manner.
It is a still further ob~ect to provide an extrusion die for use in forming a unitary headpiece of two thermoplastio materials.
~'7~
~ 3 --Brief Descriptio_ In accordance with an aspect of the invention there is provided in a die for extruding a hot plastic material from an exit port at an end of the die to form an annulus of plastic material~ the improvement comprising a cooled wiper member movable ~e~ said end of said die to wipe off whatever annulus of plastic material is formed on said end of said die.
A unitary plastic headpiece for a collapsible squeeze tube has two plastic portions. One of the two plastics is compatible with bonding the headpiece to the plastic ply of the collapsible side wall of the squeeze tube. The other plastic is selected to prevent deterioration or migration of the substances contained within the collapsible tube. This dual-plastic unitary headpiece is achieved by extruding a first plastic annulus and a second plastic annulus, each of which have a torus type of shape, in succession, on top of one another from a single extruder die. This dual annulus structure is wiped from the die onto a lower mold piece which mold piece has a configuration that defines the inner surface of the headpiece to be formed. An upper mold piece defining the outer surface of the headpiece to be formed is brought into engagement with the lower mold piece to force the two annuli into the shape of the desired headpiece.
Concurrently, the sidewall is supported around the lower mold piece so that the upper edge of the sidewall comes into contact with the plastic annuli and is bonded thereto.
During this essentially transfer molding technique, the lower annulus becomes -an inner portion of the headpiece while the upper annulus becomes the outer portion of the headpiece. The upper annulus thus must be of a plastic material compatible with bonding to the plastic ply of the sidwall while the lower annulus must be of a plastic material compatible with the ingredients of the tube and tending to serve the functions of preventing deterioration or migration of the substances within the tube.
~.:
Variations in the xelative amounts of the plastics in the upper and lower annul.i can affect the extent to which, for example, the plastic forming the inner portioll of the headpiece can also be used to form or define a portion of the neck and threads of the headpiece.
'7~
Brief Description of the Drawings FIG. 1 is a view of the top portion of a col-lasible squeeze tube having a headpiece according to the present invention. FIG. 1 is in part an elevation view and in part a longitudinal sec~ional view of the headpiece.
FIG. 2 is a longitudinal sectional view of the extruder die employed to form the two annuli which are the starting points for molding the plastic head-piece of this invention, such as the headpiece shown in FIG. 1.
FIG. 3 is a schematic illustration of a first stage in the molding of the FIG. 1 headpiece. FIG. 3 illustrates the two annuli 28a/ 28b formed on the end of the extruder die and positioned immediately above the mold piece 34 employed to define the inner surface of the plastic headpiece.
FIG. 4 is a view similar to FIGo 3 showing the next stage in the operation in which a chilled wiper plate 32 has pushed the two annuli 28a, 28b off the die piece and dropped them onto the inner mold piece 34.
FIG. 5 shows the inner mold piece carrying the two plastic annuli indexed over to a position under and in alignment with the outer mold piece 36 which defines the outer surface of the headpiece to be molded.
FIG. 6 is a view similar to that of FIG. 5 showing the ouker mold piece 36 having engaged the inner mold piece 34 to define the mold cavity which forms the plastic headpiece from the two plastic annuli.
FIG. 7 through 10 show the progressive forming of the headpiece as the tube mold parts come together.
These four FIG~. are in simplified schematic form and illustrate the annuli in cross section, More specifi-cally, FIG. 7 illustrates the two plastic annuli in a condition correspond~ng to that of FIG. 4, ~IG. 8 illustrates the annult immediately after the inner mold par~ has contacted the two annuli. ~IG. 9 illustrates a furth.er staye in the molding where the two mold parts have partially come together, FIG, 10 illustrates the flnal stage of the molding when the two mold parts have completed their progression toward one another.
FIG. 11 is a cross sectional view showing a second embodiment of the headpiece in which substane tially less of the plastic B of the upper annulus 28b and substantially more of the plastic A of the lower annulus 28a is employed than is represented by the embodiment shown in TIGS. 7 through 10.
FIG. 12 illustrates a still further embodiment of this invention in whtch the amount of plastic B
employed in the upper annulus 28b and the amount of plastic A of the lower annulus 28a are intermediate between the amount~ employed to manufacture the head~
piece of FIG. 10 and FIG. 11, ~.~'7~L~
Description of the Preferred Emhodiments FIG. 1 illustrates a collapsible tube 20 having a cylindrical sidewall portion 22 and a plastic head-piece portion 24. The collapsible wall portion 22 is formed from one of the flexible web materials known in the art such as a multi-ply web having outer polyethylene plies and a center or interior aluminum ply . , The headpiece portion 24 has an inner plastic portion 24a and an outer plastic portion 24b. The two portions together form a unitary headpiece 24. The headpiece 24 is bonded to the wall 22 by plastic ad-hesion of the outer plastic 24b of the headpiece 24 to the inner plastic ply of the wall 22. That bonding is accomplished during molding of the headpiece.
The material of the outer plastic 24b is selected to be bondable with the inner plastic ply of the wall 22~ Most tube walls 22 presently employed in the art have outer and inner polyethylene plies.
Therefore, the outer plastic 24b of the headpiece 24 is preferably formed of polyethylene. However, should the composition of the inner plastic ply of the wall 22 be different, the outer plastic 24b of the head-piece can be varied accordingly.
The inner plastic 24a must be compatible with the contents of the tube and, in many cases, must act to prevent deterioration of those contents; for example, by preventing oxygen penetration. In cases where the inner plastic 24a must be hygroscopic, it can be formed of any of the standard polyamide mate-rials generally sold under the name nylon. Though nylon is particularly useful when it is important that the inner plastic 24a be hygroscopic, nylon has disadvantages. In particular, a hi~her temperature 749L~
is required to effect molding of the nylon so that, other factors being equal, greater cooli~g is also required after formation of the headpiece. Thus, slower processing is experienced employing nylon as the inner plastic 24aO
Other materials which can be employed in forming the inner plastic 24a are ionomers, such as those sold by DuPont under the trademark Surlyn. At present, polypropylene is the preferred material for tha inner plastic 24a for the combined reasons of cost, effecti~eness, and speed of manufacture.
The examples just given for the material of the inner plastic 24a, i.e., polypropylene, polyamide and ionomers, are the presently preferred types of mate-rials for the inner plastic 24a when the outer plastic24b is formed of polyethylene. If the composition of the outer plastic 24b is varied, the composition of the inner plastic may have to be varied, so as to be compatible with the material of the outer plastic, while still retaining the necessary properties for the inner plastic. -Because ~f the method of forming this head-piece, it is a unitary structure of plast.ic 24b com-patible with bonding to a plastic ply of the sidewall 22 and plastic 24a providing protection for the pro-duct contained in the tube. Thus it is not necessary to insert a barrier member into the headpiece to pro vide any additional properties.
FIGS. 2 and 3 show the die 26 for coextrusion of the two plastics into the composite extrusion which is then molded to form the headpiece 24. The plastic A, which forms the lower annulus 28a and thus the inner portion 24a of the headpiece, is fed to the die 26 through inlet 26a as indicated by the arrow in FIG. 2. The plastic B, which ~orms the upper annulus ~.~'7~
g 28b, and thus the outer layer 24b, is fed to the die 26 at inlet 26b, as indicated by the arrow in FIG. 2. The structure of the die 26, including mandrels, collars, etc., is known in the art and thus need not be more speci-fically illustrated or described.
The thermoplastic material A fed at inlet 26a follows a path in the die generally desiqnated ~y the ref-erence designation A to exit at the port designated 30u The thermoplastic material B enters the die at inlet 26b and follows the path B to exit at the port 30. The extru-sion sequence in the extrusion die 26 assures that the plastic A is extruded first so as to form a lower annulus 28a and that plastic B is extruded immediately thereafter to form the upper annulus 28b.
An a~ially movable water cooled wiper 32 in the form of an annulus around the outlet neck of the extrusion die 26 is used to wipe the plastic annuli 28a, 28b off the neck of the die 26. After the two plastic annuli 28a, 28b have been extruded from the outlet noz~le 30 of the extru-sion die 26, these two annuli 28a, 28b will be sitting on the lower end of the extrusion die 26. As soon as the two hot plastic annuli 2Ba and 28b have been formed, the water cooled wiper 32, is brought axially downward to wipe the two annuli off the end of the die and cause them to drop onto a lower mold piece 34, (see FIG. 4~.
The mold piece 34 is configured to define the inner surface of the headpiece to be molded and thus can be termed the inner mold piece. The sidewall 22 is held by light friction fit around the inner mold piece 34 and ex-tends upward into the area adjacent to where the hot plasticannuli fall to assure that contact will be made between the inner plastic ply of the sidewall 22 and the hot plas-tic of the annuli thereby causing the desired adhesion of headpiece to sidewall. The wiper 32 is water cooled to avoid having the hot plastic of the annuli stick to the wiper 32 during the wiping operation.
7~
After the annuli have dropped onto the inner mold piece 34 shown in FIG. 4, the inner mold piece 34 is indexed to a position under and in alignment with an upper mold piece 36 as shown in FIG. 5. The upper mold piece 36 has a surface configured to define the outer surface of the headpiece and thus can be called the outer mold piece.
This outer mold piece 36 includes a spring 38 loaded pin 40 that extends down into the cavity defined by the outer mold piece 360 After the two mold pieces 34 and 36 have been brought into the alignment shown in FIG. 5, they are brought together, as shown in FIG. ~, into engagement thereby de-fining a cavity in which the headpiece is molded. The pin 40 abuts against the upper edge of the inner mold piece 34 and is held tightly against the inner mold piece 34 by the spring 38 to assure that the plastic material being molded does not block the passage way 42 required through the head-piece 24.
As can be seen in FIG. 6, the mold cavity although primarily defined by the two major mold pieces 34 and 36 is also, in part, defined by the lower rim of the pin 40 and by the upper edge portion of the sidewall 22.
The mold is water cooled by water passages 44 to effect cooling and solidifying of the plastic materials A and B that form the molded head 24.
After formation of the headpiece in the mold as described, the tube now having a formed headpiece is moved to other positions for whatever finishing operations may be required.
FIGS. 7 through 10 illustrate in somewhat ideal-ized form the configuration of the plastic materials A and B during the process of molding the finished headpiece 24 from the composite annulus structure 28a, 28b. FIG. 7 illustrates the composite extrusion of plastics A and B
on their formation as they are dropped from the outlet end of die 26 onto the inner mold piece 34. As soon as these ~7~
hot, fluid plastic mate~ials A and B contact the surface of the inner ~old piece 34, they tend to assume the shape shown in FIG. 8. Upon further movement of the two mold parts 34 and 36 together, the plastics A and B form the configura-tion illustrated in FIG. 9 in which it can be seen that thelower annulus 28a has begun for form the inner plastic por-tion A and the upper annulus 28b has begun to form the outer plastic portion B. The completion of bringing together the two mold pieces 34 and 36 provides the end result as shown in FIG. 10; namely a headpiece 46 having integral plastic por-tions A and B.
The headpiece 46 shown in FIG. 10 differs from the headpiece 24 shown in ~IG. 1 in that the proportion of the two plastics A and B are different. More particularly, FIG.
10 represents a situation where there is relatively more of the plastic B than is the case in FIG. 1~
Further headpiece configurations 48 and 50 are shown in FIGS. 11 and 12 in which different amounts of the plastics A and B have been employed. The differences in the various headpieces shown herein 24, 46, 48 and S0 are not due to different methods of formation but are rather due to the relative amounts of plastic materials A and B employed for forming the upper and lower annuli 28b and 28a. Thus, for a configuration of a headpiece shown in FIG. 11, the annulus 28a has to be substantially thicker than the annulus 28b whereas in the configuration shown in FIG. 10, the relative sizes of the annuli 28a and 28b are much more similar.
It is important that the outer part of the shoulder portion of the headpiece be of the plastic B which is adapt-ed to bond to the plastic ply of the sidewall 22. Dependingupon the materials involved, their relative costs and the application, the neck portion of the headpiece may be formed solely o the inner plastic material A with no covering of the plastic material B.
~L~IL7~
The change in rela~ive amounts of the two plastics A and B can readily be accomplished by varying the shape of the die 26 or by increasing the pressure on the plastics fed at inlets 26a or 26b as appropriate, to vary the amount of plastic extruded at the exit port 30~
In each case, the peripheral lower edge portion of the headpiece is composed of the B plastic in order to bond to the plastic ply of the tube sidewall 22. In each case, the A plastic extends over the entire inner wall of the head-piece to assure that the entire headpiece is impermeable.
The composition extrusion 28a, 28b can be formedby first extruding one of the plastics A through the annular outlet 48a and annular exit port 30 as an annulus followed by extrusion of the second plastic B through the annular outlet 48b and exit port 30 as a second annulus. A slightly different die configuration would permit extrusion of the two annuli simultaneously. in any case, the composite dual annulus 28a, 28b is extruded on the tip 26t of the die 260
Claims (3)
1. In a die for extruding a hot plastic material from an exit port at an end of the die to form an annulus of plastic material, the improvement comprising:
a cooled wiper member movable along said end of said die to wipe off whatever annulus of plastic material is formed on said end of said die,
a cooled wiper member movable along said end of said die to wipe off whatever annulus of plastic material is formed on said end of said die,
2. The die of claim 1, wherein two annuli are coextruded from two plastics materials, wherein the die includes:
a first flow path for one of said two plastics materials, said first flow path including:
a first inlet, a first path for conducting said one of said two plastics materials from said first inlet, wherein said exit port is a first outlet for extruding said annulus of plastics material to provide one of said two annuli;
a second flow path for the other of said two plastics materials, said second flow path including;
a second inlet;
a second path for conducting the other of said two plastics materials from said second inlet; and a second outlet, at said end of the die for extruding a second annulus of plastics material to provide a second of said two annuli.
a first flow path for one of said two plastics materials, said first flow path including:
a first inlet, a first path for conducting said one of said two plastics materials from said first inlet, wherein said exit port is a first outlet for extruding said annulus of plastics material to provide one of said two annuli;
a second flow path for the other of said two plastics materials, said second flow path including;
a second inlet;
a second path for conducting the other of said two plastics materials from said second inlet; and a second outlet, at said end of the die for extruding a second annulus of plastics material to provide a second of said two annuli.
3. The die of claim 1 wherein said exit port is along the cylindrical surface near the end of a cylindrical die and wherein axial movement of said wiper member along said die causes said member to move across said port.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA000372033A CA1174418A (en) | 1981-03-02 | 1981-03-02 | Extrusion die with wiper means movable along die |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA000372033A CA1174418A (en) | 1981-03-02 | 1981-03-02 | Extrusion die with wiper means movable along die |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1174418A true CA1174418A (en) | 1984-09-18 |
Family
ID=4119341
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000372033A Expired CA1174418A (en) | 1981-03-02 | 1981-03-02 | Extrusion die with wiper means movable along die |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA1174418A (en) |
-
1981
- 1981-03-02 CA CA000372033A patent/CA1174418A/en not_active Expired
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| MKEX | Expiry | ||
| MKEX | Expiry |
Effective date: 20010918 |