WO2011033538A1 - Injection molding system and method for plastic material articles - Google Patents

Injection molding system and method for plastic material articles Download PDF

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Publication number
WO2011033538A1
WO2011033538A1 PCT/IT2009/000421 IT2009000421W WO2011033538A1 WO 2011033538 A1 WO2011033538 A1 WO 2011033538A1 IT 2009000421 W IT2009000421 W IT 2009000421W WO 2011033538 A1 WO2011033538 A1 WO 2011033538A1
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WO
WIPO (PCT)
Prior art keywords
pin
plug tip
axis
injector
reference surface
Prior art date
Application number
PCT/IT2009/000421
Other languages
French (fr)
Inventor
Maurizio Bazzo
Tiziano Boscariol
Original Assignee
Inglass S.R.L
Priority date (The priority date 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 date listed.)
Filing date
Publication date
Application filed by Inglass S.R.L filed Critical Inglass S.R.L
Priority to PCT/IT2009/000421 priority Critical patent/WO2011033538A1/en
Publication of WO2011033538A1 publication Critical patent/WO2011033538A1/en

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Classifications

    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C45/00—Injection moulding, i.e. forcing the required volume of moulding material through a nozzle into a closed mould; Apparatus therefor
    • B29C45/17—Component parts, details or accessories; Auxiliary operations
    • B29C45/26—Moulds
    • B29C45/27—Sprue channels ; Runner channels or runner nozzles
    • B29C45/28—Closure devices therefor
    • B29C45/2806—Closure devices therefor consisting of needle valve systems
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C45/00—Injection moulding, i.e. forcing the required volume of moulding material through a nozzle into a closed mould; Apparatus therefor
    • B29C45/0025—Preventing defects on the moulded article, e.g. weld lines, shrinkage marks
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C45/00—Injection moulding, i.e. forcing the required volume of moulding material through a nozzle into a closed mould; Apparatus therefor
    • B29C45/17—Component parts, details or accessories; Auxiliary operations
    • B29C45/26—Moulds
    • B29C45/27—Sprue channels ; Runner channels or runner nozzles
    • B29C2045/2788—Nozzles having a polygonal cross section

Definitions

  • the present invention generally refers to the plastic material injection molding industry.
  • the invention regards a system and method for the injection molding of articles having a rib or web or a "vertical" peripheral wall, i.e. generally directed orthogonally with respect to the general plane or a main surface of the article, at which the plastic material is injected.
  • Articles thus made may for example consist in aesthetic elements such as television frames, frames for electronic appliances or household appliances instrument panel, automobile interior elements and any other plastic molded element requiring high quality aesthetic properties.
  • systems for the injection molding of plastic articles thus made include apparatus having at least one plug injector and one mold having a cavity communicating with a tapered injection gate, facing a surface of the rib or vertical peripheral wall of the article undergoing, molding, which shall be referred to hereinafter as "reference surface”.
  • the injector comprises a hollow body having a nozzle tip communicating with the injection gate of the mold, and a pin coaxially moveable in the hollow body.
  • the pin has a tapered plug tip complementary to that of the injection gate, which is moveable between a retreated position and an advanced position wherein the abovementioned plug tip respectively opens and closes the flow through the injection gate.
  • a system thus conceived is known for example from the United States patent application US-2008/031997 on behalf of the same Applicant, addressed in which is the problem regarding improving the aesthetic qualities of the molded articles, and proposes a solution for limiting - as much as possible - the aesthetic flaws of the injected articles (particularly transparent lenses, typically made of polycarbonate, for automobile lights formed with reinforcement ribs or webs) derived from unwanted flows of plastic material into the zones corresponding to the or to each injector.
  • the solution proposed herein consists of providing the plug tip of the pin, as well as the nozzle tip of the injector provided directly on the figure, with an elongated transverse cross-section. Though efficient in most cases especially regarding low visibility of the sprue mark, such known solution is not entirely satisfactory when the aforementioned "reference surface" is that of the top of a rib or a peripheral wall generally orthogonal to the general plane of the article.
  • the object of the invention is that of providing a more efficient and ⁇ ⁇ complete solution to the abovementioned technical drawback, and such object is attained by means of an injection molding system of the type defined in the preamble of claim 1, whose peculiar characteristic resides in the fact that the plug tip of the pin of the injector and the injection gate have an asymmetric arrangement having axes inclined in an oblique manner with respect to said reference surface of the article, said asymmetric arrangement having, at said reference surface, an oblong end configuration.
  • the abovementioned asymmetric arrangement conveniently generally has an irregular frustoconical shape, and the abovementioned elongated end portion is flat and generally rectangular with the shorter sides curved or oval-shaped or elliptical.
  • the hollow body of the injector and the pin may have their axis generally coinciding with the inclined axis of the plug tip of the pin of the injector and injection gate but more conveniently, in that less expensive with respect to the machining operations that the inclined injector generally requires, such axis is preferably oriented orthogonally to the reference surface of the article to be molded.
  • the combination between asymmetric arrangement and obliquely inclined axis of the plug tip of the pin and injection gate allows preventing both unwanted flows of material from altering the aesthetic quality of the article and also enabling, even in the initial injection step, the fluid plastic material to intercept the wall of the cavity of the mold which laterally delimits the rib or peripheral wall of the article to be molded, instead of being released openly inside such cavity, thus also eliminating the negative effects derived from "jetting" phenomena.
  • Such result is optimised through an inclination of the axis of the asymmetric arrangement with respect to the axis of the injector, orthogonal to the reference surface of the article, in the order of 15°.
  • a draft angle between the plug tip of the pin and the injection gate comprised between 3° and 7°, preferably 5°, and a length of the plug tip of the pin slightly greater with respect to that of the injection gate, in such a manner that after injection, the reference surface of the piece shall have a slight recess which, from a functional point of view, is preferable with respect to a possible unwanted projection which could complicate or jeopardise subsequent assembling of the molded article.
  • the invention is also directed to a method for injection molding of the articles of the type described above, by using at least one injector also of the type indicated above, essentially characterised in that the injection is carried out according to an obliquely inclined direction with respect to the abovementioned reference surface of the article and through a flow gate of the plastic material having an oblong configuration.
  • Figure 1 is an overall schematic perspective view showing an example of an apparatus for the injection molding of plastic material articles which incorporates the system according to the invention
  • Figure 2 is an enlarged axial sectional view showing the detail of the apparatus of figure 1 corresponding to the end part of one of the injectors,
  • Figure 3 is a perspective representation of figure 2
  • Figure 4 is a view analogous to figure 2 rotated by 90 degrees
  • Figure 5 is an enlarged perspective view showing the plug tip of the pin of the injector represented in figures 2 to 4.
  • an example of the apparatus for the injection molding of plastic material which incorporates the system according to the invention comprises a mold for making a perimeter frame of a television flat screen, by injecting plastic material such as polycarbonate or the like.
  • reference F generally indicates such frame or, on the contrary, the cavity of the mold within which it is obtained.
  • the frame F has a perimeter rib or web R projecting perpendicularly with respect to its general plane, for example by a height equivalent to or greater than 5 mm., and whose free end or top defines what is indicated in the present invention and in the claims that follow as "reference surface" S.
  • the mold of the apparatus is generally indicated with M in figures 2 and 4 and, as mentioned, the respective cavity corresponds in negative to the frame F.
  • the apparatus represented in figure 1 comprises, in a generally conventional manner, a hot runner assembly H intended to operate being supplied with fluid plastic material, and several injectors I to introduce the plastic material under pressure into the cavity of the mold M to obtain the frame F.
  • Each injector I also has a generally conventional shape, for example of the type described and illustrated in the previously mentioned document US- 2008/031997.
  • each injector I comprises a tubular body 1 whose cavity defines a duct 2 for supplying the fluid plastic material from the hot runner assembly H to the cavity of the mold M.
  • a nozzle tip 3 Arranged at the lower end of the body 1 is a nozzle tip 3 from which the plastic material is injected directly into the mold M, through an injection gate 6.
  • the nozzle tip 3 generally conventionally comprises an inner hollow element 4 and an outer hollow element 5, connected to the end of the body 1 facing the injection gate 6.
  • the nozzle tip 3 thus defines a flow gate for introducing the fluid plastic material from the cavity 2 of the body 1 into the cavity of the mold M, controlled - also conventionally - by means of a pin 7 which is extended coaxially into the cavity 2.
  • the movement of the pin 7 between the advanced and retreated position is controlled, also conventionally, by means of an actuator J generally of the fluid linear type, conventionally having a damped piston.
  • the pin 7 has a circular section, with a coaxial free end or plug tip 8 having a regular frustoconical tapered shape.
  • the injection gate 6 of the mold M traditionally has the same regular frustoconical tapered shape.
  • the plug tip 8 of the pin 7, represented in enlarged detail in figure 5, instead has an irregular frustoconical configuration and more precisely asymmetric, with axis A not coinciding with axis B of the pin 7, but obliquely inclined with respect thereto.
  • the inclination angle of axis A with respect to axis B, which is perpendicular to the reference surface S in this case, is indicated as C in figure 2 and it is conveniently in the order of 15°.
  • the arrangement of the injection gate 6 is complementary to that of the plug tip 8, i.e. it also has a an irregular and asymmetric frustoconical inner surface, with axis coinciding with axis A.
  • the free end of the asymmetric frustoconical arrangement of the plug tip 8 of the pin 7, as also observable in figure 5, is indicated with 9 and it has a flat oblong or elongated configuration extended in the direction of the length of the rib or wall R and the respective "reference surface" S.
  • such configuration is generally rectangular with shorter sides curved, but it could also alternatively be elliptical or oval-shaped.
  • the flat and elongated end surface 9 of the plug tip 8 of the pin 7 is generally parallel to the reference surface S of the rib R of the molded article F.
  • the conicity angle of the plug tip 8 of the pin 7, measured in a plane passing through the centreline of the end surface 9 orthogonally to its long sides is conveniently in the order of 40°.
  • the conical surface of the plug tip 8 conveniently has a slightly smaller conicity (or draft angle), for example 3°-7° and preferably 5°, with respect to the conicity of the injection gate 6, in such a manner to prevent - during operation - risks of mutual seizing.
  • the directrix of the conical surface on which the minimum draft angle is verified shall depend on the specific complementary geometric configuration of the plug tip 8 and injection gate 6.
  • the axial length of the plug tip 8 of the pin 7 may be slightly greater than that of the injection gate 6, in such a manner that it projects beyond the passage 6 by about 0.2 - 0.3 mm in the closure position represented in figures 2-4.
  • Conveniently employed to obtain the abovementioned arrangement of the plug tip 8 of the pin 7 and the injection gate 6 of the mold M may be machines tools for chip removal, and in particular milling machines, preferably avoiding grinding or etching.
  • the process is carried out along the directrix of the conical surface so as to increase the finishing degree, and vibrating polishing may then be carried out between the plug tip 8 and the injection gate 6, with interposition of diamond paste.
  • Electrochemical polishing, as well as applying a coating using anti-sticking material (TiN or superlattice), may be conveniently carried out.
  • the pin 7 shall have a single angular positioning with respect to the body 1, for example predefined by a facing not illustrated, and provided for in the area for coupling the pin 7 to the stem of the piston of the respective fluid actuator, is an anti-rotation system, for example as outlined in the previously mentioned document US-2008/031997.
  • the plastic material injected through the injection gate 6 in the retracted opening position of the pin 7, and thus of its plug tip 8, allows forming the rib or vertical wall of the molded article F solving the aesthetic problems due to the visibility of unwanted flows of plastic material thereon, also making the sprue mark less visible at the reference surface S.
  • the axis B of the pin 7 and thus of the injector I is substantially perpendicular to the reference surface S
  • the axis A of the asymmetric plug tip 8 of the pin 7 is obliquely inclined with respect to such surface S. This implies that during the injection step, the flow of plastic material introduced through the injection gate 6 into the cavity of the mold M does not generate an open jet in such cavity, but intercepts one of the walls delimiting the rib or wall R, thus avoiding the "jetting" phenomena.
  • the greater axial length of the plug tip 8 of the pin 7, slightly greater than that of the injection gate 6 as mentioned, is capable of generating a slight recess on the reference surface S, which is preferable with respect to possible unwanted protrusion or step that could hinder or even jeopardize the assembly of the molded article F.
  • the construction details and embodiments may vary widely with respect to what has been described and illustrated, without departing from the scope of the present invention, as described in the claims that follow.
  • the injector 1 could be positioned in such a manner that the respective axis B is arranged, not orthogonally to the reference surface S, but obliquely with respect thereto.
  • the asymmetric frustoconical surface of the injection gate 6 could be obtained in an applied steel block having hardness exceeding 40 HRC, instead of being obtained directly on the mold M.

Abstract

System and method for the injection molding of plastic material articles having a rib or peripheral wall (R) generally orthogonal to the general plane of the article (F) and defining a reference surface (S), through at least one plug injector (I) and one mold (M) having an injection gate (6) facing said reference surface (S) of the article (F), wherein the injection is carried out according to a direction (A) obliquely inclined with respect to the reference surface (S) and through a flow passage (9) having an oblong configuration.

Description

"Injection molding system and method for plastic material articles"
Field of the invention
The present invention generally refers to the plastic material injection molding industry.
More in particular, the invention regards a system and method for the injection molding of articles having a rib or web or a "vertical" peripheral wall, i.e. generally directed orthogonally with respect to the general plane or a main surface of the article, at which the plastic material is injected.
Articles thus made may for example consist in aesthetic elements such as television frames, frames for electronic appliances or household appliances instrument panel, automobile interior elements and any other plastic molded element requiring high quality aesthetic properties.
Prior art
Traditionally, systems for the injection molding of plastic articles thus made include apparatus having at least one plug injector and one mold having a cavity communicating with a tapered injection gate, facing a surface of the rib or vertical peripheral wall of the article undergoing, molding, which shall be referred to hereinafter as "reference surface".
Traditionally, the injector comprises a hollow body having a nozzle tip communicating with the injection gate of the mold, and a pin coaxially moveable in the hollow body. The pin has a tapered plug tip complementary to that of the injection gate, which is moveable between a retreated position and an advanced position wherein the abovementioned plug tip respectively opens and closes the flow through the injection gate.
A system thus conceived is known for example from the United States patent application US-2008/031997 on behalf of the same Applicant, addressed in which is the problem regarding improving the aesthetic qualities of the molded articles, and proposes a solution for limiting - as much as possible - the aesthetic flaws of the injected articles (particularly transparent lenses, typically made of polycarbonate, for automobile lights formed with reinforcement ribs or webs) derived from unwanted flows of plastic material into the zones corresponding to the or to each injector. The solution proposed herein consists of providing the plug tip of the pin, as well as the nozzle tip of the injector provided directly on the figure, with an elongated transverse cross-section. Though efficient in most cases especially regarding low visibility of the sprue mark, such known solution is not entirely satisfactory when the aforementioned "reference surface" is that of the top of a rib or a peripheral wall generally orthogonal to the general plane of the article.
Furthermore, such solution may lead to risks implying further aesthetic flaws due to the so-called "jetting" phenomenon which occurs when the plastic material injected in the first injection steps generates an open jet in the area of the mold corresponding to the rib or wall, which subsequently swirls hence generating aesthetic flaws.
Summary of the invention
The object of the invention is that of providing a more efficient and ··■ complete solution to the abovementioned technical drawback, and such object is attained by means of an injection molding system of the type defined in the preamble of claim 1, whose peculiar characteristic resides in the fact that the plug tip of the pin of the injector and the injection gate have an asymmetric arrangement having axes inclined in an oblique manner with respect to said reference surface of the article, said asymmetric arrangement having, at said reference surface, an oblong end configuration.
The abovementioned asymmetric arrangement conveniently generally has an irregular frustoconical shape, and the abovementioned elongated end portion is flat and generally rectangular with the shorter sides curved or oval-shaped or elliptical.
The hollow body of the injector and the pin may have their axis generally coinciding with the inclined axis of the plug tip of the pin of the injector and injection gate but more conveniently, in that less expensive with respect to the machining operations that the inclined injector generally requires, such axis is preferably oriented orthogonally to the reference surface of the article to be molded.
The combination between asymmetric arrangement and obliquely inclined axis of the plug tip of the pin and injection gate allows preventing both unwanted flows of material from altering the aesthetic quality of the article and also enabling, even in the initial injection step, the fluid plastic material to intercept the wall of the cavity of the mold which laterally delimits the rib or peripheral wall of the article to be molded, instead of being released openly inside such cavity, thus also eliminating the negative effects derived from "jetting" phenomena. Such result is optimised through an inclination of the axis of the asymmetric arrangement with respect to the axis of the injector, orthogonal to the reference surface of the article, in the order of 15°.
Provided for may be other solutions such as for example a draft angle between the plug tip of the pin and the injection gate comprised between 3° and 7°, preferably 5°, and a length of the plug tip of the pin slightly greater with respect to that of the injection gate, in such a manner that after injection, the reference surface of the piece shall have a slight recess which, from a functional point of view, is preferable with respect to a possible unwanted projection which could complicate or jeopardise subsequent assembling of the molded article.
Also particular solutions regarding the method for manufacturing or processing the plug tip of the pin and injection gate of the mold may contribute to attain the final result.
The invention is also directed to a method for injection molding of the articles of the type described above, by using at least one injector also of the type indicated above, essentially characterised in that the injection is carried out according to an obliquely inclined direction with respect to the abovementioned reference surface of the article and through a flow gate of the plastic material having an oblong configuration.
Brief description of the drawings
Now, the invention shall be described in detail with reference to the attached drawings, strictly provided for exemplifying and non-limiting purposes, wherein:
Figure 1 is an overall schematic perspective view showing an example of an apparatus for the injection molding of plastic material articles which incorporates the system according to the invention,
Figure 2 is an enlarged axial sectional view showing the detail of the apparatus of figure 1 corresponding to the end part of one of the injectors,
Figure 3 is a perspective representation of figure 2,
Figure 4 is a view analogous to figure 2 rotated by 90 degrees, and
Figure 5 is an enlarged perspective view showing the plug tip of the pin of the injector represented in figures 2 to 4.
Detailed description of the invention
Initially referring to figure 1, an example of the apparatus for the injection molding of plastic material which incorporates the system according to the invention comprises a mold for making a perimeter frame of a television flat screen, by injecting plastic material such as polycarbonate or the like. In figure 1 reference F generally indicates such frame or, on the contrary, the cavity of the mold within which it is obtained.
With reference to figures 2-4, the frame F has a perimeter rib or web R projecting perpendicularly with respect to its general plane, for example by a height equivalent to or greater than 5 mm., and whose free end or top defines what is indicated in the present invention and in the claims that follow as "reference surface" S.
The mold of the apparatus is generally indicated with M in figures 2 and 4 and, as mentioned, the respective cavity corresponds in negative to the frame F.
The apparatus represented in figure 1 comprises, in a generally conventional manner, a hot runner assembly H intended to operate being supplied with fluid plastic material, and several injectors I to introduce the plastic material under pressure into the cavity of the mold M to obtain the frame F.
Each injector I also has a generally conventional shape, for example of the type described and illustrated in the previously mentioned document US- 2008/031997.
Regarding the present invention it is sufficient to clarify that each injector I comprises a tubular body 1 whose cavity defines a duct 2 for supplying the fluid plastic material from the hot runner assembly H to the cavity of the mold M.
Arranged at the lower end of the body 1 is a nozzle tip 3 from which the plastic material is injected directly into the mold M, through an injection gate 6. The nozzle tip 3 generally conventionally comprises an inner hollow element 4 and an outer hollow element 5, connected to the end of the body 1 facing the injection gate 6.
The nozzle tip 3 thus defines a flow gate for introducing the fluid plastic material from the cavity 2 of the body 1 into the cavity of the mold M, controlled - also conventionally - by means of a pin 7 which is extended coaxially into the cavity 2. The pin 7, formed by a substantially extended cylindrical body whose general axis is indicated with B, is moveable between an advanced closure position (represented in the drawings) and a retreated position for opening the flow of plastic material from the cavity 2 of the body 1 to the injection gate 6, and thus to the cavity of the mold M. The movement of the pin 7 between the advanced and retreated position is controlled, also conventionally, by means of an actuator J generally of the fluid linear type, conventionally having a damped piston.
Traditionally, the pin 7 has a circular section, with a coaxial free end or plug tip 8 having a regular frustoconical tapered shape. In a corresponding manner, also the injection gate 6 of the mold M traditionally has the same regular frustoconical tapered shape.
According to the fundamental characteristic of the invention, the plug tip 8 of the pin 7, represented in enlarged detail in figure 5, instead has an irregular frustoconical configuration and more precisely asymmetric, with axis A not coinciding with axis B of the pin 7, but obliquely inclined with respect thereto. The inclination angle of axis A with respect to axis B, which is perpendicular to the reference surface S in this case, is indicated as C in figure 2 and it is conveniently in the order of 15°.
The arrangement of the injection gate 6 is complementary to that of the plug tip 8, i.e. it also has a an irregular and asymmetric frustoconical inner surface, with axis coinciding with axis A.
The free end of the asymmetric frustoconical arrangement of the plug tip 8 of the pin 7, as also observable in figure 5, is indicated with 9 and it has a flat oblong or elongated configuration extended in the direction of the length of the rib or wall R and the respective "reference surface" S. In the case of the illustrated example such configuration is generally rectangular with shorter sides curved, but it could also alternatively be elliptical or oval-shaped.
As observable in the figures 2-4, the flat and elongated end surface 9 of the plug tip 8 of the pin 7 is generally parallel to the reference surface S of the rib R of the molded article F.
The conicity angle of the plug tip 8 of the pin 7, measured in a plane passing through the centreline of the end surface 9 orthogonally to its long sides is conveniently in the order of 40°.
The conical surface of the plug tip 8 conveniently has a slightly smaller conicity (or draft angle), for example 3°-7° and preferably 5°, with respect to the conicity of the injection gate 6, in such a manner to prevent - during operation - risks of mutual seizing. The directrix of the conical surface on which the minimum draft angle is verified shall depend on the specific complementary geometric configuration of the plug tip 8 and injection gate 6. Preferably,, the axial length of the plug tip 8 of the pin 7 may be slightly greater than that of the injection gate 6, in such a manner that it projects beyond the passage 6 by about 0.2 - 0.3 mm in the closure position represented in figures 2-4.
Conveniently employed to obtain the abovementioned arrangement of the plug tip 8 of the pin 7 and the injection gate 6 of the mold M may be machines tools for chip removal, and in particular milling machines, preferably avoiding grinding or etching. The process is carried out along the directrix of the conical surface so as to increase the finishing degree, and vibrating polishing may then be carried out between the plug tip 8 and the injection gate 6, with interposition of diamond paste. Electrochemical polishing, as well as applying a coating using anti-sticking material (TiN or superlattice), may be conveniently carried out.
Obviously, the pin 7 shall have a single angular positioning with respect to the body 1, for example predefined by a facing not illustrated, and provided for in the area for coupling the pin 7 to the stem of the piston of the respective fluid actuator, is an anti-rotation system, for example as outlined in the previously mentioned document US-2008/031997.
During operation, the plastic material injected through the injection gate 6 in the retracted opening position of the pin 7, and thus of its plug tip 8, allows forming the rib or vertical wall of the molded article F solving the aesthetic problems due to the visibility of unwanted flows of plastic material thereon, also making the sprue mark less visible at the reference surface S. As observable in figures 2 to 4, which as already mentioned represent the advanced closure state of the pin 7 after the formation of the article F inside the mold M, while the axis B of the pin 7 and thus of the injector I is substantially perpendicular to the reference surface S, the axis A of the asymmetric plug tip 8 of the pin 7 is obliquely inclined with respect to such surface S. This implies that during the injection step, the flow of plastic material introduced through the injection gate 6 into the cavity of the mold M does not generate an open jet in such cavity, but intercepts one of the walls delimiting the rib or wall R, thus avoiding the "jetting" phenomena.
The greater axial length of the plug tip 8 of the pin 7, slightly greater than that of the injection gate 6 as mentioned, is capable of generating a slight recess on the reference surface S, which is preferable with respect to possible unwanted protrusion or step that could hinder or even jeopardize the assembly of the molded article F. Obviously,, the construction details and embodiments may vary widely with respect to what has been described and illustrated, without departing from the scope of the present invention, as described in the claims that follow.
Hence, for example, the injector 1 could be positioned in such a manner that the respective axis B is arranged, not orthogonally to the reference surface S, but obliquely with respect thereto.
Furthermore, the asymmetric frustoconical surface of the injection gate 6 could be obtained in an applied steel block having hardness exceeding 40 HRC, instead of being obtained directly on the mold M.

Claims

1. System for the injection of plastic material articles (F) having a rib or peripheral wall (R) generally orthogonal to the general plane of the article (F) and defining a reference surface (S), wherein said system comprises at least one plug injector (I) and one mold (M) having a cavity communicating with a tapered injection gate (6) and facing said reference surface (S) of the article (F), and wherein said injector (I) comprises a hollow body (1) having a nozzle tip (3) communicating with said injection gate (6), and a pin (7) coaxially moveable in the hollow body (1) and having a plug tip (8) having a tapered shape complementary to that of said injection gate (6), said pin (7) being moveable between a retreated position and an advanced position wherein said plug tip (8) respectively opens and closes the flow through said nozzle tip (4) towards said injection gate (6), characterised in that the plug tip (8) of the pin (7) of the injector (I) and the injection gate (6) of the mold (M) have an asymmetric arrangement having axis (A) obliquely inclined with respect to said reference surface (S) of the article (F), said asymmetric arrangement having, at said reference surface (S) of the piece (F), an oblong end configuration (9).
2. System according to claim 1, characterised in that said asymmetric arrangement of the plug tip (8) of the pin (7) and the injection gate (6) has a generally irregular frustoconical shape.
3. System according to claim 1 or 2, characterised in that said oblong end configuration (9) of the plug tip (8) of the pin (7) is flat.
4. System according to claim 3, characterised in that said flat oblong end configuration (9) is parallel to said reference surface (S) of the article (F).
5. System according to claim 3 or 4, characterised in that said flat oblong end configuration (9) is generally rectangular with the shorter sides curved, or elliptic or oval-shaped.
6. System according to any one of the preceding claims, characterised in that the hollow body (1) of the injector (I) and the pin (7) have axis (B) substantially orthogonal to said reference surface (S) of the article (F).
7. System according to claim 6, characterised in that the axis (A) of said asymmetric arrangement of the plug tip (8) of the pin (7) and injection gate (6) form, with respect to the axis (B) of the hollow body (1) and of the pin (7) of the injector (I), an angle (C) comprised between 10° and 15°.
8. System according to one or more of claims 1 - 5, characterised in that the hollow body (1) of the injector (I) and the pin (7) have axis (B) obliquely inclined with respect to said reference surface (S) of the article (F).
9. System according to claim 2, characterised in that said plug tip (8) of the pin (7) has a slightly smaller conicity with respect to the conicity of said injection gate (6).
10. Molding system according to one or more of the preceding claims, characterised in that said plug tip (8) of the pin (7) has a slightly greater axial length with respect to that of said injection gate (6).
11. Method for the injection molding of plastic material articles (F) having a rib or peripheral wall (R) generally orthogonal to the general plane of the article
(F) and defining a reference surface (S), through at least one plug injector (I) and one mold (M) having an injection gate (6) facing said reference surface (S) of the article (F), characterised in that the injection is carried out according to a direction (A) obliquely inclined with respect to said reference surface (S) of the article (F) and through a flow passage (9) having an oblong configuration.
12. Method according to claim 11, characterised in that said oblong configuration (9) is flat and parallel to said reference surface (S).
13. Method according to claim 13, characterised in that said oblong configuration (9) is rectangular with shorter sides curved, or elliptical or oval- shaped.
14. Injector for apparatus for injection molding of plastic material articles (F) comprising a hollow body (1) with a nozzle tip (3) and a pin (7) coaxially moveable in the hollow body (1) and having a plug tip (8) having a tapered configuration, said pin (7) being moveable between a retracted position and an advanced position wherein said plug tip (8) respectively opens and closes the flow through said nozzle tip (4), characterised in that the plug tip (8) of the pin (7) has an asymmetric arrangement having its axis (A) obliquely inclined with respect to the axis (B) of said pin (7) and an end surface (9) having an oblong configuration.
15. Injector according to claim 14, characterised in that said asymmetric arrangement of the plug tip (8) of the pin (7) has a generally irregular frustoconical shape.
16. Injector according to claim 14 or 15, characterised in that said end surface (9) of the plug tip (8) of the pin (7) is flat.
17. Injector according to claim 16, characterised in that said flat end surface (9) is generally rectangular with shorter sides curved, or elliptical or oval- shaped.
18. Injector according to any one of claims 14 - 17, characterised in that the axis (A) of said asymmetric arrangement of the plug tip (8) of the pin (7) forms - with respect to the axis (B) of the pin (7) - an angle (C) comprised between 10° and 15°.
19. Injector according to any one of claims 14 - 18, characterised in that said plug tip (8) of the pin (7) has a conicity angle, measured on a plane passing through the centreline of said end surface (9) having an elongated configuration orthogonally to its greater dimension, in the order of 40°.
20. Pin for plug injectors of apparatus for the injection molding of plastic material articles (F) having a general axis (B) and a plug tip (8) having a tapered configuration, characterised in that said plug tip (8) has an asymmetric arrangement having axis (A) obliquely inclined with respect to the general axis (B) of said pin (7) and an end surface (9) having an oblong configuration.
21. Pin according to claim 20, characterised in that said asymmetric arrangement of the plug tip (8) has a generally irregular frustoconical shape.
22. Pin according to claim 20 or 21, characterised in that said end surface (9) is flat.
23. Pin according to claim 22, characterised in that said flat end surface (9) is generally rectangular with shorter sides curved, or elliptical or oval-shaped.
24. Pin according to any one of claims 20 - 23, characterised in that the axis (A) of said asymmetric arrangement of the plug tip (8) forms - with respect to the general axis (B) of the pin (7) - an angle (C) comprised between 10° and 15°.
25. Pin according to any one of claims 20 - 24, characterised in that said plug tip (8) has a conicity angle, measured on a plane passing through said end surface (9) having an elongated configuration orthogonally to its greater dimension, in the order of 40°.
PCT/IT2009/000421 2009-09-18 2009-09-18 Injection molding system and method for plastic material articles WO2011033538A1 (en)

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Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP2607047A1 (en) 2011-12-19 2013-06-26 Valeo Vision Device for moulding an element comprising a lip
US11148332B2 (en) 2014-09-10 2021-10-19 Haidlmair Holding Gmbh Injection molding nozzle for manufacturing injection molded components from plastic

Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0520345A2 (en) * 1991-06-28 1992-12-30 ACRILUX S.p.A. Injection nozzle for an injection mould
JPH07251428A (en) * 1994-03-15 1995-10-03 Daicel Chem Ind Ltd Gate structure of hot runner mold for injection molding
JPH10109332A (en) * 1996-10-07 1998-04-28 Toshiba Mach Co Ltd Valve gate device for skin molding injection mold
JP2006240038A (en) * 2005-03-03 2006-09-14 Ricoh Co Ltd Mold, molding method, and molded product
US20080031997A1 (en) * 2006-01-27 2008-02-07 Inglass S.P.A. Injector for injection moulding equipment of plastic materials

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0520345A2 (en) * 1991-06-28 1992-12-30 ACRILUX S.p.A. Injection nozzle for an injection mould
JPH07251428A (en) * 1994-03-15 1995-10-03 Daicel Chem Ind Ltd Gate structure of hot runner mold for injection molding
JPH10109332A (en) * 1996-10-07 1998-04-28 Toshiba Mach Co Ltd Valve gate device for skin molding injection mold
JP2006240038A (en) * 2005-03-03 2006-09-14 Ricoh Co Ltd Mold, molding method, and molded product
US20080031997A1 (en) * 2006-01-27 2008-02-07 Inglass S.P.A. Injector for injection moulding equipment of plastic materials

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP2607047A1 (en) 2011-12-19 2013-06-26 Valeo Vision Device for moulding an element comprising a lip
US11148332B2 (en) 2014-09-10 2021-10-19 Haidlmair Holding Gmbh Injection molding nozzle for manufacturing injection molded components from plastic

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