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WO2007012994A2 - Procede et dispositif de formation d'une structure en plastique moulee par ecoulement - Google Patents

Procede et dispositif de formation d'une structure en plastique moulee par ecoulement Download PDF

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Publication number
WO2007012994A2
WO2007012994A2 PCT/IB2006/052405 IB2006052405W WO2007012994A2 WO 2007012994 A2 WO2007012994 A2 WO 2007012994A2 IB 2006052405 W IB2006052405 W IB 2006052405W WO 2007012994 A2 WO2007012994 A2 WO 2007012994A2
Authority
WO
WIPO (PCT)
Prior art keywords
flow
cavity
runner
runner cavity
molded
Prior art date
Application number
PCT/IB2006/052405
Other languages
English (en)
Other versions
WO2007012994A3 (fr
Inventor
Caspar M. M. Van Spaendonck
Original Assignee
Koninklijke Philips Electronics N.V.
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 Koninklijke Philips Electronics N.V. filed Critical Koninklijke Philips Electronics N.V.
Publication of WO2007012994A2 publication Critical patent/WO2007012994A2/fr
Publication of WO2007012994A3 publication Critical patent/WO2007012994A3/fr

Links

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
    • B29C45/0025—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
    • B29C45/2701—Details not specific to hot or cold runner channels
    • B29C45/2708—Gates
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29L—INDEXING SCHEME ASSOCIATED WITH SUBCLASS B29C, RELATING TO PARTICULAR ARTICLES
    • B29L2031/00—Other particular articles
    • B29L2031/30—Vehicles, e.g. ships or aircraft, or body parts thereof
    • B29L2031/3055—Cars
    • B29L2031/3061—Number plates
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29L—INDEXING SCHEME ASSOCIATED WITH SUBCLASS B29C, RELATING TO PARTICULAR ARTICLES
    • B29L2031/00—Other particular articles
    • B29L2031/44—Furniture or parts thereof
    • B29L2031/445—Cabinets

Definitions

  • the invention relates to a method of forming a flow-molded plastic structure in a mold, in which two flows of plastic material meet.
  • the invention also relates to a device for forming a flow-molded plastic structure in a mold, in which two flows of plastic material meet, and to a display device having a flow-molded plastic structure.
  • a problem in flow-molding is the occurrence of weld lines.
  • the flow-molded material flows into the structure cavity and a weld line or weld surface occurs at the contact surface of two flows of material, because the two flows do not fuse completely.
  • This weld line is usually visible and may form a weak spot in the flow-molded piece.
  • US 2,360,023 discloses a solution which consists in using heating devices which locally heat the material to fuse the meeting flows of plastic material.
  • the known solution requires a rather complex method and device.
  • local heating may provoke thermal stress in the molded structure which in itself may cause visible cracks or structurally weak spots.
  • the method according to the invention is characterized in that a runner cavity is provided, which extends alongside a structure cavity corresponding to the plastic structure, wherein the flow resistance in the runner cavity is lower than the flow resistance in and/or to said structure cavity, and wherein, during molding, a flow of plastic material is supplied to the runner cavity, via which the structure cavity is filled with a flow of plastic material, such that the flow front in the structure cavity trails the flow front in the runner cavity at such a trailing angle that one fused flow front filling the structure cavity without formation of a weld line is formed when the two flow fronts meet.
  • the runner cavity is filled before the structure cavity is.
  • the structure cavity fills up in the wake of filling the runner cavity.
  • the flow front of the material filling up the structure cavity thus trails the flow front in the runner cavity. Since the runner cavity extends alongside the structure cavity, the flow front in and to the structure cavity forms a trailing angle.
  • the part of the flow front within the structure cavity near the runner cavity advances the part of the flow front opposite the runner cavity, so that a trailing angle is formed.
  • a weld line is formed in this cavity. However, there is no weld line when the trailing flow fronts meet in the structure cavity.
  • the flow fronts preferably meet in the structure cavity at an angle of more than approximately 120° (twice 60°) to each other. In most materials, a trailing angle of such a magnitude will cause the flow fronts to fuse.
  • the trailing angle is preferably more than 75°. This further reduces the occurrence of a weld line in the structure cavity.
  • the runner cavity may be left in place, i.e. attached to the flow-molded structure if the weld line in the runner cavity does not pose a problem, for instance, if the weld line is out of sight or not at a location where any structural weakness would be a problem.
  • the runner cavity is cut from the flow-molded structure after completion of the flow-molding process.
  • the flow-molded structure and the corresponding structure cavity may have any form, but the invention is very useful for flow-molded structures which have a closed form around an open area, such as circular forms, rectangular forms, oval forms or any closed profile form.
  • the runner cavity When the structure cavity has a closed form, the runner cavity may be provided alongside an inner or an outer perimeter or it may extend parallel to the closed form.
  • a flow-resistance passage may be provided between the runner cavity and the structure cavity so as to amplify the trailing effect of the flow front.
  • Embodiments of the method according to the invention are defined in claims 1 to 6.
  • Embodiments of the device according to the invention are defined in claims 7 to 11.
  • the display device according to the invention is defined in claim 12.
  • Fig. 1 schematically shows a conventional method and die.
  • Fig. 2 schematically illustrates the method and a die for a device according to the invention.
  • Figs. 3 A, 3B, 4 and 5 illustrate a preferred embodiment of the method and device according to the invention.
  • Figs. 6 to 8 illustrate a method and device in which a double feed is used.
  • Fig. 9 shows two possible mutual arrangements of the runner cavity and the structure cavity.
  • Fig. 10 shows two more possible mutual arrangements of the runner cavity and the structure cavity.
  • Fig. 11 illustrates a display device with a rim structure surrounding a display.
  • Fig. 1 illustrates a conventional method and device for flow-molding a structure by means of a flow-molding method wherein two flows of plastic material meet. Two flows of plastic material are fed into a structure cavity 1. As schematically shown in the upper part of the Figure, the two flow fronts approach each other. The flow-molded material flows into the structure cavity 1 and a weld line 4 or weld surface occurs at the contact surface of the two flows 2, 3 of material, because they do not fuse completely. This weld line 4 is usually visible and may form a weak spot in the flow-molded piece.
  • Fig. 2 schematically illustrates the basic principle of the method and device according to the invention.
  • cavities and parts formed in the cavities are generally denoted by the same reference numerals.
  • plastic material and plastic material flows outside the actual structure cavity are shaded slightly darker than those inside the structure cavity in Figs. 3 to 10, even though the same material is concerned.
  • a runner cavity 5 is provided alongside the structure cavity 1.
  • the flow resistance in the runner cavity is (or is made) smaller than the flow resistance in the structure cavity.
  • the flowing material seeks its path of least resistance and, during flow-molding, has thus further advanced in the runner cavity 5 than in the structure cavity 1.
  • a resistance passage e.g. a slit, is provided in between the runner cavity 5 and the structure cavity 1 so as to cause the flow in the runner cavity to advance even more than the flow in the structure cavity. Because of the different flow resistances, the flow front outside the runner cavity trails the flow front in the runner cavity at a trailing angle ⁇ . The approaching flow fronts will make first contact in the runner cavity 5 in which a weld line 4 is formed.
  • the slanted trailing flow fronts will iuse to one flow front and no weld line is formed when these slanted trailing flow fronts meet outside the runner cavity. Consequently, no weld line is formed inside the structure cavity 1.
  • the trailing angle is preferably more than 75°.
  • the trailing angle ⁇ has a reference plane which corresponds to a plane extending perpendicularly to the flow direction. The trailing angle ⁇ is dependent on the flow resistance within the runner cavity and the structure cavity and on any flow resistance between the runner cavity and the structure cavity, i.e.
  • the flow resistance passage or restriction to the structure cavity such as a restriction 6 in the form of a slit arranged between the runner cavity 5 and the structure cavity 1, as schematically shown in Fig. 2.
  • the flow resistances can be calculated by a person skilled in the art and/or can be measured experimentally.
  • the trailing angle ⁇ can be calculated or established experimentally and, if necessary, regulated by adjusting the different flow resistances, for instance, by increasing or decreasing the diameter of the runner cavity, the restriction 6 between the runner cavity and the structure cavity, or the temperature of the runner cavity. In any case, the restriction in the runner cavity must be smaller than the restriction in the structure cavity.
  • the "cut-off trailing angle ⁇ i.e.
  • the angle above which two slanted flow fronts fuse into a single flow front can be easily established by a person skilled in the art by means of experiments in which e.g. an arrangement of a transparent runner cavity, slit and structure cavity of variable flow resistance is made in such a way that the trailing angle is varied and in which it is checked when the trailing flow fronts fuse. For instance, by narrowing the slit, the flow resistance to the structure cavity can be varied easily.
  • the flow fronts in the structure cavity preferably meet at an angle of more than approximately 120° (twice 60°) to each other. In most materials, a trailing angle of such a magnitude will cause the flow fronts to fuse.
  • the trailing angle is preferably more than 75°. This further reduces the occurrence of a weld line in the structure cavity.
  • the structure cavity itself may have any form, shape or size. However, the invention is most advantageous for flow-molding plastic structures having a closed form, such as ring-shaped structures, e.g. circular, rectangular or oval structures. The invention is also suitable for avoiding weld lines in any closed profile around a hole/open area.
  • Figs. 3 A, 3B, 4 and 5 illustrate a preferred embodiment of the method and device according to the invention.
  • Plastic material is supplied to runner cavity 5 through a feed 5a, which is schematically indicated by a circle and a double line extending to runner cavity 5 in this Figure and the following Figures.
  • the material flows into runner cavity 5 and into structure cavity 1 through the restriction 6.
  • the plastic flows fill up the runner cavity 5, the restriction 6 and the structure cavity 1, see Figs.
  • Figs. 6 to 8 illustrate a method and device in which a double feed 5a is used. Two pairs of meeting flows are generated. The same principle applies.
  • the material flows into runner cavity 5 via the feed 5a and then into structure cavity 1, in this example via restriction 6.
  • the flow fronts meet as depicted in Fig. 7, lower part, and Fig. 8.
  • a weld line 4 is formed inside the runner cavity 5. No such weld line is formed outside the runner cavity.
  • the runner cavity 5 and the restriction 6 can be cut from the flow-molded structure 1. This may be done by means of any useful method such as e.g. simple cutting with a knife or a heated wire or cutting by means of a laser.
  • Fig. 9 shows two possible mutual arrangements of runner cavity 5 and structure cavity 1.
  • the runner cavity and the structure cavity are arranged substantially in a plane, connected by a restriction 6, e.g. a slit. This is a simple arrangement.
  • the cut may be visible to a viewer looking at part 1 from above.
  • it may be advantageous if the cut is made at a position which is out of sight.
  • the lower part of Fig. 9 shows a mutual arrangement of runner cavity 5, restriction 6 and flow-molded structure cavity 1, which is advantageous in this respect. The cut may now be made at the back of structure 1 and thus out of sight to a viewer looking at the flow-molded structure from above.
  • the runner cavity may extend alongside an inner perimeter of the closed form, as is schematically shown in Fig. 10, upper part, or alongside an outer perimeter of the closed form, as is schematically shown in Fig. 10, lower part.
  • the invention is advantageous for a great variety of applications.
  • the invention is particularly advantageous for display devices having a rim structure around a display area. Any weld line visible in such a rim structure is immediately noticed by the viewer and distracts from the visual appeal of the display. Viewers will often interpret the weld line as a crack and thus as a potential hazard.
  • the invention therefore also relates to a display device comprising a display surrounded by a rim structure formed by means of the method of the invention.
  • Fig. 11 illustrates a display device 10 with a rim structure 12 surrounding a display 11.
  • a runner cavity In a method and device for forming a flow-molded structure, a runner cavity

Landscapes

  • Engineering & Computer Science (AREA)
  • Manufacturing & Machinery (AREA)
  • Mechanical Engineering (AREA)
  • Moulds For Moulding Plastics Or The Like (AREA)

Abstract

L'invention concerne un procédé et un dispositif permettant de former une structure moulée par écoulement, qui consistent à fournir une cavité de roue (5) le long d'une cavité à structure (1). Le matériau s'écoule par la cavité de roue (5) dans la cavité à structure (1) suivant un angle de traînée α. A un angle de traînée α suffisamment grand, aucune ligne de soudure ne se formera dans la cavité à structure lorsque les deux fronts d'écoulement se rencontrent, on obtient alors une structure moulée par écoulement sans ligne de soudure (4).
PCT/IB2006/052405 2005-07-25 2006-07-14 Procede et dispositif de formation d'une structure en plastique moulee par ecoulement WO2007012994A2 (fr)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
EP05106810.4 2005-07-25
EP05106810 2005-07-25

Publications (2)

Publication Number Publication Date
WO2007012994A2 true WO2007012994A2 (fr) 2007-02-01
WO2007012994A3 WO2007012994A3 (fr) 2007-08-09

Family

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Family Applications (1)

Application Number Title Priority Date Filing Date
PCT/IB2006/052405 WO2007012994A2 (fr) 2005-07-25 2006-07-14 Procede et dispositif de formation d'une structure en plastique moulee par ecoulement

Country Status (1)

Country Link
WO (1) WO2007012994A2 (fr)

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
FR2925387A1 (fr) * 2007-12-21 2009-06-26 Valeo Systemes Thermiques Procede de moulage d'une piece en matiere plastique, moule pour la mise en oeuvre du procede et collecteur pour echangeur de chaleur

Family Cites Families (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS5915809B2 (ja) * 1976-08-11 1984-04-11 株式会社日立製作所 射出成形品の金型
JPH0274316A (ja) * 1988-09-12 1990-03-14 Hitachi Ltd プラスチック成形方法
JPH0339218A (ja) * 1989-07-07 1991-02-20 Hitachi Ltd プラスチックレンズ成形用金型
JPH09216256A (ja) * 1996-02-14 1997-08-19 Sumitomo Rubber Ind Ltd ゴム部材の成形装置
JP2003154550A (ja) * 2001-11-26 2003-05-27 Toyoda Gosei Co Ltd 成形品および成形品の設計方法ならびにウエルドラインの長さの予測方法

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
FR2925387A1 (fr) * 2007-12-21 2009-06-26 Valeo Systemes Thermiques Procede de moulage d'une piece en matiere plastique, moule pour la mise en oeuvre du procede et collecteur pour echangeur de chaleur

Also Published As

Publication number Publication date
WO2007012994A3 (fr) 2007-08-09

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