JP3764369B2 - Injection molding equipment - Google Patents

Description

【００６６】
【数２】

【００６７】
ここで、
Ｐは射出圧力
Ｓｎは底板の上から見た投影面積
Ｓｍは上型の下から見た投影面積
Ｓａはシール面積
Ｓｒは支持部材（支持部材本体）の断面積
Ｓｐは第２の下型の断面積
Ｆｎは射出圧力によって発生する底板の下向きの力（＝Ｐ・Ｓｎ）
Ｆｍは射出圧力によって金型を押し上げようとする力（＝Ｐ・Ｓｍ）
Ｆｒは支持部材に加わる力
Ｆｐは第２の下型に加わる力
Ｌｐは第２の下型のフランジ間の長さ
Ｌｒは支持部材の長さ
Δｌは支持部材の縮み量
Ｅは支持部材のヤング率（第２の下型のヤング率と同じと仮定）
ｎは支持部材の本数である。
第２の下型５６のフランジ部５６ｂ，５６ｃと連結ボルト１０３は変形しないものと仮定する。
【００６８】
力の釣り合いを考えると
（Ｆｎ−Ｆｍ）＝ｎＦｒ＋Ｆｐ ・・・（２）
上記（Ａ）式を（２）式に代入数ると
【００６９】
【数３】

【００７０】
上記（Ｂ）式を用いてシール比Ｋを求める。シール圧Ｐａは次式によって表される。
【００７１】
【数４】

上記（４）式の両辺をＰで除してシール比Ｋを求める。
【数５】

【００７２】
【数６】

【００７３】
上記（６）式の前項は、通常のシール比、後項は支持部材による減少分で、シール比の低減率は次式で表される。
【００７４】
【数７】

【００７５】
なお、上記した実施の形態は、電磁流量計用測定管の内周面とフランジの配管接続端面にライニングを施す射出成形装置２０に適用した例を示したが、本発明はこれに何等特定されるものではなく、例えば容器やカップ状のもの、特に半導体製造工場のクリーンルームで使用されるものは、略１００％弗素樹脂製なので、本発明による射出成形装置を用いることにより、安価に製作することができる。
また、上記した実施の形態においては、成形品が測定管のため、金型３０の下型４５を、第１、第２の下型５５，５６および中子５７とで構成し、第２の下型５６を測定管で構成した例を示したが、成形品によっては金型が上型、下型および中子で構成されるものであってもよい。
さらに、プッシャ３２の推力付与手段としては、油圧シリンダ２２によってプランジャ３３を下降させプッシャ３２を押し下げるものではなくて、逆に、プッシャ３２を固定しておき、油圧ジャッキを用いて金型３０を上昇させることでプッシャ３２に相対的に推力を付与するものであってもよい。
【００７６】
【発明の効果】
以上説明したように本発明に係る射出成形装置は、ゲートリングによって中子を下型に対して位置決めしているので、偏肉が生じず、成形体の肉厚の寸法精度を高めることができる。さらに、ゲートを小径ゲートと大径ゲートとで構成し、これらのゲートを通過する成形材料の流速を異ならせたので、成形品の表面にウエルドラインが発生せず、品質を向上させることができる。
【００７７】
また、本発明によれば、プッシャの成形材料を押圧する力を利用して金型のシール面に面圧を発生させ、成形材料が外部へ漏れ出るのを防止するようにしたので、ボルトによる締結や油圧による型締め機構によって金型を型締めする必要がなく、射出成形装置の簡素化および金型製作費の低減を達成するとともに、金型の組立、分解作業が容易で生産性を向上させることができる。また、成形材料の漏出がないため、不良率を低減することができる。さらに、成形体を成す部品の一部を金型として兼用するので、別途金型を必要としない。
【図面の簡単な説明】
【図１】 本発明に係る射出成形装置の一実施の形態の一部を破断して示す概略構成図である。
【図２】 射出成形用金型の一実施の形態を示す断面図である。
【図３】 底板の上から見た投影面積を示す図である。
【図４】 上型の下から見た投影面積を示す図である。
【図５】 金型の要部の拡大断面図である。
【図６】 ゲートリングの平面図である。
【図７】 同ゲートリングの断面図である。
【図８】 第１の下型部材の平面図である。
【図９】 中子の底面図である。
【図１０】 （ａ）〜（ｄ）は図９のＡ−Ａ線、Ｂ−Ｂ線、Ｃ−Ｃ線、Ｄ−Ｄ線断面図である
【図１１】 冷却のシーケンスを示す図である。
【図１２】 従来の射出成形装置用金型の断面図である。
【符号の説明】
８…キャビティ、９…成形材料、２０…射出成形装置、２２…油圧シリンダ、３０…射出成形用金型、３１…トランスファポット、３１Ａ…円筒体、３１Ｂ…底板、３２…プッシャ、４０…ノズル孔、４１ａ…シール面、４４…上型、４５…下型、４６…ゲートリング、４９…湯道、５０…スプルー、５１…ゲート、５３ａ…シール面、５５…第１の下型、５６…第２の下型、５６ｂ，５６ｃ…フランジ、５７…中子、６４ａ，６５ａ，６６ａ，６７ａ…シール面、７５…ゲート、７５Ａ…小径ゲート、７５Ｂ…大径ゲート、Ａ1 ，Ａ2 ，Ｂ，Ｃ…シール部。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an injection molding apparatus, for example, an injection molding apparatus suitable for use in molding a lining in a measurement pipe of an electromagnetic flow meter, molding a resin pipe, or the like.
[0002]
[Prior art]
An electromagnetic flowmeter that measures the flow rate of a conductive fluid that flows in a measurement tube by using an electromagnetic induction phenomenon prevents a short circuit between an electromotive force generated in the fluid and a measurement tube made of a non-magnetic material such as stainless steel. In addition, the inner peripheral surface, which is usually the wetted surface of the measurement tube, and the surface to which the flange pipes integrally provided at both ends of the measurement tube are connected (hereinafter referred to as the pipe connection end surface) are covered with a lining material. . As the lining material, heat resistance, corrosion resistance, electrical insulation, etc. are required, so insulating materials such as fluorine resin are usually used, and it is formed by injection molding on the inner peripheral surface of the measurement tube and the pipe connection end surface of the flange Is formed by.
[0003]
When molding such a lining measuring tube with a transfer molding machine, load the measuring tube without lining into the mold and heat the mold to a temperature equal to or higher than the melting temperature of the lining material. The prepared lining material is injected under pressure into the mold, and the inner peripheral surface of the measurement tube and the pipe connection end surface of the flange are covered with the lining material.
[0004]
When lining the measuring tube, the fluororesin used as the lining material has poor adhesion to the metal and is easily peeled off from the measuring tube. Therefore, a reinforcing tube usually formed by a perforated plate called a punching plate is placed inside the measuring tube. By attaching this reinforcing tube in advance and covering it with a lining material, the mechanical coupling strength between the lining material and the measuring tube is increased to prevent the lining material from peeling, and the lining caused by temperature changes or pressure changes in the measuring tube. The deformation of the material is prevented (Japanese Patent Publication No. 5-48846, Japanese Patent Publication No. 5-48845, Japanese Utility Model Publication No. 2-28411).
[0005]
FIG. 12 is a cross-sectional view showing a conventional injection molding apparatus used for molding a measuring tube. The injection molding apparatus 1 includes a mold 4 including an upper mold 2 and a lower mold 3 and an injection nozzle (not shown). The lower mold 3 is a first lower mold 5, a second lower mold 6 and A core 7 is formed, and a molding material 9 such as a fluorine resin is injected into the cavity 8 of the mold 4 under pressure to pressurize the inner peripheral surface of the second lower mold 6 and the pipe connection end surface 10a of the flange 10 thereof. The second lower mold 6 is taken out as the measuring tube 11 by lining the annular recess 15 provided in the measuring tube 11. That is, the injection molding apparatus 1 performs outsert molding using the measurement tube 11 that is not lined as the second lower mold 6. Reference numeral 16 denotes a reinforcing pipe attached to the inside of the second lower mold 6 via a spacer 17, and 18 denotes a cooling circuit for the mold 4.
[0006]
In injection molding of the measuring tube, when the clamping pressure (clamping force) of the mold 4 is insufficient with respect to the molding pressure (injection pressure), the joint 12A between the upper mold 2 and the second lower mold 6 When the molten molding material 9 leaks from the joint portion 12B (hereinafter, these joint portions are referred to as seal portions) between the first lower mold 5 and the second lower mold 6 and solidifies, burrs are generated and excessive leakage occurs. If it does, it becomes impossible to mold. For this reason, the mold 4 is clamped by a plurality of bolts 13 and the clamping plate 14 or is clamped by a hydraulic clamping mechanism so that the seal portions 12A and 12B are not opened.
[0007]
The condition for preventing the seal portions 12A and 12B from opening is that the total projected area of the molded product is D (cm ² ), And the injection pressure is P (Kg / cm ² ) If the clamping force is W (Kg), the following conditions
DP <W
It is necessary to satisfy. The total projected area D is an area in which the inner wall surface of the mold 4 in contact with the molten resin is viewed in the mold clamping force direction (the axial direction of the bolt 13). Therefore, DP represents the component force in the mold clamping direction of the force that the mold 4 receives from the molten resin.
[0008]
[Problems to be solved by the invention]
When the measuring pipe 11 of the electromagnetic flowmeter is a flange type, the flange 10 is usually fitted to the outer periphery of both ends of the pipe body 6a and joined by welding. For this reason, the dimensional accuracy is low, and the axis of the pipe body 6a and the flange 10 may not coincide with each other, or the flange 10 may be inclined with respect to the pipe body 6a. Therefore, there has been a problem that the thickness of the lining material is uneven when injection molding is performed, or the reinforcing pipe 16 is exposed to the outside and becomes defective. Such a problem particularly deteriorates the quality of the molded product because the uneven thickness increases as the measurement pipe having a longer flange-to-face distance (distance between pipe connection end faces) increases.
[0009]
The present invention has been made to solve the above-described problems. The object of the present invention is to reliably prevent the occurrence of uneven thickness of the molding material and to prevent the occurrence of weld lines. Another object of the present invention is to provide an injection molding apparatus.
[0010]
[Means for Solving the Problems]
In order to achieve the above object, a first invention includes a container having a nozzle hole at the bottom for containing a molten molding material, a mold filled with the molding material injected from the container, An injection molding apparatus comprising: a pusher that pressurizes the molding material; and a thrust imparting unit that imparts thrust in a direction in which the pusher substantially pressurizes the molding material in the container to the pusher or the mold. The mold includes a lower mold and an upper mold arranged in a stacked manner, and a core disposed in the lower mold so as to be movable in a horizontal direction, and between the upper portion of the core and the upper mold. A gate ring that forms a runner communicating with the nozzle hole and has a gate that communicates the runner with a cavity of a mold, and has a gate ring that positions the core with respect to the lower mold, the upper mold and the lower mold Between the two. In the present invention, since the core is positioned with respect to the lower mold by the gate ring, the cavity dimension can be maintained correctly, and the occurrence of uneven thickness is prevented.
[0011]
In a second aspect based on the first aspect, the thrust applying means is provided around the nozzle hole and the sprue by applying a downward thrust to the pusher relative to the mold. The seal surfaces and the seal surfaces between the upper mold, the lower mold and the gate ring are in close contact with each other over the entire circumference.
In this invention, since the pusher presses the molding material to make the sealing surfaces in close contact with each other to generate a predetermined surface pressure, the molding material does not leak from the sealing surface, and the mechanism for clamping the mold Or do not need work.
[0013]
Third The invention of the first aspect Or second In the invention, the gate of the gate ring is composed of a plurality of small-diameter gates and large-diameter gates composed of through holes alternately arranged on the same circumference.
In the present invention, the flow rate of the molding material passing through the small-diameter gate is faster than the molding material passing through the large-diameter gate. For this reason, the molding material after passing through the small-diameter gate and the large-diameter gate is mixed with each other to prevent the generation of weld lines.
[0014]
4th The invention of the first, second Or third In the invention, the lower mold is composed of a plurality of stacked members, and at least one of them forms a part of the molded body after molding.
In this invention, since the stacking member also serves as a part of the molded body, no separate mold is required.
[0015]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the present invention will be described in detail based on embodiments shown in the drawings.
FIG. 1 is a schematic configuration diagram showing a part of an embodiment of an injection molding apparatus according to the present invention in a broken state, FIG. 2 is a cross-sectional view showing an embodiment of an injection molding die, and FIG. FIG. 4 is a diagram showing a projected area seen from above, FIG. 4 is a diagram showing a projected area seen from below the upper mold, FIG. 5 is an enlarged sectional view of the main part of the mold, FIG. 6 is a plan view of the gate ring, FIG. Is a sectional view of the gate ring, FIG. 8 is a plan view of the first lower mold member, FIG. 9 is a bottom view of the core, and FIGS. 10A to 10D are AA lines in FIG. It is B line, CC line, and DD line sectional drawing. This embodiment shows an example applied to a pot type vertical injection molding apparatus 20 used for molding for lining a flange type measuring pipe for an electromagnetic flow meter. In FIG. 3, the hatched portion indicates the projected area, and the second circle from the inside indicates the outline of the conical recess formed on the top surface of the bottom plate. In FIG. 4, the hatched portion indicates the projected area, the second circle from the outside indicates the outline of the annular recess formed on the bottom surface of the upper mold, and the third circle from the outside indicates the outline of the conical recess. Yes.
[0016]
In FIG. 1, a frame 25 having sufficient mechanical strength is provided by a base plate 21 with legs installed on the floor, a cylinder mounting plate 23 to which a hydraulic cylinder 22 is fixed, and four struts 24 connecting them. Is configured. The frame 25 works as a thrust applying means for giving a thrust to a pusher 32 described later in cooperation with the hydraulic cylinder 22. Further, a mold mounting plate 26 installed on the base plate 21, an injection molding mold 30 installed on the mold mounting plate 26 via a heat insulating material 27 such as ceramic, and the mold 30 A bottomed cylindrical transfer pot 31 (container) placed on the pusher 32, the pusher 32 that pressurizes the molten molding material 9 in the transfer pot 31, the hydraulic cylinder 22 (thrust applying means) that lowers the pusher 32, etc. Thus, a pot type vertical injection molding apparatus 20 is configured.
[0017]
The hydraulic cylinder 22 is installed downward on the cylinder mounting plate 23 installed above the support column 24, and has a plunger 33 that can be raised and lowered. When the plunger 33 is lowered by hydraulic pressure, the lower end surface of the plunger 33 comes into contact with the upper surface of the pusher 32 and is separated from the upper surface of the pusher 32 when the plunger 33 returns to its upper position.
[0018]
The pusher 32 is formed in a disc shape and is inserted into the transfer pot 31. An appropriate gap is provided between the inner peripheral surface of the transfer pot 31 and the pusher 32, and the work of fitting the pusher 32 into the transfer pot 31 is facilitated by letting air escape through the gap.
[0019]
The transfer pot 31 includes a cylindrical body 31A and a disk-shaped bottom plate 31B that covers the lower opening of the cylindrical body 31A. An annular groove 35 into which the bottom plate 31B is fitted is formed on the inner peripheral surface of the lower end portion of the cylindrical body 31A. It is made slidable in a state where there is almost no gap between the inner peripheral surface of the annular groove 35 and the outer peripheral surface of the bottom plate 31B (that is, a state in which the molten molding material 9 does not leak). A plurality of pins (stopping members) 37 project from the inner periphery of the lower end of the cylindrical body 31A so that the cylindrical body 31A and the bottom plate 31B are not separated, thereby supporting the bottom plate 31B and falling off from the cylindrical body 31A. Is preventing. The bottom plate 31B is restricted in the amount of displacement in the vertical direction by the step portion 38 formed on the inner peripheral surface of the cylindrical body 31A by the annular groove 35 and the pin 37. Further, the bottom plate 31B has a nozzle hole 40 made of a through hole in the center, and a hemispherical protrusion 41 surrounding the nozzle hole 40 is integrally projected at the center of the lower surface. A lower end portion of the peripheral surface of the protrusion 41 forms a seal surface 41 a with the injection mold 30.
[0020]
The injection mold 30 includes an upper mold 44, a lower mold 45, and a gate ring 46 that constitute a stacking member. The upper mold 44 has a conical recess 47 formed at the center of the lower surface and a sixth cooling circuit 80F constituting a cooling mechanism 66 described later formed in the thickness. The upper die 44 further comprises two members, the first and second upper die members 44A and 44B, in order to form the cooling circuit 80F between these members. After the cooling circuit 80F is formed, The first and second upper mold members 44A and 44B are integrated by being fastened by bolts.
[0021]
The concave portion 47 of the upper mold 44 forms a runner 49 together with a core 57 described later. In particular, a portion that opens on the upper surface of the upper mold 44 and communicates with the nozzle hole 40 forms a sprue 50, and the lower end side is The gate ring 46 communicates with a gate 75 described later. A hemispherical recess 53 is formed around the sprue 50 at the center of the upper surface of the upper mold 44, and the protrusion 41 of the bottom plate 31 </ b> B is fitted in the recess 53. The inner wall surface of the recess 53 forms a seal surface 53a in close contact with the seal surface 41a of the protrusion 41, and a seal portion C is formed by these seal surfaces 41a and 53a.
[0022]
When the transfer pot 31 is placed on the upper die 44, when the protrusion 41 of the bottom plate 31B is fitted into the recess 53 of the upper die 44 and the sealing surfaces 41a and 53a are brought into close contact with each other, the nozzle hole 40 and the sprue 50 is automatically positioned and communicated to form the seal portion C. The area of the seal portion C is set to be sufficiently smaller than the areas of the other three seal portions A1, A2, and B described later of the mold 30. In the state where the transfer pot 31 is placed on the upper die 44, the lower end of the cylindrical body 31A is in contact with the upper surface of the upper die 44, so that the transfer pot 31 is satisfactorily seated. Since the transfer pot 31 is simply placed on the upper die 44 and is not fixed at all, if the pusher 32 is not receiving thrust from the hydraulic cylinder 22, it is placed on the upper die 44. It is also possible to rotate in the horizontal plane with the projection 41 and the recess 53 as the rotation axis (necessary for cutting the solidified molding material between the nozzle hole and the sprue described later).
[0023]
The lower mold 45 includes first and second lower molds 55 and 56 (both are stacked members) and the core 57. The first lower mold 55 includes first and second lower mold members 55A and 55B arranged in a stacked manner, and is positioned on the mold attachment plate 26 via the heat insulating material 27. It is fixed. The second lower mold 56 and the core 57 are installed on the first lower mold 55, and the upper mold 44 is installed on the first lower mold 55 via the gate ring 46.
[0024]
The first lower mold member 55A has a hole 60 through which a lower end portion of the core 57 is inserted with an appropriate gap at the center, and an annular recess 61 surrounding the hole 60 on the upper surface. Is formed. The upper surface outside the concave portion 61 forms a seal surface 66a with which the outer peripheral portion of the lower surface of the second lower mold 56 is in close contact.
[0025]
As the second lower mold 56, a measuring tube for an electromagnetic flow meter that has not been subjected to a lining process is used. The second lower die 56 has a cylindrical tube main body 56a whose inner diameter is larger than the outer diameter of the core 57, and the same shape that is fitted to both end openings of the tube main body 56a and fixed by welding 62. It consists of two flanges 56b and 56c. A reinforcing tube 16 formed of a perforated plate is disposed inside the tube main body 56 a via a spacer 17.
[0026]
On the pipe connection end faces of the flanges 56b and 56c, annular grooves 63A and 63B filled with the molding material 9 are formed, respectively. The lower surface of the upper flange 56b forms a seal surface 65a in contact with the lower surface side seal surface 64a of the gate ring 46, and the seal portion A2 is formed by these seal surfaces 64a and 65a.
[0027]
The lower surface of the lower flange 56c forms a seal surface 67a in close contact with the seal surface 66a of the first lower mold member 55A, and the seal portion B is formed by these seal surfaces 66a and 67a. Yes. The seal surface 66a is a surface outside the annular groove 63B.
[0028]
The core 57 includes a cylindrical core main body 57A, the cylindrical body 57B fitted to the core main body 57A, and a conical body 57C fixed to the upper surface of the cylindrical body 57B by welding. First to fifth cooling circuits 80A to 80E of the cooling mechanism 66 are formed. A space provided between the core 57 and the first and second lower molds 55 and 56 forms a cavity 8 filled with the molding material 9. The cylindrical body 57B is fitted into the core main body 57A, and a lower end portion is inserted into an annular groove 70 formed on the upper surface of the second lower mold member 55B so as to be movable in the radial direction. The conical body 57 </ b> C is inserted into the recess 47 of the upper mold 44 with an appropriate gap, and this gap forms the runner 49 through which the molding material 9 passes.
[0029]
5 to 7, the gate ring 46 is used for positioning the core 57 with respect to the second lower mold 56 and for communicating the runner 49 and the cavity 8 of the mold 30. It is interposed between the upper die 44 and the second lower die 56, and the outer periphery of the upper end portion of the cylindrical body 57B is detachably inserted. For this reason, the gate ring 46 has a center hole 70 through which the core 57 passes, and the fitting tolerance between the center hole 70 and the core 57 is set to be small so that the axes of these members substantially coincide. Has been. The upper surface of the gate ring 46 is a flat surface, and is fitted in close contact with an annular groove 71 provided on the lower surface of the upper mold 44. Therefore, the outer peripheral portion of the upper surface of the gate ring 46 and the outer peripheral portion of the bottom surface of the annular groove 71 form seal surfaces 46a and 71a that are in close contact with each other, and the seal portion A1 is formed by these seal surfaces 46a and 71a. ing. The areas of the seal portions A1, A2, and B are substantially equal.
[0030]
Further, the gate ring 46 has an annular groove 64 on the lower surface side, and the annular groove 64 is fitted to a projection 65 projecting from the pipe connection end surface of the upper flange 56b of the second lower mold 56, and these are mutually connected. The close contact portion forms a seal portion A2 composed of the seal surfaces 64a and 65a. The seal surface 64a is an outer peripheral portion of the bottom surface of the annular groove 64, and the seal surface 65a is an upper surface of the protrusion 65a.
[0031]
Further, the gate ring 46 has a gate 75 for communicating the runner 49 formed by the upper mold 44 and the core 57 with the cavity 8 of the mold 30 through the annular groove 64. As shown in FIG. 6, the gate 75 is composed of a plurality of small-diameter gates 75A and large-diameter gates 75B each formed of a through hole formed on the same circumference with the center of the gate ring 46 as the center. . Further, the small-diameter gates 75A and the large-diameter gates 75B are formed so as to be adjacent to each other, and are located near the outer periphery of the annular groove 63A of the upper flange 56b. When such a gate ring 46 is installed on the upper surface of the upper flange 56b by fitting the projection 65 and the annular groove 64, the core 57 is forcibly positioned with respect to the second lower mold 56 and is centered. Match.
[0032]
2 and 8 to 10, the cooling mechanism 66 of the mold 30 has first to sixth cooling circuits 80A to 80F. The first cooling circuit 80A is composed of an annular groove 81 formed on the lower surface side of the first lower mold member 55A, and a through hole provided in the second lower mold member 55B, and communicates with the annular groove 81, respectively. It comprises a port 82, an air discharge port 83 and the like. The air supply port 82 is connected to an air supply source (not shown), and the air discharge port 83 is open to the atmosphere.
[0033]
The second to fifth cooling circuits 80B to 80E are formed inside the core 57, and have annular grooves 85 to 88 formed on the outer peripheral surface of the core body 57A so as to be spaced apart in the axial direction. The annular grooves 85 to 88 are communicated with the air supply passages 89a to 89d and the air discharge passage 90 formed in the core body 57A through the communication passages 91a to 91d and 92a to 92d, respectively. . The air supply passages 89a to 89d are non-through holes that open to the lower surface of the core body 57A, and are formed around the air discharge passage 90 at a required angle in the circumferential direction. That is, as shown in FIG. 90, the air supply passages 89a to 89d are formed to be spaced apart by 135 ° in the clockwise direction. Therefore, the air supply passage 89b is spaced 135 ° clockwise from the air supply passage 89a, the air supply passage 89c is spaced 135 ° clockwise from the air supply passage 89b, and the air supply passage 89d is It is spaced 135 ° clockwise from the supply passage 89c. The air discharge passage 90 is a non-through hole that opens to the center of the lower surface of the core body 57A, and has a larger hole diameter than the air supply passages 89a to 89d.
[0034]
In FIG. 8, the second lower mold member 55B includes passages 95a to 95d, 96 communicating with the air supply passages 89a to 89d and the air discharge passage 90 in addition to the air supply port 82 and the air discharge port 83. Is formed. These passages 95a to 95d, 96 are formed by through holes penetrating the upper and lower surfaces of the second lower mold member 55B. Each of the passages 95a to 95d is connected to an air supply source, and the passage 96 is open to the atmosphere.
[0035]
In FIG. 2, the sixth cooling circuit 80 </ b> F has an annular groove 98 formed in the upper mold 44, and an air supply port 99 and an air discharge port 100 communicating with the annular groove 98. The air supply port 99 is connected to an air supply source (not shown), and the air discharge port 100 is open to the atmosphere.
[0036]
A plurality of support members 102 are provided between the upper mold 44 and the first lower mold 55. The support member 102 is erected on the first lower mold 55, the connecting bolt 103 is screwed to the upper end, and the head abuts against the lower surface of the second upper mold member 44 B, and is molded. You can choose whether to attach or remove depending on conditions. Here, since it demonstrates supposing the removed state first, please refer FIG. 1, FIG. 2 as what the support member 102 and the connection bolt 103 are not drawn. The state where the support member 102 and the connecting bolt 103 are mounted as shown in FIGS. 1 and 2 will be described later.
[0037]
Such an injection mold 30 is simply assembled by stacking and arranging the upper mold 44, the lower mold 45 and the transfer pot 31 by their own weight, and the bolt 13 and the mold clamping plate 14 shown in FIG. Is not equipped with a mold clamping mechanism, and the conventional mold is sealed in that the four seal portions A1, A2, B, and C are sealed by using the force of pressing the molding material 9 with the pusher 32. Basically different.
[0038]
In order to form the measuring pipe of the electromagnetic flow meter by lining the inner peripheral surface of the second lower mold 56 and the annular grooves 63A and 63B of the flanges 56b and 56c using such an injection molding apparatus 20, first, The mold 30 is installed on the mold mounting plate 26. At this time, the core 57 is positioned by the gate ring 46. That is, when the upper outer periphery of the core 57 is fitted in the annular groove 70 of the gate ring 46 in advance and the gate ring 46 is fitted to the annular projection 65 of the upper flange 56b, the second lower mold 56 and the gate ring 46 are fitted. And the axis of the core 57 is forcibly matched with the axis of the second lower mold 56. Therefore, the core 57 is positioned at the center of the first and second lower molds 55 and 56 without being displaced or inclined with respect to the second lower mold 56. After the core 57 is positioned by the gate ring 46, the annular groove 71 of the upper die 44 is further fitted to the gate ring 46 from above so that the axes of the upper die 44 and the second lower die 56 are aligned with each other. A transfer pot 31 is installed on the top.
[0039]
Next, the metal mold | die 30 is installed in a heating furnace with the transfer pot 31 and the molding material 9, and it heats to predetermined temperature (350-370 degreeC). While the molding material 9 is heated and melted, the pusher 32 is removed from the transfer pot 31 and kept at room temperature, and is attached to the transfer pot 31 immediately before the operation of injecting the molten molding material 9 into the cavity 8. .
[0040]
The heated mold 30 and transfer pot 31 are placed on the mold mounting plate 26, the hydraulic cylinder 22 is driven, and the pusher 32 is pressed by the plunger 33, thereby giving a predetermined thrust Fl to the pusher 32. When the pusher 32 is given a thrust Fl and pressurizes the molding material 9, the molding material 9 is pressurized and injected into the cavity 8 from the nozzle hole 40 of the bottom plate 31 </ b> B through the sprue 50, the runner 49 and the gate 75. The pressure injection time of the molding material 9 by the pusher 32 is about 2 minutes, and the air in the cavity 8 is discharged from the seal portions A1, A2, and B to the outside by the injection pressure P by the pusher 32. That is, the seal portions A1, A2, and B are processed to have a surface roughness enough to discharge air but not molten resin. Since air and molten resin have vastly different viscosities, this can be achieved by adjusting the surface roughness of the seal portions A1, A2, and B.
[0041]
When the molten molding material 9 is pressurized by pushing down the pusher 32, the molding material 9 is injected from the nozzle hole 40 while pressing the bottom plate 31B downward, and a radial gap between the transfer pot 31 and the pusher 32 (usually normal) Trying to leak upward through one side (about 0.3-1.0 mm). If the temperature of the pusher 32 is set lower than the temperature of the molding material 9, the molding material 9 in contact with the pusher 32 is rapidly cooled and solidified to close the gap and act as a packing. There is no leakage to the outside. Further, the molten molding material 9 pushes the molding material 9 solidified in the gap by the pressure upward. The molding material 9 solidified in the gap acts to lift the transfer pot 31 upward by the frictional force with the transfer pot 31. Then, the lower end of the cylindrical body 31 </ b> A of the transfer pot 31 is separated from the upper surface of the upper mold 44. When the pin 37 eventually hits the lower surface of the bottom plate 31B, the transfer pot 31 is prevented from being lifted further. In this state, the transfer pot 31 and the upper mold 44 are in contact with each other only at the seal portion C, and most of the thrust Pl applied to the pusher 32 is added to the seal portion C. As described above, since the area of the seal portion C is smaller than any of the seal portions A1, A2, and B, a sufficiently large seal pressure is generated in the seal portion C, and the molten molding material 9 from the seal portion C is generated. Leakage can be prevented.
[0042]
The force Fl that the hydraulic cylinder 22 pushes down the pusher 32 acts on the area S1 of the lower surface of the pusher 32 and generates an injection pressure P in the molding material 9 melted inside the transfer pot 31. The force Fn generated on the bottom plate 31B in response to the injection pressure P is downward and acts to press the upper die 44 against the gate ring 46 via the seal portion C. Strictly speaking, the weights of the pusher 32, the transfer pot 31, the molding material 9, and the upper die 44 also work so as to press the upper die 44 downward, but as will be described later, they are negligibly small with respect to Fn. When the second lower mold 56 is pressed against the first lower mold 55, a clamping force of the same magnitude is generated between them. The pressing force Fn of the bottom plate 31B against the mold 30 is obtained from the projected area Sn (hatched portion in FIG. 3) when the pressure receiving surface of the bottom plate 31B is viewed in the direction of the force Fl and the injection pressure P.
Fn = P · Sn = Fl · Sn / Sl
[0043]
On the contrary, an upward thrust (force for pulling the upper mold 44 away from the second lower mold 56) Fm is generated in the mold 30 by the injection pressure P. This thrust Fm is obtained from the projected area Sm (shaded portion in FIG. 4) of the upper mold 44 and the injection pressure P.
Fm = P · Sm
[0044]
Therefore, the force F pressing the seal portions A1, A2, B of the mold 30 by the pressing force Fn against the upper mold 44 of the bottom plate 31B is:
F = Fn−Fm
It becomes.
When Fn is smaller than Fm, the upper mold 44 is lifted, so that the seal is damaged.
[0045]
When the area of each seal portion A1, A2, B is S1, S2, S3 and the pressure (seal pressure) generated in each seal portion A1, A2, B is Pa1, Pa2, Pa3, the seal pressure Pa1 at the seal portion A1. Is
Pa1 = (Fn-Fm) / S1 = (Sn-Sm) P / S1
It becomes.
The seal pressure Pa2 at the seal part A2 is
Pa2 = (Fn-Fm) / S2 = (Sn-Sm) P / S2
It becomes.
The seal pressure Pa3 at the seal part B is
Pa3 = (Fn-Fm) / S3 = (Sn-Sm) P / S3
It becomes.
[0046]
Here, how much the weight of the molding material 9, the upper mold 44, the second lower mold 56, the transfer pot 31 and the like actually affects the seal ratio (a value obtained by dividing the seal pressure Pa by the injection pressure P) K. As a result, the total weight of the molding material 9, the upper mold 44, the second lower mold 56, the transfer pot 31 and the like when the diameter of the measurement tube is 100 mm and 40 mm is about 21.5 kg and 4.3 kg, respectively. Then, since the total weight is extremely small compared to the pressing force Fn by the bottom plate 31B (when the diameter is 100 mm: 5148 Kgf, when the diameter is 40 mm: 1825 Kgf) and the thrust Fm (when the diameter is 100 mm: 3382 Kgf, when the diameter is 40 mm: 1378 Kgf). It has been found that the influence on the seal ratio K is extremely small and can be ignored as the error range. As will be described later, the seal ratio K was 2.04 when the aperture was 100 mm, and 1.41 when the aperture was 40 mm.
[0047]
In order to prevent leakage of the molding material 9 from the seal portions A1, A2, and B, the minimum condition (that is, the necessary condition) is that the seal pressures Pa1, Pa2, and Pa3 are positive values. Experiments were conducted to determine whether the molding material 9 would not leak if pressure was applied.
As is clear from the above formula, if the thrust of the pusher 32 is increased, the injection pressure P and the sealing pressures Pa1, Pa2, Pa3 are increased. However, it has been found that if the thrust of the pusher 32 is excessively increased, internal stress remains in the molded product, causing deformation and cracking due to cracks.
[0048]
Here, the concept of seal ratio K is introduced. That is, the seal ratios K (K1, K2, K3) are values Pa1 / P, Pa2 / P, Pa3 / P obtained by dividing the seal pressures Pa1, Pa2, Pa3 by the injection pressure P.
[0049]
The seal ratios K1, K2, and K3 are determined at the time of designing the injection molding apparatus 20. As described above, when the actual molding is smaller than the constant value C determined by the type, viscosity, temperature, etc. of the molding material 9, the molding material 9 is used. Leaks from the seal portions A1, A2 and B, and if it is large, it will not leak. The constant value C is a value obtained inductively by experiment, and when molding is actually performed by changing the seal ratios K1, K2, and K3, the type, viscosity, and temperature of the molding material 9, the leakage of the molding material 9 stops. The seal ratios K1, K2, and K3. For example, assuming that the leakage of the molding material 9 from the seal portion A1 is stopped when molding is performed with the seal ratio K1 being 0.3, the constant value C is 0.3. Therefore, in order to prevent the molding material 9 from leaking from the seal portion A1, the seal ratio K1 needs to be larger than 0.3. That is, in order to prevent the molding material 9 from leaking from the seal portions A1, A2, and B,
Pa / P> C
It is sufficient to satisfy the conditions.
[0050]
In the experiment, a mold having a large seal area S1, S2, and S3 is manufactured and molded, and the seal portions A1, A2, and B are gradually scraped to gradually reduce the seal areas S1, S2, and S3. The molding is repeated by increasing the ratios K1, K2, and K3, and the seal ratios K1, K2, and K3 when the leakage of the molding material 9 from the seal portions A1, A2, and B stops are set to a constant value C. As described above, since the seal portion C has a smaller area than the seal portions A1, A2 and B, a considerably large seal ratio can be obtained, and there is no practical problem.
[0051]
After the injection of the molding material 9 is completed, it is left for several minutes while maintaining the thrust Fl from the hydraulic cylinder 22, and the residual stress distribution of the molded body is made uniform. Next, air as a cooling medium is supplied to the cooling circuit 66 to cool the mold 30 from the inside for a certain time, and the molding material 9 in the cavity 8 is solidified.
[0052]
FIG. 11 shows a procedure for cooling the mold 30. The mold 30 is cooled by sequentially supplying the compressed air 120 to the first to sixth cooling circuits 80A to 80F for a predetermined time, and the molding material 9 in the cavity 8 is gradually solidified from the bottom to the top. Let In this way, the molten molding material 9 is replenished from the transfer pot 31 in accordance with the volume shrinkage generated by the solidification of the molding material 9 in the cavity 8, and a clean molded body free from sink marks can be obtained.
[0053]
When the transfer pot 31 is rotated after the molding material 9 is solidified, the molding material 9 can be easily cut at the connection portion between the nozzle hole 40 and the sprue 50. Next, the upper die 44 is lifted together with the transfer pot 31 to take out the second lower die 56 from the first lower die 55, and the molding material 9 solidified at the flash, runner 49 and gate 75 portions is cut. Finish molding. The second lower mold 56 is used as a measurement pipe which is a molded product in which the inner peripheral surface and the pipe connection end faces of the flanges 56b and 56c are covered with a lining material. When the measurement tube is subsequently formed, a new second lower die 56 is placed on the first lower die 55, and the upper die 44 and the transfer pot 31 are further placed thereon, and the above procedure is followed. Therefore, molding is performed.
[0054]
In such an injection molding apparatus 20, since it is not necessary to clamp the mold 30, the structure is simple and the number of parts can be reduced as compared with the conventional injection mold 4 shown in FIG. A molding cycle can be shortened and productivity can be improved.
[0055]
Further, since the core 57 is installed on the first lower mold 55 so as to be movable in the radial direction, when the gate ring 46 is positioned and installed on the second lower mold 56, the gate ring 46 is placed in the middle. The child 57 is positioned with respect to the second lower mold 56 so that the axes are substantially coincident. Therefore, uneven thickness does not occur, the dimensional accuracy of the thickness of the molded body can be increased, and the defect rate can be reduced.
[0056]
Further, since the gate 75 of the gate ring 46 is composed of a plurality of alternately adjacent small-diameter gates 75A and large-diameter gates 75B, the generation of weld lines can be prevented. That is, when the gate 75 is composed of a plurality of holes having the same size, the molding material 9 immediately after passing through each hole comes into contact with each other in a laminar flow with a substantially constant velocity. Therefore, the contact portion becomes a weld line, and a striped pattern is formed on the surface of the molded product. In order to minimize the generation of weld lines, it is effective to reduce the gate diameter and the gate interval. However, since the gate diameter and the ease of flow of the molding material are generally proportional to the cube of the gate diameter, the smaller the gate diameter, the less difficult it will flow, and the molding time will be longer and it will cause molding defects. Therefore, it is not preferable.
[0057]
Therefore, when the gate 75 is composed of two types of gates 75A and 75B having different hole diameters and these are alternately arranged, the occurrence of weld lines can be remarkably reduced. The reason why the weld line decreases is not clear, but the flow rates of the molding material 9 passing through the small-diameter gate 75A and the large-diameter gate 75B are different. It is thought that the weld line is made difficult to be generated by mixing with each other due to the difference in speed upon contact.
[0058]
【Example】
When PFA resin 450HP-J manufactured by Mitsui DuPont Fluoro Chemical Co. is used as the molding material 9, when the mold temperature is 360 ° C, the resin temperature is 360 ° C, and the seal ratio K is 0.32, It was confirmed that no leakage occurred.
[0059]
In the above description, the case where the supporting member 102 and the connecting bolt 103 are removed and molding is performed in FIG. 2 has been described. However, when the pressing force F = Fn−Fm is large and the mold 30, particularly the second lower mold 56 that is a molded product is thin and the strength is low, the second lower mold 56 is plastically deformed by buckling. Or may be destroyed.
[0060]
Then, in order to solve such a problem, an embodiment in the case where the supporting member 102 and the connecting bolt 103 are mounted and molded in FIG. 2 will be described.
In the present embodiment, the support member 102 is interposed between the upper die 44 and the first lower die 55, and the connecting bolt 103 is brought into contact with the upper die 44 so that the upper die 44 and the second lower die are in contact. A part of the pressing force Fn transmitted to 56 is received by the support member 102 to reduce the pressing force F applied to the second lower mold 56.
[0061]
The support member 102 is formed in a columnar shape that can be elastically deformed by compression, and is vertically erected at equal intervals in the circumferential direction near the outer periphery of the first lower die 55 so that the upper end thereof is the first. It extends above the lower die 55 and has a screw hole 104 into which the connecting bolt 103 is screwed at the center of the upper and lower surfaces. As the material of the support member 102, hardened steel or the like is used.
[0062]
The connection bolt 103 is made of hardened steel, and is screwed into the screw hole 104 of each support member 102 and is adjusted so that the head of the upper connection bolt contacts the lower surface of the upper mold 44. The structure of the mold 30 itself is exactly the same as when the support member 102 is not used.
[0063]
In the injection mold 30 using such a support member 102, when a thrust Fl is applied to the pusher 32 to press the molten molding material 9 in the transfer pot 31 and inject it into the cavity 8 of the mold 30, the pressing force Fn is added to the mold 30 and the support member 102 through the mold 30. For this reason, although the support member 102 mainly bends, the elastic force (reaction force) R of the support member 102 acts on the upper mold | type 44 at this time, and functions as a tension rod. Therefore, the pressing force F applied to the mold 30 is reduced, and even if the second lower mold 56 has a low strength, it is not plastically deformed or broken due to buckling, and the resin that requires high pressure is used. The present invention can also be applied to lining and molding of a measuring tube with low strength.
[0064]
Next, the seal ratio K in the injection mold 30 will be described.
The support member 102 and the second lower mold 56 are contracted by Δl by the injection pressure P.
[0065]
[Expression 1]

[0066]
[Expression 2]

[0067]
here,
P is injection pressure
Sn is the projected area viewed from above the bottom plate
Sm is the projected area viewed from below the upper mold
Sa is the seal area
Sr is the cross-sectional area of the support member (support member body)
Sp is the cross-sectional area of the second lower mold
Fn is the downward force generated by the injection pressure (= P · Sn)
Fm is the force to push up the mold by the injection pressure (= P · Sm)
Fr is the force applied to the support member
Fp is the force applied to the second lower mold
Lp is the length between the flanges of the second lower mold
Lr is the length of the support member
Δl is the amount of shrinkage of the support member
E is the Young's modulus of the support member (assuming the same as the Young's modulus of the second lower mold)
n is the number of support members.
It is assumed that the flange portions 56b and 56c of the second lower mold 56 and the connecting bolt 103 are not deformed.
[0068]
Considering the balance of power
(Fn−Fm) = nFr + Fp (2)
When the above equation (A) is substituted into equation (2)
[0069]
[Equation 3]

[0070]
The seal ratio K is obtained using the above equation (B). The seal pressure Pa is expressed by the following formula.
[0071]
[Expression 4]

The seal ratio K is obtained by dividing both sides of the above equation (4) by P.
[Equation 5]

[0072]
[Formula 6]

[0073]
The previous term of the above equation (6) is a normal seal ratio, the latter term is a decrease by the support member, and the reduction ratio of the seal ratio is expressed by the following equation.
[0074]
[Expression 7]

[0075]
In the above-described embodiment, an example is shown in which the present invention is applied to the injection molding apparatus 20 for lining the inner peripheral surface of the measurement pipe for electromagnetic flowmeter and the pipe connection end face of the flange. However, the present invention is not limited to this. For example, containers and cups, especially those used in the clean room of a semiconductor manufacturing plant, are made of approximately 100% fluororesin, so they can be manufactured at low cost by using the injection molding apparatus according to the present invention. Can do.
In the above-described embodiment, since the molded product is a measurement tube, the lower mold 45 of the mold 30 is configured by the first and second lower molds 55 and 56 and the core 57, and the second Although an example in which the lower die 56 is configured with a measuring tube has been shown, the mold may be configured with an upper die, a lower die, and a core depending on a molded product.
Further, as a means for giving thrust to the pusher 32, the plunger 33 is not lowered by the hydraulic cylinder 22 to push down the pusher 32. Conversely, the pusher 32 is fixed and the die 30 is lifted using a hydraulic jack. Thus, a thrust may be relatively applied to the pusher 32.
[0076]
【The invention's effect】
As described above, since the injection molding apparatus according to the present invention positions the core with respect to the lower mold by the gate ring, uneven thickness does not occur, and the dimensional accuracy of the thickness of the molded body can be improved. . Furthermore, since the gate is composed of a small-diameter gate and a large-diameter gate, and the flow rate of the molding material passing through these gates is varied, a weld line is not generated on the surface of the molded product, and the quality can be improved. .
[0077]
In addition, according to the present invention, the pressure that presses the molding material of the pusher is used to generate a surface pressure on the sealing surface of the mold, thereby preventing the molding material from leaking outside. There is no need to clamp the mold with a clamping or hydraulic mold clamping mechanism, which simplifies the injection molding device and reduces the cost of mold production, and facilitates assembly and disassembly of the mold to improve productivity. Can be made. Further, since there is no leakage of the molding material, the defect rate can be reduced. Furthermore, since a part of the parts constituting the molded body is also used as a mold, a separate mold is not required.
[Brief description of the drawings]
FIG. 1 is a schematic configuration diagram showing a part of an embodiment of an injection molding apparatus according to the present invention in a cutaway manner.
FIG. 2 is a cross-sectional view showing an embodiment of an injection mold.
FIG. 3 is a diagram showing a projected area viewed from above the bottom plate.
FIG. 4 is a diagram showing a projected area viewed from below the upper mold.
FIG. 5 is an enlarged cross-sectional view of a main part of a mold.
FIG. 6 is a plan view of the gate ring.
FIG. 7 is a cross-sectional view of the gate ring.
FIG. 8 is a plan view of a first lower mold member.
FIG. 9 is a bottom view of the core.
10A to 10D are cross-sectional views taken along lines AA, BB, CC, and DD in FIG.
FIG. 11 is a diagram showing a cooling sequence.
FIG. 12 is a cross-sectional view of a conventional mold for an injection molding apparatus.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 8 ... Cavity, 9 ... Molding material, 20 ... Injection molding apparatus, 22 ... Hydraulic cylinder, 30 ... Mold for injection molding, 31 ... Transfer pot, 31A ... Cylindrical body, 31B ... Bottom plate, 32 ... Pusher, 40 ... Nozzle hole 41a ... sealing surface, 44 ... upper die, 45 ... lower die, 46 ... gate ring, 49 ... runner, 50 ... sprue, 51 ... gate, 53a ... seal surface, 55 ... first lower die, 56 ... first 2 lower molds, 56b, 56c ... flange, 57 ... core, 64a, 65a, 66a, 67a ... sealing surface, 75 ... gate, 75A ... small diameter gate, 75B ... large diameter gate, A1, A2, B, C ... Seal part.

Claims (4)

A container having a nozzle hole at the bottom and containing a molten molding material, a mold filled with the molding material injected from the container, a pusher that pressurizes the molding material in the container, and the pusher or the An injection molding apparatus comprising: a thrust imparting means that imparts thrust in a direction in which the pusher substantially pressurizes the molding material in the container to a mold;
The mold includes a lower mold and an upper mold arranged in a stacked manner, and a core disposed in the lower mold so as to be movable in a horizontal direction, and the upper mold is interposed between the upper mold and the upper mold. A runner communicating with the nozzle hole is formed, and a gate ring is provided between the upper mold and the lower mold, the gate ring having a gate that communicates the runner and the mold cavity, and positioning the core with respect to the lower mold. An injection molding apparatus characterized by being interposed therebetween. The injection molding apparatus according to claim 1, wherein
The thrust applying means applies a downward thrust to the pusher relative to the mold, thereby sealing surfaces provided around the nozzle hole and the sprue, and the upper mold, the lower mold, and An injection molding apparatus characterized in that the sealing surfaces between the gate rings are in close contact with each other over the entire circumference. The injection molding apparatus according to claim 1 or 2 ,
The gate of the said gate ring is comprised with the some small diameter gate which consists of the through-hole arranged in parallel by turns on the same periphery, and a large diameter gate, The injection molding apparatus characterized by the above-mentioned. In the injection molding apparatus according to claim 1, 2, or 3 ,
The lower mold includes a plurality of stacked members, and at least one of them forms a part of a molded body after molding.

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