JP2009090602A - Sink mark-preventing device in resin molding - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a technique capable of preventing generation of a sink mark only by using resin pressure. <P>SOLUTION: The sink mark-preventing device 10 has a first pin 11, a first elastic member 32, a second pin 16, a second elastic member 35, a clutch ball 20, and a tubular body 21 as fundamental components. The first elastic member urging the first pin is compressed by the first pin and the second pin, and sufficiently strong elastic energy is stored in the first elastic member. When the second pin 2 recedes at a predetermined distance, the clutch ball is detached and the first pin becomes free. When the resin solidifies and shrinks, the first pin is pushed out by the first elastic member to push the resin strongly. Consequently the sink mark can be sufficiently prevented. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an apparatus for suppressing the occurrence of sink marks that occur during resin molding.

FIG. 5 is a view for explaining sink marks that occur during resin molding. The resin product 100 may be provided with thick ribs 101. The rib 101 is used for a reinforcing part, a screw seat, and the like.
The molten resin is cooled by the mold, but the rib 101 is thick, so the cooling to the center is slow. On the other hand, volume contraction occurs when the molten resin is cooled and solidified.
For this reason, sink marks 102 are generated in the resin product 100 by being pulled by the ribs 101.

In order to reduce the product quality, sink 102 needs to be prevented from occurring, and a countermeasure for this has been proposed (for example, see Patent Document 1).
JP-A-9-76306 (FIG. 2)

Patent document 1 is demonstrated based on the following figure.
FIG. 6 is a diagram for explaining the basic principle of the prior art. As shown in FIG. 6A, a movable pin 112 is provided so that the tip faces the cavity 111. This movable pin 112 is an elastic member 113. It is energized.
When the molten resin 114 is filled into the cavity 111, the pressure of the resin acts on the movable pin 112 indicated by the imaginary line, and the retracted (lowered) to the position indicated by the solid line. That is, the vehicle moves backward by the distance L1.

  The molten resin 114 is cooled by the mold 115 and solidifies. Shrink during solidification. As shown in (b), the movable pin 112 rises in conjunction with the contraction and suppresses the occurrence of sink marks.

  However, it has been found that the movable pin 112 is not sufficiently raised, and the occurrence of sink marks has not been sufficiently prevented. That is, the conventional technique of lowering the movable pin 112 using the pressure of the resin is not sufficient as a countermeasure.

  As a further countermeasure, a method of forcibly moving the movable pin with the hydraulic cylinder is conceivable. However, it is necessary to separately install the hydraulic cylinder and provide a hydraulic supply source and a hydraulic switching valve, which increases the equipment cost.

  Therefore, there is a demand for a technique that can sufficiently suppress the occurrence of sink marks only by using the pressure of the resin.

  This invention makes it a subject to provide the technique which can suppress generation | occurrence | production of sink marks only by utilizing the pressure of resin.

According to the first aspect of the present invention, the front end faces the cavity, is supported by the moving plate disposed outside the mold so as to be axially movable, the rear end is pressed against the cavity by the first elastic member, and the front end A first pin in which a side is a small diameter portion and a rear end side is a large diameter portion, and a step portion of the large diameter portion and the small diameter portion is connected by a concave curved surface;
A hollow second pin that has a front end facing the cavity, is supported by the moving plate so as to be axially movable, a rear end is pressed by a second elastic member, and the first pin is movably accommodated;
The ball diameter is set to a half value of the difference between the outer diameter of the second pin and the outer diameter of the small-diameter portion of the first pin, and the ball hole penetratingly formed in the hollow second pin A clutch ball housed so as to be movable in a direction perpendicular to the axis of the second pin;
A clutch ball fixed to the moving plate for accommodating the second pin so as to be movable in the axial direction, and a clutch ball facing the inner peripheral surface of the cylinder has a constant second pin. A cylinder whose length is set so as to be disengaged from the end of the cylinder when the distance is retracted;
An sink suppression device in resin molding comprising:

  The invention according to claim 2 is characterized in that the second pin is a protruding pin that plays a role of protruding the product from the mold, and the moving plate is a protruding plate that moves the protruding pin.

  The invention according to claim 3 is characterized in that the rear end of the second pin is pressed by a second elastic member having a smaller elastic coefficient than that of the first elastic member.

  The invention according to claim 4 is characterized in that the thickness of the cylindrical body is set to a value that is half the difference between the outer diameter of the large-diameter portion of the first pin and the outer diameter of the small-diameter portion.

In the present invention, the pressure of the resin acts on the first pin and the second pin. The second pin is connected to the first pin by the clutch ball. Then, the 1st elastic member which is energizing the 1st pin is compressed with the 1st pin and the 2nd pin. A sufficiently strong elastic energy is accumulated in the first elastic member.
When the second pin moves backward by a certain distance, the clutch ball is released and the first pin becomes free. When the resin solidifies and contracts, the first pin is pushed out by the first elastic member and strongly presses the resin. As a result, the occurrence of sink marks can be sufficiently suppressed.
That is, according to the present invention, there is provided a technique capable of suppressing the occurrence of sink marks only by using the pressure of the resin.

  In particular, in the invention according to claim 2, the second pin is a protruding pin, and the moving plate is a protruding plate that moves the protruding pin. The protruding pin and protruding board are ancillary facilities essential to the mold. Since the incidental facility is used, the manufacturing cost of the sink suppression device can be suppressed.

The best mode for carrying out the present invention will be described below with reference to the accompanying drawings. The drawings are viewed in the direction of the reference numerals.
FIG. 1 is a configuration diagram of a sink suppression device according to the present invention. The sink suppression device 10 includes a first pin 11, a first elastic member 32, a second pin 16, and a second elastic member 35. The clutch ball 20 and the cylinder 21 are the basic elements.

These basic elements are described in detail below.
The first pin 11 is a stepped solid member having a small diameter portion 12 on the front end side, a large diameter portion 13 on the rear end side, and a spring receiver 14 on the rear end. The steps of the small diameter portion 12 and the large diameter portion 13 are smoothly connected by a concave curved surface 15. The radius of curvature of the concave curved surface 15 is set to a size corresponding to the radius of the clutch ball 20.

  The second pin 16 is a hollow member that accommodates the first pin 11 so as to be movable in the axial direction. The second pin 16 includes ball holes 17 and 17 that are formed so as to penetrate in the direction perpendicular to the axis. 18 is provided.

The clutch balls 20 will be described with reference to FIG.
The cylindrical body 21 is fixed by a protruding board 24 as a moving board with a flange 22 and a bolt 23, accommodates the second pin 16 movably, and includes a tapered portion 25 at the end. In addition, the taper part 25 is set in the place extended only L (FIG. 3 (a)) from the clutch ball 20 in an initial position. This distance L is a predetermined moving distance of the second pin 16, and will be described in detail later.

  A protruding board 24 is arranged outside the mold 27 indicated by an imaginary line, and an auxiliary board 28 is arranged outside the protruding board 24. The protruding board 24 and the auxiliary board 28 are separated for convenience, and can be moved together by the connecting plate 29 and the protruding cylinder 31.

  The auxiliary board 28 is provided with a first recess 33 for storing the spring receiver 14 of the first pin 11 and for storing the first elastic member 32 having a large elastic coefficient. A spring receiving plate 34 for preventing the first elastic member 32 from coming off is provided.

  The protruding plate 24 is provided with a second recess 36 for storing the spring receiver 18 of the second pin 16 and a second elastic member 35 having a small elastic coefficient. The second recess 36 stores the second recess 36. A spring receiving plate 37 is provided to prevent the second elastic member 35 from coming off.

2 is a cross-sectional view taken along line 2-2 of FIG. 1, and a hollow second pin 16 is accommodated in the cylindrical body 21, and the small-diameter portion 12 of the first pin 11 is accommodated in the second pin 16. The clutch ball 20 is housed in the ball hole 17 of the second pin 16.
The clutch ball 20 has a spherical diameter that is half the difference between the outer diameter D2 of the second pin 16 and the outer diameter D1 of the small-diameter portion 12 of the first pin.
Further, as shown in FIG. 1, the thickness T of the cylindrical body 21 is set to a value that is half of the difference between the outer diameter D3 of the large-diameter portion 13 of the first pin 11 and the outer diameter D1 of the small-diameter portion 12. Has been.

The operation of the sink suppression device having the above configuration will be described next.
FIG. 3 is a diagram for explaining from the initial setting to the middle of resin filling. Before filling the resin, that is, at the initial setting, as shown in FIG. 3A, the first pin 11 and the second pin 16 move forward. It is held in the limit position. The clutch ball 20 is also held at the forward limit position, and the distance between the clutch ball 20 and the end (taper portion 25) of the cylindrical body 21 at this time is the movement distance L of the clutch ball 20 (second pin 16). Become.

  Next, when the cavity 38 is filled with high-pressure molten resin, the pressure of the resin is applied to the front end surface of the first pin 11 and the front end surface of the second pin 16. If the pressure of the resin is p, the area of the tip surface of the first pin 11 is S1, and the tip surface S2 of the second pin 16, the axial force of p · S1 is applied to the first pin 11, and the second An axial force of p · S2 is applied to the pin 16.

Then, as shown in (b), the first pin 11 is retracted, the first elastic member 32 is compressed, the second pin 16 is retracted, and the second elastic member 35 is compressed. . However, part of the axial force applied to the second pin 16 acts on the first pin 11 due to the coupling action of the clutch ball 20.
If the elastic coefficient of the first elastic member 32 is k1, the elastic coefficient of the second elastic member 35 is k2, and the retraction amount of the first pin 11 is L1, the following equation is established.
(P · S1 + p · S2) = k1 · L1 + k2 · L1

Next, the magnitude relationship between S1 and S2 is examined. If the outer diameter of the first pin 11 (the outer diameter of the small diameter portion) is 10 mm, S1 is π · 1 ² /4=0.25π (cm ² ). If the outer diameter of the second pin 16 is 30 mm and the inner diameter is 10 mm, S2 is π · (3 ² −1 ² ) / 4 = π · (9-1) / 4 = 2π (cm ² ). . In this case, S2 is 8 times S1.

  Next, the elastic coefficients K1 and K2 are examined. The elastic coefficient k1 (kg / mm) of the first elastic member 32 is set large, and the elastic coefficient k2 (kg / mm) of the second elastic member 35 is set small. If the elastic modulus K2 is sufficiently small and is ignored for convenience, the above equation becomes (p · S1 + p · S2) = k1 · L1.

  That is, the first elastic member 32 having a large elastic coefficient is compressed by (p · S1 + p · S2). This (p · S1 + p · S2) is, for example, 9 (= 1 + 8) times p · S1.

  In the conventional technique, the elastic member is compressed only by p · S1. On the other hand, according to the present invention, since the elastic member is compressed with 9 times the elastic energy, it is possible to accumulate extremely large elastic energy as compared with the conventional case.

  That is, as shown in FIG. 3B, the force obtained by combining the axial force p · S1 due to the high-pressure molten resin in the cavity 38 and the larger axial force p · S2 is the elastic force of the first elastic member 32. The first pin 11 and the second pin 16 are caused to retreat against the force combined with the elastic force of the second elastic member 35. At this time, since the elastic coefficient k1 of the first elastic member 32 is set to be larger than the elastic coefficient k2 of the second elastic member 35, the first pin is caused by the drag as the elastic force of the first elastic member 32. A clutch ball 20 is pushed by a concave curved surface 15 of a step provided in 11, and the clutch ball 20 is accommodated in the ball hole 17 while pressing the inner wall of the cylindrical body 21 radially outward.

  FIG. 4 is a diagram for explaining from the unlocking of the clutch ball to the completion of the solidification of the resin. As shown in FIG. 4A, when the first pin 11 and the second pin 16 are retracted together, the clutch ball 20 is disengaged from the end of the cylinder 21 (the right end in the figure). Then, the clutch balls 20 and 20 can move outward of the diameter of the first pin 11 as indicated by arrows (1) and (1). As a result, the coupling action of the clutch ball 20 disappears, and the first pin 11 can move freely with respect to the second pin 16.

As shown in (b), when the resin starts to solidify and contraction starts, the second pin 16 hardly advances, but the first pin 11 is pushed by the strong first elastic member 32, Strongly press the resin 39 in the middle of solidification. As a result, the occurrence of sink marks is effectively suppressed.
When the resin solidification is completed, the mold 27 is opened, and the protruding board 24 and the auxiliary board 28 are moved. As a result, the product can be projected by the second pin 16. When the protrusion ends, the process returns to FIG.

The invention described above can be summarized as follows.
The sink suppression device 10 in resin molding has a front end facing the cavity 38 and is supported by the protruding plate 24 arranged outside the mold 27 so as to be movable in the axial direction, and a rear end is the first elastic member 32 and the cavity 38, the first pin 11 whose front end side is the small diameter portion 12 and whose rear end side is the large diameter portion 13;
The front end faces the cavity 38, is supported by the protruding plate 24 so as to be movable in the axial direction, the rear end is pressed by the second elastic member 35 having a smaller elastic coefficient than the first elastic member 32, and the first pin A hollow second pin 16 for movably storing 11;
The spherical diameter is set to a value that is half the difference between the outer diameter D2 of the second pin 16 and the outer diameter D1 of the small-diameter portion of the first pin. A clutch ball 20 accommodated in the ball hole 17 movably in the direction perpendicular to the axis of the second pin 16;
A value that is half of the difference between the outer diameter D3 of the large-diameter portion of the first pin and the outer diameter D1 of the small-diameter portion of the first pin is fixed to the protruding plate 24 so as to accommodate the second pin 16 so as to be movable in the axial direction. The clutch ball facing the inner peripheral surface of the cylinder 21 is formed in the cylinder 21 when the second pin 16 is retracted by a predetermined distance D. A cylinder 21 having a length D set so as to be disengaged from the end 25.

In this configuration, the resin pressure acts on the first pin and the second pin. The second pin is connected to the first pin by the clutch ball. Then, the 1st elastic member which is energizing the 1st pin is compressed with the 1st pin and the 2nd pin. A sufficiently strong elastic energy is accumulated in the first elastic member.
When the second pin moves backward by a certain distance, the clutch ball is released and the first pin becomes free. When the resin solidifies and contracts, the first pin is pushed out by the first elastic member and strongly presses the resin. As a result, the occurrence of sink marks can be sufficiently suppressed.

  In the present embodiment, the second pin 16 is a protruding pin, and the moving plate is a protruding plate 24 that moves the protruding pin. The protruding pin and the protruding board 24 are ancillary facilities essential to the mold 27. Since the incidental equipment is used, the manufacturing cost of the sink suppression device 10 can be suppressed.

  The present invention is suitable for a resin sink suppression device.

It is a block diagram of the sink suppression apparatus which concerns on this invention. FIG. 2 is a sectional view taken along line 2-2 of FIG. It is a figure explaining from the time of initialization to the middle of resin filling. It is a figure explaining from lock release of a clutch ball to completion of solidification of resin. It is a figure explaining the sink which generate | occur | produces at the time of resin molding. It is a figure explaining the basic principle of the prior art.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 10 ... Sink suppression apparatus, 11 ... 1st pin, 12 ... Small diameter part, 13 ... Large diameter part, 15 ... Concave curved surface, 16 ... 2nd pin, 17 ... Ball hole, 20 ... Clutch ball, 21 ... Cylindrical body , 24 ... A protruding board as a moving board, 27 ... a mold, 32 ... a first elastic member, 35 ... a second elastic member, 38 ... a cavity, L ... a moving distance, D1 ... an outer diameter of a small diameter part, D2 ... The outer diameter of the second pin, D3, the outer diameter of the large diameter portion, T, the thickness of the cylindrical body.

Claims (4)

The front end faces the cavity, is supported by a moving plate arranged outside the mold so as to be axially movable, the rear end is pressed against the cavity by the first elastic member, the front end side is a small diameter portion, and the rear end side is large A first pin in which a step portion of the large-diameter portion and the small-diameter portion is connected by a concave curved surface;
A hollow second pin that has a front end facing the cavity, is supported by the moving plate so as to be axially movable, a rear end is pressed by a second elastic member, and the first pin is movably accommodated;
The ball diameter is set to a half value of the difference between the outer diameter of the second pin and the outer diameter of the small-diameter portion of the first pin, and the ball hole penetratingly formed in the hollow second pin A clutch ball housed so as to be movable in a direction perpendicular to the axis of the second pin;
A clutch ball fixed to the moving plate for accommodating the second pin so as to be movable in the axial direction, and a clutch ball facing the inner peripheral surface of the cylinder has a constant second pin. A cylinder whose length is set so as to be disengaged from the end of the cylinder when the distance is retracted;
A sink suppression device in resin molding comprising:   2. The sink in resin molding according to claim 1, wherein the second pin is a protruding pin that plays a role of protruding a product from a mold, and the moving plate is a protruding plate that moves the protruding pin. Suppression device.   3. The sink suppression device for resin molding according to claim 1, wherein the second pin is pressed by a second elastic member having a smaller elastic coefficient than that of the first elastic member at a rear end thereof. .   2. The resin molding according to claim 1, wherein the cylindrical body has a thickness set to a half value of a difference between an outer diameter of the large diameter portion and an outer diameter of the small diameter portion of the first pin. Sink suppression device.

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