JP3759827B2 - Hot runner mold - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a valve gate type hot runner mold, and more particularly, to a hot runner mold that does not cause wear and damage of a gate pin and burning a molten resin.
[0002]
[Prior art]
The resin in the runner portion of the hot runner mold is supplied to the manifold and then heated to a set temperature and maintained in a molten state. This molten resin is injected from the gate at the tip of the nozzle into the mold cavity, but the gate is closed after the injection is completed so that the resin in the runner portion does not leak from the gate except during injection.
[0003]
In the valve gate type hot runner mold, as shown in FIG. 9, a gate pin 7 is inserted into a resin flow path 10 provided inside the manifold 4 and the nozzle 3, and the nozzle moves as the gate pin 7 moves up and down. The side gate 1 is opened and closed.
A guide (not shown) is separately provided in the resin flow path 10 in order to guide the gate pin 7 to the gate 1 and prevent vibration.
As shown in FIG. 10, the hot runner mold gate pin 7 is inserted into the resin flow path 10 through a pin hole 15 provided from the upper surface of the manifold 4 toward the resin flow path 10. In order to prevent the resin from leaking through the gap 7, the clearance between the gate pin 7 and the pin hole 15 is minimized.
[0004]
However, when such a hot runner mold is used, the center axis N of the gate pin 7 and the center axis P of the pin hole 15 are shifted due to thermal expansion of the manifold 4 as shown in FIG. However, the contact with the inner wall surface of the pin hole 15 hinders the operation of the gate pin 7 and causes wear and damage to the gate pin 7 and the pin hole 15.
[0005]
Therefore, conventionally, the amount of thermal expansion of the manifold 4 is predicted from the material used and the set temperature, and correction is performed by shifting the position of the pin hole 15 from the position where the gate pin 7 is attached in advance by the amount of thermal expansion.
As shown in FIG. 12 (a), the center axis N of the gate pin 7 mounting position and the center axis P of the pin hole 15 are provided in advance in a position shifted by the thermal expansion amount S in the longitudinal direction, and FIG. As shown, after the manifold 4 is thermally expanded, the central axis N of the gate pin 7 attachment position and the central axis P of the pin hole 15 are made to coincide.
[0006]
[Problems to be solved by the invention]
However, in this method, it is necessary to accurately predict the amount of thermal expansion of the manifold 4 and to process it with higher positional accuracy. If the prediction is inaccurate or the processing accuracy is poor, the gate pin 7 is pinned after thermal expansion. 15 is difficult to design and process the manifold 4.
In addition, when the apparatus is assembled, high positional accuracy is required for the positional relationship between the gate pin 7 and the pin hole 15.
[0007]
Further, since the conventional manifold has the gate pin inserted directly into the resin flow path, the gate pin and the guide of the gate pin become an obstacle to prevent the resin from flowing, and the resin stays around the gate pin and in the guide.
Therefore, there is a problem in that the staying resin is overheated and the molten resin is burnt.
[0008]
SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a hot runner mold that prevents wear and damage of the gate pin due to contact between the gate pin and the inner wall surface of the resin flow path, and does not cause the molten resin to burn.
[0009]
[Means for Solving the Problems]
The present invention is a valve gate type hot runner mold, wherein the tip of the gate portion is fitted into the cavity opening end of the mold plate, and the nozzle can rotate around the tip of the gate portion. The resin flow path in the manifold and the resin flow path in the nozzle are connected by a resin flow portion connecting ring, and there is a gate pin hole separate from the resin flow path, and the resin flow path and the gate pin hole merge at the nozzle tip. The clearance between the gate pin and the gate pin hole is large so that the gate pin does not come into contact with the gate pin hole even when the manifold is thermally expanded, and the central axis of the gate pin passes through the central position of the tip of the gate portion. This is a hot runner mold.
[0010]
(Function)
As shown in FIG. 8A in which the inside of the manifold 4 is seen through, the manifold 4 undergoes thermal expansion when heated to a set temperature by the heating of the heater 16, and the resin flow path 10 on the lower surface of the manifold 4 is accompanied by the thermal expansion. The manifold-side opening A1 of the resin flow part connecting ring 9 connected to is moved by the thermal expansion amount S.
[0011]
Thereby, the resin flow part connecting ring 9 receives the force which goes to the longitudinal direction outer side of a manifold.
Then, the force received by the resin flow portion connecting ring 9 is applied to the nozzle 3 from the connecting portion with the nozzle 3, and the nozzle 3 rotates counterclockwise about the gate portion tip 18 as shown by an arrow G. As a result, the resin flow part connection ring 9 moves to the outside in the longitudinal direction of the manifold while being slightly deformed with the rotation of the nozzle 3, and the load on the resin flow part connection ring 9 is alleviated.
[0012]
When the load applied to the resin flow part connecting ring 9 is eliminated, the nozzle 3 stops rotating.
[0013]
The gate pin hole 12 also moves in the longitudinal direction due to the thermal expansion of the manifold 4. However, since the inner diameter of the gate pin hole 12 is sufficiently larger than the outer diameter of the gate pin 7 as shown in FIG. 8B, the gate pin 7 is in contact with the gate pin hole 12 even after the gate pin hole 12 has moved by the thermal expansion amount S. It works normally without.
[0014]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a vertical sectional view of a hot runner mold according to the present invention.
The manifold 4 used in the hot runner mold of the present invention is attached between a mold plate 6 and a mounting plate 5, and a sprue bush 13 is attached to the center upper surface.
The central lower surface of the manifold 4 is fixed to the template 6 by the fixing ring 2, and the upper surface of the manifold 4 is brought into contact with the mounting plate 5 via a surface contact type knock pin 11.
[0015]
It is desirable that the manifold 4 is not completely fixed to the template 6 or the mounting plate 5 with a knock pin or the like other than the center.
This is because if the amount of thermal expansion of the surface of the fixed portion is suppressed by the resistance of a knock pin or the like, the amount of thermal expansion inside the manifold 4 becomes relatively larger than that of the surface. It is because it distorts.
[0016]
FIG. 2 shows an enlarged vertical cross-sectional view of the tip of the nozzle 3, and the gate portion tip 18 is fitted to a bearing structure 20 provided at the cavity opening end of the template 6. The nozzle 3 can rotate about the gate tip 18 as a center.
The tip of the gate pin 7 can move up and down between D.
[0017]
The structure of the nozzle 3 will be described with reference to a partially enlarged view around the nozzle 3 in FIG.
In FIG. 3A, the inside of the nozzle 3 is seen through, the gate pin 7 passes through the central axis of the nozzle 3, and the resin flow portion connecting ring 9 is provided at a position off the central axis of the nozzle 3. The openings A1 and A2 of the resin flow portion connecting ring 9 are communicated with the resin flow path 10 in the manifold 4 and the resin flow path 10 in the nozzle 3, respectively.
Further, a slight gap is opened between the manifold 4 and the nozzle 3, and the nozzle 3 and the manifold 4 are connected only by the resin flow portion connecting ring 9.
[0018]
FIG. 3B is a BB vertical sectional view of FIG.
The gate pin 7 is passed through the gate pin holes 12 and 13 provided through the manifold 4 and the nozzle 3, and the resin flow path 10 opens and closes the nozzle tip 8 that joins the gate pin hole 13.
[0019]
In addition, since the clearance between the gate pin 7 and the gate pin hole 13 in the nozzle 3 is provided separately from the resin flow path 10, it may be extremely large.
However, since the gate pin 7 blocks the resin flow path 10 at the nozzle tip 8, the clearance between the nozzle tip 8 and the gate pin 7 must be minimized to prevent leakage of the molten resin.
[0020]
4 is a cross-sectional view taken along the line AA in FIG.
The gate pins 7 are on a straight line intersecting the resin flow path 10 at the center of the manifold 4 which is the intersection of the X axis and the Y axis, and are provided at symmetrical positions at equal intervals from the center of the manifold 4.
Note that the inner diameter of the gate pin hole 12 in the manifold 4 is sufficiently larger than the outer diameter of the gate pin 7 so that the gate pin 7 does not come into contact with the inner surface of the gate pin hole 12 even if the manifold 4 is thermally expanded.
[0021]
Next, FIG. 5, FIG. 6, FIG. 6, which is a top view of the resin nozzle 3 seen from the bottom surface of the manifold, for a method of correcting the positional deviation of the gate pin hole when the manifold of the hot runner mold of the present invention is thermally expanded. 7 will be described in order.
FIG. 5 shows the state of the nozzle upper surface seen through the manifold lower surface before the manifold thermally expands.
Here, the central axes R and T of the manifold side opening A1 on the lower surface of the manifold 4 and the nozzle side opening A2 that similarly opens on the upper surface of the nozzle 3 coincide with each other.
[0022]
Next, the state after the manifold 4 undergoes thermal expansion will be described.
FIG. 6 is a diagram showing a state in which a load is applied to the resin flow portion connecting ring 9 immediately after thermal expansion.
The manifold 4 side opening A1 moves a distance S in the longitudinal direction with thermal expansion. Although the nozzle 3 is pulled outward in the longitudinal direction via the resin flow path connecting ring 9, since the resin flow portion connecting ring 9 can be deformed to some extent, the nozzle side opening A2 is located at the same position even after thermal expansion.
As a result, the center axis T of the nozzle side opening A2 is shifted by the movement amount S from the center axis R ′ of the manifold 4 side opening A1.
[0023]
Next, a state in which the load applied to the resin flow portion connecting ring 9 is eliminated will be described.
As shown in FIG. 7, since the restoring force of the resin flow portion connecting ring 9 acts in the tangential direction H around the central axis of the nozzle 3, the nozzle 3 starts to rotate counterclockwise.
By rotating the nozzle 3 by W degrees sandwiched between TQT ′, the nozzle-side opening A2 is positioned at a position with the nozzle 3-side opening A2 having T ′ as the central axis.
As a result, the positions of the central axes R ′ and T ′ do not completely coincide with each other, but the resin flow portion connection ring 9 is allowed to have a certain amount of deformation without causing damage to the resin flow portion connection ring 9. The movement of the resin flow path due to the thermal expansion of the manifold 4 can be corrected.
[0024]
When the amount of thermal expansion is large, the movement of the resin flow path due to thermal expansion is continuously corrected in the manifold 4 while repeating a slightly loaded state and a state in which it is eliminated.
On the other hand, the gate pin hole 12 provided in the manifold 4 also moves due to thermal expansion, but the gate pin 7 does not come into contact even if a positional shift occurs because the inner diameter of the gate pin hole 12 is large.
[0025]
Further, since the nozzle 3 rotates and the central axis of the nozzle 3 is always located at the same position regardless of the thermal expansion of the manifold 4, the nozzle tip is not displaced from the central axis of the gate pin 13. The part 8 can be opened and closed.
[0026]
【The invention's effect】
Since no gate pin is inserted into the resin flow path in the manifold, a gate pin hole can be provided without considering resin leakage, and the gate pin hole can be made sufficiently large. Therefore, even if the manifold undergoes thermal expansion, the gate pin does not contact the pin hole.
[0027]
Even if the manifold undergoes thermal expansion, the center axis of the gate pin and the center position of the tip of the gate portion do not shift due to the rotation of the nozzle.
As a result, wear and damage to the gate pin can be prevented, and the nozzle in contact with the manifold can be rotated, so that the displacement of the resin flow path between the manifold and the nozzle caused by thermal expansion can be prevented by rotating the nozzle. The amount can be absorbed.
[0028]
Further, by separating the resin channel and the pin hole of the gate pin to the tip of the nozzle, there is no blockage in the resin channel and the stay can be eliminated.
[Brief description of the drawings]
FIG. 1 is a vertical sectional view showing the shape of a manifold of the present invention. FIG. 2 is a vertical sectional view of an enlarged nozzle tip. FIG. 3 (a) is a partially enlarged view of the inside of a hot runner mold according to the present invention. Fig. (B) BB vertical sectional view of Fig. 3 (a) [Fig. 4] AA sectional view of Fig. 1 showing the positional relationship between the resin flow path and the gate pin [Fig. 5] Before the manifold is thermally expanded Top view of the nozzle seen through the bottom surface of the manifold. [Fig. 6] Top view of the nozzle seen through the bottom surface of the manifold showing the state where the manifold is subjected to a load on the resin flow connection ring immediately after thermal expansion. [Fig. FIG. 8A is a top view of the nozzle seen through the lower surface of the manifold showing the state where the load applied to the fluid connection ring is eliminated. FIG. 8A is a partially enlarged view of the mold for hot runner of the present invention seen through the interior of the manifold after thermal expansion. Figure (b) Game Fig. 9 is a top view of the manifold with the pin periphery enlarged. Fig. 9 is a vertical sectional view showing the shape of a conventional hot runner mold. Fig. 10 is a partially enlarged view of the manifold with some of the gate pins of the conventional hot runner mold omitted. FIG. 11 is a top view of a manifold in which the periphery of a gate pin of a conventional hot runner mold is enlarged. FIG. 12 (a) is a schematic diagram of a conventional hot runner mold in which pin holes are corrected in advance. Schematic diagram of conventional hot runner mold after thermal expansion
3 Nozzle 4 Manifold 5 Mounting plate 6 Mold plate 7 Gate pin 8 Nozzle tip 9 Resin flow part connecting ring 10 Resin flow path 12, 13 Gate pin hole 15 Pin hole 16 Heater 18 Gate part tip 20 Bearing structure A1 Manifold side opening A2 Nozzle side opening

Claims (1)

In the valve gate type hot runner mold, the tip of the gate is fitted into the cavity opening end of the mold plate, and the nozzle can rotate around the tip of the gate. The resin flow path and the resin flow path in the nozzle are connected by a resin flow part connecting ring, and there is a gate pin hole separate from the resin flow path, and the resin flow path and the gate pin hole are joined at the nozzle tip. The clearance between the gate pin and the gate pin hole is large so that the gate pin does not come into contact with the gate pin hole even if the manifold is thermally expanded, and the center axis of the gate pin passes through the center position of the tip of the gate portion. Characteristic hot runner mold.

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