JP2002283413A - Injection molding machine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To certainly prevent the generation of stringing and to shorten a molding cycle. SOLUTION: An injection molding machine has a fixed mold 15 to which a sprue 16 is formed, a heating cylinder, an injection nozzle 31 having a nozzle orifice 37 formed to the front end thereof and also having a valve seat 36 formed thereto rearwardly from the nozzle orifice 37 and a needle valve 41 having a valve head part 55 formed to the front end thereof to close the nozzle orifice 37 at an advance limit position. A resin exclusion means for excluding the resin of the center part is arranged to the end part on the side of the injection nozzle of the sprue 16. When the needle valve 41 is advanced and the valve head part 55 is pressed to the valve seat 36, the resin does not remain between the needle valve 41 and the resin exclusion means.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an injection molding machine.

[0002]

2. Description of the Related Art Conventionally, in an injection molding machine, a resin heated and melted in a heating cylinder is injected, filled into a cavity space of a mold apparatus, and cooled in the cavity space. A molded product is obtained by solidification.

[0003] To this end, the injection molding machine is a mold clamping device,
It has a mold device and an injection device, the mold clamping device includes a fixed platen and a movable platen, and a mold closing cylinder advances and retreats the movable platen to close the mold of the mold device,
Perform mold clamping and mold opening.

Further, the mold apparatus includes a fixed mold and a movable mold, and a cavity space is formed between the fixed mold and the movable mold as the mold is closed.

On the other hand, the injection device includes a heating cylinder for heating and melting the resin supplied from the hopper, and an injection nozzle for injecting the melted resin, wherein a screw is rotatable in the heating cylinder. And it is arranged so that it can move forward and backward. Then, the screw is rotated by a driving source, and the screw is retreated, whereby the resin is measured. When the screw is advanced by the driving source, the resin is injected from an injection nozzle to fill the cavity space.

Next, the injection nozzle will be described.

FIG. 2 is a cross-sectional view showing a main part of a conventional injection molding machine, and FIG. 3 is an explanatory diagram of stringing occurring in the conventional injection molding machine.

In FIG. 1, reference numeral 11 denotes a cylindrical injection nozzle. The injection nozzle 11 includes a cylindrical main body 50 and a nozzle heater 13 disposed on an outer peripheral surface of the main body 50.
A resin flow path 50a is formed in the main body 50. The resin in the resin flow path 50a can be heated by energizing the nozzle heater 13.

The injection nozzle 11 is attached to a front end of a heating cylinder (not shown), and connects a resin flow path in the heating cylinder with the resin flow path 50a. And
At the front end (left end in FIG. 2) of the injection nozzle 11, a tapered portion 19 and a reverse tapered portion 20 are formed by the resin flow path 50a, and a cut having the smallest diameter is formed at the boundary between the tapered portion 19 and the reverse tapered portion 20. The part S1 is formed.

In the injection step, the injection nozzle 11 is pressed against a fixed die 15 of a die apparatus, and when a screw in the heating cylinder is advanced by driving a drive source (not shown), the injection nozzle 11 is stored in front of the screw. The injected resin is injected from the injection nozzle 11 and filled into a cavity space (not shown) via a sprue 16 and a runner (not shown) in the fixed mold 15.

Thereafter, when the mold apparatus is cooled, the resin filled in the cavity space is cooled and solidified to form a molded article 21. The mold apparatus is opened, and the molded article 21 is opened. Is taken out. Further, with the cooling of the mold apparatus, the resin in the runner and the sprue 16 are solidified integrally with the molded product 21 to form the runner sprue portion 22. The runner sprue portion 22 is taken out together with the molded product 21 when the mold opening is performed.

At this time, the resin in the resin flow path 50a is cut at the cutting portion S1, and is separated into the tapered portion 19 side and the reverse tapered portion 20 side.

By the way, the heating cylinder is retracted in the measuring step and separated from the fixed mold 15, but when it is necessary to use a resin having a low viscosity in a molten state, the inner diameter of the nozzle hole 51 is increased. In the case where it is necessary, for example, the threading occurs at the front end of the injection nozzle 11, and the thread-like portion 24 is formed integrally with the runner / sprue portion 22.

Therefore, an injection molding machine has been provided which can suppress the occurrence of stringing.

FIG. 4 is a sectional view showing a main part of another conventional injection molding machine. Incidentally, elements having the same structure as the injection molding machine of FIG. 2, the description thereof is omitted by giving the same reference numerals.

In this case, the needle valve 21 is disposed in the injection nozzle 11 and moves the needle valve 21 forward (moves to the left in the drawing) in the injection nozzle 11 at a timing when a heating cylinder (not shown) is retracted. , And abut against the tapered portion 19. Then, the tapered portion 19
Since the side and the reverse tapered portion 20 are shut off, the resin in the resin flow path 50a can be prevented from flowing out to the reverse tapered portion 20 when the heating cylinder is retracted.

Also, in the mold apparatus, the sprue 1
6, an insertion body 22 having a cross section of “10” is inserted into the end on the side of the injection nozzle 11, that is, the rear end (right end in the figure). Therefore, the resin in the central portion where the cooling of the resin is the slowest in the sprue 16 is eliminated, so that the occurrence of stringing can be suppressed.

[0018]

However, in the conventional injection molding machine, when the needle valve 21 is advanced, the needle valve 21 and the insert 2
2, that is, the resin remains in the reverse taper portion 20, so that when the heating cylinder is retracted, the resin in the reverse taper portion 20 causes stringing. Therefore, it is conceivable to wait for the heating cylinder to retreat until the resin in the reverse taper portion 20 is completely solidified, and to discharge the resin in the reverse taper portion 20 that has solidified together with the runner sprue portion 22. The molding cycle is lengthened accordingly.

The present invention solves the above-mentioned problems of the conventional injection molding machine, and provides an injection molding machine capable of reliably preventing stringing from occurring and shortening a molding cycle. The purpose is to:

[0020]

For this purpose, in an injection molding machine according to the present invention, a fixed mold having a sprue formed therein, a heating cylinder arranged to be able to move forward and backward, and a front end of the heating cylinder are mounted. A nozzle hole at the front end, an injection nozzle having a valve seat formed rearward from the nozzle hole,
A valve head portion having a shape corresponding to the valve seat is formed at a front end, which is disposed so as to be able to advance and retreat in the injection nozzle,
A needle valve for closing the nozzle hole at the forward limit position.

At the end of the sprue on the side of the injection nozzle, there is provided resin removing means for removing the resin at the center.

In another injection molding machine according to the present invention, the valve seat and the valve head have a tapered shape.

In still another injection molding machine of the present invention,
Further, at the forward end position of the needle valve, the front end face of the valve head and the front end face of the injection nozzle are placed on the same plane.

In still another injection molding machine of the present invention,
Further, the resin removing means is an insert inserted into the sprue.

In still another injection molding machine of the present invention,
Further, the resin removing means is a front end portion of the valve head portion projected forward from the nozzle hole.

[0026]

Embodiments of the present invention will be described below in detail with reference to the drawings.

FIG. 1 is a sectional view showing a main part of an injection molding machine according to a first embodiment of the present invention, and FIG. 5 is a perspective view of an insert according to the first embodiment of the present invention.

In the figure, reference numeral 31 denotes a cylindrical injection nozzle. The injection nozzle 31 includes a cylindrical main body 32 and a nozzle heater 33 disposed on the outer peripheral surface of the main body 32.
A resin flow path 35 is formed in the main body 32. When the nozzle heater 33 is energized, the resin flow path 3
5 can be heated.

The injection nozzle 31 is attached to the front end of a heating cylinder (not shown) constituting the injection device, and connects the resin flow path in the heating cylinder with the resin flow path 35. In the injection device, the heating cylinder is disposed so as to be able to move forward and backward, and is advanced so that the injection nozzle 31 is pressed against the fixed mold 15 of the mold device to perform nozzle touch. The mold device includes a fixed mold 15 attached to a fixed platen not shown, and a movable mold not shown attached to a movable platen not shown, and the movable platen is moved forward and backward by a mold clamping device not shown, and is movable. The mold can be closed, clamped and opened by moving the mold toward and away from the fixed mold 15, and a cavity space (not shown) is provided between the fixed mold 15 and the movable mold at the time of mold clamping. Is formed. And
The fixed mold 15 is provided with a sprue 16 and a runner (not shown).

In the injection step, when the injection nozzle 31 is pressed against the fixed mold 15 and the screw in the heating cylinder is advanced by driving a drive source (not shown), the resin accumulated in front of the screw is
It is injected from the injection nozzle 31 and is filled into the cavity space via the sprue 16 and the runner. Therefore, a nozzle hole 37 is formed at the front end (left end in FIG. 1) of the injection nozzle 31.

Thereafter, when the mold device is cooled, the resin filled in the cavity space is cooled and solidified to form a molded product (not shown). The mold device is opened, and the molded product is opened. Is taken out. Further, with cooling of the mold apparatus, the resin in the runner and the resin in the sprue 16 are solidified integrally with the molded product, and
Become a sprue part. The runner sprue is taken out together with the molded product when the mold is opened.

By the way, the heating cylinder is retracted in the measuring step and separated from the fixed mold 15, but when it is necessary to use a resin having a low viscosity in a molten state, the inner diameter of the nozzle hole 37 is reduced. When stringing occurs at the front end of the injection nozzle 31 when it is necessary to increase the size, a thread-like portion (not shown) is formed integrally with the runner sprue portion.

Therefore, a needle valve 41 is disposed in the injection nozzle 31 so as to be able to advance and retreat (move in the left-right direction in FIG. 1). At the timing when the heating cylinder is retracted, the heating cylinder is advanced (moved to the left in FIG. 1) in the injection nozzle 31 at the timing of retracting the heating cylinder, and is positioned at the advance limit position shown in FIG.
Therefore, at the front end of the injection nozzle 31, from the nozzle hole 37 to the rear (right side in FIG. 1),
The valve seat 3 having a tapered shape is formed by the resin flow path 35.
6 are formed. The valve seat 36 has an inner peripheral surface having a conical shape. In addition, the needle valve 41
A valve head portion 55 having a shape corresponding to the valve seat 36, that is, having a tapered shape having the same angle as the valve seat 36 is formed at the front end of the valve seat 36. The valve head 55 has an outer peripheral surface having a frusto-conical shape. The valve head 55 has a front end face (left end face in FIG. 1) having a predetermined area and having a flat (straight) surface or a spherical surface. A link mechanism (not shown) is connected to the rear end (the right end in FIG. 1) of the needle valve 41, and a hydraulic cylinder as a drive unit (not shown) is provided in the link mechanism.

In this case, when the needle valve 41 is advanced, the needle valve 41 is placed at the advance limit position, and the valve head 55 is pressed against the valve seat 36, the inside and outside of the resin flow path 35 are shut off. When the cylinder is retracted, the resin in the resin flow path 35 can be prevented from flowing out to the fixed mold 15 side.

In the mold apparatus, the sprue 1
6 is provided at the rear end thereof with an insert 43 as a resin removing means having a cross section of “10” shape, and the insert 43 is integrally formed by protruding radially outward from an axis 48. The distance from the axis 48 is gradually shortened from the front end to the rear end. When the insert 43 is disposed in the sprue 16, the sprue 1
The resin in the central portion where the cooling of the resin is the slowest in 6 is excluded. When the needle valve 41 is advanced to the forward limit position, the front end face of the main body 32 and the front end face of the valve head 55 are placed on the same plane, and the needle valve 4
1 is almost in contact with the rear end of the insert 43, and the nozzle hole 37 is closed.
No resin remains between the resin and No. 3.

Therefore, when the heating cylinder is retracted, stringing can be reliably prevented from occurring. Further, even if the heating cylinder is retracted before the resin between the pieces 44 to 47 is completely solidified, stringing can be prevented from occurring, and the molding cycle can be shortened accordingly.

Since the valve seat 36 and the valve head 55 have a tapered shape, the valve head 55 can be guided by the valve seat 36 when the needle valve 41 is advanced. Therefore, the needle valve 41 can be advanced smoothly.

Next, a second embodiment of the present invention will be described. In addition, about what has the same structure as 1st Embodiment, the description is abbreviate | omitted by attaching the same code | symbol.

FIG. 6 is a sectional view showing a main part of an injection molding machine according to a second embodiment of the present invention.

In this case, a valve head 61 having a tapered shape corresponding to the valve seat 36 is formed at the front end (left end in the figure) of the needle valve 41. The valve head 61 has an outer peripheral surface having a conical shape. In this case, the needle valve 41 is moved forward (moved to the left in the figure) to be at the forward limit position shown in FIG.
When the valve head 61 is pressed against 6, the inside and outside of the resin flow path 35 are shut off, so that when the heating cylinder (not shown) is retracted, the resin in the resin flow path 35 flows out to the fixed mold 15 side. Can be prevented.

When the needle valve 41 is advanced to the forward limit position, the front end portion 62 of the valve head 61 as a resin removing means is projected forward from the nozzle hole 37 to close the nozzle hole 37. , Into the sprue 16. When the front end 62 enters the sprue 16, the resin in the central portion of the sprue 16 where the cooling of the resin is slowest is eliminated.

Therefore, when the heating cylinder is moved backward, stringing can be reliably prevented from occurring. Further, even if the heating cylinder is retracted before the resin in the sprue 16 is completely solidified, the occurrence of stringing can be prevented, so that the molding cycle can be shortened accordingly.

Then, the front end portion 62 is
It is not necessary to dispose the insert in the sprue 16 because the resin in the central portion where the cooling of the resin is the slowest is excluded. Therefore, at the time of the injection step, not only can the flow of the resin in the sprue 16 be smooth, but also the structure of the mold apparatus can be simplified.

The present invention is not limited to the above embodiments, but can be variously modified based on the gist of the present invention, and they are not excluded from the scope of the present invention.

[0045]

As described above in detail, according to the present invention, in an injection molding machine, a fixed mold having a sprue formed therein, a heating cylinder disposed to be able to move forward and backward, and a At the front end, there is a nozzle hole at the front end,
An injection nozzle having a valve seat formed rearward from the nozzle hole, and a valve head portion having a shape corresponding to the valve seat is formed at a front end of the injection nozzle so as to be able to advance and retreat inside the injection nozzle. A needle valve for closing the nozzle hole.

At the end of the sprue on the side of the injection nozzle, there is provided a resin removing means for removing the resin at the central portion.

In this case, when the needle valve is advanced to the advance limit position and the valve head is pressed against the valve seat, the inside of the resin flow path is shut off. In addition, it is possible to prevent the resin in the resin flow path from flowing out to the fixed mold side.

In the mold apparatus, since the resin removing means is provided at the end of the sprue on the side of the injection nozzle, the resin in the center of the sprue where the cooling of the resin is slowest is eliminated. Then, when the needle valve is advanced to the forward limit position, the nozzle hole is blocked, so that no resin remains between the needle valve and the resin removing means.

Therefore, when the heating cylinder is retracted, it is possible to reliably prevent stringing from occurring due to the resin in the sprue. Further, even if the heating cylinder is retracted before the resin in the sprue is completely solidified, stringing can be prevented from occurring, so that the molding cycle can be shortened accordingly.

In another injection molding machine according to the present invention, the valve seat and the valve head have a tapered shape.

In this case, since the valve seat and the valve head have a tapered shape, the valve head can be guided by the valve seat when the needle valve is advanced. Therefore, the needle valve can be advanced smoothly.

In still another injection molding machine of the present invention,
Further, the resin removing means is a front end portion of the valve head portion projected forward from the nozzle hole.

In this case, since the resin removing means is located at the front end of the valve head, the resin in the central portion of the sprue where cooling of the resin is slowest is removed. Therefore, there is no need to dispose the insert in the sprue. As a result, at the time of the injection step, not only can the resin flow in the sprue be smooth, but also the structure of the mold apparatus can be simplified.

[Brief description of the drawings]

FIG. 1 is a sectional view showing a main part of an injection molding machine according to a first embodiment of the present invention.

FIG. 2 is a sectional view showing a main part of a conventional injection molding machine.

FIG. 3 is an explanatory diagram of stringing that occurs in a conventional injection molding machine.

FIG. 4 is a cross-sectional view showing a main part of another conventional injection molding machine.

FIG. 5 is a perspective view of the insert according to the first embodiment of the present invention.

FIG. 6 is a sectional view showing a main part of an injection molding machine according to a second embodiment of the present invention.

[Explanation of symbols]

 15 Fixed die 16 Sprue 31 Injection nozzle 36 Valve seat 37 Nozzle hole 41 Needle valve 43 Insert 55, 61 Valve head 62 Front end

Claims (5)

[Claims] (A) a fixed mold having a sprue formed therein, (b) a heating cylinder arranged to be able to move forward and backward, and
(C) an injection nozzle which is attached to a front end of the heating cylinder and has a nozzle hole formed at the front end and a valve seat formed rearward from the nozzle hole; and (d) an injection nozzle which is provided so as to be able to advance and retreat within the injection nozzle. (E) having a valve head portion having a shape corresponding to the valve seat, and having a needle valve for closing the nozzle hole at the forward limit position.
An injection molding machine, characterized in that a resin removing means for removing a resin in a central portion is provided at an end of the sprue on an injection nozzle side. 2. The injection molding machine according to claim 1, wherein the valve seat and the valve head have a tapered shape. 3. The injection molding machine according to claim 1, wherein a front end face of the valve head portion and a front end face of the injection nozzle are located on the same plane in a forward limit position of the needle valve. 4. The injection molding machine according to claim 1, wherein said resin removing means is an insert inserted into said sprue. 5. The injection molding machine according to claim 1, wherein the resin removing means is a front end of a valve head protruding forward from the nozzle hole.