JPH0452024Y2 - - Google Patents

Description

[Detailed description of the invention] (Technical field) The present invention relates to a valve nozzle for an injection molding machine.
In particular, the present invention relates to a valve nozzle for an injection molding machine that can reduce pressure loss during injection operation.

(Prior Art) In an injection molding machine, as a nozzle attached to the tip of the heating cylinder, a valve seat is conventionally formed at the tip side of the injection resin passage of the nozzle body attached to the tip of the heating cylinder. A needle valve member having a needle valve portion at its tip is disposed within the injection resin passage of the nozzle body in a state that it can move a predetermined distance in the axial direction of the nozzle body, and the needle valve member has a needle valve portion at its tip. The movement toward the distal end seats the needle valve portion of the needle valve member on the valve seat to prevent injection of resin material, while also causing the needle valve member to move toward the proximal end of the nozzle body. A valve nozzle is known in which the needle valve portion is moved away from the valve seat to allow injection of resin material.

According to such a valve nozzle, by seating the needle valve portion of the needle valve member on the valve seat of the nozzle body, it is possible to prevent the resin material from leaking from the nozzle during non-injection operations.
It has the advantage of preventing drooling and stringing of resin materials.

By the way, this type of valve nozzle conventionally has a nozzle body 2, as shown in FIG. 3, for example.
The needle valve member 6 disposed in the injection resin passage 4 has a structure in which the needle valve member 6 is always biased toward its distal end side by a spring member 8. Thus, the needle valve portion 10 of the needle valve member 6 was seated on the valve seat 12 of the injection resin passage 4. When the resin material is injected, the resin pressure is increased, and only when the resin pressure in the injection resin passage 4 overcomes the biasing force of the spring member 8 and moves the needle valve member 6 backward, the needle valve member 6 The needle valve portion 10 was designed to be detached from the valve seat 12. In other words, when injecting the resin material, the injection resin passage 4
When the resin pressure inside is increased to a level greater than enough to overcome the biasing force of the spring member 8, injection of the resin material is allowed.

(Problem) For this reason, with conventional valve nozzles,
The needle valve member 10 resists the biasing force of the spring member 8.
There was a problem in that the resin pressure during injection decreased by the amount that was operated backwards, resulting in increased pressure loss.

On the other hand, in the valve nozzle as described above, it is possible to adopt a structure in which the needle valve member is forcibly moved in the axial direction by a hydraulic cylinder or a pneumatic cylinder provided outside the nozzle body. Conceivable. If the needle valve member is forcibly moved in the axial direction by a cylinder provided outside the nozzle body, it is possible to avoid a drop in the resin pressure due to the movement of the needle valve member. Therefore, it is possible to effectively prevent pressure loss from increasing due to movement of the needle valve member.

However, in this case, due to its structure, it is difficult to provide a heater means outside the nozzle body, which causes the problem that the resin temperature decreases and the flow resistance of the resin material increases during injection. In addition, especially when using a pneumatic cylinder, there is a limit to how much air pressure can be increased, so if the cylinder becomes significantly larger due to the need to move the needle valve member against the resin pressure, it will be difficult to increase the air pressure. There is a problem.

(Solution) The present invention has been made in view of the above circumstances, and its gist is that the injection resin passage of the nozzle body attached to the tip of the heating cylinder as described above a needle valve member having a valve seat formed at the distal end thereof, and having a needle valve portion at the distal end thereof, the needle valve member being movable a predetermined distance in the axial direction of the nozzle main body within the injection resin passage of the nozzle main body; is arranged, and by moving the needle valve member toward the distal end side of the nozzle body, the needle valve portion of the needle valve member is seated on the valve seat to prevent injection of the resin material;
In the valve nozzle for an injection molding machine, the needle valve member is moved toward the proximal end side of the nozzle body to separate the needle valve portion from the valve seat and permit injection of a resin material. A valve member is attached to a bottomed cylindrical portion having a bottomed hole of a predetermined depth that serves as a resin passage, and a tip portion extending coaxially with the bottomed cylindrical portion from the bottom wall of the bottomed cylindrical portion. Consisting of a needle plunger including a needle portion of a predetermined length including the needle valve portion, and one or more resin through holes formed to penetrate inside and outside the bottom wall of the bottomed cylindrical portion. On the other hand, the needle plunger is inserted into the injection resin passage of the nozzle body in a state in which the bottomed cylinder part is slidably fitted into the injection resin passage, and the needle valve part of the needle part is inserted into the injection resin passage. A forward end position where the valve seat of the injection resin passage is seated, and a retreating end position where the annular end surface on the proximal end side of the bottomed cylindrical portion abuts an annular stepped surface formed on the proximal side portion of the injection resin passage. In addition, at the retreating end position of the needle plunger, the annular end surface of the bottomed cylindrical portion is at least at its annular inner peripheral edge with the annular stepped surface of the injection resin passage. The bottomed cylindrical portion of the needle plunger and the inner wall of the nozzle body are in contact with each other to prevent the flow of resin material from hitting the annular end surface of the bottomed cylindrical portion during injection. During this period, the needle plunger is moved to its tip by supplying compressed air to the first air chamber, and the needle plunger is moved to its base by supplying compressed air to the second air chamber. A pneumatic piston mechanism for moving the needle plunger is provided at the end, and compressed air is selectively supplied to the first and second air chambers of the pneumatic piston mechanism to move the needle plunger between the forward end position and the backward end position. The reason is that it can be selectively moved.

(Operation/Effect) According to the valve nozzle according to the present invention, by selectively supplying compressed air to the first and second air chambers of the pneumatic piston mechanism, the needle plunger as a needle valve member is made of resin material. Since injection can be selectively moved between a position that blocks injection (advance end position) and a position that permits injection (retreat end position), by moving the needle plunger to its forward end position using a pneumatic piston mechanism, It is possible to prevent dripping and stringiness of the resin material during non-injection, and by moving the needle plunger to its retracted end position using a pneumatic piston mechanism, injection caused by moving the needle plunger can be prevented. This makes it possible to effectively prevent an increase in pressure loss during the process. In the present invention, since such a pneumatic piston mechanism is provided within the nozzle body, heater means such as a band heater can be easily disposed on the outer periphery of the nozzle body.
Therefore, it is possible to effectively avoid a decrease in the resin temperature and an increase in the flow resistance of the resin material.

Further, according to the valve nozzle according to the present invention, when the needle plunger is moved to the retracted end position, the annular end surface on the proximal end side of the needle plunger comes into contact with the annular stepped surface formed in the injection resin passage, Since the flow of resin material during injection is prevented from impinging on the annular end surface, less force is required to hold the needle plunger in the retracted end position, thus reducing the impact on the pneumatic piston mechanism and, therefore, on the entire nozzle. The pneumatic piston mechanism can stably hold the needle plunger at its retracted end position without increasing the size of the needle plunger. Therefore, it is possible to stably perform the injection operation while keeping the overall size of the nozzle compact.

In other words, since the resin pressure during injection is significantly higher than the air pressure of compressed air, if the flow of resin material during injection hits the annular end surface on the proximal end of the needle plunger, the resin material will be applied to the annular end surface. Due to the impingement of the flow, the force in the direction of moving the needle plunger forward becomes significantly large, and therefore, unless the pneumatic piston mechanism and, by extension, the entire nozzle are made extremely large, it will not be possible to act by the pneumatic piston mechanism. Regardless of the force exerted on the needle plunger in the direction of the backward movement, the needle plunger is moved from its backward end position to its forward end position. When the injection of the resin material is stopped by moving the needle plunger to the forward end position and the flow of the resin material disappears, the needle plunger is moved back to the backward end position by the force in the backward operation direction by the pneumatic piston mechanism. This repeated operation (hunting) makes the injection operation extremely unstable.

In contrast, in the present invention, as described above, when the needle plunger is moved to the retreating end position, the flow of resin material is prevented from hitting the annular end surface on the base end side of the needle plunger. The flow of the resin material does not significantly increase the force in the direction of moving the needle plunger forward, and therefore the relatively compact pneumatic piston mechanism moves the needle plunger to its rearward end position. It is possible to stably hold the nozzle, and therefore it is possible to stably perform the injection operation without increasing the size of the nozzle.

(Example) Hereinafter, in order to clarify the present invention more specifically, one example thereof will be described in detail based on the drawings.

First, FIG. 1 shows an example of a valve nozzle for an injection molding machine according to the present invention. As shown therein, the valve nozzle of this embodiment has the following features:
A needle plunger 22 serving as a needle valve member also having a longitudinal shape is housed in a nozzle body 20 having a longitudinal cylindrical shape so as to be movable a predetermined distance in the longitudinal direction. The nozzle body 20 is adapted to be attached to the tip of a heating cylinder of an injection molding machine at a mounting screw portion 24 provided on the outer circumferential surface of the base end portion of the nozzle body 20.

Here, the nozzle main body 20 has the above-mentioned mounting screw part 24 at the base end, and a relatively large-diameter longitudinal cylindrical nozzle base 26 equipped with a female thread part 25 at the distal end, and a nozzle base 26 formed at the base end. The male threaded portion 27 is screwed onto the female threaded portion 25 of the nozzle base 26 to form a nozzle head 28 in the form of a longitudinal tube with a relatively small diameter.
A through hole 30 serving as an injection resin passage is formed passing through them in the axial direction. Here, the through hole 30 of the nozzle body 20 is located on the proximal end side of the nozzle body 20,
That is, from the upstream side of the injection resin passage, in order, the tapered part 32, the small diameter part 34, the large diameter part 36, and the medium diameter part 38.
and small-diameter land portions 40, and the resin material heated and fluidized in the heating cylinder, as the injection screw or injection plunger in the heating cylinder moves forward, such tapered portions 32, small-diameter portions 34, The liquid is guided sequentially through the large-diameter portion 36 and the medium-diameter portion 38 to a land portion 40 at the tip of the nozzle body 20, and is ejected from this land portion 40 to the outside.

As shown in the figure, the tapered part 32, small diameter part 34 and large diameter part 36 of the through hole 30 are formed on the nozzle base 26 side, and the medium diameter part 38 and land part 40 are formed on the nozzle head 28 side. has been done. Further, the large diameter portion 36 and the medium diameter portion 38 and the medium diameter portion 38 and the land portion 40 of the through hole 30 are continuously connected by the tapered portions 44 and 46, respectively. An annular stepped surface 42 is formed between the large diameter portion 36 and the large diameter portion 36 . Further, as shown in the figure, here, the outer circumferential surface of the nozzle head 28, the outer circumferential surface of the axially central portion of the nozzle base 26, and the outer circumferential surface of the female thread forming portion 48 at the tip of the nozzle base 26 are ,Each,
Band heaters 50a, 50b, and 50c, which are heater means for heating the nozzle body 20, are provided.

On the other hand, as shown in the figure, the needle plunger 22 includes a plunger body 52 as a bottomed cylindrical portion having a bottomed hole 51 of a predetermined depth, and a bottom wall of the plunger body 52. A needle portion 56 having a predetermined length and having a conical needle valve portion 54 at its tip, extending coaxially with the plunger body 52 from the plunger body 5;
The structure includes three resin through holes 58 (only one resin through hole 58 is shown in the figure) that are radially formed to penetrate the bottom wall of the second resin member 2 from the inside to the outside. Here, the needle plunger 22 having such a structure is slidably fitted into the large diameter portion 36 in the plunger body 52 with the needle portion 56 protruding into the medium diameter portion 38. In the pressed state, the needle valve portion 54 at the tip of the needle portion 56 touches the land portion 4.
It is movable a predetermined distance in the axial direction between a forward end position where it abuts the opening edge of the plunger body 52 and a retreat end position where the proximal annular end surface 60 of the plunger body 52 abuts the annular stepped surface 42. is disposed within the through hole 30 of the nozzle body 20, thereby preventing injection of the resin material when the needle plunger 22 is moved to its forward end position, and Needle plunger 2
Injection of the resin material is allowed in a state in which the retractor 2 is moved to its retracted end position.

As is clear from the above description, in this embodiment, the opening edge of the land portion 40 on which the needle valve portion 54 is seated serves as the valve seat 62, and the needle plunger 22 is moved to the rearward end position. When the needle valve portion 54 is removed from its valve seat 62, the through hole 3 is removed from the tapered portion 32.
The resin material introduced into the 0 is injected through the land portion 40.
And, as is clear from Figure 1, here,
The resin material injected through the land portion 40 passes through the small diameter portion 34 to the plunger body 52.
The bottomed hole 51 is guided into the bottomed hole 51 of
from the resin through hole 58 to the medium diameter portion 3 of the through hole 30.
8 and then to the land portion 40.

Here, in this embodiment, as shown in FIG. 1, the diameter of the bottomed hole 51 of the plunger body 52: A is the diameter of the small diameter portion 34 that guides the resin material into the bottomed hole 51: The annular end surface 60 on the base end side of the plunger body 52 is slightly larger than B.
The entire surface of the ring is brought into contact with the annular stepped surface 42 of the through hole 30,
This prevents the flow of resin material from hitting the annular end surface 60 of the plunger body 52 during injection.

By the way, in the nozzle base 26, as shown in FIG. 1, a cylinder member 63 on the base end side and a joint member 65 on the distal end side are connected to a female threaded portion 67 formed on the distal end side, respectively. It has a structure in which it is screwed with a male threaded portion 69 formed on the end side, and thereby these cylinder members 6
An annular groove 64 having a predetermined depth and width is formed between the large diameter portion 36 and the joint member 65 and opening in the axially intermediate portion of the large diameter portion 36 . On the other hand, the plunger body 5 of the needle plunger 22
The annular groove 64 is formed on the outer circumferential surface of the axially intermediate portion of 2.
A piston portion 68 having an outer diameter approximately the same as the diameter of the bottom wall 66 is integrally formed. As shown in the figure, the piston portion 68 of the plunger body 52 is slidably fitted into the bottom wall 66 of the annular groove 64.
The annular space within 4 is divided into a first air chamber 70 on the proximal end side of the nozzle body 20 and a second air chamber 72 on the distal end side of the nozzle body 20.

The first air chamber 70 includes a through hole 7 formed in the cylinder member 63 and extending toward the base end side of the nozzle body 20.
4 and the second air chamber 72 are opened at both sides of the band heater 50b in the axial direction through a through hole 76 formed in the joint member 65 and extending toward the distal end side of the nozzle body 20. are connected to ports 78 and 80.
Further, the ports 78 and 80 are connected to the electromagnetic switching valve 8.
2 to an air pressure source 83. As a result, the first air chamber 70 and the second air chamber 72 are switched in accordance with the switching operation of the electromagnetic switching valve 82.
Compressed air from an air pressure source 83 is selectively supplied to the first air chamber 70.
By supplying compressed air to the second air chamber 72, a force in the direction of moving the needle plunger 22 forward is generated, and by supplying compressed air to the second air chamber 72, a force in the direction of moving the needle plunger 22 backward is generated. ,
Each of them is adapted to act on a piston portion 68 of the plunger body 52.

That is, in this embodiment, the annular groove 64 formed in the nozzle base 26 of the nozzle body 20 and the annular groove 64 are connected to the first air chamber 70 and the second air chamber 72.
The piston portion 6 of the plunger body 52 is divided into two parts.
8 constitute a pneumatic piston mechanism.

In this embodiment, the area of the pressure receiving surface 84 of the piston section 68 facing the first air chamber 70 of the pneumatic piston mechanism and the area of the pressure receiving surface 86 of the piston section 68 facing the second air chamber 72 are as follows: Each of them is set to a size that allows the needle plunger 22 to move against the resin pressure applied to the needle plunger 22, and thereby,
The first air chamber 70 and the second air chamber 72
By selectively supplying compressed air to the needle plunger 22, the needle plunger 22 can be selectively moved to the forward end position and the backward end position.

As is clear from FIG. 1, in this embodiment, the area of the pressure receiving surface 84 of the piston portion 68 facing the first air chamber 70 is larger than the area of the pressure receiving surface 86 of the piston portion 68 facing the second air chamber 72. It is slightly larger than the area of Also, as shown,
The band heater 50b is arranged on the outer peripheral surface of the cylinder member 63. Further, in the figure, 88 is a piston ring disposed on the outer circumferential surface of the piston portion 68, and 90 and 92 are piston rings that respectively sandwich the annular groove 64 in the axial direction, and the side wall of the nozzle base 26. Formed in a state that penetrates inside and out,
This is an escape hole for leaked air, gas, resin, etc.

Therefore, according to the valve nozzle having such a structure, during non-injection, compressed air is supplied to the first air chamber 70 and the needle plunger 22 is moved to its forward position, so that the nose of the resin material is Dragging and stringiness can be effectively prevented, and during injection, by supplying compressed air to the second air chamber 72 and moving the needle plunger 22 to its retracted position, the needle plunger 22 This makes it possible to effectively prevent the pressure loss during injection from increasing due to the movement of the cylinder. Furthermore, according to the valve nozzle of this embodiment, as described above, the nozzle body 2
Since the band heaters (50a to 50c) can be disposed so as to cover almost the entire surface of the resin, it is possible to effectively prevent the resin temperature from decreasing and increasing the flow resistance of the resin material. This effectively prevents losses from becoming large.

Incidentally, Fig. 2 a shows the valve nozzle of this embodiment attached to the heating cylinder of an in-line screw injection molding machine, and the 6-nylon is heated at the maximum injection speed of 20, 40, 60, 80, and 99, respectively. This shows the results of measuring the pressure loss when injecting in % by the oil pressure of the injection cylinder, and also
Using the conventional valve nozzle shown in Fig. 3,
The results of pressure loss measurements under similar conditions are shown, and the comparison shows that by adopting the valve nozzle of this example, the pressure loss during injection can be significantly reduced compared to the conventional method. can be clearly recognized.

Further, according to the valve nozzle of this embodiment, as described above, when the needle plunger 22 is moved to its rearward end position, the plunger body 5
The annular end surface 60 of the needle plunger 22 is in contact with the annular stepped surface 42 of the through hole 30 on its entire surface, and the flow of the resin material during injection is prevented from hitting the annular end surface 60 of the needle plunger 22. It requires less force to hold it in place,
Therefore, the piston portion 68 facing the second air chamber 72
The needle plunger 22 can be stably held at its retracted end position without increasing the area of the pressure receiving surface 86 that much. Therefore, it is possible to stably perform the injection operation while keeping the pneumatic piston mechanism and, by extension, the nozzle body 20 sufficiently compact.

One embodiment of the present invention has been described in detail above, but
This is a literal example, and it goes without saying that the present invention should not be construed as being limited to this specific example.

For example, in the embodiment described above, by making the diameter A of the bottomed hole 51 of the needle plunger 22 larger than the diameter B of the small diameter portion 34 of the through hole 30, the annular shape on the proximal end side of the needle plunger 22 is Although the flow of resin material during injection was prevented from hitting the end face 60, the needle plunger 22
If the flow of resin material during injection is prevented from hitting the annular end surface 60 when the is moved to the retreated end position, the diameter A of the bottomed hole 51 is set equal to the diameter B of the small diameter portion 34. Furthermore, it is also possible to make only the annular inner peripheral edge portion of the annular end surface 60 come into contact with the annular stepped surface 42 of the through hole 30.

Further, in the embodiment, the needle plunger 2
Although it has been described that a plurality (specifically, three) of resin through holes 58 are formed in the bottom wall of the plunger body 52 of No. 2, the number of resin through holes does not necessarily have to be plural. There isn't.

In addition, specific examples such as the structure of the nozzle body 20, the needle plunger 22, or the pneumatic piston mechanism will not be enumerated one by one; It goes without saying that various changes, modifications, improvements, etc. can be made based on this invention.

[Brief explanation of the drawing]

FIG. 1 is a sectional view showing an example of a valve nozzle according to the present invention. 2a is a graph showing an example of the measurement results of pressure loss when using the valve nozzle shown in FIG. 1, and b of FIG. It is a figure corresponding to a of a figure. FIG. 3 is a sectional view showing an example of a conventional valve nozzle. 20... Nozzle body, 22... Needle plunger (needle valve member), 26... Nozzle base,
28... Nozzle head, 30... Through hole (injection resin passage), 42... Annular stepped surface, 50a, 50b,
50c...Band heater, 51...Bottomed hole, 52
... Plunger body (bottomed cylinder part), 54 ... Needle valve part, 56 ... Needle part, 58 ... Resin through hole, 60 ... Annular end surface, 62 ... Valve seat, 64 ...
Annular groove, 68... Piston portion, 70... First air chamber, 72... Second air chamber, 82... Solenoid switching valve.

Claims (1)

[Claims for Utility Model Registration] A valve seat is formed at the tip side of the injection resin passage of the nozzle body attached to the tip of the heating cylinder, and the axis of the nozzle body is formed in the injection resin passage of the nozzle body. A needle valve member having a needle valve portion at its tip is disposed in a state where it can be moved a predetermined distance in the direction, and by moving the needle valve member toward the tip of the nozzle body, the needle valve portion of the needle valve member is moved. is seated on the valve seat to prevent injection of the resin material, while moving the needle valve member toward the proximal end of the nozzle body to cause the needle valve portion to separate from the valve seat. , a valve nozzle for an injection molding machine that allows injection of a resin material, wherein the needle valve member is connected to a bottomed cylindrical portion having a bottomed hole of a predetermined depth that serves as a resin passage; Extending from the bottom wall coaxially with the bottomed cylinder part,
A needle plunger comprising a needle portion of a predetermined length having the needle valve portion at the tip thereof, and one or more resin through holes formed to penetrate inside and outside the bottom wall of the bottomed cylindrical portion. The needle plunger is arranged in a state in which the bottomed cylindrical part is slidably fitted into the injection resin passage of the nozzle body, and the needle valve of the needle part a forward end position where the part is seated on the valve seat of the injection resin passage, and an annular end surface on the proximal end side of the bottomed cylindrical part abuts an annular stepped surface formed on the proximal part of the injection resin passage. At the retreating end position of the needle plunger, the annular end surface of the bottomed cylindrical portion is arranged so as to be movable between the retracting end position and the annular step of the injection resin passage at least at the annular inner peripheral edge thereof. Make sure it is in contact with the attached surface,
The flow of the resin material during injection is prevented from hitting the annular end surface of the bottomed cylindrical portion, and a first A pneumatic piston that moves the needle plunger toward its distal end by supplying compressed air to an air chamber and moves the needle plunger toward its proximal end by supplying compressed air to a second air chamber. A mechanism may be provided to selectively move the needle plunger between the forward end position and the retracted end position by selectively supplying compressed air to the first and second air chambers of the pneumatic piston mechanism. A valve nozzle for an injection molding machine characterized by the following features: