JPH068285A - Injection molding equipment - Google Patents

Abstract

(57) [Summary] [Purpose] To improve productivity by shortening the injection molding cycle time. According to the injection molding apparatus of the present invention, a pressure holding screw 122 is provided in a resin flow path of a hot runner block 22b.
Is equipped with. The pressure-holding screw 122 can be advanced along the resin flow path while rotating around the axis by a hydraulic motor and hydraulic cylinder 122m. Further, the pressure-holding screw 122 has a flange-shaped valve body 12
2b is attached, and the valve body 122b abuts the valve seat portion 22t of the hot runner block 22b to close the resin flow passage. As a result, if the resin flow path is closed by the pressure-holding screw 122 when the injection of the molten resin is completed, the molten resin will not flow backward from the cavity 26 even if the injection pressure on the heating cylinder 14 side is released. Therefore, the injection screw 15 in the heating cylinder 14 can be quickly returned to the measuring position.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an injection molding apparatus for guiding a molten resin injected from an injection cylinder to a cavity formed in a mold through a resin flow path provided in the mold.

[0002]

2. Description of the Related Art The prior art relating to this is disclosed in Japanese Patent Laid-Open No. 1-20
No. 8114, a longitudinal sectional view of the injection molding apparatus is shown in FIGS. 3 and 4 attached to the application of the present application. The injection molding apparatus includes a heating cylinder 14 having a function of adjusting the temperature of the molten resin. This heating cylinder 14
A hopper 12 is attached to the rear part of the hopper 12, and resin pellets are supplied from the hopper 12 into the heating cylinder 14. Further, an injection screw 15 is housed inside the heating cylinder 14. A hydraulic motor and hydraulic cylinder 16 for rotating the injection screw 15 around the axis and moving it in the axis direction are coaxially attached to the rear end of the heating cylinder 14. Also, the heating cylinder 14
A nozzle 13 for injecting resin is formed at the tip of the. On the other hand, the injection molding die is composed of a fixed die 22 and a movable die 24. Inside the die, the product molding portion 26 (cavity 26) and the resin flow are made up of a fixed die 22 and a movable die 24. A gate portion 27 and a runner 28 that function as a path are formed. The fixed mold 22 is also provided with a hot runner block 22b and a sprue 22c that also form a resin flow path. A heater 22h for holding the resin in a molten state is installed around the hot runner block 22b. The nozzle 13 formed at the tip of the heating cylinder 14 is connected to the resin injection port 22a formed in the hot runner block 22b of the fixed die 22. As a result, the resin injected from the nozzle 13 is guided to the cavity 26 through the resin flow path.

When the injection molding die is clamped, the injection screw 15 is rotated by the hydraulic motor and hydraulic cylinder 16 so that the resin pellets in the hopper 12 are supplied into the heating cylinder 14. The resin pellets are melted by the heat of the heating cylinder 14 and the heat generated by being compressed and sheared by the injection screw 15. In this state, the injection screw 15 is displaced by the hydraulic motor and hydraulic cylinder 16 toward the tip of the heating cylinder 14, and the molten resin is injected from the nozzle 13. The resin injected from the nozzle 13 is filled in the cavity 26 through the hot runner block 22b, the sprue 22c, the runner 28 and the gate portion 27.
Here, the resin in the cavity 26 receives a predetermined pressure (injection pressure) from the heating cylinder 14 side through the injection process and the pressure holding process, and the pressure is released only when the resin located in the gate portion 27 is solidified. It The pressure is applied to the molten resin in the injection process in order to reliably fill the cavity 26 with the resin, and the pressure is applied in the pressure holding process to compensate for the loss due to the volume contraction of the resin. In this way, the surface quality of the molded product is ensured by the injection pressure applied from the heating cylinder 14 side.

[0004]

However, according to the conventional injection molding apparatus, as shown in FIG. 4, the pressure applied to the resin at the time of shifting from the injection process to the pressure-holding process is reduced, or the pressure-holding process is performed. If the pressure applied to the resin is lowered when shifting to the cooling process, the phenomenon in which the resin in the cavity 26 flows out (backflow phenomenon) occurs when the resin in the gate portion 27 is not solidified. When this backflow phenomenon occurs, surface distortion and sink marks of the product occur. Therefore, in the conventional injection molding apparatus, in order to prevent product defects, it is necessary to continue to apply injection pressure from the heating cylinder 14 side until the resin positioned in the gate portion 27 solidifies. That is, the injection screw 15 in the heating cylinder 14 cannot be returned from the injection completion position to the original measurement position until the resin of the gate portion 27 is solidified. Therefore, for example, when a large gate is adopted, it takes a very long time for the resin of the gate portion 27 to solidify,
During this time, it is necessary to hold the injection screw 15 at the injection completion position. Therefore, the measurement of the resin pellet for the next injection molding cannot be performed until the resin of the gate portion 27 is solidified, the cycle time of the injection molding becomes long, and the productivity is lowered. The technical problem of the present invention is to provide a backflow prevention mechanism for preventing backflow of resin in the resin flow path of the hot runner block, so that the injection pressure on the heating cylinder side can be quickly released after the injection is completed. Then, the cycle time of injection molding is shortened and the productivity is improved.

[0005]

The above-mentioned problems can be solved by an injection molding apparatus having the following respective structures. That is, in the injection molding apparatus according to the present invention, the molten resin injected from the injection cylinder is introduced into the cavity formed in the mold through the resin flow path provided in the mold. It is installed inside, can be moved along this resin flow path, and is attached to the pressure-holding screw that flows molten resin by rotating around the axis and the pressure-holding screw. A flow path closing member for closing the resin flow path by moving a predetermined distance in a direction approaching the cavity from a position,
It has a pressure-holding screw driving means for rotating the pressure-holding screw so that the molten resin flows in the direction of the cavity, and further for moving the pressure-holding screw from the reference position toward the cavity by a predetermined distance. .

[0006]

According to the present invention, for example, when the injection of the molten resin is completed, the pressure-holding screw driving means causes the pressure-holding screw to rotate, and the pressure-holding screw is moved a predetermined distance in the direction from the reference position toward the cavity. By moving the resin, the resin flow passage can be closed by the flow passage closing member while flowing the molten resin in the direction of the cavity. As a result, the cavity is maintained in a state where a pressure substantially equal to the injection pressure is applied. Therefore, even if the pressure on the injection cylinder side is released immediately after the injection of the molten resin is completed, the molten resin does not flow back from the cavity.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An injection molding apparatus according to an embodiment of the present invention will be described below with reference to FIGS. The injection molding apparatus according to the present embodiment is an improvement of the structure of the hot runner block 22b of the conventional injection molding apparatus shown in FIG. 3, and the other structures are the same as those of the conventional injection molding apparatus.
The injection molding apparatus according to this embodiment includes a heating cylinder 14 having a function of adjusting the temperature of the molten resin. A hopper 12 is attached to the rear portion of the heating cylinder 14, and resin pellets are supplied from the hopper 12 into the heating cylinder 14. Further, an injection screw 15 is housed inside the heating cylinder 14. A hydraulic motor and hydraulic cylinder 16 for rotating the injection screw 15 around the axis and moving it in the axis direction are coaxially attached to the rear end of the heating cylinder 14. A nozzle 13 for injecting resin is formed at the tip of the heating cylinder 14. In addition, a position detector (not shown) for detecting the position of the injection screw 15 in the axial direction is installed in the hydraulic motor & hydraulic cylinder 16 that moves the injection screw 15 in the axial direction. There is. The position of the injection screw 15 can determine whether the injection is completed.

On the other hand, the injection molding die is composed of a fixed die 22 and a movable die 24. Inside the die, the product molding portion 26 (cavity 26) is formed with the fixed die 22 and the movable die 24 engaged with each other. And a gate portion 27 that functions as a resin flow path,
The runner 28 is formed. In addition, the fixed mold 22 has a hot runner block 22b and a sprue 2 that form a resin flow path.
2c is provided. The hot runner block 22
As shown in FIG. 3, the resin flow path of b is U-shaped in plan view, and a pressure holding screw 122 is installed at a bent portion of this flow path as shown in FIG. The pressure-holding screw 122 has a flange-shaped valve body 122b in the central portion.
Is provided, and a screw 122s is formed closer to the tip than the valve body 122b. The screw 122s is coaxial with the flow path, and the screw 1
The front end side of 22s is arranged so as to face the end side of the flow path. Further, a taper surface 122t is formed on the front surface side of the valve body 122b, and the hot runner block 2 facing the taper surface 122t of the valve body 122b.
A valve seat portion 22t is formed at the bent portion of 2b.

A shaft portion 122h is formed on the rear side of the valve body 122b of the pressure-holding screw 122, and the shaft portion 122h is slidably inserted into a through hole 22k formed in the hot runner block 22b. Has been done. A hydraulic motor & hydraulic cylinder 122m is connected to the end of the shaft 122h. As a result, when the hydraulic motor & hydraulic cylinder 122m is driven, the pressure-holding screw 122 rotates around the axis and also moves in the axis direction. When the pressure-holding screw 122 moves forward from the reference position by a predetermined distance and the tapered surface 122t of the valve body 122b contacts the valve seat portion 22t of the hot runner block 22b, the flow passage is closed. That is, the valve element 122b functions as a flow path closing member, and the hydraulic motor & hydraulic cylinder 122m functions as a pressure maintaining screw driving means. The hot runner block 22
A heater 22h for holding the resin in a molten state is installed around b. Further, a resin injection port 22a is formed in the hot runner block 22b, and the nozzle 13 formed at the tip of the heating cylinder 14 is connected to the resin injection port 22a.

Next, the operation of the injection molding apparatus according to this embodiment will be described. First, the injection mold is clamped. At this time, the hot runner block 22b of the fixed die 22
As shown in FIG. 2 (A), the pressure-holding screw 122 installed at is held at the reference position, and the flow path formed in the hot runner block 22b is held open. Further, the injection screw 15 in the heating cylinder 14
Is rotated by the hydraulic motor and hydraulic cylinder 16,
The resin pellets in the hopper 12 are supplied into the heating cylinder 14. The resin pellets are melted by the heat of the heating cylinder 14 and the heat generated by being compressed and sheared by the injection screw 15. In this state, the injection screw 15 is displaced toward the tip of the heating cylinder 14 by the hydraulic motor and hydraulic cylinder 16, and the molten resin is injected from the nozzle 13. The resin injected from the nozzle 13 is the hot runner block 22b and the sprue 22.
The cavity 26 is filled through the c, the runner 28, and the gate portion 27.

The position of the injection screw 15 in the axial direction is detected by the position detector, and the hydraulic motor of the pressure-holding screw 122 immediately before the injection screw 15 reaches the injection completion position. The hydraulic cylinder 122m is activated. This pressure-holding screw 12
The molten resin flows in the direction of the cavity 26 due to the rotation of 2 around the axis, and the pressure-holding screw 122
Moves forward in the axial direction by a predetermined distance, so that the valve body 1
The taper surface 122t of 22b is the hot runner block 22.
The flow path is blocked by contacting the valve seat portion 22t of b. As a result, the cavity 26 is maintained in a state where a pressure substantially equal to the injection pressure is applied. Therefore, even if the injection pressure on the heating cylinder 14 side is released, the molten resin does not flow back from the cavity. That is, when the injection of the molten resin is completed, the injection screw 15 in the heating cylinder 14 can be quickly returned from the injection completion position to the original measurement position, and the measurement for the next injection molding can be performed. it can.
In this state, when the resin in the gate portion 27 and the cavity 26 is solidified after a predetermined time elapses, the pressure holding screw 122 is returned to the reference position by the hydraulic motor & hydraulic cylinder 122m to open the flow path. Then, the injection mold is opened. As described above, according to this embodiment, when the injection of the molten resin is completed, the measurement for the next injection molding can be performed, so that the cycle time of injection molding is shortened and the productivity is improved.

[0012]

According to the present invention, if the resin flow passage is closed by the pressure-holding screw and the flow passage closing member at the stage when the injection of the molten resin is completed, the molten resin will be released even if the injection pressure on the injection cylinder side is released. There is no backflow from the cavity. Therefore, the injection screw in the injection cylinder can be quickly returned to the measuring position, and the measurement for the next injection molding becomes possible. Therefore, the cycle time of injection molding is shortened and the productivity is improved.

[Brief description of drawings]

FIG. 1 is a detailed sectional view of an essential part of an injection molding device according to an embodiment of the present invention.

FIG. 2 is a cross-sectional view showing a moving range of a pressure holding screw.

FIG. 3 is a vertical cross-sectional view of a conventional injection molding device.

FIG. 4 is a cross-sectional view showing a position of an injection screw of an injection molding device.

[Explanation of symbols]

14 heating cylinder (injection cylinder) 22 fixed mold (mold) 24 movable mold (mold) 22b hot runner block 26 cavity 122 pressure holding screw 122b valve body (flow passage closing member) 122m hydraulic motor & hydraulic cylinder (pressure holding screw) Drive means)

Claims (1)

[Claims] 1. An injection molding device for guiding molten resin injected from an injection cylinder to a cavity formed in the mold through a resin flow path provided in a mold, the injection molding device being installed in the resin flow path, It is attached to the pressure-holding screw that can move along the resin flow path and that flows the molten resin by rotating around the axis, and the pressure-holding screw, and the pressure-holding screw approaches the cavity from the reference position. A flow path closing member that closes the flow path by moving a predetermined distance in the direction, and the pressure holding screw is rotated so that the molten resin flows in the direction of the cavity. An injection molding apparatus comprising: a pressure-holding screw driving unit that moves a predetermined distance in a direction approaching the cavity.