JPH06328529A - Method for preventing resin from leaking in vertical injection molding machine and its structure - Google Patents

Abstract

PURPOSE:To avoid surely sagging phenomenon by adding a simple suck back hydraulic circuit and a suck back cylinder to a hydraulic circuit. CONSTITUTION:Hydraulic oil is fed into a suck back cylinder 6 while pressure is applied at the time of metering of a resin and the hydraulic oil fed in the suck back cylinder 6 is closed in the suck back cylinder 6 under pressurized condition when metering of the resin is completed and suck back is completed after metering and a load to be applied on the metered resin 4 is supported by the pressurized hydraulic oil. When the metering is completed and the suck back is completed after metering, the hydraulic oil in the suck back cylinder 6 under an already compressed condition is closed in the suck back cylinder 6. Therefore, the pressurized hydraulic oil is not applied any more on the metered resin 4 by loading.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention prevents a resin leak in a new vertical injection molding machine capable of preventing a so-called "nasal drooling phenomenon" which is likely to occur at the time of nozzle back after completion of suck back after resin measurement. Regarding the method and its structure.

[0002]

2. Description of the Related Art Generally, plasticization of resin in the injection molding process
In the measuring stage, the screw is rotated while heating the resin inside while the nozzle is in contact with the mold, the molten resin is sent to the tip of the heating cylinder, and the molten resin is accumulated in a fixed amount at the tip of the heating cylinder. . When the molten resin is sent to the tip of the heating cylinder, the screw gradually retracts as a reaction. Then, after measuring a predetermined injection amount, the rotation of the screw must be stopped and the measuring position must be held until the next injection process is started. In this case, depending on the type of resin, it is extremely sensitive to temperature, and if the tip nozzle of the heating cylinder is held in contact with a die with a large heat capacity, the heat at the tip end is taken away by the die and the temperature drops. However, the resin inside the nozzle tip may solidify. In such a case, it is necessary to separate the nozzle from the mold by the nozzle back so that heat is not taken away.

Particularly, in a vertical injection molding machine using an open nozzle, when the tip nozzle is held apart from the mold, the weight of the screw, screw rotating device, etc. works downward, so that heating occurs. Large pressure is applied to the measuring resin stored and retained at the tip of the cylinder. As a result, when the tip portion of the heating cylinder is separated from the mold as described above, a so-called “nasal drool phenomenon” occurs in which the molten resin is pushed down by the weight and pushed out from the tip of the nozzle of the heating cylinder. .

Therefore, in order to eliminate the "dripping phenomenon", after the measurement is completed, the injection cylinder is operated to slightly raise (retract) the screw so that pressure is not applied to the measuring resin. Was also proposed (so-called suck back process), but with suck back by the injection cylinder, holding of the injection piston after suck back became insufficient, and there was a problem in completely eliminating the "nasal drool phenomenon". .

Therefore, in the conventional vertical injection molding machine, the "dripping phenomenon" of the molten resin is prevented by closing the nozzle at the time of plasticizing by using a needle type check nozzle. An additional opening / closing mechanism is required, resulting in a new inconvenience that the device becomes complicated.

[0006]

SUMMARY OF THE INVENTION The present invention has been made in view of the drawbacks of the conventional example, and an object of the present invention is to provide a suck back hydraulic circuit and a suck back cylinder which are simple to the conventional hydraulic circuit. It is necessary to ensure that the nasal drooping phenomenon can be avoided simply by adding.

[0007]

According to a first aspect of the present invention, there is provided a "resin kneading screw (1), and the screw according to claim 1".
A heating cylinder (2) that stores (1) in a rotatable and retractable manner,
The screw (1) is connected to the screw (1) and the mold (3)
Injection cylinder that advances in the direction and injects the measured resin (4) measured at the tip of the heating cylinder (2) into the mold (3).
(5) and suck back cylinder connected to the screw (1)
In the injection molding machine configured with (6), when measuring resin, pressure oil is supplied to the suck back cylinder (6) while applying pressure, and when sucking back resin is completed or suck back is completed after measuring, the suck back cylinder ( The pressure oil supplied to 6) is blocked under pressure in the suck back cylinder (6), and the measuring resin
The load that should be applied to (4) is carried by the pressurized oil. ” As a result, the pressure oil in the suck back cylinder (6) will be blocked in the suck back cylinder (6) in a state of being compressed at the time of completion of the weighing or the completion of the suck back after the weighing. The pressure oil is no longer compressed by the load that should be applied to the resin (4) (for example, the weight of the screw or screw rotating device that works downward), and before injection at the completion of weighing or the completion of suck back after weighing. For holding the screw (1)
(1) does not go down, it is held exactly at the stop position, and as a result, the "nasal drool phenomenon" is eliminated.

A second aspect of the present invention is a structure for carrying out the method of the invention, which comprises a "resin kneading screw (1) and the screw (1)".
Is connected to the screw (1) and is rotated and moved back and forth, and the screw (1) is advanced in the direction of the mold (3) and weighed at the tip of the heating cylinder (2). Injection cylinder (5) for injecting the measured resin (4) into the mold (3)
And a suck back cylinder (6) connected to the screw (1)
And a non-leak valve (7) which operates when the resin is measured or when the suckback after the measurement is completed to close the pressurized oil under pressure in the suckback cylinder (6) '. As a result, the pressurized pressure oil in the suck back cylinder (6) is completely blocked when the weighing is completed or suck back is completed, and the screw (1) and the screw rotation device (10) are attached to the weighing resin (4). ) And the downward weight of the injection piston (5a) are supported without being compressed by the pressurized oil in the suck back cylinder (6), and the measuring resin (4)
The above-mentioned downward load is not applied to the
Even if (24) is opened, the "nasal drool phenomenon" does not occur.

A third aspect of the present invention is that "a suck back cylinder (6) is provided in an injection piston (5a) slidably disposed in the injection cylinder (5)". According to this, the space for the suck back cylinder (6) is not particularly required, and the appearance and the space are excellent.

[0010]

The present invention will be described in detail below with reference to the embodiments of the vertical injection molding machine shown in the drawings. (2) is a heating cylinder held vertically, and (1) is a screw, which is housed in the heating cylinder (2) so as to be rotatable and retractable. A band heater (8) is wound around the outer periphery of the heating cylinder (2) to heat and melt the resin (4) in the heating cylinder (2).
(9) is a cylinder holding plate that holds the heating cylinder (2), and the upper end portion of the heating cylinder (2) is fixed.

Reference numeral (5) is an injection cylinder provided at both ends of the cylinder holding plate (9), in which an injection piston (5a) is slidably inserted and fixed to the rotating device holding plate (11). In the center of the rotation device holding plate (11), for example, a screw rotation device such as an oil motor or an electric motor
(10) is installed, and the screw (1) and the screw rotating device (10) are connected via the coupling (10a).

In the present embodiment, the suck back cylinder (6) is formed in the injection piston (5a), and the suck back cylinder (6) is provided so as to project from the inner surface facing the suck back cylinder (6). The suck back piston (6a) is slidably inserted. Of course, suck back cylinder
(6) may be provided at another position. Suck back cylinder
A pressure oil supply passage (6b) communicating with (6) is formed in the suck back piston (6a) to supply pressure oil into the suck back cylinder (6). Also, since the suck back cylinder (6) has a thin inner diameter, quick suck back can be performed with a small amount of pressure oil.

A nozzle touch cylinder (13) is provided upright on both sides of the die plate (14), and a nozzle touch piston (13a) is slidably inserted therein. The nozzle touch piston (13a) is provided on the lower surface of the cylinder holding plate (9) so that the heating cylinder (2) and the entire plasticized plasticizing portion can be moved forward and backward.

(16) is a fixed mold, (15) is a movable mold, the sprue (17) formed in the fixed mold (16) is in communication with the cavity (18), the injected measuring resin (4) is the cavity (1
It is designed to be filled in 8).

FIG. 2 shows a hydraulic circuit applied to the present invention.
(7a) and (7b) are non-leak valves connected in parallel, (19) is a back pressure setting valve, (20) is a two-way switching valve, (SOL BP) is a solenoid for the two-way switching valve (20), Reference numeral (21) is a four-way switching valve, and (SOL SR) and (SOL I) are solenoids of the four-way switching valve (21). Suck back cylinder
The pressure oil supply passage (12) of (6) is connected to the non-leak valves (7a) and (7b), respectively, and further connected to the four-way switching valve (21). The four-way switching valve (21) is connected to the hydraulic pressure source (22) and the tank (23). The suck back process requires a retreat speed rather than force, so the suck back cylinder
(6) is thin. As a result, the amount of pressure oil does not have to be small.

Both the injection side oil supply chamber (5b) of the injection cylinder (5) is connected to the tank (23) through a back pressure setting valve (19) and a two-way switching valve (20). The back pressure hydraulic line (25) between the injection side oil supply chamber (5b) and the back pressure setting valve (19) and one solenoid (SOL SC) side non-leak valve (7a) to the four-way switching valve ( Suck back release hydraulic line up to 21) (26)
Are connected.

However, in the injection process, the solenoid (SOL I) and solenoid (SOL NL) of the four-way switching valve (21) are used.
Side non-leak valve (7b) is activated, injection cylinder (5)
The pressure oil from the hydraulic pressure source (22) enters the injection side oil supply chamber (5b)
It is supplied through (27) and the injection piston (5a) advances.
On the other hand, as the injection piston (5a) advances, the suck back piston (6a) will be inserted into the suck back cylinder (6) formed in the injection piston (5a), and the suck back cylinder (6) The pressure oil will be pushed out. The pushed pressure oil returns to the tank (23) through the solenoid (SOL NL) side non-leak valve (7b) in operation. Therefore, the injection piston (5a) can move forward without the resistance of the suck back cylinder (6).

Since the injection piston (5a) is connected to the screw (1) via the rotating device holding plate (11), the screw (1) also advances as the injection piston (5a) advances, and the heating cylinder (2) The resin (4) stored at the tip of () is injected into the mold cavity (18).

Next, in the plasticizing / measuring process, the solenoid (SOL I) and solenoid (SOL NL) side non-leak valve (7b) of the four-way switching valve (21) are turned off and replaced. Solenoid (SOL SC) side non-leak valve (7a) and 2-way switching valve (20) solenoid (SOL B
P) turns on. Further, the screw rotating device (10) is operated in conjunction with the operation of the valves (7a) (20) to rotate the screw (1). As a result, the resin (4) in the heating cylinder (2) is heated and melted by the band heater (8) and is kneaded by the rotation of the screw (1) while being extruded toward the tip of the heating cylinder (2). . In accordance with this, the screw (1) will go up (back).

As the screw (1) rises, the injection piston (5a) also rises, the pressure oil in the injection side oil supply chamber (5b) in the injection cylinder (5) is pushed out, and the back pressure setting valve ( It is discharged to the tank (23) through the (19) and the two-way switching valve (20). At this time, since the pressure oil passes through the back pressure setting valve (19), the set back pressure can be applied to the backward movement of the screw (1). At the same time, the suck back cylinder (6) is connected to the injection side pipe line (27) of the injection cylinder (5) through the non-leak valve (7a) on the solenoid (SOL SC) side, so that the injection cylinder (5) can be raised. At the same time, the volume of the suck back cylinder (6) expands, but the pressure oil is sucked in as the volume expands. Since the set pressure is applied to the pressure oil as described above, the pressurized pressure oil is supplied to the suck back cylinder (6).

When a predetermined amount of resin is weighed and stored in the tip portion of the heating cylinder (2), the weighing is completed and the suck back process is started. Solenoid (SOL S
The non-leak valve (7a) on the C) side and the solenoid (SOL BP) of the 2-way switching valve (20) are turned off, and then the suckback side solenoid (SOL SR) and solenoid (SOL SR) of the 4-way switching valve (21). The non-leak valve (7b) on the (NL) side is turned on to start the suck back process.

In the suck back process, a four-way switching valve
(21) and solenoid (SOL NL) side non-leak valve (7b)
The pressure oil is supplied into the suck back cylinder (6) via the, and the injection piston (5a) is slightly pushed up (retracted). The pressure oil in the injection cylinder (5) is pushed out by the above-mentioned amount of rise, but this pushed pressure oil is a four-way switching valve.
It is discharged to the tank (23) via (21). The suck back is completed by a small amount of ascending (retracting) so that the resin (4) measured and stored at the tip of the heating cylinder (2) is not pressured. When the suck back process is completed, the four-way switching valve (21) and the solenoid (SOL NL) side non-leak valve (7b) are switched off. At this time, both non-leak valves (7a) and (7b) are a poppet valve type check valve mechanism with almost no leak in the off state, so that the pressure oil trapped in the suck back cylinder (6) is completely eliminated. There is no leakage. Moreover, suck back cylinder
Since the pressure oil in (6) will be blocked under pressure, the screw (1), injection piston (5a), screw rotation device (10)
Also, even if a downward load such as the rotating device holding plate (11) is applied to the pressure oil, the pressure oil is no longer compressed, and as a result, the screw (1) is carried by the suck back cylinder (6) at the position where the suck back is completed. Therefore, the measuring resin (4) stored at the tip of the heating cylinder (2) is not overloaded. Depending on the molded product, it may be extremely disliked to entrap air bubbles in the resin.In such a case, the screw (1) may be held in the completed measurement state without performing suck back. Even in this case, since the downward load is carried by the pressurized oil, it is possible to hold the position at the time of completion of the measurement as it is, as in the case of performing the suck back.

After the end of the suck back or before the suck back, the nozzle touch cylinder (13) is operated to move the tip nozzle (24) of the heating cylinder (2) to the sprue (1) of the fixed mold (15).
It is separated from 7) to prevent cooling of the tip nozzle (24). After the completion of one cycle, the first injection molding process "001
Returning to 7 ”, injection is performed. Table 1 is a solenoid valve operation table in the present invention. Table 1 mainly describes the case where suck back is performed. However, when suck back is not performed and the injection process is started after the completion of weighing, “SOL SR” and “SOL NL” in the suck back of Table 1 are used. Should be omitted.

[0024]

According to the method of the present invention, the pressure oil is supplied to the suck back cylinder while pressurizing at the time of measuring the resin, and the pressure oil supplied to the suck back cylinder is supplied at the time of the completion of the resin measurement or the completion of the suck back after the measurement. In the pressurized state, the suck back cylinder is closed, and the load to be applied to the measuring resin is carried by the pressurized pressure oil. When the suck back is completed afterward, the screw does not lower during the holding of the screw before the injection, and the screw is accurately held at the backward stop position, and as a result, the "nasal drooping phenomenon" is eliminated. Further, in claim 2, the pressurized pressure oil in the suck back cylinder is closed by the non-leak valve when the resin measurement is completed or the suck back after the measurement is completed. There is an advantage that it is completely blocked without leaking, the downward load is not applied to the measuring resin at all, and the "nasal dripping phenomenon" does not occur. Further, claim 3
Since the suck back cylinder is provided in the injection piston slidably arranged in the injection cylinder, the space for the suck back cylinder is not particularly required, and the appearance and space are not only excellent. Instead, the suck back speed can be increased with a small amount of pressure oil.

[Brief description of drawings]

FIG. 1 is a schematic sectional view of essential parts of a vertical injection molding machine of the present invention.

FIG. 2 is a hydraulic circuit diagram of the present invention.

[Explanation of symbols]

(1)… Screw for resin kneading (2)… Heating cylinder (3)… Mold (4)… Measuring resin (5)… Injection cylinder (6)… Suck back cylinder

Claims (3)

[Claims] 1. A resin kneading screw, a heating cylinder in which the screw is rotatably and reciprocally housed, a screw connected to the screw and advanced in the direction of the mold, and weighing is measured at the tip of the heating cylinder. In an injection molding machine consisting of an injection cylinder that injects resin into the mold and a suck back cylinder connected to the screw, when measuring resin, supply pressure oil to the suck back cylinder while applying pressure to complete resin measurement. The present invention is characterized in that the pressure oil supplied to the suckback cylinder is closed in the suckback cylinder in a pressurized state at the time of completion of suckback after weighing, and the load to be applied to the weighing resin is carried by the pressurized pressure oil. Resin leakage prevention method for vertical injection molding machine. 2. A resin kneading screw, a heating cylinder that accommodates the screw so that the screw can rotate and move forward and backward, a meter connected to the screw and moved forward in the mold direction to measure the tip of the heating cylinder. An injection cylinder that injects resin into the mold, a suck back cylinder connected to the screw, and a non-leak that shuts off pressurized oil in the suck back cylinder when the resin is measured or sucked back after measurement. A vertical injection molding machine characterized by being configured with a valve. 3. The vertical injection molding machine according to claim 2, wherein a suck back cylinder is provided in an injection piston slidably provided in the injection cylinder.