JP3159014B2 - Measuring method for pre-plastic injection system - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a weighing method in a pre-plastic injection device used for injection molding of a synthetic resin.

[0002]

2. Description of the Related Art In general, a pre-plastic injection device has a plasticizing cylinder in which a plasticizing member such as a plasticizing screw or a plunger is provided in parallel with an injection cylinder in which a plunger for injection is mounted. The tip of the plasticizing cylinder is connected to the tip of the injection cylinder via a large-diameter, short cylinder, etc., and the cylinder, etc. is melted and kneaded by a plasticizing cylinder as a resin path (hereinafter referred to as plasticization). After the measurement is performed at the front part of the plunger, the injection is performed by advancing the plunger.

Further, in the pre-plastic injection device, a part of the measuring resin flows backward to the plasticizing cylinder due to the injection pressure, and the measuring resin is reduced by that amount. Therefore, a closing means for preventing this is provided at the tip of the plasticizing cylinder. It is said that it is preferable to provide it in an outflow path, a resin path, or the like.

As the closing means, a spring member provided on the outside of the valve body constantly presses a valve seat formed on the plasticizing cylinder side of the resin path through a movable pin through a movable pin, and pressurizes the resin pressure from the plasticizing cylinder. A valve system that opens the valve only by itself to prevent backflow of resin from the injection cylinder,
There is a screw system in which the screw is advanced when the measurement is completed, and the inside of the tip of the plasticizing cylinder is closed by pushing the tip of the screw with the screw tip surface. However, in any case, the valve is closed at the start of injection because the purpose of the valve is to prevent the resin from flowing back.

[0005]

In the pre-plastic injection apparatus, the plasticizing and pressure-feeding of the resin are performed by the forward movement or rotation of the plasticizing member. Therefore, even if the plasticizing member is stopped to stop the plasticization of the resin, the flow of the resin toward the injection cylinder remains. When the plasticizing member is a screw, the flow is: screw diameter 36 mm, rotation speed 100 rpm, back pressure 5 kg / cm ² ,
An amount corresponding to about 2 mm of the resin GPPS, measured at 20 mm, flows out to the injection cylinder side.

[0006] The flow rate of the resin after the plasticization is stopped is excessive in terms of measurement, and the flow rate is not always constant but varies every time. You can't do it. This variation in the measurement results in a variation in the injection filling amount, which causes a defective product in molding a molded product requiring dimensional accuracy.

The present invention has been conceived in order to solve the above-mentioned problem, and an object of the present invention is to utilize a check valve adopted for backflow prevention for preventing resin flow after plasticization is stopped. It is an object of the present invention to provide a new weighing method in a pre-plastic injection apparatus which can prevent excessive weighing and stabilize weighing at all times.

[0008]

SUMMARY OF THE INVENTION According to the present invention, there is provided an injection cylinder in which an injection plunger is mounted, and a plasticizing cylinder in which a plasticizing screw is rotatably mounted. In a pre-plastic injection apparatus, which communicates with the plasticizing cylinder by a resin path, performs measurement by feeding the resin from the plasticizing cylinder side to the injection cylinder via the resin path, and stops plasticization by stopping rotation of the screw, At the tip of the screw, a check valve having a cone-shaped mushroom-shaped valve body is provided, and the check valve is retracted together with the screw and closed immediately after the screw stops rotating. .

In the present invention, the check valve retreats together with the screw and closes immediately after the screw stops, and shuts off the flow of resin from the plasticizing cylinder. Therefore, the amount of resin measured in the injection cylinder is always constant. It will be constant. Further, since the closing operation of the check valve is performed by retreating movement, the resin downstream of the check valve is not pressurized. Is prevented, and the amount of resin measured in the injection cylinder is further stabilized.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS In the drawings, reference numeral 1 denotes an injection device, 2 denotes a plasticizing device juxtaposed on the injection device, and both devices communicate with each other via a resin path 3 provided at the tip end.

The injection device 1 includes an injection plunger 10.
And a hydraulic cylinder 14 for injection in which a piston 13 is connected to a rear end of the injection cylinder 12 and a piston 13 is connected to the plunger 10. ing.

The injection cylinder 12 has an inflow passage 15 of the resin passage 3 at an upper portion corresponding to a plunger advance limit at a tip end.
The inflow passage 15 is provided at the tip 1 of the injection cylinder 12.
The plasticized resin from the resin passage 3 flows along the inner peripheral surface by being inclined toward the inner peripheral surface of 2a.

Further, resin injection holes 16 are provided above and below the plunger stroke of the injection cylinder 12, and a band heater 17 is provided to the periphery of the cylinder after the resin extraction hole 16 to set a long heater zone. is there.

The plasticizing apparatus 2 comprises a plasticizing cylinder 22 having a plasticizing screw 20 rotatably mounted therein and having an outflow passage 21 at a front end, and a rear end holding the plasticizing cylinder 22. It comprises a cylinder 23, a hydraulic cylinder 24 for screw advance / retreat connected to the rear end of the holding cylinder 23, and a rotation drive device 25 for the screw 20 attached to the rear end of the hydraulic cylinder 24.

The drive shaft 25a of the rotary drive 25 is
Insert the rear end into the piston 24a of the hydraulic cylinder 24,
The shaft 20 is movably connected in the axial direction to a rotating shaft 23a which is supported inside the holding cylinder 23. The rear end of the screw 20 is connected to the tip of the rotating shaft 23a. The rotating shaft 23a is connected to the piston 24a via a member 23b so as to be movable only in the axial direction, and moves forward and backward together with the piston 24a to move the screw 10 forward and backward. Further, a stopper member 23c for limiting the forward movement of the screw 20 to a certain range is attached to the member 23b.

A band heater 26 is attached to the outer periphery of the plasticizing cylinder 22, and a supply hole 27 is provided upward at the rear end of the plasticizing cylinder 22 fitted to the holding cylinder 23.

At the tip of the screw 20, a check valve 28 having a conical and mushroom-shaped valve body is attached. The plasticizing cylinder 22 in which the check valve 28 is located
Is formed in a recess corresponding to the valve body tip,
A required flow passage communicating with the outflow passage 21 is formed around the check valve 28, and an annular valve seat 29 is provided on the cylinder side facing the inclined rear surface of the check valve 28.

The above flow path differs depending on the resin. When the check valve 28 has a diameter of 36 mm, a flow gap 21a of 1.0 mm to 1.5 mm is formed at least between the check valve 28 and the valve seat 29. It is designed so that a sufficient flow path is formed between the check valve 28 and the wall surface of the recess. When the flow gap 21a is 0.5 mm or less, the heat generated in the plasticizing cylinder is large. When the flow gap 21a is 2.0 mm or more, it takes a long time to close the valve, and the backflow of the measured resin tends to be incomplete.

The resin path 3 is formed by a thin tube 30 and is provided with a band heater 31 around its outer periphery, and has a required mixing member 32 in its upper part. The thin tube 30 is provided obliquely with the joints 30a and 30b over the inflow path 15 of the injection cylinder 12 and the outflow path 21 of the plasticizing cylinder 22.

The injection device 1 and the plasticizing device 2 are integrally connected in two upper and lower stages by mounting and holding the holding cylinder 23 on a support base 18 provided on the hydraulic cylinder 14.
The hydraulic cylinder 14 of the injection device 1 is mounted and fixed on a machine base 7 on a slidable base block 6 connected to a fixed plate 4 of a mold clamping device via a nozzle touch cylinder 5. .

Next, the weighing operation will be described. The hydraulic oil is supplied to the rear chamber side of the hydraulic cylinder 24 so that the piston 24
a and the rotary shaft 23a to advance the screw 20 (1.0
mm), and the valve is opened with the inclined rear surface separated from the valve seat 29. At approximately the same time, the screw 20 is rotated together with the rotation shaft 23a by the rotation driving device 25. As a result, the material resin fed into the plasticizing cylinder 22 from the supply hole 27 is plasticized by the heating by the band heater 26 and the rotation of the screw 20 and is sequentially pressure-fed forward, and further, the check valve 28 and the valve seat 29. Outflow path 21 connected to the flow gap from the gap between
Through the plasticized resin path 3.

In the resin passage 3, the resin is repeatedly divided and mixed by the mixing member 32, and the resin flows into the inflow passage 15 while being further plasticized or mixed. Further, the resin flows obliquely into the injection cylinder 12 through the inclined inflow path 15, and pressurizes the distal end surface of the plunger 10 to be accumulated in the distal end portion of the cylinder while the plunger 10 is moved backward. This accumulation is performed until the plunger 10 moves back to the set position.

When the plunger 10 is retracted to the metering stop position and stopped, the rotation of the screw 20 is stopped, and the plasticization of the resin is temporarily stopped. Immediately after that, the hydraulic cylinder 2
The pressure oil is supplied to the front chamber 4 to forcibly move the screw 20 backward. As a result, the check valve 28 moves upstream with respect to the resin path 3, closes the inclined back surface strongly in contact with the valve seat 29, closes the inside of the tip of the plasticizing cylinder 22, and stops the flow of resin. After the rotation of the screw 20 is stopped, the resin is prevented from flowing into the injection cylinder.

Further, since the valve is closed by retreating the screw 20, there is no extrusion of the resin on the front side of the valve body, so that the measuring stop position of the plunger 10 is stabilized. As a result, a predetermined amount of resin is accumulated in the front part of the plunger of the injection cylinder 12.

The above steps are generally referred to as measurement, after which the measured resin is injected. When the plunger 10 is moved forward with the check valve 28 closed, the resin in the injection cylinder is injected and filled from the nozzle 11 into a mold (not shown). The injection pressure by the plunger 10 also acts on the plasticizing cylinder side via the resin remaining in the resin path 3. However, since the check valve 28 is in the closed state, backflow of the resin toward the plasticizing cylinder is prevented, and the entire amount of the metered resin is injected from the nozzle 11.

When the completion of the injection step is confirmed, the screw 20 advances by the hydraulic cylinder 14 to open the valve, and the rotary drive unit 25 rotates to start the metering of new resin.

Next, a comparison between the present invention in which the valve is closed immediately after the screw rotation is stopped and a conventional example in which the valve is closed during injection will be described.

[0028]

[Table 1]

However, the set measurement stop position: 20.0 mm, material resin: GPPS plasticizing screw diameter: 36.0 mm, injection plunger diameter: 36.0 mm

[0030]

As described above, according to the present invention, at the tip of the screw, a check valve is provided with a cone-shaped mushroom-shaped valve body, and the check valve is connected to the screw together with the screw immediately after the screw stops rotating. By moving backward and closing the valve, the metering stop position of the injection plunger is stable, there is no variation in the resin metering for each shot, and at the time of injection, the check valve is applied to the plasticizing cylinder by the check valve. Backflow is prevented, and resin is prevented from being sent to the downstream side when the valve is closed.Therefore, there is no error in metering due to valve closing, and the amount of resin to be injected is stabilized, and the amount of resin to be metered is determined. Poor molding can be prevented.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view of a pre-plastic injection apparatus according to the present invention.

FIG. 2 is a vertical cross-sectional view of the plasticizing device in a state in which a distal end portion of the plasticizing device is closed.

FIG. 3 is a vertical cross-sectional view of the plasticizing device in a state in which a distal end of the plasticizing device is opened.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Injection apparatus 2 Plasticization apparatus 3 Resin path 10 Injection plunger 12 Injection cylinder 12a Injection cylinder tip part 15 Inflow path 20 Plasticization screw 21 Outflow path 22 Plasticization cylinder 22a Plasticization cylinder tip part 23a Rotating shaft 23c Stopper Member 24 Hydraulic cylinder 24a Piston 25 Rotary drive 28 Check valve 29 Valve seat

Claims (1)

(57) [Claims] 1. A plasticizing cylinder in which a plasticizing screw is rotatably mounted in parallel with an injection cylinder in which an injection plunger is mounted, and the injection cylinder and the plasticizing cylinder are communicated with each other by a resin path. In a pre-plastic injection device in which the resin is pressure-fed from the plasticizing cylinder side to the injection cylinder through the resin path to measure and stop plasticization by stopping rotation of the screw, the tip of the screw has a conical tip shape. A metering method in a prepra-type injection device, characterized in that a check valve having a mushroom-shaped valve body is provided, and the check valve is moved back together with the screw immediately after rotation of the screw is stopped to close the valve.