JP2912861B2 - Pre-plastic injection device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pre-plastic injection device for plasticizing and injecting material resin by using different cylinders.

[0002]

2. Description of the Related Art In general, a prepra-type injection device has a plasticizing cylinder containing a plasticizing screw or a plunger arranged side by side with an injection cylinder containing an injection plunger, and the tip of the plasticizing cylinder is attached to the injection cylinder. It is connected to the tip of the injection cylinder via a large-diameter, short cylinder, etc., and the cylinder, etc. is melted and kneaded with a plasticizing cylinder as a resin path (hereinafter referred to as plasticization). After the measurement, the injection is performed by advancing the plunger.

[0003]

A clearance is provided between the injection cylinder and the plunger so that the plunger can slide. This clearance is designed to the minimum size that makes it difficult for molten resin to enter,
Regardless of the clearance, some resin enters during repeated metering and injection.

[0004] As long as the resin that has entered the clearance is in a molten state and is thinly interposed between the injection cylinder and the plunger, it does not greatly affect the sliding of the plunger. , The sliding resistance increases and a pressure loss is caused. In addition, misalignment occurs between the injection cylinder and the plunger, and the engagement also occurs.

As a means for removing the obstacle of the resin in the clearance, it is conceivable to provide a hole for the resin at the rear of the injection cylinder and sequentially discharge the resin that has entered through the hole. It is limited to the case where the resin has fluidity in the state, and it is not possible to exclude a resin that has lost fluidity due to solidification.

In general, a heater zone of an injection cylinder having a plunger therein is defined as a stroke range of the plunger. In order to prevent solidification of resin that has entered around the plunger, a heater is provided to the rear of the hole. Even in such a case, the mounting of the heater is limited to the exposed portion of the injection cylinder, and it is difficult to maintain a predetermined temperature by the heater up to the rear end portion inserted and held in the front of the injection hydraulic cylinder. For this reason, even the resin in the molten state cools and solidifies at the end of the injection cylinder behind the heater, and this acts as a sliding resistance when the plunger moves forward and backward.

[0007] The sliding resistance of the resin at the rear end of the injection cylinder has a remarkable effect on material metering even if its frictional force is slight. Material weighing in a pre-plasticization type injection device is performed by feeding the material resin plasticized by the plasticizing cylinder into the tip of the injection cylinder through the resin path at the tip, and pressurizing the tip of the plunger by the resin pressure, thereby injecting the injection hydraulic pressure. Since the plasticized resin is accumulated in the tip of the cylinder while the plunger to which a predetermined pressure (back pressure) is applied by the cylinder is moved backward, even a slight frictional force is a major obstacle to the backward movement of the plunger due to the resin pressure. As a result, there are the following problems.

Since the plunger does not smoothly move backward due to the sliding resistance of the solidified resin, and requires a resin pressure exceeding the resistance, the resin pressure in the tip of the injection cylinder is (resin pressure> back pressure + friction). If the force is not reached, the plunger does not move backward, and as a result, the weighing time tends to take a long time, and in some cases, the weighing becomes impossible.

When the back pressure is removed at the same time as the completion of the measurement, the plunger retreats to some extent due to the resin pressure, whereby the uniformity of the measured resin pressure is naturally performed and the residual pressure is removed. Is poor, and a residual pressure is generated in the measuring resin, and a part of the resin comes out of the nozzle and drips.

[0010] Since the sliding resistance of the solidified resin varies, the frictional force differs for each measurement of the material. Therefore, not only does the density of the measuring resin change every measurement, but also the sliding resistance varies during the retreating process of the plunger. , The density of the resin itself is partially changed, which also affects the molding accuracy of the molded product.

The present invention has been made to solve the above-mentioned conventional problems, and an object of the present invention is to employ a sleeve to ensure that molten resin adhered to a shaft portion of a plunger is scraped off. An object of the present invention is to provide a new prepra-type injection device configured to positively discharge from a hole in a wall portion of an injection cylinder to eliminate sliding resistance due to solidification of resin and to hold and fix a sleeve by a cylinder liner. .

[0012]

According to the present invention, there is provided an injection cylinder in which a plunger is provided with a required clearance so as to be able to move forward and backward, and a plasticizing cylinder is arranged in parallel with the injection cylinder and the plasticizing cylinder. The inflow path at the part corresponding to the plunger advance limit at the tip of the injection cylinder communicates with the resin path provided over the outflow path at the tip of the plasticizing cylinder, and a resin hole is provided in the cylinder wall after the plunger stroke of the plunger. A pre-plasticity injection device, wherein the inner diameter of the front part of the injection cylinder is expanded to a position after the hole, and a step formed at the end of the expanded part is formed with a shaft of the plunger. A scraping sleeve located with a required gap between them is provided, and the sleeve is clamped and fixed by the tip of a complementary cylinder liner that is inserted into the enlarged diameter portion. To become disposed around the cylinder on the rear wall of the drain hole, is that.

Although the plunger may be of the same diameter as a whole, in order to reduce the sliding resistance due to the resin entering the clearance, the shaft portion is formed smaller in diameter than the head portion to increase the clearance around the shaft. It is preferable to reduce the sliding resistance by facilitating the backward movement of the molten resin that has entered the clearance of the head.

In the above configuration, since most of the resin that has entered the clearance due to the retreating movement of the plunger is sent in a molten state to the portion of the hole, the resin is discharged from the hole through the hole without being accumulated in the clearance. It is being done. In addition, the resin adhering to the plunger is scraped off by the sleeve, falls into the hole, and is discharged out of the injection cylinder. This prevents the resin from entering the clearance behind the sleeve, and solves the above-mentioned conventional problem in material measurement due to sliding resistance caused by solidification of the resin generated at the rear end of the injection cylinder. Furthermore, in the case where the sleeve is sandwiched and fixed by the step portion and the tip of the cylinder liner, the sleeve can be provided so as to overlap the punched hole.

[0015]

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. A clearance required for the plunger 10 to move forward and backward is provided between the outer peripheral surface of the plunger 10 and the inner peripheral surface of the injection cylinder 12.

The injection cylinder 12 has an inflow path 15 for the resin path 3 at an upper portion corresponding to a plunger advance limit of a tip portion 12a. Further, after the plunger stroke of the injection cylinder 12, there is provided a hole 16 for the resin that has entered the clearance, and a band heater 17 is provided around the cylinder after the hole 16.

In the injection plunger 10, the shaft portion 10a is formed to have a smaller diameter than the head portion 10b to enlarge the clearance 18 around the shaft, thereby facilitating the backward movement of the molten resin that has entered the clearance of the head portion 10b. What, head 10b
, The sliding resistance is reduced. Due to the expansion of the clearance 18, the resin that has entered the fine clearance (0.005 to 0.01 mm) around the outer periphery of the head 10 b adheres and remains on the injection cylinder side of the clearance 18 when the injection plunger 10 moves forward. Become, head 1
At the time of retreat of 0b, the rear end edge of the head 10b can be scraped up to the above-mentioned hole 16.

A sleeve 19 for scraping is provided around the inside of the cylinder on the rear wall of the hole 16 and a shaft 10a of the plunger 10.
With a required gap (0.02 to 0.05 mm). The inner diameter of the front portion of the injection cylinder 12 is enlarged to a position after the hole 16. The sleeve 19 is provided at the step formed at the end of the enlarged diameter portion from the opening at the tip of the cylinder into the enlarged diameter portion. It is inserted and installed. The sleeve 19
When the enlarged diameter portion is complemented by the insertion of the cylinder liner 12b having the same inner diameter as the rear inner diameter of the cylinder and having a notch at the lower end thereof, it is clamped and fixed between the cylinder liner tip and the step.

The plasticizing apparatus 2 includes 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 device 25 is
Insert the rear end into the piston 24a of the hydraulic cylinder 24,
The rotary shaft 23a is movably axially connected to a rotating shaft 23a that is supported inside the holding cylinder 23, and the leading end of the rotating shaft 23a is connected to the rear end of the screw 20. The rotating shaft 23a is connected to the piston 24a and moves forward and backward together with the piston 24a to rotate and move the piston 24a forward and backward.

A band heater 26 is attached to the outer periphery of the plasticizing cylinder 22, and a supply hole 27 is provided upward at a rear end of the plasticizing cylinder 22 fitted to the holding cylinder 23. A mushroom-shaped valve body 28 is attached to the tip of the screw 20. The tip of the plasticizing cylinder 22 in which the valve body 28 is located is formed in a conical shape, and the screw body 20 has a conical shape. A required flow gap communicating with the outflow passage 21 is formed, and an annular valve seat 29 is provided at a portion where the inclined back surface of the valve body 28 faces.

The resin path 3 is formed by a thin tube 30 and is provided with a band heater 31 on the outer periphery, and has a required mixing member 32 in the 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 vertical stages by mounting and holding the holding cylinder 23 on a support provided on the hydraulic cylinder 14 of the injection device 1. Nozzle touch cylinder 5 on fixed platen 4 of mold clamping device
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 via a.

In the above configuration, the material resin is supplied to the supply hole 27.
From the plasticizing cylinder 22, the material resin is plasticized by the heating by the band heater 26 and the rotation of the screw 20, and is sequentially fed forward. Since the resin pressure applies a forward pressure to the screw 20, a resin flow gap is secured between the valve element 28 at the tip and the valve seat 29, and the plasticized resin is sequentially fed to the resin path 3. Is done.

In the resin path 3, the resin is repeatedly divided and mixed by the mixing member 32, and the resin flows into the inflow path 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 retreats to the set position, the hydraulic cylinder 24 retreats and the screw 20
Is forcibly moved backward to press the valve body 28 against the valve seat 29. As a result, the inside of the tip of the plasticizing cylinder 22 is closed, and the pressure feed of the plasticized resin is temporarily stopped. As a result, a predetermined amount of resin is accumulated in the front part of the plunger of the injection cylinder 12. The steps so far are generally referred to as molding material measurement, and thereafter, the measured resin is injected.

With the valve body 28 closed, the plunger 1
0 moves forward, the resin in the injection cylinder
Injection filling from 1 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 valve body 28 is in the valve closed state, backflow of the resin to the plasticizing cylinder side is prevented, and the entire amount of the metered resin is
Emitted from.

When the completion of the injection process is confirmed, the hydraulic cylinder 24 moves forward to move the screw 20 forward by a required dimension. As a result, the valve element 28 at the tip is
A flow path communicating with a flow gap formed on the front surface of the valve body is formed at a greater distance, and the plasticized resin is pressure-fed to the injection device via the resin path 3 and the process shifts to measuring again.

As the plunger 10 moves forward and backward during the measurement and injection, the resin that has entered the clearance of the head 10b sequentially moves rearward in the cylinder. Since this resin is heated by the band heater 17 on the outer periphery of the injection cylinder to the rear of the above-mentioned hole 16, it does not cool down and solidify in the middle even if it moves to the rear of the cylinder, and the resin is melted in the hole. The resin that has reached 16 and adhered to the shaft portion 10a is scraped off by the sleeve 19 by the retreating force of the shaft portion 10a and falls into the hole 16, and is discharged out of the injection cylinder over time. You. Therefore, the resin is prevented from entering the clearance behind the sleeve, and even if the resin adheres to the shaft 10a and enters the rear as it is, the resin is a thin resin film on the surface of the shaft and is solidified as it is. Even so, a sufficient clearance is secured at the rear end of the injection cylinder, so that it is difficult for the plunger 10 to have a sliding resistance against the forward / backward movement. As a result, in the present invention, the sliding resistance at the time of material measurement due to the resin solidified by the clearance is eliminated, and the measurement time, the density of the measurement resin, the leakage of the measurement resin, and the like are improved.

Although the plasticizing cylinder of the above embodiment has a screw inside, the present invention is also applicable to a plunger inside, so the present invention is particularly limited to a screw pre-plastic injection device. is not.

[Brief description of the drawings]

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

FIG. 2 is a longitudinal sectional view of a main part of an injection cylinder.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Injection apparatus 2 Plasticization apparatus 3 Resin path 10 Injection plunger 10a Shaft part 10b Head 12 Injection cylinder 12b Cylinder liner 15 Inflow path 16 Resin extraction hole 17 Band heater 18 Clearance around shaft part 19 Scrape sleeve 22 Plasticizing cylinder

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-4-347614 (JP, A) JP-A-8-156049 (JP, A) JP-A-6-143345 (JP, A) JP-A-6-143345 31775 (JP, A) Japanese Utility Model Application Hei 4-113918 (JP, U) Japanese Utility Model Application No. 61-67116 (JP, U) Japanese Utility Model Application No. 56-79313 (JP, U) International Publication No. 94/11174 (WO, A1) ( 58) Field surveyed (Int.Cl. ⁶ , DB name) B29C 45/54 B29C 45/02 B29C 45/62

Claims (1)

(57) [Claims] 1. A plasticizing cylinder is provided in parallel with an injection cylinder in which a plunger is provided with a required clearance so as to be able to move forward and backward, and the injection cylinder and the plasticizing cylinder are connected to a portion of the tip end of the injection cylinder which corresponds to a plunger advance limit. A pre-plastic injection device, which communicates with a resin passage provided between an inflow passage and an outflow passage at the tip of a plasticizing cylinder, and has a resin hole in a cylinder wall after a plunger stroke of the plunger, wherein The inside diameter of the front part of the cylinder is increased to the position after the above-described hole, and a scraping sleeve located at a required gap from the shaft of the plunger is provided at a step formed at the end thereof. The sleeve is clamped and fixed by the tip of a complementary cylinder liner fitted and inserted into the enlarged diameter portion, and is not provided around the inside of the cylinder on the rear wall of the hole. Preplasticization injection apparatus characterized by.