JP3234869B2 - Injection device of plunger type injection molding machine - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an injection device for a plunger type injection molding machine, and more particularly, to a plunger type injection molding in which a molten resin plasticized by a plasticizing device and sent to the injection device is injected by the injection plunger. The present invention relates to an injection device of a plunger type injection molding machine that discharges resin leaked from a plunger head of an injection plunger to a plunger shaft side during an injection operation from a discharge guide attached to a rear end of an injection cylinder.

[0002]

2. Description of the Related Art A plunger type injection molding machine is often used practically as a screw pre-plastic injection molding machine. The screw prepra injection molding machine has a plasticizing screw in the plasticizing chamber of the plasticizing device, an injection plunger in the injection chamber of the injection device, and a plasticizing passage connecting the plasticizing chamber and the injection chamber. It is provided between the device and the injection device. First, a synthetic resin material (hereinafter, referred to as resin) supplied from a hopper to a plasticizing chamber is kneaded and melted by rotation of a plasticizing screw and heating of the plasticizing chamber (hereinafter, referred to as plasticizing), and is plasticized. The resin is pressure-fed to the injection chamber from the communication passage. At this time, the retreat amount of the injection plunger which retreats with the pressure feeding is detected, and the plasticizing amount of the resin is measured. Next, the injection plunger advances, and the molten resin is injected into the mold cavity.

In such a plunger type injection device, the plunger shaft of the injection plunger has a slightly smaller diameter than the plunger head so that the injection plunger does not bite into the injection cylinder during the forward / backward movement. A step is formed between the head and the plunger shaft. Further, a slight gap is secured between the plunger head and the inner wall of the injection cylinder. Therefore, during the injection operation of filling the molten resin into the mold at a high pressure, a very small amount of the molten resin leaks out of the gap and accumulates in the gap between the plunger shaft and the inner wall of the injection cylinder. Then, during a long molding operation, the leaked resin (hereinafter referred to as leaked resin) is pushed by the step portion of the plunger head and is pushed backward along the plunger axis, and the rear portion (the base portion) of the injection cylinder. ) Or from the outlet provided near the rear end. At this time, if the leaked resin is not discharged smoothly, the accumulated leaked resin acts as a weir and hinders the retreat operation of the injection plunger, which hinders the measuring process.

Therefore, a discharge device for discharging the leaked resin to the outside of the injection cylinder has been proposed. For example,
Japanese Patent Application Laid-Open No. 8-15649 discloses an injection device provided with a scraper ring 23 for dropping discharged resin adhered around an injection plunger shaft and supporting the injection plunger. Also, JP-A-8-2299
No. 97 proposes an injection cylinder provided with a resin hole 16 directly in the injection cylinder in order to discharge the leaked resin in the form of a molten resin, and also provided with a heater behind the hole. Further, Japanese Patent Application Laid-Open No. 9-85787 proposes a device in which a scraping sleeve 19 is provided immediately after a resin drain hole of an injection cylinder so that molten resin does not leak backward from the scraping sleeve.

In the case of molding using a general-purpose resin material, since the resin material is thermally stable, it does not deteriorate even if the leaked resin is exposed to a high temperature for a long time around the plunger shaft. Therefore, as long as the molding is performed while maintaining the molding temperature sufficiently higher than the temperature at which the resin material starts to melt, the leaked resin is discharged in the molten state and falls in the molten state.

[0006]

However, the resin leaked from the plunger head is discharged from the discharge device in various states depending on the type of the resin and the molding conditions of the same resin.

When molding using an engineering plastic material or a super engineering plastic material, the molding temperature at which these are melted and injected is high.
Since many of these resins have properties that are easily decomposed, these resins are sometimes molded at a molding temperature that does not exceed a temperature at which melting starts. Further, in order to improve the strength of the molded product, an alloy material obtained by mixing two types of plastic materials having different melting temperatures may be used. In these cases, when the temperature of the resin material is slightly lower than the molding temperature, the viscosity of the molten resin may increase, or the resin may be in a state of being partially solidified. May not fall in the state.

In addition, when additives are added to impart flame retardancy or to impart other properties,
The molten resin may be slightly thermally degraded. Even when the molding operation is performed at an unnecessarily high temperature, the heat is slightly deteriorated. Also,
In the case of performing a molding in which the amount of one injection is very small, since the injection stroke length of the injection plunger is very small compared to the entire stroke length, the injection plunger is exposed to high heat for a long time before the leaked resin is discharged. As a result, the molten resin is slightly thermally degraded.
Even in such a case, the viscosity of the molten resin may increase, or the resin may be partially solidified, and the discharged leaked resin is likely to solidify before falling.

As described above, when the leaked resin is solidified at the outlet of the discharge port of the discharge device, the resin may form a thick film around the plunger axis, accumulate and grow, or form a dumpling. There is. In this case, simply heating the vicinity of the discharge device to the same temperature as the injection cylinder does not cause the leaked resin discharged in the molten state to drop at the outlet of the outlet, but to solidify at the outlet.

An object of the present invention is to reliably discharge a leaked resin discharged in a molten state even when the resin is solidified without falling from a discharge port as described above. It is an object of the present invention to provide a discharge device in which the discharged resin is discharged in a solid state, not in a state, and the solidified resin is divided into thin lines and discharged, so that the discharged resin is easily broken and easily dropped.

[0011]

Means for Solving the Problems 1) In an injection device of a plunger type injection molding machine which solves the above problems, a discharge guide having a guide hole through which a plunger shaft of an injection plunger passes is connected to a rear end of an injection cylinder. The inner diameter of the front guide hole in contact with the injection cylinder is substantially the same size as the inner diameter of the injection cylinder, and the rear guide hole is formed in a cylindrical surface having an inner diameter with a slight clearance in the plunger shaft. A large number of discharge grooves are formed on the cylindrical surface in parallel with the plunger axis.

2) In addition, the injection device of the plunger type injection molding machine which solves the above problem is provided with a discharge guide having a guide hole through which the plunger shaft of the injection plunger is connected, connected to the rear end of the injection cylinder. The temperature of the discharge guide is controlled by a heating means whose temperature is controlled independently of the injection cylinder.The inside diameter of the front guide hole in contact with the injection cylinder is almost the same as the inside diameter of the injection cylinder, and the rear guide hole is connected to the plunger shaft. It is characterized in that it is formed on a cylindrical surface having an inner diameter with a small gap, and on the cylindrical surface, a number of discharge grooves are formed in parallel with the plunger axis.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS As shown in FIG. 1, an injection device 1 of a screw prepra type injection molding machine includes a plasticizing device 2 and an injection device 3, and a plasticizing cylinder 20 of the plasticizing device 2.
The plasticizing chamber 12 formed therein and the injection chamber 13 formed in the injection cylinder 30 of the injection device 3 are communicated by the communication path 11. A check device 22 containing a hydraulic piston is connected to the rear end of the plasticizing cylinder 20,
A rotary drive device 23 such as a hydraulic motor is connected to this. The rear end of the plasticizing screw 21 housed in the plasticizing chamber 12 is connected to the hydraulic piston of the check device 22, and the hydraulic piston is further connected to the hydraulic motor of the rotary drive device 23, so that the plasticizing screw 21 is plasticized. It is rotatable and reciprocable in the cylinder 20.

The injection cylinder 30 is connected to the frame 41 of the injection driving device 40 by a connecting member 42.
An injection hydraulic cylinder 34 is fixed in the frame 41, and an injection piston 35 is mounted therein so as to advance and retreat. Injection plunger 31 housed in injection chamber 13
Is connected at its rear end to a connecting rod 33 by a coupling 32, and the connecting rod 33 is connected to a ram 35a of an injection piston 35.
The injection plunger 31 is fixed to the distal end so as to move forward and backward in the injection cylinder 30.

The resin supplied from the hopper 24 is plasticized by the heat of the band heater of the plasticizing cylinder 20 (not shown) and the rotation of the plasticizing screw 21, and is sent forward. At this time, if the hydraulic pressure of the operating oil of the check device 22 is released to allow the plasticized screw 21 to be retracted, the plasticized screw 21 is retracted by the reaction force of the molten resin to be sent, and the communication passage 11 is released. You. The molten resin that has passed through the communication passage 11 is sent to the injection cylinder 30 and the injection plunger 3
Retreat one. The position of the retreating injection plunger 31 is measured by a position detector 37 such as a linear encoder, and the molten resin is measured. When weighing is complete,
The injection is performed by moving the piston 35 of the injection hydraulic cylinder 34 forward. At this time, the plasticizing screw 21 is advanced by the thrust of the check device 22, and the communication path 11 is closed, that is, the check is performed.

As shown in FIG. 2, the plunger head 31
The diameter of the plunger shaft 31b is slightly larger than the diameter of the plunger shaft 31b.
b, a step 31c having a diameter difference of about 0.2 mm is formed. Further, a gap of about 0.1 mm is secured between the inner diameter of the inner wall 30a of the injection cylinder 30 and the outer diameter of the plunger head 31a in a diameter difference. During the injection operation, the plunger head 31a moves the injection cylinder 30
This is so as not to bite. For this reason, during the injection operation, a very small amount of molten resin is discharged from the plunger head 31a.
Leaks from the gap between the cylinder and the injection cylinder 30 and accumulates in the gap between the plunger shaft 31b and the injection cylinder 30. Although the amount of the leaked resin slightly varies depending on the resin material and the molding temperature, it is actually very small, and the amount of the resin injected is 0.1 μm.
It is about 03% to 0.1%. Then, during the long molding operation, the leakage of the molten resin is repeated, and the leaked resin eventually accumulates around the plunger shaft 31b in the injection cylinder 30 and moves backward. A discharge device for discharging the leaked resin from the inside of the injection cylinder 30 to the outside is provided as follows.

First, the configuration near the discharge device will be described in detail. The front end 4 of the connecting member 42 is
A small-diameter cylindrical portion 30b fitted to 2a is formed, and the injection cylinder 30 is fixed coaxially with the connecting member 42 via the heat insulating member 43. Also, at the rear end of the small-diameter cylindrical portion 30b,
A fitting hole 30c into which the front end 51a of the discharge guide 51 described below fits is formed concentrically with the axis of the injection cylinder 30. A drop port 42b through which the discharged resin falls is provided on the lower surface of the tubular body of the connecting member 42, and an opening 42c having substantially the same shape as the drop port 42b is formed on the upper surface.

The discharge guide 51 has a cylindrical portion 51b and a flange 51c, and is connected to the rear end of the injection cylinder 30 as follows. The flange 51c is fastened to the back surface of the front end 42a of the connecting member 42 by a bolt 52, and the front end 51a of the cylindrical body 51b is fitted into the fitting hole 30c on the rear end surface of the injection cylinder 30, so that the discharge guide 51 is connected to the injection cylinder. 30 is concentrically fixed to the rear end.

FIG. 3A shows the discharge guide 5 shown in FIG.
FIG. 3B is a cross-sectional view taken along the line AA of FIG. 1, and FIG. 1 and FIG.
1 is a cross-sectional view taken along the line AA. The discharge guide 51 includes
Guide holes 51d and 51e through which the plunger shaft 31b passes
Are formed. The inside diameter of the guide hole 51d in the substantially front half portion in contact with the injection cylinder 30 is formed to have substantially the same size as the inside diameter of the injection cylinder 30. It is formed to have a size obtained by adding a small gap to the diameter. A large number of discharge grooves 51f are formed in the cylindrical surface in parallel with the plunger axis. The rear end face of the flange 51c is located above the drop port 42b so that the resin discharged from the rear end of the discharge groove 51f easily falls.

Since the discharge guide 51 is configured as described above, as shown in FIG.
Are solidified and discharged in a state of being divided into a large number of fine lines at the outlet of the discharge groove 51f. The fine-lined discharge resin naturally spreads radially along the plunger axis, and eventually falls down and breaks down due to the reciprocation of the plunger.

Since the discharge guide 51 is made compact and is in contact with the injection cylinder 30 with a small area, and because the injection cylinder 30 and the connecting member 42 are connected via the heat insulating member 43, The discharge guide 51 and the injection cylinder 30 are thermally separated.
Therefore, even if the temperature of the discharge guide 51 and the temperature of the injection cylinder 30 are controlled independently of each other, there is little adverse effect on each other. Therefore, a band heater 5 is provided around the outer periphery of the cylindrical body 51b.
3 can be wound so that the temperature is controlled independently of the band heater 38 of the injection cylinder 30.
By doing so, the temperature of the band heater 53 can be set independently so that the leaked resin is reliably melted in the guide hole 51d of the discharge guide 51. There is no. In particular, when a resin that is less likely to deteriorate due to heat is used, the temperature control is easy because the allowable range of the temperature setting width of the band heater 38 is large.

The front surface 32a of the coupling 32 for connecting the injection plunger 31 can be formed in a tapered shape. By doing so, as shown in FIG. 4, when the injection plunger 31 moves forward in the injection step, the thin wire is forcibly pushed open at the front surface 32a of the coupling, so that the thin wire-shaped discharged resin breaks and falls. It will be easier.

Further, as shown in FIG.
A cooling means for cooling the vicinity of the outlet of the discharge groove 51f may be added to ensure that the discharged resin is solidified. As an example of the cooling means, a nozzle 54 that blows air toward the vicinity of the outlet of the discharge groove 51f to cool may be provided.
Further, a cooling water pipe 55 for winding the flange portion may be attached. By doing so, since the fine wire resin discharged from the discharge groove 51f is reliably discharged in a solidified state, there is no adhesion of adjacent fine wires, and the discharged resin can be reliably dropped. it can.

Depending on the type of the resin to be molded and the same resin, depending on the molding conditions, the resin discharged from the discharge guide 51 may be discharged in a form different from the above-described discharge form. In this case, since another discharge guide separately filed at the same time can be used at the same time, it is desirable that the discharge guide 51 of the present invention and the discharge guide according to another invention can be easily exchanged. For this purpose, the external dimensions of the discharge guide 51 of the present invention are made common to those of the discharge guides of other inventions so that the discharge guide can be easily replaced. In addition, the coupling 32 is configured to combine half the coupling.

By setting the outer dimensions of the discharge guide 51 and the mounting dimensions around it to be the same as those of the discharge guides of the above-mentioned other inventions,
Removal can be facilitated as follows. First, the upper opening 42c and the lower drop port 42b of the connecting member 42
After the coupling 32 is moved to a position where it can be easily removed from the coupling plunger 31, the injection piston 35 is advanced by moving the injection piston 35 forward with the separately prepared spacer inserted between the connecting rod 33 and the injection plunger 31. Move to the forward limit. Next, only the connecting rod 33 is retracted, the spacer is removed, and the bolt 52 is loosened and removed. Then, the discharge guide 51 is pulled rearward along the injection plunger 31, and the upper opening 42c or the lower drop port 42b is pulled out.
Remove from In this way, the discharge guide 51 can be removed by a simple disassembling operation. Next, the discharge guide is replaced with another discharge guide. This mounting operation is performed in the reverse order, and is still a simple mounting operation. In this way, by making the discharge guide of the present invention replaceable with another discharge guide, it is possible to easily cope with other discharge forms of the leaked resin.

[0026]

As described above, according to the present invention, even if the leaked resin is hardened in the vicinity of the discharge port and hardly falls, the resin is solidified and discharged in a state of being divided into a large number of fine lines. Therefore, the discharged resin surely falls from the drop port.

Further, since the discharge guide and the injection cylinder are thermally separated from each other, if the temperature of the discharge guide is controlled independently of the injection cylinder by the band heater, there is no possibility that the leakage resin is clogged in the middle. .

Further, when the front surface of the coupling for connecting the injection plunger is formed in a tapered shape, when the injection plunger moves forward, the thin wire is forcibly expanded at the front surface of the coupling. The discharged resin breaks and falls reliably.

Further, when a cooling means for cooling the vicinity of the outlet of the discharge groove of the discharge guide is added, a large number of fine lines are surely solidified and then discharged, so that adjacent fine lines may adhere. Absent.

Further, when the discharge guide of the present invention is made replaceable with another discharge guide filed in another application, it is easy to cope with other discharge forms of the leaked resin material.

[Brief description of the drawings]

FIG. 1 is an overall view showing an injection device of a plunger type injection molding machine according to the present invention in a partial cross section.

FIG. 2 is a cross-sectional view around a discharge guide.

FIG. 3 is a detailed view of a discharge guide.

FIG. 4 is a cross-sectional view illustrating a discharge state around a discharge guide.

[Explanation of symbols]

 1: Injection device 13: Injection chamber 30: Injection cylinder 31: Injection plunger 31a: Plunger head 31b: Plunger shaft 32: Coupling 43: Heat insulation member 51: Discharge guide 51d: Front guide hole 51e: Rear guide hole 51f : Discharge groove 53: heating means (band heater) 54: cooling means (nozzle) 55: cooling means (cooling pipe) 1 12

Continuation of the front page (56) References JP-A-11-277593 (JP, A) JP-A-11-277592 (JP, A) JP-A-11-165334 (JP, A) JP-A-10-6372 (JP) , A) JP-A-8-156049 (JP, A) JP-A-9-85787 (JP, A) JP-A-8-229997 (JP, A) Registered utility model 3032857 (JP, U) International publication 99/50044 (WO, A1) (58) Field surveyed (Int. Cl. ⁷ , DB name) B29C 45/46-45/84

Claims (2)

(57) [Claims] 1. An injection device of a plunger type injection molding machine for injecting a molten resin in an injection chamber by an injection plunger, wherein a discharge guide having a guide hole through which a plunger shaft of the injection plunger passes is connected to a rear end of the injection cylinder. The inner diameter of the front side of the guide hole in contact with the injection cylinder is substantially the same size as the inner diameter of the injection cylinder, and the rear side of the guide hole is formed on a cylindrical surface having an inner diameter with a slight clearance in the plunger shaft. An injection device for a plunger-type injection molding machine, wherein a number of discharge grooves are formed on the cylindrical surface in parallel with the axis of the plunger shaft. 2. An injection device of a plunger type injection molding machine for injecting a molten resin in an injection chamber by an injection plunger, wherein a discharge guide having a guide hole through which a plunger shaft of the injection plunger passes is connected to a rear end of the injection cylinder. The discharge guide is heated by a heating means whose temperature is controlled independently of the injection cylinder, and the inside diameter of the front side of the guide hole in contact with the injection cylinder is substantially the same as the inside diameter of the injection cylinder. The rear side of the guide hole is formed in a cylindrical surface having an inside diameter with a small gap to the plunger shaft, and a number of discharge grooves are formed on the cylindrical surface in parallel with the axis of the plunger shaft. Injection device for plunger type injection molding machine.