JPH0985791A - Screw head of injection molding machine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To avoid the occurrence of molding failures, a peak injection pressure in a full period of the cavity, and flashes. SOLUTION: The screw head of an injection molding machine is unique in that a head main body 10 formed of a metal material and provided with a screw securing part 9 has no valued ring (b) operating for introducing molten resin 5 sent from the rear through the rotation of a screw 1 to a forward injection nozzle 4 and precluding molten resin 5 from escaping and returning rearward through injection pressure at the time of the screw 1 thrust forward, and the head main body 10 is made smooth in its surface having no attachments and also having no unevennesses, grooves, and interstices completely where molten resin 5 can round and comes therein.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a screw head of an injection molding machine.

[0002]

2. Description of the Related Art Generally, an injection molding machine has the following structure.

As shown in FIG. 5, while a resin material 2 introduced into a cylinder 1 is melted by a screw 3 which rotates, it is sent to an injection nozzle portion 4 at the tip of the cylinder 1 and is sent to the injection nozzle portion 4 and is retained there. The resin 5 is configured to be injected and injected into the cavity 7 in the mold 6 through the runner portion 8 by pushing the screw 1 retracted by this amount of resin forward.

As shown in FIG. 5, the screw 3 has a screw head a screwed on the tip of a screw rod having spiral blades for resin feeding formed on its peripheral surface.
In this screw head a, a sharp bulging portion that matches the tapered shape of the injection nozzle portion is formed in the front portion of a head body 10 provided with a mounting portion 9 that is screwed to a screw rod, and a non-return portion is formed at this bulging portion. The ring b is fitted.

The non-return ring b is set so that the outer diameter thereof matches the inner peripheral surface of the cylinder while leaving a slide clearance of about 1/100 mm so that the molten resin does not escape rearward during injection. A resin passage hole is formed inside the ring b for feeding the molten resin 5 forward of the screw head a by the rotation of the screw 3 and stopping it. When the screw 3 is extruded and injected, the check ring b moves backward. The resin passage hole is closed by sliding a little to prevent the molten resin 5 from returning to the rear of the ring by injection.

The inventor of the present invention has developed this kind of non-return ring in the course of developing and researching the injection molding machine, so that the resin that has entered the inside of the resin passage hole or the ring fitting gap is repeatedly molded. It has been found that there are cases in which the foreign matter stays in the state of being burned and becomes foreign matter, and this foreign matter is mixed with the molten resin to be injected, which causes problems such as defective molding and troubles in the color of the molded product.

As a result of further research, it is not when the screw starts to move forward at the time of injection that the check ring slides backward to close and seal the resin passage hole. It was found that when the molten resin injected into the cavity became full and a large injection reaction force was applied, it slid backward and sealed.

Therefore, as shown in FIG. 7, as shown in the experimental results showing the relationship between the time indicating the forward movement distance (stroke movement amount) of the screw and the injection pressure applied to the cavity at that time, When injecting, the injection pressure to the cavity gradually increases, and when the cavity is full, not only the high injection pressure that gradually increases but the check ring suddenly moves backwards only at this time. In order to move and instantly block and seal the resin passage hole, an extremely high injection pressure of about twice the injection peak value that gradually increases is suddenly applied to the cavity.

Therefore, due to the sudden generation of the peak injection pressure, burrs easily leak out of the injected resin from the parting surface of the cavity, and a sudden increase in exhaust pressure causes burns. Found out.

[0010] Therefore, the present inventor has focused on the above-mentioned problems found after such research, and after repeated research on the non-return ring, further injects the molten resin forward from the outer periphery with a screw to perform the non-return operation. It was found that even if the ring was removed, the molten resin would not move back to the extent that it interferes with injection, and by eliminating the check ring, no foreign matter is generated and a high peak injection pressure is applied to the cavity. We have completed the epoch-making present invention that can perform good molding without fail.

[0011]

The gist of the present invention will be described with reference to the accompanying drawings.

While the resin material 2 introduced into the cylinder 1 is melted by the screw 3 which rotates, the cylinder 1
It is sent to the injection nozzle portion 4 at the tip, and the molten resin 5 fed into the injection nozzle portion 4 and retained is pushed forward by the screw 1 that has retreated by this amount of resin, and the runner portion 8 is fed to the cavity 7 in the mold 6. In the screw head a provided at the front end of the screw 1 of the injection molding machine that is injected through the
In the head body 10 provided with, the molten resin 5 fed from the rear by the rotation of the screw 1 is introduced into the front injection nozzle portion 4, and when the screw 1 is pushed forward, the molten resin 5 is moved backward by the injection pressure. The non-return ring b for preventing escape and return is not provided, and the surface of the head body 10 has no attachment and has a smooth surface without any irregularities, grooves, gaps, etc. around which the molten resin 5 enters or enters. The present invention relates to a screw head of an injection molding machine characterized by the above.

A bulging portion 10 at the front end of the head body 10 is also provided.
The outer diameter of A is set to be slightly smaller than the inner diameter of the cylinder, and a feeding gap 11 for feeding the molten resin 5 to the front injection nozzle portion 4 between the outer peripheral surface of the bulging portion 10A and the inner peripheral surface of the cylinder.
2. The structure according to claim 1, wherein
It relates to the screw head of the described injection molding machine.

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION A preferred embodiment of the present invention (how to carry out the invention) will be briefly described with reference to the drawings showing its function and effect.

Due to the rotation of the screw 1, the molten resin 5 is fed into the injection nozzle 4 in front of the head body 10 through the feeding gap 11 between the outer peripheral surface of the head body 10 of the screw head a and the inner peripheral surface of the cylinder 1 and is retained there. .

When the screw 3 moved rearward by the staying molten resin 5 is pushed out at the time of injection, a predetermined amount of the staying molten resin 5 is pushed by the screw head a and ejected from the injection nozzle portion 4 to make a runner. It is injected and injected into the cavity 7 in the mold 6 through the portion 8.

During the injection and injection of pushing out the screw 3 forward, the cavity 7 is not yet full, so the injection pressure (injection reaction force) is small, and the molten resin 5 for the next injection is behind. Since the cylinder 1 is continuously filled in the cylinder 1, a large amount of the molten resin 5 to be injected, which has stayed and escapes to the rear of the head body 10 of the screw head a, does not hinder the amount of injected resin.

Even when the cavity 7 is almost completely filled and the cavity 7 is full and a high injection reaction force is suddenly applied, the molten resin 5 remaining due to this injection reaction force is not removed. 10 Because it can return to the rear and escape, there is no suddenly high peak injection pressure in the cavity 7.

As described above, the remaining molten resin 5 is followed by the molten resin 5 for the next injection. The residual molten resin 5 is, so to speak, the molten resin 5 behind the screw head a. Since it is not supported and is not able to freely move backward, it is possible to apply sufficient holding pressure to the cavity 7 after the cavity 7 is full.

Therefore, for example, as shown in FIG. 6, as shown in the experimental results showing the relationship between the forward movement distance (stroke movement amount) of the screw and the injection pressure applied to the cavity at that time, The injection pressure gradually increases due to the forward movement of the cylinder 1, and even when the cavity 7 is full, the injection pressure does not suddenly increase (a sufficient holding pressure can be given), so burrs etc. occur due to the design of the molding conditions. In addition, the surface of the head body 10 can be a smooth metal surface with no attachments, which not only facilitates manufacturing and manufacturing, but also prevents foreign matter from occurring and enables good molding. .

[0021]

Embodiments of the present invention will be described with reference to the drawings.

Although the specific shape and size are appropriately designed according to various conditions, in the present embodiment, the head main body 10 provided with a projecting screw rod that is screwed into the screw hole at the front end of the screw rod as the screw mounting portion 9 is made of metal. However, unlike the conventional product, this head body 10 is not provided with a non-return ring, and is formed on a smooth surface that does not have any irregularities or gaps where molten resin wraps around or enters and foreign matter is generated. ing.

More specifically, the front end portion is formed to have a shape bulging as compared with the rear end portion, and the front end is formed in a sharpened shape corresponding to the tapered shape of the injection nozzle portion 4 as in the conventional case, and the sharpened bulging portion 10 is formed.
The outer diameter of A is set to be slightly smaller than the inner diameter of the cylinder, and 1 is set between the outer peripheral surface of the sharp bulging portion 10A and the inner peripheral surface of the cylinder.
A feeding gap 11 through which resin of about / 10 mm can pass is formed.

The base end of the head body 10 has a screw 3
The blade is made to have a small diameter so as to substantially match the outer diameter of the blade, and the diameter is gradually increased from the small diameter portion toward the sharply bulged portion 10A, and there is no sharp step edge on the outer peripheral surface. Without this, the entire circumference of the head body 10 is processed to have a smooth surface.

The outer peripheral surface may have a step, but the stepped edge may be rounded so that the molten resin 5 does not accumulate and foreign matter is generated, and at least the inner edge does not have any step. desirable.

Therefore, in this embodiment, when the molten resin 5 is fed forward of the sharp bulging portion 10A by the rotation of the screw 3, the molten resin 5 flows from the small-diameter base end portion of the head main body 10 along the outer peripheral surface. Wrap around to the outside and sharply swell 10A
Feed gap between the outer peripheral surface of the cylinder and the inner peripheral surface of the cylinder 1
Since it is fed through the injection nozzle 4, it is very smoothly fed to the injection nozzle 4 in front of the sharp bulging portion 10A and stays there.

Further, in this embodiment, as a result of a trial experiment, when the screw 3 is pushed to inject the staying molten resin 5 as described above, there is an unblocked feeding gap 11 through which the molten resin 5 can return. However, the molten resin 5 does not return to such an extent that it interferes with the injection amount, and even when the cavity 7 is full and the injection pressure becomes high, as shown in FIG. It was confirmed that the injection pressure did not rise at this full time.

That is, even if a high injection pressure is applied at the time when the cavity 7 is full, a sharp peak injection pressure unlike the conventional case does not occur because of the feed gap 11 which is not blocked.

Moreover, it was also confirmed that sufficient holding pressure can be applied even if the feeding gap 11 is not closed.

Therefore, foreign matters are less likely to occur, molding defects are less likely to occur, and burrs are hardly generated.

[0031]

EFFECTS OF THE INVENTION Since the present invention is configured as described above, it is easier to process and manufacture than conventional products and is excellent in mass productivity, and durability is also improved because it has no movable check ring. In addition to being extremely advantageous in maintenance, since there is no gap that causes molten resin to enter the surface of the head main body to generate foreign matter, molding defects are less likely to occur, and at the time of injection, the sharpness is high. Since the peak injection pressure does not occur, burrs are less likely to occur and the screw head of a revolutionary injection molding machine is extremely useful.

[Brief description of drawings]

FIG. 1 is an explanatory diagram illustrating a use state of the present embodiment.

FIG. 2 is a front view of the present embodiment.

FIG. 3 is a plan view of this embodiment.

FIG. 4 is a rear view of this embodiment.

FIG. 5 is an explanatory diagram showing a usage state of a conventional example.

FIG. 6 is a graph showing a result of an experiment showing a relationship between a time indicating a forward moving distance (stroke moving amount) of a screw and an injection pressure applied to the cavity at that time in the present embodiment. .

FIG. 7 is a graph showing an experimental result showing a relationship between a time indicating a forward moving distance (stroke moving amount) of a screw and an injection pressure applied to the cavity at that time in a conventional example.

[Explanation of symbols]

 a screw head b check ring 1 cylinder 2 resin material 3 screw 4 injection nozzle part 5 molten resin 6 mold 7 cavity 8 runner part 9 screw mounting part 10 head body 10A bulge part 11 feed gap

Claims (2)

[Claims] 1. A resin material introduced into a cylinder is sent to an injection nozzle section at the tip of the cylinder while being melted by a screw that rotates, and the molten resin that has been retained at the injection nozzle section is retracted by this resin amount. In the screw head provided at the front end of the screw of the injection molding machine that injects through the runner into the cavity in the mold by pushing forward, in the head body provided with a screw mounting part, formed of a metal material. Is equipped with a non-return ring that introduces the molten resin fed from the rear by the rotation of the screw into the injection nozzle in the front and prevents the molten resin from escaping and returning due to the injection pressure when the screw is pushed forward. The surface of the head body has no attachments, and unevenness, grooves, or gaps around which molten resin wraps or enters A screw head for an injection molding machine, which has a smooth surface that does not have any of the above. 2. An outer diameter of a bulged portion at the front end of the head body is set to be slightly smaller than a cylinder inner diameter, and a molten resin is injected between the outer peripheral surface of the bulged portion and the inner peripheral surface of the cylinder. The screw head of the injection molding machine according to claim 1, wherein the screw head is configured to form a feed gap.