JPH07256716A - Screw head for injection molding machine - Google Patents

Abstract

PURPOSE:To uniformize the plasticizing temp. of the molten resin stored in front of a screw head. CONSTITUTION:In the screw head 5 for an injection molding machine fixed to the leading end part of a screw 4 so as to be freely advance and retreat within a barrel in a rotatable manner, an insertion hole 17 extending in the axial direction of the screw is provided to the conical part of the screw head 5 and a spring 26 having an alamost triangular shape is arranged in front of the screw head 5 in the same direction and the rear end part of the spring 26 is inserted in the insertion hole 17.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a screw head for an injection molding machine.

[0002]

2. Description of the Related Art A screw head of a conventional injection molding machine is often simply a conical shape, a groove having a concave shape, or a threaded spline. .

[0003]

However, depending on the shape of such a screw head, the function of simply feeding the molten resin toward the nozzle by rotating the screw can be exerted, but the molten resin is homogeneously plasticized. That is, the temperature of the molten resin stored ahead of the screw head due to the rotation of the screw during metering is higher in the molten resin stored earlier and lower in the molten resin stored later, so that the cavity There was a problem that it was difficult to obtain a uniform product because the resin flow could not be kept constant when the molten resin was filled inside.

The present invention has been made in view of the above problems, and an object of the present invention is to provide a screw head for an injection molding machine which makes the plasticizing temperature of the molten resin stored in front of the screw head uniform. Is.

[0005]

SUMMARY OF THE INVENTION In order to solve the above technical problems, the present invention provides a screw head for an injection molding machine, which is fixed to the tip of a screw so as to be rotatable and forward and backward in a barrel. , A conical portion of the screw head is provided with an insertion hole directed in the axial direction of the screw, and a spring having a substantially triangular shape is arranged in the same direction in front of the screw head, and The end was attached to the insertion hole.

[0006]

In the present invention, when the screw is rotated and retracted in the measuring process, the screw expands due to the elastic force of the spring. After that, by storing the molten resin while the spring is stretched until the completion of the measuring process, the resin stored in the resin storage part is vigorously stirred by the spring, and the temperature of the resin stored in front of the screw head during the measuring process becomes uniform. The resin flow at the time of injection filling can be stabilized and the kneading property is improved.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Specific embodiments of the screw head for an injection molding machine according to the present invention will be described in detail below with reference to the drawings.

FIG. 1 is a sectional view of a screw head for an injection molding machine according to the present invention, FIG. 2 is a partial sectional view of an injection molding machine having a screw head for an injection molding machine according to the present invention, and FIG. FIG. 4 is a partial sectional view showing a state after injection is started, FIG. 5 is an explanatory view showing a resin flow of the screw head portion after the start of measurement, and FIG. 6 is a screw head portion before and after the injection process is started. It is explanatory drawing which shows the state of the spring attached to.

The injection molding machine will be described with reference to FIG. 2. Reference numeral 6 denotes a raw material resin supply hopper attached to the heating cylinder 2. Reference numeral 3 is a heater mounted on the outer peripheral surface of the heating cylinder 2, and the temperature can be adjusted by a temperature adjusting device (not shown).

Reference numeral 4 denotes a screw that is inserted into the heating cylinder 2 so that it can rotate and move forward and backward. The screw 4 is configured to be moved forward and backward by a hydraulic cylinder (not shown) and rotated by a hydraulic motor.

A heating cylinder head 2a is attached to the tip of the heating cylinder 2 with a bolt 19, and a nozzle 2b is screwed onto the tip of the heating cylinder head 2a so as to be superposed.

A screw head 5 is attached to the front end portion of the screw 4 via an assembling shaft 11, and a check ring 10 is loosely fitted between the screw 4 and the screw head 5. A communication passage 12, which is a molten resin passage, is provided between the inner peripheral surface of the check ring 10 and the outer peripheral surface of the assembly shaft 11.

At the front end of the check ring 10, there are provided molten resin passages 14 formed at regular intervals so that the communication passage 12 will not be blocked even if the check ring 10 is pressed against the straight body portion 5b. It has become.

The opening of the communication passage 7 in the rear end surface 15 of the check ring is opposed to the entire screw front surface 16 of the screw body so that when the rear end surface 15 of the check ring abuts on the screw front surface 16. Is to be completely closed.

The screw head 5 has a conical head portion 5a at the tip end portion and a cylindrical straight body portion 5b at the rear end portion, which is substantially the same shape as the conventional screw head 5. An insertion hole 17 is bored in the axial direction of the head portion 5a near the inner wall of the heating cylinder 2, and the rear end portion of the substantially triangular spring 26 is inserted into the insertion hole 17 to form a straight body portion. A fixing screw is screwed into a fixing hole of a spring 26 provided in 5b so as not to be inserted and removed.

Reference numeral 18 is a resin storage portion, 30 is a fixed mold, and 32 is a sprue.

The operation when the screw head for an injection molding machine configured as described above is used will be described.

After a predetermined amount of molten resin has been stored in the resin storage portion 18 in front of the screw head 5 in the heating cylinder 2 as is conventionally done, when the screw 4 is moved forward, it is stored in the resin storage portion 18. The molten resin passes through the sprue 32 and forms a cavity between the male and female molds (not shown).
Injection filled.

When the injection filling is completed, the next weighing process is started. At this time, when the screw 4 is rotated and the retreat is started, the extension force of the spring 26 causes the protrusion (Fig.
In (2)), the molten resin flows in the order of screw 4-communication passage 12-front surface of screw head 5 and is stored in the resin storage portion 18.

In the above-described metering step, the spring 26 also rotates with the rotation of the screw 4 until the screw 4 retracts, and the molten resin stored in the resin storage portion 18 is vigorously stirred by the spring 26 to store the resin. The resin temperature of the portion 18 becomes uniform.

Next, when the measuring process of the molten resin is completed and the screw 4 starts advancing with the injection process (see FIG. 6).
(1)) The spring 26 is contracted by the pressure of the molten resin located in front of the screw head 5 (resin storage portion 18).

Then, as shown in FIG. 6 (2), the spring 26
Is advanced to the limit of advancement of the screw 4 while being contracted, and the molten resin in the resin reservoir 18 is injected and filled into the mold cavity through the sprue 32 to complete one cycle.

[0023]

As is apparent from the above description, according to the present invention, in the screw head for an injection molding machine, which is fixed to the tip of the screw and is rotatable and forward / backward in the barrel. An insertion hole is formed in the conical part of the screw in the axial direction of the screw, a spring having a substantially triangular shape is arranged in the same direction in front of the screw head, and the rear end of the spring is By installing it in the insertion hole, the spring acts as a stirring blade protruding from the screw head from the beginning to the end of the weighing process, so the resin stored in the resin storage part is vigorously stirred and the temperature of the molten resin becomes uniform. A good product with high dimensional accuracy can be produced, and the kneading property is significantly improved.

[Brief description of drawings]

FIG. 1 is a sectional view of a screw head for an injection molding machine according to the present invention.

FIG. 2 is a partial cross-sectional view of an injection molding machine having a screw head for an injection molding machine according to the present invention.

FIG. 3 is a partial cross-sectional view showing a state after the start of weighing.

FIG. 4 is a partial cross-sectional view showing a state after the start of injection.

FIG. 5 is an explanatory diagram showing a resin flow of the screw head portion after the start of measurement.

FIG. 6 is an explanatory view showing a state of a spring mounted on a screw head portion before and after starting an injection process.

[Explanation of symbols]

 2 heating cylinder 3 heater 4 screw 5 screw head 5a head part 5b straight body part 7, 12 communication passage 10 check ring 11 assembly shaft 14 molten resin passage 15 back end surface of check ring 16 screw front surface 18 resin storage portion 26 spring

Claims (1)

[Claims] 1. A screw head for an injection molding machine, which is fixed to the tip of a screw and is rotatable and forward / backward in a barrel, and is inserted into a conical portion of the screw head in the axial direction of the screw. An injection molding machine characterized in that a hole having a substantially triangular shape is provided in the same direction in front of the screw head, and a rear end portion of the spring is attached to the insertion hole. Screw head.