JPH04369518A - Screw head structure - Google Patents

Abstract

PURPOSE:To prevent the generation of resin burning due to the abnormal heating of a resin between a screw head and a non-return ring. CONSTITUTION:A screw 4 is disposed into a heating cylinder 5, and a screw head 1 is installed at the front end of the screw 4. The screw head 1 is composed of a conical section 1a, a large diametral section 1b and a small diametral section 1c, a non-return ring 2 is arranged around the small diametral section 1c, and a resin path is formed between the small diametral section 1c and the non-return ring 2. Beveling grooves 17 guiding a resin 6 in the resin path are formed at a plurality of positions in the circumferential direction of the rear end surface of the large diametral section 1b in the connecting sections of the large diametral section 1b and the small diametral section 1c. Consequently, when the resin 6 in the resin path intends to flow out through the beveling grooves 17, resin pressure is generated, and the non-return ring 2 is pushed backward by resin pressure. Accordingly, the resin flow path is formed between the rear end face of the large diametral section 1b and the non-return ring 2 at all times during a weighing process, thus improving abrasion resistance while preventing the generation of resin burning.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a screw head structure.

0002

[Prior Art] Conventionally, resin that has been heated and fluidized in a heating cylinder is injected into a mold under high pressure, cooled and solidified or hardened therein, and then the mold is opened to take out the molded product. In such an injection molding machine, a screw is disposed in the heating cylinder so as to be rotatable and movable back and forth, and molten resin is injected by the screw.

[0003] Therefore, a screw head for extruding the resin is provided at the tip of the screw, and is attached to the screw by an internal screw. FIG. 2 is a sectional view of a screw head structure of a conventional injection molding machine. In the figure, 1 is a screw head, 2 is a check ring for preventing the backflow of the resin 6, 3 is a seal ring that comes into contact when the check ring 2 retreats, 4 is a screw, 5 is a heating cylinder, and 6 is a 7 is a cylinder head; 8 is a nozzle attached to the cylinder head 7;

After the screw 4 moves forward and the resin 6 is filled into the mold, the resin 6 is melted, plasticized, and stored at the tip of the screw head 1 prior to the next shot.
That is, weighing is performed. In the measuring process, the screw 4 is driven by a drive system (not shown) and retreats, and at this time,
The resin 6 dropped and supplied from the hopper, that is, the material supply port, is melted in the heating cylinder 5 while moving forward in the groove 4a by the rotation of the screw 4, and is stored at the tip of the screw head 1. The pressure of the resin 6 in the heating cylinder 5 generated as it melts becomes a reaction force against the screw 4, and the screw 4 is caused to retreat by this reaction force.

The resin 6 thus accumulated at the tip of the screw head 1 is then injected into the mold from the nozzle 8 by pushing the screw 4 forward by the drive system. Here, a part of the resin 6 flows backward through the groove 4a of the screw 4 due to the reaction force of the pressure applied within the mold during injection. In order to prevent this, a check ring 2 is provided at the front end of the screw 4. In order to prevent the check ring 2 from coming off the screw 4, a screw head 1 separate from the screw 4 is formed, a female thread is formed on the screw 4, and a male thread is formed on the rear end of the screw head 1. Both are screwed together.

The screw head 1 also has a conical part 1a for pushing out the resin 6 when moving forward, a large diameter part 1b located behind the conical part 1a, and a small diameter part 1c located further behind the large diameter part 1b. The outer diameter of the large diameter portion 1b is made larger than the inner diameter of the check ring 2 to prevent the check ring 2 from coming off, and the small diameter portion 1c
An annular passage 14 is formed between the check ring 2 and the check ring 2.

In the screw head structure configured as described above, the check ring 2 is designed to be able to freely rotate with respect to the screw head 1 (non-rotating check ring), and the check ring 2 is designed to be able to freely rotate with respect to the screw head 1 (non-corotating check ring), and the check ring 2 is designed to be able to freely rotate with respect to the screw head 1 (non-corotating check ring). Due to friction between the stop ring 2 and the heating cylinder 5, resistance due to the resin, etc., the check ring 2 moves forward relative to the screw head 1 and comes into contact with the rear end surface of the large diameter portion 1b of the screw head 1. It looks like this.

FIG. 3 is a state diagram of a conventional screw head structure in a metering process, and FIG. 4 is a sectional view taken along line AA in FIG. In the figure, reference numeral 15 indicates notches formed at four locations in the circumferential direction at the connecting portion between the large diameter portion 1b and the small diameter portion 1c of the screw head 1. The resin 6 sent between the check ring 2 and the seal ring 3 through the groove 4a of the screw 4 escapes from the annular passage 14 into the notch 15, and is transferred to the screw head 1.
sent to the tip of the

As shown in FIG. 4, the notch 15 has a radial dimension equal to the radial dimension of the annular passage 14 when the check ring 2 is in contact with the rear end surface of the large diameter portion 1b of the screw head 1. This allows a sufficient amount of resin 6 to flow.

0010

However, in the conventional screw head structure described above, while the screw 4 rotates and retreats during the metering process, the check ring 2 retreats together with the screw 4 without rotating. therefore,
Not only does the check ring 2 and the rear end surface of the large diameter portion 1b of the screw head 1 slide, causing wear on both sliding surfaces,
Resin burn may occur between the two.

That is, during the metering process, the check ring 2 moves forward and comes into contact with the rear end surface of the large diameter portion 1b. Then, as the screw 4 rotates, the screw head 1 rotates, the rear end surface of the large diameter portion 1b and the check ring 2 slide, and a shearing force is generated in the resin 6 between them. At this time, the resin 6, which was about to burn, is washed away between the check ring 2 and the seal ring 3. However, screw head 1
Between the check ring 2 and the non-return ring 2, both are constantly sliding, and the resin 6, which is about to burn, receives shearing force and generates heat, and in the case of resins with poor thermal stability such as PA66/AS, It gets burnt from the heat. This burnt resin 6 is pushed out into the mold as the screw 4 moves forward during the injection process, and comes out as burnt on the molded product.

The present invention solves the problems of the conventional screw head structure described above, and provides a screw head structure that does not cause resin burning due to abnormal heating of the resin between the screw head and the check ring. The purpose is to provide.

[0013]

[Means for Solving the Problems] To this end, in the screw head structure of the present invention, a screw is disposed within a heating cylinder, and the screw head is attached to the tip of the screw. The screw head consists of a conical part, a large diameter part, and a small diameter part, a check ring is disposed around the small diameter part, and a resin passage is formed between the small diameter part and the small diameter part.

[0014] Chamfered grooves for guiding the resin in the resin passage are formed at a plurality of locations in the circumferential direction of the rear end face of the large diameter portion at the connecting portion between the large diameter portion and the small diameter portion.

[0015]

According to the present invention, a screw is disposed within the heating cylinder as described above, and a screw head is attached to the tip of the screw. The screw head has a conical part,
It consists of a large diameter part and a small diameter part, a check ring is disposed around the small diameter part, and a resin passage is formed between the small diameter part and the small diameter part.

In the injection process, the check ring retreats as the screw moves forward. Furthermore, when the screw rotates and retreats during the metering process, the check ring moves forward due to the resin pressure behind the check ring. Chamfered grooves for guiding the resin in the resin passage are formed at a plurality of locations in the circumferential direction of the rear end surface of the large diameter portion at the connecting portion between the large diameter portion and the small diameter portion. Therefore, when the resin in the resin passage tries to flow out through the chamfered groove,
Resin pressure is generated between the rear end surface of the large diameter part and the check ring,
The resin pressure pushes the check ring backward.

[0017]

Embodiments Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 is a sectional view of a screw head structure showing an embodiment of the present invention, FIG. 5 is a sectional view taken along line BB in FIG. 1, and FIG. 6 is a state diagram of the screw head structure during a metering process. In the figure, 1 is the screw head, 2 is the resin 6
3 is a seal ring that comes into contact with the check ring 2 when it retreats; 4 is a screw; 5 is a heating cylinder; 6 is a resin; 7 is a cylinder head;
8 is a nozzle attached to the cylinder head 7.

After the screw 4 moves forward and the mold is filled with resin 6, the resin 6 is melted, plasticized, and stored at the tip of the screw head 1 prior to the next shot.
That is, weighing is performed. In the measuring process, the screw 4 is driven by a drive system (not shown) and retreats, and at this time,
The resin 6 dropped and supplied from the hopper, that is, the material supply port, is melted in the heating cylinder 5 while moving forward in the groove 4a by the rotation of the screw 4, and is stored at the tip of the screw head 1. The pressure of the resin 6 in the heating cylinder 5 generated as it melts becomes a reaction force against the screw 4, and the screw 4 is caused to retreat by this reaction force.

The resin 6 thus accumulated at the tip of the screw head 1 is then injected into the mold from the nozzle 8 by pushing the screw 4 forward by the drive system. Here, a part of the resin 6 flows backward through the groove 4a of the screw 4 due to the reaction force of the pressure applied within the mold during injection. In order to prevent this, a check ring 2 is provided at the front end of the screw 4. In order to prevent the check ring 2 from coming off the screw 4, a screw head 1 separate from the screw 4 is formed, a female thread is formed on the screw 4, and a male thread is formed on the rear end of the screw head 1. Both are screwed together.

The screw head 1 also has a conical portion 1a for pushing out the resin 6 during forward movement, a large diameter portion 1b located behind the conical portion 1a, and a small diameter portion 1c located further behind the large diameter portion 1b. The outer diameter of the large diameter portion 1b is made larger than the inner diameter of the check ring 2 to prevent the check ring 2 from coming off, and the small diameter portion 1c
An annular passage 14 is formed between the check ring 2 and the check ring 2.

In the screw head structure configured as described above, the check ring 2 is designed to be able to freely rotate with respect to the screw head 1 (non-rotating check ring), and the check ring 2 is designed to be able to freely rotate with respect to the screw head 1 (non-corotating check ring). Due to friction between the stop ring 2 and the heating cylinder 5, resistance due to the resin, etc., the check ring 2 moves forward relative to the screw head 1 and comes into contact with the rear end surface of the large diameter portion 1b of the screw head 1. It looks like this.

Chamfer grooves 17 are formed at four locations in the circumferential direction on the rear end surface of the large diameter portion 1b at the connection portion between the large diameter portion 1b and the small diameter portion 1c of the screw head 1. The chamfer groove 17 is connected to the rear end surface of the large diameter portion 1b and the check ring 2.
It is formed as a guide to ensure a resin flow path between them. Therefore, as shown in FIG. 5, when the rear end surfaces of the large diameter portions 1b are in contact with each other, only a small radial dimension t is exposed into the annular passage 14.

In the measuring step, the resin 6 sent between the check ring 2 and the seal ring 3 via the groove 4a of the screw 4 reaches the annular passage 14,
The resin 6 in the screw head 4 is guided by the chamfered groove 17 and moves forward, trying to separate the large diameter portion 1b of the screw head 1 from the check ring 2. That is, as shown in FIG. 6, the resin pressure generated by the resin 6 flowing between the large diameter portion 1b and the check ring 2 causes the check ring 2 to retreat.

Further, the magnitude of the resin pressure can be adjusted by changing the radial dimension t. In the screw head structure having the above configuration, the check ring 2 and the seal ring 3 are in contact with each other as shown in FIG. 1 before starting metering. When metering is started, the check ring 2 is pushed forward by the resin pressure behind the check ring 2, as shown in FIG. Here, as described above, resin pressure is generated between the rear end surface of the large diameter portion 1b of the screw head 1 and the check ring 2, and the resin pressure changes depending on the metering program. Then, the check ring 2 is pushed back rearward by this resin pressure, and stops at a neutral position corresponding to the resin pressure on the front and rear sides of the check ring 2.

Therefore, during the metering process, the screw head 1 rotates without coming into contact with the check ring 2. Note that the present invention is not limited to the above-mentioned embodiments, and various modifications can be made based on the spirit of the present invention, and these are not excluded from the scope of the present invention.

[0026]

As described above in detail, according to the present invention, a screw is disposed within the heating cylinder, and a screw head is attached to the tip of the screw. The screw head consists of a conical part, a large diameter part, and a small diameter part, a check ring is disposed around the small diameter part, and a resin passage is formed between the small diameter part and the small diameter part.

Chamfered grooves for guiding the resin in the resin passageway are formed at a plurality of locations in the circumferential direction of the rear end surface of the large diameter portion at the connecting portion between the large diameter portion and the small diameter portion. Therefore, when the resin in the resin passage tries to flow out through the chamfered groove, resin pressure is generated between the rear end surface of the large diameter portion and the check ring, and the check ring is pushed backward by the resin pressure. It will be done.

[0028] Therefore, during the metering process, a resin flow path is always formed between the rear end face of the large diameter portion and the check ring, and there is no sliding between the two, improving the wear resistance of the screw head and check ring. At the same time, it is possible to prevent the occurrence of resin burning. Furthermore, since the chamfered groove is shallow, it is possible to eliminate a resin retention area, and it is possible to improve resin changeability and color changeability.

[Brief explanation of drawings]

FIG. 1 is a sectional view of a screw head structure showing an embodiment of the present invention.

FIG. 2 is a sectional view of a screw head structure of a conventional injection molding machine.

FIG. 3 is a state diagram of a conventional screw head structure in a metering process.

FIG. 4 is a sectional view taken along line AA in FIG. 2;

FIG. 5 is a sectional view taken along line BB in FIG. 1;

FIG. 6 is a state diagram of the screw head structure during the metering process.

[Explanation of symbols]

1 Screw head 1a Cone part 1b Large diameter part 1c Small diameter part 2 Check ring 3 Seal ring 4 Screw 4a groove 5 Heating cylinder 6 Resin 7 Cylinder head 8 Nozzle 14 Annular passage 17 Chamfer groove

Claims (1)

[Claims] Claim 1: (a) a screw disposed within a heating cylinder; (b) a screw head attached to the tip of the screw and consisting of a conical portion, a large diameter portion, and a small diameter portion;
c) a cylindrical check ring disposed around the small diameter part and forming a resin passage between the small diameter part; and (d) a large diameter part at the connection part between the large diameter part and the small diameter part. A screw head structure characterized in that chamfered grooves for guiding the resin in the resin passage are formed at a plurality of locations in the circumferential direction of the rear end surface of the screw head structure.