JP2022076013A - Screw head - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a screw head capable of suppressing sticking of a resin, a screw having the screw head, and an injection molding machine having the screw.

SOLUTION: In an injection molding machine 1, a shaft portion 43 connected to a rear end surface 42c of a head portion 42 is inserted into a backflow prevention ring 46 of a screw head 41, and an annular resin flow path R is formed between the shaft portion 43 and the backflow prevention ring. Moreover, a plurality of balls 47 are arranged side by side in a state of being packed in a circumferential direction between the head portion 42 and the backflow prevention ring 46, a plurality of spiral grooves 48 are provided on a surface of the head portion 42, and a plurality of spiral flights 49 are provided on an outer peripheral surface of the shaft portion 43.

SELECTED DRAWING: Figure 3

COPYRIGHT: (C)2022,JPO&INPIT

Description

The present invention relates to a screw head having a backflow prevention function, a screw having this screw head, and an injection molding machine having this screw.

A conventional screw head is disclosed in Patent Document 1. The screw head has a tapered portion and a columnar shaft connected to the rear end of the tapered portion. A backflow prevention ring is arranged on the outer side in the radial direction of the shaft. The backflow prevention ring forms a ring-shaped resin flow path between the ring and the shaft. A plurality of balls are arranged side by side in the circumferential direction between the tapered portion and the backflow prevention ring. This screw head is attached to the tip of the screw and is arranged in the injection cylinder of the injection molding machine.

Japanese Unexamined Patent Publication No. 59-120431

In the plasticizing operation, the molten resin flows from the rear side to the front side of the screw. At this time, since the resin flow path of the screw head has a complicated shape, there is a place where the molten resin does not easily flow. Further, the molten resin that has passed through the resin flow path collides with the ball and the tapered portion and spreads outward, and flows along the inner peripheral surface of the injection cylinder. As a result, there are places where the molten resin does not easily flow even near the surface of the tapered portion. Therefore, the molten resin may stay in a place where it is difficult to flow, and the resin may stick to the backflow prevention ring, the tapered portion, or the like.

Therefore, an object of the present invention is to provide a screw head capable of suppressing the sticking of the resin, a screw having the screw head, and an injection molding machine having the screw.

In order to achieve the above object, the screw head according to one aspect of the present invention is a screw head provided at the tip of a screw for injection molding, and has a tapered head portion and a rear end of the head portion. A state in which a continuous shaft portion, a backflow prevention ring through which the shaft portion is inserted and an annular resin flow path is formed between the shaft portion, and a head portion and the backflow prevention ring are packed in the circumferential direction. It has a plurality of balls arranged side by side, and a plurality of spiral grooves are provided at equal intervals on the surface of the head portion, and a plurality of spiral grooves are provided on the outer peripheral surface of the shaft portion. Are provided at equal intervals, the number of grooves and the number of balls are the same, and the number of flights and the number of balls are different.

In the present invention, it is preferable that the number of flights is 4 and the number of grooves is 6.

In order to achieve the above object, the screw according to another aspect of the present invention is a screw for injection molding, and the screw head is provided at the tip thereof.

In order to achieve the above object, the injection molding machine according to another aspect of the present invention is an injection molding machine having an injection cylinder and a screw housed in the injection cylinder, and the screw is the screw. It is characterized by being composed of.

According to the present invention, the backflow prevention ring of the screw head is inserted into the shaft portion connected to the rear end of the head portion, and forms an annular resin flow path between the shaft portion and the shaft portion. A plurality of balls are arranged side by side in a state of being packed in the circumferential direction between the head portion and the backflow prevention ring. A plurality of spiral grooves are provided at equal intervals on the surface of the head portion, and a plurality of spiral flights are provided at equal intervals on the outer peripheral surface of the shaft portion. And the number of spiral grooves and the number of balls are the same, and the number of flights and the number of balls are different. As a result, the molten resin inside the backflow prevention ring is agitated by the rotation of the flight, and the molten resin near the surface of the head portion is agitated by the rotation of the spiral groove, so that the molten resin stays. Can be effectively suppressed. Since the number of flights and the number of balls are different, it is possible to positively generate turbulence in the molten resin from the flight to the balls in the plasticizing operation, and to more effectively suppress the retention of the molten resin. Furthermore, since the number of spiral grooves and the number of balls are the same, the positional relationship between each groove and the ball becomes equal, which causes the spiral groove when the screw head advances in the injection operation. A rotational force is uniformly applied to the molten resin near the surface of the head portion. Therefore, since the entire molten resin near the surface of the head portion is rotated without bias, the retention of the molten resin can be suppressed more effectively. Therefore, it is possible to prevent the resin from sticking.

It is a figure which shows the schematic structure of the injection molding machine which concerns on one Embodiment of this invention. It is sectional drawing near the tip of the injection cylinder of the injection molding machine of FIG. It is a figure explaining the screw head provided in the screw of the injection molding machine of FIG.

Hereinafter, the injection molding machine according to the embodiment of the present invention will be described with reference to FIGS. 1 to 3.

FIG. 1 is a diagram showing a schematic configuration of an injection molding machine according to an embodiment of the present invention. FIG. 2 is a cross-sectional view of the vicinity of the tip of the injection cylinder of the injection molding machine of FIG. In FIG. 2, only the backflow prevention ring and the seat of the screw head are shown in cross section. FIG. 3 is a diagram illustrating a screw head provided on the screw of the injection molding machine of FIG. 3A is a side view of the screw head, FIG. 3B is a front view, and FIG. 3C is a front view of a plurality of balls out of phase. In FIG. 3A, the backflow prevention ring and the sheet are shown in cross section along the rotation axis. Further, the tip side of the injection cylinder (the left side of FIGS. 1, 2, 3 (a), or the front side of the paper surface of FIGS. 3 (b), 3 (c)) is set as the front, and the base end side of the cylinder (FIG. 1). , The left side of FIGS. 2 and 3 (a), or the back side of the paper in FIGS. 3 (b) and 3 (c)) is the rear.

As shown in FIG. 1, the injection molding machine 1 includes an injection cylinder 11, a nozzle 12, a heating device 13, a hopper 15, a hopper block 16, a toggle link mechanism 17, a movable die plate 18, and a fixed die. It has a plate 19. Further, the injection molding machine 1 has a screw 30 for injection molding and a screw drive unit 50.

The injection cylinder 11 is formed in a cylindrical shape. The nozzle 12 is provided at the tip of the injection cylinder 11. The heating device 13 is composed of, for example, a plurality of band heaters, and is provided on the outer peripheral surface of the injection cylinder 11. The hopper 15 has a funnel shape, and the supply path 15a at the lower portion thereof communicates with the base end portion of the injection cylinder 11 in the hopper block 16.

The toggle link mechanism 17 moves the movable die plate 18 forward and backward with respect to the fixed die plate 19 by being bent and stretched by a mold clamping drive unit (not shown). As a result, the moving mold K1 attached to the movable die plate 18 is closed and opened with respect to the fixed mold K2 attached to the fixed die plate 19.

The screw 30 is housed in the injection cylinder 11 so as to be rotatable and forward / backward. The screw 30 is rotated in the injection cylinder 11 by the screw drive unit 50 and is moved in the axial direction.

As shown in FIG. 2, the screw 30 has a screw main body 31 and a screw head 41 attached to the tip of the screw main body 31.

The screw body 31 is formed in a columnar shape, and a screw flight 32 is provided on the outer peripheral surface. The base end portion of the screw body 31 is connected to the screw drive portion 50.

As shown in FIG. 3, the screw head 41 has a head portion 42, a shaft portion 43, a mounting portion 44, a seat 45, a backflow prevention ring 46, and a plurality of balls 47.

The head portion 42 integrally has a front portion 42a having a conical shape (tapered shape) and a rear portion 42b having a cylindrical shape connected to the rear end of the front portion 42a. A plurality of spiral grooves 48 are provided on the surface of the head portion 42. In the present embodiment, six spiral grooves 48 are provided, and are arranged at equal intervals of 60 degrees in the rotation direction (circumferential direction) about the rotation axis L. The head portion 42 is provided with a flat portion 42d for gripping with a tool when the screw head 41 is attached or detached. A configuration in which the flat portion 42d is not provided may be used.

The shaft portion 43 is coaxially and integrally connected to the rear end surface 42c of the head portion 42. The shaft portion 43 integrally has a columnar portion 43a having a diameter smaller than that of the rear end surface 42c, and a tapered skirt portion 43b that is connected to the rear end of the columnar portion 43a and whose diameter gradually increases toward the rear. There is. A plurality of spiral flights 49 are provided on the outer peripheral surface of the shaft portion 43. In the present embodiment, four flights 49 are provided, and are arranged at equal intervals of 90 degrees in the rotation direction about the rotation axis L. In this embodiment, the orientation of the spiral groove 48 and the spiral of the flight 49 is the same as the orientation of the spiral of the screw flight 32 of the screw body 31.

The mounting portion 44 is formed in a columnar shape and is coaxially and integrally connected to the rear end surface 43c of the shaft portion 43. At the rear end of the mounting portion 44, a male screw 44a screwed with a female screw provided at the tip of the screw body 31 is cut. The mounting portion 44 is mounted on the tip of the screw body 31 by a screw structure. That is, the screw head 41 is provided at the tip of the screw 30.

The sheet 45 is formed in an annular shape having the same inner diameter as the mounting portion 44 and an outer diameter larger than the inner diameter of the backflow prevention ring 46 described later. The seat 45 has a mounting portion 44 inserted and fitted inside, and the front surface 45a is in contact with the rear end surface 43c of the shaft portion 43.

The backflow prevention ring 46 is formed in a cylindrical shape. The backflow prevention ring 46 is formed so that the outer diameter is substantially the same as the inner diameter of the injection cylinder 11 and the inner diameter is larger than the outer diameter of the shaft portion 43 including the plurality of flights 49. The backflow prevention ring 46 has a shaft portion 43 inserted inside and can move in the front-rear direction with respect to the shaft portion 43. In other words, the backflow prevention ring 46 is fitted to the shaft portion 43 with play. The backflow prevention ring 46 forms an annular resin flow path R with the shaft portion 43. When the backflow prevention ring 46 moves forward with respect to the shaft portion 43, a gap is formed between the front surface 45a of the seat 45 and the rear end surface 46b of the backflow prevention ring 46. This allows the molten resin to flow in the resin flow path R. Further, when the backflow prevention ring 46 moves rearward with respect to the shaft portion 43, the rear end surface 46b of the backflow prevention ring 46 comes into contact with the front surface 45a of the seat 45, and the gap disappears. As a result, the backward flow (backflow) of the molten resin in the resin flow path R is restricted.

The plurality of balls 47 are arranged between the rear end surface 42c of the head portion 42 and the front end surface 46a of the backflow prevention ring 46. Further, the plurality of balls 47 are all of the same size (diameter) and are arranged side by side on the outer peripheral surface of the shaft portion 43 in a state of being packed in the circumferential direction. Here, the "packed state" means a state in which a plurality of balls 47 are adjacent to each other with a slight gap so that each ball 47 can rotate. In the present embodiment, six balls are provided, and the center points of the balls 47 are arranged evenly separated by about 60 degrees about the rotation axis L.

The injection molding machine 1 has a control unit (not shown) that controls the overall operation. The control unit includes, for example, a microcomputer for an embedded device having a CPU, ROM, RAM, EEPROM, various I / O interfaces, and the like. The control unit controls each drive unit of the injection molding machine 1 in various operations such as a mold closing operation, a plasticizing operation (weighing operation), an injection operation, a mold opening operation, and a product taking-out operation.

Next, an example of the operation in the injection molding machine 1 of the present embodiment will be described.

The control unit of the injection molding machine 1 controls a mold clamping drive unit (not shown) to superimpose and clamp the moving mold K1 and the fixed mold K2 (mold closing operation). The nozzle 12 at the tip of the injection cylinder 11 communicates with a resin flow path (not shown) provided in the fixed mold K2.

Further, the control unit controls the heating device 13 to heat the injection cylinder 11. As a result, the viscosity of the resin material is lowered to bring it into a molten state (molten resin) near the tip of the injection cylinder 11. Further, the control unit controls the screw drive unit 50 to rotate and retract the screw 30, and supplies the amount of molten resin required for one injection to the tip of the injection cylinder 11 (plasticization operation). ..

Next, the control unit controls the screw drive unit 50 to advance the screw 30. As a result, the molten resin at the tip of the injection cylinder 11 is pushed into the cavity through the resin flow path (injection operation).

Next, the control unit controls the mold clamping drive unit to open the moving mold K1 and the fixed mold K2 (mold opening operation), and ejects the product from the cavity by an ejector pin (not shown) (product ejecting operation).

After that, the product is molded by repeating the mold closing operation and the product taking-out operation.

Next, the operation of the screw head 41 of the injection molding machine 1 will be described.

In the plasticization operation, when the screw 30 is rotated by the screw drive unit 50, the screw main body 31 retracts while sending the molten resin forward. As a result, the screw head 41 is also rotated and retracted, and the backflow prevention ring 46 moves relatively forward, so that a plurality of balls are formed between the rear end surface 42c of the head portion 42 and the front end surface 46a of the backflow prevention ring 46. 47 is sandwiched. The molten resin passes through the resin flow path R as the screw head 41 retracts. At this time, the molten resin is pushed forward while being agitated by the flight 49 rotating in the resin flow path R. The flight 49 causes four large flows in the molten resin, and when the four flows of the molten resin pass through the resin flow path R and reach the plurality of balls 47, the six balls formed between the plurality of balls 47 are formed. It will pass through the gap. Therefore, when passing through these gaps, the four flows are dispersed into six to generate turbulent flow. Further, in the plasticization operation, the molten resin near the surface of the head portion 42 is agitated by the plurality of spiral grooves 48 as the head portion 42 is rotated.

Further, in the injection operation, when the screw 30 is advanced at high speed by the screw drive unit 50, the screw head 41 is also advanced at high speed. As a result, the molten resin near the screw head 41 and the backflow prevention ring 46 move relatively backward. Then, until the rear end surface 46b of the backflow prevention ring 46 abuts on the front surface 45a of the sheet 45, the molten resin near the surface of the head portion 42 is subjected to rotational force by the plurality of spiral grooves 48. Try to move backwards. At this time, since the number of spiral grooves 48 and the number of balls 47 are the same, the positional relationship between each groove and the ball is equal. That is, in the example shown in FIG. 3 (b), the ball 47 is located behind all the spiral grooves 48, and in the example shown in FIG. 3 (c), the ball 47 is located behind all the spiral grooves 48. The gaps are located, and the positional relationship between each groove 48 and the ball 47 becomes equal. Therefore, the spiral groove 48 uniformly applies a rotational force to the molten resin near the surface of the head portion, and the entire molten resin moves with respect to the surface of the head portion 42.

As described above, according to the injection molding machine 1 of the present embodiment, the backflow prevention ring 46 of the screw head 41 is inserted between the shaft portion 43 connected to the rear end surface 42c of the head portion 42 and the shaft portion 43. An annular resin flow path R is formed in the ring. A plurality of balls 47 are arranged side by side in a state of being packed in the circumferential direction between the head portion 42 and the backflow prevention ring 46. A plurality of spiral grooves 48 are provided at equal intervals on the surface of the head portion 42, and a plurality of spiral flights 49 are provided at equal intervals on the outer peripheral surface of the shaft portion 43. The number of spiral grooves 48 and the number of balls 47 are the same, and the number of flights 49 and the number of balls 47 are different. As a result, the rotation of the flight 49 agitates the molten resin inside the backflow prevention ring 46, and the rotation of the spiral groove 48 agitates the molten resin near the surface of the head portion 42. The retention of the molten resin can be effectively suppressed. Since the number of flights 49 and the number of balls 47 are different, a turbulent flow is positively generated in the molten resin from the flight 49 to the balls 47 in the plasticizing operation, and the retention of the molten resin is more effectively suppressed. can. Further, since the number of spiral grooves 48 and the number of balls 47 are the same, the positional relationship between each groove 48 and the balls 47 becomes equal. As a result, when the screw head 41 advances in the injection operation, the rotational force is uniformly applied to the molten resin near the surface of the head portion 42 by the spiral groove 48. Therefore, since the entire molten resin near the surface of the head portion is rotated without bias, the retention of the molten resin can be suppressed more effectively. Therefore, it is possible to prevent the resin from sticking.

In the above-described embodiment, the number of balls 47 is 6, the number of spiral grooves 48 is 6, and the number of flights 49 is 4, but the configuration is not limited to this. For example, the number of balls 47 and the number of spiral grooves 48 is eight, the number of flights 49 is six, and the number of spiral grooves 48 and the number of balls 47 are the same, and the number of flights 49 is the same. If the number of balls 47 and the number of balls 47 are different, the respective numbers are arbitrary.

Although embodiments of the present invention have been described above, the present invention is not limited to these examples. As long as the gist of the present invention is provided, a person skilled in the art may add, delete, or change the design of the above-described embodiment as appropriate, or combine the features of the embodiment as appropriate. Included in the scope of the invention.

1 ... Injection molding machine, 11 ... Injection cylinder, 12 ... Nozzle, 13 ... Heating device, 15 ... Hopper, 15a ... Supply path, 16 ... Hopper block, 17 ... Toggle link mechanism, 18 ... Movable die plate, 19 ... Fixed die Plate, 30 ... screw, 31 ... screw body, 32 ... screw flight, 41 ... screw head, 42 ... head part, 42a ... front part, 42b ... rear part, 42c ... rear end surface, 42d ... flat part, 43 ... shaft part , 43a ... Cylindrical part, 43b ... Skirt part, 43c ... Rear end surface, 44 ... Mounting part, 44a ... Male screw, 45 ... Sheet, 45a ... Front surface, 46 ... Backflow prevention ring, 46a ... Front end surface, 46b ... Rear end surface , 47 ... ball, 48 ... groove, 49 ... flight, 50 ... screw drive, K1 ... moving mold, K2 ... fixed mold, L ... rotating shaft, R ... resin flow path

Claims (4)

A screw head provided at the tip of a screw for injection molding.
The head part with a tapered shape and
A shaft portion connected to the rear end of the head portion and
A backflow prevention ring through which the shaft portion is inserted and an annular resin flow path is formed between the shaft portion and the shaft portion.
It has a plurality of balls arranged side by side in a state of being packed in the circumferential direction between the head portion and the backflow prevention ring.
A plurality of spiral grooves are provided at equal intervals on the surface of the head portion.
Multiple spiral flights are provided at equal intervals on the outer peripheral surface of the shaft portion.
The number of grooves and the number of balls are the same,
A screw head characterized in that the number of flights and the number of balls are different. The number of the flights is four
The screw head according to claim 1, wherein the number of grooves is 6. A screw for injection molding
A screw according to claim 1 or 2, wherein the screw head is provided at the tip thereof. An injection molding machine having an injection cylinder and a screw housed in the injection cylinder.
An injection molding machine, wherein the screw is composed of the screw according to claim 3.

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