JP7209882B2 - screw head - Google Patents

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 US Pat. 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 radially outer side of the shaft. The anti-backflow ring forms a ring-shaped resin flow path between itself and the shaft. A plurality of balls are arranged 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 placed in the injection cylinder of the injection molding machine.

JP-A-59-120431

In the plasticizing operation, molten resin flows from the rear side of the screw toward the front side. At this time, since the resin channel of the screw head has a complicated shape, there are places 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, spreads outward, and flows along the inner peripheral surface of the injection cylinder. As a result, there are places near the surface of the tapered portion where the molten resin does not easily flow. Therefore, there is a risk that the molten resin will stay in places where it is difficult to flow, and the resin will stick to the backflow prevention ring, the tapered portion, and the like.

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a screw head capable of suppressing sticking of resin, a screw having this screw head, and an injection molding machine having this screw.

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

In the present invention, it is preferable that the number of flights is four and the number of grooves is six.

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

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

According to the present invention, the backflow prevention ring of the screw head is inserted through the shaft portion that continues to the rear end of the head portion, and forms an annular resin flow path between the shaft portion and the backflow prevention ring. A plurality of balls are arranged side by side in a circumferentially packed state between the head portion and the backflow prevention ring. A plurality of spiral grooves are provided at regular intervals on the surface of the head portion, and a plurality of spiral flights are provided at regular intervals on the outer peripheral surface of the shaft portion. The number of spiral grooves is the same as the number of balls, and the number of flights is different from the number of balls. Because of this configuration, the rotation of the flight agitates the molten resin inside the backflow prevention ring, and the rotation of the spiral groove agitates the molten resin near the surface of the head, so that the molten resin stays. can be effectively suppressed. Since the number of flights and the number of balls are different, turbulence is actively generated in the molten resin flowing from the flights to the balls during the plasticizing operation, and the retention of the molten resin can be suppressed more effectively. Furthermore, since the number of spiral grooves and the number of balls are the same, the positional relationship between each groove and the balls is the same. A rotational force is uniformly applied to the molten resin in the vicinity of the surface of the head portion. Therefore, the entire molten resin in the vicinity of the surface of the head portion is rotated evenly, so that the stagnation of the molten resin can be suppressed more effectively. Therefore, sticking of the resin can be suppressed.

It is a figure showing a schematic structure of an injection molding machine concerning one embodiment of the present invention. 2 is a cross-sectional view of the vicinity of the tip of an injection cylinder of the injection molding machine of FIG. 1; FIG. FIG. 2 is a diagram illustrating a screw head provided on a screw of the injection molding machine of FIG. 1;

An injection molding machine according to an embodiment of the present invention will be described below with reference to FIGS. 1 to 3. FIG.

FIG. 1 is a diagram showing a schematic configuration of an injection molding machine according to one embodiment of the present invention. 2 is a cross-sectional view of the vicinity of the tip of the injection cylinder of the injection molding machine of FIG. 1. FIG. In FIG. 2, only the anti-backflow ring and seat of the screw head are shown in cross section. FIG. 3 is a view for explaining a screw head provided on the screw of the injection molding machine of FIG. 1. FIG. 3(a) is a side view of the screw head, FIG. 3(b) is a front view, and FIG. 3(c) is a front view of a plurality of balls out of phase. In FIG. 3(a), the anti-reflux ring and seat are shown in cross section along the axis of rotation. In addition, the tip side of the injection cylinder (the left side in FIGS. 1, 2, and 3(a), or the front side of the paper surface of FIGS. 3(b) and (c)) is defined as the front, , the left side of FIGS. 2 and 3(a), or the back side of the paper surface of FIGS. 3(b) and 3(c)).

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, a fixed die a plate 19; The injection molding machine 1 also has a screw 30 for injection molding and a screw driving section 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 a supply passage 15 a at the bottom thereof communicates with the base end of the injection cylinder 11 inside the hopper block 16 .

The toggle link mechanism 17 moves the movable die plate 18 back and forth with respect to the fixed die plate 19 by being bent and stretched by a mold clamping drive section (not shown). As a result, the movable 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. As shown in FIG.

The screw 30 is accommodated in the injection cylinder 11 so as to be rotatable and forward and backward. The screw 30 is rotated and axially moved within the injection cylinder 11 by a screw drive 50 .

The screw 30 has a screw body 31 and a screw head 41 attached to the tip of the screw body 31, as shown in FIG.

The screw main body 31 is formed in a cylindrical shape, and screw flights 32 are provided on the outer peripheral surface thereof. A proximal end portion of the screw main body 31 is connected to the screw driving portion 50 .

The screw head 41 has, as shown in FIG.

The head portion 42 integrally has a front portion 42a having a conical shape (tapered shape) and a rear portion 42b having a columnar shape that continues 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 this embodiment, six helical grooves 48 are provided, and are arranged at even intervals of 60 degrees in the rotational direction (circumferential direction) with the rotation axis L as the center. The head portion 42 is provided with a flat portion 42d for gripping with a tool when attaching and detaching the screw head 41 . A configuration in which the flat portion 42d is not provided may also be used.

The shaft portion 43 is coaxially and integrally connected to the rear end surface 42 c of the head portion 42 . The shaft portion 43 integrally has a cylindrical portion 43a having a diameter smaller than that of the rear end surface 42c and a tapered skirt portion 43b that continues to the rear end of the cylindrical portion 43a and gradually increases in diameter toward the rear. there is A plurality of spiral flights 49 are provided on the outer peripheral surface of the shaft portion 43 . In this embodiment, four flights 49 are provided, and they are arranged at even intervals of 90 degrees in the rotation direction with the rotation axis L as the center. In this embodiment, the helical orientation of the helical groove 48 and flight 49 is the same as the helical orientation 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 43 c of the shaft portion 43 . A male thread 44 a is formed at the rear end of the mounting portion 44 to be screwed with a female thread provided at the tip of the screw body 31 . The attachment portion 44 is attached to 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 seat 45 is formed in an annular shape having the same inner diameter as the mounting portion 44 and having an outer diameter larger than the inner diameter of a backflow prevention ring 46 described later. The mounting portion 44 is inserted and fitted inside the seat 45 , and the front surface 45 a is in contact with the rear end surface 43 c of the shaft portion 43 .

The anti-backflow ring 46 is formed in a cylindrical shape. The anti-backflow ring 46 is formed so that its outer diameter is substantially the same as the inner diameter of the injection cylinder 11 and its 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 the shaft portion 43 inserted therein and is movable in the front-rear direction with respect to the shaft portion 43 . In other words, the anti-backflow ring 46 is fitted on the shaft portion 43 with play. The anti-backflow ring 46 forms an annular resin flow path R between itself and 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 45 a of the seat 45 and the rear end surface 46 b of the backflow prevention ring 46 . As a result, the molten resin can 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. Thereby, 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 42 c of the head portion 42 and the front end surface 46 a of the anti-backflow ring 46 . The plurality of balls 47 all have 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 closely packed in the circumferential direction. Here, the “closed state” refers to a state in which a plurality of balls 47 are adjacent to each other with a slight gap that allows each ball 47 to rotate. In this embodiment, six balls are provided, and the center points of the balls 47 are evenly spaced apart from each other by approximately 60 degrees around the rotation axis L. As shown in FIG.

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

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

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

The controller also controls the heating device 13 to heat the injection cylinder 11 . As a result, the viscosity of the resin material is lowered, and the vicinity of the tip of the injection cylinder 11 is brought into a molten state (molten resin). Furthermore, the control unit controls the screw driving unit 50 to rotate and retreat the screw 30, and supplies the amount of molten resin required for one injection to the tip of the injection cylinder 11 (plasticizing operation). .

The controller then controls the screw drive 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 movable mold K1 and the fixed mold K2 (mold opening operation), and eject the product from the cavity by ejector pins (not shown) (product take-out operation).

After that, the mold closing operation to the product taking-out operation are repeated to mold the product.

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

In the plasticizing operation, when the screw 30 is rotated by the screw driving section 50, the screw main body 31 retreats while feeding the molten resin forward. As a result, the screw head 41 is also rotated and retreated, and the anti-reflux ring 46 is relatively moved forward, and 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 anti-reflux ring 46. 47 is sandwiched. The molten resin passes through the resin flow path R as the screw head 41 retreats. At this time, the molten resin is pushed forward while being agitated by the flights 49 rotating in the resin flow path R. As shown in FIG. The flights 49 generate four large flows of the molten resin, and when the four flows of the molten resin pass through the resin channel R and reach the plurality of balls 47, the six flows formed between the plurality of balls 47 You will pass through the gap. Therefore, when passing through these gaps, four flows can be dispersed into six to generate turbulence. Further, in the plasticizing 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, when the screw 30 is advanced at high speed by the screw driving section 50 during the injection operation, the screw head 41 is also advanced at high speed. As a result, the molten resin near the screw head 41 and the anti-backflow ring 46 move relatively rearward. Until the rear end surface 46b of the backflow prevention ring 46 abuts against the front surface 45a of the seat 45, the molten resin near the surface of the head portion 42 is rotated 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 the respective grooves and the balls is the same. That is, in the example shown in FIG. 3B, the balls 47 are positioned behind all spiral grooves 48, and in the example shown in FIG. are located, and the positional relationship between the respective grooves 48 and the balls 47 is the same. 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 through the shaft portion 43 continuing to the rear end surface 42c of the head portion 42, and the gap between the shaft portion 43 and the backflow prevention ring 46 is inserted. An annular resin flow path R is formed in the . A plurality of balls 47 are arranged side by side in a circumferentially packed state between the head portion 42 and the backflow prevention ring 46 . A plurality of spiral grooves 48 are provided on the surface of the head portion 42 at regular intervals, and a plurality of spiral flights 49 are provided on the outer peripheral surface of the shaft portion 43 at regular intervals. 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. In this way, 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. Retention of molten resin can be effectively suppressed. Since the number of flights 49 and the number of balls 47 are different, turbulence is actively generated in the molten resin flowing from the flights 49 toward the balls 47 in the plasticizing operation, thereby more effectively suppressing the stagnation of the molten resin. can. Furthermore, 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 is the same. As a result, when the screw head 41 moves forward in the injection operation, the spiral groove 48 uniformly applies a rotational force to the molten resin near the surface of the head portion 42 . Therefore, the entire molten resin in the vicinity of the surface of the head portion is rotated evenly, so that the stagnation of the molten resin can be suppressed more effectively. Therefore, sticking of the resin can be suppressed.

In the above-described embodiment, the number of balls 47 is six, the number of spiral grooves 48 is six, and the number of flights 49 is four. However, the number of flights 49 is not limited to this. For example, the number of balls 47 and spiral grooves 48 may be eight, and the number of flights 49 may be six, and so on. , and the number of balls 47 may be any number.

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

DESCRIPTION OF SYMBOLS 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 main body 32 Screw flight 41 Screw head 42 Head portion 42a Front portion 42b Rear portion 42c Rear end surface 42d Flat portion 43 Shaft , 43a... Cylindrical part 43b... Skirt part 43c... Rear end surface 44... Mounting part 44a... External thread 45... Seat 45a... Front surface 46... Backflow prevention ring 46a... Front end surface 46b... Rear end surface , 47... Ball, 48... Groove, 49... Flight, 50... Screw driving part, K1... Moving mold, K2... Fixed mold, L... Rotating shaft, R... Resin channel

Claims (4)

A screw head provided at the tip of a screw for injection molding,
a head portion having a tapered shape;
a shaft portion connected to the rear end of the head portion;
a backflow prevention ring through which the shaft portion is inserted and which forms an annular resin flow path between itself and the shaft portion;
a plurality of balls arranged side by side in a circumferentially packed state between the head portion and the backflow prevention ring;
A plurality of spiral grooves are provided on the surface of the head portion,
A screw head, wherein a plurality of helical flights are provided on the outer peripheral surface of the shaft portion. The screw head according to claim 1, characterized in that the number of said grooves and the number of said balls are the same . 3. A screw head according to claim 1 or 2, wherein the number of flights and the number of balls are different . The screw head according to any one of claims 1 to 3, wherein the pitch of the flight is longer than the length of the shank .

Images