JPH059257B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a vent device for a vent-type molding machine that is provided with a vent hole that opens on the top surface of a heating cylinder.

[Prior art and issues]

Generally, a vent type molding machine is constructed as shown in FIG.

In the figure, 70 is an injection device in an injection molding machine, and is equipped with a heating cylinder 71. The heating cylinder 71 has a built-in screw 72, and the heating cylinder 71
The rear end of the injection cylinder is connected to the tip 73 of the injection cylinder.
Note that the screw 72 includes a first stage part 72a and a second stage part 72b, and the second stage part 72
The screw groove at the transition point to b suddenly becomes deeper. Further, an injection nozzle 74 is provided at the tip of the heating cylinder 71, and a hopper 75 for supplying the resin material is provided near the rear end of the heating cylinder 71. On the other hand, the heating cylinder 71
A vent device having a vent hole 76 opening upward is provided at an intermediate position.

In such an injection device 70, the resin material is supplied from the hopper 75 to the first stage portion 72a of the screw 72, and as the screw 72 rotates, the resin material is pressurized and melted. The resin material passes through the vent hole 76 (vent field), is transferred to the second stage section 72a, and is charged to the tip of the heating cylinder 71. Note that when the resin material passes through the vent hole 76, the resin pressure is suddenly released.
Gases such as volatile components, moisture, and air from the material are exhausted to the outside through the vent holes 76. However, in this type of vent device, since the resin material expands when passing through the vent hole 76, this expansion clogs the vent hole 76 (vent up), making the vent function impossible.

In order to solve this problem, various proposals have been made in the past. For example, in Japanese Utility Model Publication No. 60-27613, the vent hole is inclined in the opposite direction to the direction of rotation of the screw, and the inner wall of the vent hole in the direction of rotation of the screw is Disclosed is a vent device in which a surface including a tangent to the inner circumferential surface of a cylinder or a surface including an extension curve of the same tangent coincides with each other.

However, this type of device cannot secure a vent space corresponding to the state of expansion of the resin material, so the resin material overflows into the vent hole, which has the drawback that vent up-up cannot be reliably prevented.

On the other hand, Special Publication No. 55-38253 and Special Publication No. 55-38253
Publication No. 38255 discloses that a vent member is attached to the upper side of the vent field portion of the cylinder, and the shape of the vent member in the cross section of the cylinder is such that the vent hole opens vertically forward in the direction of rotation of the screw, and the vent hole is opened vertically in the forward direction in the direction of rotation of the screw. A vent device is disclosed that is recessed to form a resin pool.

However, this type of device requires a separate vent member to be attached to the cylinder, which limits the shape and size of the resin pool, has poor workability, and has a complicated structure, resulting in a significant increase in cost. Be strong. In addition, since there is no continuity between the vent hole and the resin pool, if the expanded resin exceeds the volume of the resin pool, it will overflow into the vent hole, and the overflowing resin will be inside the cylinder. Because it is difficult to get caught, it remains in the vent hole, resulting in a problem in which vent build-up cannot be reliably prevented.

An object of the present invention is to provide a vent device for a vent-type molding machine that eliminates the problems existing in the conventional technology.

[Means to solve the problem]

The vent device 1 of the vent type molding machine according to the present invention heats the inner wall surface 3a of the vent hole 3 in the forward direction of the screw rotation direction when configuring the vent device equipped with the vent hole 3 that opens on the upper surface of the heating cylinder 2. It is formed at a position approximately parallel to the tangent line P of the inner circumferential surface 2a of the cylinder 2 and its extension line, and at a position offset radially outward from the tangent line P by a predetermined width S, and further from the vicinity of the contact point of the tangent line. The inner wall surface 3a of the vent hole 3 located below is connected to the inner peripheral surface 2 of the heating cylinder 2.
It is characterized in that the resin accommodating portion D is provided by forming a concave curved surface that is continuous with respect to a. In this case, the vent hole 3 is formed vertically or inclined with respect to the vertical line. Further, the offset of the vent hole 3 is preferably gradually reduced from the hopper side to the injection nozzle side, and is zero at the end on the injection nozzle side. Furthermore, the planar shape of the vent hole 3 is the same as that of the heating cylinder 2.
It can be formed to have approximately the same width from the injection nozzle side to the hopper side, or it can be formed to gradually become wider toward the hopper side. Note that the boundary between the inner wall surface 3a of the vent hole 3 and the inner peripheral surface 2a of the heating cylinder 2 on the injection nozzle side is desirably chamfered.

[Effect]

According to the vent device 1 according to the present invention, the vent hole 3 can be directly machined into the heating tube 2, so that the process is easy and the configuration is simplified.

Furthermore, since the inner wall surface 3a of the vent hole 3 is formed at a position offset outward from the tangent P of the inner circumferential surface 2a of the heating cylinder 2, a resin storage portion D that can sufficiently accommodate the expanded resin material is ensured. can. In addition, even if the resin material expands excessively, the resin material overflowing into the vent hole 3 can be smoothly removed because the inner wall surface 3a of the vent hole 3 and the resin storage portion D are formed as continuous surfaces in substantially the same direction. It can be returned to the resin storage part D at the same time.

On the other hand, by changing the size of the offset in accordance with the longitudinal position of the vent hole 3, the resin storage portion D can be formed with an appropriate volume depending on the timing and degree of expansion of the resin material. In addition, the inner peripheral surface 2 of the heating cylinder 2
Since the concave curved surface provides continuity with respect to a, the overflowing resin material is smoothly rolled up into the screw.

〔Example〕

Below, preferred embodiments according to the present invention are listed,
This will be explained in detail based on the drawings.

First, the configuration and functions of the vent device 1 according to the present invention will be specifically explained with reference to FIGS. 1 to 5.

In FIG. 5, reference numeral 2 denotes a heating cylinder, and a horizontal surface portion 11 is formed on the upper surface at an intermediate position (vent field), and a vent hole 3 is provided that penetrates from this horizontal surface portion 11 into the inside of the heating cylinder 2.

The vent hole 3 is formed directly in the heating cylinder 3. Also,
As shown in FIG. 3, the vent hole 3 is formed into an elongated planar shape that gradually becomes wider from the injection nozzle side to the hopper side. In this case, it is desirable that the length of the vent hole 3 in the longitudinal direction is selected to be about 1.0 to 1.5 screw pitches, and by such selection, the gas can be released appropriately. In addition, if the pitch is less than 1.0, there is a risk that the vent hole 3 will be blocked by the resin material, and if it exceeds 1.5, the heating of the bunt heater attached to the heating tube 2 should be properly controlled. I can't. On the other hand, the vent hole 3 is inclined with respect to the vertical line when viewed from the front of the cross section, that is, it is inclined by a predetermined angle K (for example, about 30 degrees) as shown in FIG. Further, the rotating direction of the screw 12 (the first
The inner wall surface 3a of the vent hole 3 located at the front (in the direction of arrow H in the figure) is formed to be approximately parallel to the tangent P of the inner circumferential surface 2a of the heating cylinder 2 and its extension line (the extension line includes a curved line). and is formed at a position offset by a predetermined width S toward the outside of the heating cylinder 2 in the radial direction. In this case, the inner wall surface of the vent hole 3 located below the vicinity of the contact point of the tangent line P is formed into a concave curved surface that is continuous with the inner circumferential surface of the heating cylinder 2. Thereby, it is possible to provide a resin storage portion D that can temporarily store the expanded resin material. Furthermore, the inner wall surface 3a of the vent hole 3 on the offset side is formed obliquely with respect to the axis of the heating cylinder 2. That is, FIGS. 3 and 1
As shown in the figure, the offset near the end on the hopper side is set to be the largest, and as shown in Figure 2, the offset at the end on the injection nozzle side is set to zero, and the offset is gradually decreased from the hopper side to the injection nozzle side. . In this case, it is desirable that the offset be selected to be approximately 10% of the inner diameter of the heating cylinder 2 at its largest point. In addition, in FIG. 3, Q indicates the intersection line between the bottom of the inner circumferential surface 2a and the round end mill.

Therefore, the vent device 1 having such a shape
A resin storage portion D for storing the expanded resin material is formed laterally below the screw 12, and its volume becomes relatively large on the hopper side, gradually decreases on the injection nozzle side, and becomes zero at the end. Therefore, the expanded resin material can be accommodated with a margin on the hopper side where the expansion is largest in the vent hole 3, and the expanded resin material can be smoothly rolled into the screw on the injection nozzle side. Moreover, since the insertion direction of the resin material into the resin storage part D and the opening direction of the vent hole 3 substantially match, the resin material overflowing into the vent hole 3 can be smoothly returned to the resin storage part D. Since the hole 3 is formed by forming the inner wall surface below the vicinity of the contact point of the tangent line P into a concave curved surface that is continuous with respect to the inner peripheral surface 2a, the resin material of the resin storage portion D is also similar to the screw 12.
can be easily drawn into.

Note that FIGS. 6 and 7 show the case where chamfering is applied. In this case, a chamfer R is applied to the boundary between the inner wall surface 3a of the vent hole 3 and the inner peripheral surface 2a of the heating cylinder 2 on the injection nozzle side of the heating cylinder 2, thereby allowing the resin material to flow into the screw 12. I'm trying to get involved smoothly.

Next, a modified example will be described with reference to FIGS. 8 and 9.

In the modified embodiment, the planar shape of the vent hole 3 is formed to be elongated so as to have substantially the same width from the injection nozzle side to the hopper side. The inner wall surface of the vent hole 3 on the offset side is formed in the same manner as in the previous embodiment. In the case of the modified embodiment, the same effects as in the previous embodiment can be obtained.

Although the embodiments have been described in detail above, the present invention is not limited to these embodiments. For example, the angle of the vent hole may be vertical, and the shape, size, offset size, etc. of the vent hole can be arbitrarily changed depending on the type of resin material, etc. Other changes may be made in the detailed structure and the like without departing from the gist of the present invention.

〔Effect of the invention〕

In this way, the vent device according to the present invention allows the inner wall surface of the vent hole in front of the screw rotation direction to
It is formed at a position that is approximately parallel to the tangent to the inner peripheral surface of the heating cylinder and its extension line, and is offset radially outward from the tangent by a predetermined width, and is located below the vicinity of the contact point of the tangent. Since the inner wall surface of the vent hole is formed into a concave curved surface that is continuous with the inner circumferential surface of the heating cylinder, the following significant effects are obtained.

In addition to forming vent holes directly in the heating cylinder,
Since the inner wall surface is offset, it is possible to provide a resin accommodating portion that can smoothly accommodate the expanded resin material, and the resin accommodating portion can be provided with an appropriate volume and shape corresponding to the amount of resin expansion. can be reliably prevented.

In order to form the inner wall surface of the vent hole (including the resin storage part) and the inner peripheral surface of the heating cylinder into a continuous shape,
The resin material accommodated in the resin storage portion of the vent hole or the resin material overflowing into the vent hole can be smoothly rolled up into the screw.

Since the vent hole can be formed directly on the heating cylinder, processing becomes easy, the configuration can be simplified, and costs can be reduced.

[Brief explanation of the drawing]

Fig. 1: A longitudinal sectional front view of the vent device according to the present invention (sectional view taken along the line B-B in Fig. 3), Fig. 2: A longitudinal sectional front view of the same vent device (sectional view taken along the line A-A in Fig. 3), Fig. 3 : Plan view of the vent device, Fig. 4: Side view of the vent device, Fig. 5: External perspective view of the vent device, Fig. 6
Figure: Plan view of the same vent device with chamfering, Figure 7: Side view of the same vent device with chamfering, Figure 8: External perspective view of the vent device according to a modified embodiment of the present invention. , FIG. 9: A plan view of the vent device, and FIG. 10: A vertical sectional side view of a general vent-type molding machine equipped with the vent device. In addition, in the drawing, 1... vent device, 2... heating cylinder,
2a...inner peripheral surface, 3...vent hole, 3a...inner wall surface, P...tangent, S...predetermined width, R...chamfering,
D...Resin storage section.

Claims (1)

[Scope of Claims] 1. In a vent device for a vent-type molding machine that is equipped with a vent hole that opens on the top surface of a heating cylinder, the inner wall surface of the vent hole in the forward direction of the screw rotation direction is defined by a tangent to the inner circumferential surface of the heating cylinder. Formed at a position approximately parallel to the extension line and offset radially outward from the tangent line by a predetermined width,
A vent-type molding machine characterized in that a resin storage part is provided by forming the inner wall surface of the vent hole located below the vicinity of the tangent contact point into a concave curved surface that is continuous with the inner peripheral surface of the heating cylinder. Venting device. 2. The vent device for a vent type molding machine according to claim 1, wherein the vent hole is vertical or inclined with respect to the vertical line. 3. A vent device for a vent type molding machine according to claim 1, wherein the offset is gradually reduced from the hopper side to the injection nozzle side. 4. The vent device for a vent type molding machine according to claim 3, wherein the offset is zero at an end on the side of the injection nozzle. 5. The vent device for a vent type molding machine according to claim 3, wherein the planar shape of the vent hole is formed to gradually become wider from the injection nozzle side to the hopper side. 6. The vent device for a vent type molding machine according to claim 3, wherein the planar shape of the vent hole is formed to have substantially the same width from the injection nozzle side to the hopper side. 7. The vent device for a vent type molding machine according to claim 1, wherein the boundary between the inner wall surface of the vent hole and the inner circumferential surface of the heating cylinder on the injection nozzle side is chamfered.