JP4466917B2 - Bent type injection molding machine screw and vent type injection molding machine incorporating the screw - Google Patents

Description

  The present invention relates to a vent type injection molding machine that sucks and discharges gas components and air generated from a material in a heating cylinder through a vent hole.

This type of vent type injection molding machine has a built-in screw in which a two-flight flight is provided on the outer periphery from the rear end side (material supply side) to the front end side (screw head side). A vent hole for exhaust is provided in a substantially middle portion. That is, a material such as rubber is supplied into the heating cylinder from a supply port provided at the rear portion of the heating cylinder, and the supplied material is transferred forward while being plasticized and melted by heating and rotation of the screw. The At this time, a configuration is adopted in which air contained in the material, gas components generated from the molten material, and the like are discharged to the outside through the vent hole. This is because if air and gas components are mixed and melted and injected into the mold, bubbles may be formed in the molded product, so air and gas components are discharged from the material in advance. I am letting.
As described above, it is known that the vent type injection molding machine has a very small amount of air and gas components contained in the product and is very effective as a countermeasure against burless, air separation, and appearance defects.

For example, as such an injection molding machine, a vent portion having a groove depth larger than the groove of the supply portion before moving from the supply portion (first stage) to the measuring portion (second stage). What is equipped with is known.
By providing the vent portion having a large groove depth in this way, the material sent to the vent portion is reduced in pressure in the vent portion, and is in a foamed state due to air and gas components in the material ( A bubble film is formed). When the material is kneaded by the rotation of the screw, the bubble film is broken to separate gas components and the like, and is discharged out of the heating cylinder through the vent hole (see Patent Document 1).
JP-A-6-134826

  However, in such prior art, the effect of exhausting air and gas components has not been sufficient yet.

Therefore, a screw structure shown in FIG. 4 is provided as a screw structure that sufficiently discharges air or gas components contained in the material (hereinafter also referred to as a second prior art structure).
This second prior art configuration is a screw 300 in which two flights 201 and 202 are provided on the outer periphery from the rear end side (material supply side) 101 to the front end side (screw head side) 102. The supply zone 400 is provided with a metering zone 600 on the tip side, and the vent zone 500 is provided between the supply zone 400 and the metering zone 600.

That is, the second prior art configuration shown in the figure is provided with a temporary damming portion 700 of material in the vent zone 500, contrary to the vent portion configuration disclosed in Patent Document 1, and the damming portion. A plurality of extremely narrow grooves (total groove area is about 20 mm ² ) for material passage (not shown) are formed in the flights 201 and 202 in the vicinity of 700.
That is, in the second prior art configuration, the air or gas component contained in the material is sequentially released by passing the extremely narrow material passage groove to make the material a thin film. In this configuration, air and gas components can be efficiently discharged.

However, since the second prior art configuration described above is a configuration that focuses only on the discharge of air / gas components in the material, the following problems remain.
That is, since the material is intended to pass through the narrow material passage groove, the material stays in the vent zone 500. When the material in the supply zone 400 becomes full (oversupply) due to the material remaining in the vent zone 500, the material supplied from the material supply port loses its place, returns to the material supply port, and returns from the material supply port. Material overflows (also called backflow).
As a result, the supply from the vent zone 500 to the preceding metering zone 600 is reduced, and the material has run out in the metering zone 600. In addition, it takes time for measurement and a loss occurs in molding time.
Therefore, since it had such a subject, it had a problem to use it as a mass production machine.

  The present invention has been made in order to solve such problems, and the object of the present invention is to provide a vent that eliminates material backflow in the supply zone and out of material in the metering zone, and has improved plasticizing ability. It is to provide a type injection molding machine.

  In order to achieve such an object, the first invention is a vent in which a spiral material feed groove is formed on the outer periphery of the surface of the screw shaft by two flights and is rotatably and reciprocally incorporated in the heating cylinder. A screw for a plastic injection molding machine, wherein the screw includes a supply zone for plasticizing a material supplied from a material supply port of a heating cylinder, an air / gas component from the material on the downstream side of the supply zone, etc. Is formed of a vent zone that ejects and discharges the material to the outside, and a weighing zone that feeds the material that has passed through the vent zone forward while kneading, and a material damming portion is provided in the spiral material feed groove of the vent zone The flight in the vicinity of the damming portion is formed with one or a plurality of small grooves for material passage for supplying the material to the measurement zone. DOO is that the vent type injection molding machine screw, characterized in that it is constituted by a position only a strip which faces the material supply port of the heating cylinder.

According to a second aspect of the invention, in the first aspect of the invention, the one-flight flight portion facing the material supply port of the heating cylinder is provided at a distance of about twice the screw diameter. This is a machine screw .

  According to a third aspect, in the second aspect, the one flight portion facing the material supply port of the heating cylinder is in a range of 60 to 90 mm in the axial length of the screw from the base end of the one flight portion. This is a screw for a vent type injection molding machine.

  A fourth invention is the vent according to the third invention, wherein the one flight part is provided within a range of 70 mm in the axial length of the screw from the base end of the one flight part. This is a screw for an injection molding machine.

A fifth invention is a vent type injection molding machine screw according to any one of the first to fourth inventions, wherein the small groove for passing material is 40 mm ^{2 in} total groove area.

  In a sixth aspect of the present invention, a heating cylinder having a material supply port and a vent hole provided in front of the material supply port, and a spiral material feed groove is formed on the outer periphery of the surface of the screw shaft by two flights. And a screw incorporated in the heating cylinder so as to be rotatable and movable back and forth, and the screw is a screw for a vent type injection molding machine according to any one of the first to fifth aspects. This is a vent type injection molding machine.

According to the present invention, since one flight is provided only at a position facing the material supply port, in a situation where the material supply is excessive, the material supplied from the material supply port slips in the feed groove between the one flight ( Since the supply of the material to the supply zone is restricted, the supply amount can always be set to an appropriate value, and the amount of backflow can be significantly reduced.
Further, according to the present invention, since the small groove for material passage in the vent zone is 40 mm ^{2 in} total groove area, it is possible to increase the material delivery amount to the measuring zone while maintaining the deaeration effect of air / gas components and the like. Therefore, the plasticizing ability can be improved.

  According to the present invention, it is possible to provide a vent type injection molding machine that eliminates material shortage in the backflow / metering zone of the material in the supply zone and has improved plasticizing ability.

  An embodiment of the present invention will be described in detail with the following examples. Note that this embodiment is merely an example of the present invention, and is not construed as being limited thereto. The design can be changed within the scope of the present invention.

  FIG. 1 is a front view showing an embodiment of a screw for a vent type injection molding machine to which the present invention is applied, FIG. 2 is a schematic sectional view of a vent zone, and FIG. 3 is an embodiment of the vent type injection molding machine of the present invention. It is a front view which shows the outline of an example in a section.

The screw 1 is provided with a screw head 2 at the tip, and two flights 4 and 5 are spirally provided on the outer periphery of the surface of the screw shaft 3 over the entire length in the axial direction at a predetermined interval.
Then, spiral material feed grooves 6 a and 6 b are formed on the outer periphery of the surface of the screw shaft 3 by the two flights 4 and 5.
In this embodiment, the supply zone S for plasticizing the material supplied from the material supply port 11 of the heating cylinder 9 in which the screw 1 is housed, and the air / gas components from the material on the downstream side of the supply zone S, etc. It consists of a vent zone V that ejects and discharges to the outside, and a metering zone M that feeds the material that has passed through the vent zone V forward while being kneaded.
In the present embodiment, the groove depths of the spiral material feed grooves 6a and 6b described above are the same over the length direction of the screw 1, but the groove depths of the supply zone S and the measurement zone M are different. It may be configured as follows.

  The flights 4, 5 located in the supply zone S are provided with two flights 4, 5 spirally in the longitudinal direction of the screw 1, but facing the material supply port 11 of the heating cylinder 9. Only one flight 4 is formed (the range indicated by the symbol A in FIG. 1).

  One flight 4 portion facing the material supply port 11 of the heating cylinder 9 is provided at a distance of about twice the screw diameter, for example. Specifically, in the present embodiment, with respect to the diameter φ40 of the screw 1, one flight 4 portion is within a range of 60 to 90 mm in the axial length of the screw 1 from the base end 4a of the one flight 4 portion. Preferably it is provided. In the present embodiment, it is particularly preferable that the length of the screw 1 in the axial direction is 70 mm from the base end 4a of one flight 4 portion.

Material damming portions 7 a and 7 b are provided in the spiral material feed grooves 6 a and 6 b in the vent zone V.
The material damming portions 7a and 7b are provided one by one with a predetermined thickness and height so as to close the groove directions of the respective material feed grooves 6a and 6b located in the vent zone V. In the present embodiment, the heights of the blocking portions 7a and 7b are the same as the heights of the flights 4 and 5.

In the flights 4 and 5 in the vicinity of the damming portions 7a and 7b, one or a plurality of small grooves 8a and 8b for material passage for supplying material to the measuring zone M are formed.
If the small grooves 8a and 8b for passing the material are too large, the effect of ejecting the air / gas component becomes thin. Conversely, if the groove is too small, the supply amount to the measuring zone M becomes extremely small. Is set within the scope of the present invention so as to satisfy the effect that the material supply amount to the measuring zone M is not extremely reduced.
For example, the small grooves 8a and 8b in the screw 1 of the present embodiment preferably have a total groove area of 40 mm ² or less and 20 mm ² or more, and particularly preferably 40 mm ² .
Further, the number of small grooves 8a and 8b is not particularly limited, but in the present embodiment, it is preferable that 22 to 36 are disposed on the flights 4 and 5 in the vicinity of the respective damming portions 7a and 7b. The number is particularly preferably 32. Further, the interval between the small grooves 8a and 8b is not particularly limited, and the design can be changed within the scope of the present invention.

  In the screw 1 of the present embodiment, the supply zone S, the vent zone V, and the measuring zone M are integrally formed. However, the supply zone S, the vent zone V, and the measuring zone M are respectively attached and detached. It is also possible to adopt a configuration formed separately as possible, and the supply zone S and the vent zone V can be formed integrally, and the measuring zone M can be formed separately from the vent zone V so as to be detachable. It is also possible to form the vent zone V and the metering zone M integrally and to form the supply zone S separately from the vent zone V so as to be detachable.

  Next, an example of a vent type injection molding machine incorporating the screw 1 of this embodiment will be described with reference to FIG.

  The vent type injection molding machine has a nozzle 10 at the tip, a cylindrical heating cylinder 9 provided with a heater (not shown) on the outer periphery, and the screw incorporated in the heating cylinder 9 so as to be rotatable and movable back and forth. 1 and a material supply device 13 provided at the rear end of the heating cylinder 9. The material supply device 13 includes, for example, a hopper and a feed screw (not shown), and supplies the material into the heating cylinder 9 in a ribbon shape (band shape).

At the rear end of the heating cylinder 9, a material supply port 11 for receiving a material supplied from the material supply device 13 and a vent hole 12 provided in front of the material supply port 11 are provided.
A vacuum device (not shown) is connected to the vent hole 12, and air or gas components ejected by the vent zone V are effectively discharged (desorbed) out of the device by reducing the vacuum with the vacuum device. I care). The heating cylinder 9 can be appropriately modified within the scope of the present embodiment as long as it has a nozzle 10 at least at the tip and is provided with a material supply port 11 and a vent hole 12.
Further, the outer diameter of the screw 1 is configured to be slightly smaller than the inner diameter of the heating cylinder 9. That is, the material sent through the heating cylinder 9 is configured so as not to pass a large amount between the outer diameter of the screw 1 and the inner diameter of the heating cylinder 9.

Next, the operation of the vent type injection molding machine of this embodiment will be described.
First, the material (rubber) is sequentially supplied from the material supply device 13 into the heating cylinder 9 through the material supply port 11 of the heating cylinder 9 in a ribbon shape. The supplied material is fed forward in the feed zone S by the material feed grooves 6a and 6b between the flights 4 and 5 by the rotation operation of the screw 1. The sequentially fed material reaches the vent zone V and is blocked by the material damming portions 7a and 7b in the vent zone V, and the dammed material passes through the material passing small grooves 8a and 8b. Then, it is sent to the measuring zone M. At this time, since the material passing through the small grooves 8a and 8b passes through the small grooves 8a and 8b so as to be pushed out to the measuring zone M, air and gas components contained in the material are repelled. It is. The blown air, gas components, and the like are discharged to the outside by the vacuum device through the vent hole 12. According to the present embodiment, since the small groove for passing material is 40 mm ² , the material feed amount to the measuring zone can be increased while maintaining the deaeration effect of air / gas components, etc. Can be improved.

  And when the material sequentially sent out from the material supply port 11 becomes larger than the passing amount to the measurement zone M, the material stays in the vent zone V, and in the situation where the material supply is excessive, in the material supply port direction. It becomes clogged (residence state). However, according to the present embodiment, as shown in FIG. 1 and FIG. 3, since the flight 4 located at the material supply port 11 is one, the material supplied from the material supply port 11 is the first item. Slip in the feed groove between the flights 4 (range of reference A), and the supply of material to the supply zone S is restricted. Therefore, the supply amount can always be an appropriate value, and the amount of backflow can be significantly reduced.

Here, with the vent type injection molding machine of the present embodiment (hereinafter referred to as an example) and a conventional vent type injection molding machine (hereinafter referred to as a comparative example) incorporating the screw 300 shown in FIG. A comparative test was performed on the number of occurrences of rubber breakage and the plasticizing ability (cc / sec).
(Test conditions)
Test material: Synthetic rubber, viscosity 38.6p
Machine used: Vertical type 100ton, 1000cc
Screw outer diameter: Example φ40 Comparative example φ40
Small groove for material passage (groove total area): Example 40 mm ² Comparative example 20 mm ²

  Table 1 shows the test results. According to this, it can be confirmed that the vent type injection molding machine of this example does not cause any rubber breakage even if the measurement time is increased as compared with the conventional vent type injection molding machine.

The front view which shows one Example of the screw for this invention vent type injection molding machines. The cross-sectional schematic of a vent zone. BRIEF DESCRIPTION OF THE DRAWINGS The front view which shows the outline of one Example of this invention vent type injection molding machine in cross section. The front view which shows an example of the screw for conventional vent type injection molding machines.

Explanation of symbols

1: Screw 4, 5: Flight 6a, 6b: Material feed groove 7a, 7b: Material damming portion 8a, 8b: Small groove for material passage 9: Heating cylinder 11: Material supply port 12: Vent hole S: Supply zone V : Vent zone M: Weighing zone

Claims (6)

A screw for a vent type injection molding machine in which a spiral material feed groove is formed on the outer periphery of the surface of the screw shaft by two flights, and is rotatably and reciprocally incorporated in a heating cylinder,
The screw includes a supply zone for plasticizing the material supplied from the material supply port of the heating cylinder, and a vent zone for ejecting air gas components and the like from the material on the downstream side of the supply zone and discharging them to the outside. A weighing zone that feeds the material that has passed through the vent zone forward while kneading,
The spiral material feed groove in the vent zone is provided with a material damming portion, and the flight in the vicinity of the damming portion has one or more small grooves for material passage for supplying material to the measuring zone. It is formed individually
A screw for a vent type injection molding machine, wherein the flight located in the supply zone is composed of one line only at a position facing the material supply port of the heating cylinder. 2. A screw for a vent type injection molding machine according to claim 1, wherein the one flight portion facing the material supply port of the heating cylinder is provided at a distance of about twice the screw diameter.
  The single flight portion facing the material supply port of the heating cylinder is provided in a range of 60 to 90 mm in the axial length of the screw from the base end of the single flight portion. 2. A screw for a vent type injection molding machine according to 2.   4. The screw for a vent type injection molding machine according to claim 3, wherein the one flight part is provided in a range of 70 mm in the axial length of the screw from the base end of the one flight part. . Materials small grooves for passing the vent type injection molding machine screw according to any one of claims 1 to 4, characterized in that a 40 mm ² in the groove total area. A heating cylinder having a material supply port and a vent hole provided in front of the material supply port;
A spiral material feed groove is formed on the outer periphery of the surface of the screw shaft by two flights, and is constituted by a screw that is rotatably and reversibly incorporated in the heating cylinder,
The vent type injection molding machine according to any one of claims 1 to 5, wherein the screw is a screw for a vent type injection molding machine.

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