JPS6210090Y2 - - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to a screw for a vent type molding machine.

Screws for vented molding machines are used in resin molding machines such as injection molding machines and extrusion molding machines.
It has a structure as shown in FIG.

In FIG. 1, the reference numeral 1 indicates a vent type molding machine, in which a screw 3 is fitted into a barrel 2 so as to be rotatable and slidable in the axial direction.

A heating means (not shown) is provided on the outer periphery of the barrel 2, a resin material supply port 4 is provided at the base end thereof, and a vent hole 5 for degassing is provided in the middle.

On the other hand, the screw 3 has a structure in which the shape changes approximately in two stages.

That is, the base portion of the screw 3 is a portion called the first stage A, as shown in FIG. 1, and a first feed zone a consisting of a deep portion of the screw groove is formed at the base of this portion. , a first compression zone b that gradually becomes shallower in the middle
is formed, and a kneading part c having a dalmage part 6 is formed on the tip side. Although the depths of the screw grooves in each zone a to c are different as described above, the diameter of the screw flight 7 is the same and has a diameter close to the inner surface of the barrel 2.

On the other hand, a portion called a second stage B is continuous beyond the first stage A of the screw 3, and a connecting portion between the two faces the vent hole 5.

The second stage B has a vent zone d which is a deep part of the screw groove at its base, a second compression zone e whose valley diameter gradually increases in the middle, and a uniform diameter at the leading edge. Measuring part f
is provided. Flight 7 in this second stage B portion also has the same diameter.

A discharge port 2a is formed at the tip of the barrel 2.

Under the structure described above, the resin material supplied from the supply port 4 enters the first feed zone a, and is sent toward the first compression zone b by the flight 7 of the rotating screw 3, and the material passes through the cross-sectional area As the pressure decreases, it is compressed and pressed against the heated inner wall of the barrel 2.

The resin material is gradually melted by the heat received from the inner wall and the shear heat generated by the rotation of the screw 3, and is led to the kneading section c and kneaded. The dalmage section 6 provided in the kneading section c is a screw having a dense pitch with different pitches of flights, and kneads the molten resin to a uniform kneading state.

The resin leaving this kneading section c enters the vent zone d of the second stage B. In this vent zone d, the groove depth of the screw is deeper than in the kneading part c, and
Because it is located near the vent hole 5, the resin that has been compressed until now is released to the atmosphere, that is, the pressure is reduced, and the moisture and volatile matter in the molten resin expands, increasing its volume and forming a foamed state. Become. Then, degassing is performed here.

Therefore, it is necessary that the groove depth of the screw in the vent zone d is sufficient to allow the expanded molten resin to be transferred without clogging the vent 5. That is, between the kneading section and the vent zone, there is provided a portion where the root diameter of the screw 3 suddenly changes, that is, a transition region 8.

The molten resin that has exited the vent zone d is sent to the second compression zone e, where it is compressed again, completely melted, and heated to a constant temperature, and then enters the metering zone f where it is discharged at a predetermined discharge pressure. It is kneaded to the desired amount.

In a molding machine having such a structure, as described above, a transition region is provided between the vent zone d and the kneading section c, where the root diameter of the screw 3 is significantly different. Conventionally, the shape of the screw in the transition region 8 has been adopted as shown in FIGS. 2 and 3.

That is, in the examples shown in FIGS. 2A and B,
The shape of the transition region 8 of the screw 3 is such that the grooves are continuous and gradually become deeper from the kneading section side, as shown in FIG. 2B in a developed state and in a cross-sectional state. This groove part is denoted by 9 in Fig. 2B.
Indicated by

Furthermore, in the examples shown in FIGS. 3A to 3D, the grooves 9 are shaped to become gradually deeper from the kneading section to the transition region. The difference between the example shown in FIG. 2 and the example shown in FIG. 3 is whether the shape of the transition region 8 is conical or conical.

The conventional structure shown in FIGS. 2 and 3 has the effect of gradually deepening the groove depth in the transition region and providing the necessary space for the expansion of the molten resin, but the naturally emitted gas is removed. However, it did not have the function of actively removing gas from the volumetrically expanded molten resin.

On the other hand, the resin that is gradually melted from the first stage to the second stage is melted closer to the inner circumferential surface of the heated barrel 2, and this melted portion is applied to the insufficiently melted resin inside. On the other hand, this results in the formation of a film.

For this reason, the gas emitted from the insufficiently melted resin located on the inside is blocked by this film and cannot escape, and in the structure shown in Figures 2 and 3, the molten resin suddenly There are disadvantages in that a so-called vent-up phenomenon occurs in which the coating expands and blocks the vent hole 5, and voids are formed in the molded product due to insufficient gas removal, resulting in poor appearance and deterioration of physical properties.

The present invention was made in order to eliminate the above-mentioned drawbacks of the conventional method, and in the transition region of the vent zone of the screw of a vent-type molding machine, the groove width of the screw is divided into two or more division bands, and each By shifting the start positions of the groove depth changes between the dividing zones, a step is created between adjacent dividing zones, and the molten resin is deformed and reversed at this step, causing expansion of the molten resin and breakage of the resin film. It is an object of the present invention to provide a screw for a vent-type molding machine that can perform the following steps and sufficiently remove gas.

Hereinafter, the present invention will be described in detail based on embodiments shown in the drawings.

4A to 4C illustrate one embodiment of the present invention, and the same or corresponding parts as in FIGS. 1 to 3 are denoted by the same reference numerals, and the explanation thereof will be omitted.

In this embodiment, in the transition region 8, the screw groove is divided into two zones 8a and 8b in the axial direction, and the depth of each groove is changed independently. The phases of the change start point and change end point are shifted by θ, for example, by a quarter of a revolution.

Therefore, a step 10 is created between the partition bands 8a and 8b due to the difference in groove depth.

When such a structure is adopted, the molten resin that has been guided to the transition region 8 is transferred to the respective partition zones 8a,
8b, but in addition to moving in the groove width direction as shown by reference numeral 11 in FIG. 4B due to the rotation of the screw,
The step 10 allows the resin in both zones to merge, separate,
Causes movement such as reversal. This state is indicated by an arrow in FIG. 4B.

When such actions such as merging, splitting, and reversal occur due to the step 10, the resin film on the surface of the molten resin is broken and stretched, and the gas pressure helps it expand, and shearing action is also added, causing the molten resin to spread deep inside. It is also possible to exhaust the gas in a sufficiently effective manner. Therefore, the vent-up phenomenon described above does not occur.

In addition, in the above-mentioned embodiment, a structure was shown in which the screw groove in the transition region is divided into two zones, and the starting point of change in groove depth for each zone is shifted. You can divide it into sections.

As is clear from the above description, according to the present invention, the screw groove in the transition area between the first stage and the second stage of the screw of the molding machine is divided into at least two division zones, and Because the structure uses a structure that shifts the starting point of groove depth change, a step is created between the partitions, and this step causes merging, splitting, and reversal of the molten resin as the screw rotates, and also causes a shearing effect. In addition, the resin film is broken and stretched, resulting in the excellent effect of sufficient degassing.

[Brief explanation of the drawing]

Fig. 1 is a longitudinal sectional view showing an example of a conventional molding machine;
Figures 2A and B are partially enlarged front views and developed views illustrating a conventional structure, and longitudinal cross-sectional views of various parts, and Figures 3 A to D are partially enlarged front views and developed views illustrating different examples of conventional structures. Figures, vertical cross-sectional views of various parts, - line cross-sectional views, and developed views of - line cross-sectional areas; Figures 4A to C are partially enlarged front views, developed views, and longitudinal cross-sectional views of various parts, illustrating one embodiment of the present invention. FIG. DESCRIPTION OF SYMBOLS 1... Molding machine, 2... Barrel, 3... Screw, 4... Supply port, 5... Vent, 6... Dalmage part, 7... Flight, 8... Transition area, 9...
…groove.

Claims (1)

[Scope of utility model registration request] In the part where the depth of the screw groove becomes deeper at the transition part to the vent zone of the screw for a vent-type molding machine, the screw groove width is divided into at least two zones, and the starting position of the change in groove depth in each zone is determined. A screw for a vent-type molding machine characterized by being offset from each other.