JPH043778Y2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a check valve used in a screw-type injection molding machine for resin.

[Conventional technology]

The injection molding machine for resin (April 15, 1985, published by Sanko Publishing, written by Akiri Hiroe and Atsushi Iida. "Easy injection molding machine - from basics and applications to the latest technology") has a screw-type injection device. However, the molten material may flow back to the screw side at the pressurizing part of the screw head, resulting in a decrease in the injection amount and injection pressure, which may hinder work. A device with a check valve is used.

[Problem that the invention attempts to solve]

In order to explain the problems to be solved by the present invention, the structure, operation, and problems of conventional check valves will be described next.

Figure 1 shows an outline of the structure around the check valve of a screw type injection device with a check valve.

1 is a screw that feeds the material toward the nozzle;
2 is a ring-shaped seat (valve seat), and the combination of the ring valve 3 and the torpedo head 4 constitutes a backflow prevention valve. 5 is a heating cylinder that heats the resin and maintains it in a molten state;
6 is a nozzle that injects the material into the mold.

To explain the function of the valve, during the metering process, the screw 1 rotates and retreats to the right, so the ring valve 3 separates from the seat 2 to the left, the valve is opened, and the material is distributed longitudinally around the outer circumference of the torpedo head 4. It flows towards the left nozzle through several grooves provided.

Next, during the injection process, the screw 1 advances to the left and compresses the molten material in front of the torpedo head 4, so the ring 3 is pushed to the right by the reaction force and is brought into close contact with the sheet 2. The valve closes, preventing backflow and injecting material.

The abutment surfaces of the ring 3 and the seat 2 may be a combination of flat surfaces as shown in FIG. 1, or a combination of conical surfaces and conical surfaces.

Conventional ring valves and seats are mainly made of tool steel and do not have sufficient wear and corrosion resistance. Particularly in recent years, glass fibers as reinforcing agents, glass particles as fillers and pigments, and various oxides added to improve the performance of resins accelerate wear of valve parts and damage the surfaces of valves and seats. Abrasion and corrosion scratches are likely to occur, which can cause backflow and damage due to valve leakage.

To solve this problem, it is necessary to improve the material of the ring valve and seat to prevent surface scratches.

[Means for solving problems]

In order to prevent wear and corrosion scratches that occur on the surface of tool steel rings and seats, it is possible to use cemented carbide, which has better wear and corrosion resistance than tool steel, but resin Considering that hard substances such as oxides are mixed, even cemented carbide is not sufficient, and it is desirable to use a material with hardness and wear resistance equal to or greater than fillers such as oxides. However, such high-hardness materials have poor toughness, and are therefore unsuitable for use in molding machines where injection pressures have recently become high, as there is a risk of breakage.

The present invention uses fillers equivalent to or similar to oxides and other fillers contained in resin materials on the surfaces of rings and sheets manufactured using materials with stable strength such as conventional tool steel or cemented carbide with sufficient toughness. By providing a coating layer of hard material with a hardness of
The purpose is to improve corrosion resistance and prevent scratches on the surface of the valve, thereby solving this problem. In this invention, the hard material used for coating is one that has excellent hardness and corrosion resistance, and can be applied using ordinary coating techniques, and is based on the materials listed in periodic table 4a,
5a, 6a group metals and silicon carbides, nitrides,
Carbonitride or hard carbon (including diamond) was selected. The coating layer can be effective by providing one or more of the above-mentioned hard substances in one layer or in multiple layers.

For example, the first layer is a substance A that has a high affinity with the base material and has a high peel strength, and then a substance B that has a high wear resistance is placed on top of it.
If A or B is coated as a second layer, a coating layer superior in both peel strength and abrasion resistance can be obtained compared to a single layer coating of A or B. As described above, the various excellent properties of hard materials can be utilized to increase the effect of multilayer coating.

According to test results, if the thickness of the coating layer is 0.5 μm or more, it is effective in preventing surface scratches. In addition, the thicker the layer, the more effective it is in extending the lifespan, but it also increases the cost, so it is limited by economic conditions.However, considering that the thicker the layer, the smoothness of the surface also deteriorates.
A thickness of 20 μm or less is desirable.

〔Example〕

Examples of the present invention will be described below.

Example 1 The ring valve and seat were made of relatively tough cemented carbide (WC85%-Co15%), and a 7 μm thick TiN coating layer was provided on the surface, and glass fiber 30Vo1%, When injection molding is performed using resin containing 50% filler by volume, the tool life is more than 10 times that of conventional tool steel, and more than 20 times that of TiN-coated cemented carbide. It was hot.

Example 2 In the same work as Example 1, when the coating layer was made of two layers of TiC with a thickness of 2 μm as the first layer and TiN with a thickness of 5 μm as the second layer, the lifespan was equal to or longer than that of Example 1, but TiC Since it has a high affinity with the base material, it is superior to Example 1 in terms of peeling resistance of the coating layer.

Although cemented carbide was used as the coating base material in the above embodiments, the effect of hard coating can be expected even if tool steel or other alloy is selected as the base material.

Furthermore, the formation of the coating layer can employ various chemical and physical techniques, such as
This includes the CVD method, vacuum evaporation method, ion plating method, etc.

Further, the coating may be applied to the entire surface of the ring and the sheet, or may be applied only partially if necessary.

[Effect of idea]

As explained in detail above, the check valve according to the present invention prevents wear and corrosion scratches that occur on the surface by coating the surfaces of the ring valve and seat with a hard material that has high wear resistance and corrosion resistance. By preventing and eliminating leakage and damage caused by scratches, reliability and lifespan have been improved.

[Brief explanation of drawings]

FIG. 1 is a sectional view showing an outline of the structure around the check valve. 1... Screw, 2... Seat, 3... Ring valve, 4... Torpedo head, 5... Heating cylinder, 6... Nozzle.

Claims (1)

[Claims for Utility Model Registration] 1. A screw type injection molding machine for resin with a backflow prevention valve, characterized in that a hard coating layer is provided on the surface of the ring valve and the seat. 2. In the check valve according to claim 1 of the utility model registration claim, the coating layer comprises four elements of the periodic table of elements.
At least one coating layer selected from substances such as carbides, nitrides or carbonitrides of group a, 5a and 6a metals and silicon, or hard carbon (including diamond) is provided in one or more layers. Features a backflow prevention valve.