JPS593879Y2 - Synthetic resin injection machine - Google Patents

Description

[Detailed description of the invention] The invention is based on the thermoplastic resin being thermoplasticized in advance using an extruder, etc., and the amount required for molding being accumulated in the resin storage chamber after injection.
This invention relates to a synthetic resin injection machine that solves the difficulties faced when trying to obtain a desired molded product by injection, extrusion, etc. into a mold.

Conventionally, this technology has been widely used as an accumulator method in high-speed injection molding technology, injection molding of large products, hollow blow molding technology, etc., but there are two main difficulties in implementing this technology.

One of these is the so-called galling problem caused by sliding friction between the injection piston and the resin accumulator.

Traditionally, this problem has been solved by accurate alignment of the injection piston and the resin accumulator.

However, a bearing is required for this centering, which makes the injection unit complicated and long.

Another difficulty is the problem of thermal deterioration of the resin.

That is, in other injection molding methods, extrusion molding methods, etc.
The resin raw material is supplied to the hopper at room temperature, heated and plasticized in sequence toward the downstream extrusion port without stagnation, so local deterioration of the resin is unlikely to occur. However, in this accumulator type molding machine, Stagnation of the resin in contact with the injection part of the injection piston is unavoidable, and therefore, deteriorated and discolored resin tends to accumulate on the iron part, and some of it mixes with the injected resin, resulting in molded products containing discolored substances, which seriously deteriorates the product. Loss of value, physical properties, etc.

This bad phenomenon can sometimes be prevented by leaking a small amount of resin from the gap between the injection piston and the inner wall of the resin accumulator, but regulating the amount of leakage varies depending on the resin. It is almost impossible to prepare injection pistons with various outer diameters depending on the type and viscosity depending on the appropriate injection temperature.

'Furthermore, this leakage often causes unexpected adverse phenomena.

In particular, polyethylene tends to stick to metal when melted,
And the resin that is easily affected by oxygen corresponds to the gap,
The resin remains stuck to the inner wall of the resin accumulator and is exposed to air as the piston is driven, causing discoloration, and some of it is injected along with high-quality resin, resulting in molded products. cause contamination.

Furthermore, even with a mechanism that can almost completely prevent resin from leaking, such as a piston ring, the inner wall of the resin accumulator always comes into contact with the outside air as the piston operates, and then comes into contact with the next accumulated resin, causing this air to leak out. As the piston moves, the resin that comes in contact with the piston accumulates and stays in the sliding part of the piston, causing discoloration, and some of it is carried along with the injected resin, causing contamination of the molded product.

The present invention solves the above-mentioned two difficulties at once, that is, the galling problem caused by sliding of the injection piston and the problem of deterioration caused by resin stagnation, and provides an accumulator type injection machine with a wide range of applications. The purpose is to

That is, the present invention provides a synthetic resin injection machine that accumulates the amount of thermoplasticized synthetic resin necessary for molding in a resin storage chamber and then injects it. The gap between the inner wall of the container is 0.01~0.1mm
an injection part in the range of , then a leakage resin collection groove continuous on the circumference of the outer wall of the injection piston, and then a piston ring mechanism that can slide on the inner wall of the resin accumulator, and the bottom of the leakage resin collection groove. This is a synthetic resin injection machine having an injection piston provided with a passage communicating with the atmosphere beyond the inside of the piston ring portion.

Next, the present invention will be explained in more detail based on the drawings.

Reference numeral 1 denotes a resin accumulator, which forms a resin accumulating chamber 4 between the injection piston 2 and the nozzle portion 3.

Resin thermoplasticized by a plasticizer such as an extruder (not shown) is sent from the resin supply port 5, and in order to close the nozzle valve 6, the resin is pushed back into the resin storage chamber formed by pushing back the injection piston 2. When the nozzle valve 6 is opened and the rod 7 of the hydraulic cylinder is driven forward, the resin is injected from a nozzle 61 (not shown) into the mold.

At this time, the location where resin deterioration is likely to occur is on the opposite side of the resin supply port 5 of the resin storage chamber 4.

The resin in this part is compressed by the pressure of the resin into the injection part 2 of the injection piston 2.
A small amount leaks from the gap between the outer wall of the resin accumulator 1 and the inner wall of the resin accumulator 1, is collected in the leakage resin collecting groove 8, passes through an appropriate number of introduction holes 9 provided at the bottom of the groove, and enters the central passage 10. Then, the discharge hole 11 provided in the piston rod portion 22
More is discharged to the outside.

Note that the amount of resin leaking varies depending on the viscosity of the resin and the injection pressure, and in order to keep it constant, prepare a threaded frame with pores that suit each condition and install it at the outlet of the discharge hole 11. It is very effective to do so.

In addition, it is of course preferable that the amount of resin leaked is as small as possible unless discolored parts are observed on the molded product, and this amount is determined by trial, but it is usually 0.1% of the amount of resin used.
That's about it.

Usually, three or more piston rings 12 are provided in the piston ring portion 23 to completely prevent resin from entering or exiting from the iron portion.

The method and dimensions for inserting this piston ring may be any conventional method (for example, JISB 8032).

As mentioned above, the function of the piston ring 12 is to eliminate the gap between the injection piston 2 and the inner wall of the resin accumulator 1, prevent the backflow of contaminated resin, and act as a bearing, eliminating the need for adjusting the liquid core stand. This has the effect of preventing the difficulty of twisting and, by omitting the bearing, preventing the injection mechanism from becoming unnecessarily long.

What is important here is the gap between the injection part 21 of the piston and the inner wall of the resin accumulator 1. If the gap is too small, the action of the piston ring 12, which also acts as a bearing, will not be effective, leading to a difficult phenomenon of galling. However, if it is too large, the contaminated resin in the leaked resin collection groove 8 will flow back into the resin accumulation chamber 4;
Usually in the range of 0.01 to 0.1 mm, preferably 0.01
The thickness is selected from a range of 5 to 0.05 mm.

Although the dimensions of the leaked resin collecting groove 8 are arbitrary, it is not preferable for both the width and the depth to be less than 2 mm, and it is preferable to avoid a width of 10 mm or more for the purpose of preventing resin backflow as described above.

Since the synthetic resin injection machine of the present invention has the above-described structure, it is possible to solve the problem of deterioration caused by sliding of the injection piston and resin stagnation.

Further, since the gap between the outer wall of the injection portion of the injection piston and the inner wall of the resin accumulator can be arbitrarily determined within the above-mentioned range, manufacturing of the apparatus is greatly simplified.

[Brief explanation of the drawing]

The drawing shows a sectional view of the device of the present invention, in which 1 is a resin accumulator, 2 is an injection piston, 21 is an injection part of the injection piston 2, 22 is a piston rod part of the injection piston 2, and 23 is a part of the injection piston 2. Piston ring part, 24 is the tip of the injection piston 2, 3 is the nozzle part, 4 is the resin storage chamber, 5 is the resin supply port, 6 is the nozzle valve, 61 is the nozzle, 7 is the rod of the hydraulic cylinder, 8 is the leaked resin 9 is a collecting groove, 9 is a leakage resin introduction hole, 10 is a passage, 11 is a leakage resin discharge hole, and 12 is a piston ring.

Claims (1)

[Scope of utility model registration request] In a synthetic resin injection machine that accumulates thermoplasticized synthetic resin in a resin storage chamber in an amount necessary for molding and then injects it, a resin storage chamber 1, an injection piston 2, and a nozzle section 3 are used to inject a resin storage chamber 4.
The injection piston 2 includes, from the nozzle part 3 side, a tip part 24, an injection part 21 . It is composed of a piston ring part 23 and a piston rod part 22 connected to a hydraulic cylinder,
On the outer wall of the injection piston 2, there is an injection part 21° with a gap between the nozzle part 3 side and the inner wall of the resin accumulator 1 in the range of 0.01 to 0.1 mm, and then leaked resin continuous on the circumference of the injection piston 2. A collecting groove 8 and a piston ring part 23 are provided next, and the leaked resin collecting groove 8 communicates with a passage 10 that communicates with the piston rod part 22 in the center of the injection piston 2 through an introduction hole 9, and further discharges the resin. A synthetic resin injection machine having an injection piston 2, which communicates with the atmosphere around the outer periphery of a piston rod portion 22 through a hole 11.