JPH0234016Y2 - - Google Patents

Description

[Detailed description of the invention] "Industrial application field" This invention is based on the invention that when a plastic material such as millable silicone rubber is supplied from a material pushing cylinder to a temperature control screw cylinder, it is metered by the cylinder, and the temperature control injection is performed. The present invention relates to a plunger-type injection molding machine that prevents discoloration of the plastic material when it is injected into a mold by an advancing plunger after being supplied into a cylinder.

``Prior art'' Milky white and transparent millable silicone rubber is a plastic material that, like rubber, does not need to be plasticized in an injection cylinder.In order to degas and prevent vulcanization in the cylinder, a temperature-controlled cylinder is used. At the same time, a screw for measuring and a plunger for pushing are used, but the injected product changes color and reduces the commercial value of the product.

The factors that cause the product to discolor are the various fillers (such as quartz powder) mixed into millable silicone rubber as additives that scrape off the metal, or the inner wall of the temperature control cylinder and the metal plunger shaft as shown in Figure 3. It is estimated that the silicone rubber that has entered the space between the plungers 1 attached to one end of the plunger 2 is rubbed and contaminated, causing discoloration of the silicone rubber injected into the mold.

Furthermore, there is known a method of forming irregularities on the outer circumferential surface of the plunger and forming a synthetic resin coating layer on the irregularities. (Refer to Japanese Patent Application Laid-Open No. 51-97568.) However, in the method of coating the entire plunger head, the replacement cost is high, and the coating layer (approximately 1/100 to 5/100) is thin and easily damaged, and once scratched. If it gets attached, it has the disadvantage that it is easy to peel off from that part.

``Problems that the invention attempts to solve'' This invention was made in view of these problems, and the plunger scrapes off the inner peripheral surface of the temperature regulating cylinder when moving forward and backward inside the temperature regulating cylinder. The technical problem is to make the outer circumferential surface of the plunger smooth and to reduce the hardness to some extent, while at the same time making it possible to adjust the ring body.

"Means for Solving the Problems" In order to solve the above problems, the present invention has the following technical configuration.

A plunger characterized in that a plunger is detachably attached to the tip of a plunger shaft, an annular groove is formed on the outer periphery of the plunger, and a ring body and a collar made of a hard plastic material are fitted into the annular groove. Our objective is to provide a type injection molding machine.

"Operation" An annular cut is formed on the outer peripheral surface of the plunger,
An ultra-high molecular weight polyethylene ring and a collar are fitted into the notch so as to protrude somewhat from the outer circumferential surface of the plunger, so that silicone rubber that tries to enter between the temperature control cylinder and the plunger will be stuck on the outer circumferential surface of the forward plunger. In addition to being pressed smoothly by the polyethylene ring, it also has a sealing function that seals between the inner wall of the temperature control cylinder and the outer circumferential surface of the plunger, preventing silicone rubber from entering.
In addition, it is possible to prevent the inner wall from being scraped off by the silicone rubber, and it is possible to sufficiently deal with wear of the ring body, thereby preventing discoloration of the injected silicone rubber.

"Example" An embodiment of the present invention will be described based on the drawings.

As mentioned above, the specific material to be filled into the pre-plastic injection cylinder of the present invention, such as silicone rubber, does not need to be plasticized in the injection cylinder 10, screw cylinder 11, and material pushing cylinder 12, as is the case with rubber. It is preferable that these cylinders 10, 11, and 12 be temperature-controlled or cooled with hot oil or hot water.

Reference numeral 13 denotes a plunger that advances or retreats within the injection cylinder 10. The plunger 13 is formed at one end of the plunger shaft 19, and has an annular stepped portion 15 of an appropriately shaped shape as shown in FIG. 2 on the outer periphery 14 of the plunger 13. A collar 17 is fitted into the annular stepped portion 15 together with a ring 16 made of an ultra-high polymer material such as polyethylene and fixed thereto via an adhesive.

Note that although a tapered portion 18 is formed at one end of the annular step portion 15, a right-angled or other shape other than the tapered portion may be used without any problem.

In the drawing, reference numeral 21 is a screw, 22 is a hydraulic motor, 23 is a nozzle, 24 is a plunger shaft of a plunger 25 for pushing material, 26 is an annular body, 2
7 is a check valve.

``Effect of the invention'' As shown in Figure 1, a ring made of ultra-high molecular weight polyethylene is fitted into the outer periphery of the plunger of the invention, so that specific materials that try to enter between the inner periphery of the cylinder and the plunger can be removed. (Mirable silicone rubber) is pressed by a hard polyethylene ring that advances integrally with the plunger, and the sealing function of the hard polyethylene ring prevents specific materials from entering between the inner peripheral surface of the injection cylinder and the outer peripheral surface of the plunger. However, as a result, there is no rubbing due to the high-pressure contact between the millable silicone rubber and the metal surface, and a special effect is achieved in that discoloration during injection molding of the millable silicone rubber can be prevented.

Furthermore, if the ring body becomes worn out, only the ring body needs to be replaced, which is advantageous in terms of cost.

If the amount of wear is small, the ring body will be compressed by tightening the plunger more.
By expanding its outer diameter and restoring the amount of wear, it is possible to extend its life.

The injection molding machine of the present invention uses a pre-plastic type, but this is because the injection amount (MAX) can be freely changed according to the screw diameter, and the injection molding machine is limited to this. Alternatively, an in-line injection molding machine can also be used, in which case the same effect can be achieved by using plastic for the plunger of the push cylinder.

[Brief explanation of the drawing]

Figure 1 is a schematic cross-sectional view showing a state in which a plunger with a plastic ring fitted around its outer periphery is assembled into a pre-plastic injection molding machine, and Figure 2 shows a plunger fitted with a plastic ring fitted into an annular step formed on its outer periphery. FIG. 3 is a cross-sectional view of a known metal plunger. Explanation of symbols, 13: Plunger, 16, 26:
Ring body, 19: plunger shaft, 20: coated plastic layer.

Claims (1)

[Scope of utility model registration request] A plunger characterized in that a plunger is detachably attached to the tip of a plunger shaft, an annular groove is formed on the outer periphery of the plunger, and a ring body and a collar made of a hard plastic material are fitted into the annular groove. type injection molding machine.