JPS6141284B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to various molding methods using thermoplastic synthetic resin powder, and its purpose is to mold a synthetic resin molded product by inserting a metal fitting into the outlet pipe portion of a container. An object of the present invention is to provide a manufacturing method using a powder rotary molding method.

Thermoplastic synthetic resin powder is placed in a desired mold, heated from the outside while rotating the mold to form a molten or semi-molten layer of synthetic resin within the mold, and then cooled to obtain a molded product. Containers such as tanks and containers formed by the powder molding method usually have outlet pipes and valve plugs attached to their lower portions for discharging the stored liquid.

Conventionally, the method of attaching an outlet pipe and valve plugs to this liquid discharge part has been carried out, for example, in the first step when molding the container body.
As shown in the figure, a ready-made synthetic resin or metal nipple 2 is screwed and connected to a molded part that has a thread groove (female thread) on the inside of the outlet pipe equivalent part,
Furthermore, there is a method for connecting valve plugs, or as shown in Fig. 2, the container is formed so as to have a groove 3 on the outer circumference of the part corresponding to the outlet pipe, and a short pipe 4 having a diameter slightly larger than that of the outlet pipe is formed. The split ring 5 is inserted into the groove, and the nipple 6 is screwed into the female thread of the short tube 4.

However, this installation method does not have sufficient strength when using short synthetic resin pipes.
In addition, if a short metal tube is used to provide strength, it must be made of a material that is chemically resistant to the liquid it is filled with.

The inventors of the present invention have conducted intensive studies on the mounting structure of outlet pipes for synthetic resin molded products that have problems in terms of strength or material quality after molding.As a result, they have decided to insert a ready-made metal molded product to form a buried integrally molded outlet pipe. This solves the problem of strength, and since the threaded part and other metal parts do not come into contact with the internal liquid, we discovered the advantage that, for example, commercially available metal nipples can be inserted and molded as they are, leading to the present invention. Ivy.

In other words, in the present invention, when inserting a metal tube into the outlet of a powder molding container, the metal tube is screwed into a threaded part provided in a powder molding mold, and thermoplastic synthetic resin powder is loaded into the mold. heated from the outside of the
This method of inserting a metal tube into an outlet pipe of a container is characterized by embedding the metal tube to form a molten layer or a semi-molten layer of a predetermined thickness, and then cooling and releasing the mold.

The powder molding method used in the present invention can be any known rotary molding method such as the Rot'n Roll method, McNeil method, Rotocast method, Heisler method, or TDM method. As the thermoplastic resin for powder molding, polyethylene Although any thermoplastic resin such as , polypropylene, polycarbonate, polyamide, etc. can be used, it is preferable to use polyethylene in consideration of economical efficiency and moldability.

During molding, an internally threaded part is usually attached to a mold made of a thin sheet of mild steel, and a metal tube such as an externally threaded nipple is screwed onto the inside of the mold, and then powder is charged and rotational molding is performed. It is desirable to provide a slight gap between the metal tube and the tube mold as shown in FIG. 3, so that the metal tube can be reliably buried and the inner surface can be covered with the synthetic resin. Further, when the diameter of the outlet pipe is relatively large, it is preferable that the center line of this metal pipe coincides with the rotation axis of the mold.

An example of an embodiment of the present invention will be described below using the drawings.

FIG. 3 is a partial cross-sectional view showing a method of inserting a commercially available metal nipple into a short pipe for attaching a valve to the outlet pipe of a container. In the figure, 7 is a mold, A is a bolt attached to B of the main body, and C is a threaded part attached to the main body. Screw the iron nipple 8 into the threaded part of A. In this case, if the nipple 8 is not screwed all the way into the threaded part A of the mold, but is stopped at a position where only a few threads remain, the end of the nipple will not be exposed to the outside. Furthermore, if a protrusion filled with a heat insulating material 9 is provided at the end of the mold, the inside of the outlet pipe can be molded more completely.

After installing the nipple, add thermoplastic synthetic resin powder using the usual method and rotate the mold while heating it to form a molten layer or semi-molten layer 10.If the mold is cooled, the molded product with the nipple inserted will be formed. is obtained. After that, turn the mold part to remove it, and then release the mold body. In this way, there is no chance for the inserted metal to come into contact with the liquid in the container, so there is no need to select the type of metal to insert depending on the type of liquid, even if the liquid in the container corrodes the metal. This is advantageous because it is not necessary to use a chemically resistant metal material even if it has a chemical resistance.

Therefore, the metal nipple can be freely selected from commercially available mild steel such as aluminum, gunmetal, and stainless steel. In addition, the strength of the connection part, which is connected to the valve plugs by a short pipe in which the metal tube obtained by the method of the present invention is inserted, can be improved by molding the internal thread with synthetic resin and connecting it to the valve plugs with a nipple.
It goes without saying that this method is far superior to the conventional method in which a short pipe is connected to an outlet pipe having a groove with a split ring.

[Brief explanation of the drawing]

1 and 2 are sectional views showing a conventional connection method, and FIG. 3 is a partial sectional view showing an example of the insert method of the present invention.

Claims (1)

[Claims] 1. When inserting the metal tube into the outlet of the powder molding container, screw the metal tube into the female thread provided in the powder molding mold, load the thermoplastic synthetic resin powder into the mold, and insert the metal tube into the mold. A method for inserting a metal tube, which comprises: heating the metal tube from its outer surface, burying the metal tube to form a molten layer or a semi-molten layer to a predetermined thickness, and then cooling and releasing the mold.