JPS62161520A - Process for molding hollow member - Google Patents

Abstract

PURPOSE:To obtain a molding process of providing leakless pipes and unnecessary of secondary processing as formed integrally at the molding time, by setting up the cavity of the pipe at a position that is in a parting surface and rectangular to the setting direction of a parison, and by supporting under interposing the parison at the base of the cavity of the pipe on the time of mold closing. CONSTITUTION:A parison sags into the space of divided molds 11, 11, and an inserting mold 12 set up on the center line of a parison 22 is retained at a position corresponding to mold retaining portion 14. The divided molds 11, 11 are closed and the end 22' of the parison 22 is abutted against the inserting mold 12, then covers the surface of the divided molds side of the pipe cavity concaved portion 15. When pressurized fluid is flowed into the parison 22 and blow molding is executed, the end 22' of the parison 22 is adhered under swelling out to the pipe cavity concaved portion. After the divided molds 11, 11 are opened and the moldings is released from the molds, flashes 17 are separated from pinch-off portion 16 and the outer end of the pipe is cut off. By this molding process, it is possible to finish the outer and inner surface of the pipe very smooth, and therefore to prevent completely the leakage of a liquid when the pipe is connected.

Description

DETAILED DESCRIPTION OF THE INVENTION Wide range of industrial applications <Regarding a method of manufacturing a plastic tank used for industrial use, in particular, a method of manufacturing a tank partially having a pipe body.

Prior Art A tank that has a pipe body to which a pipe or the like is connected from the outside and allows fluid to enter or exit from the inside is designed to prevent fluid leakage at the connection between the pipe and the pipe body. Various proposals have been made in order to
962, JP-A-60-13521, etc.).

Problems to be Solved by the Invention Japanese Patent Application Laid-Open No. 54-43269 discloses that although the dimensions of the tube body can be precisely finished and the above-mentioned leakage can be prevented, after blow molding, cutting of the tank wall and cutting of the tube body are necessary. The work was complicated because it required a secondary process called welding. Japanese Unexamined Patent Publication 1983-1966
Publication No. 962 not only requires cutting of the tubular body, but also has the disadvantage that the tubular body breaks at the base (root portion) due to cutting resistance during cutting work.

Furthermore, although the dimensions of the pipe body can be precisely finished according to Japanese Patent Application Laid-open No. 60-13521, it has the disadvantage that holes must be drilled and the resulting cut ends up entering the tank, requiring a cleaning process. Was.

Therefore, in view of these various problems, the present invention provides a molding method that provides a pipe body that does not cause the above-mentioned leakage, and also forms these pipes integrally during molding, thereby eliminating the need for secondary processing. The purpose is to

Means for Solving the Problems The present invention has the following technical means for achieving the object. That is, a parison is placed between split molds each having a cavity formed into the shape of a hollow body with a tube on the opposing inner surfaces, and the split molds are tightened to introduce pressure fluid into the inside of the parison to create a hollow body. In the method of blow molding a body, the cavity of the tube is arranged on the parting surface and at a position perpendicular to the arrangement direction of the parison, and the parison is held at the base of the cavity of the tube when the split mold is clamped. This is a characteristic feature.

Operation The molding method of the present invention configured as described above pinches the parison at the base of the cavity of the tube, so there is no pinch-off part on the outside of the tube, so there is no pinch-off on the inner and outer surfaces of the tube. The surface can be finished smooth without causing any recesses or deformation, and the base, which is the joint between the tube and the hollow body, is not thinner than a hollow body, so the strength is increased. It does not break due to external force.

Example Embodiments of the present invention will be described based on the drawings.

FIG. 1 is an overall perspective view of a tank 1 obtained by the present invention. Reference numeral 2 denotes a pipe body that communicates between the inside and outside of the tank 1 and is formed integrally with the tank 1.

3 is an injection port, and 4 is a parting line during blow molding. This parting line 4 is located at the base B of the tube body 2.
It passes through and disappears at the central part A, and there is no concave part inside or outside the tube body 2.

FIG. 2 is an overall perspective view of a mold used for implementing the present invention. In the figure, reference numeral 11 denotes a split mold, and one side thereof has a cavity 13 recessed inward. The cavity 13 includes a body cavity 13a, a mouth cavity 13b, and a tube cavity 13c. 12 is an insertion mold and split mold 1
A tubular body cavity recess 15 corresponding to the tubular body 2 is formed in the surface of the split mold 11. A mold holding portion 14 corresponding to the shape of the outer peripheral surface of the insertion mold 12 is provided on the surface of the split mold 11 on the insertion mold 12 side.

Next, the manufacturing method of the present invention will be explained step by step.

First, the parison 22 is extruded between the split molds 11 and 11.
Push it out more and let it hang down. The diameter of the parison 22 at this time is assumed to be D (see FIG. 3).

Next, the insertion mold 12 is placed on the center line of the parison 22.
is moved straight and held at a position corresponding to the mold holding part 14 (see FIG. 4).

Then, by tightening the split mold 11.11, the end 22' of the parison 22 is brought into contact with the insertion mold 12, and the surface of the tube cavity recess 15 on the split mold side is covered (see FIG. 5, (See Figure 6). At this time, the width W of the parison 22 held between the split molds is generally set from πD W =−(1).

Furthermore, blow molding is performed by blowing pressure fluid into the burr sleeve 22 (see FIG. 7). At this time, the parison end 22' bulges into the concave portion of the tube cavity. Note that 16 in the figure is a pinch-off portion.

Open the split mold 11.11, release the molded product, and remove the burr 1.
7 is separated from the pinch-off portion 16 and the outer end of the tube body 2 is cut off, thereby completing the manufacturing method of the present invention.

According to this molding method, since the tubular body cavity recess 15 is formed in the insertion mold 12, not only no pinch-off part is formed in this part of the tubular body, but also a parting line does not appear. The surface can be finished extremely smooth, completely preventing liquid leakage when connecting pipes. Note that the center line in FIG. 1 is the end point of the parting line 4 on the pipe body. This end point A is
It is necessary that it is located at least outwardly from the base B of the tube body, and it is necessary that it be located inwardly from the part where the pipe is connected.

By the way, the hollow tube of the present invention has a base diameter of D'.
and its length is L, then the ratio of length to diameter (
L/D') is from 2 to 10.

In the above embodiment, the width W of the parison clamping was set according to formula (1) so as to cover the surface of the tube cavity recess 15 of the insertion mold 12 on the split mold side. In addition to this method, even if the diameter is smaller than the diameter obtained by the above formula, by moving the parison on the concave side of the tube cavity before clamping the split mold by means such as vacuum suction. The surface on the split mold side may be covered.

Effects of the Invention With the structure as described above, there will be no recesses or protrusions caused by pinch-off of the parison on the inside and outside of the pipe connecting portion of the tank body obtained according to the present invention, so that the pipe can be connected easily. It is possible to obtain a tank that does not leak liquid from the connection part with the body, and the tube body can be easily manufactured without performing any secondary processing after molding.

[Brief explanation of drawings]

The drawings show one embodiment of the present invention, and FIG. 1 is an overall perspective view of a tank obtained by the manufacturing method of the present invention, FIG. 2 is a perspective view of a mold used for carrying out the present invention, and FIG. 5 is a front view for explaining the manufacturing process, FIG. 6 is a partially enlarged sectional view during mold clamping, and FIG. 7 is a partially enlarged sectional view during blowing. 1...Tank 2...Pipe body 11.11...Divided mold 12...Insertion mold 1
3... Cavity 14... Mold holding part 15...
・Pipe body cavity recess

Claims (1)

[Claims] A parison is placed between split molds having a cavity shaped into the shape of a hollow body having a tubular body on the opposing inner surfaces, and the split molds are tightened to introduce pressure fluid into the parison to form the hollow body. The blow molding method is characterized by arranging the cavity of the tube at a position perpendicular to the direction of arrangement of the parison on the parting surface, and holding the parison at the base of the cavity of the tube when the split mold is clamped. A method for forming a hollow body.