JPS582049B2 - How plastics can be used - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method of forming an annular groove in the end of a plastic tube.

When connecting plastic pipes, provide an enlarged diameter socket with an annular rubber ring mounting groove at one end of the plastic pipe, and attach a rubber ring to the enlarged diameter socket at the other end of the plastic pipe, that is, the socket. It may be inserted through.

In this case, as shown in FIG. 5A, the diameter of the expanded diameter socket is expanded by press-fitting the heated plastic pipe end 10 with a diameter expanding core 20, and the outer diameter of the expanded diameter socket is Mold 50
is set so that the ring groove 510 of the outer mold 50 is aligned with the segment mold protruding and retracting slit 40 of the core bar 20 for diameter expansion, and then the segment is inserted through the same slit 40 as shown in FIG. 5B. It is known to mold an annular groove by raising the mold 30.

However, the forming method shown in FIGS. 5A1 and 5B has the disadvantage that the wall thickness of the plastic tube in the annular groove is considerably reduced.

In particular, when the annular groove has a vertical wall portion 610 as shown in FIG. 6, the thickness of the vertical tube wall portion 610 is significantly reduced, making it impossible to form the ring-shaped groove shown in FIG.

The method of forming an annular groove in the end of a plastic pipe according to the present invention is a method that can solve the above-mentioned difficulties, and is a method in which a segment mold is placed inside the heated end of the plastic pipe, and the segment mold is inserted into the plastic pipe. The plastic tube is characterized by expanding its diameter by moving in an upwardly inclined direction from the distal end of the tube toward the inner side of the plastic tube.

The present invention will be explained below with reference to the drawings.

In FIG. 1, 1 is the heated plastic tube end;
Reference numeral 2 denotes a core metal that is press-fitted into the plastic tube end 1, and a segment mold 3 is moved onto the core metal 2 in an upwardly inclined direction from the tip side of the plastic tube toward the inner side of the plastic tube. A slit 4 is provided for this purpose.

5 is an outer mold set on the outer periphery of the plastic tube end 1, and the front surface 51 is a vertical surface, and the vertical surface 51 corresponds to the stopper surface 41 of the slit 4 and corresponds to the wall thickness t of the plastic tube 1. are separated by an interval of

The front surface 31 of the segment mold 3 is a vertical surface, and the stopper surface 41 of the slit 4 against which the front surface 31 of the segment mold 3 comes into contact is also a vertical surface.

The segment mold 3 described above has a core metal 2 as shown in FIG.
is guided by the tapered surface 42 of the slit 4 and moved diagonally upward.

This movement of the segment mold 3 causes the tube wall of the plastic tube end 1 to bulge out into an annular groove, and the vertical wall 61 of this bulge 6 is connected to the front surface 31 of the segment mold 3 and the front surface 5 of the outer mold 5.
1.

In FIG. 2, the segment mold 3 before movement is shown by a dotted line, and the plastic pipe portion l between the front upper end M of the segment mold 3 and the front surface 51 of the outer mold 5 is erected. This is the vertical wall portion 61 of the bulge portion 6 .

The dimensions of the plastic tube section l and the vertical wall section 61 can be made approximately equal as shown in FIG.
The tube is molded without being subjected to tensile stress in the axial direction, and the thinning of the tube can be reduced.

In FIG. 2, a dotted line 1 indicates the tip of the plastic tube before groove forming, and this tip 1l slides against the inner cylindrical portion 2' of the core metal 2 as the segment mold 3 moves.

Therefore, the plastic tube tip 1' serves as a sliding fulcrum against the axial tensile stress acting on the portions 62, 63 of the bulging wall 6, and the tensile stress acting on the portions 62, 63 can be made sufficiently small. .

Therefore, thinning of these parts can also be reduced.

FIG. 3 shows an example of a forming tool used in the present invention, in which the core metal 2 has a structure in which a cylindrical slider 2' is fitted into a core body A in which a head 22 is provided at the tip of a core rod 21. The slit described above is formed by moving the slider 2' in the direction A.

As shown in FIG. 4, the segment mold 3 includes molds 3a, 3a, .
3b... After the fan-shaped mold 3a is pushed out of the slit by the push rod 7a, the rectangular mold 3
b passes through the gap between the fan-shaped molds 3a, 3a, .

According to the method of molding an annular groove at the end of a plastic pipe according to the present invention, when molding an annular bulge at the end of a plastic pipe, thinning of the plastic pipe wall can be sufficiently reduced. It is possible to form a mechanically strong groove for attaching a rubber ring in the part.

Furthermore, as shown at 610 in FIG. 6, since a rubber ring mounting groove having a vertical wall can be formed, the rubber ring can be completely prevented from coming off when inserting the socket into the socket.

[Brief explanation of drawings]

1 and 2 are explanatory views showing the present invention, FIG. 3 is an explanatory view showing an example of a molding tool used in the present invention, and FIG. 4 is an explanatory view showing the segment mold in FIG. 3, 5A and 5B are explanatory views showing a conventional example, and FIG. 6 is an explanatory view showing an example of a rubber ring mounting groove formed in a socket of a plastic pipe. In the figure, 1 is a plastic tube end, 3 is a segment mold, and 6 is an annular groove.

Claims (1)

[Claims] 1. A segment mold is disposed within the heated end of the plastic tube, and the diameter of the segment mold is expanded by moving the segment mold upward in an inclined direction from the tip side of the plastic tube toward the back side of the plastic tube. A method of forming an annular groove on the end of a plastic tube.