JPH04101828A - Chamfering method for end of plastic pipe - Google Patents

Abstract

PURPOSE:To make the chamfered surface of plastic pipe-end into smooth low friction-surface by a method in which the end of a heated plastic pipe is covered with the outer mold whose inner diameter is equal to the outer diameter of the pipe-end, and then the diameter-expanding part of a diameter-expanding inner mold is inserted into said pipe-end, and the diameter of the inner mold is expanded. CONSTITUTION:The end P of the plastic pipe softened under heating is covered with the molding part 31 of an outer mold 3 and the intermediate part of the chamber-molding face 30 of the inner end of said molding part 31 is positioned at the end (e) of the pipe. The outer peripheral side of the pipe-end (e) is pushed by the chamber-molding face 30, and the inner peripheral side of the pipe-end (e) deforms inside more than the inner diameter of the pipe-end. Next when the segment 190 of a diameter-expanding inner mold 4 is inserted into the end-part P of the pipe, and the pipe is expanded, the part which deforms inside more than the inner diameter of the plastic pipe-end P at the pipe-end (e) may be compressed. The tapered surface may be molded at the peripheral side of the pipe-end (e) by the chamber- molding face 30 of the outer mold 3. Then the segment 190 has the chamber-molding face 30 between he small diameter part 192 and the large diameter part 193, and the outer diameter of the large diameter part 193 becomes equal to the outer diameter of the pipe-end, and the outer diameter of the small diameter-part 192 becomes equal to the inner diameter of the pipe-end at maximum diameter-expansion.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a method for chamfering the outer or inner circumferential side of the end of a plastic pipe.

(Prior art) Pipes are often used by being inserted into each other, and in this case, one pipe end is chamfered on the outer circumference, and the other pipe end is chamfered on the inner circumference. There is.

In the case of plastic pipes, chamfering of the pipe has traditionally been done by cutting, but due to the viscoelastic properties of plastic, the cut surface often ends up with a rough, chipped-off surface, especially when the depth of cut is This roughening is noticeable when the cutting depth is increased and the cutting speed is increased. Also,
Due to the viscoelasticity and properties of plastic, chips tend to become discontinuous chips, and the generation of so-called chips is noticeable.

Therefore, by the chamfering process described above, the center alignment of the pipes to be joined can be performed with a margin (if the chamfer thickness is Δt, the positional deviation of the center of the pipe can be tolerated within the limit of Δt), and the center alignment of both pipes can be performed with a margin. Matching becomes easier.

(Problem to be solved) However, as mentioned above, if the surface roughness of the chamfered surface is poor, the chamfered surface will exhibit high frictional resistance when inserting one pipe end into the other pipe end, and the pipe The advantage of smooth insertion is the chamfering process: the precision is lost. Further, the generation of chips has a negative impact on the working environment, and furthermore, since they tend to adhere to the inner surface of the pipe, depending on the use of the pipe, this may become a restriction on the use of the pipe.

Heat forming, which takes advantage of the thermoplasticity and viscoelasticity of the plastic, is widely used to form the ends of plastic pipes. In other words, thermoplastic plastics soften when heated and become elastic, so they can be easily shaped, and when they are cooled, the shaped shape can be fixed. widely used. The molded surface obtained by such heat processing has a gloss similar to the skin of a plastic pipe and is smooth.

Conventionally, heat forming has not been applied solely for the purpose of chamfering the ends of plastic pipes, but it is known to chamfer the ends of plastic pipes by heat forming for other purposes. For example, in a plastic pipe that has many channels that communicate in the axial direction on the pipe wall, even if damage occurs that reaches the channels from the outside of the pipe wall, groundwater is prevented from flowing into the pipe from the damaged area through the channels. In order to do this, the end of the plastic pipe on the insertion side is heated, a mandrel is inserted into this end, and then a socket-shaped molding tool with a tapered inner surface is rotated and rubbed against the pipe end surface. It is known to crush and close the channel and to make the end of the pipe a tapered surface (Japanese Patent Publication No. 57-4411
Publication No. 1).

However, this heat forming method assumes that a channel exists in the pipe wall, and it is impossible to crush the end of a plastic pipe with a solid wall using the socket-shaped forming tool described above. , escape of heat-softened plastic from the socket-shaped former is unavoidable. Of course, if the mandrel is omitted, such escape of plastic will not occur, but the end of the plastic pipe will shrink and act as a fluid resistance after piping, and in the case of sewer pipes, clogging of the sewer due to stagnation of filth etc. is inevitable. .

Conventionally, as a method of heat-forming a socket at the end of a plastic pipe, a molding gap in the shape of a socket was provided, and in that gap,
It is known to press in heat-softened plastic ends. However, with this method, the end of the plastic pipe that is heated and softened is likely to buckle, and in order to prevent this buckling, it is necessary to make the mold MIta more complicated and increase the cost. Therefore, it is uneconomical to use such a high-cost mold.

An object of the present invention is to provide a method for easily heat-molding the chamfered surface of the end of a plastic pipe using a normal mold in order to make the chamfered surface a smooth, low-friction surface.

(Means for Solving the Problems) The method for chamfering the end of a plastic pipe according to the present invention includes:
The heated plastic pipe end is covered with an outer mold whose inner diameter is equal to the outer diameter of the pipe end, and then the enlarged diameter part of the expandable inner mold is inserted into the pipe end, and after facing, By expanding the diameter of the inner mold, a product is created in which the outer or inner peripheral side of the pipe end is chamfered on the chamfered molding surface of the outer mold side or the inner mold side. It is.

(Explanation of Examples) Hereinafter, the present invention will be explained in detail with reference to the drawings.

FIG. 1 is a partially cutaway front view showing an example of a diameter-expanding inner mold used in the present invention, and FIG. 2 is a sectional view taken along line nn in FIG. 1.

In FIG. 1 and FIG. 2, 10 is a frame,
It has a front plate 1-11 and a rear plate 12. 13 is a core frame, and the rear plate 12 of the frame 10
I support it. 14 is a ladder attached to the front end of the core frame 12. 15 is a core, which is inserted into the core frame 13 (U) so as to be movable; 16 is a core receiver;
0, and a core 15 is slidably supported by this core receiver 16. 17 is a piston cylinder for sliding the core 15, and a stay 18
It is connected to the core 15 via.

19,..., 19'... are two types of segments, each having leg portions 191, 191'.
It is inserted into 1'. Therefore, the piston cylinder 17
Therefore, if the core 15 is moved forward, the segment 19
．． ..., 19'... expands in diameter.

The inclination gradient of the groove 151 with respect to the leg 191 of the segment 19 is made different from the inclination gradient of the groove 151' with respect to the leg 191' of the segment 19', so that when the tip of the core 15 contacts the header 14, the entire segment 19. ...
, 19'... coincide with each other, and the diameter expansion is completed. 2
0 is all segments 19. ..., 19'..., and all segments 1, 19', . ..., 1
9'... is reduced in diameter to its original state.

FIGS. 3A to 3C show an embodiment in which the outer peripheral side of the end of a plastic pipe is chamfered (external chamfering).

3A to 3C, 3 is an outer mold, and a molding part 31 having an inner diameter equal to the outer diameter of the end of the plastic pipe.
and an inner mold insertion hole 32, and the rear end of the molding part 31 is formed into a chamfered molding surface 30. Reference numeral 4 denotes a diameter-expanding inner mold, which allows the diameter of the segment 190 to be expanded to the inner diameter dimension of the end of the plastic pipe. In order to allow this enlarged diameter segment 190 to be brought into close contact with the inner mold insertion hole 32 of the outer mold 3, the inner diameter of the inner mold insertion hole 32 is made equal to the inner diameter of the end of the plastic pipe.

According to this embodiment, in order to chamfer the outer peripheral side of the end of a plastic pipe, first, the end of the plastic pipe is heated and softened, and as shown in FIG. 31, and the middle of the chamfered molding surface 30 at the rear end of the molding part 31 is positioned at the pipe end e. As a result, the outer circumferential side of the pipe end e is pressed against the chamfered forming surface 30, and the inner circumferential side of the pipe end C enters inside the inner diameter of the pipe end.

In this case, the axial force acting on the pipe can be made sufficiently small because the pipe end e is not fixed but slides, and buckling of the plastic pipe end in a heated softened state can be avoided.

After covering the plastic pipe end P with the outer mold 3 in this way, as shown in FIG. 3B, insert the 190 into the segment I of the inner mold 4 into the plastic pipe end P
Then, as shown in FIG. 3C, the segment 190 of the inner mold 4 is expanded to the inner diameter of the plastic pipe end P. By this diameter expansion, it is possible to compress the portion of the pipe end e mentioned above that is inside the inner diameter of the plastic pipe end P, and the chamfered molding surface 30 of the outer mold 3 forms a tapered surface on the outer peripheral side of the pipe end e. Can be molded. After finishing, wait for cooling and solidification of the plastic pipe end P.
The mold is removed, and the chamfering process (external chamfering) on the outer peripheral side of the end of the plastic pipe is completed.

FIGS. 4A to 4C show an embodiment in which the inner peripheral side of the end of a plastic pipe is chamfered.

A chamfered molding surface 30 is provided between the small diameter portion 192 and the large diameter portion 193.
At maximum diameter expansion, the outer diameter of the large diameter portion 193 becomes equal to the outer diameter of the pipe end, and the outer diameter of the small diameter portion 192 becomes equal to the inner diameter of the pipe end.

According to this embodiment, in order to chamfer the inner peripheral side of the plastic pipe end, heat the plastic pipe end P.
After softening, as shown in FIG. 4A, an outer mold 3 having an inner diameter equal to the outer diameter of the plastic pipe end P is placed over the plastic pipe end P. Then, as shown in FIG. 4B, a segment 190 of the inner mold 3 is inserted into this pipe end P.
and insert the chamfered molding surface 30 of the segment 190.
The plastic pipe end e is positioned in the middle of the segment 190, and then the diameter of the segment 190 is expanded as shown in FIG. 4C. By this diameter expansion, the plastic pipe end e is shaped into the shape of the chamfered molding surface 30 of the segment 190, and after cooling and assimilation of the plastic pipe end P, the mold is removed. Finish chamfering the inner circumferential side (inner chamfering).

(Effects of the Invention) The method for chamfering the end of a plastic pipe according to the present invention has the configuration described above, and since the chamfer is formed by thermoplastic deformation of the end of the plastic pipe, unlike the conventional cutting process, the chamfered surface is It can be formed into a smooth, low-friction surface, allowing smooth insertion when joining pipes, and does not generate chips, which is advantageous in terms of the working environment. Moreover, since the axial force applied to the plastic pipe can be kept to a small force that is enough to insert an outer mold with an inner diameter equal to the pipe outer diameter into the pipe end, buckling of the heated and softened plastic pipe end can occur. Since pressurization is performed by expanding the diameter of the pipe end from the inner surface using an inner mold, it is possible to avoid shrinkage of the pipe end, and there is no fear of sewage clogging after piping.

[Brief explanation of the drawing]

Fig. 1 is a partially cutaway front view showing an example of the diameter-expanding inner mold used in the present invention, and Fig. 2 is a - - in Fig. 1.
■Cross-sectional views, Figures 3A, 3B, and 3C show one embodiment of the present invention, and Figure 3A shows the state immediately after the outer mold is placed over the end of the plastic pipe. FIG. 3B shows the state immediately after the expanded diameter part of the inner mold is inserted into the end of the plastic pipe, and FIG. 3C shows the state immediately after the diameter of the inner mold is expanded. 4A, 4B, and 4C show another embodiment of the present invention, and FIG. 4A shows the state immediately after the outer mold is placed over the end of the plastic pipe. B shows the state immediately after the expanded diameter part of the inner mold is inserted into the end of the plastic pipe, and FIG. 4C shows the state immediately after the diameter of the inner mold is expanded. 1P... End of plastic pipe, 3... Outer mold, 4... Inner mold, 19... Segment of inner mold, 30... Chamfered molding surface. Patent applicant Sekisui Chemical Co., Ltd. Representative Hiroshi 1) Kaoru Figure 3A Figure 3B Figure 2Figure 3C

Claims (1)

[Claims] The heated plastic pipe end is covered with an outer mold whose inside diameter is equal to the outside diameter of the pipe end, and then the expanded diameter part of the expandable inner mold is inserted into the pipe end, and then, Chamfering of the end of a plastic pipe, characterized in that by expanding the diameter of the inner mold, the outer or inner peripheral side of the pipe end is chamfered on the chamfered surface of the outer mold side or the inner mold side. Method.