JPH02266908A - Molding process of cylindrical resin product and male mold for molding the same product - Google Patents

Abstract

PURPOSE:To enable the axes of parts to coincide each other correctly by a method in which the mold energized in centrifugal direction so that the shape and dimension of the inner peripheral surface of a cylindrical molded object is kept onto a male mold desirably and uniformly in each part, is used, and then the cylindrical body with the true circular shape in section is integrally molded on the inner peripheral surface of the molded object. CONSTITUTION:The mold for molding a cylindrical resin product, i.e., a movable male mold 100 is inserted into a stationary female mold 200. The axis of the inserted movable male mold 100 coincides perfectly with the axis of the stationary female mold 200. Resin is injected into the gap with desired width formed between both molds from the injecting port 202 of the stationary female mold 200. This state is kept until the injected resin is cured. Thus, until the resin is cured, since the movable male mold 100 is in operative condition, a sliding bearing 12 is firmly supported by a collet ring 50 from its inside, and there is no clearance between the sliding bearing 12 and the collet ring 50. Accordingly, even if the resin shrinks in resin-curing, the sliding bearing 12 does not deform and the concentric degree between the sliding bearing 12 and the cylindrical part of a rear cylinder 300 is not shifted.

Description

Detailed Description of the Invention (Field of Industrial Application) The present invention relates to a method for molding a cylindrical resin product and a male mold for molding the resin product, and particularly relates to a cylindrical mold that requires roundness accuracy. The present invention relates to a new molding method and a male mold for molding resin products.

(Prior Art) An electromagnetic reciprocating compressor used as an air compression pump or the like includes a cylinder as described in, for example, Japanese Utility Model Application Publication No. 57-103385.

FIG. 13 is a longitudinal sectional view of this electromagnetic reciprocating compressor, in which the piston body 1 has a front piston 1A in front of it,
It also has a rear piston IB behind it. Further, an armature 4 is arranged between each of the pistons IA and IB. The piston body 1 includes each piston IA.
and IB are arranged on the same axis so as to slide within the front cylinder 2 and rear cylinder 11, respectively.

In this type of electromagnetic reciprocating compressor, the rear cylinder 1
1 is molded by aluminum die-casting, and a metal sliding bearing 12 is arranged on its sliding surface.

A ball 13 is disposed at the bottom of the rear cylinder 11, and a washer 14 is disposed between the ball 13 and the rear piston 18.
A coil spring 5 is disposed through the coil spring 5. coil spring 5
By interposing the ball 13 and the washer 14 between the coil spring 5 and the rear cylinder 11, the coil spring 5 and the rear piston I
B and the rear cylinder 11 can be made concentric with each other.

A fixed iron core 6 around which an induction coil 7 is wound is disposed outside the piston body 1. By applying half-wave alternating current, pulse current, etc. to this induction coil 7, the armature 4 is attracted toward the fixed iron core 6 against the elastic force of the coil spring 5, and the piston body 1
vibrates.

Due to this vibration, through the suction hole IC and suction valve ID,
Air is drawn into the compression chamber IB and is discharged to the outside through a discharge hole, a discharge valve, and a discharge port 10 (not shown).

In addition, in FIG. 13, reference numeral 11A is a collar formed on the rear cylinder 11 for attaching the rear cylinder 11, reference numeral 15 is a male screw for fixing the rear cylinder 11 to the casing 8, and reference numeral 9 is a fixing collar. Iron core 6 and casing 8
This is a rear side cover that is held between the

One possible method for reducing the manufacturing cost of such an electromagnetic reciprocating compressor is to mold the rear cylinder 11, which has conventionally been molded by aluminum die-casting, from resin.

Here, as mentioned above, the sliding bearing 12 is fixedly arranged inside the rear cylinder 11, but the piston body 1
The cylinders 2 and 1 repeat reciprocating motion while rotating within the front cylinder 2 and the rear cylinder 11.
11 must maintain a perfect circular cross-sectional shape.

When this cylinder 2.11 is injection molded from resin, for example, as shown in FIG. 14, the movement and separation W:! 21 and a fixed female mold 22, a metal sliding bearing 12 is fixed in advance to the female mold 22 in order to improve roundness precision, while the male mold 21 has a protrusion 2 for inserting the coaxial bearing 12.
A projection 21B is formed to form a hole for inserting the male screw 15 shown in FIG. 1A1 and FIG. Insert into the mold 22 and open the injection port 22 of the female mold.
After injection molding, the molded product is taken out by separating the mold 21 and the mold 22, pushing the extrusion tool 23, and protruding the push bottle 23A toward the protrusion 21A. A resin rear cylinder with an integrated sliding bearing 12 was molded.

(Problems to be Solved by the Invention) In the conventional method of molding a cylindrical resin product as described above, the sliding bearing 12 is inserted into the protrusion 21A, and after resin molding, the molded product is taken out from the mold 21. for,
The outer diameter of the protrusion 21A is set slightly smaller than the inner diameter of the slide bearing 12, and the protrusion 21A and the slide bearing 1
It has been attempted to provide a clearance between the two.

However, when the molded resin shrinks during resin curing,
Due to this clearance, non-uniform stress acts on the outer circumferential surface of the slide bearing 12, causing a situation where the inner surface of the slide bearing 12 is deformed and the roundness is reduced. , the center lines of the molded rear cylinder and the sliding bearing 12 no longer match. That is, a gap occurred where the rear cylinder and the sliding bearing 12 could no longer be concentrically aligned.

In the electromagnetic reciprocating compressor shown in FIG.
The piston body 1 vibrates with the front piston IA and the rear piston IB formed at the front and rear parts serving as sliding parts, so unless the inner surface of the slide bearing 12 is machined with high precision, the piston body It is not possible to obtain enough cylinder 2.11 to expect smooth reciprocating motion of 1.

Therefore, in the conventional molding method, the inner surface of the slide bearing 12 must be reprocessed after the rear cylinder is molded, which is troublesome.

Furthermore, for example, if the slide bearing 12 is made of die-cast aluminum, its surface must be insulated (for example, alumite treated), which makes manufacturing the slide bearing 12 even more troublesome.

The present invention has been made in order to solve the above-mentioned problems, and its purpose is to injection mold a cylindrical product using resin that requires high precision on the inner peripheral surface of the cylindrical body ( For example, a method for molding a cylindrical resin product that does not deform the slide bearing 12), that allows for easy alignment processing, and that allows the axes of mutually fitting parts to align accurately, and for the molding of the resin product. The purpose of the present invention is to provide a male mold for molding.

(Means and effects for solving the problems) In order to solve the above-mentioned problems, the present invention provides a cylindrical male mold that is attached to a cylindrical female mold for injection molding. In a resin product molding method in which a cylindrical product is molded with resin filled in between, the male mold is biased in a centrifugal direction so as to maintain the inner peripheral surface shape and dimensions of the cylindrical product uniformly as desired at each part. A cylindrical body having a perfect circular cross section is integrally formed on the inner circumferential surface of the molded product by pressing the mold uniformly from the inner circumferential side of the cylindrical molded product. It is characterized by the fact that it is made to do so. As a result, a small gap between the cylindrical body and the male mold supporting the cylindrical body can be removed during curing of the resin.

The present invention also provides a member for supporting the cylindrical body, in which at least a portion of the inner circumferential surface corresponding to the length of the cylindrical product is formed as a gently tapered surface, and a plurality of A collet ring in which split grooves alternately extend in the axial direction from both ends of the collet ring is used, and a collet shaft is arranged inside the collet ring and has at least a part of its outer diameter tapered. Another feature is that the male mold for molding the cylindrical resin product is configured so that the inner surface of the collet ring can be suppressed by sliding in the center direction. By pressing the inner surface of the collet ring, the outer surface dimension of the collet ring increases, and the cylindrical body can be uniformly pressed from the inner surface.

Another feature is that a magnet is attached to the tip of the core head inserted into the axial center of the collet shaft, which attracts the ball placed on the bottom of the cylindrical product. By attracting the ball to the magnet, the ball can be easily supported.

(Example) The present invention will be described in detail below with reference to the drawings.

FIG. 1 is a longitudinal sectional side view showing a first embodiment of a mold for molding cylindrical resin products according to the present invention, that is, a movable male mold 100;
FIG. 2 is a longitudinal sectional side view showing the configuration of a female mold, that is, a fixed shaft mold 200, which is paired with the mold shown in FIG. m1.

The pair of movable male molds 100 and fixed female mold 200 shown in FIG. 1.2 correspond to the pair of molds shown in FIG. I will explain about it.

Among the parts constituting the movable male mold 100, the core 30
．． Perspective views of the collet shaft 40 and the collet ring 5G are shown in FIGS. 3 to 5. The core 30 shown in FIG. 3 includes a core shaft 32, a core head 31 formed at one end of the core shaft 32, and the core shaft 3
2 and a male screw 33 formed at the other end of the screw.

The outer diameter of the core helad 31 is set to a size that allows the sliding bearing 12 to be inserted therein.

Further, a ball holding member 34 is embedded in the tip of the core head 31. This ball holding member 34 is a magnet, and a spherical recess 34A is formed on the ball 13 so that it can hold the cylindrical product to be molded, that is, the ball (ball 13 in FIG. 13) fixedly arranged at the bottom of the rear cylinder. It is formed slightly shallower than the radius dimension.

The collet shaft 40 shown in FIG.
It is a cylindrical body having a cylindrical hole 44 for inserting the core shaft 32 of 0, and its outer periphery consists of a tapered part 41 with a gentle slope (a conical part with a steep angle) and a straight part with an outer diameter of the same size between each part. 42 (cylindrical part). The tapered portion 41 is formed such that its outer diameter gradually increases toward the end of the collet shaft 40.

Furthermore, a male thread 43 is formed at the end of the straight portion 42 .

In addition, in the figure, the symbol S1 indicates the length of the tapered portion 41.

The collet ring 50 shown in FIG. 5 has a cylindrical outer circumferential surface with the same diameter at each part, and a tapered portion 53 on the inner circumferential surface where the inner diameter at one end is slightly smaller than the inner diameter at the other end. It is a shape body. The gradient of the tapered portion 53 is set to be the same as the gradient of the tapered portion 41 of the collet shaft 40.

Further, as shown in the figure, grooves 51 and 52 are alternately formed in the collet ring 50 from both ends thereof. At the ends of these grooves 51 and 52,
Circular crack preventers 51A and 52A are formed to alleviate stress concentration occurring at the ends.

Again, in FIG. 1, the core 30 is inserted into the collet shaft 40 from the tapered portion 41 side of the collet shaft 40.
This collet shaft 40 is inserted into the collet ring 50 from its straight portion 42 side. This insertion is performed so that the inclination directions of the tapered portion 41 and the tapered portion 53 of the collet ring 50 are aligned.

The straight part 42 of the collet shaft 40 is attached to the base 60.
A hole 62 having a diameter larger than the external dimensions of the hole 62 is formed, and a protrusion 61 is planted on one surface of the hole 62 . The length of the protrusion 61 is set to be the same as the depth of the recess 201B, which will be described later with reference to FIG.

Furthermore, a positioning plate 90 is fixed to the other surface of the base 60.

A positioning hole 91 is formed in the positioning plate 90 and has an inner diameter that is approximately the same as the outer diameter of the straight portion 42 .

Next, the straight portion 42 of the collet shaft 40
The side of the positioning plate 9 is inserted into the hole 62 formed in the base 60.
Insert from the side where 0 is not fixed. As a result, the straight portion 42 is inserted into the positioning hole 91, and the collet shaft 40 is positioned with respect to the base 60.

After that, disc springs 81 and 8 are placed between the positioning plate 90 and the positioning plate 90.
2, and the male thread 43 of the collet shaft 40,
It is screwed into a female thread 72 formed on the extrusion tool 70. At this time, the pusher bottle 71 set on the pusher 70 is inserted into the six 63 formed on the base 60.

Finally, the nut 80 is screwed onto the male thread 33 of the core 30.

In the state shown in FIG. 1, the pushing tool 70 is pressed in the direction of the nut 80 by the elastic force of the disc springs 81 and 82, and is in contact with the nut 80. As a result,
The push pin 71 is in the retracted state within the base 60 or the base 6
Also, the taper part 41 of the collet shaft 40 moves in the direction of the extruder 70 between the collet ring 50 and the core 30, and the taper part 41 is flush with the inner surface of the collet ring 50. The outer diameter of the collet ring 50 is increased by uniformly suppressing the taper portion 53 (in the direction of the arrow).

In the following description, this state will be referred to as an operating state.

Note that between this operating state and the initial state described later, the collet shaft 40 and each component are adjusted so that the boundary between the tapered part 41 and the straight part 42 is located within the hole 62 of the base 60. Dimensions are set.

In addition, in this operating state, the pushing tool 70 is pressed in the direction of the nut 80 and is in contact with the nut 80, so by changing the screwing position of the nut 80, the position of the pushing tool 70 and the collet shaft 40 can be changed. can be adjusted, and the retracted position of the push pin 71 and the outer diameter of the collet ring 50 in the operating state can be adjusted.

Now, the movable male mold 100 configured in this way is
As shown in the figure, by pushing the pushing tool 70 in the direction of the arrow, the push bottle 71 projects from the base 60. Also, at this time, the collet shaft 40 slides between the core 30 and the collet ring 50, and the pressing force exerted by the tapered part 41 on the tapered part 53 on the inner surface of the collet ring 50 decreases, causing the collet ring 50 to increase its elasticity. This results in a small diameter state.

In the following description, this state will be referred to as an initial state.

In this initial state, the outer diameter of the collet ring 50 is approximately the same as or smaller than the outer diameter of the core head 31, and in the operating state,
The dimensions of each part of the movable male mold 100 are set so that the outer diameter of the collet ring 50 is approximately the same as or larger than the inner diameter of the slide bearing 12.

Next, the fixed female mold 200 will be explained.

As shown in FIG. 2, the fixed female mold 200 has a recess 201A having the outer shape of a cylindrical portion of the rear cylinder to be injection molded, and a recess 201B having a shape corresponding to the outer shape of the flange of the rear cylinder. It is equipped with The recess 20
A resin injection port 202 is formed at the bottom of 1A.

Movable male mold 100 and fixed female mold 2 having the above configurations
Next, a method of injection molding a rear cylinder using 00 will be explained.

Figures 7 to 10 are diagrams for explaining this resin product molding method step by step.
The same or equivalent parts as in FIGS. 1 to 6 are indicated using the same reference numerals.

First, as shown in FIG. 7, the extruder 70 is pushed in the direction of the arrow to bring the movable male mold 100 into an initial state. Then, when the outer diameter of the collet ring 50 is reduced, the slide bearing 12 whose at least the inner surface is precisely molded is attached to the collet ring 50 (in the direction of arrow B). Furthermore, a metal reinforcing ring 301 is attached to the protrusion 61 erected on the base 60. Said reinforcement ring 30
Reference numeral 1 is for reinforcing a screw hole (a hole into which a male screw 15 shown in FIG. 13 is inserted) formed in the collar of the rear cylinder to be molded.

Furthermore, the ball 13 is brought into contact with the recess 34A and is attracted to the ball holding member 34.

Next, as shown in FIG. 8, the pressing by the pushing tool 70 is stopped, and the pushing tool 70 is restored in the direction of arrow B by the elastic force of the disk springs 81 and 82. That is, the movable male mold 100 is brought into operation, and the outer diameter of the collet ring 50 is increased.

As a result, the slide bearing 12 is held more firmly from its inner surface by the pressure of the collet ring 50, and there is no clearance between the slide bearing 12 and the collet ring 50.

In this state, the movable male mold 100 is moved in the direction of arrow A, and the movable male mold 100 is inserted into the fixed female mold 200.

The axis of the inserted movable male mold 100 is connected to the fixed female mold 20.
Completely aligned with the axis center line of 0, both molds 100.200
A gap of a required width is formed between them, and resin is injected into this gap from the injection port 202 of the fixed female mold 200, as shown by arrow C in FIG. This state is maintained until the injected resin hardens.

After the resin hardens, as shown in FIG. 10, the movable male mold 100 is moved back in the direction of arrow B, and the rear cylinder 300 formed by injection molding is moved together with the movable male mold 100 into the fixed female mold 200. After that, use the extrusion tool 7
0 in the direction of arrow A in the same figure, the molded rear cylinder 300 is removed from the movable male mold 100, and the movable male mold 100 is brought to an initial state. In this case, the molded rear cylinder 300 is removed by reducing the outer diameter of the collet ring 50 and by pushing out the push pin 71. FIG. 11 shows the molded rear cylinder 30.
FIG.

Since the movable male mold 100 is in operation until the resin is injected and hardened in this way, the slide bearing 12 is firmly supported from the inside by the collet ring 50.
There is no clearance between the slide bearing 12 and the collet ring 50. Therefore, even if the resin contracts during resin curing, the slide bearing 12 will not be deformed or the concentricity between the slide bearing 12 and the cylindrical portion of the rear cylinder 300 will not shift.

Furthermore, when mounting the sliding bearing 12 on the movable male mold 100 and taking out the rear cylinder 300 after hardening, the outer diameter of the collet ring 50Ω that holds the sliding bearing 12 is small, so the mounting and Easy to take out.

Furthermore, in this embodiment, the collet shaft 40
and fixing the push pin 71 to the same extrusion tool 70, changing the outer dimensions of the collet ring 50, and pushing the push pin 7
Since the two extrusion operations are performed simultaneously, the molded rear cylinder 300 can be easily taken out from the movable male mold 100.

FIG. 12 is a longitudinal sectional side view showing the structure of a second embodiment of the male mold for molding cylindrical resin products according to the present invention, and shows the operating state similarly to FIG. 1. In Figure 12, the first
The same reference numerals as in the figures indicate the same or equivalent parts.

In FIG. 12, a tapered portion 441 formed on the collet shaft 440 is formed in a region indicated by the symbol S2.

Further, the hole 462 formed in the base 460 has an inner diameter that corresponds to the straight part 442 of the collet shaft 440.
It is formed to have approximately the same diameter as the outer diameter of.

Further, the tapered portion 453 on the inner surface of the collet ring 450 is formed only in the region indicated by the symbol S3. The tapered portion 4 on the inner surface of this collet ring 450
A portion 454 other than 53 is formed into a cylindrical shape.

Now, in this embodiment, the collet shaft 440
Since the straight portion 442 of the straight portion 442 is supported by the hole portion 462 of the base 460, which has an inner diameter dimension that is approximately the same as the outer dimension of the straight portion 442, the positioning plate 90 as shown in FIG. 1 is unnecessary. be.

Further, while the movable male mold 400 is in the operating state to the initial state, the boundary between the tapered part 441 and the straight part 442 of the collet shaft 440 is in contact with the collet as shown in FIG. Since the dimensions of each part of the movable male die 400 are set so as to be located opposite the straight part 454 of the ring 450, the extrusion tool 70 is By pushing the collet shaft 440 to slide between the core 30 and the collet ring 450, the outer dimensions of the collet ring 450 can be reduced due to its elasticity.

In addition, in the above explanation, the collet ring 50.4
The outer surface of the collet shaft 40.44 is formed into a cylindrical shape, and the inner surface thereof is formed into a tapered shape.
The taper portions 41 and 441 of 0 are connected to the collet ring 50.
, 450, but the present invention is not particularly limited to this.

That is, in the initial state of the movable male mold 100, 400, the outer circumferential surface of the collet ring 50 is not cylindrical with the same diameter, and the inner circumferential surface of the collet ring 50 is not cylindrical with the same diameter.
It is not necessary to have the same arrangement as the taper part 41° 441 of 0,440, but at least the movable male mold
In the operating state of 0.400, the collet ring 5θ
, 450 should be in the above-mentioned state. At least when the movable male mold 100, 400 is in operation, the inner peripheral surface of the collet rings 50, 450 is aligned with the collet shaft 40.
, 440, and in this case, if the outer peripheral surface of the collet ring 50.450 is cylindrical, the collet ring 50.45G
The slide bearing 12 to be supported can be evenly pressed from inside.

Furthermore, in the above description, the collet shaft 40 or 440 and the pusher bottle 71 are fixed to the same pushing tool 70, and the operation of changing the external dimensions of the collet ring 50 and the operation of pushing out the pusher bottle 71 are performed at the same time. However, the present invention is not particularly limited to this,
It goes without saying that each operation may be performed separately.

Further, disc springs 81 and 82 are arranged between the base 60 or 460 and the pusher 70, and the disc springs 81 and 82
Although it is assumed that the movable male mold 100 or 400 transitions from the initial state to the operating state by the elastic force of It may also be done by.

The present invention has been explained above using the case of molding the rear cylinder of an electromagnetic reciprocating compressor as an example, but it is not limited to the above-mentioned cylinder, but it can also be used for molding a cylindrical body whose inner diameter requires relatively high precision. The present invention is applicable to the molding of any type of parts or products.

(Effects of the Invention) As is clear from the above description, according to the present invention, the following effects are achieved.

(1) II In the resin product molding method described in claim 1, even if the resin contracts when it hardens, there is no gap between the cylindrical body and the male mold that supports the inner peripheral surface of the molded product. Therefore, the molded product is firmly supported by the male mold, and there is no room for deformation of the inner circumferential surface of the molded product, which requires high-precision molding. Therefore, even when a molded product is integrally molded with a cylindrical body, the concentricity between the cylindrical body and the resin product will not be disturbed at all, so there is no need to reprocess the cylindrical body after molding. It becomes easier to manufacture resin products with high processing precision.

(2) In all the molds for molding oil products described in Gyuhi 2, during injection molding of a cylindrical resin product, the outer diameter of the collet ring that supports the inner peripheral surface side of the cylindrical body is the inner diameter of the cylindrical body. Since each part can be kept uniform at all times according to the dimensions, the male mold can be made to follow the surrounding temperature changes during the cooling process after injection molding, and the cylindrical body can be deformed or There is no misalignment of the axes of the shaped body and the cylindrical resin product = (3) In the mold for molding a resin product according to claim 3,
Since the ball can be easily fixed during molding, it becomes easier to manufacture a cylindrical resin product in which the ball needs to be fixedly arranged.

[Brief explanation of drawings]

Figure 1 shows a male mold for molding a cylindrical resin product according to the present invention (
FIG. 2 is a vertical cross-sectional side view showing the configuration of an example of a movable male mold. FIG. 2 is a longitudinal sectional side view showing the structure of a fixed female mold that is paired with the mold shown in FIG. 111. Figure j13 is a perspective view of the core. 114'E is a perspective view of the collet shaft. FIG. 15 is a perspective view of the collet ring. FIG. 6 is a longitudinal sectional side view showing a state in which the extrusion tool of the movable male mold shown in FIG. 1 is advanced. Figures WJ7 to 1110 are longitudinal sectional side views illustrating the method for molding a cylindrical resin product according to the present invention in the order of steps. FIG. ffllll is a longitudinal sectional side view showing a rear cylinder of a reciprocating compressor molded by the method of molding a cylindrical resin product of the present invention. Figure 12 shows condensation W for molding cylindrical resin products according to the present invention.
1 (movable male mold) is a longitudinal sectional side view showing the configuration of another example. FIG. 13 is a longitudinal sectional side view of an electromagnetic reciprocating compressor equipped with a rear cylinder. FIG. 14 is a schematic diagram for explaining a conventional molding method for injection molding the rear cylinder using resin. 12...Sliding bearing, 13...Ball, 30...
Core, 31... Core head, 32... Core shaft, 34... Ball holding member, 34A... Recessed portion, 40
．． 440...collet shaft, 41.441...
Tapered part, 42.442...Straight part, 44...
・Cylindrical hole, 50.450...collet ring, 51.
52...Split groove, 51A, 52A...Crack prevention, 5
3,453...Tapered part, 60,460...Base,
62,462... Hole portion, 63... Hole, 70... Push tool, 71... Push pin, 80... Nut, 8.
1.82... Belleville spring, 90... Positioning plate, 91.
...Positioning hole, 100,400...Movable male mold, 2
00...Fixed female mold, 3-00...Rear cylinder Attorney Patent attorney Sent by Hiraki and 1 other person Fig. 6 Fig. 12 Fig. 13

Claims (3)

[Claims] (1) A method for molding a resin product, in which a cylindrical male mold is attached to a cylindrical female mold for injection molding, and a cylindrical product is molded with resin filled between the male and female molds, the method comprising: A mold is used that is biased in the centrifugal direction so as to maintain the shape and dimensions of the inner peripheral surface of the cylindrical product uniformly as desired. A method for molding a cylindrical resin product, characterized in that a cylindrical body with a perfect circular cross section is integrally molded on the inner peripheral surface of the molded product by uniformly pressing each part from the peripheral surface side. (2) A male mold for molding a cylindrical resin product, in which a cylindrical part with a cylindrical body whose inner circumferential surface is machined with high precision is injection molded using resin, wherein at least the inner circumferential surface of the mold is formed into a cylinder. The part corresponding to the length dimension of the molded product is formed as a gently tapered surface,
and a collet ring in which a plurality of grooves extend alternately in the axial direction from both ends thereof, and at least a portion of the outer circumferential surface corresponding to the above-mentioned length dimension is formed into a gently inclined taper surface at approximately the same angle in the opposite direction. formed collet shaft;
A male mold for molding a cylindrical resin product, comprising means for pulling the collet shaft in the axial direction of the collet ring. (3) A cylindrical cylinder according to claim 2, characterized in that a magnet is attached to the tip of the core head inserted into the axial center of the collet shaft to attract a ball arranged on the bottom surface of the cylindrical molded product. Male mold for molding shaped resin products.