JP2018001553A - Centrifugal molding die and manufacturing method of hollow cylindrical body - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a centrifugal molding die and a manufacturing method of a hollow cylindrical body, with which, even when burrs are formed in an outer peripheral edge of an end face of the hollow cylindrical body, bonding strength between the burrs and the hollow cylindrical body is strong so that the burrs are taken out from the centrifugal molding die along with the hollow cylindrical body when removing the hollow cylindrical body from the die.SOLUTION: A conical inner lid 42A is provided on an inner face of a seal plate 32 of a centrifugal molding die 10A. An outer peripheral edge 42e of the inner lid 42A is distant from an inner peripheral face of a mold main body 11 by a prescribed distance L. An end face 2a of a molded hollow cylindrical body 2 is configured with a tapered face 2d and an end projected face 2e that is substantially perpendicular to an axial line direction.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a centrifugal mold, and more particularly, to a centrifugal mold having a tubular mold body for forming a hollow cylindrical body and a closing member that is detachably provided at both end openings of the mold body. The present invention also relates to a method for producing a hollow cylindrical body using this centrifugal mold.

  As a method of molding a resin hollow cylindrical body, a raw material resin is injected into a centrifugal mold composed of a tubular mold body and a lid for closing the opening of the mold body, and the mold is centered on the axis. A centrifugal molding method is known in which a raw material resin is cured while being rotated (see, for example, Patent Document 1).

  FIG. 4 shows a centrifugal mold described in Patent Document 1. The centrifugal mold 10 includes a tubular mold body 11 and a pair of lids 12 that cover both end openings of the mold body 11, and the mold is mounted with one lid mounted on the mold body. After injecting the raw material resin into the mold body 11 and attaching the other lid to close the opening at both ends of the mold body, the mold body 11 is rotated at a high speed around the mold axis so that the inner peripheral surface of the mold body 11 A cylindrical molded product is obtained.

  In this embodiment, the lock device 21 for fixing the lid 12 to the mold body 11 includes a lock claw support portion 22 provided at equal intervals on the outer periphery of the lid 12 and a pin 23 on each lock claw support portion. And a locking spring 26 for biasing the locking claw 24 in the locking direction, and a locking portion 26 provided at the front end of the locking claw 24. Are fixed to the outer edges of the flanges 13 provided at both ends of the mold body 11 so that the lid 12 can be fixed in a state of covering the opening of the mold body 11. Further, the rear end portion of the lock claw 24 is in a state of protruding from the outer surface of the lid, and the protruding portion is tilted in the inner circumferential direction of the lid, whereby the locking portion 26 and the flange 13 are locked. That is, the locked state can be released.

  A seal plate 32 that covers the tubular portion opening 31 of the mold body 11 is provided on the inner surface of the lid 12. The seal plate 32 is supported by three guide bolts 33 penetrating the lid 12 so as to be movable in the mold axial direction, and in the direction of the tubular portion opening 31 by a pressure contact spring 34 sheathed on the guide bolt 33. It is energized towards.

  In the state where the lid 12 is attached to the mold body 11 and the locking portion 26 of the lock claw 24 is locked to the flange 13, the pressure contact spring 34 pushes the seal plate 32 to the mold body end surface with a strong force. Press. Thereby, the tubular portion opening 31 is reliably sealed, and at the same time, the locking state between the locking portion 26 and the flange 13 is held together with the lock spring 25.

  A disc-shaped packing 41 for sealing the end face of the tubular portion opening 31 is provided on the inner surface of the seal plate 32, and a disc shape having an outer diameter corresponding to the diameter of the tubular portion opening 31 is provided on the inner surface side of the packing 41. The metal inner lid 42 is provided.

  The packing 41 is provided so as to cover the entire inner surface of the seal plate 32. As this packing 41, a silicon-based packing material 41a having an appropriate cushioning property on the seal plate 32 side and a fluororesin-based packing material 41b having an excellent heat resistance on the mold body 11 side are laminated, thereby providing a sufficient seal. Sufficient heat resistance can be obtained while obtaining properties.

  The metal inner lid 42 has a substantially disc shape that is inserted into the end of the tubular portion of the mold main body 11 and has a conical surface whose center projects in the mold inner direction. The metal inner lid 42 is fixed by a bolt 43 passing through the center of the seal plate 32 so that the packing 41 is sandwiched between the inner surface of the seal plate 32.

  By providing such a metal inner lid 42 on the inner surface of the seal plate 32, most of the raw material resin injected into the mold body 11 comes into contact with the metal inner lid 42. Since the contact with the raw material resin can be minimized, the life of the packing 41 can be extended. Moreover, by making the inner surface of the metal inner lid 42 into a conical surface, the peelability between the molded product and the metal inner lid 42 can be improved. Moreover, it becomes possible to deal with a plurality of types of mold main bodies having different diameters of the tubular portions simply by replacing the metal inner lid 42.

  FIG. 5 shows a state in which the raw material resin R is injected into the centrifugal mold 10 and the centrifugal mold 10 is rotated around its axis to perform centrifugal molding. FIG. The hollow cylinder 1 is shown immediately after being molded and removed from the centrifugal mold 10. FIG.6 (b) is an enlarged view of B part of Fig.6 (a).

  In this centrifugal molding, since the centrifugal force acts on the raw material resin R, the raw material resin R easily enters between the end surface of the mold body 11 and the packing 41 (fluororesin-based packing material 41b). Therefore, the burr | flash 1b which protrudes in a radial direction is easy to be formed from the outer periphery of the end surface 1a of the hollow cylinder 1 obtained by demolding.

  If this burr 1b is removed from the molded product, ie, the hollow cylindrical body 1, the burr 1b does not remain in the centrifugal mold. However, in the centrifugal mold of FIG. 4, the outer peripheral edge of the conical inner lid 42 is positioned in the immediate vicinity of the inner peripheral surface of the mold body 11, so that the end surface 1 a and the outer peripheral surface 1 c of the hollow cylindrical body 1 are formed. The intersecting outer peripheral edges have an acute angle with a cross-sectional shape of less than 90 °. Therefore, in this hollow cylindrical body 1, the root portion of the burr 1b, that is, the connecting portion between the burr 1b and the hollow cylindrical body 1 is thin, and the burr 1b is easily separated from the root. If the burr 1b is cut off from the root at the time of mold removal, the burr 1b may remain in the centrifugal mold 10 and cause a defective product in the next centrifugal molding process.

Japanese Unexamined Patent Publication No. 2004-142109

  In the present invention, even if burrs are formed on the outer peripheral edge of the end surface of the hollow cylinder, the bonding strength between the burrs and the hollow cylinder is high, and when the hollow cylinder is removed, the burrs are centrifugally formed together with the hollow cylinder. It is an object of the present invention to provide a centrifugal mold that is removed from the mold and a method for producing a hollow cylindrical body using the centrifugal mold.

  The centrifugal mold of the present invention is a centrifugal mold having a tubular mold body for centrifugally forming a hollow cylindrical body, and a closing member for closing the opening of the mold body, The inner surface of the closing member facing inward of the mold is provided with a convex portion protruding inward of the centrifugal mold, and the outer peripheral edge of the convex portion is separated from the inner peripheral surface of the mold body by a predetermined distance L. The outer peripheral side of the inner surface of the closing member with respect to the convex portion is a plane substantially perpendicular to the axial direction of the centrifugal mold.

  In one aspect of the present invention, the convex portion has a conical shape or a truncated cone shape whose diameter decreases toward the inside of the centrifugal mold. The inclination angle of the conical convex portion may be different between the outer peripheral side and the central side. The convex portion may be disk-shaped.

  In one aspect of the present invention, the predetermined distance L is not less than 0.5 mm and not more than 50.0 mm.

  The method for producing a hollow cylinder of the present invention includes the steps of injecting a raw material resin into the centrifugal mold of the present invention, forming the hollow cylinder by centrifugal molding, and then removing the mold.

  In one aspect of the method for producing the hollow cylindrical body, the hollow cylindrical body is molded in a state where the raw material resin is in contact with the convex portion of the centrifugal mold and the clearance surface on the outer peripheral side of the convex portion. The raw material resin is poured into the centrifugal mold, and a hollow cylindrical body is formed.

  The hollow cylinder formed by the centrifugal mold and the hollow cylinder manufacturing method of the present invention has a clearance surface that is substantially perpendicular to the axial direction of the hollow cylinder on the outer peripheral side of the end surface. For this reason, the thickness of the root portion of the burr formed on the outer peripheral edge of the end surface of the hollow cylindrical body is larger than that of the conventional (FIG. 6), and the bonding strength between the burr and the main body portion of the hollow cylindrical body is high. .

  As a result, when the hollow cylindrical body is removed from the centrifugal mold, the burr is prevented from being separated from the root, and the burr is integrally removed from the hollow cylindrical body. As a result, burrs are prevented from remaining in the centrifugal mold, and defective products are prevented from occurring in the hollow cylindrical body molded in the subsequent molding cycles.

It is sectional drawing of the centrifugal mold which concerns on embodiment, and has shown the cross section which follows the axial center line direction in the axial center line direction one end side of a centrifugal mold. (A) is sectional drawing of the hollow cylindrical body shape | molded by the centrifugal molding method which concerns on embodiment, and has shown the cross section in alignment with the axial center line direction in the axial center line direction one end side of a hollow cylindrical body. (B) is an enlarged view of a part of (a). (A) is sectional drawing of the centrifugal mold which concerns on another embodiment, and has shown the cross section which follows the axial center line direction in the axial center line direction one end side of a centrifugal mold. (B) is a cross-sectional view of a part of a hollow molded body centrifugally molded using the centrifugal mold of (a). It is sectional drawing of the conventional centrifugal mold. It is sectional drawing which shows the centrifugal molding method using the centrifugal mold of FIG. It is sectional drawing of the molded object which carried out the centrifugal molding using the centrifugal mold of FIG. It is sectional drawing of the centrifugal mold which concerns on another embodiment. It is sectional drawing of the centrifugal mold which concerns on another embodiment. It is sectional drawing of the centrifugal mold which concerns on another embodiment. It is sectional drawing of the centrifugal mold which concerns on another embodiment. It is sectional drawing of the centrifugal mold which concerns on another embodiment. (A) is sectional drawing of the centrifugal mold which concerns on another embodiment. (B) is a cross-sectional view of a part of a hollow molded body centrifugally molded using the centrifugal mold of (a). (A) is sectional drawing of the centrifugal mold which concerns on another embodiment. (B) is a cross-sectional view of a part of a hollow molded body centrifugally molded using the centrifugal mold of (a).

  Hereinafter, embodiments will be described with reference to the drawings. 1 and 2 show a first embodiment. FIG. 1 shows a centrifugal mold 10A, and FIG. 2 shows a hollow cylindrical body 2 that is centrifugally molded using the centrifugal mold 10A. .

  In the centrifugal mold 10A of this embodiment, the lid 12A and the inner lid 42A are integrated. The inner lid 42A has a conical shape with a smaller diameter than the inner lid 42 of the centrifugal mold 10 in FIG. 4, and the outer peripheral edge 42e of the inner lid 42A is separated from the inner peripheral surface of the mold body 11 by a predetermined distance L. Yes. R1 shown in FIG. 1 indicates the shortest distance from the rotation axis to the outer peripheral edge of the inner surface convex portion of the closing member, and r2 indicates the shortest distance from the rotation axis to the inner peripheral edge of the end of the mold body. In other words, the predetermined distance L means a clearance between the outer peripheral edge of the protrusion on the inner surface of the closing member and the inner peripheral edge of the inner peripheral surface end of the mold body in the centrifugal mold, and is r2-r1. On the other hand, the end surface of the hollow cylindrical body obtained using the centrifugal mold of the present invention has a convex shape (hereinafter referred to as “end convex shape”) over the entire circumference. Although the magnitude | size of L is not limited, Preferably it is 0.5 mm or more and 50.0 mm or less, Most preferably, it is 0.8 mm or more, 2.0 mm or less, Furthermore, it is 1.3 mm or less. The other configuration of the centrifugal mold 10A is the same as that of the centrifugal mold 10 of FIG.

  In this embodiment, the lid 12A is a closing member, and the inner lid 42A is a convex portion on the inner surface of the closing member. A packing such as an O-ring may be interposed between the lid 12 </ b> A and the end surface of the mold body 11.

When the hollow cylinder 2 is molded using the centrifugal mold 10A, the amount of the raw material resin injected is such that the end surface 2a of the hollow cylinder 2 that is centrifugally molded along the inner peripheral surface of the mold body 11 is the inner lid. The amount is also in contact with 42A. Thereby, the end surface 2a of the molded body 2 is formed by contacting the tapered surface 2d formed by contacting the inner lid 42A and the packing 41 (fluororesin-based packing material 41b) in the range of L. It is comprised by the edge part convex surface 2e substantially perpendicular to the axial center line direction of the body 2. FIG. The width t ₂ of the end convex surface 2 e in the radial direction of the hollow cylindrical body 2 is a value that matches the distance L. The sum of the width t ₁ in the radial direction of the tapered surface 2 d and the width t ₂ (T = t ₁ + t ₂ ) is the thickness of the hollow cylindrical body 2 in the radial direction. The end convex surface 2e does not necessarily have to be perpendicular to the axis of the molded body 2.

  The inclination angle θ of the tapered surface 2d with respect to the plane perpendicular to the axial center line of the hollow cylindrical body 2 is not limited, but is preferably 90 ° or less, and more preferably 10 to 50 ° in order to improve the releasability. Furthermore, about 15-40 degrees is preferable. In addition, as shown in FIG. 11, it is also preferable to change the inclination angle of the rising portion (outer peripheral side) and the central portion (center side). Further, like the centrifugal mold 10A ′ shown in FIG. 10, the inner lid 42A ′ may be disk-shaped. Other configurations in FIG. 10 are the same as those in FIG. 1, and the same reference numerals indicate the same parts.

The width t ₂ of the end convex surface 2e, that is, the distance L depends on the thickness T of the hollow cylindrical body 2, but is preferably 0.5 mm or more and 50.0 mm or less, particularly 0.8 mm or more and 2.0 mm. Hereinafter, it is more preferably 1.3 mm or less. Incidentally, when t ₂ is small, the thickness of the vicinity of the base of the burr 2b is not sufficiently large. If t ₂ is excessively large, relatively t ₁ decreases, the effect of providing the conical inner lid 42A becomes lower.

  By forming such an end convex surface 2e, the burr 2b formed so as to protrude radially from the outer peripheral edge of the end surface 2a (the intersection angle edge between the end surface 2a and the outer peripheral surface 2c) has a root thickness. Becomes larger than the conventional one (FIG. 6), and the connection strength between the burr 2b and the hollow cylindrical body 2 is increased. As a result, when the hollow cylindrical body 2 is removed, the burr 2b is not separated near the root, and is removed integrally with the main body portion of the hollow cylindrical body 2. This prevents the burr 2b from remaining in the centrifugal mold and prevents the generation of defective products.

  In the above embodiment, the inner lid 42A has a conical shape, and the inner surface of the inner lid 42A (the surface facing the inside of the centrifugal mold 10A) has a conical surface as a whole, but the centrifugal mold 50 shown in FIG. As described above, the inner lid 70 attached to the inner surface side of the seal plate 60 may have a truncated cone shape. That is, the surface of the inner lid 70 facing the inside of the centrifugal mold 50 is a tapered surface 71 in the vicinity of the outer peripheral edge, and the other surface is a plane 72 perpendicular to the axial direction of the centrifugal mold 50. . The outer peripheral edge of the inner lid 70 is separated from the inner peripheral surface of the mold body 51 by a distance L.

  An opening 61 is provided in the central portion of the seal plate 60, and a convex portion 73 protruding from the inner lid 70 is fitted into the opening 61. The inner lid 70 is fixed to the sealing plate 60 by bolts (not shown) that pass through the sealing plate 60 and screwed into the inner lid 70, but the fixing method of the inner lid 70 is not limited to this.

  The packing 80 interposed between the seal plate 60 and the inner lid 70 is formed by laminating a silicon-based packing material 81 that overlaps the seal plate 60 and a fluororesin-based packing material 82 that overlaps the inner lid 70. Yes.

  A flange 53 is provided at the end of the mold body 51 of the centrifugal mold. The seal plate 60 overlaps the end surface of the mold body 51 via the packing 80.

  Although illustration is omitted, a lid for fixing the seal plate 60 to the mold body 51 is provided. As this lid, one having the same configuration as the lid 12 can be used. The sealing plate 60, the inner lid 70, the packing 80, and the lid constitute a closing member.

When the hollow cylindrical body 3 is molded using the centrifugal mold 50, the amount of raw material resin injected is such that the end surface 3a of the hollow cylindrical body 3 that is centrifugally molded along the inner peripheral surface of the mold body 11 is the inner lid. The amount is also in contact with the outer peripheral side of the tapered surface 71 and the flat surface 72. Thereby, the end surface 3 a of the hollow cylindrical body 3 is formed by contacting the flat surface 72, and the tapered surface formed by contacting the vertical surface 3 f perpendicular to the axial direction of the molded body 3 and the tapered surface 37. 3d and a vertical surface 3e perpendicular to the axial direction of the molded body 3 formed by contacting the packing 80 (fluororesin-based packing material 82) in the L range. Preferred range of the radial width t ₃ of the vertical surface 3e is similar to t ₂ of FIG. 2.

  Even in the hollow cylindrical body 3, the thickness in the vicinity of the root of the burr 3b protruding from the outer periphery of the intersection between the end surface 3a and the outer peripheral surface 3c is increased. Thereby, it is prevented that the burr 3b is divided at the time of demolding, and generation of defective products is prevented. FIGS. 12 and 13 (a) show molds 10A ′ and 10A ″ obtained by slightly changing the shape of the mold 10A of this embodiment. FIGS. FIG. 3 is a cross-sectional view of a part of a hollow molded body that is centrifugally molded using the centrifugal molding die.

  In the embodiment of FIG. 3, the inner lid 70 constitutes a convex portion protruding inward of the centrifugal mold 50. The centrifugal mold 50 ′ of FIG. 11 has a rising edge in which the inner lid 70 has a tapered surface 71 and a second tapered surface 72 ′ having a gentler slope than that in the centrifugal mold 50 of FIG. This is a centrifugal mold in which the taper angle between the central part and the central part is changed. 11 is the same as that shown in FIG. 3A, and the same reference numerals denote the same parts.

  FIG. 7 shows a centrifugal mold 10B in which the inner lid 42A has a small diameter in the centrifugal mold 10 of FIG. Other configurations of the centrifugal mold 10B are the same as those in FIG.

  In the case where the hollow cylinder body is formed by the centrifugal mold 10B, the burr 2b is divided in the vicinity of the root when the hollow cylinder body 2 is removed as in the case of forming the hollow cylinder body 2 by the centrifugal mold 10A. And without being integrated with the main body portion of the hollow cylindrical body 2. This prevents the burr 2b from remaining in the centrifugal mold and prevents the generation of defective products.

  In this embodiment, the sealing plate 32, the packing 41, the inner lid 42A, and the lid 12 constitute a closing member. The inner lid 42A is a convex portion that protrudes from the inside of the closing member to the inside of the centrifugal mold 10B.

  In the centrifugal mold 10B of FIG. 7, the lock mechanism shown in FIG. 4 is provided, but the lock mechanism is not limited to this, and various types can be adopted. An example of such a centrifugal mold with a lock mechanism is shown in FIGS.

  The centrifugal mold 100 in FIG. 8 includes a tubular mold body 111 and a lid 112 for closing the opening of the mold body 111. The lid 112 is provided with the concave portion or the convex portion. After injecting the raw material resin into the mold body 111 and mounting the lid 112, a cylindrical molded product along the inner peripheral surface of the mold body 111 is formed by rotating at high speed around the mold axis. . The lid 112 is provided so as to follow a disc-shaped lid plate 113 that closes the opening end surface of the mold main body 111 and from the outer periphery of the lid plate 113 to the outer peripheral surface of the mold main body 111 with a predetermined interval. And a cylindrical side tube portion 114.

  The lock device 121 for fixing the lid 112 to the mold body 111 includes a lock claw support portion 122 provided at a plurality of locations, for example, 3 to 4 locations at equal intervals on the side cylinder portion 114 of the lid 112, and each lock claw. It has a lock claw 123 attached to each support portion 122, a spring 124 that urges the lock claw 123 in the lock position direction, and a lock release ring 125 provided at the tip of the side tube portion 114.

  The lock claw support portion 122 supports a pin hole for attaching a pin (support shaft) 126 for pivotally supporting the lock claw 123, a spring accommodating portion 127 for mounting the spring 124, and the lock release ring 125. And an internal thread portion to which the bolt 128 is attached. Note that the female screw portion to which the bolt 128 is attached supports the unlocking ring 125 provided over the entire circumference of the side tube portion 114, so that the arbitrary position of the side tube portion 114 is independent of the position of the lock claw support portion 122. It can be provided in the position.

  The unlocking ring 125 includes an unlocking piece 131 inserted between the outer peripheral surface of the mold body and the inner peripheral surface of the side cylinder portion, an attachment piece 132 in a state along the outer peripheral surface of the side cylinder portion, and the attachment pieces 131 and 132. It has a U-shaped cross section composed of connecting pieces 33 to be connected. The mounting piece 132 is provided with a long hole 134 having a long axis in the mold axial direction so as to correspond to the mounting position of the bolt 128. The lock release ring 125 is attached to the tip of the side tube portion 114 in a movable state with respect to the mold axial direction by the bolt 128 inserted through the elongated hole 134.

  The lock claw 123 has a base end portion supported by the pin 126 and is in a rotatable state. The rotation end (inner end) protrudes from the inner peripheral surface of the side tube portion toward the mold main body, and is a mold. It is in a state where it can contact the outer peripheral surface of the main body. The lock claw 123 is urged in the projecting direction by the spring 124, and in a state where the lid 112 is not attached to the mold body 111, the lock claw 123 reaches a position where it comes into contact with the tip of the lock release piece 131 in the lock release ring 125. It is held in a rotated state. At this time, the lock release ring 125 is pressed to a position (on the side opposite to the cover plate) away from the end of the side tube by the lock claw 123 biased by the spring 124, and the lock claw 123 at this time The rotating end is in a state of projecting to the inner peripheral side from the position corresponding to the outer peripheral surface of the mold body.

  The lock device 121 formed in this manner resists the biasing force of the spring 124 by the rotation end of the lock claw 123 coming into contact with the outer peripheral surface of the mold body when the lid 112 is mounted on the mold body 111. Thus, the lock claw 123 is pushed back to the lid plate 113 side. When the lid 112 is in a position to close the opening of the mold main body 111 and the packing 115 provided on the lid plate 113 is crushed and closed, the lock claw 123 is rotated at the end of the mold by the urging force of the spring 124. The main body is held in contact with the outer peripheral surface.

  In this closed state, the position where the rotation end of the lock claw 123 abuts on the outer peripheral surface of the mold body 111 is the size of each part so that the position is closer to the opening side (the cover plate 113 side) than the pin 126. The positional relationship is set. Thereby, the lock claw 123 that rotates about the pin 126 is in a locked state in which it is wedged between the mold main body and the side tube portion due to the positional relationship between the pin 126 and the rotation end contact portion. . Therefore, the movement of the lid 112 in the opening direction is prevented, and the lid 112 is held in a state where the opening of the mold body 111 is closed. That is, the lid 112 is automatically held in a closed state only by being assembled in the axial direction with respect to the mold body 111.

  On the other hand, when the lid 112 is removed from the mold body 111 after molding, the lock release ring 125 is moved to the lid plate side, and the lock claw 123 is rotated to the lid plate side by the lock release piece 131 to rotate. The contact state between the end and the outer peripheral surface of the mold body, that is, the locked state by the lock claw 123 can be released.

  9 includes a tubular mold body 211 and a lid 212 for closing the opening of the mold body 211, and the lid 212 is provided with the concave portion or the convex portion. ing. After injecting the raw material resin into the mold main body 211 and attaching the lid 212, a cylindrical molded product along the inner peripheral surface of the mold main body 211 is obtained by rotating at high speed around the mold axis. is there.

  The lock device 221 for fixing the lid 212 to the mold body 211 includes a lock claw support portion 222 provided at equal intervals on the outer periphery of the lid 212 and a lock claw 223 attached to each lock claw support portion. And have. The lock claw support portion 222 has a pair of support pieces 224 that sandwich the lock claw 223. Each support piece 224 is formed by cutting the outer periphery of the lid 212, and the top surface of the lock claw support portion 222. 222a is inclined so that the outer peripheral side of the lid is lowered. The support piece 224 is provided with a pin hole for attaching a pin 225 for supporting the lock claw 223.

  The lock claw 223 has a locking portion 226 that locks on a flange 213 provided on the mold main body 211 at the front end, and a male screw portion for nut screwing at the rear end. The lock claw 223 can be moved in the mold axial direction by being pivotally supported by the support piece 224 with the pin 225 inserted through a long hole 227 in the claw longitudinal direction provided in an intermediate portion. It can be tilted in the linear direction.

  Further, when the lock claw 223 is attached to the lid 212, the coil spring 230 is compressed between the nut 228 screwed into the male screw portion at the rear end and the lock claw support portion 222 via the washer 229. It is attached with. The coil spring 230 is pressed against the upper surface 222a of the lock claw support portion 222, that is, the coil spring abutting surface, with the outer peripheral side displaced in the direction of the claw tip. The amount of side deflection increases. Accordingly, a force in a direction in which the rear end side (nut side) falls to the outer periphery of the lid by the restoring force of the coil spring 230 acts on the lock claw 223, and a force in a direction to lock the locking portion 226 with the flange 213. Become.

  The lock device 221 formed in this manner is in a state where the locking portion 226 of the lock claw 223 is securely locked to the flange 213 by the action of the coil spring 230 when the lid 212 is mounted on the mold body 211. At the same time, the lid 212 is pressed against the opening of the mold body 211. At this time, the lid 212 can be brought into close contact with the mold body 211 with a necessary and sufficient pressing force by appropriately selecting the performance of the coil spring 230. Further, the pressing force by the coil spring 230 can be finely adjusted by changing the screwing amount of the nut 228 to the lock claw 223.

  The lock device 221 can be unlocked by tilting the rear end of the lock claw 223 toward the inner peripheral side of the lid. The tilting operation of the lock claw 223 can be easily performed by pressing a lock release jig (not shown) having a conical taper surface with the lid side widened on the inner periphery in the mold axis direction. Further, by forming the tapered surface of the unlocking jig in the shape of a conical surface having the maximum diameter corresponding to the lid 212, the three lock claws 223 can be tilted at the same time regardless of these positions. . Accordingly, by combining the unlocking jig having such a conical surface and the jig for gripping the lid 212, the attachment / detachment of the lid 212 with respect to the mold body 211 and the opening / closing operation of the locking device 221 are automatically performed. Can be done.

  In the present invention, the inner hole of the hollow cylinder does not need to be completely coaxial with the outer peripheral surface of the hollow cylinder, and may be slightly decentered.

  In the above-described embodiment, the inner lids 42A and 70 each have a conical shape (that is, a tapered shape) or a shape having a tapered surface 71, but the present invention is not limited to this. For example, although not shown, the tapered surface 71 of the inner lid 70 in FIG. 3 may be a surface parallel to the axial direction of the centrifugal mold 50 (a surface perpendicular to the packing 80).

  The above embodiment is an example of the present invention, and the present invention may have a configuration other than the above. A surface treatment such as plating (for example, chromium plating) or plasma treatment may be applied to the inner surface of the hollow cylindrical body formed according to the present invention. Alternatively, a layered structure may be formed by forming a layer of silicon-based material or fluorine-based material on the inner surface of the hollow cylindrical body.

  The resin material used in the present invention is not particularly limited, but various materials such as anion-polymerizable polyamide MC nylon such as polyamide obtained by the monomer casting method and two-component curable urethane resin are applicable because of moldability by rotational molding. Is possible. Of these, anionic polymerizable polyamides are preferably used for reasons such as mechanical strength.

  The hollow cylinder formed by the method of the present invention is suitable for producing a resin gear using the hollow cylinder. In order to manufacture a resin gear from a hollow cylindrical body, the hollow cylindrical body is cut into a ring shape with a predetermined thickness to obtain a ring body. Then, a metal hub is fitted into the inner hole of the ring body, and the outer periphery of the ring body is cut to form teeth.

  Since this ring body suppresses the generation of burrs, foreign matters remaining in the mold can be prevented. Among these, it is suitable for continuous molding. In addition, since sharp burrs are hardly formed and are excellent in safety, they are suitable as resin gears used as parts for automobiles and electronic devices.

1, 2, 3 Hollow cylinder 1a, 2a, 3a End face 1b, 2b, 3b Burr 10, 10A, 10A ', 10A ", 10B, 50, 100, 200 Centrifugal mold 11, 51 Mold body 32, 60 Seal Plate 41, 80 Packing 42, 42A, 70 Inner lid

Claims (9)

A centrifugal mold having a tubular mold body for centrifugally forming a hollow cylindrical body, and a closing member for closing an opening of the mold body,
On the inner surface of the closing member facing the inside of the centrifugal mold of the closing member, a convex portion protruding inward of the centrifugal mold is provided,
A centrifugal mold characterized in that an outer peripheral edge of the convex portion is separated from the inner peripheral surface of the mold body by a predetermined distance L.   2. The centrifugal mold according to claim 1, wherein the convex portion has a conical shape or a truncated cone shape that is reduced in diameter toward the inside of the centrifugal mold.   The centrifugal mold according to claim 2, wherein the cone has different inclination angles on the outer peripheral side and the center side.   The centrifugal mold according to claim 1, wherein the convex portion has a disk shape.   The centrifugal molding die according to any one of claims 1 to 4, wherein the predetermined distance L is 0.5 mm or more and 50.0 mm or less.   A method for producing a hollow cylinder comprising the steps of injecting a raw material resin into the centrifugal mold according to any one of claims 1 to 5, forming a hollow cylinder by centrifugal molding, and then demolding.   7. The material resin according to claim 6, wherein the material resin is centrifuged so that a hollow cylindrical body is formed in a state where the material resin is in contact with the convex portion of the centrifugal mold and the vertical surface on the outer peripheral side of the convex portion. A method for producing a hollow cylindrical body, characterized in that the hollow cylindrical body is molded by pouring into a mold.   The method for producing a hollow cylindrical body according to claim 6 or 7, wherein an anionically polymerizable polyamide composition is used.   A method for producing a metal resin composite, wherein a metal core material is fitted and fixed to an inner diameter surface of a hollow cylindrical body obtained by using the centrifugal mold according to any one of claims 1 to 5.

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