JPH0140654Y2 - - Google Patents

Description

[Detailed Description of the Invention] (Object of the Invention) The present invention relates to a mold for forming a hollow cylindrical body made of plastic and having an undercut in the inner circumferential wall.

(Prior art) Molding of a plastic hollow cylinder having an undercut on the inner circumferential wall (hereinafter simply referred to as a plastic hollow cylinder) involves moving the core in the axial direction of the hollow cylinder after molding and removing it. Since this is not possible, the core is divided in the circumferential direction to create a structure that allows the diameter to be reduced or expanded, and the divided core is reduced in diameter and removed from the undercut portion of the hollow cylindrical body.

Various molding molds having the above-mentioned structure have been developed, but all of them have problems such as a complicated structure of a core that can be freely contracted and expanded, and are prone to failure.

(Structure of the invention) In view of the above-mentioned problems, the present invention has simplified the structure of the core, ensured its operation, and made it possible to easily remove the core from the undercut portion of the hollow cylindrical body made of plastic. Embodiments will be described below with reference to the accompanying drawings.

In FIGS. 1 to 7, a hollow portion 3 (see FIG. 8) formed when the fixed mold 1 and the movable mold 2 are closed.
A tapered recess 5 is formed in one end surface of a cylindrical core 4 for forming the cylindrical portion A' of a hollow cylinder A made of plastic having an undercut on the inner circumferential wall. A shaft 6 for fitting a truncated right circular conical core 8, which will be described later, is connected thereto. The axis of the cylindrical core 4 and the axis of the shaft 6 are aligned, and a part of the undercut portion A'' of the hollow plastic cylinder A is molded at one end of the cylindrical core 4. A flange portion 7 is provided to protrude.

Also, a truncated right conical core 8 for forming the undercut portion A'' of the hollow cylindrical body A made of plastic.
is slidably fitted on a shaft 6 provided in the cylindrical core 4 with its axes aligned, and the inner end surface of a flange 9 provided at the base end of the truncated right conical core 8 is the core 8
A contact surface 1 for positioning is formed perpendicular to the axis of the
It is set to 0.

The gradients are varied along a generatrix consisting of a straight line that passes through the apex on the axis of the shaft 6 that supports the truncated conical core 8 and equally divides the outer circumferential surface of the truncated conical body into a plurality of parts. First and second guide grooves 11, 1 having a trapezoidal cross section
2 are alternately spaced at equal intervals (in the example, 6
(book) address is provided. The first guide groove 11 has a steeper slope than the second guide groove 12.

Further, a connecting ring 1 is attached to a predetermined position of the shaft 6 of the cylindrical core 4.
3 is fitted and fixed, and a slide piece attachment ring 15 is attached to the connecting ring 13 via a plurality of connecting bolts 14.
are connected. The axis of the slide piece attachment ring 15 and the axis of the shaft 6 of the cylindrical core 4 are aligned. The inner circumferential surface of the slide piece attachment ring 15 is shaped so that the base end of the truncated right-conical core 8 can be fitted therein, and the inner circumferential surface of the slide piece attachment ring 15 is shaped so that the base end of the truncated right-conical core 8 can be fitted therein. A contact surface 16 for positioning that contacts the contact surface 10 of the flange portion 9 is provided, and a tapered surface 17 that fits with the base end of the truncated right conical core 8 is provided.
is provided. The slide piece attachment ring 15 is provided with a plurality of T-grooves 18 that are open on one end surface and are provided in the radial direction at equal intervals on the circumference.

In addition, the first slide piece 19 and the second slide piece 20, as shown in FIGS. 3 and 6,
Undercut part of hollow plastic cylinder A
A tapered cylindrical object that fits on the inner peripheral surface of A″,
It is divided equally in the circumferential direction so that one side wedges into the other in a wedge shape, and each slide piece 19,
There is an undercut part on the outer peripheral surface of the tip of 20.
Projections 21 and 22 for forming the A'' are provided protrudingly, and slide plates 23 and 24 each having a trapezoidal cross section are fixed to the inner circumferential surface of the proximal end using tightening bolts 25 and 26. T-shaped protrusions 27 and 28 are provided protruding between the inner circumferential surface and the outer circumferential surface of the base end surface.The slide plate 23 is fixed to the inner circumferential surface of the base end of the first slide piece 19. It is slidably fitted into the steeply sloped first guide groove 11 provided on the outer peripheral surface of the truncated right conical core 8, and a T-shaped protrusion 27 protruding from the base end surface is connected to the slide piece attachment ring. 15 so as to be able to slide in the radial direction of the mounting ring 15.Similarly, the slide plate 2 fixed to the inner circumferential surface of the base end of the second slide piece 20
4 is slidably fitted into the gently sloped second guide groove 12 provided on the outer peripheral surface of the truncated conical core 8, and the T-shaped protrusion 28 provided protruding from the base end surface is slidably fitted. It fits into the T-groove 18 of the single mounting ring 15 so that it can slide in the radial direction of the mounting ring 15. with this,
A truncated right conical core 8 is connected to the axis 6 of the cylindrical core 4.
When moved in the axial direction, both the first and second slide pieces 19 and 20 move toward the truncated right conical core 8.
The slope of the first guide groove 11 provided on the outer peripheral surface of the core 8 is different from that of the second guide groove 1.
2, so the first slide piece 1
The amount of movement in the radial direction of 9 is the amount of movement of the second slide piece 20
It becomes large compared to the amount of movement. Therefore, as shown in FIGS. 3 and 4, the first slide piece 1
9 separates from between the second slide pieces 20 toward the center or wedges between the second slide pieces 20, so that the plurality of first slide pieces 9
The tapered cylindrical object formed by the second slide pieces 19 and 20 can be freely contracted or expanded in diameter.

Further, a connecting ring 29 is slidably fitted onto the shaft 6 of the cylindrical core 4, and the connecting ring 29 and the truncated right conical core 8 are connected via a plurality of connecting bolts 30. There is. Separate hydraulic cylinder rods (none of which are shown) are connected to the connecting ring 29 and the shaft 6 of the cylindrical core 4, respectively.
Therefore, the cylindrical core 4 and the truncated right conical core 8 can move independently of each other in the axial direction.

Further, 31 is another cylindrical core for molding another cylindrical part A' of the hollow cylinder A made of plastic,
A tapered protrusion 32 that fits into the tapered recess 5 of the cylindrical core 4 in the hollow portion 3 formed by the fixed mold 1 and the movable mold 2 is provided on the inner end surface. This cylindrical core 31 is configured to be movable in the axial direction by a hydraulic cylinder (not shown).

(effect of invention) Next, the operation of the present invention will be explained.

First, as shown in FIG. 9, the cylindrical core 4 is gradually advanced while the truncated conical core 8 is kept at the retreating end, and the mold is formed by the fixed mold 1 and the movable mold 2. When the slide piece attachment ring 15 is inserted into the hollow part 3, as shown in FIG. The forward end position of the cylindrical core 4 is determined by contacting the side surfaces of the mold 1 and the movable mold 2. Next, when another cylindrical core 31 is advanced and the tapered protrusion 32 of the cylindrical core 31 is fitted into the tapered recess of the cylindrical core 4, the cylindrical core 4 and The position of the axis with respect to the cylindrical core 31 is determined. Next, when the truncated conical core 8 is gradually advanced, the first and second guide grooves 11 and 12 provided in the truncated conical core 8 have first and second guide grooves, respectively. Slide plates 23 and 24 fixed to the inner circumferential surfaces of the base end portions of the slide pieces 19 and 20 are fitted, and T-shaped protrusions 27 and 28 provided on the base end surfaces of each slide piece 19 and 20 allow the sliding Single mounting ring 15
Since the first and second slide pieces 19 and 20 are fitted into the T-groove 18 provided in the cylindrical core 4, the first and second slide pieces 19 and 20 move in the radial direction away from the axis of the shaft 6 of the cylindrical core 4. Here, since the slope of the first guide groove 11 provided in the truncated conical core 8 is larger than the slope of the second guide groove 12, the amount of movement of the first slide piece 19 in the radial direction is , is larger than the amount of movement of the second slide piece 20. Therefore, as shown in FIG. 3A and FIG. 4A, between the second slide pieces 20,
The first slide piece 19 bites into a wedge shape. As shown in FIG. 1, when the contact surface 10 of the truncated conical core 8 contacts the contact surface 16 of the slide piece attachment ring 15, the plurality of first and second slides The tapered cylindrical body formed by the pieces 19 and 20 is expanded in diameter, and its outer peripheral surface shape matches the inner peripheral surface shape of the hollow plastic cylinder A to be molded.

Then, a fixed mold 1, a movable mold 2, a cylindrical core 4,
When molten plastic is injected into the cavity formed by the slider 31 and the plurality of first and second slide pieces 19, 20 and cooled and solidified, a desired plastic hollow cylinder A is formed.

After molding the plastic hollow cylindrical body A, each core 4,
All you have to do is remove 8 and 31.

That is, if the cylindrical core 4 is left as it is and only the truncated conical core 8 is gradually retreated, the amount of movement in the radial direction of each slide piece 19, 20 will be different as described above. Slide pieces 19, 20
The diameter of the tapered cylindrical object formed is reduced from the state shown in FIG. 3A and FIG. 4A to the state shown in FIG. 3B and FIG. 4B, and the positional relationship shown in FIG. becomes.

Next, when the cylindrical core 4 and the cylindrical core 31 are gradually retreated, the diameter of the tapered cylindrical object formed by each slide piece 19, 20 has been reduced, so that each slide piece 19, 20 is made of plastic. At the same time as it leaves the undercut portion A'' of the hollow cylindrical body A, the truncated right conical core 8 located at the retreating end retreats from the movable mold 2 together with the cylindrical core 4.

Next, when the movable mold 2 is lowered, the plastic hollow cylinder A remains on the movable mold 2, as shown in FIG. 9, and the plastic hollow cylinder A is taken out from the movable mold 2 by a necessary means.

By repeating each of the above operations, the plastic hollow cylindrical body A can be continuously formed.

(Effect of the invention) As described above, the mold of the present invention has each slide fixed to the inner peripheral surface of the proximal end of the first and second slide pieces for molding the undercut part of the hollow cylinder made of plastic. The plate is slidably fitted into first and second guide grooves with different slopes provided on the outer peripheral surface of the truncated right conical core, and the base end surfaces of the first and second slide pieces. The T-shaped protrusion provided in
Since it is slidably fitted into the T-groove of the slide piece attachment ring fixed to the shaft of the cylindrical core, when the truncated right conical core is moved relative to the shaft of the cylindrical core, Ensure that each slide piece moves radially,
A tapered cylindrical object formed by a plurality of first and second slide pieces can freely expand or contract in diameter, and can be easily separated from and removed from an undercut portion of a hollow plastic cylinder. Moreover, since each slide piece and the truncated conical core are in a fitted state, breakdowns are unlikely to occur even if used frequently.

In addition, since the truncated right conical core is slidably fitted on the shaft connected to the cylindrical core, after molding, the truncated right conical core is first inserted into the cylindrical core. , each slide piece is detached from the undercut of the plastic hollow cylinder and removed, and then the cylindrical core is removed.
The truncated conical core can be removed from the hollow part of the mold together with the cylindrical core 4. Therefore, a hollow cylindrical plastic body having an undercut in the inner circumferential wall can be efficiently molded.

[Brief explanation of drawings]

FIG. 1 is a front sectional view of a state in which both a cylindrical core 4 and a truncated right conical core 8 are inserted into a hollow portion 3 formed by a fixed mold 1 and a movable mold 2;
The figure is an enlarged view of the main part of Fig. 1, Fig. 3 A is an enlarged sectional view taken along the line X-X of Fig. 1, and Fig. 3 B is an enlarged view of the main part of Fig. 8.
An enlarged cross-sectional view along the X'-X' line, Figure 4 A is Y in Figure 1.
-Y-line enlarged cross-sectional view;
5 is a perspective view of the first slide piece 19, and FIG. 6 is a perspective view of the second slide piece 20.
7 is a perspective view of the T of the second slide piece 20.
The protrusion 28 and the T-slot 1 of the slide piece attachment ring 15
8 is a front sectional view showing only the truncated conical core 8 removed from the hollow part 3, and FIG. 9 is a plan view showing the fitted state with the hollow part 3. FIG. 3 is a front sectional view with all the cores removed. Explanation of the symbols of the main parts, 1...Fixed type, 2...
Movable type, 3...Hollow part, 4...Cylindrical core, 6...
...Axis of cylindrical core, 8...Truncated right conical core, 1
1...First guide groove, 12...Second guide groove, 1
5...Slide piece mounting ring, 18...T groove, 19
...First slide piece, 20...Second slide piece, 21, 22...Protrusion, 23, 24...Slide plate, 27, 28...T-shaped protrusion, A...Plastic hollow cylinder body, A'...cylindrical part of the plastic hollow cylinder body, A''...undercut part of the plastic hollow cylinder body.

Claims (1)

[Scope of utility model registration request] A concentric shaft 6 is connected to a cylindrical core 4 for forming a cylindrical portion A' of a hollow cylinder A made of plastic having an undercut on the inner circumferential wall, and a concentric shaft 6 for forming an undercut portion A''. A truncated right conical core 8 is slidably fitted onto the shaft 6 of the cylindrical core 4, and its apex on the axis of the shaft 6 supporting the truncated right conical core 8 is A plurality of first and second guide grooves 11 and 12 having trapezoidal cross-sections with different slopes are alternately provided along a generating line consisting of a straight line that equally divides the outer circumferential surface of the truncated right circular cone into a plurality of pieces. A plurality of T grooves 18 are attached to the slide piece mounting ring 15 which is fixed with the axis aligned with the predetermined position of the shaft 6 of the columnar core 4.
are provided in the radial direction, and protrusions 21 and 22 for forming the undercut portion A'' are provided on the outer circumferential surface of the tip, and
Slide plates 23 and 24 having a trapezoidal cross section on the inner peripheral surface of the base end.
are fixedly installed, and further provided with T-shaped protrusions 27, 28 on the base end surfaces. First and second slide pieces 19, 20 are formed,
The slide plates 23 and 24 are slidably fitted into the first and second guide grooves 11 and 12 provided in the truncated right-conical core 8, respectively, and the slide plates 19 and 20 are fitted in the respective slide plates 19 and 20. The T-shaped protrusions 27 and 28 are slidably fitted into the T-groove 18 of the slide piece attachment ring 15, and the cylindrical medium is inserted into the hollow portion 3 formed when the fixed mold 1 and the movable mold 2 are closed. A mold for molding a hollow cylindrical body made of plastic and having an undercut on an inner circumferential wall, the mold is configured such that the core 4 and the truncated conical core 8 can be moved in and out independently of each other.