JPH1190961A - Molding die for seal ring with cut section and molding method thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a molding die and a molding method thereof for improving the molding quality of cut sections of a seal ring with the cut sections of particular shape. SOLUTION: A molding die is provided with a cavity for molding a seal ring 1 with cut sections 1a and 1b as a mold product, a pair of gate sections 24 and 25 disposed on both ends of respective sections 1a and 1b and a tape 27 for discharging a molten material of a weld section 26 out of the cavity formed on the weld section 26 of the molten material injected into the cavity.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a molding die and a molding method for a seal ring having a cut portion, and more particularly to a technique for improving the molding quality of a cut portion of a seal ring.

[0002]

2. Description of the Related Art Conventionally, an annular seal ring made of a resin material has been used for sealing an annular gap between a shaft hole and a shaft. FIG. 6 shows a seal ring 10 of this kind.
1 is fitted into a groove 102a provided in the shaft 102 to seal a ring-shaped gap 104 between the inner peripheral surface of the shaft hole 103a of the housing 103 and the outer peripheral surface of the shaft 102. FIG.

The main purpose of this seal ring 101 is to prevent the sealing fluid contained in the sealing side M from leaking to the atmosphere side O. As shown in FIG. In some cases, a higher degree of sealing may be exhibited by combining with sealing means such as an O-ring or a sealing device (not shown).

When the seal ring is fitted into the groove 102a, if the material of the seal ring 101 is a resin having a predetermined elasticity, the seal ring 101 has a certain degree of elasticity like the O-ring of a rubber-like elastic body. Therefore, the diameter of the shaft 102 may be temporarily expanded to be equal to or slightly larger than the diameter of the shaft 102, the surface of the shaft 102 may be slid and moved to the groove 102a, and the diameter may be reduced at that position. is there.

[0005] However, in the case of a seal ring made of a resin having low elasticity, problems such as cracking when the diameter is expanded or the diameter being expanded without returning to the original size may occur. As shown in FIG. 7A, a cut portion 101a is provided, and the seal ring is once bent in the radially expanding direction and fitted.

Although various shapes of the cut portion 101a have been proposed, FIG. 7B shows a straight cut 101b having a cut surface parallel to the radial direction of the seal ring, and FIG. This is a bias cut 101c that is a cut surface oblique from the radial direction of the seal ring.

The straight cut and the bias cut can be provided simply by making a straight cut in the seal ring, and the manufacture is easy. However, the step cut 101d as shown in FIG. The special step cut 101f shown in FIG. 7 (e) has a complicated cut surface (joining surface) and requires a long time to be manufactured by machining. Therefore, the seal ring is manufactured by injection molding. FIG. 7F is an enlarged view of a portion D101 in FIG.

[0008] Regarding the cut shape, the characteristics of the leakage amount with respect to the temperature change and the pressure change are different from each other.
A shape that satisfies required characteristics while taking into account other factors such as durability and cost has been appropriately adopted.

[0009]

FIG. 8 shows a seal ring 110 having a special step cut 101e at a cut portion.
FIG. 2 is a diagram of a molded product for explaining a conventional injection molding die and a molding method of the present invention, in which a cavity shape of a molding die (not shown) can be understood.

The seal ring 110 is formed with the cut portion slightly opened. The spool 121 is located at the center of the seal ring 110,
A runner 122 extending toward the opposite side of the cut portion, and a gate portion 123 which is a connection portion between the runner 122 and the seal ring 110 are provided (side gate type in which the gate portion is provided on the mold opening surface).

However, when the seal ring 110 is molded by the molding die and the molding method having such a configuration, the portion of the special step cut 101e located at the end of the cavity with respect to the gate portion 123 is caused by the pressure loss of the mold flow. There is a concern that the filling protrusion pressure is apt to decrease, and the tip protrusion, which is particularly thin, has a large shrinkage after molding, causing sink marks (dents) and a problem of poor shape (insufficient running of hot water, etc.). there were.

FIG. 9 is a view for explaining the state of the seal ring 110 in which such a problem at the time of molding has occurred.
(A) is a perspective view showing a state where the special step cuts 101e on both sides are combined. C1 and C2 are cross sections of the overlapping portion of the special step cut 101e.

FIGS. 9 (b) and 9 (c) are cross-sectional views of the cross sections C1 and C2 in a state in which sink marks S are formed on the tip projections 131a and 131b, and FIGS. C
It is sectional drawing in the state where shape defect D generate | occur | produced in the front-end | tip protrusion part 131c, 131d in 1 and C2.

[0014] If such a poorly formed seal ring is used, gaps S1 and S2 are generated in the cross sections C1 and C2, forming a flow path, thereby increasing the leakage of the sealed fluid. I do.

The present invention has been made to solve the above-mentioned problems of the prior art, and an object of the present invention is to improve the molding quality of a cut portion of a seal ring having a cut portion having a special shape. An object of the present invention is to provide a molding die and a molding method that can be used.

[0016]

In order to achieve the above object, according to the present invention, there is provided a cavity for molding a seal ring having a cut portion as a molded product, and a cavity for forming both ends near the cut portion of the cavity. It is characterized in that a pair of gate portions respectively arranged and a tab for discharging the molten material in the welded portion from the cavity are provided in the welded portion of the molten material injected into the cavity.

According to the molding die having this configuration, the pressure loss of the molten material supplied to the cut portion in the cavity can be reduced, and the molding quality of the cut portion can be improved. In addition, the molten material in the weld portion generated on the opposite side of the cut portion of the seal ring is discharged from the cavity, so that the welded portion where the leading ends of the flows abut and are in a joined state is present in the molded product. To prevent

A spool portion disposed in an inner region of the C-shaped cavity, a runner portion connecting the pair of gate portions and the spool portion, and a tab disposed in the inner region of the cavity; In addition, it is preferable that the tab has an undercut shape for being held by the mold on the side where the molded product is left when the mold is opened.

With such a mold configuration, the molded article can be stably held in the mold on the side where the molded article remains when the mold is opened.

Further, the parting line on the inner peripheral wall side of the cavity is located on the side of the mold for releasing the molded product when the mold is opened from the center of the inner peripheral wall in the mold opening direction. It is also suitable.

Accordingly, the inner peripheral wall surface of the cavity is more present in the mold on the side where the molded product is left when the mold is opened. By utilizing the fact that the seal ring shrinks during molding and sticks to the inner peripheral wall surface of the cavity, the molded product is more stably held in the mold on the side where the molded product remains when the mold is opened. Can be.

Still further, a first parting line located on a mold side for releasing the molded product is formed on an inner peripheral wall surface of a cavity closer to a tub side than the pair of gate portions. A second parting line formed on the inner peripheral wall surface of the cavity on the cut portion side sandwiched between the gate portions is located at the center of the inner peripheral wall surface in the mold opening direction, and the first parting line is formed. It is also preferable to provide a circumferential gap on the mating surface of the mold of the step portion connecting the line and the second parting line, and to use this gap as the gate portion.

Accordingly, it is possible to suppress the occurrence of galling and burrs in the mold opening direction of the step portion for eliminating the step between the first and second parting lines.

Further, a method of forming a seal ring having a cut portion is such that a molten material is injected into a cavity from a pair of gate portions of the molding die using the molding die described above, and the cavity is formed by the tab. The molten material in a weld portion in the inside is discharged from the cavity.

[0025]

BEST MODE FOR CARRYING OUT THE INVENTION

(Embodiment 1) FIG.
A mold for injection-molding a seal ring 1 having a special step cut similar to that shown in FIGS. 7 (e) and 7 (f) in a cut portion and a molded product W for describing a molding method.
FIG. 3 is a diagram (including portions other than products such as runners and gates), and the configuration of a molding die (not shown) can be understood.

The seal ring 1 is formed with the cut portions 1a and 1b slightly opened. The spool 21 for guiding the molten resin material to the cavity of the mold is located inside the substantially C-shaped seal ring 1.
Runner 2 extending toward the vicinity of cut portions 1a and 1b of
2, 23, and gate portions 24, 25, which are connection portions between the runners 22, 23 and the seal ring 1, are provided.

Further, a tab 27 (in the cavity) for discharging the molten resin material in the weld portion 26 from the cavity is provided in the weld portion 26 where the ends of the flow of the molten resin material injected from the gate portions 24 and 25 abut. Connected cavity) is arranged in the inner region of the seal ring 1.

FIG. 2 is a sectional view taken along the line C3 of FIG. The upper side of the mold is a fixed mold 31 and the lower side is a movable mold 32 with the mold opening surface PL (parting line) as a boundary.

The seal ring 1 needs to be held on the movable mold 32 with the molding die opened, and regardless of the shape of the seal ring 1 itself and the position of the mold opening plane PL.
Undercut side surfaces 27a, 2 provided on tab 27
7b holds the tab 27 on the movable mold 32, so that the weld portion 26 of the seal ring 1 can also be held on the movable mold 32, thereby improving the releasability from the fixed mold 31 and deforming the seal ring 1. suppress.

By providing similar undercuts on the runners 22 and 23, deformation of the cut portions 1a and 1b of the seal ring 1 can be suppressed.

The push pins (not shown) may be appropriately arranged so as to contact not only the molded product but also predetermined portions of the tab 27 and the runners 22 and 23.

FIG. 3 shows a flow state of the molten resin material in the weld portion, and FIG. 3 (a) shows a tub 2 according to the embodiment of the present invention.
FIG. 3B is a diagram showing a weld portion 26 provided with a first metal layer 7 and FIG.
FIG. 4 is a diagram showing a weld portion in a configuration without a tab 27.

In general, the types of welds include a Butt-Weld where flow stops and a streaming weld where a weld line is formed continuously.
aming-Weld). In FIG. 3, (a)
Indicates a streaming weld, and (b) indicates a buttoweld.

The butwel in FIG. 3B changes its shape and size due to the occurrence of a dent or a bulge due to the flow or pressure concentration toward the periphery of the weld line L2 (merging surface). Is expected to decrease in strength.

On the other hand, in the case of the streaming weld shown in FIG. 3A, the weld line L1 is formed continuously toward the tub 27, so that the strength is superior to the weld line L2 of the but weld, and the shape and dimensions are improved. The change can also be reduced more than Butweld.

Accordingly, the cut portions 1a,
By providing a pair of gate portions 24 and 25 at both ends near 1b, cut portions 1a and 1b in the cavity are provided.
The pressure loss of the molten material supplied to the heater can be reduced, and the molding quality of the cut portions 1a and 1b can be improved.

The cut portions 1a, 1 of the seal ring 1
tab 27 at the position of the weld portion 26 generated on the side opposite to
, The welding portion 26 can be formed as a streaming weld, and the shape and dimension of the welding portion 26 can be stabilized and the strength can be increased.
It should be noted that an improvement in the molding quality of the weld portion 26 cannot be expected by a simple multipoint gate molding method in which the tab 27 is not provided.

The shape of the special step cut is shown in FIG.
The present invention is not limited to the shapes (e) and (f), but can be applied to other shapes. Although no particular mention is made of the material of the seal ring, for example, a thermoplastic polyamide resin can be used.

In the present embodiment, the molding die has been described for injection molding. However, the arrangement of the gate and the tab according to the present invention is applied to a molding die of another molding method. Is also possible.

(Embodiment 2) In the first embodiment,
The parting line PL on the inner peripheral wall surface 1c side of the seal ring 1 is located at the center in the mold opening direction as shown in FIG. This is because the cut portions 1a and 1b have a surface located at the center in the mold opening direction (see FIG. 9). The reason for this is that the manufacture of the mold becomes simple, which is convenient.

FIG. 4 is a view for explaining in detail the state of the parting line PL of the mold described in the first embodiment. FIG. 4 (a) is a view of a molded product W, and FIG. Is the molded product W
FIG. 4C is a view for explaining the end face shape of the mold corresponding to the C4-C4 cut surface of FIG.
FIG. 4D is a diagram for explaining a cross section of the mold corresponding to FIG. 10, and FIG. 4D is a cross-sectional view of the mold corresponding to a section taken along line C11-C11 in FIG.

C5 and C10 shown in FIGS. 4B and 4C
As shown in cross section, the gate portions 24, 2
The parting line PL in the region up to 5 (the region excluding the cut portions 1a and 1b) is located at the end surface position on the movable mold 32 side on the outer peripheral side of the seal ring 1, and is located at the center in the mold opening direction on the inner peripheral side of the seal ring 1. Located in the department.

In the region of the cut portion, as shown in the cross section C6 to C9 in FIG. 4C, the inner peripheral side of the seal ring 1 is located at the center in the mold opening direction, and the cut portion 1a On the outer peripheral side of the center of the mold opening direction (C6, C7),
On the outer peripheral side of the cut portion 1b, the end surface position (C
8, C9).

FIG. 4D shows the positional relationship between the gate 24 and the parting line PL. The parting line PL is located exactly at the center of the gate 24 in the opening direction.

Therefore, in the seal ring 1 injection-molded in the cavity, the inner peripheral wall surface 1c (see FIG. 4A) of the seal ring 1 is fixed to the fixed die 31 by the shrinkage behavior when the resin is solidified in the mold. And the movable mold 32 sticks to the inner periphery of both cavities.

When the mold is opened in such a state, the portion attached to the fixed mold 31 remains on the fixed mold 31 with respect to the seal ring 1 to be moved together with the movable mold 32 in the mold opening direction. There is a concern that the sealing force may be deformed by the force of the sealing.

In order to solve this problem, in the molding die according to the second embodiment, the parting line on the inner peripheral wall surface of the cavity is set at a position as shown in FIG.

FIG. 5 (a) shows the second section corresponding to the C4-C4 cut surface of the molded product W of FIG. 4 (a), similarly to FIG. 4 (b).
FIG. 5 is a view for explaining an end face shape of a molding die according to the embodiment.
(B) shows the cut surfaces C12 to C1 of the D1 portion of the molded product W in the same manner.
FIG. 5 is a view for explaining a cross section of a molding die according to the second embodiment corresponding to FIG. 7, and FIG. 5 (c) is a molding die according to the second embodiment corresponding to the C18-C18 cut surface of FIG. It is sectional drawing of a type | mold.

In FIG. 5, the same components as those in the first embodiment are denoted by the same reference numerals.

In the molding die according to the second embodiment,
The parting line PL on the outer peripheral side of the seal ring 1 is
It is provided at the same position as that of the first embodiment.

However, the parting line PL1 (first parting line) on the inner peripheral wall surface 1c side of the seal ring 1 is, as shown by the cross-sections C12 and C17 in FIGS. 5A and 5B. The seal ring 1 is located closer to the fixed mold 31 that releases the seal ring 1 when the mold is opened than the center of the inner peripheral wall 1c.

The circumferential region of the parting line PL1 is formed in the region from the tab 27 to the gate portions 24 and 25 (the region indicated by oblique lines).

The parting line PL2 on the inner peripheral side of the seal ring 1 in the cut portion is indicated by C in FIG.
13 to C17, the seal ring 1 is located at the center in the mold opening direction. This position is the same as that of the first embodiment, and the circumferential region on the mold opening surface is formed in a region indicated by oblique mesh lines.

Therefore, parting lines PL1 and PL
2 has a step in the mold opening direction, and it is necessary to provide a step portion to eliminate the step.
As shown in (c), a circumferential gap G1 is provided on the mating surface of the molds of the step portion ST of the fixed mold 31 and the movable mold 32, and the gap G1 is used as the gate section 24.

With such a configuration, the inner peripheral wall surface of the cavity is more present in the movable mold 32, and it is possible to prevent the seal ring 1 from contracting and sticking to the inner peripheral wall surface of the cavity during molding. By utilizing this, the seal ring 1 can be stably held by the movable mold 32 when the mold is opened, and the deformation of the seal ring 1 is prevented.

Further, by positioning the step portion ST of the parting line at the gate portions 24 and 25, the occurrence of galling and burrs in the mold opening direction of the step portion ST can be suppressed.

[0057]

According to the present invention, the pressure loss of the molten material supplied to the cut portion in the cavity can be reduced, and the molding quality of the cut portion can be improved.

Further, it is possible to stabilize the shape and size of the weld portion generated on the side opposite to the cut portion of the seal ring and to achieve an increase in strength.

Providing the tab with an undercut shape,
Alternatively, by specifying the position of the parting line, the holding and release of the molded product when the mold is opened can be reliably performed, and the deformation of the seal ring can be suppressed.

By locating the step portion of the parting line at the gate portion, occurrence of galling and burrs in the mold opening direction of the step portion can be suppressed.

[Brief description of the drawings]

FIG. 1 is a diagram of a molded product of a seal ring according to an embodiment.

FIG. 2 is a sectional view taken along line C3 of FIG. 1, showing a sectional shape near a tab.

FIG. 3 is a view showing a flow state of a molten resin material in a weld portion.

FIG. 4 is a diagram illustrating a parting line of a molding die according to the first embodiment.

FIG. 5 is a diagram illustrating a parting line of a molding die according to a second embodiment.

FIG. 6 is a cross-sectional configuration explanatory view showing a usage form of a seal ring.

FIG. 7 is a view of a seal ring.

FIG. 8 is a view for explaining a conventional molding method of a seal ring having a cut portion.

FIG. 9 is a view for explaining a molding failure of a seal ring having a special step cut in a conventional molding method.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Seal ring 1a, 1b Cut part 1c Inner peripheral wall surface 21 Spool 22, 23 Runner 24, 25 Gate part 26 Weld part 27 Tab 27a, 27b Side surface 31 Fixed type 32 Movable W molded product PL, PL1, PL2 Parting line ( Mold opening surface)

Claims (5)

[Claims] 1. A cavity for molding a seal ring having a cut portion as a molded product, a pair of gate portions disposed at both ends of the cavity in the vicinity of the cut portion, and injected into the cavity. A mold for forming a seal ring having a cut portion, wherein a tab for discharging the molten material in the weld portion from the cavity is provided in the weld portion of the molten material. 2. A spool portion disposed in an inner region of the C-shaped cavity, a runner portion connecting the pair of gate portions and the spool portion, and a tab disposed in the inner region of the cavity; The seal ring having a cut portion according to claim 1, wherein the tab has an undercut shape to be held by a mold on a side where a molded product is left when the mold is opened. Molding mold. 3. The parting line on the inner peripheral wall side of the cavity is located closer to the mold than the center of the inner peripheral wall in the mold opening direction to release the molded product when the mold is opened. A molding die for a seal ring having a cut portion according to claim 1 or 2. 4. A first parting line located on a mold side for releasing the molded product is formed on an inner peripheral wall surface of a cavity closer to a tub side than the pair of gate portions. The second parting line formed on the inner peripheral wall surface of the cavity on the cut portion side sandwiched by the gate portion is located at the center of the inner peripheral wall surface in the mold opening direction, and the first parting line is provided. 4. A seal having a cut portion according to claim 3, wherein a circumferential gap is provided on a mating surface of a mold of a step portion connecting the first and second parting lines, and the gap is used as the gate portion. Mold for forming rings. 5. A molding material according to claim 1, 2, 3 or 4, wherein a molten material is injected into the cavity from a pair of gate portions of the molding die, and the molten metal is injected into the cavity by the tab. A method of forming a seal ring having a cut portion, wherein a molten material in a weld portion in a cavity is discharged from the cavity.