JPH0442971B2 - - Google Patents

Description

[Detailed Description of the Invention] "Technical Field" This invention relates to a product having screws, protrusions, depressions, etc. on the inner surface of the product.
The present invention relates to an improvement in an open core that is used by being attached to a mold when injection molding synthetic resin products having undercuts such as recessed holes.

``Prior art'' As a conventionally known open core,
There is one described in Publication No. 59-14333. This open core, as shown in FIGS. 4 to 8,
It consists of a core rod 1 and first slide members 2 . . . and second slide members 3 . . . arranged alternately around the core rod 1. As shown in FIGS. 6 to 8, the core rod 1 has its base end 1a,
It is fixed to a substrate 6 on the movable mold 5 side of the mold 4.
Further, the main body portion 1b is provided with a conical outer surface having a size that is closely inscribed in the space between the combined first slide member 2... and second slide member 3... In the example, since three first and second slide members 2..., 3... are provided, the main body portion 1b is formed in a hexagonal pyramid shape.

The angle α of the outer surface 7a of the main body portion 1b, which is in contact with the first slide member 2, with respect to the core axis
is formed smaller than the angle of the outer surface 7b with which the second slide member 3 contacts with respect to the core axis.

The first slide member 2 has a substantially arcuate cross-sectional shape, and the center part of the part that corresponds to the string is a sliding surface 2a that contacts the outer surface 7a of the core rod 1. A dovetail 9 is provided for dovetail engagement with a dovetail groove 8 on the outer surface 7a of the second embodiment.
Further, both sides of the sliding surface 2a of the first sliding member 2 that are in contact with the outer surface 7a of the core rod 1 are in contact with the second sliding member 3.

The second slide member 3 has a substantially trapezoidal cross-sectional shape, and the bottom portion of the second slide member 3 has a core rod 1.
The sliding surface 3a is in contact with the outer surface 7b of the core rod 1, and a dovetail 9 is provided in the center thereof for dovetail engagement with the dovetail groove 8 of the outer surface 7b of the core rod 1. The first of these,
The dovetails 9 of the second slide members 2..., 3... and the dovetail grooves 8 of the core rod 1 are provided along the axial direction of the core rod 1, and their dovetail engagement allows the dovetail grooves 8... 1 and 2 slide members 2 and 3 are adapted to slide on outer surfaces 7a and 7b of the core rod 1 along the axial direction of the core rod 1. Moreover, the proximal ends of these slide members 2..., 3... are provided with moving protrusions 10... that protrude outward. These moving protrusions 10 are fitted into recesses 12 provided between slide member guide plates 11, 11 provided overlappingly on the base plate 6 of the movable mold 5. A stripper plate 13 is further provided on the sliding member guide plates 11, 11 of the movable mold 5. When this open core is in the injection molding state shown in FIG. 6, the stripper plate 13
The outer surfaces of the slide members 2..., 3... that protrude further than the above are provided with a shape corresponding to the inner surface of the desired molded product.
In this example, a thread 14 is machined, thereby forming a cavity between the mold 4 and the fixed mold 15 for molding a molded product 16 having an internal thread.

Next, the operation of this open core is shown in Figures 6 to 8.
This will be explained along the diagram.

First, in the injection molding state in which the fixed mold 15 and the movable mold are closed together as shown in FIG.
The slide member 2...
. . , 3 . . . are arranged in an injection molded state that matches the inner shape of the desired molded product 16 (see FIG. 4). In this state, a molding material is injected and filled into the cavity of the mold 4 to obtain a molded product 16.

Next, the mold 4 is opened, and the fixed mold 15 is replaced with the movable mold 5.
When the slide member guide plates 11, 11 of the movable mold 5 are further moved after being separated from the movable mold 5, the slide members 2..., 3... are moved by the moving protrusions 10...
... along the axial direction of the core rod 1. As a result, the slide members 2..., 3... not only move along the axial direction of the core rod 1, but also
It moves inwardly along the inclined outer surfaces 7a, 7b of the conical core rod 1 so as to approach the axis of the core rod 1. At this time, the inclination angle β of the outer surface 7b of the core rod 1 that is in contact with the second slide member 3 is the first
Since the inclination angle α of the outer surface 7a with which the slide members 2 are in contact is larger than the inclination angle α, the second slide members 3 move inwardly than the first slide members 2. Thus, the slide member 2...
..., 3..., as shown in FIGS. 5 and 7, are arranged in the mold open state, and the outer shape is smaller than the arrangement in the injection molded state. Next, the molded product 16 released from the mold in this manner is pushed down by advancing the stripper plate 13, as shown in FIG. 8, and is taken out as the molded product 16.

After completing the molding of the molded product 16 in this way, when the stripper plate 13 and the slide guide plates 11, 11 are sequentially stacked on the substrate 6,
Slide members 2..., 3... are the outer surface 7 of the core rod 1
a..., 7b... and return to the injection molded state shown in FIG. After this, a new injection molding operation can be started by closing the mold 4.

"Conventional Problems" In the open core having such a structure, the positions of the slide members 2 and 3 are determined only by the dovetail engagement with the core rod 1, so the slide members 2 and 3 do not form a dovetail engagement. When dovetail rod 8 and dovetail 9 wear out, the fourth
As shown by the two-dot chain line in the figure, the slide member 2...
..., 3... is out of position, and burrs and steps occur on the inner surface of the molded product 16 corresponding to the joints of the first slide member 2 and the second slide member 3, resulting in poor quality of the molded product 16. There was a problem where the performance decreased significantly.

"Object of the invention" This invention was made in view of the above circumstances,
It is an object of the present invention to provide an open core capable of producing high-quality molded products with few burrs and steps without causing displacement of a sliding member.

"Means for Solving the Problems" Hereinafter, means for solving the above problems will be described in detail with reference to examples.

1 and 2 show an embodiment of the open core of the present invention, and the same components as those of the conventional example shown in FIGS. 4 to 8 are denoted by the same reference numerals. Simplify the explanation.

The open core of this example is for molding a molded product 16 having an internal thread similar to the open core of the conventional example,
In this case, the sliding surface 20 of the first sliding member 2 that contacts the outer surface 7a of the core rod 1 is formed by three planes. 3 of this sliding surface 20
The two planes are respectively formed along the axial direction of the core rod 1, and include a main sliding surface 20a at the center of the sliding surface 20 provided with a dovetail 9 that engages with a dovetail groove 8 of the core rod 1; Side sliding surfaces 20b, 20b on both sides
It consists of. This side sliding surface 20b opens on the same plane, extends outward from the core, and is in sliding contact with the second sliding member 3.

The angle γ of this side sliding surface 20b with respect to the main sliding surface 20a is set between 180° and 150°. If the angle γ is 180°, the side sliding surface 20b and the main sliding surface 20a become one plane, and the object of the invention cannot be achieved.
The slide members 3 cannot slide inward of the first slide members 2, and the opening core cannot transition from the injection molding state to the mold opening state.

The cross-sectional shape of the first slide member 2 includes an outer surface 21 of the first slide member 2, the side sliding surface 20b,
20b and the side sliding surfaces 20b, 2.
0b and the main sliding surface 20a.
is formed into a trapezoidal shape that narrows toward the axis of the core rod 1, and a portion c forming the inner surface of the molded product 15 surrounded by the line segment a and the outer surface 21 is formed into an arcuate shape.

The second slide member 3 sandwiched between the first slide member 2 has a substantially trapezoidal cross-sectional shape. The surfaces 22, 22 of the second slide member 3 in contact with the first slide member 2 are
The width is narrower than that of the side sliding surface 20b of the slide member 2.

Moreover, the core rod 1 fitted between these slide members 2..., 3... has a size and shape that closely inscribes the space formed by these slide members 2..., 3... The outer surface 7a in contact with the first slide member 2 is connected to the main sliding surface 20a of the sliding surface 20 of the first sliding member 2 and the side sliding surface 2.
0b and 20b are formed by three planes that are in sliding contact with each other.

"Specific effects of the invention" In the open core configured in this way, the sliding surface 20 of the first sliding member 2 that contacts the outer surface 7a of the core rod 1 is in contact with the main sliding surface 20a and the side sliding surface. Moving surface 20
b, 20b, and in addition to the main sliding surface 20a dovetailed with the outer surface 7a of the core rod 1, the side sliding surfaces 20b, 20b also have contact with the outer surface 7a of the core rod 1. Since they are in contact with each other, movement of the first slide member 2 in the lateral direction (indicated by arrows in FIG. 1) is restricted by the side sliding surfaces 20b, 20b. Therefore, even if the dovetail 9 or the dovetail groove 8 that engages with the dovetail 9 wears out, the first slide member 2 does not shift laterally, and the slide member 2...
. . , 3 . . . The occurrence of burrs and steps on the inner surface of the molded product 16 due to the misalignment of the positional relationship is greatly reduced. Note that the second slide member 3 with the open core is
The slide member 2 is sandwiched between the slide members 2, and its movement in the lateral direction is restricted.

Further, the first sliding member 2 having an open core configured in this way has a side sliding surface 20 of the sliding surface 20.
b, 20b prevent the first slide member 2 from moving in the lateral direction. The load applied to the dovetail 9 and the dovetail groove 8 that engages with the dovetail 9 is small, and therefore the dovetail 9 and the dovetail groove 8 form a dovetail engagement.
This also reduces the occurrence of burrs and steps on the inner surface of the molded product 16.

In addition, in the case of the conventional open core, since the cross-sectional shape of the first slide member 2 is arcuate, the sliding surface 2
The angle δ at the corner where a and the outer surface 21 intersect is small;
Since the wall thickness of this part is thin, there was a problem that it was not possible to machine the screw thread 14 etc. with high precision in this part, but in the case of the open core of this example, the first slide member 2
A trapezoidal part b, which has a cross-sectional shape, is formed by a main sliding surface 20a and side sliding surfaces 20b, 20b, and is connected to an arcuate part c formed by the inner surface of the molded product via a line segment a. Because of the shape, the angle δ between the outer surface 21 and the side sliding surface 20b is large, and the wall thickness in this part is thicker, which has the advantage that the screw thread 14 etc. can be machined with high precision also in this part. There is. Further, according to the open core of this example, the corner portion where the extended side sliding surface 2b of the first sliding member 2 intersects the outer surface 21 is unlikely to be chipped or damaged.

"Other Embodiments of the Invention" FIG. 3 shows a second embodiment of the invention, in which the same components as those of the first embodiment shown in FIGS. 1 and 2 are given the same reference numerals. to simplify the explanation.

The open core of this example is for molding a molded product 16 having an internal thread similar to that of the first example.
In this case, the inner surface of the molded product 16 is divided into eight parts, and four first slide members 2 and four second slide members 3 are provided. The angle γ between the main sliding surface 20a and the side sliding surface 20b of the first slide member 2 in this example is 135°<γ<180° for the same reason as in the first embodiment. It is formed like this.

In the case of the open core of this example, in addition to obtaining the same effect as that of the first example, the side sliding surface 2
Since the angle δ between 0b and the outer surface 21 is made larger than that of the first embodiment, there is an advantage that this corner can be processed with higher precision.

Note that the open core of the present invention is not limited to the above-mentioned embodiments, and for example, in the above embodiment, only the open core for molding the molded product 16 having an internal thread was shown as an example. The open core of the present invention can also be used as an open core for molding a molded product whose inner surface is square or other polygonal. In that case, slide members 2..., 3...
The shapes of the ... are so defined that when they are in the injection molded configuration they form a shape that corresponds to the inner surface of the molded article.

"Effects of the Invention" As explained above, the open core of this invention has
The sliding surface of one of the first sliding members, of the first sliding members and the second sliding members arranged alternately around the stationary core rod having a conical outer surface, is defined by at least three flat surfaces. With this configuration, the position of the first slide member with respect to the core rod is regulated not only by the dovetail engagement but also by the sliding surface. Therefore, in the first sliding member, there is little wear on the dovetail grooves that form the dovetail engagement, and even if these are worn out, their position is regulated by the sliding surface and no misalignment occurs. from,
According to this open core, it is possible to manufacture a high-quality molded product with few burrs or steps on the inner surface.

Furthermore, in the open core of the present invention, since the angle between the main sliding surface and the side sliding surface of the first sliding member is set to less than 180 degrees, the side sliding surface of the first sliding member is extended. The angle at the corner where the outer surface intersects with the outer peripheral surface becomes larger, and the wall thickness of this corner becomes thicker.
Therefore, according to the open core of the present invention, chipping and breakage of the front corner of the first slide member are reduced.

That is, according to the open core of the present invention, chipping and breakage of the corners of the first slide member can be reduced in the open core in which the first slide member and the outer surface of the core rod are dovetailed.

[Brief explanation of drawings]

1 and 2 show a first embodiment of the open core of the present invention, in which FIG. 1 is a plan view showing the injection molding state, FIG. 2 is a plan view showing the mold opening state, and FIG. 3 is a plan view showing a second embodiment of the present invention, FIGS. 4 to 8 show a conventional open core, FIG. 4 is a plan view showing an injection molding state, and FIG. 5 is a plan view showing a conventional open core. FIG. 6 is a plan view showing the mold opening state, FIG. 6 is a sectional view taken along the - line in FIG. 4, FIG. 7 is a sectional view taken along the - line in FIG. It is a sectional view showing a state. 1... Core rod, 2... First slide member, 3...
...Second slide member, 7a, 7b...Outer surface, α,
β...Angle, 8...Dovetail groove, 9...Yes, 20...
...Sliding surface, 20a...Main sliding surface, 20b...Side sliding surface.

Claims (1)

[Scope of Claims] 1. A stationary core rod having a conical outer surface.
The slide members and the second slide members are arranged alternately, and the angle of the outer surface of the core rod that the first slide member contacts with the core rod axis is set to be smaller than the angle of the outer surface of the core rod that the second slide member contacts with the core rod axis. The slide members are formed to be small in size and each slide member is guided axially along the slope of the outer surface of the core rod so that the slide members are slid along the axis of the core rod from the injection molded arrangement. When the core rod is moved to an open position closer to the axis of the core rod, dovetail grooves are provided on the outer surface of the core rod and the sliding surface of the first slide member in contact therewith along the sliding direction. In an open core in which these are dovetailed and engaged, a portion of the sliding surface of the first slide member that contacts the core member is a main sliding surface that includes the portion provided with the dovetail or dovetail groove. It is formed by at least three flat surfaces of the side sliding surfaces on both sides, the angle between the side sliding surfaces and the main sliding surface is less than 180 degrees, and the sliding surface of the first sliding member is An open core characterized in that the outer surface of the core rod is formed so as to be in sliding contact.