JPH115150A - Manufacturing device for low-melting metal core - Google Patents

Abstract

PROBLEM TO BE SOLVED: To steadily cast a lost-core shaped like a sack having an opening at only one end by installing inlets for gas on holes drilled from the top of a mold through a cavity of the mold, and inserting sharp-point loose pieces into the holes allowing free-sliding. SOLUTION: The mold 7 is closed by extending a piston rod of a cylinder for opening/closing the mold. By extending the piston rod, the tips of the loose pieces 22 are stuck out to the cavity 18 of the mold 7 by a given length. The inside of a storage furnace is pressurized by compressed gas, and molten steel is pushed up via a stoke to the cavity 18 to be filled. Upon releasing the pressure, the piston rod of the cylinder is drown back so that the holes 19 and the inlets 21 for gas are connected. The air flows into the cavity 18. By the pressure of the air, non-solidified metal in the cavity 18 and the stoke return smoothly into the storage furnace. After a product W is sufficiently cooled in the mold 7, the mold 7 is opened to remove the product W.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus for manufacturing a low-melting metal core used for molding plastic.

[0002]

2. Description of the Related Art A plastic product may have a hollow portion or an undercut shape in terms of function or integration of components. It is generally difficult to integrally mold a plastic product having such a shape, and various attempts have been made in molding. One of them is to use a lost core. This makes a core of a low melting point alloy with the same internal shape as the hollow part and the undercut part of the product, that is, a lost core, set it in a mold for plastic molding, mold plastic around the core, Later, the lost core is eluted to obtain a product having a predetermined shape. This lost core is often made by casting with an alloy made of Bi, Sn, Pb or the like. However, when an attempt is made to produce a large plastic product, the lost core becomes large and the weight becomes very heavy, which makes it difficult to handle and takes a long time to elute.

[0003] The present applicant has proposed in Japanese Patent Application Laid-Open
A method for producing a low-melting metal core as disclosed in Japanese Patent No. 38761 was developed. The method aims to reduce the weight by hollowing the lost core, and more specifically,
With the loose piece with built-in heater fitted and inserted into the ceiling of the mold, the molten metal of the low-melting metal in the holding furnace is pushed up to the cavity of the mold via the stalk, and casting is performed. By maintaining the predetermined time, the unsolidified molten metal is left in the central part, the casting of the molten metal is lifted and the casting is released, and the loose piece is pulled out from the ceiling of the mold to introduce outside air into the mold cavity. The solidified molten metal is returned to the holding furnace.

However, the above method is suitable for casting a cylindrical lost core having both ends opened. However, when casting a bag-shaped product having only one end opened, pressurization is required during the solidification of the molten metal. Even if it is released, the outer periphery of the lost core is solidified, so air does not enter the mold cavity from the outside (gap between the molds), and it is difficult for unsolidified metal to return to the holding furnace, and the return timing is not constant. . For this reason, there was a problem that a stable hollow product was not obtained. If it does not become a stable hollow product, the wall thickness of the lost core will not be constant and it will not be able to withstand the molding pressure when molding plastic,
There is a problem that the elution conditions after molding are not constant and automation is difficult to achieve. In order to increase productivity, it is necessary to lower the temperature of the mold to shorten the solidification time of the molten metal in the cavity. However, the above method incorporates a heater in the loose piece, so rapid cooling of the mold Is difficult.

[Problems to be solved by the invention]

The present invention has been made in view of the above problems, and an object of the present invention is to provide an apparatus capable of casting a stable hollow product even when casting a bag-shaped lost core having only one end opened. The purpose is.

[Means for Solving the Problems]

In order to solve the above-mentioned problems, the present invention provides a mold for a low-pressure casting machine, wherein a through hole having one end opening to the cavity of the mold and the other end opening to the upper surface of the mold is provided. A gas introduction hole which is connected to the through hole and has the other end opened on the side surface of the mold is formed, and a loose piece having a sharpened tip is slidably inserted into the through hole. Then, while the tip of the loose piece is protruding into the cavity of the mold, the molten metal of the low melting point metal in the holding furnace is pushed up to the cavity through the stalk to perform casting, and the filled state of the molten metal is maintained for a predetermined time, With the unsolidified molten metal remaining in the central part, the casting of the molten metal is lifted to cancel the casting, and at the same time, the loose piece is pulled up to allow the gas introduction hole to communicate with the through hole so that outside air is introduced into the cavity.

[0007]

Embodiment 1 Hereinafter, an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a longitudinal sectional view of a main part of an apparatus for producing a low melting point metal core according to the present invention, and FIGS. 2 and 3 are enlarged views of a part A in FIG. In the drawing, reference numeral 1 denotes a closed holding furnace, and a molten metal 2 in the holding furnace 1 is maintained at a constant temperature by a temperature detector (not shown) and a heater 3 whose temperature is controlled by a control device. Reference numeral 4 denotes a stalk. The lower part of the stalk 4 is immersed in the molten metal 2 in the holding furnace 1 and the upper part thereof penetrates the holding furnace 1 and protrudes upward. A mold 7 composed of an upper mold 5 and a lower mold 6 is mounted on the lower die base 8 above the stalk 4, and the upper end of the stalk 4 is located at the center opening of the lower die base 8. Through the sprue 12 of the mold 7.

On the lower die base 8, a gate-shaped frame 13 is provided.
A mold opening / closing cylinder 14 is attached to the ceiling of the frame body 13 in a downward direction. The piston rod 15 of the cylinder 14 is connected to the upper die 5 via an upper die base 16, and the upper die 5 can be moved up and down by the expansion and contraction operation of the piston rod 15. The holding furnace 1 is provided with a pipe 17 from a pressure control device (not shown).
Then, compressed air is supplied, and the compressed air pressurizes the inside of the furnace 1 to push up the molten metal 2 through the stalk 4 and into the cavity 18 of the mold 7.

Two through-holes 19 are vertically formed through the upper die base 16 and the upper die 5.
Are opened at appropriate places in the cavity 18 of the mold 7. Each of the through holes 19 is connected in communication with the other end of a gas inlet 21 formed in the upper die 5 horizontally so that one end opens to the side wall of the upper die 5. Mouth 2
1 and the through hole 19 so as to be able to flow into the cavity 18. A round bar-shaped loose piece 22 (see FIG. 4A) whose tip is pointed at an angle of 30 ° is slidably inserted into the through hole 19. The loose piece 22
Is connected to a piston rod 24 of a cylinder 23 installed downward on the upper die base 16, and when the piston rod 24 is extended, the loose piece 22 is connected to the through hole 19 and the gas inlet port. When the piston rod 24 contracts and contracts, the tip of the loose piece 22 is connected to the through hole 19 and the gas inlet 21. Is raised up to the vicinity of the connection point to connect the two.

In the apparatus constructed as described above, the piston rod 15 of the mold opening / closing cylinder 14 extends to close the mold 7, and then the piston rod 24 of the cylinder 23 extends to actuate the loose piece 22. The tip protrudes into the cavity 18 of the mold 7 by a predetermined size. Next, the holding furnace 1 is pressurized with a compressed gas by a control device (not shown), and the molten metal 2 is pushed up and filled into the cavity 18 via the stalk 4. FIG. 2 shows the state of FIG. 1A at that time. After the pressurization is maintained for a predetermined time, the pressurization is released, and the piston rod 24 of the cylinder 23 is contracted to communicate the through hole 19 and the gas inlet 21. Then, the unsolidified metal 2 in the cavity 18 and the stalk 4 is smoothly returned to the holding furnace 1 by the pressure of the atmosphere. FIG. 3 shows the state of FIG. 1A at that time. When the product W is sufficiently cooled in the mold 7, the mold 7 is opened and the product W is taken out.

Using the above apparatus, low melting point metal 2 (Sn)
43 wt% -Bi 57 wt% alloy: mp 138
C.) in a holding furnace 1 at 180 ° C., pressurizing the inside of the furnace 1 with compressed air to fill a mold 7 having a mold temperature of 50 ° C. and pressurizing for 30 seconds, then releasing the pressing force and Loose piece 22
To return the unsolidified molten metal 2 into the furnace 1. When the molten metal 2 is filled into the entire cavity 18 and solidified, the weight becomes 10 kg.
A hollow lost core W having a very small variation in weight of 5 kg was obtained. In addition, a hole was made in the contact portion of the loose piece 22 at the tip of the lost core W. When a plastic product was molded with the lost core W thus obtained, the plastic product could be molded stably without any deformation problem.

[0012]

Embodiment 2 FIG. 4B shows a modification of the loose piece 22 used in the apparatus of the present invention. The loose piece 22 is the same as that of the first embodiment except that the tip is formed in a small-diameter stepped portion, and the stepped portion is pointed at an angle of 30 °. When the loose piece 22 was cast in the same manner as in Example 1, 7.2 ± 0.2 k
g, a hollow lost core W having less variation in weight than in Example 1 was obtained.

[0013]

Comparative Example 1 FIG. 4C shows an example of the loose piece 22 used for comparison. The loose piece 2
Reference numeral 2 is the same as the first embodiment except that the tip is pointed at an angle of 50 °. Casting was performed using the loose piece 22 in the same manner as in Example 1. As a result, no hole was found in the contact portion at the tip of the loose piece 22 of the obtained lost core W. The weight of the obtained lost core W is 7.5 to 9.9.
The variation was as large as 7 kg, and the inside of a heavy one was not sufficiently hollow.

[0014]

Comparative Example 2 FIG. 4D shows a modification of the loose piece 22 used for comparison. The loose piece 22 has a square cross section and a tip pointed at an angle of 90 °. Casting was performed using the loose piece 22 in the same manner as in Example 1. As a result, no hole was found in the contact portion at the tip of the loose piece 22 of the obtained lost core W. Moreover, the weight of the obtained lost core W varied greatly from 7.7 to 9.8 kg, and the heavy one did not have a sufficiently hollow inside.

[0015]

According to the present invention as described above, a stable hollow product can be obtained even when casting a bag-shaped lost core having only one end opened, and the molding of plastic is also stable.
It is easy to automate elution. Further, since the loose piece used in the present invention does not use a heater, rapid cooling of the mold becomes possible, and productivity is improved. As is clear from the above Examples and Comparative Examples, the tip of the loose piece
It is necessary to sharpen the angle to 5 ° or less, preferably 30 ° or less. If the angle is larger than this, the heat capacity at the tip of the loose piece increases, and the molten metal around it loosens, making it difficult for outside air to enter the cavity even if the loose piece is pulled up.

In the above embodiment, the loose piece has a round bar shape and a conical tip, but the loose piece may have a square rod shape and the tip may have a pyramid shape. In addition, as for the one whose tip is formed in a stepped portion having a small diameter, the tip is made into a pyramid shape by making the body a round bar, or the tip is made conical by making the body into a square bar. Good. Loose pieces are also
The inside may be hollow or the material may have a smaller heat capacity than a mold such as ceramics. This allows
During casting, the temperature of the tip is likely to rise, the solidification of the molten metal near the tip is slower than that of the surroundings, and the loose piece is smoothly pulled up from the mold cavity. Further, in the above embodiment, two loose pieces are used, but the number can be increased or decreased depending on the shape of the lost core. In the above embodiment, the casting method is performed by low pressure casting. However, as long as the effects of the present invention are not impaired, not only low pressure casting but also suction casting, pressure casting using a plunger, or a combination thereof may be used. Various other variations are possible without departing from the spirit of the present invention.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view of a main part of the apparatus of the present invention.

FIG. 2 is an enlarged view of a part A of FIG. 1 and shows a state at the time of filling a molten metal.

FIG. 3 is an enlarged view of FIG. 1A and shows a state in which unsolidified molten metal is discharged.

FIG. 4 (A) is an example of a loose piece used in the apparatus of the present invention.

FIG. 4 (B) is a modified example of the loose piece used in the apparatus of the present invention.

FIG. 4C is an example of a loose piece used for comparison.

FIG. 4D is a modification of the loose piece used for comparison.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Holding furnace 2 Molten metal 4 Stoke 7 Mold 18 Cavity 19 Through hole 21 Gas introduction hole 22 Loose piece

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[Procedure amendment]

[Submission date] August 22, 1997

[Procedure amendment 1]

[Document name to be amended] Drawing

[Correction target item name] All figures

[Correction method] Change

[Correction contents]

FIG. 2

FIG. 3

FIG.

FIG. 4 ────────────────────────────────────────────────── ───

[Procedure amendment]

[Submission date] September 18, 1997

[Procedure amendment 1]

[Document name to be amended] Drawing

[Correction target item name] All figures

[Correction method] Change

[Correction contents]

FIG. 2

FIG. 3

FIG.

FIG. 4

Claims (5)

[Claims] 1. A low melting point metal melt (2) stored in a holding furnace (1) is pressurized to rise in a stalk (4).
An apparatus for manufacturing a low-melting metal core in which the molten metal 2 is filled into a cavity 18 of a mold 7 disposed at an upper portion thereof to form the same. A through hole 19 opening into the cavity 18 and the other end opening into the upper surface of the mold 7; and a through hole 19 also formed in the mold 7, one end of which is connected to the through hole 19 and the other end is connected to the mold. A gas introduction hole 21 opening on the side surface of the mold 7; and a loose piece 22 slidably inserted into the through hole 19 with the tip sharpened at an angle of 45 ° or less. Is reciprocally movable between a position protruding into the cavity 18 of the mold 7 and the vicinity of a communication connection point between the through hole 19 and the gas introduction hole 21. Equipment for manufacturing melting point metal cores. 2. The low melting point metal core manufacturing apparatus according to claim 1, wherein the tip of the loose piece 22 is pointed at an angle of 30 ° or less. 3. The method according to claim 1, wherein the tip of the loose piece 22 is formed in a step portion having a small diameter, and the step portion is pointed at an angle of 30 ° or less. Equipment for manufacturing low melting metal cores. 4. The apparatus according to claim 1, wherein said loose piece has a smaller heat capacity than that of said mold. 5. The loose piece 22 is formed in a hollow rod shape.
An apparatus for producing a low-melting metal core as described in the above.