JP3410331B2 - Equipment for manufacturing low-melting metal cores - Google Patents

Description

Detailed Description of the Invention

[0001]

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

[0002]

2. Description of the Related Art A plastic product may have a hollow portion or an undercut shape because of its function and integration of parts. It is generally difficult to integrally mold a plastic product having such a shape, and various ideas have been made in molding. One of them is to use lost core. This is a low melting point alloy core that has the same internal shape as the hollow part and undercut part of the product, that is, lost core, and set it in the mold for plastic molding and mold the plastic around the core, This is a method in which the lost core is later eluted to obtain a product having a predetermined shape. This lost core is often made of an alloy of Bi, Sn, Pb, etc. by casting. However, when trying to make 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.

In order to improve this, the applicant of the present invention has disclosed in Japanese Patent Laid-Open No.
A method for producing a low melting point metal core as disclosed in Japanese Patent Publication No. 38761 has been developed. The method is based on hollowing the lost core to reduce the weight, 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 point metal in the holding furnace is pushed up into the cavity of the mold through the stoke to perform casting and It is maintained for a certain period of time, and while the unsolidified molten metal remains in the center part, the molten metal push-up casting is canceled, and the loose piece is pulled out from the ceiling part of the mold to introduce the 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 with both ends open, but when casting a bag-shaped product with only one end open, pressurization is performed during solidification of the molten metal. Since the outer circumference of the lost core is solidified even after the release, air does not enter the mold cavity from the outside (such as the mold gap), and it is difficult for unsolidified metal to return to the holding furnace, and the return timing is not constant. . Therefore, there is a problem that a stable hollow product cannot be obtained. If it is not a stable hollow product, the thickness of the lost core will not be constant and it will not be able to withstand the molding pressure during plastic molding, or it will deform,
There is a problem that the elution conditions after molding are not constant and automation is difficult to achieve. In order to improve productivity, it is necessary to lower the mold temperature to shorten the solidification time of the molten metal in the cavity, but the above method has a built-in heater in the loose piece, so rapid cooling of the mold is required. Is difficult.

[Problems to be Solved by the Invention]

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

[Means for Solving the Problems]

In order to solve the above-mentioned problems, the present invention provides a die of a low-pressure casting machine, a through hole having one end opened to a cavity of the die and the other end opened to an upper surface of the die, and one end of the die. A gas introduction hole, which is connected to the through hole and has the other end opened to the side surface of the mold, is bored, and a loose piece having a sharp tip is slidably inserted into the through hole. Then, while the tip of the loose piece is projected into the cavity of the mold, the molten metal of the low melting point metal in the holding furnace is pushed up into the cavity through the stoke to perform casting, and the molten metal filling state is maintained for a predetermined time, With the unsolidified molten metal remaining in the central portion, the push-up casting of the molten metal is canceled, and the loose piece is pulled up so that the gas introduction hole and the through hole communicate with each other so that the outside air is introduced into the cavity.

[0007]

Embodiment 1 An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a longitudinal sectional view of an essential part of a low melting point metal core manufacturing apparatus according to the present invention, and FIGS. In the figure, reference numeral 1 is a closed holding furnace, and the molten metal 2 in the holding furnace 1 is held at a constant temperature by a heater 3 whose temperature is controlled by a temperature detecting means and a control device (not shown). Reference numeral 4 denotes a stalk, and a lower portion of the stalk 4 is immersed in the molten metal 2 in the holding furnace 1, and an upper portion thereof penetrates the holding furnace 1 and projects upward. A die 7 including an upper die 5 and a lower die 6 is placed and disposed on the lower die base 8 above the stalk 4, and an upper end portion of the stalk 4 has a central opening portion of the lower die base 8. And is in pressure contact with the sprue 12 of the mold 7.

A gate-shaped frame 13 is provided on the lower die base 8.
Is installed upright, and a mold opening / closing cylinder 14 is attached downward to the ceiling of the frame 13. A 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 raised and lowered by the expansion and contraction operation of the piston rod 15. In the holding furnace 1, a pipe 17 is provided 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 the molten metal 2 through the stalk 4 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, and the through holes 19 are formed.
The lower end of each of them is opened at an appropriate position of the cavity 18 of the mold 7. Each of the through holes 19 is connected to the other end of a gas introduction port 21 that is horizontally formed in the upper mold 5 so that one end of the through hole 19 opens on the side wall of the upper mold 5, and the atmosphere introduces the gas. Mouth 2
1 and the through hole 19 so as to be able to flow into the cavity 18. A round rod-shaped loose piece 22 (see FIG. 4A) having a sharpened tip 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 causes the loose hole 22 and the gas introduction port. When the piston rod 24 contracts and moves in the opposite direction while blocking the communication with 21, the tip of the loose piece 22 connects with the through hole 19 and the gas introduction port 21. It is designed so that it will rise up to the vicinity of the connection point of and connect them.

In the apparatus constructed as described above, the piston rod 15 of the mold opening / closing cylinder 14 is extended to close the die 7, and then the piston rod 24 of the cylinder 23 is extended to operate the loose piece 22. The tip projects into the cavity 18 of the mold 7 by a predetermined size. Next, the inside of the holding furnace 1 is pressurized with compressed gas by a control device (not shown), and the molten metal 2 is pushed up and filled into the cavity 18 through the stalk 4. The state of the portion A in FIG. 1 at that time is shown in FIG. After the pressurization is maintained for a predetermined time, the pressurization is released, and the piston rod 24 of the cylinder 23 is contracted and retracted so that the through hole 19 and the gas introduction port 21 communicate with each other. Inflowing, the unsolidified metal 2 in the cavity 18 and the stalk 4 smoothly returns to the holding furnace 1 due to the pressure of the atmosphere. The state of the portion A in FIG. 1 at that time is shown in FIG. 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, the low melting point metal 2 (Sn
43 wt% -Bi 57 wt% alloy: melting point 138
C.) in the holding furnace 1 at 180.degree. C., the inside of the furnace 1 is pressurized with compressed air to fill the mold 7 with a mold temperature of 50.degree. C., and the pressure is applied for 30 seconds, and then the pressure is released. Loose Piece 22
Was pulled up and the unsolidified molten metal 2 was returned into the furnace 1. When the molten metal 2 is filled in all the cavities 18 and solidified, the weight becomes 10 kg.
A hollow lost core W having a very small weight variation of 5 kg was obtained. It should be noted that the lost core W had a hole at the tip abutting portion of the loose piece 22. When a plastic product was molded with the lost core W thus obtained, it could be stably molded without a problem of deformation.

[0012]

Second Embodiment FIG. 4B shows a modification of the loose piece 22 used in the device of the present invention. The loose piece 22 is similar to that of the first embodiment except that the tip thereof is formed as a stepped portion having a small diameter and the stepped portion is sharpened at an angle of 30 °. When the loose piece 22 was cast in the same manner as in Example 1, the result was 7.2 ± 0.2 k.
A hollow lost core W having a smaller weight variation than that of 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
2 is the same as Example 1 except that its tip is sharpened at an angle of 50 °. When casting was performed in the same manner as in Example 1 using the loose piece 22, no hole was formed in the loose piece 22 tip abutting portion of the obtained lost core W. The weight of the obtained lost core W is 7.5 to 9.
There was a large variation of 7 kg, and the inside of the heavy one was not hollow enough.

[0014]

Comparative Example 2 FIG. 4D shows a modified example of the loose piece 22 used for comparison. The loose piece 22 has a square cross section and its tip is sharpened at an angle of 90 °. When casting was performed in the same manner as in Example 1 using the loose piece 22, no hole was formed in the loose piece 22 tip abutting portion of the obtained lost core W. Further, the weight of the obtained lost core W varied widely from 7.7 to 9.8 kg, and the inside of the heavy weight one was not sufficiently hollow.

[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 plastic molding is stable,
Elution can be automated easily. Further, since the loose piece used in the present invention does not use a heater, the mold can be rapidly cooled, and the productivity is improved. As is clear from the above-mentioned Examples and Comparative Examples, the tip of the loose piece is 4
It is necessary to sharpen at an angle of 5 ° or less, preferably 30 ° or less. When the angle is more than that, the heat capacity of the tip of the loose piece becomes large, and the molten metal around the tip solidifies, so that even if the loose piece is pulled up, it is difficult for the outside air to enter the cavity.

In the above embodiment, the loose piece has a round bar-shaped body and a conical tip part, but the barrel part may have a rectangular bar shape and the tip part may have a pyramidal shape. If the tip is formed as a stepped part with a small diameter, the body part may be round bar shaped to have a pyramidal shape, or conversely, the body part may be shaped like a square bar to have a conical shaped tip part. Good. In addition, loose pieces are
The inside may be hollow, or the material may have a smaller heat capacity than a metal mold such as ceramics. This allows
During casting, the temperature of the tip easily rises, the solidification of the molten metal in the vicinity of the tip becomes slower than that in 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. Although the casting method is low pressure casting in the above embodiment, not only low pressure casting but also suction casting, pressure casting with a plunger, or a combination thereof may be used as long as the effects of the present invention are not impaired. Other various variations are possible without departing from the spirit of the present invention.

[Brief description of drawings]

FIG. 1 is a vertical cross-sectional view of a main part of a device of the present invention.

FIG. 2 is an enlarged view of a portion of FIG. 1A, showing a state at the time of filling molten metal.

FIG. 3 is an enlarged view of a portion of FIG. 1A, showing a state in which unsolidified molten metal is discharged.

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

FIG. 4 (B) is a modification of the loose piece used in the device 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]

1 holding furnace 2 molten metal 4 Stoke 7 mold 18 cavities 19 through holes 21 gas inlet 22 Loose Piece

Claims (5)

(57) [Claims] 1. A stalk 4 is raised by pressurizing a molten metal 2 of a low melting point metal stored in a holding furnace 1.
A low melting metal core manufacturing apparatus for filling and molding the molten metal 2 in a cavity 18 of a mold 7 arranged at an upper part, wherein one end of the mold 7 is punched in the mold 7. A through hole 19 which is open to the cavity 18 and the other end of which is opened to the upper surface of the mold 7, and which is also formed in the mold 7 so that one end is connected to the through hole 19 and the other end is connected to the mold. The mold 7 is provided with a gas introduction hole 21 opening to the side surface, 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 projecting in 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 sharpened at an angle of 30 ° or less. 3. The loose piece 22 is formed with a stepped portion having a small diameter at the tip thereof, and the stepped portion is sharpened at an angle of 30 ° or less. Low melting point metal core manufacturing equipment. 4. The low melting point metal core manufacturing apparatus according to claim 1, wherein the material of said loose piece 22 has a smaller heat capacity than that of said mold 7. 5. The loose piece 22 is formed in a hollow rod shape.
The low melting metal core manufacturing apparatus described.