MOLD APPARATUS FOR HIGH PRESSURE CASTING

Abstract

A mold apparatus for high pressure casting includes an upper mold having an internal space filled with a molten metal and a core pin elevating groove at an inner wall of the upper mold. A lower mold is disposed at a lower part of the upper mold and fixed with an insert. A core pin portion is elevatably installed in the core pin elevating groove to be elevated depending on a filling pressure of the molten metal filled in the internal space.

Description

CROSS REFERENCE TO RELATED APPLICATION

The present application claims the benefit of priority to Korean Patent Application No. 10-2015-0170023, filed on Dec. 1, 2015, the entire content of which is incorporated herein for all purposes by this reference.

TECHNICAL FIELD

The present disclosure relates to a mold apparatus for high pressure casting, and more particularly, to a mold apparatus for high pressure casting having improved durability and quality by preventing an insert portion coupled to a core pin from being exposed to outside when a casting into which an insert is inserted is manufactured by high pressure casting.

BACKGROUND

Generally, a core pin is used to cast a casting into which an, insert is inserted or a casting having a hollow portion. As a representative example of the core pin, there is a resin-coated sand core used for low pressure and gravity casting.

On the other hand, high pressure casting has a casting production cycle time shorter than that of other casting methods, and therefore, is suitable for mass production of the casting. As a core for the high pressure casting, instead of using the sand core whose strength is weak, a mold core pin which can bear a high pressure is used.

FIG. 1 is a photograph showing an existing insert exposed to an outside of a core pin insertion portion, after a casting is taken out.

As illustrated in FIG. 1, when the casting is casted under a high pressure by supporting the insert using the above-mentioned core pin, a part of the insert fixed and supported by the core pin after the casting is taken out is not filled with molten metal, and therefore, may be exposed to outside.

When the insert is exposed to the outside, the exposed part may be corroded, or water or oil may be leaked to the outside.

Therefore, a method for inserting a cap made of a silicon or rubber material into the insert, which is exposed to the outside due to the core pin used to fix the existing insert to protect the exposed part, has been used.

However, the method may degrade durability and quality of the casting, that is, a finished product in the end and increase man hours due to a post-processing operation such as cap insertion to increase manufacturing costs.

SUMMARY

An object of the present disclosure is to provide a mold apparatus for high pressure casting capable of preventing exposure of an insert due to the fact that a core pin insertion portion is not filled with a molten metal when a casting into which the insert is inserted is manufactured by high pressure casting.

According to an exemplary embodiment in the preset disclosure, a mold apparatus for high pressure casting includes an upper mold having an internal space filled with a molten metal and a core pin elevating groove at an inner wall of the upper mold; a lower mold disposed at a lower part of the upper mold and fixed with an insert; and a core pin portion elevatably disposed in the core pin elevating groove to be elevated depending on a filling pressure of the molten metal filled in the internal space.

The core pin portion may include: a fixed bar having one side inserted into and fixed to the core pin elevating groove; a core pin disposed at another side of the fixed bar to be elevated along an inner circumferential surface of the core pin elevating groove; and a spring having one side fixed to the core pin and another side fixed to an inner circumferential surface of a ceiling of the core pin elevating groove to provide an elastic force to the core pin.

The spring may satisfy a spring constant value calculated by the following Equation:

spring constant=casting pressure x core pin area/core pin moving distance.

The spring may be made of any one of a spring steel, an oil-tempered wire for a valve spring, a hard drawn steel wire, a piano wire, and a stainless steel wire that have a lateral modulus of 7000 to 8000 kgf/mm².

The molten metal filled in the internal space may be filled at a pressure of 10 to 1000 kg/cm².

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a photograph showing an existing insert exposed to outside of a core pin insertion portion after a casting is taken out.

FIG. 2 is a cross--sectional view illustrating a mold apparatus for high pressure casting according to an exemplary embodiment in the present disclosure.

FIG. 3 is a diagram for describing an operation of the mold apparatus for high pressure casting according to the exemplary embodiment in the present disclosure.

FIG. 4 is a photograph showing a core pin according to an exemplary embodiment in the present disclosure.

FIG. 5 is a photograph showing a core pin insertion portion after the casting manufactured using the mold apparatus for high pressure casting according to the exemplary embodiment in the present disclosure is taken out.

DETAILED DESCRIPTION

Terminologies used herein are to mention only a specific exemplary embodiment, and are not to limit the present disclosure. Singular forms used herein include plural forms as long as phrases do not clearly indicate an opposite meaning. A term “ including” used in the present specification concretely indicates specific properties, regions, integer numbers, steps, operations, elements, and/or components, and is not to exclude presence or addition of other properties, regions, integer numbers, steps, operations, elements, components, and/or a group thereof.

All terms including technical terms and scientific terms used herein have the same meaning as the meaning generally understood by those skilled in the art to which the present disclosure pertains unless defined otherwise. Terms defined in a generally used dictionary are additionally interpreted as having the meaning matched to the related art document and the currently disclosed contents and are not interpreted as ideal or formal meaning unless defined.

Hereinafter, a mold apparatus for high pressure casting according to an embodiment in the present disclosure will be described with reference to the accompanying drawings.

Generally, to prevent an insert from being moved or deformed upon high pressure casting, a casting into which the insert is inserted is cast by fixing a total of three points, that is, two points of the insert fixed in a lower mold and one point thereof fixed in a core pin.

According to an exemplary embodiment in the present disclosure, durability and quality of the casting into which the manufactured insert is inserted may be improved by preventing the exposure of the insert to the outside due to the fact that the part into which the core pin for fixing the insert is inserted is not filled with a molten metal.

FIG. 2 is a cross-sectional view illustrating a mold apparatus for high pressure casting according to an exemplary embodiment in the present disclosure, FIG. 3 is a diagram for describing an operation of a mold apparatus for high pressure casting according to an exemplary embodiment in the, present disclosure, and FIG. 4 is a photograph showing a core pin according to an exemplary embodiment in the present disclosure.

As illustrated in FIGS. 2 to 4, a mold apparatus for high pressure casting includes an upper mold 100, a lower mold 200 to which an insert 10 is fixed, and a core pin portion 300 elevatably installed in the upper mold 100 to selectively support the insert 10.

The upper mold 100 has an internal space 120 filled with a molten metal and includes at least one core pin elevating groove 110 so that a ceiling thereof may have the core pin portion 300.

The core pin portion 300 is elevatably installed along an inner circumferential surface of the core pin portion 300 depending on whether the internal space 120 is filled with the molten metal, and thus, descends in a direction of the insert 10. Therefore, core pin portion 300 may support the insert 10 when the molten metal is not filled, and the core pin portion 300 moves up along an inner circumferential surface of the core pin elevating groove 110 by a pressure of the molten metal filled in the internal space 120 when the molten metal is filled.

Therefore, a core pin insertion portion of the internal space 120 may be also filled with the molten metal to prevent the insert 10 from being exposed to outside.

The core pin portion 300 includes a fixed bar 310 having one side fixed to a ceiling of the core pin elevating groove 110, a core pin 320 installed at another side of the fixed bar 310 to be elevated along the core pin elevating groove 110, and a spring 330 providing an elastic force to the core pin 320 to provide a support force for supporting the insert 10.

The fixed bar 310 has a cylindrical shape and has one side fixed to a ceiling of the core pin elevating groove 110 and another side provided with a core pin separation preventing portion (not illustrated) to elevate the core pin 320 while preventing the core pin 320 from being separated and thus is coupled to the core pin 320.

The core pin 320 has a cylindrical shape having a diameter corresponding to that of the core pin elevating groove 110, in which the diameter ranges from 0.7 to 3.4 cm.

The spring 330 has one side fixed to the ceiling of the core pin elevating groove 110 and another side fixed to the core pin 320 to push the core pin 320 in the direction of the insert 10, thereby providing support force for supplying the M insert 10. Hereinafter, a material of the spring 330 used in the present disclosure is shown.

	TABLE 1
	Division	Kind of steel	Remarks
	Spring steel	SUP4/6/7/9/9A/10/	Hot forming
		11A
	Oil-tempered	SWO, SWO-V,	Cold forming
	wire for valve	SWOSC-V
	spring
	Hard drawn	SWB, SWC, SWP	Cold forming
	steel wire, piano
	wire
	Stainless steel	SUS302, SUS304,	Cold forming
	wire	SUS316/631

In one embodiment, a stainless steel wire having a lateral modulus (G) of 7000 to 8000 kgf/mm² is used as a material for the spring 330. Here, the spring 330 needs to be made of a material having excellent heat resistance to minimize deformation and damage of the spring 330 due to a hot molten metal.

Further, the spring 330 according to present disclosure is made of a material satisfying a spring constant (K) value calculated by the following Equation (1)

spring constant (K)=casting pressure (P)×core pin area (A)/core pin moving distance (S)   (1).

Generally, the diameter of the core pin 320 used upon the high pressure casting ranges from 0.7 to 3.4 cm and the pressure of the molten metal filled in the internal space 120, that is, a casting pressure (P) ranges from 10 to 1000 kg/cm².

Therefore, a force applied to the core pin 320 under the above casting pressure (P) is calculated by the following Equation (2):

force (N) applied to core pin=core pin area (A)×casting pressure (P)   (2).

Therefore, under the casting pressure (P) of 10 to 1000 kg/cm², the force N applied to the core pin having a diameter of 0.7 to 3.4 cm ranges from 0.385 to 9074.6 kg.

The core pin 320 needs to move up by at least 0.1 mm to prevent the insert 10 in the core pin insertion portion from being exposed to outside upon casting.

Therefore, the spring constant (K) value that may move the spring 330 by 0.1 mm under the casting pressure P becomes a value obtained by dividing the force (N) applied to the core pin by the core pin moving distance (S).

That is, the spring constant (K) value of the spring according to the present disclosure may satisfy 38.5 to 90,746 kg/mm.

Therefore, when the internal space 120 of the upper mold 100 is filled with the molten metal, the core pin 320 moves up by at lea 0.1 mm by the pressure of the molten metal, that is, the casting pressure (P), by preventing the exposure of the insert 10 to the outside due to the fact that the core pin insertion portion is not filled with the molten metal. Thus, durability, appearance quality, or the like of the manufactured product are prevented from being degraded.

FIG. 5 is a photograph showing a core pin insertion portion after the casting manufactured using the mold apparatus for high pressure casting according to the exemplary embodiment of the present invention is taken out.

As illustrated in FIG. 5, the core pin 320 moves up by at least 0.1 mm by the pressure of the molten metal upon the high pressure casting and the internal space 120 is filled with the molten metal to prevent the insert 10 from being exposed, thereby manufacturing a product having excellent surface quality and durability.

According to the exemplary embodiments in the present disclosure, the core pin supporting the insert may naturally move back by the molten metal, and thus, the insert may be prevented from being exposed to the outside, thereby improving durability and quality of the casting into which the insert is inserted.

Further, unnecessary processes such as a core pin removing process and a cap inserting process may be omitted, thereby reducing saving manufacturing costs and time.

Although exemplary embodiments have been described with reference to the accompanying drawings, those skilled in the art will appreciate that various modifications and alterations may be made without departing from the spirit or essential feature of the present invention.

Therefore, it should be understood that the above-mentioned embodiments are not restrictive but are exemplary in all aspects. It is to be understood that the scope of the present invention will be defined by the claims rather than the above-mentioned description and all modifications and alternations derived from the claims and their equivalents are included in the scope of the present invention.

Claims

1. A mold apparatus for high pressure casting, comprising:

an upper mold having an internal space filled with a molten metal and a core pin elevating groove at an inner wall of the upper mold;

a lower mold disposed at a lower side of the upper mold and fixed with an insert; and

a core pin portion elevatably disposed in the core pin elevating groove to be elevated depending on a filling pressure of the molten metal filled in the internal space.

2. The mold apparatus for high pressure casting of claim 1, wherein the core pin portion includes:

a fixed bar having one side inserted into and fixed to the core pin elevating groove;

a core pin disposed at another side of the fixed bar to be elevated along an inner circumferential surface of the core pin elevating groove; and

a spring having one side fixed to the core pin and another side fixed to an inner circumferential surface of a ceiling of the core pin elevating groove to provide an elastic force to the core pin.

3. The mold apparatus for high pressure casting of claim 2, wherein the spring satisfies a spring constant value calculated by the following Equation:

spring constant=casting pressure×core pin area/core pin moving distance.

4. The mold apparatus for high pressure casting of claim 3, wherein the spring is made of any one of a spring steel, an oil-tempered wire for a valve spring, a hard drawn steel wire, a piano wire, and a stainless steel wire that have a lateral modulus of 7000 to 8000 kgf/mm2.

5. The mold apparatus for high pressure casting of claim 1, wherein the molten metal filled in the internal space is filled at a pressure of 10 to 1000 kg/cm2.

6. The mold apparatus high pressure casting of claim 1, wherein the core pin portion selectively supports the insert.