Low-pressure casting equipment

Abstract

A low-pressure casting apparatus provided with a lower mold 1 disposed above a holding furnace 50, an upper mold 2, a lower casting mold main part 1A that forms a cavity 7 between the lower casting mold main part 1A and a plurality of side molds 3-6 and in which the lower mold 1 forms the inner bottom surface of the cavity 7, and a lower base part 1B, the lower casting mold main part 1A having a sprue bush 8, at least one of the side molds 3-6 being capable of advancing and retreating with respect to the mold center, the lower base part 1B having a guide strut 10 for restricting the advancement position of the side mold 3-6 that is capable of advancing and retreating, and a horizontal-direction adjustment gap S being provided between the lower casting mold main part 1A and the lower base part 1B. The formation of an excessively large gap between casting molds due to thermal expansion of the lower mold 1 is prevented, and the mold-closing accuracy is improved.

Description

[Technical Field]

[0001] The present invention relates to an improvement in a low-pressure casting apparatus. [Background technology]

[0002] An example of a conventional low-pressure casting apparatus is described in Patent Document 1. The low-pressure casting apparatus described in Patent Document 1 includes a lower mold placed on a holding furnace, an upper mold that can be raised and lowered relative to the lower mold, and multiple horizontal molds that can move forward and backward relative to the center of the mold on the lower mold. The low-pressure casting apparatus forms a cavity between the lower mold, the lowered upper mold, and the advanced horizontal mold. The lower mold has a sprue portion that communicates with a stalk.

[0003] After closing the mold, the low-pressure casting machine applies pressure to the holding furnace, causing the molten metal in the holding furnace to pass through the stalk and the gate and fill the cavity. After the molten metal in the cavity cools and solidifies, the low-pressure casting machine opens the mold and releases the casting. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Publication No. 2007-319891 Summary of the Invention [Problem to be solved by the invention]

[0005] Generally, in a low-pressure casting apparatus equipped with a lower mold, a top mold, and a horizontal mold, a guide support is provided on the lower mold to restrict the forward position of the horizontal mold, and the temperature of the lower mold, which has a gate, becomes relatively high. For this reason, in conventional low-pressure casting apparatuses, the lower mold is prone to thermal expansion in the horizontal direction. When this thermal expansion occurs, the position of the guide support is displaced toward the outside of the mold, causing the forward position of the horizontal mold to shift forward. As a result, in conventional low-pressure casting apparatuses, there is a risk of a gap exceeding the clearance between the top mold and the horizontal mold, and solving this problem has been an issue.

[0006] The present invention has been made in response to the above-mentioned conventional problems, and aims to provide a low-pressure casting device that can prevent excessive gaps between molds caused by thermal expansion of the lower mold, thereby improving mold closing accuracy. [Means for solving the problem]

[0007] The low-pressure casting apparatus according to the present invention comprises a lower mold disposed on a holding furnace, an upper mold that can be raised and lowered relative to the lower mold, and multiple side molds disposed on the lower mold, forming a cavity between the lower mold, the upper mold, and the side molds. The lower mold comprises a lower mold essential part that forms the interior bottom surface of the cavity, and a lower mold base that holds the lower mold essential part. The lower mold essential part has a gate bushing that opens into the cavity. At least one of the side molds is movable forward and backward relative to the mold center, and the lower mold base has guide supports that regulate the forward position of the movable side mold. The low-pressure casting apparatus is characterized by providing a horizontal adjustment gap between the lower mold essential part and the lower mold base.

[0008] In a low-pressure casting apparatus with the above configuration, the temperature of the lower mold essential part containing the gate bushing becomes relatively high during casting, causing thermal expansion primarily in the horizontal direction. In response to this, the low-pressure casting apparatus divides the lower mold into the lower mold essential part and the lower mold base part, with an adjustment gap provided between the two parts. This adjustment gap absorbs the thermal expansion of the lower mold essential part and suppresses thermal deformation of the lower mold base part. This prevents displacement of the guide support columns in the lower mold base part, ensures the correct forward position of the retractable side molds, and prevents an excessive gap greater than the clearance between the side molds and the upper mold. [Effects of the Invention]

[0009] By adopting the above-described configuration, the low-pressure casting apparatus according to the present invention can prevent excessive gaps between the molds caused by thermal expansion of the lower mold, thereby improving mold closing accuracy. [Brief explanation of the drawings]

[0010] [Figure 1] FIG. 1 is a plan view of a lower mold showing a mold open state in a first embodiment of a low-pressure casting apparatus according to the present invention. [Figure 2] FIG. 2 is a vertical cross-sectional view showing the mold open state. [Figure 3] FIG. 2 is a plan view of the lower mold showing the mold closed state following FIG. [Figure 4] FIG. 3 is a vertical cross-sectional view showing the mold closed state following FIG. 2. [Figure 5] FIG. 5 is a vertical cross-sectional view showing a mold open state in a second embodiment of a low-pressure casting apparatus according to the present invention. [Figure 6] FIG. 2 is a plan view of the lower mold showing the mold open state. [Figure 7] FIG. 6 is a vertical cross-sectional view showing the mold closed state following FIG. 5. [Figure 8] FIG. 10 is a vertical cross-sectional view showing a mold closed state in a third embodiment of a low-pressure casting apparatus according to the present invention. [Figure 9] FIG. 9 is an explanatory circuit diagram showing a suction mechanism of the low-pressure casting apparatus shown in FIG. 8. DETAILED DESCRIPTION OF THE INVENTION

[0011] First Embodiment The low-pressure casting apparatus shown in Figures 1 and 2 includes a lower mold 1 arranged above a holding furnace 50, an upper mold 2 that can be raised and lowered relative to the lower mold 1, and a plurality of side molds 3 to 6 (four in the illustrated example) arranged above the lower mold 1. As shown in Figures 3 and 4, the low-pressure casting apparatus forms a cavity 7, which is a casting space, among the lower mold 1, upper mold 2, and the plurality of side molds 3 to 6. Note that Figures 2 and 4 only show the side molds 3 and 5 arranged on the left and right sides of the figures.

[0012] Although not shown in detail, the holding furnace 50 is a well-known furnace that stores molten metal and is equipped with a stalk through which the molten metal is filled, an internal pressurizing mechanism, and the like.

[0013] The lower mold 1 includes a lower mold portion 1A that forms the inner bottom surface of the cavity 7, and a lower mold base portion (die base) 1B that holds this lower mold portion 1A. The lower mold portion 1A in the illustrated example is square in plan view, with four gate bushings 8 arranged lengthwise and widthwise in the center. The lower portion of each gate bushing 8 communicates with the stalk of the holding furnace 50, and the upper portion of each gate bushing 8 opens to the cavity 7.

[0014] In the illustrated example, the lower mold 1 has a lower mold main part 1A with a downward step on its outer periphery, and a lower mold base part 1B with an upward step on the inner periphery of the part housing the lower mold main part 1A, and these two steps engage with each other. As a result, the lower mold main part 1A and the lower mold base part 1B are combined so that their upper surfaces are connected on the same plane, and a horizontal adjustment gap S is provided between them.

[0015] The upper mold 2 integrally comprises an upper mold main part 2A that forms the inner upper surface of the cavity 7 and an upper mold base part 2B, and is equipped with a release plate 9 that can be raised and lowered by a drive mechanism (not shown) and has a plurality of release pins 9A that penetrate the upper mold main part 2A from top to bottom. This release plate 9 can be raised and lowered by a drive mechanism separate from the drive mechanism for the upper mold.

[0016] At least one of the side dies 3-6 of the low-pressure casting apparatus according to the present invention can move forward and backward relative to the center of the die. The side dies 3-6 in the illustrated example have side mold portions 3A-6A that form the inner side surfaces of the cavity 7 and plates 3B-6B arranged on their backsides, and are arranged on all four sides of the cavity 7, and each can move forward and backward relative to the center of the die by a drive mechanism not shown. These side dies 3-6 are arranged at positions corresponding to each side of the square-shaped lower mold portion 1A.

[0017] In contrast, the lower mold base 1B of the lower mold 1 has guide posts 10 located outside the four corners of the square-shaped lower mold main part 1A, between adjacent side dies 3 to 6, that regulate the forward position of the retractable side dies 3 to 6. When each side dies 3 to 6 is advanced toward the mold center from the state shown in Fig. 1, these guide posts 10 abut against the plates 3B to 6B of the side dies 3 to 6, as shown in Fig. 3, thereby regulating the forward position of each side dies 3 to 6.

[0018] The low-pressure casting apparatus having the above configuration moves from the mold-open state shown in Figures 1 and 2 to the mold-closed state shown in Figures 3 and 4 by advancing the side dies 3 to 6 and lowering the upper die 2, thereby forming the cavity 7. The low-pressure casting apparatus then appropriately pressurizes the holding furnace 50 and depressurizes the cavity 7, thereby passing the molten metal in the holding furnace 50 through the stalk and each gate bushing 8 and filling the cavity 7. After the molten metal has solidified, the mold is opened as shown in Figures 1 and 2, a mold release plate 9 is lowered relative to the upper die 2, and a mold release pin 9A is protruded from the upper die 2 to release the casting.

[0019] During the above-described casting, the temperature of the lower mold essential part 1A, which includes the gate bushing 8, becomes relatively high in the low-pressure casting apparatus, causing the lower mold essential part 1A to thermally expand horizontally. In response to this, the low-pressure casting apparatus divides the lower mold 1 into the lower mold essential part 1A and the lower mold base part 1B, with an adjustment gap S provided between the two. This allows the thermal expansion of the lower mold essential part 1A to be absorbed by the adjustment gap S, thereby suppressing thermal deformation of the lower mold base part 1B.

[0020] This allows the low-pressure casting device to prevent displacement of the guide pillars 10 at the lower mold base portion 1B, and these guide pillars 10 ensure the correct forward position of the side molds 3 to 6, which can move back and forth, and prevent excessive gaps greater than the clearance from occurring between the lower mold 1 and the side molds 3 to 6, or between the side molds 3 to 6 and the upper mold 2.

[0021] In this way, the low-pressure casting apparatus can improve mold closing accuracy by preventing excessive gaps between the molds caused by thermal expansion of the lower mold 1. As a result, the low-pressure casting apparatus can improve the dimensional accuracy of the cast product along with the improved mold closing accuracy, and can reduce penetration defects, particularly in castings using aluminum as the material.

[0022] 5 to 9 are diagrams illustrating second and third embodiments of a low-pressure casting apparatus according to the present invention. In the following embodiments, the same components as those in the first embodiment are denoted by the same reference numerals, and detailed description thereof will be omitted.

[0023] Second Embodiment The low-pressure casting apparatus shown in Figures 5 and 6 has multiple sets (two sets in the illustrated example) of combinations of a lower mold 1, a top mold 2, and multiple side molds 3 to 6. In this case, the lower mold 1 has two lower mold main parts 1A, but the lower mold base part 1A is common to both. On the other hand, the top mold 2 is divided into an upper mold main part 2A that forms the internal upper surface of the cavity 7, and a top mold base part 2B, and the top mold base part 2B holds the upper mold main part 2A so that it can reciprocate in the arrangement direction of the side molds 3 to 6.

[0024] In the illustrated example, the upper mold main part 2A can move back and forth in the direction of arrangement of the side molds 3 and 5, which is the left-right direction in the figure. The upper mold main part 2A is connected to the upper mold base part 2B by a slidable uneven structure such as grooves and protrusions, or by an elastic body. In this case, the range of reciprocal movement of the upper mold main part 2A is sufficient as long as it is within a range that allows mold closure. In addition, the upper mold main part 2B has an insertion hole for the release pin 9A with an elongated cross section to allow relative movement with the release pin 9A.

[0025] The low-pressure casting apparatus further includes a center base 11 that positions at least one of the side molds. The center base 11 is a structure that extends from between the two upper mold base portions 2B, 2B to the lower mold 1, and positions the two side molds 3, 5 whose back surfaces face each other, i.e., the right side mold 5 in the right-side set in FIG. 5 and the left side mold 3 in the left-side set in the same figure.

[0026] In addition, the center base 11 may be made movable up and down by a drive mechanism not shown, and horizontal positioning is achieved by engaging the recess 11A provided at its lower end with the protrusion 1C of the lower mold base portion 1B.

[0027] The low-pressure casting apparatus separates the center base 11 and the side dies 5, 3, which are positioned by the center base 11, so that an adjustment shim 12 can be inserted between them. In other words, the opposing surfaces of the center base 11 and the side dies 3, 5 are flat, and a flat adjustment shim 12 can be inserted between the opposing surfaces.

[0028] Here, the center base 11 can also constitute a center mold including the side molds 3 and 5. In this case, similar to the lower mold 1 and upper mold 2 described above, the side molds 3 and 5 correspond to the side mold main parts (3A, 5A) that form the internal side surfaces of the cavity 7, and the center base 11 corresponds to the center mold base part. As a result, the center mold is divided into the side mold main parts (3, 5) and the center mold base part (11), and a structure is created in which an adjustment shim 12 can be interposed between the two.

[0029] As in the first embodiment, the low-pressure casting apparatus having the above configuration uses an adjustment gap S provided between the lower mold essential parts 1A, 1A and the lower mold base part 1B in the lower mold 1 to absorb thermal expansion of the lower mold essential parts 1A, 1A and suppress thermal expansion of the lower mold base part 1B, thereby preventing deviations in the position of the guide support 10 and the forward positions of the retractable side molds 3, 4, 6, and maintaining good mold closing accuracy.

[0030] In addition, the above-mentioned low-pressure casting device divides the upper mold 2 into an upper mold main part 2A and an upper mold base part 2B, and presses the upper mold base part 2B against the center base 11, while the lower mold main part 2A can move back and forth relative to the upper mold base part 2B.

[0031] As a result, as shown in Figure 7, when the low-pressure casting device closes the mold, each upper mold main part 2A can move in the opposite direction (arrow direction) based on the center base 11, so that each upper mold main part 2A can be corrected to the correct mold closing position, thereby further improving mold closing accuracy.

[0032] Furthermore, the above-mentioned low-pressure casting apparatus employs a center base 11 for positioning the two side dies 3, 5 and an adjustment shim 12, which allows the positions of the side dies 3, 5 to be adjusted. Moreover, the fixed side dies 3, 5 are used as a reference for closing the other side dies and the main upper mold portion 2A, thereby achieving further improvements in mold closing accuracy.

[0033] Furthermore, the adoption of the center base 11 in the above-mentioned low-pressure casting apparatus eliminates the need for a drive mechanism for the positioned side molds 3, 5, making it possible to make the entire apparatus more compact than if multiple casting apparatuses were simply arranged in parallel.

[0034] Third Embodiment The low-pressure casting apparatus shown in Figure 8 has a basic configuration equivalent to that of the second embodiment (Figures 5 to 7), and has an exhaust passage P1 between the upper mold 1 and the side molds 3, 5 for discharging air from the cavity 7, and is equipped with a suction mechanism 60 that sucks the air from the cavity 7 to the outside through the exhaust passage P.

[0035] A well-known chill vent may be used for the exhaust path P. As shown in Fig. 9, the suction mechanism 60 has two systems of exhaust pipes 61A, 61B connected to each set of exhaust paths P of the low-pressure casting apparatus. Each exhaust pipe 61A, 61B is connected to a suction source 62 consisting of a vacuum pump or a vacuum tank, and is provided with pressure adjustment valves V1, V2 and an exhaust valve V3 between them, and the suction source 62 and each valve V1 to V3 are controlled based on the measurements of the pressure gauges M1, M2 in each cavities 7, 7.

[0036] As described in the first and second embodiments, the low-pressure casting apparatus having the above configuration has good mold closing accuracy, making it possible to differentiate between the general clearance between the molds and the exhaust path P. As a result, the low-pressure casting apparatus has no unnecessary gaps between the molds, so it is possible to intentionally suck and exhaust the air inside the cavity 7 using the exhaust path P, and it is possible to increase the degree of vacuum in the cavity 7 without having to enclose the entire casting apparatus in a large housing. Furthermore, the low-pressure casting apparatus enables low-pressure casting using a multi-cavity mold, making it possible to produce thin-walled castings.

[0037] The configuration of the low-pressure casting apparatus according to the present invention is not limited to the above-described embodiments, but can be modified as appropriate without departing from the spirit of the present invention, and can naturally be applied to casting using a core, etc. [Explanation of symbols]

[0038] 1 Lower mold 1A Lower mold main part 1B Lower die base 2 Upper mold 2A Upper mold main part 2B Upper die base 3~6 Side Type 7 Cavity 8 Sprue bush 10 Guide support 11 Center Base 12 Adjustment shims 50 holding furnace 60 Suction mechanism P exhaust duct S Adjustment gap

Claims

1. The apparatus comprises a lower mold disposed on a holding furnace, an upper mold capable of ascending and descending relative to the lower mold, and a plurality of side molds disposed on the lower mold, forming a cavity between the lower mold, the upper mold, and the side mold; the lower mold comprises a lower mold main part that forms an inner bottom surface of the cavity, and a lower mold base part that holds the lower mold main part; the lower mold main portion has a gate bushing that opens into the cavity, At least one of the side molds is movable forward and backward relative to a mold center, and the lower mold base portion has a guide support that regulates the forward position of the movable side mold, A low-pressure casting apparatus characterized in that a horizontal adjustment gap is provided between the main portion of the lower mold and the base portion of the lower mold.

2. A plurality of combinations of the lower mold, the upper mold, and a plurality of the side molds are provided, 2. The low-pressure casting apparatus according to claim 1, wherein the upper mold comprises an upper mold main portion that forms the internal upper surface of the cavity, and an upper mold base portion that holds the upper mold main portion so that it can move back and forth in the arrangement direction of the side molds.

3. a center base for positioning at least one of the side molds; 3. The low-pressure casting apparatus according to claim 2, wherein the center base and the side molds positioned by the center base are separated so that an adjustment shim can be inserted therebetween.

4. an exhaust passage for discharging air from the cavity between the upper mold and the side mold; 4. The low-pressure casting apparatus according to claim 1, further comprising a suction mechanism for sucking air from within the cavity to the outside through the exhaust path.

5. The lower mold main part has a downward step on its outer periphery, and the lower mold base part has an upward step on the inner periphery of the accommodating part of the lower mold main part, 2. The low-pressure casting apparatus according to claim 1, wherein the stepped portions of the lower mold main portion and the lower mold base portion are engaged with each other.

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