Mold preheating system and mold preheating device

Abstract

To provide a mold preheating system and a mold preheating device which dispense with test shot, and can finish a preheating step in a short time.SOLUTION: A mold preheating system includes a casting mold 1 for obtaining a cast product by supplying molten metal to a cavity part 2 formed of an upper mold 3 and a lower mold 4, a melting furnace 5 provided below the lower mold 4, a molten metal supply path 6 for supplying the molten metal in the melting furnace 5 to the cavity part 2, and a mold preheating device 10 for preheating the casting mold 1. The upper mold 3 is formed with a projection 3a forming a product shape, and the lower mold 4 is formed with a recess 4a where the projection 3a is stored. The mold preheating device 10 includes a burner 11 for upper mold preheating which is arranged along an outer peripheral wall 3b of the projection 3a, and preheats the outer peripheral wall 3b, and a burner 12 for lower mold preheating which is arranged inside the recess 4a, and preheats a side wall 4b and a bottom wall 4c of the recess 4a.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a mold preheating system and a mold preheating device. [Background technology]

[0002] Conventionally, a mold preheating system has been disclosed that has a structure in which an electric heater for preheating the interior space of the mold is inserted into a sprue from the interior space of the mold (see, for example, Patent Document 1, etc.). Also, a configuration is known in which a sleeve is provided to be inserted into the intermediate stalk, and hot air from a burner is blown into the intermediate stalk from one end of the sleeve (see, for example, Patent Document 2, etc.). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent No. 5555078 [Patent Document 2] Patent No. 5359718 Summary of the Invention [Problem to be solved by the invention]

[0004] In conventional mold preheating systems, if the mold temperature is low relative to the molten metal when it is supplied into the cavity, the molten metal cools and solidifies, resulting in poor product yield, poor molding quality, deformation due to poor demolding, etc. For this reason, it is necessary to sufficiently preheat each part of the mold before casting. However, when the hot air from an electric heater or a burner cannot sufficiently preheat each part of the mold, a method called "batch casting" is used to preheat the mold using the temperature of the molten metal. Cast products manufactured by this method are of poor quality and are discarded or recycled. Therefore, the time required for the batch casting increases, which reduces manufacturing efficiency, leaving room for further improvement. An object of the present invention is to provide a mold preheating system and a mold preheating device which can complete the preheating process in a short time without requiring waste injection. [Means for solving the problem]

[0005] In order to solve the above problems, the mold preheating system of the present invention includes a casting mold for supplying molten metal to a cavity portion formed by an upper mold and a lower mold to obtain a casting product, a melting furnace provided below the lower mold, a molten metal supply passage for supplying the molten metal in the melting furnace to the cavity portion, and a mold preheating device for preheating the casting mold. The upper mold is formed with a convex portion for forming a product shape, and the lower mold is formed with a concave portion for accommodating the convex portion. The mold preheating device is characterized in that it includes an upper mold preheating burner arranged along an outer peripheral wall of the convex portion for preheating the outer peripheral wall, and a lower mold preheating burner arranged inside the concave portion for preheating a side wall and a bottom wall of the concave portion. Effect of the Invention

[0006] According to the present invention, there is provided a mold preheating system and a mold preheating device which can complete the preheating process in a short time without requiring waste injection. [Brief description of the drawings]

[0007] [Figure 1] 1 is a vertical cross-sectional view illustrating an overall configuration of a mold in a mold preheating system according to an embodiment of the present invention. FIG. [Diagram 2] FIG. 2 is a vertical cross-sectional view illustrating the configuration of a mold preheating device in the mold preheating system. [Diagram 3] FIG. 2 is a plan view of a mold preheating device used in the mold preheating system of the embodiment, viewed from above. [Figure 4] FIG. 2 is a perspective view showing the mold preheating device with the front and rear burner tips removed for explanation. [Diagram 5] FIG. 2 is a front view showing the configuration of a middle stalk preheating burner in the mold preheating device. [Figure 6]FIG. 2 is a side view illustrating the overall configuration of the mold preheating device. [Figure 7] FIG. 2 is a front view illustrating the overall configuration of the mold preheating device. [Figure 8] FIG. 11 is a top view illustrating how the intermediate stalk preheating burner of the mold preheating device preheats the inside of the intermediate stalk. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0008] [Embodiment] Hereinafter, an embodiment of the present invention will be described with reference to the drawings as appropriate. The same components are given the same reference numerals, and duplicated descriptions will be omitted. In the description, the same components are given the same reference numerals, and duplicated descriptions will be omitted. For convenience of description, when describing directions, the directions indicated by the arrows in FIG. 1 are referred to as "up, down, left, right," and the front side of the paper in FIG. 1 is referred to as "front," and the back side of the paper is referred to as "rear."

[0009] FIG. 1 shows the relative positions of a casting mold 1 and a mold preheating device 10 in a mold preheating system 100 according to an embodiment of the present invention. [Mold preheating system] The die preheating system 100 includes a casting die 1 for obtaining a cast product by supplying molten metal to a cavity 2 as a hollow space formed by an upper die 3 and a lower die 4. The casting die 1 includes an opening / closing mechanism (not shown) for moving the upper die 3 in the vertical direction to change the vertical distance between the lower die 4 and the upper die 3. The opening and closing mechanism changes the mold open state in which the upper mold 3 is separated upward from the lower mold 4 to a mold clamped state in which the upper mold 3 is moved downward and brought into contact with the lower mold 4. Then, molten metal supplied from a melting furnace 5 provided below the lower mold 4 is poured into the cavity portion 2 through a molten metal supply passage 6, thereby performing low-pressure casting.

[0010] The opening and closing mechanism moves the upper die 3 upward to open the die. Then, the casting product is taken out from between the upper die 3 and the lower die 4 of the casting die 1. Note that a temperature sensor may be provided in the casting die 1 and the detected die temperature may be reflected in the preheating conditions of the preheating step described below.

[0011] A convex portion 3a that forms the product shape of a casting product is provided on an upper mold 3 of a casting mold 1. The convex portion 3a in the embodiment has a quadrangular pyramid shape with a substantially flat outer peripheral wall 3b arranged on all four sides and tapered inwardly as it extends downward. A recess 3g, which is a part of the upper shape of the casting product, is formed in the lower end surface 3f of the protruding portion 3a in a concave shape recessed upward from the bottom surface. In addition, a plurality of stud pins 3h are provided protruding downward around the recess 3g to form fastening holes used for stud bolts for fastening parts.

[0012] The lower die 4 of the casting mold 1 is further provided with a slide mold section 7 which is horizontally movable in the lateral opening direction. The slide mold section 7 is provided so as to be able to slide horizontally from the center of the cavity section 2 to approach and separate from each other. The slide mold section 7 forms an internal space of the cavity section 2 in the mold closed state, and shapes the uneven shape of the side surface of the casting product. Furthermore, when the slide mold section 7 slides outward in the mold open state, at least one side surface is opened, allowing the casting product to be easily removed.

[0013] A concave portion 4a is formed in the slide mold portion 7 of the lower mold 4. The upper portion of the concave portion 4a opens its upper opening upward and slopes inward as it approaches downward. When the upper mold 3 is lowered from the mold open state, the convex portion 3a is received in the concave portion 4a, and the casting mold 1 is closed in the vertical direction. A side wall 4b and a bottom wall 4c are provided at the bottom of the recessed portion 4a. The side walls 4b, 4b are provided parallel to each other and spaced apart from each other with a space therebetween, and the side wall 4b, the bottom wall 4c and the lower end surface 3f of the upper mold 3 form an internal space of the cavity portion 2 in a mold clamped state.

[0014] In addition, a plurality of gates 14 are formed on the bottom wall 4c of the lower mold 4. The gates 14 are formed at four locations approximately equally spaced apart along the inner peripheral wall 15a of the intermediate stalk 15 when viewed from above, and communicate with the melting furnace 5 arranged below the lower mold 4 via the molten metal supply passage 6. The melting furnace 5 sends molten metal, which is a molten metal material, from bottom to top at a relatively low pressure and at a low speed into the cavity portion 2 through a molten metal supply passage 6 provided between the melting furnace 5 and the casting mold 1. The molten metal supply passage 6 has a cylindrical intermediate stalk 15. The upper end surface of the intermediate stalk 15 is connected to the lower surface of the bottom wall 4c of the lower mold 4. The molten metal pushed up from the melting furnace 5 through the intermediate stalk 15 is distributed to each of the four gates 14 and sent into the cavity 2. The molten metal poured into the cavity 2 hardens by the heat removed from the mold and becomes a cast product.

[0015] [Mold preheating device] 2, the die preheating system 100 includes a die preheating device 10 that preheats the casting die 1. The die preheating device 10 is interposed between the upper die 3 and the lower die 4 that are in an open state before low-pressure casting, and preheats the casting die 1 to a desired temperature by ejecting flames from a plurality of burner tips. The mold preheating device 10 of the embodiment is provided with an upper mold preheating burner 11 arranged along the outer peripheral wall 3b of the convex portion 3a and preheating the outer peripheral wall 3b. The mold preheating device 10 is also provided with a lower mold preheating burner 12 arranged inside the concave portion 4a and preheating the side wall 4b and bottom wall 4c of the concave portion 4a, and a middle stalk preheating burner 13.

[0016] 3 and 4, the mold preheating system 100 includes a mixture supplying device 20 that supplies a mixture of air and gas (hereinafter, also referred to as a mixture). The mixture supplying device 20 is connected to the upper mold preheating burner 11 and the lower mold preheating burner 12, and supplies the mixture to each burner tip. The gas mixture supplying device 20 of the embodiment is connected to a piping branching section 23 via a mold piping 22. The piping branching section 23 has connection ports that communicate with each other on all four sides, with the mold piping 22 connected to the upper connection port, the upper mold piping 11c, 11c connected to the left and right connection ports, and the lower mold piping 25 connected to the lower connection port. The piping branch section 23 distributes the mixture sent from the mixture supply device 20 through the mold piping 22 to the upper mold piping 11c and the lower mold piping 25. The distributed mixture is supplied to the upper mold preheating burner 11 and the lower mold preheating burner 12, respectively.

[0017] [Upper mold preheating burner] The upper mold preheating burner 11 has an upper mold piping 11c (see FIG. 2) surrounding an outer peripheral wall 3b (see FIG. 1) formed on the convex portion 3a of the upper mold 3. Moreover, the upper die pipe 11c is arranged so as to have a substantially U-shape when viewed from above and to surround at least three of the multiple outer circumferential walls 3b formed on the convex portion 3a of the upper die 3. Although the pipe 11c has a U-shape in this embodiment, the shape is not limited to this and may be, for example, a mouth shape. The upper mold piping 11c in this embodiment has two straight pipes 11f arranged in parallel with the left and right outer peripheral walls 3b of the convex portion 3a at a predetermined interval.

[0018] The upper die 3 is preheated by flames ejected from a plurality of burner tips for preheating the upper die. The upper mold pipe 11c is provided with a first row burner tip 11a, a second row burner tip 11b, a front burner tip 11d, and a rear burner tip 11e that eject flames as burner tips for preheating the upper mold. Note that the front burner tip 11d and the rear burner tip 11e are omitted in the perspective view of FIG. 4. In this embodiment, the first row burner tips 11a are arranged facing four sides, but this is not limited to this. For example, two or three sides are also acceptable as long as the flame is ejected toward at least two sides. The upper-die preheating burners 11 eject flames from their respective burner tips toward the lower end surface 3f and the outer peripheral wall 3b of the convex portion 3a. This allows the upper-die preheating burners 11 to efficiently and uniformly preheat the four surfaces of the lower end surface 3f and the outer peripheral wall 3b of the convex portion 3a of the upper die 3, which are difficult to preheat in the cavity portion 2.

[0019] [First row burner tip] More specifically, a pair of left and right straight pipes 11f are disposed diagonally below the left and right outer peripheral walls 3b. A plurality of extension pipes are protruded from the outer surface of each straight pipe 11f at equal intervals in the pipe length direction. Each extension pipe is roughly L-shaped in side view, and a first row burner tip 11a is attached to the tip facing diagonally upward. The tip of each first row burner tip 11a is disposed so as to be equidistant from the opposing corner 3d. As a result, the first row burner tip 11a ejects flames obliquely upward from below toward the lower end surface 3f (see FIG. 1) of the convex portion 3a formed in the upper mold 3. As a result, the lower end surface 3f adjacent to the corner portion 3d and a part of the outer peripheral wall 3b are uniformly heated, mainly as well as the corner portion 3d.

[0020] [Second row burner tip] As shown in Fig. 3, a plurality of second row burner tips 11b are arranged on the outer surface of each straight tube 11f. The second row burner tips 11b are arranged above the intermediate positions of the adjacent first row burner tips 11a, 11a and protrude so as to alternate with the first row burner tips 11a in the tube length direction.

[0021] The tips of the second row burner tips 11b are disposed equidistantly and obliquely downward from the outer peripheral wall 3b of the convex portion 3a shown in FIG. The tip of the second row burner tip 11b is directed obliquely upward. The second row burner tip 11b ejects flames obliquely upward toward the outer peripheral wall 3b of the convex portion 3a of the upper die 3 and toward the inside corner portion 3e located between the lower surface 3c of the upper die 3 and the outer peripheral wall 3b. This heats the upper die 3 mainly from the outer peripheral wall 3b to a part of the lower surface 3c adjacent to the inside corner portion 3e. In this way, the flames from the multiple second row burner tips 11b are ejected obliquely upward from below, and can uniformly heat a wide area obliquely relative to the outer peripheral wall 3b.

[0022] At this time, the corner 3d is located between the flame ejected from the first row burner tip 11a and the flame ejected from the second row burner tip 11b. Therefore, the preheating efficiency for the corner 3d is good, and the desired temperature can be reached quickly. In addition, generally, the inside corner 3e located between the outer peripheral wall 3b and the lower surface 3c of the upper mold 3 is difficult to preheat because the temperature rises locally with a flame ejected perpendicularly to the lower surface 3c or the outer peripheral wall 3b. In contrast, the mold preheating device 10 of the embodiment includes the inside corner 3e located between the lower surface 3c and the outer peripheral wall 3b within the range of the flame obliquely directed toward the inside corner 3e, so that the heating efficiency is good in the inside corner 3e as well as in the outer peripheral wall 3b.

[0023] [Front and rear burner tips] Furthermore, as shown in FIG. 3, the upper-mold preheating burner 11 of the embodiment has a front burner tip 11d and a rear burner tip 11e. These front burner tip 11d and rear burner tip 11e are attached to the ends of extension pipes 11g extended from two straight pipes 11f of the upper mold piping 11c (see Figs. 6 and 7). Each extension pipe 11g is extended from the outer surface of each straight pipe 11f near the front and rear ends thereof in a Z-shaped bent shape. As a result, the front burner tip 11d or the rear burner tip 11e is fixed at an angle to eject flames obliquely upward from below. The ejected flames can heat a wide range of the front and rear outer peripheral walls (not shown) that are perpendicular to the outer peripheral wall 3b of the convex portion 3a without directly contacting the upper mold 3. Therefore, the front and rear outer peripheral walls of the convex portion 3a are preheated uniformly and quickly to a temperature similar to that of the left and right outer peripheral walls 3b, 3b.

[0024] [Lower mold preheating burner] The lower mold preheating burner 12 has a burner tip assembly 12a that is placed inside the recessed portion 4a shown in Figure 1 during preheating, and a lower mold piping 25 that connects the base end 25b to the lower connection port of the piping branch portion 23 (see Figure 4). Of these, the lower die pipe 25 branches downward from the pipe branching portion 23, extends horizontally to an intermediate position within the lower die 4, and has a crank-like shape with its tip bent further downward. A burner tip assembly 12a is connected to a tip portion 25a of the lower die pipe 25. Then, the mixture of air and gas supplied from the mixture supply device 20 via the mold piping 22 is supplied from the lower mold piping 25 into the burner tip assembly portion 12a.

[0025] As shown in Fig. 4, the burner tip assembly 12a has a rectangular parallelepiped shape, with multiple burner tips densely arranged on each of the left and right sides (see Fig. 6). Each burner tip ejects a flame outward to the left and right. The lower die 4 is located directly above the intermediate stalk 15 and heated by the flame of the intermediate stalk preheating burner 13. For this reason, the burner tip assembly 12a of the embodiment is inserted into the center of the relatively large internal space of the cavity 2 and spaced apart from each side wall 4b. This allows the heat used to preheat the lower die 4 to be adjusted to uniformly preheat the entire cavity 2.

[0026] As shown in Fig. 7, a plurality of extension tubes 12b are protruded from the burner tip assembly 12a. A single lower-mold preheating burner tip 12c is attached to the tip of the extension tube 12b. The extension tubes 12b are bent so that the direction of the flame ejected from the lower-mold preheating burner tip 12c is at a predetermined angle with respect to the side wall 4b or the bottom wall 4c in the cavity portion 2.

[0027] [Middle stalk preheating burner] As shown in FIG. 4, the mold preheating device 10 further includes intermediate stalk preheating burners 13 inserted into the intermediate stalk 15 from the multiple gates 14, respectively. The intermediate stalk preheating burner 13 is connected to the mixture supply device 20 (see FIG. 3) through a pipe 24 for the intermediate stalk. The pipe 24 for the intermediate stalk extends a tip mounting pipe 28 downward through a pipe connection part 26 for the intermediate stalk. In other words, the pipe 24 for the intermediate stalk is a separate route from the pipe 22 for the mold. 5, the lower part of the tip mounting pipe 28 is inserted up to the middle position of the intermediate stalk 15. A plurality of burner tips 27 for the supply passage are attached to the lower part of the tip mounting pipe 28. Each of the burner tips 27 for the supply passage ejects a flame along the inner peripheral wall 15a of the intermediate stalk 15 (see FIG. 8). This allows the intermediate stalk 15 provided in the molten metal supply passage 6 to be preheated efficiently.

[0028] More specifically, the intermediate stalk preheating burner 13 has a pipe 24 for the intermediate stalk that is bent downward from the upper mold preheating burner 11. The pipe 24 for the intermediate stalk is connected to a pipe connection portion 26 for the intermediate stalk that is bifurcated so as to be parallel to the straight pipes 11f, 11f of the upper mold preheating burner 11 below the outer peripheral wall 3b located on the left and right of the convex portion 3a. The intermediate stalk preheating burner 13 has an intermediate stalk pipe connection portion 26 further downward, and the lower portion bent into an L shape is further branched into two, with two tip attachment pipes 28 each extending downward for a total of four. Each tip mounting pipe 28 has a plurality of supply path burner tips 27. Three supply path burner tips 27 are provided protruding along the tube axis direction from the outer surface of the lower part of each tip mounting pipe 28. The number of burner tips can be set appropriately and is not limited to this.

[0029] As shown in Fig. 5, when preheating, each tip mounting pipe 28 is inserted from the cavity portion 2 through the gate 14 into the intermediate stalk 15. The supply path burner tip 27 is disposed at a vertically intermediate position within the intermediate stalk 15 so as to be spaced apart from the inner peripheral wall 15a. The supply passage burner tips 27 are attached to the outer surface of the tip attachment pipe 28 with their tips aligned in the same circumferential direction and angled at different angles of about 90 degrees each, as shown in Fig. 7. In other words, the supply passage burner tips 27 are arranged so as to eject a flame in a direction intersecting the radial direction of the intermediate stalk 15. In general, if the flame of the supply passage burner tip 27 is directed in a direction perpendicular to the inner peripheral wall 15a, the inner peripheral wall 15a may become locally hot and may be damaged. The intermediate stalk preheating burner 13 of the mold preheating device 10 of the embodiment is inserted into the intermediate stalk 15 through multiple gates 14 and preheats the intermediate stalk 15 by spraying flames along the inner wall 15a of the intermediate stalk 15, as shown by the arrows in Figure 7. This allows the flame direction to rotate circumferentially, providing even heating.

[0030] The intermediate stalk preheating burner 13 may be inserted into the intermediate stalk 15 except for at least one gate 14 among the multiple gates 14. For example, as shown in Fig. 8, among the gates 14 formed in four places, three tip mounting pipes 28 may be inserted into the three gates 14, respectively, and the tip mounting pipe 28 may not be inserted into the remaining gate 14. In this case, the sprue 14 into which the intermediate stalk preheating burner 13 is not inserted can be used as an air vent to supply sufficient air to burn the mixture. This prevents the flame of the intermediate stalk preheating burner 13 from going out, allowing for stable preheating.

[0031] Furthermore, the mold preheating system 100 of the embodiment includes a positioning device 30 shown by a phantom line in FIG. The positioning device 30 includes a base 31 that is placed on the lower mold 4 (see FIG. 3). The base 31 includes front, rear, left and right frames 32, 33 that are connected to form a generally rectangular frame shape in a plan view, and a plurality of (three in this embodiment) cylindrical portions 34 that protrude upward from the portion where the frames 32, 33 intersect at right angles. The positioning device 30 also has an upper mold preheating burner positioning section 40 that positions the upper mold preheating burner 11 on the stand 31, and a lower mold preheating burner positioning section 50 that positions the lower mold preheating burner 12. The positioning device 30 also has a middle stalk preheating burner positioning section 60 that positions the middle stalk preheating burner 13.

[0032] The upper die preheating burner 11 and the lower die preheating burner 12 are positioned and held in the space between the upper die 3 and the lower die 4 by the upper die preheating burner positioning portion 40 and the lower die preheating burner positioning portion 50, respectively. In addition, the intermediate stalk preheating burner 13 has the supply path burner tip 27 positioned and held in the intermediate position within the intermediate stalk 15 by the intermediate stalk preheating burner positioning portion 60. As a result, in the preheating process, the burner tips are disposed at a desired interval and angle for good preheating efficiency with respect to the upper die 3 and the lower die 4. In addition, the upper die 3 and the lower die 4 are maintained at an appropriate interval by the cylindrical portion 34.

[0033] In addition, in the preheating process in which the intermediate stalk piping connection portion 26 is positioned by the positioning device 30 shown in Figure 6, the portion that branches into two at the bottom is offset downward from the vertical position of the burner tip collection portion 12a of the lower mold preheating burner 12. As a result, the flame ejected laterally from the burner tip assembly 12a avoids the bifurcated portion and the tip mounting pipe 28 and heads toward the side wall 4b of the lower die 4, thereby achieving sufficient preheating efficiency.

[0034] As described above, the mold preheating system 100 of the embodiment includes a casting mold 1 that supplies molten metal to a cavity portion 2 formed by an upper mold 3 and a lower mold 4 to obtain a cast product, a melting furnace 5 provided below the lower mold 4, a molten metal supply passage 6 that supplies the molten metal in the melting furnace 5 to the cavity portion 2, and a mold preheating device 10 that preheats the casting mold 1. The upper die 3 is formed with a convex portion 3a that forms the product shape, and the lower die 4 is formed with a concave portion 4a that receives the convex portion 3a. The mold preheating device 10 is provided with an upper mold preheating burner 11 arranged along the outer peripheral wall 3b of the convex portion 3a and preheating the outer peripheral wall 3b, and a lower mold preheating burner 12 arranged inside the concave portion 4a and preheating the side wall 4b and bottom wall 4c of the concave portion 4a.

[0035] The mold preheating system 100 of the embodiment configured as above can improve thermal efficiency and complete the preheating process in a short time while saving energy. In detail, as shown in FIG. 1, the upper mold preheating burner 11 ejects a flame toward the outer peripheral wall 3b of the convex portion 3a protruding from the upper mold 3, thereby efficiently preheating the upper mold 3 in accordance with the shape of the convex portion 3a of the cavity portion 2, which is difficult to preheat. As a result, just like the side wall 4b and bottom wall 4c of the lower mold 4, which are preheated from the inside of the concave portion 4a by the lower mold preheating burner 12, the upper mold 3 is preheated uniformly and the entire cavity reaches a temperature at which a quality casting can be obtained quickly. Therefore, a waste casting is not necessary, and a sufficient preheating temperature is applied to the entire cavity portion 2 from the early stage of the casting process, so that the preheating process can be completed in a short time.

[0036] 3, the upper-die preheating burner 11 has an upper-die piping 11c surrounding the outer peripheral wall 3b of the convex portion 3a. The upper-die preheating burner 11 also has a first row burner tip 11a that ejects flames from the upper-die piping 11c toward the outer peripheral wall 3b of the convex portion 3a and the lower end surface 3f of the upper die 3.

[0037] In the mold closed state, the corners of the upper surface where the flow speed of the molten metal slows down inside the cavity portion 2 are located at corners 3d of the convex portion 3a formed in the upper mold 3. For this reason, the upper mold preheating burners 11 of the upper mold piping 11c surrounding the outer peripheral wall 3b of the convex portion 3a eject flames from the first row burner tips 11a toward the corners 3d, directly preheating the portions of the upper surface of the cavity portion 2 that will become the corners. As a result, in the casting process, the flow speed of the molten metal does not decrease at the corners of the upper surface, and the molten metal can be smoothly distributed to all corners within the cavity portion 2.

[0038] The upper die pipe 11c is disposed so as to surround the outer peripheral wall 3b of the convex portion 3a. Therefore, even if the upper die 3 is lowered in a direction approaching the lower die 4 to the same height as the upper die pipe 11c, the upper die preheating burner 11 does not interfere with the convex portion 3a. Therefore, the first row burner tips 11a and the like can be arranged close to the convex portion 3a so as to eject flames toward the center of the upper die 3. Furthermore, in the preheating step, the distance between the upper die 3 and the lower die 4 can be made narrower than when the upper die piping 11c is located directly below the convex portion 3a. Therefore, the amount of heat of the flame escaping to the outside through the gap between the upper mold 3 and the lower mold 4 can be reduced, and the preheating efficiency can be further improved.

[0039] In this embodiment, a pair of left and right straight tubes 11f provided on the upper mold preheating burner 11 are arranged diagonally below and parallel to a pair of outer peripheral walls 3b, 3b located on the left and right opposite sides of the convex portion 3a, respectively, so as to surround the periphery. The first row burner tips 11a provided on each straight tube 11f spout flames toward the corner 3d located between the outer peripheral wall 3b and the lower end face 3f of the convex portion 3a. At the same time, the second row burner tips 11b spout flames toward the recessed corner 3e located between the lower face 3c of the upper mold 3 and the outer peripheral wall 3b. Therefore, as shown in FIG. 1, the convex portion 3a is uniformly preheated from the lower end surface 3f to the corner 3d, the outer peripheral wall 3b, the inside corner 3e, and the lower surface 3c of the upper mold 3, centered on the corner 3d.

[0040] More specifically, the first row burner tips 11a of the embodiment can eject flames obliquely upward from below, and uniformly heat a wide area obliquely from opposite directions to the left and right of the lower end surface 3f. For example, a portion such as the corner 3d located between the lower end surface 3f and the outer peripheral wall 3b is difficult to heat with a flame that directly heats the lower end surface 3f or the outer peripheral wall 3b. In contrast, the mold preheating device 10 of the embodiment can heat the lower end surface 3f within a range with good heating efficiency, similar to the corner surface 3d, by using a flame directed toward the corner surface 3d located between the lower end surface 3f and the outer peripheral wall 3b, thereby achieving good preheating efficiency.

[0041] In addition, flames from a plurality of second row burner tips 11b arranged alternately with the first row burner tips 11a are ejected obliquely upward from below, and can uniformly heat a wide range obliquely toward the outer peripheral wall 3b. For example, a portion such as the recessed corner 3e located between the outer peripheral wall 3b and the lower surface 3c of the upper mold 3 is generally difficult to heat with flames ejected perpendicularly to the lower surface 3c or the outer peripheral wall 3b. In contrast, the second row burner tip 11b can include the inside corner 3e located between the lower surface 3c and the outer peripheral wall 3b in the range with good heating efficiency by emitting flames obliquely toward the inside corner 3e. This allows the inside corner 3e to be heated uniformly in the same way as the outer peripheral wall 3b, improving preheating efficiency.

[0042] Furthermore, as shown in FIG. 3, the upper-mold preheating burner 11 of the embodiment has a front burner tip 11d and a rear burner tip 11e. These front burner tip 11d and rear burner tip 11e are attached to the ends of extension pipes 11g extended from two straight pipes 11f of the upper mold piping 11c (see Figs. 6 and 7). Each extension pipe 11g is extended from the outer surface of each straight pipe 11f near the front and rear ends thereof in a Z-shaped bent shape.

[0043] As a result, the front burner tip 11d or the rear burner tip 11e is fixed at an angle to eject flames obliquely upward from below. The ejected flames can heat a wide range of the front and rear outer peripheral walls (not shown) that are perpendicular to the outer peripheral wall 3b of the convex portion 3a without directly contacting the upper die 3. Therefore, the preheating efficiency of the front and rear outer peripheral walls as well as the pair of left and right outer peripheral walls 3b of the convex portion 3a is good, and the preheating process can be completed in a short time. Therefore, within the cavity portion 2 of the casting mold 1 that has been clamped during the casting process, a sufficient preheat temperature is uniformly applied from the beginning, including the four sides located at the corners of the upper surface and the corners between adjacent sides, so that the first casting can begin in a short time.

[0044] Furthermore, as shown in FIG. 8, the lower mold 4 is provided with a plurality of gates 14 communicating with the molten metal supply passage 6. As shown in FIG. 5, the molten metal supply passage 6 is also provided with an intermediate stalk 15 that distributes the molten metal to a plurality of gates 14 . The mold preheating device 10 further includes a middle stalk preheating burner 13 that is inserted into the middle stalk 15 through a plurality of gates 14. As shown in FIG. 8, the middle stalk preheating burner 13 ejects a flame along an inner peripheral wall 15a of the middle stalk 15.

[0045] The flames ejected from the intermediate stalk preheating burners 13 at an angle, not directly toward the inner peripheral wall 15a, flow in a swirling manner along the annular inner peripheral wall 15a, uniformly heating the inner peripheral wall 15a. Therefore, the inner peripheral wall 15a of the intermediate stalk 15 is preheated evenly by the flames from the multiple intermediate stalk preheating burners 13, allowing the molten metal to pass through smoothly and quickly. In this embodiment, the gates 14 are arranged in a ring shape at four locations. However, the number and arrangement are not limited to this, and the gates may be arranged in a single location or multiple locations other than four locations, in a lattice pattern, a honeycomb pattern, or randomly.

[0046] In addition, the intermediate stalk preheating burner 13 may be inserted into the intermediate stalk 15 except for at least one of the multiple gates 14. By using the sprue 14 into which the intermediate stalk preheating burner 13 is not inserted as a vent hole for ventilation, air can be sufficiently supplied to stably eject the flame of the intermediate stalk preheating burner 13 without causing it to misfire.

[0047] The mold preheating system 100 includes a mixture supplying device 20 that supplies a mixture of air and gas, and a mold piping 22 that supplies the mixture from the mixture supplying device 20 to the upper mold preheating burner 11 and the lower mold preheating burner 12. The mold preheating system 100 further includes an intermediate stalk piping 24 that supplies the mixture from the mixture supplying device 20 to the intermediate stalk preheating burner 13 shown in FIG. The intermediate stalk pipe 24 is a separate route from the mold pipe 22 .

[0048] An intermediate stalk piping 24 for supplying a mixture of air and gas to the intermediate stalk preheating burner 13 is a separate route from the mold piping 22. Therefore, it is easy to change the amount of gas supplied from the gas mixture supply device 20. By increasing the amount of gas mixture supplied to the intermediate stalk preheating burner 13 independently of the amount of gas mixture supplied to the mold pipe 22, the preheat temperature of the intermediate stalk 15 can be maintained at a high temperature. That is, in the intermediate stalk 15 where the molten metal is temporarily stored in order to distribute it to the multiple gates 14, the molten metal must be preheated to be constantly at a high temperature, otherwise it will cool and solidify. In such a case, the molten metal supply passage 6 or the gates 14 will become clogged and blocked, making it impossible to carry out the casting process. In the mold preheating system 100 of the embodiment, the intermediate stalk piping 24 is a separate path from the mold piping 22, and a desired mixture is supplied to the intermediate stalk preheating burner 13. This makes it possible to achieve a preheat temperature required for the molten metal to pass through. The molten metal can be smoothly passed through the intermediate stalk 15, which has been sufficiently preheated from the beginning of the casting process, and poured into the cavity portion 2.

[0049] In addition, since the intermediate stalk pipe 24 is a separate route from the mold pipe 22, the amount of the mixture supplied from the mixture supply device 20 can be easily controlled.

[0050] Furthermore, in the embodiment, even if the same air-fuel mixture is supplied at the same flow rate to the upper-die preheating burner 11 and the lower-die preheating burner 12, the burner tip assembly 12a located in the center of the lower die 4 can adjust the amount of heat by the number of flames by closing unnecessary tips. Also, the burner tip assembly 12a can reduce uneven preheating by densely assembling multiple burner tips. Therefore, even if the mixture gas is supplied from the same route to the upper mold preheating burner 11 and the lower mold preheating burner 12 using the piping branch section 23, appropriate preheating can be performed for each part in the cavity section 2, and the entire cavity section 2 can be preheated efficiently, and the preheating process can be completed in a short time and at approximately the same time. Therefore, the preheating time can be shortened, and the number of mixture supply devices 20 and piping parts can be reduced, leading to a reduction in manufacturing costs.

[0051] A cavity 2 of a casting die 1 is formed by an upper die 3 having a convex portion 3a that forms a product shape, and a lower die 4 having a concave portion 4a in which the convex portion 3a is accommodated. A die preheating device 10 preheats the casting die 1, which obtains a cast product by supplying molten metal from a melting furnace 5 provided below the lower die 4 through a molten metal supply path 6 to the cavity portion 2. The die preheating device 10 includes an upper die preheating burner 11 that is disposed along an outer peripheral wall 3b of the convex portion 3a and preheats the outer peripheral wall 3b, and a lower die preheating burner 12 that is disposed inside the concave portion 4a and preheats a side wall 4b and a bottom wall 4c of the concave portion 4a.

[0052] This provides the mold preheating device 10 that can complete the preheating process in a short time without requiring waste injection. Specifically, the upper die preheating burner 11 ejects a flame toward the outer peripheral wall 3b of the convex portion 3a protruding from the upper die 3. Therefore, even if the shape of the convex portion 3a of the upper die 3 is difficult to preheat in the cavity portion 2, it can be efficiently preheated according to the shape of the convex portion 3a. This allows the upper mold 3 to be preheated uniformly with the inner wall of the lower mold 4, which has been preheated by the flame ejected from the lower mold preheating burner 12, and the entire cavity portion 2 to be preheated to a predetermined temperature. Therefore, a waste cast is not necessary, and a sufficient preheating temperature is applied to the entire cavity portion 2 from the early stage of the casting process, so that the preheating process can be completed in a short time.

[0053] Furthermore, the lower mold 4 is provided with a plurality of gates 14 communicating with the molten metal supply passage 6. The molten metal supply passage 6 is provided with an intermediate stalk 15 that distributes the molten metal to the plurality of gates 14. The mold preheating device 10 is further provided with an intermediate stalk preheating burner 13 that is inserted into the intermediate stalk 15 from the plurality of gates 14. The intermediate stalk preheating burner 13 ejects a flame along an inner peripheral wall 15a of the intermediate stalk 15.

[0054] The flame ejected from the intermediate stalk preheating burners 13 inserted inside the intermediate stalk 15 along the inner peripheral wall 15a of the intermediate stalk 15 can flow in a circular manner so as to swirl along the inner peripheral wall 15a. Therefore, the inner peripheral wall 15a of the intermediate stalk 15 is preheated evenly by the flames from the multiple intermediate stalk preheating burners 13. Therefore, the preheating process can be completed in a short time, and the molten metal can be smoothly passed through the intermediate stalk 15, which is a unique effect of the present invention.

[0055] Furthermore, the mold preheating system 100 of the embodiment includes a positioning device 30 as shown in FIG. 6 or 7, the positioning device 30 supports the upper-die preheating burner 11 to improve the positioning accuracy of each of the first row burner tips 11a and the second row burner tips 11b. This allows the positioning device 30 to accurately position each burner tip close to the area to be preheated. Therefore, the preheating efficiency is better than, for example, a case where sufficient positional accuracy is not provided and the burner tip is positioned away from the wall surface. Furthermore, in this embodiment, even if the flame is directed obliquely upward, the positional accuracy of the burner tip is good, so preheating can be performed with the same or even higher heating efficiency as when the flame is directly applied vertically to the burner tip in close proximity. As a result, the lower end surface 3f and the corner portion 3d located between the lower end surface 3f and the outer peripheral wall 3b are preheated to a desired temperature almost uniformly and quickly by the multiple first row burner tips 11a on both the left and right sides. In this case, even if there is a recess 3g that forms the upper part of the casting product in the center of the lower end face 3f, the flame from the first row burner tip 11a that is ejected from the left and right diagonally downward reaches and spreads inside the recess 3g diagonally upward, and can heat it quickly in the same way as other parts of the lower end face 3f.

[0056] The lower die preheating burner 12 is disposed at a desired position inside the recessed portion 4a, and can preheat the side wall 4b and bottom wall 4c of the recessed portion 4a. In this embodiment, the dimension between the opposing side walls 4b, 4b sandwiching the internal space of the cavity portion 2 is formed to be larger than the recessed portion 4a, and a burner tip assembly portion 12a is provided at the center of the internal space. Therefore, the flames ejected from the plurality of burner tips concentratedly arranged on the side surface of the burner tip assembly 12a are appropriately dispersed, enabling the side wall 4b to be preheated uniformly.

[0057] As described above, the upper mold preheating burner 11, the lower mold preheating burner 12 and the intermediate stalk preheating burner 13 in the embodiment are each positioned in the gap where the upper mold 3 is close to the lower mold 4, and can preheat each part in the cavity portion 2 early. Therefore, when the casting process begins and the molten metal in the melting furnace 5 is first supplied from the molten metal supply passage 6 into the cavity portion 2, the entire cavity portion 2 has been uniformly heated to a temperature that will produce a good casting. Therefore, there is no need for a trial cast, and good quality can be achieved from the initial casting. Therefore, it is possible to provide a die preheating system and a die preheating device that eliminate the time required for trial casts and have good manufacturing efficiency.

[0058] The present invention is not limited to the above-described embodiment, and various modifications are possible. The above-described embodiment is exemplified to explain the present invention in an easy-to-understand manner, and is not necessarily limited to those having all of the configurations described. In addition, it is possible to replace a part of the configuration of one embodiment with the configuration of another embodiment, and it is also possible to add the configuration of another embodiment to the configuration of one embodiment. In addition, it is possible to delete a part of the configuration of each embodiment, or to add or replace other configurations. Possible modifications of the above-described embodiment are, for example, as follows.

[0059] In this embodiment, as shown in Fig. 3, the upper mold preheating burner 11 has a front burner tip 11d and a rear burner tip 11e. However, this is not particularly limited, and the front burner tip 11d and the rear burner tip 11e may be either one or not provided. Furthermore, the lower mold 4 of the casting mold 1 does not have to be provided with the slide mold part 7.

[0060] Moreover, the mixture supplying device 20 of the embodiment is configured to supply different mixtures to the mold pipe 22 and the intermediate stoke pipe 24, which are separate paths. The mixture supply device 20 may be a single device that supplies different mixtures to the mold pipe 22 and the intermediate stalk pipe 24, which are separate paths. Also, a mixture supply device dedicated to the mold pipe 22 and a mixer supply device dedicated to the intermediate stalk pipe 24 may be configured as separate devices that supply different mixtures to each of them.

[0061] The mold preheating system 100 of the embodiment includes a positioning device 30 as shown in Fig. 3. However, the present invention is not limited to this, and it is sufficient that the upper mold preheating burner 11 for preheating the outer peripheral wall 3b is arranged along the outer peripheral wall 3b of the convex portion 3a without using the positioning device 30. In other words, as long as at least the upper mold preheating burner 11 can be arranged at an appropriate position, the shape, number and material of the positioning device 30 are not particularly limited. [Explanation of symbols]

[0062] 1 Casting mold 2 Cavity 3 Upper mold 3a Convex part 4 Lower mold 4a Concave part 4b side wall 4c bottom wall 5 Melting furnace 6 Molten metal supply line 11 Upper mold preheating burner 12 Lower mold preheating burner

Claims

1. a casting die for supplying molten metal into a cavity formed by an upper die and a lower die to obtain a casting product; A melting furnace provided below the lower mold; a molten metal supply passage for supplying the molten metal in the melting furnace to the cavity portion; A mold preheating device for preheating the casting mold; A mold preheating system comprising: The upper die is formed with a convex portion that forms a product shape, The lower mold has a concave portion in which the convex portion is accommodated and a plurality of sprues communicating with the molten metal supply passage, The molten metal supply passage has an intermediate stalk that distributes the molten metal to the plurality of gates; the die preheating device includes an upper die preheating burner disposed along an outer peripheral wall of the convex portion and preheating the outer peripheral wall, a lower die preheating burner disposed inside the concave portion and preheating a side wall and a bottom wall of the concave portion, and a middle stalk preheating burner inserted into the middle stalk from the multiple sprues, A mold preheating system characterized in that the intermediate stalk preheating burner ejects a flame along an inner peripheral wall of the intermediate stalk.

2. 2. The mold preheating system according to claim 1, wherein the intermediate stalk preheating burner is inserted into the intermediate stalk except for at least one of the plurality of gates.

3. Further comprising: a mixture supplying device for supplying a mixture of air and gas; a mold piping for supplying the mixture from the mixture supplying device to the upper mold preheating burner and the lower mold preheating burner; and an intermediate stalk piping for supplying the mixture from the mixture supplying device to the intermediate stalk preheating burner, 2. The mold preheating system according to claim 1, wherein the intermediate stalk piping is a separate route from the mold piping.

4. A mold preheating device for preheating a casting mold for obtaining a cast product by supplying molten metal from a melting furnace provided below the lower mold through molten metal supply passages communicating with a plurality of sprues into a cavity formed by an upper mold in which a convex portion forming a product shape is formed and a lower mold in which a concave portion for accommodating the convex portion is formed, The molten metal supply passage has an intermediate stalk that distributes the molten metal to the plurality of gates; the die preheating device includes an upper die preheating burner disposed along an outer peripheral wall of the convex portion and preheating the outer peripheral wall, a lower die preheating burner disposed inside the concave portion and preheating a side wall and a bottom wall of the concave portion, and a middle stalk preheating burner inserted into the middle stalk from the multiple sprues, A mold preheating device characterized in that the intermediate stalk preheating burner ejects a flame along an inner peripheral wall of the intermediate stalk.

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