Sand Neutron Manufacturing Device

Abstract

The present invention provides a sand core manufacturing apparatus (1) that can produce sand cores (5) with stable quality even when manufactured continuously over a long period of time. [Solution] A sand core is manufactured by blowing casting sand from above into a molding space (102) formed by stacking two molds (100, 101) and heating the molds. Casting sand is replenished from a sand hopper (210) into a blowhead (200) that fills the molding space with casting sand. Since the side of the sand hopper on the mold side (212a) is heated by the heat from the mold, the side on the mold side is formed with a steeper slope than the side on the side furthest from the mold (212b). This not only suppresses heating of the side on the mold side, but also ensures that the casting sand near the side on the mold side is supplied to the blowhead before its temperature rises, making it possible to manufacture sand cores of stable quality even when manufacturing continuously for a long period of time.

Description

TECHNICAL FIELD

[0001] The present invention relates to a sand core manufacturing apparatus that manufactures a sand core by filling casting sand into a molding space formed by bringing a pair of molds into contact with each other at their respective contact surfaces, and heating the molds to solidify the casting sand in the molding space.

BACKGROUND ART

[0002] Casting is the most widely used method for manufacturing metal products in large quantities at low cost. When manufacturing a product having a shape with a hollow portion by casting, a member called a core having the shape of the hollow portion is used. The core is generally manufactured by heating and solidifying sand coated with a special resin called resin (hereinafter referred to as casting sand), and the core manufactured using casting sand is called a sand core.

[0003] Sand cores are manufactured as follows. First, an upper mold with a recess formed on its bottom surface and a lower mold with a recess formed on its top surface are prepared. By placing the upper mold on top of the lower mold, a space (hereinafter referred to as the molding space) is created in which the recesses of the two molds are continuous. The shape of the recesses formed in the upper and lower molds is such that a molding space with the desired shape of the sand core can be obtained. Then, casting sand is blown into the molding space by blowing it through a blowing passage formed in the upper mold. The sand core manufacturing apparatus is equipped with a storage container (hereinafter referred to as the sand hopper) for storing casting sand and a blowing head (hereinafter referred to as the blowing head) from which casting sand is blown out from a nozzle (hereinafter referred to as the blowing nozzle) formed on the bottom surface. After supplying casting sand from the sand hopper to the blowing head, pressurized air is supplied to the blowing head, and the casting sand blown out from the blowing nozzle is filled into the molding space through the blowing passage. Once the molding space is filled with casting sand, the blowhead is moved away from the blowing position, and the upper and lower molds are heated to a high temperature. As a result, the casting sand in the molding space is heated, and the resin on the surface melts, causing the sand to fuse together and form a sand core that takes the shape of the molding space. After that, the sand core can be removed by separating the upper and lower molds.

[0004] Here, in order to produce high-quality sand cores, it is important to fill the molding space with casting sand uniformly and at sufficient density. To this end, techniques have been proposed such as filling the mold with casting sand while vibrating it with a vibrating device (Patent Document 1), and dividing the blow head into multiple small sections and providing a blow nozzle in each section, so that casting sand and pressurized air can be supplied independently to each section, thereby allowing casting sand to be filled into the molding space independently from multiple blow nozzles (Patent Document 2). [Prior art documents] [Patent Documents]

[0005] [Patent Document 1] Japanese Patent Publication No. 2013-188767 [Patent Document 2] Japanese Patent Publication No. 2009-039777 [Overview of the project] [Problems that the invention aims to solve]

[0006] However, with the conventional technology described above, there was a problem in that if sand cores were manufactured continuously over a long period of time, it became impossible to uniformly fill the molding space with casting sand, which could lead to a decrease in the manufacturing quality of the sand cores.

[0007] This invention was made to solve the aforementioned problems of the conventional technology, and aims to realize a sand core manufacturing apparatus that can manufacture sand cores with stable quality even when manufacturing sand cores continuously over a long period of time. [Means for solving the problem]

[0008] To solve the above-mentioned problems, the sand core manufacturing apparatus of the present invention employs the following configuration. That is, A sand core manufacturing apparatus for producing a sand core in which the casting sand is solidified into the shape of the molding space by stacking two molds vertically to form a molding space between the two molds, filling the molding space with casting sand through a blowing passage opening on the upper surface of the upper mold, and then heating the two molds, the apparatus comprises: A blowhead fills the molding space with casting sand by blowing the casting sand into the blowing passage from a blowing position set above the upper mold, and after the casting sand is filled, the blowhead retracts laterally from the blowing position, After the blowhead is retracted, the heating means moves to a heating position set above the upper mold to heat the upper mold, and after the upper mold is heated, it retracts from the heating position. A sand hopper is mounted above the blowhead, which has been retracted laterally from the blowing position, and is formed in a tapering shape toward the discharge port on its bottom surface, and replenishes the blowhead by discharging the casting sand stored inside through the discharge port. Equipped with, The aforementioned blowhead is A blow nozzle is provided, which opens on the bottom surface of the blow head and from which the casting sand filling the molding space is blown out. A circular opening formed on the upper surface of the blow head, A cylindrical measuring tube extends from the position where the opening is located toward the bottom surface of the blowhead, and It has, The measuring cylinder is mounted such that its outer diameter is smaller than the opening, and a gap is formed between its lower end and the bottom surface of the blow head. When the casting sand is replenished from the sand hopper to the blowhead, the casting sand discharged from the outlet of the sand hopper flows into the measuring cylinder and is held within the measuring cylinder. When filling the molding space with the casting sand, pressurized air is supplied into the blow head from the opening. A portion of the pressurized air flows through the outside of the measuring cylinder towards the blow nozzle, while the remaining pressurized air pushes out the casting sand inside the measuring cylinder, causing it to flow out from the lower end of the measuring cylinder. The flowing casting sand, along with the pressurized air that has passed through the outside of the measuring cylinder, is then blown out from the blow nozzle. The aforementioned sand hopper is The side surface of the sand hopper is formed to have a steeper slope than the angle of repose of the casting sand. The side closer to the aforementioned mold The aforementioned Side of the mold teeth , the side furthest from the mold The aforementioned It is formed with a steeper slope than the side surface, which is the side surface opposite the mold. It is characterized by the following:

[0009] In the sand core manufacturing apparatus of the present invention described above, a molding space is formed between two molds by stacking them vertically, and a blowing passage leading to the molding space is opened on the upper surface of the upper mold. Casting sand is then blown into the blowing passage from above the mold using a blow head to fill the molding space with casting sand, and then the two molds are heated to manufacture a sand core in the shape of the molding space. After filling the molding space with casting sand, the blow head is moved laterally from the blowing position above the mold to a position below the sand hopper, and then casting sand is replenished from the sand hopper. Then the blow head is moved again to the blowing position above the mold, casting sand is filled into the molding space between the two molds, and then the molds are heated to manufacture a sand core. Here, the sand hopper is The sides are formed with a slope steeper than the angle of repose of the casting sand, The side closest to the mold is the mold-side side. teeth It is formed with a steeper slope than the side furthest from the mold, which is the side opposite the mold.

[0010] During the production of sand cores, the two molds are at a high temperature. If sand cores are produced continuously for a long period of time, the temperature of the mold-side side surface of the sand hopper will rise, the resin coated on the casting sand will start to melt, and there is a risk that the casting sands will weld to each other to form large casting sand masses. When large casting sand masses are generated, it becomes impossible to fill the molding space with casting sand uniformly and at a sufficient density, making it difficult to manufacture sand cores with stable quality. However, if the mold-side side surface of the sand hopper is formed to have a steeper slope than the non-mold-side side surface, not only can the heating of the mold-side side surface by radiant heat from the mold be suppressed, but also the casting sand near the mold-side side surface can be supplied to the blowhead with priority over the casting sand near the non-mold-side side surface. Therefore, even if the temperature of the mold-side side surface rises and reaches the temperature at which the resin coated on the casting sand starts to melt, the casting sand can be supplied to the blowhead before the resin starts to melt, so that sand cores can be manufactured with stable quality even when sand cores are produced continuously for a long period of time.

[0011] Further, in the above-described sand core manufacturing apparatus of the present invention, the inclination angle formed by the mold-side side surface with respect to the vertical direction may be formed to be an angle equal to or less than half of the inclination angle formed by the non-mold-side side surface with respect to the vertical direction.

[0012] With this configuration, among the casting sand stored in the sand hopper, the casting sand near the mold-side side surface can be supplied to the blowhead in a state of being sufficiently prioritized over the casting sand near the non-mold-side side surface. As a result, even if the temperature of the mold-side side surface becomes high, the casting sand near the mold-side side surface can be supplied to the blowhead before the resin coated on the casting sand starts to melt, so that sand cores can be manufactured with stable quality.

[0013] Further, in the above-described sand core manufacturing apparatus of the present invention, the inclination angle of the mold-side side surface with respect to the vertical direction may be set to 0 degrees.

[0014] In this way, among the casting sand stored in the sand hopper, the casting sand near the mold side surface can be supplied to the blow head with the highest priority. Therefore, even when the temperature of the mold side surface of the sand hopper rises due to continuous production of sand cores over a long period of time, the casting sand near the mold side surface can be supplied to the blow head with sufficient margin before the resin coated thereon starts to melt, making it possible to produce sand cores with stable quality. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] [Figure 1] It is an explanatory view showing the general structure of the sand core manufacturing apparatus 1 of the present embodiment. [Figure 2] It is an explanatory view showing a state in which the sand core manufacturing apparatus 1 of the present embodiment replenishes the blow head 200 with casting sand. [Figure 3] It is an explanatory view showing a state in which the sand core manufacturing apparatus 1 of the present embodiment fills the molding space between the upper mold 100 and the lower mold 101 with casting sand. [Figure 4] It is an explanatory view showing a state in which the sand core manufacturing apparatus 1 of the present embodiment heats the casting sand filled in the molding space. [Figure 5] It is an explanatory view showing a state in which the sand core manufacturing apparatus 1 of the present embodiment separates the lower mold 101 from the upper mold 100 to take out the sand core 5. [Figure 6] It is an explanatory view of the sand hopper 210 mounted on the sand core manufacturing apparatus 1 of the present embodiment. [Figure 7] It is an explanatory view of the structure of the blow head 200 mounted on the sand core manufacturing apparatus 1 of the present embodiment. [Figure 8] It is an explanatory view showing a state in which the sand core manufacturing apparatus 1 of the present embodiment blows out casting sand from the blow nozzle 200a after replenishing the blow head 200 with casting sand. [Figure 9] In the conventional sand core manufacturing apparatus 9 as a reference example, it is an explanatory view showing the reason why casting sand with large grains is generated in the sand hopper 910 when sand cores are continuously manufactured over a long period of time. [Figure 10]This diagram illustrates why the mold side surface 212a of the sand hopper 210 does not easily become hot even when sand cores are continuously manufactured for a long period of time in the sand core manufacturing apparatus 1 of this embodiment. [Figure 11] This diagram illustrates why, in the sand core manufacturing apparatus 1 of this embodiment, large-grained casting sand does not form inside the sand hopper 210 even when the mold side surface 212a of the sand hopper 210 becomes hot. [Figure 12] This is an explanatory diagram of another embodiment of the sand hopper 210 of the sand core manufacturing apparatus 1 of this embodiment. [Figure 13] This diagram illustrates the case where the inclination angle θa of the mold side surface 212a of the sand hopper 210 is negative. [Modes for carrying out the invention]

[0016] Figure 1 is an explanatory diagram showing the general structure of the sand core manufacturing apparatus 1 of this embodiment. The sand core manufacturing apparatus 1 of this embodiment has a structure in which an upper mold 100, a lower mold 101, an upper burner 120 for heating the upper mold 100, a lower burner 121 for heating the lower mold 101, and a lifting cylinder 115 for pushing up the lower mold 101 and bringing it into contact with the upper mold 100 are attached to a frame 10 formed by combining multiple steel materials. A recess (not shown) is formed on the lower surface of the upper mold 100, and a recess (not shown) is also formed on the upper surface of the lower mold 101. When the lower mold 101 is raised and brought into contact with the upper mold 100, the recesses of the two molds combine to form a molding space (not shown).

[0017] Furthermore, the sand core manufacturing apparatus 1 is equipped with a blow head 200 for blowing casting sand into the molding space to fill it. The upper mold 100 has a blowing passage (not shown) for blowing casting sand into the molding space, and the blowing passage opens to the upper surface of the upper mold 100. Casting sand is stored inside the blow head 200, and a blow nozzle 200a for blowing casting sand into the molding space opens to the bottom surface of the blow head 200. The blow head 200 is mounted on a blow carriage 203, which is movable along rails 11 laid on the upper surface of the frame 10.

[0018] When blowing casting sand into the molding space, the blow head 200 is moved to the "blowing position" set above the upper mold 100. A pressure cap 204 is mounted directly above the blow head 200 when it is moved to the blowing position, and a pressure hose 205 for supplying pressurized air is connected to the pressure cap 204. Furthermore, the pressure cap 204 can be pushed down using a pressure cylinder 206. After moving the blow head 200 to the blowing position, when the pressure cap 204 is pushed down using the pressure cylinder 206, the pressure cap 204 comes into contact with the upper end of the blow head 200. When pressurized air is supplied to the pressure cap 204 from the pressure hose 205 in this state, the pressurized air is supplied to the blow head 200 and blown out from the blow nozzle 200a together with the casting sand inside the blow head 200. As will be described in detail later, the casting sand blown out together with the air in this way is filled into the molding space through a blowing passage (not shown) formed in the upper mold 100.

[0019] After blowing casting sand into the molding space, the blow head 200 is returned to its original position (shown in Figure 1) using the blow carriage 203 in order to replenish the casting sand in the blow head 200. A sand hopper 210 for storing the replenishment casting sand is mounted directly above the blow head 200 when it is returned to its original position. The sand hopper 210 is formed in a roughly funnel shape. The top surface of the sand hopper 210 is formed by a large opening 210a, and the lower part of the sand hopper 210 is a hollow, straight pipe section 211. Between the opening 210a and the straight pipe section 211, there is a tapering section 212 that narrows downwards. A shutter section 215 is attached to the lower end of the straight pipe section 211. Casting sand is fed into the sand hopper 210 through an opening 210a on the top surface. When the shutter (not shown) of the shutter section 215 is opened, the casting sand in the sand hopper 210 is replenished into the blow head 200, which had returned to its lower position. As shown in Figure 1, the position in which the blow head 200 is returned to below the sand hopper 210 and casting sand is replenished is sometimes referred to as the "replenishment position" of the blow head 200 in this specification.

[0020] As shown in Figure 1, the upper mold 100 is mounted on a rectangular upper mold mounting plate 110, and the lower mold 101 is mounted on a rectangular lower mold mounting plate 111. Cylindrical guide columns 112 are erected downwards from the four corners of the upper mold mounting plate 110, and the lower ends of each guide column 112 are fixed to rectangular guide column fixing plates 113. The lower mold mounting plate 111 is guided by the guide columns 112 and can move in the vertical direction, and the lifting shaft 115a of the lifting cylinder 115 is attached to the lower surface of the lower mold mounting plate 111. Therefore, by raising the lower mold mounting plate 111 using the lifting cylinder 115, the lower mold 101 can be brought into contact with the upper mold 100. Furthermore, by lowering the lifting cylinder 115 from that state, the lower mold 101 can be separated from the upper mold 100.

[0021] Furthermore, a lower burner 121 is mounted on the lower mold mounting plate 111, and the lower mold 101 is heated from below by the lower burner 121. On the other hand, the upper mold 100 can be heated from above by the upper burner 120. The upper burner 120 is mounted on a burner carriage 123, and the burner carriage 123, like the blow carriage 203 described above, is movable along the upper surface of the frame 10. The burner carriage 123 on which the upper burner 120 is mounted and the blow carriage 203 on which the blow head 200 is mounted are connected by a connecting part 124, so that when the blow carriage 203 is moved, the burner carriage 123 also moves. When the blow head 200 is moved to the replenishment position directly below the sand hopper 210, the upper burner 120 moves to a position directly above the upper mold 100 (see Figure 1). In this embodiment, the upper burner 120 corresponds to the "heating means" in the present invention.

[0022] The sand core manufacturing apparatus 1 of this embodiment, having the structure described above, manufactures sand cores as follows. First, as shown in Figure 2, the blow head 200 is moved to a replenishment position directly below the sand hopper 210, and then the shutter section 215 of the sand hopper 210 is opened to replenish the casting sand in the sand hopper 210 into the blow head 200. Also, while the blow head 200 is in the replenishment position, the upper burner 120 is directly above the upper mold 100, but at this stage the lower mold 101 is in a lowered position (i.e., separated from the upper mold 100). For this reason, the heat output of the upper burner 120 and the lower burner 121 is low.

[0023] After filling the blowhead 200 with casting sand, as shown in Figure 3, the blowhead 200 is moved to the injection position above the upper mold 100, and the lower mold mounting plate 111 is raised, causing the lower mold 101 to come into contact with the upper mold 100. This creates a molding space 102 between the upper mold 100 and the lower mold 101. An injection passage 100a is formed upward from the molding space 102, and the injection passage 100a opens onto the upper surface of the upper mold 100. With the blowhead 200 in the injection position, the pressure cap 204 is lowered using the pressure cylinder 206, causing the pressure cap 204 to come into contact with the upper surface of the blowhead 200. Further lowering of the pressure cap 204 pushes down the blowhead 200, causing the bottom surface of the blowhead 200 to come into contact with the upper surface of the upper mold 100. In this state, the position of the blow nozzle 200a opening on the bottom surface of the blow head 200 coincides with the position of the blowing passage 100a opening on the top surface of the upper mold 100. When pressurized air is supplied from the pressurizing hose 205 to the pressurizing cap 204, the casting sand replenished in the blow head 200 is blown out from the blow nozzle 200a together with the pressurized air and blown into the molding space 102 through the blowing passage 100a. In this way, the molding space 102 between the upper mold 100 and the lower mold 101 is filled with casting sand.

[0024] After filling the molding space 102 with casting sand, the upper burner 120 and lower burner 121 are heated to the upper mold 100 and lower mold 101, as shown in Figure 4. This heats the casting sand filling the molding space 102, melting the resin covering the surface of the casting sand and causing the casting sand particles within the molding space 102 to fuse together. Subsequently, as shown in Figure 5, the upper burner 120 and lower burner 121 are reduced to lower the lower mold 101, separating it from the upper mold 100. As a result, the casting sand that has fused and solidified into the shape of the molding space 102 (i.e., the sand core 5) also descends with the lower mold 101, and by removing this sand core 5, one sand core 5 can be obtained.

[0025] In this state, the blowhead 200 has returned to the filling position, so after replenishing the blowhead 200 with casting sand as described above using Figure 2, the sand core 5 can be manufactured in the same manner. Also, as shown in Figure 4, the heat output of the upper burner 120 and lower burner 121 is high only while the upper mold 100 and lower mold 101 are being heated, and the heat output of the upper burner 120 and lower burner 121 is low at other times. However, since the upper mold 100 and lower mold 101 have a large heat capacity and do not cool down easily, the temperature hardly drops even if the heat output of the upper burner 120 and lower burner 121 is reduced. Therefore, as explained using Figure 3, when blowing casting sand into the molding space 102 between the upper mold 100 and the lower mold 101, the casting sand is blown in while the upper mold 100 and lower mold 101 are at a high temperature.

[0026] Here, the surface of the sand hopper 210 facing the upper mold 100 and the lower mold 101 is constantly heated by radiant heat. As a result, when sand cores are manufactured continuously for a long period of time, the temperature of the casting sand near the surface of the sand hopper 210 may rise and exceed the temperature at which the resin coating on the surface begins to melt. When this happens, multiple pieces of casting sand fuse together, creating large pieces of casting sand. The casting sand needs to be filled into the molding space 102 with sufficient density and uniformity, so it is manufactured with an appropriate particle size to allow the casting sand to flow smoothly within the molding space 102. Therefore, if large pieces of casting sand are mixed in with such casting sand, the casting sand will not flow smoothly within the molding space 102, resulting in areas where the casting sand is not sufficiently filled. As a result, it may become difficult to manufacture sand cores of stable quality. To avoid this situation, the sand core manufacturing apparatus 1 of this embodiment is equipped with a sand hopper 210 with the following novel shape.

[0027] Figure 6 is an explanatory diagram showing the shape of the sand hopper 210 mounted on the sand core manufacturing apparatus 1 of this embodiment. The sand hopper 210 of this embodiment can be broadly divided into three parts: a straight pipe section 211, a tapering section 212, and a peripheral wall section 213. The straight pipe section 211 is formed in the shape of a hollow straight pipe and constitutes the lower part of the sand hopper 210. The tapering section 212 is formed at the top of the straight pipe section 211 and is formed in a tapering shape with a cross-sectional area that decreases towards the bottom. The peripheral wall section 213 is composed of a peripheral wall erected upward from the upper end of the tapering section 212, and the upper end of the peripheral wall section 213 is wide open to form an opening 210a.

[0028] Furthermore, a shutter section 215 is attached to the lower end of the straight pipe section 211. The shutter section 215 is a thick rectangular member, and a rectangular cross-section slit 215a is formed therein, penetrating from one side to the other. A thin shutter plate 216 is slidably mounted within this slit 215a. A circular discharge port 216a is formed in the shutter plate 216, and by sliding the shutter plate 216 using an actuator (not shown), the discharge port 216a of the shutter plate 216 is moved to a position directly below the straight pipe section 211, at which point the casting sand in the sand hopper 210 is discharged from the discharge port 216a and supplied to the blow head 200 below.

[0029] Furthermore, in this embodiment, the sand hopper 210 has a side surface that forms the narrowing portion 212, the side surface that faces the upper mold 100 and the lower mold 101 (or the side closer to the upper mold 100 and the lower mold 101) (hereinafter referred to as the mold-side side surface 212a) formed to face vertically upward. In contrast, the side surface on the opposite side of the mold-side side surface 212a (the side further from the upper mold 100 and the lower mold 101) (hereinafter referred to as the anti-mold-side side surface 212b) is formed to be inclined with respect to the vertical. In this specification, the angle θ that the side surface of the sand hopper 210 makes with respect to the vertical upward direction is referred to as the inclination angle.

[0030] Here, the inclination angle of the side of the sand hopper 210 is set to an angle smaller than the angle determined by the angle of repose of the casting sand, that is, the angle obtained by subtracting the angle of repose of the casting sand from 90 degrees. The angle of repose of casting sand is the angle formed by the slope of the mound relative to the horizontal plane when casting sand is piled up in a mound shape on a horizontal plane. It is known that casting sand cannot exist stably on a slope steeper than the angle of repose (a slope with a small inclination angle relative to the vertical direction). Therefore, by setting the inclination angle of the side of the sand hopper 210 to an angle smaller than the angle obtained by subtracting the angle of repose of the casting sand from 90 degrees, when the shutter section 215 is opened, the casting sand inside the sand hopper 210 will be discharged from the discharge port 216a of the shutter section 215 by its own weight. Furthermore, in this embodiment, the inclination angle of the mold side side 212a of the sand hopper 210 is set to be particularly small (0 degrees in this case). To prepare for explaining this reason, the following describes how the blowhead 200 of this embodiment blows casting sand supplied from the sand hopper 210 into the molding space 102 between the upper mold 100 and the lower mold 101.

[0031] Figure 7 is an explanatory diagram showing the internal structure of the blow head 200 of this embodiment. The blow head 200 of this embodiment has a hollow, large-diameter main body 200b on which a hollow introduction section 200c, smaller in diameter than the main body 200b, is attached, and the lower end of the main body 200b is closed by a disc-shaped bottom plate 200d. A circular through hole is formed at the center of the bottom plate 200d, and this through hole becomes the blow nozzle 200a. Above the blow nozzle 200a, inside the main body 200b, a disc-shaped retaining plate 202, larger in diameter than the blow nozzle 200a, is attached with a predetermined gap from the blow nozzle 200a. In addition, a straight-tube-shaped measuring cylinder 201 is attached to the inside of the hollow introduction section 200c, coaxial with the introduction section 200c. The outer diameter of the measuring cylinder 201 is smaller than the inner diameter of the introduction section 200c, and therefore, an annular air passage 201a is formed between the inner circumference of the introduction section 200c and the outer circumference of the measuring cylinder 201. The inner diameter of the measuring cylinder 201 is set to be slightly larger than the discharge port 216a formed in the shutter plate 216 of the shutter section 215, and the upper end surface of the measuring cylinder 201 is on the same plane as the upper end surface of the introduction section 200c. In addition, the retaining plate 202 provided below the measuring cylinder 201 is larger than the outer diameter of the measuring cylinder 201, but a predetermined gap is provided between the lower end surface of the measuring cylinder 201 and the upper surface of the retaining plate 202.

[0032] Figure 8 is an explanatory diagram showing how the blow head 200 of this embodiment blows out casting sand together with pressurized air from the blow nozzle 200a after receiving replenishment of casting sand from the sand hopper 210. Figure 8(a) shows how the blow head 200 receives replenishment of casting sand from the sand hopper 210. When replenishing casting sand in the blow head 200, the blow head 200 is moved to a replenishment position directly below the sand hopper 210, and then the shutter plate 216 is slid using an actuator (not shown) to move the discharge port 216a of the shutter plate 216 directly above the measuring cylinder 201, thereby opening the shutter section 215. As a result, the casting sand stored in the sand hopper 210 is discharged from the discharge port 216a and supplied to the inside of the measuring cylinder 201 (hereinafter referred to as the measuring passage 201b) provided in the blow head 200.

[0033] As mentioned above, the lower end of the measuring cylinder 201 is not blocked, so the casting sand supplied into the measuring passage 201b of the measuring cylinder 201 accumulates on the retaining plate 202 located below the measuring cylinder 201, forming a mound of casting sand with a slope at the angle of repose relative to the horizontal. As casting sand is supplied from the measuring passage 201b, this mound of casting sand grows while maintaining the angle of the slope at the angle of repose, and eventually the top of the mound reaches the lower end of the measuring cylinder 201. Then, the casting sand supplied into the measuring passage 201b thereafter does not flow out from the lower end of the measuring passage 201b but accumulates within the measuring passage 201b, and finally the entire measuring passage 201b is filled with casting sand. Figure 8(a) shows the state in which the entire measuring passage 201b is filled with casting sand in this way.

[0034] Once casting sand has accumulated throughout the entire weighing passage 201b, no more casting sand will be added, so the shutter section 215 is closed by sliding the shutter plate 216. As is clear from the above explanation, the total amount of casting sand supplied from the sand hopper 210 to the blowhead 200 is determined by the volume of the weighing passage 201b of the weighing cylinder 201. Therefore, by changing the length (or diameter) of the weighing cylinder 201, it is possible to adjust the volume of casting sand supplied from the sand hopper 210 to the blowhead 200.

[0035] After closing the shutter section 215 of the sand hopper 210, the blow head 200 is moved to a blowing position directly below the pressure cap 204 (directly above the upper mold 100), and then the pressure cap 204 is lowered. As the pressure cap 204 comes into contact with the upper end of the blow head 200, the blow head 200 is pushed down by the pressure cap 204, pressing it against the upper mold 100. In this state, pressurized air is supplied from the pressure hose 205 to the pressure cap 204. The pressurized air then flows from the pressure cap 204 into the air passage 201a of the blow head 200. Then, while drawing in the casting sand accumulated on the upper surface of the bottom plate 200d of the blow head 200, it is ejected from the blow nozzle 200a towards the upper mold 100. As a result, the pile of casting sand formed below the measuring cylinder 201 becomes unstable, causing the casting sand to be discharged from the measuring passage 201b. At the same time, the casting sand in the measuring passage 201b is quickly blown into the upper mold 100 from the blow nozzle 200a, pushed by the flow of pressurized air supplied from the pressure cap 204. In Figure 8(b), the flow of pressurized air blowing the casting sand in the blow head 200 into the upper mold 100 is shown by dashed arrows. In this embodiment, the sand core manufacturing apparatus 1 fills the molding space 102 between the upper mold 100 and the lower mold 101 with casting sand from the blow head 200 in a short time and uniformly. Based on the above circumstances, the reason why the mold-side surface 212a of the sand hopper 210 has a steeper slope than the non-mold-side surface 212b will now be explained.

[0036] Figure 9 is an explanatory diagram illustrating a conventional sand core manufacturing apparatus 9 equipped with a typical sand hopper 910 in which the mold-side surface 912a and the non-mold-side surface 912b are inclined in the same way. In the conventional sand core manufacturing apparatus 9, the upper mold 100 and lower mold 101 are heated to high temperatures, so when sand cores are manufactured continuously for a long period of time, the mold-side surface 912a of the sand hopper 910 is heated by radiant heat. As a result, the resin coating on the casting sand begins to melt near the mold-side surface 912a inside the sand hopper 910, and the casting sand pieces may fuse together, potentially generating large pieces of casting sand. In Figure 9, the way the mold-side surface 912a of the sand hopper 910 is heated by radiant heat from the upper mold 100 and lower mold 101 is represented by dashed wavy arrows. In contrast, the non-mold-side surface 912b is not heated by radiant heat, so large pieces of casting sand are not generated near the non-mold-side surface 912b. Generally, casting sand is carefully controlled in terms of particle size so that it can reach every corner of the molding space when blown into the mold. Therefore, if large particles of casting sand are present, it becomes difficult to fill every corner of the molding space with the casting sand.

[0037] In addition, as described above with reference to Figure 8, in the sand core manufacturing apparatus 1 of this embodiment, the casting sand in the sand hopper 910 is supplied from the discharge port 216a formed in the shutter plate 216 into the metering passage 201b of the metering cylinder 201. Since the inner diameter of the metering passage 201b is only slightly larger than the discharge port 216a, the casting sand near the mold side surface 912a and the casting sand near the opposite mold side surface 912b in the sand hopper 910 are supplied into the metering passage 201b with almost no mixing, and are then blown into the molding space 102 between the upper mold 100 and the lower mold 101 in the same state. As a result, in the area where the casting sand near the mold side surface 912a (casting sand containing large casting sand particles) is mainly blown, it is difficult to blow the casting sand uniformly compared to the area where the casting sand near the opposite mold side surface 912b is mainly blown. From this point of view as well, it is difficult to stably manufacture high-quality sand cores.

[0038] In contrast, in the sand core manufacturing apparatus 1 of this embodiment, the mold-side surface 212a that forms the narrowing portion 212 of the sand hopper 210 is formed with a steeper incline than the opposite mold-side surface 212b. As a result, as shown in Figure 10, the mold-side surface 212a of the sand hopper 210 is inclined with respect to the upper mold 100 and lower mold 101, and is not directly exposed to radiant heat from the upper mold 100 and lower mold 101 compared to the mold-side surface 912a of the sand hopper 910 shown in Figure 9. As a result, the rise in temperature of the casting sand near the mold-side surface 212a inside the sand hopper 210 is suppressed, and the situation in which the resin coating on the casting sand begins to melt and the casting sand pieces fuse together is less likely to occur.

[0039] However, even though it does not directly receive radiant heat, the mold side surface 212a of the sand hopper 210 in this embodiment still receives radiant heat from the upper mold 100 and the lower mold 101. Therefore, if sand cores are manufactured continuously for too long, the temperature of the mold side surface 212a will rise, potentially reaching a temperature at which the resin coating on the casting begins to melt. However, even if the temperature of the mold side surface 212a rises to such a temperature, the sand core manufacturing apparatus 1 in this embodiment can still stably manufacture high-quality sand cores. The reason for this will be explained below.

[0040] Figure 11 is an explanatory diagram showing how casting sand in the sand hopper 210 of this embodiment is supplied to the blow head 200. In the figure, the shaded area represents the casting sand stored in the sand hopper 210, and the thick solid arrows represent the flow of casting sand supplied to the blow head 200. As described above, in this embodiment, the mold-side surface 212a of the sand hopper 210 is formed vertically, while the opposite-mold-side surface 212b is formed at an inclination with respect to the vertical. Therefore, the casting sand near the opposite-mold-side surface 212b slides along the surface 212b towards the blow head 200, while the casting sand near the mold-side surface 212a falls straight down due to its own weight. Consequently, the speed at which the casting sand moves within the sand hopper 210 is greater near the mold-side surface 212a than near the opposite-mold-side surface 212b. In other words, the casting sand stored in the sand hopper 210 is supplied to the blowhead 200 with priority given to the casting sand near the mold side surface 212a over the casting sand near the opposite mold side surface 212b. In Figure 11, the movement of the casting sand near the mold side surface 212a is represented by a long arrow, and the movement near the opposite mold side surface 212b is represented by a short arrow, indicating that the movement speed of the casting sand is greater near the mold side surface 212a than near the opposite mold side surface 212b.

[0041] Here, although the mold side surface 212a of the sand hopper 210 is heated, it does not become as hot as the upper mold 100 or the lower mold 101. Therefore, some time is required between the time the casting sand comes into contact with the mold side surface 212a and the time the coated resin begins to melt. As mentioned above, the casting sand near the mold side surface 212a is supplied to the blowhead 200 with priority over the casting sand near the opposite mold side surface 212b, so the coated resin can be supplied to the blowhead 200 before it begins to melt.

[0042] However, as the time required for the casting sand near the mold side surface 212a to be supplied to the blowhead 200 is shortened, the time required for the casting sand near the opposite mold side surface 212b to be supplied to the blowhead 200 is longer. However, since the opposite mold side surface 212b is not heated by the radiant heat of the upper mold 100 or lower mold 101, it does not reach the temperature at which the resin coating on the casting sand begins to melt. Therefore, even if the time required for the casting sand near the opposite mold side surface 212b to be supplied to the blowhead 200 is longer, the resin coating will not begin to melt. As a result, all the casting sand from near the mold side surface 212a to near the opposite mold side surface 212b can be supplied into the blowhead 200 while maintaining the appropriate particle size. For these reasons, the sand core manufacturing apparatus 1 of this embodiment can stably manufacture high-quality sand cores even when sand cores are manufactured continuously for a long period of time.

[0043] In the above explanation, it was assumed that the mold-side surface 212a of the sand hopper 210 is formed in the vertical direction. However, the mold-side surface 212a only needs to be formed on a steeper slope than the opposite mold-side surface 212b, and the mold-side surface 212a does not necessarily have to be formed in the vertical direction.

[0044] In another embodiment of the sand hopper 210 illustrated in Figure 12, the mold-side surface 212a is formed at an inclination angle θa with respect to the vertical. However, this inclination angle θa is smaller than the inclination angle θb of the non-mold-side surface 212b with respect to the vertical. In this other embodiment of the sand hopper 210 as well, the casting sand near the mold-side surface 212a is supplied to the blowhead 200 with priority over the casting sand near the non-mold-side surface 212b. Therefore, even if the temperature of the mold-side surface 212a rises to the temperature at which the resin coating the casting sand begins to melt, the sand can be supplied to the blowhead 200 before the resin begins to melt. As a result, even when sand cores are manufactured continuously for a long period of time, it is possible to stably produce high-quality sand cores.

[0045] Furthermore, from the viewpoint of supplying casting sand near the mold side surface 212a to the blowhead 200 with priority over casting sand near the opposite mold side surface 212b, it is most desirable that the inclination angle θa of the mold side surface 212a be 0 degrees (i.e., vertical). However, it has been empirically proven that if the inclination angle θa of the mold side surface 212a is set to half or less (preferably one-third or less) of the inclination angle θb of the opposite mold side surface 212b, casting sand near the mold side surface 212a can be supplied to the blowhead 200 with sufficient priority. For this reason, even when sand cores are manufactured continuously over a long period of time, it is possible to stably manufacture high-quality sand cores.

[0046] Finally, let's explain the case where the inclination angle θa of the mold side surface 212a is negative (i.e., the mold side surface 212a tilts inward). In the sand hopper 510 shown as an example in Figure 13, the inclination angle θa of the mold side surface 512a is set to negative. As shown in Figure 13(a), if a sufficient amount of casting sand is stored in the sand hopper 510, casting sand can be supplied to the blow head 200 in the same way as the sand hopper 210 in the embodiment described above. However, as shown in Figure 13(b), as the amount of casting sand in the sand hopper 510 decreases, the amount of casting sand supplied from the mold side surface 512a decreases. As a result, it may become difficult to replenish the casting sand to the blow head 200 in time, and it may become difficult to fill the molding space in the upper mold 100 and lower mold 101 with sufficient casting sand. For this reason, it is preferable not to set the inclination angle θa of the mold side surface 212a to negative.

[0047] Although the sand core manufacturing apparatus 1 and sand hopper 210 of this embodiment have been described above, the present invention is not limited to the above embodiment and can be implemented in various forms without departing from the spirit of the invention. [Explanation of symbols]

[0048] 1...Sand core manufacturing device, 5...Sand core, 9...Sand core manufacturing device, 10...Frame, 11...rail, 100...upper mold, 100a...blowing passage, 101...lower mold, 102...molding space, 110...upper mold mounting plate, 111...Lower mold mounting plate, 112...Guide column, 113...Guide column fixing plate, 115... Lifting cylinder, 115a... Lifting shaft, 120... Upper burner, 121...Lower burner, 123...Burner carriage, 124...Connecting section 200...Blow head, 200a...Blow nozzle, 200b...Main unit 200c...Introduction part, 200d...Bottom plate, 201...Measuring tube, 201a...Air passage, 201b...Weighing passage, 202...Holding plate, 203...Blow carriage, 204...Pressure cap, 205...Pressure hose 206...Pressurizing cylinder, 210...Sand hopper, 210a...Opening, 211...Straight pipe section, 212...Narrowing section, 212a...Side surface of the mold, 212b... Side surface opposite the mold, 213... Peripheral wall portion, 215... Shutter portion, 215a... Slit, 216... Shutter plate, 216a... Discharge port, 510... Sand hopper, 910... Sand hopper.

Claims

1. A sand core manufacturing apparatus for producing a sand core in which the casting sand is solidified into the shape of the molding space by stacking two molds vertically to form a molding space between the two molds, filling the molding space with casting sand through a blowing passage opening on the upper surface of the upper mold, and then heating the two molds, the apparatus comprises: A blowhead fills the molding space with casting sand by blowing the casting sand into the blowing passage from a blowing position set above the upper mold, and after the casting sand is filled, the blowhead retracts laterally from the blowing position, After the blowhead is retracted, the heating means moves to a heating position set above the upper mold to heat the upper mold, and after the upper mold is heated, it retracts from the heating position. A sand hopper is mounted above the blowhead, which has been retracted laterally from the blowing position, and is formed in a tapering shape toward the discharge port on its bottom surface, and replenishes the blowhead by discharging the casting sand stored inside through the discharge port. Equipped with, The aforementioned blowhead is A blow nozzle is provided, which opens on the bottom surface of the blow head and from which the casting sand filling the molding space is blown out. A circular opening formed on the upper surface of the blowhead, A cylindrical measuring tube extends from the position where the opening is located toward the bottom surface of the blowhead, and It has, The measuring cylinder is mounted such that its outer diameter is smaller than the opening, and a gap is formed between its lower end and the bottom surface of the blow head. When the casting sand is replenished from the sand hopper to the blowhead, the casting sand discharged from the outlet of the sand hopper flows into the measuring cylinder and is held within the measuring cylinder. When filling the molding space with the casting sand, pressurized air is supplied into the blow head from the opening. A portion of the pressurized air flows through the outside of the measuring cylinder towards the blow nozzle, while the remaining pressurized air pushes out the casting sand inside the measuring cylinder, causing it to flow out from the lower end of the measuring cylinder. The flowing casting sand, along with the pressurized air that has passed through the outside of the measuring cylinder, is then blown out from the blow nozzle. The aforementioned sand hopper is The side surface of the sand hopper is formed to have a steeper slope than the angle of repose of the casting sand. The side surface closest to the mold, the mold-side side surface, is formed with a steeper incline than the side surface furthest from the mold, the anti-mold side surface. A sand core manufacturing apparatus characterized by the following features.

2. In the sand core manufacturing apparatus according to claim 1, The side surface of the mold is formed such that the angle of inclination, which is the angle it makes with respect to the vertical, is less than or equal to half the angle of inclination of the side surface opposite the mold. A sand core manufacturing apparatus characterized by the following features.

3. In the sand core manufacturing apparatus according to claim 2, The side surface of the mold is formed with an inclination angle of 0 degrees. A sand core manufacturing apparatus characterized by the following features.

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