JP2012170965A - Vacuum casting apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a vacuum casting apparatus capable of appropriately preventing molten metal from boiling over into a vacuum cup by the backward flow of molten metal at the time of emergency stop.SOLUTION: In the vacuum casting apparatus including a vacuum cup 9 that surrounds the end portion of an injection sleeve 6 on the side opposite to a mold and performs casting in a state where the inside of a mold (cavity 4) and the vacuum cup 9 is depressurized, the internal pressure of the vacuum cup 9 at the time of emergency stop is made higher than the internal pressure of the mold (cavity 4) by opening an atmosphere opening valve 17 to expose the vacuum cup 9 to the atmosphere.

Description

  The present invention relates to a reduced pressure casting apparatus that includes a reduced pressure cup that surrounds an end of an injection sleeve on the side opposite to a mold, and performs casting in a state where the inside of the mold and the reduced pressure cup is decompressed.

  Conventionally, as a device for casting metal products and resin products, there is a vacuum casting device such as a vacuum die casting device that prevents bubbles from being caught in a molded product by reducing the pressure inside the cavity prior to casting. Are known. Conventionally, as seen in, for example, Patent Literatures 1 and 2, a vacuum cup that includes a vacuum cup that surrounds the end of the injection sleeve on the side opposite to the mold, and performs casting in a state where the inside of the mold and the vacuum cup is decompressed. The device is in practical use.

  The configuration of such a vacuum casting apparatus is shown in FIG. Next to a fixed mold 50 fixed to a die casting machine platen (not shown), there is provided a movable mold 51 disposed so as to be close to and away from the fixed mold 50. The fixed mold 50 and the movable mold 51 are brought into close contact with each other so that a cavity 52 is formed between them.

  A cylindrical injection sleeve 54 is attached to the fixed mold 50, and a hot water supply port 55 for supplying molten metal is formed in the vicinity of the end on the side opposite to the mold. Inside the injection sleeve 54, an injection tip 56 for extruding the molten metal supplied to the inside and injecting it into the cavity 52 is slidably disposed. A pressure reducing cup 57 is provided at the end of the injection sleeve 54 on the side opposite to the mold so as to surround the end. The cavity 52 and the decompression cup 57 are connected to decompression hoses 58 and 59 for extracting air from the inside.

  In the vacuum casting apparatus configured as described above, at the time of casting, first, the fixed mold 50 and the movable mold 51 are clamped by a mold clamping hydraulic cylinder (not shown). Then, after supplying the molten metal into the injection sleeve 54 from the hot water supply port 55, the decompression cup 57 is closed to seal the periphery of the end portion of the injection sleeve 54 on the side opposite to the mold. Thereafter, the insides of the cavity 52 and the decompression cup 57 are decompressed, and the molten metal in the injection sleeve 54 is pushed out by the injection tip 56 and injected into the cavity 52, thereby casting the product.

JP 2008-093712 A JP 2009-202179 A

  By the way, in such a vacuum casting apparatus, depending on the situation, an emergency stop may be applied during the injection of the molten metal. In this case, the molten metal may flow backward in the pressure reducing cup 57, although rarely.

  The cause is as follows. That is, when an emergency stop is applied, the cylinder hydraulic pressure of the mold clamping hydraulic cylinder is lowered, and the mold clamping between the fixed mold 50 and the movable mold 51 is released. Then, since there is no restriction on both molds, the mold may be warped by heat, and the seal part between the molds may open. When the seal portion is opened, air flows into the decompressed cavity 52 from the opened seal portion, and the air flows into the decompression cup 57 that is also decompressed. And when the seal part of the lower part of both metal mold | dies opens, as shown in FIG. 5, air will flow in the direction which lifts the molten metal M in the injection sleeve 54. As shown in FIG. Therefore, the molten metal M may be blown up and blown from the hot water supply port 55 into the decompression cup 57.

  The present invention has been made in view of such circumstances, and the problem to be solved is a vacuum casting that can suitably prevent the molten metal from overflowing into the vacuum cup due to the reverse flow of the molten metal during an emergency stop. To provide an apparatus.

  In order to solve the above-mentioned problem, the pressure reduction casting apparatus according to claim 1, comprising a pressure reduction cup surrounding an end portion of the injection sleeve on the side opposite to the mold, and performing casting in a state where the inside of the mold and the pressure reduction cup is decompressed. The invention includes a pressure-reducing cup pressure-increasing means for making the internal pressure of the pressure-reducing cup higher than that of the mold when the casting apparatus is in an emergency stop.

  In the above configuration, even if the mold clamping is released due to an emergency stop and the seal portion between the molds is opened, the internal pressure of the decompression cup is made higher than the internal pressure of the mold by the decompression cup internal pressure increase means. The air flowing in from the open seal portion does not flow toward the decompression cup. Therefore, the backflow of the molten metal is suppressed, and the overflow of the molten metal into the decompression cup due to the backflow of the molten metal at the time of emergency stop is suitably prevented. In addition, as the pressure increasing means in the decompression cup, an atmosphere release valve that enables the interior of the decompression cup to be opened to the atmosphere can be used.

  If it is desired to reliably prevent the backflow of the molten metal at the time of emergency stop, the internal pressure of the pressure reducing cup is increased to a pressure that can prevent the molten metal from scattering into the inside by the pressure increasing means in the pressure reducing cup. Therefore, it is preferable to set the time required for this to be shorter than the time from the emergency stop until the seal part of the mold opens.

  Furthermore, when a hydraulic circuit for clamping the mold is provided, the hydraulic pressure maintenance for maintaining the mold clamping until the internal pressure of the pressure reducing cup becomes a pressure capable of suppressing the scattering of the molten metal as in claim 4. And a mold clamping release means for releasing the mold clamping after the internal pressure of the pressure reducing cup reaches a pressure capable of suppressing the scattering of the molten metal as in claim 5, thereby ensuring a more reliable backflow of the molten metal. Can be prevented.

BRIEF DESCRIPTION OF THE DRAWINGS Schematic which shows typically the structure of the pressure reduction casting apparatus which concerns on the 1st Embodiment of this invention. The schematic diagram which shows transition of the cylinder hydraulic pressure before and behind an emergency stop, the pressure reduction cup internal pressure, and the mold opening amount in the pressure reduction casting apparatus of the embodiment. The schematic diagram which shows typically the structure of the pressure reduction casting apparatus which concerns on the 2nd Embodiment of this invention. The schematic diagram which shows the structure of the conventional pressure reduction casting apparatus typically. The schematic diagram which shows typically the state after an emergency stop of the conventional vacuum casting apparatus.

(First embodiment)
Hereinafter, an embodiment embodying the reduced pressure casting apparatus of the present invention will be described in detail with reference to FIG. 1 and FIG.

  As shown in FIG. 1, in the reduced pressure casting apparatus of this embodiment, a fixed mold 1 is disposed in a state of being fixed to a fixed platen. On the left side of the fixed mold 1 in the figure, there is disposed a movable mold 3 that is driven by a hydraulic cylinder 2 so as to approach and separate from the fixed mold 1. When the movable mold 3 is brought into close contact with the fixed mold 1, a cavity 4 is formed between both molds. The movable mold 3 is provided with an extrusion pin 5 for releasing the cast product.

  A cylindrical injection sleeve 6 is attached to the fixed mold 1. Near the end of the injection sleeve 6 on the side opposite to the mold, a hot water supply port 7 for supplying molten metal is formed. An injection tip 8 for extruding the molten metal supplied to the inside of the injection sleeve 6 and injecting it into the cavity 4 is slidably disposed. A pressure reducing cup 9 is provided at the end of the injection sleeve 6 where the hot water supply port 7 is formed on the side opposite to the mold.

  On the other hand, the cavity 4 and the decompression cup 9 are connected to decompression hoses 10 and 11 for extracting air from the inside thereof. In the reduced pressure casting apparatus of the present embodiment, a reduced pressure cutoff valve 12 that blocks air suction is installed in the middle of the reduced pressure hose 11 connected to the reduced pressure cup 9. Both decompression hoses 10 and 11 are connected to a decompression pump 15 for sucking air through a decompression switching valve 13 for turning on / off air suction and a decompression tank 14 having a constant volume.

  Furthermore, in the reduced pressure casting apparatus of the present embodiment, an air release pipe 16 whose tip is open to the atmosphere is connected to the vacuum cup 9. The atmosphere release pipe 16 is provided with an atmosphere release valve 17 so that the inside of the decompression cup 9 is opened to the atmosphere in accordance with the opening. In the reduced pressure casting apparatus of the present embodiment, the atmospheric release pipe 16 and the atmospheric release valve 17 are configured so that the internal pressure of the vacuum cup 9 is set to the internal pressure of the mold (internal pressure of the cavity 4) when the casting apparatus is in an emergency stop. This is equivalent to the pressure-increasing means in the decompression cup that is also increased.

Next, the operation of the present embodiment configured as described above will be described.
In casting the product, after the release agent is sprayed on the inner peripheral surface of the cavity 4, the movable die 3 is brought into close contact with the fixed die 1 by the hydraulic cylinder 2. It should be noted that the hydraulic cylinder 2 continues to be applied with hydraulic pressure after that, so that both molds are clamped.

  Subsequently, the molten metal is supplied into the injection sleeve 6 from the hot water supply port 7. When the supply of the molten metal is finished, the decompression cup 9 is closed, and the end portion on the side opposite to the mold of the injection sleeve 6 where the hot water supply port 7 is formed is sealed.

  When the decompression cup 9 is closed, the decompression cutoff valve 12 and the decompression switching valve 13 are opened. As a result, air is removed from the inside of the cavity 4 and the decompression cup 9 by the decompression pump 15. When the inside of the cavity 4 and the decompression cup 9 is sufficiently decompressed, the injection tip 8 advances and the molten metal in the injection sleeve 6 is injected into the cavity 4.

  When the molten metal injected into the cavity 4 cools and hardens, the movable mold 3 is separated from the fixed mold 1 by the hydraulic cylinder 2. Then, the cast product is released from the movable mold 3 by the extrusion pin 5.

  In such a vacuum casting apparatus, depending on the situation, the operation may be stopped in the middle of the casting operation. Next, the operation at the time of emergency stop in the reduced pressure casting apparatus of the present embodiment will be described.

  When an emergency stop is instructed after the molten metal is poured and the decompression cup 9 is closed and decompression is started, first, the extrusion of the molten metal by the injection tip 8 and the application of cylinder hydraulic pressure to the hydraulic cylinder 2 are performed. Stopped. At this time, in the vacuum casting apparatus of the present embodiment, the vacuum shutoff valve 12 is closed and the atmosphere release valve 17 is opened. As a result, the decompressed cup 9 is opened to the atmosphere.

  FIG. 2 shows changes in the cylinder hydraulic pressure Pm, the pressure reducing cup internal pressure Pc, and the mold opening amount L at this time. As shown in the figure, when an emergency stop is performed, the hydraulic pressure (the cylinder pressure Pm) applied to the hydraulic cylinder 2 is rapidly reduced. When the cylinder hydraulic pressure Pm decreases and the clamping force of the fixed mold 1 and the movable mold 3 decreases, the mold warps due to heat and the seal portions of both molds open. For this reason, as the cylinder hydraulic pressure Pm decreases, the opening amount (mold opening amount L) of the seal portions of the fixed mold 1 and the movable mold 3 increases.

  On the other hand, in the reduced pressure casting apparatus of the present embodiment, the pressure reducing cup 9 is opened to the atmosphere along with the emergency stop, so that the pressure reducing cup internal pressure Pc gradually increases to the atmospheric pressure after the emergency stop. Therefore, if the decompression cup internal pressure Pc can be increased to a level that does not cause a rapid backflow of air from the cavity 4 side before the mold opening occurs, the inside of the decompression cup 9 due to the backflow of air corresponding to the mold opening. It is possible to prevent the molten metal from overflowing.

  Here, the time from the emergency stop instruction until the pressure reduction cup internal pressure Pc increases to the pressure Px that can prevent the molten metal from overflowing is “Tc”, and the mold opening occurs due to the cylinder hydraulic pressure drop from the emergency stop instruction. The time until is “Tm”. In the reduced pressure casting apparatus of the present embodiment, the opening area when the air release valve 17 is opened is set so that the time Tc is shorter than the time Tm. Specifically, the opening area of the air release valve 17 when the valve is opened is set to be twice or more the area of the mold opening that is assumed at the time of emergency stop, so that the cavity 4 can be moved into the decompression cup 9. It has been confirmed that the backflow of air can be effectively prevented.

  In such a reduced pressure casting apparatus of the present embodiment, even if mold opening occurs, the inside of the reduced pressure cup 9 at that time is sufficiently high enough to overcome the backflow of air from the cavity 4 side. . Therefore, in this reduced pressure casting apparatus, the overflow of the molten metal due to the backflow of air at the time of emergency stop is effectively prevented.

According to the vacuum casting apparatus of the present embodiment described above, the following effects can be achieved.
(1) In the present embodiment, the atmospheric release pipe 16 and the atmospheric release valve 17 are provided for making the internal pressure of the pressure reducing cup 9 higher than the internal pressure of the mold during an emergency stop. Therefore, it is possible to suitably prevent the molten metal from overflowing into the decompression cup due to the reverse flow of the molten metal during an emergency stop.

  (2) In this embodiment, the time Tc required for the pressure reducing cup internal pressure Pc to rise to the pressure Px that can prevent the molten metal from overflowing by the opening of the air release valve 17 is reduced by the emergency stop. Thus, the time until the seal portion of the mold is opened is made shorter than Tm. Therefore, the backflow of the molten metal at the time of an emergency stop can be prevented reliably.

(Second Embodiment)
Next, a second embodiment in which the reduced pressure casting apparatus of the present invention is embodied will be described in detail with reference to FIG. In the present embodiment, the same components as those in the above embodiment are denoted by the same reference numerals, and detailed description thereof is omitted.

  In the first embodiment, the atmosphere release valve 17 is configured so that the pressure reducing cup internal pressure Pc can be increased to the pressure Px before the mold seal portion is opened, so that the molten metal overflows due to the reverse flow at the time of emergency stop. I was trying to prevent. However, when there is a restriction on the physique or the like of the air release valve 17 that can be installed, the rising time of the pressure reducing cup internal pressure Pc may not be shortened sufficiently. Even in such a case, if the decrease in the cylinder hydraulic pressure Pm after the emergency stop can be delayed, it is possible to prevent the molten metal from overflowing.

  Therefore, in the present embodiment, hydraulic pressure maintaining means for maintaining mold clamping is provided until the internal pressure of the decompression cup 9 reaches a pressure that can suppress the scattering of the molten metal. In other words, in the present embodiment, there is provided mold clamping releasing means for releasing mold clamping after the internal pressure of the pressure reducing cup 9 becomes a pressure capable of suppressing the scattering of the molten metal. .

  FIG. 3 shows the configuration of the reduced pressure casting apparatus of this embodiment. As shown in the figure, the reduced-pressure casting apparatus of the present embodiment includes a hydraulic circuit for clamping the mold.

  Such a hydraulic circuit is provided with a hydraulic hose 18 for supplying cylinder hydraulic pressure to be applied to the hydraulic cylinder 2. In the middle of the hydraulic hose 18, there is a check valve 19 that allows oil to be supplied to the hydraulic cylinder 2 while prohibiting oil from being discharged from the hydraulic cylinder 2, and a throttle 20 that restricts the flow of oil. They are arranged in parallel.

  The hydraulic hose 18 is branched into a hydraulic supply hose 21 and a hydraulic discharge hose 23 on the upstream side of the check valve 19 and the throttle 20. The hydraulic supply hose 21 is provided with an oil pump 24 that supplies pressurized oil toward the hydraulic cylinder 2 and an oil supply cutoff valve 22 that shuts off the supply of such oil. On the other hand, the oil pressure discharge hose 23 is provided with an oil discharge cutoff valve 25 for blocking oil discharge through the hose.

Next, the operation at the time of emergency stop of the reduced pressure casting apparatus of the present embodiment configured as described above will be described.
Even in the reduced pressure casting apparatus of the present embodiment, when an emergency stop instruction is given, the extrusion of the molten metal by the injection tip 8 and the application of the cylinder hydraulic pressure to the hydraulic cylinder 2 are stopped. At this time, the decompression shutoff valve 12 is closed and the air release valve 17 is opened. As a result, the decompressed cup 9 is opened to the atmosphere.

  On the other hand, in the reduced pressure casting apparatus of the present embodiment, in response to an emergency stop instruction, the oil supply shutoff valve 22 is closed to stop the oil supply to the hydraulic cylinder 2, and the oil discharge shutoff valve 25 is opened to open the hydraulic cylinder. 2 starts to drain oil. However, since the oil is discharged through the throttle 20 at this time, the cylinder hydraulic pressure Pm gradually decreases. Therefore, in the reduced pressure casting apparatus of the present embodiment, the decrease in the cylinder hydraulic pressure Pm at the time of emergency stop and the accompanying mold opening (opening of the mold seal portion) are delayed. Therefore, in the present embodiment, the mold clamping is maintained until the internal pressure of the decompression cup 9 reaches the pressure Px that can suppress the scattering of the molten metal. In other words, in the present embodiment, when the internal pressure of the decompression cup 9 reaches a pressure at which the molten metal can be prevented from being scattered, the substantial mold clamping is released.

  In this embodiment, the throttle 20 has a hydraulic pressure maintaining means for maintaining mold clamping until the internal pressure of the decompression cup 9 becomes a pressure at which the molten metal can be suppressed, or the internal pressure of the decompression cup 9 is reduced. When the pressure reaches a level at which the molten metal can be prevented from being scattered, the structure corresponds to mold clamping release means that substantially releases mold clamping.

According to the present embodiment, in addition to the effects (1) and (2), the following effects can be further achieved.
(3) In the present embodiment, the clamping of the mold is maintained until the internal pressure of the decompression cup 9 reaches the pressure Px that can suppress the scattering of the molten metal by installing the throttle 20. Further, in the present embodiment, the mold 20 is released from the mold clamping after the inner pressure of the decompression cup 9 becomes a pressure capable of suppressing the scattering of the molten metal by the installation of the throttle 20. Therefore, even when the increase in the pressure reducing cup internal pressure Pc due to the opening of the air release valve 17 cannot be made too early, the backflow of the molten metal can be reliably prevented.

It should be noted that each of the above embodiments can be modified as follows.
In the second embodiment, the check valve 19 and the throttle 20 are provided in the hydraulic hose 18 so as to delay the time when mold opening occurs. The reverse flow of the molten metal can be prevented by providing it instead. That is, by closing such a shutoff valve together with an emergency stop instruction, oil discharge from the hydraulic cylinder 2 is stopped to maintain the clamping, and when it is confirmed that the pressure reducing cup internal pressure Pc has sufficiently increased, or the pressure reducing The shut-off valve is opened when a time during which the cup internal pressure Pc can be sufficiently increased has elapsed. In this way, the mold clamping is maintained until the pressure reduction cup internal pressure Pc reaches a pressure Px at which the molten metal scattering can be suppressed, or the pressure reduction cup internal pressure Pc becomes the pressure Px at which the molten metal scattering can be suppressed. At this point, the mold clamping can be released.

  In the above embodiment, the decompression shut-off valve 12 is closed to stop the decompression in the decompression cup 9, and the atmosphere release pipe 16 is opened to allow the outside air to flow into the decompression cup 9, so that the emergency stop is performed. However, it is possible to substitute these two valves with a single three-way valve. In this case, the three-way valve is configured to selectively connect either the decompression hose provided with the decompression pump 15 or the air release hose whose tip is open to the atmosphere to the hose connected to the decompression cup 9. For example, it is possible to increase the pressure reducing cup internal pressure Pc at the time of emergency stop similar to the above embodiment.

  In the above embodiment, the decompression cup 9 is opened to the atmosphere to increase the decompression cup internal pressure Pc at the time of emergency stop. However, air pressurized by an air pump or the like is sent into the decompression cup 9. Thus, the pressure reducing cup internal pressure Pc at the time of emergency stop may be increased.

  M ... molten metal, 1 ... fixed type, 2 ... hydraulic cylinder, 3 ... movable type, 4 ... cavity, 5 ... extrusion pin, 6 ... injection sleeve, 7 ... hot water inlet, 8 ... injection tip, 9 ... decompression cup, 10 DESCRIPTION OF SYMBOLS ... Pressure-reducing hose, 11 ... Pressure-reducing hose, 12 ... Pressure-reducing cutoff valve, 13 ... Pressure-reducing switching valve, 14 ... Pressure-reducing tank, 15 ... Pressure-reducing pump, 16 ... Air release pipe, 17 ... Air release valve, 18 ... Hydraulic hose, 19 ... Check valve, 20 ... throttle, 21 ... hydraulic supply hose, 22 ... oil supply cutoff valve, 23 ... hydraulic discharge hose, 24 ... oil pump, 25 ... oil discharge cutoff valve, 50 ... fixed type, 51 ... movable type, 52 ... cavity, 54 ... injection sleeve, 55 ... hot water inlet, 56 ... injection tip, 57 ... decompression cup, 58 ... decompression hose, 59 ... decompression hose.

Claims (5)

In a reduced pressure casting apparatus that includes a reduced pressure cup that surrounds an end of the injection sleeve on the side opposite to the mold, and performs casting in a state where the inside of the mold and the reduced pressure cup is decompressed,
A decompression casting apparatus, comprising: a decompression cup internal pressure-increasing means for making the internal pressure of the decompression cup higher than the internal pressure of the mold when the casting apparatus is in an emergency stop. The reduced pressure casting apparatus according to claim 1, wherein the pressure reducing cup pressurizing means is an air release valve that allows the pressure reducing cup to be opened to the atmosphere. The time required for increasing the internal pressure of the pressure reducing cup to a pressure that can prevent the molten metal from splashing into the inside by the pressure increasing means in the pressure reducing cup is longer than the time from the emergency stop until the seal portion of the mold opens. The reduced pressure casting apparatus according to claim 1 or 2, wherein the reduced pressure casting apparatus is set to be shorter. A hydraulic circuit for clamping the mold and a hydraulic pressure maintaining means for maintaining the mold clamping until the internal pressure of the decompression cup reaches a pressure that can suppress the scattering of the molten metal. The reduced pressure casting apparatus according to any one of the above. A hydraulic circuit that clamps the mold and a mold release unit that releases the mold clamping after the internal pressure of the pressure reducing cup reaches a pressure that can suppress the scattering of the molten metal. 4. The vacuum casting apparatus according to any one of 3 above.

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