MXPA99001687A - Method for ventilating a mold of foundry to the troquel, and apparatus to realize the met - Google Patents

Abstract

The present invention relates to a valve assembly for venting a die-casting mold of a die-casting machine that is provided with a casting piston located in a pressure chamber for compressing the liquid melting material into a die-casting cavity. mold of said die-casting mold, wherein said die-casting mold is provided with a ventilation channel communicating with said mold cavity, said valve assembly comprising: a first vent valve communicating with said vent channel; vent, an impact transmitter that is operatively connected to said first vent valve, said impact transmitter being exposed to, and being moved by said liquid casting material advancing from said mold cavity toward said vent, said transmitter of impact closes said first vent valve when said impact transmitter is moved said liquid melting material, a second venting valve communicating with said venting channel, and separate, independent means for operating said second venting valve, said first venting valve and said second venting valve being located below said mold cavity, in said impact transmitter, said ventilation channel includes a first essentially straight portion of the ventilation channel, said second vent valve being located at the end of said first essentially straight portion of the ventilation channel; Ventilation channel includes a second portion of ventilation channel having corners, said first ventilation valve being located in said second portion of the ventilation channel.

Description

METHOD FOR VENTILATING A MOLD OF FOUNDRY TO THE TROQUEL. AND APPARATUS TO PERFORM THE METHOD FIELD OF THE INVENTION The present invention relates to a method for ventilating a die-casting mold of a die-casting machine which is provided with a casting piston located in a pressure chamber, and adapted to compress the casting material. liquid in the cavity of the die-casting mold. The die-casting mold is provided with at least one vent channel communicating with the mold cavity, and comprising a first vent valve that is operatively connected to an impact transmitter. The impact transmitter is exposed to, and is moved by, the molten liquid material advancing from the mold cavity into the ventilation channel. In addition, the present invention also relates to an apparatus for performing this method. In order to prevent the presentation of trapped air in the finished molten workpiece, the die-casting mold and die cavity of the die-casting mold, respectively, must be ventilated during the die-casting operation. In this way, it must be ensured that not only the air contained in the cavities of the die-casting machine and the die-casting mold can escape, but also that the gases can be removed in the same manner. that escape from the liquid melting material. In the ventilation of a die-casting mold, there is a problem that the vent valve must be closed as late as possible, in order to ensure that the mold cavity is ventilated, if possible, until be completely filled; On the other hand, liquid melting material must be prevented from entering the ventilation valve. Taking this problem into account, ventilation assemblies have been disclosed in the prior art having a ventilation cavity that is operatively connected to an impact transmitter operated by the liquid melting material advancing from the mold cavity into the channel of ventilation. With the help of this design, very reliable valve assemblies can be realized that can be operated very quickly. In order to be able to accumulate a tamping pressure in the impact transmission, sufficient to perform the closing operation, the ventilation channel comprises returns and variations in the cross-sectional area. Furthermore, the ventilation channel must have a certain minimum length between the impact transmitter and the actual body member of the vent valve, and must be filled with corners in order to ensure that the vent valve is closed before the liquid melting material has reached the vent valve. By designing the ventilation channel that runs between the impact transmitter and the ventilation valve that is full of corners, moreover, it can prevent the splashes that lead the actual flow of the casting material between the ventilation valve and block it. In order to increase the efficiency of these valve assemblies, a vacuum pump is normally connected to the vent valve.

BACKGROUND OF THE INVENTION European Patent Document Number EP-A-0,612,573 discloses a valve assembly referred to herein for die-casting molds with ventilation, which comprises a ventilation channel, a ventilation valve located in the ventilation channel, and an operating element to close the ventilation valve. The operating element comprises an impact transmitter which is exposed to the liquid melting material advancing from the mold cavity towards the ventilation channel. The impact transmitter is coupled in a mechanically operative manner with the movable closure member of the vent valve. In this way, the impact transmitter is designed as a thrust member having an operating stroke that is limited to a fraction of the stroke that is to be passed through the movable element of the vent valve. Moreover, the closing element of the vent valve can move freely along the path, exceeding the operating stroke of the impact transmitter, and the operating element comprises a power transmission member for transmitting the impact pulse. from the impact transmitter to the movable closing member of the vent valve. Even when these valve assemblies operate very reliably in practice, it would be desirable to increase the efficiency of ventilation, particularly in the case of mold cavities having a large volume. The maximum ventilation efficiency is particularly limited by the turns and variations of the cross-sectional area in the ventilation channel, because in this way the flow resistance for the gas escaping from the mold cavity is substantially increased. In order to solve the problems discussed hereinabove, it would be obvious to increase the cross-sectional area of the ventilation valve and the ventilation channel already present. However, the tests conducted with this design have shown that an increase of the cross-sectional area of the valve and of the ventilation channel does not offer the desired success, due to the resistance of the flow of the ventilation channel, due to its full design. corners, which hinders efficient ventilation as is always the case. Moreover, an increase in the size of the vent valve results in an increase in the mass of the movable parts of the valve assembly. Therefore, accordingly, the force required to close the vent valve is correspondingly increased, and / or the closing time of the vent valve is increased to an undesired high value.

Moreover, an increase of the cross-sectional area of the ventilation valve and of the ventilation channel, results in the fact that the dimensions of the valve assembly are also increased; This is not desired either.

OBJECTS AND ADVANTAGES OF THE INVENTION Accordingly, it is the object of the present invention to propose a method for ventilating the die-casting mold of a die-casting machine, by means of which higher ventilation efficiency can be achieved, still maintaining a reliable operation. In order to satisfy this and other objects, the present invention provides a method for ventilating a die-casting mold of a die-casting machine that is provided with a casting piston located in a pressure chamber, and adapted to compress the liquid melting material into the cavity of the die-casting mold. The die-casting mold is provided with at least one vent channel communicating with the mold cavity, and comprising a first vent valve that is operatively connected to an impact transmitter. The impact transmitter is exposed to, and is moved by, the molten liquid material advancing from the mold cavity into the ventilation channel. In this way, the mold cavity and / or the pressure chamber during the filling operation are ventilated by means of a second ventilation valve in addition to the first ventilation valve. The second vent valve closes before the mold cavity is completely filled. Moreover, the first vent valve is subsequently closed, by the casting material advancing towards the ventilation channel and impacting the impact transmitter. With the method described above, the ventilation efficiency can be increased considerably, because the provision of a second venting valve that closes before the mold cavity is completely filled, results in at least a doubling of the area of ventilation. average cross-section of the relevant channels for ventilation efficiency, by means of which the portion of the ventilation channel that leads to the second ventilation valve can be optimized simultaneously, in terms of resistance to flow. In a preferred embodiment of the method, the criterion for closing the second vent valve is constituted by the time elapsed since the start of the filling operation, or the position of the casting piston, or the path along which it has been placed. moved the casting piston, or the filling speed of the chamber under pressure, or the filling speed of the mold cavity. By this measure, it is ensured that the second vent valve is closed when the casting material has advanced to it. A further object of the invention is to provide an apparatus for performing the aforementioned method. The apparatus for performing the method discussed hereinabove comprises a valve assembly comprising a first vent valve and a second vent valve. The first vent valve is operatively coupled with an impact transmitter which is exposed to, and adapted to be operated by, the casting material advancing from the mold cavity into the ventilation channel. The second vent valve comprises separate separate elements for its operation.

DESCRIPTION OF THE DRAWINGS In the following, the method according to the invention will be further described, as well as an embodiment of the apparatus for carrying out the method according to the invention, with reference to the accompanying drawings, in which: Figure 1 shows a schematic cross-sectional view of a die-casting machine, with a die-casting mold and a valve assembly mounted thereon, in the initial position. Figure 2 shows a schematic cross-sectional view of a die-casting machine, with a die-casting mold and a valve assembly mounted thereon, in a first phase of operation. Figure 3 shows a schematic cross-sectional view of a die-casting machine, with a die-casting mold and a valve assembly mounted thereon, in a second operation phase. Figure 4 shows a schematic cross-sectional view of a die-casting machine, with a die-casting mold and a valve assembly mounted thereon, in a third operation phase.

Figure 5 shows a schematic cross-sectional view of a die-casting machine, with a die-casting mold and a valve assembly mounted thereon, in a fourth operation phase. Figure 6 shows a top view of the valve assembly in greater detail. Figure 7 shows a first cross-sectional view of the valve assembly shown in Figure 6, taken along line AA of Figure 6. Figure 8 shows a second cross-sectional view of the valve assembly shown in FIG. Figure 6, taken along line BB of Figure 6. Figure 9 shows a cross-sectional view of the valve assembly, mounted on a die-casting machine, taken along line AA of the Figure 6 DETAILED DESCRIPTION OF THE INVENTION With the help of Figure 1, the general design and general mode of operation of a mode of the die-casting machine according to the invention, as well as the valve assembly assigned to the invention, will be further explained. same, wherein only the characteristics and steps of the method that are essential in relation to the present invention will be discussed. As the essential components of the die-casting machine, in the present example, and in Figure 1 are illustrated a pressure chamber 1 and a casting piston 2, located inside the pressure chamber 1, and hydraulically driven . The pressure chamber 1 is provided with a filling opening 4 for filling the pressure chamber 1 with the liquid melting material. At the outlet end of the pressure chamber 1, a die-casting mold 5 is located comprising two mold halves 5a and 5b. A connecting channel 6 runs from the pressure chamber 1 to the mold cavity 8 located between the two mold halves 5a and 5b. On the upper side of the die-casting mold 5, a valve assembly 10 is provided. A ventilation channel 9 interconnects the valve assembly 10 and the mold cavity 8. The valve assembly 10 is provided with two ventilation valves 11 and 12, respectively, which are connected to a vacuum pump 18 by means of two connection pipes 14 and 15, respectively. Each of the connecting tubes 14, 15 is provided with a non-return valve A and B respectively. The vent valve 11, located on the left side, as seen in Figure 1, is operatively connected to an impact transmission member that is not illustrated in Figure 1, but which will be discussed further hereinafter.

The impact transmission member is operated by the die-cast material advancing from the mold cavity 8 to the ventilation channel 9. The left-side ventilation valve 12 is operated by a separate element; this is indicated in Figure 1 by the dashed line 16, by which the vent valve 12 is connected to a control apparatus 19. In order to detect the position of the casting piston 2, a sensor 17 is provided which is connects to the control device 19 as well. Figures 2 to 5 show the die-casting machine and the valve assembly in four different operating phases. As can be seen in Figure 2, in a first phase, the liquid melting material G is filled in the pressure chamber 1 by means of the filling opening 4. Subsequently, the operation of feeding the casting material is started. liquid G towards the mold cavity 8. For this purpose, the casting piston 2 is moved to the right, as seen in Figure 2, that is, towards the die-casting mold 5. As can be seen in FIG. Figure 3, in a second phase, the pressure piston has moved towards the die-casting mold 5, to such an extent that the filling opening 4 is closed. At this time, the vacuum pump 18 is started, and the two valves without return A and B are opened. By this measure, the gases contained in the pressure chamber 1 and in the mold cavity 8 can escape and are sucked, respectively, by means of the two open non-return valves A and B. As can be seen in Figure 4, in a third In this step, the pressure piston has moved to the right, that is, towards the die-casting mold 5, to such an extent that the portion of the pressure chamber 1 which is located to the right of the casting piston 2 completely filled with the liquid melting material G. However, the liquid melting material has not yet reached the mold cavity 8. In this phase, the left-side ventilation valve 12 is closed. This operation is performed in a manner pneumatic on the line 16. As a criterion for closing the ventilation valve on the left side 12, the absolute position of the casting piston 2 is used in this example, since the filling speed of the pressure chamber is known. 1 and can be calculated respectively, based on its geometry, the amount of liquid melt material G that has been filled, and the absolute position of the casting piston 2. Because the mold cavity 8 is filled with casting material G, as a rule, within 20 to 80 milliseconds, the vent valve on the left side 12 is closed before the liquid melting material G has entered the mold cavity 8. It is understood that the vent valve on the left side 12 must be closed only immediately before the liquid melting material G has reached it. This is the case as soon as the mold cavity 8 is completely filled and the casting material advances towards the ventilation channel 9. However, in this case there is a danger that the splashes which lead to the actual casting material G will enter. to the ventilation valve on the left side 12 and lock it. Therefore, these circumstances are taken into account when closing the left-side ventilation valve 12 sooner. Furthermore, an early closing of the left-side ventilation valve 12 offers the advantage that the fluctuations of certain operating parameters do not are critical to a reliable mode of operation of the valve assembly; these fluctuations are qualified by the principle of operation of this die-casting machine, such as, for example, a fluctuation of the amount of liquid melting material G that is filled in the pressure chamber 1. Furthermore, an apparatus can be used of relatively simple control. However, it is understood that the exact moment of closing of the ventilation valve on the left side 12 can be adapted to the operating parameters present in any individual case.

Instead of the absolute position of the casting piston 2, its relative position can also be used as a criterion for closing the left side ventilation valve 12. Other possibilities are that the time elapsed since the start of the filling operation is used. , the filling level of the pressure chamber 1, or the level of filling of the mold cavity 8, as a criterion for closing the ventilation valve on the left side 12, although these examples are by no means final. Since the ventilation valve on the left side 12 has been closed, the non-return valve A of the vacuum pump 18 can be closed. Any gases still contained in the mold cavity 8 can escape and can be sucked, respectively, by the right-side vent valve 11. The right-side vent valve 11 remains open until the cast material G advancing towards the vent channel 9 has reached an impact transmitter not shown in Figures 2 to 5. will be explained in more detail later herein, the impact transmitter, together with the body member of the right-side vent valve 11, moves, and in this way the valve 11 is closed by the kinetic energy contained in the casting material in motion G. This fourth phase of operation is shown in Figure 5.

Figure 6 shows a top view of the valve assembly 10 in greater detail. The ventilation channel that runs towards the valve assembly 10 is designated with the reference numeral 9, while the portion of the channel that runs towards the first ventilation valve 11 is designated with the reference numeral 9b, and the portion of the channel which runs towards the second vent valve 12 is designated with the reference numeral 9a. The portion of the channel 9a running towards the second vent valve 12 is of a straight design in order to maintain the flow resistance for the gases escaping as low as possible. The portion of the channel 9b that runs towards the impact transmitter 20 and towards the body member 30 of the first vent valve 11 is full of corners. This design of the portion of the channel 9b serves to trap the spatter of the casting material which conducts the actual casting material G, and to retard the flow of the casting material G, after having reached the impact transmitter 20, in such a manner that the valve body member 30 has reached its closed position in time, before the casting material has advanced to the valve body member 30. The impact transmitter 20 is located at the end of a lateral branch 9c of the portion of channel 9b. Furthermore, a dam chamber 9d is provided in the region of the impact transmitter 20, where the impact pressure required for the closing movement of the impact transmitter 20 and the elements operatively connected to the transmitter of the transmitter can be established. impact 20. Further, two push rods 38 and 39 are illustrated which are provided to force a non-visible spring assembly in the illustration of Figure 6. Figure 7 shows a cross-sectional view of the valve assembly 10, taken along line AA of Figure 6; in this way, the valve assembly 10 is in its rest position. For a better understanding, the two push rods 38, 39 located in a common vertical plane are shown. In addition to the impact transmitter 20, the valve body member 30 received in a valve channel 34, and the two push rods 38, 39, this illustration also shows a working piston 24 forced by means of a spring member 25. , a vertical movement valve 27, a driving plate 23, a pressure plate member 35, as well as a spring assembly 36. The valve body member 30 comprises a collar 32 provided with axial recesses 33., through which gases coming from the ventilation channel portion 9b can pass, to enter an outlet channel 41 located above the valve body member 30, and connected to the vacuum pump 18. The transmitter of impact 20 is provided with a collar 21 which engages with the driving plate 23 on a movement in the rearward direction. The upper side of the driving plate 23 engages with the valve body member 30, and its lower side is engaged with the working piston 24. On the rear side of the driving plate, the spring assembly 36 is located which forces , by means of the press-on plate member 35, the impact transmitter 20, as well as the valve body member 30 and the work piston 24, to a forward position at rest, as shown in Figure 7. The assembly spring 36 is forced when the valve assembly 10 is mounted in the die-casting machine by means of the push rods 38, 39 which pass through the drive plate 23. Consequently, the impact transmitter 20 can be moved backwards under the influence of the kinetic energy contained in the melting material G which impacts the impact transmitter, as will be explained in more detail later herein. The path of the closing movement of the impact transmitter 20 is limited to a fraction of the closing movement paths of the valve body member 30 and the work piston 24. For this reason, the kinetic energy transmitted from the casting material G until the movable parts 20, 23, 24, and 30 can be kept within certain reasonable limits. In order to move the valve body member 30 from the open position, as shown in Figure 7, to the closed position, the impact transmitter 20 has to transmit only one moment of impact. By means of this impact momentum, the driving plate 23, together with the valve body member 30 and the working piston 24, move passively to their final position. In order to support the closing movement and / or in order to maintain the working piston 24, the driving plate 23, and the valve body member 30 in their final positions, the working piston 24 can be subjected to a force pneumatic by means of pressurized air supplied by means of an air channel 28. As soon as the work piston 24 has left the vertical movement valve 27, the entire front face of the working piston is subjected to pressurized air; in this way, the closing movement is supported, and the work piston 24 is maintained in its final position, respectively. Figure 8 shows a cross-sectional view, taken along the line BB of Figure 6, of the second vent valve 12 of the valve assembly 10. The vent valve 12 comprises a closing piston 45, a plate impeller 48, a pressure plate 49, two spring members 50, 51, as well as a valve body member 52 received in a valve channel 54.

Again, the movable closing piston 45 is provided with a collar 46 which engages the driving plate 48 on a backward movement. The driving plate 48 is operatively connected to the valve body member 52 by engagement of the valve body member 52 with its upper side. The driving plate 48, together with the valve body member 52 and the closing piston 45, is pushed forward by means of the two spring members 50 and 51. In order to move the valve body member 52 from the open position, as shown in Figure 8, to its closed position, a pressurized medium is fed by means of a channel 44 leading to the closing piston 45. This pressurized medium takes effect on the front face of the piston of closure 45 and moves it, together with the driving plate 48 and the valve body member 52, against the force of the spring members 50, 51 in the rearward direction, towards an end stop member. In this way, the head 53 of the valve body member 52, which advances towards the valve channel 54, seals the valve channel 54. Due to the extent to which the second ventilation valve 12 is operated by independent separate elements, the portion of the ventilation channel 9a running towards the vent valve 12 can be straight, with the result of a very low flow resistance. However, it must be ensured that the second vent valve 12 is closed before the casting material has advanced to it. Figure 9 shows a cross-sectional view, taken along line A-A of Figure 6, of the valve assembly mounted on a die-casting mold 5 consisting of two halves 5a and 5b. In the mounted position as shown in Figure 9, the spring assembly 36 is forced by means of the two push rods 38 and 39 which abut against one of the halves 5b of the die-casting mold 5. In addition, the member valve body 30 is in its open position, that is, under the influence of the spring member 25 of the working piston 24. Accordingly, the gases contained in the mold cavity 8 can flow to the outlet channel 41 by means of of the vent channel 9 and the valve channel 34, as indicated by the arrows 57 in Figure 9. As soon as the casting material G has reached the impact transmitter 20, the latter suddenly moves to its end stop under the impact of the casting material that impacts its front face. The collar 21 provided on the impact transmitter 20 transmits this impact force to the driving plate 23. The driving plate 23 is released from the impact transmitter under the influence of the kinetic energy transferred from the impact transmitter 20 to the driving plate 23, as soon as the impact transmitter has reached its final position, and continues its movement, together with the valve body member 30 and the work piston 24, against the force of the closing spring member 25. In this way , the vent valve 11 is closed while the head 31 of the valve body member advances to the valve channel 34. The closing movement of the vent valve 11 is supported by the force of a pressurized medium having effect in the closing piston 24. This pressurized medium has effect on the entire front face of the closing piston 24, as soon as the closing piston of the control valve 27 has been released. However, it should be informed that the vent valve 11 can be closed, as a rule, even without the support of the work piston 24, since the energy required for the closing movement of the vent valve 11 is raised by the material of liquid melt G advancing from the mold cavity 8 to the ventilation channel 9. After the casting material hardens G, half of the right side 5b of the casting mold 5 is removed. In this way, the air gate is ejected by means of the two push rods 38, 39 which are under the influence of the spring assembly 36. By means of a valve assembly 10 as explained hereinabove, the ventilation efficiency, compared to conventional vent valve assemblies, substantially preventing the valve assembly from becoming substantially larger. A particularly reliable mode of operation can be ensured by the two-stage ventilation method, wherein a vent valve 12 is operated by a separate independent element before the mold cavity is completely filled, and wherein the other valve ventilation 11 is operated by the liquid melting material advancing from the mold cavity 8 towards the ventilation channel 9.

Claims (14)

NOVELTY OF THE INVENTION Having described the above invention, it is considered as a novelty, and therefore, the content of the following is claimed as property: CLAIMS

1. A method for venting a die-casting mold of a die-casting machine that is provided with a casting piston located in a pressure chamber, and adapted to compress the liquid melting material into the casting mold cavity. to die, wherein the die-casting mold is provided with at least one vent channel communicating with the mold cavity, and comprising a first vent valve that is operatively connected to an impact transmitter, this transmitter being of impact exposed to, and being moved by, the liquid melting material advancing from the mold cavity towards the ventilation channel, characterized in that the mold cavity and / or the pressure chamber are ventilated during the filling operation, by means of a second vent valve in addition to the first vent valve, where the second vent valve closes before the mold cavity is completely filled, and where the first vent valve is subsequently closed by the casting material advancing towards the vent channel and impacting the impact transmitter.

2. The method according to claim 1, characterized in that the second vent valve is operated by a separate independent element, wherein the criterion for closing the second valve is constituted by the time elapsed since the start of operation of filling, or the position of the casting piston, or the trajectory along which the casting piston has moved, or the filling speed of the pressurized chamber, or the filling speed of the mold cavity.

The method according to claim 1 or 2, characterized in that the second vent valve is closed before more than half of the mold cavity is filled with the cast material, preferably before the casting material advances from the pressurized chamber into the mold cavity.

4. The method according to claim 1 of claim 1, characterized in that a vacuum is created in the ventilation channel to support the ventilation operation.

5. The method according to claim 1 in one of the preceding claims, characterized in that the second vent valve is closed in a hydraulic or pneumatic manner.

6. An apparatus for carrying out the method according to claim 1 of claim 1, characterized by a valve assembly comprising a first vent valve and a second vent valve, the first vent valve being operatively coupled with a vent valve. impact transmitter that is exposed to, and adapted to be operated by, the casting material advancing from the mold cavity into the ventilation channel, and wherein the second ventilation valve comprises a separate independent element for its operation.

7. An apparatus according to claim 6, characterized in that the valve assembly comprises a substantially straight portion of the ventilation channel, the second vent valve being located at the end of the straight portion of the ventilation channel.

An apparatus according to claim 6 or claim 7, characterized in that an additional portion of the ventilation channel is provided which is full of corners, the first vent valve being located in this additional portion of the ventilation channel.

9. An apparatus according to claim 7 or 8, characterized in that the essentially straight ventilation channel portion and the additional portion of the ventilation channel communicate with a common ventilation channel.

10. An apparatus according to claim 8, characterized in that the cross-sectional area of the portion of the straight ventilation channel is larger than the average cross-sectional area of the additional portion of the ventilation channel.

11. An apparatus according to claim one of claims 6 to 10, characterized in that the impact transmitter is located in the additional portion of the ventilation channel that is full of corners, and because the impact transmitter is located before the The first vent valve, as seen in the flow direction of the casting material.

12. An apparatus according to claim 11, characterized in that the impact transmitter is designed as an impuje member having an operating stroke that is limited to a fraction of the stroke that is to be passed by the limb member. valve body of the first vent valve, wherein the valve body member of the first vent valve can move freely along the path, exceeding the operating stroke of the impact transmitter.

13. An apparatus according to claim 1 in claim 6, characterized in that the valve assembly comprises a first portion and a second portion, in addition because the two valve body members of the two vent valves are forced. each by a spring element, and in that the spring elements rest on one of the first and second valve assembly portions.

14. An apparatus according to claim one of claims 6 to 12, characterized in that elements are provided to determine the position of the casting piston, or to determine the length of the path through which the piston has run. casting, or to determine the time elapsed since the start of the filling operation, or to determine the filling speed of the mold cavity.