Vacuum extrusion casting method

Abstract

The invention relates to a vacuum extrusion casting method, which is used for a vacuum extrusion device, and comprises the following steps of: filling a set amount of molten metal into a sealed holding furnace, then closing a mold, and vacuumizing a sealing cover and the sealed holding furnace; dry compressed air is injected into the sealed heat preservation furnace, and the compressed air rapidly conveys the molten metal in the sealed heat preservation furnace into a cavity of the mold in a pressing mode; after mold filling is finished, an extrusion assembly is started immediately, molten metal in an extrusion hole in the mold is extruded into a mold cavity through high pressure for material supplementing, and a casting is extruded and continuously pressurized; feeding of the compressed air is stopped, the vent valve is opened, the vacuum valve is closed, the switching valve is opened, the sealing cover and the sealing heat preservation furnace return to the normal pressure, and the unsolidified molten metal in the feeding pipe flows back into the sealing heat preservation furnace; and cooling the casting to proper solid strength, opening the mold and taking out the casting. According to the method, the molten metal in the feeding cavity is pressurized and supplemented through the extrusion assembly, so that a product is attractive, exquisite and free of defects, the uniformity and compactness are good, and the casting quality is high.

Description

Technical Field

[0001] The invention relates to a casting method, in particular to a vacuum extrusion casting method. Background Art

[0002] In today's highly developed industrial manufacturing field, casting technology, as a basic and key process, plays an indispensable role in the production of various metal parts. Among them, vacuum casting, as a relatively advanced casting process, has been applied in many fields.

[0003] By using the vacuum exhaust component to extract the gas in the cavity and related parts, a near-vacuum environment is created, which significantly reduces the chance of gas mixing into the molten metal and reduces the occurrence of pore defects to a certain extent. However, the existing vacuum casting technology still has many problems in practical applications: first, when the molten metal enters the mold, it will carry a certain amount of air into the cavity; second, the vacuum degree in the cavity is not high. Due to the molten metal carrying air, the low vacuum degree of the cavity, and the residual air in the cavity, the casting is prone to pores and oxide slag, which affects the density and uniformity and reduces the strength. In addition, at the end of the filling, the tiny slits and corners form resistance due to air compression, which hinders the filling and has obvious appearance defects. Summary of the invention

[0004] In order to solve the above problems, the present invention provides a vacuum squeeze casting method, and the specific technical solution is as follows:

[0005] A vacuum extrusion casting method, used for a vacuum extrusion device, comprises the following steps:

[0006] Fill a set amount of molten metal into the sealed insulation furnace, then close the mold and evacuate the sealing cover and the sealed insulation furnace;

[0007] The switching valve is closed to cut off the connection between the sealed insulation furnace and the sealing cover, and then dry compressed air is injected into the sealed insulation furnace. The compressed air quickly presses the molten metal in the sealed insulation furnace into the cavity of the mold;

[0008] After the filling is completed, the extrusion assembly is immediately started to squeeze the molten metal in the extrusion hole on the mold into the cavity under high pressure to fill the material, and the casting is extruded and continuously pressurized;

[0009] Stop supplying compressed air and open the vent valve, close the vacuum valve, open the switching valve, and restore the sealing cover and the sealed insulation furnace to normal pressure. The unsolidified metal liquid in the feed pipe flows back into the sealed insulation furnace;

[0010] The casting is cooled to a suitable solid strength, the mold is opened and the casting is removed.

[0011] Preferably, when multiple extrusion holes are provided, extrusion is performed in sequence according to the solidification shrinkage order of each part of the casting, and extrusion starts from the extrusion hole connected to the inlet of the mold. Multiple extrusion hole locations are set according to the requirements of the heat section, and the corresponding extrusion time is set.

[0012] Preferably, when evacuating the sealed insulation furnace and the sealing cover, evacuation is first performed through the vacuum bag. When the pressure of the vacuum bag is balanced with the internal pressure of the sealed insulation furnace and the sealing cover, the vacuum bag is cut off and evacuation is performed through the vacuum pump. When the mold is filled and cooled, the vacuum pump evacuates the vacuum bag.

[0013] Preferably, vacuum is continuously drawn during the filling process.

[0014] Preferably, the vacuum extrusion device comprises: a mold, the mold is provided with a cavity and an in-mold feed hole communicating with the cavity, the mold is also provided with an extrusion hole, when the extrusion hole is provided with one, the extrusion hole is communicated with the in-mold feed hole, when the extrusion hole is provided with multiple, at least one extrusion hole is communicated with the in-mold feed hole, and the remaining extrusion holes are communicated with the cavity; an extrusion assembly, provided on the extrusion hole, and used to hydraulically inject the metal in the extrusion hole into the cavity; a sealing cover, sleeved on the mold, and used to provide a vacuum environment for the mold; a feed pipe, provided on the mold and communicating with the in-mold feed hole; a sealed insulation furnace, provided on the feed pipe, and used to store molten metal; a vacuuming assembly, respectively connected to the sealed insulation furnace and the sealing cover; a pressurizing assembly, provided on the sealed insulation furnace, and used to pass dry compressed air to allow the molten metal to flow into the cavity; and a ventilation assembly, respectively connected to the sealed insulation furnace and the sealing cover.

[0015] Preferably, the extrusion assembly comprises: an extrusion drive cylinder, which is arranged on the mold; and an extrusion piston, which is arranged on the extrusion drive cylinder and movably inserted into the extrusion hole.

[0016] Preferably, the vacuum pumping assembly includes: a vacuum tube, which is respectively connected to the sealing cover and the sealed insulation furnace; a vacuum valve, which is arranged on the vacuum tube; and a vacuum pump, which is connected to the vacuum tube.

[0017] Furthermore, the vacuum pumping assembly also includes: a vacuum bag; a first air extraction valve, which is connected to the vacuum bag and the vacuum tube respectively; and a second air extraction valve, which is connected to the vacuum bag and the vacuum pump respectively.

[0018] Preferably, it also includes: a conducting pipe, which is communicated with the sealing cover and the sealed insulation furnace respectively, and is connected to the vacuum pumping component, the pressurizing component and the ventilation component; and a switching valve, which is arranged on the conducting pipe and is located between the vacuum pumping component and the pressurizing component.

[0019] Compared with the prior art, the present invention has the following beneficial effects:

[0020] The vacuum extrusion casting method provided by the present invention pressurizes and replenishes the molten metal in the feed cavity through an extrusion component, and continuously increases the pressure. Since the mold is filled under vacuum, metal oxidation and filling resistance are avoided, and the product can be beautiful, exquisite and defect-free. Since the crystallization and solidification are formed under continuous high pressure, the product has good uniformity, which effectively improves the quality of the casting. High-pressure extrusion can refine the grain size, increase the density, and the physical properties are comparable to forging. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 It is a structural schematic diagram of a vacuum extrusion device. DETAILED DESCRIPTION

[0022] The present invention will be further described with reference to the accompanying drawings.

[0023] like Figure 1 As shown, a vacuum extrusion casting method for a vacuum extrusion device comprises the following steps:

[0024] A set amount of molten metal is added into the sealed heat preservation furnace 4, and then the mold is closed and the sealing cover 1 and the sealed heat preservation furnace 4 are evacuated;

[0025] The switching valve 62 is closed to cut off the connection between the sealed insulation furnace 4 and the sealing cover 1, and then dry compressed air is injected into the sealed insulation furnace 4. The compressed air quickly presses the molten metal in the sealed insulation furnace 4 into the cavity 23 of the mold 2;

[0026] After the filling is completed, the extrusion assembly 5 is immediately started to squeeze the molten metal in the extrusion hole 25 on the mold 2 into the mold cavity 23 under high pressure to fill the material, extrude the casting and continuously increase the pressure;

[0027] Stop feeding compressed air and open the vent valve 76, close the vacuum valve 72, open the switching valve 62, and restore the sealing cover 1 and the sealed insulation furnace 4 to normal pressure, and the unsolidified metal liquid in the feed pipe 4 flows back into the sealed insulation furnace 4;

[0028] The casting is cooled to a suitable solid strength, the mold is opened and the casting is removed.

[0029] When a plurality of extrusion holes 25 are provided, extrusion is performed in sequence according to the solidification shrinkage order of each part of the casting, and extrusion starts from the extrusion hole 25 connected to the feed port in the mold.

[0030] When evacuating the sealed insulation furnace 4 and the sealing cover 1, first evacuate through the vacuum bag. When the vacuum bag is balanced with the internal pressure of the sealed insulation furnace 4 and the sealing cover 1, cut off the vacuum bag and evacuate through the vacuum pump. When the filling is completed and then cooled, cut off the vacuum valve and evacuate the vacuum bag with the vacuum pump.

[0031] The vacuum is continuously applied during filling.

[0032] The vacuum extrusion casting device includes a mold 2, a sealing cover 1, an extrusion assembly 5, a feed pipe 4, a sealed insulation furnace 4, a vacuum assembly, a pressurizing assembly and a ventilation assembly. The mold 2 includes a movable mold 21, a static mold 22 and a driving device connected to the movable mold 21. The movable mold 21 and the static mold 22 are both provided with cavities. After the movable mold 21 and the static mold 22 are molded together, the two cavities form a mold cavity 23 of the workpiece. The movable mold 21 and the static mold 22 are also provided with an in-mold feed hole 24 that communicates with the mold cavity 23. The mold 2 is installed in the sealing cover 1, and the sealing cover 1 is used to provide a vacuum environment to solve the problem that the existing mold 2 has insufficient vacuum in the mold cavity 23 and residual air due to poor sealing. The sealing cover 1 is easier to seal and improves the sealing performance. The mold 2 is also provided with an extrusion hole 25. When there is only one extrusion hole 25, the extrusion hole 25 is communicated with the in-mold feed hole 24. When there are multiple extrusion holes 25, at least one extrusion hole 25 is communicated with the in-mold feed hole 24, and the remaining extrusion holes 25 are communicated with the cavity 23; the extrusion assembly 5 is installed on the extrusion hole 25, and is used to hydraulically inject the metal in the extrusion hole 25 into the cavity 23; the two ends of the feed pipe 4 are respectively connected to the mold 2 and the sealed insulation furnace 4, and are communicated with the in-mold feed hole 24; the sealed insulation furnace 4 is used to store the molten metal and maintain the temperature of the molten metal; the vacuum assembly is respectively connected to the sealed insulation furnace 4 and the sealing cover 1; the pressurizing assembly is installed on the sealed insulation furnace 4, and is used to pass dry compressed air to allow the molten metal to flow into the cavity 23; the ventilation assembly is respectively connected to the sealed insulation furnace 4 and the sealing cover 1.

[0033] The mold 2 is installed on the frame.

[0034] After the filling is completed, the piston is started for high-pressure extrusion and continuous pressurization. Extrusion can refine the grain size and increase the density. The physical properties are comparable to those of forging. For example, there are no hidden cracks caused by forging, and parts with complex structures cannot be forged.

[0035] The vacuuming component evacuates the sealing cover 1 and the sealing insulation furnace 4, closes the switching valve 62 to cut off the connection between the sealing insulation furnace and the sealing cover, and then pressurizes the sealing insulation furnace 4 through the pressurizing component to transport the molten metal through pressure.

[0036] The existing squeeze casting uses a piston to hydraulically inject metal into the mold cavity 23, so the amount of injection is limited by the piston area and the length of the barrel. When the density needs to be increased, the area of ​​the piston must be made relatively small to increase the extrusion pressure, resulting in only casting of relatively small workpieces. The present application pushes the metal liquid through compressed air, and there is no limit on the size of the product, so large workpieces can be cast. The compressed air pressure during filling is above 0.1MPa. The pressure can be increased at any time according to the filling requirements. The mold can be filled quickly to achieve an ideal filling effect, and then extrusion is performed immediately. The extrusion pressure can be set above 50MPa, and can even reach more than 100MPa as needed, which is better than the current squeeze casting. In addition, the liquid feeding amount of the present application is not limited, which is convenient for die-casting large workpieces. The conventional die-casting liquid feeding amount is related to the equipment, and is limited by the diameter of the equipment piston, the barrel and the length of the piston rod. When the equipment pressure remains unchanged, the larger the diameter of the piston, the smaller the pressure. The metal liquid of the present application is transported by compressed air and is not limited by the piston.

[0037] The extrusion assembly 5 includes an extrusion drive cylinder 52 and an extrusion piston 51. The extrusion drive cylinder 52 can be a hydraulic cylinder and is installed on the mold 2. The extrusion piston 51 is arranged on the extrusion drive cylinder 52 and is movably inserted into the extrusion hole 25. In the case where there is only one extrusion hole 25, the extrusion hole 25 is arranged on one side of the feed port, and the extrusion hole 25 is communicated with the feed port. In the case where multiple extrusion holes 25 are arranged, the remaining extrusion holes 25 are communicated with the cavity 23. The extrusion hole 25 can be on the movable mold 21, on the static mold 22, or on both the static mold 22 and the movable mold 21.

[0038] The sealing cover 1 includes a fixed sealing half cover 12, a movable sealing half cover 21 and a sealing ring 13. The fixed sealing half cover 12 is arranged on the static mold 22 of the mold 2, and can also be fixed on the frame; the movable sealing half cover 21 is arranged on the movable mold 21 of the mold 2; the sealing ring 13 is arranged on the fixed sealing half cover 12 and is arranged opposite to the movable sealing half cover 21, so as to realize the sealing between the fixed sealing half cover 12 and the movable sealing half cover 21, improve the sealing performance, and then improve the vacuum performance.

[0039] The vacuum pumping assembly includes a vacuum tube 71, a vacuum valve 72 and a vacuum pump. The vacuum tube 71 is connected to the vacuum pump, the sealing cover 1 and the sealing insulation furnace 4 respectively; the vacuum valve 72 is installed on the vacuum tube 71. The vacuum pump is used for vacuuming.

[0040] In order to improve efficiency and shorten the overall filling time, the vacuum pumping assembly also includes a vacuum bag, a first exhaust valve and a second exhaust valve. The vacuum bag is connected to the vacuum tube 71 through the first exhaust valve and connected to the vacuum pump through the second exhaust valve. Before casting, the vacuum bag is first evacuated by a vacuum pump. When the set vacuum degree is reached, the vacuum pump and the second exhaust valve are closed. When it is necessary to evacuate the sealing cover 1 and the sealing insulation furnace 4, the first exhaust valve is opened first, and the vacuum bag quickly evacuates the sealing cover 1 and the sealing insulation furnace 4. When the pressure balance is reached, the first exhaust valve is closed, and the vacuum pump is started. The vacuum pump directly evacuates the sealing cover 1 and the sealing insulation furnace 4. When filling the mold, the second exhaust valve can be opened, and the vacuum pump evacuates the vacuum bag. Since the vacuum pump is limited by power, the evacuation time is long, and the vacuum bag can be evacuated quickly, which is equivalent to completing part of the evacuation work. Therefore, the evacuation time of the vacuum pump to the sealing cover 1 and the sealing insulation furnace 4 can be greatly shortened, thereby improving efficiency.

[0041] The pressurizing assembly includes a pressurizing pipe 81, a pressurizing valve 82 and an air compressor. The pressurizing pipe 81 is connected to the sealed insulation furnace 4 and the air compressor respectively, and the pressurizing valve 82 is fixed on the pressurizing pipe 81. The air compressor is used to increase dry compressed air, and the compressed air is used to push the molten metal into the cavity 23 of the mold 2. The pressurizing valve 82 is a proportional control valve that can adjust the pressure and flow.

[0042] The ventilation assembly includes a ventilation pipe 77 and a ventilation valve 76 . The ventilation pipe 77 is connected to the sealing cover 1 and the sealed insulation furnace 4 respectively; the ventilation valve 76 is installed on the ventilation pipe 77 .

[0043] It also includes a conducting pipe 61 and a switching valve 62. The conducting pipe 61 is respectively connected to the sealing cover 1 and the sealing and heat preservation furnace 4, and is connected to the vacuuming component, the pressurizing component and the ventilation component; the switching valve 62 is arranged on the conducting pipe 61 and is located between the vacuuming component and the pressurizing component. The switching valve 62 is opened when the vacuuming is done, and is closed when the pressurizing device is working. It also needs to be opened when the ventilation valve 76 is opened before the mold is opened.

[0044] The conducting pipe 61 is connected to the pressurizing pipe 81 , the vacuum pipe 71 and the ventilation pipe 77 respectively, thus simplifying the overall piping.

[0045] When the molten metal in the sealed insulation furnace 4 flows rapidly into the in-mold feed hole 24 of the mold 2 along the feed pipe 4 under the strong pressure generated by the air compressor, the filling is completed quickly. After the filling is completed, the extrusion assembly 5 is started immediately, and the extrusion drive cylinder 52 in the extrusion assembly 5 drives the extrusion piston 51 installed at its end to move forward smoothly in the extrusion hole 25. As the extrusion piston 51 moves forward, the space inside the extrusion hole 25 gradually decreases, and the extrusion piston 51 applies uniform and strong pressure to the high-temperature liquid metal that has not yet been completely cooled in the extrusion hole 25. The molten metal is compressed into the cavity 23 from each extrusion hole 25 at the same time. The molten metal can be evenly distributed in the cavity 23 and run through the entire crystallization and solidification process from liquid, semi-molten state to solid state. There will be no situation where a certain area is insufficiently filled or the density is uneven and dense. This process not only ensures that the molten metal can fully and evenly fill the entire cavity 4, but also can be completed under very high pressure, so that the cast product has better density and more excellent physical properties.

[0046] A heater is provided at the bottom of the sealed heat preservation furnace 47, and the heater is a super-frequency heater.

[0047] Since the filling is carried out under a good vacuum condition, residual air is avoided in the cavity 23 of the mold 2, and high-pressure extrusion is performed by the extrusion assembly 5, which can effectively fill the tiny gaps and corners at the end of the filling, thereby ensuring the appearance quality of the casting.

[0048] The working principle of the utility model is as follows: before the casting operation is started, the vacuum exhaust component is first started. With its powerful exhaust efficiency, the vacuum exhaust component quickly extracts the air inside the sealing cover 1. As the exhaust process continues, the gas inside the cavity 23, the in-mold feeding hole 24, the extrusion hole 25, the sealed insulation furnace 4 and the connecting pipe 61 therebetween is also gradually extracted, thereby creating an environment highly close to vacuum in the entire system. When the vacuum degree reaches a preset value, the molten metal in the sealed insulation furnace 4 is continuously heated by the external heating device. , always maintain a suitable insulation temperature to ensure that the molten metal has good fluidity, then close the vacuum valve 72, and then close the switching valve 62. The switching valve 62 isolates the sealing cover 1 from the sealed insulation furnace 4; at the same time, the air compressor of the pressurizing component located outside the sealed insulation furnace 4 starts to operate, and the compressed air generated enters the sealed insulation furnace 4 through the pressurizing valve 82 and acts on the surface of the molten metal. The molten metal then enters the feed hole 24, the extrusion hole 25 and the cavity 23 in the mold along the feed pipe 4 under the action of the compressed air, until the molten metal fills the cavity 23. After the filling is completed, the extrusion drive cylinder 52 of the extrusion device is started, and the extrusion piston 51 presses the metal liquid into the cavity 23 for effective material replenishment, and the extrusion component 5 continues to apply pressure to prompt the metal liquid to more fully fill the various tiny corners and complex structures of the cavity 23, reduce possible casting defects such as pores and looseness, and significantly improve the density and internal quality of the casting. The pressure is increased until solidification. After solidification, it reaches a certain solid mechanical strength and is separated from the mold. The formed casting is ejected by the ejection device of the mold 2, and the operator can easily take it out, thereby successfully completing the entire casting process. Through the above-mentioned sophisticated and coordinated working principles, the vacuum extrusion casting device can stably and efficiently achieve high-quality casting production, and manufacture casting products with excellent performance and few defects to meet various high-precision and high-performance industrial needs.

[0049] The technical principle of the present invention is described above in conjunction with specific embodiments. These descriptions are only for explaining the principle of the present invention and cannot be interpreted as limiting the protection scope of the present invention in any way. Based on the explanations herein, those skilled in the art can associate other specific implementations of the present invention without paying creative labor, and these methods will fall within the protection scope of the claims of the present invention.

Claims

1. A vacuum extrusion casting method for a vacuum extrusion device, characterized in that: The following steps are involved: A set amount of molten metal is added into the sealed heat preservation furnace (4), and then the mold is closed and the sealing cover (1) and the sealed heat preservation furnace (4) are evacuated; The switching valve (62) is closed to cut off the connection between the sealed heat preservation furnace (4) and the sealing cover (1), and dry compressed air is then injected into the sealed heat preservation furnace (4), so that the compressed air quickly presses the molten metal in the sealed heat preservation furnace (4) into the mold cavity (23) of the mold (2); After the filling is completed, the extrusion assembly (5) is immediately started to squeeze the molten metal in the extrusion hole (25) on the mold (2) into the mold cavity (23) under high pressure, thereby extruding and continuously pressurizing the casting; Stop feeding compressed air and open the vent valve (76), close the vacuum valve (72), open the switching valve (62), restore the sealing cover (1) and the sealed insulation furnace (4) to normal pressure, and the unsolidified metal liquid in the feed pipe (4) flows back into the sealed insulation furnace (4); The casting is cooled to a suitable solid strength, the mold is opened and the casting is removed.

2. A vacuum squeeze casting method according to claim 1, characterized in that: When a plurality of extrusion holes (25) are provided, extrusion is performed in sequence according to the solidification shrinkage order of each part of the casting, and extrusion starts from the extrusion hole (25) closest to the sealed insulation furnace (4) and connected to the inlet of the mold.

3. A vacuum squeeze casting method according to claim 1, characterized in that: When evacuating the sealed heat preservation furnace (4) and the sealed cover (1), the vacuum is first evacuated through the vacuum bag. When the pressure inside the vacuum bag, the sealed heat preservation furnace (4) and the sealed cover (1) is balanced, the vacuum bag is cut off and the vacuum is evacuated through the vacuum pump. When the mold is filled and cooled, the vacuum pump evacuates the vacuum bag.

4. A vacuum squeeze casting method according to claim 1, characterized in that: The vacuum is continuously drawn during the filling process.

5. The vacuum squeeze casting method according to claim 1, characterized in that: The vacuum extrusion device comprises: A mold (2), wherein the mold (2) is provided with a mold cavity (23) and an in-mold feed hole (24) communicating with the mold cavity (23); the mold (2) is also provided with an extrusion hole (25); when the extrusion hole (25) is provided with one, the extrusion hole (25) is communicated with the in-mold feed hole (24); when the extrusion hole (25) is provided with a plurality of extrusion holes (25), at least one extrusion hole (25) is communicated with the in-mold feed hole (24), and the remaining extrusion holes (25) are communicated with the mold cavity (23); An extrusion assembly (5) is disposed on the extrusion hole (25) and is used to hydraulically inject the metal in the extrusion hole (25) into the mold cavity (23); A sealing cover (1) is sleeved on the mold (2) and is used to provide a vacuum environment for the mold (2); A feed pipe (4) is provided on the mold (2) and communicates with the feed hole (24) in the mold; A sealed heat-insulating furnace (4), arranged on the feed pipe (4), for storing molten metal; A vacuum pumping assembly, connected to the sealed heat preservation furnace (4) and the sealed cover (1) respectively; a pressurizing assembly, arranged on the sealed heat-insulating furnace (4), and used for introducing dry compressed air to allow the molten metal to flow into the mold cavity (23); and A ventilation assembly is connected to the sealed heat-insulating furnace (4) and the sealed cover (1) respectively.

6. A vacuum squeeze casting method according to claim 5, characterized in that: The extrusion assembly (5) comprises: an extrusion drive cylinder (52), wherein the extrusion drive cylinder (52) is arranged on the mold (2); and An extrusion piston (51), wherein the extrusion piston (51) is disposed on the extrusion drive cylinder (52) and is movably inserted into the extrusion hole (25).

7. A vacuum squeeze casting method according to claim 5, characterized in that: The vacuum assembly comprises: A vacuum tube (71), the vacuum tube (71) being connected to the sealing cover (1) and the sealing insulation furnace (4) respectively; a vacuum valve (72), the vacuum valve (72) being arranged on the vacuum tube (71); and A vacuum pump is connected to the vacuum pipe (71).

8. A vacuum squeeze casting method according to claim 7, characterized in that: The vacuum assembly also includes: Vacuum bag; a first air extraction valve, the first air extraction valve being connected to the vacuum bag and the vacuum tube (71) respectively; and A second air extraction valve is connected to the vacuum bag and the vacuum pump respectively.

9. A vacuum squeeze casting method according to claim 5, characterized in that: Also includes: a conducting pipe (61), the conducting pipe (61) being in communication with the sealing cover (1) and the sealing and heat-insulating furnace (4) respectively, and being connected with the vacuuming component, the pressurizing component and the ventilation component; and A switching valve (62), wherein the switching valve (62) is arranged on the conducting pipe (61) and is located between the vacuum pumping component and the pressurizing component.

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