Vacuum degassing apparatus, injection apparatus equipped therewith, and vacuum degassing method

Abstract

The present invention provides a vacuum degassing device that can more efficiently remove moisture and volatile components contained in molding materials. [Solution] The vacuum degassing device 4 includes a transport device 44 for transporting molding material to the injection cylinder 32, a material supply passage 45 provided between the injection cylinder 32 and the transport device 44 for supplying molding material to the injection cylinder 32, a shut-off device 46 for separating the material supply passage 45 into an upstream section 451 communicating with the transport device 44 and a downstream section 452 communicating with the injection cylinder 32, a vacuum pump 47 connected to the downstream section 452, and an atmospheric release valve V3 communicating with the downstream section 452. The atmospheric release valve V3 is opened before the metering process, when the shut-off device 46 and the atmospheric release valve V3 are closed and the vacuum pump 47 is operating.

Description

[[Technical Field]]

[0001] The present invention relates to a vacuum degassing apparatus, an injection apparatus including the same, and a vacuum degassing method. [[Background Art]]

[0002] Moisture and volatile components contained in a molding material cause various defects such as air bubbles in molded articles. Patent Document 1 describes a vacuum degassing apparatus that removes moisture and volatile components from a molding material by creating a vacuum around the molding material. The vacuum degassing apparatus includes a shut-off device that maintains an injection cylinder in a vacuum state, and a vacuum pump that sucks gas inside the injection cylinder. [[Prior Art Literature]] [[Patent Literature]]

[0003] [[Patent Document 1]] Japanese Unexamined Patent Application Publication No. 2011-83953 [[Summary of the Invention]] [[Problem to be Solved by the Invention]]

[0004] The vacuum degassing apparatus described in Patent Document 1 removes moisture and volatile components from a molding material only by the suction force of a vacuum pump, so the efficiency of removing moisture and volatile components is low.

[0005] An object of the present disclosure is to provide a vacuum degassing apparatus capable of more efficiently removing moisture and volatile components contained in a molding material. [[Means for Solving the Problem]]

[0006] The vacuum degassing apparatus of the present disclosure includes: a shut-off device that separates a material supply path into an upstream portion communicating with a conveying device and a downstream portion communicating with an injection cylinder; a vacuum pump connected to the downstream portion; and an atmosphere release valve communicating with the downstream portion. Before a metering step, in a state where the shut-off device and the atmosphere release valve are closed and the vacuum pump is in operation, the atmosphere release valve is opened. [Effects of the Invention]

[0007] According to this disclosure, it is possible to provide a vacuum degassing device that can more efficiently remove moisture and volatile components contained in molding materials. [Brief explanation of the drawing]

[0008] [Figure 1] This is a schematic front view of an injection molding machine according to one embodiment of the present disclosure. [Figure 2] Figure 1 is a schematic diagram of the vacuum degassing device for an injection molding machine. [Figure 3A] Figure 2 shows the operating method of the vacuum degassing apparatus. [Figure 3B] Figure 2 shows the operating method of the vacuum degassing apparatus. [Figure 3C] Figure 2 shows the operating method of the vacuum degassing apparatus. [Figure 3D] Figure 2 shows the operating method of the vacuum degassing apparatus. [Figure 3E] Figure 2 shows the operating method of the vacuum degassing apparatus. [Figure 4A] This figure shows the operating method of a vacuum degassing apparatus in a comparative example. [Figure 4B] This figure shows the operating method of a vacuum degassing apparatus in a comparative example. [Figure 4C] This figure shows the operating method of a vacuum degassing apparatus in a comparative example. [Figure 4D] This figure shows the operating method of a vacuum degassing apparatus in a comparative example. [Modes for carrying out the invention]

[0009] An embodiment of the present disclosure will be described below with reference to the drawings. The embodiment described below relates to a horizontal injection molding device for injecting resin and a horizontal injection molding machine equipped therewith, but the present disclosure can also be applied to vertical injection molding devices and metal injection molding devices. In the following description and drawings, the axial direction of the injection cylinder and injection screw is referred to as the X direction. The X direction is parallel to the horizontal direction. The direction from the injection molding device toward the clamping device or the injection direction is referred to as the +X direction, and the direction from the clamping device toward the injection molding device is referred to as the -X direction. The vertical direction is referred to as the Z direction.

[0010] <Overall Structure> Figure 1 shows a schematic front view of an injection molding machine 1 according to one embodiment of the present disclosure. Figure 2 shows a schematic front view of the injection device 3 of the injection molding machine 1 shown in Figure 1. The injection molding machine 1 is generally composed of a mold clamping device 2 that supports the mold and opens and closes the mold, and an injection device 3 that heats and melts the material to be injected and molded (molding material) and injects it.

[0011] As shown in Figure 1, the clamping device 2 comprises a fixed platen 22 fixed on the bed 21 to which a fixed mold M1 is attached, a clamping housing 24 that is slidable on the bed 21, and a movable platen 23 that is slidable on the bed 21 to which a movable mold M2 is attached. The fixed platen 22 and the clamping housing 24 are connected by a number of tie bars 25. A clamping mechanism 26 for opening and closing the mold is provided between the movable platen 23 and the clamping housing 24. The clamping mechanism 26 is composed of a toggle mechanism, but may also be composed of a hydraulic clamping injection cylinder.

[0012] The injection device 3 is mounted on a base 31. The injection device 3 comprises an injection cylinder 32, an injection screw 33 housed in the injection cylinder 32 for kneading and plasticizing the molding material (e.g., resin pellets), and a drive mechanism 34 that drives the injection screw 33 in the X direction and rotates the injection screw 33 around its central axis. The injection cylinder 32 is a generally cylindrical member and has an internal space that houses the injection screw 33 and through which the molding material flows. An injection nozzle 35 for injecting the molding material is provided at the tip of the injection cylinder 32 in the +X direction. The drive mechanism 34 is covered by a cover 36.

[0013] <Vacuum degassing apparatus 4> Figure 2 shows a schematic configuration of the vacuum degassing apparatus 4. The injection apparatus 3 includes the vacuum degassing apparatus 4 attached to an injection cylinder 32. The vacuum degassing apparatus 4 removes moisture and volatile components from a molding material supplied to the injection cylinder 32, and supplies the molding material from which moisture and volatile components have been removed to the injection cylinder 32. The vacuum degassing apparatus 4 includes a hopper 41, a material tank 42, an exhaust blower 43, a conveying device 44, a material supply path 45, a shutoff device 46, a vacuum pump 47, a detection device 48, a control device 49, an atmosphere release valve V3, and the like. The control device 49 controls the operations of the exhaust blower 43, the conveying device 44, the shutoff device 46, the vacuum pump 47, the atmosphere release valve V3, and the like. In the present embodiment, the control device 49 is configured as a part of the vacuum degassing apparatus 4, but may also be configured as a part of a control panel (not shown) of the injection apparatus 3.

[0014] The hopper 41 and the material tank 42 are containers that temporarily store the molding material supplied to the injection cylinder 32, and can be formed of a steel plate or the like. The material tank 42 includes an input port (not shown) for inputting the molding material from the outside. The hopper 41 and the material tank 42 are connected via a material input pipe L1. The material input pipe L1 is provided with an input control valve V1. The exhaust blower 43 is connected to the hopper 41 via a blower suction pipe L2. The blower suction pipe L2 is provided with a suction control valve V2.

[0015] Communication between the hopper 41 and the material tank 42 is shut off by closing the input control valve V1, and communication between the hopper 41 and the exhaust blower 43 is shut off by closing the suction control valve V2. The input control valve V1 and the suction control valve V2 are closed except when conveying the molding material from the material tank 42 to the hopper 41. The input control valve V1 and the suction control valve V2 are closed while the shutoff device 46 is open. The input control valve V1, the suction control valve V2, and the exhaust blower 43 are connected to the control device 49.

[0016] The timing for supplying the molding material to the hopper 41 is not limited as long as the shut-off device 46 is closed, and may be any timing between the end of the metering step of the previous cycle and the start of the metering step of the next cycle. Further, since molding materials corresponding to a plurality of injection shots can be supplied to the hopper 41 collectively, the opening and closing operations of the input control valve V1 and the suction control valve V2 can be performed only once for a plurality of injection cycles. The metering step refers to a step of heating and melting (plasticizing) the molding material and a step of conveying the melted molding material to the front side (the +X direction side) of the injection screw 33, and these steps are performed simultaneously.

[0017] The conveying device 44 includes a feed cylinder 441 and a feed screw 442. The conveying device 44 conveys the molding material to the injection cylinder 32. The feed screw 442 is housed in the feed cylinder 441. The feed cylinder 441 is located directly below the hopper 41 and communicates with the hopper 41 and the material supply path 45. The rotation of the feed screw 442 conveys the molding material retained on the feed screw 442, and the molding material drops through the material supply path 45 and is supplied to the injection cylinder 32.

[0018] The material supply path 45 is provided between the conveying device 44 and the injection cylinder 32. The material supply path 45 functions as a guide path for supplying the molding material conveyed by the feed screw 442 to the injection cylinder 32. The material supply path 45 can be separated by the shut-off device 46 into an upstream portion 451 communicating with the conveying device 44 and a downstream portion 452 communicating with the injection cylinder 32. The upstream portion 451 is located above the downstream portion 452 in the Z direction. When the shut-off device 46 is closed, the upstream portion 451 forms an integral space with the feed cylinder 441 and the hopper 41, and the downstream portion 452 forms an integral space with the injection cylinder 32. The shut-off device 46 can be formed of, for example, a valve. The shut-off device 46 is connected to a control device 49.

[0019] The vacuum pump 47 is connected to the downstream section 452 by a pump suction pipe L3. An atmospheric release pipe L4 is connected to the pump suction pipe L3. An atmospheric release valve V3 is provided in the atmospheric release pipe L4. The atmospheric release valve V3 only needs to be in communication with or connected to the downstream section 452, and the atmospheric release pipe L4 can be attached, for example, to the downstream section 452 or the injection cylinder 32. The atmospheric release valve V3 is connected to the control device 49. The vacuum pump 47 is in continuous operation.

[0020] The detection device 48 detects the start and end of the metering process. The detection device 48 can be composed of, for example, an angle sensor that detects the rotation angle of the injection screw 33 and a position sensor that detects the position of the injection screw 33 in the X direction. The detection device 48 is connected to the control device 49. When the angle sensor detects the start of rotation of the injection screw 33, the control device 49 determines that the metering process of the molding material has started. When the position sensor detects that the injection screw 33 has retracted in the -X direction and reached a predetermined position in the X direction, the control device 49 determines that the metering process has ended. The above predetermined position is determined in advance according to the amount of molding material used in one injection process and is stored in the control device (not shown) of the injection device 3. Even if the injection screw 33 retracts after it has started rotating, the control device 49 determines that the metering process has started when the injection screw 33 started rotating.

[0021] The detection device 48 outputs a metering process start signal when the metering process begins and outputs a metering process end signal when the metering process ends. The metering process start signal and the metering process end signal are sent to the control device 49. When the control device 49 receives the metering process start signal, it opens the shut-off device 46, and when it receives the metering process end signal, it closes the shut-off device 46.

[0022] <Operation method and vacuum degassing method of vacuum degassing device 4> Referring to Figures 3A to 3E, the operation method and vacuum degassing method of the vacuum degassing apparatus 4 shown in Figure 2 will be explained. First, as shown in Figure 3A, the control device 49 opens the input control valve V1 and the suction control valve V2 and starts the exhaust blower 43. The exhaust blower 43 sucks air from inside the hopper 41, creating negative pressure inside the hopper 41. The molding material stored in the material tank 42 is fed into the hopper 41 through the material input pipe L1. A filter (not shown) is placed at the connection between the hopper 41 and the blower suction pipe L2 to prevent the molding material from flowing into the blower suction pipe L2. Since the feed screw 442 is stopped, the molding material fed from the material tank 42 remains on top of the feed screw 442 inside the hopper 41.

[0023] Since the shut-off device 46 and the atmospheric release valve V3 are closed, the injection cylinder 32 and the downstream section 452 are in a sealed space. Whether the injection process in the previous cycle is completed or not, moisture and volatile components remain inside the injection cylinder 32. The moisture and volatile components remaining in the injection cylinder 32 and the downstream section 452 are removed by the vacuum pump 47. In particular, if the injection process in the previous cycle is not completed, moisture and volatile components may be generated from the heated and melted molding material as described later, but both such moisture and volatile components are removed by the vacuum pump 47.

[0024] Next, as shown in Figure 3B, the control device 49 closes the input control valve V1 and the suction control valve V2. The upstream section 451 of the material supply passage 45 and the hopper 41 become a sealed space. Since the injection cylinder 32 and the downstream section 452 remain a sealed space, any moisture or volatile components remaining in the injection cylinder 32 and the downstream section 452 are continuously removed by the vacuum pump 47.

[0025] Next, as shown in Figure 3C, the control device 49 opens the atmospheric release valve V3. The atmospheric release valve V3 is opened before the metering process, when the shut-off device 46 and the atmospheric release valve V3 are closed and the vacuum pump 47 is operating. The pressure in the injection cylinder 32 and the downstream section 452 rises, but remains below atmospheric pressure because the vacuum pump 47 is operating.

[0026] Next, as shown in Figure 3D, the control device 49 starts the injection screw 33 and begins the metering process. The control device 49 receives a metering process start signal from the detection device 48. Upon receiving this signal, the control device 49 opens the shut-off device 46 and starts the feed screw 442. The vacuum pump 47 continues to operate even while the shut-off device 46 is open. The molding material that had been accumulating in the hopper 41 is transported by the feed screw 442 and falls down the material supply passage 45 to be supplied to the injection cylinder 32. The injection screw 33 rotates and retracts in the -X direction, transporting the molten molding material forward (towards the +X direction) of the injection screw 33. The atmospheric release valve V3 remains open during the metering process. The injection cylinder 32, material supply passage 45, transport device 44, and hopper 41 form a single space while the shut-off device 46 is open.

[0027] When the control device 49 receives a signal from the detection device 48 indicating the end of the metering process, it closes the shut-off device 46 and the atmospheric release valve V3, as shown in Figure 3E, and stops the feed screw 442. The supply of molding material from the material supply passage 45 to the injection cylinder 32 stops. Although not shown in the illustration, the injection screw 33 then moves forward in the +X direction to perform the injection process, injecting the molten molding material. After that, it returns to the state shown in Figure 3A and repeats the processes shown in Figures 3A to 3E.

[0028] <Effects of this embodiment> The effects of this embodiment will be explained in comparison with a comparative example. Figures 4A to 4D are similar to Figures 3A to 3E, which show the operation of the vacuum degassing device 104 of the comparative example. The control device is not shown. In the comparative example, a shut-off device 46 is located on the hopper 41, and the shut-off device 46 separates the hopper 41 into an upstream section 411 and a downstream section 412. A hopper suction pipe L5 is connected to the upstream section 411 of the hopper 41 and joins the pump suction pipe L3. The hopper suction pipe L5 is equipped with a valve V4. The vacuum pump 47 is operated continuously.

[0029] First, as shown in Figure 4A, the input control valve V1 and the suction control valve V2 are opened, and the exhaust blower 43 is started. The molding material stored in the material tank 42 is fed into the hopper 41 through the material input pipe L1. Because the shut-off device 46 is closed, the molding material fed from the material tank 42 remains in the upstream part 411 of the hopper 41 (above the shut-off device 46).

[0030] Next, as shown in Figure 4B, the input control valve V1 and the suction control valve V2 are closed. This seals the upstream section 411 of the hopper 41. Then, as shown in Figure 4C, the valve V4 of the hopper suction pipe L5 is opened to evacuate the upstream section 411 of the hopper 41. The upstream section 411 and downstream section 412 of the hopper 41, the material supply passage 45, and the injection cylinder 32 are all simultaneously evacuated by the vacuum pump 47, resulting in the same pressure.

[0031] As shown in Figure 4D, when the metering process begins, the shut-off device 46 is opened and the feed screw 442 is activated. The molding material that was accumulated on the shut-off device 46 is transported by the feed screw 442 and supplied to the injection cylinder 32 through the material supply path 45. When the metering process is completed, the shut-off device 46 is closed. The process shown in Figures 4A to 4D is then repeated.

[0032] In the comparative example, the shut-off device 46 is closed and the vacuum pump 47 is operating during the process shown in Figures 4A to 4B, so the injection cylinder 32, the material supply passage 45, and the downstream section 412 of the hopper 41 are maintained at a nearly constant pressure. In the process shown in Figure 4C, with the injection cylinder 32, the material supply passage 45, and the downstream section 412 of the hopper 41 maintained at approximately the same pressure as in the process shown in Figures 4A to 4B, the upstream section 411 of the hopper 41 is depressurized until it reaches a pressure similar to that of the downstream section 412. The process shown in Figure 4D is performed with the upstream section 411 and the downstream section 412 of the hopper 41 under equal pressure.

[0033] Therefore, in the process shown in Figures 4A to 4D, the pressure in the injection cylinder 32, the material supply passage 45, and the downstream section 412 of the hopper 41 is maintained at a nearly constant level, making it difficult for airflow to occur in these spaces. Although the vacuum pump 47 is operating, the injection cylinder 32, the material supply passage 45, and the downstream section 412 of the hopper 41 are always in a high vacuum state, resulting in a small amount of exhaust per unit time. For these reasons, it is difficult to efficiently remove moisture and volatile components that have accumulated in the injection cylinder 32, the material supply passage 45, and the downstream section 412 of the hopper 41.

[0034] In this embodiment, the atmospheric release valve V3 is opened in the process shown in Figure 3C, so that a portion of the air flowing in from the atmospheric release valve V3 flows into the injection cylinder 32 and the downstream section 452 of the material supply passage 45. This disturbs the air in the downstream section 452 of the injection cylinder 32 and the material supply passage 45, generating an airflow in the downstream section 452 of the injection cylinder 32 and the material supply passage 45. This airflow makes it easier for moisture and volatile components that have been accumulating in the downstream section 452 of the injection cylinder 32 and the material supply passage 45 to flow, and they are efficiently discharged by the vacuum pump 47.

[0035] By opening the shut-off device 46 in the process shown in Figure 3D, the upstream section 451 and the downstream section 452 of the material supply passage 45 are connected, making it easier for airflow to be generated in the upstream section 451 as well. In other words, airflow is generated from the upstream section 451 and the downstream section 452 of the material supply passage 45, the hopper 41 and the injection cylinder 32 toward the vacuum pump 47. Although the upstream section 451 of the material supply passage 45 has already been exhausted by the exhaust blower 43, the pressure does not drop significantly and remains at approximately the same pressure as atmospheric pressure. Therefore, the pressure difference between the upstream section 451 and the downstream section 452 of the material supply passage 45 makes it even easier for airflow to be generated.

[0036] In other words, the injection cylinder 32 and the downstream section 452 of the material supply passage 45 repeatedly experience low pressure (Figures 3A, 3B, 3E) and high pressure (Figures 3C, 3D) during a single injection cycle. This pressure difference generates an airflow between the injection cylinder 32 and the downstream section 452 of the material supply passage 45. This airflow disrupts any moisture or volatile components that have accumulated in these spaces, allowing them to be efficiently expelled by the vacuum pump 47. Furthermore, in the process shown in Figure 3D, the upstream section 451 of the material supply passage 45, which is at approximately atmospheric pressure, is connected to the downstream section 452 and the injection cylinder 32. As a result, the amount of exhaust by the vacuum pump 47 is increased compared to the comparative example, and the airflow velocity is also increased. This allows for even more efficient removal of moisture and volatile components.

[0037] The atmospheric release valve V3 can be opened after the metering process has started, but it is preferable to open it before the metering process has started. Moisture and volatile components adhere to the surface of the molding material, while others are inside the molding material and are released by heating and melting. In this embodiment, after generating an airflow between the injection cylinder 32 and the downstream part 452 of the material supply passage 45 by the process shown in Figure 3C, the molding material is supplied to the material supply passage 45 by the process shown in Figure 3D. In other words, when supplying the molding material to the material supply passage 45, an airflow has already been generated between the injection cylinder 32 and the downstream part 452 of the material supply passage 45. Therefore, moisture and volatile components adhering to the surface of the molding material can be quickly removed after the molding material is introduced into the material supply passage 45.

[0038] As explained above, this embodiment can remove moisture and volatile components from the molding material more efficiently than the comparative example, and it has several further advantages. First, the hopper suction pipe L5 and valve V4 of the comparative example are unnecessary. Second, the hopper 41 of the comparative example has a pressure drop to a level of vacuum similar to that of the injection cylinder 32 (see Figure 4C), requiring high airtightness, whereas the hopper 41 of this embodiment has only a slight negative pressure inside due to the exhaust blower 43, so high airtightness is not required.

[0039] Furthermore, while the comparative example required the use of a hopper 41 connected to a hopper suction pipe L5, the type of hopper 41 is not limited in this embodiment. In this embodiment, a sealed hopper 41 connected to a material input pipe L1 and a blower suction pipe L2, and a material tank 42 are used, but a less expensive hopper with an open top can also be used, and the material tank 42 can be omitted. In this case, instead of the process shown in Figures 3A to 3C, an operator can manually load the molding material into the hopper 41. [Explanation of symbols]

[0040] 3 Injection device 4. Vacuum degassing device 32 Injection Cylinder 33 Injection screw 41 Hoppa 44 Conveying device 45 Material supply route 46 Circuit breaker 47 Vacuum pump 48 sensors 49 Control device 451 Upstream section 452 Downstream L3 Pump suction tube L4 Atmospheric Vent Pipe V3 Atmospheric release valve

Claims

1. A conveying device for transporting molding material to the injection cylinder, A material supply passage is provided between the injection cylinder and the transport device, for supplying the molding material to the injection cylinder, A blocking device that separates the material supply path into an upstream section communicating with the conveying device and a downstream section communicating with the injection cylinder, A vacuum pump connected to the downstream section, It has an atmospheric release valve that communicates with the downstream section, The aforementioned atmospheric release valve is opened before the metering process, while the shut-off device and the atmospheric release valve are closed and the vacuum pump is operating, in a vacuum degassing device.

2. A pump suction pipe connecting the downstream section and the vacuum pump, It has an atmospheric vent pipe connected to the pump suction pipe, The vacuum degassing apparatus according to claim 1, wherein the atmospheric release valve is provided in the atmospheric release pipe.

3. The vacuum degassing apparatus according to claim 1, wherein the atmospheric release valve is open during the metering process.

4. The vacuum degassing apparatus according to claim 3, wherein the atmospheric release valve is closed after the completion of the metering process.

5. The vacuum degassing apparatus according to claim 1, wherein the shut-off device is opened during the metering step, and the vacuum pump is operated while the shut-off device is open.

6. It has a sensor that detects the start and end of the aforementioned weighing process, The vacuum degassing apparatus according to any one of claims 1 to 5, wherein the shut-off device is opened after the sensor detects the start of the metering process, and the shut-off device is closed after the sensor detects the end of the metering process.

7. It comprises an injection cylinder and a vacuum degassing device attached to the injection cylinder, The vacuum degassing apparatus is, A conveying device for conveying molding material to the injection cylinder, A material supply passage is provided between the injection cylinder and the transport device, for supplying the molding material to the injection cylinder, A blocking device that separates the material supply path into an upstream section communicating with the conveying device and a downstream section communicating with the injection cylinder, A vacuum pump connected to the downstream section, It has an atmospheric release valve that communicates with the downstream section, The injection device wherein the atmospheric release valve is opened before the metering process, when the shut-off device and the atmospheric release valve are closed and the vacuum pump is operating.

8. A pump suction pipe connecting the downstream section and the vacuum pump, It has an atmospheric vent pipe connected to the pump suction pipe, The injection device according to claim 7, wherein the atmospheric release valve is provided in the atmospheric release pipe.

9. The injection apparatus according to claim 7, wherein the atmospheric release valve is open during the metering process.

10. The injection apparatus according to claim 9, wherein the atmospheric release valve is closed after the completion of the metering process.

11. The injection apparatus according to claim 7, wherein the shut-off device is opened during the metering step, and the vacuum pump is operated while the shut-off device is open.

12. A sensor for detecting the start and end of the aforementioned weighing process, The control device for the aforementioned circuit breaker has, It has a sensor that detects the start and end of the aforementioned weighing process, The injection device according to any one of claims 7 to 11, wherein the shut-off device is opened after the sensor detects the start of the metering process, and the shut-off device is closed after the sensor detects the end of the metering process.

13. A conveying device for transporting molding material to the injection cylinder, A material supply passage is provided between the injection cylinder and the transport device, for supplying the molding material to the injection cylinder, A blocking device that separates the material supply path into an upstream section communicating with the conveying device and a downstream section communicating with the injection cylinder, A vacuum pump connected to the downstream section, A vacuum degassing method using a vacuum degassing apparatus having an atmospheric release valve in communication with the downstream section, A vacuum degassing method comprising opening the atmospheric release valve before the metering process, while the shut-off device and the atmospheric release valve are closed and the vacuum pump is operating.

14. A pump suction pipe connecting the downstream section and the vacuum pump, It has an atmospheric vent pipe connected to the pump suction pipe, The vacuum degassing method according to claim 13, wherein the atmospheric release valve is provided in the atmospheric release pipe.

15. The vacuum degassing method according to claim 13, wherein the atmospheric release valve is opened during the metering step.

16. The vacuum degassing method according to claim 15, wherein the atmospheric release valve is closed after the completion of the metering step.

17. The vacuum degassing method according to claim 13, wherein the shut-off device is opened in the metering step, and the vacuum pump is operated while the shut-off device is open.

18. The vacuum degassing apparatus has a sensor that detects the start and end of the weighing process, The vacuum degassing method according to any one of claims 13 to 17, wherein the shut-off device is opened after the sensor detects the start of the metering process, and the shut-off device is closed after the sensor detects the end of the metering process.

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