KR20210102478A - Vacuum-generating pumping system and pumping method using this pumping system - Google Patents

Abstract

The vacuum-generating pumping system SP is a dry type having a gas inlet 2 connected to a vacuum chamber 1 and a gas outlet 4 open to a conduit 5 for evacuating gas from the pumping system to a gas outlet 8 . and a main vacuum pump, which is a screw pump (3). The pumping system comprises a non-return valve (6) disposed between the gas outlet (4) and the gas outlet (8), and an auxiliary vacuum pump (7) connected in parallel to the non-return valve. . The main vacuum pump 3 is started to pump the gas contained in the vacuum chamber 1 to discharge this gas through the gas outlet 4 , and at the same time the auxiliary vacuum pump 7 is started. Moreover, the auxiliary vacuum pump 7 ensures that the main vacuum pump 3 pumps gas in the vacuum chamber 1 all the way and/or the main vacuum pump 3 maintains a prescribed pressure in the vacuum chamber 1 . Keep pumping all the way through.

Description

Vacuum-generating pumping system and pumping method using this pumping system

The present invention relates to the field of vacuum technology. More particularly, the present invention relates to a pumping system comprising a dry screw pump and a pumping method by means of the pumping system.

In order to reduce the cost and energy consumption of equipment in the industry, for example in the chemical industry, pharmaceutical industry, vacuum deposition industry, semiconductor industry, etc., the general purpose of improving the performance of a vacuum pump is the performance in the drive, energy economy, It has led to significant advances in terms of bulkiness, etc. In the field of vacuum pumps, as is known in the art, there have been vacuum pumps of the multi-stage Roots or multi-stage claw type.

The current state of the art shows that supplemental steps must be added to vacuum pumps of the multi-stage Roots or multi-stage claw type to improve the final vacuum. It is known for screw type dry vacuum pumps that additional rotations of the screw must be provided and/or the internal compression ratio must be increased.

The rotational speed of the pump plays a very important role by defining the operation of the pump during discrete and successive stages within the evacuation process of the vacuum pump. For internal compression ratios of pumps available on the market (eg sizes between approx. 2 to 20), they operate at high mass flow rates when the pressure at the suction end is between atmospheric and approx. 100 mbar. In the meantime, the power required in the first pumping stage will be very high if the rotational speed of the pump cannot be reduced. A typical solution is to use a variable speed drive which makes it possible to reduce or increase the speed according to different criteria such as type pressure, maximum current, limit torque, temperature, etc. and consequently reduce or increase the power. will be. However, during the period of operation at reduced rotational speed, the flow rate proportional to the rotational speed at high pressure decreases. Changing the speed with a variable speed drive entails additional cost and greater volume. Another common solution is to use bypass type valves at certain stages, in multistage vacuum pumps of Roots or claw type, or some well defined along the screw in screw type dry vacuum pumps. By-pass type valves are used in places where This solution requires many parts and has reliability problems.

The current state of the art related to pumping systems aimed at improving the final vacuum and increasing the flow rate comprises a Roots type booster pump arranged upstream from the main dry pumps. Systems of this type are bulky and operate with bypass valves that present reliability problems or by employing measuring, controlling, regulating or servo-control means. However, such control, regulation or servo-control means must be actively controlled, which inevitably leads to an increase in the number, complexity and cost of the parts of the system. With respect to prior art, US Patent Application Publication No. US2003/0068233 (issued on April 10, 2003), Japanese Patent Application Laid-Open No. 2002-339864 (issued on November 27, 2002), and Chinese Patent Application Laid-Open No. 1541307 issue (issued on October 27, 2004).

The invention has the object of making it possible to obtain a better vacuum (at the level of 0.0001 mbar) than one dry vacuum pump of the screw type can generate in the vacuum chamber.

The invention also has the object of obtaining a faster evacuation or evacuation rate at lower pressures than can be achieved with the aid of a single dry vacuum pump of screw type during pumping to achieve a vacuum in the vacuum chamber.

Likewise, the present invention has an object to achieve a reduction in the temperature of the exhaust gas as well as to enable the reduction of the electrical energy required for evacuation of the vacuum chamber and for maintaining the vacuum.

The objects of the present invention are achieved with the aid of a pumping system for generating a vacuum, said pumping system comprising a main vacuum pump, said main vacuum pump having a gas inlet connected to the vacuum chamber and a gas outlet outside the pumping system. It is a dry screw pump with a gas discharge outlet leading to the gas exhaust pipe in the direction of the exhaust outlet. The pumping system is

- a non-return valve disposed between the gas outlet and the gas outlet, and

- Further comprising an auxiliary vacuum pump connected in parallel to the non-return valve.

The auxiliary vacuum pump may be a dry screw pump, a claw pump, a multi-stage Roots pump, a diaphragm pump, a dry rotary vane pump, or a type of a lubricated rotary vane pump. have.

The invention likewise has a pumping method with a pumping system as previously defined as a subject. This pumping method is

- starting the main vacuum pump to pump the gases contained in the vacuum chamber and to evacuate these gases through its gas outlet;

- simultaneously starting the auxiliary vacuum pump;

- the auxiliary vacuum pump continues pumping while the main vacuum pump pumps the gases contained in the vacuum chamber and/or while the main vacuum pump maintains a prescribed pressure in the vacuum chamber; include

In the method according to the invention, the auxiliary vacuum pump evacuates the vacuum all the way while the main vacuum pump of the dry screw type evacuates the vacuum chamber, and the main dry screw vacuum pump evacuates the gases through its discharge end. It is operated continuously and continuously while maintaining a prescribed pressure (eg final vacuum) in the chamber.

Thanks to the method according to the invention, no specific measurements or devices (e.g. sensors for pressure, temperature, current, etc.) are required, no servo-control and data management, no calculations, A combination of the dry screw type main vacuum pump and the auxiliary vacuum pump may be made. As a result, a pumping system suitable for carrying out the pumping method according to the invention comprises only a minimal number of components, is very simple and has a significantly lower cost compared to existing systems.

Thanks to the method according to the invention, the main vacuum pump of the dry screw type can be operated by turning it at one constant speed of the power grid or at a variable speed depending on its own mode of operation. Consequently, the complexity and cost of a pumping system suitable for carrying out the pumping method according to the invention can be further reduced.

Essentially, the auxiliary pump integrated into the pumping system can always operate without damage according to the pumping method of the present invention. It is sized to minimize energy consumption for operation of the device. The nominal flow rate of the auxiliary pump is selected according to the volume of the exhaust line between the main dry screw vacuum pump and the non-return valve. This flow rate may advantageously be 1/500 to 1/20 of the nominal flow rate of the main dry screw vacuum pump, but may be smaller or larger than these values, in particular 1/500 of the nominal flow rate of the main vacuum pump 500 to 1/10 or 1/500 to 1/5.

The non-return valve is provided in a pipeline downstream from the main dry screw vacuum pump and may be a standard commercially available element. It is sized according to the nominal flow rate of the main dry screw vacuum pump. In particular, the non-return valve is expected to close when the pressure at the suction end of the main dry screw vacuum pump is between 500 mbar absolute and a final vacuum (eg 100 mbar).

According to another variant, the auxiliary pump may have a high chemical resistance to materials and gases commonly used in the semiconductor industry.

The auxiliary pump is preferably of small size.

Preferably, according to the pumping method employing the pumping system according to the present invention, the auxiliary vacuum pump always pumps the volume between the gas outlet of the main vacuum pump and the non-return valve.

According to another variant of the method of the present invention, the operation of the auxiliary vacuum pump is controlled in an "all or nothing" manner in order to fulfill a particular demand. This control measures one or more parameters and obeys a certain rule to start or stop the auxiliary vacuum pump. These parameters are provided by suitable sensors, for example the current of the motor of the main dry screw vacuum pump, the gas at its discharge end, ie in the space upstream from the non-return valve in the exhaust conduit. temperature or pressure, or a combination of these parameters.

The size of the auxiliary vacuum pump aims to minimize the energy consumption of its motor. Its nominal flow rate is selected according to the flow rate of the main dry screw vacuum pump, and also takes into account the volume defined by the gas exhaust pipe between the main vacuum pump and the non-return valve (6). This flow rate may be 1/500 to 1/20 of the nominal flow rate of the main dry screw vacuum pump, but may be smaller or larger than these values.

Starting from the exhaust cycle of the chamber, the pressure is high, eg equal to atmospheric pressure. Considering the compression in the main dry screw vacuum pump, the pressure of the gases discharged at the outlet is higher than atmospheric pressure (when the gases are discharged directly into the atmosphere at the outlet of the main pump) or other device connected downstream higher than the pressure at the inlet of This results in the opening of the non-return valve.

When the non-return valve is open, the operation of the auxiliary vacuum pump feels very weak because the pressure at its suction end is almost equal to the pressure at its discharge end. On the other hand, when the non-return valve is closed at a certain pressure (because the pressure in the chamber has dropped in the meantime), the operation of the auxiliary vacuum pump is the difference in pressure between the vacuum chamber and the exhaust pipe upstream from the valve. is gradually reduced. The pressure at the outlet of the main dry screw vacuum pump becomes the pressure at the inlet of the auxiliary vacuum pump, and the pressure at the outlet of the auxiliary vacuum pump always becomes the pressure in the conduit after the non-return valve. The more the auxiliary vacuum pump pumps, the lower the pressure at the outlet of the main dry screw vacuum pump within the space defined by the closed non-return valve, and consequently the lower the pressure between the chamber and the outlet of the main dry screw vacuum pump. The difference decreases.

A slight difference reduces internal leakage in the main dry screw vacuum pump, resulting in a decrease in pressure in the chamber, which improves the final vacuum. Additionally, the main dry screw vacuum pump consumes less and less energy for compression and generates less and less heat of compression.

On the other hand, it is clear that the study of the mechanical concept, which seeks to reduce the space between the gas outlet of the main dry screw vacuum pump and the non-return valve, aims to make it possible to lower the pressure more quickly.

The features and advantages of the present invention will appear in more detail in the context of the description of exemplary embodiments given in a non-limiting manner by way of reference to the accompanying drawings.
1 shows in a schematic manner a pumping system suitable for carrying out a pumping method according to a first embodiment of the invention;
2 shows in a schematic manner a pumping system suitable for carrying out a pumping method according to a second embodiment of the invention;

1 shows in a schematic manner a pumping system suitable for carrying out a pumping method according to a first embodiment of the invention;

The pumping system SP comprises a chamber 1 , which is connected to the suction end 2 of a main vacuum pump consisting of a dry screw pump 3 . The gas outlet of the main dry screw vacuum pump (3) is connected to the exhaust pipe (5). A non-return discharge valve (6) is located in the exhaust pipe (5), which continues to the gas discharge pipe (8) after this non-return valve. The non-return valve 6, when closed, permits the formation of a contained volume 4 between the gas outlet of the main vacuum pump 3 and the non-return valve.

The pumping system SP also comprises an auxiliary vacuum pump 7 connected in parallel to the non-return valve 6 . The suction end of the auxiliary vacuum pump is connected to the volume portion 4 of the space of the exhaust conduit 5 and the discharge end is connected to the conduit 8 .

Since the main dry screw vacuum pump 3 is already in operation, the auxiliary vacuum pump 7 operates by itself. The main dry screw vacuum pump 3 sucks and compresses the gas in the chamber 1 through a conduit 2 connected to its inlet, and then at the outlet in the exhaust conduit 5, the non-return valve 6 ) through the When the closing pressure for the non-return valve 6 is reached, the non-return valve closes. The pumping of the auxiliary vacuum pump 7 starting from this point causes the pressure in the volume part 4 to gradually lower to the pressure limit value. At the same time, the power consumed by the main dry screw vacuum pump 3 is gradually reduced. This takes place over a short period of time, for example some cycle within 5 to 10 seconds.

Precise regulation of the flow rate of the main dry screw vacuum pump (3) and the flow rate of the auxiliary vacuum pump (7) according to the volume of the chamber (1) and the closing pressure of the non-return valve (6), the non-return valve It is possible to reduce the time related to the duration of the exhaust cycle before closing of (6), thus reducing the amount of energy consumed during the operating time of the auxiliary pump (7) without affecting the pumping. On the other hand, the advantage of simplicity gives the system excellent reliability.

According to a first possibility, the auxiliary vacuum pump 7 itself is a dry screw pump. Thus, the main pump and the auxiliary pump are of the same type, which simplifies operation and handling. Also, the combination of these pumps allows the pumping system SP to be used in all applications where only dry screw pumps can be used.

Further, according to another possibility, the auxiliary vacuum pump 7 is a claw pump, a multi-stage roots pump, a diaphragm pump, a dry rotary vane pump or a lubricated rotary vane pump. Any combination of these pumps has advantages linked to the specific characteristics of each type of individual pumps.

2 shows in a schematic way a pumping system SPP suitable for carrying out a pumping method according to a second embodiment of the invention.

With respect to the system shown in FIG. 1 , the system shown in FIG. 2 represents a controlled pumping system SSP and further comprises suitable sensors 11 , 12 , 13 . The sensors 11 , 12 , 13 check the current (sensor 11 ) of the motor of the main dry screw vacuum pump 3 , or are limited by a non-return valve 6 , the main dry screw vacuum Check the pressure of the gas in the space of the outlet conduit of the pump (sensor 13), or the temperature of the gas in the space of the outlet conduit at the outlet of the main dry screw vacuum pump, limited by the non-return valve 6 pressure gas temperature (sensor 12), or a combination of these parameters. In fact, when the main dry screw vacuum pump 3 starts pumping the gas in the vacuum chamber 1, parameters such as the current of the motor, the temperature and pressure of the gas in the volume part of the outlet conduit begin to change and the Threshold values detected by the sensors are reached. This results in starting of the auxiliary vacuum pump 7 after a time lag. When these parameters return to their initial ranges (out of set values), with a time delay the auxiliary vacuum pump is stopped.

In the second embodiment of the present invention of Fig. 2, the auxiliary vacuum pump, as in the first embodiment of the present invention of Fig. 1, a dry screw, claw, multi-stage roots, diaphragm, dry rotary vane or lubricated rotary vane It can be a type.

Although various embodiments have been described, it will be understood that it is not possible to exhaustively identify all possible embodiments. Of course, it may be envisaged to replace the described means with equivalent means without departing from the scope of the invention. All such variations form part of the ordinary knowledge of a person skilled in the vacuum art.

1: vacuum chamber 2: gas inlet
3: Main vacuum pump 5: Gas exhaust pipe
7: auxiliary vacuum pump 8: gas exhaust port

Claims (11)

Dry screw pump having a gas inlet (2) connected to the vacuum chamber (1) and a gas discharge outlet leading to a gas exhaust conduit (5) in the direction of a gas exhaust outlet (8) outside the pumping system A pumping system (SP) for generating a vacuum, comprising an in-main vacuum pump (3), comprising:
The pumping system is
- a non-return valve (6) arranged between the gas outlet and the gas outlet (8), and
- an auxiliary vacuum pump (7) having its own motor and connected in parallel to said non-return valve;
The auxiliary vacuum pump 7 is caused to start at the same time as the main vacuum pump 3 , all the way while the main vacuum pump 3 pumps the gases contained in the vacuum chamber 1 and the main vacuum pump (3) is capable of pumping all the way while maintaining a prescribed pressure in the vacuum chamber (1),
The non-return valve 6, when closed, allows the formation of a volume portion 4 between the non-return valve and the gas outlet of the main vacuum pump 3, the volume portion 4 being the main vacuum disposed on a straight path extending from the gas outlet of the pump (3) to the inlet of the auxiliary vacuum pump (7),
Pumping system, characterized in that the connection between the main vacuum pump (3) and the auxiliary vacuum pump (7) is made without the need for a measuring, sensor or control unit. The method of claim 1,
The auxiliary vacuum pump 7 is selected from a dry screw pump, a claw pump, a multi-stage Roots pump, a diaphragm pump, a dry rotary vane pump and a lubricated rotary vane pump. A pumping system, characterized in that it becomes. The method of claim 1,
A pumping system, characterized in that the auxiliary vacuum pump (7) has a discharge end connected to the gas exhaust conduit (5) downstream from the non-return valve (6). The method of claim 1,
The nominal flow rate of the auxiliary vacuum pump (7) is selected according to the volume defined by the gas exhaust pipe (5) between the main vacuum pump (3) and the non-return valve (6) to the pumping system. The method of claim 1,
Pumping system, characterized in that the nominal flow rate of the auxiliary vacuum pump (7) is 1/500 to 1/20 of the nominal flow rate of the main vacuum pump (3). The method of claim 1,
Pumping system, characterized in that the auxiliary vacuum pump (7) is single-staged or multi-staged. The method of claim 1,
Pumping system, characterized in that the non-return valve (6) is configured to close when the pressure at the suction end of the main vacuum pump (3) is less than 500 mbar in absolute value. The method of claim 1,
A pumping system, characterized in that the auxiliary vacuum pump (7) is made of a material with chemical resistance. A method of pumping by means of a pumping system (SP) according to claim 1, comprising:
- starting the main vacuum pump (3) for pumping the gases contained in the vacuum chamber (1) and evacuating these gases through its gas outlet (4);
- simultaneously starting the auxiliary vacuum pump (7); and
- all the while the main vacuum pump (3) pumps the gases contained in the vacuum chamber (1) and all the time while the main vacuum pump (3) maintains a prescribed pressure in the vacuum chamber (1), the auxiliary Pumping method, characterized in that it comprises; vacuum pump (7) continues pumping. 10. The method of claim 9,
Pumping method, characterized in that the auxiliary vacuum pump (7) pumps at a flow rate of about 1/500 to 1/20 of the nominal flow rate of the main vacuum pump (3). 11. The method according to claim 9 or 10,
Pumping method, characterized in that the non-return valve (6) is closed when the pressure at the suction end of the main vacuum pump (3) is less than 500 mbar in absolute value.

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