RU2670640C9 - Pumping system for creating a vacuum and a handling method with the use of this pumping system - Google Patents

Abstract

FIELD: motors and pumps.

SUBSTANCE: group of inventions relates to the field of vacuum technology. Pump system (SP), designed to create a vacuum, includes main oil-free screw pump (3), which has suction inlet (2) for gas, connected to vacuum chamber (1), and outlet (4) for blowing gas out to gas discharge channel (5) in the direction of outlet (8) for gas to exit the pumping system. System (SP) includes non-return valve (6) located between outlets (4, 8) and auxiliary vacuum pump (7) connected in parallel with valve (6). Pump (3) is driven to pump out the gas in chamber (1) and to blow out this gas through outlet (4), while pump (7) is also activated. Pump (7) continues to work all the time during which pump (3) evacuates gas from chamber (1), and / or all the time during which pump (3) maintains a certain pressure in chamber (1).

EFFECT: group of inventions is aimed at ensuring the possibility of obtaining a high vacuum and high pumping speed at low pressure, which can be obtained using a single vacuum oil-free screw pump, and also aims to reduce the amount of electricity needed to create and maintain a vacuum in a vacuum chamber and to reduce the temperature of the outgoing gas.

15 cl, 2 dwg

Description

FIELD OF TECHNOLOGY

The present invention relates to the field of vacuum technology. More specifically, the invention relates to a pumping system including an oil-free vacuum pump, as well as to a pumping method using this pumping system.

BACKGROUND

The general tasks of improving the operation parameters of vacuum pumps, reducing the cost of equipment and energy consumption in industries such as chemical, pharmaceutical, vacuum spraying, semiconductor manufacturing, etc., have led to significant progress in terms of performance, energy savings, overall dimensions, drive devices.

The state of the art shows that in order to increase the final vacuum, multistage vacuum pumps such as Roots pumps or cam pumps need to be equipped with additional stages. As you know, for screw-type oil-free vacuum pumps, it is necessary to introduce additional turns of the screw and / or increase the degree of internal compression.

The speed of rotation of the pump plays a very important role, affecting the functioning of the pump during various successive phases during the creation of vacuum in a vacuum chamber. With the degree of internal compression of the pumps available on the market (the order of magnitude of which lies in the range, for example, from 2 to 20), the required electric power in the first phases of pumping, when the suction pressure lies approximately in the range from atmospheric to 100 mbar, i.e. , during operation at a large mass flow rate, would be very large if the speed of the pump could not be reduced. A trivial solution is to use a speed controller that allows you to increase or decrease speed and, consequently, power, depending on various criteria such as pressure, maximum current, maximum torque, temperature, etc. However, during operation with a reduced speed of rotation, a decrease in flow rate occurs at high pressure, since the flow rate is proportional to the speed of rotation. Changing the speed with a variable speed drive entails additional costs and an increase in the dimensions of the equipment. Another well-known solution is to use bypass valves at certain stages - in multi-stage vacuum pumps such as Roots pumps or cam pumps, or in precisely defined positions along the screw - in screw-free oil-free vacuum pumps. This solution requires a lot of detail and causes reliability issues.

The prior art in the field of vacuum pumping systems, with the goal of increasing the final vacuum and increasing the flow rate, is also represented by “booster” pumps of the Roots type, installed up to the main oil-free pump. This type of system is cumbersome, it works either with bypass valves, which are characterized by problems in terms of reliability, or with the use of control, control or feedback tools that need active control, which inevitably entails an increase in the number of system components, its complexity and its cost .

SUMMARY OF THE INVENTION

The present invention aims to provide a higher vacuum (of the order of 0.0001 mbar) than that which can be obtained in a vacuum chamber using a single oil-free vacuum screw pump.

The present invention aims to provide the possibility of obtaining a higher pumping speed at low pressure than can be obtained using a single oil-free vacuum screw pump during pumping to create a vacuum in a vacuum chamber.

The present invention also aims to reduce the amount of electricity required to create and maintain a vacuum in a vacuum chamber, as well as to reduce the temperature of the outgoing gas.

These objectives of the invention are achieved by means of a pump system designed to create a vacuum, comprising a main vacuum pump, which is an oil-free screw pump, in which there is a gas intake inlet connected to the vacuum chamber, and an outlet for blowing gas exiting into the gas discharge channel in the direction exhaust gas outlet from the pumping system. In addition, the pumping system includes:

- a non-return valve located between the outlet (4) for blowing gas and the outlet for the exit of gas, and

- an auxiliary vacuum pump connected in parallel with a non-return valve.

The auxiliary vacuum pump can be of the type of oil-free screw pumps, cam pumps, multi-stage Roots pumps, diaphragm pumps, oil-free vane pumps, lubricated vane pumps.

The invention is also directed to a pumping method using the pumping system described previously. This method includes the stages in which:

- the main vacuum pump is activated to pump out the gas in the vacuum chamber and blow it out through the gas outlet;

- the auxiliary vacuum pump is simultaneously driven; and

- the auxiliary vacuum pump continues to work all the time during which the main vacuum pump pumps gas from the vacuum chamber and / or all the time during which the main vacuum pump maintains a certain pressure in the vacuum chamber.

In the method according to the invention, the auxiliary pump operates continuously all the time during which the main vacuum oil-free screw pump is pumping out of the vacuum chamber, as well as all the time during which the main vacuum oil-free screw pump maintains a certain pressure (for example, final vacuum) in vacuum chamber, pumping gas through the blowing element.

Thanks to the method of the present invention, the connection of the main vacuum oil-free screw pump and the auxiliary pump can be performed without the use of specialized measures or devices (for example, pressure, temperature, current sensors, etc.), monitoring system, data management system and without calculations. Therefore, a pumping system suitable for implementing the pumping method of the present invention may include only a minimal number of components, be characterized by simplicity and significantly lower cost in comparison with existing systems.

Thanks to the method of the present invention, the main vacuum oil-free screw pump can operate at one constant speed determined by the mains, or switch between different speed values in accordance with its own mode of operation. Therefore, the complexity and cost of a pumping system suitable for implementing the pumping method of the present invention can be further reduced.

By nature, the auxiliary pump included in the pumping system can always operate in accordance with the pumping method of the present invention without damage. The determination of its size is determined by the minimum energy consumption necessary for the operation of this device. Its nominal capacity is selected in accordance with the volume of the gas exhaust channel between the main vacuum oil-free screw pump and a non-return valve. Its value, mainly, can be from 1/500 to 1/20 of the nominal capacity of the main vacuum oil-free screw pump, however, it can also be more or less of these values, namely, from 1/500 to 1/10 or from 1/500 up to 1/5 of the nominal capacity of the main vacuum pump.

A non-return valve located downstream of the main vacuum oil-free screw pump may be a standard commercially available device. Its size is selected according to the nominal capacity of the main vacuum oil-free screw pump. In particular, it is envisaged that the non-return valve closes when the pressure at the suction end of the main vacuum oil-free screw pump is from 500 mbar abs. to the final vacuum (e.g. 100 mbar).

According to another embodiment, the auxiliary pump may have enhanced chemical resistance to substances and gases commonly used in the semiconductor industry.

Preferably, the auxiliary pump is small.

Preferably, according to the evacuation method using the pumping system of the present invention, the auxiliary vacuum pump always evacuates from 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, in the case of fulfillment of special conditions, the auxiliary vacuum pump is switched on according to the “on / off” principle. Such control consists in measuring one or many parameters and, according to certain rules, turning on the auxiliary vacuum pump or stopping it. The parameters, the values of which are measured using appropriate sensors, are, for example, the current of the engine of the main vacuum oil-free screw pump, the temperature or pressure of the gas at the end of the discharge, that is, in the volume downstream of the non-return valve of the gas exhaust channel, or a combination of these parameters.

Sizing of the auxiliary vacuum pump is aimed at minimizing the energy consumption of its engine. Its nominal capacity is selected depending on the performance of the main vacuum oil-free screw pump, and also take into account the volume of the gas exhaust channel between the main vacuum pump and the non-return valve. The capacity value can be from 1/500 to 1/20 of the rated capacity of the main vacuum oil-free screw pump, but it can also be more or less of these values.

At the beginning of the pumping cycle of the vacuum chamber, the pressure in it is increased, for example, it is equal to atmospheric pressure. Taking into account the compression in the main vacuum oil-free screw pump, the pressure of the blown gas at the pump outlet is greater than atmospheric pressure (if the gas at the outlet of the main pump is released directly into the atmosphere) or more than the pressure at the inlet to another device connected downstream. This causes the non-return valve to open.

When the non-return valve is open, the operation of the auxiliary vacuum pump is barely noticeable, since the pressure at the suction end of this pump is almost equal to the pressure at the end of the discharge. On the contrary, when the non-return valve closes at a certain pressure (as the pressure in the chamber decreases in the meantime), the operation of the auxiliary vacuum pump causes a progressive decrease in the pressure difference between the vacuum chamber and the gas outlet channel upstream of the valve. The pressure at the outlet of the main vacuum oil-free screw pump becomes equal to the pressure at the inlet of the auxiliary vacuum pump, and the pressure at its outlet is always equal to the pressure in the channel after the non-return valve. The longer the auxiliary vacuum pump operates, the more the pressure at the outlet of the main vacuum oil-free screw pump decreases in the volume limited by the closed non-return valve, and therefore the pressure difference between the chamber and the outlet of the main vacuum oil-free screw pump decreases.

Due to such a small difference, internal leaks in the main vacuum oil-free screw pump are reduced and the pressure in the chamber is reduced, which contributes to an increase in the final vacuum. In addition, the main vacuum oil-free screw pump consumes less and less compression energy and produces less and less compression heat.

On the other hand, it is also obvious that the study of the mechanics of the process is aimed at reducing the volume between the gas outlet for blowing the main vacuum oil-free screw pump and the non-return valve in order to enable faster pressure reduction.

BRIEF DESCRIPTION OF THE DRAWINGS

Distinctive features and advantages of the present invention are presented in more detail in the description, accompanied by examples of implementation, which are explanatory and not restrictive, with reference to the accompanying drawings, in which:

FIG. 1 is a diagram of a pumping system for implementing a pumping method according to a first embodiment of the present invention; and

FIG. 2 is a diagram of a pumping system for implementing a pumping method according to a second embodiment of the present invention.

DETAILED DESCRIPTION OF EMBODIMENTS OF THE INVENTION

In FIG. 1 shows a pumping system SP (système de pompage) for creating a vacuum in accordance with a pumping method according to a first embodiment of the present invention.

The pumping system SP includes a chamber 1 connected to the intake inlet 2 of the main vacuum pump, which is an oil-free screw pump 3. The gas outlet for blowing gas of the main vacuum oil-free screw pump 3 is connected to the gas exhaust channel 5. A non-return valve 6 for blowing out is placed in the channel 5 of the discharge, which after the non-return valve continues as a channel 8 for the exit of gas. The non-return valve 6, when it is closed, causes the formation of a volume 4, enclosed between it and the outlet for blowing gas of the main vacuum pump 3.

The pump system SP also includes an auxiliary vacuum pump 7, connected in parallel with the non-return valve 6. The suction end of the auxiliary vacuum pump is connected to the volume 4 of the gas exhaust channel 5, and the end of the discharge to the channel 8.

When the main vacuum oil-free screw pump 3 is turned on, the auxiliary vacuum pump 7 is also activated. The main vacuum oil-free screw pump 3 draws gas from the chamber 1 through a channel 2 connected to its inlet and subsequently compresses it at the outlet to the gas discharge channel 5 through the non-return valve 6. When the closing pressure of the non-return valve 6 is reached, it closes. From this moment, the operation of the auxiliary vacuum pump 7 causes a steady decrease in pressure in the volume 4 until the limit pressure is reached. In parallel with this, the power consumed by the main vacuum oil-free screw pump 3 gradually decreases. This occurs for a short period of time, for example, in a certain cycle for a period of 5 to 10 seconds.

With reasonable control of the capacity of the auxiliary vacuum pump 7 and the closing pressure of the non-return valve 6 depending on the performance of the main vacuum oil-free screw pump 3 and the volume of the chamber 1, it is also possible to reduce the time elapsing before closing the non-return valve 6 with respect to the duration of the pumping cycle and, therefore, reduce the number of energy consumed during this time of operation of the auxiliary pump 7 without any effect on pumping. On the other hand, thanks to the advantage of simplicity, unsurpassed system reliability is ensured.

According to a first possibility, the auxiliary pump 7 is also an oil-free screw pump. Thus, the main pump and the auxiliary pump can be of the same type, which simplifies the work with them. Therefore, this combination of pumps allows the use of the SP pump system in all those applications where only an oil-free screw pump can be used.

According to other possibilities, the auxiliary pump 7 may be a cam pump, a multi-stage Roots pump, a diaphragm pump, an oil-free vane pump or a lubricated type vane pump. All these pump combinations have advantages that are determined by the specific properties of each individual pump type.

In FIG. 2 illustrates an SPP (système de pompage piloté) pumping system for implementing a pumping method according to a second embodiment of the present invention.

Unlike the system shown in FIG. 1, the system of FIG. 2 is a controllable pumping system, further comprising appropriate sensors 11, 12, 13, which monitor either the motor current (sensor 11) of the main oil-free screw pump 3 or the pressure (sensor 13) of gas in the channel volume at the outlet of the main oil-free screw pump limited by a non-return valve 6, or the temperature (sensor 12) of gas in the channel volume at the outlet of the main vacuum oil-free screw pump, limited by a non-return valve 6, or a combination of these parameters. Indeed, when the main vacuum oil-free screw pump 3 starts pumping gas out of the vacuum chamber 1, parameters such as its current, temperature and gas pressure in the volume of the outlet channel 4 begin to change, reaching threshold values detected by the sensors. After a certain delay time, this causes the auxiliary vacuum pump 7 to turn on. When these parameters return to the initial range again (outside the set values), the auxiliary pump stops with a certain delay in time.

In the second embodiment of the invention illustrated in FIG. 2, the auxiliary vacuum pump may be of the type of oil-free screw pumps, cam pumps, multi-stage Roots pumps, diaphragm pumps, oil-free vane pumps or lubricated vane pumps, as in the first embodiment of the invention explained in FIG. one.

Although various embodiments of the invention have been described, it is understood that they in no way exhaust all possible options for its implementation. Of course, it is contemplated that the described embodiment can be replaced with an equivalent one, without departing from the scope of the present invention. All such modifications are within the competence of specialists in the field of vacuum technology.

Claims (21)

1. The pump system (SP), designed to create a vacuum, including the main vacuum pump, which is an oil-free screw pump (3), in which there is an intake inlet (2) for gas connected to the vacuum chamber (1), and outlet (4 ) for blowing gas leaving the channel (5) of the gas outlet in the discharge direction (8) for the gas to exit the pump system, while the pump system includes: - a non-return valve (6) located between the outlet (4) for blowing gas and the outlet (8) for gas outlet, and - an auxiliary vacuum pump (7) connected in parallel with a non-return valve, characterized in that the auxiliary vacuum pump (7) is configured to operate during the entire period of pumping gas from the vacuum chamber (1) by the main vacuum pump (3) and / or during the entire period the main vacuum pump (3) maintains the set pressure in the vacuum camera (1). 2. The pump system according to claim 1, characterized in that the auxiliary vacuum pump (7) is selected from the group comprising an oil-free screw pump, a cam pump, a multi-stage Roots pump, a diaphragm pump, an oil-free vane pump and a lubricated type vane pump. 3. The pump system according to any one of paragraphs. 1 or 2, characterized in that the auxiliary vacuum pump (7) is an oil-free screw pump. 4. The pump system according to any one of paragraphs. 1 or 2, characterized in that the auxiliary vacuum pump (7) is a cam pump. 5. The pump system according to any one of paragraphs. 1 or 2, characterized in that the auxiliary vacuum pump (7) is a multi-stage Roots pump. 6. The pump system according to any one of paragraphs. 1 or 2, characterized in that the auxiliary vacuum pump (7) is a diaphragm pump. 7. The pump system according to any one of paragraphs. 1 or 2, characterized in that the auxiliary vacuum pump (7) is an oil-free vane pump. 8. The pump system according to any one of paragraphs. 1 or 2, characterized in that the auxiliary vacuum pump (7) is a lubricated type vane pump. 9. The pump system according to claim 1, characterized in that the nominal capacity of the auxiliary vacuum pump (7) is from 1/500 to 1/20 of the nominal capacity of the main vacuum pump (3). 10. The pump system according to any one of paragraphs. 1 or 2, characterized in that the auxiliary vacuum pump (7) is a single-stage or multi-stage. 11. The pump system according to claim 1, characterized in that the non-return valve (6) is configured to close when the suction pressure of the main vacuum pump (3) is less than 500 mbar abs. 12. The pump system according to claim 1, characterized in that the main vacuum pump (3) is configured to operate at one constant speed. 13. The pumping method using a pumping system (SP) according to any one of the preceding paragraphs, characterized in that: - drive the main vacuum pump (3) to pump out the gas in the vacuum chamber (1), and blow this gas through the outlet (4) to blow gas; - actuate the auxiliary vacuum pump (7) simultaneously with the actuation of the main vacuum pump (3) and - the auxiliary vacuum pump (7) continues to operate during the entire period of pumping gas from the vacuum chamber (1) by the main vacuum pump (3) and / or throughout the entire period of maintaining the set pressure in the vacuum chamber (1) by the main vacuum pump (3). 14. The pumping method according to claim 13, characterized in that the capacity of the auxiliary vacuum pump (7) is from 1/500 to 1/20 of the nominal capacity of the main vacuum pump (3). 15. The pumping method according to any one of paragraphs. 13 or 14, characterized in that the non-return valve (6) closes when the suction pressure of the main vacuum pump (3) is less than 500 mbar abs.

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