KR20230146559A - dry vacuum pump - Google Patents

Abstract

A dry vacuum pump (1), whose first half-shell (3) is positioned within the mating surface (10) of the half-shells (3, 4) which receives the lateral rail (14b) of the first seal (14). Semi-shells (3, 4) A dry vacuum pump (1) is provided, which has at least one connecting surface (17) open therebetween.

Description

dry vacuum pump

The present invention relates to a dry vacuum pump.

Vacuum pumps of the dry type have one or more pumping stages in series within which the gas to be pumped circulates. Among known vacuum pumps, a distinction is made between pumps with rotating lobes, also known as “Roots” pumps, or pumps with claws, also known as “claw” pumps. These vacuum pumps, in operation, the rotors rotate inside the stator without any mechanical contact between the rotors or with the stator, which makes it possible to avoid using oil in the pumping stages. It is referred to as “dry”.

However, in some pumping applications, such as in pumping methods used in the semiconductor, flat panel display and photovoltaic industries, the gases used can cause the vacuum pump to be maintained at particularly high temperatures, such as on the order of 200°C. This is especially the case when the gases employed are corrosive, such as gases employed during the process of cleaning the processing chambers, or when these gases contain, for example, resin vapors. These high temperatures, associated with aggressive chemical species, lead to the use of high-performance elastomeric materials of the high-temperature FKM or other high-temperature FFKM types in the static seals of the stator components of pumps. Likewise, the design of seal/seal groove pairs must be designed to take into account the requirements for sealing both in cold and hot conditions, and also the inherent thermodynamic characteristics of these elastomers.

Multi-stage vacuum pumps having a segmented structure, in which the stators consist of an axial assembly of a plurality of stator elements, with O-ring seals received in seal grooves of rectangular cross-section, axially extending between the stator elements. By using O-ring seals, which are compressed, this problem is easily solved.

Multistage vacuum pumps with a semi-skinned structure have disadvantages. Specifically, this structure involves the use of sealing paste or end-to-end bonded seals, or other three-dimensional seals, or a combination of these embodiments. However, with the use of three-dimensional seals, since the expansion coefficients of elastomeric and metallic materials are very different, a “knife” effect may occur on the seals at the entrances of the seal grooves. This effect can be exacerbated with the high operating temperatures of vacuum pumps and can lead to irreversible deterioration of the seals and ultimately loss of seal associated with the cooling return of the vacuum pump.

The object of the present invention is to at least partially eliminate one of the above-mentioned drawbacks, especially by improving the sealing of stator parts of vacuum pumps with a semi-skinned structure.

For this purpose, the subject of the present invention is a dry vacuum pump,

- a stator comprising at least a first complementary half-shell and a second complementary half-shell and a first tip member and a second tip member, the semi-shells and the tip members being connected to at least one pumping chamber of the pumping stage A stator, which is joined together to form a

- two rotor shafts configured to rotate within at least one pumping stage,

- a first seal, a first annular tip and a second annular tip sandwiched between the respective tip members and the semi-shells, and two lateral rails connecting the annular tips, which are sandwiched between the semi-shells. , a first seal comprising two lateral rails

In the dry vacuum pump (1) comprising,

The first half-shell has at least one seal groove provided in the mating surface of the half-shells receiving the side rail of the first seal, the bottom of the seal groove forming a smooth transition for the first seal. A dry vacuum pump characterized by having at least one connecting surface open between the semi-shells, which is shaped as a “saddle” in order to achieve this.

The “saddle” shape is also known as a hyperbolic paraboloid. The saddle-shaped contact surface is formed by continuous arcs (or hyperbolas) that are convex in the transverse plane, so as to form a concave portion in the longitudinal plane. A substantially orthogonal joint area between the annular tip of the first seal and the lateral rail is received within the concave portion of the connecting surface. The smooth saddle shape, which replaces the sharp edges of the rectangular cross-section of the grooves of the prior art, allows compression of the first seal in the joint area, which is uniform and compatible with the thermodynamic characteristics of the seal.

The vacuum pump may also have one or more of the features described below, considered on their own or in combination.

The second half-shell may have at least one connecting surface open from the half-shells, facing the connecting surface of the first half-shell, which is shaped into a round shape to form a smooth transition for the first seal. You will be able to. The bonding area of the first seal is then also compressed by the convex portion of the bonding surface. The smooth round shape, replacing the sharp edges of the semi-skin of the prior art, allows compression of the first seal that is uniform and compatible with the thermodynamic characteristics at the connecting surfaces.

The semi-shells may have at least one individual semi-recess, shaped to cooperate with the nose portion of the tip member, with at least one connecting surface open into the semi-recesses.

The two connecting surfaces, formed in a round shape, may be realized by contour milling followed by machining of the semi-recesses of the second half-shell. The connecting surfaces may thus be molded into a round shape, continuous with the semi-recess, without changing the tool.

The two connecting surfaces, formed in a saddle shape, could be realized by contour milling followed by machining of the seal groove. The connecting surfaces may thus be molded saddle-shaped and continuous with the seal groove, without changing the tool.

The radius of curvature of the cross section of the connecting surface formed into a saddle shape and/or the radius of curvature of the connecting surface formed into a round shape are, for example, 2 mm or more.

The radius of curvature of the cross section of the connecting surface formed into a saddle shape and/or the radius of curvature of the connecting surface formed into a round shape are, for example, 5 mm or less.

The vacuum pump, with at least one second seal:

- a first annular tip and a second annular tip sandwiched between the individual tip members and the semi-shells, and

- two lateral rails connecting the annular tips, the lateral rails being sandwiched between the half-shells, the first seal comprising: a first seal and at least one second seal forming at least two continuous seals against gas; two side rails arranged inside the second seal to form a barrier

It may include at least one second seal.

The plurality of sealing barriers makes it possible to ensure a good seal both from the outside to the inside and vice versa, and the heat resistance decreases with the distance from the pumping chambers and/or which may present corrosive gases. It makes it possible to use different materials that can provide levels. Specifically, the preparation may be such that the at least one first seal on the inner side is formed of a material that is more resistant to corrosion, abrasion and/or high temperatures than the material of the second seal. The material of the second seal can therefore be more economical than the material of the first internal seal while at the same time being acceptable from a safety point of view. The second seal is made of, for example, a fluoroelastomer material (FKM), and the first seal is made of, for example, a perfluoroelastomer material (FFKM).

All contact surfaces of the seal grooves opening from the half-shells are molded saddle-shaped, for example to form a smooth transition for each seal. The connecting surfaces may be shaped to be round, with the plurality of connecting surfaces being molded into the saddle shape of the first half-shell.

The vacuum pump may be equipped with a heating device configured to heat the stator to a temperature greater than 150°C.

The semi-shells of the stator form at least two pumping stages, mounted in series, for example between the suction orifice and the delivery orifice of the vacuum pump.

Other advantages and features will become apparent on the basis of the following description of specific, but not limiting, embodiments of the invention, and also the accompanying drawings:
1 is a schematic exploded view of elements of an example dry vacuum pump.
Figure 2 is a similar view of the vacuum pump of Figure 1 pivoted upward.
Figure 3 is an enlarged detail A view of elements of the dry vacuum pump of Figure 1;
Figure 4 is an enlarged detail B view of elements of the dry vacuum pump of Figure 2;
Figure 5 is a view of the combined half-shells of the vacuum pump of Figures 1 to 3 in detail A and detail B;
Figure 6 is a view of one half-shell of the vacuum pump of Figures 1-3 joined together with two seals;
Figure 7 is a cross-sectional view of the elements of the vacuum pump of Figure 1 in an assembled state, the cross-section being taken at the second seal mounted on the nose portion of the tip member;
Figure 8 is a view in enlarged detail C of elements of the vacuum pump of Figure 7;
In these drawings, identical or similar elements bear identical reference numerals.
Only elements necessary for understanding the present invention are shown.

The embodiments that follow are examples. Although the description refers to more than one embodiment, this does not necessarily mean that each reference relates to the same embodiment or that features apply only to a single embodiment. Individual features of different embodiments may also be combined or interchanged to provide other embodiments.

A primary-vacuum pump is defined as a positive displacement vacuum pump, which is configured, using two rotor shafts, to attract, deliver and then transport the gas to be pumped at atmospheric pressure. The rotor shafts are driven in rotation by the motor of the primary-vacuum pump. The primary-vacuum pump can be started at atmospheric pressure.

A Roots type vacuum pump or Roots compressor (also known as a Roots blower) is defined as a positive displacement vacuum pump, configured to draw, deliver and then transport the gas to be pumped, using Roots type rotors. do. A vacuum pump of the Roots type is mounted upstream of and in series with the primary-vacuum pump. The rotors are supported by two shafts driven in rotation by a motor of a Roots type vacuum pump. The Roots vacuum pump has one to three pumping stages.

The “upstream” element should be understood as that which comes before the other with respect to the direction of circulation of the gas to be pumped. In contrast, the “downstream” element should be understood as coming after the other with respect to the direction of circulation of the gas to be pumped.

The axial direction is defined as the longitudinal direction of the pump along which the axes of the rotor shafts extend. The transverse direction is a direction perpendicular to the axial direction. The transverse plane is a plane perpendicular to the longitudinal plane.

1 and 2 illustrate an example of a dry vacuum pump 1.

The vacuum pump (1) comprises a stator having at least a first complementary half-shell (3) and a second complementary half-shell (4) and a first tip member (5) and a second tip member (6). (2) is provided. The half-shells 3, 4 and tip members 5, 6 are joined together to form at least one pumping chamber of the pumping stages T1-T6.

The semi-shells 3, 4 of the stator 2 are positioned at the suction orifice of the vacuum pump 1, for example between two and ten pumping stages (six in the illustrated embodiment). 7) and the transport orifice (8), which forms at least two pumping stages (T1-T6) mounted in series. The vacuum pump 1 can be a primary-vacuum pump (Figure 1) or a Roots type vacuum pump.

The vacuum pump 1 further comprises two rotors configured to rotate within at least one pumping stage T1-T6 such that the rotors propel the gas to be pumped between the suction orifice 7 and the delivery orifice 8. Provided with a shaft (not shown).

The rotors have lobes with identical outlines, for example of the “roots” type or claw type, or are based on another similar positive displacement vacuum pump principle. The shafts carrying the rotors are driven by a motor (not shown), located for example at one end of the vacuum pump 1.

Each pumping chamber accommodates two mating rotors, and the pumping chambers have separate inlets and outlets. During rotation, gases drawn through the inlet are captured in the volume created by the rotors and stator 2 and are then propelled by the rotors towards the following stage.

Successive pumping stages (T1-T6) are connected in series one after another by individual inter-stage channels (9) connecting the outlet of the preceding pumping stage to the inlet of the following pumping stage. The inlet of the first pumping stage (T1) communicates with the suction orifice (7). The outlet of the last pumping stage (T6) communicates with the conveying orifice (8). The axial dimensions of the rotors and of the pumping chambers (and therefore the swept-volume outputs) may be, for example, the same or the pumping stage T1, located on the side of the suction orifice 7, is the longest. It accommodates rotors of axial dimension and decreases with the pumping stages to have the largest output displacement.

These vacuum pumps, when operating, the rotors rotate inside the stator 2 without any mechanical contact between the rotors or with the stator 2, which makes it possible to use no oil in the pumping stages. Because it does so, it is referred to as “dry”.

The vacuum pump 1 may be equipped with a heating device 11 configured to heat the stator 2 to a temperature above 150° C. (Figure 1).

The half-shells 3, 4 are joined together at a joining surface 10. At least one compression chamber and delivery channels 9 are formed, if appropriate, partly within the first half-shell 3 and partly within the second half-shell 4.

The engaging surface 10 is, for example, a flat engaging surface, passing for example through the middle plane of the dry vacuum pump 1 . The flat engagement surface 10 receives, for example, the axes of the rotor shafts.

The first end of the half-shells (3, 4) is closed by the first tip member (5), and the second end of the half-shells (3, 4) is closed by the second tip member (6). It is closed. Orifices are, of course, provided, where appropriate, in the transverse walls of the semi-shells 3, 4 separating the pumping chambers and in the tip members 5, 6 for the passage of the rotor shafts.

The half-shells 3, 4 and the tip members 5, 6 are formed by assembly, for example, into the nose portions 12 and the semi-shells ( They are joined by complementary assembly of recesses provided at the ends of 3 and 4). The nose portion 12 protrudes in the axial direction. For example, the nose portion has an oblong transverse shape, for example solid. Semi-recesses 13 are provided, for example, in the pumping chamber of the first pumping stage T1 and in the pumping chamber of the last pumping stage T6.

The vacuum pump 1 also has a first seal 14. This seal 14 is three-dimensional and may exist as a single member, i.e. one member, or may be joined end-to-end, i.e. by arranging a plurality of elastic seals end-to-end. can be formed.

The first seal 14 has a first annular tip and a second annular tip 14a sandwiched between the individual tip members 5, 6 and the semi-shells 3, 4, and annular tips 14a. It has two lateral rails 14b connecting the two lateral rails 14b, which are sandwiched between the half-shells 3 and 4.

The first seal 14 is elastic, especially since it has an elastomeric material. This is obtained, for example, by pressing or injection molding. The first seal 14 has a cross-section, for example substantially circular in the non-compressed state.

At least one annular groove 19 is located within at least one nose portion 12 (FIGS. 1 and 2) and/or at least one lip for receiving the annular tip 14a of seal 14. It can be provided within a session.

The first half-shell (3), which lies at the bottom of the exemplary embodiment, has at least one seal groove (16) provided in the mating surface (10) of the half-shells (3, 4). The seal groove 16 accommodates the side rail 14b of the first seal 14. For example, two coupling surfaces 10 of the first half-shell 3, on both sides of the at least one compression chamber, are provided for receiving the individual side rails 14b of the first seal 14. A seal groove 16 exists.

As can be seen more clearly in FIGS. 3 and 5 , the bottom of the seal groove 16 is semi-shaped, shaped “saddle-shaped” to form a smooth transition for the first seal 14. It has at least one connecting surface (17) opening from the shells (3, 4). The “saddle” shape is also known as a hyperbolic paraboloid.

The connection surface 17 is formed by continuous arcs (or hyperbolas) that are convex in the transverse plane, so as to form a concave portion in the longitudinal plane. The radius of curvature R1 of the cross section of the connection surface 17 is greater than or equal to 2 mm and/or less than or equal to 5 mm, for example 2.65 mm (Figures 7 and 8).

In an illustrative example, the connecting surfaces 17 open into recesses, formed by assembly of the semi-recesses 13 . The contact surface 17 forms a smooth transition between the bottom of the seal groove 16 and the face of the semi-recess 13 in this case.

A substantially orthogonal joint area between the annular tip 14a of the first seal 14 and the lateral rail 14b is received within the concave portion of the connecting surface 17 (Figure 6). The soft saddle shape, which replaces the sharp edges of the rectangular cross-section of the grooves of the prior art, allows compression of the first seal 14 in the joint area, which is uniform and compatible with the thermodynamic characteristics of the seal.

The two connecting surfaces 17, formed in a saddle shape, can be realized by contour milling followed by machining of the seal grooves 16. In this case, the tool of the diameter of the seal groove 16 first machines the first contact surface 17 at one end of the seal groove 16, in this case the seal groove 16, and then the seal groove 16. ) at the other end of the second connection surface 17 is machined. The connecting surfaces 17 can thus be molded saddle-shaped and continuous with the seal groove 16 without changing the tool.

As can be seen in Figures 4 and 5, the second half-shell 4 is formed into a round shape to form a smooth transition for the first seal 14. It may have at least one contact surface 18 opening from the semi-shells 3, 4, pointing towards the contact surface 17 of.

The radius of curvature R2 of the round-shaped connecting surface 18 is greater than or equal to 2 mm and/or less than or equal to 5 mm, for example 2.65 mm (Figures 7 and 8).

At this time, the bonding area of the first seal 14 is also compressed by the convex portion of the connecting surface 18 (FIG. 8). The smooth round shape, replacing the sharp edges of the semi-skin of the prior art, allows compression of the first seal 14 that is uniform and compatible with the thermodynamic characteristics at the connecting surfaces.

The two connecting surfaces 18 , formed in a round shape, may be realized by contour milling followed by machining of the half-recess 13 of the second half-shell 4 . In this case, the tool first machines the first contact surface 18 at one end of the semi-recess 13 , in this case the semi-recess 13 , and then the semi-recess 13 . At the other end a second connection surface 18 is machined. The connecting surfaces 18 can thus be formed roundly and continuously in the semi-recess 13 without changing the tool.

The connection surfaces 17, 18 make it possible to reduce the risk of breakage of the first seal 14 as a result of differences in thermodynamic behavior, and this makes it possible to limit the risk of seal loss and It makes it possible to increase the time between two maintenance operations.

The vacuum pump 1 may also be equipped with two seals 14, 15.

Similar to the first seal 14, the second seal 15 is three-dimensional and may exist as a single member, ie one member, or may be joined end-to-end. The second seal connects the first and second annular tips 15a, which are sandwiched between the individual tip members 5, 6 and the semi-shells 3, 4, and the annular tips 15a. It comprises two lateral rails 15b, which are sandwiched between the half-shells 3, 4.

The first seal 14 is arranged inside the second seal 15 such that the first seal 14 and the at least one second seal 15 form at least two continuous sealing barriers to gas.

The annular ends 14a, 15a are parallel to each other and perpendicular to the side rails 14b, 15b. The first annular tips 14a, 15a, for example at the first axial ends of the semi-shells 3, 4, provide a first pumping contact with the nose portion 12 of the first tip member 5. It is sandwiched between recesses in the pumping chamber of stage T1. The second annular tips 14a, 15a are located at the second axial ends of the half-shells 3, 4, at the nose portion 12 of the second tip member 6 and of the last pumping stage T6. It is sandwiched between recesses in the pumping chamber. Accordingly, for example, there are two annular grooves 19, axially offset, within the nose portion 12 of each of the two tip members 5, 6.

The plurality of sealing barriers makes it possible to ensure a good seal both from the outside to the inside and vice versa, and the heat resistance decreases with the distance from the pumping chambers and/or which may present corrosive gases. It makes it possible to use different materials that can provide levels. Specifically, the preparation is such that the at least one first seal 14 on the inner side is formed of a material more resistant to corrosion, abrasion and/or high temperatures than the material of the second seal 15. You can. The material of the second seal 15 can thus be more economical than the material of the first inner seal 14 while at the same time being acceptable from a safety point of view. The second seal 15 is made of, for example, a fluoroelastomer material (FKM), and the first seal 14 is made of, for example, a perfluoroelastomer material (FFKM).

All contact surfaces 17 of the seal grooves 16 opening from the half-shells 3, 4, in this case four, form, for example, a smooth transition for each seal 14, 15. In order to do this, it is molded into a saddle shape.

A plurality of contact surfaces 17 , in this case two, are molded into the saddle of the first half-shell 3 so as to form a smooth transition for each seal 14, 15. ) can be molded into a round shape to be oriented.

Although the figures illustrate a vacuum pump 1 in which the tip members are provided with nose portions 12 and the semi-shells 3, 4 are provided with complementary recesses, the invention also provides: This also applies to vacuum pumps, which do not have noses or recesses. In this case, the connection surfaces, which are molded saddle-shaped and/or round, open from the transverse faces of the ends of the half-shells 3, 4. One or more seals 14, 15 are then compressed between the faces of the tip members and the transverse faces of the ends of the semi-shells 3, 4.

Claims (12)

As a dry vacuum pump (1),
- a stator (2) comprising at least a first complementary half-shell (3) and a second complementary half-shell (4) and a first tip member (5) and a second tip member (6), A stator (2), wherein the shells (3, 4) and the tip members (5, 6) are joined together to form at least one pumping chamber of the pumping stages (T1-T6).
- two rotor shafts configured to rotate within at least one pumping stage (T1-T6),
- As the first seal:
- a first annular tip and a second annular tip (14a) sandwiched between the individual tip members (5, 6) and the semi-shells (3, 4), and
- two lateral rails 14b connecting the annular ends 14a and sandwiched between the semi-shells 3, 4
A first seal comprising:
In the dry vacuum pump (1) comprising,
The first half-shell (3) has at least one seal groove (16) provided in the mating surface (10) of the half-shells (3, 4) which receives the lateral rail (14b) of the first seal (14). ), and the bottom of the seal groove is open between the semi-shells 3, 4, shaped as a “saddle” to form a smooth transition for the first seal 14. Dry vacuum pump, characterized in that it has at least one contact surface (17). According to paragraph 1,
The second half-shell (4) is oriented towards the connecting surface (17) of the first half-shell (3), which is shaped into a round shape to form a smooth transition for the first seal (14). Dry vacuum pump, characterized in that it has at least one contact surface (18) opening from the fields (3, 4). According to paragraph 2,
A dry vacuum pump, characterized in that the radius of curvature (R2) of the connection surface (18) formed into a round shape is 2 mm or more. According to paragraph 2 or 3,
A dry vacuum pump, characterized in that the radius of curvature (R2) of the connection surface (18) formed into a round shape is 5 mm or less. According to any one of claims 1 to 4,
The half-shells 3, 4 have at least one individual half-recess 13, shaped to cooperate with the nose portion 12 of the tip members 5, 6, and have at least one connecting surface. (17, 18) is a dry vacuum pump, characterized in that it opens into the semi-recesses (13). According to any one of claims 2 to 4 and claim 5,
Dry vacuum pump, characterized in that the two connecting surfaces (18), which are formed in a round shape, are realized by contour milling followed by machining of the semi-recess (13) of the second semi-shell (4). According to any one of claims 1 to 6,
Dry vacuum pump, characterized in that the two connecting surfaces (17), formed in a saddle shape, are realized by contour milling followed by machining of the seal groove (16). According to any one of claims 1 to 7,
A dry vacuum pump, characterized in that the radius of curvature (R1) of the cross section of the connection surface (17) formed into a saddle shape is 2 mm or more. According to any one of claims 1 to 8,
A dry vacuum pump, characterized in that the radius of curvature (R1) of the cross section of the connecting surface (17) formed into a saddle shape is 5 mm or less. According to any one of claims 1 to 9,
As at least one second seal (15):
- a first annular tip and a second annular tip (15a) sandwiched between the individual tip members (5, 6) and the semi-shells (3, 4), and
- two lateral rails 15b connecting the annular ends 15a, the lateral rails 15b being sandwiched between the half-shells 3, 4, the first seal 14 being Two side rails (15b), wherein the first seal (14) and the at least one second seal (15) are arranged inside the second seal (15) so that they form at least two continuous sealing barriers to gas.
At least one second seal comprising
A dry vacuum pump comprising: According to any one of claims 1 to 10,
Dry vacuum pump, characterized in that it has a heating device (11), configured to heat the stator (2) to a temperature above 150°C. According to any one of claims 1 to 11,
The semi-shells (3, 4) of the stator (2) comprise at least two pumping stages (T1-T6) mounted in series between the suction orifice (7) and the delivery orifice (8) of the vacuum pump (1). A dry vacuum pump, characterized in that forming a.

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