EP1443214A1 - Turbomolecular pump stator - Google Patents

Abstract

The pump has a stator including blade sectors (26a-26j) arranged around a rotor (18), where the blade sectors are divided into axial lines. The blade sectors are connected and integrated with a concave internal face of corresponding peripheral structure (24,25) of the stator to form a multi-stage sector. The internal face has retaining units (24a-24j) for retaining individually each sector blade in a position.

Description

The present invention relates to pumps turbomolecular, suitable for pumping gases and creating a vacuum pushed into an empty enclosure.

Turbomolecular pumps usually have a stator multistage device with fins engaged between fins of a multi-stage central rotor.

A multistage turbomolecular pump rotor includes a axial series of rotor stages each consisting of a crown central from which depart, in a substantially radial direction, rotor fins regularly distributed around the periphery of the central crown. The assembly is rotatably mounted along an axis of rotation, and is driven by motor means.

The multistage stator is composed of an axial series of annular stators each forming a stator stage, each stage stator being formed of an annular rim from which depart, in substantially radial direction, inclined fins.

The stator stage inclined fins come engage between the inclined fins of two rotor stages successive.

We therefore understand that the presence of nested fins one inside the other prevents any axial movement of the rotor by report to the stator, either for mounting the pump turbomolecular, either for its disassembly.

Therefore, turbomolecular pumps include means for mounting and dismounting radial elements stator around the rotor.

After having produced a multi-stage monobloc rotor, we realizes the stator by gradually assembling around the rotor elements or sub-assemblies intended to constitute the stator.

A first known pump stator structure turbomolecular is illustrated in figure 1. Around a rotor monobloc, not shown in the figure, we just adapt gradually a plurality of fin stator sectors, on the one hand to form annular stator stages, on the other hand to form the plurality of staggered annular stator stages axially to make the successive stages of the stator.

If we consider a rotor oriented with its axis of vertical rotation, we just position a first sector of stator with fins 1 between two successive stages rotor with fins, by radial displacement illustrated by arrow 2, and a second stator sector 3 by opposite radial displacement according to the arrow 4 to engage it between the same two stages rotors to fins, the two stator sectors 1 and 3 forming a stage ring stator.

Then, an annular spacer 5 is axially engaged, by movement according to arrow 6, the spacer 5 coming to bear on the periphery of the two stator sectors 1 and 3. The spacer 5 has the dimension necessary to separate two successive stator stages according to the spacing of two corresponding successive rotor stages.

Then we position the two in a similar way following stator sectors 7 and 8, then an annular spacer 9, then two stator sectors 10 and 11 and a spacer annular 12, and so on depending on the number of stages of the stator.

We understand that the mounting of such a structure is tedious, and it requires the provision of components whose dimensions are determined with sufficient precision that the cumulation of any dimensional tolerances of the components is less than the axial dimensional tolerance of the rotor, so avoid contact between the rotor fins and the fins of the stator during pump operation. This results in a relatively high cost of realization that one could find advantage to reduce.

Figure 2 illustrates a second known pump structure turbomolecular, with different means to solve the problem of the nesting of the stator fins in the fins of the rotor.

In this known structure, the rotor 13 has been illustrated, rotatably mounted around its axis of rotation I-I as illustrated by arrow 14, and comprising a series of rotor stages each having inclined fins. We thus distinguish the rotor stages successive identified by the reference numerals 13a, 13b, 13c, 13d, 13e, 13f, 13g, 13h and 13i. The stator 15 is formed of the assembly of two half-stators 15a and 15b, each half-stator 15a and 15b consisting of a half-shell 16a or 16b in the form of half cylinder from which radially inward stator fins such as fins 17a and 17b, arranged in a series of stator stages overlapping with the fins of the rotor stages 13a-13i.

The presence of two monoblock half-stators 15a and 15b allows for insertable pumps, intended to be housed directly into a customer's pre-defined housing or system.

In this structure, each half-stator 15a or 15b monobloc is machined in a metal block to constitute the fins 17a or 17b. Because of the configuration and the convergent radial orientation of the fins, protruding from the concave inner face of the peripheral half-shell 16a or 16b, it is not possible to machine fins 17a or 17b whose radial length exceeds a maximum length determined by the possibility of passage of the milling tools of the fins.

As a result, this known pump structure turbomolecular limits the maximum flow rate of the pump turbomolecular, the flow limit being determined by the radial length of the fins.

In addition, the production of the half-stators 15a and 15b by machining is relatively complex and expensive, so that the advantage of this pump structure is limited.

The problem proposed by the present invention is to design a new turbomolecular pump structure which can be carried out at lower cost, avoiding the assembly of too much large number of parts or the production of complex parts, and which allows for insertable turbomolecular pumps whose flow is greater than that obtained by the structure of the figure 2.

Another problem is also to avoid having to make component parts whose dimensions are very precise because it increases the production cost of the pump turbomolecular.

• le stator comporte plusieurs secteurs de stator à ailettes assemblés autour du rotor,
• les secteurs de stator à ailettes sont répartis en plusieurs rangées axiales de secteurs annulaires de stator à ailettes,
• chaque rangée axiale de secteurs de stator à ailettes est solidaire d'un secteur de coque périphérique et forme ainsi un secteur multiétagé de stator,
• les secteurs de stator à ailettes constituent chacun un élément individuel,
• les secteurs de stator à ailettes d'une même rangée axiale de secteurs de stator à ailettes sont rapportés et solidarisés à la face interne concave du secteur de coque périphérique correspondant, pour former le secteur multiétagé de stator,
• la face interne concave du secteur de coque périphérique comprend des moyens de retenue pour retenir individuellement en position les secteurs de stator à ailettes.

To achieve these and other aims, the invention provides a turbomolecular pump having a multi-stage peripheral stator with fins engaged between fins of a central multi-stage rotor, in which:

• the stator comprises several stator sectors with fins assembled around the rotor,
• the stator sectors with fins are divided into several axial rows of annular sectors with stator fins,
• each axial row of stator sectors with fins is integral with a peripheral shell sector and thus forms a multistage stator sector,
• the stator sectors with fins each constitute an individual element,
• the stator sectors with fins of the same axial row of stator sectors with fins are attached and secured to the concave internal face of the corresponding peripheral shell sector, to form the multistage stator sector,
• the concave inner face of the peripheral shell sector includes retaining means for individually retaining the stator sectors with fins.

In such a structure, the stator sectors to fins constitute individual elements which can be easily manufactured by machining metal parts, and the ease of machining makes it possible to produce stators with fins have a radial dimension greater than that which can be achieved in a structure of figure 2.

Simultaneously, the number of parts to be assembled during the mounting of a turbomolecular pump is reduced compared to the known structure of figure 1.

And simultaneously, the constituent parts of such turbomolecular pump structure can be realized with less tight tolerances than the structural parts of the FIG. 1, because the peripheral shell sector achieves by itself, with the retaining means, a multi-stage spacer which individually positions the stator sectors with fins, so there is not a stack of multiple pieces put them one after the other.

According to an advantageous embodiment, the sectors of stator with fins include a single row of fins, each constituting a single-stage stator sector.

We can, however, without leaving the domain of the invention, imagine fin stator sectors comprising two or more rows of fins, each constituting a sector multi-stage finned partial stator, insofar as the machining of the fins allows this.

The stator sectors with fins can thus include at least one annular row of fins integral with a rim in crown sector shape.

According to a first possibility, the rim can connect the outer ends of the fins, and it's the rim that forms then the peripheral edge of the finned stator sector and which attaches to the concave inner face of the peripheral shell sector corresponding to form the multistage stator sector.

However, it may be advantageous to provide that the rim connects the inner ends of the fins. Indeed, this structure achieves better performance efficiency empty, and the realization is facilitated by the fact that the machining of fins is made from outside the rim in the sector of crown, on fins in divergent radial orientations. This are then the outer ends of the fins which form the peripheral edge of the stator sector with fins and which are fixed to the concave inner face of the peripheral hull sector corresponding to form the multistage stator sector.

The means of restraint of the stator sectors with fins on the concave inner face of the peripheral shell sector can be of different kinds. According to one embodiment advantageous, the concave inner face of the hull sector peripheral comprises a plurality of annular grooves, and the finned stator sectors each have at least one edge peripheral which is radially embedded in force in one annular grooves in the peripheral hull sector.

In the case where the stator sectors have a rim which connects the inner ends of the fins, the edge (s) devices of the finned stator sectors are constituted by the outer ends of the fins of said stator sectors which are radially embedded in force in the grooves corresponding annulars of the peripheral hull sector.

In the case where the stator sectors have a rim which connects the outer ends of the fins, the edge (s) devices of the finned stator sectors are constituted by the rims themselves which fit into the grooves annulars of the peripheral hull sector.

• la figure 1 est une vue éclatée en perspective illustrant une première structure de stator de pompe turbomoléculaire connue dans l'état de la technique ;
• la figure 2 illustre en perspective une vue éclatée d'une seconde structure de pompe turbomoléculaire connue dans l'état de la technique ;
• la figure 3 est une vue en perspective éclatée montrant la structure générale d'une pompe turbomoléculaire selon un mode de réalisation de la présente invention ;
• la figure 4 est une vue en perspective illustrant le montage successif des secteurs de stator à ailettes sur les secteurs de coque périphérique correspondants selon l'invention ; et
• les figures 5 et 6 illustrent deux modes de réalisation de secteurs de stator à ailettes selon l'invention.

Other objects, characteristics and advantages of the present invention will emerge from the following description of particular embodiments, given in relation to the attached figures, among which:

• FIG. 1 is an exploded perspective view illustrating a first structure of a turbomolecular pump stator known in the state of the art;
• FIG. 2 illustrates in perspective an exploded view of a second turbomolecular pump structure known in the state of the art;
• FIG. 3 is an exploded perspective view showing the general structure of a turbomolecular pump according to an embodiment of the present invention;
• Figure 4 is a perspective view illustrating the successive mounting of the stator sectors with fins on the corresponding peripheral shell sectors according to the invention; and
• Figures 5 and 6 illustrate two embodiments of fin stator sectors according to the invention.

The known structures of turbomolecular pumps of Figures 1 and 2 have been described previously.

We now refer to Figures 3 and 4 illustrating the structure of a turbomolecular pump according to one embodiment of the present invention.

In FIG. 3, the turbomolecular pump according to the invention comprises a multistage rotor 18, comprising a series rotor stages axially offset from each other and identified by the reference numbers 18a, 18b, 18c, 18d, 18th, 18f, 18g, 18h, 18i and 18d. Each stage of the rotor 18 is formed of a inner crown such as crown 19 from which depart inclined fins such as the fin 18a oriented in substantially radial outward direction.

The rotor 18 is rotatably mounted around an axis of rotation I-I as indicated by arrow 20.

The stator is formed from the assembly of two sub-assemblies 21 and 22 each forming a multistage stator sector, which are reported radially around the rotor 18 as indicated by the respective arrows 23 and 23a.

Each sub-assembly 21 or 22 is formed from the assembly a respective peripheral hull sector 24 or 25 and a axial row of stator sectors with fins 26 or 27.

We thus distinguish, in the embodiment shown, a first axial row of stator sectors to fins 26 formed by the stator sectors with fins 26a, 26b, 26c, 26d, 26e, 26f, 26g, 26h, 26i and 26j aligned parallel to the axis of rotation I-I. Similarly, there is a second row axial of finned stator sectors formed by the sectors of stator with fins 27a, 27b, 27c, 27d, 27e, 27f, 27g, 27h, 27i and 27j aligned parallel to the axis of rotation I-I.

In the embodiment of Figure 3, the sectors stator with fins are of the inner rim type, as see better in Figure 5. In this embodiment, the sector stator of fins 26a includes an annular row of fins 126a integral with a rim 226a itself in the form of a sector of crowned. Rim 226a connects the inner ends of the fins of the annular row of fins 126a. The edge device 326a of the finned stator sector 26a is then formed by the outer ends of the row fins fin ring 126a.

The invention can also be applied to a second mode of realization of stator sector with fins illustrated in the figure 6. In this case, there is a rim 226a and an annular row of fins 126a. Rim 226a connects the outer ends of the fins of the annular row of fins 126a. The edge device 326a of the finned stator sector 26a is then constituted by the rim 226a itself.

As seen in relation to the hull sector peripheral 24 of FIG. 3, the concave internal face of each peripheral shell sector 24 or 25 comprises a plurality of annular grooves. We can thus distinguish the annular grooves 24a, 24b, 24c, 24d, 24e, 24f, 24g, 24h, 24i and 24d.

Each annular groove 24a-24j is arranged and shaped to receive the peripheral edge of one of the stator sectors 26a-26j, and to thereby hold said positions individually stator sectors 26a-26j.

It is the same for the peripheral shell sector 25 which receives and retains the finned stator sectors 27a-27j.

During assembly, we start by engaging the stator sectors with fins 26a-26j and 27a-27j by radial engagement of their edge peripheral (such as the peripheral edge 326a of the sector of stator with fins 26a) in the corresponding annular grooves 24a-24j of the respective peripheral shell sectors 24 and 25, as illustrated for example by arrows 28 and 28a. We realize thus the two multistage stator sectors 21 and 22, which are can then assemble radially on the rotor 18 as illustrated by arrows 23 and 23a in Figure 3.

It will also be noted that the hull sectors peripheral such as the peripheral shell sector 25 can if necessary, include holes such as hole 29, to favor the degassing of the space located on the periphery of the sectors peripheral hulls 24 and 25.

In the embodiment illustrated in Figures 3 and 4, the stator is made by assembling two half-stators multistage 21 and 22 each consisting of a 180 ° sector. In in this case, each peripheral shell sector 24 or 25 is a half-cylinder, and each fin stator sector 26a-26j and 27a-27j is a half ring.

According to the invention, depending on the conformations fins, we could find advantage in providing a stator made by the assembly of three multistage stator sectors of 120 ° each, or four multi-stage stator sectors of 90 ° each, or even multistage stator sectors with different angles.

However, the structure illustrated minimizes the number of parts to be assembled, which can be advantageous.

Also, in the embodiment illustrated on the Figures 3 and 4, the stator is a radial assembly of a single stage of multi-stage sectors of stator 21 and 22. In other words, in this case, each peripheral shell sector 24 or 25 covers the entire length of the stator of the turbomolecular pump.

Alternatively, the stator can be an assembly of several stages of multistage stator sectors. We can by example imagine a first stator stage as illustrated on the FIG. 3, to which a second coaxial stage of stator with similar structure, possibly with structures different fins and different diameters. The stator is then an assembly of several floors of multi-level sectors of stator.

After completing the pump assembly turbomolecular as illustrated in Figure 3, the assembly must be inserted into a housing, to make a pump functionally complete turbomolecular. We can then predict a specific casing, with means for fixing to an enclosure to empty.

However, according to the invention, a pump can be produced. insertable turbomolecular, i.e. adapted to be inserted in a housing or customer system such as a vacuum enclosure. The pump is then installed as close as possible to the application and optimizes pumping performance. The sectors of shell 24 and 25 allow the pump elements to be enclosed turbomolecular, to form a possibly held whole by means of temporary assembly, which can be removed during the introduction of the pump into the customer's system.

In all cases, the hull sectors 24 and 25 must preferably fit with little play in the housing or the system of the customer, to ensure between hull sectors 24 and 25 and the housing or customer system a good contact that promotes heat exchanges.

The turbomolecular pump structure according to the invention authorizes all possible fin geometries in terms inclination, inside diameter, outside diameter, floor height and thickness.

This system also simplifies the stacking of spacers and stators, and to get rid of the chain of ratings of these different elements.

In addition, this structure improves the heat exchange between the rotor and the environment, via hull areas, promoting thermal contact between the stator fins and hull sectors, then between the hull sectors and the peripheral casing or shell of the pump, and reducing the number of transmission discontinuities thermal thanks to the monobloc character of the hull sectors multistage.

This structure makes it possible to offer an insertable version for higher flow rate vacuum pumps.

The number of precise parts is reduced compared to a classic assembly. The production cost of the pump is thus greatly decreased.

The present invention is not limited to the modes of which have been explicitly described, but it includes the various variants and generalizations which are within the reach of the skilled person.

Claims (11)

Turbomolecular pump having a multi-stage peripheral stator with fins engaged between fins of a multi-stage central rotor (18), in which: the stator comprises several stator sectors with fins (26a-26j; 27a-27j) assembled around the rotor (18), the stator sectors with fins (26a-26j; 27a-27j) are distributed in several axial rows of stator sectors with fins (26, 27), each axial row of finned stator sectors (26, 27) is integral with a peripheral shell sector (24, 25) and thus forms a multistage stator sector, characterized in that : the stator sectors with fins (26a-26j; 27a-27j) each constitute an individual element, the finned stator sectors of the same axial row of finned stator sectors (26, 27) are attached and secured to the concave internal face of the corresponding peripheral shell sector (24, 25), to form the multistage sector of stator, the concave inner face of the peripheral shell sector (24, 25) comprises retaining means (24a-24j) for individually retaining the finned stator sectors (26a-26j) in position. Turbomolecular pump according to claim 1, characterized in that the finned stator sectors (26a-26j; 27a-27j) comprise a single row of fins, each constituting a single-stage stator sector. Turbomolecular pump according to one of claims 1 or 2, characterized in that the stator sectors with fins (26a-26j; 27a-27j) comprise at least one annular row of fins (126a) integral with a rim (226a ). Turbomolecular pump according to claim 3, characterized in that the rim (226a) connects the inner ends of the fins of the annular row of fins (126a). Turbomolecular pump according to claim 3, characterized in that the rim (226a) connects the outer ends of the fins of the annular row of fins (126a). Turbomolecular pump according to any one of Claims 1 to 5, characterized in that : the concave internal face of the peripheral shell sector (24, 25) comprises a plurality of annular grooves (24a-24j), the finned stator sectors (26a-26j) each have at least one peripheral edge (326a) which is radially embedded in force in one of the annular grooves (24a-24j) of the peripheral shell sector (24). Turbomolecular pump according to claim 6, characterized in that the peripheral edges (326a) of the finned stator sectors (26a-26j) are constituted by the outer ends of the fins of said stator sectors (26a-26j). Turbomolecular pump according to claim 6, characterized in that the peripheral edges (326a) of the fin stator sectors (26a-26j) are constituted by rims (226a) which connect the outer ends of the fins of said fin stator sectors ( 26a-26j). Turbomolecular pump according to any one of claims 1 to 8, characterized in that the stator is a radial assembly of a single stage of multistage stator sectors (21, 22). Turbomolecular pump according to any one of Claims 1 to 8, characterized in that the stator is an assembly of several stages of multistage sectors of the stator. Turbomolecular pump according to one of claims 9 or 10, characterized in that the multistage stator sectors (21, 22) are sectors of 180 °.

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