Patent Publication Number: US-2015064033-A1

Title: Vacuum pump and arrangement with vacuum pump

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a vacuum pump and an arrangement with a vacuum pump. 
     2. Description of the Prior Art 
     Vacuum pumps, in particular turbomolecular pumps have at least one rotor that is arranged in the pump housing. The rotor is surrounded by a stator package or several stators which are supported in the housing. Further, a drive, e.g., an electric motor that drives the at least one rotor, is also arranged in the pump housing. Usually, the drive shaft is arranged coaxially with the rotor axis. 
     With the turbomolecular pumps, high compression ratios can be achieved. The turbomolecular pumps have a very small outlet opening or outlet nipple in comparison with an inlet opening or inlet nipple. Usually, a conduit connects a forevacuum pump with the outlet nipple. 
     Arrangements which include vacuum pumps and recipients, which further refer to as chambers, present a number of requirements, with regard to their geometrical design. E.g., with mass-spectrometers, it is desirable that the entire system has compact dimensions. Often, this results in such positioning of the vacuum pump in the end apparatus that its access is noticeably limited. Despite this, the servicing of the vacuum pump, e.g., preventive replacement of shaft bearings, should be possible. 
     According to the state of the art (EP 2 228 540 A2), there is provided an arrangement with a vacuum pump having a pump flange. The arrangement also has a chamber flange and flange connecting means for vacuum-tight connection of the chamber and the vacuum pump. The arrangement also includes a force transmitting structure for transmitting force from an application point to an operating point located in the flange connection means. 
     This means that the vacuum pump is usually arranged in a receiver provided in the arrangement to this end. The receiver can be formed as some type of a rail system. The pump flange and the chamber flange are vacuum-tightly connected with each other. Here, the inlet openings of the pump are so arranged that they are aligned with outlet openings of the chamber, overlaying each other. This state-of-the art pump can be easily extracted from the arrangement after loosening respective connection and connection means, e.g., to effect a preventive replacement of shaft bearings. 
     These state-of-the art arrangements should meet customer-specific requirements with regard to position of the chamber outlets and the geometry of the pump receiver. 
     In a system with several suction openings for different pressure levels, as known in practice, several separate pumps are used. In particular, with mass-spectrometers with time-of-flight systems, the increased distances between different suction openings are observed. The time-of-flight mass-spectrometers form a sub-class of mass-spectrometers. 
     In practice, with the time-of-flight mass-spectrometers, so-called split-flow pumps are used. Split-flow pumps represent vacuum pump systems for multi-stage gas inlet systems disclosed, e.g., in DE 43 31 589 A1. 
     These state-of-the art split-flow pumps usually have a constructional length of 500 mm. If, however, the suction openings are spaced by a large distance, as it is known from practice, the pump houses, which are long enough to bridge large distances between the suction openings, can be produced only with very expensive machine-tools. 
     The object of the invention is to so improve the state-of-the art vacuum pumps and arrangements with vacuum pumps that the customer-specific requirement can be realized in a simpler and more cost-effective manner, and that cheaper vacuum pumps with a large length are produced. 
     SUMMARY OF THE INVENTION 
     The object of the invention is achieved with a vacuum pump including a housing having an axial inlet a pumping unit including a stator, a rotor rotatably supported in the stator, and a drive for driving the rotor, and at least one additional placed-on housing part attachable to the housing in an axial direction, connectable with the housing, and having at least one outlet. 
     The advantage of the inventive vacuum pump consists in that with the additional housing part placed on in the axial direction, a greater constructional length of the vacuum pump which is often required in the field, can be realized. In addition, a standard vacuum pump can be used, and the placed-on housing part then is provided with dimensions capable to meet customer-specific requirements. 
     In addition, the vacuum pumps can be formed with through-housings having greater lengths then it was possible with tools known up to now. Namely, the state-of-the art machine-tools limit the constructional length of the housing. 
     With the provision of at least one additional housing part, in principle, any arbitrary length can be provided. 
     The placed-on housing part has an advantage, in comparison with, e.g., attached tube, that consists in that the diameter and the outer profile of the housing are formed so that they remain the same as for the entire vacuum pump, so that flanges, openings, rail system and the like of the inventive pump can be used in arrangements, e.g., including a mass-spectrometer. 
     In addition the placed-on tubes often have a bent-off section in order to be able to connect the tube with an outlet of a pump chamber arranged radially with respect to the longitudinal axis of the pump. Because of the bent-off section, a state-of-the art vacuum pump with a placed-on tube cannot be received in existing receivers. 
     According to a particular advantageous embodiment of the invention, the at least one placed-on part has at least one radial inlet. 
     This radial inlet serves for connection, with an outlet of a pumped chamber of the arrangement in which the vacuum pump is arranged. 
     If the arrangement has several chambers, advantageously, the placed-on part has a corresponding number of inlets which overlay respective outlets of the chambers. 
     According to a further advantageous embodiment of the invention, the at least one radial inlet of the placed-on housing part is provided at the end of the placed-on housing part remote from the drive. 
     Arrangements with mass-spectrometers having time-of flight systems often have increased distances between different suction openings. Because in the placed-on housing part, customer-specific radial inlets can be formed, it is advantageous when at least one radial inlet or the last radial inlet is provided at the end remote from the drive, i.e., at the end of the housing part remote from the pump-active structures. 
     According to a further advantageous embodiment of the invention, the housing of the vacuum pump has at least one radial inlet. This means that the vacuum pump itself has at least one radial inlet provided in the housing to which the additional housing part is attached. 
     According to a further advantageous embodiment of the invention, the at least one placed-on housing part has an outer profile at least partially similar to that of the housing. Thereby, it is insured that the vacuum pump housing and the placed-on housing part have an outer profile of a one-piece housing. Thereby, it becomes possible to particularly advantageously arrange the vacuum pump in a receiver of an arrangement with mass-spectrometer. 
     Identical outer profiles of a housing and a placed-on housing part can advantageously be interrupted by a necking. 
     According to yet another advantageous embodiment of the invention, pump-active structures of the vacuum pump can at least partially be located in the placed-on housing part. There also exists a possibility to arrange a bearing star for a rotor bearing in the placed-on housing part. 
     Other components likewise can be provided in the housing part. 
     According to another embodiment of the invention, no pump-active structures of the vacuum pump are arranged in the placed-on housing part. In this case, the at least one placed-on housing part forms a pure extension of the vacuum pump housing. 
     The housing and at least one placed-on housing part have advantageously a total length of at least 550 mm. Vacuum pump housings with a length less than 500 mm can be manufactured with usual expenses by conventional machine-tools. 
     The invention, advantageously, permits to achieve lengths of more than 550 mm, e.g., lengths of more than 700 mm can be practically obtained. 
     According to yet further advantageous embodiment of the invention, the inlet openings of the housing and the outlet openings of the placed-on housing part are so formed that they overlay each other. Thereby, it is insured that the placed-on housing part functions as an extension of the vacuum pump housing. 
     According to a still further embodiment of the invention, two placed-on housing parts placed one onto the other can be provided, with the outer opening of the second housing part overlaying the inlet opening of the first housing part, whereby a further extension of the vacuum pump housing becomes possible. 
     According to another particularly advantageous embodiment of the invention, at least one thermally isolating sealing element, and/or vibration-isolating sealing element, and/or electrically isolating sealing element is provided between the housing of the vacuum pump and the placed-on housing part, and/or between two placed-on housing parts when two housing parts are placed one upon the other. This function can be incorporated in a particularly formed sealing element. 
     This embodiment permits, e.g., to achieve a thermal separation of housing parts. Also, electrical isolation and/or vibration-isolation also become possible. 
     According to an advantageous embodiment of the invention, the vacuum pump is formed as a turbomolecular pump. 
     However, it is also possible to provide other types of pumps with the inventive housing extension. 
     According to another embodiment, the vacuum pumps can be formed with two gas inlets. This type of pumps is called split-flow pumps. This type of pumps are often used in arrangements with multi-stage gas inlet system, e.g., with mass-spectrometers. It is particularly in this arrangements, it is often desirable to have housings adapted to customer-specific requirements. 
     The vacuum pump can have, e.g., at least one turbomolecular pump stage and/or at least one Holweck pump stage. The at least one Holweck pump stage usually is arranged downstream of the at least one turbomolecular pump stage in the gas flow direction. The gas inlets are advantageously arranged in front of, between, or behind the turbomolecular pump stages and/or Holweck pump stages. 
     An inventive arrangement comprises a vacuum pump including a housing having an axial inlet, a pumping unit having a stator, a rotor rotatably supported in the stator, and a drive for driving the rotor, and a pump flange; a chamber having a chamber flange; means for vacuum-tightly connecting the vacuum pump and the chamber and including both the pump flange and the chamber flange; with the vacuum pump further including at least one additional placed-on housing part attachable to the housing in an axial direction, connectable with the housing, and having at least one outlet and at least one radial inlet connectable with the chamber. 
     With this embodiment of the arrangement that includes a vacuum pump, the vacuum pump can be used in an arrangement with several suction openings spaced from each other, without particularly high machining and finishing costs in housing manufacturing. 
     According to a particularly advantageous embodiment of the invention, the arrangement has a force-transmitting structure for transmitting force from an application point to at least one operating point provided on the connecting means. This force-transmitting structure is disclosed in EP 2 228 540 A2. 
     As discussed, the inventive arrangements are particular advantageous when used with mass-spectrometers because in these arrangements several gas inlets are available which, under circumstances, can form suction openings spaced from each other by large distances. 
     According to a yet particularly advantageous embodiment of the invention, the housing of the vacuum pump and the at least one placed-on housing part have an outer profile adapted to a receiver provided in the arrangement. Thereby, it became possible to fit the vacuum pump with the placed-on housing part in an available structure of the arrangement. The arrangement receivers for vacuum pump housing are so formed that they are adapted to the outer profile of the vacuum pump housings. In this case, it is advantageous when the placed-on housing part has the same outer profiled to insure fitting of the housing with the placed-on housing part in the receiver. 
     Basically, there exists also a possibility that the placed-on housing part is offset relative to the vacuum pump housing. This embodiment is formed in response to corresponding requirements specified by the customer. 
     Because of the tolerances of separate housing parts and form and position deviations of the housings and the at least one housing part during the fitting process, it is advantageous to provide the bearing of the high vacuum side in the vacuum pump housing. In this case, the tolerances of the placed-on housing part can be greater. 
     Advantageously, the inventive pump is secured in the arrangement with a rail system. The rail system enables mounting and dismounting of the vacuum pump from one side by axial push-in or pull-out, as described in EP 2 228 540 A2. The pump access then must be provided only from one side for carrying out mounting and dismounting, whereby the system can be compactly formed, e.g., with smaller costs of the pump or the pump replacement. 
     Advantageously, the regions between the sealing planes are formed complementary to each other so that the housing is not subjected to pressure or non-acceptably deformed because of crowning and like position errors. 
     By greater spacing of the radial suction openings in the placed-on housing part with respect to the housing, it became possible to subject, in particular, the high vacuum region of the pump to high temperatures. The large surface and the length of the at least one placed-on housing part positively influence the temperature behavior of the pump. 
     Due to use of several parts, it became possible, in addition, to realize a thermal separation of the housing part or parts from the vacuum pump housing. This can be carried out by reduction of the contact surfaces or by using isolating intermediate elements or sealing elements. An electrical isolation or vibration isolation can also be realized. 
     The invention made possible a modular construction, with the vacuum pump housing forming a base of the pump with different housing extensions, i.e., with placed-on housing parts having different lengths. It is also possible to provide the base pump with a cover instead of an extension. 
     The novel features of the present invention, which are considered as characteristic for the invention, are set forth in the appended claims. The invention itself, however, both as to its construction and its mode of operation, together with additional advantages and objects thereof, will be best understood from the following detailed description of preferred embodiments, when read with reference to the accompanying drawings which show several exemplary embodiments of the inventive vacuum system. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The drawings show: 
         FIG. 1  a longitudinal cross-sectional view of a vacuum pump with a total of three inlets; 
         FIG. 2  a longitudinal cross-sectional view of a vacuum pump with a total of two inlets; 
         FIG. 3  a longitudinal cross-sectional view of a vacuum pump without pump-active structures; 
         FIG. 4  a perspective view of a vacuum pump; 
         FIG. 5  a longitudinal cross-sectional view of a connection between a housing and a housing part; 
         FIG. 6  a longitudinal cross-sectional view of a connection between a housing and a housing part according to another embodiment of the present invention; 
         FIG. 7  a longitudinal cross-sectional view of a connection between a housing and a housing part according to yet another embodiment of the present invention; 
         FIG. 8  a cross-sectional view of a screw connection between a housing and a housing part; 
         FIG. 9  a cross-sectional view of an arrangement with chambers and a vacuum pump that represents an integrated system; 
         FIG. 10  a cross-sectional view of a flange connection along line I-I′ in  FIG. 9 ; and 
         FIG. 11  a cross-sectional view of a flange connection along line II-II′ in  FIG. 9 . 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       FIG. 1  shows a vacuum pump  1  having a housing  2 . The vacuum pump  1  has a rotor  3  carrying rotor vanes  4 . The rotor vanes  4  alternate with stator vanes  5  and form different vacuum pump stages of the pump  1 . 
     At the high-vacuum side, the rotor  3  is supported by a bearing star  6 . For the sake of clarity the bearing is not shown. At the forevacuum side, the rotor  3  is likewise supported by bearings, e.g., ball bearings. 
     The housing  2  of the vacuum pump has an axial inlet  7 . In addition, there are provided two radial inlets  8  and  9 . 
     On the housing  2 , an additional housing part  10  is arranged having a further radial inlet  11 . The housing part  10  has the same cross-section and the same outer profile as the housing  2 . An outlet  12  of the housing part is so formed that it completely overlays the inlet  7  of the housing  2 . 
     In addition, the housing  2  has a radial outlet  13  that can be connected with a forevacuum pump (not shown). 
     The pump-active structures of the rotor  3 , the rotor vanes  4 , the stator vanes  5 , the bearing star  6  are completely arranged in the housing  2  according to  FIG. 1 . The placed-on housing part forms an extension of the housing  2 . With this arrangement, it is possible to achieve a total length L of the housing  2  and the placed-on housing part  10  of at least 550 mm, advantageously of at least 700 mm. Thereby, it becomes possible to remove the suction opening  11  (inlet  11 ) relatively far from the suction openings  8 ,  9  (inlets  8 ,  9 ), without a need to manufacture the housing  2  with expensive machine-tools when the housing is formed as a one-piece member. 
     An interface  19  is provided between the housing  2  and the housing part  10 , as discussed with reference to  FIGS. 5 through 8 . 
       FIG. 2  likewise shows a vacuum pump  1  with a housing  2  and a housing part  10 . 
     The same components are designated with the same reference numerals and would not be precisely described again. According to this embodiment, the housing  2  has only one radial inlet  9 . 
     The placed-on housing part  10  increases the length of the housing  2  so that the combined length of the housing  2  and the placed-on component  10  is almost twice of the length of the housing  2 . 
     As shown in  FIG. 2 , a portion of the pump-active structures is located in the placed-on housing part  10 . Thus, e.g., the bearing star  6  and the high-vacuum pump stage are located in the housing part  10 . 
       FIG. 3  shows a further vacuum pump  1  without any pump-active structures in the housing  2 . The housing  2  has inlets  8 ,  9  and a radial outlet  13 . The housing part  10  has a radial inlet  11 . In addition, the housing  2  has a necking  14  in order to reduce the heat flow from high vacuum to the rotor or the housing  2 . 
       FIG. 4  shows a vacuum pump  1  with a housing  2  and the placed-on housing part as well as with the inlets  8 ,  9  and  11 . As shown in  FIG. 4  the housing  2  and the housing part  10  have the same outer profile. E.g., cooling ribs  15  of the housing  2  continue as cooling ribs  16  of the housing part  10 . A necking  14  is also clearly shown in  FIG. 4 . In addition, on the housing  2  and the housing part  10 , there are provided strips  17 ,  18  which insure an additional stabilization of the housing  2  and the housing part  10  relative to each other and over the entire length of the vacuum pump  1 . 
     The connection of the housing  2  and the housing part  10  is effected over an interface  19 . According to  FIG. 5 , in the interface  19 , there is provided an O-ring seal  20  to achieve a vacuum-tight connection of the housing  2  with the housing part  10 . 
     According to  FIG. 6 , the interface  19  has, in addition to the O-ring seal  20 , a sealing element  21 . The sealing element  20  can be formed as a thermal, and/or vibration-isolating, and/or electrical sealing element. 
       FIG. 7  shows an interface  19  with the O-ring seal  20  and a sealing element  22  which is likewise formed as a thermal, and/or vibration-isolating, and/or electrical sealing element. 
       FIG. 8  shows a screw connection of the housing  2  and the housing part  10 . The screw connection serves for a vacuum-tight and mechanical connection of the housing  2  and the housing part  10 . The screw connection consists of a screw  25 , a washer  26 , and an elastomeric member  24  for vibration isolation. A sleeve  23  is provided as a force-transmitting element. 
       FIG. 9  shows the arrangement of a vacuum pump  1  in a system including a vacuum pump  1  and a chamber  102 . 
     The chamber  102  is formed as a multi-chamber system for operating with different pumps and has, to that end, a forevacuum chamber  121 , an intermediate chamber  122 , another intermediate chamber  123 , and a high-vacuum chamber  166 . These chambers are connected with each other by openings  125 ,  126 ,  127  through which, e.g., a stream of gas particles flows. In the high vacuum chamber  166 , there is provided a detector, e.g., a mass-spectrometer  124  which is controlled by a control packaged circuit  136 . The chamber  102  has a chamber flange  120  with which the pump flange  110  is connected. 
     The pump flange  110  forms part of the vacuum pump  1  which also includes a shaft  111  which is rotatably supported, at its high-vacuum side, by a bearing  113 , e.g., by a permanent magnet bearing. The shaft  111  is rotated by drive  114  so that in the pump stages  115 ,  116 , compression and suction take place. 
     A suction opening  127  connects the inlet of the pump stage  115  with the intermediate chamber  122 . The suction opening  128  connects the pump stage  116  with the intermediate chamber  123 . The suction opening  169  connects the pump stage  168  with the high-vacuum chamber  166 . 
     The gas enters the vacuum pump  1  through the suction opening  169 , is compressed in the pump stage  168  and then is compressed, together with the gas entering the vacuum pump  1  through the suction opening  128 , in the pump stage  116 . A further compression, together with the gas flowing from the intermediate chamber  122  into the vacuum pump  1  through the suction opening  127 , takes place in the pump stage  115 . The outlets of the vacuum pump  1  and the forevacuum chamber  121  are connected by a vacuum conduit  141  with a forevacuum pump  140  which further compresses the gas and discharges it against the atmosphere. The pump stages  115 ,  116 , and  168 , advantageously, are formed as turbomolecular pump stages. 
     The vacuum pump  1  and the chamber  102  are arranged in a stand  130 . The vacuum pump  1  is connected with the vacuum-tight chamber by a flange connection, i.e., via the chamber flange and the pump flange. The stand  130  also carries the control packaged circuit  136  of the mass-spectrometer and further components  133 ,  134 ,  135 , e.g., network elements, calculation unit, and the like. The frame  130  is covered with lining  131 . The vacuum pump  1  and the chamber  102  are accessible through a hinged lid  132 , but other components, however, are surrounded by the stand  130 . The flange connection is, therefore, accessible with much difficulty and only from the side adjacent to the hinged lid  132 . Mounting and dismounting of the vacuum pump is only possible from the lid side. 
     The vacuum pump  1  has a housing  2  and a placed-on housing part  10 . The placed-on housing part  10  has the inlet  11  connected with the suction opening  169 . With the placed-on housing part  10 , the vacuum pump has an increased length made possible by the arrangement shown in  FIG. 9 . 
     The mounting without problems is made possible by a force-transmitting structure according to  FIGS. 10 and 11 . 
       FIG. 10  shows a cross-sectional view of a force-transmitting structure  165  transverse to the shaft  111  along line I-I′ in  FIG. 9 . The chamber flange  120  and the pump flange  110  are in contact with each other. For providing a vacuum-tight connection, a seal  119  that surrounds the suction opening  127 , is used. In this cross-section, in the vacuum pump  1 , a distance sleeve  118  which is provided between the pump stages and spaces their components, and the last stator disc  117  of the high-vacuum pump stage  168  can be seen. A connecting screw  151  secures a retaining angle  150  to the chamber flange. A first expansion member  152  and a second expansion member  153  are arranged between the retaining angle and the pump flange. 
       FIG. 11  shows an associated cross-sectional view along line II-II′ in  FIG. 10  and parallel to the shaft  111 . It can be seen that a portion of the retaining angle  150 , the first expansion member  152  and the second expansion member  153 , and a portion of the pump flange  110  lay in a common plane. The first expansion member  152  has a wedge surface  158 ′ and the second expansion member has a wedge surface  158 . The wedge surfaces  158  and  158 ′ are so contact each other that their displacement relative to each other becomes possible. The displacement is effected by a force-applying screw  155  that extends through a through-bore in an arm  154  of the first expansion member, with its threaded part engaging in the thread of the second expansion member  153 . By tightening the screw, a planar force is produced that displaces the expansion members  152 ,  153  relative to each other. The action of the wedge surfaces converts the force direction in an axial direction. As a result, an axial press-on force  160  is produced in the operating point  159  and that presses the pump flange  110  and the chamber flange  120  against each other and that provides, thus, for a vacuum-tight connection. The expansion members  152 ,  153  provide for force direction conversion. Mounting and dismounting of the vacuum pump  1  is achieved by tightening and loosening the screw  155 . 
     The expansion member  152 ,  153  insure transmission of a force from an application point  156  to the operating point  159  in the force transmitting structure  165 . The force transmission enables to produce a press-on force at points which are not accessible as a result of the vacuum pump  1  being surrounded by components described with reference to  FIG. 9 . Advantageously, in this embodiment, in addition to force transmission, force distribution over the pump flange takes place, so that a uniform pressure is achieved. With an appropriate number of the wedge surfaces and their angles, the force distribution of the applied force over the flange  110  can be adjusted. 
     Because the housing  2  and the placed-on housing part  10  have the same outer profile, as shown in  FIG. 4 , the vacuum pump  1  can be mounted in an arrangement shown in  FIG. 9  without any problem. As described with reference to  FIGS. 10 and 11 , the vacuum pump is fixedly secured in the arrangement. With the placed-on housing part  10  it becomes possible to meet customized requirements economically and without problem, as shown in the arrangement of  FIG. 9 . 
     Though the present invention was shown and described with references to the preferred embodiments, those are merely illustrative of the present invention and is not to be construed as a limitation thereof and various modifications of the present invention will be apparent to those skilled in the art. It is, therefore, not intended that the present invention be limited to the disclosed embodiments or details thereof, and the present invention includes all variations and/or alternative embodiments within the spirit and scope of the present invention as defined by the appended claims.