Abstract:
A vacuum pump housing comprises a pump housing formed in a pumping chamber. In the pumping chamber, pumping elements are arranged. On a planar outer side of the pump housing, a cooling element is arranged. The cooling element comprises at least one cooling channel which is open towards the outer side of the pump housing. The disclosure further relates to a set of cooling elements comprising a plurality of cooling elements having different outer dimensions.

Description:
BACKGROUND 
       [0001]    1. Field of the Invention 
         [0002]    The present disclosure relates to a vacuum pump housing and a set of cooling elements for a vacuum pump housing. 
         [0003]    2. Discussion of the Background Art 
         [0004]    Vacuum pumps comprise pumping elements arranged in a pumping chamber formed by a housing. Vacuum pumps are primarily configured as screw pumps, one- or multi-stage Roots pumps, rotary vacuum pumps and claw pumps. For generating a vacuum, it is required that a gap of the smallest possible size is realized between the pumping elements and the inner wall of the pumping chamber. For this reason, it is required to operate vacuum pumps at an operating temperature as uniform as possible, in order to avoid changes of said gap which may happen to occur due to differences in the thermal expansion of the pump housing and the pump elements. 
         [0005]    It is known to provide vacuum pumps with cooling ribs and to cool the pump housings by use of an air flow. With these approaches, however, a uniform and well-aimed cooling of the housings will normally be possible only with the aid of special measures, e.g. by installation of an outer shell with well-aimed guidance of the air and with an external ventilation system (driven by one of the pump shafts or by a separate drive unit). Such an arrangement has the disadvantage that the specific cooling performance (heat flow per area unit) will be low. Further, dissipation of heat into the ambience is often undesired. Especially in clean room environments, an occurrence of air flows has to avoided to the largest extent possible. Further, ventilator units are undesirable sources of noise. 
         [0006]    Further, it is known to effect the cooling of vacuum pump housings with the aid of water or a cooling liquid. Cooling by water will necessitate special constructive measures. On the one hand, for achieving the highest possible cooling effect, the water has to be guided as closely as possible to the regions which have to be cooled. On the other hand, the corrosive effect of water on most materials will make it impossible to use water without the need of taking special protective measures. To avoid corrosion, it would be possible to use corrosion-free materials such as e.g. stainless steel or specific aluminum alloys. Such materials, however, are expensive and do not meet other preconditions for vacuum pump housings, such as e.g. resistance to high temperatures, particularly of more than 250° C. Further, it is possible to apply lacquer onto those surfaces which will be contacted by the water. However, reliably lacquering of corresponding channels arranged internally of the housing would be very complex. The lacquering process would have to be performed by immersion baths or by rotating or tumbling movements for distributing the liquid lacquer. Further known are galvanic surface treatment methods such as e.g. zinc or nickel coating in case of steel and grey cast iron, or hard anodizing in case of aluminum. Also these methods, however, are very complex. A further known approach consists in the use of consumable electrodes while, however, also this method is complex and, especially in case of internal cooling channels, does not allow for reliable prevention of corrosion. 
         [0007]    Instead of using water as a cooling agent, use can also be made of special cooling liquids. This, however, will be possible only if the cooling circuits are closed in themselves, at the penalty of increased complexity. Particularly, it is required to cool the cooling agent by heat exchangers which have to be additionally provided. 
         [0008]    The provision of cooling channels in vacuum pump housings made of cast iron is also possible by retrofitting the housings with such channels by machining, particularly by milling and drilling. The resultant need for time-consuming additional processing steps will make this option extremely complex. It is also possible to form the cooling channels already during the casting process. For this purpose, sand cores are provided. This method, too, is complex and even involves the risk that the cooling water may suffer long-term contamination by sand residuals. Further still, the provision of insert-molded channels shaped by sand cores, although possible, will impose massive limitations on the shape, the cross section and the course of the channels because the molding is performed with the aid of sand cores which are required to have a sufficient stability for the casting process. Thus, the provision of cooling channels of this type will massively restrict the range of possible shapes and possible operating conditions, the latter including e.g. the stability, the operational temperatures and the media compatibility. 
         [0009]    It is an object of the disclosure to provide a vacuum pump housing which can be cooled in a simple manner, particularly by use of a liquid cooling medium. Further, an independent object of the disclosure resides in providing a set of cooling elements for vacuum pumps which has a high variability. 
       SUMMARY 
       [0010]    A housing for a vacuum pump comprises a pump housing defining a pumping chamber. Arranged in the pumping chamber are the pump elements, such as e.g. helical rotors. According to the disclosure, the pump housing comprises at least one planar outer side. Said preferably flat, planar outer side is connected to a cooling element. According to the disclosure, said cooling element comprises at least one and optionally a plurality of cooling channels which are open towards the outer side of the pump housing. By connecting the cooling element, which preferably is formed as a separate component, to the pump housing, so that a preferably planar abutment face of the cooling element is facing towards the planar outer side of the pump housing, there will be generated cooling channels of a closed cross-sectional shape. Thus, in the inventive arrangement of a cooling element which preferably is formed as a separate component, it is not required to provide cooling ribs or the like on the pump housing itself. Thereby, the pump housing can be given a simpler configuration, thus lowering the production costs. For cooling the pump housing, the cooling element of the disclosure will then be connected to the planar outer side. Particularly, this has the advantage that the cooling element can be produced as a separate component. 
         [0011]    Since the cooling element does not comprise internally arranged cooling channels while, instead, its cooling channels are open towards the outer side of the pump housing, production of the cooling element is simple. The cooling elements can be provided as cast components, it being preferred that the cooling channels will not be formed at a later time in the production process but will already have been provided beforehand in the cooling element as corresponding grooves or recesses. The cooling channels herein can have a suitable configuration for allowing the cooling element to be produced in casting molds. The cooling channels preferably comprise mold release slopes. As a result, it is not necessarily required to generate the cooling channels by subsequent treatment of the cooling element such as e.g. by milling the cooling channels. In case of flat, wider cooling channels with larger mold release slopes, it will also not be required to provide sand cores or the like for generating the cooling channels. Preferably, the cooling element comprises a planar abutment face which in the assembled condition is facing towards the outer side of the pump housing. In the assembled condition, said abutment face is thus preferably parallel to the outer side of the pump housing. 
         [0012]    It is possible to fasten the cooling element directly on the outer side, e.g. by use of screws or other fastening means. Preferably, a sealing element is arranged at least in the edge region of the cooling element, again on the surface facing towards the outer side of the pump housing. Said sealing element can be a liquid sealing element, a sealing compound or the like. Preference is given to an annular sealing element which is closed in itself and preferably has a circular cross section; such a sealing element preferably is an O-ring. It is preferred that a sealing groove is provided in the outer side of the pump housing and/or in a side of the cooling element opposite to said outer side, i.e.—according to a particularly preferred embodiment—in the abutment face of the cooling element. In this sealing groove, the sealing element is arranged. It is possible to provide both surfaces with respectively one sealing groove so that there will exist two sealing grooves which preferably arranged opposite to each other. In addition to—or in place of—such sealing elements, it is according to a preferred embodiment provided that a sealing element, preferably of an areal type, is located on the outer side of the pump housing. Said sealing element preferably fully covers the outer side. In addition to its sealing function, the sealing element can thus also assume the function of protecting the outer side of the pump housing from corrosion. This obviates the need to apply a coating of an anti-corrosive agent such as e.g. lacquer onto a planar and preferably treated outer side of the pump housing. 
         [0013]    The at least one cooling channel provided in the cooling element is preferably of a meandering configuration. Optionally, also a plurality of cooling channels, e.g. having different cross sections, can be provided in a cooling element. This makes it possible to connect one and the selfsame cooling element in a different manner and thus achieve a different cooling effect. Of course, the different cooling channels can also be connected together. 
         [0014]    Each cooling channel comprises at least one inlet and at least one outlet. With preference, a plurality of inlets and/or outlets are provided, more preferably two of each. This advantageously provides a plurality of connection options, making it possible to select that connection which e.g. is better accessible or allows for easier mounting. 
         [0015]    Said at least one inlet and/or outlet is preferably arranged in a lateral surface of the cooling element. Said lateral surface is a side oriented at an angle relative to the abutment face of the cooling element, i.e. relative to the side of the cooling element facing towards the outer side. In a substantially parallelepipedic cooling element, for instance, said lateral surface extends vertically to the abutment face. Alternatively, an inlet and/or outlet can be arranged on an outer side, i.e. particularly on that side of the cooling element which is arranged opposite to the side of the abutment face. 
         [0016]    According to an especially preferred embodiment, said inlets and/or outlets are arranged in such a manner that they are closed towards the outer side of the pump housing. Thereby, the sealing will be made considerably easier. Preferably, the inlets and/or outlets are formed as bores. These bores, which preferably are formed as a cylindrical opening, connect the cooling channels which are open towards the outer side of the pump housing. Said cylindrical opening is closed towards the outer side of the pump housing, i.e. towards the abutment face of the cooling element. 
         [0017]    Since, according to a particularly preferred embodiment, the cooling medium used will be a cooling liquid such as e.g. water, a risk of corrosion exists. To avoid such corrosion, it is possible to provide the inner sides of the cooling channels with an anti-corrosion layer. For this purpose, it is possible e.g. to lacquer the corresponding surfaces or to subject them to a galvanic treatment, e.g. zinc plating or nickel plating. Further, e.g. in case of aluminum casting, a hard anodizing process can be applied. Also a consumable electrode can be provided for protection from corrosion. Preferably, the cooling element is made of a material serving as a consumable electrode. Further, the cooling elements can comprise a consumable electrode and be entirely or partially made of a corresponding material. 
         [0018]    According to an especially preferred embodiment, the cooling element is produced as a grey-casting or spheroidal-casting component or also from corrosion-resistant aluminum or stainless-steel cast alloys. The resultant cast surfaces will not be susceptible to corrosion when exposed to water. Producing such component parts by grey-casting, spheroidal-casting or aluminum casting will also be inexpensive. A further possibility resides in producing the cooling elements from copper, brass or bronze alloys. 
         [0019]    The present disclosure further relates to a set of cooling elements for vacuum pumps. Said set of cooling elements comprises a plurality of cooling elements with different outer dimensions. Each cooling element is provided with at least one cooling channel which is open towards the abutment face of the cooling element. In the assembled state, the abutment face of the cooling element is facing towards an outer side of the vacuum pump housing and, together with said outer side, forms a cooling channel having a closed cross section. By designing a set of cooling elements comprising different cooling elements, it is possible to provide different pump types with the respective suitable cooling elements in a highly variable manner. 
         [0020]    The cooling elements of the set of cooling elements comprise e.g. differently large, preferably rectangular abutment faces. When designing the vacuum pump housings, one merely has to take care to generate outer surfaces which correspond to the size of one or a plurality of the cooling elements. It will thus not be required to design different cooling elements for different vacuum pump housings. 
         [0021]    For instance, the set of cooling elements may comprise not only cooling elements with differently large abutment faces and/or with abutment faces of different geometric configurations, but also cooling elements having cooling channels of different cross-sectional shapes. Thus, for a given vacuum pump and a given use of the vacuum pump, one can conveniently provide different cooling elements having different cooling performances. According to a preferred embodiment, the individual cooling elements are designed in the manner described above in connection with the vacuum pump housing. Particularly, the cooling elements, preferably being of a parallelepipedic shape or comprising a parallelepipedic base body, have at least one inlet and at least one outlet. These, as already explained above, are preferably located in lateral surfaces or on an outer side of the cooling elements. Consequently, connecting the cooling channels to a cooling system via cooling conduits is possible in an easy manner. 
         [0022]    The disclosure will be described in greater detail hereunder by way of preferred embodiments and with reference to the accompanying drawings. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0023]    In the drawings, the following is shown: 
           [0024]      FIG. 1  is a schematic perspective view of a first embodiment of a cooling element; 
           [0025]      FIG. 2  is a schematic sectional view taken along the line II-II in  FIG. 1 ; 
           [0026]      FIG. 3  is a partial view of a cooling element similar to the cooling element shown in  FIG. 2 ; 
           [0027]      FIG. 4  is a schematic sectional view taken along the line III-III in  FIG. 4 ; and 
           [0028]      FIG. 5  is a view of an example of a set of cooling elements. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
       [0029]    A cooling element  10  which in the illustrated embodiment ( FIG. 1 ) is formed as a parallelepipedic cast component, comprises a meander-shaped cooling channel  12 . The cooling channel  12  is shaped as a groove which is open towards an abutment face  14 . Said groove can be produced already during the casting process by using a corresponding casting mold. Alternatively, the groove for forming the cooling channel  12  can be produced e.g. by machining processes such as milling, for instance. Cooling channel  12  has a U-shaped cross section ( FIG. 2 ) so that the cooling element is closed on its outer face  16 . In the illustrated embodiment, inlets  20  and outlets  22  for connection of the cooling channel to cooling conduits are provided on outer sides  18 . Said inlets  20  and outlets  22  are formed as transverse bores ( FIG. 4 ). The abutment face  14  is thus closed in the region of these transverse bores  20 , 22 . This has the advantage that the provisions for sealing can be realized in a simpler manner. 
         [0030]    In the illustrated embodiment, two inlets  20  and two outlets  22  are provided. These are arranged respectively in different, mutually vertically outer sides  18 , each time in a corner region. This arrangement has the advantage that the connection of the cooling channel can be realized via one of the two inlet openings  20  and respectively one of the outlet openings  22 , the connection being freely selectable in accordance to the respective requirements. This is advantageous because, depending on the pump type for which the cooling element  10  is used, there will exist different space conditions. 
         [0031]    Further, pump element  10  is provided with a plurality of through bores  24  for attachment, said bores extending from outer face  16  to abutment face  14 . Thereby, the cooling element  10  can be easily fastened to a pump housing  26  ( FIG. 2 ), e.g. by screws. This is schematically outlined by the chain-dotted line  28  in  FIG. 2 . 
         [0032]    In the illustrated embodiment, abutment face  14  is not in immediate abutment on a planar, treated outer face  30  of pump housing  26 . Instead, an areal sealing  32  is provided between the two components. Said sealing  32  fully covers the outer face  30  as well as the abutment face  14 . Thus, the sealing  32  does not only serve for achieving a sealed arrangement of the cooling element  10  on the housing but is used also to seal the individual portions ( FIG. 2 ) of cooling channel  12  against each other. Further, by the provision of such an areal sealing  32 , the treated outer face  30  of pump housing  26  is protected against corrosion. Further still, the areal sealing  32  also serves for anti-corrosion protection of abutment face  14  which in the embodiment shown in  FIG. 2  has also been given a full-surfaced treatment. An inner face  34  of cooling channel  12  can be provided with an anti-corrosion protective coating such as e.g. lacquer. Preferably, however, said inner face  34  is an untreated cast surface, wherein the cooling element  10  is preferably produced by a grey-casting or spheroidal-casting process or is made of corrosion-resistant aluminum or stainless-steel cast alloys, so that the resultant cast surface is corrosion-resistant towards the cooling agent, i.e. particularly to water. 
         [0033]    In a further embodiment ( FIG. 3 ), the cooling element  10  has a configuration similar to that shown in  FIG. 2 . The only difference resides in that web portions  36 , arranged between adjacent portions of cooling channel  12 , have been left untreated in a region  38  of abutment face  14 . When providing a correspondingly thick areal sealing element  32 , a treatment of said portions is not required because the sealing element  32  is compressed in said region  38  and the sealing element  32  will thus partially project into the lateral faces  34  of cooling channel  12  and thus will seal adjacent portions of cooling channel  12  against each other. 
         [0034]    When providing a correspondingly thick sealing element  32  in the embodiment shown in  FIG. 2 , it is also not absolutely required to use an anti-corrosion agent for protecting the abutment face  14  from corrosion. This is not required because, if a sealing  32  with a suitable thickness is used, the sealing will project into the lateral faces  34  and thus will prevent the cooling agent from reaching the abutment face  14 . 
         [0035]    In embodiments which do not comprise an areal sealing element  32 , it is also possible to provide a sealing groove in an outer edge region  40  ( FIG. 2 ) of abutment face  14  for accommodating a sealing element formed e.g. as an O-ring. Optionally, the corresponding sealing groove can also be arranged in a corresponding region opposite to the outer side  30  of pump housing  26 . 
         [0036]      FIG. 5  illustrates, by way of example, a set of cooling elements comprising a plurality of cooling elements  42 , 44 , 46 . Said cooling elements  42 , 44 , 46  are designed substantially in the manner of cooling element  10 . 
         [0037]    Thus, the two cooling elements  42 , 44  each comprise a meander-shaped cooling channel  12  which, corresponding to the above described cooling element  10 , is open towards an abutment face  14 . Cooling element  42  is on its lateral faces  18  provided with inlets  20  and outlets  22 , wherein also herein, two inlet and respectively outlets are provided in the edge regions so as to safeguard a high variability with respect to the connection options. 
         [0038]    The cooling element  44  is of a design corresponding to cooling element  10  wherein the parallelepipedic cooling element does not comprise a quadratic but a rectangular abutment face  14 . The further cooling element  46 , shown in  FIG. 5 , comprises two cooling channels extending substantially parallel to each other. Each of the two cooling channels  12  has an inlet  20  as well as an outlet  22 . The two cooling channels  12  can e.g. conduct flows in different directions. Further, it is possible to connect only one of the cooling channels  12 , which will depend on the requirements posed to the cooling of the vacuum pump. 
         [0039]    By the above set of cooling elements comprising a plurality of cooling elements as illustrated by way of example in  FIGS. 5 to 7 , it is rendered possible to create cooling elements for different vacuum pumps. These cooling elements are designed in the manner of a modular construction kit so that the individual cooling elements of the set of cooling elements can be used for different vacuum pumps. This has the advantage that the different vacuum pumps merely must have correspondingly designed outer sides  30  and that, depending on the size and the requirements, there can then be used a corresponding cooling element of the set of cooling elements. In this manner, an extremely high flexibility is achieved.