Abstract:
A filter device ( 10 ) for an internal combustion engine includes a separator that is embodied as a cyclone preseparator ( 26 ), a main filter element ( 36 ) exchangeably arranged in a housing compartment ( 68 ) of the filter housing ( 12 ), and a secondary filter element ( 38.  The housing compartment ( 68 ) includes insertion stays ( 64 ). The main filter element ( 36 ) is embodied in as a double bellows filter including a first radially inwardly positioned filter bellows ( 40 ) and a second radially outwardly positioned filter bellows ( 42 ) surrounding it. Upon closing of a servicing housing cover ( 18 ) a sealing force is generated that acts onto the main filter element ( 36 ) and is maintained in the closed state of the servicing cover ( 18 ).

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
       [0001]    The present patent application is a continuation of U.S. patent application Ser. No. 12/645,706 filed Dec. 14, 2009, the entire contents of which are incorporated herein by reference and to the fullest extent of the law. Priority is claimed through U.S. patent application Ser. No. 12/645,706 to German patent application DE 20 2008 017 059.1 filed Dec. 23, 2008. 
     
    
     TECHNICAL FIELD 
       [0002]    The invention concerns a filter device, in particular an air filter for internal combustion engines. 
       BACKGROUND OF THE INVENTION 
       [0003]    EP 1 509 311 B1 concerns an air filter with a wound filter medium. The air filter according to EP 1 509 311 B1 comprises a housing with an inlet end and an outlet end opposite thereto and a sidewall that extends between the inlet end and the outlet end. The sidewall comprises an access opening as an access to the interior of the housing. The access opening, in turn, is arranged between the inlet end and the outlet end. The air filter comprises furthermore a filter element with a sealing element that is operatively mounted in the housing. This sealing element separates the clean air from the raw air side. The housing is constructed and arranged such that it may receive the filter element through the access opening in the sidewall. A servicing cover is provided that is detachably mounted on the access opening between the inlet end and the outlet end. 
         [0004]    The filter element comprises a first flow surface and an opposed second flow surface. The filter element comprises several fold chambers wherein each of the fold chambers comprises, adjacent to the first flow surface, a portion that is positioned upstream and, adjacent to the second flow surface, a flow portion that is positioned downstream. 
         [0005]    The filter element is arranged such that the air flows via the inlet end of the housing through the first flow surface and the second flow surface and exits the housing through the outlet end. The filter element comprises a terminal disk about a periphery of the first flow surface. A portion of the frame projects into the periphery of the first flow surface. The servicing cover comprises a shoulder that extends in the direction of the interior of the housing and supports the filter element when the filter element is installed in the housing. The shoulder of the servicing cover engages the frame and rests against the first flow surface in order to secure the filter element. 
       SUMMARY OF THE INVENTION 
       [0006]    The invention has the object to realize a simple handling of the filter element and to transfer it in a way as simply as possible into its operating position within the filter housing of a filter device, in particular to provide in a very simple way a sealing action of the filter element. 
         [0007]    According to the invention, this object is solved by the features of the independent claims. 
         [0008]    The dependent claims relate to advantageous further embodiments of the principle upon which the invention is based. 
         [0009]    According to the invention, it is proposed to design a servicing cover for closing a housing compartment of a filter housing of a filter device in such a way that, when closing the servicing cover, the filter element that has been inserted before into the housing compartment of the filter housing will be positioned properly and, by closing the servicing cover, a sealing force is generated with which the filter element that is pre-mounted in its proper position in the housing compartment is moved against a lateral surface of the housing compartment in the filter housing. 
         [0010]    The filter device proposed according to the invention is advantageously one that comprises several components, for example, a prefilter stage in the form of a cyclone preseparator, the already mentioned main filter element as well as a secondary or safety filter element that is arranged in axial direction, i.e., in the flow direction of the fluid to be filtered, downstream thereof. The cyclone preseparator that is upstream of the main filter element or the housing compartment of the filter housing comprises a discharge opening through which coarse particles of the fluid to be filtered are discharged. The cyclone preseparator can be connected in an advantageous way by a screw connection that extends from the end face of the cyclone preseparator along the side walls of the housing compartment to the filter housing. In this way, a seal-tight connection along a butt joint between the cyclone separator and the housing compartment of the filter housing is provided so in that no foreign air can be taken in that has not passed through the cyclone preseparator. Moreover, the screw connection provides a possibility for servicing the cyclone separator. 
         [0011]    The secondary filter element that is arranged downstream of the exchangeable filter element arranged in the housing compartment can be secured on the rib-shaped or cupola-shaped projections within a funnel-shaped compartment at the outlet side of the filter housing without this requiring additional fixation elements. In an advantageous way, the secondary filter element downstream of the main filter element can be changed without tools, in particular by a simple one-hand operation. 
         [0012]    The main filter element that is exchangeably received in the housing compartment of the filter housing is preferably a multi bellows filter, in particular a double bellows filter. It comprises a first radially inwardly positioned filter bellows that is cylindrical or conical relative to its outer diameter and is surrounded with formation of an optionally conical or cylindrical flow space by a further second radially outwardly positioned filter bellows. Both filter bellows of the multi filter bellows are embodied advantageously so as to be glued at the front edges. The individual filter folds extend preferably in axial direction, i.e., parallel to the flow path of the fluid to be cleaned that is passing through the filter housing. 
         [0013]    As already mentioned, in an advantageous way on the housing compartment that is formed within the filter housing a servicing cover is provided. The latter is supported by means of hinges such that the servicing cover can be gripped by a grip and can be pivoted about the hinges positioned opposite the grip. As a result of the sizing of the diameter of the hinges the servicing cover can be locked in its open position, can simply be moved out of this position for closing and positionally secured by a locking action, in particular, a locking action provided on the cyclone preseparator. For this purpose, the grip member of the servicing cover engages a grip depression at the top side of the cyclone preseparator that is preferably manufactured by plastic injection molding and locks thereat. By a simple pressing action against the grip member that is substantially oriented perpendicularly to the servicing cover, the locking action within a depression at the end face of the cyclone preseparator can be canceled and the servicing cover can be opened, in particular by a one-hand operation. 
         [0014]    After the servicing cover has been opened, the main filter element mounted in the housing compartment of the filter housing can be removed easily. For this purpose, the main filter element is provided with a grip tab so that a one-hand action is possible. This seal of the main filter element is released in axial direction so that the main filter element can be removed in the upward direction. As a result of the design of the hinges the servicing cover after having been opened remains in its open position so that the operator who has possibly only one hand available can grip the main filter element at the grip tab or the grip member while, with the other hand, he holds onto a grip, for example, above the engine compartment of a tractor or a construction machine. 
         [0015]    After removing a spent main filter element a new main filter element can be simply inserted into the housing compartment. The main filter element can also be cleaned off and after cleaning can be reinstalled and can thus be used several times. For this purpose, the two oppositely positioned lateral surfaces of the housing compartment receiving the main filter element each can be provided with ramp-shaped projections. The ramp-shaped projections that are preferably integrally injection-molded with a reinforcement structure onto the lateral surfaces of the housing compartment ensure insertion of the main filter element into the housing compartment of the filter housing in correct orientation. Moreover, a wrong insertion of the filter element is prevented in that through the housing compartment the screw guides extend that represent a further safety detail with regard to mounting the main filter element in the housing compartment of the filter housing in the proper position. 
         [0016]    As soon as the main filter element with its upper circumferentially extending rim has been inserted into the housing compartment along the ramps, the servicing cover can be closed. For this purpose, the servicing cover that is open is gripped at the grip member and pivoted about the hinges. On the inner side the servicing cover advantageously comprises at least one, preferably two spaced apart shoulders. Upon closing of the servicing cover these shoulders engage the circumferentially extending collar on the topside of the main filter element that is already pre-positioned by the ramp-shaped stays integrally injection-molded on the lateral surfaces of the housing compartment. When closing the servicing cover, the sealing force in the filter device according to the invention is generated because by means of the preferably two shoulders that are integrally injection-molded on the inner side of the servicing cover a circumferentially extending collar on the main filter element is engaged and sealed against a complementary sealing surface on the inner side of the filter housing on that side that is facing the secondary filter element. In the filter device proposed according to the invention the sealing force is generated upon closing the servicing cover. The sealing force that acts preferably in axial direction is maintained in the closed state of the servicing cover and is released only when opening the servicing cover. The sealing force is advantageously maintained in the already mentioned locking action between the grip member of the servicing cover and a depression, formed, for example, on the cyclone preseparator, during the closed state of the servicing cover. 
         [0017]    In an advantageous embodiment of the principle upon which the invention is based, the servicing cover is manufactured by injection molding of plastic material wherein the grip member is integrally injection-molded onto the front side of the servicing cover, opposite to at least one hinge. The grip member is advantageously designed such that a one-hand operation is possible. For this purpose, the grip member may comprise an opening, but it can also be designed without an opening. The grip member is advantageously provided with a contour that forms a depression-like recess that interacts with a counter member of the locking action—formed in the depression—and thus ensures the locking action of the servicing cover in the closed state and maintaining the sealing force in relation to the main filter element in the housing compartment of the filter housing by the shoulders contacting a circumferentially extending collar of the main filter element in the closed state of the servicing cover. Alternatively, the grip member can also be of a multi-part configuration. 
         [0018]    In an advantageous further embodiment of the principle upon which the invention is based, the secondary filter element that is arranged downstream of the main filter element, embodied preferably as a multi bellows filter element, is exchangeably arranged in a funnel-shaped recess of the filter housing. For this purpose, in the funnel-shaped recess in the filter housing several cupola-shaped projections can be formed. Between these cupola-shaped projections that are formed, for example, on the bottom side and topside of the funnel-shaped openings, the secondary filter element is inserted; this can also be done with one hand. No further fixation elements are needed for the secondary filter element that is to be positioned downstream of the main filter element in the funnel-shaped area of the filter housing at the outlet side. 
         [0019]    In an advantageous manner the main filter element is embodied as a multi bellows filter, in particular as a double bellows filter, in which the axial end faces at the inlet side each are closed off by cover. While, for example, the radially outwardly positioned filter bellows is cylindrical or conical, the inwardly positioned inner bellows can have a conical shape so that between the inner diameter of the radially outwardly positioned filter bellows and the conically extending outer diameter of the radially inwardly positioned filter bellows a conically extending flow space is provided. This flow space that has the aforementioned conical shape is filled by a support structure that has a rib-shaped structure that extends in axial direction as well as in circumferential direction. By means of the support structure, in particular for other sizes of the filter device proposed according to the invention, it is ensured that the configuration of the geometry of the flow space of the main filter element is maintained even after extended operation and that outflow is ensured. The radially inwardly positioned filter bellows delimits an interior that, in turn, is closed off by a cover disk. As a result of the selected positioning of the cover disks or the cover disk on the outlet side or the annular ring at the inlet side, it is ensured that the fluid to be filtered that has passed the cyclone preseparator flows into the interior of the main filter element that is closed off at the outlet side by the cover disk. In this way, a radial deflection is imparted onto the fluid to be filtered so that the first radially inwardly positioned filter bellows is flowed through in the radial direction. Cleaned fluid thus enters the conically extending flow space. Since the axial end face of the radially outwardly positioned filter bellows is also closed off by the annular cover, flow-through of the radially outwardly positioned filter bellows is done from the exterior side. The fluid to be cleaned enters the flow space coming from the outer surface of the radially outwardly positioned filter bellows in radial direction and passing through it. The flow space that has a conical configuration comprises an outlet opening from which the cleaned fluid flows into the secondary filter element. 
         [0020]    The main filter element is in particular in the form of the aforementioned multi bellows filter, preferably a double bellows filter. Its cover at the inlet side can be made from a plastic material, for example, as a PUR ring and can be circular or oval. The axial end faces of the inwardly positioned conically shaped filter bellows and of the outwardly positioned cylindrically embodied filter bellows can be integrated therein by foaming. Downstream on the main filter element, formed on the circumferentially extending rim, the grip member is provided as well as a blade-shaped structure for stabilization of a seal. The circumferentially extending rim as well as the blade-shaped contour that is preferably provided with penetrations, are injection-molded of a harder plastic material and serve for stabilization of the seal that can also be produced by foaming of PUR. Advantageously, the blade-shaped structure of the frame is provided with penetrations so that the plastic material, for example, PUR, of which the seal is preferably produced by foaming, is reliably secured on the blade and stabilized. This increases the service life and sealing action of the seal that is circumferentially foamed onto the frame. Instead of the aforementioned plastic material PUR, other easily processable plastic materials that generate a high sealing force and have elastic properties can also be integrally injection-molded onto the blade-shaped structure. In an alternative possible embodiment variant on the ramps, integrally injection-molded onto the lateral surfaces of the housing compartment of the filter housing and interrupted by reinforcement ribs, shoulders can be provided also into which leaf springs can snap. The leaf springs, in turn, are connected to the bottom side of the circumferentially extending injection molded frame of the main filter element. When the main filter element is inserted into the housing compartment with one hand, the operator will sense haptically that upon reaching the first locking position a correct insertion process has been realized and upon exertion of greater insertion force and overcoming a second spring force when reaching the second shoulder haptically a correct position of the filter element. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0021]    Embodiments of the filter device according to the invention for an internal combustion engine will be explained in more detail with the aid of the Figures in the drawings. 
           [0022]      FIG. 1  is a perspective illustration of the filter device proposed according to the invention with cyclone preseparator, filter housing, and servicing cover shown in closed position with grip member; 
           [0023]      FIG. 2  illustrates the servicing cover with which the filter device in  FIG. 1  is closed, with integrally injection-molded grip member and recess as well as hinges on the side facing away from the grip member; 
           [0024]      FIG. 3  is a section of the filter device according to  FIG. 1  proposed according to the invention with cyclone preseparator, a multi bellows filter embodied as a double bellows filter, and a secondary filter element arranged downstream thereof, with servicing cover in closed position; 
           [0025]      FIG. 4  is a detail illustration of the servicing cover in the closed state when closing the housing compartment of the filter housing; 
           [0026]      FIG. 5  illustrates the filter housing of the filter device according to the invention in the open state without servicing cover with main filter element to be installed in the insertion direction, with grip member integrated into the plastic disk; 
           [0027]      FIG. 6  depicts the generation of the sealing force between the filter housing and the main filter element upon closing of the servicing cover; 
           [0028]      FIGS. 7 ,  8 ,  9  show details of the circumferentially extending collar on the topside of the main filter element with integrally injection-molded grip member; 
           [0029]      FIG. 10  depicts a tear-off seal provided on a filter element; 
           [0030]      FIG. 11  depicts a PUR seal extending circumferentially on an end face of a filter bellows; 
           [0031]      FIG. 12  depicts a simplified illustration of the folding geometry; and 
           [0032]      FIG. 13  depicts a leaf spring-like filter element locking action in the filter housing: a) housing-side and element-side structure; b) two-stage locking possibility; c) and d) possible position of locking action on the housing and the filter element. 
       
    
    
       [0033]    Same parts in the following Figures are identified with identical reference numerals. 
       DETAILED DESCRIPTION 
       [0034]    The illustration according to  FIG. 1  shows in a perspective view a filter device proposed according to the invention. 
         [0035]    The filter device  10  according to the perspective illustration in  FIG. 1  is in particular used as an air filter element for off-highway applications such as tractors, combines, agricultural machines, construction machinery. The filter device  10  proposed according to the invention is manufactured in various sizes, depending on the fluid volume flow to be filtered. 
         [0036]    In  FIG. 1  the filter device  10  proposed according to the invention comprises a filter housing  12 . The fluid to be cleaned flows into the filter device  10  at the inlet side  14  and exits the filter device at the outlet side  16 . The filter housing  12  comprises a servicing cover  18  that closes off a housing compartment of the filter housing  12 . The servicing cover  18  is pivotably received in two hinges  20  that are arranged adjacent to one another and are formed preferably as plastic hinges and have a variable diameter so that the servicing cover in the open state is lockable and a one-hand exchange of a main filter element of the filter device  10  proposed in accordance with the invention is ensured even under difficult conditions. 
         [0037]    The servicing cover  18  comprises a grip member  22  on the side opposite the at least one hinge  20 . The grip member  22  in the illustration according to  FIG. 1  is provided with an opening  30  but could also be of an uninterrupted configuration, i.e., could have a continuous grip surface without the formation of an opening  30 . 
         [0038]    The illustration according to  FIG. 1  discloses that the servicing cover  18  is shown in the closed position and is locked with its grip member  22  in a locking action  24 . The locking action  24  is realized between grip member  22  and cyclone preseparator  26  arranged upstream of the filter housing. 
         [0039]    As can be seen also in the perspective illustration according to  FIG. 1 , the cyclone preseparator  26  is connected with the filter housing  12  by means of a screw guide  86 , i.e., by a screw connection. In this way, a butt joint  28  between the cyclone preseparator  26  and the filter housing  12  is seal-tightly closed so that no foreign air intake can be sucked in which has circumvented the cyclone preseparator  26 . 
         [0040]    The servicing cover  18  has a projection  32  that as illustrated in  FIG. 1  covers seal-tightly the filter housing  12  and the housing compartment formed therein. 
         [0041]    The cyclone preseparator  26  illustrated in  FIG. 1  and positioned at the inlet side  14  as well as the filter housing  12  and the servicing cover  18  are manufactured as injection-molded plastic parts. This enables on the one hand an inexpensive mass production and on the other hand also the formation of reinforcement ribs on the hinges or the grip member  22  and the opening  30  formed therein within a single processing step. For mounting, the cyclone preseparator  26  is simply screw-connected in the screw guides  86  extending laterally along the filter housing  12  so that a seal-tight connection between the filter housing  12  and the cyclone preseparator arranged upstream at the inlet side  14  is provided. When the components filter housing  12  and cyclone preseparator  26  are joined by the screw guides  86 , the servicing cover  18  can be inserted in a simple way into the hinges  20  and with a slight deflection movement of the grip member  22  can be opened. 
         [0042]    The illustration according to  FIG. 2  shows a perspective representation of the servicing cover according to the illustration in  FIG. 1 . 
         [0043]    The servicing cover  18  comprises in addition to the projection  32  a circumferential collar  34  and the grip member  22  on the side opposite the at least one hinge  20 . The grip member  22  comprises according to the embodiment of the servicing cover  18  of  FIG. 2  an opening  30 . Of course, it is also possible to manufacture the grip member  22  without the aforementioned opening  30  illustrated in  FIG. 2 . On the topside of the servicing cover  18  between longitudinal edges of the servicing cover  18  reinforcement ribs extend from the grip member  22  to the two hinges  20  of this embodiment that are positioned adjacent one another and spaced apart from one another. Since the servicing cover  18  also is a plastic part produced by injection molding, the reinforcement ribs, the grip member  22 , the projection  32 , the circumferential collar  34  as well as the hinges  20  can be produced without problems in a single processing step without requiring any fine processing. 
         [0044]      FIG. 3  shows a longitudinal section of the filter device proposed according to the invention in accordance with the perspective illustration in  FIG. 1 . 
         [0045]    In the illustration according to  FIG. 1  it can be seen that the filter device  10  comprises on the inlet side  14  the cyclone preseparator  26  and that in the filter housing  12  of the filter device  10  at the outlet side  16  a secondary filter element  38  is received. Downstream of the cyclone preseparator  26  within the filter housing  12  the main filter element  36  that is preferably embodied as a double bellows is in its locked position in the filter housing  12 . An opening in the filter housing  12  is closed off by the closed servicing cover  18 . The closed servicing cover  18  comprises a rib structure  52  that extend substantially in the longitudinal direction from the grip member  22  to the at least one hinge  20 . The rib structure  52  stiffens the servicing cover  18  mechanically. 
         [0046]    The grip member  22  in the illustration according to  FIG. 3  is received in a locking action  24  which is formed in the cyclone preseparator  26 . In the cyclone preseparator  26  according to the section illustration of  FIG. 3  a recess  54  is formed. In the closed state of the servicing cover  18 , its grip member penetrates into this recess. The locking action  24  is produced by the recess  54  in interaction with a locking depression  56  on the grip member  22 . 
         [0047]    As shown in  FIG. 3 , the main filter element  36  is embodied preferably as a double bellows filter element with inwardly positioned first filter bellows  40  that has a conical shape as well as an outwardly positioned second filter bellows  42  that is substantially cylindrical. Between the second filter bellows  42  and the first filter bellows  40  a support structure  50  is provided. The support structure  50  maintains the geometry of a flow space that is facing at the outlet side the secondary filter element  38 . The support structure  50  is preferably formed by a plastic construction that comprises ribs extending axially and in the circumferential direction. 
         [0048]    At the inlet side the first filter bellows  40  and the second filter bellows  42  are closed off by an annular cover  46  while the interior  44  is closed off in axial direction by the cover disk  48 . In this way, the filter bellows  40  and  42  of the main filter element  36  are substantially flowed through in radial direction and the filtered fluid flows out through the space that opens conically at the outlet side and in which the support structure  50  that also has a conical shape is received. 
         [0049]    Preferably, the annular cover  46  and the cover disk  48  of the main filter element  36  are connected by foaming to the axial end faces of the filter bellows  40  and  42 . This has advantages with regard to manufacturing technology. 
         [0050]      FIG. 4  shows the locking action of the servicing cover  18  on the cyclone preseparator  26  of the filter device proposed according to the invention in enlarged perspective illustration. 
         [0051]      FIG. 4  shows that the servicing cover  18  with its rib structure  52  extending in the longitudinal direction is locked on the cyclone preseparator  26 . The butt joint  28  between the filter housing  12  and the cyclone preseparator  26  is sealed in that the cyclone preseparator  26  is screw-connected by means of the screw guides that are illustrated in  FIG. 1  and identified with reference numeral  86  with the filter housing and therefore the butt joint  28  is sealed as a result of the pretension generated by the screw connection. This prevents that through the butt joint  28  unfiltered fluid, i.e., fluid that has not passed through the cyclone preseparator  26  and is particle-loaded, reaches the main filter element  36 . 
         [0052]    As also illustrated in the illustration of  FIG. 4 , the locking depression  56  that is formed on the grip member  22  with openings  30  is locked at a counter member  58  within the recess  54  of the cyclone preseparator  26  so that in this way the locking action identified by reference numeral  24  is realized. In this state, the servicing cover  18  is permanently secured in its closed position. The grip member  22  on which the opening  30  is formed projects into the recess  54  of the cyclone preseparator  26  to such an extent that the counter member  58  of the cyclone preseparator  26  can engage the locking depression  56  of the grip member  22 . For releasing the locking action that is identified by reference numeral  24  the grip member  22  is deflected laterally within the recess  54  of the cyclone preseparator  26 . In this way, the locking action  24  between the counter member  58  of the cyclone preseparator  26  and the grip depression  56  of the grip member  22  is released and opening of the servicing cover  18 , rotatably supported on the filter housing by at least one hinge  20 , is possible with one hand without a problem. 
         [0053]      FIG. 5  shows premounting of the main element that is embodied preferably as a double bellows filter in the housing compartment of the filter housing of the filter device proposed according to the invention. 
         [0054]    As can be seen in the perspective illustration according to  FIG. 5 , the main filter element  36  is inserted in the installation direction  60  into the housing compartment  68  of the filter housing  12 . The illustration according to  FIG. 5  shows that the main filter element  36  on the one hand has at the inlet side the annular cover  46  that covers the axial end faces of the two filter bellows  40 ,  42  combined to the main filter element  36 . At the outlet side, the main filter element  36  has the circumferential rim  72  on which a grip tap  62  is integrally injection-molded. The annular cover  46  surrounds an opening through which the fluid that has passed through the cyclone preseparator  26  flows into the interior  44  of the main filter element  36 . 
         [0055]    The perspective illustration according to  FIG. 5  shows that the sidewalls of the filter housing  12  that adjoin the housing compartment  68  are provided with insertion stays  64  that optionally may be made stiffer by means of reinforcement ribs  70 . 
         [0056]    The main filter element  36  that is gripped with one hand by the grip tab  62  is inserted along the insertions stays  64  into the housing compartment  68  of the filter housing  12  of the filter device  10 . The farther the circumferential rim  72  extending about the topside of the main filter element  36  is inserted along the insertion stays  64  in the insertion direction, the farther the circumferential rim  72  on which the seal  76  is formed is positioned on the contact surface  66  of the filter housing  12  facing the secondary filter element  68 . The geometry of the insertion stays  64  prevents false mounting of the main filter element  36  because upon rotation of the filter element  36  about 180 degrees, in comparison to the illustration according to  FIG. 5 , its insertion into the housing compartment  68  is no longer possible because of the insertion stays  64  that laterally project from the sidewalls of the housing compartment  68 . 
         [0057]      FIG. 5  shows that on the lateral boundary walls of the housing compartment  68  of the filter housing  12  below the insertion stays  64  the screw guides  86  are formed that extend substantially in horizontal direction. 
         [0058]    The illustration according to  FIG. 5  also shows that the secondary element  38  that is received in a funnel-shaped constricted portion of the filter housing  12  also can be exchanged with a one-hand operation as long as the main filter element  36  has not yet been inserted into the housing compartment  68  of the filter housing  12 . 
         [0059]    The secondary filter element  38  can be inserted simply into integrally injection-molded cupola-shaped projections in the funnel-shaped area of the filter housing  12  at the outlet side  16  and can be secured therein without further measures. The cupola-shaped projections serve as a defined terminal stop for the secondary filter elements  38 . 
         [0060]    As a result of the oversize of the streamy injection-molded parts in the funnel-shaped area of the filter housing  12  at its outlet side  16  the secondary filter element  38  is secured therein. 
         [0061]      FIG. 6  shows the positioning of the main filter element  36  premounted in the housing compartment of the filter housing  12  when closing the servicing cover  18 . 
         [0062]    The illustration according to  FIG. 6  shows that the main filter element  36  along the insertion stays  64  has been completely inserted along the lateral surfaces of the housing compartment  68  into the latter. In this connection, the servicing cover  18  may be pivoted either into an open position or it may be removed from the integrally injection-molded hinges  28  whose counterpart is integrally injection-molded onto the filter housing  12 . The main filter element  36  is gripped at the grip tab  62  that is integrally injection-molded on the circumferential rim  72  and inserted into the housing compartment  68  of the filter housing  12  of the filter device  10  proposed according to the invention. 
         [0063]    After complete insertion of the main filter element  36  into the housing compartment  68  of the filter housing  12  as illustrated in  FIG. 6 , the main filter element  36  is pre-positioned in the housing compartment  68 . Now the servicing cover  18  that is in the open position is pushed downwardly about its hinges  20  in the closing direction so that a locking action  24  is created between the locking depression  56  of the grip member  22  and its counterpart  58  and the cyclone preseparator  26  of the filter device  10  proposed in accordance with the invention. During closing of the servicing cover  18 , i.e., during the one-hand closing movement of the servicing cover  18 , shoulders  74  that are integrally injection-molded thereon in the area of the circumferentially extending collar  34  engage the circumferential rim  72  of the main filter element  36 . As a result of the ramp-shaped structure of the insertion stays  64  the main filter element  36  upon its insertion into the housing compartment  68  is already positioned very close to the contact surface  66  of the housing compartment  68  of the filter housing  12 . When closing the servicing cover  18 , contacting of the circumferential rim  72  is realized by means of the shoulders  74  of the servicing cover  18  that engage the circumferential rim so that the seal  76  on the topside of the circumferential rim  72 , compare illustration according to  FIGS. 7-9 , is seal-tightly moved against the matching contact surface  66  of the housing compartment  68  of the filter housing  12 . In this way, the sealing force that pushes the seal  76  against the contact surface  66  of the filter housing  12  is generated by the shoulders  74  when closing the servicing cover  18 . The sealing action is realized in radial direction wherein for maintaining the sealing position a force is required that acts in the axial direction. 
         [0064]    Wrong premounting of the main filter element  36  is prevented, on the one hand, by the configuration of the insertion stays  64  on the lateral surfaces of the housing compartment  68  and, on the other hand, in that the screw guides  86  extend horizontally on the lateral surfaces of the housing compartment  68  below the insertion stays  64 . The screw guides  86  serve for receiving screws with which the cyclone preseparator  26 , with formation of a seal-tight butt joint  28 , is screw-connected to the filter housing  12  of the filter device  10  proposed according to the present invention. By means of the axial pretension generated by the screw connection, the butt joint  28  between the cyclone preseparator  26  and the filter housing  12  is achieved. 
         [0065]      FIGS. 7 ,  8 , and  9  show embodiment variants of the circumferential rim of the exchangeably configured main filter element  36 . 
         [0066]    The illustration according to  FIG. 7  shows that the circumferential rim  72  of the main filter element  36  according to the illustrations in  FIGS. 5 and 6  is injection-molded from a plastic material  84 . When injection molding the circumferential rim  72 , the rim is designed such that with the injection process of the circumferential rim  72  of a plastic material  84 , to which the grip tab  62  is directly integrally injection-molded, and when manufacturing the circumferential rim  72  at the same time a plastic stabilization blade  78  is integrally injection-molded. The latter may comprise penetrations  80  that are separated from one another by webs. These penetrations  80  have the task, compare also illustration according to  FIG. 9 , that the seal  76  that is integrally injection-molded of a material, for example, PUR, having elastic properties, may flow into the penetrations  80  of the stabilizing blade  78  of the circumferential rim  72  so that a positive-locking and material-liquid connection of the seal  76  with the stabilizing blade  78  as a result of flowing of the PUR material into the penetrations  80  is achieved. This means that a seal  76  produced in this way can survive a large number of load changes because a mechanically stable connection between the seal  76 , upon closing of the servicing cover  18 , at the contact surface  66  of the housing compartment  68  and the circumferential rim  72  can be achieved. 
         [0067]    In the illustration according to  FIG. 8  it is shown that the main filter element  36  has integrally injection-molded thereto, compare  FIG. 5 , the annular cover  46  in which the two filter bellows  40  and  42 , not illustrated in  FIG. 8 , are foamed in with their axial end faces. The illustration according to  FIG. 8  also shows that in the area of the circumferential rim  72  the interior  44  is closed off by the cover disk  48 . On the bottom side or topside of the circumferential rim  72 , as shown in the perspective illustration according to  FIG. 8 , the grip tab  62  is integrally injection-molded and enables a one-hand exchange of the main filter element  36 , with the servicing cover  18  in the open position, from the housing compartment  68  of the filter housing  12  of the filter device  10  proposed according to the invention. 
         [0068]    The illustration according to  FIG. 9  is a perspective top view onto a circumferential rim  72 . The circumferential rim  72  which is located at the topside of the main filter element  36  is produced from a blade material  84  which is significantly more stable than the material of which the seal  76  is subsequently injection-molded. The material of which the seal  76  is injection-molded is a plastic material which has substantially better elasticity properties and therefore, when producing the seal  76 , flows also through the penetrations  80  in the stabilizing blade  78  at the circumferential rim  72  and therefore generates an integrally injection-molded connection between the sealing material  76  and the material of which the stabilizing blade  78  or the circumferential rim  72  is injection-molded. 
         [0069]    In the illustration according to  FIG. 8  the seal  76  is illustrated that extends about the stabilizing blade  78  and is comprised of material such as PUR material  82 , an easily foamable plastic material. 
         [0070]      FIG. 10  shows a tear-off seal provided on the filter element which in the perspective illustration according to  FIG. 10  is located on an inner side  92  of the filter bellows  40  or  42 . The tear-off seal  90  is enclosed by a plastic frame  88 ; an exterior side of the filter bellows  40  or  42  is characterized by reference  94 . 
         [0071]      FIG. 11  shows a seal  76  on a filter bellows  40  or  42  which again surrounds a cover. The seal  76  that is preferably embodied as a circumferential seal is foamed of a materials such as PUR. 
         [0072]    The illustration according to  FIG. 12  is a simplified representation of the folding geometry of a filter bellows. The folding geometry  96 , here embodied as a star-shaped fold arrangement  104 , is flowed through in the flow direction  102  by raw air  98  that is unfiltered. The reference numeral  100  indicates the filtered clean air that exits from the filter material in which the separated particles remain. The folding geometry  96  schematically indicated in  FIG. 12  that is a star-shaped folding arrangement  104  is characterized by a distinct zigzag contour of peaks and valleys which is embodied oval or circular on a filter bellows  40  or  42 . 
         [0073]      FIG. 13  shows a filter element that is pressed by means of a leaf spring in the housing axially against a seal seat. In order to facilitate servicing of element, a pressure action can be generated in two stages (I and II). These two stages are realized by “bumps” of different height in the spring. Until the first stage is reached the filter element rests freely in its guide. When the element is pushed across the first stage, the lower part of the seal is pressed onto the seal seat. When the element is pressed farther into the seal seat, by means of a correspondingly shaped ramp on the filter element terminal disk, the second stage is reached and also the upper part of the seal is pressed against the seal seat. The end position is defined by an undercut that is provided on the terminal disk. This undercut secures the element in its end position in the vertical direction and provides a haptic feedback to the person performing servicing of the element.