Abstract:
A filter apparatus including a housing ( 2 ) and a filter insert ( 4 ), with an inlet opening formed on the housing ( 2 ) and an outlet fitting ( 6 ) mounted on a housing wall. The outlet fitting ( 6 ) has a contact face ( 7 ) for contact with the housing ( 2 ) and is provided with a tubular segment ( 13 ), which protrudes through an opening ( 9 ) of the housing, and a mounting element ( 22 ) is attached to the tubular segment ( 13 ) such that a region ( 10 ) of the housing ( 2 ) surrounding the opening ( 9 ) is clamped between the contact face ( 7 ) of the outlet fitting ( 6 ) and the mounting element ( 22 ).

Description:
BACKGROUND OF THE INVENTION 
   The present invention relates to a filter apparatus comprising a housing and a filter insert arranged in the housing between an inlet opening and an outlet. 
   U.S. Pat. No. 5,882,367 discloses a filter apparatus in which a filter cartridge is disposed in a substantially cylindrical housing. On the lateral surface of the filter housing, an inlet opening is provided, which communicates with an annular space formed between the filter cartridge and the housing. Within the filter cartridge, a chamber is formed from which the filtered air is discharged through an outlet fitting. The outlet fitting is fixed in snap-in relation to the end face of the housing. 
   In this known arrangement, the connection fitting for the air outlet is inserted into an opening of the housing in snap-in relation. For this purpose, the material of the housing must, on the one hand, be sufficiently elastic to enable the temporary deflection necessary for the snap-in connection. On the other hand, the material must have sufficient rigidity to hold the connection fitting securely on the housing. These requirements can at best be satisfied by expensive synthetic resin materials, which would, however, result in very expensive filter devices and therefore do not usually come into consideration. 
   SUMMARY OF THE INVENTION 
   An object of the present invention is to provide an improved filter apparatus. 
   Another object is to provide a filter apparatus in which a dimensionally stable and play-free arrangement of the outlet fitting on the housing can be achieved in a simple manner. 
   A further object of the invention is to provide a filter apparatus having a housing with an outlet fitting mounted thereof which can be produced in a cost effective manner. 
   These and other objects are achieved in accordance with the present invention by providing a filter apparatus comprising a housing with an inlet opening formed therein and a further opening formed in a housing wall; a filter insert arranged in the housing in a flow path between the inlet opening and the further opening; an outlet fitting having a tube segment which protrudes through the further opening and a contact face for contacting the housing wall surrounding the further opening; and a mounting element affixed to the tube segment such that a region of the housing surrounding the further opening is clamped between the contact face of the outlet fitting and the mounting element. 
   In the present invention, a filter device is provided in which the outlet fitting is mounted play-free on the housing. Due to the possible material selection, high stiffness and a long service life of the connection can be achieved. Because the region of the housing surrounding the opening receiving the outlet fitting is clamped between a contact face of the outlet fitting and the mounting element, no additional sealing means are required. The play-free arrangement is achieved in that any dimensional tolerances of the parts to be mounted are compensated in a simple manner. A further advantage is that the entire system can be easily adjusted through a strict separation between holding forces and mounting forces. For outlet fittings that extend in a curve, an adjustment in the desired direction of the outlet is possible even after mounting. 
   According to a preferred embodiment of the invention, a mounting ring is provided as the mounting element, which is fixed to the lateral surface of the tube segment. This mounting ring has the advantage that it can be easily mounted to the tube segment and forms a support face over the entire circumference of the opening relative to the housing, so that sufficient contact force is provided even though the surface pressure is low. It is furthermore advantageous that the contact face of the outlet fitting is formed on an annular flange of the outlet fitting. 
   One advantageous embodiment for fixing the mounting ring on the tube segment is that a snap-in or locking connection is provided. As a result, the mounting ring only needs to be pushed onto the tube segment until it automatically snaps into place. For the design of the snap-in or locking connection it is advantageous if at least one circumferential projection is formed either on the tube segment or on the mounting ring and cooperates with a radial projection or a radial recess formed on the other component. Because the projection is circumferential, no special rotational position of the mounting ring is required in relation to the tube segment, so that mounting is further simplified. On the other hand, the holding forces are distributed over the entire circumference. 
   In another embodiment of the locking connection it is advantageous that both the tube segment and the mounting ring are provided with a circumferential projection, and an insertion taper or an inclined insertion surface are provided in front of the respective projection as seen in mounting direction. This configuration of an insertion taper or an inclined insertion surface causes a gradual widening or constriction until the maximum required dimensional change is reached, so that any impermissible mechanical stress of the material is avoided. It is considered a further advantageous measure that, behind the respective projection or recess as seen in mounting direction, a wedge-shaped geometry is formed by the inclined faces, which causes the mounting ring to be securely seated in the region of the housing which surrounds the opening for receiving the tube segment, and the ring is furthermore pressed against this region with a corresponding force. In a further embodiment of the locking connection, an annular groove may be provided on the tube segment, which is limited by the inclined face and with which the projection formed on the mounting ring engages. As a result of this measure, greater radial widening is required in the extraction direction of the mounting ring, so that the mounting ring is secured on the tube segment with a high holding force. 
   In an alternative kind of attachment of the mounting ring on the tube segment, the mounting ring has an internal thread and the tube segment an external thread, so that the mounting ring is screwed onto the tube segment. In this type of attachment, the mounting ring is screwed far enough onto the tube segment until the region of the housing surrounding the opening is clamped between the annular flange of the connection fitting and the mounting ring. To further secure the mounting ring on the tube segment, it is considered advantageous if a device preventing unscrewing is provided on the mounting ring and/or the tube segment. In this manner, the mounting ring is secured on the tube segment even if the outlet fitting is rotated relative to the housing in a direction that corresponds to the unscrewing direction of the thread. 
   In yet another embodiment, the mounting ring can have a radially outwardly directed flange on which one end of the filter insert rests. Preferably, the housing has a substantially cylindrical form, and the filter insert is configured as a filter cartridge. In an embodiment of this kind it is advantageous if the outlet fitting is disposed on an end face of the housing and centric relative to the filter cartridge. To support the filter material against radially inwardly acting forces in the filter cartridge, it is advantageous if a support grid extending within the filter cartridge at least across a portion of the axial length is disposed at the free end of the tube segment. The support grid can be formed of the same material as the connection fitting, such that an integral production is preferred. 
   In another advantageous embodiment, an axial segment is formed at the end face of the housing and merges into a radial shoulder in which is located the opening that allows the tube segment to pass through. This radial segment forms a corresponding space for the mounting ring. A configuration of this type is dimensionally stable even if the walls are relatively thin. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The invention will be described in further detail hereinafter with reference to illustrative preferred embodiments shown in the accompanying drawing figures, in which: 
       FIG. 1  is an exploded view showing parts of a filter apparatus according to the invention; 
       FIG. 2  is a longitudinal section of the upper part of the filter housing showing a portion of the connection fitting and the mounting ring; 
       FIG. 3  is a slightly enlarged detail view of the section shown in  FIG. 2  with the fitting in locked condition; 
       FIG. 4  shows an outlet fitting with a thread for screwing on a mounting ring; 
       FIG. 5  is an enlarged detail view V from  FIG. 4 ; 
       FIG. 6  is an enlarged perspective representation of the mounting ring, and 
       FIG. 7  is an enlarged detail view VII from  FIG. 6 . 
   

   DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
     FIG. 1  shows an air filter  1  with a housing  2 , which is substantially cylindrical. On the lower margin  15  of the housing  2 , a lower housing section is disposed, which is not depicted in the drawing. To this end, the lower margin  15  has a plurality of projections  16  which are distributed across the circumference and engage the other housing section in a form-fit connection. On the lateral surface of the housing  2 , an inlet fitting  3  is provided in which an inlet opening is formed. At one end face  8  of the housing  2  an outlet fitting  6  is disposed, which has an annular flange  7 , from which a tube segment  13  extends into the interior of the housing  2 . A filter element, which in the embodiment depicted in  FIG. 1  is a filter cartridge  4 , is inserted into the housing  2 . At each of its axial ends, this filter cartridge  4  has a closure  5  formed of an elastic material, for example, in which the ends of the filter material are embedded.  FIG. 1  furthermore shows a mounting ring  22 , which is pushed onto the tube segment  13  of the outlet fitting  6  from the inside and is fixed thereto. 
     FIG. 2  is a longitudinal section of the upper area of the housing  2  during mounting of the connection fitting  6  to the end face  8 . On the connection fitting  6 , below the annular flange  7 , is located the tube segment  13 , at the free end of which, i.e. facing the interior of the housing  2 , a support grid  14  is formed. The connection fitting  6  is inserted, with the support grid  14  first, through the centric opening  9  of the end face  8 . The connection fitting  6  is inserted far enough until the annular flange  7  contacts a radial shoulder  10  of the end face  8  of the housing  2 . The radial shoulder  10  is formed onto an axial segment  11  of the end face  8 . 
   As  FIG. 2  further shows, the tube segment  13 , on its outer lateral surface has an annular groove  17 , on whose end which faces the interior of the housing  2 , a circumferential projection  20  is provided. The circumferential projection  20  has an insertion taper  19  as seen in mounting direction, i.e., in the insertion direction of the tube segment  13 , and an inclined face  18  sloping toward the annular groove  17 . A mounting ring  22  having a circumferential projection  24  on its inner lateral surface is pushed over the support grid  14 . As seen in mounting direction, i.e. toward the radial shoulder  10 , the inner contour is configured as an inclined insertion surface  25 , so that, as the tube segment  13  and the mounting ring  22  are pushed into each other, a gradual widening is effected by the insertion taper  19  and the inclined insertion surface  25 . Adjacent the other side of the circumferential projection  25  is an inclined face  26 , the angle of which corresponds at least substantially to the inclined face  18  on the tube segment  13 . On the side facing the filter cartridge  4 , the mounting ring  22  has a radial flange  23 . 
     FIG. 2  shows a portion of the filter cartridge  4 , but the filter cartridge is not inserted into the housing  2  until after the connection fitting  6  has been fixed to the end face  8  of the housing  2  by snapping the mounting ring  22  onto the tube segment  13 . As may further be seen from  FIG. 2 , an annular space  12 , into which opens the inlet fitting  3  depicted in  FIG. 1 , is located between the wall of the housing  2  and the filter cartridge  4 . 
     FIG. 3  shows a slightly enlarged detail from  FIG. 2  in the mounted state of the connection fitting  6  on the end face  8  of the housing  2 . Here, the annular flange  7  rests on the radial shoulder  10 . The mounting ring  22  is pushed far enough onto the tube segment  13  that the circumferential projection  24  engages the circumferential projection  20  on the tube segment  13 . The inclined faces  18  and  26  form a wedge-shaped geometry that presses the mounting ring  22  against the inside of the radial shoulder  10 , so that the radial shoulder  10  is clamped between the annular flange  7  and the mounting ring  22 . The circumferential projection  24  is located within the annular groove  17  on the tube segment  13 . The function of the inclined insertion surface  25  and the insertion taper  19  has already been explained with reference to  FIG. 2 . 
     FIG. 4  depicts a connection fitting  6 ′ having an annular flange  7 ′, a tube segment  13 ′ and a support grid  14 ′, the tube segment being provided with an external thread  27 . The external thread  27  has a small pitch and enables the mounting ring  30  depicted in  FIG. 6 , which is provided with a corresponding internal thread  28 , to be screwed onto the tube segment  13 ′. The radial shoulder  10  (see  FIGS. 2 and 3 ) is received between the annular flange  7 ′ and the mounting ring  30 , such that a tight seal is formed at the point where the tube section  13 ′ penetrates the shoulder  10 . The mounting ring  30  has a radial flange  23 ′. 
   As may be seen from  FIGS. 4 and 6  and, in particular, the enlarged details depicted in  FIGS. 5 and 7 , the respective thread  27 ,  28  is provided with devices which prevent a reverse rotation of the mounting ring  30  relative to the tube segment  13 ′ once a defined mounting state has been reached, i.e., the mounting ring  30  has been screwed onto the tube segment  13 ′. These devices comprise, on the one hand, a tab  29  extending along a thread section and disposed at the end of the external thread  27  adjacent the annular flange  7 . The tab  29  is deflectable in axial direction of the tube segment  13 ′ by a certain path if the latter is loaded in that direction. At the free end of the tab  29 , the tab is provided with a locking edge  31 . Spaced at a distance behind the locking edge  31  in thread direction, a stop  33  is formed. 
   On the other hand, the devices comprise a locking projection  32 , which is formed on the internal thread  28 , namely at its front end as seen in screw-on direction. The height of the locking projection  32  is axially dimensioned in such a way that there is sufficient play in the flight of the external thread  27  so that the mounting ring  30  can be easily screwed on. When the tab  29  is reached, the locking projection presses the tab  29  toward the annular flange  7 ′. As soon as the locking projection  32  has fully passed the locking edge  31 , the tab  29  springs back, so that the locking edge  31  engages the locking projection  32 . This forms a lock against reverse rotation to secure the mounting ring on the tube fitting  13 ′. To prevent further rotation in screw-on direction in the predefined position, a stop  33  visible in  FIG. 5  is provided. 
   As soon as the connection fitting  6 ,  6 ′ is mounted to the housing  2  in the above-described manner, the filter cartridge  4  can be inserted into the housing  2 , with the support grid  14 ,  14 ′ protruding into the central space of the filter cartridge  4 . The filter cartridge  4  is inserted far enough so that the end face closure  5  rests on the radial flange  23 ,  23 ′ of the mounting ring  22 ,  30  and on support elements  21  on the inside of the end face  8  of the housing  2 . 
   The foregoing description and examples have been set forth merely to illustrate the invention and are not intended to be limiting. Since modifications of the described embodiments incorporating the spirit and substance of the invention may occur to persons skilled in the art, the invention should be construed broadly to include all variations within the scope of the appended claims and equivalents thereof.