Abstract:
A filter apparatus has a filter housing ( 1 ) accommodating at least one filter element ( 17 ) having an inner filter cavity ( 23 ) enclosed by a filter medium ( 27 ). The housing ( 1 ) contains an element holder ( 19 ) that interacts with the filter element ( 17 ) located in its functional position. The element holder ( 19 ) has a projecting accommodating part ( 43 ) with an outer configuration adapted to the shape of an opening ( 37 ) located at the end of the filter element ( 17 ) to be secured to the element holder ( 19 ). The accommodating part ( 43 ) fits through the opening ( 37 ) of the filter element ( 17 ) located in the functional position.

Description:
FIELD OF THE INVENTION 
     The invention relates to a filter apparatus having a filter housing that accommodates at least one filter element having an inner filter cavity enclosed by a filter medium. The housing contains an element holder that interacts with the filter element, when the filter element is in the functional position. The invention further relates to a filter element that is provided for use inside such a filter apparatus. 
     BACKGROUND OF THE INVENTION 
     Filter devices of this kind are known from the prior art. They are widely used in configurations varying in terms of the structural type, size and/or pressure level thereof, for the filtration of the most varied technical fluids, such as hydraulic fluids, cooling lubricants, fuels, lubricating oils, and the like. Since operating disturbances, which disturbances can range as far as to failure of such filter devices, are potentially responsible for damaging or destroying the systems downstream of where the damage occurred and can cause considerable financial damage, the operational reliability of such filter devices is of great importance. Therefore, when operating such filter devices, it must be ensured that, on the one hand, the filtration process is performed using a filter element that is in the ready state and disposed inside the filter housing and, on the other hand, that the specifications of a filter element that is used in this process are precisely matched to the operational requirements of the associated system with regard to the quality of the filter, assignment to the corresponding pressure level, flow resistance and the like. 
     SUMMARY OF THE INVENTION 
     An object of the present invention to provide an improved filter apparatus with increased reliability to protect against malfunctions during the filtering process. 
     According to the invention, this object is basically achieved with a filter apparatus including, as an essential special aspect of the invention, an element holder provided inside the filter housing and including a projecting accommodating part for securing the respective filter element. The exterior shape of the projecting accommodating part is adapted to the shape of an opening disposed on the end of the related filter element that must be secured on the accommodating part of the element. The accommodating part then fits through the opening of the filter element, when the filter element is in the functional position. This way, only such filter elements are ensured to be brought in the functional position inside the filter housing that allow for the appropriate projecting accommodating part, which accommodating part is matched to the shape of the element holder, to fit through the opening. This way, the risk of using filter elements that are not compliant with the specifications in terms of the filter quality, the permissible pressure level and the like, can be avoided, thereby providing better operational reliability. 
     In especially advantageous embodiments, the accommodating part of the element holder is disposed such that it extends, when the related filter element is in the functional position thereof, into an accommodating space that is disposed on an allocated end cap and reaches into the inner filter cavity. With this structural design, it is ensured that, were an attempt made at inserting a wrong filter element, a filter element that does not have an accommodating space at the element holder thereof for the accommodating part that extends into the interior of the filter cavity, the insertion movement of the filter element would be blocked prior to reaching the functional position in that the accommodating part would be stopped, and thereby blocked, by the end cap. Thus the operator is provided with a clear signal that insertion of the “wrong” filter element is being attempted. 
     Preferably, the accommodating part, provided for the engagement in the opening of the accommodating space of the filter element, has a shape that is not round. 
     In especially preferred embodiments, the accommodating part can be configured in the manner of a spike, and the accommodating space on the element holder can be configured in the manner of a dome. 
     Especially advantageously, the chosen apparatus can provide that the spike has planar surface portions along the circumference thereof that define a cross section that has the shape of four straight sides that are inscribed in a square. The size of the cross section of the spike becomes smaller toward the top, free end thereof. Due to the slender, free end of the spike, achieving the engagement with the dome is especially easy and convenient. 
     The non-round shape of the spike having planar surface portions along the circumference thereof and the corresponding non-round shape of the opening of the accommodating dome require a corresponding relative rotational position between the filter element and the spike to engage in the accommodating dome. Especially preferred embodiments rotatably support the spike on a shaft disposed on the element holder extending into a central bore of the dome. When combining the accommodating dome and the spike, the spike positions itself automatically by the more slender free end in the rotary position that is necessary for the combining action. 
     In especially advantageous embodiments, the shaft has a collar that secures the spike, against, against any axial movement that is directed away from the respective filter element. 
     To protect against any lifting action of the spike from the shaft in the other direction, a snap ring is provided on the shaft. The snap ring acts in conjunction with a groove disposed in the central bore of the spike, thereby axially securing the spike. 
     The shaft can be screwed into a sealable oil discharge opening of the filter housing, producing an especially simple and compact structural assembly. 
     For the oil discharge opening to be able to fulfill its discharge function despite the shaft, which is screwed thereto, the apparatus can be especially advantageously provided with an internal fluid path between the exterior of the collar and the discharge opening of the housing. Even when the shaft is screwed in, opening a discharge screw on the discharge opening will then allow for a discharge to occur. 
     Another object of the present invention seeks to provide a filter element for use in that filter apparatus, wherein the filter element has the appropriate characteristics described above. 
     Further configurations of the filter element are also set forth hereinafter. 
     Other objects, advantages and salient features of the present invention will become apparent from the following detailed description, which, taken in conjunction with the annexed drawings, discloses preferred embodiments of the present invention. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Referring to the drawings that form a part of this disclosure: 
         FIG. 1  is a perspective view, partially in section of a filter apparatus according to an exemplary embodiment of the invention; 
         FIG. 2  is a perspective view of the filter element of  FIG. 1  installed inside a filter housing of a common structural type; 
         FIG. 3  is a greatly enlarged, exploded perspective view showing only the end cap of the filter element and the element holder of the filter housing of  FIG. 1 ; 
         FIG. 4  is a side view of a shaft of the element holder of  FIG. 3 ; 
         FIG. 5  is a side view in section of the shaft of  FIG. 4 ; 
         FIG. 6  is a side view in section of only one spike serving as the accommodating part for the element holder of  FIG. 3 ; 
         FIG. 7  is a top view of the spike of  FIG. 6 ; 
         FIG. 8  is a bottom perspective view of only the end cap of the filter element of  FIG. 1 ; and 
         FIG. 9  is a top perspective view of the end cap of  FIG. 8 . 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       FIG. 1  shows an embodiment of the filter apparatus according to the invention that is provided for the filtration of pressurized fluids. The filter housing  1 , which defines a vertical axis  3 , includes a cylindrical main part  5  that has a head part  7  screwed to the top end thereof. At the bottom end, the main part  5  is closed, except for a discharge opening  9 , and a discharge screw  11  is screwed into the internal thread of the discharge opening. The top head part  7  includes a connection inlet  13  for inflowing unfiltered fluid and a connection or outlet  15  for the filtrate out flow. Fluid paths that are disposed within the head part  7  and that correspond to the pertinent prior art, are not depicted in further detail, and connect the connection  13  and  15  to the untreated side and the clean side of the respective filter element  17  retained inside the housing  1 . A bypass device inside the head part  7  creates a secondary closure, if necessary, also corresponding to the prior art. 
     The filter housing  1  is cut open in the drawing along the longitudinal axis  3  such that the exterior of the filter element  17  is visible. The same is also depicted as cut open in a bottom longitudinal section, by which the filter element  17  is mounted in an element holder  19  on the floor  21  of the filter housing  1 . This drawing opens up a view to the inside upon the filter cavity  23  that is coaxially disposed relative to the vertical axis  3  and surrounded by a fluid-permeable support pipe  25 . In turn, a filter medium  27  that constitutes a hollow cylinder is disposed on hollow pipe  25 . During the filtration process, the filter medium receives the flow-through from the exterior, which constitutes the untreated side  29 , toward the filter cavity  23 , which constitutes the clean side. 
     The element holder  19  of the filter housing  1  that serves to secure the filter element  17  in its functional position, as shown in  FIG. 1 , and interacts with an end cap  31  of the filter element  17  as shown more clearly from  FIGS. 3 to 9 . The end cap  31  includes a projecting rim  33 , as known from the prior art, that is allocated to the end region of the filter medium  27  framing the same. An essential difference in contrast to common end caps presently lies in the fact that the end cap  31  includes a body provided as a component fashioned in one piece therewith. That body is centrally disposed, extends along the vertical axis  3  into the interior of the filter element  17 , has the shape of an inverted goblet or a dome  35  and is tapered from the end-side opening  37  thereof (see particularly  FIG. 8 ) toward the internal end. The dome  35  then constitutes an internal accommodating space  39  in the manner of a sleeve, which is also tapered toward the internal end. An opening of the accommodating space  39  that is disposed at the internal end can be sealed by a screw  41 . Instead of the screw  41 , the use of a plug, preferably manufactured of a sintered metal, is also possible, which can be driven into the corresponding opening. The sintered metal material has a certain degree of porousness, whereby a pressure equalization is possible with the closure plug placed on the filter element, while also achieving a kind of a small filter that is able, when it is disposed inside the filter, to separate even the finest particle impurities. To this end, the closure screw  41  could also be made of a sintered metal material with a predefinable porousness. 
     The element holder  19  includes an accommodating part in the shape of a spike  43  accommodated inside the accommodating space  39  of the dome  35 , when the filter element  17  is in its functional position. As can be derived from  FIGS. 3, 6 and 7 , the spike  43  has a non-round shape, wherein planar surface parts  45  are provided along or about the circumference of the spike  43  in the longitudinal section that engages in the accommodating space  39 . A cross section of the spike  43  then has four straight edges  47  inscribed inside a square, see  FIG. 7 . These planar surface parts  45  converge toward the end  49  in a manner that corresponds to the tapering of the accommodating space  39 . When the spike  43  is accommodated inside the accommodating space  39 , the interior surfaces  51  of the dome  35  then fit against the planar surface parts  45  of the spike  43 . The longitudinal ribs  53  (not all of which are identified by reference numerals in the drawings) extend along the exterior of the dome  35 , and are disposed with a spacing there between, ranging from a collar  55 , which is provided as a stop for the support pipe  25 , toward the internal end of the dome  35 . 
     As can be derived from  FIGS. 3, 6 and 7 , the spike  43  includes rounded connecting surfaces  57  between the planar surface parts  45 , as well as radially projecting flange parts  59  on two opposing sides. A central bore  61  extends inside the spike  43  from the thicker bottom end thereof to a compensation bore  63  on the tapered top end  49 . The spike  43  is rotatably supported by the central bore  61  thereof on a shaft  65  of the element holder  19 . This rotatable support of the spike  43  facilitates moving the non-round spike  43  into the accommodating space  39  of the dome  35 , when the filter element  17  is inserted into the filter housing  1 . Due to the tapered shape of the spike  43 , the spike  43  adjusts itself automatically to the appropriate rotational position when moving into the dome. The shaft  65  includes an external thread  67  on the bottom end thereof, by which it is screwed into the internal thread of the discharge opening  9  of the filter housing  1 . A hexagonal insert bit  69  is provided for the screwing action on the top end of the shaft  65 . Following the hexagonal insert bit  69  is a circular cylindrical longitudinal section  71  by which the shaft  65  is rotatably supported, fitted in a supporting section  73  of the central bore  61  of the spike  43 . The bore  61  includes, as can be seen in  FIG. 6 , an extension  75  at the bottom end thereof with a groove  77  configured therein. The groove interacts with a snap ring  78  (only indicated in  FIG. 3 ) disposed in a groove  79  of the shaft  65  to protect against any axial movement of the spike  43  in the removal direction from the spike shaft  65 . In this regard, the shaft  65  constitutes, together with the spike  43 , a structural unit in two parts. 
     Below the snap ring  78  disposed inside the groove  79 , the shaft  65  includes a collar  81  that constitutes a radial extension. Collar  81  forms a stop surface  83  for securing the spike  43  against any axial downward movement and includes a fluid connection  87  that is disposed between opening  85  on the exterior thereof and the bottom end that can be screwed into the discharge opening  9  of the housing  1 . Fluid connection  87  allows for emptying the housing  1 , after the discharge screw  11  has been removed. 
       FIG. 2  depicts a situation where a filter element  17  according to the invention is provided with an end cap  31  having a dome  35  for forming an accommodating space  39  for a spike  43 , as is present as an element holder of a filter apparatus according to the invention, and is in its functional position. However, contrary to  FIG. 1 , in the representation in  FIG. 2 , the filter element  17  is not inserted into a filter housing  1  according to the invention. Instead, it is inserted in a filter housing of a common structural type, which includes a closed floor part  21  without an element holder with a projecting accommodating part in form of a spike disposed thereupon. Therefore, as depicted in  FIG. 2 , the filter element  17  that is configured according to the invention can also be inserted and brought into the functional position inside such a common filter housing. 
     In the present embodiment, the element holder  19  is made of steel parts in form of a spike  43  and shaft  65 . Preferably, the end cap  31  of the filter element  17  is a die-cast part made of an aluminum/zinc alloy. Alternately, the end cap  31  could also be die-cast from a plastic material. 
     While various embodiments have been chosen to illustrate the invention, it will be understood by those skilled in the art that various changes and modifications can be made therein without departing from the scope of the invention as defined in the claims.