Abstract:
A filtering device for fluids includes a filter housing ( 1 ) and a filter element ( 9 ) received in the filter housing. The filter element has an end cap ( 17 ) on at least one end. The end cap forms an enclosure for the corresponding end edge of the filtering material ( 23, 35 ) and is fixed on an element receiver ( 13 ) interacting with the bottom part ( 5 ) of the filter housing ( 1 ) to fix the position of the filter element ( 9 ) in its functional position. The element receiver forms a fluid path for the cleaned fluid exiting the hollow chamber ( 19 ) of the filter element ( 9 ). The element receiver ( 13 ) contains a valve arrangement ( 55 ) blocking the fluid path ( 35 ). A control device ( 79, 83 ) releasing the valve arrangement ( 55 ) in the functional position is on the end cap ( 17 ) of the filtering element ( 9 ). The end cap is fixed on the element receiver ( 13 ).

Description:
FIELD OF THE INVENTION 
     The invention relates to a filtering device for fluids, comprising a filter housing in which at least one filtering element, which defines a longitudinal axis, can be accommodated in the form of a filter cartridge. At least one filter cartridge end has an end cap forming an enclosure for the pertinent end edge of the filter material. The filter cartridge can be fixed on an element receiver which interacts with the bottom part of the filter housing in order to fix the position of the filtering element in its functional position forming a fluid path for the cleaned fluid which emerges from the filter cavity of the filtering element. Furthermore, the invention relates to a filtering element for such a filtering device. 
     BACKGROUND OF THE INVENTION 
     Filter devices of this type are readily available on the market in various versions. To a large extent, such filter devices are used for filtration of working fluids such as hydraulic fluids, fuels, lubricants, and the like. In fluid systems, specifically hydraulic systems, in which filter devices are used, the operational reliability of the system depends largely on the reliable operation of the filter devices located in the system. In other words, a failure or malfunction of the filter device can lead to failure or serious damage of the pertinent system and thus can cause significant economic loss. 
     A filter device and its parts as well as a method for operating the filter device are known from DE 10 2006 039 826 A1. The filter device has a filter housing part which encloses the filter element and which can be detachably connected to another filter housing part. A valve apparatus in the interconnected state of the housing parts clears a fluid path and, in the separated state of the housing parts from one another, at least partially blocks it. The valve apparatus preferably has a valve element which can be actuated via an actuating part of at least one of the two filter housing parts and/or of the filter element. Especially in the connected state of the housing parts, it opens the valve element and, in its state separated from one another, at least partially closes it. In this case, the first filter housing part forms a filter bowl for receiving the filter element. The second filter housing part forms the filter bowl with the fluid connections, especially in the form of a supply and drain. When the filter element is missing and the valve apparatus is closed, a control unit of the hydraulic circuit delivers a fault message and/or shuts off the hydraulic circuit. 
     DE 92 15 351 U discloses a filter device for filtering of fluids with a filter element and with a back pressure and an overload valve located in the bypass to the filter element and the back pressure valve. The filter device has a first connection site for supply of the unfiltered fluid from a load site which is supplied as part of a fluid circuit by a fluid pump and a second connection site between the filter element and the back pressure valve for discharging the filter fluid by a differential pressure-controlled valve located in the bypass to the filter element. Depending on the differential pressure on the filter element, a connection between the second connection site and a third connection site can be established which can be connected to the fluid circuit between the fluid pump and the load site. In this case, a switching valve can be provided which, in the absence of the filter element, establishes this connection between the second connection site and the third connection site. Furthermore, a movable element receiver for the filter element can be provided which, at a definable threshold value of the differential pressure on the filter element that is smaller than the threshold value necessary to open the differential pressure-controlled valve, travels against a stop against the force of the energy storage mechanism of the valve piston. 
     SUMMARY OF THE INVENTION 
     An object of the invention is to provide an improved filter device which is characterized by a high degree of operational reliability. 
     This object is basically achieved according to the invention by a filter device where the element receiver contains a valve arrangement which normally blocks the fluid path for the cleaned fluid, but which can be unblocked by a control device located on the end cap of the filter element, which end cap is to be fixed on the element receiver. This arrangement results in an increase of the operational reliability of the device in two respects. On the one hand, the risk is avoided that the pertinent system is inadvertently started in the event that the insertion of a filter element in the valve housing has been forgotten. In this case, due to the absence of the control device necessary for unblocking the valve arrangement on the end cap of the filter element to be used, the valve arrangement remains in the blocked state. Another especially important safety aspect is that the operation of the device is possible only when a filter element is used that has the control device which is suitable for unblocking the valve on the end cap which is to be fixed on the element receiver. 
     Thus, it is not only precluded that a filter element will be used which is unsuitable for the respective specific use and which does not satisfy the pertinent applicable specifications that ensure operational reliability, because it is, for example, not assigned to a corresponding pressure stage or has an unsuitable filter fineness, but the risk is also avoided that possibly a “discount element” available on the market will be used which does not meet the applicable safety standards. 
     In especially preferred exemplary embodiments, the element receiver for forming the fluid path for the cleaned fluid has a seating connection which projects from the housing bottom part axially in the direction of the filter element which is located in the operating position, and which connection contains the valve arrangement. Since the component which forms the fluid connection to the filter element is used at the same time as a valve housing for the valve arrangement, an especially simple and compact construction can be implemented. 
     In advantageous exemplary embodiments, the end cap of the filter element has a threaded connection which in the filtration process forms the fluid outlet from the filter cavity of the filter element which forms the clean side and can be screwed to the seating connection. The control device for the valve arrangement on the threaded connection is a control body which, in the course of being screwed to the seating connection, acts on the valve arrangement to unblock it. Because the end cap of the filter element is fixed by screwing it to the element receiver, for the control body, as a result of the axial force generated during the screw coupling process, a high actuating force for unblocking of the valve arrangement is available so that reliable actuation of the valve arrangement is possible even if it is preloaded in the blocking position with a comparatively high closing force. 
     With respect to the configuration of the valve arrangement, the arrangement can be designed such that the valve arrangement has a ring body which projects on the inside wall on the seating connection and which forms the valve seat for an axially movable valve body which is preloaded into the blocking position by a spring arrangement in the direction of the end cap. 
     In this type of configuration of the valve arrangement, the control body on the threaded connection forms an axial projection which acts on the valve body during the screw coupling process and moves it out of the blocking position against the force of the spring arrangement. Such a configuration is characterized by an especially simple, economical configuration both with respect to the threaded connection of the filter element and the element receiver. 
     In advantageous exemplary embodiments, the valve arrangement can have a ring body which projects on the inside wall of the seating connection and which forms the valve seat for the plate-shaped valve body. Such a valve arrangement in the form of a plate valve can be economically produced. 
     The seating connection of the element receiver is, however, also equally well suited as a valve housing for a spool valve with a valve spool having axial fluid passages. The seating connection has an end plate which closes the fluid passages of the spool in the blocking position. 
     In one configuration of the valve arrangement as a plate valve or as spool valve, a disk spring has fluid passages on the end region facing the housing bottom part in the seating connection for supporting the compression spring unit which is supported on the other hand on the valve body. The disk spring can have a central hollow pin which projects in the direction of the valve body and which forms the guide for a helical spring arrangement which surrounds it. 
     In order to easily make available the high closing force which is desirable for the valve arrangement, the helical spring arrangement can be formed by a spring assembly of two helical springs which are located coaxially to one another. 
     Filter devices of the type under consideration here can be equipped with a clogging indicator which, at a back pressure that exceeds a defined threshold value on the dirty side of the filter housing, generates an indicator signal. Due to the high actuating force that, in the course of screwing the threaded connection to the seating connection, is available to the control body for its actuation of the valve arrangement, it becomes advantageously possible to dimension the closing force of the spring arrangement of the valve arrangement to be sufficiently high such that the valve arrangement remains in the blocking position even at a fluid pressure that acts on the sealing body for purposes of opening and which is higher than the threshold value generating the indicator signal. This arrangement has the particular advantage of the clogging indicator having multiple functions. On the one hand, the indicator signal is delivered conventionally, which at the back pressure rising due to clogging of a contaminated filter element, delivers the signal for the required replacement process of the filter element. On the other hand, at the high closing force generated by the spring arrangement and provided according to the invention for the valve arrangement, an indicator signal is delivered even when an attempt is made to inadvertently operate the device without an inserted filter element or with an inserted, but unsuitable filter element. Due to the blocking characteristic of the valve arrangement provided according to the invention, before its opening, a back pressure builds up which triggers the signal of the clogging indicator. 
     The subject matter of the invention is also a filter element for use in a filter device with the filter element having these features. 
     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 which form a part of this disclosure: 
         FIG. 1  is a side elevational view in section of a filter device corresponding to the prior art; 
         FIG. 2  is a side elevational view in section of a filter device according to a first exemplary embodiment of the invention, the state being shown in which a filter element suitable for use in the filter housing is in the operating position; 
         FIG. 3  is a partial side elevational view in section of the bottom-side region of the filter device of  FIG. 2 , exploded and enlarged compared to  FIG. 2 ; 
         FIG. 4  is a perspective view in section of only the seating connection of the filter device of  FIG. 2 , approximately on the scale of  FIG. 3 ; 
         FIG. 5  is a schematically simplified, and partially cutaway perspective view in section of one end section of a filter element intended for use in the filter device according to the invention; 
         FIG. 6  is a partial side elevational view in section of the bottom side region of a filter device according to a second exemplary embodiment of the invention being shown in the state in which a filter element suitable for use has not yet been completely inserted into the operating position; 
         FIG. 7  is a perspective view in section of the seating connection of the filter device of  FIG. 6 ; 
         FIG. 8  is a perspective view in section of the filter device of  FIG. 6  with the valve arrangement of the seating connection shown in the unblocked state; and 
         FIG. 9  is an enlarged perspective view in section of the end section of one filter element for use in the filter device of  FIG. 6 . 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     A filter device of conventional type that is shown in  FIG. 1 , comprises a hollow cylindrical filter housing  1  having a main part  3  and a bottom part  5  screwed together. The upper end of the main part  3 , which is opposite the bottom part  5 , can be closed by a screw-on housing cover  7 . The housing  1  can accommodate a filter element  9  coaxially to the longitudinal axis  11  of the housing  1 . For positioning and fixing in position, on the bottom part  5 , there is an element receiver  13  in the form of a hollow body whose upper peripheral edge facing the filter element  9  for positioning of the filter element  9  with formation of a seal  14  interacts with a connection unit  15  located on the end cap  17  of the filter element  9  facing the bottom part  5 . The connection unit  15  forms a fluid connection to the inner filter cavity  19  within the filter element  9 , forming the clean side in the filtration process. The cleaned fluid, which emerges from the clean side via the connection unit  15 , flows through the element receiver  13  and can emerge from the bottom part  5  via a bottom valve  21  which protects the housing outlet in the conventional manner. 
     In  FIG. 1 , the filter element  9  is designed as a two-stage element. Filter material  23  of coarser filter fineness is located on the outside of the filter element  9 , with its outside bordering the outer housing space  25  which forms the dirty side in the filtration process and forming a prefilter. The lower edge of the filter material  23  on the bottom side is enclosed by the end cap  17 . The top end of the filter material  23  is enclosed by an upper cover cap  27  on which there is a bypass valve arrangement  29  which, at a specified dirt-side pressure level, enables throughflow from the space  25  to the prefiltration space  31  on the inside of the filter material  23 . In the two-stage version of the filter element  9 , the prefiltration space  31  is not directly connected to the connection unit  15  of the end cap  17 . Located upstream of the connection unit  15 , a fine filter unit  33  with a filter material  35  of greater filter fineness surrounds a fluid-permeable support pipe  37 , which is open to the connection unit  15  of the end cap  17 , and together with the lower edge of the filter material  35  on the outside of the connection unit  15  is attached to the end cap  17 . Thus, the space  19  forming the clean side in the filtration process is connected via the connection unit  15  to the fluid passage of the element receiver  13 . 
     In  FIG. 1 , the fluid inlet  43  to the dirt-side space  25  on the housing bottom part  5  is in the vicinity of the end cap  17  of the filter element  9 , which is in the operating position. As impact protection, on the outside of the end cap  17  in the peripheral area of the filter element  9  facing the inlet  43 , a shielding plate  45  is attached which in the pertinent peripheral region extends arched along the outside of the outer filter material  23 . In the lee region, which is opposite the fluid inlet  43 , which faces away from the incident flow region and in which a flow-stabilized dirt trap basket  46  is formed, there is a trap magnet apparatus  47 . 
     The differences between the construction according to the invention and the construction from  FIG. 1  corresponding to the prior art, are explained below. In this instance as well, the filter element  9  is designed as a two-stage element so that the interior of the filter housing  1 , as shown above, is divided into a space  25  which forms the dirty side and which adjoins the fluid inlet  43 , a prefiltration space  31  and an inner filter cavity  19  which forms the clean side. The major differences vis-á-vis the prior art, however, lie in the construction of the element receiver  13  and the construction of the end cap  17  of the filter element  9 . The cap is to be affixed to the element receiver in the operating position. With respect to the configuration of the element receiver  13 , there is the important particularity that it has a seating connection  51  projecting from the housing bottom part axially in the direction of the filter element  9 , shown separately in  FIG. 4 . In this first exemplary embodiment, seating connection  51  forms an additional component of the element receiver  13 , which, in the illustrated exemplary embodiment, is screwed to the remaining portion of the element receiver  13  and forms an axial extension of the element receiver  13 . The interior of the seating connection  51  forms not only the fluid path  53  for fluid emerging from the clean side  19  of the filter element  9 , but also forms the valve housing of a valve arrangement  55  which normally blocks the fluid path  53 . The valve arrangement has a disk-shaped sealing body  57  which is preloaded by a spring force in the axial direction of movement against a ring body  59  projecting on the inside wall of the seating connection  51  and which forms an annular valve seat  60  for the sealing body  57 . To generate the spring force which preloads the sealing body  57 , there is a spring arrangement formed of two helical springs  61  and  63  which form a spring assembly. Spring  61 ,  63  are arranged coaxially to one another and, on the one hand, are supported on a spring cup  65  and, on the other hand, are supported on the bottom of the sealing body  57 . The spring cup  65 , which is fixed in the seating connection, has a central hollow pin  57  projecting in the direction of the sealing body  57  as a guide for the helical springs  61  and  63  which surround it and has a fluid passage  69  which forms the continuation of the fluid path  53  in the open state of the valve arrangement  55 . 
     For the interaction with the seating connection  51 , the end cap  17  of the assigned filter element  9 , as already indicated, has a special configuration which is shown in  FIGS. 2, 3, and 5 . As is apparent, the end cap  17 , within a connecting part  71  ( FIG. 5 ) that extends over the outside of the seating connection  51 , has a coaxially projecting threaded connection  73  provided with an external thread  75  by which it can be screwed to an internal thread  74  on the top end region of the seating connection  51 . A seal arrangement  77  is located at the start of the external thread  75  forming a seal. Within the threaded connection  73 , there is a control device which controls the valve arrangement  55  out of the normal blocking position into the open position when a filter element  9  intended for use is moved into the operating position by screwing the threaded connection  73  to the seating connection  51 , as is shown in  FIGS. 2 and 3 . The control device has a control body in the form of a coaxial projection  79  within the threaded connection  73 . The projection  79  forms a hollow body with fluid passages  81  ( FIG. 5 ). The end of projection  79  facing the sealing body  57  has a ball  83 . When the threaded connection  73  is screwed to the seating connection  51 , ball  83  transfers the screw force as an actuating force to a recessed ball seat  85  of the sealing body  57  in order to raise it against the force of the helical springs  61 ,  63  off the valve seat  60  on the ring body  59  so that the operating state shown in  FIGS. 2 and 3  results in the fluid path  53  being cleared by the element receiver  13 . 
     Because the connection between the filter element  9  and element receiver  13  takes place by screwing the threaded connection  73  of the end cap  17  of the filter element  9  to the seating connection  51  of the element receiver  13 , for the control device for actuating the valve arrangement  55 , when the threaded connection  73  is being screwed in, a high actuating force is available which moves the sealing body  57  against the closing force via the ball  83 . This arrangement makes it possible to design the spring assembly of the helical springs  61  and  63  such that the sealing body  57  remains in the blocking position even at a high pressure difference within the seating connection  51  which seeks to open the valve arrangement  55 . This structure not only ensures that the filter device cannot be operated in a case in which a filter element  9  has inadvertently not been inserted into the filter housing  1 , because the operating system pressure is not sufficient to unblock the valve arrangement  55 . It also advantageously enables the generation of an indicator signal in conjunction with a clogging indicator  87  which is typically provided in such filter devices.  FIG. 2  shows on the bottom part  5  of the filter housing  1  such a clogging indicator  87 , which as a result of a specified pressure difference between a channel  89  which leads to the dirty side  25 , and a channel  91 , which leads to the exterior, generates an electrical indicator signal. The specified signal-generating pressure difference is chosen such that an increase of the back pressure on the fluid inlet  43  is signaled which corresponds to a clogging state of the filter element  9  at which the filter element  9  should be replaced. Due to the aforementioned high actuating force that is available for the unblocking of the valve arrangement  55 , the spring preload of the valve arrangement  55  can be chosen such that the valve arrangement  55  remains blocked, even if a pressure difference is active at which the clogging indicator  87  responds. Thus the valve arrangement  55  not only prevents operation of the device without an inserted filter element or with an inserted “incorrect” filter element which does not contain the control device which unblocks the valve arrangement  55 , but also signaling of this unallowable operating state takes place via the clogging indicator  87  as an additional function thereof. 
     The second exemplary embodiment shown in  FIGS. 6 to 9  differs from the first exemplary embodiment in that the valve arrangement  55  is not designed in the form of a plate valve, but in the form of a spool valve. As in the first exemplary embodiment, the seating connection  51  of the element receiver  13  forms the valve housing for the valve body located therein in the form of a valve spool  58 .  FIGS. 7 and 8  show the details of the spool valve.  FIG. 9  shows the configuration of the threaded connection  73  which has been altered compared to  FIG. 5  on the end cap  17  of the filter element  9 . Unlike in the first exemplary embodiment, the threaded connection  73  has an internal thread  74 , and the seating connection  51  on the element receiver  13  is provided with an external thread  75 . As above, in the interior of the threaded connection  73 , there is an axially projecting control body in the form of a projection  79  with an end ball  83  on which there is a fluid passage  81 . Unlike in the example described first, the seating connection  51  on the end facing the filter element  9  is not open, but has an end plate  70  underneath which fluid inlets  72  enable fluid entry into the interior of the seating connection  51  when the valve arrangement is in the unblocked state, as is shown in  FIG. 8 , in which the valve spool  58  is pushed against the force of the spring  61 . For this displacement motion in interaction with the projection  79  on the threaded connection  73 , the valve spool  58  has a shaft  76  which extends through the end plate  70 .  FIG. 7  shows the blocking position of the spool valve in which closing edges  78  of the valve spool  58  adjoin the inside of the end plate  70  so that fluid cannot enter through the lateral inlets  72 . When the valve spool  58  is moved away from the end plate  70  as a suitable filter element  9  is being screwed to the seating connection  51 , which is shown in  FIG. 8 , fluid entering via the inlets  72  travels through fluid passages  64  of the valve spool  58  into the interior of the seating connection  51  so that the valve arrangement  55  is unblocked. 
     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 appended claims.