Abstract:
A filter device has a filter element ( 37 ) in a filter housing having a connection unit ( 29 ) forming a fluid connection to the filter element ( 37 ). The connection unit ( 29 ) feeds fluid to be purified to the dirty side ( 41 ) of the filter element ( 37 ) and is a component of the element receiver mounting the filter element ( 37 ) in the functioning position. The connection unit ( 29 ) is a component of the filter housing. The valve arrangement ( 61; 67, 69 ) is movable such that by removing the filter element ( 37 ) from the filter housing, the valve arrangement ( 61; 67, 69 ) closes and by insertion of the filter element ( 37 ) into the filter housing, the valve arrangement ( 61; 67, 69 ) opens.

Description:
FIELD OF THE INVENTION 
     The invention relates to a filter device having at least one filter element that can be accommodated in a filter housing. The filter housing has at least one connection unit for forming a fluid connection to the filter element. The connection unit is intended to supply the fluid to be cleaned to the dirty side of the filter element and is a component of the element receiver. The filter element in the operating position interacts with the element receiver. 
     BACKGROUND OF THE INVENTION 
     Filter devices of this type are readily available on the market in a plurality of constructions and versions. Such filter devices are used mainly to filter out fouling in fluids, such as hydraulic. Fouling of the hydraulic oil occurs in the installation or at the start-up of the respective hydraulic system. In addition to this initial fouling, fouling can occur during operation, for example, by penetration of dirt at the hydraulic tank as a result of inadequate tank ventilation, pipe penetrations, piston rod seals, and the like. Fouling can occur within the fluid stored in the hydraulic tank, especially in the hydraulic systems of heavy machinery such as earth moving machines, excavators, or the like. Furthermore, in these types of applications of the filter device, effecting filtration directly in the region of the hydraulic tank, for example, by installing the filter device directly in the tank, can be useful. 
     DE 10 7007 056 362 A1 discloses a filter device, especially in the form of a return intake filter, having at least one filter housing in which at least one filter element defines one longitudinal axis and can be accommodated. At least two valve units, especially in the form of a bypass valve and a back pressure valve, are located in an arrangement concentric to and along the longitudinal axis of the respective filter. 
     DE 10 2006 011 844 B4 discloses a filter element with a filter bowl that borders an interior, with a bottom part having a flow passage, with a filter medium located in the interior of the filter bowl, and with a valve body of a valve apparatus. The valve body can be actuated by the fluid pressure on the fluid passage of the bottom part, and has a screen-like, flexible closing jacket. In the opened-up state, the closing jacket blocks the fluid passage, is moved by the fluid pressure in the direction to its closed position, and clears the fluid passage. 
     In these two aforementioned filter solutions, the respective valve arrangements for the filter element installed in the filter housing are actuated accordingly in their respectively provided operating position and by the respectively prevailing fluid pressure, especially of the fluid to be filtered. Under the conditions of use prevailing in the operation of the filter device in construction machinery or other machinery operated in the open, due to the higher fouling rates that arise, frequent changing of the filter element must be done. In the course of handling the used, i.e., fouled, filter elements, in these known solutions, the risk exists that contamination both of the system, i.e., especially of the filter housing and the tank, and also of the environment, will occur. 
     DE 10 2005 001 828 A1 discloses a fitting forming a fluid-conducting connection to a plastic tank, in particular a tank for accommodating a fluid, specifically a hydraulic fluid. The tank has a connection part in the form of a hollow body with a jacket that extends along one longitudinal axis of the hollow body between its ends. The hollow body is embedded in the plastic of the wall of the tank such that one open end of the hollow body on the edge of an opening of the tank and at least one partial region of the jacket of the hollow body are surrounded by the plastic of the wall of the tank. A filter element can be reliably integrated in a tank by this fitting. However, in a replacement of the used filter element by a new element in turn it cannot be precluded that the above-described fouling problems will occur. 
     SUMMARY OF THE INVENTION 
     An object of the invention is to provide an improved filter device in which the risk of fouling is largely precluded when used filter elements are replaced. 
     This object is basically achieved according to the invention by a filter device having a valve arrangement in the filter element being movable by the connection unit as a component of the filter housing or of the parts assigned to the filter housing. When the filter device is shut off by removing the filter element from the filter housing, the valve arrangement moves into its closed position. When the filter device is started up by inserting the filter element into its operating position within the filter housing, the valve arrangement moves into its opened position. This arrangement eliminates the risk that when the filter element is being replaced, fouling attached and/or deposited on the used filter element on the dirty side when the used filter element is withdrawn from the element receiver, can fall off the filter element and can travel to the clean side. Therefore, no subsequent operations need be carried out to clean the filter housing in conjunction with changing the filter element. 
     Preferably, in the relative motion of the filter element and filter housing toward one another for start-up of the filter device, the opening of the valve arrangement by the connection unit from the closed position into the open position takes place in succession. 
     To form the valve arrangement, the end of an inlet fitting can be spanned by a cap of elastomer material that is provided with notches such that the connection fitting of the connection unit, which fitting penetrates the inlet fitting in the operating position, opens the notches of the cap to form flow slots by mechanical action on the cap. This construction of the valve arrangement can be easily produced especially economically so that the presence of the valve arrangement on the filter element increases its production costs only slightly. 
     Alternatively, the valve arrangement on the inlet fitting can have a movable valve body pretensioned by mechanical closing force into the closed position that blocks the inlet fitting. When the filter element is attached to the element receiver, it can be moved out of the closed position by the mechanical action of the connection fitting against the closing force. Advantageously, in this valve design, likewise as in the use of an elastomer valve cap, no mechanical effort on the part of the connection unit is necessary for valve actuation, because in both cases the valve opening takes place by mechanical action by the connection fitting of the connection unit that in the operating position of the filter element penetrates its inlet fitting. 
     In especially advantageous exemplary embodiments, the filter housing is formed by a filter bowl molded integrally into a tank. On the bowl bottom, the connection unit of the element receiver is located. Especially advantageously, this arrangement eliminates a separate filter housing to be installed in the tank because the filter bowl itself as an integral component of the tank forms the filter housing. 
     Especially advantageously, the filter element, through which flow can take place from its inner filter cavity to the outside of its filter medium during filtration, is provided with at least one end cap. This end cap, that is the lower one in the operating position of the filter element, interacts with the element receiver having the inlet fitting projecting into the filter cavity, attached to the valve arrangement and engaging the connection fitting of the connection unit as a component of the element receiver with sealing in the operating position. 
     In especially advantageous exemplary embodiments, on the bottom of the filter bowl, a connection piece is molded and joined to a bottom-side wall section of the tank. This wall section forms a passage for the connection fitting, and through which the connection fitting extends from the outside of the tank into the filter bowl. 
     Especially advantageously, the wall section of the tank adjoining the connecting piece is located in a local indentation extending upward from the base of the tank. This arrangement permits a “countersink” on the bottom-side connection completely into the bottom of the tank. As a result, advantages arise for the installation of the tank in heavy machinery with little available installation space. 
     Preferably, the connection fitting in the connecting piece is fixed by a screw union that can be a standard screw-in design. 
     The tank, together with the filter bowl that forms an integrated component of it, can be especially advantageously molded out of plastic. 
     Furthermore, the filter bowl that is open on the top of the tank can be advantageously closed by a plastic cover screwed to an internal thread located on the edge region of the filter bowl. The cover with its outside then forms a part of the upper tank wall. In these exemplary embodiments, the tank can be configured such that in a fluid connection proceeding from the tank bottom, the tank with one wall part forms an outer skin part of the pertinent machinery, and only the cover of the filter bowl on the outer skin is visible on the entire filter device. 
     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 side elevational view in section of a fluid tank with a filter device according to a first exemplary embodiment of the invention; and 
         FIG. 2  is a side elevational view in section of a fluid tank with a filter device according to a second exemplary embodiment of the invention. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     The fluid tank  1 , designed to accommodate a supply of hydraulic fluid, is shown in the drawings only by an upper wall section  3  and a lower wall section  5 . Together with other wall parts that are not shown, wall sections  3 ,  5  delineate an interior  7  for hydraulic fluid at a level  9 . Tank  1  is a component of a hydraulic system of a heavy machine, for example, in the form of a small excavator. Of the hydraulic system, only one tank return line  11  is shown via which hydraulic fluid to be cleaned is supplied to the filter device and, after completed cleaning, is returned by it to the interior  7  of the tank  1 . 
     Tank  1  is made out of plastic material compatible with hydraulic fluid in a rotary molding method. A filter bowl  13  molded integrally to the tank walls extends inward. The bowl  13  is open on the top  15  of the tank and extends vertically from the top  15  of the tank into the vicinity of the base of the tank  1 , relative to the installation position of the tank  1 . The bowl bottom  17  has a centrally located connection opening  19  and outflow openings  21  located laterally from opening  19  via which cleaned fluid travels out of the filter bowl  13  into the interior  7  of the tank  1 . The connection opening  19  on the bowl bottom  17  is connected to a connecting piece  23  via which the bowl bottom  17  is connected to the lower wall section  5  of the tank  1 . As the drawings show, a port connection  27  of the return line  11  on the filter device is placed within an indentation  25  arched upward from the base of the tank  1  so that the connection fitting is “countersunk” within the tank bottom. 
     From the port connection  27  of the return line  11 , a connection fitting  29  extends in the form of a cylindrical hollow body that is stepped on its outside through the connecting piece  23  and the bottom opening  19  of the bowl  13  into its interior. The end  31  of the connection fitting  29  is located at a distance from the bowl bottom  17 . The connection fitting  29  is fixed in the connecting piece  23  by a threaded insert  33  and forms a component of an element receiver that interacts with the lower end cap  35  of a filter element  37  to fix the filter element  37  within the filter bowl  13  in its operating position. The filter bowl  13  acts as a filter housing. 
     The filter element  37 , shown in its operating position in the drawing, on its lower end cap  35  conventionally forms an enclosure for a filter medium  39  in the form of a hollow cylinder surrounds an inner filter cavity  41  and has a central inlet fitting  43  that can be slipped onto the connection fitting  29  in the operating position. A sealing element  45  on the inlet fitting  43  seals relative to the connection fitting  29 . The element receiver completes a spacer ring  47  of elastomer material surrounding the inlet fitting  43  and defining the axial positioning between the end cap  35  and the bowl bottom  17 . 
     The filter bowl  13  is open on the top  15  of the tank and can be closed by a plastic cover  49  screwed to an internal thread  51  located on the edge region of the filter bowl  13 . The cover  49  is visible only with its outside on the top  15  of the tank. A bypass valve  55  is located between the cover  49  and the upper end cap  53  of the filter element  37 . With a correspondingly prevailing differential pressure, bypass valve  55  conventionally clears a fluid connection between the inner filter cavity  41  and the outside of the filter element  37 . Closing spring  57  keeps the bypass valve  55  in the closed, normal operating position. 
     During filtration, the hydraulic fluid flowing into the filter cavity  41 , via the connection fitting  29 , flows through the filter medium  39  from the inside to the outside. The cleaned fluid from the space of the filter bowl  13  surrounding the filter medium  39  and forming the clean side  59  flows back into the interior  7  of the tank  1  via the outflow openings  21 . In the exemplary embodiment of  FIG. 1 , on the free end region of the inlet fitting  43  projecting into the filter cavity  41 , a valve arrangement is formed from a valve cap  61  of elastomer material and traverses the end of the inlet fitting  43 . This cap  61  has several notches  63 . Without mechanical action applied to the valve cap  61 , the valve cap  61  with the notches  63  closed forms a closure of the inlet fitting  43 . If, however, the filter element  37 , as is shown in  FIG. 1 , is moved into the operating position and is slipped onto the connection fitting  29 , with the inlet fitting  43 , the valve cap  61  is opened up by mechanical action of the free end  31  of the connection fitting  29  in the manner shown in  FIG. 1 . As a result, the notches  63  are widened into flow slots, so that fluid flows into the filter cavity  41  through the connection fitting  29  for the filtration process. If the filter element  37  is withdrawn from the connection fitting  29  for element replacement, the valve cap  61  returns into the unwidened position in which the cap  61  with the notches  63  closed closes the end of the inlet fitting  43 . This process prevents fouling located in the filter cavity  41 , i.e., the dirty side, from falling out of the filter element  37 , and fouling the clean side when the filter element is being replaced. In the handling of the used filter element  37  that has been removed from the filter bowl  13 , this structure reduces the risk of fouling of the environment. 
     The exemplary embodiment shown in  FIG. 2  differs from the first exemplary embodiment only by the construction of the valve arrangement on the inlet fitting  43  of the end cap  35 . In this exemplary embodiment, the inlet fitting  43  is extended into the interior of the filter cavity  41 . The free end  65  of the inlet fitting  43  is then located above the end  31  of the connection fitting  29 . With its free end  65 , the inlet fitting  43  forms a valve seat for a disk-shaped valve body  67  of the valve arrangement. In the operating position shown in  FIG. 2 , the axially movable valve body  67  is raised off the end of the inlet fitting  43  against the action of a closing spring  69  because the connection fitting  29  with its inner end  31  has moved a spring carrier  71  upward, which spring carrier is movably guided within the inlet fitting  43 . As a result of this movement, the valve body  67  is moved up and raised off the valve seat, with the closing spring  69  being more strongly compressed between the spring carrier  71  and a second spring carrier  73  located stationary in the inlet fitting  43 . If at this point the filter element  37  is pulled off the element receiver and removed from the filter bowl  13  when the element is being changed, the closing spring  69  is only partially released such that the valve body  67  moves onto the valve seat on the end  65  of the inlet fitting  43  and closes the inlet fitting  43 . Thus, the second exemplary embodiment works in exactly the same way as in the example of the first embodiment. Since, except for the different design of the valve arrangement, in the two exemplary embodiments, the other components are comparable, not all details which are made the same in the two exemplary embodiments are numbered in  FIG. 2 . 
     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.