Abstract:
A filter device has a filter housing part ( 10 ) with a filter element ( 12 ) and can be detachably connected to another filter housing part ( 20 ). A valve ( 24 ) clears a fluid path in the interconnected state of the housing parts ( 10, 20 ) with the filter element, and in the separated state of the housing parts ( 10, 20 ) from one another or without the filter element at least partially blocks it. Instead of known quarter-turn fastener and stopper solutions, a blocking is devised which can be economically implemented and which requires decidedly less installation space. A process for operation of a filter device is also provided.

Description:
FIELD OF THE INVENTION 
   The present invention relates to a filter device having a filter housing part comprising a filter element and detachably connected to another filter housing part. The present invention furthermore relates to certain parts of the filter device and a method for its operation. 
   BACKGROUND OF THE INVENTION 
   The prior filter devices include, among others, so-called spin-on filters. In their filter housing parts, a filter element designed especially for the respective filtration task is integrated. If the filter element is clogged with dirt causing the filter device to become unusable for its filtration task, the entire filter device, that is, the filter housing in addition to the filter element, must be replaced by a new filter device. This replacement has the disadvantage that the entire unit must be disposed of, although the actual filter housing part would still be usable. To remedy this situation, conventionally in the spin-on filter only the used filter element need be replaced such that the filter housing part with a new filter element can be used as a newly assembled filter device, especially for removing dirt from hydraulic circuits. Fundamentally, the problem arises that operators or even specially trained maintenance personnel forget to use a new filter element. Then, the reconnected filter housing part designed as a screw-in cartridge, even without the filter element, enables operation of the hydraulic system, but without dirt in the fluid flow being removed. Serious damage to the entire hydraulic system can then occur. Comparable problems also arise for other fluid media such as gases or pasty media. 
   To be able to establish greater operating reliability in this respect, DE 10 2004 014 149 A1 discloses a quarter-turn fastener as a fastening means by which the filter housing can be detachably mounted on the fluid means of the hydraulic circuit. By the rotary motion of the filter housing when the quarter-turn fastener is released and locked, a blocking part is controllable which blocks and clears the pertinent fluid connection. In this way, the filter can be reliably changed. A comparably designed solution is also shown in DE 10 2004 008 879 A1, where, instead of the quarter-turn fastener, a stopper with a plate-shaped slide part is provided for blocking and clearing the fluid connections. These solutions are very reliable in operation. Both the quarter-turn fastener and the stopper however require a relatively large amount of installation space, and thus, engender the corresponding production costs. 
   SUMMARY OF THE INVENTION 
   An object of the present invention is to provide an improved filter device having low production costs, reduced installation space, and a blocking solution which ensures that the filter device can only be operated together with its associated filter element, even when the filter element is replaced by a new, unused element. 
   This object is basically achieved by a filter device where the blocking solution is a valve. In the interconnected state of the housing parts with a filter element, the valve clears a fluid path. In the separated state of the housing parts from one another or when connected without a filter element, the valve at least partially blocks the fluid path. This blocking solution can be economically implemented and requires considerably less installation space, compared to the described quarter-turn fastener and stopper solutions described above. 
   If the fluid flow through the filter device is completely stopped by the valve, the hydraulic control unit evaluates this as a problem, resulting in an error report being delivered from which the operating or maintenance personal can then detect the absence of the filter element or by choking the fluid volumetric flow the respective hydraulic function is maintained. However, the differential pressure on the filter device increases such that a correspondingly mounted fouling display responds when the element is absent and delivers the message “Fouled filter element to be replaced”. The message is intended to cause the filter device to be checked with respect to its serviceability such that the possible absence of the filter element can be established without failure of the hydraulic components of the system occurring. Operators experienced in the handling of hydraulic machinery will moreover be able to recognize even without the display that the filter element is missing when the corresponding noise or slackening of machine performance occurs due to this choking of the volumetric flow. 
   In one preferred embodiment of the filter device of the present invention, the valve has a valve element which can be actuated via a trigger 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, the trigger part opens the valve element. In their state with the housing parts separated from one another, the trigger part at least partially closes the valve element. In addition to the opening and closing function with possible choking of the volumetric fluid flow, via the indicated trigger part forced actuation of the valve element of the valve is ensured. In this respect, malfunctions are precluded. Preferably, the trigger part is a component of the interchangeable filter element, and the valve element is a component of the other filter housing part. 
   In another especially preferred embodiment of the filter device of the present invention, the valve element includes at least one valve component which, in the closed state of the valve element forms a fluid-tight membrane surface or borders fluid-choking passage points within the membrane surface. In the opened state essentially, the valve component enables free fluid passage from one filter housing part with the filter element inserted via it in the direction of the other housing part and vice versa. Based on the possible reversible fluid direction it is possible, with the valve actuated, to induce a backflushing process for the filter element to remove dirt from it in counterflow. The configuration of the valve element in the shape of a membrane makes it possible to still further reduce the required installation space. 
   The valve component preferably includes a type of spiral arm with spring-elastic properties. At least one of the spiral arms can end in a fixing ring which, designed as a locking or snap ring, then enables fixing of the valve in one of the filter housing parts with simple handling. 
   The present invention furthermore relates to a valve for the filter device and a specially designed filter element with a trigger part. The present invention furthermore relates to a method in which a fouling display based on the differential pressure is connected between a supply and discharge for fluid in the filter housing in such a way that in the absence of the filter element the valve chokes the fluid flow to maintain the function of the hydraulic circuit. The present invention furthermore relates to a method which calls for the control of the hydraulic circuit to deliver an error report and/or to turn off the hydraulic circuit in the absence of a filter element and with the valve closed. 
   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 partial, front elevational view in section, not to scale, of the head-side part of the filter device according to an embodiment of the present invention; 
       FIG. 2  is a top perspective view of a filter element to be inserted into the filter device of  FIG. 1  with a trigger part; 
       FIG. 3  is a perspective top view of the trigger part of  FIGS. 1 and 2 ; 
       FIG. 4  is a perspective top view of an insertable valve according to a first embodiment of the present invention; 
       FIG. 5  is a perspective top plan view of an insertable valve according to a second embodiment of the present invention; 
       FIG. 6  is a perspective top view of the insertable valve of  FIG. 5  in an open operating state; and 
       FIG. 7  is a perspective top view of an insertable valve according to a third embodiment of the present invention. 
   

   DETAILED DESCRIPTION OF THE INVENTION 
   The filter device shown in  FIG. 1  has a cup-shaped filter housing part  10  surrounding the filter element  12 , as is shown, for example, in  FIG. 2 . Flow takes place through the filter element  12  from the outside to the inside, as viewed in  FIG. 1 . The filter element has a conventional filter element structure which is not detailed, for example, comprising a pleated, multilayer filter mat supported against a fluid-permeable support pipe. Fouled fluid is optionally supplied from a hydraulic circuit (not detailed) via the fluid supply  14  to the filter device. Cleaned, filtered fluid travels via a center channel  16  of the filter element  12  to the fluid discharge  18  of the filter device. To be able to backflush the filter element  12 , it would also be conceivable to operate the filter device in the reverse fluid direction. Likewise, it would be possible in a specially designed filter element  12  to reverse the direction of fluid throughflow so that then the fluid to be cleaned flows through the filter element  12  from the inside to the outside. In these instances, generally to support the pleated filter material, a support pipe or other support element such as a grating must be attached on the outer peripheral side of the filter element. This structure of a filter device is conventional will not be detailed. Conventionally, another filter housing part  20  forming a filter head and having a supply  14  and a discharge  18  extends over the filter housing part  10  on its upper free end on the front and to be detachably connected to the filter housing part  10  via a screw-on or threaded section  22 . 
   The filter device furthermore has a valve  24 , as shown in  FIG. 4 . Other solutions or embodiments for the valve  24  are shown in  FIGS. 5 to 7 . If, as shown in  FIG. 1 , the two housing parts  10 ,  20  are connected to one another, the valve  24  is moved into the open position to clear the fluid-carrying path. In the separated state of the housing parts  10 ,  20  from one another, the fluid-carrying path between the center channel  16  and the fluid discharge  18  is blocked. In the absence of a control part and designed as a complete closure (valve function), the valve remains closed until the pressure p 1  has reached or exceeded the opening pressure p 0  of the valve, i.e., p 1 &lt;p 0 :p 2 =0 for an unpressurized connection to the tank, volumetric flow Q=0, p 1 &gt;=p 0 :p 2 =p 1 ·Δp valve , ideally for Δp valve =0:p 2 =p 1 . 
   In the absence of the control part and designed as a choke (spiral disk with passages), a pressure drop will take place over the component so that p 1 &gt;p 2 . The resulting pressure difference Δp valve  is used to trigger a signal of an optionally connected fouling display. 
   As shown in greater detail in  FIG. 4 , the valve  24  has a valve element  26  which can be actuated via a trigger part  28 , as is detailed in  FIG. 3 . In this case, the trigger part as shown in  FIGS. 1 and 2  is a component of the filter element  12 . As a result of the trigger part&#39;s conically tapering control parts on its free front end in the form of opposing bridge surfaces, the trigger part is able to push against the closed valve disk as shown in  FIG. 4 , into an open spiral configuration, as shown in  FIG. 1 . If the two filter housing parts  10 ,  20  are separated from one another by unscrewing over the screw-on section  22 , the trigger part  28  disengages from the valve  24 , and the valve element  26  assumes its largely closed position in the form of a flat membrane surface as shown in  FIG. 4 . 
   Since the valve component of the valve element  26  in the embodiments as shown in  FIGS. 1 and 4  is formed from a spiral arm  32  with spring-elastic or resilient properties, this process of pushing can be repeated as often as desired for an opening process and spring-elastic resetting for closing the valve  24 . In this way, a very large number of changing processes for new filter elements  12  is possible if, when fouled, they are to be replaced by new filter elements. Since the valve  24  can be fixed interchangeably in the upper filter housing part  20 , upon a possible failure of the spiral arm  32 , replacement of the valve element  26  is possible. This interchangeability is however not absolutely necessary. The spiral arm  32  made from a flat metal plate can be obtained by conventional cutting technology, also including laser cutting, water jet cutting, etc. A correspondingly wound wire with round or rectangular cross section could likewise be used. 
   The metal base plate as the base material, preferably made in circle form, need not be spring-elastic. The resetting moment or force for closing the valve  24  can likewise arise exclusively by the raising of the spiral arm  32  in helical form by the trigger part. The raising plug  34  tapers to the outside (compare enlargement as shown in  FIG. 3 ), and, in terms of its outside contour is matched to the spiral line of the raising arm. In this way, the spiral arm  32  undergoes guidance both for the pushing process and also for the resetting process to ensure especially careful actuation of the valve element  26 . 
   The trigger part  28  is shown as an individual component in  FIG. 3  for better illustration. The trigger part  28  on the bottom side has a contact-making plate  36  which can be moved into the top end of the filter element  12  until the free end of the filter element  12  comes into contact with the encompassing edge  38 . This encompassing edge  38 , on its outer peripheral side, has an engagement groove  40  interrupted by engagement points  42  which point down and are preferably diametrically opposite one another. Points  42  ensure that by a corresponding catch or lock connection the annular trigger part  28  is detachably fixed with a corresponding strip-like or cam-like engagement part  44  on the inside of the cup-shaped filter housing part  10  (compare  FIG. 1 ). A cylindrical center plug  48  is located on the top of the contact-making plate  36  by individual stiffening bridges  46 , and is permanently connected to the contact-making plate  36  and to the stiffening bridges  46 , and is permanently connected to the contact-making plate  36  and to the encompassing edge  38 . The individual stiffening bridges  46  extend radially to the outside away from the longitudinal axis  50 . 
   The top of the center plug  48  is connected to the raising plug  34 . The three inserted control parts  30  extend between an annular flange  52 , on the top end of the center plug  48 , and a contact-making and pushing pin  54  on the free end of the trigger part  28 . These bridge-like trigger parts  30  can be further stiffened by at least one middle ring  56 . The fluid passages  58 , bordered by the stiffening bridges  46 , the top of the contact-making plate  36  and the bottom of the encompassing edge  38  are used for incident flow onto the actual filter element with its filter medium in the seated state. The fluid passages  58  more or less form the inflow channel between the filter element and the optional “dirt catcher” used to catch dirt in the direction of flow through from the outside to the inside. The insertion bevels  60  point down on the stiffening bridges  46  to facilitate insertion of the trigger part  28  into the (optional) dirt catcher along its upper edge. This trigger part  28  preferably is formed of a plastic material which can be economically produced, for example, by an injection molding process. For permanent connection of the trigger part  28  made in one piece to the filter material of the filter element  12  a cement connection (not detailed) can be used. Instead of three control parts  30 , a different number of control parts (not shown) can also be used. 
   The filter element  12  with the trigger part  28  forms a manageable function unit which can be completely replaced as a replacement part and thrown away. But it is possible to reuse or recycle the plastic trigger part  28 . It is still within the scope of the present invention, in an embodiment (not shown), to assign the trigger part  28  to the other filter housing part  20  and to provide the valve  24  on the filter element  12  accordingly. 
   If, as shown in  FIG. 4 , the valve element  26  of the valve  24  forms an essentially closed membrane surface, when the filter element is replaced and insertion of a new filter element  12  is forgotten. The valve  24  cannot be pushed by the trigger part  28  of the filter element  12  as shown in  FIG. 1  into its open position, but remains in the closed valve position, causing a reporting or control means immediately to relay an error report to the operator indicating that the filter element  12  needs to be inserted for reliable operation of the system. In this way, dirt damage caused by lack of filtration within the hydraulic circuit can be reliably avoided. 
   Another approach for a functional valve  24  is given by the embodiment as shown in  FIGS. 5 and 6 . In the closed position shown in  FIG. 5 , between the parts of the spiral arm  32 , a choking passage site  62  is provided both in the open position of the spiral spring valve shown in  FIG. 6  and in its closed state shown in  FIG. 5 . The choking passage site enables a choked fluid flow coming from the middle channel  16  in the direction of the fluid discharge  18 . Due to this fluid passage point, the hydraulic function can be further maintained. A fouling indicator (not detailed) operates based on pressure difference detection to be able, in the absence of the filter element  12  and accordingly with the closed spiral spring valve configuration as shown in  FIG. 5 , to signal the pertinent system state as fouling to compel filter element replacement. Thus, it is then established that the element  12  is not in its place in the housing part  10 . 
   These pressure difference-controlled fouling displays are easily commercially available in a plurality of versions. When a working new filter element has been inserted, the pressure difference to be detected between the fluid supply  14  and the fluid drain  18  in the ideal case is near 0. As fouling increases, the pressure difference value then increases until the fouling indicator suggests replacement of the used filter element  12 . A comparable pressure difference situation arises when the helical spring valve as shown in  FIG. 5  remains closed without the filter element  12  inserted and choked fluid flow takes place only by the passage point  62 . As a result of the spring elastic or resilient configuration of the spiral arm  32 , an adjustment force is applied on the top of the filter element  12  pressing the filter element  12  in the direction of the bottom part of the filter housing part  10 . This biasing force likewise contributes to an increase of operating reliability. 
   The other embodiment of the valve element  26  shown in  FIG. 7  for the valve  24  has the particularity that in addition to the spiral arm  32 , a fixing ring  64  is molded in one piece to the outside. The fixing ring  64  has two continuous points of application  66  for an actuating tool (not detailed), designed as spreading pliers. The pliers again allow detachably fixing of the valve element  26  as a snap ring in an assignable engagement groove  68  (compare  FIG. 1 ) in the head-side filter housing part  20 . In this configuration shown in  FIG. 7 , the valve element  26  in turn in the middle has an engagement opening  70  for passage of the contact-making and pushing pin  54  (compare  FIG. 3 ). 
   Another desirable side effect in the described configuration of the filter device is that a key port system is achieved. For obtaining a serviceable filter device for a hydraulic circuit, it is necessary for the filter element  12  to have the indicated trigger solution  28 . Otherwise, malfunctions on the hydraulic system occur. Since fundamentally knockoffs are being found to an increased degree in the replacement parts business and are often of lower quality, which the user cannot easily detect, it is possible for only original filter elements with the trigger part  28  and the fluid housing to be used with special valve technology. Cheap single elements conversely cannot be serviceably used. The bridges  30  with the center ring  56  of the trigger part moreover form a capture structure which keeps small parts such as screws, nuts or the like from falling into the interior of the filter element  12 . 
   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.