Abstract:
A filter device has a filter housing having two separable housing parts ( 1  and  11 ) that can receive at least one filter element ( 21 ). The housing parts can be connected to one another by a coupling device ( 7 ). The filter element ( 21 ), or an adapter that can be connected to it, forms a functionally essential component of the coupling device ( 7 ). Only when the filter element ( 21 ) has been placed in its functional position within at least one of the housing parts ( 1, 11 ), can the housing parts ( 1, 11 ) be connected to form the filter housing of a functional filter device.

Description:
FIELD OF THE INVENTION 
     The invention relates to a filter device having a filter housing having at least two housing parts, which can be separated from one another to receive at least one filter element, and which can be connected to one another by a coupling device. 
     BACKGROUND OF THE INVENTION 
     Filter devices of this type are prior art and are used in a wide variety of fields. In the prior art, such devices are especially widely used in applications for cleaning operating fluids such as hydraulic fluids, fuels or lubricants, coolants and the like. Since the filter devices form important system components, proper functioning and filter performance are a prerequisite for the smooth operation of the respective systems. Taking into consideration the fact that malfunctions, which may include damages and failures, may result in very high costs, the functional reliability of the filter devices represents a significant economic factor. 
     SUMMARY OF THE INVENTION 
     In terms of this problem, an object of the invention is to provide a filter device of the type considered here, which is characterized by a high degree of operational reliability. 
     This object is achieved according to the invention by a filter device having a filter element accommodated in the filter housing, or an adapter associated therewith forming a functionally essential component of the coupling device. Only when the filter element has been placed in its functional position within at least one of the housing parts that the respective other housing part can be connected to this first housing part to form the filter housing of a functional filter device. On the one hand, since in the absence of a filter element, no connection between the housing parts is possible. Without a filter, the filter housing cannot be placed in an operational state, ensuring that a filter element is always installed. As a result, no risk of a functional failure exists as a result of operation without an inserted filter element. On the other hand, also ensured is that only a suitable filter element can be used, which can serve as a component of the coupling device due to the construction thereof. Operation with unsuitable filter elements that do not correspond to the required specifications is thereby excluded. 
     The coupling device can be advantageously designed such that the device has at least a first connecting element, which is a component of the respective one housing part, and has at least a second connecting element as a component of the respective other housing part. At least a third connecting element is provided, which third connecting element fixes the first and second connecting elements to one another as soon as the respective filter element is in a functional position. At the same time, the third connecting element can be a component of the filter element and/or a component of the adapter, which, when in its fixed position on the first and second connecting elements, allows the filter element to be coupled to the adapter at least in the functional position thereof. 
     In an especially advantageous manner, the third connecting element may be a component of the end cap of the filter element, which at least in part comprises the filter element material. The third connecting element is disposed such that it is concentric to the longitudinal axis of the filter element. 
     In the case of especially advantageous embodiments, the individual connecting elements are formed from threads that preferably each have an identical pitch with an identical thread formation. The coupling device with the connecting elements thereof thereby forms a screw connection, so that the connection of the housing parts can be implemented easily and conveniently by a screwing process. 
     In an especially advantageous manner, the respective thread, which forms the third connecting element, can be formed out of plastic, preferably out of the same material as the end cap. In the case of plastic threads thus formed, the plastic element of the thread system with which the filter element is associated, and which enters into threaded engagement with the threads of the housing parts, which are usually made out of metal, is replaced each time the filter element is changed. As a result, any kind of plastic including less wear-resistant plastic can be used for the end cap with its threads. In addition, in the case of plastic threads, no metal debris is formed during screwing processes, so that both wear and contamination within the interior of the housing are minimized. 
     The threads of the first and second connecting elements may be formed having essentially the same length. In a functional position of the filter element, the threads of the third connecting element essentially completely cover the respective other threads, which are meshed therewith. 
     In the case of the standard design of such a filter housing, the configuration may be such that the thread of the first connecting element leads to a releasable opening, which is a component of a housing pot as the one housing part. The thread of the second connecting element leads to this releasable opening or to the additional housing part adjacent thereto, which is a component of a housing head fitted on the housing pot and connected thereto by screwing to close off the opening externally. 
     In advantageous embodiments, the end cap of the respective filter element has a ring flange, which protrudes outward, and which divides the threads of the end cap into two thread sections. When the filter element is in the functional position in the filter housing, the one thread section meshes with the respective one connecting element, and the other thread section meshes with the respective other connecting element. The ring flange is in contact with the frontal wall sections of the adjacently disposed housing parts, with the wall sections being disposed such that they face one another. 
     In terms of the design of the end cap, the configuration may advantageously be such that the one or the other thread section leads out to the outside at the upper side or, respectively, at the underside of the end cap. 
     In especially advantageous embodiments, the one housing part, for example in the form of the housing pot, is provided with a fixing device on the outer circumference thereof for a seal. The seal is overlapped by wall elements of the respective other housing part, such as the housing head, as soon as the housing parts are connected to one another in their final position. The ring flange of the filter element, when viewed in the longitudinal direction thereof, is disposed above the seal oriented towards an inflow opening of the filter element. 
     The subject matter of the invention is also a filter element, which is preferably provided for a filter device according to the invention. 
     Other objects, advantages and salient features of the present invention will become apparent from the following detailed description, which, taken in conjunction with the drawings, discloses a preferred embodiment 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 view in section of a filter device according to an exemplary embodiment of the invention; 
         FIG. 2  is an enlarged, partial side view in section of the filter housing section having a coupling device between the housing pot and the housing head of  FIG. 1 ; and 
         FIG. 3  is a partial perspective view in section of the upper housing part of the filter device of  FIG. 1 . 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     The embodiment of the filter device according to the invention shown in its entirety in  FIG. 1  has, as a housing part, a housing pot  1  in the form of a circular cylinder that tapers inward slightly towards the bottom  3  of the pot. The bottom  3  is closed, except for a centrally located housing discharge element  5 , the closing member of which is not shown in  FIG. 1 . The housing pot  1  is connected at the upper opening  9  thereof via a coupling device  7  to a housing head  11  as the second housing part. The head  11  has connections for the supply and discharge of the appropriate fluids. In the figures, of these connections, only the centrally located inlet  3  is visible. An outlet for the discharge of the filtrate is located laterally on the head  11  and is not visible in the drawing. Fluid passages for the unfiltrate and filtrate are provided in the head  11 , of which the fluid passage that is connected to the inlet  13  is formed by an inner cylinder  17  that is concentric to the longitudinal axis  15 . The surrounding chamber  19  in the inner cylinder  17  is connected to the filtrate outlet. 
     A filter element  21  having a conventional, circular cylindrical design can be accommodated in the filter housing, which is formed by the filter pot  1  and filter head  11 . The filter element has a hollow cylindrical shaped filter material  23 , through which the fluid flows from the inner filter cavity that is surrounded by the filter material  23  and then outward during the filtering process. The fluid passes through a support structure  25  that encloses the filter material  23 , which support structure is formed by a perforated shell member or a mesh pack. The filter material  23  is enclosed by an end cap  27  at one end, shown below in  FIG. 1 . An upper cap end  29  is located at the opposite end of the filter material  23 . Both end caps  27 ,  29  are made of a plastic material, by injection molding. 
     The figures show the filter element  21  in its functional position, inserted into the filter housing  1 ,  11 . The inner cylinder  17  of the head  11  overlaps a connecting part on the end cap  29  to form a fluid connection between the inlet  13  on the head  11  and the inner filter cavity of the filter element  21 . This connecting part is formed by a projection that has the shape of a pipe socket  31 . Pipe socket  31  projects from the flat upper side of the end cap  29  is concentric to the axis  15 , and is sealed by a sealing ring  33  on the interior of the inner cylinder  17 . The lower end of the pipe socket  31  leads into the inner filter cavity of the filter element  21  that forms the unfiltered side during the filtering process, from which the cleaned fluid passes to the chamber  35  surrounding the support structure  25 , which forms the filtered side, after the fluid passes through the filter material  23 . The cleaned fluid passes from this chamber  35  to the fluid chamber  19  located in the head  11 . Fluid chamber  19  is connected to the fluid outlet (not visible) on the head  11 . 
     The upper end cap  29  is designed as a one-piece injection molded part made of plastic, such that it forms an indispensable component of the coupling device  7 . This means that, in the case that the filter element  21  having the special end cap  29  is absent, no connection is possible between the pot  1  and the head  11 . Therefore the formation of a functional filter housing that is formed from the pot  1  and the head  11  is not possible. To form a component of the coupling device  7 , the end cap  29  has a disk  37 , which encloses the pipe socket  31  and which is flat on the upper side  38  thereof. From the underside of disk  37 , an annular body  39  having a square cross section axially projects. The outer diameter of the annular body  39  is adapted to the inner diameter of the fluid chamber  19  of the head  11  and the inner diameter of the pot  1  in the region of the opening  9  thereof. The cylindrical inner surface  41  of the annular body  39  overlaps the associated edge section of the support structure  25  of the filter material  23 . Gaps  43  are distributed in the annular body  39  such that they are spaced apart from one another as fluid passages between the chamber  35  of the pot  1  on the filtered side and the fluid chamber  19  in the head  11 . 
     A sleeve-like extension  45  is connected to the underside of the annular body  39  of the end cap  29 , which extension continues the outer diameter of the annular body  39  and extends axially as a sleeve body that is concentric to the axis  15 . Extension  45  has a wall thickness that is slightly reduced towards the free end  47 . With the annular body  39  and extension  45 , a total axial extension is obtained for the end cap  29 . The length of the total axial extension when measured from the end  47  to the upper side of the filter element  21 , corresponds to approximately half of the diameter of the end cap  29 . A radial projecting ring flange  49  is located approximately half way along the length between the end  47  and the upper side of the end cap  29 . In the case of the functional position of the filter element  21  in the filter housing  1 ,  11  shown in the Figures, the ring flange  49  is in contact with a wall element  51  on the front surface at the edge of the opening  9  of the pot  1 , and with a facing wall element  53  on the front surface on the head  11 , when the pot  1  and the head  11  are connected to one another by the coupling device  7 , see  FIG. 2 . 
     On the outside of the annular body  39  and of the extension  45 , the end cap  29  forms a connecting element in the form of a thread for the coupling device  7 . The connecting element having a first thread section  55  between the lower free end  47  and the ring flange  49 , and a second thread section  57  between the ring flange  49  and the upper side of the disk  37  of the end cap  29 . Both thread sections  55  and  57  have approximately the same length and are formed by an external thread having the same thread formation and pitch. A further thread  59  is formed on the interior of the pot  1 , connecting to the opening  9 , as an additional connecting element of the coupling device  7 . A thread  61  is located on the head  11 , extending from the wall element  53  at the front side, as an additional connecting element of the coupling device  7 . These threads  59  and  61  likewise have the same thread formation and pitch as the threads formed by the thread sections  55  and  57  on the end cap  29 . The axial length of the threads  59  and  61  are each formed by an internal thread on the pot  1  or, respectively, head  11 . 
     In the case of this configuration, the coupling device  7  only allows a screwed connection between the pot  1  and the head  11  when the filter element  21  has been inserted into the housing  1 ,  11 . The insertion process may be carried out such that the filter element  21  is screwed with the thread section  57  of the end cap  29  into the thread  51  in the head  11  until the ring flange  49  on the wall element  53  abuts the head  11 . The unit comprising the head  11  and filter element  21  thus formed can now be connected to the pot  1  in that the thread section  55  on the extension  45  of the end cap  29  is screwed into the thread  59  of the pot  1  until the ring flange  49  abuts the wall element  51  of the pot  1  on the front surface. As the Figures show, in the screw connection that is formed, the threads  59  and  61  on the pot  1  or, respectively, on the head  11  are essentially completely covered by the thread sections  59  and  61  of the end cap  29 . 
     To form a seal between the pot  1  and the head  11  of the housing when the screw connection has been formed, an annular groove  35  is formed on the outside of the pot  1  in the wall region adjacent to the opening  9 . A sealing element  67  is incorporated in groove  35 . An axially projecting external ring  69  is located on the facing edge of the head  11 . This external ring  69  is radially offset radially outward vis-à-vis the thread  61 . The inner wall of external ring  69  overlaps the sealing element  67  to form the seal with the pot  1 . 
     While one embodiment has 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.