Abstract:
A filter device for fluids, in particular for low viscosity fluids such as water, includes a filter housing ( 1 ) in which element holders ( 31 ) are provided for a plurality of filter elements ( 21 ). Filter medium ( 35 ) of each filter element in the filter housing ( 1 ) separates an unfiltered side ( 5 ) from a clean side ( 7 ). The filter housing ( 1 ) can be opened for inserting and removing the filter elements ( 21 ). A carrier in the form of a basket ( 19 ) is provided for the filter elements ( 21 ). The basket can be inserted into and removed from the filter housing ( 1 ). The filter elements ( 21 ) can be releasably secured at the basket.

Description:
FIELD OF THE INVENTION 
     The invention relates to a filter device for fluids, in particular for low viscosity fluids such as water, comprising a filter housing in which element holders are provided for a plurality of filter elements. The filter medium of the filter elements in the filter housing separates an unfiltered side from a clean side. The filter housing can be opened for the purpose of inserting and removing the filter elements. Furthermore, the invention relates to a filter cartridge for use in that filter device as well as to a filter element as a component of that filter cartridge. 
     BACKGROUND OF THE INVENTION 
     Filter devices of the aforementioned type are state of the art and are used in a variety of fields. A few examples that can be mentioned from the vast number of possible applications include the applications for water treatment, potable water filtration, the production of pure water and ultrapure water, the filtration of cooling lubricants and washing fluids, etc. With respect to the state of the art, reference is made to the line filter marketed by Hydac Process Technology GmbH of Neunkirchen, Germany, under the product name PLF1 and embodies a filter device of the type described in the foregoing. 
     When such line filters are to be used for applications in which a fine filtration of large volumetric flow rates is necessary and a correspondingly large filter surface area, for example, exceeding 500 m 2 , has to be provided, problems arise both with respect to the design of the filter housing and with respect to carrying out the replacement procedures for replacing the used filter elements. In the case of filter surface areas exceeding 500 m 2  using filter elements in the form of conventional filter cartridges having a diameter of 67 mm and a length of 40 inches, dimensions that correspond to a filter surface area of about 1 m 2 , the filter housing must provide more than 500 element holders as installation slots for the filter elements. The result is housing dimensions that are difficult to service, in particular, with respect to replacing the elements. Therefore, the state of the art provides such filter surface areas only by a plurality of filter housings. 
     SUMMARY OF THE INVENTION 
     An object of the present invention is to provide an improved filter device conforming to the genre under consideration that provides a filter surface area inside a filter housing that is considerably larger than that of the conventional filter devices, but nevertheless is characterized by its extreme ease of maintenance with respect to the replacement of the used filter elements. 
     The invention basically achieves this object by providing a filter device having a carrier in the form of a basket provided for the filter elements. The basket can be inserted into and removed from the filter housing. The filter elements can be releasably secured at the basket. Since a basket holding the filter elements is provided as a replaceable insert of the filter housing, a large number of filter elements can be removed jointly from the housing and inserted into the housing. This arrangement makes the maintenance work associated with the replacement of the elements much simpler, even if the basket has a large number of filter elements to achieve large filter surface areas. Since this large number of filter elements significantly increases the weight of the basket, the basket can be lifted out of the housing, for example, by attaching a lifting tool and then moving the basket into a position outside the housing, in which the basket can be easily and conveniently equipped with new elements. The resulting ease of maintenance also permits the filter device to be used even under challenging conditions, such as on drilling platforms in offshore oil fields. If, during the operation of the respective oil fields a pressure increase is necessary, treated sea water is pumped from a corresponding drilling platform into the oil field. In such applications the filter device provided for treating the sea water is designed for a filter surface area exceeding 500 m 2  at a filter fineness of 5μ. Due to the arrangement of the filter elements in a basket, which basket can be removed from the filter housing, these requirements can be met with a single filter housing. In addition, the replacement of the filter elements can be carried out easily and reliably, after the basket has been removed by a lifting means, on board the platform even under harsh environmental conditions. 
     In advantageous exemplary embodiments, the basket has a support plate, which support plate in the installation position in the housing separates the unfiltered side from the clean side and has fluid flow passages for forming the element holders. In this context, the filter elements can be releasably secured at the fluid flow passages such that the fluid flow passages are connected to the inner filter cavity surrounded by the filter medium. 
     In this respect, the arrangement can be configured with a distinct advantage where the filter housing has a circularly cylindrical section that receives the basket and exhibits an opening that can be closed by a removable cover. In this case, the basket can be inserted and removed through the opening. The support plate is circularly round and circumferentially sealed off at the housing wall in the installation position. 
     If an abutment ring projecting from the inner wall is provided for supporting the support plate of the basket in the filter housing, the procedure for replacing the filter can be carried out in a very simple and convenient way. All one has to do to remove the basket is to lift the basket off of the abutment ring. To re-install the basket, one need only place the basket down on the abutment ring without additional installation steps being necessary. 
     To secure the basket in the functional position during a filtering operation, the interior of the cover can have at least one axially projecting hold-down device. To hold the support plate of the basket on the abutment ring, this hold-down device extends through a clean-side outflow space, in which a housing outlet for the cleaned fluid is located. 
     The arrangement can be configured with a distinct advantage such that the element holders for securing the filter elements in the form of filter cartridges comprise a connecting device. The connecting device secures a fluid permeable support cylinder at the respective fluid flow passage of the support plate such that an assigned filter cartridge can be pushed onto the exterior of the support cylinder and pulled off from the same. Owing to such support cylinder, even filter cartridges exhibiting a longer length and correspondingly large filter surface area can be held securely in position. At the same time, the replacement steps can be performed easily and conveniently by stripping them off the associated support cylinder. 
     The subject matter of the invention is also a filter cartridge for use in a filter device, with the filter cartridge having preferably at least two filter elements. The filter elements are designed as identical parts and have a filter medium surrounding an inner filter cavity. The respective end of the filter medium is enclosed by an end cap, which end cap leaves open the access to the inner filter cavity. The respective filter elements are arranged coaxially to each other and are sealingly connected to each other at the end caps that interact with each other. If in this case there are, for example, three filter elements and each one of these filter elements exhibits a filter surface area of about 5 m 2 , each filter cartridge has a filter surface area of about 15 m 2 . A requisite total filter surface area of more than 500 m 2  can then be provided with 36 filter cartridges. When arranged in a removable basket, even that large number of filter cartridges can be housed in a single filter housing in such a way that they are easy to service. 
     Furthermore, the subject matter of the invention is also a filter element, which is a component of a filter cartridge, forming sealed connections between a plurality of filter elements. The sealed connections are formed by identical parts and are arranged coaxially to each other. The tilter element has an end cap of a first type and a complementary end cap of a second type. With a design of the end caps, the individual elements can be easily stacked to form a filter cartridge composed of a plurality of elements. 
     Preferably, at least the end cap of one type has a sealing element for forming a seal with the end cap of the respective other type of the adjacent additional filter element. The seal is formed when the end caps lie next to each other. 
     At the same time, the end cap of the first type has in an especially advantageous way a funnel at its opening. The funnel forms the access to the filter cavity, with this funnel expanding conically outward the opening of the end cap. The end cap of the second type has an axially projecting annular body surrounding the opening, with this annular body forming an outer cone for a fitting engagement with the funnel of the end cap of the first type. 
     To form a seal between the adjacent elements, an O-ring can be arranged on the inside of the funnel of the end cap of the first type to form an axial and radial seal that is easy to disassemble. 
     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 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 perspective view in section of a filter device according to one exemplary embodiment of the invention; 
         FIG. 2  is a perspective view of the basket of the filter device of  FIG. 1 , with this basket provided as the carrier for filter cartridges being drawn to a larger scale than in  FIG. 1 ; 
         FIG. 3  is a perspective view of a filter cartridge of the filter device of  FIG. 1 ; 
         FIG. 4  is a side elevational view in section of the filter cartridge of  FIG. 3 ; 
         FIG. 5  is a side elevational view in section of the filter cartridge of  FIG. 4  shown with breaks and drawn to a larger scale than in  FIGS. 3 and 4 ; 
         FIG. 6  is a side elevational view in section, drawn to an even larger scale, of a single filter element of the filter cartridge of  FIGS. 3 to 5 ; and 
         FIG. 7  is an enlarged, partial side elevational view in section of a detail of the region VII in  FIG. 6 . 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     The invention is explained below with reference to the drawings showing a line filter as an example that can be used with a distinct advantage for fine filtering of sea water. The sea water can be conveyed from a drilling platform of an offshore oil field into this oil field to increase the pressure where high volumetric flow rates are to be filtered at a filter fineness of 5μ with filter surface areas in the range of 500 m 2 .  FIG. 1  shows a filter housing  1  with a fluid inlet  3  for the inflow of sea water to an unfiltered space  5  of the housing  1 . The outflow or filtered space  7  on the clean side has an outlet  9  on the housing  1 . The housing  1  has a circular cylindrical shape, aside from a curved, closed bottom part  11 , and has an upper opening  13  that can be closed with a removable cover  15 . The cover  15  can be rotated and removably secured at the housing  1  by a bayonet lock  17 . 
     Between the inflow space  5  on the unfiltered side and the outflow space  7  on the clean side, the filter arrangement is provided including a basket  19  as a carrier for a number of filter cartridges  21  (not all numbered in the drawing). The basket  19 , shown alone in  FIG. 2 , can be inserted through the opening  13  into the housing  1  and removed from the housing. As the carrier element for the filter cartridges  21 , the basket  19  has a circularly round support plate  23  resting against an abutment ring  25  that projects at the interior of the housing  1 . When the basket  19  in its functional position is inserted into the housing  1 , a collar  27  of the support plate  23  is sealed off at the abutment ring  25 . The support plate  23  separates the inflow space  5  on the unfiltered side from the outflow space  7  on the clean side in the housing  1 . To hold the basket  19  in engagement with the abutment ring  25 , the cover  15  has a plurality of rod shaped hold-down devices  29 . Devices  29  extend from the cover  15  axially through the outflow space  7  to the support plate  23 . 
     Support plate  23  has a fluid flow passage  31  for each filter cartridge  21 , of these fluid flow passages only some of them being numbered in  FIG. 1  for the sake of a better overview. In the example shown in the drawing, 36 fluid flow passages  31  are provided to match the 36 filter cartridges  21 . At each fluid flow passage  31 , an element holder is provided to secure releasably the respective filter cartridge  21 . This feature is shown in greater detail in  FIGS. 3 to 7 . 
     The filter cartridges  21 , shown alone in  FIGS. 3 to 5 , are constructed in each instance from three stacked filter elements  33  formed of identical parts. One of these filter elements is shown alone in  FIG. 6 . These filter elements have a filter medium  35  conventionally surrounding an inner filter cavity  37  in the form of a hollow cylinder, for example, in conformity with the line filter PLF1, marketed by the applicant. This filter medium provides a large pleated filter surface area. Such filter media can contain a polyester material and/or polypropylene and can be multi-layered. In the present case, the filter medium  35  is surrounded by a support fabric  39  (see  FIG. 7 ). Similarly, in this case a mesh pack can be provided. On each end side, the filter medium  35  is enclosed by a respective end cap  41  or  43  made of polyamide in the present example. The resulting filter element  33  can be totally ashed as a disposable element. Such a filter element can provide a filter surface area of about 5 m 2 , so that a filter cartridge  21  with three filter elements  33  provides about 15 m 2  of filter surface area. If, for an application for increasing the pressure of sea water, a total filter surface area of about 500 m 2  is necessary, then this requirement can be met by providing 36 slots for the filter cartridges  21  in the basket  19  of the filter housing  1 , as shown in the illustrated example. 
     For easy stacking of the filter elements  33 , the end caps of each filter element are designed differently for each end. One end cap  41  of the first type has a shape that is complementary to an end cap  43  of the second type. More specifically, the end cap  41  of the first type has an axially projecting funnel  47  expanded conically outward and surrounding the cap opening  45 . An O-ring  49  may be found on the inside of said funnel. The end cap  43  of the second type has an axially projecting annular body  51  connected to the opening  45 . This annular body  51  forms an outer cone for a fitting engagement with the funnel  47  of the end cap  41  of the first type. When the individual elements  33  are easily assembled to form the filter cartridge  21 , an axial/radial seal is formed in each instance between the respective end caps  41 ,  43 . 
     The filter cartridges  21  can be releasably secured at the fluid flow passages  31  of the support plate  23  of the basket  19  by a connecting device having a star-shaped retaining body  53  extending over the top side of the support plate  23  (see  FIG. 4 ). One end of a connecting rod  55  is secured to retaining body  53 . The connecting rod  55  extends in the axial direction as far as beyond the lower end of a filter cartridge  21  that is to be secured; see, in particular,  FIG. 4 . In the region of the corresponding end, the connecting rod  55  is provided with an outer thread  57 . As very clear from  FIG. 5 , the connecting rod  55  is used to secure a fluid permeable support cylinder  59  that forms a displaceable mounting for a filter cartridge  21  that is pushed on, at the support plate  23  of the basket  19 . For this purpose, a holding disk  61  is screwed with a nut  66  on the thread  57  of the connecting rod  55  such that the holding disk  61  clamps the support cylinder  59  against a conical ring  63  and thereby against the support plate  23 . The conical ring  63  is sealed off at the support plate  23  by an O-ring  65  and engages with the funnel  47  of the adjacent end cap  41 . The tightening nut  67  for the holding disk  61  is secured against loosening at the holding disk by a sheet metal lock  67 . 
     To hold the respective filter cartridges  21  in position on the support cylinder  59  such that the elements  33  are sealed off from each other at the end caps  41 ,  43  and such that the end cap  41  of the uppermost element  33  is in sealed fluid connection with the fluid flow passage  31  of the support plate  23  by the conical ring  63 , the free end of the connecting rod  55  has a wing nut  69  on the thread  57 . With this wing nut, a locking body  71  can be releasably pressed against the end cap  43  of the bottommost element  33 . As a result, the end cap  41  of the uppermost element  33  is held against the conical ring  63  and is sealed off thereat by the O-ring  49 . The locking body  71  in turn is sealed off at the assigned end cap  43  by an O-ring  73 . As a result, the clean-side filter cavity  37  connected to the outflow space  7  by the fluid flow passage  31  is connected to the inflow space  5  on the unfiltered side only by way of the filter medium of the filter cartridges  21 , but is otherwise sealed off. 
     For the purpose of a replacement operation, the basket  19  with the used filter cartridges  21  is lifted out of the housing  1 , for example, by attaching a lifting device at the lifting eye  75 , and is set down in a position in which the bottom side of the basket  19  is freely accessible, as shown in  FIG. 2 . The holding disk  71  can then be removed by loosening the wing nuts  69 , with only some of the wing nuts being numbered in the drawing. The used filter cartridges  21  are released and can be pulled off from the support cylinder  59 . After the new filter cartridges  21  are pushed on and fastened with tightening screws of the holding disks  71 , the re-equipped basket  19  is ready again for insertion into the housing  1 .  FIGS. 1 and 2  show that the basket  19  has an enclosing ring  77 . Concentrically to the collar  27  of the support plate  23 , enclosing ring  77  surrounds the group of filter cartridges  21  at their bottom, free ends and is connected to the collar  27  by struts  79 . Struts  79  are welded to the collar  27  and the ring  77 . Lifting eyes  75  for handling the basket  19  are likewise attached by welding. 
     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 appended claims.