Abstract:
In a filter, a rotatable connection flange with two kidney-shaped openings and a diametral web between the openings is located between the top part and bottom part of the filter. Rotating the connection flange allows the direction in which a gas flows through the filter element located in the filter housing to be reversed. In this way, the filter can be operated as a coalescence filter or as a dust filter by simply rotating the connection flange.

Description:
BACKGROUND OF THE INVENTION 
   The present invention relates to a multifunctional filter and claims the priority of German patent application 103 09 428.8-23, to the contents of which reference is hereby made. 
   Compressed-gas, in particular compressed-air, systems require filters for separating out solid and liquid foreign substances, such as dirt particles, condensate and oil, entrained in the gas stream. 
   Conventional compressed-air filters generally comprise a two-part housing having a top part and a bottom part, which are either screwed together or connected to one another by means of a union nut or a bayonet fitting. The housing top part usually has an inflow passage and an outflow passage on diametrically opposite sides. The inflow passage opens out either centrally into a hollow-cylindrical filter element, which is screwed or adhesively bonded into the top part, or into the annular space between the filter element and the housing. Accordingly, the outflow passage leads either out of the annular space or out of the interior of the filter element, depending on whether the gas is to flow through the filter element from the inside outward or from, the outside inward. Consequently, the direction of flow in the filter is fixed after assembly and cannot be altered in the assembled position. The direction of flow at the same also defines the field of use of the filter; since in the case of dust filtering, the gas flows through the filter element from the outside and in the case of coalescence filtering the gas flows through the filter element from the inside in order for compressed-air condensate to be separated out. Consequently, conventional filters are only suitable for use either as a dust filter or as a coalescence filter once the direction of flow has been fixed after installation in the compressed-air system. 
   European laid-open specification 0 808 206 has disclosed a filter which is provided with a differential pressure indicator for monitoring the filter contamination, and this differential pressure indicator is connected to the inflow passage and the outflow passage of the filter via respective measurement passages. In filters of this type, a change in function is particularly complex since it is not only the filter which then has to be rotated through 180°, but also the differential pressure indicator, in order to return its display to the visible side. 
   Since liquid, in particular condensate, which is separated out in the filter collects in the bottom part of the housing and the capacity of the latter is very restricted, it is also necessary for the liquid to be discharged from time to time. This is usually done automatically under level control with the aid of a condensate discharge, wherein a level sensor in a collection space for the condensate drives a solenoid valve, which for its part actuates a diaphragm valve for opening and closing a liquid outlet in the lower part of the filter housing. As described in PCT laid-open specification WO 98/45 641, the condensate discharge may be arranged below the filter housing bottom part, which functions as a collection space for the condensate, and releases the condensate downward via an outlet passage. On account of the line connections, it is likewise no longer necessary to change the function or direction of the flow after assembly in a filter having a condensate discharge of this type. 
   Although a change in function is not usually necessary while the filter is operating, the drawback remains that filters provided with a differential pressure indicator and/or with a condensate discharge are in each case designed for just one direction of flow; consequently, they can be used either only as coalescence filters (direction of flow from the inside outward) or as dust filters (direction of flow from the outside inward) without being converted. 
   SUMMERY OF THE INVENTION 
   Therefore, the invention is based on the problem of providing a filter which allows a function change in situ in a simple way. 
   The solution to this problem consists in a rotatable connection flange being arranged between the two housing parts of a filter which has a housing composed of a top part and a bottom part. This enables a function change to be implemented by simply rotating the connection flange through 180°. The rotation causes the two filter spaces, namely the interior of the filter element on the one hand and the annular space between the filter element and the housing on the other hand, to be respectively switched from one passage to the other. 
   Therefore, the user can decide which function he wants to use the filter for in situ or before assembly. Consequently, the top part can be provided with a front side, for example having display instruments, a viewing window or a functional block, and can therefore always require a set installation position. Nevertheless, the adaptor flange according to the invention allows the filter to be operated in both directions of flow. This simplifies stock-keeping very considerably and leads to a significant cost saving, since both directions of flow are possible with one top part. 
   When seen in plan view, the connection flange preferably comprises a plate with two openings and a web, with two openings which are of the same cross section or congruent arranged laterally reversed with respect to one another on either side of the web. In the operating position, the openings connect the two filter spaces (annular space/interior of the filter element) to the two passages in the housing top part. For this purpose, a passage (flange passage) leads from one of the flange openings to the interior of the filter element, and a passage (flange passage) leads from the other flange opening to the annular space between the filter element and the housing. 
   If the two flange openings are each surrounded by a sealing ring and are in this way sealed with respect to the housing top part, there can be no leaks between the inflow passage and the outflow passage if one or both sealing rings are defective. 
   To enable the condensate which collects in the housing bottom part to be discharged upward, it is preferable for an axial condensate line to extend from the housing top part through the connection flange and the filter element into the lower region of the housing bottom part. In this case, a, for example, capacitive level sensor is located in said lower region of the housing bottom part and is connected, via an electrical line following the condensate line, to the housing top part and a condensate discharge located there. 
   The capacitive level sensor may also be connected to a functional block via a riser line (condensate line) for discharging the condensate which collects in the lower part of the filter housing, a plug connection between the riser line and a condensate passage leading to an outlet valve and an electrical plug connection, which connects electrical lines leading from the level sensor to electronics in the functional block. The functional block may also be arranged on the housing bottom part and connected to the interior of the bottom part and to a level sensor via a passage. 
   The riser line can run within the annular space between a hollow-cylindrical filter element and the filter housing and may preferably be connected to a headpiece which engages around an upper end cap of the filter element. To fix the riser line and the filter element in the housing, the filter element may be provided with radial supporting ribs and the headpiece may be arranged between in each case two supporting ribs. 
   The level sensor arranged at the lower end of the riser line can engage beneath the filter element in the manner of a claw and can if appropriate also support the filter element. The riser line and with it also the required electrical lines for the level sensor may also be routed centrally through the filter element to the functional block. 
   To release condensate from to time as a function of the control by the level sensor, the functional block may include a directly controlled solenoid valve, preferably with a horizontal electromagnetic plunger. However, it is particularly advantageous to use a diaphragm valve which is driven by way of a solenoid valve and preferably has a vertical diaphragm. 
   Assembly and dismantling are simplified if the transmission of energy and information between the discharge adaptor and the functional unit is carried out with the aid of two coils and a ferrite core. 
   Finally, simple adjustment to different pipe diameters of the compressed-air system and simplified stock-keeping result if the inflow passage and the outflow passage are provided with a connection adaptor. 

   
     BRIEF DESCRIPTION OF THE DRAWING 
     The invention is explained in more detail below on the basis of exemplary embodiments illustrated in the drawing, in which: 
       FIG. 1  diagrammatically depicts an axial longitudinal section through a filter; 
       FIG. 2  diagrammatically depicts a plan view of a connection flange; 
       FIG. 3  diagrammatically depicts the main components of the filter; 
       FIG. 4  shows a side view of a filter element with a connection flange as a single building block; 
       FIG. 5  shows a plan view of the connection flange of the building block shown in  FIG. 4 ; 
       FIG. 6  shows a filter with a differential pressure indicator in the functional position for coalescence filtration; 
       FIG. 7  shows the filter shown in  FIG. 4  in the dust filtration functional position; 
       FIG. 8  shows the lower housing part of a filter for a top part with condensate discharge; 
       FIG. 9  shows a filter element which is integrally joined to a connection flange on one side and also to a level sensor and a condensate line. 
       FIG. 10  diagrammatically depicts the inner structure of a filter with a condensate discharge and a functional block; 
       FIG. 11  shows a perspective illustration of a functional block with a diaphragm valve for discharging condensate; 
       FIG. 12  shows a section on line XI-XI in  FIG. 12 ; and 
       FIG. 13  shows a section through the housing top part in the plane of the center axes of the inlet and outlet. 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
   The filter  1  illustrated comprises a top part  2  and a bottom part  3 , between which a connection flange  4  is arranged. The top part  2  has two connection adaptors  5 ,  6 , by means of which the filter  1  can be introduced, for example, into a compressed-air line (not shown). The loosely inserted connection flange  4  is clamped between an inner collar  7  of the top part  2  and a connection ring  8  of the housing bottom part with the aid of a union nut  9 . The connection ring  8  is fixedly connected to a cylindrical center piece  10  of the housing, which is adjoined by a bottom cap  11 . 
   The upper edge of a hollow-cylindrical filter element  14 , which is closed off at the bottom by a cover  13 , is clamped in a sealed or adhesively bonded manner in a groove  12  in the connection flange  4 . The cover  13  likewise has a peripheral groove  15 , in which the lower edge of the filter element  14  is adhesively bonded or clamped. The cover  13  bears a capacitive level sensor  16  with two annular electrodes  17 ,  18 . A condensate tube  19  extends as a riser line through a web  20  of the connection flange  4 , the interior  21  of the filter element  14  and its cover  13  into the interior  22  of the housing bottom part  3 . An electrical line (not shown), which is connected to a contact pin  23  in the connection flange  4 , follows the condensate tube  19 . The contact pin  23  engages in a contact bush (not shown) of the housing top part  2  and is electrically connected to a functional block  24  on the housing top part  2 . 
   The functional block  24  includes a differential pressure gauge  61  having a display  25  and is connected, via a passage  26 , to an inflow passage  27  for unfiltered gas and via a passage  28  to an outflow passage  29  for the fresh gas ( FIG. 10 ). The inflow passage  27  and the outflow passage  29  are separated from one another by a partition wall  81 , which may be very thin but is also suitable for holding lines or even instruments. 
   The inflow passage  27  opens out into the opening  30  of a flange passage  31  which connects the inflow passage  27  to the interior  21  of the filter element  14 . The outflow passage  29 , on the other hand, is connected to the opening  32  of a flange passage  33  which leads to the annular space  34  of the housing bottom part  3 . 
   The passage openings  30 ,  32  are surrounded by sealing rings  35 ,  36  in grooves  37 ,  38 . Accordingly, in the event of a defective seal, it is impossible for a leak to form between the two gas passages  27 ,  29 . Rather, in the event of a defective sealing ring  35 , the unfiltered gas passes to atmosphere, or in the case of a defective sealing ring  36  the purified gas passes to atmosphere, in accordance with the direction arrows  39 ,  40 . In the position of the connection flange shown in  FIG. 1 ,  3 ,  5 ,  6 , the unfiltered gas flows through the inflow passage  27  and the flange passage  31  into the interior  21  of the filter element  14 ; the filter then serves as a coalescence filter. From there, the unfiltered gas flows through the filter layers of the filter element  14  and ultimately emerges as purified gas from the annular space  34  through the flange passage  33  and the outflow passage  39  into a purified-gas line (not shown). 
   If the same filter is to be used for a different function, i.e. as a dust filter, the connection flange  4 , prior to installation, after slight loosening of the union nut  9 , is rotated through 180° from the position shown in  FIG. 1 ,  3 ,  5 ,  6  into the position shown in  FIG. 7 . Then, the union nut is tightened again and the filter is fitted. During the adjustment of the connection flange  4 , the flange passage  33  is rotated to beneath the inflow passage  27  and therefore produces a connection to the annular space  34 , while the opening  32  of the flange passage moves to beneath the outflow passage  29 , so that the flange passage  31  produces a connection to the interior  21  of the filter element  14 . In this situation, illustrated in  FIG. 7 , the unfiltered gas flows from the inflow passage  29  through the flange passage  33  into the annular space  34  and from the outside into the interior  21  of the filter element  14  and, from there, via the flange passage  31  to the outflow passage  27 . As will be clear from a comparison of  FIGS. 6 and 5 , the passage  27  is the inflow passage in  FIG. 6  and the outflow passage in  FIG. 7 , whereas the passage  29  is the outflow passage in  FIG. 6  and the inflow passage in  FIG. 7 . 
   In the case of the filter illustrated, the change of function is possible by simply rotating the connection flange  4  through 180° with respect to the housing top part  2 , since the passage openings  30 ,  32  and the openings of the inflow passage  27  and of the outflow passage  29  located opposite them are arranged laterally reverse with respect to one another and are formed congruently, as can be seen most clearly for the passage openings  30 ,  32  from  FIG. 5 . 
   To move the connection flange  4  into the correct, i.e. functionally intended, installation position during a change of filter element, a positioning pin  41  on the housing top part  2  engages in a corresponding bore  42  at the connection flange  4 , as illustrated in  FIG. 1 ,  6 ,  7 . 
   The level of the condensate which collects at the bottom of the housing bottom part, over the course of time, reaches the electrodes  17 ,  18  and thereby closes a circuit which includes the solenoid valve of the condensate discharge located in the functional block  24 , with the result that a valve of the condensate discharge (cf.  FIG. 10 ,  11 ) opens and the condensate flows out via the condensate tube  19 , under the influence of the system pressure prevailing in the interior  22  of the filter housing  2 ,  3 , until the level of the condensate in the housing bottom part  3  has dropped back below the electrodes  17 ,  18  and the circuit has been opened again. 
   In the case of the filter which is depicted diagrammatically in  FIG. 8 , the connection flange  4  and the filter element  14 , on the one hand, and the condensate tube  19  together with the level sensor  16 , on the other hand, each form a structural unit. The condensate tube  19  is surrounded by an outer tube  43  which also accommodates the electrical lines  44  running from the electrodes  17 ,  18  to the functional block  24 . The condensate tube  19  and the electrical lines  44  end in a plug connector  45  which engages in a bush (not shown) in the housing top part  2 . 
   The building block comprising connection flange  4 , filter element  14 , level sensor  16  and condensate tube  19  illustrated in  FIG. 9  shows a perspective illustration of the two symmetrically arranged flange openings  30 ,  32  with the encircling grooves  37 ,  38  for the sealing rings  35 ,  36 , which prevent untreated gas from passing into the fresh gas passage  29  in the event of a defective sealing ring  35 . 
   In the exemplary embodiment illustrated in  FIG. 10 , a connection flange  4  is once again arranged between the housing top part  2  and the housing bottom part  3 , and this connection flange at the same time produces a connection between a discharge adaptor  46  and the functional block  24 . The discharge adaptor  46  comprises a level sensor  47  having a printed circuit board  48 , which engages beneath the filter element  14  in the manner of a claw and is connected to a riser line  49 . The riser line  49  accommodates the electrical lines  44  from the printed circuit board  48  and opens out in a plug connection  45  of the connection flange  4 . The condensate passage  19  which leads from the lower part of the filter housing  2 ,  3  continues through the connection flange  4 , the housing top part  2  and the functional block  24  into a discharge chamber  50  of the functional block  24 . This discharge chamber is provided with an electromagnetic outlet valve  51 , the solenoid plunger  52  of which is arranged horizontally and opens and closes the valve opening  53  of a discharge passage  54  under the control of the level sensor  47 . For this purpose, the level sensor  47  or its printed circuit board  48  is connected via the lines  44  and two plug connections in the region of the connection flange  4  as well as a plug connection  58  between the housing top part  2  and the functional block  24  to a printed circuit board  59  in the functional block  24 , from which an electrical line  60  leads to the solenoid valve  51 . 
   The passages  26 ,  28  from the inflow passage  27  for unfiltered gas and from the outflow passage  29  for the fresh gas lead to a differential pressure gauge  61 , which is likewise connected to the printed circuit board  59  via an electrical line  62 . Furthermore, the printed circuit board  59  is connected via an electrical line  63  to the display  25  and via a line  64  to a plug connector  65  for the power supply. 
   As an alternative to the solenoid valve  51  which is directly controlled by the level sensor  47 , it is also possible, as illustrated in  FIG. 11 , to use a diaphragm valve  67 , which is controlled by an electromagnetic pilot control valve  66  electrically connected to the level sensor  47  and of which only the diaphragm cover  68  with a valve opening  69 , which leads to a discharge passage (not shown) running transversely to the valve opening  53 , is illustrated in  FIG. 11 . The diaphragm cover  68  accommodates the diaphragm, the control chamber of which is connected to the discharge passage  53  via a bypass line (not shown). This control line is opened and closed by the electromagnetic pilot control valve  66  as a function of the signals from the level sensor  47 . When the control line opens, the control chamber is vented, so that the diaphragm lifts off from the valve opening  69  and the condensate which has collected in the lower part of the filter housing  3  can flow out via the riser line  49  under the influence of the compressed air which is acting therein until the level of the condensate has dropped sufficiently far for the level sensor  47  to emit a corresponding signal to the pilot control valve. 
   Connection adaptors  5 ,  6  which are adapted to nominal widths of the compressed-air lines are screwed or plugged into the inflow and outflow passages  28 ,  29 . 
     FIG. 12  shows a sectional illustration, in part also in plan view, of the housing top part  2  with the filter element  14 , its annular space  22  and the inflow passage  27  with the connection adaptor  5 . This figure clearly reveals how the inflow passage  27  opens out directly into the interior  21  of the filter element  14  via the flange passage  31 . Rotating the connection flange  4  with the flange passage  21  into the position illustrated in  FIG. 13  changes the function, since the connection adaptor  6  is then connected to the unfiltered air line and the connection adaptor  5  or the passages  27 ,  31  are connected to the purified air line, and the compressed air also flows through into the filter element from the outside inward. 
   Furthermore, the filter element illustrated in  FIG. 11 ,  12 ,  13  is provided with the radial supporting ribs  71 ,  72 ,  73  which center the filter element in the housing and between them accommodate a headpiece  74  at the upper end of the discharge adaptor  46 .