Abstract:
A filter device for the insertion of filter elements ( 28 ) to be positioned in a filter housing ( 10 ) having a filter inlet ( 20 ) and a filter outlet ( 22 ) for the fluid to be filtered. The filter elements ( 28 ) are traversed in both directions for filtration or backwashing. Certain filter elements ( 28 ) perform the filtration in a filtration position and at least one additional filter element ( 28 ) can be backwashed in a backwashing position to clean its active filtration surface. As the individual filter elements ( 28 ) are brought into the backwashing position and are then returned to their filtration position in succession by a pivoting device ( 30 ), the filter elements are individually displaced into the backwashing position in a temporal sequence, in contrast to prior art, where an arm-type backwashing device is pivoted towards the individual filter elements to carry out the backwashing process.

Description:
FIELD OF THE INVENTION 
     The present invention relates to a filter device for use of filter elements held in a filter housing with a filter inlet and a filter outlet for the fluid to be filtered. Flow through the filter elements is possible in both directions for filtration or backflushing. Some filter elements performing filtration in the filtration position. At least one other filter element can be backflushed in a backflushing position to clean out its effective filter surface. 
     BACKGROUND OF THE INVENTION 
     A generic filter device, a reversible flow filter device in particular, is disclosed in WO 98/42426. In the known reversible flow filter device, some of the filter elements used are made conical, especially in the form of tubular, wedge-wire screen filter elements. As a result of the conical execution, the distance between the individual conical wedge-wire screen filter elements or between them and cylindrical filter elements is increased, with the result that the outflow space in the filter housing is enlarged. Consequently, the offlow resistance in filter operation is reduced. During backflushing the conical filter element is obviously superior to a cylindrical one. First of all, this superiority is because of the relatively larger exit cross section of the conical filter elements compared to cylindrical ones for the same filter surface. Since the exit cross section for the conical filter elements compared to the entry cross section formed by the filter surface, that is to say, the free element area, is however relatively small, depending on the magnitude of the flow resistance of the slotted tube a bottleneck forms in which by large part of the system pressure falling off. Therefore, smaller pressure losses occur. This smaller pressure loss is more favorable in terms of energy during backflushing. 
     During backflushing, a large part of the volumetric throughput for conical and cylindrical filter elements is achieved basically on the bottom end of the filter. The volumetric flows then decrease very quickly. Since the conical element is essentially backflushed much farther, the velocity gradient is additionally smaller. With the inclusion of the velocity profiles relative to the filter surface as a result of the element conicity, an additional cleaning effect compared to cylindrical elements is then achieved. Due to the essentially constant velocity achieved in the cleaning of the conical filter elements, this flow takes place carefully prolonging the service life of these filter elements. 
     During backflushing, preferably all filter elements are regenerated in succession in chronological order. During backflushing of individual elements, filtration is continued over the remaining slotted tubes so that filtration operation in the known solution is never interrupted. The overpressure prevailing in the reversible flow filter device during the backflushing phase allows a small partial stream of filtrate to flow through the filter element to be cleaned in the reverse direction. The dirt is detached from the element and carried away. The amount of discharge accompanying backflushing cannot be exactly metered, and is based on empirical values. Generally, backflushing takes longer with large amounts in order to ensure reliable cleaning. 
     In the known solutions (WO 98/42426, DE 195 42 578 and DE 199 56 859), a hollow arm is pivoted to under one free entry cross section of the filter element to be cleaned and accordingly backflushed to remove the quantity of dirty backflushed fluid and from there the backflushed amount travels via the corresponding connecting pieces out of the filter housing for further treatment. In the known solutions, sealing problems arise with respect to connection of the flushing arm to the respective filter element to be backflushed. Otherwise, the pertinent discharge for the backflushed amount accordingly requires a large amount of installation space. Here, with respect to the number of fluid deflections for the backflushed amount, operating states which are unfavorable in terms of energy occur in the known solutions. 
     SUMMARY OF THE INVENTION 
     An object of the present invention is to provide an improved filter device, while maintaining the advantages of the prior art filter devices such that sealing problems in backflushing are for the most part prevented, that backflushing favorable in terms of energy is enabled, and that only little installation space is required on the filter device for backflushing. 
     This object is basically achieved by a filter device where the individual filter elements are moved in succession from their filtration positions into the backflushing positions and back into the filtration positions by a pivoting device. The filter elements are moved individually in succession in time into the backflushing positions. An arm-like backflushing means is no longer pivoted to the individual filter elements for the backflushing process. Since the pertinent pivoting motion for the filter elements can be easily controlled, possible sealing problems can be better managed. Furthermore, the filter device according to the present invention, relative to the seal configuration and the pivoting drive for the filter elements, requires less installation space within the filter housing. Even when space conditions are tight, these filter devices with a backflush mode can then be implemented. This condition has posed problems in the past. Furthermore, with the present invention improved inflow and outflow behavior for the amounts of fluid to be controlled is achieved, even with respect to the backflushing amounts. In terms of energy, this improved flow benefits the filtration operation of the overall filter device. 
     In the known reversible flow filter devices for backflushing a drivable flushing arm can be moved in succession to positions under the free inlet cross sections of the filter elements for fluid exit of dirty fluid. In contrast, with the filter device of the present invention, the pivoting device requires a correspondingly designed receiving element for holding the filter elements, enabling the individual filter elements for backflushing to approach the backflushing station by a drive pivotable around a pivoting axis within the filter housing. 
     By preference, the receiving element has two opposing end parts between which the individual filter elements extend. At least the end part facing the filter inlet is pivotably guided along the interior of the filter housing by a sealing means. In this way, a prompt replacement process for used filter elements is achieved by the end parts of the receiving element, if the filter elements are to be replaced by new elements. The sealing means can be designed to be reliable in terms of its sealing action and can be operated over the long term. 
     In one preferred embodiment of the filter device of the present invention, the filter elements are configured within the filter housing coaxially to the pivoting axis formed by a rod-like drive part. The drive part detachably connects the two end parts to each other. Preferably, the drive part can be driven by a motor, especially a pneumatic motor, with alternating back and forth motion. This motion can be converted by a free-wheeling or free wheel device into a constant drive motion in one driving direction for the drive part of the receiving element. With this configuration, a drive concept for moving the individual filter elements from their filtration positions into the backflushing position and from there again into the filtration positions can be achieved in a very economical and space-saving manner. This drive concept also requires less energy. 
     In another especially preferred embodiment of the filter device of the present invention, part of the filter housing is designed as a cover. Towards its free ends, it has a cavity with an axial extension corresponding more or less to the overall length of the filter elements. In filtration operation in which flow takes place through the preferably conical wedge-wire screen filter elements from the inside to the outside, in the top part of the filter housing a fluid collection space is formed offering few obstacles to filtration operation, and is extremely favorable in terms of the overall energy balance of the filter device. This favorable energy balance also applies to the case in which from there the corresponding amounts are used for backflushing operation, for which fluid is flowing through the filter element to be backflushed in the reverse sequence from the outside to the inside. 
     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 which form a part of this disclosure and which are schematic and not to scale: 
         FIG. 1  is a side elevational view in section of a filter device according to an exemplary embodiment of the present invention; 
         FIG. 2  is a perspective side view of the filter device of  FIG. 1 ; and 
         FIG. 3  is a top plan view of the filter device of  FIGS. 1 and 2 , partially in a section. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     The filter device shown in  FIG. 1 , especially a reversible flow filter device, has a cylindrical housing  10  including of a top housing part  12  and a bottom housing part  14 . The two housing parts  12 ,  14  can be detachably connected to each other via a detachable bracket clip  16  (compare  FIG. 2 ). The housing  10  can be attached to other components, for example, those of a hydraulic type, at the bottom housing part  14  by flange-shaped fastening parts  18 . The filter housing  10  of the reversible flow filter device has a filter inlet  20  for the fluid to be filtered and a filter outlet  22  for the filtered fluid. Within the bottom housing part  14 , diametrically opposite to the filter inlet  20  relative to longitudinal axis  24 , a fluid outlet  26  is provided via which a quantity of backflushing liquid can be withdrawn from the device. 
     Filter elements  28  tapering conically to the top are inserted into the filter device. At least partially cylindrical filter elements (not shown) are able to replace the conical filter elements  28 . The conical filter elements  28  of wedge-wire screen filter elements are configured at distances from each other along a cylindrical arc (compare  FIG. 3 ) within the filter housing  10 . In an embodiment (not shown), the filter elements  28  can also be configured repeatedly divided into groups along cylindrical arcs. For the embodiment shown in the figures however a total of four filter elements  28  are diametrically opposite each other viewed toward the longitudinal axis  24  of the device. Viewed in the direction of  FIG. 3 , the top filter element  28  is shown in its backflushing position, and the filter elements  28  located underneath are in their filtration positions. 
     By a pivoting device  30 , the individual filter elements  28  can be moved in succession from their filtration positions into the backflushing position and back into the filtration positions. The rotary motion can take place both clockwise and counterclockwise for the individual filter elements  28 . 
     The pivoting device  30  itself has a receiving element  32  for holding the individual filter elements  28 . The receiving element  32  is pivotably mounted within the filter housing  10  for rotation around a pivoting axis  36  by a drive or motor  34 . This pivoting axis  36  is essentially congruent with the longitudinal axis  24  of the filter device. 
     The receiving element  32  has two opposing end parts  38 ,  40  between which the individual filter elements  28  extend. At least the end part  40  facing the filter inlet  20  is guided along the interior of the filter housing  10  via a sealing means or seal  42 . The respective end part  38 ,  40  is designed as a cylindrical plate. The lower end part  40  on the outer peripheral side has recesses for holding the sealing parts of the sealing means or seal  42 . In this way, a sliding seal is attained between the interior of the filter housing  10  and the outer periphery of the lower end part  40 . 
     As is to be seen especially from  FIG. 3 , the lower end part  40  has a kidney-shaped recess  44  which can be supplied with fluid from the filter inlet  20 . As long as the three filter elements  28  with their lower free opening cross sections  46  as shown in  FIG. 3  are located over the kidney-shaped or arcuate recess  44 , the fluid to be filtered flows via the filter inlet  20  and the recess  44  as well as the lower opening cross section  46  into the interior of the respective filter element  28 . For this purpose, fluid flows through the filter elements  28  from the inside to the outside. Dirt present in the fluid is deposited on the inner wall of the respective hollow filter element. The filter element  28  which is the upper one when viewed in the direction of  FIG. 3  is removed therefrom. The filtrate or clean fluid present in the filter housing is routed in the reverse direction, that is, from the outside to the inside, through the upper filter element  28  to be cleaned out since the exterior of each filter element is in fluid communication, as shown. The fluid dirt removed and obtained in this way travels out of the interior of the filter element  28  being backflushed, and in turn flows via its lower free opening cross section  46  in the direction of the fluid outlet  26 , and accordingly, out of the device. 
     For the transport of the backflushing fluid, the lower end part  40  has a circular through opening  48 . On the opposing or top end, the individual filter elements  28  are closed, and held in the upper end part  38  having individual recesses  50  engaging or receiving the upper free ends of the filter elements  28 . The two end parts  38 ,  40  are detachably connected to each other along the pivoting axis  26  via a rod-like drive part  52 . With the upper cover part  12  removed and the two end parts  38 ,  40  released from each other, a used filter element  28  can be replaced with a new element in the event this should become necessary. The drive part  52  can be driven by the drive  34  of the filter device designed in particular as a pneumatic motor. 
     This pneumatic motor has a journal-shaped driven part  54 . Depending on the pump motion of the piston parts of the pneumatic motor, as a drive  34  executes alternating back and forth motion, the pertinent back and forth motion then can be converted by a free-wheeling device or free wheel device  56  into a constant drive motion in one driving direction for the drive part  52  of the receiving element  32 . The free-wheeling means  56  is especially a free-wheeling sleeve  56   a  which with its movable components couples the driven part  54  to the drive part  52 . For this coupling, the rod-like drive part  52  viewed in the direction of  FIG. 1  on its bottom is coupled to a drive axle  58  guided to turn or pivot in the lower housing part  14 . 
     This free-wheeling sleeve  56   a  of the free-wheeling device  56  is able to relay the alternating back and forth motion of the drive  34  in only one direction to the drive line of the pivoting device  30  including of the driven part  54 , the drive axle  58  and the drive part  52 . In the other direction, the free-wheeling device  56  does not transmit any torque to the drive line. The free-wheeling sleeve used with an inner star and individually sprung rollers is prior art, and is especially suitable due to its low slip as far as entrainment of the drive axle  58 . For the opposite rotary motion for the free-wheeling sleeve, a moment is not delivered to the device or consequently to the drive line. These free-wheeling sleeves and free-wheeling devices  56  are prior art so that they will not be described in detail. The drive axle  58  can also be made in several parts to ensure interchangeability of parts of the axle when wear occurs. 
     With this drive, alternative back and forth motion of the pneumatic motor as a drive  34  can be converted into pivoting motion by 90° at a time for the filter elements  28  by the pivoting device  30 . In this way, in succession one filter element  28  can be cleaned at a time in the backflushing position, while maintaining ordinary filtration operation with the other three filter elements. For a different number of filter elements  2 ,  3 , or  5  and more, then different staggering for the rotary motion by the free-wheeling sleeve is necessary. Based on the kidney-shaped or arcuate configuration of the recess  44  on the bottom end  40 , it is moreover ensured for the re-positioning motion that filtration can largely continue always with three filter elements. The backflushing process for the respective filter element  28  can take place in a more or less continuous time intervals. It is also possible to ascertain via difference pressure measurements on the filter elements  28  when they are to be used for backflushing. The pertinent element could then be delivered directly to the backflushing opening  48  with the corresponding control. 
     From the sectional representation shown in  FIG. 1 , the upper housing part  12  has a free cavity  60  with an axial extension corresponding more or less to the overall length of the filter elements  28 . This configuration has proven especially favorable in terms of energy and the resistance opposing the flow through the filter elements  28  in conventional filtration operation. The resistance of parts of the housing  10  is thus distinctly reduced. Within the cavity  60 , essentially laminar flow behavior occurs. This helps flow reduce the outflow resistance in conventional filtration operation. 
     The tubular wedge-wire screen filter elements preferably used have support rods tilted in the direction of the longitudinal axis  24  of the device and around which a wire section is wound into individual turns, with gaps through which fluid can pass being left open. In the area of each contact point of the wire profile with the support rod, a weld spot is located. The gap size provided for the free fluid passage, that is, the distance between two gaps, prevents passage of dirt if the particle size exceeds the gap width. Dirt trapped in the gaps can then be removed from the filter device by the backflushing operation. The filter element  28  cleaned out in this way then moves from the backflushing position back into the filtration positions and can be used there for further filtration use. 
     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.