FILTER DEVICE, HYDRAULIC SYSTEM AND BACKWASHING METHOD

Abstract

A filter device (10) includes a filter element (12) in a filter housing (14) with fluid connection points (16, 18) for the non-filtrate and filtrate. Fluid can be passed through the filter element in both directions for filtrating the non-filtrate or for backwashing for cleaning particle contaminations (72). A pressure control (36) generates a post-suctioning effect to improve the cleaning of the particle contaminations (72). The filter device (10) is designed as a one filter-element solution. In a predetermined exchange, the single filter element (12) for filtering can be used for backwashing or can be backwashed using the pressure control device (36). A hydraulic system (64) and a method for backwashing a filter element (12) of a filter device (10) is provided.

Claims

1-13. (canceled)

14. A filter device, comprising: a filter housing with a non-filtrate fluid connection point and a filtrate connection point; only a single filter element in said filter housing allowing fluid flow therethrough in both directions for selectively filtering the non-filtrate or for backwashing to clean particle contamination; and a pressure control in said filter housing generating a post-suctioning effect for improving cleaning of the particle contamination on said filter element during backwashing of said filter element.

15. A filter device according to claim 14 wherein said fluid connection points are in a head piece of said filter housing and are connected to one another in fluid communication via said filter element; a first fluid-conveying path is between said non-filtrate connection point and an input side of said filter element; and a displaceable blocking part of said pressure control at least partially shutting off fluid communication through said first fluid-conveying path.

16. A filter device according to claim 15 wherein said blocking part forms with a valve seat in said filter housing a nozzle in a partial shut-off position of said blocking part that accelerates non-filtrate fluid flow inside of said filter element.

17. A filter device according to claim 15 wherein said first fluid-conveying path extends through an angle at a diversion in said head piece; and said blocking part is movable at said diversion from an open position towards a closed position of blocking part along a guide separating said non-filtrate connection point from said filtrate connection point.

18. A filter device according to claim 17 wherein said angle is a right angle.

19. A filter device according to claim 15 wherein said filter element extends between and is connected to first and second fluid-conveying receptacles inside said filter housing, said first fluid-conveying receptacle being connected to said first fluid-conveying path, and said second fluid-conveying receptacle being connected to a second fluid-conveying path forming a backwash line extending out of said filter housing and being activated by a backwash valve.

20. A filter device according to claim 19 wherein said backwash valve is a 2/2-way valve.

21. A filter device according to claim 19 wherein a third fluid-conveying path extends between and connects said pressure control and said backwash valve in a straight line.

22. A filter device according to claim 21 wherein said straight line is along a longitudinal axis of said filter element.

23. A filter device according to claim 19 wherein a combined volume of an interior of said filter element and of said backwash line is sufficiently large that a pressure shock can be generated on said filter element for backwashing by displacement of said blocking point into a closed position from an opened position of said blocking part.

24. A filter device according to claim 19 wherein said filter element is conical and is received in a pot-shaped receiving part of said filter housing, a filtrate receiving compartment between said pot-shaped receiving part and said filter element widening due to tapering of said filter element.

25. A filter device according to claim 24 wherein said filter element comprises a slotted sieve tube.

26. A filter device according to claim 24 wherein an isokinetic flow course is established between an inside of said filter element towards said backwash valve.

27. A filter device according to claim 15 wherein said pressure control comprises a drive moving said blocking part between an opened position and a closed position.

28. A filter device according to claim 27 wherein said drive comprises a pneumatically-activatable working cylinder.

29. A filter device according to claim 15 wherein said blocking part is plate-shaped.

30. A hydraulic system, comprising: a filter housing with a non-filtrate fluid connection point and a filtrate connection point; only a single filter element in said filter housing allowing fluid flow therethrough in both directions for selectively filtering the non-filtrate or for backwashing to clean particle contamination; a pressure control in said filter housing generating a post-suctioning effect for improving cleaning of the particle contamination on said filter element during backwashing of said filter element; and a tank connected in fluid communication with said filter connection point.

31. A method of backwashing a filter device with only a single filter element in a filter housing having a non-filtrate connection point and a filtrate connection point, the method comprising the steps of: opening a backwash valve connected to said filter housing to connect in fluid communication an inside of the filter element with a backwash line; allowing non-filtrate to flow from the non-filtrate connection point through the inside of the filter element into the backwash line; displacing a blocking part of a pressure control into a blocking position to stall flow of the non-filtrate into the inside of the filter element and to produce a suction effect sucking filtrate from a filtrate compartment between the filter element and the filter housing into the inside of the filter element; displacing the blocking part into an opened position to flush the inside of the filter element with filtrate; and closing the backwash valve.

32. A method according to claim 31 wherein the blocking part remains in the blocking position for a maximum of two seconds.

33. A method according to claim 31 wherein the blocking part remains in the blocking position for a maximum of one second.

34. A method according to claim 31 wherein the blocking part remains in the blocking position for a maximum of 0.5 seconds.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Referring to the drawings that form a part of this disclosure:

[0031] FIG. 1 is a perspective side view of the filter device according to an exemplary embodiment of the invention;

[0032] FIG. 2 is a side view in section through the filter device according to FIG. 1;

[0033] FIG. 3 is a partial perspective section of a filter element, schematically illustrating the effect of a backwashing operation; and

[0034] FIG. 4 is a schematic diagram of the isokinetic flow course forming in the filter element of FIG. 1 during backwashing.

DETAILED DESCRIPTION OF THE INVENTION

[0035] FIGS. 1 and 2 show a filter device 10 according to an exemplary embodiment of the invention with a filter element 12. The filter element 12 is accommodated in a filter housing 14 with fluid connection points 16, 18 for non-filtrate or filtrate. The fluid connection points 16, 18 are connected to one another in a fluid-conveying manner by the filter element 12. The filter housing 14 has a head piece 20 and a pot-shaped receiving part 22. The head piece 20 has the fluid connection points 16, 18 for non-filtrate and filtrate. From the fluid connection point 16 for the non-filtrate, the non-filtrate is guided along a first fluid-conveying path 24 towards the inside of the filter element 12. This first fluid-conveying path 24 extends at a right angle at a diversion 26. The fluid then flows during the filtration operation through the filter element 12 from the inside to the outside.

[0036] Contamination, in particular particles, attaches to the inner side 28 of the filter element 12. On the outer side 30 of the filter element 12 is the filtrate compartment or the filtrate side 32, which is connected by another fluid-conveying path 34 to the fluid connection point 18 in the filter housing 14 for the removal of the filtrate from the device.

[0037] The filter element 12 is formed conical. In particular, the filter element 12 is formed as a slotted sieve tube, preferably with a filter fineness of 30 μm to 3000 μm. The filter element 12 can however also be a multilayer wire mesh, in particular a three-layer wire mesh, which is preferably sintered. Such a filter element 12 usually has a filter fineness of 25 μm to 100 μm. Such filter elements 12 are generally produced from stainless steel, and their use in such filtration tasks is standard, so that their construction shall not be addressed in greater detail. The filter element 12 is accommodated in the pot-shaped receiving part 22 of the filter housing 14 in such a way that, with increasing tapering of the filter element 12, the filtrate compartment 32 formed in the receiving part 22 and surrounding the filter element 12 widens in an upwards direction in cross section viewed in the direction of FIG. 2.

[0038] According to the invention, the filter device 10 is formed as a single filter element solution. In a predefinable changeover and in a consecutive time period, this single filter element 12 can be used for filtration or can be backwashed by using the pressure control or pressure control device 36. Depending on the quantity of the particle contamination present in the fluid and to be cleaned by the filter element, the filtration operation nevertheless takes more time than the respective backwashing operation. In the filtration operation itself, the particle contamination often attaches to the inner side 28 of the filter element 12. This situation leads to an increasing pressure difference between the fluid connection points 16, 18. A backwashing can then be automatically triggered when a predetermined pressure difference is exceeded, in that such a backwashing operation is triggered by a differential pressure measuring device (not depicted or described in greater detail). The backwashing can also be triggered in a time-controlled or manual manner. The filter element 12 can thus be flowed through in both directions for a filtration of the non-filtrate or for a backwashing for cleaning particle contamination. In addition, the filter device 10 has a pressure control device 36, which activates the backwashing operation and by which a post-suctioning effect is generated to improve the cleaning of particle contamination on the filter element 12 to be backwashed.

[0039] The first fluid-conveying path 24 can be partially or fully shut off between the fluid connection point 16 for non-filtrate and an input side 38 of the filter element 12 on its non-filtrate side by a displaceable blocking part 40 of the pressure control device 36. In a partially shut-off position, the blocking part 40 forms with its valve seat 42 a kind of nozzle or restriction point, by which the fluid flow of the non-filtrate is further accelerated towards the center 44 of the filter element 12 and, additionally, downwards when viewed in the direction of FIG. 2. This effect is supported by the downwards-widening output cone of the filter element 12. The blocking part 40 is formed plate-shaped or saucer-shaped to allow it to cover as large as possible an opening cross section on the input side 38 of the filter element 12. The blocking part 40 can be moved at the diversion 26 from out of a releasing opened position OS towards its blocking position along a guide 46 in the form of a vertically aligned wall. This guide 46 separates the fluid connection points 16, 18 for non-filtrate and filtrate on the head side of the filter housing 14 from one another. The blocking part 40 can be moved by a pneumatically-activatable working cylinder 48 mounted on the top side of the head piece 20 and by an axially displaceable piston rod or activating rod 50 between its starting position or opened position OS and its partially or fully shut-off positions, with the fully opened blocking part position being represented in FIG. 2.

[0040] The filter element 12 extends between two fluid-conveying receptacles 52, 54 inside the filter housing 14 and is connected to them in a pressure-tight manner at the respective receiving points. One receptacle 52 is connected to the first fluid-conveying path 24, and the other is connected to a second fluid-conveying path 56 in the form of a backwash line. The backwash line is led or extends out of the filter housing 14 and can be activated by a backwash valve 58, in particular a 2/2-way valve, by a pneumatically-activatable working cylinder 60. A third fluid-conveying path 62 extends in a straight line between the pressure control device 36 and the backwash valve 58, in particular along the longitudinal axis LA of the filter element 12. The pneumatic drive systems for the blocking part 40 and the valve 58 can also be replaced with an electric servomotor or an electrically-actuatable magnet device.

[0041] The combined volume, made up of the inside of the filter element 12 and the backwash line 56, is sufficiently large that, by a rapid displacement of the blocking part 40 of the pressure control device 36 into the blocking position, a pressure shock can be generated on the filter element 12 to effect the backwashing. The filter device is connected, as part of a hydraulic system 64, to a tank T by its fluid connection point 18 for the discharge of the filtrate. The tank serves as a storage device for additional hydraulic components connected to the tank T, such as mobile machine parts, for example, which components can still be supplied with fluid from the tank T, even when the filter device is in backwashing mode. A valve (not depicted) is advantageously connected between the tank T and the filter device, which valve cooperates with the pressure control device for an obvious operation and which is in any case also closed as part of the backwashing operation, to thus avoid an undesirable post-suctioning of air or residue from the tank T. The valve can also be arranged on the tank side or the device side, to define the backwash quantity on the filtrate side of the filter device, so that precisely portionable backwash quantities (packages) with a minimal input volume are available to the filter device, and can accordingly, in spite of their sometimes high viscosity, be significantly accelerated in a prompt manner for the backwash operation and with their total volume.

[0042] In filtration operation, the non-filtrate flows at the associated fluid connection point 16 into the head piece 20 of the filter device 10 and is diverted at the diversion 26 towards the inside of the filter element 12. The filter element 12 is flowed through with the fluid from the inside to the outside, with contamination being collected on the inner side 28 of the filter element 12. The filtrate side 32 is formed on the outer side 30 of the filter element 12, which filtrate side is connected by a corresponding opening 66 in the head piece 20 to the fluid connection point 18 for the filtrate.

[0043] In the method according to the invention for backwashing the filter element 12, the backwash valve 58 on the underside 68 of the filter device is opened to establish a fluid-conveying connection from the inside 44 of the filter element 12 to the backwash line 56. In this way, non-filtrate can still flow through the filter element 12 into the backwash line 56 along the thus formed fall line and can be accelerated in the axial direction. It cleans at least a portion of the particle contamination 72 from the inner wall of the filter element 12. To trigger further backwashing of the filter element 12, the blocking part 40 of the pressure control device 36 is then displaced into its blocking position. A stall of the fluid flow on the inside of the filter element 12 is then generated such that a suction effect is produced, which effect sucks filtrate 70 from the filtrate compartment 32 from the outside to the inside through the filter element 12 in a radial manner to remove the remaining particle contamination 72 from the filter element 12 (in this regard see also the schematic diagram according to FIG. 3).

[0044] FIG. 3 shows a section of a slotted sieve tube, which substantially forms the filter element 12. A wire is wound in an “endless” manner along tapered longitudinal rods, which face one another and which are arranged axially, and is firmly connected to the longitudinal rods. The tapered cross-sectional extension of the wire is tapered to the outside towards the filtrate side 32 in order to thus present low resistance for the fluid during filtration operation on the outflow side and to form on the inflow side in a widening manner and with the respective adjacent connecting wire coil narrowed passage gaps. The gaps prevent the particle contamination 72 from passing over to the clean side of the filter device. By contrast, in the backwashing operation, as is depicted in a schematic manner in FIG. 3, the wire coils arranged adjacent to one another thus form with their outwards-oriented conical cross-sectional tapering a conical outwards-widening intake funnel. The funnel permits an accelerated guiding of the fluid towards the free gap cross sections to thus carry out the particle contamination 72 accumulated there in the context of the previous filtration towards the inside 44 of the filter element 12 for the described output operation from the filter device with the filter element 12 at the bottom side.

[0045] During the backwashing, an isokinetic fluid flow course 74 is generally established on the inside 44 of the conical filter element 12 towards the backwash valve 58, in particular due to the conical slotted sieve tube construction, which is illustrated by the flow arrows shown in FIG. 4. Due to this isokinetic flow course 74, the backflowed filtrate on the inside of the filter element 12 has over its length I approximately the same flow energy. Due to the described acceleration effects, the flow velocity itself is able to increase even further in a downwards direction towards the opened backwash valve 58 and the fall line-shaped backwash line 56 connected thereto. To complete the backwash operation, the blocking part 40 is in any case again displaced back to its opened position OS depicted in FIG. 2 and the inside 44 of the filter element 12 is briefly rinsed with non-filtrate in order to “wash out” any remaining particle contamination 72 from the inside 44 of the filter element 12. Finally, the backwash valve 58 is closed again to place the filter device 10 in a state in which the normal filter operation can be resumed.

[0046] In this regard the blocking part 40 remaining, for a backwashing of the filter element 12, in the blocking position for a maximum of 2 seconds, preferably for a maximum of 1 second, still more preferably for a maximum of 0.5 seconds has proven to be particularly advantageous. This operation further enhances the backwashing effect.

[0047] The filter device 10 according to the invention has only a single filter element 12 and, for this reason alone, it is formed in a very compact and space-saving manner and also in a manner which can be realized cost-efficiently. The compact construction of the single filter element solution according to the invention permits retrofitting this solution in confined spaces and also in already installed machinery arrangements, such as machine tools, for example. In particular the machining of work pieces often involves significant particulate contamination 72 of lubricating-, cooling- and hydraulic fluids. These fluids can be reliably filtered off with the filter device 10, with the filter element 12 having a particularly long service life for actual filter operation due to time-based or demand-based backwashing. The separation rate is very high due to the use of proven-quality, tough filter element technology. In addition, a particularly high fluid pressure for the non-filtrate at the fluid connection point 16 is not required to be able to reliably filter the fluid and to trigger a backwashing. The only requirement is an input pressure of at least 0.7 bar (=70 kPa). The pressure loss in the filter device 10 is usually approx. 0.5 bar (=50 kPa). Another advantage can be seen in the fact that, due to the large cross sections of the fluid-conveying paths 24, 56, 62 in the filter device 10, the risk of an undesirable blocking for the filter element 12 is minimized in any operational state of the filter device.

[0048] The fluid volume, which is surrounded by the filter element 12 on the non-filtrate side, is approximately 0.3 to 0.6 liters, preferably approximately 0.4 liters. The volume only on the filtrate side inside the filter housing 14 is approximately 1 to 4 liters, preferably approximately 2 liters. The preferred volume ratio of the filter housing 14 to the filter element 12 is thus approximately 5:1. However, ratio values from 2:1 to 7:1 are also conceivable. The fluid volume in the inlet connection 16 and in the run-off region between the outlet of the filter element 12 and the valve 58 and thus on the non-filtrate side is approx. 0.1 to 0.4 liters, preferably approximately 0.2 liters. The fluid volume of the outlet connection 18 on the filtrate side is approximately 0.1 to 0.4 liters, preferably approximately 0.23 liters. Due to the volume ratio of approximately 5:1 of the filter housing 14 to the filter element 12, the afore-mentioned self-cleaning operations on the filter element 12 are established in the backwashing even in the case of highly viscous fluids. To determine the volume inside the filter housing 14 on the filtrate side, the possible total fluid volume inside the filter housing 14 is considered less the fluid quantity surrounded by the filter element 12.

[0049] 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.