FILTER DEVICE AND FILTER ELEMENT

The invention relates to a filter device, in particular intended for incorporation into a fluid supply tank, having at least one, preferably exchangeable, filter element, the element material of which can be flowed through by a fluid from the inside outward, viewed in the radial direction, and which is enclosed by a support tube which has passage openings and is surrounded, in each case maintaining a settable radial distance and with formation of a fluid flow space, by a housing wall having a plurality of passage points. The invention additionally relates to a filter element, in particular provided for such a filter device.

During filtration with such in-tank filter devices, in the case of high working pressure and/or large fluid volumes when the fluid to be cleaned passes through the filter element, splashing and foam formation occurs; with the latter being produced by gas bubbles, in particular air bubbles which, in the hydraulic working circuit preceding the fluid supply tank, can reach the fluid, in particular in the form of hydraulic oil. Such a foam formation in the fluid occurs in particular when such filter devices are used for mobile machines, such as diggers, wheeled loaders or telescopic loaders, etc., which are provided with corresponding working hydraulics, for example in the form of hydraulic cylinders which can be actuated and supplied by means of pumps. To prevent the fluid which splashes out of the filter element and which is subject to foam formation from coming into direct contact with the other fluid volume or oil volume in the supply tank, in the known solutions the filter elements are enclosed in corresponding encasing housings inside the tank, each of which forms a kind of presettling space or pre-chamber, in which the cleaned fluid can come to rest and any gas bubbles can be discharged upwards as a result of buoyancy. However, said settling chambers take up a relatively large installation space inside the actual tank volume and ultimately thus also result in a supply tank which has a large overall design, and in particular in the case of said high working pressure and/or very large volumes of fluid to be filtered, the pre-chamber volumes are often insufficient to bring about to an adequate extent a settling of the oil and an air outflow before output into the actual supply tank.

As part of the modern downsizing in such mobile machines with the retention of the performance of the hydraulic system, a size reduction of technical system parts such as the tank volumes also necessarily takes place so that the input times and settling times for the fluid in the tank are necessarily reduced, which is in turn accompanied by increased foam formation.

In order to deal with such foam formation, solutions have already been proposed in the prior art, for example in the form of EP 2 249 941 B1, which relates to a generically formed filter device and filter element. In this known solution, the plurality of passage points of the housing wall are partially arranged below a respective changeable fluid level in the supply tank and the other portion of the passage points is arranged above this fluid level. Because, in the known solution, the respective passage points are additionally part of at least one screen structural layer or grid structural layer, which covers passage regions arranged in the housing wall which are preferably window-like, and because the free opening cross sections for the passage points of the housing wall are selected such that any gas bubbles located in the cleaned fluid can be separated at the thus perforated housing wall and/or can be collected for a discharge close to the fluid level, the fluid entering into the fluid flow space and which is cleaned by the respective element material flows in the region of the respective fluid level and above same in a laminar manner via the assignable passage points into the supply tank, and the undesirable splash formation or foam formation when the fluid flows out into the supply tank is thus reliably prevented.

Due to the pressure difference between the inflowing, not cleaned fluid and the flowing off, cleaned fluid, the latter can be raised in the fluid flow space via the fluid level in the tank with uniform distribution along the inner side of the housing wall with the passage points, with capillary effects also being able to contribute thereto, and the thus created uniform fluid film then permits the splash- and foam-free outlet from said passage points transverse to the housing wall.

For the known filter device, a filter element is used in a preferably exchangeable manner, in which a pleated element material for cleaning the particulate contamination from the fluid extends between two end caps, wherein said element material is enclosed by a support tube which, in order to increase the pressure stability of the element material, supports same towards the outside, and this support sleeve has corresponding passage openings in the form of a perforation, which allows the fluid to pass from the inside to the outside firstly through the element material and then through the support tube of the filter element in the radial outlet direction.

On the basis of the above-mentioned prior art, the problem addressed by the invention is to further improve the known solution such that an increased air output from the fluid, in particular in the form of hydraulic medium, is obtained in a fluid supply tank. This problem is solved by means of a filter device having the features of claim 1 in its entirety and a filter element having the configuration of features of the additional independent claim 10.

Because, according to the characterizing part of claim 1, at least a portion of the passage openings in the support tube of the filter element has a flow guide, which provide the fluid with a flow direction which is different from the radial flow direction through the filter element, this results in improved removal of the air content, including in the bubble form, from the fluid to be filtered, in particular in the form of hydraulic oil. In addition, by means of the respective flow guide the coalescability for the air bubbles or air droplets inside the fluid is increased, which thus join together to form larger bubbles or drops due to their surface tension, which in turn allows, due to their buoyancy behavior, an improved discharge of the thus collected air from the fluid into the environment, in that the air discharge occurs in an unforced manner via the respective fluid level into the above-situated air space of the fluid supply tank.

In addition, the targeted fluid flow, brought about by means of the respective flow guide, means that no type of short circuit occurs in front of or behind the support tube, rather it is ensured that in any case the air volumes existing between the outer side of the pleated element material and the facing inner side of the support tube can also be discharged in a defined manner via the flow guide. In the region of the respective flow guide and its respective discharge opening in the form of free opening cross sections, an acceleration of the fluid can also occur with an establishing swirl flow about the filter element with the support tube, so that an increased and improved air output from the fluid can take place. It has proven to be advantageous to direct the swirl flow counterclockwise about the filter element, with all of the flow guides preferably having to face in the same direction with their free opening cross sections, in order to thus not impede the air outlet from the fluid medium as a result of undesirable turbulence. However, it is also very possible to select the reverse swirl direction, in other words, in the clockwise direction.

It has also been proven to be particularly advantageous if the respective flow guide of the support tube delimits the associated free opening cross section in such a way that said flow guide is inclined relative to the longitudinal axis of the filter element by 10° to 80°, preferably by approximately 30° to 60°, particularly preferably by approximately 45°, which has a positive effect on the swirl flow to be obtained about the filter element.

The respective flow guide is formed from the material of the support tube and is shaped projecting outwards as a flow pocket, the top edge of which delimits the opening cross section for the fluid discharge of the flow guide. The flow guide is thus formed, stamped out or cut out in the manner of a pocket from the support tube sleeve from the inside outwards, which permits a particularly cost-effective production of the support tube and thus of the filter element as a whole.

In one particularly preferred embodiment of the filter device according to the invention, in addition to the respective flow guide, the support tube has additional passage openings, which surround the respective flow guide in groups. The total of the free opening cross sections of the flow guides is preferably smaller than that of the passage openings in the support tube. While the flow guides with their free opening cross sections produce the swirl flows about the filter element, the other passage openings in the form of a perforation in the support tube still ensure that the fluid passes through the support tube in the radial direction from the inside outwards, which helps to prevent undesirable pressure increases on the inside of the support tube, which could otherwise compromise the free filtration through the pleated element material. It has also been proven to be advantageous to group both the flow guides of the support guide and the other radial passage openings in groups and at defined distances relative to one another around the support tube.

The subject matter of the invention is also a filter element, in particular intended for such a filter device, having an element material extending between two end caps, which is enclosed by a support tube with passage openings, with improved air output values being able to be achieved with this filter element provided that at least a portion of the passage openings in the support tube of said filter element have a flow guide, which provide the fluid with a flow direction which is different from the radial flow direction through the support tube.

The solution according to the invention is explained in detail below with reference to different exemplary embodiments according to the drawings in which, in a schematic and not to scale manner,

FIG. 1 shows a longitudinal section through an exemplary embodiment according to the prior art;

FIG. 2 shows, in a partially cut open depiction, an additional exemplary embodiment of the filter device according to the prior art, which nevertheless corresponds as much as possible to the embodiment according to FIG. 1;

FIG. 3 shows a perspective oblique view of a filter element of the kind used for one of the filter devices according to FIGS. 1 and 2;

FIG. 4 shows a top view of the filter element according to FIG. 3 in the erect state;

FIG. 5 shows an enlarged partial view of the notional circle depicted in FIG. 4 with the reference B;

FIGS. 6, 6
a, b show a top view of an amended embodiment of a support tube with an uncoiled support tube sleeve and, in the viewing direction of the arrows identified with X and Y, in each case a frontal view of the support tube sleeve according to FIG. 6; and

FIG. 7 shows an enlarged depiction of the circle section identified in FIG. 6 with the reference A.

The filter device shown in longitudinal section in FIG. 1 serves for installation in a reservoir-like fluid supply tank 10, comparable with the installation situation according to EP 2 249 941 B1. Of the fluid supply tank 10 the depiction of FIG. 1 depicts only the top tank wall 12 and an associated receiving wall 14 for the attachment of the filter device as a whole. A similar installation situation for filter elements and filter devices is also disclosed in EP 1 419 807 B1. Extending between the depicted wall sections 12, 14 is an inlet channel 16 for fluid frequently contaminated with particles, for example from the hydraulic circuit of the working hydraulics of a construction machine or the like, which is not depicted in detail.

The filter device also has a filter element 18 with a preferably pleated filter mat as the element material 20; otherwise the filter element 18 substantially forms a type of circular hollow cylinder. The element material 20 is guided between a top end cap 22 and a bottom end cap 24 as parts of the filter element 18. The bottom end cap 24 has, centrally and extending coaxial to the longitudinal axis 26 of the filter device, a bypass valve 28 which is conventional per se, which opens in the case of an element material mat 20 which is clogged with particulate contamination and, with bypassing of the element material 20, allows the fluid to flow off uncleaned via a bottom bypass opening 30 into the supply tank 10.

Because the element material 20 is flowed through from the inside to the outside in the radial direction, in other words, the throughflow takes place from the inner side 32 of the filter element 18 in the direction of the inside 34 of the fluid supply tank 10, the element material 20 is enclosed by a sleeve-like support tube 36 for the purpose of reinforcement towards the outside, which is preferably likewise formed circular cylindrical and has corresponding passage openings 37, which in the prior art are formed as a perforation in the support tube 36 (cf. FIG. 2). These passage openings 37 in the support tube 36 serve for passage of the fluid cleaned by means of the element material 20. A correspondingly formed support sleeve (not depicted) could however in principle also follow the outer contour of the pleated element material 20 and to this extent realize the support for the purpose of increasing the pressure stability of the element towards the outside. Such a support sleeve would then also have corresponding passage openings for the fluid medium. The fluid inflow of the uncleaned fluid, coming from the inlet channel 16, takes place via the top inflow opening 38 of the filter element 18 in the direction of said inner side 32 of the filter element.

The filter element 18 is housed in a housing which is identified as a whole with the reference numeral 40, which has a flange-like broadening 42 on its top side, by means of which the filter device is supported in this region on the top side of the top tank wall 12. A cylindrical housing wall 44 is in turn connected in a downward direction to said broadening 42, which cylindrical housing wall is formed closed in a pot-shaped manner towards its bottom side 46, up to said bypass opening 30. This bottom side 46 of the housing wall 44 preferably to this extent forms a separate base part and the housing wall 44 is supported with its respective free end on a shoulder-like step of the base part 46 and on the flange-like broadening 42. In order that the described composite structure of the housing 40 remains in the assembly depicted in FIG. 1, on the external circumference side relative to the element material 20 with the support tube 36 supporting rods 48 are arranged, of which only one supporting rod 48 is fully depicted in FIG. 1 and, of the two other thus inserted supporting rods 48, for the sake of simplicity only one additional rod 48 is shown in FIG. 1 with its bottom final end, which projects below the bottom side of the base part 46. In this region the respective supporting rod 48 is screwed via a threaded nut 50 and the top end of the respective supporting rod 48 is screwed in in a fixed manner via a corresponding internal thread into the flange-like broadening 42. The housing wall 44 can thus be fixed between the broadening 42 and the base part 42 under a set pretensioning.

In order that the housing 40 can be inserted into the top tank wall 12, a corresponding circular cylindrical recess 52 is introduced into said top tank wall, the diameter of which is in any case larger than the external diameter in the region of the transition between the flange-like broadening 42 and the external circumference of the housing wall 44. Furthermore, a cover part 54 is provided as part of the filter device with a handle 56 for simpler installation and removal of the filter device in the depicted tank 10. The cover part 54 has a shoulder-like broadening 58, which projects on the top side of the receiving wall 14, and a shoulder of the broadening 58 engages in the free internal diameter of the receiving wall 14 while contacting on same. An annular sealing element 60 of standard design serves for fluid sealing in this region. Fixing screws 62 lying opposite each other are provided arranged diametrical to the longitudinal axis 26, which serve for fixing of the cover part 54 to the receiving wall 14. Once the screws 62 have been loosened, the filter device can be removed from the tank 10 and reinstalled in the reverse mounting sequence. These mounting operations are necessary if a used filter element 18 is to be replaced with a new element.

A magnetic rod 64 extends concentric to the longitudinal axis 26 inside the filter device, which magnetic rod in particular has the function of a permanent magnet and which, viewed in the viewing direction of FIG. 1, is fixed with its top end in the cover part 54, and is in particular screwed therein, and with its other opposite free end it penetrates the inner side 32 of the filter element 18. This magnetic rod 64 permits a separation of magnetizable metal components in the fluid to be filtered. Both the magnetic rod 64 and the bypass valve 28 are optional and do not necessarily have to be provided for the functioning of the filter device as a whole.

As is additionally shown in FIG. 1, the cylindrical housing wall 44 occupies a settable radial distance relative to the external circumference surface of the filter element 18, so that to this extent a fluid flow space 66 is formed. This fluid flow space 66 extends parallel to the external circumference surface of the filter element 18, in particular it extends in the axial longitudinal direction parallel to the longitudinal axis 26 of the device between the top side of the base part 46 and the bottom side of the flange-like broadening 42. Furthermore, the fluid flow space 66 is substantially delimited towards the outside by the housing wall 44 and towards the inside by the external circumference surface of the element material 20 in the form of the filter mat. If the sleeve-shaped support tube 36 is used for the element material 20, this external circumference surface forms the boundary for the fluid flow space 66.

In the exemplary embodiment according to FIG. 1, a fluid level 68 inside the supply tank 10 is shown, and the filter element 18 and thus the fluid flow space 66 lie partially below the level 68 and partially above same. Depending on the volume of fluid to be cleaned flowing in via the inlet channel 16 or the volume flowing off required for the working hydraulics (not depicted), the fluid level 68 changes relative to the shown current position in FIG. 1. The fluid flow space 66 is otherwise not compromised from its flow space up to the penetration of the individual supporting rods 48.

The exemplary embodiment according to FIG. 2 is changed compared with the embodiment according to FIG. 1 to the extent that a compression spring 78 is provided, which extends between the bottom side of the cover part 54 and the housing 40 in order to press the housing 40 of the filter device against the top side of the top tank wall 12 in the case of a fixed cover part 54 and thus fix the filter device inside the tank 10.

As is additionally shown in FIG. 2, which at least partially relates to an external view of the filter device according to FIG. 1, window-like passage points 74 are provided in the housing wall 44 of the housing 40, which penetrate the housing wall 44 in two groups spaced apart from one another which lie above one another in an annular manner and which circulate at the circumference. The two adjacent groups have the same axial distance relative to each other, and the individual passage openings 74 within a group likewise have the same distance measurements relative to each other when viewed in the radial circumferential direction. As the depictions according to FIGS. 1 and 2 additionally show, the bottom group of passage points 74 is still partially covered by the fluid level in the case of a given fluid level 68, and the group lying above it ends above the level top side and without engaging in same. In the present exemplary embodiment, at least one screen structural layer or grid structural layer 76 should be arranged inside the housing wall 44 and abutting the inner side thereof, which forms a continuous cylinder sleeve and overlaps all identically formed window-like passage points 74 at the edge side. In order that the respective structural layer 76 remains on the inner side of the housing wall 44, it can be correspondingly fixed by means of a spot welding which is not depicted in detail. It is in principle also possible to stamp said screen structure into the housing wall 44 of the housing 40, so that to this extent the screen structure is an integral component of the housing wall 44. Furthermore, instead of a single structural layer 76, in principle said structural layer can however also have a separate grid, even formed multilayered, for each window opening as a passage point 74. The choice of the free opening cross sections for the passage points 74 of the respective structural layer 76 depends on the environmental conditions, such as for example the viscosity of the fluid used, in particular in the form of the hydraulic oil, which is ultimately also dependent on ambient temperature values. The presented window openings 74 as passage points in the housing 40 or in the housing wall 44 are preferably realized in a rectangular shape; however other opening geometries are also possible in this regard.

If the filter device according to FIGS. 1 and 2 is now activated, fluid flows through the mat-like element material 20 from the inside towards the outside and is thereby cleaned. Because a portion of the fluid stored in the tank 10, which is situated below the level 68, flows into the bottom passage points 74, the inflow space 66 to this extent situated below the level 68 fills with fluid with the result that fluid additionally flowing in from the inner side 32 is pushed upwards, so that a film-like hollow column is formed in the fluid flow space 66 with fluid which contacts on the inner side of the housing wall 44, and on the passage points of the to this extent perforated screen structural layer or grid structural layer 76. This rising fluid arrangement above the fluid level 68 flows out through the passage openings in the window-like passage points 74, which occurs in an essentially laminar manner and splashing or foaming processes during the passage are to this extent reliably avoided. Depending on the fluid volumes encountered and the fluid pressure, as obtained by means of the fluid inflow in the inlet channel 16, this laminar fluid outflow can occur in the region of the fluid level 68 or above it in an appropriate manner. Depending on the volume size for the fluid flow space 66, in the case of a corresponding narrow radial layout, in other words, in the case of a small radial distance measurement, a supporting capillary effect can also be established towards the outside of the filter element 18 for the upwards movement.

Depending on the mesh size for the structural layer 76, the free opening cross sections for the passage openings can be chosen such that any gas bubbles located in the cleaned fluid, such as air bubbles, are separated at the thus perforated structural layer 76, with the bubbles being collected at the structural layer 76 for a close to fluid-level discharge of the gas and, for a simpler discharge, being increased in volume under the influence of their surface tension, which corresponds to a coalescence effect. They thus fizz, in a manner comparable with the C0₂bubbles in a carbonated beverage, upwards out of the filter device, so that to this extent the fluid in the tank 10 is effectively degased. Because hydraulic working devices are often sensitive to such a gas input, this risk of disruption is in this regard already dealt with.

In order to further improve this gas bubble discharge from the fluid, according to the invention it is provided that at least a portion of the passage openings 37 in the support tube 36 of the filter element 18 has a flow guide 80, which provide the fluid with a flow direction, which is different from the previously described radial flow direction of the fluid from the inside towards the outside through the filter element 18.

As is shown in particular by the depictions according to FIGS. 3 to 5 for an exemplary embodiment of a thus-designed support tube 36, the respective flow guide 80 facilitates for the fluid which passes through the support tube 36 a flow direction in the form of a swirl flow about the support tube 36. According to the depictions of FIGS. 3 to 5, all of the flow guides 80 with their free opening cross sections 82, which can be seen only in FIG. 3, face in the same direction, which results in a helical swirl flow for the passage fluid. As is seen in particular from the depictions according to FIGS. 4 and 5, the respective flow guide 80 of the support tube 36 delimits a free opening cross section 82, which is inclined relative to the longitudinal axis 26 of the filter element by an angle α of preferably 45°. However, other angle settings between 30° and 60° are also conceivable to thus be able to also set within the settable limits the course of the swirl flow about the filter element 18.

As is additionally shown in FIG. 3, the respective flow guide 80 is formed from the sleeve material of the support tube 36 projecting outwards as a flow pocket 84 which, up to its free opening cross section 82 transitions at its top side in an integral manner into the support tube element material. This flow pocket 84 can be formed, cut out or preferably stamped out from the support tube sleeve 85 (cf. FIGS. 6, 6a, 6b) from the inside outwards. The stamping operation can take place in such a way that, virtually automatically during formation of the flow pocket 84, said flow pocket breaks away in the top region from the support tube sleeve material 85, and then clears the slot-like opening cross section 82 with its surrounding edge, with the pocket 84 being delimited towards the support tube 36 by the overlying sleeve material 85 of the support tube 36. As is seen from the depictions according to FIGS. 3 to 5, a swirl flow occurs with respect to the inclined position of the respective flow pocket 84 from the bottom left to the top right about the angle a of 45° relative to the vertical, which swirl flow is guided clockwise about the filter element 18.

In addition to said respective flow guide 80, the support tube 36 has additional passage openings 37, which surround the respective flow guide 80 in groups, with the total of the free opening cross sections 82 of flow guides 80 being smaller than that of the other passage openings 37 in the support tube 36. These conditions can be seen in particular from the sectional drawing according to FIG. 5. The additional passage openings 37 in the support tube 36 are formed in the form of a perforation which, by contrast with the solution according to FIG. 2 of the prior art, do not consist of circular passage openings, but are instead, as is shown in FIG. 5, formed rectangular. These passage openings 37 of the support tube 36 ensure that, during the filter operation of the device, an undesirable increase in the resistance on the discharge side of the element material 20 does not take place due to an in principle closed support tube surface, which resistance increase could limit the filtration operation with the pleated filter mat. FIG. 5 additionally shows how the cylindrical support tube sleeve 36 is connected, in particular crimped, to the top end cap 22.

As is additionally shown in FIG. 4, the flow guides 80 in the support tube 36 are arranged in groups at the same height relative to one another and are grouped continuously at constant settable distances about the support tube 36.

The filter element 18 shown in FIGS. 3 and 4 as an exchangeable element thus comprises the element material 20 extending between the two end caps 22, 24 which, as already described, is enclosed by the support tube 36 with the passage openings 37. At least a portion of these passage openings 37 in the support tube 36 of the filter element 18 has the flow guide 80, which provides the fluid with a flow direction, which is different from the radial flow direction through the element material 20 from the inside towards the outside. If this filter element is correspondingly contaminated with particulate matter, it can be, as already disclosed for FIG. 1, exchanged in a simple manner for a corresponding new element.

The following exemplary embodiment according to FIGS. 6, 6a, 6b and 7 is explained only to the extent that is differs substantially from the preceding exemplary embodiment of a support tube 36 with flow guides 80. In the embodiment according to FIG. 6, the opening cross sections 82 of the individual flow guides 80 are inclined in the other direction, i.e., they extend at an angle a inclined 45° relative to the longitudinal axis 26 of the filter element 18, viewed in the viewing direction of FIGS. 6 and 7 from the top left to the bottom right. Furthermore, the support tube 36 is depicted according to the depiction of FIG. 6 in its uncoiled situation as a flat sheet blank which, correspondingly rolled up to form a circular cylinder, forms a common welded longitudinal seam 90 with its two opposite longitudinal edges 86, 88.

FIGS. 6a, 6b additionally show along the arrows X and Y front-side views of the uncoiled support tube 36 in the form of its flat sleeve 85. In particular, this shows the pocket design for the individual flow guides 80 in the support tube sleeve. Due to the opposite orientation of the opening cross sections 82 for the flow guide 80, the swirl flow thus takes place counterclockwise about the filter element 18, viewed in the longitudinal orientation thereof. Depending on how one wishes to configure the flow resistance inside the support tube sleeve 85, it is also possible to provide more pocket-like flow guides 80, and reduce the number of radial passage points 71 in the form of a perforation.

The flow pockets 84 in the form of projecting gills on the support tube 36 or, in other words, the flow guides 80, can be uniformly distributed over the entire external circumference of the support tube 36 as described above. In the case of embodiments which are not depicted in detail, it is however possible to distribute these flow pockets 84 over the circumference of the support tube 36 in a different arrangement. For example, the flow pockets 84 could be grouped in the manner of a cluster arrangement about the support tube 36. It has been proven to be particularly advantageous to arrange the flow pockets 84 or the flow guide 80 below the fluid level to be expected inside the supply tank on the support tube 36. The gill-like flow guides 80 and the flow pockets 84 are then preferably exclusively arranged in the bottom third of the support tube 36 viewed in the viewing direction of FIGS. 1 to 4, and otherwise the support tube 36 is formed as a full sleeve or provided with the already described passage openings 37 in a rectangular shape or another multisided shape and circular or elliptical.

Thanks to the swirl flow set by means of the respective flow guide of the support tube, in a guided manner the fluid with the air input arrives via the cylindrically designed fluid flow space 66 at the window-like passage points 74 in the housing 40, which surrounds the support tube 36, which then leads in a surprising manner to an increased gas output to the window-like passage points 74 of the housing 40 caused by the higher energy input of the swirl flow into the fluid to be carried along. The flow guides 80 which project, in the manner of gills, upwards in the direction of the fluid level 68 permit a direct discharge of the fluid or oil mixed with air in the direction of the fluid level 68 and beyond, which further promotes the air discharge. There is no equivalent of this solution in the prior art.

FILTER DEVICE AND FILTER ELEMENT

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