Filter element

Abstract

A filter element (1), with a preferably multilayer structure of a filter medium (3), in pleated form has filter pleats (5, 7) of different pleat heights (h1, h2). The filter pleats (7) with a first pleat height (h1) oppose the filter pleats (5) lower second pleat height (h2). The filter element has a throughflow direction for fluid to be cleaned away from a dirty side to a clean side (R). The transitions arranged adjacent to the inner side all conclude along a fictitious circular cylinder (9), which penetrates the filter medium (3) coaxially to its longitudinal axis (LA).

Claims

1. A filter element, comprising: a tubular and pleated filter medium with a multi-layer structure configured for fluid to be filtered to flow between inner and outer sides of said filter medium; first pleats in said filter medium having a first pleat height; second pleats in said filter medium having a second pleat height, said second pleat height being approximately two-thirds of said first pleat height, each said second pleat being bounded by adjacent ones of said first pleats defining an M-pleat configuration as viewed from a top of the filter medium and as viewed from the at least one of said inner side or said outer side; a support tube supporting said first and second pleats at said inner side; inner transitions of all of said first and second pleats being adjacent said inner side and being along a circular cylinder extending through said filter medium coaxially to a longitudinal axis of said filter medium, each of said first and second pleats being separated from an adjacent one of said first and second pleats by a tapered space tapering toward a respective one of said inner transitions of said first and second pleats along said circular cylinder extending through said filter medium, said tapered spaces extending along entire radial extents of said first and second pleats, each of said first and second pleats having inner planar surfaces lying directly against one another, said inner planar surfaces of each of said first and second pleats directly contacting one another along entire lengths thereof between said inner transitions and outer transitions between said inner planar surfaces, said inner and outer transitions extending along a same bend radius; and an open holding space being between each pair of adjacent ones of said first pleats bounding one of said second pleats therebetween and being defined by the respective M-pleat configuration, said open holding space being on said outer side of said filter medium configured for standardizing and reducing flow velocity of fluid through said filter medium during filtering operation; whereby, during filtering operation, fluid contaminated with particles electrostatically charges said filter medium upon passing through said filter medium and reduced electrostatic charges are a result of the flow velocity of fluid induced by said holding spaces.

2. A filter element according to claim 1 wherein said first and second pleats alternate about a circumference of said filter medium.

3. A filter element according to claim 1 wherein said second pleats are configured to stabilize alignments and configurations of said first pleats.

4. A filter element according to claim 1 wherein said second pleats are configured to prevent said first pleats from at least one of contacting or adhering to one another to an extent said first pleats project toward said outer side of said filter medium over said second pleats.

5. A filter element according to claim 1 wherein said filter medium is configured to have an effective filter surface, despite a reduced surface thereof, at least as great as a pleated filter medium having pleats with a uniform pleat height equal to said first pleat height.

6. A filter element according to claim 1 wherein a clean side is on said inner side of said filter medium, is encompassed by said filter medium and forms the circular cylinder.

7. A filter element according to claim 1 wherein a clean side is on said outer side of said filter medium facing away from the circular cylinder.

8. A filter element according to claim 1 wherein said pleats extend apart from one another at acute angles, while forming said M-pleat configuration, forming slit-shaped fine filtration regions at bases of said filter medium.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) Referring to the drawings that form a part of this disclosure:

(2) FIG. 1 is a perspective view of a filter medium according to an exemplary embodiment of the invention;

(3) FIG. 2 is a top view of the filter medium of FIG. 1; and

(4) FIG. 3 is an enlarged, partial top view of the circled portion of the filter medium of FIG. 2.

DETAILED DESCRIPTION OF THE INVENTION

(5) FIGS. 1 and 3 show a filter element 1 according to an exemplary embodiment of the invention having a filter medium 3 with a multi-layer structure. The filter medium 3 includes, in pleated form, filter pleats 5, 7 having different pleat heights h1, h2. Filter pleats 7 of a first pleat height h1 differ from filter pleats 5 by filter pleats 5 having a comparatively lower second pleat height h2. The second pleat height h2 is approximately ⅔ the height h1 of the filter pleats 7. The filter element 1 includes a flow-through direction for a fluid to be cleaned from an outer lying dirty side S to an inner lying clean side R. All of the filter pleats 5, 7 end toward the clean side R along a fictitious circular cylinder 9, which extends through the filter medium 3 coaxially along its longitudinal axis LA.

(6) The filter pleats 7 having the first pleat height h1 and the filter pleats 5 having the second pleat height h2 are situated alternatingly relative to one another. Specifically, the filter pleats 5 having the second pleat height h2 stabilize the alignment and configuration of the filter pleats 7 having the first pleat height h1.

(7) The filter pleats 5 having the second pleat height h2 prevent the filter pleats 7 of the first pleat height h1 from contacting or adhering to one another, because the filter pleats 7 of the first pleat height h1 project toward the dirty side over or beyond the filter pleats 5 having the second pleat height h2 and are spaced apart from one another.

(8) Particularly advantageously, the effective filter surface of the filter medium 3, in spite of the reduction in filter surface area, is the same or even increased, as compared to a filter medium having filter pleats of uniform height comparable to the first pleat height h1. Each filter pleat 5, 7 is formed from two planar filter surfaces 11, 13 lying against one another and are connected to form the pleated filter medium 3. The planar filter surfaces 11, 13 in this case have the same bend radius BR in the area of the transitions 15 to the adjacent filter surface and to the respective adjacent filter pleat 7, 5.

(9) The filter pleats 5, 7 are supported on the clean side R by a support tube 9 forming the fictitious circular cylinder. The support tube 9 is made of metal and includes circular holes distributed on its circumferential surface for the passage of fluid.

(10) The filter pleat 5 having the second pleat height h2, bounded on each side by an adjacent filter pleat 7 having the first pleat height h1 forms a type of M-pleat configuration M, as seen in axial top view of the filter medium 3 and from the clean side R. To obtain slit-like fine filtration regions 16 at the base 17 of the filter medium 3 on the clean side, the individual filter pleats 5, 7 of differing pleat heights h1, h2 split apart conically or at acute angles, while forming the M-pleat configuration M.

(11) Due to the M-pleat configuration M between two adjacent filter pleats 7 of the first pleat height h1, which bound a filter pleat 5 having the second pleat height h2, an open holding space 19 for fluid is formed on the dirty side S in the manner of a fictitious cylindrical segment. During operation of the filter element 1, the open holding space 19 results in a standardization and in a reduction of the flow velocity of the fluid through the filter element 1.

(12) Furthermore, during operation of the filter element, in which the filter element is normally perfused by a fluid contaminated with particles resulting in an electrostatic charging of the filter element 1, particularly advantageously, due to the M-pleat configuration, this charging is reduced as a result of the reduction of the fluid flow velocity induced by the respective holding space 19. In this case, the charging increases with increasing flow velocity and, accordingly decreases when the flow velocity drops. The aim, therefore, is to reduce the flow-through velocity to the point that any remaining charge may be dissipated by grounding the fluid in components of the hydraulic circuit situated downstream.

(13) Thus, the filter element 1 according to the invention, even after a longer service life, exhibits a high filter performance at a low flow-through velocity. The filter element 1 is therefore more cost-effective and more reliable during operation due to the reduced charging of the passing fluid, which charging may lead to undesirable discharges, resulting in the destruction of the element material, in increasing oil ageing and in an increased fire hazard.

(14) In the figures, the clean side R is provided on the inside, and the dirty side S is provided on the outside of the filter medium 3. It is understood that the clean side R may also be situated on the outside and the dirty side on the inside of the filter medium 3.

(15) 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.