Filter element and method for the production thereof
A filter element includes a filter cylinder whose outer side rests against a fluid-permeable supporting tube ( 15 ). The inside ( 3 ) of the filter cylinder can be flown through by the fluid to be filtered. The filter cylinder is formed by a filter mat web. The filter mat web has a series of folds ( 9 ) that rest against one another at least in areas. Both ends of the filter mat web are joined to one another at a junction ( 5 ) to form an annular body ( 1 ). The filter element includes a device that acts upon the junction ( 5 ) to prevent, in the area of the junction ( 5 ), a bulging of the folds ( 9 ) caused by the flow of the fluid.
1. A filter element, comprising:
a filter cylinder having a filter mat web arranged in a series of folds adjacent to one another at least in individual areas thereof, each of said folds having two radial members extending radially inwardly and connected by a crown on radial outward fold ends, said filter mat web having two web ends extending a height of said filter mat web and connected to one another at a junction point forming said filter mat web into an annular element, two of said folds being adjacent to said junction point and on opposite sides thereof;
a fluid permeable support tube surrounding said filter cylinder; and
a retaining device with retaining elements overlapping said two of said folds on outer surfaces of said radial members thereof remote from said junction point;
whereby, when fluid to be filtered flows through said filter element from an interior thereof to an exterior thereof, said retaining device resists bulging of said two of said folds and separation of said web ends of said filter mat web.
2. A filter element according to claim 1 wherein
said ends of said filter mat web are joined along end edges facing interiorly of said annular element; and
said crowns of two of said folds face said support tube.
3. A filter element according to claim 2 wherein
said filter mat web comprises a flexible mat of metal-free, plastic-supported filter mats.
4. A filter element according to claim 3 wherein
said junction point comprises a fusion seam.
5. A filter element according to claim 4 wherein
said filter mat web has dimensions allowing reversal of said annular element, whereby said fusion seam can be formed on an exterior of said annular element and then be reversed to be located in an interior of said annular element.
6. A filter element according to claim 1 wherein
said retaining elements comprise retaining projections extending radially inwardly from an inner surface of said support tube.
7. A filter element according to claim 6 wherein
said support tube comprises a transfer-molded plastic tube with said retaining projections formed integrally thereon.
8. A filter element according to claim 6 wherein
one of said projections comprises a series of members spaced by interstices and arranged along a length of said support tube.
9. A filter element according to claim 1 wherein
said retaining device comprises a U-shaped clamping element with legs thereof forming said retaining elements and with a bight portion thereof connecting said legs and being adjacent an inner surface of said support tube.
10. A filter element according to claim 5 wherein
said dimensions are determined by the following relationships
L
M
=
2
*
F
Ans
*
(
F
H
-
2
*
M
+
π
*
M
2
)
D
a
max
=
D
i
+
2
*
L
max
L
max
=
D
a
max
-
D
i
2
D
i2
=
F
Ans
*
F
D
π
L
M
max
=
D
a
max
*
π
D
a
max
=
L
M
max
π
D
a
max
=
D
i
+
2
*
L
max
L
max
=
D
a
max
-
D
i
2
L
max
=
L
M
max
π
-
D
i
2
L
max
=
L
M
max
-
F
Ans
*
F
D
2
*
π
L
max
=
F
Ans
*
(
F
H
-
2
*
M
+
π
*
M
2
-
F
D
2
)
π
where
F ANZ =number of folds in said filter mat web
F H =height of each fold
F D =thickness of each fold
M=strength of material of structure of said filter mat web
L M =extended length of said filter mat web
L Mmax =maximum extended length of said filter mat web
D amax =maximum external diameter of a filter disk formed from said annular element
D i =internal diameter of said filter disk formed from said annular element
L max =maximum length of said filter cylinder.