U.S. patent application number 12/304831 was filed with the patent office on 2009-09-17 for fuel filter.
Invention is credited to Michael Braunheim.
Application Number | 20090230048 12/304831 |
Document ID | / |
Family ID | 38521108 |
Filed Date | 2009-09-17 |
United States Patent
Application |
20090230048 |
Kind Code |
A1 |
Braunheim; Michael |
September 17, 2009 |
FUEL FILTER
Abstract
The present invention relates to a fuel filter (1) for a fuel
supply system of an internal combustion engine, in particular in a
motor vehicle, comprising a filter housing (2) and a filter element
(3). The filter housing (2) has an untreated-side inlet (4), a
treated-side outlet (5) and an untreated-side return line (6). The
filter element (3) is arranged in the filter housing (2) and,
therein, separates an untreated space (13), which communicates with
the inlet (4) and with the return line (6), from a treated space
which communicates with the outlet (5). Additionally provided is a
closure element (20) which, in the operationally ready state of the
fuel filter (1), closes off the return line (6).
Inventors: |
Braunheim; Michael;
(Goppingen, DE) |
Correspondence
Address: |
RADER, FISHMAN & GRAUER PLLC
39533 WOODWARD AVENUE, SUITE 140
BLOOMFIELD HILLS
MI
48304-0610
US
|
Family ID: |
38521108 |
Appl. No.: |
12/304831 |
Filed: |
June 4, 2007 |
PCT Filed: |
June 4, 2007 |
PCT NO: |
PCT/EP07/55469 |
371 Date: |
December 15, 2008 |
Current U.S.
Class: |
210/236 ;
210/232; 210/416.4 |
Current CPC
Class: |
B01D 35/153 20130101;
F02N 15/10 20130101; F02M 37/46 20190101; F02M 37/0052 20130101;
B01D 35/16 20130101; F02M 37/04 20130101; B01D 2201/4007 20130101;
F02N 2200/02 20130101; F02M 37/42 20190101; B01D 35/30 20130101;
B01D 35/147 20130101 |
Class at
Publication: |
210/236 ;
210/416.4; 210/232 |
International
Class: |
F02M 37/22 20060101
F02M037/22; B01D 35/02 20060101 B01D035/02; B01D 35/30 20060101
B01D035/30 |
Foreign Application Data
Date |
Code |
Application Number |
Jun 16, 2006 |
DE |
10-2006-028-148.9 |
Claims
1. A fuel filter for an fuel supply system of an internal
combustion engine, comprising: a filter housing, which has an
untreated-side inlet, a treated-side outlet and an untreated-side
return line, a filter element which is arranged in the filter
housing, the filter element including an untreated space and a
treated space, and which separates in the filter housing the
untreated space communicating with an inlet and the return line
from the treated space communicating with the outlet, a closure
element which in an operationally ready state of the fuel filter
closes-off the return line.
2. The fuel filter according to claim 1, wherein the closure
element is one of formed and arranged at the filter element, and,
with the filter element inserted into the filter housing,
closes-off the return line.
3. The fuel filter according to claim 1, wherein the closure
element is arranged at an end disk of the filter element shaped as
ring filter element having at least one axial end disk.
4. The fuel filter according to claim 3, wherein the closure
element is shaped as a pin which projects axially from the
respective end disk, and which, for closing the return line,
closes-off a return line opening, which connects the return line
with the untreated space.
5. The fuel filter according to claim 1, wherein a positioning
device is provided which comprises at least one positioning element
on a filter element side, and at least one positioning element on a
filter housing side, which interact during insertion of the filter
element into the filter housing for finding of an orientation,
which is aligned with an insertion direction of the closure element
shaped as a pin, between the pin and a return line opening, which
is open towards the untreated space, of the return line.
6. The fuel filter according to claim 4, wherein the filter housing
comprises a ramp which projects into the untreated space, which
begins at the return line opening, extends circular concentric to a
longitudinal center axis of the filter housing, ends at the return
line opening, and declines from a beginning of the ramp to an end
of the ramp towards the return line opening, and that the pin is
arranged eccentric to a longitudinal center axis of the filter
element and comprises a slide face which slides along the ramp
during turning of the filter element around the longitudinal center
axis of the filter housing for orienting the pin towards the return
line opening.
7. The fuel filter according to claim 6, wherein a guiding device
is provided which comprises at least one guiding element on the
filter element side, and at least one guiding element on the filter
housing side, which interact during insertion of the filter element
into the filter housing according to a key-lock principle such that
the at least one guiding element on the filter element side and the
at least one guiding element of the filter housing side allow for
at least one of the following: interacting between the slide face
and the ramp and interacting between the ramp and the slide face
only in case the at least one guiding element on the filter element
side matches the at least one guiding element on the filter hosing
side.
8. The fuel filter according to claim 7, wherein the ramp along one
of an entire extension of the ramp, and at least along an extension
section of the ramp, is bordered at least one of radially inside
and radially outside by at least one guiding wall which projects
axially beyond the ramp, and that the pin comprises an axially
projecting guiding section which comprises the slide face and which
is positioned and dimensioned such that the pin extends radially
alongside the respective guiding wall and thereby rests the slide
face axially against the ramp, and keeps the pin axially spaced
apart from the respective guiding wall.
9. The fuel filter according to claim 1, wherein the return line in
addition communicates with the untreated space through a vent
throttle, the flow-through resistance of which is higher than the
flow-through resistance through the filter element and through the
outlet at the return line that is closed off.
10. The fuel filter according to claim 1, wherein a pressure sensor
is provided for measuring a treated-side fuel pressure.
11. The fuel filter according to claim 1, wherein the filter
element is shaped as a ring filter element, and comprises at least
one axial end disk, from which a closure element projects axially
and eccentrically, and a filter element is inserted into a filter
housing of the fuel filter, closes-off an untreated-side return
line of the filter housing.
12. The fuel filter according to claim 11, wherein the closure
element is a pin.
13. The fuel filter according to claim 2, wherein the closure
element is arranged at an end disk of the filter element shaped as
ring filter element having at least one axial end disk.
14. The fuel filter according to claim 2, wherein a positioning
device is provided which comprises at least one positioning element
on a filter element side, and at least one positioning element on a
filter housing side, which interact during insertion of the filter
element into the filter housing for finding of an orientation,
which is aligned with an insertion direction of the closure element
shaped as a pin, between the pin and a return line opening, which
is open towards the untreated space, of the return line.
15. The fuel filter according to claim 2, wherein the return line
in addition communicates with the untreated space through a vent
throttle, the flow-through resistance of which is higher than the
flow-through resistance through the filter element and through the
outlet at the return line that is closed off.
16. The fuel filter according to claim 2, wherein a pressure sensor
is provided for measuring a treated-side fuel pressure.
17. The fuel filter according to claim 2, wherein the filter
element is shaped as a ring filter element, and comprises at least
one axial end disk, from which a closure element projects axially
and eccentrically, and a filter element is inserted into a filter
housing of the fuel filter, closes-off an untreated-side return
line of the filter housing.
18. The fuel filter according to claim 3, wherein the return line
in addition communicates with the untreated space through a vent
throttle, the flow-through resistance of which is higher than the
flow-through resistance through the filter element and through the
outlet at the return line that is closed off.
19. The fuel filter according to claim 3, wherein a pressure sensor
is provided for measuring a treated-side fuel pressure.
20. The fuel filter according to claim 3, wherein the filter
element is shaped as a ring filter element, and comprises at least
one axial end disk, from which a closure element projects axially
and eccentrically, and a filter element is inserted into a filter
housing of the fuel filter, closes-off an untreated-side return
line of the filter housing.
Description
[0001] The present invention relates to a fuel filter for a fuel
supply system of an internal combustion engine, in particular in a
motor vehicle.
[0002] Internal combustion engines have a fuel supply system for
their supply with liquid fuel. Such a fuel supply system comprises
typically a fuel tank, a fuel pump, a fuel filter, and an injection
system. To reduce the risk of damage of the injection system or the
internal combustion engine, respectively, it is required to clean
the fuel supplied to the internal combustion engine from
contamination carried along with the fuel. Hence, the fuel filter
is a component which is relevant for the functional reliability of
the internal combustion engine. Such a fuel filter has typically a
filter housing which comprises an untreated-side inlet and a
treated-side outlet. Furthermore, a filter element is provided,
which is arranged in the filter housing and which separates in the
filter housing an untreated space communicating with the inlet from
a treated space communicating with the outlet. The filter element
is a wear part which is replaced in certain maintenance intervals.
When replacing the filter element, there is a risk that it is not
properly installed in the filter housing. Moreover, there is a risk
that the fuel filter is operated, accidentally or knowingly,
without filter element. With missing or improper installed filter
element, there is the risk that contamination can get unhindered to
the injection system or to the internal combustion engine,
respectively.
[0003] The present invention is concerned with the problem to
propose an improved embodiment for a fuel filter, for which in
particular the risk is reduced that unfiltered fuel can get to the
internal combustion engine.
[0004] This problem is solved in the invention by means of the
subject matters of the independent claims. Advantageous embodiments
are subject matter of the dependent claims.
[0005] The invention is based on the general idea to in addition
provide the fuel filter with an untreated-side return line, which,
in the operationally ready state, is closed by means of a closure
element. In an inoperable state of the fuel filter, thus, for
example, with missing closure element and/or missing filter
element, the return line is open, so that fuel supplied through the
inlet into the filter housing preferably flows off through the
return line and, for example, flows back into the fuel tank. In
this case, no, or not enough, fuel is supplied. Subsequently, the
internal combustion engine cannot be started. The risk of damage of
the injection system, or the internal combustion engine,
respectively, can thereby be reduced. To ensure that with missing
filter element, the fuel entering the filter housing exits through
the return line and not through the outlet, the flow resistance
through the return line to the tank, for example, can be rated
considerably lower than the flow resistance from the outlet to the
internal combustion engine. With inserted filter element and with
missing or improper attached closure element, the return line to
the untreated space is open, while the outlet towards the treated
space is open and is separated by the filter element from the
untreated space. By means of the filter element, an increased flow
resistance is forced to occur towards the outlet. Accordingly, also
in this constellation, the fuel discharges through the return line
from the filter housing. In this constellation, the filter element
subsequently prevents the supply of contamination to the internal
combustion engine, whereby the same cannot be started at the same
time, since it is not supplied, or only insufficiently, with fuel
through the outlet.
[0006] In a preferred embodiment, the closure element is formed or
arranged at the filter element such that the closure element, with
a filter element properly inserted into the filter housing, closes
off the return line. By means of this integrated construction, it
is ensured that the return line is closed off only with inserted,
and correctly inserted, filter element. In other words, the proper
installation state of the filter element, or the operationally
ready state of the fuel filter, respectively, is only given when
the filter element is inserted into the filter housing such that
the closure element closes off the return line. The reliability or
the handling of the fuel filter is thereby improved.
[0007] In another embodiment, a positioning device can be provided,
which comprises at least one positioning element on the filter
element side, and one positioning element on the filter housing
side, which interact during inserting of the filter element into
the housing for finding of an orientation, which is aligned with
the insertion direction of the closure element shaped as a pin,
between the pin and a return line opening, which is open towards
the untreated space, of the return line. By means of this design,
during mounting of the fuel filter, the finding of the relative
position between filter element and filter housing is made easier.
The risk of a faulty installation is thereby reduced.
[0008] In another advantageous embodiment, a guiding device can be
provided, which comprises at least one guiding element on the
filter element side, and at least one guiding element on the filter
housing side, which interact during insertion of the filter element
into the filter housing according to the key-lock principle, such
that they allow the interacting between the positioning elements of
the positioning device only with matching guiding elements. By
means of this construction, the risk is reduced that a wrong filter
element, thus a filter element, which is not specifically adapted
to the fuel filter, can be inserted into the filter housing. In the
ideal case, an internal combustion engine, the fuel supply system
of which is equipped with the fuel filter according to the
invention, can be started only when the associated and correct
filter element is properly inserted into filter housing.
[0009] Further important features are apparent from the sub-claims,
from the drawings, and from the associated description of the
figures by means of the drawings.
[0010] It is to be understood the aforementioned and the following
features still to be illustrated are not only usable in the
respective mentioned combination, but also in other combinations or
on its own, without departing from the scope of the present
invention.
[0011] Preferred exemplary embodiments of the invention are
illustrated in the drawings, and are explained in the following
description in more detail, wherein identical reference numbers
refer to identical, or similar, or functionally identical
components.
[0012] In the figures
[0013] FIG. 1 shows schematically a perspective and partial cross
section of a fuel filter,
[0014] FIG. 2 shows schematically a partial cross section and a
greatly simplified side view in the region of a return line during
installation of a filter element,
[0015] FIG. 3 shows schematically a perspective view on a cover of
the filter housing in a simplified illustration,
[0016] FIG. 4 shows a top view on the cover according to FIG. 3
corresponding to an arrow IV in FIG. 3,
[0017] FIG. 5 shows a view as in FIG. 4, but for a different
embodiment,
[0018] FIG. 6 shows schematically a detail section along the
section lines VI in FIG. 4.
[0019] According to FIG. 1, a fuel filter 1, which is suitable for
filtering a liquid fuel, such as, e.g., gasoline or diesel,
comprises a filter housing 2 and a filter element 3. The filter
housing 2 comprises an untreated-side inlet 4, a treated-side
outlet 5, and an untreated-side return line 6. The filter housing 2
is assembled from a cup-shaped cover 7 and a cup-shaped bottom 8,
which can be screwed together by means of a threaded connection 9.
Inlet 4, outlet 5 and return line 6 are formed here at the cover 7.
The filter housing 2 is preferably provided for a hanging mounting
position so that for maintenance of the fuel filter 1, the bottom 8
can be screwed off downwards, while the upper cover 7 remains
stationary. Alternatively, a standing mounting position can also be
provided, whereby then the cover 7 comprising the connections 4, 5,
and 6 is arranged at the bottom, remains stationary, and
functionally forms rather a "housing bottom", while in this
mounting situation the bottom 8 is arranged at the top, and
functionally rather forms a "housing cover". The axial dimension
can vary here. In particular, in the standing arrangement, the
cover 7, thus the functional housing bottom, can accommodate the
bigger portion of the filter element 3, while in the shown hanging
arrangement, the bottom 8 accommodates the bigger portion of the
filter element 3.
[0020] The fuel filter 1 is provided for mounting into a fuel
supply system of an internal combustion engine, which is preferably
arranged in a motor vehicle. For this, the inlet 4 can be connected
to an inlet line 10, symbolized by an arrow, of the fuel supply
system, the outlet 5 to an outlet line 11, symbolized by an arrow,
of the fuel supply system, and the return line 6 to a return pipe
12, symbolized by an arrow, of the fuel supply system. The inlet
line 10 includes, for example, a fuel pump, and comes from a fuel
tank. The outlet line 11 runs, for example, to a fuel injection
system. The return pipe 12 runs preferably back to the fuel
tank.
[0021] The filter element 3 is arranged in the mounted state of the
fuel filter 1 in the filter housing 2 such that it separates within
the filter housing 2 an untreated space 13 from a treated space 14.
In the shown exemplary embodiment, the filter element 3, without
restriction of the generality, is shaped as ring filter element,
which, with respect to a longitudinal center axis 15 of the ring
filter element 3, is arranged coaxial to a longitudinal center axis
16 of the filter housing 2. Furthermore, the ring filter element 3
includes at least one axial end disk 17, wherein in FIG. 1 only one
end disk is visible. The respective end disk 17 borders axially a
filter material 18 which allows a radial flow-through.
[0022] The inlet 4 communicates via an inlet opening, not shown
here, with the untreated space 13, and the outlet 5 communicates
via an outlet opening, not shown, with the treated space 14.
Furthermore, the return line 6 communicates with the untreated
space 13 as well. For this, the return line 6 includes, for
example, a return line opening 19, which is open towards the
untreated space 13.
[0023] For the fuel filter 1, in addition, a closure element 20 is
provided which serves for closing off the return line 6 in the
operationally ready state of the fuel filter 1. Here, the closure
element 20 closes off, for example, the return line opening 19. In
the operationally ready state of the fuel filter 1, hence with
closed return line 6, the fuel pump supplies, during the operation
of the fuel supply system, fuel through the inlet 4 into the
untreated space 13. From the untreated space 13, the fuel gets
through the filter material 18 radially to the treated space 14.
From the treated space 14, the fuel discharges again through the
outlet 5 from the filter housing 2. With missing closure element
20, or when the return line 6 is not closed off by the closure
element 20, respectively, the fuel from the untreated space 13 can
exit directly through the return line 6 out of the filter housing
2. The flow resistance through the filter material 18 to the
treated side 14 hereby provides that within the treated space, thus
at the outlet 5, the required fuel pressure for starting the
internal combustion engine cannot be built up since the fuel from
the untreated space 13 can discharge substantially unrestricted
through the return line 6.
[0024] In the preferred embodiment shown here, the fuel filter 1
can in addition be equipped with a pressure sensor 21, by means of
which the treated fuel pressure can be measured. The pressure
sensor 21 is attached, for example, at the cover 7. For example,
when starting the internal combustion engine, an engine control
device can monitor the pressure build-up in the treated space, and
generates the respective start signals for starting the internal
combustion engine only at a sufficient pressure build-up. With a
closed return line 6, the here required pressure in the treated
space cannot build up, so that the necessary start signals are not
generated. Besides, with an open return line 6, the pressure
build-up in the treaded space can turn out so low that the required
fuel supply for starting the internal combustion engine is not
possible, so that the internal combustion engine cannot be started
due to the insufficient or missing fuel supply. This construction
is based on the idea that the unclosed return line is evaluated as
an indication that the closure element 20 is not, or not properly,
inserted into the return line opening 19, and/or that the filter
element 3 is not, or not properly, inserted into the filter housing
2. The unclosed return line 6 can also indicate that a wrong filter
element was inserted into the filter housing 2. In the mentioned
states, the fuel filter 1 is not operationally ready. The internal
combustion engine should then not be started to avoid damage of the
internal combustion engine, or the injection system, respectively,
by unfiltered fuel. By means of the proposed fuel filter 1, this
goal is achieved comparatively easily and effectively.
[0025] In the preferred embodiment shown here, the closure element
20 is formed at the filter element 3, or is arranged thereon,
respectively. Thus, the return line 6 is automatically closed off
when the filter element 3 is inserted properly into the filter
housing 2. A missing filter element 3, a wrongly inserted filter
element, and the use of a wrong filter element 3 result in each
case in an unclosed return line 6, whereby the starting of the
internal combustion engine can be prevented.
[0026] In the example, the closure element 20 is arranged at the
end disk 17 facing towards the cover 7. The closure element 20 is
shaped here as pin 22, which projects axially from the end disk 17,
thus parallel to the longitudinal center axis 15 of the ring filter
element 3. The pin 22 interacts with the return line opening 19 for
closing off the return line 6. In particular, the pin 22 can be
plugged in axially into the return line opening 19. The pin 22 can
be equipped with a radial seal 23, in particular with an O-ring.
The return line opening 19 can be equipped with a fitting or a tube
section, which are not described here in more detail. In the
plugged-in state, the radial seal 23 causes a sufficient sealing of
the return line opening 19.
[0027] In the embodiment shown here, the fuel filter 1 is
additionally equipped with a vent throttle 24, through which the
return line 6 also communicates with the untreated space 13. The
vent throttle 24 is characterized by a flow-through resistance,
which is substantially higher than the flow-through resistance of
the filter element 3 and the outlet 5 with closed-off return line
6. With closed-off return line 6, the vent throttle 24 allows a
ventilation of the filter housing 2 during starting of the internal
combustion engine. In the subsequent normal operation, it allows a
comparatively small return flow through the return line 6, which,
however, due to the comparatively strong throttle effect of the
vent throttle 24, does not hinder the required pressure build up in
the treated space 14. In particular, the flow-through resistance of
the vent throttle 24 is even higher than the flow-through
resistance of the filter element 3 alone.
[0028] For a standing arrangement, a different, in particular
higher, positioning of the vent throttle is thinkable. In the
standing position, the return line 6, which is then arranged at the
bottom, can serve as idle, which, at removal of the bottom 8
located at the top, or at pulling out of the filter element 3,
opens up automatically.
[0029] According to FIG. 2, the fuel filter 1 can be equipped with
a positioning device 25. The positioning device 25 comprises on the
filter element side at least one position element, which is formed
here by a slide face 26 at the free end of the pin 22, and, on the
filter housing side, at least one positioning element, which is
formed here by a ramp 27. The positioning elements 26, 27 are
shaped such that they interact during placing of the filter element
3 into the filter housing 2 for finding of an orientation, which is
aligned with the insertion direction of the pin 22, between the pin
22 and the return line opening 19.
[0030] In the preferred embodiments shown here, as a positioning
element on the filter housing side, the said ramp 27 is provided,
which projects axially into the untreated space 13. The ramp 27
begins at 29 at the return line opening 19 and ends at 30 at the
return line opening 19 as well. Between its beginning 29 and its
end 30, the ramp 27 extends circular or helical, respectively,
concentric to the longitudinal center axis 16 of the filter
housing. From its beginning 29 to its end 30, the ramp 27 declines
towards the return line opening 19. The said slide face 26 is
formed at the pin 22 as a position element on the filter element
side, in fact on a side of the pin 22 remote from the end disk 17.
Here, the pin 22 is arranged eccentrically with respect to the
longitudinal center axis 15 of the filter element 3, wherein the
eccentricity of the pin 22 is selected approximately equal to the
radius of the ramp 27. Accordingly, the pin 22 can rest with its
slide face 26 axially against the ramp 27 during insertion of the
filter element 3, coaxial to the longitudinal center axis 16 of the
filter housing 2. During turning of the filter element 3 around its
longitudinal center axis 15 corresponding to an arrow 31, the pin
22 slides with its slide face 26 along the ramp 27. Hereby, the
orientation of the pin 22 is forced to occur towards the return
line opening 19. A corresponding sliding movement is symbolized in
FIG. 2 by an arrow 32. The orientation of the ramp slope is
preferably selected such that the turning direction during
tightening of the bottom 8 is forced to generate the desired
turning direction 31 for the filter element 3 arranged therein,
whereby the filter element 3 during attaching of the bottom 8
automatically slides along the ramp 27. Upon obtaining the aligned
orientation between pin 22 and the return line opening 19, the
beginning 29 of the ramp 27 restricts a further turning of the
filter element 3. With further tightening of the bottom 8, the
filter element 3 is forced to be inserted corresponding to the
insertion direction 28 with its pin 22 into the return line opening
19.
[0031] According to FIGS. 3 to 6, the fuel filter 1 can
additionally be equipped with a guiding device 33. This guiding
device 33 can comprise on the filter element side at least one
guiding element, which, for example, can be formed by a guiding
section 34 formed at the pin 22, as well as on the filter housing
side at least one guiding element, which, for example, can be
formed by one or more guiding walls 35. The guiding elements 34, 35
are shaped such that they interact during insertion of the filter
element 3 into the filter housing 2 according to the "key-lock
principle". This means that the guiding elements 34, 35 allow
interacting between the positioning elements 26, 27, thus between
the ramp 27 and the slide face 26, only when the matching guiding
elements 34, 35 interact with each other. In the case that the
guiding elements 34, 35 interacting with each other during
insertion of the filter element 3 into the filter housing 2 do not
match, the interacting of the positioning elements 26, 27 for
finding the aligned orientation between the pin 22 and the return
line opening 19, is considerably hindered or made impossible by the
guiding device 33.
[0032] In the shown embodiment, the guiding elements on the filter
housing side are formed by guiding walls 35 which extend radially
inside and/or radially outside along at least one extension section
36 of the ramp 27, thereby projecting beyond the ramp 27 in axial
direction. In each of the examples of FIGS. 3 and 4, respectively,
only one extension section 36 is provided, which is positioned in
the region of the end 30 of the ramp 27. Here, in the extension
section 36, two parallel guiding walls 35 are provided, one of
which borders the ramp 27 radially inside and the other one
radially outside. In the embodiment shown in FIG. 5, a total of
three extension sections 36 are provided, in each of which two
parallel extending guiding walls 35 are provided, which border the
ramp 27 radially inside and outside. The guiding element on the
filter element side of the embodiments shown here is formed by the
guiding section 34, which projects axially on the side of the pin
22, which is facing away or is remote from the end disk 17. The
said guiding section 34 comprises the slide face 26 of the pin 22.
Furthermore, the guiding section 34 is adjusted with respect to its
positioning at the pin 22 and with respect to its dimensioning to
the guiding walls 35 such that the guiding section 34, during
installation of the fuel filter 1, extends radially alongside the
respective guiding wall 35 or between the two parallel guiding
walls 35, respectively, thereby resting with the slide face 26
axially against the ramp 27 and keeping the pin 22 axially spaced
apart from the respective guiding wall 35. This relationship is
particularly apparent in FIG. 6. There, the guiding section 34
contacts the ramp 27 running between the guiding walls 35 with the
slide face 26, and ensures an axial clearance between the walls 35
and an outer side 37, facing away from or remote from the end disk
17, of the pin 22, and from which the guiding section 34 projects.
The said outer side 37 can be plane and can merge via a chamfer 38
into the rest of the pin 22.
[0033] The above mentioned key-lock principle now causes that the
pin 22 with its slide face 26 can slide along the entire ramp 27
only until the aligned orientation to the return line opening 19
when the guiding section 34 is present, when the guiding section 34
is sufficiently narrow in radial direction to fit through the
opposing guiding walls 35, and when the guiding section 35 is
sufficiently long in axial direction to adjust the required axial
clearance between pin 22 and the guiding walls 35. With missing or
wrong guiding section 34, the pin 22 would rest against the face
ends of the walls 35 when sliding along the ramp 27 in
circumferential direction, whereby the turnability of the filter
element 3 is blocked. Then, the filter element 3 cannot be readily
installed properly.
[0034] In the FIGS. 3 to 6, in addition an outlet fitting 39 is
illustrated, which is provided at the cover 7 and onto which the
filter element can be slipped. FIG. 6 shows a special embodiment in
which the pin 22 is attached through a web 40 to the end disk 17.
Said web 40 is flexible in radial direction and allows a tolerance
compensation between the radial position of the guiding section 34
and the radial position of the guiding walls 35. As is apparent
from FIG. 1, the pin 22 also can be attached comparatively rigid to
the end disk 17.
* * * * *