Note: Descriptions are shown in the official language in which they were submitted.
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1
SEAL ARRANGEMENT
The invention relates to seal arrangements for the sealing of a rotatable
shaft extending through a bore in a housing wall.
One class of conventional shaft seal arrangements include a radially
sealing seal ring and a first stiffening ring of essentially L-shaped cross-
section.
The seal ring has at least one sealing lip which is made of elastic, rubbery
material and sealingly engages the circumference of the shaft to be sealed
under radial pretension. The first stiffening ring is L-shaped in cross-
section
with a first leg which extends radially inward and a second leg which extends
parallel to the axis of the shaft. The second leg at least partly overlaps and
engages the outer ring of an anti-friction bearing positioned between the
shaft
and the second leg. The seal ring is fixed to the first leg. The second leg is
enclosed by elastic material at least on the side facing the bore wall and is
fixable in the bore by radial prestressing.
A seal of that type is known from German Utility Model DE-GM 19 17
623. That seal arrangement is constructed as a tolerance ring for the mounting
of anti-friction bearings in seal receiving housings. If, for example, the
housing is made of aluminum and the anti-friction bearing is made of steel,
variations in the clearance between the housing and the bearing ring, for
example due to heat, are compensated by the elastic, rubbery material. The
dimensions and type of the elastic material are thereby selected according to
the clearance range which is to be compensated. However, sealing problems
are observed with this type of seal especially when used in conjunction with
shafts which do not rotate optimally round, for example drive shafts of
automative transmissions. Thus, the sealing of shafts which are vibrating or
rotate out of round is not satisfactory. Furthermore, although the elastic,
rubbery coating of the tolerance ring is radially prestressed and, thus, is
radially
forced against the bore in the housing, the bore wall is provided with a
specific
surface structure to reliably prevent displacements of the tolerance ring in
axial
direction, which surface structure interlocks with the coating. However, the
manufacture of a bore of such construction is not economical.
It is now an object of the present invention to provide a further
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developed seal arrangement of the above described general type which has
substantially improved sealing characteristics over a long service period,
provides for the installation/damping of vibrations of the rotating shaft, and
reliably prevents axial displacement of the seal in relation to the housing.
S This object is achieved with a seal arrangement in accordance with the
invention wherein the coating of the first stiffening ring on the side facing
the
housing is surrounded at least in a portion of its extent parallel to the
shaft's
axis (axial portion) by a second stiffening ring made of tough and hard
material and an intermediate coating, which second stiffening ring is at least
partly radially prestressed and forces against the bore wall during use. The
coating outside the axial portion extends in radial direction beyond the
second
stiffening ring subsequent to manufacture. The type of elastic, rubbery
material
used and its thickness depend on the parameters of the respective application.
Accordingly, the invention provides a seal axrangement for the sealing of
1 S a shaft extending through a shaft receiving bore in a housing wall,
including a
radially sealing seal ring, first and second stiffening rings with an
intermediate
elastic coating and an anti-friction bearing. The seal ring has an annular
main
sealing lip made of elastic, rubbery material which is radially biased by the
shaft during use to sealingly engage the outer circumference of the shaft. The
first stiffening ring is L-shaped in cross-section and has a radially inwardly
directed first leg and a second leg extending parallel to the axis of the
shaft.
The sealing lip is fixed to the first leg of the first stiffening ring. The
second
leg at least partly overlaps and engages the outer ring of the anti-friction
bearing, and is surrounded in at least a portion of its axial extent (axial
portion)
and on the side directed toward the bore wall by the second stiffening ring.
The seal is fixable in the bore by radial prestressing. The anti-friction
bearing . .
is positioned in radial direction between the shaft and the second leg of the
first stiffening ring. Outside the axial portion, the coating extends in axial
and
radial direction beyond the second stiffening zing subsequent to manufacture.
When the shaft to be sealed is rotating out of round, a significant reduction
in
acoustically prominent vibrations of the shaft is achieved and propagation of
this unwanted noise is substantially prevented. The seal ring preferably
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includes a garter spring which evenly forces the sealing lip against the shaft
for
improved sealing results. The second stiffening ring which, for example, may
be made of metal provides for a reliable fixing of the seal arrangement in the
housing wall since it is radially prestressed, which means that the second
stiffening ring is forced in radial direction against the bore wall, which
results
in friction between the second stiffening ring and the bore wall. Axial
displacements of the whole seal arrangement in the bore are prevented with
this
construction even when the shaft to be sealed moves in axial direction during
rotation and/or is subject to heat expansion. Thus, the seal arrangement is
first
pressed into the bore in the housing wall during installation and the
frictionally
retained therein during the intended use. For the achievement of an excellent
sealing of the housing, the coating of the first stiffening ring autside the
axial
portion extends in radial direction around and beyond the second stiffening
ring
and is compressed between the housing wall to be sealed and the first
stiffening ring in the installed condition of the seal. It is an advantage of
such
a construction that an excellent guiding of the shaft to be sealed is achieved
by
the supported anti-friction bearing, that, simultaneously, vibrations of the
shaft
are insulated/dampened and that an excellent spatial positioning of the seal
between the bore wall and the shaft is achieved even over a long service
period. The propagation of vibration noise to the surrounding structures is
minimized. The coating may be vulcanized onto the second stiffening ring or
adhesively connected thereto. Such a fastening of the two parts to each other
is exceptionally reliable and generally remains intact even over a long
service
period. The second stiffening ring is preferably L-shaped in cross-section,
which is advantageous from a manufacturing technology standpoint and
simplifies installation. The second stiffening ring has a radially protruding
flange for engagement with a radially extending surface of the housing. The
manufacture is simplified especially when the coating is vulcanized onto the
second stiffening ring. The installation and exact positioning of the seal in
the
bore is simplified by the radially protruding flange, since the seal is simply
pressed in axial direction into the bore until the radial flange of the second
stiffening ring comes to rest against the housing wall.
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Depending on the parameters of the respective application, the radial
flange of the second stiffening ring may be enclosed by an elastic material
which may be an integral part of the coating and may have an axially
protruding annular sealing lip on the side facing the wall. Leakage between
the
seal and the bore wall is practically prevented with this construction. The
annular sealing lip and/or radially protruding sealing ridges provided on a
portion of the coating engaging the bore wall reliably retain the liquid to be
sealed in the space to be sealed. The second stiffening ring and the first
stiffening ring are preferably concentrical, whereby the coating extends
therebetween. Vibration insulation or damping is optimized and noise
propagation minimized when the coating between the two stiffening rings has a
radial thickness of 0.7 to 3 millimeters, preferably 0.8 to L5 millimeter.
This
coating thickness is especially well suited for most applications and provides
a
good compromise between a small seal diameter and an effective vibration
insulation/damping.
In another preferred embodiment, the second leg has an offset profile
with a portion of relatively larger diameter and a portion of relatively
smaller
diameter. The portion of larger diameter at least partly surrounds the outer
ring of the anti-friction bearing, and the portion of smaller diameter is
positioned radially inwardly of the second stiffening ring, whereby the
intermediate layer of elastic coating extends between that portion and the
second stiffening ring. It is an advantage of this embodiment that the seal
arrangement has an especially small diameter. In addition, a coating around
the first stiffening ring of substantially constant thickness is achieved, so
that
unwanted accumulations of material are avoided. Furthermore, the portion of
smaller diameter is used for improved support of the outer bearing ring in
axial
direction so that an exact positioning of the anti-friction bearing within the
seal
is achieved.
The coating preferably includes at least two axially spaced apart sealing
ridges on the surface facing the bore wall. These sealing ridges provide for a
static sealing. Depending on the pressure and the viscosity of 'the medium to
be sealed, a large number of sealing ridges may be positioned in series
parallel
hl
to the shaft's axis to form a labyrinth, so that a good static seal is
reliably
achieved. The seal ring may be provided with an auxiliary sealing lip which is
axially spaced apart from the main sealing lip, surrounds the shaft and is
located on that side of the main sealing lip which is remote from the medium
5 to be sealed so that the main sealing lip, the auxiliary sealing lip and the
shaft
define a hollow chamber. This chamber may be filled with grease during use
of the seal for improvement of its operating characteristics over an extended
period of time. The auxiliary sealing lip which acts as serial seal and the
grease filled chamber keep dirt away from the main sealing lip which dirt
would otherwise reduce the service period of the main sealing lip. It is
especially advantageous that a shaft seal in accordance with the invention may
be used even under extremely tough operating conditions.
The invention will now be further described by way of example only and
with reference to the attached drawings, wherein:
Figure 1 shows a seal arrangement which includes a first stiffening ring
having a straight, axially extending second leg and a flange which is coated
at
its radial end by an elastic material, whereby the elastic material is an
integral
part of the coating;
Figure 2 illustrates a seal similar to the embodiment shown in Figure 1,
whereby the second leg has an offset profile, the second stiffening ring is
not
completely coated at its radial end, and the overall diameter of the seal is
smaller; and
Figure 3 shows a seal arrangement which includes some features of both
seal arrangements illustrated in Figures 1 and 2. The radial flange of the
second ring is at its outer end coated with an elastic, rubbery material,
whereby
the elastic material includes an annular sealing lip which protrudes towards
the
housing. Furthermore, the second stiffening ring has an offset profile in
axial
direction.
Figures 1 and 2 show preferred embodiments of a seal arrangement for
the sealing of a shaft 2 which extends through a bore 1.1 in a housing 1. The
seal arrangement essentially includes a radially sealing seal ring 3, first
and
second stiffening rings 6 and 11 and an integrated anti-friction bearing 9
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having inner and outer rings 8 and 22. The seal ring 3 statically seals the
bore
1.1 and dynamically seals the shaft 2 which rotates relatively to the housing
I.
Static sealing at the bore wall is achieved by sealing ridges 15, 16 (see Fig.
2).
In the depicted embodiments, the dynamic sealing of the shaft 2 is achieved
with a main sealing lip 4, and an auxiliary sealing lip 19 which sealingly
engage the shaft 2 to be sealed along its circumference. The auxiliary sealing
lip 19 is axially spaced apart from the main sealing lip 4 and positioned on
that
side of the main sealing lip remote from the medium to be sealed 20. The
main sealing lip 4, the shaft 2 and the auxiliary sealing lip 19 together
define a
hollow chamber 21 which may be filled with grease for protection of the main
sealing lip 4. A garter spring 25 is provided which evenly forces the main
sealing lip 4 against the shaft 2 for improved sealing results. In both
embodiments, the first stiffening ring 6 is L-shaped in cross-section with a
radially extending first leg 5 and an axially extending second leg 7 which
overlaps and tightly engages the outer ring 8 of the bearing 9. The inner ring
22 of the anti-friction bearing 9 is xetained on the shaft and the outer ring
8 is
held by the second flange 7 of the first stiffening ring 6. A coating 10 of
elastic, rubbery material is provided between the first and second stiffening
rings 6, 11, which coating is constructed so that heat generated clearance
variations observed during the intended use of the seal arrangement are
compensated. Simultaneously, the seal arrangement in accordance with the
invention provides good support for the rotating shaft 2 and a vibration
insulation/damping with simultaneous reduction in noise propagation. To
achieve a reliable spatial fixation of the seal arrangement in the gap between
the bore wall 1.1 and the shaft 2, the second stiffening ring 11 is made of a
;.
tough, hard material and is constructed so that it is radially stressed when
inserted into the housing and, thus, radially outwardly forces against the
bore
wall along its outer circumference. Consequently, the second stiffening ring
11
and with it the whole seal arrangement is frictionally retained in the bore
1.1.
The sealing in this region is achieved in that the coating extends in radial
direction beyond the second stiffening ring subsequent to manufacture and is
radially compressed between the bore wall and the first stiffening ring 6 upon
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insertion of the seal into the bore 1.1. The axially extending second leg 7 of
the first stiffening ring 6 shown in Figure 1 is straight. The second
stiffening
ring 11 and the first stiffening ring 6 are of substantially the same axial
length.
At the axial end 23 of the second leg 7 the coating 10 extends in radial
direction around and slightly beyond the second stiffening ring 11 so that a
~ reliable sealing of the medium to be sealed 20 in the space to be sealed is
guaranteed in that region during the intended use. In addition, the radially
outwardly projecting flange 12 of the second stiffening ring 11 is surrounded
by
a coating of elastic, rubbery material which forms an integral part of the
coating 10 in this embodiment. The seal arrangement is reliably retained in
the
bore 1.1 by friction between the outer circumferential surface of the second
stiffening ring 11 and the wall of the bore 1.1. The annular sealing lip 14
provides additional safety with respect to the sealing of the housing and
seals
the gap between the radially projecting flange 12 of the second stiffening
ring
11 and the radial surface 13 of the housing 1.
In Figure 2, the second leg 7 of the first stiffening ring 6 has an offset
profile and first and second portions 17 and 18. The first portion 17 is of
relatively larger diameter and overlaps and tightly engages the outer ring 8
of
the anti-friction bearing 9. The second portion 18 is of relatively small
diameter and is positioned radially inward from the second stiffening ring 11
with the radially intermediate coating 10 extending therebetween. It is an
advantage that the thickness of coating 10 is substantially constant, so that
undesired accumulations of material are prevented. This is especially
advantageous from a production technology standpoint. As in the embodiment
of Figure 1, the friction connection for the retaining of the seal arrangement
is
formed between the wall of, the bore 1.1 and the second stiffening ring 11
which is shorter in axial direction than the second stiffening ring shown in
Figure 1. In this embodiment, the coating 10 also extends in radial direction
beyond the second stiffening ring 11 so that reliable sealing of the medium to
be sealed 20 is achieved. The coating in that region is provided with spaced
apart parallel sealing ribs 15, 16 which form a labyrinth. The integral radial
flange 12 of the second stiffening ring 11 provides for an exact positioning
of
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the seal arrangement in the bore 1.1 and directly engages the housing 1 with
no
intermediate coating.
The embodiment of Figure 3 incorporates a combination of the
advantageous features of the embodiments shown in Figures 1 and 2. The
radial flange 12 is surrounded by an elastic coating having an integral
annular
sealing lip 14 which sealingly engages the radially extending surface 13 of
the
housing 1. Because the second stiffening ring 11 has an offset profile, the
diameter of this seal arrangement is smaller than the one shown in Figure I.
As in the other embodiments, the seal is retained in the bore 1.1 by friction
between the second stiffening ring and the bore wall.
