Note: Descriptions are shown in the official language in which they were submitted.
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SEALING ARRANGEMENT FOR CENTRIFUGAL PUMPS,
PARlTCULARLY FOR COOLING WATER PUMPS IN MOTOR VEHICLES
The invention relates to a sealing arrangement
for centrifugal pumps, particularlv for cooling water
pumps in motor vehicles, with a check ring arranged
fixedly on the pump shaft and with a slip ring seal
arrangement pressed into the pump housing, which
comprises a sleeve, a bellows seal, a helicoidal spring
and a slip ring which is pressed by the spring into
sliding abutment against the check ring.
Sealing arrangements for centrifugal pumps of
the type initially defined are already known in a variety
of constructions.
A sealing arrangement for centrifugal pumps is
15 known from German Offenlegungsschrift 2,850,394 published
May 31, 1979, in the name of Garlock Inc., e.g., in
Figure 1, wherein the check ring and the slip ring seal
arrangement are combined into a subassembly in order to
facilitate the assembly.
However, this widespread form of a sealing
arrangement for centrifugal pumps, particularly for
cooling water pumps in motor vehicles, exhibits, as is
further explained in the said German Offenlegungsschrift
2,850,394, the disadvantage that grains of sand etc.,
enter between the planar sliding seal surfaces on the
check ring and on the slip ring and cause abrasive wear
there. Such grains of sand occur in the cooling system
of internal combustion engines as residues of the casting
cores required for casting the components of the internal
combustion engine.
According to the said German
Offenlegungsschrift 2,850,394, it is proposed, in order
to obviate this disadvantage, to use, instead of the
sealing arrangement heretofore customary for centrifugal
35 pumps, a novel seal ring arrangement constructed after
the fashion of a radial shaft seal ring, wherein, on the
main sealing lip, one or more auxiliary sealing lips are
arranged axially inwards from the actual sealing lip,
which have the function to keep abrasive particles, such
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as grains of sand, present in the liquid away from the
actual sealing lip.
However, the construction of German
Offenlegungsschrift 2,850,394 may exhibit the
5 disadvantage that the abrasive particles settling on the
auxiliary sealing lips gradually lead to a wear of the
auxiliary sealing lips, and therefore sooner or later
abrasive particles may reach the main sealing lip and
damage it. Moreover, the auxiliary sealing lip also
10 allows no liquid to pass, so that the main sealing lip
may be subject to wear by dry running.
Another sealing arrangement for centrifugal
pumps is known from German Offenlegungsschrift 2,623,583
published December 15, 1977, in the name of Goetzewerke
15 Friedrich Goetz A.G., wherein the check ring and the slip
ring seal arrangement are likewise combined into a
subassembly in order to facilitate the assembly.
In this case the seal housing of said
subassembly also encloses the check ring in such a way
20 that abrasive particles such as sand grains which are
present in the liquid can only reach the planar sliding
seal surfaces between the check ring and the slip ring by
passing through a plurality of narrow annular gaps.
Although this arrangement largely prevents the
25 access of coarse abrasive particles, correspondingly
small particles can gradually overcome the narrow annular
gaps and still reach the plane sliding seal surfaces and
cause wear to them.
The aim of the present invention is to improve
30 a sealing arrangement for centrifugal pumps, particularly
for cooling water pumps for motor vehicles, so that the
disadvantages of known seal arrangements referred to are
avoided.
This aim is achieved according to the present
35 invention by providing a seal construction for
centrifugal pumps that includes a check ring arranged
fixedly on the pump shaft and a slip ring seal
construction pressed into the pump housing. The seal
construction comprises a sleeve, a bellows seal, a
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helicoidal spring and a slip ring which is pressed by the
spring into sliding abutment with the check ring. The
slip ring is provided with a planar slip sealing surface
and, radiallv outwardly of that surface, a filter ring
made of waterproof but porous water permeable material
which abuts elastically against the check ring. In one
embodiment, the filter ring consists of felt. In another
embodiment, the filter ring consists of porous plastics
material. In still another embodiment, the filter ring
consists of porous ceramic material.
Due to the fact that the slip ring is provided
radially outside its planar sliding seal surface with a
filter ring made of waterproof but water permeable
material which abuts the check ring elastically, the
following essential effect is achieved. Because the
filter ring exhibits a comparatively large cross-section
and is water permeable, no pressure differential builds
up on the auxiliary sealing surface. Therefore, the
penetration of liquid and particles into the auxiliary
sealing surface is minimized and the leakage volume which
is desirable for lubricating the sliding seal surface
does not flow through the contact gap on the check ring,
but through the total cross-section of the filter ring,
whereby abrasive particles contained in the liquid enter
25 the porous material of the filter ring elsewhere than at
the contact gap with the check ring and are retained
there. It is however thereby ensured that a large number
of abrasive particles can no longer enter the region of
the contact gap with the check ring, because they are
retained in the filter ring. From this it follows that
the filter ring wears less in the region of the contact
gap with the check ring than the auxiliary sealing lips
previously known, because here in contradistinction to
the auxiliary sealing lips, where particles initially
35 retained may pass back into the contact gap at a
subsequent time. The particles once retained in the
filter ring are eliminated from the circuit.
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The invention is explained more fully with
reference to an exemplary embodiment illustrated in the
accompanying drawing, wherein:
Figure 1 shows a vertical section through a
5 unique sealing arrangement on a conventional cooling
water pump of a motor vehicle; and
Figure 2 shows a section on a larger scale
through the check ring and the slip ring with the filter
ring according to the invention.
The cooling water pump of a motor vehicle
illustrated in Figure 1 substantially comprises a pump
housing 1, in which a pump shaft 3 is mounted rotatably
via a shaft bearing 2. Mounted fixedly on the inner end
of the pump shaft 3 is a pump rotor 4, on the
15 outward-pointing hub of which a check ring 5 is mounted
fixedly. A slip ring seal assembly 6, which comprises a
sleeve 7, a bellows seal 8, a helicoidal spring 9, a
bracing ring 10 and a slip ring 11, is pressed into a
bore of the pump housing 1.
Insofar as heretofore described, the sealing
arrangement of the cooling water pump is of conventional
construction.
As may be seen from Figure 2, the slip ring 11
is provided radially outside its planar sliding seal
surface 13 with a filter ring 12 made of waterproof but
porous water permeable material, which abuts elastically
against the check ring 5.
The filter ring 12 here may consist of various
suitable materials such as felt, porous plastics material
or porous ceramics material.
Because abrasive particles, such as grains of
sand etc., which reach the filter ring 12, are caught and
retained in the compara~ively large filter cross-section
of the filter ring 12, only a much smaller proportion of
abrasive particles can enter the contact gap with the
check ring 5 and can consequently also cause only a small
degree of wear there. The porosity of the filter ring 12
also permits, in addition to the trapping of abrasive
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particles, a desirable lubrication of the plane sliding
seal surface 13.
Obviously, the embodiment illustrated in the
drawing represents only one possible construction, a
plurality of radially consecutively arranged filter
rings, optionally with porosity of different fineness, is
also conceivable according to the individual application.
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