|Title of Invention||
AN OIL SEAL
|Abstract||An oil seal having a seal element coupled with an annular wear sleeve comprising a tubular section having a polished outer surface serving as a wear surface and the seal element has a functional lip and a dust lip and the polished outer surface of the tubular section and the said lips are sealingly engaged.|
THE PATENTS ACT, 1970
(39 of 1970)
(Section 10, rule 13)
AN OIL SEAL
POONA PRESSINGS PRIVATE LIMITED
of 39/39, 'Darshangadh', 1' floor, Prabhat Road, Lane No. 9-C,
Pune 411 004, Maharashtra, India, an Indian Company
THE FOLLOWING SPECIFICATION PARTICULARLY DESCRIBES THE NATURE OF THIS INVENTION AND THE MANNER IN WHICH IT IS TO BE PERFORMED:-
This invention relates to an oil seal.
In particular, this invention relates to an oil seal with improved wear resistant properties and adequate oil leak preventing and dust preventing functions.
The present invention relates generally to fluid seals for establishing a seal between a rotating shaft and housing, more particularly, to so-called integrated oil seals. In particular, the present invention is concerned with a novel integrated seal structure having an improved dirt exclusion capability and wherein a good oil sealing action is accomplished without causing damage to the shaft.
Oil seals have been in use for many years to prevent leakage from oil reservoirs and are interposed between a shaft and a housing, one of which rotates. The problem has been that even with an oil seal that theoretically should be perfect, there has been leakage due to imperfections of the shaft surface. For example, a scratch along the shaft can let oil leak out, under both static and rotating conditions. In some instances the scratches or imperfections are such as to increase leakage during rotating conditions.
To combat this, shaft seals with hydrodynamic action have been used. Some such seals exhibit the desired function in only one direction; for that one direction of shaft rotation they utilize such things as spiral grooves or flutes formed on the air side of an
elastomeric sealing lip to return oil from the air side of the oil seal to and beyond the lip, back into the oil reservoir.
Again in the oil seals of the prior art, a baffle is provided to stop oil throw on the shaft. These prior art seals cannot be mounted on soft shafts because of excessive wear as the lip of the seal comes into contact with the shaft.
An object of the present invention is to provide oil seals, which are fluid resistant.
Another object of the invention is to provide an oil seal with reduced friction.
Another object of the invention is to provide an oil seal, which can withstand a high total indicator reading as compared to the conventional prior art oil seals.
Another object of the invention is to provide an oil seal, which is suitable for very low and very high running speeds, and therefore the oil seal can be used over a wide range of applications.
Yet another object of the invention is to provide an oil seal having dry running ability.
Still another object of the invention is to provide an oil seal, which can also be used on an unhardened shaft.
Another object of the invention is to provide an oil seal, which can withstand a very large range in temperature differences.
Another object of the invention is to provide an oil seal, which has a relatively longer shelf life and virtually no aging effect.
Another object of the invention is to provide an oil seal having a special construction for oil throwing.
Another object of the invention is to provide an oil seal with virtually no shaft wear,
In use, the wear sleeve element is press fit over a shaft such as a fixed or rotary axle and the seal element is press fit within a counterbore of housing.
When the sealing lip of the seal element or the wear surface of the wear sleeve are worn out, the integrated seal may be replaced as a whole with a new one. The benefit of the integrated seal is that the outer surface of the shaft is fi-ee fi*om wear so that the life of the shaft is increased. The integrated oil seal includes a so-called dust lip or dirt exclusion lip and a collar serving to prevent ingress of dust and dirt. The fiinction of the dust lip is important in protecting the primary sealing lip fi-om premature wear. It is desirable that the dust lips properly sustain their intended fiinction throughout the life of the integrated seals. It is therefore an object of the present
invention to provide an integrated oil seal having a high degree of dirt exclusion capability.
The invention will now be described with reference to the
accompanying drawings, in which
Figure 1 shows a sectional view of an oil seal in the prior art when
mounted on a shaft;
Figure 2 shows a sectional view of the oil seal when assembled in
the prior art;
Figure 3 shows a sectional view of the integrated oil seal with wear
sleeve in accordance with this invention;
Figure 4 is a mounted view of the oil seal with wear sleeve of
Figure 3; and
Figure 5 is an enlarged view of the portion encircled in Figure 4.
Referring to the drawings, initially to Figures 1 and 2, there is shown an oil seal of the prior art in which, the oil seal assembly, is intended to seal a fixed or rotary shaft, such as a crank shaft , with respect to a housing secured to a crankcase CC. According to the terminology commonly used in the art, the sealed region will be referred to as the "oil side" and the opposite region as the "air side" AS, as shown in Figure 1 of the drawings. Briefly described, the oil seal of the prior art consists of an assembly of a fiinctional lip 120, on the oil side 23, and a dust lip 122, on the airside. These lips are flexible polymeric elements, typically PTFE elements held in place and separated apart by gaskets 104. The assembly of the lips and the gaskets are held in place within a metallic inner ring 100,
and a metallic outer casing press 102, fitted or form fitted to hold the assembly rigidly in place. The functional lip and the dust lip are flexed against the shaft, S typically a crank shaft. As seen in Figure 2, which shows the assembly of the prior art oil seal (OS) on a crankshaft the oil seal is rigidly fitted into a housing (H) on the oil side, with the outer wall of the oil seal firictionally abutting the inner wall of the housing to achieve a tight fit engagement between the two. Extra precautions need to be taken at the time of installing these seals, such as the insertion of a dowel D.
In use therefore when the crankshaft rotates, the oil seal is stationary. However as can be easily understood, the functional lip and the dust lip abrade against the outer surface of the shaft and cause minimum wear on the shaft. The functional lip prevents oil from within the housing to leak out through the oil seal and therefore on to the shaft, whereas the dust lip prevents dust from the environment from entering the inner mechanism supported within the housing.
The disadvantages of the prior art oil seal have already been discussed herein above.
Figures 3 to 5 illustrate the oil seal with wear sleeve in accordance with this invention.
As can be seen in the sectional view on Figure 3, the oil seal, generally indicated by the reference numeral 10 includes a wear
sleeve element 12 and a seal element 14 which are coupled together.
The integrated seal assembly 10 is intended to seal a fixed or rotary shaft, such as a crankshaft, with respect to housing,
The wear sleeve element 12 includes an annular wear sleeve 16 made, for example, by stamping of a sheet metal blank. The wear sleeve 16 includes a tubular section 18 having a polished outer surface serving as a wear surface with which the functional lip 20 and the dust lip 22 of the oil seal element 14, the so called primary and auxiliary sealing lips, are sealingly engaged. The upright section of the tubular section presents an. axially inner abutment surface 40 extending perpendicular to the axis of the seal assembly 10.
The axially outer end of the tubular section 18 is extends into a radially outwardly extending flange 32. The term "axially outer" or "axially outwardly" as used herein is intended to mean the direction toward the airside of the seal. Conversely, the term "axially inner" or "axially inwardly" means the direction toward the oil side of the seal. The axially inner end of the tubular section of the wear sleeve extends to a relatively thinner walled angularly tapered inwardly extending flange 34.
The radial flange 32 is configured to form a radially inner section extending from the upright section. The inner section has a
precision finished, axially inner, dust-sealing surface 38, which tapers axially outwardly and radially inwardly.
Preferably, an elastomeric annular coating of synthetic material is bonded to the radially inner surface of the tubular section 18. The elastomeric coating prevents the shaft from being damaged as the wear sleeve element 12 is press fit thereover.
The seal element 14 includes an annular casing 46 made by stamping of a sheet metal blank. In the illustrated embodiment, the casing 46 has a tubular mounting section 48, and an intumed radial flange 52. Together the section 48 and the flange 52 form a recessed seat for receiving the functional elements of the oil seal namely the functional lip 20 the dust lip 22 and the intervening gaskets 24. An inner metallic annular ring 26 holds the assembly together in the recessed seat of the outer casing 46. This inner ring 26 is fitted into position by a bent inner peripheral flange 28 provided on the outer casing 46. Alternatively, the inner ring could be crimped or spap fitted. The arrangement as clearly seen in Figure 3, shows how the edge feature of the inner ring and the flange 28 folded over it lock the assembly in place. The axially outer end of the flange 28 is bent radially inwardly to extend closely to and axially outwardly of the upright section of the inner ring. The intumed end is engageable with the upright section and concerts with the functional lip to limit the axial displacement of the wear sleeve element 12 relative to the seal element 14.
In use, as can be seen in Figures 4 and 5, the oil seal with wear sleeve is mounted on a shaft S within a housing H. The wear sleeve is rigidly mounted on the shaft and the oil seal is fitted to the irmer wall of the housing. The wear sleeve rotates with the shaft and the oil seal is stationary relative to the housing. Therefore abutment resilient contact is established between the moving inner surface of the wear sleeve and the fimctional and dust lips which are typically of synthetic polymeric material such as 'Teflon'.
As a result of the unique arrangement in accordance with this invention a high degree of oil leak stoppage is achieved by the wear sleeve and fimctional lip combination and dirt exclusion fijnction is achieved by the dust sealing arrangement, the service life of the fimctional lip and the dust lip and, hence, of the integrated seal 10 is remarkably increased.
Easy installation and removal of oil seal as compared to the seal of the prior art.
The shaft does not wear out because the lip does not come into contact with the shaft.
The oil seal in accordance with this invention can be mounted even on a soft shaft because the sleeve is press fitted to the shaft and there is not direct contact between the seal and the shaft.
A baffle is not needed because a collar is provided to restrict the oil throw because of the arrangement of the wear sleeve in front of the ftinctional lip.
Dust prevention is increased because of the collar provided of the wear sleeve.
Tests were conducted on a conventional oil seal and the seal in accordance with this invention on hardened and unhardened shaft. The wear pattern on the shafts were recorded after 500 hours of testing.
The test results are shown in figures 6 to 9 of the accompanying drawings. The results for roughness value showed that the roughness value for unhardened shaft was 0.70|a,m for the conventional seal and 0.30 for the seal in accordance with this invention and correspondingly the values were O.SOfim and 0.30 on hardened shaft. This shows that the shaft even if unhardened does not wear out if a seal in accordance with this invention is used.
The seals were also subject to endurance testing. In the conventional seal oil sweating was observed near the dust lip after 2000 hours of testing with oil flow concentrated on the oil seal. Even after 5000 hours of testing with the oil seal in accordance with this invention no oil sweating or leakage was observed.
While the present invention has been described herein with reference to a specific embodiment thereof, it is contemplated that the present invention is not limited thereby and various changes and modifications may be made therein for those skilled in the art without departing from the scope of the invention. -
1. An oil seal having a seal element coupled with an annular wear sleeve comprising a tubular section having a polished outer surface serving as a wear surface and the seal element has a functional lip and a dust lip and the polished outer surface of the tubular section and the said lips are sealingly engaged.
2. An oil seal as claimed in claim 1, in which the tubular section has an operative upright section which presents an axially inner abutment surface extending perpendicular to the axis of the seal assembly.
3. An oil seal as claimed in claim 1, in which the axial outer end of the tubular section extends into a radially outwardly extending flange.
4. An oil seal as claimed in claim 1, in which the axial inner end of the tubular section of the wear sleeve extends to a relatively thinner walled angularly tapered inwardly extending flange .
5. An oil seal as claimed in claim 3, in which the radial flange is configured to form a radially inner section extending from the upright section.
6. An oil seal as claimed in claim 1, in which the inner section of the tubular section of the wear sleeve has a precision finished,
axially inner, dust-sealing surface , which tapers axially outwardly and radially inwardly.
7. An oil seal as claimed in claim 6, in which, an elastomeric annular coating of synthetic material is bonded to the radially inner surface of the tubular section .
8. An oil seal as claimed in claim 1, in which the seal element includes an annular casing made by stamping of a sheet metal blank.
9. An oil seal as claimed in claim 8, in which , the casing has a tubular mounting section , and an intumed radial flange which form a recessed seat for receiving the seal element.
10.An oil seal as claimed in claim 9, in which an inner metallic annular ring holds the assembly together in the recessed seat of the outer casing the said inner ring being fitted into position by a bent inner peripheral flange provided on the outer casing .
11. An oil seal as claimed in claim 10, in which the inner ring is fitted by crimping.
12.An oil seal as claimed in claim 11, in which the inner ring is fitted by snap fitting .
13.An oil seal as claimed in claim 11, in which an edge feature of the inner ring and the flange folded over it lock the assembly in place, the axially outer end of the flange being bent radially inwardly to extend closely to and axially outwardly of the upright section of the inner ring, the intumed end being engageable with the upright section and concerted with the functional lip to limit the axial displacement of the wear sleeve element relative to the seal element.
14.An oil seal as described herein with reference to the figures 3 to 5 of the accompanying drawings.
Dated this 8* day of January, 2003.
OfR. K. Dewan&Co.,
Applicants' Patent Attorney.
|Indian Patent Application Number||993/MUM/2001|
|PG Journal Number||42/2008|
|Date of Filing||10-Oct-2001|
|Name of Patentee||POONA PRESSINGS PRIVATE LIMITED|
|Applicant Address||39/39, 'DARSHANGADH', 1ST FLOOR, PRABHAT ROAD, LANE NO. 9-C, PUNE 411 004, MAHARASHTRA, INDIA.|
|PCT International Classification Number||N/A|
|PCT International Application Number||N/A|
|PCT International Filing date|