Seals for cylindrical surfaces

A shaft seal for sealing fluids includes a rotating shaft means having an axis and an external cylindrical surface. A seal ring is disposed about the shaft and has an internal cylindrical surface juxtaposed to the external cylindrical surface and mating therewith to form mating cylindrical surfaces. One of the cylindrical surfaces is a smooth cylindrical surface, and a plurality of spaced, generally parallel indentations are formed in the smooth cylindrical surface, the indentations extending at an acute angle relative to the axial direction of the shaft such that fluid entering the mating cylindrical surfaces is returned by the indentations as the shaft rotates.

BACKGROUND OF THE INVENTION 
The present invention relates to a seal for a cylindrical surface which is 
used as a shaft seal devices. 
One example of the seal of this kind has been heretofore known as shown in 
FIGS. 18 to 20, wherein a segment seal 1 is brought into sliding contact 
with a liner 14 on the side of a shaft 11. 
More specifically, this segment seal 1 has a housing 2 which houses therein 
a seal element (seal ring kit 3) comprising the combination of a seal ring 
4, a cover ring 5, a key 6, an extension spring (garter spring 7) and a 
compression spring (coil spring 8), which is covered with a spring 
retainer (spring adapter 9) and fixed by a snap ring 10. The seal ring 4 
and the cover ring 5 are principally formed of a carbon material, and both 
the rings 4 and 5 are equally divided into more than two sections 
depending on the size of a shaft 11, which are combined with the 
divisional phase deviated in the circumferential direction. A divisional 
portion of the seal ring 4 is formed into a step joint 12 in order to 
prevent leakage in an axial direction. The seal element 3 is stopped in 
rotation through the key 6 by means of a rotation lock pin 13 disposed 
upright on the housing 2, and held on the shaft 11 by means of the 
extension spring 7 so as to be able to follow the radial movement of the 
shaft 11. The internal diameter surface of the seal ring 4 comes into 
sliding contact with the external diameter surface of a liner 14 slipped 
over the shaft 11 to constitute a sliding seal portion (a dynamic seal 
portion 15) which forms a primary seal portion. The seal element 3 is 
axially biased by the compression spring 8, and the perpendicular end 
thereof is pressed against the end wall of the housing 2 to constitute a 
static seal portion 16 which forms a secondary seal portion. The aforesaid 
internal diameter surface and perpendicular end which form both the seal 
portions 15 and 16, respectively, are formed with pressure balance grooves 
17 and 18 to relieve loads resulting from fluid pressures. FIG. 21 shows 
one example of the pressure balance groove 17 formed in the internal 
diameter surface. The liner 14 in sliding contact with the internal 
diameter surface of the seal ring 4 is generally formed of hardened steel, 
and the external diameter surface is finished into a flat surface. 
The segment seal 1 constructed as described above is used to seal various 
fluids. However, in the case where a gas G is sealed by this segment seal 
1, a sliding seal portion 15 operates under a dry condition, and therefore 
the resulting from sliding cannot be sometimes removed efficiently. To 
cope with this situation, in the segment seal 1, the internal diameter 
surface of the seal ring 4 is formed in advance with the pressure balance 
groove 17 to positively introduce gas pressure therein to keep the seal 
surface pressure lower so as to prevent the heat result from sliding from 
exceeding a level above a limit value. However, when a differential 
pressure between both sides of the seal exceeds a level above the 
functional limit of the lowering the surface pressure caused by the 
pressure balance groove 17 or when the number of revolutions of the shaft 
increases, sliding heat in excess of the heat limit of the sliding 
material occurs. Under the condition as described in excess of the heat 
limit, liquids (cooling liquids) such as oil or water are sprayed by a jet 
against the shaft portion in the vicinity of the sliding seal portion 15 
on the low pressure side to cool the sliding seal portion 15. 
Further, in jet engines for aircraft, gas compressors or gas turbines, 
etc., high pressure gas such as compressed air, combustion gas and the 
like flow into bearing portions failing to properly lubricate the 
bearings. Therefore, it becomes necessary to provide a seal with a 
partition between a bearing chamber and a high pressure gas portion, and 
the segment seal 1 is used for that partitioning portion. FIG. 22 shows a 
construction of a bearing chamber 19 and peripheral portions thereof of a 
jet engine on which the segment seal 1 is mounted for the reason as 
described above. The segment seals 1 are mounted on both axial sides so as 
to isolate the bearing chamber 19. Oil for lubrication and cooling of a 
bearing 20 is supplied by jets 21 and 22 into the bearing chamber 19, the 
oil also having a function to cool the segment seal 1. 
As described above, the segment seal 1 is incorporated into a variety of 
devices to seal gas, and the segment seal 1 is sometimes used under the 
situation that in the working atmosphere, the front receives high pressure 
gas and the back receives low pressure liquid, as described above. Under 
these circumstances, when the pressure difference between the gas and 
liquid is small, the liquid enters the sliding seal portion 15 and the 
liquid sometimes further leaks into the gas side. 
The phenomenon wherein when the pressure difference is small, the low 
pressure liquid leaks into the high pressure gas side is explained as 
follows: 
The case of the aforementioned jet engine is here taken as an example. Oil 
O in the form of mists for lubrication and cooling of the bearing 20 and 
cooling of the sliding seal portion 15 is present on the low pressure side 
of the segment seal 1, and the seal 1 is in an atmosphere wherein the oil 
O leaks, and the oil O also enters the seal element 3. When the pressure 
difference between the gas G and the oil O is large, the gas pressure 
overcomes the surface tension of the oil O and enters a clearance of the 
seal element 3 to prevent further entry of the oil O, whereas when the 
pressure difference becomes low, particularly, less than 0.3 kgf/cm.sup.2, 
the surface tension of the oil O becomes greater than the gas pressure so 
that the oil O enters even the interior of the seal element 3, which has 
been experimentally understood. Particularly, in the segment seal 1, the 
leakage of the gas G is concentrated on the divisional portion of the seal 
element 3 in terms of the divisional construction of the seal element 3, 
and therefore in the circumferential seal portion (sliding seal portion 15 
and static seal portion 16) other than the divisional portion, leakage of 
the gas G is extremely small, and the oil O is liable to enter that 
portion. In addition, in the sliding seal portion 15 in sliding contact 
with the liner 14, oscillations resulting from the rotation of the shaft 
11 occur, and therefore, a variation in surface pressure occurs in the 
sliding seal portion 15 in terms of the following operation with respect 
to the oscillations of the seal element 3, as a result of which the state 
of the oil film of the entered oil O tends to change. Furthermore, in the 
sliding seal portion 15, the seal ring 4 assumes a state wherein the seal 
ring 4 is levitated from the liner 14 (just like the state wherein a 
surfboard rides on the waves) due to the oil film formed on the portion 15 
to further promote an entry of the oil O and a formation of an oil film. 
The oil film formed on the sliding portion 15 is scraped at the divisional 
portion of the seal ring 4 as the shaft 11 rotates and leaks into the gas 
G side. 
In the prior art, it is considered that in order to effectively operate the 
segment seal 1 under the condition of low pressure difference as described 
above, two opposed seal elements 3 are used, as shown in FIG. 23, to feed 
high pressure gas (air or the like is suitable) into an intermediate 
chamber 23 to intentionally create the condition of a high pressure 
difference. However, in this case, a space to some extent is required and 
the construction is complicated, which is not an adequate measure. 
Alternatively, if this measure is used on a jet engine, the high pressure 
gas is bled from the compressor portion of the engine, resulting in a 
complex engine construction of the engine and the lowering in efficiency 
caused by bleeding. 
SUMMARY OF THE INVENTION 
In view of the foregoing, it is an object of the present invention to 
provide a construction which is designed so that even when a pressure 
difference between gas and liquid is small and when no pressure difference 
is present, the entry of liquid into the gas side can be minimized, and 
which can be widely applied not only to segment seals but also to seals 
for cylindrical surfaces. 
For achieving the aforesaid object, the present invention provides a seal 
characterized in that an internal diameter seal surface of the seal member 
on the fixed side in direct contact with the seal member on the rotational 
side or an external diameter seal surface of the seal member on the 
rotational side in direct contact with the seal member on the fixed side 
is formed with a number of inclined grooves or stripes. In the segment 
seal, the seal member on the fixed side comprises seal rings which are 
divided into plural sections in the circumferential direction, and the 
seal member on the rotational side comprises a liner on the shaft side in 
terms of the relationship between the segment seal and the liner. 
In the seal according to the present invention, liquids entering the 
sliding seal portion formed between the seal member on the rotational side 
and the seal member on the fixed side can be discharged toward the liquid 
side by the viscosity of such liquids and by the pumping action of a 
number of grooves or stripes formed in the seal member on the fixed side 
or on the rotational side, to prevent such liquids from leakage. 
While the outline of the present invention has been described simply, other 
objects and new features of the present invention will be completely 
apparent from reading the ensuing detailed description in conjunction with 
the embodiments shown in the accompanying drawing. It is to be noted 
however that the drawings merely show one embodiment for describing the 
present invention and the technical scope of the present invention is not 
limited thereby.

DESCRIPTION OF THE PREFERED EMBODIMENTS 
Embodiments of the present invention will be described hereinafter with 
reference to the accompanying drawings. 
FIG. 1 depicts a section showing the state wherein a segment seal 24 
corresponding to that shown in FIG. 19 of the prior art is mounted. As 
will be apparent from a comparison between these Figures, in the segment 
seal 24 according to this embodiment, a pressure balance groove 17 is not 
formed in an internal diameter seal surface 25 of a seal ring 4 
constituting a seal element 3 but the entire surface of the internal 
diameter seal surface 25 is placed in close contact with the liner 14 to 
form a sliding seal portion 15, which is formed with a number of elongated 
indentations 26 as shown in FIG. 2. That is, the segment seal 24 is 
mounted so as to partition a high pressure gas G from a low pressure 
liquid L and is constructed on the assumption that it is used under the 
condition that a pressure difference between the gas G and the liquid L is 
small. In the case where the pressure difference is small as described and 
more specifically the pressure difference is less than 0.3 kgf/cm.sup.2, 
the internal diameter of the seal ring 4 can be sufficiently applied as a 
flat type which has no pressure balance groove 17. Conversely, when the 
pressure balance groove 17 is present, the liquid L entered the sliding 
seal portion 15 is scraped by a dam portion of the pressure balance groove 
17 to further promote the entry of the liquid L. In addition, in the 
arrangement wherein the pressure balance groove 17 is eliminated to 
provide a simple flat surface, the seal ring 4 is levitated as in the 
phenomenon in which a surfboard rides on the wave, failing to prevent the 
entry of the liquid L. In view of the foregoing, the segment seal 24 is 
designed so that an internal diameter surface 25 formed into a flat 
configuration is formed with the indentations 26 so as to return the 
liquid L entered the sliding seal portion 15 by making use of the 
rotational peripheral speed of the shaft 11. 
FIG. 2 shows the internal diameter seal surface 25 in a developed form, in 
which the high pressure gas G and the low pressure liquid L are positioned 
on the right-hand and left-hand, respectively, as viewed in the Figure. 
The rotational direction relative to the liner 14 as the shaft 11 rotates 
is indicated by arrow A in the Figure. The indentations 26 are formed so 
as to reach the edge 27 on the liquid side of the internal diameter seal 
surface 25 but not to reach the edge 28 on the gas side, and the 
indentations 26 are formed while being inclined at an angle of 
0.degree.&lt;.theta.&lt;90.degree. in the rotational direction A starting at a 
portion formed at the edge 27 on the liquid side. FIG. 3 shows an example 
in which the indentations 26 are widened to form grooves 29. It is noted 
that in FIGS. 2 and 3, the indentations 26 or grooves 29 are not provided 
in step joints 12. 
The arrangement wherein the segment seal 24 is mounted on the bearing 20 
portion of a jet engine shown in FIG. 23 is as shown in FIG. 4. As will be 
apparent from a comparison between both the Figures, according to the 
segment seal 24, the construction can be simplified and the occupying 
space can be considerably reduced. A mounting position of a fan (not 
shown) arranged on the left side as viewed in the Figure can be made 
closer to the bearing 20. The device can be light-weight as a whole, and 
at the same time, bleeding from the compressor portion is not required 
thus enhancing the efficiency of the engine. 
FIGS. 5 to 7 show a type which can be utilized when the pressure difference 
between the gas G and the liquid L is larger to some extent as compared 
with the situation in the case of the above-described two examples (FIGS. 
2 and 3). In FIGS. 5 to 7 both the indentations 26 in FIGS. 5 and 6 and 
the grooves 29 in FIG. 7 for discharging the liquid are provided and the 
grooves 30 in FIGS. 5 and 7 and indentations 31 in FIG. 6 are provided for 
the pressure balance. 
It is contemplated that in the case where the pressure difference between 
the gas G and the liquid L is further large, the segment seal 24 according 
to the present invention with the indentations 26 or grooves 29 for 
discharging the liquid and the segment seal 1 of the conventional type are 
arranged. This construction is particularly effective where during the 
operation, the liquid L causes the seal portion 15 to be wetted and during 
the stoppage or at the time of start, the liquid L enters the seal portion 
15. That is, in the case where the pressure difference is large during 
high speed rotation, the sliding heat of the seal portion 15 increases 
accordingly. Therefore, when the seal portion 15 is wetted by the liquid 
L, the liquid L, particularly the oil O, becomes thermally decomposed due 
to the heat generation during the high speed operation to produce sludge, 
and the oil O is carbonized or caulked to materially deteriorate the 
operability of the seal or to lose the sealing function as the case may 
be. On the other hand, in the FIG. 8 construction, the segment seal 24 of 
the present invention is arranged on the liquid L side, and the segment 
seal 1 of the conventional type on the gas G side is operated under a dry 
condition, thus eliminating a liquid leakage of the seal 1. In the segment 
seal 24 of the present invention having the aforesaid construction, the 
indentations 26 or grooves 29 are formed to extend through the axial 
length as shown in FIGS. 9 and 10. In FIG. 8, reference numeral 32 
designates a vent hole bored in a chamber 33 between both the segment 
seals 1 and 24. More specifically, the vent hole 32 is provided to vent 
the gas G leaked from the segment seal 1 on the high pressure side, and 
machined in a direction at which the liquid L is difficult to flow in. Any 
number of such vent holes 32 can be provided in the circumferential 
direction, and particularly the vent hole 32 provided at the lower side of 
the chamber 33 can also function as a drain hole for the liquid L. 
The above-described construction can be applied not only to the segment 
seal of the 2-ring type so far described but to a segment seal of the 
1-ring type without the cover ring 5 and to a segment seal of the 3-ring 
type also serving as a back ring. FIG. 24 shows one example of a segment 
seal 34 of the 3-ring type according to the prior art, in which the seal 
ring 4 and the back ring 35 are formed in their internal diameter surfaces 
with pressure balance grooves 17 and 36. On the other hand, a segment seal 
37 of the same type as that previously mentioned according to the present 
invention is not provided with pressure balance grooves but has an 
internal diameter surface 25 of the seal ring 4 formed with the 
indentations 28 or grooves 29 for discharging the liquid so far described, 
as shown in FIG. 11. 
FIG. 12 is a graph showing the results of performance experiments conducted 
on the segment seal 24 according to the present invention in which the 
indentations 26 shown in FIGS. 2 and 9 are formed in the internal diameter 
seal surface 25 of the seal ring 4. The experiments was carried out in the 
following procedure: 
______________________________________ 
Size of seal: .PHI.250 mm 
Oil: Lubricating oil for aircraft (60.degree. C.) 
Roundness of liner: 
0.015 mm (elliptical shape) 
Pressure difference: 
none 
Temperature: Normal temperature 
Width of indentations: 
0.2 mm 
Depth of indentations: 
0.1 mm 
Inclined angle 15.degree. 
of indentations (.theta.) 
Pitch of indentations: 
6 mm 
.cndot. Plot: FIG. 2 type 
.circleincircle. Plot: 
FIG. 9 type 
.increment.Plot: 
Flat face type 
______________________________________ 
COMATIVE EXAMPLE 
The results showed that the segment seal 24 according to the present 
invention remarkably reduced oil leakage as compared with the seal of the 
flat face type as a comparative example. This experiment was conducted 
under the condition close to the peripheral speed of the rotational shaft 
of the front fan of an aircraft engine and under the condition close to 
practical use since the pressure of the fan portion rarely occurs. As the 
result of the experiments, the effect for the liner 14 slightly modified 
was also confirmed. Furthermore, it has been confirmed as the result of 
other experiments that the depth of the indentations 26 or grooves 29 is 
preferably less than approximately 0.5 mm (approximately 0.02 inch). 
An example in which the characteristic construction of the present 
invention is applied to a rotational member will be described hereinafter. 
FIG. 13 depicts the mounting state of a segment seal 38 corresponding to 
FIG. 19 according to the above-described prior art. An external diameter 
surface 39 of the liner 14 in sliding contact with an internal diameter 
surface 25 of the seal ring 4 of the segment seal 38 is formed with a 
number of indentations 26. The indentations 26 can be processed when the 
external diameter surface 39 of the liner 14 is surface-finished. In case 
of turning-finish, the indentations 26 are of a single continuous form as 
shown in FIG. 13, and in case of grinding-finish, they are of a 
discontinuous form as shown in FIG. 14. The indentations 26 can be 
replaced by grooves 29 having greater widths but if the grooves 29 are 
employed as shown in FIG. 15, the depth thereof need be smaller than that 
of the indentations 26. 
In these FIGS. 13 to 15, the shaft 11 and the liner 14 slipped thereover 
are to be rotated counterclockwise as viewed in the direction of B, and 
the indentations 26 or grooves 29 are inclined in the direction as shown 
so as to push back the liquid L by the pumping action thereof, the angle 
.theta. inclined with respect to the axis thereof being set to 
30.degree.&lt;.theta.&lt;90.degree., and the depth being set to 0.25 mm (0.01 
inch) or less. 
In FIGS. 13 to 15, the indentations 26 or grooves 29 are formed in the 
entire external diameter surface of the liner 14. That is, they are formed 
to extend through the axial length of the sliding seal portion 15 but the 
indentations 26 or grooves 29 are very finely formed and therefore, 
leaking of the gas G toward the liquid L through the indentations 26 or 
grooves 29 can be ignored in a sense of quantity. To stop the leakage of 
the gas G, a non-processed zone 40 of the indentations 26 or grooves 29 
may be provided in the edge on the gas side of the sliding seal portion 15 
as shown in FIG. 16. Preferably, the width W of the non-processed zone 28 
is more than 0.5 mm. 
In FIGS. 13 to 15, the internal diameter surface 25 of the seal ring 4 in 
sliding contact with the external diameter surface 39 of the liner 14 
formed with the indentations 26 or grooves 29 is formed with pressure 
balance grooves 17 as illustrated in FIG. 21. Accordingly, the external 
diameter surface 39 of the liner 14 merely comes into sliding contact with 
the seal dam portion other than those formed with the pressure balance 
grooves 17 out of the internal diameter surface 25 of the seal ring 4, but 
even with such a construction, the indentations 26 or grooves 29 can 
sufficiently perform their function. However, as shown in FIG. 16, the 
internal diameter surface 25 of the seal ring 4 is not formed with the 
pressure balance grooves 17 but the internal diameter surface 25 is formed 
into a flat configuration and brought with overall contact with the 
external diameter surface 39 of the liner 14, which will no doubt enhance 
the function of the indentations 26 or grooves 29. Therefore, preferably, 
the internal diameter surface 25 of the seal ring 4 is formed with the 
pressure balance grooves 17 if necessary. As shown in FIG. 17, it is 
considered that the internal diameter surface 25 of the seal ring 4 is 
formed into a flat configuration and the indentations 26 or grooves 29 are 
adjusted to the external diameter surface 39 of the liner 14 to form the 
pressure balance grooves 30. 
When the present seal is mounted on the bearing portion 20 of a jet engine 
shown in FIG. 23, the state thereof assumes to the state similar to that 
previously shown in FIG. 4. As will be apparent from a comparison between 
both the Figures, according to the present seal, the construction can be 
simplified and the occupying space can be considerably reduced. The 
mounting position of a fan (not shown) arranged on the left side as viewed 
in the Figure can be made closer to the bearing 20. The device can be 
light-weight as a whole and at the same time, bleeding from the compressor 
portion is not required thus enhancing the efficiency of the engine. 
In the case where the device of the present invention is used for machinery 
in which the pressure of the gas G increases with the result that the 
pressure difference between the gas G and the liquid L further increases, 
it is considered that the seal construction of the present invention 
comprising a combination of the liner 14 with the external diameter 
surface 39 formed with the liquid discharging indentations 26 or grooves 
29 and the seal ring 4 with the internal diameter surface 25 formed into a 
flat configuration and the conventional type segment seal construction may 
be arranged. This construction is particularly effective in the case where 
during the operation, the liquid L causes the seal portion 15 to be 
wetted, and during the stoppage or at the time of start, the liquid L 
enters the seal portion 15. Namely, for example, in the compressor, where 
the pressure of the liquid L during high speed operation is high, the 
sliding heat of the seal portion 15 increases accordingly. Therefore, when 
the seal portion 15 is in the state wetted by the liquid L, particularly 
the oil O becomes heat decomposed to produce sludge, and the oil O is 
carbonized or caulked to materially lower the operability of the seal and 
lose the sealing function as the case may be. On the other hand, in the 
present construction, the seal construction of the present invention is 
arranged on the liquid L side and the conventional type segment seal 
construction is operated under the dry condition. With this, a liquid leak 
can be eliminated in the seal. 
The above-described construction can be applied, other than a 2-ring type 
segment seal so far described, to the 1-ring type segment seal without the 
cover ring 5, and a 3-ring type segment seal provided with a back ring. 
Furthermore, generally, formation of the external diameter surface 39 of 
the liner 14 made of hardened steel with the indentations 26 or grooves 27 
is extremely easily processed as compared with the case of formation of 
the internal diameter surface 25 of the seal ring 4 made of carbon with 
the indentations or grooves. In addition, particularly in the processing 
of indentations and finish-processed portions, it is possible to obtain 
high precision easily by the machining feed (similar to the feed of 
machining threads) during the machining of parts, which results in 
extremely high utility for practical use. 
While a description has been made of the preferred embodiments of the 
present invention, it is to be noted that various modification can be made 
in the present invention without departing form the principle thereof. It 
is therefore desired that all the modifications by which the advantageous 
effects of the present invention are substantially obtained through the 
use of the structure substantially identical or corresponding thereto be 
included in the scope of the present invention.