Torsionally flexible metallic annular seal

A torsionally flexible annular seal in the form of a metallic, resilient sealing ring for a pair of concentric, hollow annular bodies having high pressure and temperature fluid flowing therethrough and having different thermal expansion rates and/or temperatures. The sealing ring comprises a central tapering portion, a first curvilinear sealing portion at one end of the central portion, and a second curvilinear sealing portion at the other end of the central portion. In one embodiment the central tapering portion is frustoconical, and in a second it has convex and concave portions. The first and second sealing portions seal against inner and outer cylindrical surfaces defined by the pair of annular bodies, this sealing including at least two circular sealing lines in different planes.

FIELD OF THE INVENTION 
The invention relates to a torsionally flexible annular seal formed as a 
metallic, resilient sealing ring for a pair of concentric, hollow annular 
bodies having high pressure and temperature fluid flowing therethrough. 
The sealing ring includes a central tapering portion, a first curvilinear 
sealing portion at one end of the central portion, and a second 
curvilinear sealing portion at the other end of the central portion. The 
sealing ring is especially useful in turbine engine assemblies between 
concentric, hollow annular bodies that thermally expand at different rates 
and are exposed to temperatures up to about 1400.degree. F. and pressures 
of 400-500 psi. 
BACKGROUND OF THE INVENTION 
Resilient, metallic sealing rings are well known in the art for sealing 
between a pair of coupled concentric, hollow annular bodies having high 
temperature and pressure fluid flowing therethrough. These sealing rings 
have numerous configurations, usually depending upon the cavity to be 
sealed. While these seals are effective in many situations, a need has 
long existed for a resilient metallic sealing ring capable of maintaining 
a tight seal between two cylindrical surfaces that expand at different 
rates, due to differences in their temperatures or in their coefficients 
of thermal expansion. The basic problem with providing such a seal is that 
the expansion of the cylindrical surfaces tends to compress the seal 
beyond its elastic range and thus the seal does not recover to a sealing 
configuration once the expansion cycle is completed. In other words, the 
cross sectional width of the sealing ring is permanently decreased, 
thereby causing leakage to commence almost as soon as the differentially 
expanded cylindrical surfaces begin to return to their original 
dimensions. This is usually caused by significant bending deflections in 
the seals. 
Examples of U.S. patents disclosing prior art annular seals are: 2,774,618 
to Alderson; 3,490,777 to Emmerson; 3,561,793 to Rode; 3,751,048 to Rode; 
3,797,836 to Halling; 3,857,572 to Taylor et al; 3,869,132 to Taylor et 
al; 4,054,306 to Sadoff, Jr. et al; 4,121,843 to Halling; 4,218,067 to 
Halling; 4,281,841 to Kim et al; and 4,336,943 to Chaplin. U.K. Pat. No. 
1,511,384 also discloses a prior art annular seal. 
SUMMARY 
Accordingly, a primary object of the invention is to provide a torsionally 
flexible annular seal in the form of a metallic, resilient sealing ring 
that is capable of establishing and maintaining an effective seal between 
a pair of annular bodies having high pressure and temperature fluid 
flowing therethrough and that have different rates of thermal expansion. 
Another object of the invention is to provide such a metallic resilient 
sealing ring that can maintain its sealing capability during axial 
displacement of the annular bodies. 
Another object of the invention is to provide such a metallic resilient 
sealing ring that absorbs radial expansion and contraction of adjacent 
annular bodies in the elastic range by means of a rotational deflection, 
not a bending deflection and seals along circular sealing lines in 
different planes. 
The foregoing objects are basically attained by providing a resilient, 
metallic sealing ring comprising a central tapering annular portion having 
first and second ends; a first annular sealing portion extending from the 
first end of the central portion and being curvilinear in cross section; 
and a second annular sealing portion extending from the second end of the 
central portion and being curvilinear in cross section. 
Advantageously, the first and second sealing portions are substantially 
semi-circular in cross section, the central portion is upwardly and 
inwardly tapering from the second end to the first end, and the first and 
second sealing portions extend radially inwardly of the central portion. 
In a first embodiment shown in FIGS. 1-5, the sealing ring central portion 
is frustoconical and tapers at an angle of about 60.degree. before 
installation and at about 75.degree. when preloaded and installed. 
In a second embodiment shown in FIGS. 6-8, the central portion comprises a 
concave portion extending from the second sealing portion and a convex 
portion extending from the first sealing portion. 
These first and second sealing portions, extending from the tapering 
central portion, seal against inner and outer cylindrical surfaces defined 
by the pair of concentric, annular bodies, this sealing including at least 
two circular sealing lines in different planes. 
Other objects, advantages and salient features of the present invention 
will become apparent from the following detailed description, which, taken 
in conjunction with the annexed drawings, discloses preferred embodiments 
of the invention.

DETAILED DESCRIPTION OF THE INVENTION 
As seen in FIGS. 1-5, a sealing assembly 10 in accordance with the 
invention includes a metallic, resilient sealing ring 12 for use in 
sealing against a first cylindrical surface 14 on the inner surface of a 
first outer hollow annular body 16 and a second concentric cylindrical 
surface 18 on the outer surface of a second inner hollow annular body 20. 
The sealing ring 12 cross section is torsionally deflected from a 
condition shown in FIG. 3 to the preloaded condition shown in FIGS. 1 and 
2 so that it can torsionally deflect in either direction of torsional 
rotation upon thermal expansion of the first and second bodies. This is 
accomplished because the sealing portions seal in different planes, as 
described hereinafter. 
As seen best in FIG. 3, the first outer annular body 16 is tubular and 
includes above radially inwardly facing cylindrical inner surface 14 a 
downwardly and inwardly tapering frustoconical surface 22 that tapers at 
about 6.degree. 30'. This taper is an assembly aid and could be up to 
about 15.degree. as desired. Below inner cylindrical surface 14 is a 
curved annular surface 25 that extends into an axially facing annular 
surface 26 which in turn extends into a downwardly and inwardly tapering 
frustoconical surface 27. This frustoconical surface tapers at an angle 
substantially equal to the angle of taper of frustoconical surface 22. 
Frustoconical surface 27 extends into an inwardly facing cylindrical 
surface 28 through which the high temperature and pressure fluid flows. 
The second inner body 20 below the radially outwardly facing cylindrical 
surface 18 has a downwardly and inwardly tapering frustoconical surface 31 
leading to an annular axially facing surface 32. Above the cylindrical 
surface 18 is an axially facing annular surface 34 extending at right 
angles to surface 18. Above surface 34 is a downwardly and inwardly 
tapering frustoconical surface 35 which leads into an outwardly facing 
cylindrical surface 36. As seen in FIGS. 1-3 the second body 20 is hollow 
with a flow-through end defined by annular surface 32 so that the high 
pressure and temperature fluid flowing along the first body 16 can pass 
through the sealing assembly 10 and then into the second body 20. As shown 
in FIG. 3, the frustoconical surface 31 tapers at an angle of about 
15.degree.. 
The first and second bodies are connected together once the sealing ring 12 
is installed in any conventional fashion which allows relative axial 
movement due to thermal expansion, but not enough to axially crush ring 
12. 
The sealing ring 12, as shown in FIGS. 3, 4 and 5, comprises a central 
tapering portion 42 having a first end 43 and a second end 44, a first 
annular sealing portion 46 extending from the first end of the central 
portion and terminating in a free annular edge, and a second annular 
sealing portion 47 extending from the second end of the central portion 
and terminating in a free annular edge. Each of these sealing portions is 
curvilinear in cross section, this cross section being arcuate and 
substantially semi-circular. Thus, the overall cross section of the ring 
including the two sealing portions and the central portion is 
substantially C-shaped. 
The sealing portions each extend radially inwardly of the central portion 
42. This central portion is upwardly and inwardly tapering from the second 
end 44 to the first end 43 and is frustoconical, the taper being shown as 
about 60.degree. in FIG. 4, although the angle of taper can vary depending 
upon the size of the cavity receiving the ring and the potential expansion 
of the annular bodies. The diameter of the first sealing portion 46 is 
smaller than the diameter of the second sealing portion 47, with this 
first sealing portion intended to sealingly engage the outwardly facing 
cylindrical surface 18 on the inner second body and with the second 
sealing portion 47 intended to sealingly engage the inwardly facing 
cylindrical surface 14 on the first body 16, as seen in FIGS. 1-3. 
Preferably, the central portion and two sealing portions of the sealing 
ring are integrally formed from a precipitation hardened high temperature 
alloy such as Waspaloy or Inconel. 
In the particular sealing assembly 10 shown in FIGS. 1-5, the outer 
diameter of the sealing ring 12 is 9.130-9.135 inches, the inner diameter 
is 8.740-8.745 inches, the height is 0.400 inch and the thickness of the 
material is 0.010 inch. The radius of curvature of the first and second 
sealing portions 46 and 47 on the ring is about 0.063 inch. The diameter 
of the inwardly facing cylindrical surface 14 on the first body is 
9.115-9.120 inches and the diameter of the outwardly facing cylindrical 
surface 18 on the second body is 8.755-8.760 inches. The radius of 
curvature of curved annular surface 25 is 0.040-0.060 inch and the axial 
length of cylindrical surface 14 is a minimum of 0.555 inch. Since the 
sealing ring experiences frequent sliding and the surfaces against which 
it rubs are prone to wear, a wear resistant coating is advantageously 
applied to the sealing ring or the cylindrical surfaces 14 and 18. One 
such suitable combination for applications at about 1,000.degree. F. is a 
coating of Tribaloy 800 on the sealing ring and a coating of Tribaloy 700 
on the cylindrical surfaces 14 and 18. Alternatively, the sealing ring can 
be coated with Tribaloy 800 and the material forming the first and second 
bodies in the area of cylindrical surfaces 14 and 18 can be Incoloy 913. 
The sealing assembly can advantageously be used at temperatures up to 
1400.degree. F. and pressures of 400-500 psi. 
ASSEMBLY AND OPERATION 
To assemble the sealing assembly 10, the sealing ring 12 is first received 
on the cylindrical surface 18 on the second body 20 with an interference 
fit of about 0.010-0.020 inch shown in FIG. 3. Then, the first body 16 is 
moved axially towards the second body so that the second sealing portion 
47 on the sealing ring engages frustoconical surface 22 on the first body. 
Continued axial movement of the first body towards the second body will 
cause the sealing ring to be radially inwardly deflected into a preload 
condition until the second sealing portion 47 is fully received in the 
cylindrical surface 14 of the first body, as seen in FIG. 1. This axial 
movement is continued until the seal 12 is enclosed in the cavity defined 
by surfaces 14, 18, 26 and 34 with sufficient axial clearance to permit 
operating axial movements of the bodies without causing axial compression 
of the seal as seen in FIG. 1. The bodies are then conventionally 
connected. In this position, the preloaded sealing ring is torsionally 
deflected so that it tapers at an angle of about 75.degree.. As seen in 
FIG. 1, a primary circular sealing line 49, shown in phantom, is 
established between cylindrical surface 18 and the inner surface of the 
first sealing portion 46 of the sealing ring. In addition, a second 
primary circular sealing line 50, shown in phantom, is established in a 
different plane by engagement of the outer surface of the second sealing 
portion 47 with the inwardly facing cylindrical surface 14 of the first 
body. Thus, the seal 12 effectively seals the cavity defined by the 
opposed cylindrical surfaces 14 and 18, axially facing annular surface 34 
on the second body and axially facing annular surface 26 on the first 
body. 
When high pressure fluid is introduced into the assembly 10, the pressure 
thrusts the sealing ring 12 against axially facing surface 34, as seen in 
FIG. 2. Thus, the primary circular sealing lines 49 and 50 are axially 
displaced but a secondary circular sealing line 51 is established between 
the upper surface of the first sealing portion 46 and the axially facing 
annular surface 34 as shown in FIG. 2. As is evident, these circular 
sealing lines are constantly in different planes. 
In the conditions shown in FIG. 1 or 2, any thermal expansion or slight 
axial displacement of the first and second bodies will result in a 
maintenance of the sealing thereof by sealing ring 12 due to its preload 
and torsionally or rotational deflection capability. Typically, the 
bending rigidity of the sealing portions is greater than the torsional 
rigidity of the central portion, so the expansion of the bodies is 
reflected in a torsional deflection of the central portion rather than 
bending of the sealing portions since the sealing portions are in 
different planes. 
The interference fit mentioned above regarding surface 18 and ring 12 is by 
way of example only since the interference fit must be adjusted in 
specific cases to allow for the different expansion rates of the specific 
materials used. 
EMBODIMENT OF FIGS. 6-8 
As shown in FIGS. 6-8, a second embodiment of the invention is illustrated 
where the configurations of the first and second bodies 16 and 20 are the 
same but the configuration of the sealing ring 12' is different. 
Accordingly, the reference numerals used with regard to the first and 
second bodies above regarding FIGS. 1-5 remain the same. 
As seen in FIG. 6, the sealing ring 12' comprises a central tapering 
portion 42' having first and second ends 43' and 44', a first sealing 
portion 46' extending from the first end and a second sealing portion 47' 
extending from the second end. This structure is similar to that described 
above regarding sealing ring 12. In this embodiment, however, the central 
tapering portion 42' has a concave portion 54 extending from the second 
sealing portion 47' and a convex portion 55 extending from the first 
sealing portion 46', these concave and convex portions extending into each 
other near the middle of the central portion. 
The assembly and operation of the sealing ring 12' is similar to that 
described above regarding sealing ring 12, except that sealing ring 12' is 
more suitable to higher pressure environments. 
Thus, once the sealing ring 12' is installed as shown in FIG. 7, a primary 
sealing line 49', shown in phantom, is established between cylindrical 
surface 18 and the first sealing portion 46'. Similarly, a second primary 
circular sealing line 50', shown in phantom, is established between 
engagement of the second sealing portion 47' and the inwardly facing 
cylindrical surface 14. In this condition shown in FIG. 7, the convex 
portion 55 on the sealing ring 12' is lightly touching or slightly spaced 
away from cylindrical surface 14. 
However, upon conduction of high pressure and temperature fluid through the 
first and second bodies 16 and 20, the sealing ring 12' will move axially 
to a position seen in FIG. 8. In this configuration, the primary circular 
sealing lines 49' and 50' have been upwardly displaced and in addition a 
secondary circular sealing line 51' has been established between the upper 
surface of the first sealing portion 46' and the axially facing annular 
surface 34. Moreover, a second secondary circular sealing line 52' has 
been established between the outwardly facing and now outwardly deflected 
convex portion 55 of the sealing ring and the inwardly facing cylindrical 
surface 14 of the first body 16. The addition of this sealing line adds to 
the sealing capability of the sealing ring 12'. 
While two advantageous embodiments have been chosen to illustrate the 
invention, it will be understood by those skilled in the art that various 
changes and modifications can be made therein without departing from the 
scope of the invention as defined in the appended claims.