Note: Descriptions are shown in the official language in which they were submitted.
`" l~l(~Z92
1 BACKGROUND OF THE INVENTION
2 This invention is an improvement in the gas-tight
3 flange coupling art, and has particular application with
4 respect to high-vacuum and high-pressure flange joints.
A11-metal flange joints for use in applications
6 requiring high-temperature and/or frequent bake-out
7 of an assembled joint are known to the prior art.
8 In particular, U.S. patent 3,208,758 to M. A. Carlson
9 et al., assigned to Varian Associates, Inc., discloses
an all-metal flange joint in which a gas-tight seal
11 between mating flanges is provided by the flowing of
12 soft metal gasket material into an annular groove formed
13 between the facing flange surfaces when the two mating
14 flanges are pressed together.
In the flange joint disclosed in U.S. patent 3,208,758,
16 the opposing flange faces were configured so that a soft
17 metal gasket could be received in a recess provided there-
18 between when the flanges are pressed together. Corresponding
l9 annular ridges were provided on the opposing flange faces
to project into the recess so as to penetrate into opposite
21 sides of a peripheral region of the gasket located in the
22 recess. A portion of the gasket material was thereby caused
23 to flow into an annular groove that formed the periphery
24 of the recess between the opposing flange faces. This groove
was dimensioned to have a volume larger than the volume
26 of gasket material that could flow into the groove, therby
27 preventing gasket material from completely filling the groove.
28 If an excess of gasket material were permitted to enter the
29 annular groove, the opposing flange faces would be pushed
apart. Proper dimensioning of the groove served to provide
31 a gas-tight seal in the nature of a compressed O-ring,
32 which could withstand pressure differentials limited only
3jjmll2878 - 2 - 77-28
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` 1~ii~2~2
1 by the tensile strength of the metal gasket.
2 With prior art flanges of the type described above,
3 however, difficulty was encountered in disassembling the
4 flange joint after a seal had been made. Typically, such
prior art flanges were coupled by bolting the two opposing
6 flanges together. Such bolting or other compressive coupling
7 of the mating flange faces caused compression of the gasket
8 disposed therebetween, and resulted in the extrusion of
9 soft metal from the periphery of the gasket into an annular
groove formed at the periphery of the recess between the
11 opposing flange faces. When the mating flanges were sub-
12 sequently unbolted in order to disassemble the joint,
13 however, the metal g~cket frequently remained stuck to one
14 or the other, or to both, of the flange faces.
When a soft metal gasket has been severely compressed
16 against the surface of a harder metal, a surface bonding
17 phenomenon in the nature of a weld occurs. In addition,
18 a frictional restraining force dependent upon the coefficient
l9 of friction of the soft metal gasket material with respect
to the harder surface of the flange tends to oppose movement
21 of the gasket away from the flange.
22 In the prior art, the tendency of the metal gasket to
23 remain affixed to one or the other, or to both, of the mating
24 flanges was not an insurmountable problem in disassembling
the joint when sufficient leverage was possible for applying
26 an external force to separate the flanges. If, after separa-
27 tion of the flanges, the soft metal gasket remained attached
28 to one or other of the flanges, the gasket could usually be
29 removed quite easily by a hand tool for prying the gasket
away from the flange to which it was attached. However, with
31 the recent proliferation of applications requiring mini-
32 flanges (i.e., flanges having a seal diameter of less
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1 than about one inch), the inaccessibility of mini-flange
2 gaskets to removal by hand-held prying tools has become
3 a significant problem. Also, with large-diameter flanges
4 (e.g., diameters larger than 2-3/4 inches), difficulty
has been encountered in disassembling flange joints
6 because of the large external force required to separate
7 the gasket from either one of the flange faces. In many
8 applications, it is advantageous from a system design
9 standpoint to locate flanged coupling ports in places that
are relatively inaccessible; and hence, a flange joint that
11 does not readily disassemble is a serious inconvenience.
12 What is needed, therefore, is an all-metal flange
13 joint in which the gasket tends to break away from the
~ mating flange faces when the joint is disassembled.
SUMMAR~ OF THE INVE~TION
16 It is an object of the present invention to provide
17 an all-metal flange joint having a soft metal gasket dis-
18 posed between mating flange faces, which gasket can be
l9 easily removed when the joint is disassembled.
It is a particular object of this invention to provide
21 an all-metal joint for coupling mini-flanges (i.e., flanges
22 ~ having a diameter of less than about one inch), the joint
23 comprising a soft metal gasket disposed between opposing
24 faces of the mating mini-flanges, the gasket being easily
removable when the joint is disassembled.
26 In order to accomplish the foregoing objects, the
27 opposing faces of the mating flanges are configured to
28 form a recess therebetween in which a soft metal gasket
29 can be disposed when the opposing flange faces are pressed
together. Oppositely disposed annular ridges on the faces
31 of the mating flanges project into the recess so as to
32 penetrate into opposite sides of a peripheral portion of
3jjmll2878 - 4 - 77-2
2~2
1 the gasket. Compression of the gasket caused by the pressing
2 of the opposing flange faces together causes a portion of
3 the gasket material to extrude into an annular groove formed
4 at the periphery of the recess between the two opposing
flange faces. This compressed gasket material in the annular
6 groove provides a gas-tight seal in the nature of a com-
7 pressed metal O-ring in the groove between the flange faces.
As in the prior art, the annular groove is dimensioned to
9 have a volume larger than the volume of the gasket material
that can flow into the groove. In this way, the volume of
11 the groove can accommodate all of the gasket material that
12 flows therein: and any excess of gasket material that might
13 otherwise tend to push apart the mating flange faces is
14 prevented from entering the groove. By way of distinction
from the prior art, the configuration of the opposing flange
16 faces according to the present invention is such that the
17 residual compressive forces present when the flange coupling1~ mechanism is released, distributed over the surface of
19 the gasket, are substantially equal to or greater than
the frictional and bonding forces that tend to retain the
21 gasket in contact with either flange.
22 In particular, according to the present invention, the
23 surface portions of the flange faces defining the annular
~4 groove into which the gasket material can be extruded
are inclined at other than a right angle with respect to
26 the interface between the mating flange faces. In this way,
27 the distributed compressive force exerted upon the gasket
28 by each surface defining the groove has a component that
29 tends to push the gasket away from contact with the flange
face. Thus, according to the present invention, the gasket
31 tends to break away from the mating flange faces when the
32 joint is disassembled.
. .
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-5a-
More particularly, there i6 provided:
: An all metal joint compxising:
a pair of flange members, each flange member having a face
portion configured to confront a corresponding face portion on
the other flange member when said flange members are joined,
said flange members making contact with each other at a junction
plane;
said face portion of each flange member comprising a
first annular surface region, the first surface region on one
: 10 flange member intersecting the first surface region on the
other flange member at said junction plane, said first surface
.~ regions enclosing an angle therebetween that is less than 180;
said face portion of each flange member further comprising
a second annular surface region and a third annular surface
region, said second and third surface regions intersecting each
other to form a ridge, said ridge being spaced apart from
said junction plane, said second surface region intersecting
i said first surface region on said face portion of each flange
: member to form in the face portion of each flange member an
: 20 annular recess bounded by said first and second surface regions;
said ridge on one of said flange members confronting and
spaced apart from said ridge on the other flange member when
said flange members are joined;
a continuous annular gasket of soft metal configured
to be received between said face portions, said ridge on the
face portion of each of said flange members penetrating into
said gasket when said flange members are joined, whereby gasket
material extrudes into said recess and contacts the first sur-
face region on the face portion of each flange member when said
flange members are joined;
~ aid first and second surface regions on the face portion
of each of said flange members being configured so that the
volume of said recess formed thereby is larger than the volume
of gasket material that can be extruded into said recess when
said flange members are joined; and
the distributive compressive force exerted by each of the
first, second and third surface regions of the face portion of
each flange member upon the gasket material having a oomponent
perpendicular to said ~unction plane, which component acts in a
direction tending to ~eparate the gasket from the flange member~
when the flange member~ are moved away from each other.
l~ Z~Z
1 BRIEF DESCRIPTION OF THE ~RAWING
2 FIG. 1 is a cross-sectional view in the longitudinal
3 plane of an all-metal joint between two mating flanges
4 coupled by a union comprising a male member on one flange
and a female member on the other flange.
6 FIG. 2 is an enlarged view of a portion of the joint
7 between the mating flanges shown in FIG. 1.
8 FIG. 3 is a cross-sectional view of a portion of the
9 face of one of the flanges shown in FIG. 2.
FIG. 4 is a cross-sectional view in the longitudinal
11 plane of an all-metal joint between two mating flanges
12 coupled by a union comprising a threaded male member
13 bearing on each flange and a double-ended female member
14 for engaging both male members.
FIG. 5 is a cross-sectional view in the longitudinal
16 ~ plane of a portion of an all-metal joint between two mating
17 flanges coupled by bolting.
18 FIG. 6 is a force diagram representing the distributed
19 compressive forces exerted on a gasket by the surfaces of a-
flange face configured according to the present invention
21 when the flange coupling mechanism is released.
22 FIG. 7 is a force diagram representing the distributed
23 compressive forces exerted on a gasket by the surfaces of
24 a flange face configured according to the prior art when
the flange coupling mechanism is released.
26 DES~RIPTI~N OF PREFERRÉD EM~O~IMENTS
27 FIG. 1 illustrates an all-metal flange joint according
28 to the present invention, whereby a gas-tight seal is pro-
29 vided between flanged end portions 10 and 20 of pipes 11 and
21, respectively. The flanges 10 and 20 are coupled by means
31 of a union comprising a male member 12 bearing on the pipe
32 11 and a female member 22 bearing on the pipe 21.
,
: . .
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- 1 As shown in FIG. 1, the male member 12 is of annular2 configuration having a threadecl outer surface portion, and
3 is disposed to slide longitudinally along the pipe 11. The
4 inside dia~eter of the male member 12 is less than the out-
side diameter of the flange 10, whereby the male member 12
6 is prevented from slipping off the flanged end of the pipe
7 11. Correspondingly, the female member 22 is of annular
8 configuration having a threaded inner surface portion, and
9 is disposed to slide longitudinally along the pipe 21. The
female member 22 has an inside diameter that is less than
11 the outside diameter of the flange 20, whereby the female
12 member 22 is prevented from slipping off the flanged end
13 of the pipe 21.
14 When opposing faces of the flanges 10 and 20 are brought
into mating contact, the female member 22 extends over the
16 flanges 20 and 10 and engages the threaded outer surface
17 portion of the male member 12. In this way, coupling of
18 the flanged pipes 11 and 22 is accomplished by tightening
19 the female member 22 around the male member 12.
The opposing faces of the flanged end portions 10 and
21 20 are configured to provide a recess 30 therebetween,
22 in which a soft metal gasket 31 can be disposed. The gasket
23 31 is of annular configuration and is made of a material
24 that is more malleable than the material from which the
flanged end portions 10 and 20 are composed. Typically,
26 the flanged end portions 10 and 20 are made of stainless
27 steel, in which case the metal gasket 31 can suitably be an
28 annular copper ring of planar configuration. Other suitable
29 gasket materials for use in conjunction with stainless steel
mating flanges include nickel, aluminum, various alloys,
31 and combinations of base metal coated with soft metal.
32 ~s shown in greater detail in FIG. 2, the face of
3jjmll2878 - 7 - 77-28
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. ' .
1 the flanged portion 10 of the pipe 11 is configured to
2 have an annular ridge 13 projectiny into the recess 30.
3 Similarly, an opposing annular ridge 23 on the face of the
4 flanged portion 20 of the pipe 21 projects from the opposite
direction into the recess 30, whereby the ridges 13 and 23
6 penetrate into the soft metal material on opposite sides
7 of the periphery of the gasket 31. Compression of the
8 gasket 31 by the mating of the flanges 10 and 20 causes
9 extrusion of gasket material into a groove formed at the
periphery of the recess 30.
11 With further reference to FIG. 2, the annular ridge 13
12 is formed on the face of the flange 10 by the intersection
13 of conical surface regions 14 and 15; and an annular trough
14 16 is formed by the intersection of conical surface regions
15 and 17. Similarly, the annular ridge 23 is formed on the
16 face of the flange 20 by the intersection of conical surface
17 regions 24 and 25; and an annular trough 26 is formed by
18 the intersection of conical surface regions 25 and 27. When
19 the flan~es 10 and 20 are fitted tightly together, the conical
surface regions 15, 17, 25 and 27 together form the boundary
21 of the annular groove into which the soft metal gasket
22 material is extruded. This extruded gasket material forms
23 the equivalent of a compressed metal O-ring, which provides
24 a gas-tight seal between the flanges 10 and 20.
The annular groove, which is bounded by the surface
26 regions 15 and 17 on flange 10 and the surface regions 27
27 and 25 on flange 20, is dimensioned to have a volume that
28 is larger than the volume of gasket material that can be
29 extruded therein due to the pinching effect of the ridges
13 and 23 upon the gasket 31. Thus, the amount of gasket
31 material that can enter the annular groove is small enough
32 to prevent separation of the flanges 10 and 20.
3jjmll287~ - 8 - 77-28
-` lll~Z~Z
1 In FIG. 3, the orientations with respect to each other
2 of surface regions 24, 25 and 27 on the face of the flange
3 20 are shown in greater detail. Correspondingly symmetric
4 orientations of the surface regions 14, 15 and 17 on the
face of the flange 10 are similarly provided.
6 As shown in FIG. 3, the surface region 25 declines
7 away from the ridge 23 to the trough 26, from whence the
8 surface region 27 extends to the interface plane between
9 the mating flanges 20 and 10. The conical surface region
24 makes an acute angle ~ with respect to the inter-
11 face plane of the mating flanges. Similarly, the surface
12 region 25 makes an acute angle ~ with respect to that same
13 interface plane. The angle ~ is preferably in the range
14 from 60 to 75, and the angle ~ is preferably in the range
from 15 to 30.
16 In a symmetrically similar manner, the conical surface
17 region 14 on the face of the flange 10 makes an acute angle
18 ~ with respect to the interface plane between the flanges
19 10 and 20; and the conical surface region 15 makes an acute
angle ~ with respect to the same interface plane. Thus,
21 facing surfaces of the flanges 10 and 20 are symmetrically
22 arranged with respect to each other.
23 Both the conical surface region 27 on the flange 20 and
24 the corresponding conical surface region 17 on the flange 10
make an angle ~ with respect to the interface plane
26 of the mating flanges 10 and 20. According to the present
27 invention, the angle ~ is an acute angle. In the prior art,
28 there was no suggestion to make the angle ~ an acute angle.
29 The schematic illustration in FIG. 7 on the other hand
is representative of flange joints of the prior art wherein,
31 unlike the joint of the present invention, the terminal
32 wall 27' of the annular groove into which extruded gasket
3jjmll2878 - 9 - 77-28
", . ~. .
92
.
1 material was confined was perpendicular to the interface
2 plane between the mating flanges. The angle ~ of the present
3 invention, by way of contrast with the prior art, is an
4 acute angle (preferably in the range from 60 to 75). This
novel configuration for the terminal wall of the annular
6 groove (i.e., the wall formed by the surface regions 27
7 and 17), together with the prescribed configuration for
8 the surface regions 24 and 14, enables the gasket 31 to
9 be removed much more easily when the joint is disassembled
than was possible in the prior art.
11 For convenience in fabrication, the conical surfaces 24
12 and 27 on the face of the flange 20 could be parallel to
13 each other, i.e., it is possible for ~ = ~ provided that
14 ~ is an acute angle. However, it is not necessary for
the practice of this invention that ~ = ~ . It is desirable
16 that the ang~e ~ be less than 75 so that the normal to the
17 ~ surface region 27 will have a relatively large component
lS perpendicular to the interface plane between the mating
19 flanges. If ~ becomes too small, however, the outside
diameter of the flanges 10 and 20 would correspondingly
21 become inconveniently large for standard design
22 considerations. It is not desirable for ~ to be much
23 smaller than about 30, because the extension of the ridge
24 23 into the recess 30 decreases as ~ decreases. An
appropriate range for the angle ~ is from 60 to 75;
26 and an appropriate range for the angle ~ is from 15 to 30.
27 When the flanges 10 and 20 are pressed together, whether
28 by the technique shown in FIG. 1 whereby the threaded
29 female union member 22 is tightened over the threaded male
member 12, or by any other appropriate coupling technique
31 such as those to be discussed hereinafter in connection
32 with FIGS. 4 and 5, the ridges 13 and 23 protrude into the
3jjmll2878 - 10 - - 77-28
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29Z
soft metal gasket 31 and cause a peripheral portion thereof
2 to be extruded into the annular groove bounded by the surface
3 regions 15, 17, 27 and 25. In the flange coupling technique
4 shown in FIG. 4, the female member 22 of FIG. 1 is replaced
by a male member 42 that is disposed to slide longitudinally
6 along the pipe 21. The inside diameter of the male member 42
7 is less than the outside diameter of the flange 20, whereby
8 the male member 42 is prevented from slipping off the flanged
9 end of the pipe 21. An outer surface portion of the male
member 42 is threaded, just as is a corresponding outer
11 surface portion of the male member 12 on the pipe 11. A
12 cylindrical female member 52, whose inner surface is
13 threaded, can simultaneously engage the threaded outer
14 surface portions of the male members 12 and 42 when the
flanges 10 and 20 are in mating contact. In practice,
16 the female member 52 is first tightened onto one of the
17 male members (e.g., male member 42), and then the other
18 male member 12 is threaded into the female member 52 and
19 tightened. In this way, the flanges 10 and 20 are brought
into mating contact.
21 Another flange coupling technique is shown in FIG. 5,
22 wherein a flange member 10' is affixed to an end of the pipe
23 11 by an appropriate technique such as welding. Similarly,
24 a flange member 20' is affixed to an end of the pipe 21.
The soft metal gasket 31 is compressed between the opposing
26 flange members 10' and 20' by bolting one flange member
27 to the other. As shown in FIG. S, a bolt 61 passed through
28 aligned holes in the flange members 10' and 20', and a
29 nut 62 threadably engages the protruding end of the bolt
61. The bolt 61 and the nut 62 are representative of a
31 plurality of similar bolts and nuts peripherally disposed
32 (and preferably uniformly spaced) around the mating flanged
3jjmll2878 ~ 77-28
29Z
..
1 members 10' and 20'.
2 When the flanged portions 10 and 20 as shown in FIGS.
3 1 and 4 (or the flanged members 10' and 20' of the embodiment
4 shown in FIG. 5) are pressed together, the ridges 13 and
23 of the opposing flange faces protrude into the soft metal
6 gasket 31, thereby causing a peripheral portion of the gasket
7 material to flow into an annular groove formed at the peri-
8 meter of the recess 30 between the opposing flanged faces.
9 This groove, which is bounded by the surfaces 15 and 17 on
flanged portion 10 and by the surfaces 27 and 25 on flanged
11 portion 20, has a total volume that is greater than the
12 volume of gasket material that can be extruded into the
13 groove. As explained above, since less than the entire
14 volume of the groove can be occupied by gasket material,
the contacting faces of the flanged portions 10 and 20
16 cannot be pushed apart by gasket material in the groove.
17 The compressed gasket material in the annular groove
18 functions as a metal O-ring under compression to provide
19 a gas-tight seal between the mating faces of the flanged
portions 10 and 20.
21 As illustrated in FIG. 6, the residual distribu.ed
22 compressive forces F~ , F and F3 present when the flange
23 coupling mechanism is released, and which are exerted,
24 respectively, by the surface regions 27, 25 and 24 of the
flanged portion 20 upon the gasket 31, are represented by
26 arrows normal to their respective surfaces. These
27 compressive forces tend to push the gasket 31 away from
28 contact with the flanged portion 20. Corresponding
29 symmetrically acting distributed compressive forces exerted
by the corresponding surface regions 17, 15 and 14 of the
31 flanged portion 10 upon the other side of gasket 31 likewise
32 tend to push the gasket 31 away from contact with the flanged
~,
.
3jjmll2778 - 12 - 77-28
?2~2
1 portion 10.
2 When it is desired to uncouple the flanges 10 and 20 in
3 order to disassemble the joint, it is usually also desirable
4 to remove the gasket 31. Quite often in the prior art, how-
ever, it was difficult to break the seai between two mating
6 flanges because of bonding and frictional forces that tended
7 to keep the gasket in contact with the faces of the flanges.
8 Bonding forces in the nature of cold welds would develop due
9 to the compression of the gasket against the flanges.
Frictional forces acting parallel to the surfaces of the
11 flanges in directions opposite to the forces tending to
12 push the gasket away from contact with the flanges would
13 also develop. Even after the two mating flanges were
14 separated in the prior art, the gasket would frequently
remain attached to one or other of the flanges. In
16 accordance with the present invention, the faces of the
17 opposing flanges are configured in such a way as to mini-
18 mize the forces that tend to prevent removal of the gasket
19 after the flan~e coupling mechanism has been released te-g-,
by uncoupling the threaded unions shown in FIGS. 1 and 4, or
21 by loosening and removing the nuts 62 shown in FIG. 5).
22 Referring to FIG. 6, the residual compressive force
23 component F acting to push the gasket 31 away from contact
24 with the flange 20 is given by the equation:
26 F = F, cos ~ ~ F~ cos 4 + F3 cos ~ .
27
28 This net compressive force component F increases as the
29 angles ~ , 4 and ~ decrease. It is desirable for ~ to
be in the range from 15 to 30, and for ~ to be in the
31 range from 60 to 75, so that the ridge 23 will protrude
32 sharply enough into the recess 30 so as to cause extrusion
3jjmll2878 - 13 - 77-28
Z9Z
1 of material from the periphery of the gasket 31. According
2 to the present invention, the angle ~ is minimized to the
3 extent practicable in order to provide a component of the
4 compressive force F~ in the direction opposite to the
frictional force component that tends to keep the gasket
6 31 in contact with the surface region 27.
7 Ease in disassembling an all-metal flange joint of
8 the kind used in high-pressure and high-vacuum applications
g is the primary objective of this invention. The diameter
of the flanges to be joined is not material to the defini-
11 tion of this invention, although the invention is of
12 special value with respect to mini-flange joints located
13 in areas that are not readily accessible to disassembly
14 by means of hand-held tools.
The practice of this invention may be accommodated
16 by providing a variety of coupling techniques for mating
17 the opposing faces of the flanges to be joined. In
18 particular, the coupling technique illustrated in FIG.
19 4 (i.e, use of a union comprising a male member on each
flange and a female member that engages each male member)
21 provides a convenient way to join a number of sections of
22 flanged piping without having to arrange components so as
23 to provide matching male and female union members on the
24 respective ends of flanges to be joined. Where appropriate,
a helium gas access hole could be provided through one or
26 both mating flange members to the peripheral region of the
27 recess formed therebetween, whereby the gas-tight integrity
28 of the flange joint can be monitored by techniques well-known
29 to those skilled in the art. The nature of the piping to
be joined can vary according to the type of system in which
31 the piping is used. It is contemplated that a flange joint
32 according to this invention can be used to couple pipes
.
3jjmll2878 - 14 - 77-28
.,
Zg2
1 of any diameter and configuration, including pipes having
2 expandable "bellows" sections. Other uses for an all-metal
3 joint according to this invention will become apparent
4 to those skilled in the art from a perusal of the foregoing
specification. Thus, the scope of the invention is limited
6 only by the following claims.
g
11
12
13
14
16
17
18
1 9
21
22
23
24
26
27
28
29
31
32
3jjmll2878 - 15 - 77-28
