U.S. patent number RE30,206 [Application Number 05/795,668] was granted by the patent office on 1980-02-05 for seals and method of manufacture thereof.
This patent grant is currently assigned to Rolls Royce (1971) Limited. Invention is credited to John G. Ferguson, Geoffrey D. Waters.
United States Patent |
RE30,206 |
Ferguson , et al. |
February 5, 1980 |
Seals and method of manufacture thereof
Abstract
A method of manufacture of an annular seal element comprises the
steps of providing an apertured backing ring with closely packed
bristles extending radially outwardly from the circumference
thereof, clamping the free ends of the bristle between a pair of
co-axial rings and welding the rings and the outermost tips of the
bristles into a unitary structure and subsequently machining away
the original backing ring to leave the rings with radially inwardly
extending bristles. The invention also includes a sealing element
made by the method.
Inventors: |
Ferguson; John G. (Bristol,
GB2), Waters; Geoffrey D. (Bristol, GB2) |
Assignee: |
Rolls Royce (1971) Limited
(London, GB2)
|
Family
ID: |
27260360 |
Appl.
No.: |
05/795,668 |
Filed: |
May 10, 1977 |
Related U.S. Patent Documents
|
|
|
|
|
|
|
Application
Number |
Filing Date |
Patent Number |
Issue Date |
|
Reissue of: |
524379 |
Nov 15, 1974 |
03917150 |
Nov 4, 1975 |
|
|
Foreign Application Priority Data
|
|
|
|
|
Nov 23, 1973 [GB] |
|
|
54518/73 |
|
Current U.S.
Class: |
415/173.7;
228/159; 228/160; 228/178; 228/212; 277/355; 300/21; 415/174.2 |
Current CPC
Class: |
A46B
3/06 (20130101); A46D 3/05 (20130101); F01D
11/001 (20130101); F16J 15/3288 (20130101); F05D
2240/56 (20130101) |
Current International
Class: |
A46B
3/00 (20060101); A46B 3/06 (20060101); A46D
3/05 (20060101); A46D 3/00 (20060101); F01D
11/00 (20060101); F16J 15/32 (20060101); F16J
015/48 (); B23K 031/02 () |
Field of
Search: |
;228/159,160,178,212
;300/21 ;277/53,55,95 ;415/174,172A |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
|
|
|
|
|
|
|
1568312 |
|
Apr 1969 |
|
FR |
|
839731 |
|
Jun 1960 |
|
GB |
|
Primary Examiner: Lanham; C. W.
Assistant Examiner: Ramsey; K. J.
Attorney, Agent or Firm: Stevens, Davis, Miller &
Mosher
Claims
We claim:
1. A method of manufacturing a seal element comprising the steps of
making a brush having a plurality of tightly packed bristles
secured to and projecting from a surface of a backing member,
clamping the free ends of the bristles between a pair of clamping
members, integrally .[.joining.]. .Iadd.fusing .Iaddend.the
clamping members and the tips of the bristles, and subsequently
removing the backing member and the ends of the bristles attached
thereto.
2. A method according to claim 1 and in which the bristles and
clamping rings are metallic and are integrally .[.joined.].
.Iadd.fused .Iaddend.by welding, brazing of diffusion bonding.
3. A method according to claim 1 and wherein the bristles are made
to project at an angle to the surface of the backing member,
whereby in the finished seal element, the bristles project at an
angle from the clamping members.
4. A method according to claim 1 and wherein the backing member is
annular and the bristles project radially from the radially inner
circumferential surface thereof, and the clamping members are
co-axial rings which clamp the free radially outer ends of the
bristles whereby the resulting seal element is annular and has
radially inwardly extending bristles.
5. A method according to claim 1 and wherein the backing member is
annular and the bristles project radially from the radially outer
circumferential surface thereof, and the clamping members are
co-axial rings which clamp the free radially outer ends of the
bristles whereby the resulting seal element is annular and has
radially inwardly extending bristles.
6. A seal element manufactured by the .[.method according to claim
1.]. .Iadd.steps comprising making a brush having a plurality of
tightly packed bristles secured to and projecting from a surface of
a backing member, clamping the free ends of the bristles between a
pair of clamping members, integrally fusing the clamping members
and the tips of the bristles and subsequently removing the backing
member and the ends of the bristles attached thereto.Iaddend..
.Iadd. 7. A gas sealing element for reducing leakage of gas between
two parts of a fluid flow machine, said element comprising an
annular array of tightly-packed bristles sandwiched between a pair
of side-plates and integrally fused therewith, said bristles
projecting from between the side-plates with a circumferential
component of direction. .Iaddend..Iadd. 8. A gas sealing element as
claimed in claim 7, and in which the side-plates are annular and
the bristles project in a generally radial direction. .Iaddend.
.Iadd. 9. A gas sealing element as claimed in claim 8 and in which
one of the side-plates has a greater radial depth than the other.
.Iaddend..Iadd. 10. A gas sealing element as claimed in claim 9 and
in which the bristles project radially inwardly from the inner
circumferential side edges of the side-plates. .Iaddend. .Iadd. 11.
A gas sealing element as claimed in claim 10 and in which the
bristles are metallic. .Iaddend..Iadd. 12. A gas sealing element as
claimed in claim 11 and in which the bristles are welded to the
side-plates at the radially outer circumferential side edges of the
side-plates. .Iaddend..Iadd. 13. A gas sealing element as claimed
in claim 9 and in which the bristles project radially outwardly
from the outer circumferential side edges of the side-plates.
.Iaddend. .Iadd. 14. A combination of a gas sealing element and a
fluid flow machine, the gas sealing element for reducing leakage of
gas between two parts of the fluid flow machine, said sealing
element comprising that claimed in claim 7 wherein the side plates
are connected to one of the parts and the bristles extend into
contiguous relationship with the other of the parts to effect a
seal. .Iaddend. .Iadd. 15. A combination as claimed in claim 14 and
in which one of the parts is rotatable, and the other part is
static, the sealing element being connected to the static part,
with the bristles oriented in the direction of rotation of the
rotating part. .Iaddend..Iadd. 16. A combination as claimed in
claim 15 and in which the sealing element is annular, and the
bristles project in a generally radial direction from the entire
circumference thereof. .Iaddend..Iadd. 17. A combination as claimed
in claim 16 and in which the rotatable part includes a
circumferential flange, and said bristles extend into contiguous
relationship with said flange. .Iaddend..Iadd. 18. A combination as
claimed in claim 17 and in which the bristles extend generally
radially inwardly from said static part. .Iaddend..Iadd. 19. A
combination as claimed in claim 17 and in which the bristles extend
generally radially outwardly from said static part. .Iaddend..Iadd.
20. A combination as claimed in claim 16 and in which one of the
side-plates has a greater radial depth than the other for thereby
resisting flexing of the bristles due to a pressure difference
across the seal. .Iaddend..Iadd. 21. A combination as claimed in
claim 14 and in which the bristles are metallic. .Iaddend. .Iadd.
22. A gas turbine apparatus including two parts across which exists
a gas pressure difference, and a gas seal for reducing leakage of
gas between the two parts said seal comprising a sealing element as
claimed in claim 7 wherein the side plates are connected to one of
the parts and the bristles extend into contiguous relationship with
the other of the parts to effect a seal. .Iaddend. .Iadd. 23. A gas
turbine apparatus as claimed in claim 22 and in which one of the
two parts is rotatable, and the other part is static, the sealing
element being connected to the static part, with the bristles
oriented in the direction of rotation of the rotating part.
.Iaddend..Iadd. 24. A gas turbine apparatus as claimed in claim 23
and in which the sealing element is connected to the static part,
the rotatable part includes a circumferential flange, and said
bristles extend into contiguous relationship with said flange.
.Iaddend..Iadd. 25. A gas turbine apparatus as claimed in claim 24
and in which the bristles extend generally radially outwardly from
the static part. .Iaddend..Iadd. 26. A gas turbine apparatus as
claimed in claim 24 and in which the bristles extend generally
radially outwardly from the static part. .Iaddend..Iadd. 27. A gas
turbine apparatus as claimed in claim 22 and in which one of the
side-plates extends further along the lengths of the bristles
towards the free ends thereof than the other side-plate for
resisting flexing of the bristles under said pressure difference.
.Iaddend..Iadd. 28. A gas turbine apparatus as claimed in claim 27
and in which the bristles are metallic. .Iaddend.
Description
This invention relates to seals, and relates in particular to a
method of making seal elements and to seal elements made by the
method.
In seals between relatively moving parts, there is always a danger
of excessive movement of one of the parts towards the other, which
can cause severe rubbing contact between the opposite elements of
the seal. This is a particular problem in gas turbine engines which
have many high speed rotating components carrying seal elements,
and rubbing of seals at high speeds can cause excessive heating of
the seal elements and even destruction of the seal.
This problem has been tackled in the past, for example, by
providing abradable coatings on the static seal element which can
be worn away by the rotating seal element. This disadvantage of
this solution is that once a rub has occurred, the clearance
between the rotating seal element and the worn-away coating is
increased and sealing efficiency is lost.
The object of the present invention is to provide a seal which
overcomes this disadvantage.
According to the present invention a method of manufacturing a seal
element comprises the steps of making a brush having a plurality of
tightly packed bristles secured to and projecting from a surface of
a backing member, clamping the free ends of the bristles between a
pair of clamping members, integrally joining the clamping members
and the tips of the bristles, and subsequently removing the backing
member and the ends of the bristles attached thereto.
Where the seal element is to form part of a seal between static and
rotating structure the original backing member is made as a ring
and the bristles may extend either outwardly or inwardly from the
ring. The clamping members are also rings and are axially spaced to
sandwich the bristles between them.
For gas turbine engine application the bristles will normally be
metallic and more specifically for high temperature applications
the metal will be a heat resistant metal.
Also according to the invention there is provided a seal including
a seal element made according to the method described above.
The invention will now be more particularly described, by way of
example only, with reference to the accompanying drawings in
which:
FIG. 1 is a sectional elevation of a brush which forms the first
stage of the manufacture of a seal element of the present
invention,
FIG. 2 is a sectional elevation of the brush of FIG. 1 with the
clamping members attached,
FIG. 3 is an end elevation of the brush of FIG. 2,
FIG. 4 is a part of a gas turbine engine showing a typical
application of a seal element of the present invention.
Referring now to the drawings in FIG. 1 there is shown a backing
ring 1 through which are formed a plurality of holes 3 having a
step 5 adjacent their radially inner ends. The left hand side of
the figure shows radial holes but on the right-hand side an
alternative construction is shown in which the holes 3 are shown to
lie at an angle to the radial direction.
The holes are formed as close together as they can possibly be made
without breaking into one another and into each hole is pulled a
bundle of metallic bristles 6. The bristles are usually straight
pieces of small diameter wire i.e. less than 0.005 in diameter and
as many as possible are disposed in each of the holes.
The bristles are held in place by a wire lacing which consists of a
small diameter copper wire which passes up through one hole, over
the central portion of the bent-up bundle of bristles, back down
the same hole and up into the next hole, so that all the bundles of
bristles are wired together and can be pulled down into their
respective holes to seat on the step 5.
The number of bristles projecting outwardly from the holes should
be as large as possible and in one example 140 wires of 0.003 in
diameter were doubled over and pulled into each hole so that 280
bristles were formed. The diameter of the hole in this example was
0.0625 ins. and the width of the brush produced, i.e. the axial
spacing between the clamping rings is 0.10 ins.
The brush construction so far described results in groups of
substantially parallel bristles emerging from the holes, but each
group is spaced from the next by the wall thickness between the
holes. This clearly would not be acceptable for a seal element
since the spaces provide a leakage path.
However, at their free ends, the fibres, being not quite parallel,
having become intermixed and no spacing such as occurs between the
groups at the ring is discernable.
A pair of clamping rings 8 are arranged, one on each side of the
brush, and the radially outer ends of the bristles are welded to
these rings to form an integral bond. The ring 1 and the wire laced
ends of the bristles are then machined away, for example along the
dotted line 10 to leave free bristle ends of the desired length
protruding from the rings 8.
Provided the initial lengths of wire are sufficiently long to form
brush bristles up to 0.75 ins long, the bristles will be
sufficiently compact and sufficiently intermixed at their radially
outer ends to allow for them to be cut off to approximately 0.25
ins. as the final step. The length of bristle allows sufficient
flexibility while allowing also for the bristles to be tightly
picked together.
The above described method produces a brush with radially inwardly
extending bristles but clearly the method can be applied to the
production of a brush having radially outwardly extending bristles.
In this case the brush formed initially would be produced with
radially inwardly projecting bristles, the radially inner free ends
would be clamped and welded and then the original ring and bristle
mountings would be machined away to leave radially outwardly
projecting bristles.
Clearly also, the seal element formed need not be annular but can
be flat, and this can be achieved by making the original brush
flat.
The method of joining the bristles to the clamping rings is
preferably by welding and a suitable method is the use of an
electron beam which is directed at the outer circumference of the
bristles and rings. This melts the outer tips of the bristles and
the rings to form a weld 12 which integrally unites the bristles
and rings. Clearly however, other methods of .Iadd.fusion
.Iaddend.joining can be used to produce a similar integral joint,
for example, brazing and diffusion bonding.
In order to simplify the joining of the bristles and the rings 8
they are preferably made from the same material, for example, in
gas turbine engine seals stainless steel can be used, or for high
temperature seals one of the range of nickel based alloys sold
under the trade name NIMONIC, is used.
It is also envisaged that the bristles need not be metallic but the
method described above is still applicable to non-metallic
bristles.
A typical application of a seal element made according to the
invention is shown in FIG. 4 in which there are shown two stator
stages 20 of a compressor of a gas turbine engine with a rotor
stage therebetween. The rotor stage comprises a disc 19 having a
plurality of blades 18 mounted on the periphery thereof. Between a
flange 24 on the rotor disc 19 and a flange 21 on one of the
stators 20 there is formed a seal which comprises a seal element 25
in the form of a brush constructed in accordance with the method of
the present invention. The seal element 25 co-operates with the
flange 24 to form the complete seal which reduces leakage of air
between the rotating and static structures.
The advantages of the seal element of the present invention are
that should the flange 24 grow outwardly excessively due to
excessive differential thermal expansion during transient running
conditions of the engine, contact will be made between the flange
24 and the bristles, but the flexibility and resilience of the
bristles will allow them to deflect during such contact so that
little wear is produced. After rubbing contact has ended, i.e. when
normal engine running conditions are renewed, the bristles will
return substantially to their normal position and the sealing
clearance will be maintained at a small value.
Another effect of the bristles, is that they do not heat up as
quickly as a solid piece of material, as for example in a
conventional labyrinth seal. This is partly because the deflection
of the bristles reduces the rubbing pressure and partly because,
although the bristles are tightly packed there is a tendency for a
very small leakage flow of air to pass between the bristles in an
axial direction, which will carry some heat generated by the
rubbing away with it. Thus there will be less tendency for the heat
generated by the rubbing to cause increased thermal expansion of
the flange and aggravate the rubbing conditions.
To aid deflection of the bristles, they may be angled in the
direction of rotation of the flange 24 by using the alternative
method of manufacture described in relation to FIG. 1.
Further, a plurality of seal elements including the bristles may be
used in series depending on the degree of sealing required, and to
this end a multiple seal element may be made by clamping a second
brush between one of the clamping rings of a seal element as
described and a third clamping ring, and welding them to the seal
element. Further brush elements can be added in this manner as
desired.
The brush seal elements may be used either as the static or
rotating components of a seal between relatively rotating parts,
but preferably the brush seal elements are the static elements to
avoid centrifugal effects on the bristles affecting the sealing
characteristics. Clearly also brush sealing elements of this type
can be used to seal static parts.
One of the clamping rings 8 may have a greater radial depth than
the other (as shown in FIG. 4) to resist sideways flexing of the
bristles due to a pressure difference across them.
* * * * *