U.S. patent application number 10/585756 was filed with the patent office on 2008-09-11 for method for producing hollow blades.
Invention is credited to Ulrich Knott, Wolfgang Krueger.
Application Number | 20080216316 10/585756 |
Document ID | / |
Family ID | 34716468 |
Filed Date | 2008-09-11 |
United States Patent
Application |
20080216316 |
Kind Code |
A1 |
Knott; Ulrich ; et
al. |
September 11, 2008 |
Method for Producing Hollow Blades
Abstract
A method for producing hollow blade blades, in particular for
gas turbines such as aircraft jet engines is provided. At least
three elements (20, 21, 22) are located one on top of the other in
a sandwich structure, are joined together at least in sections by
diffusion welding and are then superplastically formed by expansion
in such a way that a first element (20) forms a first external wall
of the hollow blade to be produced, a second element (22) forms a
second external wall of the hollow blade to be produced and a third
element (21) forms a central element running between the two
external walls of the hollow blade to be produced. At least one
nick-minimizing structure is introduced into the first element (20)
and the second element (22), which form the two external walls of
the hollow blade to be produced, before said elements are arranged
together with the third element (21) in the sandwich structure.
Inventors: |
Knott; Ulrich; (Muenchen,
DE) ; Krueger; Wolfgang; (Reichertshausen,
DE) |
Correspondence
Address: |
Davidson, Davidson & Kappel, LLC
485 7th Avenue, 14th Floor
New York
NY
10018
US
|
Family ID: |
34716468 |
Appl. No.: |
10/585756 |
Filed: |
December 21, 2004 |
PCT Filed: |
December 21, 2004 |
PCT NO: |
PCT/DE04/02779 |
371 Date: |
July 12, 2006 |
Current U.S.
Class: |
29/889.72 |
Current CPC
Class: |
B21D 26/055 20130101;
B23P 15/04 20130101; B21D 53/78 20130101; B23K 2101/001 20180801;
B23K 20/02 20130101; Y10T 29/49339 20150115 |
Class at
Publication: |
29/889.72 |
International
Class: |
B21K 3/04 20060101
B21K003/04 |
Foreign Application Data
Date |
Code |
Application Number |
Jan 12, 2004 |
DE |
10 2004 001 666.6 |
Claims
1-11. (canceled)
12. A method for manufacturing hollow blades, comprises: providing
at least a first element, a second element, and a third element, an
inner side of each of the first and second elements having a planar
recess; arranging the first, second and third elements one over
another in a sandwich-type structure; joining the first, second and
third elements to one another at least in portions thereof by
diffusion welding; superplastically deforming the sandwich-type
structure via an inflation processes, such that the first element
forms a first outer wall of a hollow blade to be manufactured, the
second element forms a second outer wall of the hollow blade to be
manufactured, and the third element forms a middle element of the
hollow blade to be manufactured which extends in between the first
and second outer walls, and a portion of the third element is
spaced apart from the planar recesses.
13. The method of claim 12, wherein the inner side of the first
element faces one side of the third element, and the inner side of
the second element faces an opposite side of the third element.
14. The method as recited in claim 13, wherein the planar recesses
extend over a portion of the inner sides of the first element and
of the second element., such that a middle section of the first
element and a middle section of the second element has a smaller
material thickness than lateral sections of the first and second
elements respectively.
15. The method as recited in claim 14, wherein, between the middle
section and the lateral sections of each of the first and second
elements, the respective recesses have a continuous or stepless
transitional profile.
16. The method as recited in claim 15, wherein, in cross section,
the continuous or stepless transitional profile has a circular or
elliptical form.
17. The method as recited in claim 16, wherein the recesses are
introduced into the inner sides of the first element and of the
second element, respectively, by milling.
18. The method as recited in claim 13, wherein the pressure
required for diffusion welding is supplied such that, during the
diffusion welding process, the first element and the second element
are pressurized in the area of the or of each continuous or
stepless transitional profile such that, following the diffusion
welding in the area of the or of each transitional profile, a
groove space is formed.
19. The method as recited in claim 18, wherein the pressure is
supplied by a mechanical press.
Description
[0001] The present invention relates to a method for manufacturing
hollow blades, in particular for gas turbines, according to the
definition of the species set forth in claim 1.
[0002] Present-day gas turbines, in particular aircraft engines,
must meet exceedingly stringent requirements in terms of
reliability, weight, performance, economy and service life. In
recent decades, aircraft engines have been developed, particularly
for use in the civil sector, which have fully satisfied the above
requirements and have attained a high level of technical
perfection. The selection of material, the search for new types of
suitable material, as well as the quest for novel manufacturing
processes play a decisive role in aircraft engine development.
[0003] To reduce the weight of gas turbine components, it is
already known from the related art to design gas turbine blades as
hollow blades. The blades of a gas turbine account namely for a
considerable proportion of its weight. The more appreciably the
weight of the gas turbine can be reduced, the more favorable the
so-called thrust-to-weight ratio of the aircraft engine is
obtained, which is a decisive feature for aircraft engines in terms
of achieving a competitive advantage.
[0004] A related art method commonly used for manufacturing hollow
blades is the so-called SPF DB method, SPF being an acronym for
super plastic forming and DB an acronym for diffusion bonding. In
the SPF DB method for manufacturing hollow blades, at least three
elements are arranged one over another in a sandwich-type
structure, joined to one another at least in portions thereof by
diffusion welding, and subsequently superplastically deformed by
inflation or blow-up processes. A first element forms a first outer
wall of the hollow blade to be manufactured, a second element forms
a second outer wall of the hollow blade to be manufactured, and a
third element, which is placed prior to the diffusion welding
process in a sandwich-type structure between the first and the
second element, forms a middle element of the hollow blade to be
manufactured that extends in between the two outer walls. In the
SPF DB methods known from the related art for manufacturing hollow
blades, nicks, which have a strength-reducing effect, may form
inside of the hollow blade. This is disadvantageous.
[0005] Against this background, the object of the present invention
is to devise a novel method for manufacturing hollow blades.
[0006] This objective is achieved in that the method mentioned at
the outset is further refined by the features set forth in the
characterizing portion of claim 1. In accordance with the present
invention, at least one nick-minimizing structure is introduced in
each case into the first element and the second element which form
the two outer walls of the hollow blade to be manufactured, before
assembling the same, together with the third element, to form a
sandwich-type structure. In the method according to the present
invention presented here, an SPF DB method for manufacturing hollow
blades is provided, the hollow blades not having any
strength-reducing, internal nicks.
[0007] One advantageous further refinement of the present invention
provides for the or each nick-minimizing structure to be introduced
into an inner side of the first element and of the second element
in a way that results in a smaller material thickness for the
elements in a middle section than in the lateral sections. Between
the middle section and the lateral sections, the elements have a
continuous or stepless transitional profile.
[0008] The pressure required for diffusion welding is preferably
supplied in such a way that, during the diffusion welding process,
the first element and the second element are pressurized in the
area of the or of each continuous or stepless transitional profile
in such a way that, following the diffusion welding in the area of
the or of each transitional profile, a groove space is formed.
[0009] Preferred embodiments of the present invention are derived
from the dependent claims and from the following description. The
present invention is described in greater detail in the following
on the basis of exemplary embodiments, without being limited
thereto. Reference is made to the drawing, whose:
[0010] FIG. 1: shows a schematized representation for clarifying a
method according to the related art for manufacturing hollow
blades;
[0011] FIG. 2: shows another schematized representation for
explaining the method according to the related art for
manufacturing hollow blades;
[0012] FIG. 3: shows another schematized representation for
clarifying the method according to the related art for
manufacturing hollow blades;
[0013] FIG. 4: shows a schematized representation for illustrating
the method according to the related art for manufacturing hollow
blades;
[0014] FIG. 5: shows another schematized representation for
clarifying the method according to the related art for
manufacturing hollow blades; and
[0015] FIG. 6: shows another schematized representation for
explaining the method according to the present invention for
manufacturing hollow blades.
[0016] Prior to describing the method according to the present
invention for manufacturing hollow blades in detail in the
following with reference to FIG. 4 through 6, the SPF DB method
known from the related art for manufacturing hollow blade shall be
described first, in order to elucidate the differences between the
related art and the invention presented here.
[0017] In the SPF (super plastic forming) DB (diffusion bonding)
method known from the related art for manufacturing hollow blades,
three plate-shaped or sheet-shaped elements 10, 11 and 12 are
arranged one over the other in a sandwich-type structure, frame
elements or frame strips 13 being positioned between each of two
adjacent, plate-shaped elements 10 and 11, as well as 11 and 12.
This sandwich-type structure is illustrated in FIG. 1, hollow
spaces 14 being formed in those regions in which no frame strips 13
are positioned between two adjacent elements 10 and 11, as well as
11 and 12, respectively.
[0018] In accordance with the related art, elements 10, 11, 12 and
13 assembled in this manner one over another in a sandwich-type
structure are joined to one another at least in portions thereof by
diffusion welding. To this end, the sandwich-type structure of FIG.
I is placed in a suitable device 15, and a pressure required for
diffusion welding is applied to the sandwich-type structure.
Elements 10, 11, 12 and 13 are diffusion-welded to one another, at
least in portions thereof, under the action of the pressure that is
graphically represented by arrows 16. This is illustrated by FIG.
2.
[0019] Thus, in accordance with the related art as shown in FIG. 3,
the diffusion-welded stack composed of elements 10 through 13 is
superplastically deformed by inflation or blow-up processes. To
this end, gas in introduced into the diffusion-welded stack made up
of elements 10, 11, 12 and 13, in the direction of arrows 17.
During the superplastic deformation process, elements 10 and 12
acquire a shape that corresponds to the desired blade profile of
the hollow blade. This blade profile is curved in order to provide
an intake side as well as a thrust side for the blades. For the
sake of a simpler representation, in FIG. 3, the two elements 10
and 12, which form the outer walls of the hollow blade to be
manufactured, extend in parallel to one another following the
inflation or superplastic deformation process.
[0020] As can be inferred from FIG. 3, element 11, which extends in
between the two elements 10 and 12 functioning as outer walls,
takes on the shape of a meander structure in the region between
frame strips 13. As can likewise be inferred from FIG. 3, element
11, which extends in between the two elements 10 and 12 functioning
as outer walls, is joined in portions thereof to one of the two
elements 10 and 12 functioning as outer walls. In those portions in
which middle element 11 is not joined to one of the two elements 10
and 12, subsequently to the superplastic deformation, element 11
extends in a zigzag or meander shape between the two elements 10
and 12 forming the two outer walls. To ensure that middle element
11 is joined in parts or portions thereof to the two elements 10
and 12 along the lines of FIG. 3, middle element 11 is coated in
sections with an antidiffusion coating, middle element 11 not being
joined to elements 10 or 12 in the region of the antidiffusion
coating.
[0021] As can be inferred from FIG. 3, under the related art, nicks
19, which seriously degrade the strength of the manufactured hollow
blades, form in a transitional region between elements 10 and 12
and frame strips 13.
[0022] The method according to the present invention for
manufacturing hollow blades is described in the following with
reference to FIG. 4 through 6. In accordance with the present
invention, three elements 20, 21 and 22 are again arranged one over
another in a sandwich-type structure, joined to one another at
least in portions thereof by diffusion welding, and, subsequently
to the diffusion welding process, superplastically deformed. A
first element 20 forms a first outer wall of the hollow blade to be
manufactured, a second element 22 forms a second outer wall of the
hollow blade to be manufactured, and a third element 21, which
extends in between the two outer walls of the hollow blade to be
manufactured, forms a middle element.
[0023] Along the lines of the present invention, nick-minimizing
structures are introduced into first element 20, as well as into
second element 22, which form the two outer walls of the hollow
blade to be manufactured, before assembling the same, together with
third element 21, to form a sandwich-type structure. In this
context, the nick-minimizing structures are introduced into one
inner side 23 and 24 of the two elements 20 and 22, respectively.
FIG. 4 shows that, once elements 20, 21 and 22 are assembled to
form a sandwich-type structure, inner sides 23 and 24 face middle
element 21.
[0024] The nick-minimizing structures are constituted of recesses
25 and 26. Recesses 25 and 26 extend as planar regions over
respective inner sides 23 and 24 of elements 20 and 22. Recesses 25
and 26 are introduced into inner sides 23 and 24 of elements 20 and
22 in such a way that, in one middle section 27 or 28, elements 20
and 22 have a smaller material thickness or cross-sectional area
than in lateral sections 29 or 30. In a transitional region between
middle section 27 and 28 and lateral sections 29 and 30,
respectively, recesses 25 and 26 exhibit a continuous or stepless
transitional profile 31. In cross section, transitional profiles 31
have a circular or elliptical form. Recesses 25 and 26 are machined
into inner sides 23 and 24 of elements 20 and 22, respectively, in
particular by milling.
[0025] In accordance with FIG. 4, elements 20 through 22 designed
in this manner are arranged one over another to form a
sandwich-type structure, as already mentioned, inner sides 23 and
24 having recesses 25 and 26, respectively, facing middle element
21.
[0026] A sandwich-type structure designed in this manner is then
diffusion-welded together at least in portions or regions thereof
in a diffusion welding process. To this end, here as well, an
appropriate pressure is applied to the sandwich-type structure in
the direction of arrows 32. The pressure required for diffusion
welding is supplied in such a way that, following the diffusion
welding process, a groove space 33 is formed in the region of
transitional profiles 31. To prevent groove spaces 33 from
collapsing during the diffusion welding process, the pressure
required for diffusion welding is supplied by a mechanical press
which limits the pressure introduced in the region of transitional
profiles 31. FIG. 5 shows the structure that forms following the
diffusion welding process, as well as groove spaces 33 which form
following the diffusion welding process in the region of
transitional profiles 31.
[0027] The assembly of elements 20 through 22 diffusion-welded in
the above manner is subsequently superplastically deformed, in
turn, by inflation or blow-up processes. To this end, by
introducing gas into the diffusion-welded structure, pressure acts,
in turn, in the direction of arrows 34 on inner sides 23 and 24 of
elements 20 and 22. Following the superplastic deformation, a
nick-free structure of the hollow blade is produced, particularly
in the region of transitional profiles 31 (see FIG. 6).
[0028] Accordingly, the method according to the present invention
along the lines of FIG. 4 through 6 is distinguished from the known
related-art method along the lines of FIG. I through 3 in that
specially designed elements 20 and 22, which later form the outer
walls of the hollow blade to be manufactured, are provided. In this
manner, strength-reducing nicks may be avoided, on the one hand,
inside of the hollow blade; on the other hand, the need is
eliminated for separately formed frame strips. The function of the
frame strips required in accordance with the related art is assumed
in the method according to the present invention by the lateral
sections 29 and 30 of elements 20 and 22, respectively. In this
way, the manufacturing method is able to be clearly simplified over
the related art.
* * * * *