U.S. patent application number 10/168814 was filed with the patent office on 2003-07-24 for butt joint for hollow profiles.
Invention is credited to Wobben, Aloys.
Application Number | 20030138290 10/168814 |
Document ID | / |
Family ID | 7934489 |
Filed Date | 2003-07-24 |
United States Patent
Application |
20030138290 |
Kind Code |
A1 |
Wobben, Aloys |
July 24, 2003 |
Butt joint for hollow profiles
Abstract
A butt connection of divided hollow profile members, which is
suitable in particular for rotor blades of wind power
installations, comprises a multiplicity of straps which are
arranged along the join and which bridge over same and which are
respectively fixed with their ends to one of the profile members to
be connected. In this respect the arrangement is preferably such
that one of the two bolts fixing the strap at the ends thereof has
a wedge-shaped flattening, by means of which a tensile prestressing
can be imparted to the strap.
Inventors: |
Wobben, Aloys; (Aurich,
DE) |
Correspondence
Address: |
SEED INTELLECTUAL PROPERTY LAW GROUP PLLC
701 FIFTH AVE
SUITE 6300
SEATTLE
WA
98104-7092
US
|
Family ID: |
7934489 |
Appl. No.: |
10/168814 |
Filed: |
October 7, 2002 |
PCT Filed: |
December 22, 2000 |
PCT NO: |
PCT/EP00/13167 |
Current U.S.
Class: |
403/293 |
Current CPC
Class: |
Y10T 403/50 20150115;
Y10T 403/1624 20150115; F16B 5/0008 20130101; F16B 2/08 20130101;
Y10T 29/49339 20150115; F05B 2240/30 20130101; Y10S 403/15
20130101; F05B 2240/40 20130101; Y10T 403/55 20150115; F05B
2250/292 20130101; Y10T 403/75 20150115; F05B 2240/221 20130101;
F05B 2230/604 20130101; Y10T 29/49336 20150115; F03D 80/00
20160501; Y02E 10/72 20130101; Y10T 403/551 20150115; Y10T 403/76
20150115; F05B 2240/302 20130101; Y10T 29/49337 20150115; Y10T
403/11 20150115; Y10T 403/725 20150115; Y10T 403/553 20150115; B64C
27/46 20130101; F05B 2260/301 20130101; Y02P 70/50 20151101; F03D
1/0675 20130101 |
Class at
Publication: |
403/293 |
International
Class: |
F16B 012/36 |
Foreign Application Data
Date |
Code |
Application Number |
Dec 24, 1999 |
DE |
199 62 989.7 |
Claims
1. A butt connection for divided hollow profile members, in
particular for rotor blades of wind power installations,
characterised by a multiplicity of straps (5) which are arranged
along the join (2) and which bridge over same and which are
respectively fixed with their ends to one of the profile members
parts (1a, 1b) to be connected.
2. A butt connection as set forth in claim 1 for transversely
divided hollow profile members of non-round cross-section
characterised in that the straps (5) are arranged at the periphery
of the hollow profile member (1).
3. A butt connection as set forth in claim 1 or claim 2
characterised in that the density of arrangement (proximity) of the
straps (5) along the join (2) is different in dependence on the
tensile forces to be transmitted at the join (2).
4. A butt connection as set forth in one of claims 1 to 3
characterised in that there are respectively provided double straps
with a respective strap (5) arranged on the outside and on the
inside of the hollow profile member (1).
5. A butt connection as set forth in one of the preceding claims
characterised in that each strap (5) or double strap can be
prestressed with a defined tensile force.
6. A butt connection as set forth in claim 5 characterised in that
the straps (5) are fixed to the profile member parts (1a, 1b) by
means of two bolts (6a, 6b) and at least one of the bolts (6a) in
the contact regions with the straps (5) has a wedge-shaped
flattening (10) in its axial direction and is held
non-rotatably.
7. A butt connection as set forth in claim 4 and claim 6
characterised in that the bolt (6a) comprises a sleeve provided
with the wedge-shaped flattenings (10) and a screw (8) with nut
(9), which passes axially through the sleeve, wherein both the
screw head and also the nut press by means of cup-shaped pressure
portions (12) against the associated strap (5) and prestress same
by movement along the wedge surface.
8. A butt connection as set forth in claim 5 characterised in that
the straps (5) are fixed to the profile member parts (1a, 1b) by
means of two bolts (6) and at least one of the bolts respectively
has in the contact regions with the straps (5) a bulge which is
eccentric with respect to the axis thereof.
Description
[0001] The invention concerns a butt connection for divided hollow
profile members, in particular for rotor blades of wind power
installations.
[0002] Similarly to aircraft propellers, the rotors of wind power
installations have rotor blades comprising a load-bearing spar or
beam member--in most cases with an upper and a lower flange--and a
hollow profile member which determines the aerodynamic properties
of the rotor. Nowadays the hollow profile members generally
comprise composite materials, namely glass or carbon fibers with
polyester or epoxy resins as binders. What has become the usual
practice is producing the rotor blade hollow profile members (whose
cross-section generally changes over the length thereof) in the
form of two longitudinally divided half-shell portions which are
assembled to the spar to form the finished blade.
[0003] With the increasing power of modern wind power
installations, the rotors thereof are also becoming larger in
diameter, which requires the production of correspondingly longer
rotor blades. If the production of such long rotor blades, that is
to say the half-shell portions required for same, in one piece, is
already not without its problems (inter alia because of the
correspondingly large factory building), transportation which is
then required to the location at which the wind power installation
is erected represents a serious obstacle.
[0004] Having regard thereto and having regard to the foreseeable
further increase in the length of rotor blades for wind power
installations, consideration is to be given to transversely
dividing rotor blades of that kind and in that respect more
specifically the hollow profile members thereof, transporting them
separately, and only finishing the rotor blades at the location of
erection of the wind power installation, by assembling the
individual parts at their butt joins. The problem which arises out
of that approach however is that of developing a butt connection
which does not seriously influence the aerodynamic properties of
the rotor blade, which is of low weight, and which in particular is
capable of withstanding the considerable fluctuating loads to which
the rotor blades are exposed in operation of a wind power
installation.
[0005] The invention resolves that problem by a multiplicity of
bars or straps which are arranged along the join line and which
bridge over same and which are fixed with their ends respectively
to one of the profile member parts to be connected. The straps or
bars replace entirely the one-piece flange connection
conventionally usual for connecting hollow profile members; they
are substantially lighter than that and can be arranged distributed
over the periphery of the hollow profile member discretely at
different spacings from each other, namely in dependence on the
forces to be transmitted at the join line, so that the design of
the connection--with very good application of the forces
involved--is simpler in terms of its operating strength, than when
using a conventional flange/screw connection. Although this kind of
connection can also be used for longitudinally divided hollow
profile members (rotor blades), it is suitable in particular for
transversely divided hollow profile members of non-round
cross-section, with the bars or straps being arranged at the
periphery of the hollow profile member.
[0006] The freedom from maintenance of the new butt connection is
of particular advantage because the connection is not
self-releasing and therefore there are no prestressing losses that
also have to be tolerated.
[0007] Preferably each strap connection comprises double bars or
straps with a respective bar or strap arranged on the outside and
on the inside of the hollow profile member. In addition it is
advantageously provided that each strap can be prestressed with a
defined tensile force. A sufficiently high tensile force
prestressing provides that, in spite of an alternate loading
(tensile force/compression force) in the course of a revolution of
the rotor, the situation at the butt connection still remains one
involving tensile forces and it is only the magnitude of such
forces that changes over the course of a revolution.
[0008] In order to apply the tensile force prestressing required
for that purpose to the individual straps which jointly form the
butt connection, it is preferably provided that each strap is fixed
to the hollow profile member parts by means of two bolts and at
least one of the bolts, in the respective contact region with the
strap or straps, has a wedge-shaped flattening in its axial
direction and is held non-rotatably. Alternatively the bolt could
also be of a part-conical configuration, and then it can also be
rotated. At any event, when fixing the straps, when they are pushed
with their (suitably configured) ends over the bolt and urged in a
direction towards the surface in question of the hollow profile
member, at the same time tensile force prestressing is built up in
the longitudinal direction of the strap and thus perpendicularly to
the join line. In order to implement that in a simple fashion, the
bolt advantageously comprises a sleeve provided with the
wedge-shaped flattenings, and a screw which passes axially through
the sleeve and which has a nut, wherein both the screw head and
also the nut press by means of cup-like pressure portions against
the associated strap and prestress same by movement along the wedge
surface (or cone surface).
[0009] A further alternative form of the prestressing mechanism can
provide that at least one of the bolts, in the respective contact
regions with the straps, has a bulge which is eccentric with
respect to its axis. By rotating the bolt--which moreover does not
need to be rotated to fix the straps--it is also possible in that
way to produce the desired tensile force prestressing in the
strap.
[0010] The drawing illustrates the invention by means of an
embodiment. In the drawing:
[0011] FIG. 1 shows a plan view of a (singly) transversely divided
rotor blade for the rotor of a wind power installation in the form
of a diagrammatic cross-section (the gap between the parts serves
only for enhanced clarity of the drawing),
[0012] FIG. 2 shows a plan view of the portion x of the butt
connection according to the invention between the two rotor blade
parts in FIG. 1,
[0013] FIG. 3 shows a perspective view of the entire butt
connection between the two rotor blade parts in FIG. 1, but which
is opened up as in FIG. 1,
[0014] FIG. 4 is a view in longitudinal section on an enlarged
scale through one of the strap connections forming the butt
connection in the entirety thereof,
[0015] FIG. 5 shows a plan view of the strap connection in FIG. 4,
and
[0016] FIG. 6 shows a partial view taken along line A-A in FIG.
4.
[0017] FIG. 1 is a diagrammatic view in cross-section of a
transversely divided rotor blade of a wind power installation. The
join 2 between the parts 1a and 1b of the rotor blade 1 is open.
The two rotor blade parts 1a and 1b comprise a load-bearing core
profile member 3 and an aerodynamically shaped shell portion 4.
[0018] FIG. 2 is a plan view showing a part of the butt connection
between the parts 1a and 1b of the rotor blade 1 when the join 2 is
closed. The butt connection comprises a plurality of bars or straps
5 which bridge over the join 2 and which are respectively fixed by
means of bolts 6a, 6b to both rotor blade parts 1a, 1b.
[0019] In FIG. 3--as in FIG. 1--the join 2 is opened, and portions
of the two rotor parts 1a, 1b are shown in a perspective view. The
bars or straps 5 are also cut away (only for the purposes of
clearer illustration) and the overall view of the (opened) butt
connection shows how the straps 5 with their bolts 6a, 6b are
distributed over the--non-round--cross-section of the divided
hollow profile member. The arrangement of the straps 5 is at its
densest in the region of the core profile member 3 because it is
there that the highest transmission of forces occurs; in the other
regions, there are larger spacings between the straps 5.
[0020] FIGS. 4 to 6 show a strap connection in detail. A respective
strap 5 is arranged above and below the hollow profile member parts
1a, 1b. Both straps 5 are fixed to the part 1b by means of a bolt
6b, with the interposition of washers 7, by a screw 8 with nut 9.
Fixing of the straps 5 to the part 1a is similar, but the bolt 6a
has wedge-shaped flattened portions 10 which taper from the center
of the bolt towards its ends and towards the axis 11 of the
(longer) screw 8 with nut 9. Cup-like pressure portions 12 are
provided between the head of the screw 8 and the strap 5 adjacent
thereto on the one hand and between the nut 9 and the strap 5
adjacent thereto on the other hand. When the screw 8 with the nut 9
is tightened, the pressure portions 12 exert corresponding forces
on the straps 5; the approach movement thereof, in particular
towards the profile member part 1a, causes them to slide upwardly
along the flattened portions 10 of the bolt 6a, whereby a tensile
stress is built up in the straps 5 (in the contact regions of the
straps 5 with the flattened portions 10, the inside wall of the
straps 5 can be adapted to the surfaces of the flattened portions
10). The tensile stress in the straps 5 results in a closing
pressure stress applied to the hollow profile parts 1a, 1b in the
region of their join 2.
* * * * *