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June 1, 1948.
Filed Jan: 26, 1944
B/mrow B. DUNCAN
J W Ms‘ib‘v
Patented June 1, 1948
4 2,442,641
Bartow B. Duncan, Dayton, Ohio, assignor to
General Motors Corporation, Detroit, Mich., a
corporation of Delaware
Application January 26, 1944, Serial No. 519,756
6 Claims. (Cl. 29—156.8)
This invention relates to an airfoil for aircraft
and a method of making the same with an inte
ration at the joints of the bond which introduce
grally joined thrust member foranchoring the
airfoil and a pair of integrally joined face‘ mem
bers for giving cross sectional contour to the
One of the objects of the invention is to pro
vide an airfoil of one piece construction thereby
vibration if not serious damage or failure of a‘
blade. Once a bond starts to open, the early
failure of the blade is assured, and the defect may
seriously affect the function and performance of
an engine, even if it does not immediately result
in a substantial loss of emciency, or complete
failure. Herein is disclosed a method of making
a propeller blade with the rib or spar comprising
10 an integral part of they blade root, thrust face.
separation or rupture.
and camber face. The blade could be rolled,
Another object of the invention is to provide an
eliminating all joints of assembly, subject to
airfoil, particularly a propeller blade, that has
formed or forged or both from a billet of steel or
the face members integrally joined to ‘a thrust
the like. and could be rolled into a tapered I-beam
or H-beam with extended ?anges as shown in
Another object of the invention is to provide a 15 Figs. 4, 5_ and 7. . That could be accomplished by I
rolling the web on rollers which taper around
propeller blade with a minimum number of parts
the circumference and with a circumference equal
that must be bonded together.
to or greater than the length of the blade to be
Still another object of the invention is to pro
vide a method for fabricating a hollow propeller
rolled. On the other hand, the same result can
blade of airfoil section from a single billet of 20 be accomplished by rolling through a succession
of or train of stepped rolling elements. The
?anges could be rolled at the same time by rollers
Further objects and advantages of the present
on each side of the ?anges or_ during a separate
invention will be apparent from the following
operation. By operating the rollers on pivots the
description, reference being had to the accom
panying drawings wherein a preferred embodi
twist could be put in the blade. Otherwise the
rib or spar could be twisted as a separate opera
ment of the present invention is clearly shown.
In the drawings:
tion. After rolling or other forming the ?anges.
Fig. l is a view in plan form showing a billet of
could be formed into proper contour by hot or .
metal after working through certain of the steps
cold forming of the sheets on a mandrel or by
herein disclosed, with a superposed outline of the 80 forming under heat in a press. In?ation by inert
gas may follow while so heated and clamped.
?nished blade.
Fig. 2 is a longitudinal sectional view thereof
The edges of the ?anges could be either brazed or
substantially as indicated by the line and arrows ’ welded to secure the airfoil section and‘ form the
2-2 of Fig, 1.
trailing and leading edges. While the plan form
Fig. 3 is an end view of the blade at the root 35 in Fig. {1 shows the face plates with a maximum
member or spar.
end looking toward the tip, substantially as indi
cated by the line and arrows 3-—3 of Fig. 2.
Figs. 4 and 5 are sectional views transverse of
the blade after certain steps in the process of
width at the root, and gradually increasing in
cord from the tip inward toward the root, the
plan form could be varied with design. In the
form shown cuffs for the shank of the blade are
forming. but before the ?nal forming operation, 40 not needed since the thrust face and camber face
substantially as indicated by the lines and arrows
vextend from the tip to the root of the blade
t-? and 5—5 of Fig. 1. the dot and dash lines
showing the ultimate cross sectionalcontour to
which the forming is to be reduced.
. »
where the juncture is made with a spinner. The
root of the blade could be rolled into a square
section to be later turned externally and bored
Fig. 6 is an enlarged sectional view illustrating 45 axially.‘ The terminal exterior makes for pitch
the structural con?guration of one form of blade
shifting movement of the blade within the hub
socket‘, and the bore extending into the rib a
suggested by the dot and dash lines of Fig. 4.
depth determined by design makes for the hous
Fig. '7 is a view of a modi?ed form of rolled
ing of a blade torque unit by which the pitch
stack from which a hollow blade of integral con
of the blade is accomplished, and for loca
struction may be built.
Airfoils, particularly propeller blades, of com
tion of the center of massof the blade.
posite form or those in which a plurality of struc
axial bore of the root aside from boring or drill
tural members such as spars and face plates are
ing may be drawn or otherwise cavitated. It
assembled and bonded together by welding, braz
ing, or the like, are subject to rupture and sepa
may be desirable to weld a filler section to the
base end of the sheath around the root to close
Referring specifically to the drawim. Fig. i
1 represents a roughly formed blade unit in which a
billet of metal has been rolled. forged or other- V
wise fashioned to provide a root portion I8 rap
idly merging at I2 into a narrow rib portion 14,
on each side of which there are a pair of co
start with a metal blank of suitable dimensions
to provide the plan form and having a thickness
suitable for the rib member and two thicknesses
'ofthebladefacemembers, which blankisthen
slit along its edge inward toward the mid-section
with the bottom or the kerfs for the slits diverg
ing in approach from the tip toward the root end
of the blank. After the slitting operation the
extensive ?anges l8 and 18 for the leading por
tion of the blade, and ?anges 28 and 22 for the
trailing portion. The extent of the ?anges will
roughly exceed the plan form con?guration of
materiai, such as the slabs on each side of each
of the kerfs are spread apart and bent down
to form the ?anges l8, i8, 28 and 22, which may
be done under heated conditions to save rupture
of the connecting ?bers. The spreading of the
the blade blank somewhat as indicated by the
?anges and bending down to form relatively ?at
irregular outline 24 bounding the definite plan
form lines of Fig. l. Trimming or shearing of 15 faces accomplishes the same con?guration shown
in Figs. 4 and 5, from which point the procedure
the ?anges to the preferred design may result in
outlined above may be followed for ?nishing the
the plan form indicated by the lines 28 along the
blade fabrication Another form of rolling or
root, then along 28 for the'inward end of the
forging a billet is shown in Fig. '7 where the cen
sheath member or thrust face and camber face.
However, instead of cutting the skirt portion of 20 tral or spar section I48 is integrally joined to the
webs I68. I88, 288 and 228, for subsequent work
the face members o? squarely as indicated at 28,
ing into the ?nished blade. The result of either
web portions 88, 32 of suitable contour may be
procedure is to provide a hollow blade having a
retained for folding along the lines 28. At any
rib or spar and integrally joined face plates that
rate the ?anges are suitably sheared or trimmed
are proof against springing or tearing loose by
along the line 34 for the leading edge of the face
members. along the line 38 for the tip, which
reason of insecure bonds“ Bonds between metal
parts are contemplated only along the edges of
blends into the curve 38 at the juncture of the
tip and the trailing edge, and along the line 48
the members de?ning the plan contour of the
for the trailing edge of the face members.
blade and since the torsional stresses between the
That trimming will leave a work piece approxi 30 spar and face plates are taken by the molecular
structure of the integral unit rather than some
mating the details of the unit for trimming and
supplemental union of face members and spar.
?nishing, and resulting in a relative square sec
there is rendered a blade structure that is e?i
tion for the root and square edges along the
cient, and structurally perfect beyond any ques~
lines 28, 34, 36, 38 and 48. The root portion i8
tion of failure.
is turned down or otherwise fashioned into a
.While the embodiment of the present inven
cylindrical section 42 for rotatable mounting in
a hub socket, and may be bored, or drilled deeply
at 44 to provide a chamber to house the torque
tion as herein disclosed, constitutes a preferred
form, it is to be understood that other forms
might be adopted, all coming within the scope
unit and balance assembly for the blade. The
bore 44 extends into the tapered or merging 40 of the claims which follow.
portion of the root I 8 and rib l4 so as to thin
down the walls 46 which are drilled or bored at
48 to open the interior chambers of the blade to
the hollow root, which facilitate ?nal forming
of the blade by ‘the blow up method using an
inert gas introduced through a ?xture secured to
the ?nished root 42. At the tip end of the work
piece the end of the rib I4 is cut away between
What is claimed is as follows:
1. In propeller manufacture, the method of
making propeller blades which comprises work
ing a piece of metal into rough shaped root and
blade portions by extending the metal of a billet
laterally thereof to provide pairs of oppositely
disposed wide ?anges converging along the length
of the billet, trimming the pairs of ?anges to
blade plan form, working the trimmed ?anges
the face plates as indicated at 58 in Fig. 2, which
allows for pinching or pressing the ends of the 50 into a transverse spaced relation giving a contour
face plates together as indicated at 52 for clos
of airfoil section bounded by the flanges, so as to
ing the tip of the blade. The ?anges of the
meet in leading and trailing edge portions of the
face plates are appropriately beveled or ma
blade, bonding the'meeting edges of the ?anges
chined along the lines or edges 34, 38, 38 and 48
to provide closed leading, trailing and tip edge
as indicated at 54 and 56 in Fig. 6, so that the
portions, and working one end of the billet to pro
?anges when formed to desired contour will close
vide a hollow cylindrical root portion having
ly meet and be subject to bonding by weld or
communication with the hollow spaces of the
braze as indicated at 58 for the leading edge and
blade portion.
2. The method of making a hollow propeller
88 for the trailing edge. In the form of the
juncture there shown the camber face 82 is made 60 blade which comprises working a rectangular sec
tion of metal billet into a deep ?anged section
up of the ?anges i8 and 22 and are lapped over
with a connecting web of reduced dimension at
the edge of the ?anges i8 and 28 forming the
one end, a pair of ?anges being disposed on
thrust face 83 of the blade, and when secured
opposite sides of the web, trimming the pairs
by the bonding at 58, 88 and 52 form a hollow
blade and spar of integral construction in which 65 of ?anges along the web to provide the face mem
bers of the blade in plan form, and trimming away
the hollow blade is divided into two coextensive
chambers 84 and 68 extending along each side
the ?anges of the worked billet remote from the
reduced web to provide a root portion of the
of the rib l4 with a ‘cross communication ‘at
blade, reforming the opposed ?anges along the
58, and both leading out to the hollow root 42
through the passages 48.
web portion to provide cross-sectional contour
It is contemplated that other forms of blades
to the blade with the edges of the opposed ?anges
may be fabricated by the same'methods, and also
meeting along the periphery of the blade. bond
that blades of integral hollow construction may
ing the meeting edges of the ?anges to close the
be formed by other than the exact steps set out
in the foregoing. an alternative of which is to
tip, leading and trailing edge of the blade, and
boring the root portion of the billet to communi
cate with the interior of the blade formed by the
closed edges of the ?anges and web.
3. The method of working ‘a solid billet of
metal into a hollow propeller blade, comprising
the steps in combinatiomrolling the billet to pro
vide an elongated central structure with diminish
ing solid cross section from one end to the other,
and with longitudinally extending ?anges in pairs
diminishing in spacing coextensive with the di
ber, boring axially of the mounting portion to
open into both of the sealed chambers, and in
?ating the chambers through the axial boring
while the formed body is under heat and pres
sure to give predetermined airfoil section to the
6. The method of making a reinforced hollow
propeller blade from a solid body of metal, com
prising the steps in combination, forming the body
minishing of solid section of the central struc l0 into an elongated solid generally central member
with two pairs of wide ?anges extending trans
ture, shearing the ?anges away from the central
structure at the end having the greater solid sec
versely therefrom, each pair of ?anges relatively
tion to provide a blade root portion, trimming the
widely spaced from one another at one end of
remaining portions of each ?ange to provide plan
said central structure and decreasing gradually
form for the blade throughout the length of the 15 in spacing toward the opposite end of said central
structure, bending, the free edges of each pair of
diminished solid section of the central structure,
decreasingly spaced ?anges to a meeting line
reworking the trimmed ?anges to give enclosed
hollow contour for the blade with diminishing
to form an edge of the blade and close a longi
airfoil section coextensive with the diminishing
tudinal space on each side of the central struc
solid section of the central structure, and bond 20 ture, trimming the bent edges of the bent ?anges
ing the engaging edges of the reworked ?anges to
to give plan form to the blade, bending the
close off the blade edges.
trimmed and bent edges of the ?anges to seal the
4. The method of making a hollow propeller
chambers along the central structure, working the
central structure at the end of the widely spaced
blade from a solid body of metal, comprising the
steps in combination, working a portion of said 25 ?anges into a blade mounting portion, and drill
metal body into a central web with oppositely
ing axially ‘of the central structure to open into
disposed wide ?anges at each edge of said'web,
the chambers along each side thereof, thence in
bending the ?anges at one end of the web to
?ating the chambers while the body is heated
meet the ?anges at the ‘other edge of the web to
to give airfoil section and continuity of surface
form a pair of coextensive parallelly arranged 80 to the blade.
coextensive chambers, bonding together the meet
ing portions of the ?anges to seal the chambers,
working the remaining portion of said body into
a cylindrical root portion, boring axially of the
root portion to open into both chambers, and in
?ating the chambers through the root while under
heat and pressure.
5. The method of making a reinforced hollow
propeller blade from a solid body of metal, com
prising the steps in combination, forming the body 40
into an elongated solid generally central member
with two pairs of wide ?anges extending trans
versely therefrom, bending the free edges of each
pair of said ?anges together, trimming the edges
of the bent ?anges to give contour to each edge 45
. of the blade, bonding the trimmed edge of the
?anges to form a sealed chamber on each side
of the central member, forming a blade mount
ing portion on one end of the solid central mem
The following references are of record in the
?le of this patent:
Timms ___________ _- Apr. 30, 1901
Witherow ________ __ July 23, 1929
Whitworth ___1_____ Feb. 26, 1935
Gehret ______ -7---“ Nov. 28.
Blanchard ________ __ June 18,
McKee __________ __ Sept. 10,
Damerell _________ _- Feb. 11,
Germany ____ _.'___--- Apr. 10, 1933
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