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Патент USA US2129206

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Sept» 5, 1933'-
.Filed Nov. 21, 1936
2 7n veni‘or
3/- iy/mz/zgmsen
Patented Sept. 6, 1938
Hermann" Ellinghausen, Bremen, Germany
Application November 21, 1936, Serial No. 112,154
‘In Germany November 23, 1935
5 Claims. (Cl. 170-459)
The present invention relates to ‘propellers and longitudinal section of a blade, Fig. 2 the blade
more particularly to means, for fastening the socket with the stlmip of the blade in a cross
blades of wood propellers to the hub socket.
section and Fig. 3 a portion of an anchor in ele
For some purposes wooden propellers are pre
vation. Referring to the drawing, the fastening
5 ferred to the metallicones. The increase of speed arrangement comprises a plurality of round steel 5
resulting from the steady development of the
aeroplanes and which is not yet definitive, on
account of the large difference of the starting
and service speeds almost generally requires pro
” pellers with variable pitch or adjustable blades,
and thus a propeller having adjustable wooden
blades is of paramount importance in the con
struction of aeroplanes.
When however the two blades of a wooden ‘pro
15 peller are, ‘separated from one another with a
rods or anchors a uniformly distributed over the
cross ‘section of the blade'stump, secured by nuts
0 in the socket bottom and having a diameter
which is towards the free end reduced in a step
by-step manner, these rods having the highest
possible tensile strength and carrying a plurality
of round steel washers b properly spaced and
prevented from being stripped off the red by
the latter being provided with collars obtained 15
by upsetting in a red-hot condition.
As these
view to their adjustability the advantage afforded - collars are made by upsetting, all fibres of the a
by the high tensile strength of wood in the direc
tion of its ?bres will be lost at the hub. ‘On the
other hand it has not yet been possible to fasten
20 the wooden blades in the metallic sockets, by
means of which the blades are revolubly con
nected to the hub in the same way as metallic
blades, in such a manner that this connection is
able to safely and durably stand the centrifugal
and vibration forces to which such wooden blades
are subjected.
steel of the rods remain uninjured and transi
tions of suilicient radii are formed between the
collar and the rod proper so that in all cross 20 1
sections the said rods are not injured and may
be fully stressed with the particular permissible
stress. As compared with the systems already
known this arrangement not only results in a
reduction of weight but also prevents both the
cross section of the blade stump and the glued 25
joints of the wood lamellas from being materially
Various systems have already been known weakened.
which are based on the prospective idea that
The washers I; inserted with the steel rods be
the centrifugal forces acting in the blade‘ be . tween at least two layers of the wooden blade will
30 taken up at as many points as possible; however subject an imagined wood cylinder to shear, the 80
the manner in which these forces are to be taken diameter of which corresponds to that of the par
up by no means corresponds to the magnitude
of the forces developed nor to the conditions of
service so that no practical success was secured in
this way.
The present invention relates to means for fas
tening wooden blades in the sockets of air pro
pellers and more particularly adjustable pro
pellers, and the object ‘of the invention is to
40 provide for means by which the centrifugal and
vibration forces are'taken up in the wooden blades
and transmittedgtherefrom to the blade sockets
thereof in a very safe way.
This eifect is ob-_
tained by, the fact that the tensile strength of
"' the fibres as lost by the separation of the two
blades is replaced by one or several areas re
sisting to shearing forces in the‘ wood of the
blades and the size of which corresponds to the
stress undergone, and that~ according to the in
50 ventionrsuch an arrangement is provided for
that a uniform stress in the shearing area or
areas is ensured without the tensile‘ and bend
ing strength of the woodenblade being thereby
adversely affected,
In the accompanying drawing Fig. 1 shows a
ticular washer and the length of which corre
sponds to the distance of two adjacent washers.
According to loading tests accomplished, the re
sistance to shear of.such a cylinder surface is 85
so high that as a rule 7 to 8 washers will be suf
As hereinabove described the rods 0 are at
tached to the socket by means of the nuts 0.
The socket ‘comprises an outer cup-shaped mem 40
ber 0 having an annular ?ange h by means of
which the blade may be bolted to the propeller
hub. An inner cup-shaped member I in the
nature of a lining may-be provided within the
member e but such an inner member. is not
necessary and forms no part of the present in
The steel rods are inserted between the layers
of the wooden blade with a definite play so that, '
when themgts are tightened in order that the 50
anchors comprising the rods and washers are put
under tension, these rods are allowed to freely
move-"in their grooves and to integrally transmit
the stress to the washers. A new effect acting
in the same direction, of the anchors will result
‘from the loose seating of the washers on the rods
and from the rounded shape of the collars (shown
at d) obtained by upsetting. Asxit is rather dif
?cult practically to produce the hollow spaces
for the washers exactly registering in two ad
jacent layers of the blades, the mobility of the
washers allowing an inclination of them on the
anchors will cause a uniform distribution of the
pressure over the two adjacent layers without
the rod being stressed unilaterally, the rounded
collars permitting of a corresponding attitude to
the washers.
When at any point of the bedding of an an
chor the distance of adjacent seatings in the
wood of, the blade does not exactly equal the
each tension member being arranged between two
laminations, collars carried by said tension mem
bers and a washer adiacent the hub socket side
of each collar for engaging two laminations.
2. Supporting means for propeller blades ac
cording to claim 1 characterized by the features
that the washers are tiltablymounted on the .
tension members. '
3. Supporting means for propeller blades ac
the blade.
4. Supporting
means ‘ for
formed of wood laminations which extend lon
on account of the high shearing strength of the
cracking of the wood will take place. In this
gitudinally in the’ direction of the length of each
blade comprising, a hub socket for receiving the
inner end of the blade, metallictension mem
bers extending into the wood blade, said tension
members being uniformly distributed over the
way again the pressure will be distributed more
cross section of the blade and each tension mem
against the pressure surface of the washers and
> uniformly over all washers of the anchors. , '
The design and the bedding of these novel an
25 chors thus largely warrant that tightening the
anchors after the blade stump having been in—
troduced into" its socket, by uniformly tightening
the glued joints.
ber being arranged between two ‘laminations,
said hub socket, integral collars on said tension
members at spaced points along. the length there
being uniformly distributed over the cross section
of the blade and each rod being arranged be
' prising, a hub socket for receiving the inner end
tween two laminations, means for fastening said
rods to. said hub socket, arcuate shouldered col
lars carried by said rods,»washers mounted on
said rods adjacent each collar and between the
collar and the hub sbcket, and said washers en
of the blade, metallic tension members extend
gaging two adjacent laminations whereby each
I claim:
1. Supporting means for propeller blades
formed of wood laminations which extend in
the direction of the length of each blade com
45 ing into the wood blade and secured to said sock
et, said tension .members being uniformly dis
means for fastening said tension members to ‘
of, washers mounted on said tension members
the‘nuts, will result not only in a uniform initial adjacent the hub socket side of each collar, and
-' tension in the various blade and blade stump said washers engaging equal parts of two lami
80 cross sections but also in an initial tension which - nations.
5. Supporting means for propeller blades
is uniformly distributed over the whole length
of each anchor and thus also over a correspond
formed of wood laminations which extend in
ingly large portion of the wood of the blade. In the direction of the length of each blade com
comparison with arrangements already ‘known prising, a hub socket for receiving the inner end
35 the novei fastening means further distinguishes of the blade, rods extending into the wood blade
itself by the fact that the loose bedding of the and through the'rbase of said socket, said. rods
‘ washers, developes no forces tending to cleave
cording to claim l'characterized by the feature
that the tension members are embedded with
play in the adjacent‘faces of two laminations of
spacing of the washers concerned the result will,
cylindrical shearing surface, be a corresponding
compression of the wood ?bre ends contacting
tributed over the cross section of the blade and
washer may tilt» on said arcuate shoulders.
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