A self-feathering propeller for use on sail boats having an auxiliary power source. The propeller blades are rotated automatically to working pitch positions to provide an ahead or an astern thrust in accordance with the direction of rotation of the propeller shaft. When the shaft is stationary and water flow is substantially parallel to the shaft axis, as when the boat is under sail, the blades are automatically feathered thereby to minimize resistance to movement of the boat.

BACKGROUND OF THE INVENTION 
In self-feathering propellers used on auxiliary powered vessels the blades 
are constructed and arranged for limited rotation about individual axes 
normal to the axis of the propeller shaft. Various constructions of such 
propellers have been proposed heretofore. 
In J. M. Casey U.S. Pat. No. 1,718,525, June 25, 1929, the propeller blades 
are journaled on eccentric axes in a split casing which is attached to the 
propeller shaft. The blades are provided with flanged base portions which 
serve as bearing surfaces and the blades are rotated about their axes by 
cooperating lugs and helical ribs provided on the flanged base portions 
and the shaft. Such blade-base-bearings, generally referred to as "table 
bearings" are notoriously troublesome when the load is applied at some 
distance from the bearing surfaces. 
In M. D. Thompson U.S. Pat. Nos. 2,134,157, Oct. 25, 1938, and 2,283,774, 
May 10, 1942, the blades also are provided with flanged base portions 
serving as bearing surfaces. The blades are rotated about their axes by 
means of lugs extending from the base portions and slidably received in 
helical grooves formed in the peripheral surface of the propeller shaft. 
In the prior devices, the propeller blades are rotated about their axes to 
working pitch positions by mechanical force. The operating principle is 
that of a cam and cam follower, requiring precision machining of the 
co-acting parts. In general, the prior devices are complex and costly and 
have a low reliability factor. 
A self-feathering propeller made in accordance with this invention requires 
a minimum number of simple, sturdy parts which are loosely fitted together 
to provide an operative assembly. 
SUMMARY OF THE INVENTION 
The propeller blades are loosely supported by and rotatable about 
individual spindles extending radially from a sleeve member which is 
rotatable about a hub secured to the propeller shaft. The hub carries 
pintles which serve to transmit torque from the shaft to the sleeve 
member. The pintles also position the blades for reverse thrust when the 
shaft is rotated in the astern direction. Stops extending from the sleeve 
member serve to limit the rotation of the blades to provide a forward 
thrust when the propeller shaft is rotated in the ahead direction. 
An object of this invention is the provision of a self-feathering propeller 
for use on an auxiliary powered vessel, which propeller is of simple, 
sturdy and economical construction, and which has a high reliability 
factor. 
An object of this invention is the provision of a self-feathering propeller 
in which the blades are supported by and loosely rotatable about 
individual spindles extending radially from a sleeve member rotatable by 
the propeller shaft. 
An object of this invention is the provision of a self-feathering propeller 
in which water pressure causes the blades to assume proper pitch position 
for imparting a forward thrust. 
The above stated and other objects and advantages of the invention will 
become apparent from the following description when taken with the 
accompanying drawings. It will be understood, however, that the drawings 
are for purposes of illustration and are not to be construed as defining 
the scope or limits of the invention, reference being had for the latter 
purpose to the claims appended hereto.

DESCRIPTION OF THE PREFERRED EMBODIMENT 
Referring to FIG. 1, the propeller comprises a sleeve member 10 provided 
with diametrically-opposed end slots, only the upper slot 11 being visible 
in this particular view. Secured to the sleeve member are a pair of 
spindles 12 and 13 which extend normal to the axis of the sleeve member 
or, alternatively, are raked slightly aft. The spindles are loosely 
slidable through clearance holes formed in the blades 14 and 15, said 
blades being so configured that the holes for the spindles lie in the 
blades leading edge region, whereby a greater blade area constitutes the 
trailing portion of the blade. The blade profiles and cross-sections may 
be of various shapes depending upon the intended usage and loading of the 
particular propeller. Although the blades are freely rotatable about the 
axes of the supporting spindles, the extent of such rotation in one 
direction is limited by a pair of stops 16 and 16' carried by the sleeve 
member. A pair of cotter pins 17 and 18 retain the blades on the spindles. 
A hub 20 is slidably positionable within the sleeve member 10 and carries 
diametrically-opposed pintles 21 and 22. These pintles extend through the 
longitudinal slots formed in the sleeve member when the hub is positioned 
within the sleeve member, said pintles being long enough to overlap and 
abut the blade surfaces. The threaded end of a propeller shaft 23 is 
slidable through the central hole of the hub, said hub being retained 
within the sleeve member by means of the washers 24 and 25 and the nuts 
26, 27 and 28. An end of the sleeve member is provided with a chamfer 30 
which accommodates an O-ring 31. In the assembled propeller, the washer 25 
compresses the O-ring between the sleeve member and the hub. Thus, the 
O-ring functions as a friction clutch while the pintles 21 and 22 serve as 
torque transmitters to rotate the sleeve member spindles in correspondence 
with shaft rotation. 
Referring now to FIG. 2, when the propeller shaft 23 is rotated in the 
indicated direction, the pintles 21 and 22 engage walls of the slots 
formed in the sleeve member 10, thereby rotating the sleeve member and the 
blades 14 and 15 in a corresponding direction. Since the blade-supporting 
spindles lie near the leading edges of the blades, the blades tend to 
trail and abut against the stops 16 and 16'. These stops are located so 
that the blades assume proper pitch position to provide a forward thrust 
to the boat. When the propeller shaft is stationary and water flows 
parallel or nearly parallel to the shaft axis, because of movement of the 
boat under sail, the trailing edges of the blades causes them to stream, 
or feather, as shown in FIG. 3. The blades, being loosely fitted to the 
supporting spindles, offer very low resistance to rotation about the 
spindle axes and, thus, they readily assume a feathering attitude. 
When the propeller shaft is rotated in the astern direction, as shown in 
FIG. 4, the sequence of operation is as follows. The hub pintles engage 
the opposite side walls defining the slots in the sleeve member 10 and 
thereby impart astern rotation to the sleeve member and the blades. As the 
hub pintles traverse the slots they abut the blade surfaces and force the 
blades into proper pitch position to provide an astern thrust. 
When the blades are feathered as shown in FIG. 3, the shaft being idle and 
the craft moving ahead, most blade cross sections result in the blades 
assuming a streaming position angled several degrees to the water flow 
lines. This is caused by the well-known Bernoulli effect, with a lower 
pressure on the cambered side of the foil. The angled blades would case 
the sleeve member 10 to rotate in the flow lines and thus cause the blades 
to be locked into working pitch positions, thereby resulting in the loss 
of the advantages to be gained by blade feathering. This action, known as 
the Flettner effect, is avoided in the described propeller by provision of 
a frictional coupling, or clutch drag, between the sleeve member and the 
hub by means of the compressed O-ring 31. The clutch torque preventing 
relative rotation between the sleeve member and the hub must be greater 
than the torque developed as a result of the Flettner effect. However, 
tests demonstrate that only a modest restraining clutch torque is needed, 
that is, of the order of only a small fraction of the torque transmitted 
by the propeller shaft. 
For feathering the blades it is necessary that the propeller be operated in 
the ahead direction prior to stopping the propeller shaft. By stopping the 
propeller shaft while the propeller is rotating in the ahead direction, 
the pintles of the hub remain in engagement with the side walls of the 
slots formed in the sleeve member, as shown in FIG. 2. This permits 
unobstructed rotation of the blades about their individual axes to the 
feathered positions as shown in FIG. 3. 
Reference now is made to FIG. 5 wherein the pintles 21' and 22', carried by 
the hub 20, are shorter than the corresponding pintles 21 and 22 shown in 
FIGS. 1-4. More specifically, the pintles 21' and 22' do not protrude 
beyond the outer surface of the sleeve member 10 when the hub is 
positioned within the sleeve member. Consequently, these pins do not 
extend into the path of travel of the propeller blades and they function 
only to transmit torque to the sleeve member 10, with an angular play 
defined by the width of the slots formed in the end of the sleeve member. 
A pair of bores are formed in the end of the hub 20 for receiving the pins 
32 and 33 secured to an end washer 34 provided with integral arms 35 and 
36. The end washer 34, hub 20 and sleeve member 10 are assembled together 
in operative relationship by means of the nuts 26 and 27 threaded onto the 
threaded end portion of the shaft 23. In such assembly, the arms 35 and 36 
project into the path of travel of the propeller blades and act in the 
same way as the elongated pintles shown in FIGS. 1-4. 
In the illustrated forms of the invention, the hub is frictionally secured 
to the propeller shaft by means of nuts threaded onto a threaded end of 
the propeller shaft. Preferably, the hub will have an internal taper and 
keyway to accommodate a tapered propeller shaft and key, thereby to 
securely attach the hub to the shaft in accordance with conventional 
practice in this field. Also, although the invention has been described 
with specific reference to a two-bladed propeller, it will be apparent 
that three or four bladed propellers may be constructed to incorporate the 
inventive features herein disclosed. Those skilled in this art will be 
able to make other changes and modifications without thereby departing 
from the spirit and scope of the invention as recited in the following 
claims.