Improvements in and relating to Screw Propellers.
Year: 1891

page_text: Date of Application, 2nd June, 1891-Accepted, 4th July, 1891
COMPLETE SPECIFICATION.
Improvements in and relating to Screw Propellers.
I, JOHN HENRY OSBORNE, a Citizen of the United States of America, residing
at Auburn, in the County of Cayuga, and State of New York, one of the United
States of America, Gentleman, do hereby declare the nature of this invention, and
in what manner the same is to be performed, to be particularly described and ascer-
tained in and by the following statement :-
My invention relates mainly to the construction of the blades of screw propellers
whereby they are made clastic so as to yield or bend under the resistance of the
water to their action and by such yielding or bending to avoid or prevent any
unnecessary commotion in or movement of the water.
It is well known that the greater the depth to which a propeller wheel is
submerged, the greater is the resulting power exerted by the blade of the wheel
upon the water. It is also well known as a correlative fact that the propeller blade
performs more work upon, or encounters greater resistance from the water while
passing through the lower half or portion of its stroke than while passing through
the upper half, or portion of its stroke. As a result of these unequal resistances
encountered at these two portions of the stroke made by a rigid blade, there is a
jarring, tremulous or vibratory motion communicated to the vessel. If, however,
the blade of the propeller were made elastic it would yield to the greater resistance
of the water at the lower portion of the stroke, and then recover, yielding less to
the lesser resistance at the upper portion of the stroke, and thus cause the vessel
to proceed without or with much less jarring, tremulous or vibratory motion, and
It will
also to pass with greater ease and steadiness through and over the water.
also be manifest that with the blade thus adapting itself by means of its elasticity
to the varying pressures encountered at different points in its revolution, the
reaction of the propeller wheel upon the engine or motor caused by such unequal
pressures of the water is avoided, and the motor will move the wheel with an
equal and steady motion and with corresponding ease and economy to the motor.
The object of the present invention is to overcome the defects referred to by the
employment of an elastic or flexible blade or screw that will bend and unbend under
and in proportion to the different pressures encountered in its circular path through
the water.
I
It will be understood from the following description and claims, reference being
had to the accompanying drawings, in which:
Figure 1 is a plan view of a screw propeller wheel showing my improvement.
Figure 2 is a similar view of the hub of the wheel showing a modification in the
construction of the flexible blade thereof.
Figure 3 is an end view of the hub and its wings, employed in the construction
shown in Figure 1.
Figure 4 is a similar view of the hub forming a basis for the construction shown
in Figure 2.
Figure 5 is a detail view of the blade constructed as shown in Figure 1.
Figure 6 shows in side and edge elevation an elastic blade made in one piece.
Figure 7 is a side view of the hub with the blades removed, and
Figure 8 is an edge view, showing the blade curved from end to end.
In the form of construction shown in Figure 1, the cylindrical hub of the wheel,
indicated at, A, has a central longitudinal bore to receive the propeller shaft, and a
key seat for securing it to said shaft, and is shown provided with wings, a, a,
arranged in oblique relation to the line of the shaft or central perforation therefor,
thereby giving to them and to the blades to be attached thereto, the necessary
spiral or screw form arrangement. These wings are made flat on their rear or

page_text: .
operative faces and are provided, each, at, a', with a perforation for the reception
of a pivotal bolt, b, and at a², with a slot formed in an arc of a circle of which the
bolt., is the centre, for the reception of a second bolt, 1, which permits adjust-
ment of the blade in or out on its pivotal bolt, and in connection with the latter,
serves to unite the blade rigidly, to the wing. The slot, a², may of course, be
dispensed with and a simple bolt hole substituted therefor, where no adjustment of
the blade is desired.
"Although I do not confine myself to any particular form or construction of the
blade, the form or construction preferred is shown in Figures 1 and 5, the latter
figure showing the parts thereof in detail. In this construction the blade is
composed of a series of plates or leaves, similar to the several leaves of a carriage
spring. These may be of uniform length and tapering, like that shown in Figure 6,
but, preferably, is made up of plates or leaves of different lengths, C, indicating
the main or longest plate, C, a shorter one, pivoted at its outer end at c, preferably
to the back or inoperative face of the plate, C, and slotted at, c', to receive and
permit its movement on plate, C, relative to a pivot, c², connecting the outer end of
a still shorter plate, C2, through said slot, c, to the plate, C. The operative face
of plate, C, is countersunk to allow the heads of the pivoting rivets, c, and e², to be
let in flush with said face, thereby giving the latter a smooth unobstructed surface
for the action on the water. The blade thus formed is secured to the wing, a, by
means of the bolts, b, and ', which also serve to secure a keeper plate, C³, on the
outer or operative face of the plate, C, and to the wing, al. This plate at its
forward end conforms in shape to the end of the blade plates, but is made shorter,
projecting beyond the rear end of the wing, a, however, sufficiently far to stiffen
the blade during a reverse rotation of the wheel and relieve the latter from undue
strain at said rear end of the wing.
In Figure 2 the blade is shown formed in one piece with the hub by casting the
hub with one, two, three or more (if desired) projections or protuberances similar
to those shown in Figure 4, and of steel or other metal or alloy of metal which is
both ductile and elastic, such as will permit the casting of the hub in the form
indicated, after which the projecting knobs or protuberances indicated at a³, can be
hammered or drawn out into the tapering form indicated at C4, in Figure 2, and to
the desired shape and thinness and then tempered to give it the required degree of
elasticity or flexibility, which, as will be readily seen, increases toward the point
or outer and thinner part of the blade, where the movement of the blade is the
most rapid and the resistance to such movement is the greatest, and where, con-
sequently, the greatest elasticity is required. This feature of flexibility pertains
also to the construction shown in Figures 1 and 5, as also to that shown in Figure 6,
in which the blade is shown in a single piece, C5, tapering like that shown in
Figure 2, but separate from the hub and adapted to be bolted to wings on the latter
in a manner similar to the leaved blades in Figure 1. In this last named con-
struction the keepers, C³, may be used or left off, as preferred, the tapering form of
the single plate giving the required stiffness to the fixed end of the blade.
Figure 2 the hub is shown provided with a single blade only, while in the other
figures where the hub is shown, it is provided with three blades, or provision is made
therefor, but any desired number may be employed.
In
Where the laminated blade is employed, the slots, c', in the shorter plates provide
for the necessary movement thereof, relative to the longer plates in bending under
the resistance of the water to the action of the blade, which, under such action,
owing to its flexibility and rapid rotation, will be made to assume a spiral form,
varying at different points in its length to conform to the varying speed of such
.points and the varying resistance of the water consequent thercon. It is therefore
made to assume just that form which is most effective in its action on the water and
which produces the least disturbance in the new water to be acted upon by the
following blade.
Propeller blades, in their ordinary construction, are made inflexible and are
projected from the hub in planes oblique in the direction of their width, to the

page_text: axial line of the hub, and, generally, in planes perpendicular or nearly perpendicular,
in the direction of their length, to the axial line; so, in the arrangement and use
of an elastic blade, and particularly in the adaptation of hubs with elastic blades
to the propeller shafts and "wheel spaces" of vessels now in use, it will often be
found desirable to arrange the elastic blades upon the hubs in the manner above
described, and as indicated in dotted lines in Figure 7.
In Figure 8 the blade is shown with a permanent curve backward, from its heel
end, which connects with the wing, to its outer end or point. This construction
may also be found desirable, as facilitating the passage of the blade through the
water.
Having now particularly described and ascertained the nature of my said inven-
tion and in what manner the same is to be performed, I declare that what 1
claim is:-
-
1. In a screw propeller wheel, a wheel hub arranged in line parallel or substantially
parallel with the line of propulsion in combination with one or more blades made
elastic throughout their length and set in oblique relation to said hub, substantially
as described.
2. In a screw propeller wheel, a propeller blade composed of thin, elastic plates
made flexible throughout their length and secured to the hub of the wheel in oblique
relation thereto, substantially as described.
3. A screw propeller blade composed of thin elastic plates or leaves of different
lengths each freely flexible throughout its length and united to form a single
blade, varying in flexibility at different points in its length, the shorter leaves
being applied to the inoperative face only, of the longer leaf, substantially as
described.
4. A screw propeller blade composed of thin elastic plates of varying lengths,
each freely flexible throughout its length, the shorter of which plates are pivoted to
the longer plate through slots permitting movement or play of their outer ends
relative to said longer plate, substantially as described.
5. The combination with the hub of a screw propeller wheel having the obliquely
arranged wing for the attachment of the blade, of a propeller blade made elastic
throughout its length and secured to said wing, and the keeper plate also secured to
said wing outside of the elastic blade and projecting beyond the hub for stiffening
said elastic blade, substantially as described.
6. The combination in a screw propeller wheel, of the hub, having the oblique
wing slotted to permit the adjustment of the blade and a propeller blade made
elastic throughout its length and adjustably connected with said wing, substantially
as described.
7. The combination in a screw propeller wheel, of a hub having obliquely
arranged wings, clastic propeller blades adjustably secured to said wings and com-
posed of thin plates or leaves freely flexible throughout their length, and keeper
plates for said blades extended beyond the wings to which the blades are secured,
substantially as described.
Dated this 2nd day of Tune 1801
JENSEN & SON,
77, Chancery Lane, London, W.C., Patent Agents.