Year: 1886

page_text: I BENJAMIN JOSEPH BARNARD MILLS of the firm of Harris and Mills of
23 Southampton Buildings in the County of Middlesex, Patent Agent do hereby
declare the nature of the said invention, a communication to me from abroad by
Louis Bidauld of 11 Place Morand, Lyons, in the Republic of France to be as
follows:-
The propeller forming the subject of the present invention is based upon the
property of cycloidal curves or of approaching forms, of being traversed more
rapidly than a straight line by a heavy body which runs along the concavity of
these curves.
In order to apply this principle to propulsion, an immersed winged propeller is
employed which rotates like a screw in a plane normal to the direction of the
vessel, and to the wings of this wheel is given the form of an epicycloidal curve.
If we suppose in such a wheel one of the wings to be stopped, and struck by
the water on its concave face, the molecules of water in sliding upon this curve
will occupy less time in passing from the front to the rear of the wheel than with
a straight wing having like extremities.
The same result will take place if, the water remaining immovable, it is the
wheel which strikes it in turning; in this case, it is the blades which advance
more rapidly than with any other form of wing which will enable the same effect
of propulsion to be obtained with a slower speed of the wheel and with less work
expended.
The wings thus constructed produce less vacuum in the water consequent on
their convex form at the rear; they have also the advantage of attacking the
water at an angle as acute as may be desired, preventing thereby the suction of
the water and its repulse forward as also the loss of useful effect consequent

page_text: thereon; the facility with which the water passes on their surface, further permits
of multiplying their number and of giving them greater dimensions than can be
given to the wings of an ordinary screw.
Finally the new propeller gives to the water which traverses it its maximum
speed at the same time avoiding injurious reactions, it will be able therefore for a
given result to receive a slower speed or to be made of smaller diameter; further
the vibrations and the swell or wash being to a great extent suppressed; it will be
able to work at less depth and at the commencement sooner give its impulse to
the ship because it puts very little water in motion.

page_text: I BENJAMIN JOSEPH BARNARD MILLS of the firm of Harris and Mills of
23 Southampton Buildings in the County of Middlesex, Patent Agent do hereby
declare the nature of this invention, a communication to me from abroad by Louis
Bidauld, of 11 Place Morand, Lyons in the Republic of France, and in what
manner the same is to be performed, to be particularly described and ascertained
in and by the following statement, reference being had to the drawings hereunto
annexed and to the letters and figures marked thereon, that is to say :-
The propeller forming the subject of the present invention is based upon the
property of cycloidal curves or of approaching forms, of being traversed more
rapidly than a straight line by a heavy body which runs along the concavity of
these curves.
Thus in Figure 1, A B representing the half of a cycloid, the body m leaving
the point A will arrive at B in a shorter time by following this are than by any
other way.
In order to apply this principle to propulsion an immersed winged propeller is
employed which rotates like a screw in a plane normal to the direction of the
vessel, and to the wings of this wheel is given the form of an epicycloidal curve
see Figure 2.
If we suppose in this wheel one of the wings A, B, to be stopped and struck on
its concave face by the water travelling in the direction indicated by the arrow we
see that it will act upon the water as the preceding curve acted upon the body m
and consequently the molecules of water will occupy less time in passing from
the front to the rear of the wheel than with any other form. The same result
will take place if the water remaining immovable, the wheel turns in the contrary
direction to that indicated by the arrow; in this case it is the blades which will
advance more rapidly than with any other form of wing which will enable the
same effect of propulsion to be obtained with a slower speed of the wheel and
with less work expended.
In practice the wings cannot have the entire development A, B, of half a cycloid;
to facilitate the entrance into the water it is necessary that the first part A of the
curve should not be quite parallel with the plane of rotation; and to leave the
water as much as possible without speed it is necessary that the last part B should
not be quite perpendicular to this plane; this result is obtained by cutting off
the extreme ends of the curve so as only to retain the part comprised between the
two parallel planes a a b b.
The wings thus constructed produce less vacuum in the water consequent on
their convex form at the rear; they have also the advantage of attacking the water
at an angle as acute as may be desired, preventing thereby the suction of the water
and its repulse forward as also the loss of useful effect consequent thereon; the
facility with which the water passes on their surface, further permits of multi-
plying their number and of giving them greater dimensions than can be given to
the wings of an ordinary screw, as is shown in Figure 3 which represents a front
view of the propeller; the number and dimensions of these wings may be varied
according to requirements.

page_text: The propeller above described is essentially arranged for working forward.
Equally good results may be obtained for working backwards by adding to the
back of the wing a curved portion slightly concave c, d, Figure 4, taking care that
this supplemental part is so slightly extended as not to interfere with the forward
motion, that is to say it ought to remain entirely in the slight wash inevitable at
the back of the blade or wing.
Finally the new propeller gives to the water which traverses it, its maximum
speed at the same time avoiding injurious reactions it will be able therefore for a
given result to receive a slower speed or to be made of smaller diameter; further the
vibrations and the swell or wash being to a great extent suppressed it will be able
to work at less depth and at the commencement sooner give its impulse to the ship
because it puts very little water in motion.
Having now particularly described the nature of this invention, and in what
manner the same is to be performed, I declare that what I claim is:
A propeller with curved wings of which the form approaches a portion of an
epicycloid, the said wings attacking the water at an angle more or less acute and
throwing it almost parallel to the axis of rotation.