An Improved Propeller for Marine Vessels.
Year: 1891

page_text: Date of Application, 18th Nov., 1891-Accepted, 30th Jan., 1892
COMPLETE SPECIFICATION.
An Improved Propeller for Marine Vessels.
We, BENJAMIN FRANKLYN SPARR, and MILLARD FILLMORE SPARK, both of
No. 148 St. James Place Brooklyn, County of Kings, State of New York,
United States of America, Engineers, do hereby declare the nature of this
invention and in what manner the same is to be performed to be particularly
described and ascertained in and by the following statement :-
Our invention consists in the construction of a propeller by fixing helically upon
a shaft, two or more sets of helical tapering propeller blades, the succeeding blades
of each set increasing, in length and width, and having such relative inclination
that cach set of blades forms part of a true screw around the shaft. In other
words, the propeller consists of two or more tapering blades, each formed as part
of a helix around a shaft, and cach consisting of two or more separate blades fixed
beside each other.
Our invention further relates to a propeller formed as above set forth, and having
in addition to the sets of helical blades, two or more tapering helical blades, so
placed as not to be included in any of the helices formed by the other blades.
The object of our invention is to provide a propeller by which increased speed
may be attained without requiring a corresponding expenditure of energy.
In the accompanying drawings which illustrate our invention, similar letters of
reference indicate like parts.
Fig. 1 is a plan of a propeller consisting of three bosses cach carrying
one blade.
Fig. 2 is an elevation of the same propeller, and Fig. 3 is an end view thereof.
Fig. is an end view illustrating a propeller having three bosses and three
blades on each boss, the corresponding blades of each boss arranged to follow each
other helically forming three screws around the shaft.
Fig. 5 is an end view shewing a propeller having three bosses each carrying two
blades, the corresponding blades of each boss arranged to follow each other helically
forming two screws round the shaft.
Fig. 6 is an end view shewing a propeller having three bosses with two blades on
each of the two inner bosses and four blades on the outer boss, two of which
helically follow the blades of the inner bosses, and two are auxiliary blades at right
angles to the latter.
Fig. 7 is a side view of part of a vessel provided with a screw of the kind shown
in Fig. 6.
A represents a propeller shaft.
B, C and D are blades secured to bosses on the shaft. The blades B are the
shortest and are nearest to the engine.
Each boss may carry two or more blades. In practice two or three blades give
the best results.
Any desired pitch may be given to the blades, but the blades of each set should
correspond in inclination, so that they follow each other helically from the engine
end of the shaft forming a true screw around the shaft.
The blades B, C and D do not touch each other but are separated by spaces
for the purpose of allowing a portion of the water acted upon by the blades,
to pass between the blades thus relieving the propeller from part of its load.
In the propeller shewn in Figure 5 there are two true screws around the
propeller shaft, each screw formed of three separate screw blades. Thus while
the two sets of blades act as true screws turning through a considerable body of
water, each independent screw also turns through a smaller body of water and a
motive effect is obtained greater than would be obtained by the independent action

page_text: of the separate screws. Although we have described our invention as consisting
of several bosses each carrying a certain number of blades, obviously there might
be only a single boss with all the blades cast or otherwise fixed on it in proper
positions so as to form true screws.
For a propeller constructed as shown in Fig. 5 we have found it advantageous
to use auxiliary blades F placed as shown in Fig. 6; these being arranged at right
angles to the blades D. The object of this arrangement is to break up the body
of water delivered from the two screws formed by the pairs of blades B, C and D.
Instead of using two auxiliary blades we may use three, as indicated by the dotted
lines F in Fig. 4 these blades F being at an angle of 60° to the blades D. We do
not limit ourselves to any particular angular relation between the auxiliary
blades F and the blades D. whether two or three blades be used, as the position of
the auxiliary blades will depend somewhat upon the pitch given to the true screws
composed of the blades D, C and B.
Having now particularly described and ascertained the nature of our said
invention and in what manner the same is to be performed we declare that what
we claim is :-
:―
1. A. screw propeller, consisting of two or more sets of blades of successively
increasing length and width, arranged helically around a boss so as to form two or
more true screws of increasing diameter around the boss.
2. A screw propeller, consisting of two or more sets of blades, arranged helically
around a shaft, and two or more auxiliary blades, substantially as and for the
purpose set forth.
Dated this 18th day of November 1891
ABEL & IMRAY,
Agents for the Applicants.