Improvements in Screw Propellers
Year: 1895

page_text: Date of Application, 29th Apr 1895-Accepted, 31st Aug, 1895
Improvements in Screw Propellers
I, BENJAMIN FRANKLYN SI ARK of Nos 80 & 82 Bate Street, the City of
Detroit, County of Wavne and State of Michigan, United States of America,
Engineer, 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
This invention iclates to screw propellers and has for its object an improvement
to be applied to that class of screw propellers shown and described in the United
States Patent 463,322, issued to my elf and Millard Sparr It has been found
in use, that when propeller blades of the class shown in said Patent were cist from
bronze or gun metal, that the thin nariow blades were not sufficiently rigid to
prevent them from vibrating somewhat, and such vibration detracted from their
perfect working, and the improvement embodying this invention overcomes the
defect mentioned, as well as increases the efficiency of the propeller
In the diawings
F
Figure 1 shows an end view of the propeller heel
Figure 2 shows a side elevation of a smile et of blades
bigure 3 shows the tip of a blade on set of blade-
Ꮀ igure
4 indicates the way in which a set of blades is cat in order that several
selles may be assembled on a single hub o boss, is in sectional propellet
Figureo shows a plan of a single series of blades
A indicate the hub, arranged to be secured to the batt by a key or in any other
suitable way, and to this hub are secured several serius of blades As shown in
the drawing there are three such series but there may be two or any number
deemed most u etui Lich series consists of a plaiality of blades, arranged in
spiral partially around the hub, and the opposing edges of contiguous blades coincide
in pitch, whether such pitch be that of a true screw or a variable screw, so that
the following blade moves in the track of the one which precedes it The three
blades of the series a b c are all cast integral on a common root or base and
this root may ci may not be cast integral with the hub A The simpler and more
preferable way buing to employ the way indicated in the drawing to cast each
sees independent, securing it to the common hub by Lolts which piss through the
holes sss or any other su able manner
Ihe three blades or the series a b c are
separated from each other from the summit of the root C, nearly to their outer
ends, and a proferably united at their outer ends by wchs a b' which greatly
strengthen the construction and aid in preventing vibration when the wheel is used
under high speed I find that by connecting the tips in the way described, a greatly
increased speed can be given to the propeller with decrease in vibration of the
blades
When the biee blades of the series a b c are cast on a common root which is
itself separable from, but is adapted to be bolted to, the common hub, the screw is
known as a ectional sciew and in such sectional screws any one of the several
series is easily replaced in case a blade is bioken, thus making this form in some
respects preferable I find that where the several blades were cast separably as
shown in the previous Patent referred to, there was able to be electrical action
between the bronze hub and the steel shaft, especially in the case of large wheels
used in salt water, and such action tended to destroy the wheel and the shaft more
rapidly than consistent with proper use The present construction, owing to the

page_text: blades of a series being cast integral on a common root and in some cases integral
also with the bub, decreases greatly the surfaces that are in frictional or rubbing
contact, and thus decreases the aforesaid electrical action, the destructive effects
of which are largely due to the difference in vibration between contiguous blades
and their separate hubs, that is, to the metals moving the one with respect to the
other
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 I
claim is
1 In a screw propeller, the combination of a hub and two or more series of
blades, each series formed of a plurality of blades springing from a common root
or base, tie webs uniting the outer ends of the blades of a series, substantially as
described
2 In a screw propeller the combination of a hub, two or more series of blades,
a root common to the blades of each series, the said blades being arranged spirally
around the hub and increasing in length from the first to the last blade and being
provided with tie webs which unite the outer ends of the blades of the series,
substantially as described
3 In a screw propeller the combination of a hub, two or more series of blades,
a root common to the blades of each series, the said blades being arranged
spirally around the hub and increasing in length from first to last, substantially as
described
4 In a screw propeller, the combination of a hub and two or more series of
blades, each series formed with a plurality of blades springing from a common root
or base, substantially as described
5 In a sectional propeller the combination of a base and a series of blades
integral therewith, substantially as described
6 In a sectional propeller the combination of a base and a series of blades
integral therewith, a hub and means for securing the series thereto, substantially as
described
Dated this 27th day of April 1895
WM P THOMPSON & Co,
Of 6 Lord Street, Liverpool, Patent Agents for the Applicant