AN IMPROVED SCREW PROPELIER
Year: 1878

page_text: LETTERS PATENT to William Robert Lake, of the Firm of Haseltine, Lake,
"
& Co., Patent Agents, Southampton Buildings, London, for the Invention of
AN IMPROVED SCREW PROPELIER." A communication from abroad by
Samuel Turner Swasey, of the City and State of New York, United States of
America.
Sealed the 20th December 1878, and dated the 28th October 1878.
COMPLETE SPECIFICATION filed by the said William Robert Lake at the
Office of the Commissioners of Patents on the 28th October 1878.
WILLIAM ROBERT LAKE, of the Firm of Haseltine, Lake, & Co., Patent Agents,
Southampton Buildings, London. "AN IMPROVED SCREW PROPELLER." A com-
munication from abroad by Samuel Turner Swasey, of the City and State of New
York, United States of America.
This Invention relates to a screw propeller, and consists in the peculiar form and
construction of the propeller blades herein shown and described, whereby the
slip" of the screw is diminished and the re-action of the water on the screw is
augmented.
"
In the accompanying Drawing,
Figure 1 is a surface view of the force face of a screw propeller embodying this
Invention.
Figure 2 is a longitudinal section of one of the blades of the same on the line x, x,
Figures 1, 5, and 6.
Figure 3 is a cross section on the line 3, y, Figure 5.
Figure 4 is a surface view of the reverse face of one of the blades.
Figure 5 is a force face view of one of the blades showing the grooves tapering
in width from the front edge of the blade to the opposite edge, the same being
open at the front end and closed at the opposite end.
Figure 6 is a similar view except that it shows the said-grooves running entirely
across the blade, and open at both ends.

page_text: Figure 7 is a force face view of a blade showing two series of grooves, a series of
smaller grooves being formed intermediately of or between the tapering ends of the
principal grooves, and also showing-the-principal grooves open at the forward end
--and closed at the opposite end.
Figure 8 is a face view showing the-principal grooves open at both ends with
plane-ridges.instead of small grooves-intermediate to the principal grooves.
Figure 9 is a cross section of a blade on the line 2, 2, Figure 7, and Figure 10 is a
cross-section-on-the line u, u, Figures 4 and 8.
a represents the shaft; b, the hub of the wheel; and-c, the blades.. There may
be any desired number of these blades, and each one may have any shape, curvature,
or inclination that may be preferred. Upon the force faces of the said blades are a
number of curved grooves d, which are preferably about equal in width, the series.
extending from a point near the hub to the extreme periphery of the blade. These
grooves should have the form shown in Figure 2, representing a cross section, that
is to say, the outer face e with a short curve, and the inner face e¹ nearly a plane,
extending from the bottom of the short curve to the crest or shoulders o of the
ridge between it and the next inner groove. The shoulders o of these grooves thus
form an angle of about 30 or 40 degrees, while the bottoms form a gentle curve, and
the inner faces form nearly a plane.
The grooves may be made of uniform depth from end to end, and may be open
at each end as shown in Figures 6 and 8, and the right and left blades of Figure 1,
or they may extend from the front sharp edges of the blades until just before the
rear edges are reached, when they may be closed by ribs frunning along the rear
edges of the blades. By grooves of this form, the water, as the screw revolves,
instead of running idly in the grooves is continually forced from the shoulders o
inward against the curved bottom of the grooves and along the planes of the
opposite or inner faces, thus increasing the re-action of the water on the blades, and
thereby forcing the boat more rapidly along.
The grooves, instead of being forined on concentric circles drawn from the centre
of the hub, as indicated by the dotted lines on the upper blade in Figure 1, are
excentric to said centre, so that the ends of the grooves on the forward or sharp
edges of the blades are nearer to the centre of the hub, than are the opposite
ends.
Another important peculiarity of these grooves, as shown in the Drawing, is that
they decrease in width gradually from the forward or sharp edges of the blades
across to the opposite edges, as clearly shewn in Figures 7 and 8, whereby the
water is forced into them like a wedge, giving thereby a more effective re-action of
the water against the blades. This form of the grooves when the intervening
ridges are of uniform width increases the excentricity of each groove as compared
with that of the next outward one, as clearly shown in the upper blade of Figure 1.
They may however be made taper without increasing their excentricity by leaving
a gradually broadening space between-them at the tapering ends, as seen in Figure 8.
These taper grooves & may either run entirely across the blade, as in Figure 8; or
they may be closed at the rear ends as in Figure 7.
The several grooves are substantially of uniform depth from end to end across
the blades, except that just at the forward edges of the said blades they are bevelled
slightly downward to meet the curvature of the rear faces of the blades, thereby
forming sharp front edges, enabling the blade thereby to cut through the water
more easily. The ends of the ridges between the grooves are also bevelled down at
the forward edges of the blades, so that said edges are uniformly sharp throughout
their entire length.
When the grooves are concentric with each other and are nevertheless made taper
in width, as in Figures 7 and 8, a second series of grooves t may be formed at the
rear edge of the blade between the taper ends of the principal grooves. These
second grooves will also be taper with the wider ends opening out on the rear edge
of the blade, as seen in Figure 7. By this construction the broad taper spaces of
the rear ends of the ridges between the principal grooves are utilized by grooves

page_text: which co-operate with the larger and principal grooves in securing a maximum of
re-action of the water upon the blades.
If preferred grooves may be formed on the reverse face of the propeller blades,
thus constituting with the grooves on the force face true corrugations.
When the taper grooves d extend entirely across the blade and the small grooves t
are not formed, thus leaving the ridges t¹ plane, the edges of the blade are
corrugated by cutting short' grooves n on the reverse face to make the edge sharp
throughout its whole extent, thereby enabling it to cut the water with the least
possible resistance.
Having thus fully described the said Invention as communicated to me by my
foreign correspondent, and the manner of performing the same, I wish it understood
that I claim,
First. A screw propeller which has across the force face of its blades a series
of curved grooves made taper in width from the forward to the rear edges of the
blades, and whose ends at the forward edges of the blades are nearer to the centre
of the hub than their opposite ends, and the ends of which grooves at the front
edges of the blade are each nearer to the centre of the hub than the next outer one,
and which grooves are open at both edges or open at the front edges of the blade
and closed at the opposite ends, all as and for the purposes specified.
Second. A screw propeller which has across the force face of its blades two
series of grooves as above described and for the purpose specified.
Third. A screw propeller which has across the rear or force face of its blades a
series of grooves having the form in cross section, shown in Figure 2 of the
Drawing, that is to say, having the outer face curved and the inner face nearly
a plane extending from the bottom of the curve to the crest of the ridge between
it and the next inner groove, as and for the purpose set forth.
In witness whereof, I, the said William Robert Lake, have hereunto set my
hand and seal, this Twenty-eighth day of October, in the year of our
Lord One thousand eight hundred and seventy-eight.
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