Improvements in or relating to Propellers for Vessels.
Year: 1899

page_text: Date of Application, 27th Oct., 1899-Accepted, 10th Feb., 1900
COMPLETE SPECIFICATION.
Improvements in or relating to Propellers for Vessels.
I, CHARLES RULF EMRICH, a Lieutenant in the United States Navy, stationed
at Norfolk, Virginia, United States of America, do hereby declare the nature
of this invention and in what manner the same is to be performed, to be par-
ticularly described and ascertained in and by the following statement: -
My invention relates to improvements in the form and construction of pro-
pellers for steamships and the like, both as to the shape of the blades with respect
to the curve of the surface of the driving face of the blades, and to the design and
dimensions of the hub in its relation to the blades, and in the construction of
the hub when the blades are made to be separately detachable from the hub.
Generally speaking, the propeller consists of a hub carrying a plural number
of blades, which are placed about the hub symmetrically, all the blades being as
nearly as possible alike. The propeller is to be made of steel, iron, composition,
or other suitable material, and to be shaped by forging, casting or other suit-
able means. The propeller is to be attached to the vessel and driven in the same
way as is in general use for attaching and driving ordinary propellers, such as
screw propellers, or by such other means as may be found suitable.
Particularly speaking, the surface of the driving face of each blade is made
part of a surface such as would be generated by swinging a straight line about
the axis of the propeller, one end of the said straight line being kept in a given
point in the axis of the propeller, the line in its swinging, being guided near
its free end, by sliding along a co-axial true helical curve whose pitch angle
is 45° or approximately 45°; or, to describe this surface in other words:-a
surface such that the line of intersection of this surface and the surface of any
co-axial cylinder is a true helical curve, the pitch angle of which is 45° or
approximately 45°, that is to say that a tangent to this curve of intersection
makes an angle of 45° or approximately 45°, with a plane perpendicular to the
axis of the propeller.
The hub is made circular in transverse section and the diameter of its surface
where it is intersected by the leading edges of the blades, is preferably governed
where d represents the diameter in feet, S represents the velocity, in feet per
minute, of the propeller in axial direction relative to the water with which it
comes in contact, R represents the number of revolutions per minute of the pro-
peller, represents 3.1416, and represents the exact pitch angle of the helix
of intersection of the blades' surface and the surface of a co-axial cylinder of
diameter equal to d. This formula gives the theoretical minimum diameter
that the hub should have but it can be varied from, according to practical con-
ditions in particular cases of design.
The construction of the hub depends on whether the blades are made integral
therewith, or separately detachable from the hub. If the blades are made

page_text: integral with the hub, the hub should be cored out and ribbed for lightness and
strength. If the blades are made separately detachable from the hub, its con-
struction is as follows its outer surface shall be carried by the blades, as
Hanges, each blade carrying its proportion of the hub's surface; the hub proper
then to consist of a boss carrying a plural number of transverse circular collars,
each integral with the boss, and at intervals along the boss; the blades shall
carry, on the flanges on the side towards the axis, projecting lugs so arranged
that they will fit neatly between the collars on the hub, the outer surface of the
collars and the inner surface of the Hanges being made to fit neatly together.
When the blades are in position around the hub, the collars and lugs shall be
perforated by sets of taper holes, so that a taper pin can be inserted in each set
of holes, by which pins, the blades will be held firmly and securely to the hub,
the pins being held in place by studs set into the after collar, and nuts, the pins
being fitted with suitable heads for this purpose.
Referring to the accompanying drawings, wherein I have shown a propeller
constructed according to my invention as regards the curve of the driving face,
and have illustrated the curve of the driving faces of the blades, and the con-
struction of the hub when arranged for making the blades detachable:
Figures 1 and 2, represent an end and a side elevation of a propeller constructed
according to my invention. The point indicated by a is the fixed given point
about which the generating line of the blades' surface swings.
Figures 3, 4 and 5, represent a plan view, and two elevations, at 90° with each
other, of a hollow half-cylinder which has been cut away so that its upper surface
is a surface such as would be generated by swinging a straight line about a fixed
point in the axis of the cylinder, the line being guided in its swinging by a co-
axial true helical curve of 45° pitch angle. The point indicated by a in the
figures is the point about which the line swings and the curve indicated by the
lines -B-C-L in the three figures is the co-axial true helical curve of 45°
pitch angle. In each of the figures, the part of the surface enclosed by the heavy
ines, and indicated by A-B-C-D is that part of the surfaces that is used for
the driving faces of the blades of the propeller shown in Figures 1 and 2, the
hollow part of the cylinder corresponding to the hub. The light broken lines
extending across the surface represent the generating line in various positions,
(being used also as construction lines for the drawing.)
Figure 6 represents a face elevation of part of the propeller showing the hub as
constructed for making the blades detachable. In the figure, part of the blades
are broken off, and one blade is omitted entirely, for the purpose of illustration.
Figure represents a part section, part side elevation of what is shown in
Figure 6. The upper half of Figure 7 is a section on -B in Figure 6, and
the lower half is a side elevation of the lower half of Figure 6. Figure S is a
face elevation of a part of one blade, showing particularly the flange and lugs.
Figure 9 represents a section -A in Figure 6. In Figures 6, 7, 8 and 9 like
letters mark like parts. R represents the boss, which is shown bored out and
key seated for attachment to a driving shaft; C, one of the collars on the boss,
which are shown cut away at O, for the purpose of lightening the structure;
Pone of the taper pins for holding the blades and hub together; S one of the
studs and nuts for keeping the pins P in place; H is a hole through the collar
for the pin.
In Figures 1 and 2, the propeller shown has four blades, each blade occupying
40° in projection, and the driving face is of 45° pitch angle; in Figures 3, 4
and 5, the surface shown is also of 45° pitch angle, but 1 do not limit myself
to any particular number of blades, nor to any particular outline of blade, nor
to exactly 45° pitch angle of the whole surface, but vary these to suit particular
cases of design. In Figures 6, 7, 8 and 9, are shown three collars on the boss, and
four lugs on each blade, with two securing pins for each blade, but I do not
limit myself to the exact number shown, but vary these to suit particular cases
of design.

page_text: Having now particularly described and ascertained the nature of my said
invention and in what manner the same is to be performed I declare that what
I claim is
1. A propeller for steamships and the like, having a plurality of blades, the
driving face of each blade being substantially part of a surface generated by
swinging a straight line about a fixed given point in the axis of the propeller,
and guided near its free end by a co-axial true helix; or to describe such a sur-
face in other words, the driving face of each blade being a surface such that the
lines of intersection of the surface and the surfaces of all co-axial cylinders shall
be, substantially similar true helical curves, that is, helical curves of the same
pitch angle; substantially as described.
2. A propeller for steamships and the like, having a plurality of blades, the
driving face of each blade being substantially part of a surface generated by
swinging a straight line about a fixed given point in the axis of the propeller,
and guided near its free end by a co-axial true helix, said helix, when inaximum
efficiency of propeller is required above all other considerations, to have a pitch
angle of 45° or approximately 45°; or, to describe such a surface in other words,
the driving face of each blade being a surface such that the lines of intersection
of the surface and the surfaces of all co-axial cylinders shall be, substantially,
similar true helical curves, that is, helical curves of the same pitch angle said
helical curves, when maximum efficiency of propeller is required above all other
considerations, to have a pitch angle of 45°, or approximately 45°, substantially
as described.
3. A propeller for steamships and the like, as herein before described, provided
with a hub whose exterior diameter, at the entering edges of the blades, is sub-
stantially and approximately indicated by the formula
where represents the diameter in feet, S represents the velocity, in feet per
minute, of the propeller in axial direction, relative to the water with which it
comes in contact, R represents the number of revolutions of the propeller per
minute, T represents 3.1416, and p represents the exact pitch angle of the
helix of intersection of the blades' surface and the surface of a co-axial cylinder
equal to , substantially as described.
4. With propellers for steamships and the like, the combination of a hub having
a boss from which project a plural number of perforated transverse collars, and
blades provided with flanges enclosing said collars, and with perforated lugs pro-
jecting from said flanges and fitting neatly between said collars, and taper pins
which, fitting in the perforations in the collars and lugs when these are in posi-
tion, will hold the whole securely and firmly together, substantially as described.
5. The improvement in propellers for steamships and the like, substantially
as herein described and as shewn in Figures 1 and 2 of the drawings.
6. The combination with the hub of the detachable blades secured thereto sub-
stantially in the manner herein described, and as shewn in Figures 6 to 9 of
the drawings.