IMPROVEMENTS IN THE MACHINERY FOR AND METHOD OF DRIVING OR COMMUNICATING MOTION TO A SHIP'S PROPELLER
Year: 1860

page_text: LETTERS PATENT to Thomas Silver, of Philadelphia, in the State of
Pensylvania, in the United States of North America, Gentleman, for the
Invention of "IMPROVEMENTS IN THE MACHINERY FOR AND METHOD OF
DRIVING OR COMMUNICATING MOTION TO A SHIP'S PROPELLER."
Scaled the 1st November 1860, and dated the 2nd May 1860.
PROVISIONAL SPECIFICATION left by the said Thomas Silver at the
Office of the Commissioners of Patents, with his Petition, on the
2nd May 1860.
I, THOMAS SILVER, of Philadelphia, in the State of Pensylvania, in the
United States of North America, Gentleman, do hereby declare the nature of
the said Invention for "IMPROVEMENTS IN THE MACHINERY FOR AND METHOD OF
DRIVING OR COMMUNICATING MOTION TO A SHIP'S PROPELLER," to be as follows:-
Instead of placing, disposing, and arranging steam engines for driving or
giving motion to a rotating or other propeller working at the stern or the
bow of a ship in the usual manner, that is to say, either horizontally athwart
ship or at right angles to the keel, or as in the inverted cylinder engines at
right angles to and immediately over the propeller shaft, in either of these and
in other ordinary arrangements in use, the cylinders are placed at right angles
to the keel line and with the propeller shaft, upon which (or on to an

page_text: independent piece of shafting) the cranks are formed, and liave communicated
to them the motion of the pistons by means of connecting rods. Now, it is
found in all heavily powered steam ships, particularly in screw ships of war
and vessels of great length, that the rapid changes of direction of the pistons
and of the working masses of material in motion, and the changes of the
direction of strain in the transmission of the power from the pistons to the
screw produces a transverse motion of the frame or body of the ship, which
besides being mischevious to the structure as producing disruption therein, also
detracts from the forward progress of the ship through the water, and absorbs
power uselessly; the vibrations of the lateral motion of the ship's frame either
being in exact accordance with the strokes of the pistons, or, as more generally
with heavy engines when working at their full speed and power at some multiple
of the engine's strokes, just as the lateral oscillations of the stern of a screw steam
ship are produced by the unequal resistance of the water to the rotation
through it of the blades of the propeller, and the consequent unequal absorp
tion of power.
From the position in which the engines are ordinarily placed and worked in
screw steam ships a portion of their energy is expended uselessly, and the
more so the more the parts in motion, as well as the stationary masses, are
unbalanced. The tendancy of the varying thrust on the screw shaft to affect
the efficiency of the engines and to impede their perfect transmission of inotion
and power, arises also from the relation of the engines and their cranks to the
line of shafting, and whilst the mode which is ordinarily adopted of rotating
or driving the screw shaft direct does not admit of any longitudinal change in
the form of the ship, the introduction of gearing for speeding the rotation of
the screw, as ordinarily practised, does permit of a small amount of such
action without serious damage to the engines; still the strain is thrown upon
thrust blocks and collars, which by their friction absorb power.
Now, my present Invention consists in disposing of the cylinder or cylinders
fore and aft the ship, the motions of the piston or pistons being parallel with
the keel, and in the direction of the motion of the ship; and where two engines
are employed, I prefer to place one on each side of the centre line of the keel,
and cause them to work or reciprocate in opposite directions; and I commu-
nicate or give motion to the crank belonging to each engine by means of a
connecting rod; and I prefer to fit upon a short cross shaft, having at each end
thereof a half crank and mitre, or other bevil wheel gearing, as herein-after
described. The inner end of the propeller shaft having fitted upon it, in tho
manner herein-after set forth, a corresponding bevil wheel of the description
and for the purpose, as herein-after mentioned.

page_text: Where two screw propellers can be advantageously employed, one imme-
diately in advance of the other, I mount the propeller farthest from the engine
upon a shaft of suitable diameter and strength, and I mount the other pro-
peller, the one nearer to the engine, upon a hollow shaft, through which or
within which the other shaft works, and on the inner ends of each of these
shafts I fix a bevil wheel, each of which works into the opposite side of the
bevil wheels fitted upon the crank shafts.
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For the purpose of driving or rotating a single propeller by the motion
communicated from the longitudinally working horizontal engines before
described, I dispenso with the ordinary thrust blocks or bearings, and I
mount a bevil wheel of the form and construction, as hereafter mentioned,
upon the inner end of the screw shaft, by means of a gimbal universal
joint, or equivalent means, for permitting a limited amount of lateral motion
or play upon the end of the shaft. This wheel so mounted and fixed upon tho
shaft has, in addition to its bevil teeth, a disc or flange of suitably large
diameter and strength projecting from its back face, and this disc or flange
should run between two friction guides or rollers fitted and revolving upon
vertical spindles fixed centrically below the disc. Now the driving bevil
wheels fitted upon the crank shaft or shafts of the engine or engines have each
a disc or flange with a square or other suitable form of edge, so formed as to
run against the face or edge, or partly against the face and partly against the
edge of the disc or flange of the driven wheel fitted on the end of the screw
shaft, thus the square edge of the flange of the drivers may each run against
the flat square face of the disc or flange of the driven wheel, or the edge of the
disc or flange of each driving wheel may be rounded, and a curved grove he
formed in the face of or on the edge or periphery of the disc of the driven
wheel, or any other suitable form may be given to the edge or face of each of
these discs or flanges for the purpose of enabling the thrust of the propeller to
be received by the edges of the discs or flanges of the driving wheels in aid of
the transmission of motion and power from the engines.
By the introduction of clutch boxes or friction couplings upon each of the
crank shafts I am enabled to disconnect either engine.
I adopt a similar arrangement of gearing when two propellers are employed
at the stern of a ship, one under each quarter; and when screws or other
similar propellers are fitted to the bow instead of the stern, I employ similar
gearing to that which I have described as applicable for giving motion to pro-
pellers fitted at the stern, but provide for the reception and employment of the
thrust of the propeller or propellers in aid of the transmission of motion and
power from the engines thereto.

page_text: Instead of the engines being placed side by side, one cylinder and its gearing
on each side of the keel, I prefer for some purposes to place one cylinder
above the other, and thus combine the power obtainable from each in the same
vertical line, giving motion to the same crank, or any other arrangement may
be given to the cylinders, and the number whereof may be increased, so long
as their longitudinal position and arrangement be maintained, that the recipro-
cating motion of the pistons be in the direction of the length of the ship.