IMPROVEMENTS IN SCREW GEAR FOR IMPARTING MOTION TO MACHINERY, AND IN STEERING APPARATUS ACTUATED BY SUCH GEAR
Year: 1875

page_text: LETTERS PATENT to Louis Franciscus Elisa Ittmann, of the City of
London, for the Invention of "IMPROVEMENTS IN SCREW GEAR FOR
IMPARTING MOTION TO MACHINERY, AND IN STEERING APPARATUS ACTUATED
BY SUCH GEAR."-A communication from abroad by David Newell
Brown Coffin, of Newton, in the County of Middlesex, and State of
TT Stator of & manis
PROVISIONAL SPECIFICATION left by the said Louis Franciscus Elisa
Ittmann at the Office of the Commissioners of Patents, with his
Petition, on the 29th March 1875.
I, LOUIS FRANCISCUS ELISA ITTMANN, of the City of London, do
hereby declare the nature of the said Invention for "IMPROVEMENTS IN
SCREW GEAR FOR IMPARTING MOTION TO MACHINERY, AND IN STEERING APPARATUS
ACTUATED BY SUCH GEAR," a communication to me from abroad by David
Newell Brown Coffin, of Newton, in the County of Middlesex, and State
of Massachusetts, United States of America, to be as follows :—
According to this Invention the circumference of a worm or screw
"
"

page_text: a spur wheel with corresponding teeth of a width or face broad enough
to gear into at least one entire revolution of the thread of the worm.
The worm constructed as described is applied to a rack or to a worm
wheel or segment having teeth externally, or to a worm wheel or segment
having teeth internally, and by preference of hollowed out form; in that
case two worms of the described form are by preference applied opposite
one another, and the spur wheel gearing into them both, the centres of
the two worms or worm being by preference below the top edge of the
worm wheel; or the worm may be applied to a nut, in which case an
aperture must be left in the nut for the spur wheel teeth to pass through
to gear with the worm teeth.
The peculiar construction of the thread of the worm is such that any
section taken transversely to the spiral direction of the thread around its
axis, and through that part thereof directly opposite to the axis of the
internal worm wheel or nut wheel, or segment, worm, or nut wheel,
holds a uniform or approximately uniform relation to a radial line
drawn perpendicularly to the axis of the internal worm wheel, and
through the middle of said thread, but ordinary worm or screw threads
may also be formed with teeth according to this Invention.
The internally toothed worm gear or nut wheel is by preference so
formed that the screw thread above described will so nearly fit the teeth
or nut as to approximately equal in point of fair bearing and wearing
surfaces to an ordinary or linear screw and nut, or as it might be
described, the form or construction of tooth or nut which would be pro-
duced by the use of a milling tool or cutter having the same form as the
above described screw and thread.
I will now proceed to describe a special application of worms and worm
wheel constructed as set forth, videlicet, to steering apparatus. The
whole apparatus rests on two supports fastened on deck; each support
is formed with a recess or mortice fitted with a block or trunnion placed
between two india-rubber or other springs; projecting pins on the top
frame of the apparatus fit into holes in the said trunnions. The object
of the springs is to act as cushions to resist the tendency of the top
frame to revolve with the rudder, and also thereby to relieve the
dangerous effect of surges upon the rudder in a rough sea and other
strains. A clamp on each side unites the top frame and the rudder
head, but so that the latter can turn against the former, which of course

page_text: is stationary. The rudder head is by preference fastened on to the
rudder post so as to be easily unshipped in case of accident to the
steering apparatus, which may be done by forming both with corrc-
sponding flanges or lugs, and holding them together by bolts or screws;
the rudder post should also have a hole for inserting a temporary tiller
for the same contingency.
The rudder head is a hollow or chambered casting open at top,
formed as part of a sphere and provided with a set of worm teeth on cach
side, but right hand on one side and left hand on the other. Into each
set gears a corresponding toothed worm of the construction already
described, and these two worms are actuated by a broad-faced spur
wheel fixed on the tiller or spoke wheel spindle. This spindle, as well
as the spindles of the two worms, have their bearings in the top frame
which is formed with an opening at top, that is, covered in by a cap.
The rudder head has a projection to indicate the position of the rudder
relatively to the vessel; it is formed with an inside bottom dish for con-
taining oil, in which the worms constantly work. When it is desirable
to make both sets of worm teeth wind in the same direction and to avoid
the opposite or right and left-hand construction of said teeth and to have
a uniform set of teeth all round if desired it is only necessary to add an
intermediate pinion between the broad faced spur wheel and one of the
Antifriction washers may be provided at each end of the worms
worms.
to take the thrust.
The rudder head works on rollers arranged on deck or on a separate
sloping ring frame all round or in sets, which rollers arc conical and let
the water run off, and also serve as guides concentrically.
From the foregoing it will be understood that the rudder, rudder post,
rudder head, and top frame may all lift together and safely when by
grounding or other casualty the rudder is lifted out of its proper position,
the top frame then separates from its supports, the projections on the
former lifting more or less out of the trunnions in the latter.
A brake may be applied to the spoke wheel and be worked by the foot
of the man at the helm. For this purpose the spoke wheel has a pro-
jecting rim on the face opposite the helmsman, and a treadle lever
pivoted on a sliding jaw forces a die against the lower edge of said rim,
which is thereby pushed against another die abutting against the upper
or inner side of the rim. When it is desired to keep the friction on a

page_text: block is forced between an upright arm of the treadle lever and the jaw
or stand. When the foot of the operator is lifted or the block removed
the spoke wheel is free to revolve.
SPECIFICATION in pursuance of the conditions of the Letters Patent,
filed by the said Louis Franciscus Elisa Ittmann in the Great Scal
Patent Office on the 7th September 1875.
TO ALL TO WHOM THESE PRESENTS SHALL COME, I, LOUIS
FRANCISCUS ELISA ITTMANN, of the City of London, send greeting.
WHEREAS Her most Excellent Majesty Queen Victoria, by Her
Letters Patent, bearing date the Twenty-ninth day of March, in the year
of our Lord One thousand eight hundred and seventy-five, in the thirty-
cighth year of Her reign, did, for Herself, Her heirs and successors,
give and grant unto me, the said Louis Franciscus Elisa Ittmann, Her
special licence that I, the said Louis Franciscus Elisa Ittmann, my
executors, administrators, and assigns, or such others as I, the said
Louis Franciscus Elisa Ittmann, my executors, administrators, and
assigns, should at any time agree with, and no others, from time to
time and at all times thereafter during the term therein expressed,
should and lawfully might make, use, exercise, and vend, within the
United Kingdom of Great Britain and Ireland, the Channel Islands,
and Isle of Man, an Invention for "IMPROVEMENTS IN SCREW GEAR FOR
IMPARTING MOTION TO MACHINERY, AND IN STEERING APPARATUS ACTUATED BY
SUCH GEAR," (a communication to me from abroad by David Newell
Brown Coffin, of Newton, in the County of Middlesex, and State of
Massachusetts, United States of America,) upon the condition (amongst
others) that I, the said Louis Franciscus Elisa Ittmann, my executors
or administrators, by an instrument in writing under my, or their, or
one of their hands and seals, should particularly describe and ascertain
the nature of the said Invention, and in what manner the same was
to be performed, and cause the same to be filed in the Great Seal
Patent Office within six calendar months next and immediately after
the date of the said Letters Patent.
NOW KNOW YE, that I, the said Louis Franciscus Elisa Ittmann,
do hereby declare the nature of the said Invention, and in what

page_text: manner the same is to be performed, to be particularly described and
ascertained in and by the following statement:-
This said Invention, which relates to improvements on steering
apparatus, consists mainly in the employment of tangent screws or
worms gearing with internal or external toothed racks or worm wheels,
and actuated by a broad faced spur wheel, in the manner herein-after
described and illustrated upon the accompanying Sheet of Drawings.
Figure 1 illustrates the peculiar construction of the thread b, b, of the
improved screw or worm a, b, the form thereof being such that any
section taken transversely to the spiral direction of the thread around
its axis, and through that part directly opposite to the axis of the
internal nut or worm wheel or segments c, holds an uniform or approxi-
mately uniform relation to a radial line drawn perpendicularly to the
axis of the wheel c, and through the middle of the said thread b. This
construction adapts the worm a, b, to the conditions for the most perfect
working in connection with the internal globular form of the wheel c.
A worm a, b, of this construction, or the ordinary linear screw thread
worm, may be toothed on its periphery, as shewn at Figure 2, and be
driven by a spur wheel e, which is broad enough to gear into at least
an entire revolution of the screw thread, as shewn at Figure 3, which is
a plan of Figure 2. The ordinary linear worm may be used for gearing
with an externally toothed worm wheel a, as shewn at Figure 4, or with
a rack nut d, d, as shewn at Figure 4. The above described toothed
worm gear may be applied for changing the speed and direction of motion
of machinery.
Figures 5 and 6 are vertical sections at right angles to one another of
a steering apparatus actuated by the improved worm gear; Fig. 7 is a
plan of same; Figure 8, a plan with the cap and top frame removed;
Figure 9, a plan of under side of top frame; and Figure 10, a plan
section through the line x, x, Figure 5.
The spindle A carries the steering wheel a¹ and the broad faced spur
wheel B; the spindle has its bearings in the top frame C, in which are
also formed bearings for the two toothed worms D and D¹, which are
right and left handed, and with their teeth gear into the spur wheel B;
the threads of the worms D and D¹ gear into a set of right and left-
handed teeth formed on the interior spherical rim of the rudder head E.
The opening in the upper part of the top frame C is closed by a cap d¹.

page_text: The top frame C has at each end a peg c fitting into a trunnion or
socket in two halves, which are kept together by india-rubber block
springs or cushions f¹. The sockets and springs rest in recesses formed
These cushions resist the tendency
rudder, and also thereby relieve the
into the standards or supports F, F.
of the frame C to revolve with the
dangerous effect of surges upon the rudder in a rough sca and under
other strains. The two clasps e, shewn separately in two views at
Fig. 11, hold the top frame C and rudder head E together to prevent
any lifting of the former, but as will be seen both may lift together
(the pegs e rising out of their sockets f) and safely when by grounding
or other casualty the rudder is lifted out of its normal position. G is an
annular pan supplied plentifully with oil which keeps the worms D, D¹,
constantly oiled. Antifriction washers may be provided at each end of
the worms to take the thrust.
The rudder post H ought to be so united with the rudder head E as to
be easily disconnected when required. One such mode is shewn here,
where the rudder head E has a bottom flange, and the rudder post a
corresponding flange I fixed to it, the two flanges being joined by bolts.
fitting in slots. The flanch I has also a socket i for inserting a tempo-
rary tiller J, dotted in at Fig. 6; this socket i coming against the
stops h, h, dotted in at Figure 7, limits the angular movement of the
rudder. The socket i and auxiliary or temporary tiller J may if desired
be placed on the opposite side. The rudder head E may at the bottom
be formed with a face or rim, which works against rollers & on the deck,
all so arranged that the water will flow freely away so as not to freeze
up and obstruct the working, and so as to guide the rudder head con-
centrically.
When it is desirable to make both worm threads wind in the same
direction and avoid the opposite or right and left construction of worm
and worm wheel it is only necessary to add an intermediate pinion L, as
shewn at the diagram Figure 12.
If on account of wear and tear or from other reasons it be ever
required to tighten the fit of the worms in the worm wheel teeth new
worms with thicker threads may be put in, or the worms may be made
in two parts, the division occurring in coincidence with radial lines
drawn from the middle of the thread at its periphery, perpendicularly to
their axis; then as they wear the two parts may be forced apart by a
screw, wedge, or a packing interposed between the two parts.

page_text: A tell-tale or pointer M is formed on or attached to the rudder head E
(see Figures 5 and 6) to indicate the position of the rudder.
For the purpose of steering in the forward part of the vessel a wheel
may be erected there, and be provided with a chain wheel and shaft,
and a chain to connect with a line of shafting on or under the deck,
extending aft to the steerer, this shaft to be similarly provided with a
chain wheel and chain belt connecting it to the steerer wheel shaft, on
which in that case a chain wheel would also be placed, or the longi-
tudinal shafting may be connected to both steering wheel shafts by
means of upright or inclined shafts and the proper bevel or mitre tooth
wheels, or by a train of spur wheels.
A brake may be applied to the steering apparatus; this brake is shewn
at Figures 13 to 16. The brake is applied by pressing with the foot on
the lever (Figure 15), the opposite nose formed end of which grasps a
die or clamp 2, which is thus pressed hard against a projecting flange p
on the side of the rim ¹ of the steering wheel. m is the stand or bracket
to which the brake is attached; o is an upper die or clamp, which
adjusts itself to the flange p; n is a sliding jaw on which the treadle
lever is pivoted. When it is required to keep the friction on the
blocks, (Figure 16) is forced between the upwardly projecting arm of
lever and the jaw n or stand. When the operator's foot is lifted or the
blocks removed the wheel is free to revolve.
Having now described this said Invention and the system or mode of
carrying the same into practical effect, I would observe in conclusion
that without confining myself to the exact details of mechanism herein-
before set forth, what I claim as the Invention secured by the herein-
before in part recited Letters Patent is,-
First. The complex or toothed screw or worm, employed as and for
the purposes described.
Second. The toothed worm in combination with the wheel B, substan-
tially as described.
Third. The toothed worm in combination with internal or external
nut wheel or worm wheel or rack or rack nut, substantially as described.
Fourth. The construction of the worm thread in connection with the
internal worm wheel, and the construction of the said internal worm
wheel, substantially as described.