IMPROVED MEANS OF AND APPARATUS FOR REGULATING THE ACTION OF SCREW SHAFTS AND FOR PREVENTING BREAKAGE OR DAMAGE TO THE ENGINE OR ITS APPENDAGES FROM 'LASH.
Year: 1873

page_text: LETTERS PATENT to Hamilton Weldon Pendred, of 22, Leadenhall
Street, in the City of London, Civil Engineer, for the Invention of
"IMPROVED MEANS OF AND APPARATUS FOR REGULATING THE ACTION OF SCREW
SHAFTS AND FOR PREVENTING BREAKAGE OR DAMAGE TO THE ENGINE OR ITS
APPENDAGES FROM 'LASH.'
" "
Sealed the 20th January 1874, and dated the 23rd July 1873.
PROVISIONAL SPECIFICATION left by the said Hamilton Weldon
Pendred at the Office of the Commissioners of Patents, with his
Petition, on the 23rd July 1873.
I, HAMILTON WELDON PENDRED, of 22, Leadenhall Street, in the
City of London, Civil Engineer, do hereby declare the nature of the
said Invention for "IMPROVED MEANS OF AND APPARATUS FOR REGULATING THE
ACTION OF SCREW SHAFTS AND FOR PREVENTING BREAKAGE OR DAMAGE TO THE
ENGINE OR ITS APPENDAGES FROM 'LASH,'" to be as follows:-
This Invention relates to the employment of an elastic or flexible
medium between the engine and the propeller of a screw steam vessel

page_text: "
for the purpose of counteracting the dead thrust upon the shaft at the
point where the shaft terminates within the vessel, and so relieve the
screw shaft from shocks and vibrations now usually transmitted to the
engine and to the vessel's hull when struck by a wave or from other
causes; also to absorb or vitiate the tendency of the engine "racing
when the screw is temporarily out of the water from the pitching of the
vessel; also to increase the efficiency of the screw and to regulate the
action of the power by preventing sudden resistances occurring between
the screw and the engine.
One way of carrying my Invention into effect is to enclose or encase
a portion of the shaft in an elastic or flexible cage or framework com-
posed of metal bars arranged in any suitable manner. The ends of the
bars are connected to discs, collars, or other appliances fitted upon or
close to the adjoining ends of two portions of the shaft, so that the
turning of one portion is communicated to the other portion through
the elastic or flexible medium, and from that to the screw.
The elastic or flexible medium may be formed of parallel strips, plain
or twisted, or the strips may be coiled in the same or in contrary direc-
tions, and the expansion produced by the twist caused by the turning
can be counteracted by rings or collars slipped or fitted over the strips.
It is not essential that the two portions of the shaft should be in
proximity, as the elastic or flexible medium can be arranged to discs or
their equivalents on the ends of the shafts, the cage or framework being
between them.
In lieu of employing an elastic framework as above explained the
shaft itself or a portion of it only may be of flattened or of oval form in
cross section, whereby great tortional elasticity is obtained to counteract
the rigidity of the shaft and to produce a flexibility between the engine
and the screw.
Clutch boxes packed with an elastic body may be fitted to the ends of

page_text: SPECIFICATION in pursuance of the conditions of the Letters Patent,
filed by the said Hamilton Weldon Pendred in the Great Seal Patent
Office on the 23rd January 1874.
TO ALL TO WHOM THESE PRESENTS SHALL COME, I, HAMILTON
WELDON PENDRED, of 22, Leadenhall Street, in the City of London,
Civil Engineer, send greeting. .
WHEREAS Her most Excellent Majesty Queen Victoria, by Her Letters
Patent, bearing date the Twenty-third day of July, in the year of our
Lord One thousand eight hundred and seventy-three, in the thirty-
seventh year of Her reign, did, for Herself, Her heirs and successors,
give and grant unto me, the said Hamilton Weldon Pendred, Her special
licence that I, the said Hamilton Weldon Pendred, my executors,
administrators, and assigns, or such others as I, the said Hamilton
Weldon Pendred, 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 In-
vention for “IMPROVED MEANS OF AND APPARATUS FOR REGULATING THE ACTION
OF SCREW SHAFTS AND FOR PREVENTING BREAKAGE OR DAMAGE TO THE ENGINE OR
ITS APPENDAGES FROM 'LASH,'" upon the condition (amongst others) that I,
the said Hamilton Weldon Pendred, 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 Hamilton Weldon Pendred, do
hereby declare the nature of my said Invention, and in what manner
the same is to be performed, to be particularly described and ascertained
in and by the following statement thereof, reference being had to the
Drawings hereunto annexed, that is to say :-
This Invention relates to the employment of an elastic or flexible
medium between the engine and the propeller of a screw steam vessel
for the purpose of counteracting the dead thrust upon the shaft at the

page_text: a
although I do not limit myself to the exact manner of constructing or
arranging my apparatus for the purpose :—
Figures 1 and 2 show elevation and sectional views of a series of
spring or tempered metal bars or strips A, A, arranged in radial order
around a ring, disc, or collar B keyed upon one end of a shaft C, there
being another ring D over them to hold them firmly to the ring B, which
can be rigidly fixed to the shaft C by tightening screws E, E. The
opposite ends of the bars or strips are thus left free to play or slide
within a notched disc F keyed upon the end of the adjoining shaft G, as
shown in Figure 3, to limit or to extend the degree of tortional strain
it is necessary to put upon the bars or strips for the proper working of
the screw and the engine by which the shaft is driven; or instead of
permitting the bars or strips to slide as before mentioned they can be
fixed to the notched disc F. In these views and also in Figure 4 I have
· shown an arrangement for eight bars or strips, but these may be
diminished or increased as desired, or a fewer number can be employed
than that for which the discs are notched, for should any one or more
of the strips or bars become broken it can easily be removed and a fresh
one slipped into the collar D, and be held in place by a set screw a or
other device.
Figures 5 and 6 represent spring plates A, A, arranged at right angles
upon a collar B on the end of one shaft C to bear against a stud or
arm H projecting from an extension piece I on a collar or disc F on the
end of the adjoining shaft G, and by which the shaft G is driven. Any
number of these spring-like plates can be arranged for driving in one
direction only or for driving in both directions, as is found necessary, or a
double set of springs can be arranged on the collar B, one for the forward
-rotation of the engine and the other for backward rotation, such as is
required when a vessel has to move astern. Both of these collars are
shown keyed upon the ends of the shafts C and G, but the extension I
and that J carrying the springs may be in a piece with the shafts. It
will be seen in these Figures that no sliding motion of the springs can
take place, but in Figures 7 and 8 I have shown a plan by which a
sliding motion of the piston K within a cup L can be obtained, the resisting
5 medium being a column or body of air or other fluid or rubber within
the cylinder-like cup L, when the pressure of the arm I bears against
the plunger rod M. The piston or plunger in this arrangement preferably
acts against a cushion of air which is kept hermetically enclosed by the

page_text: tight fitting of the plunger against the side wall of the cup, but an
elastic or flexible bag charged with air may be fitted within the cup to
receive the thrust of the arm. One or more coiled springs may be
arranged in the cup or upon a rod for that purpose.
When the screw is struck by a wave, which usually causes a tremulous
motion or shock to pass through the vessel's hull and to be communi-
cated more or less to the engine, this air cushion or the coiled spring
arrangement is of great value, for the shock will be absorbed by the
cushion or the spring, and the steady motion of the engine will not be
interfered with. Racing of the engine when the screw lifts in the water 1
through the pitching of the vessel will also be considerably lessened, and
the biting of the water by the blades when the screw lowers into it will
be easy compared to the present system, as the springs will become more
or less compressed as the bite increases or diminishes.
Figures 9 and 10 show a combination of the spring bars and the air 1
cushion arrangements applied to the same corresponding ends of the
two shafts, the two acting in combination, one the bars A, A, for torsional
elasticity, and the other the cushion for longitudinal elasticity by means
of the sliding piston K on the collar Bacting within the cup or cylinder
L on the disc F.
2
Figures 11 and 12 show a single bar A of springy metal forming a
portion of the shaft itself. This springy portion is flattened out for a
given length, in which the torsional strain or elasticity can be obtained,
but not so effectively as by the previous methods. This single spriny
portion may however be fitted between the adjoining ends of the two 2
shafts by collars B and F, as in Figures 13 and 14, the collars rigidly
fixed upon the shafts with the springy bar clamped between them, as
shown, or in other convenient manner, and these collars may be of any
length and be made to slide upon the shafts, which I prefer should be
of oval, of square, or some equivalent shape to enable set screws to be 3
dispensed with, the collars or sleeves being free to adjust themselves by
sliding upon the shafts without coming apart therefrom.
This plan will be more particularly understood by Figures 19, 20, and
21, so that the torsional elasticity is borne by the springy bar between the
collars or sleeves. The springy bar may in this method be dispensed 3
with in the case of repairing a broken shaft, as by making that portion
of the shaft most liable to fracture of an oval, square, or equivalent

page_text: shape in cross section, and by fitting a correspondingly shaped sleeve
upon it in a loose manner, the sleeve can be slid over the broken part
and so connect the two ends, one being driven by the other through the
intermediation of the sleeve or long collar, which can be prevented
shifting by a key being driven in at each end. This sleeve over a broken
shaft is clearly shown on the left of Figure 19, and needs no further
description.
Figures 15 and 16 show an arrangement of air cushions upon or
against which the "thrust" of the screw and its shaft is received. The
air cushion, or it may be a spring cushion, is composed of one or two
cylinders L, in each of which a piston or plunger K is free to slide, the
plunger forming part of a block M sliding in a fixed bed plate N. The
block M encircles the shaft C between the two collars P, P, and as the
shaft is forced in from any cause the shock is received and absorbed by
the cushion, and does not proceed further to interfere with the engine or
apparatus connected with it.
This method of providing longitudinal elasticity can also be modified
in many ways, and in Figures 17 and 18 I have shown a disconnected
shaft, the two ends of which have each a disc D, F, upon them, one F
formed with apertures to act as cylinders L for the reception of plungers
or pistons K upon the disc D.
And having now described the nature of my said Invention and in
what manner the same is to be performed, I declare that I claim,―
Firstly. The improved means of and apparatus for regulating the
action of screw shafts and for preventing breakage or damage to the
engine or its appendages from lash, as herein-before set forth and shown
in the annexed Drawings or any mere modification thereof.
Secondly. I claim the special means and appliances herein-before
described and shown in Figures 1, 2, 3, and 4 of the Drawings, by which.
a rotation of the screw shaft proper can be conveyed from the engine
shaft, and by which shocks and concussions can be absorbed.
•
Thirdly. I claim the special means and appliances herein-before
described and shown in Figures 5 and 6 of the Drawings, by which a
corresponding action as set forth in second claim can be obtained.
Fourthly. I claim the special means and appliances herein-before
described and shown in Figures 7 and 8 of the Drawings, by which a
°

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HAMILTON WELDON PENDRED. (L.S.)
Witness,
H. GARDNER,
166, Fleet Street,
London.