Improved Means and Apparatus for Balancing the Forward Thrust of the Screw Propellers of Vessels.
Year: 1892

page_text: Date of Application, 20th June, 1892
Complete Specification Left, 18th Mar., 1893-Accepted, 22nd Apr.,
1893
PROVISIONAL SPECIFICATION.
Improved Means and Apparatus for Balancing the Forward Thrust
of the Screw Propellers of Vessels.
I THOMAS INGLIS of Bonnington Brae, in the City and County of Edinburgh,
Engineer, do hereby declare the nature of this invention to be as follows:-
The object of my invention is to provide means for equalizing the pressure and
thereby balancing the forward thrust upon their shafts of the screw propellers of
steam and other vessels and so to reduce and minimise friction.
In thrust-blocks for this purpose as usually constructed the surfaces of metallic
rings or flanges upon the shaft revolve in contact with fixed metallic or other
hard and corresponding surfaces in the thrust-block, and in use there is much
friction, and from wear and tear and various causes the arrangement is found
to be defective, and wasteful of power as well as to give trouble.
According to my invention I employ and apply to the shaft a re-active liquid
force equal to and adapted to resist and balance all the forward thrust thereupon.
To this end I fix to or forge on and around the shaft a piston-like collar of
suitable dimensions, the superficial area of its forward surface being calculated for
the liquid pressure available for application thereto; the said piston is enclosed in
a suitably constructed strong metal cylindrical casing, wherein it is made to fit
accurately circumferentially by means of suitable packing such for example as
piston rings whereby a liquid tight joint is made between the periphery of the
said piston and the casing. The said casing is of such form and dimensions as to
permit of some longitudinal motion of the shaft and piston, and the arrangement
acts in effect like the piston in the cylinder of an ordinary engine.
"
Into the space between the front surface of the piston and the inner walls of the
front part of the cylinder I force by a pump or pumps worked by the main
engine or otherwise a suitable fluid, such as oil or water or both, by which
a re-acting pressure sufficient to balance the pressure exerted by the propeller
in driving the ship is created and maintained: and thus the forward thrust is
constantly resisted and balanced by an annular cushion of the liquid, instead of
by metallic surfaces as heretofore.
Suitable stuffing boxes and packing glands are provided fore and aft of the
cylinder for the passage of the propeller shaft, and the pressure pipes are led to the
cylinder in any convenient positions and provided with such valves as are required.
I do not confine myself to the use of only one such arrangement upon a shaft as
in some cases it may be desirable to provide more than one.
Dated this 20th day of June 1892.
J. C. CHAPMAN,
Agent.
COMPLETE SPECIFICATION.
Improved Means and Apparatus for Balancing the Forward Thrust
of the Screw Propellers of Vessels.
1, THOMAS INGLIS, of Bonnington Brae, in the City and County of Edinburgh,
Miller, do hereby declare the nature of this invention and in what manner the
same is to be performed to be particularly described and ascertained in and by
the following statement :-
The object of my invention is to provide means for equalizing the pressure and
thereby balancing the forward thrust upon their shafts of the screw propellers of

page_text: steam or other vessels whether going ahead or astern and so to reduce and
minimise friction.
In thrust blocks for this purpose as usually constructed the surfaces of metallic
rings or flanges upon the shaft revolve in contact with fixed metallic or other hard
and corresponding surfaces in the thrust block, and in use there is much friction,
and from wear and tear and various causes the arrangement is found to be
defective and wasteful of power.
According to my invention I employ and apply to the shaft a re-active liquid
force equal to and adapted to resist and balance all the forward or longitudinal
thrust thereupon.
To this end I mount upon the propeller shaft a piston-like collar or collars
enclosed in a suitably arranged cylinder and having liquid tight joints therewith.
The shaft and collar are capable of some longitudinal motion in the cylinder and
to the said collar I apply the reactive and balancing liquid force and arrange the
parts substantially as hereinafter set forth. I do not confine myself to the use of
only one such arrangement upon a shaft as in some cases it may be desirable to
provide more than one, and such apparatus may also be used as supplementary to
the usual thrust block in which case the liquid pressure is to be so regulated as in
effect to relieve the bearing surfaces of the usual block of practically all the
pressure.
I will now fully describe one arrangement for carrying my invention into effect
whereby the balancing liquid force may be applied to the shaft whether the engines
be going ahead or astern.
Fig. 1 is a sectional elevation
Fig. 2 a plan, half in section, and
Fig. 3 an end elevation of the apparatus.
Similar letters refer to similar parts throughout.
A is the propeller shaft upon and around which in convenient position I fix or
forge the collars B and C of suitable diameter and width of surface, the superficial
area of the latter being calculated for the liquid pressure available for application
thereto. The collars B and C are enclosed in the strong metal cylindrical
casing a which may be of any convenient external form such as is shown. It is
provided with internal annular flanges or ribs a' a² each having an annular metallic
working face L and O for the collars C, B respectively fixed thereto as shown.
Suitable stuffing boxes S S with packing glands are provided fore and aft for the
passage of the shaft A and all the parts may be disposed and arranged substantially
as illustrated, or in other convenient manner according to space available and
other local arrangements. Fore and aft between the collars and the casing annular
spaces E and P about inch wide are provided and an accurate fit between the
collars and casing may be effected by peripheral rings such as are commonly used
in pistons, or by circumferential face rings such as are shown at F, Q let into
suitable grooves in the casting and constantly maintained in proper positions by
spiral or wave springs such as G G whereby liquid tight joints are ensured. In
the casing a a small amount of longitudinal motion, say about of an inch, is
allowed to the shaft and collars and the arrangement acts in effect like the piston
in an ordinary engine cylinder.
I will first describe the action when going ahead.
"
Into the annular fore end space E between collar B and casing a any suitable
fluid such as water, oil, glycerine solution, or the like is forced by any ordinary
pump or pumps worked by the main engine (not shown in the drawings) through
pipe D by which a reacting pressure sufficient to balance the "go-ahead thrust
of the collar B exerted by the propeller in driving the ship is created and
maintained, and then the forward thrust is constantly resisted and balanced by an
annular cushion of the liquid in space E instead of by metallic surfaces as hereto-
fore. H is a channel or pipe leading to the escape valve J which is regulated to
the normal pressure required to keep the back collar C off its face L. The face L
takes the thrust of the collar C at starting, and so long as these two surfaces are

page_text: in contact no liquid can escape from the fore space E, but when the supply pumps
have exerted sufficient pressure to force back the shaft far enough to allow the
liquid to pass between the surfaces C and L, then both the collars are parted from
and maintained off their faces or, as it were, floating in the compressed liquid.
Any overflow or excess of pressure then passes through passage H, valve J,
and pipe to the space K and thence between the faces C and L to the central
annular space M from which it can escape by the exhaust orifice N. Any leakage
past the after face ring Q exhausts through a suitably arranged pipe, and all
exhausts are returned to the pump supply. Thus the regulation of the pressure
is to some extent automatic, and to prevent accident a safety valve may with
advantage be placed on the supply pipe D.
The action in going astern is precisely the same, the face O taking the thrust
of collar B and making a liquid tight joint therewith until the pressure through
the supply pipe D¹ is sufficient to part the faces O and B and "float" the collars.
Overflow then escapes through passage H¹, valve J¹, and pipe j¹, to space K¹ and
thence between O and B to M and N to exhaust as described.
Although the apparatus above described is specially designed for liquid reaction,
yet in some cases where the pumps fail, or in working a vessel in or out of dock
or the like, the liquid may be dispensed with and the apparatus is nevertheless a
serviceable thrust block.
Having now, particularly described and ascertained the nature of this inven-
tion and in what manner the same is to be performed I declare that what I
claim is :-
(1). The herein before described improved means for balancing the thrust of the
screw propellers of vessels which consists in the employment and application to
the screw shaft of a reactive liquid force substantially in the manner set forth.
(2). The apparatus for balancing thrusts of screw propellers consisting of a
piston-like collar or collars mounted upon the screw shaft capable of some longi-
tudinal motion and enclosed and fitted in a cylindrical casing to which fluid pressure
is admitted and adapted to act upon the said collars and shaft substantially as
hereinabove set forth.
(3). The improved arrangement of apparatus hereinabove described and illustrated
in the drawings.