IMPROVEMENTS IN HIGH SPEED AND ROTARY MOTORS
Year: 1878

page_text: LETTERS PATENT to Middleton Pratt, of 23, Rood Lane, in the City of London,
Engineer, for the Invention of "IMPROVEMENTS IN HIGH SPEED AND ROTARY
MOTORS"
Sealed the 25th February 1879, and dated the 21st November 1878.
PROVISIONAL SPECIFICATION left by the said Middleton Pratt at the Office
of the Commissioners of Patents on the 21st November 1878.
MIDDLETON PRATT, of 23, Rood Lane, in the City of London, Engineer.
PROVEMENTS IN HIGH SPEED AND ROTARY MOTORS."
"IM-
The object of my Invention is to produce a motor which is capable of running at
very high speeds with economy and without jar or rattle, and which also may be
modified so as to become a rotary engine round a fixed axis.
I may arrange my engine, fixed to a suitable frame or foundation, with one, two,
three, four, or more cylinders, arranged at suitable angles round a centre in which
revolves a crank and shaft.
This revolving power crank I make of such suitable shape that it may act as a
valve for admission and exit of the steam or motive fluid either through one side
or both.
When a double crank is used I utilize both sides of my power crank, so as to
make one side a revolving valve for the admission of the live steam or other fluid,
and the other side a similar revolving valve for the exit of the exhaust steam or
discharged fluid. The final means of entrance and exit for the live and exhaust
steam or fluid may be either conducted from the crank valve through the body of
the cylinder or through the central axis of the crank shaft. Into this hollow axis
the ends of pipes may be introduced and securely packed to carry off the exhaust
and admit the live steam or fluid.
I may also use a loose ring or rings, sleeves, or bushes upon the power crank or
shaft, which I make use of for the admission of live steam or fluid on the one side
through a separate port or ports, and also for the exit of the exhaust steam or
discharged fluid through other separate port or ports to the opposite side of the
power crank.
In an engine with single disc shaft I use the crank disc for a revolving valve

page_text: with or without rings or sleeves, as above described, and also apply a cranked pipe
revolving on the same axis, and entering the crank disc valve through the crank
pin, which may thus be used either for admission or discharge.
I apply the above power crank valve and arrangements as described to either
compounded cylinders or to a combined arrangement of two, three, four, or more
cylinders arranged either radially round a centre shaft, or side by side, acting upon
the same shaft.
To any of the before described engines I may apply an alternative valve arrange-
ment, which shall reduce the length of the ports between the valve and the cylinder
to the shortest possible length.
To effect this I use by preference a piston valve worked by an eccentric crank or
other suitable meaus at the extreme end of the working cylinders in a small bored
valve, bush, or cylinder. This cylinder may be solid or closed with a cover, and the
live steam or other fluid is admitted to this valve chamber at the outer end of the
valve, so that there is always a constant pressure from the live steam or other fluid
upon the piston valve to keep it bearing home always in compression upon the
eccentric crank or other actuating medium.
This constant compression valve may be modified by the use of one or more
pistons with differential areas in connection with a slide valve of any description to
an engine of any form.
In the case of an engine with two or more cylinders arranged radially around a
centre shaft, and fitted with link motion for expansion or reversal, I use a circular
plate or plates, around the centre axis to which are applied the aforesaid reversing
or expansion links. By the rotation of this circular plate all the valves may be
reversed and caused to vary their rate of expansion simultaneously.
My Invention in the second place is a modification of the foregoing valve and
cylinder arrangements, but with the central axis (herein-before described as the
crank shaft) now fixed, and thus becoming a fixed axis, round which the whole
casting containing the cylinders now revolves. The outside of this casting may be
cast with a rim and turned true, and thus is able to act the part of a fly-wheel and
driving rigger, or it may be fitted as a clip pulley, or as a circular saw, or with
gearing, as may be required. In this engine the valves remain stationary when they
are formed in the power disc, or are loose bushes or sleeves upon that crank or
shaft, and the engine may be reversed by shifting round the crank or the valves.
If the piston valves are used, the tumbler or usual actuating medium remains
stationary with the axis, and the valves and bearing blocks revolve round the
tumbler with the revolving cylinders. To reverse the engine the shaft or tumbler
has to be rotated through a suitable angle.
The specific apparatus I use by preference for reversing either a shaft or valves is
a system of three or more bevil wheels, of which two are keyed to the support and
the other to the crank, eccentric, or valve to be actuated. The intermediate wheel
or wheels are mounted on the reversing lever or apparatus. This apparatus is
applicable to any class of engine for the purposes described.
A further modification of my Invention is the construction of compounded
cylinders either to fixed, rotary, or any other engines, so that the connections
actuated by such compounded cylinders are always kept in constant compression.
This I effect by using the live steam or fluid first on the small area of the high
pressure piston furthest from the crank producing compression. The steam or fluid
is there expanded and worked, and then discharged into the nearest side of the low
pressure cylinder, which is open at the outer end to the atmosphere. The discharged
steam or fluid from the small cylinder is passed on through the large cylinder to
the condenser, where a vacuum is produced in the usual manner.
Such vacuum
again produces compression upon all the connections of the compounded cylinders
to the crank. When two or more cylinders are placed side by side the compression
valves may be actuated from an eccentric by a balanced beam.

page_text: SPECIFICATION in pursuance of the conditions of the Letters Patent filed by
the said Middleton Pratt in the Great Seal Patent Office on the 21st May
1879.
MIDDLETON PRATT, of 23, Rood Lane, in the City of London, Engineer.
PROVEMENTS IN HIGH SPEED AND ROTARY MOTORS."
«IM-
The object of my Invention is to produce a motor which is capable of running at
yery high speeds with economy, and without jar or rattle, and which may be
advantageously arranged so as to become a rotary engine round a fixed axis.
I may arrange my engine fixed to a suitable frame or foundation with two, three,
four, or more cylinders arranged at suitable angles round a centre, in which re-
volves a crank and shaft. This revolving crank may be made of such suitable
shape as to act as a valve for admission and exit of the steam or motive fluid, either
through one side or both. A loose ring or sleeves may be used on the power crank
or shaft for the admission and exit of the steam or other motive fluid.
But the arrangement I would wish particularly to claim and describe by the
Drawings annexed is that in which the central axis (hereinbefore described as the
crank shaft) is fixed, and thus becomes a fixed axis, round which the whole casting
containing the cylinders now revolves. The outside of this casting may be cast
with a rim and turned true, and thus is able to act the part of a fly-wheel and
driving rigger, or it may be fitted as a clip pulley, or as a circular saw, or with
gearing, as may be required. In this engine the valves remain stationary when
they are formed in the power disc, or are loose bushes or sleeves upon that crank
or shaft, and the engine may be reversed by shifting round the crank or valves.
If piston valves are used the tumbler or usual actuating medium remains stationary
with the axis, and the valves and bearing blocks revolve round the tumbler with
the revolving cylinders. To reverse the engine the shaft or tumbler has to be
rotated through a suitable angle.
I may use an apparatus for reversing either a shaft or valves in the form of
three or more bevil wheels, of which two are keyed to the support and the other to
the crank, eccentric, or valves to be actuated. The intermediate wheel or wheels
are mounted on the reversing lever or apparatus. This apparatus is applicable to
any class of engine for the purposes described, but I find the simplest method is as
illustrated in the Drawing annexed by means of a hand lever attached to the
sleeve valve or to the fixed crank.
To any of the before described engines I may apply an alternative valve arrange-
ment, which shall reduce the length of the ports between the valve and the cylinder
to the shortest possible length. To effect this I may use a piston valve worked by
an eccentric, crank, or other suitable means at the extreme end of the working
cylinders in a small bored valve, bush, or cylinder. This cylinder may be solid or
closed with a cover, and the live steam or other fluid is admitted to this valve
chamber at the outer end of the valve, so that there is always a constant pressure
from the live steam or other fluid upon the piston valve to keep it bearing home
always in compression upon the eccentric, crank, or other actuating medium.
in practice I find that in high speed motors the requisite compression of the exhaust
steam renders preferable the sleeve or crank valve, as hereinbefore described and
hereinafter more fully detailed and illustrated by the Drawing hereunto annexed.
But
A constant compression valve may be produced, as hereinafter more fully.
described, by the use of one or more pistons with differential areas in connection
with a slide valve of any description, and may be adapted to an engine of any
form.

page_text: In the case of an engine with two or more cylinders arranged radially around a
centre shaft, and fitted with link notion for expansion or reversal I use a circular
plate or plates around the central axis, to which are applied the aforesaid reversing
or expansion links, as hereinafter more fully described and illustrated by the
Drawing hereunto annexed. By the rotation of this circular plate all the valves
may be reversed and caused to vary their rate of expansion simultaneously.
I may modify my Invention by the application of compounded cylinders, either
to fixed or rotary engines, so that the connecting rods actuated by such compounded
cylinders are always kept in constant compression, but I find in practice that there
is no material advantage in the application of compounded cylinders to the rotary
motors I hereinafter more fully describe and claim, and I therefore restrict my
claim to the use of simple cylinders only, as therein described.
And in order that my Invention may be the better understood I now proceed to
describe the Drawings as hereunto annexed, that is to say,-
Figs. 1 and 2 show a sectional transverse and an outside longitudinal elevation
respectively of my improved rotary motor, arranged in this instance with three
cylinders A, A, A, surrounding a fixed cranked centre B. This cranked centre is
fixed by a plate C (Figs. 1 and 4) with hexagonal centre hole by studs to the
pedestal of the foundation plate D. The main casting formed by the three or more
cylinders A, A, A, has two strong hollow trunnions E, E, which, rotating with the
cylinders, form the supporting journals in the two side pedestals D, D. The
bearings for these journals are cast half out of the side pedestals and closed on the
upper half by two caps F, F, which are securely bolted to the pedestals. In the
Drawing the outside drum G is shown of wrought iron shrunk or fixed by wooden
blocks H over the end covers I of the three cylinders. But I may also cast this
circular drum as part of the same casting as the cylinders, and arrange that the
cylinder covers shall be moveable from the face of this circular drum by means of
suitable counter sunk studs.
The pistons J may be of any suitable form, but as shown, K is the connecting
rod, of suitable material, with a T head L, which takes the bearing in the piston
on a gun-metal setting, rivetted, or otherwise secured into its place. The other
end of the connecting rod contains the usual gun metal bearings on the fixed
crauk-pin, which are held in their position by circular wrought iron straps. The
pressure between the piston and the crank pin is always in compression from the
fact that in one half of the stroke the live steam is operating behind the
piston from the port M, and in the return stroke the resistance of the exhaust
steam is so arranged that it forms an ample cushion at the back of the piston to
keep it pressing home on its bearing on the fixed crank.
The fixed crank centre B may be made double so as to project both sides
through the centre of the hollow trunnions E, E, in which case the live steam
would be admitted through the hollow shaft, suitable port exits being arranged on
the circumference of the shaft similar to the valve piece N. This valve piece N, as
shown in Fig. 1, is an independent hollow tube, the inner end being enlarged into a
cone, in which there are two opposite openings or ports O and O', Figs. 1 and 3,
which latter Fig, shows a transverse section through the said valve. One of these
ports O, communicating with the hollow interior of the valve piece, admits the live
steam to the outer ends of the three or more pistons made use of by means of the
cast ports M, M, M, Fig. 3, respectively. When the piston has completed its stroke
the exhaust steam is driven back down these same ports M, M, M, through the
port O' in the valve, which, by the rotation of the cylinder, then comes into proper
juxtaposition into the interior chamber P of the main casting, and from thence is
delivered through the passage in the hollow fixed crank centre into the
atmosphere.
In this arrangement then the valve piece N remains stationary, being held in
position by the lever R keyed to it, and which rests upon either of the alternative
studs S, S', according to the direction in which it is wished that the cylinders

page_text: should rotate. When the lever rests on one of the studs, and rotation in that
direction consequently ensues, the motion may be instantly reversed by moving
over the lever R and the valve piece N attached to it so as to rest on the other
stud S. The coned end of the valve piece rests in a female coned bush inserted
into the revolving casting, and the valve piece is kept bearing upon this seating by
the spiral spring N¹.
The steam flange T is attached to the valve piece N by a loose coupling T¹, so
that whilst the valve piece N is free to move over for reversal with the lever R the
flange T remains a fixture with the steam pipe. The exhaust fange U is simply
screwed on to the fixed crank centre Q, since this is a fixture with the arrangement
described, and the exhaust pipe may thus be attached direct to it.
Fig. 5 shows an alternative arrangement of the valve piece for securing it in a
fixed position, when no reversing is required, with the fixed crank centre B. This
fixed crank centre B may be made with a projecting piece B¹ entering into a lug
bolted to the valve piece; this simplifies the attachment of the steam pipe to the
valve piece as it may be effected in this case by an ordinary steam pipe coupling T.
Figs. 6 and 7 are again alternative arrangements of the valve piece N arranged for
reversing and bringing the exit of the exhaust steam through the valve piece. In
Fig. 6 the live steam is admitted as before through the flange T and the port O,
and the exhaust is allowed to return through the port O' in the exterior chamber
of the valve piece to the exhaust flange U. In Fig. 7 the live steam is admitted
as before, but the exhaust is received in the hollow pedestal D, and issues therefrom
through the flanged orifice U.
Figs. 8 is two outside views of an arrangement of my improved rotary engine,
fixed inside a coned drum, for driving with different speeds any large lathe or
machine; T is the flange for the steam admission; U, the exhaust exit; and R is
the reversing lever by which the machine may be reversed.
Figs. 9, 10, and 11 show alternative arrangements by which a valve may always
be kept in compression bearing upon its eccentric connections always in the che
direction so as to prevent the possibility of rattle by wear. In Fig. 9 is shown the
arrangement of two piston valves, one being kept in constant compression by the
steam supply being behind it opposite to the eccentric tumbler. The lower a
arrange-
ment shows a differential piston valve in which the steam is carried between the
pistons, and thus throws an effective pressure on the larger piston to keep the
eccentric and connections always in compression. Fig. 10 shows a pair of such
differential compression piston valves operated through rocking links pivotted to a
radially moving frame which allows of different degrees of travel to be given to
the valves. Fig. 11 is a pair of ordinary slide valves operated as above through
expansive rocking links pivotted on radially moving frames, but to the slide valves
are applied pistons, one at the exterior of the valve chest, opposite to the eccentric,
working in a closed steam tight chamber with live steam pressure admitted to the
outside of the piston, and on the other side the piston is placed in an intermediate
position between the slide valve and eccentric, and the ordinary live steam in the
steam chest is used to press home the piston upon the eccentric and connections.
Fig. 12 shows an arrangement in which three or more ordinary expansion
links X, X, X, operated each by two ordinary eccentrics and rods, shown by the
thick lines, may be mounted on a circular frame which is geared at its circum-
ference, and may be rotated by a pinion y so as to cause all the rocking or
expansion links to alter their action on their respective valves simultaneously and
to an equal extent.
And from all the apparatus and arrangements herein described I would wish it
to be clearly understood that what I claim only as my Invention is,―
1st. The application to a rotary motor, as herein described, of single acting
pistons of any suitable number, which are supplied with steam or other fluid to
effect motion on the side of piston most distant from the fixed cranked centre,
round which the pistons revolve.

page_text: 2nd. The application of slide valve motions worked in compression, as herein
described, to any form of motor or steam engine in which such motion may be
advantageously employed.
In witness whereof, I, the said Middleton Pratt, have hereunto set my hand
and seal, this Nineteenth day of May, in the year of our Lord One
thousand eight hundred and seventy-nine.
.
Witness,
HENRY BOOTH,
Draughtsman to
The City Patent Office,
23, Rood Lane,
London, E.C.
MIDDLETON PRATT. (L.S.)