IMPROVEMENTS IN STEAM ENGINES."
Year: 1878

page_text: LETTERS PATENT to John Leake Dexter, of Bourne End, in the County of
Bucks, Engineer, for the Invention of "IMPROVEMENTS IN STEAM ENGINES."
PROVISIONAL SPECIFICATION left by the said John Leake Dexter at the
Office of the Commissioners of Patents on the 4th December 1878.
JOHN LEAKE DEXTER, of Bourne End, in the County of Bucks, Engineer. “IM-
PROVEMENTS IN STEAM ENGINES."
This Invention relates to certain useful and economical improvements in the con-
struction of steam engines.
In carrying out my Invention I construct the engine in a form somewhat similar
to a rotary engine, and I obtain the power by causing the steam to act on two or
more slides in such a manner as to cause a roller (in which they reciprocate or
work) to revolve in a cylinder and give the desired rotation to a shaft or shafts
connected to it and to the machinery or apparatus which is required to be driven.
The cylinder is formed with guides fitted or cast within it, and is provided with
a roller concentric within it, mounted on axles carried or supported by the cylinder
covers, and one of which is prolonged through its cover, or both of which may be
prolonged through their respective covers, to form the shaft or shafts for connection
with the machinery.
The roller has a through slot in which slides are fitted so as to reciprocate therein
in opposite radial directions should there be but two, and its ends are recessed to
take in cams which are attached one to each cylinder cover, and the slides are so.
formed as to clear the cams behind shoulders thereof which abut thereupon.
The interior of the cylinder is divided preferably at the top by a steam tight
divider, which fits well down onto the roller, and in order that the engine may be
worked expansively it is fitted with an expansion valve which is worked by an
eccentric from the main shaft in the ordinary way so as to cut off the steam at any

page_text: required portion of the stroke; and so that it may be made reversible it is fitted
with a two-way regulator-cock, the plug of which is made so as to admit steam to
either side of the divider as required, the exhaust being effected through the body
of the cock, or vice-versa.
Upon steam being admitted to the cylinder it acts upon the slide on the same
side of the divider, and which is kept against the inner periphery of the cylinder
by the cams, causing the revolution of the roller and its shaft or shafts. Upon this
slide reaching a certain point the second (and opposite) slide receives the full pressure
of steam, the first slide being gradually forced into the roller by the guides within
the cylinder until it gets flush therewith as it passes under the divider, when it is
again gradually forced out by the cams until it reaches a point in the cylinder
opposite to that last mentioned, when it is full out and again takes the pressure of
the steam, the guides on this side of the divider admitting of the expansion of the
steam against the second slide until the first slide is fully out, when it receives the
pressure of the steam and the guides on the opposite side of the divider, allowing of
the exhaust, through the cock into the exhaust pipe from the moment the first slide
takes the steam. This motion and action of the slides is continuous, and is caused
upon steam being admitted to the cylinder by the said guides and cams, and results
in the rotation of the roller and the main or driving shaft or shafts in connection
therewith.
The engine can be momentarily stopped or reversed by simply shifting the
position of the through way in the plug of the cock to over or to the other side of
the divider.
In the case of stationary engines running always one way the roller may be
placed excentric with the cylinder instead of concentric therewith, as above
described.

page_text: SPECIFICATION in pursuance of the conditions of the Letters Patent filed by
the said John Leake Dexter in the Great Seal Patent Office on the 3rd
June 1879.
JOHN LEAKE DEXTER, of Bourne End, in the County of Bucks, Engineer. "IM-
PROVEMENTS IN STEAM ENGINES."
This Invention relates to certain useful and economical improvements in the
construction of steam engines.
The Invention is illustrated on the accompanying Sheet of Drawings in Figures 1
and 2, which respectively represent a transverse section and a longitudinal section.
In carrying out my Invention I construct the engine as or in a form somewhat
similar to a rotary engine, as shown most clearly in Figure 1, and I obtain the
power by causing the steam to act on two or more slides 1, 2, in such a manner as
to cause a roller 3 (in which they reciprocate or work) to revolve in a "cylinder" 4
and give the desired rotation to a shaft (or shafts) 5 connected to it and to the
machinery or apparatus which is required to be driven.
The cylinder 4 is formed with guides 7, 8, fitted or cast within it, and is pro-
vided with the roller concentric within it and mounted on axles 5, one or both of
which may be prolonged to form the, shaft or shafts for connection with the
machinery requiring to be driven.
The axles 5 are preferably coned at 26 and fitted in bushes of brass or some
equivalent bearing metal; the glands fit this, and as the bushes wear away are
tightened up so as to keep the roller at all times perfectly céntral.
The roller 3 has a through slot 10 in which the slides 1, 2, are fitted so as to
reciprocate therein in opposite radial directions should there be but two, as shewn
in Figure 1, and its ends are recessed as at 11 to take in cams 12 which are attached
one to each cylinder cover 9, and the slides 1, 2, are so formed as to clear the cams 12
behind shoulders 13, with which they are formed, and which shoulders abut upon
the outer peripheries of the cams.
The interior of the cylinder is divided preferably at the top by a steam tight
divider 14, which fits well down onto the roller, as shown most clearly in Figure 1.
Or the guides may be fitted to the cylinder and divider in such a manner by recessing
the divider that the guides are flush with the surface fitting on the roller, an
advantage of which arrangement would be that as the divider wears it can be
adjusted by set screws, and the guides being brought down with it everything
would work smoothly.
In order that the engine may be worked expansively it is fitted with an expansion
valve 15, which is worked by an excentric 16 from the main shaft 5 in the ordinary
way so as to cut off the steam at any required portion of the stroke; and so that
it may be made reversible it is fitted with a sort of two way regulator cock 17, the
plug 18 of which is made so as to admit steam to either side of the divider 14 as
required, the exhaust being effected through the body of the cock, or vice versa.
Now the action of the above described improved engine is as follows :-
Upon steam being admitted to the cylinder on (say) the side indicated by the
arrows 19 through the port 6 it acts upon the slide 1 on the same side of the
divider, and which is kept against the inner periphery of the cylinder by the cams 12
upon which its shoulders 13 abut, causing the revolution of the roller and its shaft or
shafts 5. Upon the slide 1 reaching a certain point 20 the second and opposite
slide 2 reaches the point 21 and receives the full pressure of steam; as the slide 2
then progresses in its motion the slide 1 is gradually forced into the slot or recess 10
of the roller 3 by the guides 7 until it gets flush therewith as it passes under the
divider 14, so as during all this time to allow of the exhaust steam escaping through
the port 22 and through the body of the cock 17 into the exhaust pipe, as indicated
by the arrows 23. As the slide 1 emerges from under the divider 14 it is again

page_text: gradually forced out by the cams 12 until it reaches the point 21 when it is full
out and again takes the pressure of the steam; the guides 8 on this side of the
divider, and the clearance 24 with which the cylinder is formed, admitting of the
expansion of the steam against the slide 2 until the slide 1 is fully out, when it
receives the pressure of the steam; and the guides 7 on the other side of the divider,
and the clearance 25 with which the cylinder is formed, allowing of the exhaust
through the cock 17 into the exhaust pipe from the moment the slide 1 takes the
steam.
This motion and action of the slides is continuous upon steam being admitted to
the cylinder, and is caused by the said guides and cams, and results in the rotation
of the roller and the main or driving shaft or shafts in connection therewith.
The engine can be momentarily stopped or reversed by simply shifting the
position of the through way of the plug of the cock to over or to the other side of
the divider.
In the case of stationary engines running always one way the roller may be
placed excentric with the cylinder instead of concentric therewith, as above
described, so as to give a larger area of the slides for the steam to act on at the
latter end of the stroke when pressure is diminished by expansion, and prevent the
irregularity in the work caused by such diminished pressure.
Having now described the nature and object of my said Invention, together 2
with the manner in which the same is to be or may be performed or carried into
practical effect, I would remark in conclusion that what I clain as the Invention
secured to me by the hereinbefore in part recited Letters Patent is,-
The manufacture or construction of the cylinders of steam engines in the improved
form shown in Figure 1 of the accompanying Sheet of Drawings, and the use in 2
combination therewith of a roller to which the shaft (or shafts) of the machinery
requiring to be driven is connected, or with which it is in connection, the roller
being rotated so as to effect the driving of the said shaft or shafts by causing steam
to act on or against two or more slides which reciprocate or work in the roller, and
the reciprocating movements of which are effected and controlled by guides and 3
cams fixed within the cylinder, and by a steam tight divider, substantially as above
described, and as illustrated on the accompanying Sheet of Drawings. And I also
claim,――
The rendering of such an engine instantly reversible by fitting the same with a
two way regulator cock, by the simple shifting of the plug of which to over or to 3
either side of the said steam-tight divider the engine may be instantly stopped or
driven in either direction as required, substantially as above described.
In witness whereof, I, the said John Leake Dexter, 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.
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