IMPROVEMENTS IN STEAM ENGINES
Year: 1865

page_text: LETTERS PATENT to Thomas Lester, of Wordesley, in the County of
Stafford, Engineer, for the Invention of "IMPROVEMENTS IN STEAM
ENGINES."
Sealed the 18th July 1865, and dated the 21st January 1865.
PROVISIONAL SPECIFICATION left by the said Thomas Lester at the
Office of the Commissioners of Patents, with his Petition, on the 21st
January 1865.
I, THOMAS LESTER, of Wordesley, in the County of Stafford, Engineer,
do hereby declare the nature of the said Invention for "IMPROVEMENTS IN
STEAM ENGINES," to be as follows:-
My Invention consists of the improvements herein-after described in the
steam passages, whereby the steam is made to enter and escape from the
cylinders of steam engines, and in the construction and working of the slide
valves of steam engines; the objects of my said improvements being to
secure the quick introduction of steam into the cylinder and the rapid escape
of the waste steam from the cylinder. I make the induction and eduction
passages in the cylinder much wider than usual, that is, I make them as
wide, or nearly as wide, as the diameter of the cylinder. I make the slide
valve and the steam chest or slide box in which it works of a like width. In
order to work the slide valve I fix at the top of its rod a vertical ring, within
which ring a horizontal axis made to rotate by the engine, and rotating at

page_text: the same speed as the crank shaft works. The ring described is of much
larger diameter than the end of the axis within it. The said vertical ring
carries two projections, one at top and the other at bottom, one being on one
side and the other on the other side of the ring. The end of the said axis
carries two cams or tappets, one of the said cams or tappets being so situated
that on the rotation of the axis it acts upon the upper projection on the ring,
and the other cam or tappet being so situated that it acts on the lower pro-
jection on the ring. On the working of the engine the position of the slide
valve is changed rapidly as the piston arrives near the end of its stroke, and
the steam is allowed to enter quickly into the cylinder on one side of the
piston, and the waste steam is allowed to escape quickly from the cylinder on
the opposite side of the piston, the back action of the waste steam thus being
got rid of.
My improvements are applicable to stationary, marine, and locomotive
steam engines, and are equally applicable to high-pressure and to condensing
steam engines.
SPECIFICATION in pursuance of the conditions of the Letters Patent, filed
by the said Thomas Lester in the Great Seal Patent Office on the 21st
July 1865.
TO ALL TO WHOM THESE PRESENTS SHALL COME, I, THOMAS
LESTER, of Wordesley, in the County of Stafford, Engineer, send greeting.
WHEREAS Her most Excellent Majesty Queen Victoria, by Her Letters
Patent, bearing date the Twenty-first day of January, in the year of our
Lord One thousand eight hundred and sixty-five, in the twenty-seventh year
Her reign, did, for Herself, Her heirs and successors, give and grant unto
me, the said Thomas Lester, Her special licence that I, the said Thomas
Lester, my executors, administrators, and assigns, or such others as I, the
said Thomas Lester, my executors, administrators, and assigns, should at any
time agree with, and no others, from time to time and at all times there-
after 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 STEAM ENGINES," upon the condition (amongst others) that I, the said
Thomas Lester, 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

page_text: 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 Thomas Lester, do hereby declare the
nature of my said Invention, and in what manner the same is to be per-
formed, to be particularly described and ascertained in and by the following
statement:-
The improvements which constitute this Invention (and as described in my
Provisional Specification thereof, lodged and recorded in the Great Seal
Patent Office on the 21st day of January 1865, No. 188) relate to steam
engines generally, in which the said Invention has for its object, first, an
improvement in the form of the steam passages for admitting the steam from
the steam chest, and allowing the escape of the waste steam from the cylinder
with greater rapidity. Secondly, an improvement in the slide valve and in
the mode of actuating the same for more rapidly changing the position of the
slide, thereby allowing the piston to work with the full power of the steam
nearer to the end of the stroke, while by the first-mentioned improvement
the back action of the waste steam is obviated or greatly reduced.
In carrying my first-mentioned improvement into effect I make the induc-
tion and eduction apertures in the cylinder and valve or steam chest, and the
passages between the same, of a width nearly equal to the inside diameter of
the cylinder.
In carrying out my second improvement I fit the connected. end of the
slide valve rod into or form it with a ring, within which ring (and to rotate
therein) I fit a transverse axis; this axis contains a short transverse shaft,
which is driven from the crank shaft, so that it revolves in equal times there-
with. Between the inner and outer diameters of the ring there is sufficient
depth of metal or space to form thereon or affix thereto cam studs or projec-
tions with inclined curved surfaces on each side of the said ring, one stud being
at the top and the other at the bottom of the ring. The end of the before-
mentioned rotating axis or short shaft which rotates within this ring carries
one cam or tappet on each side, which as this shaft rotates come into contact
with the inclined curved surfaces of the ring studs at the top and bottom, and
thus very rapidly raise and lower or move the ring and valve rod up and
down, the latter being stationary until the piston in the cylinder arrives very
close to the end of the stroke each way. The axis which carries the rotating
cams is made of sufficient length to allow one of the cams to clear the studs
on one side of the ring while the other cam is rotating in contact with the
studs on the opposite side of the ring. The axis slides upon its shaft upon a

page_text: I
feather and is moved laterally by a lever, so that the valve can be actuated
by. the cam and studs on either side, their contact on the right giving the
lead in one direction and on the left in the opposite direction, the simple
movement of the lever to the right or left being all that is required to reverse
the engine.
The said improvements are further illustrated upon the accompanying
Drawing, to which the following explanation refers :-
Fig. 1 is a front elevation of a steam cylinder as formed with the enlarged
ports; Fig. 2, a transverse section through the centre, shewing the slide valve,
steam chest, and enlarged passage; Fig. 3, a plan view at the line A, B, of
Figs. 1 and 2; Fig. 4 shows the face plan of the valve, and Fig. 5, a vertical
section through C, D, of Fig. 4; Fig. 6 is a side view of the ring, axes, and
shaft, shewing the cam and studs; Fig. 7, a side view of the same, and
Fig. 8, a plan view thereof.
I claim the improvements substantially as described, but do not restrict
myself to the precise dimensions shown upon the Drawings.
In witness whereof, I, the said Thomas Lester, have hereunto set my
hand and seal, this Twenty-first day of July, in the year of our Lord
One thousand eight hundred and sixty-five.
תnamז חmriTAIL
T
T
THOMAS
(1.5.)