IMPROVEMENTS IN STEAM ENGINES
Year: 1874

page_text: LETTERS PATENT to John Henry Johnson, of 47, Lincoln's Inn
Fields, in the County of Middlesex, Gentleman, for the Invention
of "IMPROVEMENTS IN STEAM ENGINES." A communication from
abroad by François Correy, of Paris, in the Republic of France.
Scaled the 14th August 1874, and dated the 16th May 1874.
PROVISIONAL SPECIFICATION left by the said John Henry Johnson
at the Office of the Commissioners of Patents, with his Petition, on
the 16th May 1874.
I, JOHN HENRY JOHNSON, of 47, Lincoln's Inn Fields, in the
County of Middlesex, Gentleman, do hereby declare the nature of the
said Invention for "IMPROVEMENTS IN STEAM ENGINES," a communica-
tion to me from abroad by François Correy, of Paris, in the Republic
of France, to be as follows:-
This Invention relates to variable expansion gear to be applied to two.
cylinder, vertical, and horizontal engines, and consists of a peculiar
arrangement and construction of apparatus whereby the period or part.

page_text: admission orifices or ports are opened with rapidity and instantaneously
closed.
In carrying out this Invention the slide valve of the small cylinder is
formed with two openings or ports which extend through its entire
thickness and open a communication between the valve chest and the
two sides of the piston alternately, such slide valve being actuated by an
eccentric in the usual manner. On the outside of the valve there are
placed two sliding plates or valves which are arranged independently of
each other, but so as to work in contact with the outer surface of the
slide valve of the cylinder and to respectively cover at the required time
the corresponding orifices or ports. These sliding plates or valves are
actuated by eccentrics from the same shaft as the slide valve of the
cylinder, but are so connected with the eccentric or connecting rods that
while the effect of cach eccentric is to remove the sliding plate or valve
from and uncover the corresponding orifice or port, the eccentric or
connecting rod becomes detached from the sliding plate or valve at the
required period, and such sliding plate or valve is caused to fall
instantaneously and cover its corresponding orifice or port and cut off
the communication between the valve chest and the cylinder. In order
to effect this each eccentric or connecting rod slides or works in a tube
or casing which is secured to a rod carried by the sliding plate or valve,
and the end of the rod is formed with a shoulder or projection which is
caused to come in contact with a stop capable of lateral motion, through
the intervention of which stop the motion of the eccentric is transmitted
to the sliding plate or valve for the purpose of opening the orifice or
port. The stop is attached to a bell-crank lever, which, by the motion
of the eccentric rod, is caused to come in contact with a curved segment
or projection connected with the governor which acts upon the stop and
releases the eccentric or connecting rod, so that the sliding plate or valve
being free, instantaneously falls and covers the corresponding orifice or
port and cuts off the steam, a spring being employed for the purpose of
bringing back the stop to its normal position. The rods of the sliding
plates or valves are provided with the pistons, on which the steam acts so
as to aid in their descent, an air chamber being formed at the opposite side
of such pistons (the escape of air from which is capable of being
regulated) for the purpose of deadening or diminishing the shock. This

page_text: arrangement in conjunction with the use of an india-rubber washer
admits of stuffing boxes being dispensed with.
In some cases a single sliding plate or valve acting upon both orifices
or ports may be employed, the eccentric being carried on a shaft
actuated through the intervention of gearing so as to admit of the
sliding plate or valve being opened and closed twice during one revolu-
tion of the crank shaft.
SPECIFICATION in pursuance of the conditions of the Letters Patent,
filed by the said John Henry Johnson in the Great Seal Patent
Office on the 23rd October 1874.
TO ALL TO WHOM THESE PRESENTS SHALL COME, I, JOHN
HENRY JOHNSON, of 47, Lincoln's Inn Fields, in the County of
Middlesex, Gentleman, send greeting.
WHEREAS Her most Excellent Majesty Queen Victoria, by Her
Letters Patent, bearing date the Sixteenth day of May, in the year of
our Lord One thousand eight hundred and seventy-four, in the 37th
year of Her reign, did, for Herself, Her heirs and successors, give and
grant unto me, the said John Henry Johnson, Her special license that I,
the said John Henry Johnson, my executors, administrators, and assigns,
or such others as I, the said John Henry Johnson, my executors, admi-
nistrators, or 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 Invention for "IMPROVEMENTS IN STEAM
ENGINES," a communication to me from abroad by Francois Correy,
of Paris, in the Republic of France, upon the condition (amongst
others) that I, the said John Henry Johnson, my executors or admi-
nistrators, by an instrument in writing under my hand and seal,
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

page_text: NOW KNOW YE, that I, the said John Henry Johnson, do hereby
declare the nature of the said Invention, and in what manner the same
is to be performed, to be particularly described and ascertained in and
by the following statement, reference being had to the accompanying
Drawings, and to the letters and figures marked thereon, that is to
say:-
The said Invention relates to variable expansion gear to be applied to
compound or two cylinder, vertical, and horizontal engines, and which
is also applicable to engines in which a single cylinder is employed, and
it consists of a peculiar arrangement and construction of apparatus
whereby the period or portion of the stroke at which the steam is cut off
in the small cylinder (when two cylinders of different diameters are
employed) or in the single cylinder (when only one is used) is regulated
by means of the position of the balls of the governor, and the admission
orifices or ports are opened with rapidity and instantaneously closed.
And in order that the said Invention may be fully understood I shall
now proceed more particularly to describe the same, and for that purpose
shall refer to the several Figures on the annexed Sheet of Drawings, the
same letters of reference indicating corresponding parts in all the
corresponding Figures.
Figure 1 of the Drawings is a vertical section taken through the
centre of the valve box or steam chest, and shewing the application to
the small cylinder of a vertical compound engine of an apparatus con-
structed in accordance with this Invention. Figure 2 is a sectional
elevation and Figure 3 a horizontal section of same.
Figure 4 is a vertical section and Figure 5 a horizontal section,
showing the detent apparatus employed in effecting the motion of the
expansion valves.
Figure 6 is a sectional elevation, and Figure 7 a corresponding sectional
plan of a portion of a single cylinder horizontal engine having the
improved system of expansion gear applied thereto.
Figure 8 shews the detent apparatus for the expansion valve of the
rear end of the cylinder, which apparatus in this modification acts in
the opposite direction to that shewn in Figures 4 and 5.
In the arrangement Figures 1, 2, and 3, the ordinary slide valves for
both the small and large cylinder are retained with the triangular
eccentric keyed on the shaft A for actuating such valves,

page_text: The slide valve of the small cylinder is provided with two rectangular
openings or ports which extend through its entire thickness, and two
sliding plates or valves b, b¹, are employed, working in contact with the
back surface of such valve, which sliding plates or valves are capable,
by falling suddenly, of closing the openings or ports in the main valve
and cutting off the supply of steam to the small cylinder at any portion
(varying from say nought to three-quarters) of the stroke of the piston.
The sliding plates or valves b, b', are respectively carried on rods a, a',
which are entirely independent of and arranged parallel to each other,
and each rod enters a tubular opening bored out for its reception in the
valve box or steam chest B, and forms a tight piston therein on which
the steam exercises its pressure. The ordinary stuffing boxes and springs
are dispensed with, the small pistons herein-before described, together
with india-rubber washers c³, which are gripped or pressed by the
attachments C, C₁, being employed in substitution therefor. These
attachments C, C¹, which are bolted to the valve box or steam chest
constitute air cylinders, in which work pistons d, d¹, formed on or
carried by the rods a, a¹, respectively. Screws e, e¹, a portion of the
thread of which is removed by forming a small groove therein are
employed so as to admit of the regulating of the escape of the air under
the pistons in order to deaden or lessen the shock produced by the
instantaneous closing of the openings or ports. A blow-off cock com-
municating with the two cylinders is provided at f opposite a space or
clearance formed around the rods for the purpose of preventing water or
steam from penetrating into the air cylinders should the washers not
produce a perfectly tight joint.
To the lower extremity of the rods K, K', of the pistons d, d¹³, there
are respectively keyed the tubes h, h¹, which carry the detent apparatus
of the valve gear, shewn more clearly on an enlarged scale in Figures
4 and 5, and two other rods i, ¹, actuated directly by the two eccentrics
j, j', keyed on the shaft A enter the interior of the tubes h, h¹,
respectively, which serve as a guide in which the rods i, i, may move
without undue friction. The upper extremity of the rods i, i, is made
of an elliptical form (as shewn in the sectional plan Figure 5) by cutting
away a portion of the rod on one side to the same radius as that of the
rod itself, and thus forming a shoulder which is faced with hardened
steel. K³ are stop pieces composed of steel which fit into square
openings formed in the tubes h, h', respectively, and are moved back-

page_text: wards horizontally by means of the bell-crank levers 1, 1, when the
latter are acted upon by the segments or cams g, g¹, as herein-after
explained. The stop pieces K2 are made tubular and of a semi-circular
form on their interior so as to exactly fit on to their respective rods i, i¹,
against which they are maintained by the helical springs m. Taking
the valve b as an example when the eccentric arrives at the end of its
down stroke the shoulder of the rod i comes in contact with the stop
piece K, and the tube is thereby caused to rise during the up-stroke
of the eccentric, the sliding plate or valve partaking of its motion and
uncovering the admission opening or port until the motion of the stud
which is carried on the bell-crank lever is arrested by coming in
contact with the segment or cam g connected with the governor, which
action has the effect of pressing the stop piece K2 outwards so as to
cause it to become clear of the shoulder of the rod, at the same time
compressing the spring m. The stud /² is composed of steel, and secured
to the bell-crank lever by means of two nuts, which admit of the
position of such stud being regulated with facility so as to compensate
for wear or for any other required purpose. When the rod i is released
from the stop piece K² the connection between the sliding plate or valve
and the eccentric ceases, and the pressure of the steam acting upon the
small piston d causes it to fall suddenly, conducting with it the sliding
plate or valve, which is then caused to cover the opening or port and cut
off the supply of steam to the cylinder. The curvature of the segments
or cams 9, 9', is so arranged that the closing of the admission openings
or ports will correspond to cach position of the governor balls. The
distance which the stud moves is always the same, whatever may be the
position of the segment or cam and the strain produced by the act of
the parts coming into contact has simply a vertical component passing
through the centre of the shaft, and has no effect upon the action of the
governor.
:
With the apparatus herein-before described having two eccentrics and
two separate sliding plates or valves, the period during which the steam
is supplied to the cylinder may be varied from nought, that is to say, the
stopping of the engine to three-quarters of the stroke. In the case of small
engines performing light duty a supply to the cylinder for a period
varying from nought to half of the stroke will be sufficient, and one only
of the apparatus herein-before described may be employed. The two
sliding plates or valves will then simply form a single slide valve of small
.

page_text: dimensions, such valve being composed of two valve faces united by a
tube or socket which is carried on a single rod keyed to the rod of the
small piston. In this case it is necessary that the eccentric should be so
arranged as to effect the opening and closing twice during one turn of
the crank, for which purpose such eccentric may be carried on a small
shaft actuated by means of a pinion and spur wheel in the proportion of
one to two. This method of actuating by means of gearing admits of
the axis of the shaft carrying the eccentric which operates the expansion
gear being arranged in the vertical plane passing through the rod of the
small valve.
Figures 6 and 7 shew the application of this system of expansion
gear to a horizontal engine having a single cylinder. In this arrange-
ment the apparatus acts upon independent admission slide valves placed
at each end of the cylinder and worked by a single eccentric, which also
operates the exhaust valves. This eccentric, which thus actuates the
whole of the valves, transmits its motion through the intervention of the
bar a and a lever c to a shaft 6 arranged at right angles to the centre of
the engine. To the shaft there are keyed three other levers d, e, f,
the one d of which attached to the connecting rod works the two
exhaust valves h, h', which operate in a similar manner to ordinary slide
valves, the steam passing to the condenser by the passages j, j', whilst
the other two levers e, f, actuate the two admission valves by means of
the two rods i, i, corresponding to the rods i, i, of the apparatus hercin-
before described (Figures 1 and 2). K, K', are the admission slide
valves, which are formed with plane surfaces, and are maintained in
equilibrium by a friction surface parallel to the valve face. The detent
apparatus for the valve K at the front of the cylinder is identical with
that shewn in Figures 4 and 5, and the detent apparatus for the valve
K' at the rear of the cylinder is also similar in construction, and operates
in a similar manner to the former, but in the opposite direction as shewn
in the enlarged view Figure 8.
When the valve K is forced back steam is admitted to the front of the
piston until the stud 2 of the detent apparatus comes in contact with the
segment or cam 1, which is controlled by the governor.. The lever f
which actuates the valve K¹ also operates in a similar manner to the
lever e, but it is requisite that during the motion of the valve K the
valve K' should be closed (the rod of such latter valve having been
disengaged during the preceding half stroke) and that the valve itself

page_text: should rest against the india-rubber washer with which the bottom of
the small air cylinder is provided. During the reverse motion from the
rear to the front the valve K is closed, and its rod is disconnected by the
release of the detent, whilst the valve K' is brought by means of the
shoulder m (Figure 8) of its rod into a position to open the port until
the stud h² of the detent apparatus comes in contact with the segment
or cam when the detent is released from the shoulder, and the valve
thus becomes free to be conducted by the pressure of the steam acting
upon the small piston of its rod towards the rear of the cylinder, and
thus closes the port. The two segments or cams 1, 1, are both fast on a
small shaft n, which is actuated from the governor through the inter-
vention of levers.
Having now described and particularly ascertained the nature of the
said Invention and the manner in which the same is or may be used or
carried into effect, I would observe in conclusion that what I consider
to be novel and original, and therefore claim as the Invention secured
to me by the herein-before in part recited Letters Patent is, the
peculiar arrangement and combination of variable expansion gcar
whereby the period or portion of the stroke of the piston at which the
steam is cut off is regulated by the action of the governor, substan-
tially as herein-before described and illustrated by the accompanying
Drawings.
In witness whereof, I, the said John Henry Johnson, have to this
my Specification set my hand and seal, the Twenty-second
day of October One thousand eight hundred and seventy-
four.