IMPROVEMENTS IN STEAM ENGINE INDICATORS
Year: 1875

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 ENGINE INDICATORS."A communication
from abroad by Albert Michel Jouët-Pastré, Manager, and acting
in the name of the Société Nouvelle des Forges et Chantiers de la
Mediterranée, of Paris, in the Republic of France.
Sealed the 12th May 1876, and dated the 17th December 1875.
¿PROVISIONAL SPECIFICATION left by the said John Henry Johnson
: at the Office of the Commissioners of Patents, with his Petition,
on the 17th December 1875..
I, JOHN HENRY JOHNSON, of 47, Lincoln's Inn Fields, in the County
5 of Middlesex, Gentleman, do hereby declare the nature of the said
Invention for "IMPROVEMENTS IN STEAM ENGINE INDICATORS," a communi-
cation to me from abroad by Albert Michel Jouët-Pastré, Manager, and
acting in the name of the Société Nouvelle des Forges et Chantiers de
·la Mediterranée, of Paris, in the Republic of France, to be as
0 follows:
:

page_text: "
indicator, adapted more particularly for obtaining diagrams when the
engines are working at a high speed, and this object is attained by
constructing the apparatus in the manner herein-after described.
In carrying out this Invention a small cylinder is employed containing
a piston, which forms one with a spring susceptible of compression
according to the force exerted on such piston. The rod of the piston
prolonged is directly connected to the metallic pencil for drawing the
diagram, and an axis is provided mounted at a suitable height on a
pinching collar surrounding the cylinder.
The whole of the preceding combination forms one constituent portion
of the apparatus. The other portion of the apparatus, which is destined
to present to the pencil the paper on which the diagrams are to be
traced, is composed of a small fly wheel independent of the portion of
the apparatus first herein-before described, and of the engine which
forms the subject of the experiment. The fly wheel is arranged to
receive the paper on the plane surface of one of the sides of its rim, such
paper cut out in an annular shape being introduced into a circular
groove or rabbet, and retained at its internal circumference by a hoop
carrying pins which form a bayonet joint. The centre of the fly wheel is
provided with; a small socket bored to the diameter of the axis carried
on the first part of the apparatus, as before mentioned, which socket is
fitted at the bottom with a spring and pin retained by a knob or handle,
which itself carries a moveable knob.or button.
The two parts of the indicator are fitted together when the observation
is to be taken by placing the small fly wheel provided with the paper
upon the axis before mentioned.
In applying the instrument it is simply.necessary to screw the first
part of the apparatus into the side or end of the cylinder of the, engine
to be tried, the direction of the axis being, rendered capable of adjustment
by means of the pinching collar so as to maintain, the flywheel in the
.required position.
The apparatus is operated in the following manner: After;blowing
off as usual by opening the cock situate at the foot of the indicator: the
small fly wheel is placed upon its axis, and a rotary motion is; imparted
'to it by the aid of the knob ort handle, or otherwise, the operator at the
same time depressing the outer knob or button, whereby the spring of
the pin is compressed, and the paper carried on the fly wheel in motion

page_text: brought in contact with the pencil for the latter to trace in the first
instance the line of atmospheric pressure. After opening the cock which
places the apparatus in communication with the interior of the cylinder
of the engine to be tried a fresh impulse is given to the fly wheel so as
to cause it to make about 1/10th of the number of revolutions of the
engine, and the knob or button is again depressed, when the curves or
diagrams will be obtained.
The diagrams obtained with this apparatus present the following
peculiarities:-
The counter pressure follows the pressure instead of returning and
ending the curve. In order to find the points of separation, after
drawing radiating lines to the summits of the diagrams, which are
always clearly defined, and dividing equally the distance between them,
the respective extremities of the individual strokes will be obtained.
The rotatory motion of the fly wheel, which may be regarded as
uniform, during the time employed in tracing a diagram, that is to say,
for about one-tenth of a second, produces a curve or diagram, which in
order to express the corresponding pressure at each point of the course
of the piston of the engine which is being tried should be interpreted by
a diagram of the relations of the points of the circumference described
by the stud of the crank with the corresponding points passed over by
the piston, taking into consideration the length of the connecting rod in
each particular case.
It is obvious that the details of the apparatus may be greatly modified
in practice, the Invention consisting partly in dispensing in the first
portion of the apparatus with all intermediate devices connected with
the pencil, but more particularly in the use of the small fly wheel
carrying the paper, and actuated by hand or otherwise.

page_text: WHEREAS Her most Excellent Majesty Queen Victoria, by Her
Letters Patent, bearing date the Seventeenth day of December, in the
year of our Lord One thousand eight hundred and seventy-five, in the
39th 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, administrators, 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 ENGINE INDICATORS," a communication to me
from abroad by Albert Michel Jouet-Pastré, Manager, and acting in
the name of the Société Nouvelle des Forges et Chantiers de la
Mediterranée, of Paris, in the Republic of France, upon the condition
(amongst others) that I, the said John Henry Johnson, my executors
or administrators, 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.
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 has for its object the production of a steam engine
indicator adapted more particularly for obtaining diagrams when the
engines are working at a high speed, and this object is attained by
constructing the apparatus in the manner herein-after described.
The indicator at present in use are constructed upon the principal of
what is known as Watts' indicator, from which they differ only in
arrangements of detail in their action; they consist of two principal
parts, namely,

page_text: .
First. A small steam cylinder with its piston acted upon by the
pressure and diminution in pressure of the steam operating in the
interior of a steam engine cylinder during a complete stroke of the.
motive piston. Under the influence of these pressures and variations.
the small piston forming one with a spring is caused to move above or
below the point corresponding to the pressure of the atmosphere, the
extent of which movements is in proportion at all points to the intensity
of the pressure. The rod of the small piston has fixed to it a style or
pencil by means of a suitable holder which maintains it in contact
with the paper on which it is intended to trace the indicator diagrams.
The second part of the apparatus consists of devices for presenting
to the style or pencil a sheet of paper having a rectilinear motion, the
extent of which may vary without ceasing to be precisely similar to the.
rectilinear motion of the motive piston; this movement is obtained by
attaching the end of the spring drum on which the paper is rolled to
the rod of the motive piston by means of levers or pullies, at the same.
time reducing the rectilinear traverse of the piston.
The diagrams obtained with these instruments when well made and
in good condition, and applied directly to the ends or sides of the
cylinders with orifices of wide section are considered sufficiently exact
when the engine is working at a speed not exceeding, say from 250
to 300 revolutions, but beyond this speed the influence of the inertia of
the parts in motion chiefly in the second portion of the apparatus
paralyzes its functions, so that it is rendered altogether unsuitable for a
speed exceeding 350 revolutions. Now this Invention has for its object
rendering it practicable to obtain similar diagrams with a far higher
number of revolutions say, from 500 to 1000 revolutions for example.
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 Figures.
The improved apparatus like the ordinary apparatus is also composed
of two principal parts.
Figure 1 of the accompanying Drawing represents a sectional elevation
of the first part of the apparatus; and Figure 2 is a corresponding front
view of the same.

page_text: Figure 3 is a transverse section shewing a small fly wheel which is
employed to receive the paper on which the diagrams are to be recorded,
such fly wheel being independent of the engine; and Figure 4 is a detail
view shewing the mode of connecting the ring which retains the paper
to the rim of the wheel as herein-after described.
The first part of the indicator comprises a small cylinder A containing
a piston A'; this piston forms one with a spring B which may be con-
structed of various shapes provided that it fulfils the condition of being
susceptible of degrees of compression proportional to the force exerted
on the small piston A¹. The rod Ċ prolonged is directly connected to
the style or metallic pencil C. It has been found that by reducing
these latter parts to the greatest simplicity and lightness, as many
as 1,000 oscillations per minute may be obtained reproducing in a
pratically satisfactory manner the pressures in the cylinder of the engine
which is being tried. This first part of the apparatus carries an axis D
at a suitable height mounted on a pinching collar E.
The second part of the apparatus, the function of which is to present
to the style or pencil C¹ the paper on which the diagrams are to be traced
is composed of a small fly wheel V wholly independent of the first portion
of the apparatus, and of the engine which forms the subject of the
experiment. The fly wheel is arranged to receive the paper on the
plane surface of one of the sides of its rim; for this purpose the paper
cut out in an annular shape is introduced at its external circumference
into a small circular groove or rabbet F, and is retained at its internal
circumference by a hoop G carrying pins G¹, which form a bayonet
joint, as shewn in Figure 4. The centre of the fly wheel V is provided
with a small socket H bored and rimed to the diameter of the axis D of
the first part of the apparatus, and fitted at the bottom with a spring
and pin I retained by the knob or handle K, which itself carries a
moveable knob or button K¹.
The two parts of the indicator are fitted together when the observation
is to be taken by placing the small fly wheel V provided with paper
upon the axes D, as shewn by dotted lines in Figure 1.
In applying the instrument it is simply necessary to screw the first
part of the apparatus into the side or end of the cylinder of the engine
to be tried; its position may be vertical, horizontal, or oblique, provided
that the axis D, the direction of which can be adjusted as required by

page_text: means of the pinching collar E, is not inclined out of the horizontal so
as to allow the fly wheel to spring back by its weight at the moment of
taking the observation.
31144
The working of the instrument is most simple. After blowing off as
usual by opening the cock situate at the foot of the indicator the small
fly wheel V is placed upon its axis D, and a rotary motion is imparted
to it by the aid of the knob or handle K, the operator at the same time
depressing the outer knob or button K', whereby the spring of the pin I
is comprised, and the paper carried on the fly wheel V in motion is
brought in contact with the style- or pencil O¹ for the latter to trace in
the first instance the line of atmospheric pressure. After opening the
cock which places the apparatus in communication with the interior of
the cylinder of the engine to be tried a fresh impulse is given to the fly
wheel so as to cause it to make about one-tenth of the number, of revolu-
tions of the engine, and the knob or button K' is again depressed for the
space,of, say, about one second, and ten curves or diagrams will be
obtained for one observation. In the form indicated in Figure 2 the
upper portion shows diagrams as obtained from a high-pressure non-
condensing engine, and the lower half diagrams from a condensing
engine.
1
The diagrams obtained with this apparatus present the following
peculiarities-The counter pressure follows the pressure instead of
returning and ending-the curve. In order to find the points-of-separa-
tion after drawing radiating lines, as shewn by the red full lines in
Figure 2, to the summits of the diagrams, which are always clearly
defined, and dividing equally the distance between them, as shewn by
the red dotted lines in that Figure, the respective extremities of the
individual strokes will be obtained.
The rotatory motion of the fly wheel, which may be regarded as
uniform during the short time occupied in tracing a diagram, that is to
say, for about one-tenth of a second produces a curve or diagram, which in
order to express the corresponding pressure at each point of the stroke
of the piston of the engine under trial should be interpreted by the very
simple diagram of the relations of the points of the circumference
described by the stud of the crank with the corresponding points passed
over by the piston, taking into account the length of the connecting rod
in each particular case.

page_text: The improved apparatus, the details of which may be greatly modified
in practice, in addition to its great simplicity, possesses the further
advantage of being completely preserved from all influence of inertia in
its second portion, whatever may be the number of revolutions of the
engine which is being tried.
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 employment in a steam engine indicator of a fly wheel actuated by
-the hand or otherwise for carrying the paper on which the diagram is to
be traced, and presenting such paper to the tracing style or pencil, con-
"nected without the aid of intermediate devices to the rod of the auxiliary
piston, the whole being constructed, arranged, and combined sub-
stantially in the manner and for the purposes herein-before described,
´ and as 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 Fifteenth
day of June, One thousand eight hundred and seventy-six.
J. HENRY JOHNSON. (L.S.)