IMPROve- MENTS IN STEAM ENGINE INDICATORS
Year: 1862

page_text: LETTERS PATENT to Charles Talbot Porter, of the City, County, and
State of New York, in the United States of America, now of 100, Fleet
Street, in the City of London, Engineer, for the Invention of "IMPROve-
MENTS IN STEAM ENGINE INDICATORS."-A communication from abroad by
Charles Richards, of the City of Hartford, in the State of Connecticut, in
the United States of America.
Sealed the 1st August 1862, and dated the 14th May 1862.
PROVISIONAL SPECIFICATION left by the said Charles Talbot Porter
at tho Office of the Commissioners of Patents, with his Petition, on. the
14th May 1862.
I, CHARLES TALBOT PORTER, of the City, County, and State of New York,
in the United States of America, now of 100, Fleet Street, in the City of
London, Engineer, do hereby declare the nature of the said Invention for
"IMPROVEMENTS IN STEAM ENGINE INDICATORS," a communication to me from
abroad by Charles Richards, of the City of Hartford, in the State of Con-
necticut, in the United States of America, to be as follows:
The said Invention relates to an improvement in apparatus for indicating
and delineating the action of steam in the cylinder of a steam engine so as to
reduce the momentum of the parts which are moved by the varying pressures
of the steam and also to cause the pencil or marking point to move in a
straight line in order that its delineations, which should be on a large scale,
may be readily measured with accuracy.
To this end the said Invention consists in the employment of a lever or its

page_text: equivalent, so connected with the pencil and the piston as to give to the pencil
a range of motion greater than that of the piston, in combination with a system
of levers so arranged as to cause the pencil's point to travel in a straight
line.
A small steam cylinder in which a piston moves, having its movements regu-
lated by a spiral spring, is arranged and constructed in a manner similar but
much shorter than an ordinary indicator. To the outside an arm is secured to
support a cylindrical paper holder, which receives the proper reciprocating
movements in the usual manner. Around the upper part of the cylinder case
a ferule is made, to which are attached two arms to support the fulcrum pins
of two delicate levers or radius bars. These levers are connected by a lever or
link, in the centre of which a pencil holder is attached, and the levers are so
proportioned that the pencil holder and consequently the marking point of the
pencil is caused to move in a straight line in the same manner that the
parallel motion" of a steam engine acts upon the end of the piston rod in
steam engines. The rod of the piston moving in said cylinder is connected by
means of a forked link to one of the above-mentioned delicate levers, at a point
distant from its fulcrum about one-fourth of the length of the lever, or at any
other point which may be desired, whereby the pencil receives from the piston
a range of perpendicular motion about four times greater than that of the
piston or any other desired relative movement corresponding with the point of
attachment on the lever. The movements of the pencil's point in a straight
line permits the use of a cylindrical paper holder, which is the most compact,
convenient, and easily operated.
SPECIFICATION in pursuance of the conditions of the Letters Patent,
filed by the said Charles Talbot Porter in the Great Seal Patent
Office, on the 15th October 1862.
TO ALL TO WHOM THESE PRESENTS SHALL COME, I, CHARLES
TALBOT PORTER, of the City, County, and State of New York, in the United
States of America, now of 100, Fleet Street, in the City of London, Engineer,
send greeting.
WHEREAS Her most Excellent Majesty Queen Victoria, by Her Letters
Patent, bearing date the Fourteenth day of May, in the year of our Lord
One thousand eight hundred and sixty-two, in the twenty-fifth year of Her
reign, did, for Herself, Her heirs and successors, give and grant unto me,
the said Charles Talbot Porter, Her special license that I, the said

page_text: .
Charles Talbot Porter, my executors, administrators, and assigns, or such
others as I, the said Charles Talbot Porter, my executors, administrators,
and 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," being a com-
munication to him from abroad by Charles Richards, of the City of Hartford.
in the State of Connecticut, in the United States of America, upon the
condition (amongst others) that I, the said Charles Talbot Porter, 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 Charles Talbot Porter, 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 bad to the Drawings hereunto annexed,
and to the letters and figures marked thereon (that is to say) :-
This Invention relates to an improvement in apparatus for indicating
and delineating the action of steam in the cylinder of a steam engine.
The form of steam engine indicator in most general use is that commonly
known as the "McNaught Indicator," in which the piston and its guiding rod
have the same range of motion as the pencil, but as the piston and rod are
necessarily made quite heavy, and their range of motion extensive, in order to
produce delineations on a sufficiently large scale, the momentum of these parts
is so great, and the tremulousness of the spring is so considerable as to render
the instrument unserviceable for application to engines having rapid move-
ments. While, therefore, it is desirable to reduce the momentum of the parts
which are moved by the varying pressures of the steam, as well as the length
and consequent tremulousness of the spring, it is also desirable that the pencil
or marking point should move in a straight line, in order that its delineations,
which should be on a large scale, may readily be measured with accuracy, and
in order also that the paper on which the delineations are made may be
clamped in the usual manner around a cylindrical drum to which the requisite
movements can be readily given by the customary means. To furnish an
instrument possessing the above-mentioned desirable features is the object of
this Invention, and to this end the said Invention consists in the employment

page_text: of a lever or its equivalent, so connected with the pencil and the piston as to give
to the pencil a range of motion greater than that of the piston, in combination
with a system of levers or an equivalent therefor, so arranged as to cause the
pencil's point to travel in a straight line, substantially in the manner herein-
after clearly set forth.
In order to explain this Invention as completely as possible I now proceed
to describe the best means I am acquainted with for carrying the same into
practical effect, reference being had to the illustrative Sheet of Drawings
hereunto annexed, and the numerical figures and letters of reference marked
thereon respectively as follows:-
DESCRIPTION OF THE DRAWINGS.
Figure 1 is a plan of the instrument; Figure II, is a side elevation of the
same; Figure III. is a vertical section through the centre of the spring
case A; and Figures IV., V., and VI., show parts of the instrument in
detail. Similar letters of reference denote the same parts in the several
Figures.
In the accompanying Drawings A is a cylindrical case containing a small
steam cylinder B, in which moves a piston C, the movements of which are
regulated by a spiral spring D. These parts are constructed and arranged in
a manner similar to but are much shorter than the corresponding parts of an
ordinary McNaught indicator, making delineations on the same scale. To the
outside of the case A is secured a ferule E, an arm from which supports a
cylindrical paper holder F, which in construction and arrangement is similar to
the paper-holding drum of a McNaught indicator, and it receives the proper
reciprocating movements in the same manner. Around the upper part of the
case A is a ferule G, to which are attached two arms H and J, one of which,
J, supports the fulcrum pin K of a light lever L, the extreme end of which
lever is jointed to the end of a lever or link M, the opposite end of which is
jointed to the extremity of a delicate lever or radius bar N, the fulcrum pin O
of which is supported by the arm H. To the lever L, at a point distant from
its fulcrum K, about one-fourth of the length of the lever, the rod P of the
piston C is connected by means of a forked link Q, which is jointed by a
knuckle R to the upper end of the rod P. In the centre of the link M is a
holder for the pencil S; which receives from the piston C, through the lever L,
a range of perpendicular motion about four times greater than that of the
said piston, and the levers L and N are so proportioned and their fulcrums
are so adjusted that the marking point of the pencil S is caused to move in a
straight line in the same manner that the "parallel motion" of a steam engine

page_text: causes the end of the piston rod to move in a straight line. The movements
of the lever are indicated in Figure II. The application and mode of using
this improved indicator are essentially the same as of McNaught's instrument,
and need no description.
Although I have described the movement of the piston as being about one-
fourth part of the pencil, yet in some it may be desirable to give a relative
movement to the piston less than that specified, as in the case of engines with
very rapid reciprocating movements, and in which the steam is cut off early in
the stroke. The pencil may be guided in a straight line by a slide attached
thereto, and moving in straight guides instead of the parallel motion described.
By reducing the range of movement of the piston, its rod, and the spring, the
weight and momentum of these parts, which are necessarily made of con-
siderable strength, are much reduced, and the stiffness of the spring is greatly
increased. The pencil, though it has a long range of motion, and consequently
makes its indications on a desirably large scale, has but little momentum,
because of its extreme lightness and the lightness of the levers which give it
motion. The movement of the pencil's point in a straight line permits the use
of a cylindrical paper holder, which is the most compact, convenient, and most
casily operated of any of the devices which have been contrived for presenting
the paper to the action of the pencil. The delineations made by a pencil
moving in a straight line are much more readily measured with accuracy than
those produced by a pencil moving in a curved path.
Having now fully described and set forth this Invention, I hereby declare
that I claim and desire to secure by Letters Patent, the means substantially
herein-before described for giving to the marking point a range of motion
greater than that of the piston by which it is actuated, in combination with the
described means or any equivalent therefor by which the marking point is
caused to travel in a straight line, substantially as and for the purpose herein-
before specified.
In witness whereof, I, the said Charles Talbot Porter, have hereunto
set my hand and seal, this Sixteenth day of September, in the year of
our Lord One thousand eight hundred and sixty-two.
CHARLES TALBOT PORTER. (L.S.)