Improvements in and relating to Steam Engine Indicators.
Year: 1895

page_text: Date of Application, 2nd May, 1895-Accepted, 8th June, 1895
COMPLETE SPECIFICATION.
Improvements in and relating to Steam Engine Indicators.
I, ALBERT FRANCIS HALL, a citizen of the United States of America, of
No. 3 Cordis Street Charlestown, in the City of Boston, County of Suffolk and
State of Massachusetts, one of the United States of America, Mechanical
Engineer do hereby declare the nature of this invention, and in what manner the
same is to be performed, to be particularly described and ascertained in and by the
following statement :-
This invention relates to improvements in steam engine indicators, which will be
hercin-after more particularly described, and pointed out in the claims.
In the drawings
Figure 1 is an end view, and
Figure 2 a view partly in section and partly in elevation, of the indicator;
Figure 3 is a diagram representing the correlation of the moving parts, and
Figure 4 is an enlarged view partly in section, of the cylinder.
In these drawings, the letter A indicates a steam engine indicator of any approved
type, in which there is the usual recording barrel or cylinder B, pencil lever C,
and a steam cylinder and piston for moving the pencil lever C. The cylinder B is
secured at one end of the supporting bracket D. At the other end is formed a
hollow cylindrical projection, F, which has an extension, f, above, and an
extension,, below the bracket, D. The extension, f, has an exterior annular
seat,, and is interiorly threaded at f³ at the top. The extension is of greater
diameter inside and outside than the extension, and is interiorly threaded at f* at
the bottom. A small passage f runs from the interior of the projection F to the
outside. A cylinder G, having an enlarged smooth end f, is placed within the
projection and against a shoulder f. This cylinder is secured in place by a
cylindrical shell H, the upper end h of which bears against the enlarged end of
the cylinder G and is screw-threaded and engages the threads of the projection f1.
The enlarged smooth end of the cylinder G forms a guide for centering this
cylinder in place. Between the cylinder G and the cylindrical shell H, there is an
annular space . At its lower end, the shell H has means, as usual, for securing
it to the engine, there being the usual steam way from the steam space of the
engine to the interior of the shell H. Fitting into the top of the projection f, and
secured to the threads ³, is the cap I, having the central hole i. Immediately
above the screw threads f, there is a guide surface n on the cap I, which is
accurately fitted to the corresponding interior recess in the cylinder F; the purpose
of this construction is to cause the cap I to fit precisely into the cylinder F, and
compel the concentricity of all the moving parts which are so essential to the
accuracy of the pencil movement. In practice it is well known that, owing to the
inaccuracy of screw thread cutting, the male and female threads do not always fit
with perfect accuracy but by the guide surface n, and corresponding recess in the
cylinder the parts are forced into their proper concentricity. This is a very
Important improvement in fitting the cap I to its place, and which I consider to be
new, and has proved in practice to accomplish the purpose effectually.
Within the cylinder G is the usual pistou K, having the stem k, which projects
up through the hole, the piston and its concomitant parts being constructed and
rranged in the usual way. The cap I has a projecting flange, and in the space
etween this flange and the seat is placed the annular sleeve L, carrying the
rm on the side towards the cylinder B. To the opposite side of the sleeve L is

page_text: pivoted, in the usual way, the link O, to which is pivoted the pencil lever C.
This pencil lever C is connected to the top of the piston stem k, by a link
0, which
is loosely pivoted to both the pencil lever and piston stem. From this link o a
steadying link of extends to the arm this steadying link being loosely pivoted to
the link o and the arm 1.
Without a correct movement of the pencil, or recording mechanism, an indicator
would be of little value. The fundamental kinematic principle of the new device is
that found in the pantograph; the fulcrum of the mechanism, as a whole; the
point attached to the piston rod; and the pencil or recording point, always lie in a
straight line, whatever be the position of the pencil.
The principle enunciated above is easily shown by reference to the diagrammatic
drawing, Figure 3. In this illustration the parallel lines N and M, represent,
respectively, the paths of movement of the piston and pencil. d is the fulcrum of
the mechanism, ac, the pencil arm, and ad and be links, the lower end of the
latter e, being joined to the head of the piston rod. If the various members of
this mechanism are properly constructed relatively to one another, and the point e
is constrained to move in a straight line, then the pencil point, e, will not only move
in a line M parallel to the line N of motion of point e, but the distance traveled
by point will be an exact and constant multiple of the distance traveled, by
point e. For example, let a², ', and e¹, he new positions of the points, then
point c will be found on the line M, and the distance cc', will be an exact multiple
of distance e e¹. To attain this result, the length of the pencil arm a c, divided by
that of the link ad, must be exactly equal to the distance cb divided by the length
of the like be. The links, ad and he will also be always parallel. Further, the
ratios ac divided by ab, gd divided by df, and cd divided by de, will always
be equal.
The above represent the fundamental and essential conditions in the construction
of the recording mechanism.
In the actual construction it has been found advisable to introduce a steadying
link to prevent undue swaying of the mechanism, and thus obtain a clear and well
defined movement of the pencil under all variations of speed.
This line hi, must be so designed, both as to length and position, that the
points e and c, will still be free to move in parallel lines, as illustrated.
In order that the axis of the piston and of its rod shall always coincide with the
axis of the cylinder, the cap 1, Figure 4, should be so constructed that the central
hole, which serves as a guide for the piston rod, will always be coincident with
the axial line of the cylinder. To obtain this result, a plain cylindrical portion or
guide n, is turned on the cap exactly concentric with its center, and this guide is
carefully and closely fitted to a recess turned in the cylinder exactly concentric
with its axis, so that, when the cap screwed down upon the top of the cylinder,
the axial lines of cap and cylinder shall be exactly coincident.
The sleeve L, shown in Figure 2, bored to accurately fit the outside, of the
projection, and concentric therewith, just fills the space between the under side of
the cap I and the seat. The circular parts being all, therefore, truly concentric
with the axis of the piston and of its rod, will always coincide with that of the
cylinder, thereby insuring a movement of the pencil point in a line strictly parallel
with that of the piston's.
The annular space ', between the cylinder, G, and cylindrical shell, H, allows
steam to surround the cylinder G, and keep it at an even temperature, allowing
free movement of the piston, K.
Having now particularly described and ascertained the nature of my said inven-
tion, and in what manner the same is to be performed, I declare that what I
claim, is:-
1. The combination with the cylinder, F, having the seat, the sleeve, L,
fitted to the same; the link, O, pivoted to the sleeve, L, the pencil lever, C, with
the nencil the link a pivoted to the stom & and the steadying link o nivoted to

page_text: the arm 1, and to the link o; the cap, I, having the flange, ¹¹, and hole ¹, and
provided with the guide surface, n, fitted to the corresponding interior surface of
the cylinder, F; all substantially as set forth.
2. The combination of the cylinder, F, having the seat f, the removable
cylinders, G and H, between which is the narrow steam space, h¹, the cylinder, G,
being held in place by the recess in the projecting part, fe, bearing on the end of
the cylinder, H, substantially as set forth.
Dated this and d
JENSEN & SON,
77, Chancery Lane, London, W.C., Patent Agents.

page_text: ate of Application, 2nd May, 1895-Accepted, 8th June, 1895
COMPLETE SPECIFICATION.
Improvements in and relating to Steam Engine Indicators.
1, ALBERT FRANCIS HALL, a citizen of the United States of America, of
No. 3 Cordis Street Charlestown, in the City of Boston, County of Suffolk and
State of Massachusetts, one of the United States of America, Mechanical
Engineer do hereby declare the nature of this invention, and in what manner the
same is to be performed, to be particularly described and ascertained in and by the
following statement :-
This invention relates to improvements in steam engine indicators, which will be
herein-after more particularly described, and pointed out in the claims.
In the drawings-
Figure 1 is an end view, and
Figure 2 a view partly in section and partly in elevation, of the indicator;
Figure 3 is a diagram representing the correlation of the moving parts, and
Figure 4 is an enlarged view partly in section, of the cylinder.
of
In these drawings, the letter A indicates a steam engine indicator of any approved
type, in which there is the usual recording barrel or cylinder B, pencil lever C,
and a steam cylinder and piston for moving the pencil lever C. The cylinder B is
secured at one end of the supporting bracket D. At the other end is formed a
hollow cylindrical projection, F, which has an extension, f, above, and an
extension,, below the bracket, D. The extension, f, has an exterior annular
seat,, and is interiorly threaded at 3 at the top. The extension f' is of greater
diameter inside and outside than the extension, and is interiorly threaded at fat
the bottom. A small passage f runs from the interior of the projection F to the
outside. A cylinder G, having an enlarged smooth end f, is placed within the
projection and against a shoulder f'. This cylinder is secured in place by a
cylindrical shell H, the upper end of which bears against the enlarged end
the cylinder G and is screw-threaded and engages the threads of the projection f
The enlarged smooth end of the cylinder G forms a guide for centering this
cylinder in place. Between the cylinder G and the cylindrical shell H, there is an
annular space h¹. At its lower end ", the shell H has means, as usual, for securing
it to the engine, there being the usual steam way from the steam space of the
engine to the interior of the shell H. Fitting into the top of the projection f, and
secured to the threads 3, is the cap I, having the central hole . Immediately
above the screw threads, there is a guide surface on the cap I, which is
accurately fitted to the corresponding interior recess in the cylinder F; the purpose
of this construction is to cause the cap I to fit precisely into the cylinder F, and
compel the concentricity of all the moving parts which are so essential to the
accuracy of the pencil movement. In practice it is well known that, owing to the
inaccuracy of screw thread cutting, the male and female threads do not always fit
with perfect accuracy but by the guide surface n, and corresponding recess in the
cylinder the parts are forced into their proper concentricity. This is a very
important improvement in fitting the cap I to its place, and which I consider to be
new, and has proved in practice to accomplish the purpose effectually.
Within the cylinder Ġ is the usual pistou K, having the stem k, which projects
up through the hole, the piston and its concomitant parts being constructed and
arranged in the usual way. The cap I has a projecting flange, and in the space
between this flange and the seat is placed the annular sleeve L, carrying the
arm l on the side towards the cylinder B. To the opposite side of the sleeve L is-
D

page_text: pivoted, in the usual way, the link O, to which is pivoted the pencil lever C.
This pencil lever C is connected to the top of the piston stem k, by a link 0, which
is loosely pivoted to both the pencil lever and piston stem. From this link o a
steadying link o' extends to the arm this steadying link being loosely pivoted to
the link o and the arm l.
Without a correct movement of the pencil, or recording mechanism, an indicator
would be of little value. The fundamental kinematic principle of the new device is
that found in the pantograph; the fulcrum of the mechanism, as a whole; the
point attached to the piston rod; and the pencil or recording point, always lie in a
straight line, whatever be the position of the pencil.
The principle enunciated above is easily shown by reference to the diagrammatic
drawing, Figure 3. In this illustration the parallel lines N and M, represent,
respectively, the paths of movement of the piston and pencil. d is the fulcrum of
the mechanism, ac, the pencil arm, and ad and be links, the lower end of the
latter e, being joined to the head of the piston rod. If the various members of
this mechanism are properly constructed relatively to one another, and the point e
is constrained to move in a straight line, then the pencil point, c, will not only move
in a line M parallel to the line N of motion of point e, but the distance traveled
by point will be an exact and constant multiple of the distance traveled by
point e. For example, let a, b, and e¹, he new positions of the points, then
point c will be found on the line M, and the distance cc', will be an exact multiple
of distance ee. To attain this result, the length of the pencil arm a c, divided by
that of the link ad, must be exactly equal to the distance cb divided by the length
of the like be. The links, ad and be will also be always parallel. Further, the
ratios ac divided by ab, gd divided by df, and cd divided by de, will always
be equal.
The above represent the fundamental and essential conditions in the construction
of the recording mechanism.
In the actual construction it has been found advisable to introduce a steadying
link to prevent undue swaying of the mechanism, and thus obtain a clear and well
defined movement of the pencil under all variations of speed.
This line hi, must be so designed, both as to length and position, that the
points e and C, will still be free to move in parallel lines, as illustrated.
In order that the axis of the piston and of its rod shall always coincide with the
axis of the cylinder, the cap 1, Figure 4, should be so constructed that the central
hole, which serves as a guide for the piston rod, will always be coincident with
the axial line of the cylinder. To obtain this result, a plain cylindrical portion or
guiden, is turned on the cap exactly concentric with its center, and this guide is
carefully and closely fitted to a recess turned in the cylinder exactly concentric
with its axis, so that, when the cap is screwed down upon the top of the cylinder,
the axial lines of cap and cylinder shall be exactly coincident.
The sleeve L, shown in Figure 2, bored to accurately fit the outside of the
projection, and concentric therewith, just fills the space between the under side of
the cap I and the seat. The circular parts being all, therefore, truly concentric
with the axis of the piston and of its rod, will always coincide with that of the
cylinder, thereby insuring a movement of the pencil point in a line strictly parallel
with that of the piston's.
The annular space h', between the cylinder, G, and cylindrical shell, H, allows
steam to surround the cylinder G, and keep it at an even temperature, allowing
free movement of the piston, K.
Having now particularly described and ascertained the nature of my said inven-
tion, and in what manner the same is to be performed, I declare that what I
claim, is :-
1. The combination with the cylinder, F, having the seat, the sleeve, L,
fitted to the same; the link, O, pivoted to the sleeve, L, the pencil lever, C, with
the pencil; the link o, pivoted to the stem k. and the steadying link o¹ nivoted to

page_text: the arm I, and to the link o; the cap, I, having the flange, 1, and hole i¹, and
provided with the guide surface, n, fitted to the corresponding interior surface of
the cylinder, F; all substantially as set forth.
2. The combination of the cylinder, F, having the seat f³, the removable
cylinders, G and H, between which is the narrow steam space, ', the cylinder, G,
being held in place by the recess in the projecting part, fe, bearing on the end of
the cylinder, H, substantially as set forth.
11h an11.
JENSEN & SON,
77, Chancery Lane, London, W.C., Patent Agents.