IMPROVEMENTS IN INDICATORS FOR REGESTERING PRESSURE
Year: 1857

page_text: LETTERS PATENT to Thomas Baldwin, of Bury, in the County of Lan-
caster, Civil Engineer, for the Invention of "IMPROVEMENTS IN INDICATORS
FOR REGESTERING PRESSURE."
Sealed the 16th October 1857, and dated the 30th April 1857.
PROVISIONAL SPECIFICATION left by the said Thomas Baldwin at
the Office of the Commissioners of Patents, with his Petition, on the
80th April 1857.
I, THOMAS BALDWIN, of Bury, in the County of Lancaster, Civil Engineer,
do hereby declare the nature of the said Invention for "IMPROVEMENTS IN
INDICATORS FOR REGESTERING PRESSURE," to be as follows:-
My Invention has for its object the recording of the effective pressure of the
steam acting expansively or otherwise in the interior of the cylinders of steam
engines, and consists of a cylinder or cylinders each fitted with a movable
piston; the said cylinder or cylinders communicate by pipes and cocks with
each end of the large cylinder of the engine in such a way that whatever.
pressure is propelling or retarding the piston of the steam engine, the same
pressure will be propelling or retarding the piston of the small cylinder belong-
ing to the indicator. I attach to the piston rod of the indicator, or to a rod
5 or rods actuated thereby, a cross slide containing a sliding block for the
purpose of moving in a lateral direction relative to the motion of the piston

page_text: rod. To the said sliding block I attach another sliding block or slide which
moves in a grove or slide fixed on a plate secured to the end of a shaft, to
which shaft is attached a lever; the said lever and plate have communicated
to them an oscillating motion by the engine, which motion is governed by a
conical pendulum driven by the engine in such a manner that when the engine
varies in its speed, the angle of oscillation shall vary also, and thus rectify the
effect of any variable velocity of the engine upon the indicator; the last-named
slide is so constructed that when the indicator is not in action the slide block
will be at rest. I also attach a stud or neck to the sliding blocks before
named, on which is placed a movable link; to each end of the said link I
attach a radius rod, the other ends of these radius rods being attached to two
seperate levers moving upon centres, which levers are kept at a constant
distance from each other by a rod passing from one to the other. I attach to
these levers or to the radius rods a ratchet wheel to be actuated by them, tho
motion of which wheel will bear a constant ratio to the effective pressure on
the piston, and by this wheel setting in motion a train of wheels, the said
effective pressure is regestered on one or both of the levers attached to the
radius rods. I attach a pointer so that the effective pressure may be read off
at every stroke of the piston. When required I also attach to any convenient
part of the instrument a counter for the purpose of regestering the number of
strokes made by the engine.
And further, my Invention consists of a vessel or vessels containing mercury
into which is immerced a lighter body or bodies than mercury, so that it will
require a certain amount of force to press the lighter body or bodies down
into the fluid; this force increasing with the depth to which the bodies are
pressed. To this lighter body or bodies, I attach a rod or rods acting by
means of racks or links upon a wheel or lever, to which wheel or lever by
means of a shaft, I attach another lever or wheel to the small piston rod
of the indicator in order that the action of the steam in the cylinder may.
press on the light body or bodies immersed in the mercury, and so meet with
a resistance equal to the pressure of the said steam, and measure its amount
when the vessels containing mercury and their appendages are not suitable, as
might occur in the case of their application to marine engines. I attach to
the piston rod of the indicator a helical or other spring of steel for the purpose
of resisting the action of the steam and measuring its amount.

page_text: SPECIFICATION in pursuance of the conditions of the Letters Patent, filed
by the said Thomas Baldwin in the Great Seal Patent Office on the
27th October 1857.
TO ALL TO WHOM THESE PRESENTS SHALL COME, I, THOMAS
BALDWIN, of Bury, in the County of Lancaster, Civil Engineer, send
greeting.
WHEREAS Her most Excellent Majesty Queen Victoria, by Her Letters
Patent, bearing date the Thirtieth day of April, in the year of our Lord One
thousand eight hundred and fifty-seven, in the twenty-first year of Her reign,
did, for Herself, Her heirs and successors, give and grant unto me, the said
Thomas Baldwin, Her special licence that I, the said Thomas Baldwin, my
executors, administrators, and assigns, or such others as I, the said Thomas
Baldwin, 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 INDICATORS FOR
REGESTERING PRESSURE," upon the condition (amongst others) that I, the said
Thomas Baldwin, my executors or administrators, by an instrument in writing
under my, or their, or one of their bands and seals, 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 Thomas Baldwin, do hereby declare the
nature of my said Invention, and in what manner the same is to be performed,
to be particularly described and ascertained in and by the following state-
ment and accompanying Drawings (that is to say) :-
The first part of my Invention has for its object the recording of the effective
pressure of the steam acting expansively or otherwise in the interior of the
cylinders of steam engines during the time the velocity of the engine is con-
stant; but when the velocity varies, the action of the governor of the indicator
upon the measuring apparatus is such as to cause it to measure a propor-
tionally greater pressure when the velocity increases, and a proportionally
less pressure when the velocity decreases, than the true pressure which is
measured when the engine has a constant velocity. The sum of these pres-
sures being multiplied by the constant velocity will give the force exerted by
the engine during the time it has been in motion.

page_text: Fig. 1 of the accompanying Drawings shows an elevation, and Fig. 2 a
plan of the indicator. a is the framework, to the bottom and top of which
are fixed the cylinders b, b, the bottom cylinder being shown in section sur-
rounded by a helical spring and case c; to each end of the spring is secured n
metalic ring, the bottom ring being secured to the cylinder and frame by
projecting snugs, one of which is shown at d, Fig..2, the other being on the
other side of the cylinder. To the upper ring is attached two rods e, e, these
rods being secured to the cross slide fattached to the piston rod g; the pistons
are shown at h, h', and the steam ways i, i, communicate with the cylinder
of the engine. The link k is movable on a stud passing through the slide
block 7, the said stud being fixed on the slide block m, which block is movable
along the oscillating slido plate n. o is the shaft to which the slide plate n
is fixed; p is a double lever fixed on the shaft and carrying the joint g,
through which the round part of the lever r slides; s is a sliding pedestal
carrying the lever r, and movable along the cross plate t. The connecting
rod u is attached at one end of the lever r by a universal joint, the other end
being attached to the crank v in a similar manner. w is a shaft put in motion
by the engine on which is fixed the crank v and the wheel ; the said wheel
is geered into another wheel fixed on the governor spindle y. To the sliding
bush of the governor is attached a rod A passing down the spindle y; on the
top of the said rod is fitted a plate B which slides in a grove cut in the cross
plate t. The plate B contains a curvilinear grove into which is placed the
stud C; this grovo is constructed of such a form that when the governor D, D,
varies in speed, and thereby rises or lowers the plate B, the sliding pedestal s
shall move equal distances for equal variations in the speed of the governor.
E is a lever movable on a stud fixed in the bracket F; to the said lever, by
means of a stud, is connected at one end the radius rod G, the other end
being connected to the link k. Another radius rod H is also connected at
one end to the link k, tho other end being attached to the lever I. A rod K
passes from the lever E to the lever I for the purpose of keeping the said
levers at a constant distance from each other. The lever I is movable on
the shaft L, upon which is fixed a ratchet wheel M, which is actuated by a
lever N fixed to the lever I and containing the clicks O. A rod P is attached
to the cross slide of the piston rod, on the top of which is fixed a pencil and
holder Q, so that diagrams showing the working state of the engine may bo
taken on the cylinder R which contains a spring in the usual manner, and is
moved by the string S attached to the lever r. A worm T is fixed on the
shaft L, which by actuating a wheel connected in the ordinary manner with
a counting apparatus, the index of which is shown under the words Mean

page_text: Pressure in the Drawing. There is also an index shown under the word
Revolutions, which, by having its working parts connected with the shaft o or
other parts of the apparatus, is made to regester the number of revolutions
made by the engine.
Having described the first part of my Invention, I will now proceed to
describe its action. The shaft w being. put in, motion by the engine, and
inaking one revolution in the same time as the engine, completes a double
stroke; the rod u, and the levers r and p will be caused to vibrate once by the
action of the crank v, for each single stroke of the engine, thereby causing the
plate n to vibrate once in the same time. The steam from the engine on
entering the under side of the piston h, and being of superior pressure to the
steam on the upper side of the upper piston, motion will take place in an up-
ward direction, and if the plate n be situate, as shown by the dotted line U,U',
the centre of the link k may be at U', whilst the levers r, p, &c. will be in the
position shown by the dotted lines. If the engine now makes one stroke, tho
plate n, with the link k, will move over to V, and the radius rods and levers
occupy the position shown by the other dotted lines. The ratchet wheel will
now have moved through a space proportional to the space passed over by the
plate n, whilst describing the line V, U³, and so on, in proportion to the dis-
tance of the link k from the centre of the plate n. If the steam be now
changed to the upper side of the piston h', the link k may be carried by the
piston rod down to the point V, and cause the lever N to move backwards
without moving the wheel M; but the engine by continuing its motion will
carry the plate n, and the link k, over to the point U, and thereby turn the
wheel M, and the worm T, acting on the counter, will regester the mean
pressure corresponding to the line V, U. If the eugine now increase in
speed, the governor will rise the plate B, which, acting upon the stud C, will
move the sliding pedestals, and the lever towards the left hand; and since
the vibrations of the lever r do not vary in extent, the lever p will be caused
by its increased distance from the centre C to move through a greater anglo
in the same time, and therefore cause the wheel M to pass through more
space than that which represents the true pressure, and regester the same as
required. When the engine decreases in speed the reverse of the last opera-
tion will take place, and the pressure regestered will be less than the true
pressure. The index will, therefore, show the sum of the true and falso
pressures; this sum, being multiplied by the velocity of the engine when the
instrument is regestering true pressure, will give the force exerted during the
time the engine has been in motion. That part of the instrument for taking

page_text: diagrams is worked by the string S, and takes a diagram answering to one
complete revolution of the engine, as shown at X, X.
The next part of my Invention has for its object the regestering of pressure
by substituting in the place of springs a vessel or vessels containing mercury,
into which is placed a float or floats specifically lighter than mercury.
Fig. 3 of the accompanying Drawings shows an elevation, and Fig. 4 a
plan, of the arrangement in which vessels containing mercury are used. a is a
pillar supporting the beam or lever b, to which is attached the floats c, c, by
means of the links d, d; tho said floats are each provided with guide rods,
marked e, to prevent them from touching the interior of the vessels f, f. The
vessels and floats must be made of such materials as have no affinity for mer-
cury, or are liable to be oxidized; otherwise they must be coated with materials
of that nature, such as glass or carthenware, gutta percha, shell-lac, &c. The
vessels ff, each contain mercury, as shown at g, and the dotted lines i, i, show
the surface of the mercury before the floats c, c, are immersed; h, h, are two
cylinders containing the pistons k, k, which are attached to the beam or lever
b by means of the piston rods 1, 1, and links m, m. The under side of one
piston communicates with one side of the steam engine piston, and the under
side of the other piston communicates with the other side of the steam engine
piston, by means of the passages n, n, which are connected to the ends of the
steam engine cylinder by means of pipes containing cocks. To one of the
guide rods e, or other convenient part of the instrument, I attach a pencil and
holder o, for the purpose of marking diagrams on the cylinder p, which con-
tains a spring in its interior, in the usual manner, and is caused to revolve by
the action of the string 9 passing over the pulley r, and actuated by the
engine.
Having described the second part of my Invention, I will now proceed to
describe the manner in which it operates:-When the steam from the engino
enters the cylinders of the instrument, that cylinder which receives the
greatest pressure will have its piston moved in an upward direction; at the
same time, the float attached at the same side of the centre of the beam b will
move also in an upward direction, but the other piston and float will move in
a downward direction. The mercury contained in the vessel, wherein the float
moved upwards, will descend, whilst the mercury contained in the other vessel
will ascend, and the column of mercury above the bottom of the descending
float will be greater than the column of mercury above the bottom of the
ascending float, and the difference between the height of these two columns,
multiplied by the area of the bottom of the float, and by the distance of the

page_text: centre of the cylinder from the beam centre, will be always equal to the differ-
ence of the pressures acting in the cylinders h, h, multiplied by the area of the
piston k, and by the distance of the centre of the float, on the other side of the
beam 6, from the centre of that beam; and if the greater pressure be put into
the other cylinder, the operation will be reversed. Hence the pencil o, being
attached to one of the slides e, will move over spaces proportional to the spaces
moved over by the pistons of the instrument, and therefore measure the
amount of effective pressure acting upon the piston, which may also be shown
by attaching a pointer to the beam b, or other suitable part of the instrument.
To make the instrument, shown in Figs. 3 and 4, available for regestering
the force exerted by a steam engine in a similar manner to the instrument,
shown in Figs. 1 and 2, I fix on one of the piston rods 1, or other part par-
taking of a similar motion, a cross slide similar to the one marked f, in
Figs. 2 and 3, to which slide all the measuring apparatus, including the
governor there shown, is attached, thereby dispensing with the use of a spring.
The advantage of the use of vessels containing mercury, with floats acting
therein, over that of any class of springs must be evident, as the mercury and
its appendages are not so liable to vary or get out of order.
I have used two cylinders in both the instruments shown in the accompany-
ing Drawings, but it is evident that in Figs. 1 and 2, one cylinder with a
cover and piston rods passing through each end, the steam acting on both
sides of the piston through apertures made for the purpose, would answer the
same end. In Figs. 3 and 4, one of the cylinders may be dispensed with by
using a cover for the piston rod to pass through at the top of the cylinder, and
allowing the other end of the piston rod to pass through the bottom, the steam
having access to both sides of the piston by apertures made for that purpose;
but I prefer two cylinders, because the piston rods require no packing, and
the pistons may be easily lubricated, and their proper working at all times
examined without taking the machine in pieces.
Having thus described the nature of my Invention in connection with parts
not new, and the manner in which the said Invention is to be performed, I
wish it to be understood that what I claim as new and applicable to indicators
for regestering pressure, and of my Invention, is,―
Firstly, the application of radius rods, with movable centres, held at a con-
stant distance from each other by a tie rod, directly or indirectly.
Secondly, the application of an oscillating plate or bar n, containing a slide
or grove, as shown in Figs. 1 and 2, and for the purpose herein set forth.
Thirdly, the application of a conical pendulum for the purpose of altering

page_text: the indications of pressure when the steam engine varies in velocity, as herein
set forth.
Fourthly, the application of a sliding lever for the purpose of altering the
angle of oscillation of the plate or bar n.
Fifthly, the application of a vessel or vessels containing mercury, and a float
or floats for the purpose of measuring or regestering pressure.
Sixthly, the application of a beam or lever, with a cylinder or cylinders, as
shown and mentioned in connection with Figs. 3 and 4.
In witness whereof, I, the said Thomas Baldwin, have hereunto set
my hand and seal, this Twenty-fourth day of October, in the year of
our Lord One thousand eight hundred and fifty-seven.
THOMAS DALDWIN