IMPROVEMENTS IN INDICATORS
Year: 1882

page_text: PROVISIONAL SPECIFICATION left by the said Gustav Hambruch at the
Office of the Commissioners of Patents on the 19th May 1882.
GUSTAV HAMBRUCH of Berlin German Empire
FOR STEAM-ENGINES"
"IMPROVEMENTS IN INDICATORS
This invention relates to improvements in the construction of indicators for
steam engines.
One form of indicator embodying said improvemente consists of two metal
cylinders connected by a short sleeve. In the two cylinders move two pistons
attached to a single piston rod on which is placed a coiled spring confined by two
washers and by collars on the piston rod. Teeth are out on part of the length of
the piston rod and the rack thus formed gears with a toothed segment capable of
rotating on a pin or stud on one of the cylinders. From the toothed segment
extends an index finger which carries a pencil.
India rubber pipes connect each of the cylinders above mentioned with one end
of the engine cylinder and suitable stopcocks allow communication to be established
or interrupted.
The motion of the diagram sheet is in this form of my indicator obtained as
follows:
On the screw of the stuffing box of the engine cylinder a fork is fixed to which
fork the indicator Cylinders are hinged by a lug provided on one of said Cylinders
and by a bolt. The bolt which carries the indicator Cylinder likewise carries two
downwardly extending arms and upon these is fixed a frame in which a trough
shaped Carriage is free to slide transversely to the stroke of the piston the carriage
serves for the reception of the diagram sheet. Underneath a quick threaded screw
is attached to the carriage and this screw passes through a nut on the frame herein
above referred to; said Nut is so mounted that, although free to revolve, it cannot
shift, this rotation of the nut causes the screw to be moved in the direction of its

page_text: own length. The nut may be recessed on its outside and have an India rubber
ring inserted in the recess, Now when the nut just described bears upon the piston
rod of the Engine it will act as a friction roller which transmits motion from the
piston rod to the indicator-mechanism.
Suitable provision is made for attaching the diagram sheet to the concave side
of the sliding carriage
When a diagram is to be taken the indicator mechanism receives by means of
the friction roller or nut hereinabove mentioned motion from the piston rod (the
friction of the roller being increased if required, by a spring) and steam is admitted
into the indicator Cylinders or in either of them, and by these means the pencil
will draw the diagram upon the diagram sheet. When the diagram is completed
the friction roller is placed out of contact with the piston rod, and the diagram
sheet can readily be removed and a new one put in place. Instead of causing the
piston to act directly on the friction roller a wooden bar or rail may be attached
to the crosshead, and, if required be guided by a pin or roller on the Cylinder
body and this bar may operate the friction roller. In this case the indicator may
advantageously be mounted on a bolt in the Cylinder cover.
Instead of a screw arrangement I may use other means for transmitting motion
from the friction roller to the sliding carriage such as a cord or chain passing
around suitable rollers.
Where the piston rod projects from the Cylinder at both ends, the two ends of
said rod may directly cause the travel of the Carriage.
I will now proceed to describe another form of my improved indicator.
A holder of suitable shape is fastened to the Cylinder cover by one of the screws
which hold the latter. The holder has an oblong slot which renders it adaptable
to various engines, it carries a three armed piece upon which the indicator
mechanism is mounted, a rod is capable of rotating in bearings on the two arms
of the three armed piece; upon the said rod two side pieces or cheeks are free to
swing, a bar at the end of the side pieces connects the latter so that a frame is
formed by the bar between the two arms of the three armed piece, the two side
pieces and the bar connecting the ends of these latter.
In the bar at the end of the frame and at its centre I provide a female thread
in which a set screw works and this set screw bears against the third arm of the
three arm piece.
A small cross piece is from below screwed into this third arm and coiled springs
between the cross piece and the end bar of the frame tend to draw this latter apon
said third arm of the three armed piece.
The cheeks afford bearings for a sarew which operates a sliding tablet upon which
the diagram sheet is fixed and two guide bars are fixed at equal distances from the
screw and parallel therewith in the frame.
Upon the last named screw moves a nut made in halves the halves being
so constructed that wear of the threads can be taken up or compensated for by
the nut.
One end of the screw for actuating the sliding tablet herein before referred to
passes through the corresponding side piece of the frame and carries & friction roller
covered with or made of india rubber wood or suitable material and this roller is
opposite a guiding roller which rotates on a stud provided for this purpose on the
holder which carries the whole mechanism.
:
A wooden rod moves between these two rollers and being attached to the
piston rod or to some similarly moving part of the engine follows the motions of
the piston.
Under the screw that moves the diagram tablet another screw is inserted in the
cheeks of the frame it has a milled head and sorves to limit the extent of motion of
the tablet and passes through a lug on the nut.
The rod round which the frame swings carries an indicator cylinder also
swinging round it. The piston rod of the indicator cylinder gears by a pin with a
lever arrangement similar to a lazy tongs the rearmost joint of which is attached to

page_text: the indicator cylinder by a pin and the foremost joint carries the pencil this gives
a longer stroke to the pencil besides making the stroke rectilinear.
A spring always tends to raise the indicator cylinder but when indications are
taken it will be depressed by hand; the oscillation of the cylinder round the bar is
limited by a tooth on the rod.
To the end of the indicator cylinder an india rubber pipe for supplying the steam
is fixed by a coupling of peculiar construction.
This coupling consists of a cone shaped nozzle upon which the india rubber pipe
is slipped after having been passed through a conical sleeve a nut fits on a screw
threaded part of the nozzle and bears against the conical sleeve so that when the
nut is screwed home the pipe is compressed between the sleeve and nozzle.
To make the last described form of indicator applicable to different engines
friction rollers of various diameters are provided
In a further modification of the said indicator a drum carries the-indicator
sheet; its periphery must be more than the stroke of the engine so as to prevent
its making a complete revolution. Two studs one fixed and one adjustable limit
the oscillation of the dram which is actuated in substantially the same manner as
the second form of indicator above described. The last specified form of indicator
is particularly adapted for use with engines of short stroke and great velocity.

page_text: SPECIFICATION in pursuance of the conditions of the Letters Patent filed
by the said Gustav Hambruch in the Great Seal Patent Office on the
18th November 1882.
GUSTAV HAMBRUCH of Berlin German Empire. "IMPROVEMENTS IN INDICATORS
FOR STEAM ENGINES
"
My invention relates to a new system of indicators represented in the annexed
drawings. It differs from those heretofore in use partly by the manner in which
the alternating, or one sided steam pressure in the cylinder is transmitted to the
indicator piston and the pencil and partly also by the transmission of the piston
stroke to the diagram sheet.
The indicator shown in Figure 1 Sheet I consists of the two metal cylinders a
and b connected by the cylindrical piece cand furthermore of the two pistons d
and e connected with each other by the rod f which has two collars g and h which
enclose a coiled spring i. The rod f is toothed at its central part as shown and
with the rack so formed gears a segment i capable of rotating round a pin on the
cylinder a and having at its lower end an arm k¹ in which a pencil is carried
Flexible pipes and m lead to the ends of the cylinders of the steam engine
where stopcocks are provided for connection of the pipes. This yielding connection
of the indicator with the engine to be tested is necessary, because as will berein-
after be shown, the indicator must remain movable
The motion of the diagram sheet in accordance with the motion of the piston I
attain by the following arrangement
On the screw b¹ of the stuffing box of the engine cylinder, is fixed a fork g to
which the indicator cylinders a and b are jointed by means of the lug r cast on a
and the bolt 8. The same bolt a supports the arms t' which extend downward.
These arms carry a frame v fixed thereon in which the trough shaped carriage w
can slide in guiding grooves transversely to the line of motion of the piston rod.
Underneath the carriage a quick threaded screw is attached to the same which
is also placed transversely to the line of motion of the piston. The nut y has
bearings in eyes on the frame vin such manner that it is capable of rotation but
not of motion in the direction of its length. Now if the nut rotates the screw co is
compelled to move length-ways. The nut is moreover recessed upon the outside
and in the recess carries an India rubber ring which pressed against the piston rod,
transmits the motion of the latter to the nut in such a manner that the nut rotates
and thereby causes reciprocal motion of the screw in which the carriage w
participates.
The sheet of paper upon which the diagram is to be recorded is placed on the
upper concave surface of the carriage and fastened thereon by clamps. The whole
apparatus is capable of rotation round the bolt 8 and thus bears with its weight on
the piston rod z. This pressure can be increased by the tension of a spring -ly
this pressure sufficient friction is produced between the India rubber covering of
the nut y and the piston rod s to actuate the apparatus.
For taking a diagram the nut y of the frame with the carriage w is lowered
upon the moving piston rod, and then the cylinders a and b with the pencil k
attached to the toothed segment are lowered upon the diagram sheet.
The stopcocks on the ends of the steam engine cylinder remain as yet closed.
The indicator pistons d and therefore still remain in their central position.
Consequently the pencil on the arm k¹ draws the straight atmospheric line on the
diagram sheet. Both cocks are now opened and thus steam pressure from both
sides of the cylinder of the engine under examination is transmitted by the

page_text: pipes lm, to the indicator pistons d and e. By the excess pressure on the one
side these are moved in the direction of such excess of pressure and guide by the
rack and segment i, the pencil of the arm k' which registers on the diagram sheet.
The curve of the ordinate of the excess of pressure on the one side of the steam
piston. When pressure is exerted upon the other side of the engine piston excess
of pressure takes place at the pressure side of the other indicator piston and effects
consequently a movement of the indicator piston to the other side A similar curve
or ordinate is thus produced by the pencil according to the varying pressure that
obtains in the varying positions of the piston, at the other side of the atmospheric-
line on the diagram sheet
The entire diagram of a complete stroke of the piston is therefore transferred
upon the diagram sheet at the two sides of the atmospheric line and the absolute
steam pressure (less the counter pressure of the condenser, or the counter pressure
of the atmosphere) on for one side of the steam piston is shown upon one side of
said line, and the excess of pressure of the other side of the piston on the other
side of the atmospheric line. A diagramatic surface is therefore produced which
exactly represents the effective pressure during one revolution of the crank.
The calculation of the average piston pressure is therefore exceedingly simple
and reliable as the difference of pressure at the two sides of the piston is always
recorded on the one side of the atmospheric line of the diagram thus obtained,
which is joined, at the other side of this line, by the diagram of the difference in
pressure in the second stroke of the piston whereby a complete diagram for the
duty of the engine during one revolution of the crank is furnished
The raising of the rollar from the piston rod suffices to interrupt the action of
the motion of the piston upon the carriage, the diagram sheet may then be
changed the frame and roller again lowered upon the piston rod and with a few
motions of the hand a new diagram can be registered on the sheet.
If it is desired to leave a complete diagram of the absolute full pressure,
expansive pressure and pressure of compression without deduction of the counter
pressure during a stroke of the piston for one side of the piston only, both cocks
are not opened at the same time but one or the other alternately.
Instead of allowing the piston rod to act directly upon the nut y operating as a
friction roller the arrangement shown in Figure 4 may be used. In this instance a
wooden bar p is screwed to the cross head which is moreover guided by a pin or a
roller 9: In this arrangement a screw of the cylinder cover may serve for attaching
the indicator, the motion may also be transmitted from the friction roller to the
carriage by other mechanical devices instead of by the screw and nut, for instance
by a strong cord or chain wound round the same the ends whereof are suitably
conducted over rollers and connected with the ends of the carriage. The principal
consideration is the use of the friction roller for actuating the indicator whereby
the construction and manipulation of the latter are considerably simplified.
The advantages of this indicator are very essential. Its connection with the
piston-stroke. is readily effected as its indicated by the example shown in Figure 5
whilst in engines the piston of which passes through both cylinder covers it can be
effected directly. The lever arrangement or differential rollers necessary in ordinary
indicators as well as the cords for transmitting the motion of the piston, are
dispensed with. When quick running engines are to be tested these cords almost
always break. A further advantage is that the indicator spring is strained only
by compression whilst in ordinary indicators it is strained both by compression and
extension.
In the modification of my indicator shown in sheet II of the accompanying
drawing the holder p Figure 3 is screwed against the end of the cylinder cover of
an engine by the cylinder cover screws The oblong hole p¹ has for its object to
adapt the holder to the varying distances of the cylinder cover screws in larger or
smaller engines. The holder carries the three armed piece o Figure 1 at the side
of which the roller h Figure 3 is fixed..
Into two of the arms of the three armed piece o the bolts d' are screwed in the

page_text: eyes of which the rod k is capable of rotating Two cheeks d are slipped upon the
rod k and can swing around it. At the opposite end the cheeks are connected with
the bolt m so that a firm frame kd m d is formed.
A set screw n is inserted into a ferrule screw. cut at the centre of said bolt m
and bears upon the third arm of o A finger p¹¹ is screwed from below into this
third arm as shown in Figure 4. The coiled springs qq, on the one hand attached
to said finger and on the other to the connecting bolt m, pull the bolt m and with
it the cheeks d d down upon the last named arm, of o. The cheeks d afford
bearings for the screw e serving to cause sliding of the sheet metal tablet. which
receives the diagram-sheet, and two connecting bolts are fixed between the
cheeks at equal distances from the screw e
One end of the screw e passes through the cheek and their carries a roller ƒ which
is covered with India rubber or other material having an equally high co-efficient of
friction. A massive roller of wood rubber or the like may also be used.
Between this roller and the guiding roller which is below the former and
rotates on a stud of one arm of the holder p, there is a wooden rod g which is
connected with the piston rod or with a similarly moving part of the engine and
follows the motion of the latter
Upon the screw e a nut moves and consists of two parts h¹ and h¹ These two
parts may be connected by screws or may be separated by washers or by tightening
screws so as to allow the slack working of the screw to be taken up by pressing
the surface of the female thread of one part upon the male thread at one side and
the surface of the other part against the same on the other side so that the screw
is kept bearing tight in both directions. The part h¹ surrounds the connecting
bolts which serve as guides therefor and the part h¹ carries the above
mentioned sheet metal tablet i upon which the diagram sheet is stretched.
A screw y for limiting the stroke having a head is screwed into the cheeks d
below the screw e and passes through an aperture in a lug upon the part ⁄ of said
nut. The collar serves to regulate the stroke of the nut
The rod k round which the whole frame swings, carries the indicator cylinder r
which can swing up and down round k
The piston rod of this indicator cylinder gears by a pin with an arrangement
of joints w similar to a "lazy-tongs" the last joints of which are attached to the
indicator cylinder by a pin and the foremost joint of which carries the pencil t.
By reason of this arrangement the stroke of the pencil t is increased in
comparison to that of the indicator piston and the motion of the pencil caused
exactly in the projected axis of the cylinder and is consequently absolutely
rectilinear which is not the case in the usual arrangements for guiding the indicator
pencil in a straight line.
A spring s tends always to rotate the cylinder around the rod k, whilst when
the indications are taken the front end is depressed by hand so as to maintain the
pencil t in contact with the indicator sheet
The oscillation of the cylinder is limited at both sides by a tooth on the rod k
At the end of the cylinder the India rubber pipe which conducts the steam is
coupled to a nozzle whose end is cone shaped.
Á nut 2 is capable of being screwed on this nozzle and its inwardly projecting
edge extends behind a conical sleeve 4.
Between the sleeve and the cone of the nozzle the end of the India rubber
tube 1 is inserted so that, when the nut 2 is tightened it will be compressed and be
fastened, closing tightly upon the cylinder.
The manipulation of the apparatus is as follows, Upon the sheet metal tablet i
the diagram sheet is stretched. The screw n is so turned that the frame kd md is
lowered by reason of the tension of the springs q, q
The friction roller f then touches the wooden bar g which is moved to and fro by
an arm fixed on the piston rod or on the cross head this causing rotation of the
friction roller f and screw e and causes the plate i to move to and fro transversely
to the frame.

page_text: By the screw y the stroke of the sheet metal tablet i is limited as may be
required
The pipe is connected with one and of the steam cylinder whereby the indicator
piston with its piston rod v assumes a motion corresponding to the state of
pressures in the steam cylinder. This motion is, amplified by the lever arrange-
ment w transferred to the pencil t. At the commencement of the stroke of the
steam piston the front end of the indicator is depressed and thereby the diagram
is recorded on the diagram sheet. If the indicator is then released it will swing
back by the tension of the springs and the pencil is lifted off the diagram sheet.
The screw n is then so turned that the frame k dm d is raised and contact of
the friction roller fis interrupted and the sheet metal tablet is stopped.
The paper can now be changed and by turning the screw n back a new diagram
can be taken.
To make the apparatus applicable to any stroke, several friction rollers of
different diameters are provided. For locomotives and similar engines, where the
indicator is not accessible whilst the engine is in motion the screw n is
replaced by a lever arrangement capable of being operated from the foot plate.
Likewise the pressing down takes place from the foot plate.
In sheet is represented an indicator which differs from the one above
described only in this, that instead of the screw e a drum i is provided which is
mounted between the cheeks d d and on one end of the axle whereof the friction
roller is placed. This construction is applied with advantage to engines with
short stroke and high speed of the piston.
=
The stroke of the engine from which a diagram is to be taken must be less than
the periphery of the disc f so that this and the cylinder i can not make a complete
revolution.
The indicator cylinder is arranged on the one cheek d opposite to the roller f
and the transmission of motion from the indicator piston to the pencil is effected as
was described with reference to Sheet II.
The diagram paper is laid round the drum i and the India rubber pipe 1 is con-
ducted to the end of the steam cylinder Whilst the drum revolves in accordance
with the piston-stroke the pencil t describes the curves of pressure on the paper
The limitation of stroke is effected by a pin s fastened at one end of the drum i
(Figure 3) and abutting against the fixed stud and the adjustable stud y' of one
of the cheeks d.
Otherwise the apparatus corresponds with that represented on Sheet II and
above described.
As the amount of movement of the drum and indicator piston and "lazy-
tonga" w can be reduced to a minimum, this form of the indicator is suitable even
for high speed engines
Having now described the nature of my said invention and the manner of
performing the same I wish it understood that what I claim and desire to protect
under the hereinbefore in part recited Letters Patent is.
First. In indicators, in combination with the piston rod of the steam cylinders,
or with a rod screwed to the cross head the friction roller y, which acting as a nut
upon a fixed screw or otherwise suitably transmits the motion of the piston to a
carriage carrying the diagram sheet substantially as described with reference to the
figures on Sheet I
Second-In combination with the carriage w carrying the diagram sheet, the
screw upon which screw the friction roller y acting as a nut revolves and travels,
transmitting to the carriage w the motion of the piston rod of the engine
Third For transmitting the motion of the indicator piston to the pencil of the
arm k¹, a toothed segment which gears with the connecting rod of the pistons
(formed into a rack in combination with a carriage w, of a trough shape
corresponding with the curvilinear motion of the writing point, for receiving the
sheet to be written upon
Fourth. The employment of elastic tubes for connecting the indicator cylinder

page_text: with the engine cylinder to enable the indicator to be set in motion independently
from the engine cylinder whose working capacity is to be examined
Fifth. In indicators in combination with the piston rod of the steam engine or
other similarly moving part thereof, the rod g Sheets II and III which, by means
of a friction roller or in some other suitable manner affects the rotation of a screw
whose non rotating nut, in its motion to and fro moves a carriage carrying the
diagram sheet also to and fro according to the motion of the engine piston
substantially as described
Sixth. In indicators the rod g which effects the rotation of a drum around
which the diagram sheet is laid substantially as described.
Seventh. In combination with the carriage carrying the diagram sheet, or the
sheet metal tablet i, the nut h¹ h¹, the screw e mounted in the frame d km d
capable of swinging around k to enable contact of the friction roller y with the
rod g to be effected during the working of the engine substantially as described
Eighth. The construction of the nut h' h for the motion screw 6 in two parts
connected by screws with each other and kept apart by washers or tightening
screws so as to enable the slack to be taken up when the thread becomes worn
substantially as described
Ninth. For transmitting the motion of the indicator piston to the pencil ta
jointed connection w similar to a “lazy-tongs” to increase the travel of the pencil
over that of the indicator piston.
Tenth. The pipe coupling described with reference to Figure 5 Sheet II
consisting of the conical nozzle of the cylinder the conical sleeve 4 and the nut 2
substantially as set forth & shown
Eleventh. The herein described construction of indicators for steam engines
substantially as set forth and shown in the accompanying drawings
In witness whereof I the said Gustav Hambruch have hereunto set my hand
and seal this fifteenth day of November in the year of Our Lord One
thousand eight hundred eighty two.
GUST
USTAY HAMBRUCH.
(حمد)
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