IMPROVEMENTS IN INDICATORS FOR INDICATING THE SPEED OF REVOLVING AXLES
Year: 1874

page_text: LETTERS PATENT to David Alexander Halket, of 4, Anglesea Villas,
"
New Road, Hammersmith, in the County of Middlesex, for the
Invention of "IMPROVEMENTS IN INDICATORS FOR INDICATING THE SPEED OF
REVOLVING AXLES."
Sealed the 25th September 1874, and dated the 31st March 1874.
PROVISIONAL SPECIFICATION left by the said David Alexander
Halket at the Office of the Commissioners of Patents, with his
Petition, on the 31st March 1874.
I, DAVID ALEXANDER HALKET, of 4, Anglesea Villas, New Road,
Hammersmith, in the County of Middlesex, do hereby declare the
nature of the said Invention for "IMPROVEMENTS IN INDICATORS FOR INDICATING
THE SPEED OF REVOLVING AXLES," to be as follows:
The object of this Invention is to provide an indicator, by which the
number of revolutions being made at any moment by a revolving shaft
may be seen at a glance. To effect this I cause the revolving shaft or
some shaft revolving in connection with it to drive a revolving fan or

page_text: mechanical equivalent therefor, and force a current of air into or from
a pipe or chamber. The pressure of air in this pipe or chamber will
increase or decrease as the velocity or speed at which the fan is driven
increases or decreases. I measure or gauge this pressure by means of a
pressure gauge so adjusted and graduated that it indicates the number
of revolutions being made by the axle during a minute or other division
of time. I prefer to employ a column of liquid for indicating the speed,
although other forms of pressure gauge may be employed. The liquid
may be in a bent syphon tube with the current of air from the fan
pressing upon the liquid in one limb of the syphon and causing it to
rise in the other limb, and these limbs may be tapered and so pro-
portioned to one another that each increase of speed shall be indicated
by a uniform rise of the liquid in the indicating limb.
Provision may be made for adjusting the indicator by allowing a
small regulated escape of air into or from the chamber.
'the
Instead of pumping or compressing a column of air to act upon
surface of the fluid in the graduated tube, or to be otherwise gauged or
measured, I can also indicate the number of revolutions made by any
revolving axle by means of a column of fluid alone. To effect this I
cause any revolving or rotatory pump or turbine to raise a column of
fluid from out of a cistern or cup into an upright tube. It is evident
that the quicker the pump rotates the higher the fluid will be raised in
the tube, and the tube can be graduated in degrees or divisions, shewing
the number of revolutions. The pump must of course be in connection
with the revolving axle, the same as the fan, and under the same.
conditions.
SPECIFICATION in pursuance of the conditions of the Letters Patent,
filed by the said David Alexander Halket in the Great Seal Patent
Office on the 30th September 1874.
TO ALL TO WHOM THESE PRESENTS SHALL COME, I, DAVID 30
ALEXANDER HALKET, of 4, Anglesea Villas, New Road, Hammersmith,
in the County of Middlesex, send greeting.
WHEREAS Her most Excellent Majesty Queen Victoria by Her Letters
Patent, bearing date the Thirty-first day of March, in the year of our

page_text: Lord One thousand eight hundred and seventy-four, in the thirty-seventh
year of Her reign, did, for Herself, Her heirs and successors, give and
grant unto me, the said David Alexander Halket, Her special license that
I, the said David Alexander Halket, my executors, administrators, and
assigns, or such others as I, the said David Alexander Halket, 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 INDICATING THE SPEED OF REVOLVING AXLES," upon the condition
(amongst others) that I, the said David Alexander Halket, my executors
or administrators, by an instrument in writing under my, or their, or one
of their hands and scals, 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 David Alexander Halket, 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 thereof, that is to say:-
The object of this Invention is to provide an indicator, by which the
number of revolutions being made at any moment by a revolving shaft
may be seen at a glance. To effect this I cause the revolving shaft.or
some shaft revolving in connection with it to drive a revolving fan or
mechanical equivalent therefor, and force a current of air into or from
a pipe or chamber. The pressure of air in this pipe or chamber will
increase or decrease as the velocity or speed at which the fan is driven
increases or decreases. I measure or gauge this pressure by means of a
pressure gauge so adjusted and graduated that it indicates the number
of revolutions being made by the axle during a minute or other division
of time. I prefer to employ a column of liquid for indicating the speed,
although other forms of pressure gauge may be employed. The liquid
may be in a bent syphon tube with the current of air from the fan
pressing upon the liquid in one limb of the syphon, and causing it to
rise in the other limb, and these limbs may be tapered and so pro-

page_text: portioned to one another that each increase of speed shall be indicated
by a uniform rise of the liquid in the indicating limb.
Provision may be made for adjusting. the indicator by allowing a
small regulated escape of air into or from the chamber or by other
means.
Instead of pumping or compressing a column of air to act upon the
surface of the fluid in the graduated tube, or to be otherwise gauged or
measured, I can also indicate the number of revolutions made by any
revolving axle by means of a column of fluid alone. To effect this I
cause any revolving or rotatory pump or turbine to raise a column of
fluid from out of a cistern or cup into an upright tube. It is evident
that the quicker the pump rotates the higher the fluid will be raised in
the tube, and the tube can be graduated in degrees or divisions, showing
the number of revolutions. The pump must of course be in connection
with the revolving axle, the same as the fan, and under the same
conditions.
In order that my Invention may be fully understood and readily
carried into effect, I have in the Drawings hereunto annexed shown
various examples of revolution indicators constructed according to my
Invention.
Figure 1 shews a front view, full size, of one construction of revolution
indicator. In this Figure O, B, is an inverted glass syphon tube
mounted in the ordinary manner upon a boxwood or other scale, and
filled to the level o, o, with any liquid, the scale being properly divided |
and the divisions numbered, so that whatever point the liquid in the
limbs may rise to will shew at a glance the number of revolutions per
minute being made at any moment by the revolving axle, with which
the revolving fan or its mechanical equivalent is connected. The end a
of the limb O is left open to the atmosphere, which in order to exclude
the dust is admitted through a small aperture in the holding down cap
or fastener w. The other limb B is connected with the air tube T,
through which the current of air is conducted from a small fan which
is not shewn, the construction of a fan being so well known, which
current of air passing along the tube T and down through the regulator R
(hereafter described) thus impinges upon the surface of the liquid in
the limb B, and the pressure of the current of air thus causes the liquid
to rise in the limb O. As the same number of revolutions will always

page_text: produce the same pressure it is evident that if the scale be properly
graduated, divided, and numbered, the number of revolutions being made
at any moment can be seen at a glance.
If I employ a small centrifugal fan to produce the current of air the
pressure will, as is well known, increase as the square of the speed or
thereabouts, if therefore at 30 revolutions of the axle the pressure of the
current of air be such as will raise the liquid in the limb O from 0, 0,
to 30, then at 60 revolutions the liquid will. rise 4. times as high, or
to 60, as shewn, and so on, the successive divisions increasing in length
in the same ratio as the pressure, viz., as the square of the speed, as
shewn by the scale in Figure 1. It is evident that if the two limbs O
and B were of an equal internal diameter or area the liquid would fall
in the limb B as much as it rose in the limb O, and as the rise or fall of
the liquid in one limb only can be most conveniently graduated one
half of the rise or fall or pressure would be lost. I prefer therefore to
make the area of the graduated portion of the limb O much less than
that of the limb B. In the Drawing the respective internal diameters
of the limbs O and B are th and th so that the areas are as 1 to 144.
If therefore the liquid be depressed, say, to 16th of an inch in the
limb B it will rise (143 1") in the limb O, the total difference in the
141"
level of the liquid being 14" I thus utilize the whole of the pressure.
given out by the fan within a fraction.
It is evident that if the limbs O and B were of equal internal area I'
should require the fan to be able to give out double the pressure in
order to have the same graduated length upon the limb O.
Figure 2 is a section drawn full size of the regulator R before referred
to, and which as shewn in the Drawing, can be conveniently mounted
upon the same box wood or other scale as the glass tube; P is a tapered
plug which can be revolved around the screwed end c of the air tube T,
and fitting air-tight into its similarly tapered chamber D. When
screwed home tight into its chamber D there will of course be no escape
of air, but if the plug P be revolved so as to withdraw it more or less
from its chamber D there will evidently be an escape of air more
or less in the direction shewn by the arrows. The plug and its
chamber being tapered a small regulated escape of air can be thus
provided for and the adjustment can be made with the greatest nicety.
The use of this regulator in adjusting the indicator is this, it is evident

page_text: that there might be a difficulty in making a number of fans which at
any given speed should all give the exact pressure required and it would
be very inconvenient to make every indicator to a different scale. If
therefore the fans be constructed to give a little more than the exact
pressure required at any given number of revolutions then by means of
the regulator as much air can be allowed to escape as will reduce the
pressure of the current of air down to the exact pressure required. Any
number of fans can thus be all easily adjusted to the same scale and
any number of indicating tubes connected with the same fan can be thus
brought into unison with each other. It is evident that a simple tap or
any mechanical equivalent which will allow a certain portion of the
pressure or current of air to escape will answer the purpose equally
well, but I prefer such an arrangement as shewn in Figure 2. Again a
graduated scale can be fixed against the edge k of the crown of the tapered
plug P, and a permanent point marked and fixed upon in the leg O at
which the liquid shall always at any given number of revolutions be kept
standing under the pressure from the fan, and the scale is then marked
with the number of revolutions at the different degrees or divisions to
which the plug being drawn back, and being thus so much opened will
keep the liquid stationary at the point fixed upon and marked on the
leg O, and of course if the liquid either rises above the point fixed upon or
falls below it, it shews that the axle is revolving either quicker or slower
than the number of revolutions required, and a scale can be graduated
upwards and downwards from the point fixed upon to shew the increased
or decreased number of revolutions at which the axle may be revolving
above or below the actual number of revolutions at which it is required
to drive the revolving axle.
Figure shews an indicator constructed with the limb O laid hori-
zontally or at a slight inclination. The advantage with this form of
indicator is that it is very delicate and sensitive and only a very slight
pressure upon the liquid in the limb B is required, and consequently a
much smaller fan is sufficient than when the limb O is perpendicular.
It also has the advantage that the limb O may without difficulty be
made any length wished; the divisions on the scale marking.each
revolution may consequently be made any length wished, and also, as
shewn in Figure 4, the inclination of the limb O may be made to
vary in its length, a very important advantage, as the divisions at any
portion of the length may thus be increased or decreased, as shewn.

page_text: divided.
Another important advantage also with this form of indicator is that
no regulator is required, as the indicator can be easily adjusted by simply
increasing or decreasing the inclination of the limb O, care being of
course taken that the liquid stands at o, o, when no pressure of air is
acting upon the liquid in the limb B. Instead of adjusting the indicator
by allowing a small regulated escape of air I can also adjust the
indicator by varying the proportion which the internal area of the one
limb bears to that of the other limb, thus if the diameter of the limb O
and B of any syphon tube be respectively 1 and 2 their areas will be
as 1 and 4, with a pressure sufficient to produce a total difference in
the level of the liquid of, say 15., the liquid would be depressed 3". in
the limb B and raised 12'. in the leg O. If I increase the difference
between the areas of the two limbs the rise in the limb O will be greater
and the fall in the limb B will be less. If I decrease the difference the
rise in the limb O will be less and the fall in the limb B will be greater.
I can thus produce in the limb O any rise required from any given
number of revolutions by substituting syphon tubes for each other, in
which the proportion between the areas of the two limbs slightly varies
as may be required, but as it would be inconvenient so to adjust the
indicator to any nicety, I vary the proportion between the areas
of the two limbs by means of the arrangement shewn in Figure 5.
O, B, Figure 5, is an inverted syphon tube as before, the current of air
from the fan entering the limb B at the side. E is a solid rod passed
through the air-tight stuffing box F fixed on the top of the limb B, and
suspended thus in the centre of the limb B. Let the total area of the
limb B be 5, and that of the rod El, also the area of the limb 01, as in
the case last supposed, the area of the annular ring of liquid in the
limb B will then be to the area of the liquid in the limb O as 4 to 1, as
in the case last supposed. It is evident that by increasing or decreasing
the area or contents of the rod E the indicator can be adjusted with
facility to the greatest nicety. If the rod E be made larger the
difference between the areas in O and B will be decreased, the rise in
the limb O will be less and the fall in the limb B will be greater. If
the rod E be made less the difference between the areas in O and B will

page_text: limb B will be less.
When I obtain the pressure of the current of air from a centrifugal
fan the divisions marking each increased number of revolutions will, as
already explained, increase in length as the square of the speed. It may
in some cases be more convenient that these divisions should be equal,
which I can accomplish by tapering one of the limbs, as will be under-
stood by the diagram F. If, say, one revolution per minute produce a
difference in the level of the liquid of, say, one degree, which the limbs
at o, o, being of equal areas, will be degree rise and fall in each limb,
then 1, 2, 3, revolutions will produce a total difference in level of
1, 4, 9, degrees, and if at each successive increase in the number of
revolutions the increased rise in the limb O. is required to be only.
1 degree, then it is evident that the total fall from o, o, in the limb B
at each successive increase in the number of revolutions must. be
2,6 degrees, and at each successive increase in the number of
revolutions the increased number of degrees fallen in the limb B must.
be 2, 4, 6, degrees, and therefore the limb B must be constructed with its
capacity decreasing downwards. The total capacity of each successive
division on the limb B being equal to the capacity of one division or
degree on the limb O. Thus in the diagram the total capacity of each
division, b, c, d, e, f, g, h, on the limb B, must be each equal to 1 division
or degree on the limb O; and if each division be supposed to be a
parallel tube the area of each would be to the area of the parallel
limb O as,th, th, th, th, th, th, respectively, and so on, but
it is evident that each of those divisions may also be a frustra or portion
of a cone, tapered one into another, or any other shape, so long as their
proper capacities are not altered.
Also on the other hand it is evident that if I construct the limb B of
a capacity increasing downwards in the proper proportion I can then
place a scale against the limb B and indicate cach successive revolution
by an equal division downwards.
a.
Also in the first case instead of actually making the limb of a
decreasing area or capacity downwards I can insert a rod, as in E,
Figure 5, but of an increasing size downwards so as to reduce the actual
body of liquid in the proportion required.
.

page_text: Also in the second case I can also insert a rod, as in E, Figure 5, but
decreasing in bulk downwards.
It is also evident that in any case the bulk of the liquid in either of
the limbs or both of the limbs can be cither increased or decreased by
either of the above methods so as to obtain the required proportion of
liquid in each limb.
Also it is evident from Fig. 4 that I can curve a horizontally laid tube
so as to produce equal divisions.
Also either by altering the proportion of the tubes at any particular
point or by use of the rod E I can it is evident obtain with a perpen-
dicular tube a scale similar to that shewn in Figure 4 or otherwise.
The fan can be driven by the revolving axle or any part revolving in
connection with it by means of toothed wheels, friction gear, or a belt,
or other mechanical equivalent, provided due care be taken to prevent
any slipping of the belt or friction goar; and the speed of the fan
relatively to that of the revolving axle can be anything required, either
greater or less, so as to produce any desired pressure.
Any mechanical arrangement producing a current or pressure of air
will answer my purpose equally well as an ordinary centrifugal fan
provided always that the pressure shall increase or decrease as the speed
of the revolving axle with which it is connected and by which it is
driven increases or decreases and the pressure must be immediately
dependent upon the speed of the revolving axle. Thus a reciprocating
or intermittent blowing arrangement would answer my purpose, but it'
would not have to be so intermittent in its action as to produce such an
ebullition of the liquid as would render the indicator difficult to read off,
and if there be any valves in the air pipes or mechanical arrangement
then the use of the regulator cannot be dispensed with, as otherwise the
liquid would be forced out and would not fall upon any decrease of
speed nor return to zero, but the regulator being opened and properly
adjusted the liquid will rise in the limb O until the pressure or head is
sufficient to drive out through the opened regulator all the surplus
air.
In some cases I prefer using some of the different "blowers" now in
common use, as they will give a higher pressure than a centrifugal fan
at a much less speed which is a convenience; they should of course be

page_text: speciany
size. .
Constructed IOT the purpose of a very small or miniature
The fluid in the syphon tube may be either mercury, water, spirit, or
any other fluid, according as a greater or less pressure is available, or as
may be preferred.
The tubes, as also the adjusting and regulating rods, may be of any
shape and may be of glass, or metal, or any other suitable material or a
combination of them. If not of a transparent material a piece or strip of
glass can be let in on the face to read off the level of the fluid, or a float'
can be used pointing to the marks on the scale, but I prefer to read the
levels direct.
In some cases the tubes may be faced with glass and the back may be
in the form of a packing piece adjustable and liquid tight between the
two sides so that the area can be easily adjusted to anything required.
Instead of gauging the pressure of air against a column of liquid it is
evident that its pressure can be measured or gauged against a spring
weight or any pressure gauge in ordinary use, but I prefer to use a
column of liquid as being equally convenient, the most simple, and the
most likely to give accurate results, and not subject to any getting out
of order. Of course whatever gauge be used must be suitably divided
and numbered so as to shew the number of revolutions per minute.
Instead of gauging the pressure of the current of air it is evident that
I can gauge the vacuum produced by an exhaust, and where I use a
liquid syphon gauge it is evident that whilst I apply the pressure to,
say, the limb B, the air can also be exhausted from the limb O.
When intended for use on board steam ships, in order to prevent the
accuracy of the instrument being affected by the heel or oscillations of
the ship, the indicating syphon tube and scale can be hung in gimbals
the same as an ordinary marine barometer, the connection with the fixed
air tubes being by means of an india-rubber tube in order to allow
free motion in the gimbals, or a ball-and-socket joint, through which the
current of air can pass, can be introduced where the indicating syphon
tube is connected with the air tubes, so that the former may hang freely
and accommodate itself to the motion of the ship, or it may be hung in
any other convenient manner.

page_text: An ordinary centrifugal fan will force air more or less whichever way
it may be revolved, but one other advantage of using a "blower" such
as already referred to is that when its motion is reversed the blower will
exhaust the air from the limb B; the scale can therefore in this case be
continued below zero, so as to shew in the case of a steamer the number
of revolutions being made astern, which is a very important advantage.
When intended for use on either a ship or a locomotive a scale can also
be attached shewing the rate in knots or miles per hour of the ship or
locomotive.
Instead of a syphon tube a tube O, Figure 7, may be used, with its
lower end immersed in a cup or cistern B. The top of the tube O is
open to the air at a, as before; the cup or cistern B is closed air-tight
at the top.
The current or pressure of air is conducted from the fan through the
air tube T, which enters the cup or cistern B above the level of the
liquid. The cistern is filled with the liquid through the open end a of
the tube O till the liquid stands in the tube or cistern at zero or 0, 0,
the fan or axle being at rest. The top of the cistern is depressed round
the tube O to allow of the zero point 0, 0, being seen.
The pressure
from the fan will then cause the liquid to rise in the tube O, which is of
course provided with a scale suitably marked.
In any case, instead of the tube O being left at the top a open to the
atmosphere it can be closed air-tight, so that as the liquid rises in the
leg O it will compress the air enclosed at the top of the tube. In this
case the pressure of air from the revolving fan will be measured by the
space into which it is able to compress the air in the top of the tube O,
together with the height of the column of fluid.
A small float can be placed in the limb O, the same as in a maximum
thermometer, so that the instrument can thus be made to shew the
maximum speed at which the revolving axle may have been driven at
any moment. This is a very important advantage.
.
Amongst other important advantages which I claim for my Invention
is the great ease with which by means of small air tubes 2 or more
indicating tubes or gauges, each with its own regulator when a regulator
is used, may be attached to the same fan or blower," and these indi-
cating tubes or gauges may be placed wherever required; thus on board
ship one may be placed in the engine room, another on the bridge, and
"

page_text: another in the cabin or wherever thought desirable. Also in mills or
manufactories they can be placed in the manager's office or wherever
required..
Also another very important advantage is that I entirely overcome in
the simplest manner possible what has hitherto been found to be a very
great difficulty and obstacle in the practical application of any such
instrument, viz., that where the fluctuations in the speed of the revolving
axle are very sudden and violent, as is the case in screw steamers where
the engines are liable to race or revolve at an immense speed when the
screw owing to the motion of the steamer is lifted out of the water, then
if there be a rigid connection between the index or the pointer on the
index and the apparatus and its revolving axle the pointer owing to its
following rigidly every sudden and violent fluctuation in the revolving
axle oscillates so violently over the index that it is almost impossible to
obscrve it accurately or to any practical good. This difficulty is in my
instrument entirely overcome in the simplest manner possible by merely
making the total capacity of the air tubes bear a proper proportion to
the volume of air delivered by each revolution or any given number of
revolutions of the fan or "blower." Thus if it take so many revolutions
of the fan or «
blower," and consequently of the revolving axle to fill
the air tubes with air of the pressure due, or to increase the pressure to
the pressure due to that number of revolutions it is evident that the
index will shew the average speed of every such number of revolutions of
the revolving axle. The instrument can thus be made as." dead" or as
lively" as may be required.
"
If necessary in some cases air chambers can be introduced in any portion
of the length of the air tubes. These are very important advantages which
entrance immeasurably the value of my Invention. The instrument can
also be adapted to register the maximum and minimum number of revo-
lutions at which the axle may be revolving at any time exactly the same
as any registering thermometer. For instance, if mercury be the liquid
used in either the perpendicular or horizontally laid tubes a float can be
inserted in the limb O to register the maximum speed. Again, for
instance, if spirit be used in a horizontally laid tube a float can bo
inserted in the limb O to shew the minimum speed.
Figure 10 shews an arrangement to register both the maximum and
minimum speed the same as an ordinary maximum and minimum
registering or Six's thermometer. The additional registering portion

page_text: being upon exactly the same principle as such a thermometer, O, B, is
the inverted syphon tube partially filled with liquid as before. The
limb O is continued and bent round so as to form another syphon
tube U, V. The end of the limb V is formed into a bulb, and of course
closed at the top exactly as in the thermometers referred to. The
limbs U, V, are filled with mercury up to 0, 0. The limb B is of
course connected with the air tubes leading from the fan or blower as
before. The pressure of the current of air from the fan pressing upon
the surface of the liquid in the limb B as before will of course cause the
liquid to rise in the limb O as before, which will set in motion the addi-
tional maximum and minimum registering arrangement. In the limb U,
which is graduated downwards from 0, 0, zero, the mercury will be
depressed. The axle having attained its normal speed the float x must
then be set down upon the mercury in the usual way. If the speed of
the axle decreases the mercury will then of course rise again, raising the
float x, which will of course then register whatever may be the least
speed the axle may revolve at. As the mercury falls below 0, 0, zero in
the limb U it will of course rise above 0, 0, zero in the limb V, which is
graduated upwards from 0, 0, zero, and pushing with it the float Z the.
maximum speed will of course be registered.
When the axle is at rest the liquid in O, B, will not be level, as in the
case of a simple inverted syphon tube O, B, but the level of the liquid in
the limb B must be as much higher as the level of the liquid in the
limb O as will give as sufficient head or pressure as will overcome what-
ever pressure of air may be required in the bulb A, A, to work the
arrangement. It is evident I can also register the maximum and
minimum speed in any inverted parallel syphon tube if care be taken
that the minimum float be so arranged as not to be forced down by the
current or pressure of air from the fan, or the arrangement shewn in
Figure 10 can be laid horizontally. If it be required that whenever the
motion of the revolving axle be stopped the minumum float should
nevertheless not recede to zero, this can be easily accomplished by
inserting a tap in the air tube immediately above the limb B. If this
tap be closed the pressure of air will be retained in B, and the gauge
can thus be kept stationary until the axle be again set in motion, when
the tap can be again opened. Again, if wished the instrument can be
made to register or give a permanent record of the revolutions exactly
the same as a barometer is sometimes made to do, viz., by placing in the

page_text: limb O, which is left open to the air, a float with a pencil or marker
attached, making upon a revolving cylinder or band of paper properly
divided by lines into squares or spaces to shew the varying speeds at
different periods of the revolving axle. The revolving cylinder or band
of paper must of course be kept revolving at a fixed and regular speed
by clockwork or otherwise.
Instead of pumping or compressing a column of air to act upon the
surface of the liquid in the graduated tube, or to be otherwise gauged or
measured, I can also indicate the number of revolutions made by any
revolving axle by means of a column of fluid alone. To effect this I
cause any revolving or rotatory pump or turbine to raise a column of
fluid from out of a cistern or cup into an upright or inclined tube. It
is evident that the quicker the pump rotates the higher the fluid will be
raised in the tube, and the tube can be graduated in degrees or devisions,
shewing the number of revolutions. The pump must of course be in
connection with the revolving axle the same as the fan and under the
same conditions. Figure 8 shews a very simple arrangement to effect
this. B is a cup or cistern; O is a tube open to the air at the top a as
before, and which revolves in the cross pieces G, G, by means of a
toothed wheel or pulley M connected with the revolving axle. The
lower end of the tube O is immersed in the fluid, and from it project
the arms L, L, which are bell-mouthed and open to the fluid on opposite
sides, and shaped as shewn in the section F 9. The cistern and tube O
are filled with fluid to the level zero 0, 0. It is evident that as the
tube O and arms L, L, revolve the fluid will enter the open bell-mouthed
limbs and rise in the tube O above the level of the fluid in the cup or
cistern, the height to which the fluid will thus rise in the tube O
depending upon the speed at which it revolves. This height will there-
fore be an indication of the speed at which the tube O and the revolving
axle from which it receives its motion revolve; and the tube O can
therefore be graduated in degrees or divisions to shew the number of
revolutions made by the axle revolving in connection with it. In order
to render their action more effective the arms L, L, may revolve in.
different planes.
Instead of the whole of the tube O revolving only its lower end, to
which are attached the limbs or arms L, L, and pulley M need revolve,
the upper or fixed portion being of glass to observe the level of the

page_text: In the above arrangement the fluid will not rise in the tube O above
the level of the fluid in the cup or cistern more than the height due to
the speed at which the limbs L, L, revolve, but if the pump arrangement
be such that the fluid is forced into the tube then, as already mentioned
in the case of any blowing arrangement with valves, a regulator must
be introduced between the pump and the indicating tube. In this case
it would be convenient to place the indicating tube or gauge away from
the pump, connecting the two by means of a length of pipe or tube, in
which length the regulator could be most conveniently placed.
The regulator being opened and properly adjusted the fluid will bo
forced into the pipe or tube and rise in the indexed portion O until the
pressure or head is sufficient to drive out through the opened regulator
all the surplus fluid, which can be reconveyed back to the cistern or
cup or otherwise disposed of. The regulator will thus prevent the fluid
being forced out at the open end a of the tube O. The gauge can in
this case very conveniently be an inverted syphon tube, as before, filled
with mercury, against which the fluid pumped up can act.
Having thus described the nature of my Invention and the manner of
performing the same, I would have it understood that I claim,―
1. The combined arrangement of fan and pressure indicator, sub-
stantially as herein described, to indicate the speed of revolution of any
shaft from which the fan may be driven.
2. The combined arrangement of pressure indicators, substantially as
herein described and shewn by Figures 1, 3, 4, 5, 7, 8, 9, & 10 of the
Drawings annexed.
3. The employment of the regulator shewn at Figure 2 of the
Drawings in a revolution indicator, substantially in the manner herein
described.
4. The employment of the rod E as a regulator in a revolution indi-
cator, substantially in the manner herein described.
5. Tapering either or both of the limbs of the revolution indicators,
substantially as and for the purposes herein described.
6. Constructing the revolution indicators to register the maximum or
minimum speed, or both, substantially in the manner herein described.

page_text: 7. The combined. arrangement of pressure indicator, substantially as
herein described and shewn at Figure 8.
In witness whereof, I, the said David Alexander Halket, have here-
unto set my hand and seal, this Thirtieth day of September, in
the year of our Lord One thousand eight hundred and seventy-
four.
D. A. HALKET. (L.S.)