OR IMPROVED APPARATUS FOR INDICATING AND RECORDING THE AVERAGE PRESSURE, NUMBER OF REVOLUTIONS, AND ACTUAL HORSE POWER OF STEAM OR OTHER ENGINES, THE IMPROVEMENTS BEING ALSO PARTLY APPLICABLE TO OTHER PURPOSES."
Year: 1877

page_text: €
PROVISIONAL SPECIFICATION left by John Troughton Birchall at the Office
of the Commissioners of Patents on the 16th January 1877.
JOHN TROUGHTON BIRCHALL, of Preston, in the County of Lancaster, Engineer,
NEW OR IMPROVED APPARATUS FOR INDICATING AND RECORDING THE AVERAGE
PRESSURE, NUMBER OF REVOLUTIONS, AND ACTUAL HORSE POWER OF STEAM OR
OTHER ENGINES, THE IMPROVEMENTS BEING ALSO PARTLY APPLICABLE TO OTHER
PURPOSES."
The object of this Invention is the construction of a simple and efficient instru-
ment for indicating upon a dial or dials the average pressure throughout the
stroke of a steam or other engine, also the speed of such engine, a modification of
which may be arranged to indicate the actual horse power of the engine, and also
to record the average pressure, number of revolutions, and horse power of the
engine over any required period of time.
In carrying out my Invention as applied to high pressure or non-condensing
engines, I arrange one or a series of chambers communicating with each other
through a small passage. One end of the chamber or series of chambers is in com-
munication with a pressure gauge, and the other end opens into a chamber which
may surround the entire series; this outer vessel is in constant communication
through a double passage and slide valve controlled by the engine with the pressure
side of the cylinder. The effect of this combination of chambers, so connected and
communicating with the cylinder as described is, that the average pressure through-
out the stroke is indicated upon the gauge.
For condensing engines, or compound engines, I arrange a compound gauge with
two dials, back to back; upon one dial the amount of vacuum is indicated, either
in the ordinary manner, or a series of the chambers herein-before mentioned may be
employed to ensure the average vacuum being indicated. The arbor carrying the
pointer of the vacuum side also carries the dial of the pressure side, which revolves
therewith; the pointer of the pressure side indicates the average pressure as herein-
before described, but as the dial of the pressure side has likewise been moved
through a space corresponding with the amount of vacuum or back pressure, the
result is an indication of the average pressure upon the piston throughout the
stroke, arising both from pressure and vacuum, or back pressure; for this purpose a
liaphragm gauge may be used, having the under side of the diaphragm in com-
LD 0.17

page_text: munication with a series of chambers herein-before described, and the upper side
connected to the condenser, or in the case of a compound engine intermittently to
the back pressure side of the cylinder, thus deducting from or adding to the mean
pressure. Knowing the area of the piston, and in the case of engines having a
uniform piston speed, the pressure dial admits of being graduated with a special
series of gradations and figures for indicating the actual horse power of the engine to
which the apparatus is applied.
In some cases I arrange that the same rod which controls the slide valve herein-
before mentioned shall work a cylinder carrying a sheet of paper, upon which a
record of the average pressure may be obtained by means of a pointer or pencil
worked by the mechanism of the pressure gauge, and upon which paper the
number of revolutions of the engine may also be recorded by the same pointer
or pencil.
And in order to provide a constant indication of the speed at which the engine
is running, I arrange a cylindrical vessel to revolve on a vertical axis, and either to
be driven directly by the engine or to be driven by a special arrangement of
mechanism peculiar to this Invention, but which is equally applicable for driving
other speed indicators which run at a higher velocity than the prime mover under-
going indication. This driving mechanism consists of a spring drum and wheel-
work for increasing the speed, and which spring is constantly being wound up by
means of a ratchet wheel, the ratchet lever of which, in this case, is worked by the
engine, but when applied for indicating the speed or number of revolutions or
strokes of any other mechanism may be connected to and driven by such mechanism.
The interior of this cylindrical vessel contains mercury or other fluid, upon the
surface of which rests an annular float, which is capable of rising with the mercury
as by centrifugal force; such mercury rises up the sides of the vessel, and thus, by
means of a spindle attached to such annular float, and carrying at its upper ex-
tremity a rack gearing with a pinion upon the spindle of an index finger an
indication of the speed at which the engine is running at any moment may be
obtained upon a graduated dial.