A NEW OR IMPROVED APPARATUS FOR INDICATING THE SPEED OF ENGINES AND OTHER MACHINERY AND SHIPS, SUITABLE ALSO FOR OTHER PURPOSES
Year: 1874

page_text: PROVISIONAL SPECIFICATION left by Lewis Potter Muirhead at the
Office of the Commissioners of Patents, with his Petition, on the
1st June 1874.
I, LEWIS POTTER MUIRHEAD, of the Firm of James Muirhead and
Sons, Nautical Instrument Makers, of Glasgow, in the County of
Lanark, North Britain, do hereby declare the nature of the said In-
vention for "A NEW OR IMPROVED APPARATUS FOR INDICATING THE SPEED
OF ENGINES AND OTHER MACHINERY AND SHIPS, SUITABLE ALSO FOR OTHER PURPOSES,"
to be as follows :-
My said Invention consists of a new or improved construction and
arrangement of the parts of a machine, instrument, or apparatus for
indicating at any moment the speed of steam and other motive engines,,
or the number of revolutions of their shafts or other parts, and of
other rotating shafts and machinery or pumps; suitable also as a liquid
meter, and for registering the speed of ships through the water, and
as a regulating safety valve for steam boilers and other fluid-pressure
vessels; all as herein described or specified in connection with the two
Figures on the accompanying Sheet of Drawings, that is to say:-
Figure 1 is an external elevation of the instrument which is preferably

page_text: made of brass throughout; Figure 2 is a section showing the working]
parts of the same suitable for registering the speed of a motive-power
engine, formed or constructed and operated all as follows:-A is the
inlet pipe; B is the outlet pipe; D, a disc (valve, lid, or piston)
attached to a piston rod P working through a tube, bearing, or guide
T, T; the piston rod has a mushroom-shaped head M to compress the
vulcanized india-rubber air ball R; J is a union joint through which
the air in the ball communicates with the indicator or dial by means
of a tube leading thereto. The ball is sprung over the flange F attached
to the union joint, and fixed tightly against the top of the cone tube
Q, Q; S, S, are stays supporting the lower end of the tube, bearing, or
guide T, T.
When in use the instrument is firmly bolted by the flange of the
inlet branch A to the delivery pipe of a reciprocating pump of any
construction giving a continuous flow, but preferably to a California
pump, the lever of which is connected to the engines whose revolutions
are to be indicated in such a way as to maintain the fall stroke of the
pump with each half revolution of the engine shaft: The delivery
pipe of the pump, and the inlet A of the instrument are of the same
internal diameter. A tube from J goes to the deck, and a branch to
the engineer's platform, the indicators being placed' wherever most con-
venient for consultation.
1.
A' movement of the same type as an ancroid' barometer is used to
register the indication's, that being found to be the most sensitive and"
reliable, but with this difference, that' the case and glass front are
so fitted as to be absolutely air-tight, as in spirit compasses, and
therefore the movement is unaffected by changes of thic atmospheric
pressure, the only communication being with the ball R by the pipe"
leading therefrom: The hand play's over a white ground' between* it
and the glass on which is marked the scale divided to show the number.
of revolutions' made per minute' as the pneumatic pressure varies with
the length of the tube, and number of dials required. The dials are
marked off when attached to tlie proper length of tube, and in con!
nection with their own instrument and pump. Hence I propose to
mount the indicators on pillars, round which are coiled about 30 feet.
of tubing previous to marking off the dials that in fitting up the length
of tube required, say, from the deck' to 'the engine room; may be wound
off without disturbing the pneumatic equilibrium: The ornamental'

page_text: casing which closes in the tube and forms the finished pillar makes a
handsome stand on deck.
When in action the pump drives the water against the disc D with
more or less pressure, according to the speed of the engines; the disc
rises until it reaches a point in the cone-shaped tube Q at which the
water gets freely past, and there it will obviously remain as long as
the speed is the same.
The mushroom head attached to D compresses
the air in-R,-and-the hands of the barometic indicator's rise 'steadily
until they point to the number of revolutions the engines are making
per minute. As the speed of the engines vary so does the flow of
water, and the disc, with the piston rod and mushroom head attached,
rises and falls accordingly, the hand of the barometer indicating every
change. The water passing through the instrument is returned from
the outlet pipe to the cistern which supplies the pump.
A Bourdon's gauge may be used instead of the barometic indicator
described above. An advantage this has is that it admits of continuous
self-registration in conjunction with a drum revolved by an eight day
lever timepiece.
I also desire to claim the apparatus for the following applications or
purposes for which it is also applicable by merely marking the size
and strength of the different parts and the dials to suit such appli-
cations.
it.
As a water meter to register the number of gallons passing through
As a speed indicator for ships in connection with "Pitots' tubes,"
the tube with orifice looking forward connected with the inlet branch A,
and that looking aft with the outlet branch B.
As a safety valve, the mushroom head buried in the ball R so that
the area pressed upon is equal to the area of the disc D exposed to the
steam in the boiler. The ball R is charged with air to the pressure at
which it is required to act by a compressing pump with gauge attached
fitted to the union J.
Without restricting myself to dimensions, what I desire to claim is,
the arrangement of air ball and piston or valve D in cone tube Q,
shown in the Drawing, as a means of indicating, by the compression
of the air in the ball R, first, the number of revolutions of any shaft

page_text: or part of an engine; second, the number of gallons of fluid passing.
through the coned tube Q; third, the speed of a ship's passage through
the water; and fourth, by the elasticity of the air in the ball R acting
as a spring in retaining the disc or piston D as a valve in its place
against a given pressure as a safety valve.