In- PROVED APPARATUS FOR INDICATING THE DIRECTION AND SPEED OF REVOLVING- SHAFTS, PARTICULARLY THOSE OF MARINE STEAM ENGINES
Year: 1875

page_text: PROVISIONAL SPECIFICATION left by William Chadburn at tho
Office of the Commissioners of Patents, with his Petition, on the
12th January 1875.
I, WILLIAM CHADBURN, of Liverpool, in the County of Lancaster,
Optician, do hereby declare the nature of the said Invention for “In-
PROVED APPARATUS FOR INDICATING THE DIRECTION AND SPEED OF REVOLVING-
SHAFTS, PARTICULARLY THOSE OF MARINE STEAM ENGINES," to be as follows:-
The object of this Invention is to transmit to an indicator the varying
motions, both as respects speed and direction of rotation of driving
shafts and particularly of the crank shafts of marine engines.
In order that the indicator may show only the mean variations in
speed and not by sudden pulsations exhibit every momentary increase of
speed, I transmit the motion derived from the engine or shaft to bo.
speeded through a circular mercury box to the mechanism that works
the indicator. This box is mounted loosely on a short vertical spindle.
which carries a band pulley that is driven by the engine whose speed is-
to be indicated. The bottom of this box is raised at its centro to
-

page_text: prevent the escape of the fluid contained therein at its junction with the
spindle.
On the inner face of the bottom of the box are formed radial ribs,
immediately above which is mounted a disc or wheel furnished on both
sides with ribs, and having a raised or convex centre. This disc is made
fast to the short spindle before mentioned in order that it may rotate
therewith, and above it is a central division plate of the box ribbed at
both sides like the disc. In the centre of this division plate a conical
hole is made to receive the foot of a vertical spindle which stands up in
the line of the axis of the pulley spindle, and secured to this vertical
spindle near its foot is a second disc or wheel similar to that already
described. A ribbed cover overlying this disc completes the box in
which the discs are free to rotate. This box is charged with mercury or
other suitable fluid, say glycerine, that fills the spaces between the discs
and the top, bottom, and division plato of the box. The connection
therefore between the lower and upper spindles is made by the mercury
filling, which when actuated by the rotation of the lower disc will act
upon the upper disc and give rotary motion to its spindle. This spindlo
through the greater portion of its length is converted into a four-
threaded quick screw upon which a disc works after the manner of a
nut.
The spindle is supported near its extremities by bracket bearings, and
between these and the disc, both above and below the latter, coiled
springs are placed, interposed for the purpose of pressing against tho
disc as it is forced up or down out of its normal position. While,
however, the disc retains its normal position, a central bracket takes tho
pressure of the springs. The object of theso springs is to retain the disc
in a central position, it being free to traverse on the screwed spindle by
reason of the rotation of that spindle, as it is prevented from turning by
mcans of fixed guide rods passing through the disc or nut. Attached
to this disc or nut and standing up vertically therefrom, is a rack which
gears into a pinion, the arbor of which carries an index hand or pointer.
A graduated dial is provided for this pointer to move over, the same
being marked to indicate increase and decrease of speeds.
A means of adjustment is provided for equalizing the pressure of the
springs upon the disc, and ensuring that the pointer shall stand at 0
when the apparatus is quiescent.

page_text: When rotary motion is imparted to the apparatus in one direction the
disc situate between the springs will be forced upwards to a distance
proportioned to the speed of the driving power, and in rising the rack
which it carries will impart motion to the pointer and indicate the mean
rate of speed.
If the direction of rotation is reversed the screwed spindle will forco
down the disc against the pressure of tho-under spring, and its rack will
thereby be caused to pull round the pointer in the opposite direction.
"
Coiled springs in boxes may in some cases be used for acting upon
the travelling disc, but I prefer the arrangement above described.
'
Instead of this arrangement of screwed spindle disc and springs
actuated through the intervention of the mercury box, I may use tho
governor for which I obtained Letters Patent, bearing date October 22nd
1873, No. 3434, and driving it through the intervention of the mercury
box obtain an up-and-down motion, such as that required for working
the pointer.
•
By applying to this combination of mechanism, or to that first
described, an elastic box similar to the chamber of an aneroid barometer
and connecting the same with an air or water tube leading to an
indicator at any desired distance from the mechanism, the speed and
direction of the engines of a steamer may be indicated on the bridge or
other part of the vessel; or the motion for working the indox may be
taken direct from the screw spindle by a band passing over a pulley
keyed to the spindlė..
.