AN IMPROVEMENT IN APPARATUS FOR INDICATING THE SPEED OF ROTATING SHAFTS
Year: 1884

page_text: COMPLETE SPECIFICATION.
"
I BEAUCHAMP TOWER of N° 19 Great George Street, Westminster in the
County of Middlesex do hereby declare the nature of my Invention for "AN
IMPROVEMENT IN APPARATUS FOR INDICATING THE SPEED OF ROTATING SHAFTS
and in what manner the same is to be performed to be particularly described and
ascertained in and by the following statement:-
In the Specification to Letters Patent granted to me on the 2nd October 1880,
No 3989, I described apparatus for indicating the speed of rotating shafts. In this
apparatus there is a pump worked from from the rotary shaft compressing air
into a pipe communicating with a pressure gauge, and having an escape aperture
governed by a valve subject to the centrifugal force of a weight caused to revolve
by gearing connecting it to the rotating shaft. The indications of pressure on the
gauge serve to shew the velocity of the shaft. My present Invention consists in
an improved construction and arrangement of apparatus of this kind, as I will
describe, referring to the accompanying Drawings.
Fig. 1 is a longitudinal section, Fig. 2 a transverse and Fig. 3 is a section of the
centrifugal part of the apparatus. A is the shaft, the speed of which is to be
indicated, or it may be a countershaft geared thereto. This shaft, by means of a
crank B, works the piston of the air compressing pump C which has a slide
alternating the admission and emission of air, worked froin a second crank D, or
it might be an occentric on the shaft A. Air is compressed by the pump C into
a chamber E from which a small hole e opens into a second chamber F. This
chamber communicates by a pipe with a pressure guage G, of which there may
be several situated at different places, but all in communication with the same-
pipe.
The shaft A, by means of bevil-gearing a works a vertical tubular spindle H
which passes through a stuffing box into the chamber F. The bore of the
spindle H is fitted at its lower end with a valve I against which an arm J is
pressed by one end of a blade spring K, the other end of which is engaged in a
notch in one of two tie bolts L L. These tio bolts connect two cylindrical
vessels M M which are pivotted to a ring shaped frame O forming part of the
vertical spindle H. The vessels M M are filled with liquid somewhat viscous, such
as glycerine, and within each of them there is fixed a cylindrical shell N. I prefer

page_text: to add to the apparatus a second pump P which serves to shew, by communication
with a gauge, the direction of revolution of the shaft A in the manner described
in the Specification of Letters Patent, granted to me on 19th December 1879,
N° 5205, but this pump P with its connections forms no part of my present
Invention.
The action of the apparatus is as follows:-When the shaft A revolves, causing
the pump C to compress air into the vessel E and chamber F, a portion of this
air tends to escape past the valve I, but at the same time, the two tie bolts L L
tend by their centrifugal force to take such a position as to communicate through
the spring K and the arm J, a pressure closing the valve I. Consequently, the
pressure maintained in the chamber Fand in the gauge or gauges G, communi-
cating with it, is such as is determined by the centrifugal force of the tie bolts L L,
and the gauge therefore gives an indication of the speed of the shaft which
produces this centrifugal force. When the movements due to variations of the
centrifugal force communicated through a spring are not damped, the result is a
continued oscillation of the moving parts and of the index of the gauge. The
inertia of the liquid contained in the vessels M M serves by its friction on the
interior of the vessels M M and on the shells N N to retard the movements of
those vessels round their axes and to prevent such sudden movements as would be
productive of oscillation. By this means, the gauge is made to give a steady
indication of the average speed of the shaft to which the apparatus is applied.
Having now particularly described and ascertained the nature of my Invention
and in what manner the same is to be performed, I declare that what I claim is :-
In apparatus for indicating speed of rotating shafts by gauging air pressure
governed by an escape valve, subject to the centrifugal action of revolving weights
communicated to it through a spring, applying to the axis of vibration of tho
weights, vessels containing liquid, so arranged as to damp their vibrations,
substantially as and for the purpose herein set forth.