An Improved Tachometer or Speed Indicator.
Year: 1894

page_text: Date of Application, 27th June, 1894
Complete Specification Left, 21st Mar., 1895-Accepted, 4th May, 1895
PROVISIONAL SPECIFICATION.
An Improved Tachometer or Speed Indicator.
1, THOMAS WALTER HARDING of The Tower Works, Globe Road, Leeds,
Engineer do hereby declare the nature of this invention to be as follows:-
My invention consists in improvements in the speed indicator described in
Harding & Willis's Specification No. 1444-April 12th 1877.
The improvements consist chiefly in the method of driving the instrument from
the side instead of the back as heretofore, by means of bevil wheels and a
horizontal shaft passing through a projecting boss on the body of the instrument
and fitted at its outer end with a driving pulley; and in the manner in which the
body of the instrument is swivelled in its pedestal by means of the before-
mentioned projecting boss passing through the head of the pedestal so that the
dial may be tilted to any angle. The spindle on which the pointer or hand is fixed
is fitted with a cam which engages with a spring and acts as a brake for checking
vibration of the pointer when indicating high speeds.
Dated thin oath down of Tum 1901
COMPLETE SPECIFICATION.
An Improved Tachometer or Speed Indicator.
1, THOMAS WALTER HARDING of The Tower Works, Globe Road, Leeds in
the County of York, Engineer do hereby declare the nature of this invention and
in what manner the same is to be performed, to be particularly described and
ascertained in and by the following statement:
My invention consists in. improvements in the speed indicator described in
Harding and Willis's Specification No. 1444 A.D. 1877. The improvements
consist chiefly in the method of driving the instrument from the side instead of the
back as heretofore by means of bevel wheels and a horizontal shaft passing through
a projecting boss on the body of the instrument and fitted at its outer end with a
driving pulley; and in the manner in which the body of the instrument is swivelled
in its pedestal by means of the above mentioned projecting boss passing through
the head of the pedestal so that the dial may be tilted to any angle.
The spindle on which the pointer or hand is fixed is fitted with a cam which
engages with a spring and acts as a brake for checking vibration of the pointer
when indicating high speeds.
Reference is made to the sheet of drawings forming part of this Specification in
which similar letters indicate corresponding parts in each of the figures.
Fig. 1 is an elevation and Fig. 4 is a plan of my tachometer.
Figs. 2 and 3 are enlarged views of certain parts hereafter referred to.
A is the pedestal through the head of which passes the boss B forming part of the
body of the tachometer. The body may be rotated round the axis of the boss Band
held fast in any position by tightening up the set screw C. D is the driving pulley
fastened to the shaft E which is held from moving laterally by the plate which
is in halves and fits into the groove e'. The plate F is screwed to the boss P. To

page_text: the shaft E is fastened the bevel wheel G which gears into the bevel wheel H
which is fastened to the shaft J to which is fastened the fan K. L is a secondary
fan fastened to the spindle M shown more particularly in Figs. 2 and 3 which is
free to revolve in the hardened steel bush N screwed into the front plate O. The
spindle M has fastened to it the cam P which has fastened to it one end of the steel
spring Q the other end being fastened to the plate O by means of the connecting
bar R. S is a spring fastened to the front plate O with its free end pressing upon
the cam P. T is a pointer which is fastened to the spindle M by the milled edge
mut U which is screwed on the spindle M and clamps the pointer T against the
plate V which is pinned to the cam P. W is the dial of the tachometer and is
marked with a scale with a suitable number of divisions representing different
speeds of revolutions.
It will be readily seen that when the driving pulley D is caused to revolve it
carries with it the shaft E and by means of the bevel wheels G and H the fan K
which in turn would carry round with it fan L by means of the friction of the air
passing between the vanes on each of the fans, but the rotation of the fan L is
retarded by the action of the spring Q and the pressure of the spring $ upon the
periphery of the cam P. As the pointer T is fastened to the spindle M it
necessarily moves with it until the tendency of the fan L to rotate is balanced by
the retarding action of the springs Q and S and the proportions of these springs
are so arranged that the division of the scale upon the dial at which the pointer T
stops indicates the speed of rotation of the driving pulley D.
It will also be readily seen that when the fan L rotates and with it the cam P,
the increasing periphery of the cam P exerts an increasing tension on the spring S
which thus acts as a brake upon any excessive vibration of the fan L consequent
upon a rapid variation of the speed of rotation of the fan K.
Having now particularly described my said invention and in what manner the
same is to be performed I declare that what I claim is :-
(1.) A tachometer working on the fan principle as described driven by means of
the driving pulley D, the shaft E and the gear wheels G and H. The plane of
the driving pulley being at right angles to the plane of the dial substantially as
described and shewn.
(2.) A tachometer working on the fan principle as described, the dial of which
may be tilted at any angle by partially rotating the body round the axis of the
boss B which passes through the head of the pedestal A and can be locked in any
position by tightening the set screw C in the head of the pedestal substantially as
described and shewn.
(3.) In the tachometer described a cam P rotating with the fan L and the
spring S pressing upon the periphery of the cani P in such a manner as to act as a
brake upon the rotation of the fan L.
Dated this 20th day of March 1895.
T. WALTER HARDING.