AN IMPROVED SPEED INDICATOR
Year: 1884

page_text: We, JOHN FARQUHARSON, of Fulham, in the County of Middlesex, and DANIEL
WILLIAM LANE, of Southsea, in the County of Hampshire, both Electricians,
do hereby declare the nature of the said invention for "AN IMPROVED SPEED
INDICATOR to be as follows:-
Our invention relates to a device designed to indicate the speed of rotation of a
revolving shaft or crank or other moving part, at any distance therefrom, and at
any time, in a simple and efficacious manner.
We effect our objects by the combination of certain mechanical and electrical
appliances as follows:-
A finger or pointer is made to travel round a graduated dial, and this travel is
caused by a coiled spring against the tension of which the pointer is turned. The
spindle of the pointer carries in rigid attachment an insulating piece, a ratchet
wheel, and a finger corresponding to the pointer. This finger engages with a
detent at the position of maximum coil of the actuating spring, which the zero of
the scale on the dial, and this detent is controlled by the armature of an électro
magnet. The circuit of the electro magnet controlled by a contact button is closed
by a contact on one point of the revolving shaft or crank, and, the armature being
drawn to the electro magnet, the detent is released and the finger (and conse-
quently the pointer) commences to travel. There is, however, another electro
magnet, and the circuit (now broken by the revolution of the shaft) is diverted to
this by a contact spring which falls, on the commencement of the travel, from the
insulating piece on the spindle on to a metal collar; the first circuit being cut by
the same means. Upon the contact on the shaft, crank, or moving part, again
coming into action after completing its revolution; the new circuit is closed, the
second electro magnet attracts its armature, which operates a spring detent
normally holding a pawl, and the pawl engages with the ratchet wheel in rigid
attachment to the spindle, and the further travel of the finger is stopped. Alter-
natively, the ratchet wheel may be dispensed with, and a detent may be substituted
for the pawl, to stop an isochronous fly, conveniently provided to control the
mechanism. The graduations on the dial and the tension of the spring are
relatively calibrated to indicate the speed of revolution relatively to any given unit
of time.

page_text: Weights may be used to cause the travel of the finger, though we prefer a spring
as specified. In the latter case, the spacing of the graduations must be made with
regard to the diminishing clasticity of the spring while uncoiling, or a pair of
compensating wheels, spirally or eccentrically geared, may be interposed between
the pointer and the actuating mechanism to produce uniformity in the divisions
upon the dial.
1 ..
1
D 100
We, JOHN FARQUHARSON, of Pomona House, Fulham, in the County of Mid-
dlesex, and DANIEL WILLIAM LANE, of Southsea, in the County of Hampshire,
both Electricians, do hereby declare the nature of the said invention for "AN
IMPROVED SPEED INDICATOR and in what manner the same is to be performed to
be particularly described and ascertained in and by the following statement:-
"
Our invention relates to a devico designed to indicate the speed of rotation of a
revolving shaft, crank, or other moving part, at any distance therefrom, and at any
time, in a simple and efficacious manner. We effect our objects by the combination
of certain mechanical and electrical appliances, and in order that the same may be
fully understood we now proceed to describe them in relation to the drawings
hereunto annexed, reference being had to the letters and figures marked thereon.
Like letters refer to like parts throughout the figures.
Figure 1 is a plan of our device with the face removed.
Figure 2 is a plan showing. face and dial.
Figure 3 is a sectional elevation through X X.
Figure 4 is a sectional elevation through Y Y.
Figure 5 is a detail of the spindle..
The finger or pointer A is made to travel round the graduated dial B, and this
travel is caused by a coiled spring C, against the tension of which the pointer is
turned. The spindle of the pointer carries, in rigid attachment, a collar with the
insulating piece D (Figure 5) and a finger F rigid with the pointer. This finger F
engages with a detent G, at the position of maximum coil of the actuating spring,
which is the zero of the scale on the dial, and this detent is controlled by the
armature H of an electro magnet H¹. The circuit of the electro magnet H¹,
controlled by a contact button K, is closed by a contact piece R on one point of
the revolving shaft or crank Q, of which the speed is required to be indicated.
The circuit thus closed is-a, R, b, c, k, case, spindle N, f, g, H¹, h, k; and the
armature being thereby drawn to the electro magnet H¹, the detent G is released,
and the finger F (and the spindle and pointer A) commences to travel. There is,
however, another electro magnet L, and the circuit (now broken by the revolution
of the shaft Q) is eventually diverted thereto by a contact spring M which passes,
on the commencement of the travel of the pointer, from the insulating piece D on
the spindle, on to a metal collar N (Fig 5) the first circuit being cut by the release
of the detent G. Upon the contact R on the shaft, crank, or moving part Q, again

page_text: :-
coming into action after completing its revolution, the new circuit is closed thus:
a, R, b, c, K, case, spindle N, M, m, L, n, k; the second electro magnet L attracts
its armature O, which stops the isochronous fly P, which is provided to control
the mechanism, and the further travel of the finger is thus stopped the time
occupied in the rotation of Q being thus indicated.
Alternatively, the movement of the armature may operate a spring detent
normally holding a pawl, which would thereby be released and engage with a
ratchet wheel in rigid attachment to the spindle.
The graduations on the dial and the tension of the spring are relatively calibrated
to indicate the speed of revolution in relation to any given unit of time.
It is obvious that weights might be used to cause the travel of the finger, though
we prefer the spring as specified; in the latter case the spacing of the graduations
must be made with regard to the diminishing elasticity of the spring while
uncoiling, as shown in Figure 1; or a pair of compensated wheels spirally or
eccentrically geared may be interposed between the pointer and the actuating
mechanism to produce uniformity in the divisions upon the dial.
Having now particularly described and ascertained the nature of our said
invention and in what manner the same is to be performed We declare that what
We claim is:-
In a speed indicator the combination of two electrical circuits consecutively
closed by a contact piece on a revolving shaft (or other moving part) operating
two electro magnets successively setting in motion and stopping by means of
suitable detents on their armatures spring mechanism causing a pointer to travel
over a calibrated dial between the period of the contacts (representing one
revolution) substantially as specified.
Dated this sixth day of November A.D. 1884.