Improvements in Speed indicating Apparatus.
Year: 1894

page_text: Date of Application, 7th Nov., 1894
Complete Specification Left, 7th Aug., 1895-Accepted, 7th Sept., 1895
Improvements in Speed indicating Apparatus.
1, HENRY SIMPSON, of 10 Crooked Lane, Liverpool in the County of
Lancaster, Lamp Manufacturer, do hereby declare the nature of this invention
to be as follows:-
This invention relates to apparatus for indicating at any moment the speed of n
rotating shaft or reciprocating piece in revolutions or strokes, as the case may be,
per unit of time.
In carrying out my invention I take advantage of the fact that if a regular
succession of impulses be given to a body possessing inertia which tend to move it
in a certain direction in opposition to a force which increases as the body is moved
in that direction and which force tends to move the body in the opposite direction,
then for any given number of impulses, say, per minute, the body will take up
a position such that the said force will, in the interval between successive
impulses, move the body back an amount equal to that which it was moved
forward by the impulse; if therefore the number of impulses be proportional to,
say, the number of revolutions of a rotating shaft, this position will correspond to
that number.
In one of its simplest forms my apparatus consists of a toothed rack adapted to
be moved, say, vertically upwards, in opposition to a spiral spring, by a reciprocating
pawl operated by the rotating shaft whose speed is to be indicated; neglecting the
effect of gravity and assuming the spiral spring to be in its zero position, that is to
say, exerting no force on the rack, the latter will be fed upwards by the inter-
mittent action of the pawl till the force exerted by the spring moves the rack down,
during the interval of disengagement of the pawl, an amount sufficient to ensure
the pawl engaging with the same tooth at successive strokes. It follows therefore,
that for any given number of strokes per minute of the pawl, the rack will
take up a position where it has a small vibratory motion only, and further, that
this position, as indicated by a pointer attached to the rack and moving over
a fixed scale, will correspond to the speed of the shaft, since the latter drives
the pawl.
Instead of a rack I find it more convenient to use a toothed wheel which, as it is
rotated by the pawl, coils up or compresses a spiral spring, the said wheel carrying
a pointer moving over a circular scale; or instead of using a reciprocating pawl, 1
may use a continuously rotating piece, operated by the rotating shaft and adapted to.
intermittently engage with the teeth of the wheel. In the latter case the said rotating
piece would have to be flexible, to prevent accidental jamming with the teeth of the
wheel, and, as the direction of rotation of the latter, would be reversed if the shaft's.
motion were reversed, the spring attachment would have to be modified accordingly,
or two springs used.
When a pawl is used I prefer to make it inoperative for a greater part of its
working stroke, and, as the sensitiveness of the apparatus depends upon the fineness.
of the pitch of the teeth, I prefer in some cases to obtain an effect, equivalent to
fineness of pitch, by using a number of pawls of different length.

page_text: It will be seen that the apparatus may be equally well applied to measure the
number of strokes, say per minute, of a reciprocating piece, or to any use to which
an ordinary speed indicator may be applied.
Dated this 6th day of November 1894.
SLOAN & LLOYD BARNES,
Castle Chambers, 26 Castle Street, Liverpool, Agents for the Applicant.
Improvements in Speed Indicating Apparatus.
I, HENRY SIMPSON, of 10 Crooked Lane, Liverpool in the County of
Lancaster, Lamp Manufacturer, 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 :—
This invention relates to apparatus for indicating at any moment the speed of a
rotating shaft or reciprocating piece in revolutions or strokes, as the case may be,
per unit of time.
In carrying out my invention I take advantage of the fact that if a regular
succession of impulses be given to a body possessing inertia, which tend to move
it in a certain direction in opposition to a force which increases as the body is
moved in that direction and which force tends to move the body in the opposite
direction, then for any given number of impulses, say, per minute, the body will
take up a position such that the said force will, in the interval between successive
impulses, move the body back an amount equal to that which it was moved forward
by the impulse; if therefore the number of impulses be proportional to, say, the
number of revolutions per minute of a rotating shaft, this position will correspond
to that number.
In one of its simplest forms my apparatus consists of a toothed rack adapted to
be moved, say, vertically upwards, in opposition to a spiral spring, by a reciprocating
pawl operated by the rotating shaft whose speed is to be indicated; neglecting the
effect of gravity, and assuming the spiral spring to be in its zero position, that
is to say, exerting no force on the rack, the latter will be fed upwards by the
intermittent action of the pawl till the force exerted by the spring moves the rack
down, during the interval of disengagement of the pawl, an amount sutficient to
ensure the pawl engaging with the same tooth at successive strokes. It follows
therefore, that for any given number of strokes per minute of the pawl, the rack
will take up a position where it has a small vibratory motion only, and further,
that this position, as indicated by a pointer attached to the rack and moving over
a fixed scale, will correspond to the speed of the shaft, since the latter drives
the pawl.
Instead of a rack I find it more convenient to use a toothed wheel which, as it is
rotated by the pawl, coils up or compresses a spiral spring, the said wheel carrying
a pointer moving over a circular scale; or instead of using a reciprocating pawl,
I may use a continuously rotating piece, operated by the rotating shaft and adapted
to intermittently engage with the teeth of the wheel. In the latter case the said
rotating piece would have to be flexible, to prevent accidental jamming with the teeth
of the wheel, and, as the direction of rotation of the latter would be reversed if the
shaft's motion were reversed, the spring attachment would have to be modified
accordingly, or two springs used.
When a pawl is used I prefer to make it inoperative for a greater part of its
working stroke, and, as the sensitiveness of the apparatus depends upon the fineness
of the pitch of the teeth, I prefer in some cases to obtain an effect, equivalent to
fineness of pitch, by using a number of pawls of different lengths.
It will be seen that the apparatus may be equally well-applied to measure the

page_text: a reciprocating piece, or to any use to which
an ordinary speed indicator may be applied.
In the accompanying drawings, in which I have illustrated a speed indicator
constructed according to my invention,
Fig. I is an elevation with the portion of the casing and dial removed to show
the mechanism more clearly,
Fig. 1 is an end elevation partly in section on the line A. A. of Fig. I and
Figs. III and IV are detail views.
Throughout the drawings, similar parts are indicated by the same reference
figures, and in the case of sections, the direction in which they are viewed is
indicated by the small arrows placed adjacent to the letters denoting the plane of
section.
The toothed wheel 1 is mounted on a spindle 2 to which it is keyed and which
rotates in two bearings, one at the back formed in the casing 3, and one at the front
formed by the cross bar 4 which is secured to the casing. The teeth of the wheel I
are formed of thin steel strips fixed in slots in the periphery of the wheel, and
the boss of the wheel is elastically connected to the casing by means of a spiral
spring 5.
The driving shaft 6 is provided with a driving pulley 7 and has keyed to it two
eccentrics 8 and 81; the eccentric straps have rods 9 formed integral therewith, and
the ends of the rods are tubular; the driving pawis 10 and 10' have stems 11 which
fit freely in the tubular rods 9, and the rods and pawls are elastically connected by
spiral springs 12 which are secured to the rods and the pawls, respectively, by
forming on the cylindrical portions thereof helical grooves corresponding to the
pitch of the spirals of the springs, into which grooves the ends of the springs are
screwed. The construction of the pawl mechanism is shown to a larger scale in
Figs. III and IV.
The eccentrics are pinned to the shaft so that their centres are opposite to each
other, and the elliptical motion of the engaging portion of the pawl is obtained by
linking each rod 9, by means of a link 13, to a fixed point 14 carried on a pivoted
arm 15; the arm 15 can be adjusted angularly by means of the screw 16 and nut 17,
and by these means the position of the fixed point 14 can be adjusted within limits,
so as to regulate the amount of engagement of the pawls.
The pawls may be prevented from rotating on their stems either by rigidly fixing
the ends of the springs (when they are properly adjusted) to the pawls and eccentric
rods, or by providing a plate having slots in which the bodies of the pawls work and
which prevent them turning.
The wheel is articulated to the hand or pointer which indicates the speed by
means of the spur gear shown. The pinion 18 is keyed to the spindle 2 and gears
with the wheel 19, which is formed integral with the pinion 20 and which is carried
on a stad from the cross bar 4; the pinion 20 gears with a wheel 21 which rides
loosely on the spindle 2 and on to which the hand or pointer 22 is secured. The object
of this gearing is to reduce the motion of the wheel 1 (which may amount to two or
nore revolutions from the zero position in either direction) which is transmitted to
the pointer, so that the latter may move over the whole of the scale, on either side
of the zero mark, in about one third of a revolution.
The scale is engraved on a suitable plate 23 and the instrument has the usual
glass front.
The action is as follows;--The driving pulley is geared to the shaft whose
revolutions have to be indicated, say for example the crank shaft of an engine, and
is of course driven at a speed proportional to that of the said shaft; the pawls
alternately engage with the teeth of the wheel 1 and rotate it either in one direction
or the other according to whether the engine is moving "ahead" or
46 astern."
The rotation of the wheel is opposed by the spring, and the turning effect of the
spring, by which it tends to rotate the wheel in the opposite direction to that in
which it is being driven by the pawls, increases the further the wheel is moved
from the zero position, and a position is reached in which the wheel simply

page_text: vibrates through a small angle, being driven back by the spring, during the period
of disengagement of the pawls, through a distance exactly equal to that through
which it was moved, in the opposite direction, during the immediately preceding
engagement of a pawl, and the scale is so graduated that in each such position
of the wheel the hand indicates the corresponding speed of revolution. As
the pawls turn the wheel in a direction corresponding with their own direction
of rotation the pointer indicates the direction of rotation as well as the speed of
rotation.
Ordinary rotating pieces may be substituted for the pawls provided that, between
each engagement, there is a period during which the wheel is free to rotate under
the influence of the spring. An ordinary cylindrical spiral spring may be used instead
of the flat spiral spring shown and a
❝ fuzee
or "snail" may be used to
modify the turning effect of the spring; where the speed indicator is required
to indicate the direction of motion as well as the speed, and considerable accuracy
is required on both sides of the scale, two spiral springs, and suitable engaging
clutches by means of which one. spring only is rendered operative for each
direction, may be employed, one for ahead and one for astern, instead of subjecting
the same spring to opposite kinds of stress as in the instrument shown in the
drawings.
I have found it best in practice to give the engaging points of the pawls au
elliptical motion as shown in dotted lines in Fig. 111 from which it will be
seen that the major axis of the ellipse passes approximately through the centre of
the toothed wheel and that the ellipse cuts but a small are of the periphery
thereof.
Having now particularly described and ascertained the nature of my said
invention, and in what manner the same is to be performed, I declare that what
I claim is ;-
1. The improved speed indicating apparatus, which consists of a rotatable toothed
wheel having a suitable pointer moving over a scale; a tooth or pawl reciprocated
by the shaft whose speed has to be indicated, at a rate always proportional to the said
speed, and adapted to drive the said wheel by intermittently engaging with the teeth
thereof; and a spring adapted, during the period of disengagement of the said driving
mechanism, to rotate the wheel in opposition thereto; substantially as and for the
purpose described and illustrated.
2. In a speed indicator in combination with a toothed wheel and its attached
spring, a driving mechanism comprising a pair of pawls operated by cranks or
eccentrics and adapted to alternately engage with the teeth of the wheel;
substantially as described and illustrated.
3. In a speed indicator, in combination, the toothed wheel, the spring, and the
driving pawls operated by eccentrics and linked to an adjustable point;
substantially as described and illustrated.
4. The combination and arrangement of parts forming the improved speed
indicator, substantially as described and illustrated in the drawings.
Dated this 6th dove of & nonet 1905
SLOAN & LLOYD BARNES,
Castle Chambers, 26 Castle Street, Liverpool, Agents for the Applicant.