IMPROVED APPARATUS FOR MEASURING AND INDICATING SPEED DIRECTLY IN ANY DETERMINED UNIT OF LENGTH PER UNIT OF TIME
Year: 1884

page_text: "
PARTIDIONAL
SPECIFICATION.
We, HENRY DAVIS, of All Saints Works, Derby, and ARTHUR DAVIS, of
118 Newgate Street, London, both of the firm of John Davis and Son, Mining
Instrument Manufacturers, do hereby declare the nature of our invention for
IMPROVED APPARATUS FOR MEASURING AND INDICATING SPEED DIRECTLY IN ANY
DETERMINED UNIT OF LENGTH PER UNIT OF TIME" to be as follows:-
The improved apparatus is especially applicable to anemometers or instruments
for indicating the velocity with which air or other gases are travelling, and it is
designed to indicate the speed directly in feet per second or per minute, but it can
also be applied to instruments for indicating the speed of any moving body in any
determined unit of length per unit of time, by which means it is rendered
unnecessary to employ a watch or other timer with the instrument for measuring
the speed as has hitherto been the case..
•
As applied to an anemometer use is made of the known arrangement of inclined
vanes arranged round a central axis and upon which vanes the current of air or
other gas is caused to act in passing through the instrument, and the movement
thereby given to the vanes being transmitted to their axis moves a pointer carried
by the latter over a suitable dial.
In the improved instrument the central axis is only capable of making one
complete revolution, a stop being provided which comes in contact with an abut-
ment fixed to the casing at the limit of the revolution in each direction. Instead
of being capable of making a complete revolution, the movement of this axis may
be limited to any suitable arc of a circle.
The movement of the axis in the direction in which it is caused to travel by the
action of the gases on the vanes is opposed by the tension of a helical spring, one
end of which is secured to the axis and the other end to a fixed point of the casing,
so that the axis in turning continually increases the tension of the spring and
opposes a correspondingly increasing resistance to the revolution of the axis. It
will be thus seen that a current of gas travelling at a certain speed will by acting
upon the vanes cause them to revolve a certain distance, when the tension of the
spring will become sufficiently strong to prevent their further rotation, and
consequently the pointer carried by the axis will remain stationary at a certain
point on the dial.___

page_text: The strength of the spring is so calculated and the divisions on the dial are so
arranged that the pointer will indicato on the latter the rate of speed, i.e., distanco
travelled in a given unit of time, preferably in feet per second.
When the instrument is removed from the influence of the travelling body the
spring causes the pointer to at once return to the zero position on the dial. In
order to prevent oscillation of the vanes and indicating hand a cam is provided
upon which a spring acts; and as in greater velocities or currents of air the greater
is the liability to oscillate, this spring has an increasing friction on the cam at
greater velocities.
It will be readily understood that by substituting for the vanes upon which the
travelling gas acts any suitable means of communicating motion from a moving
body to the central axis of the improved apparatus, the instrument may be used
for indicating the movement of such body directly in units of length por unit of
time.

page_text: COMPLETE SPECIFICATION.
We, HENRY DAVIS, of All Saint's Works, Derby, and ARTHUR DAVIS, of
118 Newgate Street, London, both of the firm of John Davis and Son, Mining
Instrument Manufacturers, do hereby declare the nature of our invention for
"IMPROVED APPARATUS FOR MEASURING AND INDICATING SPEED DIRECTLY IN ANY
DETERMINED UNIT OF LENGTH PER UNIT OF TIME," and in what manner the
same is to be performed, to be particularly described and ascertained in and
by the following statement :-
The improved apparatus is especially applicable to anemometers or instruments
for indicating the velocity with which air or other gases are travelling, and it is
designed to indicate the speed directly in feet per second or per minute, but it can
also be applied to instruments for indicating the speed of any moving body in any
determined unit of length per unit of time, by which means it is rendered
unnecessary to employ a watch or other timer with the instrument for measuring
the speed.
The invention as applied to an anemometer is illustrated in the accompanying
sheet of drawings, in which
Fig. 1 is a front elevation of the complete apparatus.
Fig. 2 is a rear elevation with the fan wheel removed, and
Fig. 3 is a transverse section of Fig. 1.
It will be seen that in this anemometer use is made of the known arrangement of
inclined vanes A arranged round a central axis B, and upon which vanes the current
of air or other gas is caused to act in passing through the instrument, the movement
thereby given to the vanes A being transmitted to their axis B, and by a suitablo
arrangement, hereinafter described, caused to move a pointer C over a dial D.
In the improved instrument the pointer C may be capable of making one
complete revolution, a stop being provided to limit its revolution in each direction;
or the movement of such pointer may be limited to any suitable arc of a circle.
But such pointer is preferably arranged so that it can make more than one
revolution, in which case, as shown in the drawings, provision is made on the dial
to indicato whether the position occupied by the pointer is in its first or second
revolution, the arrangement for indicating this being hereinafter more fully
described.
The arrangement for transmitting the motion of the axis B to the pointer C is
shown more clearly in Figs. 4 and 5, which are drawn on an enlarged scale.
The pointer C is carried at the outer end of an axis E, the inner end of which
terminates in close proximity to the inner end of shaft B, to which the vanes A are
attached. The inner end of shaft B carries a disc B¹, from which a stud or pin B³.
projects. The inner end of shaft E is made square and on it a boss or sleeve C¹ is
capable of sliding, such boss or sleevo having a pin C³ projecting radially from its
periphery. Near its inner end the shaft E is supported to revolve in a bridgo
piece X, upon which a flat spring Y is secured, the outer free end of which engages
a groove formed in the boss C¹. Between the spring Y and bridge piece ✗ a

page_text: snding weage is introduced, suen wedge being formed on the lower end or a pusn
pin or rod Z¹ terminating in a button or head outside the casing G. A spring Z
tends to keep the wedge Z in its raised position; and the tension of spring Y tends
to keep the boss C against the bridge picce X. When the push pin or rod Z¹ is
depressed, the wedge Z shifts the boss C along the square end of shaft E, thus
bringing the pin C in the path of the pin B2 on disc B¹, when shaft B is
rotating, whereby the movement of shaft B will be transmitted to shaft E and
cause the pointer C to move over dial D. When the pressure is removed from the
head of push pin Z, the spring Z raises wedge Z, and spring Y forces boss C
back until the pin C is disengaged from pin B. A projection Z on the wedge Z
engages with a slot X¹ in the bridge piece X, so as to guide the wedge in its move-
ment up and down.
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The rotation of the axis E is opposed by the tension of a spiral spring H, one
end of which is secured to the axis E and the other end to a fixed. portion of the
casing G', so that the axis E in turning continually increases the tension of the
spring H, and opposes a correspondingly increasing resistance to the revolution of
such axis.
The action of the apparatus is as follows:-
The instrument is held or fixed in the current of air for a second or two, until
the fan wheel A rotates at full speed due to the air current. The push pin Zis
then pressed downwards throwing the spiral spring axis E into gear with the fan
wheel axis B, and the spiral spring H is thereby coiled or wound up until the
tension of the spring balances the force of the air current. The pointer C carried
by axis E thereby indicates on the face of the dial the velocity of the air current.
The strength of the spring H is so calculated and the divisions on the dial D
are so arranged that the pointer C will indicate on the latter the rate of speed,
that is, distance travelled in a given unit of time, preferably in feet per second.
The pointer C is caused to remain in the position it has been moved to on the
dial by fixing a ratchet wheel F on axis E, and arranging a spring pawl I to engage
with the teeth of same when the push pin Z' is depressed. For this purpose a
pin O on wedge Z is arranged so that when the latter is depressed, the spring I'
acting on pawl I forces it against the ratchet wheel F, whereby, although the pawl
will allow shaft E to revolve in the direction to coil or wind up spring H, it will
prevent the movement of the shaft in the opposite direction. As the wedge Z
rises under the action of its spring Z when pressure is removed from the head of
the push pin Z, the pin O will lift pawl I out of engagement with ratchet wheel F,
and thus leave the shaft E free to turn back under the action of spring H, until
the pointer C returns to tho zero position on dial D.
In order to obtain the necessary range, and at the same time to keep the
mechanism as simple as possible, the face of the instrument has preferably two
concentric index circles, and for the purpose of indicating which circle has to be
read, a small pointer J and circle K are provided. The circle K has the word
"outer" on one semicircle and the word "inner" on the other semicircle, such
words meaning respectively the outer and inner index circles, and the position of
pointer J on circle K indicates which index circle the reading of pointer C is to
be taken from, or in other words whether the position occupied by pointer C is in
its first or second revolution. To effect this the shaft E carries a pinion L gearing
with a wheel M on the shaft of pointer J, so that as shaft E revolves its movement
will be communicated to such pointer J, causing it to move over its circle K, the
pinion L and wheel M being so proportioned that the latter revolves once while
the shaft E makes two revolutions. By this arrangement during the first revolution
of shaft E, pointer J will be directed to the word "outer on circle K, and during
the second revolution of such shaft pointer J will point to the word "inner."
When the pointer C is allowed to return to the zero position, pointer J will travel
back to an intermediate position between the words "inner" and "outer." If
desired the pinion L and wheel M might be so. proportioned that the pointer J will

page_text: make one revolution for every 3, 4 or more of the shaft E, in which case a corre-
sponding number of index circles will be provided on dial D, and the circle K over
which pointer J moves will have a corresponding number of divisions marked
respectively first, second, third, etc.
It will be readily understood that by substituting for the vanes A upon which
the travelling gas acts, any suitable means of communicating motion from a moving
body to the spring axis E of the improved apparatus, the instrument may be used
for indicating the movement of such body directly in units of length per unit of
time.
A sheet of glass N is preferably placed over the indicating hands or pointers C
and J and the dial D, so as to protect them from injury.
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
1. An improved instrument for measuring speed directly in given units of length
per unit of time, consisting in a shaft E to which the motion of the moving body
is communicated by any suitable means, such shaft as it revolves being caused to
continually increase the tension of a spring H arranged so as to oppose the rotation
of the shaft, whereby a pointer C secured to such shaft is made to move over and
stop at a certain position on a dial, the divisions of which are graduated to
represent speed, or distance travelled in a given unit of time, all substantially as
described and shown.
2. The combination with the instrument for measuring speed in any given units
of length per unit of time described in the preceding claim, of the means for
connecting the fan wheel shaft B with, and disconnecting it' from, the shaft E
carrying the pointer C, substantially as described and shown.
3. The combination with the instrument for measuring speed in any given units
of length per unit of time described in claim 1, of the ratchet wheel F and spring
pawl I operating substantially in the manner and for the purpose specified.
4. The combination with the instrument for measuring speed in any given
units of length per unit of time described in claim 1, of the pinion L on the
shaft E carrying pointer C, and wheel M gearing with such pinion and mounted
on a shaft carrying a pointer J moving over a circle K, all substantially as and for
the purpose specified.