IMPROVEMENTS IN APPARATUS FOR INDICATING THE VELOCITY OF ROTATION OF ANY REVOLVING SHAFT OR SPINDLE
Year: 1874

page_text: PROVISIONAL SPECIFICATION left by Beauchamp Tower at the
Office of the Commissioners of Patents, with his Petition, on the
28th May 1874.
I, BEAUCHAMP TOWER, of Moreton; in the County of Essex, Engineer,
5 do hereby declare the nature of the said Invention for "IMPROVEMENTS IN
APPARATUS FOR INDICATING THE VELOCITY OF ROTATION OF ANY REVOLVING SHAFT
OR SPINDLE," to be as follows:-
My Invention consists of an improved apparatus for indicating at a
glance the velocity of rotation of any shaft, axle, or other spindle, the
O speed of rotation of which, say in revolutions per minute, it is desirable
to know. If applied to the wheels of a vehicle it can be made to indicate
the velocity at which the vehicle is travelling in miles per hour, or
other convenient standard of speed.

page_text: To the shaft, axle, spindle, or other revolving piece of mechanism, the
speed of rotation of which it is desirable to know, I connect either
directly or by a band, toothed wheels, or other known means, a fan
having arms or blades of any convenient form for giving rotation to
water or other fluid contained within a case, within which case the fan
is caused to revolve at a speed bearing some constant proportion to the
speed of the mechanism to be indicated. Two pipes or passages com-
municate one to the periphery and the other to the centre of the case in
which the fan revolves. The centrifugal force generated by the
rotation of the water or other fluid within the case causes an excess of
pressure in the pipe or passage communicating with the periphery and
a deficiency of pressure in that communicating with the centre of the
case, and consequently a difference between the pressure of the fluid in
these two pipes or passages. This difference of pressure is directly
proportioned to the square of the velocity of rotation of the fan; and by
rendering it visible by a suitable gauge I use it as a measure of the
velocity of rotation of the fan or of the mechanism to which it is con-
nected. There are several methods by which this difference of pressure
may be rendered visible, as follows:-
:-
If the indication is required at only one place I connect the aforesaid
pipes or passages each to a separate vertical tube or chamber, both of
which are open at the top when the fan is at rest; the surface of the
fluid in both of these tubes or chambers is at the same level, there being
a free communication between them through the fan case. But when
by the rotation of the fan a difference of pressure is caused in the tubes
or chambers there will also be a difference in the level of the surface of
the fluid in them corresponding to the difference of pressure, and this
variation of the level of the fluid in either or both of the said tubes or
chambers I render visible by making one or both of them of glass or
other transparent material, so that the level of the fluid may be seen
through it or I make a float or floats rest: on the surface of the fluid,
which, being connected in any convinient way to an index pointer, will
exhibit the variations of its level. In either case the level of the fluid is
exhibited on a properly graduated scale, and indicates the velocity of
rotation of the fan or the mechanism to which it is connected.
. When it is required to indicate the speed of the mechanism at several
places at once, and those places are at a distance from the fan and at

page_text: various levels, I carry two small pipes, one connected with the periphery
and the other with the centre of the fan case, to all these places. These
two pipes are connected at their highest point with a small funnel or
tank for the purpose of conveniently filling them with water or other
fluid.
At each place where the indication is required I place a pressure
gauge, which is connected to both pipes, and is capable of measuring
and indicating the difference between the pressure of the fluid in the
two pipes and consequently the velocity of rotation of the fan or of the
mechanism with which it is connected. There are various methods of
constructing such a pressure gauge. It may consist simply of a glass
tube bent into the form of the letter U, and containing mercury or other
fluid having a different specific gravity to the fluid in the pipes and fan
The extremities of this bent glass tube are each connected to one
of the aforesaid pipes, and the relative levels of the surface of the
mercury or other fluid in the two legs of the bent tube will change in
accordance with the difference between the pressures of the fluid in the
two pipes, and will indicate the speed of the fan or of the mechanism
with which it is connected on a properly graduated scale.
case.
Or the fluid in each pipe may be made to press on either side of a
piston or an elastic diaphragm, the difference between the two pressures
being measured by a spring and indicated by a pointer in the same
manner as in ordinary pressure gauges used for indicating the pressure
of steam.
Or the two pressures may be made to act each on one side of two
pistons or elastic diaphragms in such a manner that the two pistons or
diaphragms will act against one another, and the difference between
their two pressures will be measured by a spring and indicated by a
pointer, as before mentioned.
Or instead of a piston or elastic diaphragm an elastic bent tube, such
as is used in Bourdon's pressure gauge, or any other known means
capable of effecting the same purpose may be used singly or in com-
bination, as described above.
When air is the fluid used in the fan case, then only one pipe will be

page_text: the fan case, the passage to which it is not connected being left open to
the atmosphere. This pipe being led to any place where an indication
is required, any known form of pressure, or vacuum gauge, or barometer,
applied to it will shew the variation of pressure within it caused by the
rotation of the fan, and consequently the velocity of the fan or of the
mechanism to which it is connected.