Volume at High Velocity.
Year: 1886

page_text: Volume at High Velocity.
I GEORGE SEAGRAVE of Chelsea Gardens, Chelsea, Middlesex Engineer do hereby
declare the nature of my said invention and in what manner the same is to be
performed to be particularly described and ascertained in and by the following
statement:
In applying jets of air or other fluid issuing from a nozzle for the purpose of
inducing currents of air or other fluid I have found by experience that the best
result as regards the volume induced with the least expenditure of the jet fluid
and of the power producing same is obtained by means of a jet orifice fixed at a
minimum degree of opening so as to economize the volume of air gases or fluids
issuing therefrom provided the pressure of the jet fluid and its corresponding
velocity is maintained as nearly as possible uniform.
When a number of such jets are worked from one engine or generator and some-
times the whole, sometimes only a few, of such jets are set in action thereby
causing irregular draft upon the source of pressure supply considerable variations
are produced in the main pressure which thereby produces irregular and conse-
quently uneconomical working of the jet nozzles. In all cases the velocity of jet
at the nozzle should be kept as nearly uniform as possible. It may also be
necessary that one or more out of the series of nozzles should work at a different
pressure and velocity from the others. For the above named reasons it is important
that the pressure of the jet fluid should be so regulated in each nozzle as to main-
tain it approximately at the best available point of maximum usefulness required
in each case where it issues from the nozzle no matter how the pressure may vary
in the pipe or main conveying the compressed air or other fluid to the nozzle.
My invention consists of an automatic nozzle for the purpose of regulating the
flow of gases and fluids to effect which I form within the nozzle a chamber leading
to the jet orifice and containing a valve so arranged that it may open more or
less a passage for the admission of the compressed air or fluid into the chamber,
such valve being set by a spring and screw stud or their equivalent so as to close
on the desired pressure being exceeded and to open upon a diminution of that

page_text: pressure and being otherwise held in partial equilibrium by the pressure of air
acting on opposite sides and different areas of a piston diaphragm or their
equivalent connected with and actuating said valve, the issuing or jet orifice of the
nozzle being unalterable when once fixed.
My invention is illustrated by the annexed drawings in which at Figure 1
I show a longitudinal section of one form and at Figure 2 of another form of such
a nozzle. A is the outer shell provided with two inlets B, B, for the supply of air
from any suitable air compressor or air pump capable of forcing air or other fluid
at the desired pressure to the interior of the shell. One end of the shell is closed
by a screw cap C and the other end E which is tapered off to a fine edge is of such
a diameter that only a thin annular opening is left between it and the shoulder F
of the plug G within the outer shell.
The shell A has an internal seating H for the valve I of plug G to close more or
less and so determine the passage of air from the main pressure chamber J to the
reduced pressure chamber K,
The plug is hollow and provided with holes for the free passage of air throughout
the chamber J. The bottom of the hollow plug is provided, with a piston (Figure 1)
or diaphragm T (Figure 2). The hollow plug is also provided with openings R
communicating with the low pressure chamber K. so that its interior and the space
beneath the piston or diaphragm T are filled with air or fluid at the same pressure
as in the chamber K and a crossbar M in the plug forms an abutment for a
spring N whose opposite end bears against a screw pin Qin the cap C the adjust-
ment of which screw regulates the pressure in the chamber K the low pressure air
on the underside of the piston or diaphragm T combining with the spring to close
the valve against the higher pressure of air or the smaller area exposed thereto on
the opposite side whenever the pressure in the chamber K. exceeds the amount
determined.
The shoulder F of the plug may be provided with ribs S as at Figure 3 bearing
against the tapered end E of the shell A so as to keep it truly central.
Figure 14 is a section through the line a, b, of Figure 2, showing the spaces
between the webs L, L, in communication by the apertures.
:
The areas exposed to the internal pressures above and below the piston or
diaphragm are so proportioned that force exerted upwards and downwards upon
the valve at the normal pressures is nearly equal, the difference being made up by
the spring. For example, in Figure 2 the apparatus is arranged to maintain a
practically uniform pressure of 5 lbs in the chamber K with a minimum of 10 lbs
in the main and the chamber J. The difference of area's between the valve I and
the area inside the chamber J of the diaphragm T is 5.99 square inches effective
area exposed to the downward pressure of 10 lbs per square inch. The area
exposed to the upward pressure of 5 lbs per square inch in the low pressure
chamber K and underneath the diaphragm T is that of the whole diameter of the
diaphragm and plug combined namely 10-32 square inches. Hence we have
5.99 square inches acted upon by a downward pressure of 10 lbs per square inch
or total of 59.9 lbs and we have 10.32 square inches acted upon by an upward
pressure of 5 lbs per square inch or total of 51.6 lbs. This excess of 8.3 lbs acting
downwards would tend to keep the valve I constantly open were it not counter-
acted by the force of the spring N which makes up the difference. Should the
pressure in K rise above 5 lbs the valve I will then close by the excess of upward
pressure. Should the pressure in K fall below 5 lbs the valve I will open by
excess of pressure in J. When the apparatus is not in use the spring closes the
valve. When the compressed air is admitted it draws the valve from its seat
against the spring admitting air to the chamber K. Immediately on the air
passing the valve and lifting it the desired distance, the chamber K, the interior of
the plug, and the space below become filled with air at the determined pressure
the relative areas of above and below the piston or diaphragm T and the force of
the spring being proportioned to suit the main pressure and the required pressure
in the chamber K

page_text: In applying the nozzle it should be fixed or carried inside a pipe or casing
through which the free air is drawn by the inducing action of the jet.
I have herein described my invention and some modes of carrying it into effect
I would however have it understood that I do not confine myself to the precise
details.
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
An apparatus, constructed substantially as shown in the annexed drawings,
having a fixed jet orifice with an internal valve for regulating and maintaining
nearly uniform the pressure of the jet fluid as and for the purposes herein
described.