IMPROVEMENTS IN PUMPS FOR LIQUIDS AND GASES
Year: 1880

page_text: LETTERS PATENT to Alexander Melville Clark, of 53, Chancery Lane, in the
County of Middlesex, Patent Agent, for an Invention of "IMPROVEMENTS IN
PUMPS FOR LIQUIDS AND GASES." A communication from abroad by George
Henry Felt, of New York City, United States of America.
PROVISIONAL SPECIFICATION left by the said Alexander Melville Clark at
the Office of the Commissioners of Patents on the 25th February 1880.
"
ALEXANDER MELVILLE CLARK, of 53, Chancery Lane, in the County of Middlesex,
Patent Agent.
IMPROVEMENTS IN PUMPS FOR LIQUIDS AND GASES." [A com-
munication from abroad by George Henry Felt, of New York City, United States
of America.]
It is well known that in pumping air, either for obtaining a vacuum or for
compressing, it is necessary to avoid all air clearance in the pump cylinder, else its
action becomes quite inefficient.
Charging the ends of the air cylinder with a quantity of water sufficient to fill the
clearance spaces, and thus ensuring the full discharge of air from the pump cylinder
at each stroke, has been tried. In this case however a small portion of the water
works over into the air reservoir at each stroke, thus causing air clearance to gradually
form, which expands during the return stroke, and prevents the free admission of
more air, to avoid which it has been suggested to return this water from the reservoir
to the ends or beads of the cylinder, but it has not been successfully effected.
Now this Invention may be stated to consist in an improved arrangement of
return tubes or ducts extending from the reservoir above the discharge valves to
the cylinder, and opening into the side of the cylinder at points behind the piston
when near the end of its stroke, through which a quantity of the water is returned
under pressure to the cylinder, thus avoiding all air clearance, and at the same
time rendering the back pressure from the reservoir effective on the back or
retreating side of the piston as an auxiliary to the steam pressure in compressing
or forcing out the charge in front of the piston, whereby air or gas may be
compressed to a greater density, or water pumped to a greater height than would
be otherwise possible.
The return ducts or ports extend to the cylinder, preferably through the walls of
the valve chest, and open into the side of the cylinder across the stroke of the
piston at points between the discharge ports, and respectively towards each end of
the cylinder, and in such position relatively to the stroke of the piston that when

page_text: the piston approaches the end of its stroke in either direction both of the return
ducts open bobind it.
The opening of these passages from the reservoir is controlled by valves, by
which the amount of water admitted through them to the cylinder may be regulated
as required. These valves are preferably check valves, which permit the water to
flow through the ducts into the cylinder, but prevent its return.
Now when the supplementary valves are pressed open, small streams of water
will enter the cylinder under the full pressure in the reservoir. These entering
streams of water will not only serve to keep the clearances fully charged, but in
being admitted across the stroke of the piston the back pressure of this entering
water not only does not resist the movement of the piston, but becomes a positive
auxiliary to the pressure of the steam piston.
Thus, considering the piston at the middle of its stroke between the two return
ducts or ports, it will be seen that the back pressure from the reservoir on each side
of tho piston will be equalized, while the pressure of the steam piston forms an
additional force, pressing the piston forward to compress or force out the charge in
front, and when the piston reaches the end of its stroke both return ports open
behind it, thus giving the piston a strong forward impulse in terminating its
stroke..
The first part of the return stroke of the pump, which would appear some what
paradoxical, is performed as follows:-The lead of the steam valvo on the steam
cylinder is such that the steam is admitted in advance of its piston at about the
time the pump piston is passing over the last return port toward the end of its
stroke, and as the pump piston is then being pressed forward by the back pressure
from the reservoir through the return duct, which pressure is of course much higher
than the steam pressure, the steam thus admitted in front of the steam piston
becomes cushioned to about the same pressure as that impelling the pump piston.
As the pump piston reaches the end of its stroke however, so that both return
ducts open behind it, it receives a sudden powerful impulse, which drives it a little
farther forward and cushions the steam to a somewhat higher pressure than that
on the pump piston. This impulse quickly ceasing, the pressure of the highly
compressed steam cushion now reacts and forces the pump piston back on its return
stroke with a positive pressure, till it passes over the first return duct, during
which time a fresh charge is drawn into the pump cylinder through the suction
passages, after which the remainder of the stroke of the pump is performed by the
pressure from the reservoir admitted through the return duct, together with the
steam pressure on the steam piston, against which a fresh charge of steam is
admitted to continue the motion as soon as the steam cushion expands below the
pressure on the steam valves. By this means the pump will discharge air or water
under a much higher pressure than that of the steam which impels the pump, for
the reason that the back pressure is either equalised on the pump piston, or applied
behind it, so that the steam pressure thus forms always an effective working margin
over and above the pressure in the reservoir into which the pump discharges. The
pump will thus continue to accumulate pressure, pumping higher and higher if the
pressure is continued in the reservoir, for it will be seen that no matter how high
the pressure in the reservoir may be, the steam always forms an overbalancing
addition against it. In this way a pressure theoretically unlimited may be obtained
with a small steam pressure, and with a steam piston having the same diameter
and stroke as that of the pump piston.
The pump is adapted for either liquids or gases for compressing air or gases to a
great density in tanks or reservoirs, or for raising water to great heights. When
the pump is used for water or other liquids, it is preferred to have the discharge
ports somewhat larger than when used for air or gases, and to have the mouth of
the return ports where they open into the cylinder prolonged by a groove in the
side of the cylinder, but this is not essential.

page_text: SPECIFICATION in pursuance of the conditions of the Letters Patent filed
by the said Alexander Melville Clark in the Great Seal Patent Office on the
25th August 1880.
ALEXANDER MELVILLE CLARK, of 53, Chancery Lane, in the County of Middlesex,
A com-
Patent Agent.
"IMPROVEMENTS IN PUMPS FOR LIQUIDS AND GASES."
munication from abroad by George Henry Felt, of New York City, United States
of America.
It is well known that in pumping air, either for obtaining a vacuum or for
compressing, it is necessary to avoid all air clearance in the pump cylinder, else its
action becomes quite inefficient.
Charging the ends of the air cylinder with a quantity of water sufficient to fill
the clearance spaces, and thus ensuring the full discharge of air from the pump
cylinder at each stroke, has been tried. In this case however a small portion of the
water works over into the nir reservoir at each stroke, thus causing air clearance to
gradually form, which expands during the return stroke, and prevents the free
adinission of more air, to avoid which it has been suggested to return this water
from the reservoir to the ends of or heads of the cylinder, but it has not been
successfully effected.
Now this Invention may be stated to consist in an improved arrangement of
return tubes or ducts extending from the reservoir to the cylinder, and opening into
the sides of the cylinder at points behind the piston when near the end of its stroke,
through which a quantity of the water is returned under pressure to the cylinder,
thus avoiding all air clearance, and at the same time rendering the back pressure
from the reservoir effective on the back or retreating side of the piston as an
auxiliary to the steam pressure in compressing or forcing out the charge in front of
the piston, whereby air or gas may be compressed to a greater density, or water
pumped to a greater height than would be otherwise possible.
In the annexed Drawing the Figure presents a vertical section of a pump of the
ordinary kind embodying the Invention.
As illustrated, a indicates the pump cylinder, and b its piston which is impelled
in the usual manner by the piston of a steam cylinder or equivalent motor
arranged in line therewith at the opposite end of the piston rod; c, c, is the valve
chest of the pump; d, d, the suction valves; c, e, the discharge valves; f, the
suction port; and g, g, the discharge ports, which are all of about the usual form,
and is the usual air vessel or reservoir, which may be connected by the pipe h'
with tanks or other suitable vessels.
Now the novel feature lies in the return ducts or ports A, A, opening from the
reservoir above the discharge valves, and extending into the sides of the cylinder
between the discharge ports thereof. These ducts extend to the cylinder,
preferably through the walls of the valve chest, as shown, and open into the side of
the cylinder across the stroke of the piston at points between the discharge ports,
and respectively towards each end of the cylinder, and in such position relatively
to the stroke of the piston that when the piston approaches the end of its stroke
in either direction both of the return ducts A, A', open behind it. Valves B, B¹,
control the opening of these passages from the reservoir, by which the amount of
water admitted through them to the cylinder may be regulated as required. These
valves are preferably check valves as shown, which permit the water to flow
through the ducts into the cylinder, but prevent its return.
Now when the supplementary valves B, B', are pressed open, it will be seen that

page_text: small streams of water will enter the cylinder under the full pressure in the
reservoir. These ontering streams of water will not only serve to keep the
clearances fully charged, as will be readily understood, but in being admitted across
the stroke of the piston, as shown, the back pressure of this entering water not
only does not resist the movement of the piston, but becomes a positive auxiliary
to the pressure of the steam piston.
Thus, considering the piston at the middle of its stroke between the two ports
A, A¹, it will be seen that the back pressure from the reservoir on each side of the
piston will be equalized, while the pressure of the steam piston forms an additional
force, pressing the piston forward to compress or force out the charge in front, and
when the piston reaches the end of its stroke both parts A, A' open behind it, thus
giving the piston a strong forward impulse in terminating its stroke.
Now the first part of the return stroke of the pump, which would appear
somewhat paradoxical, is performed as follows:-
The lead of the steam valve on the steam cylinder is such that the steam is
admitted in advance of its piston at about the time the pump piston is passing over
the last return port toward the end of its stroke, and as the pump piston is then
being pressed forward by the back pressure from the reservoir through the return
duct, which pressure is of course much higher than the steam pressure, the steam
thus admitted in front of the steam piston becomes cushioned to about the same
pressure as that impelling the pump piston. As the pump piston reaches the end
of its stroke however, so that both return ducts open behind it, it receives a sudden
powerful impulse, which drives it a little farther forward and cushions the steam to
a somewhat higher pressure than that on the pump piston. This impulse quickly
ceasing, the pressure of the highly compressed steam cushion now reacts and forces
the pump piston back on its return stroke with a positive pressure, till it passes
over the first return duct, during which time a fresh charge is drawn into the pump
cylinder through the suction passages, after which the remainder of the stroke of
the pump is performed by the pressure from the reservoir admitted through the
return duct, together with the steam pressure on the steam piston, against which
a fresh charge of steam is admitted to continue the motion as soon as the steam
cushion expands below the pressure on the steam valves.
By this means the pump will discharge air or water under a much higher pressure
than that of the steam which impels the pump, for the reason that the back pressure
is either equalized on the pump piston, or applied behind it, so that the steam
pressure thus forms always an effective working margin over and above the
pressure in the reservoir into which the pump discharges. The pump will thus
continue to accumulate pressure, pumping higher and higher if the pressure is
continued in the reservoir for it will be seen that no matter how high the pressure
in the reservoir may be, the steam always forms an overbalancing addition against
it. In this way a pressure theoretically unlimited may be obtained with a small
steam pressure, and with a steam piston having the same diameter and stroke as
that of the pump piston.
The pump is adapted for either liquids or gases for compressing air or gases to a
great density in tanks or reservoirs, or for raising water to great heights.
In the Drawing the pump is shown as adapted for compressing air or gases, but
precisely the same pump may be used for water or other liquids. For this purpose
however I prefer to have the discharge ports somewhat larger, and to have the
mouth of the return ports where they open into the cylinder prolonged by a groove
in the side of the cylinder, as indicated by dotted lines, but this is not essential.
Having described the nature of the said Invention, and the manner of performing
the same, I declare that what I claim as the Invention to be protected by the
herein before in part recited Letters Patent is,—
A pump constructed with the return duct or ducts A or A' extending from the
reservoir of the pump to the sides of the pump cylinder, and opening into the

page_text: latter at points behind the piston when at the end of its stroke, substantially as
and for the purpose herein set forth.
In witness whereof, I, the said Alexander Melville Clark, have hereunto set
my hand and seal, this 24th day of August, in the year of our Lord One
thousand eight hundred and eighty.
Ant
A. M. CLARK.
ARK. (LS)