IMPROVEMENTS IN AIR PUMPS
Year: 1868

page_text: LETTERS PATENT to Andrew Barclay, of Kilmarnock, in the County
of Ayr, North Britain, for the Invention of "IMPROVEMENTS IN AIR
PUMPS."
Sealed the 25th June 1869, and dated the 31st December 1868.
PROVISIONAL SPECIFICATION left by the said Andrew Barclay at the
Office of the Commissioners of Patents, with his Petition, on the
31st December 1868.
I, ANDREW BARCLAY, of Kilmarnock, in the County of Ayr, North
Britain, do hereby declare the nature of the said Invention of "IMPROVE-
MENTS IN AIR PUMPS," to be as follows, that is to say:-
This Invention, which relates to an arrangement or construction of
air pump whereby a vacuum may be formed in a receiver or other vessel
of any assigned degree of completeness or perfection, consists as
follows: The lower part of the air pump barrel or cylinder is connected
by a pipe or passage to an upright hollow column, the column terminating
at the upper end in a cup or receptacle, the latter being provided at its
junction with the hollow column with a valve. At a distance below the
cup or receptacle herein-before mentioned a branch proceeds from the.

page_text: hollow column by which the hollow column communicates to the
receiver, a suitable valve and valve seat being placed between the hollow
column and the receiver. In the cup or receptacle at the head of the
hollow column an overflow is formed, and situated immediately below
the overflow is a reservoir communicating with the barrel or cylinder
of the air pump, the communication however being closed by valves
except at the time, as herein-after set forth, when it is requisite that the
communication should be open. The required quantity of mercury is
placed in the barrel or cylinder, the communicating pipe or passage, the
upright hollow column, and the branch leading to the receiver, as well
as in the reservoir in connection with the barrel or cylinder.
The action of the pump is as follows: -When the ram, piston, or
plunger of the air pump barrel is raised to the complete stroke the
mercury in the upright hollow column falls below the level of the branch
which communicates to the receiver, the withdrawal of the mercury
which previously supported the valve situated between the hollow
column and the receiver allows the valve to fall, and the air contained
in the receiver expands and fills in addition to the receiver the space of
the hollow column now left empty by the withdrawal of the mercury.
On the return or downward stroke of the ram, piston, or plunger being
made the mercury is correspondingly raised in the hollow column, and
the valve situated between the latter and the receiver is closed, so that
the air which by virtue of its expansion had previously passed out there-
from cannot pass back again. The portion of the air then which has
passed out from the receiver is therefore pressed between the mercury
and the valve situated at the top of the hollow column until it acquires
pressure sufficient to raise the valve, when by the continuance of the
downward stroke of the ram, piston, or plunger it is forced upward
through the mercury in the receptacle situated at the head of the hollow
.column, and at the same time a certain portion of the mercury is forced
out of the hollow column, ensuring thereby that the whole of the air
withdrawn from the receiver is entirely expelled from the pump. The
mercury thus forced out of the hollow column of the pump causes the
level of the mercury in the receptacle at its head to be raised, the surplus
overflows into the reservoir which is in communication with the pump
barrel or cylinder. As the mercury overflows and collects in the
reservoir it raises a float and a valve attached thereto, so that the
mercury which is expelled from the pump at each downward stroke of

page_text: the ram, piston, or plunger is supplied by an equal quantity passing into
the barrel or cylinder during the upward stroke of the ram, piston, or
plunger, thus ensuring that the quantity of mercury in the pump is at
all times equal or nearly so. The mercury is prevented from passing
out of the barrel or cylinder back into the reservoir connected to it by
means of a valve which is shut by the lifting action of the mercury on
the downward stroke of the ram, piston, or plunger.
SPECIFICATION in pursuance of the conditions of the Letters Patent,
filed by the said Andrew Barclay in the Great Seal Patent Office on
the 29th June 1869.
TO ALL TO WHOM THESE PRESENTS SHALL COME, I, ANDREW
BARCLAY, of Kilmarnock, in the County of Ayr, North Britain, send
greeting.
WHEREAS Her most Excellent Majesty Queen Victoria, by Her
Letters Patent, bearing date the Thirty-first day of December, in the
year of our Lord One thousand cight hundred and sixty-eight, in the
thirty-second year of Her reign, did, for Herself, Her heirs and suc-
cessors, give and grant unto me, the said Andrew Barclay, Her special
license that I, the said Andrew Barclay, my executors, administrators,
and assigns, or such others as I, the said Andrew Barclay, iny executors,,
administrators, or assigns, should at any time agree with, and no others,.
from time to time and at all times thereafter during the term therein
expressed, should and lawfully might make, use, exercise, and vend,
within the United Kingdom of Great Britain and Ireland, the Channel
Islands, and Isle of Man, an Invention for "IMPROVEMENTS IN AIR FUMPS,"
upon the condition (amongst others) that I, the said Andrew Barclay,
my executors or administrators, by an instrument in writing under my
land and scal, should particularly describe and ascertain the nature of
the said Invention, and in what manner the same was to be performed,
and cause the same to be filed in the Great Scal Patent Office within
six calendar months next and immediately after the date of the said.
Letters Patent.
NOW KNOW YE, that I, the said Andrew Barclay, 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

page_text: the following statement, reference being had to the accompanying
Drawings, and to the letters and figures marked thereon, that is
to say-
At a
This Invention, which relates to an arrangement or construction of
air pumps whereby a vacuum may be formed in a receiver or other
vessel of any assigned degree of completeness or perfection, consists as
follows: The lower part of the air pump barrel or cylinder is con-
nected by a pipe or passage to an upright hollow column, the column
terminating at the upper end in a cup or receptacle, the latter being
provided at its junction with the hollow column with a valve.
distance below the cup or receptacle herein-before mentioned a branch
proceeds from the hollow column by which the hollow column communi-
cates to the receiver, a suitable valve and valve seat being placed
between the hollow column and the receiver. In the cup or receptacle
at the head of the hollow column an overflow is formed, and situated
immediately below the overflow is a reservoir communicating with the
barrel or cylinder of the air pump, the communication however being
closed by valves except at the time, as hercin-after set forth, when it
is requisite that the communication should be open. The required
quantity of mercury is placed in the barrel or cylinder, the communi-
cating pipe or passage, the upright hollow column, and the branch
leading to the receiver, as well as in the reservoir in connection with the
barrel or cylinder.
The action of the pump is as follows:-When the ram, piston, or
plunger of the air pump barrel is raised to the complete stroke the
mercury in the upright hollow column falls below the level of the
branch which communicates to the receiver; the withdrawal of the
mercury which previously supported the valve situated between the
hollow column and the receiver allows the valve to fall, and the air
contained in the receiver expands and fills, in addition to the receiver,
the space of the hollow column now left empty by the withdrawal of the
mercury. On the return or downward stroke of the ram, piston, or plunger
being made the mercury is correspondingly raised in the hollow column,
and the valve situated between the latter and the receiver is closed, so
that the air which by virtue of its expansion had previously passed out
therefrom cannot pass back again. The portion of the air then which
has passed out from the receiver is therefore pressed between the
mercury and the valve situated at the top of the hollow column, until it

page_text: acquires pressure sufficient to raise the valve, when by the continuance
of the downward stroke of the ram, piston, or plunger it is forced
upward through the mercury in the receptacle situated at the head
of the hollow column, and at the same time a certain portion of the
mercury is forced out of the hollow column, ensuring thereby that the
whole of the air withdrawn from the receiver is entirely expelled from
the pump. The mercury thus forced out of the hollow column of the
pump causes the level of the mercury in the receptacle at its head to be
raised; the surplus overflows into the reservoir which is in commu-
nication with the pump barrel or cylinder. As the mercury overflows
and collects in the reservoir it raises a float and a valve attached thereto,
so that the mercury which is expelled from the pump at each downward
stroke of the ram, pistou, or plunger is supplied by an equal quantity
passing into the barrel or cylinder during the upward stroke of the ram,
piston, or plunger, thus ensuring that the quantity of mercury in the
pump is at all times equal or nearly so. The mercury is prevented from
passing out of the barrel or cylinder back into the reservoir connected
to it by means of a valve which is shut by the lifting action of the
mercury on the downward stroke of the ram, piston, or plunger.
And in order that my said Invention may be properly understood I
now proceed more particularly to specify the system, mode, or manner
in or under which the same is or may be used or practically carried into
effect, reference being had, for the sake of more complete elucidation, to
the Figure upon the explanatory Sheet of Drawings hereunto appended,
which represents a vertical section of an air pump constructed in
accordance with this Invention.
The plunger or ram of the pump is marked A, and it is operated by
means of the hand lever B, to which it is coupled by the pin C; D is
the air pump cylinder in which a branch E is formed uniting it to the
mercury trough F, but the passage G, between which is interrupted as
required by means of valves, as herein-after described. From the lower
part of the cylinder D a pipe H proceeds connecting the cylinder with
the chamber I, and the chamber I is further connected to the receiver K
by the branch and passage L and M. Above the chamber I is a
cistern N, but the connection between it and the chamber I is closed or
opened by the valve o. When the pump is ready for exhausting the air
or other gas or vapour contained. in the receiver K (and it is further to
be understood that a receiver of any form or dimensions other than what

page_text: chamber I, branch L, cistern N, as well as the cistern F and gland P are
filled with mercury.
into the chamber I.
The action of the pump is as follows:-When the plunger or ram A
is at its lowest position the chamber I, branch L, pipe H, and the space
below and surrounding the plunger A in the cylinder, together with the
branch E, being occupied by mercury, the lifting of the plunger or
ram A causes the mercury column in the chamber I and pipe H to fall
until the plunger or ram reaches the top of its stroke, at which time the
mercury in the chamber I has fallen below the level of the branch L.
During the time that the branch L is occupied by mercury the valve a
(which is by preference provided with a float at the under side) remains
closed, but as soon as the mercury is withdrawn from it the valve a falls,
and the air or gas in the receiver K expands through the passage M
When the downward stroke of the plunger or ram
takes place the mercury again rises in the chamber I and branch L; it
shuts the valve a close upon its seat, and compresses the portion of air
or gas which had escaped into the chamber I until the air or gas
acquires sufficient pressure to lift the valve, and in effecting which the
air escapes up through the mercury in the cistern N. To ensure that
the whole of the air which passes into the chamber I is expelled at each
downward stroke of the plunger or ram the proportions of the parts of
the pump are so arranged that a small quantity of mercury is also
expelled from the chamber I through the valve o at each downward
stroke of the plunger A. It is thus obvious that during cach upward
stroke of the plunger or ram A the chamber I is exhausted, and therefore
as long as any air or gas remains in the receiver K it is constantly
reduced in pressure by expanding into the chamber I, and all return of
the air or gas thereto is prevented by the closing of the valve a during
the return stroke. The receiver K is by preference connected to a
barometer tube and scale Q, a passage being opened thereto from the
passage M by the three-way cock R; the extent of vacuum in the
receiver K is therefore indicated by the mercurial column in the tube.
It has been herein stated that at the end of each downward stroke of the
plunger or ram A a small portion of mercury is expelled from the
chamber I, so that unless some provision is made for maintaining a
constant quantity of vacuum in the pump it is obvious that the quantity
therein would become reduced. To maintain then a constant supply the

page_text: cistern N is furnished with an overflow pipe S, so that the cistern N
being always full of mercury to the level of the overflow pipe S, each
instant that a portion of mercury is forced up therein from the chamber I
at the same instant a corresponding quantity of mercury overflows
through the pipe S into the cistern F. The cistern F is provided with
a valve c for closing over the passage E, and the valve is connected, as
shown in the Drawing, to a lever and float T. The quantity of mercury
which overflows from the cistern N raises the surface of the mercury in
the cistern F, lifts the float and valve T, and therefore allows the same
quantity of mercury to flow back into the passage E, and thence into the
cylinder D, at the end of each upward stroke, when the mercury being
free from the float valve e allowes it to open. In this manner a constant
quantity of mercury is maintained in the pump.
Having now described the nature of my said Invention, and the
system, mode, or manner in or under which the same is or may be used
or practically carried into effect, I wish to observe in conclusion that
what I consider novel and original and therefore claim as the Invention
secured to me by the hercin-before in part recited Letters Patent is,―
First. The arrangement and construction of pumps for exhausting air
or gases, substantially as hercin-before mentioned and shown on the
annexed Sheet of Drawings.
Second. The exhaustion of chambers or receivers by means of mercury
being employed to act in chamber or chambers contiguous thereto, for
the purpose of opening and closing the valves and for expelling the air,
as herein-before described, or any mere modification thereof.
In witness whereof, I, the said Andrew Barclay, have hereunto
set my hand and seal, this Twenty-eigth day of June, One
thousand eight hundred and sixty-nine.
ANDREW BARCLAY. (L.S.)