Improved Construction of Air Pumps.
Year: 1892

page_text: Date of Application, 11th Nov., 1892
Complete Specification Left, 28th July, 1893—Accepted, 2nd Sept., 1893
PROVISIONAL SPECIFICATION.
[Communicated from abroad by Messrs. SIEMENS & HALSKE, of 94, Mark-
grafeustrasse, Berlin, in the German Empire, Electrical Engineers.]
Improved Construction of Air Pumps.
We, SIEMENS BROTHERS & Co. LIMITED, of 12 Queen Anne's Gate,
Westminster, in the County of Middlesex, Electrical Engineers, do hereby declare
the nature of this invention to be as follows:-
This invention relates to a construction of air pump which combines the
advantages of the mercury pump, namely perfect air tight action and avoidance of
dead spaces, with the advantages of the piston pump, namely easy manipulation
and rapid action.
According to this invention the recipient or chamber from which the air is to he
exhausted is connected by a descending exhaust pipe with the lower part of a
vertical pump barrel containing a reciprocating piston. The lower part of the
pump barrel contains a suitable liquid such as oil or mercury, and some of the
latter is also contained in the barrel above the piston so as to insure an air tight
fit thereof.
A valve is provided in the lower part of the exhaust pipe of the receiver, closing
in an upward direction, and a valve opening outwards is also provided in the piston
so as to allow air and liquid to be discharged from below it. The piston is formed
with a hollow space on its underside, or it consists of an upper and lower part,
having a space between them. With the above described construction, assuming
the piston to be in the lowered position and consequently partly immersed in the
liquid, and to be then raised, a vacuum will be formed in the space on its underside
as it emerges out of the liquid, and, the valve in the exhaust pipe being open, the
air in the receiver will be drawn through the pipe into such space. On the piston
descending into the liquid again, the air will be forced out of the hollow space
through the valve into the open air, while at the same time, the liquid being made
to rise in the exhaust pipe by displacement, it will cause the valve to close so as to
cut off the communication between the receiver and the pump.
Owing to want of perfect tightness of the valves and piston, some liquid will
penetrate pass them, but no air can pass back into the receiver or to the lower
side of the piston from without so that a perfectly air tight action is insured. On
the rising of the piston again, more air will be drawn from the receiver and so on,
till a more or less perfect vacuum is attained.
The apparatus may be variously constructed for operating in the above described
manner; thus according to one arrangement the piston is extended downwards in
annular form, leaving a space between such extension and the sides of the pump
barrel, the lower end of which is also formed annular by a central upward pro-
jection, and channels are made to establish a communication between the central
hollow of the piston and the narrow annular space between the extension of the
piston and the barrel, so that as the annular part of the piston rises out of the
liquid, the air is drawn from the receiver and exhaust pipe through the said annular
space and channels into the central hollow of the piston, from which it is afterwards
forced on the descent of the piston as described. According to another construction,
the piston has suspended from it by chains or cords, a cylindrical weight which,
as the piston descends, sinks into the liquid so as to displace this to a higher level
and thereby close the inlet of the exhaust pipe, after which the piston itself is
immersed in the liquid so as to expel the air previously drawn in under it. On
rising, a space is formed between the piston and the liquid, into which the air is
drawn from the receiver as before.

page_text: According to another modification, instead of fixing the exhaust pipe of the
receiver to the pump barrel, it is carried by and passes down through the piston so
as to travel up and down with this, carrying the receiver with it; the lower end
of the exhaust pipe is open to the space below the piston during the upstroke,
but is immersed in and consequently sealed by the liquid when the piston commences
its downstroke.
Dated this 11th day of November 1892.
ABEL & IMRAY,
Agents for the Applicants.
COMPLETE SPECIFICATION.
Improved Construction of Air Pumps.
We, SIEMENS BROTHERS & Co., LIMITED, of 12 Queen Anne's Gate,
Westminster, in the County of Middlesex, Electrical Engineers, do hereby
declare the nature of this invention and in what manner the same is to be
performed, to be particularly described and ascertained in and by the following
statement:-
This invention relates to a construction of air pump which combines the
advantages of the mercury pump, namely perfectly air tight action and avoidance
of dead spaces, with the advantages of the piston pump, namely easy manipulation
and rapid action.
According to one arrangement of this invention the recipient or chamber from
which the air is to be exhausted is connected by a descending exhaust pipe with
the lower part of a vertical pump barrel containing a reciprocating piston. The
lower part of the pump barrel contains a suitable liquid such as oil or mercury, and
some of the latter is also contained in the barrel above the piston so as to insure an
air tight fit thereof.
A valve is provided in the lower part of the exhaust pipe of the receiver, closing
in an upward direction, and a valve opening outwards is also provided in the
piston so as to allow air and liquid to be discharged from below it. The piston is
formed with a hollow space on its underside, or it consists of an upper and lower
part having a space between them.
With the above described construction, assuming the piston to be in the lowered
position and consequently partly immersed in the liquid, and to be then raised, a
vacuum will be formed in the space on its underside as it imerges out of the liquid,
and, the valve in the exhaust pipe being open, the air in the receiver will be drawn
through the pipe into such space. On the piston descending into the liquid again,
the air will be forced out of the hollow space through the valve into the open air,
while at the same time, the liquid being made to rise in the exhaust pipe by
displacement, it will cause the valve to close so as to cut off the communication
between the receiver and the pump.
Owing to want of perfect tightness of the valves and piston some liquid will
penetrate past them, but no air can pass back into the receiver or to the lower side
of the piston from without so that a perfectly air tight action is insured. On the
rising of the piston again, more air will be drawn from the receiver, and so on, till
a more or less perfect vacuum is attained.
According to another modification instead of fixing the exhaust pipe of the
receiver to the pump barrel, it is carried by and passes down through the piston
so as to travel up and down with this, carrying the receiver with it; the lower end
of the exhaust pipe is open to the space below the piston during the upstroke,
but is immersed in and consequently sealed by the liquid when the piston com-
mences its downstroke.
Figs. 1 and 2 of the accompanying drawings shew the simplest form of the above
described pump. In this construction the suction pipe S connecting the recipient R
with the interior of the pump barrel St is fixed rigidly to the latter. It is provided

page_text: with a valve V2 which closes the said communication against the passage of fluid
from the pump barrel to the recipient but allows of the passage of air from the
latter to the former. In the barrel St is contained a piston P (worked by any
suitable means, not shown) and also a quantity of suitable liquid such as oil or
mercury, both above and below the piston, which serves to insure the air-tight
working both of the piston P and the valve V2, and which during the downward
motion of the piston fills out the dead space.
Fig. 2 shews the piston in its lowest position, the space below it being entirely
filled with the liquid, which also passes up the suction pipe to a certain extent
above the valve V².
When the piston K performs its upstroke as at Fig. 1 the level of the liquid in
the pump barrel falls, and leaves the passage between the recipient and the barrel
open, so that the air contained in the former can expand into the barrel.
As the piston K is subject to atmospheric pressure and both this and the
valve V' will have a certain amount of leakage, some liquid will leak from above
the piston into the space below during the upstroke. As however there is always
sufficient liquid above the piston to keep the joint thereof with the cylinder as also
the valve V covered, no air can penetrate below the piston.
When the piston performs its downstroke, the lower extension P, acting as a
plunger, forces the liquid up out of the annular part of the pump barrel, so as to
cause it to enter the tube S and thereby to cut off the communication between the
pump and the recipient. The valve V2 at the same time closes against its upper
seat, but as both this valve and the piston K admit of a certain amount of leakage,
some of the liquid will leak past them, so as to be situated above the valve.
But under no circumstances can air pass from the pump barrel to the recipient
during the downstroke.
When the piston has arrived at its lowest position, the air contained in the barrel
will have passed out from below the piston through the valve V₁ together with a
quantity of the liquid corresponding to that which leaked past the piston K and
valve V₁ during the upstroke.
The above described action is repeated at each stroke.
Figs. 3, 4, 5 and 6 shew two modifications of the above described pump.
In the arrangement at Figs. 3 and 4 the plunger P is separate from the piston K
and is connected thereto by cbains or other suitable flexible connection.
In consequence of this alteration the pump might be constructed somewhat
shorter than in the first described arrangement. The action is otherwise precisely
the same.
It will be readily understood that the suction pipe S instead of being arranged
outside the pump barrel as described, might pass through a suitably packed
opening in the piston, which would consequently slide up and down upon the same
in an air tight manner owing to the layer of liquid always situated above the
piston.
Figs. 5 and 6 shew another modification in which the suction pipe S passes
through the piston and is formed in one therewith, so that the suction pipe and
receiver move up and down with the piston. As the essential feature of the
invention consists in causing the liquid in the pump barrel to automatically
alternately close and open the communication between the pump and the
receiver, it will clearly be immaterial whether the level of the liquid be
moved relatively to the opening of the suction tube or whether the latter be moved
relatively to the liquid; the latter is the case in the arrangement of Figs. 5 and 6,
in which, as the piston descends, the lower end of the suction rod is immersed in
the liquid, which thus seals the communication with the receiver.
Having now particularly described and ascertained the nature of this inven-
tion and in what manner the same is to be performed, we declare that what we
claim is :-
1. An air pump containing liquid in the lower part of the pump barrel into which

page_text: the piston or plunger penetrates on the downstroke so that by the up and down
motion of the piston, the level of the liquid and the orifice of the suction passage
leading to the receiver are shifted relatively to each other so as to seal the suction
passage during the downstroke and leave it open during the upstroke substantially
as described.
2. In an air pump arranged and operating as set forth in the preceding claim,
fixing the suction pipe of the receiver to the pump barrel, while the pump piston is
provided with a suitably formed plunger which at the commencement of the piston's
downstroke forces the level of the liquid above the opening of the suction pipe so
as to seal the same, substantially as described.
3. In an air pump operating as set forth in the first claim, connecting the suction
pipe of the receiver with the piston so that at the commencement of the downstroke
the lower end of the suction pipe dips into the liquid so as to be sealed thereby,
substantially as described.
ABEL & IMRAY,
Agents for the Applicants.