Improvements in Mercurial Air-pumps.
Year: 1898

page_text: Improvements in Mercurial Air-pumps.
I, HIRAM STEVENS MAXIM, of 18, Queen's Gate Place, in the County of Middle-
sex, Chevalier of the Legion of Honour, Civil and Mechanical Engineer, do
hereby declare the nature of this invention to be as follows:-
This invention relates to mercurial air-pumps and especially to those of the
kind known as the Geissler pump and the Sprengel pump.
According to my present invention I provide the "auxiliary reservoir," that
is to say the enlarged upper portion of the U shaped tube into which the mercury
flows from a main reservoir, with a hollow float which is adapted to act as an
automatic device for checking the inlet of the mercury to the auxiliary reservoir
when its flow through the pump is unduly retarded or is stopped. The said
hollow float is also so constructed that the mercury, when its flow is not checked,
will pass through the float in a finely divided condition whereby any air or gas
contained in the mercury will be effectually liberated so as to be easily removed
from the auxiliary reservoir by suitable means such as an air pump connected
therewith. The entrance of air and impurities into the mercurial pump with
the mercury is thus avoided.
The said float may be in the form of a tube or cylinder of glass provided at
its ends with cork or other stoppers which are perforated or otherwise formed
to permit the mercury to flow into and through the said float. The intervening
space between the two stoppers contains particles of glass or other suitable
substance that will not have a detrimental effect on the mercury, the particles
being of such a size and shape that there will be left between them innumerable
small interstices through which the mercury will flow in a very fine state of
division. I find that glass beads answer my purpose very well.
The said float, together with the beads it contains, is sufficiently buoyant to
float on the mercury within the auxiliary reservoir, with its. upper stopper a
short distance below the inlet nozzle through which the mercury flows to enter
the said auxiliary reservoir. The portion of the upper stopper that lies im-
mediately below the said inlet nozzle is unprovided with perforations. When
the inflow of the mercury becomes in excess of the outflow, the level of the
mercury in the auxiliary reservoir will rise and thereby raise the float and bring
the imperforate portion of its upper stopper against the said inlet nozzle, thus
checking the inflow until the level of mercury in the said auxiliary reservoir
falls again and removes the float from contact with the inlet nozzle. The float
may be furnished with circumferential ribs or rings to act as guides.
According to another part of my present invention, I arrange the upper ends
of the "fall tubes" to extend a short distance into the chamber into which they
open, the said chamber being in communication with the auxiliary reservoir by
a suitable U shaped tube formed in one or more pieces appropriately connected
together. The level of the said upper ends of the fall tubes is above that of
the opening through which the mercury gains access to the said chamber, so
that in order for the mercury to descend the fall tubes, it has to enter the said
chamber and overflow into said tubes. I find that by this arrangement the flow

page_text: of the mercury into the fall tubes is not continuous but is intermittent and
enables the stream of mercury flowing through them to be in the condition of a
succession of drops or pistons which effectually act to withdraw the air or gas
from the lamp globes or other vessels that are being exhausted.
The lower ends of the fall tubes may dip into a vessel from which the mercury
is taken by suitable means back to the main reservoir.
The lower portion of the aforesaid U tube may be provided with suitably
arranged stop cocks for enabling the mercury from the vertical limb of the Ů
tube leading to the chamber that encloses the upper ends of the fall tubes, to
be discharged into a suitable vessel, without disturbing the mercury in the
other portion of the U tube and in the auxiliary reservoir.
Dated this 9th day of August 1898.
HASELTINE, LAKE & Co.,
45, Southampton Buildings, London, W.C.,
Agents for the Applicant.
Cia Air-pumps.
I, HIRAM STEVENS MAXIM, of 18, Queen's Gate Place, in the County of Middle-
sex, Chevalier of the Legion of Honour, Civil and Mechanical Engineer, 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 follow-
ing statement:-
This invention relates to mercurial air-pumps and especially to those of the
kind known as the "Geissler" and the "Sprengel."
According to my present invention I provide the head, that is to say the
enlarged upper portion of the bent tube, into which the mercury Hows from a
reservoir, with a float which is adapted to act as an automatic device for checking
the inlet of the mercury to the said head when its flow through the pump is
unduly retarded or is stopped.
The said float is preferably made hollow and is so constructed that the mercury,
when its flow is not checked, will pass through the float in a finely divided or
comminuted condition, whereby any air or gas contained in the mercury will
be effectually liberated so as to be easily removed from the head by suitable
means such as an air pump connected therewith. The entrance of air and
impurities into the mercurial pump with the mercury is thus avoided.
I furthermore arrange the upper ends of the "fall tubes" to extend into the
chamber connected with the vessels to be exhausted and which I hereinafter
term the vacuum chamber," so that their mouths occupy a position above the
point of entrance of the mercury into said vacuum chamber from the aforesaid
head, whereby the mercury enters the fall tubes by rising in said chamber and
overflowing into their mouths.
In order that my said invention may be clearly understood and readily carried
into effect I will proceed to describe the same more fully with reference to the
accompanying drawing which shews a sectional elevation of my improved mer-
curial air pump.
A is the head which is connected by the pipe A¹ to the vacuum chamber B.
C is one of the fall tubes of which there are several, but only one is illustrated
in the drawings. D is a vessel into which the lower ends of the fall tubes dip
and from which the mercury flowing through the pump is returned by any
suitable elevating apparatus to the head A for use over again.

page_text: E is the float which is shewn in the form of a tube or cylinder; it is preferably
of glass provided at its ends with cork or other stoppers e. These stoppers are
perforated or otherwise formed to permit the mercury to flow through the said
float. The intervening space between the two stoppers contains particles of
glass e or other suitable substance that will not have a detrimental effect on
the mercury, the particles being of such a size and shape that there will be left
between them innumerable small interstices through which the mercury will
How in a very fine state of division. I find that glass beads answer my purpose
very well.
The said float, together with its contents is made sufliciently buoyant to float
on the mercury within the head A, with its upper stopper a short distance below
the inlet nozzle a through which the mercury enters the said head. The portion
of the upper stopper that lies immediately below the said inlet nozzle is unpro-
vided with perforations. When the inflow of the mercury is in excess of the
outflow the level of the mercury in the head A will rise and thereby elevate the
float and bring the imperforate portion of its upper stopper against the said
inlet nozzle a, thus checking the inflow until the level of mercury in the said
head falls again and allows the float to come out of contact with the said inlet
nozzle. The float is also furnished with circumferential ribs or rings e² to act
as guides.
The upper ends of the fall tubes C are enlarged at c where they enter the
vacuum chamber B and the mouths of these tubes are situated in a position above
that of the opening or openings a through which the mercury enters the said
chamber, so that in order for the mercury to descend the fall tubes C, it has to enter
and rise in the said chamber until it overflows into the fall tubes. By this
arrangement I ensure the intermittent flow of the mercury into and through the
fall tubes in a succession of large drops serving as pistons which effectually act
to exhaust the air or gas from the lamp globes or other vessels that are, for
this purpose, connected with the chamber B by the pipe B'.
A2 is a stopper of glass or other appropriate material by which the mouth of
the head A is closed. It is made hollow to contain hygroscopic material such as
phospheric anhydride, the inlet nozzle a extending vertically through said
stopper and having a stop cock al for controlling the flow of the mercury to
the head A. is another stop-cock on the stopper for controlling the passage a
leading to an air pump by which the space above the mercury in the head A is
kept in a vacuous condition. The mouth of the head A is trumpet shaped so
that a space a is left around the portion of the stopper entering said head, to
receive mercury or other substance to make an hermetic joint at this part.
The tube A is made in straight sections which are connected together by
collars or bands a composed of india rubber or other appropriate material. The
lower horizontal section is furnished with a stop cock as to enable the flow of
the mercury in the head A and its tube to be stopped and permit the mercury
in the vertical section leading to the vacuum chamber B to be discharged into
a vessel G when a stop cock a is opened. This construction enables the mercury
in the head A and its tube, to remain undisturbed while the other part of the
apparatus is being emptied of its mercury. When the apparatus is in operation
the stopcock a' is closed and the stopcock a opened. The aforesaid vessel G is
provided with a pipe g, furnished with a stopcock g', leading to an apparatus for
elevating the mercury in the vessel G, to the head A or to a reservoir from
which such head is supplied.
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
-
1. A mercurial air pump provided with a float for regulating the flow of
mercury substantially as and for the purpose specified.
2. The float containing glass beads or other particles of suitable material

page_text: through which the mercury flows from the inlet nozzle and thereby becomes
comminuted for the purpose specified.
3. In a mercurial air pump, the fall tubes having extended and enlarged
upper ends opening into the vacuum chamber at a point above that at which the
mercury enters the said chamber, for the purpose specified.
4. A mercurial air pump having its parts, constructed combined and arranged
te operate substantially as described with reference to the accompanying drawing
and for the purposes specified.
HASELTINE, LAKE & Co.,
45, Southampton Buildings, London, W.C.,
Agents for the Applicant.