An Improved Method of and Apparatus for Obtaining a High Vacuum.
Year: 1898

page_text: Date of Application, 25th Feb., 1898
Complete Specification Left, 24th Nov., 1898-Accepted, 25th May, 1899
PROVISIONAL SPECIFICATION.
An Improved Method of and Apparatus for Obtaining a High
Vacuum.
I, HIRAM STEVENS MAXIM, of 18, Queen's Gate Place, in the County of
Middlesex, Chevalier of the Legion of Honour, Civil and Mechanical Engineer,
do hereby declare the nature of this invention to be as follows:-
The pumps most commonly employed at the present time for obtaining high
vacuum are those known as the Geissler pump and the Sprengel pump.
In the Sprengel pump, as ordinarily used, the mercury flows through it from
a mercury reservoir, and in an ordinary damp climate the degree of vacuity
obtained with ordinary mercury generally approaches about 1/1000000 (one-
millionth) of an atmosphere. Beyond this point the mercury is found to take
about the same amount of air (or other gas) into the pump as it removes, so that,
no matter how long the operation is continued, the quantity of air present remains
constant. However, if the surrounding atmosphere is very cold and dry, and
sufficient care on the part of the operator is exercised, it is possible to obtain
still higher degrees of vacuity.
An important feature of my present invention is that I am able to construct a
pump, working on the Sprengel principle, which, in the hands of an ordinary
workman, will produce a higher degree of vacuity than has been heretofore prac-
ticable with the Sprengel pump used under ordinary circumstances.
In order to avoid the introduction of air into the pump by the mercury, I
provide an arrangement by which the mercury is first subjected to a vacuum in
the presence of phosphoric anhydride (PO) or other highly hygroscopic material.
In this way the mercury is freed from both air and water, and flowing downward
from the bottom of the reservoir enters an auxiliary reservoir of the pump in a
pure condition.
I find it advantageous to allow the mercury, as it enters the said auxiliary
reservoir to fall upon a plate or some other device that will impede the flow of
the mercury and cause it to be broken up into innumerable small drops, in which
condition the mercury will be effectually relieved of the air or other undesirable
gaseous matter it may contain. In this manner I am able to so purify the mer-
cury before it enters the pump that a highly vacuous condition can be obtained
by the apparatus.
In using the mercury pump, it is preferably so arranged with respect to a
mechanical pump that the bulk of the air (or other gas) to be exhausted is
removed by mechanical means before the mercury pump is put into operation.
But an ordinary mechanical air pump never produces a very high degree of
vacuity and I have therefore found it best to employ an air-pump constructed
expressly for producing a high degree of vacuity without the aid of mercury and
hereinafter referred to as a mechanical air pump. My mechanical air pump is
constructed on the compound principle i.e. it has three pistons and three

page_text: cylinders. Two of the cylinders have conical valves which are held against
their seats by powerful spiral springs, and which open outwardly. These valves
do not depend upon air pressure to move them, but they are operated by an
eccentric, connecting rod, and levers or other suitable mechanism, from the
main shaft of the pump. The first cylinder or that which is connected directly
to the mercury pump, has two of the said valves, each valve having around it's
stem a cup filled with oil, the said cup being attached to, and forming part of the
stuffing box nut or gland through which the said stem can work. The lever by
which the aforesaid valves are operated is so arranged that one valve forms a
fulcrum for the other, so that when one valve is raised from its seat, it is raised
at the expense of pressing the other one firmly against its seat, and vice versa.
The second cylinder is provided with valves which operate in an analogous
manner, the lever by which such valves are operated being attached to the first
mentioned lever by a short connecting rod, or other suitable means. As the
pistons reciprocate the valves are opened exactly at the proper time by means
of the aforesaid eccentric acting on the lever mechanism of the valves As the
piston of the first cylinder descends it finds the eduction valve firmly closed and
the induction valve wide open. Upon the return stroke of the piston the reverse
action of the valves takes place, and the air is discharged from the first into the
second cylinder without any appreciable obstruction to its passage.
The third cylinder is provided with ordinary valves, that is to say valves that
are not operated by the lever mechanism above referred to. Each of the two first
mentioned cylinders is open at its outer end and the pistons of these two cylinders
are so constructed that at their outward stroke they project slightly from the
outer or open end of the cylinders. The outer or open ends of these cylinders
are immersed in an oil tank, so that as the pistons reciprocate the oil alternately
enters the open end of first one and then the other cylinder, the level of the oil
in the tank remaining approximately constant. The piston rods pass through
stuffing boxes in the bottom of the oil tank, and the connecting rods and piston
rods are coupled together and attached to a cross head slide as in a steam engine.
Or I may employ trunk pistons, with no cross heads, the oil being supplied
by an annular cup into which the pistons dip at each outward stroke.
I may so construct the mercury pump that the mercury flows into a reservoir
or container from any suitable source and enters a U-shaped pipe, descending in
one limb thereof and ascending in the other where it reaches a stop cock. It
flows past this cock into the aforesaid auxiliary reservoir which is connected
with the mechanical air pump in such a manner that the space above the mer-
cury in such auxiliary reservoir is maintained in a highly vacuous state. Within
the said space in the auxiliary reservoir I arrange a pendent cage or perforated
bag or chamber to contain the hygroscopic material, a suitable plug being pro-
vided for permitting the said material to be readily inserted in to the said cage,
or the cage or bag may be attached to the plug and withdrawn with it for re-
charging. The mercury descends from the auxiliary reservoir through another
U shaped tube and enters a suitably shaped chamber (which I will term the
upper chamber) arranged at the upper part of the ascending limb of the last
mentioned U-shaped tube. From this chamber the mercury descends through
a series of vertical "fall tubes" communicating at their lower ends with the
lower part of another chamber which I will term the lower" chamber.
"
"
In mercurial pumps of the kind my invention has reference to, it very often
happens that a fine stream of mercury will descend the
"
fall tubes without
taking much air along with it, that is to say, the mercury does not descend in
the fall tubes like a tightly fitting piston, as it should do. It is therefore advan-
tageous to cause the mercury to fall intermittently in large portions or globules
so that the mercury will descend in the fall tubes in the form of pistons follow-
ing each other in rapid succession with a considerable space between them.
For this purpose I admit the mercury to the upper chamber in an upward or
angular direction and cause it to be thrown or squirted into short inclined tubes

page_text: or cavities suitably arranged or formed in the wall of the said chamber. As
these tubes or cavities become charged with a sufficient quantity of mercury to
overcome the dynamic force of the small incoming stream of mercury that is
ejected into them, the mercury in such tubes or cavities escapes, and descends
the fall tubes in the form of comparatively large portions or pistons. This alter-
nate charging and discharging of the inclined tubes or cavities continues so long
as the pump is working and in this way causes the mercury to flow down the fall
tubes in the form of an intermittent stream or of a succession of pistons with
spaces between them as above stated.
The aforesaid upper chamber is connected with the vessel to be exhausted
and is also connected by pipes controlled by cocks to an acetylene gas reservoir
and to a third chamber, which I will term an air collecting chamber" situated
in proximity to the said upper chamber; or it may be directed directly to the
air pump. This air collecting chamber is connected by a pipe to the aforesaid
lower chamber and to a mercury elevator or device for returning the mercury
to the mercury reservoir. The said air collecting chamber is likewise connected
by a pipe controlled by a cock to the mechanical air pump.
the
to
main
or
The aforesaid mercury elevator or device for raising and returning
the mercury
reservoir ready for re-use after it has
passed through the apparatus, preferably comprises long steel tubes
barrels having plungers or pistons of a diameter only slightly less than
that of the interior of the pump barrels. The said plungers extend
barrels
of the pump
which
through the upper ends
are unprovided
with stuffing boxes for the plungers. The outer end of each of the plungers
may be furnished with a block of metal or a weight sufficiently heavy to keep
the rod by which each plunger is connected to the crank shaft always in a state
of tension and so prevent chattering of the parts. The mercury elevator is
located a sufficient distance below the level of the mercurial pump to ensure
that the mercury shall flow by gravity into the tubes or pump barrels thereof.
As no stuffing boxes or greasy packings are employed, the mercury remains in
a pure condition with the exception of the slight amount of contamination that
takes place by its contact with the air and by its contact with the steel pump
barrels and valves.
The vessel to be exhausted having been connected with the upper chamber
either with or without an intervening vessel containing hygroscopic material, the
air cock on the pipe leading from said upper chamber to the air collecting
chamber is opened, as also is the cock on the pipe leading from the air collecting
chamber to the mechanical air pump. The mechanical air pump is then put into
operation and draws the greater part of the air out of the vessel to be exhausted
and out of all of the tubes and chambers of the mercury pump connected there-
with, thereby producing a degree of vacuity as high as can be obtained with a
mechanical pump.
The aforesaid cocks are then closed, and the cock on the
U shaped tube connecting the mercury reservoir with the auxiliary reservoir is
opened sufficiently to supply mercury to the mercury pump. The air as it is
withdrawn from the vessel to be exhausted, by the flowing mercury then passes
downward through the aforesaid series of fall tubes connecting the upper chamber
with the lower one, in company with the mercury, and is separated therefrom
in the lower chamber from which the air escapes or is drawn off into the air
collecting chamber, the mercury being returned to the mercury reservoir by the
return pipe and mercury elevator already mentioned.
When the apparatus is used for exhausting incandescent lamp globes, after a
sufficient degree of vacuity has been obtained therein, an electric current is
allowed to pass through the lamp filaments and the mercury pump allowed to
continue working while the filaments are hot. The occluded gases will then be
extracted through the aforesaid series of fall tubes and will accumulate in the
air collecting chamber; or the cock on the tube leading from said air collecting

page_text: chamber to the mechanical pump may be opened and such occluded gases be
pumped out of the apparatus.
While the above stated operation is proceeding the cock on the pipe leading
from the upper chamber to the air collecting chamber is of course kept closed.
When the occluded gases have been removed to the cock on the pipe leading
from the upper chamber to the acetylene reservoir is opened and a quantity of
acetylene gas or other carbonaceous gas, is allowed to enter the mercury pump,
the current of electricity through the lamps being turned off before this cock is
opened. As soon as the acetylene or other gas has filled the lamps and the
various parts of the mercury pump, the cock on the acetylene gas pipe is again
closed and the cock on the mechanical air pump pipe is opened. The operation
of the mechanical air pump then removes all the gases from the apparatus except
a mere trace of acetylene gas, when the mercury pump may again be put into
operation.
Da L
0211
HASELTINE, LAKE & Co.,
45, Southampton Buildings, London, W.C.,
Agents for the Applicant.
An Improved Method of and Apparatus for Obtaining a High
Vacuum,
I, HIRAM STEVENS MAXIM, of 18, Queen's Gate Place, in the County of
Middlesex, 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
following statement:-
-
This invention has reference to an improved method of and apparatus for
obtaining high vacuum.
"
The pumps most commonly employed at the present time for obtaining high
vacuum are those known as the Geissler" pump and the "Sprengel" pump.
In the Sprengel pump, as usually employed, the mercury flows through it from
a reservoir, and in a climate of ordinary dampness the degree of vacuity obtained
generally approaches about 1/1000000 (one-millionth) part of
Beyond this point the mercury is found to take about the same amount of air
an atmosphere.
into the pump as it removes, so that, no matter how long the pumping operation
is continued, the quantity of air present in the vessel which is being exhausted
remains practically constant. But if the surrounding atmosphere be very cold
and dry and sufficient care on the part of the operator be exercised, it is possible
to obtain still higher degrees of vacuity.
Now an important feature of my present invention is that I am able to con-
struct a mercurial air pump, working on the Sprengel" principle, which, in
the hands of an ordinary workman, will produce a higher degree of vacuity than
has been heretofore practicable with such pumps used under ordinary circum-
stances.
In conjunction with the mercurial air pump, I employ a mechanical air pump
which is so arranged that it removes the principal portion of the air (or other
gas) to be exhausted, before the mercurial air pump is put into operation.
I also employ a specially constructed mercury elevator for raising and return-
ing the mercury to a reservoir after it has passed through the mercurial air
pump ready for re-use in the said pump.

page_text: I so construct the said mercurial air pump that the mercury flows from the
aforesaid reservoir into the head or auxiliary mercury reservoir of the pump,
whence it flows through a U-shaped pipe, into a chamber which I term the
upper chamber. The said head is connected with the mechanical air pump in
such a manner that the space above the mercury' in such head is maintained in
a highly vacuous state. Within the said space in the head I arrange a pendent
cage or perforated bag or container charged with hygroscopic material such as
phosphoric anhydride (P₂0).
I find it advantageous to allow the mercury, as it enters the said head, to fall
upon a plate or some other device that will impede the flow of the mercury and
cause it to be broken up into innumerable small particles, in which condition
the mercury will be effectually freed from the air or other undesirable gaseous
matter it may contain. In this manner I am able to remove from the mercury
the air and moisture, before it enters the pump so that a highly vacuous con-
dition can be obtained by the apparatus. From the said upper chamber the
mercury descends through a series of fall tubes into another chamber which I
term the lower chamber. I cause the mercury to fall intermittently into these
tubes in large drops or globules of greater diameter than the cross-sectional
area of the tubes, so that such drops or globules will pass through the tubes like
so many separate plugs or pistons following each other in rapid succession with
a considerable space between them. I thus avoid the liability of the mercury
to descend through the fall tubes without coming into contact with the walls of
the tubes and therefore taking very little air along with it, a result which not
infrequently occurs in ordinary mercurial air pumps.
The said upper chamber of the pump is connected with the vessel or vessels to
be exhausted and is also connected by pipes controlled by cocks to an acetylene
gas reservoir in order that after the vessel or vessels have been exhausted to the
required extent, a quantity of such gas can be admitted to them to neutralize
the minute residue of oxygen remaining in them. The lower chamber is con-
nected to an air collecting chamber communicating with the mechanical air
pump and to the mercury elevator for returning the mercury to its reservoir.
My mechanical air pump is constructed on the compound principle, ie. it has
three pistons and three cylinders. Two of the cylinders have conical valves
which open outwardly and are held against their seats by powerful spiral springs.
These valves do not depend upon air pressure to operate them, but are actuated
from the main shaft of the pump. The first cylinder, or that which is connected
directly to the mercurial air pump, has two of the said valves and they are
operated by a lever which is so arranged that in raising one valve the other
serves as its fulcrum, so that the act of raising one valve has the effect of
pressing the other one firmly against its seat, and vice versa. The second cylinder
is provided with valves which operate in an analogous manner, the lever by
which they are operated being attached to the first mentioned lever by a link
or other suitable means. The third cylinder is provided with ordinary valves,
that is to say valves that are not operated by lever mechanism.
The cylinders are open at their lower ends and their pistons are so constructed
that at their outward stroke they project into an annular oil cup with which the
cylinders are provided so that in their return stroke they carry with them a
sufficient quantity of oil to lubricate the pistons and avoid the passage of air
past them into the cylinders. Or the open ends of the two first mentioned
cylinders may dip into an oil tank, so that as the pistons reciprocate the oil
alternately enters the open end of first one and then the other cylinder, the
level of the oil in the tank remaining approximately constant.
The said mercury elevator comprises long steel tubes or pump barrels which
are unprovided with ordinary stuffing boxes for the plungers. The outer end of
each of the plungers extends through the upper ends of the barrels and is fur-
nished with a block of metal or is otherwise weighted so as to be sufficiently
heavy to keep in a state of tension the rod by which each plunger is connected

page_text: to the crank shaft and so prevent chattering of the parts. As no stuffing boxes
or greasy packings are employed at a point where the mercury can reach them,
the mercury remains in a pure condition with the exception of the slight amount
of contamination thereof that takes place by its contact with the air and with
the steel pump barrels and the valves.
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 drawings in which:-
Figure 1 is an elevation partly in section and Figure 2 a vertical section on
the line 1, 1, of Figure 1, showing a mercurial air pump constructed in accordance
with my invention.
Figure 3 is a front elevation, and
Figure 4 an end elevation of one form of my mechanical air pump.
Figure 5 is a vertical section on a larger scale of the upper portion of the
cylinders of the mechanical air pump and their valves. The pistons are also
shown in this figure.
Figure 6 is a vertical section of the lower end of one of the said cylinders and
its piston. This section is taken at right angles to Figure 5.
Figure 7 is an elevation of a spring ring or cap for use in conjunction with
the piston, as hereinafter explained.
Figures 8 and 9 are sectional elevations of slightly modified constructions of
the said mechanical air pump.
Figure 10 is a front elevation and Figure 11 an end elevation of one form of
the mercury elevator.
Figure 12 is a sectional elevation and Figure 13 a sectional end view of
another form of the mercury elevator.
Figure 14 is a vertical section on a larger scale of one of the pump barrels
and plungers of the mercury elevator.
Figure 15 is a vertical section of an air valve with which each of the plungers
is provided as hereinafter described.
Like letters of reference indicate similar parts throughout the drawings.
Referring first to the mercurial air pump illustrated by Figures 1 and 2:-
A is the head or auxiliary mercury reservoir which is connected by the
U-shaped pipe A¹ to the upper chamber B. CC are the fall tubes by which the
said upper chamber is connected with the lower chamber 1). E is the air
collecting chamber which communicates with the said lower chamber D.
The upper end of the said head A is provided with a mouth a into which a
tightly fitting plug or stopper is adapted to fit. This plug or stopper is hollow
and furnished with an internal hook from which the perforated bag or container
charged with the hygroscopic material is suspended. It is also provided with a
manometer at for indicating the vacuous condition of the space within said head.
In order to prevent the entrance of air into the said head through the mouth
thereof, I provide the latter with a lip forming a channel to contain mercury
or other appropriate liquid which acts as a liquid seal around the stopper.
a a aª are branch pipes on the said head, each having a stop cock so that they
can be opened and closed as required. The pipe 6 communicates with the main
reservoir of mercury and terminates at its inner end in a nozzle a through which
the mercury enters the head in the condition of a fine stream. Suspended from
the said nozzle and lying directly below it is a plate a upon which the mercury
falls and thereby becomes comminuted as it enters the head so as to liberate
any air it contains. The pipe a' serves to permit mercury from the main reser-
voir to enter the outlet a" and thereby withdraw from the head any air that may
accumulate therein. In other words the pipe a acts as a fall tube or Sprengel
pump to the head A for keeping the space above the mercury in the said head
in a highly vacuous condition after as much air as possible has been removed
therefrom by the mechanical air pump. The pipe is in communication with
the mechanical air pump.

page_text: The end A2 of the aforesaid U-shaped pipe A¹ is prolonged horizontally into
the upper chamber B where it is formed with several lateral outlet nozzles a*
which project upwardly (as best seen in Figure 2) and lie opposite short tubes
or cavities b in the wall of the upper chamber, so that the mercury will enter
these cavities in the form of a fine stream. As these cavities become charged
with a sufficient quantity of mercury to overcome the dynamic force of the
small incoming stream that is ejected into them, the mercury in such cavities
escapes and descends the fall tubes C in the form of large drops that fit the bore
of the tubes like plugs or pistons as above specified.
This alternate charging
and discharging of the cavities b continues so long as the pump is working and
in this way causes the mercury to flow down the fall tubes in the form of an
intermittent stream or of a succession of piston-like drops with spaces between
them. The lower ends of the fall tubes communicate with the bottom of the
said lower chamber D so that the air carried into said chamber by the mercury
will not tend to ascend the fall tubes but will enter the air collecting chamber E
through the passage el. This air collecting chamber is provided with a pipe e
having a stop cock by which such chamber is placed in communication with the
mechanical air pump for removing the air that collects in the said chamber,
thereby keeping it in a vacuous condition.
The said lower chamber I also has a descending pipe D' which conveys the
mercury entering said chamber from the fall tubes to a receptacle communicating
with the mercury elevator.
1 is a pipe on the upper chamber B to which the vessels to be exhausted are
connected and 132 is another pipe having a stop cock, and communicating with
the mechanical air pump. Bis a third pipe for admitting, when required,
acetylene or similar gas into the said upper chamber, a stop cock being provided
on this pipe for controlling the entrance of the gas.
I will now proceed to describe my mechanical air pump illustrated by
Figures 3 to 7:-
FF and F are the three pump-cylinders and G G G are their pistons
which are connected by rods G to cranks on a shaft H having a belt pulley H'
by which it is driven from any suitable source of motive power.
The said pump cylinders are closed at their upper ends by covers F and are
carried by a transverse plate F forming part of the framing of the pump. The
cylinder F is furnished with conical valves f f and the cylinder F with similar
valves ff. The stems of these valves pass through stuffing boxes of having
cups to contain oil for preventing the entrance of external air into the
cylinders through such stuffing boxes. The said valves are coupled together in
pairs by levers F 15 the connection of the said levers to the valve stems being
effected by pivot pins f f f f which during the working of the pump serve
as fulcrums about which the levers can freely pivot as hereinafter explained. The
adjacent ends of the said levers are connected together by a link. F and the free
end of the lever F is coupled by a link F7 to a reciprocating rod Fs to which is
connected a rod F9 that is actuated by an eccentric or crank plate H2 on the
end of the shaft H of the pump. The said levers are each provided with
a yoke piece I at a point midway between the stems of each pair of valves, and
these yoke pieces have pistons or plungers i controlled by springs contained
in spring boxes pivotally connected at to the covers of the cylinders F1 F2.
The said plungers are kept constantly pressed downwardly by their springs, such
pressure being transmitted to the levers FF and the aforesaid valves by adjust-
able screws carried by the said yoke pieces. In the position that the valves
are represented in Figure 5 the eccentric or crank plate H2 has shifted the con-
necting rod F upward, thereby raising the outer end of the lever by moving
it about the pin F as its fulcrum against the resistance of its springs. Thus
the valve fis raised and opened but the valve f firmly retained closed by reason
of its serving as the fulcrum of the said lever. The piston G₁ is at this time
descending and consequently draws air into the cylinder F¹ from the mercurial

page_text: air pump which is connected with said cylinder by the inlet pipe J. As the
outer end of the lever Frises about the fulcrum f as above stated, its inner end
descends, and, through the medium of the link F, causes the adjacent end of the
lever of the other pair of valves f f on the cylinder F to also descend by
turning about the pivot fi as its fulcrum. This lever F therefore acts to firmly
retain the valve closed while the valve fat the opposite end of said lever is
raised and opened against the resistance of its spring. The piston of this
cylinder is now performing its upward stroke and therefore the air which at
the previous downward stroke of the piston was withdrawn from the cylinder Fl
into the cylinder F2, through the passages J, is forced from said cylinder F
through the passage J2 and inlet valve ] into the cylinder 13 whose piston is
performing its downward stroke.
On the return stroke of the pistons, the aforesaid eccentric or crank plate H²
reverses the position of the levers FF That is to say, the outer end of
lever is depressed and closes the valve f¹ whereupon it turns about the
pivot fas its fulcrum, and opens the valve f2. The adjacent end of the other
lever is also elevated through the link coupling F, thus causing the valve f
to be closed and the valve to be opened, by said lever turning about the
pivot f as its fulcrum after the valve f* has been closed. Therefore as the
piston Gascends it forces the air contained in cylinder Ft past the open
valves and through the passage J1 they control, into the cylinder F, whose
piston G³ is at such time descending, the air contained in cylinder F3 being
meanwhile forced by its piston G³ into the atmosphere through the eduction
valve J On the reversal of the stroke of the pistons the valves f f f³ fi are
again caused to assume the position represented in Figure 5 and a fresh quantity
of air is drawn into the cylinder F from the mercurial air pump, while the air
in cylinder F is forced into cylinder F3 as already stated.
9
The pistons G¹ G2 G3 are, in the example illustrated, of the trunk type with cup
leathers that are kept pressed outwardly against the walls of the pump cylinders
by spring rings or caps g' interposed between the said cup leathers and the body
of the pistons. The said cup leather and spring ring or cap are held in place on
the piston by a disc g² having a central screw stem which extends into the hollow
portion of the piston and receives a screw head or nut having a forked end to
which the connecting rod G is hinged by a pin g. The open ends of the pump
cylinders are provided with internal lips 96 (see Figure 6) which constitute
annular channels to contain oil supplied thereto from oil receptacles g7 situated
on the outside of the said cylinders and communicating therewith by a passage g³.
The open ends of the said pistons are also formed with internal angular
flanges constituting annular channels which, each time the pistons terminate
their outward or downward stroke, dip into and become charged with the oil
contained in the annular channels on the cylinders. Transverse perfora-
tions go extend from said annular channels 9 through the walls of the pistons
and thereby permit the oil in the said channels to reach the internal surface of
the pump cylinders as the pistons reciprocate. A film of oil is thus constantly
applied to the cylinders, such film serving as a lubricant and also assisting in
preventing the passage of external air past the pistons to the cylinders.
The aforesaid spring rings or caps glare composed of thin metal, preferably
steel, slotted at gas shewn in Figure 7, so that they virtually act as a series of
blade springs for keeping the cup leathers of the pistons pressed against the
surface of the cylinders.
In the modified construction of the mechanical air pump illustrated by
Figures 8 and 9, the cylinders F1 and F2 are provided with an oil tank K and
the oil contained in such tank is alternately drawn into the said cylinders behind
the pistons as the latter ascend and is again forced therefrom as said pistons
descend. The pistons of these two cylinders are in these cases furnished with
piston rods g which pass through stuffing boxes in the bottom of the oil
tank and the free ends of such piston rods are connected with crossheads working

page_text: in guides as shewn. In Figure 8 the oil tank completely encloses, the
cylinders FF2, and their lower ends extend to the bottom of the oil tank where
they are formed with lateral openings f for the entrance and exit of the oil.
In Figure 9 the oil tank does not completely enclose the cylinders and their open
ends do not extend completely to the bottom of the tank. The entrance and
exit of the oil to the cylinders therefore take place through the open ends of.
the cylinders. In other respects the construction and operation of the pumps
shewn by Figures 8 and 9 are substantially the same as described above with
respect to Figures 3 to 7 and they therefore need no further description.
I will now describe the mercury elevator illustrated by Figures 10 and 11 and
employed for conveying the mercury that passes through the mercurial air pump
back to the mercury reservoir of such pump. L L are the pump barrels and
M M are their pistons or plungers. These plungers extend through the upper
ends of the pump barrels and are unprovided with ordinary stuffing boxes so as
to avoid the contamination of the mercury by its contact with greasy packings.
The length of the pump barrels is such that their upper ends are above the tank
into which the mercury is elevated so that the mercury in the pump barrels will
not leak past the plungers and escape from the mouths of the said barrels. m m
are blocks of metal applied to the upper ends of the plungers for increasing
their weight and insuring that the connecting rods m¹ by which said plungers
are coupled to the crank discs m² shall always be kept in a state of tension
during working. Without weighting the plungers they would have a tendency
to float on the mercury as it entered the barrels and would give rise to chatter-
ing of the parts during the working of the elevator. N¹ №2 are valves located at
the lower end of each of the pump barrels L, one of such valves acting
as the inlet
valve, past which the mercury flows by gravity from the mercurial air pump (or
a tank connected therewith), as the plungers rise, and the other acting as the
outlet valve for the mercury as the plungers descend.
In Figures 12 to 15 I have shown a modified construction of the mercury
elevator in which the blocks of metal m are substituted by weights in the
form of caps or sleeves m³ connected by screws m³ to the upper ends of the
plungers which at their ends are made to fit the barrels as best seen in Figure 14.
The lower end of each of these caps or sleeves is furnished with a stuffing boxi m
and a leather packing ring m which, it will be observed, occupies a position
entirely out of reach of the mercury so that the latter cannot become contami-
nated by contact therewith. The said sleeve is also provided with an absorbent
ring m" which at each downward stroke of the plunger enters an oil cup m² on
the pump barrel, thereby becoming charged with oil and supplying the same to
the outside of the barrel, thus lubricating it. The leather packing m³ forms an
air tight joint. When the plunger descends the air contained in the space
between the sleeve m* and the barrel L is compressed thereby creating a pressure
in the said space, which serves to prevent the mercury from rising between the
plungers and the barrel to such an extent as to escape over the top edge of the
barrel. In order to release the compressed air in the said space as the sleeve
and plunger complete their downward stroke I provide a valve m8 (Figure 15)
which is opened, each time the plunger descends, by a finger m³ on the oscil-
lating connecting rod m¹0. This finger acts on the outer end or head of the
stem m of the valve each time the said connecting rod oscillates during the
downward stroke of the plunger, thereby depressing the valve against the resist-
ance of a spring m¹ and uncovering outlet apertures m¹³ in the valve casing and
allowing the air to escape. The lower end of the plunger is provided with a
hardened steel sleeve m¹ which is held in place by a collar and screw m¹³ such
sleeve being of a diameter to fit the lower end of the pump barrel. The portion
of the plungers between the ends thereof is of less diameter than the barrels to
reduce friction in the working of the said plungers.
and P are tanks for containing the mercury. The tank 0 is arranged at a
level above the mercury reservoir of the mercurial air pump and receives the

page_text: mercury as it is raised by the elevator, and the tank P is arranged at a lower
level than the mercurial air pump so that the mercury will flow therefrom into
this tank by gravity. The lower tank P is connected with the inlet valve N¹
by a pipe N and the upper tank 0 is connected with the outlet valve N2 by a
pipe N
The general working of the entire apparatus i.c. the mercurial air pump, the
mechanical air pump and the mercury elevator is as follows, and in describing
such working I will assume that incandescent electric lamps are to be dealt with.
The lamp globes are connected with the pipe B₁ of the mercurial air pump,
either (with or without an intervening vessel containing hygroscopic material)
and the stop cock on the pipe B leading to the mechanical air pump is opened.
The mechanical air pump is then started working and thereby exhausts the
greater part of the air in the lamp globes. At the same time the stop-cocks on
the pipes and e leading to the mechanical air pump are also opened, whereby
the head A and the air collecting chamber E are likewise exhausted. After the
mechanical air pump has been allowed to work long enough to obtain a degree
of vacuity as high as practicable by such pump, the stop-cocks on the said
pipes and e are closed and the action of the mechanical air pump is stopped. The
stop cock on the pipe is then opened to admit mercury from the main reservoir
(which may be the tank shewn in Figures 12 and 13) into the head A of the
mercurial air pump, any moisture that is carried into the said head by the
incoming mercury being absorbed by the hygroscopic material in the con-
tainer, and any air liberated by said mercury being rarefied by its entrance
into the vacuous space in the head A. The mercury flows through the U-shaped
pipe A into the upper chamber B in the form of upwardly inclined jets and
enters the cavities b, whence it escapes and descends through the fall tubes C in
the form of large tightly fitting drops or pistons as hereinbefore explained. The
mercury, together with the air it removes from the lamp globes, enters the lower
chamber D the air passing therefrom into the collecting chamber E and the
mercury flowing down the pipe D₁ into a suitable receptacle which may be the
tank Pin Figures 12 and 13. It is raised from this tank to the aforesaid main
reservoir or elevated tank 0, whence it again flows into the head A through the
pipe a
After a sufficient degree of vacuity has been obtained which will be indicated
by the manometer, an electric current is allowed to pass through the filaments
of the lamps under treatment, the mercurial air pump being still kept working
while the filaments are hot. The occluded gases will then be extracted through
the aforesaid fall tubes and will accumulate in the air collecting chamber E;
or the cock on the tube e leading from said air collecting chamber to the
mechanical air pump may be opened and such occluded gases be thereby directly
withdrawn from the apparatus. When the occluded gases have been removed,
the cock on the pipe B leading from the upper chamber B to the reservoir con-
taining the acetylene or other suitable carbonaceous gas is opened and a quantity
of such gas admitted; the action of the mercurial air pump being stopped and
the current of electricity through the lamps being turned off, before this cock
is opened. As soon as the acetylene or other gas has entered the lamps and
the various parts of the mercury pump connected therewith, the cock on the
acetylene gas pipe B3 is again closed and the cock on the pipe 132 leading to the
mechanical air pump opened. The mechanical air pump is then again started
to work and removes all the acetylene or other gas, except a mere trace thereof,
from the apparatus. The mercurial air pump may then again be put into
operation. By having present in the lamp globe a gaseous substance such as
acetylene, the carbon of which is easily separated from the hydrogen, the said
carbon, while in a nascent state, will absorb any minute residuum of oxygen
that may be present in the lamp globe and thereby avoid the detrimental effects
which the presence of such oxygen brings about. The quantity of acetylene gas
that it is necessary to employ is not sufficient to injure the mercury in the mer-

page_text: curial air pump, as it only requires a mere trace of the gas to get rid of the
residuum of oxygen. Acetylene gas, on account of its being rather an unstable
compound and easily decomposed, is more suitable for the purpose than petro-
leum gas, or other common hydrocarbon gas, which is rather difficult to decom-
pose. Moreover it is very easy to obtain acetylene gas free from sulphur, car-
bonic oxide and other impurities. It is preferable that the lamp should be
sealed off while the filament is in a high state of incandescence and when there
is nothing in the globe except a minute trace of the acetylene gas.
It will be obvious that when my method of obtaining a high degree of vacuity
is employed for exhausting other vessels than electric lamp globes, the use of
the acetylene or similar gas may be dispensed with.
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. The method of obtaining a high vacuum by the combined use of a mercurial
air pump and a mechanical air pump which are constructed and arranged to
operate substantially as described.
2. The admission of acetylene or similar gas to the electric lamp-globes during
the process of their exhaustion substantially as and for the purpose described.
3. The means, substantially as described, whereby the mercury, prior to its
passage through the mercurial air pump, is freed from air and moisture, for the
purpose specified.
4. The means, substantially as described, for ensuring that the mercury shall
descend the fall tubes of the mercurial air pump in the form of tightly fitting
plugs or pistons for the purpose specified.
5. A mercurial air pump having its parts constructed combined and arranged
to operate substantially as described with reference to Figures 1 and 2 of the
drawings.
6. The method of operating the valves of the mechanical air pump by spring-
controlled levers pivotally supported by the valves so that the pivots alternately
act as fulcrums for the levers substantially as and for the purpose described.
7. The construction of the pistons of the mechanical air pump with the in-
ternal annular channels to receive oil from an oil cup at the open end of the
pump cylinders substantially as and for the purposes described.
8. The combination with the mechanical air pump cylinders of an oil tank
into which such cylinders dip, or by which they are surrounded, substantially as
described and for the purpose specified.
9. A mechanical air pump having its parts constructed combined and
arranged to operate substantially as described with reference to Figures 3 to 7,
or Figure S, or Figure 9 of the drawings for the purposes specified.
10. The construction of the pump plungers of the mercury elevator with
weighted heads substantially as described and for the purpose specified.
11. A mercury elevator in which the packings and stuffing boxes are entirely
dispensed with substantially as described and for the purpose specified.
12. A mercury elevator having its parts constructed arranged and operating
substantially as described with reference to Figures 10 and 11 or Figures 12 to 15
of the drawings for the purpose specified.
13. Apparatus for obtaining a high vacuum, comprising the mercurial air
pump, and the mechanical air pump, with or without the mercury elevator, all
constructed and operating substantially as described with reference to the accom-
panying drawings.
Dated this 24th day of November 1898.
HASELTINE, LAKE & Co.,
45, Southampton Buildings, London, W.C.,
Agents for the Applicant.