IMPROVEMENTS IN MERCURIAL VACUUM PUMPS
Year: 1885

page_text: We, ROBERT DICK, Manufacturer, and RANKIN KENNEDY, Electrical Engineer,
both of Greenhead, Glasgow, Lanarkshire do hereby declare the nature of my
invention for "IMPROVEMENTS IN MERCURIAL VACUUM PUMPS " to be as follows:-
Our invention consists of an improved construction of mercurial vacuum pump
in which are combined the elements of a displacement pump and of a Sprengel's
pump.
The improved vacuum pump comprises a displacement cylinder of considerable
capacity relatively to that of the vessel to be exhausted, which cylinder is fitted
horizontally or in a slightly inclined position and has attached to its lower end
a long upright tube having at its upper end a mercury cup through which is passed
the tubular stem of the incandescence lamp or other vessel in which a vacuum is
to be produced. To the opposite end of the cylinder is connected the limb of a
U-tube whose other limb is connected to a trough or other vessel containing
a supply of mercury at a higher level than the cylinder. A stop cock is fitted
on the connecting tube from the supply trough and a bulb is formed at or near the
lower end of this U-tube a little over 30 inches below the cylinder to which the
other limb is directly connected. This U-tube forms a supply pipe through
which mercury is supplied to fill the cylinder by opening the stop cock. To the
lower end of the cylinder is connected a discharge tube the lower end of which is
bent upwards and is formed with a bulb the centre of which is over 30 inches
below the cylinder. From this tube the mercury from the cylinder is discharged
into a trough or other vessel below a stop cock being provided between the bulb
and the outlet of the tube or the supply tube may be used as a discharge tube.
To the upper end of the displacement cylinder an outlet tube for carrying off air
or gas and vapour is connected and is bent over and extends downwards over
30 inches and is trapped at its lower end which discharges over the lower mercury
trough. This air outlet also serves to operate as Sprengel's pump as hereinafter
described.
The incandescence lamp or other vessel to be exhausted having been fitted in
place through the mercury cup at the top of the upright tube, the exhaustion from
it of air or gas is effected as follows:-The supply cock is turned on to admit
מ.
.

page_text: mercury from the upper mercury trough through the U-tube to the displacement
cylinder until that cylinder is completely filled and overflows by the air outlet
tube. The upright tube communicating with the lamp being connected to the
lower end of the cylinder is sealed by the first few drops of mercury admitted to
the cylinder and the air displaced by the inflowing mercury can only escape by the
air outlet or "sprengel" tube.
When the cylinder is completely filled the supply cock is turned off and the
discharge cock is opened so that the mercury flows out of the displacement
cylinder by the outlet tube through the bulb and cock to the mercury trough below.
The air or gas contained within the lamp globe or other vessel expands and fills
the displacement cylinder as the mercury is discharged.
When the discharge of the mercury has been completed the outlet cock is turned
off and the supply cock turned on to displace the rarefied air or gas in the
cylinder. When the cylinder is filled the supply cock is shut off and the discharge
cock is turned on to empty the cylinder. The air or gas in the lamp globe is
further rarefied by expanding into the displacement cylinder and the same cycle of
operations is repeated until the exhaustion is deemed complete. The final traces
of air or gas and of mercurial vapour and moisture which collect in the bend at
the top of the outlet tube are drawn off by turning on and off the supply cock
to cause the mercury to pass over from the displacement cylinder by the air
outlet.

page_text: Improvements in Mercurial Vacuum Pumps.
We, ROBERT DICK, Manufacturer, and RANKIN KENNEDY, Electrical Engineer,
both of Greenhead, Glasgow, Lanarkshire, do hereby declare the nature of our said
invention, and in what manner the same is to be performed, to be particularly
described and ascertained in and by the following statement in writing, reference
being had to the accompanying Sheet of Drawings, and to the letters and figures
marked thereon, that is to say :—
Our said invention consists of an improved construction of mercurial vacuum
pump in which are combined the elements of a displacement pump and of a
Sprengel's pump, and which would give a greater exhausting action at each
operation than the mercurial vacuum pumps heretofore in use.
And in order that the full nature and novelty of our said Invention and the
mode and means of performing or carrying the same into effect or practice, may be
properly understood, we shall now proceed to describe the figures on the Sheet of
Drawings which we have hereunto appended for that purpose; the same reference
letters indicating the same or equivalent parts in the figures where shown.
Figure 1 is a front elevation and Figure 2 a corresponding end elevation of two
mercurial vacuum pumps complete with their essential accessories, all constructed
in accordance with and illustrative of one modification of our invention, with
a supply and discharge mercurial cistern M, M¹, and an ordinary hand or motive
power pump P for returning the mercury from the latter to the former cistern.
Referring to Figures 1 and 2 :-Each of our new or improved vacuum pumps
consists of or comprises a displacement cylinder A of considerable capacity
relatively to that of the vessel to be exhausted, and preferably constructed of glass
as also its tubes; which cylinder is fitted horizontally or in a slightly inclined
position upwards from the air exhausting to the discharge end, and is shown
supported on a bracket A¹. To the lower end of the cylinder A is attached a long
upright exhaust tube a, having at its upper end a mercury cup a' through which
is passed the tubular stem 7 of the incandescence lamp L, (or other vessel) in
which a vacuum is to be produced. To the lower side and end of this cylinder A
is connected the upper long vertical limb of a U-tube b, whose other limb is
connected through an intermediate bulb 611 to the descending supply tube 6¹ from
the trough or vessel M, containing a supply of mercury, at a higher level than
the cylinder A A stop cock b is fitted on the connecting tube b' from the supply
trough M, and the bulb 611 is formed at or near the lower end of the duplex
U-tube b, b1, a little over 30 inches below the cylinder A to which the limb b is
directly connected.
The U-tube b b and bulb 611 form a supply pipe through which the mercury is
supplied to fill the cylinder A, by opening the stop cock 63, when a stop cock c¹ on the
discharge tube c is shut. When the limb 6 of this supply tube is to be used as a
discharge tube, the bulb 61 has a discharge branch tube c connected to its upper side,

page_text: leading to the discharge mercury trough M³, fitted with a stop cock c¹; and from the
upper end of the bulb 6 a long upright pipe open to the air at the top is led
up considerably higher or above the level of the displacement cylinder A as shown.
The mercury from the cylinder A is discharged through the tubes b, and c into the
receiving trough M¹ (or other vessel) below, a stop cock c¹ being provided between
the bulb b1 and the outlet cll of the tube c To the upper side of the high end of
the cylinder A, and outlet tube d, for carrying off air or gas and vapour, is
connected and is bent over and extended downwards over 30 inches and is sealed
or trapped by the mercurial bulb d' at its lower end, which discharges into the
lower mercury trough M¹. This air outlet tube d also serves to operate as a
Sprengel's pump, as hereinafter described. The incandescence lamp L (or other
vessel) to be exhausted having been fitted in place through the mercury cup a¹
at the top of the exhanst upright tube a, as before stated, the exhaustion from it
of air or gas is effected as follows:-The supply cock 6' is turned on to admit
mercury from the upper mercury trough M through the U-tubes b¹, b, to the
displacement cylinder A, until that cylinder is completely filled and overflows by
the air outlet tube d. The upright exhaust tube a communicating with the lamp
being connected to the lower end of the cylinder, is sealed by the first few drops of
mercury admitted to the cylinder and the air displaced from the cylinder by the
inflowing mercury can only escape by the air outlet or "Sprengel" tube d.
When the cylinder is completely filled, the supply cock 6' is turned off and the
discharge cock c¹ is opened, so that the mercury flows out of the displacement
cylinder A, by the outlet tube b, through the bulb 6" and cock c¹ to the discharge
mercury trough M¹ below. The air or gas contained within the lamp globe L
(or other vessel) expands and fills the displacement cylinder A as the mercury is
discharged therefrom.
When the discharge of the mercury has been completed the outlet cock c¹ is
turned off and the supply cock 6' turned on to displace the rarefied air or gas in
the cylinder. When the cylinder is filled again the supply cock 62 is shut off and
the discharge cock c¹ is again turned on to empty the cylinder. The air or gas
in the lamp globe L is further rarefied by expanding into the displacement cylinder,
and the same cycle of operations is repeated until the exhaustion is deemed
complete. The final traces of air or gas and of mercurial vapour and moisture
which collect in the upper end of the cylinder and in the top of the outlet tube d,
are drawn off by turning on and off the supply cock 6' to cause a portion of the
mercury at times to pass over from the displacement cylinder A by the air outlet
duct d, which thus acts as a "Sprengel's pump.
Instead of using the inlet tube b for drawing off the mercury from the lower
part of the displacement cylinder A, a separate tube may be fitted with a bulb led
to the discharge tube and cock c, c¹.
It will be understood that the mercury troughs M, M¹, might be made to run
along the whole side of a room or strong frame and that any desired number of
these new or improved vacuum pumps may be fitted up as shown, having the
displacement cylinders and their inlet, exhausting, and discharge tubes, all carried
and secured, as shown, to brackets in front of and over the mercury troughs, all
otherwise substantially as described in reference to the two examples shown.
An ordinary arrangement of plunger pump P is fitted at one end of the arrange-
ment of vacuum pumps for drawing the mercury from the lower discharge
trough M¹ by the pipe p, and forcing it through the pipe p¹ into the upper trough M,
so as to keep the whole range of mercury vacuum pumps constantly supplied. The
pump P is shown that it can either be worked by the long connecting rod P¹ from
an eccentric pin disc and motive shaft P11 above, or when this is not in motion the
long rod P' can be disconnected at the plunger joint P³, and the short connecting
rod jointed instead, of a hand lever arrangement Ps mounted on the frame of
the pump, applied so as to work the pump P, by hand when that is more
convenient

page_text: When a great number of these mercurial vacuum pumps are used together, it
would be preferred to have an ordinary air exhausting pump constantly at work
producing a vacuum of 10 or 12 lbs. or so in a vacuum vessel close thereto and to
have a tube led from this to the lower part of each exhaust pipe or cylinder a or A,,
with a cock on it for turning on at first to produce this vacuum in the lamp or
vessel at once or nearly so, and then turn this cock off and commence to work the
mercurial vacuum pump to produce the high or perfect vacuum, which would
save considerable time and get through more work with a smaller number of
vacuum pumps.
Having now particularly described and ascertained the nature of our said
invention, and in what manner the same is to be performed, we declare that what
we claim is,
-
First. The general construction of a mercurial vacuum pump for exhausting
incandescence lamps or other vessels, with displacement cylinder and tube fittings,
all substantially as herein described in reference to and shown in the accompanying
Drawings.
Second. In mercurial vacuum pumps for exhausting incandescence lamps and
other vessels, the application and construction of a displacement horizontal cylinder
with exhaust tube and inlet and outlet mercurial tubes, substantially as berein
described in reference to and shown in the accompanying Drawings.