IMPROVEMENTS IN VACUUM PUMPS
Year: 1882

page_text: PROVISIONAL SPECIFICATION left by Charles Denton Abel at the Office
of the Commissioners of Patents on the 23rd January 1882. A communi-
cation from abroad by Joseph Patrick of Frankfort-o-Main in the German
Empire.
CHARLES DENTON ABEL of No. 28 Southampton Buildings Chancery Lane in
the County of Middlesex. "IMPROVEMENTS IN VACUUM PUMPS." A communi-
cation from abroad by Joseph Patrick of Frankfort-o-Main in the German
Empire.
These improvements have reference to that class of pumps used for producing a
vacuum which are commonly known as mercury, or gravity pumps, and the improve-
ments are such as to enable a vessel which has been exhausted to be removed from
the pump whilst retaining the vacuum obtained.
The pump constructed according to these improvements consists in its more simple
form of a tube having an internal ring a little distance froin the top and this tube
is widened or contracted at parts instead of being of uniform bore. The internal
ring is ground on the top and inside so as to receive an air-tight stopper, the space
above the ring serving as a reservoir for a small quantity of mercury or other liquid
to act as a lute to the stopper.
The stopper forms part of a second tube of such dimensions that when the stopper
upon it is fitted into its place in the outer tube before described, the top of the second
tube projects a short distance above that of the outer tube. The top of this outer
tube is enlarged so as to be conveniently fitted with a cork, or other contrivance,
for making a good joint, and the lower part of this enlarged portion is also fitted
with a perforated clastic plug for preventing the luting of mercury from descending
to the inner tube. The lower part of this second, or internal tube is widened
internally, or it may be formed with a collar internally, at which part on its
underside and within it, it is ground so as to take a stopper. The stopper of this
internal tube may consist of a third tube sealed up at both ends so as to constitute
a rod, it being preferably in the form of a tube for the sake of lightness and buoyancy
and being ground at one end to form the stopper. After this last mentioned tube
or rod has been inserted within what has been described as the widened lower end
of the second tube this end of the second tube is drawn away by a quick reduction

page_text: to a capillary opening at its lower end so as to retain the short tube or rod within
it and yet so as to afford to this short tube or rod sufficient movement to allow of
passage around the stopper. If the pump be used as a inercury pump the external
tube must extend more than 32 inches below the lowest point of the internal tube
and if a fluid of less specific gravity be employed this external tube must be
proportionally lengthened. At the bottom of the external tube is a flexible pipe of
adequate length attached to a reservoir of adequate size so as that if the reservoir
be lowered mercury in the external tube will tend to flow into it and if the reservoir
be raised mercury in the reservoir will tend to flow into the tube.
The action of the pump is as follows:-The vessel to be exhausted is attached to
the top of the second tube by means of the cork or other device and the reservoir
before described having been filled with mercury it is raised to such height as is
necessary to charge the pump, that is to say to fill the external tube, to raise the
upper stopper and to flow above the upper stopper and also to flow by the capillary
opening into the lower end of the second tube thereby raising the short tube or
rod with its stopper thereon. The reservoir is then lowered and as the mercury
begins to sink, the upper stopper shuts down into its sent, retaining a portion of
the fluid above it, so as to act as a lute. The mercury below the stopper continues
to flow downwards and as no supply of air can be got from around the top stopper,
air is drawn out or through the capillary opening from the second tube and from
the vessel attached to it for exhaustion. When the effort of exhaustion thus
produced, is thus completed, the reservoir is again raised and the mercury ascends
within the tube as before. A larger quantity of mercury this time enters by the
capillary opening at the lower end of the second tube and by its weight tends to
close the lower valve or stopper, at the same time serving as a lute for this stopper.
The air contained within the space between the second and outer tubes above the
capillary opening of the former as the mercury rises, acquires gradually more
pressure and at last lifts the stopper at the top and escapes up through the luting
of mercury, and the mercury in the tube continues to flow up as before so as to
expel all air throughout the operations, continuing to lute the stopper. When by
sufficient repetition of the operations set forth sufficient exhaustion is obtained, the
internal tube may be removed the vacuum being retained therein and in the
attached vessel by the lower stopper and lute described, and another internal tube
may be inserted to exhaust another vessel.
.
At the lower part of the barrel, or outer tube of the pump a stop-cock may be
fitted in connection with a reservoir or vessel containing a hydrocarbon or other
gas. By opening the stop cock after tho vessel has been exhausted any desired
quantity of the hydrocarbon or other gas may be admitted into the exhausted
vessel. In place of fitting such stop-cock on the barrel, or outer tube, of the
vacuum pump, such stop cock may be fitted to the upper part of the second tube
which holds or contains the stem of the vessel exhausted, or to be exhausted, or
the second tube may be fitted with such stop cock in addition to the stop-cock on
the barrel or outer tube. In either case the stop-cocks are connected to a reservoir
containing hydrocarbon, or other gas.
In place of constructing the pump so that the second or internal tube shall have
a stopper so as to seat itself in the upper part of the barrel or outer tube of the
pump, this second or inner tube may be formed with a flange, or with an analogous
attachment for connecting it to the upper part of the outer tube or barrel of the
pump. In this case the joint between the two parts may be made by screw bolts
in slots, or the mechanical equivalents of these, which will readily admit of the
joint being rapidly loosened or tightened. The pump when so constructed is
provided with a valve-chamber, the valve in which is the equivalent of the stopper
and acts correspondingly with the stopper on the upper part of the interual or
second tube hereinbefore described in reference to the simpler form of the improved
vacuum pump. The lower part of the internal or second tube in this case as in
the preceding modification is fitted with a stopper as in that modification. The
outer tube or 'barrel of the pump may be provided with a glass gauge tube and

page_text: stop cock attached near to or at the upper part of the barrel and dipping into a
cup
of mercury below. This arrangement is only required in the case of the pump
being made of metal or other opaque material. By opening the stop cock on this
gauge tube the height to which the mercury rises therein shows at any time the
degree of vacuum obtained. But with pumps whose barrel or outer tube is made
of glass or other transparent material such gauge tube is unnecessary.
It is to be understood that pumps constructed as hereinbefore described are
especially applicable for producing vacuum in the glass chambers of what are
known as incandescent electric lamps (not necessarily however is their use and
application so limited, for it is obvious that the said pumps may be used for
exhausting vessels other than vacuum vessels of incandescent lamps) and from
what has been herein stated it will also be obvious that the said pump and
the several parts thereof may be constructed of glass, metal, or other suitable
material.
In using auch pumps for manufacturing incandescent electric lamps in quantity
it is to be understood that they are arranged in a series consisting of any desired
number, for example, in one or more rows, or in a circle, or circles. In such case
the lower part of each pump is provided with a stop-cock for opening or closing
communication between the pump and a large chamber containing mercury, which
chamber is common to all pumps in the series and which by being raised or lowered
correspondingly acts upon all those pumps of the series whose stop cocks are opened
to the mercury main.
For the purpose of rendering any or all of the stop cocks in connection with the
improvements in vacuum pumps as hereinbefore set forth as tight as practicable
it is preferred that each stop cock have a vessel surrounding them for containing
mercury in which when mercury is placed the said stop-cocks become immersed.
For the purpose of absorbing moisture the exposed surfaces of the mercury are
brought into contact with trays containing pumice stone, asbestos, or other porous
material, which will hold sulphuric acid, this having the effect of absorbing, or
attracting moisture from the pumps and their connections.