IMPROVEMENTS IN VACUUM PUMPS FOR EXHAUSTING BULBS OF ELECTRIC LAMPS OR OTHER VESSELS."
Year: 1882

page_text: LETTERS PATENT to Frank Wright and Matthew William Wallbank Mackie,
both of No 80, Gray's Inn Road, in the County of Middlesex, for an invention
of "IMPROVEMENTS IN VACUUM PUMPS FOR EXHAUSTING BULBS OF ELECTRIC
LAMPS OR OTHER VESSELS."
PROVISIONAL SPECIFICATION left by the said Frank Wright and Matthew
William Wallbank Mackie at the Office of the Commissioners of Patents on
the 3rd March 1882.
FRANK WRIGHT and MATTHEW WILLIAM WALLBANK MACKIE both of No. 80
Gray's Inn Road in the County of Middlesex " IMPROVEMENTS IN VACUUM
PUMPS FOR EXHAUSTING BULBS OF ELECTRIC LAMPS OR OTHER VESSELS "
Our invention relates to vacuum pumps for exhausting the bulbs of electric
lamps or other vessels in which great rarefaction of air is required, our object being
to provide in simple and compact form for utilising the barometric column of
mercury as a seal for the outlet of the discharged air.
For this purpose we
provide first an exhaust tube descending from the junction of the bulb or vessel to
be exhausted a distance exceeding 30 inches. This tube is closed at at the lower end
and has a small lateral aperture or several such apertures at its closed end. The lower
part of the exhaust tube passes through a throat slightly larger than itself into a
vessel which we may term the vacuum vessel and reaches nearly to the bottom
thereof. At the throat of this vessel there is a seating for a valve which may be
simply a caoutchouc washer sprung on the tube and covering the small annular
passage surrounding the tube." The throat of the vacuum vessel is expanded to a
larger diameter above the valve seating so as to form a seal chamber for mercury
above the valve. From the bottom of the vacuum vessel a tube extends down-
wards more than 30 inches and the lower end of this tube is connected either to a
pump or by a flexible tube to a mercury bottle which can be raised and lowered
through a height exceeding 30 inches. The operation of the pump is as follows.
The mercury bottle being raised or the pump being caused to make its instroke
the vacuum vessel becomes filled with mercury displacing past the valve the air
Price B21

page_text: As the
which it contained. On now lowering the mercury bottle or giving the pump its
outstroke the mercury descends from the vacuum vessel and the valve closing
against access of external air the place of the mercury is taken by air exhausted
from the bulb or other vessel. On again raising the mercury bottle or giving the
pump its instroke, the mercury is raised again into the vacuum vessel expelling
the air from it past the valve. Thus by repeated strokes the air in the bulb or
other vessel becomes more and more rarefied to the degree required.
mercury would accumulate in the seal chamber above the valve, we prefer to
provide this chamber with an overflow pipe which can communicate with the
mercury bottle or pump so that the excess of mercury after attaining a certain
level in the seal chamber passes to the bottle or pump. The exhaust tube may be
provided with a number of branches so that a number of bulbs or vessels can be
exhausted simultaneously and at any convenient point it may be connected to a
vessel containing chloride of calcium or other hygroscopic substance for drying
the air.
Although we have described the escape valve as a caoutchouc washer covering
an annular passage round the exhaust tube, this tube may be hermetically
connected into the vacuum vessel and the valve may be arranged to cover the
outlet of a separate branch tube from the top of the vacuum vessel, this branch
tube being provided with a mercury seal for the valve as already described.

page_text: SPECIFICATION in pursuance of the conditions of the Letters Patent filed
by the said Frank Wright and Matthew William Wallbank Mackie in the
Great Seal Patent Office on the 31st August 1882.
FRANK WRIGHT and MATTHEW WILLIAM WALLBANK MACKIE both of No 80
Gray's Inn Road in the County of Middlesex "IMPROVEMENTS IN VACUUM
PUMPS FOR EXHAUSTING BULBS OF ELECTRIC LAMPS OR OTHER VESSELS."
Our invention relates to vacuum pumps for exhausting the bulbs of electric
lamps or other vessels in which great rarefaction of air is required, our object being
to provide in simple and compact form for utilising the barometric column of
mercury as a seal for the outlet of the discharged air. For this purpose we provide
first an exhaust tube descending from the junction of the bulb or vessel to be
exhausted a distance exceeding 30 inches. This tube is closed at the lower end
and has a small lateral aperture or several such apertures at its closed end. The
lower part of the exhaust tube passes through a throat slightly larger than itself
into a vessel which we may term the vacuum vessel and reaches nearly to the
bottom thereof. At the throat of this vessel there is a seating for a valve which
may be simply a caoutchouc washer sprung on the tube and covering the small
annular passage surrounding the tube. The throat of the vacuum vessel is
expanded to a larger diameter above the valve seating so as to form a seal
chamber for mercury above the valve. From the bottom of the vacuum vessel a
tube extends downwards more than 30 inches and the lower end of this tube is
connected either to a pump or by a flexible tube to a mercury bottle which can be
raised and lowered through a height exceeding 30 inches. The operation of the
pump is as follows:-The mercury bottle being raised or the pump being caused
to make its instroke the vacuum vessel becomes filled with mercury displacing past
the valve the air which it contained. On now lowering the mercury bottle or
giving the pump its outstroke the mercury descends from the vacuum vessel and
the valve closing against access of external air the place of the mercury is taken
by air exhausted from the bulb or other vessel. On again raising the mercury
bottle or giving the pump its instroke, the mercury is raised again into the vacuum
vessel expelling the air from it past the valve. Thus by repeated strokes the air
in the bulb or other vessel becomes more and more rarefied to the degree required.
As the mercury would accumulate in the seal chamber above the valve, we prefer
to provide this chamber with an overflow pipe which can communicate with the
mercury bottle or pump so that the excess of mercury after attaining a certain
level in the seal chamber passes to the bottle or pump. The exhaust tube may be
provided with a number of branches so that a number of bulbs or vessels can be
exhausted simultaneously and at any convenient point it may be connected to a
vessel containing chloride of calcium or other hygroscopic substance for drying
the air.
Although we have described the escape valve as a caoutchouc washer covering
an annular passage round the exhaust tube, this tube may be hermetically con-
nected into the vacuum vessel and the valve may be arranged to cover the outlet
of a separate branch tube from the top of the vacuum vessel, this branch tube
being provided with a mercury seal for the valve as already described.
DESCRIPTION OR THE DRAWINGS

page_text: ascending a height of more than 30 inches descends again and enters the vacuum
vessel C, in which it descends some distance as shewn, and being closed at its
lower end, has a small lateral opening or openings A' formed in it, as shewn more
clearly in the enlarged view at Fig 2. The vessel C has a narrow neck C¹ through
which the tube A passes, and above which it is expanded into a cup C³. The
tube A carries a caoutchouc washer D that closes the neck C¹ as a valve, and the
cup C above it is partly filled with mercury acting as a seal. The vacuum
vessel C has a tube C³ extending down more than 30 inches and connected by a
flexible tube E to the tube F' of a vessel F filled with mercury, and supported so
that it can be raised and lowered to a certain extent. The vessel C and tubes C³,
E and F¹ being also filled with mercury it will be seen that on raising the vessel F
the mercury will also rise in C thereby forcing the air in its upper part out
through the valve D. On again lowering the vessel F the mercury in sinking in C
will cause air to be drawn from the bulbs B through the tube A and opening A¹
into the vacuum thus formed in the upper part of C and this air will be again
expelled through the valve D on causing the mercury to rise in C by raising the
vessel F again the opening A' being closed by the mercury so as to prevent any
escape of the air back into the tube A. The above operation of causing the
mercury alternately to descend and ascend in the vessel C being repeated, the air
will be gradually exhausted from the bulbs B to any required degree. The cup C
has an overflow branch C connected by a flexible tube G to the mercury vessel F,
so that any excess of mercury can flow back from C into F.
Having thus described the nature of our invention and in what manner the
same is to be performed we wish it to be understood that we do not claim generally
exhausting air from bulbs or vessels by connecting the same to a vessel in which
mercury in alternately descending and ascending is caused to draw air from the
bulb and expel it into the atmosphere, as we are aware that this has before been
done, but we claim :-
The use of apparatus for this purpose combined and operating as herein set
forth.
In witness whereof I the said Frank Wright have hereunto set my hand
and seal this thirty-first day of August in the year of our Lord One
thousand eight hundred and eighty-two.
FRANK WRIGHT. (L.S.)