Improvements in and relating to Mercurial Vacuum Pumps.
Year: 1888

page_text: COMPLETE SPECIFICATION.
Improvements in and relating to Mercurial Vacuum Pumps.
I, RANKIN KENNEDY, of the Electric Lamp Works, 115 Woodside Road, Glasgow,
Lanarkshire, Electrical Engineer, do hereby declare the nature of my 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:
This Invention has reference to and comprises a new or improved construction or
arrangement and combination of the parts, of a mercurial vacuum pump, specially
applicable for acting in combination with an air suction pump, to withdraw the air
or gas from, and cause a vacuum in the glass globes of incandescent electric lamps
of large area or illuminating power; and which will be more simple and efficient
in action for the said purposes than the mercurial vacuum pumps or appliances
heretofore in use.
And in order that my said invention, and the manner of performing or carrying
the same into effect or practice may be properly understood I have hereunto appended
an explanatory sheet of Drawings, representing a perspective elevation of the new
or improved mercurial vacuum pump and its connecting or accessory fittings, as
applied for exhausting the air or gas from, and causing a vacuum in, incandescent
electric lamps with globes of large area or illuminating power, but not showing the
suction air pump which acts in combination therewith, as this may be of any ordinary
construction of air exhaust pump. The arrows indicate the direction of air suction
in the tubes and vessels where shown.
Referring to these Drawings, the new or improved construction of mercurial
vacuum pump consists all as follows:-Of two vessels or chambers A, B, one placed
above the other, and a third smaller chamber C, adjacent to the latter, all working
in concert and preferably made of glass. To the upper part of the lower vessel Á

page_text: is attached or secured a pine D fitted with a hand regulating tap D1 and connected
to the main air suction pipe F leading to the air suction pump engine. While
another pipe E fitted with a hand tap E leads from the top of the smaller vessel C to
this air with-drawing or suction pipe F. The vessel A is partially filled with mercury,
up to some little distance from the entrance to the exhaust pipe D, and communicates
by the lower open end of the centre pipe A', with the lower part of the vessel B, and
the vessel B communicates with the vessel C through the pipe 11 from the top leading
down through the centre of the vessel to the bottom, where the lower end is sealed
by a small depth of mercury c and any surplus accumulation of mercury in this
vessel C is periodically returned to the upper part of the vessel A through the pipe C²
and hand tap C which in its normal state is always closed. The vessels A, B, and C
are supported on or within the wood frame A over a bottom vessel A³ which in the
case of accidental breakage of the vessels would receive all the mercury,
A glass
pipe G leads from near the lower part of the vessel B, to a horizontal glass chamber G'
having phosphoric acid placed in it to absorb any mercury or air moisture that may
pass over and this chamber G is connected by a bent pipe G" to a general exhaust
pipe G2, with a series of vertical glass stem tubes g for sealing the globes of the
incandescent electric lamps to be exhausted of air, one large incandescent lamp g²
being shown in the Drawing as so connected, these pipes and fittings G to G² g, being
supported on the top of a longitudinal table or frame H at a proper height for the
workmen to attach or detach the globes by blow pipes at 9. The action of the
mercurial vacuum pump and its fittings is as follows:-The taps E¹ and D', are
first both open to their vacuum pipes E and D when the air pump exhausts the air
or gas from the three vessels C, B, and A, thus bringing the vacuum in these equal
to that of the mechanical pump. The air from the vessels g2 and B passes through
the mercury scale in the bottom of the vessel C, and the vacuum in the vessel A
prevents the mercury ascending to the vessel B until the mechanical pump vacuum
is completed. The tap D is then closed to the vacuum pipe D, but is open to
the atmosphere through the hole d, and the atmospheric pressure in the vessel A
forces up the mercury through the tube A¹ closing the communication G with the
lamp g, and forcing the whole contents of the vessel B through the pipe B', and
through the mercury seal c of vessel C. The tap D is then turned on to the
vacuum pipe D and shut off from the atmosphere, and withdraws any air in the
vessel A and causes a suction in it through the pipe D to the exhaust pipe F, and
this gradually withdraws all the mercury from the vessel B through the tube A¹
to the vessel A, leaving a perfect vacuum in vessel B, which comes into communi-
cation with pipe G, when the mercury falls below it, and the gases from the lamps g²,
expand into vessel B, to increase the vacuum in these lamps. When all the mercury
has flowed from the vessel B to A, the tap D is closed to the vacuum, and air
enters through the hole d in the tap D' and forces the mercury from the vessel A
through the pipe A' to the vessel B, and the contents of vessel B, are forced through
the pipe B, and through the mercury seal c in the vessel C.
This action goes on
intermittently and successively, the hand tap D¹ being turned on and off to the
vacuum as the vessel B is filled and emptied respectively of mercury, until a sufficient
vacuum is obtained in the lamps g. Any little mercury passed into the vessel C,
from the vessel B, through the pipe B is periodically run into the vessel A through
the pipe C² and tap C when the exhaust is taking place from this vessel A.
Any number of these mercurial vacuum pumps may be fitted in the frame A2
alongside the bench H of incandescent lamps 2 corresponding to the degree of
vacuum and quantity of lamps g² required or fitted on the glass tube G².
Having now particularly described and ascertained the nature of my said inven-
tion, and in what manner the same is to be performed, I declare that what I
claim is :-
First. The construction, or general arrangement and combination of the parts, of a
mercurial vacuum pump, to act in combination with a suction air pump, to exhaust

page_text: the air or gas from, and cause a vacuum in, incandescent lamps, or for other purposes,
substantially as herein described, in reference to and shown in the accompanying
Drawings.
Second. A mercurial vacuum pump, consisting of lower and upper vessels A, B,
communicating with a third or separate mercurial sealed vessel C, and operated in the
manner, and for the purposes herein described, in reference to and shown in the
accompanying Drawings.