An Improved Double-acting Vacuum Pump.
Year: 1898

page_text: Date of Application, 6th Dec., 1898-Accepted, 21st Jan., 1899
COMPLETE SPECIFICATION.
An Improved Double-acting Vacuum Pump.
I, ADOLPH BERRENBERG, of Frederica, West Side, Wandsworth Common, Surrey,
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: -
The subject-matter of the present invention is a vacuum pump in which double
action is obtained by arranging the discharge of the pipe channel conducting the
air from the vessel or space to be evacuated so as to enter the pump barrel approxi-
mately in the centre, so that this orifice is opened or closed by the pump piston,
respectively, just before its arrival at the end of its stroke or immediately after
the commencement of a further stroke. For the purpose of discharging the air
from underneath the piston in its downward stroke the piston is provided with
a bottom valve and a hollow piston rod, while the air above the piston is dis-
charged during the upward stroke, in the known manner, by means of valves
arranged in the cylinder cover.
Pumps of the kind just referred to can be coupled so as to be dependent on each
other in their motion, and in such a manner as to cause the piston of one pump,
on its arrival at its lowest position, to remain in this position,-while being forced
with a certain amount of pressure against the cylinder bottom, until the piston
of the other pump has arrived in its highest position, in which this piston, on its
part, is retained, and forced with a certain pressure against the cylinder cover,
until the first piston has again returned to its highest position, and so on. The
piston of each pump is therefore retained after each stroke, in its terminal position
and forced with a certain pressure against the cylinder bottom or cover, for a-
period equal to the time occupied by a complete piston-stroke.
This mode of working vacuum pumps is of great practical significance because,
thanks to the fact that the piston is pressed against the cylinder bottom or covered
with some considerable force for some length of time, a more complete expulsion
from the bottom cylinder, of the extenuated air (which in this state is very inert
in its motion) is insured.
The annexed drawing illustrates one mode of execution of this invention; it
shows two identical vacuum pumps, coupled in the manner stated, in longitudinal
section. Both pumps are of exactly identical construction; each consists of a
pump barrel or cylinder a, connected above with the power cylinder b. Within
the pump barrel or cylinder there is a hollow pump piston c with bottom valve c¹.
This pump piston is connected by a hollow piston rod, which is perforated in
its upper part, with the piston rod d of the power cylinder b..
The pipe channel connecting the pump barrel with the vessel or space to be
evacuated discharges into the pump barrel approximately in its centre at f, motive
power is communicated to the pump by some suitable medium, for instance oil
which is introduced under pressure into the slide cylinder g. The latter is
arranged immediately by the side of the power cylinder, is open at the top and
bottom and is inserted into the hollow annular slide h which serves to regulate

page_text: the admission of the pressure medium, through the apertures i, ¹, into the power
cylinder. Both pumps to which the pressure medium is supplied by one common
tube kare mounted in a tank I, which up to its covering plate 1, is filled with
oil, and sealed hermetically. The extended piston-rods as well as the slide rods
are passed through the covering plate 1, through air-tight stuffing boxes, and the
projecting rim of the tank permits of putting the cover plate also under oil.
The working of the two pumps is made dependent on each other, by arranging
the slide-valve gear of the pumps so that the motion of the slide valve of the one
is controlled by the motion of the piston of the other, by means of a tappet arm m,
or a lever n.
The mode of action of the pumps is as follows:-
Supposing the piston of pump B, to have just arrived at the end of its down-
ward stroke and all parts to be in the position shown in the drawing. While now,
the said piston c is forced against the cylinder bottom by the pressure acting on
its driving piston, the pressure medium admitted over the driving piston d of
pump A, will press on this piston, forcing it down, and with it the pump piston c.
Immediately on the commencement of this downward stroke, the pump piston
will shut off the aperture of the air channel f, and the air underneath the piston
will now be expelled during the further descent of the pump piston, through the
bottom valve c¹, and the oil with which the hollow piston may suitably be filled
is forced through the hollow piston rod e, and out through the perforations e, at
its upper end, into the power cylinder b from which it escaped, together with the
pressure medium contained therein, through the upper cylinder orifice i, into
the large tank 1. Shortly before the arrival of the pump piston c at its lowest
position it will again lay against the orifice f of the air channel, and the vacuum
produced behind the piston on its further descent will be filled with air entering
through the orifice f, from the vessel or space to be evacuated. At the same time
the arm fixed at the upper end of the extension of the piston rod o, will strike with
its eye against a lower adjusting ring of the slide-rod and carry it downward so
that at the moment when the pump piston c of pump A, arrives at the bottom
of the cylinder the reversal of slide valve h, of pump 6, will at the same time have
been completed.
While now the pump piston of pump A, is being forced under pressure against
the cylinder bottom, the pump piston c of pump B, owing to the reversal of its
slide valve which has just been effected, will commence its upward stroke. There
by, after the orifice f has been shut off by the pump piston, the air over this piston
will be forced through the valves a¹, arranged in the cylinder cover, into the
outer chamber q, from which it passes into the oil tank 1. On the arrival of the
pump piston at its highest position it will again expose the orifice f of the air
channel, and the air of this channel will be again enabled to fill the lower cylinder
chamber; but at the same time, by means of lever n, the reversal of slide valve h,
of pump A, is effected, as the piston rod o¹, strikes with its boss o², against the
fork lever, thus causing the slide rod p¹, to move downward. The position now
occupied respectively by the various parts of both pumps would be exactly the
reverse to that shown in the drawing.
The piston c of pump B, will now again remain in this its highest position, in
close contact with the cylinder cover, until the piston of pump A, has finished its
stroke, which is completed with the same effect as just described with regard to
pump. B. On its arrival in the highest position (as shown in drawing) it will
again have effected the reversal of the slide-valve of pump B, by means of the
tappet-arm m which this time strikes the upper adjusting ring of the slide rod p,
so that, now, pump piston c of pump B, will descend while the piston of pump A,
will remain in its position, forced against the cylinder cover, until the downward
stroke of the piston of pump B, is completed.
The pressure medium ejected from the driving cylinders into the tank 1, may
again be fed, through tube r, into the driving pump. The air forced by the pumps
into the tank may preferably be extracted from the tank through a pipe channel's,
by means of a separate air numn

page_text: From the description just given as to the mode of action of the pumps, the double
action of the pump is clearly apparent, being simply based on the circumstance that
in each up and down stroke of the pump piston the connection of the air channel
with the pump cylinder is twice opened, and the air entering in consequence is
expelled.
The retention, obtained by the driving arrangement and mode of coupling, of
the pump pistons in their terminal positions, and their being forced during such
retention against the cylinder bottoms or covers, has the effect, highly significant
for practical purposes, that. the expulsion of air from the cylinder heads is carried
to the furthest extent which is practically attainable.
As the pistons are firmly forced for a considerable time against the cylinder
bottom, the intervening particles of air, which when highly extenuated are very
inert in their motion, will be afforded sufficient time to escape, which would scarcely
be possible with the usual quick return of the pistons.
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. Double acting vacuum pump characterised by the circumstance that the air
suction channel f discharges into the centre of the pump barrel or cylinder a, that
is to say, half-way between the cylinder bottom and cover, the hollow piston e of
this cylinder being provided with a bottom valve c', and a hollow piston rod e.
2. The coupling of two pumps of the kind characterised under Claim 1 by means
of a tappet arm m, establishing communication between the piston rod o of
pump A, and the slide rod p of the pump B, as well as a lever n, which establishes
communication between the piston rod o¹, of pump B, and the slide rod p¹, of
pump A, as well as the arrangement of adjusting rings on the piston rod o¹, and
the slide rods, P, p', for the purpose of causing the latter to be shifted by the
piston rods.
Dated this 5th day of December 1898