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Патент USA US3042302

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July 3, 1962
A. LORENZ
3,042,292
VACUUM PUMP WITH GAS BALLAST DEVICE
Filed May 22. 1959
2 Sheets-Sheet 1
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July 3, 1962
A. LORENZ
3,042,292
VACUUM PUMP WITH GAS BALLAST DEVICE
Filed May 22, 1959
2 Sheets-Sheet 2
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nited States
1.
ice
3,042,292
Patented July 3, 1962
1
2
3,042,292
communicated directly with the piston chamber by being
VACUUM PUMP WITH GAS BALLAST DEVICE
Albert Lorenz, Hanan, Germany, assignor to W. C.
Heraeus G.m.bH., Hanan (Main) Germany, a corpo
ration of Germany
tiled May 22, 1959, Ser. No. 815,194
Claims priority, application Germany May 30, 1958
3 Claims. (Cl. 230-207)
connected to a bore in the wall of the pump housing
which led directly into the piston chamber.
It is an object of the present invention to provide a
vacuum pump operating with a gas ballast which com
pletely overcomes the above-mentioned disadvantages.
A further object of the invention is to provide a vac
uum pump with a special two-way valve which allows
the air or gases conveyed by the pump to be discharged
The present invention relates to improvements‘ in 10 during the exhaust stroke of the pump piston and the
gas ballast to be admitted into the piston chamber only
which has at least one piston revolving eccentrically within
as soon as the exhaust stroke is completed and when the
a piston chamber and sealed therein by means of oil, and
pump piston begins its suction stroke.
which is provided with a device for supplying secondary
The present invention therefore obviates the necessity
air or gas at certain times into the piston chamber.
15 of a special bore through the wall of the piston chamber
vacuum pumps, and more particularly to a vacuum pump
It is a well-known fact that in the operation of vacuum
pumps, normally liquid substances, especially Water, which
are subjected to the suction of such a pump become
vaporized, and thus enter the pump in the form of vapor
or steam. In the subsequent compression of the evacu
ated air or gas, these substances again condense and con
taminate the oil contained in the pump, thereby inter
fering with the proper operation of the pump. In order
to serve as an inlet of the gas ballast channel by pro
viding an exhaust opening in the wall of the piston cham
ber which also forms the inlet opening of the gas ballast
channel. The exhaust opening then leads to a valve
disk which ?rmly closes the gas ballast channel during
the period of the exhaust stroke of the pump piston
and thus prevents any entry of oil from the piston cham
her into the gas ballast channel at any time. On the
to remove these substances from the pump, a small amount
other hand, as soon as the exhaust stroke of the pump
of secondary air or gas, the so-called “gas ballast,” is 25 piston is completed ‘and the letter proceeds with its suc
fed into the pump shortly before the air or gas evacuated
tion stroke, the ballast gas may freely pass through the
by it is discharged therefrom. This gas ballast is "at least
valve into the piston chamben Such unrestricted entry
partly taken along by the condensed substances when
leaving the pump and it is thus sooner or later removed
from the pump oil. However, since the pump conveys
the air or gas continuously in the same direction from
the suction side toward the pressure side, a considerable
amount of lubricating and sealing oil is also discharged
from the pump and has to be replenished to maintain
the piston in a properly sealed condition.
Prior vacuum pumps of this type which were equipped
with such gas ballast devices had a channel provided
with a control valve which terminated into an end wall
of the piston chamber. This had the considerable dis—
advantage that, during the operation of the pump, the
oil penetrated continuously from the piston chamber into
the gas ballast channel and had to be forced out there
of the ballast gas has the additional advantage that the
vacuum pump according to the invention is capable of
conveying a considerably greater amount of vapor or
steam than could be conveyed by any of the known vac
uum pumps with gas ballast devices. Furthermore, the
reaction exerted by the gas ballast device according to
35 the invention upon the suction side of the pump piston
is considerably lower than the reaction exerted by the
previous gas ballast devices.
The e?icient operation of the gas ballast control valve
depends to a considerable extent upon providing its valve
40 disk with a suitable spring of an initial tension which is
just su?‘icient to maintain the valve in the closed position
when it is not actuated during the exhaust stroke of the
piston. Thus, even a slight pressure above atmospheric
within the piston chamber will be su?cient to press the
from by the newly injected ballast gas at every revolu
tion of the pump piston. Since the end wall of the
valve disk upon its seat so that no oil can enter into the
piston chamber was also continuously covered with an 45 gas ballast channel. 011 the other hand, even a slight
oil coating, an oil foam was formed at the point of
under-pressure within the piston chamber will be suffi
entry of the gas ballast channel into the piston chamber,
cient to lift the valve disk off its seat on the mouth of
and this foam was at least partly taken along by the piston
the gas ballast channel so that the ballast gas can pass
between its end surface and the end surface of the piston
freely into the piston chamber.
chamber and passed to the suction side of the latter. 50
Another feature of the present invention consists in
Consequently, the degree of e?iciency of such a pump
combining the gas ballast control valve with the exhaust
was seriously impaired by the gas ballast device and the
valve in such a manner that the control supporting shaft
degree of vacuum ‘attainable was reduced considerably
of the valve disks of the exhaust valve is secured to and
as soon as the gas ballast device was in operation. Al~
extends entirely through the valve plate which forms the
though efforts have been made to overcome this de?ciency 55 main body of the exhaust valve, and that this central
by providing the gas ballast channel so as to terminate
into the area between the piston chamber and the ex
supporting shaft is provided with a longitudinal bore so as
to form a tubular member, the upper end of which is con
haust valve, this exhaust opening was also thickly coated
nected to the gas ballast channel proper, while the lower
with pump oil which then necessarily penetrated into
end forms the valve seat of the gas ballast valve.
60
the gas ballast channel and was again passed together
In order to permit the entire two-way valve as well as
with the ballast gas into the piston chamber and to the
the two individual valves thereof to be easily assembled,
suction side thereof. Although the amount of air-sat
removed and exchanged, the invention further provides
urated oil which was transferred by the piston to the
that the central supporting shaft, the lower end of which
suction side thereof was far less than in a vacuum pump
forms the seat of the valve disk of the gas ballast valve, is
of the type as ?rst described, it was still considerable
removably secured to the valve plate which forms the
so that the ?nal vacuum attainable by the pump was
main body of the exhaust valve, and that the latter is also
impaired when the pump was operated with a gas ballast.
removably secured within the valve housing which may
The present invention is based upon a. proper recog
form an integral part of the wall of the piston chamber.
nition of the fact that the failure of all the previous 70 The entire gas ballast device may then be installed or
vacuum pump designs operating with a gas ballast was
removed by inserting or removing the central supporting
due to the provision of a gas ballast inlet channel which
shaft. The removal of the supporting shaft is preferably
3,042,292
carried out by ?rst removing the entire exhaust valve body
from the pump and by then unscrewing the supporting
shaft therefrom. The valve disk of the gas ballast valve
may also be very easily inserted or removed when the
exhaust valve body is ?rst removed.
The gas ballast channel leading to the outside of the
pump is preferably provided with a branch conduit lead—
ing into an oil separator so that a part of the oil mist
of conduit 24 from the separator 12. This air or gas
serves to quiet the chattering of the valve 10 during op
eration of the pump and by being connected to the sep~
arator, the air or gas is scrubbed free of ambient dust and
water vapor.
For closing bore 19 in shaft 18 and the gas ballast
conduit 21 during the exhaust stroke of pump piston 3,
the lower side of valve body 13 is provided with a valve
disk 25 which is normally held under a slight pressure
contained in the oil separating chamber will be drawn
back into the piston chamber by the air or gas passing 10 of a spring 26 in engagement with the lower annular end
surface 27 of shaft 18 which projects slightly from the
through the gas ballast channel. For regulating the
lower surface of valve body 13 and forms the valve seat
amount of this sucked-up oil, the branch conduit may be
for valve disk 25.
provided with a control valve.
As illustrated in FIGURE 3, valve spring 26 preferably
These and other objects, features, and advantages of
the present invention will become further apparent from 15 consists of a leaf spring with three radially projecting
arms 26a, 26b, and 26c which extend at an angle of 120°
the following detailed description thereof, particularly
to each other and rests on a surface 28 within a cham
when read with reference to the accompanying drawings
of one preferred embodiment of the invention, in which-—
ber 29.
It will be evident from the foregoing description that
an entry of oil from piston chamber 1 into bore 19 in
FIGURE 1 shows a cross section of a vacuum pump
with a gas ballast device according to the invention;
supporting shaft 18 and conduit 21 is absolutely prevent
ed by valve disk 25 in cooperation with spring 26 and the
FIGURE 2 shows an enlarged cross-sectional detail
view of the exhaust valve of the vacuum pump according
to FIGURE 1; while
FIGURE 3 shows a plan view of the valve disk of the
valve seat 27 on the lower end surface of supporting
shaft 18.
Although my invention has been illustrated and de
exhaust valve for closing and opening the mouth of the
scribed with reference to the preferred embodiment there
of, I wish to have it understood that it is in no way limited
to the details of such embodiment, but is capable of
numerous modi?cations within the scope of the appended
gas ballast channel.
Referring to the drawings, the vacuum pump illustrated
therein consists of a pump housing with a piston chamber
1 within which the rotary pump shaft 2 carries an eccen
tric 2a which is slidable within a piston 3 and thus adapted
to revolve the latter within piston chamber 1 along and
in engagement with the inner cylindrical surface thereof.
Piston 3 is provided with a short intake or suction pipe
4 forming an intake channel 5 through which the intake
claims.
_
Having thus fully described my invention, what 1
claim is:
1. In a vacuum pump having a housing, at least one
piston chamber within said housing, a piston eccentrically
revolvable in said piston chamber and oil-sealed therein,
a suction chamber intermittently communicable with said
chamber 6 communicates with the piston chamber 1 when
the intake opening 7 of channel 5 is disposed below the
rotary guide member 8.
According to the invention, piston chamber 1 is further
provided with an exhaust channel 9 which leads through
an exhaust valve 10 to the oil collecting and exhaust
piston chamber, said piston chamber having an exhaust
opening, an exhaust chamber connected to said exhaust
opening, an exhaust valve adapted to close said exhaust
opening toward said exhaust chamber during the suction
stroke of said piston, conduit means for intermittently
passing a gaseous medium from the outside of said pump
chamber 11 which is connected to an oil separator 12 in
the form of a cyclone separator.
As illustrated more clearly in FIGURE 2, the exhaust
into said piston chamber, said conduit means passing
through said exhaust chamber and being connected sub
valve 10 consists of a valve body 13 which may, for ex
stantially centrally to said exhaust valve, the end of said
ample, consist of a circular plate which is preferably re 45 conduit means passing through said exhaust valve and
movably secured within a recess in the wall of the pump
facing toward said exhaust opening of said piston cham
housing and is provided with a plurality of bores 14 form
ing the exhaust channels from piston chamber 1. These
ber forming a valve seat, a valve disk adapted to engage
with said valve seat to close said conduit means during
exhaust channels 14 are adapted to be closed at their
outer end by individual valve disks 15 which are con
nected to a supporting plate 16 by means of springs 17
the exhaust stroke of said piston, leaf spring means for
holding said valve disk under a very slight pressure in
engagement with said valve seat when said valve disk is
which press valve disks 15 against the upper surface of
plate 16 to close channels 14.
not being actuated by said gaseous medium passing from
Supporting plate 16 is
rigidly secured to a short supporting shaft 13, for ex
ample, by being welded thereto. This supporting shaft
18 is centrally secured to valve body 13, preferably by
being screwed into the same. According to the invention,
shaft 18 has a longitudinal bore 19 and is removably con
nected by a sleeve 20 to a gas ballast conduit 21 which
leads to the outside of the pump housing where it is con
nected to a control valve 22 for opening and closing the
channel 21 and regulating the supply of air or gas, i.e.
the gas ballast, into piston chamber 1. By means of a T
the outside of said pump through said conduit means.
55
E2. In a vacuum pump having a housing, at least one
piston chamber within said housing, a piston eccentrically
revolvable in said piston chamber and oil-sealed therein,
a suction chamber intermittently communicable with said
piston chamber, said piston chamber having an exhaust
opening, an exhaust chamber connected to said exhaust
opening, an exhaust valve adapted to close said exhaust
opening toward said exhaust chamber during the suction
stroke of said piston, conduit means ‘for intermittently
passing a gaseous medium from the outside of said pump
joint 23, a branch pipe 24 leading into the cyclone sep
into said piston chamber, said conduit means passing
arator 12 is connected to the gas ballast conduit 21 within
through said exhaust chamber and being connected sub
chamber 11 and may also be provided with a suitable
stantially centrally to said exhaust valve, said exhaust
control valve 24a. This branch pipe 24 serves to conduct
valve including a valve body being formed with channels
small quantities of air or gas from the separator 12 to
therethrough extending from the side facing toward said
the pump chamber 1 after initial start-up of the pump and 70 exhaust opening toward the side facing toward said ex
haust chamber, said valve body having a central aperture,
when the ballast valve is closed. In normal operation,
a tubular shaftlike member mounted on said valve body
the ballast valve is closed after the water vapor in the
within said aperture, means for connecting the free end
system to be evacuated is substantially removed. Upon
of said tubular member to said conduit means, a support
this occurrence, the valve 22 is closed allowing small
quantities of air or gas to enter pump chamber 1 by way 75 ing member mounted on said tubular member, a plurality
5
3,042,292
of exhaust valve disks resiliently mounted on ‘said sup
porting member and being adapted during the suction
stroke of said piston to close said channels in said valve
body, a valve disk adapted to close said central aperture
in said valve body at the side facing toward said exhaust
opening during the exhaust stroke of said piston, and
spring means for holding said valve disk under a very
slight pressure in engagement ‘with said valve body when
said valve disk is not being actuated by said gaseous
medium passing from the outside of said pump through
said conduit means and said tubular member.
3. In a vacuum pump having a housing, ‘at least one
piston chamber Within said housing, a piston eccentrically
revolving in said piston chamber and oil-sealed therein, a
suction chamber intermittently communicable with said
piston chamber, said piston chamber having an exhaust
opening, an exhaust chamber connected to said exhaust
opening, an exhaust valve adapted to close said exhaust
opening toward said exhaust chamber during the suction
stroke of said piston, conduit means for intermittently
passing a gaseous medium from the outside of said pump
into said piston chamber, said conduit means passing
through said exhaust chamber and being connected sub
stantially centrally to said exhaust valve, said exhaust
valve including a valve body being formed with channels
therethrough extending from the side facing toward said
exhaust opening toward the side facing toward said ex
6
haust chamber, said valve body having a central aperture,
a tubular shaftlike member mounted on said valve body
within said aperture, means for connecting the free end
of said tubular member to said conduit means, a support
ing member mounted on said tubular member, a plurality
of exhaust valve disks resiliently mounted on said sup
porting member and being adapted during the suction
stroke of said piston to close said channels in said valve
body, a valve disk adapted to close said central aperture
in said valve body at the side facing toward said exhaust
opening during the exhaust stroke of said piston, and
spring means for holding said valve disk under a very
slight pressure in engagement with said valve body when
said valve disk is not being actuated by said gaseous
medium passing from the outside of said pump through
said conduit means and said tubular member, the annular
end surface of said tubular member facing toward said
exhaust opening and slightly projecting from said valve
body forming a valve seal adapted to be closed by said
20 valve disk.
References Cited in the ?le of this patent
UNITED STATES PATENTS
1,650,494
Dally et al ____________ __ Nov. 22, 1927
2,191,345
2,196,287
2,779,533
Gaede _______________ __ Feb. 20, 1940
Baudette _____________ __ Apr. 9, 1940
Ziock _______________ __ Jan. 29, 1957
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