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Патент USA US2126553

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Aug. 9, 1938.
C. S. HORNBERGER El' AL'
2,126,553
VAÓUUMIKPUMP
' Filed April 26, 1935'
6 Sheets-»Sheet 1
Aùg. 9, 1938.
c. s. HORNBERGER Er AL.
ì
-2,125,553-
VACUUM PUMP
Filed April 26, 1955
»
6 Sheets-Sheet 2
M
Aug. 9, 1938.
»
c. s. HQRNBERGER ET Al. v
'
_
VACUUM
« 2,126,553
PUMP
Filed April _26, 1935
_
' 6 Sheets-Sheet 5 ’
'.5
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Z5
'.
' Aug. 9, 1938, .
cß s. HORNBÈRGER Er' AL
2,126,553
VACUUM PUMP
Filed April 26, -1935 I
6 Sheets-Sheet 4
,MUN
$2271
Allg- 9, 1938~ ,
c. s. HoRNBl-:RGER Er AL
2,126,553
VACUUM PUMP
Filed April 26, 1935
6 Sheets-Sheet 5
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Aug. 9, 1938.
2,126,553
c. s. HORNBERGER Er AL
VACUUM PUMP
Filed Aprií 26, 1935 '
6 Sheets-»Sheet 6
,37250775
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42,126,553
PaantedvAug. 9,1938.
UNITED STATES
PATENT OFFICE
n
`'VACUUM PUMP
Carl S. Bamberger, Glen Ellyn, and Marshall N.
States, Evanston, IIL, assignors to Central Sci
entiïlic Company, a corporation of Illinois
Application April 26, 1935, Serial No. 18,364
15 Claims. (Cl. Mil-_207)
cinc description are used for the purpose of dis
This invention relates to apparatus for’pro
ducing high vacua commonly called vacuum: closure because they conform to an embodiment
pumps, and the principal object is to increase
the degree of exhaustion, or the heightof the
5 vacuum and the speed of producing it.
that has demonstrated its ñtness for the purpose,
and they are not intended to indicate the limits
of the invention, which is susceptible of other 5
_ Generally speaking, this is accomplished by
connecting two eccentric pumps in series, the
embodiments.
first, or iinishing stage, being of large capacity
main pump, or finishing stage is indicated at A,
and the fore pump, or roughing stage, is indicated
10
at E.
The pump A comprises a casing it having a
cylindrical pump chamber Ill, having an intake
port l2 and a vestibule chamber lli connected with
the chamber il by an exhaust port it, the intake
and exhaust being divided by a vane, or blade llt,
sliding in the casing and cooperating with the
and arranged to deliver past the other in the
l0 initial operation, or until the pressure in the sys
tem is materially reduced, and then to deliver to
the other that serves as a roughing stage, or lore
pump, and by protecting the large finishing pump
with a complete oil seal, and making the rough
15 ingstage of sufûcient capacity to really out-gas
the oil in the sealing and lubricating system of
the ñnishing stage, and thus prevent the oil nec
periphery of an eccentric rotor it that serves as a
' essary for lubrication and sealing from placing a
piston.
worir on the system to be exhausted with all its
intatte port it, an exhaust port it, and between
them is a vane, or blade 2l, sliding in the casing
and cooperating with the periphery‘of an eccen
tric rotor it.
The pipe it leads from the vessel, or system, to
be exhausted, and is connected with the pump
casing by a fitting tti which, together with the
adjacent portion of the casing, provides a copious
inlet passage leading to the intake port li.
The vestibule chamber it is provided with a 30
ball check valve (several in a row) tti, by which
the vestibule chamber may be exhausted to an
exhaust chamber tit open to the atmosphere at
capacity.
till..
tem is approached.
`
At atmospheric pressure lubricating oil contains
dissolved air, absorbed gases, and volatiles which
are released at lower pressures, and even a small
25 quantity of gas released to the pump chamber at
extremely low pressure expands greatly and when
regularly supplied by the necessary feed of oil, it
slows down the exhaust and eventually deter
‘ mines the limit of vacuum that the apparatus can
3d produce. By practically out-gassing all the oil
that goes into the sealing and lubricating system
of the :finishing stage that pump is lei't free to
tion will appear as the disclosure proceeds and the
description is read in connection with the accortin
intake
and theoiexhaust
the pump
portid»itis of
indicated
the pump
by Ba istube
shown
connected with the exhaust chamber 2t by a
panying drawings, in which
Fig. l is a perspective of the apparatus with
4,0 part of the casing at the right and the inter
mediate portion removed to reveal the interior;
Fig. 2 is an end-elevation looking ’from the
right in Fig. l, with parts out away _on the line
,
in these diagrammatic views it to it, the con 35
nection between the vestibule chamber and the
Further objects and advantages ci the intenn
tube it. .But this is for the purpose of simpliíy- ‘
ing thev illustrations, and the actual connections
are quite different.
`
'
A comparison of thesuccessive positions shown
Fig. 3 is a plan section taken on the line t-At
in Figs. l2 to lll indicates the operation of the two
pumps as the driving motor turns the large rotor
countercloclrwise and the other rotor clockwise.
Figs. íi, 5, 6 and 'Z are sections taken on the lines
in considering the diderence in capacities appar
t-ii of Fig. 3;
e of Fig. 2;
til-«tt .li-_5, t-t and 'l-l, respectively, of Fig. 3;
Fig. 8 is a section taken on the line 1li-«t ot
Fig. 6;
Fig. 9 is a section on the line t--t of Fig. 3;
Figs. 10 and 1l are enlarged portions of Fig. "l';
Figs. l2, 13 and 14 are diagrammatic sectional
views of the two pumps and their connections.
55
\
The pump B comprises a casing il having a
cylindrical pump chamber it, provided with an 20
limit on the finishing pump by releasing gas to
20 the chamber as the complete exhaust of the sys
‘
’
In the diagrams, Figs. l2, 13 and 14, sheet 4, the
But these drawings and the corresponding spe
ent from these drawings, it will be seen that in
the initial operation the fore pump B cannot
handle all oi the gas delivered by the finishing
pump A, and the pressure rises in the vestibule
chamber lli until the check valve tti opens to
discharge the contents directly into the chamber
tti until the delivery or the finishing stage A comes
within the capacity of the roughing stage B, 55
2,126,553
2 .
when me valve 2| win close and thereafter uie
pumps will work in series.
.
'I‘he casing I8 is made in several parts, but in
the main is composed of end pieces 88 and 8l (Fig.
6) and an intermediate body piece 82 containing
the cylindrical bore ofthe main pump chamber
II. 'I‘he end piece 88 has a bearing 88 for the
shaft 84, driven by the pulley 45, and equipped
with two stuiiing boxœ 88 and I1.
8| also has'a bearing (not shown) forl the shaft
84 and a stumng box 88, a portion ot which ap
pears in Fig. 8.
.
The vane, or blade I5 runs in a slot 88 in the
body member 82 of the casing and is urged to
15 wards the rotor I8 by springs 48,~ Fig. 1, con
nected to the ends of a bar 4I (Fig. 6) on top
. of the blade andy to the end pieces Il and 8| by
screws 42, near the lower ends of spring bores 48.
One wall 444 of the exhaust port I4 is inclined
towards the blade Il (Fig. 1), and receives a tube
45, which serves as a valve cooperating with the
inclined wall 44 and the adjacent surface oi the
“ blade to close the exhaust passage against re
entry of gas and the flow oi' oil from the vestibule
chamber Il after the fashion disclosed in the pat
ent to Dubrovin, No. 1,890,571 ofDecember'13,
1932, the ends of the tube beingslightly reduced
externally to admit a small amount of oil for
lubrication and sealing.
' In the ordinary operation of the pump there
is no occasion for the valve 45 to open wider than
in the position shown in Fig. 10, but when the
pump has been standing for a long time and a
large amount of oil has seeped into the pump
chamber the ?rst revolution of the- rotor must
discharge the bulk of that oil through the exhaust
port. This makes it appropriate to vprovide for
an emergency wide opening by permitting the
valve to rise to the position shown in Fig. 1l.
To achieve this the body member 82 of the
casing is provided with a iiat seat 46, which con
stitutes a retaining wall for the body of oil in
the vestibule and upon which is secured angular
keeper blocks 41 having spaces 48 (Fig. 6) be
tween them to receive the teeth 48'on a bar 55
Yprovided with a plurality of holes 5I for screws
that compress springs 58 against the bar 5|), and
normally hold it in the position shown in Fig. 10,
but upon being pressed from below by the valve 45,
allow it to take the position shown in Fig. 11.
The gas discharged from the iinishing pump
passes through the spaces 48 into the vestibule.
Likewise, oil in a thin layer ilows’over the seat
or retaining wall 48 for supplying the cylinder
I I with lubricant. The oil at a depth below the
surface vcannot be entirely degassed because of
hydrostatic pressure but the surface oil in the
vestibule, being free of this pressure, is eil'ectively
degassed at low pressure and since the oil sup
plied to the cylinder is from the surface, the pump
is not handicapped by the adsorbedvair contained
in the oil and consequently, extreme low pressures
have been obtained.
'I'he wide slot in the body member 52 necessary
to admit this valve mechanism is partially closed
by a grating 54, made fast by machine screws 55
(Fig. 7) and having copious openings 56 to es
>tablish communication between the vestibule
chamber I8 and the dome of an arched cover 51,
secured to the top of the casing forming an
70 extension of said chamber and aiïording working
space for the blade l5.
l
The vestibule chamber i8 has an upright wall
58 and a substantially horizontal wall' 59, the
The opening movement of those valvesvis lim
ited by a stopßl secured to the vertical wall 58
of the vestibule chamber (Fig. 3) by screws 62
passing through it and spacers G3.
'I'he rush of the oil from the vestibule cham
ber during the initial operation of the pump is
likely to reduce the level in the system below what
is desirable and it is automatically returned
through a iloat valve mechanism, as shown par
ticularly in Figs. 3, 'I and 9. This iioat valve 10.
mechanism in like ymanner replenishes the oil
gradually withdrawn from the vestibule chamber
for lubricating and sealing the ports of the fin
ishing pump. 'I'he wall 58 of the vestibule cham
ber is drilled and tapped at 54 to receive a valve 15
'
plug 85, Fig. 9, having inlet openings 55 in a cen
tral passageway 81 leading through a valve seat l
88 near the bottom. A lever 85 fulcrumed on a
pin 1l in the forked end of the valve plug car
ries a valve stem 1i through a pin 12, and the 20
lower end of the stem cooperates with the valve
seat 58 to close the passageway when the lever
is in the appropriate position, and open the pas-f
sageway when the lever is raised above that“
position.V
'I'he control is by means of a float 18,at the
free end of the lever, acted upon by the oil in
the exhaust chamber, where vthe normal level
is substantially as indicated in Fig. 9 by the line
14. In order to prevent the rush of oil from
the adjacent valve displacing the iloat'13, the 30
valve stop 6| (Fig. 3) is equipped with an angu
lar plate 15, which serves as a shield or baille.
The exhaust chamber 2,6 is also provided with a
baille 15 (Fig. 9) to prevent loss of oil through
the exhaust outlet 21.
'
35
Incidentally, this baille 15 (Fig. 9) is so placed
in the exhaust chamber as to provide two paths
of unequal length leading from valves 25 to the
exhaust outlet 21. These paths are so related to
the exhaust impulse of the pump that the noise 40
is damped, that is, one path is longer than the
other whereby the crest of the impulse going
around one end of the 'baille will engage the
trough, as it were, of that portion going around
the otherV end whereby they tend to neutralize 45
each other thereby resulting in a quieter, smooth
er, ilow of the exhaust air through the exhaust
conduit 21,
'I'he right end piece 3i of the casing is cored
out to form a chamber ‘18 (Figs. 3, 5 and 6) pro
vided with a door 19 (Figs. 1 and 5) to afford ac
cess to the shaft bearing, the stufling box 38
and screws 42.
The end piece 3|,is also cored out to provide
a chamber 80 (Figs. 4 and 5), the end Wall 8| of 55
which is provided with a large opening closed by
the plate 85 to permit the fore pump B to be
inserted as a unit.
The pump B in this illustration is really two
eccentric pumps in series, the casing of which in-" w
cludes the end plate 82 (Fig. 6) < the cylinder rings
88 and 84, the intermediate plate 85, and the large
end plate 85, the latter being bolted to the end
wall 8l to secure the fore pump in place.
Two stage eccentric pumps of this general char
acter are well known on the market, and may be
had somewhat in the form shown by the patents
to Dubrovin, No. 1,890,572 of Dec. 13, 1932 and to _
Klopsteg, No. 1,890,614 of Dec. 13, 1932.
l 'I'he main pump shaft 34 projects through the
70
end piece 3i and is equipped with a gear,81 (Fig.
1) meshing with a gear 88 on the shaft 89 of the
latter equipped with valve seats 88 (Figs. 9, 12, Afore pump B. The gears are enclosed by a cover
75 13 and 14) to receive the ball valves 25.v
90 which also serves to enclose part of the pss 75
3
2,126,553
sageway from the vestibule chamber I3 to the
’ intake oi the fore pump.
As shown, an opening 9| (Figs. 1 andv 2)
through the end wall 3| puts the upper portion
of the chamber 13 in communication with the
inside of the cover 90, and an opening 98 (Figs.
2 and 6)., puts the lower portion of the chamber
1l in communication with the inside oi the cover
9|.
»
-
`
10. The intake port 92 of the fore pump is through
' the end plate 96. the exhaust port from the first
stage and the intake for the second stage is a
f bore 93 `through the intermediate plate 35, and
the exhaust port 94 (Figs. 4 and 6) of the second
stage leads into the chamber 90, which is in com
munication with the exhaust chamber 26 through
a cored passage 95.
`
The end plates 30 and 3| are each provided
with a groove 96 (Figs. 6 and 8) which has its
upper end in communication with the dome of
the cover 61, which is in communication with the
vestibule chamber through the openings 56 (Fig.
7). 'I'he other end 91 of each groove 96 is in
communication with the vestibule chamber at the>
end of the valve cylinder 45. v
f
The grooves 36 at their lowermost portions are
connected by a transverse bore 99 (Fig. 6) which
also°commuhicates with vertical bores |00 and
|9|, which establish communication with the
spring bores 43 and.’ hence, with the vestibule
chamber.
is ample when geared down to drive vthe main
shaft 34 at 450 R. P. M. which, with the ratio indi
cated would drive the fore pump shaft at 375
R.. P. M.
With such a pump vacuum, less than one
hundredth oi’ a micron has been produced with
ten microns in the vestibule chamber.
The best mechanical pumps having similar vol
ume heretofore available have reached a limit at
10
about one micron.
It frequently happens in the use of this ap~
paratus'that it is shut down, without being re
lieved, long enough for atmosphere to force oil
from the exhaust chamber into the Dump cham
bers of the roughing stage. Upon starting the 15
motor with the apparatus in this condition the
load is unduly heavy, and to relieve it, a friction
clutch |04 (Figs. 1 and 6) is introduced into the
gear 99 to allow the finishing stage to operate
with comparativefireedom while the oil in the 20
chambers of the roughing stage gradually works
out through the restricted ports. As soon as the
great Jresistance offered by the oil has been re
lieved, the clutch engages and the roughing stage
begins to operate. This delayed operation of the 25
roughing stage is no detriment to the efiiciency of
the apparatus, for during the period that it is
inactive, the finishing stage is working against
comparatively high pressure, and is therefore de
livering so much gas that the valves 25 are open 30
and the operation of the roughing stage would
’
The opening 9| (Figs.- l, 2 land 3)> through the
end wall 3| of the end piece 3l allows oil in the
system to enter the chamber formed by that end
wall and the cover 90 enclosing the gearing, and
-the normal oil level in this chamber is about as
indicated by the line |02 (Figs. 1 and 10) and is
the same as that of the oil in the vestibule cham
ber I3 (Figs. l2, 13 and 14) . The baffle |03 shields
the intake port 92 of the forepump and deter
mines the maximum height of the oil level‘in
the vestibule chamber I3 -and chamber 10. When
the oil level rises abovethe upper end of the
plate |03, the oil will flow over the baiile and will
be drawn into the roughing pump andv discharged
into the chamber` 90, which is in communication
with the reservoir 26, on the discharge side of the
rough/ing pump. The height of the oil in the
chamber may be observed through the glass
covered sight opening lll (Fig. 6).
y
These various passages and grooves put oil in
every joint of the pump casing to seal it, and
all of the oil in the system for lubrication and
sealing is in communication with the vestibule
55 chamber and subject to the pressure in that
chamber. The fore pump, having its intake con
nected with the vestibule chamber in addition to
’I‘he stuiling boxes 36 and 31 are of the ring
seal type shown and described in Dubrovin, No.
1,890,573, Dec. 13, 1932; and the box 31 is con 35
nected by a pipe |05 (Figs. 6 and 9) with the
vestibule chamber 26 below the oil level. Hence,
any leakage past the box is degassed oil.
The ñtting 24 (Fig. 1) has a Wide flange |06
fitted to a machined face |01 on the body piece 40
32 of the pump casing I0; and the flange is pro
vided with a sealing groove |08 connected by a
drilled passage |09 (Fig. 8) through the body
piece with sealing groove 96. As a result, any
leakage, upon reaching the groove, passes to the 45
vestibule and is taken ofi by the fore pump.
We claim as our inventionz-
’
l. In apparatus for producing high» vacua., a
pump of large capacity having a pump chamber
and an exhaust vestibule chamber, a check valve 50
permitting gas to iiow from the pump chamber
to the vestibule, an oil seal for the pump charn
ber connected with the vestibule and subject’to
the pressure in the vestibule, a second pump
having its inlet connected with the vestibule 55
chamber and of small capacity relative to the
first pump, but of sufficient capacity to outgas
exhausting it, serves to outgas all the oil in‘the the oil inthe seal and vestibule, a check valve
exhaust from the vestibule when the
system and, thereby prevent gas'reaching the permitting
delivery of the first pump exceeds the capacity 60
,the
finishing
stage,
either
as
anl
chamber Il of
of the second pump, an exhaust chamber receiv
incident to lubrication, or as seepage through the ing the exhaust from the vestibule chamber, a
joints ci' the casing.
The inlet ports i2 of the finishing stage and return passage connecting the exhaust -and the
all passages leading to them are made very wide vestibule chamber, a valve controlling the return
65 as compared with their length to reduce the im
pediment to rai'eñedv gas finding its Way into the
chamber of` the finishing stage.
The main pump chamber ii is ’7l/2 inches long
and d inches inside diameter and the rotor it is
(ii/2`inches outside diameter.
7
The cylindrical chambers of the fore pump are
. 2%» inches inside 4_diameter and l inch long, and
v the rotors are 2 inches in diameter.
The gear' 31 has sixty teeth and the gear bt
75 seventy-two teeth, and 11/2 i-l. P. electric motor
passage, a lever for operating the valve, and a 65
float for the lever.
2. A pump comprising a casing having a pump
chamber, a vestibule chamber normally at sub
atmospherlc pressure and an exhaust chamber
having sealing oil therein, a rotor in the pump 70
chamber, a check valve between the pump cham
ber and the vestibule chamber, another check
valve between the vestibule chamber and the
exhaust chamber, a. second pump chamber, an
intake passage for said second pump chamber in 75
4
2,126,553
communication with said vestibule chamber, an
oil seal for the first pump supplied solely from
the vestibule chamber and means including valve
mechanism to return oil to the _vestibule chamber
when oil in the exhaust chamber reaches a
selected level.
3. A pump comprising a casing having a pump
chamber, a vestibule chamber and an exhaust
chamber, a rotor in the pump chamber, a check
10 valve between the pump chamber and the ves
tibule chamber, another check valve between the
vestibule chamber and the exhaust chamber, an
oil seal for the pump supplied from the vestibule
chamber, means including valve mechanism for
15 returning oil to the vestibule chamber when oil
in the exhaust chamber reaches a selected level,
a> second pump having an intake connected with
the vestibule chamber and an exhaust connected
with the exhaust chamber.
A
4. In a vacuum pump mechanism, a ñnishing
pump having a rotary piston and intake and
discharge passages, a two-stage roughing pump,
a chamber for containing oil for supplying the
same to said finishing pump only, for sealing and
lubricating the same, a shallow mass of oil in
said chamber, oneY of said passages being in com
munication with said chamber beneath, but ad
jacent to, the surface of said oil, the intake pas
sage of said roughing pump being in communica
tion with said chamber above the level of said oil
whereby said oil will be degassed prior to the entry
into said finishing pump, a reservoir in the dis
charge passage of said roughing pump for col-~
lecting oil contained in the discharge gases of
35 said pump, and float controlled valve means for
supplying oil from said discharge passage to said
chamber when the oil in said last-named passage
rises above a predetermined level.
5. In a vacuum pump, a cylinder, a piston for
40
for said cylinder and an exhaust vestibule for
containing oil for lubricating said cylinder and
into which said' pump exhausts, a check valve in
said vestibule at the level of said oil, said valve
arranged for admitting oil to said cylinder from y
the surface only of said oil in a thin layer for
lubricating the cylinder. a roughing pump, and
a passage connecting the intake of the roughing
pump with said vestibule above the level of the oil
therein whereby the amount of oil supplied to said
cylinder is degassed.
9. An apparatus for producing high vacua com
prising a ñnlshing pump having a cylinder, -an
intake for said cylinder, a piston movable in said
cylinder and an exhaust vestibule for containing
oil for lubricating said cylinder and into which
said pump exhausts, a check valve in said vesti
bule, a valve seat for said check valve, a retainer
wall associated with said seat, 'said wall con
stituting retaining means for said oil whereby 20
oil supplied to said cylinder fiows over said wall
from the surface of the oil ln said vestibule, a
two stage roughing pump in series having intake
and discharge passages, and a passage connect
ing the intake of said roughing pump with said 25
vestibule above the level of the oil therein, where
by the oil in said vestibule will be under partial
vacuum for degassing the oil supplied to said
cylinder.
10. An apparatus for producing high vacua 30
comprising a finishing pump having a cylinder,
intake and discharge passages for said cylinder,
a piston movable in said cylinder, a roughing
pump in series with said finishing pump and
having intake and discharge passages, a reser 35
voir for containing'a mass of oil for lubricating
s_aid cylinder, means for maintaining the oil in
said reservoir at a pressure not substantially
above that of the intake of said roughing pump
said cylinder, intake and discharge passages .for for
degassing said oil, and a passage in communi
the pump, valves in the discharge passage, and
cation
with said reservoir at substantially the
a baille in the discharge passage so positioned rel
ative to said valves as to cause the discharge gas
to strike said baiiie at right angles thereto closer
to one end of said baille than to the other whereby
said gas is caused to take two paths of unequal
lengths, whereby the noise incident to the opera
tion of said pump will be reduced to a minimum.
6. In a vacuum pump, a finishing pump, a
50 roughing stage pump, a chamber for containing
a small amount of oil for lubricating said pumps,
an exhaust port for said finishing pump opening
into said chamber and constituting the principal
means for conducting oil from said reservoir to
55 said finishing pump for lubricating the same, an
intake passage for said roughing pump in com
munication with said chamber above the level of
the oil therein, a discharge passage for said
roughing pump, a reservoir in said discharge pas
sage, a passage between said chamber and reser- .
voir, and a float valve for controlling the passage
, of oil from said reservoir into said chamber.
7. In a vacuum pump, a casing having a finish
ing pump therein, an oil chamber for receiving the
65 discharge from said pump, an end piece for said
casing, said end piece having a chamber therein,
the outer wall of said chamber having an open
ing therethough, a closure plate for said opening,
a roughing pump secured to said closure and in
70 sertable through said opening, and an intake for
said roughing pump in communication with said
oil chamber.
8. An apparatus for producing high vacua com
prising a finishing pump having a cylinder, a pis
76 ton movable in said cylinder, an intake passage
40
oil level therein for conducting degassed oil from
the surface of said mass to said cylinder for
lubricating the same.
’
il. An apparatus for producing high vacua
comprising a finishing pump of large capacity,
a roughing pump of small capacity, a discharge
passage comprising a vestibule containing oil
for said finishing pump in communication with
the intake of said roughing pump, an oil sealed
relief check valve in a Wall of said vestibule for
permitting the escape of the exhaust through
said passage from said finishing pump only when
the delivery of the finishing pump exceeds the
capacity of said roughing pump.
l2. In apparatus for producing high vacua, a
pump of large capacity having a pump chamber,
an intake passage for said chamber, and an ex
haust vestibule, said vestibule being adapted to
contain oil for lubricating said pump, a check 60
valve permitting gas to flow from the pump
chamber to the vestibule, an oil seal for the
pump chamber connected with the vestibule and
subject to the pressure in the vestibule, a sec
ond pump having intake and discharge passages, 65
said last-named intake passage connected with
the vestibule above the level of the oil therein
and of small capacity relative to the first pump,
but of sufiicient capacity to outgas the oil in
the seal and vestibule. a check valve permitting 70
exhaust to be discharged from the vestibule in
dependently oi’ the second pump when the de
livery of the first pump exceeds the capacity of
the second pump, and an oil seal for said last
named valve.
‘
75
2,126,553
5
,
13. A high vacuum pump comprising a ñnish
ing pump, an intake and a discharge port for
said ñnishing pump, an oil reservoir for receiv
intake passage for said roughing pump being in
communication with said chamber above the
level of the oil therein for outgassing the oil
ing the discharge from the discharge port of
said ñnishing pump, a valve for said port, oil
within said reservoir at substantially the level
of said valve and arranged to escape from the
surface thereof past said valve into the discharge
side only of said iinishing pump for lubricating
10 the latter, a roughing stage pump provided with
in said chamber, a reservoir in the discharge pas
sage of said roughing pump, a passage between
said chamber and reservoir, and a float valve
for controlling the passage of oil'from said reser
voir into said chamber.
15. In a high vacuum pump, a rotary ñnishing
pump of large capacity, a rotary two-stage rough
an intake passage and a discharge passage and
ing pump of smaller capacity arranged in series,
having its intake passage in communication with
said reservoir above the oil level therein whereby
oil supplied to said finishing pump will be out
a vestibule chamber for receiving the discharge
from said iinishing pump, an oil retaining wall in
said vestibule'for forming a chamber for con-t
15 gassed by said roughing pump.
14. In a vacuum pump, a finishing pump„a
taining oil for lubricating said finishing pump
by supplying the same directly to the discharge
roughing stage pump, intake and discharge pas
sages foi' said pumps, a chamber having its major
portion above said finishing pump for contain
20 ing a shallow body of oil for lubricating said fin
ishing pump by gravity, the discharge passage
for said iinishing pump opening into said cham
ber through which finishing pump discharge
passage oil is supplied to the ilnishing pump, the
side of said ñnishing pump in a thin layer over
said wall, and means for connecting the intake
of said roughing pump to said chamber above
said wall andthe level of the oil in' said chamber _
for degassing all of the oil supplied to the dis
charge side of the finishing pump.
CARL S. HORN'BERGER.
MARSHALL N. STATES.
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