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Патент USA US3057556

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Oct. 9, 1962
Filed Jan. 29, 1958
United States Patent @??ce
Patented Oct. 9, 1962
arranged to permit the supply to all the various oil ways
leading to the parts of the pump requiring oil from the
main oil way at a desired steady pressure whatever the
Basil Dixon Power and Alfred Aristides Runlri, Langley
operating condition and to by-pass back into the main
Green, (Jrawley, England, assignors to Edwards High
reservoir any excess oil delivered from the main oil way.
Vacuum Limited, (Irawiey, England, a 1liritish company
According to a feature of the invention, the composite
control valve is constructed so that, when the oil pump
Filed .lan. 29, W58, §er. No. 711,861
Claims priority, application Great ?ritain Feb. 7, 1957
8 Claims. (Cl. 230-407)
This invention relates to rotary vacuum pumps em
and the vacuum pump are stopped due to any cause, the
interior of the vacuum pump is sealed both from the
10 main oil way and from the oil reservoir with the result
ploying oil as a lubricating and/or sealing medium and
incorporating a reservoir, or the equivalent, for oil stor
that, provided an outlet valve of a sealing type is used
as the exhaust valve of the main vacuum pump, neither
oil nor air can be forced back into the main vacuum
pump, not through the latter into the system to be
It is a characteristic of such pumps that, when they are
stopped under vacuum, oil is sucked from the reservoir 15 evacuated.
According to a further feature of the invention, certain
through the oil feed ducts, and also past the pump outlet
parts associated with the composite valve are so con
valve if that valve is an oil covered and non sealing type,
the oil then passing into the system being evacuated
structed that, should the valve fail to seal securely due,
for example, to the presence of dirt or grit between the
reservoir has been su?iciently emptied, the oil is fol 20 sealing faces, a minimum quantity of oil and, thereafter,
only air will be sucked back through the valve into the
lowed by atmospheric air which may scatter the oil
vacuum system, thus ensuring minimum contamination
about the system being evacuated and ?nally raise the
of the vacuum system even if it should be raised to
pressure in the system to atmospheric.
where it may cause serious contamination.
When the
Many methods have previously been suggested to
overcome the di?iculty referred to but they suffer from 25
the disadvantage, either of adding to the expense of the
pump out of proportion to the degree to which they over
come the problem, or they only partially solve the prob
A possible arrangement or system for preventing oil
suck-back is to draw the oil from the reservoir and to
atmospheric pressure.
One form of vacuum pump embodying the invention
and incorporating an oil suck-back reducing or eliminat
ing valve and an alternative form of valve, will now be
described in greater detail by way of example with refer
ence to the accompanying drawings, in which:
FIGURE 1 is an elevation, in section, of such a pump;
FiGURE 2 is a view of the valve to an enlarged scale;
drive it along a single main oil way to the pump by
suck-back, but it is both complex, involving, as it does
two adjustable valves and the adjustment necessary to
ensure that the valves open always in the right sequence
municates with the oil in the reservoir providing the
intake 13!) and outlet 130 of the small oil pump. An 0
ring is accommodated in a recess in the plate 14 and
clamped in position by a screw held plate 16, seals the
FIGURE 3 shows one alternative form of valve.
means of a positive displacement oil pump driven by
Referring to FIGS. 1 and 2 of the drawings, a rotary
the prime mover of the vacuum pump itself. The main
vacuum pump 1 is mounted within a tank of main reser
oil way is closed by a spring or gravity closed shut off
voir 2 containing oil, the normal level of which is indi
valve when the pumps are not in action and this valve
cated by the line 3. The rotor 4 of the pump is mounted
must be capable of resisting an atmospheric pressure
on a shaft 5 which carries a driving pulley wheel 6. The
difference without leaking. When the pumps are started
front bearing block 7 of the pump shaft is formed with
however the oil pump is able to produce a high enough
oil pressure in the main oil way to force open the valve 40 a recess or bore 8 which is slightly eccentric with respect
to the centre of the main bearing indicated at 9. The
and to supply oil to the vacuum pump. The oil ?ow
walls of the bore 8 constitute the stator of a small oil
required by the vacuum pump may vary greatly with
pump P of the well known vane type. The rotor 10 of
operating temperature and with the tolerance of an in
the oil pump P is mounted on the main vacuum pump
dividual pump and it is therefore necessary to select an
shaft 5 and is driven thereby, and a pair of blades ltib
oil pump capable of supplying an excess of oil at all
are ?tted in known manner in slots of the rotor 10‘ the
times and to provide a spring or gravity loaded by-pass
blades being spring urged against the inner wall of the
valve from the pressure side of the oil pump back to the
bore 8 and serving to sweep out a crescent shaped pump
reservoir to accommodate the excess flow of oil. The
by-pass valve must be adjusted to open always after the 50 ing chamber as the shaft 5 rotates. Any other conveni
ent type of small oil pump may be used.
main valve has been forced open, but it is usually un
Concentric with the bearing 9 is a further recess 11
desirable to set it to open at a pressure greatly exceeding
which accommodates an elastomer O ring 12 to seal off
that at which the main valve operates, both because the
the oil pump from the main or vacuum pump. A rec
load on the small oil pump is increased and also because
it is often undesirable for the oil feed to the vacuum 55 tangular duct 13, formed by a milling cut in the front
face of the bearing block 7 and completed by the rear
pump to be supplied at too high a pressure. The system
surface of the front plate 14 of the tank reservoir, com
described can provide a complete safeguard against oil
and that the oil feed to the vacuum pump is always sup
plied at the most suitable pressure may be complicated
and sometimes a little uncertain.
The object of the present invention is to provide a
oil pump from-the outside.
The upper part of the duct 13 which serves as the
outlet of the oil pump, communicates through a main
oil way 13a with a circular recess 17 indicated by an
system for preventing oil suck-back having the merits of 65 arrow lead line and forming a small chamber which
the system referred to, without its defects.
constitutes a container of predetermined limited capacity
According to the present invention, a positive displace
ment oil pump preferably driven by the same prime
mover as the main vacuum pump and preferably built in
which lies higher than the oil level in the reservoir and
which is formed in a head box 17a at the upper end of
bearing block 7. From this chamber the main pump re
as an integral part of the main pump, is arranged to draw 70 ceives all its lubricating and sealing oil by suitable oil
oil from the reservoir and to pump it along a main oil
The recess 17 has a flat bottom formed with two con
way to a single composite control valve constructed and
tion of the screw 23 and spring 22 combination shown
in FIGURES 1 and 2 is, in FIGURE 3, performed by a
centric grooves 18 and 19. An elastomer disc 20 form
ing a closure member is placed over the grooves 18 and
19 and is covered by a metal plate 21 of the same size. A
spring 22 held in place by a screw 23 keeps the elastomer
spring 33 held under compression by a bridge piece 34
formed with a hole mid-way of its length and through
disc, with the aid of the metal disc, pressed evenly
which a stem 35 projects vertically from the plate 32 to
against the ?at bottom of the recess. It will be seen
from FIGURE 2 that the clamping screw 23 is formed
permit raising and lowering of that plate and with it the
disc 20 under varying oil pressure. The plate 34 is
secured in position by screws 36.
The device affording protection against oil suck-back in
A second step 25 is formed by deeply undercutting the 10 the system described will operate whenever the pump
screw as shown, the step 25 serving to clamp the disc
stops for any cause and will exclude oil from the pump
with a shoulder or step 24 which provides a de?nite
stop position limiting the downward travel of the screw.
entirely while leaving both the pump and the system
being evacuated by it under vacuum. Further the pro
20 near its centre but with a controlled amount of com
The groove 18 communicates with the duct 13 on the
tective device will ensure that whenever the vacuum
discharge side of the oil pump via the main oil way 13a 15 pump is operating, oil is fed to it always at the most
and the groove 19 communicates with the oil ways 26
suitable pressure which usually is at or a little above
supplying the main vacuum pump. The assembly com
atmospheric pressure, whatever the temperature or vis
cosity of the oil used. Again, no adjustment or critical
prising the recess 17, the grooves 18, 19, the discs 20, 2.1,
the spring 22 and screw 23, together constitute a com
manufacture is necessary to ensure that any valves open
posite control valve.
20 and close in a desired sequence and, ?nally, it Will be
When the vacuum pump is started the gas being ex
seen that the device is compact and may be made cheaply
hausted enters the main pump through an inlet spout 27
enough to build into the smallest vacuum pump without
and the oil pump will immediately start to deliver oil
undue increase in price.
into the groove 18. After this groove is ?lled with oil,
We claim:
the pressure of the oil will raise the elastomer disc 20 and 25
1. A vacuum pumping device, comprising, in combina
the oil will ?ow over and into the outer groove 19. The
oil pump is designed so that it will deliver more oil than
(a) a housing for containing a quantity of lubricating
is required for the main pump. Thus the outer groove
and sealing oil;
19 will also ?ll up and over?ow through a circular gap
([1) a small open head box disposed above the normal
formed between the periphery of the elastomer disc 20
oil level in said housing and constituting an oil con
and the bottom of the recess 17 by the lifting of the disc,
tainer of predetermined limited capacity;
although a certain amount of the oil is constantly sucked
(c) an oil pump in said housing having an intake ar
away by the main pump.
ranged to draw oil from said housing and an outlet
As the groove 19 is very close to the periphery of the
terminating in a main oil way delivering to said
elastomer disc which is forced downward by the spring 35
head box;
22, and as only a light spring is normally employed the
(d) a rotary vacuum pump in said housing including
oil is only under slightly higher pressure than atmospheric.
oil way means connected for receiving lubricating
The excess oil not required by the main pump will ?ll up
and sealing oil from said head box and for deliver
the whole of the recess 17 and eventually flow over its
ing such oil to moving parts of said vacuum pump;
rim and back into the main reservoir of the pump.
If during operation the main pump be stopped for
(e) valve means responsive to the delivery of oil from
any reason, the oil supply to the inner groove 18 will
said oil pump to said head box for controlling com
cease, while the vacuum of the main pump will cause
cunication between said head box and both said oil
the elastomer disc 20 to be forced down by atmospheric
way means and said main oil way, and closing com
pressure on to the outer groove 19, thus closing the way
munication between said head box and both said
for further oil and, consequently for any air to enter the
oil way means and said main oil way in the absence
main pump, provided the exhaust valve 28 of the main
of delivery of oil from said oil pump to said head box,
pump is of the sealing type. The return of the elastomer
and opening communication therebetween by the de
disc 20 to the closed position is accelerated by the spring
livery of oil at predetermined pressure from said
22. The oil remaining above the elastomer disc 20 after 50
oil pump to said head box.
closing, acts as sealing ?uid.
2. A device as de?ned in claim 1 wherein said head
If for any cause, such as the presence of foreign matter
box has a bottom wall, said oil way means comprises
such as dirt or grit or imperfection of the elastomer
an annular oil groove in said bottom wall, said main oil
valve disc 20, this should fail to seal completely, then
way enters said head box through said bottom wall in
the only oil to enter the pump will be the small quantity 55 inwardly spaced relation to said annular oil groove, and
contained in the recess 17 and as soon as this recess is
said valve means comprises a closure member which in
empty, air will enter the pump. The very small quantity
closed position interrupts communication between said
of oil from the recess will fall to the bottom of the pump
oil groove and said head box, between said oil groove
stator, and only air will get through to the system beyond
and said main oil way, and between said main oil way
the pump.
60 and said head box, and which is movable by the pressure
It is of course desirable that the outlet valve arrange
of oil being delivered through said main oil way to
ments be generally as illustrated diagrammatically, the
open such communication.
valve 28 being of the sealing type and surrounded by a
3. Vacuum pumping means as de?ned in claim 2 and
low wall 29 to form a chamber or the equivalent so that,
in the case of the valve failing to seal for any reason
only the small amount of oil contained in the chamber
at the level indicated by the line 30 will be sucked into
the pump. This small amount of oil will not be suf?cient
to ?ll up the pump and only air will get through to the
system beyond the pump.
In the alternative form of oil suck-back preventing 70
valve shown in FIGURE 3, a central recess 31 replaces
the groove 18 of FIGURES 1 and 2 and the disc 20 may
be free under a plate 32 which replaces the disc 21 of
FIGURES 1 and 2, or the disc 20 may be bonded,
clamped or otherwise secured to the plate 32. The func
which comprises resilient means yieldingly pressing said
closure member toward its closed position.
4. Vacuum pumping means as de?ned in claim 2
wherein said bottom wall is ?at and said main oil way
terminates in a recess in said bottom wall concentric
with said annular oil groove, and said closure member is
in the form of a flat sealing element which in closed posi
tion sealingly contacts said bottom wall in closing rela
tion to said annular groove and said concentric recess.
5. Vacuum pumping means as de?ned in claim 4 in
which said ?at sealing element is carried by a spring
loaded rigid plate.
References Cited in the ?le of this patent
6. Vacuum pumping means as de?ned in claim 4 in
which said closure member is annular, said concentric
recess is annular, and a supporting post is carried by said
bottom wall in concentrically spaced relation inwardly of
said annular recess and which passes through said an
nular closure member.
7. Vacuum pumping means as de?ned in claim 6 in
which said annular closure member comprises an an
nular sealing member and an annular rigid plate, said
annular scaling element extends inwardly of said an
nular rigid plate, and said supporting post comprises a
stop overlying and clamping the inner portions of said
sealing member to said bottom wall inwardly of said
annular recess.
10 2,285,426
8. Vacuum pumping means as de?ned in claim 7 in 15
which a coil spring surrounds and is supported by said
posts and bears against said rigid plate.
Wishart _____________ __ June 17,
Freeman ______________ __ June 9,
Reed ________________ __ Feb. 27,
Matricon ______________ __ Apr. 6,
Boyce ________________ __ Nov. 1,
Ziock ________________ __ J an. 29,
Machlet ______________ _.. Dec. 8,
Case ________________ _._ Feb. 5',
Cuthbert ____________ __ Aug. 14,
Money ______________ __ Nov. 29,
Stoltz ______________ __ Sept. 17,
Germany _____________ _._ June 9,
Great Britain __________ __ Oct. 23,
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