Rotary kinetic fluid motors or pumps – With lubricating – sealing – packing or bearing means having... – For shaft sealing – packing – lubricating or bearing means
Reexamination Certificate
1999-09-09
2001-11-20
Look, Edward K. (Department: 3745)
Rotary kinetic fluid motors or pumps
With lubricating, sealing, packing or bearing means having...
For shaft sealing, packing, lubricating or bearing means
C415S175000, C415S230000
Reexamination Certificate
active
06318959
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a multi-stage rotary vacuum pump used for high-temperature gas, and is applicable to a vacuum pump handling gas at, for instance, about 150° C. to 250° C.
2. Description of the Related Arts
Where high temperature gas is sucked by a vacuum pump, a method for cooling the gas by cooling water applied outside a housing of the pump or rotors of the pump, a method for cooling the gas by a gas cooler located immediately before the inlet of the pump, or the like have been used. Since the heat of the high-temperature gas inside the housing is transferred through the shaft supporting the rotor to heat the bearings to a temperature higher than an allowable temperature, cooling from outside of a vacuum pump causes the following serious problems in using the vacuum pump. Since coolant water is to be supplied to a rotating rotor, the cooling of the gas by the coolant inside the rotating rotor must overcome structural problems. Since the gas may be solidified at a temperature lower than the solidification temperature, determined by the pressure and the temperature of the gas, in the cooling of the gas immediately before entering to the vacuum pump, it is required to design and construct a vacuum pump to overcome this problem of solidification.
A vacuum pump with first, second, and third pump sections as an example of a multi-stage vacuum pump cooled peripherally from outside is shown in FIG.
13
. The XIV—XIV cross-section thereof is shown in
FIG. 14
, and the XV—XV cross-section thereof is shown in FIG.
15
. The structure of the vacuum pump of
FIG. 13
is as follows. The first pump section and the second pump section are separated by the wall
1
, the second pump section and the third pump section are separated by the wall
2
as shown in FIG.
13
. The first shaft
3
and the second shaft
4
penetrate each pump section, are supported by two bearing mechanisms
5
, and are arranged to rotate in opposite directions by the timing gear set
6
. The passage for the flow of the coolant water
7
is formed in the periphery of the housing. The first shaft, which penetrates to the outside, can be driven by an electric motor.
The suction gas G
51
of the vacuum pump is sucked as a suction gas through the suction inlet
8
of the vacuum pump and the suction inlet
9
of the first section, and is transferred by the action of the rotors
10
A and
10
B. The exhaust gas G
52
cooled by the coolant water in the periphery of the housing is led to the next stage through the communication path
11
. These operations are repeated in each of the stages, and the gas is finally exhausted from the exhaust outlet
12
of the vacuum pump.
The cover
60
for the gear side is shown in FIG.
14
. The input and output of the cooling water are indicated by symbol C in FIG.
15
. the journal joint
13
, the rotors
10
A and
10
B, the first axis
15
, the second axis
16
, the discharge openings
17
and
18
of the cooling water, and the flow C of the cooling water are shown in FIG.
16
.
In this vacuum pump, the gas which is transferred and compressed by rotors in the housing is heated due to the heat of compression. A part of the heat is removed by the cooling by the coolant water
7
in the periphery of the housing. However, since the rotor is not cooled, the heat of the high temperature gas in the housing is transmitted through the shafts
3
and
4
which support the rotors to cause a problem in that the bearings are heated to a temperature higher than the allowable temperature.
In a method to solve this problem a gas cooling device is arranged immediately before the suction inlet to supply cooled gas through the suction inlet. The gas, however, is often solidified when the temperature of the gas becomes lower than the solidification temperature (which is determined by the pressure and temperature of the gas).
SUMMARY OF THE INVENTION
It is a primary object of the present invention, in view of the problems in the prior arts, to propose an improved rotary type multi-stage vacuum pump in which a high temperature gas is safely handled without cooling the gas.
According to the present invention, there is provided a multiple-stage rotary type vacuum pump, comprising: a housing with a plurality of pump sections having operable shafts and synchronously driven rotors supported by bearings mounted relative thereto, mechanical seals with supporting bodies arranged relative to the housing to be adjacent to said bearings, and an oil system providing oil to said mechanical seals and said bearings to lubricate and cool said bearings.
There is also provided a multiple-stage rotary type vacuum pump having a pump housing with a plurality of pump sections in which there are provided shafts supported by bearings, a rotor in each pump section fixed to each shaft with said shafts and rotors being arranged to be synchronously driven, and oil vessels for reserving lubrication oil, said pump housing having a suction inlet and an exhaust outlet and a communication path so that one pump section is in communication with the next pump section so that gas compressed in said one pump section passes through the communication path into the next pump section to cause the gas to be successively compressed in the plurality of pump sections, said vacuum pump comprising: mechanical seals with supporting bodies arranged relative to the pump housing to be adjacent to said bearings, an oil pump for providing lubricating oil to said supporting bodies for said mechanical seals and said bearings so that the lubricating oil is returned to said oil vessels, said vacuum pump having an oil supply piping system between said oil pump and the supporting bodies and a return oil piping system between said oil vessels and said oil pump, wherein said lubricating oil lubricates said bearings and also keeps them cool relative to said pump sections.
In general, the housing of the first stage of a vacuum pump is in the state of high vacuum, and that of the third stage is in the state of nearly atmospheric pressure. The oil vessel of the gear side and the oil vessel of the driving side have different pressures, and therefore, if these vessels are made in communication with each other, the lubrication oil in the oil vessel of the driving side cannot flow into the oil vessel of the gear side, since the oil tends to flow from the oil vessel of high pressure to that of low pressure.
In the vacuum pump according to the present invention, it is possible to arrange a mechanical seal in the housing side of the bearing, to seal the pressure, to cause both the oil vessels to communicate with the atmospheric pressure, to equalize the inner pressures, and to arrange a return oil piping to cause both oil vessels to communicate with each other. By equalizing the pressures of both oil vessels, it is possible to prevent the existence of a thrust load in the shaft, to facilitate the fixing of the shaft, and to extend the life of the bearing.
REFERENCES:
patent: 2937807 (1960-05-01), Lorenz
patent: 4173440 (1979-11-01), Libis
patent: 4394113 (1983-07-01), Bammert
patent: 5364245 (1994-11-01), Kriehn et al.
patent: 5727936 (1998-03-01), Eriksson et al.
patent: 6045343 (2000-04-01), Liou
patent: 194 825 A (1937-12-01), None
patent: 10 21 530 B (1957-12-01), None
patent: 0 476 631 A1 (1992-03-01), None
patent: 0 814 267 A1 (1997-12-01), None
patent: 3-89080 (1991-04-01), None
patent: 5-71487 (1993-03-01), None
patent: 6-101674 (1994-04-01), None
Look Edward K.
McAleenan James M
Merchant & Gould P.C.
Unozawa-Gumi Iron Works, Ltd.
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