Pumps – Motor driven – Electric or magnetic motor
Reexamination Certificate
1999-09-30
2002-10-29
Freay, Charles G. (Department: 3746)
Pumps
Motor driven
Electric or magnetic motor
C417S354000, C417S423140
Reexamination Certificate
active
06471494
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention is directed to a vacuum pumping apparatus.
2. Description of the Related Art
As a conventional vacuum pumping apparatus, a roots-type vacuum pumping apparatus is shown in FIG.
4
. This conventional roots-type vacuum pumping apparatus includes a pair of intermeshed rotors
21
a
and
21
b
which rotate with a fixed phase difference maintained therebetween. When the rotors rotate, a gas is sucked into an inlet port (not shown) and is discharged from an outlet port (not shown) to create a vacuum. The rotors
21
a
and
21
b
are fixedly mounted on a driving shaft
29
and a driven shaft
30
, respectively. The output shaft of a driving motor
24
is connected to a synchronizing gear
22
a
which is in meshing engagement with another synchronizing gear
22
b.
The synchronizing gear
22
b
is also in meshing engagement with a third synchronizing gear
22
c.
The synchronizing gear
22
b
is mounted to one end portion of the driving shaft
29
, while the synchronizing gear
22
c
is mounted to one end portion of the driven shaft
30
. Thus the driving force of the motor
24
is transmitted to the rotor
21
a
by way of the synchronizing gears
22
a,
the synchronizing gear
22
b
meshed therewith and the driving shaft
29
coupled thereto, thereby rotating the rotor
21
a.
Concurrently, the driving force transmitted to the synchronizing gear
22
b
is also fed to the rotor
21
b
by way of the synchronizing gear
22
c
meshed with the synchronizing gear
22
b
and the driven shaft
30
, thereby rotating the rotor
21
b.
Due to the fact that the synchronizing gear
22
b
and the synchronizing gear
22
c
are meshed with each other, the rotor
21
a
is brought into synchronization with the rotor
21
b,
thereby establishing concurrent rotations of the rotors
21
a
and
22
b
with a fixed phase difference kept therebetween.
A lower portion of the synchronizing gear
22
c
is in a lubricating oil bath
25
, and the lubricating oil
25
adhered to the synchronizing gear
22
c
is applied to the synchronizing gears
22
b
and
22
a
while the synchronizing gears
22
a,
22
b
and
22
c
are in concurrent rotation, which ensures lubricating and cooling of the synchronizing gears
22
a,
22
b
and
22
c.
In addition, for preventing the lubrication oil
25
from entering the pump housing
26
, an oil seal member
28
is provided between the rotor
21
a
and the synchronizing gear
22
b,
and between the rotor
21
b
and the synchronizing gear
22
c.
A mechanical seal mechanism
23
is also placed between the motor
24
and gear chamber
27
, and the driving force transmitting path passes through the seal mechanism
23
. While the synchronizing gears
22
a,
22
b
and
22
c
are in rotation, the gear chamber
27
accommodating the synchronizing gears
22
a,
22
b
and
22
c
is in fluid communication with the interior of the housing
26
for the rotors
21
a
and
22
b.
As a result, both the housing
26
and the gear chamber
27
are at the low vacuum pressure. On the other hand, the motor
24
and its related portions are at atmospheric pressure. Thus, the mechanical seal mechanism
23
must prevent the atmospheric pressure from leaking into the gear chamber
27
and the housing
26
.
In detail, the mechanical seal mechanism
23
includes a rubber member through which the output shaft of the motor
24
passes and an oil film extending between the rubber member and the output shaft of the motor
24
. This means that the oil establishes a boundary lubrication condition between the rubber member and the output shaft of the motor
24
, and the boundary lubrication condition assures the foregoing sealing function.
However, the mechanical seal mechanism
23
is relatively high in production cost. In addition, a small amount of gas leakage is inevitable in the mechanical seal mechanism
23
, which results in air or atmospheric pressure leaking into the chamber
27
and the housing
26
in which the rotors
21
a
and
21
b
are accommodated, thereby lowering the vacuum producing ability of the vacuum pumping apparatus.
Japanese Patent Laid-open Publication No. Hei. 4 (1992)-31690 also discloses a vacuum pumping apparatus which is s similar to the above-described apparatus in concept, but is different therefrom in the number of synchronizing gears.
SUMMARY OF THE INVENTION
It is therefore a principal object of the present invention to provide a vacuum pumping apparatus without the foregoing drawbacks.
In order to attain the above and other objects, a vacuum pumping apparatus such as a pulse tube refrigerator includes a pump part including a pump housing, a pair of intermeshed rotors inside the pump housing, a pair of synchronizing gears for maintaining a phase difference between the rotors at a fixed value, the synchronizing gears meshed with each other and lubricated by oil, and an oil seal member preventing entry of the oil into the pump housing; and a motor part which is in the form of a sealed structure and is connected to the pump part in fluid-tight manner.
REFERENCES:
patent: 3192861 (1965-07-01), Haegh
patent: 4050855 (1977-09-01), Sakami et al.
patent: 4272224 (1981-06-01), Kabele
patent: 5190438 (1993-03-01), Taniyama et al.
patent: 5267842 (1993-12-01), Harmsen et al.
patent: 5393201 (1995-02-01), Okutani et al.
patent: 5577883 (1996-11-01), Schultz et al.
patent: 5616973 (1997-04-01), Khazanov et al.
patent: 5650676 (1997-07-01), Blumenberg
patent: 5954489 (1999-09-01), Kinoshita
patent: 6123516 (2000-09-01), Burghard et al.
patent: 6235074 (2001-05-01), Murano et al.
Furuhashi Toyoki
Miura Atsuyuki
Naito Yoshihiro
Nakayama Koichi
Aisin Seiki Kabushiki Kaisha
Freay Charles G.
Gray Michael K.
Oblon & Spivak, McClelland, Maier & Neustadt P.C.
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