Rotary kinetic fluid motors or pumps – Smooth runner surface for working fluid frictional contact
Reexamination Certificate
2002-11-14
2004-06-22
Look, Edward K. (Department: 3745)
Rotary kinetic fluid motors or pumps
Smooth runner surface for working fluid frictional contact
C415S143000, C415S214100
Reexamination Certificate
active
06752588
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a vacuum pump, such as a turbo-molecular pump, which produce a vacuum by using the rotation of its rotor, used for a semiconductor manufacturing apparatus, an electron microscope, a surface analyzing apparatus, a mass spectroscope, a particle accelerator, a nuclear fusion experiment apparatus
2. Description of the Related Art
For example, a process such as dry etching process or chemical vapor deposition (CVD) of semiconductor manufacturing process is required to be performed in a vacuum environment, and a vacuum pump such as a turbo-molecular pump having a high-speed rotor is used to produce such a vacuum.
As a conventional vacuum pump, for example, it is disclosed in Japanese Utility Model Application No. Hei.4-52644 (Kokai-publication No.Hei.6-14491). In this type of vacuum pump, as shown in
FIG. 9
, a gas suction port
2
provided at the top portion of a pump case
1
is in communication with an exhaust port
21
of a vacuum chamber
200
. In this communication structure, a flange portion
1
a
provided around the top periphery of the pump case
1
is attached and fixed to the vacuum chamber
200
with a pump-chamber fastening bolt
30
.
More particularly, several pump fastening bolt-holes
22
are equally spaced and formed around the chamber exhaust port
21
of the vacuum chamber
200
, while the flange portion
1
a
of the vacuum pump
100
is formed so as to surround the gas suction port
2
and bolt-holes
3
are equally spaced and formed at the flange portion
1
so as to correspond to several pump fastening bolt-holes
22
. The pump-chamber fastening bolt
30
is inserted and screwed from the lower side of the flange portion
1
a
into the pump fastening bolt-holes
22
through each bolt-holes
3
, thereby attaching and fixing the vacuum chamber
200
to the vacuum pump
100
. The gap between the shank of each fastening bolt
30
and the inner wall of the corresponding fastening bolt-hole
3
is set in accordance with the normal standardized sizes of a bolt and a bolt-hole. For example, the bolt-hole
3
is formed to have a diameter of 11 mm for the shank of the bolt
30
having a diameter of 10 mm.
A base member
4
, which is separated from the pump case
1
, is provided at the lower side of the pump case
1
. Similarly to the connecting structure between the vacuum pump
100
and the vacuum chamber
200
, the connecting between the separated base member
4
and the pump case
1
are performed by that a flange shaped base fastening portion
1
b
formed at the bottom periphery of the pump case
1
is fastened and fixed to the separated base member
4
by bolts (not shown).
In the vacuum pump
100
attached and fixed to the vacuum chamber
200
, the rotor shaft
5
rotates at high speed together with the rotor
6
and the rotor blades
7
when the vacuum pump
100
is in operation. With this structure, the interaction between the rotor blades
7
rotating at high speed and the stator blades
8
and the other interaction between the rotor
6
rotating at high speed and the screw stator
10
having the screw grooves
10
a
cause gas molecules in the vacuum chamber
200
to pass through the gas suction port
2
and subsequently the pump case
1
, and to be eventually exhausted from the pump exhaust port
11
.
A light alloy is generally used and, in particular, an aluminum alloy is widely used as the structural material of the rotor
6
, the rotor blades
7
, the stator blades
5
and so forth which form the vacuum pump
100
, since the aluminum alloy is excellent in machining and can be precisely processed without difficulty. However, the hardness of aluminum alloy is relatively low as compared with other materials used for the structural material, and accordingly aluminum alloy may cause a creep fracture depending on the operating condition. Also, a brittle fracture may occur mainly caused by a stress concentration at the lower portion of the rotor
2
, when the vacuum pump is in operation.
In the conventional vacuum pump
100
having the above-described structure, when a brittle fracture occurs in the rotor
6
rotating at high-speed, for example, and a part of the rotor
6
crashes into the screw stator
10
, since the screw stator
10
has an insufficient strength against a shock load caused by this crash, the screw stator
10
cannot absorb such a shock load and therefore radially moves and crashes into a base member
4
. Accordingly, this shock load produces a high rotating torque (hereinafter, referred to as “damaging torque”) which causes the entire vacuum pump to rotate and which causes problems in that the entire pump case
1
is distorted, the fastening bolts
30
fastening the vacuum pump
100
to the vacuum chamber
200
are broken by this distortion torque, and the vacuum chamber
200
is broken by the large damaging torque transferred thereto.
SUMMARY OF THE INVENTION
The present invention is made to solve the above-described problems. Accordingly, it is an object of the present invention to provide a vacuum pump which reduces a damaging torque produced and prevent transferring of the damage torque to the outside when a rotor rotating at high-speed crashes into a screw stator or the like so as to prevents a vacuum chamber or the like from being broken by the damaging torque transferred to the vacuum chamber or the like.
A vacuum pump according to the present invention comprises: a rotor
6
; a pump case
1
surrounding the rotor; a flange portion
1
a
formed around the top periphery of the pump case; a plurality of pump fastening holes
22
provided at a periphery of an exhaust port
21
of a vacuum chamber
200
facing the upper surface of the flange portion; a plurality of vacuum chamber fastening bolt-holes
3
provided in the flange portion
1
a
so as to correspond to the pump fastening holes
22
, said vacuum chamber fastening bolt-holes being passed through with a pump-chamber fastening bolt
30
; a base fastening portion
1
b
formed around the bottom periphery of the pump case; a base
4
covering the lower side of rotor
6
and facing the lower surface of the base fastening portion
1
b
; a plurality of pump case-base member fastening holes
17
and
18
provided so as to correspond to the base fastening portion
1
b
and the base
4
, respectively; and a plurality of pump case-base member fastening bolts
19
for fastening the pump case
1
and the base
4
by inserting and screwing into the pump case-base member fastening holes
17
and
18
; wherein the dimensional relationships between the diameter of each bolt-hole and that of the shank of the corresponding bolt satisfy both or either one of the following conditions (a) and (b):
(a) a vacuum chamber fastening bolt-hole
3
has a larger diameter than the shank diameter
30
d
of the corresponding pump-chamber fastening bolt
30
by 20% or more; and
(b) a bolt-hole, which is either one of the pump case-base member fastening bolt-holes
17
and
18
provided in the base fastening portion
1
b
and the base
4
, has a larger diameter than the shank diameter
19
d
of the corresponding pump case-base member fastening bolt
19
by 20% or more.
A vacuum pump according to the present invention further comprises: a rotor
6
; a pump case
1
surrounding the rotor; a flange portion
1
a
formed around the top periphery of the pump case; a plurality of pump fastening holes
22
provided at a periphery of an exhaust port
21
of a vacuum chamber
200
facing the upper surface of the flange portion; a plurality of vacuum chamber fastening bolt-holes
3
provided in the flange portion so as to correspond to the pump fastening holes
22
, said vacuum chamber fastening bolt-holes being passed through with a pump-chamber fastening bolt
30
; a base fastening portion
1
b
formed around the bottom periphery of the pump case; and a plurality of pump case-base member fastening bolts
19
for fastening the pump case
1
and the base
4
by inserting and screwing into the pump case-base member fastening holes
17
and
18
,
Kawanishi Shinji
Maejima Yasushi
Okudera Satoshi
Sakaguchi Yoshiyuki
Adams & Wilks
BOC Edwards Technologies Limited
Look Edward K.
White Dwayne J.
LandOfFree
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