Rotary kinetic fluid motors or pumps – With separating means or guard for solid matter in working...
Reexamination Certificate
2000-09-15
2002-11-26
Look, Edward K. (Department: 3745)
Rotary kinetic fluid motors or pumps
With separating means or guard for solid matter in working...
C415S184000, C415S205000, C415S206000
Reexamination Certificate
active
06485257
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to the fluid pumping and filtration arts. It finds particular application in conjunction with a top-flow centrifugal fluid pump for use in pumping highly-corrosive fluids, such as used in a semi-conductor etching system, and will be described with particular reference thereto. However, it should be appreciated that the present invention may also find application in conjunction with other systems and applications where the pumping and/or filtration of fluids is performed.
FIG. 1
illustrates an exemplary impeller-type fluid pump and filtration unit A for a semi-conductor etching system. The pump and filtration unit is disclosed in commonly-owned U.S. Pat. No. 5,021,151, which is hereby incorporated by reference for all that it teaches.
Briefly, the pump and filtration unit A includes a housing
10
having a pump chamber
12
and a filter chamber
14
spaced apart from the pump chamber. The pump and filter chambers
12
,
14
communicate through an intermediate passageway or bore
16
. An inlet port
18
of the housing communicates with an inlet
20
of the pump chamber. An outlet port
22
of the housing communicates with an outlet
24
of the filter chamber. A centrifugal-type fluid pump within the housing
10
includes an impeller
26
positioned within the pump chamber
12
. A hollow impeller shaft sleeve
28
is secured to the impeller and extends through a bore
30
in the housing. A drive motor assembly
32
is secured to the housing by an adapter plate
34
. An output shaft
36
of the drive motor extends through the adapter plate
34
and impeller shaft sleeve
28
and is secured to the impeller
26
. A replaceable filter element
38
is located within the filter chamber
14
.
The impeller
26
is formed from a first section
40
and a second section
42
, each of which has a plurality of impeller vanes associated therewith. In particular, the impeller vanes
44
associated with first impeller section
40
draw fluid from the inlet port
20
to the pump chamber
12
in a direction toward the drive motor assembly
32
. The impeller vanes
46
associated with the second impeller section
42
move fluid more efficiently than the impeller vanes
44
associated with the first section
40
. As a result, a positive suction force is created by the impeller vanes
46
to prevent fluid from being pushed up into the bore
30
and potentially reaching the drive motor unit
32
.
In operation, the pump and filtration unit A is located in a tank or tub together with a weir basket that holds microelectronic circuits or chips. The tub contains a corrosive chemical solution or fluid (e.g. corrosive acid(s) heated to 160-180° C.) which overflows the top of the basket and engulfs the unit A, and which is intended to etch the microelectronic circuits or chips. When the pump and filtration unit A is energized, the corrosive fluid is drawn from the inlet port
16
to the pump chamber
12
by the impeller
26
. The impeller then pumps the fluid into the filtration chamber
14
and through the filter
38
before being discharged back into the tub at the outlet
22
. Notwithstanding the positive suction force generated by the second impeller section
42
, a seal assembly
48
(
FIG. 2
) such as a labyrinth seal assembly further prevents corrosive fluid from flowing between the shaft sleeve
38
and the adapter plate
34
to the drive motor assembly
32
.
It should be appreciated that the drive motor assembly provides a very efficient means of pumping fluids when coupled to the centrifugal-type pump. High rotational speeds of the centrifugal-type pump
26
can produce high fluid-flow rates at moderate outlet pressures. However, when the outlet pressure increases (such as when the filter
38
becomes at least partially blocked with particles generated by the etching process), the fluid flow drops off sharply beyond the design parameters of the pump. In the most extreme case when the pump is “dead headed” (i.e. outlet
22
and/or
24
is blocked completely), the pressure created by the first impeller section
40
can force the corrosive fluid up the bore
30
, past the seal assembly
48
, and into the drive motor assembly
32
. When pumping aggressive (i.e. highly-corrosive) fluids, this can result in the premature failure of the drive motor and/or the drive bearings.
Accordingly, it has been considered desirable to develop a new and improved top-flow centrifugal fluid pump for use in pumping corrosive fluids, which pump meets the above-stated needs and overcomes the foregoing difficulties and others while providing better and more advantageous results.
SUMMARY OF THE INVENTION
The present invention is directed to a fluid pump that is made from a high-purity fluroplastic material. The pump is used to circulate extremely corrosive fluids that are heated to temperatures of 160-180° C. through at least one filtration unit. The pump can be used in a semiconductor etching system. The pump utilizes the driven side of an impeller to generate a suction force that draws the corrosive fluid into a pumping chamber from at least one inlet port.
A pedestal support or shaft sleeve, through which a motor drive shaft extends, is modified to create an annular passageway that permits the corrosive fluid to enter the pumping chamber from the inlet. With the inlet design of the present invention, a drive motor seal assembly is no longer subjected to corrosive fluid because the seal assembly is positioned on the suction side of the impeller. In a “dead headed” condition the corrosive fluid flow stops completely as the fluid within the pumping chamber simply remains in shear.
Thus, in one aspect of the present invention a fluid pump is disclosed. The fluid pump includes a housing defining a pump chamber; a single fluid inlet communicating with the pump chamber; an impeller positioned within the pump chamber; and a drive shaft extending through the fluid inlet and coupled to the impeller.
In a second aspect of the present invention, a corrosive fluid pumping system including a tub adapted to hold a corrosive fluid and a fluid pump is disclosed. The fluid pump includes a housing defining a pump chamber; a single fluid inlet communicating with the pump chamber; an impeller positioned within the pump chamber; and a drive shaft extending through the fluid inlet and coupled to the impeller.
Accordingly, one advantage of the present invention is the provision of a fluid pump that prevents corrosive fluid from reaching a drive motor unit during a worst-case, “dead-headed” operating condition of the fluid pump.
Another advantage of the present invention is the provision of a fluid pump having at least one inlet port positioned intermediate a pumping chamber and a drive motor housing.
Yet another advantage of the present invention is the provision of a fluid pump having an impeller that draws fluid into a pumping chamber in a direction away from a drive motor housing.
Still further advantages of the present invention will become apparent to those of ordinary skill in the art upon reading and understanding the following detailed description of the preferred embodiments.
REFERENCES:
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patent: 2808782 (1957-10-01), Thompson et al.
patent: 3326134 (1967-06-01), Ohmann
patent: 4253798 (1981-03-01), Sugiura
patent: 4331458 (1982-05-01), Liljestrand
patent: 4349434 (1982-09-01), Jaworski
patent: 4373860 (1983-02-01), Sloan
patent: 4618425 (1986-10-01), Yates
patent: 4786230 (1988-11-01), Thut
patent: 4817561 (1989-04-01), Byrne et al.
patent: 4840535 (1989-06-01), Skarstad
patent: 5021151 (1991-06-01), Yane
patent: 5028211 (1991-07-01), Mordue et al.
patent: 5246336 (1993-09-01), Furukawa
patent: 5330328 (1994-07-01), Cooper
Base Howard J.
Olson Daniel J
Look Edward K.
Nguyen Ninh
Tom Richards, Inc.
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