Pumps – Motor driven – Including means utilizing pump fluid for augmenting cooling,...
Reexamination Certificate
2000-06-07
2001-10-30
Freay, Charles G. (Department: 3746)
Pumps
Motor driven
Including means utilizing pump fluid for augmenting cooling,...
C417S423120, C310S087000
Reexamination Certificate
active
06309188
ABSTRACT:
This application is related to my two earlier U.S. Pat. Nos. 5,586,862 and 5,967,744, the complete disclosures of which are hereby incorporated herein by reference.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to centrifugal pumps. More particularly, the invention relates to a centrifugal pump having ceramic bearings, ceramic thrust washers, and a water cooling channel.
2. State of the Art
Centrifugal pumps utilize an impeller housed in a volute. Fluid enters the volute either axially, radially, or tangentially relative to the impeller and exits either axially, radially, or tangentially depending on the direction of impeller rotation. Centrifugal pumps may be driven by an AC motor or a DC motor. In either case, the pump impeller may be magnetically coupled to the rotor of the motor so that the workings of the motor can be hermetically sealed and isolated from the fluids passing through the pump.
Prior art
FIG. 1
illustrate a typical AC motor driven volute pump
10
. The pump
10
includes an AC motor
12
, a pump volute
14
and an impeller shaft
16
which is coupled to an impeller
18
having a plurality of radial vanes or fins
20
. The pump volute
14
is symmetrical about a vertical axis with an axial inlet port
22
and a radial outlet port
24
. The impeller
18
is arranged axially with the inlet port
22
. Fluid entering the inlet port
22
is free to flow around the impeller
18
and into the spaces between the vanes
20
. Regardless of the direction of rotation of the impeller hub
18
and vanes
20
, the vanes will create a centripetal force resulting in a low pressure condition at the impeller
18
. This low pressure condition will draw fluid into the volute
14
via the inlet port
22
. The fluid will enter the spaces between the vanes
20
whereupon it will be driven radially outward from the volute
14
in either a clockwise or counterclockwise flow.
In a magnetic drive type centrifugal pump, the impeller shaft
16
has permanent magnets embedded in it which are acted upon by alternating magnetic fields inside the motor
12
to cause the shaft to rotate. The shaft
16
must be rotatably supported by two bearing surfaces
16
a
,
16
b
at opposite ends of the shaft. These bearing surfaces must be very low friction and must also be resistant to abrasion caused by gritty substances contained in the fluid being pumped. The exact design and construction of such bearing surfaces have been the subject of much research and many complicated and expensive designs have been proposed. In particular, ceramic bearing surfaces have been proposed for radial and thrust surfaces. Ceramics are difficult to mold or machine into complex shapes and need to be kept cool especially if they are mounted in a material having a relatively low melting point such as a thermoplastic. These issues are further complicated by the need for both radial and thrust bearings in centrifugal pumps.
SUMMARY OF THE INVENTION
It is therefore an object of the invention to provide a ceramic bearing system for a centrifugal pump.
It is also an object of the invention to provide both radial and thrust ceramic bearings for a centrifugal pump.
It is another object of the invention to provide a ceramic bearing system for a centrifugal pump which is easy and inexpensive to manufacture.
It is still another object of the invention to provide a ceramic bearing system which is easy to incorporate into a centrifugal pump.
It is another object of the invention to provide a ceramic bearing system which is easy to incorporate into a centrifugal pump having thermoplastic components.
It is still another object of the invention to provide a centrifugal pump having ceramic bearings mounted in thermoplastic materials and cooling channel.
In accord with these objects which will be discussed in detail below, the ceramic bearing system of the present invention include two substantially identical circular ceramic shafts, two substantially identical non-circular ceramic washers and two substantially identical non-circular ceramic bearing members. The centrifugal pump incorporating the bearing system includes an impeller shaft having one of the circular ceramic shafts mounted in each end and a non-circular recess in a rear end thereof for receiving one of the non-circular ceramic washers. The impeller is provided with a non-circular recess in a front end thereof for receiving the other non-circular ceramic washer. One of the non-circular ceramic bearing members is mounted in a non-circular hole or recess in the pump volute and the other non-circular ceramic bearing member is mounted in a non-circular hole or recess in the rear of the motor. When assembled, the circular ceramic shafts are rotatably mounted in the respective non-circular ceramic bearing members and the non-circular ceramic washers act as thrust bearings between the impeller and the bearing in the volute and between the impeller shaft and the bearing in the motor. According to the presently preferred embodiment, a fluid channel is provided along the length and around the back of the impeller shaft such that fluid being pumped by the pump circulates around the shaft and the bearings thereby cooling the assembly.
Additional objects and advantages of the invention will become apparent to those skilled in the art upon reference to the detailed description taken in conjunction with the provided figures.
REFERENCES:
patent: 1680775 (1928-08-01), Faber
patent: 4516915 (1985-05-01), Jensen et al.
patent: 4653977 (1987-03-01), Fries
patent: 4728260 (1988-03-01), Ishii
patent: 4778000 (1988-10-01), Maas
patent: 4874298 (1989-10-01), Mainardi et al.
patent: 5302091 (1994-04-01), Horiuchi
patent: 5580216 (1996-12-01), Munsch
patent: 5586862 (1996-12-01), Danner
patent: 5957656 (1999-09-01), De Long
patent: 5967744 (1999-10-01), Danner
patent: 5997264 (1999-12-01), Klein et al.
patent: 138666 (1901-10-01), None
patent: 1088813 (1958-11-01), None
patent: 2199080 (1987-12-01), None
Freay Charles G.
Galgano & Burke
Gray Michael K.
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