Bearings – Rotary bearing – Antifriction bearing
Reexamination Certificate
2002-03-12
2003-09-30
Footland, Lenard A (Department: 3682)
Bearings
Rotary bearing
Antifriction bearing
C384S446000, C384S448000, C384S624000
Reexamination Certificate
active
06626578
ABSTRACT:
The present invention relates to a rotary pump for liquid and more particularly to a rotary pump of the immersed rotor type with a bearing wear indicator.
INCORPORATION BY REFERENCE
The present invention is particularly applicable to a liquid rotary pump where the liquid immerses the motor rotor that is isolated from the motor stator by a seal often referred to as a can or jacket. This type of speciality pump has been manufactured for many years and includes a shaft for rotatably mounting the rotor of the motor element of the pump. To center the rotor in the pump housing, it has proven quite beneficial to use a mechanism having axially spaced conical bearings. Such pump and bearings are disclosed in Young U.S. Pat. No. 3,195,466. Conical shaft bearings not only center the rotor and maintain the axial position of the pump impeller, but also provides the friction bearing surfaces between the pump housing and rotating elements within the pump. Young U.S. Pat. No. 3,195,466 is incorporated by reference as background information so that the details of the particular pump and bearings to which the present invention is directed need not be repeated by merely describing known pump technology. Through the years, patents have issued directed toward certain mechanical changes in an immersed rotor type of liquid pump. Two of these patents are Spisiak U.S. Pat. No. 3,225,698 and Neal U.S. Pat. No. 3,433,164. These patents are also incorporated by reference herein as background pump technology that need not be repeated in describing and understanding of the present invention. Recently, anew design for an immersed rotor rotary pump was the subject of Brunet U.S. Pat. No. 6,350,109. This patent replaces the conical bearings with a combination of radial and thrust or axial magnetic bearings whereby the immersed rotor essentially levitates as it rotates. This is a drastic departure from the simple conical bearing construction used over the years and requires substantial electromagnetic controls to maintain the levitation gaps. However, this patent does teach a pump of the type to which the present invention is directed and is incorporated by reference herein as background information and for again showing pump components not involved in the present invention. The rotary pump to which the present invention is directed is an improvement or modification of an existing pump sold by Buffalo Pumps of North Tonawanda, N.Y. The interior design of the preferred embodiment is the same as the pumps marketed by Buffalo Pumps for some years. This well known design is disclosed in Bulletins 929A and 985 which are incorporated by reference herein as background information that shows how the pump to which the present invention is directed complies with the background technology of the patents heretofore incorporated by reference. These bulletins also disclose the fluid thrust balancing mechanism used in some of the immersed rotor pumps, but this feature does not constitute a part of the present invention. All this material is disclosed to show the concept of a pump to which the present invention is directed and use of axially spaced conical bearings for supporting the immersed rotor of such pump.
BACKGROUND OF INVENTION
The immersed rotor type of rotary pump which has proven to be the most successful through the years includes axially spaced conical bearings. The conical bearings have a journal element that is self lubricating carbon graphite with an internal taper and mounted for axial movement in the pump housing. The internal taper or conical bearing surface of the journal matches the taper or conical bearing surface of an element supported on the shaft of the immersed motor rotor. In this type of pump, stainless steel coil springs in the journal recess of the pump housing force the axially movable bearing elements or journals toward the fixed, matching elements on the rotor shaft. Thus, from both ends of the rotor a coil spring biases the two journal elements of the spaced conical bearings into engagement with the shaft elements to provide a bearing force that maintains the radial position of the rotating rotor. In addition, the conical bearings have a force component that maintains the axial position of the rotor within the pump housing. Consequently, the conical bearings which have been used for decades are quite successful and constitutes an inexpensive mechanism to maintain self-centering of the rotor for control of both the radial and axial positions of the rotating components of the rotary pump. During normal bearing wear, the conical bearings maintain the radial position of the rotating components of the pump. In addition, one of the beneficial features of using conical bearings is that the bearings have a self-centering ability in a axial direction based upon the liquid pressure around the rotor. The thrust balancing feature uses the pressure differential between the front of the rotor and the back of the rotor so that the hydraulic forces move the conical bearings slightly to center the rotor. This balancing is accommodated by spring biased conical bearings.
The conical bearings that are spring biased have an initial axial position after thrust balance, which position should be maintained over long term use of the pump. When the conical bearings have reached approximately ⅛ inch of wear, it is desirable to replace or repair the journals of the pump to maintain trouble free operation. Wear of the conical bearings is normally discovered during regular inspection involving disassembly of the pump. However, it is desirable to know the extent of bearing wear for the purpose of tending to proper preventive maintenance. At this time, rotary pumps of the immersed rotor type are subject to periodic maintenance or inspection. The time between such inspections must be quite short to assure that maintenance is performed before the pump fails due to bearing wear. Catastrophic bearing failure must be avoided. Bearing wear can be accelerated by the type of liquid being pumped or contaminants. Consequently, it is preferred practice to inspect the conical bearings long before they need to be refurbished to assure long term operation of the pump. These factors make maintenance of the conical bearings a relatively costly and time consuming activity.
THE INVENTION
The present invention relates to the concept of monitoring wear of the conical bearings to determine when they should be replaced and/or refurbished. Consequently, frequent inspection of the bearings is not necessary. Bearings are given attention only when actually needed. This is a substantial advantage, is cost effective and prevents catastrophic failure based upon bearing malfunction. In the past, such failure could occur between even short term inspections. The invention involves an improvement in a rotary pump of the type described and incorporated by reference herein. Real time monitoring of conical bearing wear is the result of using the invention. A wear monitoring device using a magnetic mechanism is associated with each of the axially spaced conical bearings. A simple base line position is set during initial installation or start-up of the rotary pump. This base line compensates for assembly tolerances associated with bearing spacing. After initial set-up, the monitoring device is periodically inspected to reveal when the conical bearings need to be inspected or replaced. The magnetic device is installed on the motor housing at a position dictated by the location of the conical bearings. A magnet is implanted in each spring biased, axially movable journal of the pair of conical bearings. During operation of the pump, the conical bearings and the rotor assembly move axially to maintain the hydraulic thrust balance as previously described. In this instance, the magnets on the bearings move in the same direction and retain a balanced condition. As the conical bearings wear, the magnets in the bearing journals move toward each other as the journals move toward each other. The actual positions of the journal magnets are monitored by using the p
Goodnick Douglas J.
Leslie Martin G.
Reasinger Joseph D.
Buffalo Pumps, Inc.
Footland Lenard A
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