US3542494A - Canned motor pump - Google Patents

Description

Unite States Patent 114,111, 202; 308/1; l84/lc, lb; 253/59B;73/9, 86;417/321 Primary ExaminerR0bert M, Walker Attorney Blum, Moscovitz, Friedman, IBlum & Kaplan ABSTRACT: A canned motor pump in which bearing means carry a rotating shaft for an impeller and a rotor. Should the bearing means become worn beyond permissible limits due to thrust and radial loads exerted on the shaft, the impeller and rotor could make contact with the pump housing and stator can, thereby damaging the pump and motor. There is provided a bearing wear checking device in which a pressure gauge has a pipe filled with an inert gas with the pipe being fitted closely to the pump housing in such manner that the tip of the pipe is arranged at a spacing with the moving parts so as to register the wear limit before the parts can be irrevocably damaged.

Patented Nov. 24, 1970 v 3,542,494

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2 MW INVENTOR dM/ 04 5 ATTORNEY Patented Nov. 24, 1970 i 3,542,494

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ATTORNEY Patented Ndv. 24, 1970 Sheet 258 I28 I27 I26 5% INVENTOR ATTORNEY Patented Nov. 24, 1970 Sheet 4- or 4 C? W4; j; INVENTOR LAM/0 M BY 4 I ATTORNEY CANNED MOTOR PUMP BACKGROUND OF THE INVENTION impeller and rotor are mounted on a shaft. Rotational movement of the shaft causes thrust and radial loads to be applied to the bearings. Should the loads become unbalanced or change in response to variations in operation or the character of liquid being pumped, unbalanced loads will be imposed on the bearings and bearing wear will occur. Due to the'construction of a canned motor pump,'it is difficult to check the extent of bearing wear after the pump has been installed.

In pumps of this type, anti-corrosion metal foils enclose the rotor and stator in a fluid-tight manner with the foil being referred to as the can. It is desirable that the spacing 20 between the cans be as narrow as possible for motor efficiency while the can foil should be of minimal thickness for improved radiation. Accordingly, when the bearings become worn beyond the permissible limits in the radial direction, the stator can will make contact with the rotor can and one or both of 5 the cans will become damaged. This would permit the liquid being pumped to leak into the motor, damage the motor and leak out of the motor. This may not only lead to damage of the pump beyond repair, but may also create a hazardous condition, depending on the liquid being pumped.

If the bearings become worn beyond permissible limits in the thrust direction, damage to the impeller or other parts of the unit may occur.

Also, the liquid being pumped generally acts to lubricate the bearings and if the bearings become worn due to a thrust load, 35

the channels for the lubricating liquid may also be worn away thereby reducing lubrication and increasing bearing wear.

SUMMARY OF THE INVENTION Generally speaking, in accordance with the invention, means are provided to check or monitor bearing wear in order to signal the need for replacing the bearing before it becomes worn beyond permissible limits and damages the motor pump.

One or more pressure gauges are provided for monitoring a 45 change in state with each gauge having a pipe filled with an inert fluid with the tip of the pipe so located that, as wear approaches the permissible limit, the tip of the pipe will be ruptured to cause a change in pressure in the pipe to thereby provide a signal that the'pressure change has occurred.

Accordingly, it is an object of this invention to provide improved means for monitoring bearing wear in a canned motor pump.

Another object of the invention is to provide an improved canned motor pump with a plurality of pressure gauges for indicating a pressure change as bearingwear approaches permissible limits.

Still other object and advantages of the invention will in part be obvious and will in part be apparent from the specification.

The invention accordingly comprises the features of con- 60 struction, combination of elements, and arrangement of parts which will be exemplified in the constructions hereinafter set forth, and the scope of the invention will be indicated in the claims.

BRIEF DESCRIPTION OF THE DRAWINGS For a fuller understanding of the invention, reference is had to the following description taken in connection with the accompanying drawings, in which:

FIG. I is a front elevational view, partly in section. showing 70 FIG. 3 is a view similar to FIG. 2 showing an alternate construction of the bearing monitoring device:

FIGS. 4a and 4b are diagrammatic views illustrating additional variations of the bearing wear monitoring device;

FIG. 5 is a partial sectional view showing a further embodiment ofa bearing wear monitoring device; and

FIGS. 6 and 7 are circuit diagrams of alarm and control systems adapted to be operated by the bearing wear monitoring device.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring-now to F IG. 1, a partial sectional view of a canned motor pump is disclosed therein. A fluid medium is supplied into pump casing 11 through inlet port 12 and is discharged through outlet port 18 by the action of impeller 13. A portion of the fluid medium from outlet port 14 is delivered by a pipe 15 to therear section in of the rotor chamber. The fluid medium entering into rear section to passes through suitable channels provided on the inner and outer peripheral surfaces of rear bearing 17 to lubricate the rear bearing. The lubricating fluid subsequently flows through a gap 18 between the rotor and stator to cool the motor and the fluid returns to pump casing lll through inner and outer peripheral surfaces of the front bearing 19, to lubricate the front bearing, and annular clearance 20 between the casing and the impeller shaft and the balancing holes 21 in the impeller. The front and rear v bearings are carried by front bearing housing 22 and rear bearing housing 23, respectively. Impeller shaft 25 is rotatably mounted in the front and rear bearings and has the impeller 113 connected thereto. Rotor 24 is also carried by shaft 25.

Thrust washers 26 are located on opposite sides of rotor 24- to axially locate the rotor and shaft. A rotor can 27 formed of nonmagnetic, anti-corrosion metal foil tightly covers the outside of the rotor to provide an air tight can for the rotor and a stator can 28 formed of nonmagnetic and anti-corrosion metal foil is mounted in the motor casing for providing an air tight seal along the inner surface of stator 29.

A plurality of pressure gauges 50 are carried by the casing or housing proximate to impeller 13 and shaft 25. Portions of the pressure gauges extend into rotor chamber 30 and impeller chamber 3i to check bearing wear caused by thrust and radial loads and the locations of the pressure gauges are shown by way ofillustration.

For example, pressure gauges A, S DB and 50C check bearing wear resulting from thrust loads while pressure gauges 50D and 50E check bearing wear caused by radial loads. The surfaces'of the impeller and shaft proximate to the various 0 pressure gauges will be considered to be an opposed member" in the description below.

Referring now to FIG. 2, a pressure gauge 50 includes an indicator 51, an operator 52 and a support 53, the support being connected, as appropriate, to the motor pump casing or housing.

Operator 52 is in a form of a resilient pipe 54 which is filled with an inert fluid under pressure higher than the pressure that will be encountered as fluid is' pumped by the motor pump.

Resilient pipe 54- is sealedat its lower end and the pipe extends through the housing wall or casing toward the opposed member to be monitored. A suitable spacing is provided between the extremity of pipe 54 and opposed member 60 as will now be described. In the canned motor pump, it is preferred that the gap provided between the rotor can and the stator can can gap) is as narrow as possible for motor efficiency while the cans are as thin as possible to obtain improved radiation. It is also preferred that the gap between the impeller and its housing (impeller gap) be as small as possible to aid in thrust balancing. With small gaps. there is danger that bearing wear can exceed permissible limits to allow the impeller or rotor can to make contact with stationary parts of the motor pump to cause damage thereto.

With pressure gauge 50, when the bearings reach the permissible limit of wear, the'outer most end of pipe 54 will be engaged by opposed member 60 to tear away the outer most end of the pipe'and release the inert gas sealed therein under pressure. Due to a change in pressure, the pipe will deform and indicator 51 will give a warning that the permissible wear limit has been exceeded.

Pressure gauges 50 can be manufactured at moderate cost since they need not accurately record the pressure in pipe 54. It is only necessary that the indicator show that a change in pressure has occurred.

A visible indicator 51 may take the form of an instrument in which a pointer and graduated scale or dial are combined in the conventional manner of pressure gauges or a plate 56 responsive to the pressure may be provided which moves to show a change in condition through a window 55. For example, a portion 57 of the plate may be red in color to show a red condition through the window when the limit of wear has been exceeded and suitable instructions 58 may appear on the face of indicator 51.

The distance 2 between the inner surface of the tip of pipe 54 and opposed member 60 must be at least as great as the permissible wear limit but must be smaller than the can gap or impeller gap so that the end will be torn away and the pipe opened before bearing wear reaches the limit of the can gap or impeller gap.

The surface of opposed member 60 may be provided with notches 61 for tearing the end of resilient pipe 54 when contact is made therewith.

A modified form of pressure gauge is shown in FIG. 3 wherein like elements are indicated by like numerals with prime notations. The primary difference between the FIG. 3 and FIG. 2 embodiments is that the lower most end of pipe 54 is pointed or cone shaped in order that it may be torn off more easily when the limit of wear is exceeded.

The pressure gauges shown, in FIGS. 2 and 3 are designed to check bearing wear at a fixed location. However, since the bearings may wear unevenly it may be desirable to monitor bearing wear along a greater area. For example, pressure gauge 150 shown in FlG.'4a has the resilient pipe formed as a ring-shaped end 159 lying in a plane at right angles to the axis of pipe 154. The ring-shaped end 159 would be arranged adjacent a side of the impeller along the circumference to check bearing wear in the thrust or axial direction.

As shown in FIG. 4b a ring-shaped end 159' is formed in the same plane as pipe 154' and would surround the peripheral surface of the shaft to monitor bearing wear in the radial direction. Thus, regardless of the orientation of bearing wear and the movement of the shaft due to such wear, opposed member 60, when striking the ring-shaped ends would rupture or tear a portion of such ends to cause a pressure change within the resilient pipe. I

Referring now to FIG. 5, the pressure gauge shown therein is capable of monitoring wear in both the thrust and radial directions. The bearing housing is indicated at 123 and the shaft at 125. A sleeve 126 is fitted over the shaft with a washer 127 and a lock nut 128 being carried by the end of the shaft. The end of the shaft is provided with a counterbore 160. Pressure gauge 250 includes an indicator 251, an operator 252 and a support 253 for connecting the pressure gauge to the housing. A cylindrical end portion 254 on operator 252 extends into the counterbore with the end portion being provided with projections 255 extending therefrom in an axial direction toward bottom wall 256 of the counterbore. The end portion is also provided with a flange 257 extending in a radial direction toward the cylindrical surface 258 of the counterbore to check bearing wear in the radial direction. The spacing of projections 255 and flange 258 will be determined by the can gap and impeller gap so that the end will be torn by radial or axial movement of the shaft when the bearing wear limit has been exceeded.

An alarm system may be provided for audibly signaling a change in pressure in a pressure gauge. A suitable circuit is shown in FIG. 9 wherein a power source 64 is applied across the primary windings of a transformer 63 through a fuse 62.

The secondary windings are serially connected to a relay 65 and a switch 50 controlled in any suitable manner by a change in pressure of the pressure gauge. On closing of switch 56, relay 65 operates to close a switch 66 in the primary circuit which actuates a relay 67 to close a switch 68 which thereupon connects an alarm device 69 into the circuit.

The canned pump motor may also be controlled by the pressure gauge by means of a suitable circuit such as is shown in FIG. 7. The circuit of FIG. 7 is substantially the same as the circuit of FIG. 6 except that a parallel path including a switch 70 and an electromagnetic switch 71 has been added. Switch 70 is ganged to switch 68 to operate under the influence of relay 67 and, when an alarm signal is generated, electromagnetic switch 71 is deenerg ized to disconnect the main motor. The main motor would be connected to electromagnetic switch 71 in any suitable manner.

It will thus be seen that the objectsset forth above, among those made apparent from the preceding description, are efficiently attained and, since certain changes may be made in the above constructions without departing from the spirit and scope of the invention, it is intended that all matter contained in the above description or shown in the accompanying drawings shall be interpreted as illustrative and not in a limiting sense.

It is also to be understood that the following claims are intended to cover all of the generic and specific features of the invention herein described, and all statements of the scope of the invention which, as a matter of language, might be said to fall therebetween.

We claim:

1. In a canned motor pump including a casing; bearings mounted in said casing; a stator mounted in said casing; and a rotary member having a shaft and impeller journaled in said bearing, the improvement which comprises a bearing wear limit signaling comprising an independent fluid chamber normally free of fluid communication with said motor, said chamber having a portion thereof extending into said casing to a position proximate a portion of said rotating member and pressure sensing means communicating with said pressure chamber outside of said casing for signaling a change is pressure in said pressure chamber, at least one end of said pressure chamber portion proximate said rotating member being constructed and arranged to be ruptured by said rotating member proximate portion when frictionally engaged thereby to effect a change in pressure when the wear limit of said bearing has been exceeded.

2. A bearing wear limit signaling device as claimed in claim 1, wherein said rotating member shaft includes an axially directed bore extending into said shaft from at least one end thereof, said portion of said pressure vessel within said casing extending into said bore along said shaft axis, said portion of said pressure chamber being constructed and arranged to be ruptured be either the circumferential or base walls of said axially extending bore when frictionally engaged thereby when the wear limit of said bearing has been exceeded.

3. A bearing wear limit signaling device as claimed in claim 1 wherein said pressure chamber has a generally tubular configuration and said one end thereof is cone-shaped to effect the sealing of said tube.

4. A bearing wear limit signaling device as claimed in claim 1 wherein said portion of said rotating member has a notched surface for aiding in the rupturing of said one end by said portion of said rotating member when said one end is contacted by said notched surface.

5. A bearing wear limit signaling device as claimed in claim 1 wherein said one end of said pressure chamber is formed as a tubular, ring-shaped element located within said casing and extending concentrically about said shaft.

6. A bearing wear limit signaling device as claimed in claim 1 and further including electrical control means responsive to said pressure sensing means for controlling an external electric circuit when the wear limit of said bearings has been exceeded.

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