Motor bearing with locking pins

An electric motor has features for preventing the bearings from rotating. The motor has a stator mounted in a housing. A rotor is rotated within the stator. The rotor is divided into rotor sections, with bearings spaced between. Each bearing has an outer portion that contains outwardly biased pins. The pins engage slot gaps formed in the stator laminations.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
This invention relates in general to submersible pump motors, and in 
particular to a bearing assembly that resists rotation and is located 
between rotor sections for supporting the shaft of the motor. 
2. Description of the Prior Art 
A submersible pump is a centrifugal pump having a submersible motor that 
rotates the shaft to drive the pump. The motors for high volume oil and 
water production may be from six to sixty feet in length and be rated at 
several hundred horsepower. Each motor has a stator secured within a 
tubular housing. A rotor secured to a shaft rotates within the stator. 
Because of the long length, the rotor is made up of a number of rotor 
sections. Each rotor section comprises a large number of flat disks called 
laminations that are secured by copper rods. The rotor sections are 
spaced-apart from each other, and a bearing assembly is located between 
each section for maintaining the shaft in axial alignment. The rotor 
sections are keyed to the shaft for rotation, but are axially movable with 
respect to the shaft. 
Each bearing assembly includes a sleeve keyed to the shaft for rotation. A 
journal, commonly called a bearing, has a bore with a periphery that 
frictionally engages the inner wall of the stator at operating 
temperatures to prevent the bearing from rotating and to support the shaft 
in alignment. 
As the motor heats up to operating temperature, the bearing will expand 
slightly outward to more tightly grip the stator. Also, the rotor will 
likely grow longitudinally at a rate greater than the stator, causing the 
bearing to move longitudinally with respect to the stator. The bearing 
must be precisely dimensioned so that it does not engage the stator wall 
so tightly as to create excessive thrust loads on the bearing member. For 
accurate dimensioning, the bearing is normally constructed of a metal with 
an outer wall ground to a 0.0005 inch tolerance. While usually 
satisfactory, on occasion the bearing begins to spin with the shaft, 
causing heat and metal surfaces galling which ultimately leads to oil 
contamination and dielectric breakdown. 
Proposals have been made to prevent the bearing from rotating. For example, 
in application Ser. No. 538,646, filed Oct. 3, 1983, Anti-Rotation Motor 
Bearing, David I. Del Serra, an annular elastomer for fitting about the 
bearing periphery is shown. The elastomer swells during operation to 
engage the stator inner wall to prevent rotation of the bearing. In U.S. 
Pat. No. 4,435,661, issued Mar. 6, 1984, Submersible Pump Motor Flexible 
Bearing, Raymond L. Witten, a resilient bearing is shown. The bearing has 
slots through the periphery to allow the bearing to be compressed during 
operation, to prevent rotation of the bearing. While these proposals have 
merit, other manners of solving the problem may be possible. 
SUMMARY OF THE INVENTION 
In this invention, the bearing is provided with pins which move outward 
during operation to prevent rotation of the bearing. In the preferred 
embodiment, the pins are located in radial cavities spaced around the 
periphery of the bearing. The pins are located so as to engage gaps 
provided between the slot teeth of the stator laminations. A coil spring 
behind each pin pushes the pin outwardly into the gap to resist rotation 
of the bearing. Each pin has a piston portion, which augments the force of 
the spring by hydraulic pressure created in the inner diameter of the 
bearing.

DESCRIPTION OF THE PREFERRED EMBODIMENT 
Referring to FIG. 1, electric motor 11 includes a cylindrical housing 13. A 
stator 15 is rigidly mounted within housing 13. Stator 15 is made up of a 
large number of flat metallic disks 17, called laminations. Each 
lamination 17 has a central or axial aperture that aligns with all the 
other laminations 17, defining an inner wall 19. Inner wall 19 is 
cylindrical and of uniform diameter. 
Referring to FIG. 2, each lamination 17 has a plurality of slots 21 
uniformly spaced in a circular pattern. Each slot 21 has on its inner edge 
a pair of teeth 23 that face each other. Teeth 23 are spaced apart from 
each other by a gap 25. Wires (not shown) are wound through liners (not 
shown) in the slots 21, which are subsequently filled with epoxy. The gaps 
25 remain open, and free of epoxy, resulting in parallel vertical grooves 
extending down the length of the inner wall 19 and spaced around the 
diameter. 
Referring to FIG. 1, a rotor 27 is rotatably mounted within the inner wall 
19 of stator 15. Rotor 27 comprises a shaft 29 and a large number of 
metallic disks or laminations. The laminations are grouped in rotor 
sections 31, which are approximately 15 inches in length. Each rotor 
section 31 has copper rods (not shown) extending through it. The rods are 
secured at their ends by means of end rings 35. Each rotor section 31 is 
secured by a key (not shown) to shaft 29 for rotation. The rotor sections 
31 are free to move vertically to some extent on shaft 29 to accommodate 
increase in length due to rise in temperature. 
A bearing assembly is located between each of the rotor sections 31. The 
bearing assembly includes a bearing 37 which has an inner portion 39. 
Inner portion 39 is cylindrical and has an inner diameter mounted on a 
bushing 41. Bushing 41 is keyed to shaft 29 for rotation, while the 
bearing inner portion 39 will remain stationary. Thrust washers 43 are 
located at the top and bottom of bearing inner portion 39. Bushing 41 
supports the weight of the rotor sections 31 and transmits any force 
between one rotor section 31 to the other rotor section 31. The thickness 
of the thrust washers 43 is selected to provide a total height from the 
lower edge of the lower thrust washer 43 to the upper edge of the upper 
thrust washer 43 that is less than the height of bushing 41. This prevents 
the thrust washers 43 from bearing the weight of the rotor sections 31 
located above. 
Bearing 37 has a flange or outer portion 45 that extends radially outward 
from the inner portion 39. Outer portion 45 has a cylindrical periphery 
that is spaced inward from inner wall 19 of the stator 15, and has a 
diameter slightly greater than the rotor sections 31. The longitudinal 
thickness or height of the outer portion 45 is less than the distance 
between two adjacent end rings 35. A plurality of passages 46 (FIG. 2) 
extend through the outer portion 45 for communicating oil contained within 
the housing 13. Bearing 37 is of a metallic material, preferably. 
Referring to FIG. 3, bearing outer portion 45 has a plurality of horizontal 
cavities or holes 47 extending through it. Each hole 47 has an axis that 
lies on a radial line of the axis of shaft 29. Preferably, there are three 
of the holes 47, each spaced 120 degrees apart from the other. Each hole 
47 extends from the inner diameter of the inner portion 39 into a 
counterbore section 49. The counterbore 49 extends to the periphery of the 
outer portion 45 and is of greater diameter than the inner portion of the 
hole 47. 
A metal pin 51 is carried within each counterbore 49. Pin 51 has a 
cylindrical base 53 that is slidingly and closely received within the 
counterbore 49. Base 53 is of larger diameter than the protruding portion 
of pin 51, defining an outwardly facing shoulder 55. A snap ring 57 is 
located in a groove formed in the counterbore 49. Snap ring 57 serves as 
stop means to limit the outward travel of pin 51 by contact with shoulder 
55. An O-ring 59 encircles base 53 for providing sealing within the 
counterbore 49, and causes base 53 to act as a piston in a cylinder. A 
coil spring 61 is compressed between the inner end of pin 51 and the inner 
end of counterbore 49. Coil spring 61 acts as spring means for urging the 
pin 51 outward to protrude past the periphery of the bearing outer portion 
45 and the outer diameter of the rotor sections 31. The spring 61 can be 
compressed to allow the pin 51 to move back substantially flush with the 
outer diameter of bearing outer portion 45. 
In assembling the motor 11, the bearing is assembled between the rotor 
sections 31 and the rotor 27 is inserted into the stator 15. The pins 51 
are not aligned with the gaps 25 during insertion, and will move back into 
holes 47, compressing springs 61. The coil spring 61 urges each pin 51 out 
to contact stator inner wall 19. Rotor 27 will be secured in a 
conventional manner and the housing 13 will be filled with oil. 
In operation, electrical current passed through the windings of the stator 
15 will cause the rotor 27 to rotate. The bushing 41 will rotate with the 
shaft 29. Any torque on bearing 37 will rotate bearing 37 until pins 51 
snap into gaps 25. The spinning bushing 41 creates a hydraulic positive 
pressure in hole 47, which acts against the piston formed by base 53 to 
push pin 51 outwardly. The hydraulic force augments the force provided by 
springs 61. The bearing 37 will remain stationary because of the 
engagement of the pins 51 in the gaps 25. Torque on the bearing 37 is 
resisted by the pins 51 bearing against the sides of teeth 23. Heat will 
cause the rotor sections 31 to expand longitudinally. The bearing 37 will 
be allowed to move longitudinally to accommodate growth, with the pins 51 
sliding within the gaps 25. Bearing 37 will also expand radially with heat 
and its periphery may engage the inner wall 19 of stator 15. 
The invention has significant advantages. The locking pins provide a 
positive means for the bearing to engage the stator to prevent rotation. 
Because the periphery of the bearing does not contact the inner wall of 
the stator, close tolerances are not required. The springs allow easy 
insertion of the rotor into the stator. 
While the invention has been shown in only one of its forms, it should be 
apparent to skilled in the art that it is not so limited but is 
susceptible to various changes without departing from the scope of the 
invention.