Patent Publication Number: US-2003228080-A1

Title: Bearing insert for motor operators

Description:
BACKGROUND OF THE INVENTION  
       [0001] 1. Field of the Invention  
       [0002] The present invention relates to motor operators for circuit breakers. More specifically, the invention relates to an improved structure and method of assembly for a motor operator, providing a bearing insert at each end of the screw shaft, with the bearing adapted for easy insertion into opposing walls of the motor operator&#39;s housing.  
       [0003] 2. Description of the Related Art  
       [0004] Circuit breakers are frequently actuated remotely, by securing a motor operator over the face of the circuit breaker, so that the motor operator can actuate the circuit breaker. A typical motor operator includes an electric motor, operatively connected through a system of gears to a threaded rod. A sliding actuator is threadedly connected to the threaded rod, so that rotation of the threaded rod causes the sliding actuator to reciprocate back and forth. The sliding actuator fits over the circuit breaker&#39;s operating handle, so that movement of the actuator moves the operating handle. A kill/toggle switch at each end of the sliding actuator&#39;s range of travel shuts off the current, and reverses the direction of current that will be supplied to the motor, upon being depressed by the sliding actuator. A printed circuit board will typically contain the motor operator&#39;s control circuitry. When the user transmits a signal to close the circuit breaker, the control circuitry will supply current to the motor, thereby rotating the threaded shaft to slide the sliding actuator from one end of its range of travel to the other, thereby moving the circuit breaker&#39;s operating handle, and closing the circuit breaker. Upon reaching the end of its range of travel wherein the circuit breaker is closed, the sliding actuator hits the toggle switch at that location, thereby shutting off current to the motor, and reversing the direction of current to the motor. When the user transmits a signal to open the circuit breaker, the control circuit will again supply current to the motor, thereby moving the sliding actuator to the opposite end of its range of travel, moving the circuit breaker&#39;s operating handle to its open position. As before, when the sliding actuator reaches the position wherein the circuit breaker is open, it strikes a kill/toggle switch, shutting off current to the motor, and reversing the direction of current flow to the motor.  
       [0005] The screw shaft of presently available motor operators is secured between opposing walls of the housing, so that assembly of the motor operator requires first installing various washers, retaining rings, bearings, a gear, and a sliding actuator on the screw shaft, bending the housing, inserting the screw shaft between the appropriate walls, and then allowing the housing to deflect back to its original position. In addition to making assembly of the motor operator unnecessarily difficult, the present design also precludes automated assembly of the motor operator.  
       [0006] Accordingly, a motor operator having an improved structure permitting simplified, and possibly automated, assembly is desired. Additionally, an improved method of assembling a motor operator is desired.  
       SUMMARY OF THE INVENTION  
       [0007] The present invention provides a bearing insert for the screw shaft of a motor operator, thereby permitting the screw shaft to be installed within the housing without the need to bend the opposing housing walls away from each other.  
       [0008] A preferred embodiment of the bearing insert is generally rectangular, and some embodiments may have a radiused or tapered bottom end. The bottom end of the bearing insert includes an aperture dimensioned and configured to receive one end of a screw shaft for a motor operator. The sides and bottom of the bearing insert include a plurality of flanges, dimensioned and configured to fit along both sides of the wall of a motor operators housing. In some preferred embodiments, at least one of these flanges may be extended, and may define an aperture, such as a threaded aperture, for receiving a screw or bolt.  
       [0009] To assemble a motor operator incorporating the present invention, a gear, sliding acuator, and other components typically installed on the threaded rod are first installed on this rod. Next, a bearing insert of the present invention is installed on each end of the screw shaft. The bearing inserts are then placed into channels dimensioned and configured to receive them, defined within opposing walls of the motor operators housing, with the flanges of each bearing insert fitting on each side of its corresponding wall. Lastly, bolts or screws may be passed through apertures within the housing, into the screw holes defined within the bearing insert.  
       [0010] Placing the screw shaft between a pair of bearing inserts of the present invention, and then installing the bearing inserts into appropriately configured channels within opposing walls of the motor operators housing, eliminates the need to bend the opposing walls of the motor operators housing away from each other in order to fit the ends of the screw shaft with an aperture as defined directly within these walls. Additionally, eliminating the need to bend the walls of the motor operators housing raises the possibility of using automated assembly methods, thereby reducing the cost of the motor operator. 
     
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
     [0011]FIG. 1 is a top isometric view of a circuit breaker with its associated motor operator.  
     [0012]FIG. 2 is a top isometric view of a circuit breaker and its associated motor operator, with the cover of the motor operator removed.  
     [0013]FIG. 3 is a top isometric view of a circuit breaker and motor operator, with the cover of the motor operator removed  
     [0014]FIG. 4 is a top isometric view of a circuit breaker and motor operator, with the cover and printed circuit board of the motor operator removed  
     [0015]FIG. 5 is an isometric view of a bearing insert according to the present invention.  
     [0016]FIG. 6 is a top view of a bearing insert according to the present invention.  
     [0017]FIG. 7 is a front view of a bearing insert according to the present invention.  
     [0018]FIG. 8 is a side view of a bearing insert according to the present invention.  
     [0019]FIG. 9 is an exploded isometric view of a motor operator housing, screw shaft, and associated bearing inserts according to the present invention.  
     [0020]FIG. 10 is an isometric view of a housing for a motor operator, into which a screw shaft and its associated bearing inserts have been installed, according to the present invention. 
    
    
     [0021] Like reference characters denote like features throughout the drawings.  
     DETAILED DESCRIPTION  
     [0022] The present invention provides an improved structure and method of assembly for motor operators for circuit breakers.  
     [0023] FIGS.  1 - 4  illustrate a motor operator  10  mounted on the face  12  of a circuit breaker  14 . The motor operator  10  includes a housing  16  having a base  18 , mounting bracket  20 , and cover  22 . The base  18  is hingedly secured to the mounting bracket  20 , which is in turn secured to the face  12  of the circuit breaker  14  by means well known in the art of circuit breakers, for example, screws passing through the apertures  24 . The base  18  also includes a lifting tab  26 , for lifting the hingedly secured base  18  away from the mounting bracket  20  to provide manual control of the circuit breaker  14 . The housing  16  of the motor operator  10  also includes a cover  22 , which, in conjunction with the base  18 , fully encloses the motor operator  10 .  
     [0024] Referring to FIGS.  2 - 4 , the motor operator  10  includes a motor  28 , which in the present example is an electrical motor  28  secured between one wall  30  of the base  18  and the motor bracket  32 . A screw shaft  34  extends between the wall  30  and wall  36  of the base  18 , being rotatably secured therein at either end. Gear  38  is located at one end of the screw shaft  34 , with the gear  38  operatively engaging a corresponding gear that is driven by the motor  28 , so that the screw shaft  34  is thereby driven by the motor  32 . A sliding actuator  40  includes an upper portion  42  that is threadedly connected to the screw shaft  34 , and a lower portion  44  that engages the operating handle  46  of the circuit breaker  14 . A kill/toggle switch is located at either end of the range of travel of the sliding actuator  40 . The kill/toggle switches, which are not shown but are well known in the art, when actuated by the sliding actuator  40 , will simultaneously shut off current to the motor  28 , and reverse the direction of current through the motor  28 . The flow of current through the motor  28  is further controlled through the printed circuit board  48 , and its associated signal processing circuitry (well known in the art).  
     [0025] The motor operator  10  will typically be used to remotely control the operation of the circuit breaker  14  or for larger breakers that require substantial force on the operating handle. When the user transmits a signal to close the circuit breaker  14 , the control circuitry within the PC board  48  will supply current to the motor  28 , thereby rotating the screw shaft  34  to move the sliding actuator  40  from one end of its range of travel to the other, thereby moving the circuit breaker&#39;s operating handle  46 , and closing the circuit breaker  14 . Upon reaching the end of its range of travel wherein the circuit breaker  14  is closed, the sliding actuator  40  hits the kill/toggle switch at that location, thereby shutting off current to the motor  28 , and reversing the direction of current to the motor  28 . When the user opens the circuit breaker  14 , the control circuit within the PC board  48  will again supply current to the motor  28 , thereby moving the sliding actuator  40  to the opposite end of its range of travel along the screw shaft  34 , moving the circuit breaker&#39;s operating handle  46  to the open position. As before, when a sliding actuator  40  reaches the position wherein the circuit breaker is open, it strikes a kill/toggle switch, shutting off current to the motor  28 , and also reversing the direction of current flow to the motor  28 .  
     [0026] From the above description, it becomes apparent that assembling a motor operator  10  must include the step of bending the wall  30  and/or the wall  36  so that the ends  50 ,  52  of the screw shaft  34  may be inserted into the apertures  35  of the walls  30 ,  36 . This step must of course be done after installing the sliding actuator  40 , gear  38 , and other mounting hardware known in the art of motor operators on the screw shaft  34 , while holding the other components on the screw shaft. Such an assembly procedure makes assembling the motor operator unnecessarily difficult, precluding automatic assembly methods.  
     [0027] Referring to FIGS.  5  to  8 , this need is addressed by a bearing insert  54  of the present invention. Some preferred embodiments of the bearing insert  54  is generally rectangular, including a pair of substantially parallel sides  56 ,  58 , a bottom  60 , a top  62 , an outside face  64 , and an inside face  66 . For purposes of this description, the term generally rectangular is defined as having substantially parallel sides  56 ,  58 , and may include a rounded or tapered bottom  60  in some preferred embodiments, with the illustrated embodiments having a rounded, semi-circular bottom  60 . Such a configuration both facilitates assembly, and provides complete covering of the channel  78  (described below). The bearing insert  54  includes an aperture  68 , dimensioned and configured to receive an end  50 ,  52  of the screw shaft  34 . The bearing insert  54  also includes means for securing the bearing insert  54  within a wall of a motor operators housing. Many preferred embodiments of the bearing insert  54  will include a channel  70  extending along its sides  56 ,  58  and bottom  60 , dimensioned and configured to receive a wall  30 ,  36  of the motor operators housing  16 . In the illustrated example, the channel  70  is defined between a plurality of outside flanges  72 , depending outward from the sides  56 ,  58  and bottom  60  adjacent to the outside face  64 , and the inside flanges  74 , also depending outward from the sides  56 , 58  and bottom  60 , adjacent to the inside face  66 . In some preferred embodiments, at least one of the flanges  72 ,  74  may be extended, defining an aperture  76  dimensioned and configured to receive a bolt or a screw. In the illustrated example, two of the inside flanges  74 , designated  74   a , each define an aperture  76 . In some preferred embodiments, the aperture  76  may be threaded.  
     [0028] The above-described preferred embodiment, utilizing the alternating flanges  72 ,  74 , has the additional advantage of being easy to manufacture. Some preferred embodiments of the bearing insert  54  may be made from a molded polymer or resin. The alternating flanges  72 ,  74  provide for easy use of a straight draw mold to form the bearing insert  54 , and facilitate removal of the bearing insert  54  from the mold.  
     [0029] Referring to FIGS.  9  to  10 , a method of installing a screw shaft  34  within a housing  16 , using the bearing insert  54 , is illustrated. The walls  30   a ,  36   a  of the housings base  18   a  each include a channel  78 , dimensioned and configured to receive the bearing insert  54 . After the gear  38 , sliding actuator  40 , and any other necessary mounting hardware (not shown and well known in the art of motor operators) are installed on the screw shaft  34 , the ends  50 ,  52  of the screw shaft  34  are each inserted into an aperture  68  of a bearing insert  54 . The ends  50 ,  52  may have a smaller diameter than the remainder of the screw shaft  34 , thereby defining a shoulder limiting the extent to which the screw shaft  34  may be inserted into the bearing insert  54 , and locating the screw shaft  34 . Each bearing insert  54  is then inserted into one of the channels  78  defined within the walls  30   a ,  36   a , while maintaining the ends  50 ,  52  of the screw shaft  34  within the apertures  68 . The rounded or tapered bottom  60  may facilitate this insertion is some embodiments. Lastly, the screws  80  are inserted through the apertures  82  within the walls  30   a ,  36   a , and into the threaded apertures  76 , thereby securing the bearing inserts  54  within the channels  78 .  
     [0030] While a specific embodiment of the invention has been described in detail, it will be appreciated by those skilled in the art that various modifications and alternatives to those details could be developed in light of the overall teachings of the disclosure. Accordingly, the particular arrangements disclosed are meant to be illustrative only and not limiting as to the scope of the invention which is to be given the full breadth of the appended claims and any and all equivalents thereof