Patent Publication Number: US-6657338-B2

Title: Two compartment motor

Description:
BACKGROUND OF THE INVENTION 
     This invention relates generally to electric motors and, more particularly, to a two compartment electric motor. 
     Electric motors such as, for example, single phase induction motors, are manufactured in a variety of configurations for use in a number of different applications. For example, swimming pools and whirlpool spas typically use a number of electric motors for various purposes such as, for example, driving a water pump for water circulation purposes. Moisture, dust, and other contaminants, which may be prevalent in the environments associated with these types of applications, may adversely interfere with the operation of the motor and, over time, may lead to failure of the motor. To provide protection against the adverse effects posed by these contaminants, various techniques and motor designs have been utilized. 
     One approach to facilitate minimizing adverse effects from contaminants is to utilize a two-compartment motor. In a two-compartment motor, the stator, armature, and other primary motor components are contained in a first compartment and the secondary electrical components are contained in a second compartment. For example, U.S. Pat. No. 4,593,163 discloses a two compartment motor in which a starting capacitor, a thermal protector, a terminal board, a starting switch assembly, and a manually actuable switch are mounted to an end shield of an induction motor. A thermoplastic molded cover is secured to the motor with axially directed screws to define the second compartment of the motor. 
     U.S. Pat. No. 5,245,237 discloses another two-compartment motor in which a control assembly is mounted within a second compartment of a two-compartment motor. The control assembly includes a control plate, a plurality of electrical components, and mounting means for securing the electrical components in position on the control plate. To switch the voltage setting of the motor between high and low settings, a voltage selection switch is mounted on the control plate within the secondary compartment. 
     Constructing a two-compartment electric motor may be more costly than constructing other types of electric motors. For example, the costs of manufacturing a two-compartment motor are higher than the cost associated with manufacturing a one-compartment motor because of, for example, the inherent material costs associated with the second compartment. Second, in at least some known two-compartment motors, minimizing exposure to moisture, dust, and other contaminants is difficult because the components must be ventilated. 
     BRIEF DESCRIPTION OF THE INVENTION 
     In one aspect, a motor including a first compartment, a second compartment, a frame, a first end shield, a second end shield, an armature shaft, a stator winding, an armature, a cover, and a switchboard is provided. The first and second end shields are disposed adjacent opposing ends of the frame to define the first compartment. The armature shaft extends between the first and second end shields. The stator winding is supported by the frame within the first compartment. The armature is rotatably supported by the end shields and disposed within the first compartment adjacent the stator winding. The cover includes a first end, a peripheral edge, and ventilation openings. The cover peripheral edge is mounted to the motor adjacent the second end shield. The ventilation openings include a plurality of openings positioned along at least part of the cover peripheral edge and in the cover first end. The switchboard is mounted to the second end shield to define the second compartment between the switchboard and the second end shield. The switchboard includes a mounting means for securing a plurality of electrical components. 
     In another aspect, a two compartment motor including a frame, a first end shield, a second end shield, a stator winding, an armature, a cover, and a switchboard is provided. The first end shield and the second end shield are disposed adjacent opposing ends of the frame to define a first compartment. The stator winding is supported by the frame within the first compartment. The armature is rotatably supported by the end shields within the first compartment. The cover includes a plurality of cooling openings. The cover is mounted to the motor adjacent the second end shield. The switchboard is mounted to the second end shield to define the second compartment between the switchboard and the second end shield. The switchboard includes a mounting means for securing a plurality of electrical components within the second compartment. 
     In another aspect, a motor including a first compartment, a second compartment, a cover, and a switchboard assembly is provided. The first compartment is defined between a first end shield and a second end shield. The cover having ventilation openings is mounted adjacent the second end shield. The switchboard assembly is mounted to the second end shield to define the second compartment. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a perspective view of a two compartment motor. 
     FIG. 2 is a bottom view of the two compartment motor shown in FIG.  1 . 
     FIG. 3 is an exploded view of the two compartment motor shown in FIG.  1 . 
     FIG. 4 is a plan view of an end shield that is part of the two compartment motor shown in FIG.  1 . 
     FIG. 5 is an elevational view the end shield shown in FIG.  4 . 
     FIG. 6 is a plan view of the exterior side of a switchboard that is part of the two compartment motor shown in FIG.  1 . 
     FIG. 7 is plan view of the interior or back side of the switchboard shown in FIG.  6 . 
     FIG. 8 is an exploded view of an end shield, a switchboard, and a cover that are part of the two compartment motor shown in FIG.  1 . 
     FIG. 9 is another exploded view of the end shield, the switchboard, and the cover shown in FIG.  8 . 
     FIG. 10 is yet another exploded view of the end shield, the switchboard, and the cover shown in FIG.  8 . 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     FIG. 1 shows a perspective view of a two compartment motor  10  constructed in accordance with the present invention. Motor  10  has a first compartment which is defined by a first end shield  12 , a second end shield  14  and a generally cylindrical frame  16 . Frame  16  provides support for stator windings (not shown in FIG.  1 ), while end shields  12  and  14  are fitted with bearings to rotatably support an armature assembly within the first compartment adjacent the stator winding, as is well-known in the art. Armature shaft  18  extends from one end of motor  10  and is threaded, keyed or otherwise adapted for coupling to a load. End shield  12  is provided with a plurality of mounting lugs  20  which are used to securely mount motor  10  in operating position adjacent the load. 
     Motor  10  includes a second compartment (which may be referred to as the control compartment) which is generally defined by end shield  14  and a switchboard  21 . As discussed in more detail below, the control compartment is used to house a plurality of electrical components used in the control and operation of motor  10 . A cover  22  is secured to motor  10  by threaded, hex-head screw  24  and encases switchboard  21 . Electrical access to the control compartment is provided by a conduit receiving opening  26  which is integrally formed in end shield  14 . 
     Cover  22  is a one-piece, cup-shaped element having a first end  28 , a peripheral edge  30  that is mounted to the motor adjacent second end shield  14 , and a plurality of ventilation openings which are shown in greater detail in FIG.  2 . 
     FIG. 2 is a bottom view of motor  10  in which a plurality of ventilation openings  32  and  34  are visible. Openings  32  and  34  are integrally formed in cover  22  and are in flow communication with ventilation openings in end shield  14 , which are described in greater detail hereinbelow. Ventilation openings  32  are relatively short, narrow openings integrally formed in cover  22  that extend along peripheral edge  30  of cover  20  from one lateral portion of the bottom of motor  10  to the opposing lateral portion of the bottom of motor  10 , as shown in FIG.  1 . Openings  32  extend longitudinally along motor  10  from peripheral edge  30  and are in flow communication with the ventilation openings in end shield  14  (shown in FIG.  3 ). Openings  34  are relatively long and wide openings integrally formed in cover  22  which are laterally centered in cover  10  on the bottom-side of motor  10 . Openings  34  extend perpendicular to shaft  18 . This arrangement, in combination with the ventilation openings in end shield  14 , is intended to provide adequate ventilation and air discharge channels for motor  10 , while reducing contamination of the two motor compartments with dust and moisture. 
     FIG. 3 shows an exploded view of motor  10  in which the major components are visible. The right-hand side of FIG. 3 shows the major components which define the first compartment of two compartment motor  10 . These components include end shield  12 , frame  16  and end shield  14 . As noted above, stator windings  36  are supported by frame  16  within the first compartment. An armature  38  (not shown) is rotatably supported by end shields  12  and  14  adjacent stator windings  36 . Armature shaft  18  extends from the first compartment through end plate  12  for connection to a load as previously discussed. On the other end of motor  10 , shaft  18  extends through end shield  14  into the second compartment defined by switchboard  21  and end shield  14 . This end of shaft  18  is provided with a slot  40  and wrench flats  42  to facilitate manual rotation of, or to secure against rotation of, armature  38  after the opposing end of shaft  18  is connected to a load. Shaft  18  is also provided with two circumferential grooves (not shown in FIG. 3) which accept two locking clips (not shown in FIG. 3) that secure centrifugal speed switch assembly  44  in position on shaft  18 . A plurality of electrical conductors (not shown in FIG.  3 ), which are electrically connected to stator windings  36 , extend from the first compartment through end plate  14  and electrically communicate with switchboard  21 . 
     Defining the second compartment of motor  10  is switchboard  21  and end shield  14 . In the embodiment illustrated, switchboard  21  is a one-piece molded plastic structure which provides a mounting base for securing a plurality of electrical components used in the control and operation of motor  10 . The exact structure of the illustrated embodiment of switchboard  21  will be discussed in detail in connection with FIGS. 3,  6 , and  7  below. Switchboard  21  is mounted to motor  10  by a pair of bolts  50  which extend through switchboard  21  and into end shield  14  to engage threads formed in end shield  14 . Bolts  52  serve to secure end shields  12  and  14  to frame  16 . In the assembly process, this arrangement allows switchboard  21  to be separately mounted to the sub-assembly which includes the first compartment of motor  10 . 
     In the illustrated embodiment, cover  22  mounts, via screw  24  which extends through opening  53 , to a threaded screw-receiving boss  54  which is an integrally formed element of switchboard  21 . In an exemplary embodiment, screw  24  is “captured” in opening  53  so as to remain with cover  22  upon removal from motor  10 . In this embodiment of the invention, both switchboard  21  and cover  22  are molded plastic components. 
     In an exemplary embodiment, a ground screw  56  which threads into an opening in boss  78  of end shield  14  to provide a convenient means by which to connect the metal components of motor  10  to a ground wire provided by the user. 
     FIG. 4 is a plan view of end shield  14  of motor  10  and FIG. 5 is an elevational view of end shield  14 . End shield  14  utilizes a “semi-skeleton” design which includes a central portion  60 , four radially-extending spokes  62 , a circumferential portion  64 , and an upper portion  65  extending between central portion  60  and circumferential portion  64  at the top-side of motor  10 . This arrangement provides relatively large openings  66 - 70  for the passage of ventilating air and power conductors through end shield  14 . With reference to FIGS. 4 and 5, central portion  60  of end shield  14  includes a generally circular, annular recess  72  which faces away from armature  38  (not shown) when end plate  14  is assembled in motor  10 . Recess  72  provides clearance for centrifugal switch assembly  44 . Central portion  60  further includes, on the side of end shield  14  which faces the armature, a machined recess which is adapted to receive the bearing (not shown) which supports the respective end of armature  38 . 
     End shield  14  is provided with four holes for receiving mounting bolts  50  and  52 . Holes  74  receive bolts  52  to attach end shield  12  to frame  16  and end shield  14 . Mounting holes  76  are formed to accept bolts  50  to mount switchboard  21  to end shield  14 . An additional raised projection or boss  78  is provided as an additional locating and orientation landmark for switchboard  21 , and provides a grounding point for connecting the metallic elements of motor  10  to a user supplied ground wire (shown in FIG.  3 ). 
     An additional feature of end shield  14  is integrally formed conduit receiving opening  26 . Opening  26  is integrally formed in an upstanding portion  83  of end shield  14 . Opening  26  is threaded to receive a conduit nipple to facilitate connection of the motor to an external power source. A recessed shoulder  84  is formed around three sides of opening  26  to mate with a similarly shaped cut-out  86  (shown in FIG. 1) in cover  22  to provide a step flange-type seal around the three sides of opening  26 . 
     End shield  14  is also provided with a raised projection  87  on the outwardly facing side surface of circumferential portion  64 . Projection  87  extends substantially parallel to the longitudinal axis of motor  10  across substantially the full width of circumferential portion  64  of end shield  14 . The function of projection  87  is to provide an alignment and anti-rotation feature for a separately mounted “bonding lug” such as is commonly used in the swimming pool industry. 
     In the embodiment of the invention illustrated, end shields  12  and  14  are formed in one piece of a metallic material, such as cast aluminum. 
     As provided above, ventilation openings  32  (shown in FIG. 2) are integrally formed in cover  22  extending along peripheral edge  30  from one lateral portion of the bottom of motor  10  to the opposing lateral portion of the bottom of motor  10 , and are in flow communication with the ventilation openings  66 - 70  in end shield  14 . Vent openings  32 , in combination with the open “semi-skeletal” construction of end shield  14  and large ventilation openings  34 , ensure adequate ventilation of motor  10 . These features further allow for simplified compliance with U.L. standards regarding molten metal protection. The integrally formed air channels in cover  22  improve the air intake and discharge capabilities of the motor, resulting in reduced motor operating temperature rises. 
     FIG. 6 is a plan view of the exterior side of switchboard  21  without a plurality of electrical components mounted thereon. The various features of switchboard  21  and the components will be described with reference to FIGS. 3 and 6, starting at the top or twelve o&#39;clock position, as viewed in the figures, and moving clockwise around the switchboard. Near the top of switchboard  21  is an area  90  for mounting a portion of a centrifugal switch  92 . Centrifugal switch  92  has an actuator portion which extends through an opening  94  formed in switchboard  21 . Mounting holes  96  and  98  are also provided in switchboard  21  to receive screws  50  which secure centrifugal switch  92  in position and secure switchboard  21  to end shield  14 . 
     The top surface  104  of centrifugal switch  92  is provided with a plurality of slots (e.g.,  106 ,  108 , and  110 ), some of which receive male terminals. In an exemplary embodiment, the male terminals are connected to female terminals which, in turn, are connected to electrical conductors (not shown). 
     Immediately below centrifugal switch  92  is integrally molded boss  54  which, as previously discussed in connection with FIG. 3, receives screw  24  to secure cover  22  in position. A pair of reinforcing gussets  120  and  122  are integrally molded to provide additional support for boss  54 . 
     Leads  130  and  132  terminate in female terminals  134  and  136 . Female terminals  134  and  136  mate with upwardly extending (i.e., out of the page) blade portions of S-shaped terminals  138  and  140 , respectively. With reference to FIG. 3, three sets of mounting openings are provided for the S-shaped terminals. Each set includes a relatively small opening which is sized to receive a rivet, screw or other fastening device to mechanically secure the terminals to switchboard  21 . Each set further includes a larger recess  144  to provide clearance for terminal screws, such as the screws shown in FIG. 3, which may be used to secure spade terminals or other conductors in electrical contact with the S-shaped terminals. S-shaped terminals  138  and  140  include a “lance” portion (not shown) to partially secure them to switchboard  21 . 
     In the center of switchboard  21  is an opening  152  which provides clearance for armature shaft  18 . Immediately adjacent opening  152  is an arcuate shield  154  which extends outwardly from switchboard  21  (i.e., out of the drawing in FIG.  6 ). Shield  154 , in conjunction with a shield positioned within cover  22  (not shown), serves to shield terminals  134  and  136  and conductors  130  and  132  (shown in FIG. 3) from rotating armature shaft  18 . 
     Adjacent lead  132  is a voltage selector switch  156  with a movable switch portion (not shown in FIG.  6 ). Switch  156  includes an outwardly extending arcuate portion  160  having inwardly and transversely extending lips near the top thereof to prevent or limit complete removal of the moveable switch portion from its position adjacent switchboard  21 . A separate arcuate shaped portion  164  is formed between the opposing ends of arcuate portion  160  to provide two gaps  166  and  168 . Within the circular area defined by arcuate portion  160  and  164  are a plurality of openings  170 - 174 . At least some of these openings (i.e.,  170 - 173 ) are fitted with electrical terminals (not shown). The female ends of each of the terminals receive one end of U-shaped conductors which are part of the movable switch portion (not shown). When the movable portion is engaged in the high position (shown in FIG.  6 ), the conductors connect a first set of terminals. When movable switch portion is engaged in the low position (shown in FIG.  6 ), different pairs of terminals are connected. The opposite ends of the terminals extend through switchboard  21  and are connected, such as by crimping, to electrical conductors (not shown). 
     Switch  156  is operated (i.e., moved from the high to low position or vice-versa}, by grasping an upstanding portion of the movable portion (not shown) and pulling the upstanding portion outwardly to disengage the conductors from the terminals until the edge portion of the moveable portion contacts the lips on arcuate portion  160 . The movable portion is then rotated to the desired position and moved inwardly to engage the ends of the U-shaped conductors into the terminals. This arrangement provides an easy, convenient and inexpensive mechanism for selecting between high and low voltage settings. If desired, additional switch mechanisms of this type may be provided for, among other things, speed selection. 
     At approximately the nine o&#39;clock position on switchboard  21  is a recess area  194  integrally formed with switchboard  21  to receive and hold starting capacitor  196  (shown in FIG. 3) in position. In an exemplary embodiment, a hole  198  is provided in switchboard  21  to accept a bolt  200  (shown in FIG. 3) to secure capacitor  196  to switchboard  21 . A plurality of molded projections  202  serve as stand-offs to laterally position capacitor  196  on switchboard  21 . 
     FIG. 7 is plan view of the interior or back side of switchboard  21 . The features of the back side of switchboard  21  will be discussed beginning at the top or twelve o&#39;clock position and moving counterclockwise around the circumference of switchboard  21 . To the extent features discussed in connection with FIG. 6 are shown unchanged in FIG. 7 (for example, mounting holes  96  and  98 , etc.), such features are identified with like reference numbers in all figures, but are not separately discussed below. 
     A recess, generally indicated by reference numeral  205 , is provided near the top of switchboard  21  to accommodate a multi-terminal electrical connector (not shown) which is configured to mate with an electrical connector (not shown) which, in turn, is connected to conductors (not shown) which extend into the first or motor compartment of motor  10 . The multi-terminal electrical connector is connected to a plurality of electrical conductors which, in turn, are connected to various ones of the electrical components mounted on switchboard  21 . The electrical connectors allow the electrical components on switchboard  21  to be conveniently and reliably connected to the other major components (e.g., stator windings  36 ) of motor  10  in a single operation to improve the quality and manufacturability of the motor. 
     Inwardly of recess  205  and opening  94  is a wall  208  which extends 360 degrees around an inner centrally located portion of switchboard  21  The inner surface of wall  208  defines a protected space for centrifugal speed switch assembly  44 . Extending into this space is an actuator (not shown) which interacts with a rotating portion of switch  44  to open or close an electrical circuit, via centrifugal switch  92 , when armature  36  (not shown) reaches a specified rotational speed. 
     Switch  156  was previously discussed in connection with FIG. 6 above. At approximately the three o&#39;clock position, as viewed in FIG. 7, is a space  216  which is provided for mounting a thermal overload device (not shown) to switchboard  21 . Projections  219  integral to switchboard  21  are provided along with a plurality of bosses  220  with openings  222  for receiving fasteners  224  (not shown) provided for mounting the thermal overload devise to switchboard  21 . As with the other integrally formed features discussed above, projections  219  and bosses  220  are preferably molded of a plastic material to provide a one-piece, completely integrated structure. 
     FIGS. 8,  9  and  10  are various exploded views of end shield  14 , cover  22 , and switchboard  21 . Switchboard  21  and end shield  14  define the second compartment. As described above, in an exemplary embodiment, switchboard  21  is a one-piece molded plastic structure which provides a mounting base for securing a plurality of electrical components used in the control and operation of motor  10  (not shown in FIGS. 8,  9 , and  10 ). 
     Switchboard  21  is mounted to motor  10  at end shield  14 . In the assembly process of the exemplary embodiment, switchboard  21  can be separately mounted to the sub-assembly which includes the first compartment of motor  10 . Cover  22  mounts, via screw  24 , to a threaded screw-receiving boss  54  which is an integrally formed element of switchboard  21 . In an exemplary embodiment, screw  24  is “captured” so as to remain with cover  22  upon removal from motor  10 . In this embodiment of the invention, both switchboard  21  and cover  22  are molded plastic components. In this embodiment, end shields  14  is formed in one piece of a metallic material, such as cast aluminum. 
     In a two-compartment motor, the stator, armature, and other primary motor components are contained in a first compartment and the secondary electrical components are contained in a second compartment. The present invention provides a two compartment electric motor design which includes a switchboard to which a plurality of electrical components may be conveniently mounted. The present invention also provides a two compartment motor design in which a plurality of electrical control components may be premounted to a switchboard to form a subassembly prior to the assembly of the electrical component compartment of the motor. Furthermore, the present invention provides a two compartment motor that protects the electrical components from moisture, dust and other contaminants by enclosing the components within the switchboard. Also, the present invention provides a two compartment motor with improved ventilation features which may be integrally formed in the cover. Lastly, the present invention provides a more easily and reliably manufactured two compartment motor with fewer components, a reduced assembly time, and a reduced assembly cost. 
     While the invention has been described in terms of various specific embodiments, those skilled in the art will recognize that the invention can be practiced with modification within the spirit and scope of the claims.