Abstract:
A stator assembly includes a stator stack and a plurality of conductors extending from the stator stack. An isolator/assembly ring is located on the stator stack. The isolator/assembly ring includes a plurality of inwardly protruding fingers. A method of assembling the stator assembly includes threading the plurality of conductors through the stator stack such that each of the plurality of fingers on the isolator/assembly ring is located between respective ones of the plurality of conductors.

Description:
CLAIM OF PRIORITY AND CROSS-REFERENCE TO RELATED APPLICATION 
     This application claims the benefit of and priority to U.S. Provisional Patent Application No. 61/167,229, filed on Apr. 7, 2009, which is hereby incorporated by reference in its entirety. 
    
    
     TECHNICAL FIELD 
     The present invention relates, generally, to an electric motor, and more specifically, to an isolator ring for a stator assembly of the electric motor. 
     BACKGROUND OF THE INVENTION 
     Electric motors include stator assemblies which have conductors for the motor. In a bar wound stator assembly the conductors are solid copper bars individually threaded into a stator stack. Following threading of the conductors in the stator stack, the conductors are individually twisted into the required positions. 
     During assembly of the stator assembly, metal tooling is located adjacent to the stator stack on a crown-side of the stator stack. Additional metal tooling is also located on a twist-side of the stator stack. At both the crown-side and the twist-side of the stator stack, the metal tooling is a plurality of metal fingers arranged around the circumference of the stator stack. The fingers extend radially between the individual conductors being threaded into the stator stack. 
     On the crown-side of the stator stack, the metal fingers assist in maintaining the desired position of the conductors during the assembly and the twisting operation. On the twist-side of the stator stack the metal fingers assist in maintaining the desired position of the conductors and provide guides for twisting the individual conductors during the twist operation. After assembly is complete the metal fingers are removed, leaving space between the conductors. The space, previously occupied by the metal fingers, electrically isolates the conductors from the stator stack and from one another as required for operation of the stator assembly. 
     SUMMARY OF THE INVENTION 
     A stator assembly includes a stator stack and a plurality of conductors extending from the stator stack. An isolator ring is located on the stator stack. The isolator ring includes a plurality of inwardly protruding fingers. Each of the inwardly protruding fingers is located between respective ones of the plurality of conductors. 
     The isolator ring includes a generally annularly shaped main body and the plurality of inwardly protruding fingers. The isolator ring also includes a plurality of attachment features to secure the main body of the isolator ring to the stator assembly. The plurality of attachment features are spaced about the circumference of the main body. 
     A method of assembling the stator assembly includes securing at least one assembly ring to the stator stack and threading the plurality of conductors through the stator stack such that each of the plurality of fingers on the assembly ring is located between respective ones of the plurality of conductors. 
     The above features and advantages and other features and advantages of the present invention are readily apparent from the following detailed description of the best modes for carrying out the invention when taken in connection with the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a partial schematic perspective illustration of a crown-side of a stator assembly; 
         FIG. 2  is an enlarged schematic side-view illustration of a portion of a crown-side of the stator assembly of  FIG. 1  showing a portion of an isolator/assembly ring and a plurality of conductors; 
         FIG. 3  is a partial schematic perspective illustration of a twist-side of the stator assembly of  FIG. 1 ; 
         FIG. 4  is a enlarged schematic illustration of a portion of a twist-side of the stator assembly of  FIG. 1  and  FIG. 3  showing a portion of an isolator/assembly ring and a plurality of conductors; 
         FIG. 5  is a partial schematic cross-sectional illustration of a first embodiment of an attachment feature for the isolator/assembly ring for the stator assembly of  FIG. 1  and  FIG. 3 ; and 
         FIG. 6  is a partial schematic cross-sectional illustration of a second embodiment of an attachment feature for the isolator/assembly ring for the stator assembly of  FIG. 1  and  FIG. 3 . 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Referring to the Figures, wherein like reference numbers refer to the same or similar components throughout the several views,  FIG. 1  schematically illustrates a partial view of a stator assembly  10  for an electric motor (not shown). The stator assembly  10  includes a stator stack  12 . The stator stack  12  defines a plurality of slots  14  (shown in  FIG. 2 ) which extend entirely through the stator stack  12 . A plurality of conductors  16  are threaded through the slots  14  from the crown-side  18  of the stator stack  12 . The conductors  16  extend from the crown side  18  of the stator stack  12 . The conductors  16  also extend from the slots  14  on a twist-side  20  (shown in  FIG. 3 ) of the stator stack  12 . An isolator ring  22 A is assembled on the stator stack  12  prior to insertion of the conductors  16 . The isolator ring  22 A electrically isolates the conductors  16  from one another and from the ends of the stator stack  12 . 
     Because the isolator ring  22 A may be assembled on the stator stack  12  prior to insertion of the conductors  16  the isolator ring  22 A may also act as an assembly ring to assist in assembly of the stator assembly  10 , as described in further detail below. The isolator ring  22 A may act as an isolating device, as an assembly device, or as a combination of both an isolating and assembly device and will hereinafter be referred to as an isolator/assembly ring  22 A to indicate the possible applications of the isolator/assembly ring  22 A. One skilled in the art would be able to determine the particular intent and application on the isolator/assembly ring  22 A for a particular stator assembly  10 . 
     The isolator/assembly ring  22 A has a generally annular shape and is made from an electrically isolating material, such as plastic. The isolator/assembly ring  22 A may be manufactured by injection molding. Alternately, the isolator/assembly ring  22 A may be manufactured from a conductive material and coated in an electrically isolating material. The isolator/assembly ring  22 A has a plurality of fingers  24 . The fingers  24  protrude radially inward from a main body  26  of the isolator/assembly ring  22 A. Additionally, attachment features  28  are located around the circumference of the isolator/assembly ring  22 A for securing the isolator/assembly ring  22 A to the stator stack  12 . The attachment features  28  may include various locations about the circumference of the main body  26  for adhering the isolator/assembly ring  22 A to the stator stack  12 . 
       FIG. 2  is an enlarged schematic side-view illustration of a portion of the crown-side  18  of the stator assembly  10  showing a portion of the isolator/assembly ring  22 A looking outward from the center of the stator stack  12  and the isolator/assembly ring  22 A. The conductors  16  extend from the slots  14  in the stator stack  12 . Slot liners  30  are located on each side of the slot  14  between the conductors  16  and the stator stack  12 . The slot liners  30  isolate the conductors  16  from the stator stack  12 . 
     The fingers  24  of the isolator/assembly ring  22 A extend radially inward from the main body  26  (shown in  FIG. 1 ) of the isolator/assembly ring  22 A. The isolator/assembly ring  22 A rests on an end  32  of the stator stack  12  on the crown-side  18  of the stator assembly  10 . 
     In the embodiment shown, the isolator/assembly ring  22 A has generally U-shaped cross-section. The cross-sectional shape of the fingers  24  may vary from one application to another depending on the application for the isolator/assembly ring  22 A and the specific stator assembly  10  the isolator/assembly ring  22 A is to be used with. Although the U-shape reduces the mass of the isolator/assembly ring  22 A the isolator/assembly ring  22 A may be solid or have other cross-sectional shapes according to the specific stator assembly  10 . One skilled in the art would be able to determined the desired cross-sectional shape of the isolator/assembly ring  22 A for a stator assembly  10 . 
     The fingers  24  include sides  34  which each define an angled portion  36 . The angled portion  36  assists in guiding the conductors  16  to the desired position between each of the fingers  24 . Additionally, the angled portion  36  assists in guiding and in preventing damage to the slot liners  30  during assembly. 
     The sides  34  of the fingers  24  also each define a chamfer  40 . The chamfer  40  is located at the same axial position on the stator stack  12  as the slot liners  30 . As mentioned above, the isolator/assembly ring  22 A is secured to the stator stack  12  prior to threading of the conductors  16  and the slot liners  30  into the stator stack  12 . Thus, the chamfer  40  aligns the slot liners  30  in the desired axial position relative to the stator stack  12 . The chamfer  40  also protects the slot liners  30  during assembly of the stator assembly  10  and reduces the stress placed on the ends of slot liners  30  from the conductors  16 . 
     The embodiment described above is for a stator assembly  10  having axially inserted conductors  16 . However, the isolator/assembly ring  22  may also be utilized with radially inserted conductors  16  as well. 
     The sides  34  of the fingers  24  also each define a curved portion  38 . The curved portion  38  corresponds to a curve  42  on the conductors  16 . On the crown-side  18  of the stator assembly  10 , the curved portion  38  assists in aligning the conductors  16  during assembly and preventing movement, i.e. pulling, of the conductors  16  during the twist operation. 
       FIG. 3  is a partial schematic perspective illustration of the stator assembly  10  from the twist-side  20  of the of the stator assembly  10 . Similar to the crown-side  18  (shown in  FIG. 1 ), the conductors  16  extend from the slots  14  (shown in  FIG. 2 ) defined by the stator stack  12 . Another isolator/assembly ring  22 B is assembled on the stator stack  12  prior to insertion of the plurality of conductors  16  from the crown-side  18  of the stator stack  12 . The isolator/assembly ring  22 B may be a common shape with the isolator/assembly ring  22 A that is located on the crown side  18  of the stator stack  12 . 
     The isolator/assembly ring  22 B has a generally annular shape and is made from an electrically isolating material, such as plastic. The isolator/assembly ring  22 B may be injection molded. The fingers  24  protrude radially inward from the main body  26  of the isolator/assembly ring  22 B. The attachment features  28  are located around the circumference of the isolator/assembly ring  22 B for securing the isolator/assembly ring  22 B to the stator stack  12 . The attachment features  28  may include various locations about the circumference of the main body  26  for adhering the isolator/assembly ring  22 B to the stator stack  12 . 
       FIG. 4  is an enlarged schematic side-view illustration of a portion of the twist-side  20  of the stator assembly  10  showing a portion of the isolator/assembly ring  22 B looking inward toward the center of the stator stack  12  and the isolator/assembly ring  22 B. A plurality of conductors  16  extend from slots  14  in the stator stack  12 . The fingers  24  of the isolator/assembly ring  22 B extend radially inward from the main body  26  of the isolator/assembly ring  22 B. The isolator/assembly ring  22 B is secured to the stator stack  12  on the twist-side  20  of the stator assembly  10 . 
     The fingers  24  include sides  34  (shown in  FIG. 2 ) which each define a curved portion  38 . On the twist-side  20  of the stator assembly  10 , the curved portion  38  assists in guiding the conductors  16  during the twist operation. Additionally, the isolator/assembly ring  22 B assists in preventing the conductors  16  from being pulled into the stator stack  12  during the twist operation, which often leads to tearing of the slot liners  30  (shown in  FIG. 2 ). 
     The curved portion  38  corresponds to a desired curve  42  on the conductors  16 . That is, the radius of the curved portion  38  corresponds to the desired radius of a curve  42  on the conductors  16  once the twist operation is complete. The curved portion  38  assists in maintaining a consistent curve  42  on the plurality of conductors  16 . Because the isolator/assembly ring  22 B is an electrical isolator, the isolator/assembly ring  22 B can remain with the stator assembly  10  once the assembly is complete and not effect operation of the stator assembly  10 . Therefore, the isolator/assembly ring  22  assists in assembly of the stator assembly  10  to reduce manufacturing time and costs. 
       FIG. 5  is a cross-sectional view of the isolator/assembly ring  22  mounted on the stator stack  12  illustrating a first embodiment of the attachment feature  28 . The attachment feature  28  includes a tab  44  which protrudes radially outward from the main body  26  of the isolator/assembly ring  22 . A pin  46  extends from the tab  44 . An attachment hole  48  is defined by the stator stack  12  to receive the pin  46 . The attachment hole  48  may be formed, such as during stamping of the stator stack  12 , for receiving a pin  46  for each attachment point. The attachment hole  48  may be specially formed for the pin  46  or the pin  46  may be designed to fit into a pre-existing hole in the stator stack  12 . Multiple attachment holes  48  may be located about the circumference of the stator stack  12 . 
     The pin  46  defines an enlarged ridged portion  50  to assist in retaining the pin  46  within the attachment hole  48  and assist in securing the isolator/assembly ring  22  to the stator stack  12  during assembly of the stator assembly  10 . The enlarged ridged portion  50  has an interference fit with the stator stack  12 . Following assembly of the stator assembly  10  including the twist operation, the isolator/assembly ring  22  is also secured to the stator stack  12  by the conductors  16 . 
     The embodiment described above is for a stator assembly  10  having axially inserted conductors  16  using the isolator/assembly ring  22 . However, the isolator/assembly ring  22  may also be utilized in isolating and assembling conductors  16  within a stator assembly  10  having radially inserted conductors  16 . 
       FIG. 6  is a cross-sectional view of the isolator/assembly ring  22  mounted on the stator stack  12  illustrating a second embodiment of the attachment feature  128 . The attachment feature  128  includes a tab  144  which protrudes radially outward from the main body  26  of the isolator/assembly ring  22 . A pin  146  extends from the tab  144 . An attachment hole  148  is defined by the stator stack  12  to receive the pin  146 . The attachment hole  148  may be formed for receiving the pin  146  or the pin  146  may be designed to fit into a pre-existing hole formed in the stator stack  12 . Multiple attachment holes  148  may be located about the circumference of the stator stack  12 . 
     The pin  146  has a tapered edge  152  to assist in aligning the pin  146  within the attachment hole  148  and to assist in securing the isolator/assembly ring  22  to the stator stack  12  during assembly of the stator assembly  10 . Following assembly of the stator assembly  10  including the twist operation, the isolator/assembly ring  22  is also secured to the stator stack  12  by the conductors  16 . 
     Referring to  FIG. 5  and  FIG. 6 , the attachment features  28  and the attachment features  128  may both be included on the same isolator/assembly ring  22  in an alternating arrangement. 
     While the best modes for carrying out the invention have been described in detail, those familiar with the art to which this invention relates will recognize various alternative designs and embodiments for practicing the invention within the scope of the appended claims.