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You are an expert at summarizing long articles. Proceed to summarize the following text: 
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    The present patent application is a continuation of U.S. patent application Ser. No. 13/452,380, titled “STRAIGHT TAPER DIPPER” and filed Apr. 20, 2012 by Dan Feld et al., which claims priority to U.S. Provisional Patent Application No. 61/481,615, titled “STRAIGHT TAPER DIPPER” filed May 2, 2011 by Dan Feld et al., the entire contents of all of which are incorporated by reference herein. 
     
    
     FIELD 
       [0002]    The present invention generally relates to dippers for surface mining. 
       SUMMARY 
       [0003]    Typical power shovels or excavators use a bucket or dipper assembly to scoop earthen material from horizontal or vertical faces. A conventional power shovel has a boom, and the dipper is mounted on the boom via a crowd mechanism. The crowd mechanism includes a crowd pinion on the boom, and crowd rack as part of the dipper handle which pivots about the pinion and which moves translationally along the pinion. The dipper is mounted on the end of the handle. The bucket or dipper is normally provided with sharp teeth to provide a digging action against the surface being worked and further includes a cavity for collecting the material so removed. Once the earthen material is received within the dipper, the dipper is typically moved to another location for transfer of the material. The material is usually discharged into a dump truck, onto a conveyor, or merely onto a pile. 
         [0004]    In one independent embodiment, a dipper has an inlet and an outlet and includes a front wall and an opposite back wall extending between the inlet and the outlet. A first reference plane extends from the inlet to the outlet and is positioned between the front wall and the back wall. The front wall may have a substantially linear inner surface and may be arranged relative to the first reference plane at an angle of at least 0 degrees and no more than 3 degrees. The dipper further includes two side walls connected between the front wall and the back wall and extending between the inlet and the outlet. A second reference plane extends from the inlet to the outlet and is positioned between the side walls. A lip is coupled to at least the front wall and extends outwardly from the inlet. The back wall may taper outwardly relative to the first reference plane from the inlet toward the outlet at an angle greater than 0 degrees and no more than 30 degrees, and each of the side walls may taper outwardly relative to the second reference plane from the inlet toward the outlet at an angle greater than 0 degrees and no more than 30 degrees. 
         [0005]    In another independent embodiment of a dipper, each of the side walls of the dipper may taper outwardly relative to the second reference plane from the inlet toward the outlet at an angle greater than 0 degrees and no more than 30 degrees. The lip has opposite side surfaces, and each of the side surfaces of the lip may taper outwardly relative to the second reference plane from the inlet toward the outer surface at an angle greater than 0 degrees and no more than 30 degrees. 
         [0006]    In yet another independent embodiment of the dipper, an inlet reference plane is defined at the inlet, and a front wall reference plane extends from the inlet to the outlet and is positioned between the front wall and the back wall. The front wall may have a substantially linear inner surface and be arranged relative to the front wall reference plane at an angle of at least 0 degrees and no more than 3 degrees. The inlet has an inlet area in the inlet reference plane, and the outlet has an outlet area in an outlet reference plane substantially parallel to the inlet reference plane. The front wall, the back wall, and the two side walls may be arranged such that the outlet area is at least 3 percent and no more than 25 percent greater than the inlet area. 
         [0007]    Other independent aspects of the invention will become apparent by consideration of the detailed description and accompanying drawings. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0008]      FIG. 1  is a perspective view of a dipper according to the invention. 
           [0009]      FIG. 2  is a top view of the dipper shown in  FIG. 1 . 
           [0010]      FIG. 3  is a right side view of the dipper shown in  FIG. 1 . 
           [0011]      FIG. 4  is a front view of the dipper shown in  FIG. 1 . 
           [0012]      FIG. 5  is a section view taken along line  5 - 5  in  FIG. 3 . 
           [0013]      FIG. 6  is a section view taken along line  6 - 6  in  FIG. 4 . 
           [0014]      FIG. 7  is a representative view comparing an inlet area to an outlet area of the dipper shown in  FIG. 1 . 
       
    
    
     DETAILED DESCRIPTION 
       [0015]    Before any independent embodiments of the invention are explained in detail, it is to be understood that the invention is not limited in its application to the details of construction and the arrangement of components set forth in the following description or illustrated in the following drawings. The invention is capable of other independent embodiments and of being practiced or of being carried out in various ways. 
         [0016]      FIG. 1  shows a dipper  10  for use with a power shovel or another piece of mining equipment. The dipper  10  includes a front wall  14 , a back wall  18 , a left side wall  22 , and a right side wall  24  and defines an inlet  28  and an outlet  32 . A lip  36  is coupled to the front wall  14 , the left side wall  22 , and the right side wall  24  and extends forward of the front wall  14 . A heel  38  of the dipper is defined on the front wall  14  adjacent the outlet  32  and includes a latch portion  39  (see  FIGS. 2-6 ) for receiving the latch of a dipper door (not shown).  FIGS. 2-4  show alternate views of the dipper  10 . 
         [0017]      FIGS. 1-6  show an x-axis in a side-to-side direction, a y-axis in an inlet-to-outlet direction, and a z-axis in a front-to-back direction. These directions will be referenced throughout this description for the purpose of illustration and should not be regarded as limiting. 
         [0018]    With reference to  FIG. 5 , a side wall reference plane  40  is defined in the y-z plane and intersects the front wall  14  and the back wall  18  (e.g., in the center). The left side wall  22  defines (see  FIG. 2 ) a planar portion and two curved portions that connect the planar portion of the left side wall  22  to the front wall  14  and the back wall  18 . As shown in  FIG. 5 , the left side wall  22  is tapered or skewed outwardly from the inlet  28  to the outlet  32  and defines a left wall plane  44  that parallels the planar portion and that is angled with respect to the side wall reference plane  40  at a left wall angle  46 . The left wall plane  44  may be angled with respect to the side wall reference plane  40  at between about zero degrees and about thirty degrees (0°≦x≦30°). In some embodiments, the left wall plane  44  may be angled with respect to the side wall reference plane  40  at between about one degree and about ten degrees (1°≦x≦10°). In the illustrated embodiment, the left wall angle  46  is about three degrees)(3°). 
         [0019]    The right side wall  24  defines (see  FIG. 2 ) a planar portion and two curved portions that connect the planar portion of the right side wall  24  to the front wall  14  and the back wall  18 . As shown in  FIG. 5 , the right side wall  24  is tapered or skewed outwardly from the inlet  28  to the outlet  32  and defines a right wall plane  48  that parallels the planar portion and that is angled with respect to the side wall reference plane  40  at a right wall angle  52 . The right wall plane  48  may be angled with respect to the side wall reference plane  40  at between about zero degrees and about thirty degrees (0°≦x≦30°). In some embodiments, the right wall plane  48  may be angled with respect to the side wall reference plane  40  at between about one degree and about ten degrees (1°≦x≦10°). In the illustrated embodiment, the right wall angle  52  is about three degrees)(3°). 
         [0020]      FIG. 5  shows the lip  36  coupled to the front wall  14 , the left side wall  22 , and the right side wall  24 . The lip  36  defines an outer dimension  56  along the x-axis, a left lip plane  60  running parallel to the left side of the lip  36 , and a right lip plane  68  running parallel to the right side of the lip  36 . 
         [0021]    The left lip plane  60  is arranged at a left lip angle  64  with respect to the side wall reference plane  40 . The left lip angle  64  may be between about zero degrees and about thirty degrees (0°≦x≦30°). In some embodiments, the left lip angle  64  is between about one degree and about ten degrees (1°≦x≦10°). In the illustrated embodiment, the left lip angle  64  is about zero degrees)(0°). 
         [0022]    The right lip plane  68  is arranged at a right lip angle  72  with respect to the side wall reference plane  40 . The right lip angle  72  may be between about zero degrees and about thirty degrees (0°≦x≦30°). In some embodiments, the right lip angle  72  is between about one degree and about ten degrees (1°≦x≦10°). In the illustrated embodiment, the right lip angle  72  is about zero degrees)(0°). 
         [0023]    Further, in some embodiments, the lip  36  may be arranged with the outer dimension  56  of the lip  36  larger than a comparative outer dimension at the outlet  32  of the dipper  10  so that the outlet  32  or heel  38  of the dipper  10  does not plow or rake though the material being mined, which would increase the wear on the dipper  10  and increase the force required to move the dipper  10  through the material. The left and right lip angles  64 ,  72  affect the outer dimension  56  and can be manipulated to provide clearance for the outlet  32 , as desired. 
         [0024]    With respect to  FIG. 6 , a floor reference plane  76  is defined in the x-y plane. A front/back wall reference plane  80  is positioned between the front wall  14  and the back wall  18 , and angled with respect to the floor reference plane  76  at about ten degrees)(10°). 
         [0025]    The front wall  14  defines a straight surface from the inlet  28  to the outlet  32  (as shown in  FIG. 6 ). In the x-axis (generally), the front wall  14  is curved (as shown in  FIG. 2 ). In the illustrated construction, throughout the curved portion of the front wall  14 , the line from the inlet  28  to the outlet  32  is substantially straight, as shown in  FIG. 6 . A front wall line  84  is arranged relative to the front/back wall reference plane  80  at a front wall angle  88 . The front wall angle  88  may be greater than or equal to zero degrees (x≧0°). In some embodiments, the front wall angle  88  is between about zero degrees and about three degrees (0°≦x≦3°). In the illustrated embodiment, the front wall angle  88  is about zero degrees)(0°). 
         [0026]    In the illustrated embodiment (see  FIG. 6 ), the lip  36  is in line or parallel with the front wall  14 . In other embodiments, the lip  36  could be skewed or angled relative to the front wall  14 , as desired. 
         [0027]    The back wall  18  defines (see  FIG. 2 ) a planar portion, and two curved portions that connect the back wall  18  to the left side wall  22  and the right side wall  24 . A straight surface is defined from the inlet  28  to the outlet  32  (as shown in  FIG. 6 ). A back wall line  92  is angled or skewed relative to the front/back wall reference plane  80  at a back wall angle  96 . The back wall angle  96  may be between about zero degrees and about thirty degrees (0°≦x≦30°). In some embodiments, the back wall angle  96  is between about one degree and about ten degrees (1°≦x≦10°). In the illustrated embodiment, the back wall angle  96  is about five degrees)(5°. 
         [0028]    With continued reference to  FIG. 6 , an inlet plane  100  is defined generally perpendicular to the floor reference plane  76  at the inlet  28 . An inlet area  104  for the dipper  10  is defined in the inlet plane  100 . That is to say, the front wall  14 , the back wall  18 , the left side wall  22 , and the right side wall  26  define an inlet perimeter in the inlet plane  100 , and the area within the inlet perimeter defines the inlet area  104  in the inlet plane  100 . 
         [0029]    An outlet plane  108  is defined parallel to the inlet plane  100  (and generally perpendicular to the floor reference plane  76 ) at the outlet  32 . An outlet area  112  for the dipper  10  (e.g., at the door) is defined in the outlet plane  108 . That is to say, the front wall  14 , the back wall  18 , the left side wall  22 , and the right side wall  26  define an outlet perimeter in the outlet plane  108 , and the area within the outlet perimeter defines the outlet area  112  in the outlet plane  108 . 
         [0030]    As a result of arrangement of the front wall  14 , the back wall  18 , the left side wall  22 , and the right side wall  24 , the outlet area  112  is larger than the inlet area  104  (see  FIG. 7 ). The outlet area  112  may be between about three percent and about twenty-five percent (3%≦x≦25%) larger than the inlet area  104 . In some embodiments, the outlet area  112  may be more than about four percent (4%) larger than the inlet area  104 . In other embodiments, the outlet area  112  may be about eight percent to about nine percent (8%≦x≦9%) larger than the inlet area  104 . In the illustrated embodiment, the outlet area  112  is about ten percent (10%) larger than the inlet area  104 . 
         [0031]    The inventive arrangement provides a dipper  10  that improves performance in digging. For example, the dipper  10  may have improved fill, dump and/or full/dump cycle time. The dipper  10  may have reduced drag during digging. 
         [0032]    The dipper  10  may be advantageous for oil sands digging. Oil sands expand after being unearthed. The increased volume of the dipper  10  toward the outlet  32  of the dipper  10  allows the oil sands to expand within the dipper  10  while a digging action is occurring, and the oil sands will not be compacted within the dipper  10 . Typically, oil sands expand about four percent (4%) in volume during a digging action (e.g., 30 seconds). The straight tapered design of the dipper  10  allows expansion without compaction and/or improves digging characteristics and efficiency. The dipper  10  may also be used to remove/mine other materials, such as, for example, copper, iron ore, overburden material, etc.

Summary:
A dipper having an inlet and an outlet. The dipper includes a front wall and an opposite back wall extending between the inlet and the outlet. The front wall has a substantially linear inner surface between the inlet and the outlet. The dipper further includes two side walls connected between the front wall and the back wall and extending between the inlet and the outlet. Further, the dipper has a lip coupled to the front wall and extending outwardly from the inlet in a direction away from the outlet, the lip having a lip inner surface arranged generally parallel with the substantially linear inner surface of the front wall.