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CROSS REFERENCE TO RELATED APPLICATIONS 
       [0001]    This is a continuation-in-part of application Ser. No. 13/647,105, filed on Oct. 8, 2012. 
     
    
     TECHNICAL FIELD 
       [0002]    This disclosure relates generally to a quick coupling device for a tool/implement for a machine and, more particularly, to a quick coupling device that may be actuated by the operator from the cab of the machine. 
       BACKGROUND 
       [0003]    Machines frequently have lift arms with tools or implements disposed at the ends of the lift arms. The tools or implements may include as buckets, blades and the like. To simplify and expedite the exchanging or replacement of such tools, the lift arms are typically equipped with an attachment frame that includes coupling devices for quickly coupling and decoupling the various implements from the frame. Some of these coupling devices may also be power-operated to reduce the necessity for manual intervention and for ease of operation. Further, some coupling devices may be actuated from inside the cab of the machine. 
         [0004]    In U.S. Pat. No. 6,866,467, a hydraulically-actuated quick coupling device includes an attachment frame. A pair of latch members is disposed at each end of the attachment frame and the latch members are movable between a latched position and an unlatched position. A link has first and second end portions with the first end portion of the link connected to the latch member. A pivot member has first and second end portions and a central portion with the first end portion pivotally connected on the attachment frame and the second end portion pivotally connected on the second end portion of the link. A cylinder has a head end connected to the attachment frame and a rod end connected to the central portion of the pivot member. The cylinder is operable for moving the latch member between the disengaged and engaged positions. 
         [0005]    A low amount of force is required when the tool and coupler are very clean, but in dirty conditions or with a lack of scheduled lubrication or maintenance, the linkage can stick or jam, causing the operator to have to use a pry bar to force the linkage loose and engage/disengage the work tool. 
       SUMMARY 
       [0006]    In one aspect, an electrically actuated coupling device is disclosed. The disclosed device may include a frame having a right end and a left end. The disclosed device may also include an electric motor with a drive shaft extending between the right and left ends of the frame. The motor may be used to cause the shaft to expand outwards towards the right and left ends of the frame simultaneously and to retract the shaft inwards away from the left and right ends of the frame simultaneously. The right end of the frame may include a right guide for slidably receiving a right latch. The left end of the frame may include a left guide for slidably receiving a left latch. The right latch may be pivotally coupled to a right spring. The right spring may pivotally couple the right latch to a right lever at a first pivot point. The right lever may be pivotally connected to the frame at a second pivot point. The right lever may also be pivotally connected to the shaft at a third pivot point. Similarly, the left latch may be pivotally coupled to a left spring. The left spring may pivotally couple the left latch to a left lever at a fourth pivot point. The left lever may also be pivotally connected to the frame at a fifth pivot point. The left lever may also be pivotally connected to the shaft at a sixth pivot point. Further, an angle between a first line extending through the first and second pivot points and a second line extending through the second and third pivot points may range from greater than 20° to less than 35°, and, similarly, an angle between a third line extending through the fourth and fifth pivot points and a fourth line extending through the fifth and sixth pivot points may also ranges from greater than 20° to less than 35°. 
         [0007]    In another aspect, a machine is disclosed that may include a cab. The machine may also include right and left lift arms that may be coupled to a frame having a right end and a left end. The machine may also include an electric motor with a drive shaft that extends between the right and left ends of the frame. The motor may cause the shaft to expand outwards towards the right and left ends of the frame simultaneously and retract inwards away from the left and right ends of the frame simultaneously. The right end of the frame may include a right guide for slidably receiving a right latch and the left end of the frame may include a left guide for slidably receiving a left latch. The right latch may be pivotally coupled to a right spring. The right spring may pivotally couple the right latch to a right lever at a first pivot point. The right lever may be pivotally connected to the frame at a second pivot point. The right lever may also be pivotally connected to the shaft at a third pivot point. The left latch may also be pivotally coupled to a left spring. The left spring may pivotally couple the left latch to a left lever at a fourth pivot point. The left lever may be pivotally connected to the frame at a fifth pivot point and the left lever may be pivotally connected to the shaft at a sixth pivot point. The machine may also include a control switch for controlling the motor wherein the control switch is disposed inside the cab. Further, the second and third pivot points are separated by a first length and the first and second pivot points are separated by a second length. The first length is greater than the second length. The fifth and sixth pivot points are separated by a third length and the fourth and fifth pivot points are separated by a fourth length. The third length is greater than the fourth length. A ratio of the first length to the second length ranges from greater than 1.31 to less than 1.75, and a ratio of the third length to the fourth length ranges from greater than 1.31 to less than 1.75. 
         [0008]    In another aspect, a method for coupling and decoupling a tool to and from a machine having right and left lift arms is also disclosed. The method may include coupling a frame having a right end and a left end to the right and left lift arms. The frame may support an electric motor with a drive shaft extending between the right and left ends of the frame. The right end of the frame may include a right guide for slidably receiving a right latch and the left end of the frame may include a left guide for slidably receiving a left latch. The right latch may be pivotally coupled to a right spring and the right spring may pivotally couple the right latch to a right lever at a first pivot point. The right lever may also be pivotally connected to the frame at a second pivot point and to the shaft at a third pivot point. The left latch may be pivotally coupled to a left spring. The left spring may pivotally couple the left latch to a left lever at a fourth pivot point. The left lever may be pivotally connected to the frame at a fifth pivot point and to the shaft at a sixth pivot point. The method may include aligning the right and left latches with right and left openings in the tool. The method may further include activating the motor to expand the shaft outwards towards the right and left ends of the frame thereby causing the right and left latches to be received in the right and left openings of the tool. Further, the method may also include activating the motor to retract the shaft inwards away from the right and left ends of the frame thereby causing right and left latches to be withdrawn from right and left openings of the tool. Further, an angle between a second line extending through the second and third pivot points and an axis of the shaft ranges from about 13° to about 18° and an angle between a fourth line extending through the fifth and sixth pivot points and an axis of the shaft ranges from about 13° to about 18°. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0009]      FIG. 1  is a perspective view of a machine coupled to a bucket. 
           [0010]      FIG. 2  is a plan view of a disclosed coupling device, with the latches in an intermediate position. 
           [0011]      FIG. 3  is a perspective view of the disclosed coupling device, particularly illustrating the latches in an intermediate position. 
           [0012]      FIG. 4  is a partial perspective view of the disclosed coupling device, particularly illustrating the right latch in an intermediate position. 
           [0013]      FIG. 5  is a partial plan view of the disclosed coupling device, particularly illustrating the right latch in an intermediate position. 
           [0014]      FIG. 6  is a partial plan view of the disclosed coupling device, particularly illustrating the left latch in an intermediate position. 
           [0015]      FIGS. 7-8  are partial plan views showing the left latches and associated linkages in retracted and extended positions respectively. 
           [0016]      FIG. 9  is another partial plan view of the disclosed coupling device, particularly illustrating the right latch in a retracted position and an angle defined by a line drawn through the first and second pivot points and a line drawn through the second and third pivot points as well as an angle defined by a line drawn through the third and second pivot points and an axis of the shaft; and 
           [0017]      FIG. 10  is a plan view of the left lever of the disclosed coupling device. 
       
    
    
     DESCRIPTION 
       [0018]      FIG. 1  illustrates a machine  10  that may be equipped with the quick coupling device  11  shown in  FIG. 2 . In the example shown, the machine  10  is a skid steer loader. The machine  10  includes a frame  16  that is supported above ground by a plurality of ground engaging elements  13 . While the ground engaging elements  13  are wheels, in the example shown, this disclosure is also applicable to track-type machines as well. The machine  10  also includes a pair of spaced apart lift arms  14  and an implement  15 , in the form of a bucket that may be coupled to the lift arms  14 . The machine  10  may be used with a variety of implements, other than the bucket shown at  15 . To quickly and easily disconnect or decouple the implement  15  from the machine  10 , it would be advantageous to include a quick coupling/decoupling device like that shown at  11  in  FIG. 2 . 
         [0019]    Turning to  FIG. 2 , the coupling device  11  includes a frame  16  with a right end  17  and a left end  18 . The frame supports a motor  19  that drives an expandable and retractable shaft assembly  21 . As will be apparent to those skilled in the art, the motor  19 /shaft assembly  21  combination may be replaced by a hydraulic cylinder or another type of actuator and extendable member. The shaft assembly  21  includes a right end  22  and a left end  23 . The right and left end  22 ,  23  of the shaft assembly  21  are coupled to right and left levers  24 ,  25  respectively. As will be explained in greater detail below, the right and left levers  24 ,  25  pivot when the shaft assembly  21  is expanded or retracted. For example, when the shaft assembly  21  is retracted, upward bias is imposed upon the right and left springs  26 ,  27  respectively. The right and left springs  26 ,  27 , as explained in greater detail below, are coupled to right and left latches  28 ,  29  at the pivot points  20 ,  30  respectively. The right and left latches  28 ,  29  are used to couple the frame  16  to the implement  15  as shown in  FIG. 1 . Also shown in  FIG. 2  are right and left guides  31 ,  32  which slidably receive the latches  28 ,  29  respectively. 
         [0020]    Turning to  FIG. 3 , the right and left latches  28  are also shown in extended positions. To retract the latches  28 ,  29 , the shaft assembly  21  is retracted inwardly, that is, both the right end  22  and the left end  23  are retracted inwards or away from the right and left ends  17 ,  18  of the frame  16 . The right spring  26  may be pivotally coupled to the lever  24  at a first pivot point  33 . The right lever  24  may be pivotally coupled to the right end  17  of the frame  16  at a second pivot point  34 . Further, the right lever  24  may be pivotally coupled to the right end  22  of the shaft assembly  21  at a third pivot point  35 . Similarly, the left lever  25  may be pivotally coupled to the left spring at a fourth pivot point  36 . The left lever  25  may also be pivotally coupled to the left end  18  of the frame  16  at a fifth pivot point  37 , and the left lever  25  may be pivotally coupled to the left end  23  of the shaft assembly  21  at a sixth pivot point  38 . 
         [0021]    Turning to  FIG. 4 , the right lever  24  includes a front plate  41  coupled to a rear plate  42 . The plates  41 ,  42  may be welded together, connected together in some other fashion or may be a unitary structure. As shown in  FIG. 4 , the right end  22  of the shaft assembly  21  has been moved to the left in the orientation of  FIG. 4  thereby biasing the third pivot point  35  to the left. This causes the right lever  24  to pivot about the second pivot point  34  in a downward direction as indicated by the arrow  43 . Movement of the right lever  24  in the direction of the arrow  43  causes the first pivot point  33  to move downward thereby compressing the right spring  26 . The right spring  26  which is pivotally coupled to the right latch  28  at the pivot point  20  presses the right latch  28  downward through the right guide  31  to the latching or coupling position shown in  FIG. 4 . 
         [0022]    A plan view of the position shown in  FIG. 4  is also shown in  FIG. 5  and a plan view of the left side  18  of the frame in the coupled or extended position is shown in  FIG. 6 . Also shown in  FIGS. 5-6  are shaped opening  44 ,  57  which can receive a tool in the event the coupling device  11  becomes stuck or jammed. Further,  FIGS. 5-6  also illustrates the outwardly extending tabs  45 ,  47  of the front and rear plates  41 ,  42  and  141 ,  142  of the right and left levers  24 ,  25  respectively. The tabs  45 ,  47  are visible to the operator in the cab  46  of the machine  10  so the operator has a visual indication that the coupling device  11  is in the coupled or latched position shown in  FIGS. 4-6 . As shown in  FIG. 9 , the tab  45  is obscured and not clearly visible to the operator, thereby indicating to the operator that the coupling device  11  is in the decoupled or detached position shown in  FIG. 3 . 
         [0023]      FIGS. 7-8  illustrate the retraction and extension of the left latch  29 , which may operate in the same fashion as the right latch  28 . In  FIG. 7 , the shaft assembly  21  has been retracted, or moved to the left in the orientation of  FIGS. 7-8 . The pivot point  38  of the lever  25  has been moved to the left and upwards, thereby causing the pivot point  36  to pull upward on the spring  27 , which causes the left latch  29  to retract upward into the guide  32 . Conversely, in  FIG. 8 , the shaft assembly  21  has been extended, or moved to the right in the orientation of  FIGS. 7-8 . The pivot point  38  of the lever  25  has been moved to the right and downwards, thereby causing the pivot point  36  to bias the spring  27  downwards, which causes the left latch  29  to outward from the guide  32 . 
         [0024]      FIG. 9  illustrates geometrically the improved performance of the coupling device  11 . Specifically, the lever  24  includes three pivot points including the first pivot point  33 , which pivotally couples the lever  24  to the spring  26 . The lever  24  also includes a second pivot point  34  which may pivotally couple the lever  24  to the frame  16 . Finally, the lever  24  includes a third pivot point  35  which may pivotally couple the lever  24  to the right end  22  of the shaft assembly  21 . It has been found that an angle  51  defined by a first line  52  that extends through the first pivot point  33  and the second pivot point  34  and a second line  53  that extends through the second pivot point  34  and the third pivot point  35  may be greater than 20° and less than 35° for optimal operation. While the angle  51  may range from greater than 20° to less than 35°, a narrower range of from about 27° to about 31° may provide even better performance. In one example, the angle  51  may be about 29°. Similarly, another angle  54  has surprisingly been found to have an effect on the performance on the coupling device  11 . The angle  54  is defined by the line  53  that extends through the second and third pivot points  34 ,  35  and the axis  55  of the shaft assembly  21 . The angle  54  may range from greater than 10° to less than 25°. While the angle  54  may range from greater than 10° to less than 25°, a narrower range of from about 13° to about 18° may provide a more optimal performance. In one example, the angle  54  is about 16°. 
         [0025]    The dimensions of the levers  24 ,  25  have also been surprisingly found to be useful in optimizing the performance of the coupling device  11 . The left lever  25  is illustrated in  FIG. 7 . It also includes a shaped opening  57  for receiving a tool in the event the coupling device  11  becomes stuck or jammed. The fourth, fifth and sixth pivot points are shown at  36 ,  37 ,  38  respectively and they correspond to the first, second and third pivot points  33 ,  34 ,  35  of the right lever  24 . The distance between the fourth and fifth pivot points is shown at  61 . The distance between the fifth and sixth pivot points is shown at  62 . It has been surprisingly found that the ratio of these two distances affects the performance of the coupling device  11 . First, the length or length  62  is greater than the length or length  61 . Further, a ratio of the length  62  to the length  61 , for effective operation of the coupling device  11 , may range from greater than 1 to about 1.5. While the ratio of the length  62 :length  61  may range from greater than 1 to about 1.5, and more optimal performance may be found using a ratio falling within the range of from about 1.32 to about 1.45. In one embodiment, the ratio of the length  62  to the length  61  is about 1.4. It has been found that using two pivot points  36 ,  38  instead of a single pivot point coupling the lever  25  to both the left spring  27  and the shaft assembly  21  permits the coupling device  11  to have a higher engagement force, which enables the coupling device  11  to operate effectively in non-optimal conditions such as where corrosion may exist, debris or dirt may have infested the linkage, maintenance or lubrication may be required, etc. 
       INDUSTRIAL APPLICABILITY 
       [0026]    The coupling device  11  has been described above. It may be used to quickly and easily change implements  15  on the machine  10  and the activation of the coupling device  11  may be performed by the operator in the cab  46 . All that is required is that the right and left latches  28 ,  29  be aligned with corresponding openings in the tool or implement  15 . Then the operator activates the motor  19  (or hydraulic system or actuator) to extend the shaft assembly  21  (or cylinder or extendable member) outward which results in the right and left latches  28 ,  29  extending downward through their respective guides into the openings of the tool or implement  15 . Disengagement of the tool or implement  15  from the frame  16  is also easily accomplished by activating the motor and retracting the shaft assembly  21  laterally inwards away from the right and left ends  17 ,  18  of the frame  16 .

Summary:
An electrically actuated coupling device for a machine and an implement is disclosed. The device includes a frame and an electric motor coupled to a drive shaft that extends between right and left ends of the frame. The motor causes the shaft to extend or retract from each end of the frame simultaneously. Each end of the frame includes a guide for receiving a latch. Each latch is pivotally coupled to a spring and each spring is pivotally coupled to a specially shaped lever which is pivotally coupled to the frame as well as an end of the shaft. The electric motor may be activated by the operator from within the cab.