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TECHNICAL FIELD 
   The present invention relates to vehicles having lift arms such as skid-steer loaders, and more particularly to a quick attach device for releasably connecting a variety of working implements with a carrier mounted to the lift arms of such vehicles. 
   BACKGROUND OF THE INVENTION 
   Working vehicles such as skid-steer loaders or other small utility loaders have lift arms that can be used with various work implements such as buckets, blades, and lift forks. Various mechanisms have been proposed to provide quick interchange of the work implements so the same loader can be used for different work functions. 
   Working vehicles frequently have tool carriers supported at the end of their lift arms. These carriers are adapted to be attached to a variety of implements. To simplify and expedite the mounting and removal of various implements, the carriers are equipped with quick-attach devices. The carrier and/or quick-attach devices typically include positioning structures to orient and locate one part of the carrier relative to the implement as well as a latching structure to secure the implement to the carrier. 
   Some quick-attach mechanisms rely on pins which must be inserted into aligned holes in the implement. This type of mechanism can require careful and time consuming alignment of the pins and holes. Additionally, dirt or other obstructions may make insertion and removal of the pins somewhat difficult. It would be desirable to visually inform the operator of the existence of a misalignment or non-engagement of the pin with the implement. Additionally, it would be desirable to provide some mechanical advantage to assist in engaging the pin with the implement, such as during a misalignment condition. 
   Accordingly, it would be desirable to provide a coupling assembly which avoids deficiencies in the prior art and is easy to use and provides for efficient releasable coupling of an implement to a working vehicle. 
   SUMMARY OF THE INVENTION 
   Accordingly, it would be desirable to provide a coupling assembly which avoids deficiencies in the prior art and is easy to use and provides for efficient releasable coupling of an implement to a working vehicle. 
   Toward these ends, there is broadly provided a coupling assembly including a tool carrier attached to the work vehicle and supporting a pin guide. A pin is supported upon the carrier by the pin guide and interacts with one or more cam surfaces supported by the carrier. During rotation of the pins, the cam surfaces transfer an axial force to the pin to assist in the extraction or insertion of the pins into the implement. In one embodiment, the pin has a graspable handle which may be rotated and axially moved by an operator. As a result, the pin and cam surfaces cooperate to convert a rotational motion of the pin handle into a linear motion assisting in the extension of the pin into its engaged position within an implement aperture or in the retraction of the pin into its disengaged position so that implement may be removed. 
   The cam surface which engages the pin may be provided upon a small insert or upon the guide block or both. In one embodiment, two cam surfaces are provided so that axially forces may be transferred to the pin to assist in both the extraction and insert of the pin relative to the implement. 
   In a preferred embodiment of this invention, the improved coupling assembly includes a carrier supporting a pair of similar pin assemblies, each as described above. 
   One object of the present invention is the provision of a visual indication that the pin is not fully engaged with the implement. An operator may visually reference the pin assembly to determine that the pin is properly engaged with the implement. 
   Yet another object of the present invention is the provision of a locking mechanism which prevents a pin from disengagement under axial-only force. As described herein, to disengage the pin from the implement an axial and rotation force must be applied. 
   These and other objects, features, and advantages of the invention will be evident from the following description of the preferred embodiment of this invention, with reference to the accompanying drawings. 

   
     DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a perspective view of a working vehicle having an implement carrier according to the present invention and positioned relative to an implement. 
       FIG. 2  is a perspective view of an implement and carrier according to the present invention, wherein the pin assembly is illustrated in an engaged orientation. 
       FIG. 3  is a detailed exploded view of a pin assembly and carrier according to the present invention. 
       FIG. 4  is an elevational view of a pin assembly and carrier of  FIG. 1 , illustrating the engaged orientation of the elements. 
       FIG. 5  is an elevational view of a pin assembly and carrier of  FIG. 1 , illustrating an intermediate orientation of the elements. 
       FIG. 6  is an elevational view of a pin assembly and carrier of  FIG. 1 , illustrating the disengaged orientation of the elements. 
       FIG. 7  is a cross-sectional view of the pin assembly and carrier taken along lines  7 — 7  of FIG.  4 . 
       FIG. 8  is a cross-sectional view of the pin assembly and carrier taken along lines  8 — 8  of FIG.  5 . 
       FIG. 9  is a cross-sectional view of the pin assembly and carrier taken along lines  9 — 9  of FIG.  6 . 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
   While this invention can be embodied in many different forms, there is shown in the drawings and described in detail, a preferred embodiment of the invention. The present disclosure is to be considered as an exemplification of the principles of the invention and is not intended to limit the invention to the embodiment illustrated. 
   For ease of description, the coupling assembly embodying this invention will be described in a normal upright operating position and such terms as upper, lower, upwardly, downwardly, will be used with reference to this position. It will be understood, however, that the coupler assembly embodying this invention can be used in an orientation other than the position described. 
   Referring to the Figures, a tractor or utility loader  10  having a lift arm assembly  12  and dump cylinder  14 , and commonly referred to as a skid steer loader, is shown in association with a work implement  16 , a bucket. The illustrated tractor  10  is a DINGO brand compact utility loader manufactured by The Toro Company. As described in more detail herein, a carrier  18  engages implement  16 . Alternative tractors  10  or utility loaders may utilize a coupling assembly according to the present invention. 
   The present invention, a coupling assembly, can be used with other mechanized equipment having a lift arm assembly and can be used to couple a variety of implement such as a bucket, blade, or fork assembly, etc. to a carrier of a machine. The term “carrier” is meant to broadly cover an intermediate structure between a loader  10  and an implement  16 . Typical carriers  18  are movably connected to lift arms  12  of loader  10  so that implement  16  may be raised or lowered by lift cylinders  13  attached between lift arms  12  and a frame of loader  10 . A variety of carriers  18  could be utilized to practice the present invention. Alternative carriers  18  may not have a “plate-like” structure  32  for engaging implement  16 , but instead may have a plurality of contact points between carrier  18  and implement  16 . 
   Implement  16  is provided with an attachment structure  20  which includes a downwardly facing recess  22  and an upwardly facing member  24  having a pair of apertures  26  for engaging tractor  10 . Attachment structure  20  is designed to cooperate with carrier  18  as further described herein to facilitate alignment and connection between the elements. Various implements, such as a bucket, auger, loading forks and the like having associated attachment structure  20  can be connected to carrier  18 . 
   Referring to  FIGS. 1 and 2 , carrier  18  is attached to lift arm assembly  12  with 3 pins  30 , (2 pins are shown in FIG.  1 ). Carrier  18  includes a plate surface  32  for engaging a generally flat surface  34  of implement  16 . Pins  30  pass through appropriately sized apertures  35 ,  36  upon carrier  18 . Dump cylinder  14  is connected at an upper aperture  36 , allowing carrier  18  to pivot in operation relative to lower pins  30 . Carrier  18  further includes a plurality of guide block structures  38 A,  38 B for slidably receiving a pair of pins  40  of the coupling structure of the present invention. Guide block structures  38 A,  38 B include a pair of upper guides  38 A and a pair of lower guides  38 B. 
   Carrier  18  is selectively connected to attachment structure  20  of implement  16  through the coupling assembly of the present invention. As described herein, the coupling assembly of the present invention provides a selective connection between attachment structure  20  of implement  16  and carrier  18  of loader  10 . 
   In overview, a preferred embodiment of the coupling assembly of the present invention includes a pair of pins  40 , upper and lower inserts  42 ,  44 , a spring  46 , and upper and lower guide blocks  38 A,  38 B. 
   Referring particularly to  FIG. 3 , pin  40  has a handle  50  adapted to be grasped by an operator during a coupling method as described herein. Pin  40  is slidably received within bores  52  of both upper guide  38 A and lower guide  38 B of mounting frame  18  so that pin  40  may both rotate and translate relative to its longitudinal axis. Lower guide  38 B includes a grease fitting  54  permitting lubrication of the coupling assembly. 
   Lower guide  38 B further includes a cam surface  56 . A shoulder  58  is positioned at a top portion of cam surface  56 . As described hereinafter, cam surface  56  may be engaged by lower insert  44  causing pin  40  to rotate during a coupling operation. In this embodiment, cam surface  56  is an inclined surface which is generally planar. Alternative cam surfaces  56  may include curves or more complex surfaces. As used herein the term “cam surface” means a surface which is at least partially oblique relative to an axis passing through bore  52  centers. 
   Upper insert  42 , spring  46 , and lower insert  44  are positioned relative pin  40  between upper guide  38 A and lower guide  38 B. Inserts  42 ,  44  and spring  46  are sized to slidably receive pin  40 . Lower insert  44  is connected to pin  40  by a small pin  60  passing through an aperture  62  in insert  44  and an aperture  64  in pin  40 . As a result, lower insert  44  and pin  40  rotate and move together. Upper insert  42  includes a second cam surface  70 . As described herein, second cam surface  70  may be engaged by lower insert  44  causing pin  40  to extend into its engaged position. Upper insert  42  includes a birfucated end  72  which engages a protrusion  74  of carrier  18 . Bifurcated end  72  prevents upper insert  42  from rotating relative to pin  40 . Spring  46  is compressed during assembly so that spring  46  biases apart inserts  42 ,  44 . 
   Operation of the coupling assembly may be described with reference to the figures. In overview, attachment and detachment of the implement  16  is made by manually grasping pin handle  50  to engage and retract pin  40  relative to apertures  26  of implement  16 . 
   As depicted in  FIG. 1 , loader  10  may engage implement  16  by retracting pins  40 , tilting carrier  18  relative to implement  16 , moving the loader  10  forward, and inserting the upper lip of carrier  18  into the downwardly facing recess  22  of implement  16 .  FIGS. 1 ,  6  and  9  illustrate pins  40  in their retracted position. With the upper lip of carrier  18  retained within downwardly facing recess  22 , carrier  18  may be rotated by action of cylinder  14  so that the plate surface  32  engages flat surface  35  of implement  16 . At this point, pin  40  handles  50  may be rotated to engage pins  40  into apertures  26  of implement  16 .  FIGS. 2 ,  4  and  7  illustrate pins  40  in their extended position (implement engaged position). 
   To remove the implement  16 , pin  40  handles  50  are rotated and lifted to retract pins  40  from apertures  26  of implement  16 . The implement  16  may then be lowered to the ground and carrier  18  rotated so that the upper lip of carrier  18  is removed downwardly facing recess  22 . Additional features of the coupling assembly of the present invention are revealed by closer examination of  FIGS. 2 through 7 . 
     FIGS. 2-7  illustrate three orientations of pin  40  relative to mounting plate  18 .  FIGS. 2 ,  3 ,  4  and  7  illustrate the coupling assembly in its engaged position, wherein pins  40  are extended from the bottom of carrier  18  and may be engaged with apertures  26  of implement  16  to connect implement  16  to loader  10 .  FIGS. 5 and 8  illustrate the coupling assembly in an intermediate position with handle  50  partially rotated from an engaged position. Pin  40  in intermediate orientation is not engaged with implement  16 . When handle  50  is in the intermediate position of  FIGS. 5 and 8 , handle  50  provides a visual indication to the operator that pin  40  is not engaged with implement  16 .  FIGS. 6 and 9  illustrate the coupling assembly in its detached position, wherein pins  40  are retracted within carrier  18  allowing the implement  16  to be detached from loader  10 . 
   To couple implement  16  to carrier  18 , pins  40  are each placed into respective retracted positions as illustrated in  FIGS. 6 and 9  and carrier  18  is inserted into attachment structure  20  of implement  16 , typically by moving loader  10  into engagement with implement  16 . In the retracted position, a flat  78  of lower insert  44  fully engages shoulder  58  of lower guide  38 B as spring  46  biases upper insert  342  and lower insert  44  apart. Next an operator grasps pin handle  50  and rotates pin  40  toward its engaged orientation. As pin  40  and lower insert  44  are rotated into the intermediate position of  FIGS. 5 and 8 , a portion of flat  78  engages shoulder  58 . 
   As pins  40  are further rotated past an intermediate position toward an engaged (extended) position, flat  58  may engage cam surface  56  as spring  46  biases inserts  42 ,  44  apart. Alternatively, if pin assembly is dirty or a lower aperture is partially blocked or misaligned with aperture  26  of implement  16  an upper portion  80  of lower insert  44  may engage second cam surface  70  so that as pin  40  is rotated, a downward force is transferred through second cam surface  70  to insert  44  forcing pin  40  to align with implement aperture  26  and extend thereinto. 
   In this manner, a positive alignment and engagement between pin  40  and implement aperture  26  is provided when pin  40  is rotated from its disengaged position into its engaged position. In the absence of second cam surface  70 , pin handle  50  could be rotated into its engaged position without pin  40  extending into position within implement aperture  26 . The pin  40 , lower insert  44 , and second cam surface  70  cooperate to convert a rotational motion of handle  50  into a linear motion assisting in the extension of pin  40  into its engaged position within implement aperture  26 . 
   If pin  40  is blocked or misaligned relative to apertures  26 , the operator will be prevented from further rotating pin handle  50  toward the engaged orientation of  FIGS. 2 ,  3 ,  4  and  7  as upper surface  80  of lower insert  44  engages and is blocked by cam surface  70  of upper insert  42 . In this regard, a visual indication may be presented to the operator that a misalignment and non-engagement situation exists. In some situations, upon subsequent alignment of pin  40  with aperture  26  (such as upon rocking the implement, etc.), spring  46  may bias insert  44  causing pin  40  to rotate into its engaged orientation. An operator may visually monitor the pin  40  transition from an intermediate non-engaged position to the engaged position, and may facilitate the transition by manipulating the implement  16  (manually or through operation of dump cylinder  14  and/or lift cylinder  13 ) so that pin  40  aligns with aperture  26 . 
   Regarding the engaged position, as illustrated in  FIGS. 2 ,  3 ,  4  and  7 , an inclined surface  82  of lower insert  44  fully engages cam surface  56 . Pin  40  is prevented from substantially displacing in an axial direction, e.g., upwardly, as an upper surface  80  of the lower insert  44  engages and is blocked by a lower surface  84  of the upper insert  42  upon slight axial movement. This provides a positive lock mechanism which prevents pin  40  from axially displacing when in its engaged position. As a result, forces transferred in an upward axial direction at the pin  40  bottom or upward axial forces alone at the handle  50  will not disengaged pin  40  from its engaged position. As described hereinafter, handle  50  must be both axially lifted and rotated to retract pin  40  into carrier  18 . 
   To disengage implement  16  from carrier  18 , pin handle  50  is grasped and rotated. Pin  40  may be upwardly lifted by the operator as pin handle  50  is rotated. Alternatively, in the absence of an upward force by the operator, lower insert  44  positively engages cam surface  56  as the pin handle  50  is rotated to cause an upward force retracting pin  40 . In this manner, as pin handle  50  is rotated, cam surface  56  may provide an upward force to assist in the retraction of pin  40  from implement aperture  26 . The pin  40 , lower insert  44 , and cam surface  56  cooperate to convert a rotational motion of the handle  50  into a linear motion assisting in the retraction of pin  40  into its disengaged position. 
   Those skilled in the relevant arts will appreciate that a variety of connections may be utilized to connect carrier  18  to lift arm assembly  12 . Additionally, a variety of differently configured attachment structures  20  and carrier  18  may be utilized in conjunction with the coupling assembly of the present invention. For example, a different attachment structure may include a pair of flange structures, each for separately engaging one of a pair of upper lips of a carrier. 
   Other alternatives to the illustrated embodiment may include forming the second cam surface  70  not on a separate upper insert  42 , but instead as a portion of carrier  18 , e.g. a machined second cam surface being integral with carrier  18 . Lower insert  44  may be formed as an integrated part of pin  40 . The lower insert  44  features of an upper surface  80  to engage the second cam surface  70  and a lower surface  82  to engage the first cam surface  56  may be formed into a single pin, rather than a two-piece pin and insert  42 ,  44  of the illustrated embodiment. For example, a pin  40  may have one or more weldment or other protrusion which engage cam surfaces  56 ,  70  causing the pin to extend or retract as the pin is rotated. Yet other pins (not shown) for engaging cam surfaces  56 ,  70  and converting a rotation motion into a linear motion would be practicable. 
   In another embodiment, handle  50  may be eliminated and a hydraulic or other actuator may be used to provide a rotation motion to a pin  40 . The term actuator as used herein means any type of power actuator that provides for extension or retraction under control of an operator. Appropriate linkages between an actuator and a pin  40  would be within the scope of those of ordinary skill in the art. In this regard a positive lock and release mechanism may be provided as the linear motion of the actuator causes pin  40  to rotate and extend or retract in response to engagement with cam surfaces  56 ,  70 . 
   Various other modifications can be made in the present invention without departing from the scope and spirit of the invention.

Summary:
An improved coupling assembly and method of use are disclosed herein to include a tool carrier attached to a utility loader or other work vehicle and supporting a pin guide. A pin is supported upon the carrier by the pin guide and interacts with one or more cam surfaces supported by the carrier. During axial rotation of the pin, the cam surface transfers a force to the pin to assist in the extraction and/or retraction of the pin into the implement. In one embodiment, the pin has a user graspable handle which may be rotated and axially moved by an operator. A visual indication that the pin is not fully engaged with the implement is also provided. Additionally, a locking mechanism is provided which prevents a pin from disengagement with the implement.