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CROSS REFERENCE TO RELATED PATENT APPLICATIONS 
   This divisional application claims priority under 35 U.S.C. § 120 from U.S. patent application Ser. No. 10/832,942 filed on Apr. 27, 2004, issued as U.S. Pat. No. 7,043,858 on May 16, 2006. 

   FIELD OF THE INVENTION 
   This invention relates to generally to work vehicles. More particularly, it relates to couplings for work vehicles. Even more particularly it relates to pivot joints for excavators and loaders. 
   BACKGROUND OF THE INVENTION 
   Work vehicles such as wheel loaders, backhoes, loader-backhoes, excavators, skid steers, graders, trenchers, tractors, combines, balers, cotton pickers, telehandlers, forklifts, and other material handling or ground engaging vehicles often include members that are coupled together to pivot with respect to one another at pivot joints. These members are most commonly moved by actuators, for example, hydraulic actuators such as hydraulic cylinders. 
   In a common arrangement, such as the backhoe attachment of a loader-backhoe, or the excavating attachment to an excavator, two elongate rigid members such as boom swing towers, booms, dippers or buckets are coupled together with a pivot pin at a pivot joint. A hydraulic cylinder extends between and is coupled to the two members. The cylinder pivots the two members with respect to one another about the pivot pin by extending and retracting. 
   Typically, the pin in a pivot joint has a structure for retaining the pin in place. In one arrangement snap rings are fastened to both ends of the pivot pin. The snap ring on one end prevents the pin from moving in one direction and the snap ring on the other end prevents the pin from moving in the other direction. In another arrangement, a shoulder or head is provided on one end of the pin, replacing one snap ring. The dual snap ring and ring-and-shoulder arrangements are acceptable for pivot joints that are not blind—i.e. when an operator can get access to both ends of the pivot pin. 
   Blind pivot joints, however, require different structures since one has no access to both ends of the pivot pin in its blind hole. In these situations, pivot pins have been provided with a retainer that is welded to and extends away from the pin. This retainer is fixed to the member in which the pin is inserted, typically with a bolt. This fixes the pin in the member by a connection at just one end, preventing pin movement either into or out of the joint. It also holds the pin stationary with respect to the member to which the retainer is fastened, and thus forces the pin to pivot with respect to one of the two members. Disadvantageously, this welded arrangement holds the pin rigidly with respect to the member, and does not let it float within the pivot pin hole. 
   An alternative arrangement for blind pivot joints includes a pin with a circumferential groove at one end and a retainer that fits into this groove. An advantage to this arrangement is the pin&#39;s ability to (1) wobble, float or self-align slightly within the pivot pin hole and (2) to rotate freely about its longitudinal axis. 
   Recently, however, this free rotation has been identified as a problem in some situations where the pin binds or corrodes in the pivot pin hole that supports it. In these situations it is beneficial to prevent the pin from rotating. 
   The free rotation could be prevented by welding the pin and retainer together in the prior art manner. This arrangement would, however, prevent the pin from self-aligning with respect to the hole. 
   What is needed, therefore, is an improved pivot pin assembly for blind holes that permits the pin to float, wobble or self-align slightly in the hole (like the arrangement with the circumferential groove), yet also retains the pin in a blind hole (like the welded arrangement). 
   It is an object of this invention to provide such a pivot pin assembly. 
   SUMMARY OF THE INVENTION 
   In accordance with a first embodiment of the invention, a backhoe pivot joint is provided, including a first backhoe member having first cylindrical opening; a second backhoe member having a second cylindrical opening, wherein said first and second longitudinal openings are disposed in a coaxial relation; a circular metal cylinder disposed in said first and second openings, said cylinder having a first end and a second end, said first end having a circumferential groove having at least one blocked groove portion; and a retaining plate removably fixed to said first member and having a first edge disposed in said circumferential groove. 
   The circumferential groove may have first and second blocked portions. The first and second blocked portions may be disposed about 180 degrees apart. The first and second blocked portions may subdivide the circumferential groove into a first arcuate portion and a second arcuate portion, each of the first and second arcuate portions having substantially equal length. The first end may have first and second recesses adjacent to the first and second blocked portions. The groove may have a finish that indicates the groove was formed by turning the cylinder on a machine tool. The first and second blocked portions may have a finish that indicates the first and second blocked portions were formed by pressing or stamping the groove. 
   In accordance with a second embodiment of the invention, a pivot pin assembly for a pivot joint of a work vehicle is provided, including a circular metal cylinder, the cylinder having a first end and a second end, the first end having a circumferential groove with at least one blocked groove portion; and a retaining plate removably fixed to the first member and having a first edge disposed in the circumferential groove. 
   The circumferential groove may have first and second blocked portions. The first and second blocked portions may be disposed about 180 degrees apart. The first and second blocked portions may subdivide the circumferential groove into a first arcuate portion and a second arcuate portion, each of the first and second arcuate portions having substantially equal length. The first end may have first and second recesses adjacent to the first and second blocked portions. The groove may have a finish that indicates the groove was formed by turning the cylinder on a machine tool. The first and second blocked portions may have a finish that indicates the first and second blocked portions were formed by pressing or stamping the groove. The first and second arcuate portions may have an angular extent of 140-175 degrees. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a left side view of a work vehicle, in particular a loader-backhoe in accordance with the present invention. 
       FIG. 2  is a front view of a pivot pin of the vehicle of  FIG. 1  shown in partial cross section. 
       FIG. 3  is a top view of the pin of  FIGS. 1-2  showing the pin and the pin retaining plate as they are inter-engaged when used. 
       FIG. 4  is a left side view of the pin of  FIGS. 1-3 . 
       FIG. 5  is a fragmentary detail left side view of the rear portion of the tractor, the boom swing tower, and the boom of  FIG. 1 . 
       FIG. 6  is a fragmentary detail rear view of the vehicle of  FIG. 1  showing the boom swing tower and the boom. 
       FIG. 7  is a fragmentary detail left side view of the rear portion of the vehicle of  FIG. 1  showing the boom swing tower, boom, and upper portion of the dipper. 
       FIG. 8  is a fragmentary right side view of the upper portion of the boom and dipper of  FIG. 1  showing the pivot joints. 
       FIG. 9  is a perspective view of a pin and its pin retaining plate showing their mode of assembly. 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
   Referring to  FIG. 1 , a loader-backhoe  100  is shown having a loader attachment  102  and a backhoe attachment  104 . The loader attachment  102  and backhoe attachment  104  are pivotally coupled to a tractor  106 . Tractor  106  is supported on front wheels  108  and rear wheels  110  for movement over the ground. The rear  112  of loader-backhoe  100  has two elongate extending members including upper member  114  and lower member  116  that extend from rear  112 . These members are disposed one above the other. Two through passages  118  and  120  ( FIG. 5 ) extend through members  114  and  116 , respectively. 
   Backhoe attachment  104  is coupled to members  114  and  116  to pivot about a substantially vertical axis with respect to tractor  106 . In particular, swing tower  122  is coupled to members  114  and  116  by pivot pin assemblies  124  and  126  ( FIG. 5 ). 
   Backhoe  104  also includes a boom  128  that is pivotally coupled to swing tower  122  by pivot pin assemblies  130  and  132 . Pivot pin assemblies  130  and  132  define a substantially horizontal pivotal axis between boom  128  and swing tower  122 . Pivot pin assemblies  130  and  132  extend through swing tower  122  and boom  128  to define horizontal pivotal axis  134  about which boom  128  pivots with respect to swing tower  122 . 
   Backhoe attachment  104  also includes dipper  136  that is pivotally coupled to the upper end of boom  128 . Dipper  136  is coupled to boom  128  by two pivot pin assemblies  138  and  140 . Pivot pin assemblies  138  and  140  define a substantially horizontal pivotal axis about which dipper  136  pivots with respect to boom  128 . 
   Backhoe attachment  104  also includes a dipper cylinder  142  that is coupled to and between boom  128  and dipper  136  to pivot dipper  136  with respect to boom  128  when cylinder  142  extends and retracts. The upper end of hydraulic dipper cylinder  142  is pivotally coupled to dipper  136  by pivot pin assembly  144 . Pivot pin assembly  144  extends through openings in both dipper  136  and the upper end of cylinder  142 . 
   Backhoe attachment  104  also includes a hydraulic bucket cylinder  146  that is pivotally coupled to dipper  136  by pivot pin assembly  148 . Pivot pin assembly  148  defines a substantially horizontal pivotal axis between dipper  136  and bucket cylinder  146 . 
     FIGS. 2 ,  3 ,  4 , and  9  illustrate details of the construction of all of pivot pin assemblies  124 ,  126 ,  130 ,  132 ,  138 ,  140 ,  144 , and  148  which are identically constructed 
   Each pin assembly  124 ,  126 ,  130 ,  132 ,  138 ,  140 ,  144 , and  148  shown in detail in  FIGS. 2 ,  3 ,  4 , and  9  includes a pin  152  and a pin retaining plate (or pin retainer)  154 . Pin  152  is cylindrical in form having a major diameter  156  that extends substantially the entire length of the pin. A circumferential groove  158  is disposed at one end of pin  152 . Groove  158  is configured to receive retainer  154 . Groove  158  preferably extends around the entire circumference of pin  152 , preferably having a width of between 0.1 and 0.3 inches. It has a depth measured from the major diameter of pin  152  of between 0.2 and 0.5 inches. 
   Groove  158  is disposed at one end of pin  152  and is spaced between 0.1 and 0.3 inches from the end of the pin. This spacing produces a flange  160  that extends around the entire circumference of pin  152 . 
   The pin is manufactured by turning an elongate metal member such as a steel rod on a machine tool (for example a lathe or screw machine) reducing its diameter with a turning tool until it has the desired outer diameter of the pin. The rod is further turned on a lathe or screw machine to create the groove. A turning tool reduces the diameter of the pin thereby creating the groove. 
   These turning processes cold-work the surface of the pin and the groove walls, leaving striations, indentations or scores  153  on the surface of the pin and groove that typically extend circumferentially around the outer diameter of the pin, and on the walls and bottom of the groove. These marks  153  indicate that the pin was turned to create its outer diameter and also that the groove was formed by turning. They indicate the process by which the surface of the pin and the surface of the groove were formed. 
   Once the basic pin body and groove have been made, the pin is placed in a press and two opposing sections  162  and  164  of flange  160  are bent in a direction parallel to the longitudinal axis  166  of pin  152  such that the opposing sections  162 ,  164  of the flange  160  are recessed below the end surface of the pin, and block two opposing portions  168 ,  170  of groove  158 . By recessing sections  162 ,  164  of flange  160  into blocked portions  168 ,  170  of groove  158 , the circumferential groove  158  is subdivided into two semicircular arcuate groove portions that are sized to receive the retaining plate. The blocked portions  168 ,  170  of groove  158  are disposed 180 degrees apart. The semicircular arcuate groove portions each have a length of between 140 and 175 degrees. They are preferably of equal length. 
   This process of recessing the flange into the groove leaves characteristic striations, indentations and scores  153  on the surface of the two opposing sections  162 ,  164  of flange  160  indicating that they are formed by being pressed or stamped in a direction generally parallel to the longitudinal axis of the pin until the recessed portions of the flange are plastically deformed into the groove  158 . 
   Retainer  154  is in the form of a planar sheet of metal, preferably steel, that has an aperture  172  passing therethrough and one edge  174  that is configured to be inserted into either one of the semicircular arcuate portions of groove  158  that are formed when portions  168 ,  170  of groove  158  are blocked. Retainer  154  has a thickness along edge  174  that is slightly smaller than the width of groove  158 . In this manner, retainer  154  can be easily inserted into groove  158  with no special tools. Retainer  154  is inserted into groove  158  in a direction generally perpendicular to longitudinal axis  166  of pin  152 . It preferably is inserted to the bottom of groove  158  such that it engages the groove to a depth of 0.3 to 0.5 inches along an arc of 90 to 140 degrees. 
   The ends  176 ,  178  of edge  174  are preferably just adjacent to the crushed portions  168 ,  170  of groove  158 . With retainer  154  in this position, pin  152  can rotate only a few degrees, preferably at least 5 degrees, but preferably no more than 90 degrees, more preferably no more than 45 degrees, even more preferably no more than 25 degrees, and most preferably no more than 10 degrees with respect to retainer  154 . Groove  158  and retainer  154  are sized to provide a slight spacing between retainer  154  and pin  152  both in a direction parallel to longitudinal axis  166  and a direction perpendicular to axis  166 . This spacing permits pin  152  to “float” slightly with respect to retainer  154 , yet preventing pin  152  from leaving the members in which it is inserted. This allows for slight mechanical misalignments, roughness or irregularities in surfaces or other manufacturing tolerances that might otherwise prevent the use of a pin. 
   Pin  152  includes lubricating passageways formed integral with the pin that permit an operator of the vehicle to lubricate the pivot joints. These lubricating passageways include a first grease passage  180  that extends longitudinally through the center of pin  152  from the end of the pin at which groove  158  is located to a point  182  that is generally located midway between the two ends of pin  152 . 
   A second passageway  184  extends from one side of cylindrical sidewall  186  of pin  152  to the other side of cylindrical sidewall  186  of pin  152 . Passageway  184  intersects longitudinal axis  166  of pin  152  and passage  180 . In this manner, a lubricant such as grease can be injected into the end of passage  180 , can be forced down the length of passage  180  and can be forced outward through passage  184  until it exits pin  152  coating opposing sides of sidewall  186 . The opposing ends of passageway  184  are configured to be located within the joint itself, preferably abutting the second member of the pivot joint (i.e. the member to which retaining plate  154  is not attached). Pin  152  is forced by retainer  154  to rotate with respect to the second member, and therefore the movement of the second member with respect to passageway  184  serves to distribute the lubricant that exits passageway  184 . Any grease exiting the opposing ends of passageway  184  is thereby forced between the pin and the apertures of the vehicles in which it&#39;s received to lubricate the pin. This reduces wear and extends the life of the pin  152  and the components in which it is inserted. A grease fitting  188  is preferably inserted into the open end  190  of passage  180  to ensure that no water enters the lubricating passages and that no grease can escape except through the ends of passageway  184 . 
   The insertion of the pivot pin assemblies illustrated in  FIGS. 2 ,  3 ,  4 , and  9  into any of the locations indicated in the figures is relatively simple. First, the two pivoting members that are to be pivotally joined or coupled together are positioned with respect to each other such that mating holes on each component are coaxial. Once in this position, the operator inserts pin  152  into the aligned apertures until groove  158  is only slightly above the surface of the assembly. 
   At this point, the operator inserts edge  174  of retainer  154  into one of the semicircular groove portions formed by crushing opposing portions of circular groove  158 . With retainer  154  in this position, the operator then slides a pin further into the aligned apertures of the structures that it is pinning together until retainer  154  abuts the surface of one of the structures. Using pivot pin assembly  124  ( FIG. 5 ) as an example, the operator positions retainer  154  to abut surface  190  of swing tower  122 . The operator aligns aperture  172  with threaded hole  194 , inserts threaded fastener  192  through aperture  172  of retainer  154  and into threaded hole  194  of swing tower  122 . 
   The operator rotates fastener  192  until the head of fastener  192  compresses retainer  154  against surface  190  and fixes retainer  154  in position against the top surface of the swing tower  122 . Aperture  172  and threaded hole  194  are located such that when fastener  192  is threadedly engaged with hole  194  retainer  154  extends into groove  158  of pin  152  such that pin  152  can neither be inserted deeper into the holes in which it is received nor withdrawn from those holes. 
   The various holes and apertures are positioned such that pin  152  is not fixed rigidly with respect to swing tower  122  or to elongate member  114 , when fastener  192  fixes retainer  154  against surface  190 . Instead, the components are configured to provide pin  152  a slight amount of axial play (typically on the order of 0.050-0.100 inches) and also to provide pin  152  a small degree of rotational play about its longitudinal axis  166  (e.g. the 90, 45, 25, or most preferably 10 degrees of pin-to-retainer play mentioned above). 
   By permitting a slight degree of play with respect to retainer  154  and with respect to the structure retainer  154  is fastened to, pin  152  of pin assembly  124  can float lightly with respect to both structures and preferably seize against neither one of them. This floatation combined with the internal lubricating passageways  180 ,  184 , substantially reduces the wear of the pin and the joint that it defines. 
   From the foregoing, it will be observed that numerous modifications and variations can be effected without departing from the true spirit and scope of the novel concept of the present invention. For example, the pins may be made of any of a variety of metals, such as steel, iron, aluminum, titanium, copper, brass, bronze, and nickel, or alloys or mixtures containing one or more of these metals, or other elements. 
   As another example, the particular arrangement and lengths of the couplings and elongated arms and members shown herein can be changed into their configurations. As another example more or fewer elongated members may be added to the backhoe or excavator linkage to make it longer or shorter without departing from this invention. 
   As another example, one or more members may be removed from the illustrated work vehicle members and still fall within the scope of the claims. The individual members may be reconfigured, such as by changing their length, their orientation, their construction, the size of the holes coupling the members, and the length of the holes that defined the pivot joints, while still falling within the scope of the appended claims. 
   It will be appreciated that the present disclosure is intended as an exemplification of the invention, and is not intended to limit the invention to the specific embodiment illustrated. The disclosure is intended to cover by the appended claims all such modifications as fall within the scope of the claims.

Summary:
A backhoe coupling for joining members of a backhoe attachment is provided, the coupling having a pivot pin assembly that includes a pivot pin and a retaining plate. The pin has a groove for receiving the retaining plate. The retaining plate has an edge that is sized to fit into the groove and prevent it from being extracted. The groove has two blocked regions on opposing sides of the pin that prevent the pin from rotating freely with respect to the retaining plate.