Abstract:
The quick hitch drawbar assembly accepts a standard yoke hitch but simplifies the tractor/scraper connection. Holes in the drawbar are replaced with slots which are angled to prevent accidental disconnection. These slots are wider at the top to simplify alignment of the yoke pin down the slots to be seated in a pin cradle. The forward portion of the drawbar ears are raised to form a stop for the horizontal pin when positioning the tractor.

Description:
FIELD OF THE INVENTION 
     The present invention relates to the field of earth moving equipment and more particularly to a system for quick and accurate connection and disconnection of earth moving equipment and a tractor. 
     BACKGROUND OF THE INVENTION 
     A basic hitch connection, used since the early 1950&#39;s, consists of a yoke arrangement and a drawbar especially made to accept the horizontal pin used to connect a scraper or other earth moving equipment to a towing tractor. The drawbar consists of a steel bar fastened to the belly of the towing tractor and fitted with two or four ears at the rear of the tractor. Each of the ears includes a hole. The rear portion of the drawbar is supported by a cross member in the tractor frame or an added cross member. 
     The drawbar and yoke hitch provide a flexible connection between the scraper and tractor. This hitch arrangement has been accepted by most manufacturers and is pervasive in the industry. 
     This design allows the vertical load of the scraper to be placed as far forward as possible to reduce the effect of raising the tractor front, while keeping the vertical pivot point as far away as possible from the tires to allow full turns. The yoke assembly provides a hinge between the tractor and scraper and lets the scraper rock from side to side over uneven ground. Side travel is limited to 30 degrees due to the arrangement of the yoke halves. 
     Connection of the scraper to a tractor is accomplished by positioning the tractor at the correct distance and angle to allow installation of a horizontal pin through both the drawbar ears and the scraper hitch. This process requires a “spotter” to direct the tractor driver into position and, when properly positioned, to attempt to install the pin connecting the scraper and tractor by passage of the pin through a series of aligned holes of the drawbar ears and the scraper hitch. This exposes the “spotter” to danger since they must be in the critical zone between the moving tractor and the stationary scraper. 
     The drawbar pin is a steel shaft with a head welded on one end and threads and a nut on the opposite end. Installation of the pin is not easy since the alignment of the holes of the drawbar ears and the scraper hitch is imprecise, and usually requires the use of a large hammer to drive the pin into place. This may result in damage to the pin, drawbar, or yoke hitch. 
     SUMMARY OF THE INVENTION 
     The new quick hitch drawbar assembly of the present invention accepts a standard yoke hitch but simplifies the tractor/scraper connection. Holes in the drawbar are replaced with slots which are angled away from the scraper and toward the rear of the tractor to prevent accidental disconnection. These slots are wider at the top to simplify alignment of the yoke pin down into the slots to seat the yoke pin in a pin cradle. The forward portion of the drawbar ears are raised to form a stop for the horizontal pin when positioning the tractor. 
     The tractors&#39;s hydraulic system is used to raise or lower the scraper to the correct height for connection. The tractor is backed into the scraper yoke hitch where the raised portions of the drawbar ears and locking or latching cam are contacted. The scraper hydraulics, connected to the hydraulic system of the tractor, are then used to lower the scraper into the drawbar slots. 
     Once the hitch pin is bottomed in the drawbar slots, the locking cams are manually rotated by a removable actuating lever to a locking position to latch the yoke pin in place. A cam pivot pin is situated to prevent accidental hitch disconnection. 
     The locking cams are retained in position by their weight and two spring loaded ball screws engaging dimples in detents located in the sides of the locking cams. Further, there are physical stops to prevent the cams from traveling past the dimples and causing the ball screws from losing their frictional connection on the cam. 
     The pivot pin for the latching cams has two notches/grooves located at the edges of the cams. The purpose of these are to provide a “breakaway” point, preventing a rollover of the scraper. The size and depth of the notches allows the cam pin to break as a result of excessive forces, releasing the cams and allowing the scraper to separate from the tractor, therefore preventing a rollover. 
     Accordingly, it is an object of the present invention to provide a drawbar assembly having a plurality of slotted ears which guide a yoke pin down into a pin cradle. 
     It is another object of the present invention to provide a drawbar assembly having a plurality of slotted ears which guide a yoke pin down into a pin cradle and having pivotally mounted locking cams rotatable into the path of the slotted ears to engage and retain the yoke pin at the bottom of the pin cradle. 
     It is still yet another object of the present invention to provide a drawbar assembly having a plurality of slotted ears which guide a yoke pin down into a pin cradle and having pivotally mounted locking cams rotatable into the path of the slotted ears to engage and retain the yoke pin at the bottom of the pin cradle, the locking cams having side grooves engaged by a biased pin in detents at opposite ends of the side grooves for guiding and maintaining the locking cams between a locked and an unlocked position. 
     It is still yet another object of the present invention to provide a drawbar assembly having a plurality of slotted ears which guide a yoke pin down into a pin cradle and having pivotally mounted locking cams rotatable into the path of the slotted ears to engage and retain the yoke pin at the bottom of the pin cradle, the locking cams having side grooves engaged by a biased pin in detents at opposite ends of the side grooves for guiding and maintaining the locking cams between a locked position and an unlocked position, the locking cams having a removable cams actuating lever for rotation of the locking cam through approximately 180 degrees of motion. 
    
    
     These and other objects of the invention, as well as many of the intended advantages thereof, will become more readily apparent when reference is made to the following description taken in conjunction with the accompanying drawings. 
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a perspective view of the drawbar assembly of the present invention in which a two ear slotted drawbar retains a yoke pin of a scraper mechanism for quickly engaging and releasing the scraper assembly from the tractor. 
     FIG. 2 is a plan view of a four ear drawbar mounted at the end of a connector plate for mounting the drawbar at a rear of a tractor. 
     FIG. 3 is a side view of the drawbar shown in FIG.  2 . 
     FIG. 4 is an enlarged view of the locking mechanism at one end of the drawbar shown in FIG.  2 . 
     FIG. 5 is a partial view of the drawbar illustrating the locking cams moved to the open position for receipt of a yoke pin between the slotted ears of the drawbar. 
     FIG. 6 is a side perspective view of a four ear slotted drawbar embodiment with the locking cams pivoted to the open position. 
     FIG. 7 is a side view of a yoke pin approaching the slotted ears of the drawbar assembly, with the locking cams pivoted to the open position. 
     FIG. 8 is a perspective view showing the locking cams moved by a removable cam actuating lever to the locked position of the locking cams to retain a yoke pin in the pin cradle of the slotted ears. 
     FIG. 9 is a front view of a yoke pin seated in the pin cradle of the slotted ears of the drawbar assembly. 
     FIG. 10 schematically illustrates the rotation of the locking cams over a yoke pin held in the pin cradle of the slotted ears of the drawbar assembly and the rotation of the locking cams by the removable cam actuating lever to a position away from the pin cradle, as illustrated in dotted lines, to remove the yoke pin from the pin cradle. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     In describing a preferred embodiment of the invention illustrated in the drawings, specific terminology will be resorted to for the sake of clarity. However, the invention is not intended to be limited to the specific terms so selected, and it is to be understood that each specific term includes all technical equivalents which operate in a similar manner to accomplish a similar purpose. 
     With reference to the drawings, in general, and to FIGS. 1 through 4, in particular, a quick hitch drawbar assembly embodying the teachings of the subject invention is generally designated as  20 . With reference to its orientation in FIG. 1, the drawbar  22  cooperates with a yoke  24  having a yoke pin  26 . 
     The yoke  24  may be mounted on a scrapper or other earth moving equipment, or equipment to be mounted on a rear end of a tractor. The drawbar  22  is mounted on the rear of a tractor, its wheels  28   a ,  28   b  being shown in phantom. The drawbar is connected at a trailing end  30  of a plate  32  which extends underneath and is connected to the underside of the tractor. 
     In FIG. 1, the drawbar  22  includes two ears  32   a ,  32   b . However, in the embodiment shown in FIGS. 2 through 4, a drawbar  22  includes four ears  34   a ,  34   b ,  34   c  and  34   d . Both of these embodiments operate in the same way to connect a yoke pin to the drawbar. 
     In FIGS. 2 and 3, two interconnected locking cams  36   a ,  36   b  are pivotally mounted between ears  34   b  and  34   c  about pivot axis  38  passing through pivot pin  40 . Pivot pin  40  is shown in FIGS. 2 and 4. The locking cams are pivoted about pivot axis  38  by a removable cam actuating lever  42 . Lever  42  has one end  42   a  engaged in an opening  44  of drawbar block  70  and secured in place by a rotatable thumb screw  46 . 
     As best shown in FIG. 4, the locking cam plates  36   a ,  36   b  are retained at the opposite ends of their arcuate path of rotation by opposed spring biased pins  48   a ,  48   b  which extend into grooves  52  at detents  50   a , located at one end of the grooves  52 , for locking the cams in a closed or locked position. The pins  48   a ,  48   b  extend into grooves  52  at detents  50   b  located at the opposite ends of grooves  52 , for locking the locking cams in an open position. Each groove  52  is located in a side wall of one of locking cams  36   a ,  36   b . Groove  52  extends between the detents  50   a ,  50   b.    
     As shown in FIGS. 5 through 7, and especially in FIG. 6, each of the ears  34   a  through  34   d  of the drawbar  22  include a groove, opening or slot  54  which will be explained with reference to ear or plate  34   d  in FIG.  6 . The ear  34   d  includes a flat bottom surface  56  leading to a perpendicular extending surface  58 . Surface  58  raises to a height of approximately 5.7 inches and extends by a curved surface  60  into a downwardly tapered surface  62 . Surface  62  extends at an angle of approximately 50 degrees with respect to surface  58 . 
     Surface  62  leads into U-shaped or pin cradle surface  64  having legs  64   a ,  64   b , interconnected by curved crosspiece  64   c . Surface  64   a  extends at an angle of approximately 57 degrees with respect to surface  62 . Surface  64   b  extends at an angle of approximately 5 degrees with respect to surface  64   a . Surface  64   b  leads to inclined surface  66 . The described shape of the groove, opening or slot  54  is the same for each of the ears or plates  34   a  through  34   d.    
     The shape of the surfaces of the slot  54  is advantageous in combination for seating a yoke pin  26 , as is shown in FIG. 7, in the drawbar  22 . Initially, to connect the yoke pin and the equipment it is connected to, a tractor, for example, is started and brought to operating temperature. The tractor is then backed up to the front of the scraper, approaching the yoke pin. The tractor is brought adjacent to the scraper so that the hydraulic lines of the scraper can be connected to the work spools of the tractor. Wood blocks are placed at the front end of the scraper closest to the yoke pin and spaced from the rear wheels of the scraper. By slightly lowering the wheels of the scraper, to achieve a “teeter-toter” affect, the front end of the scraper is slightly elevated above curved surface  60  of the ears  34   a  through  34   d.    
     In this tipped up position of the yoke pin, the tractor is backed up so that the yoke pin moves into the hitching zone between surfaces  62  and  66  of the ears  34   a through  34   d . With the locking cams  36   a ,  36   b  in the open position, the tractor continues to move rearwardly towards the yoke pin until the yoke pin engages surface  66 . 
     The yoke pin is then directed down into the pin cradle  64  so as to engage surfaces  64   a ,  64   b  and  64   c . This is accomplished by raising the wheels of the scraper by its hydraulic circuit. 
     The yoke pin comes to rest at the bottom of the pin cradle formed by the ears  34   a  through  34   d  as shown in FIG.  9 . The yoke pin is now fully engaged with the drawbar. 
     The cam actuating lever is then inserted into the drawbar block  70  and the thumb screw  46  rotated to lock the lever  42  in position. The handle is then moved in the direction of arrow  72  to the position shown in solid lines in FIG. 10 so as to pivot the cams  36   a ,  36   b  to the closed position shown in solid lines in FIG.  10 . 
     In this position, the locking position, spring biased pins  48   a  and  48   b  engage in detent openings  50   a  in the sidewalls of the cam plates  36   a ,  36   b . The yoke pin  26  is thereby locked in the drawbar. The lever handle  42  is then removed. 
     Similarly, to remove the yoke pin  26 , the handle  42  is reinserted and locked in the drawbar block  70  and the handle rotated in the direction of arrow  74  to the position shown in dotted lines in FIG.  10 . The bias force of the pins  48   a ,  48   b  is overcome so that the pins  48   a ,  48   b  are allowed to slide in the grooves  52  until engaging detents  50   b . To prevent over-extension of the cam plates  36   a ,  36   b  beyond the position shown in dotted lines in FIG. 10, a cam stop plate  76  is interposed in the continued path of movement of the cam plates in the direction of movement of the lever  42  towards arrow  74  as shown in FIGS. 5 and 6. 
     By the drawbar assembly of the present invention, a tractor and rear traveling equipment may be quickly and easily interconnected. Similarly, the two pieces of machinery may be separated for subsequent use of the tractor with a different piece of equipment. 
     The foregoing description should be considered as illustrative only of the principles of the invention. Since numerous modifications and changes will readily occur to those skilled in the art, it is not desired to limit the invention to the exact construction and operation shown and described, and, accordingly, all suitable modifications and equivalents may be resorted to, falling within the scope of the invention.