Abstract:
A pintle hitch adaptor enables a vehicle equipped with a drawbar or DMI bumper to tow trailers having different towing components. The pintle hitch adaptor comprises a sleeve that fits over arid is held to the drawbar. A pintle hitch is mounted to the sleeve. Aligned holes in the sleeve and the drawbar receive a hitch ball shank. A trailer tongue with a cup or eye engages the ball. A pintle hitch latch locks to prevent disengagement of the trailer tongue cup or eye from the ball. Shoulders on a pintle hitch post prevent: the latch from contacting the cup. Alternately, the ball can be removed, and a tow pin can to used between a hole in the trailer tongue and the drawbar and sleeve holes. A locking screw on the sleeve holds the sleeve and drawbar holes in alignment when the ball is removed.

Description:
RELATED APPLICATION 
   This application is a divisional of U.S. patent application Ser. No. 11/825,874 filed 10 Jul. 2007 now U.S. Pat. No. 7,478,821, which is a divisional of application Ser. No. 11/080,134, filed 15 Mar. 2005, now U.S. Pat. No. 7,264,261 entitled “Pintle Hitch Adaptor for Drawbar or DMI Bumper.” 

   BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The present invention pertains to towing vehicles, and more particularly to an apparatus that enables a first vehicle equipped with a drawbar to tow a second vehicle equipped with any of a variety of towing components. 
   2. Description of the Related Art 
   Various kinds of apparatus have been developed to tow trailers. A typical towing vehicle and trailer have complementary components that are engaged during a towing operation, and that are disengaged when the towing vehicle operates without a trailer. 
   Generally speaking, there are three major types of towing apparatus. The first type is called herein a simple receiver hitch. It comprises a receiver that is more or less permanently installed on the towing vehicle. The receiver is usually in the form of a longitudinally extending tube near the back end of the towing vehicle. One end of a shank is removably insertable into the receiver. A pin passing through the receiver and the shank retains the shank in the receiver. A second end of the shank protrudes from the receiver and is equipped with a hitch ball. The trailer has a cup, usually at the end of a tongue, that fits over the ball. A mechanism in the cup releasably locks the cup to the ball. Releasing the cup from the ball disengages the towing and trailers from each other. The strength of the entire simple receiver hitch system is limited by the strength of the pin and of the components that install the receiver to the trailer. Normally, the simple receiver hitch is limited to relatively small trailers, such as small boat and utility trailers. 
   Another type of towing apparatus is a pintle hitch, which is installed on a towing vehicle. A first kind of pintle hitch is comprised of a vertically oriented base with an upwardly oriented hook. Hinged to the base above the hook is a latch. The trailer has a tongue with an eye that fits over the hook. The latch is releasably lockable close to the hook tip to prevent the trailer eye from unintentionally disengaging from the hook. U.S. Pat. No. 5,332,250 teaches a typical hook kind of pintle hitch. Others are marketed by Northern Tool &amp; Equipment Co. of Menomonee Falls, Wis. 
   A second kind of pintle hitch uses a hitch ball instead of a hook. The trailer may have an eye that engages the ball. The pintle hitch latch is lockable over the ball to prevent the trailer eye from unintentionally disengaging from the ball. Alternately, the trailer may be equipped with a cup that fits over and releasably locks to the ball. In that situation, the pintle hitch latch rests on but does not lock over the trailer cup. The latch therefore rubs and wears on the cup. U.S. Pat. No. 4,434,996 shows both the first and second kinds of pintle hitch. 
   The pintle hitch is generally considered to be stronger than the simple receiver hitch. However, a major problem with the pintle hitch is the difficulty in installing it to a towing vehicle. For maximum benefit of the pintle hitch, it is often fastened to a vertical surface of the towing vehicle frame. Doing so is not an easy task. Properly aligned holes must be drilled into the towing vehicle frame. Because the pintle hitch is heavy, it is difficult to hold in place while laying out the mounting holes. Even if a template is used, the installation process is cumbersome and time consuming. Further, there are significant safety concerns involved. The fasteners may be over-torqued or under-torqued. The fasteners may rust, thus both compromising their strength and making the pintle hitch difficult to remove. Drilling holes in the towing vehicle frame tends to weaken it. The overall capacity of the pintle hitch system is thus limited by the joint and fasteners between the pintle hitch and the towing vehicle. 
   In an attempt to ease the task of installing a pintle hitch to a towing vehicle, it is known to provide an adaptor that utilizes a receiver on the towing vehicle. The adaptor has a vertical mounting plate with pre-drilled holes to which the pintle hitch is fastened. The adaptor has a shank that is insertable into the receiver. A typical adaptor may be seen in the catalog of Northern Tool &amp; Equipment Co. Although the adaptor simplifies the installation procedure, the entire system is limited in capacity by the strength and integrity of the fasteners between the receiver and the towing vehicle, by the fasteners between the pintle hitch and the adaptor, and by the pin between the receiver and the adaptor shank. In addition, it is known for the mounting plate to break, thus putting the trailer in the ditch. 
   U.S. Pat. No. 6,139,043 (&#39;043 patent) describes a one-piece shank and pintle hitch. The shank is removeably insertable into a towing vehicle receiver. The one-piece hitch of the &#39;043 patent eliminates the problem of a joint with fasteners between a pintle hitch and a vertical installation surface. Nevertheless, the capacity of the system is limited by the strength of the retaining pin between the shank and the towing vehicle receiver. 
   Other kinds of pintle hitches may be seen in U.S. Pat. Nos. 5,106,114 and 4,568,098. 
   The third major type of towing apparatus is a drawbar. Drawbars may be fixed to a towing vehicle, such as an agricultural tractor. Alternately, the drawbar may have limited motion relative to the towing vehicle, such as the drawbars of well know DMI bumpers. Drawbars are invariably horizontally oriented, and they have relatively large holes through them. A tow pin passes through the drawbar hole and a similar hole in a trailer tongue to engage the towed and towing vehicles. It is generally agreed that drawbars are the strongest and safest towing component for a towing vehicle. However, the tow pin and hole design for engaging a trailer is of rather limited usefulness. Versatility is an advantage of pintle hitches that is lacking in drawbars. 
   A major disadvantage of prior towing apparatus is related to the number of components that are required to suit different trailers. For the receiver type towing apparatus, one style of component is required for use with a hitch ball, while a different component is required for use with a pintle hitch. Thus, three different towing vehicle components are needed to suit just two types of towing apparatus. In fact, a third component is needed if a trailer is to be towed using a tow pin. 
   Thus, a need exists for improvement to towing apparatus. 
   SUMMARY OF THE INVENTION 
   In accordance with the present invention, a pintle hitch adaptor is provided that enables a vehicle equipped with a drawbar or DMI bumper to tow trailers having any of a variety of towing components. This is accomplished by a novel apparatus that includes a sleeve that fits over the drawbar and a pintle hitch mounted on the sleeve. 
   The sleeve is preferably sized and shaped to fit over a drawbar of an agricultural tractor, DMI bumper, or other similarly equipped vehicle. A lock screw on the sleeve bears against the drawbar and holds the sleeve at a desired location on it. There is a relatively large hole through a first end of the sleeve. 
   The pintle hitch is mounted on the second end of the sleeve. The pintle hitch is comprised of an upstanding post, to which is hinged a latch. The latch is pivotable between locked and open positions. A lever rotatable in the latch is used to selectively lock the latch in its locked position and to unlock the latch so it can be rotated to its open position. 
   In use, the sleeve of the adaptor is installed over the drawbar of a DMI bumper or agricultural tractor. The hole in the sleeve is aligned with the hole in the drawbar. The pintle hitch latch is rotated to its open position. The shank of a conventional hitch ball is passed through the holes in the sleeve and the drawbar and held in place with lockwasher and nut. The locking screw on the sleeve is tightened against the drawbar. The pintle hitch with the ball is then ready to tow a vehicle. 
   The trailer may have a cup that engages the hitch ball. It is a feature of the invention that the latch working end does not contact the trailer cup when the latch is in its locked position. Consequently, the latch does not wear on the cup during use. Alternately, the trailer may have an eye that engages the pintle hitch ball. Rotating the latch to its locked position prevents the trailer eye from unintentionally disengaging from the ball. 
   After a towing operation in which the hitch ball on the pintle hitch has been used to engage the trailer, it may be desirable to use the towing vehicle to tow a vehicle without using the ball. In that case, the ball is removed from the pintle hitch and drawbar. The aligned holes in the adaptor and drawbar are thus exposed for receiving a towing pin. The locking screw holds the adaptor sleeve at the proper location on the drawbar such that the ball is easily replaced when desired. 
   The method and apparatus of the invention, using a sleeve with a pintle hitch mounted on it, thus combines the versatility of a pintle hitch with the strength of a drawbar for towing operations. The probability of the adaptor being unable to tow a particular vehicle is remote, even though the adaptor can be removed from the towing vehicle for some towing operations. 
   Other advantages, benefits, and features of the invention will become apparent to those skilled in the art upon reading the detailed description of the invention and studying the drawings. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a side view of the pintle hitch adaptor of the present invention with the latch thereof in the locked position. 
       FIG. 2  is a top view of the pintle hitch adaptor of the invention. 
       FIG. 3  is a bottom view of the pintle hitch adaptor of the present invention. 
       FIG. 4  is longitudinal cross-sectional view of the pintle hitch adaptor showing the latch in the open position. 
       FIG. 5  is a view similar to  FIG. 1 , but showing a trailer with a cup that engages the pintle hitch adaptor hitch ball. 
       FIG. 6  is a view showing a trailer with an eye that engages the pintle hitch adaptor hitch ball. 
       FIG. 7  is a view showing the pintle hitch adaptor in use to tow a trailer by means of a tow pin. 
       FIG. 8  is a side view showing a conventional way of towing a trailer by means of a drawbar on the towing vehicle. 
   

   DETAILED DESCRIPTION OF THE INVENTION 
   Although the disclosure hereof is detailed and exact to enable those skilled in the art to practice the invention, the physical embodiments herein disclosed merely exemplify the invention, which may be embodied in other specific structure. The scope of the invention is defined in the claims appended hereto. 
   Referring first to  FIG. 8 , a conventional way of towing a trailer  4  with a towing vehicle  2  equipped with a drawbar  3  is shown. The drawbar  3  has a hole  27  through it. The trailer  4  has a tongue  6  with similar holes  8 . In towing configuration, the tongue  6  is located over the drawbar  3  such that the holes  8  and  27  align. Then a tow pin  10  is dropped through the aligned holes,  8  and  27 . 
   Next looking at  FIGS. 1-4 , a pintle hitch adaptor  1  is illustrated that includes the present invention. The pintle hitch adaptor  1  is particularly useful for enabling the towing vehicle  2  equipped with the drawbar  3  to tow a trailer (not seen in these views) by means other than the towing pin  10  of  FIG. 8 . However, it will be understood that the invention is not limited to vehicle related applications. 
   The drawbar  3  of the towing vehicle  2  to be used with the present invention is conventional. Drawbars  3  are typically found on agricultural tractors (not shown), in which case the drawbar  3  is a permanent and fixed part of the tractor. Alternately, the drawbar  3  may be part of a conventional DMI bumper. In that case, the drawbar  3  is capable of limited sideways motion as well as being spring loaded for limited longitudinal motion relative to the trailer. Near the drawbar free end  25  is hole  27 . 
   The pintle hitch adaptor  1  is preferably comprised of a sleeve  5  having a top wall  7 , bottom wall  9 , and opposed side walls  11 . The sleeve  5  has a back end  14  and a front end  16 . Although not required for the proper functioning of the invention, it is preferred that the sleeve  5  also have a front wall  13 . As may be seen, the sleeve bottom wall  9  may include a lock screw  17  near the back end  14 . For example, a nut  19  may be welded to the sleeve bottom wall  9 , with the lock screw  17  threading through the nut  19  and through a hole  21  in the bottom wall  9 . Preferably, there is a relatively large hole  23  through the top wall  7  near the front wall  13 , see particularly  FIGS. 4 and 7 . Further, the bottom wall  9  may be cut out for a distance X from the front end  16 , such that the bottom wall  9  has a front edge  15 . A typical value for the distance X is approximately 2.25 inches. 
   The adaptor walls  7 ,  9 , and  11  are sized and shaped to enable the sleeve  5  to fit easily over the drawbar  3 . When the sleeve front wall  13  is proximate the drawbar free end  25 , the sleeve hole  23  is aligned with the drawbar hole  27 . 
   Upstanding from the adaptor sleeve  5  is a pintle hitch  29 . In the illustrated construction, the pintle hitch  29  is comprised of a post  31  welded or otherwise mounted to the sleeve  5 . The post  31  may be seen to include a bottom section  32  and a top section  34 . As may be seen particularly in  FIG. 2 , the post  31  has a first width W along its bottom section  32 , and a narrower width Wl along its upper section  34 . Consequently, there is a shoulder  36  on each side of the post  31 . As illustrated in  FIG. 4 , a notch  33  is provided at the junction of the post top surface  35  and the front surface  37 . 
   Hinged to the post  31  is a latch  39 . As illustrated, spaced apart arms  43  of the latch  39  are hinged by such means as the bolt and nut  41  shown. The latch  39  has a working end  45  between the arms  43  opposite the bolt and nut  41 . 
   A lever  47  is rotatable in the latch  39 , as by means of the bolt and nut  49  shown. With particular reference to  FIG. 4 , the lever  47  is seen to have a first end  52  that is inside the latch working end  45 , and an opposed second end  55 . The second end  55  is composed of a first surface  57 , and a second surface  59  that is approximately perpendicular to the first surface  57 . A pair of rods  50  extends oppositely from the lever  47  near the second end  55  and outside of the latch  39 . A spring  51 , or other means, biases the lever  47  to rotate in the direction of arrow  61 . 
   In  FIGS. 1 and 2 , the latch  39  is shown in a locked position. In that situation, the lever first surface  57  is adjacent the post notch  33  (seen in phantom). The spring  51  retains the lever first surface  57  adjacent the post notch  33 . The coaction of the lever  47 , post  31 , and bolt and nut  49  prevent the latch  39  from opening in the direction of arrow  61 . To open the latch  39 , a person pushes the rods  50  in the direction of arrow  63  against the spring  51 . That action rotates the lever  47  in the direction of arrow  63  and removes the lever first surface  57  from the vicinity of the notch  33 . Consequently, the latch  39  is able to pivot in the direction of arrow  61  to the open position seen in  FIG. 4 . When the latch  39  is pivoted back in the direction of arrow  61 , the lever second surface  59  contacts the post upper surface  35  to rotate the lever against the spring  51  and enable the lever second surface  59  to slide along the post upper surface  35  until the lever first surface  57  is at the post notch  33 . At that point the latch spring  51  rotates the lever  47  such that the first surface  57  falls to again be adjacent the post notch  33 , see particularly  FIGS. 1 and 2 . 
   The pintle hitch adaptor  1  enables a vehicle  2  equipped with the drawbar  3  to tow trailers other than those having a tongue  6  with holes  8  ( FIG. 8 ). In  FIGS. 1-4 , the pintle hitch adaptor is installed on a drawbar  3  with the sleeve hole  23  aligned with the drawbar hole  27 . The pintle hitch adaptor locking screw  17  is tightened. As seen in phantom, the shank  64  of a hitch ball  65 , which may be conventional, is passed through the holes  23  and  27 , with a flange  67  of the ball resting on the sleeve top wall  7 . The ball  65  is held in place with a lock washer and nut  69 . 
   In  FIG. 5 , a cup  71  is shown engaging the hitch ball  65  (shown in phantom). The cup  71  is commonly used at the end of a tongue of a trailer  4 ′, and is well known in the art. To enable the cup  71  to engage the ball  65 , the pintle hitch adaptor latch  39  is first opened, as shown and described in connection with  FIG. 4 . After the cup  71  is engaged with the ball  65 , the latch  39  is locked. It is a feature of the invention that the latch working end  45  does not contact the cup  71  during operation. Instead the latch arms  43  contact the post shoulders  36  to limit pivoting of the latch  39 . When the latch  39  is in its locked position, there is a clearance C between the latch working end  45  and the cup  71 . Accordingly, the latch  39  does not wear on the cup  71  during use. After the towing operation, the latch  39  is opened as previously described, and the cup  71  is disengaged from the ball  65  in known manner. 
   According to another aspect of the invention, the hitch ball  65  is removable from the pintle hitch adaptor  1  and the drawbar  3 . Because of the locking screw  17 , the pintle hitch adaptor  1  and drawbar holes  23  and  27 , respectively, remain aligned. In that manner, the pintle hitch adaptor  1  and drawbar  3  remain ready for later use with a ball  65  without any adjustment needed of the pintle hitch adaptor  1  on the drawbar  3 . 
   The versatility of the pintle hitch adaptor  1  is further demonstrated in  FIG. 6 . As is illustrated in phantom, a trailer having a tongue with an eye  73  is towable by means of the pintle hitch adaptor  1  and drawbar  3 . The eye  73  engages over the hitch ball  65  and is prevented from disengaging by the locked latch  39 . 
   Further in accordance with the present invention, a trailer  4  having a conventional tongue  6  ( FIG. 8 ) is towable when the pintle hitch adaptor  1  is installed on the drawbar  3 .  FIG. 7  shows a pintle hitch adaptor  1  installed on the drawbar  3 , but no hitch ball  65  is used. After the latch  39  is pivoted to the open position, illustrated in  FIG. 4 , the trailer tongue  6  is maneuvered such that its holes  8  are aligned with the pintle hitch adaptor  1  and drawbar holes  23  and  27 , respectively. In this configuration, a tow pin  10 , or other similar device, is dropped through the aligned holes  8 ,  23 , and  27 . The latch  39  is pivoted to its locked position. The trailer  4  is then towable in the manner seen in  FIG. 8 , but with the latch  39  preventing the tow pin  10  from bouncing out of the holes  8 ,  23 ,  27 . The locking screw  17  holds the pintle hitch adaptor  1  in proper place on the drawbar  3  such that a hitch ball  65  is easily usable again at a later time without having to realign the holes  23  and  27 . Further, the lever  47  of the pintle hitch adaptor  1  may be supplied with an aperture  80  for receiving a safety clip or other device (not shown) to thereby provide added security in maintaining the lever  47  in closed position. 
   In summary, the results and advantages of trailers  4  can now be more fully realized. The pintle hitch adaptor  1  provides both versatility to a conventional drawbar  3  as well as improved safety in the connection between the towing vehicles and trailers. This desirable result comes from using the combined functions of the sleeve  5 . The sleeve may be used without a hitch ball  65 . With the ball  65 , a trailer having a cup  71  or an eye  73  is towable. The latch  39  is selectively openable and lockable to allow engagement and prevent disengagement, respectively, of the trailer  4  from the ball  65 . The ball  65  is removable from the pintle hitch adaptor  1  to enable the drawbar  3  to function in the same manner as if the pintle hitch adaptor  1  were not present. 
   It will also be recognized that in addition to the superior performance of the pintle hitch adaptor  1 , its construction is such as to be of modest cost in relation to the benefits it provides. In fact, the increased productivity and versatility that the pintle hitch adaptor  1  provides to a towing vehicle  2  equipped with a drawbar quickly recoups the initial cost. 
   Thus, it is apparent that there has been provided, in accordance with the invention, a pintle hitch adaptor  1  that fully satisfies the objects, aims, and advantages set forth above. While the invention has been described in conjunction with specific embodiments thereof, it is evident that many alternatives, modifications, and variations will be apparent to those skilled in the art in light of the foregoing description. Accordingly, it is intended to embrace all such alternatives, modifications, and variations as fall within the spirit and broad scope of the appended claims.