1. Field of the Invention.
The present invention relates to hitch pins and in particular to an improved hitch pin to connect a farm implement to a drawbar of a towing vehicle.
2. Description of the Related Art.
Hitch pins are commonly used to connect a drawn vehicle to a towing vehicle. For example a farmer normally has a number of different implements which must be connected to the drawbar of a farm tractor. There are numerous designs of such pins for connecting a vehicle to a towing vehicle and preventing the pin from inadvertently falling out from the drawbar.
One particular hitch pin is relatively a simple and durable self-locking hitch pin that positively prevents the pin from inadvertently falling out of the connected members. U.S. Pat. No. 4,555,125 (patent '125) discloses an improved safety-lock hitch pin having a pin with a collar formed near its upper end and a transversely extending handle mounting member. A handle has a main body with a transversely extending opening through it to provide for pivotal mounting of the handle on the transverse member of the pin. A second opening in the main body of the handle contains a locking member biased by a spring into a locking position when the handle is lowered into a closed position with the lower end of the handle. From a closed and locked position, the locking member is manually depressed which allows the handle to pivot upwardly so that the pin can be removed. In the unlocked position, the handle provides for additional leverage for removal of a tight pin. However, it is more desirable to improve the ease of use and efficiency of manufacturing.
The hitch pin of patent '125 may be difficult to use in certain situations. First, from the closed and locked position, the locking member is manually pushed or depressed, typically, away and downwardly from the user. When a circumferential groove of the locking member is in alignment with the mounting member, the handle can be unlocked and pivoted through a limited arc. However, for some individuals, a seemingly large amount of force is required upon the point of contact on the locking member to unlock the hitch pin because of the limited amount of leverage that is provided to the user. Due to the relatively limited surface area for the point of contact provided on the locking member, some users may direct energy incorrectly on an angle, rather than directly thereon, leading to a relatively large amount of energy used and repeated attempts to unlock the hitch pin. For some individuals, the surface area upon which force is applied only allows for a small portion of, for example, the user's thumb or finger to support force to compress the spring. Additionally, the locking member, thus the spring, must be fully depressed for substantial alignment to unlock the handle. Otherwise, the end of the locking member will remain engaged with the groove of the mounting member, preventing the desired movement of the handle.
Next, when the locking member is depressed, the handle may be pivoted upwardly until the front surface of the main body engages with the collar of the pin; however, the handle may be pivoted upwardly only about 45 degrees until the surface engages with the collar stopping movement thereof. This sometimes provides difficulty to the user in connecting and disconnecting the drawn vehicle and the towing vehicle. Some drawbars or hitches may be positioned such that a greater angle of movement of the handle is desired for easier connection or disconnection of two vehicles. As a result, in order to connect the vehicles, the user is required to first insert the pin on an angle to clear the handle from any obstructions. In some circumstances, a 45-degree angle of movement may not provide adequate space to connect or disconnect the drawn vehicle and the towing vehicle.
It is desired to improve the manufacturing efficiency of the patent '125 hitch pin. First, the main body of the handle includes many internal cavities having precise measurements in order to properly receive the locking member. Thus, cast iron simply may not be used to manufacture the hitch pin disclosed in patent '125. Rather, more complex processes are necessary to create the bores and cavities within the main body, resulting in a greater amount of time spent manufacturing each item. This, in turn, results in higher costs.
Other pins have been designed which use a hasp that is inserted through an opening in the bottom of the pin after the connection is made. However, if the hasp is bumped or becomes caught on a corn stalk, for example, the hasp can be lost and the hitch pin can work its way out of the connection between the drawbar and the tongue of the drawn vehicle.
Some other hitch pins are provided with a self-contained over-center wedge in the bottom end of the pin which wedge by force of gravity will pivot to a transverse position at the bottom of the pin thus preventing the pin from being withdrawn unless the wedge is manually moved into an upright position. However, through use, the wedge can bounce back into the pin or it can become bent and, therefore, fail to drop into a locking position.
Other hitch pins have used wire spring yokes or chain yokes some with catches or padlocks. The wire spring yokes can become easily broken, particularly when used to provide extra leverage for removing a tight pin.
Thus, it is desired to provide an improved self-locking hitch pin that is easier to use and easier to manufacture, and yet positively prevents the pin from inadvertently falling out of the connected members. It is further desired to provide a hitch pin that is lower in costs and improves durability.