Abstract:
A three point tractor hitch permitting an implement to be attached or detached by an operator without leaving the tractor seat. The upper hitch arm includes a linear actuator with a hand grip and a hand operated switch controlling extension and contraction of the upper arm. A latching mechanism and a hand operated latch release are mounted on the upper arm facilitating attachment and release of the upper arm to an upper attaching pin of an implement hitch mast. One of the two lower arms of the hitch can be shifted laterally by a hydraulically actuated cylinder.

Description:
TECHNICAL FIELD 
     This invention relates to a three point hitch for connecting an implement to a tractor. 
     BACKGROUND OF THE INVENTION 
     Currently available three point hitch systems require two people to connect implements to a tractor. One person drives the tractor and one person on the ground attaches the two lower arms which require a precise alignment. With two people, one hitch arm can be attached and then with a slight forward or backward movement of the tractor, the other arm is attached. For one person to attempt to attach a tractor to a three point hitch implement, the task becomes onerous requiring a lot of back and forth movement of the tractor and much mounting and dismounting to and from the tractor seat. With one hitch arm attached and one hitch arm loose, hitching can become very dangerous should the tractor move and the operator get caught between the tractor and the implement. 
     The upper center arm is just as precise to attach as the two lower arms. It has to be readjusted in length every time a different implement is used. This becomes very time consuming because typically it is extended and retracted by manually screwing a turnbuckle in or out. 
     Efforts to solve these problems have resulted in a variety of aftermarket designs which require the purchase and use of an additional intermediate devices that are attached to the tractor to facilitate its connection with various implements. 
     U.S. Pat. No. 2,688,865 discloses a hand operated hydraulic lock for locking the trunk compartment of a motor car and is it not applicable to a attachment of implements to a tractor. 
     U.S. Pat. No. 3,312,478 is a very complex intermediate device with many moving parts and chains and offers as much of a attaching problem as those presented by conventional implement hitches. 
     U.S. Pat. No. 3,434,737 offers an intermediate hitching device with an excessive number of parts requiring manual adjustment in order to hitch an implement to a tractor. 
     U.S. Pat. No. 3,561,789 solves part of the problems of attaching tractor to implement but still uses a hitch adaptor as an additional device between tractor and the implement and is of a complex design. 
     U.S. Pat. No. 4,125,271 relates to a tool suspension for either front or rear mounting of tools from vehicles in the form of a three point suspension for hydraulic lifting and lowering. Front and rear mounted tools are used on motor vehicles for road maintenance, snow clearing, street cleaning and grass cutting. No adaptation was found for use with farm implements. 
     U.S. Pat. No. 5,029,650 discloses an intermediate frame mounted on the tractor hitch links. 
     U.S. Pat. No. 5,743,339 discloses a two part steel plate device. One plate is attached to the three point hitch of the tractor and the other plate is attached to the implement. Steel plate of a size and strength to accomplish the task would be very heavy. Another drawback to this system is that there are no provisions for the fore and aft adjustment of the upper link. A still further problem is a matching plate would have to be purchased for each implement used. This represents a substantial investment for the operator. 
     U.S. Pat. No. 5,975,215 is a low profile transferable hydraulic three point hitch designed for use on the front or rear of a truck. The truck can then be used to attach to three point implements instead of using a tractor. 
     U.S. Pat. No. 5,997,024 illustrates a hitching mechanism for tractors to aid in steering the implements in specific agricultural uses such as in a track laying application where both a steering function and a lateral shifting capability in needed. This is a specialized function and not needed for general use of tractors and implements. 
     OBJECTS AND SUMMARY OF THE INVENTION 
     It is an important object of the invention to provide a power operated tractor hitching system which can be readily aligned and secured to an implement without the operator leaving the tractor seat and without the use of intermediate devices. 
     It is a further object of the invention to provide an improved three point hitch which is economical to manufacture, permits quick attachment of the implement and provides long trouble free service. 
     The invention solves the problems present in prior implement hitch designs by a redesign of the tractor hitch so as to eliminate the need for intermediate hitch devices. The ends of the hitch arms are redesigned and controls added to permit the operator to hitch the tractor to an implement without dismounting from the tractor seat. The tractor is easily and quickly hitched to an implement by one person in a safe manner. The weight and expense of intermediate hitch devices is avoided. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The invention is illustrated in the accompanying drawings in which: 
     FIG. 1 is a partial perspective view of an agricultural tractor with a portion of the left wheel removed showing an embodiment of a three point tractor hitch system. 
     FIG. 2 is a side view of a fixed lower jaw in an open position and with a hydraulic locking shaft in a retracted position. 
     FIG. 3 is a side view of the fixed jaw with the hydraulic locking shaft extended to a closed position. 
     FIG. 4 is a perspective view of upper fixed and moveable jaws. 
     FIG. 5 is a perspective view of the upper fixed and moveable jaws being lowered to attach to a pin mounted in the upper center of an implement hitch mast. 
     FIG. 6 is a side view showing the upper moveable jaw in an open position. 
     FIG. 7 is a side view showing the upper jaw in a closed position. 
     FIG. 8 is a schematic illustration of a control system for the hydraulic actuators of the three point tractor hitch. 
     FIG. 9 is a side view of the lower arm of a standard three point tractor hitch, and 
     FIG. 10 is a side view of an upper center arm of a standard three point tractor hitch. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Referring to FIG. 1, the forward ends of a pair of laterally spaced lower hitch arms  1 ,  5  are connected to an agricultural tractor  46  by a pair of ball joints  8 , only one of which is illustrated. The rear ends of the lower arms  1 ,  5  have upwardly open jaws  2  rigidly secured thereto which are adapted to connect to pins or studs  31  on an implement  30 . Thus the lower arms  1 , 5  differ from the standard arm shown in FIG. 9 which has a ball joint at both ends. The hitch includes an upper arm  10  which is connected at its forward end to the tractor  46  by a ball joint  24 . The rear end of the arm  10  includes an upper fixed jaw  11  and an upper moveable jaw  12  which are adapted to connect to an upper pin  33  of a hitch mast on the implement  30 . 
     The agricultural tractor  46  includes an operator&#39;s station including a seat  40  for the operator and a control system  42  with hydraulic control valve and a steering wheel  50 . A portion of the left rear wheel  48  has been removed for illustration purposes. 
     FIG. 2 shows the fixed open jaw  2 , on the lower lift arm  1  with the locking shaft  4  retracted to an unlocked position in which the jaw  2  can receive the stud  31  of the implement. The mouth of the open fixed jaw  2  has sufficient width to readily enclose the lower hitch studs  31  of the implement  30 . The flared width of the two fixed jaws  2  allows the operator to back the tractor  46  and attach it to the implement  30  without the tractor being in perfect alignment horizontally, vertically or laterally. In operation the fixed open jaws  1 ,  5  of the two lower arms  1 ,  5  are positioned under the lower hitch studs  31  of an implement  30 . As the arms  1 ,  5  are hydraulically raised by a pair of tractor mounted life arms  47 , the jaws  2  encompass the implement studs  31 . Hydraulic cylinders  3  secured to the lower hitch arms  1 ,  5  are extended causing the locking shafts  4  to extend to positions above the implement studs  31  thereby locking the rear ends of the lower arms  1 ,  5  to the implement  30 . 
     The lateral spacing of the implement studs  31  vary from implement to implement. To overcome this problem, a hydraulic cylinder  9  has its opposite ends attached, respectively, to the tractor  46  and to the lower arm  5 . This enables the operator to change the lateral distance between the trailing ends of the arms  1 ,  5  to accommodate the different, lateral spacings of the implement studs  31 . The opposing arm may be left in it&#39;s original position. 
     Instead of using the standard turnbuckle  32  illustrated in FIG. 10, the present invention uses a linear hydraulic actuator in the form of a hydraulic cylinder  23  which has a fixed jaw  11  and a moveable jaw  12  rigidly secured to the cylinder component of the hydraulic cylinder  23 . The rod component of the cylinder  23  is connected to the tractor  46  by a ball joint  24 . 
     The implement  30 , when not in use, is almost never parked in the exact fore and aft position. The hydraulic cylinder  23  enables the operator to change the fore and aft position of the jaws  11 ,  12  to a proper distance to engage the upper center pin  33  on the hitch mast of the implement  30 . 
     As shown in FIGS. 4 through 7, the downwardly open fixed upper jaw  11  is fixedly attached to the cylinder component of the hydraulic actuator  23 , which constitutes the upper centrally positioned arm of the three point hitch. The moveable jaw  12  is pivotally connected by a transverse pin  16  to the fixed jaw  11 . FIGS. 5 and 6 show the moveable jaw  12  in a downwardly pivoted open position in which it can receive the implement pin  33 . As the rear end of the upper hitch arm  10  is lowered, the implement pin  33  engages the crotch of the moveable jaw  12  and pivots the moveable jaw  12  to a latched or locked position shown in FIG. 7 in which a latching or locking block  13  engages a complementary notch in the movable jaw  12 . The latching block  13  is pivotally connected to the rear end of the latching lever  14  which in turn is pivotally connected to the fixed jaw  11 . Guide pins  17  on the fixed jaw  11  guide the up and down movement of the latching block  13 . The latching lever  14  is biased toward its latching position shown in FIG. 7 by a latching lever spring in the form of a coil spring  15  interposed between the fixed jaw  11  and the lever  14 . 
     A hand grip  18  is rigidly secured to the cylinder component of the hydraulic cylinder  23  with a laterally extending hand gripable portion disposed in vertically spaced relation to and above the cylinder  23 . A fore and aft extending hand operated release  19  has an intermediate part which is pivotably connected to the hand grip  18  and includes a release handle on its fore end parallel to and disposed between the gripable portion of the hand grip  18  and the cylinder  23 . The aft end of the release  19  is operatively associated with the forward end of the latching lever  14  so that upward movement of the release handle of said release  19  pivots said latching lever  14  to move the latching block  13  to it&#39;s release position shown in FIGS. 4,  5  and  6 . 
     In order to disengage the fixed and movable upper jaws  11 ,  12  from the upper pin  33 , the operator with one hand, grasps the release handle of the latching block release  19  and the hand grip  18 . By closing these handles together, the release handle  19  depresses the fore end of latching lever  14 , collapsing the latching lever spring  15  and releasing the latching block  13 . With the latching block  13  released from the moveable jaw  12 , the operator can lift the fixed jaw and the moveable jaw  12  clear of the implement pin  33 , disengaging the upper arm from the implement as shown in FIG.  5 . 
     The controls for operating the hydraulic cylinders  3 ,  6 ,  9  and  23  are shown schematically in FIG.  8  and include an electric or solenoid valve  22  mounted on the tractor which controls the actuation of the hydraulic cylinder  23  of the upper arm  10 . The electric valve  22  is controlled through operation of a remote three position thumb switch  20  mounted on the hand grip  18  secured to the hydraulic cylinder  23 . With one hand, an operator can adjust the length of the upper arm  10  and manoeuver the upper arm  10  and the jaws  11  and  12  into an implement attaching position with relative ease. Hydraulic fluid, under pressure, leaves a tractor hydraulic pump  49  and passes through a hydraulic hose  100  to the electric valve  22 . The electric valve  22  serves as a junction box for the hydraulic fluid to be distributed either to the upper arm cylinder  23  or to the lower arm cylinders  3 ,  6  or to the cylinder  9 . If the upper arm cylinder  23  is not being actuated the fluid passes through the electric valve  22  on to the manual control valve of the control  42  by way of a hose  101 . If no cylinders are being actuated by the manual valve of the control  42  the fluid passes through the valve  42  and returns back to a tractor hydraulic reservoir  51  by a return hose  102 . To actuate the upper arm cylinder  23 , the electric thumb switch  20  is moved from its neutral position which opens a port in the electric valve  22  to divert fluid into either, a hose  108  or a hose  109  to retract or extend the cylinder  23 . 
     The manual hydraulic valve of the control  42  is used to deliver fluid to cylinder  9  by way of hose  130  or  131  to extend or retract this cylinder. The manual hydraulic valve of the  42  is also used to deliver fluid to cylinders  3  and  6  by hoses  120  or  121  to extend or retract these cylinders simultaneously. 
     Electric current flows from a tractor coil  45  through an electric line  200  via a fuse  44  to the thumb switch  20  attached to the hand grip  18  mounted on the hydraulic cylinder  23 . When activated, the thumb switch  20  sends an electrical current via wire  201  or  202  to open ports in the electric valve  22  to direct hydraulic fluid through either hose  108  or  109  to retract or extend the cylinder  23 . The electrical circuit is made compete by a ground wire  300  attached to the side of the electric valve  22  to which a jumper wire  301  is attached to complete the circuit for wire  201  or  202  as they are individually energized by the thumb switch  20 . 
     The herein described three point hitch obviates the need for an intermediate hitch device to aid in hitching up misaligned implements. This invention also permits a single person to hitch up implements previously requiring two persons. By using this invention a lone operator is able to hitch up an implement without dismounting from the tractor operator seat. 
     While specific embodiments of the invention have been shown and described, it will be understood, of course, that the invention is not limited thereto since modifications may be made and other embodiments of the principles of this invention will occur to those skilled in the art to which this invention pertains. Therefore, it is contemplated by the appended claims to cover any such modifications and other embodiments as incorporate, the features of this invention within the true spirit and scope of the following claims.