Abstract:
A grubbing plow mounted on two lower arms and an upper attachment point of a 3-point tractor hitch includes a frame having (1) a horizontal pivotal bar journaled at opposite ends thereof on the lower hitch arms; (2) an upper crank arm; and (3) a lower member. The pivot bar is pivotally mounted for rotational movement about a horizontal axis. The upper crank arm and lower member are aligned and oppositely directed from the pivot bar. 
     A knife-edged, V-shaped blade is rigidly attached to the lower end of the lower member and lies in a plane perpendicular to the length of the lower member. 
     A hydraulic cylinder is connected between the upper attachment point and the upper end of the upper crank arm for forcibly swinging the blade in an arc around the axis of the pivot bar to engage and remove roots encountered within said arc.

Description:
TECHNICAL FIELD 
     This invention relates to a hydraulically actuated tractor-mounted tool for removing unwanted trees, roots, sprouts and the like. 
     BACKGROUND ART 
     The control of unwanted plants, particularly small trees such as mesquite and the like, in pasture areas is a significant problem over wide areas of the earth. Control by chemical sprays, frequent mowings, individual extractions, have been utilized. Regardless of the devices and procedures heretofore used, there remains the problem of providing systems and procedures which are economically viable in the control of unwanted sprouts, small trees and the like from pasture areas. 
     Heretofore, various grubber units have been provided for use in connection with tractor-powered systems. For example, in the Tuttle U.S. Pat. No. 2,734,290, a tree and stone grubber is disclosed in which the vertical lifting mechanism of a 3-point tractor hitch is utilized for removing stones and small trees. Further, U.S. Pat. No. 2,735,198 to Zogg, et al., discloses a tractor-actuated grubbing implement for small trees and the like, with the vertical hoisting arrangement of a tractor hitch system being utilized. 
     DISCLOSURE OF THE INVENTION 
     The present invention relates to a hydraulic assisted grubbing plow that can quickly and easily be installed on any farm tractor having a standard 3-point hitch. The invention is used for digging up or grubbing small trees and plants, primarily in the complete removal of undesirable trees or brush-size plants. Mesquite, thorn bushes and many more plants which infest forests, ranges, meadows and cultivated land are significant detriments to the desirable plant growth and utilization of such areas. 
     The invention involves a knife-edged, V-shaped blade which is driven in an arcuate path centered on the pivots of two lower members of a standard 3-point tractor hitch. A driving force is provided by utilization of a double-acting hydraulic cylinder in place of the upper member of a standard 3-point tractor hitch. By providing a hydraulic cylinder on the upper member, a unique combination is provided. 
     Conventionally, the top member of a 3-point hitch provides for leveling or orienting the attached implement which is then lifted or lowered by hydraulic actuators coupled to the two lower members of the 3-point hitch. In standard tractor hitch systems, the top member is a mechanically adjustable device with a screw linkage for initial adjusting, such as leveling, but thereafter is passive. 
     In accordance with the present invention, a hydraulic top cylinder member is provided as an active member. It is a source of horizontal moving power which is transformed into a rotational arc-swing of the blade of the grubbing plow as it performs its grubbing operation. In the present invention, the two lower members of the standard 3-point hitch serve only to lower the plow into position to begin the grubbing operation, and to raise the plow to lift the grubbed plant above ground as may be desired. 
     In a more specific aspect, a grubbing plow for mounting on a 3-point tractor hitch is provided. It includes two lower arms and a frame having a horizontal pivot bar journaled in the two lower members of a 3-point tractor hitch. The frame has an upper member and a lower member extending upwardly from the pivot bar and downwardly from the pivot bar, respectively. The lower member rigidly attaches to a knife-edged, V-shaped blade. An active translational force generator is interposed between the upper end of the upper member and the upper connection of a standard 3-point tractor hitch for forcibly swinging the blade in an arc around the pivot bar axis of rotation. 
    
    
     BRIEF DESCRIPTION OF DRAWINGS 
     A more complete understanding of the invention and its advantages will be apparent from the following Detailed Description taken in conjunction with the accompanying drawings in which: 
     FIG. 1 is a side view showing an installation of the present invention; 
     FIG. 2 is an isometric view of an embodiment where the tractor moves backward to position the blade; 
     FIG. 3 illustrates a position of the grubber blade preparatory to removal of a root system; 
     FIG. 4 illustrates the position of the blade with the tree removed; and 
     FIG. 5 is an isometric view of the grubbing system oriented the reverse of the position shown in FIG. 2. 
    
    
     DETAILED DESCRIPTION 
     Referring now to FIG. 1, a farm tractor 10 is illustrated as having a 3-point tractor hitch in which two lower members 11 and 12 are connected at laterally spaced points for pivotal motion about an axis 13. The arms 11 and 12 are supported by conventional lifting means (not shown) so that the arms may swing up or down about axis 13. The third point of the 3-point hitch provides for pivotal movement about axis 14. 
     Conventionally, the upper member of the 3-point hitch pivoted at point 14 is a threaded screw-nut arrangement which is manually adjusted in order to set an initial attitude of an implement connected to the 3-point hitch. 
     In accordance with the present invention, the grubbing tool includes a horizontal pivot bar 20 which is mounted for pivotal movement about horizontal axis 21, the connecting point at the rear ends of the lower hitch members 11 and 12. Pivot bar 20 comprises a frame thus journaled in the lower members of the 3-point hitch. Pivot bar 20 has an upper member 22 and a lower member 23. A V-shaped blade 24 is mounted on the bottom of the lower member 23. Blade 24 is a flat blade whose surface is perpendicular to the axis of the members 22 and 23. 
     As best shown in FIG. 2, pivot bar 20 is of square cross section with short stub shafts 20a and 20b extending from opposite ends thereof on axis 21. Shafts 20a and 20b are journaled in the rear ends of the lower hitch members 11 and 12. 
     The upper member 22 is of the same general cross sectional configuration as the pivot bar 20 and extends from the upper surface of bar 20. A 3-hole adjustable clevis structure 22a is formed in the upper end of the upper member 22 and is provided with holes to receive pin 22b. 
     A double acting hydraulic cylinder 30 is fastened by way of link 31 to the pivot axis 14, the upper attachment point for the standard 3-point hitch. The piston 32 then extends to and is secured in the clevis 22a by pin 22b. 
     The lower member of the grubbing unit comprises a pair of bars 23a and 23b which extend downward from the lower surface of pivot bar 20. The lower ends are perpendicular to the length of the bars 23a and 23b. The blade 24 is secured to the lower ends of the bars 23a and 23b. The plane of the blade 24 is perpendicular to the length of the bars 23a and 23b. 
     The operation of the system as attached to a 3-point hitch of a tractor is illustrated in FIGS. 1, 3 and 4. 
     Referring to FIG. 1, the vertical hoist mechanism (not shown) of the 3-point hitch is actuated to position the tip of the blade 24 to the ground two or three feet away from the location of a plant 40 which is to be removed. Tractor 10 is then propelled backwards with the vertical hoist mechanism in a floating condition. As tractor 10 moves backward the blade follows a line, such as line 41, extending downward to a point preferably below the bud line of plant 40. 
     In FIG. 3, the blade 24 is shown in contact with the plant 40 with the grubbing frame tilted backward at a slight angle relative to vertical. With the blade positioned as indicated in FIG. 3, the hydraulic actuator 30 is energized to change the position of the grubbing frame from the angle shown in FIG. 3 to the angle shown in FIG. 4. The directed movement of the blade 24 in contact with the plant 40 generally causes the tap root of a plant 40 to be withdrawn as the blade-plant contact point moves in an arcuate path. Thus, the hydraulic actuator 30 may perform all of the operations that a standard top member of a 3-point hitch performs, but in addition affords a source of horizontal power to the grubbing system which is transformed into a rotational arc-swing of blade 24, thereby doing the work involved in the grubbing operation. 
     The vertical lift power afforded by the two lower members of the standard 3-point hitch serve only to raise and lower the plow and place it in position ready for work. Thus, in operation the tractor moves the grubbing plow adjacent to a tree or plant. The bottom blade 24 is tilted downwardly toward the plant by the hydraulic actuator 30. The tilted blade is lowered by the vertical hoist mechanism (not shown) via lower hitch members 11, 12 so that the points of blade 24 touch the ground surface. The vertical hoist mechanism is then set to a floating condition such that all restraints on lower hitch members 11, 12 are removed so that blade 24 may penetrate below ground with linear motion of the tractor. Movement toward the plant by tractor 10 causes the blade to penetrate below ground and contact the root of the plant, engaging it in the bottom of the V-shaped notch of blade 24. Pressure of blade 24 against the plant is maintained by continued torque of the tractor drive wheels or application of the tractor brakes. When this relationship is achieved, hydraulic cylinder 30 is activated to move blade 24 along an arc from (a) downward tilt to (b) horizontal to (c) upward tilt, providing thereby the downward to horizontal to upward rotational force which pulls the plant roots free of the soil. The wedging action of the V-shaped blade 24 and the partial cutting of the plant by the sharpened edges of the V notch in blade 24 provide secure grasping of the plant root throughout the grubbing operation. 
     In contrast, units in the prior art involve a fixed top link which results essentially in a parallelogram configuration. As such, there is no arc-swing of the blade. Only a slight horizontal movement of the blade as the parallelogram is moved vertically. The fixed downward inclination of the blade remains unchanged throughout the work and is conducive to the slippage of the sprout out of the grasp of the blade as the blade is lifted. Strictly vertical lifting of the blade by this configuration disturbs all of the soil above the blade and adjacent to the sprout, further loosening the grasp of the blade on the sprout, neither does it provide any horizontal cutting action of the blade. 
     In contrast, the arc-swing of the blade afforded by the active top link permits the leading edge of the blade to encounter the sprout, force it first downward, then horizontally and finally upward with constant pressure against the sprout and with minimum disturbance or loosening of the soil adjacent to it. This action, coupled with the wedging action of the V blade and the cutting, or partial cutting into, by the knife-sharp edge, assures the maximum grasping of the sprout. This is far different and beyond the grasp possible with strictly passive top linkage. At the completion of the arc-swing the sprout is pulled free of the soil, or cut below the bud line. It can be lifted completely free of the ground by continued linear travel of the tractor, by use of the tractor lift arms or by hand, but it is pulled loose by the arc-swing with the arc-swing doing all of the work. This is a significant difference over prior systems. 
     It has been established that the use of this grubbing unit results in complete removal of 91 percent of plants. In 5 percent of the plants, the stem was cut below the bud growth ring. Of the remaining 4 percent there was partial destruction of the plant. Tests, carefully controlled, show that the plow operates with great speed and requires a minimal expenditure of energy, making it the most efficient tool and method yet devised for controlling brush. The system works best for removal of trees and plants having tap roots, but it also works well on other types of plants. In all cases the main stump is removed, and generally along with the tap root and/or lateral roots. It has been found that the arcuate motion achieved by utilization of the active upper link in the 3-point hitch system, together with the structure of the blade as provided by the present invention, readily and efficiently performs the desired removal operation. 
     In the foregoing description it has been noted that the blade 24 is rearward facing and that the blade is positioned for extraction by a reverse movement of the tractor which drives the blade into the ground to a depth below the bud growth line. The blade direction may be reversed, as in FIG. 5. In such case, blade 24 would be tilted forward and downward. The tractor would be moved forward into position over the tree. The action of hydraulic cylinder 30 of the system would then be actuated to push on the top of the upper member 22 to rotate the blade from a rearward position to a forward position as it follows its arcuate path. Thus, it will be appreciated that the system is reversible, providing for either operation, as may be deemed optimum by the operator. Thus, the system may be mounted for use in either of two directions by merely disconnecting the 3-point linkages as shown in FIG. 2 and rotating the unit about a vertical axis so that the direction of the blade 24 is simply reversed. 
     Having described the invention in connection with certain specific embodiments thereof, it is to be understood that further modifications may now suggest themselves to those skilled in the art, and it is intended to cover such modifications as fall within the scope of the appended claims.