This invention relates to a tillage attachment for mounting on an agricultural implement of the type comprising a tool bar, ground wheels for supporting the tool bar for movement across the ground and means for causing the tool bar to move in a direction transverse to its length.
Rod weeders are known and are conventional agricultural implements. These generally comprise a tool bar mounted upon ground wheels and attached to a hitch for movement of the tool bar across the ground. The rods are then attached to the tool bar on shanks which extend downwardly from the tool bar with the rods parallel to the tool bar and mounted on bearings at the lower end of the shanks. A number of separate rods can be arranged across the tool bar to match the full length of the tool bar. The rod or each of the rods is then driven by suitable mechanism so that it rotates about a longitudinal axis in a reverse direction relative to a normal rolling direction. Such a device is intended to work just below the soil surface to cut weeds and to lift the weed parts to the surface of the soil where they wither and die.
Rod weeders of this conventional type have been well known for many years and have been manufactured and sold in large numbers. However, they have a number of significant disadvantages, the most important of these being that as the level of the ground varies relative to the tool bar due to any local changes in surface height, the depth of the rod relative to the surface of the ground significantly varies and unless the rod is working at exactly the right depth, its effectiveness is seriously reduced.
My prior U.S. Pat. No. 4,690,223 discloses a rod weeder attachment which includes a clamp arrangement for mounting upon a tool bar of an agricultural implement, an arm arrangement which extends rearwardly from the clamp arrangement and is spring biased downwardly toward the ground, a ground wheel mounted upon the rear end of the arm which has a peripheral surface for running upon the ground and for defining the height of the arm above the ground, a pair of shanks which extend downwardly from the arm, a rod supported on the lower end of the shanks in bearings which allow rotation of the rod about its axis and a drive arrangement which communicates drive from the ground to the rod to rotate the rod as it moves through the ground.
This arrangement was designed to provide accurate control of the depth of the rod in the ground since the ground wheel runs on the surface of the ground and thus accurately controls the height of the arm and the rod which is coupled to the arm by the rigid shanks. The rod is thus of a limited length and is controlled accurately by its ground wheel.
One problem which has however arisen from the design disclosed in my above patent is that of starting the operation of the device. As in the previous design the ground wheel is necessarily above the level of the rod, when the arm is lowered toward the ground in a start up process, the rod firstly engages the ground and holds the wheel above the ground. As the attachment is moved forward there is no drive to the rod since the ground wheel remains above the ground and hence the rod in many cases encounters difficulty in entering the ground to commence proper operation.