Earth working – Mast type hitch
Reexamination Certificate
1999-10-22
2001-05-08
Pezzuto, Robert E. (Department: 3671)
Earth working
Mast type hitch
C280S478100
Reexamination Certificate
active
06227305
ABSTRACT:
CROSS-REFERENCE TO RELATED APPLICATION
This application claims priority upon German application 198 49 061.5 filed Oct. 24, 1998, which is incorporated herein by reference.
BACKGROUND OF THE INVENTION
The invention relates to a lower steering arm assembly for an attaching device of a tractor.
EP 0 608 750 A1 describes a lower steering arm assembly for a three-point attaching device of a tractor. A forged strut, at one end, has a ball eye to be connected to a pivot pin at the rear of the tractor. The strut has a rectangular cross-section and is stepped. Near its free end, the strut is forged to be U-shaped. A cover is welded to the arms of the U-shaped portion forming a closed chamber. The forged web of the strut has a formed-in pocket. A blocking pawl is pivotably arranged around a pin connection in the pocket. The blocking pawl is spring loaded into the blocking position where it is pivoted out of the chamber. Two further pins are provided at a distance from the pivot pins. One of the pins is guided outwardly through an opening in one of the arms of the U-shaped portion. A knob is on the end of the pin to enable manual manipulation of the pawl. Thus, it is possible to move the blocking pawl, loaded by the spring, into a position which is withdrawn into the pocket. A stop face is provided at the end of the chamber of the forged strut. An insertable end is inserted into the chamber. The end has a substantially rectangular cross-section. A recess extends through the entire side face of its shank. The end has a supporting face for the locking face of the blocking pawl. The supporting face extends substantially transversely to the longitudinal axis of the insertable end. The end face of the insertable end comes to rest against the stop face of the chamber. At its end projecting from the chamber, the insertable end has a ball eye. The ball eye provides a connection with a corresponding attaching pin of the implement. After the blocking pawl has been retracted, the insertable end may at least be partially extracted from the chamber to facilitate the coupling operation. The setting recesses in the shank enable angular adjustment relative to the strut remaining at the tractor in order to facilitate the coupling operation. By reversing the tractor, the insertable end can be driven into the chamber. As this occurs, the blocking pawl, after the end face of the shank of the insertable end has stopped against the stop face of the chamber, drops into the recess in the side face of the shank.
The stop face at the end of the U-shaped recess of the strut must be machined to be able to observe the tolerances required for accurate locking. The stop face is adapted to the distance between the end face of the shank of the insertable end and the blocking face of the recess, and also to the locking face of the blocking pawl. In practice, close tolerances cannot be observed because subsequent machining, when the cover has already been associated with the U-shaped region, is not possible. This design makes it necessary for the entire strut to be forged, which, in turn, means high costs. Furthermore, since the blocking pawl is supported by a journal, a great deal of machining is required. Finally, the actuating knob has to be associated with different parts, depending on whether it is used for the left-hand or right-hand steering arm. In addition, due to the direction of the force acting on the actuating knob, remote actuation, by a cable operated from the tractor seat, is not possible.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide a lower steering arm assembly that is cost-effective. The steering arm assembly also includes close tolerances relative to locking conditions between the strut and the attaching end.
In accordance with the invention, a lower steering arm assembly has a strut produced from a flat material. The strut has two narrow faces, two side faces, a first end to permit pivotable attachment to the tractor, and a second end. The second end has an attaching end which enables connection with the implement. The attaching end is removably secured to the second end by a locking mechanism. The locking mechanism, in the released condition, is movable relative to the second end of the strut. The locking mechanism enables a pivot movement in the extracted condition. The locking mechanism includes a recess in a side face of the strut towards the second end. The recess has a blocking face. A blocking pawl is associated with the attaching end. The blocking pawl engages the recess and is pivotably held in a pocket of the attaching end. The blocking pawl has a locking face cooperating with the blocking face. A spring loads the blocking pawl which operates the blocking face. The spring which loads the blocking pawl enables the pawl to assume the engaged position. An actuating means disengages the blocking pawl from the recess. The recess has a truncated cone-shape. The blocking pawl is pivotable around a pivot axis which intersects the longitudinal axis at a distance at a right angle. The pawl has a locking face adapted to the inner side face of the recess. The inner side face serves as the blocking face. The attaching end has two parts which are non-removably connected to one another. Together, the two parts form a chamber which is open on one side. The chamber receives the second end of the strut. A first part of the second end of the strut constitutes a base member which includes the pocket for receiving the blocking pawl and the mechanism connecting to an implement. The second part constitutes a cover. The second part has a stop face co-operating with an end face at the second end of the strut.
An advantage of this embodiment is that the strut does not have to be forged. Instead, it is possible to use a relatively cheap profiled material as a starting material. Furthermore, it is possible to observe relatively close tolerances without the need of a chip-forming machining operation. Accordingly, the cover includes the stop face. For tolerance reasons, the position of the stop face may be adjusted when connecting the cover to the base member. As at great distances from the point where the strut is articulated at the tractor, there is no need for any welding work to be carried out at the strut, there are no endangered portions. The attaching end, and especially the base member, is a relatively small and light part in comparison to the strut.
Thus, the base member can be produced cost-effectively as a forging. Also, the recess to receive a bearing ball can be forged in at the same time. Whereas, the base member is preferably forged, the cover is preferably hot-formed out of plate metal and welded to the base member. Setting recesses are provided to achieve a sufficiently large pivot movement of the attaching end in the extracted condition. The setting recesses open to the narrow faces of the strut. The recesses begin at a distance from the end face of the strut. The recesses extend over a certain length. The shape of the recess in the side face of the strut and the locking face of the blocking pawl are adapted to enable easy centering of the attaching end relative to the strut. Additionally, positive engagement of the blocking pawl and an advantageous distribution of loads is provided. Furthermore, by dividing the attaching end, the attaching may be easily adapted to struts with different thicknesses. Accordingly, only the cover needs to be modified. The expensive forging can be identical for all strut sizes.
According to a further embodiment of the invention, the blocking pawl has a supporting face at its end removed from the locking face. The supporting face, in its cross-section, is delimited by a circular arch. The circular arch is pivotably supported on a corresponding bearing face in the pocket. The spring is a leaf spring supported in the pocket. The blocking pawl is loaded by the spring such that the supporting face is held in contact with the bearing face. Accordingly, force is introduced advantageously from the blocking pawl into the base member of the attaching
GKN Walterscheid GmbH
Harness & Dickey & Pierce P.L.C.
Pezzuto Robert E.
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