The present invention relates to tractor-mounted loaders and more particularly relates to leveling linkages for the implements attached to the arms of such loaders.
The desired leveling characteristics of various attachments adapted for connection to the arms of tractor-mounted loaders are not the same. For example, fork lifts must remain near level at all lift heights, whereas buckets should roll back slightly (never forward) as it is raised. Therefore, separate leveling linkage geometries are required for forklift and bucket applications.
The prior art recognizes the above-noted requirement of separate leveling linkage geometries. Specifically, in some leveling linkages which utilize a so called cross-over link, it is known to provide the link with adjustment holes to which the end of a link, forming part of the leveling linkage, may alternately be attached to change the way the leveling linkage acts on the implement to automatically change the attitude of the latter relative to the lift arms as the arms are raised and lowered. U.S. Pat. No. 3,966,070 granted 29 Jun., 1976 shows a representative structure of this type.
Some prior art loader arms are in an angular form having a knee to which a knee or pivot plate assembly forming part of the leveling linkage is pivotally attached, the plate assembly having a further pair of attachment points respectively attached to a pair of further leveling link components. In one of these known leveling linkage designs, the knee or pivot plate assembly can be disconnected from the arm knee, rotated 180.degree. about a vertical axis and reconnected to the arm knee to convert the linkage between a first arrangement for operating a fork lift and a second arrangement for operating a bucket. An example of such a linkage is disclosed in German Patent No. 2928278, granted 29 Jan. 1981. In another leveling linkage of this type, the pivot connection for one of the links attached to the knee plate assembly is carried by an eccentric which is rotatable between a first position for establishing a first linkage geometry for operation with a fork lift and a second position for establishing a second linkage geometry for operation with a bucket. Such a knee plate assembly is incorporated in the Model B3518 loader marketed by Bomford Turner Ltd. of Great Britain.
The prior art attempts at providing leveling linkages for accommodating the leveling needs of different attachments have one or more of the drawbacks of requiring pins to be removed and reinserted while manipulating relatively heavy leveling linkage components, or, as in the case of the eccentric, of not affording sufficient change in the geometry of the linkage for accommodating the change necessary for many loader designs.