This invention relates to an improved timber stacking assembly. More particularly, the invention is directed to an improved stop mechanism for the lifting arms of a timber stacker.
There is depicted and described in our prior copending U.S. patent application Ser. No. 747,553, filed Dec. 6, 1976, an improved sawmill apparatus wherein one of the components thereof comprises a timber stacker. Reference may be had to the aforesaid U.S. patent application for details of the sawmill apparatus and the disclosure of said patent is considered incorporated herein for all intents and purposes.
The timber stacker of the aforementioned patent application is specifically illustrated in FIGS. 26-28 and is described in detail therein as to mode of operation and construction. The essential features of the therein described timber stacker comprise at least one lifting arm that is movable between a first generally horizontal position to a second generally vertical position. The lifting arm includes a stop member indicated at 166 for holding the timbers in alignment on the lifting arm as the arm is moved into its upright position. After the timbers have been stacked vertically, the lifting arm is returned to its horizontal position for receipt thereon of a second row of timbers.
Use of the timber stacker of the aforesaid patent application has revealed that under ideal operating conditions, it will load and stack timbers with reasonable effectiveness. Furthermore it possesses the significant advantage that it is much simpler in construction and is more efficient to use than the more conventional timber stackers heretofore known.
On the other hand, the timber stacker of our aforesaid U.S. patent application has been found subject to certain limitations. Thus, the timber stacker mechanism is effective in aligning the timbers onto the arm thereof. The stop member is effective to hold the timbers on the lifting arm in its path of travel to the vertical. However, certain problems have been encountered as the lifting arm is moved from the vertical position and back to the horizontal. These problems have been attributed mainly to the presence of the stop member 166. It has been found, for example, that upon occasion, the stop member will engage the lower timber of the stack as the lifting arm is returned to the horizontal position for reloading. Such engagement of the stop member with the lowermost timber of the stack has caused this lowermost timber to be moved, thereby producing wobbling and instability in the timber stack. Upon occasion, the stop member has caused the erect timber stack to topple over, thus of course, effectively defeating the intended purpose of the timber stacking assembly. Even if the timber stack does not topple over, any slight wobbling of the stack is undesirable since any instability in the timber stack moves these timbers out of stacked alignment one with the other. Furthermore, if one stack of timbers is caused to wobble or tumber over, this in turn wobbles or tumbles over the next adjacent timber stack, and thus instabilities are produced in a domino-like fashion.
It will be readily apparent from a consideration of the teachings hereinafter set forth that a timber stacker is provided and which is of improved construction over that depicted in our prior application. Basically, the herein disclosed timber stacker is of identical construction as described in our prior patent application except for the details of the stop member on the lifting arm, hereinafter referred to as the stacking foot element. Thus, the stacking foot element of the present invention takes the place of the stop member of our prior application, and provides the timber stacker of the present invention with improved operational modes absent from the prior timber stacker assembly.
More particularly, the timber stacker of U.S. patent application Ser. No. 747,553, includes at least one lifting arm that has provided at one end thereof a stationarily mounted stop member. This stop member provides an abutment surface for the timbers as they are loaded onto the horizontally positioned arm. As the arm is raised to the vertical, the stop member further provides a base for maintaining the timbers in alignment. The improved stop member or stacking foot element of the present invention functions in a fashion similar as aforesaid, except that the stacking foot element of the present invention also has the capability of pivoting away from contact with the timbers on the return path of the lifting arm from vertical to horizontal. It is this pivoting of the stop member that avoids the problems inherent in the timber stacker of the prior application.
Since the stop member of the prior application is fixed to the lifting arm, the return of the lifting arm from vertical to horizontal causes the stop member to bump or engage the lowermost timber of the stack. This limitation is overcome by the stacking foot element of the herein described invention by virtue of the fact that as the stacking foot element comes into contact with the lowermost timber of the stack it is caused to pivot away from engagement with the timber, and thereby freely passing thereunder without bumping the timber or causing movement thereof. Thus, the limitations of the prior application are overcome with the present invention.