Releasable backhoe boom lock

In an earthworking implement having one end of a boom pivoted on a swing tower between transport and working positions and a dipper assembly including a member having an intermediate portion pivoted on said boom at a location spaced from the swing tower and boom pivot, said dipper assembly being pivoted on said boom by a fluid ram having a first element pivoted on said boom and a second element pivoted on one end of said intermediate member and movable between fully extended and retracted positions respectively defining a transport position and a maximum extended position of an opposite end of said dipper assembly with respect to said boom, and releasable lock means between said boom and said swing tower, said releasable lock means including a latch pivoted on said swing tower between first and second positions, said latch having a recess adjacent one end thereof, pin means carried by said boom and adapted to be received in said recess and positioned so that movement of said boom to said transport position will produce engagement between said latch and said pin means to cause said latch to be pivoted from said first position to said second position until said recess is aligned with said pin means and have said pin means received into said recess, and unlatching means for pivoting said latch between said positions to release said latch, said unlatching means including an extension on said first element, said extension being aligned with said latch to engage and release said latch when said boom is in said transport position and said fluid ram is moved from said fully extended position toward said retracted position.