Selectively releasable overshot and pull tool

A tool used to retrieve an article in a well bore, comprising:

• a first assembly adapted to be connected to apparatus extending down in to the bore, said first assembly including:
• a pin extending radially of the bore;
• a shoulder for butting against the article to limit movement of said first assembly toward the article;
• and
• caged fingers with each finger having an end movable to a position for engaging the article;
• a second assembly movably mounted with said first assembly for moving the fingers into the engaging position, said second assembly including:
• a body having a cavity with two grooves of unequal length extending axially of the bore, the pin of said first assembly being disposed within the cavity for moving within the grooves;
• a spring mounted with the body for moving the pin from alignment with the shorter groove to alignment with the longer groove when said second assembly is moved relative to the first assembly;
• an annular shoulder sloping radially of the well bore for moving the ends of the fingers into the engaging position as the pin moves in the longer groove;
• and
• means mounted with said first assembly for urging said second assembly axially of the well bore, said urging means moving the annular shoulder of said second assembly toward the caged fingers of said first assembly for moving each end of the fingers radially into the engaging position after the shoulder on said first assembly limits its movement toward the article.