Wellhead retrieval tool assembly

A wellhead retrieval tool assembly for retrieving a valve comprising:

• a generally cylindrical tool body having a first end, a second end, and a middle section;
• said first end being adapted to receive means for grasping and manipulating said tool body;
• a spear comprising a generally ring-shaped base having a plurality of resilient fingers extending therefrom and having free ends opposite said base;
• said base being positioned generally concentrically around said second end of said body such that said fingers extend toward said middle section;
• retaining means positioned on said second end adapted to retain said spear on said body while permitting limited axial movement of said spear on said body;
• wedge means for engagement with an inner cam surface on each of said fingers when said body is moved relative to said spear whereby said wedge means and cam surfaces bias said fingers radially outward when said spear is moved axially relative to said body, said wedge means being releasably fixed to said body;
• engagement means extending radially on the outer surface of each said finger for engaging an annular retrieval groove on an inner circumferential surface of said valve when said tool assembly is inserted concentrically in said valve;
• shear means for releasably fixing said wedge means to said body, said shear means being adapted to shear and release said wedge means from said body causing said wedge means to fall out of engagement with said cam surfaces when an axial force imposed on said wedge means attributable to said relative axial movement between said body and said spear reaches a predetermined limit, whereby continued relative movement causes said retaining means to contact said spear and cause said spear to move with said body.