Patent ID: 7578348

Claim:
An overshot tool for retrieving an object in a well, the tool comprising: a stationary housing having an upper end for attaching to a string for lowering the tool into the well, a housing bore having upper and lower portions, the lower portion having a lower portion inner wall surface defined by a lower portion inner diameter and a lower portion axis, the lower portion axis being defined relative to the lower portion inner wall surface; a cam carried in the upper portion of the bore, the cam having a cam bore that has a lower cam bore portion comprising a lower portion cam bore inner wall surface defined by a lower portion cam bore inner diameter, the lower portion cam bore inner diameter being constant, and a cam bore axis, the cam bore axis being defined relative to the lower portion cam bore inner wall surface; the cam being rotatable relative to the stationary housing from an aligned position wherein the cam bore axis and the lower portion axis coincide, to a misaligned position wherein the cam bore axis and the lower portion axis are offset and parallel to each other; and the lower portion of the housing bore and the cam bore being open at a lower end of the housing for sliding over an object in the well while the cam bore axis and lower portion axis are in the aligned position, so that subsequent rotation of the cam relative to the stationary housing causes the cam bore axis and the lower portion axis to move toward the misaligned position, thereby gripping the object for retrieval.