US Patent 7775280 Jars for wellbore operations

An example of an apparatus for jarring a wellbore tool from an obstruction includes four sub-assemblies in communication with three springs such that the springs may be compressed forcing the subassemblies to become adjacent to one another. When the springs are actuated, the sub-assembly units spring apart from one another force dislodging the lower most sub-assembly component from the obstruction.