elastomeric packer element 30 is of the type that when compressed axially extrudes radially to form a fluid seal within a wellbore a number of such elements are available commercially and their structure and operation is of course well known to those of skill in the art at the lower end of the slip element 28 is a setting piston 32 that is disposed in an axially moveable relation upon an outer radial surface 34 of the central mandrel 12 initially the setting piston 32 is secured against axial movement with respect to the central mandrel 12 by a shear pin 36 the shear pin 36 is a frangible member that is designed to break away or fail upon encountering a predetermined level of shear stress a bridge sleeve 38 is secured to the lower end of the setting piston 32 by a threaded connection 40 the lower end of the bridge sleeve 38 is secured by a second threaded connection 41 to a body lock ring housing 42 an annular ring 44 radially surrounds the central mandrel 12 within the bridge sleeve 38 and is threaded at 46 to securely affix the annular ring 44 to the central mandrel 12 an upper hydraulic fluid chamber 48 is defined radially between the central mandrel 12 and the bridge sleeve 38 the upper end of the upper hydraulic fluid chamber 48 is defined by the setting piston 32 while the lower end of the upper hydraulic fluid chamber 48 is defined by the annular ring 44 a fluid communication port 50 see fig1 b is disposed through the central mandrel 12 to permit fluid communication between the flowbore 14 and the upper hydraulic chamber.