Patent ID: 7896067

Claim:
A service tool for a hydraulically actuated downhole device including a tubular sheath for covering at least part of the device when the device is run into a wellbore; and a piston assembly disposed in the tubular sheath, abutting the upper extremity of the device, said assembly including: a hydraulic piston, said piston to displace the device between an upper position where the sheath covers at least part of the device and a lower position where the device is essentially outside the sheath; and said piston including a tubular body and a dynamic seat translating along said tubular body; means for preventing fluid circulation into the device while the piston is displacing said device and reestablishing circulation when the device is outside the sheath; wherein the tubular body includes locking means to prevent translation of the dynamic seat as long as the piston is not in its lower position.