Life Cycle Reliability Engineering, Guangbin Yang, Chichester, Wiley, 2007, ISBN 978-0471715290. 0471715298

This power wrench includes a wrench head that rotatably supports a ring having a non-circular internal profile. A ratchet device moves the ring only in one direction of rotation with respect to the wrench head. The wrench head has an internal extension and a support element is coaxially pivotally attached to the wrench head. A piston cylinder unit, including a piston and a piston rod is provided. The first end of the piston cylinder unit is rigidly connected to the integral extension of the wrench head and the second end of the unit is in contact with the support element. The distance between the center of the wrench head and the first end of the piston cylinder unit is about the same as the distance between the center of the wrench head and the second end of the unit. One end of the piston rod is flexibly held at the piston and the other end is flexibly held at the support element.