Patent ID: 7931077

Claim:
A top drive well drilling apparatus designed to be suspended from a travelling block in a drawworks and laterally supported by a dolly running together with the well drilling apparatus along tracks or rails attached to a derrick, said drilling apparatus comprising: at least one driving motor, one power transmission powered by the at least one driving motor, a drive shaft driven from the power transmission and designed to be connected to a drill string, load transferring means, and a torque arresting device attached to and depending from the power transmission, wherein the load transferring means are in the form of a load frame that load relieves the drive shaft and the power transmission at the same time as it forms a central component which the other components are constructed around, and the torque arresting device comprises a clamping device that is able to retain a stub shaft which includes one or more valves, which shaft stub, while it is held stationary by the clamping device, is pivotal about a horizontal axis through the clamping device for laying down towards a horizontal position by means of a hydraulic cylinder.