Abstract: A hydraulic travel drive includes a primary hydraulic machine and at least one secondary hydraulic machine connected in a closed hydraulic circuit via a first and a second working line. A first accumulator is connected via a first valve to the first working line and via a second valve to the second working line. A second accumulator is connected via a third valve to the first working line and via a fourth valve to the second working line. The four valves are non-proportional switching valves each having two defined switching positions. A method for operating the drive includes comparing the high pressure working line to the first accumulator. If pressure in the accumulator is lower than in the working line, the first accumulator is connected to the high pressure working line for charging until pressure in the accumulator corresponds to that of the working line.

Abstract: A system for controlling the vertical movement of a pipe through a stripping ram. The system includes a throttle for controlling vertical movement of the pipe, a ram controller in operative communication with the ram for controlling the open or closed position of the ram, and a selector in operative communication with the ram controller and the throttle. The selector is responsive to the open or closed position of the ram. The system further includes a switch in operative communication with the selector for selectively enabling or disabling the throttle. When enabled, the throttle controls vertical movement of the pipe and when disabled, the throttle is incapable of controlling the vertical movement of the pipe.

Abstract: An apparatus for escaping the area of an accident on a drilling rig platform or the like is disclosed. A frame defines an interior space sized to accommodate a worker. A locking system includes a locking mechanism and also a foot-actuated disengager that is located at least proximate to the bottom of the frame. The locking mechanism is adapted to interlock with a mating portion on the platform to prevent the frame from travel away from the platform when the locking mechanism engages the mating portion. The disengager is connected to the locking mechanism and has a foot receiving surface region upon which force can be applied to displace the disengager between a first, engaged position and a second position to disengage the locking mechanism from the mating portion. The frame will travel away from the platform to the terminal location under gravity when the locking mechanism is disengaged.

Abstract: A housing, having at least a top wall and a spaced parallel bottom wall, has aligned openings in the top and bottom walls and a path extending between the aligned openings. The housing is mounted over a well bore so that the openings are aligned with the well bore. In the housing are a pair of blocks which are pivotable from an open position, in which the path is cleared, to a closed position, in which the blocks extend across the path. Wire line tools are mounted through the housing into the bore and thence into the well. When the tools are raised from the well, the blocks are in their closed position whereby to prevent the tools from falling back into the well should the wire break.