Abstract: The upward and/or downward travel of a traveling block in a derrick is controlled to prevent travel beyond normal, safe operating limits. A control line is positioned across the vertical movement axis of the traveling block and upon being moved by the traveling block will actuate sensors to brake and deactivate the draw works, in the event the traveling block traverses beyond safe predetermined limits.

Abstract: An escape device for allowing an endangered person to be safely lowered from a drilling tower or other elevated structure includes an automatic brake which controls the descent of a trolley assembly downwardly along an escape cable extending from the elevated structure to a ground level anchor remote from the structure. The automatic brake includes a reel rotatably secured to the elevated structure and a brake cable wound about the reel and attached at one end to the trolley assembly. A fluid pump coupled to the reel causes the reel to rotate at a constant speed when the trolley assembly descends the escape cable. The effective diameter of the reel decreases as the brake cable is unwound therefrom, thereby slowing the rate of descent of the trolley assembly as it approaches the lower end of the escape cable. The escape device is adapted to be used with both the upper and lower stations of a derrick or similar elevated structure.

Abstract: A three-phase motor system is described incorporating a small fractional horsepower three-phase control motor that is connected to rotate in a predetermined direction when a three-phase drive motor is rotating in a predetermined direction. A plurality of microswitches having actuating arms with cam follower portions are mounted with the arms contacting a cam plate. When the system is energized, the cam plate is rotated to open the microswitches if the rotation of the fractional horsepower motor is reversed. The microswitches, when opened, de-energize the fractional horsepower motor and concurrently prevent the closure of a solenoid-operated start switch to prevent energization of the drive motor.