ELECTRIC WINCH

The present invention relates generally to methods and apparatus for lifting and hoisting. More particularly, the present invention relates to winches and more specifically for winches used to lift personnel.
In many working environments, personnel are required to perform certain functions at elevated locations where platforms or other working surfaces are not provided. In these situations, a winch, or other type of lifting appliance, is often used to lift and support the worker while performing the task. Among the working environments where winches are commonly used for handling personnel are offshore oil and gas platforms and vessels.
Most facilities have dedicated, specially designed winches that are used only for handling personnel. These winches are known as `manrider` winches and are often designed with higher safety design factors as compared to standard utility winches. In certain regions, such as both the Norwegian and UK Sectors of the North Sea, manrider winches are subject to stringent rules and regulations as equipment used in handling personnel. Manrider winches, which must safely support a worker in an elevated working position, must also allow that worker some freedom of movement to perform the assigned task. It is often difficult to balance the need for complete safety and fall support with the need to allow the worker being supported some freedom of movement.
Thus, there remains a need to develop methods and apparatus for winches developed within rules and regulations such as those used in the North Sea that govern equipment for handling personnel, which overcome some of the foregoing difficulties while providing more advantageous overall results.
The problems discussed above are addressed by apparatus and methods for operating a winch system comprising a wire spooled onto a drum rotatably mounted to a shaft. A permanent magnet is mounted to the drum such that, when an electric current is applied to a coiled winding mounted to the shaft, the drum rotates about the shaft. The winch comprises a first braking system that controls the rotation of the drum about the shaft by controlling the application of the electric current to the coiled winding. The winch also comprises a second braking system that mechanically engages the drum so as to prevent the rotation of the drum about the shaft. The winch is used in conjunction with a control system that facilitates the use of the winch with lifting and supporting personnel working in elevated environments.
The preferred embodiments include an electric winch utilizing a permanent magnet electric motor integrated into the wire rope spool. The permanent magnet electric motor provides resistor induced emergency braking and motor-controlled emergency lowering if power is lost. Because the speed and torque of the motor are easily and precisely controllable, preferred embodiments may include climbing and walking functions to safely support worker movement while maintaining safety. Some embodiments are configured for top of derrick mounting, i.e. reduced number of wire lines. Because the motor is integrated into the drum, the total number of parts required is reduced. The fully electrical winch requires no other power sources, i.e. hydraulic or pneumatic supplies.
Thus, the present invention comprises a combination of features and advantages that enable it to overcome various problems of prior devices. The various characteristics described above, as well as other features, will be readily apparent to those skilled in the art upon reading the following detailed description of the preferred embodiments of the invention, and by referring to the accompanying drawings.