Abstract:
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.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
   The present application claims the benefit of, and incorporates by reference, provisional application Ser. No. 60/565,750, filed Apr. 27, 2004, and entitled “Electric Winch.” 

   STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT 
   Not Applicable. 
   BACKGROUND 
   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. 
   SUMMARY OF THE PREFERRED EMBODIMENTS 
   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. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     For a more detailed description of the preferred embodiment of the present invention, reference will now be made to the accompanying drawings, wherein: 
       FIG. 1  is a schematic representation of a winch system constructed in accordance with embodiments of the invention; 
       FIG. 2  is a cross-sectional view of the winch of  FIG. 1 ; and 
       FIG. 3  is a layout view of a remote control unit of the system of  FIG. 1 . 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
   Referring now to  FIG. 1 , a schematic diagram illustrating the interconnection of winch system  10  is shown. Winch system  100  comprises winch  120 , control panel  140 , local operator station  160 , base unit  180 , and remote control  190 . Winch  120  is an electric motor operated drum  122  mounted in frame  124 . Wire  126  is reeled on drum  122  and extends from the bottom of frame  124 . Mechanical braking system  128  is mounted to drum  122 . 
   Control panel  140  is supplied by power cable  130  and includes the electronics required to operate winch  120 . These electronics may include programmable logic controllers with a control system, a frequency drive, a power distribution system, resistors, and electric relays and barriers. Control panel  140  supplies control signals and power to winch  120  along connection  132 . 
   Local operator station  160  is connected to control panel  140  via connection  134 , which transmits control signals for winch  120  to control panel  140 . Local operator station  140  may include a full set of control switches including activators for emergency functions such as stop and lowering. Local operator station  160  is fixably mounted to the facility in a desired location. Several local operator stations  160  may be connected to a single control panel  140  and be equipped with interlocks to prevent the use of more than one operator station at a time. Similarly, one local operator station  160  may selectively communicate with several control panels  140  to control a selected winch  120 . 
   Base unit  180  and remote control  190  operate together to provide remote, mobile operation of winch  120 . Base unit  180  comprises a radio communication unit that can be housed in a safe area and is connected to and communicates with control panel  140  via connection  182 . Remote control  190  includes operator controls  192  and a radio transmitter to transmit signals  194  to base unit  180 . In some embodiments, remote control  190  may be connected to base unit  180  by a cable. 
   A cross-sectional view of winch  120  is shown in  FIG. 2 . Winch  120  includes frame  124 , drum  122 , and braking system  128 . Winch  120  is preferably built for overhead installation, with wire running downwards in order to reduce wire wear and eliminate slack wire and spooling problems like backlash. Winch  120  is preferably built as an inside out permanent magnet motor where drum  122  rotates about shaft  206 . The motor is frequency controlled, giving full control over motor speed and torque. 
   Drum  122  surrounds and is fixably attached to rotor  202  that includes permanent magnets. Rotor  202  is disposed about stator  204  that is fixably connected to shaft  206  and is formed from coiled windings. Shaft  206  and stator  204  are stationarily connected to frame  124  such that when a current is applied to stator  204 , drum  122 , supported by bearings  208 , rotates about shaft  206 . Drum  122  is preferably made with right hand winded grooves spooling of one layer of 10 mm wire. The speed of the drum is monitored by an external digital encoder. 
   Braking system  128  may include three different braking systems, namely an electric motor brake, an external fail safe brake, and a motor magnet brake. The electric motor operates as an electric motor brake by reducing the speed and torque of the rotor by reducing the electrical current supplied to the coiled windings. The speed and torque can be monitored by the control system, and the motor speed controlled to reduce and stop the drum according to the operator signals. An external fail safe brake  210  is energized and disengages when the winch is started. Brake  210  controls pinion  212  that engages gear  214  that is connected to drum  122 . Brake  210  will stay disengaged until winch  120  is turned off or an emergency switch is pressed. Brake  210  will also engage in case of power failure and can be manually disengaged by actuating lever  216 . In case of power failure to the motor and a failure of brake  210 , the motor will start acting as a dynamo. In this mode drum  122  will rotate and pay out wire a constant slow rate according to the loading in the wire. High speed emergency lowering will be impossible. 
   Winch  120  may also be equipped with an arrangement for manual release of the brake. This manual release may be actuated directly at winch  120  or actuated from drill floor via a pneumatic system. A manual pneumatic valve on the drill floor supplies air to a pneumatic cylinder on the winch activating brake lever  216 . When the air is shut off, the brake is applied. The winch speed will still be limited by the resistor arrangement. 
   To ensure correct wire spooling, winch  120  is preferably made for only one layer of wire on drum  122 . In addition to this, the drum is fitted with grooves  218 . The wire is guided onto the drum using spooling device  220  that directs the wire into the grooves. 
   The power system that operates winch  120  may also comprise a frequency converter including braking chopper for running the winch motor clockwise and counterclockwise. A braking resistor may be used for dissipating regenerated energy when braking with the electrical motor. A contactor/resistor arrangement may be supplied to short circuit the motor windings for braking in case of loss of frequency converter and for protection against motor over-voltage. The winch control system can be equipped with a separate potential free contactor that can be connected to other drill floor machines emergency shut down circuits, disabling other connected machinery when the winch is in operation. On drilling rigs with advanced drilling control and monitoring system, the winch can easily be incorporated into the rig&#39;s anti collision system. The winch may also be fitted with a heave compensating system, making it possible to work on fixed well equipment on a floating vessel. 
   One embodiment of remote control  190  is shown in  FIG. 3 . Remote control  190  includes on/off switch  300 , joystick  302 , start/stop switch  304 , walk button  306 , climb button  308 , display  310 , display controls  312  and  314 , warning lights  316  and  318 , and emergency stop button  320 . Once remote control  190  is activated by on/off switch  300 , pushing the start/stop switch  304  will send a pulse signal to control panel  140  to initiate a start sequence during which, the motor will be powered up, the brake resistor arrangement disabled and the brake released. Pushing the start/stop switch  204  again will initiate a stop sequence during which, motor speed is set to zero, the mechanical brake is applied, and the brake resistor arrangement is enabled. When the shut down sequence is confirmed, the motor is powered down. 
   To operate the winch upwards or downwards, joystick  302  is utilized. Joystick  302  is preferably fitted with a dead man&#39;s grip, i.e. a separate activation switch in the joystick handle. The activation switch must be pressed with joystick  202  in the zero position in order to start operations. If the activation switch is released during operation with joystick  202  out of the zero position, the winch will continue running but a new start from the zero position requires depressing of the activation switch. When receiving the hoist signal from joystick  202 , the frequency converter will change the motor speed according to joystick position. The maximum hoisting speed and acceleration is limited by the control system. 
   When lowering the load in normal operation, the frequency converter/braking chopper will measure the DC-bus voltage and start operating (dissipating regenerated energy in the braking resistor) when exceeding the preset limit. Max tension in the wire will be controlled by the frequency converter. In case of excessive external force, the tension will not exceed a programmable hard-coded value. The winch will be equipped with a sensor for upper and lower position stops such that a signal from this sensor will cause the winch to stop at downwards position independently of other control signals. The joystick can be operated in “left” position, in this position the winch is in creep speed mode, giving maximum 10% of normal speed. 
   Winch  120  may be equipped with a climb function  308  that can be selected/deselected at the remote control panel. When selected, the rider can adjust his position by applying additional force in downwards or relieving tension in an upward direction. Maximum speed limits in both directions are 0.15 m/s when this function is activated. The operator can at all time take control of the movement by using the joystick, which deactivates the climb function. 
   Winch  120  may also be equipped with a walk function  306  that can be selected/deselected at the remote control panel. When activated, winch  120  will keep a constant low tension in the wire, preventing a slack wire situation. The rider can move around with a small pull in the wire. The function can only be activated when the load is below 15% of max load. In case of a person falling from an elevated position with this function activated, the person will be lowered with a preset speed of 0.15 m/s. The operator can at all time take control of the operation of the winch, either by activating the joystick, which deactivates the walk function. 
   When the control system detects “slack wire”, a red indicator lamp  216  will illuminate on the console. The slack wire function will stop downwards movement if the wire tension drops below 2% of max tension. 
   Referring back to  FIG. 1 , winch  120  is equipped with three emergency stops located at remote control console  190 , at local operator station  160  and at winch  120 . These are hard wired emergency stop buttons  220  (see  FIG. 3 ) that will engage the mechanical brake, engage the magnetic brake and disconnect power from the motor. Pressing the emergency stop switch  220  will immediately stop winch  120  and apply the parking brake. The power to the motor will also be shut down but control system  140  will still be monitoring winch  120 . Any detection of internal failures, including overspeed, overpull, power problems, and communication problems, will also produce an emergency shutdown. 
   To be able to lower the load in case of equipment failure or loss of power, winch  120  is equipped with an emergency lowering circuit. This arrangement will lower the load in a controlled manner in case of loss of power from the frequency converter. If the mechanical brake is engaged and the PLC/remote control is working, the brake can be released by operating an emergency release switch at local operator station  160 . The control power to the emergency brake release circuit comes from the rig UPS system. A diode bridge will allow for dual brake release signal, both for the PLC (in normal operation) and for the emergency lowering circuit. Overspeed detection will still be operating, and if overspeed is detected, the brake will engage. 
   In case of failure in the PLC/remote control system, but with UPS power available, the load can be lowered by activating the emergency lowering switch at local operator station  160 . In case of no UPS power available, the mechanical brake can be disengaged manually by a hand operated lever  216  (see  FIG. 2 ) on the brake. In this mode, the winch speed will still be limited by the resistor arrangement and all control system safety features are disabled. Emergency lowering speed is always limited by the motor braking resistance (dynamo effect) and the load being lowered. Free fall will never be possible except for wire breakage or complete mechanical failure of the winch. 
   Winch  120  can also be equipped with an arrangement for manual release of the brake from drill floor. A manual pneumatic valve on the drill floor can supply air to a pneumatic cylinder on the winch activating brake lever  216  (see  FIG. 2 ). When the air is shut off, the brake is applied. The winch speed will still be limited by the resistor arrangement. An emergency hoisting feature can also be included, wherein a crank handle can be inserted onto the drum, and the winch wire may be manually spooled in at a gear ratio of 1:8. 
   At loss of main power to the frequency converter, the mechanical brake will engage and the contactor/emergency lowering resistor arrangement will make sure that the motor does not generate overvoltage at the motor terminals. In case of loss of power to the PLC, the mechanical brake will engage and the contactor/emergency lowering resistor arrangement will make sure that the motor does not generate overvoltage at the motor terminals. 
   PLC failure will cause the mechanical brake to engage and the emergency lowering contactor will short-circuit the motor windings over the emergency lowering resistor arrangement. 
   If the PLC detects a failure in remote control system  190 , winch  120  will be shut down in a safe sequence. All special functions will be shut off. Speed will be set to zero, and the mechanical brake will be applied. Remote control failure will cause the mechanical brake to engage and the emergency lowering contactor will short-circuit the motor windings over the emergency lowering resistor arrangement. Failure on the remote control system  190  will not affect operation from local operator station  160 , which always can be activated. 
   Frequency converter failure will cause the mechanical brake to engage and the contactor/emergency lowering resistor arrangement will make sure that the motor does not generate overvoltage at the motor terminals. 
   At all times, the PLC will monitor and regulate the speed of the winch drum by use of two independent sensors. In case of speed exceeding the preset limit, the PLC will engage the mechanical brake. The detection has the same priority in the emergency stop loop as the emergency stop push button. 
   At all times, the PLC will monitor the wire tension through the motor torque. In case of tension exceeding the preset limit, the winch will pay out wire unless the speed exceeds the overspeed limit. As a backup torque measurement, the input current to the frequency converter is monitored. If the current exceeds a preset limit, the winch will be stopped and shut down. 
   The PLC may be equipped with a system monitoring and diagnosing software. This software monitors the PLC, frequency converter and remote radio control status, and also the communication links and instrumentation on the winch. Any fault detected will generate an alarm. Alarms generate a message that will be displayed on the LCD-screen  310  on the remote radio console  190  (see  FIG. 3 ). 
   The remote radio console  190  may be equipped with a system monitoring and diagnosing software. Internal errors related to the remote radio console  190  will be displayed on the LCD-screen  310  on the console. The frequency converter is equipped with a system monitoring and diagnosing software. Internal errors related to the frequency converter will be displayed on an LCD-screen on the frequency converter. 
   The unique features of this winch are derived from the electrical motor that is used. This is a slow rotating permanent magnet motor integrated into the drum that provides very good torque control, which can be used for various new functions. Also, this motor will produce torque even at loss of power, so normal free falling is impossible. 
   While preferred embodiments of this invention have been shown and described, modifications thereof can be made by one skilled in the art without departing from the scope or teaching of this invention. The embodiments described herein are exemplary only and are not limiting. Many variations and modifications of the system and apparatus are possible and are within the scope of the invention. For example, the relative dimensions of various parts, the materials from which the various parts are made, and other parameters can be varied, so long as the winch apparatus retain the advantages discussed herein. Accordingly, the scope of protection is not limited to the embodiments described herein, but is only limited by the claims that follow, the scope of which shall include all equivalents of the subject matter of the claims.