Method and apparatus for an emergency lowering kit

Abstract

A method and apparatus are disclosed for lowering a load on a direct current hoist motor during an electrical power interruption, the method including but not limited to determining in a crane processor that the electrical power interruption has occurred; and providing a brake assist current to shunt field on the direct current hoist motor to produce a counter torque in the hoist motor.

1 . A system for lowering a load on a direct current hoist motor during an electrical power interruption to the direct current hoist motor, the system comprising:
 a crane processor in data communication with a non-transitory computer readable medium;   a first computer program component that determines in the crane processor that an electrical power interruption to the direct current hoist motor has occurred; and   providing a brake assist current to a shunt field on the direct current hoist motor to produce a counter torque in the direct current hoist motor;   a second computer program component that electrically connects a variable resistance brake assist resistor in series with a dc power supply and the shunt field wherein a brake assist resistance value for the variable resistance brake assist resistor is controlled by the crane processor; and   a third computer program component that varies the brake assist resistance value proportionately to a measured hoist hook speed to proportionately increase the brake assist value to proportionately provide counter torque with an increase in hoist hook speed.   
     
     
         2 . The computer program product of  claim 1 , the computer program product further comprising:
 a fourth computer program component that electrically connects a brake assist resistor in series with a dc power supply and the shunt field.   
     
     
         3 . The computer program product of  claim 2 , wherein an accelerometer measures hoist hook speed. 
     
     
         4 . The computer program component of  claim 3 , the computer program product further comprising:
 a fifth computer program product that places a braking resistor across a pair of electrical terminals on the hoist motor to create a counter torque in the hoist motor wherein the counter torque opposes a torque of a freewheeling hoist motor with an attached load.   
     
     
         5 . The computer program product of  claim 4 , further comprising:
 a fifth computer program component that senses a first normally open switch limit switch and a second normally closed limit switch.   
     
     
         6 . A computer program product for lowering a load on a direct current hoist motor during an electrical power interruption, the computer program product comprising:
 a computer program embedded in a non-transitory computer readable medium, the computer program comprising instructions that when executed by a computer, perform functions, the computer program further comprising:   instructions to determine that the electrical power interruption has occurred;   instructions to electrically connect a brake assist resistor in series with a dc power supply and the shunt field;   and   instructions to provide a brake assist current to shunt field on the direct current hoist motor to produce a counter torque in the hoist motor wherein the brake assist resistor is a variable resistance resistor wherein a brake assist resistance value is controlled by the crane processor, the method further comprising:   instructions to vary the brake assist resistance value proportionately with a measure hoist hook speed to proportionately increase the counter torque with an increase in hoist hook speed.   
     
     
         7 . The computer program product of  claim 6 , the computer program further comprising:
 instructions to electrically connect a brake assist resistor in series with a dc power supply and the shunt field.   
     
     
         8 . The computer program product of  claim 7 , wherein the brake assist resistor is a variable resistance resistor wherein a brake assist resistance value is controlled by the crane processor, the method further comprising:
 instructions to vary the brake assist resistance value proportionately with a measure hoist hook speed to proportionately increase the counter torque with an increase in hoist hook speed.   
     
     
         9 . The computer program product of  claim 8 , the computer further comprising:
 instructions to send a command to a braking resistor relay to electrically a braking resistor across the terminal of the hoist motor to create a counter torque in the hoist motor wherein the counter torque opposes the torque of a freewheeling hoist motor with an attached load.   
     
     
         10 . The computer program product of  claim 9 , wherein the braking resistor is a variable resistance resistor wherein a braking resistor resistance value is controlled by the crane processor, the computer program further comprising:
 instructions to vary the braking resistor resistance value proportionately with a measure hoist hook speed to proportionately increase the counter torque with an increase in hoist hook speed.