Device for measuring a load at the end of a rope wrapped over a rod

Abstract

A machine for raising and lowering a load, the machine including a platform, a boom attached at one end to the platform, a rod mounted transverse to the longitudinal axis of the boom on the other end of a boom, the rod having a central bore there through, with at least two strain gauges mounted therein and angled relative to each other, a hoist rope extending over the rod and having an end adapted to be attached to the load, and a mechanism connected to the at least two strain gauges for determining the angle of departure of the hoist rope from the rod and the amount of pull of the load on the hoist rope.

1 . A machine for raising and lowering a load, said machine including a platform,
 a boom attached at one end to said platform,   a rod mounted transverse to the longitudinal axis of said boom on the other end of said boom, the rod having a central bore there through, with at least two strain gauges mounted therein and angled relative to each other,   a hoist rope having one end connected to one of said base and said one end of said arm and extending over said rod and having another end adapted to be attached to the load, and   means connected to said at least two strain gauges for determining the angle of departure of said hoist rope from said rod and the amount of pull of said load on said hoist rope.   
   
   
       2 . A machine in accordance with  claim 1  wherein said means connected to said at least two strain gauges is a central processing unit including software and memory. 
   
   
       3 . A machine in accordance with  claim 1  wherein said memory includes strain gauge calibration information. 
   
   
       4 . A method of determining the force and angle of a rope wrapped over a rod, the rod having a central bore there through, with at least two strain gauges mounted therein and angled relative to each other, the method comprising the steps of
 creating a calibration table of a plurality of outputs from each of said at least two strain gauges, given various rope tensions and rope angles,   then, when encountering an unknown rope tension and rope angle,   taking the output from one strain gauge and creating a set of data point angle and tension pairs from said plurality of calibration outputs that correspond to said one output from said one strain gauge,   taking the output from the other strain gauge and creating a set of data point angle and tension pairs from said plurality of calibration outputs that correspond to said one output from said other strain gauge, and   determining, based on where said two sets of data points intersect, the rope tension and rope angle.   
   
   
       5 . A method in accordance with  claim 4  wherein said strain gauges are perpendicular to each other. 
   
   
       6 . A method in accordance with  claim 4  wherein a curve is fitted to said created strain gauge outputs for a given rope angle or rope tension. 
   
   
       7 . A method in accordance with  claim 6  wherein said curve is a fifth order curve. 
   
   
       8 . A method in accordance with  claim 6  wherein said sets of data point angle and tension pairs is created from said curve fitted to said created strain gauge outputs. 
   
   
       9 . A method in accordance with  claim 4  wherein a curve is fitted to each of said sets of data point angle and tension pairs. 
   
   
       10 . A method in accordance with  claim 4  wherein said curve is a fifth order curve. 
   
   
       11 . A method, for a shovel including a base, a dipper, a boom pivotally mounted on the base, a hoist rope extending from the base to the dipper and wrapped over a sheave mounted on the end of the boom, and a dipper arm supported the dipper on the end thereof, the dipper arm being pivotally mounted on the boom, the method automatically recalibrating dipper position information, a arm resolver mounted on the boom and responsive to record arm extension and retraction, the arm length being equal to a arm offset plus a arm gain times said arm resolver reading, the method automatically recalibrating dipper position information, the method including the steps of:
 storing the maximum values of the crowd resolver,   using the known length of the arm at the maximum extension positions, calculate the offset value for each resolver maximum value,   obtaining an array of readings from the crowd resolver to calculate an array of calculated rope wrap angles,   obtaining an array of rope wrap angles from another device for measuring the rope wrap angles, and   selecting a crowd length offset that minimizes the difference between the two sets of calculations.   
   
   
       12 . A method in accordance with  claim 11  wherein said crowd length offset is selected by minimizing the square of the differences between the two sets of values. 
   
   
       13 . A method in accordance with  claim 12  wherein said crowd length offset is selected by using nonlinear programming to determine the offset value that minimizes the difference between the calculated rope wrap angles from the resolver data and the calculated rope wrap angle from the other device for measuring the rope wrap angles. 
   
   
       14 . A method, for a shovel including a base, a dipper, a boom pivotally mounted on the base, a hoist rope extending from the base to the dipper and wrapped over a sheave mounted on the end of the boom, and a dipper arm supported the dipper on the end thereof, the dipper arm being pivotally mounted on the boom, the method automatically recalibrating dipper position information, a arm resolver mounted on the boom and responsive to record arm extension and retraction, the arm length being equal to a arm offset plus a arm gain times said arm resolver reading, a hoist resolver mounted on the shovel and responsive to record hoist rope extension and retraction, the hoist rope length being equal to a hoist rope offset plus a hoist rope gain times said hoist rope resolver reading, the method automatically recalibrating dipper position information, the method including the steps of:
 obtaining a hoist rope wrap angle from a device for measuring the rope wrap angle, and   then using the rope wrap angle, together with the known length of the boom between the dipper arm and the end of the boom, and the length of the hoist rope between the end of the boom and the dipper calculated using the hoist rope resolver, to then calculate the length of the dipper arm and the arm offset.