Load monitoring system

Abstract

A load monitoring system for a mobile work platform includes a load cell ( 12 ) having at least one strain gauge ( 16 ) and a sensing circuit ( 14 ) connected to receive a strain signal from the strain gauge. The sensing circuit ( 14 ) includes a first sensing device ( 24 ) for sensing the strain in the strain gauge ( 16 ), and a second sensing device ( 26 ) for sensing a negative shift in the strain signal.

1 . A load monitoring system for a mobile work platform, the system including a load cell having at least one strain gauge and a sensing circuit connected to receive a strain signal from the strain gauge, the sensing circuit including a first sensing device for sensing the load on the load cell and a second sensing device for sensing a negative shift in the unloaded strain signal. 
   
   
       2 . A load monitoring system according to  claim 1 , wherein the strain gauge is connected in a bridge circuit configuration. 
   
   
       3 . A load monitoring system according to  claim 1 , wherein the strain gauge is connected to an amplifier that amplifies the strain signal. 
   
   
       4 . A load monitoring system according to  claim 1 , wherein the first sensing device is a first comparator. 
   
   
       5 . A load monitoring system according to  claim 4 , wherein the first comparator has a first input terminal connected to receive a load signal that represents the strain in the strain gauge, a second input terminal connected to receive a load reference signal, and an output terminal for an overload signal that is generated when the load signal exceeds the load reference signal. 
   
   
       6 . A load monitoring system according to  claim 5 , wherein the output signal of the first comparator is connected to a safety device that is activated by said overload signal. 
   
   
       7 . A load monitoring system according to  claim 1 , wherein the second sensing device is a second comparator. 
   
   
       8 . A load monitoring system according to  claim 7 , wherein the second comparator has a first input terminal connected to receive a load signal that represents the strain in the strain gauge, a second input terminal connected to receive a second reference signal, and an output terminal for a negative shift signal that is generated when the load signal is less than the second reference signal. 
   
   
       9 . A load monitoring system according to  claim 8 , wherein the output signal of the second comparator is connected to a safety device that is activated by said negative shift signal. 
   
   
       10 . A load monitoring system according to  claim 1 , wherein the system includes at least two strain gauges, each of which is connected to a respective load sensing circuit, wherein the load sensing circuits operate in parallel. 
   
   
       11 . (canceled) 
   
   
       12 . A mobile work platform that includes an operator platform, a base and a lift mechanism for lifting the operator platform relative to the base, and a load monitoring system according to  claim 1  for monitoring the load on the operator platform. 
   
   
       13 . A mobile work platform according to  claim 12 , wherein the load cell of the load monitoring system is connected between the lift mechanism and the operator platform. 
   
   
       14 . (canceled)