Level sensor for an elevating platform assembly and elevating platform assembly incorporating the same

Abstract

An elevating platform assembly comprises a pair of laterally spaced, generally vertical masts and an elongated working platform extending generally horizontally between the masts. Hoist mechanisms act between the ends of the working platform the masts and are actuable to move the working platform along the masts to different elevations. At least one level sensor is provided on the working platform and detects when the working platform deviates from a generally horizontal orientation. At least one controller is responsive to the at least one level sensor and controls the hoist mechanisms to adjust movement of the working platform when the working platform deviates from the generally horizontal orientation thereby to return the working platform to the generally horizontal orientation.

What is claimed is:  
     
         1 . An elevating platform assembly comprising: 
 a pair of laterally spaced generally vertical masts;    an elongated working platform extending generally horizontally between said masts;    hoist mechanisms acting between opposite ends of said working platform and said masts, said hoist mechanisms being actuable to move said elevating platform along said masts to different elevations;    at least one level sensor on said working platform and detecting when said working platform deviates from a generally horizontal orientation; and    at least one controller responsive to said at least one level sensor and controlling said hoist mechanisms to adjust movement of said working platform when said working platform deviates from said generally horizontal orientation thereby to return said working platform to said generally horizontal orientation.    
     
     
         2 . An elevating platform assembly according to  claim 1  wherein said at least one controller stops said hoist mechanisms when said at least one level sensor detects deviation of said working platform from said generally horizontal orientation beyond a maximum threshold.  
     
     
         3 . An elevating platform assembly according to  claim 2  wherein said maximum threshold is a 5 degree deviation of said working platform from said generally horizontal orientation.  
     
     
         4 . An elevating platform assembly according to  claim 2  wherein when said working platform is moving along said masts and deviates from said generally horizontal orientation at least by an intermediate threshold that is less than said maximum threshold, said at least one controller adjusts the speed of at least one of said hoist mechanisms relative to the other of said hoist mechanisms to return said working platform to said generally horizontal orientation.  
     
     
         5 . An elevating platform assembly according to  claim 4  wherein said at least one controller adjusts the speed of both of said hoist mechanisms.  
     
     
         6 . An elevating platform assembly according to  claim 4  wherein said at least one controller slows one of said hoist mechanisms in response to said at least one level sensor when said working platform is upwardly inclined in a direction away from the mast to which said one hoist mechanism is coupled and said working platform is descending along said masts and wherein said at least one controller speeds up one of said hoist mechanisms in response to said at least one level sensor when said working platform is downwardly inclined in a direction away from the mast to which said one hoist mechanism is coupled and said working platform is ascending said masts.  
     
     
         7 . An elevating platform assembly according to  claim 6  wherein said intermediate threshold is a 3 degree deviation of said working platform from said generally horizontal orientation.  
     
     
         8 . An elevating platform assembly according to  claim 2  including at least one level sensor on said working platform and one controller controlling operation of both hoist mechanisms.  
     
     
         9 . An elevating platform assembly according to  claim 2  including a pair of level sensors and a pair of controllers, each level sensor being positioned on said working platform adjacent a respective one of said masts and being associated with a respective one of said controllers, each of said controllers controlling a respective hoist mechanism in response to said associated level sensor.  
     
     
         10 . An elevating platform assembly according to  claim 4  wherein said at least one level sensor includes a pendulum that swings in a generally vertical plane about an arc as said working platform deviates from said generally horizontal orientation, movement of said pendulum being detected thereby to detect said deviation.  
     
     
         11 . An elevating platform assembly according to  claim 10  wherein said at least one level sensor includes proximity sensors to detect swinging movement of said pendulum.  
     
     
         12 . An elevating platform assembly according to  claim 11  wherein said pendulum is disposed between a sensor plate and a pair of stationary proximity sensors, swinging of said pendulum exposing one or both of said proximity sensors to said sensor plate and causing said one or both proximity sensors to generate output signifying deviation of said working platform from said generally horizontal orientation.  
     
     
         13 . An elevating platform assembly according to  claim 12  wherein one of said proximity sensors is exposed to said sensor plate when said working platform deviates from said generally horizontal orientation by said intermediate threshold but below said maximum threshold.  
     
     
         14 . An elevating platform assembly according to  claim 13  wherein both of said proximity sensors are exposed to said sensor plate when said working platform deviates from said generally horizontal orientation by said maximum threshold.  
     
     
         15 . An elevating platform assembly according to  claim 14  wherein said proximity sensors are exposed to said sensor plate through spaced passages in said pendulum.  
     
     
         16 . An elevating platform assembly according to  claim 16  wherein said at least one level sensor further includes stops to limit movement of said pendulum so that both of said proximity sensors remain exposed to said sensor plate when said working platform deviates from said generally horizontal orientation beyond said maximum threshold.  
     
     
         17 . An elevating platform assembly according to  claim 16  wherein said proximity sensors are magnetic proximity sensors, said sensor plate is formed of magnetic material and said pendulum is formed of non-magnetic material.  
     
     
         18 . An elevating platform assembly according to  claim 4  further including visual indicators providing a visual indication of the orientation of said working platform.  
     
     
         19 . An elevating platform assembly according to  claim 18  wherein said visual indicators are carried by said at least one level sensor.  
     
     
         20 . A level sensor to detect deviations of a surface from the horizontal comprising: 
 a pendulum coupled to said surface and swinging in a generally vertical plane about an arc when said surface deviates from said horizontal; and    a sensor arrangement detecting swinging movement of said pendulum and generating output signifying deviation of said surface beyond a threshold amount.    
     
     
         21 . A level sensor according to  claim 20  wherein said pendulum is disposed between a sensor plate and a pair of stationary proximity sensors, swinging of said pendulum exposing one or both of said proximity sensors to said sensor plate and causing said one or both proximity sensors to generate said output.  
     
     
         22 . A level sensor according to  claim 21  wherein one of said proximity sensors is exposed to said sensor plate when said surface deviates from said horizontal by at least an intermediate threshold but below a maximum threshold.  
     
     
         23 . A level sensor according to  claim 22  wherein both of said proximity sensors are exposed to said sensor plate when said surface deviates from said horizontal by said maximum threshold.  
     
     
         24 . A level sensor according to  claim 23  wherein said proximity sensors are exposed to said sensor plate through spaced passages in said pendulum.  
     
     
         25 . A level sensor according to  claim 24  wherein said level sensor further includes stops to limit movement of said pendulum so that said proximity sensors remain exposed to said sensor plate when said surface deviates from said horizontal beyond said maximum threshold.  
     
     
         26 . A level sensor according to  claim 25  wherein said proximity sensors are magnetic proximity sensors, said sensor plate is formed of magnetic material and said pendulum is formed of non-magnetic material.  
     
     
         27 . A level sensor according to  claim 23  further including visual indicators providing a visual indication of the orientation of said surface.  
     
     
         28 . A level sensor according to  claim 27  wherein said pendulum, and sensor arrangement are accommodated within a housing, said visual indicators being provided on a door of said housing.  
     
     
         29 . In an elevating platform assembly including a pair of spaced apart generally vertical masts, an elongated working platform extending generally horizontally between said masts and a hoist mechanism acting between each end of said working platform and a respective mast to move said working platform to different elevations, a method of controlling the hoist mechanisms comprising the steps of: 
 monitoring the working platform to detect deviations of said working platform from the horizontal;    controlling the hoist mechanisms while the working platform is moving to return the working platform to said horizontal when the working platform deviates from the horizontal by at least a first threshold that is less than a maximum threshold; and    stopping the hoist mechanisms when the working platform deviates from the horizontal by said maximum threshold.    
     
     
         30 . The method of  claim 29  wherein said maximum threshold is a 5° deviation of said working platform from said horizontal.  
     
     
         31 . The method of  claim 30  wherein said first threshold is a 3° deviation of said working platform from said horizontal.