Safety toe-sensor for lift table

Abstract

A lift table includes a toe sensor responsive to contact around the entire perimeter of the base. Multiple pressure switches are installed over two sides of the base and capped by an overlapping four-sided suspended guard. Multiple guides and springs of appropriate stiffness support the guard suspended over the base, so that any appreciable pressure exerted on the guard causes the compression of the springs and the direct application of pressure on an underlying switch which, in turn, de-energizes the mechanism controlling the descent of the platform. The pressure switches are incorporated into a control circuit that is activated only when the platform is descending. The platform may be sized to extend over the base enough to overlap the guard of the toe-sensor.

I claim:  
     
         1 . A lift table comprising: 
 a base, a load platform, and a vertically extendible means for raising and lowering the platform relative to the base;    a sensor mechanism including a plurality of sensors mounted on said base of the table and affecting a perimeter of the base;    a guard operably connected to the base and mounted over said sensor mechanism and adapted to activate the sensor mechanism when pressure is exerted upon the guard; and    a plurality of springs between the base and the guard, such that the guard is suspended over the base;    thereby providing a means for interrupting a descent of the platform in response to an object encroaching said perimeter of the base and exerting pressure on the guard.    
     
     
         2 . The lift table of  claim 1 , wherein said sensors comprise a pressure switch.  
     
     
         3 . The lift table of  claim 1 , wherein said sensors comprise a Hall-effect switch.  
     
     
         4 . The lift table of  claim 1 , wherein said sensors comprise an optic-electronic fiber switch.  
     
     
         5 . The lift table of  claim 1 , further comprising a valve actuated by any one of said sensors to close and hydraulically interrupt the descent of the platform when pressure is exerted on the guard.