Waste Water Safety Element Torque Limiter and Method of Construction

Abstract

A resettable torque limiter in which major components are cast from stainless steel in order to minimize material requirements and which are thereafter annealed to provide corrosion resistance in service.

1 . A method of manufacturing a safety element torque limiter including:
 a carrier hub;   a pocket plate rotatable on said carrier hub;   a retainer plate fixed to said carrier hub and together with a flange on said carrier hub confining said pocket plate axially on said carrier hub;   a drive ball held on a seat in a recess formed in said pocket plate by an aligned spring loaded plunger mounted on a hub of said carrier hub so as to create a spring force acting on said plunger to thereby hold said drive ball on said seat, said drive ball positioned partially within said recess in said pocket plate and a normally aligned recess in said carrier hub, said spring acting on said drive ball though a ramp ring and a set of interposed secondary drive balls which are moved up and past said ramp as onto an outside diameter of said plunger when torque exceeds a predetermined maximum level to discontinue exertion of said spring force on said plunger and allow said drive ball to be forced out of said recess in said pocket plate and disconnect drive between said pocket plate and said carrier hub;   wherein said retainer plate, said carrier hub and said pocket plate are each precision cast from a low carbon stainless steel and thereafter annealed by heating to a temperature in the range of 1850° to 2050° F. and thereafter rapidly quenched.   
     
     
         2 . The method according to  claim 1  wherein said quenching is carried out in sand fluidized by nitrogen gas. 
     
     
         3 . The method according to  claim 1  wherein 316L stainless steel with 0.03% carbon is used in casting said retainer plate, carrier hub and pocket plate. 
     
     
         4 . The method according to  claim 3  wherein a series of voids are in cast into each of said retainer plate, carrier hub and pocket plate intermediate holes therein. 
     
     
         5 . The torque limiter made by the method of  claim 1 .