Stepless speed change electric chain block

A stepless speed change electric chain block including;

• a DC motor for driving a load sheave, comprising a phase control circuit having a variable resistor, a capacitor, a two-way trigger diode, a source of alternating current, and a triode AC switch for receiving alternating current from said alternating current source to control the phase of said alternating current, a full-wave-rectifier for receiving alternating current from said phase control circuit to convert said alternating current into direct current which is supplied into the DC motor, and mechanical brake means provided a transmission between said DC motor and said load sheave for braking rotation of the load sheave in a lowering direction, wherein said mechanical brake means comprises a cam support rotatably and axially slidably fitted on a load sheave shaft, a retainer disc fitted on said load sheave shaft axially slidably but nonrotatably relative thereto, a brake receiving disc fitted on the load sheave shaft axially slidably but nonrotatably relative thereto, a ratchet wheel rotatably fitted on a boss of the brake receiving disc, a pawl pivotally mounted on a stationary member of the block and urged into engagement with the ratchet wheel by resilient means, an intermediate driven gear fitted on said cam support axially slidably but against rotation thereto, a resiliently urging means for holding said ratchet wheel through said retainer disc, said brake receiving disc and the intermediate driven gear, and brake releasing cam members received in cam grooves each formed in one side of said cam support and having a sloped bottom to change its depth, thereby causing said brake releasing cam members to move into deeper positions in the cam grooves when the cam support is rotated in a lifting direction, and into shallower positions in the cam grooves when the cam support is rotated in a lowering direction.