Variable grip lifting mechanism

A gripping mechanism comprising complemental article engaging members mounted for movement towards and away from one another, powered means for relatively moving said members forceably to grip an article, holding means operable to maintain applied gripping force, multiple limit means operable to effect such operation of said holding means in response to gripping force reaching respective predetermined values, selector means for rendering operative any selected one of said limit means, and spring means drivingly interconnected between said powered means and said members for resiliently urging said members against the article gripped thereby, said multiple limit means including respective limit switch means mechanically actuable in response to respective degrees of compression of said spring means, each said limit switch means being selectively connectable by said selector means to said holding means for effecting operation of said holding means upon actuation.

A gripping mechanism comprising a tong support structure, a pair of tongs mounted to said tong support structure for movement towards and away from one another, an electric motor mounted with respect to said tong support structure for relatively moving said members towards one another forceably to grip an article therebetween, an electrically operated brake means operable when actuated to prevent relative movement of said tongs away from one another thereby to maintain then existing gripping force, power supply line means for supplying electric current to said electric motor, plural load sensing relay means operably associated with said power supply line means for effecting operation of said brake means in response to respective different predetermined currents in said power supply line means, relay selector means for selecting any one of said load sensing relay menas to be operative in response to the respective predetermined current in said power supply line means to effect actuation of said brake means.

A gripping mechanism comprising complemental article engaging members mounted for movement towards and away from one another, an electric motor for relatively moving said members forceably to grip an article, spring means interconnected between said electric motor and said members for resiliently urging said members against the article gripped thereby, holding means operable to maintain the applied gripping force, plural current monitoring means operably connected in circuit with said motor for monitoring motor current and effecting operation of said holding means in response to respective different predetermined currents, plural limit switch means mechanically actuable in response to respective different predetermined degrees of compression of said spring means for effecting operation of said holding means upon mechanical actuation, each one of a plurality of said current monitoring means being paired with a respective one of said plural limit switch means, and selector means for selecting any one of such pairs of current monitoring means and limit switch means to be operative for effecting actuation of said holding means.