Cam operated spring biased counterbalance hinge mechanism for cabinet lid or the like

A combination hinge and counterbalance mechanism for hingedly mounting a lid on a cabinet for vertically directed swinging movements between first and second positions, said mechanism including:

• an elongated hinge pin;
• means adapted for removably fixing opposite ends of said hinge pin to said cabinet;
• at least one cam member adapted to be fixed to said lid, said cam member being supported on said hinge pin for rotation about the axis thereof, while being constrained against movement in at least one direction axially thereof;
• at least one cam follower member associated one with each said cam member, said cam follower member being supported on said hinge pin for reciprocating movements axially thereof while being constrained against rotation relative thereto;
• and
• a spring assembly arranged for biasing said cam follower member for movement in said one direction into operative engagement with its associated cam member for counterbalancing the torque effects of gravity on said lid throughout at least a substantial portion of the range of lid swinging movements, said cam member being configured to render said mechanism inactive for counterbalancing said torque effects at a point of lid swinging movements, whereby to permit said hinge pin to be removed from said cabinet when said lid is at said point of lid swinging movement in the absence of counterbalancing induced reaction forces therebetween.