Patent ID: 8025090

Claim:
An operating assembly for a door comprising: a shaft coupled to a door wherein said shaft rotates in a first direction as the door is opened and rotates in a second direction as the door is closed; a graduated drum coupled to said shaft for rotation therewith, said graduated drum having a groove having a smallest diameter near a first end and a largest diameter near a second end, said graduated drum including a nonlinear portion extending along a major portion of the drum along the axis of the drum substantially from the grooves with the smallest diameter to the grooves with the largest diameter and having at least three consecutive graduations of the groove between the first and second ends, the difference in diameter between the first graduation and the second graduation is different than the difference in diameter between the second graduation and the third graduation; an energy storing member coupled to said at least partially nonlinearly graduated drum wherein said energy storing member stores energy as the door is closed and releases stored energy as the door is opened wherein said energy storing member is coupled to said nonlinearly graduated drum via a cable, said cable having a first end mounted to the first end of the drum along the smallest diameter of said drum and wrapping at least one and a half revolutions around said drum and connected at the other end to said energy storing member.