Patent ID: 8267146

Claim:
An adjustable counterbalance system for use with a flexible rollup covering or door system which comprises a drum means having and supported by a generally horizontal hub; a flexible rollup covering or door having a top edge, a bottom edge, and opposing side edges, the top edge affixed to the drum means, and the bottom edge adapted for vertical cyclic movement between an unwound position and a wound-up position; and at least one adjustable counterbalance system comprising: a tension resisting biasing device extendible against a tension force, the biasing device having a first end fixed to resist linear displacement, and a second end; a belt means having a first end and a second end, wherein the first end of the belt means is fixed to a portion of the hub or drum means for winding upon a portion of the hub or drum means in a first direction or a second direction, and the second end of the belt means is coupled to the second end of the biasing device, wherein the belt means is operatively attached to the portion of the hub or drum means such that rotation of the hub or drum means in a first direction causes the belt means to wind about in a first direction and rotation of the hub or drum mean in a second direction causes the belt means to wind about in a second direction, and the adjustable counterbalance system applies a first force to the drum means through a first point, the first force directed substantially perpendicular to a longitudinal axis of the drum means, the first point being a center of rotation of the drum means, when the door is in first position, a second force applied through a second point on a diameter of the drum means when the door is at least partially unwound from the first position and a third force through a third point on a diameter of the drum means when the door is at least partially wound up from the first position.