Door operator system

An overhead door operator system, comprising:

• a door frame adjacent an opening comprising a first frame section at a first side of the opening and a second frame section at a second side of the opening;
• a door arranged to be moved between an open (O) and closed (C) position, the door being movably connected to the door frame;
• a drive unit mounted on the door, the drive unit comprising at least one motor arranged to move the door from the closed position (C) to the open position, and
• an elongated transmission member extending along the first side of the opening and the first frame section,
• whereby the drive unit further comprises a driven transmission member in driving connection with the at least one motor, the driven transmission member being movably connected to the elongated transmission member and arranged to interplay with said elongated transmission member for driving the driven transmission member along said elongated transmission member by means of the elongated transmission member at least partially wrapping around the driven transmission member;
• at least one guide member mounted to the door arranged to interplay with the elongated transmission member for guiding the door along the elongated transmission member by means of the elongated transmission member at least partially wrapping around the at least one guide member;
• and
• a first set of guide rollers mounted to the door arranged to interplay with the first frame section and a second set of guide rollers arranged to interplay with the second frame section, wherein the at least one guide member is arranged coaxially with one of the guide rollers,
• wherein a top end of the elongated transmission member is fixedly mounted to the frame and a bottom portion of the elongated transmission member engages a console at a fixed position proximal to a floor of the opening, wherein the bottom portion extends around the console and upward, and wherein the bottom portion is connected to a connection point on the frame by a biasing member, wherein the console and the connection point are fixed with respect to one another on the frame,
• wherein the biasing member comprises a spring arrangement connected at one end with the bottom end of the elongated transmission member and extending upwardly and connected at another end with the connection point on the frame.