Corner piece-less duct, Method of producing the same, and duct-forming machine

A seam forming apparatus of a cornerplate-less duct comprising:

• plural forming roll pairs arranged in a flow of a forming process, the apparatus being configured to sequentially pass a plate between forming rolls of each of the plural forming roll pairs to form seam joint portions at side end portions adapted to connect plate members forming the cornerplate-less duct having a rectangular cross-section, the plate having corner forming portions at both side end portions of a wall forming portion of the duct, the corner forming portion being a corner portion in the assembled state of the duct and being located with a cut portion interposed between the seam forming portion and the corner forming portion in a direction in which the plate is traveled, wherein rotation shafts of at least the forming roll pair which is located at an upstream end in the flow of the forming process are oriented in X-direction which is perpendicular to the direction in which the plate is traveled, and the forming rolls of the forming roll pair are cantilever-mounted to the rotation shafts;
• press rolls each of which is disposed such that an outer peripheral face of the press roll makes contact with an end face on a free end side of one of the forming rolls of each forming roll pair, the press rolls having rotation shafts extending in a Y-axis direction perpendicular to the rotation shafts of the forming rolls and the direction in which the plate is traveled, wherein a non-forming process region is formed in a space ranging from a free end of an opposite forming roll of the forming roll pair to a position apart from the free end, and a plate support face on which the plate is supported is provided on upstream side of the forming roll pair such that a boundary face between the press roll and the corresponding forming roll is an upper face of the plate support face;
• and
• a guide member configured to guide a side end portion of the plate placed on the plate support face, which is to be subjected to a seam joint forming process, along the direction in which the plate is traveled.

A duct manufacturing apparatus comprising:

• plural forming roll pairs arranged in a flow of a forming process, the apparatus being configured to sequentially pass a plate between forming rolls of each of plural forming roll pairs to form seam joint portions at side end portions adapted to connect plate members forming a cornerplate-less duct having a rectangular cross-section;
• wherein the forming roll pairs are each composed of forming rolls having rotation shafts and are mounted on a base such that the rotation shafts are oriented in X-axis direction perpendicular to a direction in which the plate is traveled;
• a press roll mounted for one of the forming rolls of at least one forming roll pair, which is adapted to make contact with a duct wall forming portion of the plate such that a rotation shaft of the press roll is oriented to have a crossing angle with respect to the direction in which the plate is traveled and the X-axis direction, the plate being held between the press roll and an end face of the forming roll with which the press roll is substantially in surface contact;
• and
• a drive feed roll pair mounted at a location apart from the press roll in a direction from a portion of the plate which is being processed toward the duct wall forming portion and configured to forcibly feed the plate in the flow of the forming process with the plate sandwiched from both sides.