Self-sealing reinforcement tie rod for ventilating ducts

Abstract

A tie rod for reinforcing heating, ventilating and air conditioning (HVAC) ducts against excessive wall flexure in response to positive and/or negative static or dynamic pressure differentials between the interior and exterior of the duct includes a threaded steel rod having a pair of abutment structures irrotatably fastened to longitudinally opposed end portions of the rod. Each abutment structure has a central coaxial bore which receives the rod, and includes a tubular portion terminated at an outer longitudinal end thereof by a transversely disposed, radially outwardly protruding annular flange. The bore wall of the abutment structure's tubular portion flares in an arcuate curve radially and axially outwardly to join the outer transverse wall surface of the flange, forming a tapered annular cavity between the bore wall and the end portion of the threaded rod protruding out from the abutment structures. An O-ring is slipped over each end portion of the threaded rod, the rod placed within a duct, and opposed ends of the rod inserted into respective ones of a pair of perpendicularly aligned perforations provided through opposed walls of the duct. A separate one of a pair of flare nuts is then tightened down onto the outer surface of each duct wall, compressing the O-ring between the inner surface of the duct wall and the outer transverse flange wall of the abutment structure, thus causing the O-ring to cold flow partially into the tapered annular cavity, and thereby forming a highly effective hermetic seal of each duct wall perforation.