Heater unit for use in an air conditioner for automotive vehicles

Claim 1

A heater unit for use in an air conditioner, which comprises: a casing having an interior thereof formed with an air inlet passage, a face-level air outlet opening in a peripheral wall of said casing at an upper portion thereof, a floor air outlet opening in a peripheral wall of said casing at a lower portion thereof, a discharging air passage extending between said air inlet passage and said face-level air outlet, a floor discharging air passage extending between said discharging air passage and said floor air outlet, a heating air passage branching from said air inlet passage, a hot air passage extending between said heating air passage and said discharging air passage, and a defroster air outlet opening in a peripheral wall of said casing in communicating with same; a heater core arranged within said casing at an intersection of said heating air passage with said hot air passage, said heater core having a first end wall formed with an inlet and facing said heating air passage, a second end wall formed with an outlet and facing said hot air passage, and two side walls extending between said end walls; said hot air passage extending along said second end wall of said heater core and also extending at least as far as one of said side walls thereof; a first damper for selectively opening and closing said face-level air outlet; a second damper for selectively opening and closing either said floor air outlet or said floor discharging air passage; a third damper pivotally arranged at a location between said air inlet passage and said discharging air passage; said third damper being disposed to allow air introduced into said air inlet passage to be guided into said discharging air passage alone, at a first extreme position thereof and allow said air to be guided into said heating air passage alone, at a second extreme position thereof, substantially all said air thus guided into said heating air passage being delivered into said heater core, while allowing said air to be guided into both said discharging air passage and said heating air passage, at an intermediate position thereof between said first and second extreme positions; a fourth damper located remotely of said heater core and arranged at an intersection between said discharging air passage and said hot air passage or at a location in the vicinity of the last-mentioned intersection for selectively allowing and interrupting communication therebetween, said fourth damper being movable to a fully closed position to prevent any backflow to said heater core through said hot air passage when in said fully closed position; and coupling means operatively connecting said third damper with said fourth damper, said coupling means being operable to bias said fourth damper in a position to interrupt the communication between said discharging air passage and said hot air passage to prevent part of air in said discharging air passage from being guided to said heater core through said hot air passage when said third damper is in said first extreme position, and in a position to allow the same communication when said third damper is in either of said second extreme position and said intermediate position.