Shaft Seal

A shaft seal for an exhaust fan, the shaft seal for limiting the leakage of a fluid from within an exhaust fan housing around an exhaust fan drive shaft that extends between a position exterior to the exhaust fan housing and a position within the exhaust fan housing, the shaft seal comprising:

• a plenum generally positioned about the exhaust fan drive shaft at the point where the exhaust fan drive shaft extends into the exhaust fan housing;
• an auxiliary blower comprising an auxiliary blower housing, an internal auxiliary blower blade or impeller driven by an auxiliary blower drive shaft, and an auxiliary blower drive to rotate the auxiliary blower drive shaft, said auxiliary blower drive comprising a first pulley mounted to said auxiliary blower drive shaft, said first pulley rotated by a belt driven by a second pulley mounted to either the exhaust fan drive shaft or to a rotating shaft of an exhaust fan motor;
• and
• a duct fluidly connecting said auxiliary blower housing to said plenum,
• said auxiliary blower mounted upon a track such that the position of said first pulley relative to said second pulley can be altered between a position wherein said belt engages each of said first and said second pulleys such that rotation of said second pulley causes a rotation of said first pulley, and a position wherein said belt is disengaged from one or both of said first and second pulleys,
• wherein during operation of the auxiliary blower the pressure within said plenum greater than the ambient pressure exterior to said plenum and greater than the pressure within the exhaust fan housing.

A shaft seal for an exhaust fan, the shaft seal limiting the leakage of gas from within an exhaust fan housing past an exhaust fan drive shaft extending between an external exhaust fan motor and an exhaust fan blade or impeller within the exhaust fan housing, the shaft seal comprising:

• a plenum generally positioned about the exhaust fan drive shaft at the point where the exhaust fan drive shaft extends into the exhaust fan housing;
• an auxiliary blower comprising an auxiliary blower housing, an internal auxiliary blower blade or impeller driven by an auxiliary blower drive shaft, and an auxiliary blower drive comprising a first pulley mounted on said auxiliary blower drive shaft and rotated by a belt driven by a second pulley mounted to either the exhaust fan drive shaft or to a rotating shaft of the exhaust fan motor;
• and
• a duct fluidly connecting said auxiliary blower to said plenum, at least a portion of said duct being flexible and said auxiliary blower mounted upon a track, said auxiliary blower including one or more linear actuators such that activation of said one or more linear actuators alters the position of said first and second pulleys between a position wherein said belt engages each of said first and said second pulleys such that rotation of said second pulley causes a rotation of said first pulley, and a position wherein said belt is disengaged from one or both of said first and second pulleys;
• wherein, during operation of the auxiliary blower the pressure within said plenum is greater than the ambient pressure exterior to said plenum and greater than the pressure within the exhaust fan housing.