Patent ID: 8950401
Filing Date: 2015-02-10
Classification: A61M,A62B

Abstract:
1. A breathing apparatus, comprising: a conduit defining a passageway for a breathable gas having a first inlet for receiving breathable gas from a pressurized source of breathing gas, a second inlet for receiving filtered ambient air, and an outlet for delivering breathable gas to a user; a suction source in fluid communication with said second inlet for drawing ambient air into said passageway; a main filter assembly positioned between said second inlet and said passageway for removing contaminants from said ambient air; a prefilter assembly positioned upstream of the main filter assembly, said prefilter assembly including one or more prefilter elements, said prefilter assembly including a prefilter housing receiving said one or more prefilter elements, said prefilter housing movable between a closed position wherein said second inlet is closed to ambient air and an open position wherein said second inlet is open to ambient air; a pneumatically operated piston reciprocally movably within a cylinder, said piston mechanically coupled to said prefilter housing; a normally closed passage extending between said cylinder and the pressurized source of breathing gas; and a valve for selectively opening said normally closed passage to deliver pressurized breathing gas to said cylinder, wherein when the prefilter housing is in the open position, the pressurized breathing gas delivered to the cylinder causes the prefilter housing to be moved to the closed position and wherein when the prefilter housing is in the closed position, the pressurized breathing gas delivered to the cylinder causes the prefilter housing to be moved to the open position.