Patent ID: 8118025

Claim:
A blow filter device for breathing masks and hoods including a blower driven by a motor and at least one filter arranged upstream from the blower, as well as an electronic control system associated with the blower motor for adjusting a predefined airflow volume, wherein the blower motor is an electronically commutated direct current motor controlled by a pulse width modulation (PWM) ratio and equipped with speed sensors, the pulse width modulation (PWM) ratio being used as a control variable generally determining motor speed and thus blower speed and air flow volume; wherein: a calibration curve is created and stored in a memory of the electronic control system for a specific airflow volume based on a plurality of different filter resistances, respective corresponding pulse width modulation (PWM) ratios, and respective blower motor speeds (n); the direct current motor is controlled in a hood operating mode using the pulse width modulation ratio read from the calibration curve associated with the blower speed (n) measured after the direct current motor is switched on, the blower speed (n) related to a filter resistance; and the pulse width modulation (PWM) ratio used in a mask operating mode comprises a constant pulse width modulation (PWM) ratio specific to a type of mask regardless of the respective filter resistance; and further including a sensing and control system, a portion thereof being integrated into an air outlet port of the blow filter device and connected to the electronic control system, said sensing and control system including an identification switch, a first hose connection for attaching breathing masks to the air outlet port, the first hose connection is provided with an actuator for the identification switch, and a second hose connection for attaching breathing hoods to the air outlet port, the second hose connection is devoid of an actuator, the sensing and control system generating a signal corresponding to an actuation state of the identification switch upon completion of the first or second hose connection to the air outlet port.