Vacuum cleaner filter bag condition indicator

Claim 1

In a vacuum cleaner having a housing including a suction compartment, an air permeable filter bag mounted in said compartment, means defining an air inlet in said housing communicating with said filter bag, means defining an outlet in said housing, an air-moving unit in flow communication with said compartment and said outlet for drawing dirt-laden air through said inlet and discharging filtered air through the outlet, the improvement comprising: indicator means for detecting a pressure drop of predetermined amount through said filter bag thereby to indicate that the filter bag is substantially full of dirt, said indicator means comprising a casing mounted in the housing, pressure responsive means including a movable partition member mounted in said casing and separating said casing into first and second chambers, means communicating said suction compartment with the first chamber, said second chamber including a wall having an orifice, said orifice being smaller than said partition member, means communicating said filter bag with said orifice, means for urging said partition member against said wall to normally seal said orifice until said predetermined pressure drop is reached, bleed means for balancing the pressure across the partition member adjacent the wall about the orifice until said predetermined pressure drop is reached, and an indicator associated with said pressure responsive means extending from said casing, whereby the partition member unseats and the indicator is rapidly forced out the casing when the pressure in the filter bag is greater by said predetermined amount than the pressure in the compartment.