Filter change indicator

Abstract

This invention relates to a filter change indicator that is operable in various orientations of the device incorporating it. For example, the filter change indicator is operable when the device is positioned in either the upright or sideways position. The device incorporating the filter change indicator can be any air moving device which incorporates a cleanable or replaceable filter. The filter change indicator includes a transparent viewing window and a tubulation. The viewing window displays a visible signal when the filter needs changing. The visible signal can be a float retained in the tubulation. The tubulation is a hollow transparent tube which forms an incline plane within the housing. The tubulation includes a first end, a second end and a step. The first end is in fluid communication with an air flow path through the tubulation, and this air flow path is exposed to atmospheric pressure. The second end opens into an air flow path formed between the inlet and outlet at a location downstream of an air filter. When a predetermined pressure differential develops across the tubulation, a predetermined force develops inside the tube which lifts the float from the first end of the tubulation to a position at the second end. The lifting force causes the float to come to rest in the tubulation at a position adjacent the viewing window.