Importance

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Abstract

A filter indicator system for indicating when air flow through a filter is restricted includes an indicator mounted in a filter assembly downstream of the filter. The indicator includes a housing having a central space, a side wall, an end wall, an end inlet in the end wall, and a side outlet. A pop-up member is located in the central space and includes a signal portion which extends adjacent the end inlet. A moving device is then used for moving the pop-up member between a non-signalling position where the signal member does not extend noticeably through the end inlet and a signalling position where the signal portion extends noticeably through the end inlet. A pressure responsive releasing mechanism in the side outlet is associated with the pop-up member for initially holding the pop-up member in the non-signalling position and preventing movement by the moving device, and for subsequently releasing the pop-up member when the suction pressure in the side outlet drops below a predetermined value relative to an ambient air pressure present in the central space. The releasing mechanism includes: (a) a clearance between the signal portion and the end inlet to conduct ambient air pressure to the central space; (b) a seal member which is subject to the ambient air pressure on one side and the suction pressure on the other side; and (c) a biasing member for biasing the seal member against movement until a predetermined suction pressure is exceeded.

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First Claim