Pressure differential switch

Claim 1

In an apparatus for indicating a clogged condition of a fluid filter having an inlet and an outlet; electrically conductive housing means defining a chamber, electrically conductive snap-action wall means extending across said chamber dividing the chamber into a first portion and a second portion, said wall means being electrically connected to said housing, means for providing fluid communication between said first chamber portion and the filter inlet, means for providing fluid communication between said second chamber portion and the filter outlet, said wall means being self-biased toward a normal conical disposition projecting toward said first chamber portion, contact means, insulating means threaded to said housing and carrying said contact means to have normally closed electrical engagement with said wall means, the improvement comprising circuit means having a first portion electrically connected to said contact means, and a second portion retained in electrically connected engagement with said housing by said insulating means, said wall means being prestressed by said contact means and arranged to snap away from said contact means to open the circuit between said first and second circuit portions when the differential fluid pressure between said first and second chamber portions reaches a preselected elevated value; and means responsive to the opening of the circuit to indicate the reaching of said elevated pressure.