Abstract: Security screens for windows and other openings may include a screen pattern generally conforming to a two-dimensional foam topology, such that solid segments outline a plurality of openings or cells. The solid segments may include circular arcs of varying length and radius, intersecting at 120-degree angles, in threes, at a plurality of vertices. Manufacturing methods may include simulation of a two-dimensional foam subject to certain constraints, such as a target range for the areas of cell openings.

Abstract: A disposable filter bowl assembly includes i) a filter bowl; ii) a filter located in the filter bowl; and iii) a non-removable retainer ring with tabular portions engaging an annular groove internal to the filter bowl in a manner permanently securing the element in the bowl.