US Patent 9435149 Vent stop for window sashes

A fully functioning, pivoting vent stop for sliding windows has only two parts, a housing and a pivoting tumbler, both formed of injection molded plastic material. The tumbler is pivotally mounted in the housing and has integral detent elements cooperating with detent elements on the housing walls to position the tumbler in recessed or extended limit positions. The cooperating detent elements also provide an over-centering spring action as the tumbler is actuated between its limit positions. Assembly of the two-part device is achieved in a highly simplified and economical manner by configuring an internal cavity in the housing with inclined slots in the internal side walls of the housing. This enables the tumbler to be resiliently pressed into the cavity, temporarily displacing the housing side walls outwardly, until the cooperating pivot and detent elements are fully engaged.