Integrated end stops for zipper slider

A leakproof plastic zipper with integrated end stops for a zipper slider particularly suited for thermoplastic bags and the like comprising a pair of flexible plastic strips having separable fastener means extending along the length thereof comprising reclosable interlocking rib and groove profile elements on the respective strips, said strips each including profiled flange structure extending along the length thereof parallel to the rib and groove elements, a straddling slider on said strips for closing or opening the reclosable rib and groove elements comprising an inverted U-shaped plastic member having a back for moving along the top edges of the flange structure with depending side walls projecting therefrom for maintaining said flange structure and said rib and groove elements therebetween, said slider including separator structure depending from said back and inserted between said flange structure to open said rib and groove elements, said sidewalls extending from an opening end of the slider to a closing end, the sidewalls being spaced wider apart at the opening end to permit separation of the rib and groove elements and being spaced sufficiently close together at the closing end to press the rib and groove elements into interlocking relationship as the slider is moved in a zipper closing direction, said flange structure and said rib and groove elements being vertically sealed together at both ends of said pair of strips to maintain the zipper closed at said ends and to provide integrated end stops for the zipper slider, and window structure in said flange structure beneath the top thereof and above said rib and groove elements and adjacent one of said end stops, said window structure being dimensioned to receive said separator structure at the opening end of said slider whereby when said slider is moved in the zipper closing direction, said interlocking rib and groove elements are closed throughout the length of said strips by said closing end of said slider and said separator structure at said opening end of said slider is received in said window structure and thus is ineffective on said flange structure to maintain open said interlocking rib and groove elements thereby to prevent leakage through said zipper.