Wide top narrow bottom type double-layer zipper for luggage and zipper slider for same

A wide top narrow bottom type double-layer zipper, comprising a top and bottom zipper set, and a zipper slider coupled to said top and bottom zipper set and movable in one of two opposite directions to close or open said top and bottom zipper set, said top and bottom zipper set comprising left and right zipper tapes, top and bottom interlocking coils stitched to opposing top and bottom surfaces of said left and right zipper tapes to form two left series of interlocking teeth and two right series of interlocking teeth, said top and bottom interlocking coils each comprising a filler cord and a polyester coil spirally extended around said filler cord, wherein:

• the combined width of the interlocked said bottom interlocking coils is smaller than the combined width of the interlocked said top interlocking coils;
• said top interlocking coils and said bottom interlocking coils have the same spiral pitch;
• the top and bottom layers of the wide top narrow bottom type double-layer zipper are vertically aligned and sewed;
• the diameter of the said polyester coils that extend spirally around the respective said filler cords of the respective said bottom interlocking coils monofilament is about 0.02 mm˜0.1 mm smaller than the diameter of the said polyester coils monofilament that extend spirally around the respective said filler cords of the respective said top interlocking coils;
• said zipper slider comprises a top cover panel, an opposing bottom cover panel, opposing left and right guard flanges respectively and perpendicularly located at respective opposite lateral sides of said top cover panel and said bottom cover panel, an upright base center connected between said top cover panel and said bottom cover panel on the middle, a top chamber defined by said top cover panel for accommodating said top interlocking coils and a bottom chamber defined by said bottom cover panel for accommodating said bottom interlocking coils, the width of said bottom cover panel being smaller than the width of said top cover panel, said bottom chamber being relatively narrower and shorter than said top chamber.