Plastic sealing washer and fastener assembly

Claim 1

A FASTENING ASSEMBLY COMPRISING A FASTENING DEVICE AND A SEALING WASHER SAID DEVICE INCLUDING A HEAD PORTION FOR OVERLYING ONE SIDE OF AN APERTURE WORK STRUCTURE, AND A PLURALITY OF AXIALLY EXTENDING SHANK SECTIONS FOR INSERTION THROUGH THE APERTURE OF SAID WORK STRUCTURE, SAID DEVICE HAVING A PASSAGEWAY EXTENDING AXIALLY THEREIN AND PARTIALLY DEFINED BY INNER SURFACES OF SAID SHANK SECTIONS AND ADAPTED TO ACCOMMODATE AN ELEMENT INSERTABLE THEREIN FOR EXPANDING SAID SHANK SECTIONS, AND SAID WASHER INCLUDING A RESILIENT ANNULAR IMPERFORATE BODY SURROUNDING SAID SHANK SECTIONS AND HAVING AXIALLY OFFSET INNER AND OUTER MARGINS, SAID INNER MARGIN BEING IN ENGAGEMENT WITH SAID SHANK SECTIONS FOR RETAINING SAID DEVICE AND WASHER IN ASSEMBLED RELATIONSHIP, ONE OF SAID WASHER BODY MARGINS BEING SEALINGLY ENGAGEBLE WITH AN UNDER SURFACE OF SAID HEAD PORTION AND THE OTHER OF SAID WASHER MARGINS BEING SEALINGLY ENGAGEABLE WITH THE WORK STRUCTURE WHEN THE ASSEMBLY IS APPLIED THERETO, SAID WASHER MARGIN ENGAGEABLE WITH THE WORD STRUCTURE HAVING AN AXIALLY PROJECTED EDGE WHEREBY THE SURFACE AREA INITIALLY ENGAGEABLE IS LESS THAN THE RADIAL CROSS SECTIONSL AREA OF THE WASHER BODY AND AN AXIALLY EXTENDING THIN-WALLED EXPANDABLE SLEEVE INTEGRAL WITH SAID INNER MARGIN AND HAVING A CLOSED END SPACED FROM SAID INNER MARGIN AND ADAPTED TO RECEIVE AND ENVELOP SAID SHANK SECTIONS.