Invisible butt joint fastener

Abstract

A fastener for connecting two structural pieces over abutting surfaces with no or minimum exposure of the fastener itself. Each fastener comprises a male and a female member to be fixed into abutting surfaces of the structural pieces to be connected. The tongue of the male member can be inserted into and slide inside the socket of the female member when the two structural pieces slide against each other along the abutting surface. The socket surface is partially covered with raised ribs, that can catch the ribs on the male tongue when the tongue is at the locking position but not at the releasing position. All the ribs are slopped relative to the sliding direction to convert part of the sliding action into a pulling action, so as to create a preload between the structural pieces when connected.

The claims are: 
     
         1 . A fastener for joining structural pieces over abutting surfaces, comprising
 a) a male member, which further comprising a tongue for extending from a mating surface of a first structural piece to be connected, and a plurality of outward-facing ribs on surface of said tongue running generally alongside said mating surface of said first structural pieces, and,   b) a female member, which further comprising a generally slotted socket for receding from a mating surface of a second structural piece to be connected, and said socket further comprising a ribbed section covered with a plurality of inward-facing ribs running generally alongside said mating surface of said second structural piece for engaging said outward-facing ribs on said tongue, and a flat section for allowing said tongue to be inserted into or extracted from freely,   
       therefore, said tongue may be locked inside said socket in a locking action, which is sliding from said flat section to said ribbed section of said socket, and unlocked in a releasing action, which is sliding from said ribbed section to said flat section of said socket. 
     
     
         2 . The fastener of  claim 1 , wherein,
 a) said outward-facing ribs of said tongue comprising a rail edge, which faces and inclines towards said mating surface of said first structural piece at a small lead angle along said opening action direction, and   b) said inward-facing ribs of said socket comprising a rail edge, which faces against and inclines towards said mating surface of said second structural piece at said small lead angle along said opening action direction,   
       therefore, said rail edge of outward-facing ribs of said tongue can glide against said rail edge of inward-facing ribs of said socket to pull said male member and said female member closer in said locking action. 
     
     
         3 . The fastener of  claim 1 , wherein said male member comprising an elastic retaining clip, normally extending from but can be depressed into said mating surface of said first structural piece, and is located relative to said tongue so that when said tongue is fully locked into said ribbed section of said socket, said retaining clip springs right into said flat section of said socket to restrict said opening action.