Expansion anchor

Abstract

An expansion anchor includes an anchor bolt, a nut, a spring washer, first and second outer metal plates, and first to fifth inner metal plates. Each of the first and second outer plates is subjected to the dovetail-correspondence elevation-angle bending-processing. The width of the first to fifth inner metal plates is set larger in the order of the fifth inner metal plate to the first inner metal plate, and the upper portions or the whole surfaces of the four side surfaces of the first to fifth inner metal plates are subjected to the chamfering-processing so that they become the continuation surfaces with the same inclination angle as the side-wall of the dovetail when the first to fifth inner metal plates are piled up in the same direction.

1 . An expansion anchor for use in combination with a dovetail, a mouth width of said dovetail being narrower than a bottom width of said dovetail, the expansion anchor comprising:
 an anchor bolt;   two or more inner metal plates inserted into said dovetail; and   two outer plates inserted between two side-walls of said dovetail and said inner metal plates,   wherein each of said two outer plates has a substantially L-shaped cross-section which comprises a top plate portion and a side plate portion.   
   
   
       2 . An elongated expansion anchor having a threaded portion in a center portion thereof, the expansion anchor being configured to engage a dovetail, a mouth width of said dovetail being narrower than a bottom width of said dovetail, the expansion anchor comprising:
 an anchor bolt;   a nut;   first and second outer plates; and   two or more inner metal plates,   wherein each of said first and second outer plates has a substantially L-shaped cross-section, which comprises a top plate portion and a side plate portion; and   wherein a width of a first inner metal plate is selected to be greater than a width of a second inner metal plate.   
   
   
       3 . The expansion anchor according to  claim 2 , wherein a length of said second inner metal plate is selected to be greater than the width of said first inner metal plate, so that side surfaces of said first and second inner metal plates become surfaces having the same inclination angle as a side-wall of said dovetail when said first inner metal plate is turned 90 degrees to be stacked with said second inner metal plate. 
   
   
       4 . The expansion anchor according to  claim 2 , wherein
 a width of at least one inner metal plate of said two or more inner metal plates is selected to be larger than the mouth width of said dovetail; and wherein   a penetration-hole, a bore of which is larger than a diameter of said anchor bolt, is provided in a center portion of at least one inner metal plate of said two or more inner metal plates.   
   
   
       5 . An elongated expansion anchor having threaded portions in opposed end portions thereof, the expansion anchor being configured to engage a dovetail, a mouth width of said dovetail being narrower than a bottom width of said dovetail, the expansion anchor comprising:
 first and second anchor bolts;   first and second outer plates; and   an upper inner metal plate and a lower inner metal plate,   wherein each of said first and second outer plates has a substantially L-shaped cross-section, which comprises a top plate portion and a side plate portion; and   wherein each of said upper inner and lower inner metal plates includes first and second upper internal threaded portions formed in respective holes defined therein, to enable threaded engagement with said first and second anchor bolts.   
   
   
       6 . The expansion anchor according to  claim 5 , wherein
 a width of each of said upper and lower inner metal plates is selected to be smaller than the mouth width of said dovetail;   a cross-sectional shape of said lower inner metal plate viewed from a side thereof is substantially trapezoidal; and   a width of said side plate portions of said first and second outer plates is selected to be less in a bottom portion thereof than in a central portion thereof.   
   
   
       7 . A substantially cross-shaped expansion anchor having internal threaded portions defined in four end portions thereof, the expansion anchor being configured to engage a dovetail, a mouth width of said dovetail being narrower than a bottom width of said dovetail, comprising:
 first to fourth anchor bolts;   first to eighth outer plates; and   an upper inner metal plate and a lower inner metal plate, each including first through fourth projection portions, wherein:   each of said first to eighth outer plates has a substantially L-shaped cross-section, which comprises a top plate portion and a side plate portion;   said upper inner metal plate and said lower inner metal plate have a shape similar to the shape of said dovetail when viewed from a the same direction; and   said first to fourth projection portions of each of the upper and lower internal plates respectively include threaded portions formed in respective holes defined therein, to enable threaded engagement with respective ones of said first to fourth anchor bolts.   
   
   
       8 . The expansion anchor according to  claim 7 , wherein
 a width of each of said first to fourth upper projection portions of said upper inner metal plate and said first to fourth lower projection portions of said lower inner metal plate is selected to be smaller than the mouth width of said dovetail;   tip portions of said first to fourth lower projection portions of said lower inner metal plate are cut by an acute angle toward a bottom portion of said lower inner metal plate; and   a width of each of said side plate portions of said first to eighth outer plates is selected to be less in a bottom portion there of than in a central portion thereof.   
   
   
       9 . The expansion anchor according to  claim 3 , wherein
 a width of at least one inner metal plate of said two or more inner metal plates is selected to be greater than the mouth width of said dovetail; and   a penetration-hole, a bore of which is larger than a diameter of said anchor bolt, is defined in a center portion of said at least one inner metal plate of said two or more inner metal plates.