Screw anchor

A screw anchor formed from a stamped blank. The nut has inner, outer and intermediate layers which are folded prior to rolling the nut into its final form. The inner and outer layers have a common edge and the inner layer tapers inwardly from the ends of the common edge. The formed nut exhibits tremendous strength.

SPECIFICATION 
The present invention relates to blind screw anchors or inserts which are 
formed by stamping the part from strip stock in a die transfer process and 
rolling the stamped part into the cylindrical insert. 
In such state of the art manufacture a head portion defined by an annular 
sleeve closed by a cap through which a fastener is inserted is defined at 
one end and an annular nut portion is defined at the other. Legs which are 
slightly bent at knee locations interconnect these ends. Threads are 
defined on the inner diameter of the nut end to receive the fastener which 
will collapse the legs thereby securing the insert. The nut may be defined 
by two layers of sheet stock which are folded together in a coining punch 
and die. Threading the fastener into the nut will tend to expand (open) 
the nut and the seam is accordingly welded to prevent such opening. 
It is an object of the present invention to provide an improved stamped and 
formed insert wherein the nut end will not open even though it has not 
been welded. 
Other objects and advantages of the present invention will become apparent 
from the following portion of the specification and from the following 
drawings which illustrate in accordance with the mandate of the patent 
statutes a presently preferred embodiment incorporating the principles of 
the invention.

Blind screw anchors 10 include a flanged end or cap 12 which is secured to 
a sleeve 13. The sleeve is connected to the anchor nut 14 by a number of 
legs 16. A fastener 18 which passes through a hole in the cap is received 
by the threaded inner diameter of the nut. Tightening the fastener 
collapses the legs and draws them into engagement with the panel to which 
the insert is being secured. The legs are bent to form knees 22 which 
define the break location of the legs. 
The blind screw anchor is formed from a flat blank which is stamped from a 
metal strip and then rolled to the final shape. The nut end 146 as it is 
stamped from a metal strip is shown in FIG. 2. The nut end 146 of the 
blank has a first rectangular portion 30 which defines the end of the 
blank, a substantially rectangular second portion 31 from which the legs 
16a extend at one end and an intermediate portion 32 which tapers 34 down 
from the second portion 31 to a longitudinally extending segment 35 which 
defines a step 36 at either side of the first portion joining the wider 
first portion 30. 
The first portion 30 is folded at the first bend line B1 in a conventional 
coining punch and die and the end is again folded at the second bend line 
B2 in the conventional coining punch and die to form the fully folded nut 
end as shown in FIG. 3. 
When this fully folded end is rolled into the fully formed nut 14, the 
formed seam 145 is not welded or otherwise joined (it is an open seam). 
While the state of the art single folded double walled nut will open 
unless the seam is welded, and a man skilled in this art would believe 
that the same would occur in a triple fold. This triple fold exhibits 
extreme strength. The open seam will not open (the shaft of a screw will 
bend before the nut opens). Internal threads are rolled or cut on the 
inner surface (middle portion 32).