Wall fastener

An improved wall fastener for hollow walls, the fastener having two spreadable anchoring blades designed to spread behind the wall following insertion of a screw thereinbetween. The fastener is made of thin sheet metal which has been hardened through a heat treating process, such as quenching. Complementary engaging means on the blades are used to hold the blades together during the heat treatment and to prevent the separation thereof until the screw insertion.

FIELD OF THE INVENTION 
This invention relates to a wall anchor and more particularly a wall anchor 
made from a folded thin piece of sheet metal which has been heat treated 
subsequently to the folding. 
BACKGROUND OF THE INVENTION 
Various degisns of wall fastening member have been in existence for a 
number of years. An advanced type is described in U.S. Pat. No. 4,500,238. 
It comprises a sword-like anchor made of thin sheet metal, having two 
spreadable pointed flat blades for easy insertion in a wall. After 
insertion, the blades are spread apart by driving a fastener, typically a 
screw, thereinbetween to provide resistance to withdrawal. 
The ability of the anchor to enter the wall, and its holding power depend 
to a degree on the material used for the anchor, among other factors. Thus 
it is desirable to employ thin sheet metal of high strength, such as for 
example, spring steel metal or the like. However, to facilitate 
manufacturing, it is desirable to use a soft malleable material which can 
be easily shaped, cut and folded with conventional dies. 
To satisfy both requirements, a soft malleable sheet of metal is first used 
to cut, shape and fold to produce the desired shape for the anchor. The 
anchor is then heat treated by heating and quenching then tempering at an 
appropriate temperature in accordance with well known technology to harden 
the metal. During the quenching step it has been found that the folded 
article under the treatment stresses has a tendency to resume its original 
unfolded shape. The result of this tendency is a partial separation of the 
blades especially near the tip thereof which renders the article inferior 
for its intended purpose and reduces productivity. 
There is thus need for an inexpensive solution to the aforementioned 
problem and a need for an inexpensive way to hold the blades of such 
anchors in contact with each other during the hardening and particularly 
the quenching process. 
SUMMARY OF THE INVENTION 
A solution to the aforementioned problem is obtained by a wall fastening 
member design comprising a thin, sheet metal anchor having a substantially 
flat head portion and a hole therethrough, said hole having an axis 
perpendicular to the head. The axis extends through and is contained in 
the plane of a substantially flat neck adajcent said head. The neck 
includes an elongated opening therethrough extending in the plane of the 
neck the full length of the neck along the axis. First and second thin, 
flat sheet metal spreadable anchoring blades extend from the neck in the 
direction of the axis, coplanar with the neck, each having an inner and an 
outer surface, the inner surface of the first blade in close contact with 
the inner surface of the second blade, at least one of said blades 
terminating in a point; complementary engaging means are provided on each 
of the first and second blades, the engaging means of the first blade 
extending at least partially into the engaging means in the second blade. 
Typically, the complementary engaging means may comprise a boss extending 
from the inner surface of the first blade into a cutout portion in the 
body of the second blade, the outer dimension of the boss being sized to 
frictionally engage at least a portion of the cutout sides with a 
frictional force sufficient to resist blade separation forces produced 
during quenching of the anchor, yet insufficient to prevent blade 
separation and spreading upon insertion of a fastener thereinbetween. 
In the alternative the complementary engaging means may comprise a narrow, 
flexible strip portion of the first blade extending into snapping 
engagement through an aperture in the second blade. 
It is also an objective of the present invention to provide a method of 
producing a wall fastening member of the type comprising a thin, sheel 
metal anchor having a substantially flat head portion and a hole 
therethrough, said hole having an axis perpendicular to the head, the axis 
extending through and contained in the plane of a substantially flat neck 
adjacent to said head, the neck including an elongated opening 
therethrough extending in the plane of the neck the full length of the 
neck along the axis, first and second thin, flat sheet metal spreadable 
anchoring blades extending from the neck in the direction of the axis, 
coplanar with the neck, each having an inner and an outer surface, the 
inner surface of the first blade in close contact with the inner surface 
of the second blade, at least one of said blades terminating in a point, 
the method comprising: 
shaping, cutting and folding a thin malleable sheet of metal, 
engaging complementary engaging means on each of said first and second 
blades, and 
heat treating said anchor to harden the sheet metal. 
The engaging step may comprise frictional engagement of a boss extending 
from one of the blades in an aperture in the other blade or it may 
comprise a snapping engagement of a portion of the first blade by a 
receiving opening in the second.

DETAILED DESCRIPTION OF THE INVENTION 
Throughout the following description similar reference numerals refer to 
similar elements in all figures in the drawings. 
Referring not to FIG. 1 there is shown a piece of thin sheet metal 10 which 
has been shaped so that following folding along indicated fold lines, 12, 
14, 16 and 18, will produce an anchor of the type shown in FIG. 3. 
Throughout this description when the term thin metal is used it is 
understood to mean sheet metal varying in thickness depending on the wall 
size and usually between about 0.005 inches (0.0127 cm) to 0.060 inches 
(0.15 cm). This thickness range has been selected to produce optimum 
holding power without significant damage to the wall the anchor is 
inserted in. Thicknesses below 0.005 inches do not provide sufficient 
strength for driving them forcibly, as by hammering, into a wall. 
Reinforcing ribs may optionally be provided to give additional stiffness 
to the anchor. Unless stated differently, an anchor in accordance with 
this invention is produced by a series of operations comprising first 
shaping the sheet metal through cutting then folding the shaped metal into 
a final shape resembling the depiction of FIG. 3 and finally heat treating 
the folded article through quenching, optionally followed by tempering 
treatment. 
Referring back to FIGS. 1 and 2 the anchor is shown comprising two blades 
20 and 22 terminating respectively to pointed ends 32 and 34. The portion 
between folding lines 12 and 18 forms the anchor head after folding, as 
better shown in FIG. 3. The head contains an opening 30 through which a 
fastener such as a screw may be threaded into the anchor to secure an 
article thereto. 
Two openings 24 and 26 extend along the long dimension of the sheet metal 
piece in that portion of the blade adjacent the head which following the 
folding operation becomes the neck of the anchor. The neck is preferably 
simply an extension of the blades. In some structures, not shown here, as 
disclosed in the aforementioned U.S. Pat. No. 4,500,238 tabs extending 
from one of the neck portions enfold the other to assure that the blades 
will not spread but beginning at a point away from the head by a 
predetermined amount. The elongated openings 24 and 26 serve the purpose 
of allowing an inserted fastener to penetrate a given distance in the 
anchor before exerting a spreading pressure on the blades, thus also 
controlling the spreading point of the blades. 
As better shown in FIG. 2 in accordance with this invention there are 
complementary engaging means on each of the blades cooperating to provide 
a force to hold the folded blades together during the heat treatment. In 
this embodiment the complementary means comprises a boss 36 stamped in one 
of the blades and a cutout 38 on the other. 
An axis D--D extends the length of the shaped metal piece dividing it into 
two symmetrical sides. The boss 36, openings 24 and 26, a screw threading 
opening 30, and cutout 38 are located coaxially with axis D--D along its 
length. Upon folding of the sheet metal along the folding lines, the axis 
D--D assumes the orientation shown in FIG. 3, in which the head plane is 
perpendicular to the axis, while the blades extend in a plane containing 
the axis. 
The blades have an inner surface 25 and an outer surface 27. Upon folding, 
inner surface 25 on the first blade 20 is brought against inner surface 25 
on the second blade 22. Typically one blade is sized smaller than the 
other for easier wall penetration. 
Boss 36 and cutout 38 are placed and sized to form complementary engaging 
means such that upon folding the boss 36 is inserted into the cutout 38. 
FIG. 15 shows a desirably shaped boss 36 which comprises a generally 
cylindrical body portion 31 rising substantially vertically from the inner 
surface of blade 22, topped with a conical section 33. The conical shape 
of the boss top allows easy insertion in the cutout 38. The diameter of 
the cylindrical portion of the boss is selected to enter cutout 38 with 
some resistance so that there is a frictional force opposing withdrawal of 
the boss once inserted. 
In the preferred embodiment, the boss is generally circular, and so is the 
cutout as shown by numeral 38' in FIG. 5. With reference to FIG. 4 there 
is shown another possible boss 36 which has a crater-like form, open at 
the top, rising from the inner surface of blade 22 with walls 
substantially vertical, relative to the plane of the balde taken as 
horizontal. The walls of the crater-like boss are received and held by the 
sides of cutout 38' with sufficient frictional force to satisfy the 
aforestated requirements. The height of the boss walls has been sized so 
that following engagement in the cutout 38' they do not extend above the 
outer surface 27 of the blade in any substantial degree. 
FIG. 6 depicts a slight variation of the embodiment shown in FIGS. 4 and 5. 
Boss 36" resembles 36, but is not open at the top. Furthermore the boss 
may extend above the surface of blade 20 as shown here, and the cutout 38" 
may also be shaped in a crater-like fashion extending in the direction of 
the boss providing extra frictional surface contact. So long as the amount 
by which the engaging means rise from the surface of the blades is small 
they are not detrimental to the operation of the fastener. On the other 
hand this structure is advantageous in cases combining the open top boss 
36 of FIG. 4 with the cutout 38" of FIG. 6 to produce an engaging means 
that may be placed on the anchor through a single punching operation after 
folding. 
FIG. 7 is a further variation of the subject of this invention, in which 
the cutout 38 is elongated. This structure is advantageous in mass 
production through automated equipment since it requires less accurate 
placement of the cutout relative to the boss and can compensate for 
folding slightly outside of the design folding lines. Of course in this 
embodiment the frictional force is provided by the engagement of the means 
only along a portion of their surface. 
Another variation is shown in FIGS. 8 and 9 in which a square cutout 38'" 
is used in blade 20 to receive and frictionally engage two tabs 37 
extending vertically from the inner surface of blade 22. 
FIG. 10 shows yet another embodiment in which a small cutout 39 in the 
longer of the two blades, here blade 20, engages the tip 34 of blade 22. 
In this instance, the tip of the shorter blade may be designed with an 
elongation to allow easier and more positive insertion in the cutout 39. 
Insertion of the tip in the hole 39 prevents spreading of the blades 
during the heat treatment of the article, yet the elongated tip of the 
blade after treatment is flexible enough to snap out of the cutout and 
separate upon insertion of a fastener thereinbetween. 
A further variation of this embodiment is shown in FIGS. 11 and 12 in which 
a small tongue 41 has been bent up from one of the blades into snapping 
engagement in an opening 40 in the other. This arrangement operates much 
the same way as the one shown in FIG. 10. 
Finally there is yet another embodiment within the scope of this invention, 
shown in FIG. 13. In this instance, a certain portion of one of the two 
blades extending partially along its edges has been bent toward the other 
to create a channel defined by upturned right and left portions 43 and 43' 
into which the two sides of the other blade are frictionally engaged to 
hold the blades together during the heat treatment process. 
Preferably, the engaging means will be placed near the tip of the shorter 
of the two blades. This position may, in some embodiments, coincide with 
the tip of the shorter blade as discussed above with reference to FIG. 10.