Self-drilling anchor and bearing plate assembly

A self-drilling anchor and bearing plate assembly adapted to secure a membrane or other layer onto a roof deck or a similar substrate formed of a material that requires a drilled hole to receive the anchor. The bearing plate which rests on the layer and includes barbs which press into the layer to resist rotation of the plate, has an opening therein to accommodate the anchor, the opening being surrounded by a series of ratchet teeth. The anchor head is provided with at least one pawl which when the head overlies the plate is then in operative relation with the ratchet teeth. Extending from the head is a shank section in an auger formation, and extending from the shank section is a drill section having at least one cutting blade. When the anchor is inserted in the plate opening and is turned in by a tool, the drill section then proceeds to drill a hole in the substrate, and as the shank section enters this hole, its auger taps an internal thread in the hole to securely retain the anchor therein. When the anchor reaches the point where its head rests on the plate, then further turning in of the anchor to urge the plate against the layer causes the pawl to ride over the ratchet teeth, thereby permitting further turning in. But should the anchor thereafter seek to turn out, the pawl then engages the ratchet teeth to resist this motion and prevent loosening of the installed assembly.

BACKGROUND OF INVENTION 
1. Field of Invention 
The invention relates generally to an anchor and bearing plate assembly for 
fastening a membrane or other layer to the deck of a roof or a similar 
substrate, and more particularly to an assembly of this type whose anchor 
includes a drill section extending from an auger-type shank section so 
that the anchor is usable with a deck formed of a material that resists 
entry therein of an auger and therefore requires a drilled hole in the 
material to receive the anchor. 
2. Status of Prior Art 
It is common practice to cover the roof of a building with a layer of 
thermal insulation formed of pads or panels of lightweight material such 
as fiberglass or rigid foam plastic. These panels are laid down on the 
roof deck and covered by a sheet of polyvinyl chloride, or other 
water-impermeable membrane to protect the layer against water penetration. 
Since the roof is exposed to the elements, it may on occasion be subject to 
high velocity winds as high as 150 miles per hour. Unless the insulation 
and membrane layer are firmly secured in place, the resultant updraft may 
blow the layer off the roof. For various reasons, the use of bonding 
agents to adhere the insulation layer to the deck of the roof is now being 
replaced by mechanical fasteners which serve to retain the layer in place 
when strong winds are encountered. The present practice of securing the 
insulation layer to the roof deck is by means of load-bearing plates of 
sheet metal which overlie the insulation layer and are bolted or otherwise 
mechanically fastened to the deck. 
Among the patents which disclose load-bearing or stress plates for this 
purpose are the Giannuzzi U.S. Pat. No. 4,574,551, The Williams U.S. Pat. 
No. 1,286,862, the Sandquist U.S. Pat. No. 4,074,501 and the Carlson U.S. 
Pat. No. 4,288,951. 
While the usual practice, when a roof deck is covered by an insulation 
layer, is to face this layer with a thin, waterproof membrane to prevent 
water seepage into the insulation layer, in many situations, use is made 
only of a waterproofing layer or membrane to cover the roof deck, in which 
case the anchor and bearing plate assembly serves to fasten the membrane 
to the roof deck. The present invention is applicable to both situations. 
My prior U.S. Pat. No. 4,763,456 discloses an anchor and stress plate 
assembly adapted to secure an insulation layer to the deck of a roof 
formed either of relatively soft or hard decking material. The anchor is 
provided with a flanged head and a shank whose leading section takes the 
form of an auger screw having a root which tapers toward the tip and a 
threading spiralled about the root whose crests are of approximately 
uniform diameter. When the anchor is turned into pulverizable decking 
material, the tapered root of the auger screw then acts to pack particles 
of this material into a dense mass in the region surrounding the screw to 
enhance the holding power of the anchor. 
In hard decking material, a hole must first be drilled therein to receive 
the auger screw whose root when the anchor is turned in, fits within the 
hole and whose crests then tap a thread in the hole wall to securely 
retain the anchor. The stress plate which overlies the insulation layer to 
prevent uplift thereof has a central depression surrounding an opening 
defined by a circular series of ratchet teeth. When the anchor is fully 
turned into the decking material, its head then lies within the plate 
opening and the flange on the head rests within the depression. The anchor 
head is provided with a pawl that is deflected by the ratchet teeth when 
the anchor is being turned in, the pawl engaging the teeth when the anchor 
seeks to turn out, thereby preventing loosening of the installed assembly. 
The anchor and stress bearing plate assembly disclosed in my prior U.S. 
Pat. No. 4,763,456 is usable with soft decking material, such as porous 
wood and fiber composites known commercially as Tectum. In the case of 
soft decking material, the auger screw of the anchor turns into this 
material without difficulty. The same assembly is also usable with hard 
decking material such as gypsum, plaster board to pre-drill a hole in the 
material before the anchor to tap this hole to internally thread its wall 
and thereby retain the anchor in the hole. 
The main concern of this invention is with a roof anchor and bearing or 
stress plate assembly adapted to secure a protective membrane or an 
insulation layer covered by this membrane to a roof deck or similar 
substrate made of medium-hard material, such as wooden chip board, 
structural composite board, water board or oriented wood-strand board. 
Medium-hard material has sufficient hardness to resist the turning in 
thereto of an auger type anchor such as those disclosed in my prior U.S. 
Pat. Nos. 4,763,456 and 4,892,429. Hence to use these anchors with a 
medium-hard roof deck, it would be necessary to first drill a hole in the 
deck. 
This requirement complicates the installation procedure, for the installer 
of the assembly would first have to run a drill bit through the 
medium-hard roof deck before installing the assembly. The amount of time 
consumed in drilling operations in situations where thousands of 
assemblies must be installed would add substantially to installation 
costs. 
In my copending application Ser. No. 396,109, there is disclosed a 
self-drilling anchor having a head adapted to receive a screwdriver or 
other torque-producing tool, the anchor including an externally-threaded 
shank section functioning as an auger and a drill section extending from 
the shank section formed by a pair of opposed cutting blades and a pair of 
guide blades, each angled relative to a respective cutting blade. When 
this anchor is turned into a substrate, the cutting blades guided by the 
guide blades proceed to bore a hole in the substrate, and when the shank 
section enters this hole, the hole is tapped by the threading of the shank 
section, thereby retaining the anchor in place. 
But while an anchor of the type disclosed in my copending application Ser. 
No. 396,109 is usable for installation in medium-hard and hard substrates, 
it is not suitable for use in combination with a stress or bearing plate 
having a circular series of ratchet teeth surrounding the opening in the 
plate, for this anchor lacks a pawl to engage these teeth to prevent 
turning out of the anchor and loosening of the installed assembly. 
Of prior art interest in regard to anchors having a drilling section is the 
patent to Ernst et al., U.S. Pat. No. 4,601,625. 
SUMMARY OF INVENTION 
In view of the foregoing, the main object of this invention is to provide a 
self-drilling anchor and bearing plate assembly adapted to fasten a 
membrane or another layer of material, such as an insulation layer, to a 
roof deck or similar substrate formed of a material of sufficient hardness 
to require that a hole be drilled therein to receive the anchor. While the 
assembly is especially useful for installation in roof decks or similar 
substrates formed of medium-hard material, in practice it may also be used 
for hard substrates which are drillable. 
A significant advantage of the invention is that it obviates the need for 
pre-drilling of the substrate and facilitates fast and easy installation 
of the assembly. 
More particularly, an object of the invention is to provide an assembly of 
the above type having a bearing plate which when pressed by the anchor 
against the membrane or other layer to be secured to the substrate is then 
resistant to rotation relative to the membrane, and in which the anchor, 
when installed with its head pressed against the bearing plate, is then 
resistant to being turned out, as a consequence of which the installed 
assembly is highly stable. 
Also an object of this invention is to provide an assembly of the above 
type which may be mass-produced at relatively low cost and which can be 
installed without difficulty by a simple torque-producing tool. 
Briefly stated, these objects are attained in a self-drilling anchor and 
bearing plate assembly adapted to secure a membrane or other layer onto a 
roof deck or a similar substrate formed of a material that requires a 
drilled hole to receive the anchor. The bearing plate which rests on the 
layer and includes barbs which press into the layer to resist rotation of 
the plate, has an opening therein to accommodate the anchor, the opening 
being surrounded by a series of ratchet teeth. The anchor head is provided 
with at least one pawl which when the head overlies the plate is then in 
operative relation with the ratchet teeth. Extending from the head is a 
shank section in an auger formation, and extending from the shank section 
is a drill section having at least one cutting blade. 
When the anchor is inserted in the plate opening and is turned in by a 
tool, the drill section then proceeds to drill a hole in the substrate, 
and as the shank section enters this hole, its auger taps an internal 
thread in the hole to securely retain the anchor therein. When the anchor 
reaches the point where its head rests on the plate, then further turning 
in of the anchor to press the plate against the layer causes the pawl to 
ride over the ratchet teeth thereby permitting further turning in. But 
should the anchor thereafter seek to turn out, the pawl then engages the 
ratchet teeth to resist this motion and thereby prevent loosening of the 
installed assembly.

DESCRIPTION OF INVENTION 
The Assembly 
Referring now to FIGS. 1 to 3, there is shown the self-drilling anchor, 
generally designated by numeral 10, included in an anchor and bearing or 
stress plate assembly in accordance with the invention. Anchor 10 may be 
molded or otherwise fabricated of a corrosion-resistant zinc alloy or 
other suitable metal, or of a high-strength synthetic plastic material 
such as nylon reinforced with long glass fibers to provide a moldable 
composite. 
Anchor 10 includes an enlarged head 11 having a truncated conical form, a 
series of fingers or pawls 12 being formed on the inclined wall of the 
head. An axial cavity 13 extending through head 11 and having a cruciform 
cross section or other suitable shape acts as a socket 14 to receive a 
similarly shaped blade of a torque producing tool (see tool 15 in FIG. 8) 
such as a Phillips-type screwdriver or a conventional manually-driven or 
motor-powered screw driver. 
Anchor 10 further includes a shank section 16 extending axially from head 
11. Shank section 16 takes the form of an auger screw whose root 17 tapers 
from its junction with head 11 to its junction with a drill section 18 
extending axially from shank section 16. 
Spiralled about root 17 is a threading T whose crests are of substantially 
uniform diameter throughout the length of the shank section. The 
relationship of the threading to the root, as pointed out in my 
above-identified prior patents which also disclose a tapered root, is such 
as to cause material pulverized by the auger as the shank section is 
turned into a substrate, to create a densified mass surrounding this 
section to resist withdrawal of the anchor from the substrate. 
Drill section 18, as best seen in FIG. 3, is provided with a pair of 
cutting blades B.sub.1 and B.sub.2. These extend in opposite directions 
from the longitudinal axis of the drill section 18 so that the cutting 
edges of the blades are diametrically opposed and act to cut a hole in the 
substrate when the anchor is turned therein by a tool. At right angles to 
the respective cutting blades B.sub.1 and B.sub.2 is a pair of guide 
blades G.sub.1 and G.sub.2 which engage the wall of the hole being drilled 
to ensure circularity thereof. In practice, the outer ends of cutting 
blades B.sub.1 and B.sub.2 are made convex to conform to the curvature of 
the hole wall and to sweep this wall as the drill section is turned in. 
The lower ends of the cutting and guide blades are chamfered. Cutting 
blades B.sub.1 and B.sub.2 are somewhat longer than guide blades G.sub.1 
and G.sub.2 to define a triangular point P. Thus when the anchor is 
pressed down on a membrane-covered substrate, point P penetrates therein, 
and as the anchor is then turned in by a tool, a hole is bored in the 
substrate by the cutting blades as guided by the guide blades to ensure 
the formation of a round hole. 
Bearing plate 19, as shown in FIGS. 4 to 7, is preferably formed of 
rust-resistant sheet metal, such as a zinc alloy. The plate has a circular 
form and is provided with corrugations concentric with a central circular 
opening 20 surrounded by a circular series of ratchet teeth 21. The 
ratchet teeth lie within a concave depression D whose dimensions are such 
as to receive head 11 of the anchor. Also formed in the anchor is an 
annular depressed region 22. 
The concentric corrugations in the plate render the plate resistant to 
flexure. Struck out of plate 19 in region 22 at equi-spaced positions are 
four pointed prongs or barbs 23. These barbs project below the plate and 
press into or penetrate the membrane when plate 19 is secured thereto by 
the anchor. The barbs act to resist rotation of the plate. 
Depending on the nature of the membrane or layer being secured to the deck, 
it is sometime necessary to prevent the bearing plate from rotating or 
being otherwise displaced while the anchor is being installed. To this 
end, the tool used to turn the anchor, such as an electric screwdriver, 
may be provided with a spring-biased depressible holding plate having an 
opening therein for the screwdriver blade. This holding plate presses 
against the bearing plate to hold it in place as the anchor is being 
turned into the substrate by the tool. 
Installation Procedure 
FIGS. 8 to 10 illustrate the procedure by which a membrane 24 or other 
layer covering a roof deck 25 or a similar substrate formed of medium hard 
or hard drillable material is fastened to this substrate by an anchor and 
bearing plate assembly in accordance with the invention. 
In the first step, as shown in FIG. 8, bearing plate 19 is placed atop 
membrane 24 at a desired location, and the tip P of drill section 18 is 
inserted in opening 20 in the stress plate. The blade of tool 15 is then 
inserted in the mating socket in head 11 of the anchor. 
The tool is now rotated clockwise, as shown in FIG. 9, to cause drill 
section 18 to drill a hole in substrate 25. As the tool continues to be 
turned, the auger-type shank section 16 then proceeds to tap its way 
through the hole to create an internal threading on the wall of the hole 
which acts to retain the anchor thereon. The installation is completed 
when head 11, as shown in FIG. 10, lies within depression D in bearing 
plate 19 and presses the plate against membrane 24 so that the barbs 23 on 
the underside of the plate press into or penetrate the membrane and 
thereby prevent rotation of the plate. 
In the final phase of installation, when head 11 of the anchor lies within 
the concave depression D of the bearing plate, then the pawls 12 are in 
operative relation to the ratchet teeth 21 surrounding the circular 
opening of the plate. As one continues to turn in the anchor to firmly 
press its head against the bearing plate and thereby urge this plate 
against the membrane to be fastened, pawls 12 ride over the ratchet teeth; 
hence in the clockwise direction of anchor rotation, the pawls do not 
impede such turning. Where the anchor material is such that the pawls are 
flexible, they are deflected by the ratchet teeth and thereby ride over 
the teeth. Where the pawls are inflexible, then the pawls press the plate 
into the membrane therebelow so that they can ride over the teeth. 
But should vibration or other forces thereafter seek to turn the anchor out 
counterclockwise, pawls 12 are then engaged by the ratchet teeth of the 
bearing plate to prevent rotation of the anchor relative to the bearing 
plate. And because the bearing plate is prevented by its barbs 23 from 
rotating, the anchor is not permitted to turn counterclockwise, and the 
installation cannot be loosened. 
Modified Assembly 
In the assembly shown in FIGS. 8 to 10, the length of anchor 10 relative to 
the combined thickness of membrane 24 and substrate 25 are such that when 
the assembly is fully installed, drill section 18 then projects below 
substrate 25, while the auger-type shank section 16 lies within the 
substrate, thereby maximizing the holding power of the anchor. 
In a situation where, as shown in FIG. 11, roof deck 25 is covered by a 
relatively thick and soft insulation layer 26 which in turn is covered by 
the thin waterproofing membrane 24, the anchor shown in the previous 
figures would be unsuitable for this application, for the shank section 
which provides the holding power would then be mainly with the soft 
insulation layer. 
In order, therefore, to provide an anchor having a length suitable for this 
application, the anchor 10' shown in FIG. 11 has an elongated shank 
section, the upper portion 27 which is free of threading and is of uniform 
diameter, the lower portion 16' having a tapered root and threading of 
substantially uniform diameter, as in the other embodiment of the anchor, 
as well as a drill section 18' as before. 
The length of anchor 10', as shown in FIG. 11, relative to the combined 
thickness of membrane 24, insulation layer 26 and substrate 25 is such 
that the upper portion 27 of uniform diameter of shank section 16 lies 
within the membrane and insulation layer, while the lower auger-type 
portion 16' of the shank section lies within substrate 25 and the drill 
section 18' extends beyond the substrate. 
It will be seen in FIG. 11 that surrounding the threaded shank portion 16' 
is a densified mass M of particles, resulting from the packing action 
produced by its tapered root and its substantially uniform diameter 
threading T. 
Thus in both embodiments of the self-drilling anchor and bearing plate 
assembly, the anchor acts to pre-drill its own hole in the substrate, and 
to then tap this hole, the anchor after engaging the stress-distributing 
bearing plate becoming locked in place whereby the installed assembly 
cannot be loosened by vibratory or other forces seeking to turn out the 
anchor. 
The assembly affords maximum pull out strength, for the packing and 
densifying of the substrate about the shank section in conjunction with 
the deep-reaching threads of this section give rise to an exceptional 
holding power. And the drill section, which includes guide blades, ensures 
a round hole, and this, too, enhances the holding power of the anchor. 
It is to be noted that in order to simplify the drawing, the ratchet teeth 
surrounding the opening of the bearing plate and the cooperating fingers 
in the anchor head have been omitted in FIGS. 8 to 11. In practice, 
however, these elements are included to prevent loosening of the installed 
assembly. 
Modified Drill Section 
In the drill section of the anchor shown in FIG. 3, cutting blades B.sub.1 
and B.sub.2 are provided with longitudinally-extending cutting edges which 
when the drill section is turned in,, act to drill a hole in the roofing 
deck, whereas guide blades G.sub.1 and G.sub.2 perform no cutting 
function, for they are adapted to engage the wall of the hole as it is 
being drilled to ensure its circularity. 
The lower ends of both the cutting blades and the guide blades are 
chamfered so that, as shown in FIG. 3, these ends are upwardly inclined 
relative to the axis of the drill section. However, cutting blades B.sub.1 
and B.sub.2 are somewhat longer than guide blades G.sub.1 and G.sub.2 so 
that the upwardly inclined ends thereof define a triangular point P. 
Because the membrane which covers the roofing deck is usually made of 
rubber or other elastomeric material, an anchor drill section of the type 
shown in FIG. 3 does not physically cut a hole in the membrane whose 
diameter corresponds to the diameter of the hole drilled in the roofing 
deck. As a consequence, the membrane tends to cluster or bunch about the 
shank of the anchor in the installed assembly, thereby making it difficult 
to end up with a wrinkle-free assembly. 
To overcome this drawback, a modified drill section is provided which is 
adapted to slice away the membrane in the region entered into by the 
anchor so as to provide a clean, wrinkle-free installation. 
The modified drill section, as shown in FIG. 12, includes a pair of cutting 
blades B.sub.1 and B.sub.2 identical to those shown in FIG. 3, and a pair 
of guide blades G.sub.1a and G.sub.2a which are the same as guide blades 
G.sub.1 and G.sub.2 in FIG. 3, except for one important detail. In this 
instance, the ends of guide blades G.sub.1a and G.sub.2a are downwardly 
inclined with respect to the axis of the drill section to define sharp 
slicing tips T.sub.1 and T.sub.2. 
When the drill section is turned into the membrane-covered roofing deck, 
tips T.sub.1 and T.sub.2, when they engage the membrane, act to slice it 
away in the region entered into by the anchor, thereby avoiding bunching 
or deformation of the membrane to provide a winkle-free installation. 
Modified Shank Section 
To resist unscrewing of the anchor, in the embodiment of the assembly shown 
in FIGS. 1 and 4, the anchor is provided on its head with pawls or fingers 
12 which engage ratchet teeth 21 surrounding the opening of the bearing 
plate. 
To further enhance resistance to loosening of the anchor, in the modified 
version thereof shown in FIG. 13, the tapered root 17' of the shank 
section 16' which generally correspond to the tapered root 17 of shank 
section 16 in FIG. 1, just below the head 11 of the anchor root 17' is 
provided with one-way external teeth 28. When during installation of the 
assembly the anchor is turned into a roofing deck or other substrate, 
teeth 28 then slip over the hole surface of the substrate. But should the 
anchor, as a result of vibratory or other forces, thereafter seek to turn 
out and loosen, teeth 28 will then bite into the substrate material to 
resist unloosening of the anchor. 
The threading T' of uniform diameter spiralled about the tapered root 16' 
is provided with triangular notches N. These notches, in certain 
materials, serve to assist the shank section in tapping the hole drilled 
in the substrate by the drill section of the anchor. The notches also 
serve to enhance resistance to unscrewing of the installed anchor. 
Anti-Rotation Assembly 
In the anti-rotation assembly shown in FIGS. 14, 15 and 16, the anchor 10' 
is the same as anchor 10 in FIG. 1, except that no pawls or fingers are 
provided on head 11. And there are no ratchet teeth as in bearing plate 19 
in FIG. 4; for as shown in FIGS. 15 and 16, the opening in bearing plate 
19' is defined by a series of forwardly projecting teeth 29. 
When, therefore, the anchor 10' which passes through the opening in bearing 
plate 19' is turned in and its head rests in the concave depression 
surrounding the opening in the bearing plate, the length of teeth 29 are 
such that the teeth seek to dig into the tapered shank 17 in the region 
thereof just under head 11, thereby resisting rotation of the anchor and 
preventing loosening of the assembly. 
Reverse Ratchet Assembly 
In the assembly shown in FIGS. 1 and 4, pawls or fingers on the head of 
anchor 10 engage ratchet teeth surrounding the opening in bearing plate 
19. 
A reverse ratchet assembly is shown in FIGS. 17, 18 and 19, where it will 
be seen that the underside of the head 11 of anchor 10''is provided with a 
circular series of indentations or recesses 30. These recesses are engaged 
by a circular series of ratchet teeth 31 surrounding the opening in 
bearing plate 19'' which match the recesses. 
Thus when the anchor is inserted in the opening in the plate and turned in 
until the head of the anchor lies within the concave depression in the 
bearing plate, further clockwise turning in of the anchor to press the 
plate against the substrate causes the ratchet teeth to slip over the 
recesses. But should the anchor thereafter seek to turn out and thereby 
loosen the installed assembly, this is prevented by the ratchet teeth 
whose orientation relative to the matching recesses is such as to resist 
counterclockwise movement. 
Lock Washer Assembly 
In the self-drilling anchor & bearing plate assembly shown in FIGS. 20, 21, 
and 23, the anchor 10''' is the same as anchor 10 in FIG. 1, except that 
no pawl or finger is provided on head 11. Bearing plate 19''' in this 
instance differs from bearing plate 19 in FIG. 4, in that provided around 
its opening is a series of upwardly protruding spring-like fingers 32 very 
much like those found in a lock washer. 
Reverse Ratchet Assembly 
In the assembly shown in FIGS. 1 and 4, pawls or fingers on the head of 
anchor 10 engage ratchet teeth surrounding the opening in bearing plate 
19. 
A reverse ratchet assembly is shown in FIGS. 17, 18 and 19, where it will 
be seen that the underside of the head 11 of anchor 10'' is provided with 
a circular series of ratchet indentations or recesses 30. These recesses 
are engaged by a circular series of teeth 31 surrounding the opening in 
bearing plate 19'' which match the recesses. 
Thus when the anchor is inserted in the opening in the plate and turned in 
until the head of the anchor lies within the concave depression in the 
bearing plate, further clockwise turning in of the anchor to press the 
plate against the substrate causes the teeth to slip over the ratchet 
recesses. But should the anchor thereafter seek to turn out and thereby 
loosen the installed assembly, this is prevented by the ratchet recesses 
whose orientation relative to the matching teeth is such as to resist 
counterclockwise movement. 
Lock Washer Assembly 
In the self-drilling anchor & bearing plate assembly shown in FIGS. 20, 21, 
and 23, the anchor 10''' is the same as anchor 10 in FIG. 1, except that 
no pawl or finger is provided on head 11. Bearing plate 19''' in this 
instance differs from bearing plate 19 in FIG. 4, in that provided around 
its opening is a series of upwardly protruding spring-like fingers 32 very 
much like those found in a lock washer. 
Hence when anchor 10''' is turned in and its head 11 is seated in the 
concave depression surrounding the opening in the bearing plate 19''', 
then the underside of the head 11 is engaged by the fingers 31 and the 
anchor is prevented from turning in the manner of a lock washer. 
While there have been shown and described preferred embodiments of a 
self-drilling anchor and bearing plate assembly in accordance with the 
invention, it will be appreciated that many changes and modifications may 
be made therein without, however, departing from the essential spirit 
thereof.