Mechanical fastener for roofing membrane and method of applying same

A non-penetrating mechanical fastener for securing a flexible sheet of an elastomeric material to the upper surface of a roof via the use of a plurality of such fasteners, each of which includes upper and lower members, wherein the latter are anchored to the roofing surface. The upper member includes a snap-ring which clamps the sheet within an annular boss formed on the lower member and a locking cap which is engaged by an interference fit with the snap-ring to lock the ring in position within the boss. A method for securing the flexible sheet to the roofing substrate also is presented.

TECHNICAL FIELD 
The field of art to which this invention pertains is that of mechanical 
fasteners and particularly to a fastener for mechanically securing a 
flexible sheet or membrane to the roof without penetrating the membrane 
and to the method of applying the same. 
BACKGROUND ART 
A large number of commercial and factory plant roofs are of a flat roof 
design wherein the roofing material itself is often of a builtup asphalt 
and in more modern systems of a single ply EPDM elastomeric sheet or 
membrane. In terms of securing a single ply EPDM membrane to the roof 
itself, one design utilizes a mechanical ballast system that uses a layer 
of stone over the membrane. While the ballast system is least expensive it 
has a disadvantage of being quite heavy (approximately 10 pounds per 
square foot) thus requiring a heavy roof support structure and in addition 
the roof slope cannot exceed 10%. 
Adhered roof membrane retention systems suffer from the cost penalty while 
mechanical fasteners and related fastening systems generally require 
fixation to the roofing substrate via mechanical fasteners. There are two 
basic kinds of mechanical fasteners namely, membrane penetrating and 
non-penetrating ones. Each of these types of fasteners has a number of 
favorable features and each of them is also subject to various drawbacks 
and disadvantages. 
Mechanical fastening systems of the pentrating type generally require 
fixation to the roofing substrate by a metal fastener with metal or 
rubberized nailing strips. U.S. Pat. Nos. 4,445,306; 4,074,501; 4,455,804; 
and 4,467,581 are examples of penetrating type fastening systems in which 
various rigid and semi-rigid members are used to secure the membrane to 
the roof. These systems require openings to be formed in the membrane 
either for receiving a fastening plate or by the attaching anchoring 
members. 
Examples of a non-penetrating type fastener is shown in German Patent 
Publication 24 33 669 in which the membrane fastener comprises a lower 
disc which is attached to a roofing substrate by an anchoring member. The 
roofing membrane is fitted over the lower disc and an upper disc is 
snapped over the lower disc to perfect the fastening and exert a sealing 
effect. In another embodiment of this Patent Publication, a plug is driven 
into the upper disc to expand the body thereof into an annular space 
provided in the lower disc to anchor the upper disc thereto. Another type 
of non-penetrating fastening system is shown in U.S. Pat. No. 3,426,412 
which has a flexible fastening cover which is snapped over a base member 
to trap the membrane therebetween. Another embodiment shown in this U.S. 
patent uses a plug-like member which is snap-fitted into a recess formed 
in a lower member which is rigidly connected to the roof to trap and clamp 
the membrane therebetween. 
Although both the penetrating and non-penetrating type fastening system do 
work satisfactory for many applications, it is desirable to have a 
non-penetrating system for certain applications to eliminate piercing the 
membrane. Also such a fastener can be installed in a minimum amount of 
time and without requiring skilled labor, and the fastening element can be 
securely retained in clamping engagement with the trapped membrane to 
reduce the accidental disengagement thereof upon the membrane experiencing 
severe uplift wind forces. 
DISCLOSURE OF THE INVENTION 
Objectives of the invention include providing an improved mechanical 
fastener for a roofing membrane and a method of applying the same in which 
the membrane is secured to the roof without any opening or puncture being 
imparted into the membrane thereby lessening the possibility of membrane 
damage during installation; in which a plurality of the fasteners can be 
placed in various arrangements over the roof surface to provide the 
required holding power; and in which the fasteners can be installed in a 
minimum amount of time and in an extremely efficient manner while reducing 
the possibility of the fasteners being installed incorrectly. 
Another object of the invention is to provide such an improved fastener and 
method in which a lower member of the fastener is rigidly attached to the 
roof at selected locations with one or more securing anchors after which 
the membrane is spread over the roof and the attached lower members 
followed by the subsequent insertion of a snap-ring into the recess of an 
annular boss formed in each of the lower members which traps and secures 
the membrane therein; in which a locking cap can be snap-fitted into a 
recess formed by the trapped snap-ring and membrane to force the snap-ring 
radially outwardly into a more secure clamping engagement with the 
membrane than that provided by the natural elasticity of the snap ring; 
and in which the locking cap covers a pocket formed by the trapped 
membrane and provides a seal with the membrane to prevent the accumulation 
of snow, ice and water in the membrane formed pocket. 
A still further objective of the invention is to provide such an improved 
fastener which may be formed out of a rigid lightweight metal such as 
aluminum, or a rigid plastic material; in which the fastener can be mass 
produced relatively inexpensively, yet provide an extremely sturdy and 
durable member which will secure the membrane to the roof and will retain 
the membrane in the installed position over a considerable period of time 
without damage to the membrane and which will enable the membrane to 
withstand the required wind forces without additional ballast, tiedown or 
fastening members which require the membrane to be pierced. Another 
objective is to provide such a fastener which can be produced in various 
sizes and for use with various thicknesses of membranes; in which a 
limited range of membrane thicknesses can be used with a single type and 
size of fastener since the membrane can be compressed sufficiently by the 
cooperating edges of the lower housing snap-ring and locking cap since 
these components are free of sharp projections; and in which the fastener 
is able to be used on any flat or irregular roofing geometry such as dome 
shaped roofs, since the fastener can be placed at various positions on the 
roof with the flexible membrane conforming to the shape and configuration 
of the roof. 
Still another objective of the invention is to provide such an improved 
fastener and method for installing the same in which the lower housing 
component of the fastener may have an external annular flange that is 
provided with a plurality of anchoring holes or in which the anchoring 
holes can be formed in a bottom wall of the housing which is located 
within the interior of an annular boss, which boss is engaged by the 
snap-ring; in which the snap-ring can be formed of various sizes and 
elasticity of metal to provide various amounts of clamping action for 
trapping and securing the membrane within the annular boss of the lower 
member; and in which the fastener and method provides an extremely 
inexpensive and efficient device and method of installing the same which 
achieves the objectives of the invention in a simple, economically and 
efficient manner. 
These objectives and advantages are obtained by the improved mechanical 
fastener of the invention, the general nature of which may be stated as a 
fastener for securing a flexible sheet to the upper surface of a roof 
wherein said fastener includes a rigid housing adapted to be secured to 
the upper surface of the roof and underlie the elastomeric sheet; 
fastening means for securing the housing to the upper surface of the roof; 
an elastic ring mounted in a stressed state on the housing for clamping 
the elastomeric sheet against the housing; ledge means formed on the 
housing for retaining the elastic ring in a stressed state on the housing 
with the elastomeric sheet being clamped between the ring and ledge means; 
and cap means cap means mounted on the housing by a snap-fit engagement 
with the elastic ring for locking the ring in clamped engagement with the 
elastomeric sheet. 
These objectives and advantages are further obtained by the improved method 
of the invention the general nature of which may be stated as a method for 
mechanically securing an elastomeric sheet to the upper surface of the 
roof via the use of a plurality of spaced non-penetrating fastening 
devices, each of said fastening devices includes upper and lower members 
with said lower member having an upstanding annular boss formed with an 
undercut circular recess and with said upper member including an elastic 
snap-ring, a locking cap and anchoring means for securing said lower 
member to said roof upper surface, wherein said methods comprising the 
steps of anchoring a plurality of the lower members at spaced locations to 
the upper surface of the roof; spreading the flexible elastomeric sheet 
over the roof upper surface and anchored lower members; placing the 
snap-ring in a stressed condition; installing the snap-ring in the 
undercut circular recess formed in the annular boss of the lower member to 
clamp and secure the elastomeric sheet therebetween free of any 
penetration through said sheet; and engaging the locking cap with the 
snap-ring with an interference fit to retain the snap-ring in clamping 
engagement with the elastomeric sheet.

BEST MODE FOR CARRYING OUT THE INVENTION 
The improved mechanical fastener is indicated generally at 1, and a 
plurality of said fasteners are shown in FIG. 1 securing a flexible 
elastomeric sheet or membrane 2 to upper surface 3 of a roof which is 
indicated generally at 4. In a typical installation, a plurality of 
fasteners 1 will be spaced in a predetermined fashion on roof surface 3 
such as shown in FIG. 1. 
Fastener 1 includes a rigid lower member or housing which is indicated 
generally at 6, an elastic snap-ring 7 and a locking cap indicated 
generally at 8. Referring to FIGS. 2, 3 and 4, housing 6 has an annular 
configuration with a disc-shaped bottom wall 10 having a circular flat 
bottom surface 11 which is adapted to lay flush against a top panel 12 of 
roof 4. Bottom wall 10 is formed with a central hole 13 and a plurality of 
circularly arranged spaced holes 14. Holes 13 and 14 are countersunk as 
shown in FIG. 3, so as to receive head 15 of an anchoring device which is 
indicated generally at 16. 
An annular-shaped boss indicated generally at 18, is formed integrally with 
bottom wall 10 and extends axially therefrom. Boss 18 includes an annular 
wall 19 having a smooth outer surface and a top annular ledge 20 formed 
with an undercut circular recess 21. Ledge 20 is connected with recess 21 
by a smooth generally curved annular surface 22. Ledge 20 futher includes 
a flat horizontally extending smooth top edge 23 with recess 21 being 
connected to bottom wall 10 by a vertical wall section 27 and a smooth 
curved radial surface 24. Anchoring devices 16 are of a usual 
construction, preferably having lower threaded ends 25 and smooth upper 
shanks 26. The number of anchoring devices 16 will vary depending upon the 
particular roofing installation and for certain applications only a single 
anchor may be required through central hole 13 or several anchors may be 
inserted through certain of holes 14. The plurality and different 
locations of holes 13 and 14 insures that housing 6 will always be 
securely attached to the roof even though one of the anchoring devices 
could enter a void in the roof or hit a nonpenetrating portion of the 
roof. 
Snap-ring 7 has a circular configuration and is formed of an elastic spring 
metal material and is circular in cross section as shown in FIG. 3. A gap 
28 is formed at one location in ring 7 with separated gap ends 29 having 
rounded configurations so as to be free of sharp points which could cut 
into the membrane. When in an unstressed or uncompressed condition, ring 7 
will have an outer diameter generally equal to the internal diameter of 
recess 21 and in particular generally equal to the inner diameter of 
vertical wall 27, less twice the thickness of membrane 2. This will insure 
that ring 7 will be retained beneath ledge 20 without excessively clamping 
membrane 2 into recess 21. Gap 28 must be sufficiently large so that the 
circumference of the ring when in a compressed state with ends 29 touching 
must be less than the circumference defined by the outer annular surfaces 
22 of ledge 20 less twice the thickness of membrane 2 to enable the ring 
to be inserted within annular wall 19 of housing boss 18 after which it 
can expand outwardly into recess 21 as shown in FIG. 3 to clamp membrane 2 
securely therein. 
Locking cap 8 includes a disc-shaped top wall 31 and an annular axially 
extending peripheral flange 32. Flange 32 is formed with an undercut 
circular recess 33 in the outer surface thereof. Recess 33 has a diameter 
equal to and preferably greater than the inside diameter of snap-ring 7 
when the ring is in an unstressed condition. Cap recess 33 is connected 
with the smooth top surface of top wall 31 by a generally flat smooth 
annular outer edge 35. Edge 35 has a diameter generally equal to the 
diameter defined by annular surface 22 of ledge 20 minus twice the 
thickness of membrane 2 so as to form a tight seal therewith when cap 8 is 
in an installed position as shown in FIG. 3. Annular bottom edge 37 of cap 
flange 32 has a smooth surface to eliminate any sharp edges which could 
cut into membrane 2. 
As shown in FIG. 3, housing 6 is secured by one or more anchoring devices 
16 which can be screws, nails, expansion bolts, or the like into a main 
roof deck 39 so as to be firmly secured thereto. Roof 4 may also include a 
sheet 40 of insulation covered by top panel 12. A plurality of housings 6 
are placed in a spaced relationship throughout the roof top surface 3. The 
number of housings 6 and their location will depend upon the size of 
fasteners 1, the thickness and size of membrane 2, the particular 
construction of roof 4, and the particular wind loads to which the 
membrane is designed to withstand. After the housings are rigidly secured 
to the roof, membrane 2 is laid over the installed housings and workmen 
will install a snap-ring 7 at each housing location. Snap-rings 7 can be 
installed manually or with a tool by placing the ring in a compressed 
position wherein rounded ends 29 preferably will be touching. The 
compressed ring is then inserted into the interior of annular boss 18 
pressing part of the membrane 2 into the boss. Ring 7 then is permitted to 
expand outwardly into undercut circular recess 21 clamping membrane 2 into 
the recess. The adjacent membrane portions will curve upwardly around 
ledge 20 and continue generally horizontally therefrom as shown in FIG. 3. 
Next, a locking cap 8 is snap-fitted into each of the circular pockets 
formed within bosses 18 by clamped membrane 2. Due to the particular 
diameter of cap recess 33, it forms an interference fit with ring 7 and 
presses ring 7 into clamping engagement with the trapped portion of 
membrane 2 located in housing recess 21. Cap 8 also provides a seal with 
membrane 2 adjacent ledge 20 preventing water from entering the pocket 
formed by trapped membrane 2 and mainly prevents accidental disengagement 
of snap-ring 7 from its clamped position within housing recess 21 upon the 
membrane experiencing strong uplifting wind forces. Preferably the top 
surface of cap 8 is generally parallel with the top surface of membrane 2 
to provide a generally continuous smooth surface preventing the 
accumulation of water at each of the fastener locations. 
In accordance with one of the main features of the invention, improved 
fastener 1 does not require any holes or other openings to be formed in 
membrane 2 for securing it to the roof as in prior penetrating fastening 
systems. The smooth edges and curved undercut recess and flat bottom 
surface of housing 6 and the smooth edge of ledge 20, ledge edge surface 
22 and cap edge 35 eliminate any sharp corners or protrusions which could 
pierce and damage the membrane. Also, bottom annular edge 37 of locking 
cap 8 retains an annular portion of membrane 2 against housing bottom wall 
10. Thus, no openings or holes are created in the membrane which would 
require sealing and which could be subject to leakage over extended 
periods of time as in penetrating type fastening systems. 
In terms of the method process for utilizing non-penetrating fastener 1, a 
plurality of housings 6 are secured to roof 4 by anchor devices 16 after 
which membrane 2 is layed over the roof and housings. Snap-rings 7 then 
are installed at housing locations to securely clamp the membrane to the 
housings after which locking caps 8 are installed at each housing 
location. The location of each housing will be readily detected by a 
slight upward bulge of the membrane at the housing location and a workman 
can easily feel the recess within the housing for installing snap-ring 7 
manually or with an appropriate installation tool. As discussed above, in 
installing housings 6, one or more anchoring means may be used depending 
upon the structure of the roof and particular roof covering application. 
The plurality of holes spaced throughout bottom wall 10 generally insures 
that at least one anchor will provide a firm engagement with the roof for 
securing the housing thereto. Housing 6 and locking cap 8 preferably are 
made of a rigid lightweight material such as aluminum, as indicated in 
FIGS. 2 and 3 of the drawings or can be formed of a rigid plastic 
material. 
A modified form of the improved fastener is indicated generally at 45 and 
is shown in FIGS. 5 and 6. The only difference between fastener 45 and 
fastener 1 is that disc-shaped bottom wall 10 of housing 6 has been 
eliminated and replaced by an outer annular flange 46 of a modified 
housing 50, which flange extends radially outwardly with respect to an 
annular boss 47 which is similar to boss 18 of fastener 1. A plurality of 
mounting holes 48 are formed in flange 46 and are spaced circumferentially 
thereabout for receiving anchoring devices 16 or other fastening means. 
Holes 48 need not be countersunk as are attachment holes 13 and 14 of 
fastener 1 since clearance is not required from membrane 2 as in fastener 
1. 
Locking cap 8 and the particular configuration of annular boss 47 is the 
same as that described above with respect to fastener 1 and therefore need 
not be described in further detail. Bottom annular edge 37 of cap 8 will 
hold an annular portion of membrane 2 against roof panel 12 as shown in 
FIG. 6 instead of retaining it against the top surface of housing bottom 
wall 10. However, the clamping action of snap-ring 7 and end cap 8 are the 
same as in fastener 1. 
When mounting modified housing 50 on roof 4, preferably two or more anchor 
devices are used to securely attach housing 50 to the roof and prevent any 
pivotal movement thereof which could occur if it were attached with only a 
single anchor. The particular method of installing fastener 45 is the same 
as previously described with respect to fastener 1. Fastener 45 is shown 
in the drawings as being formed of plastic instead of the aluminum as 
illustrated in FIGS. 2 and 3 for fastener 1. However, fasteners 1 and 45 
can be formed either of metal, plastic or similar rigid material without 
affecting the concept of the invention. Fastener 1 is shown as metal and 
fastener 45 is being shown of plastic for illustrative purposes only. 
Flange 46 of housing 50 preferably has a flat annular bottom wall 51 and a 
flat top wall 52 with bottom wall 51 permitting the housing to lie flat 
against the top surface of roof panel 12 as does bottom surface 11 of 
fastener 1. 
The actual dimensions of fasteners 1 and 45 including the individual 
components thereof, can vary depending upon the wind lift requirements at 
the installation site and the size and thickness of membrane 2 to be 
secured thereby. In a typical installation, membrane 2 will have a 
thickness in the range of 0.045 to 0.060 inches and locking cap 8 will 
have a outer diameter of approximately 2.8 inches, snap-ring 7 will have 
an unstressed diameter of approximately 3.035 inches, with a gap 
separation of approximately 0.375 inches with the outer diameter of 
annular flange 46 of fastener 45 being 4.57 inches. The above figures are 
for illustrative purposes only and it is readily understood by anyone 
skilled in the art that these dimensions can vary depending upon the 
particular installation without affecting the concept of the invention. 
Non-penetrating fasteners 1 and 45 and the method of installation has a 
number of advantages over prior art fasteners, especially the penetrating 
type of fastener. When a membrane is pierced, it can result in a problem 
area in the roof membrane especially after the membrane has been installed 
for a number of years. Also, fastener housings 6 and 50 are provided with 
a plurality of mounting holes insuring that each fastener housing can be 
rigidly secured to the roof even though void areas are located under 
certain portions of the housings. Also, the amount of clamping force 
exerted by snap-ring 7 against membrane 2 can be varied by changing the 
characteristics of the elasticity of the ring as well as its size with 
respect to the diameter of the undercut circular recess of the boss in 
addition to changing the external diameter of the undercut recess in the 
locking cap. Locking cap 8 increases the clamping action of the snap-ring 
against the membrane and mainly reduces the possibility of the snap-ring 
becoming disengaged from its clamped position with the membrane. Cap 8 
also prevents the accumulation of water, ice and snow within the pocket 
formed by the membrane when in clamped position within the fastener boss. 
Ring 7 need not clamp membrane 2 excessively tight against vertical wall 
portion 27 but expands sufficiently outwardly beneath ledge 20 to prevent 
it from becoming dislodged therefrom. 
The improved fastener is suitable for flat roofs as well as spherical roofs 
and also requires no additional sealants as in prior fastening systems. 
The improved non-penetrating fastener also is believed to be an advantage 
over prior non-penetrating fasteners since it replaces the heretofore 
expanding plug with a locking ring which is believed to be more securely 
retained within the undercut recess of the associated component housing 
and therefore less acceptible to dislodging upon uplifting wind forces 
being exerted on the membrane. Furthermore, the locking ring is a readily 
available and easily obtained component and can have various 
characteristics such as its elasticity and size to correspond to various 
roof installations. 
Accordingly, the improved fastener is simplified, provides an effective, 
safe, inexpensive, and efficient device and associated mehtod which 
achieves all the enumerated objectives, provides for eliminating 
difficulties encountered with prior fastening devices and methods, and 
solves problems and obtains new results in the art. 
In the foregoing description, certain terms have been used for brevity, 
clearness and understanding; but no unnecessary limitations are to be 
implied therefrom beyond the requirements of the prior art, because such 
terms are used for descriptive purposes and are intended to be broadly 
construed. 
Moreover, the description and illustration of the invention is be way of 
example, and the scope of the invention is not limited to the exact 
details shown or described. 
Having now described the features, discoveries, and principles of the 
invention, the manner in which the improved mechanical fastener for 
securing a flexible membrane to the upper surface of a roof is constructed 
and used, the characteristics of the construction, and the advantageous, 
new and useful results obtained; the new and useful structures, devices, 
elements, arrangements, parts, combinations and method steps for 
installing the same are set forth in the appended claims.