Note: Descriptions are shown in the official language in which they were submitted.
1 8 ~
ROOFING INSULATION FASThNER ASSEMBLY
BAcKG~ouND AND SUMMARY OF THE INVENTION
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Thls application is related to my co-pending Canadian application
serlal no. 385,282 filed September 4, l9~l. The present invention
is directed to a roofing insulation faseener assembly.
The fa~tening of compressible insulations to metal or
concrete roof decks has required new fastening techniques,
one of which is depicted in the abovenoted application. With
some washer ronfigurations, a problem can arise in seating
the fastener. Typically, power driven screwdrivers are used
to install these fastener assemblies. Many of these screw-
drivers have clutches or other drive engaging means which rely
on axial displacement of the fastener head to disengage the
drive. If the washer has a planar configuration, ~here is little
movement of the head during seating. This can result in the
assembly being left loose. If the clutch is adjusted for deeper
drive, an over-drive situation can develop in which the insulation
is compressed beyond its elastic limit.
The present invention provides a solution to this problem.
A crushable region of the washer adjacent the fastener receiving
aperture insures that a proper preloading o f the joint occurs
prior to drive disengagement. This provides a larger margin for
error in adjustment of the clutch settings and reduces the chances
of underdriving and overdriving.
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Thus, broadly, the invention contemplates a roofing
insulation fastener assembly for use with a power driven
screwdriver in which axial displacement of a fastener causes
the fastener to disengage from the screwdriver. The assembly
comprises a fastener with a shank having a head at one end,
with the head having a first predetermined lateral dimension
and drive-receiving surfaces thereon. The shank has threads
thereon with a second lesser predetermined lateral dimension.
A washer is provided having a broad load-distributing flange.
~ centrally located aperture defines a third predetermined
dimension less than the first and greater than the second
predetermined dimension. A crushable axially extending portion
is formed integrally with the washer flange in the vicinity of
the aperture and is axially deformable to an extent sufficient
lS to cause disengagement between the screwdriver and the drive
receiving surfaces as the head of the fastener becomes fully
seated and requires a predetermined pre-load to collapse thus
insuring proper joint loading.
Other features, characteristics and advantages of the
present invention will become apparent after a reading of the
following specification taken in conjunction with the appended
drawings.
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BRIEF DESCRIPTION OF THE DRAWINGS
1 Fig. 1 is a side elevational view in partial cross section
of the fastener assembly of the present invention;
Fig. 2 is a side elevational view in partial section of the
assembly in fully seated position;
Fig. 3 is a top elevational view of one configuration of the
washer of the present assembly;
Fig. 4 is a cross-sectional side view of an alternate form
of the washer of the present assembly;
Fig. 5 is a top elevational view of a metal washer employing
the teachings of the present invention;
Fig. 6 is a cross-sectional view of the washer shown in Fig.
5 taken along line 6-6.
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DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
1 The fastener assembly of the present invention is shown
generally at 10. The assembly 10 comprises a fastener 12 having
a head 14 with a first predetermined lateral dimension at one
end with drive surfaces thereon, in the case depicted, formed
as an internal drive recess 16. A threaded shank 18 extends
from the head and has a second lesser predetermined lateral
dimension. Depending on the application, the thread may be of
the self-tapping variety and the tip may have a drill point 19
to enable the fastener to penetrate a variety of materials.
The second element of the assembly 10 is washer 20 which
is preferably made of a plastic or elastomeric material.
Washer 20 has a broad load-distributing flange 22 and a centrally
located aperture 24. The aperture defines a third predeter-
mined lateral dimension which is less than the first but greater
than the second predetermined dimension. The upper surface of
the flange may be provided with a recess 26 of sufficient size to
accommodate the head 14 of fastener 12. A crushable portion 28
îs provided adjacent the aperture 24 for purposes which will be
detailed hereafter. The upper surface of the flange 22 may be
provided with a locater ring 30 to facilitate positioning of a
conventional nosepiece 31 from a power screwdriver (not shown).
In Fig. l, fastener assembly lO is depicted in a partially
installed position which, but for the features of the present
invention, could exist after installation. Roofing insulation
board 33 is shown as being warped with steel girt 35 positioned
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1 therebeneath. As can be appreciated, without crushable portion
28, there would be little relative change in position between
head 16 of fastener 12 and flange 22 of the washer. Since many
screwguns rely on such an axial displacement in order to disengage
the drive through a clutch or the like, lack of such movement
creates a problem. No setting of the depth gauge will be correct
for successive applications resulting in a high percentage of
underdriven and overdriven fasteners.
As depicted in Fig. 2, the insulation board 33 is drawn up
against girt 35 before the pre-load of crushable region 28 is
overcome and the head reaches its fully seated position. Of course
the amount of pre-load can be varied for each board application by
varying the height and diameter of the crushable region. As viewed
in Fig. 2, drive to the driver bit 37 has been disengaged or the
bit withdrawn from recess 16, depending on the type of drive employed,
as the fastener assembly is fully seated. An additional benefit is
that the material from the crushable region collapses toward the
shank 18 providing a seal as well as prevailing torque for the
fastener. This assembly insures that a certain preloading of the
joint occurs before the drive is disengaged. Further, it provides
a range of acceptable depth settings for the power screwdriver
when no particular setting would have been appropriate before.
Fig. 4 shows an alternative embodiment of the washer 20
usable in the assembly of the present invention. The crushable
region is formed as a cylindrical boss 28' which can again be
varied to fit the application. Whether the crushable region takes
the form of a cylindrical boss or the fillet of the previous
embodiment depends largely on the nature of the material of the
washer and the desired crush resistance to establish the preload.
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1 Figures 5 and 6 depict the principles of the invention
utiliæed with a low profile metallic wasller. With such a low
profile, there would be virtually -no relative axial movement
without the crushable ~one 28.
~, Although the fastener assembly has been depicted as being
used with roofing insulati()n~ it wlll be appreciated that this
invention may be used with any compressible material where similar
problems might arise.
Various changes, modifications and alternatives will beco~e
apparent following a reading of the foregoing specification.
Accordingly, it is intended that all such changes~ modifications
and alternatives A9 come within the scope of the appended claims
be considered part of the present invention.
