Apparatus for edge mounting security window film in a window frame

An apparatus for mounting security window film to a window frame, includes an elongate tensile loading transfer member having first and second adjacent elongate load bearing flanges and corresponding first and second respective elongate bearing surfaces thereon, first and second elongate double sided foam adhesive tape strips mountable, on first sides of the adhesive tape strips, along respective the first and second bearing surfaces, the first adhesive tape strip mountable on its second side, opposite to the first side, to an edge of a sheet of security window film having a thickness of at least 10 mil adhered to a glass window pane, the second adhesive tape strip mountable on its second side, opposite to the first side, to an edge of a window frame adjacent the edge of sheet of security window film, wherein, the first and second adhesive tape strips are adapted to bear approximately 225 lbs per square inch in tension applied to the first and second adhesive tape strips and to the security window film when adhesively mounted to the tensile load transfer member by the first adhesive tape strip and to the window frame when mounted to the tensile load transfer member by the second adhesive tape strip.

FIELD OF THE INVENTION 
This invention relates to the field of security window film and its 
application to glass windows, and, in particular, to a method and 
apparatus for edge mounting security window film in a window frame. 
BACKGROUND OF THE INVENTION 
Break and entry crimes are a well documented and, apparently, daily 
occurrence in many, if not all, cities. Break and entry into commercial 
retail establishments is a particularly vexing problem in that, on the one 
hand, it is desirable for the retail establishment to have large 
attractive displays of their wares behind panoramic glass windows so as to 
advertise and promote the establishment's wares, and on the other hand, 
such large windows and their associated displays of wares, provide an 
enticing target for the criminal element who count on being able to break 
the glass from the outside and grab the wares on display through the open 
window frame. 
In the prior art, it is common, especially in high crime areas, for 
commercial retail outlets to have either permanently installed metal bars 
either in front of or behind the glass storefront displays, thereby, 
marring the attractiveness of the display, or to have pull down shutters 
or grates so as to lock an obstacle into place between the glass windows 
and a person attempting to break and enter. Both of these prior art 
solutions are not only unsightly, but expensive to install and, in the 
latter case, unreliable to maintain, in that employees must be relied on 
to lower and lock into place the shutters or grates. 
So called security film has become available more recently to address the 
problem of break and enter through glass windows. Security film is 
typically a thin, transparent, polymer film providing a resilient high 
tensile strength barrier which, when adhered against an interior surface 
of a glass window, resists complete shattering of the glass when an 
attempt at penetration is made from the outside. One commercial supplier 
of security window film are Metallized Products in St. Petersburg, Fla., 
U.S.A., who supply 12 mil and 14 mil cross weaved polyester film under the 
trademark Sun-gard. Another supplier of security window film is 3M.TM. who 
market safety and security film under the trademark Scotchshield. 
Scotchshield.TM. is held out by 3M.TM. as resisting penetration by keeping 
the glass in place during attempted break-ins, storms and earthquakes. 
However, it is the applicant's experience that merely applying security 
window film is not sufficient in many instances to prohibit break and 
enter. In particular, it is quite often the case that a glass window, 
whether it has security film applied or whether it has embedded wire mesh 
or the like, will not prevent a break and enter at the hands of a 
determined assailant because the edges of the glass window are typically 
not secured to the window frame. Consequently, to affect a break and 
enter, the glass window, held together by its embedded wire mesh or 
security window film applied to an inner surface, merely has to be broken 
and bowed sufficiently to draw the edges of the glass free of the window 
frame, at which point the entire window may be pushed free of the frame. 
In the prior art an attempt to overcome this problem has been made by an 
entity doing business under the trademark Glasslock in San Jose, Calif., 
U.S.A. The Glasslock.TM. solution is to extend the edge of security window 
film beyond the edge of the glass so as to overlap a significant portion 
of the window frame with security window film. Rigid base plates are then 
overlaid over the overlapping area. The rigid base plates are screwed into 
the window frame so as to sandwich the edges of the window security film 
between the rigid base plate and the window frame. In this fashion, when 
bowing of the broken glass tensions the film, the tension is resisted by 
the mechanical mounting of the edges of the window security film to the 
window frame. In particular, the Glasslock.TM. device is typically 
employed to bend the edges of the security window film at 90 degrees to 
the plane of the window so that the mechanical mounting of the film to the 
window frame by means of screws through the rigid base plate is assisted 
by bending of the film around an edge of the plate adjacent the window. 
Applicant has determined that it is unnecessary and likely 
counter-productive to perforate the security window film by screws or the 
like extending through rigid plates. It is, further, unnecessary to bend 
the film over the edge of the rigid base plate as a means of applying the 
tensile load from the film to the rigid base plate, although it does help 
prevent the film merely tearing free of the mounting screws due to the 
stress concentrations around the holes punctured in the film by the 
mounting screws. 
It is an object of the present invention to provide an adhesive based 
method and apparatus for adhesively mounting the edge of security window 
film to a window frame so as to offer tensile resistance to bowing of the 
glass once broken, so that the same or better result is achieved as 
compared with the more difficult to install mechanical Glasslock.TM. 
device which requires a significant window frame depth, and requires 
drilling and screwing of a rigid base plate to the window frame. It is a 
further object to provide for adhesively mounting the edge of security 
window film to the edge of the glass window pane. 
SUMMARY OF THE INVENTION 
Applicant's invention resides in the applicant's discovery that certain 
commercially available double sided very high bond (VHB) tape, such as 
that available commercially from 3M.TM. Industrial Specialties Division of 
St. Paul, Minn., U.S.A., under the trademark Scotch VHB and in particular, 
models #4925 and #4945 doubled coated acrylic foam tape, in combination 
with a thin metal tensile loading transfer strip, resulted, unexpectedly, 
in significant resistance to bowing of broken glass within a window frame. 
Applicant has determined that VHB 4945 double sided adhesive tape when 
used in the method and apparatus of the present invention, resists 
straight pull tension of approximately 1,000 pounds per square inch on 
security window film. Applicant has determined that if lesser security 
applications are required, for example, requiring approximately 225 pounds 
per square inch, resistance to straight pull tension on the security 
window film, VHB 4925 double sided adhesive tape may be employed. 
Thus, as described herein and as may be seen in the accompanying drawings 
and photographs, the present invention is one of attractive simplicity. In 
addition, the present invention is well adapted to retrofitting security 
window film onto existing glass windows. 
In summary, the apparatus of the present invention for mounting security 
window film to a window frame comprises an elongate tensile loading 
transfer member having first and second adjacent elongate load bearing 
flanges and corresponding first and second respective elongate bearing 
surfaces thereon. 
In one embodiment, first and second elongate double sided foam adhesive 
tape strips are mounted or mountable, on first sides of the adhesive tape 
strips, along respective the first and second bearing surfaces. 
The first adhesive tape strip or mounted or mountable on its second side, 
opposite to the first side, to an edge of a sheet of security window film 
having a thickness of at least 10 mil adhered to a glass window pane 
second adhesive tape strip is mounted or mountable on its second side, 
opposite to the first side, to an edge of a window frame adjacent the edge 
of the sheet of security window film. 
In a first aspect of the invention, the first and second adhesive tape 
strips are adapted to bear approximately 225 lbs per square inch in 
tension applied to the tape strips and to said security window film when 
adhesively mounted to the tensile load transfer member by said first 
adhesive tape strip and to the window frame when mounted to the tensile 
load transfer member by the second adhesive tape strip. 
In a second aspect of the invention, the first and second adhesive tape 
strips are adapted to bear approximately 1000 lbs per square inch in 
tension applied to the tape strips and to the security window film when 
adhesively mounted to the tensile load transfer member by the first 
adhesive tape strip and to said window frame when mounted to the tensile 
load transfer member by the second adhesive tape strip. 
In a further aspect, the tensile load transfer member is a metal strip 
shaped to conform to the intersection between the edge of the sheet of 
security window film and the edge of the window frame adjacent the edge of 
the sheet of security window film, and the first and second flanges extend 
over the edge of the sheet of security window film and the window frame 
respectively so as to sandwich the first and second adhesive tape strips 
respectively between the flanges and the security window film and edge of 
the window frame respectively. 
In a second embodiment, the first adhesive tape strip is mountable to the 
first bearing surface, and the second load bearing flange is formed as a 
lip relative to the first load bearing flange for mounting the lip over an 
edge of the window pane so as to extend the first load bearing flange 
inwardly over the window pane, from the edge of the window pane, and over 
the edge of the sheet of security window film to thereby sandwich the 
first adhesive tape strip between the first load bearing flange and the 
edge of the sheet of security window film. 
In the method of the present invention, a first method of mounting security 
window film to a window frame using an elongate tensile loading transfer 
member having first and second adjacent elongate load bearing flanges and 
corresponding first and second respective elongate bearing surfaces 
thereon, first and second elongate double sided foam adhesive tape strips 
mountable, on first sides of the adhesive tape strips, along respective 
said first and second bearing surfaces, the first adhesive tape strip 
mountable on its second side, opposite to the first side, to an edge of a 
sheet of security window film having a thickness of at least 10 mil 
adhered to a glass window pane, the second adhesive tape strip mountable 
on its second side, opposite to the first side, to an edge of a window 
frame adjacent the edge of sheet of security window film, wherein the 
first and second adhesive tape strips are adapted to bear 225 lbs per 
square inch in tension applied to the tape strips and to the security 
window film when adhesively mounted to the tensile load transfer member by 
the first adhesive tape strip and to the window frame when mounted to the 
tensile load transfer member by the second adhesive tape strip, comprises 
the steps of: 
(a) cutting the sheet of security window film sized to fit from edge to 
edge across the window pane when adhered thereto, 
(b) adhering the sheet of security window film to the window pane from edge 
to edge and allowing to cure, 
(c) selecting, or shaping, the tensile load transfer member of, or to, a 
shape wherein the tensile load transfer member is shaped to conform to the 
intersection between the edge of the sheet of security window film and the 
edge of the window frame adjacent the edge of the sheet of security window 
film, and the first and second flanges extend over the edge of the sheet 
of security window film and the window frame respectively so as to 
sandwich the first and second adhesive tape strips respectively between 
the flanges and the security window film, 
(d) applying the first and second adhesive tape strips to the first and 
second flanges respectively, 
(e) applying the load transfer member to the sheet of security window film 
and the window frame so that the first and second flanges extend over the 
edge of the sheet of security window film and the window frame 
respectively and so as to sandwich the first and second adhesive tape 
strips respectively between the flanges and the security window film. 
In a second method of the present invention, a method of mounting security 
window film to a window frame using an elongate tensile loading transfer 
member having first and second adjacent elongate load bearing flanges and 
corresponding first and second respective elongate bearing surfaces 
thereon; a first elongate double sided foam adhesive tape strip mountable, 
on a first side of the adhesive tape strip, along the first bearing 
surfaces, the first adhesive tape strip mountable on its second side, 
opposite to the first side, to an edge of a sheet of security window film 
having a thickness of at least 10 mil adhered to a glass window pane, 
wherein the first adhesive tape strip is adapted to bear 225 lbs per 
square inch in tension applied to the tape strip and to the security 
window film when adhesively mounted to the tensile load transfer member by 
the first adhesive tape strip, wherein the second load bearing flange is a 
lip for mounting over an edge of the glass window pane so as to extend the 
first load bearing flange inwardly over the window pane, from the edge of 
the window pane, and over the edge of said sheet of security window film 
to thereby sandwich the first adhesive tape strip between the first load 
bearing flange and the edge of the sheet of security window film, 
comprising the steps of: 
(a) cutting the sheet of security window film sized to fit from edge to 
edge across the window pane when adhered thereto, 
(b) adhering the sheet of security window film to the window pane from edge 
to edge and allowing to cure, 
(c) selecting, or shaping, the tensile load transfer member of, or to, a 
shape wherein the tensile load transfer member is shaped to conform to the 
edge of the glass window pane generally adjacent the intersection between 
the edge of the sheet of security window film and the edge of the window 
frame adjacent the edge of the sheet of security window film, and the 
first flange extends over the edge of the sheet of security window film so 
as to sandwich the first adhesive tape strip between the flange and the 
security window film, 
(d) applying the first adhesive tape strip to the first flange, 
(e) applying the load transfer member to the sheet of security window film 
and the glass window pane so that the first flange extends over the edge 
of the sheet of security window film and the glass window pane and so as 
to sandwich the first adhesive tape strip between the flange and said 
security window film.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
As may be seen in FIG. 1, in a typical arrangement, glass window pane 10 is 
mounted within window frame 12 within channel 14 and secured between 
resilient gaskets 16. Glass window pane 10 has outwardly facing exterior 
surface 10a and inwardly facing interior surface 10b. 
Security window film 18, which advantageously may be 12 mil or 14 mil cross 
weaved polyester film is cut to the size of the exposed or exposable area 
of window frame 12 and mounted thereto by methods well known in the art. 
An appropriately shaped tensile loading transfer strip 20 is selected 
depending on the manner in which the edge portion of 18a of security 
window film 18 is to be adhesively mounted and secured to either interior 
surface 12a of window frame 12 or edge 10c of glass windowpane 10. 
In the embodiment illustrated in FIG. 1, tensile loading transfer strip 20 
is, in cross section, bent at 90 degrees so that first bearing flange 22 
is at right angles to second bearing flange 24. The edges 22a and 24a of 
first and second bearing flanges 22 and 24 are bent, and in particular at 
least edge 24a, so as to form cavities 26 and 28 between, respectively, 
first and second bearing flanges 22 and 24 when tensile loading transfer 
strip 20 is mounted as illustrated into the intersection between security 
window film 18, at edge portion of 18a, and window frame 12 at interior 
surface 12a. Cavities 26 and 28 are sized to respectively accommodate 
snugly therein corresponding strips of double sided adhesive tape 30 such 
as VHB 4925 double sided foam tape for low security applications and VHB 
4945 double sided foam tape for high security applications. 
Double sided tape strips 30 provide resilient adhesive bonding between edge 
portion 18a and first bearing flange 22 and between interior surface 12a 
and second bearing flange 24. Once adhered, double sided tape strips 30 
act to transfer a tensile load in direction A on security window film 18 
such as would occur if glass window pane 10 was broken inwardly in 
direction B, and transfers the tensile load via double sided tape strips 
30 and tensile loading transfer strip 20 to interior surface 12a and 
window frame 12. 
Tensile loading transfer strip 20 is preferably a metal strip 
advantageously according to the following specifications: 
______________________________________ 
Galvanized Carbon manganese 
CQ Commercial Quality 
ASTM A526 R-A653 (m) 
SAE 1006-1012 
Chemical Composition % Max 
C.0.15 Mn 0.60 
Yield Strength PSI 35,000-45,000 
MPA 240-310 
Melt (HEAT) 800.degree. F. 
Paint Coating (Melt) 350.degree.--400.degree. F. 
mm (IN) mm IN 
Thickness 0.38 0.015 4.27 0.166 
Elongation 32-42 mm. 
in 50 mm (2 inches) % 
______________________________________ 
Of course, it may be that other high tensile strength strips may also 
function so long as double sided tape strips 30 may be strongly adhered to 
them and there are sufficiently strong to transfer a tensile load in 
direction A to window frame 18. 
In the embodiments illustrated in FIGS. 2 and 3, tensile loading transfer 
strips 20 are shaped so as to accommodate differently shaped and sized 
mullions 32 on the interior of window frame 12. 
In FIG. 2, tensile loading transfer strip 20 is generally planar with 
second bearing flange 24 being offset from first bearing flange 22 by 
generally the thickness of mullion 32. The end result is the same as the 
embodiment of FIG. 1 wherein a tensile load applied in direction A to 
security window film 18 is transferred to window frame 12 via double sided 
tape strips 30, tensile loading transfer strip 20 and mullion 32. In FIG. 
3, transfer of the tensile load does not include transfer of the load 
through mullion 32 in that tensile loading transfer strip 20 is W shaped 
to fit over mullion 32 so that first and second bearing flanges 22 and 24 
extend outwardly on either side of mullion 32. In this fashion, the 
tensile load is transferred between security window film 18 and interior 
surface 12a of window frame 12 directly between double sided tape strips 
30 via tensile loading transfer strip 20 only. 
In the embodiment illustrated in FIG. 4, tensile loading transfer strip 20 
secures security window film 18 at edge portion 18a to edge 10c of glass 
window pane 10 rather than window frame 12. In particular, rather than 
first and second bearing flanges 22 and 24 being bent at 90 degrees with 
respect to each other so as to direct second bearing flange 24 outwardly 
of glass window pane 10 and over interior surface 12a of window frame 12, 
second bearing flange 24 is bent inwardly at 90 degrees to first bearing 
flange 22 so as to form a lip which may be hooked behind glass window pane 
10 residing in channel 14 so as to extend second bearing flange 24 at 
least partially over edge 10c. In this embodiment, only one double sided 
tape strip 30 is required, namely, between edge portion 18a of security 
window film 18 and first bearing flange 22. 
Illustrated in FIG. 4 in dotted outline is stop 34 and resilient gasket or 
wedge 36. In this embodiment, when installing security window film 18, 
stop 34 and the associated gasket 16 (not shown) is first removed so as to 
expose more of interior surface 10b. Tensile loading transfer strip 20 and 
its associated double sided tape strip 30 is then installed over edge 
portion 18a. Stop 34 is then reinstalled and a resilient gasket or wedge 
36, for example, having a thickness of 0.090 inches, inserted between 
first bearing flange 22 and stop 34. 
FIGS. 4b and 4c illustrate, respectively, the embodiment of FIG. 4 once 
installed looking from the interior of glass window pane 10 and looking 
from the exterior of glass window pane 10. In FIG. 4b, wedge 36 is being 
installed into the gap between first bearing flange and stop 34. In FIG. 
4c, looking through glass window pane 10 from exterior surface 10a, double 
sided tape strip 30 may be viewed as adhesively adhered to interior 
surface 10b and first bearing flange 22 within cavity 26. 
As will be apparent to those skilled in the art in the light of the 
foregoing disclosure, many alterations and modifications are possible in 
the practice of this invention without departing from the spirit or scope 
thereof. Accordingly, the scope of the invention is to be construed in 
accordance with the substance defined by the following claims.