Method of adhering glass products to a work surface

A method for adhering glass products to a work surface which comprises placing adjacent to the surfaces of the pieces to be joined a continuous, non-perforated metallic foil strip, which absorbs electromagnetic waves. The strip which is contiguous with a heat activatable adhesive material, is positioned between the pieces and exposed to electromagnetic waves while the pieces are held together to form a bonded relationship between the pieces.

BACKGROUND OF THE INVENTION 
This disclosure relates to the installation of glass products by adhesive 
attachment. "Glass products" is the term used in the construction and home 
furnishings industries to describe glass tiles and mirrors. These glass 
products are generally employed to construct and adorn walls and, 
occasionally, ceilings. On the job, the glass products are typically 
affixed to an underlayment of plaster, dry wall, concrete, cinder blocks 
and a variety of other decorative and non-decorative wall panels or 
coverings, including, occasionally, glass and tile wall panels. 
The attachment of glass products to the work surface is typically effected 
by employing mechanical fastening devices such as brackets and adhesives. 
However, these attachment devices are rapidly falling into disfavor and 
new adhesives are being developed which are safer to work with and produce 
attachments that are actually more secure than the traditional attachment 
methods. However, the use of new adhesives alone is not the final answer. 
Current adhesives are messy and difficult to apply to "hidden" or 
inaccessible places. It is apparent, then, that inventions are waiting to 
be made which address the placement of adhesive material in a neat, clean, 
safe and effective manner that can be used beneficially in the 
construction trades, and especially with regard to the placement of glass 
products to a work surface. 
Not surprisingly then, others have experimented with alternatives to 
traditional fastening and adhering devices for the attachment of 
construction products to a work surface. 
DESCRIPTION OF THE PRIOR ART 
U.S. Pat. No. 4,038,120 to Russell describes the use of an energized 
heating element or wire to heat a hot melt glue resulting in adhesion 
between contiguously assembled panels. The reference method involves 
heating a glue-coated wire to liquefy the glue producing a cohesive state 
and facilitating the assembly of panels. This method is particularly 
useful for introducing a cohesive material (glue) to an area of limited 
accessibility (groove), but the heating element (wire) requires the direct 
application of energy (electricity) to provide the heat to melt glue. 
U.S. Pat. No. 3,574,031 to Heller et al. describes a method and material 
for welding thermoplastic bodies by using a susceptor between the bodies 
to be joined. The susceptor sealant is characterized by having particles, 
heatable by induction, dielectric or radiant energy, dispersed in a 
thermoplastic carrier compatible with the thermoplastic sheets to be 
welded. The welding of the thermoplastic sheets is effected by exposing 
the susceptor sealant to heat energy, softening the carrier material and 
joining all thermoplastic materials. 
U.S. Pat. No. 3,996,402 to Sindt relates to the assembly of sheet materials 
by the use of a fastening device utilizing an apertured sheet of eddy 
current-conducting material sandwiched between coatings of hot-melt glue. 
An induction heating system is activated causing eddy current heating in 
the EC-conducting material with consequent melting of the hot-melt glue 
thus resulting in fusion and, ultimately, bonding of the sheet materials 
in accordance with the desired construction. 
SUMMARY OF THE INVENTION 
The presently disclosed method of adhering glass products to a work surface 
is distinguished from, and improves upon, the prior art by utilizing a 
device to be placed adjacent to the surfaces to be joined which comprises 
a target element contiguous with a heat activatable adhesive material said 
target element being absorbent of electromagnetic waves which are 
convertible to heat energy for activating the adhesive material, holding 
said surfaces together, and exposing said device to electromagnetic waves 
to produce heat sufficient to activate the adhesive material to effect an 
adhesive bond between the glass products and the work surface.

DESCRIPTION OF THE PREFERRED EMBODIMENT 
Glass products comprising, for example, mirrors and glass tiles can be 
adhesively joined to a variety of work surfaces such as dry wall, plaster, 
cinder block, cement, wood, wallpaper, coated board, plastic laminate, 
painted sheet metal and other decorative and non-decorative work surfaces 
using the method and device herein described. 
The method entails little more than simply placing, or perhaps securing, 
units of the disclosed device between or adjacent to the surfaces of the 
glass product and the work surface, putting the glass product in place and 
then activating the adhesive device with electromagnetic waves to 
adhesively join the glass product to its work surface. 
Looking at the adhesive device employed in the disclosed method in greater 
detail, we see that the target element must, for the most part, be 
fashioned from materials or substances that are not transparent to 
electromagnetic waves. Indeed, the target element will necessarily be 
constructed of a composition that will absorb electromagnetic waves. Once 
absorbed by the target element, these waves will produce magnetic 
hysteresis and eddy currents resulting in heat energy which will melt or 
activate the contiguous adhesive material. 
A suitable device is taught in U.S. application Ser. No.08/689,180 entitled 
Adhesive Device which was filed on Aug. 5, 1996, and is assigned to the 
assignee of the present invention. This application is hereby incorporated 
by reference into the present application. 
Typically, the target element will be fashioned from metallic materials 
such as steel, aluminum, copper, nickel or amalgams thereof which have 
proven utility and are readily available; although, some semi-metallic 
materials such as carbon and silicon are also known to be suitable for the 
absorption of electromagnetic waves. 
The target element can assume any form or shape consistent with the overall 
configuration of the adhesive device. Frequently, the target element will 
be presented as a metallic foil or strip, and, in some instances, it will 
be more effective to present the target element in the form of a fiber of 
an electromagnetic absorbable material. The point to be made is that the 
target element need only be fashioned from a material reasonably 
impervious to, and absorptive of, electromagnetic waves. 
In use, the adhesive device needs to be situated adjacent to the glass 
product and the work surface. As a practical matter, of course, the glass 
product needs to be mostly transparent to electromagnetic waves. Some 
glass materials will be more transparent than others, and empirical 
adjustments can and will be made to modulate the quantity and intensity of 
electromagnetic wave energy needed to optimally activate the adhesive 
material. 
In many instances, it will be sufficient for the adhesive device simply to 
be placed adjacent to the glass product and the work surface. In other 
construction or assembly situations, it will be necessary to make some 
arrangements or take additional steps to make sure the adhesive device 
remains in place prior to activation. Such an additional step need be 
little more than introducing an additional attachment element such as a 
small pressure sensitive adhesive area on the surface of the device. But 
such a measure, of course, would be optional procedure and in no way 
essential to the performance of the device in its broadest typical and 
routine applications. 
When desirably situated adjacent to the glass product and the work surface, 
the adhesive device is ready to be exposed to electromagnetic waves, 
produced by and emanating from a generator powered by a source of 
alternating electric current. The generator can be held in a fixed 
position for assembly-line production or designed to be manipulated so as 
to quickly and easily pass over, around or near the strategically "hidden" 
device while emitting electromagnetic waves which will penetrate the 
"transparent" glass products, be absorbed by the target element, be 
converted to heat energy, activate the adhesive material resulting in a 
bonded relationship between the glass products and the work surface. To 
elaborate, somewhat, heat is produced in the conductive target element by 
two mechanisms: eddy current resistive heating and magnetic hysteresis. 
Eddy current resistive heating applies to all conductive materials and is 
produced in the target element by the electromagnetic waves emanating from 
the generator. The heat resulting from magnetic hysteresis is observed 
only in magnetic materials. As the electromagnetic field produced by the 
generator reverses polarity, the magnetized atoms or molecules in the 
target element also reverse. There is an energy loss in this reversal 
which is analogous to friction: this energy loss is magnetic hysteresis. 
The "lost" energy is quickly converted to heat and conducted by the target 
material to the contiguous, and frequently enveloping, heat-activatable 
adhesive material to initiate adhesion. 
While the aforementioned heating mechanisms apply to most forms of 
absorbent target materials, there are factors which favor the use of a 
continuous, non-perforated metallic foil. These factors make foil targets 
having no apertures heat faster, more efficiently, and safer than other 
forms. In the eddy current resistive heating mechanism, the foil presents 
a larger target area; thus, more of the EM field is absorbed when compared 
to either particles or mesh. Thus, for a given EM field strength, the foil 
target heats more rapidly. Also, the foil allows the eddy currents to have 
an unobstructed current loop path. Meanwhile, particles are effectively 
unheatable by eddy currents since the gaps between particles do not allow 
a current loop path. In meshes, the current loop path is disrupted by the 
mesh which has the effect of regional uneven heating and localized hot 
spots. 
In the magnetic hysteresis heating mechanism, the target must be formed of 
magnetically susceptible materials such as iron, nickel, cobalt, and 
compounds containing these elements. Magnetic hysteresis takes place each 
time the EM field reverses, thus higher heating rates are observed at 
higher frequency. Adhesives which are loaded with magnetically susceptible 
powders are generally heated at or above 10 megahertz. 
The use of a foil target material allows a weaker EM field at a lower 
frequency than either meshes or particles. This yields several benefits. 
The EM field generator is smaller, lighter, and requires lower input 
energy. The lower frequency is also safer and allows operation without 
special guarding or other safety provisions. The preferred range for this 
invention is 50 kilohertz to 900 kilohertz; ideally, the frequency range 
is between 150 kilohertz and 300 kilohertz. The IEEE (Institute of 
Electrical and Electronic Engineers) standard C95.1-1991 refers to human 
safety for electromagnetic field exposure. This standard has also been 
adopted by the ACGIH (American Conference of Governmental and Industrial 
Hygenists) for "Biological Exposure Indices" 1996. 
When heated to the necessary temperature, the adhesive material will 
liquefy or become heat-activated, attach itself to the work surface and, 
on cooling, create an adhesive relationship between the glass products and 
the work surface. 
Two adhesion mechanisms, hot-melt and heat-activated cure, are proposed for 
use with the disclosed device. Both mechanisms are initiated by heat 
emanating from the target element. Hot-melt adhesives are solid at ambient 
temperatures, but melt or liquefy when the temperature is elevated by, for 
instance, heat accumulating in the target element. The melted adhesive 
"wets" the adherends and, in the case of porous, foraminous, or fibrous 
adherends, penetrates the surface of the pieces to be bonded. As the 
adhesive cools, the adherends and adhesive are bonded by the electrostatic 
attraction of polar molecular groups. Note that for the hot-melt 
mechanism, the bonding is reversible. Thus by repeating the induction 
heating procedure, the bond can be undone and the adherends separated. The 
ability to reverse the adhesion and separate fixed millwork is not a 
trivial attribute. In addition to the obvious advantage of being able to 
reassemble or repair misaligned glass products, it may also desirable to 
be able to disassemble affixed glass products to facilitate serviceability 
and repair. 
Heat-activated curing adhesives are also solid and easy to manipulate at 
ambient temperatures, but when the adhesive temperature is elevated by, 
for example, the heat emanating from the target element, a chemical 
reaction is initiated. This reaction involves a cure or crosslinked 
bonding either within the adhesive or between the adherends. Such bonds 
are typically irreversible. Frequently, a heat-activated curing adhesive 
bond will demonstrate an electrostatic attraction between the adhesive and 
the adherends and a crosslinked bond within itself. 
While the foregoing is a complete description of the disclosed method, 
numerous variations and modifications may also be employed to implement 
the purpose of the invention. And, therefore, the elaboration provided 
should not be assumed to limit the scope of the invention which is 
intended to be defined by the appended claims.