Note: Descriptions are shown in the official language in which they were submitted.
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METHOD OF FORMING WEATHERTIGHT SEAL
This invention is related to forming and bonding
seals between surfaces which move in relation to each other,
such as panels in a building.
There are in current use a variety of methods of
sealing seams or joints in buildings and highways that are
based upon silicone sealants. A common method makes use of a
backer rod to fill the joint and shape the bottom of the
seal, then extruding a silicone sealant into the joint to
fill it from side to side over the top of the backer rod. The
sealant is then tooled to aid in shaping the top of the seal
and to aid in forcing the sealant into contact with the sides
of the joint. The sealant then cures over time to an
elastomer which is bonded to the surface it was in contact
with at the time it cured.
United States Patent Number 3,119,204, issued
January 28, 1964, to Williams, discloses a molded sealing
device which po#itions the panels to be sealed, seals the
~oint and acts as a backer rod in forming the yieldable
caulking compound inserted in the joint. He does not specify
the material used other than an elastomer such as rubber,
synthetic rubber, synthetic plastic, or the like having
ela~tic deformable properties.
United States Patent Number 3,292,330, issued
December 20, 1966 to Tennison, discloses an elongated strip
of resilient rubber like material which is adhered to the
walls of the space to be sealed with an adhesive.
United States Patent Number 3,581,450, issued
June 1, 1971, to Patry discloses an expansion joint cover in
which corrugated metal strips are imbedded in the edges of a
flexible impregnated strip of fabric. The cover is attached
to the substrate as by nailing through the metal strips.
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A pavement expansion joint is shown in United
States Patent Number 3,829,228, issued August 13, 1974, to
Miyazaki et al. in which a prefabricated expansion joint seal
is used.
A sealing means for breaches in architectural
barriers is shown in United States Patent Number 4,237,667,
issued December 9, 1980, to Pallucci et al. an expansion seal
which is constructed of reinforced silicone rubber sheet
stock material. The sheet stock material is attached to the
surface by means of clamps and a layer of adhesive such as
silicone adhesive.
Canadian Patent Number 1,138,715, issued January 4,
1983, teaches a framed dual glazed window unit, especially
for use in high temperature environments. Panes of glass are
separated by a gasket of silicone material, the combination
being enclosed in a frame comprising a U-shaped channel of
sllicone material. The panes of gla~s, gasket and frame are
bonded together with a silicone sealant material.
German Offenlegungsschrift DE 31 31 677 A1,
published February 24, 1983, teaches adhesive joints for wall
part~, especially for lnsulating glass panes. A prior
construction having a spacer between the panes and a
surroundlng ~pace filled wlth an adhesive to hold the
lndividual panes together is modified by the insertion of a
proflled strlp lnto the adheslve to ~erve as a strength
bridge between the parts to be joined. The thin layer of
adhosive remainlng between the profiled strip and the wall
parts cures in a relatively short period of time. A
preferred materlal is an adhesive of uncured silicone rubber
and a profiled strip material of an at least partially
vulcanized silicone rubber with essentially the ~ame chemical
base as the uncured silicone rubber of the adhesive.
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United States Patent Number 4,516,876, issued May
14, 1985, to Wicks discloses a precast concrete expansion
joint that include~ an elastomeric strip bonded to the sides
of a groove.
None of these methods are directed to the problem
of sealing joints that move during the placement and/or cure
of the sealant means.
This invention relates to a method of sealing
joints that are subject to movement during the placement and
cure of the sealant. The method makes use of a preformed
silicone elastomeric gasket shaped to extend from a first
surface to be sealed to a second surface to be sealed, in
combination with a thin layer of silicone a& esive between
each surface to be sealed and the preformed silicone
elastomeric gasket. The silicone adhesive quickly cures
because only a thin layer i8 used to bond the gasket to the
surfaces. The preformed gasket is shaped so as to compress
or extend without excessive strain upon the bonded joint.
It is an object of this invention to describe a
method of formlng a weathertight seal between surfaces which
are ~ub~ect to movement during the period required for cure
of the adhesive or ~ealant used to form or bond the seal in
place.
In the drawings appended to this specification:
Figure 1 is a cross-section of a silicone gasket
bonded between two blocks to seal the space between the
blocks.
Figure 2 is a cross-section of a silicone gasket
formed to create a minimum strain on the bonded joint between
two blocks.
Flgure 3 is a cross-section of a metal roof
expanslon jolnt covered with a preformed sllicone elastomeric
gasket bonded to the roof.
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Figure 4 is a cross-section of a glass plate bonded
to a metal mullion.
Figure 5 i8 a cross-section of a split mullion
having a glass plate bonded to each piece.
The present invention resides in a
, . . .
method of forming a weather tight seal
between surfaces which move in relation to each other
comprising:
(A) placing a preformed silicone elastomeric
gasket shaped so as to compress or extend during and
after cure, without placement of excessive strain on the
resultant bonded seal, between the surfaces to be
sealed, said gasket having a thin layer of silicone
adhesive applied to the gasket surfaces which contact the
surfaces to be sealed, or a thin layer of silicone
adhesive being applied to the surfaces to be sealed which
contact the gasket surfaces in those areas in which there
is contact between the surfaces to be sealed and the
gasket surfaces, and
(B) allowing the adhesive to cure to a
permanent bond, to give a quickly curing, weather tight
seal which does not leak when subjected to movement of
the surfaces in either a compressive or expansive
dlrection.
One of the most common methods of sealing a gap
between ~urfaces, at the present time, is the use of a
~oalant composition which i8 extruded into place to fill the
gap to be sealed. After the gap is filled, the sealant is
generally tooled to force it in contact with the sides of the
gap ~o that it can adhere. The sealant is then allowed to
cure in most cases. The cured ~ealant is of an elastomeric
nature 80 that it can expand and contract as the gap itself
expands and contracts, due to changes in temperature,
shrinkage of the materials making up the surfaces. vibrations
and movements of the building itself, as due to ~ettling, or
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even such things a~ ~eismic movements. In order for the gap
to remain sealed during all such movements, it is necessary
that the sealant adhere to the sides of the gap so that
during periods of expansion of the gap, the sealant ls also
expanded. If there is no adhesion between the sealant and
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the gap surfaces, a space will form when the gap expands due
to movement or shrinkage of the gap walls.
In cases where the size of the gap to be sealed is
varying at a rapid rate, such as when night fall~ and the gap
to be sealed has been in the full sun, it i8 difficult to get
a proper seal; because the size of the gap is changing while
the sealant i8 curing. If the gap widens after the sealant
starts to cure, but before the sealant has developed adhesion
to the surface, a space will form between the sealant and the
surface. As the sealant continues to cure, the adhesion
between the sealant and the surface is lost at that point.
The method of this invention is designed to be useful in
situations such as this where the size of the gap to be
sealed is changing during the period normally required for a
sealant to cure, a time which is normally in the order of
several hours at best.
The invention will be illustrated by reference to
the drawings. Figure l is a cross-section of a gap between
two pieces of material, for example, the expansion joint in a
cement block building or the joint between two cement panels
in a curtain-wall building construction. The surfaces l and
2 form the gap to be sealed. A preformed silicone
elastomeric gasket 3 is selected that will fill the gap to be
sealed ~o that the gasket is compressed slightly during
in~ertion into the gap 80 that the gasket is held in place by
friction with the walls of the gap. The gasket is held in
place by a silicone adhesive 4 between each surface and the
gasket.
The silicone adhesive 4 can be either a pressure
sensitive adhesive, a curing adhesive or a combination. Th~
silicone adhesive 4 must have sufficient adhesion to both t~
surfaces l and 2 and to the gasket 3 that when the gap
expands due to shrinkage of the pieces having surfaces l
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2, the gasket 3 is stretched out to maintain a weather-tight
seal between the surfaces without a loss of adhesion.
When a silicone pressure sensitive adhesive i~
used, the adhesive would be applied to the edges of the
gasket just before placement in the gap. At the time of
application, the adhesive is a solvent solution and after
application gives the edges of the gasket to which it is
applied a slippery surface, allowing the gasket to be forced
into the gap. Because the gasket is a silicone elastomer,
the solvent quickly passes through the gasket and the
adhesive develops a bond to the surfaces and the gasket and
also develops a strength and elongation itself. This rapid
development of adhesion and internal strength and elongation
of the adhesive allows the gasket to be stretched and the
adhesion preserved if the gap then widens due to thermal or
mechanical stresses.
When a curing silicone adhesive is used, the
adheslve can be either a one or two part adhesive. When a
two part adhesive is used, the two parts are mixed and
appllod to the gasket or to the surfaces to be sealed or to
both, then the gasket is forced into place. The two part
adhe~ive ia chosen to have a short cure time after mixing so
that the gasket is bonded to the surfaces before the surfaces
have an opportunity to move away from the gasket, causing a
1088 of adhesion becau~e the adhesive is not yet cured or
bonded.
When a one part curing silicone adhesive is used,
it is preferred that the adhesive be cured by reaction with
water vapor in the air. Because the gasket being used is
silicone elastomer, the gasket is very permeable to moisture
vapor and the entire area of the adhesive is exposed to
moisture through the gasket in a short period of time.
Because only a thin layer of adhesive is used, the entire
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adhesive layer cures in a short period of time because the
moisture does not have to penetrate and react with a large
amount of material as is true when a conventional sealant i8
used to fill and seal a gap between panels.
A preferred one part silicone adhesive is any of
the common silicone sealant materials that are used as
sealants and caulks. The type of cure system or the exact
sealant chosen depends upon the surfaces to be sealed. An
adhesive is chosen which will provide a strong bond to the
material making up the surfaces to be sealed. The choice of
the proper type of sealant for different types of substrates
i8 well known in the art.
The preformed silicone elastomeric gasket 3 can be
an extruded shape made from a heat curable silicone rubber,
for example, as well as from a moisture curable silicone
sealant or from a two part room temperature curable sealant
or rubber. In any case, the material is extruded or shaped
to the deqired size and cured. The cured gasket is then used
in this invention because the cured silicone rubber will
allow the quick curing of the adhesive layer. The cured
gasket is designed to exert little strain upon the curing or
cured seal. Where the preformed elastomeric silicone gasket
is a simple rectangle, as in Figure 1, the silicone rubber or
sealant is chosen to have a low modulu~ of elasticity so that
when the surfaces 1 and 2 move relative to each other, the
#train on the bonded surfaces is not excessive.
Figure 2 is a cross section of of a silicone gasket
formed to create a minimum strain on the bonded joint between
two blocks. The blocks, having surfaces 21 and 22, create a
gap which is sealed by the pleated gasket 23. A preferred
form of gasket 23 is a molded silicone rubber having a fabric
layer reinforcement in the rubber. The size and number of
pleats in the gasket can be varied to change the amount of
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expansion and contraction the gasket can accommodate while
placing only a minimum of strain on the adhesively bonded
joints. The adhesive 24 can be any of the types mentioned
above. This construction is particularly adaptable to the
use of a pressure sensitive adhesive in that the adhesive can
be applied to the gasket surfaces and allowed to dry and
develop its pressure sensitive characteristics. The gasket
is then installed by forcing the pressure sensitive adhesive
coated surface into place against the wall of the gap to form
a seal across the gap. Because the pressure sensitive
adhesive gives rapid bonding to the surface, the gasket can
bond to the surfaces rapidly so that if the surfaces are
moving during sealing or shortly thereafter, it is still
possible to get a good bond which is not destroyed by the
fact that the surfaces move.
Eigure 3 is a cross-section of a metal roof
expansion ~oint covered with a preformed silicone elastomeric
~eal bonded to the roof with silicone adhesive. The separate
metal panels 31 and 32 are subject to movement as from
thermal expanslon and contraction due to exposure to the sun
and then shade from clouds or night. On a hot summer day,
with cloud~ passing by, the panels can expand and contract at
a relatively rapid rate. If the panels were attempted to be
~ealed with a conventional sealant, applied as a bead between
the two surfaces, the moving surfaces could very easily
destroy the lntegrity of the seal while it was curing due to
the movement of the two surfaces relative to each other
during the cure period. In this type of application, a
preerred method would consist of applying a silicone
adhesive, preferably a moisture curable silicone adhesive or
sealant bead upon the flange of the preformed silicone gasket
in the location shown, then placing the gasket over the joint
and pressing the gasket flange firmly into contact with the
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panels. The silicone adhesive flows out to form a thin layer
of adhesive between the panel and the gasket. Because of the
porosity of the silicone gasket to moisture vapor, the thin
layer of moisture curable silicone adhesive quickly cures to
give a bond between the gasket and the panels. The shape of
the gasket and the quick cure maintains a weathertight seal
even though the panels move relative to each other at a
relatively rapid rate.
Figure 4 is a cross-section of a glass plate bonded
to a metal mullion, as in the construction of a curtain wall
building. The glass plate 45 is held in contact with the
mullion 41 through the preformed silicone gasket 43 and the
adhesive layers 44. A preferred method of constructing this
joint extrudes a bead of silicone adhesive, preferably a
moisture curable silicone adhesive, onto the surface of the
mullion, then the preformed silicone elastomeric gasket 43 is
pressed over the bead of adhesive to form a thin layer of
adhe~ive bonding the gasket to the mullion. A bead of
~ilicone adhe~ive is then applied to the exposed surface of
the gasket, and the gla~s plate 45 is forced into contact
with the adhesive bead to form a thin layer of adhesive,
bonding the glass plate to the gasket. If necessary,
temporary holder~ are attached to the mullion ~pacer to hold
the gla~s in place as the adhesive cure~. Because the
adhesive 18 present in a thin layer and because the silicone
gasket is silicone and is permeable to gases, the adhesive
layer quickly cures to form a bond between the mullion and
the glass. This bond is formed even though the glass may
move relative to the mullion because the layer of adhesive is
thin and cures at a rapid rate. The elasticity of the gasket
43 also allows movement between the glass plate and mullion
without applying large stresses to the adhesive joint. The
area of the gasket bonded to the mullion and to the glass is
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determined by the design strength required to hold the glass
plate in place. The thickness of the silicone rubber gasket
is determined by the useful elongation of the gasket material
and the amount of relative movement expected between the
metal mullion and the glass plate due the temperature
changes, building movements and wind loads.
Figure 5 is a cross-section of a split mullion
having a glass plate bonded to each piece. This is a
variation of the application shown in Figure 4. This
variation is particularly adapted to use in the shop
prefabrication of panels for use in curtain wall
construction. Four split mullions are arranged in a
rectangle in a shop on a horizontal surface so as to form a
rectangle to enclose the glass plate. A bead of silicone
adhesive is applied to the mullion, the gasket 53 is forced
into place, forming a thin adhesive layer 54, then a bead of
adhesive is applied to the gasket and the glass plate 55 is
forced into place, forming the other thin layer of adhesive
54. In this application, the method is particularly useful,
not because of movement of the surfaces during cure, but
bocause the rapid cure of the adhesive, due to the thin layer
and the poroslty of the silicone ga~ket, allows the assembly
to be removed from the assembly area in a short period of
time and allows application of the assembly to the building
without a lengthy time for curing of the adhesive.
Conventional con~truction of this type, using a spacer and an
area of sealant to bond the glass plate in place and provide
sufficient thickness and area to allow for all the necessary
movement and load~, requires a cure period of from 14 to 21
days before the assembly can be applied to the building. In
a large application, such as a skyscraper, this requires a
large area for the storage and inventory of the assemblies
during the cure period. With the instant method, the
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assembly needs only to cure for a period such as two days
before it i8 placed on the building.
In an application such as this, where experience
has shown that a silicone sealant has the required physical
properties to function in the application, it is preferred to
manufacture the preformed silicone gasket using the silicone
sealant as the material of choice. The ~ealant is placed in
a form of the desired size and allowed to cure, then is removed
from the form to give the preformed silicone gasket. The
same silicone sealant is then used as the silicone adhesive
in the construction of the assembly as discussed above. The
cured product is essentially the same as that obtained in the
previous method, except the assembly cures to a useful unit
in a short period of time as the long period of time required
for the preformed gasket to cure is not a part of the
assembly cure time.
After the split mullion assemblies are cured, they
are placed on the building and fastened into place, as by
boltlng or riveting. The space between the mullion halves is
thon ~ealed ln the conventional manner as shown at 57. The
~eals 56 aro formed of conventional sealant either in the
shop or after assembly on the building.
