Note: Descriptions are shown in the official language in which they were submitted.
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1 ¦APPLICATION FOR UNITED STATES LETTERS PATENT
2 1
3 1IMSULATING GL~SS UNIT ~ND SPACER B~R T~IERE~OR
4 I _
5 ¦This invention relates to insulating glass units
6 ¦ which are essentially free of glass deflection, and to unique
7 ¦ spacer bars for use in such insulating glass units.
8 I
9 ¦ BACKGROUND OF T~IE INV~NTION
10 ~ .
11 ¦ Insulating glass units generally consist of two or mor~
12 ¦ parallel panes of glass which are spaced apart from each other
13 ¦ and which have the space between the panes sealed along the
14 ¦ peripheries of the panes to enclose an air space between them.
15 ¦ The most commonly used insulating glass units are double glazed
¦ windows. A double glazed window consists of two usually
,~ 16 ~ Oe ~ fe~
i~ 1 I rectangular panes of glass which are placed in cGng~ucnt
18 ¦ relationship. Spacer bars are placed along the periphery of the
19 ¦ space between the two panes. The spacer bars are long, hollow
20 ¦ prisms having cross sections which are generally shaped in the
21 ¦ form of isosceles trapezoids. The peripheries of the two panes
22 ¦ and the spacer bars lying between them are sealed with a sealing
231 composition so that the air space enclosed ketween the panes is
241 sealed from contact with the outside atmosphere. The surfaces of
25 ¦ the spacer bars facing the interior of the enclosed air space are
26¦ perforated or slotted and the spacer bars themselves are filled
27 ¦ with a solid adsorbent capable of taking up water vapor and
281 organic materials which may be present in the enclosed air space
291 when the unit is sealed with an organic sealant or which may
301 enter the enclosed air space by diffusion from the sealant after
31
32
~ 1 17251s
1 sealing. Air enclosed in the space between the panes diffuses
2 through the slots or perforations in the spacer bars and contacts
3 the adsorbent in the interior of the spacer bars with the result
4 that water vapor and any solvent or organic material getting into
the enclosed air space from the sealing compound are adsorbed on
6 ¦ the adsorbent employed. The result is ~hat cooling of the
7 ¦ interior air does not cause deposition of water vapor or organic
8 material on the interior surfaces of the panes.
9 Insulating glass units of this design are frequently
subjected to deflection of the glass panes due tc pressure changec
11 when ~he~temperat~re o~ the o~tside air changes; àdsorption or
12 desorption of nitrogen or other gases on or from the adsorbent,
13 and changes in atmospheric pressure. When the pressure of the
14 air in the space enclosed between the panes becomes less than
~5 the exterior pressure, the panes are forced closer together.
16 When the pressure in the space between the panes is greater than
17 the exterior pressure the panes are forced apart. Since the
18 peripheries of the panes are held in pretty much fixed position
19 by the sealant deflection is observed to occur in the area of
the glass lying inside the peripheries of the panes.
21 Deflection gives rise to several problems which must
22 be faced by the manufacturer and/or the user of the insulated
23 glass units. When appreciable deflection occurs the reflect~
24 images from the windows are dis~orted and present an undesirable
cosmetic effect. This effect is not functionally serious but
26 users of the insulating glass units object to the distorted
27 reflections. Deflection which results in the movement of the two
28 panes of glass closer toge~her or farther apart when the exterior
29 pressure is greater or less than the pressure of the enclosed
air space between the panes places stress on the sealing
31
32 _
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1 ¦ compounds which lie along ~he periphery of the insulating glass
2 ¦ unit and gradually weaken the seals so that leaka~e of the
3 ¦ relatively moist exterior air into the enclosed space occurs
4 ¦ with the result that the capacity of the adsorbent in the spacer
S ¦ bars is exhausted and condensation of moisture at low temperature
6 ¦ begins to appear in the windows. Deflection which results when
7 ¦ the panes are forced closer together decreases the insulating
8 ¦ properties of the unit since these properties are a function of
9 ¦ the width of the air space between the panes. _If the panes are
10 ¦ forced into contact with each other insulating properties are lost .
11 ¦ Serious deflection can also cause cracking and even breakage of
12 ¦ the windows particularly along the peripheries of the panes.
13 ¦ The deflection problem has been recognized and steps
14 ¦ have been taken to reduce the amount of deflection experienced
~5 ¦ during transportation or use of the insulating glass uni's.
16 ~ For example,- it has been recognized that pressure
17 I problems arise when insulating glass units are shipped from a
18 ¦ point of manufacture to a point of use and the altitudes between
19 I the two points are substantially different. In these situations
20 it has been common practice to inser' a small open tube,
21 ¦ commonly known as a "breather tube", into the side of the spacer
22 ¦ bar facing the exterior of the insulating glass unit. The
231 breather tube permits flow of air between the interior of the
24 ¦ insulating glass unit and the ambient atmosphere and thereby
25 ¦ equilibrates the pressure. Typically, the breather tube is
26¦ sealed immediately after the unit is transported to the altitude
27¦ at which it is to be installed.
28 ¦ More recently it has been found that if the diameter
291 of the breather tube is sufficiently small (of the order of 0.01
31¦ inch) and sufficiently long (generally of the order of at least
32 . _
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~ 1 1 725~S
1 1 one foot or more) entry of outside air into the insulatlng glass
2 ¦ unit by simple diffusion is minimized and the insulating glass
3 ¦ unit will exhibit sufficiently long life even if a breather tube
4 1 of these dimensions is not sealed. It should be noted that
S ¦ breather tubes of this kind generally enter the side of the
6 ¦ spaccr bar facing the exterior of the insulating glass unit, and
7 ¦ gas flow as air is "inhaled" into the air space enclosed
8 ¦ between the panes of the unit is through the breather tube,
¦ through a small segment of the spacer bar and a small segment of
10 ¦ the adsorbent contained in it with the flow of gas essentially
11 ¦ perpendicular to the length of the spacer bar, then through the
12 ¦ crack or slot or perforations in the spacer bar into the air
13 1 space enclosed between the panes of the unit. During "exhaling"
14 ¦ the gas flow is in the reverse direction.
15 ¦ Only recently it has been recognized that a serious
16 cause of deflection in insulating gla~s units is the fact that
17 ¦ the adsorbents with which the spacer bars have been filled
18 ¦ adsorb nitrogen when the temperature in the interior of the space
19 I between the panes is low and desorb nitrogen when the temperature
20 ¦ of the space between the panes is high. Deflection caused by
21¦ nitrogen adsorption and desorption as temperature changes has
22 ¦ been substantially elminiated by using adsorbents to fill the
23 ¦ spacer bars which are incapable of adsorbing nitrogen but which
24 ¦ do adsorb water vapor. This reduction of the nitrogen adsorption
25 ¦ problem as relating to deflection is described in U.S. Patent
261 4,144,196.
27~
28 ¦ BRIEF DESCRIPTION OF THE INVENTION
291
l It has now been found that deflection of the panes
301 of insulating glass uni-ts, however caused, may be substantially
31 ¦ eliminated by employing a spacer bar so constructed that a portio
321
of its surface which is in contact with the space between
the panes (inner surface) is perforated or slotted and the
remainder of the interior surface is imperforate and the
opposite surface of the spacer bar has a small opening in
its surface, which opening is opposite the imperforate
portion of the inner surface. The small opening is in
communication with the exterior atmosphere.
Therefore, the present invention may be broadly
considered as providing, in a double glazed window comprising
two panes of glass in coextensive relationship defining an
internal air space and generally horizontal and generally
vertical spacer bars enclosing the air space, each spacer
bar having two opposing planar surfaces, one surface facing
the enclosed air space, and the other surface facing the
ambient atmosphere, the improvement which comprises employing
as at least one of the generally vertical spacer bars a
spacer bar filled with a solid adsorbent capable of adsorbing
water vapor, the at least one spacer bar being provided with
an opening at one end of the planar surface facing the
enclosed air space and having a small open-ng in the other
planar surface facing toward the atmosphere, the small opening
being so placed that the openings in the two planar surfaces
are at opposite ends of the spacer bar whereby water vapor
is adsorbed when the temperature in the enclosed space drops
and air from the ambient atmosphere flows through the solid
adsorbent into the enclosed space, and water vapor is
desorbed when air in the enclosed space is heated and the
heated air flows from the enclosed space through the solid
adsorbent into the atmosphere.
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THE DRAWINGS
Figure 1 of .he drawings is an offset view of a
double glazed window.
Figure 2 of the drawings is a cutaway of a corner
of a double glazed window, showing the construction of the
window and of the spacer barO
Figure 3 shows another and preferred embodiment of
the spacer bar of the invention.
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1¦ DETAILED DESCRIPTION OF THE INVENTION
21
31 - Figure l of the appended drawings shows a double
41 glazed window generally indicated by the numeral l. Outside
l glass pane 2 and inside glass ~ane 3 are rectangular sheets of
5 1 ~O~f~nS~ ~
61 glass and are placed in CVng~e~ relationship. Top spacer bar
1 4, bottom spacer bar 5, left-hand spacer bar 6 and right-hand
7 ¦ spacer bar 7 lie between the peripheries of the two panes.
81 The spacer bars and the panes are held together in the position
1 shown by sealar.t ll shown in Figure 2. The sealant is typically
10¦ a material such as a polysulphide resin or polyolefin resin.
11¦ Spacer bars 4, 5 and 6 are conventional spacer bars and spacer
21 bar 7 is the spacer bar of the invention which is shown in
141 greater detail in Figure 2. At least one of the two vertical spa( er
bars 6 and 7 is~ filled with a solid adsorbent having a high
61 capacity for adsorption of water vapor Suitable adsorbents
17 1 are molecular sieve zeolites, al~m-ina, and silica gel. In a
1 preferred embodiment of the invention top spacer bar 4 is filled
l8¦ with a molecular sieve zeolite, such as l3X zeolite. The
1 vertical spacer bars are filled with either a mixture of silica
gel or alumina with a molecular sieve zeolite, preferably
l zeolite 3A or they may be filled with either silica gel or
231 alumina. Spacer bar 7 is preferably filled with silica ~el or
241 alumina. Bottom spacer bar 5 may be left empty or it may be `
l filled with adsorbent. In the preferred embodiment of the inven-
tion top spacer bar 4 and/or bottom spacer bar 5 are filled with
227 adsorbent. Activated alumina, silica gel or molecular sieve
281 zeolites or mixtures thereof or one or more of the aforemelltioned
291 adsorbents in admixture with activated carbon are suitable
301 adsorbents, but zeolites are the preferred adsorbent. In
311 . . .321
. ! 172515
1 insulating glass units in which hydrocarbon vapors may bc prcsent
2 o~ are likely to be released from the sealing composition, at
3 least a portion of the adsorbent in thc spaccr bars, preferably
4~ 4 and/cr 5 should have an average pore diameter which permits
51 entry of benzene into the pore spacc so that solvcn-t and
61 hydrocarbon vapors will bc adsorbed.
7 Figure 2 of the drawings is a cutaway showing in
81 detail the lower right corner of the double glazed window of
9 Figure l. Panes 2 and 3 are the outer and inner panes of glass,
10¦ respectively. Spacer bar 7 shows details of the improve~ spacer
11 bar of the invention. Spacer hars are conventionally made by
12¦ roll forming a long, narrow strip of metal usually aluminum.
13 ¦ In the roll forming process the outer edges of the narrow strip
14¦ are brought together to form the ~urface of the spacer bar
15¦ which is in contact with the intericr air space enclosed
16 1 between the panes. Line 9 shows the ~unction of these two edges.
17¦ The outer edges of the metal strip subjected to the rolling
18 ¦ process may be roughened so that when the two edges are brought
209 ¦ together there is a small, narrow space between them which is
I small enough in width to prevent the adsorbent with which the
i 21 ¦ bar is filled from passing through the narrow opening but the
I opening is large enough to pcrmit diffusion of air, water vapor
23 ¦ ~d organic material escaping from the sealant contained in the
24 1 space between the panes through the narrow opening and into
25 l contact with the adsorbent filling the spacer bar. Perforations
261 or slot like openings between the edges of the spacer bar are
28 1 indicated by the numeral 8. The portion of the spacer bar lying
291 between the lowest of the perforations at the upper end of the
1 spacer bar and the highest of the perforations at the lower end
: 331 ~ of the spacer bar is sealed either with a sealant or by solderlng
321
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1 172~1~
1¦ so that this segment of the spacer bar will not pcrmit p~ssage
2¦ of air through it either into or out of the enclosed air space.
3 Opening 10 is a small opening through the sealant and the surface
4¦ of the spacer bar which faces the outer atmosphere and is located .
at or near the midpoint of the sealed segment of the bar. This
6 ¦ opening no~mally ranges from about one hundredth to one tenth
7 ¦ inch in effective diameter so that air under small pressure will
8 ¦ pass through it in either direction but so small that no
9 appreciable diffusion of air through the opening will occur when
10 ¦ there is no pressure differential between the enclosed air space
11 ¦ and the outer atmosphere. Opening 10 should be small enough to
12 ¦ prevent passage of the adsorbent particles through it. The
13 cross section of the spacer bar is somewhat in the form of an
14 ¦ isosceles trapezoid. This shape is used so that there will be a
small space between the panes of glass and the sides of the space~
16 bar adjacent the peripheries of the pa-nes which is generally
17 triangular in cross section and which permits the sealing
18 ¦ composition to enter this space and seal the spacer bar to the
19 ¦ pane. Elbow member 12, commonly referred to as a corner lock, is
20 ¦ so shaped so that the arms of the elbow conform in cross section
21 ¦ to the cross section of the spacer bar but the dimensions are
22 ¦ slightly smaller so that each arm of the elbow will penetrate
23 ¦ the end of a spacer bar at the corner. The purpose of the corner
24 ¦ lock is to connect the spacer bars to form a peripheral metal
25 ¦ rectangle and to hol~ adsorbent in place.
26 ¦ Corner locks are commonly made from solid organic
27 ¦ polymers such as polyethylene, nylon and the like or from metal,
28 ¦ usually zinc. The arms of the corner lock must fit tightly
2390 against the inner surfaces of the spacer bar to prevent leakage.
31
32
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1 ¦ A sealant may be applied to the junction of thc corncr lock arm
2 ¦ and the interior of the spacer bar to ensure air~tight closure.
3 ¦ Corner locks are usually solid but may be hollow~d to provide
41 a path of communication between the adsorbent masses in the
I spacer bars which meet at a corner if desired.
6 ¦ If spacer bar 7 were constructed as shown and
8 ¦ described above, except that the bar was perforated throughout
¦ its whole length instead of having an imperforate segment lying
9 ¦ above and below opening lO, then when the pressure inside the
10 1 enclosed air space is lower than the outer ai pressure, air
121 will flow through opening lO and take the path of least resistanc~
13 1 directly through the adsorbent and through the perforations in
I the spacer bar into the space between the panes. This flow path
14 ¦ would be essentially perpendicular to the length of the spacer
15 ¦ bar and only a narrow bard of the adsorbent would be contacted
16 ¦ by the air entering the space between the panes. When the spacer
71 bar is constructed as shown in Figure 2, air flowing through
191 opening lO from the âtmosphere into the spacer bar must travel
20 1 a path parallel to the length of the spacer bar upwardly and
211 downwardly through the mass of adsorbent until it rises and
22 1 lowers to a point where it comes into contact with perforations 8
23 1 at which time it is able to pass through the spacer bar into the
241 space between the panes. This path of air travel brings it into
25 1 contact with a large mass of adsorbent before it enters the
261 space between the panes. Moisture in the air traversing the mass
271 of adsorbent lying between opening lO and the upper and lower
281 perforations is completely adsorbed. During daylight hours the
29 window is exposed to direct contact with relatively warm outside
30~ air the air enclosed in the space between the panes is warmed
311 .
321
,.. _ . , ... _,.. ,.. , .. , .. ~ __ .. -- _, .. ... ..
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1 ¦ and expands. The interior pressure then excceds thc prcssure
2 ¦ of the outside atmosphere and gas flow is from the interior of
3 ¦ the window out into the atmosphere. In order for the gas to
4 ¦ make its way from the interior of the window out it must pass
5 ¦ through the per~orations 8 above and below opening 10 and then
6 ¦ pass through the mass of adsorbent lying between the perforations
7 ¦ 8 and the opening lO. The warm air contacts the adsorbent which
8 ¦ had previously picked up moisture from entering air and desorbs
9 ¦ the moisture so picked up. The net result is that when the
10 ¦ window "inhales" moisture is picked up by the adsorbent and when
11 ¦ it "exhales" moisture is desorbed from the adsorbent so that the
12 ¦ net pickup of moisture by the adsorbent. after many cycles of
13 ¦ inhaling and exhaling is very, very small.
14 ¦ Figure 3 of the appended drawings shows an alternative
15 ¦ and desired structure for the spacer bar of the invention. The
16 ¦ spacer bar 7 is a hollo~ prism. Its c~oss section is generally
17 ¦ of the form of an isosceles trapezoid having the longer base
18 ¦ 15 of the trapezoid facing the interior of the space between
19 ¦ the panes of ~the window and the shorter base 14 of the trapezoid
20 ¦ facing the exterior atmosphere. The prism is filled wi~h a solid
21 ¦ adsorbent 13 as above described. The surface of the spacer bar
22 ¦ facing the space between the panes is entirely closed from
23 bottom almost to the top. At the top of the spacer bar communica-
241 tion between the interior of the spacer bar and the space between
251 the panes is through perforations 8 which may simply be an
26¦ unsealed portion of the junction 9 of the edges of the metal
271 strip from which the spacer bar is conventionally roll formed.
28¦ Alternatively, communication may be via slots 16 in the arm of
291 the corner key which fits into the upper open end of the spacer
31~ bar F via both perforations 8 and slot 16. Small opening 10
321 -10-
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1 through the sealant and the outer surface of the spacer bar is
2 placed at the bottom of the spacer bar so that the opening lies
3 just above u2per surface of any corner lock which is inserted in
4 the bottom of the bar. When the pressure of the outside atmos-
S phere excee~s that o~ the sp~ce betwccn the ~nes of the window
6 air flows from the outer atmosphere through opening 10 and then
7 passes through the entire column of adsorbent and escapes into
8 the space between the panes through perforations 8 or slot 16
9 at the top of the bar. Corner lock 12, an arm of which fits into
the spacer bar is shown in exploded position above. Instead of
11 placing perforations on the inner face of the bar at its upper
12 end, the entire inner face may be clcsed and slot 16 may be cut
13 in the inner face of the lower arm of the corner lock to permit
14 air to flow into or out of the space between the panes through
the slot. This embodiment of the spacer bar may be formed by
16 extrusion rather th-an by roll forming if desired. If formed by
17 extrusion, then perforations 8 may be drilled through the upper
18 interior surface of the spacer bar if desired or alternatively,
19 slots in the face of the corner lock may provide the entire
route for air to travel into the space between the panes or out
21 of it. In the event that the spacer bar is made by roll forming
22 then the rectangular metal sheet from which the bar is formed
23 may be so rolled that the junction 9 of the edges of the sheet
24 does not lie on the surface of the bar which is to face the space
between the panes but lies instead on one of its other surfaces.
26 Perforations then may be drilled at the top of the inner surface
27 of the bar or slots 16 in the arm of corner lock 12 may be used
28 to provide communication between the interior of the bar and the
29 space between the panes.
32
! 17251 ~
1 Insulating glass units employing the spacer bar as
2 described above permit continuous equalization of the pressure
3 of the air lying in the space enclosed betwccn the panes and the
4 outer atmospheric pressure. When the pressure in the space
between the panes becomes lower than the exterior atmosphcre
6 pressure then air flows from the atmosphere through the spacer ba
7 into the space between the panes. Conversely, when the pressure
8 of the air enclosed in the space between ~he panes eYceeds that
9 of the exterior atmospheric pressure, then air flows from the
space between the panes to the exterior atmosphere. When air is
11 flowing from the atmosphere into the space between the panes the
12 arrangement of the spacer bar requires ~he air to traverse a
13 long segment of the spacer bar filled with adsorbent before
14 reaching a perforation in the spacer bar or a slot in the
corner lock which permits the inflowing air to pass into the
16 space between the panes. Conversely,-when the pressure in the
17 space in the panes exceeds that of the interior atmosphere then .
18 air flows from the space between the panes to the atmosphere
19 and the flow path requires it to traverse a mass of adsorbent
lying between the top of the spacer bar and the small opening 10
21 through which the outflowing air can pass.into the.atmosphere. .
22 During inflow all of the moisture contained in the entering air
23 is adsorbed on the solid adsorbent particles filling the spacer
24 bar. When the air flow path is from the space between the panes
to the outer atmosphere the air moving outward enters the
26 perforations in the spacer.bar or the slots in the corner lock
27 and then must traverse a mass of solid adsorbent before reaching
28 opening 10 which permits it to escape into the atmosphere. The
3209 outflowing air contacts the solid adsorbent which had previously
31 .
32
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! 1~51S
1 been exposed to moist entering air and desorbs moisture from the
2 adsorbent. The most frequent cause of out~low of air f~om the
3 space between the panes is expansion due to heating of that air
4 by exposure to higher outer ambient temperature during daylight
S hours. This heating provides contact of warmed air with the
6 solid adsorbent and assists in the desorption of moisture from
7 the adsorbent. The desorption of adsorbed water which attends
8 the outflow of air from the space between the panes when the
9 spacer bar of the present invention is employed makes it possible
to obtain long window life using less expensive silica gel or
11 activated alumina as the adsorbents. They have all the capacity
12 required to take up moisture from the air and the fact that
13 during the flow of air from the interior of the space between
14 the panes to the outside atmosphere desorption of moisture occurs
extends the useful life of these materials and makes them
16 competitive with the more expensive zeolites widely used at the
17 present time.
18 Since a sealant coating is applied to the peripheries
19 of the glass panes and the outer surface of the spacer bar,
small opening 10 should be plugged during application of the
21- sealant to prev-ent closure~of opening 10 by the sealant and the
22 plug removed when application of the sealant is completed.
23 Alternatively, small opening 10 may be fitted with a short
24 cylindrical tube which extends beyond the sealant coat to ensure
that communicating means between the outside atmosphere and the
26 interior of the spacer tube will exist.
27 The sp~Çer bars of the invention should preferably be
28 in a vertical rather than a horizontal position in the finished
and installed insulating glass urit. This ensures better and mor
31 .
32 . - .
.. ~ t 172515
1 uniform contacting between the adsorbent and the air which flows
2 into or out of the insulating glass unit. If the imperforate
3 spacer bar is in a horizontal position, any settling of the
4 adsorbent particles will result in a non-uniform distribution of
the adsorbent particles with rcspect to the cross section of the
6 spacer bar and a tendency to form an adsorbent-free space across
7 the top of the channel. Under these conditions when the window
8 inhales or exhales, the air flows along the path of least
9 resistance which would be along the adsorbent-free space at the
top of the spacer bar. Contact between the air and the adsorbent
11 would thereby be reduced and the performance of the adsorbent
12 would be diminished. Suitable steps can be taken, such as
13 careful packing of the adsorbent in the spacer bar, so that
14 horizon'al imperforate spacer bars will yield favorable results,
but these steps generally require extra effort and expense.
16 Small diameter breather-tubes have been shown to -
17 minimize water vapor entry into an insulating glass unit, since
18 small diameter tubes tend to be a better diffusion barrier than
1 large diameter tubes. Breather tubes can be connected to the
2 exterior opening of the spacer bar of the present-design~as a
21 diffusion barrie~. This can be particularly helpful in minimizinc
2 the possible entry of liquid water such as that which might
2 condense on the metal surfaces of the insulating glass unit.
2 Maximizing the length of the imperforate segment of
2 the spacer bar(s) is desirable to maximize the performance of
2 the adsorbent and the life of the window. The imperforate zone
2 need not be limited to a spacer bar along one side. If the
2 spacer bars are properly filled and connected at the corners by
29 ~ suit e air-tight means such a~ welding or a tightly fitting
321 -14-
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tl72515
1 hollow corner lock, the imperforate segment can comprise two or
2 more of the spacer bars contained in an insulating glass unit.
3 It is necessary only to provide a suitable impervious barrier(s)
4 within the spacer b-r(s) or corner key(s) to ensure that the air
flow does not bypass any of the adsorbent-filled imperforate
6 segment.
7 The improved spacer bars described above find use in
8 insulating glass units which comprise more than two panes of
9 glass with the panes separated along the periphery by spacer
bars and the entire unit sealed along the periphery with a sealinc
11 compound. This results in two or more enclosed air spaces. In
12 some designs small holes in the interior panes provide communica-
13 tion between the otherwise separate air spaces. Adsorbent in
14 the spacer bars functions as described above. In multiple glazed
units without interconnecting holes, separate adsorbent-filled,
16 imperforate spacer bars as describ-ed above would be employed for
17 each of the air spaces.
18 When zeolite adsorbents are used to fill the spacer
19 bars of the invention it is desirable to employ zeolite ~A as
the adsorbent. Inhaling and exhaling of the window over a long
21 period has a tendency to produce an increase in oxygen content
22 in the space between the panes if an adsorbent which adsorbs
231 nitr n is used in the spacer bar.
3 _
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