U.S. patent application number 12/079891 was filed with the patent office on 2008-10-09 for vacuum insulated glass building component and method and apparatus for its manufacture.
Invention is credited to Wolfgang Friedl.
Application Number | 20080245011 12/079891 |
Document ID | / |
Family ID | 39363995 |
Filed Date | 2008-10-09 |
United States Patent
Application |
20080245011 |
Kind Code |
A1 |
Friedl; Wolfgang |
October 9, 2008 |
Vacuum insulated glass building component and method and apparatus
for its manufacture
Abstract
In a vacuum-insulated glass building component comprising first
and second glass panes which are supported with respect to each
other by spacers and are closed along their edges by a vacuum-tight
edge connection so as to enclose between them a thin evacuated
intermediate space, the edge connection is formed by first and
second metal foil strips which are connected to the edge areas of
the first and, respectively, second glass panes in a vacuum tight
manner and the areas of the first and second metal foil strips
projecting beyond the edges of the respective glass panes are
welded together to join the glass panes.
Inventors: |
Friedl; Wolfgang; (Kaisheim,
DE) |
Correspondence
Address: |
KLAUS BACH
4407 Twin Oaks Dr
Murrysville
PA
15668
US
|
Family ID: |
39363995 |
Appl. No.: |
12/079891 |
Filed: |
March 28, 2008 |
Current U.S.
Class: |
52/407.5 ;
52/745.19 |
Current CPC
Class: |
E06B 3/6775 20130101;
E06B 3/66304 20130101; Y02A 30/25 20180101; E06B 3/6736 20130101;
Y02B 80/22 20130101; Y02A 30/249 20180101; E06B 3/6612 20130101;
Y02B 80/24 20130101 |
Class at
Publication: |
52/407.5 ;
52/745.19 |
International
Class: |
E04B 1/74 20060101
E04B001/74 |
Foreign Application Data
Date |
Code |
Application Number |
Apr 5, 2007 |
EP |
07 007 253.3 |
Claims
1. A vacuum insulated glass building element, comprising a first
glass pane (1) and a second glass pane (2), spacer elements (4)
arranged between the glass panes (1, 2) so as to support the glass
panes (1, 2) in spaced relationship relative to each other, first
and second metal foil strips (5) connected to the edges of the
respective first and second glass panes (1, 2) in a vacuum-tight
manner, said first and second metal foil strips (5) having edge
areas extending beyond the circumferential edges of the respective
glass panes (1, 2) to which they are welded and being joined at
their projecting edges areas by a circumferential vacuum-tight weld
seam so as to enclose between them a thin sealed intermediate space
(3) which is evacuated.
2. A vacuum insulated glass building element according to claim 1,
wherein the metal foil strip (5) is connected to the respective
glass panes (1, 2) by ultrasound welding wherein, between the
respective metal foil strip (5) and the respective glass pane (1,
2), a thin aluminum foil strip (6) is interposed which, by the
ultrasound welding, is on one side connected to the glass surface
in a vacuum-tight manner and, on the other side to the metal foil
strip (5) in a vacuum tight manner.
3. A vacuum insulated glass building element according to claim 1,
wherein the metal foil strips (5) are connected to the respective
glass panels (1, 2) by welding via glass solder.
4. A vacuum insulated glass building element according to claim 1,
wherein a getter material (8) is applied to at least one of the
metal foil strips (5), so that, after the welding of the metal foil
strips, it is disposed on the side of the evacuated intermediate
space (3) between the two glass panes (1, 2) of the welding seam
(7) of the metal foil strips (5).
5. A vacuum insulated glass building element according to f claim
1, wherein the metal foil strips (5) are connected to the two glass
panes (1, 2) at the sides which face each other.
6. A vacuum insulated glass building element according to one of
claims 1, wherein the metal foil strips (5) consist of stainless
steel.
7. A vacuum insulated glass building element according to claim 1,
wherein gap spaces between the metal foil strip (5) and the
respective glass surfaces outside the respective metal foil
strip-glass surface weld areas are filled with a filler material
(9).
8. A vacuum insulated glass building element according to claim 1,
wherein one of the first and the second glass pane is combined with
an additional element, that is, one of a solar module, a
photovoltaic module and another element or is in the form of such
an element.
9. A method for the manufacture of a vacuum insulated glass
building element, comprising a first glass pane (1) and a second
glass pane (2), spacer elements (4) arranged between the glass
panes (1, 2) so as to support the glass panes (1, 2) in spaced
relationship relative to each other, first and second metal foil
strips (5) connected to the edges of the respective first and
second glass panes (1, 2) in a vacuum-tight manner, said first and
second metal foil strips (5) having edge areas extending beyond the
circumferential edges of the respective glass panes (1, 2) to which
they are welded and being joined at their projecting edges areas by
a circumferential vacuum-tight weld seam so as to enclose between
them a thin sealed intermediate space (3) which is evacuated, said
method comprising the steps of: introducing the prepared glass
panes (1, 2) together with the metal foils strips (5) connected
thereto into a vacuum chamber and placing them therein on top of
one another and performing the welding of the metal foil strips
within the vacuum chamber (13) by a laser beam which is generated
outside the vacuum chamber and is moved along the metal foil strip
and which is introduced into the vacuum chamber (13) through a
line-like window (14).
10. The method according to claim 9, wherein, before their
introduction into the vacuum chamber (13) in which the metal foil
strips (5) are welded together, the two glass-panes (1, 2) are
cleaned in another vacuum chamber (12) on both sides by one of ion
sputtering and plasma etching for the removal of moisture.
11. An apparatus for performing the method for the manufacture of a
vacuum insulated glass building element, comprising a first glass
pane (1) and a second glass pane (2), spacer elements (4) arranged
between the glass panes (1, 2) so as to support the glass panes (1,
2) in spaced relationship relative to each other, first and second
metal foil strips (5) connected to the edges of the respective
first and second glass panes (1, 2) in a vacuum-tight manner, said
first and second metal foil strips (5) having edge areas extending
beyond the circumferential edges of the respective glass panes (1,
2) to which they are welded and being joined at their projecting
edges areas by a circumferential vacuum-tight weld seam so as to
enclose between them a thin sealed intermediate space (3) which is
evacuated, said method comprising the steps of: introducing the
prepared glass panes (1, 2) together with the metal foils strips
(5) connected thereto into a vacuum chamber and placing them
therein on top of one another and performing the welding of the
metal foil strips within the vacuum chamber (13) by a laser beam
which is generated outside the vacuum chamber and is moved along
the metal foil strip and which is introduced into the vacuum
chamber (13) through a line-like window (14), said apparatus
including a vacuum chamber (13) provided with line-like windows
(14) which extend along the edge areas of the vacuum chamber (13)
and are transparent to laser radiation, a laser cannon (15) which
is movable along the windows (14), and a carriage arranged in the
vacuum chamber (13) for the limited movement of the pane
arrangement formed by the glass panes (1, 2) disposed on top of one
another in the vacuum chamber (13) on the carriage.
Description
BACKGROUND OF THE INVENTION
[0001] The invention relates to a vacuum-insulated glass building
element that is to a vacuum-insulated glass pane and also to other
building components consisting of a combination of vacuum insulated
glass including for example a solar module. The invention also
resides in a method and an apparatus for the manufacture of such
vacuum-insulated building elements.
[0002] A building element of the type with which the present
invention is concerned comprises at least two glass panes or other
areal glass structures with or without the inclusion of another
areal body which are joined together with a thin evacuated space
therebetween.
[0003] Vacuum-insulated glass as such is known. It differs from
conventional insulated glass in that the space between the panes is
evacuated whereas, in conventional insulated glass, it is filled
with a noble gas. Furthermore, the space between the glass panes of
vacuum insulated glass is substantially thinner than in normal
insulated glass, that is, it has a thickness of only about 0.7 mm
or less since, in vacuum insulated glass, there is no convection in
the space between the individual glass panes. The two individual
glass panes are supported with respect to each other by way of
supports distributed over the glass surface in a grid-like pattern
so that the ambient air pressure cannot press the panes together.
At their circumference, they are joined by a vacuum-sealed edge
connection.
[0004] In accordance with the known state of the art, vacuum
insulated glass panels are manufactured in that spacers are placed
in the predetermined grid-like pattern onto a first individual
glass pane and fixed by cementing and the second individual glass
pane is then placed on top. The top glass pane is provided at its
edge with a bore including a sealed-in evacuation nipple which is
fixed in position by glass solder or which is cemented and to which
a suction hose with a vacuum pump can be connected. The two glass
panes are then laser-welded along their edges under atmospheric
conditions using glass solder. To this end, the top glass pane is
dimensioned so as to be smaller than the bottom pane by several
millimeters so that the edge of the top pane is recessed with
respect to the edge of the bottom pane disposed below. In this way,
the two glass panes can be laser-welded together using glass solder
by a laser beam directed onto the arrangement from the top.
[0005] After the laser welding of the panes, the space between the
panes is evacuated via the suction nipple. Evacuation is performed
for about two hours or longer during which time the glass composite
is maintained at a temperature of about 400.degree. C. to about
450.degree. C. Only in this way, volatile materials, mainly water,
which are adhering to the glass surfaces can be removed from the
space between the glass panes and a vacuum of sufficient quality
can be established.
[0006] This long period of evacuation at high temperature does not
only result in an expensive manufacturing process for the vacuum
glass but also detrimentally affects the product quality. Usually a
reflective surface layer is vapor-deposited on the glass surfaces
facing the intermediate space if the glass panel is to be used as a
window panel in order to reflect heat radiation for improved heat
protection. However, because of the high temperatures used during
evacuation over a long period, highly effective coatings with a low
emission degree (soft coatings) cannot be used. As a result,
conventional vacuum glass panels of the two-pane construction can
reach heat insulation values comparable only with good conventional
insulated glass panels.
[0007] In addition, a high-temperature of about 450.degree. C.
maintained during evacuation over a period of about 2 hours results
in the de-tempering of single pane safety glass so that it
substantially loses its safety glass property.
[0008] From EP-0 771 313, it is known to perform the laser welding
of the two individual panes of a vacuum insulated panel, which are
separated by an intermediate space and held in spaced relationship
by spacers arranged in the intermediate space, in a vacuum chamber,
so that the subsequent evacuation of the intermediate space is no
longer necessary. This printed publication however recommends that
during the welding of their edges within the vacuum chamber the
whole individual glass panes are heated to, or slightly above,
their annealing temperature in order to avoid tension cracks. As a
result, the problem that none of the effective coatings for
achieving low degrees of emission can be used and safety glass
single panes are also in this case de-tempered.
[0009] However, whether the two single panes are welded together in
an atmospheric chamber with subsequent evacuation of the
intermediate space or in a vacuum chamber, in connection with
conventional vacuum-insulated glass panels, there is always the
substantial problem that the composite rigid glass panel formed by
the welding of the individual panes will not withstand the stresses
to which it is subjected during use: The two individual panes
separated by the evacuated intermediate space during use assume
different temperatures since the glass pane facing the room is warm
and the pane facing the outside air is cooler, wherein the use of a
coating for the reduction of heat losses by radiation increases
that temperature difference substantially. The temperature
difference between the individual panes generated in this way
results in substantial mechanical tensions. This means that
conventional vacuum-insulated glass panels are limited in size to
certain maximum formats. Such vacuum-panels permit only a certain
relatively small window size. In addition, no reliable information
is available concerning vacuum insulation glass panels used under
conditions where they are subjected to high mechanical
tensions.
[0010] It is therefore the object of the present invention to
provide vacuum-insulated glass building elements which reach heat
insulating values which are substantially better than those
obtained by good double pane insulation glass, but which, on the
other hand, require manufacturing expenditures which are at least
not essentially higher than the manufacturing expenditures for a
good double pane insulating glass panel, and which can accommodate
mechanical tensions occurring between the two individual panes by
temperature differences therebetween substantially better than
conventional vacuum insulated glass panels and which therefore
promise a reliable long lifespan.
SUMMARY OF THE INVENTION
[0011] In a vacuum-insulated glass building component comprising
first and second glass panes which are supported with respect to
each other by spacers and are closed along their edges by a
vacuum-tight edge connection so as to enclose between them a thin
evacuated intermediate space, the edge connection is formed by
first and second metal foil strips which are connected to the edge
areas of the first and, respectively, second glass panes in a
vacuum tight manner and the areas of the first and second metal
foil strips projecting beyond the edges of the respective glass
panes are welded together to join the glass panes.
[0012] A particularly advantageous method for the manufacture of
the vacuum insulated glass building element according to the
invention and a respective suitable and advantageous arrangement
therefore are also part of the present invention.
[0013] Since in the arrangement according to the present invention,
the two individual panes are provided at their edges each with a
metal foil strip and the metal foil strips of the two individual
panes are welded together, a durably vacuum-tight connection
between the individual panes is established which however is not
rigid but which can accommodate relative thermal expansions of the
two individual panes. Such expansion movements are accommodated,
without tensions, by the metal foil strips which are interconnected
by welding. In this way, a vacuum-tight non-rigid edge connection
of the two individual panes of the vacuum-insulated glass building
element is provided which, during use, remains essentially free
from mechanical stresses also when the individual panes are
subjected to high temperature differences. For such an arrangement
also a reliable long life for the edge connection can be considered
to be no problem and the formation of cracks as a result of thermal
effects on the panes which could lead to a loss of the vacuum
between the panes is avoided.
[0014] As essential advantages of the arrangement according to the
invention, not only a predictably long life of the vacuum-insulated
glass panel according to the invention is obtained in this way, but
also a limitation of the panel to small formats is eliminated as it
exists in connection with the rigid edge connections of
conventional vacuum-insulated glass panels obtained by
glass-welding of the two individual panes.
[0015] The glass panes can be joined along their edges with the
metal foil strips either with the aid of glass solder by melt
welding or by "cold" welding by means of ultrasound. In this
connection, ultrasound welding is preferred since it causes no
thermal stresses. In addition, the ultrasound welding procedure is
simpler than the melt welding with glass solder.
[0016] This results in a further substantial advantage of the
vacuum-insulated glass building element according to the invention
in that the ultrasound welding causes no thermal stresses, and does
not detrimentally affect the glass panes. If one of the glass panes
consists of safety glass, the glass pane is not de-tempered by the
effects of heat and the safety glass structure remains unchanged.
In addition, highly effective low-emission coatings can be used
which are not affected by the manufacture of the edge joint so that
very high heat insulation values are obtained for the vacuum
insulated building element.
[0017] The manufacture of the edge connection is possible by a
relatively simple process. The ultrasound welding (or also the
glass solder welding) of the glass pane edges with the metal strip
can occur under atmospheric conditions. The sub-sequent welding of
the metal foil strip areas which project from the glass pane edges
and are connected to the glass pane edges can be performed in a
vacuum chamber by laser welding so that subsequent evacuation of
the space between the glass panes is not necessary. Subsequently,
outside the vacuum chamber, the welded excess metal foil strip
areas can be bent over toward one or the other side and the edge
joint is completed.
[0018] The metal foil strips are preferably arranged at the sides
of the glass panes which face each other. Before the welding of the
metal foil strips in the vacuum chamber expediently a getter
material is applied to one side of the metal strips which, with
respect to the welding seam to be formed, faces the interior of the
space between the panes for the absorption of moisture molecules
possibly still present in the space between the glass panes.
[0019] An exemplary embodiment of a vacuum-insulated glass building
element according to the invention and a method and an apparatus
for the manufacture thereof will be described below in greater
detail with reference to the accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0020] FIG. 1 shows in cross-section an edge area of a vacuum
insulated glass building element according to the invention,
[0021] FIG. 2 shows the two individual glass panes of the building
element with metal foil strips attached thereto before the assembly
thereof,
[0022] FIG. 3 shows the assembled individual glass panes after the
welding of the projecting areas of the metal foil strips,
[0023] FIG. 4 shows schematically a cross-section of the edge area
of a vacuum insulated glass building element according to the
invention forming a solar module,
[0024] FIG. 5 shows a variation of the arrangement according to
FIG. 1,
[0025] FIG. 6 shows schematically a diagram which clarifies the
manufacturing procedure of vacuum insulated building elements
according to the invention,
[0026] FIG. 7 shows schematically the cleaning step of the method
according to the invention in a first vacuum chamber, and
[0027] FIG. 8 shows schematically the laser welding stage of the
method in a second vacuum chamber.
DESCRIPTION OF PARTICULAR EMBODIMENTS OF THE INVENTION
[0028] FIG. 1 shows, in cross-section, the edge area of a vacuum
insulated glass building element in the form of a vacuum insulated
glass panel with a finished edge connection. The arrangement
comprises a cover pane 1 (outer pane) and a bottom pane 2 (inner
pane), which are separated from each other by an intermediate pane
space 3. In the intermediate pane space 3, there is a vacuum. The
two panes 1 and 2 are held at a predetermined distance from each
other by spacers 4 which are fixed to the bottom pane 2 in a
grid-like pattern for example by cementing and on which the cover
pane 1 is supported. The spacers may be small glass cylinders as
shown but they may also be in the form of balls and they may also
consist of metal.
[0029] The cover pane 1 and the bottom pane 2 each may have a
thickness of 4 mm and the intermediate space 3 may have a thickness
which is preferably in the range of 0.7 mm to 1 mm.
[0030] At the edge of each of the two panes 1, 2, a metal foil
strip 5 is attached in a vacuum-tight manner. Preferably, the metal
foil strips 5 are attached at the sides of the two panes 1, 2
facing the intermediate space 3.
[0031] The metal foil strips 5 may be connected to the respective
panes either by welding by means of a glass solder, preferably
however by ultrasound welding. The ultrasound welding occurs with
the interposition of a thin aluminum foil strip 6 between the
respective metal foil strip 5 and the glass surface, wherein the
aluminum is tightly joined to the glass surface and also to the
other metal of which the metal foil 5 consists, preferably
stainless steel. The areas of the metal foil strip 5 which are
attached to the two panes and which project over the glass pane
edges are compressed and welded together preferably by laser
welding. Herein, a getter material 8 is arranged inward of the
welding seam 7 between the metal foil strips 5 that is still within
the intermediate space between the panes which getter material has
been applied to the lower metal foil strip before the welding. The
welded projecting area of the metal foil strips 5 is bent onto the
edge surface of the lower pane 2. The getter material does not need
to be arranged between the panes as shown (where with a thin
intermediate space, there is generally no space), but it may be
disposed in the bent over area of the welded metal foil strips.
[0032] FIGS. 2 and 3 show pre-stages of the finished edge
connection of the vacuum insulated glass building element according
to FIG. 1.
[0033] FIG. 2 shows the two still individual panes, that is the
cover pane 1 and the bottom pane 2, each with the metal foil strip
5 welded to the respective edge areas. On the bottom pane 2,
furthermore, the spacers 4 are already in place.
[0034] FIG. 3 shows the joined arrangement of the top pane 1 and
the bottom pane 2 with the metal foil strips 5 welded thereto,
wherein the areas of the metal foil strips 5 projecting beyond the
pane edges are welded together by a welding seam 7. By bending the
welded projecting areas of the metal foil strips 5 onto the edge
surfaces of the bottom pane 2, the edge connection is completed as
it is shown in FIG. 1.
[0035] FIG. 4 shows an arrangement as it is shown in FIG. 1,
wherein however the bottom pane 2 is combined with an additional
module (or is formed as such), here with a solar photo voltaic
module 10. Herein, the photo voltaic module 10 forms with the
bottom pane 2, a compound arrangement. If as shown in the
embodiment of FIG. 4, the additional module consists fully or
partially of glass, the metal foil strips may also be attached as
shown in FIG. 4 or, like in the basic embodiment according to FIG.
1, to the side walls of the cover pane 1 and the bottom pane 2 or,
respectively, the additional module which faces the intermediate
space 3 between the panes. However, if the additional module is not
suitable for a vacuum-tight attachment of the respective metal foil
strips 5, the arrangement as shown in FIG. 5 and described below
may be selected. Generally, however the particular pane, in this
case, the bottom pane will form the additional module by
integration of a particular function.
[0036] FIG. 5 shows a modified embodiment of the vacuum sealed edge
jointure of the arrangement according to FIG. 1. It differs from
the embodiment of FIG. 1 in that the metal foil strip 5 is not
attached to the facing surfaces of the individual glass panes 1 and
2, but to their outer surfaces. This embodiment according to FIG. 5
is possible and equally good with respect to the quality of the
vacuum sealed edge connection as the embodiment of FIG. 1, but in
that case, the outer surfaces of the finished vacuum insulated
glass element is not smooth fully to the outer edge thereof but has
a raised edge area because of the metal foil strips 5 extending
along the edge. This could be objectionable for some applications,
which is why this embodiment appears to be less preferred.
[0037] The preferred material for the edge foil strips 5 in all
embodiments is stainless steel.
[0038] As apparent from FIGS. 1 to 3, the outer gap between the
individual panes 1 and 2 and the metal foil strips 5 attached
thereto can be sealed in the area between the respective individual
outer pane edges and the connection or, respectively, weld areas to
the glass pane surface by a filler material 9. This filler material
has two functions. It ensures a long-term vacuum sealing by
protecting the weld between the metal foil strips and the glass
from outside influences and it also reduces mechanical stresses.
Furthermore, it protects the pane edges from mechanical stresses
during the bending over of the welded metal foil strips.
[0039] FIG. 6 shows the procedure of a preferred manufacturing
method for the above-described vacuum insulated building elements
in a schematic block diagram.
[0040] In a first method step A, the two individual glass panes are
prepared under atmospheric conditions. This includes the connection
of the metal foil strips to the individual glass panes and the
attachment of the spacers to the bottom pane as well as the
application of the getter material, if used.
[0041] The second method step B resides in the cleaning of the two
individual panes, particularly the removal of water molecules from
the pane surfaces. Special coatings of the panes bind water
molecules which are difficult to remove therefrom. Conventionally,
this requires heating to high temperatures over an extended period,
which, however is undesirable since high temperatures, particularly
when effective over an extended period, destroy high quality
coatings for reducing the degree of emission (so-called low
E-layers) and also the glass structure, for example, that of safety
glass, as mentioned already earlier. This cleaning step is
performed with the method according to the invention, without
temperature effects, by ion scattering, wherein the ions absorb the
moisture molecules and carry them away, or by plasma cleaning which
is also called plasma etching. This method step is performed in a
first vacuum chamber under constant suction in order to remove any
moisture released from the pane surfaces. It is very important
herein that, in each case, both sides of each individual pane are
cleaned that is the moisture is removed also from that side which
does not delimit the evacuated space between the panes. This is
necessary because any moisture input into the high vacuum chamber,
in which the laser welding of the metal foil strips takes place
must be carefully avoided since otherwise the high vacuum is
detrimentally affected.
[0042] FIG. 7 shows schematically the cleaning stage according to
the method step B in the first vacuum chamber by ion scattering,
or, respectively, vacuum etching on both sides of the plate wherein
the ion scattering or, respectively, the vacuum etching occurs
along a line over the whole width of the pane while the glass pane
is moved on a transport means 11 through the first vacuum chamber
12.
[0043] The third method step C is the laser welding of the metal
foil strips in a second vacuum chamber 13, which is schematically
shown in FIG. 8 in a sectional view. Herein, first, the lower pane
2 is introduced into the vacuum chamber 13 and subsequently the
upper pane is introduced and placed onto the lower pane. The vacuum
chamber 13 is provided at its topside along all four corner areas
with a, in each case, line-like window 14 which, of course, is
interrupted by bridge areas of supporting material as necessary for
the integrity of the top wall of the vacuum chamber 13. A laser
cannon 15 is arranged on the outside, that is, above the vacuum
chamber 13 and movable along the window 14 in order to direct the
laser beam through the window 14 onto the metal foil strips to be
welded. The pane arrangement is disposed within the vacuum chamber
13 on a corresponding carriage which is movable in the plane of the
pane since, because of the design-based interruptions of the window
14, a certain movability of the pane arrangement is necessary in
addition to the movability of the laser cannon.
[0044] This arrangement has essential advantages. Since the laser
cannon 15 is arranged outside the vacuum chamber 13 and is movable
along the window 14, no mirror or any other optical elements or
mechanisms are needed within the vacuum chamber so that the vacuum
chamber can have a minimum volume. The required length and width of
the vacuum chamber is based on the dimensions of the largest pane
arrangement to be welded therein and the height of the vacuum
chamber is determined only by the thickness of the pane arrangement
and the height required for the carriage by which it is supported.
Because of the movability of the laser cannon 15 also complicated
laser-optical equipment, particularly mirror mechanisms, are not
needed outside the vacuum chamber either, which simplifies the
arrangement.
[0045] In the last method step D, after the removal of the pane
arrangement with the welded metal foil strips out of the second
vacuum chamber 13, a final treatment of the edge areas is
performed, that is, the application of a filler material 9 and the
bending of the laser-welded projecting areas of the metal foil
strips, and, if desired, the installation of a protective cover on
the finished edge connection.
* * * * *