Process for bonding an adhesive protective edging on the edge of a multilayer panel such as a spacecraft heat shield

The protection of the straight edges of multilayer panels (10), such as spacecraft thermal protection panels or heat shields, is ensured by an adhesive protection edging (14) having two adhesive, lateral zones bonded to the faces of the panel and a non-adhesive zone (18) placed on the edge of the panel. Following the removal of a non-adhesive protection (30b), a first adhesive, lateral zone (20b) is brought onto a working plane (22), through a slot (32), and is progressively bonded to the lower face of a panel (10) moving on said plane. The second lateral, adhesive zone is then turned down and pressed onto the upper face of the panel, after which the non-adhesive protection (30a) of said zone is removed.

DESCRIPTION 
The invention relates to a process making it possible to bond an adhesive 
protective edging to a straight edge of a multilayer panel such as a panel 
to be used as the thermal protection of a spacecraft (satellite, orbiting 
station, etc.). The invention also relates to a machine performing this 
process. 
The sensitive parts of spacecraft such as satellites or orbiting stations 
are usually covered with multilayer heat protection blankets or panels. 
These panels protect the aforementioned sensitive parts against the 
extreme temperature variations to which they are exposed, depending on 
whether or not they are oriented towards the sun. Such heat protection 
panels are normally referred to as "superinsulation". They are formed from 
a stack of extremely thin sheets usually made from plastic materials such 
as MILAN, KAPTON or DACRON (registered trademarks), which may or may not 
be metallized. The number of layers is dependent on the thermal protection 
which it is wished to obtain. 
Bearing in mind the nature of certain of the materials located within the 
stack forming such a multilayer panel, it is essential to protect the edge 
of the panel, so that it is not exposed directly to the vacuum or solar 
radiation. Thus, such an exposure would have the effect of rapidly 
disintegrating certain materials, which would immediately render 
inoperative the optical systems carried on the craft. This is clearly not 
admissible, bearing in mind the cost of spacecraft. 
It is also important that the protection of the edge of the panel is 
brought about without creating heat bridges between the different sheets 
forming it, because otherwise there would be a significant reduction in 
the effectiveness of the thermal protection. 
The protection of the edge of multilayer panels of this type is normally 
obtained by bonding along each of the edges of said panel an adhesive 
protective edging. More specifically, said adhesive protective edging is 
formed from a very wide adhesive strip, in the centre of which is bonded a 
central, non-adhesive strip. Thus, two lateral, adhesive zones are 
defined, which extend over the entire width of the edging and which are 
intended to be bonded to the opposite faces of the panel along the edge in 
question. The central, non-adhesive strip is intended to be positioned 
facing the panel edge. The thus formed adhesive protective edging is 
stored in wound form, each of the two lateral, adhesive zones being 
covered by an anti-adhesion protector. 
In the present state of the art, a first anti-adhesive protector is removed 
and then the corresponding lateral, adhesive zone is manually bonded to 
the panel. The latter is then turned round and the second anti-adhesive 
protector is in turn removed in order to permit the bonding of the 
corresponding lateral, adhesive zone of the protective edging on the other 
face of the panel. 
In order to avoid the creation of heat bridges between the different sheets 
of the panel, it is essential that the bonding of the protective edging is 
carried out without forming creases on the edges of said sheets. This is 
very difficult to obtain manually, due to the very limited thickness of 
the sheets forming the panels and the presence of static electricity in 
these sheets, bearing in mind the materials from which they are formed. 
Thus, when the second lateral, adhesive zone of the protective edging is 
folded onto the panel, the different sheets forming the latter tend to be 
attracted by said zone and are bonded thereto in an unsatisfactory 
position. In order that the bonding is satisfactory, it is therefore 
necessary to cut the protective edging into portions of limited length 
(always less than 100 mm, e.g. approximately 50 mm) and then successively 
put them into place along the panel edge.) 
The manual bonding of the protective edging on the edges of the multilayer 
panels is consequently a long and tedious operation, whose cost is high, 
because in itself this represents approximately 50 to 80% of the cost of 
the finished panel, as a function of the shape complexity. 
As illustrated by FR-A-2 618 771, it is known to bond a perforated, 
auto-adhesive reinforcing strip along the edge of a sheet of paper to one 
face of the said sheet, by means of a placing apparatus facilitating the 
relative positioning between the reinforcing strip and the sheet. However, 
the apparatus described in this document does not make it possible to 
solve the problem caused by the bonding of an adhesive protective edging 
to the two faces of a multilayer panel, along the edge of said panel. 
The invention specifically relates to a process making it possible to bond 
an adhesive protective edging to the straight edge of a multilayer panel 
such as a spacecraft heat protection panel and over a virtually unlimited 
length, without any risk of creating heat ridges within the panel and in a 
particularly simple and inexpensive manner. 
According to the invention, this result is obtained by means of a process 
for bonding an adhesive protective edging to a straight edge of a 
multilayer panel, characterized in that it comprises the following stages: 
bonding a first lateral, adhesive zone of the edging to a first face of the 
panel, along the straight edge, by depositing said first face of the panel 
on a working plane, unwinding the edging from a storage reel, removing a 
first anti-adhesive protector covering the first lateral, adhesive zone, 
bringing the latter between the working plane and the first face of the 
panel, so that it is in contact with said first face along the straight 
edge of the panel and simultaneous advance of the panel and the first 
lateral, adhesive zone on the working plane, 
application of a pressure to the panel along the straight edge, 
bending the edging in such a way that a second adhesive, lateral zone of 
the latter, covered with a second anti-adhesive protector, is bent onto 
the opposite face of the panel and 
removing the second anti-adhesive protector whilst maintaining a pressure 
on the panel, along the straight edge. 
In this process, in view of the fact that the first lateral, adhesive zone 
of the protective edging is bonded to the first face of the panel by 
making the latter advance in the direction defined by its straight edge, 
the bonding of said first lateral, adhesive zone takes place without any 
difficulty, no matter what its length. Moreover, in view of the fact that 
the adhesive protective edging is folded or bent onto the panel whilst a 
pressure is applied thereto and the anti-adhesive protector covering the 
second lateral, adhesive zone of the edging has not as yet been removed, 
the bonding of said second zone is also carried out without difficulty, no 
matter what its length, during the progressive removal of the second 
anti-adhesive protector. 
Advantageously, the straight edge of the panel is guided during its advance 
on the working plane. In a first embodiment of the invention, the bending 
or folding of the edging is carried out after cutting its ends, the panel 
then being stationary on the working plane. 
However, according to a second embodiment of the invention, the bending or 
folding of the edging takes place progressively during the advance of the 
panel on the working plane, following the bonding of the first lateral, 
adhesive zone and before cutting the ends of the edging. 
The invention also relates to a machine for bonding an adhesive protection 
edging to a straight edge of a multilayer panel, characterized in that it 
comprises: 
a working plane able to receive the panel, 
a reel for storing the adhesive protective edging, placed below the working 
plane, 
a means for removing a first anti-adhesive protector covering a first 
lateral, adhesive zone of the edging on leaving the storage reel, 
a slit formed in the working plane, for the passage of the first lateral 
zone on the working plane, at a location below a first face of the panel, 
along the straight edge, 
means for applying pressure to the panel resting on the working plane, 
along the straight edge, 
means for bending the edging on the opposite face of the panel and 
a means for removing a second anti-adhesive protector covering a second, 
lateral, adhesive zone of the edging. 
In the first embodiment of the invention, the means for bending or folding 
the edging comprise a bending hinge articulated on the working plane, 
downstream of said slit. The pressure application means then comprise a 
rule which can be placed on the panel along its straight edge and in front 
of the bending hinge. 
In the second embodiment of the invention, the edging bending means 
comprise a bending guide fixed to the working plane, so as to ensure a 
progressive bending of the edging during its advance on the working plane. 
The bending means also include a bending roller, which presses the second 
lateral, adhesive zone of the edging against the opposite face of the 
panel, downstream of the bending guide and upstream of the means for 
removing the second anti-adhesive protector. 
In the latter case, the machine also has a bonding roller, which presses 
the second lateral, adhesive zone of the edging against the opposite face 
of the panel, downstream of the means for removing the second 
anti-adhesive protector. Cutting means are then placed downstream of the 
bonding roller. 
In the second embodiment of the invention, the pressure application means 
advantageously comprise a pressing shoe or block placed above the working 
plane, along the straight edge of the panel and extending downstream into 
the vicinity of a downstream end of the bending guide.

In FIG. 1, reference numeral 10 designates in general terms a multilayer 
panel constituted by a stack of very thin sheets 12. When the panel 10 is 
a superinsulation panel for providing the heat protection of certain 
sensitive parts of a spacecraft such as a satellite or orbiting station, 
the sheets 12 forming it can in particular be sheets of KAPTON (registered 
trademark) aluminized on at least one face, sheets of MYLAR (registered 
trademark) aluminized on both faces and sheets of DACRON (registered 
trademark) or glass cloth, arranged in alternating manner. The number of 
sheets varies as a function of the thermal insulation quality which it is 
wished to obtain and the nature of the materials used. 
Bearing in mind the nature of the materials constituting certain of the 
sheets 12 of the stack, the exposure of these sheets to a vacuum and to 
solar radiation on the peripheral edge of the panel would lead to the 
rapid destruction of said sheets, at least in the peripheral region of the 
panel. This would lead to an efficiency loss on the part of the heat 
protection and in particular to an unacceptable pollution, which would 
rapidly render inoperative the optical systems carried on the craft. In 
order to avoid this risk, it is conventional practice to cover the edges 
of the panels 10 with an adhesive protective edging 14, as is 
diagrammatically illustrated in FIG. 1. 
This adhesive protective edging 14 comprises an adhesive strip 16, whose 
width of e.g. 25 mm is much larger than the thickness of e.g. 4 to 5 mm of 
the panel 10, as well as a central, non-adhesive strip 18, whose width of 
e.g. 5 mm is equal to or slightly larger than the thickness of the panel 
10. The adhesive strip 16 and the central, non-adhesive strip 18 can in 
particular be made from KAPTON (registered trademark). The central, 
non-adhesive strip 18 is bonded beforehand to the centre of the adhesive 
strip 16, so that the latter has two lateral, adhesive zones 20a, 20b on 
either side of the central, non-adhesive zone constituted by the strip 18. 
These lateral, adhesive zones 20a, 20b are intended to be bonded to the 
opposite faces of the panel 10, along the straight edge of the latter 
which requires protection, as illustrated in FIG. 1. 
As has already been stated, the putting into place of the adhesive 
protection edging 14 on the edges of the panels 10 has hitherto taken 
place manually. In view of the very limited thickness of the sheets 12 and 
the electrostatic nature of the materials forming certain of these sheets, 
the manual putting into place of the adhesive protection edging 14 
constituted a long and difficult operation requiring the application of 
successive portions of very limited length (less than 100 mm). Thus, the 
application of longer adhesive protection edgings would have led to 
wrinkling of the sheets 12 creating heat bridges, so that it would not be 
possible to obtain the desired heat protection. 
According to the invention, the adhesive protection edging 14 is bonded to 
the straight edges of the panels, such as the panel 10, in such a way that 
an unlimited edging length can be deposited in one piece without leading 
to the formation of heat bridges. 
A first machine making it possible to perform the bonding process of the 
invention will now be described relative to FIGS. 2 and 3. The machine 
illustrated in FIGS. 2 and 3 comprises a preferably horizontal working 
plane 22, whereof a straight edge 23 carries two guides 24, 26, which 
project upwards, respectively at the entrance and exit of the working 
plane. 
The entrance guide 24 is located at the entrance end of the machine, on the 
left-hand side in FIGS. 2 and 3. It makes it possible to guide the 
straight edge of the panel 10 to be coated with the adhesive protective 
edging 14. This protective edging is wound onto a storage reel 28, whose 
horizontal shaft or spindle 30 is positioned below the working plane 22 
and oriented in a direction orthogonal to the straight edge 23. On the 
reel 28, each of the adhesive, lateral zones 20a, 20b of the edging 14 is 
covered with an anti-adhesive protector 30a, 30b. 
With respect to the straight edge 23 of the working plane 22, the reel 28 
is positioned laterally in such a way that the lateral, adhesive zone 20b 
of the adhesive protection edging 14 is positioned below the working plane 
22, whereas the rest of the adhesive protection edging 14 (i.e. the 
central, non-adhesive strip 18 and the other lateral, adhesive zone 20a) 
is positioned beyond the straight edge 23. In addition, the reel 28 is 
located below a slot 32 formed in the straight edge 23 of the working 
plane 22, just downstream of the guide 24 with respect to the introduction 
direction of the panel 10. 
Taking account of the two characteristics described hereinbefore, the 
adhesive protection edging 14 can be unwound from the reel 28 through the 
slot 32, so that the lateral, adhesive zone 20b rests on the working plane 
22 downstream of the slot 32, along the straight edge 23 of said plane, 
the adhesive face of said zone 20b then being turned upwards. Before the 
adhesive protection edging 14 is brought into this position, the 
anti-adhesive protector 30b covering the lateral, adhesive zone 20b is 
disengaged therefrom, below the working plane 22 and as illustrated in 
FIG. 2. 
In that part of the working plane 22 located downstream of the slot 32 with 
respect to the introduction direction of the panel 10, a bending or 
folding hinge 34, which is best visible in FIG. 3, is articulated on the 
edge 23 of the working plane 22, so as to be bent onto the latter, e.g. by 
acting on a handle 36. The bending hinge 34 extends forwards up to the 
exit guide 26. 
The bonding machine illustrated in FIGS. 2 and 3 also comprises a rule 38, 
whose length is at least equal to that of the hinge 34 and preferably 
close to that of the working plane 22. On one of its sides the rule 38 has 
a pawl 40 of very limited thickness, which rests on the panel 10 placed on 
the working plane 22 and can be placed along the edge 23 of the latter. 
The thickness of the pawl 40 is sufficiently small for the hinge 34 to be 
then turned down onto the working plane 22, as illustrated in FIG. 3. 
In the vicinity of its end which is to be turned towards the front of the 
machine, the pawl 40 of the rule 38 has a window 42 (FIG. 2), whose 
function will be described hereinafter. 
The bonding of an adhesive protection edging 14 to a straight edge of a 
multilayer panel 10 with the aid of the machine described hereinbefore 
with reference to FIGS. 2 and 3 takes place in the following way. 
With the rule 38 not placed on the useful part of the working plane 22, the 
operator deposits the panel 10 on the left-hand entrance end of the 
working plane, so that the straight edge to be coated with the adhesive 
protection edging 14 is placed along the straight edge 23 of the working 
plane and bears against the entrance guide 24. This putting into place 
occurs in such a way that the edge of the panel 10 turned towards the 
front of the machine, i.e. to the right on considering FIGS. 2 and 3, does 
not cover the slot 32 and is instead in the vicinity thereof. 
The operator then unwinds a small length of adhesive protection edging 14 
from the reel 28 through the slot 32, after having ensured the removal, 
below the working plane, of the anti-adhesive protector 30b covering the 
lateral, adhesive zone 20b. In order that said removal then takes place 
automatically during the unwinding of the adhesive protection edging, the 
end of the anti-adhesive protector 30b can be connected to a not shown 
tensioning system. Thus, unwinding takes place, above the working plane 22 
and downstream of the slot 32, of a length of the adhesive protection 
edging 14 limited to a few centimeters. In order to maintain the tension 
of the adhesive protection edging on leaving the reel 28, its end located 
above the working plane 22 can also be connected to a tensioning system 
such as a counterweight. 
When these preparatory operations are ended, the operator advances the 
panel 10 on the working plane 22 whilst maintaining the straight edge 
thereof to be protected in contact with the guide 24. As soon as the face 
of the panel 10 resting on the working plane 22 passes beyond the slot 32, 
the part of said face adjacent to the straight edge to be protected 
reaches the adhesive, lateral zone 20b of the protective edging 14 and is 
progressively bonded thereto, whilst entraining with it the edging 14, 
during its advance on the working plane 22. This results in the edging 14 
extending slightly beyond the front (right hand) edge of panel 10 as this 
panel 10 advances along the table 22 beyond the slit 32. 
In view of the fact that the panel 10 and the adhesive protection edging 14 
advance simultaneously in the same direction on the working plane 22, 
bonding easily takes place in a progressive manner over a length which is 
not limited in this case other than by the length of the hinge 34. This 
operation can be performed manually, or with the aid of a panel traction 
mechanism not illustrated in the drawings. It continues until the leading 
edge of the panel 10 is flush with the front end of the hinge 34. This 
gives the position illustrated in FIG. 2. 
The adhesive protection edging 14 is then cut in front of the slot 32 by 
any appropriate cutting system, so that portion of the edging projecting 
beyond the edge of the panel 10 to be protected can be bent onto the upper 
face of the latter. 
In order that said operation can be performed without any risk of the 
sheets forming the multilayer panel 10 forming creases leading to the 
creation of heat bridges, on said panel 10 and along its straight edge to 
be protected, is placed the rule 38, whilst the anti-adhesive protector 
30a is still in place on the adhesive, lateral zone 20a of the protective 
edging 14. The position then occupied by the rule 38 is illustrated by 
lines in FIG. 3. In this position, the pawl 40 is placed along the 
straight edge 23 of the working plane. 
The operator then bends the hinge 34 onto the pawl 40 using the handle 36. 
Therefore the adhesive protection edging 14 is preshaped in the position 
which it must finally occupy after bonding. 
The operator then brings the hinge 34 into its initial, open position and 
disengages from the adhesive, lateral zone 20a of the protective edging 14 
the end of the anti-adhesive protector 30a. More specifically, the 
operator folds said end substantially to 90.degree. with respect to the 
straight edge 23 of the working plane 22 over a relatively small length, 
but which is still sufficient to ensure that the end of the protector 
projects slightly beyond the hinge 34 when the latter is again bent onto 
the upper face of the panel 10. The portion of the lateral, adhesive zone 
20a of the protective edging 14 which is no longer covered with its 
anti-adhesive protector 30a is then positioned in front of the pawl window 
42. 
The hinge 34 is then bent onto the upper face of the panel 10 and onto the 
pawl 40, so that the portion of the lateral, adhesive zone 20a having no 
anti-adhesive protector is bonded to the panel 10 through the window 42 of 
the pawl 40. The rule 38 is then gently removed by the operator, whilst 
the hinge 34 remains bent in the manner illustrated in FIG. 3. 
To complete the bonding operation, the operator only has to grasp the end 
of the anti-adhesive protector 30a projecting beyond the hinge 34 and pull 
on said end whilst pressing onto the hinge. The lateral, adhesive zone 20a 
is then progressively bonded to the upper face of the panel 10, without 
any parasitic creases being created in the sheets forming the said panel. 
If the length of the straight edge of the panel 10 which is to be protected 
exceeds the length of the hinge 34, as is the case in FIGS. 2 and 3, the 
operation described hereinbefore can be repeated the necessary number of 
times until the entire panel edge is covered with a protective edging. 
However, it should be noted that the use of a hinge 34 longer than that 
illustrated in the drawings can make it possible to protect each of the 
edges of the presently used panels 10 in a single operation. 
The bonding machine described hereinbefore with reference to FIGS. 2 and 3 
requires manual interventions, so that it is only usable in connection 
with the manufacture of small numbers of multilayer panels. However, 
compared with the conventional bonding process, it already leads to 
essential advantages concerning the duration and cost of the operation. 
With reference to FIG. 4, a description will now be given of a preferred 
embodiment of a bonding machine for performing the process according to 
the invention. This machine makes it possible to envisage the bonding of 
an adhesive protective edging in a substantially continuous manner on the 
straight edges of multilayer panels 10 positioned one after the other on 
the machine. 
In the embodiment illustrated in FIG. 4, the working plane 22 is 
materialized by the upper face of a conveyor belt 44, which can travel on 
a horizontal table 46. The straight edge to be protected of each of the 
panels 10 placed on the conveyor belt 44 is positioned along the straight 
edge 23 of the table 46 and guided to the entrance and exit thereof by an 
entrance guide 24 and an exit guide 26. 
As in the first embodiment described relative to FIGS. 2 and 3, the machine 
of FIG. 4 has a storage reel 28 onto which is wound the adhesive 
protective edging 14. The horizontal spindle of the reel 28 is orthogonal 
to the straight edge 23 of the table 46. This reel 28 is placed below the 
table 46 facing the slot 32 formed in the edge 23, so that the lateral, 
adhesive zone 20b of the protective edging 14 can be placed on the upper 
face of the table 46, along the edge 23, alongside the conveyor belt 44 
and in front of the slot 32. The adhesive face of the lateral, adhesive 
zone 20b turned towards the upwards direction when it arrives on the upper 
face of the table 46, then loses its anti-adhesive protector 30b, which is 
detached from the edging 14 below the table 46 and is then e.g. rewound 
onto a mandrel 48. 
The bonding machine illustrated in FIG. 4 also comprises a pressing block 
38, which is permanently applied to the upper face of the panels 10 placed 
on the working plane 22 along the straight edge 23 of the table 46. In its 
portion closest to the edge 23, the pressing block 38 has a reduced 
thickness pawl 40. The pressing block 38 can be connected to the table 46 
by brackets 50. A regulatable, elastic system 52 is advantageously 
provided between each of the brackets 50 and the pressing block 38, so as 
to be able to engage the latter on the upper face of the panels 10 with a 
substantially constant force, no matter what the thickness of said panels. 
Downstream of the slot 32 with respect to the advance direction of the 
conveyor belt 44, the straight edge 23 of the table 46 carries a bending 
guide 54 making it possible to progressively bend down onto the pawl 40 
that part of the adhesive protection edging 14 projecting beyond the edge 
23, as the panels 10 and the protective edging 14 advance on the working 
plane 22. In the embodiment of FIG. 4, said bending guide incorporates 
pins 54. However, the bending guide could also assume any other 
configuration and in particular that of a continuous spout. 
Immediately downstream of the bending guide 54 and the adjacent end of the 
pressing block 38, the bending of the adhesive protection edging 14 is 
completed by a pressing roller 56 supported by the exit guide 26. This 
horizontally axed pressing roller 56 is placed above the working plane 22 
and positioned transversely with respect to the advance direction of the 
conveyor belt 44. It applies a controlled pressure to the upper face of 
each of the panels 10 travelling on the belt, as well as to that portion 
of the adhesive protection edging 14 folded onto said upper face by the 
folding guide 54. This pressure can advantageously be regulated, 
particularly to take account of the thickness of the panels 10. 
Immediately downstream of the pressing roller 50 with respect to the 
advance direction of the conveyor belt 44, the exit guide 26 also 
supports, substantially above the working plane 22, a mandrel 58 onto 
which is wound the anti-adhesive protector 30a. It should be noted that 
said protector is only removed at this level and covers the lateral, 
adhesive zone 20a of the protective edging 14 folded onto the upper face 
of the panel 10 up to the pressing roller 56. In the same way as the 
mandrel 48 used for the winding up of the anti-adhesive protector 30b, the 
mandrel 58 can be driven by a motor. 
Immediately downstream of the mandrel 58 used for removing the 
anti-adhesive protector 30a from the lateral, adhesive zone 20a of the 
protective edging 14, the bonding of said edging is completed by means of 
a bonding pressing roller 60 supported by the exit guide 26. This bonding 
pressing roller has essentially the same characteristics as the bending 
pressing roller 56, i.e. it is placed above the working plane 22, along a 
horizontal axis and is transversely oriented with respect to the advance 
direction of the conveyor belt 44, so as to apply a predetermined force to 
the upper face of the panels 10 and to that portion of the adhesive 
protective edging 14 turned down onto said face. When the panels 10 pass 
out of the pressing roller 60, the bonding of the adhesive protective 
edging 14 is completed. 
Finally, downstream of the bonding pressing roller 60, the edge 23 of the 
table 46 supports a preferably motorized cutting device 62. The actuation 
of the cutting device 62 makes it possible to cut the adhesive protective 
edging 14 behind the trailing edge of a group of panels 10. 
The starting of the machine according to FIG. 4 takes place in the same way 
as described relative to the machine of FIGS. 2 and 3. As soon as the 
lateral, adhesive zone 20b of the adhesive protective edging 14 starts to 
stick below the panel 10, the edging is moved with the panel by the 
conveyor belt 44. If necessary, tensioning strips such as 64 can be bonded 
to the front of each of the panels to ensure that the upper sheets of the 
panels do not bend when they pass below the pressing rollers 56, 60 or to 
ensure that the panels are not positioned slantwise during their advance 
on the machine. An identical system can be used for tensioning the front 
end of the adhesive protective edging 14. 
The above description shows that the bonding process according to the 
invention can be performed in a more or less automated manner, as a 
function of the desired production rates. However, in all cases, this 
process makes it possible to bond adhesive protective edgings to virtually 
unlimited lengths without any risk of creating heat bridges within the 
panels. This leads to a considerable time and financial gain compared with 
the hitherto used procedures for performing the same operations.