Note: Descriptions are shown in the official language in which they were submitted.
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DEEPLY EMBOSSED SHEET
1 AND METHOD FOR THE PRODUCTION THEREOF
The invention herein relates to deeply embossed
sheet material and to a method and apparatus for the production
thereof. More specifically the present invention relates to
deeply embossed single sheets of sheet metal su;table for use
in reflective thermal insulation structures.
Reflective thermal insulation structures are constructed
of metallic enclosing frames containing therein a plurality
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of spaced-apart reflective metal sheets. A number of such
structures are in use in the nuclear power industry~ where
reflective insulation is widely used for the thermal insulation
of nuclear reactors and associated piping. In one such type
of structure individual reflective metal sheets are separated
by protruding standoffs embossed from the surfaces of each
sheet. Reflective thermal insulation structures for use with
piping are known as well as flat panel insulation structures.
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, Sequential forming of sheet metal is also known.
Prior art reflective thermal insulation structures
u~ilizing semi-rigid or rigid sheet metal with standoff
protuberances or spacers commonly have holes and tears.
These holes and tears are often formed in the metal sheet as
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the sheet metal is being embossed with the protuberances. A
j.,
;~ ^ disadvantage of these holes and tears is that they allow
convective heat transfer (loss) from one layer of air formed
between stacked sheets of the embossed sheet metal to another
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; layer oF air. This interface and movement of air between
layers substantially lowers the thermal efficiency of the
reflective insulation structure. Thus, in an ideal situation
there are no ruptures or breaks in the sheet metal to permit
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heat transfer by air convection currents. Another disa~vantage
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1 of the ruptures and breaks in the sheet metal is that if the
standoff protuberances are significantly torn, their integrity
~- may be affected to such an extent that the protuberances will
collapse and cause the stacked sheets to have a greater
surface area ;n contact with each other resulting in an
increase of heat transfer by direct conduction.
It is an object of the present invention to overcome
the disadvantages of prior art reflective thermal insulation
structures by providing a method and appara~us for the production
of a deeply embossed sheet material especially suitable for
use in reflective thermal insulations in which any appreciable
tearing or puncturing of the sheet material is eliminated.
Accordingly, the present invention provides a
method for the deep embossment of sheet material especially
suitable for use in reflective thermal insulation, the method
comprising first embossing the sheet material with a relief
pattern of a plurality of spaced-apart hills not more than 1
cm. in height, the area around the hills forming a plurality
of intersecting valleys, and thereafter, embossing on the
. .
; relief pattern, a deep embossment pattern comprising a plurality
of large protuberances projecting outwardly from a surface of
:
the sheet material, each protuberance having a base wider than
its apex, wherein the base is sufficiently large relative to
the hills to include at least portions of several of the hills
and wherein the height of the protuberances is greater than
the height of the hills.
The present invention also provides an apparatus for
the deep embossment of sheet material especially suitable for
use in reflective thermal insulation, the apparatus comprising
a first pair of rolls~ at least one of the rolls of the first
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1 pair having an embossment pattern suitable for embossing a
relief pattern on the sheet material, and a second pair of
rolls having a surface pattern suitable for embossing deep
protuberances from a surface of the sheet material on the
relief pattern.
The present invention further provides a sheet of
; sheet material especially suitable for use in reflective
thermal insulation, the sheet having on a surface thereof a
relief pattern comprising a plurality of hills and intersecting
valleys, the hills being spaced from each other and projecting
outwardly from a surface of the sheet material not more than 1
cm., and superimposed thereon a deep embossment pattern comprising
a plurality of protuberances, each protuberance having a base
wider than its apex, wherein the base is sufficiently large
relative to the hills to include at least portions of several
of the hills and wherein the height of the protuberances is
greater than the height of the hills.
The present invention also provides a reflective
thermal insulation comprising a plurality of the embossed
sheets manufactured according to the present invention and a
plurality of spacer sheets, each of the embossed sheets
:; manufactured according to the present invention being separated
by a spacer sheet positioned in an abutting relationsh~p with `
only the apices of the protuberances.
The present invention also provides a reflective
insulation comprising a plurality of the embossed sheets
manufactured according to the present invention, each of the
embossed sheets being positioned in an abutting relationship
with only the apices of the protuberances of another of the
sheets.
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1 The product of the present invention is especially
suitable for use in reflective thermal insulation structures.
The deep protuberances formed in the sheet material separate
adjacent sheets when stacked in an insulation structure
,~ such that the only contact points between adjacent sheets
are at the apices of the protuberances. This minimal contact
between adjacent sheets stacked in an insulation structure
minimizes heat transfer by conduction and the absence of
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significant tearing of the sheets minimizes heat transfer by
convection, thus providing an e~ficient reflective insulation
structure which is relatively inexpensive to manufacture
when compared to known reflective thermal insulations which
use expensive non-integral spacers to separate individual
.,
sheets of reflective sheet material.
FIG. 1 illustrates schematically one embodiment of
,~.;
~` the apparatus according to the present invention for the
deep embossing of sheet material.
~i~ FIG. 2 is a partial elevation view showing a
typical surface configuration of a pair of relief patterned
embossing rolls.
FIG. 3 is a cross-sectional view of the relief
patterned embossing rolls taken on line 3-3 of FIG. 2, also
showing the relief pattern embossing of a sheet of sheet
; material.
FIG. 4 is a perspective view of a portion of a
sheet of sheet material prior to the deep embossing having
the relief pattern embossed thereon.
FIG. 5 is a partial elevation view showing a
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; typical surface configuration of a pair of deep embossing
rolls.
FI6. 6 is a cross-sectional view of the deep embossing
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1 ro~ls taken on line 6-6 of FIG. 5, also showing the deep
embossing of a sheet of sheet material. ..
.. FIG. 7 is a perspective view of a segment of sheet. material having thereon both the relief pattern and the deep embossment pattern.
FIG. 8 is a partial perspective view of a typical
reflective insulation structure manufactured in accordance
: with the present invention.
FIG. 9 is a frontal view of one embodiment of a
projection used in cooperation with a hole in one of the deep
` embossing rolls. .
FIG. 10 is a partial cross-sectional frontal elevation
. of another embodiment of a projection showing the projection; with a core pin and a collar.
,, . The apparatus as a whole is illustrated schematically
i in FIG. 1. A sheet material 2 to be embossed, normally 1 to
~ 5 mils thick, is typically a reflective metal foil such as
: aluminum or stainless steel. The sheet material 2 passes from
a supply roll 3 through a series of straightening rollers -
generally designated by a reference numeral 69 into a cutter
9 which severs the continuous sheet material into individual
. . ,
segments 11 of a predetermined length. The straightening
rolls 6 and the cutter 9 are conventionally designed and
nnrmally operate automatically. Suitable conventional means
(not shown) may be used to regulate the length of the metal
sheet material segments 11.
The individual metal sheet material segments (here-
inafter referred to simply as "sheets") are then transported
by a conveyor 12 into the nip 17 between a pair of rolls 15
and 18 which together constitute a relief patterning unit
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generally reFerred to by reference numeral 21 and illustrated
in more detail in FIGS. 2 and 3. The relief patterned embossing
rolls 15 and 18 impart the pattern exemplified in FIG. 4 to
the surfaces of the sheet material segments 11. The surfaces
of the illustrated rolls 15 and 18 have the configuratiorl so
as to form small hills across both surfaces of the sheet
material, reduce the sheet material in overall width and
length slightly, and provide a degree of "slack" in the sheet
material which permits the subsequent impressment of a pattern
.
of deep protuberances by a deep embossing unit 30. To this
` end the rolls 15 and 18 have a pattern of counterpart elevations 36 and depressions 39. This pattern of depressions and
elevations can be in the form of "pebbled" surfaces, or
raised and depressed pyramids, squares, rectangles and the
like of the type which produce a "hills and valleys" pattern.
The "hills-and-valleys" pattern comprises a plurality of small
"h~lls" and intersecting "valleys" wherein the hills are
spaced apart and no more than 1 cm. in height, usually only
about 0.5 to 5 millimeters. The spaces between the hills are
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referred to as "valleys". A typical pattern for the relief
patterned embossing rolls 15 and 18 for embossing both surfaces
of a sheet is shown in FIG. 2.
The sheet may also be embossed with the raised
` surfaces (hills) all projecting from one surface of the
sheet. A typical configuration for a pair of relief patterned
embossing rolls for embossing only one surface of a sheet
would include only one patterned relief roll; the opposing
roll would have a smooth, compressible surface, e.g. rubber,
.,
which would permit the embossment of the hills across a
surface of the sheet when elevations on the patterned roll
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-~ 1 were pressed into the sheet.
The exact nature of the l'hills-and-valleys" pattern
is not critical, so long as the depth and frequency of the
hills and valleys provide sufficient slack in the sheet
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material to allow the subsequent formation of the deep protu-
berances without significant tearing of th~ sheet material.
In one suitable pattern the hills are spaced-apart in two
substantially mutually perpendicular directions. In another
suitable pattern, the hills are positioned randomly so that
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~ 10 there are only short segments of directionality, the overall
- effect being multi-directional. A uni-directional pattern,
such as simple parallel or essentially parallel corrugations,
ho~ever, is unsuitable since such a pattern does not provide
sufficient slack in the sheet material to permit the subsequent
deep impressment of the protuberances. The spaced-apart hills
and intersecting valleys thus cooperate to form a pattern
- extending across at least one surface of the sheet, the hills
of the pattern being spaced-apart raised squares, rectangles,
or the like each not exceeding about 10-20 millimeters in
-`i` 20 ind;vidual width and length. For example, a pattern of 5 ~ -
millimeter square elevations (the "hills") separated by
approximately 3 millimeter spaces (the "valleys") and embossed
to a depth of approximately 1 millimeter, the hills extending
in two directions across both surfaces of a 3 mil thick
.
stainless steel sheet, permits the subsequent embossment of a
pattern of deep conical protuberances ~2.
":
The relief patterning unit 21 produces a relief
patterned sheet 16 illustrated in FIG. ~. Also, as shown in
- FIG. ~, the relief pattern of sheet 16 is generally not in
~: 30 sharp relief. The relief patterned sheet 16 is typically an
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intermediate product which is subsequently transported by
` conveyor 22 into the nip 26 of a pair of rollers 24 and 27
which together constitute the deep embossing unit 30 illustrated
in FIGS. 5 and 6. The deep embossing unit 30 imparts an
additional pattern of large protuberances 42 which project
outwardly from a surface of the relief patterned sheet 16. As
shown in FIGS. 5 and 6, the deep embossing rolls 24 and 27
; have a configuration so as to form the spaced-apart conical
protuberances 42 projecting in alternate directions ~rom both
surfaces of a sheet (see FIG. 7). In one embodiment, the deep
embossment pattern is formed by the cooperation of a pattern
of projections 48 in one roll corresponding with a pattern of
holes 51 in the opposing roll.
The projections 48 are designed such that when
e~tended through their corresponding hole to a desired depth,
there is sufficient clearance between the outer circumference
of the projections and the circumference of their corresponding
; hole to accommodate the thickness of the sheet. In one
embodiment, as exemplified in FIG. lO, the projec~ion 48
comprises a metal core pin 44 over which is placed a collar
47. The core pin 44 is fastened to one of the deep embossing
rolls by a conventional fastening means such as by cooperating
threads or by a "push-fit". The tip of the pin is preferably
rounded (e.g. spherical) to minimize the possibilities oF the
metal tearing when the protuberances are formed. The collar
47 is a hollow truncated cone which fits over the pin 44 and
is retained thereon by frictional contact or is fastened in
position by some conventional means. The collar is preferably
manufactured from a material that does not build up heat due
30 to its frictional contact with the sheet being embossed. One
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; 1 material which has been found to be especially suitable is a
durable, heat resistant urethane. Other materials, of course,
can be used provided that they do not tend to build up frictional
heat and so long as any projections comprised of the material
are sufficiently durable to withstand the forces exerted on
them when pressed into the metal sheet.
In another embodiment, the projections are a plurality
of rounded-apex cones 49 with an attachment means 50 (see FIG.
- 9). The rounded (e.g. spherical) apex cone 49 is comprised of
the same type of material suitable for use in the collar 47
discussed above.
The conical or semi-conical shape of the projection
is very advantageous since such shapes increase the surface
area of contact between the projection and the sheet, thus
decreasing the amount of deformation stress exerted on a unit
area of the sheet, especiially on that point of the sheet which
is first contacted by the projection. By deminimizing the
.
~ amount of stress exerted on a unit area of the sheet, the
; likelihood of tearing the metal during the formation of the
protuberances is also minimi~ed.
Impressment of the protuberances 42 from both
., .
surfaces of the sheet is accomplished by having both the
; projections 48 and the holes 51 on each o~ the deep embossing
~ rolls 24 and 27. In the configuration shown there are an
~ .
' equal number of projections 48 and holes 51 on each roll;
; however, this is not essential. A predominance of the conical
. ..~
~ protuberances 42 could be projected from one surface of the
ri sheet by constructing one deep embossing roll with a pre-
:.
~, dominance of the holes and the other deep embossing roll with
a predominance of the corresponding projections 48. This
,
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1 concept can, of course~ be ultimately extended to the placement
of all the proiections ~8 on one deep embossing roll and all
of the holes 51 on the opp~sing deep embossing roll to form
the protuberances 42 such that they project entirely from only
one surface of the sheet.
Like the "hills and valleys" pattern, the conical
protuberances also extend in two directions across at least
one surface of the sheet material. Depending on the configura-
tion of the deep embossing rolls 24 and 27, the pattern of
` 10 protuberances may be somewhat random or may have varying
degrees of regularity. The base of the protuberance 42 is
sufficiently large relative to the hills of the relief pattern
that each base includes at least pGrtions of several of the
hills formed by the relief patterning unit 2l. The height of
the protuberances is such that if a sheet of sheet material is
positioned in an abutting relationship with the apices of the
protuberances on another sheet of sheet material, the apices
'
- of the protuberances will generally provide the only points of
contact between the two sheets. For example, in one embodiment
- 20 of the present invention protuberances 42 are approximately 50millimeters in diameter, 15 millimeters in height, and spaced
on approximately lO0 millimeter centers. Thus, the deep
;~ embossment of the sheet material by deep embossing unit 30
forms the protuberances which serve as separators or spacers
when individual sheets of sheet material are stacked as
components of a thermal insulation structure.
It has been found that these two embossing steps
(wherein a relief pattern is first embossed and then a pattern
of deep protuberances) are necessary in order to obtain a
sheet as shown in FIG. 7 without significant puncturing or
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l tearing of the sheet. Merely attempting to impress deep
protuberances in a non-embossed shee-t is generally unsatis-
factory, for instead of forming protuberances, a single step
deep embossing procedure often results in the puncturing or
tearing of the rigid or semi-rigid sheet material. The
sequential embossment of the two patterns as taught in the
present invent;on, however, results in forming deep protu-
berances without s;gnificant tearing of the sheet material
since the first embossment of the sheet by the relief patterned
` 10 rolls provides more metal ;n a unit of area than was i~ the
same unit of area prior to the relief patterning of the sheet
; material. Thus, when the deep protuberances 42 are subsequently
formed, the metal is not stretched beyond the point at which
the metal fails. Consequently, the two steps oF embossing are
critical to this invention and it is necessary that the
relief patterning step precede the deep embossing step.
; Following the deep embossing step, the individual
sheets 75 (now containing the relatively deep protuberances 42
as well as the hills-and-valleys pattern) are transported by a
conveyor 31 to a collecting device 33, as exemplified in FIG.
l by a simple collection bin or rack.
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The apparatus of the present invention is constructed
of any suitable conventional material, normally steel.
O~viously, the heavier the gauge of sheet material to be
, embossed, the more rugged the surfaces oF the rolls 15, 18, 24and 27 and the elevatlons 36 and the projections 48 must be.
As illustrated in the accompanying figures, the
embossing units 21 and 30 provide only repeated embossments
.
of the relief pattern and the deep embossment pattern.
However, it is within the scope of this invention to provide
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1 easily interchangeable rolls to vary the embossing patterns as
desired. The rolls can also be adjustable so as to be able to
vary the amount of clearance between the rolls constituting an
embossing unit.
Further, although FIG. 1 shows the sheet material
being cut by the cutter 9 into individual sheets 11 prior to
the embossment steps, it is also within the scope of the this
invention to cut the sheet material into individual segments
either after the relief embossment step or after the deep
embossment step.
A typical reflective thermal insulation structure
utilizing the sheets manufactured in accordance with the
` present invention is shown in FIG. 8. A plurality of sheets
75 having the deep protuberances 42 and a plurality of spacer
sheets 77 are partially enclosed in a caslng 78. The spacer
sheets 77 do not have the deep protuberances 42 impressed
,:
therein. Although the surfaces of the spacer sheets can be
entirely non-embossed, in a preferred embodiment of this
. .
invention, both surfaces of the spacer sheets are embossed
with some type of relief pattern. For example, the spacer
sheets may comprise a plurality of the relief patterned
sheets 16. The conical protuberances 42 separate the sheets
75 from adjacent spacer sheets 77 positioned in an abutt;ng
relationship with the apices of the protuberances, and ~enerally
the protuberances 42 form the only points of contact between
j the adjacent sheets 75 and 77. The insulation structure can
.
be flat as shown in FIG. 8 or curved. The number of sheets
, necessary depends on the size of the insulation structure
; and the quantity of heat to be contained, but ordinarily about
5 to 24 sheets are found sufficient. The sheets 75 and 77 are.,, ~:
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1 retained in the casing 78 by a means such as straps 81, per-
forated plates, or the like.
While the spacer sheets 77 are used in the preferred
embodiment of a reflective thermal insulation structure, this
; is not essential. A plurality of sheets 75 can be positioned
in an adjacent relationship such that the only points of
contact between adjacent sheets 75 are at the apices of the
protuberances of each sheet.
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