U.S. patent application number 14/188494 was filed with the patent office on 2014-09-04 for expanded metal and process of making the same.
This patent application is currently assigned to WALLNER TOOLING\EXPAC, INC.. The applicant listed for this patent is WALLNER TOOLING\EXPAC, INC.. Invention is credited to MICHAEL H. WALLNER, PAUL WALLNER.
Application Number | 20140245711 14/188494 |
Document ID | / |
Family ID | 43447034 |
Filed Date | 2014-09-04 |
United States Patent
Application |
20140245711 |
Kind Code |
A1 |
WALLNER; MICHAEL H. ; et
al. |
September 4, 2014 |
EXPANDED METAL AND PROCESS OF MAKING THE SAME
Abstract
An expanded metal is provided including a plurality of integral
strands defining diamond shapes, each diamond shape having a long
dimension as measured from two opposing vertices and a short
dimension, generally transverse to the long direction, as measured
between two other opposing vertices, such that the long dimension
is less than twice the short dimension.
Inventors: |
WALLNER; MICHAEL H.; (ALTA
LOMA, CA) ; WALLNER; PAUL; (ALTA LOMA, CA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
WALLNER TOOLING\EXPAC, INC. |
RANCHO CUCAMONGA |
CA |
US |
|
|
Assignee: |
WALLNER TOOLING\EXPAC, INC.
RANCHO CUCAMONGA
CA
|
Family ID: |
43447034 |
Appl. No.: |
14/188494 |
Filed: |
February 24, 2014 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
12891606 |
Sep 27, 2010 |
8696781 |
|
|
14188494 |
|
|
|
|
61246943 |
Sep 29, 2009 |
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Current U.S.
Class: |
55/525 ;
428/596 |
Current CPC
Class: |
B21D 31/04 20130101;
B01D 39/2041 20130101; B01D 46/521 20130101; Y10T 428/12361
20150115; Y10T 29/18 20150115; B01D 2265/06 20130101 |
Class at
Publication: |
55/525 ;
428/596 |
International
Class: |
B01D 39/20 20060101
B01D039/20; B01D 46/52 20060101 B01D046/52 |
Claims
1. An expanded metal comprising a plurality of integral strands
defining diamond shapes, each diamond shape having a first
dimension as measured from two opposing vertices and a second
dimension, generally transverse to the first dimension, as measured
between two other opposing vertices, wherein said expanded metal is
formed by slitting a sheet of metal thereby preliminary expanding
said metal, wherein said slit preliminary expanded metal having
been further expanded after slitting along a direction by at least
15% per linear dimensional unit to form said expanded metal, and
wherein the second dimension is along the direction of
expansion.
2. The expanded metal of claim 1 wherein the second dimension is
equal to the first dimension.
3. The expanded metal of claim 1 wherein each vertex is expanded
beyond in plastic yield point.
4. The expanded metal of claim 1 wherein each strand has a width of
0.017 inch.
5. The expanded metal of claim 1 wherein the first dimension is
less than twice the second dimension.
6. The expanded metal of claim 1 wherein the second dimension is
about equal to the first dimension.
7. The expanded metal of claim 1 wherein said strands have been
expanded beyond their plastic yield point.
8. The expanded metal of claim 1 wherein the slit preliminary
expanded metal has been expanded along the direction by at least
25% per linear dimensional unit.
9. The expanded metal of claim 1 wherein the slit preliminary
expanded metal has been expanded along the direction by at least
28% per linear dimensional unit.
10. The expanded metal of claim 1 wherein the slit preliminary
expanded metal has been expanded along the direction by at least
30% per linear dimensional unit.
11. The expanded metal of claim 1 wherein after slitting the slit
preliminary expanded metal first dimension is decreased by at least
15%.
12. The expanded metal of claim 1 wherein after slitting the slit
preliminary expanded metal first dimension is decreased by at least
18.8%.
13. An expanded metal formed by slitting a sheet of metal thereby
preliminary expanding said metal and then further expanding said
slit preliminary expanded metal along a direction, said slit
preliminary expanded metal comprising a plurality of integral
strands defining diamond shapes, each diamond shape having a first
dimension as measured from two opposing vertices and a second
dimension, generally transverse to the first direction, as measured
between two other opposing vertices, wherein the second direction
is along the direction of expansion, and wherein after slitting,
the slit preliminary expanded metal first dimension is decreased by
at least 15%.
14. The expanded metal of claim 13 wherein the first dimension is
less than twice the second dimension.
15. The expanded metal of claim 13 wherein the second dimension is
about equal to the first dimension.
16. The expanded metal of claim 13 wherein said strands have been
expanded beyond their plastic yield point.
17. The expanded metal of claim 13 wherein after slitting, the slit
preliminary expanded metal first dimension is decreased by at least
18%.
18. The expanded metal of claim 13 wherein after slitting, the slit
preliminary expanded metal first dimension is decreased by at least
18.8%.
19. The expanded metal of claim 13 wherein after slitting, the slit
preliminary expanded metal first dimension is decreased by at least
20%.
20. The expanded metal of claim 13 wherein after slitting, the slit
preliminary expanded metal first dimension is decreased by at least
23%.
21. The expanded metal of claim 13 wherein the slit preliminary
expanded metal has been further expanded along the direction by at
least 25% dimensional unit.
22. A filter comprising a filter medium reinforced with an expanded
metal, wherein said reinforced filter medium and said expanded
metal are pleated, wherein said expanded metal is formed by
slitting a sheet of metal preliminary expanding said metal and then
further expanding said slit metal along a direction, said slit
preliminary expanded metal comprising a plurality of integral
strands defining diamond shapes, each diamond shape having a first
dimension as measured from two opposing vertices and a second
dimension, generally transverse to the first direction, as measured
between two other opposing vertices, wherein the second direction
is along the direction of expansion, and wherein after slitting,
the slit preliminary expanded metal first dimension is decreased by
at least 15%.
23. The filter of claim 22 wherein the first dimension is less than
twice the second dimension.
24. The filter of claim 22 wherein the second dimension is about
equal to the first dimension.
25. The filter of claim 22 wherein said strands have been expanded
beyond their plastic yield point.
26. The filter of claim 22 wherein after slitting, the slit
preliminary expanded metal first dimension is decreased by at least
18%.
27. The filter of claim 22 wherein after slitting, the slit
preliminary expanded metal first dimension is decreased by at least
18.8%.
28. The filter of claim 22 wherein after slitting, the slit
preliminary expanded metal first dimension is decreased by at least
20%.
29. The filter of claim 22 wherein after slitting, the slit
preliminary expanded metal first dimension is decreased by at least
23%.
30. The filter of claim 22 wherein the slit preliminary expanded
metal has been further expanded along the direction by at least 25%
per linear dimensional unit.
31. The filter of claim 22 wherein after being pleated said
expanded metal does not spring back toward its unpleated
position.
32. A filter comprising a filter medium reinforced with an expanded
metal, wherein said reinforced filter medium and said expanded
metal are pleated, wherein said expanded metal is formed by
slitting a sheet of metal by a die and then expanding said slit
metal along a direction, said expanded metal comprising a plurality
of integral strands defining diamond shapes, each diamond shape
having a first dimension as measured from two opposing vertices and
a second dimension, generally transverse to the first direction, as
measured between two other opposing vertices, wherein when pleated
said expanded metal does not spring back towards an unpleated
position.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is a continuation of U.S. patent
application Ser. No. 12/891,606, filed on Sep. 27, 2010, which
claims priority to and the benefit of U.S. Patent Application No.
61/246,943, filed on Sep. 29, 2009, the contents of which are fully
incorporated herein by reference.
BACKGROUND OF THE INVENTION
[0002] Expanded metal has many applications, as for example in air
filters, ventilation systems, strainers, etc. Typically, expanded
metal is formed by feeding metal sheet or plate (herein after
referred to as "base plate") 12 through feeders 14 which is then
fed through an expander 16, where it is expanded to form expanded
metal 15. The expanded metal is then fed through flattening rolls
18 and into a take-up spool 20, as for example shown in FIG. 1. The
feeders 14 are shown in FIG. 1, by way of example, as rolls. The
feeder may be any device that feeds the base plate 12 from its
spool 22 to the expander. The feeder may also be part of the
expander. The expander includes a support base 24 over which is
advanced to the base plate 12 (FIGS. 2A, 2B, 2C, and 2D). As the
base plate is advanced, a desired strand thickness 26 beyond an
edge 29 of the support base (FIG. 28), a serrated cutting die 28
descends and simultaneously shears, slits and cold forms an entire
row 30 of half-diamonds 32, as for example shown in FIG. 2C. The
die then ascends and moves over a half-diamond to the right, as for
example shown by arrow 3 (or the left in another embodiment) as the
base plate is moved forward by another strand thickness beyond the
edge of the support base. The die then descends and slits and cold
forms another full row 34 of half-diamonds 36, completing a row of
full raised diamonds 40 in two strokes, as for example shown in
FIGS. 2C and 2D. As can be seen, each diamond is formed from four
integral strands 37. The die then another row of half-diamonds as
the base plate is advanced to another strand width beyond the edge
of the support, as for example shown in FIG. 2E. The formed raised
expanded metal is then moved by the flattening rolls 18 where it is
flattened and further cold worked so as to flatten the expanded
material strands 37, especially in the areas where the vertices 44
of the diamonds are integrally connected forming what is commonly
referred to as a "bond" 46, which typically has twice the width as
the normal strands that exit the expander. The flattening rolls
also pinch and pull on the expanded metal typically at a rate
faster than the rate of the expanded metal exiting the expander.
This causes the expanded metal to stretch by desired amount. In
addition, the cutting die 28 also provides resistance against the
pulling of the expanded metal by the fattening rolls.
[0003] An expanded metal has a "long way of diamond " dimension
(LWD) 48, which is along the direction transverse to the direction
that the base plate is fed through the expander and a "short way of
diamond" dimension (SWD) 50 which is measured along the direction
which the base plate is fed through the expander (FIG. 3).
Conventional expanded metals have an LWD that is about twice the
SWD.
[0004] Conventional expanded metals and the process by which they
are made are described in the "Standards for Expanded Metal
Material" published by the National Association of Architectural
Metal Manufacturers, NAAMM Standard, EMMA 557-99. The contents of
this publication are fully incorporated herein by reference.
[0005] When forming filters for residential, commercial use,
expanded metal is attached to one side of the filter material and
the filter material is then bent into an accordion fashion to form
a pleated filter. With conventional expanded metal, Applicants have
discovered that after being pleated, the expanded metal has a
tendency to attempt to spring back to its original shape. Thus,
consistent pleats are not obtained, as some pleats after being
formed spring back more than others.
[0006] Another problem with filters incorporating conventional
expanded metal is that the pleated filter has pleats which do not
have consistent heights. As a result, the pleats have an increased
chance to collapse during filtering due to the air pressure acting
on the filter, resulting in premature failure of the filter.
Furthermore, there are less contact points between the pleat peaks
and bonds, thus, causing filter fluttering or possible pleat
collapsing, which can reduce filter optimal performance. As such,
expanded metals that would allow for more consistent pleating of
filters and more consistent height pleats are desired.
SUMMARY OF THE INVENTION
[0007] In an exemplary embodiment, an expanded metal is provided
including a plurality of integral strands defining diamond shapes,
each diamond shape having a long dimension as measured from two
opposing vertices and a short dimension, generally transverse to
the long direction, as measured between two other opposing
vertices, wherein the long dimension is less than twice the short
dimension. In another exemplary embodiment, the short dimension is
equal to the long dimension. In a further exemplary embodiment, at
least a portion of the metal is expanded beyond in plastic yield
point. In yet another exemplary embodiment, each strand has a width
of 0.017 inch.
[0008] In a further exemplary embodiment, a filter including a
filter medium reinforced with an expanded metal is provided. The
filter is pleated and the expanded metal includes a plurality of
integral strands defining diamond shapes, each diamond shape having
a long dimension as measured from two opposing vertices and a short
dimension, generally transverse to the long direction, as measured
between two other opposing vertices, wherein the long dimension is
less than twice the short dimension. In yet a further exemplary
embodiment, the short dimension is equal to the long dimension. In
another exemplary embodiment, at least a portion of the metal is
expanded beyond in plastic yield point.
[0009] In a further exemplary embodiment, a method of forming
expanded metal is provided. The method requires feeding a base
plate through a cutting die to form an expanded metal, and
stretching the expanded metal by at least 15%. In yet a further
exemplary embodiment the expanded metal is stretched by at least
30%.
[0010] In another exemplary embodiment, a method of forming
expanded metal is provide. The method includes feeding a base plate
through a cutting die to form an expanded metal, and stretching the
expanded metal wherein at least a portion of the expanded metal is
stretched beyond its plastic yield point. In one exemplary
embodiment, the expanded metal includes a plurality of integral
strands defining a plurality of adjacent diamonds, wherein each
diamond has four vertices, wherein each strand extends between two
vertices, wherein the stretching causes the strands to rotate about
the vertices causes at least a portion of at least some of the
vertices to stretch beyond their plastic yield point. In one
exemplary embodiment, the strands do not stretch beyond their
plastic yield point. In another exemplary embodiment, at least a
portion of at least some of the strands stretch beyond their
plastic yield point. In yet another exemplary embodiment, the
expanded metal includes a plurality of integral strands defining a
plurality of adjacent diamonds, wherein each diamond has four
vertices, wherein each strand extends between two vertices, wherein
the stretching causes at least a portion of at least some of the
strands to stretch beyond their plastic yield point.
[0011] In a further exemplary embodiment, a method of forming
expanded metal is provided. The method requires feeding a base
plate by a cutting die, shearing portions of the base plate with
the cutting die to form an expanded metal including a plurality of
integral strands defining a plurality of diamond shapes, each
diamond shape having a long dimension as measured from two opposing
vertices and a short dimension, generally transverse to the long
direction, as measured between two other opposing vertices, and
stretching the expanded metal along by an amount sufficient to
render the short dimension more than half of the long dimension. In
yet a further exemplary embodiment, the method includes stretching
the expanded metal by an amount sufficient to render the short
dimension equal the long dimension. In one exemplary embodiment,
the length of each strand does increase after stretching. In yet
another exemplary embodiment, the cutting die includes a plurality
of blades, each blade having opposite converging sides extending at
opposite angles relative to a common straight line, wherein the
angles are each less than 30.degree.. In a further exemplary
embodiment, angles are each 26.degree.. In yet a further exemplary
embodiment, the angles are each 22.degree.. In another exemplary
embodiment, the cutting die includes a plurality of blades, wherein
each blade includes a width greater than 1.25 inches. In yet
another exemplary embodiment, each blade includes a width of 1.33
inches. In yet a further exemplary embodiment, each blade includes
a width of 1.5 inches.
[0012] In another exemplary embodiment, a method of forming
expanded metal is provided. The method includes feeding a base
plate by a cutting die, shearing portions the base plate with the
cutting die to form an expanded metal including a plurality of
integral strands defining diamond having a long dimension and a
short dimension generally transverse to the long direction, the
cutting die includes a plurality of blades, each blade having
opposite converging sides extending at opposite angles relative to
a common straight line, wherein the angles are each less than
30.degree., and stretching the expanded metal by an amount
sufficient to render the short dimension more than half of the long
dimension. In yet another exemplary embodiment, each such blade
includes a width greater than 1.25 inches. In a further exemplary
embodiment, the angles are each 26.degree.. In yet a further
exemplary embodiment, each such blade includes a width of 1.33
inches. In one exemplary embodiment, the angles are each
22.degree.. In another exemplary embodiment, each such blade
includes a width of 1.5 inches.
[0013] In a further exemplary embodiment, a method of forming
expanded metal is provided. The method includes feeding a base
plate by a cutting die, shearing portions the base plate with the
cutting die to form an expanded metal including a plurality of
integral strands defining diamonds, each diamond having a long
dimension and a short dimension generally transverse to the long
dimension, and stretching the expanded metal by an amount
sufficient to reduce the long dimension by at least 15%. In yet a
further exemplary embodiment, the stretching includes stretching to
reduce the long direction by at least 18%. In yet another exemplary
embodiment, the stretching includes stretching to reduce the long
direction by at least 20%, In a further exemplary embodiment, the
stretching includes stretching to reduce the long direction by at
least 23%.
BRIEF DESCRIPTION OF THE DRAWINGS
[0014] FIG. 1 schematically depicts a process for forming an
expanded metal.
[0015] FIG. 2A is a schematically partial cross-sectional view
depicting a cutting die shearing base plate for forming an expanded
metal.
[0016] FIGS. 2A, 2B, 2C, 2D and 2E are partial perspective
operational views of a cutting die forming an expanded metal.
[0017] FIG. 3 is a partial front view of a prior art expanded
metal.
[0018] FIG. 4 is a partial front view of an expanded metal of an
example embodiment.
[0019] FIGS. 5A and 5B are partial front views of cutting dies used
to form an example embodiment expanded metal.
[0020] FIG. 6A is an end view of a pleated filter incorporating the
expanded metal.
[0021] FIG. 6B is a partial plan view, along arrow 6B-6B shown in
FIG. 6A, depicting a diamond of an expanded metal of an example
embodiment in comparison to a diamond of a conventional expanded
metal.
[0022] FIG. 7 is a table depicting finished width an example
embodiment expanded metals formed with 26.degree. and 30.degree.
angle blades.
[0023] FIG. 8 is a table depicting prevent reduction of the long
width dimension in an example embodiment expanded metals.
DETAILED DESCRIPTION
[0024] Applicants have discovered that they can produce a stronger
lighter weight expanded metal which has minimum, or no consistent
spring back, or no spring back at all, after bending and thus, when
attached to a filter material and pleated, has less tendency to
want to return to its original unfolded position. In addition,
Applicants have discovered that use of such expanded metal results
in pleats having more consistent height, thus having minimal or no
high/low variations in the pleat height.
[0025] In one exemplary embodiment, Applicants produce such
inventive expanded metal by further stretching the expanded metal
after it is formed. This is accomplished by increasing the feed
rate through the flattening rolls 18 relative to the feed rate
existing through the feeder or expander 16. Such further stretching
may also be accomplished due to an increase in the pull generated
by the flattening rolls against the base plate which is held by the
cutting die as the cutting die shears the base plate. As such, as
the material gets expanded, it is pulled until it causes the SWD to
increase relative the LWD of each diamond. In an exemplary
embodiment, the SWD is increased to a level such that SWD is in the
range of more than half the LWD to equal to the LWD. During
stretching, the SWD increases and the LWD decreases. In an
exemplary embodiment, the expanded metal is stretched until the
expanded metal increases in length by 15% per linear foot produced.
In another exemplary embodiment, the expanded metal is stretched
until it increases in length by 25% per linear foot. In yet another
exemplary embodiment, the expanded metal is stretched until it
increases in length by 28% per linear foot or more and in another
exemplary embodiment, by 30% per linear foot or more. In this
regard, less metal is used for a given length of expanded metal. In
addition, Applicants have discovered that this "over" stretching
produces stronger expanded metal.
[0026] In an exemplary embodiment, expanded metal of the present
invention has an SWD 52 that is almost equal to the LWD 54, as
shown in FIG. 4. In an exemplary embodiment, the expanded metal is
stretched until the angle 56 between a line 58 joining opposing
vertices 37 of a diamond, in a direction transverse to the feed
direction through the expander, and a strand 59 is increased by 10%
to 30% over the same angle in conventional expanded material. For
example, in conventional expanded material, the angle 56 is about
35.degree., whereas in an exemplary embodiment, the inventive
expanded material the angle 56 is about 45.degree..
[0027] In another exemplary embodiment, the expanded metal is
stretched such that the LWD of the formed diamonds is reduced in
comparison to the LWD created when initially formed, i.e. slit, by
the cutting die, by at least 15%. In another exemplary embodiment,
the reduction in LWD is at least 18%. In yet another exemplary
embodiment, the reduction is at least 20%. Yet in another exemplary
embodiment, the reduction is at least 23%. In the conventional
expanded metal, the reduction in such LWD caused by the pulling of
the flattening rollers tends not to exceed 14.5%. As shown in the
table in FIG. 8, are data of LWD reduction for conventional and
inventive expanded metals. As can be seen from FIG. 8, in
conventional expanded metals, the reduction in LWD, after the
expanded metal is pulled, from the initial LWD created by the
cutting die, is less than 14.5%, whereas it is at least 18.8% for
the inventive expanded metal for which data, has been provided.
[0028] Stretching of the expanded material results in the material
"necking down", i.e., reducing in width. For example, the width 63a
of the inventive expanded metal (FIG. 4) is narrower then the width
63b of a conventional expanded metal (FIG. 3) formed using the same
cutting die. Consequently, in order to obtain a desired width of
expanded material, a wider base metal needs to be used. Due to the
stretching of the SWD dimension, less material is used per linear
foot of the inventive expanded metal produced. Thus, the weight per
linear foot of the inventive expanded metal for a given width of
expanded metal is reduced.
[0029] As can be seen, the width 60 of each strand is a function of
how much the base plate material 12 is advanced beyond the edge of
the support base 24 in the expander prior to being sheared by the
cutting die 28 (FIG. 2E). The thickness 62 of each strand is
controlled by the thickness of the base plate.
[0030] As the expanded material is stretched to form the inventive
expanded material and the SWD increases causing the width of the
material to decrease. In an exemplary embodiment, the strand length
64 may also increase and the width of each strand may also may
decrease. In an exemplary embodiment, the expanded material width
decreases, i.e., it necks down, by 15% to 25%. The width of the
strands may also be reduced by the same amount. This necking down
phenomenon allows for use of thicker base plate which is easier to
obtain and more readily available. In other words, you can obtain
the desired thickness strand by using thicker base plate 12. In one
exemplary embodiment, the thickness of the base plate may be
increased by 20%. In addition, by using a thicker base plate, the
material may be pressed further by the flattening rolls, further
cold working the strands, and thereby increasing the strand length
and strength. Moreover, the flattening cold working process causes
the width of the strands to increase as they are being
flattened.
[0031] Applicants have also discovered that because of the
inventive process of forming the inventive expanded metal by over
stretching, they can use cutting dies whose blades are wider,
forming a wider LWD prior to being stretched as the stretching will
reduce the LWD to a desired level. This provides for another
advantage. The dies have blades 70 having oppositely converging
sides 71 extending at opposite angles 68 from the horizontal or a
common straight line 69. It is difficult to expand less ductile
base metal, as for example commercial quality galvanized sheet
steel, because the serrated cutting die causes cracks to form in
such less ductile material due to the aggressive angle 68 of the
cutting die 28 blades 70, measured from the horizontal (or the
straight line 69) of the blades 70 (FIG. 5A). With this inventive
process, dies having blades 70 having a wider width 72, and thus, a
narrower angle 68 may be used. Such cutting blades provide for a
less aggressive cut (i.e. shear) as the cutting die is pressed
against the base plate thus, not inducing crack growth in the less
ductile material. Applicants have discovered that they can also
reduce the blade angle 68 by 30% or more, and in one exemplary
embodiment by 27% or more, and in another exemplary embodiment by
14% or more. In one exemplary embodiment, the blade angle is
reduced from 30.degree. to 26.degree., and in another exemplary
embodiment from 30.degree. to 22.degree.. With these exemplary
embodiments, the width of the blades is 1.25 inches when the blade
angle 68 is 30.degree.; 1.33 inches when the blade angle is
26.degree.; and 1.5 inches when the blade angle is 22.degree.. In
other words, in one exemplary embodiment, the blade width is
increased by at least 6%, and in another exemplary embodiment by
20%. Consequently, the lesser the rate of penetration. FIG. 7
depicts a table of expanded metals finished widths according to
exemplary embodiments of the present invention formed with blades
having an angle 68 of 26.degree. and an angle 68 of 30.degree.. The
leftmost column of FIG. 7 depicts the finished widths of the
expanded metals of present invention, i.e., the width of expanded
metals of the present invention. FIG. 7 also provides the original
width of the base plate and the percent reduction in the width of
the base plate expanded using the 26.degree. angle and the
30.degree. angle blades during the exemplary embodiment expansion
process.
[0032] In one exemplary embodiment, the inventive expanded metal
produced by the inventive process has a thickness 60 of 30% less
than the thickness of a comparable, normally expanded metal. In an
exemplary embodiment, the inventive expanded metal strand width is
0.017 inches, whereas it is 0.024 inches for conventional expanded
metal.
[0033] Applicants have discovered that the inventive expanded metal
is stronger, has less recoil or spring back after it is bent or
pleated when forming a filter 70 (FIG. 6A). In other words, the
inventive expanded metal retains its pleated shape and tends not to
open. Consequently, it provides for more consistent pleats having a
consistent height 72, and thus less high/low variances in the pleat
height 72. Applicants believe that one reason for this benefit is
that the strands 60, as for example shown in FIG. 6B, of the
inventive expanded metal are more vertical in the direction of the
pleats than the strands 37 of a conventional expanded metal, as for
example shown in dashed line in FIG. 6B. In other words, when bent
to form a pleat for use with filter, the strands will be oriented
more in the longitudinal direction (i.e., the direction of the
expanded metal came out of the die). In an exemplary embodiment,
the number of strands in the direction of the pleat are increased
by at least 14%. Furthermore, because the inventive expanded metal
is stronger, less rigid filtering material may be used to form an
expanded metal reinforced filter, with out detrimentally effecting
the overall rigidness of such filter, resulting in the reduction of
undesirable filter induced pressure drops in a heating, ventilating
and air conditioning (HVAC) system or unit. In addition, because
with the inventive expanded metal, the area of material (i.e., the
area occupied by the strands) for a given length of expanded metal
is reduced, the inventive expanded metal provides for larger open
(i.e., unobstructed) areas in a filter incorporating such inventive
expanded metal, also resulting in the reduction of filter induced
pressure drops across such filter.
[0034] Applicants also believe that the increase in strength of the
inventive expanded metal may be caused by some or all of the
inventive expanded material having being stretched beyond its
plastic yield point. It may be that only the bonds 46, or some of
the bonds, or only the strands, or some of the strands, or any
portion of the inventive expanded metal, or the entire inventive
expanded metal may have been stretched beyond its yield point. For
example, as the expanded metal is stretched beyond its normal
limit, the strands rotate about their bonds (much like a pair of
scissors) so as to shorten the LWD and increase the SWD. This
rotation about the bonds may be sufficient to cause the bonds to
rotationally stretch beyond their yield point. In addition, the
strands may also be stretched beyond their yield point. This may
also be implied by the fact that the inventive expanded metal
retains its shape after it is bent or pleated, and does not return
to its original shape or has less tendency to return to its
original shape. Applicants also believe that the increase strength,
when using thicker base plate may also be due to the extra
flattening of the material that is accomplished by the flattening
rolls for reducing the strand thicker to a desired level, thereby
further cold work hardening the inventive expanded metal.
[0035] The weight of the inventive expanded metal per linear foot
is decreased in comparison to conventional expanded metals having
the same width. In one exemplary embodiment, the reduction in
weight exceeds 30% and in another exemplary embodiment the
reduction in weight is 32%. The increase strength and stability of
this material means that less material needs to be used, as for
example when forming air filters. As a result, the filter used when
forming the inventive expanded metal will have less flow
restriction (caused by the inventive expanded metal) than with
conventional expanded metal. It is also believed that the inventive
expanded metal has increased stiffness. Applicants have also
discovered that the inventive expanded metal is more easily
uncoiled during the laminating process prior to pleating when
forming a filter, and due to its added rigidity, resists necking
during such process, and thus, provides for a more consistent
pleated width. In addition, with the inventive process a desired
linear footage (e.g., 2700 linear feet) of expanded metal is
achieved faster reducing the times required to produce a desired
length of expanded metal. As can be seen, the inventive expanded
metal caused by an increase in the stretching of the expanded
metal, provides a myriad of unexpected benefits, at least some of
which have been described herein.
[0036] The preceding description has been presented with reference
to various embodiments of the invention. Persons skilled in the art
and technology to which this invention pertains will appreciate
that alterations and changes in the described structures and
methods of operation can be practiced without meaningfully
departing from the principles, spirit, and scope of this
invention.
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