U.S. patent application number 13/080006 was filed with the patent office on 2012-02-16 for method of expanding corrugated tube and manufacturing a heat exchanger with expansion tube.
Invention is credited to James W. Klopfenstein, II, Steven L. Stroup, SR..
Application Number | 20120036718 13/080006 |
Document ID | / |
Family ID | 45563709 |
Filed Date | 2012-02-16 |
United States Patent
Application |
20120036718 |
Kind Code |
A1 |
Stroup, SR.; Steven L. ; et
al. |
February 16, 2012 |
METHOD OF EXPANDING CORRUGATED TUBE AND MANUFACTURING A HEAT
EXCHANGER WITH EXPANSION TUBE
Abstract
A method of manufacturing a heat exchanger coil, the method
comprising the steps of reconfiguring the cross-sectional shape of
an elongate tube from a substantially round cross-sectional shape
having a first outer circumference to a reduced or corrugated
cross-sectional shape having a second outer circumference which is
less than the first outer circumference, forming a plurality of
u-shaped hairpin tubes from the elongate tube, the u-shaped hairpin
tubes each having a pair of parallel legs, inserting each of the
parallel legs of the hairpin tube through a predetermined opening
in at least one fin plate, attaching a plurality of return bends to
the u-shaped hairpin tubes to form a predetermined circuitry and
then incrementally applying fluid pressure from a fluid pressure
source to an internal channel of the circuitry to incrementally
expand the circuitry to form a tight heat transfer bond between the
circuitry and at least one wall of the predetermined opening.
Inventors: |
Stroup, SR.; Steven L.;
(Fort Wayne, IN) ; Klopfenstein, II; James W.;
(Bluffton, IN) |
Family ID: |
45563709 |
Appl. No.: |
13/080006 |
Filed: |
April 5, 2011 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
61372584 |
Aug 11, 2010 |
|
|
|
Current U.S.
Class: |
29/890.035 |
Current CPC
Class: |
Y10T 29/49359 20150115;
B21D 39/06 20130101; B21D 53/085 20130101; F28F 1/32 20130101; F28D
1/0477 20130101; F28F 1/06 20130101 |
Class at
Publication: |
29/890.035 |
International
Class: |
B21D 53/06 20060101
B21D053/06 |
Claims
1. A method of manufacturing a heat exchanger coil, the method
comprising the steps of: reconfiguring a cross-sectional shape of
an elongate tube from a substantially round cross-sectional shape
having a first outer circumference to one of a reduced and a
corrugated cross-sectional shape having a second outer
circumference less than said first outer circumference; forming a
plurality of u-shaped hairpin tubes from said elongate tube, said
u-shaped hairpin tubes each having a pair of parallel legs;
inserting each of said parallel legs through a predetermined
opening in at least one fin plate; attaching a plurality of return
bends to said u-shaped hairpin tubes to form a predetermined
circuitry; and incrementally applying fluid pressure from a fluid
pressure source to an internal channel of said circuitry to
incrementally expand said circuitry to form a tight heat transfer
bond between said circuitry and at least one wall of said
predetermined opening.
2. The method according to claim 1, wherein an end of said
circuitry is sealed prior to said application of said fluid
pressure.
3. The method according to claim 1, wherein said at least one fin
plate is a plurality of fin plates.
4. The method according to claim 1, wherein said substantially
round cross-sectional shape is one of substantially circular-shaped
and substantially oval-shaped.
5. The method according to claim 1, wherein said attachment of said
plurality of return bends to said u-shaped hairpin tubes is by
brazing.
6. The method according to claim 1, wherein said at least one fin
plate is a plurality of fin plates and said predetermined opening
is a plurality of predetermined openings in said plurality of fin
plates, said predetermined openings being arranged in a predefined
arrangement.
7. The method according to claim 1, wherein said application of
fluid pressure one of incrementally expands said reduced shape and
unfolds said corrugated shape to re-form said substantially round
cross-sectional shape.
8. The method according to claim 1, wherein said elongate tube is
sealed prior to said application of fluid pressure.
9. The method according to claim 1, wherein said fluid pressure is
applied such that an internal pressure of said hairpin tube is up
to approximately 2,500 PSI.
10. The method according to claim 9, wherein said fluid pressure is
applied such that said internal pressure of said hairpin tube is up
to approximately 2,100 PSI.
11. The method according to claim 1, wherein said fluid pressure
source is one of a hand pump, a hydraulic pump, an electric pump
and a gas pump.
12. The method according to claim 1, wherein a fluid used in said
application of said fluid pressure is leak detectable.
13. The method according to claim 1, wherein each of said pair of
parallel legs of said u-shaped hairpin tubes includes an end
portion which is not corrugated.
14. The method according to claim 1, wherein said u-shaped hairpin
tube includes a u-shaped portion between said pair of parallel
legs, said u-shaped portion not being corrugated.
15. A method of manufacturing a HVAC heat exchanger coil, the
method comprising the steps of: reconfiguring a cross-sectional
shape of a plurality of elongate tubes from a substantially round
cross-sectional shape having a first circumference to one of a
reduced and a corrugated cross-sectional shape having a second
circumference less than said first circumference; bending each of
said elongate tubes into a hairpin-shaped tube having a pair of
parallel legs; inserting each of said pair of parallel legs of said
hairpin tubes through a predetermined opening in at least one fin
plate; coupling at least one leg of said pair of parallel legs with
a return bend to form a predefined circuitry; incrementally
applying fluid pressure from a fluid pressure source to an internal
channel of said circuitry to expand said circuitry to said first
outer circumference and said substantially round cross-sectional
shape and form a tight heat transfer bond between said elongate
tube and at least one wall of said predetermined opening.
16. A method of manufacturing a heat exchanger coil, the method
comprising the steps of: reconfiguring a cross-sectional shape of
an elongate tube from a substantially round cross-sectional shape
having a first outer circumference to a corrugated cross-sectional
shape having a second outer circumference less than said first
outer circumference; forming a plurality of tube sections, said
tube sections including at least one of straight tubes, u-shaped
hairpin tubes and return bends; forming a predefined circuitry from
said at least one of said straight tubes, said u-shaped hairpin
tubes and said return bends; incrementally applying fluid pressure
from a fluid pressure source to an internal channel of said
circuitry to pressure inflate and radially expand said circuitry to
continuously contact a wall of said predetermined opening and form
a tight heat transfer bond between said circuitry and said
predetermined opening.
Description
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] This is a non-provisional application based upon U.S.
Provisional Patent Application Ser. No. 61/372,584, entitled
"METHOD OF EXPANDING CORRUGATED TUBE AND MANUFACTURING A HEAT
EXCHANGER WITH EXPANSION TUBE", filed Aug. 11, 2010, which is
incorporated herein by reference.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] The present invention relates to a method of manufacturing a
heat exchanger assembly.
[0004] 2. Description of the Related Art
[0005] Fin plate and tube heat exchanger assemblies are widely used
in both industrial and residential capacities to transfer heat from
one medium to another, for example, from refrigerant to air. A
standard fin plate and tube heat exchanger assembly includes a
number of fin plates which are typically fabricated from thin
metal, such as aluminum, and arranged parallel to one another. Each
fin plate has a number of fin holes or openings through which a
heat exchanger tube is inserted. The heat exchanger tube is then
expanded to a larger diameter so as to securely lock it into the
fin hole, thereby providing good heat exchange contact.
[0006] With the expansion of the diameter of the tube according to
known methods, however, there is a corresponding decrease or
shrinkage in the length of the tube. Accordingly, manufacturers
must factor in the approximate anticipated length reduction of the
heat exchanger tube when calculating the length of raw tubing
needed to form the final heat exchanger assembly.
[0007] What is needed in the art is a heat exchanger assembly and
method of manufacture of a heat exchanger assembly which provides a
tight interference fit or lock between the heat exchanger tube and
fin plate and, therefore, good heat exchange contact, with minimal
or no decrease in the length of the raw tube.
SUMMARY OF THE INVENTION
[0008] The present invention provides a method of manufacturing a
heat exchanger coil or assembly including at least one hairpin tube
and at least one fin plate.
[0009] According to the method of the present invention, a raw
elongate tube having an original outer circumference and a
substantially round cross-sectional shape is reconfigured to have a
reduced or corrugated cross-sectional shape. The corrugations may
be, for example, spiral or longitudinal. The reconfigured or
corrugated tube has a first outer circumference or diameter, which
is less than the original outer circumference of the raw,
uncorrugated tube. A plurality of u-shaped hairpin tubes may be
formed by inserting the reconfigured tube into a Hairpin Bender,
each u-shaped hairpin tube having a pair of parallel legs. Each leg
of the u-shaped hairpin tubes is inserted into or through a
predetermined opening in at least one fin plate, for example a
plurality of fin plates. Subsequently a plurality of return bends
are attached to the u-shaped hairpin tubes, for example by brazing,
welding or the use of an adhesive to form a predetermined
circuitry. Although the predetermined circuitry has been described
as including only u-shaped hairpin tubes and return bends, the
circuitry may be formed from any combination of straight tubes,
u-shaped hairpin tubes and return bends. Fluid pressure is
incrementally applied from a fluid pressure source to an internal
channel of the circuitry formed by the corrugated hairpin tubes,
straight tubes and/or return bends. To apply the fluid pressure,
one end of the circuitry is securely closed or sealed, for example
with an end cap. An internal channel of the circuitry is then
filled with a fluid, for example, oil, air or refrigerant, which is
then placed under pressure by the fluid pressure source. The
application of the fluid pressure incrementally pressure inflates
the corrugated tube unfolding the corrugations, thereby radially
expanding the circuitry to continuously contact the wall of the
opening in the fin plate and form a tight heat transfer bond
between the circuitry and the wall of the opening(s) in at least
one fin plate.
[0010] A heat exchanger assembly includes at least one heat
exchanger coil, for example 3 or 4 heat exchanger coils, according
to the present invention.
[0011] The substantially round cross-sectional shape of the raw,
uncorrugated tube may be, for example, substantially circular or
oval-shaped.
[0012] The fluid pressure applied to the heat exchanger coil
circuitry may be such that an internal pressure of the circuitry is
up to, for example, approximately 2,500 PSI or up to approximately
2,100 PSI.
[0013] The fluid pressure source may, for example, be a hand pump,
a hydraulic pump, an electric pump or a gas pump.
[0014] The present invention further provides a method of
manufacturing HVAC (Heating Ventalation and Air Conditioning)
coils.
[0015] According to the method of manufacturing an HVAC heat
exchanger coil, a predetermined number of fin plates, for example
at least one or a plurality of fin plates, is selected, the fin
plates being enclosed in a fixture with their mounting brackets
positioned in precise predetermined locations. A raw, elongate tube
having an original circumference and a substantially round
cross-sectional shape is reconfigured to have a reduced or
corrugated cross-sectional shape. The corrugations may be, for
example, spiral or longitudinal. The reconfigured, corrugated tube
has a first outer circumference or diameter, which is less than the
original outer circumference. A plurality of u-shaped hairpin tubes
may be formed by inserting the reconfigured tube in, for example in
a Hairpin Bender, and bending. Each u-shaped hairpin tube has a
pair of parallel legs and each leg is inserted into or through a
predetermined opening in at least one of the fin plates, for
example a plurality of fin plates. A final flare may be formed at
the open end of each hairpin tube before a plurality of return
bends are attached to or coupled with the u-shaped hairpin tubes,
for example by brazing, welding or the use of an adhesive to form a
predetermined circuitry. Although the predetermined circuitry has
been described as including only u-shaped hairpin tubes and return
bends, the circuitry may be formed from any combination of straight
tubes, u-shaped hairpin tubes and return bends. Fluid pressure is
incrementally applied from a fluid pressure source to an internal
channel of the circuitry, which is formed by the hairpin tubes,
straight tubes and/or return bends. To apply the fluid pressure,
one end of the circuitry is securely closed or sealed, for example
with an end cap. An internal channel of the circuitry is then
filled with a fluid, for example, oil, air or refrigerant, which is
then placed under pressure by the fluid pressure source. As a
result of the application of the fluid pressure, the first outer
circumference of the corrugated tubing is pressure inflated,
unfolding the corrugations and radially expanding the corrugated to
equal to or greater than the original outer circumference or
diameter of the raw, uncorrugated tube. The incremental fluid
inflation and radial expansion of the circuitry results in the tube
having continuous contact with a wall of the opening in the fin
plate and forms a tight heat transfer bond between the circuitry
and the opening in the fin plate.
BRIEF DESCRIPTION OF THE DRAWINGS
[0016] The above-mentioned and other features and advantages of
this invention, and the manner of attaining them, will become more
apparent and the invention will be better understood by reference
to the following description of embodiments of the invention taken
in conjunction with the accompanying drawings, wherein:
[0017] FIG. 1 is a sectional view of a portion of a heat exchanger
assembly configured in accordance with the present invention;
[0018] FIG. 2 is an exploded view of a heat exchanger assembly
according to the present invention;
[0019] FIG. 3 is a perspective view of a heat exchanger assembly
according to the present invention; and
[0020] FIG. 4 is a perspective view of a hairpin tube according to
the present invention;
[0021] FIG. 4A is a perspective view of a hairpin tube according to
the present invention;
[0022] FIG. 5A is a cross-sectional view of the corrugated tube of
FIG. 4; and
[0023] FIG. 5B is a cross-sectional view of the tube of FIG. 4
after pressure inflation.
[0024] Corresponding reference characters indicate corresponding
parts throughout the several views. The exemplifications set out
herein illustrate embodiments of the invention and such
exemplifications are not to be construed as limiting the scope of
the invention in any manner.
DETAILED DESCRIPTION OF THE INVENTION
[0025] Referring now to the drawings, and more particularly to
FIGS. 4 and 4A, there is shown hairpin tube 10 which has been
formed by reconfiguring pipe or raw tube, which is sized to fit a
predetermined opening. The raw pipe or tube has an original outer
circumference or diameter and a substantially round cross-sectional
shape. The raw tube is reconfigured to have a corrugated or reduced
shape, and may subsequently be bent by a Hairpin bender into
u-shaped hairpin tube 10 having a pair of parallel legs 12 and an
inner channel 14 extending therethrough or, if manufacturing a
straight tube, simply cut to length. For purposes of clarity, FIGS.
4 and 4A illustrate tube 10 as having longitudinal corrugations,
however, it is also feasible for tube 10 to have spiral
corrugations. The formation of longitudinal corrugations 16 results
in tube 10 having a compressed, first outer circumference D1, less
than original outer circumference of the raw, uncorrugated tube.
Longitudinal corrugations 16 may extend the entire length of
hairpin tube, as illustrated in FIG. 4, or may extend along only a
portion of hairpin tube 10, as illustrated in FIG. 4A. The original
outer circumference of the uncorrugated tube may be approximately
20 mm or less, or as small as, for example, approximately 3 mm or
less.
[0026] Referring now to FIG. 1, there is shown, a sectional view of
a heat exchanger coil assembly wherein one of parallel legs 12 of
hairpin tube 10 having longitudinal corrugations 16 is inserted
into or through opening 18 of fin plate 20. A plurality of return
bends (not shown) are coupled with a plurality of hairpin tubes 10
similarly inserted into or through openings 18 in at least one fin
plate 20. Although the heat exchanger coil has been described as
including u-shaped hairpin tubes and return bends, it may be formed
from any combination of straight tubes, u-shaped hairpin tubes and
return bends. Subsequently, longitudinal corrugations 16 are
pressure inflated, unfolding the corrugations and radially
expanding tube 10 so as to continuously contact a wall of opening
18 of fin plate 20 and form a tight bond or lock with the wall or
walls of opening 18 into which it has been inserted. Expanded tube
10 has a second outer circumference or diameter D2 greater than
first outer circumference D1 of the corrugated tube and equal to or
greater than the original outer circumference of the raw,
uncorrugated tube.
[0027] The radial expansion of the tube is accomplished by the
incremental application of fluidized pressure from fluid pressure
source 22 to internal channel 14 of hairpin tube 10. The method of
expansion according to the present invention, provides that one end
of the corrugated tube is first securely closed or sealed and
internal channel 14 of hairpin tube 10 is subsequently filled with
a fluid such as, for example, oil, air or refrigerant, which is
then placed under pressure by fluid pressure source 22. As fluid
pressure is incrementally increased, longitudinal corrugations 16
unfold and tube 10 is substantially restored to the original outer
circumference of the raw, uncorrugated tube.
[0028] Advantageously, the present invention results in the
requirement of a pressurized force for expansion and the avoidance
of shrinkage or shortening of the hairpin or straight tube length,
thus a predictable and precise dimensional result.
[0029] According to the present invention, the original,
uncorrugated, elongate tube may have any substantially round
cross-sectional shape having an outer circumference.
[0030] For example, the raw tube may have a substantially
oval-shaped cross-sectional shape before it is reconfigured. In
this case, the corrugation of the oval-shaped tube, according to
the present invention, reduces the original outer circumference of
the uncorrugated raw tube to compressed, first outer circumference
D1.
[0031] Alternatively, the raw tube may have a substantially
circular cross-sectional shape before reconfiguration or
corrugation. In this case also, the raw tube, sized to fit a
predetermined opening, is reconfigured to have a reduced or
corrugated shape, resulting in decreased first outer circumference
D1.
[0032] As described above, according to the method of the present
invention, end 24 of hairpin tube 10 is securely sealed or closed,
for example with plug 23, and tube 10 inserted into or through
predetermined opening 18 in fin plate 20 and may be inserted
through opening 21a in end plate 21. The end of tube 10 may be
securely sealed or closed prior to or after inserting tube 10 into
or through the predetermined opening 18. Inner channel 14 of tube
10 is then filled with a fluid, for example, oil, air or
refrigerant and the fluid placed under pressure.
[0033] As this fluid pressure is incrementally increased, the
internal pressure of tube 10 rises and causes the corrugations to
unfold and the original outer circumference or diameter of the raw,
uncorrugated tube to be substantially restored, tightly bonding or
locking the tube 10 with at least one wall of opening 18 with
minimal force, advantageously without affecting the length of the
tube. Fluid pressure may, be applied such that the internal
pressure of the tube is up to approximately 2,500 PSI, and could be
more or less than this amount of pressure, for example up to
approximately 2,100 PSI.
[0034] In accordance with the present invention, the tube may be
formed from any number of materials, for example, copper, aluminum,
steel or brass, or any alloy thereof.
[0035] The return bends may also be formed from any number of
materials including, for example, copper, aluminum, steel or brass,
or any alloy thereof.
[0036] The return bends may be coupled with the hairpin tubes
and/or straight tubes by any of a number of known methods,
including brazing, welding, or the use of adhesives.
[0037] Referring now to FIGS. 2 and 3, there is shown heat
exchanger assembly including a plurality of fin plates 20 (thin,
metal plates with a plurality of openings arranged in a specific
pattern to assure maximum heat exchange) arranged such that a
straight tube and/or parallel legs 12 of hairpin tube 10 configured
according to the present invention are inserted into openings 18 of
fin plates 20 to form a hairpin and/or straight tube and fin
assembly. The entire assembly may include all straight tubes or all
hairpins or, alternatively, may include any combination of hairpins
and straight tubes, as well as return bends.
[0038] To mechanically bond hairpin tubes 10 and/or straight tubes
to fin plate 20, fin plates 20 may be placed in a fixture for
holding fin plates 20 and end sheets 21 in their respective
locations. A plurality of return bends 26 are attached or coupled
with tubes 10 to form a predetermined circuitry. One end 24 of tube
10 is securely sealed with, for example plug 23, and the opposite
end is filled with fluid and placed under pressure. Pressure is
subsequently incrementally applied, thus unfolding longitudinal
corrugations 16 and expanding first outer circumference D1 of
corrugated tube 10 to bond fin plate 20 with hairpin and/or
straight tube 10, respectively.
[0039] Advantageously, the unfolding of the corrugations of the
hairpins and/or straight tubes according to the present invention,
results in a substantial return to the original outer circumference
of the raw, uncorrugated tube, resulting in a mechanical locking of
tube 10 to fin plates 20 with the application of minimal pressure.
This creates a rigid, tight mechanical lock or bond between the
straight tubes and/or hair pins with the fin and a very efficient
heat transfer bond, making the finished assembly a highly efficient
heat transfer coil which can be used in, for example, air
conditioning systems and refrigeration systems.
[0040] With respect to the pressure inflation of tube 10, and
unfolding of the corrugations of the tube, as discussed above,
inner channel 14 of tube 10 is filled with a fluid, for example,
oil, air or refrigerant from pressurized fluid source 22.
Pressurized fluid source 22 may be any of a number of known devices
including, for example, a hand pump, hydraulic pump, electric or
gas pump and is connected to tube 10 via suitable connection 25. As
this fluid pressure is incrementally increased, the internal
pressure of tube 10 causes the corrugations to unfold resulting in
tube 10 having second outer circumference D2, radially expanding
tube 10 and tightly bonding or locking tube 10 with opening 18 of
fin plate 20 with minimized force and without affecting the length
of the tube. The outer circumference of the tube, resulting from
the unfolding and resulting expansion of the heat exchanger tube,
is greater than outer circumference D1 and equal to or greater than
the original outer circumference of the raw, uncorrugated tube. As
a result of the expansion of heat exchanger tube 10 to correspond
with the size of opening 18 in fin plate 20, a mechanical lock
between heat exchanger tube 10, and thus the predefined circuitry,
and fin plates 20 is formed.
[0041] The present invention further provides a method of producing
HVAC heat exchanger coils whereby a predetermined number of fin
plates is selected, the fin plates then being enclosed in a fixture
with their mounting brackets positioned at precise predetermined
locations. A raw elongate tube having an original out circumference
and a substantially round cross-sectional shape is reconfigured to
have a reduced or corrugated cross-sectional shape. The
corrugations may, for example, be in the form of spiral or elongate
corrugations. The reconfigured or corrugated tube has a first outer
circumference or diameter, which is less than the original outer
circumference of the raw, uncorrugated tube. A plurality of
u-shaped hairpin tubes are formed by bending the reconfigured tube,
for example in a Hairpin Bender. Each u-shaped hairpin tube has a
pair of parallel legs and each leg is inserted into or through a
predetermined opening in at least one of the fin plates, for
example a plurality of fin plates. A final flare is formed at the
open end of each hairpin tube. Next, a plurality of return bends
are attached to the open ends of the hairpin tubes by, for example,
brazing, welding, the use of an adhesive or other means. When the
HVAC heat exchange coil assembly is completed with respect to the
desired circuitry configuration and the remaining access ports to
the tubular circuitry are securely attached to a pressure pumping
device, pressure expansion of the entire heat exchanger coil is
accomplished by closing or sealing the outlet port and applying
pressure to the inlet port through a sealed connection to the inlet
port. Accordingly, when the HVAC heat exchanger coil is removed
from the pressure expansion fixture, it is a fully complete and
fully tested heat exchanger. This fully completed HVAC heat
exchanger coil may then be bent, if desired, by a coil bending
machine while the tubular passages continue to be pressurized, thus
insuring minimal, if any, internal tubular restriction due to the
HVAC heat exchanger coil forming operation used to reform the coil
into a rectangular, circular or other shape to fit cabinetry for a
finished air conditioning unit. Although the HVAC heat exchanger
coil has been described as including hairpin tubes and return
bends, it may be formed from any combination of straight tubes,
hairpin tubes and/or return bends.
[0042] The method according to the present invention advantageously
allows for the precise placement of hairpin and/or straight tubes
and allows for insertion of hairpins and/or straight tubes into
fins while the fins and mounting brackets are precisely positioned
and enclosed in a holding and alignment fixture. The method
according to the present invention further advantageously allows
for higher production rates and an improved aesthetic quality coil
as a result of minimal handling.
[0043] The method of producing a heat exchanger assembly and/or
HVAC heat exchange coil according to the present invention utilizes
applied internal pressure for the expansion of corrugated or
reduced shape heat exchanger tube to avoid shrinkage or shortening
of the tube length, thus a predictable and precise dimensional heat
exchanger tube results. Further, due to pressure expansion of the
tubes thereby securing the tube to the fin, a good heat transfer is
formed between the hairpin or straight tube outer diameter and the
fin collar inner diameter. In addition, the utilization of pressure
expansion to produce HVAC heat exchanger coils enables the
utilization of hairpin and/or straight tube having smaller original
outer diameters, for example, less than 3 mm.
[0044] While this invention has been described with respect to at
least one embodiment, the present invention can be further modified
within the spirit and scope of this disclosure. This application is
therefore intended to cover any variations, uses, or adaptations of
the invention using its general principles. Further, this
application is intended to cover such departures from the present
disclosure as come within known or customary practice in the art to
which this invention pertains.
* * * * *