Title: Method of fabrication of a dryer fabric and a dryer fabric with backside venting for improved sheet stability
Abstract: A method of manufacturing and a papermaker's or industrial fabric, such as a dryer fabric for the dryer section of a paper machine, includes the application of a polymeric resin material onto preselected locations on the backside of a base substrate using a piezojet array which deposits the polymeric resin material in droplets having an average diameter of 10μ (10 microns) or more to build up discrete, discontinuous deposits of the polymeric resin material having a height of about 0.5 mm at the preselected locations. The preselected locations may be the knuckles formed by the interweaving of the yarns making up the fabric. The purpose of the deposits is to separate the backside of the dryer fabric from a surface, such as that of a dryer cylinder or turning roll, to enable air trapped between the dryer fabric and the surface to escape in lengthwise and crosswise directions parallel to the surface, instead of being forced through the fabric, possibly causing "drop off". The polymeric resin material is set by means appropriate to its composition, and, optionally, and, if necessary, may be abraded to provide the deposits with a uniform height above the surface plane of the base substrate.
Patent Number: 7,005,043 Issued on 02/28/2006 to Toney, et al.
| Inventors:
|
Toney; Mary M. (Wrentham, MA);
Paquin; Maurice (Plainville, MA)
|
| Assignee:
|
Albany International Corp. (Albany, NY)
|
| Appl. No.:
|
334212 |
| Filed:
|
December 31, 2002 |
| Current U.S. Class: |
162/361; 162/348; 162/358.2; 162/902; 428/196; 428/339; 442/71; 442/76; 442/148; 34/116; 34/123; 427/510; 427/513; 427/244; 427/261; 427/265; 427/288; 427/389.9 |
| Current Intern'l Class: |
D21F 1/10 (20060101); D21F 7/12 (20060101); B32B 27/12 (20060101); B05D 1/40 (20060101) |
| Field of Search: |
162/203-207,306,348,358.2,358.4,900-904,109-117,361
156/459-460
428/192-194,195.1,198,200,206,212,213,220,143,147,196,332,339
442/59,76,148,71
474/226-268
427/9,447,448,466,470,487,492,508-510,513,140,176,189,195,196,201,203,209,210,244,259,261,265,285,288,331,355,370,372.2,384,389.9,394
34/116,123
|
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|
Primary Examiner: Hug; Eric
Attorney, Agent or Firm: Frommer Lawrence & Haug LLP, Santucci; Ronald R.
Claims
What is claimed is:
1. A method for manufacturing a papermaker's or industrial fabric, said method
comprising the steps of:
a) providing a base substrate for the fabric;
b) depositing a plurality of polymeric resin material droplets onto preselected
discrete locations on said base substrate in a controlled manner to build up discrete,
discontinuous elements of said polymeric resin material having a height of about
0.5 mm at said preselected discrete locations; and
c) at least partially setting said polymeric resin material.
2. A method as claimed in claim 1 wherein said droplets have a nominal diameter
of 10μ (10 microns) or more.
3. A method as claimed in claim 1 wherein steps b) and c) are performed sequentially
on successive bands extending widthwise across said base substrate.
4. A method as claimed in claim 1 wherein steps b) and c) are performed sequentially
on successive strips extending lengthwise around said base substrate.
5. A method as claimed in claim 1 wherein steps b) and c) are performed spirally
around said base substrate.
6. A method as claimed in claim 1 wherein said base substrate is woven and in
step b), said preselected discrete locations on said base substrate are knuckles
formed by lengthwise yarns of said base substrate passing over crosswise yarns.
7. A method as claimed in claim 1 wherein said base substrate is woven and in
step b), said preselected locations on said base substrate are knuckles formed
by crosswise yarns of said base substrate passing over lengthwise yarns.
8. A method as claimed in claim 1 wherein said base substrate is woven and in
step b), said preselected locations on said base substrate are valleys between
knuckles formed by lengthwise yarns of said base substrate passing over crosswise yarns.
9. A method as claimed in claim 1 wherein said base substrate is woven and in
step b), said preselected locations on said base substrate are valleys between
knuckles formed by crosswise yarns of said base substrate passing over lengthwise yarns.
10. A method as claimed in claim 1 wherein said base substrate is woven and in
step b), said preselected locations on said base substrate run between two consecutive
knuckles formed by lengthwise yarns of said-base substrate passing over crosswise
yarns and include the valley therebetween.
11. A method as claimed in claim 1 wherein said base substrate is woven and in
step b), said preselected locations on said base substrate run between two consecutive
knuckles formed by crosswise yarns of said base substrate passing over lengthwise
yarns and include the valley therebetween.
12. A method as claimed in claim 1 wherein, in step b), said polymeric resin
material is deposited by a piezojet array comprising at least one computer-controlled piezojet.
13. A method as claimed in claim 1 wherein step b) comprises the steps of:
i) checking in real time the surface of said base substrate to locate the preselected
discrete locations and to cause the deposit thereon of said polymeric resin material
to build up said discrete, discontinuous elements; and
ii) depositing said polymeric resin material onto said preselected locations
requiring polymeric resin material to give said elements the desired height.
14. A method as claimed in claim 13 wherein said checking step is performed by
a fast pattern recognizer (FPR) processor operating in conjunction with a digital-imaging
camera in real time.
15. A method as claimed in claim 14 wherein said depositing step is performed
by a piezojet array coupled to said FPR processor.
16. A method as claimed in claim 1, wherein said polymeric resin material is
selected from the group consisting of:
1. hot melts and moisture-cured hot melts;
2. two-part reactive systems based on urethanes and epoxies;
3. photopolymer compositions consisting of reactive acrylated monomers and acrylated
oligomers derived from urethanes, polyesters, polyethers, and silicones; and
4. aqueous-based latexes and dispersions and particle-filled formulations including
acrylics and polyurethanes.
17. A method as claimed in claim 1 wherein said curing step is performed by exposing
said polymeric resin material to a heat source.
18. A method as claimed in claim 1 wherein said curing step is performed by exposing
said polymeric resin material to cold air.
19. A method as claimed in claim 1 wherein said curing step is performed by exposing
said polymeric resin material to actinic radiation.
20. A method as claimed in claim 12 wherein said piezojet array comprises a plurality
of individual computer-controlled piezojets, and wherein some of said individual
computer-controlled piezojets deposit one polymeric resin material while other
individual computer-controlled piezojets deposit a different polymeric resin material.
21. A method as claimed in claim 1 further comprising the optional step of abrading
said polymeric resin material deposited on said base substrate to provide said
polymeric resin material above the surface plain of said base substrate with a
uniform thickness.
22. A method as claimed in claim 1 wherein a first polymeric resin material is
deposited and a second polymeric resin material is deposited which is different
from the first polymeric resin material.
23. A papermaker's or industrial fabric comprising:
a base substrate taking the form of an endless loop having a backside and a paper-contacting
side; and
a plurality of discrete, discontinuous elements of polymeric resin material,
said discreet, discontinuous elements comprising a plurality of droplets at preselected
discrete locations on said backside, said elements having a height of about 0.5
mm relative to said backside.
24. A papermaker's or industrial fabric as claimed in claim 23 wherein said base
substrate is woven from lengthwise and crosswise yarns and wherein said preselected
locations are knuckles formed by said yarns on said backside.
25. A papermaker's or industrial fabric as claimed in claim 23 wherein said base
substrate is woven from lengthwise and crosswise yarns and wherein said preselected
locations are valleys between knuckles formed by said yarns on said backside.
26. A papermaker's or industrial fabric as claimed in claim 23 wherein said base
substrate is woven from lengthwise and crosswise yarns and wherein said preselected
locations encompass at least two consecutive knuckles formed by said yarns on said
backside and the valleys in between.
27. A papermaker's or industrial fabric as claimed in claim 23 wherein said fabric
is a dryer fabric.
28. A papermaker's or industrial fabric as claimed in claim 23 wherein said base
substrate is a spiral-link belt.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to the papermaking arts. More specifically, the
present invention relates to the papermaker's fabrics used on the dryer section
of a paper machine, and particularly on a single-run dryer section. Such fabrics
are commonly referred to as dryer fabrics.
2. Description of the Prior Art
As is well known to those of ordinary skill in the art, the papermaking process
begins with the deposition of a fibrous slurry, that is, an aqueous dispersion
of cellulosic fibers, onto a moving forming fabric in the forming section of a
paper machine. A large amount of water is drained from the slurry through the forming
fabric during this process, leaving a fibrous web on its surface.
The newly formed web proceeds from the forming section to a press section, which
includes a series of press nips. The fibrous web passes through the press nips
supported by a press fabric, or, as is often the case, between two press fabrics.
In the press nips, the fibrous web is subjected to compressive forces which squeeze
water therefrom, and which adhere its constituent fibers to one another to turn
the fibrous web into a sheet. The water squeezed from the web is accepted by the
press fabric or fabrics, and, ideally, does not return to the web.
The web, now a sheet, finally proceeds to a dryer section, which includes at
least one series of rotatable dryer drums or cylinders, which are internally heated
by steam. The sheet itself is directed in a serpentine path sequentially around
each in the series of drums by a dryer fabric, which holds the web closely against
the surfaces of at least some of the drums. The heated drums reduce the water content
of the sheet to a desirable level through evaporation.
It should be appreciated that the forming, press and dryer fabrics all take the
form of endless loops on the paper machine and function in the manner of conveyors.
It should further be appreciated that paper manufacture is a continuous process
which proceeds at considerable speed. That is to say, the fibrous slurry is continuously
deposited onto the forming fabric in the forming section, while a newly manufactured
paper sheet is continuously wound onto rolls after it exits from the dryer section
at the downstream end of the paper machine.
Referring, now, more specifically to the dryer section, in the dryer section,
the dryer cylinders may be arranged in a top and a bottom row or tier. Those in
the bottom tier are staggered relative to those in the top tier, rather than being
in a strict vertical relationship. As the sheet proceeds through the dryer section,
it passes alternately between the top and bottom tiers as it passes first around
a dryer cylinder in one of the two tiers, then around a dryer cylinder in the other
tier, and so on sequentially through the dryer section.
The top and bottom tiers of dryer cylinders may each be clothed with a separate
dryer fabric. In such a situation, the paper sheet being dried passes unsupported
across the space, or "pocket", between each dryer cylinder and the next dryer cylinder
on the other tier.
In a single tier dryer section, a single row of cylinders along with a number
of turning cylinders or rolls may be used. The turning rolls may be solid or vented.
In order to increase production rates and to minimize disturbance to the sheet,
single-run dryer sections are used to transport the sheet being dried at high speeds.
In a single-run dryer section, a paper sheet is transported by use of a single
dryer fabric which follows a serpentine path sequentially about the dryer cylinders
in the top and bottom tiers.
It will be appreciated that, in a single-run dryer section, the dryer fabric
holds
the paper sheet being dried directly against the dryer cylinders in one of the
two tiers, typically the top tier, but carries it around the dryer cylinders in
the bottom tier. The fabric return run is above the top dryer cylinders. On the
other hand, some single-run dryer sections have the opposite configuration in which
the dryer fabric holds the paper sheet directly against the dryer cylinders in
the bottom tier, but carries it around the top cylinders. In this case, the fabric
return run is below the bottom tier of cylinders. In either case, a compression
wedge is formed by air carried along by the backside surface of the moving dryer
fabric in the narrowing space where the moving dryer fabric approaches a dryer
cylinder. The resulting increase in air pressure in the compression wedge causes
air to flow outwardly through the dryer fabric. This air flow, in turn, forces
the paper sheet away from the surface of the dryer fabric, a phenomenon known as
"drop off". "Drop off" can reduce the quality of the paper product being manufactured
by causing edge cracks. "Drop off" can also reduce machine efficiency if it leads
to sheet breaks.
Many paper mills have addressed this problem by machining grooves into the dryer
cylinders or rolls or by adding a vacuum source to those dryer rolls. Both of these
expedients allow the air otherwise trapped in the compression wedge to be removed
without passing through the dryer fabric, although both are expensive.
In this connection, fabric manufacturers have also employed application of coatings
to fabrics to impart additional functionality to the fabric, such as "sheet restraint
methods." The importance of applying coatings as a method for adding this functionality
to, for example, dryer fabrics, has been cited by Luciano-Fagerholm (U.S. Pat.
No. 5,829,488 (Albany), titled, "Dryer Fabric With Hydrophilic Paper Contacting Surface").
Luciano and Fagerholm have demonstrated the use of a hydrophilic surface
treatment of fabrics to impart sheet-holding properties while maintaining close
to the original permeability. However, this method of treating fabric surfaces,
while successful in imparting sheet restraint, enhanced hydrophilicity and durability
of the coating is desired. WO Patent 97/14846 also recognizes the importance of
sheet restraint methods, and relates to using silicone coating materials to completely
cover and impregnate a fabric, making it substantially impermeable. However, this
significant reduction in permeability is unacceptable for dryer fabric applications.
Sheet restraint is also discussed in U.S. Pat. No. 5,397,438, which relates to
applying adhesives on lateral areas of fabrics to prevent paper shrinkage. Other
related prior art includes U.S. Pat. No. 5,731,059, which reports using silicone
sealant only on the fabric edge for high temperature and anti-raveling protection;
and U.S. Pat. No. 5,787,602 which relates to applying resins to fabric knuckles.
All of the above referenced patents are incorporated herein by reference.
The present invention is another approach toward a solution to this problem in
the form of a dryer fabric having backside vents which permit air trapped in a
compression wedge to escape without having to pass through the dryer fabric. The
present invention also includes a method for manufacturing the dryer fabric.
SUMMARY OF THE INVENTION
Accordingly, the present invention relates primarily to a dryer fabric,
although it may find application in any of the fabrics used in the forming, pressing
and drying sections of a paper machine, and in the industrial fabrics used in the
manufacture of nonwoven fabrics. As such, the papermaker's or industrial fabric
comprises a base substrate which takes the form of an endless loop having a backside
and a paper-contacting side. A plurality of discrete, discontinuous deposits of
polymeric resin material are disposed at preselected locations on the backside.
These deposits have a height, relative to the backside, of at least 0.5 mm so that
they may separate the backside from the surface of a dryer cylinder or turning
roll by that amount when passing therearound. The deposits allow air trapped between
the backside and the surface of the dryer cylinder to escape in both the lengthwise
and crosswise directions parallel to the surface rather than through the fabric
to alleviate the problem of "drop off".
The preselected locations for the discrete, discontinuous deposits of polymeric
resin material may be knuckles formed where the yarns in one direction of the fabric
pass over the yarns in the other direction. Alternatively, the preselected locations
may be "valleys" between knuckles, an alternative which carries the advantage of
bonding two intersecting yarns to one another at their crossing point. Alternatively
still, the preselected locations may be two or more consecutive knuckles aligned
in the machine or cross-machine direction and the valley or valleys in between.
When the preselected locations are aligned in the machine direction, this alternative
carries the advantage that it allows improved air channeling. Preferably, the deposits
reside only on the knuckles or on the backside surfaces of the yarns, where they
would not affect the permeability of the fabric. Further, as the deposits form
a sort of discontinuous coating on the backside, they have no effect on its bending
properties or on the location of its neutral axis of bending. Finally, by improving
the ability of the backside of the fabric to manage air in this manner, rather
than through the use of elaborate and complicated weave patterns to provide the
backside of the fabric with air channels, the base fabric weave structure used
for the base substrate may be provided with other characteristics, such as openness,
which would give it higher permeability to improve drying rate, and may be simpler
and less costly to manufacture and seam.
The present invention is also a method for manufacturing a papermaker's or industrial
fabric, such as a dryer fabric. The method comprises a first step of providing
a base substrate for the fabric.
Polymeric resin material is deposited onto preselected locations on the
base substrate in droplets having an average diameter of 10μ (10 microns)
or more to build up discrete, discontinuous deposits of the polymeric resin material
to a height of at least 0.5 mm relative to the surface of the base substrate. At
least one piezojet may be used to deposit the polymeric resin material onto the
base substrate, although other means for depositing droplets of that size may be
known to those of ordinary skill in the art or may be developed in the future.
The polymeric resin material is then set or fixed by appropriate means.
The preselected locations may, as stated above, be knuckles formed on the surface
of the fabric by the interweaving of its yarns.
Subsequently, the deposits of polymeric resin material may optionally
be abraded to provide them with a uniform height over the surface plane of the
base substrate.
The present invention will now be described in more complete detail, with frequent
reference being made to the figures identified below.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a schematic view of an apparatus used to manufacture papermaker's
and industrial fabrics according to the method of the present invention;
FIG. 2 is a cross-sectional view, taken in a lengthwise direction, of a dryer
fabric of the present invention;
FIG. 3 is a cross-sectional view of the dryer fabric taken in the crosswise
direction thereof as indicated in FIG. 2;
FIG. 4 is a perspective view of the backside of the dryer fabric;
FIG. 5 is a cross-sectional view taken in a lengthwise direction, of an alternate
embodiment of the dryer fabric;
FIG. 6 is a cross-sectional view, also taken in a lengthwise direction, of yet
another embodiment of the dryer fabric; and
FIG. 7 is a perspective view of a variety of representative shapes of the deposited material.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
The method for fabricating the papermaker's or industrial fabric of the present
invention begins with the provision of a base substrate. Typically, the base substrate
is a fabric woven from monofilament yarns. More broadly, however, the base substrate
may be a woven, nonwoven or knitted fabric comprising yarns of any of the varieties
used in the production of paper machine clothing or industrial fabrics used to
manufacture nonwoven articles and fabrics, such as monofilament, plied monofilament,
multifilament and plied multifilament yarns. These yarns may be obtained by extrusion
from any of the polymeric resin materials used for this purpose by those of ordinary
skill in the art. Accordingly, resins from the families of polyamide, polyester,
polyurethane, polyaramid, polyolefin and other resins may be used.
Alternatively, the base substrate may be composed of mesh fabrics,
such as those shown in commonly assigned U.S. Pat. No. 4,427,734 to Johnson, the
teachings of which are incorporated herein by reference. The base substrate may
further be a spiral-link belt of the variety shown in many U.S. patents, such as
U.S. Pat. No. 4,567,077 to Gauthier, the teachings of which are also incorporated
herein by reference.
Moreover, the base substrate may be produced by spirally winding a strip
of woven, nonwoven, knitted or mesh fabric in accordance with the methods shown
in commonly assigned U.S. Pat. No. 5,360,656 to Rexfelt et al., the teachings of
which are incorporated herein by reference. The base substrate may accordingly
comprise a spirally wound strip, wherein each spiral turn is joined to the next
by a continuous seam making the base substrate endless in a longitudinal direction.
The above should not be considered to be the only possible forms for the base
substrate. Any of the varieties of base substrate used by those of ordinary skill
in the paper machine clothing and related arts may alternatively be used.
Once the base substrate has been provided, one or more layers of staple fiber
batt may optionally be attached to one or both of its two sides by methods well
known to those of ordinary skill in the art. Perhaps the best known and most commonly
used method is that of needling, wherein the individual staple fibers in the batt
are driven into the base substrate by a plurality of reciprocating barbed needles.
Alternatively, the individual staple fibers may be attached to the base substrate
by hydroentangling, wherein fine high-pressure jets of water perform the same function
as the above-mentioned reciprocating barbed needles. It will be recognized that,
once staple fiber batt has been attached to the base substrate by either of these
or other methods known by those of ordinary skill in the art, one would have a
structure identical to that of a press fabric of the variety generally used to
dewater a wet paper web in the press section of a paper machine.
Once the base substrate, with or without the addition of staple fiber batt material
on one or both of its two sides, has been provided, it is mounted on the apparatus
10 shown schematically in FIG. 1, so that polymeric resin material may be
deposited on its backside in accordance with the present invention. It should be
understood that the base substrate may be either endless or seamable into endless
form during installation on a papermachine. As such, the base substrate
12
shown in FIG. 1 should be understood to be a relatively short portion of the entire
length of the base substrate
12. Where the base substrate
12 is endless,
it would most practically be mounted about a pair of rolls, not illustrated in
the figure but most familiar to those of ordinary skill in the paper machine clothing
arts. In such a situation, apparatus
10 would be disposed on one of the
two runs, most conveniently the top run, of the base substrate
12 between
the two rolls. Whether endless or not, however, the base substrate
12 is
preferably placed under an appropriate degree of tension during the process. Moreover,
to prevent sagging, the base substrate
12 may be supported from below by
a horizontal support member as it moves through apparatus
10. It should
finally be observed that, where the base substrate
12 is endless, it may
be necessary to invert it, that is, to turn it inside out, following the application
of polymeric resin material in accordance with the present invention to ensure
that the polymeric resin material resides on the backside of the base substrate
12.
Furthermore, for some applications, it may be necessary to apply the
resin pattern to the sheet contact side. Also, it is envisioned that the resin
application for air control should be applied to both sides of the fabric, either
with the same or different patterns.
Referring now more specifically to FIG. 1, where the base substrate
12
is indicated as moving in an upward direction through the apparatus
10 as
the method of the present invention is being carried out, apparatus
10 comprises
a sequence of several stations through which the base substrate
12 may pass
incrementally as a fabric is being manufactured therefrom.
The stations are identified as follows:
1. optional polymer deposition station 14;
2. imaging/precise polymer deposition station 24;
3. optional setting station 36; and
4. optional grinding station 44.
In the first station, the optional polymer deposition station
14, a piezojet
array
16 mounted on transverse rails
18,
20 and translatable
thereon in a direction transverse to that of the motion of the base substrate
12
through the apparatus
10, as well as therebetween in a direction parallel
to that of the motion of the base substrate
12, may be used to deposit a
polymeric resin material onto or within the base substrate
12 while the
base substrate
12 is at rest. Optional polymer deposition station
14
may be used to deposit the polymeric resin material more uniformly over the base
substrate than could be accomplished using conventional techniques, such as spraying,
if desired.
The piezojet array
16 comprises at least one but preferably a plurality
of individual computer-controlled piezojets, each functioning as a pump whose active
component is a piezoelectric element. As a practical matter an array of up to 256
piezo jets or more may be utilized if the technology permits. The active component
is a crystal or ceramic which is physically deformed by an applied electric signal.
This deformation enables the crystal or ceramic to function as a pump, which physically
ejects a drop of a liquid material each time an appropriate electric signal is
received. As such, this method of using piezojets to supply drops of a desired
material repeatedly so as to build up the desired amount of material in the desired
shape in response to computer-controlled electric signals is commonly referred
to as a "drop-on-demand" method.
The degree of precision of the jet in depositing the material will depend upon
the dimensions and shape of the structure being formed. The type of jet used and
the viscosity of the material being applied will also impact of the precision the
jet selected.
Referring again to FIG. 1, the piezojet array
16, starting from
an edge of the base substrate
12, or, preferably, from a reference thread
extending lengthwise therein, translates lengthwise and widthwise across the base
substrate
12, while the base substrate
12 is at rest, deposits the
polymeric resin material in the form of extremely small droplets having a nominal
diameter of 10μ (10 microns) or more such as 50μ (50 microns) or 100μ
(100 microns), onto the base substrate
12. The translation of the piezojet
array
16 lengthwise and widthwise relative to the base substrate
12,
and the deposition of droplets of the polymeric resin material from each piezojet
in the array
16, are controlled by computer in a controlled manner to apply
a desired amount of the polymeric resin material in a controlled geometry in three
planes length, width and depth or height (x, y, z dimensions or directions) and
in a per unit area of the base structure
12, if desired. In addition the
deposit of the material need not only be traversing the movement of the base substrate
but can be parallel to such movement, spiral to such movement or in any other manner
suitable for the purpose.
In the present invention, in which a piezojet array is used to deposit a polymeric
resin material onto or within the surface of the base substrate
12, the
choice of polymeric resin material is limited by the requirement that its viscosity
be 100 cps (100 centipoise) or less at the time of delivery, that is, when the
polymeric resin material is in the nozzle of a piezojet ready for deposition, so
that the individual piezojets can provide the polymeric resin material at a constant
drop delivery rate. In this regard, the viscosity of the polymeric resin material
at the point of delivery in conjunction with the jet size is important in defining
the size and shape of the droplets formed on the base substrate
12 and in
time the resolution of the pattern ultimately achieved. Another requirement limiting
the choice of polymeric resin material is that it must partially set during its
fall, as a drop, from a piezojet to the base substrate
12, or after it lands
on the base substrate
12, to prevent the polymeric resin material from flowing
and to maintain control over the polymeric resin material to ensure that it remains
in the form of a drop where it lands on the base substrate
12. Suitable
polymeric resin materials which meet these criteria and which are preferably abrasion
resistant are:
1. Hot melts and moisture-cured hot melts;
2. Two-part reactive systems based on urethanes and epoxies;
3. Photopolymer compositions consisting of reactive acrylated monomers and
acrylated oligomers derived from urethanes, polyesters, polyethers, and silicones; and
4. Aqueous-based latexes and dispersions and particle-filled formulations
including acrylics and polyurethanes.
It should be understood that the polymeric resin material needs to be fixed on
or within the base substrate
12 following its deposition thereon. The means
by which the polymeric resin material is set or fixed depends on its own physical
and/or chemical requirements. Photopolymers are cured with light, whereas hot-melt
materials are set by cooling. Aqueous-based latexes and dispersions are dried and
then cured with heat, and reactive systems are cured by heat. Accordingly, the
polymeric resin materials may be set by curing, cooling, drying or any combination thereof.
The proper fixing of the polymeric resin material is required to control its
penetration into and distribution within the base substrate
12, that is,
to control and confine the material within the desired volume of the base substrate
12. Such control is important below the surface plane of the base substrate
12 to prevent wicking and spreading. Such control may be exercised, for
example, by maintaining the base substrate
12 at a temperature which will
cause the polymeric resin material to set quickly upon contact. Control may also
be exercised by using such materials having well-known or well-defined curing or
reaction times on base substrates having a degree of openness such that the polymeric
resin material will set before it has time to spread beyond the desired volume
of the base substrate
12.
One or more passes over the base substrate
12 may be made by piezojet
array
16 to deposit the desired amount of material and to create the desired
shape. In this regard, the deposits can take any number of shapes as illustrated
generally in FIG. 7. The shapes can be square, round conical, rectangular, oval,
trapezoidal etc. with a thicker base tapering upward. Depending upon the design
chosen, the amount of material deposited can be layered in decreasing fashion as
the jet repeatedly passes over the deposit area.
When a desired amount of polymeric resin material has been applied per unit
area in a band between the transverse rails
18,
20 across the base
substrate
12, the base substrate
12 is advanced lengthwise an amount
equal to the width of the band, and the procedure described above is repeated to
apply the polymeric resin material in a new band adjacent to that previously completed.
In this repetitive manner, the entire base substrate
12 can be provided
with any desired amount of polymeric resin material per unit area.
Alternatively, the piezojet array
16, again starting from an
edge of the base substrate
12, or, preferably, from a reference thread extending
lengthwise therein, is kept in a fixed position relative to the transverse rails
18,
20, while the base substrate
12 moves beneath it, to apply
any desired amount of the polymeric resin material per unit area in a lengthwise
strip around the base substrate
12. Upon completion of the lengthwise strip,
the piezojet array
16 is moved widthwise on transverse rails
18,
20
an amount equal to the width of the lengthwise strip, and the procedure described
above is repeated to apply the polymeric resin material in a new lengthwise strip
adjacent to that previously completed. In this repetitive manner, the entire base
substrate
12 can be provided with the desired amount of polymeric resin
material per unit area, if desired.
Note the pattern can be random, a repeating random pattern on a base substrate
or such patterns that are repeatable from belt to belt for quality control.
At one end of the transverse rails
18,
20, a jet check station
22
is provided for testing the flow of polymeric resin material from each piezojet
in the piezojet array
16. There, the piezojets can be purged and cleaned
to restore operation automatically to any malfunctioning piezojet unit.
In the second station, the imaging/precise polymer deposition station
24,
the only station not optional in the present invention, transverse rails
26,
28
support a digital-imaging camera
30, which is translatable across the width
of base substrate
12, and a piezojet array
32, which is translatable
both across the width of the base substrate
12 and lengthwise relative thereto
between transverse rails
26,
28, while the base substrate
12
is at rest.
The digital-imaging camera
30 views the surface of the base substrate
12 to locate the knuckles formed where the yarns in one direction of the
base substrate
12 weave over those in the other direction. In the weaving
process these cross-over points, while being located very close to predetermined
or regular intervals, depending upon the weave pattern, do, however, vary. Accordingly,
merely attempting to deposit the polymeric resin material at discrete intervals
will not insure that all, or the desired number of cross-over points will receive
the deposit. Accordingly, a comparison between the actual surface and its desired
appearance are made by a fast pattern recognizer (FPR) processor operating in conjunction
with the digital-imaging camera
30 in real time. The FPR processor signals
the piezojet ar
