U.S. patent application number 09/971019 was filed with the patent office on 2002-02-28 for knit-deknit yarn and method and apparatus for making same.
Invention is credited to Auguste, Jean-Claude, Childs, Fred, Fink, Wilbert E..
Application Number | 20020023327 09/971019 |
Document ID | / |
Family ID | 23549916 |
Filed Date | 2002-02-28 |
United States Patent
Application |
20020023327 |
Kind Code |
A1 |
Auguste, Jean-Claude ; et
al. |
February 28, 2002 |
Knit-deknit yarn and method and apparatus for making same
Abstract
An improved heavy denier fibrillated polymer carpet yarn is
densely knit, deknit and heat treated. An improved carpet face yarn
is provided in an omnidirectional carpet pile.
Inventors: |
Auguste, Jean-Claude;
(Dayton, TN) ; Childs, Fred; (Dalton, GA) ;
Fink, Wilbert E.; (Villanova, PA) |
Correspondence
Address: |
Samuel C. Miller, III
BURNS, DOANE, SWECKER & MATHIS, L.L.P.
P.O. Box 1404
Alexandria
VA
22313-1404
US
|
Family ID: |
23549916 |
Appl. No.: |
09/971019 |
Filed: |
October 5, 2001 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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09971019 |
Oct 5, 2001 |
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09392260 |
Sep 9, 1999 |
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6321427 |
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Current U.S.
Class: |
28/218 ; 28/220;
28/247 |
Current CPC
Class: |
D04B 19/00 20130101 |
Class at
Publication: |
28/218 ; 28/220;
28/247 |
International
Class: |
D04B 019/00 |
Claims
We claim:
1. A process for making a carpet face yarn comprising: providing a
fibrillated polypropylene yarn greater than 7000 in Denier;
knitting the yarn on a knitting machine with a needle spacing less
than 0.75 inch to form a knitted fabric; pulling the knitted fabric
from the knitting machine; heat treating the knitted fabric to set
the yarn in a kinked form with a stitch length less than about one
inch; deknitting the fabric; and heat treating the yarn in situ in
the carpet.
2. The process of claim 1, wherein the yarn is knit into a sock on
a circular knitting machine with a circumferential needle spacing
of less than 0.67 inch.
3. The process of claim 2, wherein the yarn in the sock is heat set
into an approximately sinusoidal form having a wavelength .lambda.
of about 0.5 inches or less.
4. The process of claim 3, wherein the deknitted yarn is wound.
5. The process of claim 4, wherein the deknitted yarn is
essentially straightened during winding.
6. The process of claim 1, wherein, after heat treatment in situ
the yarn has a generally sinusoidal form and wherein the pile
height of the carpet above the backing is at least as great as the
wavelength,.lambda., of the yarn after the carpet is heat
treated.
7. The process of claim 1, wherein the yarn is from 7600 D to 8000
D.
8. A carpet yarn for a carpet product having a pile height of about
one inch or less, the yarn being polymeric in composition and
having a Denier of at least 7000, wherein the yarn is heat set into
a repeating curvilinear form with a repeat length in the carpet
product approximately equal to or less than the pile height.
9. The carpet yarn of claim 8, wherein the yarn is heat set into an
approximately sinusoidal form and wherein the repeat length of yarn
is on the average less than one inch.
10. The carpet yarn of claim 9, wherein the yarn is from 7600 to
8000 D.
11. Apparatus for making carpet yarn comprising: a supply of
polymer yarn of at least 7000 D; an applicator for applying a
lubricant to the yarn; a multi-needle circular knitting machine for
receiving the lubricated yarn and knitting the yarn into a sock
with a needle spacing of less than 2/3 inch; variable drive system
to pull the sock from the knitting machine at a selectable tension
to inhibit breakage of the knitting machine needles; an autoclave
for heat treating the sock; and mechanism for winding the yarn as
the sock is deknitted.
12. The apparatus of claim 11, wherein the circular knitting
machine is a 90 slot, 6.25 inch diameter knitting machine,
configured with 30 needles, one in every third slot.
13. The apparatus of claim 11, wherein the lubricant is a silicone
or oil.
14. The apparatus of claim 11, wherein the applicator is a rotating
coating roller in a reservoir of lubricant.
15. The apparatus of claim 11, wherein the knitted sock contains
yarn formed in repeating loops of less than about 1/4" edge to
edge.
16. The apparatus of claim 11, wherein the yarn in the heat treated
sock has a heat set, generally sinusoidal form.
17. The apparatus of claim 16, further comprising means for heating
yarn tufted in the carpet to cause it to partially recover its
sinusoidal form.
18. A carpet product comprising: a backing, and a carpet yarn
tufted with the backing, the carpet yarn having a Denier of at
least 7000 and having heat set, repeating open loops with a repeat
length approximately equal to or less than a pile height of the
carpet, wherein the yarn loops have an average amplitude comparable
to a separation distance between tufts in the carpet.
Description
BACKGROUND
[0001] Knit-deknit yarns have been used as carpet face yarns to
provide body and texture in carpet products produced therefrom.
[0002] Conventional methods for making such yarn involve knitting
an extruded, fibrillated polyolefin tape yarn into a sock on a
circular knitting machine. The sock is then heat treated to heat
set kinks in the yarn of the knitted sock. The yarn is then deknit
and wound for shipment. In use, the yarn may be formed into carpet,
for example, by conventional tufting techniques and heat treated to
cure the backing.
[0003] Conventionally, knit-deknit carpet yarns are of 5000 Denier
("D") or less. A typical product is 2200 D yarn knitted with 18
needles on a 90 slot, 6.25" diameter knitting machine such as an
UNRAV CY-600, or an L-R Machine Model 6-CK circular knitting
machine from Larry Rankin Machinery Co. On occasion, heavier
product has been known in the prior art, i.e. a 5700 D product
knitted with 30 needles, a 5000 D product knitted with 45 needles a
7,600 high density polyethylene yarn knitted with 22 needles and a
10,000 yarn knitted with 15 needles.
[0004] While these prior art yarns were acceptable for use in
carpets, a need exists for yarns which would provide improved face
yarns, particularly in high-end carpet products such as artificial
turf sports surfaces.
OBJECTS AND SUMARY OF THE INVENTION
[0005] It is an object of the present invention to provide a
heavier grade of polymer carpet yarn having a heat set topology
suitable for carpet products.
[0006] It is another object of the present invention to provide a
yarn for carpet product having a dense, attractive yarn pile
surface.
[0007] It is another object of the present invention to provide a
carpet yarn having a non-directional, highly resilient pile.
[0008] It is another object of the present invention to provide
methods and apparatus for making such yarns.
[0009] Applicants' initially believed that yarn of Denier greater
than about 5700 particularly relatively stiff polypropylene yarn)
could not be densely knit and commercially produced on conventional
knitting machines, at a needle count of greater than 22 on a 6.25
inch diameter circular knitting machine. However, applicants
demonstrated that a fibrillated polymer yarn of, for example, 7600
D could be knitted into a sock at a needle count of 30. A
conventional yarn lubrication applicator and conventional sock
take-up machinery was provided with variable speed and tensioning
to inhibit needle breakage in the knitting machine.
[0010] The resulting sock is densely knitted. The sock is heat
treated to produce a heavy denier product with a high number of
kinks per inch. The yarn is wound during which a twist may be
imparted and the kinks straightened. When formed into carpet and
heat-treated, the yarn blooms and produces a cut pile with a novel
upper surface characterized by a dense array of yarn fibril ends
having essentially random orientation. The carpet product also
exhibits high resilience.
[0011] Preferred embodiments of the present invention include a
process for making a carpet yarn. A fibrillated polyolefin yarn
greater than 7000 in Denier; and preferably 7600 D to 8000 D is
used. For example, the yarn may be 8000 D extruded polypropylene
tape, 700 mils wide and 2.1 mils thick, slit to produce a
fibrillated yarn. However, deniers of above 10,000, for example
11,000 D or 12,000 D may be used.
[0012] The yarn is knitted into a fabric or sock using a needle
spacing less than one inch, preferably less than 2/3 of an inch.
The sock is heat treated following which the sock is
de-knitted.
[0013] Advantageously the process is performed using a 90 needle
slot, circular knitting machine set up with 30 needles. Typically,
such a circular knitting machine is a 6.25 inch diameter machine
with a circumferential needle spacing of about 0.65" or less.
[0014] The knitting may result in a knitted sock with a loop width
of about 0.25 inches. Advantageously, the yarn is heat set in sock
form, deknitted, wound, transported to the carpet manufacturing
line, unwound and tufted as face yarn in a pile carpet. The carpet
is further heat treated which restores the general kinked form of
the yarn.
[0015] The present invention is also a carpet yarn of at least 7000
D extruded, fibrillated polyolefin tape having at least two kinks
per inch of yarn in the finished carpet.
[0016] A further aspect of the invention is an apparatus for making
the novel yarns disclosed herein. A preferred embodiment of the
apparatus includes a supply of polymer yarn of at least 7000 D. The
yarn is lubricated in a conventional fashion and fed to a
multi-needle circular knitting machine where it is knitted into a
sock preferably having a stitch length less than about one inch. A
variable drive pull roller of a type known in the art is employed
to pull the sock from the knitting machine at a selectable speed
and tension to inhibit breakage of the knitting machine needles. An
autoclave is used to heat treat the sock at for example 230.degree.
F. The yarn sock is deknitted after heat treatment and wound. After
tufting, the yarn is further heat treated causing it to take on a
repeating curvilinear form, especially a generally sinusoidal form.
In preferred embodiments, the yarn in the finished carpet product
has a repeat length or wavelength .lambda., approximately equal to
or less than the pile height of the carpet.
[0017] The foregoing is intended as a convenient summary of subject
areas described in this patent specification. However, the
invention to be protected is defined by the claims herein.
BRIEF DESCRIPTION OF THE DRAWINGS
[0018] FIG. 1 is a diagram illustrating apparatus and processes of
the present invention for making heavy denier, densely knit-deknit
yarn;
[0019] FIG. 2 illustrates a portion of a knitted sock such as
employed in embodiments of the present invention;
[0020] FIG. 3 illustrates a length of relaxed, deknit yarn,
illustrating dimensions of a preferred embodiment of the present
invention;
[0021] FIG. 4 is a side view of a tufted carpet made with heavy
denier, densely knit-deknit yarn in accordance with aspects of the
present invention;
[0022] FIG. 5 is a side view of various yarns illustrating the
location of various curvilinear portions;
[0023] FIG. 6 is a side pictorial view in partial cross section of
an apparatus for producing a yarn sock in accordance with the
present invention.
DETILED DESCRIPTION OF THE DRAWINGS
[0024] FIG. 1 is a diagram illustrating apparatus and processes of
the present invention for making heavy denier, densely knit-deknit
yarn. Dimensions and proportions have been exaggerated in the
Figure for illustration purposes and non-essential detail has been
eliminated.
[0025] A supply of high denier extruded polymer tape yarn 10 is
indicated by the yarn cone 12. In preferred embodiments, the yarn
is a fibrillated polypropylene tape yarn, the making of which is
described in U.S. Pat. Nos. 3,496,259 and 3,496,260 to Guenther et
al. The yarn is greater than 7000 D, more particularly between 7000
D and 10,000 D, most preferably between 7600 D to 8000 D.
[0026] The yarn advances in the direction indicated to a circular
knitting machine 14. In preferred embodiments the knitting machine
is a 6.25 inch diameter machine, with 90 needle slots. An example
of such a machine is the L-R Machine Model 6-CK. Typically, such
machines are used for knitting low denier yarn, for example
1000-1300 denier filament yarn with 90 or 60 needles. The highest
denier exemplified by the manufacturer is 3700 Denier Filament
Yarn, knit with 30 needles (one needle every third slot).
[0027] At their base needles 16 fit in a slot formed by top and
bottom cams that are secured in a rotating base--as that base
rotates the needles are moved up and down. The needle slots are
spaced equally in a circle. In a machine with a circumference of
19.6821 inches, the centerline needle spacing is about 0.2187
inches when 90 needles are used. Leaving out needles alters the
dimensions. The slot (gap) formed by the cams that raise and lower
the needles is set at 0.24 inches. The calculated stitch length for
the 30 needle 7600 denier yarn is 0.973 inches. This stitch length
may decrease slightly during heat treatment due to yarn shrinkage
(yarn shrinkages of 6 to 8% are typical).
[0028] Each needle in succession is lifted up by the bottom cam in
the rotating base. During the first revolution the needle is raised
and the keeper drops down opening the needle eye to grasp the first
thread at the top of its up stroke. The needle then begins its down
stroke closing the keeper as it is pulled down to the bottom of the
down stroke (by the top cam) and then pushed back up to its holding
position (by the bottom cam) to await the next full revolution of
the cam slot. During the next rotation the needle is again lifted
by the bottom cam and as it rises up the keeper opens and the yarn
loop in residence slides down the needle. At the top of the up
stroke the needle is free to grasp another portion of the yarn and
begin its next down stroke closing the keeper and pulling the new
loop through the loop already in residence as it completes the down
stroke. It then rises back to its holding position.
[0029] As shown in FIG. 1, the yarn 10 may be lubricated at
applicator 13 before reaching the knitting machine. The knitting
machine is set up with 30 needles 16 (one needle every third slot).
The needles move up and down as the base of the knitting machine
rotates to knit a sock 22 from the heavy denier yarn. It will be
understood that different needle numbers and positions may be
selected to vary the stitch dimensions.
[0030] FIG. 2 is illustrative of a stitch or loop pattern which may
be used to make the sock, a portion 18 of which is shown in the
Figure. The stitch pattern is selected so that the sock may be
readily deknit by pulling on an end 20 of the yarn.
[0031] Referring once more to FIG. 1, the knitted sock 22 exits the
bottom of the circular knitting machine 14. Rollers 24, 25, 26 and
27 direct and pull the sock into a collection bag 30. Roller 27 is
provided with a variable drive 28 which is used to adjust the
take-off speed of and tension on the sock 22.
[0032] Typically 10 to 20 lbs. of knitted sock is collected in the
collection bag 30 and then heat treated in an autoclave 32 to heat
set kinks produced by the knitting process. A typical heat set
temperature may be about 230.degree. F. for polyethylene yarns. For
polypropylene the heat set temperature may be between 240.degree.
to 290.degree. F., more preferably between 255.degree. F. to
260.degree. F.
[0033] The heat set process, as the term implies, sets a permanent
memory in the yarn. The remembered form is of repeating kinks,
repeating open loops or repeating partial loops. The yarn may be
straightened and then recover a knitted, crimped pattern when it is
again heated.
[0034] After the heat setting step, the sock is unwound from the
sock onto a conventional yarn cone or tube with enough tension to
pull the yarn flat as it is wound onto a spool of finished yarn.
The yarn is then put on a tufting machine where it is handled like
any other carpet yarn in the tufting process. The resulting greige
goods carpet generally shows only a small amount of the crimped
pattern in the face carpet fiber.
[0035] Once the carpet goes into the carpet coating process and is
heated to dry the latex backing material (for example in an oven),
the face yarn responds to the heat by returning to a crimped
pattern similar to the one earlier heat set into the yarn. In other
words, the yarn "blooms", i.e. recovers or remembers its sinusoidal
form. The resulting heat-treated carpet has a distinctive
non-directional appearance.
[0036] FIG. 6 illustrates in greater detail certain aspects of the
machinery associated with the knitting process. The knitting is
aided by lubricating the yarn with a suitable spin finish. For
example, a diluted solution of silicone in water may be used.
Alternatively, a clear oil may be used.
[0037] The finish applicator system that applies either the
silicone or oil type spin finish is shown at 13'. The finish
applicator may be located directly above and before the head of the
knitting machine 14'. The applicator uses a variable speed drive
motor 150 driving a coating roll 152 that revolves in a spin finish
reservoir 154. The yarn travels over the top part of the rotating
coating roll 152 before going down into the knitting machine 14'.
The heavier denier twisted yarns are round and the surface area
that contacts the coating roll 152 is smaller than the contact area
of lower denier flat tape type yarn. By increasing the coating roll
speed a heavier weight of coating can be applied to the twisted
yarn. The finish applicator system may be used to apply a heavier
weight of coating then would be applied by a stationary roll or a
brush device. Lubrication is critical at the point where a new
stitch is pulled through an existing stitch and where the heavier
denier yarn is pulled down through the needle slot to exit the
knitting head.
[0038] With regard to the knitting machine, the rotational speed
has been reduced from the typical 250 RPM to 190 RPM. At the higher
speed the stress on the needles is extreme and the machines can be
run for only short periods of time before severe needle breakage
occurs requiring the machine to be shutdown to replace broken
needles.
[0039] As the sock is knit it is important that the sock being
formed continues to move down and away from the knit head. Small
denier yarn socks literally fall away out of the machine, i.e.
pulling is assisted by the weight of the sock hanging below the
knit head. When yarn denier is increased the yarn tends to fill the
space in the needle slot. This makes it more difficult to pull the
new stitch through the one in residence and it also becomes harder
for the developing sock to make its exit from the knitting
head.
[0040] The process catastrophically fails if the needle cannot open
the keeper and release the last loop on its up stroke to begin a
new loop. It will also fail if upon grasping the new loop it cannot
pull it down and through the preceding yarn loop. The needle slot
must be evacuated by the forming sock or the rotating cams that
form the cam slot will push or pull the needle until the needle
breaks (often breaking most of the needles in the machine before it
can be stopped).
[0041] Accordingly, a variable speed pull roll system is employed.
Roll 27' is powered by motor and adjustable drive 28'. Through the
use of the rollers 24', 25', 26' and 27' the sock 22' is first
pulled downwardly from the knitting machine 14' then upwardly over
rolls 26' and 27' and finally deposited in the collection bag
30'.
[0042] Yarn in accordance with the present invention is shown in
FIG. 3 and is characterized by certain dimensions. In the example,
the yarn is 7600 D, knit with a needle to needle spacing of about
0.64".
[0043] The yarn in FIG. 3 is shown in a deknit, relaxed condition
(i.e. the ends are not under tension). The yarn takes on an
approximately sinusoidal form, a full wave of which consists of a
upward kink 52 and a downward kink 54. The sinusoid in the relaxed
configuration of the yarn may be characterized by dimension or
wavelength .lambda.. It will be understood that this dimension is
dictated at least in part by the density of the knitting. In
preferred embodiments, the value of .lambda. is less than 0.5 inch
more preferably less than 0.25 inch which translates into at least
about 2 kinks per linear inch (extended length of the yarn).
[0044] It will be understood that the value of .lambda. depends on
the tension on the yarn. In the example of FIG. 3, the initial
.lambda. value as the sock is knitted is approximately equal to the
needle spacing, i.e. 0.65 inches. However, the diameter of the sock
contracts after knitting resulting in a .lambda. in the knitted
sock of about 0.25 to 0.5 inches. After contraction, the edge to
edge loop width W is less than 0.25 inches. The yarn is also
characterized by a sock stitch length (the distance along the yarn
from point A to point B) which, in the example of FIG. 3 is about
0.97 inches. When the yarn is wound, the kinks are essentially
straightened thereby increasing the wavelength .lambda. to nearly
the stitch length.
[0045] FIG. 4 is a cross-sectional view of a cut pile carpet made
with heavy denier, dense knit-deknit yarn 100 in accordance with
the teachings of the preferred embodiment of the present invention.
The yarn may be tufted through a backing 102. The tufts are
separated by sufficient space to permit the yarn to bloom when the
carpet is heat treated. Advantageously, this separation S is
comparable to the amplitude A of the tufted yarn. An adhesive
coating or extruded sheet 104 is provided to bind the tufts in
place. However, it will be understood that the yarn of the present
invention may be used as the face yarn in other known carpet
constructions and products.
[0046] After heat treatment, the carpet in FIG. 4 is characterized
by a finished pile height F. Advantageously, the pile height is at
least as great as the .lambda. value of the yarn after heat
treating. The resulting carpet has a dense array of fibril ends 106
(for example 18 to 20 per tape). As shown in FIG. 4, the end of the
yarn segments making up the pile have a great variety of
orientations. This is illustrated by the dashed lines 108, which
are drawn tangent to the principle axes of the yarn segment ends.
As a result the pile is omnidirectional, i.e. it appears to have
approximately the same texture, regardless of the angle from which
it is viewed. Because of the sinusoid shape of the yarn segments,
the pile in the finished carpet has a dense, attractive
surface.
[0047] The effect of employing more needles in the knitting process
is illustrated in FIG. 5. A yarn made using a relatively high
needle density is shown in FIG. 5(a). The shaded regions 120 of the
yarn are regions where a curvilinear shape is formed during
knitting and then heat set. These regions are separated by
relatively short, substantially straight segments of length x. In
contrast, a yarn made with relatively less needle density (about
half in the example) has longer substantially straight segments of
length y (about twice as long in the example). It will be
understood that, for a given carpet pile height L, the yarn of FIG.
5(a) will provide more bloom than the yarn of FIG. 5(b), which, in
contrast, will produce tufts with more vertically upstanding yarn
regions.
[0048] This effect is illustrated in FIGS. 5(c) and (d). In FIG.
5(c), the yarn of FIG. 5(a) is tufted into backing. Tension in the
winding and tufting process has temporarily straightened most of
the shaded curvilinear regions. A tuft is shown cut at 122. After
heat treatment, the cut yarn blooms as indicated in FIG. 5(d).
[0049] In FIG. 5(e), the yarn of FIG. 5(b) is tufted into a backing
to produce approximately the same pile height L as in FIG. 5(c). A
tuft of this lower needle density yarn is shown cut at 124. After
heat treatment, the cut yarn retains more vertically upstanding
length as indicated in FIG. 5(f).
[0050] The yarn of the present invention provides better coverage
(or bulk) in that it spreads out more in the finished carpet giving
the carpet a fuller appearance then the same weight of straighter
yarn. Accordingly, the face weight can be reduced without a loss of
good appearance. The carpet also has a somewhat more resilient feel
to it as it is walked upon, particularly as the face weight of
carpet is increased.
[0051] The non-directional feature is particularly valuable in
sports applications. This feature provides ease and consistency of
footing irrespective of the directional orientation of the carpet
in sports fields such as baseball, football or soccer fields. In
surfaces for golf greens, practice putting greens, miniature golf
links and lawn bowling lanes, the yarns and carpet facilitate
improved ball roll because the carpet does not have a grain or bias
in any one direction that might tend to influence the way a ball
rolls.
[0052] The foregoing is intended as a description of preferred
embodiments of the present invention. However, the scope of the
invention claimed is defined by the literal language of the
following claims and equivalents thereof.
* * * * *