Pocket arrangement in the support surface of a woven papermaking fabric

A woven fabric for use on papermaking machines having first and second sets of filaments interwoven with each other to provide a first grouping of coplanar top surface crossovers and a second grouping of recessed sub top surface crossovers. The first grouping of top surface crossovers are in spaced relation to define a plurality of at least first and second cavities. The first ones of the cavities are arranged along substantially parallel lines in the cross machine direction and the machine direction. The second ones of the cavities are spaced from the first ones of the cavities and are arranged along substantially parallel lines which extend in both the cross machine direction and the machine direction. Individual ones of the first cavities are arranged adjacent of and are interconnected with individual ones of the second cavities. The interconnected first and second cavities form cavity pairs.

BACKGROUND OF THE INVENTION 
This invention relates to a dryer fabric for the formation of soft 
absorbent, wet-laid imprinted creped paper which is characterized by 
multi-cavity pockets arranged in randomly arranged appearing patterns over 
the support surface. 
Creped paper which presents a surface texture which is pleasing to the eye 
and yet possesses a soft feel, a high absorbency capacity, good strength 
and good stretch characteristics, has long been recognized as a product in 
demand. Numerous attempts have been made to produce forming dryer fabrics 
which form such a product with varying degrees of success. 
A dryer fabric for the formation of creped paper is disclosed in U.S. Pat. 
No. 3,974,025 to Ayers. This fabric, as disclosed by Ayers, is formed with 
spaced rows, comprised of diamond shaped patterns, which extend 
transversely thereof. The patent discloses using the back side of the 
drying fabric which is woven in a twill or semi-twill weave. 
Yet another dryer fabric for the formation of creped paper is disclosed in 
U.S. Pat. No. 4,239,065 to Trokham. The patent discloses using imprinting 
fabrics woven in various twill and semi-twill weave patterns. An Atlas 
weave pattern is preferred. It is of particular relevance to note that the 
forming fabrics used in the production of paper in Trokham have been heat 
set to provide that certain of the warp and the weft present knuckles 
having top surfaces which lie along a common plane. Certain other of the 
warp is controlled to present knuckles which lie along a sub-top surface 
plane. 
The pockets formed on the support surface of the prior art patents are 
generally uniform in shape and extend uniformly either transversely or 
diagonally across the fabric. 
SUMMARY OF THE INVENTION 
The instant invention has as its object the formation of a papermaking 
fabric in which pockets are formed over the support surface in a manner 
which appears random or non uniform. 
Another object of the instant invention is the provision of a papermaking 
fabric having interconnected pockets arranged over its support surface. 
Another object of the invention is the production of a papermaking fabric 
which produces crepe paper having pillows which are arranged over the 
surface of the paper in a non linear appearing manner. 
Another object of the invention is the formation of a dryer fabric having 
multiple interconnected pockets arranged in opposing fashion over the 
support surface. 
The instant invention is directed to a woven fabric for use on papermaking 
machines. These fabrics traditionally have a support surface and a running 
surface. The fabric comprises a first set of filaments which are disposed 
in a generally parallel relationship with each other in a first direction 
and a second set of synthetic filaments which are disposed in a generally 
parallel relationship with each other in a direction transverse of the 
first set of filaments. 
The first and second sets of filaments are interwoven with each other to be 
serpentinely configured to provide a first grouping of coplanar top 
surface crossovers of the first and second sets of filaments and a second 
grouping of recessed sub top surface crossovers of at least one of the 
first and second set of filaments. The first grouping of top surface 
crossovers are in spaced relation to define a plurality of at least first 
and second cavities with the first ones of the cavities being arranged 
along substantially parallel lines in the cross machine direction and the 
machine direction. The second ones of the cavities are spaced from the 
first ones of the cavities and are arranged along substantially parallel 
lines which extend in both the cross machine direction and the machine 
direction. Individual ones of the first cavities are arranged adjacent of 
and are interconnected with individual ones of the second cavities. The 
interconnected first and second cavities form cavity pairs. 
The cavity pairs formed by individual ones of the first set of machine 
direction cavities interconnect with individual ones of the second set of 
machine direction cavities and are arranged so that the cavities of the 
second set appear on alternate sides of the machine direction parallel 
lines along which the first set of cavities are aligned. The first 
cavities of the cavity pairs are arranged in adjacent pairs vertically 
along parallel lines in the machine direction while the second cavities of 
the cavity pairs are arranged in adjacent pairs horizontally along 
parallel lines in the cross machine direction. The points of connection 
for the first and second cavities extend along diagonal lines which are 
arranged transversely of the fabric. Each of the first and second cavities 
may encompass a pair of sub top surface crossovers. 
The fabric may be woven in a six shed modified or broken twill weave or in 
a four shed modified twill weave. 
The first and second group of yarns comprise machine direction yarns (MD) 
and cross machine direction yarns (CMD) which are synthetic monofilaments 
yarns. Normally the synthetic monofilaments are all of equal size and are 
formed of a polyester, a polyamide, a polyaryetherketones or a blend of 
polyester and polyamide. In certain instances the cross machine direction 
yarns may be larger than the machine direction yarns and in other 
instances they may be smaller than the machine direction yarns. 
The fabric may be woven to form first, second, third, and fourth cavities. 
In this arrangement, the first cavities are interconnected with the second 
cavities to form first cavity pairs and the third cavities are 
interconnected with the fourth cavities to form second cavity pairs. The 
first cavity pairs and the second cavity pairs have C shape configurations 
and are arranged as opposed pairs uniformly over the support surface of 
the fabric.

DESCRIPTION OF A PREFERRED EMBODIMENT 
Turning now to the drawings, FIGS. 1-6 show various well known support 
surface configurations for papermaking fabrics. FIGS. 1, 2, and 5 show 
papermaking fabrics in which pockets 10 formed on the support surface are 
arranged in diagonal rows along the length of the fabric and in parallel 
rows along a single pick transversely of the fabric. FIGS. 3, 4, and 6 
show papermaking fabrics in which pockets 12 formed on the support surface 
are arranged along diagonal rows while the transverse arrangement of the 
pockets are arranged over a plurality of picks and are slightly skewed. In 
each of these prior art arrangements, the pockets are symmetrically shaped 
and arranged along continuous parallel lines. 
Turning now to FIGS. 7 and 8, there is shown four repeats of papermaking 
fabric 14 woven in a six shed, six pick modified twill weave. The 
particular weave pattern has the first warp yarn (1) of warp yarns 18 of 
the weave pattern weaving under the first pick (1) of weft yarn 16 and 
over the remaining picks (2, 3, 4, 5, 6) of weft yarn 16. The second warp 
yarn (2) of warp yarn 18 weaves over picks (1 and 2) of weft yarn 16, 
under pick (3) and then over picks (4,5,6). The third warp yarn (3) of 
warp yarn 18 weaves over picks (1, 2, 3, 4). The fourth warp yarn (4) of 
warp yarn 18 weaves over the first (1) pick of weft yarn 16, under pick 
(2) and over pick (3, 4, 5, 6). The fifth warp yarn (5) of warp yarn 18 
weaves over picks (1, 2, 3, 4, 5) of weft yarn 16 and under pick (6). The 
sixth (6) and final warp yarn of warp yarns 18 of the weave pattern weaves 
over picks (1, 2, 3) of weft yarn 16, under pick (4) and over picks (5, 
6). This weave pattern creates cross machine direction (CMD) or cross 
fabric crossovers 20 which have their upper surfaces extending along a 
common plane over the support surface. Machine direction (MD) or fabric 
direction crossovers 24 are created with portions of their top surfaces 
extending along the referred to common plane at 28 and other portions of 
these crossovers extending along a sub-support surface plane creating 
sub-support crossovers 26. These sub-support surface crossovers 26 form 
separate pockets 30, 32, 34, and 36 which are defined by support surface 
crossovers 20, 24 along areas 28 and as indicated by the crossovers 
identified with an X. 
Pockets 30, 32 are interconnected at 38 forming a first group of pocket 
pairs 40. Pockets 34, 36 are also interconnected at 38 forming a second 
group of pocket pairs 42 which are mutually exclusive from said first 
group of pocket pairs. Pocket pairs 40, 42 are each shaped in somewhat of 
a C or crescent configuration. 
Pocket pairs 40 are arranged with first pockets 30 arranged along a common 
axis both along the fabric length as indicated by line B and transverse 
the fabric as indicated by line A. Second pockets 32 of pocket pairs 40 
are similarly arranged along different axis. 
First pockets 30 of pocket pairs 40 are arranged in juxtadasposed pairs 
longitudinally of or along the fabric length while second pockets 32 are 
arranged in juxtadasposed pairs transversely of the fabric. Adjacent 
pocket pairs 40 are arranged in reverse configurations so that they appear 
to fit together or face each other. 
Second pocket pairs 42 are arranged in alternating rows with first pocket 
pairs 40. Second pocket pairs consist of third pockets 34 and fourth 
pockets 36 interconnected at 38. Third pockets 34 are arranged over the 
support surface similarly to first pockets 30 and fourth pockets 36 are 
arranged similarly to second pockets 32. The longitudinal axes along which 
adjacent third pockets 34 are arranged are transversely offset from the 
longitudinal axes along which adjacent first pockets 30 are arranged. 
Transverse rows of fourth pockets 36 are separated longitudinally of the 
fabric by two rows of first pocket pairs 40. 
The support surface of papermaking fabric 14 provides superior areas of 
sub-support surface pockets, defined by pocket pairs 40, 42 which provide 
well defined pillows over the paper surface. These pillows generate a 
paper which is soft to the touch and has superior absorptive powers. Ample 
compressed areas are formed over the paper surface by support surface 
crossovers 20 and 28 to provide sufficient strength to the paper and also 
to define the pocket areas. 
A second embodiment of the invention is shown in FIGS. 9 and 10. FIG. 9 is 
a fragmentary view showing four repeats of the weave pattern forming 
papermaking fabric 46. The weave pattern is a four shed broken twill in 
which four warp yarns 48 weave with four weft yarns 50. 
As shown, the first warp yarn (1) warp yarns 48 passes over picks (1, 2) 
under pick (3) and over pick (4) of weft yarn 50. The second warp (2) of 
warp yarns 48 passes over pick (1, 2, 3) and under pick (4) of weft yarns 
50. The third warp (3) of warp yarns 48 passes over pick (1) under pick 
(2) and over picks (3, 4) of weft yarn 50. The fourth (4) and final warp 
yarns 48 passes under pick (1) and over picks (2, 3, and 4) of weft yarn 
50 to complete the weave pattern. 
The support surface of papermaking fabric 46 is composed of cross machine 
direction crossovers 52 formed by weft yarns 50 which provide upper 
surfaces along a generally common plane. The machine direction (MD) 
crossovers 54 formed by warp yarns 48 provide upper surfaces at 56 which 
extend along the same plane as CMD crossovers 52 and other crossover 
surfaces 58 which extend along a sub support surface common plane. These 
sub support surface crossovers 58 create first pockets 60 and second 
pockets 62. First and second pockets 60, 62 are interconnected at 64 to 
form pocket pairs 66. Pocket pairs 66 are arranged so that first pockets 
60 are arranged along common axes transverse and longitudinally the fabric 
46. Second pockets 62 are also arranged to appear along common axes 
transverse and longitudinally of fabric 46. First and second pockets 60, 
62 are arranged adjacent each other longitudinally of the fabric. First 
pockets 60 are separated by second pockets 62 as they appear transversely 
of fabric 46. 
Again the support surface of fabric 46 provides ample cavity or pocket area 
to produce paper in which a major portion of its surface consist of 
pillows of uncompressed fibers circumscribed by lineaments of compressed 
fibers created by the support surface crossovers. 
It is preferred that the dryer fabrics of the preferred embodiments of the 
invention be woven of monofilament synthetic yarns formed of polyamide, 
polyester, polyaryletherketones or a blend thereof. Multifilament yarns 
could also be employed as warp, weft or both. The yarns are preferably 
between 0.14 and 1.0 mm in diameter and are of one size or variable sizes 
in the warp and/or weft. The fabric may be woven with a count of between 
10.times.10 to 120.times.120 filaments per inch. Using 0.4 mm filaments, a 
count of 40.times.40 is preferred. 
While a preferred embodiment of the invention has been described using 
specific terms, such description is for illustrative purposes only, and it 
is to be understood that changes and variations may be made without 
departing from the spirit or scope of the following claims.