Note: Descriptions are shown in the official language in which they were submitted.
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APF-2.19.1
SINGLE LAYER PIN SEAM FABRIC ~AVING
PERPENDICULAR SEAMING LOOPS AND METHOD
FIELD OF THE INVENTION
This invention ralates generally to a joint
construction for a papermakers fabric. More particularly, the
invention relates to pintle seamed joints for papermakers wet
press felts.
BACKGROUND OF THE INVENTION
In conventional papermaking machines, wet felts convey
the sheet of paper, paperboard, etc., from the wire or
cylindrical mold through various water removing equipment.
Such wet felts are often woven endless and are applied
as such to the rolls of the papermaking machine. The
installation of endless wet felts in the past has required
cessation of operations for extended periods of time with the
resultant loss of production from the paper machine.
Recent developments have resulted in greater use of
seamed press felts which are joined or seamed by a pintle to
simulate the endless condition. This construction is generally
described as a pintle seamed ~oint. The inability to produce a
pintle seamed joint geometry which does not differ substantially
from the plane of the fabric body has been a major fault with
this newer construction.
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U.S. Pa~ent 2,~83,734 provided a wet felt of a woven
open-ended strip construction which wa~ made endless by joining
together the extensions of ~arn from the weave of the felt at
the joining ends thereof. One end of the wet felt is fed
through the press section of the machine, until it completes a
full loop. The yarn extensions at the joining ends of the felt
are continuous with the weave system thereof and are used for
joining together the two ends of the felt, and a textile yarn or
cord is used to secure both sets of yarn extensions together and
retain the two ends of the felt connected together to form an
endless belt structure. Thus, the wet felt is installed without
having to disassemble the machine.
The art is replete with descriptions of seam
constructions for papermakers felts; Ree for example the
disclosures of U.S. Patent Nos. 2,883,734: 3,283,388: 3,309,790;
4,123,022: 4,141,388; 4,186,780 and 4,364,421. In general, the
seam constructions of the prior art have not been entirely
satisfactory for all purposes and applications.
U.S. Patent No. 4,500,590 issued February 19, 1985 to
Smith, attempts to solve this problem via a composite pintle
including a polyester core and an outer low-melt polymeric
sheath which has been softened and deformed. This composite
pintle exhibits a profile which occupies void areas in the mesh
of the helical fabric in the area of the pintle joint.
The caliper of the seam area is one problem addressed
by my copending Canadian Patent Application number
598,354. The permeability of the seam area and assembly of the
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seam during installation of the papermakers fabric can also be
problematic. In particular, in single layer base fabrics having
the machine direction yarns formed into series of loops for pin
seaming, the machine direction yarn loops generally have an
angular orientation which i5 not orthogonal to the pintle. The
angular orientation of the loops makes the fabric more difficult
to seam during installation and may adversely effect the
permeability of the fabric at the seam area.
SUMMARY AND OBJECT OF THE INVENTION
A papermakers fabric is made with a woven base fabric
having two ends. The base fabric includes a single layer of
machine direction yarns having a system of cross machine
direction yarns interwoven in a repeat pattern. At each end of
the base fabric, the machine direction yarns are formed into a
series of loops with a common angular orientation across the end
of the base fabric. The base fabric ends can thereby be joined
by intermeshing the respective end series of loops and inserting
a pintle through the intermeshed loops.
Unlike conventional pin seam fabrics, the angular
orientation of the loops on one end of the base fabric are
formed in the opposite direction from the angular orientation of
the loops of the other end of the fabric when said respective
end loops are intermeshed. The base fabric is heat set with the
base fabric ends joined with a pintle such that both series of
end loops take on a substantially vertical orientation.
It is an object of the invention to provide a
papermakers fabric and method of making same having an improved
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pin seam which facilitates speedy installation of the
papermakers fabric. In particular it is an object to provide a
base fabric for a papermakers felt having a single layer of
machine direction yarns formed into end loops for pin seaming
which are substantially orthogonal to the pintle.
DESCRIPTION OF THE DRAWINGS
Figure 1 is a top plan view of a prior art single
layer fabric construction;
Figure 2 is a section taken through the line
2-2 of the single layer fabric shown Figure 1;
Figure 3 is the section shown in Figure 2 after
the fabric has been heat set;
Figure 4 is a plan view of the base fabric seam
area of a paper~akers fabric according to the instant invention;
Figure 5 is a section view taken along the line
5-5 of the papermakers fabric shown in Figure 4; and
Figure 6 is the section shown in FigUre 5 after
the fabric has been heat set.
DESCRIPTION OF THE PREFERRED EMBODIMENT
The terms machine direction and cross machine direction
as used herein refer to the fabric orientation on the
papermaking machine rather than in the loom.
Figure 1 is a portion of a prior art seam
construction in a woven fabric which includes a plurality of
machine direction yarns 1 interwoven with a plurality of
cross machine direction yarns 4. In order to seam the
fabric, a plurality of integral contiguous seaming loops 2,
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3 are formed at each terminal end, respectively, of the woven
fabric. The seaming loop6 2 are formed using techniques
known in the art. To place the fabric in service, loops from
each end of the fabric are intermeshed to form a channel and a
pintle, such as 5, is inserted to retain the fabric ends
together in a substantially continuous, endless structure.
With reference to F~gures 2 and 3, the prior
art construction will be explained in more detail. Generally
the end loops 2, 3 in the single layer fabric are formed
with an angular orientation represented by angle ~ with respect
to a vertical plane P which is orthogonal to the cross machine
direction pintle yarn 5. The angular orientation of the
formation of loops 2, 3 is inherent in single layer fabrics
since in forming the loop machine direction yarn one passes out
from the end of the fabric and returns next to itself to
continue the weave of the fabric. In contrast, in a base fabric
having multiple layers of machine direction yarns, the machine
direction yarns may extend from the end of the fabric, form the
loop, and be rewoven directly beneath itself thereby forming a
vertically oriented loop with no angular orientation.
Conventionally, as shown in Figures 1, 2, and
3, the loops ef a single layer base fabrics are formed at
the respective ends of the fabric such that when the loop series
are intermeshed the angular orientation of respective loops
2 and 3 is ~enerally in the same direction.
Conventionally, after the loops 2, 3 are formed,
the base fabric is heat set to render stability to the base
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fabric and seam. Heat setting is performed with the base fabric
ends joined by a pintle 5 inserted through the intermesh
series of loops 2, 3 respectively. Figure 2 illustrates
the loops prior to heat setting: Figure 3 illustrates the
loops after the heat setting operation. The pintle is then
removed to provide an open fabric for installation on
papermaking equipment.
In such seam construction, heat setting is generally
insufficient to remove the angular orientation of the seam
loops. This can cause difficulty in rejoining th~ fabric ends
when the papermakers fabric is installed on papermaking
equipment and lengthen installation time.
With reference to Figure 4 there i8 shown a portion
of the seam area of a single layer base fabric 10 made in
accordance with teachings of the present invention. The base
fabric 10 includes machine direction the yarns 11
interwoven with a single layer of cross machine direction yarns
14. Similar to conventional single layer base fabrics, the
machine direction yarns form a series of loops 12 and
13, respectively, at each end of the base fabric. The loops
may be formed durinq weaving using endless and/or double endless
weaving as discussed in my copending Canadian Patent Application
no. 598,354 or, if the fabric is woven flat, the loops may be
formed by back weaving the mach~ne direction yarns as also
discussed in that patent application.
As with the conventional formation of loops from
machine direction yarns in a single layer base fabric, the loops
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12 and 13 are formed with an angular orientation ~ with
respect a plane P which is orthogonal to the plntle 15.
As best seen in Figure 5, unlike conventional
fabrics, the loops 12 have an angular orientation in the
opposite direction as the loops 13 of the other end of the
fabric. The base fabric 10 is heat set with the respective
ends joined with a temporary pintle 15. The heat setting of
base fabric 10 causes the angular orientation of respective
loops 12 and 13 to converge towards each other and the
orthogonal plane P. As best shown in Fig~re 6, this results
in the loops 12, 13 having a substantially vertical
orientation after heat setting.
A fiberous batt 20 (shown in phantom) may be
needled on one or both sides of the base fabric after heat
setting dependant upon the intended usage of the finished
papermakers fabric.
The temporary pintle 15 used during heat setting is
removed to provide an open fabric in order to install the
papermakers fabric on papermaking equipment. The substantially
vertical orientation of the respective loops 12, 13
facilitates the rejoining of the fabric ends when the fabric is
installed.
It will be appreciated to one ordinarily skilled in the
art, that if the base fabric is woven endless, the loops 12,
13 will be formed around a pintle yarn 15 during the
weaving process. Accordingly, when the loops are formed in this
manner the base fabric may be heat set in its endless state
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without having to intermesh the loops of the respective ends to
insert a pintle therethrough. Normally the respective loops are
formed around a temporary pintle. However, if the loops having
the opposing angular orientations must be intermeshed and joined
with pintle in the fabric's non-heat set state, any difficulty
in the seaming of the non-heat set fabric is outweighed by the
benefits of the substantial vertical orientation of the loops
which they take on as a result of the heat setting process. The
substantial vertical orientation of the end loops 12, 13
after heat setting permits the speedy seaming of the fabric ends
together when the fabric is installed on papermaking equipment
where paper production cannot be continued until fabric
installation is completed.
The vertical orientation of the end loops 12, 13
also contributes to a more uniform permeability of the fabric at
the seam area. In addition to being easily installed, the seam
of a fabric must not create an irregularity in the overall
fabric which would cause the aqueous paper web which is
transported by the fabric to become marked or otherwise
disfigured.
