-
Lesson Twelve
第
12
课
Yarns
纱线
Spinning
is
the
oldest
method
of
manufacturing
yarn.
The
process
requires
aligning
a
bundle
of staple fibers, pulling them out into a rope,
known as a roving, and further pulling out and
twisting the roving to form the yarn.
The product of the spinning
operation is a twisted assembly
of fibers that is strong and flexible.
The yarn is stronger than the individual fibers
since the fibers
act in concert to
support a load. Single yarns may be twisted
together to form an even stronger yarn,
These plied yarns may be plied again
and again to make thicker and stronger cords,
cables, rope and
hawsers.
纺纱
是制造纱线最原始的方法。纺纱过程要求一束短纤维排成一线，将他们拉入一对罗
拉中，
例如粗纱，继续拉伸并加捻粗纱形成纱线。细纱工序的产品是一束具有一定强度和挠
曲性
的加捻纤维集合体。纱线比其包含的纤维的联合强度要大，因为纤维通过联合作用共同
承
担外界负荷。单根纱线可能被放在一起加捻以形成更高强力的纱线。这些合股线可能被一
次又一次的合股以形成更厚重强力更大的粗绳索。
Yarns, cords, and cables may be twisted
in either S or Z direction. An S-twist yarn is one
in
which the fibers follow a spiral
pattern parallel to the center bar of the letter
S. In a Z-twist yarn the
fibers are
parallel to the center bar of the letter Z. Often
yarns are too fine to allow the unaided eyes
to discern the twist direction.
However, if you hold a short length of yarn
vertically in your left hand
and rotate
it between the thumb and forefinger of your right
hand while pulling upward, you can
determine the twist direction. When it
is rolled clockwise by your right hand, an S-twist
yarn will
become
tighter
and
a
Z-
twist
yarn
looser.
The
direction
of
the
twist
does
not
affect
the
yarn’s
performance. However, it is customary
to produce cotton and linen yarns with a Z-twist
and woolen
and worsted yarns with an
S-twist. This custom has its roots in medieval
consumer protection laws;
consumers
could easily find out whether a cloth was really
wool by simply untwisting one of the
yarns and checking the direction of the
twist.
这些粗绳可能被加上
S
捻，
也可能被加上
Z
捻。
S
捻的纱线中的纤维成螺旋状并与字母
S
中间的斜杠平行。在
Z
捻的纱线中，纤维与字母<
/p>
Z
中间的斜杠平行。纱线通常因为太细使得
肉眼很难识别其捻向。然而，当你用左手竖直的拿着一小段纱线，再用右手的拇指和食指夹
住纱线的另一头，一边向上拉，一边旋转，这时你就可以测出它的捻向了。如果你用右手顺
< br>时针的旋转它，
S
捻的纱线会越变越紧，
Z
捻的纱线会越变越松。加捻的方向不会影响纱线的
外
观。然而，人们习惯性的生产棉和亚麻纱线时用
Z
捻，生产羊毛
和精纺毛料纱线时用
S
捻。
这种习俗起
源于中世纪的消费者保护法；消费者可以仅仅通过退捻纱线，检查纱线捻向，从
而轻易地
确定布料是否是真正的羊毛所制。
As
the
yarn
is
twisted,
internal
forces
are
built
up
in
the
direction
of
the
twist.
These
forces are known as torque. In general,
each turn adds the same amount of torque to the
yarn, so
yarns with the same number of
turns per meter have about the same amount of
torque. Since the
torque is
approximately proportional to the tpm ( turns per
meter ), we may illustrate the formation
of balanced and unbalanced yarns by
counting the turns per meter. Start with a pair of
single yarns
having 200 tpm in the S
direction. Twist them together with another 100
tpm in the S direction .The
internal
torque on each of the singles will be about 300
tpm , while torque on the two-ply yarn will
be 100 in the S direction. This yarn
will be unbalanced, and will curl. If the same two
single are
plied into a double by
twisting 100 tpm in the Z direction, the
counterclockwise twist will tend to
unwrap the single yarns and the
internal torque of the single yarns will be
reduced to 100 in the S
direction.
The
external
torque
will
be
100
in
the
Z
direction.
The
internal
and
external
torques
balance each other and the yarn will be
balanced. It is important to the manufacturer that
the yarn be
balanced during cloth
construction because the kinks and curls that may
be formed by unbalanced
yarns will
become entangled in the machinery and cause
imperfections in the product. This simple
analysis
holds
only
for
two-ply
yarns.
More
complicated
structures,
such
as
cords
and
cables,
require a more sophisticated approach.
当纱线被加捻的时候，在捻度的方向上也会相应地形成内应力。这种力被称为扭转力。<
/p>
通常，纱线每转一圈，都会增加相同的扭转力，所以每米具有相同转数的纱线就会具有相同
的扭转力。既然扭转力和每米纱线所具有的转数（
tpm
）近似成正比，因此我们通过数出纱线
每米的转数来说明平衡纱线和非
平衡纱线的形成原理。以一对
200tpm
的
< br>S
捻向的单纱为例。
用另外的
1
00tpm
的
S
捻将两个单纱加捻到一
起。每根单纱的内部扭转力就达到了
300tpm
，然
而合股线在
S
捻方向上的扭转力是
100tpm
。这时纱线则不平衡，将会形成卷曲。如果给相同
的两根单纱加上
Z
方向上
1
00tpm
的捻度使它们合成一股时，逆时针方向的加捻则会使单根纱
< br>线易于解开，
使其在
S
捻向上的
内部扭转力降到
100
。
合股线在
Z
捻向上的外部扭转力将达到
100
。内外扭转力之间相互平衡使得纱线保持平衡。对于制造商来说，布料结构中纱线的平衡
是相当重要的，因为不平衡的纱线所形成的扭结和卷曲将会被缠在机器里引起产品的瑕疵。
这些简单的分析只适合于由两根单纱合股成的纱线。像绳索这些更复杂的结构则需要更精确<
/p>
地探索。
Most
of
the
yarns
used
in
household
and
apparel
are
cords
or
smaller.
We
shall,
therefore,
concentrate on these types.
用于家具和服装的大部分
纱线都是粗线或稍微细些的线。因此，我们应该把精力放在这
种类型的研究上。
From the beginning weavers and
other users of yarn needed a standard way to
designate the
various yarn types
accurately, so that buyers and sellers could reach
mutual
the early Middle Ages, a system
of yarn numbering was devised. This system, still
in use today, is
known as
the yarn number or yarn count. ( Note
that “yarn count” also designates the number of
ends and picks in a woven cloth. Be
aware of this overlap in nomenclature and don’t
confuse the
two applications.) Yarn
number is defined as the number of standard hanks
per pound of yarn. What
is the standard
hank? It varies with the fiber. Cotton and spun-
silk yarns are measured by an 840yd
(768m)
hank;
worsted
(
a
fine
wool
yarn)
is
measured
by
the
560yd
(512m)
hank;
linen
and