纺织英语第三版课文翻译Lesson Twelve-Yarns

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. Theseforces 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。

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S捻向的单纱为例。

用另外的100tpm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100tpm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 understanding.During 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 andstandard wool yarns are measured by the 300yd (274m) hank. The lengths of the standard hanks were chosen as convenient values for the yarn sizes in use at the time the system was devised.首先，织布工人以及其他的纱线使用者需要一个标准的方法去精确的标明各种不同类型的纱线，以便于买卖双方能够达成一个相互的认同。