Page:Encyclopædia Britannica, Ninth Edition, v. 24.djvu/492

Rh 466 WEAVING conception of De Gennes, and presented some of the im portant features of the modern power-loom. The practical realization of automatic weaving was, however, deferred for forty years, and the world owes it to a clergyman of the Church of England, the Rev. Dr Edmund Cartwright. His own graphic account of the history of his invention has already been given under COTTON (see vol. vi. p. 500). Dr Cartwright s original loom was but an imperfect machine, although his patent was minute and detailed. Both he and others devoted much labour to its improve ment; and in bringing the invention to a successful issue he spent from 30,000 to 40,000, while in return he re ceived only a gift of 10,000 in 1809 from the Government. The power-loom fought its way to supremacy but slowly, for an imperfect power-loom is no better than a hand-loom ; and it was only after the minor adaptations and adjustments which frequently make the difference between success and failure were brought into operation that the real advan tages of power-loom weaving became obvious. Even yet for many purposes the power-loom has not succeeded in supplanting hand-loom weaving. The power-loom (fig. 8) differs much in appearance from the hand-loom, and is altogether more compact, from the fact that the lay, which is suspended from above in the latter, is in the power- loom centred below. The three principal motions, shedding, pick ing, and beating up, are of course the same in both. Motion is communicated to the working parts of the power-loom by the main FIG. 8. Power-Loom. or crank shaft, so called because it is provided with the two cranks which give oscillating motion to the lay. By toothed wheels the crank shaft controls the motion of the tappet shaft which carries on it the cams or tappets (1) for the picking motion called the picking tappets, and (2) for the treadles called the shedding tappets. The picking tappets have always a direct relation to the motion of the crank shaft, because for every beat of the lay there must be a corresponding pick. As there are two picking tappets the shaft is therefore geared to make half a revolution for each revolution of the crank shaft. The relation of the shedding tappets is not so regular, their rotation being dependent on the number of heddles or sheds of warp they control, and it is only in plain weaving that they correspond in motion with the picking tappets. For the successful working of a power-loom several adjustments are necessary which are not required in the case of the hand-loom. The hand-loom weaver winds up his web on the cloth beam from time to time as the work progresses, and he moves forward the temples by which the woven fabric is kept extended to its proper breadth. In the power-loom these must be accomplished automati cally, and the motions must be self-adjusting with the progress of weaving. More important still, a self-acting appliance must be provided to stop the motion of the loom in case of the weft thread becoming exhausted or being broken. This is secured by a delicate and ingenious contrivance called the &quot; fork-and-grid stop motion,&quot; which depends for its action on the lightly balanced prongs of a fork. These prongs come in contact with the weft thread between the selvedge of the web and the shuttle box each time the shuttle is shot to the side at which the apparatus is fixed. If the prongs meet no thread they are not thrown up, and being unmoved a con nexion is formed to the moving lay, and by a system of levers the loom is immediately thrown out of gear and stopped. Equally essential is it to provide means to stop the loom should the shuttle stick in the warp or otherwise fail to be carried from side to side of the lay. It is clear that, should the lay beat up with the shuttle sticking in the weft, there would ensue complete wreck of the warp. There are two ways of dealing with such a contingency. The first, invented in 1796 by Miller of Glasgow, is the &quot;stop-rod motion,&quot; the action of which depends on the shuttle raising, as it enters the shuttle-box, a catch which if left down would strike against a frog or stop, and so throw the loom out of gear. The second device is the loose reed, in which there is an appliance for liberating the lower part of the reed when any obstruction is met in the warp, and thereby preventing a blow being given by the beating-up motion. Double Cloth. For many purposes the weaving of double cloth is important. It permits of the formation of a ground of inferior material with a surface of finer texture ; and it affords great scope for the formation of coloured patterns, allowing of the production of double-faced textures, which may or may not correspond in pattern according to pleasure. It moreover increases the thickness and weight of woven fabrics, and it is the basis of tubular weaving, such as is practised for making hose, tubes, seamless sacking, &c. There are three classes of double textures. The first consists of double warp surfaces with the weft in the centre ; in the second it is the reverse a warp centre and two weft faces ; and in both these classes the two sides may be of different colours if two colours of warp and weft respectively are employed. In the third case the cloth may consist of distinct warps and wefts throughout, and practically be two separate cloths. These, if bound at the selvedges, w T ould become woven tubes, and if at regular intervals over the surface a thread of warp or weft passes from the one into the other they are united as one texture. The intersection of double warps and wefts gives the opportunity of producing great diversity of colour and pattern in any fabric without waste of material, and the manner in which patterns may pass from side to side is illustrated in the sectional diagram, fig. 9. The diagram, fig. 10, illustrates FIG. 9. Section of Double Cloth. the method of producing a plain double cloth with the use of four heddles. Heddles 1 and 2 shed the upper cloth, 3 and 4 the lower. Vhen a pick is l througll the lower web Addles being put in through the 1 2 are raiged and heddle 4 js upper warp heddle 1 is H depressed. up and all the others Gauze Weaving. Hitherto we are down ; and when the shuttle is passed 1/23 4 have dealt only with II 1 1 1 1 FIG. 10. methods of weaving in Method of Weaving Double which the warp threads run parallel with each other and are intersected at right angles by the weft. In gauze weaving, by which effects intermediate between lace and plain cloth are produced, the warp threads are made to intertwist more or less among themselves, thereby favouring the production of light open textures, in which many ornamental lace-like combinations can be effected. Plain gauze is a thin open texture, in which two contiguous threads of warp make each a half twist around the other at every pick, the cloth having in section the appearance shown in fig. 11. A leno con sists of a kind of muslin in which the crossing or whip warp inter twists with its neighbour only at every fourth pick. _ In fancy gauzes the crossing or whip warp may cross and entwine several ordinary warp threads at once, and in numerous other ways the simple principle of intertwisting may be used for ornamental effect. The mutual entwining of warp threads is accomplished by an extra heddle called a &quot;doup,&quot; placed in front of the common heddles. The doup consists of a half heddle threaded through the eye of a plain heddle, of which it forms a part. The cross or whip warps are drafted first through one of the ordinary heddles and then passed under the thread or threads they are intended to entwine, and drafted through the doup heddle, as seen in the diagram, fig. 12, which shows the drafting of a plain gauze. The whole f the warp yarns which are to be entwined must with the whip FIG. 11. Section of ordinary Gauze. of