Fig. 211.J.N.
Fig. 213.
Fig. 212.
(402) Sewing thread requires a special set of machines to fit it for the market. It is sold in one of two forms, either bright or soft finished. Bright thread is polished by being subjected to the action of a rapidly revolving brush. Some of the machines for this purpose made by Messrs. Shepherd and Ayrton are illustrated, and will serve to show the principle of this class of appliances. The doubled thread is formed into a beam, having first been wound on to special bobbins, 360 of which are placed in a creel, and the threads from them laid side by side on the beam, which is a cylindrical barrel with large flanges at its ends. The thread is then collected into a chain, or loose untwisted rope, and is bleached or dyed by means of a special plant which it is not necessary to describe. Having been so treated, the material is wound on to a beam shown in the machine illustrated in Fig. [212], which is provided with a special adjunct in a machine known as a holding back machine, by which the required tension is put on the thread. After being beamed for the second time the thread is passed through the machine shown in Fig. [213]. The beam on which it has been wound is shown at the right hand side of this illustration, and contains, as stated, 360 threads. These are first taken through a size box, in which a pure size or starch is placed, and are then passed through the bristles of two cylindrical brushes. The brushes revolve at a high velocity, and thoroughly polish the thread without altering its shape, it being very desirable to preserve its rotundity. At the end of the machine, after being dried, the threads are wound on three brass beams, each divided equally by a central flange. 120 threads are wound on each beam, 60 of these being in each of the divisions, These beams are placed, with the threads on them, contiguous to a special form of winding machine, where they are wound on to wooden spools or bobbins, each of which, when full, contains 11⁄4lb. of the finished threads. These are used to feed the spooling or balling machines afterwards described. In preparing soft thread—that is, unpolished thread—a similar procedure is followed, except that, after bleaching or dyeing, the threads, after being dried, are wound on to the second beaming machine. This system is—with special modifications adopted by various manufacturers—the one universally employed. The polishing machine will polish 120lbs. weight of 30’s 3-cord thread in 10 hours, and soft thread can be produced in the same numbers at a rate of 5,670lbs. in 56 hours. The cost in wages of this system is much lower than that of the older method of hank polishing, in addition to which fewer knots are made in the thread, owing to the longer lengths treated continuously.
Fig. 214.
(403) When thread is finally produced, by the processes described, in a suitable condition for sale, it is necessary to form it into small reels or bobbins, or into balls, each containing from 100 to 500 yards. The reels on which thread is wound for sale to the consumer are small bobbins in which a short barrel is used, with a head or flange at each end. The flange is bevelled on its inner side, and the length of the opening between the flanges is greater at their peripheries than at their roots. The reels are filled with thread by the action of a machine of great ingenuity called the “spooling machine.” This was originally invented by the late Mr. Wm. Wield, and is now made by his successors, Messrs. Shepherd and Ayrton. A perspective view of it is given in Fig. [214], and, as there shown, it has eight heads. The empty spools are placed in a trough, the mouth of which terminates immediately behind the winding head. The latter consists of two spindles which grip the spool in the centre, being formed conically at their extremities, so that they get a firm grip of the hole in the centre of the barrel. The operative mechanism in this machine is fixed in the double frame, or “headstock,” shown at the right hand of the machine, and drives, by means of longitudinal shafts and wheels, the spindles of the whole of the heads. The thread is guided by steel guides, threaded on their underside to correspond with the pitch of the spirals formed by the thread, upon which during winding they rest. The guide rods, upon which the guides are fixed, receive an oscillatory movement after the reels are filled, so as to leave the space free for the removal and replacement of the spools. In addition to this they have a reciprocal horizontal traverse equal in length to the length of the spool, and gradually increasing as the surface upon which the thread is wound increases, owing to the bevel of the heads of the reels. This reciprocal movement is obtained from the revolution of a finely pitched screw on a roller, with which two half nuts alternately engage, one on each side of its centre. As these are thrown into gear they give a traverse to the guide rail in each direction, and it will be easily understood that the period of their engagement determines the length of the guide traverse. In commencing to wind a set of reels the first operation is to place them between the spindles. One reel falls out of each trough on to a plate, which rises so as to hold the reel or spool between the open spindles. The spindles close upon the spool, which immediately begins to revolve and draw thread from its bobbin, which, with its fellows, is held in a suitable creel. The thread is passed through a spring tension clip, which holds it sufficiently to keep it tight, and afterwards over the guide referred to. Winding goes on until the required definite length is wound on, when it automatically ceases. Immediately this occurs a knife placed in an arm descends and cuts a nick in one end of the spool, and the thread is drawn into this nick. In this way the end is secured, and, as soon as this is effected the thread is drawn over a knife and cut. The spindles then open and the spools fall down a shoot. Another set of spools is then fed, as described, and the ends of the thread are so held that, immediately the spindles begin to revolve, they are drawn on to the spools, winding thus beginning automatically. Owing to the perfect automaticity of the machine a high rate of speed is obtained, and 26 gross of spools, each containing 200 yards of thread, can be produced from a machine in 101⁄2 hours.