The other threads are individually provided for, being wound upon bobbins, which are formed of two thin discs of brass, about 2 in. diameter, joined by pins, and having a very small space between for the reception of the thread. When the bobbin is placed in the carriage, the end of the thread is drawl] from it, and passed through a small hole as at h, Fig. 890, which shows the carriage and bobbin together. The former is made of thin steel, highly polished, cut in the shape shown, and having a circular hole in the centre for the bobbin. On the lower half of the circle, a thin flange c is adapted to fit between the discs of the bobbin, in order to secure it in position. The spring s, which is riveted into the carriage at a, has a projection or nib at n, which, passing between the discs, and pressing the bobbin upon the flange c, imparts the necessary tension to the thread as it is drawn off the bobbin. When the bobbins are filled, they are subjected to heat and pressure, which removes any slight inequality in thickness that may arise from filling, or other incidental causes. The bob bins aro filled by placing them upon a spindle fitting the hole in the centre, and contain from 100 to 150 yards of thread, or more, according to fineness.
The section of the carriage is shown much thicker than the reality, in order better to display its structure. The outline shows the carriage as a whole.
The bottom part b, as will be seen in the section, is made thinner in order to pass easily between the divisions of the combs. The hooks f are termed drawing-hooks, being those into which the blades of the catch-bars drop, when the carriages are being passed through the warp, and drawn upon the landing-bars. The holes e are for the purpose of facilitating the withdrawal of the carriages when the bobbins are nearly empty. A wire is passed through the holes of a large number, and several hundred at a time are lifted from the frame.
In operation, as the bobbins pass to and fro through the warp threads, around which the threads they carry are twisted, it is necessary that the por tions of lace thus formed should be removed from the way of succeeding operations. This is accom plished by the action of the point or fork-bar K (Fig. 889) inserted into the warp beneath the twist ing formed upon the threads, and then by the action of the cranks and levers is made to pull to gether in an upward direction the twisted threads, in order that the process may be continued. There are two of these combs acting alternately, as shown. After each movement, they are completely with drawn, in order to be out of the way of the lateral movement of the warp threads.
A simple illustration will dispense with a lengthy explanation. In Fig. 891, is a representation of five threads suspended from a rod h. The warp thread a has only a slight tension put upon it, compared with that upon the others. The four bobbins e, holding the remaining portion of the threads b, are intended to be represented oscillating in the direc tion of the curved lines beneath them, the point from which they move being in a vertical line from the point from which they are suspended. These threads in a state of oscillation represent the motion of the carriages containing the bobbin threads when the machine is at work. Whilst the threads oscillate
without any movement of the thread a, no effect is produced, the threads retaining the same relation ship as before. But if, during the oscillation of the four threads b, the thread a be-drawn laterally across the line being traversed by the bobbins, it will become twisted round the threads b. In this manner, the various threads round which the thread a has been twisted correspond to the lateral extent that it has been moved at each oscillation of the threads b. The function of the fork or comb has been previously explained. After each twisting, the greater tension of the threads b causes the thread a to be retained in the position to which it has been drawn, it not having power to deflect the threads b. Fig. 892 shows the effect that would result from the relative tensions of the above-mentioned being reversed. The threads 1 are, after each oscillation, drawn completely aside by the greater tension upon the thread a, and the whale structure of the fabric is thus changed. It therefore depends largely upon nice adjustment of the tensions upon the two sets of threads in relation to cach other for perfect embodiment of a design. Ordinary laces draw the yarn mostly from the warp threads ; high classes, from the bobbins.
A lace web, as it appears in the frame in the process of manufacture, presents a very different aspect to what the same fabric does when taken out of the machine. One set of threads, those from the bobbins, assume a longitudinal order, and appear scarcely deflected from a straight line, whilst the warp threads are interlaced with the preceding, as seen in Fig. 891. When the fabric is taken out of the frame, and all tension is removed, the meshes assume the form of the design, and show its beauty, though not to the full extent.
The Levers' lace-machines are made from 5- to 15-point in gauge. A 10-point requires 20 warp threads per in. to produce traversed net, which needs a full warp. In this, there will be 20 bobbins and carriages per in., in the single tier on the central comb-bar. In making fancy goods, there will be thick threads moved a greater or lees distance sideways in addition. Of these, there may be from 40 upwards in an inch. The machine makes about 100 " shogging" or lateral move ments of the warp threads, and the twisting movements of the weft threads as they pass backward and forward or through and around the warp threads, which makes about one inch of lace per minute. The bobbins and carriages are driven at this pace through the maze of tight and for the most part very fine threads of cotton or silk, or even untwisted filaments of the latter, in spaces of iu., according to the gauge, working side by aide, clear of each other and of the threads through which they pass, and which threads hAve all, between each movement of the carriages, been themselves moved in., so as to vary the particular intervals through which the carriages pass. Were the least irregularity to occur in this lateral movement, the threads would all be broken, and the machine injured.