The ground warp is on a separate beam to the pile warp, the latter having a special tension to let off the required quantity to form the pile. At the second pick in the pattern, just where the pile warp is bound, the reed is made to beat further up than on the two preceding picks, thus forming a pile by sending one half the pile ends to the face and the other half to the back. The reed beats up to the front for the second, third, and fourth picks in the pattern, as given at [Fig. 150], following which the reed is held back for two picks. [Fig. 151] is a good motion for making the reed occupy the two positions when beating up. P represents the slay, and a lever, A, centred at D, is so constructed that when A is pulled down the reed is pushed forward. The rod R is connected to a lever, M, on a shaft, N, placed under the loom. A rocking motion is given to this shaft by a box cam, P, five to the round ([Fig. 152]), so shaped as to lift and depress the lever QS for the required number of picks. This cam is driven from the picking shaft. By pulling the rod R downwards the reed is moved forwards, and the rod will have to be kept down for three picks and moved up for two picks, so as to keep the reed in its front position for three picks and a little way back for two. The effect required is really to lengthen the crank-arm at will, and the principle of the knuckle joint may be used in its simplest form—that is, by having the crank-arm jointed in the middle and fixed a little out of a straight line, and by straightening the arm when the front position of the slay is required.
The real loop pile is woven over wires. The wires can be inserted and pulled out automatically by a power-loom, but the richest kind of pile is woven on the hand-loom. The structure of the fabric is shown at [Fig. 153]. The pile end is brought up over a wire every two picks, and when the wire is pulled out the loops form a springy pile, which can be made to give beautiful effects in dress goods. The principle is also used in Brussels carpets, and similar goods. Where figured fabrics are required on this principle, it is necessary to have each pile end on a separate bobbin and weighted separately at the back of the loom, as the take-up of each end would vary so much in the figure.
FIG. 153.
FIG. 154.
With cut pile the wires are either grooved, as at [Fig. 154], or each wire has a knife at the end, as at [Fig. 155], and when the wire is pulled out it cuts the pile. The best pile is formed by the grooved wires, as the cutting wires are apt to drag the pile. When cut pile is being made, about four or five wires are constantly in the cloth, for, if the wire were pulled out immediately, the pile ends would fall away from the cloth.
FIG. 155.
