Split Cloths and Motions.
Split cloths are sometimes woven in the ordinary loom when narrow widths are required and a perfect selvage is not a necessity. Thus, a 40-inch loom may weave a cloth with a few empty dents at the centre, whilst on each side of the space thus caused the warp threads are crossed (on the gauze principle) between each pick to make a firmer selvage than could be got by ordinary lifting. The weft threads are then slit along this space by a sharp knife, giving two cloths, each 20 inches wide. One system of forming the selvage is by having an extra loop attached to the top stave of one heald, and carrying a thread which is drawn through the other heald. By correct drafting this thread can be made to lift at every pick first on one side of its neighbouring warp thread and then on the other.
The same object is attained in a split motion, patented by J. & R. Shorrock, and Taylor, of Darwen. By means of eyeletted straps revolving round a tightened warp thread, the doup or crossing threads drawn through the eyelets make a very firm selvage when slit.
The picking motions require a few further remarks. For some goods, especially fancies, the under pick is used. In this case the picking stick is rather longer than the slay sword, and is fixed parallel to it, projecting from the rocking shaft through the shuttle box and picker. The loom, [Plate VII.], possesses the under-pick arrangement. It is driven by means of the picking plate acting downwards on a lever centred at one end, whilst carrying at the other end a strap fixed to the picking stick about four or five inches from the bottom end of it.
The scroll or side pick is a favourite one for velvet looms. The picking plates are fixed on the crank-shaft, and consist simply of a disc of metal carrying a lug so as to catch against a latch or lug on a short inclined shaft at the loom side. This shaft at the bottom end actuates by means of a strap and picking stick fixed as in the under-pick loom. Obviously, the picking from each side of the loom must be done alternately, and the plates at the loom side are arranged so as to act only once in two revolutions of the crank-shaft. This motion is obtained by means of a scroll plate on the crank-shaft carrying a groove forming an inner and outer ring in the plate; in this works a slide in the inner ring for one pick, then traversing the outer part of the groove for the second pick. This slide regulates the latch on the short shaft. When in the outer ring the latch is lowered so as to be caught by the lug on the picking plate, but is out of the way when the sliding piece is in the inner ring. Of course, when the slide is in the inner part of the groove at the right-hand side of the loom, the slide of the left-hand picking scroll is in the outer ring, so as to pick alternately. This picking arrangement is very compact.
PLATE VI.—SHEDDING MOTIONS. To face p. 79.