Use of Different Stocks and Colors
The use of upper and lower fillings also allows for the use of different grades of stock in either shuttle. Colors may be used to match the face warps while white may be carried in the lower shuttle to match the back. Silk or other expensive stock may be used for the face without changing the character of the stock used for the back of the goods, which is not practicable in single shuttle work.
All this of course makes it possible to reduce the cost, making this the most economical web produced. In the making of shoe goring, a considerable quantity of which is still used for inserts for house slippers, this is a very popular form of weaving, allowing for the production of a face having a velvet-like pile of the color to match the shoe leather, while the back may be perfectly plain and white.
It is a method employed in combination with the jacquard, where fancy figures may be obtained on the face, using the cam movement for the back, binder and edge, the weave of which is the same for all of these warps, being simply a one up and one down. In such a combination the labor on the jacquard movement is much reduced, inasmuch as the travel of the lingo is much shorter than is required when made in connection with single shuttle.
The Overshot Method
The overshot method, which we have previously referred to, is another form of double shuttle web which has in it elements of economy differing from the cross shot but equally important. This kind of weaving is designed as a substitute for silk jacquard webs, which it has to a great extent supplemented. Before its introduction it was customary to use a slow running “rise and fall” lay movement, when making a silk figure with the shuttle, putting in one pick of silk filling to each two body picks, so that the output of web was only about one-half of what is possible in overshot weaving. In the old method the silk used to pass from edge to edge of the goods at each pick of the figure shuttle, and where the figure did not appear it was buried between the upper and the lower cloths.
In the overshot method the silk figure is bound down at the edge or border of the figure and none of the silk is entirely buried out of sight. In the overshot the body shuttle runs all the time, while the figure or silk shuttle only runs with every alternate pick. The main body of the goods is woven in every respect the same as in a single shuttle web, and it may embrace all the weaves, such as plains, twills or fancies, which are common to single shuttle weaving. Arrangements are made, however, for the production of an auxiliary shed, by a movement which pulls certain threads above the main shed, and while these are open to pass the extra shuttle under them, and thus bind in the figure filling. The lower part of the lay has straight shuttles, while the upper bank of shuttles is tipped down to conform to the formation of the auxiliary shed they are designed to pass through.
The binder threads from which the overshot figure is generally operated, are weighted very lightly so that the individual threads will easily stand the strain they will be subject to while making the auxiliary shed. The Crompton & Knowles overshot dobby is generally used for this purpose. This special machine is provided with two horizontal draw knives, operating any or all of the 30 hooks, and is so arranged that the connected warp threads may be lifted at either or both picks to the height of the main shed, or to the additional height of the auxiliary shed.
Fig. 5.—Simple Overshot Design