Tappets are used for simple weaves in which the number of shafts is limited. Dobby systems involve the use of a pattern chain to control the lifting of the shafts. They are the most commonly used for wool. Jacquard systems control the lifting of each individual end to create almost unlimited patterning possibilities. (Wool Web, 2007)
In the simplest type of tappet shedding motion, the shedding cams are mounted on the bottom shaft, and the motion is suitable only for weaves repeating on two picks. By mounting the tappets on a counter shaft driven by gearing from the bottom shaft at the appropriate speed, the repeat can be extended up to eight or ten picks. Bobbies are much more versatile and usually control at least sixteen, and sometimes as many as 36, head shafts. Since the lifting of the shafts is controlled by some form of pattern chain, there is virtually no limit to the number of picks per repeat. Jacquard machines are made in a wide variety of sizes to control from 100 to 2000 or more ends per repeat. A common size controls 600 ends, which, in a cloth with 30 ends/cm, gives a repeat 20 cm wide within which the designer has complete freedom. The lifting of the ends is controlled by a chain of punched cards or by a loop of punched paper (Ministry of Science and Technology, 2006).
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