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Recent innovations in loom shedding mechanisms

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Introduction

a To whom all the correspondence should be addressed.
Present address: NIFT-TEA College of Knitwear Fashion, Tiruppur 641 606, India
E-mail: advaitcbe[at]rediffmail.com
During the recent years, considerable research has been done on loom shedding mechanisms. Shedding systems have been suitably modified so that it has now become possible to weave fabrics with varied profiles to suit specific technical applications1-6. Different areas of research have been explored. In one of the areas, shedding has been done without dynamic warp loading. This has opened the possibilities of weaving the new textile structures which are difficult to weave on conventional machines. Cams have been designed that deviate from the simple harmonic motion and the results on weaving performance are found to be comparable to the conventional cams. Newer methods of regulating heald frame motions have been developed. In another interesting development.

Analytical Approach in Shedding Cam Design

Shedding cams are designed for weaving simple structures having repeat of up to 8 picks. A graphical method has been evolved for designing shedding cams considering the simplest example of a plain weave13. Subsequently, a method has been developed for calculating the pressure angle of the shedding cam and the same has been applied for the case of a plain weave shedding cam with roller reversing mechanism located under the loom14. Investigations have also been done on the influence of follower motion curves and treadle pivot location on the pressure angle and lateral force affecting treadle pivot. Also, a geometrical method has been used for deciding the factors which restrict the number of picks in the weave repeat for shedding cam mechanisms15.


Determination of Cam Profile Coordinates

An analytical method has been used for the determination of cam profile by use of envelope theory20,21. The first and second matched shedding cam profile coordinates can be accurately calculated with respect to the angle of the cam shaft, by determination of the follower displacement diagram and the cam mechanism dimensions. This holds valid for positive cam shedding motions. In the case of negative cam shedding motions, either the first or the second shedding cam profile coordinates can be determined, since there is one cam contour.