Method and apparatus for compensating warp thread tension or elongation variations during loom shedding

A loom for weaving a woven fabric by alternately shedding warp threads and inserting weft threads into successive open warp sheds, comprising:

• a warp beam supplying warp threads;
• a backrest arrangement that is supported to be oscillatingly rotatable about a backrest axis and that has said warp threads deflected thereover from said warp beam;
• and
• a motion transmission that is connected to said backrest arrangement and that is adapted and arranged to oscillatingly rotate said backrest arrangement about said backrest axis;
• wherein said backrest arrangement includes a backrest beam having a backrest beam surface, and a first warp tensioning module that is mounted on and extends along an axial length of said backrest beam and that has a first warp tensioning surface which provides a greater warp deflection path length than does said backrest beam surface by itself for said warp threads deflected thereover, such that an oscillating rotation of said backrest arrangement provides a variable tension or elongation compensation for said warp threads deflected over said backrest arrangement.

A method of compensating warp thread tension or elongation variations that arise in warp threads during shed changes while weaving on a loom, comprising the following steps:

• a) supplying a plurality of warp threads;
• b) separating said warp threads into at least a first warp thread group and a second warp thread group;
• c) deflecting said first warp thread group over a first part of a backrest of the loom and deflecting said second warp thread group over a second part of the backrest of the loom;
• d) successively shedding said warp threads to carry out successive shed changes;
• and
• e) providing a first compensating of tension or elongation variations that arise in said first warp thread group using said first part of said backrest, and providing a second compensating of tension or elongation variations that arise in said second warp thread group using said second part of said backrest, wherein said first compensating and said second compensating provide different degrees of compensation of said tension or elongation variations of said first and second warp thread groups respectively, and wherein said providing of said first compensating and said providing of said second compensating are respectively carried out so that said degree of compensation provided by said second compensating is zero and said degree of compensation provided by said first compensating comprises an additional tension or an additional deflection path length applied to said first warp thread group cyclically during said shed changes.

A method of compensating warp thread tension or elongation variations that arise in warp threads during shed changes while weaving on a loom, comprising the following steps:

• a) supplying a plurality of warp threads;
• b) separating said warp threads into at least a first warp thread group and a second warp thread group;
• c) deflecting said first warp thread group over a first part of a backrest of the loom and deflecting said second warp thread group over a second part of the backrest of the loom;
• d) successively shedding said warp threads to carry out successive shed changes;
• and
• e) providing a first compensating of tension or elongation variations that arise in said first warp thread group using said first part of said backrest, and providing a second compensating of tension or elongation variations that arise in said second warp thread group using said second part of said backrest, wherein said first compensating and said second compensating provide different degrees of compensation of said tension or elongation variations of said first and second warp thread groups respectively, and wherein said first compensating and said second compensating are carried out independently of each other.