Lecture-61) Scope: Maximum no. of heald frame it can theoretically control is 48 . Maximum no. of heald frame it can practically control is 36 for long staple yarn. For cotton yarn weaving the maximum number of heald it can control is 24. It is to produce medium size design only. It can produce both square & rectangular size designs. Position of fixation of dobby: 1) Over the centre of the loom. 2) At one side of the loom. 3) Outside of the loom frame & on the floor. Classification: The dobby looms can be classified in different ways according to 1. Types of design it can produce: a) Ordinary dobby b) Special dobby 2. Lift of heald frame: a) Single lift b) Double lift 3. Figuring capacity: 12’s,16’s,20’s…48’s. 4. Dobby mounting system: a) Horizontal dobby b) Vertical dobby 5. According to heald frame controlling mechanism: a) Positive(Both lifting & lowering of the heald frames by mechanical means ) b) Negative (Both lifting by mechanical means & lowering of the by dead weight or spring) 6. According to types of shed it can produce: a) Bottom close shed b) Centre close shed c) Semi open shed d) Open shed shed 7. According to number of jack lever used: a) Single jack lever b) Double jack lever. Lecture-7 Jacquard shedding mechanism: 1. Scope: Normally the maximum number of warp threads it can control is 1800. Any design can produce by jacquard looms. It can produce the most complex design. It can produce any shape of any design. Any number of warp thread can be lifted any shed. No heald frame is used in jacquard shedding. Lifting & lowering is done by harness cord. Classification: Jacquard loom can be classified different ways e.g.… 1. Type of design it can produce: a) Ordering jacquard b) Special jacquard 2. Type of shed it can produce: a) Bottom close b) Centre close c) Semi open d) Open shed 3. Pitch Jacquard: a) Coarse pitch b) Medium pitch 4. Figuring capacity: 100’s; 200’s, 300’s…1800’s 5. Lift & number of cylinder used: e) Single lift single cylinder (S.L.S.C ) f) Double lift single cylinder (D.L.S.C ) g) Double lift double cylinder (D.L.D.C) 6. system of harness mounting: h) Single tie-up i) Repeating tie-up j) Pointed tie-up k) Mixed tie-up 7. Jacquard mounting system: l) London system (where , loom & jacquard at 90° angle ) m)Norwich system (where , loom & jacquard at 180° angle ) 8. Source of power for driving the loom: n) Hand jacquard (Manual) o) Power jacquard 9. Mechanism of driving the loom: p) Mechanical jacquard q) Electrical jacquard Lecture-8 Picking mechanism: 1. Function: To propel the shuttle or any other weft inserting elementsprojecting, rapier, air jet, water jet. At a predetermined velocity. Along the correct flight path from one end of loom to the other end. With the object of laying weft yarn in the shed. Classification: Picking Hand Picking Throw shuttle Power Picking Fly shuttle Tappet & cone Over picking Tortional bar (projectile) Modern (shuttle less) Conventional Bowl & shoe Under picking Airjet (Compressed air) Side lever Water jet Side shaft Rapier Circular Multi phase Flat Lecture-9 »Comparison between over picking & under picking mechanism: Serial over picking under picking No: 01. Picking arm above shuttle box. Picking arm under 02. 03. 04. Lower loom speed. For narrow loom. Suitable for light & medium shuttle box. Higher loom speed. For wide loom. Suitable for heavy 05. 06. 07. 08. 09. weight fabric. Required less power. Works less smoothly. Less clean. In direct. Requires more frequent oiling. fabric. Required more power. Works more smoothly. More clean. More direct. Requires less frequent Easy to adjust & maintain. oiling. Difficult to adjust & Comparatively general in action More wear & tear Unsuitable for standardized maintain. Harsner in action Less wear & tear suitable for standardized setting because of the flexible setting because of the picking strap. flexible picking strap. 10. 11. 12. 13. Some calculation: mv 2 F , v 2as , 2s where, Where, f force and f ma F=force to drive the shuttle in N m=mass of shuttle in kg. s=Reed space in m a=acceleration of shuttle in m\sec2. v=velocity of shuttle in m\sec. Shuttle flight and its timing: There is a simple numerical relation between I. The speed at which a loom runs, PPM. II. The distance the shuttle travels. III. The degree of crank shaft rotation available for its passage & IV. Average velocity of the shuttle during its passage. If, R=Reed space L=effective length of shuttle V= Average length of shuttle p=picks per minute (PPM) =no. of degrees of crank shaft rotation available for the passage of shuttle & t=passage time for shuttle Picking faults: 1. Early picking – early timing of picking mechanism. 2. Late picking –late timing of picking mechanism.. 3. Smash or bang –off- loose picking tappet nose. 4. Short picking –wreak picking force due to wrong setting of picking tappet & cone. 5. Harsh picking –short nose. 6. Shuttle flying out Wrong setting of shuttle box & race board. Rough surface of shuttle & race board Faulty picking force. Unclear shed. etc. Beating-up 1. Objects: To push the newly inserted weft yarn (last pick) to the fell of the cloth . Classification: Beating-up Single Double Real\Fast Loose\False Crank & crank arm Cam Fixed fell Moving fell Lecture-10 Factors affecting the motion of slay: 1) The radius of arc along which the axis of the sword pin reciprocates. 2) The relative height of the sword pin & crank shaft & 3) The length of the crank in relation to that of the crank arm. Slay eccentricity ratio, e rl Where, r =radius of the crank circle l=length of the crank arm. Advantages of high eccentricity ratio: 1) More time is available for the passage of the shuttle. 2) More effective beat –up. Disadvantages of high eccentricity ratio: 1) A high value implies rapid acceleration & declaration of the slay around beat -up. 2) More robust loom is required. Lecture-11 Take-up mechanism: 1. Function: To wind the already woven fabric on the cloth roller with the progress of weaving. 2. Types: Take-up mechanism Intermittent or Discontinuous Continues Indirect Direct Positive 5 Wheel 6 Wheel Negative 7 Wheel Picanol Sulzer Tsudkoma Differences between 5 wheel take-up & 7 wheel take-up mechanism: 5 wheel take-up mechanism 1. It is used for jute & other coarse 7 wheel take-up mechanism 1. It is used for cotton & other fine fabric. 2. There are five wheel in the gear fabric 2. There are seven wheel in the gear train of the take up mechanism. 3. It is not multiple of three. train of the take up mechanism. 3. Rachel wheel is always is multiple 4. Fraction of a pick can not be of three. 4. Fraction of a pick can be controlled. controlled. 7-wheel take-up mechanism: where, A= Ratchet wheel,24T B= Standard wheel, 36T C= Change wheel, D= Swing pinion,24T E= Compound wheel,89T F = Compound pinion,15T G =Take –up wheel,90T H= Take –up roller,15.05(circumferences) Note: Movement of 1 tooth of Ratchet wheel (A)= Take –up of 1 pick of fabric. 5-wheel take-up mechanism: where, A= Ratchet wheel,50-60 T B= Change wheel, 36T C= Standard wheel,100-120T D= pinion,12T E= Beamwheel,60-100T F = Compound pinion,15T G =Take –up roller,15” (circumferences) Note: Movement of 1 tooth of Ratchet wheel (A)= Take –up of 1 pick of fabric.