Drop Box mechanism

Drop Box mechanism

dropbox mechanism definition dropbox mechanism meaning
  • Multiple Box motion is necessary on a conventional shuttle loom, when weft pattern is to be introduced across the fabric. 
  • Weft patterning may be necessary for weaving yarns of different color, count, twist or material. 
  • Each variation in the weft requires an individual shuttle and there must beg always one empty shuttle box in the system. 
  • Use of multiple box reduces the speed of the loom by 10% as compared to shuttle plain loom .
  • Some of the common fabrics produced on looms by using multiple box motions are:

                  -  Weft striped
                  -  Check
                  -  Extra weft figured effects          


Classification of multiple box motions

  • Multiple box changing motions can be classified into two main system as
  •  Circular box system.
  •  Drop box system.
                - Boxes on one side 
                - Boxes on both sides
                - Box motion can be negative or positive type, the most common being negative type
  • Circular box units consist of six compartments of six compartments for six individual shuttles revolve on a spindle.
  • The presence of over pick stick causes difficulty of applying automatic weft replenishment device on an automatic loom.
  • Drop Box System
  • Drop box units operate on a rising and falling principle

dropbox mechanism definition dropbox mechanism meaning

  • One of the limitation is that only one box movement is possible to move from the box in use to either of the adjacent boxes only, which limits 3 colours in sequence.
  • The size of the shuttle compartment is fixed and therefore any adjustment for worn out shuttle is difficult.
  • 2 x 1 box loom can insert two different wefts.
  • 4 x 1 box loom can introduce up to four different wefts.
  • In box motion with multiple boxes on one side necessitates insertion off picks of same weft in multiples of two.
  • 2 x 1 box motion also known as weft mixing motion is used for introducing same weft material of continuous filament after every second pick from two shuttle with an object of minimising possibility of weft bars in the fabric.
  • 4 x 1 drop box motion on the loom is the most common type for weft patterning to give a greater scope in cloth designing.

  • A loom having multiple box units at both sides with 2 x 2 or usually 4 x 4 can be used as pick and pick system or pick-at-will system.
  • The insertion of a single pick or any possible number of times from the either end of the loom to introduce any number of picks, whether odd or even number, from the same shuttle is known as pick-at-will.
dropbox mechanism definition dropbox mechanism meaning

  • The 4 x 1 drop box motion introduced by cowbird and peck in 1889 works on the principle of double crank and two discs.
  • The discs are free to turn on a stud.
  • The outer disc carries a fixed stud, which gives a movement from the one box.
  • A crank is loosely mounted on the stud which gives movement of two boxes and its pin passes through the slot of inner disc.
  • The lifting rod passes down from the crank to the fulcrummed bottom lever through a spring loaded lifting rod.
  • To the other end of the bottom lever is fixed a box rod which is also spring loaded and at its end it carries four drop boxes.    
  •  The disc is turned by its rack attached to a cradle which rocks through an inclined rod by the action of crank on the bottom shaft.

  • A cam fixed on the bottom shaft brings the card cylinder against needles by giving stroke to then bowl and fulcrummed bowl rod.
  • The card cylinder turns by L-lever operated from a stud on the cradle engaging with the star wheel.
  • A blank(closed card) in the pattern card pushes the needle against the rack, which causes the dice to make a half turn.
  • Each disc when not in action is loaded by a flat spring that brings a catch into the uppermost notch.

Pattern cards

  • When a hole(open card) on the pattern card is against a needle, the rack is clear of the disc pinion and the disc is locked. So a change in the box does not take place.
  • A blank card(closed card) pushes the needle to engage the rack with the pinion during its descending movement. 
  • The stud disc movement gives one revolution .
  • A slotted disc movement gives two-box movement.
  • For three box movements , both the discs should be rotated.
  • Card saving device
  • A central hole is provided in the flat steel cards of the pattern chain.
  • When it is blank(closed card), a third rack engages with a pinion to rotate a secondary card barrel of wooden tags.
dropbox mechanism,Pattern chain without card saving

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Drop Box mechanism Drop Box mechanism Reviewed by Suraj Gupta on April 28, 2020 Rating: 5

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