Lap length measuring motion in Blowroom | How it works?

BEQ : why lap length measuring motion is used in blow room Object : i) To stop the rotation of bottom calender roller and feed roller,after a particular length of lap is completed, ii) To measure the lap length and change the lap length as per out requirements by changing the lap length change wheel.

The weight per yard of the lap is based on total weight of the lap, on the assumption that the length of the lap is kept constant. If there is any small variation in the yardage of lap, it is reflected in the total weight and weighing to determine the uniformity of the lap is rendered valueless. If the operator assumes that his measuring motion is accurate and discover that the weight of lap is excessive, he will change the evener motion (feed control system) to secure a lighter lap and meet his standard. However, if the additional weight was due to inaccuracy of the measuring motion and hence to excess yardage, the operative has used the wrong remedy he is now producing a lap which is less than required weight per hard.


Working: figure indicate the position of various parts in this mechanism. As the bottom calender roller rotates the side shaft gets its movement, through the worm and worm wheel connection, and inturn the knock-off wheel (with cam and projection on its surface) is also getting its movement through the change wheel.

A support lever which supports the drop lever is arranged
very close to the knock- off wheel. The drop lever will decide
the position of the drop shaft end wheel which drive the bottom
calender roller. When the knock off wheel rotates the projection and cam on
it slowly press the supporting lever and finally move the
supporting lever away after the complete of 1 rotation of the
knock off wheel. So the drop lever loses its position from
supporting lever and drops down and drop wheel gets disengaged
from the carrier wheel and the bottom calender roller wheel, so
bottem calender roller rotation is stopped.

By means of separate lever connection, the feed roller also stopped by disengaging the clutch unit which drive the feed roller.

After doffing the lap, again the drop lever is kept in position on the supporting lever and thus drive to BCR is engaged and next lap starts to wind on lap roller.

For one rotation of the knock off wheel one lap is completed. To find out the length of lap, we should know the length delivered by a calender roller for one rotation of the knock off wheel. For ex. (Refer gearing diagram)


In modern scutcher, the required lenghth is preset by means of counter with decimeter settings, the impulse for lap change is given by a limit switch, as soon as the lap attains a definite diameter. Here the length of lap can be easily altered by simply rotating a knob in dial.