The reinforcement layer gives the apron its overall dimensional stability. Current methods with well defined parameters for this layer achieve very tight inner diameter tolerance. Thus plays an important role in determine top and bottom apron life span. At the same time reinforcement layer of bottom apron must have nominal break point so that due to some mechanical reasons if the apron is clamped between the bottom steel roller and the nose bar the tensioner unit must not damaged?

Optimum slippage over cradle nose bar (see fig 1) is expected of the inner layer. It must also with stand abrasion and scratch of the knurled bottom roller. The inner layer should also provide good friction, so that both aprons are consistently driven during drafting.

Torque value, energy consumption of top arm weighting system

In todays scenario, the number of spindles on short staple spinning machines has continually increased; the energy consumption of the top arm weighting arms was initially more. The idea is have low torque value aprons so that the whole machines energy utilization is balanced.

Low apron torque values helps in achieving it. Currently, to achieve improved yarn regularity of the drafted strand, closer spacing on the top arms are used so that the net load on bottom aprons is very high. At the same time high draft ratio is kept in most of the ring frames that again adds load to apron zone .Hence greater flexibility of apron is needed so as to accommodate the narrow radius at the nose bar (A typical bottom apron in cotton spinning ring frames makes 7000 9000 turns per day at the nose bar ) . To increase the apron flexibility and reduce the tension at the point of turn around nose, apron thickness can be reduced, without losing the elasticity of the outer layer.

Initial start up of long ring frame Vs torque value of apron:

Whenever a Ring frame is stopped for doffing or any other reason the entire drafting zone components come to rest. During re-starting, the steel bottom rollers must accelerate to reach its maximum surface speed. Based on the draft distribution or draft ratio. The crucial part is that each bottom apron having 30 mm width and a wrap angle of more than 90 must accelerate to match the surface speed of middle bottom roller. Otherwise; the entire middle zone will lag behind actual speed momentarily.

The energy consumption / spindle / drafting zone will increase if the torque value of the apron is high. Since Torque value is directly proportional to power consumption

Power consumption/spindle/drafting zone = Torque value x Angular speed of roller ..2

If the torque value of apron is less then according to the above equation the energy consumption / spindle / drafting zone will decrease relatively.

Conclusion:

Torque value of a spinning bottom aprons plays an important role in todays high speed spinning machinery. With higher spindle speeds and increased draft, low torque value aprons helps to achieve total energy balance and utilization. With smooth start up, wear and tear of the individual components gets reduced.

Useful definitions

Newton - A Newton is the amount of force required to accelerate a mass of one kilogram at a rate of one meter per second2