The reinforcement gives the apronits dimensional stability. Modern methods of apron manufacturing with definedparameters for the reinforcement layer achieve very tight internal diametertolerances. These in their turn play an important part in determining thelifespan of a top apron or a short bottom apron. The reinforcement in a bottomapron should have a nominal fracture point so that when the apron is clampedbetween the bottom steel roller and the nose bar the tension device is not damaged.


Optimum slippage over cradle andnose bars is expected of the inner layer. In the case of the bottom apron theinner layer must also withstand abrasion and notching of the knurled bottomroller. The inner layer should also provide good friction, so as to ensure thatboth aprons are consistently driven, which contradicts the need for it to beslippery.


Emphases of new developments of aprons


Since the number of spindles onshort staple ring spinning machines has continually increased, the energy consumptionof the top weighting arms was initially more crucial for the standing times ofdrives; today more emphasis is put on torque values so as to improve the wholemachines energy balance. Low apron torque values help in achieving it.


In recent years extensive testinghas been carried out in the ATPG laboratory on test benches developedespecially for this purpose. The tests have included both a variety ofdifferent compounds and various surface structures. On the test benches torquevalues can be monitored and compared over an extended period. The findings havealso helped in the ongoing development of aprons for the large variety ofconditions nowadays for machines by various manufacturers. ATPG is thusfollowing a concept that should continue to provide the spinner with a productthat can be used across the entire range of fibres, drafting system settingsand machine types. Here the need for low torque values and good slippage gohand in hand. (Fig. 2)


To achieve improved yarn regularity,closer settings on the top arms are used, requiring greater flexibility in theaprons so as to accommodate the narrow radius at the nose bar. Here the taskwas to reduce the thickness of the apron layers in order to increase theaprons flexibility and reduce the tension at the point of turn, but withoutlosing the elasticity of the outer layer, which is essential for good fibrecontrol.


Results of these developments, whichhave been tested in the field under different conditions for a long time, aretoday a constituent part of Accotex aprons produced by ATPG.


About the Author:


The author is associated with ATPGTextile Products Group GmbH.



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