117b which is connected through a suitable gearing and linkage mechanism 118a 118b to a shaft 119a 119b having a pinion 121a 121b at the end thereof each gear and linkage mechanism 118 converts a rotation of the corresponding shaft 117 into a suitable corresponding linear movement of pinion gears 121 pinion gears 121 mesh with corresponding racks 123a and 123b extending from sewing head 14 rack 123a is connected to an existing mechanism within the sewing head 14 which controls the feed rate for the upper ply of material being fed through the sewing head 14 while rack 123b connects to an existing mechanism in the sewing head which controls the rate at which the lower ply of material is fed through the sewing head thus processor 114 may by applying suitable inputs to servomotors 115a and 115b independently control the feed rate of each ply of material the manner in which the feed rate control mechanism shown in fig6 is utilized will be described later fig7 illustrates the operation of the system shown in fig1 5 assume initially that two pieces of material which are in sewing head 14 are being sewn that table extension 72 is in the raised position shown in fig4 that arm 20 and the elements connected thereto are in the preload position shown in fig1 that pressure plate assembly 42 is in the raised position shown in fig2 and that the detector assembly 97 mounted to sleeve 100 is in the up position also shown in fig2 at.