29 - Double Needle Bar Warp Knitting Machines

Abstract

Double needle bar Raschels or bearded needle Simplex machines are symmetrically arranged with each needle bed having identical facilities and knitting once during the 360-degree revolution of the machine's cam-shaft. The vertical needle bars work back-to-back with the fabric being drawn downwards in the gap between them. Guides are able to pass between needles in both beds as they swing from the front to the back of the machine and vice-versa. As the guide bar lapping sequence involves overlapping and under lapping on each bed in turn, it is not possible to achieve actions simultaneously on both beds. Compared with single-bed knitting, an extra or triple swing of the guide bars is necessary after each underlap to swing the guide bars over the bed that has completed knitting so that the other needle bar can rise to commence its knitting cycle. Double needle bed is slower than single needle bed warp knitting and basic double-faced fabrics knitted with two full-threaded guide bars are heavier and more expensive than equivalent weft knitted double-bed fabrics. It is necessary for warp knitted double-bed products to exhibit certain unique properties to be worth their production costs. When drawing a lapping notation, it is useful to indicate that every alternate row of points represents the front bed, either by lettering or by a heavier line of points or both, it might also be useful to space the rows in pairs indicating each complete cycle on the two beds.