Guide bars

Raschel Warp knit raschel fabrics are produced in a similar way as tricot fabrics except for their stitch motions. The motion results in elastic yams being put into raschel construction as lay-in-yams versus knit-in yams on tricot constractions as shown in Figure 3.7. This lay-in stmcture leads to the raschel fabrics with elastic stretch in the length direction. Other elastic bar movements are possible to increase stretch and modulus in width. Raschel machines can have up to 64 yam guide bars to produce fabric patterns as extensive as jacquard lace. Elastomeric fabrics made by raschel showed good elastic stretch, recovery, and modulus in both length and width directions as elastic yam lap increases. 

The pulling force for the gripper can be provided by an air or hydraulic cylinder, hydraulic motor, or a servo motor. The gripper is usually supported by guide bars or rails and is driven by cylinder rods, chain, and sprockets or ball screws. With air- or hydraulic-powered units, the feed length is set by adjusting a positive stop. The gripper moves between the adjustable stop and a stationary stop and employs a cushion of some sort to soften the blow at the end of each... 

After an aqueous surface treatment process, it is essential that the fiber is dried after the final surface treatment wash to ensure the correct pick up of size. After sizing, any roller, nip or guide bar that the wet sized fiber passes over will control the level of pick up of the size liquor. It is advantageous to have a level control fitted in the bath to maintain the correct level. 

It involves columns of chain stitching with yarns traversing between the chain stitches. The principal differences with tricot are that the needles are latch needles and there are 4-48 guide bars, permitting greater variation of knits. 

Weft flat knitting machines, in conjunction with computer control, can produce a variety of 3-D structures from one yarn including boxes, cones and spheres. In warp knitting, it is normal to use an adapted Raschel machine fitted with two needle bars and several guide bars. Each needle bar produces a flat fabric, with the two flat fabrics simultaneously connected forming a sandwich, which can be readily impregnated with resin. 

Other textile components fabricated from carbon fiber include heald (heddle) frames (these position the warp to allow a shuttle with weft to pass through), lay bars, flyer arms, needles, sinkers, guide bars and faller bars. Due to the controlled expansion, the components do not change overnight when the shed temperature drops. Lucas [108] describes the application of carbon fibers to modem high speed loom sley developments. 

Guide bar n. A mechanism on a warp-knitting machine that directs warp threads to the latch needles. 

Three-bar fabric n. A tricot fabric made on a machine equipped with three guide bars. 

The tubular vascular graft is generally knitted on a double needle bar Raschel warp knitting machine of fine gauge ( 56), preferably with a tricot stitch. The needle beds are straight and occupy the width of the machine. The machine has a number of guide bars, which move relative to the needles to facilitate interlooping of adjacent yarns as the fabric is knitted. The number of bars can be as many as 20, but the usual number is between 4 and 10. 

In most load-bearing medical applications, however, warp-knitted structures, which include both weaving and knitting features, will generally be preferred. Specially constructed Raschel machines that have two needle bars and several guide bars are commonly used. The two needle bars, working alternately, contribute to the versatility of the products. The basic principle is that each needle bar produces a flat fabric the two fabrics are simultaneously connected to each other to form a three-dimensional structure. Examples of structures that can be produced are a double-sided, double thickness structure two separate fabrics with different structures and yarns, joined as needed tubular structure, straight or tapered, and with branches and a sandwich or a spacer fabric with filler yarns. 

Similar to a computerised flat knitting machine with two needle beds, a double-needle bar Raschel machine has two needle bars. It is possible to knit tubes of different sizes on such a machine with a set of fully threaded guide bars to knit two separate fabrics... 

Figure 6.10 Lapping movements of guide bars for knitting a single tube.

Warp-knitted spacer fabrics are produced on double-needle bar Raschel machines the principle is schematically shown in Figure 6.22(a). While the guide bars 1 and 2 lap the front-needle bar, and the guide bars 5 and 6 lap the back-needle bar, to knit the top outer layer and the bottom outer layer, respectively, the guide bars 3 and 4 lap the spacer yams around both the needle bars in succession. A spacer fabric being produced on a double-needle bar Raschel machine RD 6 by Karl Mayer is shown in... 

D linings for jackets are produced on a Raschel machine with two guide bars of the type RD 6 N with a machine gauge of E 22. However, there are two different distances in the moulding plates introduced. Due to recent developments (Anon., 1997a), the production of a spacer fabric with a combination of an open with a closed fabric side is possible (Schubert and Umbach, 2004). 

Figure 14.10 shows how the fibres are associated with the L2 and L5 stitch-forming laying rails. The spacer threads 3 and 4 function with direct involvement in the aforementioned laying rails L2 and L5 as weft threads. Numbers 1 and 6 are elastane yams with high titres and high modulus of elasticity associated to the guide bars LI and L6. 

The guide block slides on the guide bar and is located in the sliding block by a spigot. 

This gives a solid location and at the same time allows the guide block to take up the angle of the guide bar. 

---