Projectile Weaving Machine

Overview

A projectile weaving machine inserts the weft thread across the warp by firing a small steel gripper, the projectile, that clamps the weft tip and flies through the open shed. It is the wide-loom workhorse of the industry, able to weave very wide fabric at high speed with one projectile drawing the weft straight across the full width. Sulzer introduced the design and it remains the choice for heavy and wide goods such as sheeting, denim, terry backing, technical fabric, and tarpaulin, where its long reed width and reliable insertion outweigh the higher cost over air and water jet looms. Unlike a shuttle loom, the projectile carries no weft package, it only grips the leading end, so the weft comes from a stationary supply package at the edge of the loom and there is no shuttle change.

Every loom does four motions in time: open the shed, insert the weft, beat it up, and advance the cloth. Here the Shedding Mechanism opens the shed, the Picking Unit unit fires the projectile to insert the weft, the Sley and Reed sley beats it up, and the Warp Let-off and Cloth Take-up advance the warp and cloth. A Return Conveyor returns spent projectiles, a Selvedge and Cutter unit finishes the edges, and a Main Drive and Control System run and protect the whole machine.

Picking and projectile return

The defining feature is the Picking Unit unit. Its Torsion Bar is a steel bar wound up through a fixed angle, storing energy like a spring. When released, the bar snaps back and the Picking Lever turns that twist into a fast linear stroke that the Picking Shoe delivers to the Gripper Projectile. The projectile, a hardened steel block of about 40 grams, grips the weft tip in its jaws and flies through the shed in a guide channel of Guide Tooth teeth, reaching the far side in a few thousandths of a second. There a Receiving Brake stops it gently and the Projectile Opener releases the weft. Because the projectile cannot fly back, eleven to seventeen of them circulate: each spent projectile drops onto the Return Conveyor under the warp, the Conveyor Chain carries it back to the launch side, and the Projectile Lifter returns it to the picking position. While one crosses, the next is already loaded.

Shedding

The Shedding Mechanism mechanism decides the weave. Each warp end threads through a Heddle Wire eye on a Heald Frame, and lifting some frames while lowering others opens the V-shaped shed for the projectile. On a patterned loom a Dobby Head head selects which frames lift on each pick: its Pattern Cylinder reads the weave program and engages a Selection Hook for each frame that should rise. A Shed Cam times the shed open just before the pick and closed just after, and Coil Spring returns pull the frames down. Up to fourteen frames allow fairly complex weaves, and a jacquard head replaces the dobby for figured cloth.

Beat-up, let-off, and take-up

After insertion the Sley and Reed sley swings forward and the Weaving Reed pushes the new weft pick up tight against the cloth fell, setting the picks per centimetre together with the take-up. The Rocking Shaft and Beat-up Cam drive this motion in time with the main shaft. Meanwhile the Warp Let-off releases warp from the Warp Beam: a Let-off Motor turns the beam and a Back Rest Roller roller with a Pressure Sensor holds warp tension constant as the beam empties. At the front the Cloth Take-up pulls the cloth forward over a gritted Emery Roller and winds it onto the Cloth Roll.

Selvedge and edges

Because the projectile leaves a cut weft tail at each edge rather than a continuous loop, the Selvedge and Cutter unit makes a clean tucked-in edge. A Tucking Needle folds each weft tail back into the next shed so the edge is locked and does not fray, the Weft Cutter trims the weft after the projectile releases it, and a Temple holds the cloth out to full width at the fell so it does not draw in. A small Waste Selvedge Unit grips the weft end during tucking and is cut away after.

Drive, control, and use

The Main Drive turns the Main Shaft through a Clutch-Brake that can stop the loom on an exact pick, which matters for finding the fault and restarting without a weave mark. The Control System runs the pattern on an Microcontroller, and two stop-motions protect the cloth: a Weft Feeler confirms the weft reached the far side before the next pick, and a Warp Stop-Motion halts the loom the instant a warp end breaks. The operator works from the Operator Panel. Projectile looms hold their place at the wide and heavy end of weaving, where reed widths past five metres and steady high insertion rates suit sheeting, denim, upholstery, and technical textiles better than jet looms can.