What makes a good air trim conveying system?

Last month I suggested that trim be conveyed from the converting machine in air tubes. A good operating trim system can prevent considerable downtime on the converting machine. This month I want to list some of the critical parameters that make up a good air tube conveying system.

Normally, the pick-up tube should begin with a bell-shaped mouth. A well-designed bell opening helps guide trim into the tube without adding excessive rubbing friction. However, the trim path should be as straight into the bell opening as posBible from the last roll surface. A vertical downward path will assist in threading trim in the tube. (See Figure 1.)

Air velocity at the entrance is critical for easy trim insertion into the tube. Pull on the trim from conveying air can be marginal on stiff web materials until the trim is well inside the tube. This is because the trim must flutter to provide a significant pulling force. Stiff webs do...