Pulp Paper & Logistics
HONEYWELL 23
Figure 2 (left): Outer appearance of the stabiliser, featuring two Coanda slots and one vacuum nozzle. Figure 3 (right): Coanda slots create opposing tension on the moving sheet
head split functions, key switch enable and warning light, making the laser system inherently safe. The laser device is a ‘smart’
device using a contemporary CMOS sensing pixel array. The features built into this device are designed for a diffused surface, and has proprietary algorithms to calculate a consistent interpretation of the measurement object’s surface. CMOS sensing arrays output
a ‘picture’ of the reflection intensity for further processing so it can filter stray signals. The result is a good, contemporary, application for paper measurement.
Reference surface on the other side Honeywell has dedicated much effort in this area, with the application of many patents on the subject. The first area is the
use of the Coanda air clamp. The concept is not new: by using a narrow slot to flow a jet of air, a negative pressure area is created when this flow encounters a drop step or back step. The novel approach taken by Honeywell is to use two opposing Coanda slots and back steps to ‘stretch’ the sheet, while the sheet is travelling in excess of 1,500 metres per minute (Figures 2 and 3).
This use of the Coanda effect is quite novel in contrast to perforated suction holes. Perforations provide a large area of coverage, but with each perforated hole there is an edge, a discontinuity, that can cause momentum shift to stir up dust and loose debris. Honeywell’s design rejected the use of vacuum rings which may control a large area of the sheet, but not the area at the point of
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Figure 4: Results of end-of-reel CD profile comparison between Optical Caliper, Contact Caliper and lab (TAPPI method) measurements. Scale is in microns
September 2012
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