AIR KNIFE | BlackClawson

Air Knife Coater

The Air Knife Coater operates again by utilising the pan fed kiss roll applicator applying an excess of coating to the web. The coating is then metered and smoothed from the sheet using a jet of air through a specially designed adjustable Air Knife, accurately directed onto the coating layer to shear the fluid. The excess metered coating is collected by an Air Separation Pan. The Separation Pan design changes for high speed applications.

The Air Knife Coater gives a coating layer which contours the paper achieving an even coating thickness over the sheet.

Fig 1. Simple Air Knife Coater for speeds up to 250mpm

Fig 2. Air Knife Coater for speeds up to 500mpm

This method is popular for top coating of board after a Metering Bar or Flexrod Coater. This coater works well for low solids, low viscosity coatings.

More accurate coating application can be achieved with the use of multiple roll applicators.

Coating can be smoothed using a rod or roll prior to the Air Knife metering.

The setup of the Air Knife is extremely important in order that the air is delivered so that the “sharp” air stream shears the coating at some point in the coating layer where the energy of the air stream effectively separates the “pasty” coating near the surface of the paper where the water begins to be absorbed. The Black Clawson Air Knife design consists of an Air Knife Body, usually manufactured from Mild Steel with two stainless steel lips. The bottom lip is curved for good direction of the air stream onto the web and the top lip is flat with adjusting screws along its length for adjustment of overhang and lip gap.

Fig 3. The Black Clawson Air Knife

The Air Knife brackets in which the Air Knife is mounted allow for adjustments in all directions to ensure correct Air Impingement onto the coated paper or board.

Horizontal Adjustment
Vertical adjustment

Angular Adjustment

Fig 4. Air Knife Mounting Brackets

The Air Knife Separation Pan is designed to receive the air and excess coating metered from the web by the Air Knife, separate the coating from the air, and return the coating to the coating recirculation system. The model 311 Separation Pan is designed for speeds up to 500 mpm.