Hot dip coating device and method

A hot dip coating device to provide a metal coating on a moving metal sheet having opposed first and second sides, containing a liquid bath of metal coating material to provide the metal coating on the moving metal sheet, comprising:

• a container for the liquid bath,
• a guide or sink roll provided in the container below surface level of the liquid bath in use to guide the moving metal sheet through the bath, and
• a pair of gas knives provided above the liquid bath, each said gas knife having an outlet to project wiping gas on the metal coating provided on the moving metal sheet that passes along the gas knife, and
• wherein at least four supporting rolls are provided which together with the guide or sink roll influence a shape of the moving metal sheet in a width direction at least at a location of the gas knife,
• wherein the at least four supporting rolls are placed above the surface level of the liquid bath on a position enabling them to operate on the moving metal sheet before the moving metal sheet enters the liquid bath,
• wherein at least three of said at least four supporting rolls are moveable to and fro the moving metal sheet in a direction of the moving metal sheet to influence crossbow of the moving metal sheet as the moving metal sheet is moving;
• wherein the at least four supporting rolls are adapted and configured for the moving metal sheet to be moved over the at least four supporting rolls before entering the liquid bath of metal in the container of the hot dip coating device,
• wherein the at least four supporting rolls are adapted and configured for at least two of the at least four supporting rolls to contact the first side of the moving metal sheet and at least two of the at least four supporting rolls to contact the second side of the moving metal sheet,
• wherein the at least four supporting rolls comprises a first supporting roll, a second supporting roll, a third supporting roll, and a fourth supporting roll, and
• wherein the fourth supporting roll is closest to the guide or sink roll and adapted and configured to contact a side of the moving metal sheet opposite to a side of the moving metal sheet that has contact with the guide or sink roll, and
• wherein the at least four supporting rolls are adapted and configured for contact with the opposed first and second sides of the moving metal sheet consisting of successive and alternate contact with the opposed first and second sides of the moving metal sheet relative to each other supporting roll of said at least four supporting rolls,
• wherein the second supporting roll is adapted and configured to contact the moving metal sheet successively and alternately relative to the first supporting roll,
• wherein the third supporting roll is adapted and configured to contact the moving metal sheet successively and alternately relative to the second supporting roll,
• wherein the fourth supporting roll is adapted and configured to contact the moving metal sheet successively and alternately relative to the third supporting roll;
• wherein the third supporting roll is sufficiently separated from the second supporting roll such that the third supporting roll and the second supporting roll are each movable to and fro in the direction of the moving metal sheet to exert bending forces on the moving metal sheet to influence crossbow of the moving metal sheet;
• wherein the fourth supporting roll is sufficiently separated from the third supporting roll such that the fourth supporting roll and the third supporting roll are each movable to and fro in the direction of the moving metal sheet to exert bending forces on the moving metal sheet to influence crossbow of the moving metal sheet;
• wherein the second, third and fourth supporting rolls are sufficiently separated to independently and simultaneously exert penetration on the moving metal sheet;
• wherein the hot dip coating device is adapted and configured to move the moving metal sheet, after passing the moving metal sheet between the first, second, third and fourth supporting rolls, into the liquid bath to contact the guide or sink roll provided in the container below the surface level of the liquid bath for guiding the moving metal sheet through the bath,
• wherein the hot dip coating device is adapted and configured to then move the moving metal sheet out of the liquid bath and then pass between the pair of said gas knives above the surface level of the liquid bath, each of the gas knife outlets for projecting wiping gas on the metal coating provided on the moving metal sheet that passes along the pair of gas knives;
• wherein there is an absence of the at least four supporting rolls in the liquid bath of metal,
• wherein the hot dip coating device is adapted and configured to move the moving metal sheet along a path and a portion of the path of the moving metal sheet is inclined at an inclined angle such that the moving metal sheet moves into the liquid bath at the inclined angle, and the at least four supporting rolls are located along the inclined portion of the path of the moving metal sheet.