Curved suction box apparatus in a papermaking machine press section

In a papermaking machine press section, a curved pick-up suction box apparatus for guiding a web towards a nip of a nip press, said apparatus comprising:

• initial shoe means disposed upstream relative to the nip, said shoe means defining a convex surface for guiding the web;
• a box means disposed downstream relative to said initial shoe means for guiding the web from said initial shoe means, said box means being connected to a partial vacuum means;
• said initial shoe means including:
• a solid shoe having an initial curved surface for guiding the web;
• a further shoe disposed downstream relative to said solid shoe, said further shoe having a further curved surface, said further curved surface defining a plurality of perforations which extend from said further curved surface to a variable source of partial vacuum such that the web is drawn towards said further curved surface;
• said box means including:
• a perforate surface which is connected to a partial vacuum means such that the web is drawn towards said perforate surface during movement of the web past said perforate surface;
• a first compartment disposed adjacent to said initial shoe means, said first compartment being connected to a first source of partial vacuum of said partial vacuum means for drawing the web towards said perforate surface;
• a second compartment disposed downstream relative to said first compartment, said second compartment being connected to a second source of partial vacuum of said partial vacuum means for assisting in drawing the web towards said perforate surface;
• said perforate surface further including:
• an upstream perforate closure which cooperates with said first compartment;
• and
• a downstream perforate closure which cooperates with said second compartment, the box means being arranged for permitting the application of a differential vacuum level to said upstream closure relative to said downstream closure.