Vacuum belt conveyor of a web forming machine for transferring a threading tail

A vacuum belt conveyor of a web forming machine for transferring a threading tail, said vacuum belt conveyor comprising:

• an air-permeable belt loop;
• a frame, comprising two side plates;
• a first turning roll mounted to the frame, and having an axis defining an axial direction and a circumference defining a circumferential direction;
• a second turning roll mounted to the frame, and spaced from the first turning roll, wherein the first turning roll and the second turning roll are positioned within the belt loop and arranged so that the belt loop travels over the first turning roll and the second turning roll;
• wherein the first turning roll has portions defining an axial shaft with circular disc shaped necks thereon, the necks defining circumferential grooves therebetween;
• a vacuum chamber formed between the two side plates and containing the first turning roll, the vacuum chamber having a deflector forming part of the vacuum chamber, and a distributor pipe connected to a source of compressed air, the distributor pipe arranged to blow air over the deflector to form a source of vacuum which extends in the axial direction across the vacuum chamber which creates a vacuum effect in the vacuum chamber;
• at least one cross-directional dividing structure arranged to divide the vacuum chamber and the first turning roll to create at least a first vacuum zone connected to the source of vacuum and a second vacuum zone spaced in the axial direction along the first turning roll from the first vacuum zone and connected to the source of vacuum, the at least one cross-directional dividing structure being arranged in such a manner that the negative pressure levels of adjacent vacuum zones are independent of each other.

A twin-wire dryer section in a web forming machine of a selected width comprising:

• a first plurality of dryer cylinders arranged at a first level, and comprised of first successive dryer cylinders, and having first turning rolls between the first successive dryer cylinders arranged to guide a first fabric through the first successive dryer cylinders, the first fabric forming first opening gaps where the fabric leaves one of the first successive dryer cylinders, and forming first closing gaps where the fabric joins one of the first successive dryer cylinders;
• a second plurality of dryer cylinders arranged at a second level, and comprised of second successive dryer cylinders, and having second turning rolls between the successive dryer cylinders arranged to guide a second fabric through the second successive dryer cylinders, the second fabric forming second opening gaps where the fabric leaves one of the second successive dryer cylinders, and forming second closing gaps where the fabric joins one of the second successive dryer cylinders;
• a vacuum belt conveyor comprising:
• an air-permeable belt loop of a selected width;
• a frame, comprising two side plates;
• a first turning roll mounted to the frame, the first turning roll having an axis defining an axial direction and a circumference defining a circumferential direction;
• a second turning roll mounted to the frame, and spaced from the first turning roll, wherein the first turning roll and the second turning roll are positioned within the belt loop and arranged so that the belt loop travels over the first turning roll and the second turning roll;
• wherein the first turning roll has portions defining an axial shaft with circular disc shaped necks thereon, the necks defining circumferential grooves therebetween;
• a vacuum chamber formed between the two side plates and containing the first turning roll, the vacuum chamber having a deflector forming part of the vacuum chamber, and a distributor pipe connected to a source of compressed air, the distributor pipe arranged to blow air over the deflector to form a source of vacuum which extends in the axial direction across the vacuum chamber which creates a vacuum effect in the vacuum chamber;
• at least one cross-directional dividing structure arranged to divide the vacuum chamber and the first turning roll to create at least a first vacuum zone and a second vacuum zone spaced in the axial direction along the first turning roll from the first vacuum zone, the source of vacuum arranged to create a vacuum effect in said first vacuum zone and said second vacuum zone;
• and
• wherein the distributor pipe is arranged to blow air over a second deflector mounted beneath the air-permeable belt loop to create a further vacuum zone on a section of the belt loop overlying the second deflector plate;
• wherein the vacuum belt conveyor is arranged between the first level of the first successive dryer cylinders and the second level of second successive dryer cylinders, and is arranged to transfer a threading tail from a first opening gap over an open draw to a second closing gap;
• and
• a doctoring element arranged to detach the threading tail from the surface of one of the dryer cylinders of the first plurality of dryer cylinders prior to the first turning roll.