EP0051055A1 — Apparatus for ventilating cylinder pockets in a c…

Claim 1

Independent Claim 236 words

A method of ventilating cylinder pockets in a cylinder dryer including a plurality of heated cylinders about which a web-like material is taken in zig-zag mode and pressed agaist certain of the heated cylinder surfaces by means of an endless Fourdrinier wire, cylinder pockets being formed between the cylinders, web and wire when the latter relinquishes contact with the web at a cylinder surface, to pass over a return roll arranged between the cylinders, and make contact once again with the web at the next consecutive cylinder circumference, characterized in that a current of drying air is blown over the width of the wire against its surface facing away from the cylinder in a direction forming an acute angle to and having a directing component substantially counter to the direction of wire travel, blowing taking place within an area where the wire relinquishes contact with the web, and for the purpose of reducing the spontaneous airflow in the cylinder pocket generated by the speed and texture of the wire, and in that for a given desired web speed the permeability of the wire is selected such that the difference between desired air inflow in the cylinder pocket and the spontaneous airflow out of the pocket generated by the speed and texture of the wire, is sufficiently low for the air current transverse the web generated thereby not to exceed a speed at which web flutter occurs.

Claim 2

Independent Claim 236 words

A method of ventilating cylinder pockets in a cylinder dryer including a plurality of heated cylinders about which a web-like material is taken in zig-zag mode and pressed agaist certain of the heated cylinder surfaces by means of an endless Fourdrinier wire, cylinder pockets being formed between the cylinders, web and wire when the latter relinquishes contact with the web at a cylinder surface, to pass over a return roll arranged between the cylinders, and make contact once again with the web at the next consecutive cylinder circumference, characterized in that a current of drying air is blown over the width of the wire against its surface facing away from the cylinder in a direction forming an acute angle to and having a directing component substantially counter to the direction of wire travel, blowing taking place within an area where the wire relinquishes contact with the web, and for the purpose of reducing the spontaneous airflow in the cylinder pocket generated by the speed and texture of the wire, and in that for a given desired web speed the permeability of the wire is selected such that the difference between desired air inflow in the cylinder pocket and the spontaneous airflow out of the pocket generated by the speed and texture of the wire, is sufficiently low for the air current transverse the web generated thereby not to exceed a speed at which web flutter occurs.

Claim 3

Dependent Claim 214 words

Apparatus for ventilating cylinder pockets in a cylinder dryer in- eluding a plurality of heated cylinders about which a web-like material is taken in zig-zag mode and pressed against certain of the heated cylinder surfaces by means of an endless Fourdrinier wire, cylinder pockets being formed between the cylinders, web and wire when the latter relinquishes contact with the web at a'cylinder surface, to pass over a return roll arranged between the cylinders, and made contact once again with the web at the next consecutive cylinder circumference, whereby at least one blowing box is disposed outside the cylinder pocket, extends over the width of the wire, and is provided with blowing orifices placed between the return roller and the area where the wire relinquishes contact with the web, characterized in that at least some of the blowing orifices of the blowing box are directed such that drying air is caused to flow towards the wire in a direction forming an acute angle to, and having a directing component substantially counter to the direction of travel of the wire, and in that the blowing box is provided with means adapted for preventing an interface layer of wet air around the return roll periphery from being introduced into the cylinder pocket on rotation of the roll.

Claim 4

Dependent Claim 214 words

Apparatus for ventilating cylinder pockets in a cylinder dryer in- eluding a plurality of heated cylinders about which a web-like material is taken in zig-zag mode and pressed against certain of the heated cylinder surfaces by means of an endless Fourdrinier wire, cylinder pockets being formed between the cylinders, web and wire when the latter relinquishes contact with the web at a'cylinder surface, to pass over a return roll arranged between the cylinders, and made contact once again with the web at the next consecutive cylinder circumference, whereby at least one blowing box is disposed outside the cylinder pocket, extends over the width of the wire, and is provided with blowing orifices placed between the return roller and the area where the wire relinquishes contact with the web, characterized in that at least some of the blowing orifices of the blowing box are directed such that drying air is caused to flow towards the wire in a direction forming an acute angle to, and having a directing component substantially counter to the direction of travel of the wire, and in that the blowing box is provided with means adapted for preventing an interface layer of wet air around the return roll periphery from being introduced into the cylinder pocket on rotation of the roll.

Claim 5

Dependent Claim 61 words

Apparatus as claimed in claim 2, characterized in that the blowing orifices of the blowing box are formed as louvre-type or eyelid perforations, and in that the box is subdivided into sections over the width of the web, drying air being individually suppliable to said sections and wherein the air quantity is adjustable to enable regulation of the web drying profile.

Claim 6

Dependent Claim 43 words

Apparatus as claimed in claim 2, characterized in that means preventing the wet air from recirculating to the pockets comprise a lip of yielding material connected to the blowing box and engaging against the peripheral surface of the return roll along its generatrix.

Apparatus for ventilating cylinder pockets in a cylinder dryer

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