US 5,671,895 AGranted

System and method for controlling the speed and tension of an unwinding running web

AssigneeMartin Automatic, Inc.

InventorsRoger Cederholm, James K. Ward, Emil G. Borys

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Abstract

A system and method for controlling the speed and tension of a web being unwound from a rotating roll and being run through an inertia-compensated festoon and then to a web-using production process which requires the web to run at a preselected relatively high speed and a preselected relatively low tension. Based on sensing the amount of web stored in the festoon, a brake applies a decreasing braking-force to the running roll as the diameter of the roll decreases. When the roll has decreased to an intermediate diameter, where the decreasing tension torque is inadequate to continue to accelerate the roll, a motor engages the roll and adds assisting web-unwinding torque to the roll as the diameter of the roll continues to decrease. The brake is also used to brake the roll to a stop before a subsequent zero-speed web-splice. The motor is also used to rotate the roll to line speed after splicing.

Claims10

Dependent claims

An improved method for controlling the speed and the tension of a web being unwound from a first, rotating roll where the web runs from the roll along a predetermined path through an inertia-compensated festoon, which has the capacity of storing varying amounts of running web during the operation of a web-using process without inducing tension variations into the web, and to the web-using process which requires the web to run at a preselected relatively high speed and at a preselected relatively low tension and which tends to pull the web so as to apply a web-unwinding torque to the roll;

the method including the steps of:
applying a brake force to the rotating roll, when the web begins to unwind from the roll;
decreasing the braking force applied to the roll as the diameter of the roll is reduced, due to the web being unwound from the roll, so that the web will run through the process at the preselected speed and tension as the roll unwinds;
and
when the roll has been unwound to an intermediate diameter where the decreasing web-unwinding torque is inadequate to continue to accelerate the mass of the roll assisting in rotating the roll in a web-unwinding direction by adding web-unwinding torque to the roll as the diameter of the roll continues to decrease from the intermediate diameter so that the web will continue to run through the process at the preselected speed and tension as the remaining web is unwound from the roll.

2 more elements

An improved system for controlling the speed and tension of a web running through a web-using production process which requires the web to run at a preselected relatively high speed and at a preselected low tension and which tends to pull the web so as to apply a web-unwinding torque to the roll, the system comprising:

a first roll mounted for rotation about its central longitudinal axis and having the web wound about its longitudinal axis, with the web, which is being unwound from the roll, running along a predetermined path from the roll to the process;
an inertia-compensated festoon disposed in the predetermined path so that the running web passes through the festoon, with the festoon having the capacity for storing varying amounts of running web during the operation of the process without inducing tension variations into the web;
a first shaft brake-assembly connected with the roll for applying a braking force to the roll;
a first shaft-drive assembly connected with the roll so that when engaged, the drive assembly will drive the roll in a web-unwinding direction;
means for controlling the operations of the brake assembly and of the drive assembly, with the control means causing the brake assembly to apply a decreasing braking force to the roll as the diameter of the roll decreases, due to the web being unwound therefrom, so that the running web will run through the process at the preselected speed and tension, and with the control means causing the drive assembly to engage the roll when the web on the roll has been unwound to an intermediate diameter where the decreasing web-unwinding torque is inadequate to continue to accelerate the mass of the roll so that the drive assembly will increasingly add assisting web-unwinding torque to the roll as the diameter of the roll continues to decrease so that the web will continue to run through the process at the preselected speed and tension as remaining web is unwound from the roll.

2 more elements

Dependencies are inferred from the claim text.