Winding – tensioning – or guiding – Tension control or brake – Supply controlled
Utility Patent
1998-11-20
2001-01-02
Jillions, John M. (Department: 3653)
Winding, tensioning, or guiding
Tension control or brake
Supply controlled
C242S421200, C242S421700
Utility Patent
active
06168108
ABSTRACT:
TECHNICAL FIELD
The present invention relates generally to web driven processing systems and more particularly to the control of web tension and braking systems and in particular as those systems relate to the production of envelopes.
BACKGROUND OF THE INVENTION
Precise web tension control is important in the printing and paper processing industries. Even small variations in web tension prevent effective application of ink and embossing. In high speed web lines, such as those exceeding 500 feet per minute, manual adjustment of web tension is not possible. Such systems therefore require automated tension control systems.
In systems which control tension using a dancer, one limitation on effective web tension control is the response time of the dancer. Frequently, the dancer movement lags the actual change in web tension, causing the control system to fall behind in reacting to the change and thereby not properly adjusting the tension maintained in the web. One of the primary causes of such delayed reaction is the weight of the dancer. Another cause is insufficient elasticity in the web.
Another problem with achieving precise tension control of a web is the inertia of the web unwind roll which supplies the web to the system. Current systems usually apply braking force to the unwind roll based on web tension, web speed, or supply roll diameter. However, the braking force applied to the supply roll is often poorly matched to the force actually required, since most systems make no provision for possible variations in roll size and weight. The result is that these systems frequently over-apply or under-apply the unwind roll brakes, resulting in large variations in web tension and risking damage to the web as well as the processing equipment.
The lagging response of the dancer to changes in web tension also gives rise to rapid web tension variations when shutting down the web processing line, whether the shut down is routine or as a result of an emergency shut down caused by an error which is detected by a sensor. After the shut down signal is sent, the unwind roll in previously available systems continued turning due to its inertia. This situation caused the dancer festoon to overflow rapidly and thereby waste paper and potentially damaging equipment. Current dancer controlled systems do not react to a shutdown quickly enough to prevent this.
SUMMARY OF THE INVENTION
The invention eliminates the disadvantages of previous web tension control systems by detecting downstream web tension and combining the data with information about the movement of the dancer to take into account the elasticity of the web. The invention also employs a lightweight dancer having a low-friction cylinder and pivoting on low-friction bearings. The control system of the present invention takes the unwind roll inertia into account by activating selected portions of the unwind roll brakes based on the diameter of the roll. Finally, the problems associated with shutdown are solved by monitoring the downstream shutdown controls and generating a short, closed-loop brake pulse to the unwind roll brakes when a shutdown signal is detected.
REFERENCES:
patent: 2214355 (1940-09-01), Tiselius et al.
patent: 2965326 (1960-12-01), Rockstrom
patent: 3465981 (1969-09-01), Byrt
patent: 3724733 (1973-04-01), Schaffer et al.
patent: 3811637 (1974-05-01), Abler
patent: 3936008 (1976-02-01), Crum
patent: 4000865 (1977-01-01), Gaskins
patent: 4151594 (1979-04-01), Stern
patent: 4286757 (1981-09-01), Wirth
patent: 5299753 (1994-04-01), Alexander
patent: 5441210 (1995-08-01), Hinton
patent: 5469869 (1995-11-01), Suzuki et al.
patent: 5826744 (1998-10-01), Dell 'Aglio et al.
patent: 5826774 (1998-10-01), Dell'Aglio et al.
Hallmark Cards Incorporated
Jillions John M.
Leydig, Voit & Meyer Ltd.
LandOfFree
Web tension control apparatus and method does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Web tension control apparatus and method, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Web tension control apparatus and method will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2436684