Advancing material of indeterminate length – With material-responsive control means – Responsive to break or depletion
Reexamination Certificate
1998-09-14
2001-04-17
Mansen, Michael R. (Department: 3653)
Advancing material of indeterminate length
With material-responsive control means
Responsive to break or depletion
C226S118200, C242S417100, C267S114000
Reexamination Certificate
active
06216934
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a method and system for preventing damage to a festoon should a break in a running web occur while the web is being unwound from a rotating roll, being run through the festoon, and then run to a web-using production process.
The inclusion of festoons in systems for controlling the speed and tension of running webs has been recognized as a significant improvement. Such festoons, which are capable of storing variable amounts or quantities of the running web, typically include, in simplified form, a fixed entry idler, a relatively movable dancer and a fixed exit idler. The web runs about the entry idler, the dancer and then the exit idler. A dancer tensioning cylinder assembly is connected with the dancer and is adapted to urge the dancer upwardly, vertically with respect to the fixed idlers and against the force of the web running over and about that dancer.
The dancer tensioning cylinder assembly includes a piston, which is disposed for reciprocal movement within a cylinder, which is connected to the dancer by, for instance, a cable, and to which controlled, pressurized air is applied to one surface or face of the piston so as to force the piston to move in one direction within the cylinder. Upward movement of the dancer may occur in response to movement of the piston in the one direction in the cylinder.
In the past, a break in the running web could and often did cause damage to the festoon. The break would remove the web-generated force that opposed the upwardly directed force imposed on the dancer by the dancer tensioning cylinder assembly. Upon this removal, the dancer would tend to move suddenly, upwardly in the festoon. Such out-of-control, upward movement sometimes caused the dancer to strike the festoon's supporting structure, thus damaging the dancer and/or the festoons supporting structure. Repair of such damage could be costly particularly in terms of the down time of the web-using production process.
BRIEF SUMMARY OF THE INVENTION
In principal aspects, the present invention provides an improved method and system for controlling and limiting the heretofore out-of-control upward movement of the dancer upon a breakage of the running web. The present invention is thus able to prevent damage to the festoon and to minimize down time of the web-using production process should a break in the running web occur.
This control and limitation of the upward movement of the dancer is achieved by controlling the movement of the piston in the dancer tensioning cylinder assembly. The piston is controlled by substantially instantaneously equalizing the air pressures applied to the opposite surfaces or faces of the piston after a web break occurs, and then after a preselected delay, bleeding the air pressures off. This equalization stops the movement of the piston, and in turn, stops the upward movement of the dancer by removing the force that would otherwise have been imposed on the dancer by the dancer tensioning cylinder assembly.
Accordingly, a principal object of the present invention is to provide an improved method and system for controlling and limiting the upward movement of the dancer of a festoon when the running web breaks.
Another object of the present invention is to provide an improvement in a system for controlling the speed and tension of a running web being unwound from a rotating roll and being run through an festoon and then to a web-using production process, where the festoon includes a relatively fixed idler, a relatively fixed exit idler, and a vertically movable dancer about which the running web runs; where the dancer may be moved vertically relatively with respect to the idlers depending on the amount or quantity of running web being stored in the festoon; where the dancer is connected with a dancer tensioning cylinder assembly that is used to urge the dancer vertically, against the force of the running web running over the dancer and that includes a cylinder, which has a first end and a second end, and a piston, which is connected with the dancer, which is movable within the cylinder, and which has a first surface facing the first end of the cylinder and a second surface facing the second end of the cylinder; where the first portion of the cylinder is defined between the first end of the cylinder and the first face of the piston; where the piston is movable within the cylinder in response to the air pressures being applied to and acting on the first surface of the piston; where the system includes a source of air under pressure that is adapted to be applied to the first portion of the cylinder and an air regulator for regulating the pressure of the pressurized air supplied to the first portion of the cylinder; and the improvement includes a first check valve that is adapted to move between a first position in which the second portion of the cylinder (that is defined between the second end of the cylinder and the second surface of the piston) is open to the atmosphere and a second position in which the second portion of the cylinder is closed to the atmosphere so that the pressure of the air in the second portion may increase so as to become equal with that of the pressure of the air in the first portion of the cylinder; where the first valve moves from its first position to its second position when a breakage of the running web occurs; and where the system further includes an air flow restrictor that permits air in the second portion of the cylinder to bleed from the second portion after a preselected delay after a break in the running web has occurred. A related object of the present invention is to provide an improved system, as described, where the system includes a second valve that is adapted to be moved between a first position in which the source of pressurized air is connected with the first portion of the cylinder and a second position in which the source of pressurized air is disconnected from the first portion of the cylinder, and after a preselected delay, the pressurized air in the first portion of the cylinder is permitted to bleed from the first portion of the cylinder; and where the system also further includes a sensor that is adapted to sense a breakage of the running web, and in response to such breakage, to activate the second valve so as to move the second valve from its first position to its second position.
Still another object of the present invention is to provide an improvement in a method for controlling the speed and tension of a running web being unwound from a rotating roll and being run through an festoon and then to a web-using production process where the improvement comprising the steps of sensing the occurrence of a break in the running web; causing the pressure of the air in the second portion of the cylinder of dancer tensioning cylinder assembly, which is normally open to the atmosphere, to increase so that the air pressure in the second portion of the cylinder becomes equal to the air pressure in the first portion of the cylinder; and after a preselected delay after the break in the running web, bleeding the pressurized air from the cylinder. A related object to the present invention is to provide an improved method, as described, whereafter a break in the running web occurs, the first portion of the cylinder is disconnected from the source of pressurized air, and after a preselected delay, the pressurized air in that first portion is bled off.
These and other objects, advantages and benefits of the present invention will become more apparent from the following description of the preferred embodiment of the present invention, which description may be best understood with reference to the accompanying drawing.
REFERENCES:
patent: 3025017 (1962-03-01), Wahlstrom
patent: 3796360 (1974-03-01), Alexeff
patent: 4033522 (1977-07-01), Chesnut et al.
patent: 5031847 (1991-07-01), Tanaka
patent: 5810236 (1998-09-01), Yashida et al.
Mansen Michael R.
McAndrews Held & Malloy Ltd.
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