Not applicable.
The present invention relates to rolls in paper handling machines, such as slitters, which are driven only by the web and to the brakes for stopping the rotation of such rolls when the paper web breaks.
Paper is manufactured in widths of up to 300 inches or more and wound into machine rolls which may weigh over 120,000 lbs. The machine rolls are removed from the papermaking machine as they are formed. Further processing of the machine roll to create smaller rolls or individual sheets of paper is preformed by other machines. The machine roll can be processed by sending the web through a group of slitters which cut the web into a plurality of narrower webs typically through the use of rotating circular knives. Paper webs are processed at speeds of up to 10,000 feet per minute. As the paper travels from the unwind station to the winder station, it passes over idler rolls to guide the web as it is fed into the rotating knives of the slitter.
For simplicity, the idler rolls have no drive and are simply free turning on internal bearings. As the web is drawn over the idler rolls, the rolls rotate with the speed dictated by the speed of the paper. If the paper web breaks in the slitter, it is often necessary to manually clean out broke from the slitting machine. However, the rapidly turning idler rolls may continue to rotate at several thousand RPM for a relatively long period of time. Waiting for the idler rolls to stop turning would result in the loss of valuable production time if a mechanism were not available to bring the idler rolls to a rapid stop. In existing machines a wheel can be brought into engagement with the idler rolls. The wheel is connected by a clutch brake and brings the roll to a stop. However, such braking wheels are subject to wear and contact the exterior surface of the idler roll. What is needed is a low maintenance brake without moving parts or one in which braking forces are exerted on the interior of the roll.
The idler roll brake of this invention is used in a slitting machine, or other paper handling machine, such as a winder, or a coater. The roll brake employs an electromagnet positioned external to, and close to the periphery of the idler roll. They electromagnetic brake interacts with a conductive aluminum roll, and a gear shaped steel or iron ring fitted within the aluminum roll. The electromagnet induces eddy currents in the conductive shell of the roll which produce magnetic fields in opposition to the applied magnetic field which results in a braking force applied to the roll. The energy of the rotating roll is converted into heat in the surface of at least the aluminum roll. The electromagnet is arranged transverse to the axis of the roll and the poles are positioned adjacent the surface of the roll. The gear shaped steel ring forms opposite poles which are attracted to the poles of the electromagnet intensifying the magnetic field through the aluminum shell. The attraction between the steel ring teeth and the electromagnetic poles bring the roll to a complete stop with the electromagnetic poles and the steel ring poles aligned. The brake may, for example, consist of a 400 Watt 120 V DC electromagnet positioned adjacent to an aluminum roll 7.8 inches in diameter, thirty-eight inches in length, and having a moment of inertia of about 4.5 lb ft2. The electromagnet has three ferromagnetic pole pieces with coils positioned therebetween. The three pole pieces and the magnet are positioned transverse to the axis defined by the aluminum roll. Positioned internal to the roll is a steel gear with teeth spaced apart so as to line up with the three pole pieces. Actuation of the electromagnet will bring a roll turning at up to 5000 RPM to a stop in less than one minute. The attraction between the gear teeth of the steel backing ring and the poles of electromagnet assure that the roll comes to a complete stop with individual teeth positioned over each of the three poles.
An alternative embodiment roll brake employs a brake shoe mounted to a roll end bearing. The brake shoe is positioned by one or more guides to slide forward to bring the brake shoe into engagement with the interior surface of the roll. An electromagnet positioned beneath the roll attracts a ferromagnetic armature or permanent magnet mounted to the brake to pull the brake shoe into engagement with the interior surface of the roll with a force of 10 to 20 pounds.
It is a feature of the present invention to provide a brake for an idler roll which does not contact the roll.
It is another feature of the present invention to provide a brake for an idler roll which requires less maintenance.
It is a further feature of the present invention to provide a brake for an idler roll which requires a reduced part count.
Further objects, features and advantages of the invention will be apparent from the following detailed description when taken in conjunction with the accompanying drawings.
Referring more particularly to
To supply the web 28 to the contact between the slitter blades 22 and the bottom bands 24, two coaxial idler rolls 30 are supported in front of the blades 22 on the machine 20. The rolls 30 are supported on end supports 32 by bearings 34 shown in
As shown in
The electromagnetic brake 38 may be connected directly to a paper break detection system (not shown) or may be operator initiated. Using an eddy current brake results in a relatively low cost and simple system. There is no contact between the electromagnetic brake 38 and the roll 30, greatly reducing the possibility of wear and the need for maintenance. The function of the electromagnetic brake 38 is self-regulating, i.e., because the braking force is proportional to the speed of rotation of the roll 30, the faster the roll is rotating the more braking force is applied.
Tests were performed using a roll configured as shown in
An alternative embodiment roll brake apparatus 68 is shown in
It should be understood that the electromagnet will function better the closer it is to the rolls surface in both described embodiments, because this will minimize the distance, i.e. the air gap, between the electromagnet the object it is action on. However misalignments and deflections limit how close the electromagnet can be to the roll surface in practice, for example the gap between the roll and the magnet could be about 0.1 inches or less.
It should be understood that the brake apparatus 68 and the magnetic brake 38 could be used in any kind of paper handling machine where is desirable to bring low inertia idler rolls to a stop so that the roll does not present a hazard to an operator who approaches the machine after it has been shut down.
It should be understood that the rolls 30 could be constructed of any material so long as eddy currents are produced which results in a braking actions on the roll.
It is understood that the invention is not limited to the particular construction and arrangement of parts herein illustrated and described, but embraces all such modified forms thereof as come within the scope of the following claims.
This application is a divisional of U.S. application Ser. No. 10/395,042, filed, Mar. 21, 2003 which is incorporated herein by reference.
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Number | Date | Country | |
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20060006271 A1 | Jan 2006 | US |
Number | Date | Country | |
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Parent | 10395042 | Mar 2003 | US |
Child | 11225762 | US |