Abstract:
An idler roll brake in a paper handing machine wherein the roll brake employs a brake shoe mounted to the roll end bearing. The brake shoe slides forward to bring the brake shoe against the interior surface of the roll. An electromagnet positioned external to and mounted closely spaced from the cylindrical shell the roll attracts a ferromagnetic armature or permanent magnet mounted to the brake to pull the brake shoe into engagement with the inner surface of the roll.

Description:
CROSS REFERENCES TO RELATED APPLICATIONS 
   This application is a divisional of U.S. application Ser. No. 10/395,042, filed, Mar. 21, 2003 which is incorporated herein by reference. 

   STATEMENT AS TO RIGHTS TO INVENTIONS MADE UNDER FEDERALLY SPONSORED RESEARCH AND DEVELOPMENT 
   Not applicable. 
   BACKGROUND OF THE INVENTION 
   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. 
   SUMMARY OF THE INVENTION 
   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 ft 2 . 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. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is an isometric view of the paper slitter employing the roll brake of this invention. 
       FIG. 2  is a fragmentary side elevational cross-sectional view of the roll and brake of  FIG. 1 . 
       FIG. 3  is a cross-sectional view of the roll and roll brake of  FIG. 2  taken along section line  3 — 3 . 
       FIG. 4  is a side elevational cross-sectional view of an alternative embodiment roll and roll brake of the invention. 
       FIG. 5  is a cross-sectional view of the alternative roll and roll brake of  FIG. 4 , taken along section line  5 — 5 . 
   

   DESCRIPTION OF THE PREFERRED EMBODIMENTS 
   Referring more particularly to  FIGS. 1–5  wherein like numbers refer to similar parts, a slitter  20  is shown in  FIG. 1 . The slitter  20  has a multiplicity of slitter blades  22  which engage with bottom bands  24  driven by motors  26 . During operation, a slitter blade  22  is positioned or “side loaded” so that it tightly engages the side edge of a bottom band  24 . The leading point of contact between a slitter blade  22  and a bottom band  24  forms a cut-point whereby the paper web is cut. As a result, each slitter blade  22  and bottom band  24  overlap to provide a scissors-like action for cutting the web as it unwinds from a roll and is pulled through the web slitter by a take-up roll. 
   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  FIG. 2 , and are caused to rotate by the motion of the web  28  across the outer surface  36  of the roll  30 . The web can travel at up to 10,000 feet per minute, causing the rolls to rotate at 4900 RPM for rolls which are about 7.8 inches in diameter. As shown in  FIG. 1 , a magnetic brake  38  is positioned beneath each roll  30  but does not physically engage the roll. The magnetic brake  38  stops the roll within about 30 seconds after a web brake so that an operator can approach the machine to remove the broken web without the danger of engaging the still-turning rolls  30 . 
   As shown in  FIG. 3 , the magnetic brake  38  has three poles  40  with electrical windings  42  positioned between the poles  40 . The electromagnet is powered by 120 volt AC which is rectified to DC. Because the magnetic brake  38  is only required to operate for approximately 30 seconds at infrequent intervals, it may be designed with a duty cycle of five percent and a maximum continuous operating time of one minute. The magnetic brake  38  may be sized to consume 400 watts of power. The outside poles  44  have upper surfaces  46  which are shaped to allow them to be positioned tangent to the outer surface  36  of the rolls  30 , and the middle pole  48  has an upper surface  50  which is tangent to the low point  52  of the rolls  30 . The magnetic brake  38  is an electromagnet which induces eddy currents in the electrically conductive aluminum shell  54  of the rolls  30 , and interacts with a ferromagnetic ring  56  which intensifies the applied magnetic fields which brake the rotation of the rolls  30 . As the roll  30  reaches a low velocity, the attraction between the poles  40  of the electromagnet formed by the brake  38  interact with poles  58  formed by the radially outwardly extending teeth  60  on the ferrous ring  56  to bring the rolls  30  to a complete stop as shown in  FIG. 3 , with the outside poles  40  and the middle pole  48  aligned with the poles formed by individual teeth  60 . The polls  40  are arranged with a spacing which positions of the polls beneath individual teeth of the gear. Thus the spacing the out side polls  44  from the middle poll  48  will be the sin((360/number of teeth)×(gear radius)) or in the case of 8 teeth, sin(45)×gear radius or 0.707 times the gear radius. For a larger number of polls and teeth a second set of out side poles could be used spaced at sin((360/number of teeth×2)×(gear radius)). 
   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  FIGS. 2 and 3 . The aluminum roll had an outer shell thirty-eight inches in length which was formed from two 19 inch roll shell segments. The diameter of the aluminum roll was 7.8 inches with a wall thickness of about 0.33 inches reduced to 0.217 inches along a central relief area  62  where the two 19 inch roll shells were welded together at a weld joint  64  backed by a weld ring  66 . A cold rolled steel ring  56  having an interior diameter of 6.6 inches and an outer diameter of 7.1 inches with radially projecting teeth having a diameter of 7.4 inches was press fit in the central relief area  62 . The steel ring  56  had an axial length of 1.375 inches. An electromagnet  38  of 400 watts 120 volt dc 5% duty cycle procured from Magnetech Corporation of Novi, Mich., was positioned as illustrated in  FIG. 3 . Test runs were initiated by spinning up the roll and turning on the electromagnet  38 . The results are tabulated in the table. Because of limitations of the test setup, maximum roll speed was about 2000 RPM, but a linear extrapolation of the data indicates that the magnet would bring a 4,900 RPM or 10,000 feet-per-minute roll to rest in about 38 seconds. 
   
     
       
             
             
             
             
             
           
             
             
             
             
             
             
           
         
             
                 
                 
             
             
                 
                 
               Roll 
               Roll 
                 
             
             
                 
               Test 
               Speed 
               Speed 
               Time required to Stop 
             
             
                 
               Run 
               (ft/min) 
               (RPM) 
               Roll 
             
             
                 
                 
             
           
           
             
                 
             
           
        
         
             
                 
               1 
               3000 
               1470 
               10 
               seconds 
             
             
                 
               2 
               2500 
               1224 
               9 
               seconds 
             
             
                 
               3 
               2000 
               980 
               7.5 
               seconds 
             
             
                 
               4 
               1000 
               490 
               4.0 
               seconds 
             
             
                 
               5 
               1500 
               735 
               5.0 
               seconds 
             
             
                 
               6 
               1500 
               735 
               5.5 
               seconds 
             
             
                 
               7 
               2300 
               1126 
               8.0 
               seconds 
             
             
                 
               8 
               3400 
               1665 
               14 
               seconds 
             
             
                 
               9 
               4100 
               2008 
               16 
               seconds 
             
             
                 
               10 
               4200 
               2057 
               15.5 
               seconds 
             
             
                 
               11 
               3200 
               1567 
               11.5 
               seconds 
             
             
                 
               12 
               3200 
               1567 
               14 
               seconds 
             
             
                 
                 
             
           
        
       
     
   
   An alternative embodiment roll brake apparatus  68  is shown in  FIGS. 4 and 5 . A brake shoe  70  is mounted by guide bushings  71  to a pair of guide pins  72  which are mounted to a roll support bracket  76  and are internal to the roll shell  74 . The brake shoe  70  is biased in by springs  78  away from the inside surface  80  of the roll shell  74 . The brake shoe  70  has a lining  82  which faces the inside surface of the roll shell. The brake shoe  70  may be a ferromagnetic material or may have mounted to it a ferromagnetic material or a permanent magnet. An external electromagnet  84  is positioned outside the roll shell  74 . When the electromagnet  84  is turned on, it draws the brake shoe  70  downwardly toward the roll shell  74 , bringing the brake lining  82  into engagement with the inside surface  80  to produce a frictional braking force of 20 to 30 pounds. 
   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.