Apparatus and method for braking folding sheet material

Abstract

Preferred embodiments of the present invention have brake heads located at a circumferential position with respect to a folding roll in a web folder or interfolder. In some preferred embodiments, the brake heads and vacuum lines running thereto are stationary with respect to the folding roll and are recessed within circumferential folding roll grooves permitting folding roll rotation relative to the brake heads and lines. The brake heads are preferably located downstream of the nip between the rolls and upstream of a point at which vacuum is cut off to vacuum ports in the roll to release the web material being folded. When vacuum is supplied to the brake heads, passing web material is attracted thereto and is thereby braked. Preferably, the times at which vacuum is drawn through ports in the brake heads to brake the passing web can be controlled by a valve connected to the vacuum lines.

I claim:  
     
         1 . A braking device for a vacuum roll having a roll surface upon which web material is conveyed, comprising: 
 a vacuum source;    a brake head having: 
 a brake head position at a circumferential location with respect to the vacuum roll; and  
 at least one vacuum port defined in the brake head, the brake head located substantially beneath the roll surface and over which the web material can pass; and  
   a vacuum line, the vacuum source and the brake head in fluid communication with one another via the vacuum line.    
     
     
         2 . The braking device as claimed in  claim 1 , wherein the vacuum line passes to and below the roll surface at a circumferential position of the roll and passes at least partially around the roll substantially beneath the roll surface.  
     
     
         3 . The braking device as claimed in  claim 1 , wherein the vacuum roll has a circumferential groove defined therein within which the brake head is received.  
     
     
         4 . The braking device as claimed in  claim 3 , wherein the vacuum line runs from the brake head at least partially around the roll substantially beneath the roll surface.  
     
     
         5 . The braking device as claimed in  claim 1 , further comprising a rotary valve coupled to the vacuum line, the rotary valve configured and arranged to open and close the vacuum line in substantial synchronicity with vacuum roll rotation.  
     
     
         6 . The braking device as claimed in  claim 5 , wherein the rotary valve has a plurality of apertures, the valve rotatable in substantial synchronicity with the vacuum roll to bring the plurality of apertures successively into fluid communication with and between the vacuum line and vacuum source.  
     
     
         7 . The braking device as claimed in  claim 1 , wherein the vacuum line is coupled to the brake head and thereby at least partially supports the brake head in the brake head position.  
     
     
         8 . The braking device as claimed in  claim 1 , further comprising: 
 a vacuum port in the vacuum roll through which vacuum is supplied to the roll surface; and    a sensor positioned to sense vacuum pressure of vacuum supplied to the vacuum port.    
     
     
         9 . The braking device as claimed in  claim 8 , further comprising a valve coupled to the sensor and between the vacuum source and the brake head, wherein the valve is periodically actuatable between opened and closed positions at times determined at least partially by pressure sensed by the sensor.  
     
     
         10 . The braking device as claimed in  claim 9 , wherein the valve is actuated by a motor driving the valve and wherein the intervals are adjustable by temporarily adjusting motor speed.  
     
     
         11 . The braking device as claimed in  claim 9 , further comprising a valve coupled to the sensor, to the brake head, and to the vacuum source, wherein the valve has a valve timing in which the valve is periodically opened and closed to open and close fluid communication between the vacuum source and brake head, wherein the valve timing is adjustable responsive to the sensor.  
     
     
         12 . A folding roll for use in a folding apparatus for folding web material, the folding roll comprising: 
 a brake head having at least one vacuum port defined therein;    a folding roll surface for conveying web material, the folding roll rotatable about a folding roll axis to rotate the folding roll surface with respect to the brake head;    a vacuum source; and    a vacuum line, the at least one vacuum port in the brake head in fluid communication with the vacuum source via the vacuum line;    wherein the brake head is sufficiently recessed within the folding roll surface to permit web material conveyed on the folding roll surface to pass over the brake head.    
     
     
         13 . The folding roll as claimed in  claim 12 , further comprising a circumferential groove in the folding roll surface within which the brake head is received.  
     
     
         14 . The folding roll as claimed in  claim 12 , further comprising a circumferential groove in the folding roll surface within which the vacuum line is received.  
     
     
         15 . The folding roll as claimed in  claim 12 , further comprising a vacuum port defined in the folding roll surface and rotatable with the folding roll surface for transmitting vacuum to the folding roll surface.  
     
     
         16 . The folding roll as claimed in  claim 12 , wherein the brake head is substantially stationary in a circumferential location with respect to the folding roll.  
     
     
         17 . The folding roll as claimed in  claim 16 , wherein the vacuum line is coupled to the brake head and at least partially supports the brake head in the circumferential location.  
     
     
         18 . The folding roll as claimed in  claim 12 , further comprising a valve coupled to the vacuum line for opening and closing vacuum supplied to the brake head in substantial synchronicity with folding roll rotation.  
     
     
         19 . The folding roll as claimed in  claim 18 , wherein the valve is a rotary valve.  
     
     
         20 . The folding roll as claimed in  claim 18 , further comprising: 
 a vacuum port in the folding roll surface for transmitting vacuum to the folding roll surface; and    a sensor positioned to detect vacuum pressure transmitted to the folding roll via the vacuum port.    
     
     
         21 . The folding roll as claimed in  claim 20 , wherein the valve is timed to open and close in substantial synchronicity with folding roll rotation, and wherein valve timing is adjustable responsive to vacuum pressures detected by the sensor.  
     
     
         22 . The folding roll as claimed in  claim 21 , further comprising a motor coupled to the valve for driving the valve, wherein the motor is coupled to the sensor, and wherein valve timing is adjustable by temporarily adjusting motor speed responsive to vacuum pressures detected by the sensor.  
     
     
         23 . The folding roll as claimed in  claim 18 , wherein the valve is adjustable to open and close at different times in substantial synchronicity with folding roll rotation.  
     
     
         24 . A method of braking a sheet of folding web material, comprising: 
 conveying web material upon a surface of a rotating roll in a rotational direction;    retaining the web material against the surface of the rotating roll while conveying the web material thereon;    passing the web material over a brake head at least partially recessed within the roll;    drawing the web material toward the brake head to exert a braking force upon the web in a direction substantially opposite to the first rotational direction; and    releasing the web material from the surface of the rotating roll.    
     
     
         25 . The method as claimed in  claim 24 , wherein retaining the web material against the surface of the rotating roll includes supplying vacuum through a vacuum port defined in the surface of the rotating roll to exert a vacuum force upon the web material.  
     
     
         26 . The method as claimed in  claim 25 , wherein drawing the web material toward the brake head includes supplying vacuum to a vacuum port defined in the brake head to exert a vacuum force upon the web material.  
     
     
         27 . The method as claimed in  claim 26 , further comprising: 
 detecting vacuum pressure of vacuum supplied to the vacuum port defined in the surface of the rotating roll; and    adjusting when vacuum is supplied to the vacuum port defined in the brake head based at least partially upon the vacuum pressure detected.    
     
     
         28 . The method as claimed in  claim 24 , wherein releasing the web material includes reducing vacuum supply to the surface of the rotating roll to reduce vacuum force exerted upon the web material.  
     
     
         29 . The method as claimed in  claim 24 , wherein drawing the web material toward the brake head occurs at least partially while releasing the web material from the surface of the rotating roll.  
     
     
         30 . The method as claimed in  claim 24 , wherein drawing the web material toward the brake head begins after releasing the web material from the surface of the rotating roll has begun.  
     
     
         31 . The method as claimed in  claim 24 , wherein drawing the web material toward the brake head begins after releasing the web material from the surface of the rotating roll is substantially complete.  
     
     
         32 . The method as claimed in  claim 24 , wherein drawing the web material toward the brake head begins before releasing the web material from the surface of the rotating roll has begun.  
     
     
         33 . The method as claimed in  claim 24 , wherein releasing the web material from the surface of the rotating roll is substantially complete before drawing the web material toward the brake head is substantially complete.  
     
     
         34 . The method as claimed in  claim 24 , wherein releasing the web material from the surface of the rotating roll is substantially complete after drawing the web material toward the brake head is substantially complete.  
     
     
         35 . The method as claimed in  claim 24 , further comprising opening and closing a valve to periodically supply vacuum to the brake head to draw the web material toward the brake head.  
     
     
         36 . The method as claimed in  claim 35 , wherein the valve is a rotary valve.  
     
     
         37 . The method as claimed in  claim 35 , wherein the valve is opened and closed in substantial synchronicity with rotation of the roll.  
     
     
         38 . The method as claimed in  claim 35 , wherein retaining the web material against the surface of the rotating roll includes supplying vacuum to the surface of the rotating roll, the method further comprising: 
 sensing pressure of vacuum supplied to the surface of the rotating roll; and    adjusting timing of valve opening and closing based upon the pressure sensed.    
     
     
         39 . A method of folding web material, comprising: 
 rotating a vacuum roll in a first direction;    exerting a suction force through a surface of the vacuum roll and upon the web material;    drawing the web over a brake head that is substantially stationary with respect to the roll;    reducing the suction force downstream of the brake head after drawing the web over the brake head; and    exerting a suction force through the brake head and upon the web material drawn thereover to brake the web material in a direction substantially opposite to the first direction.    
     
     
         40 . The method as claimed in  claim 39 , wherein the brake head is at least partially recessed within a groove in the vacuum roll.  
     
     
         41 . The method as claimed in  claim 39 , further comprising supplying vacuum to the brake head via a vacuum line.  
     
     
         42 . The method as claimed in  claim 41 , wherein the vacuum line is at least partially recessed beneath the surface of the vacuum roll.  
     
     
         43 . The method as claimed in  claim 39 , wherein exerting a suction force through the brake head includes opening a valve to supply vacuum to the brake head.  
     
     
         44 . The method as claimed in  claim 43 , wherein the valve opens and closes in substantial synchronicity with rotation of the vacuum roll.  
     
     
         45 . The method as claimed in  claim 44 , further comprising: 
 sensing pressure of vacuum exerted through the surface of the vacuum roll; and    adjusting timing of valve opening and closing based upon pressure sensed.    
     
     
         46 . The method as claimed in  claim 43 , wherein the valve is a rotary valve.  
     
     
         47 . The method as claimed in  claim 39 , wherein reducing the suction force downstream of the brake head occurs at least partially during exertion of the suction force through the brake head.  
     
     
         48 . The method as claimed in  claim 39 , wherein exerting the suction force through the brake head occurs after reducing the suction force downstream of the brake head.  
     
     
         49 . The method as claimed in  claim 39 , wherein reducing the suction force downstream of the brake head includes substantially eliminating the suction force downstream of the brake head.  
     
     
         50 . The method as claimed in  claim 39 , further comprising: 
 supplying vacuum to the surface of the vacuum roll to exert the suction force through the surface of the vacuum roll;    sensing vacuum pressure supplied to the surface of the vacuum roll; and    timing exertion of suction force through the brake head at least partially upon the vacuum pressure sensed.    
     
     
         51 . The method as claimed in  claim 39 , further comprising: 
 maintaining the suction force through the brake head for a period of time; and then    reducing the suction force through the brake head to stop braking the web material.