Abstract:
A telescoping roll stand for use in an extrusion line includes a linkage connecting one or more auxiliary rolls in a spatial relationship relative to each other and other auxiliary web processing components, including conveyors, load cell rolls, draw rolls, and other web handling components, when one of the auxiliary rolls is shifted in relation to a primary roll.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
   Not applicable. 
   REFERENCE REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT 
   Not applicable. 
   SEQUENTIAL LISTING 
   Not applicable. 
   BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The present invention relates to a roll stand for use in a continuous polymer web extrusion line, and more specifically to a roll stand having an auxiliary section shiftable in relation to a primary section. 
   2. Description of the Background of the Invention 
   During the process of extruding a molten polymer web, it is customary to feed the extrudate into a roll stand having at least one primary chilled roll in order to cool the extrudate below a solidification temperature thereof. Under certain conditions such as high extrusion velocities, it may be desirable to have one or more auxiliary chilling rolls in order to attain the desired cooling. Under such circumstances, it is often convenient to shift the auxiliary rolls away from or toward the primary roll during the start up process of a new web and then re-adjust the distance between the primary and auxiliary rolls after the web is sufficiently stable. 
   Nissel U.S. Pat. No. 6,575,726 discloses a roll stand for use in a polymer web extrusion line including a slot extrusion die, a primary roll stack, a plurality of auxiliary rolls, and a pair of draw rolls. The auxiliary rolls are laterally shiftable in relation to the primary roll stack in order to provide adjustability. A mechanical linkage connects the auxiliary rolls to each other in order to maintain a constant spacing therebetween when the auxiliary rolls are shifted in relation to the primary rolls. 
   However, when shifting the rolls in relation to each other while a web is passing thereover, it is usually necessary to adjust the rotational velocity of each roll during the movement in order to prevent sagging or bunching of the web on either side of the rolls being shifted. It is desirable to have a simple and efficient method of minimizing the amount of adjustment to the rotational velocity of the various rolls in a roll train in order to facilitate start-up adjustments or to perform maintenance on portions of the roll stand while the web is being passed therethrough. 
   SUMMARY OF THE INVENTION 
   In accordance with one aspect of the invention, a telescoping roll stand for transferring an elongate web includes a primary roll stack having a plurality of primary rolls carried by a primary carriage frame and an auxiliary carriage frame adjacent the primary carriage frame. The auxiliary carriage frame is shiftable in relation to the primary carriage frame between an open position and a closed position. The auxiliary carriage frame carries an auxiliary roll stack and draw rolls and maintains the auxiliary roll stack and draw rolls in a fixed relative position with respect to each other when shifted between the open and closed positions. 
   In accordance with another aspect of the invention, an apparatus for transferring a polymer web includes a primary roll for accepting the web from an extrusion die, an auxiliary roll proximate the primary roll and shiftable in relation thereto, a pair of draw rolls in a spaced relation from the auxiliary roll, and a linkage connecting the auxiliary roll and the draw rolls. The linkage maintains the spaced relation between the auxiliary roll and the draw rolls when the auxiliary roll shifts. 
   In accordance with another aspect of the invention, a telescoping roll stand for transferring an elongate web includes a primary roll stack carried by a primary carriage frame, and an auxiliary carriage frame adjacent to the primary carriage frame and carrying an auxiliary roll stack and a conveyor. The auxiliary carriage frame is shiftable relative to the primary carriage frame between an open position and a closed position, and the auxiliary carriage frame maintains a fixed spatial relationship between the auxiliary roll stack and conveyor when the auxiliary carriage frame shifts between the open and closed positions. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is an isometric schematic view of a telescoping roll stand with an auxiliary carriage frame in a forward, closed position and a primary carriage frame in a forward position directly adjacent an extrusion die; 
       FIG. 2  is an isometric schematic view of the roll stand shown in  FIG. 1  with the auxiliary carriage frame in a rearward, open position and the primary carriage frame in the forward position; 
       FIG. 3  is an isometric schematic view of another telescoping roll stand with an auxiliary carriage frame in a forward, closed position and a primary carriage frame in a forward position directly adjacent to an extrusion die; 
       FIG. 4  is an isometric schematic view of the roll stand shown in  FIG. 3  with the auxiliary carriage frame in a rearward, open position and the primary carriage in the forward position; and 
       FIG. 5  is an isometric schematic view of the roll stand shown in  FIG. 3  with the auxiliary carriage in the rearward, open position and the primary carriage in a rearward position spaced from the extrusion die. 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
   Turning now to  FIGS. 1 and 2 , a telescoping roll stand  10  includes a primary roll stack  12 , an auxiliary roll stack  14 , a conveyor  16 , and a draw roll stand  18 . A flat extrusion die  20  in communication with an extruder (not shown) feeds a continuous stream of molten polymer forming a web  22  to the nip between a nip roll  24   a  and a primary roll  24   b  on the primary roll stack  12 . A second primary roll  24   c  keeps the web in contact with the primary roll  24   b  for a pre-selected radial distance. The auxiliary roll stack  14  includes a plurality of auxiliary rolls  26  that transfer the web  22  from the primary roll stack  12  toward the conveyor  16  and may provide additional cooling, reheating, or no temperature change to the web. The primary rolls  24   b ,  24   c  and/or auxiliary rolls  26  may optionally be chilled or heated using any convenient means such as water or other suitable and conventional heat exchange medium to either cool or heat the web as it passes thereover. Hoses or pipes  25  in communication with the rolls  24   a ,  24   b ,  26  provide a supply of the heat exchange medium to the rolls to maintain a selected temperature in any conventional manner. The conveyor  16  includes a frame  28  carrying a plurality of conveyor rolls  30  journaled thereto that transfer the web from the auxiliary rolls  26  toward a pair of draw rolls  32  journaled to the draw roll stand  18 . Each roll  24   a ,  24   b ,  24   c ,  26 ,  30 ,  32  is preferably driven by a different drive unit  34 , such as a computer controlled servo motor, but any drive mechanism able to provide sufficient selective rotational velocity control to transfer the web  22  from the die  20  to the draw rolls  32  without breaking may be used. Alternatively, some or all of the conveyor rolls  30  may be free rolling without being driven by a drive unit  34 . 
   Each of the auxiliary roll stack  14 , conveyor  16 , and draw roll stand  18  is secured to an auxiliary carriage frame  36 , and the primary roll stack  12  is secured to a primary carriage frame  38 . The auxiliary carriage frame  36  is laterally shiftable in relation to the primary carriage frame  38  between a forward (i.e., extended), closed position shown in  FIG. 1  and a rearward (i.e., retracted), open position shown in  FIG. 2 . In addition, the primary roll frame  38  may be shifted between a forward position directly adjacent to the die  2  (as shown in  FIGS. 1 and 2 ) and a rearward position spaced from the die. The auxiliary carriage frame  36  links together and maintains a constant space between each of the auxiliary rolls  26 , conveyor rolls  30 , and draw rolls when the frame  36  is shifted. The auxiliary carriage frame  36  may be shifted using any convenient drive means  40 , such as a worm drive, rack and pinion, telescoping hydraulic cylinders, or individual servo drives. Preferably, each of the auxiliary and primary carriage frames  36  and  38  includes some sort of wheel  42  or roller to facilitate easier shifting of the entire roll stand  10  and the individual frames  36 ,  38 . 
   The drive units  34  vary the rotational velocity of the rolls  26 ,  30 ,  32  as the auxiliary carriage frame  36  is shifted toward or away from the primary carriage frame  38  to provide a constant global tangential velocity of the rolls so that the web does not stretch or sag. Each of the rolls  26 ,  30 ,  32  preferably is adjusted to have the same change in tangential velocity as the auxiliary carriage frame  36  is shifted in relation to the primary carriage frame  38  because of the fixed spacing between each of the rolls  26 ,  30 , and  32 . The tangential velocity of the rolls  26 ,  30 ,  32  is adjusted to compensate for positive or negative velocity of the primary carrier frame  38  relative to the auxiliary carrier frame  36  by computer controls if the drive units  34  are computer controlled servo motors. Alternatively, the rolls  26 ,  30 , and  32  may maintain a constant rotational velocity, and the rotational velocities of the rolls  24   a–c  may be varied to compensate for the relative velocity of the primary carrier frame  38  relative to the auxiliary carrier frame  36 . 
   The roll stand  10  is not limited to the precise use and arrangement described herein, and alternative arrangements and uses for a telescoping roll stand  10  are also contemplated. For example, the primary roll stack  12  may be readily adapted to accept a non-woven blown fiber extruded web or other types of continuous materials. Different web materials other than polymer may also be passed through the roll stand  10 . 
   In another alternative arrangement (not shown), either the conveyor  16  or the draw roll stand  18  may be omitted from the auxiliary carriage frame  36 , and any number of auxiliary rolls  26  may be used. Further, relative positions between the various rolls  24 ,  26 ,  30 ,  32  other than those shown may be used. In addition, different conveyor mechanisms such as a single roll, a belt, an air cushion, etc. could be used instead of or in addition to the conveyor  16 . The auxiliary carriage frame may carry additional processing mechanisms, such as additional cooling devices, coating devices, etc., in a pre-selected spacing from the other processing mechanisms in the same manner as described herein. 
   In  FIGS. 3–5 , another telescoping roll stand  100  includes a primary roll stack  102  carried by a primary carriage frame  104 , an auxiliary roll stack  106  and a conveyor  108  carried by an auxiliary carriage frame  110 , a pair of draw rolls  112  carried by a draw roll frame  114 , and a conveyor  116  between the draw rolls and the conveyor  108 . The draw roll frame  114  is fixedly mounted on or secured to the ground  115  or other support surface by any convenient means, such as friction, fasteners, adhesive, etc., and the conveyor  116  may be secured directly to the draw roll frame or fixed to the ground in a pre-selected position with respect to the draw rolls as shown in  FIGS. 3–5 . The primary roll stack  102  includes primary rolls  102   a ,  102   b ,  102   c . The auxiliary roll stack  106  includes auxiliary rolls  106   a ,  106   b , which are journaled to the auxiliary carriage frame  110 . Inlet/outlet lines  117  connected to the rolls  106   a ,  106   b  circulate thermal control fluids in rolls  106   a ,  106   b  to provide heating or cooling temperature control of the rolls. The conveyor  108  includes conveyor rolls  118  journaled to a conveyor frame  120 , which is fixedly secured to the auxiliary carriage frame  110 . Each of the primary carriage frame  102  and the auxiliary carriage frame  110  is carried by rollers  122  so that both the primary and auxiliary carriage frames may be shifted across the floor  115  or other support surface along an axis of the web. A drive unit, shown schematically at  124 , can be actuated to shift the auxiliary carriage frame  110  between a forward (i.e., extended) position directly adjacent to the primary carriage frame  104  ( FIG. 3 ) and rearward (i.e., retracted) position spaced from the primary carriage frame ( FIGS. 4 and 5 ). In addition, both the primary and auxiliary carriage frames  104 ,  110  may be shifted together or independently between a forward position directly adjacent to an extrusion die  126  ( FIGS. 3 and 4 ) and a rearward position spaced from the extrusion die and nearer to the draw roll frame  114 . The auxiliary carriage frame  110  maintains a fixed spatial relationship between each of the auxiliary rolls  106   a ,  106   b , and the conveyor  108  and conveyor rolls  118  when either or both of the primary and auxiliary carriage frames  104 ,  110  are shifted across the floor  115 . 
   Each of the rolls  102   a ,  102   b ,  102   c ,  106   a ,  106   b , and  112  includes a rotational drive unit  128  to pass the web  130  from the extrusion die  126  to a position downstream of the draw rolls. A rotational speed of each roll  102   a ,  102   b ,  102   c ,  106   a ,  106   b , and  112  is controlled by known methods, such as computer control or mechanical gearing linkages, to maintain a uniform global tangential velocity of the rolls and a web  130  passing therethrough in order to minimize and/or control tension differentials in the web between the primary rolls and the draw rolls in a similar manner as previously described herein. In addition, a load cell roll  132  or other tension sensing and controlling device, such as a dancer arm, may be carried by the conveyor frame  120  and used to control the tension in the web  128  and to sense velocity changes in the web in order to adjust and/or maintain the rotational velocities of the rolls  102   a ,  102   b ,  102   c ,  106   a ,  106   b , and  112  at a desired speed to pass the web therethrough without causing sagging or bunching in the web. 
   The conveyor  108  is vertically offset above the conveyor  116  an amount sufficient to allow the conveyor  108  to pass over the conveyor  116  such that the web transitions smoothly from underneath the conveyor roll  118  nearest the draw roll frame  114  (or in any similar fashion so as to permit stable conveyance of the web) to a position on top of a roll  118  on the conveyor stand  116 . Preferably, the conveyor rolls  118  are allowed to freely rotate when the web  130  passes thereover, although the rolls  118  may be driven by drive units with appropriate rotational velocity controls as previous described herein. 
   The roll stand  100  provides a convenient way for different sections along the roll stand to be serviced during operation thereof by creating space to access different sections when the auxiliary carriage frame is shifted between the forward and rearward positions. Rotational velocity sensing and control apparatus adjust the rotational velocities of the rolls  106   a ,  106   b  as the auxiliary carriage frame  110  is shifted between the open and closed positions in order to prevent sagging and/or bunching of the web  130  in a similar manner as described previously herein. Causing the conveyor  108  to be capable of overlapping the conveyor  116  provides additional flexibility in constrained spaces by allowing the auxiliary carriage to be shifted to the open, rearward position in web processing lines where space is limited, such as when of other components or equipment (not shown) located immediately downstream from the draw rolls  112  limit the available space for shifting. 
   Other arrangements and uses of the preferred embodiments of the telescoping roll stands described herein that are encompassed within the scope of the impending claims are specifically included.