Abstract:
A web material roll rotatable retention assembly, comprising a shaft adapted to be inserted into a web material roll core and having a hydrogel filled chamber is disclosed. A hydrogel pressure applying assembly controllably applies pressure to the hydrogel and an outward pressure applying assembly pushes pressure applying members outwardly in response to the pressure of the hydrogel.

Description:
BACKGROUND OF THE INVENTION 
     The present invention relates to web roll shafts having outwardly expansible pressure members that are driven by pressurized hydrogel. 
     In the web converting industry it is necessary to rotate large (sometimes more than 12 feet in diameter) rolls of web material. To achieve this end web material roll shafts and chucks are used which have a diameter smaller than the inner diameter of a web material roll core for easy insertion but which selectively expands after insertion so that they tightly grip the interior surface of the web material roll core. 
     The lugs or bladders that are pushed outwardly to create the selective expansion are typically pneumatically actuated. Although hydraulically actuated lugs could place more pressure against the inside surfaces of a web material roll core, hydraulics have typically been avoided in the processing of web materials because of the threat of a hydraulic fluid leak. Such a leak could easily ruin an entire role of paper or other porous web material because the centrifugal force exerted by the web material roll rotation could press the typically oily hydraulic fluid through many layers of web material. Moreover, such a leak could remain undiscovered until the fluid had leaked through to the exterior layer of web material, thereby ruining, for example, an entire roll of paper. 
     Unfortunately, the limits that the use of pneumatics place on the amount of pressure that can be applied to the inside of a web material roll core, places a limit on the acceleration and deceleration that a chuck may undergo without causing the web material roll to slip. Moreover, the desirability of applying high pressure to the expansion lugs leads to the placement of large pneumatic structures as part of each chuck assembly, because a large diaphragm (or piston) surface area is required to apply a high pressure when using pneumatics, due to elasticity of air, which is far greater than the elasticity of hydraulic fluid. The large structure needed to support a large diaphragm, however, acts as a fly wheel to the rotating chuck, placing an additional limit on the maximum acceleration and deceleration capabilities of the chuck. 
     An additional problem found in web material production and conversion facilities is that caused by the removal of a pair of chucks from either side of a web material roll. As the chucks are retracted, it is not uncommon for the web material roll to slide off of one chuck before sliding off of the other, simply due to the unpredictable frictional pull of each chuck. When this happens it is possible that the chuck upon which the roll remains will be damaged by the torque applied by the weight of the web material roll. Even if the chuck does not sustain damage some extra labor is needed at that point to remove the web material roll from the chuck to which it remains mounted. This disrupts the smooth flow of web material mill operations. 
     An additional problem encountered in the use of web material roll shafts is the variability of load demand on the expandable lugs. When a web material roll is close to empty not much lug pressure is needed to maintain control over the roll. On the other hand, too much pressure could burst the web material roll core. When the roll is full, just the opposite set of demands is encountered. A great deal of pressure must be applied to the interior of the roll core to maintain control over rotation and prevent the roll from slipping about the shaft. Moreover, there is little danger of bursting a full roll because of the many layers of web material that reinforce the central core. 
     What is therefore needed but not yet available is a web material roll shaft with expandable lugs that can be pressed outwards with a force greater than that available with pneumatics yet does not require the bulky apparatus necessary with pneumatics, and does not involve the danger of damaging the web material on the roll that appears to be inherent with the use of hydraulics. Also needed but not yet available is a web material roll chuck that could be removed from the web material roll with certainty so that a pair of chucks could be removed simultaneously without fail. Additionally needed but not yet available is a web material roll chuck that could apply pressure to the inside of a web material roll that would not burst an empty roll but could accurately control a full roll. 
     BRIEF SUMMARY OF THE INVENTION 
     In a first preferred aspect, the present invention is a web material roll rotatable retention assembly, comprising a shaft adapted to be inserted into a web material roll core and having a gelatinous hydraulic fluid (“hydrogel”) filled chamber, a hydrogel pressure applying assembly to controllably apply pressure to the hydrogel and an outward pressure applying assembly adapted to push pressure applying members outwardly in response to the pressure of the hydrogel. 
     In a separate preferred aspect the present invention is a web material roll chuck assembly that includes a sleeve and a chuck having expansion lugs and being radially disposed within the sleeve. Further, a chuck retraction assembly is adapted to push the chuck outwardly from the sleeve and to retract the chuck inwardly so that it is disposed within the sleeve to remove the chuck from an interior core of a web material roll. 
     In a further separate aspect, the present invention is a web material roll shaft assembly, comprising a shaft having a set of pressure applying members adapted to be pressed outwardly against an interior of a web material roll and an outward pressure applying assembly adapted to push said set of pressure applying members with an outward force to retain a web material roll. A web material roll mass determining assembly determines the mass of a web material roll disposed about said shaft and a pressure applying assembly control mechanism adapted to control said outward force in response to said web material roll mass determining assembly. 
     The foregoing and other objectives, features, and advantages of the invention will be more readily understood upon consideration of the following detailed description of the invention, taken in conjunction with the accompanying drawings. 
    
    
     BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS 
     FIG. 1 is a cross-sectional view of a hydrogel web roll chuck according to the present invention. 
     FIG. 2 is a cross-sectional view of the chuck of FIG. 1, with its lugs pressed outwardly against the interior of the web roll. 
     FIG. 3 is a cross-sectional view of the chuck of FIG. 1, taken along line  3 — 3  of FIG.  2 . 
     FIG. 4 is a cross-sectional view of the chuck of FIG. 1, taken along line  4 — 4  of FIG.  2 . 
     FIG. 5 is a cross-sectional view of the chuck of FIG. 1, taken along line  5 — 5  of FIG.  2 . 
     FIG. 6 is a plan view of two of the chucks of FIG. 1 stuck into a web roll. 
     FIG. 7 is a block diagram of hydrogel web roll chuck lug pressure modulating system according to the present invention. 
     FIG. 8 is a plan view of a sleeve-retractable web core chuck according to the present invention. 
     FIG. 9 is a cross-sectional of the web core chuck of FIG.  8 . 
     FIG. 10 is a cross-sectional of the web core chuck of FIG. 8, with its lugs pressed outwardly against a web roll. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Referring to FIGS. 1-6, a rotatable web material roll core retention assembly  10  constructed in accordance with the present invention includes a compressed air port  12 . An air hose  14  is coupled to port  12  so that hose  14  may remain stationary while assembly  10  rotates. Assembly  10  attaches to a rotatable base plate  16  in part by way of a set of three bolts  18 . 
     A set of three air passages  30  link port  12  to a set of three air filled cylinders  32  that each house a pressure amplifying piston  34  having a base  36  and a front end  38 . Although assembly  10  includes three cylinders  32  it would be possible to design a web roll retention assembly, according to the present invention, having just one, two, or at the other extreme, many cylinders of the type represented by cylinders  32 . Collectively, these elements form a hydrogel pressure applying assembly. As skilled persons will recognize the pressure amplification is proportional to the ratio of the area of piston base  36  with piston front end  38 . The piston front end  38  enters a second chamber  40  that is filled with hydrogel. The relative inelasticity of the hydrogel makes practical the relatively small surface area of front end  38  and the concomitant high level of pressure amplification given by the small area of base  36 , relative to what would be necessary in a purely pneumatic system. When the pistons  34  are pressed forward by compressed air, the hydrogel in the second chamber  40  transmits the pressure from piston front ends  38  to the base of a lug actuating piston  50  that protrudes into shaft or chuck  42 . Lug actuating piston  50  then pushes against a set of pressure translating pieces  52  (collectively forming an outward pressure applying assembly) which, in turn press a set of lugs or pressure applying members  54  outwardly against a web roll core  56  that is the innermost element of a web roll  57 . The pieces  52  are constrained in movement by a cylindrical housing  58  that accommodates pieces  52  in a set of slots. The housing  58  is rigidly attached to a chuck nose  70 . 
     When the pressure of compressed air at port  12  is reduced a spring  62  pushes lug actuating piston  50  backwards, causing the hydrogel in chamber  40  to press the three pistons  34  backwards, in a motion aided by a set of six springs  64 . The backwards movement of piston  50  permits the lugs  54  to retract thereby releasing core  56 . 
     The advantage of this embodiment over the presently available entirely pneumatic systems is that greater force may be applied by lugs  54  against core  56 . Because of this, faster acceleration and deceleration may be performed without inducing slippage between lugs  54  and core  56 . 
     A lug pressure control system  110 , shown in FIG. 7, is used to create maximum lug pressure when the web material roll  57  is full but to lower the amount of lug pressure when web material roll  57  is less full. When the web roll  57  is full it is also heaviest and therefore has the greatest inertia and requires the greatest torque for acceleration and deceleration. Maximum lug pressure prevents slippage under these maximum torque conditions. When roll  57  is less full, it does not have as much strength to resist the outward pressure of lugs  54  and could even suffer bursting if the lug pressure was too great. 
     A roll size measurement device  112  could include a laser range finder or a mechanical roll size measurement device. It could even be a device for weighing web material roll  57  and could be included as part of chuck  10 . One particularly easy way to measure the size of the web roll is to examine the control signal to the web roll air brake that is already present in many prior art systems. This signal occurs in a feedback loop that maintains the web tension at a constant level. Because the air brake acts by way of the roll diameter as a lever arm, the control signal for the air brake is related to the web roll core diameter and may be used as a gauge of this diameter. Another simple way to measure the web roll core diameter is to enter the starting diameter and web thickness into a control terminal and then decrease the calculated web roll diameter by the number of revolutions times the web thickness. Whatever type of measurement device  112  is used, measurements from device  112 , indicating the size of roll  57  are sent to a controller  114  which adjusts the amount of pressure applied by lugs  54  according to an algorithm which takes into account the amount of torque needed to move roll  57  and the anticipated strength of roll  57 . 
     Referring to FIGS. 8-10, a telescoping chuck assembly  210  includes a chuck  212  that is retractable into a sleeve  214  (FIG. 9 shows the retracted position). This design has the advantage that when chuck  212  is retracted into sleeve  214 , the web roll  57  is affirmatively removed from chuck  212 . Referring to FIG. 8, when two matching chucks  212  are simultaneously retracted into two sleeves  214 , there is no danger of web material roll  57  remaining about a single one of the two chucks and potentially damaging that chuck, as may occur in prior art systems. 
     In order to accomplish its tasks, chuck assembly  210  includes four pneumatic ports: A lug compression compressed air port  220 , a lug compression air exhaust port  222 , a chuck advance compressed air port  224  and a chuck retraction compressed air port  226 . When compressed air port  220  introduces air into an air cylinder  230  a pressure amplification piston  232  (FIGS. 9 and 10) is moved forward so that a piston shaft  236  is pushed into a hydrogel chamber  238 . This forces a lug actuating piston  250  forward. This, in turn, forces a set of lug pressure pieces  252  to move outwardly and, in turn, press a set of lugs or pressure members  254  outwardly against a web roll core  56 . 
     When the pneumatic pressure in air cylinder  230  is reduced a first chuck spring  260 , mounted on a chuck nose  261 , and a second chuck spring  262  force piston  250  backwards, which allows lugs  254  to retract and in turn forces piston  232  backwards. 
     Assembly  210  is divided between a rotatable subassembly  270  and a housing  272 , that includes sleeve  214  and which rotatably supports subassembly  270 . A set of bearings  274  permit the rotation of subassembly  270  within housing  272 . Air pressure at port  224  forces the rotatable subassembly  270  forward, whereas air pressure at port  226  forces the rotatable subassembly  270  backwards. Ports  224  and  226 , together with associated pressure chambers, form a chuck retraction assembly. 
     Rotatable subassembly  270  is turned by a pulley  280  that is driven by a belt  282  (FIG.  8 ). It should be noted that other power means could be used to drive subassembly  270 . Lug compression air port  220  and lug compression exhaust port  222  are connected to rotatable subassembly  270  by way of a rotary air union  284 , which permits the air pressure to be communicated from a nonrotating part to a rotating part. A telescoping spline shaft  290  telescopes outwardly to deliver compressed air to cylinder  230  when rotatable subassembly has  270  has been pushed forward. When rotatable subassembly is pushed back, spline shaft  290  telescopes inwardly. 
     A hydrogel that works to advantage in this application may be produced by mixing together and extruding at 300° F. the following proportions of ingredients (by weight): 21-25% PVC powder; 72-76% dibutylphthalate; and 3% calcium stearate. 
     The terms and expressions which have been employed in the foregoing specification are used therein as terms of description and not of limitation, and there is no intention, in the use of such terms and expressions, of excluding equivalents of the features shown and described or portions thereof, it being recognized that the scope of the invention is defined and limited only by the claims which follow.