Patent Publication Number: US-6216934-B1

Title: Festoon protection method and system

Description:
BACKGROUND OF THE INVENTION 
     The present invention relates to a method and system for preventing damage to a festoon should a break in a running web occur while the web is being unwound from a rotating roll, being run through the festoon, and then run to a web-using production process. 
     The inclusion of festoons in systems for controlling the speed and tension of running webs has been recognized as a significant improvement. Such festoons, which are capable of storing variable amounts or quantities of the running web, typically include, in simplified form, a fixed entry idler, a relatively movable dancer and a fixed exit idler. The web runs about the entry idler, the dancer and then the exit idler. A dancer tensioning cylinder assembly is connected with the dancer and is adapted to urge the dancer upwardly, vertically with respect to the fixed idlers and against the force of the web running over and about that dancer. 
     The dancer tensioning cylinder assembly includes a piston, which is disposed for reciprocal movement within a cylinder, which is connected to the dancer by, for instance, a cable, and to which controlled, pressurized air is applied to one surface or face of the piston so as to force the piston to move in one direction within the cylinder. Upward movement of the dancer may occur in response to movement of the piston in the one direction in the cylinder. 
     In the past, a break in the running web could and often did cause damage to the festoon. The break would remove the web-generated force that opposed the upwardly directed force imposed on the dancer by the dancer tensioning cylinder assembly. Upon this removal, the dancer would tend to move suddenly, upwardly in the festoon. Such out-of-control, upward movement sometimes caused the dancer to strike the festoon&#39;s supporting structure, thus damaging the dancer and/or the festoons supporting structure. Repair of such damage could be costly particularly in terms of the down time of the web-using production process. 
     BRIEF SUMMARY OF THE INVENTION 
     In principal aspects, the present invention provides an improved method and system for controlling and limiting the heretofore out-of-control upward movement of the dancer upon a breakage of the running web. The present invention is thus able to prevent damage to the festoon and to minimize down time of the web-using production process should a break in the running web occur. 
     This control and limitation of the upward movement of the dancer is achieved by controlling the movement of the piston in the dancer tensioning cylinder assembly. The piston is controlled by substantially instantaneously equalizing the air pressures applied to the opposite surfaces or faces of the piston after a web break occurs, and then after a preselected delay, bleeding the air pressures off. This equalization stops the movement of the piston, and in turn, stops the upward movement of the dancer by removing the force that would otherwise have been imposed on the dancer by the dancer tensioning cylinder assembly. 
     Accordingly, a principal object of the present invention is to provide an improved method and system for controlling and limiting the upward movement of the dancer of a festoon when the running web breaks. 
     Another object of the present invention is to provide an improvement in a system for controlling the speed and tension of a running web being unwound from a rotating roll and being run through an festoon and then to a web-using production process, where the festoon includes a relatively fixed idler, a relatively fixed exit idler, and a vertically movable dancer about which the running web runs; where the dancer may be moved vertically relatively with respect to the idlers depending on the amount or quantity of running web being stored in the festoon; where the dancer is connected with a dancer tensioning cylinder assembly that is used to urge the dancer vertically, against the force of the running web running over the dancer and that includes a cylinder, which has a first end and a second end, and a piston, which is connected with the dancer, which is movable within the cylinder, and which has a first surface facing the first end of the cylinder and a second surface facing the second end of the cylinder; where the first portion of the cylinder is defined between the first end of the cylinder and the first face of the piston; where the piston is movable within the cylinder in response to the air pressures being applied to and acting on the first surface of the piston; where the system includes a source of air under pressure that is adapted to be applied to the first portion of the cylinder and an air regulator for regulating the pressure of the pressurized air supplied to the first portion of the cylinder; and the improvement includes a first check valve that is adapted to move between a first position in which the second portion of the cylinder (that is defined between the second end of the cylinder and the second surface of the piston) is open to the atmosphere and a second position in which the second portion of the cylinder is closed to the atmosphere so that the pressure of the air in the second portion may increase so as to become equal with that of the pressure of the air in the first portion of the cylinder; where the first valve moves from its first position to its second position when a breakage of the running web occurs; and where the system further includes an air flow restrictor that permits air in the second portion of the cylinder to bleed from the second portion after a preselected delay after a break in the running web has occurred. A related object of the present invention is to provide an improved system, as described, where the system includes a second valve that is adapted to be moved between a first position in which the source of pressurized air is connected with the first portion of the cylinder and a second position in which the source of pressurized air is disconnected from the first portion of the cylinder, and after a preselected delay, the pressurized air in the first portion of the cylinder is permitted to bleed from the first portion of the cylinder; and where the system also further includes a sensor that is adapted to sense a breakage of the running web, and in response to such breakage, to activate the second valve so as to move the second valve from its first position to its second position. 
     Still another object of the present invention is to provide an improvement in a method for controlling the speed and tension of a running web being unwound from a rotating roll and being run through an festoon and then to a web-using production process where the improvement comprising the steps of sensing the occurrence of a break in the running web; causing the pressure of the air in the second portion of the cylinder of dancer tensioning cylinder assembly, which is normally open to the atmosphere, to increase so that the air pressure in the second portion of the cylinder becomes equal to the air pressure in the first portion of the cylinder; and after a preselected delay after the break in the running web, bleeding the pressurized air from the cylinder. A related object to the present invention is to provide an improved method, as described, whereafter a break in the running web occurs, the first portion of the cylinder is disconnected from the source of pressurized air, and after a preselected delay, the pressurized air in that first portion is bled off. 
     These and other objects, advantages and benefits of the present invention will become more apparent from the following description of the preferred embodiment of the present invention, which description may be best understood with reference to the accompanying drawing. 
    
    
     BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS 
     FIG. 1 is a schematic view of the preferred embodiment of the improved system for controlling the speed and tension of a running web and for preventing damage to the festoon should the running web break; and 
     FIG. 2 is partial, axial cross-sectional view of the check valve mounted in the dancer tensioning cylinder assembly of the system of FIG.  1 . 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT OF THE INVENTION 
     Referring now to FIG. 1, the preferred embodiment of the improved system of the present invention is shown generally at  12 . The system  12  includes a conventional festoon  14  that may be inertia compensated and that is adapted to receive and store variable amounts or quantities of a continuous running web  16 . As illustrated in FIG. 1, the running web  16  is being unwound from a rotating roll  18  that is mounted for rotation in a conventional manner. Between the rotating roll  18  and the festoon  14 , the web  16  may pass about idlers, one of which is shown at  22 . After running through the festoon  14 , the running web passes to a web-using production process  24  such as, for example, a disposable diaper manufacturing line. 
     The running web  16  passes through the festoon  14  in a conventional manner. In simplified form, as illustrated, the festoon  14  includes fixed entry, intermediate and exist idlers,  26 ,  28  and  32 , respectively, and a vertically, relatively movable dancer assembly  34  which includes, as shown, two idlers  36  and  38 . The web  16  runs about the idlers  26 ,  36 ,  28 ,  38  and  32 , respectively, as it passes through the festoon  14 . 
     As shown in FIG. 1, the dancer assembly  34  is movable vertically, with respect to the idlers  26 ,  28  and  32 , depending on the amount or quantity of running web  16  being stored in the festoon. A larger or greater quantity of running web  16  is being stored in the festoon when the dancer assembly  34  is at a higher position, that is, spaced farther vertically from the idlers  26 ,  28  and  32 , then when the assembly  34  is in a lower position, that is, spaced closer vertically to the idlers  26 ,  28  and  32 . 
     As is typical with such festoons, a dancer tensioning cylinder assembly  42  is connected with the dancer assembly  34  and is used to urge the dancer assembly  34  to its uppermost vertical position, with respect to the idlers  26 ,  28  and  32 . More specifically, the assembly  42  includes a piston  46 , which is reciprocally movable within a cylinder  48 . A cable  44 , or the like, interconnects the piston  46  with the assembly  34 . In a conventional manner, the cable  44  extends upward from the assembly  34 , passes about two idlers  52  and  54 , extends through the upper end  56  (as shown) of the cylinder  48 , and is attached to the piston  46 . As is also conventional, movement of the piston  46  in one direction, that is, toward the FIG. 1 illustrated lower end  58  of the cylinder  48 , will urge the dancer assembly  34  to move upwardly, away from the idlers  26 ,  28  and  32 , against the bias or force exerted by the running web  16  on the dancer assembly  34 . 
     As is also conventional, the piston  46  is urged to move toward the lower end  58  of the cylinder  48  by the application of air under pressure to the portion  62  of the cylinder, which is defined by the cylinder end  56  and the surface or face of the piston  46  adjacent to the end  56 . The pressurized air may come from a conventional source  64  of pressurized air. A conventional pressure regulator  66  may be used to regulate and control the pressure of the air being applied in the cylinder portion  62  so that the festoon  14  will function in the conventional manner. 
     As discussed above, the running web  16  may break, on occasion, as it runs to the production process  24 . In the past, such web breakage could damage, sometime seriously the festoon  14 . More particularly, web breakage will cause the dancer assembly  34  to move upwardly, by reason of the force exerted on the cable  44  by the air cylinder assembly  42 . This sudden, uncontrolled upward movement can cause the dancer assembly  34  to strike the supporting structure of the festoon  14  with sufficient force to damage the festoon, including the dancer assembly. 
     As previously stated, the present invention prevents such uncontrolled, upward movement of the dancer assembly  34  upon a breakage of the running web  16 . The invention achieves this by the inclusion of a check valve  68  in the end  58  of the cylinder  48 . 
     More particularly, and as best shown in FIG. 2, the check valve  68  includes a movable valve poppet member  72  and a relatively fixed valve base member  74 . The poppet member  72  may reciprocally move, axially, toward and away from the member base  74  within the cylinder  48 . A snap ring  76  limits the distance that the poppet member  72  may move away from the cylinder end  58 . A second snap ring  78  retains the base member  74  fixed within the cylinder end  58 . A coil compression spring  82 , biases the poppet member  72  away from the base member  74 , that is, in a direction away from the cylinder end  58  and toward the cylinder end  56 . An O-ring  84  provides a seal between the periphery of the base member  74  and the cylinder  48 . 
     The base member  74  has a central, tubular protuberance  86  that extends a preselected distance toward the poppet member  72 . The spring  82  is disposed about the protuberance  86 . The protuberance  86  includes an axial, central air passage  88 , which extends through the member, that is, from one end or side of the member  74  to the other. The end of the central passage  88 , which is adjacent to the cylinder end  58 , is preferably open to the atmosphere. 
     A plurality (two being shown) of radially off-set, spaced apart axially extending air passages  92  and  94  also extend through the member  74 , that is, from one end or side of the base member  74  to the other. As later described herein, the passages  88 ,  92  and  94  permit air to flow from the portion  96  of the cylinder  48 , which is defined by the cylinder end  58  and the piston  46 , through or across the base member  74 . The total cross-sectional area of the passages  92  and  94  are significantly less than the cross-sectional area of the passage  88 . 
     The poppet member  72  has an axial recess  98  that faces the base member  74  and that has a radial dimension such that the distal or projecting end of the protuberance  86  may be closely received within the recess. The recess  98  and the protuberance  86  are axially aligned and the axial depth of the recess is less than the projecting length of the distal end of the protuberance. When the poppet member  72  is moved toward the cylinder end  58  and into abutting contact with the distal end of the protuberance  86 , the contact blocks the flow of air through the central passage  88 . As noted, the spring  82  biases the poppet member  72  away from the base member  74  so that there is no contact between the distal end of the protuberance  86  and the adjacent, recess defined surface of the poppet member when the running web  16  is running through the system  12 . 
     A plurality of radial slots, one of which is referenced at  102 , extends between the recess  98  and the periphery of the poppet member  72 . The poppet member  72  also includes a plurality of radially off-set, spaced apart axially extending air passages, two of which are referenced at  104  and  106 . The passages  104  and  106  permit air communication across the member  72 , that is, between the cylinder portion  96  and an annular space  108 , which is defined between the members  72  and  74  and between the radially outwardly facing surface of the protuberance  86  and the cylinder  48 . The slots  102  permit air communication between the annular space  108  and the interior of the recess  98 , even when the protuberance  86  extends partially within the recess. Thus, during normal operation of the running web  16 , the cylinder portion  96  is always in communication with the atmosphere. 
     The air passages  92  and  94  in the base member  74  also communicate with the annular space  108 . Hence, even when the central passage  88  is blocked, air can flow from the portion  96  across through the member  72  and  74 , via the passages  104  and  106 , the annular space  108  and the passages  92  and  94  although the volume of air flowing is much reduced as compared to the volume of flow when the central passage  88  is open. 
     Nipples  112  and  114  are mounted in the passages  92  and  94 , respectively. These nipples are both adapted to be connected with tubing  116  that includes, downstream, a conventional, variable air restrictor  118 . The tubing  116  permits air in cylinder portion  96  to communicate, through the restrictor  118 , with the atmosphere. In a conventional manner, the restrictor  118  imposes a preselected delay on the passage or bleeding of pressurized air through the tubing  116 . 
     As noted, when the web  16  is running in a normal manner, the spring  82  biases the poppet member  72  away from the base member  74  so that air may flow from the cylinder portion  96 , across the members  72  and  74  and out to the atmosphere, primarily through the central passage  88 . Generally, some pressurized air in the cylinder portion  62  will leak across the piston  46  and into cylinder portion  96 . The sizes of the passages  104 ,  106 ,  88 ,  92  and  94  are selected to accommodate this normal across-piston air flow and to prevent any increases in the air pressure in the cylinder portion  96  that might adversely effect the normal operation of the air cylinder assembly  42 . 
     However, when a break in the running web  16  occurs, there is a rapid increase in the air pressure in the portion  96 . This increase is due to the sudden movement of the piston  46  toward the cylinder end  58 , which causes the poppet member to move toward the end  58 , against the bias of the spring  82 . This movement causes the member  72  to abut the distal end of the protuberance  86  and block further air flow through the central passage  88 . Because of the differences of the total cross-section areas of the passage  92  and  94  (as compared with the cross-sectional area of passage  88 ) and because of the restrictor  118 , such a blockage or closure of the passage  88  results in the rapid increase in the air pressure in the cylinder portion  96 . The air pressure in the cylinder portion  96  continues to increase until the pressure equals the air pressure in cylinder portion  62 . This air pressure increase in the portion  96  and the equalization of the air pressures in the portions  62  and  96  slows down, and then stops, in a controlled manner, the movement of the piston  46  and thus, the movement of the dancer assembly  34  upon a breakage of the running web  16 . 
     The delay in the restrictor  118  is preselected so that the post-web-breakage movement of the piston  46  is substantially stopped before air is bled from the cylinder portion  96 . For instance, a 4-5 second, or even a 2-3 second delay in the bleeding of the air from the portion  96  has been found to be satisfactory. 
     Referring again to FIG. 1, a conventional, two position, three way valve  122  is disposed in the tubing  124  and  126  and is adapted to connect the cylinder portion  62  with the regulator  66 , which is also connected, via tubing  126  and a check valve  128 , to a sump  132 . The valve  122  may be a high flow, ½″, 25VDC/120VAC, ½″ JIC box option model manufactured by MAC Valves, Inc. of Wixom, Mich. 48393-7011. In its first or normal (illustrated) position, that is, its position when the web  16  is running, pressured air may flow between the cylinder portion  62  and the air pressure regulator  66  (and thus, to and from the air source  62  and sump  132 , respectively). 
     A conventional transducer  134  is mounted so as to sense movement of the dancer assembly  34 , and more particularly, the movement of the assembly  34  when the running web  16  breaks. As illustrated in FIG. 1, the transducer  134  is associated with the cable  44 , but the transducer could also be associated directly with the assembly  34  itself. The transducer  134  may be a Magnetek/Gemco model (linear “Quik-Stik” 48″ long with quick disconnect) manufactured by Patriot Sensors &amp; Controls Corp. of Clawson, Mich. 48017-1097. 
     Upon movement of the dancer assembly  34  caused by a break in the running web, the transducer  134  sends a signal to the valve  122  to switch the valve from its first position (as illustrated in FIG. 1) to a second position where the communication between the cylinder portion  62  and the regulator  66  is blocked and where the cylinder portion  62  communicates, via tubing  124  and  136  with the tubing  116 , upstream of the restrictor  118 . Hence when a web breakage occurs, the valve  122  is immediately switched to its second position, and the valve portions  62  and  96  are brought into communication with each other, through the tubing  124 ,  136  and  116 . This facilitates the equalization of the air pressures in the cylinder portions  62  and  96 . As noted, the equalization of the air pressure controls and stops the upward movement of the dancer assembly  34  that would have otherwise occurred upon a break in the running web  16 , in the absence of the present invention. With the movement of the valve  122  to its second position, the air pressure in cylinder portion  62 , like that in cylinder portion  96 , is permitted to bleed, after a preselected delay, through the restrictor  118  to the atmosphere. 
     The preferred embodiment of the present invention has now been described. This preferred embodiment constitutes the best mode presently contemplated by the inventor for carrying out his invention. Because the invention may be copied without copying the precise details of the preferred embodiment, the following claims particularly point out and distinctly claim the subject matter, which the inventor regards as his invention and wishes to protect: