Abstract:
A punching station for a web includes a web transport system that operates to advance the web in a first direction at a first rate. A clamp intermittently grips a portion of the web to advance the portion in the first direction at a second rate. A punch is coupled to the clamp such that the punch moves in the first direction together with the clamp. A punch block cooperates with the punch. The punch block is coupled to the clamp such that the punch block moves in the first direction in unison with the clamp. A punch actuator causes the punch to penetrate the web and then to be withdrawn from the web while the web is gripped by the clamp.

Description:
BACKGROUND OF THE INVENTION 
   A variety of products may be made from webs of sheet materials. Webs are very long lengths of sheet material that are generally supplied in roll form. Paper, plastic sheets, fabric, and sheet metal are examples of materials that may be provided in web form. Processing material in web form may lend itself to high speed production of large numbers of items. 
   Web processes may take advantage of the ability to rapidly feed the web material to successive processing stations in a substantially continuous fashion. The processing stations may perform any of a variety of operations on the web, such as punching, cutting, sealing, or imprinting. Generally each processing station will perform a single type of operation. A series of processing stations may be arranged such that the raw web material is supplied to the first of the series of stations. The processed result of each of the series of stations may be supplied to the next station until a finished article emerges from the last of the series of stations. 
   Bags and pouches are examples of items that can be made using a web process. One process for making pouches uses two webs of raw sheet material. The two materials may be identical or dissimilar. One processing step, possibly the first step, is to laminate the two sheets along a seam line to create a pouch. The final processing step may be a cutting operation to separate the web of pouches into individual items. 
   It will be appreciated that each processing station must process the web at the same average rate. Accumulators may be used to absorb momentary differences in the speed at which the web is advancing through a processing station. But ultimately the time available for each processing station to process the same number of items is the same. 
   Returning to the example of the laminated pouch, the process for laminating the two webs may require that a seaming iron press the two webs together for a period of time, such as one second. This may require stopping the web in the processing station for a period of time that it takes to laminate the seam. As a result, the laminating station might produce one item per second. To increase the production rate of a laminating station, the seaming iron may be arranged so that more than one item is formed along the length of the web in a single laminating operation. For example, if the seaming iron produces twenty pouches along the length of the web, the laminating station might produce twenty items per second. 
   It will be appreciated that more than one item may be produced across the width of the web. For example, the seaming iron might produce four pouches across the width of the web increasing the production rate to 80 items per second. Since this merely requires duplication of the processing mechanism across the width, only the processing of one item across the width will be discussed for clarity. However, it is to be understood that all the web operations that are discussed may be extended to any number of items across the width of the web. 
   A web process that includes a processing station that requires stopping the web for a significant length of time and which produces multiple items along the length of the web to increase the production rate may create a dilemma for other processing stations in the web process. It may be desirable to minimize the starting and stopping of the web. Thus it may be desirable for each processing station that has to stop the web to stop the web at the same time and for the same duration. 
   Again returning to the example of the laminated pouch, the pouch may include one or more features that require punching operations, such as a hanging hole, a tear notch, or rounded corners. If the web moves against the punch while the punch is penetrating the web, the web may tear or crumple. Therefore, a punching operation that punches the same number of items along the length of the web as are produced by the laminating operation might be desirable. However, the tooling for punching may be more difficult or costly to replicate along the length of the web than the seaming iron tooling. 
   It would be desirable to have a punching station for a web and that does not require the use of multiple punch tooling along the length of the web. 
   SUMMARY OF THE INVENTION 
   A punching station for a web includes a web transport system that operates to advance the web in a first direction at a first rate. A clamp intermittently grips a portion of the web to advance the portion in the first direction at a second rate. A punch is coupled to the clamp such that the punch moves in the first direction together with the clamp. A punch block cooperates with the punch. The punch block is coupled to the clamp such that the punch block moves in the first direction in unison with the clamp. A punch actuator causes the punch to penetrate the web and then to be withdrawn from the web while the web is gripped by the clamp. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a schematic view of a punching station for a web that embodies the invention. 
       FIGS. 2 through 6  show the punching station of  FIG. 1  at different point of the operating cycle. 
       FIG. 7  is a schematic view of another punching station for a web that embodies the invention. 
       FIGS. 8 through 10  show the punching station of  FIG. 7  at different point of the operating cycle. 
       FIG. 11  shows the punching station of  FIG. 7  at a different point of the operating cycle and with a control system. 
   

   DETAILED DESCRIPTION OF THE INVENTION 
   The present invention provides a punching station for a web that is compatible with other processing stations that produce multiple items along the length of the web without requiring the use of multiple punch tooling along the length of the web by providing a punching station that does not require stopping the web for the punching operation. The last operation in a web process is often a cutting operation separate the completed items into individual units. It may be desirable that only one item be cut from the length of the web so that all cut items may be readily collected. 
   It may be desirable that the cutting operation be performed on a moving web such the cutting operation disclosed in U.S. Pat. No. 6,024,683. Thus the web process may begin with one or more operation which require stopping the web and then conclude with one or more operations, including punching using an embodiment of the invention, that are performed without stopping the web. 
     FIG. 1  shows a punching station  20  for a web  10  that embodies the invention. A pair of rollers  12  may feed the web  10  to the punching station  20 . Another pair of rollers  16  may pull the web  10  from the punching station  20  and may feed the web to other processing stations. The punching station  20  processes the portion of the web  10  that is between the two pairs of rollers  12 ,  16 . 
   It will be appreciated that both pairs of rollers  12 ,  16  have to feed the web  10  at the same average speed. Dancers  14 ,  18  may be provided before or after the punching station  20  to maintain loops of the web that accommodate instantaneous differences in the speed of the portion of the web  10  that is between the two pairs of rollers  12 ,  16 . Dancers  14 ,  18  may be provided both before and after the punching station  20  as shown in the figures. 
   The punching station  20  shown in  FIG. 1  includes a punch head  21  that moves with a reciprocating motion. The punch head may be motivated by any of a variety of motive devices such as hydraulic cylinders, air cylinders, screw drives, or linear actuators. The punch head  21  may be supported by one or more members  23 . The supporting member  23  or members may be of any of a variety of forms such as rails, bearing carriages, or swing links. 
   The punch head  21  may include a first toolbar  22  that is disposed to a first side of the web  10  and a second toolbar  24  that is disposed to a second side of the web opposite the first side. The first and second toolbars  22 ,  24  may be coupled by support members  26 ,  28  such that the web  10  passes between the first and second toolbars. 
   The punch head  21  includes one or more clamps  32 ,  36  that may be supported by the first toolbar  22 . The clamps  32 ,  36  may be coupled to one or more clamp actuators  30 ,  34  such that the clamps can grip a portion of the web  10  and cause the gripped portion of the web to move at the same speed as the punch head  21 . The clamp actuators  30 ,  34  may be any of a variety of actuating devices such as hydraulic cylinders, air cylinders, or solenoids. The clamps  32 ,  36  may be coupled to the punch head  21  in such a way that the clamps are actuated by the motion of the punch head such as by a cam mechanism or a linkage mechanism. 
   The clamps  32 ,  36  are actuated to grip the web  10  as the punch head  21  is moving in the same direction as the web and at substantially the same speed as the web. The dancers  14 ,  18  may operate to accommodate differences between the speed of the web  10  and the speed of the punch head  21 . The portion of the web  10  that is gripped by the clamps  32 ,  36  does not move with respect to the punch head  21 . 
   The punch head  21  includes one or more punches  42  and corresponding punch blocks  44 . The punch block  44  may be an opening that receives the punch  42  or a surface that the punch operates against. The punch  42  may be coupled to a punch actuator  40 . The punch  42  and punch block  44  are arranged on opposite sides of the web  10  such that the punch actuator  40  will drive the punch and punch block together to punch the portion of the web that is gripped by the clamps  32 ,  36 . The punch actuator  40  may be any of a variety of actuating devices such as hydraulic cylinders, air cylinders, or solenoids. The punch actuator  40  may be coupled to the punch head  21  in such a way that the punch is actuated by the motion of the punch head such as by a cam mechanism or a linkage mechanism. While the gripped portion of the web  10  is moving at substantially the same speed as the remainder of the web, that portion is not moving within the punch head  21  thus allowing the web to be punched without the need to stop the web. 
     FIGS. 1 through 6  illustrate an exemplary punching cycle. In  FIG. 1  the punch head  21  is shown near the position where the punch head has begun to move in the same direction as the web  10 . At this point the clamps  32 ,  36  are not actuated and the web  10  is moving independently of the punch head  21 . The punch head  21  may be accelerating toward substantially the same speed as the web. 
   In  FIG. 2  the clamps  32 ,  36  are actuated to hold a portion of the web  10  stationary with respect to the punch head  21 . The punch head  21  is moving at substantially the same speed as the web  10 . 
   In  FIG. 3  the punch  42  is actuated to form a hole in the web  10 . It will be appreciated that the clamping of the web  10  within the punch head  21  permits punching of the web as though it were stopped while keeping the web in motion. In  FIG. 3  it may be seen that the left dancer  14  has risen and the right dancer  18  has descended to accommodate a punch head  21  that is moving slightly faster than the web  10 . The motion of the dancers  14 ,  18  would be opposite if the punch head  21  were moving slightly slower than the web  10 . 
   In  FIG. 4  the punch actuator  40  has withdrawn the punch  42  from the web  10 . The clamps  32 ,  36  remain actuated to hold the web  10  stationary with respect to the punch head  21  and the punch  42  as the punch is withdrawn. 
   In  FIG. 5  the clamps  32 ,  36  are released and the web  10  is again moving independently of the punch head  21 . The punch head  21  may be decelerated in preparation for reversing direction. 
   In  FIG. 6  the punch head  21  is traveling in the direction opposite to the direction of travel of the web  10  to return the punch head to begin a new cycle. In  FIG. 6  it may be seen that the left dancer  14  has descended and the right dancer  18  has risen to restore the slack taken up while the web  10  was gripped by the punch head  21 . 
     FIG. 7  shows another punching station for a web  10  that embodies the invention. The web transport system may be the same as shown for the previous embodiment. 
   A first toolbar  50  may include one or more clamps  54  and one or more punches  56 . A second toolbar  52  may include corresponding punch blocks  58 . The first and second toolbars  50 ,  52  are disposed on opposite sides of the web. The toolbars move along arcuate paths  60 ,  62  that bring the toolbars together while moving at substantially the same speed as the web  10 . The arcuate paths  60 ,  62  may be circles of which only a portion is shown. 
   The clamp  54  may be resilient so that it will grip the web  10  as the toolbars  50 ,  52  are brought together by the arcuate paths  60 ,  62 . The clamp may extend beyond the punch  56  so that the web  10  is firmly gripped before the punch is driven through the web and into the punch block  58  by the motion of the toolbars. The clamp may be any resilient clamping mechanism such as spring loaded grips or a resilient elastomer pad like sponge rubber. It will be appreciated that this embodiment uses the motion of the toolbars  50 ,  52  to actuate the clamp  54  and the punch  56 . 
     FIGS. 7 through 11  illustrate a portion of an exemplary punching cycle. In  FIG. 7  the toolbars  50 ,  52  are sufficiently separated that the web  10  is moving independently of the toolbars. The toolbars may be accelerating or decelerating to substantially the same speed as the web  10 . 
     FIG. 8  shows the clamp  54  coming into contact with the web  10 . At this point the first toolbar  50  carrying the clamp  54  is separated from the second toolbar  52  on the opposite side of the web  10  and the web is not firmly gripped. The first toolbar  50  carrying the clamp  54  may be moving at substantially the same speed as the web  10  to minimize slippage between the web and the clamp. 
     FIG. 9  shows the toolbars  50 ,  52  as the second toolbar  52  begins to compress the clamp  54  to firmly grip the web  10 . In  FIG. 9  it may be seen that the left dancer  14  has descended and the right dancer  18  has risen to accommodate tool bars that are moving slightly slower than the web  10 . The dancers would move in the opposite manner to accommodate tool bars that are moving slightly faster than the web  10 . If the toolbars  50 ,  52  were moving with a constant rotational velocity, the gripped portion of the web  10  might have a slightly varying linear velocity as the distance of the web from the center of the toolbar path varied during the punching cycle. 
     FIG. 10  shows the toolbars  50 ,  52  as the toolbars are in the closest proximity which drives the punch  56  through the web  10 . It will be appreciated that the resilient clamp  54  will grip the web most securely at this point. 
   As shown in  FIG. 11  further motion of the toolbars  50 ,  52  along the arcuate paths  60 ,  62  will withdraw the punch  56  from the web  10  and then release the resilient clamp  54 . 
     FIG. 11  shows a control system  70  that may be used with a punching station that embodies the invention. It will be appreciated that a similar control system could be used with other embodiments of the invention such as the embodiment shown in  FIGS. 1 through 6 . 
   The control system  70  may receive input from a velocity sensor  72  that gives the speed of the web  10 . The motion of the punching station may be controlled by a motor  78 . In the embodiment shown, the mechanisms for moving the two toolbars  50 ,  52  may be mechanically coupled and driven by a single motor  78 . The web transport may include a pair of drive rollers  76  that control the speed of the portion of the web  10  adjacent the punching station. While the drive rollers are shown at the outlet of the punching station, it will be appreciated that the drive rollers may be positioned ahead of the punching station. In another embodiment, the speed of the portion of the web  10  adjacent the punching station may be controlled by controlling the motion of one of the dancers  14 ,  18 . 
   The control system  70  may receive input from the velocity sensor  72  and use the velocity input to control any or all of the motion of the punching station and the portion of the web  10  adjacent the punching station. The control system  70  may operate to more closely match the speed of the punching station to the speed of the web  10  when the web is clamped in the punching station. The control system may cause the punching station to move at a significantly different speed than the web  10  when the web is not clamped in the punching station. This may allow punching to be spaced on the web at distances that are not equal to the circumference of a circular path for the toolbars in the embodiment shown in  FIG. 11 . 
   The control system  70  may receive input from a feature sensor  74  such as a photo detector that senses a periodic reference mark on the web. The control system may control any or all of the motion of the punching station and the portion of the web  10  adjacent the punching station to cause punching to occur at a predetermined location along the length of the web relative to the reference mark. 
   While certain exemplary embodiments have been described and shown in the accompanying drawings, it is to be understood that such embodiments are merely illustrative of and not restrictive on the broad invention, and that this invention not be limited to the specific constructions and arrangements shown and described, since various other modifications may occur to those ordinarily skilled in the art.