Abstract:
A strapping machine feed system for automatically detecting a strap error or fault, thereby stopping strap retraction or take-up, and refeeding the strap into the strapping head following the error or fault. The feed system includes a pair of tensioning wheels disposed along a strap path proximal a strap supply, and a pair of feed wheels, defining a nip therebetween, disposed along the strap path proximal the strapping head. A feed wheel drive and a tensioning wheel drive are respectively connected to the feed wheels and the tensioning wheels. A sensor disposed along the strap path generates a signal to the feed wheel drive and tensioning wheel drive, indicating movement or lack of movement along the strap path, thus causing the feed wheels or tensioning wheels to rotate in both a forward and reverse direction.

Description:
BACKGROUND OF THE INVENTION 
   The present invention is directed to a strapping machine feed system. More particularly, the present invention is directed to a strapping machine feed system in which strap is refed following a strap error or fault. 
   Strapping machines are well known in the art for securing straps around loads. One type of known strapper is a stationary unit that includes a strapping head or weld head and drive mechanism mounted within a frame. A chute is mounted to the frame, through which the strapping material is fed. In a typical arrangement, a table-top or work surface is likewise mounted to the frame. 
   In a typical stationary strapper, the chute is mounted from about the work surface, and the strapping head is mounted below the work surface. Strap is fed from a source or dispenser to the strapping or weld head. The strapping head provides a number of functions. First, it includes a plurality of grippers for gripping portions of the strap during the course of a strapping operation. The strapping head also includes a cutter to cut the strap from a strap source or supply. Last, the strapping head includes a sealer to seal an overlying course of strapping material onto itself. This seal is commonly referred to as a weld and is effected by heating overlying courses of the strap by use of a vibrating element or a heated element. 
   Strapping material is fed from the dispenser into the strapping head first via a pair of infeed wheels and second via a feed assembly. The infeed wheels are typically located immediately inside of the strapping machine (e.g., inside of an enclosure or cabinet). The infeed wheels facilitate smoothly feeding the strapping material into the strapper and supplying strapping material into the slack box. The slack box is an area between the infeed wheels and the strapping head that is used to store a length of “slack” strapping material for use by the strapping head and is also an area for storing take-up strap that has been rewound or tensioned around the load. 
   The feed assembly includes a pair of tensioning wheels and a pair of feed wheels. The tensioning wheels are locate downstream of the infeed wheels, and a guide extends between the tensioning and feed wheels. The slack box is disposed about the guide area, between the infeed and tensioning wheels. 
   The feed wheels are located between the tensioning wheels and the strapping head. The feed wheels feed the strap material into the strapping head (and around the strap chute). A guide is disposed between the tensioning wheels and the feed wheels to provide a pathway for the strap as it is fed into the strapping head by the feed wheels and as it is pulled from the strapping head (and from around the chute) by the tensioning wheels. 
   In the event a strap error occurs, as by a failure of the gripper to grip the leading end of the strap, during the tensioning cycle, the strap will be over-retracted or over-pulled by the tensioning wheels. When this occurs, the strap is pulled rearwardly to the extent that is has essentially pulled out of the strap path. Pulling the strap from the path results in a machine fault. Operator attention is then required to stop machine operation and refeed strap into the feed system to resume operation. 
   Accordingly, there is a need for a strapping machine having a strap feeding and tensioning system with automatic refeed. Desirably, such a system automatically detects a strap error or fault, stops strap retraction or take-up and refeeds the strap into the strapping head following that error or fault. More desirably, such a system refeeds the strap into the strapping head without additional parts or assemblies beyond those employed for feeding and tensioning the strap material during normal machine operations. 
   BRIEF SUMMARY OF THE INVENTION 
   A feed system for a strapping machine automatically detects a strap error or fault, stops strap retraction or take-up and refeeds the strap into the strapping head following that error or fault. Such a system is configured for use in a strapping machine of the type having a strap supply, a strap chute and a strapping head disposed between the strap supply and the chute. 
   The feed system defines a strap path from the strap supply to the strapping head. A pair of tensioning wheels is disposed along the strap path proximal the strap supply. In a present embodiment, the tensioning wheels are movable into and out of engagement with one another. A pair of feed wheels is disposed along the strap path proximal the strapping head. The feed wheels define a nip therebetween. 
   A feed wheel drive is operably connected to one of the feed wheels and a tensioning wheel drive is operably connected to one of the tensioning wheels. Preferably, the feed and tensioning wheel drives are reversible motors. The other of the feed and tensioning wheels are idler or pinch wheels. 
   A sensor is disposed along the strap path for generating a signal to indicate a movement or a lack of movement of the strap material along the strap path. 
   In a strapping cycle, the strap material is conveyed around the strap chute by forward rotation of the feed wheels and is retracted around the load by reverse rotation of the feed wheels. The strap is tensioned around the load by forward rotation of the tensioning wheels. Forward rotation of the tensioning wheels commences upon receipt of the lack of movement of strap material signal following retracting the strap material. 
   When, following reverse rotation of the feed wheels for retracting the strap material, the machine is in a faulted strap condition (by the sensor failing to generate a lack of movement signal), the feed wheels stop rotation, and the tensioning wheels rotate in a reverse direction to convey the strap material into the nip between the feed wheels. 
   In a current embodiment, the sensor is disposed proximal the idler feed wheel to sense the movement and lack of movement of the idler feed wheel. The movement and lack of movement of the idler feed wheel correspond to the movement and lack of movement of the strap material signals, respectively. 
   Preferably, the tensioning wheels are moved out of engagement with one another when the strap material is conveyed around the strap chute and when strap material is retracted around the load. The tensioning wheels are moved into engagement with one another when the strap material is tensioned around the load and when the strap is refed into the feed wheel nip following the faulted strap condition. 
   The tensioning wheels are moved into and out of engagement with one another by a linkage that is operably connected to the pinch tensioning wheel for moving an axis of rotation of the pinch tensioning wheel toward and away from the driven tensioning wheel. The pinch tensioning wheel is mounted to an eccentric shaft that is operably connected to the linkage. 
   A strapping machine having a feed system that automatically detects a strap error or fault, stops strap retraction or take-up and refeeds the strap into the strapping head following that error or fault is also disclosed. 
   These and other features and advantages of the present invention will be apparent from the following detailed description, in conjunction with the appended claims. 

   
     BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS 
     The benefits and advantages of the present invention will become more readily apparent to those of ordinary skill in the relevant art after reviewing the following detailed description and accompanying drawings, wherein: 
       FIG. 1  is a front view of an exemplary strapping machine having a strap path access guide embodying the principles of the present invention; 
       FIG. 2  is a perspective illustration of the front of the strapping machine showing the strapping machine feed assembly with a strap path access guide in the open position for ease of illustration; 
       FIG. 3  is a perspective illustration similar to  FIG. 2  showing the access guide in the closed or operating position; and 
       FIG. 4  is a perspective illustration of the rear of the strapping machine. 
   

   DETAILED DESCRIPTION OF THE INVENTION 
   While the present invention is susceptible of embodiment in various forms, there is shown in the drawings and will hereinafter be described a presently preferred embodiment with the understanding that the present disclosure is to be considered an exemplification of the invention and is not intended to limit the invention to the specific embodiment illustrated. 
   It should be further understood that the title of this section of this specification, namely, “Detailed Description Of The Invention”, relates to a requirement of the United States Patent Office, and does not imply, nor should be inferred to limit the subject matter disclosed herein. 
   Referring to the figures and in particular  FIG. 1 , there is shown a strapping machine  10  having a feed system with automatic refeed  12  embodying the principles of the present invention. The strapping machine  10  includes, generally, a frame  14 , a strap chute  16  and a table top or work surface  18 . The feed assembly  12  and a strapping head  20  are mounted below the work surface  18 . A controller  22  provides automatic operation and control of the strapper  10 . 
   The strapping head  12  receives strapping material S from a dispenser  24 . The strap S is fed or pulled from the dispenser  24  by infeed wheels  26 . In a typical arrangement, the infeed wheels  26  are mounted immediately inside of and within the machine  10 . Strap S is conveyed from the infeed wheels  26  to the feed assembly  12  (past a slack box  28 ). The slack box  28  is used as a “storage” region for strap S that has been fed into the machine  10  but has not yet been pulled into the strapping head  20 , and for strap S that has been taken-up from around the load L, as during the take-up or tensioning cycles. 
   The feed assembly  12  includes two pairs of wheels, namely a pair of feed wheels  30 ,  32  and a pair of tensioning wheels  34 ,  36 . One of the feed wheels  30  is driven and the other is an idler or pinch wheel  32 . Likewise, one of the tensioning wheels  34  is driven and the other is an idler or pinch wheel  36 . The feed wheels  30 ,  32  are located proximal the strapping head  20 , and the tensioning wheels  34 ,  36  are located proximal the slack box  28  and infeed wheels  26 . A lower guide  38  extends between infeed wheels  26  and the tensioning wheels  34 ,  36 . An upper guide  40  extends between the tensioning wheels  34 ,  36  and the feed wheels  30 ,  32 , a portion of which guide  40  also extends beyond the feed wheels  30 ,  32  to the strapping head  20 . A portion  40   a  of the upper guide  40  is pivotable (as shown by comparison of  FIGS. 2 and 3 ) to provide ready access to the strap path P. The driven feed wheel  30  and the driven tensioning wheel  34  are operably connected to reversible motors  42 ,  44  to drive the wheels  30 ,  34  in both (i.e., clockwise and counter-clockwise) directions. 
   The driven feed and tensioning wheels  30 ,  34  are fixed relative to the frame  14 . The idler (or pinch) feed wheel  32  is biasedly mounted to the guide  40 . During the strapping cycle, the idler feed wheel  32  is maintained in contact with the driven feed wheel  30 . A stall sensor  46  is located proximal the idler wheel  32  to monitor (and provide a signal) upon indication that the idler wheel  32  has stalled or stopped rotating. 
   Unlike the idler feed wheel  32 , the pinch tensioning wheel  36  is mounted to an eccentric shaft  48  that is in turn operably connected, by a linkage  50 , to a cam  52  in the strapping head  20 . This cammed arrangement is configured to bring the pinch tensioning wheel  36  into contact with (i.e., to engage) the driven wheel  34  and to separate (i.e., disengage) the wheels  34 ,  36  from one another. In this manner, the pinch wheel  36  is moved into and out of engagement with the driven tensioning wheel  34  to drive or “idle” the strap S. 
   Briefly, in operation, there are three portions or sub-cycles of a normal strapping cycle. The first portion is the feed portion of the strapping cycle, during which strap S is “pulled” by the feed wheels  30 ,  32 , conveyed though the strapping head  20 , around the strap chute  16  and back to the strapping head  22 . The cycle then progresses to the take-up portion of the cycle which is when the strap S is released from the chute  16  and is taken-up at high speed until it contacts or lies on the load L. Following the take-up portion of the cycle, the machine  10  progresses into the tensioning portion of the strapping cycle, during which the strap S is tensioned or pulled tight around the load L. 
   The following discussion is provided for purposes of understanding the operating modes and relationships between the various components. During the feed portion of the cycle, the feed wheels  30 ,  32  rotate in a “forward” direction (as seen in  FIG. 2 , the driven wheel  30  rotates counter-clockwise), with the idler wheel  32  rotating by virtue of the movement of strap S between the driven  30  and idler  32  wheels. During the feed portion of the cycle, the tensioning wheels  34 ,  36  are separated (or open) from one another (by the strapping head cam  52 -linkage  50 -eccentric shaft  48  arrangement) to permit the feed wheels  30 ,  32  to “pull” the strap S. 
   Once the strap S moves around the chute  16  and back to the strapping head  20 , the lead end of the strap S is gripped by a gripper  54  in the strapping head  20 . Upon sensing that the strap S is gripped, the machine  10  progresses to the take-up portion of the cycle. In take-up mode, the strap chute  16  opens to allow the strap S to be pulled to the load L. The feed wheels  30 ,  32  reverse (the tensioning wheels  34 ,  36  are still separated or open) and the strap S is pulled from the chute  16  on to the load L. Take-up is carried out at a high speed but at a low force. As such, once the strap S is fully pulled to the load L (but not yet tensioned), the strap S will “stall”. By virtue of the dependence of rotation of the feed idler wheel  32  on the movement of the strap S, when the strap S “stalls”, so does the idler wheel  32 . This stall is sensed by the stall sensor  46 . 
   Upon sensing a stall in the idler wheel  32 , the machine  10  progresses to the tensioning portion of the strapping cycle. In this portion of the cycle, the strapping head  20  indexes (which moves the cam  52 ), which in turn moves the linkage  50  to bring the tensioning wheels  34 ,  36  into contact, The tensioning motor  44  then actuates (rotating in a forward direction) to tension the strap S around the load L. Upon reaching a predetermined tension, the tensioning motor  44  stops (stopping the tensioning wheels  34 ,  36 ) and the strap S is sealed and cut. The machine  10  then resets and recommences the strapping cycle (per the controller  22 ). 
   When a strap fault occurs in which the leading end of the strap S is not properly gripped at the strapping head  20 , the machine  10 , in the course of the strapping cycle will progress to the take-up portion of the cycle. When the stall sensor  46  fails to sense a stall within a predetermined period of time, for example, two seconds, the feed wheels  30 ,  32  stop the (reversed) take-up rotation and the machine  10  indexes to an “off-normal” refeed mode. In the refeed mode, the feed wheels  30 ,  32  are stopped and the tensioning wheels  34 ,  36  are engaged with one another (by operation of the strapping head cam  52 -link  50 -eccentric shaft  48  arrangement). However, in this mode the tensioning wheels  34 ,  36  are rotated in a reverse direction (the driven tensioning wheel  34  rotates counter-clockwise as seen in  FIGS. 2 and 3 ) to boost the strap S into the nip  56  formed by the feed wheels  30 ,  32 . In this manner, the strap S is refed into the feed wheels  30 ,  32  following a strap S fault. The strap S, when sensed at the idler feed wheel  32  (by movement of the wheel  32  due to the pushing or urging of the strap S into the nip  56 ), generates a signal to the machine controller  22  indicating that the machine  10  is ready to commence operation. The controller  22  is then reset and the machine  10  is ready for operation. 
   The present feed system with automatic refeed  12  provides a number of advantages over known strapping machine systems. One such advantage is the ability to automatically refeed strap S to the strapping head  20  following a faulted strap condition. Those skilled in the art will readily recognize and appreciate the advantage that such as system provides to, among other things, enhance the operational efficiency and reduce the machine “down-time” that might otherwise occur. 
   All patents referred to herein, are hereby incorporated herein by reference, whether or not specifically done so within the text of this disclosure. 
   In the present disclosure, the words “a” or “an” are to be taken to include both the singular and the plural. Conversely, any reference to plural items shall, where appropriate, include the singular. 
   From the foregoing it will be observed that numerous modifications and variations can be effectuated without departing from the true spirit and scope of the novel concepts of the present invention. It is to be understood that no limitation with respect to the specific embodiments illustrated is intended or should be inferred. The disclosure is intended to cover by the appended claims all such modifications as fall within the scope of the claims.