Patent Publication Number: US-6708606-B1

Title: Strapper with improved winder

Description:
BACKGROUND OF THE INVENTION 
     The present invention pertains to strapping machines. More particularly, the present invention pertains to an improved winder for a strapping machine that uses the strap tension to secure the strap in the winder. 
     Strapping machines are in widespread use for applying a strap, such as a plastic strap, in a tensioned loop around a load. A typical strapping machine includes a strap chute for guiding the strap around the load, a strapping head through which the leading end of the strap is fed, and a strap dispenser to dispense a desired length of strap from a coil of strap material. 
     The strapping head carries out a number of functions. It advances the strap along the chute around the load until the leading end returns to the strapping head and retracts or rewinds the strap from the chute to produce tension in the strap around the load. The strapping head typically includes an assembly for securing the strap in the tensioned loop around the load such as by welding the strap to itself at its overlapping portions. 
     A typical strapping head includes a pair of advancing rollers for advancing the strap through the strapping head and a pair of retraction rollers for retracting the strap to, for example, take-up the strap. The head also includes a winder or tensioner that rewinds or takes up the strap after it is positioned around the load so as to apply a tension in the strap. In one known configuration, the winder includes a split-type rotating element that has a channel or slot formed therethrough to essentially define split halves of the winder. The split halves are fixed relative to one another and the strap traverses through the slot between the halves. Upon an appropriate signal, the winder is actuated and rotates to tension the strap. 
     In this arrangement, the strap may not be in tension until it passes over itself around the winder, thus creating sufficient friction to prevent the strap from slipping through the winder slot. It has been observed that often, the winder must rotate in excess of 360 degrees, and with some types of readily compressible loads, it must rotate more than 720 degrees to provide sufficient friction to begin tensioning and to provide the appropriate tension on the strap. This can be problematic where there is a limit to the rewinding length due to structural constraints of the strapping head, winder and drive arrangement or due to load compression constraints (e.g., a not readily compressible load). 
     In another type of winder, a rotating head is formed having a stationary element and a pivotal element that each define an outer surface around which the strap material is wound. A slot is defined between the elements through which the strap traverses. 
     The pivotal element is biased toward the stationary element, i.e., to close the slot, by a spring. The biased element must be “pulled” away from the stationary element in order to open the strap slot so that the strap can readily traverse through the slot. The pulling of the pivotal element is carried out by a large wrap spring positioned on a shaft at the rear of the winder. 
     Although this winder has been found to work well, there are a number of drawbacks. First, the elements are biased toward one another, which requires a relatively large force to open the elements to establish the strap path. Second this arrangement uses a complex cam and plate system to properly “time” the winder operating modes, e.g., the feed and retraction operating modes and to maintain the strap slot open. It has been found that the complexity of the winder, in conjunction with the large wrap spring can require more maintenance than practicable given the operational requirements of the strapping machines, generally. 
     Accordingly, there exists a need for a winder for a strapping machine that uses the tension in the strapping material to maintain the winder closed (i.e., to secure the strap in the winder). Desirably, in such a winder, the winder nevertheless begins to close, effectively tensioning the strap, before the strap winds over itself, without the need for a high rate spring. Desirably, such a winder is effective over a range of strap gauges and can be used with highly compressible loads. More desirably, such a winder can also provide a high tension in the rewound strap. 
     BRIEF SUMMARY OF THE INVENTION 
     A winder for use in a strapping machine of the type for positioning a strap material around an associated load and tensioning the strap material around the load includes a frame for supporting the load, a chute positioned on the frame for receiving the strap material and orienting the strap material around the load, a strap supply and a strapping head for extracting the strap from the supply, feeding the strap through the chute around the load, passing the strap from the chute around the load, retracting and tensioning the strap. 
     The winder is positioned at the strapping head. Briefly, the strapping head includes a single pair of rollers for both feeding and retracting the strap, and a winder for tensioning the strap around the load. The strapping machine also includes a weld head for welding the overlapping strap sections to one another. In a present arrangement, the strapping head and weld head are separate units. 
     In one embodiment, the winder includes a rotating head portion having a stationary element and a pivotal element. The stationary and pivotal elements each define an outer surface around which the strap material is wound and also define a slot therebetween for receiving the strap material. The elements each include a gripping portion at about respective ends opposingly facing one another. 
     The pivotal element is pivotal between an open position in which the gripping portions are spaced from one another and a closed position in which the gripping portions cooperate with one another to engage and secure the strap material therebetween. Preferably, the pivotal element is biased to the open position. 
     The winder includes a pivot assist assembly to assist moving the pivotal element gripper toward the stationary element gripper to enhance securing the strap between the grippers. In a present embodiment, the pivot assist assembly includes a pin extending from the pivotal element and a track portion stationary relative to the rotating head portion. The track has a generally circular shape and is configured for the pin to traverse around the track. The track has a first portion having a first diameter and a second diameter less than the first diameter. The differences in relative diameters can be at the outer diameters. 
     The winder rotates from a home position in which the pin is in the first portion of the track and the winder is in the open position to an other than home position in which the pin is in the second portion of the track such that the pin engages a wall of the track at the second diameter urging the winder toward the closed position. 
     In one embodiment of the winder, the pivot member is positioned at about an inlet of the winder, at a location upstream of the pivotal element gripping portion. In this embodiment, the pivot member is disposed at about the outer surface, e.g., at about a periphery, of the pivotal element. Alternately, the pivot member can be disposed intermediate the pivotal element gripping portion and a strap exit of the winder. 
     Preferably, the pivotal element gripping portion is mounted in the element for pivoting movement independent of the movement of the pivotal element. This permits a gripper pad to lie on the strap and conform to the strap path as it traverses through the winder. 
     A current winder includes an over-rotation plate to permit rotation of the winder in excess of 360 degrees. The plate is positioned between the winder and the strapping head frame. 
     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 front view of an exemplary strapping machine illustrating, generally the components and arrangement thereof, the machine shown with a strapping head embodying the principles of the present invention; 
     FIG. 2 is a schematic illustration of the strapping machine showing the relative position of a load of items to be strapped, and one exemplary relative position of the strapping head on the machine; 
     FIG. 3 is a partial view of the strapping head, showing the cover pivoted and removed from the strapping head frame for clarity of illustration, the head being illustrated in the feed position, and further shown without strap material positioned therein; 
     FIG. 4 is a front view of the strapping head of FIG. 3 shown with the strap material traversing through the head, including the winder, the strapping head being shown in feed mode, and further showing the cam track formed in the cover in phantom lines overlying the winder; 
     FIG. 5 is a front view similar to FIG. 3 showing the strapping head in rewind mode with the winder commencing rotation; 
     FIG. 6 is a further front view of the strapping head showing further rotation of the winder; 
     FIG. 7 is a still further front view of the winder showing yet further rotation of the winder; 
     FIG. 8 is a front view of the over-rotation plate that is positioned between the winder and the strapping head frame; and 
     FIG. 9 is a front view of an alternate embodiment of the winder having mid-pivot pivotal element. 
    
    
     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, to FIG. 1, there is shown a strapping machine  10  having a strapping head  12  embodying the principles of the present invention. The strapping machine  10  includes generally a frame  14  supporting a strap chute  16  around which the strap S is advanced during the strapping operation. One or more strap dispensers  18  supply strap material S to the strapping head  12 . The overall arrangement and operation of such a strapping machine is disclosed in U.S. Pat. Nos. 4,605,456 and 5,299,407, which patents are incorporated herein by reference. 
     The strapping head  12  is that portion of the machine  10  that withdraws or pulls the strap S from the dispenser  18 , feeds the strap S through the chute  16 , grasps the leading edge E of the strap S so as to bring it into contact with a trailing portion T, and tensions the trailing portion T so as to compress the load L. In the illustrated embodiment, the strapping machine  10  includes a separate welding head (shown schematically at W) for sealing the overlapping strap portions E, T to one another to effect a seal, a schematic illustration of which is shown in FIG. 2. A cutter (not shown) severs the strap S at the supply end (i.e., the trailing end E) to free the strapped load L. 
     As illustrated in FIG. 3, the strapping head includes a frame  20 , a plurality of rollers  22 ,  24  and a winder  26 . The rollers  22 ,  24  serve to both feed strap S through the chute  16  around the load L, and to retract or rewind (wind) the strap S to tension the strap S around the load L. In the illustrated embodiment, the rollers  22 ,  24  include a driven roller  22  and an idler roller  24  that rotates only in frictional cooperation with the driven roller  22 . 
     The rollers  22 ,  24  are operably connected to a drive (not shown), such as a belt drive or a direct drive to provide rotational movement to the driven roller  22 . In a current embodiment, the drive is also configured for driving the winder  26  and is operably connected to the winder  26  by clutch (not shown). Such a drive arrangement will be understood and appreciated by those skilled in the art and is within the scope and spirit of the present invention. 
     As illustrated, the idler roller  24  is mounted to a pivoting bracket or link  28  for moving the idler roller  24  into and out of engagement with the driven roller  22 . As will be described in more detail below, when the strapping machine  10  is operating in a rewind or tensioning mode, the idler roller  24  is cammed out of contact with the driven roller  22  to permit rewinding the strap S. 
     The winder  26  is a biased rotating element having a stationary element  30  and a pivotal element  32 , that define a generally circular outer peripheral profile  33 . A second stationary element  34  can be positioned circumferentially along the path of the pivotal element  32  to more completely define the circular profile  33 . The second stationary element  34  is formed having an arcuate outer surface  36  continuing the circular profile. A strap path, indicated generally at  38 , is defined by and between the stationary and pivotal elements  30 ,  32 . 
     In one embodiment, the pivotal element  32  pivots about a pivot pin  40  that is positioned along the periphery  42  of the arcuate portion  44  of the element  32 , upstream of the strap path entrance, as indicated by the arrow at  46 . For purposes of the present discussion, the downstream direction is that direction that the strap travels in the feed operation, i.e., toward the items to be strapped, as indicated by the arrow at  48  in FIG. 4, and upstream is that direction toward the strap supply, as indicated by the arrow at  50 . 
     Referring briefly to FIG. 4, both the stationary and pivotal elements  30 ,  32  include gripping members  52 ,  54  at their respective upstream ends  56 ,  58 . The grippers  52 ,  54  provide frictional surfaces for securing the strap S to prevent slippage as the winder  26  begins to rotate. In a present embodiment, the gripping elements  52 ,  54  are hardened steel pads each having a ridged or corrugated surface  60  to enhance the gripping tendency of the pad  52 ,  54 . In a present embodiment, the pads  52 ,  54  are replaceable. As seen in FIG. 3, the pivotal element gripper  54  resides in a slot or channel  62  in the element  32  that is slightly larger than the gripper pad  54  and is formed having a peaked surface, indicated at  64 , rather than flat base surface. This mounting configuration permits the gripping element  54  to rock back and forth as indicated by the arrows at  66  (see FIG. 3) to conform the angle of the pad  54  surface to the angle at which the strap S lies on the pad  54 . This provides maximum surface contact area between the strap S and the gripper pad  54  surface. 
     As will be appreciated from a study of the figures, as the winder  26  begins to rotate from the open strap path  38  position (FIGS. 3 and 4) to the closed path  38  position (FIGS.  5 - 7 ), the urging of the strap S against the pivotal element  32  moves the pivotal element gripper  54  toward the stationary element gripper  52 . Continued rotation of the winder  26  results in an increased force exerted by the strap S on the pivotal element  32  which, in turn, results in an increased “gripping” force on the strap S. This, of course, prevents the strap S from slipping between the elements  30 ,  32 , and thus permits an increase in the ability to apply a tension (e.g., apply a higher tension) in the rewound strap S. As the winder  26  continues to rotate, the force exerted by the grippers  52 ,  54  on the strap S increases. And, if the winder  26  rotates to the extent that the strap S winds onto itself (i.e., greater than about 180 degrees of rotation), the force of the strap S winding onto itself maintains the strap S in place, without slippage. 
     Ultimately, the increased tension that is induced by the winder  26  results in an increase in the tension in the strap S around the items L. In that much of the tension can be induced in the strap S in a relatively small rotation of the winder  26 , it is desirable to assure that there is little to no slip of the strap S as the winder  26  commences rotation. The pivotal nature of the present winder  26  facilitates an “early” grip on the strap S. However, as seen in FIG. 4, at the start of rotation, the force exerted by the strap S on the pivotal element  32  may be minimal, thus it may not provide the necessary force on the grippers  52 ,  54  to secure the strap S without slippage. 
     To assist urging the pivotal element  32  (and thus the pivotal element gripper  54 ) into contact with the stationary element gripper  52 , the present winder  26  includes a pivot assist assembly  68 . In a present embodiment, the pivot assist assembly  68  includes a camming arrangement that further pivots the pivotal element  32  toward the stationary element  30 . 
     Referring to FIGS. 3 and 4, the exemplary pivot assist assembly  68  includes a pin  70  extending from the winder pivotal element  32 , at about the upstream end  58 , upstream of the gripper  54 . The pin  70  is configured to cooperate with a cam track  72  formed in a cover  74  of the strapping head  12 . The cover  74 , as best seen in FIG. 3, is configured to overlie the strapping head  12  to, among other things, protect the strapping head  12  from debris or interference during operation, and to protect personnel by prevent access to the moving parts of the strapping head  12  during operation. In a current embodiment, the cover  74  is mounted to the frame  20  by hinges  75 . The cam track  72  is formed in the cover  74  at that portion of the cover  74  that overlies the winder  26 . The cam track  72  is formed as a circular channel or groove  76  having a first portion  78  having a wide track width and a second portion  80  having a narrow track width. The first and second portions  78 ,  80  are contiguous with one another. 
     Referring now to FIG. 4, the winder  26  is shown with the cover  74  removed, but with the cam track  72  shown in dashed or phantom lines. In this figure, the strapping head  12  is in or near the feed mode (that is, with the winder  26  positioned so that the strap path  38  is straight-through), with the pin  70  lying in the wide track width portion  78 . In this position, the pivotal element  32  is “free” to move with the strap S. As the winder  26  commences rotation, as seen in FIG. 5, the pin  70  moves into narrow track width portion  80 . In this track portion, the pin  70  contacts an outer wall  82  of the narrow track  80  and is urged inward. This, in turn, pivots the pivotal  32  element toward the closed position (that position in which the pivotal element gripper  54  is urged toward and into contact with the stationary element gripper  52 ), thus increasing the gripping force on the strap S. This prevents the strap S from slipping through the winder  26 . 
     As seen now in FIGS. 5-7, the assistance (i.e., increased pressure) provided by the pivot assist assembly  68  continues through about  180  degrees of travel of the winder  26 . At this point, the strap S will have wound about itself, and this winding, along with the pressure exerted by the strap S to pivot the pivotal element  32  is sufficient to maintain the strap S in the winder  26  without slipping. As such, the track transitions back to the wide track portion  78  after slightly over 180 degrees. 
     The pivotal element  32  further includes, at the downstream end, a curved surface  84 . This surface  84  facilitates a smooth transition for winding the strap S around the stationary and pivotal elements&#39;  30 ,  32  outer circumferential surfaces  33  when the winder  26  is actuated. 
     Referring again to FIG. 4, to maintain the pivotal element  32  in the open position during feeding operation, the pivotal element  32  is biased toward the open position. A biasing element  86 , such as the illustrated coil spring is positioned between the pivotal element  32  and the second stationary element  34  to effect this biased orientation. 
     As set forth above, when the strapping machine  10  commences rewind mode, it is necessary to disengage the rollers  22 ,  24  so that the strap S material can be “pulled” rearward, through the rollers  22 ,  24  toward the strap supply, e.g., toward the dispensers  18 . To effect disengagement, a feed cam assembly  88  operably connects the winder  26  to the rollers  22 ,  24 . In a present embodiment, the driven roller  22  is fixedly mounted to the strapping head frame  20  and the idler roller  24  is mounted to the frame  20  by a pivoting arm or link  90 . 
     The arm  90  is configured to move the idler roller  24  toward and away from the driven roller  22  between an engaged position and a disengaged position. As the position labels provide, in the engaged position (FIG.  4 ), the idler roller  24  engages the driven roller  22  to feed strap S through the strapping head  12 , and in the disengaged position (FIGS.  5 - 7 ), the idler roller  24  is spaced, that is, pulled away from the driven roller  22  so that the strap S is able to be moved freely between the rollers  22 ,  24 . The pivoting arm  90  is biased toward the engaged position, and must be urged to the disengaged position. 
     The pivoting arm  90  includes a cam roller  92  on an end thereof. The cam roller  92  rides along an outer periphery on a flange  94  of the winder  26 . The flange  94  includes a recess  96  in which the cam roller  92  sits when the strapping machine  10  (the strapping head  12 ) is in feed mode. The cam roller  92  residing in the recess  96  permits the idler roller  24  to engage the driven roller  22 . 
     As the winder  26  commences rotation, the cam roller  92  is urged out of the recess  96  to ride along the outer periphery or flange  94 . This pivots the arm  90 , in turn, urging the idler roller  24  away from the driven roller  22 , and moving the rollers  22 ,  24  to the disengaged position. In this manner, the winder  26  cooperates with the rollers  22 ,  24  in a directly linked relationship to assure that the rollers  22 ,  24  are disengaged from the strap S during rewind mode. 
     It is recognized that certain items may be highly compressible. For example, bales of cotton or other loosely pack or soft items may require that a considerable amount of strap S be rewound in order to achieve a desired tension in the strap S (or compression in the bundled material L). In such cases, it may be necessary for the winder  26  to rotate to or over about 360 degrees. In such instances, it is necessary to assure that the cam roller  92  does not set back into the winder recess  96  to reengage the driven and idler rollers  22 ,  24 . 
     Referring to FIG. 8, to prevent reengagement of the driven and idler rollers  22 ,  24  when rewinding over 360 degrees, the strapping head  12  includes an over-rotation plate  98 . The plate  98  is mounted between the winder  26  and the head frame  20 . The plate  98  is configured with an outer periphery  100  that is the same diameter as the winder flange  94 . The plate  98  is configured so that as the winder  26  rotates, the plate outer periphery  100  will “fill-in” as the flange recess  96  passes by the cam roller  92 . 
     As seen in FIG. 8, the over-rotation plate  98  includes a recess  102  that is similar to the recess  96  in the winder flange  94  so that when the winder  26  and plate  98  are aligned with one another (i.e., during feed mode), the cam roller  92  rests in both recesses  96 ,  102  to permit engagement of the idler roller  24  with the driven roller  22 . 
     A projection  104  extends upwardly from a front face  106  of the over-rotation plate  98 , adjacent and behind the recess  102 . The projection  106  is configured to engage a stop (for example, see  108  in FIG. 7) on the winder  26 , forward of the winder recess  96 , after the winder  26  has rotated, and as the recess  96  approaches the cam roller  92 . When the projection  106  engages or contacts the stop  108 , it rotates the plate  98  to prevent alignment of the recesses  96 ,  102 , and to assure that the plate periphery  100  passes over the winder recess  96  before the winder recess  96  passes by the cam roller  92 . In this manner, the pivot arm  90  remains cammed outward when the winder recess passes the cam roller  92  during rewinding which in turn maintains the idler roller  24  disengaged from the driven roller  22 . As will be appreciated by those skilled in the art, the over-rotation plate  98  is configured to permit an additional rotation of the winder  26  to achieve almost an additional 360 degrees. 
     To prevent the over-rotation plate  98  from continuing to rotate (e.g., over rotating), a projection  110  extends from a rear surface  112  of the plate  98 , that is configured to engage a stop  114  on the head frame  20 . The plate rear surface projection  110  and the frame stop  114  can be configured to permit up to almost an additional 360 degree rotation, for a total rotation of almost 720 degrees. The rear surface projection  110  and frame stop  114  also assure that after completion of the rewind mode, the over-rotation plate  98  returns so that the winder and plate recesses  96 ,  102 , are aligned at the cam roller  92  for proper feeding operation. 
     An alternate embodiment of the winder  126  is illustrated in FIG.  9 . In this embodiment, the pivot pin  140 , rather than positioned at a periphery of the pivotal portion  132 , is disposed at about a midpoint (relative to the upstream-downstream direction) of the pivot portion  132 . In this embodiment, the pivot assist assembly pin  170  remains extending from the winder pivotal element  132 , at about the upstream end  158 , upstream of the gripper  154 . 
     The downstream end of the pivotal element  184  can be configured having an exaggerated curved portion as illustrated or it can be relatively straight, with a rounded end (not shown), again to facilitate smooth winding of strap S on, and movement of strap S across, the winder  126 . In this embodiment, the pivotal element gripper  154  moves toward the stationary element gripper  152  in a generally straight line path, rather than inward and toward the downstream direction as it moves toward the stationary gripper element  152 . 
     All patents referred to herein, are hereby incorporated herein by reference, whether or not specifically do 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.