Abstract:
A wrapping machine for wrapping film about items includes a film dispenser that wraps the film about the items. A gripper mechanism includes an electrical actuator. The gripper is electrically powered, such that a supply of compressed air or the like is not required to operate the gripper mechanism.

Description:
CROSS-REFERNCE TO RELATED APPLICATIONS  
       [0001]    This application claims the benefit of U.S. Provisional Application No. 60/423,514, filed on Nov. 4, 2002, the entire contents of which are hereby incorporated by reference. 
     
    
     
       BACKGROUND OF THE INVENTION  
         [0002]    Wrapping machines have been developed for wrapping plastic film around items on a pallet to retain the items for shipping and the like. Known wrapping machines include a film dispenser mounted on an arm to rotate about the pallet and thereby wrap the items on the pallet. The film dispenser may also be mounted for vertical travel such that the film is wrapped around the items in a spiral manner. Other known wrapping machines include a rotary table upon which the pallet is placed. In this type of machine, the wrapping device is mounted to a stationary vertical structure. During the wrapping process, the table and pallet thereon are rotated, and the wrapping device travels vertically to thereby spiral wrap the items on the pallet. Known wrapping machines include a gripper that grips the end of the film to thereby tension the film as it is fed from the film dispenser. Known grippers are pneumatically powered, and therefore require a supply of compressed air in addition to the electrical power that is required to operate the other components of the wrapping machine. The need for a supply of compressed air to operate the gripper often results in extra expense and/or inconvenience, particularly in facilities that do not already have a supply of compressed air. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0003]    [0003]FIG. 1 is perspective view of a wrap machine according to one aspect of the present invention;  
         [0004]    [0004]FIG. 2 is a right front view of the wrap machine of FIG. 1;  
         [0005]    [0005]FIG. 3 is a left front view of the wrap machine of FIG. 1;  
         [0006]    [0006]FIG. 4 is a rear view of the wrap machine of FIG. 1;  
         [0007]    [0007]FIG. 5 is a top view of a gripper for wrap machines according to the present invention, with the gripper being in an open position;  
         [0008]    [0008]FIG. 6 is a top view of the gripper wrap machines according to the present invention, with the gripper being in an open position;  
         [0009]    [0009]FIG. 7 is a perspective view of the electrically powered rack and pinion mechanism and gripping members;  
         [0010]    [0010]FIG. 8 is a partially schematic perspective view of another wrapping machine according to another aspect of the present invention, wherein the grippers are mounted to a rotary table. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0011]    For purposes of description herein, the terms “upper,” “lower,” “right,” “left,” “rear,” “front,” “vertical,” “horizontal,” and derivatives thereof shall relate to the invention as orientated in FIG. 1. However, it is to be understood that the invention may assume various alternative orientations, except where expressly specified to the contrary. It is also to be understood that the specific devices and processes illustrated in the attached drawings, and described in the following specification are simply exemplary embodiments of the inventive concepts. Hence, specific dimensions and other physical characteristics relating to the embodiments disclosed herein are not to be considered as limiting.  
         [0012]    The reference number  10  (FIG. 1) generally designates a wrap machine of the present invention. The wrap machine  10  includes a frame  12 , a rotating arm  14  having a stretch wrapping device  16  thereon and a gripper housing  18 . The frame  12  includes a substantially C-shaped base  20 , a vertical frame member  22 , an upper horizontal frame member  24  and a pair of struts  26  extending between the base  20  and the upper horizontal frame member  24 . The frame  12  further includes a cantilevered arm  28  extending from the upper horizontal frame member  24 . The rotating arm  14  is connected to the cantilevered arm  28 . The rotating arm  14  has an inverted L-shape, with an end of the horizontal portion rotatably connected to the end  29  of the cantilevered arm  28 . A first electric motor and drive assembly  15  rotates arm  14  360° about the end of cantilevered arm  28 . The stretch wrapping device  16  is operably coupled to a second electric motor and drive assembly  19 , and moves up and down the vertical portion of the rotating arm  14  to wrap a film web about a plurality of items placed on a pallet, which is placed within a wrapping area  17  defined by the C-shaped base  20  of the frame  12 . The stretch wrapping device  16  (FIG. 3) includes a web dispenser  30  which supports a roll  32  of conventional film web  34 , and prestretch rollers which stretch the film web  34  before it is dispensed from the web dispenser  30  over the items on the pallet. In the illustrated example, the rotating arm  14  further includes a wipe and burn mechanism  45  for burning the film web  34  once the items on the pallet have been wrapped and for wiping a free end of the film web  34  after it has been burnt into contact with the rest of the film web  34  on the items on the pallet. All of the elements discussed above, except the gripper housing  18 , are conventional items and are well known to those skilled in the art.  
         [0013]    In the illustrated example, the gripper housing  18  is spaced away from the C-shaped base  20  of the frame  12 . As illustrated in FIGS.  1 - 4 , the stretch wrapping device  16  is configured to rotate in a space  21  located between the gripper housing  18  and the C-shaped base  20 . The gripper housing  18  preferably includes a pair of gripping members  50  extending from a top surface  23 . As discussed in more detail below, the gripping members  50  are electrically activated, with the electricity being conducted to the gripper housing  18  by a  24  volt ribbon wire  52  that has a low profile. The ribbon wire  52  extends between the C-shaped base  20  of the frame  12  and the gripper housing  18 . The frame  12  includes a conventional electrical connection for providing power to all parts of the wrap machine  10 .  
         [0014]    Preferably, the gripping members  50  are connected to a rack and pinion system  55  (FIG. 7) that moves the gripping members  50  from an open position as shown in FIG. 5 to a closed position as shown in FIG. 6. An electrically powered linear actuator  57  includes an output shaft or member  58  that shifts horizontally upon actuation of linear actuator  57 . The output member  58  extends through an opening in an angle bracket  61 , and angle bracket  61  is fixed to rack  56 . Angle bracket  61  is positioned between stop members  59  and  60  of the output member  58  such that stops  59  and  60  contact bracket  61  and shift rack  56  horizontally upon actuation of linear actuator  57 . Rack  56  extends through a guide  64  and teeth  63  of rack  56  engage a gear  65  to rotate a first gripper member  50 A. A pair of gears  66  and  67  mesh to thereby cause gripper member  50 B to rotate in an opposite direction relative to gripper  50 A. When the output shaft  58  is in the extended position as illustrated in FIG. 7, gripper members  50 A and  50 B are rotated to the open position. As output member  58  is retracted, a spring  62  contacts the vertical wall  68  of angle bracket  61 , thereby pulling the rack  56  towards the actuator  57  and rotating the gripper members  50 A and  50 B to the closed position. The spring  62  thereby provides a relatively constant, controlled force acting on the film between the gripper members  50 A and  50 B, and reduces or eliminates the variations in force that would otherwise occur due to varying thicknesses of the film and/or variations in the amount of travel of output member  58  of actuator  57 . Other resilient members or arrangements providing a constant gripping force could also be utilized. For example, rubber or foam could be positioned on the edges of the gripper members  50 A and/or  50 B. The linear electrically powered actuator  57  is secured to a base member  71  by an actuator bracket  70 , and gripping members  50 A and  50 B are rotatably mounted in brackets  69 . The gripper housing  18  is preferably bolted into position on the ground by fasteners  73  or other suitable anchoring arrangements.  
         [0015]    In use, the wrap machine  10  is used by placing the pallet full (or partially full) of items within the area defined by the C-shaped base  20  of the frame  12  and with a circle defined by the rotation of the vertical portion of the rotating arm  14 , with the pallet abutting the gripper housing  18 . To begin, a free end of the film web  34  is clamped by the gripping members  50 . Once the pallet is in position, the rotating arm  14  begins to rotate, thereby wrapping the pallet and the items on the pallet with the film web  34 . With the wrap machine  10  of the present invention, the lowest portion of the stretch wrapping device  16  can get very close to the ground because the stretch wrapping device only has to clear the ribbon wire  52  in the lowest portion of rotation. Therefore, the pallet does not have to be raised off of the ground and/or the gripping members  50  do not have to be located in the ground to be able to wrap the pallet. Previously, the pallet was placed on a platform and/or the gripping members  50  were located in the ground to be able to wrap the pallet. Additionally, the gripper housing  18  has a height of about 3 to 3.25 inches, thereby allowing the film web  34  to be wrapped about the pallet without the gripper housing  18  interfering.  
         [0016]    As the stretch wrapping device  16  spins about the items on the pallet, moving vertically to wrap the all of the items, the gripping members  50  can release the free end of the film web  34 . Thereafter, when all of the items on the pallet have been wrapped, the rotating arm  14  can move back to an initial position that the rotating arm  14  was in before the wrap sequence begun. Thereafter, the gripping members  50  can once again be activated to grab the film web  34  between the items on the pallet and the stretch wrapping device  16 . The wipe and burn mechanism  45  will then move into contact with the film web  34  between the items on the pallet and the stretch wrapping device  16  to burn the film web  34  to thereby sever the film  34  and to wipe a free end of the film web  34  extending from the items on the pallet into contact with the film web  34  about the items on the pallet. The pallet can then be removed and another pallet can be placed into position to start the process over again to wrap items on the second pallet with the film web  34 .  
         [0017]    The gripper housing  18  and grippers  50 A and  50 B may also be utilized for a rotary table wrapping machine  80 . The gripper mechanism of FIG. 7 and housing  18  are mounted to a rotary table  82  adjacent an edge of table  82 , and thereby rotates as table  82  is rotated. A stretch wrapping device  16  dispenses a film web in a known matter, and travels vertically along vertical structure  81  of wrapping machine  80 . A conventional wipe and burn mechanism  45  is also provided. Electric drive assemblies  84 ,  85  of a conventional known design provide for vertical movement of the stretch wrapping device  16  and for rotary movement of rotary table  82 . The housing  18  is mounted on upper surface  83  of rotary table  82  and thereby provides a stop to position pallets or other items on table  82 . A conventional slip ring arrangement or the like provides electrical power from the main power supply source to the linear electric actuator mounted to the rotary table  82 . In use, a pallet is placed on rotary table  82 , and an end portion of the film web is secured by grippers  50 A and  50 B upon actuation of linear actuator  57 . Table  82  is then rotated, and stretch wrapping device  16  moves vertically to thereby wrap the items on rotary table  82 .  
         [0018]    The above description is considered that of the preferred embodiment only. Modification of the invention will occur to those skilled in the art and to those who make or use the invention. Therefore, it is understood that the embodiment shown in the drawings and described above is merely for illustrative purposes and not intended to limit the scope of the invention.