Abstract:
A method and apparatus are provided for automatic bundle transport, positioning, wrapper entry, wrapper opening, wrapper loosening, wrapper removal and wrapper dunnage takeaway. The wrapper is made from pliable material, thin film or similar material and which can comprise a variety of package types and sizes of mail, media or other items. Additionally the method and apparatus of the invention performs the tasks of wrapper removal and discharge without damaging the item contents within. A bundle unwrapping machine according to the invention includes a conveyor by which bundles are presented to the unwrapping machine for opening. An opening mechanism includes a pair of openers positioned to engage a bundle on opposite sites. The bundle is transported into an opening zone in which it is supported for engagement with the openers.

Description:
[0001]    This application claims priority of U.S. provisional application No. 61/053,904 filed May 16, 2008. 
     
    
     FIELD OF THE INVENTION 
       [0002]    The invention relates to systems for the automated opening of packages such as shrink wrapped bundles of flat mail pieces. 
       BACKGROUND OF THE INVENTION 
       [0003]    The time consuming task of opening wrapped packages of mail, media or other similar items without damaging the contents within is currently performed manually. The specific tasks of piercing an entry point into the wrapper, enlarging the entry point, loosening the wrapper surrounding the contents and then removing the wrapper from the contents and placing the removed wrapper in a waste receptacle or dunnage takeaway is today laboriously performed manually. Improvements to aid this task have been proposed as in Redford et al. United States Patent Application 20050120675, Jun. 9, 2005. According to this publication a method of preparing flat articles for sorting includes the steps of: (1) receiving a bundle of flat items to be sorted, the bundle being wrapped with a flexible film such that the film forms an enclosed package of flat items, (2) placing the bundles on a substantially horizontal, substantially frictionless work surface, moving the bundle adjacent at least one film opener, the film opener being automatically activated when the bundle is moved adjacent the film opener, (3) removing the cut film from the flat items, and (4) stacking the unbundled flat items in a cartridge. This is still fundamentally a manual process. 
         [0004]    While automated systems for opening boxes and the like are known, plastic wrapped bundles of flat items like mail are particularly difficult to unwrap by machine. The plastic conforms closely to the contents and an operation of cutting it away with blades or the like would inevitably damage the contents. The present invention attempts to resolve this problem and enable automated unwrapping of plastic wrapped bundles. See for example the system of Porter et al. U.S. Patent Pub. 2009/0113853. In this system content damage is likely during opening, and unwrapping is manual. 
       SUMMARY OF THE INVENTION 
       [0005]    The present invention provides a method and apparatus for automatic bundle transport, positioning, wrapper entry, wrapper opening, wrapper loosening, wrapper removal, and wrapper dunnage takeaway. The wrapper is made from pliable material, thin film or similar material and which can comprise a variety of package types and sizes of mail, media or other items. Additionally the method and apparatus of the invention performs the tasks of wrapper removal and discharge without damaging the item contents within. A bundle unwrapping machine according to the invention includes a conveyor by which bundles are presented to the unwrapping machine for opening. An opening mechanism includes a pair of openers positioned to engage a bundle on opposite sites. The bundle is transported into an opening zone in which it is supported for engagement with the openers. 
         [0006]    According to one aspect of the invention, a machine for removing plastic wrapping from a bundle of flat articles wrapped in plastic includes a conveyor for transporting a wrapped bundle through the machine, a first blade assembly including a pointed blade mounted on a holder provided with a mechanical actuator that slides the blade point first along the surface of the outer face of the bundle, such that the point of the blade pierces the plastic causing the blade to move beneath the plastic wrapping while sliding along the outer surface of one of the flat articles without damaging it, and the blade stretches and tears the plastic as it continues to move beneath the plastic wrapping; and an automated removal and disposal system which separates the torn plastic from the flat articles. In a preferred form a vacuum system includes a vacuum head that applies suction to an outer face of the bundle, drawing the plastic film towards the vacuum head and creating a bulge in the plastic wrap which the blade is positioned to pierce. 
         [0007]    An automated method for removing plastic wrapping from a bundle of flat articles wrapped in plastic or similar sheet material comprises transporting a wrapped bundle on a conveyor into an automated unwrapping machine. The machine slides a first blade assembly including a pointed blade mounted on a holder point first along the surface of the outer face of the bundle, such that the point of the blade pierces the plastic causing the blade to move beneath the plastic wrapping while sliding along the outer surface of one of the flat articles without damaging it. 
         [0008]    continuing movement of the blade continues after piercing of the wrapping to stretch and tear the plastic as it continues to move, and then the torn plastic is automatically separated from the flat articles. 
         [0009]    A wrapper or wrapping according to the invention can be shrink wrap or a bag that encloses the articles completely, but could also be a less than complete covering such as a band. Plastic is the most common material for the wrapper, but paper or other similar material could be used. These and other aspects of the invention are further discussed in the detailed description that follows. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0010]    In the accompanying drawing, wherein like numerals denote like elements: 
           [0011]      FIG. 1  is a simplified perspective view of an unwrapping machine according to the invention in an initial position; 
           [0012]      FIG. 1A  is a schematic diagram of an actuation system for the front end gates shown in  FIG. 1 ; 
           [0013]      FIG. 1B  is a schematic diagram of an actuation system for the rear end grippers shown in  FIG. 1 ; 
           [0014]      FIG. 1C  is a schematic diagram of an actuation system for the upper and lower blade assemblies shown in  FIG. 1 ; 
           [0015]      FIG. 2  is a simplified perspective view of the unwrapping machine of  FIG. 1  in a second position; 
           [0016]      FIG. 3  is a simplified perspective view of the unwrapping machine of  FIG. 1  in a third position; 
           [0017]      FIG. 4  is a simplified perspective view of the unwrapping machine of  FIG. 1  in a fourth position; 
           [0018]      FIG. 5  is a simplified perspective view of the unwrapping machine of  FIG. 1  in a fifth position; 
           [0019]      FIG. 6  is a simplified perspective view of the unwrapping machine of  FIG. 1  in a sixth position; 
           [0020]      FIG. 7  is a simplified perspective view of the unwrapping machine of  FIG. 1  in a seventh position; 
           [0021]      FIG. 7A  is a schematic diagram of an actuation system for moving the wrapper takeaway belts of the unwrapping machine of  FIG. 1 ; and 
           [0022]      FIG. 8  is a side view of engagement between the suction head and the plastic film during piercing of the film according to the invention. 
       
    
    
       [0023]    For like elements referred to by both a number and letter (rod  52 A, rod  52 B etc.), references to plural parts without a letter mean some or all are referred to as indicated by the context. 
       DETAILED DESCRIPTION 
       [0024]    As used herein, an operation that occurs “automatically” is performed by a machine, not a human being. In the description that follows a bundle unwrapping machine  10  according to the invention includes a number of moving parts, many of which are arranged in pairs for simultaneous coordinated movement. For the opener blades, vacuum heads, unwrapping fingers, grippers and the various movable stops, basic actuation components include linear actuators in the form of electric solenoids with extendable rods that are connected to the part to be moved by extension or retraction of the solenoid. Where needed to account for variations in position, the moving parts can be provided with proximity or contact sensors connected to the control system. In some cases a spring may be sufficient to bias the part in the desired position. Examples of these actuation systems are discussed further below. Movement is gradual, that is, at a low enough speed to avoid damage to the bundle. The control system could be a computer or PLC programmed to carry out the steps as described hereafter. The system may or may not need to be reprogrammed for bundles of different types and sizes, or can be provided with sensors that tell the control system process parameters to use. 
         [0025]    The apparatus and method of the invention are described with reference to an example showing the sequence of operations undertaken. Referring to  FIG. 1 , a bundle unwrapping machine  10  according to the invention includes a pair of horizontal, parallel spaced belt conveyors  12 A for transporting a plastic wrapped bundle  14 . A second pair of conveyors  12 B accept bundle  14  from conveyors  12 A and take it further into machine  10  as described below. Bundle  14  is typically flat on opposite top and bottom faces an most often rectangular in shape. It comprises a stack of magazines, catalogs or the like wrapped with a thin plastic film on all sides. In the process of the invention as practiced in a commercial environment, bundles  14  are removed from a pallet and placed on a roller conveyor for manual inspection. Exception bundles such as ones damaged in transit are removed for manual opening. Bundles  14  suitable for automated opening are placed one at a time on conveyors  12 A centered in the widthwise direction so that the underside of the bundle  14  can be accessed from below through the gaps between conveyors  12 A, and between conveyors  12 B. 
         [0026]    As or before bundle  14  moves forward on conveyors  12 A, one or more retractable stop gates  16  are moved into position to stop bundle  14  at a desired forward position for opening. Each gate  16  in this example pivots into and out of position by means of a pivotably mounted linear actuator  17  as shown in  FIG. 1A . However, gates  16  could also be configured to rise and drop vertically. 
         [0027]    One or more grippers  18  are provided to grip the trailing end of bundle  14  once it engages gates  16 . Grippers  18  are L-shaped brackets with an upper horizontal beam  19  and one or more downwardly depending arms or flanges  21 . Each gripper  18  is raised or lowered by means of a first linear actuator  17 A, and the assembly of gripper  18  and actuator  17 A can be moved horizontally by a second linear actuator  17 B ( FIG. 1B ). Grippers  18  start in the up position so that bundle  14  can pass beneath them, are lowered using actuator  17 A, then drawn forward by actuator  17 B so that fingers  21  engage the rear end of bundle  14 . Complete engagement can be detected by means of a pressure sensor  22  that tells the control system that the bundle  14  has been firmly held between gates  16  in front and grippers  18  behind. 
         [0028]    Once bundle  14  is in position and held as described, the operation of opening and removing the outer plastic wrap begins. A vacuum assembly  24 A is suspended above the mid-portion of machine  10  and is preferably centered on bundle  14 . Assembly  24 A may be raised and lowered by any suitable means, such as a linear actuator or an electric pulley operated by the control system. An inverted U-shaped rectangular frame  26  retains a hose  27  which extends through an opening in its top wall. Frame  26  provides a pair of control pads  28  on opposite sides of its bottom edge that move down ahead of a central vacuum head  29  at the end of hose  27 . Pads  28  move into engagement with the upper surface of the bundle  14  before suction is applied, and optionally may be biased by a coil spring  31  that exerts force against the upper surface of frame  26 . 
         [0029]    This engagement acts to control the differential deflection range of the plastic film relative to the surface of the underlying article once vacuum head  29  exerts suction against the plastic beneath it on the upper side of bundle  14 . Differential deflection refers to the difference between the distance the plastic deflects under suction as compared to the distance the underlying item deflects. Unless a sufficient differential is maintained, the first page of the top item of the bundle contents will be pulled up by the suction along with the plastic wrap. Heating as described below helps avoid this problem. With the plastic film held down by pads  28 , suction from vacuum head  29 A causes the plastic wrap to deflect upwardly, creating an upwardly extending bulge in the plastic covering that is positioned for piercing. For this purpose vacuum head  29 A may be lowered into contract with the top of bundle  14  and then raised a short distance once vacuum has been applied. A lower vacuum head  29 B of a second vacuum assembly  24 B engages the underside of bundle  14  in the same manner and is actuated at the same time and controlled in the same manner but in reverse orientation. 
         [0030]    In a preferred embodiment, heat is applied to the area of the plastic wrap that the vacuum head is about to engage. A stream of forced air is suitable, which air is heated to a temperature sufficient to soften the plastic wrap without damage to the underlying contents. This may be done manually or automatically. A temperature of up to 150° F. is usually suitable, causing the plastic wrap to deflect more than the paper of an underlying page or magazine cover. The vacuum aids this process because it draws the heated air directly to the site where the bulge is to be created. 
         [0031]    A pair of upper and lower piercing blade assemblies  32 A and  32 B are provided above and below the space reserved for bundle  14 . As shown in  FIG. 1C , assemblies  32  are each configured for horizontal and vertical movement and may be essentially identical although reverse in orientation relative to each other. Each assembly  32  includes a plastic blade  33  with a pointed tip  34  but lacking a sharp side cutting edge. Blades  33  are made of a smooth surfaced molded plastic, although other materials could be used, including metal. Plastic however is preferred because it is less likely to catch on and damage the contents of the bundle under the plastic wrap. 
         [0032]    Blades  33  are mounted to extend forwardly, flat, slightly rounded side down, from a tang or mounting block  35  that also can be made of plastic. As with other parts that need to move both horizontally and vertically at different times, the blade assemblies  32 A,B each include a vertical linear actuator  36  and a horizontal linear actuator  37 . The plunger of actuator  37  is connected to block  35  so that operation of actuator  37  extends or retracts blade  33 . A frame  38  connects actuator  37  to the operative end (plunger) of actuator  36 . By this means extension or retraction of actuator  36  raises or lowers the assembly of blade  33 , block  35 , actuator  37  and frame  38 . If needed proximity or contact sensors can be provided if needed to prevent over extension of the actuators  36  and  37 , or the cycle timing may be used to control these actuators. Once vacuum head  29 A moves into proximity to the upper surface of bundle  14 , the suction is sufficient to stretch and hold the underlying plastic wrap. A similar event takes place in the underside of bundle  14  using the bottom vacuum head  29 B. Some bundle types have voids therein on the top and bottom that the blades  33  of the invention can readily penetrate, and for bundles of this kind, vacuum assemblies  24 A,  24 B need not be used. 
         [0033]      FIG. 2  shows the bundle  14  in position for piercing the plastic wrap before the blade assemblies start to advance. Both sets of actuators  36  and  37  are then actuated so that blades  33 A and  33 B move to the correct vertical position relative to the bulges created in the plastic wrap, and the blades  33 A,  33 B advance simultaneously towards the upper and lower bulges  40 . Points  34  of the blades readily pierce the plastic wrap and slide along the surface of the topmost flat item in bundle  14 , such as a magazine. The speed of movement of blades  33 A,B is preferably slow enough to minimize the likelihood of damage to the bundle contents, for example from 0.1 m/sec to 10 m/sec, preferably 0.5 m/sec to 2 m/sec. Once the plastic film has been pierced by blades  33 A,B then suction from vacuum assemblies  24 A,  24 B is discontinued and assemblies  24 A,  24 B are moved vertically back to their starting positions. Frames  26  mounted on the vacuum heads  29 A,  29 B move far enough to avoid mechanical interference with parts moving below and above. 
         [0034]      FIG. 2  shows the bundle  14  in position for piercing the plastic wrap before the blade assemblies start to advance. This operation may be timed and pre-programmed based on the known length of bundles  14 , or based on the horizontal spacing, between stop gate  16  and grippers  18 . 
         [0035]    As shown in  FIGS. 2-3 , the sides of blades  33 A,  33 B taper towards the tip  34  to provide plow-like forces that stretch-tear the plastic wrap along the path of movement of each blade  33 A,B. This is not the same as cutting the film with a sharp edge of the blade and has the advantage of creating a wider opening in the top layer of plastic film and stretching the wrapping which relieves hoop stresses, making contents removal easier in later steps.  FIG. 3  shows blades  33 A,  33 B at the front edge of bundle  14 , which has now been partially torn open on top and bottom. The plastic wrap  41  has gathered at the front of block  35  and is stretched away from the contents of the bundle  14 . Block  35  has moved into position below a vertical opener  42 . Opener  42  includes a pin  43  that is lowered by a linear actuator thorough a hole  44  in block  35 . With pin  43  extended through the stretched film at a position in front of the bundle contents, block  35  of blade  33 A is then driven further forward by its horizontal actuator  37  carrying pin  43  with it. For this purpose it may be useful to use a hold and release style of robotic vertical actuator for openers  42  that grips, moves and then releases the head of pin  43 . 
         [0036]    As shown in  FIG. 4 , when the forward travel of pin  43  is completed, it has completely torn through the front end wall of the plastic wrap  41 . Bundle  14  has been opened on three sides and is ready for unwrapping. In this example one vertical opener  42  is provided, and this is sufficient for relatively thin bundles. For thicker bundles, a counterpart opener  42  on the underside, in reverse orientation, is preferred. 
         [0037]    For peeling the wrap away from the underlying contents, an unwrapping system  50  includes two pairs of parallel rods  52 A,  52 B above and  52 C,  52 D below the position where bundle  14  is supported on second conveyors  12 B. In the starting position shown in  FIG. 4 , rods  52  each end in a horizontally extending curved finger  53 . Finger  53  of rod  52 A is mounted on the end of rod  52 A by means of a holder  54  and extends to the left in  FIG. 4  from the left side of machine  10 . Holders  54  are preferably spring loaded to hold the fingers  53  lightly against the surface of the underlying article. Finger  53  of upper rod  52 B is offset horizontally a short distance from rod  52 A and extends to the right in  FIG. 4  from the right side of machine  10 . Finger  53  of lower rod  52 C extends in the same direction as finger  53  of rod  52 A, and finger  53  of lower rod  52 D extends in the same direction as finger  53  of rod  52 B. 
         [0038]    Linear actuators for moving rods  52  are at the ends opposite to the fingers  53 . During the unwrapping cycle rods  52  move to the positions shown in  FIG. 5  so that a pair of fingers  53  are positioned side by side facing in opposite directions above bundle  14  as shown, and below bundle  14  in the same manner. The curved ends of fingers  53  preferably present a convex outer surface that aids fingers  53  in sliding under the open edges  55  of the wrap  41 . Rods  52  are then actuated so that they assume the position shown in  FIG. 6 . Fingers  53  pull edges  55  in opposite directions on both the top and bottom of bundle  14 . By this means forward side portions  56  of wrap  41  are pulled outwardly both right and left in  FIG. 6 . 
         [0039]    The front end of bundle  14  is now free of wrap, and bundle  14  is moved further forward for the final stage of wrap removal shown in  FIG. 7 . To aid in this process pairs of driven vertical belts  60 , such as timing belts are provided on the left and right sides of machine  10 . Each belt has a gripping pad  61  on its outer surface. Belts  60  are arranged in opposing pairs with gripping pads  61  in opposing positions. The left side front belt  60 A faces left side rear belt  60 B, and the same is true of belts  60 C and  60 D on the right. Belts  60  are spaced from each other initially but must move together at the appropriate time so that pads  61  of each pair  60 A,B and  60 C,D come close to one another as shown in  FIG. 7 . One or both belts  60  of a pair can move for this purpose. 
         [0040]    As shown in  FIG. 7A , belts  60  of each pair can be driven by any suitable means such as power rollers  62 . At least one belt is provided with one or more linear actuators  63  for moving the belt assembly horizontally so that its pad  61  comes close to the pad  61  of the belt  60  facing it. By this means wrap  41  is gripped on both sides by two pairs of pads  61 . 
         [0041]    With wrap  41  held in this manner, a pair of underlying forward belt conveyors  12 C similar to conveyors  12 B move the contents  70  of bundle  14  forward into contact with a stop or stops  65  at the front end of machine  10 . Wrap  41  held on both sides by pairs of pads  61  is removed from contents  70  as contents  70  moves forward. Once stop  65  is contacted, it is possible then to drive each of belts  60  in tandem with each other so that pads  61  move out of contact by passing around the next belt pulley, allowing wrap  41  to drop free into a collection container beneath machine  10 . Contents  70  can then be removed manually or continue to be conveyed on an extension of conveyor  12 C upon removal of stop  65 . All moving parts are then reset for the next unwrapping cycle back tot the positions shown in  FIG. 1  as another bundle  14  is presented for unwrapping. Actuators  36 ,  37  are used to return blades  33 A,  33 B to their starting positions when the tearing stroke is completed. 
         [0042]    The described system thus provides for fully automated unwrapping of a plastic wrapped bundle of flat items such as magazines, catalogs or the like. Unlike known systems for opening boxes or cartons, the system of the invention does not use knives or cutting blades to open packaging. The blades of the present invention are configured to pierce the plastic film with a thrusting motion, not cut it along a line with a sharp edge or the like. The latter approach is not suitable for automated opening of plastic wrapped bundles of flat mail which could be easily damaged by a metal knife or razor blade. 
         [0043]    It will be understood that the invention can be employed in other configurations and environments. For example, for better control of bundles  14 , both upper and lower drive belts can be provided which clamp the bundle. a) The throat of the upper/lower drive belts can be configured to spread to a distance adequate to accept various wrapped bundle heights. Position and dimension sensors may be deployed as needed so that a computerized control system can adjust the positions of moving parts to accommodate bundles of different sizes. And detectors such as photocells can be used to indicate when the bundle has reached a position at which a further operation should begin. The vacuum system may be provided with a valve for turning suction off and on when required and vacuum powered suction cups may be used to assist in the removal of the plastic wrap, such as to hold it when the bundle contents are removed. It is also possible, although difficult, to omit actuators for moving the blades along the outside of the bundle and instead hold the blades stationary while moving the bundle to producing the relative motion for piercing the wrapping. These and other modifications are within the scope of the appended claims.