Patent Document

This application claims the benefit of U.S. Provisional Patent Application 60/315,421 filed Aug. 28, 2001. 
    
    
     TECHNICAL FIELD 
     This invention relates generally to stretch wrapping apparatus and, more particularly, to a method for automatically changing the rolls of stretchable film during continuous operation. 
     BACKGROUND OF THE INVENTION 
     Since its development in the 1970&#39;s stretched plastic film has been used to secure cartons and bags on pallets for shipment. Films are stretched in a carriage and wrapped around the stacked product on a pallet. Two basic designs of wrapping apparatus are in use. The pallet may be placed on a turntable and the stretchable film dispensed from a stationary roll dispenser (rotary arm wrapper). In the alternative, the load may be stationary and the film wrapped using a rotating film dispenser (rotary arm wrapper). Turntable stretch wrapping apparatus is suitable for small volume production whereas the rotary arm wrapper may be integrated into a conveyor system and is more suitable for high volume production. 
     Regardless of the design of a stretch wrap packaging machine it has heretofore been necessary to manually reload the film roll when the roll has been consumed or, in the off chance the film breaks during wrapping. In most applications a roll of film is consumed at intervals of two to three hours and someone must be designated to monitor the wrapping machine while being committed to other tasks. In an automated environment, the production line would become stopped until someone manually reloaded the film. 
     U.S. Pat. No. 6,082,081 to Mucha discloses a pre-stretched roller assembly of a clam shell-type design which opens about a hinge and facilitates the loading of a stretch film. This film stretching apparatus is the preferred carriage assembly for use in an automated system for loading replacement film rolls. 
     BRIEF SUMMARY OF THE INVENTION 
     It is the first objective of this invention to provide a completely automated system for replacing rolls of stretch film used in a carriage assembly for stretch wrapping of product on pallet and other shipping forms. 
     It is a second objective of this invention to provide a means for automatically responding to broken or torn film during wrapping with minimal stoppage of production lines. 
     It is yet another objective of this invention to facilitate unmanned operation of a packaging line with minimal attention requirements from production workers. 
     These and other objectives of the invention are obtained by providing an automatic changer for a stretch film having a turntable, a plurality of film mandrels removably attached to the turntable, an elevator, a means for opening a film delivery system prestretch roller assembly, a means for engaging the film mandrels into the roller assembly, a means for anchoring the end of the film separate from the roller assembly, a means for anchoring one end of the film away from the mandrel to provide a stationary source and a means for moving the turntable toward and away from the prestretched roller assembly. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a perspective view of the base of an automatic changer and associated to the components. 
     FIG. 2 is a plan view of the base shown in FIG.  1 . 
     FIG. 3 is a perspective view of the automatic changer of FIG. 1 showing elevated ancillary components. 
     FIG. 4 illustrates the relationship of the automatic changer to the stretch film wrapping apparatus. 
     FIG. 5 shows the film wrapping carriage in perspective view. 
     FIG. 6 shows the film wrapping carriage in plan view. 
     FIG. 7A shows the film wrapping carriage in the open position. 
     FIG. 7B shows the film wrapping carriage in the closed position. 
     FIGS. 8A and 8B show a mechanism for attaching a film mandrel to a carriage. 
    
    
     DETAILED DESCRIPTION 
     This invention provides a method for automating the loading of stretch wrap film into a commercially available prestretch roller assembly such as that disclosed in U.S. Pat. No. 6,082,081. Numerous stretchable films are commercially available and the specific chemical composition and source of the film are not critical to this invention. 
     FIG. 1 is a perspective view of the base and associated components of the film changer of this invention. A base  1  supports the operative components and is anchored to a floor using conventional angle iron brackets shown as element  3 . A turntable in the form of an oval raceway has a first sprocket  5  and a second sprocket  7  around which are wound an upper endless chain  9  and a lower endless chain  9 ′. The oval shape of the raceway is not critical and a circular, rectangular or other pathway may be used dependant on space limitations and needed capacity. Traveling on the chains are film mandrels  11  supported upon a carrier  13  which are, in turn, supported on the endless chains. Film mandrels, to be discussed infra, carry rolls of film typically wrapped around a core which may be cardboard or plastic. A holder  15  extended from carrier  13  holds the extended end of the stretch film. The film is extended so that a film drawing assembly  17  having clamp  18  may be used to pull a length of film from the roll prior to wrapping of the film around a stacked pallet. Element  19  is a film lift elevator guide which is employed to guide lift  16 , raise the film into a film delivery carriage for wrapping and to remove empty rolls or torn rolls of film. 
     FIG. 2 is a plan view of the base shown in FIG.  1 . In plan view, it may be seen that the base  1  travels on rails  21  under the control of the cylinder  23  mounted upon the base  1  and the floor mounting assembly  3 . The movement facilitates approach and withdraw from a film delivery system. 
     FIG. 3 is a perspective view of the base showing also superstructural components necessary to insert the film into a film delivery system. Element  31  is a means for opening a film delivery system including a pre-stretched roller assembly. As illustrated, cradle opening hook  32  under the control of a pneumatic cylinder  33 ,  34 ′ extends and retracts the device. As shown, the hook is also under control of a second cylinder  34  so that it may be raised and lowered. Alternatively, a magnetic or suction device may be used in lieu of a hook and the worm gear and stepper motor may be substituted for pneumatic cylinders. 
     Element  35  is an extensible device (robotic arm) employed to lock and unlock a mandrel into a stretch wrap film holder on a film delivery system. The device is extensible in the same manner as is the arm  31  and the end is adapted to a specific mandrel mounting configuration as will be discussed infra. 
     Element  36  is an extensible arm which is used to fix or hold a film delivery system carriage assembly while the mandrel and stretchable film are being loaded into place (or unloaded). Pneumatic, hydraulic or electric controls are suitable means for extending all of these devices although pneumatic is preferred. 
     FIG. 4 illustrates the relationship of the automatic changer of this invention to a stretch film delivery system. The stretch film delivery system as illustrated is that which is available from Orion Packaging, TM Montreal Canada and is exemplary of stretch wrap systems which are compatible with conveyor systems. A framework  41  which has a substantially rectangular plan view supports a rotary frame assembly  43  having a swing arm  45  and a suspended ladder bar  47  carrying the film carriage  49 . 
     FIG. 5 shows a perspective view of a stretch film carriage such as that disclosed in U.S. Pat. No. 6,082,081. The assembly  49  has a brace of idle rollers  63  and  63 ′ and pre-stretch roller cover  67 . As illustrated, cover  67  has a handle  68  engageable with hook  32 . Alternative embodiments may provide different methods for engagement of the opening apparatus with the roller cover may include, inter alia, a magnetic disc such as might be used with an alumentium or plastic cover. Various forms of lock and key arrangements are a matter of design choice. Mandrel  69  which carries the stretch film is suspended from the cradle assembly. 
     FIG. 6 is a plan view of the film carriage and illustrates the location of the first stretch roller  71  and the second stretch roller  73 , the edge attachment assembly  75  and a drive motor  74 . 
     FIG. 7 shows the film carriage assembly from U.S. Pat. No. 6,082,081 in the opened position with film  77  positioned between stretch and idle rollers. When roller cover  67  is closed the film is in frictional engagement between the stretch rollers and may be stretched at any predetermined ratio up to and including 300%. While the early frame assembly  43  is being spun around a stacked pallet on a conveyor line within the frame assembly  41 . 
     FIG. 8A shows a mandrel  81  in place on mounting bracket  83  attached to the carriage. FIG. 8B shows the actuation method whereby the mandrel is attached. Shaft  85  extends downwardly from the bracket and serves as an axle. Push rod  87  actuates latch  89  under the control of lever  91  articulated on hinge pin  93  to open and close latches  89 . Spring  95  returns to lever  91  and latch  89  to the locked position and hold the mandrel  81  in place when latch  89  engages receiver  97  of the mandrel. The lever is urged into the open position by actuation of locked controller  32 . 
     OPERATION 
     The automatic film roll changer is controlled by a CPU, preferably by the same CPU which controls the wrapping carriage. The sequence starts with the loading of the carriage. The carriage  49  parks in front of elevator  16 . Frame  1  moves across rails  21  at the urging of pneumatic or hydraulic cylinder  23  or an equivalent device such as a worm gear and gimbal nut. When in position, hook  32  or equivalent means retracts cover  67  by pulling back on handle  68  to separate rollers.  63 ,  65 ,  71  and  73  while brace  36 , in the extended position, stabilizes the carriage. Mandrel lock controller  35  actuates lever  91 . 
     Travel clamp  18  grasps film from film end holder  15  and extends the film away from the carriage. 
     Film draw assembly  17  clamps and extends an end of the film held by film end holder  15 . Elevator lift  16  engages mandrel carrier  13  to raise the film mandrel  11  until it engages shaft  85  and is locked in place by mandrel lock controller  35 . Roller cradle assembly  61  is closed by opener  31 . The extended film end is clasped by film tail treatment device  51  and released by the draw assembly  18 . The elevator returns to its lowered position and the base  1  is retracted by cylinder  23 . 
     The carriage is now loaded and may be used to wrap the next load on a pallet. 
     When the film breaks during wrapping or when the roll of film has been exhausted, the film carriage returns to the film loading position. 
     The film roll changer base is moved toward the carriage, the elevator lifts an empty carrier  13  under the empty mandrel which is released by controller  35  and lowered back to the turntable. The base  1  is withdrawn and the turntable rotated to the next full roll and loading sequence begins again. The turntable steps around one position and the aforementioned loading sequence is commenced. 
     The sequence of events may be controlled by a CPU either on the unit or remotely. Commercially available “personal computers” are sufficient although a dedicated programmable controller is preferred. 
     The invention has been illustrated and described in a preferred embodiment but any modification substitution or additions may be made as apparent to any person skilled in the art without departing from the scope of the invention and the appended claims.

Technology Category: 7