Abstract:
A method for conveying a package to a wrap station of a package wrapping machine involves the steps of providing a conveying system for moving the package to the wrap station, the conveying system being selectively adjustable for varying a lateral position of a package; sensing a lateral position of the package as it travels along the conveying system; comparing the sensed lateral position of the package with a desired lateral position of the package; and based upon the comparison, adjusting the conveying system to place the package in the desired lateral position.

Description:
This application claims the benefit of U.S. provisional application No. 60/253,844 filed Nov. 29, 2000. 
    
    
     TECHNICAL FIELD 
     This application relates generally to package wrapping machines and, more particularly, to a system and method for positioning packages prior to entering a wrap location so that the package can be correctly wrapped. 
     BACKGROUND 
     Food product wrapping machines typically feed a trayed food product or package, such a ground meat or produce, to a wrap station at which a film is drawn out over the trayed food package, wrapped around the package, and passed to a heat sealing station. If a package is not properly positioned when it reaches the wrap station, a less than desirable wrap may result. In the past, machines have used arms along a defined conveying path that contact the sides of the package and causing off-center packages to be urged toward a centered position. 
     It would be desirable to provide a system and method for positioning food packages as they move along a conveying path that involves less direct contact with the food package. 
     SUMMARY 
     In one aspect, a package wrapping machine for wrapping packages includes a wrap station at which packages are wrapped and a film dispensing station for drawing out film over a package at the wrap station. A conveying system for moving packages along a defined path to the wrap station includes a first conveyor along a first portion of the defined path and a second conveyor along a second portion of the defined path. The first conveyor has an output end which feeds to an input end of the second conveyor for feeding a package traveling along the first conveyor to the second conveyor. At least one sensor is provided for determining a lateral position of a package moving along the first conveyor. At least one actuator is provided for controlling a relative lateral position of the output end of the first conveyor to the input end of the second conveyor. A controller receives signals from the sensor and controls the actuator, wherein, for a given package moving along the first conveyor, and based upon signals received from the sensor, the controller effects movement of the actuator to define a relative position between the output end of the first conveyor and the input end of the second conveyor to place the given package in a desired lateral position on the second conveyor. 
     In another aspect, a method for conveying a package to a wrap station of a package wrapping machine involves the steps of providing a conveying system for moving the package to the wrap station, the conveying system being selectively adjustable for varying a lateral position of a package traveling along the conveying system; sensing a lateral position of the package; comparing the sensed lateral position of the package with a desired lateral position of the package; and based upon the comparison, adjusting the conveying system to place the package in the desired lateral position. 
     In yet another aspect, a package wrapping machine includes an infeed station and a wrap station. A conveying system is configured to move the packages along a path from the infeed station to the wrap station, the conveying system being selectively adjustable to individually vary a lateral position of at least certain of the packages traveling along the path. A sensor is configured to detect a lateral position. A controller is configured to receive signals from the sensor and to control the selective adjustment of the conveying system to individually position at least certain of the packages in a desired position when they reach the wrap station. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  illustrates a top view of a first state of a package positioning system in a package wrapping machine according to various embodiments of the present invention; 
         FIG. 2  illustrates a top view of a second state of one embodiment of a package positioning system in a package wrapping machine; 
         FIG. 3  illustrates a top view of a second state of another embodiment of a package positioning system in a package wrapping machine; 
         FIG. 4  illustrates a top view of another embodiment of a package positioning system in a package wrapping machine; 
         FIGS. 5A-5B  illustrate side views of a package positioning system in a package wrapping machine according to various embodiments of the present invention; 
         FIGS. 6A-6B  illustrate top views of a first and second state of a package positioning system in a package wrapping machine according to another embodiment of the present invention; 
         FIG. 6C  illustrates a right side elevation view of  FIG. 6A ; 
         FIG. 7  shows a top view of a package at a wrap station; and 
         FIG. 8  shows an exemplary prior art package wrapping machine. 
     
    
    
     DETAILED DESCRIPTION 
     Reference is made to U.S. Pat. No. 5,144,787, which discloses an exemplary food product package wrapping machine  100  that wraps meat, produce, or the like, in stretchable, heat-sealable film, an exemplary view of which is seen in  FIG. 8  of the present application. The entire teachings of this patent are hereby incorporated by reference. Generally, a package  102  is fed into the machine  100  at an infeed station  104  and is carried along a package entryway  110  by a pusher  108  to an elevator  118 . A raised position of the elevator  118  may at least partially define a wrap station  106 . Before or when the package  102  reaches the wrap station  106 , a film gripper  112  and side-clamps  116  cooperate to draw an appropriate amount of film from a source roll  111 B out over the wrap station  106  and to stretch the film in a desired manner. The amount of drawn film is determined by a height of the package  102 . The elevator  118  then moves the package  102  up through a plane of the stretched film and the film is wrapped around the package  102 . A hold down arm  120  holds the wrapped film while the package  102  is being pushed by package pusher  130  toward side under folders  128 . Finally, a heat sealing conveyor  132  receives and seals the wrapped film around the package  102  and brings the package  102  to a weigh station  134 . Other wrapping machine variations having different wrapping station configurations could also be utilized. 
     In one embodiment, a conveying system  10  is used to convey a package  12  to a wrap station, such as station  106 , where a portion of the conveying system  10  is selectively adjustable to vary a lateral position of the package  12  to center the package, or to locate the package to some other desired lateral position, before the package reaches the wrap station.  FIG. 7  shows a top view of a package  12  in a desired centered, lateral position relative to a film dispensing axis  140 , where film is drawn out over the package  12  in the direction of arrows  142 . 
       FIG. 1  illustrates a conveying system  10  in a first state. The first state may be a normal state before any part of the conveying system  10  is moved, and a second state may be an actuated state during which the conveying system  10  is moved to position the package  12 . The package  12 , which moves in the direction of arrow A, is positioned on a conveyor  14 , which may be comprised of spaced apart belts  16 . A defined path of travel of the package  12  may comprise feeding the package to an input of the conveyor  14 , feeding the package  12  at an output end  28  of the conveyor  14  to an input end  30  of a conveyor  18 , which may also be comprised of spaced apart belts  19 , and feeding the package  12  to an elevator area  20 . The elevator may be a receiving platform that is vertically movable and which at least partially defines the wrap station similar to wrap station  106  in the shown in FIG.  7 . The conveying system  10  may include a sensor  22  positioned adjacent the first conveyor  14  and configured to produce signals indicative of a lateral position of the package  12 . As used herein, the term “lateral position” of the package is intended to mean a position along the width of the conveying system  10 , that is a position relative to an axis transverse to the direction of travel A. It is recognized that in some embodiments sensor  22  could also be positioned upstream of conveyor  14 , for example at the location where an operator initially places the package on the machine. The signals may be received by controller  24 , which compares a sensed lateral position of the package  12  to a desired lateral position of the package  12  and responsively outputs signals to an actuator  26  to effect adjustment of the actuator  26  to move the output end  28  of the conveyor  14  so as to place the package  12  in the desired lateral position when transferred to conveyor  18 . For example, in one embodiment the controller  24  receives the signals from the sensor  22  and produces a value correlated to the sensed lateral position signals and compares the correlated value to a desired lateral position value, determining a difference between the two. If the difference is above or below a threshold level, the controller  24  then transmits a signal to the actuator  26 . Once the actuator  26  receives the signal from the controller  24  it moves the output end  28  of the conveyor  14  relative to the input end  30  of the conveyor  18 . 
     The actuator  26  may be configured as a motor and screw thread device with feedback or a stepper motor with feedback. In alternative embodiments, the actuator  26  can be configured as a pneumatic or hydraulic rod and cylinder type arrangement. In still further embodiments, the actuator  26  can be a cam mechanism. It is to be appreciated that the use of other actuator devices as is likewise contemplated, such as solenoid type displacement members. 
     The sensor  22  may comprise an array of optical sensors, such as infrared or visible light sensors that utilize make or break technology to determine the locations of the side edges of the package, and thus the lateral position of the package. In alternative embodiments, the sensor  22  can comprise an array of mechanical switches triggered by contact with the bottom of the package  12 . It is to be appreciated that the use of other sensor devices is likewise contemplated. 
       FIG. 2  shows actuation of the conveying system  10  into a second state according to one embodiment. The second state is initiated when the controller  24  determines the package  12  is not in the desired lateral position, which may be a centered position. In this embodiment the actuator  26  may be configured to move the output end  28  of the conveyor  14  laterally in the direction of arrow B and linearly along an axis  36 , while the input end of the conveyor  14  remains stationary as shown. The output end  28  could also be moved in a direction opposite arrow B if needed. The input end  30  of conveyor  18  remains stationary. Thus, the package  12  rotatably slides relative to the belts  16  and is moved to a desired position, which may be a centered position, on the belts  19  of conveyor  18 . 
       FIG. 3  shows actuation of the conveying system  10  into a second state according to another embodiment. In this embodiment the actuator  26  may be configured to move the output end  28  of the conveyor  14  laterally in the direction of arrow B and pivoting around pivot point  38 , while the input end of conveyor  14  also pivots about point  38  as shown. The output end  28  could also be moved in a direction opposite arrow B if needed. The input end  30  of conveyor  18  remains stationary. Thus, the package  12  is moved to a desired position, which may be a centered position, on the belts  19  of conveyor  18 . 
       FIG. 4  shows another embodiment in which two actuators  26  are configured to move the output end  28  and an input end  40  of the conveyor  14  laterally in the direction of arrow B along axes  36  and  42 , respectively. The input end  30  of conveyor  18  remains stationary. Thus, the package  12  is moved to a desired position, which may be a centered position, on the belts  19  of conveyor  18 . 
     Turning now to  FIGS. 5A and 5B , a side view of the conveying system  10  according to two embodiments is shown. In particular,  FIG. 5A  represents an embodiment such as those shown in  FIGS. 1-3 . In  FIG. 5B , a configuration of a conveying system  10 ′ is shown where the actuator  26  is located adjacent the input end  30  of the conveyor  18 . Thus, when the controller  24  receives the signal from the sensor  22  that the package  12  is not in the desired lateral position, the controller  24  transmits a signal to the actuator  26  that causes it to move the input end  30  of conveyor  18  laterally in the direction of arrow B ( FIGS. 2-3 ) along axis  44  (FIG.  1 ), while the output end  28  of conveyor  14  remains stationary. Hence, the package  12  leaves conveyor  14  and enters conveyor  18  at a desired, controlled lateral position on the belts  19 . The conveyor  18  can then be moved back to its normal position so the package is at a desired lateral position when it reaches the downstream wrap station. 
     With reference to  FIGS. 6A-6C , another embodiment of a conveying system  200  is shown. Similar elements contain similar reference numbers to  FIGS. 1-5B , but have a 200 series designation. For example a sensor  222  adjacent a conveyor  218  is similar to the sensor  22 .  FIG. 6A  shows a first state of the conveying system  200 , in which the conveyor  218  is comprised of pivotally connected first, second, and third conveying sections  218 A-C, respectively, which pivot around pivot devices  246  and are interconnected through use of connecting devices  248 . The pivoting devices  246  may be pins or bolts and the connecting devices  248  may be metallic, plastic, or elastomer hinges, or the like, that connect the conveying sections  218 A-C, respectively, in a pivoting manner. A first set of belts  217  conveys the package (not shown for convenience) from the first conveying section  218 A to the second conveying section  218 B, and a second set of belts  219  conveys the package from the second conveying section  218 B to the exit end of conveyor  128  which may feed an elevator area or another conveyor  220 , which includes a set of belts  221 . The conveying system  200  may also comprise a weighing area  254  adjacent the sensor  222 . The weighing area  254  may include portions extend upward between the belts  217  for resting the package thereon, and the belts may include spaced pushers for extending therefrom to move the packages off of the weighing area. 
       FIG. 6B  shows a second state of the conveying system  200 . The second state is initiated when the controller  224  determines the package (not shown) is not in a desired lateral position, which may be a centered position. When this occurs, a signal is sent from the controller  224  to the actuator  226  to move an output end  250  of the conveyor  218  in the direction of arrow C, while an input end  252  of the conveyor  220  remains stationary. When the actuator  226  moves the output end  250 , the second conveying section  218 B pivots around pivot device  246  relative to the first conveying section  218 A in the direction of arrow D, while the first section  218 A remains stationary. Also, when the actuator  226  moves the output end  250 , the second section  218 B pivots around pivot device  246  relative to the third conveying section  218 C in the direction of arrow E, while the third section  218 C moves in the direction of arrow C. Such controlled movement of conveying system  200  places the package in a desired lateral position as it leaves conveying section  218 E. 
     Although the invention has been described and illustrated in detail it is to be clearly understood that the same is intended by way of illustration and example only and is not intended to be taken by way of limitation. Other changes and modifications could be made without departing from the invention. For example, while various embodiments of conveying systems are shown and described herein, other variations could be utilized, such as the conveying system shown and described in U.S. Pat. No. 5,238,099, the entire specification of which is hereby incorporated by reference. Additionally, while the subject system is described primarily with reference to the package wrapping machine shown in  FIG. 8 , it is recognized that many variations of package wrapping machines are possible, such as that shown in U.S. Pat. No. 6,170,236B1. Still further, while various embodiments described herein utilize first and second conveyors back to back, conveying systems having only a single conveyor that is laterally adjusted are also contemplated. 
     Still further, it is recognized that in some embodiments the package elevator that raises the packages up into the drawn out film may be considered part of the conveying system. In such embodiments the position of the package elevator could be laterally adjusted to provide desired positioning of the package. In one variation of this type, the lateral position of package elevator could be adjusted so that each package is received on the elevator in a desired, for example centered, position on the elevator, and the elevator could then be moved laterally back to its own centered position relative to the film dispensing axis prior to, or as the elevator is raised upward. In another variation, the elevator could always be located at the same position to receive packages, in which case some packages would be off-center relative to the elevator, and then the lateral position of the elevator could be adjusted to center the package relative to the film dispensing axis as the elevator is raised upward. In either case, the elevator could be mounted to a frame that is movable along at least one guide rod. In one case the guide rod could be part of a screw type drive engaging corresponding threads on the elevator frame and rotated to adjust the lateral position of the elevator. In another case the frame could simply slide along the rod and a separate actuator could be used to push/pull the frame along the rod. 
     Another contemplated embodiment could provide a conveyor output end in which only the conveyor roller is moved laterally along a guide rod by an actuator, such that the side rails of the conveyor might not be moved. An actuator could be provided to move the conveyor roller. 
     Accordingly, the spirit and scope of the invention are to be limited only by the terms of the appended claims.