Abstract:
A wrapping apparatus including parallel conveyors for moving loaded pallets to wrapping areas of the conveyors, a mobile wrapping machine on wheels, a guide for maintaining the wrapping machine along a path, position sensors for detecting loaded pallets at loading areas, and a computer control for directing the mobile wrapping machine to wrap the loaded pallets on a prioritized basis. The invention is extremely mobile, and is computer controlled to wrap the pallets without need for an operator.

Description:
FIELD 
     This invention relates to the wrapping of multiple packages stacked on a pallet, and more particularly, to a total wrapping system in which a mobile wrapping machine is controlled and directed to perform its functions by remote control. 
     BACKGROUND 
     The common method of wrapping stacked packages on pallets, such as with stretch plastic film or netting, is by moving the pallet and its load of packages with a fork lift truck to a stationary wrapping machine. The wrapping machine then wraps the load of packages and the wrapped load and pallet is removed from the stationary wrapping machine by a fork lift truck in order to make room for the next loaded pallet to be brought to the wrapping machine. This method is relatively slow, and is quite labor-intensive because many fork lift trucks and truck operators are required in order to supply and remove loaded pallets to and from the wrapping machine in a timely manner in order for the wrapping machine to be operated in any way approaching an efficient manner. 
     An alternative approach is suggested in U.S. Pat. No. 5,140,795, which is hereby incorporated by reference, in which a wrapping machine is suspended from an overhead beam, and the machine is controlled by hard-wire controls and sliding electrical contacts along the beam so as to move along the elevated beam to multiple wrapping stations as determined by an operator. While this approach is an improvement, the suspension system requires substantial structural requirements, and the sliding contacts may give false signals, and the beam may interfere with other structures such as the overhead conveyors used in some installations. 
     SUMMARY 
     The present invention solves all of the above-indicated problems by maintaining the wrapping machine on the ground, but making it extremely mobile and responsive to wireless remote control such as by radio controls, or other wireless controls such as, for example, infra red or laser beams. In addition, the wrapping machine of the present system is completely computer controlled so that the wrapping machine wraps the pallets on a prioritized basis without the need for an operator. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a simplified side elevational view, partly in cross-section of a wrapping machine wrapping a load on a pallet which is positioned by a conveyor at a designated wrapping station; 
     FIG. 2 is a simplified and schematic top view of a plurality of loaded pallets on parallel conveyors with the wrapping machine in the process of wrapping one loaded pallet which has been designated to be wrapped in its associated wrapping station; and 
     FIG. 3 is a schematic electrical diagram illustrating the essential components of the computerized control system. 
    
    
     DETAILED DESCRIPTION 
     Referring first to FIG. 1, numeral  10  generally designates a wrapping machine which includes a lower or base portion  12 , a vertical support stand  14 , and a horizontal main frame  16 . Frame  16  houses a motor (not shown) which rotates swing arm  18  about load  20  stacked on pallet  22 . A depending downright  24  is connected at its upper end to swing arm  18 . The lower end of downright  24  carries a film carriage  26 . Carriage  26  contains a roll of wrapping material and dispensing mechanism from which a sheet of wrapping material  28 , such as stretch plastic film or netting, extends and is wrapped about load  20  as arm  18  rotates in the known manner, per se, of wrapping palletized loads. 
     The wrapping machine, per se, as described thus far, may comprise components of conventional wrapping machines such that further, detailed description is unnecessary to those skilled in the wrapping art. However, at this point it will be noted that machine  10  is not suspended from an overhead beam, nor does machine  10  have stationary support legs as required by conventional, stationary wrapping machines. Instead, it has been discovered that the most efficient and reliable operation is achieved when machine  10  rides along the floor  30  on wheels  32  mounted on axes  34  mounted in base portion  12 . The number and relative placement of the wheels is not critical so long as they permit linear movement of base  12 , and the entire machine  10 , along a linear track  36 . It has been found that the preferred form of track is a mechanical one such as U-shaped track  36  recessed into the floor  30  and including horizontal flanges  37  which are engaged by wheels  32  so as to maintain a highly level surface along the length of the track. A track following guide or fin  38  is mounted in base  12 , and preferably between wheels  32 , so as to maintain the movement of the wrapping machine along the linear length of track  36  as also shown in FIG.  2 . 
     Because horizontal frame  16 , swing arm  18  and downright support  24  create an unbalance of weight relative to support stand  14  and wheels  32  in the absence of stationary support legs, an upper guide mechanism  40  is provided. Such guide mechanism may take various forms such as, for example, a plurality of horizontal supports  41  which are connected to a plurality of vertical conveyor supports  43 . In those installations where vertical conveyor supports, or other vertical supports are not present, lower portions  43 A are not present, and upper portions  43 B may be connected to conventional supports or any other available overhead structures. Horizontal supports  41  perform a dual function in that they support a horizontally extending bus bar  45  and a horizontally extending guide bar  48 . Horizontal bus bar  45  is engaged by electrical brushes  49  carried by a support arm  52  connected to a horizontal frame member  16 A which is connected to frame  16  by connector  16 B. In this manner, electrical power is continuously supplied to machine  10  as it travels horizontally along track  36 . In addition, two or more guide wheels  54 A and  54 B are carried by frame member  16 A such that they engage the top and side surfaces of guide bar  48  and thereby stabilize the upper portion of machine  10  as it travels along the floor. 
     It will be understood that base  12  of the wrapping machine contains a reversible electric motor, a suitable gear drive connected to wheels  32  and an encoder connected to the drive shaft which monitors the position of the machine along track  36 . Thus, wrapping machine  10  may be positioned to wrap such palletized loads as are prioritized by the automatic computer control system described hereafter. For this purpose, machine  10  includes remote actuated controls in housing  13 , including a remote computer controller  14 . Such remote controls may also include a receiver  15 , which may be an antenna if radio controlled, or other sensor for receiving other remote signals as previously described. It will be understood that the above-described motor, gear drive and encoder, as well as the remote control receiver, are all commercially available components, per se, such that further detailed description is not necessary for one skilled in the art to fully understand. 
     In order to further insure the accurate positioning of the wrapping machine along track  36 , base portion  12  preferably carries a photo cell  56  which co-acts with reflectors  58  mounted at the end of each conveyor so that the reflected signal confirms that the machine is directly in front of the selected conveyor, as will be more fully described hereafter. 
     FIG. 2 schematically illustrates a simplified wrapping system of the present invention which includes at least one wrapping machine  10 , and a plurality of parallel conveyor lines such as, for example,  40 A,  40 B,  40 C and  40 D. Of course, it will be understood that one machine  10  may service many more than four conveyor lines. Conveyor lines  40 A- 40 D extend from a loading area  42  toward respective wrapping stations  44 A- 44 D. The conveyors, per se, are conventional conveyors and may include rollers or chains  46  riding over wear strips  47  as shown on line  40 A and as is well known per se. The conveyor chains move the loaded pallets from loading area  42  to the respective wrapping stations  44 A- 44 D. 
     As illustrated in FIG. 2, for example, four loaded pallets  50 A- 50 D are located at a given point in time along conveyors  40 A- 40 D. In this example, conveyor  40 A is shown as having no loaded pallets at this time. Conveyor  40 B is shown as having one loaded pallet  50 A, which is in its respective wrapping station  44 B, while conveyor  40 D has one loaded pallet  50 B approaching wrapping station  44 D, and conveyor  40 C is shown as having two loaded pallets; i.e., a first loaded pallet  50 C positioned in wrapping station  44 C, and a second loaded pallet  50 D approaching wrapping station  44 C. 
     Still referring to FIG. 2, it will be noted that a plurality of position sensors  52  are mounted on the conveyors along their lengths. Sensors  52  may comprise proximity switches, mechanically operated micro-switches, photo cells or any type of sensor which is capable of sensing the presence/absence of a loaded pallet at its position. As further illustrated in FIG. 3, each of sensors  52  is connected by wires  56  through a DH-485 Network  58  to master control computer (MCC)  60 . Therefore, it will be understood that the positions of all loaded pallets along each conveyor is sensed and known, and is continuously transmitted from sensors  52  to MCC  60  which will now be further described as follows. 
     Referring to FIG. 3, MCC  60  receives signals from each of position sensors  52  such that the presence or absence of loaded pallets at the respective wrapping areas, and at least two positions upstream thereof, is continuously fed to and known by MCC  60 . Based upon this continuous input of the positions of the loaded pallets, the MCC sends signals to the controls  13  of the mobile wrapping machine which directs the machine to the next wrapping area based upon the relative activity of each conveyor line. For example, as illustrated in FIG. 2, machine  10  has been directed to conveyor  40 C to wrap pallet  50 C because machine  10  has received the following signals: (1) a first signal that pallet  50 C is in its wrapping area, and (2) that a second pallet  50 D is approaching the same wrapping area. The combination of these two signals takes precedence over the signals from conveyors  40 A and  40 D which indicate that no loaded pallet is in their respective wrapping areas  44 A or  44 D. In addition, the two signals from conveyor  40 C take precedence over the single signal from conveyor area  44 B regarding loaded pallet  50 A because no other loaded pallet is detected as approaching this wrapping area. Accordingly, it will be understood that the system of the present invention continuously prioritizes the commands to the mobile wrapping machine so that the machine is directed to wrap the loaded pallets in the order of the activity level on each conveyor; i.e., the presence of loaded pallets in their respective wrapping areas as well as the number of loaded pallets on each conveyor which are immediately upstream of and approaching the respective wrapping area. 
     In addition to sensing the positions of the loaded pallets, and the position of the mobile wrapping machine, the present invention detects the height of each loaded pallet to be wrapped by one or more photo cells  64  as shown in FIG.  1 . If the height of the load on the pallet is greater than a pre-programmed amount, then remote computer controller  14  located in housing  13  transmits a signal to the wrapping controls in housing  13  to cause the wrapping machine to double, triple or quadruple wrap the mid portion of the load in order to substantially increase the vertical stability of the load. 
     The preferred embodiment of the invention also provides an indicator light  66  adjacent each loading area, and the indicator lights an also controlled by the MCC. MCC  60  is programmed to turn on a light, in steady illumination, at the next prioritized wrapping area where a load is to be wrapped. This lets the fork truck operators know where the car is headed next. In addition, when the load has been wrapped, as signaled by controls  13  transmitting to the MCC, then the light is made to flash on and off. This flashing light alerts the fork truck operator that this wrapped load has priority to be removed as another loaded pallet is approaching the same wrapping area. 
     With regard to the details of the controls, all individual components are individually commercially available and will be apparent to those skilled in the computer control and radio transmitting art. For example, the MCC may be a pentium PC running a Data Acquisition package that is configured for monitoring the incoming signals and transmitting directional signals to the controls on the mobile wrapping machine. For transmitting, the MCC may utilize a Master Spread Spectrum RF transmitter to send radio signals to a Slave Spread Spectrum RF receiver, or other known radio transmitter and receiver. The mobile wrapping machine controls  13  may comprise an Allen-Bradley SLC 5/03 PLC to control the movement and wrapping functions of the wrapping machine. Typically, this PLC system includes an RF modem card to communicate with the MCC, an encoder card for the previously mentioned encoder, and such additional I/O cards as are necessary to control the drive motor, an air compressor in base  12  for generating on-board pneumatic power, warning horns and other safety and diagnostic systems. 
     From the foregoing description it will be apparent that the present invention solves all of the above-indicated problems, and provides an overall wrapping system which is fully automatic and requires no operator. However, if desired, a manually operated transmitter  62  may be provided for transmitting overriding signals so that an operator may intervene if necessary. 
     Of course, it is to be understood that the foregoing description of one preferred embodiment is intended to be purely illustrative of the principles of the invention, and not limiting of the invention, and that the true legal scope of the invention is not intended to be limited other than as expressly set-forth in the following claims interpreted under the doctrine of equivalents.