Pallet load sensing system

Abstract

The present invention relates to a system for positioning pallets to be wrapped with a pallet stretch wrap machine and to adjust operation of the wrap machine according to measurements obtained from sensors, identify the relative size of the pallet load to be wrapped in stretch film, detect misalignment of the load and thereby control activation of the wrap sequence and the speed of the film applied.

What is claimed is: 
     
         1 . A pallet load sensing and control system of a floor-loaded stretch wrap apparatus having an arm that rotates around a pallet to wrap the pallet in stretch wrap, the system comprising:
 a laser sensor device for measuring at least an extent of a first face and at least an extent of a second face of a floor-loaded pallet and generating assigned values for said measurements;   a controller for electrical connection to the stretch wrap machine, said controller configured for receiving said measurement values and comparing said values to stored information regarding pallet tolerances; and   a signal generator coupled to the controller, the signal generator being configured to provide a differential signal based on comparison of the measurement values to the stored information.   
     
     
         2 . The system of  claim 1  wherein said measurement values are compared to stored information of the acceptable tolerances for the pallet being in correct position for initiating a wrap sequence of the stretch wrap apparatus. 
     
     
         3 . The system of  claim 1  wherein said measurement values are compared to stored information of pallet size and wherein the signal generator provides a differential signal for adjusting the speed of the shrink wrap apparatus. 
     
     
         4 . The system of  claim 3  wherein the controller is configured to identify the pallet dimensions within a tolerance of a pallet size, and wherein said signal generator is configured to provide alternate signals to the wrap assembly depending on the pallet size. 
     
     
         5 . The system of  claim 4  wherein said signal generator is electrically connected to a frequency drive of a motor of the wrap assembly, such that the motor is run slower for a smaller pallet size and the motor is run faster for a larger pallet size. 
     
     
         6 . The system of  claim 5  wherein the signal generator initiates a different signal depending upon the measurement values residing within one of alternate pallet sizes. 
     
     
         7 . The system of  claim 3  wherein a drive motor of the wrap assembly is driven by a current that has a lower frequency when a smaller pallet is detected and said motor is driven by a current of higher frequency when a larger pallet is detected. 
     
     
         8 . The system of  claim 7  wherein a drive motor of the wrap assembly is driven by a 60 Hz frequency current when a particular pallet size is identified and said motor is driven by a current less than 60 Hz when a smaller pallet size is identified. 
     
     
         9 . The system of  claim 7  wherein a drive motor of the wrap assembly is driven by a 60 Hz frequency current when a measurement value is about 52 inches and said motor is driven by lower frequency current when the greatest measurement value is about 40 inches. 
     
     
         10 . The system of  claim 1  wherein said controller further comprises:
 a first processor for calculating pallet position data comprising the distance from the pallet on all sides to a prestretch carriage to an arm of the wrapping assembly; 
 an encoder coupled to the arm, wherein said encoder transmits position data comprising the position of the arm relative a reference position; and 
 a second processor for calculating the distance between the arm and the pallet at points around the pallet using the arm position data and the pallet position data. 
 
     
     
         11 . A pallet load sensing and control system for use with a floor-loaded stretch wrap apparatus having an arm with a prestretch carriage configured to rotate around a pallet to wrap the pallet in stretch wrap, the system comprising:
 a sensor for determining at least a dimension of first face and a dimension of a second face of a floor-loaded pallet and generating values of the measurements;   a controller coupled to the stretch wrap machine, the controller receiving the dimension values and calculating pallet position data relative a reference position;   wherein said controller provides a signal to the stretch wrap apparatus to activate a shrink wrap sequence if the pallet is within a predetermined location in relation to the reference position.   
     
     
         12 . The system of  claim 11  wherein said controller further comprises:
 a first processor for calculating pallet position data within a zone of a wrapping apparatus and an encoder coupled to the arm, wherein said encoder transmits position data comprising the position of the arm relative a reference position; and said controller further comprising a second processor for calculating the distance between the arm and the pallet at points around the pallet using the arm position data and the pallet position data. 
 
     
     
         13 . A pallet load sensing and control system for use with a floor-loaded stretch wrap apparatus having an arm with a prestretch carriage configured to rotate around a pallet to wrap the pallet in stretch wrap, the system comprising:
 at least a first sensor for identifying a position of at least a side of a pallet load and a second sensor for identifying a position of another portion of the load;   a controller coupled to the stretch wrap machine, the controller electrically connected to receive signals from the first and second sensors and having a computer processor for calculating the position of at least a portion of the load and said controller thereby generating a signal transmitted to the stretch wrap apparatus to identify when a pallet is in position and misalignment is not detected.   
     
     
         14 . An apparatus for controlling an amount of pre-stretched packing film applied about a load, comprising:
 at least one primary sensor positioned about a packing station for a palletized load, said sensor configured to emit a detection beam directed toward a load wrapping station and configured to identify a border of the load when positioned in said station and generate a primary sensor signal;   at least one secondary sensor positioned relative said packing station, said secondary sensor configured to emit a secondary detection beam at a predetermined position relative the wrapping station, such that said secondary sensor is able to detect the presence of the load at said predetermined position;   and thereby generates a secondary sensor signal;   a processor electronically connected to said primary and secondary sensors to receive the primary signal of the load and to receive the secondary signal, said processor configured to initiate a warning condition in the event the load is misaligned within the wrapping station.   
     
     
         15 . The apparatus of  claim 14 , wherein the secondary sensor is positioned to emit said sensor beam outside a border of said wrapping station. 
     
     
         16 . The apparatus of  claim 15  wherein said secondary sensor generates an electric signal identifying mis-alignment of the load, and said signal being transmitted to the processor wherein the processor is programmed to prevent the wrapping apparatus from initiating a wrapping sequence. 
     
     
         17 . The apparatus of  claim 14  wherein the primary sensor is a laser and said secondary sensor is an electric eye. 
     
     
         18 . The apparatus of  claim 17  wherein said primary sensor laser measures a distance to the load and the processor operates to compare said distance measurement with information regarding a border of said wrapping station. 
     
     
         19 . A pallet load sensing system for use with a floor-loaded stretch wrap machine having an arm that rotates around a pallet to wrap the pallet load with stretch wrap, the system comprising:
 a first photo eye, said first photo eye positioned opposite one face of a floor-loaded pallet load for generating a signal identifying the presence of a pallet load;   a second photo eye, said second photo eye positioned adjacent a load station area and directing a photo eye beam to detect obstruction of a photo eye beam by load;   a processor for receiving said signal of the first photo eye and a signal from the second photo eye, said processor having a computer processor configured for determining whether a load is in proper position for operation of the stretch wrap apparatus;   a signal generator in communication with the processor for providing a signal to initiate operation of the stretch wrapping assembly to commence the wrapping sequence of the load.   
     
     
         20 . The system of  claim 19  further comprising two photo eyes deployed about the load station, each positioned at opposed ends of the station to detect obstruction of respective photo eye beams by the load.