Abstract:
A glass cart includes a radio frequency identification tag that transmits a signal that can be received by a receiving unit to provide the location of the glass cart for tracking between manufacturing stations or facilities. Based on its position, a status of an order or a portion of a order carried by the cart is determined.

Description:
CROSS REFERENCE TO RELATED APPLICATION  
       [0001]     This application claims priority from U.S. Provisional Patent Application Ser. No. 60/703,167 file Jul. 28, 2005, entitled “GLASS CART WITH RFID” which is incorporated herein by reference. 
     
    
     FIELD OF THE INVENTION  
       [0002]     The present invention concerns a method and apparatus for tracking the location of carts carrying insulating glass units.  
       BACKGROUND  
       [0003]     Window manufacturers typically receive orders that include a variety of different sizes and types of windows and/or patio doors. The different sizes and types of windows and/or patio doors require different sizes and types of insulating glass units (IGs) that are assembled into a frame or sash to form a completed window or patio door at one or more glazing lines. Insulating glass units employed in windows and doors commonly are manufactured by sandwiching a peripheral spacer between aligned, parallel sheets of glass. The IGs are packaged and shipped to another location, often a separate manufacturing facility, in which the IGs are provided with appropriate frames to form finished windows and doors.  
         [0004]     Glass carts have been developed for transporting sheets of glass and insulating glass units. These carts are designed to adequately protect the sheets of glass and IGs as they are transported between stations within a manufacturing facility or shipped via truck to a remote manufacturing facility. Due to the relatively high cost of the customized glass carts, the number of carts kept in service should be kept to a minimum.  
       SUMMARY  
       [0005]     A glass cart includes a radio frequency identification tag that transmits a signal that can be received by one or more receiving units to provide the location of the glass cart for tracking between manufacturing stations or facilities.  
         [0006]     One exemplary method tracks a glass cart used in transporting insulating glass units or glass plates by storing a unique identifier in memory. In this embodiment the memory is physically mounted on a glass cart. A radio signal is transmitted that includes a unique identifier using a transmitter that is physically mounted on the glass cart. A receiver receives the radio signal and determines a position of the glass cart to be within a predetermined range of the position of the receiver. Based on its position, a status of an order or a portion of a order carried by the cart is determined.  
         [0007]     These and other features of the invention will become further understood from a detailed description of an exemplary embodiment which is described in conjunction with the accompanying drawings. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0008]      FIG. 1  is a schematic depiction of an insulating glass unit manufacturing facility; and  
         [0009]      FIG. 2  is a perspective view of a glass cart constructed in accordance with one embodiment of the present invention;  
         [0010]      FIG. 2A  is an enlarged view of an RFID tag that can be used in practice of one embodiment of the present invention. 
     
    
     DESCRIPTION  
       [0011]      FIG. 1  schematically illustrates a window and/or door manufacturing facility  12 . The facility  12  includes an insulating glass unit (IG) production control terminal  18 . The production control terminal  18  receives orders for IGs and creates a sequence of runs of insulating glass units to be produced in an insulating glass unit (IG) department  26  that is part of an IG manufacturing facility  20 . In the illustrated embodiment, the IG department includes several insulating glass component processing machines or stations that construct IG components and assemble the IG components to create IGs. Glass carts  54  are used to transport the IG components between stations. In the illustrated embodiment, the IG component processing stations include a glass cutting station  28 , a spacer frame production station  30 , a muntin bar production station  32 , a muntin bar assembly station  34 , a glass washing station  36 , an IG assembly station  38 , an oven  40 , a gas fill station  42 , and a patching station  44 . Glass lites, spacer frames, and muntin bars are constructed at the glass cutting station  28 , the spacer frame production station  30 , and the muntin bar production station respectively. The glass lites, spacer frames, and muntin bar grids are assembled to form IGs at the IG assembly station  38 . The IGs are fed through the oven/press  40 , which presses the IG to a predetermined thickness and heats the adhesive/sealant that secures the lites to the spacer frame. The IGs are then filled with an inert gas at the gas fill station  42  and patched at the patching station  44 .  
         [0012]     Once patched, the finished IGs are placed on carts  54  and held in a staging area  56 . The IGs are taken from the carts  54  and are assembled with window sash and frames or doors in a glazing facility  60 . In the described embodiment the glazing facility  60  is a separate facility requiring transportation by truck of the glass carts  54 . In the glazing facility completed windows and/or doors are constructed using the IGs on the glass carts. Assembly of an IG to a window or door sash and/or a frame is broadly referred to herein as glazing. The glazing facility  60  includes several discrete glazing lines  62 .  
         [0013]      FIG. 2  illustrates a typical glass cart  54  that includes a frame  114  with a base  115  that has a number of parallel slots  116  configured to accept an IG or plate of glass. Other glass support mechanisms may be present but are not shown here. A radio frequency identification tag (“RFID tag”)  120  is attached to the glass cart. The RFID tag is used to track the location of the cart within either the IG manufacturing facility  20  or the glazing facility  60 .  
         [0014]      FIG. 2A  is an enlarged view of one suitable RFID tag. The tag  120  includes a microchip  129  that stores data and an antenna  125 . The tag  120  transmits a radio signal on a preselected frequency that is received by a reader ( 91  in  FIG. 1 ). The radio signal includes a unique identification code that is associated with the particular cart on which the RFID tag is mounted. The tag  120  can be active or passive. Active tags are self powered and use a battery for power to send the signal. Passive tags receive power from the reader via a low power radio signal from the reader that is used to power the microchip. The tag is active relatively briefly, for the time required to verify the reader and exchange data. While active tags are more expensive than passive tags, they typically have a wider broadcast range.  
         [0015]     Referring again to  FIG. 1 , several readers  91 ,  92 ,  93  are employed throughout the facility to track glass carts  54  within the IG manufacturing facility  20 . Each reader sends and receives RF data to and from the RFID tags on the glass carts  54 . Each reader may have multiple antennas that are responsible for sending and receiving the radio waves. Typically, RFID readers and tags operate on one of three primary frequency bands: low frequency (125/134 KHz), mid-frequency (13.56 MHz), and ultra high-frequency (850 MHZ-950 MHz and 2.4 GHz-2.5 GHz).  
         [0016]     It may be advantageous to provide at least one reader at each manufacturing station so that the location of a given glass cart  54  and the glass panes or IGs that it carries can pinpointed and its progress through the stations logged. An order for finished IGs can be assigned a glass cart identification code corresponding to the cart on which the unfinished glass panes that will be used for the IGs are placed. As the glass cart is moved to a new station, the radio signal from the tag is read by the reader associated with that station. In this manner, the location of the glass cart can be tracked as well as the status of the order held by the glass cart.  
         [0017]     As discussed above, finished IGs can be stored in a staging area  56  until they are needed by the glazing facility  60 . A staging area reader  92  receives signals from carts as they pass out of the staging area and leave the IG manufacturing facility  20 . When the glass cart enters the glazing facility  60 , a glazing facility reader receives a signal from the RFID tag on the cart and logs the presence of the cart within the facility in a production control computer  68 . In this manner, the number of glass carts that are present in either the IG manufacturing facility or glazing facility can be known at any given time.  
         [0018]     While several embodiments of the invention has been illustrated and described in detail, the present invention is not to be considered limited to the precise constructions disclosed. Various modifications, adaptations and uses of the invention may occur to those skilled in the art to which the invention relates. The intention is to cover all such modifications, adaptations and uses falling within the spirit or scope of the claims.