Patent Publication Number: US-9834980-B2

Title: Apparatus and method for processing sealant of an insulating glass unit

Description:
CROSS REFERENCES TO RELATED APPLICATIONS 
     The following application is a divisional application of copending U.S. patent application Ser. No. 13/351,450 filed on Jan. 17, 2012, which is a continuation of patent application Ser. No. 12/184,414 filed Aug. 1, 2008 (now abandoned), which is a divisional of patent application Ser. No. 11/109,437 filed on Apr. 19, 2005, now U.S. Pat. No. 7,422,650, which is a divisional application of U.S. patent application Ser. No. 10/183,775 filed Jun. 27, 2002, now U.S. Pat. No. 6,926,782, this divisional application incorporates the above-identified divisional applications herein by reference in their entirety and claims priority therefrom for all purposes. 
    
    
     FIELD OF THE INVENTION 
     This disclosure relates in general to equipment used in the construction of insulating glass units and, more specifically, to a method and apparatus for heating and/or pressing sealant of insulating glass units. 
     BACKGROUND OF THE INVENTION 
     Construction of insulating glass units (IGU&#39;s) generally involves forming a spacer frame by roll-forming a flat metal strip, into an elongated hollow rectangular tube or “U” shaped channel. Generally, a desiccant material is placed within the rectangular tube or channel, and some provisions are made for the desiccant to come into fluid communication with or otherwise affect the interior space of the insulated glass unit. The elongated tube or channel is notched to allow the channel to be formed into a rectangular frame. Generally, a sealant is applied to the outer three sides of the spacer frame in order to bond a pair of glass panes to either opposite side of the spacer frame. Existing heated sealants include hot melts and dual seal equivalents (DSE). The pair of glass panes are positioned on the spacer frame to form a pre-pressed insulating glass unit. Generally, the pre-pressed insulating glass unit is passed through an IGU oven to melt or activate the sealant. The pre-pressed insulating glass unit is then passed through a press that applies pressure to the glass and sealant and compresses the IGU to a selected pressed unit thickness. 
     Manufacturers may produce IGUs having a variety of different glass types, different glass thicknesses and different overall IGU thicknesses. The amount of heat required to melt the sealant of an IGU varies with the type of glass used for each pane of the IGU. Thicker glass panes and glass panes having low-E coatings have lower transmittance (higher opacities) than a thinner or clear glass pane. (opacity is inversely proportional to transmittance). Less energy passes through a pane of an IGU having a high reflectance and low transmittance. As a result, more energy is required to heat the sealant of an IGU with panes that have higher reflectance and lower transmittance. For example, less energy is required to heat the sealant of an IGU with two panes of clear, single strength glass than is required to heat the sealant of an IGU with one pane of clear, double strength glass and one pane of low-E coated double strength glass. 
     Typically, manufacturers of insulating glass units reduce the speed at which the insulating glass units pass through the IGU oven to the speed required to heat the sealant of a “worst case” IGU. This slower speed increases the dosage of exposure. In addition to the line speed sacrificed, many of the IGU&#39;s are overheated at the surface, resulting in longer required cooling times, and more work in process. 
     Some manufacturers produce IGUs in small groups that correspond to a particular job or house. As a result, these manufacturers frequently adjust the spacing between rollers of the press to press IGUs having different thicknesses. The thickness of the IGU being pressed is typically entered manually. Other manufacturers batch larger groups of IGUs together by thickness to reduce the frequency at which spacing between the rollers of the press needs to be adjusted. 
     There is a need for a method and apparatus for heating sealant of an IGU that automatically varies the energy applied to the IGU based on an optical property of the IGU. In addition, there is a need for a method and apparatus that automatically sets the spacing between press rollers for an IGU being pressed. This type of functionality can provide just in time one piece flow production resulting in constant speed, less manual intervention and more consistency in the process. 
     SUMMARY OF THE INVENTION 
     The present disclosure concerns a method and apparatus for heating and/or pressing sealant of an insulating glass unit. One aspect of the disclosure concerns an oven for applying energy to an insulating glass unit to heat sealant of the insulating glass unit. The oven includes an optical detector, an energy source, a conveyor, and a controller. The detector detects an optical property of the insulating glass unit. The conveyor moves the insulating glass unit with respect to the energy source. The energy source applies energy to the insulating glass unit to heat the sealant. The controller is coupled to the detector. The controller adjusts the amount of energy supplied by the energy source to the insulating glass unit in response to the detected optical property of the insulating glass unit. 
     The optical detector may be a transmittance detector and/or a reflectivity detector. In one embodiment, the optical detector is a bar code system that scans a bar code on the insulating glass unit that identifies the type or types of glass used in the insulating glass unit. 
     In one embodiment, the energy source is a plurality of lamps, such as infrared lamps. The controller may adjust the infrared energy supplied by the energy source by changing a number of the lamps that supply energy to the insulating glass unit, changing the speed of the conveyor or changing the intensity of one or more of the lamps. 
     In one embodiment, there are two arrays of infrared lamps. The conveyor moves the insulating glass unit between the two arrays of infrared lamps. In one embodiment, the controller activates a different number of lamps in the first array than the controller activates in the second array of lamps when a detected optical property of a first pane of glass of the insulating glass unit is different than a detected optical property of a second pane of glass of the insulating glass unit. 
     In use, an optical property or type of glass of the insulating glass unit is detected. The conveyor positions the insulating glass unit with respect to the energy source. The amount of energy supplied by the energy source to the insulating glass unit is adjusted in response to the detected optical property or type of glass to heat the sealant of the insulating glass unit. In the exemplary embodiment, the adjustment of energy supplied to the insulating glass unit allows the sealant in a given IGU to be heated more evenly and facilitates more consistent heating of sealant from unit to unit. 
     A second aspect of the present disclosure concerns a press for an insulating glass unit. The press includes a displacement transducer, a controller and a pair of rollers. The displacement transducer is configured to measure a thickness of an insulating glass unit before it is pressed. The controller is coupled to the displacement transducer. The controller is programmed to compare the measured pre-pressed thickness with a set of programmed ranges of pre-pressed thicknesses that correspond to a set of desired insulating glass unit pressed thicknesses. The controller selects one thickness from the set of insulating glass unit pressed thicknesses that corresponds to the measured pre-pressed thicknesses. The controller is coupled to the pair of rollers that can be spaced apart by a distance determined by the controller. The controller is programmed to set the distance between the rollers to achieve an insulating glass unit pressed thickness that the controller selects based on the measured pre-pressed thickness. 
     In one embodiment, the displacement transducer is positioned along a path of travel before an oven that heats sealant of the insulating glass unit. In one embodiment, the displacement transducer is a linear variable differential transformer displacement transducer. In one embodiment, the distance between the rollers is controlled by scanning a bar code that indicates the pressed thickness of the insulating glass unit. 
     In one embodiment, a pre-pressed thickness of an insulating glass unit is measured. The measured thickness is compared with a set of ranges of pre-pressed thicknesses that correspond to a set of insulating glass unit pressed thicknesses. One thickness from the set of insulating glass unit pressed thicknesses is selected that corresponds to the measured pre-pressed thickness. A distance between the rollers of a press is set to achieve the selected insulating glass unit pressed thickness before passing the insulating glass unit is passed through the press. 
     Additional features of the invention will become apparent and a fuller understanding will be obtained by reading the following detailed description in connection with the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a perspective view of an insulating glass unit; 
         FIG. 2  is a sectional view taken across lines  2 - 2  of  FIG. 1 ; 
         FIG. 3  is a sectional view of an insulating glass unit prior to pressing of the sealant to achieve the insulating glass unit of  FIG. 2 ; 
         FIG. 4  is a top plan view of an apparatus for heating and pressing sealant of an insulating glass unit; 
         FIG. 5  is a side elevational view of an apparatus for heating and pressing sealant of an insulating glass unit; 
         FIG. 6  is a side elevational view of an oven for applying energy to sealant of an insulating glass unit with a side portion removed; 
         FIG. 7  is a top plan view of an oven for applying energy to sealant of an insulating glass unit with a top portion removed; 
         FIG. 8  is a front elevational view of a press for an insulating glass unit; 
         FIG. 9A  is a side elevational view of a press for an insulating glass unit with rollers relatively spaced apart by a small distance; 
         FIG. 9B  is a side elevational view of a press for an insulating glass unit with rollers spaced apart by a relatively large distance; 
         FIG. 10  is a schematic representation of a transmittance detector detecting a transmittance of an insulating glass unit; 
         FIG. 11  is a schematic representation of a reflectivity detector detecting the reflectivity of an insulating glass unit; 
         FIG. 12  is a graph that plots the relationship between signal strength of a transmittance detector versus transmittance; 
         FIG. 13  is a graph that plots signal strength of a reflectivity detector versus reflectivity; 
         FIG. 14  is a schematic representation of a linear variable differential transformer measuring a thickness of an insulating glass unit prior to its passage through the press; 
         FIG. 15  is a schematic perspective representation of a bar code reader reading a bar code on an insulating glass unit; 
         FIG. 16  is a schematic representation of infrared lamps applying energy to sealant of an insulating glass unit; 
         FIG. 17  is a schematic representation of infrared lamps applying energy to sealant clan insulating glass unit showing an alternate lamp energization sequence; and, 
         FIG. 18  is a schematic representation of infrared lamps applying energy to sealant of an insulating glass unit showing an alternate lamp energization sequence. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     The present disclosure is directed to an apparatus  10  and method for heating and/or pressing sealant  19  of an insulating glass unit  14  (IGU). One type of insulating glass unit  14  that may be constructed with the apparatus  10  is illustrated by  FIGS. 1 and 2  as comprising a spacer assembly  16  sandwiched between glass sheets or lites  18 . Referring to  FIGS. 2 and 3 , the illustrated spacer assembly  16  includes a frame structure  20 , a sealant material  19  for hermetically joining the frame to the lites  18  to form a closed space  22  within the IGU  14  and a body of desiccant  24  in the space  22 . The IGU  14  illustrated by  FIG. 1  is in condition for final assembly into a window or door frame, not illustrated, for installation in a building. It is also contemplated that the disclosed apparatus may be used to construct an insulated window with panes bonded directly to sash elements of the window, rather than using an IGU that is constrained by the sash. 
     It should be readily apparent to those skilled in the art that the disclosed apparatus and method can be used with spacers other than the illustrated spacer. For example, a closed box shaped spacer, any rectangular shaped spacer, any foam composite spacer or any alternative material requiring heating can be used. It should also be apparent that the disclosed apparatus and method can be used to heat and press sealant in insulating glass units having any shape and size. 
     The glass lites  18  are constructed from any suitable or conventional glass. The glass lites  18  may be single strength or double strength and may include low emissivity coatings. The glass lites  18  on each side of the insulated glass unit need not be identical, and in many applications different types of glass lites are used on opposite sides of the IGU. The illustrated lites  18  are rectangular, aligned with each other and sized so that their peripheries are disposed just outwardly of the frame  20  outer periphery. 
     The spacer assembly  16  functions to maintain the lites  18  spaced apart from each other and to produce the hermetic insulating dead air space  22  between the lites  18 . The frame  16  and sealant  19  coact to provide a structure which maintains the lites  18  properly assembled with the space  22  sealed from atmospheric moisture over long time periods during which the insulating glass unit  14  is subjected to frequent significant thermal stresses. The desiccant body  24  serves to remove water vapor from air or other gases entrapped in the space  22  during construction of the insulating glass unit and any moisture that migrates through the sealant over time. 
     The sealant  19  both structurally adheres the lites  18  to the spacer assembly  16  and hermetically closes the space  22  against infiltration of air born water vapor from the atmosphere surrounding the IGU  14 . A variety of different sealants may be used to construct the IGU  14 . Examples include hot melt sealants, dual seal equivalents (DSE), and modified polyurethane sealants. In the illustrated embodiment, the sealant  19  is extruded onto the frame. This is typically accomplished, for example, by passing an elongated frame (prior to bending into a rectangular frame) through a sealant application station, such as that disclosed by U.S. Pat. No. 4,628,528 or co-pending application Ser. No. 09/733,272, entitled “Controlled Adhesive Dispensing,” assigned to Glass Equipment Development, Inc. Although a hot melt sealant is disclosed, other suitable or conventional substances (singly or in combination) for sealing and structurally carrying the unit components together may be employed. 
     Referring to  FIGS. 2 and 3 , the illustrated frame  20  is constructed from a thin ribbon of metal, such as stainless steel, tin plated steel or aluminum. For example, 304 stainless steel having a thickness of 0.006-0.010 inches may be used. The ribbon is passed through forming rolls (not shown) to produce walls  26 ,  28 ,  30 . In the illustrated embodiment, the desiccant  24  is attached to an inner surface of the frame wall  26 . The desiccant  24  may be formed by a desiccating matrix in which a particulate desiccant is incorporated in a carrier material that is adhered to the frame. The carrier material may be silicon, hot melt, polyurethane or other suitable material. The desiccant absorbs moisture from the surrounding atmosphere for a time after the desiccant is exposed to atmosphere. The desiccant absorbs moisture from the atmosphere within the space  22  for some time after the IGU  14  is fabricated. This assures that condensation within the unit does not occur. In the illustrated embodiment, the desiccant  24  is extruded onto the frame  20 . 
     To form an IGU  14  the lites  18  are placed on the spacer assembly  16 . The IGU  14  is heated and pressed together to bond the lites  18  and the spacer assembly  16  together. 
     Referring to  FIGS. 4 and 5 , the illustrated apparatus  10  for heating and pressing sealant  19  of an IGU  14  includes an oven  32  for heating the sealant  19  of an IGU  14  and a press  34  for applying pressure to the sealant  19  and compressing the IGU  14  to the desired thickness T ( FIG. 2 ). 
     Oven 
     Referring to  FIGS. 4-7 , the illustrated oven  32  includes a detector  36 , an energy source  38 , a conveyor  40  and a controller  42 . The detector  36  is used to detect an optical property of the IGU  14  and/or the type of glass used to construct the IGU. The energy source  38  applies energy to the IGU  14  to heat or activate the sealant  19 . The conveyor  40  moves the IGU  14  with respect to the energy source  38 . The controller  42  is coupled to the detector  36  and adjusts the amount of energy supplied by the energy source  38  to the IGU  14  in response to the detected optical property or glass type of the IGU  14  to heat the sealant  19  of the IGU  14 . 
     Referring to  FIGS. 4-6 , the detector  36  is mounted along a path of travel defined by the conveyor  40  before an inlet  44  of the oven  32 . Positioning the detector  36  before the inlet  44  of the oven  32  allows an optical property of the IGU  14  to be detected before the IGU  14  enters the oven  32 . In the illustrated embodiment, a plurality of detectors  36  are included for detecting an optical property along a width of an IGU  14 . It should be readily apparent to those skilled in the art that any desired number of detectors could be used. 
     The amount of energy required to heat the sealant  19  of an IGU  14  varies depending on the optical properties of the IGU  14 . Referring to  FIGS. 10 and 12 , in one embodiment, a transmittance detector  46  is used to determine the amount of energy required to heat the sealant  19  of the IGU  14 . One acceptable transmittance detector is an Allen Bradley series 5000 photo switch analog control, such as Allen Bradley part number 42DRA-5400. An IGU that is less transmissive to infrared light requires more energy (infrared light in the illustrated embodiment) to heat the sealant  19  than an IGU that is more transmissive to infrared light. For example, an IGU  14  that includes two panes of clear, single strength glass is more transmissive than an IGU that includes two panes of clear, double strength glass. As a result, more energy is required to heat the IGU with two panes of clear, double strength glass than the IGU with two panes of clear, single strength glass. Similarly, an IGU having one pane of low-E coated double strength glass and one pane of clear double strength glass is less transmissive and requires more energy to heat the sealant  19  than an IGU that includes two panes of clear, double strength glass. An IGU that includes two panes of low-E glass is less transmissive than an IGU that includes one pane of clear glass and one pane of low-E coated glass. As a result, more energy is required to heat the sealant  19  of the IGU having two panes of low-E coated glass. 
     The energy required to heat the sealant  19  of an IGU having any combination of glass types can be determined by detecting the transmittance of the IGU  14 . The transmittance detector  46  provides a signal to the controller  42  that the controller uses to adjust the amount of energy supplied to the IGU  14  for heating the sealant  19 . Referring to  FIG. 12 , in the illustrated embodiment, the transmittance detector provides a voltage signal to the controller. The magnitude of the voltage signal decreases as transmittance decreases. 
     Referring to  FIGS. 11 and 13 , a reflectivity detector  48  is used to detect the amount of energy required to heat the sealant  19  of the IGU  14 . Acceptable reflectivity detectors include model number 0CH20, available from Control Methods, model number NTL6 available from Sich, and model number LX2-13/V10W available from Keyence. An IGU  14  having a high reflectivity requires more energy to heat the sealant  19  than an IGU  14  having a low reflectivity. For example, an IGU  14  having two panes of clear glass is less reflective than an IGU  14  having one pane of clear glass and one pane of low-E coated glass. As a result, the IGU  14  having two panes of clear glass requires less energy to heat the sealant  19  than the IGU  14  having one pane of clear glass and one pane of low-E glass. Similarly, an IGU  14  having two panes of low-E coated glass is more reflective than an IGU  14  having one pane of clear glass and one pane of low-E coated glass. As a result, more energy is required to heat the IGU  14  having two panes of low-E coated glass. The reflectivity detector provides a signal to the controller  42  that the controller uses to adjust the amount of energy supplied to the IGU  14  for heating the sealant  19 . Referring to  FIG. 13 , in the illustrated embodiment, the transmittance detector provides a voltage signal to the controller. The magnitude of the voltage signal increases as reflectivity increases. 
     In one embodiment, an optical property of a lower pane  50  and an optical property of an upper pane  52  is detected. The amount of energy required to heat the sealant  19  to the lower pane  50  may be different than the amount of energy required to heat the sealant  19  to the upper pane  52 , if the optical properties of the lower pane  50  are different than the optical properties of the upper pane  52 . If the lower pane  50  is more opaque or reflective than the upper pane  52 , more energy is required to heat the sealant  19  to the lower pane  50  than the upper pane  52 . For example, the lower pane  50  may be a low-E coated piece of glass and the upper pane  52  is a clear piece of glass. The low-E coated glass lower pane  50  requires more energy to heat the sealant  19 . In this embodiment, a combination of transmittance and reflectivity detectors may be used. For example, a transmittance detector may be located either above or below the path of travel of the IGU to detect the amount of light that passes through the IGU. First and second reflectivity detectors may be positioned above and below the path of travel to detect the amount of light reflected by each side of the IGU. This information may be used to determine the type of glass the upper pane is made from and the type of glass the lower pane is made from. 
     In an alternate embodiment, the type of glass of the upper pane and lower pane are detected using one or more vision sensors. In this embodiment, the vision sensor detects the hew, color and brightness of the IGUs. In the exemplary embodiment, the ambient light and background are constant. The optical properties detected by the vision sensor are used to determine the type of glass the upper pane is made from and the type of glass the lower pane is made from. 
     Referring to  FIG. 15 , in one embodiment the detector  36  is a bar code reader  54  that is used to determine the type of glass of each lite of the IGU and the pressed thickness of the IGU. In the exemplary embodiment, the bar code reader  54  is part of a bar code system. The system includes the bar code reader  54 , a CPU and a database that identifies different IGU configurations that correspond to different bar codes. The bar code identifies one or more optical properties of the IGU  14 . A bar code read by the reader  54  is processed by the CPU that accesses the database to determine the type of glass of each pane of the given IGU and the pressed thickness of the IGU. In this embodiment, a bar code label  56  is affixed to a lite  18  of the IGU  14 . For example, the bar code label  56  for a given IGU  14  might indicate that the lower pane  50  is low-E coated double strength glass and the upper pane  52  is clear single strength glass and the pressed IGU thickness is 0.750 inches. In one embodiment, the bar code label identifies the complete construction details of the IGU. For example, the bar code may identify the glass type, glass thickness, spacer type, spacer width, muntin configuration, sealant type, sealant amount, and all other construction details of the IGU. 
     Referring to  FIGS. 4-7 , the illustrated energy source  38  comprises a plurality of elongated infrared radiating (IR) lamps  58 . One acceptable IR lamp is a Hareaus IR emitter, available from Glass Equipment Development under the part number 100-3746. As seen most clearly in  FIG. 4 , there are two side by side lower arrays  60  of IR lamps that extend across a width of an oven housing that supports the lamps. Similarly, as seen in the top view of  FIG. 4 , two side by side upper arrays  62  of IR lamps apply infrared light to heat the IGU from above. In the illustrated embodiment, the lower arrays  60  are adjacent to one another and the upper arrays  62  are adjacent to one another as illustrated by  FIG. 4 . In the exemplary embodiment, each of the lamps  58  are independently controlled. Each lamp may be independently turned on and off in the exemplary embodiment. In one embodiment, the intensity of each lamp is individually controllable. In the illustrated embodiment, each lamp  58  of the lower arrays  60  is positioned between a roller  64  of the conveyor  40  that is located inside an oven housing  66 . Each of the lamps  58  of the upper arrays  62  are located in the oven housing  66  above the conveyor  40 . The upper and lower arrays on the two sides of the oven can be operated independently of each other. This independent array energization is useful when smaller IGUs  14  are being processed. A first IGU  14  may be positioned on the left side of the oven  32  while a second IGU  14  is placed on the right side of the oven  32 . The lamps on the left side of the oven apply heat to the IGU  14  on the left side of the oven  32  and the lamps on the right side of the oven  32  apply heat to the IGU  14  on the right side of the oven  32 . 
     The arrays of lamps on the left and right side of the oven  32  can be operated in unison when a larger IGU  14  is being heated that spans both the left and the right sides of the oven  32 . 
     The lamps of the lower arrays  60  can be operated in unison with the upper arrays  62  or the lower arrays  60  may be operated independently of the upper arrays  62 . The lamps of the lower arrays  60  may be operated independently from the upper arrays  62  when the detector  36  detects two different types of lites  18  in the IGU  14 . 
       FIG. 16  shows a lower array  60  and an upper array  62  of IR lamps  58  that are all applying energy to the IGU  14 . In the exemplary embodiment, all the IR lamps  58  of the upper array  60  and the lower array  62  apply energy to the IGU  14  when the detector  36  detects an IGU  14  that is relatively opaque or reflective and, as a result, requires more energy to heat the sealant  19 . 
       FIG. 17  shows an upper array  62  and a lower array  60  of IR lamps  58  wherein half of the IR lamps  58  of the upper array  62  and the lower array  60  supply energy to the IGU  14  to heat the sealant  19 .  FIG. 17  is illustrative of the number of lamps that may be activated when the detector  36  detects an IGU  14  that is more transmissive or less reflective and requires less energy to heat the sealant  19 . 
       FIG. 18  illustrates a lower array  60  with all of the IR lamps  58  supplying energy to the lower pane  50  of the IGU  14  to heat the sealant  19  and half of the IR lamps  58  of the upper array  62  supplying energy to the upper pane  52  of the IGU  14 . The IR lamps  58  of the upper array  62  and lower array  60  may be operated in this manner when the detector  36  detects an IGU  14  having a more opaque or reflective lower pane  50  that requires more energy to heat the sealant  19  and a transmissive or less reflective upper pane  52  that requires less energy to heat the sealant  19 . It should be apparent to those skilled in the art that any number of lamps in the upper array  62  or the lower array  60  can be turned on to supply energy to the IGU  14  in response to detected optical properties. 
     In one embodiment, the oven includes one or more sensors that detect the leading and trailing edges of the IGU being heated. Each lamp that supplies energy to a given IGU may turn on when the leading edge of the IGU reaches the lamp and each lamp may turn off when the trailing edge passes the lamp. This is referred to as shadowing the IGU. 
     Referring to  FIGS. 4-7 , the illustrated conveyor  40  includes four sections that move IGUs  14  through the apparatus  10  for heating sealant  19 . The sections include an inlet conveyor  68  that supplies IGUs  14  to an inlet  44  of the oven  32 . An oven conveyor  72  that moves IGUs  14  through the oven  32 , a transition conveyor  74  that moves IGUs  14  from an outlet  76  of the oven  32  to an inlet  78  of the press  34  and an outlet conveyor  80  that moves pressed IGUs  14  away from the outlet  82  of the press  34 . It should be readily apparent to those skilled in the art that any suitable conveyor configuration could be employed. 
     In the illustrated embodiment, the inlet conveyor  68 , transition conveyor  74  and outlet conveyor  80  each comprise a plurality of drive wheels  84 . The drive wheels  84  are rotatably connected to a conveyor table  86  by drive rods  88 . Referring to  FIGS. 6 and 7 , the oven conveyor  72  comprises elongated driven rollers  90  that are rotatably mounted to a support housing  92  of the oven  32 . The driven rollers  90  are positioned adjacent to the infrared lamp  58  of the lower arrays  60 . In the exemplary embodiment, the conveyor  40  is operated to move an IGU  14  along a path of travel through the oven  32 , to the press  34 , and away from the press at a constant speed. In an alternate embodiment, the speed of the conveyor  40  is controlled by the controller  42  in response to a signal from the detector  36  to vary the amount of energy supplied to the IGUs  14  that pass through the oven  32 . 
     In the illustrated embodiment, the controller  42  is coupled to the oven  32 , the press  34 , the detector  36  and the conveyor  40 . The controller  42  receives a signal from the detector  36  that is indicative of an optical property or glass type of the IGU  14  and adjusts the amount of energy supplied by the oven  32  to the IGU  14  in response to the detected optical property or glass type. Referring to  FIGS. 10 and 12 , when a transmittance detector  46  is used, the signal provided by the transmittance detector  46  varies with the detected transmittance of the IGU  14 . Referring to  FIG. 12 , a higher output voltage provided by the transmittance detector to the controller  42  indicates a high transmittance. A lower output voltage by the transmittance detector to the controller  42  indicates that a more opaque IGU  14  has been detected by the transmittance detector. 
     In the exemplary embodiment, the controller compares the signal provided by the transmittance detector to stored values or ranges that correspond to various IGU glass configurations. For example, referring to  FIG. 12 , the signal provided by the transmittance detector may fall within range  47 , indicating an IGU having clear, single strength lites is being processed. As a second example, the signal may fall within range  49 , indicating that the IGU being processed has two lites made from double strength low-E glass. Each possible glass configuration may be detected by the controller in this manner. 
     Referring to  FIGS. 11 and 13 , when a reflectivity detector  48  is used, a signal is provided by the reflectivity detector  48  that is indicative of the reflectivity of the IGU  14 . A lower voltage output signal provided by the reflectivity detector  48  to the controller  42  indicates that a less reflective IGU  14  is being processed. A higher voltage output signal from the reflectivity detector  48  indicates that a more reflective IGU  14  is being processed. 
     In the exemplary embodiment, the controller compares the signal provided by the reflectivity detector to stored values or ranges that correspond to different IGU glass configurations. For example, referring to  FIG. 13 , the signal provided by the reflectivity detector may fall within range  51 , indicating an IGU having clear, single strength glass is being constructed. As a second example, the signal may fall within range  53 , indicating that the IGU being processed has two lites made from single to double strength, low-E glass. Each possible glass configuration can be detected and classified by the controller in this manner. In one embodiment, a combination of reflectivity and transmittance detectors are used. For example, on transmittance detector, a reflectivity detector above the IGU path and a reflectivity detector below the IGU path may be used. 
     Referring to  FIG. 15 , when a bar code reader  54  is used, the bar code reader provides a signal to the controller  42  that indicates the glass type(s) of the IGU  14 . In the exemplary embodiment, the signal provided by the bar code reader  54  to the controller  42  indicates the type of glass used for the lower pane  50  and the type of glass being used as the upper pane  52 . 
     In the exemplary embodiment, the controller  42  uses the signal from the detector  36  to adjust the amount of energy supplied by the IR lamp  58  required to bring the sealant  19  of the IGU  14  to a proper melt temperature. In the exemplary embodiment, the controller  42  adjusts the amount of energy supplied by the IR lamps  58  by changing the number of lamps in the lower arrays  60  and upper arrays  62  that supply energy to the IGU  14 .  FIG. 16  illustrates all lamps of an upper array  62  and a lower array  60  providing energy to heat the sealant  19  of the IGU  14 . The controller  42  would cause all the ER lamps  58  of the lower array  60  and the upper array  62  to supply energy to the IGU  14  when the signal provided by the detector  36  indicates that the IGU  14  is relatively opaque or reflective. If the detector  36  is configured to detect the type of glass that the lower lite  50  and the upper lite  52  is made from, the controller  42  would cause all the IR lamps  58  of the lower array  60  and the upper array  62  to supply energy to the IGU  14  when the signal provided by the detector  36  indicates that the glass of the lower pane  50  and the glass of the upper pane  52  is relatively opaque or reflective. 
       FIG. 17  shows half of the IR lamps  58  of an upper array  62  and a lower array  62  supplying energy to heat the sealant  19  of the IGU  14 . If the detector  36  is configured to detect overall transmittance of the IGU being processed, the controller  42  shuts off some of the IR lamps  58  in the upper array  62  and the lower array  60  when the signal provided by the detector  36  to the controller  42  indicates that the IGU  14  is more transmissive or less reflective. If the detector  36  is configured to detect the type of glass that the lower lite  50  and the upper lite  52  is made from, the controller  42  would shut off some of the IR lamps  58  of the lower array  60  and the upper array  62  when the detector  36  indicates that the glass of the lower pane  50  is more transmissive or less reflective and the glass of the upper pane  52  is more transmissive or less reflective. 
       FIG. 18  illustrates an upper array  62  with some of the IR lamps  58  applying energy to the IGU  14  for heating the sealant  19  and some of the IR lamps  58  turned off and all of the lamps of the lower array  60  turned on. In the exemplary embodiment, when the detector is configured to detect the type of glass that is used for the upper lite  52  and the type of glass that is used for the lower lite  50  the controller can supply different amounts of energy from above and below the IGU. For example, in  FIG. 18 , the controller  42  turns all of the lamps that supply energy to one side of the IGU  14  on when the signal from the detector  36  indicates that the pane is relatively opaque or reflective and turns some of the lamps of the second array off when the signal from the detector  36  to the controller indicates that the other pane of the IGU  14  is more transmissive or less reflective. The detector  36  may include transmittance detectors and reflectivity detectors that provide signals to the controller  42  that allow the controller  42  to determine which pane of the IGU  14  is more opaque or reflective. When a bar code reader is used to detect the types of glass used in the IGU  14  the signal provided from the bar code reader to the controller  42  allows the controller  42  to determine which pane of the IGU  14  requires more energy to heat the sealant  19  of the IGU  14 . 
     In the exemplary embodiment, the controller  42  operates the arrays on the left side of the oven  32  independently of the arrays on the right side of the oven  32  when the IGUs  14  being processed do not overlap both arrays. In the exemplary embodiment, the controller  42  operates on the left and right side of the oven  32  when the IGU  14  being processed overlaps both arrays. 
     Press 
     IGUs  14  are provided by the conveyor  40  from the oven  32  to the press  34 . In the illustrated embodiment, the press  34  includes a displacement transducer  94  and adjustable pressing members  96  that are coupled to the controller  42 . In an alternate embodiment, the displacement transducer is omitted when a bar code reader  54  is included. In this embodiment, the bar code includes the pressed IGU thickness which is used by the controller to set the press spacing. 
     The illustrated pressing members  96  are elongated rollers. However, it should be readily apparent to those skilled in the art that other pressing means, for example, adjustable belts could be used in place of rollers. Referring to  FIGS. 3, 5 and 14 , the displacement transducer  94  is mounted above the conveyor  40  before the inlet  44  to the oven  32  in the illustrated embodiment. It should be apparent to those skilled in the art that the displacement transducer  94  could be positioned at any point before the inlet  78  to the press  34 . The displacement transducer  94  includes a roller  98  that engages an upper surface  100  of the IGU  14 . The displacement transducer  94  measures a pre-pressed thickness T′ of IGUs  14 . The displacement transducer  94  provides a signal to the controller  42  that indicates the pre-pressed thickness T′ of the IGU  14 . It should be apparent to those skilled in the art that the pre-pressed thickness T′ of the IGU  14  could be manually entered to the controller  42  or, when a bar code reader  54  is included, the IGU  14  thickness T is included in the bar code. 
     The controller  42  is coupled to the displacement transducer  94 . The controller  42  is programmed to compare the measured pre-pressed thickness T′ of the IGU  14  with a stored set of ranges of pre-pressed thicknesses T′ that correspond to a set of IGU  14  pressed IGU thicknesses T. The pressed IGU thickness T is the final thickness of a pressed IGU. The controller  42  selects one pressed thickness T from the set of IGU  14  pressed thicknesses that corresponds to the pre-pressed thickness T′ measured by the transducer  94 . 
     For example, pre-pressed IGUs  14  having pre-pressed thicknesses ranging from 0.790 to 0.812 inches may correspond to a pressed IGU having a pressed thickness T of 0.750 inches. As a result, for a pre-pressed IGU  14  having a thickness of 0.800 measured by the displacement transducer  94 , the controller  42  sets the distance between the pressing members  96  of the press  34  to press an IGU  14  having a pressed thickness T of 0.750 inches. Typically, IGUs are made in distinct thicknesses. For example, ⅜ inch, ½ inch, 0.0625 inch, ¾ inch, 0.875 inch, 1 inch, etc. IGUs may be made at a particular plant. Each of these discrete thicknesses T has a corresponding range of pre-pressed thicknesses T. Each IGU thickness T will have an associated range of pre-pressed thicknesses T′ that allow the displacement transducer  94  and the controller  42  to determine the IGU thickness being pressed. The controller uses the stored set of ranges of pre-pressed thicknesses T′ and corresponding IGU pressed thicknesses to set the spacing between the pressing members. 
     The IGU thickness detection scheme disclosed is compatible with any type of press. The illustrated press  34  includes three pairs of rollers  96  that are spaced apart by a distance controlled by the controller  42 . Referring to  FIGS. 5 and 7 , the three pairs of rollers  96  are rotatably mounted in a cabinet  102 . Referring to  FIG. 8 , the illustrated rollers  96  are elongated and extend across substantially the entire width of the press  34 . 
     In operation, a pre-pressed IGU  14  moves along the conveyor  40  to a position below the detector  36  and into contact with the displacement transducer  94 . An optical property or glass type(s) of the IGU  14  is detected with the detector  36 . The detected optical property or glass type(s) is indicative of the amount of energy required to heat the sealant  19 . The pre-pressed thickness T′ of the IGU  14  being processed is measured with the displacement transducer  94 . The pre-pressed IGU is moved into the oven  32 , between the upper and lower arrays  60 ,  62  of IR lamps  58 . The controller  42  changes a number of lamps in the upper and lower arrays  60 ,  62  that supply energy to the IGU  14  in response to the detected optical property or glass type(s). The controller compares the measured pre-pressed thickness T′ of the IGU  14  with a set of ranges of pre-pressed thicknesses that correspond to a set of IGU pressed thicknesses. The controller then selects one pressed thickness from the set of pressed thicknesses that corresponds to the measured pre-pressed IGU thickness. The controller then adjusts the distance between the adjustable rollers  96  of the press  34  to the selected IGU pressed thickness T. In the exemplary embodiment, the rollers of the press are moved up and down by a screw jack coupled to a servo motor. In one embodiment, a sensor such as a LVDT, is used to monitor the distance between the rollers. The conveyor moves the IGU  14  out of the oven  32  and into the press  34 . The rollers  96  of the press  34  rotate to press the IGU  14  to the selected thickness T and move the IGU  14  to the outlet  82  of the press. The outlet conveyor  80  moves the IGU  14  away from the outlet  82  of the press. 
     Although the present invention has been described with a degree of particularity, it is the intent that the invention include all modifications and alterations falling within the spirit or scope of the appended claims.