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FIELD OF THE INVENTION 
     The present invention relates to the fabrication of insulated glass (“IG”) units. In particular, the present invention relates to an apparatus and method of sealing a spacer between a pair of spaced apart substrates. 
     BACKGROUND OF THE INVENTION 
     In the conventional manufacture of sealed insulated units comprising an assembly of two spaced apart parallel sheets of substrate (usually glass) and a bondable and/or curable spacer therebetween, assembled units are positioned in a press and the entire unit is heated to melt and/or cure the spacer allowing the spacer to bond to the substrates. Heating of the entire unit causes problems since it increases the temperature of the entire unit including the air between the substrates. In addition, if the entire unit is being heated in the vertical position, a “chimney” effect occurs whereby the upper zone of the unit may become overheated relative to the lower zone with problems resulting. 
     For example, in U.S. Pat. No. 5,567,258, an IG unit containing an aluminum spacer, aluminum tape corner keys and a thermoset resin sealant is placed within a tunnel having microwave generators on each side. The unit passes through the tunnel and the entire IG unit is subjected to microwave energy to bond the spacer to the substrates. Conventional presses ensure that the spacer is firmly bonded to the substrates. The entire spacer however, is heated which can result in softening of the spacer and changes in the shape of the spacer. 
     U.S. Pat. No. 4,683,154 discloses a window panel held in a spaced apart manner by glass beads and sealed by welded glass obtained by welding the bead spacers together with a laser beam while positioned in a vacuum furnace. The laser welding occurs while the IG unit is in the furnace and is directed around the perimeter of the IG unit by a combination of rotating the IG unit and aiming the laser with mirrors. 
     Drawbacks of the conventional art include higher energy consumption, higher heat dissipation requirement, increased fabrication time and overheating of the IG assembly and spacer. It is an object of the present invention to overcome the disadvantages of the prior art by using localized zonal heating or other energy source to heat or otherwise induce an effect (e.g. for curing) within the spacer of the IG assembly in the zone(s) of the assembly where the spacer is positioned between the substrates. 
     SUMMARY OF THE INVENTION 
     In accordance with the present invention, there is provided an improved apparatus to seal a spacer between a pair of spaced apart substrates, wherein thermal or other energy is applied locally to selected zones of the assembly where the spacer contacts the substrates. 
     According to another aspect of the present invention, there is provided in the above type of apparatus a press adapted to provide sealing between a pair of spaced part substrates (conveniently glass) and a bondable spacer, including heat sources adapted to move with glass substrates, specifically movably positioned to heat the edges of the glass substrates or IG unit. 
     According to another aspect of the present invention, there is provided in the above type of apparatus a vertical press adapted to provide sealing between a pair of spaced apart glass substrates in generally vertical orientation and a bondable spacer, including guide roller means. 
     According to yet another aspect of the present invention, multiple localized energy applicator heads, preferably one per side of the IG unit are employed. 
     In a still further aspect of the present invention, there is provided in the above type of apparatus a vertical glass press adapted to provide sealing between a pair of spaced apart glass substrates and a bondable spacer, having at least one heating means synchronized to travel a desired distance with the leading edge of a glass substrate. The apparatus may further include a second heating means synchronized to travel a desired distance with the trailing edge of a glass substrate. 
     According to another aspect of the invention, there is provided in the above type of apparatus a glass press adapted to provide sealing between a pair of spaced apart glass substrates and a bondable spacer, comprising a plurality of spaced-apart compression means such as rollers or ball bearings between which a glass assembly is adapted to pass whereby said rollers apply compressive force to the spaced apart glass substrates, means for advancing a glass assembly to and through said apparatus, a plurality of spaced apart heating means adapted to provide localized heating to said spacer in selected areas of said glass assembly where said spacer is located and without providing direct heat to the balance of said glass assembly. 
     According to a further aspect of the invention, there is provided in the above type of apparatus a preferred heating means comprising two pairs of spaced-apart heating assemblies, at least one pair of said spaced apart heating assemblies comprising at least one adjustable heater adapted to move in a generally parallel direction relative to the other heater of said one pair. 
     According to a still further aspect of the invention there is provided in the above type of apparatus wherein said heating assembly includes a first pair of spaced apart heaters, one of said heaters being mounted in a fixed relationship to said press and the other of said heaters of said one pair being movable in a generally parallel relationship to said fixed heater, and means for effecting movement of said one movable heater. 
     According to an aspect of the present invention there is provided in the above type of apparatus wherein the other of said pair of heaters comprises at least one movable heater movable in a second direction relative to the direction of movement of said first pair of heaters, and means for effecting movement of the movable heater of said second pair of heaters. 
     In another aspect of the present invention there is provided a method of sealing an insulated assembly having a pair of spaced apart substrates and a spacer therebetween, comprising; 
     (a) providing an insulated assembly, 
     (b) providing an energy source, 
     (c) selectively applying energy to selected zones of said assembly where said spacer is located without providing direct energy to the balance of the assembly. 
     In still another aspect of the present invention there is provided a method of sealing an insulated assembly having a pair of spaced apart substrates and a spacer therebetween, comprising selectively applying energy to selected zones of said assembly where said spacer is located without providing direct energy to the balance of the assembly. 
     According to a further aspect of the present invention there is provided in the above type of apparatus wherein there is provided two pairs of heater assemblies each pair being mounted in an angular relationship to the other pair of heaters, each heater means comprising an individual heater adapted to direct a heat source to a selected portion of a glass assembly containing a spacer element. 
     According to another aspect of the present invention there is provided a method of bonding a spacer to a pair of spaced apart glass substrates in which the spacer is positioned between the substrates; the method includes the steps of providing a glass assembly having a spacer between a pair of spaced apart glass substrates and in which the glass substrates of the assembly are loosely bonded by said spacer, providing a plurality of heat sources of an elongated relatively narrow width compared to the overall surface area of the glass assembly, positioning said plurality of heat sources in operative relationship to a glass surface beneath which the elongated spacer is located and selectively applying heat to said spacer along an elongated narrow strip of the glass assembly whereby the spacer is preferentially heated relative to other areas of the glass assembly. 
     In accordance with one aspect of the present invention, there is provided in the above type of apparatus a vertical press adapted to provide sealing between a pair of substrates and a bondable spacer material, having heat means adapted to provide heat to a specific area of a substrate to bond a material enclosed within said pair of substrates. 
     Having thus generally described the invention, reference will now be made to the accompanying drawings illustrating preferred embodiments and in which: 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a front view of the apparatus in accordance with the present invention; 
     FIG. 2 is a top view of the compression rollers of the apparatus illustrated in FIG. 1; 
     FIG. 3 is an end view of the apparatus illustrated in FIG. 1; 
     FIGS. 4A to  4 G inclusive diagrammatically illustrate the various sequential steps and associated apparatus for the heat sealing of an IG unit; 
     FIG. 5 is a perspective view of a portion of another apparatus with certain components removed in accordance with the present invention; 
     FIG. 6 is a perspective view of the apparatus of FIG. 5 with the vertical heating and pressing assemblies shown; 
     FIG. 7 is a partially exploded view of a vertical heating and pressing assembly of FIG. 6; 
     FIG. 8 is a partially exploded view of the rails of the vertical station of the apparatus of FIG. 6; 
     FIG. 9 is a partially exploded perspective view of a horizontal heating and pressing assembly of the apparatus of FIG. 6; 
     FIG. 10 is a perspective view of the conveyor system of the apparatus of FIG. 6; 
     FIG. 11 is a side view of the clamping system of the vertical heating and pressing assemblies of FIG. 6; and 
     FIG. 12 is an end view from the exit end of the horizontal heating and pressing assembly of FIG.  6 . 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     The terms “height” and “width” when used herein in reference to the IG assemblies refers to the IG assembly positioned generally vertically. The term “thickness” refers to the transverse axis across the substrates. “Left” and “right” are in reference to a viewer at the leading edge of the apparatus viewing the assembly along the axis of travel of the IG assembly being treated. IG assembly includes assemblies having substrates of glass or other suitable material such as plastic or aluminum. 
     Referring to FIGS. 1 to  3 , the press apparatus includes an energy applying station in the form of a heating station indicated generally by H and a pressing station indicated generally by P. The press apparatus is designed to be part of a conventional continuous production line process for the manufacture of IG units but alternatively may be used as a stand-alone unit as well. Advancing means in the form of a conveyor  12  mounted in a base  10  links stations H and P. 
     An IG unit  15  to be treated is conveyed by the conveyor  12  sequentially to stations H and P in a nearly vertical position with the substrates  13  of the IG unit  15  being generally vertical with respect to the conveying surface  125  of the conveyor  12 . It will be understood, however, by those skilled in the art that the present invention may be used to treat units conveyed to the press apparatus in the horizontal position. 
     The conveying surface  125  is inclined preferably approximately 5 degrees with respect to the horizontal such that the IG unit  15  to be treated tilts to one side of the conveyor  12 . The conveyor  12  may be controlled by suitable timing means to move an IG unit  15  as desired between the stations H and P. 
     The heating station H includes upper and lower assemblies indicated generally by  110  and  112 . The lower assembly  112  is mounted on the base  10  and houses lower left and right horizontal heater housings  32 L and  32 R and guide roller  132 . The housings  32 L and  32 R further house a plurality of linearly mounted heater means  28 . The horizontal heater housings  32 L and  32 R are movably housed within the assembly  112  by suitable means such that the separation between the housings  32 L and  32 R can be altered to accommodate IG units  15  of various thicknesses. The horizontal position of the lower assembly  112  is fixed but can be made adjustable by suitable means if needed. 
     The upper assembly  110  is mounted to support  113  which includes height adjustment means to adjust the spacing between the upper and lower assemblies  110  and  112 , thus permitting the press apparatus to accommodate IG assemblies of various sizes. The upper assembly  112  includes left and right spaced apart upper horizontal heater housings  30 L and  30 R and a single guide roller  130 . The housings  30 L and  30 R further house a plurality of linearly mounted heater means  28 . The horizontal heater housings  30 L and  30 R are movably housed within the assembly  110  by suitable means such that the separation between the housings  30 L and  30 R can be altered to accommodate IG units  15  of various thicknesses. 
     Guide roller  130  is movable with the housing  30 L. The guide rollers  130  and  132  support the IG assembly while in the station H. Additional guide rollers may be used if needed. 
     The heating station H further includes left and right leading and trailing vertical heater housings  40 L,  40 R and  50 L,  50 R respectively. The vertical heater housings  40 L,  40 R and  50 L,  50 R are tilted by an amount equivalent with the incline of the conveying surface  125  and each further house a plurality of linearly mounted heater means  28 . The heater means  28  are any suitable means such as electric, gas known in the art e.g. heat lamps and the housings  30 L, 30 R,  32 L, 32 R,  40 L, 40 R and  50 L, 50 R are constructed of suitably heat resistant materials such as aluminum. Means are provided to selectively activate and deactivate the heater means  28  when desired. 
     Leading vertical housings  40 L, 40 R are movably mounted on the base  10  to move with the leading edge of the IG unit  15  between a home position, when an IG unit  15  first enters station H, and an end position at the end of the heating cycle. Trailing vertical housings  50 L, 50 R move between like positions with the trailing edge of the IG unit  15 . The travel distance of the vertical housings  40 L, 40 R and  50 L, 50 R with the IG unit is determined by the desired heating time and can be varied as will be appreciated by those skilled in the art. 
     The housings  30 L,  30 R,  32 L,  32 R,  40 L, 40 R and  50 L, 50 R are designed to focus heat from the heater means  28  on the zones of the IG assembly where the spacer  11  is positioned and to reduce or eliminate heating of the balance of the IG assembly. The area of the heated zone corresponds approximately with the area of contact of the spacer  11  with the substrate  13 . 
     The pressing station P includes pressing means in the form of two converging press belts  60  having a wider separation at the beginning of the station P than at the end to provide a progressively decreasing passage channel through which an IG unit  15  will pass. The starting and ending separation of the belts  60  will be commensurate with the thickness of the IG unit  15  and the belts  60  can be optionally mounted on the base  10  such that the separation between the belts is adjustable manually or automatically to accommodate various thicknesses of IG units  15 . Other suitable pressing means may be used such as a series of compression rollers of progressively decreasing separation, and presses of the “butterfly” type. The press belts  60  are tilted according to the incline of the conveying surface  125  such that an IG unit  15  will pass along generally the same plane from station H to station P. 
     FIGS. 4A through 4G show the press apparatus in operation. Referring to FIG. 4A, an IG unit  15  is advanced by the conveyor  12  to the station H. If the press apparatus is part of an automatic line, the IG unit is advanced to the station H from a previous station on the line such as an automatic spacer application station. The horizontal heater housings  30 L, 30 R and  32 L,  32 R are positioned such that the spacer segments  11  along the upper and lower edges of the IG unit  15  will be adjacent the horizontal heater means  28  in housings  30 L, 30 R and  32 L,  32 R which are activated in the housings  30  and  32  as the IG unit  15  is advanced to the position shown in FIG.  4 B. Vertical housings  40 L, 40 R and  50 L, 50 R are in the home positions out of the path of the advancing IG unit. 
     As shown in FIG. 4B, the IG unit  15  is resting on the conveyor  12  tilted to one side of the conveyor  12  and supported laterally by the guide rollers  130  and  132 . Leading vertical housings  40 L, 40 R are in the home position adjacent the spacer  11  along the leading edge of the IG unit  15 . Trailing vertical housings  50 L, 50 R are in the home position adjacent leading vertical housings  40 L and  40 R. The energy generating means  28  in housings  30 L, 30 R,  32 L, 32 R and  40 L, 40 R are activated to heat the adjacent spacer  11 . 
     As shown in FIG. 4C, leading vertical housings  40 L, 40 R are in the end position having traveled with the leading edge of the IG unit  15  and upon reaching the end position, have been deactivated to prevent heating of the IG unit  15  in zones without spacer  11  as it advances past the housings  40 L, 40 R. The heater means  28  in housings  30 L, 30 R and  32 L, 32 R are still activated. 
     As shown in FIG. 4D, the leading edge of the IG unit  15  has advanced beyond the leading vertical housing  40 L, 40 R and into the station P. The trailing edge of the IG unit  15  has cleared the housings  30 L, 30 R and  32 L, 32 R and the energy generating means  28  therein have been deactivated. The trailing edge of the IG unit is now adjacent the home position of the trailing vertical housings  50 L, 50 R and the heater means  28  therein are activated. 
     As shown in FIG. 4E, the trailing vertical housing is in the end position having traveled with the trailing edge of the IG unit  15  as it advanced and upon reaching the end position, has been deactivated. Almost the entire length of the IG unit  15  is now with station P where the IG unit  15  is being progressively pressed together to bond the spacer  11  to the substrates  13  to form a sealed the IG unit. 
     As shown in FIG. 4F, the IG unit  15  has cleared the station P and a subsequent IG unit  15  is advancing into the station H. 
     As shown in FIG. 4G, the vertical housings  40 L, 40 R and  50 L, 50 R have returned to their respective home positions and the heating means in housings  30  and  32  are activated to recommence the cycle. 
     Referring to FIGS. 5 to  12  in another embodiment of the present invention, the press apparatus includes a vertical energy applying and pressing station shown generally as  200  and a horizontal energy applying and pressing station shown generally as  210 . 
     Vertical Station  200   
     An IG unit to be sealed advances on conveyor  220  to the vertical station  200 . The vertical station includes two vertical heating and pressing assemblies  230  and  232 . The assembly  230  is the trailing edge assembly, while the assembly  232  is the leading edge assembly. The heating and pressing assemblies  230  and  232  are each supported and guided by upper and lower rails  240  by means of upper and lower blocks  250  which slide along the top edge of each rail  240 . The rails  240  are shown in greater detail in FIG.  8 . The rail  240  has an inside edge  260  which is tapered in profile. The surface  260  is furthest from the outer edge  280  in the mid section of the rail  240  and closest to outer edge  280  at the end sections. The taper is achieved by slots  300  which permits the surface  260  to be tapered toward the outer edge  280 . 
     Referring to FIG. 7, each vertical heating and pressing assembly  230  and  232  includes a set of guide rollers  310  mounted on a support  320  for guiding the IG assembly. The support  320  is attached to main plate  340  with spacer blocks  360 . The main plate  340  includes a pressing surface  380  which contacts the glass of the IG unit. The pressing surface  380  is a heat resistant material such as phenolic fiber. Heating elements  402  are mounted between the support  320  and main plate  340 . The heating element  402  can be the energy generating means  28  as previously described. 
     The assemblies  230  and  232  are shown in their respective home positions in FIG.  6 . The assemblies  230  and  232  are mounted on the rails  240  such that the pressing surfaces  380  are opposed to each other. 
     The separation of the surfaces  380  must be sufficient to permit the width of the assembly to pass therebetween without being significantly pressed. The assemblies  230  and  232  move along the rails between their home position and the other end of the rails near the horizontal station  210 . As the assemblies  230  and  232  move toward the other end of the rails, the separation between the pressing surfaces  380  progressively decreases until the mid section of the rails  240  is reached, after which point the separation increases until the separation is once again such that there is no significant pressure on the IG unit. The movement of the assemblies  230  and  232  are timed with the conveyor  220  such that the assemblies  230  and  232  advance together with an advancing IG unit. The timing means for the conveyor and assemblies  230  and  232  is shown in FIG.  10 . Timing belts  400  and  410  rotate around pulleys  420  on a middle pulley assembly  430 . 
     The conveyor  220  likewise rotates around pulley  440  of middle pulley assembly  430  and guided by guide assembly  442 . The belts  400  and  220  are at their other ends, turn around pulleys  460  of the front pulley assembly  480 . Both belts  400  and  220  are driven by belt  500  rotating around drive pulley  510 . Belt  500  is driven by motor  520  at its other end. Motion is transferred from the motor  520  via belt  500  to drive pulley  510  and corresponding pulley  420 , and then to belt  400  via timing belt  410 . 
     Conventional motion sensors (not shown) sense the position of an incoming IG unit and in turn control grippers  530  which clamp the advancing IG unit to advance it toward the horizontal station  210 . The clamping operation performed by the four grippers  530  is synchronized to grip the IG unit such that it is advanced together with the assemblies  230  and  232 . 
     Each gripper  530  has an upper clamp  532  and lower clamp  534  which are actuated by air cylinders  536 . A gripper  530  is connected to each assembly  230  and  232 . With the belt  400  running, the assemblies  230  and  232  are advanced by actuating the cylinder  536  of upper clamp  532  to press upper clamp  532  against anvil  538 . Similarly, lower clamp  534  is actuated to return the assemblies  230  and  232  to the home position. 
     Referring to FIG. 6, in operation, an IG unit to be sealed such as that described previously as IG unit  15  is advanced by conveying means  220  to the assemblies  230  and  232  shown in the home position. The IG unit passes through the separation between the pressing surfaces  380  of first the trailing assembly  230  and then the leading assembly  232 , at which point the upper clamps  532  of the grippers  530  of the leading assembly  232  are actuated to clamp the assembly  232  to the belt  400 . The assembly  232  now moves with the belt  400  and in turn is synchronized with the advancing movement of the IG unit being carried by conveyor belt  220 . The assembly  232  is timed by conventional sensors (now shown) to be clamped to belt  400  when the spacer  11  is adjacent the heating element  402 . 
     As the assembly  232  advances toward horizontal station  210 , the separation between the pressing surfaces  380  of the assembly  232  diminishes which in turn progressively increases the pressure being applied to the substrates  13  to press them together. The heating element  402  is activated at this time to heat the substrates  13  adjacent the area where the vertical sections of the spacer  11  are located as the spacer  11  is being squeezed by the substrates  13 . This heats the outer surfaces of the spacer  11  which contacts the substrates  13 . Heating continues until the maximum pressing force is achieved around the mid point position of the rails  240  at which time the heating element  402  is switched off. As the IG unit  15  advances beyond the midpoint of station  200 , the separation of the pressing surfaces  380  increases until the substrates  13  are no longer being pressed together. 
     While the leading assembly  232  is advancing, the trailing edge of the IG unit  15  will be moving though the trailing assembly  230 . Once sensors (not shown) indicate that the trailing edge of the IG unit is passing through the trailing assembly  230 , the upper clamps  532  of the grippers  530  of the trailing assembly  230  are actuated to clamp the assembly  230  to the belt  400 . The trailing assembly  230  then moves with the trailing edge of the IG unit  15  in the same manner as that described above with respect to the leading edge. The trailing vertical segments of the spacer  11  are also similarly pressed and heated. 
     It will be appreciated that the heating element  402  can be switched on at various points during the advancing of the assemblies  230  and  232  to achieve various heating and pressing sequences, such as initial pressing of the substrates  13  and spacer  11  followed by simultaneous pressing and heating as described above. An alternative sequence is to begin heating immediately followed by pressing. It has been found that simultaneously pressing together of the substrates against the spacer and heating yields a good bond between the spacer and the substrates. 
     Horizontal Station  210   
     As the IG unit being sealed exits the vertical pressing station, it enters the horizontal pressing and heating station  210 . The station  210  includes upper and lower horizontal heating and pressing assemblies  600  and  610 . 
     Referring to FIG. 9, the upper assembly  600  includes two horizontal support plates  620  and  622 , below which are attached a linear array of pressing rollers  630  for guiding IG units. The plate  620  is fixed while the plate  622  is movable towards and away from the plate  620  to accommodate different thicknesses of IG units. A heating element  650  is mounted on each plate  620  and  622 . 
     The assembly  600  includes opposed arrays of pressing rollers  630 . The separation of the guide rollers  630  is greatest at the entry end of the assembly  610  shown generally at  660 , and tapers to a narrower separation at the exit end shown generally at  670 . The heating elements  650  follow the same tapering path as the pressing rollers  630 . The heating elements  650  heat the substrates  13  near the top edge of the IG unit adjacent the location of the spacer. Energy is transferred through the substrates  13  to heat the outer surfaces of the spacer  11  where it contacts the substrates  13 . 
     At the entry end  660 , the separation of the pressing rollers  630  permits passage of the top section of an IG unit without significantly pressing it together. As an IG unit proceeds towards the exit end  670 , it is progressively pressed together by the pressing rollers  630 . 
     The lower heating and pressing assembly  610  is identical to the upper assembly  600  except it is mounted inverted with respect to assembly  600 . The pressing rollers  630  are above the plates  620  and  622  and the heating elements (not shown) are below the rollers  630 . 
     The separation between the assemblies  600  and  610  can be adjusted to accommodate different sizes of IG units by raising or lowering the upper assembly  600  by motor  680  and other suitable means. The pressing rollers  630  on the assemblies  600  and  610  are inclined downwardly by approximately 3° toward the exit end  670 . This imparts downward pressure on an IG unit to press it onto the conveyor  220  to advance it. The conveyor belt  220  passes below the lower assembly  610 . 
     In operation, as suitable conventional motion sensors (not shown) detect the IG unit  15  entering the station  210 , the heating element  650  in each assembly  600  and  610  is activated to heat the substrates  13  adjacent to the upper and lower horizontal sections of the spacer  11 . As the IG unit  15  advances towards the exit end  670 , significant pressure begins to be applied to the substrates  13  around the midpoint of the station  210 . From the mid point, simultaneous heating and pressing occurs. It will be understood that the heating elements  650  can be varied to adjust the amount of heating as well as to vary the timing of the heating with respect to the pressing. 
     After the IG unit  15  exits the station  210 , the sensors and heating element  650  reset for the next IG units to be processed. 
     As will be understood, various modifications to the present invention can be made including arranging the heater means in a “picture frame” type assembly whereby the entire spacer is heated at one time, or alternatively, using a heater means which travels around the periphery of the IG unit to heat the spacer. A platinum press can also be employed with suitable modifications.

Summary:
An apparatus and method to seal a spacer between a pair of substrates within an IG assembly having a pair of spaced apart substrates and a bondable spacer therebetween, having support means for supporting an IG assembly to be treated and zonal energy applying means to locally apply energy to selected zones of the IG assembly where said spacer is located without providing direct energy to the balance of the IG assembly.