Abstract:
A high speed parallel manufacturing line for manufacturing insulated glass units, the manufacturing line including a gas filling topping press that mates a spacer applied lite supplied to the topping press and a topping lite supplied to the topping press to create an insulated glass unit and fills the insulated glass unit with a non-air gas. A heating station applies localized heat to adhesive of the spacer material. A sealing press applies pressure to the insulated glass unit and facilitates further sealing of the spacer material to the spacer applied lite and the topping lite. The line may include a fourth corner sealer that completes sealing of the airspace of the IGU prior to finishing of the IGU.

Description:
FIELD OF THE INVENTION 
       [0001]    The invention relates to production of insulated glass units. 
       BACKGROUND 
       [0002]    Insulated glass is heavily utilized in modern residential and commercial construction. In many areas of the country it is required by building code as an energy conservation measure. A single pane of glass alone has very little insulating value. Multi-pane insulated glass windows have much greater insulating value. Insulated glass units generally include at least two panes of glass having identical shapes. Sealants and adhesives are used to bond the glass panes to a perimeter spacer which separates the two panes of glass. The entire perimeter including the two panes of glass and the spacer are sealed to one another to eliminate movement of ambient air into the space between the two panes of glass. 
         [0003]    The space is filled with dehydrated air or more commonly another gas such as argon, xenon or krypton. Sulfur hexafluoride is also used for gas filling. The filling of insulated glass units with argon or another gas that is not air has been found to increase the energy efficiency of the insulated glass units markedly. Some insulated glass units includes three panes of glass with two intervening spaces which are similarly filled with argon or another gas other than air and then edge sealed. 
         [0004]    The spacer in an insulated glass unit is inset from the peripheral edges of the glass panes leading to a trough shaped space bounded on two sides by the glass panes and on one side by the spacer. In the manufacturing of some insulated glass units, this space is filled with an adhesive sealant which forms the, so called, secondary seal of the insulated glass unit. 
         [0005]    Recently, other primary sealing technologies have been developed. These edge sealing technologies utilize a primary seal that stands alone and produce an insulated glass unit that does not include a secondary seal. This may result in faster production and reduced cost for insulated glass units though the units may also have shorter lives and be useful in a narrower range of climatic conditions. 
         [0006]    If present, the secondary seal may be applied using a variety of different adhesive sealants. These include time setting sealants, such as silicones or butyl rubber sealants. Sometimes two part sealants utilizing a resin and a catalyst to polymerize the resin are utilized. More commonly in modern manufacturing, hot melt adhesive sealants are used. Hot melt adhesive sealants are general applied in a liquid state at a temperature of approximately 350° F. and harden upon cooling to ambient temperature. 
         [0007]    In high volume manufacturing facilities, the secondary seal is commonly applied by fully automated equipment in which a computer controlled robotic sealant applying head is moved around the peripheral edges of the insulated glass unit under computer control and applies the sealant to the edge or edges of the insulated glass unit. Fully automated secondary edge sealing equipment of this sort can apply the secondary seal to very large numbers of insulating glass units in a production run. Typically, the insulated glass units in these circumstances are produced in large runs of identical units. 
         [0008]    The process of manufacturing insulated glass units generally includes infeed of glass panes or lites into a washing unit that cleans both surfaces of each pane and, in particular, the surface of each pane that will be on the interior of the insulated glass unit. This is particularly important because, once the insulated glass unit is complete the interior surfaces will be inaccessible to cleaning and any visible dirt is impossible to remove. Accordingly, the washing station is generally followed by an inspection station to assure that the panes are clean. 
         [0009]    In the prior art, panes or lites are then conveyed in tandem fashion to further processing. The panes are divided into pairs, each pair including a spacer lite to which a peripheral spacer is applied and which forms the back of the IGU and a topping lite which will ultimately be applied on top of the spacer lite and sealed to the spacer to form the insulated glass unit. According to the prior art generally, the topping lite proceeds first in the pair and is followed by the spacer applied lite. When the spacer lite reaches a spacer application station the peripheral spacer is applied. The spacer lite and the topping lite are both advanced so that the topping lite can be removed from the conveyor. According to the prior art, the topping lite is picked up first at the gas press then the spacer applied lite is conveyed in and unit is gas filled and assembled. The primary sealed insulated glass unit is then conveyed to a secondary seal applicator to apply secondary sealant to the edges bordered by the spacer and the peripheral portions of the lites. The completed IGU is then conveyed to the end of the processing line for transport to next steps. 
         [0010]    According to the prior art, the heads for application of spacer and sealant are stationary in the X axis and the glass lites or IGUs are moved relative to the fixed heads. Thus the prior art requires that the glass to move though the zone three times. Once for application along bottom x axis moving forward, once across the top x axis moving backward and then removal forward to the next station. 
         [0011]    There is a need for application devices in the window industry that can increase the productivity of manufacturing of insulated glass units. 
       SUMMARY OF THE INVENTION 
       [0012]    The high speed parallel process insulating glass manufacturing line according to the embodiments of the invention solves many of the industry demands for higher cycle speed, shorter cycle time and automation of the manufacturing process. According to an example embodiment, the high speed line generally includes an infeed station, a glass washer, an inspection station, a shuttle, a driven parallel infeed conveyor, an insulated glass unit spacer applicator, a following queue station, a grid station followed by a second queue station, a gas filling station, a secondary edge sealer and an outfeed queue station. Embodiments of the invention are expected to permit a cycle time of approximately 15-20 second per unit as compared to the prior art cycle time of 25-30 seconds per unit. This cycle time is expected to be 33 to 50 percent of the prior art cycle time. Thus a doubling of production rate over the prior art is possible. 
         [0013]    The infeed station is generally conventional and receives glass panes or lites generally fed to the line one at a time by an operator. 
         [0014]    The washer is also generally conventional and according to an example embodiment of the invention, is generally vertically oriented so that lites are washed and dried in a generally vertical orientation. Vertical, in this case means that the lites are held in an orientation within about 25 degrees of true vertical, more typically within 6 to 10 degrees of vertical, for example six degrees from vertical. 
         [0015]    The inspection station is also generally conventional and permits inspection of the washed glass for cleanliness and condition. 
         [0016]    The shuttle according to an example embodiment of the invention is a double shuttle which distributes lites so that topping lites are in a back conveyor line and spacer applied lites are in a front conveyor line. According to one embodiment of the invention, the double shuttle minimizes shifting when glass lites are distributed to the front and back conveyor line. 
         [0017]    Spacer applied lites are those to which a perimeter spacer will be or has been applied in the construction of an insulated glass unit (IGU). Topping lites are those that will be or have been applied to a perimeter spacer that is already joined to a spacer applied lite to form an IGU that is partially completed in that it has been primary sealed but no secondary sealant has been applied. An insulated glass unit (IGU) includes a spacer applied lite joined to a topping lite and a perimeter spacer sealed to both the spacer applied lite joined to a topping lite with air or another gas trapped in between. Some IGUs that are made with single seal spacers are not subject to a secondary seal process. In this case, the primary seal is the only seal between the spacer and the lites and the IGU without a secondary seal represents a complete IGU unit. 
         [0018]    The driven parallel infeed conveyor is a queue conveyor and receives glass lites from the shuttle and conveys them to the insulated glass unit spacer applicator. Spacer applied lites are in a front conveyor line while topping lites are in a rear conveyor line. Separate conveying of the topping lites and the spacer applied lites eliminates time wasted conveying the topping lite through the spacer applied lite work areas and may save as much as five seconds of cycle time according to the invention. 
         [0019]    The insulated glass unit spacer applicator receives lites from the parallel infeed conveyor and applies spacers to the spacer applied lite on the front conveyor line while conveying the topping lite behind the spacer applied lite. The IGU spacer applicator is structured so that a following spacer applied lite can be staged for the applicator prior to the finishing of the application of the spacer to the first spacer applied lite. Staging the following lite prior to finishing the prior lite saves about three seconds in cycle time. 
         [0020]    According to an example embodiment of the invention, the spacer is applied while the lite is moving forward. Thus, the applicator head and glass are conveyed forward simultaneously at the same time that the applicator head is moving relative to the lite and applying the spacer. As compared to the prior art, the spacer applicator according to an embodiment of the invention eliminates backing up of the lite during the application process so that the lite is only moved forward continuously during the process. Applying the spacer while the spacer applied lite is moving a forward direction saves about five second in cycle time over the prior art approach. 
         [0021]    According to an embodiment of the invention, the spacer or primary seal is applied to the bottom of the lite then to the trailing edge of the lite, the top edge of the lite and the leading edge of the lite in sequence. This occurs while the lite is moving forward so that the lite never is required to move backward or to stop the manufacturing line. The spacer applicator head moves in the x, y and z axes plus in a rotational fashion. 
         [0022]    The spacer applied lite is conveyed through the spacer applicator by a servo-driven suction cup assembly structured to grip the lite and move the lite forward with variable speed while the spacer is applied. According to an example embodiment of the invention, the speed and rate of the servo-driven suction cup assembly are electronically controlled. The servo-driven suction cup assembly displaces the lite forward, in part, to accommodate staging of the following spacer applied lite. 
         [0023]    The topping lite and spacer applied lite with spacer now applied exit to the following queue station prior to the optional grid application station. 
         [0024]    The driven grid application station is generally conventional in structure and need not be further described here other than the grid application station has two conveyor lanes so the topping lite passes behind rather than through the grid application work zone. This arrangement permits the following spacer applied lite which may require a grid to be staged  5  seconds faster. The grid application station is used to place grids within the spacer of the spacer applied lite. The driven grid application station is optional and can be eliminated if grids are not desired. 
         [0025]    The gas press with gas fill may include, according to embodiments of the invention, a single high speed gas press with a shuttle in the press or a double gas press including two gas fill chambers with a shuttle prior to and after the double gas press. 
         [0026]    According to an embodiment of the invention, the double gas press includes two gas press compartments including a front gas press compartment and a back gas press compartment. Each of the front gas press compartment and the back gas press compartment include gas ducts and an internal conveyor. 
         [0027]    According to one embodiment of the invention, the gas ducts are arranged to dispense gas from either the leading or trailing edge of the unit. The double gas press may include three platens including a front platen, a central platen shared by both compartments and a back platen. As it is operating, the front compartment receives a first topping lite from the back line. The front compartment then transfers the first topping lite from the central platen to the front platen while shuttling the front compartment to the front line. The front compartment receives a first spacer applied lite from the front line which is received on the central platen front side. The front gas press compartment then dispenses gas and mates the first topping lite with the first spacer applied lite creating a primary sealed insulated glass unit. Meanwhile, the back compartment is aligned with a back line and receives a second topping lite from the back line. The back compartment then shuttles to the front line where it receives a second spacer applied lite from the front line. The back compartment platens then move together while dispensing gas to mate the second topping lite with the second spacer applied lite. In sequence, each of the back compartment and the front compartment shuttle to alignment with the back line or the front line to convey the partially completed first and second insulated glass units. Because there are 2 chambers according to this embodiment, each gas fill chamber has 30-40 seconds to convey glass into each chamber, fill the IGU with gas, assemble and convey the assembled IGU out of the gas fill chamber. Accordingly, the production cycle can be maintained at 15-20 seconds. The glass units alternately load and unload each of the gas press chambers during each cycle. This longer time in each chamber allows for higher than average gas fill percentages without slowing production throughput. This represents yet another improvement over traditional lines where high gas fill percentages will slow the line&#39;s production. 
         [0028]    According to another example embodiment of the invention, a single high speed gas press is used. According to an example embodiment the single high speed gas press generally includes a housing, a front platen with suction grippers, a back platen with suction grippers, side doors, an internal conveyor and gas ducts. According to embodiments of the invention, the gas ducts may be located below or on the leading edge side or the trailing edge side of the housing. 
         [0029]    The single high speed gas press shuttles from the back line to the front line. In sequence, it receives a topping lite conveyed from the back line, transfers the topping lite from the back platen to the front platen and meanwhile shuttles to the front line. The single gas press then receives the spacer applied lite from the front line. Side doors of the single gas press close and the internal conveyor moves out of the way. Gas ducts are moved into position at the bottom or side as the internal conveyor is moved out of the way. Gas is then injected and the platens move to mate the topping lite to the spacer applied lite and press them together to establish a primary seal. The internal conveyor then moves back into place and the assembled insulated glass unit is conveyed out at the same time as a following topping lite is conveyed in. 
         [0030]    The primary sealed, partially complete insulated glass unit then is conveyed to the secondary edge sealer. 
         [0031]    According to an example embodiment of the invention, the secondary edge sealer is a two headed edge sealer. According to an example embodiment, an upper head applies secondary sealant to the leading edge, the top edge and the trailing edge of the insulated glass unit. The lower head applies secondary sealant to the bottom edge of the partially completed insulated glass unit. According to an embodiment of the invention, servo-driven cups grip and transport the insulated glass unit. The servo-driven cups also displace the insulated glass unit forward to permit staging of a following unit while the first unit is being edge sealed. According to an example embodiment of the invention, each of the upper and lower secondary edge sealing heads includes a corner wiper that eliminates or minimizes the need for operator touch-up of the insulating glass unit. This is particularly helpful with the short cycle time of the present invention as the operator is unlikely to have much time to touch-up due to the 15-20 second cycle time of the high speed parallel insulated glass manufacturing line. As compared to the prior art, there is no need for the IGU to be backed up and reconveyed through the secondary sealer. In the prior art, the IGU is generally conveyed through secondary sealer three times in a forward direction and moved in reverse two times. This represents a time savings of about five seconds over the conventional approach. 
         [0032]    According to example embodiments of the invention, the two edge sealing heads are mounted on a short move x-gantry. The gantry is capable of moving in the x direction along with the IGU as the IGU is conveyed forward, for example, for about eight inches. This short move forward in the x direction allows for the finishing Y movement of the gantry to be slightly ahead of the starting y move. This allows the next IGU to be staged at the start point prior to the prior unit being completed. This feature saves up to  3  more seconds in cycle time. 
         [0033]    According to example embodiments of the invention, secondary sealants are either hot melt sealants or two part sealant that set rapidly to support the short cycle times. More conventional sealants can be utilized as well. 
         [0034]    The completed insulated glass units are then conveyed out to a driven or non-driven outfeed queue station where the operator moves the completed insulated glass unit for further processing. 
         [0035]    According to another example embodiment, the high speed line generally includes an infeed station, a glass washer, an inspection station, a shuttle, a driven parallel infeed conveyor, an insulated glass unit spacer applicator that applies single seal spacers such as, for example, spacers provided under the trade names Duraseal® and Duralite®, a following queue station, a grid station optionally followed by a second queue station, a double auto topping press optionally with gas filling and an infeed shuttle, a heating station, a vertical platen press and a fourth corner sealer. 
         [0036]    Similar to the above discussed embodiment, the infeed station is generally conventional and receives glass panes or lites generally fed to the line one at a time in a generally vertical orientation by an operator. 
         [0037]    The washer is also generally conventional as discussed above. According to this example embodiment of the invention, is generally vertically oriented so that lites are washed and dried in a generally vertical orientation. Vertical, here, has the same meaning as discussed above with relation to the earlier embodiment. 
         [0038]    The inspection station is also generally conventional and permits inspection of the washed glass for cleanliness and condition. 
         [0039]    The shuttle according to this example embodiment is a double shuttle which distributes lites so that topping lites are in a back conveyor line and spacer applied lites are in a front conveyor line. Similar to the above embodiment, the double shuttle minimizes cycle time when glass lites are distributed to the front and back conveyor line. 
         [0040]    The insulated glass unit spacer applicator according to this embodiment of the invention is adapted to apply a single seal spacer. According to this example embodiment, the spacer is applied while the lite is moving forward similar to the above discussed example embodiment. As above, the applicator head and glass are conveyed forward simultaneously at the same time that the applicator head is moving relative to the lite and applying the spacer. As compared to the prior art, the lite is only moved forward continuously during the process. Applying the spacer while the spacer applied lite is moving in a forward direction saves about five second in cycle time over a prior art approach. 
         [0041]    According to this example embodiment of the invention, the single primary seal spacer is applied to the bottom of the lite, then to the trailing edge of the lite, the top edge of the lite and the leading edge of the lite in sequence. This occurs while the lite is moving forward so that the lite never is required to move backward or to stop the manufacturing line. The spacer applicator head moves in the x, y and z axes as well as in a rotational fashion along with the spacer applied lite while the spacer is applied. 
         [0042]    Single primary seal spacers generally include a metal, flexible foam or composite spacer that is bounded on two edges by a contact sealant. A metal spacer material may be corrugated such that it can be bent around corners of the IGU. Thus, at least some single primary seal spacer materials require no notching to form corners. 
         [0043]    The contact sealant may include, for example a butyl rubber sealant that is tacky at ambient room temperature of approximately  70  degrees F. Permanent adhesion of such a sealant is heat and pressure activated. Typically in the prior art, these spacers are utilized by assembling the insulated glass unit in a horizontal position and passing the assembled insulated glass unit through an oven to heat the insulated glass unit. The insulated glass unit is then pressed with a series of staged rollers that press the lites against the spacer and sealant and to cause the sealant to wet out and make a good seal. Accordingly, the entire IGU including the glass lites are heated and raised in temperature during the sealing process. This creates a number of disadvantages. 
         [0044]    First, the ovens require the use of fans to circulate air and the fans cause additional energy consumption. Heating the entire unit also consumes considerable energy. 
         [0045]    Second, if the IGU is completely sealed immediately, as the unit cools air or gas within the unit contracts and the spacers are forced inwardly away from the edges by atmospheric pressure. This can cause the spacers to be bowed rather than straight and parallel to the edges of the unit as well as causing the glass to bow inwardly. Prior art practice is then to leave a corner vent open in the IGU and to allow the unit to cool to ambient temperature before gas filling and then to seal the corner vent. Because it takes up to fifteen minutes for the IGUs to cool, considerable storage space is required. Storage requires much additional labor to handle the work in progress and the speed of production is reduced. Gas filling is then done manually requiring further labor and time as well as increasing the possibility of errors in manufacturing. Further, moving insulated glass units between horizontal and vertical orientations requires considerable effort and labor and creates ergonomic challenges including the possibility of injury to bones and joints of workers. 
         [0046]    Embodiments of the invention include several features to address this problem. 
         [0047]    First, the spacer applicator includes a temperature controlled spacer supply drum that stores the coiled spacer material and maintains it at a desired temperature usually above ambient temperature to maintain a desired level of wettability of the sealant that is part of the single sealant spacer material. 
         [0048]    Second, a platen press or vertically oriented roller arrangement is preceded by infrared heating units that utilize focused infrared lamps to localize heating to the spacers, sealant and local area of the glass lites with which the sealant makes contact. According to one example embodiment of the invention the focused infrared lamps are movable and move along with the IGU on the line while heating the eight edges of the spacer material along the four edges of a rectangular IGU. According to another example embodiment, the focused infrared lamps are stationary but of sufficient length to heat the length and width of the largest IGU the system is capable of processing. According to an example embodiment the invention includes a vertical heater station and a horizontal heater station. According to an example embodiment, the vertical heater station includes at least two heaters that are oriented to heat vertical edges of the IGU on opposing sides of the IGU in which case the IGU is paused twice, once to heat the leading edge and once to heat the trailing edge of the IGU. Alternately, the vertical heater station includes two pairs of heating units that are adjustable for the length of the IGU and adjustable to be spaced apart by the distance from the leading edge of the IGU to the trailing edge of the IGU. The IGU is paused for a short time while the vertical edges are heated to facilitate wettability of the spacer adhesive. 
         [0049]    The horizontal heater station includes two heaters that are adjustable as to separation such that the heaters are positioned over the upper and lower edges of the IGU to heat the upper and lower edges simultaneously. The IGU may continue to be moved along the conveyor while the upper and lower spacer regions are being heated. 
         [0050]    It is expected that the lamps will have sufficient output to heat the spacer and sealant in 15 second or less. Heat output can be controlled generally by controlling voltage supplied to the lamps. The infrared heat lamps may be focused by the use of parabolic reflectors for example. Localized heating of just the spacer has several advantages. It uses approximately one fifth the energy of traditional ovens which heat the entire insulated glass unit. Because the glass is not heated the airspace is also unheated allowing the argon gas to be retained during the heating and pressing stages of the line. The elimination of the heating of the glass also allows the units to avoid the acclimation process presently needed prior to sealing the fourth corner. All of these items reduce handling and labor. 
         [0051]    According to another embodiment, heating may be accomplished by placing the entire manufacturing line or a portion of the manufacturing line in a temperature controlled environment that maintains the spacer material and lites at a temperature for optimal adhesion and wettability of the sealant, for example 80-100° F. 
         [0052]    Argon or other filling gas tends to cool as they expand from a compressed state in a pressure vessel. Accordingly, embodiments of the invention include an expansion manifold to allow the argon or other filling gas to reach ambient temperature prior to filling the IGU with gas. This is done so as not to reduce the temperature of the spacer and sealant material to a temperature at which the wettability of the sealant is less than desired. 
         [0053]    A platen press has certain advantages when used to press the lites against the spacer and sealant in that it generally creates less rebound than a roller press. Because the unit is filled with argon or other gas but a corner is not yet sealed, rebound tends to displace argon and draw ambient atmosphere into the IGU which reduces the concentration or argon or other non-air gas. A vertical roller press may also be used. Vertical here has the meaning as discussed above. A vertical roller press tends to create more rebound but also maintains constant forward motion of the IGU during the pressing process and may contribute to reduced cycle times when gas retention is not a concern. In the situation discussed above, gas loss is a primary concern because it reduces thermal performance of the finished IGU. 
         [0054]    Embodiments of the invention can use either a single press that assembles the IGU and presses it to final thickness or a first press that assembles the unit and fills the unit with gas followed by a second press that presses the unit to final thickness after heat has been applied to the spacer by application of infrared lamps. Furthermore, a double gas press may be utilized to increase throughput when gas filling, followed by heating zones that apply localize heat to the spacer material and adhesive. The IGU then is transferred to a platen press to press that presses the IGU to its final thickness dimension. In an alternate embodiment, a roller press can be used to press the IGU to its final thickness dimension. 
         [0055]    The fourth corner sealer serves to close the fourth corner and may in several embodiments include an angled rocking device, a roller device or a two part angled press device. 
         [0056]    The roller device is configured such that the roller applies a force against a first side of the fourth corner and passes around the corner to apply a force to the second side of the fourth corner. 
         [0057]    The angled rocking device includes a corner pressing structure have two sides that meet at an angle greater than ninety degrees that is rocked over the corner to compress and seal both sides. 
         [0058]    The two part angled press device includes two separate angled pressure heads that are applied to the two sides of the corner independently either in sequence of simultaneously to press the two sides of the corner together to achieve sealing. 
         [0059]    It is to be noted related to this application that the term “parallel” is to be construed broadly and is not limited to “parallel” in the geometric sense of being equidistant at all points unless otherwise noted in the application of claims. Parallel may, for example, refer to two conveyor paths that begin and end at substantially the same locations but take different paths between the beginning and end. 
         [0060]    It is expected that the high speed parallel process insulated glass manufacturing line according to an embodiment of the invention will have cycle times of approximately  17 - 18  seconds for insulated glass units depending upon size. It is possible that the high speed parallel insulated glass manufacturing line will be able to achieve cycle times of approximately  15  seconds per insulated glass unit. This is a significant gain over the prior art known to Applicant, more than doubling production without adding employees. 
         [0061]    The high speed parallel insulated glass manufacturing line can be operated by three employees if no grids are installed and four employees if grids are installed. To accomplish similar production numbers on a manual line according to known prior art that is considered a market standard nine to ten employees are required. This results in significant cost savings. 
         [0062]    Operator touch points, at which employees must act in the manufacturing process are reduced from nine to three as compared to the prior art. This reduction minimizes labor required but also reduces the potential for mistakes created by extra handling and the application of manual processes. 
         [0063]    The high speed parallel insulated glass manufacturing line uses about one fifth the energy needed on traditional prior art production lines. According to embodiments of the invention glass is not heated nor is the airspace, saving energy. Infrared heating lamps are only turned on when needed while traditional ovens require nearly constant heating to maintain required temperatures. This leads to a large energy savings because oven heating uses five times the energy of the disclosed invention. 
         [0064]    The elimination of temperature acclimation of insulated glass units to ambient temperature before sealing reduces the need for work in process carts and floor space required to store them. Also, this enables the desiccant in the insulated glass units to begin absorbing moisture from only the airspace of the IGU rather than losing effectiveness by absorbing ambient moisture during time that the IGU is open to the atmosphere as is common in the prior art. Ultimately this gives the desiccant present in the spacer more drying power for the airspace in the IGU creating a better resulting product. 
         [0065]    Argon, krypton or other non-air gas is introduced at the time of assembly by embodiments of the invention, thus reducing mistakes and the likelihood of mislabeled units that may not have been properly manually filled. 
         [0066]    According to embodiments of the invention, the fourth corner is closed and pressed by operation of the inventive machine rather than by application of a manual heat lamp and handheld stick which is a common conventional method. This leads to improvement in ergonomic safety and better quality of the finished IGU. 
         [0067]    Glass is stored in carts vertically before and after IGU production. The vertical high speed parallel insulated glass manufacturing line provides ergonomic benefits for workers as compared to prior art manual lines because the manual lines require manually tipping glass lites to horizontal at the start then manually returning IGUs to vertical at the end of the production line. Larger insulated glass units on the prior art manual line are tipped and topped vertically, to utilize gravity to line up the edges, then tipped to horizontal for heating in the oven. The vertical line according to embodiments of the invention eliminates up to four changes in orientation of the glass between vertical and horizontal. 
         [0068]    Aspects of the invention, including but not limited to gas filling , infrared heating, platen pressing and corner sealing prior to removal of the IGU from the manufacturing line can be utilized on traditional production lines. These improvements are not limited to high speed lines. Many of the improvements disclosed herein are beneficial for slower speed production lines as well. A standard vertical line or a manual IGU production line, for example, would benefit from the IR heating mechanism and platen press as described herein enabling the fourth corner to be closed and sealed immediately thus reducing energy wasted, improving ergonomics, reducing labor and handling of the IGUs as well as reducing the opportunity for mistakes in production. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0069]      FIG. 1  is a block diagram depicting a high speed parallel process insulating glass manufacturing line according to an example embodiment of the invention; 
           [0070]      FIG. 2  is an end elevational view of an IGU spacer applicator according to an example embodiment of the invention; 
           [0071]      FIG. 3  is a schematic depiction of an IGU spacer applicator at the beginning of spacer application to a spacer applied lite; 
           [0072]      FIG. 4  is a schematic depiction of an IGU spacer applicator during spacer application to a spacer applied lite bottom edge; 
           [0073]      FIG. 5  is a schematic depiction of an IGU spacer applicator during spacer application to a spacer applied lite trailing edge; 
           [0074]      FIG. 6  is a schematic depiction of an IGU spacer applicator beginning spacer application to a spacer applied lite top edge; 
           [0075]      FIG. 7  is a schematic depiction of an IGU spacer applicator continuing spacer application to a spacer applied lite top edge; 
           [0076]      FIG. 8  is a schematic depiction of an IGU spacer applicator during spacer application to a spacer applied lite leading edge; 
           [0077]      FIG. 9  is a schematic depiction of a dual head IGU secondary sealer at the initiation of an IGU sealing sequence; 
           [0078]      FIG. 10  is a schematic depiction of a dual head IGU secondary sealer as a first sealing head applies secondary sealant to a leading edge of an insulated glass unit and a second sealing head engages the bottom edge of the insulated glass unit; 
           [0079]      FIG. 11  is a schematic depiction of a dual head IGU secondary sealer as a first sealing head applies secondary sealant to a top edge of an insulated glass unit and a second sealing head applies sealant to the bottom edge of the insulated glass unit; 
           [0080]      FIG. 12  is a schematic depiction of a dual head IGU secondary sealer as the first sealing head completes application of secondary sealant to a top edge of an insulated glass unit and the second sealing head completes application of sealant to the bottom edge of the insulated glass unit; 
           [0081]      FIG. 13  is a schematic depiction of a dual head IGU secondary sealer as the first sealing head applies secondary sealant to a trailing edge of an insulated glass unit and a second sealing head disengages from the bottom edge of the insulated glass unit; 
           [0082]      FIG. 14  is an elevational view of a double gas press according to an embodiment of the invention; 
           [0083]      FIG. 15  is an elevational view of a single gas press according to an embodiment of the invention; 
           [0084]      FIG. 16  is a block diagram depicting a high speed parallel process insulating glass manufacturing line with gas filling according to another example embodiment of the invention; 
           [0085]      FIG. 17  is a front elevational view of a heating station according to an example embodiment; 
           [0086]      FIG. 18  is a side elevational view of the heating station of claim  17 ; 
           [0087]      FIG. 19  is perspective view of a vertical sealing roller press according to an example embodiment of the invention; 
           [0088]      FIG. 20A  is a perspective view of a vertical sealing platen press according to an example embodiment of the invention; 
           [0089]      FIG. 20B  is a perspective view of a gas fill manifold assembly according to an example embodiment of the invention; 
           [0090]      FIG. 21A  is a perspective view of a fourth corner sealer incorporating a roller according to an example embodiment of the invention; 
           [0091]      FIG. 21B  is a detail perspective view of a fourth corner sealer roller according to an example embodiment of the invention; 
           [0092]      FIG. 22  is a perspective view of a fourth corner sealer incorporating an angled rocking structure according to an example embodiment of the invention; 
           [0093]      FIG. 23  is a perspective view of a two part angled fourth corner sealer according to an example embodiment of the invention; 
           [0094]      FIG. 24  is a perspective view of a fourth corner infrared heater according to an example embodiment of the invention; and 
           [0095]      FIG. 25  is a perspective view of an auto-topping press according to an example embodiment of the invention. 
       
    
    
     DETAILED DESCRIPTION 
       [0096]    Referring to  FIG. 1  according to an example embodiment of the invention, high speed parallel process insulating glass manufacturing line  50  generally includes infeed station  52 , washer  54 , inspection station  56 , shuttle  58 , driven parallel infeed conveyor  60 , IGU spacer applicator  62 , following queue station  64 , driven grid station  66 , second queue station  68 , gas press and fill station  70 , secondary edge sealer  72 , and non-driven outfeed queue station  74 . This example embodiment may include elements that are optional as will be discussed herein. However, the elements of the invention are to be defined by the claims appended hereto. 
         [0097]    Infeed station  52  is generally conventional in design and known to those skilled in the art and need not be further described. 
         [0098]    Washer  54  is general conventional in design and need not be described further herein. Washers  54  are known to those skilled in the art and are available from a number of manufacturers. Washer  54  however, is a glass lite or pane washer that operates with the lite in a generally vertical orientation. 
         [0099]    Inspection station  56  is generally conventional in design and need not be further described herein. 
         [0100]    Shuttle  58  according to an example embodiment of the invention includes double shuttle mechanism  76 . Double shuttle mechanism  76  travels back and forth and divides incoming lites from infeed station  52 , washer  54  and inspection station  56  into spacer applied lites  78  and topping lites  80 . According to an example embodiment of the invention, spacer applied lites  78  are directed to front conveyor line  82  while topping lites  80  are directed to rear conveyor line  84 . For the purposes of discussion of the invention, while spacer applied lite  78  and topping lite  80  may be identical or similar pieces of glass, spacer applied lite  78  refers to lites to which a perimeter spacer has been or will be applied during the manufacturing process while topping lite  80  refers to lites that will be applied on top of the spacer applied lite and perimeter spacer to create a partially assembled insulated glass unit. 
         [0101]    Front conveyor line  82  generally transports spacer applied lites  78 . Front conveyor line  82  extends generally from shuttle  58  to gas press and fill station  74 . This should not be considered limiting as depending upon the exact design of high speed parallel manufacturing line  50  according to example embodiments of the invention, this extent may vary. Rear conveyor line  84  generally transports topping lites  80  and, similar to front conveyor line  82 , in an example embodiment, extends generally from shuttle  58  to gas press and fill station  74 . 
         [0102]    Driven parallel infeed conveyor  60  is generally conventional in design and known to those skilled in the art and need not be further described here. Driven parallel infeed conveyor  60  includes front conveyor line  82  and rear conveyor line  84  upon which spacer applied lite  78  and topping lite  80  are conveyed. 
         [0103]    Referring to  FIGS. 2-8 , IGU spacer applicator  62  generally includes applicator head  86 , applicator gantry  88  and servo driven cup  90 . Front conveyor line  82  upon which spacer applied lite  78  is transported is accessible to applicator head  86 . Rear conveyor line  84  transports topping lites through IGU spacer applicator  62  to the rear. 
         [0104]    Applicator head  86  is supported by applicator gantry  88  and applicator head  86 , in combination with applicator gantry  88 , is capable of translation in x, y and z axes. Applicator head  86  is generally also capable of rotational movement about the z axis to facilitate application of spacers to spacer applied lite  78 . 
         [0105]    Servo driven cup  90  supports suction cups configured to selectively grip spacer applied lite  78 . Such suction cups are generally conventional and need not be further described here to those of ordinary skill in the art. As best seen in  FIG. 4 , servo driven cup  90  is configured to grip spacer applied lite  78  and advance it slightly prior to the beginning of application to permit the staging of a following spacer applied lite  78  while a perimeter spacer is applied to the leading spacer applied lite  78 . 
         [0106]    IGU spacer applicator  62  generally also includes vertical support  104  in addition to front conveyor  100  and rear conveyor  102 . 
         [0107]    Referring particularly to  FIGS. 3-8 , according to an example embodiment of the invention, spacer is applied while spacer applied lite  78  is moving forward. Thus, applicator head  86  and applicator gantry  88  are configured to follow spacer applied lite  78  as it is conveyed forward and to apply spacer while spacer applied lite  78  is being conveyed forward. 
         [0108]    According to an example embodiment of the invention, movement of applicator head  86 , applicator gantry  88  and servo driven cup  90  are coordinated with each other so that spacer is applied first to bottom edge  92  of spacer applied lite  78  followed by trailing edge  94  of spacer applied lite  78  then top edge  96  and leading edge  98  in sequence while spacer applied lite  78  travels forward. Accordingly, applicator head  86  first travels backward relative to the motion of spacer applied lite  78  to apply spacer bottom edge  92  of spacer then upward to apply spacer to trailing edge  94  then forward relative to spacer applied lite  78  to apply spacer to top edge  96 . Applicator head  86  then travels downward along leading edge  96  to complete spacer application around the perimeter of spacer applied lite  78 . All the while spacer applied lite  78  travels forward on the assembly line. 
         [0109]    According to an example embodiment of the invention, applicator head  86  then rotates in a clockwise direction while returning to apply spacer to a following spacer applied lite  78 . 
         [0110]    Driven grid station  66  is generally conventional in design and includes grid applicator  106 . Driven grid station  66  is generally conventional in design and need not be further described here. 
         [0111]    Gas press and fill station  70  according to example embodiments of the invention may include double gas press  108  or single gas press  110 . 
         [0112]    According to an example embodiment, depicted in  FIG. 14 , double gas press  108  includes two gas press compartments  112  including front gas press compartment  114  and rear gas press compartment  116 . Each of front gas press compartment  114  and rear gas press compartment  116  include gas ducts  118  and internal conveyor  120 . 
         [0113]    Double gas press  108  generally includes three platens  122 . Platens  122  include front platen  124 , central platen  126  and back platen  128 . Each of the three platens  122  includes suction grippers (not depicted) on at least one surface thereof. According to an example embodiment of the invention, front platen  124  includes suction grippers (not depicted) on one surface thereof while central platen  126  includes suction grippers on two surfaces thereof and back platen  128  includes suction grippers on one surface thereof. 
         [0114]    Double gas press  108  includes gas supply  130  as well. Front gas press compartment  114  and rear gas press compartment  116  are configured to open and close to accept spacer applied lites  78  and topping lites  80 . Double gas press  108  is configured so that front gas press compartment  114  and rear gas press compartment  116  shuttle back and forth to align with front conveyor  100  and rear conveyor  102 . 
         [0115]    Front platen  124  is configured to be movable back and forth relative to central platen  126  to open and close front gas compartment  114  while also bringing spacer applied lite  78  into close proximity to topping lite  80  for mating. Rear gas press compartment  116  is configured so that back platen  128  and central platen  126  may be moved relative to each other in a similar fashion. 
         [0116]    According to another example embodiment depicted in  FIG. 15 , single gas press  110  generally includes housing  132  enclosing front platen  134  and back platen  136 . Housing  132  further includes side doors  138 , internal conveyor  140  and gas ducts  142 . Single gas press  110  is structured to travel or shuttle forward and back between front conveyor  100  and rear conveyor  102 . Front platen  134  is movable relative to back platen  136 . Gas ducts  142  may be located below, at the leading edge or at the trailing edge of single gas press  110 . Side doors  138  are configured to open and close to contain gas therein and exclude atmospheric gas during the gas filling process. 
         [0117]    If gas ducts  142  are located below the location at which spacer applied lites  78  are received, gas ducts may be configured to withdraw and advance while internal conveyor  140  is withdrawn and advanced to permit gas filling. For example, gas ducts  142  and internal conveyor  140  can be mutually coupled and movable perpendicular to their long axis. 
         [0118]    Referring to  FIGS. 9-13 , according to an example embodiment, secondary edge sealer  72  generally includes first edge sealing head  144 , second edge sealing head  146 , servo driven cup  148 , and gantry  150 . 
         [0119]    According to an example embodiment of the invention, first edge sealing head  144  is supported by gantry  150 . Second edge sealing head  146  is separately located at a lower edge of where insulated gas units that have been gas filled and pressed pass through secondary edge sealer  72 . According to an example embodiment of the invention, first edge sealing head  144  travels on gantry  140  to apply secondary edge sealant to leading edge  98 , top edge  96  and trailing edge  94  of insulated glass units. Second edge sealing head  146  applies secondary edge sealant to bottom edge  92  of insulated glass units. According to an example embodiment of the invention, servo driven cups  148  grip and transport the insulated glass unit forward. It is notable that according to the present invention, insulated glass units never travel backwards on the conveyor line but always move forward. This is also true of spacer applied lites  78  as spacers are applied to them. Servo driven cups  148  are configured to displace the insulated glass unit forward to permit staging of a following insulated glass unit  78  while the first unit is being edge sealed. 
         [0120]    According to an example embodiment of the invention, each of the first edge sealing heads  144  and lower second edge sealing heads  146  includes first corner wiper  152  and second corner wiper  154  that eliminate or minimize the need for operator touch-up of insulated glass units. First corner wiper  152  is coupled to first edge sealing head  144  while second corner wiper  154  is coupled to second edge sealing head  146 . 
         [0121]    Having been secondary edge sealed the insulated glass unit is conveyed from secondary edge sealer  72  to non-driven outfeed queue station  74 . 
         [0122]    Non-driven outfeed queue station  74  is generally conventional in design and need not be further described here. 
         [0123]    According to another embodiment of the invention, the invention includes a method of manufacturing insulated glass units. According to an embodiment of the invention, the method includes receiving glass lites at infeed station  52 ; conveying the glass lites to washer  54 ; washing and drying the glass lites in washer  54 ; conveying the glass lites to an inspection station  56  and further conveying the glass lites to shuttle  58 . The method may include shuttling alternate lites to front conveyor line  82  and rear conveyor line  84  and shuttle  58  and distributing spacer applied lites  78  to front conveyor line  82  and distributing topping lites  80  to rear conveyor line  84 . The method may then include conveying spacer applied lites  78  and topping lite  80  through infeed conveyor  60  to IGU spacer applicator  62 . 
         [0124]    The method may further include applying IGU spacer to spacer applied lite  78  while spacer applied lite  78  is constantly moving forward or at least never being moved backward. 
         [0125]    The method may further include applying spacer to spacer applied lite  78  first, along bottom edge  92 , second, along trailing edge  94 , third, along top edge  96  and fourth, along leading edge  98 . The method further includes conveying spacer applied lite  78  from IGU spacer applicator  62  to following queue station  64 . 
         [0126]    The method also includes optionally applying grids at driven grid station  66 . 
         [0127]    According to another embodiment, the method includes conveying spacer applied lite  78  and topping lite  80  via second queue station  68  to gas press and fill station  70 . 
         [0128]    According to one embodiment of the invention, the method further includes gas filling and applying topping lite  80  to spacer applied lite  78  in double gas press  108 . 
         [0129]    The method further includes in another embodiment applying topping lite  80  to spacer applied lite  78  and gas filling in single gas press  110 . 
         [0130]    A method according to an embodiment of the invention includes mating topping lite  80  with spacer applied lite  78  in a double gas press. In this embodiment of the invention, alternate insulated glass units are assembled in a front gas compartment  114  and a rear gas compartment  116  of double gas press  108 . 
         [0131]    According to another embodiment of the invention, the method further includes mating topping lite  80  with spacer applied lite  78  and gas filling in single gas press  110 . 
         [0132]    According to another embodiment of the invention, the method further includes conveying an insulated glass unit from double gas press  108  or single gas press  110  to secondary edge sealer  72 . The method further includes secondary edge sealing of the insulated glass unit by first edge sealing head  144  and second edge sealing head  146 . The method further includes sealing in sequence leading edge  98 , top edge  96 , and trailing edge  94  of the insulated glass unit with first edge sealing head  144  while simultaneously sealing bottom edge  92  with second edge sealing head  146 . The method according to the invention further includes conveying the insulated glass unit with servo driven cup  148  during the edge sealing process. The method may further include secondary edge sealing the insulated glass unit while continuously moving the insulated glass unit forward in the conveying process. 
         [0133]    Referring to  FIGS. 16-24 , another embodiment of high speed parallel manufacturing line  50  is depicted. 
         [0134]    Referring to  FIG. 16 , the depicted embodiment generally includes infeed station  156 , vertical washer  158 , inspection station  160 , shuttle  162 , driven parallel infeed conveyor  164 , single seal IGU spacer applicator  166 , following queue station  168 , driven grid station  170 , second queue station  172 , press and seal unit  174 , heating station  176 , vertical press  178 , and fourth corner sealer  180 . 
         [0135]    Infeed station  156  is generally conventional in design and similar to that described above. 
         [0136]    Vertical washer  158  is generally conventional in design and similar to that described above. 
         [0137]    Inspection station  160  is generally conventional in design and similar to that described above. 
         [0138]    Shuttle  162  is similar to that described above. 
         [0139]    Driven parallel infeed conveyor  164  is similar to that described above. 
         [0140]    Single seal IGU spacer applicator  166  is adapted to apply single seal spacer products. Single seal spacer products are utilized without the need to apply a secondary seal and without a need for corner notching as the single seal spacer products are flexible enough to be applied at corners of the IGU by bending the single seal spacer product. Referring to  FIG. 2 , single seal IGU spacer applicator  166  includes heated spacer drum  182  for storage of spacer material. The motion and structure of single seal IGU spacer applicator  166  is similar to that described above with relation to applicator head  86 , applicator gantry  88  and servo driven cup  90 . Single seal IGU spacer applicator  166  is constructed and adapted so that when spacer material is applied, a fourth corner of the insulated glass unit is left slightly open to ambient air. 
         [0141]    Following queue station  168  is generally conventional and similar to that described above. 
         [0142]    Driven grid station  170  is generally conventional and similar to that described above. 
         [0143]    Second queue station  172  is generally conventional and similar to that described above. 
         [0144]    Referring to  FIGS. 20B and 25 , press and seal unit  174  may include auto topping press with gas fill  184  and infeed shuttle  186 . Auto topping press may also include gas fill manifold assembly  187 . 
         [0145]    Referring to  FIGS. 17 and 18 , heating station  176  follows press and seal unit  174  and generally includes: heating station frame  188 , conveyor  190  and infrared heating units  192 . In the depicted embodiment, infrared heating units  192  are configured to heat eight edges of an insulated glass unit being processed. That is both sided of each edge of a rectangular IGU. Infrared heating units  192  heating units may also be adapted to heat the edges of IGUs that are not rectangular in shape, such as polygonal IGUs, circular IGUs or arch topped IGUs. 
         [0146]    In the depicted embodiment, infrared heating units  192  include focused infrared lamps  194  that are linear in nature. This should not be considered limiting. Infrared heating units  192  may be of any desired shape. Focused infrared lamps  194  may be fixed or movable. If they are movable, focused infrared lamps  194  may be movable along with the IGU as it is conveyed. Infrared heating units  192  may include vertical heater  196  and horizontal heater  198 . If movable, both vertical heater  196  and horizontal heater  198  may be moved to align with the respective vertical and horizontal edges of an insulated glass unit as it is conveyed. 
         [0147]    If fixed, vertical heater  196  and horizontal heater  198  are of sufficient length to heat the height and width of the largest insulated glass unit capable of being processed. If vertical heater  196  is fixed, the insulated glass unit may be paused as it is being conveyed twice to heat vertical edges. Horizontal heater  198  may be used to apply heat to horizontal edges of an insulated glass unit while the insulated glass unit is being conveyed. In this case, horizontal heater  198  is positionable and adjustable as to vertical separation to heat the upper and lower edges of insulated glass units passing through heating station  176  of a variety of heights of IGUs. 
         [0148]    Referring to  FIGS. 19 and 20 , vertical press  178  in various embodiments of the invention may include platen press  200  or roller press  202 . 
         [0149]    Referring to  FIGS. 20A and 20B , application of platen press  200  is expected to minimize rebound and the consequent displacement of filler gas contained within an insulated glass unit which still has an open corner. Platen press  200  generally includes: base frame  204 , front platen assembly  206 , back platen assembly  208 , conveyor assembly  212  and platen shifter assembly  214 . Base frame  204  supports front platen assembly  206  and back platen assembly  208 . At least one of front platen assembly  206  and back platen assembly  208  is movable relative to the other by the operation of platen shifter assembly  214 . Conveyor assembly  212  is located slightly below and between front platen assembly  206  and back platen assembly  208  and allows conveying of an insulated glass unit into and out of the space between front platen assembly  206  and back platen assembly  208 . 
         [0150]    Referring now to  FIG. 19 , roller press  202  generally includes roller base frame  216 , front roller set  218  and back roller set  220 . In the depicted embodiment, front roller set  218  includes seven rollers  222  and back roller set  220  includes seven rollers  222 . Rollers  222  may be heated. Roller press  202  generally also includes drive motor  224  and serpentine belt or chain  226 . Serpentine belt or chain  226  is coupled to drive motor  224  and to idler rollers as depicted in FIG.  19 . Use of roller press  202  has the advantage that it allows continuous forward movement of an IGU being processed. 
         [0151]    Referring now to  FIGS. 21A-24 , fourth corner sealer  180  generally includes base frame  228  supporting fourth corner sealing device  230 . Fourth corner sealing device  230  may include angled rocking fourth corner sealer  232 , roller fourth corner sealer  234  or two-part angled fourth corner sealer  236 . 
         [0152]    Referring to  FIG. 22 , angled rocking fourth corner sealer  232  generally includes angled portion  238  and rocking mechanism  240 . Angled portion  238  generally represents an inside corner  242 . Rocking mechanism  240  may include linear actuator  244 . Angled portion  238  acts about pivot of inside corner  246 . 
         [0153]    Roller fourth corner sealer  234 , in an embodiment depicted in  FIG. 21B , generally includes linear actuators  248  and corner roller  250 . Linear actuators  248  act orthogonally relative to each other and are configured to move corner roller  250  around a corner to be sealed. Corner roller  250  is typically of a diameter much greater than the depth of set back of the spacer of the insulated glass unit and may present multiple rollers of different widths as depicted to accommodate different thickness spacers. 
         [0154]    Two part angled fourth corner sealer  236 , in an embodiment depicted in  FIG. 23 , generally includes first angled sealer  252  for vertical edge and second angled sealer  254  for horizontal edge, vertical edge linear actuator  253  and horizontal edge linear actuator  255 . 
         [0155]    Referring now to  FIG. 24 , according to an example embodiment, fourth corner sealer  180  includes fourth corner infrared heater  256 . In the depicted embodiment fourth corner infrared heater  256  includes two heat lamps  258  inside protective shrouds  260 . 
         [0156]    In operation, glass lites are fed into high speed parallel manufacturing line  50  at infeed station  52 . Glass lites are conveyed to washer  54  where they are washed and dried. Glass lites are then conveyed to inspection station  56  for inspection. Then glass lites are conveyed to shuttle  58  which places alternate glass lites on front conveyor  100  or rear conveyor  102 . Spacer applied lites  78  are transported on front conveyor  100  while topping lites  80  are transported on rear conveyor  102 . Spacer applied lites  78  are then transported to IGU spacer applicator  62  where spacer is applied first to bottom edge  92 , then to trailing edge  94 , then to top edge  96  and finally to leading edge  98 . Spacer is applied while the spacer applied lite  78  is moving forward on the conveyor line. Spacer applied lite  78  and topping lite  80  are then transported via following queue station  64  optionally to driven grid station  66  and then to second queue station  68 . Spacer applied lites  78  and topping lites  80  are then conveyed to gas press and fill station  70  which according to alternate embodiments of the invention may include double gas press  108  or single gas press  110 . In either case, topping lites  80  are transferred to the front of the gas press and fill station  70  and are mated with spacer applied lite  78  while gas filling takes place. This creates an insulated glass unit that has been primarily sealed. The insulated glass unit is then transported to secondary edge sealer  72  which applies secondary edge sealant via two edge sealing heads including first edge sealing head  144  and second edge sealing head  146 . First edge sealing head  144  applies secondary sealant to leading edge  98 , top edge  96  and trailing edge  94  of the insulated glass unit in that sequence. Simultaneously, second edge sealing head  146  applies secondary edge sealant to bottom edge  92 . During the secondary edge sealing process, edge sealant is wiped at the corners by first corner wiper  152  and second corner wiper  154 . Completed insulated glass units having been secondarily edge sealed are then conveyed to non-driven outfeed queue station  74 . 
         [0157]    According to the embodiment depicted in  FIGS. 16-24  when spacer applied lite  78  arrives at single seal IGU spacer applicator  166  single seal spacer material is applied to spacer applied lite  78  along bottom edge  92  followed by trailing edge  94  followed by top edge  96  and leading edge  98  in sequence. The fourth corner of spacer applied light where leading edge  98  and bottom edge  92  meet is left slightly open. 
         [0158]    Spacer applied lite  78  is conveyed to press and seal unit  174  where topping lite  80  is mated to spacer applied lite  78  to create an IGU. The IGU is conveyed to heating station  176  where eight edges of the IGU are heated to increase wettability of the single seal IGU spacer adhesive. If infrared heating units  192  are moveable they are moved to heat areas of the IGU as required. The IGU is then conveyed to vertical press  178  where the IGU is pressed to enhance the seal between the lites and the single seal spacer material. The fourth corner of the IGU remains open after application of vertical press  178 . 
         [0159]    The IGU is then conveyed to fourth corner sealer  180  where the fourth corner is sealed trapping a non air filling gas within the IGU. If present, fourth corner heater  256  may be applied to raise the temperature of the fourth corner to facilitate sealing. 
         [0160]    The present invention may be embodied in other specific forms without departing from the spirit of the essential attributes thereof; therefore, the illustrated embodiments should be considered in all respects as illustrative and not restrictive, reference being made to the appended claims rather than to the foregoing description to indicate the scope of the invention.