Abstract:
A framed panel and related method of manufacture are disclosed. A framed panel unit includes a panel along the edge of which thermoplastic frame members are disposed. The frame members have first and second opposed side walls which define a channel for receiving the edge of the panel. The channel of each frame member has spacers between the panel and each side wall for spacing the panel from the side walls. Prior to welding together the ends of the frame members, the spacers retain the frame members on the panel. The panel may include multiple opposed sheet members with a spacer between the sheet members spacing them apart, and a reactive thermoplastic sealant material bonding the sheets to the frame members. An associated method of forming a named panel, frame members for a panel, and a spacer component for use in mounting a panel within a channel of a frame member are also disclosed.

Description:
This application claims the benefit of and is a National Phase Entry of International Application Serial Number PCT/CA2004/001935, filed Nov. 4, 2004. This application also claims the benefit of U.S. Provisional Patent Application 60/516,874, filed on Nov. 4, 2003, from which PCT/CA2004/001935 claims priority. 
     The International Application PCT/CA2004/001935 and U.S. Provisional Application 60/516,874 are hereby incorporated herein by reference. 
    
    
     FIELD OF THE INVENTION 
     This invention relates generally to framed panels and fenestration products and more particularly but not limited to products made from thermoplastic profiles welded around an insulating glass unit. 
     BACKGROUND OF THE INVENTION 
     To improve manufacturing efficiency and reduce product costs, various attempts have been make in recent years to develop integrated insulating glass/window frame production systems. 
     One example which is described in a presentation given at InterGlass Metal 97&#39; was developed in Germany by Meeth Fenester. With this production system, the window is, fabricated from plastic channel window frame profiles that are assembled around an insulating glass (IG) unit and corner welded using conventional hot plate technology. During the assembly process, the unit is held in position by means of a hot melt butyl adhesive bead that is located centrally in the frame channel. Twin silicone thermosetting glazing sealant beads are then applied in the two gaps either side of the IG unit. After assembly, the windows are stored in a truck container ready for shipping and the truck containers are left-parked outside the factory for a few hours while the two-part silicone sealant is cured. For the Meeth production system, there are four main drawbacks. First, because of the butyl adhesive bead, the glazing channel cannot be drained and this creates potential IG durability problems. Second, conventional hot plate welding is a slow process that is complicated by the need for corner flash removal. Third, the sash frame assemblies cannot be shipped until the two-part thermosetting sealant is fully cured. Fourth, the Meeth production is largely a manual process with manual loading of the individual frame profiles into the welding clamping fixtures and manual application of the sealant beads. 
     A second example of an integrated IG/window frame system is described in U.S. Pat. No. 5,622,017 issued to Lynn et al. and assigned to the Andersen Corporation. As with the Meeth system, the Andersen window is also fabricated from plastic channel frame profiles that are assembled around an IG unit and corner welded using conventional hot plate technology. In comparison with the Meeth System, the Andersen profile incorporates conventional plastic glazing fins on one side of the channel frame profile. A structural thermosetting sealant is then applied to one side of the unit and the single glazing sealant bead is allowed to cure. Because the IG glass unit is not held in position, the frame subassembly cannot be moved for several hours while waiting for the sealant to cure. In addition, the unit cannot be accurately centered within the channel profile and so the process of sealant application cannot be easily automated. 
     As described in U.S. Pat. No. 5,902,657 issued to Hanson et al., the channel frame profiles can be joined at the corners using friction welding with a moveable U-shaped metal platen that rapidly moves back and forth melting the plastic at the interface joint. As with conventional hot plate welding, the metal platen is then removed and the matching ends of the framing profiles are then pressured against each other. From a practical perspective, this solution is difficult to implement because as the metal plate is removed, the molten plastic material is also removed resulting in a poor weld assembly. A further concern is that the IG unit is held in position by the sloped channel walls and as a result there are potential glass breakage problems at the corners. 
     A third example of an integrated IG/window frame system is described in PCT application CA02/000842 by Field et al (See FIGS. 21-23 therein). Again, the frame assembly is welded using friction welding but instead of using a metal platen, a plastic web is used that is vibrated back and forth using an inverted vibratory welding head. To avoid potential glass breakage problems, the IG unit is isolated from the plastic channel frame profiles using conventional rubber setting blocks. However, because the unit is not firmly held in position and is not accurately centered, the sealant application process cannot easily be automated. In addition, the profiles have to be manually loaded into the clamping fixtures and this slows down the production cycle time. 
     SUMMARY OF THE INVENTION 
     According to one aspect of the present invention, there is provided a framed panel unit comprising a panel; a plurality of thermoplastic frame members disposed along the edge of said panel; each frame member having first and second opposed side walls defining a channel therebetween, the edge of said panel being received within the channel of each frame member; the channel of each frame member having spacer means therein including a first spacer between said panel and said first side wall for spacing said panel from said first side wall and a second spacer between said panel and said second side wall for spacing said panel from said second side wall, and where prior to welding together the ends of said frame profiles, the spacer means retain frame members on the panel. 
     One preferred arrangement is where at least one of said first and second spacers is positioned below the top of a respective channel wall to provide an open gap at the top of the channel between the panel and the side wall for receiving sealant. Advantageously, in this arrangement, spacers are provided in the channel, either side of the panel to center the panel in the channel and to also hold the panel in position during an assembly process, for example during application of a sealant, e.g. a reactive thermoplastic sealant, to both sides of the panel along a frame member. 
     In this arrangement, the spacers also resiliently retain the frame members on the panel when the frame members are unconnected so that the frame members can be positioned and held in place on the panel before the frame members are connected together, for example by welding. This also facilitates handling of the unit by allowing the various components to be moved and transferred together as whole between assembly stations in a production process and, in particular, facilitates the transfer and loading of the frame members into a welding apparatus so that this loading process may be automated, rather than manual. 
     One or both spacers may be formed separately from the frame member, or may be formed integrally therewith. One or both spacers may comprise a discrete protrusion extending into the channel for engaging a portion of the panel adjacent an edge thereof. Either one or each protrusion may have an upper surface which is deflected downwards to engage the surface of the panel so that when the pressure applied to the panel by the protrusion is increased if the frame member is pulled in a direction away from the panel, making it difficult to withdraw the frame member from the panel when installed thereon. 
     When separately formed from the frame members, the first and second spacer may be joined together by a third intermediate spacer which spaces the edge of the panel from the base of the channel. The first, second and third spacers may thereby form a U-shaped insert and the first and second spacers may be hingedly coupled to the third spacer and may be integrally formed therewith. The spacer insert may include locator means for positioning the insert at a predetermined lateral position between the side walls of the channel, which is particularly advantageous when, due to manufacturing tolerances, the distance between the side walls of the channel are greater than required to accommodate the width of the insert. In one embodiment, the base of the channel has oppositely sloped upper surfaces which slope transversely of the channel and the locator means includes first and second oppositely sloped lower surfaces of the third spacer which engage the sloped surfaces of the channel to urge the third spacer towards a predetermined position within the channel on applying a force, for example the weight of the panel, to the third spacer towards the base of the channel. 
     In one embodiment, the frame members are welded together by friction welding, and preferably by means of a weldable junction piece disposed between adjacent ends of the frame members. The junction piece may be a flat planar flange or may also incorporate integral legs that help position the framing members in the assembly process. In one embodiment, the framed panel unit includes a reactive thermoplastic sealant material along the junction between one or both outer surfaces of the panel and the frame member. The sealant material may have a high degree of stiffness (high modulus) to increase the structural strength and rigidity of the framed panel unit. The reactive thermoplastic sealant may for example be polyurethane or silicone based. 
     Advantageously, as the spacers effectively position and hold the panel in the desired position, relative thereto, the sealant need not have any open time to allow the panel to be repositioned relative to the joined frame members, and no repositioning is required. This allows a warm or hot applied thermoplastic sealant to be used which cools down almost immediately on its application to the panel unit so that once the application process is complete, the unit can be moved almost immediately to the next production stage, if any, for shipment, or for storage, resulting in a fast and more efficient production process. In one embodiment, the sealant may comprise a reactive thermoplastic sealant that may have an open time of 2 seconds or less but which after exposure to moisture chemically cures and bonds to the glass. 
     According to another aspect of the present invention, there is provided a panel unit comprising first and second opposed sheet members; a spacer between said sheet members spacing said sheet members apart, said spacer comprising a thermoplastic sealant material and being located proximate an edge of the sheet members; a frame member having a channel formed therein, said edge being disposed within said channel; and a reactive thermoplastic sealant material bonding said sheets to said frame member. 
     Advantageously, the provision of a reactive thermoplastic sealant material which structurally bonds the sheets to the frame member allows the perimeter seal and spacer between the sheet members to be simplified and the material used to be considerably reduced. In one embodiment, the perimeter edge seal between the glazing sheets only consists of a thermoplastic sealant spacer. 
     According to another aspect of the present invention, there is provided a method of forming a framed panel, comprising the steps of: (a) providing a panel to be framed; (b) providing a plurality of frame members for framing said panel, each frame member having a channel formed therein for receiving an edge portion of said panel and resilient means within said channel for spacing the panel from opposed side walls of said channel and for resiliently retaining said panel in said channel; (c) inserting said panel into the channel of each frame member such that said frame members are held on said panel by said resilient means; and (d) joining the ends of adjacent frame members together by welding. In one embodiment, the framing members are interconnected by junction pieces prior to transferring the frame/panel subassembly to the welding apparatus. 
     According to another aspect of the present invention, there is provided a frame member for a panel, comprising first and second opposed side walls defining a channel therebetween for receiving said panel; first and second pre-formed spacers comprising a resilient material inserted in said channel; the first spacer being positioned against said first side wall for spacing one side of said panel therefrom and said second spacer being positioned against said second side wall to space the other side of said panel therefrom. 
     According to another aspect of the present invention, there is provided a spacer component for use in mounting a panel within a channel of a frame member, comprising a base portion for spacing said panel from the base of said channel; a side portion extending from said base portion for spacing said panel from a side wall of said channel; and a protrusion extending from said side portion for engaging a face of said panel and for resiliently retaining said panel in said frame member. 
     According to another aspect of the present invention, there is provided a frame member comprising first and second opposed sidewalls defining a channel therebetween and protrusions extending from each sidewall into said channel for resiliently retaining a panel therebetween. In one embodiment, the protrusions that extend from each side wall are flexible fins and according to another embodiment, a bulb seal also extends from each side wall and is located at the top of each framing channel member. 
     According to another aspect of the present invention, there is provided a frame member comprising first and second opposed sidewalls defining a channel therebetween, at least one sidewall having an elongate recess formed therein extending along the channel and positioned below the top of a respective sidewall. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  shows an exploded elevation view of U-channel sash frame profiles assembled around an insulating glass panel. 
         FIG. 2  is a vertical cross section perspective corner detail of a U-channel sash frame incorporating a double glazed insulating panel. 
         FIG. 3  is a perspective view of a single corner vibration welding apparatus. 
         FIG. 4A  is a plan view of a single corner, vibration welding apparatus with the extrusions installed in the fixtures prior to the welding process. 
         FIG. 4B  is a view similar to  FIG. 4A  showing the single corner vibration welding apparatus during the welding process. 
         FIG. 5  shows a cross section sash frame detail of a U-channel sash frame profile incorporating a conventional dual-seal insulating glass panel and where the framing profiles are temporarily held in position by means of folding rubber spacer inserts. 
         FIG. 6A  is a perspective view of the folding rubber spacer inserts prior to insertion within the U-channel sash frame profile. 
         FIG. 6B  is a perspective detail view of the folding rubber spacer inserts after insertion within the U-channel sash frame profile. 
         FIG. 7A  shows a cross section detail of the folding rubber spacer and the perimeter edge of an insulating glass panel just prior to the insertion of the panel into the folding rubber spacer. 
         FIG. 7B  is cross section detail of the perimeter edge of an insulating glass panel after the panel has been inserted into the folding rubber spacer. 
         FIG. 8A  shows an exploded cross section detail of three window sash frame components, including: (i) bottom perimeter edge of insulating glass panel, (ii) an unfolded rubber spacer insert and (iii) U-channel sash frame profile. 
         FIG. 8B  shows a cross section detail of the folding rubber spacer inserted within the U-channel sash frame profile. 
         FIG. 8C  shows the insulating glass panel inserted within the U-channel sash frame profile. 
         FIG. 9  shows a cross section detail of the perimeter edge of a single-seal insulating glass panel incorporated within a U-channel sash frame profile. 
         FIGS. 10A-10D  show schematic plan views of the production process of an integrated IG/window frame assembly. 
         FIG. 10A  shows a schematic plan view of the insulating glass panel. 
         FIG. 10B  shows a schematic plan view of the insulating glass panel with U-shaped plastic framing profiles loosely assembled around the insulating unit. 
         FIG. 10C  shows a plan view of the insulating panel/plastic sash frame subassembly with junction pieces inserted at the corners. 
         FIG. 10D  shows a plan view of the completed window sash subassembly. 
         FIG. 11A  is a cross section plan view detail of a frame corner assembly where the thermoplastic plastic profiles are vibration welded at the corner using a corner junction piece with a diagonal web and integral legs. 
         FIG. 11B  is a cross section detail of the frame corner assembly as shown in  FIG. 11A  where the plastic framing profile is ultrasonically spot welded to the integral legs of the corner junction piece. 
         FIG. 11C  shows a vertical cross-section detail through the hollow profile shown in  FIG. 11A . 
         FIGS. 12A-12E  show schematic plan views of a high volume production process of an integrated IG/frame assembly. 
         FIG. 12A  shows a plan view of the frame profiles assembled around an insulating glass panel. 
         FIG. 12B  shows a plan view of the insulating glass panel/frame subassembly. 
         FIG. 12C  shows a plan view of the insulating glass panel/frame subassembly suspended below a gantry. 
         FIG. 12D  shows a plan view of a four headed horizontal friction corner welder with the insulating glass panel/frame assembly dropped into position. 
         FIG. 12E  shows a plan view of the four headed horizontal friction corner welder with the insulating glass panel/frame assembly clamped into position just prior to the welding process. 
         FIG. 13  is a vertical cross section of a U-channel sash frame window incorporating a double glazed insulating panel and thermoplastic U-channel framing profiles with integrally formed flexible fin spacers and glazing bulb seals. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Referring to the drawings,  FIG. 1  shows an exploded elevation view of a sash window  20  where the U-shaped thermoplastic framing profiles  21  are assembled around an insulating glass panel unit  25 . Typically, the insulating glass panel unit  25  consists of two glass sheets  26 , 27 , which are shown more clearly in  FIG. 5 , and are separated by a perimeter edge seal. As described in more detail in  FIGS. 3 to 5 , the end joint surfaces  23 , 24  of the sash frame profile members  21  are friction welded at the corners using thermoplastic planar flange junction pieces  22 . Folding rubber spacer inserts  30  are used to hold the insulating glass panel  25  in position within the U-shaped channel profile  21 . Prior to the welding process, the folding rubber spacer inserts  30  also retain the framing profiles  21  in position on the insulating glass panel  25 . In addition, the folding rubber spacer inserts  30  also prevent the vibrating junction piece  22  from striking the corners  31  of the insulating glass panel  25  during the welding process. The folding rubber spacer inserts  30  can be made from various resilient materials with one preferred material being EPDM rubber. 
       FIG. 2  shows an exploded perspective corner detail of a U-channel sash frame window  20  incorporating a double glazed insulating panel unit  25 . The ends  23 , 24  of the plastic framing profiles  21  are miter cut and vibration welded to a plastic planar flange junction piece  22 . The framing profiles  21  can be made from various thermoplastic materials but generally, the preferred material is polyvinyl chloride (PVC). In order for the junction pieces  22  to strongly bond to the framing profiles  21 , the junction pieces  22  are made from essentially the same type of plastic material as the framing profiles  21 . 
       FIG. 3  shows a top perspective view of a prototype single corner vibration welding apparatus  32 . The apparatus consists of five main components: 
     1. Vibratory Head 
     A linear vibratory head  33  that incorporates a top plate  34  which vibrates back and forth very rapidly in a predetermined plane. 
     2. Junction Piece Holding Fixture 
     A junction piece holding fixture  35  which is directly attached to the top plate  34  and firmly holds the planar flange junction piece  22  in position. 
     3. Moveable Framing Fixtures 
     Two moveable framing fixtures  36  and  37  incorporate clamping devices  38  that firmly hold the framing profiles  21  in position. 
     4. Control Systems 
     A control system  39  that regulates the various operating parameters of the vibration welding apparatus  32  including: weld time, hold time, joint pressure, weld depth, amplitude, frequency and voltage. 
     5. Machine Frame 
     A machine frame  40  which provides the structure that supports the other components. 
       FIG. 4A  shows a plan view of a single corner, vibration welding apparatus  32  in an open position. The linear vibration welding apparatus  32  features a vibratory head  33  that linearly moves back and forth in a pre-determined plane. The vibratory head  33  is similar to the vibratory heads used on commercially available linear vibration welders such as the Branson Mini Welder, but unlike these commercially available products, the vibratory head is turned upside down as this allows for more flexible and easy positioning of the framing profile members  41  and  42  during the frame assembly process. A flat plate  43  is bolted to the top surface of the vibratory head  33 . As with standard vibration welders, the vibratory head  33  is bolted to a separate heavy cast iron support (not shown) and isolated from the cast iron support structure (not shown) using rubber mounts. This cast iron support structure is in turn bolted to a machine frame  40  that positions the vibratory head  33  at a convenient working height. 
     Flat plate metal sheets  44  are bolted to the top surface of the machine frame  40  but this top working surface is separated apart from the vibratory head  33  so that a minimum of vibratory movement is transferred to the machine frame  40 . Moveable profile fixtures  36  and  37  are supported on guide rails  45  directly attached to the top table plate  44  and these fixtures hold the framing profiles  41  and  42  in position. The moveable profile fixtures  36  and  37  move over the vibratory head  33  but there is no direct contact except where the framing profiles  41  and  42  contact the junction piece  22 . The moveable fixtures also allow for the miter cut ends  23 ,  24  of the framing profiles  41  and  42  to be positioned parallel to the planar flange  48  of the junction piece  22 . 
     A fixed holding fixture  35  for the junction piece  22  is located so that the planar flange  48  of the junction piece  22  is in a balanced central position. The holding fixture  35  which is directly attached to the top plate  43  of the vibratory head  33 , firmly holds the removable tab  49  of the junction piece  22  in position. 
       FIG. 4B  shows a plan view of the vibration welding equipment  32  in operation with the miter cut ends  23  and  24  of the framing profiles  41  and  42  being pressured against the planar flange  48  of the junction piece  22 . By vibrating the junction piece  22  back and forth and by simultaneously pressuring the framing profiles  41  and  42  against the planar flange  48  of the junction piece  22 , friction heat is generated at the two joint interfaces  50  and  51 . When a molten state is reached at the two joint interfaces  50  and  51 , the vibration is stopped and the perpendicular pressure is then maintained briefly while the molten plastic solidifies to form two welded joints  52  and  53  on either side of the planar flange  48 . In order to provide for even weld strength, essentially the same perpendicular engagement force has to be simultaneously applied to each side of the junction piece  22 . 
     One of the key advantages of vibration corner welding is that by incorporating flash traps or weld beads within the junction piece  22 , it is feasible to eliminate the need for mechanical flash removal and as a result, there are substantial equipment cost savings. 
     Although frame assemblies can be manufactured using a single corner welder, it is more productive if two or more corners are welded simultaneously. The operation of a vertical four head welder is described in PCT Application CA02/00842 by Field et al. As with conventional hot plate welders, the profiles are separately loaded into the holding fixtures and the miter cut corners are welded in either a one stage or two stage operation. 
     With a two stage process, two diagonally opposite corners and are first welded together. For each corner weld, the process is essentially the same as with a single corner vibration welder. Both sets of framing profiles are independently pressurized against the two diagonally opposite junction pieces. The next step is for the other set of diagonally opposite corners to be welded together and the assembled frame is then unloaded. 
     Because the friction welding process is so fast (3 to 6 seconds), this two stage process does not significantly increase cycle time and compared with simultaneously welding all four corners, the key advantage is that the required movement and control of the heads is greatly simplified. 
     For a conventional four head, hot plate welder, the overall cycle time is about 2 minutes and this overall cycle time includes: profile loading, corner welding, cool down and frame unloading. In comparison, the overall cycle time for the two-stage vibration welding process is less than 30 seconds and so this represents a significant increase in productivity. 
     Instead of a two stage process, a second option is to simultaneously weld all four corners in one operation. During the vibration welding process, each head has to move fractionally and because the head movements involved are so small and so complex, the control system for this simultaneous four headed welding operation is very complex and requires very sophisticated software. 
     A further major advantage of vibration corner welding is that it is feasible to weld around an insulating glass unit. With a four headed welder, the frame profiles are loaded into the framing fixtures and the insulating glass unit is positioned between the four welding heads. The four heads then move centrally into position so that the U-shaped framing profiles overlap the perimeter edge of the insulating glass unit. With the insulating glass unit in position, the miter cut frame profiles are then welded using friction corner welding. 
       FIG. 5  shows a bottom cross section detail of a U-channel sash window  20 . The U-shaped channel sash framing profiles  21  are assembled around a dual seal insulating glass panel unit  25 . The two gaps  57  and  58  between the insulating glass panel unit  25  and the framing profile  21  are filled with glazing sealant material  59  forming glazing beads  54  and  55 . Various glazing sealant materials can be used but one preferred material is a reactive thermoplastic sealant. 
     Compared to conventional two-part thermosetting sealants, the advantage of a reactive thermoplastic sealant is that the one part sealant is warm or hot applied so that after a few seconds cool down, the material develops high green strength allowing the window units to be almost immediately handled. Compared to conventional widow glazing seal application where there is a need for some open time during the application process, the open time for the reactive thermoplastic sealant materials can be less than two seconds. In addition through a moisture cure process, the reactive thermoplastic material is chemically cured creating a strong adhesive bond between the glass sheets and the framing profiles. 
     Various types of reactive thermoplastic sealants can be used but one preferred material is a reactive hot melt polyurethane adhesive that is manufactured by National Starch and Chemical Company under the trade name of Purfect Glaze. A second preferred material is a reactive hot melt silicone that is manufactured by Dow Corning under the trade name of Instant Glaze. Compared to the reactive silicone material, the reactive polyurethane material generally provides for higher adhesion strength. 
     The modulus or stiffness of the Purfect Glaze sealant can be varied and generally, a high modulus material is preferred as this allows for the glass sheets to be firmly bonded to the framing profiles. As a result, structural advantage can be taken of the stiffness of the glass sheets  26 , 27  so that the structural performance of the framing profiles  21  is enhanced allowing for a reduction in profile size as well as the possible elimination of metal reinforcement that is typically required for large size PVC windows. 
     With a high modulus, stiff sealant material and because of the high differential expansion between the plastic PVC framing profiles  21  and the glass sheets,  26 , 27  there is potential for cold temperature glass breakage. However, our experience has shown that even at quite extreme Canadian winter temperatures (ie below −30° C.) glass breakage is not a problem. This is because the plastic PVC material is sufficiently ductile that differential expansion within the plastic profile cross section can be accommodated. As well, the plastic framing profiles  21  are firmly adhered to the perimeter side faces of the glass sheets  26 , 27  as opposed to the bottom edge where glass breakage problems are accentuated due to glass edge micro cracks created during the glass cutting process. 
     At cold outside temperatures, a further concern is that there can be IG edge seal failure due to loss of adhesion between the glass sheets  26 ,  27  and an IG edge spacer. To eliminate this problem, there is a need for the perimeter edge seal to be somewhat flexible and for a conventional dual-seal design. One preferred option is use an inner desiccant-filled PIB/butyl spacer  62  that is backed by outer structural thermosetting sealant  63 . Other IG dual-seal options include: flexible desiccant-filled silicone or EPDM rubber foam spacer (Trade name: Super Spacer) backed by hot melt butyl sealant. 
     Folding rubber spacer inserts  30  are used to accurately center the insulating glass panel unit  25  within the frame profile  21 . These inserts  30  temporarily hold the framing members  21  on the panel unit  25  and also positions the panel  25  in the sash frame subassembly while it is transferred to the sealant gunning application station. 
     The bottom sides  64  and  65  of the U-channel frame profile are chamfered and this helps position the folding rubber spacer inserts  30  within the sash frame profile  21 . To further help hold the folding rubber spacer inserts  30  in position, the sidewalls of the profile also incorporate inner ledges  66  and  67 . The bottom section of the folding rubber spacer inserts  30  also incorporate a V-shaped opening that provides for water drainage from the glazing cavity  69 . 
     To provide for consistent application, the sealant beads  54  and  55 , are produced using robotic application equipment. One option is separately apply each bead using a standard robot and where the sash assembly frame is rotated through 180° degrees after the application of the first bead  54 . A second option is to apply both beads  54  and  55 , simultaneously using automated double-head sealant application equipment that operates in a similar manner to automated sealant gunning equipment used for insulating glass sealing. For double bead application, the sash frame assembly is typically in a vertical position and to ensure that the sealant material does not deform or drip particularly on the top edge, the thermoplastic sealant material needs to have a high viscosity. 
       FIG. 6A  shows a perspective view of the folding rubber spacer insert  30  prior to installation within the U-channel profile  21 . The side wall sections  72  and  73  space the IG unit  25  away from the channel walls of the framing profile. The folding rubber spacer insert  30  incorporates V-notches  70  and  71 , that allow the rubber spacer insert to be folded at the corners. The purpose of the V-notches  70  and  71 , is to allow the inserts  30  to be easily installed within the frame profile  21  prior to the insertion of the IG panel  25 . The V-notches  70  and  71  also help the folding rubber spacer insert  30  accommodate dimensional tolerances in the frame profile. The rubber inserts  30  can be made from a variety of different rubber materials with one preferred option being EPDM rubber. 
     Although a one piece assembly is shown in  FIG. 6A , it can be appreciated by those skilled-in-the-art that the side wall sections could consist of two separate spacers that are individually attached to the side walls of the channel profile. Similarly the bottom section of the folding rubber spacer insert could also consist of a separate spacer that is positioned in the bottom channel of the framing profile. 
       FIG. 6B  shows a perspective view of the folding rubber spacer insert  30  with side sections  72  and  73  folded at right angles to the bottom section  74 . 
       FIG. 7A  shows an exploded cross section detail of the folding rubber spacer insert  30  and the perimeter edge  75  of an insulating glass unit panel  25  just prior to the insertion of the panel unit  25  into the folding spacer insert  30 . 
       FIG. 7B  is a cross section detail of the perimeter edge  75  of an insulating glass panel  25  after the panel has been inserted into the folding rubber spacer insert  30  that is held within a U-channel frame profile (not shown). The side wall sections  72  and  73  of the folding rubber spacer insert  30  incorporate a protrusion or positioning flange  76  that extends beyond the inner wall surfaces  77  of the side walls  72  and  73 . As the panel unit  25  is inserted into the folding rubber spacer  30 , the protrusion  76  is compressed downwards and so as a result, the insulating glass panel  25  is firmly wedged in position and centered within the frame profile  21 . 
       FIG. 8  shows the production steps involved in the fabrication of the integrated IG/sash frame assembly  20 . 
       FIG. 8A  shows an exploded bottom cross section detail of a window sash frame. There are only three components shown: an insulating glass panel  25 , a folding rubber spacer insert  30  and a U-channel sash frame profile  21 . The bottom faces  78  of the rubber spacer insert  30  are coated with a low-friction coating  79  (see dotted line). The low friction coating  79  allows the rubber spacer insert  30  to slide along the U-channel framing profile  21  during the friction corner welding process. The low friction coating  79  is compatible with standard IG sealant materials and one preferred material option is a polyurethane-based coating. In comparison, the top faces  109  of the rubber insert  30  preferably have a high friction coefficient and do not move in position during the friction corner welding process. 
       FIG. 8B  shows an exploded bottom cross section detail of a window sash frame with the folding rubber spacer insert  30  inserted within the sash frame profile  21 . The rubber spacer inserts  30  can be inserted manually or alternately, the spacer inserts  30  can be automatically inserted as part of the profile cutting and fabrication process. 
       FIG. 8C  shows a bottom cross section detail of a window sash frame  20  with the IG panel unit  25  installed within rubber spacer insert  30  that is held in position within the sash frame profile  21 . The rubber spacer inserts  30  center the IG panel unit  25  in the sash frame  21  and the corners of the frame assembly are then welded using friction corner welding techniques that are described in PCT Application CA02/000842. As well as centering the panel unit  25 , the rubber spacer inserts  30  also help isolate the IG unit  25  from any resonance or vibratory movement during the welding process. The sash frame assembly is then transported to the automated frame sealing robot (not shown) with the rubber spacer inserts  30  holding the IG unit  25  in position. 
     It should be noted that although the friction corner welding process is carried out with the IG panel unit  25  in either a horizontal or vertical position, the sealant gunning operation is typically carried out with the panel unit  25  in a vertical position. By positioning the IG panel unit  25  in a vertical position, this ensures that the IG panel unit  25  is centered within the frame profile  21  and that there is no compression of the bottom rubber side wall sections  72  and  73 . After the double bead application of the reactive hot melt sealant, the sash frame assembly can be immediately transferred to the next step in the production process which is typically hardware application. As a result through these various improvements in assembly methods, there is a continuous sash frame production process with increased throughput and productivity and no major production bottlenecks or delays. 
     Although a double glazed panel unit is illustrated in  FIG. 8 , it can be appreciated by those skilled-in-the-art that a triple glazed unit could also be used. Alternatively using a different frame profile, the same production method can be used for welding around a single glass sheet and one option is for this single glass sheet would be as the center light of a triple glazed panel unit. 
       FIG. 9  shows a cross section bottom detail of a single seal IG panel unit  80  incorporated within a slim-line U-channel sash frame profile  81 . In contrast to a dual seal IG unit, the perimeter edge seal assembly  82  consists of a single barrier seal. Various single seal assemblies can be used including: the Intercept™ edge seal product marketed by PPG Inc. and the Swiggle Seal™ product marketed by TruSeal Inc. 
     One preferred single seal design is to use a thermoplastic spacer  83  that is made from desiccant filled butyl and/or polyisobutylene sealant material. The thermoplastic spacer  83  is marketed under the trade name of TPS and is directly applied to the glass using automated sealant gunning equipment manufactured by Bystronic Inc. A key advantage of the TPS spacer is that the material remains somewhat flexible and as a result, the spacer/edge seal assembly can accommodate some degree of glass movement and bowing even at cold temperatures. Typically, the TPS spacer is backed up by a structural thermosetting sealant such as polysulphide or polyurethane sealant (See  FIG. 5 ). However with integrated IG/sash frame assembly, the glass sheets  26  and  27 , are structurally bonded to the frame profile  81  by means of structural sealant glazing beads  54 ,  55  and so as a result, there is no need for an outer structural IG sealant to hold the glass sheets  26  and  27  in position. By eliminating this outer structural sealant, there are material and equipment cost savings and as well, the frame profile size can also be reduced resulting in additional material cost savings. A further production benefit is that there are no delays while waiting for the thermosetting sealant to cure and this provides for continuous sash frame production with the resulting productivity improvements and cost savings. 
       FIG. 10  shows the key production steps for assembling U-channel sash frame profiles  21  around an insulating glass panel unit  25 .  FIG. 10A  shows a schematic plan view of an insulating glass panel unit  25 .  FIG. 10B  shows a schematic plan view of the insulating glass panel unit  25  with U-shaped plastic framing profiles  21  loosely assembled around the insulating glass panel unit  25 .  FIG. 10C  shows a schematic plan view of the insulating glass unit/frame profile sub assembly  87  with corner junction pieces  22  inserted between the cut ends  23  and  24  of the framing profiles  21 . The four corners of the sash frame subassembly  87  are then welded, using methods and techniques disclosed in PCT CA 02/000842 for example.  FIG. 10D  shows a schematic plan view of the completed sash frame window  20 . As previously explained, the insulating glass panel unit  25  is held in position and centered in the U-shaped frame profile  21  using folding rubber spacer inserts (not shown). 
     Although the production process is shown in schematic form in  FIG. 10 , it can be appreciated by those skilled-in-the-art that the process can be fully automated using four headed production equipment as described in PCT Application CA02/000842. With a conventional, four headed hot plate welder, the overall cycle time is approximately 120 seconds and the time taken to manually load the four plastic profiles into the clamping fixtures is approximately 15 seconds. With four headed friction corner welder, the overall cycle time is less than 30 seconds but the task of manually loading the profiles takes 15 seconds while the actual weld time is less than 2 seconds. 
     Instead of preloading the profiles into the clamping fixtures of the four headed welder, one option with friction corner welding is to loosely fit the profiles around the insulating glass unit (See  FIG. 10B ). The profiles  21  can be temporarily held in place, by the folding rubber spacer inserts  30  (not shown) allowing the sub assembly of IG unit/frame profiles  87  to be transferred to the four-headed welder. The planar flange junction pieces  22  are then inserted and the corners welded using friction corner welding techniques. (See  FIG. 10C ). As a result of pre-assembling the frame profiles  21  around the IG panel unit  25 , the overall cycle time can potentially be reduced to less than fifteen seconds. 
     Finally, it should be noted that in  FIG. 10  although schematic plan views are shown with the insulating glass panel unit  25  in a horizontal position, the various manufacturing operations can also be carried out with the insulating glass panel unit  25  in a vertical position. 
     Where a thermoplastic sealant spacer is used, the sealant is preferably applied directly onto the perimeter glass edge with the glass sheet in a vertical position. As previously noted, the double bead sealant gunning operation is also carried out with the IG/frame sub assembly in a vertical position and so if all the various assembly operations are consistently carried out with the glass sub assemblies in a vertical position, there are potential productivity improvements and cost savings. 
       FIGS. 11A and 11B  show a cut out cross section plan view of a corner frame assembly  89  fabricated from square profile glass fiber filled PVC profile extrusions  90  and  91  and where the profiles  90  and  91  are vibration corner welded at using a junction piece  92  incorporating integral legs  93 . 
     As shown in  FIG. 11A , the integral legs  93  of the junction piece  92  incorporate an integral spring centering device  94  that simplifies frame assembly. The planar flange  48  of the junction piece  92  is first vibration welded to the miter cut ends  23  and  24  of the profiles  90  and  91 . Because of the need to accommodate the vibration movement back and forth, the legs  93  only loosely fit within the profile. 
     As shown in  FIG. 11B , in order to provide for additional support, the plastic framing profiles  90  and  91  are ultrasonically spot welded to the legs  93  of the junction piece  92 . A double tip welding head is typically used creating spot welds  95  and  96 . Because the legs  93  only loosely fit within the profile, the ultrasonic welding process allows the plastic to flow in the gap between the junction piece legs  93  and the profile extrusions  90  and  91  creating an extra strong welded spot bond and reduced material flow on the exterior surface. Because of their complex shape, the junction pieces  92  are typically injection molded and have to be manufactured from essentially the same base thermoplastic resin material as the extruded profiles  90  and  91 . 
       FIG. 11C  shows a vertical cross section through the hollow framing profile  91 . The integral legs  93  of the junction piece  92  consist of a rigid flat bar  97  with a central positioning fin  98 . The profile extrusion incorporates a half circular indentation  99  and this allows the positioning fin  98  to be centrally located. 
       FIG. 12  shows an alternative high volume production process for welding around an insulating glazing panel unit  25 .  FIG. 12A  shows a plan view of an insulating glazing panel unit  25  with U-Channel framing profiles  21  manually assembled around an insulating glazing panel unit  25  and where the profiles  21  are loosely interconnected by junction pieces  92  that incorporate integral legs  93 .  FIG. 12B  shows a plan view of the insulating glass/frame subassembly  100  where the profiles  21  are positioned around the insulating glass panel unit  25  and where the profiles are in part held in position by folding rubber spacer inserts (not shown).  FIG. 12C  shows a plan view of the insulating glass/frame subassembly  100  suspended below a gantry  101  and held in position by means of an adjustable clamping mechanisms  102 .  FIG. 12D  shows a plan view of four headed horizontal friction corner welder  103  where the insulating glass/frame subassembly  100  is transferred by the gantry  101  and dropped into position in the friction corner welder  103 . The removeable tabs  49  of the junction pieces  92  are located in the junction piece holding fixture  35  that are attached to the vibratory heads  33 .  FIG. 12E  shows a plan view of the insulating glass/frame subassembly  100  where the frame profiles  21  are clamped in position in moveable framing fixtures  104  and where the subassembly  100  is squared prior to friction corner welding the four corners  29 . After the welding process, the removable tabs  49  are automatically cut-off and the framing fixture clamps  104  are released. The assembled sash frame window  20  is then moved by the gantry  101  to the next window production operation. 
     Because with this high volume production process, the framing profiles are not manually placed in the profile fixtures, weld cycle time is substantially reduced to less than fifteen seconds per window unit and this results in a production output of two thousand windows per eight hour shift. It should be noted that although a high volume sash frame production method is described in  FIG. 12 , it can be appreciated by those skilled-in-the-art that the same production methods and apparatus can also be used to manufacture separate window frame assemblies. 
       FIG. 13  shows a bottom cross-section detail of a U-channel sash window profile  21  featuring flexible fin spacers  105  and glazing-bulb seal  106 . U-shaped channel profiles  21  are assembled around the insulating glass panel unit  25 . The panel unit  25  is then inserted into the channel frame profile  21 . The double set of flexible fin spacers  105  that are integrally formed with the framing profile  21  are compressed downwards and hold the insulating glass unit  25  in position. Typically, the flexible fins  105  are made from flexible PVC plastic material and are extruded simultaneously with the PVC framing profiles. 
     The dual seal insulating glass panel unit  25  is supported on a rubber support pad  107  that is positioned centrally in the U-shaped framing profile  21 . The support pad  107  incorporates an opening  108  to allow for water drainage from the glazing cavity  69 . The flexible glazing bulb seal  106  that is also integrally formed with the framing profile  21  prevents rain water run-off from entering the glazing cavity  39 . The use of integrally formed flexible fin spacers and bulb seals does not provide for the same structural performance as the twin sealant bead assembly previously described in  FIG. 5 . However for smaller residential windows the use of integrally formed spacers provides for adequate structural performance and with the added advantage of lower equipment, material and labor costs.