Skylight having a molded plastic frame

The present invention provides a skylight frame design that is adapted to receive at least two panels of glass. The skylight frame comprises a stepped frame section that includes a lower step surface and an upper step surface. The lower step surface is adapted to receive a first glass panel so that a section of the first glass panel lies flush against the lower step surface. Similarly, the upper step surface is adapted to receive a second glass panel so that the second glass panel lies flush against the upper step surface. The skylight frame design of the invention is either incorporated into a skylight frame that may be attached to a curb unit on a roof or it may be an integral part of a skylight frame-curb assembly that also contains a curb section. In another embodiment of the invention, a skylight frame design which directly incorporates one or more panels of glass during molding is provided.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a skylight having a plastic frame.

2. Background Art

Skylights have been used to allow light into residential and commercial buildings through an opening. The aesthetic value and possible health benefits of having sunlight in buildings have lead to an increasing demand for these structures. Ideally, a skylight will let light in while keeping other environmental elements out. However, since the installation of a skylight requires that an opening be cut in a roof, sealing such units has presented numerous challenges.

Popular skylight configurations include, for example, fixed skylights with flat or domed-shaped glass, ventilation skylights, egress skylights, and balcony skylights. In the fixed skylight configuration, the skylight functions essentially as a window that does not open. Ventilation skylights are similar, but may be opened a few inches to allow air circulation. Ventilation skylights may be opened by a pole or by a small electric motor. Egress roof skylights are capable of being opened by a sufficient amount for a person to move through. Balcony roof skylights which are usually installed on relatively steep roofs open to form a small balcony on which a person may stand.

In the typical fixed skylight installation a rectangular opening is cut in a roof. This opening will go through the plywood sheets in the roof. A curb unit is then attached to the plywood sheets of the roof. The external curb surfaces are then flashed with either roof boards or metal sheets to provide a leak-tight seal between the curb and roof. The skylight frame is then attached to the top surface of the curb unit. The skylight frame will usually have one or more glass panels surrounded by an aluminum trim frame. The glass panels are separated by a spacer which seals the interior cavity between the panels. The configuration for the glass panels is the same as that typically used in insulated window constructions. Transparent plastic panels may be used instead of glass panels. Additionally, the panels may be domed-shaped if desired. Such curbs are usually made of wood with a metal flashing along the sides of the curb. Generally, these curbs are fabricated on-site during the installation of the skylight. For stationary skylights, a leak tight seal will be formed between the skylight and the curb. Over time this leak tight seal often degrades and leaks. Furthermore, the application of a sealant to the curb may cause complications with the skylight manufacture tolerances by leaving a space between the metal flashing along the sides of the curb and the top of the curb. Foamed tapes have been used in place of sealants. However, such tapes do not adhere as well as sealants. Gaskets have been applied to both seal the skylight frame to a curb and to file the space between the metal flashing and the curb. Such configurations tend to be expensive and require rather strict tolerances. Moreover, the gasket can not be modified on-site.

Skylights have been formed with components made by reaction injection molding (“RIM”). U.S. Pat. No. 5,061,531 (“the '531 patent”) discloses a framed insulating glass unit with an integral skylight frame and an integral curb made by the RIM process. In the framed insulating glass unit of the '531 patent, two glass plates are molded into a frame member by a polyurethane RIM process. RIM is a process of molding plastic parts using liquid monomers. It is capable of forming solid or foam parts that can vary from being flexible to extremely rigid. Polyurethanes are probably the most common plastics from which parts are made by the RIM process. RIM polyurethane is made by combining an isocyanate and a polyol.

In the typical RIM process, the liquids are pumped into and combined in a mixer under a pressure between about 1,500 and 3,000 psi. The liquids are then introduced into the mold under a low pressure (about 1 atm). An exothermic chemical reaction occurs in the mold causing the liquid to solidify without heating or cooling. Parts fabricated by RIM offer several advantages over other molding processes. Although parts produced by RIM are similar to parts made by injection molding, RIM parts may be made with shorter production time and less cost. Furthermore, RIM does not require high temperatures or pressures typical of injection molding thereby making it possible to make the molds out of inexpensive materials such as aluminum. However, the RIM process presents a number of considerations that complicates part fabrication. For example, the processing temperature, pressure and viscosity must be accurately controlled since the polymerization of the monomers takes place in the mold. Furthermore, the mixing head must be completely purged after each part is formed to prevent clogging. Finally, the relatively protracted cycle times for forming larger parts and the limited choices of polymers (mostly polyurethanes) make RIM a somewhat undesirable process.

Accordingly, there exists a need for an improved skylight that is inexpensive to fabricate with a minimal number of seamed junctions.

SUMMARY OF THE INVENTION

The present invention overcomes the prior art by providing a skylight frame-curb assembly adapted to receive at least two panels of glass. The skylight frame-curb assembly of the present invention comprises a quadrilateral frame and a stepped frame section that is integral to the quadrilateral frame. The stepped frame surface includes a lower step surface and an upper step surface. The lower step surface is adapted to receive a first glass panel so that a section of the first glass panel lies flush against the lower step surface. Similarly, the upper step surface is adapted to receive a second glass panel so that the second glass panel lies flush against the upper step surface. The first glass panel is characterized by a first length and a first width and the second glass panel is characterized by a second length and a second width, such that the first length is less than the second length and the first width is less than second width. The first and second glass panels are advantageously combined together in an insulated glass unit. The frame curb assembly further includes a curb section which is integral to the quadrilateral frame. The curb section includes a surface that is adapted to lie on a roof to which it is flashed in a leak tight manner by methods known to one skilled in the art of skylight installation.

In another embodiment of the invention, a skylight frame adapted to be attached to a curb is provided. The skylight frame includes a stepped frame section including a lower step surface and an upper step surface. Again, the lower step surface is adapted to receive a first glass panel so that a section of the first glass panel lies flush against the lower step surface. Similarly, the upper step surface is adapted to receive a second glass panel so that the second glass panel lies flush against the upper step surface. The first and second glass panels are advantageously combined together in an insulated glass unit.

In another embodiment of the present invention, a skylight frame-curb assembly having a U-shaped trough with a mounting flange extending from one side of the U-shaped trough is provided. The skylight frame-curb assembly of this embodiment also includes the stepped frame section as described above. The trough of the present embodiment is filled with a foamed plastic in order to provide rigidity while reducing the weight of the skylight frame-curb assembly.

In another embodiment of the present invention, a skylight frame having one or more central support members is provided. The sides of the frame of this embodiment also include the stepped frame section described above. The one or more central support members include a lower step surface for receiving a lower glass panel. In this embodiment several lower glass panels are mounted between the lower step surfaces of the sides and the central support member. The upper glass surface in this design is a single glass panel which is received by the upper step surface of the sides. The upper glass panel also rests on the upper surface of the central support member.

In another embodiment of the present invention, a skylight frame-curb assembly fabricated by the RIM process is provided. In this embodiment, one or more glass panels are molded into the skylight frame section during formation of the skylight frame. The skylight frame assembly includes a frame section with slot adapted to hold one or more glass panels.

In still another embodiment of the present invention, an injection molded skylight curb unit is provided. The skylight curb unit includes four hollow sides that define a substantially rectangular or square opening. A flexible apron extends outwardly from the sides to provide a surface that is adapted to be placed on a rooftop. The side of the apron opposing the roof may be sealed to the roof and the entire apron flashed to a roof by methods known to those in the art of skylight installation.

In yet another embodiment of the present invention, a method of making a skylight frame is provided. The method of this embodiment comprises extruding a plastic channel with a stepped frame section integral to a lower curb portion. The frame section is similar to that set forth above. The plastic channel is then cut into four side sections which are then combined together to form the skylight frame.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Reference will now be made in detail to presently preferred compositions or embodiments and methods of the invention, which constitute the best modes of practicing the invention presently known to the inventors.

In an embodiment of the present invention, a skylight frame-curb assembly adapted to receive at least two panels of glass is provided. The skylight frame-curb assembly of the present invention comprises a quadrilateral frame with an integral stepped frame section. The quadrilateral frame is preferably substantially rectangular. The stepped frame surface includes a lower step surface and an upper step surface. The lower step surface is adapted to receive a first glass panel so that a section of the first glass panel lies flush against the lower step surface. Similarly, the upper step surface is adapted to receive a second glass panel so that the second glass panel lies flush against the upper step surface.

With reference toFIGS. 1 and 2, a perspective view of a cross-section and a top view of the skylight frame-curb assembly of the present invention is provided. Skylight frame-curb assembly2includes sides4,6,8,10which define opening12. Opening12is of appropriate size to line up with a skylight opening curb into a roof. Sides4,6,8,10each include stepped frame section14and curb section16which are integral to skylight frame-curb assembly2. Stepped frame section14includes lower step surface18and an upper step surface20. Lower step surface18is adapted to receive glass surface22of glass panel24and upper step surface20is adapted to receive glass surface26of glass panel28. Specifically, glass peripheral surface30opposes lower step surface18and glass peripheral surface32opposes upper stepped surface20. Glass panel24is characterized by a first length and a first width and glass panel28is characterized by a second length and a second width, such that the first length is less than the second length and the first width is less than second width. Preferably, glass panel24and glass panel28are combined together in insulated glass unit34with a spacer36. Alternatively, glass panel24and glass panel28are laminated together like an automobile windshield. Suitable laminates include, for example, polyvinylbutyral. Lamination of glass panels24,28provide added protection from glass breakage. Stepped frame section14corresponds in shape to the edge detail and thickness of the insulating glass unit (or the laminated glass unit) so that the insulating glass unit is mounted flush.

The skylight of the present design lends itself to a wide array of aesthetic appearances. The insulated glass units can be fabricated using colored glass to achieve a desired color and thermal properties. Alternatively, one or more surfaces of glass panels24and28may be coated with thin films to alter the appearance of the skylight or to provide solar control properties. For example, in northern climates a low E coating is applied to one or more of the glass surfaces. In southern climates, reflective coatings capable of rejecting 80-90% of the radiant energy could be utilized to minimize air conditioning costs. Furthermore, the color of the glass panel on the peripheral portion can be selected to provide the desired aesthetic appearance. Curb section16optionally includes a number of bolt holes37so that skylight frame curb assembly2may be attached to a roof. During installation, curb section16will be flashed to the roof by methods known to those skilled in the art of skylight installation. Skylight frame-curb assembly2optionally includes trim strip38which can be provided at the overlap of insulated glass unit34and skylight frame-curb assembly2.

Skylight frame-curb assembly2may be formed from any suitable material which supplies suitable mechanical stiffness and resistance to deterioration from environment factors such as temperature, humidity, sun light, air, rain, snow, hail, and the like. Suitable materials include for example various plastics, wood, and metals. The preferred materials are plastics and in particular thermoplastic resins such as polyvinylchloride, polyethylene, polypropylene, or nylon. When a plastic is utilized to mold skylight frame-curb assembly2a glass fiber reinforcement filler may be used in the plastic composition selected in order to minimize the thermal expansion of skylight frame-curb assembly2. Skylight frame-curb assembly2may be formed by a number of different molding processes. For example, skylight frame-curb2may be formed by injection molding, vacuum molding, compression molding, or by RIM. The preferred molding process is chosen to improve strength and to minimize part weight and to provide optimum thermal insulation qualities. To this end, skylight frame-curb assembly2optionally includes one or more hollow cores39that may be filled with foamed plastic40. Skylight frame-curb assemblies with hollow cavities may be made by gas assisted injection molding which uses a conventional injection molding press equipped with a spillover control and a mold equipped with gas injection and spillover points. Suitable gas assisted injection molding processes which may be used to form the skylight frame-curb assembly of the present invention are described in U.S. Pat. No. 6,019,918. The entire disclosure of this patent is hereby incorporated by reference. The foam material is then introduced through inlet holes after the frame is molded. Alternatively, the part can be molded utilizing a plastic foaming agent, the surface of the plastic part having a smooth uniform skin while the inner core contains a series of gas bubbles forming a rigid foam or sponge-like core. The skylight frame-curb assembly may also be made by compression molding using either sheet molding compound (“SMC”) or bulk molding compound.

Insulating glass unit34is bonded to stepped flange section14of skylight frame-curb assembly2utilizing adhesives in a manner similar to mounting a flush glazed windshield in an automobile. Preferably, glass surface26of the glass panel28has a peripheral edge painted to provide an aesthetic detail as well as improve the adhesion of the bond between the glass pane28and frame curb assembly2. Optionally, grooves42,44may be formed on lower step surface18and upper step surface20in order to provide a relatively thick bead of adhesive in order to accommodate some slight relative movement due to the differential thermal expansion of insulated glass unit34in order to further minimize the mold expansion problems.

With reference toFIG. 3, a cross-section of a skylight frame-curb assembly with an attached laminated glass sheet is provided. In this variation glass panel24and glass panel28are laminated together with laminate layer50. Glass panel28is slightly larger than glass panel24. Glass edge30opposes lower step surface18and glass edge30opposes upper stepped surface20. In this variation, height52must be of appropriate dimensions to allow an effective seal when an adhesive is applied to lower set surface18and upper step surface20. Generally, height52will be several millimeters.

With reference toFIG. 4, a cross-sectional view of an embodiment of the present invention in which the stepped frame section is on a separate part from the curb is provided. Frame60includes stepped frame section14which is the same as set forth above. Stepped frame section14includes lower step surface16and upper step surface20. Lower step surface18is adapted to receive glass surface22of glass panel24and upper step surface20is adapted to receive glass surface26of glass panel28. Glass panel24is characterized by a first length and a first width and glass panel28is characterized by a second length and a second width, such that the first length is less than the second length and the first width is less than second width. Preferably, glass panel24and glass panel28are combined together in insulating glass unit34or a laminated glass unit as set forth above. Frame60may be formed from the same materials and by the same molding processes as set forth above. Frame60is attached to curb62. This attachment may be accomplished by means known to one skilled in the art of skylight installation. Preferably, frame60is bolted to curb62by bolts64. Optionally, a sealant may be placed on one or more of seams66,68,70to reduce the possibility of water leaking from the skylight. The frame assembly of this embodiment allows insulated glass unit34and frame60to be replaced in the event a window is damaged during or after construction. This is to be contrasted with a damaged insulated glass unit for the design ofFIGS. 1 and 2, which would require replacement in a manner similar to the replacement of an automobile windshield. The two piece design of the present embodiment enables a less skilled person to do the window replacement by unbolting frame60and replacing the whole unit—frame60and insulated glass unit34. Moreover, insulated glass unit and frames can be made standard sizes and matched up with curbs of a selected height and thermal quality for the specific market.

With reference toFIG. 5, a cross-section of another embodiment of the present invention in which the frame curb assembly has a U-shaped trough with a mounting flange extending from one side of the U-shaped trough is provided. Skylight frame-curb assembly70includes stepped frame section14. As set forth above, stepped frame section14includes lower step surface18and upper step surface20. Again, lower step surface18is adapted to receive glass surface22of glass panel24and upper step surface20is adapted to receive glass surface26of glass panel28. Glass panel24is characterized by a first length and a first width and glass panel28is characterized by a second length and a second width, such that the first length is less than the second length and the first width is less than second width. Preferably, glass panel24and glass panel28are combined together in insulated glass unit34with a spacer36. Skylight frame-curb assembly include sides72,74,76which define trough78. Curb section80includes mounting flange82which extends from the bottom of side72. Ribs84extend from bottom surface86of mounting flange82to provide stiffness. Skylight frame-curb assembly70may be formed by the same molding processes as described above which include injection molding from thermoplastic resins or by RIM. After skylight frame-curb assembly70is molded, trough78is filled with foamed plastic88in a second operation. Foamed plastic88provides rigidity to skylight frame-curb assembly70as well as good thermal insulation. Glass panels24,28are installed in a similar manner to the installation of an automobile windshield. Accordingly, an adhesive is applied between glass edge30and lower step surface18and between glass edge32and upper stepped surface34.

With reference toFIGS. 6 and 7, cross sectional and top views of various frame assemblies utilizing a central cross member of an embodiment of the present invention in which a series of frame configurations having a central cross member for supporting multiple insulating glass units in a single frame is provided.FIG. 6provides a cross-section of the present embodiment in which a central cross member is utilized.FIG. 7provides a top view of the assembly illustrated inFIG. 6. Skylight frame102includes side sections104,106,108,110and central cross member112. Side sections104,106,108,110each include stepped frame section14which has described above. Cross member112include cross member step section which has lower step surface114and top surface116. Skylight frame includes stepped frame section119which has been set forth above. In this configuration, glass panels118,120are placed in skylight frame102such that a peripheral section of glass surface122opposes lower step surfaces124and lower step surfaces114. Larger glass panel120is positioned in frame102such that a peripheral section of surface126opposes upper step surfaces128. Central portion136of glass panel126lies on and is supported by top surface116of cross member112. The frame assemblies of the present embodiment allows large skylights to be fabricated and ganged together to form large panels of minimal viewing area blocked by cross members of structural supports. Because the outside surface of the skylight assembly is made from a single piece of glass the outside appearance is substantially uniform.

With reference toFIGS. 8A and 8B, an alternative design for a skylight with one or more cross members is provided.FIG. 8Aprovides a top view of this embodiment utilizing a two step cross member, whileFIG. 8Bis a cross section of the cross member used in this embodiment. In this variation, frame138includes sides140,142,144,146and cross members148. Each of sides140,142,144,146include a stepped frame section as set forth above.FIG. 8Bprovides a cross section of the two step cross member of the present invention. Cross member148includes stepped frame sections150with lower step surface152and upper step surface154. Glass surface156opposes lower step surface152and glass surface158opposes upper step surface154in a similar manner as described in the discussion ofFIGS. 1 and 2.

With reference toFIGS. 9 and 10, another embodiment of the present invention in which a skylight frame is molded about an insulating glass is provided. In this embodiment, one or more glass panels are molded into the skylight frame section during formation of the frame. Preferably, this molding operation is a RIM molding process.FIG. 9provides a cross-sectional view andFIG. 10provides a top perspective view of the skylight frame assembly of this embodiment. Skylight frame assembly170includes frame section172which has U-shaped channel173. U-shaped channel173is adapted to hold one or more glass panels. Preferably, a multiglazed window unit will be held in U-shaped channel. Glass panel176and glass panel178are adhered together by spacer180to form a double glassed insulated window unit182. Bottom surface184of U-shaped channel opposes glass surface edge186of glass panel176. Similarly top surface188of U-shaped channel oppose glass surface edge190of glass panel178. Bottom surface184and top surface188in combination with back surface191define U shaped channel173. Finally, the skylight frame assembly of this embodiment optionally includes curb section192to facilitate placement of the skylight frame assembly on a roof. To enhance adhesion, glass panels176,178should be cleaned and dried prior to molding of frame170around glass panels176,178. Moreover, the application of one or more coupling agents prior to molding is found to further enhance adhesion. More preferably, two or more coupling agents are applied to the glass surfaces prior to molding of the skylight frame. Silane coupling agents include vinylsilanes, acryloxy compounds, epoxysilanes, aminosilanes, and organosilane esters. Vinylsilane coupling agents include, for example, vinyltricolosilane, vinyl tris(β-methoxyethoxy) silane, vinyltriethoxysilane. An example of an acryloxy coupling agent is 3-metacryloxypropyl-trimethoxysilane. Examples of epoxysilane coupling agents include for example, β-(3,4 epoxycyclohexyl)-ethyltrimethoxysilane, γ-glycidoxypropyl-trimethoxysilane, and γ-glycidoxypropyl-methylidiethoxysilane. Examples of aminosilane coupling agents include for example, N-β(aminoethyl)-γ-aminopropyl-trimethoxysilane, N-β(aminoethyl)-γ-aminopropyl-methyldimethoxysilane, 3-aminopropyl-triethoxysilane, N-phenyl-γ-aminopropyl-trimethoxysilane. An example of an organosilane ester is methyl triethoxysilane. Other silane coupling agents are γ-mercaptopropyl-trimethoxysilane and γ-chloropropyl-trimethoxysilane. Silane coupling agents are commercially available from Union Carbide Corporation and Mitsubishi International Corporation.

With reference toFIG. 11, a cross-section of a skylight frame with an embedded insulating glass unit having a stepped frame section is provided. Skylight frame section200includes stepped frame section202. Stepped frame section202includes lower step surface204, upper step surface206, upper channel surface208. Moreover, skylight frame section200includes channel210which is defined by upper step surface206, back surface212, and upper channel surface208. Lower step surface204opposes glass surface214of glass panel216and upper step surface206opposes glass surface218of glass panel220. Similarly, upper channel surface opposes glass surface222of glass panel220. As set forth above, glass panel216and glass panel220are combined together in insulated glass unit224with a spacer226. The skylight frame design of this embodiment is advantageously molded around glass panels216,220. The preferred method of molding this embodiment is RIM. Again, adhesion is enhanced by cleaning and drying glass plates216,220prior to molding skylight frame200followed by application of one or more coupling agents. The preferred coupling agents are the same as those set forth above.

With reference toFIGS. 12 and 13, a skylight curb unit adaptable to a skylight frame is illustrated.FIG. 12is a top perspective view andFIG. 13is a bottom perspective view of the skylight curb unit of this embodiment. The skylight curb unit is preferably made of a plastic or rigid polymer by injection molding. Skylight curb unit230includes curb sides232,234,236,238that define substantially rectangular or square opening240. Curb sides232,234,236,238include interior walls242,244,246,248and exterior walls250,252,254,256. Rigidity is provided to the curb unit by rib network that includes ribs258that connect to interior walls242,244,246,248and exterior walls250,252,254,256. The rib network in conjunction with interior walls242,244,246,248and exterior walls250,252,254,256defines slots260,262. Flexible apron264extends outwardly from curb sides232,234,236,238to provide bottom surface266that is adapted to be placed on a rooftop. Top surface268of curb unit230is adapted to receive a skylight frame unit. Optionally, a gasket and/or a sealant is placed on top surface268for this purpose. Bottom surface266includes a plurality of bolt holes270to receive bolts used to attach the skylight curb unit to a roof. These bolts are passed through slots260,262for this purpose. Moreover, apron264may be flashed to a roof by methods known to those in the art of skylight installation. The curb unit of this embodiment is preferably made by injection molding with a thermoplastic resin. Suitable thermoplastic resins include, for example, polyvinylchloride, polyethylene, polypropylene, or nylon.

With reference toFIGS. 14 and 15, a skylight frame unit adapted be attached to the curb unit ofFIGS. 12 and 13is described.FIG. 14is a cross-sectional view of the skylight frame unit with a bottom cap section inserted into the skylight curb unit ofFIGS. 12 and 13.FIG. 15is a bottom view of the skylight frame unit of this embodiment. Skylight frame300includes stepped frame section302. The details of stepped frame section302are the same as those set forth above forFIGS. 1 and 2. Stepped frame section302includes lower step surface304and an upper step surface306. Lower step surface304is adapted to receive glass surface308of glass panel310and upper step surface306is adapted to receive glass surface312of glass panel314. Skylight frame300also includes insert sections316and318which are adapted to slide into slots260,262of the skylight curb unit described inFIGS. 12 and 13. Skylight frame300is held in place by screw320which passes through wall250into insert section316. Alternatively, a pin may be used instead of screw320.

In still another embodiment of the present invention, a method of forming the skylight frame described above inFIGS. 1-3is provided. The method of this embodiment comprises extruding a plastic channel with a stepped frame section integral to the plastic channel having a lower step surface and upper step surface; cutting the plastic channel to form a first frame side, a second frame side, a third frame side, and a fourth frame side; and combining the first frame side, the second frame side, the third frame side, and the fourth frame side together to form the skylight frame. The details of the stepped frame section and curb section if present are the same as set forth above forFIGS. 1-4. Moreover, the plastic channel preferably comprises a plastic selected from the group consisting of polyvinylchloride, polyethylene, polypropylene, or nylon.

With reference toFIGS. 16A and 16B, a skylight frame assembly constructed from four sides is illustrated.FIG. 16Ais a bottom view of a skylight frame-curb assembly constructed from four sides, whileFIG. 16Bis a cross section through one of the sides when the skylight frame assembly includes a curb section. Skylight frame-curb assembly330is assembled from sides332,334,336,338which have been cut from an extruded channel. Sides332,334,336,338are mitered together as beveled joints340,342,344,346. Sides332,334,336,338include frame step section360and curb section362. Frame step section360includes lower step surface364and upper step surface366which is similar to the frame step section ofFIGS. 1-3. Moreover, sides332,334,336,338include hollow cavity368. Optionally, angular inserts370,372,374,376are placed within sides332,334,336,338as the sides are joined together. This inserts provide rigidity and support to the skylight frame-curb assembly and may extend into hollow cavity368for any length desired. Beveled joints340,342,344,346are welded together to form a leak tight seal. Suitable processes for this welding include, for example, conventional plastic welding with a heat source and a plastic welding rod, laser welding, and solvent bonding. Optionally, hollow cavity368is filled with foamed plastic380which is introduced into hollow cavity368through inlet holes382,384. Vent holes386,388provide a venting path while the foamed plastic is added. The assembly of the skylight frame-curb assembly set forth in this embodiment may be applied the fabrication of the skylight curb assembly ofFIGS. 1-3. Similarly, the present embodiment may be applied to the fabrication of the skylight frame ofFIG. 4except that the four sides do not have an integral curb section.

In still another embodiment of the present invention, a method of forming the skylight frame-curb assembly described above inFIG. 5is provided. The method of this embodiment comprises extruding a plastic U-shaped channel with a stepped frame section integral to the plastic channel having a lower step surface and upper step surface. The details of the stepped frame section and the cross section of the U-shaped channel are the same as set forth above forFIG. 5.

With reference toFIG. 17, a bottom view of a skylight frame assembly with a U-shaped channel constructed from four sides is illustrated. Skylight frame-curb assembly400is assembled from sides402,404,406,408which have been cut from an extruded U-shaped channel. Sides402,404,406,408are mitered together as beveled joints410,412,414,416. Sides402,404,406,408includes a stepped frame section and curb section (not shown) as set forth forFIG. 5. Sides402,404,406,408include U-shaped trough420. Beveled joints410,412,414,416are welded together to form a leak tight seal. Suitable processes for this welding include, for example, conventional plastic welding with a heat source and a plastic welding rod, laser welding, and solvent bonding. Optionally, U-shaped trough420is filled with foamed plastic422.