Patent Publication Number: US-2021170209-A1

Title: Ceiling fixture firestop

Description:
BACKGROUND 
     This relates to a firestop system for use with a ceiling fixture, such as a downlight, and to a ceiling fixture and associated firestop system. 
     When a fire breaks out in a building, it should be contained as much as possible. While a ceiling in a building may be designed to impede the spread of fire, openings through the ceiling accommodating fixtures present an opportunity for a fire to spread more easily. Also, some ceiling fixtures themselves, such as downlights, can be the cause of a fire. 
     Therefore, there is a need for an approach to reduce the fire hazards associated with ceiling fixtures. 
     SUMMARY 
     In accordance with an embodiment, there is provided a system for use with a ceiling fixture, a portion of which projects though an opening in a ceiling wall, for assisting in preventing spread of fire through the opening. The system has a metal collar for lining the opening. The metal collar has an upper rim overlying a top surface of the ceiling wall at the opening, a middle section facing an inner edge of the ceiling wall at the opening and a lower rim underlying a bottom surface of the ceiling wall at the opening. The system also has an intumescent ring for surrounding the projecting portion of the fixture so as to be interposed between the metal collar and the projecting portion of the fixture. 
     In an aspect, there is provided a system for use with a ceiling fixture, a portion of which projects though an opening in a ceiling wall, for assisting in preventing spread of fire through said opening, said system comprising: a metal collar for lining said opening, said metal collar having an upper rim for overlying a top surface of said ceiling wall at said opening, a middle section for facing an inner edge of said ceiling wall at said opening and a lower rim for underlying a bottom surface of said ceiling wall at said opening; and an intumescent ring for surrounding said portion of said fixture so as to be interposed between said metal collar and said portion of said fixture. 
     In another aspect, there is provided a ceiling fixture system comprising: a ceiling fixture having a portion projecting through an opening in a ceiling wall; a metal collar lining said opening with an upper rim overlying a top surface of said ceiling wall at said opening, a middle section facing an inner edge of said ceiling wall at said opening and a lower rim underlying a bottom surface of said ceiling wall at said opening, wherein said middle section is interposed between said opening and said portion of said fixture. 
     In another aspect, there is provided an intumescent ring for use with a ceiling fixture, said ceiling fixture having a portion projecting through an opening in a ceiling wall, said intumescent ring for assisting in preventing spread of fire through said opening and comprising: a radially extending flange for overlying a top surface of said ceiling wall at said opening, and a tubular section depending from said radially extending flange, said tubular section for surrounding said portion of said fixture so as to be interposed between said opening and said portion of said fixture. 
     In a further aspect, there is provided a ceiling fixture system comprising: a ceiling fixture having a portion projecting though an opening in a ceiling wall; a metal collar lining said opening and supported by said ceiling wall with an upper rim of said metal collar overlying a top surface of said ceiling wall at said opening, a middle section of said metal collar facing an inner edge of said ceiling wall at said opening and a lower rim of said metal collar underlying a bottom surface of said ceiling wall at said opening; and an intumescent ring surrounding said portion of said ceiling fixture so as to be interposed between said metal collar and said portion of said ceiling fixture. 
     Other features and advantages will become apparent from the following description in conjunction with the drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       In the figures which illustrate example embodiments, 
         FIG. 1  is a bottom perspective view of a partially installed downlight fixture with a deployed intumescent element, 
         FIG. 2  is a top perspective view of the downlight fixture of  FIG. 1  shown fully installed and provisioned with a system in accordance with an embodiment, 
         FIG. 3  is cross-sectional view along the lines of  FIG. 2 , 
         FIG. 4  is a top perspective view of a metal disk of  FIG. 3 , 
         FIG. 5  is a top perspective view of the intumescent element of  FIG. 3 , 
         FIG. 6  is an enlarged view within circle D of  FIG. 3 , 
         FIG. 7A  is a plan view of a part of the system of  FIG. 6 , 
         FIG. 7B  is a profile view of the part of  FIG. 7A , 
         FIG. 8A  is a plan view of another part of the system of  FIG. 6 , 
         FIG. 8B  is a profile view of the part of  FIG. 8A , 
         FIG. 9  is a top perspective view of a further part of the system of  FIG. 6 , 
         FIG. 10  is a cross-sectional view of the downlight fixture of  FIG. 1  with a stowed (non-deployed) intumescent element, 
         FIGS. 11-14  are bottom perspective views illustrating installation of the system of  FIG. 6 , 
         FIG. 15  is a cross-sectional view of the downlight fixture of  FIG. 1  with a deployed intumescent element. 
     
    
    
     DETAILED DESCRIPTION 
     Turning to  FIGS. 1 and 2 , a downlight fixture  50  has a metal light can  52  joined to a rectangular metal base  54  in a conventional fashion so that the light can  52  can be vertically adjusted within the base. The base also supports wiring box  56  which, if the light fixture is used with an electrical gas discharge light, may also include a ballast. The light can  52  has a body  58  shaped as a cylindrical sleeve and an end cap  60  which is joined to the body by rivets  62  ( FIG. 3 ). 
     The base  54  terminates at each end in an upturned flange  61 , with mounts  63  that hold a telescoping arm  64 . The telescoping arms terminate in feet  66  which are attached to ceiling joists  68  in order to mount the fixture  50 . An upper fire resistant drywall layer  70  is attached to the ceiling joists and a lower fire resistant drywall layer  72  is attached by furring strips  74  to the upper drywall layer. The upper and lower layers  70 ,  72  have respective openings  78 ,  79  ( FIG. 6 ) aligned with the light can  52  and a portion of the light can projects through these openings. 
     With brief reference to  FIG. 3 , the deployed intumescent element  80  within the light can  52  rests on a metal support plate  85 . Element  80  and metal support plate  85  each have a diameter similar to the inside diameter of the light can body  58 . The light can cap  60  has an opening  105 . Turning to  FIG. 4 , the metal support plate  85  is an annular disk with a central opening  101  and three peripheral openings  102 . Turning to  FIG. 5 , the intumescent element is an annular disk with a central opening  82 . The disk has a plurality of regularly spaced lands  86  on a face of the disk with a void  88  extending between each pair of lands. The voids are in the nature of radially elongated axial through slots to define a plurality of identical regularly spaced radially extending ribs  92 , with a rib between each pair of slots. The bottom surfaces of the ribs are the lands, and the ribs connect to each other at the outer and inner peripheries of the annular disk. Opening  105  in the light can cap along with the central opening  82  of the intumescent element  80  and central opening  101  of the metal support plate  85  allow electrical wiring from the wiring box  56  to reach a light within the light can. 
     Returning to  FIG. 3 , an upper end  93  of each of three flexible cables  95  is attached to the underside of the cap  60  of the light can  52  by a web  96  that is in turn joined to the cap with a screw and wing nut assembly  98 . Each of the cables passes through one of the voids  88  in intumescent  80  and one of the openings  102  in the support plate  85  and then extends downwardly adjacent the inside wall of the light can, terminating in a bulbous end  104  proximate the base of the light can. The bulbous end of each cable has a larger diameter than the holes  102  through the support plate  85 . 
     An intumescent gasket ring  190  extends about the light can  52  atop the upper drywall layer  70  and is enveloped by a metal sleeve  194 . 
     Referencing  FIG. 6  along with  FIG. 3 , a system  200  to assist in preventing the spread of fire through the openings  78 ,  79  in the drywall layers has a metal collar  210  which is C-shaped in cross-section. The metal collar lines the opening  79  of the lower drywall layer  72 . More specifically, the metal collar has an upper rim  212  overlying the top surface of drywall layer  72 , a middle section  214  facing the peripheral edge of the opening  79  and a lower rim  218  underlying a bottom surface of drywall layer  72 . The surface  216  ( FIG. 7B ) of the middle section  214  of the metal collar between the upper and lower rims  212 ,  218  has an intumescent caulking layer  230 . The system  200  also has an intumescent ring  220  surrounding the light can  52  and interposed between the metal collar  210  and the light can. 
     The intumescent element  80 , intumescent ring  190 , intumescent ring  220  and intumescent caulk  230  are fabricated of an intumescent flame retardant (IFR) that includes one or more IFR polymer composites. Suitable IFR polymer composites may include base polymers, fire retardants, and blowing agents. If the base polymers are inherently fire retardant, such as polyvinyl chloride (PVC), chlorinated polyvinyl chloride (CPVC), halogenated polyethylene Neoprene and phenolic resin, then the fire retardants can be omitted from the composite. Synergists such as antimony oxides and/or zinc borate can be added to improve the fire retardancy of a composite. Char-forming agents can be added to promote charring and increase yield (i.e., final volume after intumescence), and thereby improve the fire retardancy and thermal insulation of a composite. Optionally, other components such as smoke suppressants, pigments, and compatibilizers such as maleic anhydride grafted polyolefin and organofunctional silanes can also be added. 
     Suitable blowing agents include, but are not limited to, expandable graphites, intumescent hydrated alkali metal silicates, and intumescent hydrated alkali metal silicates with certain amounts of other components such as those described in U.S. Pat. No. 6,645,278 issued Nov. 11, 2003 to Langille et al., the contents of which are incorporated herein by reference. The start expansion temperature (SET) of suitable blowing agents may vary between 120° C. to 350° C., which is well above the normal operating temperature of the downlight fixture. Other suitable blowing agents will also be apparent to those of ordinary skill in the art. Blowing agents in the composite are generally used in amount of about 1 weight percent (wt %) to about 70 wt %. 
     Suitable fire retardants include, but are not limited to, polymeric halogen, monomeric halogen, alumina trihydrate, magnesium di-hydroxide, mica, talc, calcium carbonate, hydroxycarbonates, phosphorus compounds, red phosphorus, borate compounds, sulfur compounds, nitrogen compounds, silica, and/or various metal oxides. Other suitable fire retardants will also be apparent to those of ordinary skill in the art. The concentration of the fire retardants in a composite generally varies from 5 wt % to 55 wt %. 
     Suitable base polymers include, but are not limited to, thermoplastics, such as polyethylene, polypropylene, polyamide, ABS, polybutylene terephthalate, polyethylene terephthalate, EVA, thermosetting plastics, and elastomers, such as epoxy, Neoprene, cross-linked polyethylene, silicone, NBR, thermoplastic elastomers, or the blend of above. Other suitable base polymers will be apparent to those of ordinary skill in the art. 
     A mixture of the different components described above can be compounded into a composite. This composite can in turn be formed into desired geometries by known polymer processing methods such as injection molding, compression molding, transfer molding, or the like. The melting temperature of the base polymers should be lower than the SET of the blowing agents in the composite and higher than the normal operating temperatures expected in the downlight fixture. The temperature between the melting temperature of the base polymers and the SET of the blowing agents is the processing window for the composite. An IFR polymer composite formulated to have an expansion ratio of between 1.2 and 50 is suitable. 
     Example suitable IFR polymer composites are described in U.S. Pat. No. 6,790,893 issued Sep. 14, 2004 to Nguyen et al., the contents of which are incorporated herein by reference, US2010/0086268 to Reyes, published Apr. 8, 2010, the contents of which are incorporated herein by reference, and US2012/0022201 to Zhvanetskiy et al., published Jan. 26, 2012, the contents of which are incorporated herein by reference. 
     As will be apparent to those skilled in the art, with these compositions, the intumescent components may be fabricated so as to be rigid or flexible. In this regard, the intumescent ring  220  is fabricated with a thermoplastic or elastomer base polymer so as to be flexible. 
     The metal collar is an assembly of two arcuate parts. Turning to  FIGS. 7A and 7B , a first arcuate collar part  242  of the metal collar defines an arc that extends through more than 180°. Specifically, the arc of collar part  242  extends through 200°. Turning to  FIGS. 8A and 8B , a second arcuate collar part  244  of the metal collar defines an arc that extends through 180°. 
     Turning to  FIG. 9 , the intumescent ring  220  has a radially extending flange  222  and an axially extending tubular section  224  which depends from the inner edge of the flange  222 . In consequence, as seen in  FIG. 6 , the intumescent ring  220  is L-shaped in cross-section with the tubular section  224  interposed between the metal collar and the light can and the flange  222  extending over the upper rim  212  of the metal collar and beyond the outer edge of the metal collar over drywall layer  72 . 
       FIG. 10  illustrates the downlight fixture  50  with additional components present to support the intumescent element  80  in a non-deployed, stowed, position. Turning to  FIG. 10 , downlight fixture  50  has fire sensitive supports, namely plastic T-shaped tabs  120  supported by the light can  52  with tongues projecting inwardly from the light can. Further fire sensitive supports, namely plastic T-shaped tabs  122  supported by a heat sink  170  have tongues projecting outwardly from the heat sink. The tabs  122  of the heat sink rest on the tabs  120  of the light can such that the heat sink  170  is supported within the light can  52 . An LED light  168  is mounted within heat sink  170  by any suitable means. Wiring (not shown) extends from the wiring box  56  ( FIG. 3 ) through the light can opening  105  ( FIG. 3 ) to the LED light. The wiring includes a fire sensitive plastic connector (not shown) within the light can. The firestop element  80  and metal support plate  85  are supported on the top of the heat sink  170  such that the heat sink holds element  80  and plate  85  in a stowed position proximate the cap  60  of the light can. 
     In manufacture of downlight  50 , tabs  120  are inserted into the light can  52 . The heat sink is then moved into place within the light can and tabs  122  are inserted into the heat sink so that the tongues of tabs  122  overlie the tongues of tabs  120  whereby the heat sink is supported within the light can  52 . Next, the end  93  of each cable  95  may be threaded through a peripheral opening  102  ( FIG. 4 ) of plate  85  and a void  88  ( FIG. 5 ) of disk  80  and attached to the underside of the cap  60  of the light can  52 . The firestop element  80  with its support plate  85  can then be set in place on the top of the heat sink. The cap  60  of the light can is then brought into place on top of the body  58  of the can, allowing excess cable to move through disk and plate so that the bulbous cable ends hang proximate the base of the light can  52 . Cap  60  is then riveted in place by rivets  62 . 
     Returning to  FIGS. 1 and 2 , the assembled downlight fixture may then be installed in a ceiling by extending telescoping arms  64  so that the feet of the arms abut adjacent ceiling joists  68  and then fastening the feet to the joists. Next, circular opening  78  ( FIG. 11 ) is cut into the top drywall layer  70  so that the opening has a slightly larger diameter than that of the body  58  of the light can  52 , for example, opening  78  may be ¼″ larger in diameter. The top layer of drywall is then attached to the bottom of the ceiling joists in conventional manner with its opening  78  aligned with the light can body. The light can  52  is then pulled downwardly relative to its base  54  through opening  78 . Circular hole  79  ( FIG. 11 ) is then cut in the lower layer of drywall  72  so that the opening  79  has a slightly larger diameter than that of the body  58  of the light can  52  and a slightly larger diameter than opening  78 , for example ⅝″ larger in diameter than the diameter of the light can. The lower layer of drywall is then attached to the upper layer by furring strips, in conventional manner, with opening  79  aligned with the light can body.  FIG. 11  illustrates the installation at this stage. 
     System  200  is now installed. Referring to  FIGS. 12 and 13 , intumescent caulk  230  is applied to the face  216  ( FIG. 7B ) of each of the two collar parts  242 ,  244  of the metal collar. Before the caulk dries, collar part  242  is pressed against the periphery of the opening such that the caulk  230  adheres part  242  to the periphery of the opening and may fill imperfections in this periphery. Collar part  244  follows, being pressed against the periphery of the opening with the two ends of part  244  overlapping the two ends of part  242 .  FIG. 13  illustrates the installation after placement of the metal collar  210 . Next, with reference to  FIGS. 6 and 9 , the intumescent ring  220  is flexed as required until it is positioned with its radially extending flange  212  extending on top of the upper rim  212  of the metal collar and its depending tubular section  224  extending against the middle section  214  of the metal collar.  FIG. 14  illustrates this stage of the installation. Lastly, the light can  52  is pulled down through opening  79  in the lower drywall layer  72  so that the light can extends through opening  79  as shown in  FIG. 3 . 
     In use, referencing  FIG. 10 , in the event of a fire, tabs  120  and  122  melt or burn off as does the plastic connector in the wiring to the LED light. In consequence, heat sink  170  (with its LED light  168 ) is no longer supported within the light can  52  and it falls away, as illustrated in  FIG. 15 . Since the intumescent element  80  with its support plate  85  had rested upon the heat sink, it falls with the heat sink until the support plate  85  abuts the bulbous ends  104  of the cables  95  whereupon the support plate and intumescent disk are arrested by the cables  95 . The length of the cables is chosen so that the firestop element when arrested protrudes just below the base of the light can. Thus, the cables act as limiters, limiting the fall of the intumescent element and support plate. With the intumescent element in this deployed position, as this element intumesces, it expands to plug the light can at the bottom. This blocks flames from entering the light can and possibly extending through any openings in the can; it also reduces the heat inside the can. 
     Additionally, in the event of a fire, the intumescent ring  220  of system  200  intumesces and expands. With this expansion, the tubular section  224  of the intumescent ring  220  pushes against both the light can  52  and the middle section  214  of the metal collar  210 . At the same time, the intumescent caulk  230  expands and pushes the middle section  214  of the metal collar toward the tubular section  224  of the intumescent ring  220 . The result is that the metal collar is strongly held in place lining the periphery of the opening  79  through drywall layer  72 . This may improve the resultant fire protection as it may make the inner periphery of the drywall at the opening less susceptible to failure in a fire, and therefore less susceptible to allowing flames and heat to penetrate past the drywall. Moreover, the flange  222  of the intumescent ring  220  expands into the gap between the upper and lower drywall layers  70 ,  72 , providing further protection against the passage of flames and heat. 
     The intumescent ring  190  also expands in a fire and helps protect against flames and heat that may pass through opening  79  passing beyond opening  78  in drywall layer  70 . 
     Many modifications are possible. For example, the downlight need not be an LED downlight, but could be any other kind of downlight, such as an incandescent downlight. Also, various modifications may be made to the drop down structure for the intumescent element of the downlight and to the intumescent element itself. A number of such modifications are described in US2019/0011096 to Luo et al. published Jan. 10, 2019, the contents of which are incorporated by reference herein. Additionally, described system  200  may be used with downlights that do not have a drop down intumescent element, but which may have other features to provide a fire barrier through the light can. Some such other downlights are also described in US2019/0011096. 
     While the system  200  has been described in use with a downlight fixture, it will be apparent that system  200  also has application to provide a fire barrier for openings for other types of ceiling fixtures, such as a ceiling fan and a ceiling air duct. The drywall opening required for a ceiling fixture may have a non-circular configuration, such as a rectangular configuration. In this situation, the metal collar and intumescent ring of system  200  would be modified so as to fit the shape of the drywall opening. 
     System  200  has been shown in use with an installation having upper and lower drywall layers as two layers of fire resistant drywall provide a greater degree of fire protection. However, other installations may have only a single drywall layer. With a ceiling having a single layer of drywall, intumescent ring  190  and enveloping sleeve  194  would not be used. Moreover, the ceiling wall may not be drywall at all, but may comprise any suitable material. 
     Other modifications will be apparent to one of skill in the art and, therefore, the invention is defined in the claims.