Patent Publication Number: US-6336509-B1

Title: Low pressure fast response bulb sprinklers

Description:
CROSS REFERENCE TO RELATED APPPLICATIONS 
     This application is a continuation-in-part of U.S. Non-provisional application Ser. No. 09/183,990 filed Nov. 2, 1998, which is a continuation of U.S. Ser. No. 08/813,780, now U.S. Pat. No. 5,829,532, and a continuation-in-part of U.S. Provisional Application No. 60/124,607 filed Mar. 16, 1999. 
    
    
     BACKGROUND OF THE INVENTION 
     Early suppression fast response (“ESFR”) sprinklers are a well known and well defined class of ceiling fire sprinklers. ESFR sprinklers were developed in the 1980&#39;s by Factory Mutual Research Corporation (“FM”) with the assistance of certain sprinkler manufacturers in an effort to provide improved fire protection against certain high-challenge fire hazards. According to FM, ESFR sprinklers combine fast response with greater supplied and actually delivered water densities for greater fire suppression capability. Previous sprinklers (standard sprinklers) provided protection by merely keeping such fires under control. Ultimately the initial fuel source would deplete itself or other fire fighting equipment would have to be brought to the scene to extinguish the fire. 
     The performance requirements of ESFR sprinklers are set forth in Underwriters Laboratories, Inc. (“UL”) STANDARD FOR EARLY-SUPPRESSION FAST-RESPONSE SPRINKLERS UL 1767. This standard was first published in 1990. Factory Mutual Research Corporation (“Factory Mutual” or “FM”) also has an Approval Standard For Early Suppression—Fast Response (ESFR) Automatic Sprinklers, Class Number 2008. The current ESFR standards and all earlier ESFR standards of either organization are incorporated by reference herein in their entirety. 
     Requirements for the installation and use of ESFR sprinklers are included in various standards of the National Fire Protection Association including the Standard for the Installation of Sprinkler Systems, NFPA 13; the Standard for General Storage, NFPA 231; and the Standard for Rack Storage of Materials, NFPA 231c. The current and earlier editions of these standards to the extent that they pertain to ESFR sprinklers are incorporated by reference herein. Installation and use requirements for ESFR sprinklers are also given Loss Prevention Data sheets 2-2, “EARLY SUPPRESSION FAST RESPONSE SPRINKLERS”,  Factory Mutual System,  Factory Mutual Engineering Corp., 1987, which is also incorporated by reference herein. Loss Prevention Data sheets 2-8 N, “Installation of Sprinkler Systems”,  Factory Mutual System,  Factory Mutual Engineering Corp., 1989, presents other installation and use requirements for ESFR and other sprinklers generally which are not presented in Loss Prevention Data sheets 2-2 and is also incorporated herein. 
     The standards specify the construction, performance, installation and operation of ESFR sprinklers with significant particularity. For example, the discharge coefficient (or “K” factor) of an ESFR sprinkler is nominally 14 and must be within the range of 13.5-14.5, where the discharge coefficient is calculated by dividing the flow of water in gallons per minute through the sprinkler by the square root of the pressure of water supplied to the sprinkler in pounds per square inch gauge. Ordinary or standard sprinklers are considered to have response time indices (“RTI”) of 100 meter ½ second ½  (“m ½ sec ½ ”) or more although the response time indices actually reported for these sprinklers have all exceeded 100 m ½ sec ½ . One special class of faster operating sprinklers exists with response time indices between 50 and 80 m ½ sec ½ . Existing ESFR sprinklers must exhibit response time indices of less than 40 m ½ sec ½ . The installation and use standards further require, among other things, that a minimum operating pressure of 50 psi be provided to ESFR sprinklers. 
     ESFR sprinklers were originally designed to suppress fires in warehouses with thirty-foot ceilings where flammable stock such as certain plastics is piled up to twenty-five feet high in racks. In many instances, available water supplies are not capable of providing a minimum operating pressure of 50 psi to thirty-foot high sprinklers. In such cases, a supplemental pump is needed to boost water pressure before ESFR sprinklers can be used. The cost of providing an auxiliary pump can be significant. For example, in protecting a 40,000 square foot building with ESFR sprinklers, it is estimated that the cost of providing an auxiliary pump can represent about twenty-five (25) percent of the entire cost of the installed sprinkler system. In certain installations, a second, back-up pump may be needed. If comparable protection might be provided at pressures below the current 50 psig minimum required pressured for ESFR sprinklers, the need for a pump might be avoided. In instances where a pump would be required in any event, lower pressure requirements may permit the use of a lower capacity, less expensive pump or the use of the same pump with smaller diameter, higher friction but less expensive supply lines. Each of these three possible options could provide significant savings in installation costs of ESFR sprinklers. 
     BRIEF SUMMARY OF THE INVENTION 
     In one aspect the invention is a low pressure fast response bulb sprinkler comprising a generally tubular body having an inlet end, an opposing discharge end and an internal passageway extending between the inlet and discharge ends with a K factor greater than 16 where the K factor equals the flow of water in gallons per minute through the internal passageway divided by the square root of the pressure of water fed into the internal passageway in pounds per square inch gauge; a deflector coupled with the tubular body and spaced from and generally aligned with the discharge end of the internal passageway so as to be impacted by a flow of water issuing from the discharge end of the passageway upon activation of the sprinkler, the deflector being configured and positioned to deflect the flow of water generally radially outwardly all around the sprinkler; a closure releasably positioned at the discharge end of the tubular body so as to close the internal passageway; and a heat responsive trigger at least including a frangible liquid containing glass bulb mounted to releasably retain the closure at the discharge end of the tubular body, the glass bulb having a response time index of less than 100 meter ½ sec ½  (m ½ sec ½ ). 
    
    
     BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS 
     The foregoing summary, as well as the following detailed description of preferred embodiments of the invention, will be better understood when read in conjunction with the appended drawings. For the purpose of illustrating the invention, there is shown in the drawings embodiments which are presently preferred. It should be understood, however, that the invention is not limited to the precise arrangements and instrumentalities shown. In the drawings which are diagrammatic: 
     FIG. 1 is an elevation view of an low pressure, early suppression fast response ceiling sprinkler of the present invention; 
     FIG. 2 is a partial cross-sectional view of the sprinkler taken generally along the lines of  2 — 2  in FIG. 1; 
     FIG. 3 is a greatly enlarged view of the encircled area  3  of FIG. 2; 
     FIG. 4 is a sectional elevation of the trigger; 
     FIG. 5 is a bottom view of the sprinkler of FIG. 1; 
     FIGS. 6 and 7 are orthogonal elevation views of a first low pressure, early suppression fast response glass bulb ceiling sprinkler of the present invention; 
     FIG. 8 is a partially sectioned view of the sprinkler of FIGS. 6 and 7 taken along the lines  8 — 8  in FIG. 7 showing details of the mounting supporting the glass bulb and retaining the closure; 
     FIG. 9 is a detailed section of the pedestal in FIG. 8; 
     FIGS. 10 and 11 are orthogonal elevation views of a second low pressure, early suppression fast response glass bulb ceiling sprinkler of the present invention; and 
     FIG. 12 is a perspective view of the sprinkler of FIGS. 10 and 11 showing details of the mounting supporting the glass bulb and retaining the closure; and 
     FIG. 13 depicts diagrammatically yet another bulb equipped trigger. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     In the drawings, like numerals are used to indicate like elements throughout. There is shown in various views in FIGS. 1,  2  and  5 , a low pressure, early suppression fast response fire sprinkler of the present invention indicated generally at  10 . Sprinkler  10  includes a preferably one-piece frame  11  having an at least generally tubular body indicated generally at  12  with a preferably tapered, central, internal passageway  14 . The passageway  14  preferably extends straight between an inlet end  15  and a discharge end  16  of the tubular body  12 . Threads  17  are provided on the outside of the inlet end  15  to permit the sprinkler  10  to be coupled to a drop or supply pipe (neither depicted) for delivery of water or another fire fighting fluid. The internal passageway  14  of body  12  has a preferably straight central axis A indicated in FIGS. 1 and 2. 
     Sprinkler  10  further includes a closure  20  releasably positioned at the discharge end  16  of the tubular body  12  so as to close the internal passageway  14 , a heat responsive trigger indicated generally at  30  mounted to releasably retain the closure  20  at the discharge end  16  of the tubular body  12  closing the passageway  14  until the trigger  30  is activated, and a deflector indicated generally at  60 . 
     Referring to FIG. 1, the frame  11  further includes a pair of support arms  50 ,  52  which extend generally away from opposite sides of the discharge end  16  of the tubular body  12  and meet to form a tubular knuckle  54  located along central axis A. The arms  50 ,  52  and knuckle  54  support the deflector  60  positioned juxtaposed to, facing and spaced away from the discharge end  16  of the tubular body  12 . While at least two symmetrically positioned support arms  50 ,  52  are preferred, three or four support arms might be provided, preferably all symmetrically positioned around and spaced away from the central axis A. Where more than two support arms are provided, they may be separately attached to a tubular body, for example, by being threaded into a flange portion of such separate tubular body. 
     The frame  11  is preferably enlarged at the discharge end  16  of the tubular body  12  into a circumferential flange  18 . The flange  18  is preferably hexagonally shaped with a pair of major opposing parallel flat surfaces or “flats”  18   a  positioned to receive an open ended wrench or a specially designed hexagonal sprinkler wrench for threading the sprinkler  10  into a drop or other fluid supply line (neither depicted). 
     Referring to FIG. 2, the internal passageway  14  includes an inwardly tapering portion  14   a  extending from the inlet end  16  to a cylindrical portion  14   b  of uniform, reduced diameter. A portion  14   c  of the passageway immediately downstream from the reduced diameter portion  14   b  is provided with a greater diameter to receive the closure  20  over the reduced diameter portion  14   b . Portion  14   c  may be outwardly beveled at approximately a 10°-15° angle for its length to foster release of the closure  20  (see FIG.  3 ). The passageway  14  then abruptly and significantly enlarges in diameter into a cylindrical outlet opening  14   d  at the discharge end  16  of the frame body  12 . A lip  19  is formed around the outlet opening  14   d  by the provision of a circular groove  14   e  between the lip  19  and the beveled end of portion  14   c  of the passageway. 
     The tubular body  12  may have an axial length of about one and one-third inches with the flange  18  having a length of about one-third inch. The inwardly tapering portion  14   a  may have a length of about seven-eighths of an inch and taper down at about a one and one-half degree angle to central axis A from a width of 0.98 to a width of 0.93 inches, which is continued for about one-eighth of an inch in reduced diameter portion  14   b . Portion  14   c  may have a minimum diameter of about one inch and a length of about one-sixteenth inch. In the preferred embodiment, the outlet opening  14   d  may have a diameter of about one and one-third inches and an axial length of about one-third inch while the groove  14   e  has a diameter of about one and one-half inches and an axial length of only about one-eighth inch. 
     The preferred sprinkler  10  has a nominal discharge coefficient or K factor of 25. The discharge coefficient or K factor equals the flow of water through the internal passageway  14  in gallons per minute divided by the square root of the pressure of water fed into the tubular body in pounds per square inch gauge. The discharge coefficient is governed in a large degree by the smallest cross sectional area of the passageway  14 , in other words, the diameter of the cylindrical portion  14   b  of passageway  14 . 
     The discharge coefficient or “K” factor of a sprinkler is determined by standard flow testing. For ESFR sprinklers, passageway  14  is measured first at a pressure of 15 psig, and then in 5 psig increments up to 50 psig and then in 10 psig increments up to 100 psig, and then in 25 psig increments at 125, 150 and 175 psig. The flow is decreased in the same increments back to the original 15 psig value. The flow is measured at each increment of pressure by a flow-measuring device having an accuracy within about 2 percent of the actual flow. The actual flow in gallons per minute is divided by the square root of the pressure of the supplied water in psig at each increment. An average value is then calculated from all of the incremental values and becomes the flow coefficient or “K” factor of the sprinkler. 
     Discharge coefficients of K factors can be “nominal” values. Typically “nominal” K factors are expressed in standard sizes, which are integer or half integer values. These standard or “nominal” values encompass the stated integer or half integer value plus or minus one-half integer. Thus, a nominal K factor of 25 encompasses all measured K factors between 24.5 and 25.5. 
     Referring to FIG. 2, the closure  20  preferably is also a subassembly and has an upstream end  20   a , which is received over the reduced diameter portion  14   b  of the passageway  14  in the beveled portion  14   c  of the passageway. A downstream end  20   b  of the closure  20  engages a proximal end of the trigger  30 . Referring to FIG. 3, the closure  20  is formed by a saddle  22  and a washer subassembly that includes a Belleville washer  26  bearing a sheet of plastic film tape  28 , preferably a tetrafluoroethylene tape on one side, which is the side of the closure  20  facing the uniform reduced diameter portion  14   b  of the passageway  14 . Saddle  22  is a generally rotationally symmetric body including a cylindrical plug portion  22   a , which is received within a center opening of the Belleville washer  26  to stabilize the washer with respect to the saddle  22 . The saddle has a circular flange portion  22   b  with an outer diameter approximately equal to the outer diameter of the Belleville washer  26  and slightly greater than the diameter of reduced diameter portion  14   b . Saddle  22  further includes a central circular boss  22   c  projecting away from the plug portion  22   a  with a threaded central bore  22   d.    
     The preferred trigger  30  is an assembly which preferably includes a pair of identical, generally L-shaped levers  32 . Each lever  32  includes a short arm portion  32   a , which is positioned between lip  19  and the downstream end  20   b  of the closure  20 , releasably retaining the closure  20  in the internal passageway  14  closing the passageway. Long arm portions  32   b  of the levers  32  extend away from discharge end  16  of the tubular body  12  and passageway  14  and are held together by a lever yoke  34 . Yoke  34  preferably is a one-piece, generally octagonally-shaped body with a central circular opening. Diametrically opposed portions  34   b  and  34   c  of the body are bent around the proximal long ends  32   b  of the levers  32 , thereby holding those ends together and releasably retaining the closure  20  in the passageway  14  so as to close the passageway  14 . Cutouts can be provided on the outer edges of the flange portion  22   b  of the saddle to receive and stabilize the position of the short arm portions  32   a  of the levers  32 . 
     Referring to FIGS. 2 and 4, trigger  30  further includes a retainer body  36 , a plunger housing  38  having one end received in the retainer body  36  and a retaining nut received in a remaining end of the plunger housing  38  and forming a plunger chamber  39  receiving a plunger  40 . Those and other elements of trigger  30  are best seen in FIG. 4. A retaining nut  43  supports a finned heat collector  44  from a side of the plunger housing  38  opposite the retainer body  36 . The finned heat collector  44  is preferably coupled with and thermally insulated from the retaining nut  43  by a thermally insulative support washer  45  of a suitable material such as glass reinforced nylon. The finned heat collector  44  is hollow and contains a pellet  46  of a metal alloy having a melting temperature at the desired operating or response temperature of the sprinkler  10 . Plunger  40  is formed by a pin and a generally bulbous main body  40   a  along the pin, which divides the pin into upper and lower ends  40   b  and  40   c . The lower pin end  40   c  of plunger  40  is supported on the metal alloy pellet  46  by a cylindrical bearing disk  47  made of a material such as alumina having significant compressive strength and thermal insulative properties. The upper pin end  40   b  guides and centers the plunger  40  in the chamber  39 . The purpose of the pellet  46 , bearing disk  47  and plunger  40  is to support a plurality of balls  48  which extend through bores  38   a  in the side walls of the plunger housing  38  and into aligned recesses  36   a  in the retainer body  36  thereby releasably locking the retainer body  36  and plunger housing  38  together. The “free” or “upper end”  36   b  of the retainer body  36  ears external threads  37  (diagrammatically by phantom), which are received in the threaded central bore  22   d  of the saddle  22  of the closure  20 . Levers  32 , which are held together by lever yoke  34 , releasably retain closure  20  in the tubular body  12 . The retainer body  36  is held through saddle  22  and the remainder of the trigger  30  is coupled with the saddle through the retainer body  36  by means of the balls  48 . The balls  48 , in turn, are held by the bulbous main body  40   a  of the plunger  40 , which is forced against the balls  48  by tightening of the retaining nut  43  into the plunger housing  38 . The alloy pellet  46  will lose its load bearing strength when heated sufficiently allowing the balls to move and permitting the plunger housing  38  and lever yoke  34  to separate from the retainer body  36  and levers  32 , respectively, releasing closure  20  with trigger  30  permitting water (or other fire fighting fluid) to pass through the internal passageway  14  and from the discharge end  16  of the passageway  14  and body  12 . 
     The structure and mounting of the deflector  60  are best seen in FIGS. 1,  2  and  5 . Deflector  60  includes a plate  62 , and a nose piece positioned in an opening in the center of the plate  42 . 
     The plate  62  of the deflector is planar and circular with a circular outer perimeter  63  and a plurality of slots  64  extending radially inwardly from the circular perimeter  63  and axially entirely through the plate  62 . The plurality of slots  64  surround and define a “slotless” central area  65  as best seen in FIG.  2 . As used herein “slotless central area” refers to a circular central area at the center of the deflector, which has a radius equal to the radius of the plate member less the radial length of the longest slot extending radially from the outer perimeter of the plate member in a planar projection of the deflector perpendicular to central axis A. Thus, if the nose piece of the deflector overlaps the innermost ends of some or all of the slots, the slotless central area is the planar area of the nose piece which covers the ends of such slots. In the preferred embodiment, the outer diameter of the central area  65  is substantially equivalent to the outer diameter of the frame knuckle  54 . 
     The nose piece  66  has a head portion  66   a  facing the tubular body  14  which is suggestedly rounded in shape and preferably hemispheric. The head portion  66   a  supports a shaft portion  66   b  bearing external threads  67  (indicated diagrammatically by phantom lines) which permit the nose piece  66  to be screwed into the internally threaded knuckle  54 . A slot  66   c  may be provided at the base of the shaft portion  66   b  to receive a screw driver. The nose piece passes through a circular opening  62   a  provided in the center of the deflector plate  62  (within the central area  65 ) and holds the plate  62  firmly to the knuckle  54 . The deflector  60  is coupled with the tubular body  14  through knuckle  54  and is positioned juxtaposed to and spaced from the discharge end  16  of the tubular body  12  aligned with the discharge end  16  of the internal passageway central axis A of the tubular body. Nose piece  66  is further preferably provided with a central bore  66   d  also aligned with the central axis A of the internal passageway  14  and discharge end  16  of the tubular body  12 . The deflector  60  is configured by being generally rotationally symmetric and positioned by being centered on central axis A to deflect the flow of water issuing from the discharge end of internal passageway  14  generally symmetrically radially outwardly all around the sprinkler  10 . Bore  66   d  permits water to pass axially entirely through the center of the deflector  60  and down directly under the sprinkler  10 . This bore  66   d  combined with the much larger orifice size of internal passageway  14  in comparison to the diameter of the slotless central area of the deflector has proven sufficient to deliver adequate water densities directly beneath the sprinkler  10  to suppress high challenge fires originating directly under sprinkler  10  as well as to such fires originating between such sprinklers  10 . 
     Sprinklers  10  of the present invention are installed in accordance with standard ESFR limitations including spacing and height limitations. 
     For the preferred 25 K factor tubular body having a minimum diameter of 0.930 inches in the reduced diameter cylindrical portion  14   b  of the internal passageway  14 , the head portion  66   a  of the nose piece  66  is provided with a radius of about one-quarter inch and with a bore  66   d  having a diameter of about one-eighth inch. The deflector plate  62  is preferably 1.9 inches in outer diameter and about one-tenth of an inch thick. Plate  62  is provided with twelve slots  64  uniformly angularly arrayed in 30° increments around central axis A. Each slot  64  is about one-tenth inch in width and terminates in a radius (semicircle). The diameter of the central area surrounded by and located within the slots  64  is suggestedly about five-eighths inch. 
     The surface of the knuckle  54  closest to the tubular body  14  is spaced about two and one-half inches from the proximal end of the reduced diameter cylindrical portion  14   b  of the internal passageway  14 . The ratio of the outer diameter of the deflector  60 , more particularly the deflector plate  62 , to the radial length of the slots  64  is about 3 (1.9/0.635). The plurality of slots  64  provide a total open area of less than one-third but more than one-quarter the total planar area within the circular perimeter  63  of the deflector. All of these values are within the ranges exhibited by existing ESFR sprinklers. However, the ratio of the minimum passageway diameter of the tubular body to the diameter of the central area of the deflector is about 1.5 (0.93 in/0.624 in). The highest ratio previously exhibited in an ESFR sprinkler was less than 1.3. 
     One of the requirements for an ESFR sprinkler is fast response. Response can be measured in various ways. Factory Mutual and Underwriters Laboratories, use a combination of temperature ratings and response time indices to insure adequately fast response is being provided. 
     The response time indices or “RTI” is a measure of thermal sensitivity and is related to the thermal inertia of a heat responsive element of a sprinkler. RTI is insensitive to temperature. For fast-growing industrial fires of the type to be protected by ESFR sprinklers, it is believed that the RTI and temperature rating of the trigger are sufficient to insure adequately fast sprinkler response. The temperature rating is the range of operating temperatures at which the heat responsive element of a sprinkler will activate. 
     RTI is equal to τu ½  where τ is the thermal time constant of the trigger in units of seconds and u is the velocity of the gas across the trigger. RTI is determined experimentally in a wind tunnel by the following equation:        RTI   =       -     t   x            u     1   2            /          ln              [     1   -     (     Δ                     T   b     /   Δ                     T   g       )       ]                       
     where t x  is the actual measured response or actuation time of the sprinkler; u is the gas velocity in the test section with the sprinkler; ΔT b  is the difference between the actuation temperature of the trigger (determined by a separate heat soak test) and the ambient temperature outside the tunnel (i.e. the initial temperature of the sprinkler); and ΔT b  is the difference between the gas temperature within the tunnel where the sprinkler is located and the ambient temperature outside the tunnel. The RTI for ESFR sprinkler is determined with air heated to 197 (±2)° C. and passed at a constant velocity of 2.56 (±0.03) m/sec over the sprinkler  10  and trigger  30  inserted into the air stream in the pendent position (see FIG. 1) with a plane through frame arms  50 ,  52  being perpendicular to the direction of the heated air. The aforesaid FM and UL Standards should be consulted for further information if desired. 
     When fast response was being investigated in the 1980&#39;s, the RTI&#39;s so-called standard sprinklers were measured and were found to be more than 100 m ½ sec ½  typically up to nearly 400 m ½ sec ½ . RTI&#39;s of less than 100 m ½ sec ½  were considered quicker than standard sprinkler responses and referred to as quick response. More recently, quick response has come to denote RTI&#39;s of less than 80 m ½ sec ½ . Sprinklers incorporating such quick response triggers were referred to as fast response. A class of “special” sprinklers has been recognized having RTI&#39;s between 80 and 50 m ½ sec ½ . RTI values currently acceptable for ESFR sprinklers are less than 40 m ½ sec ½ , more particularly 19 to 36 m ½ sec ½ . 
     The 25 K factor sprinkler  10  will supply 100 gallons per minute at a flow pressure of less than 16 psig while one with a K factor of 26 will supply 100 gallons per minute at just under 15 psi. Applicants believe that 15 psi is the minimum pressure needed to drive drops of the size generated by the sprinkler  10  into the heated plume created by a high challenged fire. The nominal 25 K sprinkler of the present invention therefore is believed to be optimally-sized for its use. However, ESFR sprinklers providing 100 gallon per minute flows at pressures of more than 15 but less than 50 psi can also be commercially valuable. To supply 100 g.p.m. of water at 40 psi requires a K factor of about 16 (15.8). To supply the same amount of water at 30 psig requires a K factor of about 18.5 (18.3) while to supply the same amount of water at 20 psig requires a K factor of about 22.5 (22.4). The reduced diameter portion  14   b  of the internal passageway might have a diameter greater than 0.76 inches to yield a K-factor greater than 16, a diameter of about 0.85 inches to yield a nominal K-factor of about 20, a diameter of about 1.0 inch to yield a K-factor of about 30 and a diameter of about 1.2 inches to yield a K-factor of about 40. 
     Furthermore, investigations are underway with respect to the suppression of fires even more challenging than those addressed by the original ESFR sprinkler standards. These higher challenges include storage in warehouses piled up to forty feet under forty-five foot ceilings and up to forty-five feet under fifty-foot ceilings. High challenge fires have been successfully suppressed under the forgoing conditions with the aforesaid sprinkler. In particular, the aforesaid sprinkler has successfully suppressed fire in storage piled thirty feet high under thirty-five foot ceilings at 35 psi, in storage piled thirty-five feet high under forty foot ceilings at 40 psi, in storage piled thirty-five feet high under forty-five foot ceilings at 50 psi and in storage piled forty feet high under forty-five foot ceilings also at 50 psi. Applicants believe that water might similarly be supplied in even greater quantities at even lower flow pressures (but still of at least 15 psig to successfully control if not actually suppress such high challenge fires. For example, a flow rate of 120 gallons per minute can be supplied at a pressure of 15 psig (or less) by a K factor of about 31, 140 gallons per minute by a K factor of about 36, and 150 gallons per minute by a K factor of less than 40 (38.7). At pressures of 20 psig, 120 gallons per minute can be supplied by a K-factor of about 27 (26.8), 140 gallons per minute can be supplied by a K-factor of about 31.5 (31.3) and 150 gallons per minute can be supplied by a K-factor of about 33.5. 
     FIGS. 6-9 depict in varying views, a first sprinkler indicated generally at  110 , which is almost identical to sprinkler  10  of the previous figures but is modified to use a frangible, fluid containing glass bulb as part of the trigger. FIGS. 10-12 depict in varying views, a second sprinkler indicated generally at  210 , which is also almost identical to sprinkler  10  of FIGS. 1-5 but modified in a slightly different manner from sprinkler  110  to also use a fluid containing glass bulb as part of the trigger. 
     Each sprinkler  110  and  210  includes the same one-piece frame  11  as previously described having an at least generally tubular body indicated generally at  12  with a preferably tapered, central, internal passageway  14  extending straight between an inlet end  15  and a discharge end  16  of the tubular body  12  with straight central axis A (see FIGS.  1  and  2 ). Support arms  50 ,  52  again extend generally away from opposite sides of the discharge end  16  of the tubular body  12  and meet to form a tubular knuckle  54  located along central axis A which supports deflector  60  positioned juxtaposed to, facing and spaced away from the discharge end  16  of the tubular body  12 . Each sprinkler  110  and  210  also includes closure  20 , which is releasably positioned at the discharge end  16  of the tubular body  12  so as to close the internal passageway  14 . 
     In sprinkler  110 , a heat responsive trigger indicated generally at  130  is provided and includes a frangible, fluid containing glass bulb  136 , which is mounted to releasably retain the closure  20  at the discharge end  16  of the tubular body  12  closing the passageway  14  until the trigger  130  is activated. The preferred trigger  130  is an assembly which includes, in addition to bulb  136 , a pair of identical, generally L-shaped levers  132  and a yoke  134 . Each lever  132  again includes a short arm portion  132   a , which is again positioned between lip  19  and the downstream end of the closure  20 , specifically the saddle  22 , releasably retaining the closure  20  in the internal passageway  14  closing the passageway. Long arm portions  132   b  of the levers  132  extend away from discharge end  16  of the tubular body  12  and passageway  14  and are held together by yoke  134 . Each long arm portion  132   b  preferably includes a central preferably triangular shaped window  132   c  to provide unobstructed heat flow through the levers  132  to the lateral sides of the bulb  136 . The distal end of each long portion  132   b  is also suggestedly curved, generally convexedly toward the bulb  136 , to help direct air currents toward the centered bulb  136 . Yoke  134  preferably is a one-piece, generally rectangularly-shaped body with a smaller central circular opening  134   a  which is preferably flanked by two, larger circular openings  134   b  (all in phantom). The smaller central opening receives and seats one longitudinal end of bulb  136 . The two larger openings permit air to pass through the yoke and circulate over the bulb  136  from below the sprinkler. The yoke  134  also preferably includes a pair of longitudinal tabs  134   c , which extend through the windows  132   c  of levers  132  and turn away from the closure  20  so as to releasably engage the distal end of each lever  132  to prevent the distal ends from rotating away from each other and the bulb  136 , which movement is required to free the levers  132  and release the closure  20 . Bulb  136  is held in compression against the yoke  134 , holding the yoke in engagement with the levers  132  by a pedestal  38 . 
     Pedestal  138  includes a threaded central shaft  138   a  which is threaded into the central bore of central boss or hub  22   c  and which extends from one side of a bulb holder  138   b . Holder  138   b  preferably includes a cupped depression  138   c  (FIG. 9) at its distal end, which receives the end of the bulb  136  most proximal to the closure  20 . The cupped depression is provided with an axial bore  138   d  which receives a pointed tip of the bulb  136 . Preferably a larger bore  138   e  is made transversely into the side of the holder to provide an internal opening in which the pointed tip of the bulb  136  can move without striking a hard surface within the holder which might cause the bulb to break prematurely. 
     Referring to FIGS. 10-12, trigger  230  of sprinkler  210  is very similar to original trigger  20  and includes the same levers  32 . A retainer includes a shaft  236   a  having one end threaded into the closure boss  22   c  and an opposing end threaded into a hollow receiver  236   b . Receiver  236   b  releasably receives a plunger housing  238  which in turn is mated with a hollow cage  242 . One (or more) Belleville washers  234  are trapped between the plunger housing  238  and the receiver  236   b . The washer  234  is also generally cupped with its concave side facing the closure  22  and receiving the distal ends of the levers  32 . The washer  234  replaces yoke  34  to hold the distal ends of the levers  32  together until the sprier  210  is activated. Plunger  238  and cage  242  are joined by adjustable means such as threading to define a hollow chamber which retains a plunger (like plunger  40 ) and glass bulb  136 . The longitudinal end of bulb  136  proximal closure  22  is received in a recess in the head of the plunger. The cage  242  has openings (three)  242   a  at its distal end exposing the distal longitudinal end of the bulb  136  to the surrounding atmosphere. The plunger again supports a plurality of balls, like balls  48 , which extend through bores (not depicted) in the side walls of the plunger housing  238  and into an aligned, circumferential recess in the receiver  236   b , thereby releasably engaging the receiver  236   b  and plunger housing  238 . The receiver  236  is held through saddle  22  and the remainder of the trigger  230  is coupled with the saddle  22  through the receiver  236  by means of the balls. The plunger can be forced against the balls by tightening of the cage  242  into the plunger housing  238 . When heated sufficiently, the bulb  136  will break, permitting the plunger to move and allow the balls to move into the plunger housing thereby permitting the plunger housing  238  and washer  234  to separate from the receiver  236  and release the levers  32 , respectively, thereby releasing closure  20  and permitting water (or other fire fighting fluid) to pass through the sprinkler body  12 . 
     FIG. 13 depicts very diagrammatically, the distinguishing distal end of yet another trigger embodiment indicated generally at  330 . The trigger includes asymmetric right and left levers  332  and  333 , respectively, an asymmetric yoke  334  and frangible, fluid-filled glass bulb  136 . Each lever  332 ,  333  has a short arm portion (not depicted), bent to fit over a closure  22  and under lip  19  as before. Yoke  336  holds together the distal, longer ends of the levers  332 ,  333 . Each lever includes an opening  332   a ,  333   a , respectively, and proximal to bulb  136 . The portion of original left lever  333  cut to form opening  333   a  is bent generally perpendicularly to the plane of that lever to form a stop  333   b , which contacts the inner side of right lever  332  and prevents the two levers,  332 ,  333  from being brought closer together. Stop  332   b  includes a central depression  332   c  with opening, if necessary, to receive and seat the end bulb  136  proximal to the sprinkler closure. The extreme distal end of the levers  332 ,  333  are held together by means of the yoke  334 , which is enlarged at one end  334   a  to form a “TEE” and is bent away from the stop  333   b  at its opposing longitudinal end to form a retaining tab  334   b . The retaining tab  334   b  is maintained in an engaged position with lever  332  via the bulb  136 . Preferably, an adjustment screw  340  is provided in a threaded bore  334   c  in the yoke and has a central bore and a cup depression at the end facing the bulb  136  to receive and seat the bulb. When bulb  136  breaks, the retaining tab  334   b  is free to rotate out of engagement with lever  332 . Static pressure on the sprinkler is transmitted through the closure  22  to the levers  332 ,  333 , which will separate and release the closure. 
     The bulb  136  may be a 2.5 mm, extra fast bulb supplied by Job GmbH of Hamburg, Germany or Norbulb GmbH of Norderfledt, Germany or smaller diameter bulb (e.g., a 2.0 mm bulb supplied by Job). 
     Sprinkler  110 , in particular, offers a simplified construction verses either sprinkler  10  or  210 . Moreover, sprinkler  210  with a glass bulb, is less subject to potential failure in the event of corrosive exposure than is sprinkler  10 . 
     The sprinklers  110 ,  210  incorporate two stages of mechanical advantage for a significant load reduction. A first load reduction of about 4:1 occurs at the junction between the saddle  22  and levers  32  or  132 . The second reduction of about 5:1 occurs at the junction between the yoke  134  and bulb holder  138   b  or the Belleville washer  234  and plunger housing-cage  238 - 242 . The discharge end of the central passageway  14  is approximately 0.93 inches in diameter and includes an active seal area of approximately 0.74 in 2 . This translates to a 74 pounds of load per 100 PSIG of hydrostatic pressure. At 500 PSI, this load equals 370 pounds. (In contrast, a K-14 sprinkler has a seal area that is approximately 0.442 in 2 , which sees 44.2 pounds of load per 100 PSIG of pressure and about 220 pounds of load at 500 PSIG.) 
     Testing laboratories heretofore have imposed 500 PSI no leakage requirement and conducted 700 PSI hydrostatic tests on all sprinklers. At this pressure, the load on closure  20  increases to about 520 pounds for the K25 and 310 pounds for the K-14, both of which are considerably above compressive tolerance thresholds of known bulbs fast response bulbs, which are less than 4 mm in nominal diameter. While a linkage mechanism employing a single load reduction stage might be used, dual reduction is preferred because, under the same load conditions (e.g., 520 pounds) a bulb would see approximately 26 pounds of compressive loading, sufficient load reduction to permit the use of 2 mm (or even smaller) bulbs with higher temperature ratings (286° F. or higher) but with essentially the same RTI sensitivity of existing 200° F. 2.5 mm bulbs. The 2 mm bulbs would need to utilize thinner walls and hence be proportionately weaker. 
     The 4:1 reduction provided by the levers also reduces the frame load. Under 700 PSI hydrostatic load, the deflector/upper frame arms of a single-reduction mechanism would be subject to approximately 520 pounds of load, requiring a robust/stiff/thick component package. With dual reduction, the same components see only approximately about 130 lbs. of load under the 700 PSI hydrostatic test pressure. 
     It should be appreciated that yoke  134  is shaped with smaller tabs to act as a stop to prevent the bulb from being overcompressed by preventing the distal ends of levers  132  from coming too close to one another. 
     The undepicted short arm portions of levers  332 ,  333  are suggestedly bent at an angle of about 105 degrees with respect to the generally parallel, long arm portions of those levers. 
     Bore  138   e  can be covered by means of a tubular sleeve on receiver  138   b  to prevent possible tampering with the bulb tip in the field. Bore  138   e  is intended to prevent the tip breakage that might occur during original assembly or accidental side loading of the levers during installation. Tip breakage potential increases as the diameter of the bulb decreases. This is due to tip end verses bulb body diameter ratio. In order to assure proper bulb seating and loading, the saddle or holder&#39;s vertical bore should reduce proportionally to the bulb&#39;s diameter. 
     U.S. Pat. No. 5,829,532 and Provisional Patent Application No. 60/124,607 filed Mar. 16, 1999 are incorporated by reference herein in its entirety. 
     It will be appreciated by those skilled in the art that changes could be made to the embodiments described above without departing from the broad inventive concept thereof. It is understood, therefore, that this invention is not limited to the particular embodiments disclosed, but it is intended to cover modifications within the spirit and scope of the present invention as defined by the appended claims.