Abstract:
A dry sprinkler comprises a tubular body having a connector and a sprinkler head. The connector is adapted to be connected to the water pipe network of the fire suppression system and the sprinkler head is adapted to discharge water or other liquid suppressant. The tubular body defines a flow passage between the connector and the sprinkler head. First and second seals are arranged in spaced relation along the flow passage and contain an antifreeze fluid therebetween. The antifreeze fluid may be a liquid or gas subjected to pressure. A thermally responsive element is arranged to maintain the second seal in a state that contains the antifreeze fluid between the first and second seals. The thermally responsive element releases the second seal when an elevated temperature condition exists.

Description:
FIELD OF THE INVENTION  
         [0001]    The present invention relates generally to fire fighting apparatus, and more particularly relates to “dry sprinklers” which are typically installed in areas that are exposed to freezing conditions.  
         BACKGROUND OF THE INVENTION  
         [0002]    Dry sprinklers are used in areas that are exposed to freezing conditions, such as in freezers or walkways that may experience freezing conditions.  
           [0003]    The typical construction of a dry sprinkler comprises a sprinkler head, a tube, a pipe connector at the inlet end of the tube (for connecting the inlet end to the pipe network of the fire suppression system), a plug seal at the inlet end to prevent water from entering the tube, and an actuating mechanism to maintain the plug seal at the inlet end. Typically, the tube section of prior art dry sprinklers is vented to the external atmosphere to allow drainage of water that can condense in the tube due to the environment in which dry sprinklers may operate (e.g. temperature fluctuations and/or humidity fluctuations). Such dry sprinklers according to this arrangement are generally disclosed in U.S. Pat. Nos. 5,775,431 to Ondracek and 5,967,240 to Ondracek. As shown generally in these patents, the actuating mechanism is a rod or other similar structure that extends through the tube between the sprinkler head and the inlet end to maintain the seal at the inlet end. The actuating mechanism includes a thermally responsive support element that supports the rod and therefore the seal at the inlet end. When an elevated temperature is experienced, the thermally responsive support element fails releasing the plug seal to allow water to flow through into the tube to the sprinkler head.  
           [0004]    There are several drawbacks associated with prior attempts of dry sprinklers. One such problem as expressly recognized in the &#39;431 and &#39;240 patents is that internal actuating mechanisms can interfere with and impede the flow of water suppressant to the sprinkler head. While the &#39;431 and &#39;240 patents are asserted to reduce these flow interference problems, such internal actuating mechanisms still act on the flow water and can cause such interference. Moreover, corrosion of the metal in dry sprinklers can inevitably occur overtime and may also interfere with proper sprinkler operation.  
         BRIEF SUMMARY OF THE INVENTION  
         [0005]    In light of the above, it is a general aim of the present invention to provide a more reliable dry sprinkler for a fire suppression system.  
           [0006]    In that regard, it is also an object of the present invention to provide a commercially feasible dry sprinkler that is relatively inexpensive and competitive in the marketplace.  
           [0007]    According to one aspect of the present invention, it is an object to reduce corrosion of dry sprinklers.  
           [0008]    In accordance with these and other objectives, the present invention is directed toward a dry sprinkler in which two seals are provided to seal the inside of the apparatus from the external atmosphere. An antifreeze fluid such as pressurized gas or a liquid subjected to pressure is contained inside the dry sprinkler between seals. The seals and antifreeze provide advantages such as a reduction in corrosion inside of the dry sprinkler and that the internal actuating mechanism structures of prior dry sprinklers may be eliminated if desired.  
           [0009]    A dry sprinkler according to the invention comprises a tubular body having a connector and a sprinkler head. The connector is adapted to be connected to the fire suppression system and the sprinkler head is adapted to discharge liquid suppressant when in operation. The tubular body defines a flow passage between the connector and the sprinkler head. First and second seals are arranged in spaced relation along the flow passage and contain an antifreeze fluid therebetween. A thermally responsive element is arranged to maintain the second seal in a state that contains the antifreeze fluid between the first and second seals. The thermally responsive element releases the second seal when an elevated temperature condition exists.  
           [0010]    According to an operational aspect of the invention, when the second seal is released, the antifreeze fluid escapes from the tubular body and no longer acts upon the first seal such that the first seal is adapted to be opened by pressure of liquid suppressant and adapted to allow liquid suppressant to flow through the flow passage to the sprinkler head.  
           [0011]    Other objectives and advantages of the invention will become more apparent from the following detailed description when taken in conjunction with the accompanying drawings. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0012]    The accompanying drawings incorporated in and forming a part of the specification illustrate several aspects of the present invention, and together with the description serve to explain the principles of the invention. In the drawings:  
         [0013]    [0013]FIG. 1 is a cross section of a dry sprinkler according to a preferred embodiment of the present invention in a standby state.  
         [0014]    [0014]FIG. 2 is a cross section of the dry sprinkler of FIG. 1, illustrated in operational state.  
         [0015]    [0015]FIG. 3 is a cross section of an enlarged view of a portion of the sprinkler of FIG. 1 that has been rotated 90°.  
         [0016]    [0016]FIG. 4 is a side view of the dry sprinkler illustrated in FIG. 1 that has been rotated 90°. 
     
    
       [0017]    While the invention will be described in connection with certain preferred embodiments, there is no intent to limit it to those embodiments. On the contrary, the intent is to cover all alternatives, modifications and equivalents as included within the spirit and scope of the invention as defined by the appended claims.  
       DETAILED DESCRIPTION OF THE INVENTION  
       [0018]    For purposes of illustration, the present invention has been depicted as a dry sprinkler  20  shown in the environment of a fire suppression system  22 . The fire suppression system includes a pipe network  24  for transmitting water or other liquid fire suppressant to one or more dry sprinklers  24 . Each dry sprinkler  20  mounts onto a branch outlet pipe  26  extending from the pipe network  24 . The sprinkler  20  projects from the outlet pipe  26  into areas that may be subject to freezing conditions.  
         [0019]    The sprinkler  20  includes a tubular body  28  extending between an inlet end  30  and an outlet end  32 . The tubular body  28  may be constructed of metal with a single component or several components or portions of several components. In the disclosed embodiment, the tubular body  20  includes several components threadingly connected, including a central pipe  34 , a pipe/sprinkler adapter  36 , the pipe fitting  38  of a sprinkler head  40 , and an inlet pipe adapter  42 . The sprinkler  20  includes an inlet port  44  at the inlet end  30  and an outlet port  46  at the outlet end  32 . The sprinkler  20  generally defines an internal cavity or flow passage  48  extending from the inlet port  44  to the outlet port  46  for transmitting water to the sprinkler head  40  in the event of a fire.  
         [0020]    In accordance with the present invention, the disclosed sprinkler  20  includes a pair of spaced apart seals in the form of a check valve  50  at the inlet end  30  and a release plug  52  at the outlet end  32 . The check valve  50  and the release plug  52  contain an antifreeze fluid  54  inside the sprinkler  20  along the flow passage  48 .  
         [0021]    The antifreeze fluid  54  is a fluid that will not freeze or cause condensation of water that could damage or impede operation of the sprinkler  20 . Suitable antifreezes include gases such as: nitrogen, carbon dioxide, conditioned/dehydrated compressed air or other suitable gas that does not cause corrosion or frost that would damage or impede operation of either of the seals. Suitable antifreezes also include liquids such as proportional mixtures of water and one of the following antifreeze chemicals: Glycerin, Propylene Glycol, Diethylene Glycol, Ethylene Glycol, Calcium Chloride, or other that does not cause corrosion or frost that would damage or impede operation of either of the seals. Liquid antifreezes substantially fill the flow passage but may be subject to pressure via a pocket of pressurized gas. Preferably, the antifreeze fluid  54  is selected to have a characteristic of being generally non-combustible so as not to add fuel to a fire when the sprinkler  20  is operated.  
         [0022]    In the disclosed embodiment, the check valve  50  is situated in the inlet pipe adapter  42  to form a back-flow prevention device. The check valve  50  comprises a pivoting valve member  56  having a sealing disc  58  of resilient material that is adapted to engage a circular valve seat  60  that surrounds the inlet port  44 . A spring (not shown) may be used to bias the valve member  56  against the valve seat  60 . The check valve  50  can be installed through a side opening  62  that is subsequently plugged. Although one form of check valve is illustrated, it will be appreciated that other forms of check valves both of the spring biased and unbiased type may alternatively be used. Additionally, it is also possible to use a rupture sealing plug or other sealing mechanism at the inlet end  30 .  
         [0023]    It will be appreciated that alternate seal structures at the outlet end  32  may also be used. However, in the disclosed embodiment the release plug  52  comprises a support structure such as a belleville washer  64  having a teflon or other suitable resilient sealing material layer or coating  60  that is adapted to engage a seal seat  68  surrounding the outlet port  46 . The coating  60  may also be on the outlet end  32 . The Belleville washer  64  includes a receptacle portion  70  and a disc shaped flange portion  72 . The receptacle portion  70  receives a thermally responsive element  74  that is supported by the sprinkler head  40 . The thermally responsive element  70  is a support structure made of a material that fails or melts at a predetermined elevated temperature. The flange portion  72  is seated on the seal seat  68  which may comprise a cylindrical/disc shaped cut-out portion surrounding the outlet port  46  for radial alignment and radial retention of the flange portion  72  of the release plug  72 .  
         [0024]    Turning in greater detail to the sprinkler head  40  and thermally responsive element  74 , reference can be had to FIG. 1. The sprinkler head  40  includes a pair of curved arms  76  (See FIG. 4) projecting away from the outlet port  46  and toward each other to support a plate shaped deflector  77 . The deflector  77  is adapted to deflect water radially outwardly into a fan shaped spray trajectory or other appropriate spray pattern as is desired for extinguishing fires in the particular application. The deflector  72  includes a threaded stem portion  79  that is threaded into a threaded hole  80  formed into the intersection  78  of where the arms  76  meet. The stem portion  79  projects through the hole  80  and urges the thermally responsive element  74  against release plug  52  to load the belleville washer  64  of the release plug  52  to ensure proper sealing relation between the flange portion  72  and the seal seat  68 . The stem portion  79  can be tightened to adjust the force applied to the belleville washer  64  as desired. The belleville washer  64  stores the force or load imposed thereon to keep the flange portion  72  in sealing relation with the seal seat  68 .  
         [0025]    The sprinkler  20  may also include a bleed valve  82  and pressure sensor or pressure gauge  84  in communication with the internal flow passage  48  of the sprinkler  20 . In the disclosed embodiment, these components are mounted to the sprinkler head adapter  36 . The pressure gauge  84  provides a readout of the pressure inside the sprinkler  20 . The antifreeze fluid  54  is contained at or subject to a pressure in a preferred range of between 200 PSI and 7 PSI, and more preferably between 110 PSIG and 50 PSIG, at room temperature, 25° C. Although a preferred range is given, it will be appreciated that the actual pressure may vary and can depend upon the particular fire suppression system  22  and design of the sprinkler  22 . The bleed valve  82  is operable to relieve excess pressure from the flow passage  48  and may also be used during antifreeze fluid filling operations.  
         [0026]    In the disclosed embodiment, the antifreeze fluid  54  is filled into sprinkler  20  through the check valve  50  at the inlet end  30 . The bleed valve  82  may be opened initially during antifreeze filling operations to release air, moisture or other potentially undesirable contents inside the sprinkler  20 . After the bleed valve  82  is closed, the antifreeze fluid  54  is filled or pressurized to the desired pressure. In the disclosed embodiment, the pressure of the antifreeze fluid  54  should be sufficient to apply a force against the check valve  50  to keep the check valve  50  closed to prevent water or other liquid fire suppressant from entering through the inlet port  44 . A spring (not shown) may be used in the check valve  50  to decrease the necessary pressure of the antifreeze fluid  54 . The load applied by the thermally responsive element  74  and stored belleville washer  64  or other suitable spring mechanism is sufficient to maintain a seal between the flange portion  72  and the seal seat  68  (through the teflon coating  66 ) and thereby prevent leakage of antifreeze fluid  54  from the flow passage  48 . Under normal environmental conditions, the seals at the inlet end and the outlet end are maintained containing the antifreeze fluid in the flow passage  48 .  
         [0027]    In the event of a fire or other high temperature condition, the thermally responsive element  74  will fail or otherwise be caused to fail thereby relieving the load on the belleville washer  64 . The pressure inside the sprinkler  20  will then push the release plug  52  away from the outlet port  46  allowing the antifreeze fluid  54  to discharge through the outlet port  46 . The release plug  52  and the remnants of the thermally responsive element  74  are blown out and/or sprayed out of the sprinkler head  40  away from the deflector  77 . As the pressure of the antifreeze fluid  54  is rapidly relieved through the outlet port  46 , the closing pressure applied against the check valve  50  rapidly diminishes allowing water pressure in the pipe network  24  to push open the check valve  50  and allow flow of water into the sprinkler  20  along the flow passage  48  and then out through the outlet port  46  to be deflected as desired by the deflector  77  and then discharged over an area to suppress a fire or high temperature condition.  
         [0028]    Although one form of sprinkler  20  is illustrated, it will be appreciated that the invention is applicable to standard or special automatic sprinklers and nozzles (such nozzle and sprinkler head variations referred to herein collectively as “sprinkler heads”). Sprinkler types can be classified as being upright, pendent, and sidewall and may also be recessed. All of these possibilities are intended to be covered by the claims appended hereto. The K-factor of the sprinkler  20  may range from 1 to 50 with a more preferably range of 3 to 30 and the most preferred range from 5.6 to 25.2. As is known in the art, the K-factor is a discharge coefficient which is equal to a volume divided by the square root of the pressure over a unit of area such as the equation K=Q/{square root}P where Q is equal to the volume of flow such as gallons or liters per minute and P is the pressure usually given in pounds to square inch (psi) or in bar. The inlet pipe thread size of the sprinkler  20  typically ranges from ¼ inch to 3 inches, and more preferably ½ inch to 2 inches, and most preferably 1 inch.  
         [0029]    All of the references cited herein, including patents, patent applications, and publications, are hereby incorporated in their entireties by reference.  
         [0030]    The foregoing description of various embodiments of the invention has been presented for purposes of illustration and description. It is not intended to be exhaustive or to limit the invention to the precise embodiments disclosed. Numerous modifications or variations are possible in light of the above teachings. The embodiments discussed were chosen and described to provide the best illustration of the principles of the invention and its practical application to thereby enable one of ordinary skill in the art to utilize the invention in various embodiments and with various modifications as are suited to the particular use contemplated. All such modifications and variations are within the scope of the invention as determined by the appended claims when interpreted in accordance with the breadth to which they are fairly, legally, and equitably entitled.