Patent Publication Number: US-7584803-B2

Title: Sprinkler with motion limited lever

Description:
FIELD OF THE INVENTION 
   This invention relates to sprinklers for fire suppression systems having compressed lever and strut triggering mechanisms. 
   BACKGROUND OF THE INVENTION 
   Of the various types of sprinklers used in fire suppression systems, the compressed lever and strut variety finds extensive use. Compressed lever and strut sprinklers use an inherently unstable trigger mechanism comprising a compression member that compresses a strut and lever against a sealing member which closes the outlet of the sprinkler. The strut is positioned lengthwise between the compression member and the sealing member, and the lever is positioned between an end of the strut and the compression member. The strut has a line of action that is offset from the line of action of the compression member. This offset allows the compression member to induce a torque in the lever, which, if unrestrained, would rotate away from the strut, causing the strut to disengage from between the compression member and the sealing member and allow the sprinkler to open. A frangible link extends between the strut and the lever, normally preventing rotation of the lever. The link separates in response to an increase in the ambient temperature indicative of a fire, thereby allowing the lever to rotate and displace the strut from between the compression member and the sealing member, releasing the sealing member and opening the outlet. Fire suppressing liquid may then flow through the sprinkler to contain and extinguish the fire. 
   For proper functioning of the sprinkler, the trigger mechanism must remain unstable. It is observed however, that a force applied to the free end of lever tending to move the end toward the strut will shift the line of action of the strut, causing it to align with the line of action of the compression member. When this occurs, the mechanism becomes stable, there is no torque on the lever and the link is no longer under tension and is not needed to hold the lever in position. When a temperature increase from a fire causes the link separate, the strut and the lever remain in position between the compression member and the sealing member, holding the sealing member in position closing the sprinkler outlet. In this situation, the sprinkler fails to open and discharge water and the fire propagates. The force applied to the lever which renders the trigger mechanism stable may occur as a result of improper handling during shipping or installation. The mechanism may also be rendered stable due to improper assembly at the factory. It is, furthermore, very difficult to visually detect whether a trigger mechanism is in a stable or an unstable condition. There is clearly a need for an improved sprinkler of the compressed lever and strut type which does not suffer from this disadvantage. 
   SUMMARY OF THE INVENTION 
   The invention concerns a sprinkler for a piping network of a fire suppression system. The sprinkler comprises a body having an inlet connectable to the piping network and an outlet in fluid communication with the inlet. A compression member is mounted on the body and is positioned in facing relation with the outlet. The compression member has a first line of action extending toward the outlet. A sealing member closes the outlet. A strut extends lengthwise between the compression member and the sealing member. The strut has a second line of action that is offset from the first line of action of the compression member. A lever has a first portion that is positioned between the strut and the compression member. The lever also has a second portion spaced from the first portion. The body has an abutment surface engageable with the second portion of the lever. Engagement of the second portion with the abutment surface limits motion of the lever toward the strut so as to maintain the offset between the first and second lines of action of the strut and the compression member. A link attaches the lever to the strut. The link is frangible, and when heated to a predetermined temperature, releases the lever from the strut. The strut thereby disengages from the sealing member, allowing the sealing member to disengage from the outlet to permit fluid flow from the sprinkler. 
   The invention also includes a fire suppression system comprising a piping network to which one or more of the above described to sprinklers are attached. 
   The invention further includes a method of maintaining an offset between a first line of action of a compression member and a second line of action of a strut. The method comprises:
         (A) providing a lever;   (B) positioning a portion of the lever between the strut and the compression member;   (C) compressing the lever between the compression member and the strut;   (D) providing a link between the lever and the strut, the link preventing motion of the lever away from the strut;   (E) providing an abutment surface engageable with the lever, the abutment surface limiting motion of the lever toward the strut.       

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a side view of a sprinkler embodiment according to the invention in a fire suppression system; 
       FIG. 2  is a longitudinal sectional view of the sprinkler embodiment taken at line  2 - 2  of  FIG. 1 ; 
       FIG. 3  is a cross sectional view of the sprinkler embodiment taken at line  3 - 3  in  FIG. 1 ; 
       FIG. 4  is a longitudinal sectional view of another embodiment of the sprinkler according to the invention; 
       FIG. 5  is a longitudinal sectional view of another embodiment of the sprinkler according to the invention; and 
       FIG. 6  is a longitudinal sectional view of another embodiment of the sprinkler according to the invention. 
   

   DETAILED DESCRIPTION OF THE EMBODIMENTS 
     FIG. 1  shows a sprinkler  10  according to the invention. Sprinkler  10  comprises a body  12  having an inlet  14  threadably connected to a piping network  16  of a fire suppression system  18 . The piping network conducts water or other fire suppressing fluid from a source of pressurized fluid  20  to the sprinkler, which opens in the event of a fire to extinguish the fire and prevent its propagation. 
   As best shown in  FIG. 2 , body  12  has an outlet  22  in fluid communication with inlet  14 . The outlet faces a deflector plate  24  mounted on a housing  26  supported by legs  28  that extend from body  12 . Housing  26  receives a compression member  30 , for example, a threaded stud  32  that engages internal threads within the housing and is thus movable toward and away from the outlet  22  upon rotation of the stud. 
   A sealing member  34 , for example, disk  36 , closes outlet  22 . The sealing member  34  is held in position by a strut  38  that is compressed against the sealing member by the compression member  30  acting in conjunction with a lever  40 . Lever  40  has a first portion  40   a  positioned between one end of strut  38  and the compression member  30 , the opposite end of the strut engaging the sealing member  34 . Note that the strut and the lever are both separate components which are not fixed to each other, the sealing member, or the compression member. 
   Compression member  30  has a line of action  42 , corresponding substantially to the centerline of the threaded stud  32 . Similarly, strut  38  has a line of action  44  which generally corresponds to the strut centerline. The strut line of action  44  is offset in relation to the line of action  42  of the compression member  30 . The offset may comprise an angular offset  46  as shown, effected by angularly orienting the strut  38  relatively to the compression member  30 . When the compression member is advanced, the lever portion  40   a  is compressed against the strut  38  and the strut is compressed against the sealing member  34  (disk  36  in this example). Because there is an offset  46  between the lines of action of the compression member  30  and the strut  38 , the compression force induces a torque on lever  40 . The strut  38  is offset toward the lever  40  such that the torque acts to rotate the lever outwardly away from the strut. 
   Another portion  40   b  of the lever  40  is in spaced relation away from end  40   a . Lever portion  40   b  preferably extends upwardly alongside strut  38  to permit a link  48  to extend between the strut and the lever. Link  48  is shown in detail in  FIG. 3 . As best shown in  FIG. 2 , link  48  is formed by two plates  50  and  52  soldered to each other in facing relation using a solder with a predetermined melting temperature. One of the plates,  50 , engages the strut, the other,  52 , engages the lever. As long as the solder joint remains intact, link  48  prevents lever  40  from rotating outwardly away from the strut  38  under the torque induced by the compression of the lever and the strut by the compression member  30 . 
   In operation, with the sprinkler  10  mounted on the piping network  16  as shown in  FIG. 1 , the lever  40  is subjected to torque but is prevented from rotating by link  48 , which is under tension. During a fire, when the ambient temperature surrounding the sprinkler  10  reaches the melting point of the solder holding the plates  50  and  52  of the link  48  together (see  FIG. 2 ), the solder melts. The link can no longer withstand the tension, the plates separate and the torque on lever  40  causes it to rotate outwardly away from strut  38 . Upon rotation of the lever, the strut  38  is dislodged and falls away from the sprinkler, no longer supporting sealing member  34 , which falls away from the outlet thereby allowing water or other fire suppressing fluid to be discharged from the sprinkler head. 
   The lever  40  and strut  38 , when compressed between the compression member  30  and the sealing member  34 , constitute an unstable trigger mechanism held in place by the separable link  48 . The instability is due to the offset  46  of the line of action  44  of the strut  38  relatively to the line of action  42  of the compression member  30  which causes a torque to be induced on the lever by the applied compression force. For proper functioning of the sprinkler  10  the mechanism must remain unstable. It is observed, however, that a force applied to the end  40   b  of lever  40  tending to move the end  40   b  toward the strut  38  will shift the line of action  44  of the strut, causing it to align with the line of action  42  of the compression member  34 . If this is permitted to occur the mechanism becomes stable, there is no torque on the lever, and the link  48  is no longer under tension. When a temperature increase from a fire causes the solder holding the plates  50  and  52  of the link to melt, the plates separate but the lever and the strut remain in position between the compression member and the sealing member, holding the sealing member  34  in position closing outlet  22 . In this situation, the sprinkler  10  fails to open and discharge water and the fire propagates. 
   To prevent the trigger mechanism from becoming stable, the body  12  has an abutment surface  54 . Abutment surface  54  is located between the strut  38  and the end  40   b  of lever  40 , and these two elements are mutually positioned to cooperate with one another and limit the motion of lever  40  toward the strut  38 . In the example embodiment shown in  FIG. 1 , the lever  40  extends angularly from end  40   a  so as to position opposite end  40   b  in close proximity to the abutment surface  54 , which comprises a flat  56  on the body  12  adjacent to the outlet  22 . The lever end  40   b  may be in spaced relation to the abutment surface as shown in  FIG. 2 , or it may be in contact with the surface, as shown in  FIG. 4 . 
   In another embodiment, shown in  FIG. 5 , the abutment surface  54  may be located on a projection  58  that extends from the body  12 . The projection  58  allows a shorter lever  40  to be used but still allows cooperation between the components to limit lever motion and ensure mechanism instability. The lever end  40   b  may be in spaced relation to the abutment as shown in  FIG. 5 , or in contact with it, as shown in  FIG. 6 . 
   Use of the abutment surface in cooperation with the lever limits motion of the lever so as to avoid shifting of the line of action of the strut which might otherwise eliminate the offset necessary to the proper functioning of the sprinkler. Additionally, the abutment surface will facilitate assembly of the trigger mechanism as it provides a positive stop for ensuring proper positioning of the lever relatively to the strut. 
   Sprinklers of the compressed lever and strut type further having an abutment surface engageable with the lever according to the invention provide a more reliable sprinkler which will not become inoperative due to improper assembly or handling during shipping and installation.