Abstract:
A fire protection sprinkler is provided with a skipping shield having air flow passages therethrough to reduce the negative impact that the shield has on the thermal response of the sprinkler. By providing holes, slots, louvers, or mesh to the skipping shield, water from adjacent flowing sprinklers can still be blocked from impinging on the thermal element. The shield will block water but allow hot gas from the fire to flow through the shield thereby improving the response time of the thermal element.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application is a divisional of U.S. patent application Ser. No. 12/410,991, filed on Mar. 25, 2009. The entire disclosure of the above application is incorporated herein by reference. 
     
    
     FIELD 
       [0002]    The present disclosure relates to fire protection sprinklers, and more particularly to a fire protection sprinkler having a sprinkler skipping shield with improved airflow. 
       BACKGROUND AND SUMMARY 
       [0003]    This section provides background information related to the present disclosure which is not necessarily prior art. 
         [0004]    Sprinkler skipping is a behavior that is sometimes exhibited by an array of sprinklers during a full scale fire. Typically, a fire will initially set off one to four sprinklers in quick succession depending where the ignition source is in relation to the sprinkler array. These first few activations are usually defined as the first ring of activated sprinklers. As hot gas from the fire spreads radially outward from the center, the hot gas comes in contact with the second ring of sprinklers. The second ring of sprinklers are radially adjacent to the first ring. The next consecutive/adjacent ring would be the third ring, and the next would be the fourth ring and so on. Sprinkler skipping occurs when a sprinkler in the third or fourth ring operates before a sprinkler in the second ring. In more general terms, skipping is when a non-activated sprinkler adjacent to a flowing sprinkler fails to operate before sprinklers that are farther away from the heat source. This behavior results in the sprinkler array not performing to its highest efficiency. 
         [0005]    Some members of the fire protection industry have concluded that water impingement is the cause of sprinkler skipping. Water impingement is defined as (1) water flow from an activated sprinkler to an adjacent sprinkler; or (2) water droplets carried by the fire plume on to an adjacent sprinkler and impinging on that sprinklers thermal element. The water impingement absorbs heat from the thermal element preventing or retarding its activation (the water keeps the thermal element below its operating temperature). 
         [0006]    In order to prevent water impingement, it has been proposed that a shield be installed such that water traveling from a flowing sprinkler or water carried by the fire plume will not strike the thermal element of an adjacent sprinkler. This, in theory, prevents the thermal element from becoming wetted, thereby preventing skipping. The shield that has been proposed is of a solid cylindrical construction. 
         [0007]    There is some concern that the response time of the thermal element will be impeded by the skipping shield. The impeded response time can negatively impact the performance of a sprinkler in a fire and in a “Response Time Index” plunge oven test. Both of these tests are important to the performance of the sprinkler in terms of gaining Approvals and Listings. 
         [0008]    The present disclosure provides improvements to the design of the skipping shield to reduce the negative impact that the shield has on the thermal response of the sprinkler. By adding holes, slots, louvers, or mesh to the skipping shield, water from the flowing head can still be blocked from impinging on the thermal element. The improved shield will block water from impinging on the heat responsive element but will allow hot gas from the fire to flow through the shield thereby improving the response time of the thermal element. 
         [0009]    The present disclosure also provides a geometrical shape other than the cylindrical shape. The improved geometrical shape is designed in such a fashion to encourage laminar or turbulent gas flow around the shield and onto the thermal element of the sprinkler. The shape is made such that water impinges on the shield, yet provides improvement to the airflow that lowers the response time index as compared to that of previous skipping shield designs. 
         [0010]    The present disclosure also includes the combination of holes, slots, louver, or mesh with a geometric shape that promotes improved air flow around the thermal element. 
         [0011]    Compared to previously proposed skipping shield designs, the improved skipping shield will yield better sprinkler performance in fires by enhancing the response time. The improved skipping shield will also reduce the RTI (Response Time Index) when tested in a plunge oven. 
         [0012]    Further areas of applicability will become apparent from the description provided herein. The description and specific examples in this summary are intended for purposes of illustration only and are not intended to limit the scope of the present disclosure. 
     
    
     
       DRAWINGS 
         [0013]    The drawings described herein are for illustrative purposes only of selected embodiments and not all possible implementations, and are not intended to limit the scope of the present disclosure. 
           [0014]      FIG. 1  is a cross-sectional view of a fire protection sprinkler according to the principles of the present disclosure; 
           [0015]      FIG. 2  is a side view of the fire protection sprinkler of  FIG. 1 ; 
           [0016]      FIG. 3  is a cross-sectional view of a fire protection sprinkler with the shield removed; 
           [0017]      FIG. 4  is a side view of the fire protection sprinkler of  FIG. 3 ; 
           [0018]      FIG. 5  is a perspective view of the skipping shield shown in  FIG. 1 ; 
           [0019]      FIG. 6  is a top view of the skipping shield shown in  FIG. 5 ; 
           [0020]      FIG. 7  is a perspective view of an alternative skipping shield; 
           [0021]      FIG. 8  is a side view of the skipping shield shown in  FIG. 7 ; 
           [0022]      FIG. 9  is a cross-sectional view taken along line  9 - 9  of  FIG. 8 ; 
           [0023]      FIG. 10  is a top view of the skipping shield shown in  FIG. 7 ; 
           [0024]      FIG. 11  is a perspective view of a further alternative skipping shield; 
           [0025]      FIG. 12  is a side view of the skipping shield shown in  FIG. 11 ; 
           [0026]      FIG. 13  is a cross-sectional view taken along line  13 - 13  of  FIG. 12 ; 
           [0027]      FIG. 14  is a top view of the skipping shield shown in  FIG. 11 ; 
           [0028]      FIG. 15  is a perspective view of a still further alternative skipping shield; 
           [0029]      FIG. 16  is a side view of the skipping shield shown in  FIG. 15 ; 
           [0030]      FIG. 17  is a cross-sectional view taken along line  17 - 17  of  FIG. 16 ; 
           [0031]      FIG. 18  is a top view of the skipping shield shown in  FIG. 15 ; and 
           [0032]      FIG. 19  is a side view of an upright fire protection sprinkler having a skipping shield according to the principles of the present disclosure. 
       
    
    
       [0033]    Corresponding reference numerals indicate corresponding parts throughout the several views of the drawings. 
       DETAILED DESCRIPTION 
       [0034]    Example embodiments will now be described more fully with reference to the accompanying drawings. Example embodiments are provided so that this disclosure will be thorough, and will fully convey the scope to those who are skilled in the art. Numerous specific details are set forth such as examples of specific components, devices, and methods, to provide a thorough understanding of embodiments of the present disclosure. It will be apparent to those skilled in the art that specific details need not be employed, that example embodiments may be embodied in many different forms and that neither should be construed to limit the scope of the disclosure. In some example embodiments, well-known processes, well-known device structures, and well-known technologies are not described in detail. 
         [0035]    The terminology used herein is for the purpose of describing particular example embodiments only and is not intended to be limiting. As used herein, the singular forms “a”, “an” and “the” may be intended to include the plural forms as well, unless the context clearly indicates otherwise. The terms “comprises,” “comprising,” “including,” and “having,” are inclusive and therefore specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof. The method steps, processes, and operations described herein are not to be construed as necessarily requiring their performance in the particular order discussed or illustrated, unless specifically identified as an order of performance. It is also to be understood that additional or alternative steps may be employed. 
         [0036]    When an element or layer is referred to as being “on”, “engaged to”, “connected to” or “coupled to” another element or layer, it may be directly on, engaged, connected or coupled to the other element or layer, or intervening elements or layers may be present. In contrast, when an element is referred to as being “directly on,” “directly engaged to”, “directly connected to” or “directly coupled to” another element or layer, there may be no intervening elements or layers present. Other words used to describe the relationship between elements should be interpreted in a like fashion (e.g., “between” versus “directly between,” “adjacent” versus “directly adjacent,” etc.). 
         [0037]    Spatially relative terms, such as “inner,” “outer,” “beneath”, “below”, “lower”, “above”, “upper” and the like, may be used herein for ease of description to describe one element or feature&#39;s relationship to another element(s) or feature(s) as illustrated in the figures. Spatially relative terms may be intended to encompass different orientations of the device in use or operation in addition to the orientation depicted in the figures. For example, if the device in the figures is turned over, elements described as “below” or “beneath” other elements or features would then be oriented “above” the other elements or features. Thus, the example term “below” can encompass both an orientation of above and below. The device may be otherwise oriented (rotated 90 degrees or at other orientations) and the spatially relative descriptors used herein interpreted accordingly. 
         [0038]    With reference to  FIGS. 1-6 , a fire protection sprinkler  10  according to the principles of the present disclosure will now be described. The fire protection sprinkler  10  includes a body  12  including a fluid passage  14  extending therethrough. The sprinkler  10  can be an upright or pendent sprinkler. A pair of frame arms  16 , can extend from the body  12  and converge at an apex  18 . A deflector  20  can be mounted to the apex  18 . A plug assembly  22  can be disposed in the outlet end  24  of the fluid passage  14 . A heat responsive trigger assembly  26  or other head responsive unit can be utilized for supporting the plug assembly  22  in the outlet of the fluid passage  14 . As illustrated, the heat responsive trigger assembly  26  can include a support strut  28 , a trigger arm  30  and a heat responsive soldered link  32 . A set screw  34  can be provided in the apex  18  for engaging the heat responsive trigger assembly  26  in an assembled condition. It should be noted that other heat responsive units can be utilized including glass bulb and other types of heat responsive triggers. 
         [0039]    The sprinkler body  12  can be provided with any discharge K factor for a desired application. The heat responsive trigger assembly  26  can have any desired response temperature rating and the sprinkler  10  can be designed to have any desired response time index (RTI) for a desired application. 
         [0040]    A shield  40  is mounted to the sprinkler body  12  and can include an interior hub portion  42  which can optionally be threadedly engaged with the external threads on the sprinkler body  12 . The shield can be mounted to sprinkler body  12  via the frame arms, via the deflector, or via other exterior structure such as a supply piping or other ceiling structures. A plurality of radial spokes  44  can extend from the hub portion  42  for supporting the shield body  46 . The spokes  44  can include spaces therebetween to facilitate airflow therebetween. The shield body can include a cylindrical wall portion  48 . The wall portion  48  can have other shapes such as cone shaped and sphere shaped, and can be ellipse, square or rectangle in cross-section and can include continuous or discontinuous wall sections. The shield body  48  can include a plurality of louvers  50  that allow air flow through the shield body  46 . The louvers  50  can include an inwardly bent portion  50   a  that define air passages  52  that allow heated air from a fire to enter the shield  40  while the shield serves to prevent water droplets from entering the shield and contacting the heat responsive trigger assembly  26 . It is noted that the louvers  50  can extend around a majority of the shield and the louvers  50  can be connected by one or more web portion  54 . The louvers can be vertical or horizontal in an assembled condition. The spaces  52  between louvers  50  can be between 0.01 and 1 inch, and more specifically between 0.02 and 0.5 inches. The shield  40  can be formed in a generally cup-shape and the openings between the spokes  44  additionally provide for air circulation into and out of the shield body  46 . 
         [0041]    With reference to  FIGS. 7-10 , an alternative shield arrangement  140  is provided wherein the shield body  146  is provided with a plurality of slots  148  which can extend around a majority of the shield body  146 . As shown in  FIGS. 7-10 , the shield body  146  can be cylindrical in form, cone shaped, and spherical shaped and can be elliptical, rectangular, square in cross-section, or can include other geometric shapes. The slots  148  can be horizontal or vertical and can have a width between 0.01 inches and 1 inch, and more specifically between 0.01 and 0.5 inches. The slots  148  and the shield body  146  allow air flow through the shield  140  so as to allow rapid response to a fire while still protecting the heat responsive trigger assembly from water droplets from adjacent sprinkler heads. 
         [0042]    With reference to  FIGS. 11-14 , a further alternative embodiment of the shield  240  is shown including a shield body  246  includes a plurality of holes  248  extending therethrough. The holes  248  can be round, square, rectangular, oval or other geometric shapes. The holes can have a diameter from between 0.002 inches to 1 inch, and more specifically from 0.002 to 0.5 inches, depending upon the spacing therebetween. The plurality of holes  248  allow airflow through the shield while blocking water droplets from engaging the heat responsive trigger assembly. As a still further alternative, the shield body  246  can be formed by a mesh. 
         [0043]    With reference to  FIGS. 15-18 , a generally bulb-shaped shield  340  is shown as an alternative shield geometry. The bulb-shaped shield  340  can include a partially spherical body, or alternatively, cone shaped upper and lower wall section  346 ,  348  that are supported by spokes  344  which extend radially outward from a central hub  342 . It should be understood that the shield  340  can further include holes, slots, louvers or mesh (as described above) to further facilitate air flow through the shield into the heat responsive trigger assembly. 
         [0044]    With reference to  FIG. 19 , it is noted that the shield designs disclosed herein can be utilized with an upright sprinkler  410  as shown. The shield design can be arranged so as not to affect the water distribution pattern of the sprinkler  410 . 
         [0045]    The foregoing description of the embodiments has been provided for purposes of illustration and description. It is not intended to be exhaustive or to limit the invention. Individual elements or features of a particular embodiment are generally not limited to that particular embodiment, but, where applicable, are interchangeable and can be used in a selected embodiment, even if not specifically shown or described. The same may also be varied in many ways. Such variations are not to be regarded as a departure from the invention, and all such modifications are intended to be included within the scope of the invention.