Patent Publication Number: US-11654447-B2

Title: Satackable sprinkler riser extension kit

Description:
RELATED APPLICATIONS 
     This application claims priority to U.S. patent application Ser. No. 16/377,199 filed on Apr. 6, 2019, which claims priority to U.S. Provisional Application 62/725,970 filed Aug. 31, 2018, both of which are fully incorporated herein by reference. 
    
    
     BACKGROUND OF THE INVENTION 
     Field of the Invention 
     The present invention relates generally to irrigation systems, and more particularly to a retrofit riser kit for lawn sprinklers, especially pop-up sprinklers. 
     Description of Related Art 
     Heads for pop-up sprinklers in irrigation systems, particularly those installed in lawns and gardens, become buried over time due to soil build-up and grass growth in the immediate vicinity of the sprinkler head. This causes blockage of the pop-up action or blockage of water flow, rendering the sprinkler unable to provide desired irrigation coverage. 
     A conventional solution is to dig away the grass and dirt around the sprinkler head, then remove the sprinkler head from its riser (usually made of PVC), and add length to the riser by cutting and cementing a riser extension in place. After the cement cures, the sprinkler head can then be reinstalled to the riser extension at a higher elevation above the lawn. 
     The conventional solution, however, is labor intensive and time consuming, and also risks introducing dirt and other debris into the sprinkler line that can clog sprinkler heads and cause further problems later on. Other solutions involve installing risers internal to the sprinkler head mechanism, but these are also time consuming because they require that the sprinkler cap be removed and its internal mechanism reconstructed. Those solutions are also structurally specific to a particular make and model of sprinkler head. 
     What is needed is a universal riser that fits multiple makes and models of sprinkler heads, that is easy to install, and that doesn&#39;t require digging up the sprinkler or cutting and cementing irrigation lines. 
     SUMMARY OF THE INVENTION 
     The foregoing problems are overcome by a sprinkler riser extension kit according to the present invention. In a basic embodiment, the extension kit consists of two cooperating parts: an external gripping head (“gripping head”), and an internal riser extension (“riser extension”). Both the gripping head and the internal riser extension are configured to be stacked on one another to extend the height of a sprinkler riser in as many stages as desired. That is, the lower end of each gripping head can mate to an upper end of an identical gripping head, and the lower end of the internal riser extension can be connected to an upper end of an identical internal riser extension. 
     The gripping head may be sized to at least partially cover the cap of a conventional sprinkler head, either in an off-the-shelf condition or in a condition of prior installation in an irrigation system. In one embodiment the gripping head has an upper end and a lower end, and a channel extending through the upper end and lower end, wherein the lower end includes a means for attachment to a sprinkler. The riser extension is configured to slide within the channel, and has a first attachment means configured for attachment to a head of the sprinkler, and a second attachment means configured for attachment to a riser of the sprinkler from which the head of the sprinkler is detached. 
     The channel may run centrally through the gripping head, such that the channel is concentrically aligned with a central rotational axis of the gripping head. The channel preferably has a height substantially equal to the length of the riser extension, and allows for tight passage of the riser extension therethrough. In one embodiment, the attachment means at the lower end of the gripping head is configured with a plurality of pawls for facilitating removable attachment of the gripping head to the cap of the sprinkler head. The pawls may be evenly spaced about the perimeter of the lower end, and each pawl may include an inwardly projecting flexible finger that snap-fits to the cap when the gripping head is pressed downward over the cap. The upper end of the gripping head may also include one or more outwardly projecting tabs to provide a means for rotating the gripping head by hand. The top surface of the gripping head may include a rim surrounding the entrance to the cylindrical channel that acts as a stop to prevent passage of a sprinkler head therethrough. 
     In one embodiment, the riser extension is generally cylindrical, and may comprise a length of pipe having the first and second attachment means at opposing ends, which may be threaded attachments. Preferably, the riser extension includes male threading at its upper end configured to engage female threading of the sprinkler head. At its lower end, the riser extension may include female threading of similar configuration. Preferably, the riser extension has an outer surface configured to allow the riser extension to slide tightly but freely against interior walls of the channel when subjected to a pop-up force of the sprinkler. In another embodiment, the lower end of the riser extension may include a rim having a plurality of ridges formed on a bottom surface of the rim that act as a lock washer when the riser extension is fully attached to the sprinkler riser. 
     In another embodiment, a sprinkler riser extension kit according to the invention includes a gripping head and a riser extension. The gripping head is configured for removable attachment alternatively to both of a top end of a sprinkler and an upper end of an identical gripping head. The gripping head further defines a channel extending through the gripping head. The riser extension is configured to slide within the channel, and is further configured for attachment between: a head of the sprinkler, and a riser of the sprinkler from which the head of the sprinkler is detached. The width of the channel substantially equals the width of the sprinkler riser, or the width of the riser extension, or both, and the length of the channel corresponds to the length of the riser extension. 
     Another embodiment of the invention provides a kit for elevating a pop-up sprinkler having a riser and a head detachable from the riser, wherein the kit includes a gripping head and a riser extension. The gripping head is configured for attachment alternatively to both of a top end of the pop-up sprinkler and an upper end of an identical gripping head. The gripping head further defines a channel configured for passage of the riser of the pop-up sprinkler therethrough. The riser extension is configured to pass through the channel and is further configured to attach between the riser of the pop-up sprinkler and the head of the pop-up sprinkler. 
     In operation, the kit is configured so that an operator can raise a sprinkler riser through the cap of a pop-up sprinkler, remove the head of the pop-up sprinkler from its riser, pass the sprinkler riser through the channel of the gripping head, and attach the riser extension at its lower end to the top of the sprinkler. The sprinkler head can then be attached to the upper end of the riser extension, and the gripping head can then be attached to the cap, e.g. by pressing the gripping head downward until the pawls snap into place around the rim of the cap, to complete the installation and effectively extend the elevation of the sprinkler head according to the length of the riser extension. The stackable feature of the gripping head and internal riser extension allows the operator to extend the elevation of the sprinkler head in as many stages as desired. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Other systems, methods, features and advantages of the invention will be or will become apparent to one with skill in the art upon examination of the following figures and detailed description. It is intended that all such additional systems, methods, features and advantages be included within this description, be within the scope of the invention, and be protected by the accompanying claims. Component parts shown in the drawings are not necessarily to scale, and may be exaggerated to better illustrate the important features of the invention. Dimensions disclosed or shown are exemplary only. In the drawings, like reference numerals may designate like parts throughout the different views, wherein: 
         FIG.  1    is a perspective view of one embodiment of an external gripping head of a sprinkler riser extension kit according to the present invention. 
         FIG.  2    is a side view of the gripping head of  FIG.  1   . 
         FIG.  3    is a cross-sectional side view of the gripping head taken along Section A-A of  FIG.  2   . 
         FIG.  4    is a bottom view of the gripping head of  FIG.  1   . 
         FIG.  5    is a side view of one embodiment of an internal riser extension of a sprinkler riser extension kit according to the present invention. 
         FIG.  6    is a bottom view of the internal riser extension of  FIG.  5   . 
         FIG.  7    is a magnified view of a portion of  FIG.  6   . 
         FIG.  8    is a cross-sectional side view of the internal riser extension taken along Section B-B of  FIG.  5   . 
         FIG.  9    is a side view of one embodiment of a sprinkler riser extension kit in a condition of use as installed on a conventional pop-up sprinkler. 
         FIG.  10    is a cross-sectional side view of the sprinkler riser extension kit in the same condition of use in  FIG.  8   , taken along Section C-C. 
         FIG.  11    is a perspective view of an embodiment of an external gripping head of a stackable sprinkler riser extension kit according to the present invention. 
         FIG.  12    is a top view of the external gripping head of  FIG.  11   . 
         FIG.  13    is a cross sectional side view of the external gripping head of  FIG.  11   , taken along section lines E 1 -E 1  in  FIG.  12   . 
         FIG.  14    is a cross sectional side view of the external gripping head of  FIG.  11   , taken along section lines E 2 -E 2  in  FIG.  12   . 
         FIG.  15    is a detail view of the portion of  FIG.  14    that is enclosed within the circle labeled F. 
         FIG.  16    is a top view of one embodiment of an internal riser extension for use with the gripping head of  FIG.  11   . 
         FIG.  17    is a side view of the embodiment of  FIG.  16   . 
         FIG.  18    is another side view of the embodiment of  FIG.  16   , rotated by 90 degrees with respect to the view shown in  FIG.  17   . 
         FIG.  19    shows an exploded side view of a stackable sprinkler riser extension kit, in which multiple gripping heads of the embodiment of  FIG.  11    are assembled in a stacked configuration. 
         FIG.  20    shows a side view of the stackable sprinkler riser extension kit of  FIG.  19    assembled in the stacked configuration. 
         FIG.  21    shows a partial cross sectional side view of the stackable sprinkler riser extension kit as assembled in the stacked configuration of  FIG.  20   , taken along section line H-H. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     The foregoing problems installing risers on existing pop-up sprinklers are overcome by a sprinkler riser extension kit according to the present invention. In one embodiment, the extension kit consists of two cooperating parts: an external gripping head (“gripping head”), and an internal riser extension (“riser extension”). 
       FIG.  1    shows one embodiment according to the invention of a gripping head  10  for a sprinkler riser extension kit. Preferably, the gripping head  10  is formed as a singular component, for example, by an injection molding process using ABS or acetal plastic. In other embodiments, the gripping head  10  may be formed by machining, forging, or three-dimensional printing, from any generally rigid material among many suitable metals and plastics. Preferably, the gripping head  10  has a generally cylindrical form. In one embodiment, the gripping head  10  has an overall height of about 2.5 in. and a width or diameter of about 2.0 to 2.25 in. 
     The lower end of gripping head  10  is configured for removable attachment to the cap  24  of a sprinkler  22  that may be any one of a variety of commercially available pop-up sprinklers, such as those manufactured by Hunter®, Rainbird®, Toro® and others. The configuration of the lower end of gripping head  10  that provides the means for removable attachment of the gripping head to the cap of a sprinkler may vary. For example, the removable attachment means may comprise a threaded connection, a clamp, a friction-fit, a locking device such as a tab-and-slot connection, or any combination of the foregoing. 
     In one embodiment, as shown in  FIGS.  1 - 4   , a gripping head  10  removably attachable to a sprinkler may include a plurality of flexible claws, or pawls  12 , for facilitating removable attachment of the gripping head  10  to the cap portion  24  of any of various conventional pop-up sprinkler heads. The pawls  12  are preferably spaced evenly about the perimeter of the lower end of gripping head  10 . Each pawl  12  may be angled slightly inward. Alternatively, each pawl  12  may include a finger portion  14  that projects inwardly from an inner surface of each pawl toward the axis of the gripping head. To project inwardly means that a finger portion  14  extends in a direction toward and perpendicular to an axis of rotation  11  that is defined as an imaginary vertical line running through the center of the gripping head  10 . By way of illustration, the rotational axis  11  lies in the same plane as Section line A-A in the side view of  FIG.  2   , and emerges normal to the page at the origin point  11  shown in  FIG.  4   . Finger portion  14  preferably forms a rounded or wedge-shaped protrusion on the inner surface of each pawl. The dimensions of the pawl  12  are chosen to form a durable and resilient spring so that the pawl will flex and bend outward in response to downward pressure of the claws against the cap of a conventional pop-up sprinkler, and then snap inward when the finger portion  14  of the pawl is forced past a rim  28  of the cap  24 . In this manner, each pawl  12  attaches tightly to the cap, gripping the cap and resisting detachment by detent action of the pawls. 
       FIG.  2    shows a side view of the gripping head  10 . In this view, four pawls  12  are visible at the lower end of gripping head  10 , and another four pawls  12  are hidden from sight. Thus, this embodiment there are a total of eight pawls  12  angularly spaced about the lower end of the gripping head at regular intervals. In one implementation of the invention, each pawl  12  may be about 0.4 in. in length, and the spacing between any two adjacent pawls  12  may be about 0.5 in. The width of each pawl  12  may be about 0.44 in. Other numbers, arrangements, and dimensions of pawls  12  are possible within the scope of the invention. 
     On an upper portion of the gripping head  10 , one or more outwardly projecting tabs  16  may be formed at one or more locations about the perimeter of the gripping head to provide a means for rotating the gripping head  10  by hand. Outwardly projecting means that tabs  16  extend in a direction away from and perpendicular to the axis of rotation  11 . In a preferred embodiment, four tabs  16  are formed about the gripping head, each spaced apart angularly by 90 degrees. Each tab  16  may be about 0.5 in. high, and about 0.08 in. wide. Other numbers, arrangements, and dimensions of tabs  16  are possible within the scope of the invention. 
       FIG.  3    shows a cross-sectional side view of the gripping head  10  taken along Section A-A of  FIG.  2   . A channel  18  is shown extending centrally through the top surface  17  of gripping head  10  from an upper rim  13  of the gripping head to a lower rim  15  of the gripping head. Channel  18  is preferably cylindrical, and may be concentrically aligned with the rotational axis  11 . Channel  18  may have a height substantially equal to the length of the riser extension  20 , and an inner diameter (or other geometry) that allows for snug passage of the riser extension  20  therethrough, as a piston through a cylinder. 
     In one embodiment, gripping head  10  may be constructed with one or more interior voids  21  formed between an inner wall  19  of the gripping head and an outer wall  23  of the gripping head. The inner wall  19  of the gripping head defines a boundary around the vertical channel  18 . The outer wall  23  of the gripping head forms an exterior side surface all around the perimeter of the gripping head  10 . The interior voids  21  reduce the amount of material needed to form the gripping head, to thereby advantageously reduce the weight of the gripping head and also minimize manufacturing costs. 
     The outer wall  23  may be cylindrical, rectangular, or another multi-sided geometry, and is preferably ergonomically designed to facilitate grasping or manipulating by hand. Outer wall  23  may also be partially conical or circular, and may combine various of the foregoing or following geometrical features as a means for manual operation. For example, in the embodiment shown in the figures, the outer wall  23  comprises that part of the exterior surface of the gripping head  10  that lies between the upper rim  13  and the lower rim  15 . This part of the exterior surface includes a cylindrical portion  32  and a conical portion  34  ( FIG.  1   ). This particular structure allows an operator to get a firm grip on gripping head  10  by grasping and pressing thumb and forefingers underneath the upper rim  13 , above the conical portion  34 , and against the tabs  16  for reliable handling, pressing, lifting, and rotating. 
       FIG.  4    shows a bottom view of the gripping head  10 . This view shows the point through which axis  11  passes into and out of the page. Eight interior voids  21  are shown between the inner wall  19  and outer wall  23 . A vertical divider  25  separates each adjacent pair of interior voids  21 . In this embodiment there are eight vertical dividers  25 , formed at regular angular intervals around the axis  11 . Each vertical divider  25  extends from the inner wall  19  to the outer wall  23 , from the lower end of the gripping head  10  to the top surface  17 . Preferably, the vertical dividers  25  are integrally formed along with all other parts of the gripping head by a casting or injection molding process. The vertical dividers  25  serve to maintain the structural integrity of a gripping head  10  that is formed with one or more voids  21 , while minimizing the mass and manufacturing cost of the gripping head. In other embodiments, there may be different numbers of vertical dividers  25 , spaced at regular or irregular intervals. Alternatively, the gripping head  10  may be formed with a solid interior surrounding vertical channel  18 , with no vertical dividers or voids. 
       FIGS.  5  to  8    show one embodiment of an internal riser extension  20  for a sprinkler riser extension kit according to the invention. Preferably, the riser extension  20  is also formed as a singular component, for example, by an injection molding process using ABS or acetal plastic. In other embodiments, the riser extension  20  may be formed by machining, forging, or three-dimensional printing, from any generally rigid material among many suitable metals and plastics. The riser extension  20  may also be machined from pipe stock. 
       FIG.  5    shows a side view of the internal riser extension  20 . In one embodiment, the riser extension  20  includes a first attachment means  40 , for attaching to a conventional pop-up sprinkler head  27 . For example, the first attachment means  40  may include male threading at the top end of the riser extension (i.e. the right-most end as shown in  FIG.  5   ) that is configured to threadably engage with female threading of a conventional pop-up sprinkler head, e.g. ⅝-28 threads or otherwise. On the opposite or lower end, the riser extension  20  may be configured with a second attachment means  42 , for attaching to a riser  26  of the conventional pop-up sprinkler. For example, the second attachment means  42  may include female threading similar to that of the first attachment means. Preferably, one or both of the first and second attachment means  40 ,  42  comprise a removable attachment means. Other structures for the first and second attachment means  40 ,  42  are possible within the scope of the invention, for example, means such as a compression fitting, a pipe clamp, an adhesive, a weld, a spring-loaded connector, and a pipe fitting or junction. Whatever structure is used for the attachment means  40  and  42 , the outer surface or outer diameter of the riser extension  20  should be sized to allow it to slide tightly, i.e. freely yet snugly with minimal friction, within and against the internal wall of the vertical cylindrical channel  18 , when assembled as depicted herein and when subjected to a spring force or a pop-up force delivered by a conventional pop-up sprinkler. In one embodiment, the outer diameter of the riser extension  20  is about 0.6 in. The length of the riser extension  20  preferably conforms substantially to the length of the cylindrical channel  18 . 
       FIG.  6    shows a bottom view of the internal riser extension of  FIG.  5   , and  FIG.  7    shows a magnified view of a portion of  FIG.  6   . These figures illustrate an optional feature according to the invention on a riser extension  20 , wherein the rim  37  of the lower end of the riser extension  20  may be configured with a plurality of sharp ridges  38  formed on the bottom surface of the rim  37 . The ridges  38  cause the bottom surface of rim  37  to bite into the mating surface of a conventional riser when the riser extension  20  is threaded into full engagement with mating threads of the conventional riser. The ridges  38  thereby act as a lock washer, fixing the mating surfaces as they are rotated into engagement, while preventing disengagement by counter-rotation that is imparted without substantial effort. In one embodiment, the ridges  38  have a height of about 0.02 in., and each ridge is separated from an adjacent ridge by about 0.015 in. 
       FIG.  8    shows a cross-sectional side view of the riser extension  20  taken along Section B-B of  FIG.  5   . This view illustrates exemplary proportions for, and internal configuration of, the riser extension  20 . In one embodiment, the overall length of the riser extension  20  may be between about 1.5 to 2.0 in. The length of the threaded portion  40  (first attachment means) or threaded portion  42  (second attachment means) may be about 0.18 to 0.22 in. 
       FIG.  9    shows a side view of one embodiment of a sprinkler riser extension kit in an assembled condition 30 as installed on a conventional pop-up sprinkler  22 . Internal parts of the assembly  30  are shown in the cross-sectional side view of  FIG.  10   , which is taken along Section C-C of  FIG.  9   , and in which the sprinkler head  27  is shown in exploded view above the assembly for purposes of illustration. The assembly  30  may be achieved by a method according to the invention for extending a height of a sprinkler, as follows: A technician first raises the sprinkler riser  26  through the cap  24 , against a pop-up spring restoring force, to fully expose the sprinkler head  27 . The sprinkler head  27  can then be removed from the top 41 of sprinkler riser  26 . Sprinkler riser  26  may then be passed through the channel  18  of the gripping head  10 , and the riser extension  20  can then be attached at its lower end to the top 41 of the sprinkler riser  26 . The sprinkler head  27  can then attached onto the upper end of the riser extension  20 , and the gripping head  10  can then be attached to the cap  24  as a final step. In the embodiment shown, the final step may be achieved by pressing the gripping head  10  onto the cap  24  until the pawls  12  snap into place around the rim  28  of the cap  24  as shown, to complete the installation and effectively extend the elevation of the sprinkler head  27  of sprinkler  22  according to the length of the riser extension  20 . 
     In alternative embodiments of the method, the gripping head  10  may be attached to the cap  24  at any time after passage of sprinkler riser  26  through channel  18 . Where the means for attaching the gripping head  10  to the sprinkler  22  includes the plurality of pawls  12 , a technician can effect the attachment step by grasping the gripping head  10  and pushing it downward onto the cap  24 , forcing pawls  12  around the top of the cap  24  until the gripping head snaps into place around rim  28 . 
     A configuration of a gripping head  10  that includes the plurality of pawls  12  disposed about the lower end of the gripping head provides another advantage when installing a sprinkler riser kit according to the invention onto a buried or partially buried sprinkler  22 . Prior to the installation, a technician can place the gripping head  10  over the cap  24 , with or without snap-fitting the pawls to the cap, and rotate the gripping head. By rotating the gripping head  10  in opposite directions, the pawls  12  can be used to clear away grass, dirt, and other debris from around the cap  24 . This will prevent the debris from entering the sprinkler  22  and potentially clogging the head or interfering with internal mechanisms. The gripping head  10  may thus be configured with a means for clearing debris from a buried or partially buried sprinkler. 
       FIG.  11    shows a perspective view of an embodiment of an external gripping head  110  of a stackable sprinkler riser extension kit according to the present invention. The gripping head  110  is similar to the gripping head  10 , and differs from gripping head  10  only by the addition of several structural features formed in the top surface  17  around or within the vertical channel  18 . On gripping head  110 , the upper end of the vertical channel  18  is widened and a shelf  112  is provided to define a recessed area  114  above the shelf  112  for receiving a flanged sprinkler head when a pop-up sprinkler is depressurized and the sprinkler head retracts downward into the gripping head. The shelf  112  provides a secure seat for the flanged rim of the sprinkler head (not shown). In one embodiment, the depth of the shelf  112  from the top surface  17  may be about 0.25 in. By providing the recessed area  114  for receiving a sprinkler head, the gripping head  110  effectively protects the sprinkler head from accidental damage as it would otherwise be exposed to lawnmower blades or other potentially harmful impacts. 
     Also on gripping head  11  are formed one or more head access channels  116 . The head access channels  116  are provided adjacent to the recessed area  114 , to allow an operator to grip the underside of a recessed rim of a sprinkler head, to facilitate raising of the sprinkler head. The head access channels may have any shape, and may have the same depth as shelf  112 , or may have a slightly greater depth than the depth of the shelf  112 . In one embodiment, the shape of the head access channels may resemble a logo of the gripping head manufacturer. 
     Also formed into the top surface  17  are two key holes  120 . The keyholes  120  are preferably located equidistant from, and on opposite sides of the edge of the recess area  114 . The keyholes  120  are sized to engage with tines of a turning tool, fork, or turn-on key that is commonly used to rotate valves open and closed. With one or more gripping heads  110  installed atop a sprinkler cap, rotation of the keyholes  120  by the tines of a turn-on key will screw or unscrew a threaded sprinkler cap. 
       FIG.  12    shows a top view of the external gripping head  110 . In an exemplary embodiment, the diameter of the top surface of the gripping head  110  is about 2.25 in. This is the same diameter of the upper surface of gripping head  10 , of the upper rim  13 , and of the rim  28  of one style of commercial sprinkler cap. To further illustrate the structure of the gripping head  110 , two section lines E 1 -E 1  and E 2 -E 2  are defined through this view for further discussion below. 
       FIG.  13    shows a cross sectional side view of the external gripping head  110 , taken along section lines E 1 -E 1  in  FIG.  12   . This view illustrates several exemplary dimensional features, which are for purposes of illustration only, and are not intended to limit the scope of the invention to the dimensional examples given. Skilled artisans will recognize that these dimensions are nominal, may be scaled up or down, and each may be given reasonable tolerance, for example, in a range of 10% to 20%. Rounded edge  131  may define a radius of about 0.02 in. Angle  132  may be about 12 degrees. Upper rim  133  may have a height of about 0.35 in. Rounded edge  134  may define a radius of about 0.25 in. The beveled edge  135  at the lower end of channel  18  may have a height of about 0.04 in. slanted at about 20 degrees. Width  136  of inner wall  19  may be about 0.1 in. Width  137  of outer wall  23  may be about 0.1 in. Gripping head  110  also features a solid upper interior portion  138  surrounding the channel  18 , to provide greater overall component strength, resulting in less volume for the interior void  21 , in comparison to the more hollow configuration of the prior embodiment. 
       FIG.  14    is a cross sectional side view of the external gripping head  110 , taken along section lines E 2 -E 2  in  FIG.  12   . Like  FIG.  11   , this view is similarly provided for illustrative, and not limiting purposes. Height  141  of cap  13  may be about 0.15 in. Width  142  of the channel  18  may be about 0.82 in. Angle  143  may be about 160 degrees. Overall width  144  may be about 2.5 in. Gap  145  may be about 0.04 in. Widths  146 ,  147 , and  148  may be about 2.16, 2.19, and 2.4 in., respectively. 
       FIG.  15    is a detail view of the portion of  FIG.  14    that is enclosed within the circle labeled F, to illustrate one embodiment of a pawl  12  according to the invention. Like  FIG.  11   , this view is similarly provided for illustrative, and not limiting purposes. Width  151  of the pawl  12  may be about 0.8 in. The radius indicated at  152  may be about 0.25 in. Pawl length  153  above the finger portion  14  may be about 0.15 in. Overall pawl length  154  may be about 0.4 in. The angle  155  defining the distal shape of the pawl  12  may be about 37 degrees. The radius of the finger portion  14  indicated at  156  may be about 0.16. The angle  157  from the distal end of the pawl  12  to the lower base  158  of the gripping head  110  may be about 86 degrees. 
       FIG.  16    is a top view of one embodiment of an internal riser extension  160  for use with the gripping head  110 . This view also corresponds to a top view of the internal riser extension  20  shown in  FIG.  8   .  FIG.  17    is a side view of internal riser extension  160 .  FIG.  18    is another side view of the internal riser extension  160 , rotated by 90 degrees with respect to the view shown in  FIG.  17   . A flattened area  161  may be provided at an intermediate location between the upper and lower ends of the internal riser extension  160 , to allow the internal riser extension  160  to be held firmly in place by a tool such as an end wrench when unscrewing or removing a sprinkler head from an upper end of the extension  160 , or when unscrewing or removing the extension  160  from a threaded sprinkler riser. 
       FIG.  19    shows an exploded side view of a stackable sprinkler riser extension kit, in which multiple gripping heads of the embodiment of  FIG.  11    are assembled in a stacked configuration  200 . As in the prior embodiment of gripping head  10 , gripping head  110  may be stacked onto another gripping head of similar size and configuration by snap-fitting pawls  12  to the rim  28  of another gripping head stacked immediately below, as shown. As in the prior configuration  30 , each time a gripping head  10  or  110  is added to a sprinkler riser to raise its overall elevation, an internal riser extension  20  or  160  must be installed as described above to extend the overall length of the riser for engagement with a sprinkler head  27  at the top of the uppermost gripping head. When stacking gripping heads, it is important to maintain dimensional tolerance to ensure that the upper rim  13  of each gripping head snaps securely to the pawls  12  of the gripping head immediately above. Key dimensions to ensure stackability of the gripping heads are the diameter and height of the upper rim  13 , and the pawl-to pawl lengths  146 ,  147 ,  148  previously defined. In one embodiment, the pawls  12  are constructed so that the dimensions  146  and  148  are, respectively, about 5% less than and greater than the diameter of the top surface of gripping head  10 ,  110 , or the upper rim  13 . 
       FIG.  20    shows a side view of the stackable sprinkler riser extension kit assembled in the stacked configuration  200 . The stack consists of three gripping heads  110 , where the lower gripping head is snap-fit to the cap of a sprinkler  22 , the middle gripping head is snap-fit to the upper rim of the lower gripping head, and the upper gripping head is snap-fit to the upper rim of the middle gripping head. Thus, according to the invention, gripping heads and riser extensions are configured to be stackable atop one another, to elevate the sprinkler in multiple stages. 
       FIG.  21    shows a partial cross sectional side view of the stackable sprinkler riser extension kit as assembled in the stacked configuration  200 , taken along section line H-H of  FIG.  20   . This view illustrates the snap-fit engagement of pawls  12  to upper rims  13 , or to rim  28  of cap  24  of the sprinkler  22 . The lowest-placed internal riser extension  160  is shown installed inside of the lowest gripping head  110 . An additional internal riser extension  160  is provided (though not shown) and internally installed with each gripping head to extend the overall length of the sprinkler riser so that a sprinkler head  27  ( FIG.  10   ) may be attached to the topmost internal riser extension  160  and seated atop the top-most gripping head  160 . 
     Exemplary embodiments of the invention have been disclosed in an illustrative style. Accordingly, the terminology employed throughout should be read in a non-limiting manner. Although minor modifications to the teachings herein will occur to those well versed in the art, it shall be understood that what is intended to be circumscribed within the scope of the patent warranted hereon are all such embodiments that reasonably fall within the scope of the advancement to the art hereby contributed, and that that scope shall not be restricted, except in light of the appended claims and their equivalents.