Patent Publication Number: US-6209801-B1

Title: Closed-case impact sprinklers with fitted fluid seal assemblies

Description:
This patent application is a continuation-in-part application of pending U.S. patent application Ser. No. 09/282,366 filed on Mar. 31, 1999, which is a continuation-in-part application of pending U.S. patent application Ser. No. 09/128,269 filed on Aug. 2, 1998 which are incorporated by reference in their entirety herein. 
    
    
     FIELD OF THE INVENTION 
     The present invention is generally directed to irrigation sprinklers. More particularly, the invention relates to closed-case impact sprinkler heads with fitted fluid seal assemblies. 
     BACKGROUND OF THE INVENTION 
     Many regions of the world today use irrigation systems for artificial distribution of water. One of the most widely used irrigation systems, particularly where water is not abundant or plentiful, is a sprinkler system wherein one or more sprinkler units are positioned about a land area for distributing water over the surface of the land area. Such systems are widely used in most developed countries for a variety of applications including the irrigation of lawns, golf courses, playing fields and field crops. 
     Impact sprinklers are generally well known in the art and have been used for many years. There are essentially two broad varieties or types of impact sprinklers. The first type is the open or common riser mounted sprinkler unit which is attached to the end of a riser stem or pipe formed with a water conduit. This type of sprinkler is most often used in open areas such as flower beds or the like which do not require close trimming. These units extend upwardly from the surface and are somewhat obtrusive and unattractive. Consequently, they are used in areas where the units are not readily observed nor require maintenance with lawnmowers. The second type of impact sprinkler is a similar type of unit mounted within a housing which is, in turn, buried beneath the surface of the ground so that the sprinkler generally provides a pop-up unit. These impact sprinklers are most often used in lawn settings, and are mounted within housings or wells that are buried underground. The top of the housings are substantially flush with the ground surface so that open areas such as lawns may be easily landscaped or mowed. When water is supplied to the sprinklers, they pop-up or rise above their housings and the ground surface. In this fashion, the sprinklers remain out of sight until activated. However, the housings for this type of sprinkler, which are designed with an open-case to accommodate standard rotating impact sprinkler arms, tend to become filled with debris such as dirt, grass clippings and the like. Any of the above hamper the ability of the sprinkler to pop-up and to retract, or to effectively drive the sprinkler. 
     Another common type of irrigation device is known in the art as a gear driven sprinkler. Gear-driven sprinklers have rotating nozzles effectively driven by various gear driving mechanisms which are activated by water supplied to the sprinkler. These sprinklers provide an advantage in that their housings are enclosed by design thus avoiding the problems associated with the open or well-type design of an impact sprinkler. However, it has been observed that gear-driven sprinklers are frequently subject to failure due to debris becoming engaged or lodged within the gear drive mechanism. Many designs are also plagued with a relatively limited watering range due in part to the general power-draining design of the gear driving mechanisms. 
     The sprinkler literature includes numerous patents relating to variations of sprinkler units known in the art. U.S. Pat. No. 3,602,431 entitled A SPRINKLER DEVICE FOR FLUID DISTRIBUTION (Lockwood) is directed to a sprinkler for distributing water comprising a body, a sprinkler head rotatably connected to the body, a fluid flow interrupter for providing controlled bursts of fluid in the stream of fluid exiting from the sprinkler head, an interrupter drive, a drive means including a free rotating ball for driving the sprinkler head, and reversing means for reversing the direction of movement of the sprinkler head. U.S. Pat. No. 3,765,608 entitled AUTOMATIC INTERMITTENT BREAK-UP DEVICE (Lockwood) is directed to a sprinkler with an automatic intermittent break-up device repeatedly movable toward the center of the fluid stream exiting a nozzle to a first position to increase the break-up of the stream and movable away from the center of the fluid stream exiting the nozzle to a second position to decrease the break-up to provide more desired distribution of fluid on the surface area. U.S. Pat. No. 3,930,617 entitled IMPACT SPRINKLER (Dunmire) is directed to an impact sprinkler which uses a plastic water deflector having a number of cooperating water deflecting surfaces which improve the overall water distribution pattern of the sprinkler; the particular configuration provided for allowing the water deflector to pivot back and forth. U.S. Pat. No. 4,055,304 entitled AUXILIARY BRAKING MEANS FOR IMPACT ARM SPRINKLERS (Munson) is directed to an impact type rotary sprinkler including a rotatable body and nozzle, an impact arm which oscillates responsive to the kinetic energy of the fluid discharge stream and a primary spring which stores the rotational energy of the oscillating arm rotating to impact against the housing and impart an increment of rotation thereto. U.S. Pat. No. 4,103,828 entitled ROTARY SPRINKLER IMPACT ARM SPRING ADJUSTMENT (Ridgway) is directed to a rotary sprinkler with structure for adjusting the force applied to the impact arm by the impact arm spring, viz. a laterally directed nozzle cooperating with the arm to rotate the nozzle and an impact arm on a shaft extending above the nozzle. The arm is mounted within a cage extending above the nozzle. U.S. Pat. No. 4,164,324 entitled SPRINKLER HEAD WITH IMPROVED INTEGRAL IMPACT ARM AND ANTI-BACKSPLASH DRIVE SPOON (Bruninga) is directed to a part-circle rotary sprinkler head having an improved anti-backsplash drive spoon integrally formed as a part of the impact arm. U.S. Pat. No. 4,182,494 entitled ANTISIDE SPLASH DRIVE ARM FOR AN IMPACT DRIVE SPRINKLER (Wichman) is directed to an impact sprinkler of the full or part circle type with an anti side splash drive arm. Despite these and other known sprinkler designs, there is a need for an irrigation sprinkler that incorporates the advantages provided by both impact and gear-driven sprinkler designs. 
     SUMMARY OF THE INVENTION 
     The invention provides closed-case impact sprinkler units. The particular features of the described embodiments in the following specification may be considered individually or in combination with other variations and aspects of the invention. 
     It is an object of the present invention to provide impact sprinkler assemblies with a closed-case design. A sprinkler unit formed in accordance with the invention may include an inner housing and an outer housing which are slidably mounted relative to each other. The unit may have a central shaft slidably mounted within the inner housing, and the upper end of the central shaft may include an outlet nozzle mounted in a turret. The sprinkler units provided herein also have filters for filtering water flowing through the units, and may have an inner valve means in a main through-passage for impeding the flow of water through the sprinkler unit until they are placed in a pop-up position or when the impact arm is clear of the outer body housing. Upon retraction, the inner valve means stops the flow of water thereby allowing the arm to move back into the turret before the inner housing lowers back into the outer housing. The sprinkler units provided herein enable uniform speed of rotation of the turret with different nozzles and flow rates, and provide relatively easy installation and removal for service. 
     Another embodiment of the invention includes a sprinkler unit with delayed activation. The unit may have an outer case formed with a fluid inlet that is in fluid communication with an interior region of the outer case. A rotatable closed-case turret assembly may be formed with a fluid outlet that is in communication with a central shaft having a lower end shaft portion extending into the interior region of the outer case. An extendable riser sleeve supporting the rotatable turret assembly may be slidably positioned within at least a portion of the interior region of the outer case. The riser sleeve includes a filter with at least one spring retainer extending through a slot formed along a sidewall portion of the riser sleeve, and a valve seat formed along a top portion of the filter that may selectively disengage from the lower end shaft portion of the central shaft to permit the flow of fluid from the interior region of the case into the central shaft. A delayed riser spring assembly may be further included having a first riser spring positioned between the spring retainer and a lower end portion of the riser sleeve, and a second riser spring positioned between the spring retainer and the upper end portion of the outer case. The first riser spring may be compressed when a fluid enters the interior region of the outer casing to move the riser sleeve in a relatively upward direction. The second riser spring may be compressed upon compression of the first riser spring to disengage the valve seat from the lower end shaft portion of the central shaft to permit the flow of fluid from within the interior region of the outer casing out through the fluid outlet. Additionally, the closed-case turret assembly may include an impact sprinkler assembly having an extendable impact arm. The impact arm, turret assembly and riser sleeve may combine to form a substantially continuous cylinder positioned within the interior region of the outer case. 
     It is a farther object of the invention to provide a closed-case impact sprinkler unit. An outer case may house a riser sleeve within the interior region of the outer case that is upwardly extendable from the outer case into a pop-up position. The riser sleeve may be formed with an external surface that is complimentary to the internal surface of the outer case to prevent the introduction of debris into the interior region of the outer case when the riser sleeve is in a pop-up position. In addition, a closed-case turret assembly may be rotatably positioned on the top end portion of the riser sleeve. The turret assembly may include a fluid outlet passageway in communication with the fluid inlet, and a hinged impact arm mounted within the turret assembly that interacts with water ejected from the fluid outlet passageway. Another variation of the sprinkler unit may include a hinged impact arm extendable beyond the turret assembly into an open position when impacted by a fluid that is ejected from the fluid outlet passageway. The unit may further include means for selectively permitting the flow of fluid into the fluid outlet passageway to extend the impact arm into an open position only when the riser sleeve is placed in a pop-up position. 
     A dual-stage sprinkler head is further provided in accordance with the concepts of the invention. The sprinkler head may include an outer sleeve having an interior chamber and a fluid inlet, and an inner sleeve having a fluid outlet that is slidably positioned in at least a portion of the interior chamber of the outer sleeve. The inner sleeve may include a slidably connected spring retainer connected to a valve assembly that selectively permits the passage of a fluid from the fluid inlet to the fluid outlet when moved relatively downward with respect to the inner sleeve. In addition, the sprinkler head may include a riser spring assembly having a first spring positioned between the spring retainer and a lower end portion of the inner sleeve, and a second spring positioned between the spring retainer and an upper end portion of the outer sleeve. The first spring may be compressed during a first stage as the inner sleeve rises when fluid enters from the fluid inlet into the interior chamber of the outer sleeve, and the second spring may be compressed during a second stage as the first spring moves towards a compressed state to move the spring retainer relatively downward with respect to the inner sleeve to permit the passage of fluid through the sprinkler unit. In addition, a turret may be rotatably mounted the top portion of the inner sleeve, and an impact arm may be rotatably mounted to the turret. The impact arm may selectively extend to an open position only during the second stage when the valve assembly permits the passage of fluid to the fluid outlet. Furthermore, the impact arm may be rotatably mounted to the turret with an off-centered hinge pin. An nozzle may direct fluid towards the impact arm wherein the nozzle includes a fluid vane positioned within its interior region to direct fluid flow out of the nozzle. 
     Another aspect of the invention provides an impact sprinkler head with extended sprinkling range. The sprinkler head may include an outer sleeve formed with an end opening and an internal surface having a fixed trip, and a trip collar rotatably mounted to the end opening of the outer sleeve, wherein the trip collar includes an adjustable trip. An impact sprinkler head and turret assembly may be rotatably connected to the trip collar having a trip assembly for reversing direction of the impact sprinkler head and turret assembly. The trip assembly may further include an elongated actuator opening, and a trip pin pivotally mounted within the actuator opening to provide lateral movement of the trip pin within the actuator opening to initiate a delayed reversal of the trip assembly upon contact with either the fixed or adjustable trip to provide an extended sprinkling range. It is a further object of the invention to provide a reversible drive sprinkler unit with a rotary drive that is a significant improvement over the well-known impact arm concept, and can drive the sprinkler through a desired arc of coverage. The sprinkler arc may be a full circle or a reversible partial circle with the arc of coverage being adjustable with control mechanisms provided herein. 
     With respect to yet another aspect of the invention, closed-case sprinkler units are provided herein with fitted fluid seal assemblies. Various fluid seal assemblies described herein may reduce the entry of grit and dirt into the waterstream within the unit. An embodiment of the invention provides a dirt resistant bearing system for a sprinkler unit with a rotatable turret having a central shaft extending into a support channel formed within an inner housing. The central shaft may be formed with a relatively upper shaft portion and a relatively lower shaft portion, and the support channel may be formed with an upper channel region and a lower channel region. A first bearing and sealing assembly may be fitted substantially around an outer perimeter of the upper shaft portion and in communication with the upper channel region, and a second bearing and sealing assembly may be fitted substantially around an outer perimeter of the lower shaft portion and in communication with the lower channel region. These bearing and sealing assemblies may include various combinations of sealing and bearing washers that promote a fluid seal between movable components within the sprinkler unit such as a support channel and a central turret shaft. The outer and inner diameter regions of the assemblies may be thus sealed under a water and/or spring load while supporting the rotatable turret shaft. 
     In yet another aspect of the invention, a sprinkler head is provided with a fitted serrated seal assembly. The fitted seal assembly may include an outer case having an interior region, and a pop-up sprinkler head turret mounted on a riser sleeve slidably mounted within the interior region of the outer case. The turret may be formed with an elongated central shaft for the passage of water. A water filter may be positioned within the riser sleeve having a valve stem for communication with a lower end portion of the central shaft. The communicating surfaces of the lower end portion of the central shaft and the valve stem of the water filter may be formed with complementary serrated surfaces. Additionally, the lower end portion of the shaft may be defined by or include a removable inlet nut with matching serrations within the inner perimeter of the nut portion for contact with a complementary surface surrounding an exterior portion of the water filter valve stem. 
     Other objects and advantages of the invention will become apparent upon further consideration of the specification and drawings. While the following description may contain many specific details describing particular embodiments of the invention, this should not be construed as limitations to the scope of the invention, but rather as an exemplification of preferable embodiments. For each aspect of the invention, many variations are possible as suggested herein that are known to those of ordinary skill in the art. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is an external view of a closed-case impact sprinkler unit formed in accordance with the invention that is shown in a retracted or closed position. 
     FIG. 2 is an external view of the sprinkler unit shown in FIG. 1 having an extended or open position. 
     FIG. 3A is a detailed cross-sectional view of a closed-case impact sprinkler unit in a substantially retracted position. 
     FIG. 3B is a detailed cross-sectional view of a sprinkler unit with a washer and bearing assembly formed in accordance with an aspect of the invention. 
     FIG. 4 is a relatively simplified cross-sectional view of a unit similarly shown in FIG. 3A in a slightly open or extended position. 
     FIG. 5 is a relatively simplified cross-sectional view of the unit shown in FIG. 4 in a substantially open or extended position. 
     FIGS. 6A-C are perspective views of an inner shaft and turret assembly that is configured for placement within the interior portion of an inner sprinkler housing or riser sleeve. 
     FIG. 7 shows various sized nozzle assemblies that may be used with the closed-case impact sprinklers provided herein. 
     FIGS. 8A-B are enlarged front elevation and cross-sectional views, respectively, of a nozzle housing assembly similarly shown in FIG.  7 . 
     FIGS. 9A-D are enlarged views of an impact arm and turret cover similarly shown in FIG.  7 . 
     FIGS. 10A-B are perspective views of a filter used in accordance with the closed-case impact sprinkler units described herein. 
     FIG. 10C is a perspective view of the bottom end portion of a closed-case sprinkler formed in accordance with another aspect of the invention that includes a filter positioned between a primary and a secondary riser spring. 
     FIGS. 10D-E are perspective views of a fitted seal formed between contacting serrated surfaces of an inlet cap and a filter included within the sprinkler units provided herein. 
     FIG. 11 is a front view of a reversing or trip mechanism shown in the forward and the reverse positions with respect to a turret housing portion. 
     FIGS. 12A-B show enlarged perspective views a position controller for providing a variety of sprinkling patterns including partial or full-circle reversible sprinkler operation. 
     FIG. 12C shows a relatively simplified enlarged perspective view of a trip collar and actuator assembly for various embodiments of the invention. 
     FIG. 12D shows an enlarged cut-away view of a trip actuator assembly formed in accordance with another aspect of the invention having an elongated pin opening that provides extended sprinkler rotation. 
     FIG. 12E illustrates a cut-away view of a trip actuator assembly similarly shown in FIG. 12D positioned within a trip collar. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Referring now to FIG. 1, there is shown an external view of a closed-case sprinkler unit  10  formed in accordance with the invention. The illustrated sprinkler unit  10  is in a closed or retracted position, and is at rest (quiescent) or non-operational in this condition. The sprinkler unit  10  generally includes an outer housing  12  that may be formed with a generally cylindrical shape or any other suitable configuration. The housing  12  is typically fabricated of ABS plastic or the like. A threaded retaining cap or cover  24  may be also attached to the top portion of the outer housing  12 , and may be formed with a plurality of flanges  24 A or similar gripping structures to facilitate handling of the cap when it is engaged to, or disengaged from, the outer housing. Additionally, the top portion of the sprinkler head unit  10  may include an optional protective cap cover  90  attached to a turret cover  39  that rests on top of an inner mounted turret positioned within the outer housing  12 . A wiper seal  19  may be retained within the unit  10  in between the retaining cap  24  and the turret cover  39  when the sprinkler head remains in a retracted position. The wiper seal  19  may substantially surround the slidably mounted turret within the outer housing  12 . 
     FIG. 2 provides an external view of the sprinkler unit  10  in an open or extended position. In this operating or pop-up position, a turret  40  is extended above the cap  24 , and the unit  10  is in a condition to spray water therefrom. The top portion of the turret  40  may be enclosed with the turret cover  39  which may, in turn, include the adjacent cap cover  90 . The top sidewall portion of the turret  40  may be formed with a nozzle opening  82 . Water may be ejected through the nozzle opening  82  from a nozzle  52  enclosed within the turret  40 . The sidewall of the turret  40  may further include a shield opening  81  through which an impact arm  100  extends when the unit  10  is operational or in a pop-up position. Additionally, an inner housing or riser sleeve  20  may be snugly, but slidably, surrounded by the wiper seal  19 . The inner housing  20  may be pushed in a relatively upward direction out of the outer housing  12  by the application of pressurized water or the like. Upon removal of the water source, the inner housing  20  may slidably move downward and return to a retracted position into the interior of the outer housing  12 . An inlet or opening (not shown) may be formed at the lower end of the outer sprinkler housing  12  to receive pressurized water from a source such as a network of underground pipes. Additionally, closed-case sprinkler units described herein may provide delayed activation. A unit may include an outer case formed with a fluid inlet that is in fluid communication with an interior region of the outer case. A rotatable closed-case turret assembly may be selected that is formed with a fluid outlet in communication with a central shaft having a lower end shaft portion that extends into the interior region of the outer case. An extendable riser sleeve, which supports the rotatable turret assembly, may be slidably positioned within the interior region of the outer case. Furthermore, the riser sleeve may include a filter with one or more spring retainers extending through a slot formed along a sidewall portion of the riser sleeve. A valve seat may be also formed along a top portion of the filter that may selectively disengage from the lower end shaft portion of the central shaft to permit the flow of fluid from the interior region of the case into the central shaft. In addition, a delayed riser spring assembly having a first riser spring may be positioned between the spring retainer and a lower end portion of the riser sleeve, and a second riser spring may be positioned between the spring retainer and the upper end portion of the outer case. The first riser spring may be compressed when a fluid enters the interior region of the outer casing to move the riser sleeve in a relatively upward direction, and the second riser spring may be subsequently compressed upon compression of the first riser spring to disengage the valve seat from the lower end shaft portion of the central shaft to permit the flow of fluid from within the interior region of the outer casing out through the fluid outlet. The closed-case turret assembly may also include an impact sprinkler assembly that is driven by fluid exiting the fluid outlet. Moreover, the impact sprinkler assembly may include an impact arm that is extendable beyond an external surface of the turret assembly when fluid exits the fluid outlet. The impact arm can be formed with an external surface that is complementary to an adjacent external surface of the turret assembly. The riser sleeve may be formed with an external surface so that the external surfaces of the impact arm, turret assembly and riser sleeve combine form a substantially continuous cylinder that may positioned within the interior region of the outer case. 
     FIG. 3A provides a relatively detailed cross-sectional diagram of a closed-case sprinkler head unit  10  formed in accordance with the invention. The sprinkler unit  10  may comprise an outer housing  12  having an inlet  14  formed at its lower end which may be threaded. The sprinkler head unit  10  may be thus threadably mounted to a riser or other suitable connection to a source of pressurized water (not shown). In addition, the outer housing  12  has an upper end that may include external threads for engagement or cooperation with internal threads formed on the interior of a retaining cap  24 . The retaining cap  24  may generally assist in retaining an axially extendable or extensible inner housing  20  within the interior or bore of the outer housing  12 . The cap  24  may further include an interior annular shoulder  28  that captures and retains a wiper seal  19  mounted within the central opening of the cap. The wiper seal  19  may be formed with a central bore  38  through which the inner housing or riser sleeve  20  selectively extends and retracts. Also, the wiper seal  19  may include a seat  34  in the form of an annular rim formed on the outer surface of the seal  19 . The seat  34  may be captured by or positioned relatively underneath the internal shoulder  28  of the retaining cap  24 . The seal  19  also includes an inner lip  36  adjacent to or relatively inward from the seat  34  which slidably engages the outer surface of the inner housing  20 . The lip  36  may provide a seal against water leakage around the inner housing  20 . Moreover, the seat  34  includes an annular groove  21  formed around its lower end or interior portion. The annular groove  21  retains an adjoining spring support lip  23  that projects upwardly from a spring retainer  25 . The lower surface of the spring retainer  25  may further include an annular groove or channel  27  to capture and retain the upper end of an elongated compression or riser spring  30 . As explained in more detail below, the riser spring  30  may be compressed when the inner housing  20  is moved relatively upward within the outer housing  12  when water is applied or introduced into the sprinkler unit  10 . The spring  30  may be thus positioned between the upper portion of a radially extending flange  22  formed at the lower end of the inner housing  20 , and the annular groove  27  formed along the bottom portion of the spring retainer  25  located near the upper end of the inner housing. The flange  22  may include one or more grooves  22 A along its periphery that slidably engage the ribs  18 . As a result, the inner housing  20  may be slidably, but not rotatably, mounted within the outer housing  12  in a relatively upward and downward direction. It is understood that the ribs and grooves may be reversed as to their respective locations along the inner housing  20  and the outer housings  12 . Additionally, the spring retainer  25  may include an elongated support leg  25 A that extends downwardly therefrom for slidable engagement with the outer surface of the inner housing or riser sleeve  20 . As a result, the spring retainer  25  and its elongated leg  25 A may also function as a guide for upward and downward movement of the inner housing  20 . The lower end of the elongated leg  25 A further operates as an upper limit stop that engages the section of a guide  113  surrounding at least a portion of a filter  49  that moves upwards and downwards with the lower end portion of the inner housing  20 . One or more ribs  18  may be formed on the inner surface of the outer housing  12  to aid in guiding and orienting the inner housing  20  within the outer housing. 
     A rotatable turret assembly may be further positioned within the inner housing  20 . The assembly may include a turret  40  mounted on a partially conical member  58  at the upper end of an elongated, central hollow shaft  44 . The shaft  44  may be rotatably mounted in a support channel  46  joined to the inner surface of inner housing  20  by an annular shoulder  48 . As will be described hereinafter, the shoulder  48  participates in the upward movement of the inner housing  20  when water or other fluid applies pressure thereto. The turret  40  in the illustrated embodiment may be covered by a circular cap  39  which has an aperture or cap opening  88  through which a radius adjusting screw  66  extends. A protective cover  90 , typically formed of hard rubber, santoprene or the like, may be mounted over the cap  39  and include a cover opening  92  for access to the radius adjusting screw  66  as illustrated. A toolcoupling slot  80  may be formed in the upper end of the adjusting screw  66 . The slot  80  may be configured as a screwdriver slot or a hex key-like slot for receiving a tool that rotates the radius adjusting screw  66 . 
     Additionally, a pressed-on bearing  71  may be mounted around the midportion of the central shaft  44 . The bearing  71  assists the central shaft  44  in rotating smoothly and easily within the cylindrical support channel  46 . An inlet cap  60  may be threadedly attached to the lower end of the central shaft  44 . Furthermore, a bearing stack  73  may be disposed around the shaft  44  intermediate the inlet cap  60  and the bearing  71 . The bearing stack  73  typically includes a plurality of separate annular bearings or washer-like components that may be formed with different hardness and frictional characteristics in order to facilitate rotation of the central shaft  44  without binding or undesired interference. A spring  73 A applies a load between the support channel  46  and a thrust load bearing  75  whereby the inlet cap  60  may be continuously vertically loaded. The thrust load bearing  75  may be generally cup-shaped and formed with a hole therethrough to accommodate the shaft  44 . An annular shoulder  77  formed along a portion of the shaft  44  may rest upon the bearing  75 . The edges of the bearing  75  may slidably and rotatably engage the upper end of the support channel  46  to restrict the flow of debris into the upper portion of the bearing  71 . 
     Furthermore, a filter  49  may be connected to a relatively lower end of the inner housing or riser sleeve  20 , and may be slidably movable therewith. The filter  49  may be generally configured as a basket that readily passes water therethrough while capturing particulate matter such as, but not limited to, sand, grass and the like. The entry of debris into the internal components of the unit is thus minimized that would otherwise cause blockage. The filter  49  typically includes at least one guide  113  formed along at least a portion of the side thereof to engage a groove  112  formed along the lower end surface of inner housing  20  in order to prevent rotation of the filter  49  relative to the inner housing, and to further control the relative movement of the filter within the outer housing  12 . The filter  49  may be thus slidably, but not rotatably, mounted to the inner housing  20  to move in a relatively upward or downward direction. The filter  49  may further include a valve stem  61  that extends vertically through the center thereof. A conically shaped valve seat  62  may be formed of deformable material such as hard rubber of the like, and may be attached to the relatively upper end of the valve stem  61  by a seal retainer  64 . The seal retainer  64  may be threadedly attached or friction fitted to the valve stem  61 . It will be seen that the valve seat  62  cooperates with the inlet cap  60  to prevent or restrict water passage until relatively upward movement of the filter  49  is stopped by the elongated support leg  25 A whereupon the internal valve assembly opens and the inlet cap  60  is disengaged from the valve seat to permit water to flow therethrough. When the leg  25 A or limit stop restricts the upward movement of the filter or screen  49 , the central shaft  44  may continue to move relatively upwardly along with the inner housing  20 . 
     A check valve may be formed between the filter  49  and the lower end portion of the outer housing  12  that consist of a suitable washer or gasket  29  positioned along the under side of the filter. The gasket  29  may be maintained in a relatively fixed position or place by a plurality of fingers  61 A which extend from the lower end of the valve stem  61  and below the lower surface of filter  49 . Accordingly, the overall sprinkler head unit generally forms a flow passage between the inlet  14  and an outlet  50 A formed in the detachably mounted nozzle assembly  50 . The check valve provided at the lower end of the inner housing  20  operates to selectively open and permit the flow of water through the filter  49 , and subsequently through a bore  56  formed within the central shaft  44  and the outward portion  58  extending relatively upward and outward at an angle near the turret  40 . The gasket  29  may further prevent fluid backflow into the inlet passageway  14 . When pressurized water is no longer supplied to the sprinkler unit, the inlet cap  60  moves toward a closed position with respect to the valve seat  62 , and the valve gasket  29  may be situated in a relatively closed position. In this condition, the sprinkler unit  10  may be fully closed wherein the valve assemblies sequentially close off the passage and potential flow of water through the unit. 
     FIG. 3B provides a cross-sectional view of a washer and bearing assembly for a sprinkler unit that is formed in accordance with another aspect of the invention. This grit or dirt resistant bearing system may include a rotatable turret  40  having a central shaft  44  extending into a support channel  46  formed within an inner housing or riser sleeve  20 . The central shaft  44  may be formed with a relatively upper shaft portion  44 X and a relatively lower shaft portion  44 Y. Moreover, the support channel  46  may be also formed with an upper channel region  46 X and a lower channel region  46 Y. The support channel  46  may be formed with a generally cylindrical configuration, and may be supported or mounted by a shoulder  48  within the inner housing  20 . Additionally, a first bearing and sealing assembly may be fitted substantially around an outer perimeter of the upper shaft portion  44 X and in communication with the upper channel region  46 X. A second bearing and sealing assembly may be also fitted substantially around an outer perimeter of the lower shaft portion  44 Y and in communication with the lower channel region  46 Y. 
     The first and second bearing and sealing assemblies may be formed between the central shaft  44  and the support channel  46  to provide a fluid seal while permitting rotatable movement. Each of the bearing and sealing assemblies may have any combination of one or more bearing or sealing washers. The central shaft  44  may be formed with a relatively upper shaft portion  44 X that includes an annular shoulder  77 . The first bearing and sealing assembly may be positioned in between the annular  77  shoulder and the upper channel region  46 X. The first assembly may include a load spring  73 A, a sealing washer  72 A, and a bearing washer  74 A. It may further include a cup-shaped thrust load bearing (not shown) as described above for housing at least a portion of the sealing washer  72 A and bearing washer  74 A. In a preferable embodiment, the bearing washer  74 A is positioned adjacent to the upper channel region  46 X to provide relatively low friction rotational movement of the central shaft  44  relative to the support channel  46 . At the same time, an inlet nut  60  may be selected wherein the second bearing and sealing assembly is positioned in between the inlet nut and the lower channel region  46 Y. The second bearing and sealing assembly may include a sand/grit shroud  76 , a sealing washer  72 B, and one or more bearing washers  74 B. The bearing washer  74 B may be also positioned adjacent to the lower channel region  46 Y. Sealing washers are preferably formed of a deformable material such as rubber or plastic to promote a water resistant seal. The first and the second bearing and sealing assemblies, and the components therein, may each include an aperture formed therethrough to permit passage of the central shaft. 
     In another embodiment of the invention, in combination with other aspects and combinations of the invention described herein, a closed-case impact sprinkler unit may be provided with a bearing/sealing washer system. The unit may be formed with an outer case having an interior region, and a riser sleeve formed with a top end portion and an internal support channel. The riser sleeve may be slidably positioned within the interior region of the outer case, and may be upwardly extendable into a pop-up position. A closed-case turret assembly for the passage of water may be rotatably positioned on the top end portion of the riser sleeve. The turret assembly may include a central shaft passing through the support channel of the riser sleeve. Additionally, a bearing and sealing washer system may be fitted around the central shaft in proximity to the support channel to provide rotatable movement and a dirt-resistant fit between the support channel and the central shaft. 
     The bearing and sealing washer system may include a first and a second washer assembly. Each assembly may provide a dust seal to prevent or minimize the entry of particulate or dirt into the waterstream within the central shaft. The support channel within the riser sleeve may include a relatively upper region and a relatively lower region, wherein the first washer assembly is positioned substantially adjacent to the upper region of the support channel, and the second washer assembly is positioned substantially adjacent to the lower region of the support channel. The bearing and sealing washer system may include at least one bearing washer and at least one sealing washer. A low-friction bearing washer may carry both radial and normal loads. The bearing washer may be preferably formed of a relatively low friction material such as Teflon, and the sealing washer may be formed of rubber. With respect to the first or top bearing and sealing washer assembly, a spring may be included within a shroud or thrust load bearing to urge the sealing washer in an interference fit with the shaft, and in constant sealing contact with a Teflon or low-friction bearing washer positioned below. With respect to the second or bottom bearing and sealing washer assembly, a sand/grit shroud may substantially house the bearing and sealing washers. The shroud may be an additional separate component or integrally formed with the support channel. A bearing washer may be positioned below the support channel to support relative movement of the shaft under load, and may be located above a sealing washer. A rubber sealing washer may be selected with an inner diameter that forms a seal with the central shaft to deter grit entry. Furthermore, an inlet nut may be secured to the central shaft with complementary threaded portions to secure the bearing and sealing washer assemblies to form an interference fit that minimizes the passage of dirt or obstructions into the fluid passageway within the central shaft. Under the resulting water pressure and spring load provided by this fitted fluid seal, the inner and the outer diameter portions of the washer assemblies may be effectively fluid sealed at either end of the support channel while permitting free rotational movement of the sprinkler turret assembly. 
     FIGS. 4-5 illustrate a sprinkler unit  10  provided in accordance with the invention that is shown in relatively simplified cross-sectional view. After pressurized water is supplied through an inlet  14 , as shown in FIG. 4, a relatively non-rotating inner housing  20 , together with a filter  49 , is upwardly movable within an outer housing  12 . A turret  40  similarly moves with the inner housing  20  upwardly and out of the outer housing  12 . However, an internal shut-off valve seat  62  momentarily remains in a relatively closed position so water does not flow through an internal conduit within the central shaft  44 . This valve assembly remains closed inasmuch as the water pressure on the shoulder  48  of an adjoining support channel  46  containing the central shaft  44  is substantially the same as on the interior of a valve stem  61  within the filter  49 . The inner housing  20  and the filter  49  thus move upwardly together. The central hollow shaft  44  is also moved upwardly while the valve seat  62  and an inlet cap  60  remain in sealing contact to delay the flow of water. Water flow through the sprinkler  10  and the valve seat  62  is prevented or delayed until the turret  40  and the impact arm located therein have extended beyond and cleared out of the outer housing  12 . This prevents premature and inadvertent opening of the impact arm which may lead to unit malfunction. When the water flow is removed, the flow of water towards the turret  40  is cut-off so as to permit retraction of the impact arm before the inner housing  20  returns to the interior portion of the outer housing  12 . 
     Referring now to FIG. 5, the sprinkler unit  10  is illustrated in a substantially extended or pop-up position after pressurized water is introduced through the inlet  14 . The force of incoming water forces the inner housing  20  to extend relatively upward and out of the outer housing  12 . When the water pressure increases to the point where a guide surface  113  of the filter  49  contacts the limit stop surface  25 A of retainer the  25 , the internal valve assembly may be opened in order to allow water to flow freely into the central shaft  44  towards a nozzle  52 . Meanwhile, the riser spring  30  may be thus compressed between spring latches such as a flange  22  and a spring retainer  25 . The inner housing  20  therefore remains biased to move downwardly and back into outer housing  12  when water pressure is removed and the flow turned off by an operator to stop water from entering into the sprinkler unit  10 . In a substantially extended position, the water flow pathway through the unit  10  begins at the inlet  14 , through the filter  49 , through the opened internal shut-off valve assembly, through the central shaft  44 , and through its adjoining offset channel  58  which may further include a vane  79  to reduce turbulence of water that eventually passes and exits through the nozzle  52 . 
     Referring now to FIG. 6A-C, there are shown perspective views of a central shaft  44  and an integrally attached turret  40 . As shown in FIG. 6A, the central shaft  44  may include a through bore or conduit  56  for carrying fluids from the inlet of the sprinkler unit towards the outlet nozzle. The shaft  44  may be generally cylindrical with a reduced central portion  44 A at approximately the midpoint thereof The relatively smaller diameter for this reduced portion  44 A may reduce the friction between the shaft  44  and surrounding inner housing  20 . A shoulder  77  may be also provided along a portion of the shaft  44  relatively upward with respect to the reduced central portion  44 A. The shoulder  77  may be supported by a load bearing as described above. The central shaft  44  may further include an offset channel or vane housing  58  that is generally cylindrical but includes a tapered lower extremity and, consequently, a somewhat oblong or oval shape at the other end thereof The upper end of the vane housing  58  may be joined or integrally connected to the relatively lower or bottom portion of the turret  40 . One or more openings  41  may be formed along the bottom portion of the turret housing  40  to receive and engage locking tabs formed along the outer surface of internally mounted nozzle assembly. The turret  40  may also include a trip dog opening or window  42  that receives a portion of a trip dog reversing mechanism. In addition, the turret  40  may be formed with a substantially cylindrical configuration having a central axis or midpoint that is axially aligned with the center line of the conduit  56  and an inlet for the sprinkler unit. A relatively large shield opening  81  may be also formed along the surface of the turret  40  that comprises approximately 30% of its outer surface area. The shield opening may be arranged to receive a shield portion of an adjoining impact arm for the sprinkler unit. Additionally, a relatively smaller nozzle aperture  82  may be formed along the outer surface of the turret  40 , and may be aligned with the center line of the vane housing  58 . The nozzle aperture or opening  82  may be aligned with a nozzle so that fluid passing through central shaft  44  may exit the nozzle and pass through the nozzle opening. A small aperture  88  may be further provided along the relatively upper surface of the turret  40  that is adapted to receive a threaded spray adjusting device which may typically take the form of a set-screw with a needle-like end. 
     Referring now to FIG. 6B, there is shown another perspective view of the inner shaft  44  and the turret  40  attached thereto. This view is slightly rotated relative to illustration of FIG. 6A in order to illustrate an interior portion of the turret  40  and certain components configured for a trip dog reversing mechanism. As previously described, the central shaft  44  may include a through bore or conduit  56  for carrying fluids from the inlet of the sprinkler unit and eventually out of the unit through a nozzle opening  82 . The shaft  44  may include the generally cylindrical vane housing  58  with a tapered lower extremity for receiving fluid directing vanes. The relatively upper end of the vane housing  58  may be joined to the bottom portion of the turret  40 . Moreover, a trip dog opening  42  is similarly depicted that receives a portion of. the trip dog. A skirt  83  may be formed adjacent to the vane housing  58 . The turret housing  40  and the skirt  83  may be integrally formed if so desired. Additionally, a trip actuator pivot pin  84 , shown as a split pin, may be formed along the surface of the skirt  83  to support a trip actuator as part of the direction reversing mechanism for the sprinkler unit. Similarly, a trip dog pivot pin  85 , for supporting a trip dog, may be provided along the bottom surface of the turret  40  in proximity to the skirt  83 . 
     FIG. 6C provides a partial cut-away section of the turret  40  and the central shaft  44  similarly shown in FIGS. 6A-B. The plurality of openings  41  formed along the bottom portion of the turret housing  40  may receive and engage locking tabs on the outer surface of a nozzle assembly (not shown) that is positioned within an assembly cavity  56 A. The turret  40  also includes the trip dog opening or window  42  that receives a portion of a trip dog reversing mechanism. The relatively large shield opening  81  formed along the surface of the turret  40  receives the shield portion of an adjoining impact arm. The split trip actuator pivot pin  84  may be formed along the surface of the skirt  83 , and the trip dog pivot pin  85  may be also provided along the bottom surface of the turret  40 . Additionally, an inner surface  114  within the turret housing  40  may be opened, angled and channeled to further wipe and flush out to harmlessly any debris or particulate that may bypass a wiper seal lip or protective shield covering the shield opening  81 . The flushed surface  114  eliminates or minimizes the accumulation of debris that may be trapped within the sprinkler unit as with prior art designs. 
     A closed-case impact sprinkler unit may be thus provided that includes a riser sleeve formed with a top end portion slidably positioned within the interior region of an outer case that is upwardly extendable from the outer case into a pop-up position. The riser sleeve may be formed with an external surface that is complimentary to the internal surface of the outer case to prevent the introduction of debris into the interior region of the outer case when the riser sleeve is in a pop-up position. Furthermore, the unit may include a closed-case turret assembly as described above that is rotatably positioned on the top end portion of the riser sleeve. The turret assembly may include a fluid outlet passageway in communication with the fluid inlet, and a hinged impact arm mounted within the turret assembly that interacts with water ejected from the fluid outlet passageway. The hinged impact arm may be extendable beyond the external surface of the turret assembly into an open position when impacted by a fluid that ejected from the fluid outlet passageway. The riser sleeve and the closed-case turret assembly may be formed with external surfaces that provide a generally cylindrical shape that is complimentary to the inner surface of the outer case and formed with a generally cylindrical shape. The unit may also include means for selectively permitting the flow of fluid into the fluid outlet passageway to extend the impact arm into an open position only when the riser sleeve is placed in a pop-up position. 
     FIG. 7 illustrates a variety of nozzle housing and impact arm assemblies that may include small, medium and large sized nozzle passageways. A nozzle  52  may be attached to a nozzle support assembly or housing  50  with any suitable means, preferably by a bayonet type attachment to provide angular alignment of the nozzle to an impact arm  100 . The position of a nozzle passageway  116  may vary according to the selected nozzle size and may be positioned slightly off center with respect to the nozzle  52 . An offset nozzle passageway  116  may direct the nozzle stream into a serpentine passage along the impact arm  100  to a lesser degree in high gallonage, large nozzles, and to a greater degree in low gallonage, small nozzles, thereby controlling the reaction force imparted on the arm by the nozzle stream. This controlled reaction force generally provides a more uniform rotation speed in sprinklers of differing nozzle sizes for more precise sprinkler distance of throw and application rate. The flow-management arrangement for the sprinkler unit embodiments of the invention described herein selectively provide the flow of water through a selective nozzle for any desired flow control purpose. 
     Referring now to FIG. 8A, there is shown a front elevation view of a nozzle support assembly. A nozzle support  50  may be formed with a generally cylindrical configuration, and may include a plurality of side tabs  51  that are adapted to engage corresponding openings formed along the lower surface of a turret housing as described herein. A slot  115  may be formed along the nozzle housing  50  to receive bayonet tabs located on the outer surface of a mounted nozzle  52 . Referring now to FIG. 8B, there is shown a cross-sectional view of the sprinkler attachment shown in FIG. 8A taken along the lines A—A. A lip  53  may be formed at the relatively rearward portion of the nozzle head support  50  similar to the tabs  51  so as to interact with openings formed in the lower surface of the turret. Referring concurrently to FIGS. 8A-B, there is shown a central vane  79  which extends below the lower end of the nozzle support or housing  50  that substantially conforms to the configuration of the angled end or offset portion of a central shaft or tube extending below the turret. The vane  79  may include a forward wall or surface  78 , as shown in FIG. 8B, adapted to co-act with the inner surface of the nozzle housing  50  to form a channel which forces water or other fluid into the nozzle  52 . The wall  78  may be angled to create a directional path for the water flowing from the central shaft or tube and out of the nozzle  52 . Additionally, plurality of lateral vanes  79 A (three of which are shown in this embodiment) may be also formed on the upper end of the vane  79  so as to interact with the wall  78  and the inner surface of nozzle housing  50  to effectively reduce turbulence through the housing and create a more uniform flow through the nozzle  52  and nozzle passageway  116 . 
     FIGS. 9A-D provide various view of a compact impact arm  100  provided in accordance with the invention. A serpentine path or flow redirection tube  99  formed in the impact arm  100  interruptively redirects water flow ejected from an adjacent nozzle to provide a counter-rotating moment to the sprinkler arm relative to a turret. Additionally, the serpentine path  99  may provide a time delay to the counter-rotating moment which allows the impact arm  100  to re-enter the water stream path of the nozzle and to impact the turret to provide a force to intermittently rotate the turret relative to an inner housing of the sprinkler unit. The impact arm  100  may further include a shield  95  that closes a shield opening formed in the turret to prevent debris from entering the sprinkler unit and its upper housing area such as when the turret passes a wiper seal lip near a debris contaminated region at the soil surface. When the water stream from the nozzle strikes the serpentine path  99 , the impact arm  100  rotates around an offset fulcrum pin positioned within a pin sleeve bearing  91  formed in the impact head. By using the offset fulcrum, the sprinkler unit may include a relatively long impact arm and a smaller overall diameter in comparison to conventional impact sprinklers with a center mounted impact arm. Referring now to FIG. 9A, there is shown one elevation view of the impact arm  100 . In this view, the shield  95  is shown adjacent to the fulcrum sleeve bearing  91 . As will be seen, the sleeve bearing  91  and the shield  95  may be integral portions of the impact arm  100 . The impact arm  100  and sleeve bearing  91  may rotate around a fulcrum pin. Furthermore, the shield  95  may be adapted to effectively close the shield opening in the turret when the sprinkler unit is not operative. The shield  95  is effective in excluding sand, grass and other debris from entering the turret. A directional tab  102  may extend outwardly from the arm  100  to selectively interact with a trip dog directional mechanism. Referring now to FIG. 9B, there is shown a partially broken away, interior bottom plan view of the impact arm  100  when viewed relatively upwardly from the inlet end of the unit. The fulcrum sleeve  91  may be a hollow cylinder mounted about the fulcrum pin. The sleeve  91  may be joined to a support arm  93  which is connected to the impact shield  95  by connecting struts  96  and  97 , as well as arcuate walls  98  and  98 A. The serpentine path  99  may be defined by this series of walls together with an upper surface  101  and a lower surface, which may be referred to as a porting or exhaust tube, to perform the functions previously described. Referring to FIG. 9C, there is shown a top plan view of the impact arm  100 . The support arm  93  may be joined to the sleeve  91  as well as the struts  96  and  97  as shown in FIG. 9B. A bottom surface  103  of the serpentine path  99  may be integrally formed with the struts  96  and  97 . A central opening  105  may be formed to reduce the wall section of the impact arm for molding as well as to reduce the cost of materials and the like. Referring to FIG. 9D, there is shown a partially broken away, elevation view of the impact arm  100  rotated by 90° around the centerline thereof relative to FIG.  9 A. In FIG. 9D, the serpentine tube  99  is shown as defined by the serpentine walls  98  and  98 A together with the lower surface  103 . The upper surface  101  however is omitted in this view, and the sleeve  91  is depicted as joined to the support arm  93 . It should be noted that the ends of both serpentine wall  98  and  98 A may be tapered into or shaped into a fairly sharp edge in order to properly interact with the water stream from the nozzle. 
     Referring now to FIGS. 10A-B, there are shown perspective views of a filter  49  for sprinkler units described herein. The filter  49  may be typically formed as a porous, basket-like component with a plurality of side openings  47  formed along its outer surface, and upper openings  54  along its upper planar surface  49 B. The side openings  47  and upper openings  54  in the filter may be large enough to readily pass water or the like therethrough while filtering out most particulate matter. This action minimizes or prevents clogging of a sprinkler unit nozzle. The filter  49  may be readily cleaned, when necessary, by merely removing the inner housing from the outer housing of a unit thus exposing the filter. Additionally, a valve stem  61  may be attached to the filter  49 . A reverse flow valve seat  62  may be also attached to the upper end of the valve stem  61  by a seal retainer  64 . The valve seat  62 , which may be conically shaped, and the valve stem  64  may interact with an inlet cap attached to a central shaft within the inner housing of the unit. A check valve gasket  29  may be secured to the lower end of the valve stem  61  by extensions or fingers  61 A. The top surface  49 B of the filter  49  may contact a limit stopping surface just prior to the inner housing reaching the top of its stroke. Following contact, the valve seat  62  may be forced away from the inlet nut or cap thus opening the valve assembly. While the filter  49  is being forced away from the inlet nut, it may be continuously guided by its sides  49 A acting on guide surfaces formed along the inner housing. 
     In another embodiment of the invention, as shown in FIG. 10C, the filter  49  may be positioned between multiple riser springs  107  and  109 . A primary riser spring  107  and a secondary riser spring  109  may be selected for the sprinkler units provided herein to control the opening of the valve assembly and the relative movement of the inner housing  20  within the outer housing. The primary riser or retract spring  107  may be positioned in between a spring retainer near the top portion of the outer housing and a plurality of spring arms  108  formed along the sides of the filter  49 . The spring arms  108  may slidably fit within a series of slots or cut-outs formed along the lower portion of the riser sleeve  20  to permit relatively upward and downward movement within a preselected range. A retaining lip  108 A may be formed along the edges of the spring arms  108  to assist in retaining the primary riser spring  107  which is slidably fitted around the external surface of the riser sleeve  20 . The secondary spring  109  may be also retained in between the spring arm  108 , which may be integrally formed with the filter  49 , and a removable disk-shaped end cap or nut  60  that may be attached to the lower end of the inner housing or riser sleeve  20  with a twist-lock fit. As water enters the sprinkler unit causing the inner housing or sleeve  20  to rise, the primary riser spring  107  begins to compress and move towards a more solid-type configuration. Meanwhile, the secondary riser spring  109  or valve shut-offspring operates to temporarily prevent water from entering through the inlet cap  60  providing a positive seal so the sleeve  20  is permitted to rise while delaying extension of the impact arm. At least initially, the secondary spring force is greater than the primary spring force. However, as the primary spring  107  contracts and begins to exert a greater force against the secondary spring  109 , the secondary spring begins to compress. The valve seat  62  therefore moves away from the inlet nut or cap  60  thus opening the valve assembly. The relatively upward force applied by the secondary spring  109  is initially greater than the relatively downward force applied by the primary spring  107  when the inner sleeve  20  is rising. As the primary retracting spring  107  goes solid, it exerts a greater downward force that pushes against the filter  49  to open the valve assembly. The time-delay caused by the opposing forces of the multi-spring configuration described herein permit the two-stage activation of the sprinkler units provided herein. It is understood that the appropriate selection of riser spring combinations may be readily determined based upon known characteristics for the springs including their spring constants, selected lengths and their composition. 
     A dual-stage sprinkler head may be thus provided in accordance with the invention that basically comprises an outer sleeve, an inner sleeve and a riser spring assembly. The outer sleeve may be formed with an interior chamber and a fluid inlet for receiving a supply of water. The inner sleeve may be formed with a fluid outlet, and may be slidably positioned in the interior chamber of the outer sleeve. In addition, the inner sleeve may include a slidably connected spring retainer that is connected to a valve assembly. The valve assembly may selectively permit the passage of a fluid from the fluid inlet to the fluid outlet when moved relatively downward with respect to the inner sleeve. In addition, the valve assembly includes a water filter having a valve seat. The interior portion of the inner sleeve may include a central shaft with a end section that is configured to engage the valve seat as fluid enters the interior chamber of the sleeve, and to disengage the valve seat as the spring retainer moves relatively downward with respect to the inner sleeve. The water filter may include the spring retainer for retaining an end portion of the first spring and an end portion of the second spring. At the same time, the lower end portion of the inner sleeve may include a spring retainer for retaining an end portion of the first spring, and the upper end portion of the outer sleeve may include a spring retainer for retaining an end portion of the second spring. Furthermore, the riser spring assembly include a first spring positioned between the spring retainer and a lower end portion of the inner sleeve, and a second spring positioned between the spring retainer and an upper end portion of the outer sleeve. The first spring may be compressed during a first stage as the inner sleeve rises when fluid enters from the fluid inlet into the interior chamber of the outer sleeve, and the second spring may be compressed during a second stage as the first spring moves towards a compressed state to move the spring retainer relatively downward with respect to the inner sleeve to permit the passage of fluid through the sprinkler unit. Additionally, a turret may be rotatably mounted the top portion of the inner sleeve as described herein. An impact arm may be rotatably mounted to the turret with a hinge pin to selectively extend to an open position only during the second stage when the valve assembly permits the passage of fluid to the fluid outlet. The length of the impact arm may be maximized by mounting it with an off-centered hinge pin as opposed to a centrally mounted pin which would provide a reduced water throwing range for the sprinkler head. Furthermore, a nozzle may be positioned within the turret that is connected to the fluid outlet. The nozzle may be formed with an interior region that includes a fluid vane to direct fluid flow out of the nozzle. The fluid vane may include a plurality of fluid-directing surfaces to direct the flow of fluid ejected from the nozzle. 
     FIGS. 10D-E illustrate a fitted seal formed between contacting surfaces of an inlet cap  60  and a filter  49  included within the sprinkler units provided herein. In a preferable embodiment of the invention, a sprinkler head (not shown) is provided with a fitted serrated fluid seal assembly. The head may include an outer case having an interior region, and a pop-up sprinkler head turret mounted on a riser sleeve slidably mounted within the interior region of the outer case. The turret may be formed with an elongated central shaft for the passage of water. Additionally, a water filter  49  within the riser sleeve may include a valve stem  61  for communication with a lower end portion of the central shaft which may include an inlet nut  60 . The communicating surfaces of the lower end portion of the central shaft and the valve stem  61  of the water filter  49  are each formed with complementary serrated surfaces. Each of the serrated surfaces may be formed with a variety of matching surfaces including complementary tapered edges  60 A and  61 A. The serrated surface  61 A of the water filter  61  may also include a plurality of serrations, wherein at least one of the serrations  63  is relatively larger that the other serrations as shown with greater particularity in FIG.  10 E. 
     In a preferable embodiment of the invention, a pair of relatively larger serrations are positioned around a substantially circular diameter along an external surface  61 A surrounding the valve stem  61  of the water filter  49 . The pair of relatively larger serrations may be positioned approximately  180  degrees across from each other. These larger formations create an intended gap between the water filter  49  and the serrated inlet nut surface  60 A so that water within the fluid passageway of a central shaft may properly drain. In some instances, with other valve configurations provided herein, deformable fluid seals and valve seats may be excessively deformed over an extended period of time. As a result, the valve seat may become stuck within the inlet nut interior which prevents water from properly draining out of the fluid passageway within the central shaft. This may keep the sprinkler unit in an unintended pop-up position. With proper drainage, water may thus bleed-out by selecting a larger serration or by removing or eliminating a serration to provide the desired drainage gap. 
     The serrated seal configuration illustrated in FIGS. 10D-E further prevent the relative movement of the central shaft and connected turret assembly when the sprinkler unit is in a retracted position. The serrations form a lock-type fit or keyed arrangement that prevents the turret and/or the adjustable collar from unintended adjustment or acts of vandalism when the unit is not in a pop-up position. This serrated fluid seal configuration provides a wet-type of adjustment wherein the sprinkling range can be readily altered when the unit is operational. A dry-type of adjustment may be also provided when the unit is non-operational. When the flow of water is interrupted, the sprinkler riser assembly may be manually popped up by an operator with selected tooling such as a pull-up socket. 
     Referring now to FIG. 11, there is shown a partial view of a turret  40  together with a view of a reversing mechanism for the instant invention. As previously described herein, a skirt  83  may extend downwardly from the bottom of the turret  40 . A trip actuator  86  may be pivotally mounted on a actuator pivot pin  84  while a trip dog  87  is pivotally mounted on a trip dog pivot pin  85 . The pivot pins may be formed on or integral with the skirt  83 . A spring  89  such as a torsion spring may be connected between adjacent ends of the trip actuator  86  and the trip dog  87 . In operation, the trip dog  87  and actuator  86  may assume two different stable positions as shown by the solid line (position  1 ) and the dashed line (position  2 ). In position  1 , the trips  86  and  87  are shown in a “sprinkler reverse” condition. The trip mechanism has just finished rotating in the counter clockwise direction shown by the arrows  110 . That is, the trip actuator  86  has been rotated counter clockwise causing the spring  89  to go “over center” which the rotates trip dog  87  counter clockwise into a “sprinkler reverse position.” In position  1 , the trip dog  87  captures a trip tab  102  which may be formed as part of a sprinkler arm. In position  2 , the trip actuator  86  may be rotated clockwise causing the spring  89  to again go “over center” causing the trip dog  87  to rotate clockwise out of engagement with the tab  102  of the impact arm  100 . In this position of the trip dog  87 , the sprinkler unit is in the “forward” running condition. To move from position  1  to position  2 , the trip actuator  86  may rotate about its pivot pin  84  in the clockwise direction as shown by arrows  111 . This action initially causes the trip spring  89  to compress, until it goes “over center.” The spring  89  then expands thereby driving the trip dog  87  to the next stable condition in position  2  as shown by the dashed line. It will be noted that the spring  89  is biased to separate the trip dog lever  87  from the trip actuator lever  86 . A trip collar may act on the lower arm of the trip actuator  86  to cause the spring  89  to compress and to initiate the switching between positions  1  to  2 . 
     Referring concurrently now to FIGS. 12A-C, there is shown a position controller for determining two potential operation conditions of the unit such as forward/reverse or forward only. During the forward/reverse sprinkler rotation, the directional tab  102  of an impact arm  100  may alternately contact a reversing pawl  120  on the trip dog  87  when the sprinkler is to be driven in the reverse directions. That is, an arm biasing cam  106  selectively positions the impact arm  100  in one of two axial locations above the reversing pawl  120 . In position  1 , the arm  100  may be allowed to changeably contact the reversing tab or pawl  120  providing a “part circle” sprinkler operating condition. In position  2 , the arm  100  may be held above the reversing pawl  120  by a cam  106  such that reversing pawl can no longer contact the arm  100  effectively locking sprinkler unit in a “full only” operating condition. 
     Referring now to FIG. 12A, there is shown a partial view of the components of a turret  40  and, in particular, the adjustment mechanism for converting the sprinkler unit from a partial circle operation to a full circle only operation. The sprinkler may be initially set in a partial circuit configuration. Thus, the trip dog  87  extends through an aperture formed in the lower surface of the cut-away turret as shown and is effective to capture the tab  102  of the impact arm  100  during rotation of the turret. The position of tab  102  is controlled by the position or location of the impact arm  100 . The cam  106  may include a cam surface  106 A which is formed on an inner surface of the turret. The cam  106  may include a circular, inclined plane at its upper surface. A movable cam plate  106 B may be attached to a fulcrum pin  45  and rest on the surface of the cam surface  106 A. The cam plate  106 B has a circular, inclined plane surface which cooperates with the inclined plane surface on the cam surface  106 A. The fulcrum pin  45  may extend through the upper surface of the turret as well as the unit covering. The fulcrum pin  45  may further include a slot  45 A formed in the upper end thereof for easy manipulation thereof by a screw driver or the like. The fulcrum pin  45  may be rotated counterclockwise so that the mating surfaces of the cam surface  106 A and the cam plate  106 B achieve the illustrated position or any other. In this case, the high points of the two cam surfaces are adjacent to each other wherein the cam has attained the least vertical dimension. In this case, the arm  100  is in the position shown wherein the tab  102  is capable of engaging the trip dog  87 . 
     As shown in FIG. 12B, the fulcrum pin  45  may be rotated counterclockwise. This causes the fulcrum pin  45  to drive the cam plate  106 B which is attached thereto in the counterclockwise direction as well. In this case, the inclined planes of the cam surface  106 A and the cam plate  106 B slide relative to each other wherein the high points of the respective cam components are in abutment with each other so that the cam  106  achieves the highest or greatest vertical dimension. Inasmuch as the impact arm  100  is attached to the fulcrum pin  45 , which is raised when the cam operation occurs, the arm  100  is also raised. The distance the arm  100  is raised is designed to be sufficient to prevent tab  102  from engaging trip dog  87  even when the trip dog is in the upright position. Inasmuch as tab  102  cannot interact with and be restrained by the trip dog  87 , the arm  100  is free to rotate 360° around the fulcrum pin  45  and to produce a full 360° circular spray pattern for the sprinkler. Of course, when the partial circle pattern is desired, the fulcrum pin  45  is merely rotated counter-clockwise to return the fulcrum pin  45 , the cam  106  and the arm  100  to a position similarly shown in FIG.  12 A. 
     As shown in FIG. 12C, while the impact arm is driven rotationally around the fulcrum pin, and the sprinkler turret housing  40  may be driven first in a clockwise direction until a trip adjustable tab  123  interacts with the leg of the trip actuator  86  thereby causing the sprinkler to “trip” and change direction. As sprinkler turret housing  40  rotates in the counterclockwise direction, the trip actuator leg  86  may contact a fixed trip tab  121  causing the sprinkler to “trip” and again rotate in a clockwise direction. 
     FIG. 12D is an illustration a trip actuator assembly  122  formed in accordance with another aspect of the invention. The trip actuator and dog assembly may be connected to the turret  40  as shown in relatively close proximity to a nozzle housing  50 . A trip spring  87  may be selected to connect the trip dog  87  and the trip actuator  86  which are mounted about their respective pivot pins  85  and  84 . The trip actuator  86  may include a trip pin or leg  125  pivotally mounted within an elongated trip actuator opening  124 . The pin  125  may be connected to the trip actuator opening  124  in a ball and socket joint relationship. The interior surface of the actuator opening  124  may include a raised surface  126  that interacts with a complementary shaped surface formed along the external surface of the pin  125 . As a result, the pin  125  may pivotally move in a relatively lateral direction along the width of the opening  124 . The added lateral or wiggle movement provided by the elongated or widened configuration of the trip actuator slot  124  provides extended sprinkler rotation. When the trip pin  125  contacts a trip tab to reverse sprinkling rotation, the reversal mechanism is not immediately activated. Watering and rotation in the same direction continues for an additional period of time provided by the movable trip pin  125 . After the turret  40  rotates a few additional degrees or more during this period of lost motion, the trip pin  125  finally reaches the side edge of the actuator opening  124  which reverses the trip actuator to its other position. The additional freedom of movement provided to the trip pin  125  as described herein provides an extended or full 360 degree watering range. 
     Another aspect of the invention described in FIG. 12E is directed to an adjustable collar  127  for directing the sprinkling range. As shown in the cutaway section of the inner housing  20  and central shaft  44 , the underside of the turret  40  is revealed to illustrate the trip mechanism for the sprinkler unit that reverses direction of the rotating turret. The upper portion of the inner housing  20  may include a relatively fixed trip or ledge  121  that extends into its interior portion. The fixed trip  121  may be configured to contact a trip pin  125  loosely connected within the trip actuator opening  124  as described herein. This lost motion trip pin  125  may move between the fixed trip  121  and an adjustable trip or ledge  123  formed with the rotatable trip collar  127 . The trip collar or ring  127  may be rotatably mounted between the inner sleeve  20  and turret section, and may be set for a particular sprinkling pattern. The desired sprinkling pattern may generally correspond to a displayed identification scheme set forth on the external surface of the trip collar  127  and inner housing  20 . The identification scheme may include a variety of visible markers on the collar so that an operator may set a sprinkling pattern ranging from 0 to 360 degrees or any multiple thereof such as every 90, 180 or 270 degrees. A number of dashes or marks  128  may also denote a pattern divided in intervals of 90 degrees. For example, a setting for a single mark  128  may provide 90 degrees while a setting four marks may provide a 360 degrees pattern. A reference mark to line-up with a desired setting may be of course formed on the external surface of inner housing or riser sleeve  20 . The trip collar  127  may further include “+” or “−” symbol  129  with an arrow to denote an increase or decrease in the spraying pattern respectively if rotated in the indicated direction. When a desired 360 degree spraying pattern is desired, the trip collar  127  may be rotated to increase the setting so the adjustable trip  123  is placed immediately adjacent to the fixed trip  121 . The identification scheme may have a corresponding setting of four marks  128  that are lined up with the reference mark. As a result, the trip pin  125  travels substantially in a full circle with the turret  40  before the trip pin contacts a fixed  121  or an adjustable  123  trip. The degree of added lateral movement of the trip pin  125  may account for the otherwise lost rotation of the trip pin and turret  40  caused by the combined thickness of the trip pins  121  and  123 . Because the trip pin  125  is pivotally and slidably mounted within the trip actuator opening  124 , the turret  40  may continue rotating in an original direction for an additional few degrees before tripping the reversing mechanism and thereafter rotating in an opposite direction. This added range of free movement is provided by the wiggle room or play that results from the pivotally mounted trip pin  125 . A fuller sprinkling range of 360 degrees may be thus achieved. It shall be understood that any desired sprinkling range may be set for the sprinkler units provided herein by adjusting the trip collar accordingly. An impact sprinkler head with extended sprinkling range may be therefore provided in accordance with the invention having a trip collar formed with an adjustable trip that is rotatably mounted to the top end of an outer sleeve. The sprinkler head may include a impact sprinkler head and turret assembly rotatably connected to the trip collar having a trip assembly for reversing direction of the impact sprinkler head and turret assembly. The trip assembly may include an elongated actuator opening and a trip pin pivotally mounted within the actuator opening to provide lateral movement of the trip pin within the actuator opening to initiate a delayed reversal of the trip assembly upon contact with a fixed or adjustable trip to provide an extended sprinkling range. 
     While the present invention has been described with reference to the aforementioned applications explained in detail above, these descriptions and illustrations of the preferred embodiments and methods are not meant to be construed in a limiting sense. It shall be understood that all aspects of the present invention are not limited to the specific depictions, configurations or relative proportions set forth herein which depend upon a variety of conditions and variables. Various modifications in form and detail of the various embodiments of the disclosed invention, as well as other variations of the present invention, will be apparent to a person skilled in the art upon reference to the present disclosure. It is therefore contemplated that the appended claims shall cover any such modifications, variations or equivalents of the described embodiments as falling within the true spirit and scope of the present invention.