Patent Publication Number: US-10786823-B2

Title: Reversing mechanism for an irrigation sprinkler with a reversing gear drive

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application is a continuation application of U.S. patent application Ser. No. 14/801,654, filed Jul. 16, 2015, and entitled “REVERSING MECHANISM FOR AN IRRIGATION SPRINKLER WITH A REVERSING GEAR DRIVE.” This application is also related to U.S. patent application Ser. No. 13/925,578, filed Jun. 24, 2013, now U.S. Pat. No. 8,955,768, to U.S. patent application Ser. No. 12/710,265, filed Feb. 22, 2010, now U.S. Pat. No. 8,469,288, and to U.S. patent application Ser. No. 11/761,911 filed Jun. 12, 2007, now U.S. Pat. No. 7,677,469. The entire contents of the above applications are hereby incorporated by reference and made a part of this specification. Any and all priority claims identified in the Application Data Sheet, or any correction thereto, are hereby incorporated by reference under 37 CFR § 1.57. 
    
    
     FIELD OF THE INVENTIONS 
     The present inventions relate to apparatus for irrigating turf and landscaping, and more particularly, to rotor-type sprinklers having a turbine that rotates a nozzle through a gear train reduction. 
     BACKGROUND OF THE INVENTIONS 
     In many parts of the United States, rainfall is insufficient and/or too irregular to keep turf and landscaping green and therefore irrigation systems are installed. Such systems typically include a plurality of underground pipes connected to sprinklers and valves, the latter being controlled by an electronic irrigation controller. One of the most popular types of sprinklers is a pop-up rotor-type sprinkler. In this type of sprinkler a tubular riser is normally retracted into an outer cylindrical case by a coil spring. The case is buried in the ground and when pressurized water is fed to the sprinkler the riser extends. A turbine and a gear train reduction are mounted in the riser for rotating a nozzle turret at the top of the riser. The gear train reduction is often encased in its own housing and is often referred to as a gear box. A reversing mechanism is also normally mounted in the riser along with an arc adjustment mechanism. 
     The gear drive of a rotor-type sprinkler can include a series of staggered gears and shafts wherein a small gear on the top of the turbine shaft drives a large gear on the lower end of an adjacent second shaft. Another small gear on the top of the second shaft drives a large gear on the lower end of a third shaft, and so on. Alternately, the gear drive can comprise a planetary arrangement in which a central shaft carries a sun gear that simultaneously drives several planetary gears on rotating circular partitions or stages that transmit reduced speed rotary motion to a succession of similar rotating stages. It is common for the planetary gears of the stages to engage corresponding ring gears formed on the inner surface of the housing. See, for example, U.S. Pat. No. 5,662,545 granted to Zimmerman et al. 
     Two basic types of reversing mechanisms have been employed in commercial rotor-type sprinklers. In one design a reversing stator switches water jets that alternately drive the turbine from opposite sides to reverse the rotation of the turbine and the gear drive. See for example, U.S. Pat. No. 4,625,914 granted to Sexton et al. The reversing stator design typically employs a long metal shaft that can twist relative to components rigidly mounted on the shaft and undesirably change the reverse point. Stopping the rotation of the stator and changing direction of rotation via alternate water jets does not provide for good repeatable arc shift points. Users setting the arc of sprinklers that employ a reversing stator design do not get a tactile feel for a stop at the set reverse points. 
     A more popular design for the reversing mechanism of a rotor-type sprinkler includes four pinion gears meshed together and mounted between arc-shaped upper and lower frames that rock back and forth with the aid of Omega-shaped over-center springs. One of the inner pinion gears is driven by the gear drive and the pinion gears on opposite ends of the frames alternately engage a bull gear assembly. See for example, U.S. Pat. Nos. 3,107,056; 4,568,024; 4,624,412; 4,718,605; and 4,948,052, all granted to Edwin J. Hunter, the founder of Hunter Industries, Inc. The entire disclosures of said patents are hereby incorporated by reference. While the reversing frame design has been enormously successful, it is not without its own shortcomings. It involves a complicated assembly with many parts and can have operational failures. The main drawback of the reversing frame design is that the pinion gears are held in contact to the outer bull gear with a spring force that is relatively weak. Therefore, it is not uncommon for the pinion gears to break, wear out, or become stripped during operation of this kind of rotor-type sprinkler. 
     Non-reversing, full circle rotation sprinklers such as golf rotors and stream sprinklers have been commercialized that have incorporated planetary gear boxes. Rotor-type sprinklers have also been commercialized that have combined planetary gear boxes and reversing mechanisms, however, in all such sprinklers all parts of the reversing mechanisms have been external to the gear box. See for example, U.S. Pat. No. 4,892,252 granted to Bruniga. 
     SUMMARY OF THE INVENTIONS 
     According some embodiments, a sprinkler can include a turbine, a nozzle, a gear drive and a reversing mechanism. The gear drive and reversing mechanism can rotatably couple the turbine and the nozzle. The gear drive and reversing mechanism can be coupled to shift a direction of rotation of an output stage of the gear drive. In some embodiments, the gear drive can include a control shaft that is axially movable to shift a direction of rotation of an output stage that is coupled to the reversing mechanism. The reversing mechanism can include a shift member secured to an upper end of the control shaft. The reversing mechanism can further include a mechanism to move the control shaft from a first position to a second position. In some embodiments, the control shaft may include a drive clutch. The gear drive may have two drive gears that alternately engage with the drive clutch. 
     According to some variants, a sprinkler can include a turbine, a nozzle, and/or a gear drive. In some embodiments, the sprinkler includes a reversing mechanism rotatably coupling the turbine and the nozzle. The gear drive can include at least a portion of the reversing mechanism having a shifting drive shaft that reciprocates between raised and lowered positions to alternately engage different drive gears that are coupled to non-shifting gears and thereby change a direction of rotation of subsequent stages of the planetary gear drive. In some embodiments, the sprinkler includes at least one clutch dog connected to the drive shaft. The at least one clutch dog can be configured to selectively engage with at least one clutch tooth formed on two or more of the different drive gears. 
     In some configurations, the sprinkler includes a riser enclosing the gear drive, an outer case surrounding the riser, and/or a coil spring surrounding the riser and normally holding the riser in a retracted position within the case and compressible to allow the riser to telescope to an extended position when pressurized water is introduced into the case. 
     In some configurations, the nozzle is carried inside a nozzle turret rotatably mounted at the upper end of the riser. 
     In some configurations, the reversing mechanism includes a shift member connected to the shifting drive shaft. In some embodiments, the reversing mechanism includes a pivotable shift fork with a first cam and a second cam spaced from the first cam. The first cam can be configured to engage the shift member and raise the shifting drive shaft when the shift fork is pivoted to engage the first cam with the shift member. The second cam can be configured to engage the shift member and lower the shifting drive shaft when the first fork is pivoted to engage the second cam with the shift member. In some embodiments, the reversing mechanism includes a housing and a shift crank pivotally supporting the shift fork in the housing. 
     In some configurations, the reversing mechanism further includes an over-center spring biasing the shift fork so that either the first cam or the second cam is engaged with the shift member. 
     In some configurations, the over-center spring is a coil spring having a first end connected to the housing and a second end connected to the shift crank. 
     In some configurations, the sprinkler includes a shift toggle extending from the housing, the shift toggle being connected to the shift crank. 
     In some configurations, the sprinkler further includes a fixed arc tab extending from a gear box housing of the gear drive in a predetermined location so that the fixed arc tab can be engaged by the shift toggle as the housing is rotated by the gear drive to pivot the shift fork to cause one of the first and second cams to engage the shift member. 
     In some configurations, the sprinkler further comprises a nozzle turret carrying the nozzle, a carrier ring coupled to the nozzle turret and rotatable relative to the housing, a bull gear ring coupled to the carrier ring, and/or an adjustable arc tab extending from the carrier ring in a predetermined location so that the adjustable arc tab can be engaged by the shift toggle as the housing is rotated by the gear drive to pivot the shift fork to cause the other one of the first and second cams to engage the shift member. 
     According to some variants, a sprinkler can include a nozzle. The sprinkler can include a gear drive with an output stage and a control shaft. In some embodiments, a direction of rotation of the output stage is reversible by axial motion of the control shaft. In some embodiments, the sprinkler includes a turbine coupled to an input stage of the gear drive. In some cases, the sprinkler includes a reversing mechanism coupled between the output stage of the gear drive and the nozzle. The reversing mechanism can include a pair of cams that alternately engage a shift member connected to the control shaft. In some embodiments, the sprinkler includes a shifting drive clutch connected to the control shaft and configured to alternately rotatably lock with at least two separate gears of the gear drive. 
     In some configurations, the drive member has a barrel shape. 
     In some configurations, the cams are formed on a pivotable shift fork. 
     In some configurations, the shift fork is pivotally mounted within a housing on a shift crank. 
     In some configurations, the shift crank is pivotable by moving a shift toggle when it engages a pair of arc tabs. 
     In some configurations, the sprinkler includes an over-center spring connected between the housing and the shift crank. 
     In some configurations, each cam has a sloped surface. 
     In some configurations, the sprinkler includes a nozzle turret that encloses the nozzle and is coupled to the reversing mechanism. The reversing mechanism can be partially mounted in the nozzle turret for moving an adjustable arc tab. 
     In some configurations, the sprinkler can include a fixed arc tab connected to a gear box of the gear drive. 
     According to some variants, a sprinkler includes a riser, a gear drive mounted inside the riser, a turbine coupled to an input shaft of the gear drive, and/or a nozzle turret. The sprinkler can include a reversing mechanism coupling an output stage of the gear drive and the nozzle turret that axially shifts a drive clutch within the gear drive to change a direction of rotation of the output stage. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematic illustration of an irrigation sprinkler. 
         FIG. 1A  is a vertical sectional view of a rotor-type sprinkler incorporating an embodiment of the present inventions. 
         FIG. 2  is an enlarge view of the riser and nozzle turret of the sprinkler of  FIG. 1 . 
         FIG. 3  is an exploded view of the reversing planetary gear drive and additional reversing mechanism of the sprinkler of  FIG. 1 . 
         FIG. 4  is a sectioned view of a reversing planetary dear drive with an axial moving control shaft with a clutch that is engaged with one of two sun gears 
         FIGS. 5 and 6  illustrate raised and lowered positions, respectively, of the shifting drive clutch control shaft and clutch. 
         FIGS. 7 and 8  illustrate two different configurations of the shifting stage of the reversing planetary gear drive of  FIG. 1  that cause the nozzle turret to rotate in opposite directions. 
         FIG. 9  illustrates the clutch of the control shaft. 
         FIG. 10  illustrates the internal clutch teeth of the first drive gear. 
         FIG. 11  illustrates the internal clutch teeth of the second drive gear. 
         FIG. 12  illustrates a reversing gear drive incorporating another embodiment the present inventions in a forward operating configuration. 
         FIG. 13  illustrates the reversing gear drive of the sprinkler of  FIG. 12  in a reverse operating configuration. 
         FIG. 14  illustrates the reversing gear drive of  FIG. 12 , wherein drive gears are partially sectioned to show a shifting clutch. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Irrigation sprinklers can be used to distribute water to turf and other landscaping. Types of irrigations sprinklers include pop-up, rotor-type, impact, spray and/or rotary-stream sprinklers. In some applications, such as that shown in  FIG. 1 , an irrigation system  2  can include multiple irrigation sprinklers  1  used to water a targeted area. One or more controllers (e.g., wireless and/or wired controllers) can be used to control the operation of multiple irrigation sprinklers. For example, one or more controllers can control when each of the sprinklers of the irrigation system transitions between an irrigating (e.g., ON) configuration and a non-irrigating (e.g., OFF) configuration. In some embodiments, the one or more controllers control the amount of water distributed by the sprinklers. The water source  9  for the irrigation system can be provided by a single water source, such as a well, a body of water, or water utility system. In some applications, multiple water sources are used. 
     As schematically illustrated in  FIG. 1 , an irrigation sprinkler  1  can include an outer case  3 . The outer case  3  can have a generally cylindrical shape or some other appropriate shape. A riser  5  can be positioned at least partially within the outer case  3 . In some embodiments, such as pop-up sprinklers, the riser  5  is biased to a contracted or non-irrigating position within the outer case  3 . The riser  5  may be biased to the contracted position by gravity and/or biasing structures such as springs. In some embodiments, the riser  5  transitions to an extended or irrigating position when pressure (e.g., water pressure) within the outer case  3  is high enough to overcome a biasing force on the riser  5 . In some embodiments (e.g., non-pop-up sprinklers) the riser  5  is fixed in the extended position. 
     One or more mechanical components  7  can be positioned within the riser  5  and/or within the outer case  3 . For example, the riser  5  can include an outlet  7   a  (e.g., a nozzle or outlet port). In some embodiments, the sprinkler  1  includes a plurality of outlets. The outlet  7   a  can direct water from the irrigation sprinkler  1  when the sprinkler  1  is ON. In some embodiments, the outlet  7   a  is connected to an outlet housing (e.g., a nozzle turret). The outlet housing and/or outlet  7   a  can be rotatable or otherwise moveable with respect to the riser  5  and/or outer case  3 . 
     In some embodiments, the irrigation sprinkler  1  includes a turbine  7   b . The turbine  7   b  can rotate in response to water entering an inlet end of the riser  5  and/or the outer case  3 . The turbine  7   b  can be configured to rotate the outlet  7   a . In some embodiments, a gear train reduction  7   c  is connected to the turbine  7   b  via an input shaft or otherwise. The gear train reduction  7   c  ca transfer torque from the rotating turbine  7   b  to the outlet housing and/or outlet  7   a  via an output shaft, output clutch, or other output structure. 
     The sprinkler  1  can include a reversing mechanism  7   d . The reversing mechanism  7   d  can be positioned within the riser  5  and/or within the outer case  3 . In some embodiments, the reversing mechanism  7   d  is connected to the gear train reduction  7   c  and/or to the outlet  7   a . The reversing mechanism  7   d  can be used to reverse the direction of rotation of the outlet  7   a . In some embodiments, the reversing mechanism  7   d  reverses the direction of rotation of the outlet  7   a  without changing the direction of rotation of the turret  7   b . In some embodiments, the reversing mechanism  7   d  reverses the direction of rotation of the outlet  7   a  by reversing the direction of rotation of the turret  7   b.    
     In some embodiments, the reversing mechanism  7   d  reverses the direction of rotation of the outlet  7   a  via manual input. For example, a tool may be used to adjust the reversing mechanism  7   d  to reverse the direction of rotation of the outlet  7   a . In some embodiments, the reversing mechanism  7   d  reverses the direction of rotation of the outlet  7   a  automatically via selected arc limiters. In some cases, at least one of the selected arc limiters can be adjusted to a desired position. 
     Water may be provided to the sprinkler  1  via one or more water sources  9 . The water source  9  may be fluidly connected to the outer case  3  and/or to the riser  5 . In some embodiments, fluid communication between the water source  9  and the sprinkler  1  is controlled by one or more controllers, valves, or other apparatuses. 
     According to the present disclosure, a rotor-type sprinkler can include an outer case with a top portion and a bottom portion. A valve can be incorporated in the outer case (e.g., near the bottom of the outer case). The valve can selectively permit ingress of water into the rotor-type sprinkler. The rotor-type sprinkler can include a turbine configured to rotate in response to the ingress of water. A nozzle of the rotor-type sprinkler can be configured to rotate in response to rotation of the turbine. A gear drive can be positioned within the outer case to provide gear reduction between the turbine and the nozzle. In some embodiments, the gear drive is a reversing gear drive configured to selectively reverse the rotation of the nozzle. The rotor-type sprinkler can also include a reversing mechanism configured to reverse the rotation of an output stage of the gear drive. The reversing mechanism can be located externally of the reversing gear drive. 
     In some embodiments, a reversing mechanism can be operatively connected to one or more gears in a reversing gear drive. The reversing mechanism can transition to engage the one or more gears between a plurality of operating positions/configurations to affect, for example, the rotational direction of the nozzle. The reversing gear drive can have any number of different configurations, a few examples of which are described below. For example, the reversing gear drive can be a reversing planetary gear drive  12  ( FIG. 2 ) or a reversing spur gear drive  212  ( FIG. 12 ). Other drive systems can also be used. 
     As illustrated and described below, the reversing gear drive can include a clutch. The clutch can be configured to move in an axial direction (e.g., substantially parallel to the axis of rotation of the turbine) between two or more operative positions. For example, the clutch can be configured to transition between an upper operative position and a lower operative position. The clutch can engage with an upper drive gear when in the upper operative position. The upper drive gear can be configured to drive one or more the remaining gears in the gear drive to rotate the nozzle in a first direction in response to rotational input from the drive gear/turbine. The clutch can engage with a lower drive gear when in the lower operative position. The lower gear can be configured to drive one or more of the remaining in gears in the gear drive to rotate the nozzle in a second direction (e.g., opposite the first direction) in response to rotational input from the lower drive gear/turbine. In some embodiments, the one or more remaining gears driven by the upper and lower drive gears share one or more gears and/or gear shafts. 
     Referring to  FIG. 1A , in accordance with an embodiment of the present inventions a rotor-type sprinkler  10  incorporates a reversing planetary gear drive  12  ( FIG. 2 ) that rotates or oscillates a nozzle  14  between pre-set arc limits. The sprinkler  10  shares some features similar to those disclosed in U.S. Pat. No. 6,491,235 of Scott et al. granted Dec. 10, 2002, the entire disclosure of which is hereby incorporated by reference. Some or all of the components of the sprinkler  10  can be generally made of injection molded plastic. The sprinkler  10  can be a so-called valve-in-head sprinkler that incorporates a valve  16  in the bottom of a cylindrical outer case  18  which is opened and closed by valve actuator components  19  contained in a housing  20  on the side of the case  18 . The sprinkler  10  includes a generally tubular riser  22  ( FIG. 2 ). A coil spring  24  normally holds the riser  22  in a retracted position within the outer case  18 . The nozzle  14  is carried inside a cylindrical nozzle turret  26  rotatably mounted to the upper end of the riser  22 . The coil spring  24  is compressible to allow the riser  22  and nozzle turret  26  to telescope from their retracted positions to their extended positions when pressurized water is introduced into the female threaded inlet at the lower end of the outer case  18 . 
       FIG. 2  illustrates further details of the riser  22 , nozzle turret  26  and reversing planetary gear drive  12 . A turbine  28  is secured to the lower end of a vertically oriented drive input pinion shaft  30 . The pinion shaft  30  extends through the lower cap  32  of a cylindrical gear box housing  34  of the reversing planetary gear drive  12 . A turbine pinion gear  36  can be secured to the upper end of the pinion shaft  30 . The turbine pinion gear  36  drives a lower spur gear  38  secured to a spur gear shaft  40 . The lower end of the spur gear shaft  40  is journaled in a sleeve  41  integrally formed in the lower cap  32 . Another pinion gear  42  is integrally formed on top of the spur gear  38  and drives an upper spur gear  44  of the reversing planetary gear drive  12 . Thus the turbine  28  is coupled to an input stage of the planetary gear drive  12 . 
     Referring still to  FIG. 2 , the reversing planetary gear drive  12  has a centrally located main control shaft  46 . The lower end of the control shaft  46  is rigidly and co-axially coupled to a shifting drive clutch  48  which is vertically reciprocated by axial movement of the control shaft  46  between a raised state illustrated in  FIG. 5  and a lowered state illustrated in  FIG. 6 . The interior wall of the cylindrical gear box housing  34  is formed with two axially displaced ring gears  50  and  51 . Each of the ring gears  50  and  51  comprises a plurality of circumferentially spaced, vertically extending, radially inwardly projecting teeth that are engaged by the various planet gears of the reversing planetary gear drive  12 . The lower ring gear  50  has a larger diameter and more teeth than the upper ring gear  51 . The upper ring gear  51  has a larger axial length than the lower ring gear  50 . Together the ring gears  50  and  51  form a bi-level ring gear. 
     Referring to  FIGS. 3 and 4 , the reversing planetary gear drive  12  includes a first disc-shaped stage carrier  52 A, a second disc-shaped stage carrier  52 B, a third disc-shaped stage carrier  52 B, and/or a fourth disc-shaped stage carrier  52 D. The stage carrier  52 D functions as an output stage of the planetary gear drive  12 . The carriers  52 A,  52 B,  52 C and  52 D rotate around the control shaft  46 . A central spline opening (not illustrated) in the one way drive coupling  45  is drivingly coupled to a spline-shaped extension  47  of the shifting drive clutch  48  to allow for axial movement of the shifting drive clutch  48  relative to the upper spur gear  44 . Thus the upper spur gear  44  continuously rotates the drive coupling  45 , shifting drive clutch  48  and the control shaft  46  during vertical axial reciprocating movement of the control shaft  46  and the shifting drive clutch  48 . 
     When the shifting drive clutch  48  is in its raised state ( FIGS. 2, 4, 5 and 7 ) the clutch dogs  49  ( FIG. 9 ) thereof engage and mesh with complementary internal clutch teeth  62  ( FIG. 10 ) of the upper drive gear  60 . When the shifting drive clutch  48  is in its lowered state ( FIGS. 6 and 8 ), the clutch dogs  49  thereof engage and mesh with internal clutch teeth  68  ( FIG. 11 ) of the lower drive gear  66 . The upper drive gear  60  meshes with the upper ring gear  51  ( FIG. 5 ) formed on the interior wall of the gear box housing  34  thru the planet gear  54 . The lower drive gear  66  engages the transfer gear  56  which engages another planet gear  58 , which in turn engages the lower ring gear  50 . The direction of rotation of the disc shaped gear carrier  52   a  changes from a first direction when the shifting clutch  48  is engaged with the upper drive gear  60  to a second direction when the shifting clutch  48  is engaged with the lower drive gear  66 . The disc shaped carrier  52   b  is directly coupled to the disc shaped carrier  52   a . Thus the direction of rotation subsequently carried through the remaining stages of the reversing planetary gear drive  12  is reversed by up and down movement of the control shaft  46  and the shifting drive clutch  48 . 
     The shifting drive clutch  48  can have a neutral position between engagement with the upper drive gear  60  and with the lower drive gear  66  in which it is not engaged with either of these two gears. This can reduce the likelihood that the shifting drive clutch  48  will strip either or both of the clutch teeth  68  and  68 . The shifting drive clutch  48  is configured to rotate as a result of the upstream rotating gears that are driven by the turbine  28 . If the clutch dogs of the shifting drive clutch  48  do not immediately engage with the gears  60  and  68  during shifting, the clutch teeth  49  are configured to align within one tooth of rotation. In some embodiments, the shifting drive clutch  48  is biased both upwardly and downwardly from this neutral position (e.g., by an over-center spring mechanism inside the reversing mechanism  13 ). This can ensure that the planetary gear drive  12  will be in one of two driving states, either rotating the nozzle  14  clockwise or counter-clockwise. 
     The level of rotational torque on the planet gears  54  and  58  can be fairly low. In some embodiments, the meshing of the shifting drive clutch  48  with the drive gear  60  and the lower drive gear  66  is very smooth. The smooth shifting transition can be influenced by its position in the power transmission path of the planetary gear drive  12 . The rotational speed of the turbine  28  is very high. If the shifting drive clutch  48  is placed too close to the turbine  28  in the power transmission path, the rotational speed of the shifting drive clutch  48  can be too fast, and shifting direction can be difficult as the clutch teeth  62  and  68  may tend to skip past the clutch dogs  49  instead of meshing smoothly. Likewise, the final output stage of the reversing planetary gear drive  12  generates substantial rotational torque. If the shifting drive clutch  48  is placed too close to the output stage (carrier  52 D) in the power transmission path, the excessive torque can make it difficult for the clutch dogs  49  to slip axially across the faces of clutch teeth  62  and  68  and shifting may be difficult. 
     The reversing planetary gear drive  12  can include additional sun gears and planet gears which need not be described in detail as they will be readily understood by those skilled in the art of sprinkler design in view of  FIGS. 2 and 3 . The other planet gears also engage the ring gears  50  and  51  and rotate about corresponding fixed cylindrical posts that extend vertically from their associated disc-shaped carriers  52   a ,  52   b ,  52   c  and  52   d . Each non-shifting sun gear can be secured to, and/or integrally formed with, one of the carriers  52   b ,  52   c  and  52   d . The uppermost carrier  52   d  can have an upwardly projecting central section  59  ( FIG. 2 ) that is coupled to the underside of the reversing mechanism  13  in order to rotate the same. The reversing mechanism  13  in turn supports and rotates the nozzle turret  26 . With this arrangement of gears the high RPM of the turbine  28  is successively reduced so that the final output RPM of the control shaft  46  is relatively low, and the output torque at the central section  59  of the uppermost carrier  52   d  is relatively high. For example, the turbine  28  may rotate at speeds of greater than or less than eight hundred RPM and the output shaft  46  may rotate at an RPM of less than one, less than three, less than 5, less than 10, less than 25 and/or at some other reduced RPM. 
     In some embodiments, the sprinkler  10  uses the planetary gear drive  12  and the additional reversing mechanism  13  to change the direction of rotation of the nozzle turret  26 . The overall reversing mechanism of the sprinkler  10  can have two portions, namely, the components of the reversing mechanism  13  that are located external of the gear box housing  34 , and another portion that is contained within the planetary gear drive  12  that includes the shifting drive clutch  48 , planetary gear  54 , idler gear  56 , and/or planetary gear  58 . An advantage of including at least a portion of the overall reversing mechanism in the planetary gear drive  12  is that the shifting can be done in a low torque region of the planetary gear drive  12  where damage and wear to gears is much less likely to occur. This can reduce or eliminate the need to use conventional arc-shaped shifting frames with delicate pinion gears that engage a bull gear assembly and bear large loads. The planetary gear drive  12  can deliver relatively high rotational torque to the nozzle turret  26  in a manner that is useful in large rotor-type sprinklers used to water large areas such as golf courses and playing fields. Such high torque may prematurely wear out and/or strip conventional pivoting gear train reversing mechanisms. The different gear tooth profiles of the ring gears  50  and  51  and the upper and lower stages of the shifting drive clutch  48  desirably result in the nozzle  14  rotating in both the clockwise and counter-clockwise directions at a substantially uniform predetermined speed of rotation. 
     High output torque is important for large area sprinklers. Sprinklers of this type can discharge seventy-five gallons of water per minute at one-hundred and twenty PSI throwing water one hundred and fifteen feet from the sprinkler. Discharging water at this high rate creates substantial upward and radial forces on the nozzle turret  26  that results in significant drag and resistance to rotation of this component of a rotor-type sprinkler. The gear drives utilized in this type of sprinkler must overcome this resistance. 
     The fast spinning turbine  28  can slowly rotate the nozzle turret  26  through the reversing planetary gear drive  12  and the additional reversing mechanism  13 . The additional reversing mechanism  13  includes cams and components that lift and drop the output shaft  46 . An adjusting gear ring  80 , carrier ring (not shown), and an adjusting gear (not shown) cooperate with the reversing mechanism  13  to permit user adjustment of the size of the arc of oscillation of the nozzle  14 . To adjustment of the arc of coverage, the installer can turn the adjusting gear ring  80  by hand providing a direct one to one adjustment of the arc of coverage. 
     The reversing mechanism  13  includes an upper shift housing  72  ( FIG. 3 ) and a lower shift housing  74  that mate to form a complete housing with a hollow interior that encloses most of the other components of the reversing mechanism  13  hereafter described. The reversing mechanism  13  further includes a shift member  76  ( FIG. 4 ) that is rigidly secured to the upper end of the control shaft  46 . The shift member  76  can be semi-spherical and/or barrel-shaped. In some cases, the shift member  76  is integrally formed with the control shaft  46 . The reversing mechanism  13  can include a pivotable shift fork  78  ( FIG. 3 ) with first and second spaced apart cams  80 ,  82 . The first cam  80  can be configured with a sloped surface (not shown) that raises the control shaft  46  when the shift fork  78  is pivoted to engage the first cam with the shift member  76 . The second cam  82  can be configured with an oppositely sloped surface that lowers the control shaft  46  when the shift fork  78  is pivoted to engage the second cam with the shift member  76 . 
     The reversing mechanism  13  further includes a shift crank  84  ( FIG. 3 ) that pivotally supports the shift fork  78  inside the joined upper and lower shift housings  72  and  74 . An over-center coil spring  94  ( FIG. 3 ) biases the shift fork  78  so that either the first cam  80  or the second cam  82  is engaged with the shift member  76 . The over-center spring  94  has a first end connected to a post that extends from the lower shift housing  74  and a second end connected to a central segment of the shift crank  84 . Additional details regarding the reversing mechanism  13  are disclosed in U.S. Pat. No. 8,955,768, entitled REVERSING MECHANISM FOR AN IRRIGATION SPRINKLER WITH REVERSING GEAR DRIVE, the entire disclosure of which is hereby incorporated by reference. 
     As illustrated in  FIGS. 12-14 , in some embodiments, the sprinkler utilizes a reversing gear drive  212  having a plurality of spur gears. The spur gears can be used in additional to or instead of one or more of the planetary gears described above. 
     Referring to  FIG. 12 , the reversing gear drive  212  can be operably connected to the turbine  28 . The reversing gear drive  212  can be, for example, a reversing spur gear drive  212 . The reversing gear drive  212  can be positioned between the turbine  28  and the reversing mechanism  13 . The reversing gear drive  212  includes two alternately-engaged drive gears  260  and  266 . 
     The alternately driven drive gears  260  and  266  can be alternately coupled to a shifting clutch  249  ( FIG. 14 ). The shifting clutch  249  can share many or all of the characteristics of the clutch  49  described above, including, but not limited to, the dogs  49  (dogs  271  in  FIG. 14 ) and the spline portion  47  (spline portion  247  in  FIGS. 12-14 ). The shifting clutch  249  can be connected to and/or integrally formed with a drive shaft  248 . The shifting clutch  249  can be rotatably connected to the turbine  28 . For example, the shifting drive clutch  249  can be rotatably connected to the upper spur gear  44 . In some embodiments, a clutch  37  is configured to selectively rotationally disconnect the shifting clutch  249  from the upper spur gear  44 . The shifting drive clutch  249  can be spline-fit to the upper spur gear  44  and/or to the clutch  37  via the spline portion  247 . The shifting drive clutch  249  can translate or shift axially (e.g., parallel to the drive input  30  shaft) with respect to the upper spur gear  44  and/or with respect to the clutch  37 . In some configurations, the shifting drive clutch  249  shifts in a direction collinear with the drive input shaft  30 . The shifting drive clutch  249  and shifting drive shaft  248  can have a similar or identical connection to the reversing mechanism  13  as described above with respect to the shifting drive clutch  48  and control shaft  46 . For example, the shifting drive shaft  248  can be connected to a structure similar or identical to the shift member  76  described above. 
     As illustrated in  FIGS. 12 and 13 , the reversing gear drive  212  can be positioned within a gear box housing  234 . The gear box housing  234  includes a lower cap  232  defining a lower wall of the gear box housing  234 . In some embodiments, the reversing gear drive  212  includes a gear stage carrier  252   a . The gear stage carrier  252   a  supports one or more of the gear stages within the reversing gear drive  212 . For example, the gear stage carrier  252   a  can include one or more apertures configured to receive and/or support spline fittings, rotational shafts, and/or other components of the reversing gear drive  212 . In some embodiments, the reversing gear drive  212  includes a gear support  255  ( FIG. 14 ) configured to brace and support the gear stages (e.g., the gear shafts) of the reversing gear drive  212 . 
       FIG. 12  illustrates the reversing gear drive  212  in a forward operating configuration (e.g., a configuration wherein the nozzle turret  26  is rotated in the same direction of rotation as the shifting drive shaft  248 ). In the forward operating configuration, the shifting drive clutch  249  is in a lower position where clutch dogs  271  (e.g., similar to clutch dogs  49 ) meshes with the internal clutch teeth  273  (e.g., similar to clutch teeth  68 ) formed inside of a first drive gear  266 . The drive gear  266  is always engaged with the idler gear  256 . The idler gear  256  and drive gear  266  can have similar or identical diameters and/or the same number of gear teeth. The idler gear  256  engages with a first forward gear stage  258 . The first forward gear state  258  engages with a second gear stage  257 . The second gear stage  257  meshes and engages with a final gear stage  254 . The final gear stage  254  meshes and engages with an output gear  251  (e.g., a ring gear). The output gear  251  rotationally engages with the reversing mechanism  13  (e.g., rotation of the output gear  251  rotates the reversing mechanism  13 ). 
     The first forward gear stage can include a first forward input gear  258   a  and a first forward output gear  258   b . The first forward input gear  258   a  and/or the first forward output gear  258   b  can be spur gears. The idler gear  256  can mesh with the first forward input gear  258   a . The first forward input gear  258   a  is rotationally coupled to (e.g., rotationally locked with) the first forward output gear  258   b . For example, the first forward output gear  258   b  can be stacked with the first forward input gear  258   a  and rotationally locked thereto. In some embodiments, the first forward input gear  258   a  has a larger diameter and more teeth than the first forward output gear  258   b.    
     In the illustrated embodiment, the first forward output gear  258   b  meshes with the second stage input gear  257   a . The second stage input gear  257   a  is rotationally coupled to (e.g., rotationally locked with) to the second stage output gear  257   b . For example, the second stage output gear  257   b  can be stacked with the second stage input gear  257   a  and rotationally locked thereto. The second stage input gear  257   a  and/or the second stage output gear  257   b  can be spur gears. In some embodiments, the second stage input gear  257   a  has a larger diameter and more teeth than the second stage output gear  257   b.    
     The second stage output gear  257   b  is configured to mesh and engage with the final stage input gear  254   a . The final stage input gear  254   a  is rotationally coupled to (e.g., rotationally locked with) to the final stage output gear  254   b . For example, the final stage output gear  254   b  can be stacked with the final stage input gear  254   a  and rotationally locked thereto. In some embodiments, the final stage input gear  254   a  has a larger diameter and more teeth than the final stage output gear  254   b . The final stage input gear  254   a  and/or the final stage output gear  254   b  can be spur gears. The final stage output gear  254   b  is configured to engage with the output gear  251 . In the illustrated embodiment, the final stage output gear  254   b  is a spur gear and the output gear  251  is a ring gear. 
       FIG. 13  illustrates the reversing gear drive  212  in a reverse operating configuration (e.g., a configuration in which the nozzle turret  16  is rotated in a direction opposite that of the input gear  248 ). For example, the shifting drive clutch  249  can be shifted axially (e.g., upward) to engage the drive shaft clutch dogs with the internal teeth  275  (e.g., similar to clutch teeth  62 ) formed inside a second drive gear  260 . In some embodiments, upward shifting of the shifting drive shaft  248  disengages the clutch dogs  271  from the first drive gear  266  and brings the clutch dogs of the shifting drive clutch  249  into engagement with the clutch teeth of second drive gear  260 . The second drive gear  260  is always engaged with a first reversing gear stage  253 . The first reversing gear stage  253  can engage with and rotate the second gear stage  257 . The second gear stage  257  operates with the remaining gear stages (e.g., the final gear stage  254  and output gear  251 ) operate in substantially the same manner as discussed above with respect to the forward operating configuration. The first reversing gear stage  253  can include a first reversing input gear  253   a  and a first reversing output gear  253   b . The first reversing input gear  253   a  and/or the first reversing output gear  253   b  can be spur gears. The input gear  248  can mesh with the first reversing input gear  253   a . The first reversing input gear  253   a  is rotationally coupled to (e.g., rotationally locked with) the first reversing output gear  253   b . For example, the first reversing output gear  253   b  can be stacked with the first reversing input gear  253   a  and rotationally locked thereto. In some embodiments, the first reversing input gear  253   a  has a larger diameter and more teeth than the first reversing output gear  253   b.    
     While we have described and illustrated in detail embodiments of a sprinkler with a reversing gear drive, it should be understood that our inventions can be modified in both arrangement and detail. For example, the sprinkler  10  could be modified to a simplified shrub configuration without the valve  16 , outer case  18 , valve actuator components  19  and housing  20 . Therefore the protection afforded our inventions should only be limited in accordance with the following claims.