Patent Publication Number: US-6341733-B1

Title: Nutating sprinkler

Description:
TECHNICAL FIELD 
     This invention relates to sprinkler devices and more specifically, to an improved sprinkler which incorporates a spray plate (or rotor plate) mounted for wobbling/rotating motion referred to herein as “nutation.” 
     BACKGROUND 
     Moving irrigation systems such as conventional pivot or linear systems are known to incorporate conduit truss span assemblies which mount sprinkler heads, spaced along the truss assemblies for sprinkling or irrigating relatively large areas of land. The sprinkling heads may be mounted on top of the truss assemblies in a normal upright position, or they may be inverted and suspended from the span assemblies by means of drop tubes. Sprinkler heads are typically of the spinner type, which incorporate rotatable stream distributors (also referred to as rotor plates or spray plates, fixed spray plates or bubbler devices). 
     When irrigating large areas of land with pivot or linear sprinklers, the sprinklers need to be spaced apart as far as possible to minimize system hardware costs. To obtain an even distribution of the water at wide spacings requires sprinklers that simultaneously throw the water long distances and produce sprinkling patterns that are very even when overlapped with adjacent sprinklers. These two requirements are somewhat exclusive in that maximum radius of throw is achieved with concentrated streams of water shooting at relatively high trajectory angles. These streams, however, tend to produce a donut shaped sprinkling pattern at low pressure that does not overlap evenly. The use of nutating or wobbling sprinklers to enhance distribution uniformity particularly at low pressure is known in the art, as evidenced, for example, by U.S. Pat. Nos. 5,439,174; 5,671,885; and 5,588,595. Wobbling type sprinklers can be problematic in the sense that in some circumstances, the sprinkler simply rotates on its center axis without wobbling. This is particularly true if the sprinkler rotor plate is allowed to assume an on-center orientation when at rest. 
     A recently issued patent, No. 5,950,927, addresses this problem by mechanically constraining the rotor plate to always assume an off-center position. 
     SUMMARY OF THE INVENTION 
     This invention provides an improved rotor plate mounting arrangement which insures that the rotor plate will be tilted to an off-center position on start-up, thereby also insuring that the rotor plate will exhibit the desired nutating motion. 
     In a first exemplary embodiment, the rotor plate is supported in a center body of a removable cap assembly secured to a sprinkler body, with the rotor plate downstream of a fixed nozzle. The rotor plate is fixed to a hub protruding from the center of one side of a load disc captured loosely between a pair of annular rings located within the centerbody. In this embodiment, the hub includes a shaft extending into the rotor plate. At the same time, a tilter button or post projects upwardly toward the opposite side of the load disc and engages a center portion of the disc when the sprinkler is at an at rest position. Because of the inherently unstable nature of the engagement, i.e., where a top heavy rotor plate is supported essentially on a point contact, the rotor plate will tilt to one side. When water is supplied to the sprinkler, the rotor plate will rotate and wobble, i.e., nutate, in the desired manner, and the rotor plate will also separate slightly from the tilter button or post, thus reducing the potential for wear on the post. In this first embodiment, the tilter button or post is incorporated in a plug which is threaded into a cap center body which supports the rotor plate. In another variation of this embodiment, the tilter button or post is incorporated in a cover or plate secured to the center body by one or more fasteners. 
     In a second exemplary embodiment of the invention, the hub includes a spool and a shaft projecting from one side of the spool, with the other end of the shaft fixed in the rotor plate. The spool has upper and lower flanges, and an internal annular ring in the cap centerbody loosely supports the spool in an area between the upper and lower flanges. A tilter button or post extends vertically into a center recess in the other side of the spool, creating an unstable mounting arrangement as described hereinabove. Here again, the rotor plate assumes a tilted or off-center position when at rest, insuring that the desired nutating motion will occur on start-up. 
     In a third embodiment of the invention, the rotor plate is formed with an open-ended cylindrical stem which receives a relatively large diameter hub projecting from the center of one side of a load disc. In this embodiment, the load disc is captured between a pair of discrete, annular rings sandwiched between an interior shoulder in the cap center body and the cap cover or plug. As in the earlier described embodiments, a tilter button or post is formed integrally with the cover or plug and engages a center recess in the other side of the load disc. 
     In a fourth embodiment of the invention, an open cylindrical stem of the rotor plate receives a hub projecting from one side of a spool loosely captured within the cap center body by an internal ring or flange. The upper and lower spool flanges may be snap-fitted together, sandwiching a wear resistant spool bushing therebetween. The internal ring is held in place in the center body by the cover or plug which includes an integral post or tilter button projecting into a center recess in the other side of the spool. 
     Accordingly, in its broader aspects, the present invention relates to a nutating sprinkler assembly comprising a sprinkler body having one end connected to an adapter; a nozzle mounted in the sprinkler body captured between the adapter and the sprinkler body; at least one arm extending from the sprinkler body for supporting a removable cap assembly downstream of the nozzle, the cap assembly having a center body supporting a rotor plate having off-center grooves for distributing a stream exiting the nozzle and impinging upon the grooves; a hub having one end secured in the rotor plate and an opposite end supporting a load disc, the load disc loosely captured between opposed rings provided in the center body; the center body having an end wall formed with a tilter button extending toward and engaging a center portion on an underside of the load disc when the rotor plate is in an at rest position, thereby creating an unstable arrangement causing the rotor plate to tilt to an off-center position. 
     In another aspect, the present invention relates to a nutating sprinkler assembly comprising a sprinkler body supporting a nozzle and a rotor plate supported downstream of the sprinkler body; the rotor plate having a center axis defined by a hub extending between the rotor plate and a load disc confined within a rotor plate support such that the rotor plate is rotatable relative to the support; and wherein, at rest, the rotor plate and the load disc are supported on a tip of a post; creating an unstable arrangement causing the rotor plate and the hub to tilt relative to the center axis. 
     In still another aspect, the invention relates to a nutating sprinkler assembly comprising a sprinkler body having one end adapted to be coupled to a water supply conduit and an opposite end supporting a nozzle; at least one arm extending from the sprinkler body for supporting a removable cap assembly downstream of the nozzle, the cap assembly having a center body supporting a rotor plate having off-center grooves for distributing a stream exiting the nozzle and impinging upon the grooves; a hub secured to the rotor body and having an opposite end supporting a spool bearing having upper and lower spool flanges; the center body mounting an interior ring loosely supporting the spool bearing between the upper and lower spool flanges; the center body having an end wall formed with a tilter button extending toward and engaging a center portion of an underside of the spool bearing when the rotor plate is in an at-rest position, thereby creating an unstable arrangement causing the rotor plate to tilt to an off-center position. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a side section of a rotatable sprinkler incorporating a nutating rotor plate in accordance with the first exemplary embodiment of the invention; 
     FIG. 2 is an enlarged detail taken from FIG. 1; 
     FIG. 3 is an enlarged detail of a variation of the rotor plate assembly shown in FIGS. 1 and 2; 
     FIG. 4 is a cross section of a rotor plate assembly in accordance with a second exemplary embodiment of the invention; 
     FIG. 5 is a cross section of a rotor plate assembly in accordance with a third exemplary embodiment of the invention; and 
     FIG. 6 is a cross section of a rotor plate assembly in accordance with a fourth embodiment of the invention. 
    
    
     DETAILED DESCRIPTION OF THE DRAWINGS 
     Referring to FIG. 1, the sprinkler  2  includes an adapter  4  having a threaded inlet  6  to be secured to a coupling or conduit (not shown). The outlet end of adapter  4  has a unique external thread that engages sprinkler body  8 . A fixed nozzle  10  is captured between the outlet end of adapter  4  and the sprinkler body  8 , the nozzle having a discharge orifice  12 . Arms  14 ,  16  and  18  extend from the sprinkler body and support a removable cap assembly  20  which, in turn, supports a nutator assembly  22  within a central opening in the cap assembly. The cap assembly may be press-fit in the opening and held in place by an annular rib adapted to seat within a complementary groove defined by shoulder  24  and rib  26  formed on the nutating assembly centerbody  28 . It will be appreciated, however, that the nutator assembly can be secured relative to the nozzle by any suitable means. 
     With reference also to FIG. 2, the centerbody  28  includes a plug  30  threaded into one end of the centerbody, the plug having an internal peripheral inclined surface  32  about its inner end  34 . The plug is also formed with a tilter button or post  36  having rounded point or tip  38  at its free end. The cap centerbody  28  also includes an interior annular flange  40 , one surface  42  of which is also slightly inclined in the radial direction. 
     A rotor plate  44  includes a rotor body  46  having a series of water deflecting grooves  48  therein which are circumferentially offset to cause the rotor plate to rotate when a stream from the nozzle  16  impinges on the grooves  48 . A shaft  50  extends from a hub  52  projecting from the center of a one side of load disc  54 . The other end of the shaft is received in a stem  56  of the rotor body  46 . The load disc  54  has opposed inner and outer peripheral surfaces  58 ,  60  adapted to cooperate with surfaces  42 ,  32 , respectively. A center recess  62  on the other side of the load disc  54  exposes the shaft bottom  64 . The load disc  54  is loosely captured between the surface  42  of flange  40  and the inner surface  32  of the plug  30 . 
     When at rest, the shaft bottom  64  rests on the point or tip  38  of the tilter button  36 , creating an inherently top-heavy, unstable arrangement, that causes the rotor plate  44 , shaft  50  and load disc  54  to tilt to one side, as best seen in FIG.  2 . Notice that surface  58  of disc  54  is not engaged with surface  42  of ring  40 . 
     When water is supplied to the sprinkler  2 , the instability of the rotor plate vis-a-vis the tilter button  36  insures that rotor plate  44  will begin nutating (or wobbling) as it rotates, and not merely assume a stable, on-center position. As the rotor plate  44  begins to rotate, the tilting action will increase to the extent that both of the opposed surfaces  58 ,  60  on the load disc  54  will engage respective surfaces  42  of flange  40  and  32  of the plug  30 . With this additional degree of tilt, illustrated in FIG. 3, the shaft bottom  64  will separate slightly from the tilter button  36 , minimizing wear on the tilter button. The degree of tilt when the rotor plate is rotating may be about 10° to 12°. 
     It will also be appreciated that annular skirt  66  extending from the rotor plate  44 , and annular surface  68  at the inner end of the cap centerbody  24  cooperate to minimize intrusion of any debris into the area of the hub  52  and load disc  54 . 
     While the assembly is shown in FIG.  1  and FIG. 2 oriented so as to receive a stream from above the rotor plate  44 , it will be appreciated that the assembly may be inverted so that the stream rotor plate “hangs” by means of load disc  54 . The sprinkler nevertheless operates in substantially the same manner as described above, except that on start-up, the stream will push the rotor body  46  upwardly, causing the shaft bottom  64  to engage the tilter button  36 . Again, the instability of the arrangement will cause the rotor plate  44  to tilt, insuring the desired nutating motion will commence when the stream impinges on the grooves  48  of the rotor plate. 
     Wear resistant coatings or materials may be used as desired to reduce wear at the points of engagement of the load disc  54  with the surface  42  of the flange  40  and surface  32  of plug  30 . 
     In an alternative arrangement illustrated in FIG. 3, a cap centerbody  70  is axially shortened and the plug  30  is replaced by a cap cover or plate  72  fastened to the cap centerbody  70  via circumferentially spaced screws  74 . A tilter button  76  extends inwardly from the cap cover  72 , extending toward one side of a load disc  78 . The load disc  78  is formed integrally with the hub  82  and is loosely captured between the lower surface  81  of the interior annular flange  83  and an interior peripheral surface  84  on the cap cover  72 . The device is otherwise similar in construction and operation to the first exemplary embodiment shown in FIGS. 1 and 2, noting that hub  82  includes a shaft  86  that extends into the stem  85  of the rotor body  88 . As already noted, FIG. 3 illustrates the position of load disc  78  during rotation, when it (and the bottom  84  of shaft  86 ) separate slightly from the tip  90  of tilter button  76 . 
     In a second embodiment of the invention illustrated in FIG. 4, the hub  92  includes a shaft  94  extending from a two-piece spool  96  and received in a stem  95  of the rotor body  97 . The spool  96  includes a first or upper flange  98  providing a first peripheral surface  100  adapted to engage a first facing surface  102  of the inner flange ring  104 . The spool also includes a second or lower flange  106  providing a second peripheral surface  108  adapted to engage the undersurface  110  of the inner flange ring  104 . The cylindrical portion  112  projecting from lower flange  106  telescopes over the solid center portion  113  projecting from the upper flange  98 . 
     The cap center body  114  is closed by a cap cover or plate  116  and includes an integral tilter button  118  adapted to engage the shaft bottom  120  when the sprinkler is at rest. Note that the spool  96  does not engage any interior surface of cover  116  other than the tilter button  118 . The structure shown in FIG. 4 is otherwise similar in construction and operation to the above described alternative embodiments. 
     Turning now to FIG. 5, a third exemplary embodiment of the invention is disclosed in which modifications are made with respect to the manner in which the rotor plate is connected to the load disc. Specifically, the rotor plate  122  incorporates a rotor body  124  having an open-ended cylindrical stem  126  extending away from the grooves  128  in the external surface of the rotor plate. The stem is adapted to receive in snap-fit relationship a hub  130  which includes a reduced diameter projection  132  having an annular rib  134  adapted to cooperate with a groove  136  in the stem  126 , facilitating the snap-fit relationship within the stem. The load disc  138  is formed integrally with the hub and is loosely confined between a pair of discrete annular rings  140  and  142  sandwiched between the cap centerbody  144  and the cap end cover or plug  146 . These annular rings are preferably formed of a wear resistant plastic material with a radial surface  148  of the upper ring cooperating with a radial surface  150  of the lower ring to confine the load disc  138  therebetween. The two annular rings  140 ,  142  join at an interface  152  defined by the edges of axial portions  154 ,  156 , respectively, of the rings, and it will be appreciated that the rings must be separable in order to permit the assembly of the hub  130  within the cap centerbody  144 . The end cover or plug  146  incorporates an integral tilter button or post  158 , the free end of which engages within a center recess  160  formed in the lower side of the load disc  138 . The cap end cover or plug  146  may be secured to the cap centerbody by a plurality of screws  162 . The manner of operation of the rotor plate and the load disc vis-a-vis the tilter button is otherwise similar to the previously described embodiments. 
     FIG. 6 illustrates yet another embodiment of the subject invention, generally combining the features disclosed with respect to the embodiment illustrated in FIG.  4  and the features illustrated in FIG.  5 . Thus, the hub  162  is formed as a two-piece spool, with an upper part  164  of the spool including a hollow cylindrical projection  166  adapted to be snap-fit within the open-ended cylindrical stem  168  projecting away from the rotor body  170 . A lower spool element  172  is snap-fit within the upper spool element, with a solid projection  174  extending into the center opening of the spool upper part  164 . An annular rib  176  on the projection  166  adapted to seal in a complimentary groove  178  in the stem  168  facilitates attachment of the upper spool element to the stem, while an annular rib  180  formed on the solid projection  174  of the lower spool element cooperates with a complimentary groove  182  in the upper spool part  164  facilitates connection of the lower spool element  172  to the upper spool element. 
     Between the opposing flanges  184  and  186  of the upper and lower spool elements, respectively, there is a conforming wear element or bushing  188  (made of any suitable wear resistant material) which also includes upper and lower wear surfaces  190  and  192 , respectively. These upper and lower surfaces of the wear element are loosely confined by an internal annular ring  194  seated within the cap centerbody  196  and held in place by the end cover or cap  198 . The annular ring  194  may also be made of a wear resistant plastic. 
     The lower spool element  172  is formed with a center recess  200  adapted to receive a tilter button or post  202  extending upwardly from the end cover or plug  198 . This device operates in a manner similar to the embodiment illustrated in FIG. 4 as explained hereinabove. 
     While the invention has been described in connection with what is presently considered to be the most practical and preferred embodiment, it is to be understood that the invention is not to be limited to the disclosed embodiment, but on the contrary, is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the appended claims.