Abstract:
A seal arrangement for a rotatable shaft that is secured at one end thereof in a housing, and that mounts a water distribution plate on an opposite end thereof, the shaft seal comprising a flexible annular member having a radially inner portion including at least one tapered lip extending in one direction along the shaft and adapted to engage the shaft, and a radially outer portion seated on a support in the housing; and at least one retainer overlying the seal and holding the seal in position on the support, the at least one retainer having a radially inner portion that substantially encloses the at least one tapered lip.

Description:
[0001]     This invention relates generally to sprinkler devices and, more particularly, to an improved shaft seal for a rotatable sprinkler plate.  
       BACKGROUND OF THE INVENTION  
       [0002]     Moving irrigation systems, such as conventional pivot move and lateral move systems, are known to incorporate conduit truss span assemblies and a plurality of drop tubes by which a corresponding number of sprayheads incorporating rotatable water distribution plates (also referred to as rotor plates or spinners), fixed spray plates, or bubbler devices are suspended so as to be located in close proximity to crops or other plants.  
         [0003]     In this regard, there are currently in use modular sprayheads, also manufactured by the assignee of this invention, that include sprinkler bodies and rotary stream distributors (or rotor plates) supported in cap assemblies that are designed for quick assembly and disassembly from the respective sprinkler bodies. The cap is typically secured to the sprinkler body by a conventional screw thread arrangement in combination with a locking mechanism where a plurality of vertically extending projections on the cap engage a corresponding plurality of notches formed on the cap mounting ring when the cap reaches the full extent of its rotational movement relative to the body during threading.  
         [0004]     Rotor plates or spinners typically are fixed to a shaft that is, in turn, mounted within a housing in the sprinkler cap assembly. A rubber (or other suitable material) shaft seal is received over the shaft and held by means of a retainer on a support secured within a shaft housing on the cap. The retainer, however, leaves the sealing edge or lip of the shaft seal exposed. This arrangement can lead to damage to the seal through exposure to the elements, and may also hinder rotation of the shaft if debris migrates past the exposed lip of the seal.  
       BRIEF DESCRIPTION OF THE INVENTION  
       [0005]     This invention provides an improved shaft seal arrangement through a modification to the retainer component. Specifically, in one exemplary embodiment, the retainer is extended axially and radially in its center or hub area to substantially enclose the sealing edge or lip of the shaft seal. Only a slight radial gap or tolerance remains between the retainer and the shaft. Grease added between the shaft seal and retainer not only lubricates the lip of the seal but also prevents debris from passing through the radial gap between the retainer and the shaft.  
         [0006]     In a second exemplary embodiment, where a double lip seal is used, a second retainer, constructed as described above, may be located over a first un-modified retainer, with grease packed between the two retainers.  
         [0007]     It will be appreciated that the invention is applicable to any rotor plate or spinner shaft seal arrangement including those supported by plain bearings, ball bearings or other bearing arrangements, and is also applicable to other shaft mounting arrangements in fixed or removable cap assemblies, or, for example, where the shaft is mounted in the sprinkler body itself.  
         [0008]     Accordingly, in one embodiment, the invention relates to a seal arrangement for a rotatable shaft that is secured at one end thereof in a housing, and that mounts a water distribution plate on an opposite end thereof, the shaft seal comprising a flexible annular member having a radially inner portion including at least one tapered lip extending in one direction along the shaft and adapted to engage the shaft, and a radially outer portion seated on a support in the housing; and at least one retainer overlying the seal and holding the seal in position on the support, the at least one retainer having a radially inner portion that substantially encloses the at least one tapered lip.  
         [0009]     In another aspect, the invention relates to a sprinkler comprising a sprinkler body supporting a nozzle and a cap assembly axially spaced from the nozzle, the cap assembly supporting a rotatable water distribution plate in alignment with the nozzle for distributing water emitted from the nozzle and impinging on the plate; and a shaft seal comprising a flexible annular member having a radially inner portion including at least one tapered lip extending in one direction along the shaft and adapted to engage the shaft and a radially outer portion seated on a support in the housing; and a retainer overlying the seal and holding the seal in position on the support, the retainer having a radially inner portion that substantially encloses the at least one tapered lip.  
         [0010]     In still another aspect, the present invention relates to a sprinkler comprising a sprinkler body supporting a nozzle and a cap assembly axially spaced from the nozzle, the cap assembly supporting a rotatable water distribution plate in alignment with the nozzle for distributing water emitted from the nozzle and impinging on the plate; a shaft seal comprising a pair of lip seals extending in opposite directions from a radially outer portion of the shaft seal, the radially outer portion of the shaft seal seated on a support fixed within the housing; a first retainer overlying the radially outer portion of the shaft seal and a second retainer overlying the first retainer and including a radially inner portion substantially enclosing one of the lip seals, and wherein space between the first and second retainers is filled with lubricant to thereby lubricate the one of the lip seals. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0011]      FIG. 1  is a side elevation, partly in section, of a conventional sprinkler body and cap assembly;  
         [0012]      FIG. 2  is a side elevation, partly in section, of an enlarged cap assembly taken from  FIG. 1 , but inverted relative to the orientation in  FIG. 1 ;  
         [0013]      FIG. 3  is a side elevation, partly in section, of a cap assembly in accordance with a first exemplary embodiment of the invention;  
         [0014]      FIG. 4  is a side elevation, partly in section, of a cap shaft housing in accordance with a second exemplary embodiment of the invention; and  
         [0015]      FIG. 5  is a side elevation, partly in section, of an embodiment similar to that in  FIG. 3  but where the shaft is supported by a ball bearing. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0016]     Referring to  FIGS. 1 and 2 , a known modular sprinkler assembly  10  includes a sprinkler body  12  and a cap  14  removably attached thereto. The sprinkler body  12  threadably receives at its lower end an inlet bushing  16  which is also provided with exterior threads  18  for attachment to a water inlet hose, pipe or the like. The sprinkler body  12  is provided with an interiorly threaded outlet portion  20  which receives an exteriorly threaded nozzle  22  having a discharge orifice  24 . It will be appreciated that nozzle  22  may be removable and interchangeable with other nozzles of different orifice size.  
         [0017]     The body  12  is further provided with an upwardly and outwardly extending frusto-conical portion  26  which, in turn, supports a plurality of, e.g., three upstanding posts  28  (only one visible) which support an annular cap mounting ring  30 . Posts  28  are equally spaced about the frusto-conical portion  26 . The frusto-conical portion  26  may also be provided with a plurality of ports  32  which provide physical and visual access to the nozzle  22 . The annular ring  30  may be provided with any suitable means (not shown) cooperable with complimentary means in the cap  14  for attaching the caps to the sprinkler body for easy removal and/or replacement. See, for example, U.S. Pat. No. 5,224,653 for one suitable arrangement.  
         [0018]     The cap  14  (also preferably plastic) is a generally circular disk-like structure, including a top wall or surface  34  and an outer, annular depending skirt  36 . The cap supports a water distribution plate or spinner  38  by means of a shaft  40  ( FIG. 2 ) received in a centrally located cavity  42  in the cap, as defined primarily by an integral cylindrical wall or housing  44 , closed at one end  46  and open at an opposite end  48 . The housing  44  projects from both sides of the cap top surface  34  and may be integrally formed with the cap. The cavity  42  within housing  44  supports the shaft  40  by means of an elongated rotatable sleeve bearing  52  seated in a smaller recess  54  at the closed end  46  of the housing. The shaft  40  projects axially beyond the open end of the housing wall and is adapted to mount the spinner  38  for rotation with the shaft  40 .  
         [0019]     Axially adjacent the sleeve bearing  52  is a rigid retainer and seal support component  56  that includes a tapered flexible skirt portion  58  that engages the inner surface or wall of the housing  44 , and a cooperating groove and tab arrangement (generally indicated at  60 ) may be used to hold the support  56  in place. A center hub  62  of the support serves as a stationary plain bearing for the shaft  40  and establishes a grease reservoir  64  surrounding the shaft, between the bearing  62  and the seal  68 . An upper ring portion  66  of the support also engages the inner surface of the housing  44 , and may also employ a groove and tab arrangement similar to  60  for holding the support in place within the housing cavity. The rubber (or similar) seal  68  is located within a recess centered within the ring  64 , with an outer radial portion of the seal  68  seated in the recess. An inner, tapered lip portion (or lip)  70  provides a sealing edge that engages the shaft  40 . A disk-like retainer  72  is located over the seal  68  so as to hold the seal in place, the retainer press fit into the upper open end of cylindrical wall  44 , with resilient upturned spokes  74  engaged with the wall. Typically, grease is added behind the seal  68 , i.e., in the grease reservoir  64 , to lubricate the underside of the lip  70  and the plain bearing  62 . Note, however, that the sealing edge or lip  70  remains exposed to the elements. This arrangement can lead to premature wearing and deterioration of the lip  70  and subsequent migration of debris past the seal.  
         [0020]     Turning to  FIG. 3 , the cap  114 , spinner  138 , shaft  140 , seal  168 , etc. are identical to the corresponding components in  FIGS. 1 and 2  and, accordingly, similar reference numerals, but with the prefix “1” added, are used to indicate such components. The single differentiated component is the modified retainer  76 . Significantly, the retainer  76  now not only includes outer tapered flanges or spokes  78  that engage the inner surface of the cylindrical wall  144  of the housing cavity and a center hub portion  80 , but also a radially inner, tapered portion  82  that extends axially and radially, terminating at a center opening  84 , thus, substantially enclosing the lip  170  of the seal  168 . Sufficient clearance is provided between the radially inner edge of the inner tapered portion  82  and the shaft  140  so that the shaft can freely rotate relative to the cap  114 . Grease or other suitable lubricant may now be added to the annular space  86  above the lip  170 . The grease also fills the radial gap at the opening  84 , resulting in an effective barrier to any dirt or debris that could otherwise contact and damage the seal  168 . Moreover, not only is the lip  170  no longer exposed to the elements, but both sides of the lip are now maintained in a lubricated condition by the added grease in space  86 , thereby increasing the life of the seal.  
         [0021]     A second embodiment of this invention is shown in  FIG. 4 . Here, only the housing portion of the cap assembly is shown, and it will be appreciated that the remainder of the cap assembly may be similar to that shown in  FIGS. 1 and 2 , but may also form a part of any other cap or sprinkler component on which the shaft can be supported for rotation. For convenience, elements similar to those in  FIG. 1  or  3  are indicated by similar reference numerals but with the prefix “2” added. In this embodiment, the shaft  240  is supported in the housing  244  in a configuration where rotation of the shaft  240  is retarded by viscous fluid in the housing  244 . Specifically, the shaft  240  is seated in a recess  254  in the closed end  246  of the housing  244  and engages a thrust bearing  90  interposed between the end of the shaft and the bottom wall of the recess. A rotor  92  is secured about the shaft, and the cavity  94  surrounding the shaft and rotor is filled with a viscous silicon fluid so that the shaft  240  spins at a controlled reduced speed, rather than in a free spinning manner. The degree of speed retardation may be controlled by the amount and composition of the viscous fluid, and by the shape of the rotor.  
         [0022]     A seal support  256  is seated within the housing for supporting the shaft seal. The support  256  also incorporates a plain bearing  262  and supports the shaft seal as in the previously described embodiments, but the periphery of the support has been slightly modified to fit the housing in this particular application. The seal  96  in this embodiment is of a double lip design where the outer periphery of the seal  96  is seated on the support  256  in the same manner as described above, but lip portions  98 ,  100  extend in opposite directions to engage the shaft  240  in two axially spaced positions. The reservoir  264  between the lower lip  100  and the plain bearing  262  may be filled with grease or other suitable lubricant. A first retainer  272  that holds the seal  96  on the support  256  may be a conventional retainer, similar to retainer  72  shown in  FIGS. 1 and 2 . Here, however, a second retainer  276  similar to that shown in  FIG. 3  is applied over the first retainer  272 , creating an additional reservoir  102  between the two retainers. This reservoir is also filled with grease so that both lip portions  98 ,  100  of the seal are well lubricated. Here again, the grease in an upper portion of the reservoir  102  will effectively seal the radial gap between the radially inner edge  104  of the retainer  276  and the shaft  240 .  
         [0023]     Still another arrangement is shown in  FIG. 5  where a cap  314  is adapted to mount a spinner (not shown) similar to spinner  138  in  FIG. 3 , on a shaft  340  secured in housing  344 . In this embodiment, the housing  344  and shaft seal support  356  have been modified to eliminate the plain bearing  162  in favor of a ball bearing  362  that is held in place by a pair of bearing retainers  364 ,  366  on either side of the bearing. The shaft seal arrangement is otherwise similar to that shown in  FIG. 3 , with the retainer  376  applied over the single lip seal  368  to substantially enclose the sealing edge or lip of the seal as described hereinabove.  
         [0024]     It will be appreciated that the invention is fully applicable to any of a number of rotary plate shaft configurations mounted in sprinkler caps or other sprinkler components and where the rotor plates are free spinning or controlled by viscous retarders, and where the shafts are supported by plain or ball bearings.  
         [0025]     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.