Patent Publication Number: US-7584904-B2

Title: Sprinkler with viscous hesitator

Description:
BACKGROUND OF THE INVENTION 
   This invention relates to rotary sprinklers and, more specifically, to a rotary sprinkler having a stream interrupter or “hesitator” that operates in either a random or controlled manner to achieve greater uniformity in the sprinkling pattern and/or to create unique and otherwise difficult-to-achieve pattern shapes. 
   Stream interrupters or stream diffusers per se are utilized for a variety of reasons and representative examples may be found in U.S. Pat. Nos. 5,192,024; 4,836,450; 4,836,449; 4,375,513; and 3,727,842. 
   One reason for providing stream interrupters or diffusers is to enhance the uniformity of the sprinkling pattern. When irrigating large areas, the various sprinklers are spaced as far apart as possible in order to minimize system costs. To achieve an even distribution of water at wide sprinkler spacings requires sprinklers that simultaneously throw the water a long distance and produce a pattern that “stacks up” evenly when overlapped with adjacent sprinkler patterns. These requirements are achieved to some degree with a single concentrated stream of water shooting at a relatively high trajectory angle (approximately 24° from horizontal), but streams of this type produce a non-uniform “donut pattern”. Interrupting a single concentrated stream, by fanning some of it vertically downwardly, produces a more even pattern but also reduces the radius of throw. 
   Proposed solutions to the above problem may be found in commonly owned U.S. Pat. Nos. 5,372,307 and 5,671,886. The solutions disclosed in these patents involve intermittently interrupting the stream as it leaves a water distribution plate so that at times, the stream is undisturbed for maximum radius of throw, while at other times, it is fanned to even out the pattern. In both of the above-identified commonly owned patents, the rotational speed of the water distribution plate is slowed by a viscous fluid brake to achieve both maximum throw and maximum stream integrity. 
   There remains a need, however, for an even more efficient stream interrupter or diffuser configuration to achieve more uniform wetted pattern areas. 
   BRIEF SUMMARY OF THE INVENTION 
   One exemplary sprinkler incorporates a hesitating mechanism (or simply “hesitator” assembly) into a rotary sprinkler that causes a momentary reduction in speed of the water distribution plate. This momentary dwell, or slow-speed interval, alters the radius of throw of the sprinkler. In one exemplary embodiment, the hesitation or slow-speed interval occurs randomly, thus increasing the overall uniformity of the wetted pattern area. In this embodiment, a cam is fixed to the water distribution plate shaft, the cam (referred to herein as the “shaft cam”) located in a sealed chamber containing a viscous fluid. Surrounding the cam is a rotor ring that “floats” within the chamber and that is formed with cam lobes (referred to herein as “the hesitator lobes”) that are adapted to be engaged by the shaft cam, and more specifically, a shaft lobe on the shaft cam. In this regard, the rotor ring is free not only to rotate but also to move laterally or translate within the chamber. Thus, when a hesitator lobe is struck by the shaft lobe, the rotation of the shaft cam, shaft and water distribution plate slows until the shaft lobe pushes the hesitator lobe out of its path, moving the rotor ring laterally but also causing some degree of rotation. By moving the rotor ring laterally, the second hesitator lobe is pulled into the path of the shaft lobe, such that a second slow-speed interval is set up. It will be appreciated that, due to the slight rotation of the rotor ring, the slow-speed hesitation events or intervals are incurred in a random or non-uniform manner, thus enhancing the uniformity or the “filling-in” of the circular wetted pattern area. 
   In another exemplary embodiment, the rotor ring is split into a pair of arcuate segments that are confined to pivoting motion, i.e., the segments are not free to randomly rotate, such that the hesitation or slow-speed intervals are controlled and predictable. Thus, non-round patterns can be designed for wetting irregular areas. For example, if each arcuate segment is provided with a pair of hesitator lobes, one on either side of the segment pivot pin, four relatively short slow-speed intervals are established, separated by four relatively long fast-speed intervals, thus creating a four-legged sprinkling pattern. 
   In still another embodiment, a 360° rotor ring having a pair of diametrically opposed hesitator lobes is confined in the chamber for lateral movement or translation as the shaft lobe pushes past the hesitator lobes. With this arrangement, a pair of relatively short diametrically opposed slow-speed intervals are separated by a pair of relatively long fast-speed intervals, creating a linear sprinkling pattern. 
   Accordingly, in one aspect, the invention relates to a sprinkler device comprising: a rotatable shaft having a cam, the cam having a radially outwardly projecting shaft lobe; a water distribution plate supported on one end of the shaft and adapted to be impinged upon by a stream emitted from a nozzle causing the water distribution plate and the shaft to rotate; a hesitator assembly supported on an opposite end of the shaft the assembly including a stationary housing having a sealed chamber at least partially filled with a viscous fluid, the shaft passing through the chamber, with the cam and shaft lobe located within the chamber; and a rotor ring located within the chamber in substantially surrounding relationship to the cam, the rotor ring having two or more inwardly projecting hesitator lobes movable into and out of a path of rotation of the shaft lobe, such that rotation of the shaft and water distribution plate is slowed during intervals when the shaft lobe engages and pushes past the one or more hesitator lobes. 
   In another aspect, the invention relates to a method of controlling rotation of a water distribution plate supported on a shaft and adapted to rotate by reason of impingement of a stream emitted from a nozzle on grooves formed in the plate, the method comprising: (a) slowing rotation of the shaft under all conditions; and (b) further showing the rotation of the shaft intermittently so as to create intervals of relatively slow and relatively fast rotation and thereby correspondingly increase and decrease, respectively, a radius of throw of the stream. 
   Exemplary embodiments will now be described in detail in connection with the drawings identified below. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a cross section through a viscous hesitator device in accordance with an exemplary embodiment of the invention; 
       FIG. 2  is a perspective view of the device illustrated in  FIG. 1 ; 
       FIG. 3  is a section taken along the line  3 - 3  of  FIG. 1 ; 
       FIG. 4  is a section taken along a section line similar to line  3 - 3  of  FIG. 1 , but illustrating an alternative embodiment of the invention; 
       FIG. 5  is a view similar to  FIG. 4  but illustrating the rotor cam rotated in a clockwise direction approximately 20°; 
       FIG. 6  is a view similar to  FIGS. 4 and 5  but illustrating the rotor cam rotated approximately 70° beyond the position shown in  FIG. 5 ; 
       FIG. 7  is a view similar to  FIG. 6  but illustrating the rotor rotated 20° past the position shown in  FIG. 6 , and also, illustrating the various fast and slow rotation intervals spaced about the circumference of the hesitator device; 
       FIG. 8  illustrates a sprinkling pattern achieved by the hesitator device illustrated in  FIGS. 4-7 ; 
       FIG. 9  is a view similar to  FIG. 3  but illustrating still another embodiment of the hesitator device; 
       FIG. 10  is a view similar to  FIG. 9  but with the rotor rotated approximately 20° from the position shown in  FIG. 9 ; 
       FIG. 11  is a view similar to  FIG. 10  but with the rotor rotated approximately 156° from the position illustrated in  FIG. 10 ; and 
       FIG. 12  illustrates a plan view of a sprinkler pattern achieved by use of the hesitator mechanism shown in  FIGS. 9-11 . 
   

   DETAILED DESCRIPTION OF THE DRAWINGS 
   Referring initially to  FIGS. 1 and 2 , a hesitator assembly  10  for incorporation into a rotatable sprinkler includes a shaft  12  secured in a housing  14 . The free end of the shaft typically mounts a conventional water distribution plate  16  that substantially radially redirects a vertical stream (indicated by arrow S in  FIG. 1 ) emitted from a nozzle (not shown) in the sprinkler body (also not shown). The plate  16  is formed with one or more grooves  17  that are slightly curved in a circumferential direction so that when a stream emitted from the nozzle impinges on the plate  16 , the nozzle stream is redirected substantially radially outwardly into one or more secondary streams that flow along the groove or grooves  17  thereby causing the plate  16  and shaft  12  to rotate. 
   Shaft  12  is supported within the housing  14  by a bearing  18  that is press-fit within a counterbore  20  formed in the housing. The bearing  18  engages a shoulder  22  formed in the housing and the bearing itself is formed at one end with an annular shoulder  24  that provides a seat for a conventional flexible double-lip seal  26  that engages the shaft and is held in place by a circular retainer  28 . A shaft retainer  30  is mounted on the shaft adjacent the opposite end of the bearing  18 . 
   The downstream or remote end of the shaft is received in a blind recess  32  formed in a lid  34  that is attached to a base  36  that, in turn, is attached to the downstream end of the housing  14 . The lid  34  is formed with a skirt portion  38  that telescopes over and engages the peripheral side wall of the base  36 , and a top surface  35  that joins to a center hub  40  defining the blind recess  32 . Similarly, the base  36  is formed with a depending skirt  42  that telescopes over and engages the upper or downstream end of the housing  14 . A radial flange  44  engages the upper peripheral edge  46  of the housing. 
   Within the lid  34 , and specifically within a cavity  50  axially between the flange  44  of the base  36  and an underside surface  52  of the top surface  35 , a shaft cam  54  is fixed to the shaft  12  for rotation therewith. A substantially ring-shaped rotor  56  surrounds the cam and is otherwise unattached. More specifically, the housing  14 , base  36  and lid  34  are configured to form the cavity or chamber  50  between the bearing  18  and the lid  34 . The chamber is at least partially if not completely filled with viscous fluid (e.g., silicone). Since the outer diameter (OD) of the rotor ring  56  is greater than the inner diameter (ID) of the base  36 , the rotor is confined to chamber  50 , but is otherwise free to float on or move within the fluid in the chamber. 
   It should be noted here that placement of the shaft cam and lobe in the chamber or cavity  50  filled or at least partially filled with viscous fluid will slow the rotation of the shaft and water distribution plate under all conditions, so as to achieve a greater radius of throw as compared to a freely spinning water distribution plate. Thus, reference herein to fast and slow rotation intervals are relative, recognizing that both intervals are at speeds less than would be achieved by a freely spinning water distribution plate. 
   The shaft cam  54 , as best seen in  FIG. 3 , is formed with a smoothly curved, convex primary cam lobe  58  (the shaft lobe) projecting radially away from the cam and the shaft center. 
   The center opening  62  of the rotor ring  56  is defined by an inner diameter surface or edge  64  and is formed with three radially inwardly extending rotor or hesitator lobes  66 , equally or randomly spaced about the opening  62 . 
   The interaction between the shaft cam lobe  58  and the hesitator lobes  66  determines the rotational speed of the shaft  12  and hence the water distribution plate  16  ( FIG. 1 ). 
   More specifically, when a prescribed amount of rotation force is applied to the shaft  12  (via the stream S impinging on grooves  17 ), the shaft cam  54  will rotate with the shaft within the fluid-filled cavity or chamber  50 . The shaft cam  54  has little mass and large clearances which generate a lesser amount of resistance. As the shaft cam  54  rotates, the shaft lobe  58  will come into contact with one of the hesitator lobes  66  on the rotor ring  56 . When this takes place, the rotor ring  56  (having a much larger mass and much tighter clearances) will immediately reduce the revolutions per minute of the cam  54  (and hence the shaft  12  and water distribution plate  16 ) causing a stalling or hesitating effect. The shaft lobe  58  now has to push the hesitator lobe  66  out of the way in order to resume its previous speed. 
   The rotor ring  56 , having multiple hesitator lobes  66  is designed such that, as the shaft cam lobe  58  pushes past one hesitator lobe  66 , it pulls the next adjacent hesitator lobe into its path. Moreover, the rotor ring  56  not only moves laterally when engaged by the shaft cam lobe  58 , but also rotates slightly in the same direction of rotation as shaft cam  54  and shaft  12 . Not being fixed, the rotor ring  56  will thus provide a random stalling or hesitating action due to the periodic but random hesitation of the water distribution plate  16 . Stated otherwise, the water distribution plate  16  will rotate through repeating fast and slow angles but at random locations. Varying the outside diameter, overall thickness, the number of and engagement heights of the lobes  66  on the rotor ring  56  will adjust the frequency and length of the stall events. Changing the viscosity of the fluid will also impact the above parameters. 
   Alternatively, if a random hesitating action is not desired, the locations at which the transition from slow-to-fast, or fast-to-slow-speed can be restricted to a number of desired repeatable positions. This is done by restraining movement of the rotor ring  56  so it can move laterally but cannot rotate when the shaft cam lobe  58  comes into contact with one of the slow-speed or hesitator lobes  66 . The rotor ring may be of a one or multiple-piece design, restrained in a fashion so when the shaft cam  54  rotates and shaft lobe  58  comes into contact with a hesitator lobe, the shaft lobe  58  can slowly push the hesitator lobe laterally out of its path, in a slow-speed mode. When it pushes past, the shaft cam  54  (and shaft  12  and water distribution plate  16 ) returns to a fast-speed mode. This arrangement creates a repeatable (i.e., not a random) slow-to-fast/fast-to-slow-speed interval pattern. By increasing or decreasing the lobe clearances within the fluid-filled housing, or by altering the amount of engagement between the shaft lobe and the hesitator lobe, or both, will result in different repeatable patterns that can be customized for varying application. Changes in those areas will directly affect the start and ending positions of the slow-to-fast/fast-to-slow rotation modes as well as the rotation speed while in the slow-speed mode. 
     FIGS. 4-6  illustrate an exemplary fixed-pattern hesitator arrangement. In these views, component parts are generally similar to  FIGS. 1 and 2 , but with a modified rotor ring. Thus, the hesitator  70  includes a shaft  72  supporting a water distribution plate (not shown but similar to  16  in  FIG. 1 ) at one end thereof, with the opposite end mounted in a housing  74  in a manner similar to that described above. The shaft cam  76  fixed to the shaft  72  is generally similar to cam  54  and is also located in a sealed viscous fluid-filled chamber  78 . In this embodiment, however, the rotor ring is formed as two arcuate segments  80 ,  82 , pivotally mounted by pins  84 ,  86 , respectively, to the base  87 . Thus, the segments  80 ,  82  are limited to pivoting motion only within the chamber as described in greater detail below. The arcuate segment  80  includes a pair of radially inwardly projecting hesitator lobes  88 ,  90  while segment  82  includes a pair of substantially identical inwardly projecting hesitator lobes  92 ,  94 . Note that the lobes  88 ,  90 ,  92  and  94  are circumferentially spaced substantially 90° from each other about the shaft  72 . The shaft cam  76  is formed with a single radially outwardly projecting shaft lobe  96  that is located so as to successively engage the hesitator lobes  88 ,  90 ,  92  and  94  upon rotation of the shaft  72 . 
   With this arrangement, rotation of the shaft  72  and hence the water distribution plate will slow upon engagement of the shaft lobe  96  of cam  76  with anyone of the hesitator lobes  88 ,  90 ,  92  and  94 . In  FIG. 4 , the shaft lobe  96  has engaged the hesitator lobe  94 , slowing rotation of the shaft  72  and water distribution plate. The slow rotation interval thus starts when the shaft lobe  96  first comes into contact with the hesitator lobe  94 , and will continue until the shaft lobe  96  pushes the hesitator lobe  94  out of its path sufficiently to enable the shaft lobe  96  to pass via pivoting action of the segment  82  about pin  86  in a clockwise direction. As indicated in  FIG. 5 , the slow-speed interval extends through an angle of approximately 20°. In other words, rotation speed will increase as the apex of the shaft lobe  96  passes the apex of hesitator lobe  94  as shown in  FIG. 4 . 
   With reference now to  FIG. 5 , as the shaft lobe  96  pushes past hesitator lobe  94 , the pivoting movement of the arcuate segment  82  forces the other hesitator lobe  92  to be positioned in the path of the rotating shaft lobe  96 . The degree of rotation from when the shaft lobe  96  pushes past the hesitator lobe  94  to when it comes into contact with the next hesitator lobe  92  may be regarded as the fast-speed interval which, as indicated in  FIG. 6 , extends through an angle of approximately 70°. 
     FIG. 7  shows the shaft lobe  96  further engaged with hesitator lobe  92 , and also indicates all of the fixed 20° slow-speed intervals caused by the four hesitator lobes  88 ,  90 ,  92  and  94 , with 70° fast-speed intervals in between. 
   When the water distribution plate of the sprinkler is in the 20° slow-speed interval, it will throw the water as far as possible (this is its “maximum throw radius”). When it rotates into the 70° fast-speed interval, the throw radius will be greatly reduced. With the described configuration of four hesitator lobes  88 ,  90 ,  92  and  94 , a four-legged water pattern  98  will form as shown in  FIG. 8  as the water distribution plate rotates from fast-to-slow at the four fixed hesitator lobes. The pattern  98  thus includes four extended wetted areas or legs A, B, C and D that correspond to the four 20° slow-speed intervals, whereas areas between the areas A, B, C and D correspond to the four 70° fast-speed intervals. The orientation of all four legs can be adjusted by rotating the sprinkler on its mounting riser. The total degrees of slow and/or fast rotation can also be altered by increasing or decreasing the amount (i.e., duration) of cam/lobe engagement. In addition, the slow rotation speed and the total slow-speed time can be varied by increasing or decreasing the clearances between the moving parts. 
     FIG. 9  discloses another embodiment where, again, the overall configuration of the subassembly is similar to that described in connection with  FIGS. 1 and 2 , but with a modified rotor ring. In this embodiment, the rotor ring  100  is formed as a 360° annular ring similar to rotor ring  56  shown in  FIG. 1 , but is confined to lateral movement only by the pins  102 ,  104  fixed to the base  106 . The inner surface of the ring  100  is formed in the shape generally of a figure-eight with a pair of radially inwardly projecting hesitator lobes  108  and  110 , moveable into the path of the shaft lobe  112  of the cam  114  fixed to shaft  116 . In this case, the slow-speed or slow-rotation interval starts when the shaft lobe  112  first comes into contact with a hesitator lobe, e.g., lobe  108  and the slow rotation will continue until the shaft lobe  112  pushes the hesitator lobe  108  out of its path sufficiently to enable the shaft lobe to pass by. The slow-speed interval depicted in  FIG. 9  extends about 20°. Note that as the shaft lobe  112  pushes past the hesitator lobe  108 , the rotor ring  100  is forced to move laterally, without rotation, by reason of pins  102 ,  104  being seated in aligned longitudinal slots  118 ,  120  formed in the rotor ring  100 . 
   Once the shaft lobe  112  has pushed the hesitator lobe  108  out of its path with the same rotational load applied to the shaft, rotation speed will increase until shaft lobe  112  engages the other hesitator lobe  110  which has been drawn into its path by the lateral movement of the rotor ring.  FIG. 10  illustrates the rotor ring  100  moved laterally substantially to its maximum as the shaft lobe  112  and shaft  116  resume a normal fast-speed.  FIG. 11  illustrates commencement of the next slow-speed interval of 20° following the fast-speed interval of 156°. 
   As may be appreciated from  FIGS. 9-11 , the fixed intervals of 20° slow rotation are diametrically opposed to each other. The sprinkler water distribution plate  16 , while in the slow rotation mode, will throw the water as far as possible. The water distribution plate  16  will rotate relatively fast through the 156° angles between the 20° slow-speed intervals, causing the water to be pulled back significantly. This configuration will thus form a long narrow or linear water pattern  122  as shown in  FIG. 12 , referred to as a strip pattern, with maximum throw evident in the pattern legs  124 ,  126  corresponding to the opposed 20° slow-speed intervals explained above. The orientation of the pattern is adjustable by rotating the sprinkler on its mounting riser. In addition, the 20° slow-speed angle can again be altered by increasing or decreasing the amount of cam/stop lobe engagement while the slow rotation speed and total slow-speed time can be varied by increasing or decreasing clearances between the mating parts within the viscous-fluid chamber. 
   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.