Rotator air management system

In a rotational speed viscous dampening device comprising a housing, a shaft having one end located in the housing and rotatable relative thereto, and a rotor body on the one end of the shaft with viscous fluid at least partially filling the housing, an improvement includes various rotor configurations for managing air within the housing so that the air does not interfere with viscous shearing of molecules of the viscous fluid between the rotor body and an interior wall of the housing. The viscous dampening device may be used to control the speed of rotation of a stream distributor component of a sprinkler.

TECHNICAL FIELD 
This invention relates primarily to irrigation sprinklers having stream 
driven rotor plates utilizing viscous dampening for controlling the 
rotational speed of the rotor plates. 
BACKGROUND AND SUMMARY OF THE INVENTION 
Current viscous-damped rotator design and technology employ a cylindrical 
or conical rotor attached to a shaft that rotates within a housing having 
a cylindrical or conical chamber (rotor cavity) that is filled with a 
viscous fluid (this device is sometimes referred to as a "rotor motor"). 
The rotor motor acts as a brake or dampener to control the rotational 
speed of the stream distribution or rotor plate. The dampening or 
resistance that impedes rotation comes from the high forces required for 
shearing the viscous fluid molecules. This shearing takes place between a 
moving boundary layer, (molecules of fluid attracted to the rotor 
surface), and stationary neighboring fluid molecules (molecules attracted 
to the stator or housing surface) in the rotor cavity. 
If the viscous fluid molecules separate from neighboring molecules and a 
less viscous foreign substrate fills the gap between molecules, the rotor 
may become free spinning, i.e., it may rotate at a speed approaching that 
which would occur in the absence of any viscous dampening. In the rotor 
cavity, air is the predominant substrate that may fill this thin gap. It 
is believed that as the rotor turns, air in the rotor cavity begins to 
thinly distribute itself all the way around the rotor until it grows large 
enough (or spreads itself thin enough) to separate the viscous fluid 
molecules all around the cylindrical surface of the rotor. In effect, a 
cylindrical sleeve of air is formed in the much thicker viscous fluid. The 
result is that the viscous fluid molecules no longer shear, and the 
dampening or braking effect becomes negligible. 
An obvious solution would be to prevent air from ever entering the rotor 
housing and, more specifically, the rotor cavity. This however has proven 
to be unobtainable and probably not practical. Moreover, closer evaluation 
and testing has shown that very small amounts of air are of little 
consequence. The real problem comes to light when there is too much air 
present, and at the wrong location within the rotor cavity. In fact, the 
volume of air is less significant than its location within the cavity. For 
example, a large bubble at the top of the cavity is not a problem, but a 
smaller air volume "smeared" around the rotor may indeed be problematic. 
The goal then is two-fold: to have as little air as possible in the rotor 
cavity, and then to manage any air that is present. This invention focuses 
on the management of air present within the rotor cavity. 
A first air management technique incorporates air management features into 
the rotor design per se. Movement of the air is accomplished by 
manipulating the geometry of the rotor. It has been discovered that 
changing the geometry of the rotor to have one or more fins protruding 
outwardly to a point closely adjacent the interior surface of the housing, 
i.e., the surface defining the rotor cavity, appears to manage most of the 
air in an efficient manner. As the rotor rotates, high and low pressure 
areas are created in front of and behind the rotor fins respectively. The 
much thinner air rushes to the low pressure area behind the rotor fin and 
trails in this low pressure wake. By staying in this wake as the rotor 
rotates, the leading edge of the rotor is able to penetrate pure viscous 
fluid, maintaining an area of fluid-to-fluid shearing, resulting in the 
dampening required for proper rotation. Over an extended period of usage, 
however, fluid can leak out leaving air/water in its place. In the event 
the volume of air is large enough to fill the entire low pressure area 
behind all elements of the rotor, thus allowing the leading edge to hit 
air rather than fluid, the result will be the loss of the viscous fluid 
shearing. Further refinement of the rotor design reveals that 
non-symmetrical fins will further enhance the volume of air that can be 
managed. By making one of two fins shorter, air traveling in the shorter 
fins radial wake has been moved inward, away from the path of the 
approaching longer fin. This results in the longer fin penetrating the 
fresh fluid required for proper shearing. 
A third variation of this method utilizes a cylindrical rotor with one or 
more recesses to create low pressure pockets for the air to be contained. 
This can range from large lengthwise grooves or pockets to many thin 
shallow grooves or even dimples. 
A second air management technique utilizes a rotating disk inside the rotor 
cavity. The disk could be a part of the rotor or axially spaced from the 
rotor. This disk acts as a "decoy," i.e., it attracts air to its surface 
rather than to the rotors surface. By making the disk's major diameter 
larger than the rotor, the disk has an increased shear rate due to its 
higher velocity, which produces a higher rate of boundary layer 
separation. This separation appears to create small eddy currents near the 
disk surface that attract the air. Air is thus continuously attracted to 
the moving disk the entire time rotation is occurring, allowing the 
desired viscous shearing to occur in the area between the rotor body and 
the housing surface. Perforating the thin disk also helps more air to be 
managed by creating small, low pressure pockets that attract and capture 
air as the disk rotates. 
In the detailed description which follows, several different rotor designs 
are described, each of which is designed to efficiently manage air inside 
the rotor cavity so as not to degrade the viscous dampening function of 
the rotor motor. 
Testing has shown that with this invention, a rotor will still operate 
properly with just 50% of the original fluid volume. This is most 
significant with micro rotators due the difficulty of purging all air from 
the small rotor housing during assembly. 
Accordingly, in one aspect, the invention relates to an improvement in a 
rotary sprinkler comprising a nozzle and a rotatable stream distributor 
plate secured to one end of a shaft, wherein rotational speed of the 
stream distributor plate is controlled by a viscous damping arrangement 
including a rotor body on an opposite end of the shaft and located within 
a chamber at least partially filled with a viscous fluid, and wherein the 
rotor body is rotatable relative to a stator; the improvement wherein a 
disk is mounted within the chamber for rotation with the rotor body, the 
disk having an outside diameter greater than an outside diameter of the 
rotor body. 
In another aspect, the invention relates to an improvement in a rotary 
sprinkler comprising a nozzle and a rotatable stream distributor plate, 
wherein rotational speed of the stream distributor plate is controlled by 
a viscous damping arrangement including a rotor arranged within a chamber 
at least partially filled with a viscous fluid, and wherein the rotor is 
rotatable relative to a stator; the improvement wherein the rotor includes 
a hub and at least one fin projecting therefrom. 
In still another aspect, the present invention relates to a rotational 
speed viscous dampening device comprising a housing, a shaft having one 
end located in the housing and rotatable relative thereto, and a rotor 
body on the one end of the shaft with viscous fluid at least partially 
filling the housing, the improvement comprising means for managing air 
within the housing so that the air does not substantially interfere with 
viscous shearing of molecules of the viscous fluid between the rotor body 
and an interior wall of the housing. 
In still another aspect, the invention relates to a rotary sprinkler 
comprising a nozzle and a rotatable stream distributor plate secured to 
one end of a shaft, wherein rotational speed of the stream distributor 
plate is controlled by a viscous damping arrangement including a rotor on 
an opposite end of the shaft and arranged within a chamber at least 
partially filled with a viscous fluid, and wherein the rotor is rotatable 
relative to a stator; the improvement wherein the rotor includes a center 
hub with an annular disk at one end thereof, and a fin extending axially 
along the center hub between the disk and an opposite end of the center 
hub. 
In still another aspect, the invention relates to a rotary sprinkler 
comprising a nozzle and a rotatable stream distributor plate secured to 
one end of a shaft, wherein rotational speed of the stream distributor 
plate is controlled by a viscous damping arrangement including a rotor on 
an opposite end of the shaft and arranged within a chamber at least 
partially filled with a viscous fluid, and wherein the rotor is rotatable 
relative to a stator; the improvement wherein the rotor includes one or 
more air accumulating pockets formed therein. 
Other features of the invention will become apparent from the detailed 
description which follows.

DETAILED DESCRIPTION OF THE DRAWINGS 
Referring to FIG. 1, a conventional sprinkler head 10 is shown as an 
example of the type of sprinkler for which the present invention is 
particularly applicable. It should be understood, however, that this 
invention is not limited to the sprinkler construction shown in FIG. 1, 
but is applicable to a wide variety of rotating sprinklers and other 
devices which make use of a viscously damped rotating shaft. The sprinkler 
10 includes a sprinkler body 12 which is a static structure adapted to be 
connected to a source of water under pressure. An outlet nozzle 14 is 
secured to the sprinkler body 12 so as to direct the water under pressure 
into an atmospheric condition as a primary stream P having a generally 
vertically extending axis. The sprinkler head 10 also includes a rotary 
distributor plate 16 which is mounted for rotation about an axis coaxially 
aligned with the nozzle axis. The distributor plate 16 includes surface 
means generally indicated at 18 for engaging the primary stream and which 
establish a reactionary force component acting on the plate in a direction 
tangential to the rotational axis thereof so as to effect rotation of the 
plate about its axis, and to direct the primary stream P engaged thereby 
in the form of a predetermined pattern away from the distributor plate in 
a substantially radial outward direction. 
The sprinkler head 10 also includes a speed reducing assembly 20 
operatively associated with the distributor plate 16 for reducing the 
rotational speed of the plate from a relatively high speed which would 
occur absent the speed reducing assembly, to a relatively slow, controlled 
speed which maximizes the radial "throw" of the stream. 
The speed reducing assembly 20 includes a cup-shaped housing 22 fixed 
within a cylindrical mounting portion 24 of the sprinkler. This cup-shaped 
housing defines a rotor cavity for the rotor as described below. The end 
wall of the cup-shaped housing 22 is apertured to receive one end of a 
shaft 26, the opposite end of which is connected to the distributor plate 
16. Fixed to the shaft 26 above its lower end is an enlarged fluid damping 
rotor 28 having a diameter which leaves only a small space between the 
rotor and the interior surface of the housing. A ball bearing 30 serves to 
rotatably mount a portion of the shaft extending above the rotor. A 
flexible lip seal 32 is mounted above the ball bearing in a position to 
engage the periphery of the shaft thereabove. The entire interior of the 
cup-shaped housing 22 is filled or at least partially filled with a 
viscous fluid, preferably a silicone fluid. Speed retardation is achieved 
by frictional contact, i.e., viscous shearing, of the molecules of the 
viscous fluid between the moving rotor 28 and the fixed housing or stator 
22. It will be understood that by changing the viscosity of the fluid, the 
extent of speed reduction can be controlled in a predetermined manner. It 
should also be noted here that references to one component "above" 
another, or to orientation of the sprinkler in general are merely for 
convenience and understanding, as they relate to the drawing figure. In 
use, the sprinkler may be oriented differently, for example, it may be 
inverted from the orientation in FIG. 1. 
In the illustrated sprinkler, the speed reducing assembly (or motor) 20 is 
supported in axially spaced relation to the nozzle 14 by means of spaced 
struts 34, 36 which are joined to the sprinkler body near the nozzle 14 
and which are connected by a horizontal cross brace 38 which, in turn, 
supports the mounting portion 24 for the speed reducing assembly 20. The 
rotor 28 in the illustrated sprinkler is of conventional construction and 
subject to the air management problems discussed above. 
In accordance with this invention, new rotor configurations are presented 
which "manage" the air present within the rotor housing and which might 
otherwise degrade the rotational speed reduction characteristics of the 
device. 
FIG. 2 illustrates a sectional plan view of a rotor 40 in accordance with a 
first exemplary embodiment of this invention mounted on a shaft 42 secured 
at one end within a rotor cavity 44 at least partially (and preferably 
substantially) filled with a viscous fluid 46. The rotor 40 includes a 
center hub or rotor body 48 and a pair of outwardly projecting fins or 
paddles 50, 52. These fins do not project radially from the center axis of 
the shaft 42, but rather, are offset from the shaft axis as apparent from 
the Figure. The rotor configuration is shown more clearly in FIGS. 3 and 
4, but FIG. 2 illustrates the way in which the rotor manages the air 
present in the motor cavity. As the rotor 40 rotates, high and low 
pressure areas (designated H and L, respectively) are created in front of 
and behind the rotor fins 50, 52. The much thinner air rushes to the low 
pressure area behind the rotor fins and trails in this low pressure wake. 
By keeping the air in this wake as the rotor rotates, the leading edges of 
the rotor fins are able to penetrate pure viscous fluid, thus maintaining 
an area of fluid-to-fluid shearing between the fins and the interior 
housing surface, thereby providing the desired viscous dampening effect 
necessary for proper speed rotation control. A further refinement of this 
design includes making one of the two fins (fin 52) shorter, so that air 
traveling in the radial wake of the shorter fin 52 is moved inwardly, 
closer to the center of the hub 48, and away from the path of the 
approaching longer fin 50. This will insure that the longer fin 50 
penetrates fresh viscous fluid necessary for good viscous shearing action 
even when more significant amounts of air are in the cavity. 
As best seen in FIG. 4, the fins 50, 52 extend the full length of the 
center hub 48 of the rotor. In this embodiment, the rotor may have an 
axial length of about 0.19 inch, and each fin has a width of about 0.0180 
inch. Outer edges 54, 56 of fins 50, 52, respectively, have radii from 
about 0.0680-0.0775 inch. The center hub (or rotor body) 48 has an OD of 
about 0.0700 inch and an ID of about 0.0450 inch. These dimensions are 
applicable to very small micro-sprinklers and may vary considerably with 
the size of the sprinkler and speed reducing assembly. 
FIGS. 5 and 6 illustrate a second rotor embodiment, the rotor 58 including 
a center hub (or rotor body) 60 and a pair of fins 62, 64 which, again, 
are offset from the hub center axis. In fact, in this embodiment, the 
leading edges 63, 65 of the fins 62, 64 extend tangentially away from the 
center hub so that the leading edges are necessarily longer than the 
trailing edges but, in addition, fin 62 is longer per se than fin 64. 
Outer edges 66, 68 of the fins 62, 64, respectively, are also radiused and 
the dimensions of this rotor are generally similar to those of the 
previously described embodiment. 
FIGS. 7 and 8 illustrate a rotor 70 including a center hub (or rotor body) 
72 and outwardly projecting fins 74, 76. The fins are offset from the 
center axis of the rotor to an extent generally similar to the embodiment 
in FIG. 3. The fins have straight leading edges 78, 80, respectively, 
along with undercut trailing edges 82, 84. The outermost edges of the fins 
have two radiused portions 86, 88 and 90, 92, respectively drawn on 
different centers. Here again, the length of the fins also varies, with 
the distance from the center hub to the outermost edge of fin 80 being 
about 0.0760 inch, while the same dimension for fin 66 is 0.709 inch. 
Turning to FIGS. 9 and 10, the rotor 94 includes a center hub portion (or 
rotor body) 96 and three fins 98, 100 and 102 spaced equally 
circumferentially about the hub 96, but offset from the center axis of the 
rotor. The fins project an equal distance from the center hub and include 
substantially straight leading and trailing edges 104, 106, respectively. 
The outer edges 108 of the fins are slightly radiused to conform generally 
to the curvature of the housing. In addition, because the leading edges 
104 are tangential to the center hub 96, and the trailing edges 106 are 
radially aligned with the axis of the hub, the leading edges are 
effectively longer than the trailing edges. With this arrangement, the 
wake behind the trailing edges 106 is closer to the center hub, insuring 
that the leading edge 104 of the next fin will penetrate fluid only. 
FIGS. 11 and 12 illustrate yet another rotor configuration. In this 
version, the rotor 110 has a center hub (or rotor body) 112 and a single 
projecting fin 114, slightly offset from the center axis of the hub. The 
fin 114 has a straight leading edge 116 and a radiused trailing edge 118, 
with a hook-like end 120, including a compound radiused edge 121. With 
this arrangement, a low pressure area is formed behind the edge 118 so 
that, again, the leading edge 116 will penetrate viscous fluid only. It 
will be understood that the fins or paddles (or projections) may extend 
radially, however, and still perform the desired air management function. 
Turning to FIGS. 13 and 14, a rotor 122 is shown which includes a center 
hub (or rotor body) 124 and a pair of fins 126, 128 offset from the center 
axis of the hub, with fin 128 projecting a lesser distance from the center 
axis of the hub than fin 126. This rotor is substantially similar to the 
rotor illustrated in FIGS. 3 and 4 with the exception that the width of 
each fin has been increased from approximately 0.018 inch to 0.025 inch. 
FIGS. 15 and 16 disclose another rotor construction 130 which includes a 
center hub (or rotor body) 132 and a pair of fins 134 and 136. The fins 
extend an equal distance from the center axis of the rotor hub, and fin 
136 is substantially radially aligned with the center axis of the hub. Fin 
134, on the other hand, is slightly offset from the hub axis and has a 
substantially lesser width. Otherwise, the fins are similar, with straight 
leading edges 138, 140 and radiused or undercut trailing edges 142, 144. 
Again, the low pressure zone created in the trailing edge undercuts 
attracts and captures the air and assures good dampening action. 
FIGS. 17-28 illustrate embodiments which combine rotor design and decoy 
techniques to achieve the desired air management goal. 
FIG. 17 illustrates a rotor construction 146 located within a motor housing 
148. The rotor 146 includes a substantially cylindrical main rotor body 
150 integrally formed with a shaft 152. Above the rotor body 150, there is 
an integral, apertured disk 154, the details of which are best seen in 
FIG. 18. The disk 154 has a center hub portion 156 with a conical taper 
158 (FIG. 17) at its lower end with three equally spaced radial 
projections 160, 162 and 164, which are shaped as part annular segments. 
The outer circumferential edges of the projections have radii 
substantially similar to the interior diameter of the motor housing 142, 
to maximize the diametric difference between the hub or rotor body 150 and 
the projections 160, 162 and 164. Radiused recesses 166, 168 and 170 
separate the projections. At the same time, each of the projections is 
formed with an elongated aperture, 172, 174 and 176, respectively. The 
disk design, with a larger diameter than the rotor body, in combination 
with the projections 160, 162 and 164, cutouts 166, 168 and 170 along with 
apertures 172, 174 and 176 attract and capture whatever air is present in 
the rotor cavity, assuring good viscous shearing performance in the 
viscous fluid between the rotor body 150 and the housing wall. 
FIG. 19 illustrates a variation of the rotor shown in FIGS. 17 and 18. More 
specifically, FIG. 19 illustrates a micro-sprinkler which includes a rotor 
motor housing 180, with a rotor shaft 182 projecting out of the housing 
and mounting at its free end a rotary stream distributor or plate 184. It 
will be understood that the sprinkler body (not shown) includes a nozzle 
which directs a stream to atmosphere which impinges upon the groove 186 in 
the plate 184, the groove configured to impart rotation to the plate 184 
to thereby distribute the stream in the manner essentially as described in 
connection with FIG. 1. The speed of rotation of the plate is reduced by 
the viscous damping arrangement within the rotor motor housing 180. 
Specifically, the shaft 182 mounts a rotor 188 which rotates along with 
the shaft, in relatively close alignment to an interior stator 190. 
Details of the rotor are best seen in FIGS. 20 and 21. 
The rotor 188 includes a generally cylindrical body portion 191 with a 
tapered region 192 extending upwardly to a disk member 194, with an upper 
shaft extension portion 196 adapted to be secured within the rotor motor 
housing as shown in FIG. 19. The cylindrical portion 190 and tapered 
portion 192 of the rotor 188 are formed with three axially extending 
grooves 198 (two shown) extending upwardly to the disk 194. The latter is 
formed with three radially outward extending projections 200, 202 and 204, 
each of which has outer circumferential edges which conform generally to 
the interior surface of the rotor motor housing. In addition, the 
projections are separated by curved cut-out or recessed portions 206, 208 
and 210. Here again, the disk 194 attracts air, creating wakes behind the 
cut-outs, decoying air away from the main body 190 of the rotor. Grooves 
198 provide even greater assurance of good viscous shearing by providing 
additional space for air to accumulate. Alternatives to the grooves 198 
include numerous shallow grooves, dimples (see 198' in FIG. 22) or the 
like, all of which are designed to capture air. 
FIGS. 22 and 23 illustrate a variation of the rotor shown in FIGS. 20 and 
21 with similar reference numerals used to designate corresponding 
components, but with the prime designation added. The difference between 
the two rotors is that the disk 194' is solid, i.e., there are no discrete 
projections separated by cut-outs as in the rotor shown in FIGS. 20 and 
21, and there are no axial grooves along the rotor body. Optional dimples 
198' are shown in phantom. 
Turning now to FIGS. 24-26, an alternative rotor construction 212 includes 
a cylindrical center hub portion 214 with a lower solid disk portion 216 
and an upper solid disk portion 218. Extending between the two circular 
disk portions, there is a single fin or projection 220 which, as best seen 
in FIG. 24, is slightly offset from the center axis of the rotor. Fin 220 
includes a straight leading edge 222 and a curved undercut trailing edge 
224 substantially similar to the fin 104 shown in FIG. 11. 
FIGS. 27 and 28 show a rotor construction somewhat similar to the rotor 
construction shown in FIGS. 24-26 but wherein the upper circular disk is 
omitted. More specifically, the rotor 226 includes a generally cylindrical 
center hub 228, the lower end of which mounts a circular disk 230 having a 
generally conical upper surface 232. A single fin 234 extends along the 
length of the center hub 228 from the disk 230 through the upper end of 
the cylindrical portion. The single fin 234 projects outwardly from the 
center hub, slightly offset from the center axis of the rotor and has a 
length less than the radius of the disk 230 as best seen in FIG. 27. Air 
present within the motor cavity will be attracted to the disk 230 and/or 
to a location behind the trailing edge 236 of fin 234. 
It will be appreciated that in each of the described embodiments, effective 
air management is achieved which minimizes the otherwise undesirable 
consequences of air in the rotor motor cavity. 
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.