Note: Descriptions are shown in the official language in which they were submitted.
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BALANCED REACTION IMPACT SPRINKIER
TECHNICAL FI13ID
The present invention relates generally to water
sprinklers of the impact-arm type, and~ more particularly~
to impact-arm sprinklers for full-circle rather than
part-circle watering.
13ACKGROUND OF PRIOR ART
Typlcally, an impact-arm sprinkler has a hollow
sprinkler body for supplying water from a substantially
vertlcal riser pipe to a nozzle which is mounted on the
body at an angle of approximately 10 to 30 degrees above
the horizontal. The sprinkler body is mounted on a lower
bearlng, for rotation about a substantially vertical
axis, and an impact arm is mounted for rotation with
respect to the sprinkler~body, about the same vertical
axis. A torsional spring urges the impact arm against a
stop affixed to the sprinkler body and, in thls position,
a deflector spoon on the impact arm is located directly
in the stream of water flowing from the nozzle. The
impact arm is thereby deflected by the stream of water,
and is rotated, compressing the torsional spring. The
force of the spring slows and then reverses the rotation
of the impact arm, driving it against the stop on the
sprinkler body, and thereby applying an impulse of angu-
lar acceleration to the body. The impact arm is re-
peatedly deflected by the stream of water from the
nozzle, and continues to oscillate angularly in this
manner~ applying an impulse of angular acceleration to
~, the sprinkler body on each cycle of its oscillation.
Although the impact arm is usually balanced, in
the sense that it has its center of gravity aligned
with its axis of rotation, the deflection force applied
to the impact arm by the stream of water is necessarily
asymmetrical with respect to the axis of rotation. The
force of the stream impinging on the deflector spoon has
one horizontal component of force tending to rotate the
impact arm about its axis, and has in addition a second
horizontal component and a vertical component, both
acting in the same plane as the axis of rotation, and
both havlng a tendency to induce wear in the bearing
, surfaces between the impact arm and the sprinkler body.
Even the horizontal component which induces rotation of
the arm is not a pure torque force, and results in an
asymmetrical reaction force at the impact-arm bearing.
The problem is further compounded by the transmission of
these asymmetrical forces to the lower bearing on which
the sprinkler body is mounted.
Further asymmetry results from nozzle reaction
forces on the sprinkler body. Flow of water through the
nozzle, quite apart from the action of the impact arm,
produces vertical and horizontal components of a re-
action force, both acting in the vertical plane through
the nozzle and its axis of rotation. Again, these
asymmetrical forces result in sometimes rapid wear cf
the bearing surfaces of the lower bearing on which the
nozzle body is mounted. Moreover, water used for irri-
gation often contains abrasive silt and sand that can
accelerate the wear of both the lower bearing and the
3 impact arm bearing.
Another dlsadvantage of prior art impact-arm
sprinklers is that, when such sprinklers are mounted on
sloping ground with the axis of rotation tilted away
from the vertical, the speed of rotation is affected by
gravltational forces acting on the sprinkler body, and
varies cyclicly as the sprinkler rotates. Accordingly,
there has long been a need in the field of impact-arm
sprinklers, for a sprinkler assembly which balances the
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nozzle reaction forces and impact arm acceleration forces,
thereby reducing wear in the bearings of the assembly, and
which may be used on sloping terrain without variations in the
speed of rotation. The present invention fulfills these needs.
BRIEF SUMMARY OF INVENTION
The present invention resides in an impact-arm sprink-
ler of symmetrical construction, having two diametrically op-
posed nozzles, and an impact arm having two deflector spoons
mounted at the ends thereof for interaction with the respec-
tive streams of water from the two nozzles. The forces acting
on the deflector spoons of the impact arm are thereby perfectly
balanced, resulting in a pure torque force about the axis of
rotation, together with a component of force along the axis of
rotation, but no unbalanced forces tending to induce wear in
15 the sprinkler bearings.
Similarly, the nozzle reaction forces from the two nozzles
balance each other in the horizontal or radial direction, and
the vertical components result in a purely axial reaction along
the axis of rotation. Again, there are with no unbalanced
nozzle reaction forces tending to induce wear in the bearings.
As a consequence of the novel construction of the present inven-
tion, both the lower bearings and the impact-arm bearing last
much longer than in conventional sprinklers. In addition, the
sprinkler may be mounted on a hillside where the riser pipe is
tilted away from the vertical direction, since there will be no
unbalanced gravitational forces acting on the sprinkler body.
In a further aspect of the invention there is provided a
`~ water sprinkler of the impact-arm type comprising: a bifurcated
sprinkler body having a substantially vertically oriented in-
take portion and two symmetrically arranged diametrically op-
posed discharge portions adapted to receive two nozzles, said
sprinkler body being mounted for rotation in a first angular
direction about a substantially vertical axis; an impact arm
mounted on said sprinkler body for rotation about the same axis
as said body, said impact arm having two diametrically opposed
portions carrying oppositely facing deflector spoons at the ends
thereof; torsional spring means connected between said impact
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arm and said sprinkler body to urge said impact arm in said
first angular direction; and abutment means affixed to said
body, to limit rotation of said impact arm in said first
angular direction; whereby said deflector arm is deflected in
a second angular direction opposite said first angular direc-
tion by impingement of water on said oppositely facing deflec-
tor spoons, and returns, under the influence of said spring,
to impact said abutment means and drive said sprinkler body in
said first angular direction, and whereby non-axial nozzle
reaction forces or impact arm acceleration forces, and unbal-
anced gravitational forces acting on the sprinkler are substan-
tially eliminated.
In a further aspect of the invention there is provided an
improvement in an impact-arm water sprinkler having a sprinkler
body, nozzle means, and a spring-biased impact arm which is
repeatedly deflected by a water stream and then returns by
spring force to impact the sprinkler body and incrementally
rotate it, wherein: said nozzle means includes two symmetrical-
ly arranged, diametrically opposed nozzles; said sprinkler body
is bifurcated to provide for connection to said two nozzles,
to produce two diametrically opposed streams of water; and
said impact arm has two diametrically opposed portions which
move in unison to rotate said body, said diametrically opposed
portions carrying oppositely facing deflector spoons at the
ends thereof; whereby nozzle reaction forces and impact arm
acceleration forces are completely balanced and non-axial com-
ponents, and unbalanced gravitational forces acting on sprink-
ler body are substantially eliminated.
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Other aspects and advantages of the lnvention
will become apparent from the following more detalled
description, taken in conJunction wlth the accompanying
drawings.
BRIEF DESCRIPTION OF DRAWINGS
FIGURE 1 is an elevational view of a typlcal
lmpact arm sprinkler of the prlor art;
FIG. 2 ls a fragmentary elevational vlew, partly
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in section, of an impact-arm sprinkler embodying the
present invention; and
FIG. 3 is an end-elevational view of the sprinkler
of FIG. 2.
DETAIIED DESCRIPTION OF INVENTION
As shown in the drawings for purposes of illustra-
tion, the present invention is principally concerned with
impact-arm sprinklers, and with an improved impact-arm
sprinkler having no asymmetrical forces acting on its
bearings. The sprinkler can be made ~rom any suitable
material. Preferable materials are metal or plastic.
As shown in FIG. 1, a conventional impact arm
sprinkler comprises a threaded adapter, indicated by
reference numeral 10, for attachment to a threaded, sub-
stantially vertical riser pipe 12 (not shown), and asprinkler body 14 ~ournaled for rotation on a lower
bearing 16 with respect to the adapter 10 and the riser
pipe 12. A nozzle 18 is attachable to the sprinkler body
14, and receives water supplied through the body from
the riser pipe 12. The nozzle is typically dlrected at
an angle ~ 10 to 30 degrees to the horizontal, and is
usually replaceable in the event of wear, or to provide
for different types of spray coverage. Integral with
the sprinkler body 14 is a bridge portion 20 extending
upwardly from the body. The bridge portion 20 has a
first sideleg 20a which extends upwardly from a point
on the body close to the nozzle 18, a second sldeleg
20b located diametrically opposite the first, and a top
member 20c connecting and integral with the two side-
legs.
An impact arm 24 is mounted for rotation about avertical axis with respect to the sprinkler body 14. In
particular, the impact arm 24 is journaled for rotation
about a shaft 26 which extends upwardly from the sprink-
ler body 14, to an appropriate hole in the top member20c ~ the bridge portion 20. The impact arm 24 has an
integral hub 30 by which it is mounted for rotation about
the shaft 26, and extends above and generally parallel
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wlth the direction of the water stream emerging from the
nozzle 18. At the end of the impact arm 24 is a deflec-
tor spoon 32 which depends downwardly from the arm,
directly in the path of the water stream. Also depend-
5 lng from the arm 2~, at a posltion closer to the nozzlethan the deflector spoon~ is a vane 34. The stream of
water from the nozzle 18 passes to one side of the vane
34, and then strikes the concave surface o~ the spoon 32,
to deflect the impact arm angularly about its axis of
10 rotation.
A torsional spring 36 is mounted about the central
hub 30 of the impact arm 24, and is connected by one end
to the bridge 20 and by its other end to the impact arm,
The spring 36 urges the impact arm 24 against one face
15 of the first bridge sideleg 20a. In thls position, the
impact arm has its deflector spoon 32 located in the
path of the water stream. The weight of the impact arm
24 is usually counter-balanced by an opposing arm 36
extending from the hub 30 in a direction diametrically
20 opposite to that of the impact arm. It will be apparent
that, when water is sprayed through the nozzle 18, there
is a nozzle reaction force which may be resolved ~hto
horizontal and vertical components. Both components of
this nozzle reaction force tend to rotate the sprinkler
25 body 14 about a horizontal axis, and are resisted by
equal and opposite reactions at the lower bearing 16.
Thus, the nozzle reaction forces are likely to result in
substantial wear at the lower bearing.
Furthermore, when water impinges upon the vane 34
30 and the spoon 32 of the impact arm 24, the resultant
force acting on the impact arm may be resolved into three
components. There is the desired horizontal component
tending to rotate the arm, and a second horizontal com-
ponent and a vertical component which both act in the
35 same plane as the impact arm 24 and its axis of rotation.
The second horizontal component and the vertical com-
ponent are resisted by equal and opposite reactions at
the central hub 30 as it bears on the shaft 26. These
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reaction forces are, in turn, transmitted to the lower
bearlng 16, again adding to the likelihood of wear.
In accordance with the present lnvention, a modi-
fied sprinkler bod~ 48 (FIG. 2) having a bifurcated
upper portion 50 to which two nozzles 52 and 54 are
affixed, is journaled for rotation on a lower bearing
(not shown) in the same manner as the prlor art sprinkler
described above. An impact arm 58 having two diametri- -
cally opposed portions 58a and 58b, two deflector spoons
60 and 62, and two corresponding vanes 64 and 66, is
mounted for rotation on a central shaft 68, correspond-
ing to the shaft 26 of the prior art sprin~ler. A bridge
portion 70, having sidelegs 70a and 70b and a top member
70c, is formed integrally with the bifurcated sprinkler
body 50, and, as in the prior art design, is utilized
to provide a stop for the angular movement of the impact
arm 58. A torsional spring 72 urges the impact arm 58
against the bridge portion 70, and the arm is deflected
therefrom by water streams from the nozzles 52 and 54,
in the same manner as described for the prior art
sprinkler.
It will be appreciated that the invention provides
for complete balancing of both the nozzle reaction forces
and the forces acting on the impact arm 58. As to the
nozzle reaction forces, the horizontal components at
each nozzle are equal in magnitude and opposite in
direction, resulting in cancellation of these compon-
ents. The vertical components of the nozzle reaction
forces will be equal in magnitude and in the same direc-
tion at each nozzle, so that there will be no torsionalforce applied to the sprinkler body 50, only a net ver-
tical force directed along the axis of rotation.
With regard to the forces applied by the water
stream to accelerate the impact arm 58, it will be appar-
ent that the horizontal components o~ force applied toeach deflector spoon, to accelerate the arm angularly,
will be eq~al in magnitude, so tha~t a pure torque will
be applied to the symmetrical arm. As to the other
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horlzontal and vertical components of force acting in
the same plane as the axis of rotation, the horizontal
forces will be equal in magnitude and opposite in direc-
tion and will therefore be self-cancelllng. The vertical
components wlll be equal in magnitude and direction, but
will induce no rotational torque, merely a net vertical
force along the axis of rotation. Consequently, only
axial forces will be applied to both sprinkler bearings,
and the wear on the bearings will there~ore be consider-
ably reduced as compared with the wear in the bearingsof a conventional impact-arm sprinkler.
Another advantage of the sprinkler ~ present
invention is that it may be installed on a hillslde, with
its axis of rotation inclined from the vertlcal, and yet
the speed of rotation of the sprinkler will remain uni-
form, since the gravitational forces acting on the two
sides of the sprinkler body are always in balance. It
will be apparent that the invention described and claimed
herein represents a significant advance over conventlonal
impact~arm sprinklers having only one nozzle and one
impact arm. Although a particular form of the invention
has been illustrated and described in detail, it will be
understood that modifications in the detailed design are
possible without departing from the spirit and scope o~
the invention. Accordingly the invention is not to be
llmited except as by the appended claims.
