Note: Descriptions are shown in the official language in which they were submitted.
~L57(~7
This invention relates to a liquid oscillator and
to a method of causing a liquid jet to sweep back and forth.
In the prior art liquid oscillator nozzles as
disclosed in the Canadian application of Harry C. Bray, Jr. r
entitled "Cold Weather Fluidic Fan Spray Devices And Method"
Canadian Patent Application Serial No. 339,~59 filed November
8, 1979, and the oscillators disclosed in Bauer patents
4,157,161, 4,184,636 and Stouffer et al patents 4,1Sl,955 and
4,052,002, and Engineering World, December 1977, Vol. 2, No.
4 Page 1, (all of which are incorporated herein by reference)
liquid oscillator systems are disclosed in which a stream of
liquid is cyclically deflected back and forth, and in the case
of patent 4,157,161, Engineering World, and the above application
of Bray, the liquid is a cleaning liquid compound directed upon
the windshield of an automobile system. In those which have
the coanda effect wall attachment, or lock-on (Engineering World,
for example) there is a dwell at the ends of the sweep which
tends to make the fan spray heavier at ends of the sweep than
in the middle. Such system works very well where a single
nozz]e is used to provide a fan spray from the center of the
windshield as in the system disclosed in Engineering World
system.
The basic object of the present invention is to
provide a liquid oscillator element which produces a fan spray
in which the liquid is relatively uniform throughout the fan
spray thereby resulting in a more uniform dispersal of the
liquid.
For example, in a preferred embodiment, the liquid
is a windshield washer fluid which is sprayed on an automobile
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windshield and the uniform droplets provide a better cleaning
action. In addition, the oscillator in the present invention
retains the desirable low pressure start features of the prior
art as well as the cold weather start characteristics of the
oscillator disclosed in the above mentioned Bray patent
application.
Thus, a further object of the invention is to provide
an improved liquid oscillator for automobile windshield washer
systems.
One aspect of the present invention resides in a
liquid oscillator having an oscillation chamber, a power nozzle
for introducing a liquid power jet into the chamber, an outlet
throat downstream of the power nozzle and a pair of passages
having inlet openings in the respective sides of the outlet
throat and exit openings adjacent the power nozzle. The
oscillation chamber includes a pair of mirror image wall
surfaces beginning immediately downsteam of the exit openings
and extending to downstream therefrom and defining vortex
forming chambers, the downstream end of each wall surface being
shaped to permit vortices formed in the vortex forming chambers
to move thereover into the inlet openings, respectively, whereby
the liquid power jet is caused to oscillate back and forth in
the oscillation chamber.
Another aspect of the invention resides in a method
of causing a liquid jet to sweep ~ack and forth, the method
including the steps of issuing a liquid jet into a chamber
having mirror image vortex forming spaces to create oppositely
rotating vortices, and an outlet, and causing the vortices to
alternately move downstream to block respective entranceways
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to passages leading to exits adjacent the point of issuance
of the liquid jet into the chamber. The jet is caused to
alternately aspirate the exits until the vortice blocking the
entrance is swallowed into the passage it is blocking so that
the liquid jet is caused to deflect back and forth in the
chamber and sweep back and forth on passing through the outlet.
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BRIEF DESCRIPTION OF THE D~A~INGS
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The above and other objects advan~ages and features
of the invention will become more apparent when con-
sidered with the accompanying drawings wherein:
Figure l(a) is a silhouette of a preferred form of
the oscillator, and Figure l(b) is a sectional side ele-
vationsl view of Figure l(a),
Figure 2 is a view similar to Figure l(a~, but
wherein l~gendq have been applied and some of the num-
10 bering deleted for clarity and there is shown the posi-
tions of three of the vortices and the locati~n of the
power jet at a particular instance during operation
thereof,
Figures 3a-3h diagrammatically illustrate a sequence
15 of vortex formation and movement and resulting flow condi-
tions in.an oscillator i~corporating the inven~ion and,
7 Figure 4 illustrates the droplet formation due to
the sweeping action of the power jet.
.~ DETAILED DESCRIPTION OF THE INVENTION
The invention will be described in relation to auto-
mobile windshield washer assemblies, the oscillator of
the present invention is constit-uted by a molded plastic
body member 10 which would typically be inserted into a
housing or holder member 11 (shown in section Figure 2)
25 which ha~ a fitting 12 which recei~es ~ubing 13 connec-
tlon to the outle~ of the windshield washer pump ~not
shown). Liquid washing compound is thus introduced to the
device via power nozzle inlet 14 which thus issues fluid
through power nozzle 15. The liquid issues fr~m the power
30 nozzle 15 which at its exit EP has a width W, the liquid
: flowing initially past the exit ports 16 and 17 of liquid
passages 18 and 19 respectively. Elements 20 and 21
basically form the boundaries of the interaction chamber
and th~ liquid passages 18 and lg, respectively. This
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chamber structure is defined by a pair of walls 20-N
and 21-N which are noxmal to the cen~ral axis through
the p~wer nozzle 15 and outlet throat 24, which connect
with wall elements 20-P and 21-P which are parallel to
the direction of fluid flow9 the wall elements normal
and parallel wall elemen~s being ~oined by curved sec-
tion 20-C and 21-C respectively so that the liquid
passages fxom the inl~ts 18-I and l9-I respec~iYely are
of substantially unifonm width and about equal to the
10 width W of the power nozzle. An important feature o
the invention are the bulbous protuberances or proJec-
tions 20-B and 21-B at the downstream ends o~ parallel
portions 20-P and 21-P which preferably have smoothly
rounded surfaces. Protuberances 20-B and 21-B with
outer wall portions 36 and 37 de~ine the entranceways
38 and 39 ~o inlets 18-I and l9-I, respectively. The
outlet throat 24 has a pair o~ very short diverging
fan angle limiting walls 26-~ and 26-R, which in this
embodiment are set at an angle o~ about 110 a~d which
20 thereby defines the maximum ~an angle.
While the basic structural features of the inv~n~ion
have been described above in relation to the invention;
the ~ollowin~ description relates to the :func-
tional characteristics of each o~ the major components
of the invention
~a ~
Figure 1 shows that in the device the walls
WP of the power nozzle, are not parallel to the power
jet centerline, but converge increasingly all ~he way
30 to the power nozzle exit EP, so that the power jet
st~eam will continue to conver~e (and increase velo-
city) until the internal pressure in the jet overides
and expansion begins.
67
THE MAIN OSCILLATOR CHAMBER
The main oscillator chamber MOC includes a pair of
left and right vortex supporting or generating volumes
which vortices avoid wall attachment and boundary layer
5 effects and hence avoids dwell of the power jet at
either extremity of its sweep; the chamber is more or
less square. The terms "left" and "right" are solely
with refere~ce to the drawi~g and A~e not intended to be
limiting.
FEEDBACX PASSAGES
Exits (16', 17')
The feedback passage exits 16 and 17 (Figures 1 and
2) are not reduced in flow area. A reduction in flow
area is sometimes uaed in prior art oscillatars to in-
15 crease the velocity of feedback flow where it interacts
with the power jet; to restrict entrainment flow out
of the feedback passage; or as part of an RC feedback
system to determ~ne power jet dwell time at an attach-
ment wall. In the preferred embodiment of the inven-
20 tion, the feedback passage exits 16 and 17 of the oscil-
lator are the same size as the passages 19 and 20. No
aid to wall attachment is neces3ary because there are
no walls on which attachment might occur.
Inlet (18-I and l9-I)
The feedback inletq in many prior art oscillators
are sharp edged diviters placed so that they intercept
part of the power jet flow when ~he power jet iq at
ei.ther the right or left extreme of it9 motion. The
dividers used in prior art oscillators at the feedback
30 inlet direct a known percentage o~ the flow to the
~eedback exit (or feedback nozzle in some cases) in
order to force the power jet to move or switch to the
other s~de of the device. The feedback passages some-
times contain "capacitors" to delay the build-up of
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eedback pressure in order ~o lengthen ~he ~ime the
power jet dwells at either e~reme. In con~rast the
feedback inlets 18-I and l9-I O~ this invention are
rotated 90 relative to the usual configuration, and
thus do not intercept any power jet flow. In fact,
as will be described later under t~e ~eading "Method
of OscillatIon", there is no power jet flow in the feed-
back passages 19 and 20.
DEFLFCTORS (PROTUBER~NCES 20B AND 21B)
.. . .
The partition tha~ separates ~eedback passage ~rom
the main chamber MOC o the oscillator may also be seen
in Figure 2, this partition is terminated at the feed-
bac~ passage inlet by rounded protrusion or de~lector
members 20-B and 21-B. This par~ of the partition has
three functions; to deflect the power je~ streamj to
provide a do~s~re2m seal for the vortex generatio~ cham-
ber; and to ~orm part of the'feedback passage inlet.
.
METHO~ OF OSCILLATION
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Initially as the supply pressure applied to the
20 inlet 14 of the oscillator is increased, the power jet
leaving via EP becomes turbulent. Liquid ~rom the power
nozzle EP issues therefrom toward the outlet throat and
expa~ds to fill the oscillation chamber MOC. The turbu-
lence which begins on the free sides of the jet causes
- some entrainment o local 1u~d in the main chamber M0~,
and eventually su~ficient instability in the pressure
- surrounding the jet to cause it to begin to undulate.
This movement increases with increased pressure until
the jet impacts the deflectors and then the normal oscil-
30 lation pattern for this device begins.
In this invention there are ~our places where vor-
texes can exist. These locations, (30, 31, 32, 33), may
be se~n in FIgures 1 and 2. However,only thxee vortexes
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exist during most of the cycle, only two during thefeedback por~ion o~ the cycle, and never four at the
same time.
Assuming the power jet has just arrived at ~he left
side o~ the device in Figures 2 a~d 3a, the vortex
formation in left vorte~ generation chamber has just
begun. The de~lector 20B has formed a seal between the
power jet a~d the rest of ~he chæmber, so th~t the only
place cha~ber MOC can get a supply o~ flow to relieve
10 the low pressure genera~ed there would be from the ~eed~
back passage FBl. With normal feedback this would occur
because the feedbac~ inlet would be receiving flow at a
rate greater than the entrainment ~low out o the feed-
bac~ exi~, and the power jet would move toward the
opposi~e side. However, in this in~ention the inlet
18-I to the feedbac~ passage is sealed by a strong vor-
.
tex 32 in entranceway 38. T~is vortex at entranceway 38was larger (like the one at entranceway 39) until it
was confined in the ~eedback inlet by the power iet.
20 Being suddenly reduced in size, its rotational speed
increased, enhancing its ability to seal the feedback
inlet 18-I and to deflect the power jet toward the out-
let of the device to ambiænt-. ~eanwhile, since the vortex
fo~ming in the let vortex chambex has no flow to re-
lieve the low pressure but the power jet, it builds in
intensity. The increasing pressure unbalance across
the p~wer je~ and the motion of the vortex cause the
power jet to move fur~her l~t (Fi~ures 3b~ 3c and 3d)
and to begin to impact the de1ector 20B more on the
30 upstre~m side. As this condition increases the power
Jet deflects off the deflector at a more shallow angle
permitting the vortex 32 at entranceway 3~ to expand.
; Thus, the outlet stream begins to move before eedback
begins.
As the po~er jet moves into the left vortex chamber
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it flows right across the lower end of the partitionforming the feedback passage exit 16 following the con-
tour of the partition 20P and at the same time, by
aspiration, greatly reducing the pressure in feedback
5 passage 20. The continual lowering of the pressure in
the feedback passage, combined with the loss in energy
of the vortex 32, results in the vortex suddenly being
"swallowed" (Figure 3e) into the feedback passage 20
and dis 9 ipating there.
When the vortex 32 is i'swallowed", flow can take
place in 20 The motivation for this flow is not from
the usual positive pressure at the feed~ack inlet,
generated by splitting of~ part of the power jet, but
it is due to a L~w pressure in the feedback passage 20
15 generated by the high velocity power jet aspirating
fluid from 20 at 16. The effect of feedbac~ flow is:
1. Permits the power jet to receive entrained fl~w
(through 20), so it can begin to move away from ~he
partition at 16.
2. The additional flow (power jet plus entrained
flow) ten~s to push the vortex 30 in the left vortex
: chamber downstream.
3. The flow through 20 to 16 creat~s a low pressure
at 18 thus initiating a circulating flow from 16 co
25 18-I on the chamber side of the partitions 20P with
the return through passageway 20 (Figures 3c~ 3~ and
3g).
~ . The fluid motion described above, generates a
pressure difference across the vortex 20 in the left vor-
.~ 30 tex chamber. This push-pull effect causes th~ vortex
30 to cros~-over deflector 20B and to move into the low
pressure zone at entranceway 38 (Figures 3f, 3g, and 3h)
: 5. The i~let 18-I is thus sealed once more upon the
arrival of the vortex 32 (Figure 3~). Feedbac~ flow
exists only during that period of time from the
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annihilation of the vortex at inlet 18-I until the next
vortex, from 30, moves into 18-I. During the remainder
of the oscillator's cycle there is essentially no net
flow through 20.
S 6. As the vortex 30 generated in the left vortex
chæmber moves across deflector 20B, it forces the power
jet to the right side (Figure 3g) where the power jet
encounters the vortex 32 at entranceway 39 and the de-
flector 21B.
7. The CCW motion of the "new" vortex 32, as it
crosses over deflector 20B, and the CW motion of the
"old" ~ortex 32 at entranceway 39 cause the power jet ~o
bend sharply and exit to the left. (OppositP to the
condition shown in Figure 2).
8. When the power jet encounters the deflector 21B
(Figure 3h)~ a vortex 31 begins to form at the right
vortex generation chamber (inlet lg-I is sealed by the
"old" vortex 33) and the entire process described above
is repeated.
The vement of the outlet stream is depicted in
Figures 3a through 3h. As is shown in these figures, the
outlet stream begins to move or sweep in an opposite
direction by virtue of generation and movement of the
vortices 30 and 31 and hence before fluid flow in the
25 feedback passages. Therefore; the motion and position
of the outlet stream is not entirely dependent on feed-
back, whereas the opposite is true, in astable m~ltivi-
hrators. The angular relationship (~weeping mo~ion) of
the output stre~m versus time is more closely related to
30 sinusoidal oscillation than lt is to astable oscillation.
This is evideneed by the fact that ~he output stream
does not "linger" at either extreme of its angular move-
ment.
DROP~E~ FOgMATION
The mechanism by which the droplets are formed begins
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in the power nozzle. The convergency of the power noz-
zle generates turbulence in the power jet. Vortex
shedding on the free sides of the power jet combines
with the internal turbulenee of the jet to generate an
5 "organized" instability within the power jet. This
instability or undulation wi~hin the power jet contin-
ues to build uniformly as the power jet approaches and
passes through the exit. The frequency of the ~ndula-
tion being much higher than the frequency at which the
10 power jet sweeps from side to side, provides a pattern
~ery similar to that shown in Figure 4. This figure
shows a calculated displacement versus time plot OI the
motion of the power jet stream as it exits the oscilla-
tor. For clarity the frequency ratio of the undulation
15 in the power jet to the fre~uency of the power jet was
set to 10:1 and the amplitude ratio 3:10. Figure 4
shows only one sweep of the power ~et from left to right.
The various maxim~ and minima that occur during the
motion from left to right are labeled a through h. The
20 number of degrees of motion of the jet that occurs
between successive letters is quite different, however,
the time between each is the same. It is therefore
obvious that if the flow rate is constant, (which i~ is),
then the amount of liquid distributed between C and 3,
25 for instance, is the same a~ between D and E. Since
the amound of liquid distributed along these two paths
is the s~me, then the size of the s~ream and thus the
cohesi~e forces will be greater be~een D and E ~-han
between C ant D. Applyin~ the above argument to ~he
30 entire picture, one would predict that as the liquid
progressed away from the outlet tha stream would part
between A and B, C and D, E and F, and G and H. This is
reasonable be ause of the higher tensile stress that
exists between these points as com~ared to B and C,
D and G and G and F. Therefore, the droplets would form
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from the liquid contained in the latter group and the
remaining liquid that flows into each ar~a from the
break points in the stream.
SUM~ARY
The power nozzle design purposely generates turbu-
lence in the power ~et stream prior to the nozzle exit,
rather than attempt to generate a "low" turbulence
nozzle design with a controlled and stable velocity
profile. Moreover, the power nozzle allows the power
10 jet flow within the power nozzle to "hug" one or the
other of the power nozzle's sidewalls in order to cause
a closer interaction between the power jet and the exits
16 and 17 of the feedbac~ passages 19 and 20, thus,
enha~cing the generation of very low pressures in the
15 feedback passages.
The feedback pa~sage e~its 16 and 17 are unrestricted
so there is no RC storage (e.g. capacitance or resistance
efrects) and permit maximum flow from the ~eedback pass-
age. The large exits 16 and 17 also permit maximum
20 aspiration to occur as a result of the power jet flowing
across the exits. The feedbac~ passages l9 and 20 are at
a "low pressure-no flow" condition for most of the
oscillator cycle.
Feedback is controlled by low pressure and vortex
25 mov~ment rather than intercepting a portion of the power
jet. In act, there i9 no power jet flow in the feedback
passage. The entranceways 38 and 39 to feedback passage
inlets 18-I and l~-I are designed to provide containment
of a vortex for sealing the inlet to the feedback passage
30 against flow.
The vortices produced in le~t and right vortex
generation ch~mbers dominate t~eiprocess of oscilla~ion
and also prov~de a ne~ vortex thàt moves into the inlet
of a feedback passage to terminate each feedback occur-
enee.
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It is the vorte~ aided power jet control (asopposed to boundary layer or stream interaction) which
is the dominant oscillatory mechanism controlling all
major aspects. When a vortex moves across one of the
5 deflectors, it forces the power jet toward the opposite
deflector. In addition, this vortex, with help from
a counter rotating ~ortex on the other side of the power
jet, causes the power jet to bend sharply around the
firs~ vor~ex.
Since there is no wall loc~-on or coanda efect
utilized, there is essentially no dwell, a uniformity
of fan pattern is achieved at the relatively wide angle
(in the disclosed embodiment 110 to 120 however, I
wish it to be understood that the fan angle can be any
15 value from 30 to 160) needed for good wetting , for
example of a windshield, especially where separate driver
and passenger nozzles are used. The fan is in the direct
line of vision. At the same t~me, the device retains the
low threshold pressure for initiation of oscillation ~o
20 in the case of a windshield washer assembly for automo-
biles, there is no need to increase pump sizes for cold
weather operation when the viscosity and surface tension
of the liquid has increased. If desired, the oscillation
chamber can have the top (roof) and bottom (floor~ walls
25 thereof diverging from each other in the direction of
the outlet throat so a3 to e~pand the power jet in cold
weather but it is not necessary in regards to the pre~ent
invention.
The device illustrated i~ an actual operating
30 devlce. Variations of the output characteristics can
be achieved b~ varying the cur~ature of protuberances
20-B and 21-B. In addition, the fan angle can be de-
creased by shortening the distance between the power
nozzle 15 and outlet throat 24. In ~he drawing~, the
distance between the power nozæle 15 and the outlet throat
~3~
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~4 is about 9W and ~he distance between side walls 20
and 21 is slightly more than 6W, ~he distance between
protuberances 20-B and 21-B is slightly greater than
~W.
While the preferred embodiment of the invention
has been illustrated and described in detail, it will
be appreciated that various modifications and adapta-
tions ~f the basic invention will be obvious to those
skilled in the art and it is intended that such modifi-
10 cations and adaptations as come within the spirit andscope of the appended claims be covered thereby.
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