Fluidic oscillator and spray-forming output chamber

A fluidic oscillator includes a chamber having a common inflow and outflow opening into which a jet is issued in a generally radial direction. After impinging upon the far chamber wall the jet is redirected to form a vortex on each side of the incoming jet. The vortices alternate in strength and position to direct outflow through the common opening along one side and then the other of the inflowing jet. A spray-forming output chamber is arranged to receive the pulsating outflows from the aforementioned or other fluid oscillator and establish an output vortex which is thereby alternately spun in opposite directions. An outlet opening from the output chamber issues fluid in a sweeping spray pattern determined by the vectorial sum of a first vector, tangential to the output vortex and a function of the spin velocity, and a second vector, directed radially from the vortex and determined by the static pressure in the chamber. By increasing or decreasing the static pressure, or by increasing or decreasing the vortex spin velocity, the angle subtended by the sweeping spray can be controlled over an unusually large range. By properly configuring the oscillator and/or output chamber, concentrations and distribution of fluid in the spray pattern can be readily controlled.

BACKGROUND OF THE INVENTION 
The present invention relates to improvements in fluidic oscillators and to 
a novel spray-forming output chamber for fluidic oscillators. 
It has been recognized in the prior art that fluidic oscillators can serve 
not only as fluidic circuit components but also as fluid distribution or 
spray devices. (See U.S. Pat. Nos. 3,432,102; 3,507,275; 4,052,002). In 
all of these patents a fluid jet is caused to oscillate by means of fluid 
interaction using no moving parts, and the resulting oscillating jet is 
issued into the ambient environment to disburse the fluid therein. Other 
fluidic oscillators, such as described in U.S. Pat. No. 3,563,462, issue 
discrete pulses of fluid in alternation from two or more spray openings. 
In most applications for prior art fluidic oscillators it has been found 
that oscillator performance is dramatically affected by relatively small 
dimensional variations in the oscillator passages and chamber. It has also 
been found that prior art oscillators are extremely sensitive to 
properties of the sprayed fluid, such as viscosity, surface tension, 
temperature, etc. 
Another concern with prior art oscillators, particularly when employed to 
achieve specific spray patterns, is that the desired spray patterns are 
not achieved immediately upon start up. Generally, the desired spray 
pattern is achieved only after the oscillator is substantially filled with 
the spray fluid; however, until the oscillator is filled it is quite 
common for a non-oscillating jet to issue from the device. 
Prior art fluidic devices have been designed to operate in accordance with 
well established fluidic principles, such as Coanda effect, stream 
momentum exchange effects, and static pressure control effects. It is, in 
my opinion, this reliance upon these standard fluidic effects which brings 
about the aforementioned limitations and disadvantages. 
It is an object of the present invention to provide a fluidic oscillator 
which operates on a different principle than previous fluidic oscillators 
and, thereby, is not shackled with the aforementioned disadvantages. 
It is another object of the present invention to provide a fluidic 
oscillator which is relatively insensitive to dimensional manufacturing 
tolerances. 
It is yet another object of the present invention to provide a fluidic 
oscillator having improved operating characteristics over large ranges of 
variations of operating fluid properties and thereby offer wider 
application capabilities than prior art fluidic oscillators. 
An important aspect of fluidic oscillators, when utilized as spray or fluid 
dispersal devices, is the waveshape of the issued spray or dispersal 
pattern. Depending upon the desired distribution characteristics, the 
waveshape must be tailored accordingly. For example, as described in the 
aforementioned U.S. Pat. No. 4,052,002, relatively uniform spatial 
distribution of the fluid is achieved if the waveform is triangular with 
little or no dwell time at the extremes of the fan-shaped sweep. As more 
dwell time is introduced in the extremes of the sweep, spatial 
distribution becomes more dense at the extremes and less dense at the 
center. To achieve higher densities at the center, or between the center 
and extremes of the sweep is difficult. Moreover, to tailor the sweep 
pattern to achieve many desired spatial distributions is difficult in the 
prior art oscillators. 
Further, droplet size, in the case of liquids sprayed from prior art 
fluidic oscillators, is an important consideration in two respects. First, 
specific droplet sizes are required for different spray applications. 
Second, certain droplet sizes have been found to be dangerous to inhale 
and must be avoided. In prior art fluidic oscillators, the size of the 
oscillator pretty much determines the range of droplet sizes in the issued 
spray pattern. Often it occurs that a particular oscillator size is 
necessary to achieve the desired droplet size, but that such oscillator 
size is impractical for that application because of space requirements. 
Still another important characteristic of spray and dispersal patterns from 
fluidic oscillators is the sweep frequency. Again, this characteristic is 
determined by the oscillator size in prior art fluidic oscillators. An 
example of one frequency requirement would be in a massaging shower 
wherein the frequency should be such as to provide a massaging effect, or 
in an oral irrigator wherein a massaging effect is likewise desirable. On 
the other hand, when the oscillator is used as a nozzle for hair spray or 
anti-perspirant it is desirable that no massaging effect be felt. As 
described in the case of droplet sizes above, it often occurs that an 
oscillator size which is suitable for achieving the desired sweep 
frequency is not satisfactory for the space requirement of the overall 
device. 
It is therefore an object of the present invention to provide an 
improvement for fluidic oscillators which permits control over the spray 
pattern, droplet distribution, droplet size and sweep frequency of issued 
fluid. 
It is another object of the present invention to provide an output region, 
useful with any fluidic oscillator, which permits considerable variation 
in the spray pattern and characteristics of oscillators of specified 
sizes. 
It is still another object of the present invention to provide an output 
region for a fluidic oscillator which employs an entirely novel principle 
of spray formation and thereby permits control of the angle, frequency, 
droplet size and distribution of the issued spray pattern. 
SUMMARY OF THE INVENTION 
In accordance with the present invention a fluidic oscillator includes a 
chamber having a common inlet and outlet opening through which a fluid jet 
is issued across the chamber. Upon impacting the far wall of the chamber 
the jet forms two oppositely rotating vortices, one on either side of the 
jet, which alternate in strength and position in opposite phases in the 
chamber. Each vortex alternately conducts more or less fluid out of the 
common opening on its side of the jet. The alternating outflows may be 
issued as fluid pulses for a specific utilization or may be used in 
conjunction with the output chamber described below to achieve a desired 
spray pattern. Still another utilization of the oscillator is as a flow 
meter whereby the oscillator is disposed in a flow path and its 
oscillation frequency is measured to provide a linear function of flow. 
This configuration has been found to be relatively insensitive to 
dimensional manufacturing tolerance variations, and operates over a wide 
range of fluid characteristics. 
In accordance with another aspect of the present invention an output 
chamber for a fluidic oscillator receives fluid pulses in alternating 
opposed rotational directions. An output vortex is established in the 
output chamber and is alternately spun in opposite directions by the 
alternating input pulses. One or more outlet openings at the periphery of 
the output chamber issue a sweeping spray that is determined by the 
vectorial sum of two flow components: a first component is directed 
tangential to the output vortex and has a magnitude proportional to the 
instantaneous flow velocity at the output vortex periphery; a second 
component is directed generally radially outward from the output vortex 
and is a function of the static pressure at the vortex periphery and the 
net flow rate into the output chamber. By reducing the static pressure in 
the chamber, for example by making the outlet opening wider or reducing 
the inflow, the frequency, droplet size and spray angle can be selected 
accordingly. By contouring the chamber walls, the fluid distribution with 
the spray pattern can be selected.

DESCRIPTION OF THE PREFERRED EMBODIMENTS 
Referring specifically to FIGS. 1, 2 and 3 of the accompanying drawings, a 
basic oscillator 10 is shown as a plurality of channels, cavities, etc., 
defined as recesses in a bottom plate 11, the recesses therein being 
sealed by cover plate 12. It is to be understood that the channels and 
cavities formed as recesses in plate 11 need not necessarily be 
two-dimensional but may be of different depths at different locations, 
with stepped or gradual changes of depth from one location to another. For 
ease in reference, however, entirely planar elements are shown herein. It 
is also to be understood that whereas a two-plate (i.e. plates 11 and 12) 
structure is illustrated in each of the embodiments, this is intended only 
to show one possible means of construction for the oscillator and output 
chamber of the present invention. The invention itself resides in the 
various passages, chambers, cavities, etc. regardless of the type of 
structure in which they are formed. The oscillator 10 as formed by 
recesses in plate 11 and sealed by plate 12 includes an oscillation 
chamber 13 which in this embodiment is generally circular, having an 
opening 14 along one side which, for example, may subtend an angle of 
approximately 90.degree. on the circle. A passage extending to the end of 
plate 11 from opening 14 is divided into two outlet passages 15 and 16 by 
a generally U-shaped member disposed therein. The U-shaped member has its 
open end facing chamber 13 and may be defined by means of recesses about 
member 17 in plate 11 or as a projection from cover plate 12 which abuts 
the bottom wall of the recess in plate 11. An inlet opening 18 is defined 
through the bottom of plate 11 within the confines of U-shaped member 17 
and serves as a supply inlet for pressurized fluid. Opening 14 for chamber 
13 serves as a common inlet and outlet opening for fluid in a manner 
described below. 
Operation of oscillator 10 is best illustrated in FIGS. 11 through 15. For 
purposes of the description herein it is assumed that the working fluid is 
a liquid and that the liquid is being issued into an air ambient 
environment; however, it is to be noted that the oscillator of the present 
invention and the output chamber of the present invention both operate 
with gaseous working fluids in gaseous environments, with liquid working 
fluids in liquid environments, and with suspended solid working fluids in 
gaseous environments. Upon receiving pressurized fluid through inlet 
opening 18, member 17 directs a jet of the fluid through opening 14 into 
chamber 13. Upon impinging against the far wall of chamber 13, the jet 
divides into two oppositely directed flows which follow the contour of 
chamber 13 and egress through output passages 15 and 16 on opposite sides 
of the input jet and member 17. These two reversing flows form vortices A 
and B on opposite sides of the inflowing jet. This condition, which is 
illustrated in FIG. 11, is highly unstable due to the mutual influences of 
the flow patterns on one another. Assume, for example, that as illustrated 
in FIG. 12 the vortex B tends to predominate initially. Vortex B moves 
closer toward the center of chamber 13, directing more of the incoming 
fluid along its counter-clockwise flowing periphery and out of output 
passage 16. The weaker vortex A, in the meantime, tends to be crowded 
toward output passage 15 and directs less of the input fluid in a 
clockwise direction out through passage 15. Eventually, as illustrated in 
FIG. 13, vortex B is positioned substantially at the center of chamber 13 
while vortex A substantially blocks outlet passage 15. It is this 
condition during which the maximum outflow through passage 16 occurs. As 
vortex A is forced closer and closer to output passage 15, two things 
occur: vortex A pinches off outflow through output passage 15 and it also 
moves substantially closer to the mouth of member 17. In this condition 
vortex A receives fluid flowing at a much higher velocity than the fluid 
received by vortex B. Therefore, as vortex A moves closer to output 
passage 15 it begins spinning faster, in fact much faster than vortex B. 
With output passage 15 blocked, vortex A begins moving back toward the 
center of chamber 13 and in so doing forces the slower spinning vortex B 
back away from the center. This tendency is increased by the fact that the 
jet itself is issued toward the center of the chamber 13 and, if left 
unaffected by other influences, would tend to flow toward that center. Now 
when the vortices approach the condition illustrated in FIG. 11, vortex A 
is dominant and continues toward the center of the chamber 13. As was the 
case with vortex A when vortex B dominated, vortex B is eventually pushed 
to a position illustrated in FIG. 15 whereby it blocks outflow through 
output passage 16. During this condition vortex A is centered in chamber 
13 and substantially all of the outflow proceeds through output passage 
15. Vortex B is now in a position to receive the high velocity fluid from 
the inflowing jet so that vortex B begins spinning faster and faster, 
taking on a growing position of dominance between the two vortices. Thus 
vortex B moves closer toward the center of chamber 13 as illustrated in 
FIG. 14. More fluid begins to egress through output passage 16 and less 
through output passage 15 as vortex B moves closer toward the center, all 
the time pushing vortex A back away from the center of chamber 13. The 
cycle is complete when the two vortices achieve the positions illustrated 
in FIG. 11 once again with equal flow through output passages 15 and 16. 
The cycle then repeats in the manner described. Summarizing the 
afore-described operation, initial flow of the jet into chamber 13 
produces a straight flow across the chamber which splits into two loops 
near the far chamber wall. Each splitoff and reversed loop flow tends to 
form a vortex which exerts a force on the jet. The resulting unstable 
balance between the two vortices on either side of the flow cannot sustain 
the momentary initial condition since any minute asymmetry, causing a 
corresponding increase in one of the reverse flow loops, causes a decrease 
in reverse flow and force on the opposite side of the jet. This in turn 
begins to deflect the jet toward the side with the weaker reverse flow 
loop, which further enhances the action of the phenomenon. In other words, 
a positive feedback effect is present and it causes the flow exiting from 
the chamber to veer toward one side of the chamber until a new balance of 
vortices is reached. It must be recognized that the occurring phenomena 
are inherently of a transient dynamic nature such that any flow conditions 
are of a quasi-steady state nature wherein none of the existing flow 
patterns represents a stable state; that is, the flow state in any 
location is dependent upon its prior history due to the fact that local 
flow states influence and are influenced by those flow states in other 
locations only after a delay in time. Even though the stronger of the two 
existing vortices might appear capable of sustaining the illustrated flow 
pattern at any point, the quasi-steady state effect of the outflow into 
one or more of the output channels causes the pattern in the chamber to 
become more symmetrical. This in turn causes a diminution of reverse flow 
and, simultaneously, causes an increase in the reverse flow on the 
opposite side. Both effects become effective after a respective time 
delay. This time delay is additionally increased due to the fact that the 
rotational energy in the motion of the two vortices must dissipate before 
flow reversal can be effected. Thus for a brief period of time outflow 
through one output passage remains essentially constant (although its 
velocity may increase as its flow area is constricted) before diminishing 
and consequently its influence on the adjacent counterflow is also 
sustained for a similar period of time. The flow pattern becomes more 
symmetrical and the buildup of the opposite reverse loop flow causes 
outflow to the opposite output channel. The vortex loop effects in large 
part comprise inertance and compliance phenomena with energy storage 
mechanisms, all of which are essential to the oscillation function. 
The resulting output flow from the oscillator 10 is best illustrated in 
FIG. 1 as alternating slugs of fluid issue from passages 15 and 16. It 
should be noted that the cross section of chamber 13 illustrated in FIG. 2 
need not be rectangular but may be elliptical, in the form of a meniscus, 
or any other varying depth configuration. Similarly the plan form of 
chamber 13 need not be circular as shown but may be substantially any 
configuration such as the rectangular configuration illustrated in FIG. 4. 
Specifically, element 20 in FIG. 4 is shown with only the bottom plate 21, 
the top plate being removed for purposes of simplification and clarity of 
description. In fact, for most of the oscillators shown and described 
hereinbelow, the top plate has been removed for these purposes. Oscillator 
20 includes an inlet opening 22 similar to inlet opening 18 of FIG. 1 and 
a generally U-shaped member 23 similar to U-shaped member 17 in FIG. 1. 
Outlet passages 25 and 26 on either side of U-shaped member 23 correspond 
to outlet passages 15 and 16 of FIG. 1. An oscillation chamber 24 is 
generally rectangular in configuration with its width corresponding to the 
distance between the extremeties of passages 25 and 26. The output 
passages 25 and 26 are directed into an output chamber 27 which is a 
continuation of chamber 24 beyond U-shaped member 23 and has sidewalls 
which extend parallel all the way to outlet opening restriction 28. 
Oscillation of the jet issued from member 23 proceeds in the manner 
described in connection with FIGS. 11 through 15. The squared-off or 
rectangular shape of chamber 24 affects the shape of the output pulses but 
does not prevent oscillation from occurring. More specifically, the 
oscillation cycle in a chamber configured such as chamber 24 tends to have 
a greater dwell in the extreme positions where maximum flow through each 
output passage occurs. The resulting output slugs of fluid tend to have 
more discrete leading and trailing edges than the tapered leading and 
trailing edges shown in FIG. 1. 
Output chamber 27 receives the alternating slugs of fluid in opposing 
rotational senses; that is, the flow from passage 25 tends to create a 
clockwise flow in chamber 27 whereas the flow through passage 26 tends to 
create a counter-clockwise flow in chamber 27. The result is the 
establishment of an output vortex in chamber 27, which vortex is 
alternately spun first in a clockwise and then in a counter-clockwise 
direction in response to the alternating inflows. The manner in which 
output chamber 27 provides a cyclically sweeping spray pattern is best 
described in relation to the embodiment of FIG. 5. 
Referring specifically to FIG. 5, an oscillator/output chamber 
configuration 30 includes an input opening 31 for pressurized fluid which 
is directed into a generally circular chamber 34 by means of a generally 
U-shaped channel 32. U-shaped channel 32 is part of an overall flow 
divider section 33. Downstream of the common inlet and outlet opening 39 
of oscillation chamber 34, the sidewalls 40 and 41 of the unit diverge 
such that sidewall 40 along with flow divider 33 forms outlet passage 35 
from the oscillator, whereas sidewall 41 along with flow divider 33 forms 
outlet passage 36. The sidewalls 40 and 41 begin to converge toward outlet 
opening 38 in output chamber 37. The downstream surface 42 of flow divider 
33 is concave so that a generally rounded output chamber 37 results. 
Passages 35 and 36 deliver fluid into output chamber 37 in opposite 
rotational senses. The manner in which the spray is issued from chamber 37 
is diagrammatically illustrated in FIG. 16. Referring to FIG. 16, the 
input flows from passages 35 and 36 produce an output vortex which 
alternately rotates first in a clockwise direction and then in a 
counter-clockwise direction. At each point across outlet opening 38 there 
is a summation of flow velocity vectors which determines the overall shape 
of the issued spray pattern from this outlet opening. For ease in 
reference and simplification only two such points are illustrated in FIG. 
16, namely, the extremities 43 and 44 of outlet opening 38. For the 
following discussion it is assumed that the vortical flow in chamber 37 is 
counter-clockwise as indicated by the arrow therein. At point 43 there is 
a tangential velocity V.sub.T directed tangentially to the output vortex 
at that point, and a radial velocity component V.sub.R directed radially 
from the output vortex at that point. The summation of vectors V.sub.T and 
V.sub.R is a resultant flow velocity R emanating from point 43. Tangential 
velocity vector V.sub.T results solely from the spin effect in the vortex 
and thereby results only from the dynamic pressure at point 43 produced by 
the output vortex. The radial velocity vector V.sub.R results from the 
static pressure and net flow into chamber 37 from passages 35 and 36. A 
similar analogy is presented for vectors V'.sub.T and V'.sub.R at point 44 
on the other side of outlet opening 38. These vectors sum to provide a 
further resulting vector R'. Vectors R and R' define the extremities of 
the fluid issued from outlet opening 38 at a particular instant of time. 
At that instant of time the outflow from outlet 38 is confined between the 
vectors R and R'. These vectors diverge producing a tendency for the 
outflow to diverge; however, surface tension effects act in opposition to 
the divergence tendency to try to reconsolidate the stream. In most 
practical applications, particularly for high velocities, the issued flow 
tends to break up into droplets before too much consolidation is effected. 
Nevertheless, there is some reconsolidation so that there is no 
continuation in the divergence tendency. Important is the fact that flow 
issued from outlet opening 38 at any instant of time spreads in the plane 
of the output vortex. It is this spreading flow that is oscillated back 
and forth as the output vortex in chamber 37 continuously changes velocity 
and direction. An overall spray pattern of this type is illustrated in 
FIG. 10 wherein it is noted that the sheet 45 sweeps back and forth in an 
almost sinusoidal pattern and within a short distance, depending on the 
pressure, begins breaking up into ligaments and then droplets of fluid as 
the issued stream 45 viscously interacts with the surrounding air. This 
viscous interaction is the mechanism which causes a cyclically swept jet 
to break up into multiple droplets and form a spray pattern of a generally 
fan-shaped configuration. However in the case of the swept spreading flow 
pattern issued from outlet opening 38, the flow itself tends to break up 
into droplets much more readily than an integral jet at corresponding 
pressures. As a corollary, smaller droplet sizes can be achieved with the 
use of output chamber 37 than can normally be achieved with a conventional 
fluidic oscillator of a comparable size at the same operating pressure. 
In summary of the operation of chamber 37, it may be looked upon as serving 
as a restriction (analogous to an electrical resistance) and inertance 
(analogous to an electrical inductance) filter circuit to smooth out 
incoming pulsating signals and to combine the result in a suitable single 
output stream which remains substantially constant in amplitude but sweeps 
from side to side regularly as the vortex changes direction and speed. The 
static pressure in chamber 37 produces a radial velocity vector V.sub.R at 
each point of the outlet opening 38. The spin velocity of the vortex in 
chamber 37 produces a tangential velocity vector V.sub.T. I have observed 
that the sweep angle .alpha. illustrated in FIG. 10 varies directly with 
the tangential velocity vector V.sub.T and inversely with the radial 
velocity vector V.sub.R. When the spin velocity is exceedingly large and 
the static pressure is exceedingly small so that the tangential velocity 
vector V.sub.T dominates, I have observed fan or sweep angles .alpha. as 
large as 180 degrees. On the other hand when the static pressure dominates 
over the spin velocity so that the radial velocity vector V.sub.R is 
relatively large, a minimal or hardly noticeable sweep angle .alpha. is 
produced. Thus by increasing the width of outlet opening 38, and thereby 
decreasing the static pressure in chamber 37, I have been able to achieve 
a significant increase in the fan angle .alpha.. Likewise, by shaping the 
contour of walls 40, 41 proximate outlet 38, such as by narrowing the 
region therebetween, I have been able to considerably reduce the fan angle 
.alpha.. These and other effects are illustrated in association with other 
embodiments described hereinbelow. 
Refer now to FIGS. 6 and 7 of the accompanying drawings. There is 
illustrated another form of the oscillator of the present invention. 
Specifically, oscillator 50 includes a top plate 52 and a bottom plate 51. 
Recesses are defined in bottom plate 51 to form the oscillator, the 
recesses being covered by cover plate 52 to provide the necessary sealing. 
Oscillator 50 differs from oscillator 10 of FIG. 1 in two respects: first, 
the shape of the oscillation chamber 53 is generally trapezoidal rather 
than circular; and second, input fluid is delivered from supply passages 
54 and 55 defined through bottom and top plates 51 and 52, respectively. 
Passages 54 and 55 are angled to direct the incoming fluid into chamber 53 
as a common supply jet which oscillates in the same manner described in 
relation to the oscillator in FIG. 1. Passages 54 and 55 permit the 
U-shaped member 17 of FIG. 1 to be eliminated so that no structure is 
present in the plane of the oscillator. The trapezoidal chamber 53 and the 
rectangular chamber 24 of FIG. 4 are merely examples of the multitude of 
variations that can be utilized in the oscillator chamber configurations 
and still achieve the desired oscillation. For example, the oscillating 
chamber may be elliptical, irregularly shaped, polygonal, or whatever, so 
long as there is room for the alternating vortices to develop and move in 
the manner described in relation to FIGS. 11 through 15. 
Referring to FIG. 8 there is illustrated a fluidic oscillator 56 of a 
conventional type, well known in the prior art, having outlet passages 58 
and 59 which deliver the alternating outflow from the oscillator to an 
output region 57 constructed in accordance with the present invention. 
Chamber 57 operates in the same way described above for chamber 37 
irrespective of the nature of the oscillator which delivers the 
alternating slugs of fluid thereto. To further illustrate this point, 
there is illustrated in FIG. 9 an output chamber 60 which is fed by a 
schematically represented source of alternating pulses which may be any 
such source such as an alternating shuttle valve, a fluidic amplifier, 
etc. 
Referring now to FIG. 17 of the accompanying drawings there is illustrated 
an output chamber 61 similar in all respects to output chamber 37 in FIG. 
16 but which instead of having a single outlet opening 38 has two such 
outlet openings 62 and 63. The vector analysis applied to the embodiment 
of FIG. 16 applies equally as well to the diagrammatic embodiment of FIG. 
17 where similar vectors are illustrated. From chamber 61, however, there 
are two outflows which issue, each being swept at the same frequency. 
However, the two resulting outputs diverge from one another at any instant 
of time by somewhat more than the angle subtended between the two vectors 
V.sub.R and V'.sub.R. This is because the tangential vectors V.sub.T and 
V'.sub.T subtend a greater angle than exists between the radial vectors, 
as is the case in FIG. 16. As a consequence two synchronized (in 
frequency) sweeping sheets issue to form a composite waveshape of the type 
illustrated in FIG. 18. 
It is to be noted, by means of further explanation of the operation of 
output chambers 37 and 61, that the radial vector V.sub.R increases 
somewhat in amplitude at the time when the spin reverses direction; 
V.sub.R decreases to a minimum value when the spin has its extreme maximum 
amplitude. Therefore, a phase shift exists between the maxima of the 
pulsating input signals to chambers 37 and 61 and the spin velocity 
maximum in the output vortex. It should also be noted that depending upon 
the particular design of the chamber the pressure at the center of the 
output vortex may fluctuate from below atmospheric pressure to above 
atmospheric pressure. 
Referring to FIG. 18, an oscillator, of the general type illustrated in 
FIG. 1, is modified by incorporating two upstanding members 66, 67 on 
opposite sides of the jet issued from U-shaped member 68. Members 66 and 
67 are shown as cylinders (i.e. circular cross-section) but their cross 
sections can take substantially any shape. Importantly, they are spaced 
slightly downstream from the ends of member 68 so that respective gaps 69 
and 70 are defined between member 68 and members 66 and 67. The presence 
of members 66 and 67 and the resulting gaps has the effect of sharpening 
or "squaring off" the pulses issued from oscillator 64 as compared to the 
tapered pulses shown in FIG. 1. More specifically, in reference to the 
discussion above relating to FIGS. 11-15, the displaced vortex takes 
longer to build up when members 66 and 67 are present, partly because of 
the loss of energy in the input jet in traversing the region of gaps 69, 
70. This loss of jet energy means that the energy feeding the displaced 
vortex is less so that vortex build up takes longer. However, when the 
displaced vortex does build up sufficiently to dislodge the centered 
vortex, it has grown to the point where the transition is rapid. Hence, 
there is a relatively long dwell time in the extreme positions (i.e. FIGS. 
13 and 15) and a rapid transition between these positions; this results in 
sharp-edged pulses or slugs. 
Output chamber 65 tends to filter these sharp edges somewhat in its action 
as an RL (i.e.--restriction and inertance) filter. This is shown in the 
spray output waveforms 71 and 72 issued from output openings 73 and 74, 
respectively, in chamber 65. In addition, if the passages 75 and 76 are 
lengthened, thereby adding inertance, additional filtering is achieved. 
As described above in relation to FIG. 17, I have observed that the 
waveforms 71 and 72 issued from the two outlets of chamber 65 are 
synchronized in frequency and phase but are spread spatially by an angle 
which is greater than the angular spacing between outlet openings 73 and 
74. This is because the tangential velocity vectors V.sub.T and V'.sub.T 
are displaced from one another by an angle which is greater than the 
spacing between the radial velocity vectors V.sub.R and V'.sub.R. 
FIGS. 19 and 20 illustrate the manner in which the shape of the output 
chamber affects the sweep waveshape. In FIG. 19 a generally circular 
oscillation chamber receives a jet from U-shaped member 78 and oscillation 
ensues in the manner previously described. The alternating output pulses 
from the oscillator are conducted by passages 79 and 80 to output chamber 
81 which is formed between converging sidewalls 82 and 83. The convergence 
of the sidewalls produces a relatively narrow output chamber 81. The 
single outlet opening 84 issues a sweeping spray pattern having the 
waveform diagrammatically represented as 85. It is noted that waveform 85 
has a slower transition between sweep extremities (i.e. a longer dwell 86 
in the center) than does sweep waveform 45 of FIG. 10. Also noted is the 
fact that the sweep angle .alpha. is somewhat smaller than in waveform 45. 
These effects result from the narrowed output chamber 81, primarily 
because the radial velocity component V.sub.R is larger when the output 
chamber is narrow. The larger velocity component is due to the fact that 
the static pressure in the narrowed chamber volume is greater, and V.sub.R 
is affected by the static pressure. Waveform 85 results in a spray pattern 
having a heavier concentration of fluid droplets or particles in the 
center than at the extremities of the sweeping flow. 
In contrast oscillator/output chamber combination 90 of FIG. 20 produces a 
different waveform 91. Specifically, element 90 is in the general form of 
an oval which is wider at its outlet chamber end than at its oscillation 
chamber end. The oscillation chamber 92 receives a fluid jet from U-shaped 
member 94 and produces oscillation in much the same fashion described in 
relation to FIGS. 11 through 15. The common inlet and outlet opening for 
chamber 92, however, subtends more than 180.degree. of the generally 
circular chamber 92. In other words, the sidewalls 95, 96 of the element 
90 are straight diverging walls between the oscillation chamber 92 and 
output chamber 93. Member 94 is disposed between the sidewalls and forms 
therewith connecting passages 97, 98 between chambers 92 and 93. The 
radius of oscillation chamber 92 is substantially the same as in chamber 
77 in FIG. 19. However, output chamber 93 is considerably wider than 
chamber 81. The resulting waveform 91 is seen to be considerably different 
than waveform 85 of FIG. 19. Specifically, waveform 91 is a generally 
triangular wave, with sawtooth tendencies, in which the central 
concentration 86 of FIG. 19 is not present. This absence of central 
concentration results from the widening of chamber 93 as compared to 
chamber 81. The transition region (i.e. between the extremes) of the sweep 
waveform 91 is much smoother and it is also noted that it exhibits a 
concave (as viewed from downstream) tendency. The concavity indicates that 
the fluid in the center of the pattern is moving slightly more slowly than 
the fluid at the sweep extremities. In general, waveform 91 provides very 
even distribution across the sweep path. 
The oscillator/output chamber combination of the present invention has been 
found to provide the same pattern when scaled to different sizes. Thus, a 
small device for use as an oral irrigator may have a nozzle width at 
U-shaped member on the order of a few thousandths of an inch. This 
oscillator may be scaled upward in every dimension to provide, for 
example, a large decorative fountain and still produce the same, albeit 
larger, waveform. A scaled outline of an oscillator/output chamber 
combination 100, similar to the device in FIG. 19, is illustrated in FIG. 
21. As can be seen, all dimensions are scaled to the width of the nozzle W 
formed at the outlet of the generally U-shaped member 101. The diameter of 
the oscillation chamber 102 is 8W. The distance between the nozzle and the 
far wall of chamber 102 is 9W. The common inlet and outlet opening for 
chamber 102 is 7W and is spaced 2W from the nozzle. The closest spacing 
between member 101 and the sidewalls 103, 104 is 2.5W, and the maximum 
spacing between the sidewalls is 11W. The length of the unit 100 is 25W 
and the width of outlet opening 105 from output chamber 106 is 2.5W. 
Device 100 can be constructed to substantially any scale and operates in 
accordance with the principle described herein. It is to be stressed, 
however, that the relative dimensions of device 100 are intended to 
achieve only one of multitudinous waveforms possible in accordance with 
the present invention and that these dimensions are not to be construed as 
limiting the scope of the invention. 
FIGS. 22 through 26 illustrate comparative waveforms attained when various 
dimensions of the oscillator/output chamber are changed. Specifically, 
oscillator 110 of FIG. 22 is shown with relatively short output passages 
111, 112. The resulting issued pulses are shown with amplitude plotted 
against time. The output pulse trains consist of sawtooth waves which are 
180.degree. separated in phase. This may be compared to oscillator 113 
with considerably longer outlet passages 114 and 115. Again sawtooth 
waveforms are produced, but the individual pulses are considerably 
smoothed and the frequency is considerably less. This is primarily due to 
the fact that the longer passages 114 and 115 introduce greater inertance 
(the analog of the electrical parameter inductance) in to the oscillator, 
making the response in the oscillation chamber considerably slower. In 
FIG. 24 the oscillator 110 (of FIG. 22) with short outlet passages 111 and 
112 is combined with a relatively small volume output chamber 116. The 
waveform 117 of the sweeping spray issued from chamber 116 is a sawtooth 
waveform wherein the transition portions between sweep extremities bulges 
in a downstream direction. This signifies that the flow in the middle or 
transition portion of the sweep pattern is moving at a slightly greater 
velocity than at the extremes. This may be compared to waveform 91 of FIG. 
20 wherein the bulge is in the opposite direction, signifying slower 
travelling fluid in the central portion of the sweep pattern. The reason 
for this is that in the smaller output chamber 116 there is less vortical 
inertance so that spin velocity tends to slow down more quickly after the 
impetus of a driving pulse from the oscillator subsides. The slow down 
permits the radial velocity V.sub.R to dominate and impart a high radial 
velocity to the issued fluid during the central part of the sweep. 
Oscillator 110' illustrated in FIG. 25 is essentially the same as 
oscillator 110 but is shown, in combination with a somewhat widened output 
chamber 119. Chamber 119 affords a greater vortical inertance, providing 
less of a tendency for the vortex to slow down when a driving pulse 
subsides. The result is a waveform 118 in which the downstream bulge is 
not present, primarily because the dominance of the radial velocity vector 
is no longer present. Increasing the output chamber size even further, as 
with chamber 120 of FIG. 26, produces a waveform 121 wherein the central 
portion tends to bulge slightly in an upstream direction or opposite that 
in waveform 117 of FIG. 24. This shows a tendency toward waveform 91 of 
FIG. 20 wherein the fluid at the center of the pattern begins to flow more 
slowly than the fluid at the extremes. This results from an increased 
vortical inertance in the larger chamber 120, which inertance produces a 
tendency for the vortex to continue spinning after the driving pulse 
subsides and thereby causes the tangential velocity vector V.sub.T to take 
on dominance. Further, the dominance of the tangential vector V.sub.T 
causes the sweep angle to increase as seen from the larger angle subtended 
by waveform 121 that by waveforms 117 and 118. In all three embodiments 
(FIGS. 24, 25 and 26) distribution of fluid within the sweep pattern is 
relatively even. 
Referring next to FIG. 27, an oscillator 125 is constructed in a manner 
similar to oscillator 64 of FIG. 18 in that members 126, 127 are spaced 
slightly from U-shaped member 128 to provide gaps 130, 131 which provide 
communication between the input jet and the output pulses. As described in 
relation to FIG. 18, this construction tends to square off or sharpen the 
pulses, producing greater dwell in the extreme portions of the oscillator 
cycle and a relatively fast switching or transition between extremes. This 
is manifested by the amplitude versus time slots of the output pulses 124 
and 123, which show a flattened peak as compared to the somewhat sharper 
pulse peaks illustrated in FIGS. 22 and 23. Oscillator 125 is illustrated 
again in combination with output chamber 132 in FIG. 28. Outlet opening 
123 from chamber 132 issues a spray pattern having the waveform 134 which 
has longer dwell times at the sweep extremities than the waveforms in 
FIGS. 24, 25 and 26. As described in relation to FIG. 18, the members 126, 
127 tend to delay the re-strengthening of the displaced vortex (A in FIG. 
13) so that there is greater dwell at the extremes of the oscillation 
cycle. 
Referring to FIG. 29, there is illustrated another oscillator/output 
chamber combination 135. The oscillator portion of device 135 is 
characterized by an oscillation chamber 136 which is considerably longer 
than those described above and which includes a far wall 137 which is 
convex rather than concave. In addition, oscillator output passages 138 
and 139 are somewhat wider than those illustrated in the embodiments 
described above. The output chamber 140 of device 135 is characterized by 
an opening 142 in U-shaped member 141 which issues fluid directly into the 
output chamber. Lengthening the oscillator chamber has the effect of 
reducing the frequency of oscillation since the vortices A and B of FIGS. 
11-15 must travel greater distances during the oscillation cycle. I have 
found that such lengthening, beyond a certain point, requires a widening 
of outlet passages 138 and 139 in order to maintain uniform oscillation. 
Beyond a certain point (e.g. when the length of chamber 136 exceeds the 
outlet width of member 141 by twenty-five times) if the output passages 
are not widened there is a backloading in chamber 136 which either 
produces sporadic oscillation or a stable condition. Longer oscillation 
chambers and their inherent lower frequencies are very suitable for 
massaging showers or decorative spray fountains and may be used with or 
without the convex wall 137 feature or the fill-in jet nozzle feature 142. 
Convex wall 137 has the effect of causing the oscillation cycle to pass 
much more quickly between extreme positions than does a flat or concave 
wall. With a faster transition, the rise and fall times of the pulses 
delivered to output passages 138 and 139 are shortened. This feature may 
be used independently of the lengthened oscillation chamber and the 
fill-in jet. 
The fill-in jet from opening 142 is used to increase the amount of fluid in 
the center of the issued spray pattern. In effect, this shortens the 
transition time between extreme sweep positions, causing greater "dwell" 
in the mid-portion of the sweep cycle than at the ends. This is reflected 
in the waveform 144 of the spray pattern issued from outlet 143 wherein it 
is noted that the transition region is bowed outward considerably. 
Relating this feature to the vector discussion and FIG. 16, fill-in flow 
from nozzle 142 imparts additional magnitude to the radial vector V.sub.R, 
both in a dynamic sense (since the fill-in flow is directed along the 
radial vector direction) and as additional static pressure in output 
chamber 140. 
The features described in relation to FIG. 29 provide additional techniques 
for shaping the output spray pattern and may be used with any of the other 
oscillators and output chambers described herein. 
Oscillator 145 of FIG. 30 is illustrative of an embodiment wherein multiple 
outlets variously directed are achieved. Specifically a nozzle structure 
146 issues a fluid jet into oscillation chamber 147 which may take any 
configuration consistent with the operating principles described in 
relation to FIGS. 11-15. Outlet passages 148 and 149 are shown as being 
turned outwardly, substantially at right angles to the input jet, rather 
than being directed in 180.degree. relation to that jet. It is to be 
understood that these passages can be turned at any angle or in any 
direction, in or out of the plane of the drawing, depending upon the 
application. Further, one or more of these passages, for example passage 
149, may be bifurcated to provide two passages 150 and 151 which conduct 
co-phasal output pulses. It is to be understood that any of passages 148, 
149, 150, 151 may be lengthened or shortened to delay the issuance of 
output pulses therefrom to obtain a variety of different effects and 
results. 
The fan-shaped spray patterns described as being issued by the output 
chambers described above provide a line or one-dimensional pattern when 
they impinge upon a target. In other words, when the cyclically swept 
spray impacts against a surface interposed in the spray pattern, the fluid 
sweeps back and forth along a line on that surface. It is also possible to 
achieve a two-dimensional spray pattern from the output chamber of the 
present invention. An output chamber embodiment for achieving spray 
coverage of a two-dimensional target area is illustrated in FIGS. 31 and 
32. Specifically, an output chamber 152 is fed alternating fluid pulses 
from passages 153 and 154. The outlet opening 155 from chamber 152, 
instead of merely being a slot defined in the natural periphery of the 
chamber, is in the form of a notch cut into the chamber. In the embodiment 
shown the notch is cut along the central longitudinal axis of the device 
by a circular blade to provide an arcuate notch 156 perpendicular to the 
plane of chamber 152 and having a V-shaped cross-section. Cutting the 
outlet into the chamber allows the static pressure therein to expand in 
all directions. As a consequence, the spray issued from the outlet 155 
follows the contours of notch 156 to provide a sheet of fluid in the plane 
of the notch (i.e. perpendicular to the plane of the chamber 152). This 
sheet is swept back and forth due to the alternating vortex action 
described in relation to FIG. 16 so that the spray pattern issued from 
outlet 155 forms a cyclically sweeping sheet. This sweeping sheet covers a 
rectangular area when it impinges on a target disposed in the spray path, 
thereby affording two-dimensional spray coverage. I have found that as the 
notch is cut deeper into chamber 152, the angle of the sheet expansion in 
the vertical plane increases. Various contouring of the notch 
cross-section permits contouring of the distribution of droplets in the 
vertical plane (i.e. perpendicular to the chamber). 
Another output chamber embodiment is illustrated in FIGS. 33 and 34. In 
this embodiment the output chamber 160 receives alternating fluid pulses 
from passages 161 and 162 and delivers a planar or fan shaped swept 
pattern from a slot shaped outlet opening 163. However, outlet opening 163 
is formed in the floor (or ceiling) of the chamber rather than being 
defined in the end wall thereof. The same vectorial analysis applied to 
the chamber of FIG. 16 is applicable to chamber 160 but in chamber 160 it 
is noted that outlet opening 163 extends along the radius of the 
alternating vortex. Since the spin velocity of a vortex varies at 
different radial points, the tangential velocity vector V.sub.T varies 
along the length of opening 163. The result renders the issued spray 
pattern waveform somewhat asymmetric into the plane of the drawing in FIG. 
34, the asymmetry being greater for longer outlet openings. 
Still another output chamber configuration is illustrated in FIGS. 35 and 
36. This embodiment, like that of FIGS. 31 and 32, provides a swept sheet 
pattern which covers a two-dimensional target area rather than a lineal 
target. The output chamber 165 receives alternating fluid pulses from 
passages 166 and 167, similar to chambers described above. However, 
chamber 165 is expanded cylindrically, perpendicular to the plane of 
passages 166, 167, so that the depth of chamber 165, as best seen in FIG. 
36, is substantially greater than that of previously described chambers. 
Outlet slot 168 is defined in the periphery of the chamber and extends 
parallel to the cylindrical axis of the chamber. When pressurized fluid is 
issued from chamber 165 it is formed into a sheet 169 by slot 168, the 
sheet residing in a plane perpendicular to the plane of vortex spin in 
chamber 165. The alternating spin causes the issued sheet to oscillate 
back and forth according to the principles described in relation to FIG. 
16. The resulting waveform provides an even distribution of droplets along 
the sheet height. Distribution along the sheet width (the dimension shown 
in FIG. 35) is determined by the various features and factors described 
herein relating to oscillator and output chamber configurations. 
The oscillator/output chamber configuration 170 in FIG. 37 is characterized 
by its asymmetry with respect to its longitudinal centerline. Oscillator 
chamber 170 receives a jet from nozzle 171 of member 172 in a direction 
which is not radial but nevertheless across the chamber. As a consequence, 
the oscillation, which ensues according to the principles described in 
relation to FIGS. 11-15, is unbalanced in that the fluid slugs issued into 
outlet passage 175 are of longer duration than the pulses issued into 
outlet passage 176. As a consequence, the clockwise spin in output chamber 
173 has a longer duration than the counterclockwise spin and the spray 
pattern issued from outlet opening 174 is heavier on the bottom side (as 
viewed in FIG. 37) of the longitudinal centerline than the top side. 
Asymmetrical construction of the oscillator, output chamber, positioning 
of member 172, location of outlet 174, etc., may all be utilized to 
achieve desired spray patterns. 
The output chamber 177 of FIGS. 38 and 39 has two characterizing features. 
First, the outlet opening 185 is a generally circular hole 185 defined 
through the ceiling or floor of the chamber, substantially at the chamber 
center. Second, flow dividers 178 and 179 are positioned to divide the 
incoming fluid pulses. Specifically, divider 178 divides an incoming pulse 
between passage 183 which extends around the chamber periphery and passage 
184 which is disposed on the radially inward side of divider 178. 
Likewise, divider 179 divides an incoming pulse of the opposite sense 
between outer passage 180 and inner passage 181. The outlet opening 185, 
positioned as described, provides a hollow conical spray pattern 186 which 
alternately rotates in one direction and then the other as the output 
vortex in chamber 177 alternates spin directions. The speed angle of the 
conical pattern 186 varies with spin velocity so that as the output vortex 
speeds up and slows down during direction changes, the spray pattern 186 
alternately opens (186) and closes (187). In this manner the pattern 186, 
when impinging upon a target, covers a generally circular area. The flow 
dividers 178 and 179 impart spin components to the output vortex at four 
locations instead of two, resulting in minimal movement of the output 
vortex in the chamber. The output vortex is thus maintained centered over 
outlet opening 185 to assure the symmetry of the spray conical pattern 
186, 187. The features of FIGS. 38, 39 (namely, location of outlet 185 and 
presence of dividers 178, 179) can be used independently. 
A similar spray pattern is achieved with the outlet chamber 190 of FIGS. 
40, 41. Specifically, output chamber 190 is in the form of a cylinder 
which extends out of the plane of the incoming pulses from passages 192, 
193 and then tapers in a funnel-like fashion toward a central outlet 
opening 191. Again the resulting output spray pattern is a spinning 
conical sheet which continuously changes spin direction as the output 
vortex direction changes in chamber 190 and which goes from an expanded 
wide-angle cone 194 at maximum spin to a relatively contracted cone 195 at 
minimum spin. 
The device of FIGS. 38, 39, and that of FIGS. 40, 41 is useful for 
decorative fountains, showers, container spray nozzles, etc. 
The apparatus of FIGS. 42 and 43 expands the principles of the outlet 
chamber of the present invention to three dimensional spin in the output 
vortex. Specifically, a generally spherical chamber receives a pair of 
alternating fluid signals or pulses from a first oscillator or other 
source 201 at diametrically opposed inlet openings 202 and 203. Another 
pair of diametrically opposed inlet ports 204, 205 receive alternating 
fluid signals or pulses from a source 206. The signals from source 201 
have a frequency f.sub.1 ; the signals from source 206 have a frequency 
f.sub.2. The plane of ports 202, 203 is perpendicular to the plane of 
ports 204, 205, although this is by no means a limiting feature of the 
present invention. The outlet opening 207 for the spherical chamber 200 is 
located where the intersection of these two planes intersects the chamber 
periphery. Depending upon the relative frequency and phase of the signals 
from sources 201 and 206, a variety of output spray patterns can be 
obtained. Thus, if frequencies f.sub.1 and f.sub.2 are equal but are 
displaced in phase by 90.degree., a hollow spray pattern is issued which 
is of square cross-section if the input signals are well-defined pulses, 
of circular cross-section if the input signals are sinusoidal functions, 
etc. If frequency f.sub.1 is twice that of f.sub.2, and the input signals 
are sinusoidal, a figure eight pattern is generated. In other words, the 
cross-section of the pattern issued from outlet opening 207 takes the form 
of the well-known Lissajous patterns achieved on cathode ray oscilloscope 
displays. By choosing proper phase and frequency relationships between the 
input signals, an extremely large variety of waveshapes may be achieved. 
Referring to FIGS. 44, 45 and 46 there are three oscillator/output chamber 
combinations illustrated. In the three devices 210, 211 and 212, 
respectively, the sizes and shapes of the oscillator chamber 213 and 
output chamber 214 are substantially the same. The differences reside in 
the sizes of the common inlet and outlet openings 215, 215' and 215" of 
the three devices, the opening being smallest in device 210, largest in 
device 212. The waveforms of the spray patterns are affected as follows: 
For the smallest opening (device 210) the observed waveform was a 
well-defined sawtooth with slight rounding at the extremities. For the 
medium opening (device 211) the sawtooth waveform showed less rounding or 
curvature at the extremities as compared to that for device 210. For the 
largest opening 215" (device 212) even less rounding was observed, the 
waveform appearing almost triangular, substantially like waveform 91 of 
FIG. 20. The last mentioned waveform provides the most even droplet 
distribution of the three. In general it may be started that the wider the 
opening 215, the less the flow restriction at the oscillator output and 
the greater the filtering effect in the output chamber. 
In FIG. 47 an oscillator/output chamber combination 216 includes an 
oscillation chamber 217 and an output chamber 218. This device is 
characterized by the fact that the side walls 220 and 221 converge just 
behind U-shaped jet-issuing member 219 to form a throat 223, and then 
diverge in the output chamber 218 and converge again to form an output 
opening 222. This configuration effects a flow reversal so that fluid 
which flows along sidewall 220 out of oscillation chamber 217 is turned at 
throat 223 to flow along the opposite wall as it enters the output chamber 
218. Operation is the same as previously described for the non-reversing 
flow arrangement except that a greater spin effect is provided in chamber 
218 by the wall curvature. 
In FIGS. 48 and 49 there is illustrated an embodiment of the oscillator of 
the present invention which is employed as a flow meter. Specifically a 
flow channel 225 is illustrated as a cylindrical pipe. It is to be 
understood that the channel 225 can take any configuration, and may even 
be open along its top. Fluid flow in the flow channel 225 is represented 
by the arrows shown in FIG. 48. Two semi-oval members 226 and 227 are 
disposed with their major axes parallel to the flow direction and are 
slightly spaced apart to define a downstream tapering nozzle 229 
therebetween. The downstream ends of members 226 and 227 are formed as 
downstream-facing cusps 230 and 231, respectively. A body member 228 has 
an oscillation chamber 232 defined therein, chamber 232 being shown as 
U-shaped in FIG. 48 but capable of assuming any configuration consistent 
with the operational characteristics described herein for oscillator 
chambers. The oscillation chamber 232 is shown disposed symmetrically with 
respect to nozzle 229, but this is not a requirement. A pair of tiny 
pressure ports 233 and 234 are defined in the downstream end of chamber 
232; again, these ports are shown disposed symmetrically with respect to 
nozzle 229 but this is not a limiting feature of the invention. The 
pressure ports 233 and 234 communicate with tubes 235, 236 which extend 
out through channel 225. 
In operation, a portion of the flow in channel 225 is directed into nozzle 
229 which issues a jet into chamber 232. Oscillation ensues in chamber 232 
in the manner described in relation to FIGS. 11-15. Alternating outflow 
pulses are first directed upstream when egressing from chamber 232 and are 
then redirected by cusps 230, 231 into the main channel flow. As the jet 
in chamber 232 is swept back and forth by the alternating vortices, the 
differential pressure at ports 233, 234 (and therefore at tubes 235, 236) 
varies at the frequency of oscillation. I have found that the frequency of 
oscillation for the oscillator of the present invention varies linearly 
with the flow therethrough. Consequently, by employing a conventional 
transducer, for example an electrical pressure transducer, it is possible 
to provide a measurement of flow through channel 225. 
The flow metering arrangement of FIGS. 48, 49 is highly advantageous as 
compared to prior art attempts to employ fluid oscillations as a flow 
measurement parameter. For example, only a small oscillator need be used, 
thereby minimizing any losses introduced by the oscillator. Further, the 
channel flow which by-passes the oscillator (i.e. flow around the outside 
of members 226 and 227) serves to aspirate flow from the cusp regions 230, 
231, thereby providing a differential pressure effect across the 
oscillator. Importantly, the negative aspiration pressure permits the 
by-pass flow to affect oscillator frequency and thereby permit more than 
just the limited flow through the nozzle 229 to be part of the 
measurement. Since flow velocity tends to vary somewhat across a channel, 
this use of a greater portion of the flow without increasing losses, is 
highly advantageous. It is to be understood that all of the flow can be 
directed through the oscillator, if desired, but that losses are minimized 
if only a small part of the flow is so directed. 
The oscillation frequency can be sensed in many places. Pressure ports 233, 
234 are particularly suitable because the dynamic pressure in the jet is 
available where these ports are shown, and that pressure is easily sensed. 
It is also possible to insert a hot wire anemometer or other flow 
transducing device 237 in one of the output passages of the oscillator to 
sense flow frequency. 
The oscillator and output chamber of the present invention have been 
described as having certain advantages. Included among these is the fact 
that the oscillator oscillates without a cover plate (i.e. without plate 
12 of FIG. 1) at low pressures. This is highly advantageous for many 
applications, including flow measurement in open channels or rivers. 
The oscillator also operates with substantially all fluids in a variety of 
fluid embodiments, such as with gas or liquid in a gaseous environment, 
gas or liquid in a liquid environment, fluidized suspended solids in a gas 
or liquid environment, etc. Importantly, oscillation begins at extremely 
low applied fluid pressures, on the order of tenths of a psi, for many 
applications. Moreover, oscillation begins immediately; that is, there is 
no non-oscillating "warm-up" period because there can be no outflow until 
oscillation ensues. The oscillator and output chamber can be symmetric or 
not, can have a variable depth, can be configured in a multitude of 
shapes, all of which can be employed by the designer to achieve the 
desired spray pattern. 
The output chamber although shown herein to have smooth curved peripheries, 
can have any configuration in which a vortex will form. Thus, sharp 
corners in the output chamber periphery, while affecting the waveshape, 
will still permit operation to ensue as described in relation to FIG. 16. 
Further, the number of outlets from the output chamber, while affecting 
the waveshape, does not preclude vortex formation. Specifically, I have 
found that as the total outlet area is increased the sweep angle .alpha. 
increases. In particular, in a chamber similar to chamber 61 of FIG. 17, I 
have found that by blocking off one of the outlet openings, the spray 
pattern issued from the other outlet opening reduced considerably, with 
the shape of the wave remaining about the same. Likewise, in chamber 37 of 
FIG. 16, if the single outlet 38 is reduced in size, the angle of the 
sweep is reduced. These sweep angle changes are produced because the 
static pressure in the chamber is increased when the outlet is reduced and 
therefore the radial vector V.sub.R begins to dominate. 
While I have described and illustrated various specific embodiments of my 
invention, it will be clear that variations of the details of construction 
which are specifically illustrated and described may be resorted to 
without departing from the true spirit and scope of the invention as 
defined in the appended claims.