Fluid handling – Flow affected by fluid contact – energy field or coanda effect – Structure of body of device
Reexamination Certificate
2002-12-04
2004-10-19
Chambers, A. Michael (Department: 3753)
Fluid handling
Flow affected by fluid contact, energy field or coanda effect
Structure of body of device
C137S826000, C137S806000
Reexamination Certificate
active
06805164
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to fluid handling processes and apparatus. More particularly, this invention relates to methods and apparatus for effecting controlled dispersal of fluid to achieve specific flow patterns. Such flow patterns are of interest in a wide range of applications (e.g., shower and sink sprays, spas that provide fluid massaging actions, drying equipment).
2. Description of the Related Art
Fluidic oscillators are well known in the prior art for their ability to provide a wide range of liquid spray patterns by cyclically deflecting a liquid jet. Examples of fluidic oscillators may be found in many patents, including U.S. Pat. Nos. 3,185,166 (Horton & Bowles), 3,563,462 (Bauer), 4,052,002 (Stouffer & Bray), 4,151,955 (Stouffer), 4,157,161 (Bauer), 4,231,519 (Stouffer), which was reissued as RE 33,158, 4,508,267 (Stouffer), 5,035,361 (Stouffer), 5,213,269 (Srinath), 5,971,301 (Stouffer), 6,186,409 (Srinath) and 6,253,782 (Raghu). The technology disclosed is these patents is summarized below.
However, before reviewing these patents, it is perhaps informative to make note of some of the distinct features of fluidic oscillators. The operation of most fluidic oscillators is usually characterized by the cyclic deflection of a fluid jet without the use of mechanical moving parts. Consequently, an advantage of fluidic oscillators is that they are not subject to the wear and tear which adversely affects the reliability and operation of pneumatic oscillators and reciprocating nozzles.
The fluidic oscillators described in U.S. Pat. No. 3,185,166 (Horton & Bowles) are characterized by the use of boundary layer attachment (i.e., the “Coanda effect,” which is named after Henri Coanda who was the first to explain the tendency for a jet issuing from an orifice to defect from its normal path so as to attach to a nearby sidewall) and the use of downstream feedback passages which serve to cause the jet issuing from a power nozzle to oscillate between exiting in either the right or left side ports. See
FIG. 1
which shows the top view of a two dimensional fluidic which, as is conventional in fluidic technology, is assumed to have a transparent top surface so as to reveal the internal geometry of the fluidic.
This fluidic is symmetric about its longitudinal centerline L—L and consists of an interaction region with sidewalls which diverge downstream from a power nozzle. A jet issued by the power nozzle is cyclically deflected back and forth between the interaction region sidewalls by a portion of the jet which is captured at a feedback passage inlet and fed back to effect deflection.
The feedback force exerted by the feedback passages must not only be sufficient to deflect the jet itself, but it must also overcome the boundary layer attachment of the jet to a sidewall. The result is that the oscillator cannot operate at jet pressures below a rather significant pressure level. Moreover, the attachment of the jet to the sidewalls during each half cycle of oscillation results in a “dwell” time wherein the jet is effectively stationary. The spray pattern produced by the cyclically deflected jet, which alternately exits through one or the other of the exit ports at the top of the oscillator, consequently contains greater concentrations of jet fluid at those pattern locations corresponding to the effective stationary state of the jet (i.e., the outer edges of the spray distribution pattern), rather than at other locations. It is therefore not possible to control pattern distribution or to achieve uniformly distributed patterns, with oscillators of this type. Furthermore, the use of porous plugs in the control tubes were seen to result in even longer duration jet “dwell” times on the sidewalls.
It should be recognized that the three-dimensional character of the flow from such fluidics can take a variety of forms depending upon the three-dimensional shape of the fluidic. For example, if the depth of the fluidic shown in
FIG. 1
is approximately the same as the width of its exit ports, then an approximate, oscillating round jet with be sprayed from the fluidic. If the depth of the fluidic is much greater than the width of the exit port, then an oscillating, sheet of fluid will exit from the fluidic. If the fluidic is such that it has angular symmetry about its centerline, it's exit port will be annular in shape and from it will spray an oscillating, annular ring of fluid.
The fluidic oscillators described in U.S. Pat. No. 3,563,462 (Bauer) are characterized by what is sometimes called a flow-reversing, interaction region which results in the flow from this fluidic's power nozzle to have a bistable flow pattern. The use of downstream feedback passages, which connect at points downstream from the fluidic's power nozzle, serves to cause the flow to oscillate between exiting from the right and left side ports. See FIG.
2
. The sidewalls of the flow-reversing interaction region first diverge from the power nozzle and then converge toward an outlet throat in a downstream direction. When the jet flows along the left sidewall it is re-directed thereby toward the right as it egresses through the outlet throat; likewise, the right sidewall re-directs the jet toward the left. The entry of ambient fluid into the interaction region via the outlet throat is relatively restricted as compared to the Horton & Bowles oscillator, primarily because the outlet throat is narrower relative to the egressing jet than the downstream end of the Horton & Bowles oscillator. The limitation of ambient fluid entry reduces the boundary layer attachment to the interaction region sidewalls so that less feedback force is required to deflect the jet. Oscillation in the flow-reversing configuration is therefore possible at lower jet pressures than in the Horton & Bowles oscillator. When a liquid issues from the power nozzle into an ambient air environment, such oscillators with flow-reversing interaction regions display relatively low frequency oscilliations and have found numerous practical applications, such as in shower heads, lawn sprinklers, decorative fountains, industrial control equipments, etc.
The spray pattern produced by this type of oscillator is often nonuniform due to ambient air being ingested through the feedback passages and randomly mixed with issuing primary jet liquid. In addition, since a mixture of air and liquid has a different viscosity than the liquid alone, and since the size of the droplets exiting from this type of oscillator are a function of the viscosity of the resulting fluid spray, the sprays from these oscillators are often found to have considerable variability in droplet sizes.
The fluidic oscillators described in U.S. Pat. No. 4,052,002 (Stouffer & Bray) are characterized by the selection of the dimensions of the fluidic such that no ambient fluid or primary jet fluid is ingested back into the fluidic's interaction region. See FIGS.
3
(
a
)-
3
(
b
). This yields a spray pattern that is more uniform and with a spray that is made up of droplets of more uniform size.
The absence of inflow or ingestion from outlet region is achieved by creating a static pressure at the upstream end of interaction region which is higher than the static pressure in outlet region. This pressure difference is created by a combination of factors, including: the width T of the exhaust throat is only slightly wider than power nozzle so that the egressing power jet fully seals interaction region from outlet region; and the length D of interaction region from power nozzle to throat, which length is significantly shorter than in prior art oscillators. It should be noted that the width X of control passages is smaller than the power nozzle. If the width of power nozzle at its narrowest point is W, then the following relationships were found to be suitable, although not necessarily exclusive, for operation in the manner described: T=1.1-2.5 W and D=4-9 W, with the ratios of these dimensions also being found to control the fan angle over
Bowles Fluidics Corporation
Chambers A. Michael
Guffey Larry J.
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