US 3451409 A
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June 24, 1969 J. A. ROCHE FLUIDIC SYSTEMS Filed June 5, 1966 INVENTOR.
United States Patent Oftice 3,451,409 Patented June 24, 1969 U.S. Cl. 137-815 5 Claims ABSTRACT OF THE DISCLOSURE A fluidic system is disclosed wherein the motive fluid supply section includes a container containing a solvent for contaminants known to be in the motive gas and means for injecting the solvent into suspension in the motive lluid.
The present invention relates to improvements in fluidic devices and more particularly to supply systems therefor.
In recent years there has been an accelerated effort to vdevelop fiuidic devices most of which are commonly referred to iluid amplifiers. In such devices a fluid power stream is controlled by one or more control jets having a substantially lower pressure than the power stream. The power stream may be deflected towards and away from a receiver port to provide pressure changes therein substantially greater than the control jet pressure, hence the term fluid amplifier.
By employing air or other gases, extremely rapid pressure variations can be obtained, enabling control functions to be perfonmed by inexpensive components with little or no use of electrical or electronic elements. Among other advantages is the capability of operating in ternperature environments which cannot be tolerated by electronic components.
Another potential of iluidic controls is a high level of reliability over a long life attributable, to a large measure, to the lack of mechanical, moving parts. This potential has been diicult to fully realize in many instances, particularly where air has been employed as the motive fluid. Over a period of time it has been found that the fluid amplifier characteristics tend to change so that, for example, a uidic control circuit having a counting function will fail to count all of the input pulses thereto.
Such malfunctioning is obviously unacceptable for many, if not all, types of controls and accordingly, it is the object of the invention to improve the reliability of iluidic devices, particularly those in which air or other gases are employed as the motive Huid.
It has been discovered that air, even after having passed through a high grade filtration system, contains oil vapors or oil mist droplets which will condense or collect on the walls of the llow paths through a fluidic device. As this occurs over a period of time, there will be a sufiicient accumulation of condensate to change the ilow characteristics of the air and eventually the tluidic device can Ibe rendered wholly inoperative.
In accordance with this invention it has been discovered that the addition of small amounts of an atomized, low viscosity, oil solvent to the air supplied to Huid devices will prevent heavier oils from forming a coating adversely affecting ilow passa-ges in the device. The low viscosity solvent wets at least all critical surfaces of the `device so that both the solvent and oil contaminant will be ilushed through the device during its operation.
In a broader sense the invention comprises providing means for adding small amounts of solvent to the motive uid supply of fluidic devices and thereby preventing condensate buildup on the llow walls which would alfect operation of the device.
The above and other related objects and features of the invention will be apparent from a reading of the following description of the disclosure found in the accompanying drawing and the novelty thereof pointed out in the appended claims.
The single figure in the drawing diagrammatically illustrates the present invention supplying motive uid to an illustrative iluidic device.
A conduit 10 extends from an appropriate source of pressurized air to a filter 11 which removes solid contaminants and some vapor contaminant from the air. The air then passes through conduit 12 to an atomizer 14.
The atomizer 14 comprises a solvent container 16, a venturi throat 18 'and a passageway 2l) from the bottom of the container to the throat 18. As air passes from the inlet 12 to discharge passage 22, a controlled amount of solvent is atomized in the -air stream. The amount of solvent may be varied by adjusting a screw 24 which controls the inlet area of the: passageway 20. A conduit 25 connects the upper end of the container 16 to the conduit 12 in order to insure a substantially uniform addition of solvent as its level in container 16 varies.
A groove 28 and depending trap 30 are provided downstream of the throat 18 to collect solvent that is not atomized. The trap may be periodically drained by opening valve 32.
The solvent bearing air is then directed to a uidic device 34 by a conduit 36 which preferably is connected tto the upper side of the discharge passage 22. The iluidic device 34 is essentially the same as that disclosed in U.S. Patent No. 3,220,428, issued in the name of Robert B. Wilkerson and assigned to the same assigne as the present application. Reference is made thereto for further details beyond those given in the following brief description.
The fluidic device 34 controls iiow of lluid through a conduit 36 in response to displacement of flappers 38 and 40. When either or both of the ilappers 38, `40 are displaced towards tubes 42, 44 respectively, they will cause shifting of a valve piston 46 to either permit or shut olf the flow of Huid through the conduit 36.
The solvent bearing air enters a passageway 48 of the lluidic device 34 and is discharged from a nozzle 50 as a power stream or jet. The device 34 .may be referred to yas a bistable uid amplifier by reason of the fact that the power stream will attach itself to either of the wall surfaces 52 or 54 to maintain a constant elevated pressure level in either of vented `chamber 56 or 58. As illustrated, the power stream is attached to the surface 52 and the pressure within the chamber 56 is transmitted by passageway 60 to the lefthand end of the valve 46, maintaining it in an open position so that there is flow of duid through the conduit 36.
The solvent bearing air from conduit 26 also passes through lateral passageways 62, 64 to chambers 66, 68 respectively. Needle valves 74, 76 may be employed to provide equal pressures in the chambers 66, 68 which are vented through the tubes 42, 44. lFluid from the chambers 66, 68 is directed from control nozzles 74, 76 laterally against the power stream discharged from the nozzle 50. The power stream, once attached to either of surfaces 52, '54 will remain so attached so long as the control jets are of equal pressure or the jet from nozzle 76 is greater. Under the illustrated conditions, if the iiapper 38 is moved to restrict venting of air through the tube 42, there will be an increased pressure in the chamber 66 and the control jet discharged from nozzle 74. This will displace the power stream toward the right causing it to become attached to the surface 54 and increase the pressure in the chamber S8. This in turn will cause an increase in pressure on the right-hand end of the piston 46 which is connected to chamber 58 by passageway 59. The piston 46 will then be displaced to a position in which the ow of iluid through conduit 36 is shut ol. The power stream will remain attached to the wall surface 54 when the llapper 38 is moved outwardly to allow the tube 42 to vent air from the chamber 66 in the normal fashion and will remain so attached until ow of air from the tube 4-4 is restricted by the apper 40.
For economical operation it is desirable that the source of pressurized air to which the conduit 10 is connected is a factory air supply. It is known that such a supply is contaminated to a relatively high level with oil vapors and mists as well as vapors and mists of other relatively heavy petroleum products. For practical and economical reasons, the ilter 11 is not intended, nor does it function, to remove such vapors and mists or droplets from the air as it passes to conduit 12.
The solvent in container 16 is selected as a petroleum solvent having a relatively low viscosity, gasoline, petroleum ether, and kerosene being illustrative. For the most part, such solvents remain in suspension in the motive air as it passes through the lluidic device 34. This solvent bearing air wets the passageways of the device 34 to prevent the vapors and mist droplets of the heavier oils from condensing or depositing on any of the functional wall surfaces of the device. The contaminant vapors `and mist droplets thus pass through the fluidic device and have no effect on its operation, even over long periods of time.
It has been found that very small amounts of solvent are required for the purpose of the present invention. For example, a kerosene solvent added in the range of 1% to 1/1000 of 1% on a weight basis to air has been found successful in preventing contamination of fluidic devices using factory air supply as the motive fluid source.
Where it is known that other non-lterable (in a practical sense) contaminants are in the supply air for a iluidic device, then an appropriate solvent may be selected in accordance with the principles discussed in connection with a heavy oil contaminant. As a further example, salt spray might become ingested in the supply air source. In this case distilled water could be selected as the solvent. Similarly, a liquid device employing hard water as its motive uid could employ dilute acids as the solvent to prevent calcium deposits. It will further be recognized that temperature can have an etect on what would constitute a proper solvent. In colder temperatures gasoline would be a more effective oil solvent, whereas at higher temperatures kerosene would be preferred.
It will thus be apparent that variations from the preferred embodiment deescribed will occur to those skilled 4 in the art and that the scope of the invention is thus to be derived from the following claims.
Having thus described the invention, what is claimed as novel and desired to be secured by Letters Patent of the United States is:
1. A lluidic system comprising,
a iluidic device, having a plurality of relatively small passageways,
conduit means connected to a source of pressurized fluid and supplying motive fluid to said device, said pressurized fluid having a known contaminant therein, which has a propensity for collecting on the walls of the relatively small passageways,
means for removing the contaminant from the walls of said relatively small passageways of said lluidic device comprising, a solvent for said known contaminant, and
means for introducing a relatively small amount of said solvent into said conduit means whereby said contaminant will be maintained in suspension in said motive fluid and pass through the iluidic device in operation thereof.
2. A fluidic system as in claim 1 wherein,
the conduit means are connected to a source of pressurized gas and the introducing means take the form of atomizing means which introduce solvent as a function of the rate of gas flow through the conduit means.
3. A fluidic system as in claim 1 wherein,
. said pressurized iluid comprises air contaminated with heavy oil vapors, and
said solvent comprises a petroleum product having a relatively high vapor pressure.
4. A fluidic system as in claim 3 wherein,
the introducing means take the form of atomizing means.
5. A fluidic system as in claim |4 wherein,
the atomizing means are adjustable to add between 1/1000 of 1% and 1% of solvent to air on a weight basis.
References Cited UNITED STATES PATENTS 1,748,488 2/1930 McCabe 137-101.11 2,714,963 8/1955 Lester et al 137-101.11 3,022,743 2/1962 Engholdt 137-815 XR 3,122,165 2/1964 Horton 137-815 2,220,428 11/ 1965 Wilkerson 137-815 3,243,014 3/1966 Bjorklund 137-101.11 XR 3,267,964 8/ 1966 Steinmetz 137-93 XR SAMUEL SCOTT, Primary Examiner.