US3490475A - Load switched oscillator - Google Patents

Description

Jan. 20, 1970 P. c, M LEOD, JR 3,490,475

LOAD SWITCHED OSCILLATOR Filed June 9, 1967 INVENTOR PAUL c. McLEOD, JR.

ATTORNEYQ United States Patent York Y Filed June 9, 1967, Ser. No. 645,034 Int. Cl. F15c 1/08 US. Cl. 13781.5 Claims ABSTRACT OF THE DISCLOSURE A load switched fluid oscillator including an integral output resistor and capacitor for each leg to control the frequency of operation.

BACKGROUND OF THE INVENTION Field of the invention The present invention has general application to the fluidic field wherein a free-running oscillator may be used to measure flow, pressure or temperature of a fluid. In addition, the invention has application to the fields of gas chromatography and temperature sensing wherein the frequency of the oscillator changes uniformly with a variation in the concentration of a heavier gas within a lighter gas stream, or a variation in temperature of gas stream whose composition remains constant.

DESCRIPTION OF PRIOR ART Pure fluid devices have recently come into vogue and have great application to sophisticated control systems and to computers generally, since the pure fluid devices are characterized by a total absence of moving parts. Free-running fluid oscillators have been devised which involve the alternate discharge of a power stream through adjacent outlet ports spaced downstream from the inlet nozzle. In these devices, the oscillation frequency is determined, in most part, by the configuration of the oscillator chamber. The known types of free-running fluid oscillators rely upon the wall attachment characteristic of the power stream discharging in jet form from the inlet nozzle into the oscillator chamber for effecting mo mentary discharge through one of the two chamber fluid outlets. To achieve switching, the known free-running fluid oscillators are normally equipped with feedback passages which drain off a portion of the main power stream on the downstream side of the chamber, and direct the same at right angles to the axis of the power stream at the point where it enters the chamber, adjacent the inlet nozzle. Switching of the power stream from wall attachment on one side of the chamber to the opposite side causes discharge of the power stream alternately through the outlet ports.

These conventional free-running fluid oscillators have some disadvantages in addition to the fact that the presence of the feedback channels tend to complicate the mechanism and to materially increase the cost of manufacture. With low flow rates, the velocity of the power stream jet is insufiicient to ensure stable oscillator operation; that is, the power stream jet may not only fail to lock onto one of the other chamber side walls, but if lock-on occurs, the jet may not remain attached prior to switching as a result of normal feedback control.

SUMMARY OF INVENTION The present invention is directed to a simplified load switched fluid amplifier including a fluid oscillator chamber, an inlet nozzle for directing a continuous power stream into one end of the chamber and splitter means at the downstream end of the chamber forming a pair of outlet passages, inclined in opposite directions away from 3,490,475 Patented Jan. 20, 1970 A BRIEF DESCRIPTION OF THE DRAWING The single figure is a plan view, partially in section, of a preferred embodiment of the load switched oscillator of the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT The simplified load switched oscillator of the present invention is shown in the drawing. The construction of the fluid oscillator 10 is conventional. Fluidic devices, in general, consist of a laminar structure involving outer sheets 12 and 14 acting to sandwich at configured inter mediate sheet 16. The laminates 12, 14 and 16 may be formed of metallic, plastic, glass, ceramics and glass ceramics or like material, with the outer sheets 12 and 14 being securely attached, in sealing relation, to the intermediate sheet 16 by suitable means, such as adhesive. The sheets 12, 14 and 16 may be formed with suitable passages or apertures. 'If passages and internal apertures are formed in the outer sheets 12 and 16, they must be formed to a depth less than sheet thickness since these sheets are also covers for the device. The sheets 12, 14 and 16 are preferably bonded together by fusion. In the embodiment shown, the intermediate sheet 16 contains channels, passages, openings and the like. The relieved or cut-out portion of the intermediate sheet may be achieved by stamping, etching or any other conventional process.

In the structure shown, the intermediate sheet 16 has been cut away to form a fluid inlet line 18 terminating in inlet nozzle 20 at the upstream end of an oscillator chamber 22. A tapered splitter member 24 acts in conjunction with diverging oscillator chamber walls 26 and 28 to form a pair of diverging outlet passages 30 and 32, respectively, at the downstream end of the chamber. It is noted that the cross-sectional area of either outlet passage 30 or 32 is much greater than the cross-sectional area of the inlet nozzle 20. The structure, as so far recited, is conventional to fluid oscillators employing a single inlet and a pair of outlets.

The present invention is directed to the provision of an integral, series connected fluid capacitor and resistor acting to form an impedance load for each of the outlets 30 and 32. In this respect, capacitor chamber 34 is formed within outlet passage 30, downstream of splitter 24 and between the oscillator chamber 22 and the series resistor or fluid restricter 36. The cross-sectional area of the outlet resistor 36 is less than both the remaining section-of outlet passage 30 and the inlet nozzle 20. In the opposite outlet passage 32, there is provided, in series, an identical fluid capacitor chamber 38 and a series outlet resistor or restricter 40. Outlet resistor 40, in like manner to resistor 36, has a cross-sectional area which is less than that of the remaining section of outlet passage 32 and the inlet nozzle 20. Either one or both of the outlet passages 30 or 32, downstream of their respective fluid resistors 36 and 40, may be coupled to end load devices, such as a frequency indicator (not shown).

In operation, assuming there is a source of fluid pressure (not shown) coupled to fluid inlet 18, a fluid power stream, indicated at 42, enters the oscillator chamber 22 from inlet port and passes downstream toward the splitter 24. Oscillator chamber asymmetry will cause the power stream to enter one or the other of the fluid outlet passages or 32 by attaching itself to either side wall 26 or 28 (assuming that the device is of the wall attachment type). Assuming that initially the power stream enters outlet passage 32, it will tend to move through the capacitor chamber 38, generally adjacent to the side wall 44 of the outlet passage, and enter the necked-down side walls 48 of the outlet passage before flowing through the series resistor 40. As mentioned previously, the cross-sectional area of the series resistor is less thanthe crosssectional area of the inlet nozzle 20, and therefore, while a portion of the pressurized fluid will pass through this resistor or restricter, the impedance will cause a pressure buildup within this outlet passage and the fluid will begin to fill capacitor chamber 38. Upon filling the capacitor chamber 38 and outlet passageway 32 between capacitor chamber 38 and splitter 24, power stream 42 will switch from the right-hand fluid outlet 32, as shown, to the lefthand fluid outlet passage 30. In outlet passage 30, a similar process will take place due to the fact that the impedance offered by the fluid resistor 36 is greater than that of the inlet nozzle 20 to the oscillator chamber.

Upon detachment of the power stream 42 from wall 28 of the oscillator chamber, the power stream 42 will leave outlet passage 32 and enter outlet passage 30, attaching itself to the outer wall 26 (if the device is a wall attachment oscillator). Again, the power stream 42 will move through capacitor chamber 34, principally in an area adjacent inclined side wall 46 until it meets the converging side walls 50 which merge into series outlet resistor section 36. The cross-sectional area and therefore the impedance of the resistor section 36 is greater than the cross-sectional area of nozzle inlet 20. Again, fluid pressure will build up within the outlet passage 30. Fluid will fill capacitor section 34 and the pressure will be built up sufficiently to cause switching of the power stream 42 back into outlet passage 32.

The function of the capacitor chambers 34 and 38 is simply to provide a time delay in the flip-flop operation of the oscillator and they act in cooperation with the resistors 36 and 40 to produce a combined impedance which will determine the frequency of operation. Assuming that the size of the capacitor chambers 34 and 38 is equal and that the cross-sectional areas and therefore the impedance of the fluid resistors 36 and 40 are equal, the period of fluid oscillation for the oscillator will have equal halves. However, if the capacitance of chamber 34 is different from the capacitance of chamber 38, the operation of the device will be asymmetric. Of course, the same result could be achieved by varying the impedance characteristics of the resistor section 36 with respect to resistor section 40. It is important to note that it is the impedance value of the outlet resistors and not size alone which governs oscillator frequency. In the embodiment shown, the cross-coupling impedances of the series capacitorresistor for each leg are similar to the cross-coupling impedances of a conventional electronic free-running multivibrator.

Obviously, if the individual outlet passages 30-32 are coupled to the output devices, which in themselves provide added loads, this will have some effect on the frequency of oscillation, and whether or not the oscillator will act as an asymmetrical device. Normally, insofar as the oscillation characteristics of the load switch oscillator are concerned, the impedance of resistor sections 36 and 40 is considerably greater than the anticipated impedance of the end load devices which are coupled to the oscillator. Of course, in addition to the impedance offered by the series connected capacitor chambers and fluid resistor sections, the frequency of oscillation, to some degree, is controlled by oscillator chamber configuration, flow velocity andthe characteristics of the fluid forming the power stream, as well as other parameters. The power stream 42 maybe compressible, such as air, nitrogen or other gases, or incompressible, such as water or other liquids. Both the compressible and incompressible fluids may contain solid material. The present invention is not limited to any particular fluid.

The correct operation of the present load switched oscillator depends upon the provision of sufficient back pressure within the outlet passages 30 and 32 in the area adjacent splitter 24 to cause the power stream 42 to disattach itself from an associated oscillator chamber wall 26-28 (assuming that the device is the wall attachment device) and switch to the other outlet, which at this time is unloaded. The back pressure required for switching of the power stream is quite small and in order to seriously affect oscillator operation, it may be desirable to include bleed passages for each of the fluid outlet passages 30 and 32, at a point downstream from splitter 24. In this respect, in the instant embodiment, a right-hand bleed or vent passage 52 is shown in dotted lines as coupled to the outlet passages 32 at one end, and open to the atmosphere at the other end. In like manner, bleed or vent passage 54 is shown by the dotted lines, on the left-hand side of the device, as fluid coupled, at one end, to outlet passage 30, downstream of splitter 24 with the other end open to the atmosphere.

The presence of bleed or vent passages 52 and 54 for the respective outlet passages has some effect on both the frequency and sensitivity of the frequency of operation and the sensitivity of the oscillator 10, as well as possibly the acceptable flow rate range. By regulating the amount of fluid which is actually vented from the outletpassages 30 and 32, the oscillation frequency of the device may be readily changed.

While the present invention has been particularly shown and described with reference to a preferred embodiment, it will be understood by those skilled in the art that various changes in the form and details may be made therein without departing from the spirit and scope of the invention.

What is claimed is:

1. A simplified fluid oscillator comprising: an oscillator chamber, means forming a continuous power stream inlet to said chamber, first and second outlet means carried by said chamber and positioned downstream from said inlet means for alternately receiving said power stream, said oscillator chamber being closed except for said inlet means and said first and second outlet means, and integral fluid resistor and capacitor means connected in series within each fluid outlet means with the impedance of each fluid resistor means being greater than the impedance of said power stream inlet means for controlling the operation of said oscillator and the frequency thereof.

2. The oscillator as claimed in claim 1 wherein said integral fluid capacitor and resistor means are series connected.

3. The fluid oscillator as claimed in claim 1 wherein; in downstream order, said capacitor and resistor means are series coupled.

4. The fluid oscillator as claimed in claim 1 wherein said power stream inlet means includes an inlet nozzle and the impedance of each resistor means is greater than the impedance of said inlet nozzle.

5. The fluid oscillator as claimed in claim 1 wherein the impedance of said integral fluid resistor and capacitor means within one of said fluid outlet means is different from the impedance of said fluid resistor and capacitor means within said other fluid outlet means to effect asymmetrical operation.

6. The fluid oscillator as claimed in claim 1 wherein; said continuous power stream inlet means including an inlet nozzle at the upstream end of said oscillator chamber and a splitter positioned at the downstream end thereof, and said oscillator further includes an oscillator chamber of the wall attachment type having a pair of diverging side walls, said splitter forming, with said diverging walls, said first and outlet means in the form of diverging outlet passages.

7. The oscillator as claimed in claim 6 wherein said capacitor means comprises an enlarged capacitor chamber with the axis of said chamber being oflset from the axis of its respective upstream outlet passage and said downstream resistor means.

'8. The oscillator as claimed in claim 7 wherein said resistor means comprises a passage of reduced crosssection coupled to the downstream end of said capacitor chamber.

9. The fluid oscillator as claimed in claim 7 further including converging surfaces between the downstream end of said capacitor chamber and the upstream end of said resistor passage to prevent abrupt fluid passage transition therebetween.

10. The fluid oscillator as claimed in claim 9 wherein the cross-sectional area of said resistor passage is smaller than the cross-sectional area of either said inlet nozzle or that portion of the outlet passage between the ca- PfiCliOl chamber and said splitter.

References Cited UNITED STATES PATENTS 3,001,539 9/1961 Hurvitz 137-815 3,158,166 11/1964 Warren 137-815 3,159,168 12/1964 Reader 137-815 3,185,166 5/1965 Horton et al. 137-815 3,228,410 1/1966 Warren et a1. 137-815 3,398,758 8/1968 Unfried 137815 3,402,727 9/1968 Boothe 137-815 SAMUEL SCOTT, Primary Examiner

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