ENHANCED OUTPUT OPTO-FLUIDIC DEVICE

Abstract: The opto-fluidic device (10) includes three plates which together bound a number of passages including an interaction passage (30) having opposite ends (27,29), an inlet channel (15) which opens into one of such ends (27), and two outlet channels (50a,50b) which open into the other end (29) of the interaction passage (30) at symmetrically arranged outlet regions (51a,51b). Fluid is caused to flow through the inlet channel (15) into the interaction passage (30) to form a jet stream that flows toward the outlet regions (51a,51b). After the flow of the fluid through the inlet channel (15) has been intentionally disturbed by heating a transversely off-­ set light-absorbing zone of the inlet channel (15) by a light beam with attendant heating of the fluid flowing past such zone and initial transverse deflection of the jet stream, the extent of such deflection is enhanced by supply­ ing additional amounts of the fluid to symmetrically situated lateral locations of the interaction passage (30) so that the jet stream permits more of the fluid to enter the inter­ action passage (30) from that of the locations from which it deflected away than from the other locations with attendant additional deflection of the jet stream.

Description: Technical Field The present invention relates to actuating devices in general, and more particularly to devices which convert optical signals into fluid pressure or flow signals. Background Art There are already known various constructions of devices capable of transforming various external parameters by altering the flow of a fluid through the device. One device of this type according to the precharacterizing portion of independent claim 1 is disclosed in US-A-4,610,274 where the external parameter is the intensity of laser light that is directed into one of two inlet channels arranged upstream of an input nozzle to heat a light-absorbing zone which, in turn, warms up the fluid flowing past such zone and thus influences the flow of the fluid downstream of this zone into, through and beyond the nozzle and then as a jet stream emerging from the nozzle into a vented interaction passage substantially in the longitudinal direction of the interaction passage to one or both of two outlets. In this device, the heat imparted to the fluid at the light-absorbing zone reduces the thickness of the boundary layer at the adjacent wall bounding the respective inlet channel and this ultimately results in a deflection of the jet stream transversely of the interaction passage so that the fluid enters one of the outlet channels in an amount and/or at a pressure exceeding that or those applicable to the other outlet channel. Then, the magnitude of the optical signal determines the difference between the flow or pressure conditions in the two outlet channels. While this opto-fluidic device operates to satisfaction in many applications, experience has shown that at least in some instances the difference between the monitored conditions in the two outlet channels is too small to give adequate power to actuate hydromechanical devices. DISCLOSURE OF THE INVENTION The object of the present invention is to develop the opto-fluidic device of the type here under consideration in such a manner as to enhance the differential between its output values for the same value of the optical input signal. To achieve this, according to the invention, there is provided an opto-fluidic device, comprising means for bounding at least an interaction passage which extends along a central plane including a central axis and has two axially spaced ends, an inlet channel including a nozzle orifice which opens along said central axis into one of said ends of said interaction passage, and two outlet channels which open into the other of said ends of said interaction passage at respective outlet regions that are situated symmetrically with respect to said central axis, means for causing a fluid to flow in a streamlined manner through said inlet channel into said interaction passage to form after its emergence from said nozzle orifice a jet stream that flows axially of said interaction passage toward said outlet regions with the flowing fluid being equally distributed between said outlet channels in the absence of disturbance of the flow through said nozzle orifice and said interaction passage by external influences; and means for disturbing the flow of the fluid through said inlet channel, including light-absorbing means including at least a zone situated in said inlet channel at a transverse offset from said central axis, and means for directing a light beam through said bounding means against said zone to convert the energy of said light beam into thermal energy that locally heats the fluid flowing past said zone with attendant transverse deflection of said jet stream in one transverse direction along said central plane; characterized by means for enhancing the extent of said deflection, including means for supplying fluid at equal pressure to locations of said interaction passage that are arranged downstream of said nozzle orifice symmetrically with respect to said central axis for the jet stream to permit more of the fluid to enter said interaction passage from that of said locations from which the jet stream is deflected away than from the other of said locations with attendant additional deflection of the jet stream in said one transverse direction. Preferably, the zone is situated in the nozzle orifice and fully within the inlet channel spaced from an adjacent sidewall region of said inlet channel. The opto-fluidic device of the above type has an improved power conversion efficiency as compared to prior art devices of this type. Further, it is relatively simple in construction, inexpensive to manufacture, easy to use, and yet reliable in operation. BRIEF DESCRIPTION OF THE DRAWINGS The present invention will be described in more detail below with reference to the accompanying drawing in which: Figure 1 is an exploded perspective view of an opto-fluidic device of the present invention; Figure 2 is an enlarged top plan view taken in the direction of an arrow a of central and bottom plates of the device of Figure 1 illustrating not only the relative locations of various passages in the central plate but also the flow of fluid therethrough during the use of the device; and Figure 3 is a view similar to that of Figure 2 but at a still enlarged scale and showing only a fragment of the central plate and the flow of the fluid through the various passages thereof during the use of the device of Figure 1. Best Mode for Carrying Out the Invention Referring now to the drawing in detail, and first to Figure 1 thereof, it may be seen that the reference numeral 10 has been used therein to identify an opto-fluidic device of the present invention in its entirety. The device 10 comprises a laminar arrangement of plates 11, 12, and 13. the plate 11 is formed from, or coated on an interior surface thereof with, an optically absorbent material such as a graphite-epoxy composite 20 which incorporates graphite reinforcement fibers that are disposed generally in parallel orientation to the fluid flow through the device 10. As illustrated especially in Figure 2 of the drawing, the plate 12 has a network of flow passages or channels provided therein either by machining, etching stamping or equivalent techniques. Such passages and channels include a single input channel 15 which leads to a supply nozzle orifice 27 to feed a fluid, while the device 10 is in operation, to an open area (interaction passage) 30 situated between four generally symmetrically arranged vent channels 35a, 35b, 36a and 36b. The nozzle orifice 27 may be slightly divergent at least at its downstream end which opens into an upstream end portion 28 of the interaction passage 30 that is somewhat wider than the nozzle orifice 27 but narrower than the downstream remainder of the interaction passage 30. Furthermore, respective feedback nozzles 26a and 26b of two feedback channels 25a and 25b open substantially symmetrically into the upstream end portion 28 of the interaction passage 30 from opposite sides thereof. As also illustrated particularly in Figure 2, the feedback channels 25a and 25b inclusive of the feedback nozzles 26a and 26b are generally convergent, being separated from the inlet channel 15 by portions of the plate 12 that constitute respective flow separators 40. Each separator 40 comprises a pair of convergent sidewall regions 41a, 41b (which together laterally delimit the nozzle orifice 27) and two additional sidewall regions 42 (each of which partially laterally bounds the feedback nozzle 26a or 26b of one of the feedback channels 25a or 25b). The associated ones of the sidewall regions 41a, 41b) and 42 are joined with one another at respective relatively blunt noses 44. As a comparison with Figure 1 of the drawing will reveal, all of such areas of the separators 40 are in upstanding relationship to a bottom wall 46 of the nozzle orifice 27 which is formed by the optically absorbent composite. Respective upstream regions 51a and 51b of two outlet channels 50a and 50b, which are also provided in the plate 12 by one of the aforementioned manufacturing processes, communicate with a downstream end portion 29 of the interaction passage 30. The plate 13 is drilled and provided with a plurality of taps (ports) for making fluid connections to the various channels provided in the plate 12. Thus, an inlet port 52 connects the inlet channel 15 with a suitable source of pressurized fluid (not shown), respective feedback ports 55a and 55b may connect the feedback channels 25a and 25b with a pressurized fluid source (which may be the same as that mentioned above) or the port 55a may be connected only to the port 55b, while respective venting ports 60a, 61a, 60b and 61b communicate with the vent passages 35a, 36a, 35b and 36b. Respective outlet ports 65a and 65b communicate with the outlet channels 50a and 50b. The fluid handling portion of the opto-fluidic device 10 described hereinabove functions as a fluidic signal converter. Thus, it will be seen that fluid introduced to the inlet channel 15 through the inlet port 52 flows through the nozzle orifice 27, through the interaction passage 30 between the vent passages 35a and 36a, on the one hand, and 35b and 36b, on the other hand, and is split between the outlet channels 50a and 50b. Maintenance of a constant pressure within the interaction region 30 is effected by selectively venting the interaction region 30 at the channels 35a, 35b, 36a and 36b through the venting ports 60a, 60b, 61a and 61b, respectively. Fluidic signal generation is achieved by controlling the flow conditions through the nozzle orifice 27 in such a manner as to turn some of the flow through the device toward one or the other of the outlet channels 50a and 50b to achieve a desired difference in pressure therebetween. Similarly, the device 10 may function as a switch wherein the entire flow is diverted from one of the outlet channels 50a and 50b to the other. While in most of the prior art fluidic amplifiers or switches such input signals are fluidically applied through control ports, in the device 10 of the present invention, like in that of the aforementioned US-A-4,610,274, the input signal comprises an optical signal applied directly to an eccentric light-absorbent zone of the nozzle orifice bottom wall 46 and/or the adjacent one of the sidewall regions 41a or 41b. The optical input signal to the opto-fluidic device 10 comprises a focused optical signal applied to a discrete location on the optically absorbent composite. The means for applying this signal (not shown) typically comprises a source of light such as a laser, a light emitting diode or any other suitable light source, and an optical conducting system, such as one including an optical fiber and a collecting lens system. As indicated in Figure 2 of the drawing, optical energy from the laser or other light source is focused by the lens system onto a point 85 on the optically absorbent composite. This focused optical energy heats an area of the inlet nozzle orifice wall structure adjacent the point 85 including the adjacent area of the sidewall region 41a. The orientation of the graphite fibers, which is generally parallel to the direction of flow, minimizes the conduction of heat through the composite away from the sidewall region 41a. The effect of the sidewall region heat is lowering of the viscosity of the fluid flowing past the heated area of the sidewall region 41a. Lowering the fluid viscosity in this manner reduces the thickness of the flow boundary layer at the heated wall area, thereby enhancing the degree to which the flow remains attached to the sidewall region 41. As illustrated in Figure 3, increasing the span of the left-hand nozzle orifice sidewall region 41a to which the flow is attached effects deflection of the jet stream that emerges from the nozzle orifice 27 into the upstream end portion 28 of the interaction passage 30 and then into the remainder of the interaction passage 30 to the left, thereby establishing an initial imbalance in flow conditions between the outlet channels 50a and 50 b (shown only in Figures 1 and 2), and defining a fluidic pressure difference output signal therebetween. Similarly, increasing the span of the right-hand sidewall 41b bounding the nozzle orifice 27 to which the flow remains attached by moving the point 85 transversely of the nozzle orifice 27 toward the sidewall 41b effects deflection of the flow within the interaction passage 30 to the right to establish a fluid pressure difference output signal of opposite magnitude between the outlet channels 50a and 50b and and thus between the outlet ports 65a and 65b. These initial flow conditions, which are indicated in Figure 3 of the drawing by dotted lines representative of the approximate boundaries of the thus initial optically deflected jet stream, are basically the same as those encountered in the opto-fluidic device of the aforementioned US-A-4,610,274. Now, as the initial optically deflected jet stream flows through the upstream end portion 28 of the interaction passage 30, it passes by the feedback nozzles 26a and 26b that are arranged symmetrically at opposite sides of the jet stream. It may be ascertained from Figure 3 that the initial optically deflected jet stream flows closer to the feedback nozzle 26a than to the feedback nozzle 26b. This, in turn, means that the jet stream constitutes less of a hindrance to the entry of additional fluid from the feedback nozzle 26b than from the feedback nozzle 26a. Consequently, when the pressure of the additional fluid supplied into each of the feedback channels 25a and 25b is the same, as contemplated, a quantity Q f1 of the additional fluid (which may be close to or at zero) enters the upstream end portion 28 of the interaction passage 30 from the feedback nozzle 26a while, at the same time, a much larger quantity Q f2 of the additional fluid enters the upstream end portion 28 from the feedback nozzle 26b. While most if not all of this additional fluid will be vented through the vent channels 35a and 35b (and/or the vent channels 36a and 36b omitted from Figure 3), this additional fluid entry imbalance would have already had its desired impact on the path of flow of the jet stream through the remainder of the interaction passage 30 before then by imparting the imbalance in the kinetic energy of the additional fluid entering the upstream end portion 28 from the feedback nozzles 26a and 26b to the jet stream, thus diverting the jet stream even more to the left in the situation depicted in Figure 3, as indicated by dashed lines representative of the approximate boundaries of the thus fluidically additionally diverted jet stream. This, of course, means that the initial imbalance between the amounts of fluid reaching the outlet ports 65a and 65b, and thus, in the final analysis, the magnitude of the difference output signal, will be further enhanced or augmented, which improves the response or sensitivity of the device 10 to the optical signals directed against the point 85. It will be appreciated that, if the point 85 is located at the sidewall region 41b, the flow conditions will be akin to those described above but with the jets stream being deflected first optically and then additionally fluidically to the right rather than to the left, with attendant change in the sign of the difference output signal. It will thus be apparent that the opto-fluidic device of the present invention provides an uncomplicated yet effective and reliable control device for converting an optical input signal to an enhanced fluidic output signal. By the application of focused optical energy to a discrete location 85 of an optically absorbent portion situated at one of two divergent inlet nozzle sidewall regions 41a and 41b, the flow conditions in the device 10 and therefore the imbalances between the output ports 65a and 65b can be controlled in an enhanced fashion. With appropriate sizing of the various passages and optical input signal strength, a predetermined output (a predetermined pressure difference between the output ports 65 a and 65b) is reliably attained with accuracy and repeatability. Such accuracy and repeatability are further enhanced by the inherent insensitivity of the device to optical signal position along the sidewall region 41a or 41b. It has been observed that the device 10 of the present invention would be extremely sensitive to optical input signal position if the optical input signal were applied at the respective nose 44. That is, even a slight deviation in the optical signal position would result in a significant change in the output signal magnitude. However, the application of the optical input signal upstream from the respective nose 40 results in an output signal relatively immune to minor discrepancies in input signal location along the respective sidewall region 41a or 41b, whereby the manufacturability of the device is improved. Those skilled in the art will readily appreciate the innumerable applications for the present invention. For example, in "fly by light" aircraft control systems, optical input signals can be applied to opto-fluidic devices such as that of the present invention and the output pressure difference of the device can be applied to such apparatus as hydraulic actuators to set the position of aircraft control surfaces and the like. It will also be noted that the opto-fluidic device of the present invention is readily adaptable for use with similar fluidic devices such as known fluidic amplifiers for further amplification of the output signal across the outlet ports 65a and 65b. In such an arrangement, the output signal across the outlet ports 65a and 65b would be fed as an input signal to a second, state-of-the art fluidic amplifier. With such an arrangement, fluidic input signals (output signals from the outlet ports 65a and 65b) applied to a pressurized supply flow would result in amplification of such fluidic input signals at the output of the second amplifier. Further amplification (and if necessary, further control by way of fluidic control signals input to the amplifier control passages) would therefore be readily achieved by further cascading of the output signals with further stages of fluidic amplification. While a particular embodiment of the device 10 of the present invention has been shown and described, it will be appreciated that the disclosure herein will suggest various alternate embodiments to those skilled in the art. Thus, while in the description herein, the optical input signal is applied to one side of the inlet nozzle orifice 27, it will be readily appreciated that an opposite output pressure signal may be achieved by directing the optical input signal to the other side of the inlet nozzle orifice 27. Furthermore, while the optically absorbent material has been described as a graphite epoxy composite, various other compositions such as carbon impregnated ceramic will also suggest themselves to those skilled in the art. Also, the optical input signal may be applied either to the back of the plate 11 or, if the plate 13 is transparent, to the front of the plate 11. Similarly, various other arrangements of fluidic passages adaptable to fluidic control by boundary layer reduction resulting from the application of an optical input signal to a single optically absorbent inlet nozzle orifice 27, such as those using two inlet channels 15 instead of one, may also readily suggest themselves to those skilled in the art.

Claims: Opto-fluidic device (10), comprising means (11,12,13) for bounding at least an interaction passage (30) which extends along a central plane including a central axis and has two axially spaced ends (28,29), an inlet channel (15) including a nozzle orifice (27) which opens along said central axis into one (28) of said ends of said interaction passage (30), and two outlet channels (50a,50b) which open into the other (29) of said ends of said interaction passage (30) at respective outlet regions (51a,51b) that are situated symmetrically with respect to said central axis, means (41a,41b) for causing a fluid to flow in a streamlined manner through said inlet channel (15) into said interaction passage (30) to form after its emergence from said nozzle orifice (27) a jet stream that flows axially of said interaction passage (30) toward said outlet regions (51a,51b) with the flowing fluid being equally distributed between said outlet channels (50a,50b) in the absence of disturbance of the flow through said nozzle orifice (27) and said interaction passage (30) by external influences; and means for disturbing the flow of the fluid through said inlet channel (15), including light-absorbing means (11) including at least a zone (85) situated in said inlet channel (15) at a transverse offset from said central axis, and means for directing a light beam through said bounding means (11,12,13) against said zone (85) to convert the energy of said light beam into thermal energy that locally heats the fluid flowing past said zone with attendant transverse deflection of said jet stream in one transverse direction along said central plane; characterized by means (25a,25b) for enhancing the extent of said deflection, including means (26a,26b) for supplying fluid at equal pressure to locations of said interaction passage (30) that are arranged downstream of said nozzle orifice (27) symmetrically with respect to said central axis for the jet stream to permit more of the fluid to enter said interaction passage (30) from that of said locations from which the jet stream is deflected away than from the other of said locations with attendant additional deflection of the jet stream in said one transverse direction. Opto-fluidic device as defined in claim 1, characterized in that said bounding means (11,12,13) further bounds at least two venting channels (35a,35b) which open into said interaction passage (30) symmetrically with respect of said central axis downstream from said enhancing means (25a,25b). Opto-fluidic device as defined in claim 1, characterized in that said zone (85) is situated in said nozzle orifice (27). Opto-fluidic device as defined in claim 1, characterized in that said inlet channel (15) extends along an extension of said central axis and terminates in said nozzle orifice (27) at its downstream end. Opto-fluidic device as defined in claim 1, characterized in that said zone (85) is situated fully in said inlet channel (15) and spaced from an adjacent sidewall region (41a) of said inlet channel (15).

Inventors: HOCKADAY, BRUCE D.
Applicants: UNITED TECHNOLOGIES CORPORATION
Application year: 1989
Main classification: F15C1
IPC codes: F15C1