Abstract:
An oscillating fluid flow motor and a fluid flow power system that converts the energy in the flowing fluid to mechanical energy through a vane that automatically sweeps back and forth across the flow. In one embodiment of the oscillating fluid flow motor, the motor includes (1) a support structure, (2) an elongated swing arm pivotably and rotatably mounted to the support structure, (3) a vane having a concave face, (4) an elastic link operatively coupled in tension between the swing arm and a support, and (5) a direction control mechanism operatively coupled to the swing arm. The vane is connected to the swing arm so that, upon rotation of the swing arm about its longitudinal axis, the orientation of the concave face of the vane changes relative to the flow of a fluid confronting the face. The direction control mechanism is operative to selectively re-orient the face of the vane at each of two points that define the ends of the bidirectional stroke of the swing arm.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application is related to application Ser. No. 08/144,734 filed Oct. 28, 1993, abandoned, and U.S. Pat. No. 5,899,664 issued May 4, 1999. 
    
    
     FIELD OF THE INVENTION 
     The invention relates generally to a mechanism for converting energy of one form to another more useable form. More particularly, the invention relates to an oscillating fluid flow motor that converts energy contained in a channel of flowing fluid to mechanical energy. 
     BACKGROUND OF THE INVENTION 
     Numerous mechanisms have been designed and built for converting the energy of moving masses, such as air or water, to mechanical energy. Commonly known mechanisms for converting the energy of moving water to mechanical energy are water wheels, paddles, and turbines. Generally speaking, mechanisms for converting the energy of a moving fluid to mechanical power have tended throughout their evolution to become both more complicated and more costly to manufacture. Modern axial flow turbine systems typically require the construction of dams or diversions and penstocks to support even low-head power production. The present invention was developed in an effort to provide a low cost in-stream system for utilizing the energy in a fluid stream, particularly a small slow moving stream, as a pumping station or a small scale electrical generator such as might be used effectively in remote or undeveloped areas around the world. 
     In the early 1900s, John Roeh patented an Automatic Current Motor, U.S. Pat. Nos. 705,967 and 804,676, that extracted energy from a stream flow using a vane attached to a tiller. As the water flows past the vane, the vane automatically sweeps back and forth across the stream under the bidirectional control of a cross cabling system. A connecting rod transmits the energy in the oscillating tiller to some type of receiving machine to produce useful work. Mr. Roeh&#39;s system, while presenting a potentially workable small scale in-stream generating or pumping station, is disadvantageous because it requires a fairly complex mechanical linkage to achieve the bidirectional control necessary to make the vane sweep automatically back and forth across the stream. 
     The present invention improves upon the oscillating fluid flow motor disclosed in U.S. Pat. No. 5,889,664. The improvements result from further testing and study of the motor&#39;s basic design. 
     SUMMARY 
     The present invention is directed to an oscillating fluid flow motor and a fluid flow power system that converts the energy in the flowing fluid to mechanical energy through a vane that automatically sweeps back and forth across the flow. In one embodiment of the oscillating fluid flow motor, the motor includes (1) a support structure, (2) an elongated swing arm pivotably and rotatably mounted to the support structure, (3) a vane having a concave face, (4) an elastic link operatively coupled in tension between the swing arm and a support, and (5) a direction control mechanism operatively coupled to the swing arm. The vane is connected to the swing arm so that, upon rotation of the swing arm about its longitudinal axis, the orientation of the concave face of the vane changes relative to the flow of a fluid confronting the face. The direction control mechanism is operative to selectively re-orient the face of the vane at each of two points that define the ends of the bi-directional stroke of the swing arm. 
     In one embodiment of the invented fluid flow power system, the system includes (1) a channel, (2) fluid flowing through the channel, (3) an elongated swing arm pivotably mounted in or over the channel, (4) a vane connected to the swing arm, the vane having a concave face confronting the flowing fluid, (5) a direction control mechanism coupled to the vane, and (5) a receiving machine operatively coupled to the swing arm. The direction control mechanism is operative to selectively re-orient the vane in the flowing fluid by rotating the swing arm about its longitudinal axis at each of two points which define the ends of the bi-directional stroke of the swing arm. 
     In another embodiment of the invention, a method for converting the energy of a flowing fluid to mechanical energy includes providing a vane having a concave face connected to a swing arm, directing the face of the vane into the flowing fluid, causing the vane to traverse the flowing fluid in a reciprocating motion by selectively rotating the swing arm about its longitudinal axis to re-orient the vane in the flowing fluid at each of two points which define the ends of a bidirectional stroke of the swing arm. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is an isometric view of an oscillating fluid flow motor incorporated into an in-stream fluid power system wherein the swing arm extends away from the vane in a direction generally upstream of the vane. 
     FIG. 2 is an isometric detail view of the flexible joint of FIG. 1 coupling the extension spring to the swing arm. 
     FIG. 3 is an elevation detail view of the flexible joint coupling the connecting rod to the swing arm. 
     FIG. 4 is an isometric detail view of a direction control mechanism utilizing roller stops. 
     FIG. 5 is an isometric detail view of a second embodiment of a direction control mechanism utilizing magnetic repulsion. 
     FIG. 6 is a partial isometric view of a vane and swing arm showing the change in direction at the end of one stroke of the swing arm. 
     FIG. 7 is a detail isometric view of a vane having a front face that is concave along its longitudinal and transverse axes, a convex rear face and a curved peripheral edge. 
     FIG. 8 is a cross section taken along the longitudinal axis of the vane of FIG.  7 . 
     FIG. 9 is a cross section taken along the transverse axis of the vane of FIG.  7 . 
     FIG. 10 is a detail isometric view of a vane having a front face that is concave only along its transverse axis and a rectilinear peripheral edge. 
    
    
     DETAILED DESCRIPTION 
     FIG. 1 depicts an in-line fluid flow power system, designated generally by reference numeral  10 , such as might be used in a small stream or irrigation canal as a pumping station or electric power generator. On a larger scale the in-line fluid flow power system could be used in a river or other larger flowing body of water. Referring to FIG. 1, power system  10  includes an oscillating fluid flow motor  12  and an on-shore receiving machine  14 . Receiving machine  14  represents generally any of the various machines operable through the reciprocating motion generated by motor  12 , such as a pump, electric generator, mill or compressor. 
     Motor  12  consists of three basic components-a vane  16 , a swing arm  18 , and a direction control mechanism  20 . Vane  16  is attached to one end of swing arm  18 . Swing arm  18  is fixed along its length at a point  9  at which the swing arm pivots. In the embodiment of the invention shown in FIGS. 1,  4 - 6 , swing arm  18  is mounted to a horizontal support member  22  through a pivot assembly  24 . Pivot assembly  24  allows swing arm  18  to rotate about its longitudinal axis and to pivot relative to support member  22 . Pivot assembly  24  includes pillow block  26 , or another suitable bearing device, and pivot pin  28  (shown in FIGS.  4 - 6 ). Swing arm  18  rotates about its longitudinal axis in pillow block  26  and pivots on pivot pin  28 . Horizontal member  22  has two ends, each of which are secured to uprights  30  by block assemblies  32 . In one embodiment, horizontal member  22  and uprights  30  combine to form a base or support structure  31  for motor  12 . Horizontal member  22  rotates about its longitudinal axis within block assemblies  32 , thereby allowing vertical adjustment of vane  16  relative to the surface of the flowing water. 
     It is desirable to bias vane  16  against the flow of fluid and limit the vertical motion of swing arm  18  help keep the lower portion of vane  16  at a predetermined level with respect to the surface of the water. This is accomplished, for example, by an elastic link  38  operatively coupled in tension between swing arm  18  and a support structure  50 . In the embodiment shown in the Figures, elastic link  38  is an extension spring  54 . Other articles and devices could be used for elastic link  38 . Torsion bars, leaf springs, elastic bands, or fluid systems, for example, could be used to provide an elastic link between swing arm  18  and support structure  50 . 
     Referring to FIGS. 1 and 2, spring  54  is coupled at one end to swing arm  18  through a flexible joint  51  and at the opposite end to support structure  50 . Spring  54  is coupled to swing arm  18  below the point  19  at which swing arm  18  pivots relative to base  31  and support  50  is positioned upstream of vane  16 . Other configurations may also be used. For example, if spring  54  is coupled to swing arm  18  above pivot point  19 , then support structure  50  would be positioned downstream of base  31  to bias vane  16  against the flow. As shown in FIG. 2, flexible joint  51  incorporates a universal joint  52  and a cross link ring  53 . A ball joint or any other suitable joint allowing a free range of motion, preferably allowing link  38  and swing arm  18  to pivot relative to one another about at least two axes, could also be used. 
     Preferably, the rate or load per unit of deflection of elastic link  38  is adjustable to maintain smooth pivotal motion of the swing arm  18  and to ensure that the lower edge of vane  16  is submerged and the upper edge is kept slightly above surface level while vane  16  traverses the flow. Alternatively, a rotational stop could be installed behind horizontal support member  22  or over swing arm  18  to limit the vertical motion of swing arm  18 . As an alternative to, or in combination with, these mechanical stop mechanisms, vane  16  could be weighted or buoyancy added according to the anticipated flow conditions, in conjunction with the overall hydrodynamic design of the vane, to maintain vane  16  at the desired level. Other suitable mechanisms could be used. For example, the design of vane  16  could incorporate a wing or other hydrodynamic feature that reacts to the flow to keep the vane at the desired level in the stream. 
     In operation, swing arm  18  is positioned above a flow of fluid, preferably, at an angle near 90° relative to the surface of the fluid flow such that front face  15  of vane  16  is positioned within and confronting flow  46 . Swing arm  18  is rotated along its longitudinal axis such that one edge of vane  16  is positioned upstream, while the second and opposite edge is positioned downstream. This orientation of vane  16  causes the leading edge to push against the flow and to act as a rudder, forcing vane  16  to traverse the flow. 
     Direction control mechanism  20  regulates the pivotal and rotational movement of swing arm  18 . As swing arm  18  reaches a first outer limit of travel, the direction control mechanism  20  causes the swing arm  18  to rotate in a first direction about its longitudinal axis inside pivot assembly  24 . As swing arm  18  rotates, the orientation of vane  16  in relationship to the flow reverses. Consequently, the edge of vane  16  which was previously the leading edge, is now the trailing edge, and the edge which acted originally as the trailing edge is now the leading edge, thus reversing the direction vane  16  traverses the flow. Vane  16  traverses back across the flow until swing arm reaches a second outer limit of travel, and direction control mechanism  20  causes the swing arm to rotate in a second opposite direction about its longitudinal axis inside pivot assembly  24  again reversing the direction of vane  16  across the flow. 
     In one particular embodiment as depicted in FIGS. 4 and 5, the direction control mechanism  20  includes a limit arm  36  attached to one end of swing arm  18  and two adjustable stops  34  attached to horizontal support member  22 , one on either side of pivot assembly  24 . In FIG. 4, stops  34  include rollers to reduce wear on stops  34  and limit arm  36 . As swing arm  18  reaches either the first or second outer limit of travel, defined by the location and position of the adjustable stops  34  relative to limit arm  36 , limit arm  36  acts on the corresponding stop  34  and rotates swing arm  18  about it longitudinal axis inside pivot assembly  24 . A relatively light contact between limit arm  36  and stop  34  helps improve the operation of direction control mechanism  20 . Flexible joint  51 , described above, functions to this end assisting direction control mechanism  20  to more smoothly rotate swing arm  18  at the end of each stroke. 
     Direction control mechanism  20 , as described above, causes swing arm  18  to rotate about its longitudinal axis as limit arm  36  makes contact with stop  34 . In an alternative embodiment shown in FIG. 5, direction control mechanism  20  uses magnetic repulsion to rotate swing arm  18 . The magnets in stops  34  and the limit arm  36  are aligned such that their polarity causes each stop  34  to repel limit arm  36 . As limit arm  36  approaches stop  34 , the repulsive force acting on limit arm  36  rotates swing arm  18  about its longitudinal axis to change the direction of swing arm  18 . If electromagnets are used, the magnets may be energized when swing arm  18  or limit arm  36  triggers a proximity sensor. The strength of the magnets depends upon the size of vane  16 , the length of swing arm  18  and the force of the fluid flow. Direction control mechanism  20  is not limited to stops and magnets. Any suitable mechanism for selectively applying a rotational force to swing arm  18  may be used. For example, swing arm  18  may incorporate a rotational motor and electronic monitor. As the electronic monitor senses that swing arm  18  has reached either the predetermined first or second outer limit of travel, the electronic monitor causes rotational motor to rotate swing arm  18  about its longitudinal axis. 
     Referring again to FIG. 1, the repeated oscillation of vane  16  through the flow and the associated stroking of swing arm  18  is transferred to receiving machine  14  by a connecting rod  39 . The stroking swing arm  18  rotates crank arm  21  on receiving machine  14  through the reciprocating action of connecting rod  39 . Preferably, receiving machine  14  is located such that connecting rod  39  remains close to a 90° angle relative to swing arm  18 , and connecting rod  39  operates in the same plane as crank arm  21 . 
     The embodiment depicted in FIGS. 1 and 3, show connecting rod  39  attached to the upstream side of swing arm  18  with a flexible joint  55 . As shown, flexible joint  55  may be a universal joint, ball joint or the like that allows connecting rod  39  and swing arm  18  to pivot relative to one another about at least one axis. It is desirable to couple connecting rod  39  to the upstream side of swing arm  18  at a point below support member  22 . This point of connection between swing arm  18  and connecting rod  39  facilitates the proper orientation of vane  16  corresponding to the direction of the stroke of swing arm  18 . This results from the combined resistance of receiving machine  14  and the pressure of the fluid flow against vane  16 . Alternatively, and to the same effect, connecting rod  39  could be attached to the downstream side of swing arm  18  at a point above support member  22 . 
     The universal joint cross link ring assembly of flexible joint  51  serves as an automatic over-center latch that works counter to but in conjunction with flexible joint  55 . The direct line of pull of elastic line  38  on swing arm  18  through joint  51  falls either to the right or left of center on shaft  18 . The combined effect of flexible joints  51  and  55  helps vane  16  maintain its orientation until reaching the end of a stroke when limit arm  36  acts on a stop  34  to rotate swing arm  18 . 
     Experimentation and study have shown the required orientation, or angle of confrontation, of vane  16  relative to the fluid flow is related to the workload of receiving machine  14 . A steep angle of confrontation causes rough operation and unnecessarily increases the wear on the components. Additionally, a steeper angle of confrontation is required to start the stroking motion of swing arm  18  than is required to maintain the motion. Consequently, in the embodiment shown in FIG. 6 a limit mechanism  62  operatively coupled to swing arm  18  defines the maximum angle of confrontation of vane  16  corresponding to the stroke direction of swing arm  18 . Limit mechanism  62  includes a cross bar  64  affixed to and extending out from the longitudinal axis of swing arm  18 , adjustable strikers  66  projecting out from bar  64 , and strike plate  68 . As swing arm  18  rotates at the urging of vane  16  traversing the flow and vane  16  reaches a maximum predefined angle of confrontation, a striker  66  contacts plate  68  to prohibit further rotation of swing arm  18 . 
     Limit mechanism  62  may be adjusted to control the angle of confrontation of vane  16 . To initiate the stroking motion of swing arm  18 , limit mechanism  62  is adjusted to allow a steeper angle of confrontation. As the workload of receiving machine  14  is met, the angle of confrontation is made less steep to improve operating efficiencies. The adjustability of limit mechanism  62  may also be used to improve operating efficiency under variable workloads of receiving machine  14  and varying currents and other conditions affecting the fluid flow. 
     It appears that the proper timing of the stroke of swing arm  18  effects the power output. A relatively short stroke midstream in the fastest portion of the fluid flow, for example, appears to increase power output. Also, the motion of vane  16  across the flowing fluid creates a wave. Consequently, the stroke of swing arm  18  may be timed so that vane  16  catches the wave created by the forward stroke on the return stroke to help increase power output. Experimentation has also shown the fluid deflecting off vane  16  scours the bed of the channel. Preferably, then, the channel, in the area surrounding vane  16 , will be armored with concrete or other suitable protective material. 
     Several different configurations of vane  16  are shown in FIGS. 7-10. In FIGS. 79, front face  15  of vane  16  is concave along both a longitudinal axis L and a transverse axis T. Rear face  17  of vane  16  is convex along both longitudinal axis L and transverse axis T. Vane  16  has a curved peripheral edge  40 . Referring to FIG. 8, the primary angle of attachment e of swing arm  18  to vane  16  is preferably in the range of 90° to 225°, most preferably in the range of 150° to 170° for the embodiment of FIG. 1, where θ is the angle between swing arm  18  and a longitudinal chord  42  of vane  16 . Primary angle of attachment θ is selected to achieve the desired angle of attack Φ or “bite” of vane  16  in the fluid flow (attack angle Φ is shown in FIG.  1 ). The primary angle of attachment θ will vary, therefore, depending on the height of base  31  and the effective length of swing arm  18 , as well as the flow conditions. Referring to FIG. 9, the secondary angle of attachment σ of swing arm  18  to vane  16  is preferably in the range of 45° to 135°, most preferably about 90°, where σ is the angle between swing arm  18  and a transverse chord  44  of vane  16 . Other configurations for vane  16  are possible. For example, it is expected that vane  16  will be most efficient in certain flow conditions if it is concave only along the lateral axis T with a rectilinear peripheral edge  40 , as shown in FIG.  10 . The hydraulic energy that may be extracted from fluid passing over vane  16  depends on several factors, including the length of the vane, the shape of the vane and the depth and velocity of the flow. The maximum force against the vane is developed when the longitudinal chord  42  of vane  16  is perpendicular to the direction of flow. It is believed that the vane will be most efficient when it deflects the flow a maximum amount while the flow remains parallel across the vane. Cavitation and inefficiency will occur when vane  16  intercepts the flow lines. If the flow is slow, then vane  16  can deflect the flow lines more without cavitation. Conversely, if the flow is fast, then a smaller deflection will cause cavitation. Ideally, the fluid should enter vane  16  nearly parallel to the leading edge and exit nearly parallel to the trailing edge. The shape and chord length of the vane is dependent on the flow conditions. Some flow conditions may require circular concavity, while others may require parabolic or some other concavity. The exact equations of concavity will necessarily be determined, therefore, mathematically or empirically for the particular flow conditions or range of flow conditions in which the system is expected to operate. 
     The present invention has been shown and described with reference to the foregoing exemplary embodiments. It is to be understood, however, that other forms, details, and embodiments may be made without departing from the spirit and scope of the invention which is defined in the following claims.