Abstract:
A system ( 10 ) for generating high pressure pulses has a source ( 12, 16 ) of a pressurized working fluid ( 14 ). The working fluid is supplied to two conduits ( 22,24 ). A valve ( 26 ) has an input connected to each of the conduits ( 22, 24 ). The valve has a valve member ( 29 ) that is movable between two positions. In one position the valve member allows working fluid to flow from the first conduit ( 22 ) to an outlet and blocks the second conduit ( 24 ). In the other position the valve member allows working fluid to flow from the first conduit ( 22 ) to the outlet and blocks the first conduit ( 22 ). Flow of the working fluid causes the valve member to reciprocate and thereby generate water hammers in conduits ( 22 ) and ( 24 ). Energy from the water hammers may be harnessed for various applications.

Description:
TECHNICAL FIELD 
       [0001]    This invention relates to a hydraulic circuit for generating high pressure pulses. The circuit may be used to generate acoustic pulses for use, for example in the treatment of materials, pressure pulses for driving mechanical devices, or the like. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0002]    In the drawings which illustrate non-limiting embodiments of the invention: 
           [0003]      FIG. 1  is a partially schematic diagram of a hydraulic circuit according to the invention for generating high pressure pulses in a fluid; 
           [0004]      FIG. 2  is a detailed view of a valve portion of the circuit of  FIG. 1  in a first position; 
           [0005]      FIG. 3  is a detailed view of the valve portion of the circuit of  FIG. 1  in a second position; 
           [0006]      FIG. 4  is a partially schematic diagram illustrating an embodiment of the invention in which pressure pulses are used to drive the mechanical vibration of a rod; 
           [0007]      FIG. 5  is a detailed view of a portion of the circuit shown in  FIG. 4 ; 
           [0008]      FIG. 6  is a top view of the components illustrated in  FIG. 5 ; 
           [0009]      FIG. 7  is a partially schematic view of an embodiment of the invention adapted to generate high intensity acoustic pulses; and, 
           [0010]      FIG. 8  is a detailed view of a portion of the circuit of  FIG. 7 . 
           [0011]      FIG. 9  is a detailed view of an alternative embodiment of the invention in which sonic pulses are amplified. 
       
    
    
     DETAILED DESCRIPTION 
       [0012]    Throughout the following description, specific details are set forth in order to provide a more thorough understanding of the invention. However, the invention may be practiced without these particulars. In other instances, well known elements have not been shown or described in detail to avoid unnecessarily obscuring the invention. Accordingly, the specification and drawings are to be regarded in an illustrative, rather than a restrictive, sense. 
         [0013]      FIG. 1  shows a hydraulic circuit  10  according to the invention. Hydraulic circuit  10  includes a pump  12  which draws a fluid  14  from a reservoir  16  and pumps the fluid through a conduit  18  into a plenum  20 . Fluid  14  is preferably a substantially non-compressible fluid such as water, oil, or the like. Plenum  20  is connected to a pair of parallel conduits  22  and  24 . Both of conduits  22  and  24  are connected to different input ports of a valve  26 . Fluid exiting from valve  26  passes out from an output port, through a throttle valve  30  and into a reservoir  32 . Reservoir  16  and  32  may be the same reservoir. 
         [0014]    The construction of valve  26  is shown in detail in  FIG. 2 . Valve  26  includes a housing  27  which includes chambers  33  and  34  connected to conduits  22  and  24  respectively. Valve  26  has a movable valve member  36  which can reciprocate longitudinally as indicated by arrow  29 . Valve member  36  has sealing members  38  and  40  in its ends. Sealing members  38  and  40  can seat against valve seats  42  and  44  respectively. Valve member  36  can move between a first position, as shown in  FIG. 2 , in which fluid in conduit  24  can flow through valve  26  to output conduit  28  (while sealing member  38  bears against valve seat  42  and thereby prevents fluid from conduit  22  from flowing to output conduit  28 ) and a second position, as shown in  FIG. 3 , wherein fluid from conduit  22  can flow through valve  26  to output conduit  28  while the flow of fluid from conduit  24  to output  28  is blocked by sealing member  40  (which seals against valve seat  44 ). 
         [0015]    In operation, pump  12  pumps fluid from reservoir  16  through conduit  18  into plenum  20 . The fluid is pressurized within plenum  20 . Pump  12  does not need to be a high-pressure pump. Pump  12  may comprise, for example, a centrifugal pump. The pressure in plenum  20  causes the fluid  14  to flow down one or the other of conduits  22  and  24 . Which one of conduits  22  and  24  the flow commences in depends upon the initial position of valve member  36 . The fluid flows through valve  26  and out of conduit  28 . Suppose, for example, that valve member  36  is initially in the position shown in  FIG. 2 . In this case, fluid will flow through conduit  24 , through chamber  34 , between sealing member  40  and valve seat  44 , and out through conduit  28 . In this event, the flow of fluid between valve member  40  and valve seat  44 , will tend to drive valve member  36  towards the position shown in  FIG. 3 . 
         [0016]    When sealing member  40  contacts valve seat  44  the flow of fluid through conduit  24  is suddenly cut off. This creates a “water hammer” within conduit  24 . The water hammer creates a very high pressure pulse which propagates through conduit  24  from valve  26  toward reservoir  20 . The water hammer phenomenon is well understood. Water hammer is explained in many textbooks on the topic of fluid mechanics. One example of such a textbook is  Fluid Mechanics  (7 th Edition ) Victor L. Streeter and E. Benjamin Wylie, McGraw-Hill Book Company, 1979 and R. L. Daugherty and J. B. Franzini,  Fluid Mechanics With Engineering Applications , pages 425-431 McGraw Hill Book Company, 1977. 
         [0017]    At the same time as valve member  36  moves so as to close sealing member  40  against valve seat  44 , sealing member  38  moves away from valve seat  42 . This permits fluid to flow from conduit  22  through valve  26  to outlet  28 . In the meantime, the high pressure pulse which has been propagating upstream in conduit  24  eventually reaches plenum  20 . At this point, some fluid from conduit  24  spills into plenum  20 , and a corresponding low pressure pulse begins to propagate from plenum  20  toward valve  26  along conduit  24 . When this low pressure pulse reaches chamber  34 , it tends to draw valve member  36  back down into the position shown in  FIG. 2 . This tendency is augmented by the tendency of fluid flowing between sealing member  38  and valve seat  42  to move valve member  36  in the same direction. 
         [0018]    The sudden closure of sealing member  38  against valve seat  42  causes a water hammer pulse to be propagated upstream in conduit  22 . It can be appreciated that valve member  36  will reciprocate back and forth, alternately closing the fluid path from conduits  22  and  24 . Each time valve member  36  allows such a fluid path to be opened and re-closed, a new water hammer pressure pulse is generated. The frequency with which these pressure pulses occur is determined primarily by the lengths of conduits  22  and  24 , which are preferably equal in length. 
         [0019]    In order to initiate the oscillation of valve member  36 , it can be desirable to provide a throttle valve  30 , as shown in  FIG. 1 . By throttling conduit  28  the pressure within a central portion  46  of valve  26  may be increased in a manner that promotes the onset of reciprocation of valve member  36 . 
         [0020]    Conduits  22  and  24  are preferably equal in length. The period of reciprocation of valve member  36  is determined, at least in part, by the lengths of conduits  22  and  24  (which determines the time that it takes for a pressure pulse to propagate upstream to plenum  20  and for a reflected negative pressure pulse to be propagated back downstream into chamber  33  or  34 ). 
         [0021]    The high pressure pulses generated by circuit  10  may be utilized in various ways.  FIG. 4  shows a circuit which uses such high pressure pulses for causing high intensity vibrations of a rod  50 . As shown in more detail in  FIGS. 5 and 6 , rod  50  is connected to a piston  52  which is slidably disposed within a cylinder  54  within a housing  27 . Piston  52  divides the volume within cylinder  54  into two portions,  56  and  58 . Portion  56  is connected by means of a conduit  60  to volume  33  of valve  26 . Portion  54  is connected by means of a conduit  62  to volume  34  of valve  26 . 
         [0022]    In operation, when a high pressure pulse is generated, commencing in volume  34  by the sudden closure of sealing member  40  against valve seat  44 , the pressure within portion  58  of cylinder  54  is suddenly increased. This creates a very large upward acceleration on piston  52  which is transferred to rod  50 . During this time the pressure within volume  33  and portion  56  is relatively low since fluid is flowing through volume  33 . When valve member  36  moves so that sealing member  40  is away from valve seat  44  then the pressure within volume  34  and portion  58  is reduced. At the same time, a water hammer pressure pulse is generated within conduit  22 . This pressure pulse is conveyed through conduit  60  into portion  56  and generates a sudden acceleration on piston  52  in the downward direction. It can be appreciated that as valve member  36  reciprocates then rod  50  is violently reciprocated at the frequency of motion of valve member  36 . Rod  50  may be connected to deliver vibration or sonic energy to various mechanical structures. For example, rod  50  may be used to impart high acceleration vibrations to contacting members in a crusher for crushing rocks or other hard materials. Rod  50  may conduct vibrations into agitation paddles or other mechanical structures to be subjected to high intensity vibratory pulses. 
         [0023]      FIG. 7  discloses apparatus  10 B according to an alternative embodiment of the invention in which chambers  33  and  34  are respectively connected to conduits  70  and  72  which include gradually tapering section  73 . Gradually tapering sections  73  tend to increase the intensity of sonic pressure being carried through the fluid in conduits  70  and  72 . Conduits  70  and  72  each terminate in a narrow diameter portion  74 . In narrow diameter portion  74  the intensity of pressure pulses from chambers  33  and  34  are magnified. Portion  74  may be open-ended, as shown in  FIG. 8 , or may be closed-ended. Where portions  74  are open-ended, fluid will tend to flow out through conduits  70  and  72 . The stream of fluid exiting through the ends of portions  74  will come out in spurts in time with the pressure pulses delivered from chambers  33  and  34 . These high pressure spurts may be used in various applications. For example, they may be used in pressure washing, water jet cutting, or the like. 
         [0024]    Fluid passing through conduits  70 ,  72  and  74  will be subjected to high shear conditions. Apparatus  10 B can be used to alter the viscosity of fluid  14 . 
         [0025]    If portions  74  are closed-ended, then the ends of portions  74  will experience high energy oscillations, during and after the high pressure pulse. The frequency of such oscillations will depend on the length of portion  74 . It has been experimentally determined that this causes a rapid rise in temperature of fluid in portions  74 . 
         [0026]      FIG. 9  illustrates an alternative construction of portions  74  in which each of conduits  70 ,  72  has its end partially blocked with a plug  80  (conduits  72  will typically be significantly longer than illustrated in  FIG. 9 ). Narrow passages  82  extend between the plug and the inner walls  84  of tube  74 . Fluid motivated by high pressure pulses can be driven through these narrow passages past plugs  80 . Each plug  80  is gradually tapered and has an upstream-facing pointed end  86 . The pressure of pressure pulses propagating in tubes  74  is amplified as the pressure pulses pass into the narrow passages surrounding plugs  80 . 
         [0027]    Various alternatives to these structures described above are possible. For example:
       piston  52  could be replaced by a stiff diaphragm;   a second rod  50  could extend out of the top end of housing  27 ;   rod  50  could pass through both ends of housing  27 . If so, rod  50  could be hollow. Where rod  50  is hollow, a mechanical member to be vibrated could pass through the bore of rod  50 .       
 
         [0031]    As will be apparent to those skilled in the art in the light of the foregoing disclosure, many alterations and modifications are possible in the practice of this invention without departing from the scope thereof. Accordingly, the scope of the invention is to be construed in accordance with the substance defined by the following claims.