Abstract:
A speed limiting mechanisms for turbine-driven fluid distribution apparatus usable with compressible fluid such as compressed air and incompressible fluid such as water. In one form, a flow restrictor is located in the turbine discharge flow path, with the turbine discharge port area selected in relation to the turbine inlet port area according to the desired turbine speed with compressed air. In another form, the incoming fluid flows downstream along the surface of the turbine stator, and is then diverted to enter the rotor chamber in the proper direction. A bleed area on the stator which permits a portion of a compressible fluid which has expanded as it flows along the stator surface to flow to bypass the turbine rotor.

Description:
CROSS REFERENCE TO RELATED APPLICATION 
       [0001]    This application is based on and claims benefit of U.S. Provisional Patent Application No. 60/289,227 filed May 7, 2001, and is a continuation of U.S. patent application Ser. No. 10/141,261, filed May 7, 2002 entitled SPEED LIMITING TURBINE FOR ROTARY DRIVEN SPRINKLER, the disclosure of which is hereby incorporated by reference and to which a claim of priority is hereby made. 
     
    
     TECHNICAL FIELD 
       [0002]    The invention relates to sprinkler where a water driven turbine causes the sprinkler nozzle to rotate to provide coverage over a desired area. 
       BACKGROUND 
       [0003]    Sprinkler systems in the northern climates must be drained or blown-out with air to clear the water to prevent freezing damage. In many cases the simplest installation provides only for allowing the irrigation system pipes and sprinklers to be cleared of water by blowing out the system using compressed air. This can be very damaging to the sprinklers which have water turbines which are normally water powered and rotate at a much slower speed with the water which is a relatively heavy incompressible fluid and does not generate the high turbine stator velocities produced when air, an expandable relatively light fluid, is expanded across the turbine stator onto the turbine blades. 
         [0004]    The high turbine shaft velocities can heat the shaft and cause it to seize to the plastic housing material. This prevents the turbine from turning and renders it unusable in the future unless care is taken to limit the system air, blow-out time and pressures. This has proved to be one of the major causes for premature failure of gear driven sprinkler in colder climates, where sprinklers are used for only part of the year, and should last much longer than in warmer climates where they are run year round. 
         [0005]    Devices are known for controlling the rotational speed of turbine-driven sprinklers. One such device, shown in Clark U.S. Pat. No. 5,375,768, is designed to maintain constant turbine speed despite variations of inlet water pressure. The patented sprinkler relies on a throttling device to direct part of the water to the turbine rotor, and a pressure responsive valve to divert some of the water around the turbine. This design, however, can not effectively limit rotational speed when the turbine is driven by a compressible fluid such as air, and still allow the turbine to run at a sufficiently high speed when it is driven by an incompressible fluid such as water because of the rapid expansion of the compressed air as it enters the turbine chamber. 
         [0006]    Other turbine speed limiting mechanisms are known, but to applicant&#39;s knowledge, none of these are suitable for turbines which must run on both compressible and incompressible fluids. 
       SUMMARY 
       [0007]    It is accordingly the primary object of this invention to provide a turbine-driven sprinkler which incorporates a speed limiting mechanism which protects the turbine from damage when compressed air is used to blow out the system in preparation for winter, but still permits satisfactory operation when the turbine is water-driven. 
         [0008]    A related object of the invention is to provide a turbine-driven sprinkler having a speed limiting mechanism for air (compressible flow) as described which is reliable and can be manufactured inexpensively. 
         [0009]    The above objects are achieved according to one aspect of the invention by choking the turbine flow discharge area to be relatively the same as or slightly larger than the inlet stator area. According to another aspect of the invention, the inlet stator flow area can be separated from the turbine blades by a flow bleed area to bleed off a significant portion of the expanding flow before a portion of the gases are deflected to strike the turbine blades to produce the turbine rotation. Water, being incompressible, does not experience the continued expansion after flow through the stator inlet flow area and does not flow out the intermediate bleed but continues in its line of flow to be directed onto the turbine blades to run the turbine in a normal manner. In the case of air (compressible flow) the portion remaining after the intermediate bleed can be limited to just enough to turn the turbine at its normal speed when water-driven. 
         [0010]    Other features and advantages of the present invention will become apparent from the following description of the invention which refers to the accompanying drawings. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS  
         [0011]      FIG. 1  is a cross-section of an elevation view of the drive turbine area of a turbine-driven sprinkler according to a first embodiment of the invention. 
           [0012]      FIG. 2  is a cross-section of an elevation view of the drive turbine area of a turbine-driven sprinkler according to a second embodiment of the invention which shows the spring loaded flow bypass valve in the fully closed position. 
           [0013]      FIG. 3  is a side elevation of the rotor housing and the flow deflector according to the second embodiment. 
           [0014]      FIG. 4  shows a top view of the flow deflector stator. 
           [0015]      FIG. 5  shows a cross-section of an elevation view of the turbine area of  FIG. 2  but with the flow bypass valve in the fully open position. 
       
    
    
     DETAILED DESCRIPTION OF THE EMBODIMENTS  
       [0016]      FIG. 1  shows in cross-section, the turbine assembly, generally denoted at  1 , of a water turbine driven sprinkler such as described in detail in my U.S. Pat. No. Re 35,037, the disclosure of which is incorporated herein by reference as if fully set forth. The turbine assembly  1  is mounted in a housing  3 , and, by way of an output shaft  5 , drives a gear box  7  which rotates or oscillates a sprinkler head (not shown). As will be understood, water (or during winterization, compressed air) entering turbine assembly  1  from below at  9  drives the turbine, and thereafter flows through an outlet passage  17  to the sprinkler head. 
         [0017]    The turbine itself is comprised of a rotor  11  located in a rotor chamber  13  formed by a stator cover assembly  15  positioned on the upstream side of the turbine, and a lower cover  12  for gearbox  7 . Stator cover assembly  15  is in the form of an inverted cup with a central portion  4  that houses a flow by-pass valve sub-assembly  6  described below. Extending radially from the bottom of central portion  4  is a shoulder  18  which terminates in an upwardly extending skirt portion  19 . 
         [0018]    Circumferentially spaced around the bottom shoulder  18  of stator cover  15  are a plurality of tangentially directed turbine stator flow inlet ports  8  through which water flows into rotor chamber  13 . As the incoming fluid passes through openings  8 , it experiences acceleration due to the pressure difference between the inlet area  9  to the turbine housing and the pressure in cavity  13  as maintained by the turbine by-pass assembly valve  6 , and then tangentially strikes the turbine rotor  11 , causing it to turn, and to drive gearbox box  7  through shaft  5 . The fluid then exits rotor chamber  13  through an annular discharge port  10  between the turbine rotor  11  and a circumferential blade support ring  20  and the lower gear box cover ring  12 . Discharge port  10  communicates with an outer chamber  16  above stator cover  15 , which, in turn, communicates with discharge passage  17 . 
         [0019]    The hub portion  21  of rotor  11  passes through a circular opening  22  at the top of stator  15 . Circular opening  22  also provides communication between the interior of stator cup  4  and outer chamber  16 . 
         [0020]    Located within stator cup  4  is turbine by-pass valve assembly  6 . This is comprised of a valve plug  23  which is biased into a closed position against the upper surface of a valve seat member  25  by a spring  24 . As will be understood, when the inlet fluid pressure is sufficient to overcome the force of spring  24 , a portion of incoming fluid is diverted by valve  6  to discharge passage  17  through the interior of stator cup  4 , circular opening  22 , and outer chamber  16 . The purpose of this valve is to maintain the desired differential pressure across the turbine inlet ports  8 , to drive the turbine at the desired speed and power with water. 
         [0021]    Achieving proper performance for the sprinkler both when the turbine is water-driven and also preventing over speeding when it is air-driven depends on the selection of the area of turbine circumferential discharge port  10  and the flow pressure drop established by flow control valve  6 . To assure over-speed protection for turbine rotor  11  during blow out, the area of discharge port  10  must be restricted, but the area must be large enough for the turbine to provide the desired torque to gearbox  7  for the pressure drop established by spring  24  of the flow bypass valve assembly  6  when operating in water. 
         [0022]    In any event, the discharge port area must be, at a minimum, slightly larger than the collective area of the multiple turbine stator inlet ports  8 . However, since the water is incompressible, and does not expand, increasing the area beyond a certain point does not improve turbine torque performance and just allows for greater expansion and flow of air when the turbine is air-driven, and allows it to overspeed. 
         [0023]    For a turbine driven by an incompressible fluid such as water, and especially in the simple, single-stage turbines used to drive sprinklers the turbine flow exist velocity remains relatively high, the difference in velocity resulting from energy absorbed by the turbine wheel and flow friction inefficiencies. Thus, in accordance with the continuity equation for flow that requires that the product of inlet flow area and inlet flow velocity must equal the product of the exit flow area and the exit flow velocity, large increases in exit flow area are not required for proper operation and power for water. 
         [0024]    Taking all these factors into consideration, good results, in terms of enhancement of the life of turbine-driven sprinklers, and elimination of destructive turbine over-speeding during blowout with air, can be achieved by limiting the turbine discharge area to no more than twice the collective turbine stator inlet area, and preferably about 1.5 times the collective turbine stator inlet area. This can be made smaller (but no less than equal to the collective turbine stator inlet area) to limit even further the turbine speed when driven by air. 
         [0025]    As shown in  FIG. 1 , the area of discharge port  10  is determined by the spacing between inside wall  26  of ring  12  and the outer wall of turbine ring  20 . Thus, the area of discharge port  10  is determined by the internal diameter of ring  12  and the outside diameter of ring  20 . 
         [0026]    In most of the sprinklers being manufactured today, the turbine discharge area is not restricted and is simple to open to allow turbine flow to move through the sprinkler housing  2  and area  16  and  17  up to the sprinkler&#39;s discharge nozzle (not shown). 
         [0027]      FIGS. 2-5  illustrate a second embodiment of the invention, in which a different mechanism is employed for limiting turbine over-speed when it is run on compressed air during winterization. 
         [0028]    Referring to  FIGS. 2 and 3 , modified turbine assembly  1 A is mounted in a housing  3 A, and, by way of an output shaft  40 , drives a gearbox  60  which rotates or oscillates a sprinkler head (not shown). Water or compressed air entering turbine assembly  1 A from below at  44  drives the turbine, and thereafter flows through outlet passages  67  and  49  to the sprinkler nozzle. 
         [0029]    The turbine is comprised of a rotor  46  located in a rotor chamber  48  formed by an internal housing  50  having spaced legs  54  around its outside circumference. A flow directing swirl member  52  includes a lower (upstream) body portion  66  having a plurality of circumferentially spaced longitudinal ribs  68 . A by-pass flow valve  62  described below having a central opening  70  is positioned in radially spaced relationship around the upstream body portion  66 . As illustrated in  FIG. 2 , opening  70  cooperates with ribs  68  and surface  77  of lower body portion  66  of swirl member  52  to form a series of longitudinal passages  72  running from inlet  44  up along swirl member  66 . At its upper end  74 , surface  77  is curved outwardly as shown at  77 A. 
         [0030]    At the upper (downstream) end  74  of swirl member  66 , the radial inner edges of ribs  68  are also curved outwardly and circumferentially to form swirl deflector surfaces  80 . These cooperate with a series of circumferentially spaced swirl ribs  76  that spiral outwardly as shown in  FIG. 4  to cause the axially flowing fluid in flow passages  72  to be deflected outwardly and circumferentially so that it passes through a swirl ring opening  73  where it strikes the vanes  47  of turbine rotor  46 . After imparting energy to rotate the turbine, the fluid flows out through a series of radial exit ports  65  into a flow area  67  between interior housing  50  and exterior housing  3 A, and from there, through outlet passage  49  to the sprinkler head (not shown). 
         [0031]    When the turbine is water-driven, the inertia of the incompressible water carries it straight up ribbed passages  72 , past deflector surfaces  77 A and swirl ribs  76 , and though swirl ring opening  73  to strike turbine rotor blades  47  which are rotating in rotor chamber  48 . However, when compressed air is used to blow out the irrigation system during winterization, the air continues to expand after traveling through passage  72  as it moves upwardly, and a significant amount escapes through open bleed area  80  into a bypass flow area  67 , and from there, into discharge area  49  around gear box  60  to the sprinkler nozzle at the exit top end of the sprinklers. 
         [0032]    Only the air that continues straight up along the ribbed passages  72  passes through the swirl ring opening  73  to drive turbine rotor  46 , and thus the energy transferred to the rotor is much less than if the entire incoming air flow had been allowed to enter rotor chamber  48 . The shape and opening size of the swirl ring opening  73 A can be used to determine how much air flow is allowed to reach the turbine without limiting the water flow. 
         [0033]    Bypass flow valve  62  includes an outwardly tapered upper portion  63  that serves a valve closure member with ring  56 . A beveled radially inner surface  58  of ring  56  forms a valve seat that cooperates with valve closure member  63 . A spring  88  biases valve closure member  63  upward against valve seat  58  so that valve  62  is normally closed, as illustrated in  FIG. 2 . 
         [0034]    In  FIG. 5 , by-pass flow valve  62  is shown in its open position. This allows flow in excess of what is needed to drive the turbine to be bypassed through valve opening  90  around the turbine and up through discharge passage  49  around the gear box  60 . Once the required differential pressure is established across opening  72  to provide the desired turbine speed and power by the strength of spring  88  acting on valve member  62 , the balance of the flow is bypassed by allowing valve  62  to open as previously explained. 
         [0035]    The turbine rotor speed is a result of momentum interchange between the flowing fluid and the turbine rotor blades and depends on turbine design for simplicity and efficiency. Many different designs may be employed to achieve the required power to rotate the sprinkler head, as will be appreciated by those skilled in the art. 
         [0036]    To allow simpler construction, inner housing  50  may be eliminated. However, inner housing  50  provides protection from high bypass flow velocities and dirt for turbine rotor  46 . Discharge ports  65  also provide an additional throttling mechanism to limit the turbine speed when it is being blown out. 
         [0037]    Although the present invention has been described in relation to particular embodiments thereof, many other variations and modifications and other uses will become apparent to those skilled in the art. It is intended, therefore, that the present invention be limited not by the specific disclosure herein, but only by the appended claims.