Abstract:
A turbine assembly for a rotary sprinkler head includes a flow control valve, a turbine housing having a fluid inlet and fluid outlet ports, and a rotor mounted in the housing. The flow control valve is moveable between a closed position and a maximum open position, and is spring biased towards the closed position in which all of the fluid flowing into the sprinkler head initially flows into the turbine assembly. When the flow rate through the sprinkler head is sufficient to open the valve, a portion of the fluid flow passes through the valve to bypass the turbine assembly. As the flow rate continues to increase, the valve opens further until it reaches the maximum open position. Once the valve is opened to a predetermined point, as it opens further, up to the maximum position, the valve also increasingly throttles the fluid outlet ports up to a point short of complete blockage of the outlet ports.

Description:
This application claims priority to U.S. Provisional Application Ser. No. 60/445,271, filed Feb. 6, 2003, the entire disclosure of which is hereby incorporated by reference. 

   BACKGROUND OF THE INVENTION 
   Rotary and oscillating sprinkler systems are widely used to irrigate lawns and landscaping in both commercial and residential environments. The most effective and reliable sprinkler systems include a series or network of pop-up sprinkler heads connected to a fluid source via irrigation pipes installed underground around the area to be maintained, an example of which is illustrated in  FIG. 1 . Each pop-up type rotary sprinkler head  100  generally includes a riser assembly  102  which is slidably mounted in the sprinkler head housing  104  between a fully retracted position in which the riser assembly  102  is entirely encased within the housing  104  when no fluid is flowing through the sprinkler head  100 , and a fully extended position in which substantially the entire length of the riser assembly  102  extends out of the housing  104  when fluid is flowing through the sprinkler head  100  during operation of the irrigation system. A nozzle assembly  108  is rotatably attached at the top of riser assembly  102 , and includes at least one nozzle  110  through which irrigation fluid is distributed out of the sprinkler head  100 . 
   The sprinkler head housing is typically installed just beneath the ground surface  106  so that when no fluid is flowing into the sprinkler head, the riser assembly is also substantially below the ground surface. When irrigation fluid flows through the sprinkler head, the force of fluid pushes the riser assembly out of the housing until the riser assembly is fully extended to be appropriately positioned above the ground surface to deliver irrigation fluid. 
     FIG. 2  shows an example of a riser assembly as disclosed in U.S. Patent Application Publication No. 2002/0074432, and which includes a turbine assembly  122  having a rotor  112  and a turbine inlet  114 , a gear assembly  116 , and a turbine shaft  118 . During operation, fluid flowing into the riser assembly enters the turbine inlet  114  and causes the turbine wheel  112  to rotate. Rotor  112  is attached to turbine shaft  118 , which drives the gears in gear assembly  116 . 
   Nozzle assembly  108  is rotatably connected to the riser assembly  102  by an output shaft  120 , which also defines the flow path of fluid from the riser assembly  102  into the nozzle assembly  108 . As such, irrigation fluid flows upwardly through the riser assembly  102  and is channeled into output shaft  120  and out through nozzle  110 . In the riser assembly  102 , output shaft  120  is driven by the output of gear assembly  116 , whereby rotation of the output shaft  120  is thereby controlled by the movement of the gears in the gear assembly  116 . The gears may be configured to rotate the output shaft  120  continuously or in an oscillating manner through a predetermined arc, as disclosed, for example, in U.S. Pat. No. RE 35,037 to Kah, Jr. and U.S. Patent Application Publication No. 2002/0074432 to Kah, Jr. et al., the disclosures of which are both incorporated herein by reference. 
   In climates which experience freezing temperatures during the year, irrigation systems such as those described above must be drained or blown-out with air after seasonal use to clear any water out of the system to prevent freezing damage. In many cases, the simplest installation provides only for allowing the irrigation system pipes and sprinkler heads to be cleared of water by blowing out compressed air through the system. This can be very damaging to the turbines, which normally rotate at a much slower speed when driven by water. Air is an expandable fluid and is relatively light compared to water, which is a relatively incompressible fluid and does not generate the rotational velocities produced when air is expanded in the turbine assembly onto the rotor blades. 
   Unless care is taken to limit the system air, blow-out time and pressures, the high turbine shaft velocities resulting from blowing compressed air through the sprinkler system can heat the shaft and cause it to seize to the plastic housing material. Once this occurs, the rotor is prevented from turning any further and is rendered unusable in the future. This has proved to be one of the major causes for premature failure of gear driven sprinklers in colder climates, where sprinklers are used for only part of the year and would therefore be expected to last much longer than in warmer climates, where they are run year round. Accordingly, the longevity of gear driven sprinkler systems in colder climates would be greatly enhanced if such systems were equipped with means to prevent the turbine rotor from rotating at excessively high velocities when driven with compressed air. 
   At least one device is known for preventing excessive rotational speed in turbine-driven sprinklers. One such device is disclosed in U.S. Patent Application Publication No. 2002/0162901 to Hunter et al., in which a brake force is applied to the rotor in a turbine assembly in a rotary sprinkler head when compressed air is flushed through the sprinkler system. To achieve this result, the turbine assembly includes a float mechanism which may be seated on the turbine rotor or blocks the flow path to the rotor when air is flowing through the sprinkler head, and is lifted off the rotor or removed from obstructing the flow path when water is delivered therethrough. The default position of the float mechanism is in the position to hinder rotation of the turbine rotor, but its buouyancy in water causes the float mechanism to be moved in the direction of flow so as to enable the turbine to rotate freely when water flows through the sprinkler head. 
   Even with water flowing through the sprinkler system, however, the sprinkler heads may wear out faster with continued operation at high fluid output rates than at lower output rates. In particular, certain types of rotary irrigation sprinkler systems provide the capability to adjust the output rates and/or change between several different nozzles for applying a selected flow rate and/or distribution profile of the irrigation fluid. Changes in the output flow rate caused by changing the nozzles also affect the flow rate driving the turbine rotor which rotates the sprinkler head. This is generally the case with most known rotary sprinklers, including the system disclosed in Hunter and discussed above. When the irrigation fluid flowing through the sprinkler system disclosed in Hunter is water, the rate of rotation of the turbine assembly is directly determined by the flow rate of water through the system, and would therefore vary through the entire operation range of the sprinkler system. 
   Because water is an incompressible fluid, as the selected output rate from the sprinkler increases, the faster the velocity of water passing through the turbine assembly. The faster the velocity of water entering the turbine assembly, the faster the rotor is driven by the water striking the rotor blades. Therefore, it would be advantageous to maintain the rotational velocity of the turbine rotor as constant as possible for as great a range of flow rates as possible for both air and water. 
   SUMMARY OF THE INVENTION 
   A first aspect of this invention provides a turbine-driven sprinkler head 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. 
   A second aspect of the invention provides a turbine-driven sprinkler head having a speed limiting mechanism for air (compressible flow) which is reliable and can be manufactured inexpensively. 
   A third aspect of the invention provides a turbine-driven sprinkler head having a speed limiting mechanism which maintains a substantially constant rotational velocity of the turbine for a range of flow rates when the irrigation fluid is an incompressible fluid such as water. 
   A fourth aspect of the invention provides a turbine-driven sprinkler head which incorporates a speed limiting mechanism which maintains the rotational velocity of the turbine rotor as constant as possible for as great a range of flow rates as possible regardless of the content of the irrigation fluid through the sprinkler system. 
   The present invention includes a turbine assembly for a rotary sprinkler head which includes a turbine housing, a fluid inlet to the turbine housing, a rotor mounted in the turbine housing, at least one fluid outlet from the turbine housing, and a flow control valve which is spring biased towards the closed position, whereby all of the fluid flowing into the sprinkler head is initially allowed to flow through the turbine assembly to thereby drive the rotor. When the fluid flow into the sprinkler head is increased to a first flow rate which generates a force against the valve sufficient to counteract the force of the spring, the valve is opened, and a portion of the fluid flow is diverted around the turbine assembly to flow directly to the nozzle assembly. As the flow rate increases from the first flow rate, the flow control valve continues to open up to a predetermined amount. 
   The flow control valve is constructed so as to throttle the at least one fluid outlet from the turbine housing once the flow rate through the sprinkler head reaches a second flow rate. As the flow rate increases from the second flow rate, the flow control valve increasingly restricts fluid flow out of the turbine housing until the flow control valve reaches its maximum open position. 
   Preferably, the flow control valve is slidingly fitted around the turbine housing and includes a sleeve for throttling a plurality of exit ports from the turbine housing. 
   These and other features and advantages of the invention will become apparent from the following detailed description, which is provided in connection with the accompanying drawings and illustrate exemplary embodiments of the invention. 

   
     DESCRIPTION OF THE DRAWINGS 
       FIG. 1  illustrates a pop-up rotary sprinkler head as generally known in the art; 
       FIG. 2  is a cross-sectional view of an exemplary pop-up rotary sprinkler head as known in the art; 
       FIG. 3  is a cross-sectional view of a preferred embodiment of a turbine assembly in accordance with the present invention, wherein the flow control valve is in the closed position; 
       FIG. 4  is a cross-sectional view of the turbine assembly shown in  FIG. 3  in which the flow control valve is in an open position; 
       FIG. 5  is a cross-sectional view of the turbine assembly shown in  FIG. 3  in which the flow control valve is in the maximum opened position and the outlet ports of the turbine housing are throttled; 
       FIG. 6  shows an exemplary turbine rotor which may be incorporated in the turbine assembly in accordance with the present invention. 
       FIG. 7  shows the aperture plate fitted in the turbine housing according to the present invention; and 
       FIG. 8  is a perspective view of the turbine housing incorporated in the turbine assembly according to the present invention. 
   

   DETAILED DESCRIPTION OF THE INVENTION 
   The turbine assembly  10  according to a preferred embodiment of the present invention is shown in cross-section in  FIGS. 3–5 . Generally, turbine assembly  10  includes a rotor  22 , a turbine housing,  14 , an aperture plate  16 , and a flow control valve  36 . 
   Rother  22  has a plurality of blades  24  angularly formed around its perimeter (seen more clearly in  FIG. 6 ), and is affixed to an output shalt  28 , which in turn is connected to a gear train inside a gear box  30 . When the rotor  22  is driven as described below, the gear train in gear box  30  is driven to ultimately cause a sprinkler head (not shown) to rotate in one direction or to oscillate through a predetermined arcuate range. Irrigation fluid is output through the sprinkler head while the sprinkler head is rotating and/or oscillating, to distribute the fluid across a predetermined range and trajectory profile. 
   Rotor  22  is housed inside turbine housing  14 , which includes an upper housing section  13  shaped substantially like a petri dish, a substantially bowl-shaped lower housing section  15  and an inlet tube  8 . The upper housing section  13  is fitted over the lower housing section  15  like a cap, and the inlet tube  8  extends downwardly from a center opening in the lower housing section  15  having a diameter corresponding to the inner diameter of the inlet tube  8 . Preferably, though not necessarily, the inlet tube  8  is integrally formed with the lower housing section  15 . As shown in  FIG. 7 , inlet tube  8  has a first exterior diameter along its upper portion  9 , and a second exterior diameter which is smaller than the first exterior diameter along its bottom portion  11 , for reasons which will be explained below. Due to the difference in exterior diameters of the upper portion  9  and the bottom portion  11 , a shoulder  46  is formed around of the inlet tube  8  at the junction between the two portions. As can be seen in  FIGS. 3–5  and  7 , the turbine housing  14  as defined byte upper housing section  13 , the lower housing section  15  and the inlet tube  8  forms a structure which is cylindrically symmetrical about a central vertical axis and has a vertical cross section shaped like a hollow “T.” 
   A plurality of outlet ports  26  are formed through and spaced around the upper portion of the cylindrical wall of upper housing section  13 . An aperture plate  16  (see  FIG. 8 ) is fitted in the housing  14  at the top of lower housing section  15 , to thereby divide the space enclosed between the upper and lower housing sections  13  and  15  into rotor chamber  20  and lower turbine chamber  21 . Aperture plate  16  includes apertures  18  spaced around its periphery to establish fluid communication from the lower turbine chamber  21  to the rotor chamber  20 . The size and position of the apertures  18  in the aperture plate  16  are such that fluid entering rotor chamber  20  through apertures  18  flows directly as possible to the blades  24  of the turbine rotor  22  to thereby drive the rotor  22 . Additionally, the total area of the outlet ports  26  is preferably substantially equal to or slightly larger than the total area of apertures  18  between in the aperture plate  16 . When constructed in this manner, the flow rate entering the rotor chamber  20  will also exit the rotor chamber  20  at the same flow rate, absent any obstructions to fluid flow through the outlet ports  16  and assuming that the irrigation fluid is a compressible fluid. 
   In a sprinkler head which incorporates the turbine assembly according to the present invention, fluid thus travels through the turbine assembly by entering through the inlet passage  12  in the inlet tube  8 , flowing into the lower turbine chamber  21  under the aperture plate  16 , passing through the apertures  18  in the aperture plate  16  and into the rotor chamber  20 , and exiting through the outlet ports  26 , where the fluid then continues to flow upwardly through the sprinkler head to be distributed out of the sprinkler head via the nozzle assembly. 
   A flow control valve  36  is, in an exemplary embodiment of the invention, substantially Y-shaped in cross-section, and includes a planar bottom end  44 , a curved fluid contact surface  45 , and a sleeve  48 . The bottom end  44  has a central opening formed therethrough having a diameter corresponding to the exterior diameter of the lower portion  11  of inlet tube  8 . The outer diameter of bottom end  44  is somewhat larger than the exterior diameter of the upper portion of inlet tube  8 . The flow control valve  36  widens from the outer diameter of the bottom end  44  to the diameter of the sleeve  48 , which corresponds with the exterior diameter of the turbine housing  14  along the cylindrical wall formed by the upper housing section  13  and lower housing section  15 . The fluid contact surface  45  is defined by this variable diameter section of the flow control valve  36  between the bottom end  44  and the sleeve  48 . 
   The bottom portion  11  of the turbine inlet tube  8  is fitted through the opening  43  in the bottom end  44 . A spring  42  is arranged inside flow control valve member  36  surrounding turbine inlet tube  8  between the bottom end  44  and the bottom surface of the lower housing section  15  of interior turbine housing  14 . The spring  42  biases the bottom end  44  of flow control valve  36  to a position along the inlet tube  8  near the opening to the turbine inlet passage  12  at the bottom of the inlet tube  8 . 
   As seen in  FIG. 3 , the turbine assembly  10  is positioned inside a riser housing  2  so that the turbine inlet passage  12  opens into the main flow passage  6  through riser housing  2 . The position of the turbine assembly  10  and the gear box  30  inside the riser is fixed to prevent vertical movement of the turbine assembly  10  relative to the housing  2 . An annular flange  32  is formed around the inner surface of housing  2 , and defines a valve seat  34  around its inner circumference. 
   When no fluid is flowing through the sprinkler head, there is no force being applied against the flow control valve  36 , and therefore the flow control valve  36  rests on the valve seat  34  as illustrated in  FIG. 3 . The spring  42  is pre-compressed (biased) to a force sufficient to hold the flow control valve  36  in the closed position on the valve seat  34  until a flow rate of fluid through the sprinkler head causes the pressure across flow control valve  36  to exceed the pre-compressed force of spring  42 . 
   In an initial period of operation of the sprinkler system, the irrigation fluid source is opened to allow irrigation fluid to begin flowing to the sprinkler head. The flow of fluid enters the riser housing  2  into the main flow passage  6  thereof, and then into the turbine inlet passage  12  and through the turbine assembly as described above. As fluid flows into the main flow passage  6  of riser housing  2 , the fluid pressure pushes against the fluid contact surface  45  of the flow control valve member  36 . During this initial period of operation, the pressure exerted on the fluid contact surface  45  by the flow of fluid is less than that necessary to unseat the flow control valve member  36  from its seat. Accordingly, the upper portion of sleeve  48  contacts and surrounds the turbine housing  14  but remains below the position of the outlet ports  26 , and all of the fluid flow passes through the turbine assembly  10 , with the turbine outlet ports  26  fully uncovered by sleeve  48 . 
   When the force of the irrigation fluid against the fluid contact surface  45  is sufficient to overcome the pre-compressed force of the spring  42 , the flow control valve  36  is lifted off the valve seat  34  such that the bottom end  44  slides along the bottom portion  11  of the inlet tube  8 , as illustrated in  FIG. 4 , to enable a portion of the irrigation fluid flow to enter the flow bypass region  38  through the opening between the annular flange  32  and the flow control valve  36 . Upon opening the flow control valve  36 , any fluid flowing into the bypass region  38  does not enter the turbine flow path and does not contribute to driving the rotor  22 . The portion of the fluid flow bypassing the turbine assembly recombines with the portion of flow passing trough the turbine assembly after the latter exits the rotor chamber  20 , whereby the entire flow continues to pass through the riser assembly and into the nozzle assembly, where the fluid is discharged through the nozzle(s) in the nozzle assembly. 
   The extent to which the valve  36  is opened by a given flow rate through the sprinkler head is controlled by the pre-compressed tension of the spring  42  and the spring constant k. As the flow rate through the sprinkler head increases, the additional differential pressure across the turbine assembly caused by the tension of spring  42  upon further compressing the spring is compensated for by the further upward movement of the flow control valve  36 , which causes the sleeve  48  to begin to cover the turbine outlet ports  26 . 
   As the flow rate into the riser housing  2  is increased, the flow control valve  36  is pushed further upwards relative to the valve seat  34 . As the valve  36  is pushed upwards, the top of sleeve  48  becomes aligned with the bottom of the outlet ports  26 , whereupon further movement of the valve  36  causes the sleeve  48  to constrict the exit area of the outlet ports  26 , thus restricting the rate of flow out of chamber  20 . 
   When the irrigation fluid is an incompressible fluid such as water, restricting the size of the exit area through the outlet ports  26  causes the flow rate exiting the rotor chamber  20  to be reduced. Since an incompressible fluid can only enter the rotor chamber  20  at the same rate the fluid exits the rotor chamber  20 , reducing the exit rate out of the rotor chamber  20  likewise restricts the rate of fluid entering chamber  20 . While the input rate of fluid to the rotor chamber  20  for driving the rotor  22  is thus reduced by the position of the sleeve  48  of the flow control valve  36 , the fluid flow rate through the sprinkler head has not been reduced, and may even be continuing to increase. This causes more of the fluid flow to bypass the turbine assembly than would be the case if the flow rate exiting the turbine assembly were not being restricted. 
   Of course, it is understood that as the flow rate through the sprinkler head increases from the flow rate at which the flow control valve  36  is first opened and the flow rate at which the flow control valve  36  begins to throttle the turbine outlet ports  26 , the portion of the total flow rate bypassing the turbine assembly also increases in relation to the further opening of the flow control valve  36 . During this phase of operation, where the flow control valve is being further opened but before the outlet ports  26  of the turbine assembly  10  are constricted, the flow rate through the turbine assembly may continue to increase, despite the increasing proportion of flow bypassing the turbine assembly, albeit any rate of increase through the turbine assembly is significantly slower than would occur without the bypass operation of the flow control valve  36 . The present invention eliminates this variability in turbine speed over the range of flow rates in which the outlet ports  26  of the turbine assembly  10  are constricted. By throttling the flow rate exiting the turbine assembly in addition to diverting a portion of the flow at the inlet of the turbine assembly, the present invention provides an additional means for controlling the flow rate through the turbine assembly. The invention therefore enables the rotational speed of the rotor inside the turbine assembly to be maintained more reliably at a substantially constant level through a wider range of fluid flow rates through the sprinkler head than in prior art rotary sprinkler heads having only a bypass valve at the turbine inlet. 
   The maximum open position of the flow control valve  36  is determined by the position of the shoulder  46  formed around the inlet tube  8  at the junction of upper portion  9  and lower portion  11  of inlet tube  8 . When the flow control valve  36  is opened to the position where the end surface  44  abuts the shoulder  46 , the valve is prevented from being pushed any further upward, as shown in  FIG. 5 . Even at this position, a least a portion of the outlet ports  26  remain uncovered by the valve sleeve  48 , since if the outlet ports  26  were blocked completely, no fluid would be able to exit the rotor chamber  20 , and the rotor would stop turning due to the prevention of fluid from flowing into the chamber  20 . 
   In an exemplary embodiment of the present invention, the turbine assembly and the associated sprinkler head components are sized and constructed so that the flow control valve  36  is opened, or forced off the valve seat  34 , with an output flow rate (from the sprinkler head as a whole) of at least ½ gallons per minute (gpm) of an incompressible fluid such as water, and begins to restrict the size of the outlet ports  26  at an output flow rate of approximately 4 gpm, and maintains a constant turbine rotation speed up to an output flow rate of approximately 8 gpm. In another exemplary embodiment of the invention, the turbine assembly and the associated sprinkler head components are sized and constructed so that the flow control valve  36  maintains a constant turbine speed through an output flow rate range of between about 5 gpm to about 30 gpm. Of course, other constant speed operating ranges may be provided as desired. 
   The output flow rate range for which the rotation of the turbine rotor can be maintained at a constant speed may be controlled by several factors, including but not limited to, the spring constant of the spring  42 , the level of pre-tension biasing the spring in the valve closed position, the initial exit area of the outlet ports  26 , and the length of valve sleeve  48 . Thus, depending on the intended applications and design capacities of a sprinkler system, the variables listed above may be adjusted accordingly at the manufacturing stage to achieve constant turbine speed over as much of the operational range of the sprinkler system as possible 
   As mentioned above, in rotary sprinkler systems incorporating a turbine arrangement which does not compensate for the increasing pressure differential across the turbine assembly, the speed at which the rotor is driven directly depends upon the flow rate and velocity at which the fluid enters the rotor chamber  20  and strikes the turbine blades  24 . As such, the rotation of the rotor  22 , and hence the rotation of the nozzle head, speeds up as a greater flow rate is output from the sprinkler, and slows down as the flow rate is decreased. In contrast, the capability to throttle the turbine output flow rate in addition to controlling the flow rate into the turbine assembly at its inlet end in accordance with the present invention enables truly constant turbine speed operation in a rotary sprinkler system. 
   In addition to providing more consistently constant operation speed over a wide range of irrigation flow rates, the present invention also advantageously prevents the turbine rotor from rotating with excessive speed during the performance of winterization procedures in which compressed air is forced through the sprinkler head to clear out any remaining irrigation fluid at the end of the irrigation season in colder climates. Since excessive rotational speed of the turbine caused by the rapid decompression of the compressed air passing through an unprotected turbine assembly causes the rotor to turn at a much higher rate than normally achieved with a flow of an incompressible fluid such as water, the output shaft  28  is caused to heat up, which may damage the bearing surrounding the shaft  28  and destroy the rotational or oscillating operation of the sprinkler head. The present invention addresses this problem in dual fashion by diverting a significant portion of a flow of compressed air through the bypass flow path around the flow control valve  36  at the inlet end of the turbine assembly, and also by choking the flow path at the output end of the turbine assembly. 
   The present invention as described herein provides more consistent rotary operation of a gear driven sprinkler system over a wider operating range in terms of output flow than previously achievable with currently available sprinkler systems. While the invention has been described in detail in connection with preferred embodiments known at the time, it should be readily understood that the invention is not limited to the disclosed embodiments. Rather, the invention can be modified to incorporate any number of variations, alterations, substitutions or equivalent arrangements not heretofore described, but which are commensurate with the spirit and scope of the invention. Accordingly, the invention is not limited by the foregoing description or drawings, but is only limited by the scope of the appended claims.