Patent Publication Number: US-7216817-B2

Title: Impact sprinkler drive system

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
   This application claims benefit of U.S. Provisional Application No. 60/588,532, filed Jul. 16, 2004, entitled “Impact Sprinkler Drive System,” which is incorporated herein by reference in its entirety. 

   FIELD OF THE INVENTION 
   The invention relates to an impact sprinkler and, more particularly, to an impact sprinkler with improved rotation. 
   BACKGROUND OF THE INVENTION 
   The use and operation of impact sprinklers is well-known, as are a variety of design limitations and attendant issues. An impact sprinkler rotates in a full or partial circle to distribute water therefrom. A water stream is directed through a nozzle and against a deflector located on a rotation shaft. The water is radially distributed by rotation of the rotation shaft and deflector. 
   More specifically, the rotation shaft and deflector are periodically and incrementally rotated a short distance as a result of an impact. To permit this rotation, the rotation shaft is rotatably supported by the sprinkler. The water stream outwardly-deflected from the deflector strikes an arm or spoon formed on an impact disc, also rotatably supported by the sprinkler. The water striking the spoon forces the impact disc to rotate so that the spoon is shifted out of the path of the water stream, the shifting overcoming the bias of a spring resisting such movement and contributing to the support of the impact disc. Accordingly, such shifting causes the spring to store energy. Under desirable operating conditions, the water strikes the spoon to cause the impact disc to continue rotating a short distance beyond the water stream. 
   The spring forces the impact disc into the rotation shaft to cause the rotation of the rotation shaft. The impact disc rotating from the water stream causes a build-up of energy in the spring, and eventually the spring force slows and stops the impact arm, eventually forcing the impact disc to counter-rotate and return towards the water stream. The spoon re-enters the water stream approximately coincident with or shortly before a structure on the impact disc collides with structure on the rotation shaft. This collision causes the rotation shaft to rotate a short distance in the counter-rotation direction. In this manner, the water stream direction is rotationally re-positioned. 
   The angular amount of rotation of the rotation shaft is dependent on the magnitude of the collision, or the size of impact, between the structures of the impact arm and the rotation shaft. This collision itself is dependent on a number of factors. 
   For a nozzle providing a low flow speed or volume, the water stream striking the deflector and then the spoon will effect only a short or limited amount of rotational movement by the impact disc. Accordingly, the energy stored in the spring will be low, and the counter-rotation or return of the impact disc will be a similarly short distance. This results in the spoon or impact arm having a low dwell time and re-entering the water stream before a full emission stream pattern develops, thus shortening the throw distance for the sprinkler. The dwell time is generally the amount of time during which the spoon is not aligned with the water stream, and more specifically, the time during which the water stream is free to directly distribute water to the surrounding environment without interference by the spoon. 
   Additionally, this may result in insufficient rotation of the rotation shaft. A portion of the energy stored by the spring will be lost as the spoon re-enters the water stream, while the remainder will be transferred to the rotation shaft through the collision. The collision is resisted by a certain amount of static friction between the rotation shaft and its support by the sprinkler. If the energy stored by the spring is relatively low, the collision is consequently low also. 
   In some instances, the energy may not sufficiently rotate the rotation shaft. In such a case, the spoon merely oscillates in and out of the water making little or no collision. 
   Another problem is that the rotational force for deflecting the impact disc or arm out of the water stream may be excessive. This results in over-rotation of the impact disc, which itself may cause an impact between the impact disc and the rotation shaft in the rotation direction, consequently resulting in rotation of the direction of water stream emission in a direction opposite to that desired, this effect being referred to herein as back-impact. 
   Previous designs for impact sprinklers tend to suffer from one or more of the foregoing shortcomings. More specifically, dwell-time issues resulting from low water flow may be addressed by using a light spring (i.e., a spring having a low spring constant) for the impact disc. However, this may result in the over-rotation of the impact arm (reverse impact with rotation shaft) and/or insufficient energy stored in the spring arm for causing a forward impact with the rotation shaft. Additionally, the impact disc is supported jointly by the spring and by a stationary support, and a lighter spring results in less support provided by the spring and, consequently, more weight is supported by the stationary support resulting in greater friction between the impact disc and stationary support. As a lighter spring stores less energy for a particular amount of torsional deflection, a greater portion of the return energy is expended in overcoming the friction, thereby reducing the impact energy. Alternatively, utilization of a heavy spring requires a greater force from the water stream to deflect and rotate the impact arm and shortens the dwell time such that the full water stream pattern and throw may be unable to develop. 
   To improve dwell time, the mass of the impact disc assembly may be increased. However, an increase in mass requires greater water flow to energize, that is, to provide sufficient energy for acceleration and rotation of the impact disc. An increase in impact disc mass also requires a heavier spring, as described above. Accordingly, it has been found that variation of the mass of the impact disc assembly and corresponding variation of the spring constant of the spring generally correlate to balance the impact energy received. 
   Consequently, there has been a need for an improved impact sprinkler. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a perspective view of an impact sprinkler having a housing supporting a sprinkler assembly including an impact arm and a rotation shaft; 
       FIG. 2  is an exploded view of the impact sprinkler of  FIG. 1  showing the housing, a nozzle received by the housing, and the sprinkler assembly including rotation shaft and a deflector connectable thereto, the impact disc assembly, and a support connectable to the housing for supporting the rotation shaft and the impact disc assembly; 
       FIG. 3  is a top plan view of the impact disc assembly of  FIG. 2 ; 
       FIG. 4  is a top plan view of the impact disc assembly engaged with the rotation shaft of  FIG. 2 ; 
       FIG. 5  is a bottom plan view of the impact disc assembly and rotation shaft of  FIG. 4  showing the impact arm in cross-section; 
       FIG. 6  is a side elevation view of the impact disc assembly of  FIG. 4  showing the impact disc and the impact arm; 
       FIG. 7  is a side elevation view of the impact disc and impact arm of  FIG. 6 ; 
       FIG. 8  is a side elevation view of an alternative configuration of an impact disc assembly; 
       FIG. 9  is a side elevation view of the impact disc assembly of  FIG. 8 ; 
       FIG. 10  is a bottom plan view of the impact disc assembly of  FIG. 8  showing an impact disc and an impact arm having a cover; 
       FIG. 11  is a bottom plan view of the impact disc assembly of  FIG. 9  having the cover removed; 
       FIG. 12  is a perspective view of the cover of  FIG. 10 ; 
       FIG. 13  is a side elevation view of the cover of  FIG. 12 ; 
       FIG. 14  is a bottom plan view of the impact disc assembly of  FIG. 10  and a rotation shaft having a deflector aligned with an inlet to the impact arm; 
       FIG. 15  is a top plan view of the impact disc assembly of  FIG. 14  engaged with the rotation shaft in phantom; 
       FIG. 16  is a bottom plan view of an additional alternative form of an impact disc assembly including an impact disc and an impact arm; 
       FIG. 17  is a side elevation view of the impact disc assembly of  FIG. 16 ; 
       FIG. 18  is a side elevation view of the impact disc assembly of  FIG. 16 ; 
       FIG. 19  is a fragmentary bottom plan view of the impact disc assembly of  FIG. 16  showing the impact arm in cross-section; 
       FIG. 20  is a fragmentary bottom plan view of a prior art impact disc assembly showing a prior art impact arm in cross-section; 
       FIG. 21  is a cross-sectional view of the impact arm of  FIG. 19  and a cross-sectional view of the prior art impact arm of  FIG. 20  in phantom; and 
       FIG. 22  is a top plan view of an impact arm of an alternative form of impact sprinkler. 
   

   DESCRIPTION OF THE PREFERRED EMBODIMENTS 
   Referring initially to  FIGS. 1–7 , an impact sprinkler  10  is depicted including a sprinkler assembly  50  supported by a body or housing  12 . As can be seen in  FIG. 2 , the sprinkler assembly  50  includes a rotation shaft  14  having a deflector  16 , and an impact disc assembly  20  having an impact disc  22  and an impact arm referred to herein as a spoon  24 . The impact disc assembly  20  and rotation shaft  14  are supported by the sprinkler assembly  50  to permit rotation of the impact disc assembly  20  and rotation shaft  14  relative to each other and to the housing  12 . As will be described, the impact spoon  24  and a bias member, such as a spring, are configured to maximize an impact between the impact disc assembly  20  and the rotation shaft  14  to re-align the deflector  16 , to energize the spoon  24  with a water stream to rotate the impact disc assembly  20  for a desired amount of dwell time, and to minimize the possibility of back-impact which would otherwise cause reverse re-alignment of the deflector  16 . 
   More specifically, the spoon  24  is configured to receive a water stream in a forward drive direction to shift the spoon  24  away from the water stream in a rotation direction, and is configured so that the water stream is received in a reverse drive direction to accelerate the spoon  24  in the counter-rotation direction. The spoon is configured to receive the water stream in the forward drive direction for a sufficient time period for the water stream to impart a desired amount of energy to the impact disc assembly  20  so that, on counter-rotation, the energy is utilized for forward re-alignment of the water stream upon returning to the water stream. The spoon  24  is also configured to utilize the water stream in the reverse drive direction for reverse drive to increase the energization of the impact disc assembly  20  as the spoon  24  re-enters the water stream, thereby increasing the impact between the impact disc assembly  20  and the rotation shaft  14 . Furthermore, the spoon  24  is configured to prevent over-rotation of the impact disc assembly  20 , which would otherwise cause reverse re-alignment of the water stream. The selection of the spring is coordinated with the spoon configuration to provide a desired dwell time. 
   As used herein, forward rotation of the impact disc assembly  20  refers to a rotational movement away from a water stream, and counter-rotation of the impact disc assembly  20  refers to a rotational movement towards the water stream. Re-alignment refers to a desired direction of rotational movement by the rotation shaft  14  due to impact thereagainst by the impact disc assembly  20  counter-rotating towards the water stream, and reverse re-alignment refers to an undesired direction of rotational movement by the rotation shaft  14  due to back-impact by the impact disc assembly  20  in the rotation direction away from the water stream. To highlight and clarify, it is noted that excessive forward rotation of the impact disc assembly  20  can result in reverse re-alignment of the rotation shaft  14 , though the present forms of impact disc assemblies described herein serve to prevent or restrict this event. 
   As noted previously, variation of the mass of the impact disc assembly and corresponding variation of the spring constant of the spring generally correlate to balance the impact energy. The spring and its associated spring constant, as well as rotational inertia of the impact disc assembly  20 , are principally responsible for the dwell time for the impact disc assembly  20 , and the rotational inertia of the impact disc assembly  20  generally correlates to the mass thereof. The shape of the spoon  24  determines how much energy is stored by the impact disc assembly  20  during its forward rotation. The impact energy provided by the impact disc assembly  20  striking the rotation shaft  14  is dependent on the amount of energy stored by the impact disc assembly  20  during the forward rotation, and the amount of energy imparted as a reverse drive to the impact disc assembly  20  as the spoon  24  re-enters the water stream. 
   The impact sprinkler  10  is commonly installed as part of a larger system for irrigating an area by incorporating a plurality of sprinklers  10 . The larger system includes a water source (not shown) for delivering water to each of the sprinklers  10  via distribution pipes or conduits (not shown). The sprinkler body or housing  12  connects to the distribution conduit for receiving water therethrough. More specifically, the housing  12  includes an externally threaded neck  30  threadably received within the conduit. In the present embodiments, the neck  30  defines an interior tubular passage  32  with structure for receiving and securing a nozzle  34  therein, such as by a snap fit. 
   When the neck  30  is secured to the distribution conduit, the nozzle  34  is positioned within the conduit and in the flow of water. The nozzle  34  is selected to provide desired flow characteristics based on expected water source conditions and includes an inlet (not shown) and an outlet  36  for directing water in an upward stream. It should be noted that, alternatively, the nozzle  34  may be secured and rotate with the rotation shaft  14 , in which case a pressurized dynamic seal between the neck  30  and rotation shaft  14  is preferably present. 
   As depicted, the housing  12  includes a bottom plate  40  extending laterally from the neck  30  and protective ribs  42  which extend laterally and then vertically from the neck  30  and the bottom plate  40 . At an uppermost portion, the ribs  42  are connected to a mount ring  44 . 
   The mount ring  44  and sprinkler assembly  50  include structure cooperating to secure the sprinkler assembly  50  to the housing  12 . The sprinkler assembly  50  includes a support  52  having a generally cylindrical outer surface  54  having a lower edge  56 . The mount ring  44  includes a generally cylindrical inner surface  60  on which is formed support posts  62  extending radially inward. The sprinkler assembly  50  is received within the mount ring  44  so that the lower edge  56  abuts and is supported by the support posts  62 . Additionally, the outer surface  54  includes assembly shoulders  66  extending radially outward therefrom, and the mount ring  44  includes retainers  68  extending radially inwardly. With the sprinkler assembly  50  received within the mount ring  44 , the assembly shoulders  66  align below the retainers  68 . The sprinkler assembly  50  is then rotated relative to the mount ring  44  so that the assembly shoulders  66  are positioned below and against the retainers  68 . The assembly shoulders  66  include an upward portion  70  forming a stop against which the retainers  68  are positioned when the sprinkler assembly  50  is secured therein. 
   Rotating the sprinkler assembly  50  relative to the mount ring  44  releasably secures the sprinkler assembly  50  therein. More specifically, the outer surface  54  of the support  52  includes ramps  72  which cooperate with mount ring ramps  74  such that rotating the sprinkler assembly  50  cams the ramps  72 ,  74  against each other. Coincident with or immediately prior to the retainers  68  contacting the stops  70 , the ramps  72  clear the ramps  74 . Each of the ramps  72 ,  74  have respective stop surfaces  76 ,  78  generally radially aligned such that, when the ramps  72  are rotated clear of the ramps  74 , the stop surfaces  76 ,  78  are in a confronting relationship to secure the sprinkler assembly  50  within the mount ring  44  by restricting or preventing the sprinkler assembly  50  from rotating in an opposite direction. 
   The mount ring  44  secures the support  52  so that the housing  12  supports the sprinkler assembly  50 . As noted above, the sprinkler assembly  50  includes the impact disc assembly  20 , and the rotation shaft  14 , both of which may rotate relative to each other and to the support  52  secured with the housing  12 . During operation, the nozzle  34  secured with the housing  12  directs incoming water flow against the deflector  16  located on the rotation shaft  14 , and the water is then distributed from the deflector  16 . More specifically, the rotation shaft  14  has a lower end  80  located proximate the nozzle outlet  36 , and the deflector  16  is secured to the lower end  80  such that the water stream from the outlet  36  flows into and against the deflector  16 . 
   In simple terms, the water stream from the deflector  16  effects the operation of the sprinkler  10 . The deflector  16  and its rotation shaft  14  in a particular position direct water in a radial direction from the sprinkler  10 . With the impact disc assembly  20  aligned with the water stream from the deflector  16 , water flows into an inlet  100  of the impact spoon  24 . After a short period of time in which the impact disc assembly  20  is energized by the water stream, the impact disc assembly  20  rotates out of the water stream, thereby storing energy in a bias member or spring (not shown). After a period of rotation, the impact disc assembly  20  slows, stops, and counter-rotates to return towards the water stream. 
   The period of rotation and counter-rotation by the impact disc assembly  20  is known as the dwell time, and during this dwell time the water stream emits from the deflector  16  in a radial direction to irrigate or distribute water therefrom. Initially, the water is distributed a short distance, and subsequently is distributed a greater distance as the spoon moves out of the water stream and the water stream progresses towards a maximum throw distance. The amount of dwell time necessary for the water stream to form a pattern for the maximum throw distance depends on a variety water flow characteristics including pressure and volume. 
   The rotation shaft  14  has an upstanding arm  90  received within a partially circular cavity  92  ( FIG. 3 ) formed in the impact disc assembly  20  and defined by a bridge  94  spanning from a hub  96  to a disc body  98 . The arm  90  travels along the cavity  92  during the rotation and counter-rotation of the impact disc assembly  20  relative to the rotation shaft  14 . When the disc assembly  20  returns into the water stream, the bridge  94  strikes the arm  90 , and the kinetic energy of the disc assembly  20  is partially transferred to the rotation shaft  14 . This effects an incremental or discrete rotational movement so that the rotation shaft  14  and deflector  16  are re-aligned to distribute in a new radial direction. 
   As described above, the spoon  24  receives a combination of forward drive energy and reverse drive energy from the water stream. Once the spoon  24  re-enters the water stream, the water begins flowing through the spoon  24 . As the spoon inlet  100  initially re-enters the water stream, a portion of the spoon  24  is struck by the water to provide additional energy to drive the impact disc assembly  20  into the impact with the rotation shaft  14 . The sum of the forces of each finite portion of the water stream in the spoon  24  provides reverse drive to the spoon  24  and impact disc assembly  20  until the water stream contacts an upstream discharge portion, described herein and referred to as an exit flow portion  168  ( FIG. 5 ). While the water striking the reverse drive portions of the spoon  24  continues to provide reverse drive to the spoon  24 , the water striking the other portions and the exit portion  168  provide forward drive. The reverse drive is not immediately counteracted by the forward drive so that it may be at some point after the water strikes the exit flow portion  168  that the sum of the forces from the water stream provides a forward drive or rotation to the spoon  24 . For a particular nozzle, the speed of the water into the spoon  24  is generally dependent on the nozzle pressure. For a low pressure water stream having a low velocity or speed, the water stream may not contact the exit flow portion  168  until a short period after the impact occurs. Conversely, a high pressure water stream has a high velocity or speed, and the water stream may contact the exit flow portion  168  prior to the impact. 
   As will be discussed in greater detail below, the spoon  24  is configured to increase the reverse drive effect on the impact disc assembly  20  during re-entry to the water stream. The impact disc assembly  20  generally does not begin attempting to shift from the water stream until the water flowing therethrough strikes the downstream exit flow portion  168 . The length of the spoon  24  allows a time delay for water to strike the exit flow portion  168 . One benefit of this time delay is that water does not strike the exit flow portion  168  as quickly, preferably not until after the impact occurs, thereby allowing the reverse drive to increase the impact and lessens the forward drive effects from water flowing through the spoon  24  that would otherwise reduce the impact energy. Another benefit is that a greater amount of water, or a greater segment of the water stream, is received by the spoon  24  so that, once the spoon  24  does shift, the increased amount of water continues to energize the impact disc assembly  20  until the water has exited through the exit flow portion  168 . 
   The configuration of the impact spoon  24  facilitates the above-described operation. More specifically, the impact spoon  24  is configured to maximize the energy imparted by the water stream passing therethrough. For comparison purposes and with reference to  FIG. 20 , a configuration for a prior art impact spoon  110  mounted or formed on an impact disc  111  is depicted. As shown, the spoon  110  includes a first flow portion  112  and a second flow portion  114 . The water stream is directed from a deflector, such as the above-described deflector  16 , in the direction of arrow I for impacting the first flow portion  112 . The first flow portion  112  has an inner surface  115  including an inlet section  116 , a relatively straight section  118 , and an arcuate section  120  including an outlet section  122 . 
   The spoon  110  includes a lead-in surface  124  which is struck by the water directed in the direction of arrow M. Though the lead-in surface  124  provides a slight reverse drive, in a direction Δ, the bluntness of the lead-in surface  124  with respect to the water stream in the direction M causes a loss of energy for the water contacting there. Consequently, when the spoon  110  counter-rotates so that the water stream is directed into the spoon  110 , the water stream is slower, and the amount of available reverse drive is reduced. 
   Additionally, the lead-in surface  124  reduces the forward drive energy for the spoon  110 . As the spoon  110  rotates in the rotation direction and prior to the spoon  110  passing fully away from the water stream, the lead-in surface  124  again passes through the water stream. By doing so, a reverse-drive force is applied by the water stream against the lead-in surface  124 , thereby decreasing the forward drive of the spoon  110 . 
   As noted above, the straight section  118  provides a desirable counter-rotation driving force from the water stream. As the spoon  110  returns to the water stream immediately prior to impacting with the rotation shaft  14 , water striking the straight section  118  provides additional energization to the returning spoon  110  for assisting in delivering impact energy against the rotation shaft  14 . Moreover, the straight section  118  being angled or contoured in such a manner is generally beneficial as the radially directed water stream is necessarily re-directed through the spoon  110 . Toward this end, the shape of the straight section  118 , as well as a portion of the arcuate section  120 , which tend to direct the spoon  110  in the counter-rotation direction Φ, are designed to avoid excessive turbulence and head loss (wasted energy in the form of heat) while re-directing the water stream through the spoon  110 . 
   The arcuate section  120  generally spans angle α and has a radius of curvature of R 1 . As can be seen, the outlet section  122  directs the water somewhat inwardly, in the direction of arrow D 1 . The water then transitions into and strikes an inner surface  126  of the second flow portion  114 . 
   The inner surface  126  includes a generally straight section  130 , a second arcuate section  132 , and an outlet section  134 , each being angled or contoured so that water striking thereagainst produces forward rotation drive. The generally straight section  130  is angled so that water received along the inner surface  126  follows the direction of arrow D 2 . As can be seen, water exiting the outlet section  122  of the first flow portion  112  and following the direction of arrow D 1  is redirected outward by the straight section  130 . 
   The water passes from the straight section  130  to the second arcuate section  132 . The second arcuate section  132  redirects the water, thereby deriving energy from the water, such that water is then emitted from the spoon  110  in the direction of arrow D 3 . The second arcuate section  132  has a radius of curvature of R 2  and spans an angle β. 
   In the present form, angle α is 157 degrees and the radius of curvature R 1  is 0.260 inches. As water flows along the straight section  130 , the average length of travel is represented by length L and is approximately 0.50 inches. The radius of curvatue R 2  of the second arcuate section  132  is 0.250 inches, and the angle β is approximately 150 degrees. Accordingly, the average travel distance for water through the spoon  110  is approximately 2.41 inches. The impact disc  111  has a center of rotation  140  and a radius R 3  to a perimeter edge or surface  142  formed thereon. The center of rotation  140  is approximately coincident with the origin point of the water stream from the deflector, though it may be offset somewhat depending on the configuration of the deflector. The radius R 3  is approximately 1.14 inches. The first flow portion  112  receives water at an initial point  119 , and the second flow portion  114  includes a point  121  which is the point of greatest angular distance from the initial point  119 , these points providing an angle δ ( FIG. 20 ). This angle δ is approximately 85 degrees. 
   As stated above, the impact spoon  24  is configured for the water to follow a longer path or travel distance through the spoon  24  therefrom than the path or travel distance through the spoon  110  of the prior art. Additionally, the force acting on the spoon  24  produces a torque dependent on the distance from a center of rotation  150  ( FIG. 3 ) of the impact disc assembly  20 , and the spoon  24  is configured such that a greater portion of the spoon  24  is positioned at a greater distance from the center of rotation  150  than is present in the prior art spoon  110 . 
   With reference to  FIGS. 3–7 , the spoon  24  and impact disc  22  are depicted. In general, the impact disc  22  is substantially identical in mass, size including radius, and design to the prior art impact disc  111 . 
   The spoon  24  includes an inner surface  152  along which the water stream travels through the spoon  24 . The spoon  24  generally includes a top wall  160 , a bottom wall  162 , an outer wall  164  having an inner surface  166 , and an exit flow portion  168  having an inner surface  170  ( FIG. 6 ) for turning the water for emission, as well as deriving energy from the water stream. The spoon  24  includes an inlet section  100  ( FIGS. 5 and 7 ) formed by the walls  160 ,  162 , and  164 . As can be seen in  FIG. 7 , the lead-in surface  124  of the prior art spoon  110  has been eliminated to reduce or eliminate the above-described energy and head losses. The inlet section  100  includes a ramp surface  171  ( FIG. 7 ) assisting in directing the radially directed water from the deflector  16  into and along the spoon  24 . The inlet section  100  also includes a reverse-drive section  172  formed on the inner surface  166  of the outer wall  164  providing energy for counter-rotation of the impact disc assembly  20  when the spoon  24  re-enters the water stream, immediately prior to impact with the rotation shaft  14 . 
   The reverse-drive section  172  transitions smoothly to a forward drive section  174 , also formed on the inner surface  166 . As can be seen in  FIGS. 3 and 5 , the forward drive section  174  is positioned at a varying distance R 4  from the center of rotation  150 , but in any event generally greater than a radius R 5  of the impact disc  22  itself. As the water flows along the forward drive section  174 , a force from the water acts upon the spoon  24  resulting from the cohesion forces of the water molecules, the adhesion forces between the water and the inner surface  166 , and the kinetic energy of the water. As the water is acting at a distance, that of distance R 4 , from the center of rotation  150 , the force from the water produces a torque, thereby imparting forward drive energy to the impact disc assembly  20  and spring. 
   As can be seen in  FIG. 20  for the prior art spoon  110 , a portion  144  of the first flow portion  112  and a portion  146  of the second flow portion  114  are positioned respective distances from the center of rotation  140 , though neither is positioned a distance much greater than the radius R 3 , the outer radius of the impact disc being 1.14 inches. Additionally, the force by the water flowing against the inner surfaces  115  and  126  of the first and second flow portions  112 ,  114 , respectively, of the prior art spoon  110  produces a torque in proportion to the finite distances along the inner surfaces  115 ,  126 , of which only small portions of the prior art spoon  110  are positioned at the maximum distances of the portions  144 ,  146 . As also can be seen in  FIG. 20 , the water in the prior art spoon  110  flows through a total angle Θ, approximately 75 degrees, prior to entering the second arcuate section  132  in which the water is turned for emission. 
   With reference to  FIG. 5 , the spoon  24  allows water to travel through an angle Σ 1  prior to entering the exit flow portion  168 . This angle Σ 1  is preferably approximately 90 degrees, which is 15 degrees greater than the angle Θ for the prior art spoon  110 . Combined with the torque due to the distance of the inner surface  166  from the center of rotation  150 , it is clear that the spoon  24  produces a greater torque than the spoon  110 . In addition, and as previously stated, the angle δ for the prior art spoon  110  between its leading or initial point  119  of water contact and the point  121  of its maximum angular distance on the second flow portion  114  is approximately 85 degrees. In comparison, the spoon  24  has comparable angles Σ 2  and Σ 3  corresponding to different portions of the exit flow portion  168 , Σ 2  being preferably approximately 100 degrees and Σ 3  being preferably approximately 105 degrees. 
   As is depicted in  FIGS. 6 and 7 , it can be seen that the spoon  24  angles downward from the inlet section  100  and prior to reaching the exit flow portion  168 . The downward angle increases the length of the spoon  24  within an angular extent Ψ of the spoon  24 , between leading end  202  and trailing end  204 , shown in  FIG. 3 . The exit flow portion  168  then makes a turn, approximately 90 degrees, for emitting the water with an upward trajectory which assists in utilizing the water therethrough for irrigation or distribution purposes and reduces or eliminates the possibility that the water is merely deposited only relatively close to the sprinkler  10 . 
   While the prior art spoon  110  makes such a turn (slightly less than 180 degrees) in its second arcuate section  132 , the exit flow portion  168  makes the turn in a plane that is orthogonal to a plane of flow through the forward drive section  174 , while the flow of water through the second arcuate section  132  is in generally the same plane as the water through the balance of the spoon  110 . In this manner, the angle Σ 1  may be greater than the angle Θ, as described above, and an exit direction D 4  of water therefrom remains generally parallel to a direction D 5  as stream emits directly from the deflector  16 . The directions D 4  and D 5  are approximately parallel, and are separated by preferably approximately 1.25″. 
   The exit stream from the exit flow portion  168  produces an additional torque that is fully utilized to produce stored energy for the impact disc assembly  20 . The direction D 4  for the water stream from the exit flow portion  168  is positioned outside of the impact disc  22 . As can be seen in  FIG. 20 , the prior art spoon  110  produces an exit stream along the direction D 3 . The direction D 3  is positioned at a much lower distance from the center of rotation  140  of the disc  111  and the direction D 3  is positioned from the center of rotation  150  of the disc  22 . As these distances produce respective torque arms, the torque for equal water streams is much greater in the spoon  24  having the exit flow portion  168  than for the prior art spoon  110 . 
   The exit flow portion  168  turning the water in a second plane has an additional benefit. As the water transitions from the forward drive section  174  to the exit flow portion  168 , the water tends to be outboard from the center of rotation  150  and flowing along the bottom wall  162 . Were the exit flow portion  168  merely rotated from the orientation depicted to turn in the same plane, the water would collide in an orthogonal direction to the inner surface  170  of the exit flow portion  168 . While it may appear that this would impart a great amount of energy thereto, the negative pressure on the flow of water more than counteracts this and restricts the flow of water through the spoon  24 , and the collision causes a loss of pressure (energy lost due to heat). An entrance portion  180  of the exit flow portion  168  angles upward from the bottom wall  162 , as can be seen in  FIGS. 5 and 6 . In both the spoon  24  and the prior art spoon  110 , the radius of curvature for the exit flow portion  168  and the second arcuate section  132  should be large enough to allow the smooth transition. As can be seen for the prior art spoon  110  of  FIG. 20 , this transition is made smooth by the exit section  122  directing the water inwardly. As the exit flow portion  168  is positioned at a greater radial distance, the turn in the second plane is possible ( FIG. 2 ), and the radius of the inner surface  170  is greater than the radius R 2  for the second arcuate section  132  of the prior art spoon  110 . As a portion of the exit flow portion  168  is positioned at a distance greater than outside the radius itself R 5  ( FIG. 50 , water striking the inner surface  170  has a greater torque. 
   During operation of the sprinkler  10 , it is desired to maximize the energy derived by the spoon  24  from the water stream and maximize the dwell time, balanced against minimizing the likelihood of a back-impact due to over-rotation of the impact disc assembly  20 . The described configuration of the spoon  24  provides substantially more impact energy than does the prior art spoon  110 , while doing so with a similarly-sized, in an angular sweep, structure. As described, the inner surface  166  along which the water pulls is positioned at the distance R 4  from the center of rotation  150  greater than the distance for comparable surfaces for the prior art spoon  110  such that greater torque is produce. 
   As was noted earlier, it is beneficial that the angle Σ 1  of the spoon  24  is greater than the angle Θ for the prior art spoon  24 . Though it may seem incongruous, it is considered beneficial to utilize the exit flow portion  168  to reduce the length of the spoon  24 . Such is resolved by first noting that incorporation of the exit flow portion  168  creates extended travel distance by water flowing through the spoon  24 , yet also increases the energy that can be derived from the water stream, and by secondly noting that utilization of the exit flow portion  168  while not substantially increasing the angular sweep of the spoon  24  allows similar forward rotation of the spoon  24  and impact disc  22 , as will be discussed below. 
   The impact disc assembly  20  is constructed to minimize the likelihood of back-impact, balanced against providing the greatest travel distance by the water within the spoon  24  and, specifically, the greatest distance prior to the water striking the exit flow portion  168 . Described above, over-rotation and back-impact may result in the bridge  94  contacting the upstanding arm  90  of the rotation shaft  14  in the rotation direction, resulting in reverse re-alignment of the rotation shaft  14  and deflector  16 . As can be seen in  FIG. 4 , the bridge  94  has a first impact surface  190  which strikes against a first reaction surface  196  of the upstanding arm  90  for the desirable forward re-alignment of the rotation shaft  14 . The bridge  94  also has a second impact surface  192  which may strike a second surface  198  on the upstanding arm  90 , to cause the back-impact. To minimize this likelihood, the bridge  94  is constructed so that the surfaces  190 ,  192  combined with the surfaces  196 ,  198  form a relatively small angular sweep Ω. An indicia  206  indicates the direction and position from which the water stream is discharged by the deflector  16 , and the inlet section  100  (see  FIG. 5 ) is aligned with the indicia  206 . 
   As stated, it is also desired to have the greatest travel distance by the water within the spoon  24 . More specifically, the time delay before the water strikes the exit flow portion  168  correlates to the travel distance by the water within the spoon  24 . The impact disc assembly  20  begins shifting away from the water stream shortly after the water strikes the exit flow portion  168 . It is desired to provide a time delay sufficient to allow the water stream to act upon the reverse drive portions such as the straight section  118  to maximize the impact energy between the impact drive assembly  20  and the rotation shaft  14 , which occurs prior to the impact disc assembly  20  shifting away from the water stream. As described herein, the configuration of the spoon  24  provides additional length than the prior art spoon  110 , thus also providing a greater time delay to improve the impact energy. 
   As noted above, the impact disc  22  with the exception of the spoon  24  is generally the same as the prior art impact disc  111  in terms of mass, size, and design. Also, the spring utilized as the bias member to store the energy from the forward rotation of the impact disc assembly  20  principally determines the dwell time, and the shape of the spoon  24  principally determines how much energy is stored in the spring. The greater the spring constant, with all other values held constant, the shorter the dwell time. For the prior art impact disc  111  and spoon  110 , the spring has a spring constant of approximately 1.2×10 −4  inch-pounds/degree of rotation, and is fixed with a preload of 150 degrees rotation. As the spoon  24  derives more reverse drive energy from the water stream at it re-enters the water stream, the impact disc assembly  20  is able to operate in water flows with lower energy or, more precisely, a lower pressure and flow rate. This also allows the spring constant to be reduced, preferably to approximately 6.5×10 −5  inch-pounds/degree of rotation, with a preload of approximately 190 degrees. Thus, sprinkler  10  is able to operate at low pressures, in the range of 10–15 psi, while the prior art sprinkler tends to behave erratically or undesirably below approximately 20 psi when using low-flow rated nozzles. 
   The sprinkler  10  operates at a faster rotational rate than those of the prior art. The spoon  24  has a higher energy imparted thereto in the reverse drive direction during re-entry by the spoon  24  into the water stream and has a greater time delay before the water strikes the exit flow portion  168  so that the water stream is able to maximize the energization to the reverse drive portions, such as the straight section  118 , in the spoon  24 . Together, these factors enable the spoon  24  to have a higher impact between the bridge  94  and upstanding arm  90  of the rotation shaft  14 . Therefore, each impact therebetween causes a greater rotational re-alignment for the deflector  16 . By way of example, a prior art sprinkler operating at 30 psi makes a full revolution in approximately 80 seconds. The sprinkler  10  described herein makes a similar full revolution in approximately 30 seconds. 
   The operation of the sprinkler  10  benefits by making the full revolution in the shorter time period of approximately 30 seconds. During operation in the field, it is not uncommon for bugs, dirt, or other particulate material to intrude between components of the sprinkler  10 . Each of these intrusions retards the rotation of the sprinkler, and may cause premature wear. In any event, a number of the components will experience wear over time and usage. The faster sprinkler  10  has greater power for rotating the rotation shaft  14  and deflector  16 . This power may be utilized to overcome the impediments resulting from intrusive materials, friction, and worn surfaces. Another benefit is that the additional power created results in the sprinkler  10  operating properly at a lower flow pressure. Consequently, smaller nozzles may be used with the sprinkler  10  that would typically result in stalling by the commonly known sprinklers of the prior art if used therewith. 
   As noted, the impact disc assembly  20  and the prior art impact disc  111  generally do not begin shifting in the rotation direction Φ until the water stream has passed into and struck the exit flow portion  168 . This allows the time delay for the spoon  24  to receive a greater amount of the water stream, a greater water stream segment, so that, once the spoon  24  does shift, the water continues to energize the impact disc assembly  20  until the water has exited through the exit flow portion  168 . To some degree, energy is balanced by greater distance traveled so that the resultant energy imparted to the impact disc assembly  20  is generally similar to that of the prior art disc  111  and spoon  110 . 
   Referring now to  FIGS. 8–15 , an alternative form of an impact disc assembly  250  having an impact disc  252  and impact arm or spoon  254  is illustrated. In a manner similar to the impact spoon  24 , the spoon  254  is configured to increase the length of travel by the water therethrough. The increased length allows for a greater time delay before the water begins forcing the impact disc assembly  250  away from the water stream, and the greater time delay allows a greater amount of reverse drive to be exerted on the spoon  254  as the spoon  254  re-enters the water stream. This greater amount of reverse drive increases the impact energy, thus increasing the forward re-alignment of a deflector  316  and a rotation shaft  314 , as will be described herein. Furthermore, the spoon  254  provides for back-impact protection. 
   The impact disc assembly  250  shifts in the forward rotation direction Φ as the impact spoon  254  moves away from the water stream, and shifts in the counter-rotation direction Δ as the spoon  254  moves towards and into the water stream. The impact disc  252  is substantially identical to the prior art impact disc  111 , as well as to the impact disc  22  as described above, in terms of mass, size, and design, and the differences will be recognized in the following description of the impact disc  252  and the spoon  254  of the impact disc assembly  250 . The impact disc assembly  250  rotates around a center of rotation  251 . 
   The spoon  254  is defined by the impact disc  252  and a cover  256 . More specifically, a portion  258  of the spoon  254  is formed on a bottom side  260  of a body  262  of the impact disc  252  (see  FIG. 11 ), and the cover  256  ( FIGS. 12 and 13 ) is secured to the portion  258  to define a passageway  264  through the spoon  254 . 
   The spoon  254  includes an inlet  270  ( FIG. 8 ) for receiving water distributed radially from a deflector  316  in a direction D 10  ( FIG. 14 ). The water then passes through the spoon  254 , providing drive energy to the impact disc assembly  250 , and exits through an outlet  272  ( FIG. 9 ) in a direction D 11  ( FIGS. 10 and 14 ). As can be seen in  FIG. 14 , the direction D 10  for the water from the deflector  316  is non-parallel to the water stream direction D 11  from the outlet  272 . 
   Referring to  FIGS. 10–13 , the spoon  254  and cover  256  thereof are depicted as being somewhat S-shaped to define the S-shaped passageway  264 . The portion  258  formed on the impact disc body  262  includes a first flow portion  280  and a second flow portion  282 . 
   The water distributed from the deflector  316  enters at the inlet  270  and contacts the first flow portion  280 . More specifically, the first flow portion  280  has an inner surface  290  formed on a lead-in section  292 , a relatively straight inlet section  294 , an arcuate elbow section  296 , an arcuate perimeter section  298 , and a return section  300 , each of which will be discussed herein and is best viewed in  FIG. 11 . 
   The lead-in section  292  behaves in a generally similar to the lead-in section  116  of the prior art spoon  110 , described above. As discussed, it is preferred that a forward leading surface  302  formed on the spoon  254  is positioned as to form a sharp point, such as shown between the leading end  202  and the outer wall inner surface  166  for the impact spoon  24  in  FIG. 5 , to minimize head and energy losses. 
   The straight inlet section  294  is formed adjacent the lead-in section surface  292 . The inlet section  294  is angled into the direction of the water stream so that, as the water stream strikes the inlet section  294 , a counter-rotation force in the direction Δ is imparted to the impact spoon  254  and disc  252  by the water, thus providing reverse drive to the impact disc assembly  250 . The inlet section  294  is angled from a radius R 10  by angle υ, preferably approximately 12 degrees. 
   Consequently, as the impact disc assembly  250  counter-rotates to strike a rotation shaft  314  ( FIGS. 14 and 15 ), the spoon  254  re-enters the water stream, and the reverse drive provides additional energization to increase an impact force between the impact disc assembly  250  and the rotation shaft  314 . 
   The impact disc  254  includes the body  262  and a hub  302  connected to the body  262  by a bridge  304 . With reference to  FIG. 15 , the bridge  304  has an impact surface  306  for desirably striking a reaction surface  310  formed on an upstanding portion  312  of the rotation shaft  314 . The bridge  304  further has a second surface  308  that, due to the construction and design of the impact disc assembly  250 , advantageously does not contact a shaft surface  318 . As the impact disc assembly  250  returns to the water stream, the bridge impact surface  306  strikes the reaction surface  310  on the upstanding portion  312  to incrementally forward re-align the rotation shaft  314  in the forward direction Φ so that the water stream emitted directly to the environment from the deflector  316  is also incrementally re-aligned forwardly. 
   Referring now to  FIG. 15 , the impact disc assembly  250  is constructed to minimize the likelihood of back-impact. The spoon  254  in particular is designed so that the second flow portion  282  with the water stream restricts forward rotation and prevents back-impact. Described above, over-rotation and back-impact may result in the bridge  304  contacting the upstanding portion  312  of the rotation shaft  314  in the rotation direction, resulting in reverse re-alignment of the rotation shaft  314  and deflector  316 . As noted above, bridge  304  has the bridge impact surface  306  and the second surface  308 . The bridge  304  is constructed so that the surfaces  306 ,  308  combined with rotation shaft surfaces  310 ,  318  form a relatively small angular sweep μ. This serves to provide the impact disc assembly  250  with a rotational sweep available prior to any occurrence of the back-impact. It should be noted that structural limitations, such as strength, rigidity, and costs of various materials tend to require a minimal size for both the upstanding portion  312  and the bridge  304 . Preferably, the angle μ is approximately 125 degrees. 
   Furthermore, the spoon  254  itself provides a protection against the over-rotation. As can be seen in  FIGS. 10 and 15 , the spoon  254  has a leading end  319  and a trailing end  321  forming an angular sweep τ. The angle τ preferably is approximately 175 degrees. Water is discharged from the deflector  316  into the inlet  270  along the direction D 10 . The trailing end  321  of the spoon  254  is offset from the second shaft surface  318  by an angle γ, which preferably is approximately 173 degrees. The impact disc assembly  250  would preferably need to rotate approximately 235 degrees before the bridge second surface  308  comes into contact with the second shaft surface  318 , which would cause the undesirable back-impact and reverse re-alignment. The direction D 10  of discharge is positioned with an angular offset η of preferably 17 degrees from the leading end  319  and the trailing end  321  needs to rotate preferably approximately 202 degrees before aligning with the water stream emitting from the deflector  316  and aligned with the direction D 10  of emission. Therefore, the trailing end  321  will come into alignment with the water stream before the second surface  308  of the bridge  304  comes into contact with the second surface  318 . In the event this amount of forward rotation occurs by the impact disc assembly  250 , the water stream will strike the trailing end  321  to assist in slowing, stopping, and then returning the impact disc assembly  250  in the counter-rotation direction. Consequently, the impact spoon  254  itself serves to retard or prevent the back-impact from occurring. 
   Referring again to  FIG. 11 , the inlet section  294  transitions to the arcuate elbow section  296  having a radius of curvature R 11 , which is contoured to derive reverse-drive energy, applying force in the direction Δ, from the water stream in the same manner as the inlet section  294 . The elbow section  296  curves to direct the water in a direction that preferably is generally 90 degrees from the path of the incoming water stream from the deflector  316 , and to direct the water into the arcuate perimeter section  298 . The radius of curvature R 11  for the arcuate perimeter section  298  is preferably approximately 0.250 inches. The reverse-drive energy of the elbow section  296  increases the impact energy and, consequently, promotes a greater rotation upon impact between the impact disc assembly  250  and the rotation shaft  314 , as has been discussed. 
   The arcuate perimeter section  298  is positioned in close proximity to an outer edge  320  of the body  262 . The perimeter section  298  generally follows the outer edge  320  at a uniform distance D 11  from the center of rotation  251 . As the water flows along the perimeter section  298 , the water exerts a force against the inner surface  290 . Additionally, due to the distance D 11  from the center of rotation  251 , the force of the water exerts a torque, thereby imparting an amount of energy in the forward rotation direction Φ to the impact disc assembly  250 . The perimeter section  298  has a preferred angular sweep of approximately 90 degrees such that its angular length preferably is approximately 1.50 inches. 
   Once the water has passed through the perimeter section  298 , the water strikes the return section  300 . The return section  300  is reverse-angled and has a curved portion  301  with a radius of curvature R 12  preferably approximately 0.400 inches, and a second relatively straight portion  303  so that the length of the return section  300  is preferably approximately 0.49 inches. The water striking the return section  300  is angled inwardly and causes a rotational force to be exerted on the spoon surface  290 . As can be seen, the force of the water striking the return section  300  does so at a varying distance D 12  from the center of rotation  251  to produce a torque, and the distance D 12  is generally equal to or greater than a varying distance D 6  for the similar outlet section  122  of the prior art disc  110  ( FIG. 20 ). The water stream then crosses the passageway  264  and transitions into the second flow portion  282 . 
   The second flow portion  282  includes a lead wall portion  324  that transitions into an arcuate exit wall portion  326  for emitting the water stream, thus imparting a rotational force in the rotation direction Φ on the disc assembly  250 . The lead wall portion  324  is preferably curved outwardly from the center  251  of the impact disc assembly  252  and has a preferred radius of curvature of approximately 0.730 inches, while the radius of curvature of the exit wall portion  326  is preferably approximately 0.278 inches. The exit wall portion  326  preferably spans generally 180 degrees so that the water stream emitted from the spoon  254  is approximately tangential to the impact disc assembly  250  and so that the water stream is able to apply the greatest force and torque in the rotation direction Φ. It should be noted that transitions between the wall sections are preferably smoothly radiused such that head loss or fluid flow pressure loss is minimized, and disruption of the flow stream is minimized. 
   As discussed above, the prior art spoon  110  has included angle δ between its initial point  119  of water contact and the maximum angularly displaced point  121 , and the angle δ is approximately 85 degrees. In comparison, the spoon  254  has a comparable angle ρ ( FIG. 11 ) that is preferably approximately 160 degrees. 
   Similar to both the impact disc assembly  20  and the prior art impact disc  111 , the impact disc assembly  250  generally does not begin rotating in the rotation direction Φ until after the water stream passes from the first flow portion  280  through the channel  264  and strikes the exit wall portion  326 . Utilization of the spoon inner surface  290  as described and, in particular, the perimeter section  298  allows a delay in the time before the water stream begins to strike the exit wall portion  326 . The time delay allows the water stream to provide the above-described reverse drive energy to portions of the spoon  254 , which further energizes the spoon  254  and impact disc assembly  250  towards the rotation shaft  314 , prior to the water striking the exit wall portion  326 . This maximizes the amount of impact energy and, thus, maximizes the forward re-alignment of the rotation shaft  314  and the deflector  316 . 
   Referring now to  FIGS. 12 and 13 , the cover  256  is illustrated in further detail. As water flows through the passageway  264 , gravity acts upon the water. Accordingly, the cover  256  is provided to retain the water therein. In the present form, the spoon  254  is formed by molding the portion  258  on the body  262 , and then the cover  256  is separately formed and attached to the portion  258  to jointly form the spoon  254  and to define the passageway  264 . This construction for the spoon  254  and the impact disc  252  is to simplify the molding process, though other constructions are available such as a single mold construction for the spoon  254 , either along with the impact disc  252  or as a separate component to be joined to the body bottom surface  260 . 
   The cover  256  can be seen as generally Shaped having top surface  340  formed on an inlet section  330 , a body section  332 , a reversing section  334 , and a discharge section  336 , each of which is discussed herein. The top surface  340  includes a first ramp portion  342  on the inlet section  330  angling upward in the direction of entrance by the water into the spoon  254  at the inlet  270  (see  FIG. 8 ). The first ramp portion  342  assists in collecting the water stream from the deflector  316 , which may be a combination of a single laminar flow and an erratic spray, and in channeling the water stream through the passageway  264 , in the same manner as the ramp surface  170  of the impact disc assembly  20 . The inlet section  330  is positioned within and against the lead-in section  292 , the inlet section  294 , and the elbow section  296  of the first flow portion  280 . 
   The first ramp portion  342  leads to the body section  332  which generally corresponds in shape with and is positioned within and against the perimeter section  298  of the first flow portion  280 , discussed above. The top surface  340  is generally horizontal over the body section, as well as over the reversing section  334 . 
   The reversing section  334  generally corresponds to and is positioned within and against the return section  300  and most of the second flow portion  282 . In addition, the reversing section  334  includes a bridge portion  346  spanning across the passageway  264  between the first and second flow portions  280 ,  282 , as can be seen in  FIG. 14 . 
   The top surface  340  has a second ramp portion  344  formed on the discharge section  336  and angling upwardly. The discharge section  336  is also positioned within and against the second flow portion  282  proximate to the outlet  272 . The upward angle of the second ramp portion  344  provides an upward trajectory for the water stream emitted from the spoon  254 . 
   As the majority of the path through the passageway  264  for the water flowing through the spoon  254  is generally horizontal, distribution uniformity of the water stream is improved. The second ramp surface  344  provides a significant throw distance for the water exiting the spoon  254 , contributing to the ability of this portion of the water stream to be distributed for watering purposes and not simply dispersed unduly close to the sprinkler  10 . It should be noted, however, that the horizontal movement is not necessary for the operation of the impact disc assembly  250 . 
   The cover  256  further includes first and second walls  350 ,  352  for securement with the first and second flow portions  280 ,  282  of the spoon  254 . More specifically, the first wall  350  is positioned on a top edge  354  of the first flow portion  280 , while the second wall  352  is positioned on a top edge  356  of the second flow portion  282 . The cover  256  generally seals with the first and second flow portions  280 ,  282  to restrict or prevent water from flowing between the cover  256  and the top edges  354 ,  356 . 
   Referring now to  FIGS. 16–19 , a further form of an impact disc assembly  400  having an impact disc  402  and impact spoon  404  is illustrated. With further reference to  FIG. 21 , it can be seen that the spoon  404  has a longer length than the prior art spoon  110 . The longer length provides a greater time delay from when the spoon  404  re-enters the water stream to the time the water stream causes the spoon  404  to begin rotating away from and out of the water stream. As described for the spoons  24  and  254 , this time delay allows the water stream to provide reverse drive energy to portions of the spoon  404 , thereby providing additional energization to increase an impact between the impact disc assembly  400  and a rotation shaft  520 . The longer length also enables the spoon  404  to receive a greater amount of water prior to shifting from the water stream, this greater amount of water energizing the impact disc assembly  400  over the additional length. The spoon  404  further includes portions positioned at distances from the center of rotation that are greater than comparable portions of the prior art spoon  110  so that the torque arm produced by water acting on those portions to rotate the impact disc assembly around a center of rotation  406  is greater for the spoon  404  than for the prior art spoon  110 . 
   The impact disc  402  includes a body  410  having a bottom surface  412  on which the spoon  404  may be secured or formed. The impact disc  402  is rotatably supported by a hub  414  connected to the body  410  by a bridge  416 . The impact disc  402  is generally substantially identical to the above-discussed impact discs in terms of size, mass, and design. As such, the bridge  416  includes an impact surface  418  for a desirable impact with an upstanding arm formed on a rotation shaft  520  ( FIG. 16 ) for forward re-alignment of a deflector secured with the rotation shaft so that a water stream emitted from the deflector is re-aligned to distribute water therefrom in an angularly re-aligned direction (see above). The bridge  416  further includes a second surface  420  that, due to the design of the impact disc assembly  400 , advantageously does not impact with the rotation shaft to cause undesirable reverse re-alignment of the deflector and the water stream distributing water therefrom. 
   The impact spoon  404  includes an inlet  430  for receiving a water stream from the deflector, and an outlet  432  for emitting the water after passing through the spoon  404 . The impact spoon  404  provides a path  434  between the inlet  430  and outlet  432  along which the water flows through the spoon  404  imparting energy to the spoon  404  and, thus, to the impact disc assembly  400 . As best seen in  FIG. 19 , the path  434  is generally Shaped, the water being received at the inlet  430  in a direction D 20  and being emitted from the outlet  432  in a direction D 21 . 
   The spoon  404  includes a bottom wall  440 , a top wall  442 , and a director wall  444 . The bottom and top walls  440 ,  442  are generally parallel with each other. The bottom wall  440  includes an entrance ramp  446  for directing and channeling the water stream received therein through the spoon path  434 . 
   The director wall  444  includes a first flow portion  450  and a second flow portion  452 . The first flow portion  450  includes an inlet section  456  which is struck by water as the spoon  404  is returning to the water stream so that the water stream is directed along a direction D 22 , or in a direction located between the direction D 22  and the direction D 20  ( FIG. 19 ). The director wall  444  has an outside surface  460  which, at the inlet  430 , includes a beveled portion  462  forming a sharp or small radius point  464  with the inlet section  456 . Consequently, the loss of both forward and reverse drive that is experienced by the prior art spoon  110  having the surface  124 , discussed above, is significantly reduced as the point  464  passes through the water stream from the deflector. It should be noted that the direction D 22  is aligned with the point  464  such that any shifting of the impact disc assembly  400  in the forward rotation direction Φ allows the water stream to pass by the inlet section  456 . It should also be noted that the beveled portion  462  is generally oriented in a vertically-aligned plane P ( FIG. 19 ) that is non-parallel to water stream direction D 22  when the water is impacting at the point  456  so that any water that passes by the point  456  does not contact the beveled portion  462 . 
   The water flows from the inlet section  456  to an arcuate flow section  466  of the first flow portion  450 . Water impacting the inlet section  456  and a portion of the arcuate flow section  466  imparts counter-rotation force and reverse drive energy to assist in directing the impact disc assembly  400  into the rotation shaft as the spoon  404  returns into the water stream. The arcuate flow section  466  has a varying degree of curvature so that discrete portions therealong have different radii of curvature. Thus, the arcuate flow section  466  has a first arcuate section  468  which tends to curve slightly, a second arcuate section  470  providing a greater curvature, a third arcuate section  472  with only a slight curvature, and a fourth arcuate section  474  with a greater curvature. 
   As the water passes through the first arcuate section  468 , the amount of work done by the water thereagainst is lower in comparison to the greater curve of the second and fourth arcuate sections  470 ,  474 . By design, the second and fourth arcuate sections  470 ,  474  are positioned at respective varying distances D 23 , D 24  from the center of rotation  406  so that the water acting on these sections  470 ,  474  produces a torque in proportion to these distances D 23 , D 24 . As can be seen in  FIG. 21 , the distances D 23  and D 24  are greater than comparable distances D 25  and D 6  for the prior art spoon  110 . Accordingly, the torque arm for water passing through the second and fourth arcuate sections  470 ,  474  is greater than for the prior art spoon  110 . Additionally, the third arcuate section  472  is positioned at a distance D 26  from the center of rotation  406  so that the water acting thereupon also has a large torque arm. The distance D 26  is greater than a radius R 20  for the impact disc body  410   
   After passing through the fourth arcuate section  474 , the water flows against an outlet section  476  that is relatively straight and is positioned a varying distance D 27  from the center of rotation  406 . As can be seen in  FIG. 21 , the distance D 27  is greater than any distance along the first flow portion  112  of the prior art spoon  110 . Accordingly, the torque arm for water passing against the outlet section  476  is greater than that of the prior art spoon  110 . 
   The water passes from acting on an inwardly directed surface on the first flow portion  450  to acting on an outwardly directed surface formed on the second flow portion  452 . Water flows from the first flow portion  450  to the second flow portion  452  generally along a direction D 28 . As this flow is not necessarily a laminar flow, instead including erratic spray molecules, the second flow portion  452  has an entrance portion  480  angled to collect and channel the water from the first flow portion  450 . The entrance portion  480  transitions smoothly to a relatively straight section  482 . The entrance portion and section  482  are positioned at a distance D 29  from the center of rotation  406 . The distance D 29  varies so as to increase so that the section  482  angles outward as the water flows therealong. Accordingly, water flowing therealong produces a torque against the spoon  404 , and, as can be seen in  FIG. 21 , this distance D 29  is greater than any comparable distance along the second flow portion  114  of the prior art spoon  110 . 
   The second flow portion  452  further includes an arcuate section  490  shaped in a manner similar to the arcuate flow section  466  of the first flow portion  450 . That is, the arcuate section  490  includes first and third curved sections  492 ,  496  being more sharply curved than a second curved section  494 . As the second flow portion  452  is generally positioned at a distance equal to or greater than the second flow portion  114  of the prior art spoon  110 , the torque created by the water through the second flow portion  452  is greater. 
   Referring to  FIG. 21  in specific, the path  434  that the water travels through the spoon  404  can be seen as being Longer than a path  500  for the prior art spoon  110 . This provides the greater time delay before the impact disc assembly  400  begins shifting from the water stream, and allows a greater amount of water to be received by the spoon  404  than by the prior art spoon  110 , each noted above. More specifically, the first flow portion  450  is shaped so that a preferred average travel distance therethrough is approximately 1.93 inches, the second flow portion  452  is shaped so that a preferred average travel distance therethrough is approximately 1.05 inches, and the preferred total water travel distance through the spoon  404  is approximately 2.98 inches. In comparison, the prior art spoon  110  has a total water travel distance of approximately 2.41 inches. As previously stated, the prior art spoon  110  has an included angle δ between its leading or initial point  119  of water contact on the first flow portion  112  and the point  121  of its maximum angular distance on the second flow portion  114 , and the preferred angle δ is approximately 85 degrees. To compare, the spoon  404  has a comparable angle λ ( FIG. 21 ), approximately 100 degrees. 
   The additional length of the spoon  404  also provides for back-impact restriction or prevention. More specifically, the second flow portion  452  has an outer surface  510  with a leading point  512  located at an angle χ from the direction of the water stream D 20 . Prior to the second impact surface  420  coming into contact with the rotation shaft, the impact disc assembly  400  will rotate so that the leading point  512  interferes with the water stream. The preferred angle χ is approximately 100 degrees, and the preferred amount of rotation required for the leading point  512  to interfere with the water stream is preferably approximately 260 degrees. 
   With reference to  FIG. 16 , it can be seen that the water stream is emitted in direction D 20  when the water stream enters the spoon  404 , and the impact disc assembly  400  position is immediately after an impact with a rotation shaft  520  and prior to the impact disc assembly  400  being energized and shifted by the water stream. In this position, the first impact surface  418  of the bridge  416  is positioned against or close to the rotation shaft  520 . Once the impact disc assembly  400  is energized, it may rotate an angle ε, at which point the leading point  512  will interfere with the water stream which is shown as being in the direction D 30 . As noted previously, the directions D 30  and D 20  have an included angle χ. Were the impact disc assembly  400  to rotate the entire angle ε, the rotation shaft is in the position represented by rotation shaft  520 ′. As can be seen, there is a gap  532  between the second impact surface  420  and the rotation shaft  520 ′. Thus the water stream impacting the spoon  404  at the leading point  512  restricts or prevents continued rotation for the impact disc assembly  400 , and the second impact surface  420  is restricted or prevented from contacting the rotation shaft  520 ′. 
   As can be seen in  FIGS. 17 and 18 , the spoon  404  is angled from a horizontal plane. This angle allows the spoon  404  to have a slightly longer flow path  434  within the angular sweep required for the spoon  404  in the horizontal plane. Accordingly, the initial portion of the first flow portion  450  including the inlet section  456 , the first arcuate section  468 , and a portion of the second and third arcuate sections  470 ,  472  are is angled upward. The third arcuate section  472  curves sufficiently so that it is re-directed somewhat inwardly so that a portion is also angled downwardly as the water travels therethrough. The water path from the third arcuate section  472  flows through a portion of the second curved section  494  of the second flow portion  452 , at which point the water path curves sufficiently to be directed somewhat outwardly and angles upward. This final angle upward, at the outlet  432 , provides the water with an upward trajectory so that the water is not merely deposited from the outlet  432  at the base or within a relatively close proximity to the sprinkler. 
   The construction of the spoon  404  provides an additional benefit over then prior art spoon  110 . With reference to  FIG. 20 , the prior art spoon  110  is formed by securing a molded piece  117 , including the first and second flow portions  112  and  114 , as well as a bottom wall  113  shown in phantom and spanning the area bound by the first and second flow portions  112  and  114 . The molded piece  117 , including the first and second flow portions  112  and  114  and the bottom wall  113 , is formed and then secured to the bottom surface of the impact disc  111 . Accordingly, its size is generally limited to the size of the impact disc  111 . Each of the other spoons described herein, are constructed to have a larger size than the impact disc to which they are secured. 
   To provide for this larger size, the impact spoons described herein include top and bottom walls with the flow path for water through the spoon between the walls. However, it is desirable to minimize the number of components for the spoons, and to maximize the ease of construction of the spoon on their respective impact discs. 
   With particular reference to the impact spoon  404  in  FIG. 19 , the second flow portion  452  of the director wall  444  is formed by an insert  570  and a wall portion  572 . The bottom wall  440 , top wall  442 , first flow portion  450 , and wall portion  572  are formed as a single molded piece  445  ( FIG. 16 ) that may be secured to, or molded as a single component with, the impact disc  402 . The insert  570  may then be received through an opening  573  ( FIG. 16 ) formed in the bottom wall  440 . The first flow portion  450  generally terminates at an edge  574  along a line  576 , and the line  576  is generally coincident with an origin or first edge  578  of the wall portion  572 . With this construction, the single piece  445  is generally a single molded item securable to the impact disc  402 , with the insert  570  being a separate molded piece that may be joined with the single piece  445  either before or after the single piece  445  is joined with the impact disc  402 . It should be noted that the insert  570  may have a step (not shown) or other structure so that, once the spoon  404  is secured to the impact disc  402 , the insert  570  does not come out of the opening  573 . 
   This construction also benefits the water flow characteristics. The insert  570  has a forward edge  582 . As can be seen in  FIG. 19 , the water flowing from the first flow portion  450  to the second flow portion  452  is generally directed along the direction D 28 . The forward edge  582  is positioned sufficiently upstream to be positioned across from the first flow portion edge  574 , that is, lateral with respect to the flow direction D 28 . This reduces or eliminates any back-spray that may result from erratically flowing water, thus reducing wasted energy, head loss, or negative pressure on the flow stream. 
   In addition, as the construction of the single piece  445  for the spoon  404  reduces wasted energy, head loss, and negative pressure. For the prior art spoon  110 , it was noted that the single piece  117  is secured to the impact disc  111 . Molded parts often have burrs or flashing formed on their edges, and the joining of plastic components often produces weld flashing. When the edges of the single piece  117  are joined with the impact disc  111 , flashing can produce incongruities that disturb the flow of water across the joints. 
   The spoon  404  and its single piece  445  eliminate or reduce these incongruities. Due to the single piece molding, the single piece  445  does not generally have mold edges or weld seams that are in within the flow path  434  of the water. The bottom and top walls  440 ,  442  form smoothly contoured transition portions  447  with the first and second flow portions  450 ,  452 , as can be seen in  FIG. 19  between the top wall  442  and flow portions  450 , 452 . Accordingly, the detrimental flow characteristics of the prior art spoon  110  are reduced or eliminated. 
   It should be noted that the back-impact prevention features noted herein are applicable to a wide variety of impact sprinklers. As can be seen in  FIG. 22 , a sprinkler impact arm  600  may incorporate an angled drive plane  602  with the arm  600  such that, beyond a certain rotation, the drive plane  602  interferes with a water stream emitted in a direction D 40  from a water emission member, which may be a deflector or a nozzle or both, for instance. At this rotation amount, the water stream slows the movement of the arm  600  in order to reduce or eliminate back impact. Again, this interference assists the bias member or spring with returning the impact assembly (or arm  600 ) towards and to a position for impacting a portion on which the water emission member is located. 
   More specifically, the water stream may strike a first portion  606  of the arm  600  such that the arm  600  rotates in the forward rotation direction Φ. When the arm  600  returns, it will strike a stop  608 , thereby causing a short rotation of the stop  608  which is connected to the water emission member. In order to prevent a second portion  610  of the arm  600  from contacting the stop  608  and providing a reverse re-alignment to the water emission member, the drive plane  602  is positioned on the arm  600  such that a predetermined amount of rotation causes the drive plane  602  to interfere with the water stream. Thus, the water stream slows and assists in returning the arm  600  towards the stop  608  in the counter-rotation direction Δ. 
   While the invention has been described with respect to specific examples, including presently preferred modes of carrying out the invention, those skilled in the art will appreciate that there are numerous variations and permutations of the above described apparatuses and method that fall within the spirit and scope of the invention as set forth in the appended claims.