Abstract:
A self-cleaning screen that automatically cleans both the inside and outside surfaces of the cylindrical screen using only the rotation of the cylindrical screen itself. This self-cleaning ability is accomplished by using a fixed brush on the exterior surface of the screen, and a freely rotating brush on the interior surface of the screen, where the freely rotating brush is driven by the movement of the screen itself. The fixed brush includes first and second bristles extending to the cylindrical side portion, and third bristles that are disposed between the first and second bristles and that protrude into the openings of the cylindrical side portion. The third bristles have a diameter and/or stiffness that is less than that of the first and second bristles.

Description:
[0001]    This application claims the benefit of U.S. Provisional Patent Application No. 61/954,828, which was filed on Mar. 18, 2014. 
     
    
     FIELD OF THE INVENTION 
       [0002]    This invention relates to intake screens to exclude material from entering a water inlet, and is particularly directed to a self-cleaning intake screen. 
       BACKGROUND OF THE INVENTION 
       [0003]    Self-cleaning intake screens are well known in the art. The earliest of such devices simply employed some mechanism to cause the screen, generally cylindrical in shape, to rotate within the stream or waterway. A water vacuum is generated inside the cylindrical screen, drawing water through the screen for filtration. As the screen rotates, any debris trapped on its upstream side would be washed away as it turns downstream. More sophisticated devices employ some sort of backwash system which, either continually or at periodic intervals, spray a high pressure jet of water or air against the screen in an attempt to blow debris off of and away from the outside of the screen. However, most self-cleaning intake screen designs are complicated and/or do not effectively keep the screen free from debris. 
         [0004]    More recently, brushes and scrapers have been added to the outside of cylindrical screens, to scrape off debris and silt from the outer surface of the screen as the screen rotates, so that water flow through the screen to the interior of the screen is not unnecessarily impeded. For example, wedge wire screens have been used with a slot width of 1.75 mm (.068″), and with a single nylon fixed external brush with a bristle diameter of .040″ to .060″ and an overall trim size of 2″ to 3″ to clean the exterior of the screen during use. Screens of smaller slot widths have been proposed, for example with a slot width of .5 mm (.018″). In order to effectively clean this narrow slotted screen cylinder, a very fine bristle (.015″) stainless steel external brush has been used. In order to clean effectively, the brush bristles need to be smaller than the slot widths in the wedge wire (so the bristles can penetrate into the gap between adjacent wedge wires). The brush bristles need to have a relatively long length (e.g. 3″). If the bristles are too short, they cannot effectively maneuver down into the slots between adjacent wedge wires. However, long stainless steel bristles are prone to bending and fouling with debris. Fouling occurs when small fibrous organic material works its way into and through the brush bristles decreasing their flexibility and cleaning effectiveness. This fouling and loading of the brush is a common problem encountered with all brush strips utilized in this manner. When using a thicker nylon brush on a wider slotted screen, the answer has been is to mechanically adjust the downward pressure of the brush against the wedge wire. However, because of the thinness of the stainless steel brush bristles, this is not feasible because any fouling would compromise the bristle flexibility and its ability to reach down into the slots between the wedge wires thus rendering it ineffective. There is a need for isolating and preserving the flexible integrity of fine stainless steel brushes. 
         [0005]    For many applications, the interior of the screen still experiences an intolerable build up of debris and silt even with the use of external brushes and scrapers. For example, one application involves a screen made of wedge wires, which are thick wire strands that extend circumferentially around a support structure. The support structure includes longitudinally extending support members that are attached to the inside surface of the wedge wire screen, and are spaced one or several inches apart. It has been found that an external brush sweeping across the outer surface of the wedge wire screen fails to adequately clean the inside surface of the wedge wire and the support members, as well as possibly the laterally facing surfaces of the wedge wires. Spacing the support members further apart can reduce silt buildup, but then the screen no longer has the desired structural integrity, and the cylinder can lose its roundness as the wedge wire tends to lie flat between the support members. 
         [0006]    It is also known to place a spirally oriented, motorized cleaning brush on the inside surface of a rotating cylindrically shaped screen, where the brush rotates in the opposite direction as the moving direction of the screen. However, such motorized cleaning brushes will not work with wedge wire type screens such as the one described above, because the brush will continually encounter the support members, which are not flush with the inside surface of the wedge wire screen. Thus, any brushes designed to clear the support members will not adequately clean the interior and lateral surfaces of the wedge wire. Moreover, it is expensive and difficult to include a separate motor, inside the cylindrical screen, to operate the rotating brush. 
         [0007]    There is a need for an intake screen that reliably and effectively cleans itself, including its exterior and interior surfaces, without adding the complexity of additional motors. 
       SUMMARY OF THE INVENTION 
       [0008]    A self-cleaning intake screen that includes a rotatable intake screen having a cylindrical side portion and openings distributed across the cylindrical side portion for passing a flow of water, and a first cleaning element proximate to an outer surface of the cylindrical side portion. The first cleaning element includes first bristles extending to the cylindrical side portion, second bristles extending to the cylindrical side portion, and third bristles that are disposed between the first and second bristles and that protrude into the openings of the cylindrical side portion. The third bristles have at least one of a diameter and a stiffness that is less than that of the first and second bristles. 
         [0009]    Other aspects and advantages of the invention will become apparent from the following detailed description taken in conjunction with the accompanying drawings which illustrate, by way of example, the principles of the invention. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0010]    For a better understanding of the invention, reference should be made to the following detailed description taken in conjunction with the accompanying drawings, in which: 
           [0011]      FIG. 1  is a cross-sectional side view of the self-cleaning intake screen of the present invention. 
           [0012]      FIG. 2  is a cross-sectional end view of the self-cleaning intake screen of the present invention. 
           [0013]      FIG. 3  is a perspective view of the suction manifold of the self-cleaning intake screen of the present invention. 
           [0014]      FIGS. 4 and 5  are perspective views of the wedge wire surface and external brush of the self-cleaning intake screen of the present invention. 
           [0015]      FIG. 6  is a perspective view of the interior of the self-cleaning intake screen of the present invention. 
           [0016]      FIG. 7  is a top view of the internal brush of the self-cleaning intake screen of the present invention. 
           [0017]      FIG. 8  is a perspective view of the suction manifold and internal brush of the self-cleaning intake screen of the present invention. 
           [0018]      FIG. 9  is a perspective view of the wedge wire surface, external brush, and protruding bristles of the interior brush, of the self-cleaning intake screen of the present invention. 
           [0019]      FIG. 10  is a cross-sectional side view of an alternate embodiment of the present invention. 
           [0020]      FIG. 11  is an end view of the alternate embodiment of the present invention. 
           [0021]      FIG. 12  is a side view of an alternate embodiment of the external brush. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0022]    The present invention is self-cleaning intake screen assembly  1 , as shown in  FIGS. 1 and 2 . The assembly  1  includes a cylindrical shaped screen  10  rotatably mounted to a suction manifold  12 , an external fixed brush  14 , and an internal rotating brush  16 . The entire assembly is designed to be submerged under water, where suction applied inside the suction manifold  12  draws water through the cylindrical screen  10  and the suction manifold  12 , where the screen  10  filters out contaminants from the water. 
         [0023]    Suction manifold  12  is cylindrically shaped, having an open end  18 , a closed end  19 , and a cylindrically shaped sidewall  20 . A pump manifold  22  (attached to the intake side of a pump which is not shown) is connected to the suction manifold  12 , for drawing water through the screen  10  and the suction manifold  12  and eventually to the pump (not shown). The suction manifold  12  includes a plurality of apertures  24  formed in its cylindrical sidewall  20  through which water will flow, as better shown in  FIG. 3 . The apertures  24  are evenly spaced to ensure a more even flow of water though various portions of screen  10 . Motor  26  is mounted to the closed end  20  of suction manifold  12 , and includes a rotating drive shaft  28  that extends through the suction manifold closed end  20 . 
         [0024]    Screen  10  includes a first end plate  30  connected to the motor drive shaft  28 , a second end plate  32  with a plurality of rollers  34  attached thereto, and a sidewall  36  formed by wedge wire  38  extending circumferentially around a center of the screen  10  and supported by support members  40  that longitudinally extend between the first and second end plates  30 / 32 , as best shown in FIGS.  1  and  4 - 6 . Wires  38  are separated from each other to form small openings  39  therebetween through which the water flows (as best seen in  FIG. 9 ). Screen  10  is disposed around suction manifold  12 , and is rotatably supported at one end by the motor drive shaft  28  and the other end by the rollers  34  (which engage the suction manifold cylindrical sidewall  20 ). 
         [0025]    The external brush  14  includes bristles  42  supported by a support bracket  44 , as best illustrated in  FIGS. 2-5 . Bristles  42  sweep across the outer surface of the screen sidewall  36  (wedge wire  38 ) as the screen  10  rotates relative to the suction manifold  12 . 
         [0026]    The internal brush  16  includes a shaft  46  rotatably mounted to the suction manifold  12  via brackets  48 , and bristles  50  extending from the shaft  46  preferably, but not necessarily, in a spiral fashion, as best illustrated in  FIGS. 2 and 7 . Brackets  48  can be incorporated as end plates of a unitary trough or tray  52  for integrity, as best shown in  FIGS. 3 and 8 . The brush  16  is positioned to engage with the interior surface of screen sidewall  36  (wedge wire  38  and support members  40 ). 
         [0027]    In operation, motor  26  rotates screen  10  relative to suction manifold  12 . As screen  10  rotates, bristles  42  of fixed external brush  14  slide across the outer surface of sidewall  20  (i.e. outer surface of wedge wire  38 ) dislodging material such as debris and silt therefrom. Also, as screen  10  rotates, the support members  40  act as gear teeth by engaging with and rotating internal brush  16 . As internal brush  16  rotates, its bristles  50  engage with support members  40  and inner and side surfaces of wedge wire  38 , even poking through the wedge wire  38  as illustrated in  FIG. 9 . This engagement wipes and dislodges debris and silt from the support members  40  and the inner/side surfaces of wedge wire  38 . By rotating with the passing support members  40  (in a passive manner), the internal brush  16  effectively cleans the interior of the screen  10  in a manner that the external fixed brush  14  can not. Also, by passively rotating internal brush  16  using the rotation of screen sidewall  36 , a second motor and/or complicated gearing is avoided. Thus, the rotation of screen  10  operates both brushes (one fixed and one rotating) without the need for any additional motors or moving parts. 
         [0028]    The preferred embodiment includes a pair of screen assemblies  1  mounted to a single pump manifold. Hoist mechanisms can be used to lower and raise the intake screen assembly into a waterway for use. Components with dissimilar metals are electrically isolated to prevent electrolysis. 
         [0029]    One of skill will realize that the invention is not limited to the embodiment described above. Rather, alternate embodiments exist.  FIGS. 10-11  illustrate one such alternate embodiment. The embodiment of  FIGS. 10-11  highlights the fact that the invention is not limited to configurations in which the brush  16  is rotated only by its bristles  50 . Rather, here, the brush  16  has a gear  100  that is aligned with a complementary rack  102  that is positioned along the inner surface  104  of the screen  10 , and whose teeth  104  are configured to interlock with the teeth of the gear  100  in a rack-and-pinion type arrangement. Accordingly, rotation of the screen  10  and rack  102  also induces rotation of the gear  100  and thus the brush  16 . In this embodiment, the bristles  50  need not frictionally engage against the screen  10 , as the brush  16  is turned by the rack  102  and gear  100 . This reduces wear on the bristles  50  and extends the useful life of the brush  16 . 
         [0030]      FIG. 12  illustrates an alternate embodiment to the external brush  14  described above. A composite brush  60  is used to sweep across the outer surface of the screen sidewall  36  (wedge wire  38 ) as the screen  10  rotates relative to the suction manifold  12 . Composite brush  60  includes a stainless steel brush strip  62  sandwiched between two nylon brush strips  64 . The bristles of the nylon brush strips  64  are stiffer and of greater diameter than those of the stainless steel brush to protect and help guide the thinner stainless bristles  62  down into the narrow slots of the wedge wire  62 . In addition to placing nylon brushes  64  on either side of the stainless steel brush  62 , one or two strips of rigid material  66  (e.g. . 015 ″ plastic strips) are disposed on one or both sides of the stainless steel brush  62  (and in-between the nylon brushes  64  and the stainless steel brush  62 ). The rigid strip(s)  66  terminate before the ends of the stainless steel brush  62 , so that an end portion (e.g. about 1 cm) of the stainless steel bristles  62  are exposed by extending beyond the end(s) of rigid strip(s)  66 . The rigid strip(s)  66  further isolate and protect the stainless steel bristles  62  so they do not get bent too far out of place and so they do not mix with debris or the nylon brush bristles  64 . A brush bar clamp  68  squeezes the proximate ends of the stainless steel bristles  62 , the rigid strip(s)  66  and the nylon brush bristles  64  together so that they are all held firmly together and in place. The composite brush  60  has been shown to provide superior cleaning performance over stand-alone nylon brushes. 
         [0031]    It is to be understood that the present invention is not limited to the above embodiments, but includes others besides those already disclosed above. For example, the internal brush  16  is simply coupled to the screen  10  so that rotation of the screen  10  also moves the internal brush  16  against the screen  10 . The brush  16  need not be moved specifically by its bristles  50 , but instead can be moved by rotation of the screen  10  in any appropriate manner. The use of passively rotating internal brush  16  need not be used in conjunction with a suction manifold for applications where even water flow through the screen  10  is not needed. While internal and external brushes  14 / 16  are shown as mounted in an opposing fashion (on either side of the screen sidewall  36 ), such an opposing relationship is unnecessary. The screen sidewall  10  need not be formed of wedge wire  38  and support members  40 , but can be formed of any mesh or other known screen materials (i.e. thin wires to thick wires that resemble rigid bars) that provide the desired filtration of water flowing therethrough and can engage and rotate the internal brush  16 . The internal and external brushes  14 / 16  need not be brushes with protruding bristles  50 / 42 , but can be any cleaning element capable of removing material from the intake screen  10 , such as scrubbing pads or the like. In particular, the internal brush  16  can be a cleaning element having any configuration that allows it to engage against the intake screen  10  so as to induce rotation. The flow of water can be reversed from that shown, in which case the support members  40  are preferably on the outside of the screen as is the rotating brush  16 , and the fixed brush  14  is mounted inside the screen. The spacing and sizes of holes  24  can be varied to create more even flow. And, brush  16  can be freely disposed in tray  52 , without the ends thereof being rotatably attached to the tray ends. 
         [0032]    Thus, the foregoing descriptions of specific embodiments of the present invention are presented for purposes of illustration and description. They are not intended to be exhaustive or to limit the invention to the precise forms disclosed, obviously many modifications and variations are possible in view of the above teachings. The embodiments were chosen and described in order to best explain the principles of the invention and its practical applications, to thereby enable others skilled in the art to best utilize the invention and various embodiments with various modifications as are suited to the particular use contemplated. It is intended that the scope of the invention be defined by the following claims and their equivalents.