Patent Publication Number: US-7722762-B2

Title: Horizontally traveling water screen

Description:
BACKGROUND 
   The invention relates generally to traveling water screens and, more particularly, to water screens that travel in a generally horizontal direction across a flowing stream of water. 
   Water is diverted from rivers, lakes, and other bodies of water for municipal, irrigation, and industrial purposes. Fish or water screens serve as filters to prevent fish or debris from entering a water diversion. These screens range in size from a few square feet to several thousand and come in many shapes. 
   Rotary drum screens consist of a screen mesh wrapped around a cylinder rotating on a generally horizontal axis. The top of the cylindrical screen is above the surface of the water. Debris is carried over the screen as it rotates and is washed off on the downstream side. Because of their fixed diameters, rotary drum screens are restricted in how deep they can be submerged and do not accommodate varying water levels. If the water level is too high, fish and debris are carried over the top of the rotary drum. If the water level drops too low, the screen clogs and water flow is restricted. 
   Fixed plate screens are also widely used. These stationary plate screens consist of fixed perforated metal sheets or wedge wire panels, usually oriented vertically in a flowing stream of water. Although the fixed plate screens are themselves simple, they require an external cleaning system to prevent clogging. External cleaning systems for plate screens are high maintenance and often not effective. And, if the cleaning system fails, the clogged screen can collapse. External brush cleaners, which are often used, can injure or kill fish. 
   Another kind of frequently used screen is a vertical traveling screen, which consists of a vertically advancing mesh driven by rotating shaft-mounted sprockets. The axes of the shafts are oriented generally horizontally. The screen may be inclined in the direction of water flow to aid in debris removal. To screen wide diversions, several side-by-side vertical traveling screens have to be used because individual wide vertical traveling screens are expensive to build, support, and drive. 
   Thus, there is a need for a water screen that is easy to clean and useful in filtering debris from wide diversions. 
   SUMMARY 
   This need and other needs are satisfied by a traveling water screen embodying features of the invention. In one version, a traveling water screen comprises a foraminous belt arranged in an endless loop. The belt is disposed in a flowing stream of water generally broadside to the flow. The foraminous belt advances across the stream of water in a generally horizontal direction. 
   According to another aspect of the invention, a traveling water screen comprises a screen arranged in an endless loop having an outer surface and an inner surface. Openings extend through the thickness of the screen between the outer surface and the inner surface. Means are provided for advancing the screen generally horizontally across a flowing stream of water with the outer surface of the endless loop oriented transverse to the flow. 
   According to yet another aspect of the invention, a traveling water screen comprises a screen that extends in width from a first side edge to a second side edge. The screen is arranged in an endless loop. Means are provided for advancing the screen through a stream of water. The first side edge of the screen is at a first depth in the stream and the second side edge is elevated above the stream or is at a second depth less than the first depth. 
   Another version of a traveling water screen comprises a drive wheel below the surface of a body of water with a motor coupled to the drive wheel to rotate the drive wheel about a generally vertical axis of rotation. The traveling water screen also comprises an idle wheel arranged to rotate below the surface of the body of water about a generally vertical axis parallel to the axis of rotation of the drive wheel. A screen in the form of an endless loop is trained about the drive wheel and the idle wheel for advancement in a generally horizontal direction. 
   According to another aspect of the invention, a traveling water screen comprises a frame, a drive shaft supported in the frame for axial rotation on a generally vertical first axis, and an idle shaft supported in the frame for axial rotation on a generally vertical second axis. A drive sprocket is mounted on the drive shaft for rotation on the first axis, and an idle sprocket is mounted on the idle shaft for rotation on the second axis. A modular belt, trained around and engaging the drive and idle sprockets, has openings through its thickness. The belt is disposed at least partly submerged in a stream of water. A motor coupled to the drive shaft rotates the shaft and the drive sprocket to advance the modular belt through the stream of water. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     These features and aspects of the invention, as well as its advantages, are better understood by reference to the following description, appended claims, and accompanying drawings, in which: 
       FIG. 1  is an isometric view of a horizontally traveling water screen embodying features of the invention; 
       FIG. 2  is a front elevation view of a water screen as in  FIG. 1 , but with a slightly different drive train; 
       FIG. 3  is a top plan view of the water screen of  FIG. 2  with the belt screen eliminated from the drawing for clarity; 
       FIG. 4  is a side elevation view of the water screen of  FIG. 2  viewed along lines  4 - 4  of  FIG. 3 ; 
       FIG. 5  is a cross section view of the water screen of  FIG. 2  taken along lines  5 - 5  of  FIG. 3 ; 
       FIG. 6  is an enlarged elevation view of the belt hold down tab retention of the water screen of  FIG. 3 ; 
       FIG. 7  is an enlarged plan view of the drive sprocket portion of the water screen of  FIG. 2 ; and 
       FIG. 8  is an isometric view of a portion of the inner side of a modular belt usable as a water screen as in  FIG. 1 . 
   

   DETAILED DESCRIPTION 
   A horizontally traveling water screen embodying features of the invention is shown in  FIGS. 1-7 . In  FIG. 1  the water screen system  10  is shown largely submerged in a body of water  12 . A stream of water flows in a flow direction  14  through a water screen  16  traveling, like a window curtain, in a generally horizontal direction  18 . The traveling water screen is arranged in an endless loop trained about wheels, such as sprockets  19  or rollers  19 ′, mounted on a drive shaft  20  and one or more idle shafts  21 ,  21 ′. The axes  22 ,  22 ′,  22 ″ of the shafts are generally vertical, with an outer surface  24  of the loop vertical as well. But the entire screen assembly could be tilted, still transverse to the flow  14 , with the axes and the outer surface slanted off vertical. In either case, the screen is generally broadside to the flow with an upper edge  17  of the screen above the surface of the water or submerged at a shallower depth than an opposite lower edge  17 ′. The screen  16  is driven by a drive motor  26  coupled to the drive shaft. In this example, the motor is coupled to the drive shaft via a right-angle gearbox  28  as in  FIG. 1  or via a gearbox  28 ′, chain sprockets  30 ,  30 ′, and a roller chain  32  as in  FIG. 2 . The entire drive train is attached by a bracket  34  to a frame  36 , which supports the entire screen. The foraminous screen serves as a filter to trap leaves, trash, and other debris that could interfere with or damage downstream equipment. Debris trapped on the upstream outer surface  24  of the screen is dragged to the side of the screen where it is separated from the main diverted flow and discharged as indicated by arrow  38 . Scrubbing equipment, such as brushes, scrapers, air-burst systems, or water sprays, can be used at the end of the upstream path of the conveyor to remove the debris for discharge. 
   Further details of the horizontal traveling screen system are shown in  FIGS. 2-7 . The traveling screen is supported in the frame  36 , which includes upper and lower horizontal sections  40 ,  41  connected by left and right vertical end pieces  42 ,  43 . The lower section sits directly on the bottom of the body of water or atop a concrete base. Sets of the drive and idle sprockets  19  are mounted to the drive shaft  20  and the idle shaft  21  and retained at vertically spaced positions. Bearing blocks  44  affixed to the frame support the shafts  20 ,  21  for rotation about their axes  22 ,  22 ″. Horizontal rails  46  are attached to vertical cross members  48  that are attached at their ends to the upper and lower frame sections. The vertical cross members are arranged two abreast—one row to support rails on the upstream side of the screen and the other row to support rails on the downstream side of the screen. The upstream rails are affixed to the upstream side of their cross members, and the downstream rails are affixed to the downstream side of their cross members. Guides  50  are mounted on flanges  52  extending outward of the rails. The guides, made, for example, of UHMW plastic material, are shown L-shaped with a lip extending upward. The guides could alternatively be made of stainless steel or could be U-shaped. The traveling screen  16  has vertical rows of horizontally spaced hold down tabs  54  along an interior side  25  of the screen loop. The hold down tabs have downwardly extending lips that hook onto the upwardly extending lips of the rail guides  52 . As the screen advances in the traveling direction  18 , the hold down tabs ride along the guides. By hooking onto the guides, the hold down tabs prevent the screen from sagging under its weight between the shafts. 
   As shown in  FIG. 3 , the screen includes a second idle shaft  21 ′ that is on the downstream side of the screen. Instead of toothed sprockets, toothless rollers  19 ′ are mounted at fixed positions on the idle shaft, which is biased at each end by springs  56  pushing in the downstream direction against the shaft&#39;s bearing blocks  44  to take up slack in the loop. The bearing blocks are slidably attached to the frame. The coil springs each surround a slidable rod  58  that is attached at one end to the bearing block and extends through a hole in a stationary bracket  60  affixed to the frame. The spring surrounding the rod is compressed between the bracket and the bearing block to apply continuous downstream pressure against the bearing blocks and the shaft to take up slack in the screen. Rollers or semicircular shoes  62  at the entry into and exit from the take-up mechanism hold the screen against the downstream guides. 
   The horizontal traveling screen or curtain may be realized in many ways. For example, it may be constructed of a number of metal or plastic panels held together by hinge rods between roller chains at opposite edges of the screen. As another example, the screen may be realized as a metal mesh chain. Preferably, however, the screen is constructed of a series of rows of modular plastic belt modules as in  FIG. 8  arranged in a bricklay pattern. Each row consists of one or more belt modules  66 ,  66 ′,  66 ″ that extend in length from a first end  68  to a second end  69 . Hinge eyes  70  at each end interleave with the hinge eyes of an adjacent row. Aligned apertures  72  through the interleaved hinge eyes form a passageway across the width of the belt. Hinge rods  74  received in the passageways link the rows together at hinge joints, which allow the belt to articulate about the sprockets and backbend at the shoes. The belt is a foraminous belt with openings  76  extending through the thickness of the modules from the outer surface  24  to the inner surface  25 . The inner surface includes drive structure  78  for engaging the drive and idle sprockets. One modular plastic belt that is suitable for use as a water screen is the Series 1800 Mesh Top™ belt manufactured and sold by Intralox, L. L. C. of Harahan, La., U.S.A. The hold down tabs  54 , which are shown formed on individual small modules  79  having hinge eyes  80  at each end to interfit into the modular belt retained in a belt row by the hinge rods, extend outward of the inner surface of some of the belt modules. The hold down tab may alternatively be integrally molded in a standard module, snapped into a module, bolted into a module, or otherwise attached to the belt. Hold down tabs may be positioned on each row or on some other spacing, such on as every other belt row. 
   Thus, the invention provides a horizontal traveling water screen especially useful for filtering wide flows. 
   Although the invention has been described in detail with respect to a preferred version, other versions are possible. For example, there are means to prevent the screen from sagging other than or in addition to the use of hold down tabs and associated tab guides. Stiffer hinge rods made of stainless steel, for instance, can be used to join screen modules. Or stiffer modules with greater beam strength can be used to reduce sag between the sprockets. As another example, the preferred version uses two idle shafts, but it would be possible to use a single idle shaft or more than two idle shafts. The screen is shown driven by sprockets, but could be driven by drums or pulleys or any means capable of advancing the belt across the flow. The details of the take-up mechanism described represent one example of such a mechanism. So, as the few examples suggest, the scope of the claims is not meant to be limited to the preferred versions described in detail.