Patent Publication Number: US-6666977-B2

Title: Removable bar for bar screen

Description:
RELATED APPLICATIONS 
     This application claims the benefit of a provisional application having U.S. Serial No. 60/347,690, filed on Jan. 11, 2002, which hereby is incorporated by reference in its entirety. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Technical Field of the Invention 
     The present invention relates to rake-type cleaning screens located in water conduits such as sewers, wastewater treatment streams, water treatment plants, power plants, and cooling water streams. More particularly, this invention relates to an improved bar screen for use with a rake type screen system. 
     2. Background of the Prior Art 
     Bar screens are used for screening solids and debris from flowing liquid streams. An example of such a bar screen system can be found in U.S. Pat. No. 5,730,862 issued to Mahr. In such systems, a series of rakes pass over parallel screen bars, which make up a bar screenfield and remove the debris collected from the flowing stream. Occasionally, large pieces of debris can damage the bar screenfield by either bending or breaking one or more bars within the bar screenfield. When this occurs, the screen system must be repaired by typically cutting out the affected bars and welding new bars in their place. These repair methods are time consuming, potentially hazardous, and expensive. The screen system is typically taken out of service for a relatively long period of time in order to make these repairs, which also adds significantly to the costs of the repairs. 
     A need exists for a screen system with bars that can be repaired quickly, safely, and cost effectively. Ideally, such a system should be capable of being adapted to the specific fluid applications and also be able to be used on existing screen system equipment with minimal modification. 
     SUMMARY OF THE INVENTION 
     The present invention advantageously provides a screen system for removing debris from a flow channel. The screen system includes a screen frame having a bar screenfield that is located below a debris plate. The bar screenfield includes a plurality of individually removable bars. Rakes with a plurality of fingers fit between the bars of the bar screenfield. The rakes are movable along the bar screenfield to clear the bar screenfield of debris. 
     The bars may be releasably secured in different ways to the frame of the screenfield. Preferably opposite ends of the bars fit within slots of a bar holder. After placement in the slots, a retainer with a plurality of teeth is secured to the holder. The gaps between the teeth are wedge-shaped for wedging the bars in place on the bar holder. The retainer is fastened to the bar holder with a releasable fastener. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     So that the manner in which the features, advantages and objects of the invention, as well as others which will become apparent, may be understood in more detail, more particular description of the invention briefly summarized above may be had by reference to the embodiment thereof that is illustrated in the appended drawings, which form a part of this specification. It is to be noted, however, that the drawings illustrate only a preferred embodiment of the invention and are therefore not to be considered limiting of the invention&#39;s scope as they may admit to other equally effective embodiments. 
     FIG. 1 is a perspective view of a screen system disposed in a liquid flow stream with a singly removable bar screenfield, constructed in accordance with this invention. 
     FIG. 2 is a cross-sectional view of a removable bar installed in the bar screenfield of FIG. 1, taken along the line  2 — 2  of FIG.  1 . 
     FIG. 3 is a partial top view of the removable bar screenfield of FIG.  1 . 
     FIG. 4 is a side view of a removable bar of FIG.  1 . 
     FIG. 5 is a front view of a screenfield bar retainer for use in the bar screen of FIG.  1 . 
     FIG. 6 is a front view of the intermediate screenfield bar holder of FIG.  1 . 
     FIG. 7 is a sectional view of an upper screenfield bar holder with a bar installed in accordance with a first alternate embodiment of the present invention. 
     FIG. 8 is a sectional view of an intermediate screenfield bar holder in accordance with the first alternate embodiment of the present invention. 
     FIG. 9 is a sectional view of a lower screenfield bar holder in accordance with the first alternate embodiment of the present invention. 
     FIG. 10 is a sectional view of an upper screenfield bar holder with a bar installed in accordance with a second alternate embodiment of the present invention. 
     FIG. 11 is a sectional view of a lower screenfield bar holder in accordance with the second alternate embodiment of the present invention. 
    
    
     DETAILED DESCRIPTION OF THE DRAWINGS 
     FIG. 1 illustrates one type of screen system  10  installed in a channel  12  through which a liquid flow stream passes in the direction indicated by the arrow. This, screen system  10  generally comprises a screen frame  14 , a debris plate  16  for preventing debris from spilling over screen system  10 , a bar screenfield  18  for collecting solid waste in the flow stream, and a series of rakes  20  (only one shown) for removing solids and debris from bar screenfield  18 . 
     Screen frame  14  has a leading or forward edge  22  and a trailing or rearward edge  24 . When screen system  10  is installed in a channel  12 , screen frame leading edge  22  will be on the upstream side and screen frame trailing edge  24  will be on the downstream side. The distance between screen frame leading edge  22  and screen frame trailing edge  24  defines the depth dimension of screen frame  14 . Bar screenfield  18  and debris plate  16  are attached to screen frame trailing edge  24 , with bar screenfield  18  located immediately below debris plate  16 . 
     Bar screenfield  18  comprises a set of parallel, evenly-spaced, vertical bars  26 . The preferred embodiment of the invention uses flat bars that are trapezoidal in cross-section. The leading edge of each bar in the preferred embodiment is wider than the trailing edge. The bars are spaced to allow liquid to pass unimpeded, but to block the passage of debris or solids in the flow stream. Bar screenfield  18  contains enough bars  26  to extend across the entire width of screen frame  14 . The solids and debris accumulate on the front of bar screenfield  18 . 
     In the preferred embodiment of screen system  10 , each rake  20  has a series of tines or fingers  28  to fit in the gaps between each bar  26 . Rakes  20  are attached at each end to endless chains  30  that are driven by sprockets  31 . The two chains  30  carry rakes  20  in an upward direction over the forward surface of bar screenfield  18 . As each rake  20  travels upward along bar screenfield  18 , fingers  28  clean the accumulated solids and debris from bar screenfield  18 . The solids and debris are carried to the top of screen system  10  for disposal. 
     Bars  26  are individually removable from the bar screenfield  18 . The bars of prior art screen systems are welded in the bar screenfield, thus not individually removable. Bars  26  are long thin metal bars. Referring to FIG. 4, the edge on one end of each bar  26  has a taper  27  extending rearward from the leading edge toward the trailing edge. Taper  27  joins a reduced thickness section  29  in the bar  26 , that has parallel leading and trailing sides. 
     Bars  26  are attached to bar screenfield  18  individually by inserting bars  26  into a series of holder slots  32  (FIG. 3) that are located in two or more screenfield bar holders. FIG. 3 illustrates a multi-screenfield bar holder configuration with an upper screenfield bar holder  33 , a lower screenfield bar holder  35 , and an intermediate screenfield bar holder  37 . The upper screenfield bar holder  33 , as shown in FIG. 1, is located at the bottom edge of the debris plate  16 . The intermediate screenfield bar holder  37 , as illustrated in FIG. 3, is located midway down the bar screenfield  18 . The lower screenfield bar holder  35  is located at the bottom of the screen frame  14 . Additional intermediate screenfield bar holders  37  can be installed between the upper and lower screenfield bar holders  33 ,  35 , in addition to the midway one illustrated in FIG.  3 . Holders  33 ,  35 ,  37  may be separate members that are joined, such as by welding, to frame  14 . Alternately, upper holder  33  may be formed by bending a lower section of debris plate  16  rearward and forming slots  32  in the holder  33 . Similarly, lower holder  35  may be formed by bending a portion of frame  14  downward and forming slots  32  therein. Slots  32  in the upper and lower holders  33 ,  35  in this instance are thus closed perimeter apertures. Slots  32 , however, in intermediate holder  37 , however, have open upper ends as shown in FIG.  6 . 
     In each holder  33 ,  35 ,  37 , the holder slots  32  extend over the entire width of the screen frame  14 , as depicted in FIG.  6 . Slots  32  may be tapered in width slightly, having a wider forward side than rearward side, to mate closely with the trapezoidal bars  26 . Alternately, rectangular slots  32  are also feasible. As shown in FIG. 2, upper bar holder  33  has a forward portion  33   a  and a rearward portion  33   b . Forward portion  33   a , which contains slots  32 , is in a plane perpendicular to a plane containing bars  26 . Rearward portion  33   b  is inclined at an obtuse angle relative to forward portion  33   a . Similarly, lower bar holder  35  has a forward portion  35   a  that is parallel to forward portion  33   a  and a rearward portion  35   b  that is inclined relative to forward portion  35   a . Intermediate holder  37  is not shown in FIG. 2, and in this embodiment, lies in a single plane. If desired, intermediate holder  37  could have a similar configuration to the other holders  33 ,  35 . 
     The reduced thickness section  29  on the upper end of each bar  26  is inserted in slots  32 , which are located at the bottom edge of the debris plate  16 . A portion of reduced thickness section  29  slides rearward of debris plate  16 , as shown in FIG.  2 . The width of each slot  32  is slightly larger than the width of each bar  26  so that bar  26  inserts freely into slots  32 . Tapered edge  27  prevents bars  26  from being wedged too far up the debris plate  16 . 
     A series of holes  39  exist rearward from slots  32 . Holes  39  are used to attach screenfield bar retainers  41  to each of the locations where slots  32  reside. Screenfield bar retainers  41  are thin rectangular metal plates with tines or teeth  43  on the forward edge of the screenfield bar retainer  41 , as shown in FIG.  5 . The gap between each tine  43  is tapered and slightly smaller at the narrow portion than each bar  26 . Tines  43  are wedged between bars  26  after bars  26  are inserted in holder slots  32  as depicted in FIG.  2 . Screenfield bar retainers  41  thus stabilize and reinforce bars  26 . Bar retainers  41  are located on both the upper holder  33  as well as the lower holder  35 . Optionally, bar retainers  41  could be utilized for the intermediate holder  37  if bars  26  are sufficiently long to require additional stabilization. 
     Screenfield bar retainers  41  contain at least two attachment holes for attaching the screenfield bar retainers  41  to the holder holes  39  by fasteners or bolts. As shown in FIGS. 2 and 5, the plane containing retainer teeth  43  is at an obtuse angle relative to a central portion  41   a . Also retainer  41  has a rearward portion  41   b  that is at an obtuse angle relative to central portion  41   b . The angle of rearward portion  41   b  matches that of holder rearward portion  33   b . Screenfield bar retainers  41  are bolted to holes  39  located rearward of holder slots  32 , as shown in FIG. 2, by aligning the screenfield bar retainer holes and holes  39  and inserting a bolt through them. As the bolt is tightened, the taper of lower portions  33   b  draws retainer  41  central portion  41   a  into abutting engagement with holder forward portion  33   a . This movement causes retainer teeth  43  to wedge bars  26  between them. The angle of the inclined plane containing teeth  43  provides compliance for slightly different dimensions of bars  26 . Screenfield bar retainers  41  are installed one after another for the entire width of the screen frame  14 . 
     Each side end tine  43  of each screenfield bar retainers  41  is only about one-half of the width of the remaining tines  43 . The side end tine  43  shape allows the screenfield bar retainers  41  to be placed in side-by-side abutment and still have the end tine  43  align with the holder slots  32 . Having the screenfield bar retainers  41  so narrow in comparison to the width of the screen frame  14  allows for more versatility since individual screenfield bar retainers  41  can be added or removed to replace individual bars  26 . Alternately, a single bar retainer  41  for the entire width of bar holder  33  or  37  could be utilized. 
     A stop member  45  is secured to the lower side of each bar retainer  41  on lower holder  35 . Stop member  45  has the same width as each bar retainer  41  and is used to prevent bars  26  from sliding downward relative to lower holder  35 . Stop member  45  has a forward portion  45   a  that is offset at a lower elevation from the rearward portion  45   b . The lower ends of bars  26  abut forward portion  45   a.    
     To install bars  26 , each bar  26  is placed in holder slots  32  in holders  33 ,  35  and  37 . The upper reduced thickness end  29  of each bar  26  inserts behind the edge of debris plate  16 . The lower end of each bar  26  locates below a lower portion of frame  14 . Retainers  41  are bolted to holders  33  and  35 , with their teeth  43  wedging between each of the bars  26 . On the upper end, the contact of debris plate  16  with reduced thickness section  29  prevents forward movement when teeth  43  of the upper retainers  41  are being wedged between bars  26 . On the lower end, the lower edge of each bar  26  fits under a portion of frame  14  to prevent forward movement of bar  26  when teeth  43  of the lower retainers  41  are being wedged between bars  26 . Stop members  45  are secured to lower holder  35  at the same time that the bar retainers  41  for lower holder  35  are installed. 
     In operation, screen system  10  is installed in a channel  12 . Bar screenfield  18  blocks the passage of solid material or debris in the fluid, while allowing the fluid to pass through. A motor (not shown) turns both sprockets  31 , moving chains  30  and attached rakes  20  upward along the bar screenfield  18 . As each rake  20  travels along the bar screenfield  18 , rake fingers  28  carry solid material and debris toward the top of the screen system  10  for disposal. When a rake  20  reaches the upper sprockets  31 , chains  30  carry it over the upper sprockets  31  and down toward the bottom of screen frame  14  to begin another cleaning cycle as fingers  28  reengage bars  26 . 
     Debris and solids can sometimes damage bars  26  as a result of filtering a fluid channel. When this occurs, the damaged bar  26  is removed by detaching the screenfield bar retainer  41  that secures the damaged bar  26  and then sliding the bar  26  out of the bar screenfield  18 . A new bar  26  can be inserted and the screenfield bar retainer  41  re-attached. 
     In addition to the first embodiment, other devices can be used to secure bars  26  individually in place. Two alternate embodiments are shown, with FIGS. 7,  8 , and  9  illustrating the first alternate embodiment. FIG. 7 illustrates the support means for the upper edge of screenfield  18 . Debris plate  16 ′ has a depending support wall  46  on its lower edge. A bar retainer  47  is secured to wall  46 . Bar retainer  47  has an offset forward portion that contains teeth  50  for receiving bars  26 ′. Teeth  50  extend in a forward direction and are preferably wedge-shaped. A J-shaped holder  48  has a leg portion  48   a  that abuts and is also secured to wall  46 . Leg portion  48   a  joins a central portion  48   b  that extends downward from leg portion  48   a . Teeth  52  depend in a rearward direction from central portion  48   b , opposite to the direction of teeth  50 . Teeth  52  and teeth  50  are in parallel planes and abut and overlap each other. This overlapping engagement defines a closed perimeter aperture for receiving the tapered end  27 ′ of bar  26 . A bolt is used to secured retainer  47  and holder  48  to wall  46 . Teeth  50  wedge between tapered ends  27 ′ of bars  26 ′. The closed perimeter aperture defined by the overlapping gaps between teeth  52  and  50  prevent forward and rearward movement of bars  26 . 
     FIG. 8 illustrates the central portions of bars  26 ′ located within slots  56  of an intermediate screenfield bar holder  54 . A retainer  58  may optionally be used to wedge the central portions of bars  26 ′ tightly within slots  56 . Retainer  58  is a plate that has wedge shaped teeth  60  on its forward end for wedging bars  26 ′ between them. Retainer  58  is secured to holder  54  by bolts. 
     FIG. 9 illustrates the lower screenfield bar holder support means, which is constructed the same as the upper bar holder support means. Frame  14 ′ has a depending wall  62  that supports a retainer  64  with forward facing wedge-shaped teeth  66 . A holder  68  with rearward facing teeth  70  is also supported by wall  62 . Teeth  66 ,  70  engage each other in separate planes to define closed perimeter apertures for receiving ends of bars  26 ′. 
     FIGS. 10 and 11 illustrate a second alternate embodiment. FIG. 10 illustrates the upper screenfield bar holder support means. As in FIG. 7, debris plate  16 ″ has a depending rearward extending wall  72 . A bar holder  74  is mounted to wall  72  by bolts. Bar holder  74  has a plurality of slots or apertures  76  on its forward portion, each for receiving the tapered end  27 ″ of the bars  26 ″. Each aperture  76  has a closed perimeter to limit the forward and rearward movement of bar end  27 ″. A retainer  78  is mounted to holder  74 , retainer  78  having a plurality of wedge-shaped teeth  80  that face in a forward direction. Teeth  80  wedge bars  26 ″ between them. Apertures  76  prevent forward movement of bars  26 ″ while teeth  80  are being wedged between the bars. 
     FIG. 11 illustrates the lower screenfield bar holder support means. Frame  14 ″ has a rearward depending wall  82  that supports a bar holder  84 . Holder  84  has a plurality of apertures  86 , each having a closed perimeter for receiving one of the lower ends of one of the bars  26 ″. A retainer  88  is mounted to holder  84  and wall  82  by bolts. Retainer  88  has forward extending wedge-shaped teeth  90  that wedge bars  26 ″ between them. As in the other embodiments, a plurality of side-by-side retainers  78 ,  88  could be used for holders  74 ,  84 , or the retainers  78 ,  88  could extend the full width of each holder  74 ,  84 . 
     The present invention has many advantages when compared to prior art systems. The first advantage is that the bars do not have to be welded when they are installed. This decreases the costs of manufacturing the screen systems since the labor involved is typically less extensive and less expensive. The second advantage is if one bar breaks, it can easily be replaced without having to cut out and weld a new bar in its place. Since the bars are not welded, this provides an additional advantage in that it avoids warping the bars, which can occur as a result of welding the bars. Additional advantages exist, such as installing and replacing the bars is safer and much faster since welding is not involved. The screen system can be returned to service much faster than with previous repair methods. 
     While the invention has been shown or described in only some of its forms, it should be apparent to those skilled in the art that it is not so limited, but is susceptible to various changes without departing from the scope of the invention.