Abstract:
A device for scraping a wall of a settling tank includes a mobile carrier having opposite ends defining a front-to-rear axis of the carrier, the carrier configured to travel along the top of a wall of a settling tank. At least one scraper blade is carried by the carrier and projects downwardly therefrom. A bottom portion of each of the blades includes a scraping edge facing in a travel direction of the carrier and having a height dimensioned to scrape a band of built-up solids from a surface of the wall.

Description:
[0001]    This application claims priority under 35 U.S.C. §119 and/or 365 to U.S. Provisional Application Ser. No. 60/859,516 filed on Nov. 17, 2006, the entire content of which is hereby incorporated herein. 
     
    
     BACKGROUND OF THE INVENTION 
       [0002]    1. Field of the Invention 
         [0003]    The present invention relates to a system and method for build-up removal from wastewater treatment processing tanks, and more particularly, to a system and method for scraping build-up of solids material from walls within wastewater treatment settling tanks. 
         [0004]    2. Discussion of the Related Art 
         [0005]    The treatment of wastewater typically includes passing wastewater through a settling tank or sediment basin for separating and removing contaminants such as grease, oil, and sediment by gravity. Settling tanks may also be divided into two or more basins to accommodate down time for cleaning or inspecting one basin while allowing one or more basins to continue to function normally without impacting the overall volume of water being treated. 
         [0006]    As the sediment accumulates over time, it is necessary to periodically clean the settling tanks to ensure proper operation. To remove accumulated solids, a tank may be drained and the sediment removed. Such costly and time intensive cleaning may typically be done only about once or twice a year. 
         [0007]    While the purpose of a settling tank is to allow the collection of sediment at the bottom of the tank, over time solids material may also accumulate along the walls of the tank. The material accumulates along the wall at the water surface, which typically rises and falls a short distance, e.g. 1 to 4 inches, usually about 2 inches. Thus, the material accumulates in the form of a short (e.g. two-inch) band along the tank walls. Each assembly  230  includes a scrape blade  231  extending downwardly from a respective side of the sled assembly  200 . To reduce this accumulation and control the unwanted build-up, the walls of a settling tank are frequently cleaned with a scraper to allow the accumulation to break free and reenter the flow of water being treated. The time consuming and laborious work of scraping the walls is generally done by a person walking along the edge of each wall scraping the wall with a scraper blade on a long handle. Settling tank walls are typically ten to twelve feet tall and obviously pose significant risks, such as a fall or physical contact with waste materials, to an individual working along their sides. 
         [0008]    These risks are elevated when the person is scraping the center or separation walls between basins, because a separation wall is generally less than a foot wide and can be several hundred feet long. 
         [0009]    These and other deficiencies exist with conventional settling tank cleaning methods. Therefore, a solution to these and other problems is needed providing a settling tank scraper specifically designed for ease of use and to minimize the dangers to an operator. 
       SUMMARY OF THE INVENTION 
       [0010]    One aspect of the invention involves an apparatus for scraping a wall of a settling tank, comprising: 
         [0011]    a mobile carrier having opposite ends defining a front-to-rear axis of the carrier, the carrier configured to travel along the top of a wall of a settling tank, and 
         [0012]    a scraper blade carried by the carrier and projecting downwardly from one side of the carrier, 
         [0013]    wherein a bottom portion of the blade includes a scraping edge facing in a travel direction of the carrier and having a height dimensioned to scrape a band of built-up solids from a surface of the wall. 
         [0014]    Another aspect of the invention involves an apparatus for scraping a divider wall of a settling tank, comprising: 
         [0015]    a mobile carrier having opposite ends defining a front-to-rear axis of the carrier, the carrier configured to travel along the top of a divider wall of a settling tank; and 
         [0016]    first and second scraper blades carried by the carrier and extending downwardly from respective sides of the carrier; 
         [0017]    wherein the bottom portions of the first and second scraper blades are biased toward one another during a wall-scraping operation in order to firmly engage respective opposite surfaces of the divider wall for scraping respective bands of built-up solids from such surfaces. 
         [0018]    Yet another aspect of the invention relates to a method for scraping a wall of a settling tank comprising the steps of: 
         [0019]    moving a carrier along a top of the wall; and 
         [0020]    causing the bottom portion of a scraper blade carried by, and extending downwardly from, the carrier to engage a surface of the wall to scrape a band of built-up solids from the surface. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0021]    The accompanying drawings, which are included to provide further understanding of the invention and are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and together with the description serve to explain the principles of the invention. In the drawings: 
           [0022]      FIG. 1  provides a top view of a typical settling tank with two sediment basins separated by a center wall; 
           [0023]      FIG. 2A  shows a front view of a settling tank scraper, according to an embodiment of the present invention; 
           [0024]      FIG. 2B  shows a top view of a settling tank scraper, according to an embodiment of the present invention; 
           [0025]      FIG. 2C  shows a detailed view of scraper blade assemblies attached to a center support member for a settling tank scraper, according to an embodiment of the present invention; 
           [0026]      FIG. 2D  shows a blade assembly for a settling tank scraper, according to an embodiment of the present invention; 
           [0027]      FIG. 2E  shows a side view of a settling tank scraper, according to an embodiment of the present invention; and 
           [0028]      FIG. 2F  shows a detailed view of a roller and axle configuration for a settling tank scraper, according to an embodiment of the present invention. 
           [0029]      FIG. 2G  shows a cross-sectional view taken along plane  2 G- 2 G in  FIG. 2D . 
           [0030]      FIG. 2H  is a fragmentary view showing how a scraper blade can be in multiple pieces and vertically adjustable. 
       
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
       [0031]    Reference will now be made in detail to various embodiments of the present invention, examples of which are illustrated in the accompanying drawings. 
         [0032]      FIG. 1  provides a top view of a settling tank including two sediment basins separated by a center divider wall. A settling tank  10  typically includes a basin formed by side walls  130 A and  130 B and end walls  132 A and  132 B in which waste water enters through one or more influent lines  110 A and  110 B through end wall  132 A and exits through one or more effluent lines  120 A and  120 B through end wall  132 B. As the water passes through the basin, sediment and other waste material will separate from the water by dropping to the bottom of the basin. As shown in  FIG. 1 , settling tank  10  also includes a center or divider wall  150  to create multiple basins  140 A and  140 B within the settling tank  10 . While the sediment and waste products within the wastewater will typically settle to the bottom of the settling tank, build-up also occurs along the walls of the tank. The material accumulates along the wall at the water surface, which typically rises and falls a short distance, e.g. 1 to 4 inches, usually about 2 inches. Thus, the material typically accumulates in the form of a short (e.g. two-inch) band along the tank walls. The height H of such a band is shown in  FIG. 2A . The build-up must then be removed on a regular basis to ensure proper operation of the tank. 
         [0033]      FIG. 2A  shows a front view of a settling tank scraper, according to an embodiment of the present invention. The settling tank scraper  20  shown in  FIG. 2  includes a mobile carrier in the form of a sled assembly  200 , and one or more scraper blade assemblies  230 . The sled assembly  200  travels along the top of a settling tank wall (i.e. a side wall on a divider wall  250 ) allowing the scraper blade assemblies  230  to scrape along the side surfaces of the wall  250 . 
         [0034]    The sled assembly  200  shown in  FIG. 2A  includes a support frame assembly  210 , one or more guides  204 , and one or more floor-support rollers  206 . The support frame assembly  210  provides the basic structure of the sled assembly  200  and includes opposite ends defining a front-to-rear axis A ( FIG. 2B ). The one or more guides  204  attach to the support frame assembly  210  and extend downwardly therefrom to maintain the position of the settling tank scraper  20  on wall  250  as it is moved. 
         [0035]    As shown in  FIG. 2A , the guides  204  extend below the top of wall  250 . In further embodiments, one or more guides  204  may be configured to move along a track, groove, or some other mechanism to support the proper movement of the tank scraper  20 . 
         [0036]    The rollers  206  attach to the sled assembly and provide for a smooth movement along the wall  250 . In one embodiment, the rollers  206  connect to the guides  204 . In further embodiments, the rollers may connect directly to the frame assembly  210  or other roller supporting structures. The rollers  206  may be made of plastic, metal, or other suitable materials or combination of materials. The rollers  206  may be solid or hollow. In a hollow roller embodiment, the roller may include a sealable opening to allow for filling the roller with water or other substance to increase the weight of the roller while in use. The rollers rotate about respective horizontal axes oriented perpendicular to axis A. 
         [0037]    The embodiment shown in  FIG. 2A  is designed to ride along the top of a pre-existing center wall. However, further embodiments are envisioned in which the sled assembly  200  and the center wall  250  are specifically adapted for use of the tank scraper. For example, a track may be attached to the top of the center wall  250  providing a mating surface for the sled assembly  200 , which may use rollers as shown in  FIG. 2A , a sled, or other rolling or sliding mechanisms, for example. 
         [0038]    One or more scraper blade assemblies  230  is connected to the sled assembly  200  at a pivot point  220 . Each assembly  230  includes a scraper blade  231  extending downwardly from a respective side of the sled assembly  200 . A tensioning device, such as a tension spring  232 , is attached to both blade assemblies  230  to bias bottom scraping ends  231   a  of the blades  231  toward one another, i.e., toward a vertical center plane B of the sled assembly  200 , and thus ensure proper contact with the surface of the wall  250 . 
         [0039]    Alternatively, the blades  231  could be angled sharply toward the center plane B to firmly engage the wall by inherent elasticity of the blade, and/or separate springs could be provided for the respective blades. In the embodiment shown in  FIG. 2A , the scraper blade assembly  230  includes an attachment end with a bend and an attachment hole to allow the scraper blade assembly  230  to attach to the sled assembly. 
         [0040]      FIG. 2B  shows a top view of a settling tank scraper, according to an embodiment of the present invention. As shown in  FIG. 2B , the support frame assembly includes side members  212 A and  212 B, front support member  214 , rear support member  216 , and center support member  218 . Various attachment points  224  may also be configured for attaching a towing device  222 , such as a rope, cable, chain, or other mechanism for pulling the support frame assembly. In a further embodiment, a second towing device  223  may be attached to the rear of the sled assembly for maintaining stability of the frame assembly while it is pulled with towing device  222 , as well as for pulling the sled assembly to return the tank scraper to its starting position. The sled may also be pulled in one direction for a first scraping pass and pulled in the opposite direction when a second scraping pass is necessary. The towing devices  222  and  223  may be pulled manually or mechanically with a winch or other device, e.g., motor-driven. Rollers  206 A and  206 B, as shown in  FIG. 2B , are mounted with axles  207 A and  207 B. 
         [0041]    The scraping end  248  is sufficiently flexible to enable the lower portion of the blade  249  to somewhat flatten out and engage flush against the wall when pulled against the wall. Only a slight amount of flexing is necessary since the height H of the band of material to be scraped is relatively short, e.g., about 1-4 inches, or closer to 2 inches. 
         [0042]    Alternatively, the blade could be formed with a lower end that is bent so as to engage flush with the wall. 
         [0043]      FIG. 2C  shows a detailed view of scraper blade assemblies attached to a center support member for a settling tank scraper, according to an embodiment of the present invention. In  FIG. 2C , each scraper blade assembly  230 A and  230 B is attached to center support member  218  with support rod  219  through pivot point  220  to pivot about an axis coinciding with the front-to-rear axis A. A bushing  233  is placed within pivot point  220  to provide a wear surface between the center support member  218  and the support rod  219 . Each blade assembly  230 A and  230 B is then attached in a similar manner with a first washer  234  between the center support member  218  and the blade assembly  230 A and  230 B. The first washer  234  facilitates the movement of the blade assembly as it is tensioned against the tank wall. A second washer  235 , an adjustment nut  236 , and a locknut  237  are then used to secure the blade to the support rod. The adjustment nut  236  and locknut  237  are adjusted to allow movement of the blade assembly  230 A and  230 B. In further embodiments, multiple pivot points  220  may be provided in the center support member  218  to allow each blade assembly to be independently attached. 
         [0044]      FIG. 2D  shows a blade assembly for a settling tank scraper, according to an embodiment of the present invention. As described above, the blade assembly  230  includes an attachment end  241  and a scraping end  248 . In the embodiment shown in  FIG. 2D , the attachment end  241  includes a bend  242  of approximately 45 degrees, an attachment flange  244 , and a support flange  246 . The attachment flange provide additional strength and stiffness to the top of the attachment end  241  and further includes an attachment point  245  through which a support rod is passed. The attachment end  241  also includes a support flange  246  for increased strength and stiffness along the length of the blade assembly  230 . In one embodiment, the scraping end  248  includes a double edged scraper blade  249  (see  FIG. 2G  showing the two scraping edges  249   a ) allowing the tank scraper to scrape a tank wall while being pulled in either direction along the wall. A tensioning spring  232  is also shown connected to the attachment end of the blade assembly  230 . The scraping end  248  is sufficiently flexible to enable the lower portion of the blade  249  to somewhat flatten-out and engage flush against the wall when pulled against the wall. Only a slight amount of flexing is necessary since the height H of the band of material to be scraped is relatively short, e.g., about 1-4 inches, or closer to 2 inches. 
         [0045]    Alternatively, the blade could be formed with a lower end that is bent so as to engage flush with the wall. 
         [0046]    In a further embodiment, a scraper blade assembly  230  may be configured with a separate attachment end  241  and a separate scraper end  248 . In such an embodiment, the attachment end is configured to attach to a pivot point of the sled assembly and the blade end  248  attaches to the attachment end  241 . According to one embodiment, the attachment end  241  and the blade end  248  may be configured to slide together for ease of blade replacement. In further embodiments, the blade end  248  may be attached with bolts, rivets, or other connecting devices  251  ( FIG. 2H ). Such embodiments provide the ability to quickly change a blade that is worn or damaged without disconnecting the entire blade assembly from the sled assembly. Such embodiments may also include additional holes  253  (see  FIG. 2H ) to provide the ability to adjust the elevation at which the scraping end contacts the tank wall to accommodate differing water levels or scraping procedures. 
         [0047]      FIG. 2E  shows a side view of a settling tank scraper, according to an embodiment of the present invention. In  FIG. 2E , the tank scraper is shown in relation to a tank wall  250 . In the embodiment shown, guides  204  are attached to a support frame assembly  210  and provide an attachment point for the rollers  206 A and  206 B. As shown in  FIG. 2E , the guides  204  extend below the top of tank wall  250  for stabilizing the tank scraper as it is pulled along the tank wall  250 . Scraper assemblies  230 A and  230 B are also shown extending below the top of tank wall  250  to reach build-up collected on the side of tank wall  250 . 
         [0048]      FIG. 2F  shows a detailed view of the roller and axle configuration for a settling tank scraper, according to an embodiment of the present invention. Roller  206  is mounted to guides  204  with an axle  207  and a series of washers  260 , axle nuts  262 , adjustment nuts  264 , locknuts  266  and a cotter pin  268 . 
         [0049]    As a further alternative, the blades  249  could be pivotably mounted to a common sled at locations corresponding to the end of the lead line for numeral  242  in  FIG. 2D . The pivot axis for each blade would be horizontal and in the direction of sled travel. 
         [0050]    While various examples have been provided, it will be apparent to those skilled in the art that various modifications and variations can be made in the present invention without departing from the spirit or scope of the invention. Thus, it is intended that the present invention cover the modifications and variations of this invention provided that they come within the scope of any claims and their equivalents.