Patent Abstract:
The invention is directed to a system for removing waste material from a fluid flowing in a channel. This system may incorporate the use of a trap for collecting the waste material while allowing the fluid to pass; a rake for removing the waste material away from the trap; a drive assembly for moving the rake to remove the waste material; a prime mover for operate the drive assembly; and a variable speed controller configured for operating the prime mover over a variable range of speeds.

Full Description:
RELATED APPLICATION  
       [0001]     This application is a divisional of application Ser. No. 10/455,069, filed Jun. 5, 2003, incorporated herein by reference. 
     
    
     FIELD OF THE INVENTION  
       [0002]     The field of the invention is wastewater cleaning systems, and more particularly systems for removing debris and other materials from wastewater.  
       BACKGROUND  
       [0003]     Systems are needed for the removal of unwanted material from wastewater and other fluids. For example, bar screens are often used to protect a wastewater plant or pumping station against the entry of large objects that are likely to cause blockage in different parts of the installation, and to separate and extract bulky matter carried in the raw influent that is likely to interfere with subsequent operation or to create complications in the treatment process.  
         [0004]     Screening is typically performed either with manually-cleaned bar screens or (when the plant is sufficiently large) with an automatically-cleaned bar screen system called a mechanical bar screen. These bar screen systems are typically installed in a fluid channel prior to entry of the influent to the treatment system to physically remove debris from the fluid as it travels along the channel.  
         [0005]     These systems may utilize a hoist rope, pin rack or other such system to which a rake is attached. The bar screen extends down from the rack into the fluid channel to collect the debris. An electric motor, and possibly a hydraulic fluid pump, is typically used to drive the rake, forcing it down into the fluid, where it scoops up debris, dragging it up along the bar screen and up to a discharge apron, where the debris falls into a disposal unit, such as a cart or other conveyor.  
         [0006]     During this process, the flow of the fluid through the channel does not need to be interrupted, and continues to flow during the cleaning process. While the mechanical bar screen normally operates at predetermined speed based upon the flow rate of the influent, systems are also known that may operate at two predetermined speeds; one for the off-peak flow rate and one for the peak flow rate. The system may be switched between these two speeds by the operator.  
         [0007]     However, such systems cannot be adaptively controlled to account for ongoing variations in the flow rate of the fluid through the channel, and therefore cannot operate at maximum efficiency when fluctuations in flow rate occur. A system is therefore needed that improves upon these other designs.  
       SUMMARY OF THE INVENTION  
       [0008]     Embodiments of the invention may include a system for removing waste material from a fluid flowing in a channel. This system may incorporate the use of a trap for collecting the waste material while allowing the fluid to pass; a rake for removing the waste material away from the rack; a drive assembly for moving the rake to remove the waste material; a prime mover for operating the drive assembly; and a variable speed controller configured for operating the prime mover over a variable range of speeds. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0009]     The foregoing and other aspects and advantages will be better understood from the following detailed description of the invention with reference to the drawings, in which:  
         [0010]      FIG. 1  illustrates a mechanical bar screen system.  
         [0011]      FIG. 2  illustrates a hydraulic mechanical bar screen system.  
         [0012]      FIG. 3  illustrates an electrical mechanical bar screen system. 
     
    
     DETAILED DESCRIPTION  
       [0013]     The invention will be understood more fully from the detailed description given below and from the accompanying drawings of the preferred embodiments of the invention; which, however, should not be taken to limit the invention to a specific embodiment, but are for explanation and understanding only.  
         [0014]      FIG. 1  illustrates a mechanical bar screen system. Fluid channel  100  contains the influent, which is flowing at a given flow rate through the channel. The flow rate of this fluid may periodically vary due not only to predetermined peak and off peak flow rates, but also to changes in demand or other conditions that may vary the flow rate in a manner that has not previously been determined. Trap  102  may extend down into fluid channel  100 , trapping debris against it as the influent flows past. Those of ordinary skill in the art will appreciate that trap  102  may comprise any mechanism for collecting the debris, such as a wire screen, mesh, grating, porous material, etc. Trap  102  may be attached directly to fluid channel  100 , although the invention is not limited thereto.  
         [0015]     Rake  104  is shown in an extended position as it prepares to remove the debris collected on trap  102 . Rake  104  may be operated by drive assembly  106 , which is connected to hoist  120 . In this embodiment, hoist  120  may be a pin rack and drive assembly  106  contains a cogwheel operating on the pin rack, although any mechanism capable of moving drive assembly  106  may be used, such as a rope and pulleys, etc. Hoist  120  drive assembly  106  may be operated by prime mover  108 . Prime mover  108  may comprise any mechanism capable of moving driving assembly  106 , such as an electric motor, a hydraulic motor, etc. Prime mover maybe located on drive assembly  106 , or may be located separately. The invention is not limited.  
         [0016]     This may be accomplished in any conventional manner. For example, prime mover  108  may circle drive assembly  106  around hoist  120  within frame  116 ; causing drive assembly  106 , to move downward to the bottom of frame  116 , around, and then back up; repeating this process as necessary. The movement of drive assembly  106 , forces rake  104  down to the bottom of fluid channel  100  and up along bar screen  102 .  
         [0017]     Drive assembly  106  is preferably configured so that rake  104  is extended out away from bar screen  102  as it is lowered into fluid channel  100 . For example, drive assembly  106  moves downward along pin rack  120 , support arm  105  (which may be connected between rake  104  and drive assembly  106 ) may move outwardly due to its connection to drive assembly  106 , causing rack  104  to move outwardly as well. As drive assembly  106  rounds the bottom of pin rack  120 , support arm  105  forces rack  104  against bar screen  102 , trapping the debris therebetween.  
         [0018]     As drive assembly  106  then moves upward, rake  104  drags the debris up along bar screen  102  until it reaches discharge apron  112 . Wiper  114  may then be used to wipe the debris away from rake  104 , forcing the debris down into disposal cart  110 . Once disposal cart  110  is filled, it may be removed and emptied. Of course, those of ordinary skill in the art will appreciate that any means of disposing of the debris may be used instead of cart  110 , such as a conveyor, for example.  
         [0019]     The speed of operation of prime mover  108  may be controlled by controller unit  109 . In the case of a hydraulic motor, for example, controller unit  109  controls the amount (e.g., volume) and pressure of the hydraulic fluid circulating in the system, such as by using a flow control unit. In the case of an electric motor, controller unit  109  controls the speed of the motor, such as by varying the frequency using a variable frequency controller. Of course, those of ordinary skill in the art will appreciate that the invention is not limited thereto and that prime mover  108  and controller  109  may comprise any mechanism for moving a drive assembly  106 , such as pneumatic systems, electromagnetic systems, etc. Moreover, prime mover  108  and controller  109  may comprise one device or several devices for accomplishing the movement of drive assembly  106 .  
         [0020]     A reverse motion proximity switch  118  may also be included for preventing drive assembly  106  from reversing motion over wiper assembly  114  to avoid any damage to wiper assembly  114 . In operation, it may be necessary to reverse the motion of drive assembly  106 , such as for cleaning or manually removing debris from the system. While moving in reverse, as the cogwheel of drive assembly  106  comes into proximity to wiper  114 , proximity switch  118  disengages or stops prime mover  108 , causing drive assembly  106  to stop before it passes over wiper  114 . Similarly, an end of travel proximity switch  122  may be included to stop the motion of drive assembly  106 . As drive assembly  106  contacts end of travel proximity switch  122  it disconnects or stops prime mover  108 , stopping drive assembly  106 . The interaction of proximity switches with electric motors and hydraulic motors is well-known to those of ordinary skill in the art and will not be further elaborated upon here.  
         [0021]      FIG. 2  illustrates a schematic for one embodiment of a variable speed control system in accordance with the invention. As shown in  FIG. 2 , motor  204  is connected to fluid pump  210  via coupling assembly  208 . In this embodiment, the speed of motor  204  may remain constant (as the volume and pressure of fluid may be controlled by flow control  216 ). Coupling assembly  208  is also not particularly limited and may comprise, for example, a pump half coupling, motor half coupling, coupling spider and pump/motor adapter, the interconnection of which is well-known of those of ordinary skill in the art. Fluid pump  210  is also not limited, and may comprise, for example, a pressure compensating piston pump.  
         [0022]     Fluid pump  210  may be connected to a pressure compensated flow control  216  through check valve  214 . Shutoff valve and gauge  212  may also be incorporated for measuring the fluid flow from pump  210 . Pressure compensated flow control  216  is not particularly limited and may comprise, for example, adjustable pressure compensated flow control, in which the flow of fluid through the valve may be continuously and/or incrementally varied across the flow range by opening or closing an internal piston within the flow control valve. The variation in flow may be done manually (such as by adjusting a knob) or automatically using a logic board or similar type of controller. The operation of fluid flow control systems is well known to those of ordinary skill in the art and will not be further elaborated upon here.  
         [0023]     Pressure compensated flow control  216  may control the passage of fluid through flow meter  218  to subplate  220 , which contains relief valve  222 . Directional valve  224  may also be included for controlling the direction of hydraulic fluid flow to hydraulic motor  250 . In addition, ball valves  226  may be included to provide flow to hydraulic motor  250 , which may be in communication with drive assembly  106  and/or hoist  120 , and may be driven by the hydraulic fluid circulated through this system in order to control the operation of rake  104 .  
         [0024]     The hydraulic fluid may then flow through check valve  228  and gauge  230  to pressure switch  232 . After passing through needle valve  234 , the fluid may pass through water/oil heat exchanger  236 , where its temperature may be controlled by modulating water valve  240  and solenoid valve  242 . The practice of using heat exchangers in this manner is well known to those of ordinary skill in the art and will not be further elaborated upon here.  
         [0025]     Fluid passing through filter  238  may than be stored in reservoir  202  for reuse by fluid pump  210 . Strainer  250  may also be included for removing particles from this stored fluid to prevent the particles from being carried through fluid pump  210 .  
         [0026]     A temperature/level switch  244  and bulb well  246  may be used for monitoring the level of hydraulic fluid in the system. Ball valve  248  may also be included for draining excess fluid from the system. Fluid may be replaced using an access port at the top of reservoir  202 .  
         [0027]     An alternative embodiment is shown in  FIG. 3 . In this embodiment, a variable speed electric motor system may be used. The speed of motor  304 , which maybe located on carriage  106  or located separately therefrom, may be continuously and/or incrementally varied by controller  304 . Motor  304  and controller  306  are not particularly limited, however, but may comprise, for example, a variable frequency drive and multi-phase motor, in which the speed of the motor may be controlled by varying the frequency of the current supplied to the motor. As the speed of motor  304  is varied, the speed of cogwheel  107  of carriage  106  is varied on pin rack  105 , varying the speed of operation of rake  104 .  
         [0028]     Although this invention has been described with reference particular embodiments, it will be appreciated that many variations may be resorted to without departing from the spirit and scope of this invention. For example, any hoist system may be used for moving the rake up along the debris trap, such as, ropes and pulleys, geared systems, a pin rack, etc. Any system capable of moving a drive assembly along this hoist may be used as well, such as electrical, mechanical, hydraulic, pneumatic, electromagnetic, etc.

Technology Classification (CPC): 1