Abstract:
A stepping screen assembly bottom portion is located in a liquid waste stream containing solids. The assembly contains a grid structure containing dynamic and static bars horizontally spaced apart. An outer frame on one side of the grid structure contains a pair of hydraulic cylinders operating rods which move the dynamic grid structure outwardly, upwardly, backwardly and downwardly to cause the solids to be lifted from the liquid waste stream for deposit on a conveyor.

Description:
FIELD OF THE INVENTION 
     This invention relates to a screen assembly for collecting and discharging solid matter from a liquid-solid mixture in a waste stream. More particularly, it refers to a hydraulic drive assembly containing a stepping screen for lifting solids out of a waste water stream and depositing them in a solids repository. 
     BACKGROUND OF THE INVENTION 
     It is well known in the prior art as shown in U.S. Pat. No. 4,853,116 to use a driving motor with an associated gear box propelling a pair of chains to move a grid structure upwardly and thereby lift solids out a liquid-solid mixture in a waste stream. Saw teeth are formed on combinations of displaceable bars and stationary bars to prevent the displaceable bars from becoming blocked. Such a system, while accomplishing its intended purpose, is cumbersome and unusually complex resulting in a high cost assembly of components. A more efficient and cost effective system is needed. 
     SUMMARY OF THE INVENTION 
     The present invention overcomes the deficiencies of the assembly described in U.S. Pat. No. 4,853,116 and provides an efficient cost effective means of removing solids from a liquid waste stream. 
     The invention is directed to an assembly of a grid structure surrounded by an outer frame with the assembly bottom portion located in a liquid waste stream containing solids. The grid structure includes multiple parallel alternate static and dynamic bars. Each bar has multiple vertically spaced apart shelves at a right angle to the vertical axis of the bar. 
     The dynamic bars have multiple spacers located on each side surface to space the dynamic bars from the static bars and support the horizontal displacement of the bars. 
     The outer frame on each side of the grid structure contains a pair of hydraulic cylinders connected to the dynamic bars by a shaft and mounting plate. One hydraulic cylinder of each pair causes the dynamic bars to move in a vertical plane and the other hydraulic cylinder of each pair causes the dynamic bars to move in a horizontal plane as dictated by a preprogrammed hydraulic system. 
     The grid structure moves solid material upwards and over the top of the grid structure to fall by gravity onto a conveyor for delivery of the solids to a waste receptacle. The liquid moves through the grid structure without impediment. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The invention may be best understood by those having ordinary skill in the art by reference to the following detailed description when considered in conjunction with the accompanying drawings in which: 
     FIG. 1 is a perspective view of the stepping screen assembly of this invention and a conveyor belt. 
     FIG. 2 is a cut-away elevational view of the assembly side frame containing the hydraulic piston driving mechanism depicting a home stage. 
     FIG. 3 is a cut-away elevational view according to FIG. 2 depicting movement of the dynamic bars outwardly with respect to the static bars. 
     FIG. 4 is a cut-away elevational view of the assembly side frame containing the hydraulic piston driving mechanism depicting a dynamic bar moved upwardly to raise solid matter. 
     FIG. 5 is a cut-away elevational view according to FIG. 4 with the driving mechanism depicting movement of the dynamic bars upwardly to raise solid matter. 
     FIG. 6 is a cut-away elevational view of the assembly side frame containing the hydraulic piston driving mechanism depicting the dynamic bars moved backwardly. 
     FIG. 7 is a cut-away elevational view according to FIG. 6 depicting the dynamic bars moving backwardly. 
     FIG. 8 is a cut-away elevational view of the assembly side frame containing the hydraulic piston driving mechanism depicting the dynamic bars moved downwardly. 
     FIG. 9 is a cut-away elevational view according to FIG. 8 depicting the dynamic bars moved downwardly. 
     FIG. 10 is a magnified view of a valve controlling a piston in the extended position. 
     FIG. 11 is a magnified view of a valve controlling a piston in the retracted position. 
     FIG. 12 is a perspective view of a static bar attached to top and bottom mounting plates. 
     FIG. 13 is a perspective view of the dynamic bars mounted in intermediate mounting plates. 
     FIG. 14 is a schematic of the hydraulic system employed to move the dynamic bars. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Throughout the following detailed description, the same reference numbers refer to the same elements in all figures. 
     The stepping screen assembly  10  shown in FIG. 1, together with a conveyer assembly  12  lifts solid matter  14  from a waste water stream  16  and eventually deposits the solid matter in a waste repository. Waste water  20  free of solid matter  14  proceeds through the stepping screen without impediment. Only the bottom portion  22  of the stepping screen assembly  10  is immersed in the waste water stream  16 . 
     The stepping screen assembly  10  as shown in FIG. 1 is upwardly inclined and contains a grid structure  24  surrounded by an outer frame  26 . The grid structure  24  contains alternating static  28  and dynamic  30  elongated bars as shown in more detail in FIGS. 2-9. 
     The static bars  28  remain in a fixed position within the grid structure  24  and are mounted in relation to the dynamic bars  30  as shown in FIGS. 3,  5 ,  7  and  9 . A bottom plate  32  has slots  34  into which a bottom end  36  of static bar  28  fits as seen in FIG.  12 . Multiple shelves  44  at a right angle to the vertical axis of the static bar  28  are equally spaced apart along static bar  28  facing outwardly from a rear edge  46 . A spacer  48  is mounted along an outer surface  50  above the bottom end  36  of a first static bar positioned at the outermost edge of the grid structure  24  at each side adjacent the outer frame  26 . A top end portion  42  is attached in grooves  40  in the disposal plate  38 . 
     The dynamic bars  30  shown in FIGS. 3,  5 ,  7  and  9  are driven by a pair of hydraulic pistons mounted on one side of the stepping screen  10  within an outer frame  26 . A first hydraulic piston  52  causes connecting rod  54  to move hinged member  56  attached to shaft  58  connected to the dynamic grid to move the dynamic bars  30  in a front to back and reverse configuration. A second hydraulic piston  60  causes the shaft  58  to move up or down. A collar  62  connects to lower portion of the hinged member  56  to a shaft  58 . 
     Hydraulic piston  52  is activated by a four way, two position valve  64  and hydraulic piston  60  is activated by a four way, two position valve  66 . Oil line  68  carries oil from the oil reservoir (not shown) to the hydraulic system and oil line  70  carries the oil out of the system to the oil reservoir. Piston  52  is held in place by anchor  72  and piston  60  is held in place by anchor  74 . Stops  76  and  78  respectively on control rod  80  instruct the valve  64  as to action of piston  60 . Stops  82  and  84  respectively on control rod  86  instruct the valve  66  as to the action of piston  52 . Bearings  88  guide the control rods  80  and  86 . 
     As seen in FIGS. 2 and 3, the down stroke of piston  52  moves the dynamic plate outwardly. As seen in FIG. 4 and 5, the upstroke of piston  60  moves the dynamic plate upwardly. As seen in FIGS. 6 and 7 the downward stroke of piston  52  moves the dynamic plate backwardly. As seen in FIGS. 8 and 9 the downward stroke of piston  60  moves the dynamic plate downwardly. 
     As seen in FIG. 10, stop  76  engages valve rod  90  when control rod  80  reaches the maximum down stroke and as seen in FIG. 11, stop  78  engages valve rod  90  when control rod  80  reaches the maximum upstroke. Plate  102  supports the valve  64  and is attached to outer frame  26 . 
     As seen in FIG. 13, all the dynamic bars  30  are mounted within grooves  96  in transverse mounting plates  100 . A description of the movement of the dynamic bars is described in detail in U.S. Pat. No. 6,177,020, incorporated herein by reference. 
     As seen in FIG. 13, each dynamic bar  30  has multiple outwardly directed shelves  92  at a right angle to the vertical axis of each bar  30  and are used to lift solid matter  14  upwardly along the grid structure  24 . Each shelf  92  is equally spaced apart from the next adjacent shelf. Multiple spacers  48  are positioned on each side surface of each dynamic bar  30  to maintain a proper relationship to the static bars  28  and act as a strengthening element for the bars  28  and  30 . A back edge  98  of each dynamic bar  30  is mounted in a slot  96  in intermediate plate  100 . The diameter of each spacer  48  is 2 ml to 9 ml to determine the openings in the grid structure  24 . The spacers  48  also act to push solid material off static bars Referring to FIGS. 2-9, operation of the grid structure  24  will be described. FIGS. 2-3 show the home stage when the static bars  28  and dynamic bars  30  are perfectly aligned, but spaced apart by spacers  48 . In this mode, solid matter  14  in the waste water stream  16  is deposited on the grid structure  24 . FIGS. 4-5 show the dynamic bars  30  moving upwardly in response to an upward stroke from cylinder  60 . This stroke lifts solid matter  14  from the waste water stream  16 . FIGS. 6-7 show the inward movement of dynamic bars  30  so that the solid matter is deposited on shelves  44  of the static bars  28 . This movement is in response to a downward stroke by cylinder  52 . 
     FIGS. 8-9 show the downward movement of dynamic bars  30  in response to the downward stoke from cylinder  60 . This results in a retreat to the home stage in FIG. 3 when cylinder  52  causes an upward stroke to move dynamic bars  30  outwardly. 
     FIG. 14 shows the oil system including pressure gauge  94  to control the pressure in hydraulic pistons  52  and  60 . 
     The bars  28  and  30  as well as the other components of the grid structure  24  and the outer frame as well as the associated conveyor assembly  12  are made from stainless steel. 
     Referring back to FIG. 1, the solid matter  14  is moved upwardly along the grid structure  24  as described above until it reaches the disposal plate  38  from which it slides downwardly to standard conveyor assembly  12 . The solid matter  14  is thereafter lifted upwardly to a waste repository. In this manner, solid waste  14  is removed from waste water stream  16  and the water moves through the grid structure  24  to a waste stream  20  free of solid matter. Thereafter, the waste stream  20  can be treated in accordance with standard treatment procedure. 
     The above description has described specific structural details embodying the invention. However, it will be within one having skill in the art to make modifications without departing from the spirit and scope of the underlying inventive concept of this stepping screen assembly. The inventive concept is not limited to the structure described, but includes such modifications and equivalents within the knowledge of one having skill in this art.