Abstract:
A sewage cleaning and comminuting system is provided with a transverse semi-circular concave filtering screen that extends across an influent channel which intercepts all solids too large to pass therethrough. A combined screen cleaning and comminuting grinder unit is mounted in front of the screen in close relationship. It has a concave surface for reciprocating motion therebetween along the full extent of the screen, so as to clean and remove large solids intercepted by the screen surface, and to subsequently comminute such larger solids. As they are recirculated back into incoming flow of sewage, larger solids are ground into smaller solids by the grinder so that they can pass through the screen. A semi-circular screen in combination with a grinder is a preferred embodiment of the system. The system includes a single or multiple drive means whereby the comminuting grinder is actuated and provided with the reciprocating motion along the surface of the screen.

Description:
FIELD OF INVENTION 
     The present invention relates to a screen cleaning and comminuting system for sewage. The system comprises an intercepting and filtering screen for sweeping agglomerated or captured solids of large size and means for subsequently comminuting such particles into smaller solids that may pass through the screen. 
     BACKGROUND OF THE INVENTION 
     Prior art processing of sewage and wastewater often involves handling large volumes of sewage and wastewater flow in a channel, in order to separate solid and agglomerated matter therein and comminute such matter. It employs means of various screening and shredding devices in combination, which are positioned in the wastewater flow within the channel. 
     U.S. Pat. No. 5,490,922 discloses a sewage water installation that has a discharge basin in which is arranged a screening unit linked to a back-and-forth movable cleaning carriage. The mesh screen unit is depicted schematically and includes a plurality of parallel spaced bars forming the screen. A cleaning car, which moves back and forth, is allocated to the mesh screen. If the mesh screen is longer, several cleaning cars can be provided. A preferred cleaning car is provided with teeth that are designed correspondingly and arranged to protrude between the screen bars of the mesh screen and is intended for cleaning between the screen bars. 
     U.S. Pat. No. 2,672,985 discloses a transverse linear screen extending across an influent channel that intercepts all solids too large to pass therethrough. The screen consists of a plurality of parallelly disposed U-shaped members, with the U-shaped portions extending towards the inflowing sewage, forming a series of slots of the screen. A comminuting unit is disposed in parallel spaced relationship and in close proximity with the screen surface to remove collected solid materials therefrom by means of a cutting cylinder having a rotable shaft to which a plurality of cutting cylinders and combs are secured. As the comminuting unit travels back and forth along the width of a single linear screen by means of a direct drive motor in engagement with a rack device, the teeth project into the U-shaped portion of the slot members so as to remove solids intercepted by the screen. More details may be seen in FIGS. 5, 9, 10, 11 and 12 of the patent. 
     In U.S. Pat. No. 5,833,152, a unitary comminuting system, adapted for wastewater channel use, is provided with devices, which include a single or dual semi-cylindrical-like sizing screen. Each has a circular rotating sweeping mechanism of interactive slotted comb bars or blades. It sweeps and clears lodged or agglomerated solids adhering to the outer convex circumference surface of the screen, disposed in parallelly spaced relationship with a twin shaft shredder device having two parallel shafts with shredder or grinder teeth along the length thereof that rotate in opposite senses. The unitary system of devices is positioned perpendicularly between the influent and effluent sides of the wastewater flow in a channel so that solids therein will encounter the convex surface of the semi-cylindrical-like sizing screens or the twin shaft shredder as the wastewater flows through the channel. Both the single or dual semi-cylindrical-like screen devices cause solids, which do not flow directly there through, to be forcefully swept from the outer convex surface of the sizing screen. This employs the separate rotating sweeping interactive blade mechanism into surrounding the wastewater flow, so as to cause and divert or direct the solids to flow toward or into the contiguous twin shaft shredder device. This is aided by circulating wastewater currents generated in the wastewater flow near the entrance to the twin shaft shredder. It is generated in part by the rotating sweeping interactive blades of the screening devices, whereupon the removed solids are channeled into the twin shaft shredder device along with the other wastewater and solids flow where they are reduced in particle size. 
     These prior art devices were crudely constructed, difficult and costly to install, because they provide coarse and incomplete particulate processing and unreliable systems subject to frequent maintenance. 
     In U.S. Pat. No. 4,919,346, a moving mesh conveyor-screen allows flow to pass through while it diverts the solids to an adjacent twin shaft grinder for reduction in a unitized system. This invention is subject to screen maintenance and effectiveness problems as well as cutting efficiency problems to be discussed below. Its invention was superceded by U.S. Pat. No. 5,505,388 design because the screen was ineffective at transporting solids during low flow conditions, subject to plastering of solid debris against the mesh screen surface, and breakage due to stretching caused by water pressure. 
     U.S. Pat. No. 5,505,388 is substantially identical to the above patent with the exception that the mesh-screen is wrapped around a sprocket to form a rotating drum like member. Again, the rotating screen acts to allow flow to pass through while diverting oversized solids to the adjacent grinder. The operation can be inefficient and maintenance prone, because unreduced solids can bypass the grinder and pass downstream not masticated and because there are gaps between the rotating screen and the cutters through which a percentage of the solids pass unreduced. Further, solids become embedded in the rotating mesh drum-like screen and eventually get back-flushed downstream unprocessed. Maintenance problems include the solids are trapped within the central portion of the drum-like screen requiring maintenance for cleaning. The screen wears due to abrasion against bottom grit in the channel. In contrast to the present invention, solids accumulating within the unit during power outages often require the unit to be manually cleared of debris before it can be restarted. Only approximately one quarter of the screen area is workable, as the part closest to the channel walls cannot effectively transport the solids, and the part in the back of the drum is not active. This results in a reduction in liquid handling capacity. 
     U.S. Pat. No. 5,061,380 discloses another grinder-diverting system. It utilizes multiple parallel shafts with substantially parallel disks mounted thereupon, which intermesh one with another. The disks all rotate in a direction towards a vertically disposed grinder mounted to one side. This invention use an excessive amount of disks, drives and seal components, and thus makes it extremely difficult to maintain. Solids such as wood can become lodged within the disks and present a blockage condition requiring manual removal. 
     None of the above inventions is output controlled by any filtering device to assure a high percentage of reduction. The above devices suffer from components in the flow, which are subject to failure, wear, inefficient operation, seal failure, mechanical drive failure. 
     Accordingly, from a review of the foregoing prior art, it can be readily appreciated that it is desirable to find a comminution and screen cleaning system, which is simple and cost effective in construction and having low maintenance requirements. It is also preferred to remain rugged, efficient and effective for cleaning large size matter from the surface of a sizing screen and subsequently comminuting such removed matter along with other matter contained in the flow of wastewater at all levels in a sewage channel to smaller particle sizes. 
     SUMMARY OF THE INVENTION 
     Therefore, it is an object of the invention to create an efficient system and to provide a solution to the deficiencies of the prior art devices. 
     It is another object of the invention to provide a comminution and screening system for reducing particle sizes in high flow sewage. The system comprises two primary interacting components. One component is a traveling grinder unit, having intermeshing cutters on parallel shafts, which rotate in oppose sense to one another. The other is a continuous concave stationary semi-cylindrical filtering and sizing screen, where the grinder unit acts to clear larger sizes of solid particles off and away from a screen surface as it travels in close proximity to the screen. The grinder unit is disposed towards the outside of a rotary turn-table, which is held on a central axis with top and bottom bearing supports and is coupled to a drive means to create an oscillating or reciprocating motion. Its cutters rotate at close clearance to the concave side of the stationary semi-cylindrical surface of the sizing screen. As the twin shaft grinder clears the concave front surface of the screen, the cutters of the grinder sweep the solids in the opposite direction of the other and propel the solids back into the flow or into the upstream side of the cutters. They ultimately encounter the grinder cutters and are reduced to a size that can freely pass through the screen openings such as slots, mesh or other configuration. It should be recognized that removed particles can be re-circulated more than once before they pass through the grinder for size reduction. In addition, it should be noted that the counter-rotating intermeshing teeth of the twin shaft grinder do not protrude into the openings of the screen&#39;s surface. But they are disposed and held rigidly fixed and close enough thereto so that the grinder teeth are able to push or drag the solids from the surface of the screen as they move in either direction. Thus, there is no physical wear and tear to the surface of the screen as it is known to occur in the screen cleaning devices and systems of the prior art. 
     Further, it is another object of the invention to provide an effective and efficient self cleaning screen and grinder system that can handle very high flows of sewage with low power requirements with minimal system parts for greater reliability and with a higher level of solids processing. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The above and other objects and features of the invention will become apparent from the following description of preferred embodiments, given in conjunction with the accompanying drawings, in which: 
     FIG. 1 shows a side view of an exemplary system of the present invention, depicting a direct drive for a twin shaft grinder mounted on a support frame supported by upper and lower bearing devices, wherein the support frame is actuated by a separate hydraulic cylinder for imparting reciprocal motion to the support frame of the grinder unit; 
     FIG. 2 shows a top view of the system of FIG. 1 taken along lines  2 — 2 ; 
     FIG. 3 shows a side view of the upper portion of a second exemplary apparatus or embodiment of the present invention, depicting a single means for driving the twin shafts of a grinder mounted on a support frame supported by upper and lower bearing devices, wherein the support frame is actuated by the same single drive means for imparting reciprocal motion to the support frame of the grinder; 
     FIG. 4 shows a top view of the system of FIG. 3, when viewed as taken along lines  4 — 4 ; and 
     FIG. 5 is a partial schematic view of a twin shaft grinder and a filtering screen, depicting a close space relationship between teeth of the grinder and the concave semi-circular filtering screen surface and solid material in the fluid flow. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Referring now to FIG. 1, there is shown a side view of an exemplary screen cleaning and comminution system  10  in accordance with the present invention. This includes an electrical or hydraulic drive motor  12  operately connected to the twin shafts of a twin shaft grinder  14 . It is supported by an upper bearing device  16  and a lower bearing device  20  connected to an upper horizontal support plate  18  and a lower horizontal support plate  22  respectively. Horizontal support plates  18  and  22  are connected to a pair of parallel disposed vertical support members  24 . These form a U-shaped frame-like structure that adds stiffness and rigidity to the arrangement of three components, so that twin shaft grinder  14  is held fixedly and rigidly in place with respect to the filtering screen. As shown in FIG. 1, a filtering screen member  26  is disposed between vertical support members  24  and twin shaft grinder  14 , extending vertically between upper and lower horizontal support members  18  and  22 . The filtering screen  14  may have openings therein of different configuration, such as slots formed by spaced parallel elements, a mesh or other configuration. Since the grinder unit does not contact or penetrate the openings in the screen, the screen may have openings therein of a wide variety of configurations without departing from the scope of the present invention. 
     Continuing with the description of FIG. 1, the system  10  has an upper horizontal cover plate  28  having an arcuate-like opening  30  therein (not shown in this FIG.  1 ), through which drive motor  12  extends and where it is connected to the top of twin shaft grinder  14 . A hydraulic cylinder device  32  is connected to a frame member  34  of the system at its rear end in a swivel-linking arrangement  36 . The front end of the hydraulic cylinder  32  has a piston  38  extending therefrom that is connected and linked to a reciprocating device  40  that is connected to and supported by an upper horizontal cover plate  28 . The reciprocating device  40  is connected to the U-shaped frame-like structure noted above, including upper support plate  18 , lower support plate  22  and parallel vertical support members  24 , at the top of an upper bearing device  42  and a lower bearing device  44 . 
     By connecting reciprocating device  40  to the U-shaped frame-like structure, it is possible to move the drive motor  12 , twin shaft grinder  14  and the parallel pair of support members  24  along an arcuate path in reciprocating motion through arcuate-like opening  30 . Twin shaft grinder  14  is held in fixed and rigid spaced relationship to a screen  26  as the combination of the elements moves back and forth along the concave surface of the screen  26  so as to sweep and remove any solids contained on the screen. The lower bearing device  44  is connected to the lower support plate  22  and is further connected to and supported by a lower frame member  46 . The lower frame member  46  is connected to a bottom base support member  48  upon which system  10  resides. 
     Referring now to FIG. 2, there is shown a top view of the system shown in FIG. 1, taken along lines  2 — 2 , wherein the same reference numbers used in FIG. 1 are used in FIG.  2 . As shown, the reciprocating device  40  has a crank arm  50  connected thereto at one end. It is connected at the other end in linking or swivel manner so that twin shaft grinder  14  is moved back and forth through opening  30  along a path indicated by the curved arrows  52  and  54 , in close proximity to the surface of concave filtering screen  26 . The grinder  14  is not shown in FIG. 2 since it is hidden from view by drive motor  12 . Hydraulic cylinder  32  is actuated by a typical hydraulic system arrangement known in the prior art and in the interest of brevity is not shown here. If drive motor  12  is a hydraulic motor, it will also be actuated by a similar prior art hydraulic system and is also not shown. 
     Continuing with the detailed description of the present invention, reference is now made to FIG.  3 . There is shown in FIG. 3, a second exemplary system  56  or embodiment of the invention that is similar to the system shown in FIG.  1 . The primary difference between the two systems is that the embodiment, shown in FIG. 3, has a single drive means  58  for driving the twin shaft grinder  14  and for moving it in reciprocal motion, i.e., in back and forth motion in close proximity to the filtering screen  26 . FIG. 3 illustrates a side view of the apparatus  56  of the invention, where the lower portion has been omitted in the interest of brevity since it is constructed in essentially the same as the lower portion of the apparatus shown in FIG.  1 . 
     As can be seen in FIG. 3, a shaft  59  of drive means  58  can be linked to a coupling device  60  by means of chain, belt or gear arrangements. Coupling device  60  is connected to a speed reducing device  62 , which is in turn connected to a crank-like linking device  64 . Crank-like linking device  64  is connected to a first end of a reciprocal motion control arm 66  via a linking swivel connection  68 . The other end of control arm  66  is connected to means  72  for driving twin shaft grinder  14  and providing a bearing  78  for supporting the upper end of the twin shaft grinder  14 . A support member  74  covers means  72  and also is a support for a bearing device  80  for coupling shaft  82  of drive  58 . 
     Referring now to FIG. 4, there is shown a top view of the apparatus depicted in FIG. 3 taken along lines  4 — 4  thereof, where some of the various components discussed in connection with FIG. 3 are shown. FIG. 4 shows a view of screen cleaning apparatus  56  partly in cross-section, illustrating that means  72  for driving twin shaft grinder  14  back and forth along the concave surface of screen  26  is accomplished by crank-like linking device  64  and reciprocal motion control arm  66 . As shown, crank-like linking device  64  is connected to the first end of the reciprocal motion control arm  66  at a swivel connection  68  and a second end of control arm is connected to a second swivel joint connection  70  that is part of means  72 . Means  72  is partially covered by a cover plate  74 , such that only a coupling shaft  82  of single drive means  58  is seen. Coupling shaft  82  is the axis about which means  72  pivots as it moves the grinder back and forth in reciprocating motion adjacent to the concave surface of screen  26 . The parallel support members  24  can also be seen as part of the U-shaped frame structure, which supports the grinder in fixed rigid relationship to screen  26 . It should be noted that support members  24  are considered important to the integrity of the apparatus where the members are connected to upper and lower support plates  18  and  22 , respectively, to thereby form a component of the U-shaped frame structure noted above. A broken-line circle with the arrow heads designated by the reference number  96  illustrates the direction of rotation of crank-like linking device  64  which moves means  72  back and forth along paths indicated by curved arrows  52  and  54 . 
     FIG. 5 is a fragmented cross-sectional view of the screen cleaning and comminuting system of the present invention which clearly depicts the twin shaft grinder  14 , including a pair of parallel rotatable shafts  86  and a pair of intermeshing grinder teeth  88  disposed on the twin shafts  86 . As shown, each of the shafts  86  rotates in opposite sense to one another as indicated by the curved arrows  92  and  94 . Also shown in FIG. 5 are a plurality of solid material particles designated by reference number  90 . As can readily been seen, the drawing illustrates the solid particles  90  being pushed in opposite directions on either side of grinder  14 . Thereby the concave surface of screen  26  is swept clean, as the grinder passes close enough to make contact with the solid particles  90 , but not so close to the screen that the grinder teeth touch the surface of the screen. It is noted that removal of the solids from the surface of the screen is the result of the grinder teeth  88  intercepting the solids, so as to remove them from the screen as illustrated. The back and forth motion of the grinder generates significant fluid motion near the surface of the screen in either direction, and this fluid motion or flow is an additional aid in the removal of solids from the surface of the screen. It is further understood that the solid matter, which is removed from the screen surface, is returned to a position upstream of flow, and ultimately is comminuted by grinder  14 . 
     The principle modes of operation of the screen cleaning and comminuting systems  10  and  56  in accordance with the present invention are essentially the same as have been described. The primary difference between these two embodiments of the invention is the mechanism. By the mechanism, the twin shafts of the grinder  14  are caused to rotate and the mechanism by which the grinder unit  14  is moved in reciprocating motion in close proximity to the concave surface of screen  26  as it cleans solids therefrom. In accordance with the teachings of the present invention, the apparatus shown in FIG. 1 is driven by two drive motors. The apparatus shown in FIG. 3 is driven by a single drive means operatively connected to associated coupling means to provide both rotational motion for the twin shaft grinder and reciprocating motion to move the grinder unit  14  along the concave surface of the filtering screen  26 . 
     The operation of said twin shaft grinder  14  as a comminuting device is described briefly. As shown in FIG. 5, the grinder unit  14  includes two drive shafts  86  whose lengths extend to essentially the full depth of the liquid substance flow in channel and they rotate in opposite sense to one another. Each shaft has a shredding member disposed thereon containing shredding teeth  88  which extend to the full length thereof for shredding and grinding solid matter contained in the liquid flow of the channel such as a sewage channel. It should be noted that the twin shaft grinder unit of the present invention has two novel functions, that is to operate as a grinder for sizing solids while simultaneously operating as a sweeper to remove solid material from the surface of filtering screen  26  without making physical contact therewith. 
     In accordance with the preferred embodiment of the invention, rotatable turn-table with central support is provided for ease of sealing and securing through conventional means. Arc screen and U-shaped frame of the invention have smooth shape to prevent from hangup and promote complete processing and smooth flow. Further, support means behind screen of the invention is provided for support of grinder structures, and unique design of the invention eliminates gaps formed in prior art which can cause incomplete processing by allowing solid to pass therethrough. 
     In accordance with the present invention, the simple and unique construction provides a system, which allows the liquid sewage being processed to flow therethrough with minimum hindrance. In addition, the filtering screen, screen sweeping device and grinder may operate in a variety of configuration and are more compatible for maximum through-put performance than prior art devices and systems. The directional clearing properties of the reciprocating grinding member insure that solids which impact the screen can be aggressively removed from the screen surface and redirected by the grinder back into flow path of the sewage system during each cycle. Therefore, it is possible to keep the filtering screen clear of solids and enhance the performance and efficiency of the system. While the use of a single means to drive the various moving parts of any apparatus may be advantageous, the use of the novel screening and sweeping action in accordance with the present invention is most important when assessing whether one or more drives are utilized. 
     It should be understood that the above-described embodiments are only illustrative of the principles applicable to the invention. Various other arrangements and modifications may be made without departing from the spirit and scope of the invention as set forth in the following claims.