Disclosed herein is a non-clog shredder that is used to shred solid matter entrained in a non-homogenous liquid-solid feed. In one embodiment of the invention, the shredder is located at the bottom of a toilet bowl and is used to shred solid disposable products such as napkins and diapers that are discarded in the toilet bowl. The shredder comprises a generally cylindrical cup that is open at one end, with a circular end-cap at the other end. The end-cap has an axial opening that allows the feed to pass through the cup. In one embodiment of the invention, the opening has recesses and/or teeth on the periphery of the opening. An impeller disposed against the circular end plate creates suction for transfer of the waste through the shredder. A cutting blade on the impeller assembly projects axially through the opening in the end-cap.

BACKGROUND OF THE INVENTION 
   The present invention, in general, relates to a shredder for shredding semi-solid or particulate matter entrained in a non-homogenous liquid-solid flow. The shredder disclosed herein finds an application in process industries, for example in the ore, paper, pulp, food and fiber industries for macerating particulate or solid material in an incoming liquid-solid feed. 
   An example of the application of the shredder disclosed herein is in marine and recreational vehicle toilets. These toilets are designed to accept waste, such as human waste and toilet paper which can be easily flushed down the toilet. But if products such as feminine hygiene and diapers are discarded in the toilet, the toilet often clogs. Repeated attempts to flush such products down the toilet may eventually be successful but it results in excessive usage of fresh water. In one embodiment of the invention disclosed herein, the shredder is located downstream of the toilet bowl discharge line of a marine or recreational vehicle toilet to prevent clogging of toilets, especially when products such as feminine hygiene products and baby diapers are discarded in the toilet bowl. 
   In general, there is an unsatisfied market need for shredding solid matter in an incoming liquid-solid feed without clogging the line transporting such flow. 


   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1A  illustrates the exploded view of the shredder. 
       FIG. 1B  illustrates the impeller assembly. 
       FIG. 1C  illustrates the plan view of the impeller assembly. 
       FIG. 1D ,  FIG. 1E  and  FIG. 1F  illustrate different isometric views of another embodiment of the impeller. 
       FIG. 1G  illustrates the sectional view of the impeller taken along section line A-B of  FIG. 1E . 
       FIG. 1H  illustrates the side elevation view of the impeller assembly. 
       FIG. 1I  illustrates the isometric view of the cup. 
       FIG. 1J  illustrates another isometric view of the cup. 
       FIG. 1K  illustrates the plan view of the cup. 
       FIG. 1L  illustrates the side elevation view of the cup. 
       FIG. 1M  illustrates an isometric view of the impeller assembly abutting the cup with the cutting blade projecting through the circular opening in the cup. 
       FIG. 2A  illustrates the perspective view of the self-contained toilet system. 
       FIG. 2B  illustrates the exploded view of the self-contained toilet system with the built-in shredder. 
       FIG. 2C  is a cross-sectional rear view of the self-contained toilet system with built-in shredder. 
   


   DETAILED DESCRIPTION OF THE INVENTION 
   The method and apparatus of this invention, including all its embodiments are herein referred to as a shredder. 
     FIG. 1A  illustrates the exploded view of the shredder  100 . The shredder housing  110  comprises an inlet line  109 , also referred to herein as inlet  109 , through which the liquid-solid feed enters the reservoir  116  located in the front section of the shredder housing  110 , a generally cylindrical cup  106  that is open at the upstream end with respect to the incoming liquid-solid flow and capped at the other end by a circular end-cap  114  with an axial opening  107  through which the cutting blade  112  projects in an upstream direction  306  into the cup  106 , an impeller assembly  103  mounted on a shaft  115 , and a motor  101  that drives the shaft  115 . The cup  106  including the end-cap  114  is stationary and does not rotate. Shaft  115  has an axis of rotation  302 . 
   An O-ring  105  on the discharge side of the shredder  100  provides a seal between the front section of the housing  110  and the rear section of the housing  102 . 
     FIG. 1B  illustrates one embodiment of the impeller assembly  103 . The impeller assembly  103  consists of impellers  104  rigidly affixed to the impeller plate  119  and extending radially from the center of the impeller plate  119  towards the circumference of the impeller plate  119  and perpendicular to the upstream face  308  of the impeller plate  119  with the cutting blade  112  located at the center of the impeller  104 . In one embodiment of the invention shown in  FIG. 1B , the impeller assembly  103  consists of two impellers  104  positioned at right angle to each other with an integrally machined or cast cutting blade  112 . In another embodiment of the invention, the cutting blade  112  may be cast separately from the impeller  104  and thereafter rigidly affixed to the impeller  104 . In the assembled position, the impeller assembly  103  is positioned with the impeller  104  adjacent to and abutting the downstream surface  310  of the end-cap  114  with the cutting blade  112  projecting through and upstream of the axial opening  107  in the end-cap  114 . With the shedder in operation, the cutting surface  118  of the cutting blade  112 , also referred to herein as the blade cutting surface  118 , shreds solid matter in the liquid-solid feed as the feed approaches the opening  107  in cup  106 . The surface  117  of the impeller  104 , also referred to herein as the impeller cutting surface  117 , rotates adjacent to and immediately downstream of the end-cap  114 . The relative motion of the impeller cutting surface  117  over the downstream surface  310  of the end-cap  114  in a shredding engagement shreds the solid matter in the liquid-solid feed at the downstream surface of the opening  107 , and in one embodiment of the invention where the opening has a plurality of recesses  113 , also at the downstream surface of the recesses  113 . The blade cutting surface  118  is oriented generally parallel to the axis of rotation  302  and the impeller cutting surface  117  is oriented generally normal to the axis of rotation  302 . The impeller assembly  103  is located in the housing  110  of the shredder  100 . The shaft  115  is connected at one end to the center of the impeller plate  119  and to the variable speed motor  101  at the other end. In one embodiment of the invention, impellers  104  shown in  FIG. 1D through 1F  are axially mounted at one end of the shaft  115 , with the other end of the shaft  115  connected to the motor  101 . In one embodiment of the invention, the speed of the motor  101  is adjustable. For example, the motor  101  speed may be adjusted to provide a cutting blade  112  rotational speed of approximately 2600 revolutions per minute. 
     FIG. 1C  illustrates the plan view of the impeller assembly  103  showing the impeller  104  and the cutting blade  112  at the center of the impellers  104 . 
     FIG. 1D ,  FIG. 1E  and  FIG. 1F  illustrates another embodiment of the invention where the impeller assembly comprises only the impeller  104  and the cutting blade  112 . 
     FIG. 1G  illustrates the sectional view of the impeller assembly  103  showing the impeller  104 , cutting blade  112 , cutting surface  118  and impeller surface  117  that abuts the downstream surface of opening  107  and recesses  113 . 
     FIG. 1H  illustrates the side elevation view of the impeller assembly  103 , the impeller  104 , cutting blade  112  and impeller plate  119  as shown in  FIG. 1B . 
     FIG. 1I  illustrates an isometric view of the generally cylindrical cup  106  that is open at one end and has a circular end-cap  114  at the other end. The end-cap  114  has an axial opening  107  opening that provides a conduit  312  for transfer of the feed through the end-cap  114 . In one embodiment of the shredder, cutting teeth  111  are located along the circumference of the opening  107 . The axial opening  107  may be of any generally circular shape. In another embodiment of the invention, the opening  107  is in the shape of a circle with a plurality of recesses  113 . In another embodiment of the invention, cutting teeth  111  are located on the periphery of the opening  107 . In yet another embodiment of the invention, the cutting teeth  111  and recesses  113  are located alternately on the periphery of the opening. The relative motion of the section of the impeller blade  112  that projects through opening  107 , namely the blade cutting surface  118 , with respect the stationary cutting teeth  111  in a shredding engagement, shreds the solid material in the incoming liquid-solid feed as the feed moves through the opening  107 . The recesses  113  also provide a conduit for transfer of the incoming feed through the end-cap  114 . 
     FIG. 1J  illustrates another isometric view of the cup  106  showing the axial opening  107 , cutting teeth  111  and recesses  113  located along the periphery of the opening  107 . 
     FIG. 1K  illustrates the plan view of the cup  106  with the axial opening  107 , and the recesses  113  and cutting teeth  111  located along the periphery of the axial opening  107 . 
     FIG. 1L  and  FIG. 1M  illustrates the impeller assembly  103  in the assembled position with the impeller assembly  103  adjacent to and abutting the end-cap  114  of cup  106  with the cutting blade  112  projecting through the opening  107  in cup  106 . 
     FIG. 2A  illustrates the perspective view of the self-contained toilet system, with the built-in shredder  100 . The toilet consists of a seat cover  201 , a hand lever  203  and a toilet bowl  202 . 
     FIG. 2B  illustrates an example of the exploded view of a self-contained toilet system with the built in shredder  100 . A seat cover  201  is positioned above the toilet bowl  202 . The shredder  100  is positioned below the toilet bowl  202 . An inlet port  109  accepts the contents of the toilet bowl  202  when the flush is actuated. The shredded waste is discharged through the outlet  108  of the shredder  100 . The flush can be either manually operated using a hand lever  203  control or electronically activated using an electronic timer control circuit  206  powered off a wall switch. A solenoid valve (not shown) regulates water consumption during each flush by controlling the inlet water pressure. The hand lever  203  operates a crank (not shown) that is connected to a crank lever. Micro-switches are placed in various locations with respect to crank lever positions. Multi-functional operation of the crank lever is achieved using these micro switches. The hand lever  203  also activates the flush. The electronic timer control circuit  206  sequences the flush by first bringing water in through the intake hose  207 , emptying the toilet bowl  202  and re-filling the water in the toilet bowl. A discharge connector  204  is connected to the inlet port  109  of the front section of the shredder housing  110 . The outlet  205  of the toilet bowl  202  is connected to the discharge connector  204 . 
     FIG. 2C  is a cross-sectional rear view of the self-contained toilet system with a built-in shredder  100  showing the outlet of the toilet bowl  205 , cutting edge  112 , the semi-circular recesses  113 , and the shredder outlet  108 . 
   When the motor  101  is turned on, the rotation of the impeller over the downstream surface  114  of the cup  106  acts as a centrifugal pump  304 , creating suction to effect the transfer of the incoming liquid-solid feed from the reservoir  116  located in the front section of the housing  110  through the opening  107 . As the feed moves towards and through the opening  107 , the solid material in the feed is shredded by the following: the cutting edge  118  of the rotating cutting blade  112 , the cutting surface  117  of the rotating impeller  104  as the solid material in the feed moves to a point immediately downstream of the opening  107  and the recesses  113 , and by the rotation of the impeller  104  with respect to the stationary cutting teeth  111  located on the periphery of the opening  107 . The centrifugal action of the impeller  104  throws the shredded feed to the rear section of the housing  102  from where the shredded waste is discharged through outlet nozzle  108  located at the upper part of the rear section of the housing  102   
   In one embodiment of this invention, the apparatus comprises a toilet bowl  202 , a discharge opening at the bottom of said toilet bowl  205  and the shredder  100  positioned at the bottom of the toilet bowl  202 . When a flush hand lever  203  is actuated, the waste from the toilet bowl feeds through the shredder inlet line  109  to the upstream reservoir  116  located in the front section of the housing  110 . The outlet  108  of the shredder  100  is coupled to and in fluid communication with the exterior discharge opening of the toilet bowl  202 . 
   When the flush hand lever  203  is actuated, motor  101  is turned on and waste from the toilet enters the shredder  100  through the inlet line  109 . The cutting blade  112  rotates along the upstream surface of the stationary circular end-cap  114  to shred the incoming particulate matter in the liquid-sold feed. The feed containing the shredded particulate matter passes through the opening  107 ; and, in one embodiment of the invention, through the opening  107  and recesses  113  located on the periphery of the opening  107 . The rotation of the impeller blades  104  creates suction to transfer the waste from the upstream reservoir  116  of the shredder to the outlet  108  of the shredder  100 . The shredder  100  shreds solid wastes such as feminine hygiene and baby diaper products in addition to human sewage and toilet paper. The shredded feed is discharged through the discharge nozzle  208 . 
   The following example illustrates the working of the shredder  100  in a toilet application. Ms. Jenny goes to a restroom to use the toilet facilities, and needs to dispose off a soiled sanitary napkin. She wraps the soiled sanitary napkin and puts it into the waste basket. Even though quite simple and cost-effective, this conventional method poses a threat of infection to other toilet users through atmospheric dispersal of microbial germs and such disposal also emits an unpleasant odor. If the restroom is equipped with the shredder, Ms. Jenny need not dispose it off in the wastebasket. She can flush the soiled sanitary napkin down the toilet bowl  202 . When the flush hand lever  203  is activated, a shredder  100  mounted inside the toilet bowl  202  is also activated. The rotation of the cutting blade  112  and the impeller  104 , and the rotation of the impeller  104  with respect to the cutting teeth  111  on the opening  107  shreds the soiled sanitary napkin inside the toilet bowl  202 , and the shredded waste is flushed out without clogging the toilet system.