Abstract:
A soil separator for a dishwasher includes a centrifugal soil collection wall surrounded by a spill over guide channel, surrounded by a shallow annular soil accumulator channel. The soil accumulator channel is open to the dishwasher chamber but covered by a filter screen. The accumulator channel is shallow beneath the screen and empties downwardly into an accumulator sump where accumulated soil is periodically drained. The shallow accumulator channel allows water to flush an inside of the screen to carry soil to the accumulator sump.

Description:
This application claims the benefit of U.S. Provisional Application No.: 60/003,275 filed Aug. 25, 1995. 
    
    
     BACKGROUND OF THE INVENTION 
     The present invention is directed to a soil separator for a dishwasher and particularly an arrangement between a soil separator chamber and a soil accumulator chamber which provides an improved apparatus and method for collecting and filtering soil from dishwasher water. 
     A known arrangement for removing soil from dishwasher water is described in U.S. Pat. No. 5,165,433. This apparatus includes a combination motor-pump and soil separator assembly. The motor-pump assembly includes a wash impeller, which operates within a pump cavity located within the soil separator. As the impeller operates in a wash or rinse mode, a swirling motion is created in the wash liquid passing through the pump cavity, thereby creating a centrifugally sampled annular layer of wash liquid on the annular interior wall. A portion of the wash liquid having a high concentration of entrained soil (food particles, etc.) passes over an upper edge of the annular interior wall and into an annular guide chamber. 
     Wash liquid from this guide chamber travels to an annular soil collection chamber at a high flow rate. This high flow rate is achieved by use of a relatively small aperture located in a lower portion of the annular wall separating the guide chamber and the soil collection chamber. Upon entering the soil collection chamber, wash liquid flows outwardly and upwardly through a screen which separates the water from the soil. The wash liquid is prevented from draining out of the soil collection chamber by a ball check valve seated within a drain port. The screen contains an annular arrangement of fine mesh filters, which prevent soil particles entrained in the wash liquid from reentering the dishwasher space. The cleansed wash liquid returns to the dishwasher floor where it is picked up by the motor driven pump for recirculation within the dishwasher. 
     Typically, the apparatus such as described above allows water to pass through the hole between the guide channel and the collector chamber at a rate of about 4 gallons per minute. This flow rate can cause the heavily concentrated mixture of soil and water within the accumulator chamber to be agitated, preventing soils from readily settling. With this flow rate and configuration, there may be a tendency for the mechanical filter to clog even though back wash nozzles for spraying the filter from above are provided. Collecting soil at these flow rates cause filter screens with a 0.0049 inch mesh to have a tendency to clog. It was necessary to increase screen mesh to 0.0079 inch to prevent this clogging. However, the larger mesh screen allowed soils of larger particle size to escape through the screen and may be seen as “grit” on the dishes. 
     SUMMARY OF THE INVENTION 
     It is an object of the present invention to provide a dishwasher soil collection system which is compatible with a high flow rate soil removal dishwasher while at the same time allowing for adequate screening of soil in the dish water return to the dish compartment in a recirculating dish water system. It is an object of the invention to provide a more efficient method of soil collection and retention while reducing water and energy usage. 
     The objects are inventively achieved in that an annular soil separator wall is provided around the dish washer pump for accumulating solids by centrifugal action, a soil guide channel is provided surrounding the separator wall, and a shallow soil accumulator channel or “screening channel”, substantially annular, is arranged beneath the filter screen surrounding the soil guide channel. The soil accumulator channel is flow connected to the guide channel by a vertical tube at a first closed end of the channel and the channel surrounds the guide channel to an open channel end which empties, to an accumulator sump having a drain port closed by a ball check valve. Water and soil proceed around the accumulator channel, soil is retained beneath the filter screen and water proceeds through the filter screen. Back wash nozzles are provided to wash the filter screen of soil from a dish compartment side of the filter screen. Thus, by directing inlet water from the guide channel to the shallow accumulator channel, the inside of the filter screen is washed by the water, while the outside of the screen is washed by the backwash nozzles above. Therefore, food particles which are temporarily dislodged from the screen by the backwash nozzles may not immediately return to the screen after the backwash nozzle passes, due to the direction of flow on an inside surface of the filter screen from the water flowing inside the accumulator channel. 
     Inlet water flow into the accumulator channel is directed in a circulatory path and kept in the shallow accumulator channel in close proximity with the screen. As particles are dislodged by the backwash nozzles, they are moved around toward the stagnant soil accumulator sump. The sump is located away from the accumulator channel water inlet and therefore, more isolated and stagnant, allowing soil to settle. This is due to the fact that water and soil lose velocity as they approach the accumulator sump while most of the water escapes through the screen. The accumulator sump can be configured more compact when using the shallow accumulator channel of the present invention. The physical configuration of the system reduces water held in the accumulator by 60% or greater. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a perspective view of a dishwasher including a soil separator in accordance with the present invention; 
     FIG. 2 is a plan view of the soil separator having the wash arm assembly removed therefrom and with a portion of the soil separator screen cut away; 
     FIG. 3 is a diametric section of the soil separator including the wash arm assembly taken generally along line III-III of FIG. 2; 
     FIG. 4 is a sectional view of the soil separator taken generally along line IV—IV of FIG. 2; 
     FIG. 5 is a plan view of an accumulator chamber grating; and 
     FIG. 6 is a partial sectional view taken generally along VI—VI of FIG.  2 . 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     In accordance with the invention as shown in the drawings, and particularly as shown in FIG. 1, an automatic dishwasher generally designated  10  includes an interior tank wall  12  defining a dishwashing space  14 . A soil separator  20  is centrally located in floor  21  and has a lower wash arm assembly  22  extending form an upper portion thereof. Coarse particle grate  24  permits wash liquid to flow from floor  21  to soil separator  20 , while preventing foreign objects, such as apricot pits and pop tops, from inadvertently entering soil separator  20 . 
     The basic constructional features of the soil separator are explained in U.S. Pat. No. 5,165,433 herein incorporated by reference. Referring now to FIG. 3, the soil separator and pump assembly generally comprises a motor  27  having an output shaft  29  secured to base plate  30  by bolts  32 . The motor  27  is a reversing motor which normally operates in a clockwise direction, as viewed in FIG.  2 . When operated in a clockwise direction, such as in a wash mode or a rinse mode, the motor  27  provides a pumping action within soil separator  20 , thereby providing pressurized wash liquid to lower wash arm assembly  22 . 
     As shown in FIG. 3, lower wash arm assembly  22  includes a central hub  33  having a plurality of wash arms  35  extending radially therefrom. Each wash arm  35  includes one or more upwardly directed spray nozzles  38  for directing wash liquid upwardly within dishwashing space  14 , and one or more downwardly directed spray nozzle  40  for providing a back-washing action, as will become apparent. Liquid passageway  42  in central hub  33  permits pressurized wash liquid to flow to the lower wash arm assembly  22 . 
     As shown in FIG. 2, the soil separator  20  further includes an annular cover  44  which is disposed over and secured to soil container wall  48  by screws  50 . When in place, cover  44  and soil container wall  48  combine to form a low-pressure water seal, preventing leakage of water therebetween. Cover  44  includes a series of fine mesh filter segments  52  which are radially disposed about a central axis of the cover. Fine mesh filter segments  52  are preferably formed of a synthetic material such as nylon or polyester and have a mesh on the order of 0.0049″ to 0.0106″. Depending on the material desired to be filtered, however, a larger or smaller mesh filter may be used. 
     Referring back to FIG. 3, located radially inwardly from the fine mesh filter segments  52  and depending downwardly from cover  44  is an annular lip  54 . Annular lip  54  forms a high-pressure seal in combination with an upstanding annular wall  56 , as will become apparent. 
     Further located radially inwardly from the annular lip  54  of the cover  44  is a downwardly depending annular wall  68 . Annular wall  68  defines a centrally located interior area containing a plurality of vanes for directing pressurized wash liquid. 
     In the embodiment shown, water flows upward in passages  70  and into passages  73  into wash arms  35 . Water also flows into a channel pipe  75  to be directed vertically to feed an upper wash arm (not shown). The hub  33  holds the arms  35 . The channel pipe  75  penetrates the hub  33 . A rubber boot  77  is fastened to hub  33  and is open at a bottom thereof and has an aperture  77 a for passing water therethrough. A retainer ring  78  with external threads  78 a screws into the channel pipe  75  at internal threads  75 a to retain the boot  77 . 
     Under water pressure, the boot  77  seals against an upstanding tower (not shown) attached to the bottom rack (not shown) for delivery of water to the upper wash arm (not shown). 
     Although a top delivery of water to the upper wash arm is described, water can be delivered to the upper wash arm by a pipe such as described in U.S. Pat. No. 5,165,433. Alternately, a pipe or channel can be arranged from the passages  70  for supplying water to the upper arms and the channel can be located above the screen elements  52  extending radially from the hub  33  on the floor  21  of the dish compartment. 
     Referring to FIG. 3, it may be seen that lower wash arm assembly  22  is freely rotatably mounted about a seal ring  74 . A filter guard  80  is mounted to wash arms  35  by screws  81 . Filter guard  80  overlies the fine mesh filter segments  52  of cover  44 , protecting fine mesh filter segments  52  from damage caused by falling utensils or tableware. In operation, pressurized wash liquid flows past into wash arms  35 . Upwardly directed nozzles  38  are positioned on wash arms  35  so as to provide a chordally directed thrust, causing lower wash arm assembly  22  to rotate about the seal ring  74  when pressurized wash liquid is pumped through nozzles  38 . 
     As lower wash arm assembly  22  rotates, pressurized wash liquid is emitted from downwardly directed nozzles  40 . A deflector tab  84  integrally formed as part of filter guard  80  is disposed directly beneath each nozzle  40 , impinging on the flow of wash liquid emitted therefrom. As the flow of water from each nozzle  40  strikes the associated deflector tab  84 , a fan-shaped spray is formed. Each fan-shaped spray sweeps the top of the fine mesh filter segments  52  as lower wash arm assembly  22  rotates, thereby providing a back-washing action to keep fine mesh filter segments  52  clear of soil particles which may impede the flow of cleansed wash liquid into dishwashing space  14 . 
     The wash impeller  60  is located within pump cavity  86 . Pump cavity  86  is generally defined by the soil separator lower housing wall  88 , an inside upstanding annular wall  90 , and cover  44 . 
     Wash impeller  60  is secured to the output shaft  29  of pump motor  27  by impeller retaining bolt  92 , and pumps wash liquid when in operation. The majority of the pressurized wash liquid enters the area beneath the cover  44  defined by downwardly depending annular wall  68 , and is directed to the lower wash arm and to the upper wash arm. Under normal operating conditions, flow of pressurized wash liquid is provided to the lower wash arm and to the upper wash arm. 
     During normal operation, a third portion of the wash liquid is maintained within the soil separator to be cleansed and returned to circulation. In pump cavity  86 , a portion of the wash liquid having a high concentration of entrained soil tends to accumulate on the inside upstanding annular wall  90 . The swirling motion of the liquid tends to carry the soil upwardly over the upper edge  97  of wall  90 , whereupon the soil-laden liquid collects within annular guide chamber  100  defined between the inside upstanding annular wall  90  and the outside upstanding annular wall  56 . Undesirable pressure loss within the annular guide chamber  100  is prevented by forming a relatively water-tight, high pressure seal at the juncture of cover  44  and the outside upstanding annular wall  56 . 
     As shown in FIG. 4, soil laden water flows through an inlet  102  into a tube  104  and upward through a hole  106  into soil accumulation channel  110 . 
     Although a relatively tall wall  90  is shown, it is possible to significantly shorten the wall  90  and the wall  56  and correspondingly also lower the channel  110  and still retain effective soil separation. The tube  104  can become shorter and in effect become a nearly horizontal passage into the channel  110 . 
     In operation the soil laden water proceeds through the hole  106  and proceeds in a clockwise direction in FIG.  2 . Water passes upwardly through the screen segments  52  and the soil proceeds to the accumulator sump  120  at the second end  118 . As the water proceeds around the soil separation channel its velocity slows and soil settles out into the sump  120 . 
     By maintaining a shallow soil separation channel  11   0  under screen segments  52 , from the tube  104  to the sump  120 , any clogging of the screen segments  52  on an inside thereof can be effectively alleviated. When the backwash nozzle  40  passes, soil is back washed away from the screen, and water passing within the channel  110  moves the soil toward the sump  120  and prevents repositioning of the soil against the screen segments  52 . 
     Fine mesh filter segments  52  in cover  44  permit flow of cleansed wash liquid to return to dishwasher space  14  for recirculation. Light soil particles are screened by fine mesh filter segments  52  and retained in soil accumulator sump  120 . Accordingly, both heavy and light soil particles remain within the soil accumulator sump  120 . 
     FIG. 6 illustrates the soil accumulator channel  110  beginning at the wall  116  and terminating at the end  118 . The sump  120  is defined by walls  56 ,  48  and side walls  122 ,  124 . Soil  126  is collected within the sump  120  on the floor  127  and expelled during the drain cycle through the drain port  128 . 
     When operated in a wash or rinse mode, the dishwasher functions as a continuous fluid circuit. In a wash mode, for example, wash liquid flows from dishwashing space  14  to dishwasher floor  21  and is gravity-fed to coarse particle grate  24 . Wash liquid flows past heating unit  130  to soil separator  20 , where it is drawn inwardly by negative pressure created by impeller  60 . Wash liquid flows over sealing ring  186 , which, in combination with floor  21  and retainer ring  188 , serve to support and seal the soil separator and pump assembly within the dishwasher. Wash liquid continues to flow horizontally and inwardly over base plate  30 , until encountering soft soil chopper  190 . 
     As may best be observed in FIG. 3, soft soil chopper  190  is located on motor shaft  29  and rotates therewith to macerate large soft soil particles which travel past grate  195 . Torsion spring  192  both supports and drives chopper  190 , urging chopper  190  upwardly against collar  194 , which in turn is held in place on output shaft  29  by a downwardly depending shoulder of wash impeller  60 . 
     After passing soft soil chopper  190 , wash liquid is drawn through grate  195  and further upwardly into pump cavity  86  by wash impeller  60 . Wash impeller  60  imparts a swirling motion to the wash liquid, forcing a majority of the wash liquid upwardly to the lower wash arm and to the upper wash arm. Wash liquid sprayed from upwardly directed spray nozzles  38 , downwardly directed spray nozzles  40  and cleansed wash liquid emitted from fine mesh filter segments  52  into dishwashing space  14  returns to floor  21  to be recycled. 
     Due to centrifugal force acting on the swirling liquid in pump cavity  86 , the remainder of the wash liquid forms a band or layer on the interior of inside upstanding annular wall  90 . This band of wash liquid contains a heavy concentration of entrained soil particles having a relatively high specific gravity, which tend to be forced outwardly by centrifugal force. This band of wash liquid also contains approximately the same concentration of soil particles having a relatively low specific gravity representative as the wash liquid as a whole. 
     As soil-laden wash liquid flows around soil accumulator channel  110 , its velocity is reduced, permitting heavy soil particles to collect in sump  120  on lower housing wall  127 . As the clockwise rotation of wash impeller  60  forces soil-laden wash liquid into soil accumulator channel  110 , clockwise rotation of drain impeller  206 , as shown in FIG.  5 ,  causes a clockwise flow of wash liquid within drain pump chamber  208 . 
     Pressure created by wash liquid flow within drain pump chamber  208  causes ball check valve  210  to rise from a resting position on ball check valve support  211  to a seated position on the bottom side of soil container drain port  128 , as shown in FIG.  3 . When so positioned, ball check valve  210  prevents flow of accumulated soil particles and wash liquid therethrough. Check valve  214  located in line with and downstream of a drain port  216  prevents air from entering the drain port during operation of drain impeller  206  in a clockwise direction. 
     Upon completion of a wash or a rinse cycle, a drain cycle is initiated. At that time, pump motor  27  is reversed, causing drain impeller  206  to rotate in a counter-clockwise direction, as  when viewed from a top view as shown in FIG.  2 . Drain impeller  206  causes negative pressure to be applied within conduit  220 , which causes ball check valve  210  to fall away from soil container drain port  128 . Soil-laden water and accumulated soil within soil accumulator sump  120  is rapidly pumped out by drain impeller  206 , and expelled through drain port  216 . In addition, drain impeller  206  is further in fluid connection with floor  21 . Wash or rinse liquid draining from soil separator  20  accumulates on base plate  30 , and is pumped out through drain port  216  along with liquid from floor  21 . Accordingly, when operated in a counterclockwise direction, drain impeller  206  rapidly and effectively drains soil separator  20 . 
     An alternate further embodiment (not shown) includes providing that  a plate  108 which is substantially annular with a plurality of spaced apart slotsand that the. The sump  120  is also annularly shaped and is arranged below and coextensive with said plate  108 . Soil accumulated on said plate passes through said slots to settle to the sump below where a port  128  operates during the claim cycle as described above. 
     A further alternate embodiment (not shown) provides that two sumps, such as the sump  120  be provided below the plate  108  substantially located at 180° diametrically opposed, and that 180° of the cover  44  be fine mesh screen elements and 180° of the cover  44  be coarse mesh screen elements. The screening channel is divided into two sub channels, a fine screening channel (0.0049″ mesh) and a coarse screening channel (0.0079″ mesh). When the fine screening channel is sufficiently clogged to cause a predetermined back pressure, a valve means opens the fine screening channel to the coarse screening channel to allow soil laden water to at least be coarse screened. As described above, the fine and coarse screening channels are arranged to be shallow to allow soil to be washed from inside the screens. 
     Both of these alternate developments are the subject of other patent applications. 
     Although the present invention has been described with reference to a specific embodiment, those of skill in the art will recognize that changes may be made thereto without departing from the scope and spirit of the invention as set forth in the appended claims.