Patent Application
20120318308
A dishwashing machine is a domestic appliance into which dishes and other cooking and eating wares (e.g., plates, bowls, glasses, flatware, pots, pans, bowls, etc.) are placed to be washed. A dishwashing machine includes various filters to separate soil particles from wash fluid.
The invention relates to a dishwasher with a liquid spraying system, a liquid recirculation system, and a liquid filtering system. The liquid filtering system includes a housing defining a chamber, a rotating filter having an upstream surface and a downstream surface and located within the chamber such that the recirculation flow path passes through the filter from the upstream surface to the downstream surface to effect a filtering of the sprayed liquid, and a first artificial boundary extending from the housing and into the chamber to overly at least a portion of the upstream surface to form an increased shear force zone between the first artificial boundary and the upstream surface, wherein liquid passing between the first artificial boundary and the rotating filter applies a greater shear force on the upstream surface than liquid in an absence of the first artificial boundary.
In the drawings:
While the concepts of the present disclosure are susceptible to various modifications and alternative forms, specific exemplary embodiments thereof have been shown by way of example in the drawings and will herein be described in detail. It should be understood, however, that there is no intent to limit the concepts of the present disclosure to the particular forms disclosed, but on the contrary, the intention is to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the invention as defined by the appended claims.
Referring to
A door 24 is hinged to the lower front edge of the tub 12. The door 24 permits user access to the tub 12 to load and unload the dishwasher 10. The door 24 also seals the front of the dishwasher 10 during a wash cycle. A control panel 26 is located at the top of the door 24. The control panel 26 includes a number of controls 28, such as buttons and knobs, which are used by a controller (not shown) to control the operation of the dishwasher 10. A handle 30 is also included in the control panel 26. The user may use the handle 30 to unlatch and open the door 24 to access the tub 12.
A machine compartment 32 is located below the tub 12. The machine compartment 32 is sealed from the tub 12. In other words, unlike the tub 12, which is filled with fluid and exposed to spray during the wash cycle, the machine compartment 32 does not fill with fluid and is not exposed to spray during the operation of the dishwasher 10. Referring now to
The tub 12 of the dishwasher 10 is shown in greater detail. The tub 12 includes a number of side walls 40 extending upwardly from a bottom wall 42 to define the washing chamber 14. The open front side 44 of the tub 12 defines an access opening 46 of the dishwasher 10. The access opening 46 provides the user with access to the dish racks 16 positioned in the washing chamber 14 when the door 24 is open. When closed, the door 24 seals the access opening 46, which prevents the user from accessing the dish racks 16. The door 24 also prevents fluid from escaping through the access opening 46 of the dishwasher 10 during a wash cycle.
The bottom wall 42 of the tub 12 has a sump 50 positioned therein. At the start of a wash cycle, fluid enters the tub 12 through a hole 48 defined in the side wall 40. The sloped configuration of the bottom wall 42 directs fluid into the sump 50. The recirculation pump assembly 34 removes such water and/or wash chemistry from the sump 50 through a hole 52 defined in the bottom of the sump 50 after the sump 50 is partially filled with fluid.
The liquid recirculation system supplies liquid to a liquid spraying system, which includes a spray arm 54, to recirculate the sprayed liquid in the tub 12. The recirculation pump assembly 34 is fluidly coupled to a rotating spray arm 54 that sprays water and/or wash chemistry onto the dish racks 16 (and hence any wares positioned thereon) to effect a recirculation of the liquid from the washing chamber 14 to the liquid spraying system to define a recirculation flow path. Additional rotating spray arms (not shown) are positioned above the spray arm 54. It should also be appreciated that the dishwashing machine 10 may include other spray arms positioned at various locations in the tub 12. As shown in
After wash fluid contacts the dish racks 16, and any wares positioned in the washing chamber 14, a mixture of fluid and soil falls onto the bottom wall 42 and collects in the sump 50. The recirculation pump assembly 34 draws the mixture out of the sump 50 through the hole 52. As will be discussed in detail below, fluid is filtered in the recirculation pump assembly 34 and re-circulated onto the dish racks 16. At the conclusion of the wash cycle, the drain pump 36 removes both wash fluid and soil particles from the sump 50 and the tub 12.
Referring now to
Referring now to
The side wall 76 has an inner surface 84 facing the filter chamber 82. A number of rectangular ribs 85 extend from the inner surface 84 into the filter chamber 82. The ribs 85 are configured to create drag to counteract the movement of fluid within the filter chamber 82. It should be appreciated that in other embodiments, each of the ribs 85 may take the form of a wedge, cylinder, pyramid, or other shape configured to create drag to counteract the movement of fluid within the filter chamber 82.
The manifold 68 has a main body 86 that is secured to the end 78 of the filter casing 64. The inlet port 70 extends upwardly from the main body 86 and is configured to be coupled to a fluid hose (not shown) extending from the hole 52 defined in the sump 50. The inlet port 70 opens through a sidewall 87 of the main body 86 into the filter chamber 82 of the filter casing 64. As such, during the wash cycle, a mixture of fluid and soil particles advances from the sump 50 into the filter chamber 82 and fills the filter chamber 82. As shown in
A passageway (not shown) places the outlet port 72 of the manifold 68 in fluid communication with the filter chamber 82. When the drain pump 36 is energized, fluid and soil particles from the sump 50 pass downwardly through the inlet port 70 into the filter chamber 82. Fluid then advances from the filter chamber 82 through the passageway and out the outlet port 72.
The wash pump 60 is secured at the opposite end 80 of the filter casing 64. The wash pump 60 includes a motor 92 (see
The wash pump 60 also includes an impeller 104. The impeller 104 has a shell 106 that extends from a back end 108 to a front end 110. The back end 108 of the shell 106 is positioned in the chamber 102 and has a bore 112 formed therein. A drive shaft 114, which is rotatably coupled to the motor 92, is received in the bore 112. The motor 92 acts on the drive shaft 114 to rotate the impeller 104 about an imaginary axis 116 in the direction indicated by arrow 118 (see
The front end 110 of the impeller shell 106 is positioned in the filter chamber 82 of the filter casing 64 and has an inlet opening 120 formed in the center thereof. The shell 106 has a number of vanes 122 that extend away from the inlet opening 120 to an outer edge 124 of the shell 106. The rotation of the impeller 104 about the axis 116 draws fluid from the filter chamber 82 of the filter casing 64 into the inlet opening 120. The fluid is then forced by the rotation of the impeller 104 outward along the vanes 122. Fluid exiting the impeller 104 is advanced out of the chamber 102 through the outlet port 74 to the spray arm 54.
As shown in
A filter sheet 140 extends from one end 134 to the other end 136 of the filter drum 132 and encloses a hollow interior 142. The rotating filter 130 may be thought of as being located within the recirculation flow path and has an upstream surface 146 and a downstream surface 148 such that the recirculating liquid passes through the rotating filter 130 from the upstream surface 146 to the downstream surface 148 to effect a filtering of the liquid. In the described flow direction, the upstream surface 146 correlates to the outer surface and the downstream surface 148 correlates to the inner surface. The sheet 140 includes a number of holes 144, and each hole 144 extends from an upstream surface 146 of the sheet 140 to a downstream surface 148. In the illustrative embodiment, the sheet 140 is a sheet of chemically etched metal. Each hole 144 is sized to allow for the passage of wash fluid into the hollow interior 142 and prevent the passage of soil particles.
As such, the filter sheet 140 divides the filter chamber 82 into two parts. As wash fluid and removed soil particles enter the filter chamber 82 through the inlet port 70, a mixture 150 of fluid and soil particles is collected in the filter chamber 82 in a region 152 external to the filter sheet 140. Because the holes 144 permit fluid to pass into the hollow interior 142, a volume of filtered fluid 156 is formed in the hollow interior 142.
Referring to
An external flow diverter or artificial boundary 180 may extend from the housing 62 toward and overlaying a portion of the upstream surface 146. The artificial boundary 180 may extend along the length of the filter 130 from one end 134 to the other end 136. The artificial boundary 180 may be continuous. Alternatively, it may be discontinuous.
The artificial boundary 180 is illustrated as being a change in the cross-sectional shape of a constant-thickness housing, which extends toward and overlies the filter. In such a case, the artificial boundary 180 is integral with the housing 62 although this need not be the case. As will be seen in subsequent embodiments, it is possible to accomplish the same result by creating a projection from the housing, which essentially alters the thickness of the housing such that a portion extends towards and overlies the filter. The projection may be formed with or attached to the housing to be integrated within the housing. Another alternative is to asymmetrically locate the filter within the housing such that a portion of the housing overlies the filter.
The artificial boundary 180 may be positioned in a partially or completely radial overlapping relationship with the artificial boundary 160 and spaced apart from the artificial boundary 180 so as to create a gap 188 therebetween. The sheet 140 is positioned within the gap 188. In some cases, the shear zone benefit may be created with the artificial boundaries being in proximity to each other and not radially overlapping to any extent.
In operation, wash fluid, such as water and/or wash chemistry (i.e., water and/or detergents, enzymes, surfactants, and other cleaning or conditioning chemistry), enters the tub 12 through the hole 48 defined in the side wall 40 and flows into the sump 50 and down the hole 52 defined therein. As the filter chamber 82 fills, wash fluid passes through the holes 144 extending through the filter sheet 140 into the hollow interior 142. After the filter chamber 82 is completely filled and the sump 50 is partially filled with wash fluid, the dishwasher 10 activates the motor 92.
Activation of the motor 92 causes the impeller 104 and the filter 130 to rotate. The rotation of the impeller 104 creates a suction force that draws wash fluid from the filter chamber 82 through the filter sheet 140 and into the inlet opening 120 of the impeller shell 106. Fluid then advances outward along the vanes 122 of the impeller shell 106 and out of the chamber 102 through the outlet port 74 to the spray arm 54. When wash fluid is delivered to the spray arm 54, it is expelled from the spray arm 54 onto any dishes or other wares positioned in the washing chamber 14. Wash fluid removes soil particles located on the dishwares, and the mixture of wash fluid and soil particles falls onto the bottom wall 42 of the tub 12. The sloped configuration of the bottom wall 42 directs that mixture into the sump 50 and down the hole 52 defined in the sump 50.
While fluid is permitted to pass through the sheet 140, the size of the holes 144 prevents the soil particles of the mixture 152 from moving into the hollow interior 142. As a result, those soil particles accumulate on the upstream surface 146 of the sheet 140 and cover the holes 144, thereby preventing fluid from passing into the hollow interior 142.
The rotation of the filter 130 about the axis 116 causes the unfiltered liquid or mixture 150 of fluid and soil particles within the filter chamber 82 to rotate about the axis 116 in the direction indicated by the arrow 118. Centrifugal force urges the soil particles toward the side wall 76 as the mixture 150 rotates about the axis 116. As the liquid advances through the gap 188, the angular velocity of the liquid increases relative to its previous velocity and an increased shear zone 194 is formed by the significant increase in angular velocity of the liquid in the relatively short distance between the first artificial boundary 180 and the rotating filter 130.
As the first artificial boundary 180 is stationary, the liquid in contact with the first artificial boundary 180 is also stationary or has no rotational speed. The liquid in contact with the upstream surface 146 has the same angular speed as the rotating filter 130, which is generally in the range of 3000 rpm, which may vary between 1000 to 5000 rpm. The speed of rotation is not limiting to the invention. The increase in the angular speed of the liquid is illustrated as increasing length arrows, the longer the arrow length the faster the speed of the liquid. Thus, the liquid in the increased shear zone 194 has an angular speed profile of zero where it is constrained at the first artificial boundary 180 to approximately 3000 rpm at the upstream surface 146, which requires substantial angular acceleration, which locally generates the increased shear forces on the upstream surface 146. Thus, the proximity of the first artificial boundary 180 to the rotating filter 130 causes an increase in the angular velocity of the liquid portion 190 and results in a shear force being applied on the upstream surface 146.
This applied shear force aids in the removal of soils on the upstream surface 146 and is attributable to the interaction of the liquid and the rotating filter 130. The increased shear zone 194 functions to remove and/or prevent soils from being trapped on the upstream surface 146. The liquid passing between the first artificial boundary 180 and the rotating filter 130 applies a greater shear force on the upstream surface 146 than liquid in an absence of the first artificial boundary 180.
The orientation of the body 166 such that it has a larger leading gap 169 that reduces to a smaller trailing gap 170 results in a decreasing cross-sectional area between the outer surface 168 of the body 166 and the downstream surface 148 of the filter sheet 140 along the direction of fluid flow between the body 166 and the filter sheet 140, which creates a wedge action that forces water from the hollow interior 142 through a number of holes 144 to the upstream surface 146 of the sheet 140. Thus, a backflow is induced by the leading gap 169. The backflow of water against accumulated soil particles on the sheet 140 better cleans the sheet 140. Further, an increase in shear force may occur on the downstream surface 148 where the artificial boundary 160 overlies the downstream surface 148. The liquid would have an angular speed profile of zero at the artificial boundary 160 and would increase to approximately 3000 rpm at the downstream surface 148, which generates the increased shear forces.
One difference between the second embodiment and the first embodiment is that the second embodiment includes an artificial boundary 280 that terminates in a tip 283 near the upstream surface 246. The artificial boundary 280 includes a first surface 295 facing upstream to the recirculation flow path and a second surface 296 facing downstream to the recirculation flow path. The artificial boundary 280 has an asymmetrical cross section and the first surface 295 forms a smaller angle relative to the recirculation flow path than the second surface 296.
Another difference is that the second embodiment illustrates that the artificial boundary 280 may include at least one slot 297 such that liquid may pass through both the slot 297 and the gap 288. The slot 297 may extend along the length of the filter 230 or some portion thereof. Further, multiple slots 297 may be included. In the case where the artificial boundary 280 is not integral with the housing 62, it is contemplated that at least a portion of the slot 297 may be located between the tip 283 and the housing 62 or that the slot 297 may be located adjacent the housing 62. When the artificial boundary 280 is integral with the housing 62, as illustrated, the slot 297 may run through the housing 62.
Another difference is that the artificial boundary 260 is illustrated as having two concave deflector portions that are spaced about the downstream surface 248. The two concave deflector portions may be joined to form a single second artificial boundary 260, as illustrated, having an S-shape cross section. Alternatively, it has been contemplated that the two concave deflector portions may form two separate second artificial boundaries. The second artificial boundary 260 may extend axially within the rotating filter 230 to form a flow straightener. Such a flow straightener reduces the rotation of the liquid before the impeller 104 and improves the efficiency of the impeller 104.
The second embodiment operates much the same way as the first embodiment. That is, during operation of the dishwasher 10, liquid is recirculated and sprayed by a spray arm 54 of the spraying system to supply a spray of liquid to the washing chamber 14. The liquid then falls onto the bottom wall 42 of the tub 12 and flows to the filter chamber 82. The housing or casing 64, which defines the filter chamber 82, may be physically remote from the tub 12 such that the filter chamber 82 may form a sump that is also remote from the tub 12. Activation of the motor 92 causes the impeller 104 and the filter 230 to rotate. The rotation of the impeller 104 draws wash fluid from an upstream side in the filter chamber 82 through the rotating filter 230 to a downstream side, into the hollow interior 242, and into the inlet opening 220 where it is then advanced through the recirculation pump assembly 34 back to the spray arm 54.
Referring to
The increased shear force zone 294 is formed by the significant increase in angular velocity of the liquid in the relatively short distance between the first artificial boundary 280 and the rotating filter 230 as was described with respect the first embodiment above. The increase in the angular speed of the liquid is illustrated as increasing length arrows in
As the tip 283 extends towards the upstream surface 246, the distance between the first artificial boundary 280 and the upstream surface 246 decreases. This decrease in distance between the first artificial boundary 280 and the upstream surface 246 occurs in a direction along a rotational direction of the filter 230, which in this embodiment, is counter-clockwise as indicated by arrow 218, and forms a constriction point at the tip 283. The distance between the first artificial boundary 280 and the upstream surface 246 increases from the tip 283 in a direction along the rotational direction of the filter 230 to form a liquid expansion zone 289.
Further, a nozzle or jet-like flow through the rotating filter 230 is provided to further clean the rotating filter 230 and is formed by at least one of high pressure zones 291, 293 and lower pressure zones 289, 292 on one of the upstream surface 246 and downstream surface 248. High pressure zone 293 is formed by the decrease in the gap 288 between the first artificial boundary 280 and the rotating filter 230, which functions to create a localized and increasing pressure gradient up to the tip 283, beyond which the liquid is free to expand to form the low pressure, expansion zone 289. Similarly, a high pressure zone 291 is formed between the downstream surface 248 and the second artificial boundary 260. The high pressure zone 291 is relatively constant until it terminates at the end of the second artificial boundary 260, where the liquid is free to expand and form the low pressure, expansion zone 292.
The high pressure zone 293 is generally opposed by the high pressure zone 291 until the end of the high pressure zone 291, which is short of the constriction point 289. At this point and up to the constriction point 289, the high pressure zone 293 forms a pressure gradient across the rotating filter 230 to generate a flow of liquid through the rotating filter 230 from the upstream surface 246 to the downstream surface 248. The pressure gradient is great enough that the flow has a nozzle or jet-like effect and helps to remove particles from the rotating filter 230. The presence of the low pressure expansion zone 292 opposite the high pressure zone 293 in this area further increases the pressure gradient and the nozzle or jet-like effect. The pressure gradient is great enough at this location to accelerate the water to an angular velocity greater than the rotating filter.
As illustrated, the filter rotates in the clockwise direction and creates an increased shear force zone 394 between the artificial boundary 380 and the upstream surface 346. During operation, the liquid passing between the artificial boundary 380 and the rotating filter 330 applies a greater shear force on the upstream surface 346 than liquid in an absence of the artificial boundary 380 (i.e. in the absence of the filter 330 being offset within the housing 62).
With respect to all of the above embodiments it is contemplated that there may be multiple artificial boundaries spaced about the rotating filter and overlying the upstream surface to define multiple increased shear force zones. Further, there may be multiple artificial boundaries provided on the downstream of the rotating filter as well. The multiple artificial boundaries may be arranged in pairs, with each pair having one artificial boundary on the downstream side of the rotating filter and another artificial boundary on the upstream side of the rotating filter. Such multiple artificial boundaries may create multiple shear force zones as described above.
There are a plurality of advantages of the present disclosure arising from the various features of the method, apparatuses, and system described herein. For example, the embodiments of the apparatus described above allows for enhanced filtration such that soil is filtered from the liquid and not re-deposited on utensils. Further, the embodiments of the apparatus described above allow for cleaning of the filter throughout the life of the dishwasher and this maximizes the performance of the dishwasher. Thus, such embodiments require less user maintenance than required by typical dishwashers.
While the invention has been specifically described in connection with certain specific embodiments thereof, it is to be understood that this is by way of illustration and not of limitation. Reasonable variation and modification are possible within the scope of the forgoing disclosure and drawings without departing from the spirit of the invention which is defined in the appended claims.
