Patent Publication Number: US-2022211245-A1

Title: Filter structure of dishwasher, and dishwasher

Description:
TECHNICAL FIELD 
     The disclosure herein relates to the technical field of dishwashers, especially relates to a filter structure of a dishwasher and a dishwasher. 
     BACKGROUND 
     In the prior art, a dishwasher includes a filter and a flat filter screen. The flat filter screen of a traditional dishwasher is usually made of metal, which leads to a higher cost of flat filter screen. When the metal flat filter screen is installed on the bottom of the inner tank in the dishwasher, extra parts are needed to improve the compactness between the flat filter screen and the bottom of the inner tank. That is to narrow the gap between the flat filter screen and the bottom of the inner tank, so that to avoid washing impurities getting into and remaining in the gap, which leads to a further increase of the cost. In addition, the metal flat filter screen usually has a porous structure. The filter screen has the risk of being blocked by washing impurities due to the small size of the pore. 
     Chinese patent with application number CN201710213330.2 discloses a dishwasher which comprises an inner tank and a water tank. A part of the inner tank that connected with the water tank is recessed downwards and forms a cylindrical shape, a flat filter screen is arranged in a recess of the inner tank, and a support is arranged between the flat filter screen and a bottom surface of the recess for supporting the flat filter screen. A sealing ring is arranged between an outer side of the recess and the water tank. Parts are added between the flat filter screen and a bottom of the inner tank in the dishwasher to improve the compactness between the flat filter screen and the bottom of the inner tank, which lead to a high cost and extreme complication of the installation of the flat filter screen. 
     In view of this, the disclosure is proposed. 
     SUMMARY 
     In order to solve the technical problem above, the disclosure provides a filter structure of a dishwasher and a dishwasher. 
     To achieve this purpose, the disclosure adopts the following technical scheme: 
     The first object of the disclosure is to provide a filter structure of a dishwasher comprising a filter screen, the filter screen comprises several first filter ribs and several second filter ribs, and the second filter ribs and the first filter ribs are arranged to cross each other so as to form a mesh structure. 
     Further, a second filter screen plane formed by the second filter ribs is arranged under a first filter screen plane formed by the first filter ribs. 
     Preferably, the second filter ribs and the first filter ribs are arranged to cross each other vertically and horizontally. 
     Preferably, the filter screen is integrally formed. 
     Preferably, the filter screen is plastic filter screen. 
     Further, a width of a second filter hole formed between two adjacent second filter ribs gradually increases from an upper surface of the second filter rib which is in contact with the first filter rib to a lower surface of the second filter rib. 
     Preferably, two second sides, opposite to each other, of the second filter hole are inclined to the lower surface of the second filter rib and extend in opposite direction from each other, and a distance between the two second sides gradually increases along a direction to the lower surface. 
     More preferably, the two second sides are inclined to the lower surface of the second filter rib and extend symmetrically. 
     Further, an upper surface of the first filter rib is a circular arc surface or inclined surface, or there is fillet or chamfer between the upper surface and a side of the first filter ribs. 
     And/or, a width of a first filter hole formed between two adjacent first filter ribs gradually increases from a lower surface of the first filter rib which is in contact with the second filter rib to the upper surface of the first filter rib. 
     Preferably, two first sides, opposite to each other, of the first filter hole are inclined to the upper surface of the first filter rib and extend in opposite direction from each other, and a distance between the two first sides gradually increases along a direction to the upper surface. 
     Preferably, the two first sides are inclined to the upper surface of the first filter rib and extend symmetrically. 
     Further, the filter screen has an annular structure, and at least part of the first filter ribs extend towards an inner ring of the filter screen. 
     Preferably, the filter screen includes at least two filter zones, the first filter ribs in a first filter zone extend from an outer ring of the filter screen to the inner ring of the filter screen along a direction of water flow, and at least part of the first filter ribs in a second filter zone extend from the outer ring of the filter screen to the inner ring of the filter screen along the direction of water flow, and at least some the first filter ribs in the second filter zone extend from the outer ring of the filter screen to the first filter zone along the direction of water flow. 
     More preferably, the first filter ribs in the first filter zone are arranged parallel to each other. 
     More preferably, the first filter ribs in the second filter zone are arranged parallel to each other. 
     Further, the filter screen includes a first filter zone and two second filter zones, the two second filter zones are symmetrically arranged on two sides of the first filter zone. 
     The filter screen is an annular filter screen with a fan-shaped gap, the inner ring of the filter screen is arranged in center of the annular filter screen, the first filter ribs in the first filter zone are parallel to a symmetrical centerline of the fan-shaped gap, and the first filter ribs in the second filter zone are parallel to two sides of the fan-shaped gap. 
     The second purpose of the disclosure is to provide a dishwasher comprising a filter structure of a dishwasher, the filter structure of a dishwasher comprises the filter screen above. A water tank is provided under the filter screen, the filter screen comprises several first filter ribs and several second filter ribs, and the second filter ribs and the first filter ribs are arranged to cross each other so as to form a mesh structure. 
     Further, the dishwasher comprises an inner tank, a bottom of the inner tank is recessed downwards to form a groove, and the filter screen is installed in the groove. 
     Preferably, a side wall of the groove extends obliquely, the filter screen has an annular structure, and a side of an outer ring of the filter screen extends obliquely and is coordinated with the side wall of the groove. 
     More preferably, the side wall of the groove extends obliquely and downwards from the bottom of the inner tank to a center of the groove. 
     Preferably, the filter screen is recessed downwards from the outer ring to the inner ring and forms a funnel shape. 
     Further, a bottom of the outer ring of the filter screen is in line contact with the bottom of the groove of the inner tank. 
     Preferably, a bottom surface of the outer ring of the filter screen, which is in contact with the groove of the inner tank, is an arc surface protruding towards the groove of the inner tank. 
     Further, several outlets for water flow passing are provided between a bottom of the outer ring of the filter screen and a bottom of the groove of the inner tank. 
     Preferably, the bottom of the outer ring of the filter screen comprises several interval arranged bulges, and the recess between two adjacent bulges forms the outlets for water flow passing. 
     More preferably, an end surface of the bulge, which is coordinated with the bottom of the groove of the inner tank, is an arc surface protruding towards the bottom of groove of the inner tank. 
     The disclosure has the following beneficial effects compared with the prior art: 
     The filter screen of the disclosure comprises a mesh structure formed by first filter ribs and second filter ribs arranged to cross each other, the second filter ribs and the first filter ribs are arranged to cross each other so that the strength of the filter screen is enhanced, and the mesh structure avoids being blocked by washing impurities like the filter pores of the metal filter screen. The first filter ribs and the second filter ribs are arranged to cross each other in two layers, which further enhances the strength of the filter screen and prevents the filter screen from being damaged. Two-layer crossed mesh structure has a larger effective filter area than metal filter screen with filter pores. The filter structure comprises an integrally formed plastic filter screen, which saves cost compared with the metal filter screen. The plastic filter screen can be integrally formed so that post-perforation is not required, which saves the forming cost. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       As a part of the disclosure, the attached drawings are used to provide a further understanding of the disclosure. The embodiments and descriptions of the disclosure are used to explain the disclosure and is not to be considered as improper limitation of the disclosure. Obviously, the following drawings are only some embodiments. For the person skilled in the art, other drawings can be obtained according to these drawings without any creative work. 
       In the attached figures: 
         FIG. 1  shows a diagram of a filter screen of the disclosure; 
         FIG. 2  shows an installation diagram of the filter screen of the disclosure; 
         FIG. 3  shows a partial view of the filter screen of the disclosure; 
         FIG. 4  shows a side view of the filter screen of the disclosure; 
         FIG. 5  shows an enlarged view of part A in  FIG. 4 ; 
         FIG. 6  shows an enlarged partial sectional view of an outer ring of the filter screen of the disclosure. 
     
    
    
     Each component is named as follows: 
       1 , filter screen;  11 , outer ring;  111 , bulge;  12 , inner ring;  13 , first filter rib;  14 , second filter rib;  15 , hole;  2 , bottom of the inner tank;  21 , groove;  3 , filter. 
     It should be noted that these drawings and descriptions are not to limit the conception of the disclosure in any way, but to illustrate the concept of the disclosure for the person skilled in the art by referring to specific embodiments. 
     DETAILED DESCRIPTION 
     The technical scheme in the following embodiments will then be described clearly and completely in order to make the purpose, technical scheme and advantages of the disclosure clearer. The following embodiments are used to illustrate the disclosure but are not used to limit the scope of the disclosure. 
     As illustrated in in  FIGS. 1 to 6 , the disclosure herein provides a filter structure of a dishwasher which comprises a filter screen  1 . The filter screen  1  comprises several first filter ribs  13  and several second filter ribs  14 , and the second filter ribs  14  and the first filter ribs  13  are arranged to cross each other so as to form a mesh structure. 
     In the present disclosure, the filter screen  1  includes a mesh structure formed by the second filter ribs  14  and the first filter ribs  13  arranged to cross each other. The second filter ribs  14  and the first filter ribs  13  enhance the strength of the filter screen  1 , and the mesh structure avoids being blocked by washing impurities like the filter pores of the metal filter screen  1 . Preferably, the filter screen  1  is integrally formed so that post-perforation is not required, which saves the forming cost. Preferably, the filter screen is plastic filter screen  1 , which saves cost compared with the metal filter screen  1 . In the disclosure, the filter structure of a dishwasher comprises the filter screen  1 , and the filter screen is a flat filter screen of a dishwasher. The flat filter screen is not limited to a flat plate-shaped filter screen, it can also be a curved filter screen or an inclined filter screen. 
     Embodiment 1 
     In the embodiment, a second filter screen plane formed by the second filter ribs  14  is arranged under a first filter screen plane formed by the first filter ribs  13 . The first filter ribs  13  and the second filter ribs  14  are arranged to cross each other in two layers, so that the strength of the filter screen  1  is further enhanced and the filter screen  1  is prevent from being damaged. Two-layer crossed mesh structure has a larger effective filter area than metal filter screen  1  with filter pores. And the two-layer crossed mesh structure intercept and filter water flow twice, which achieves better filtering effect and will not be blocked by washing impurities. In addition, the second filter ribs  14  and the first filter ribs  13  are arranged to cross each in two layers, which makes it easier to collect residue so that the residue is easy to remove, or makes it easy for the residue to enter a filter  3 . 
     Preferably, the second filter ribs  14  and the first filter ribs  13  are arranged to cross each other vertically and horizontally. It avoids holes  15  of the filter screen  1  being blocked by washing impurities and makes it easier for water flow passing through. And the holes  15  formed by the first filter ribs  13  and the second filter ribs  14  arranged to cross each other vertically and horizontally are uniform in size, which avoids being partial blocked and hard to remove. 
     Preferably, the filter screen  1  is integrally formed so that post-perforation is not required, which saves fabrication cost. Preferably, the filter screen is plastic filter screen  1 , which saves cost compared with the metal filter screen  1 . 
     Embodiment 2 
     On the basis of embodiment 1, in this embodiment, a width of a second filter hole formed between two adjacent second filter ribs  14  gradually increases from an upper surface of the second filter rib  14  which is in contact with the first filter rib  13  to a lower surface of the second filter rib  14 . Here, the first filter rib  13  and the upper surface of the second filter rib  14  which is in contact with the first filter rib  13  realize the filtering. A distance of the second filter hole from the upper surface of the second filter rib to the lower surface of the second filter rib does not affect the filtering effect and can guide water flow, which represents a filter thickness of the whole filter screen is reduced to a thickness of the first filter rib  13  and achieves a good filtering effect. In addition, the strength of the filter screen  1  can be enhanced by the combination of the second filter ribs  14  and the first filter ribs  13 . On the premise that the first filter ribs  13  are as thin as possible, the strength is enhanced by increasing a thickness of the second filter ribs  14 . Two second sides, opposite to each other, of the second filter hole are inclined to the lower surface of the second filter rib  14  and extend in opposite direction from each other, and a distance between the two second sides gradually increases along a direction to the lower surface. In this case, a main part of the second filter rib  14  that coordinates with the first filter rib  13  to realize the filtering is the upper surface of the second filter rib  14 , which represents the filter thickness of the filter screen  1  in the disclosure is reduced to the thickness of the first filter rib  13 . Compared with filter screen with large thickness, it makes less easy for washing impurities to block the hole  15 , and the inclined second sides makes it easier for water flow passing when water flow passes through the second filter ribs  14 . A distance between two opposite second sides gradually increases along a direction to the lower surface. The inclined second side of the second filter rib  14  cannot be seen when looking downwards from an upper side of the first filter rib  13 . The second side has no resistance to water flow and can guide water flow flows downwards, and it enlarges the space for water flow flowing downwards making it easier for water flow flowing downwards. The second sides extend obliquely, which can be integrated formed through draft molding so that to reduce forming steps and avoid the requirement of post-processing. Preferably, the two opposite second sides of the second filter hole extend symmetrically to the lower surface of the second filter rib  14 . And the forming is simple, which is more beneficial to the flowing of water flow. 
     Embodiment 3 
     On the basis of above embodiments, in this embodiment, an upper surface of the first filter rib  13  is a circular arc surface or inclined surface, and/or, a width of a first filter hole formed between two adjacent first filter ribs  13  gradually increases from a lower surface of the first filter rib  13  which is in contact with the second filter rib  14  to the upper surface of the first filter rib  13 . Preferably, two first sides, opposite to each other, of the first filter hole are inclined to the upper surface of the first filter rib  13  and extend in opposite direction from each other, and a distance between the two first sides gradually increases along a direction to the upper surface. The embodiment herein includes four implementations: the upper surface of the first filter rib  13  is a circular arc surface; the upper surface of the first filter rib  13  is an inclined surface; two opposite first sides of the first filter hole are inclined to the upper surface of the first filter rib  13  and extend in opposite direction from each other, and the distance between the two first sides gradually increases along the direction to the upper surface; and the upper surface of the first filter rib  13  is a circular arc surface, two opposite first sides of the first filter hole are inclined to the upper surface of the first filter rib  13  and extend in opposite direction from each other, and the distance between the two first sides gradually increases along the direction to the upper surface. Another implementation also included is that the upper surface of the first filter rib  13  is an inclined surface, two opposite first sides of the first filter hole are inclined to the upper surface of the first filter rib  13  and extend in opposite direction from each other, and the distance between the two first sides gradually increases along the direction to the upper surface. Of course, it also includes that the upper surface of the first filter rib  13  is a flat surface with fillet or chamfer provided at the edge of the flat surface and the combination of the flat surface with fillet or chamfer and other implementations. Preferably, the two first sides are inclined to the lower surface of the first filter rib  13  and extend symmetrically. 
     The upper surface of the first filter rib  13  is a circular arc surface or inclined surface, making it easy for water flow flows downwards and avoiding the resistance to water flow for flowing downwards if the upper surface was a flat surface. The upper surface of the first filter rib  13  is a flat surface with fillet or chamfer provided at the edge of the flat surface, avoiding the accumulation of washing impurities that caught by sharp edge, which would further block filter holes  15 . Two opposite first sides of the first filter hole are inclined to the lower surface of the first filter rib  13  and extend in opposite direction, which can also make it easy for water flow flowing and will not cause the accumulation of washing impurities. And in coordination with the inclined second filter rib  14 , it further reduces the filter thickness of the filter screen and provides a better filtering effect. 
     Embodiment 4 
     On the basis of above embodiments, in this embodiment, the filter screen  1  has an annular structure, and the filter structure also includes a filter  3 . Generally, the filter  3  is detachably arranged at an inner ring  12  of the filter screen to fine filter the water flow, or the filter  3  is rotatably arranged at the inner ring  12  of the filter screen. For example, the filter  3  includes at least two layers of filter parts. The filter  3  is installed at the inner ring  12  of the filter screen, and at least some of the first filter ribs  13  extends along a direction towards the filter  3  installed at the inner ring of the filter screen to guide the water flow to the filter  3 . A dishwasher is usually provided with a filter screen  1 , a filter  3  is provided at center of the filter screen  1 , and the filter screen  1  and the filter  3  both filter the water flow. In the disclosure, the first filter rib  13  extends towards the inner ring  12  of the filter screen so as to guide the water flow to the filter  3  arranged at the inner ring  12 . 
     The dishwasher includes an inner tank, a bottom of the inner tank  2  is recessed downwards to form a groove  21 , and the filter screen  1  is installed in the groove  21 . An opening is provided at a bottom of the groove, and a water tank of the dishwasher is connected with the opening. The filter screen  1  and the filter  3  is provided to filter water in the dishwash, so that there is no large washing impurity in the water flowing into the water tank, avoiding adverse impact on other parts of waterway circulation. The bottom of the inner tank  2  includes a water guiding surface that guide water flow to the groove  21 , and water guiding surface obliquely extends downwards from the edge of the bottom of the inner tank to the groove  21 . Generally, the bottom of the inner tank in dishwasher is a rectangle. Four water guiding surface is formed from four edges of the rectangle to the groove  21  so as to make forming easier. At least some of the first filter ribs  13  extend along a water guiding direction of the water guiding surface, and the first filter ribs  13  coordinate with the water guiding surface to guide water flow to the filter  3 . At least some of the first filter ribs  13  extends towards the inner ring  12  of the filter screen and also coordinates with the water guiding surface, extending along the water guiding direction of the water guiding surface. 
     A preferable implementation is that the filter screen  1  includes at least two filter zones, and the first filter ribs  13  in a first filter zone extend from an outer ring  11  of the filter screen to the inner ring  12  along a direction of water flow, guiding water flow to the inner ring  12 . The first filter ribs  13  in the first filter zone coordinate with the water guiding surface and extend from the outer ring  11  of the filter screen to the inner ring  12 , guiding water flow to the inner ring  12 . At least some of the first filter ribs  13  in a second filter zone extend from the outer ring  11  of the filter screen to the inner ring along the direction of water flow, guiding water flow to the inner ring  12 . And at least some of the first filter ribs  13  in the second filter zone extend from the outer ring  11  of the filter screen to the first filter zone along water flow so as to guide water flow to the first filter ribs  13 , and then water flow is guided to the inner ring  12  by a direction of the first filter ribs  13 . 
     Specifically, the first filter ribs  13  in the first filter zone are arranged parallel to each other, and the first filter ribs  13  in the second filter zone are arranged parallel to each other. The second filter ribs  14  are arranged to cross the first filter ribs  13  and under the first filter ribs  13  so as to form a mesh structure. The second filter ribs  14  and the first filter ribs  13  are arranged to cross each other vertically and horizontally. The filter screen  1  is divided into different filter zones so that the holes  15  formed by the first filter ribs  13  and the second filter ribs  14  are more uniform in size. It can prevent that if all of the first filter ribs  13  were arranged towards the inner ring  12 , the size of the holes  15  may be different, resulting uneven filtering effect. 
     A further implementation is that the filter screen  1  includes a first filter zone and two second filter zones, the two second filter zones are symmetrically arranged on two sides of the first filter zone, providing the advantage of simple structure and easy to form. The first filter zone comprises two parts which are arranged opposite to each other at two sides of the inner ring  12  of the filter screen. Two parts of the first filter zone respectively coordinate with two water guiding surfaces at the bottom of the inner tank and the second filter zones respectively coordinate with other two water guiding surfaces at the bottom of the inner tank, guiding water flow to the inner ring  12 . 
     The filter screen  1  is an annular filter screen  1  with a fan-shaped gap, the inner ring  12  is arranged in center of the annular filter screen, the first filter ribs  13  in the first filter zone are parallel to a symmetrical centerline of the fan-shaped gap, and the first filter ribs  13  in the second filter zone are parallel to two sides of the fan-shaped gap. In other words, there are first filter ribs  13  arranged along three directions. It makes it easy to gather washing impurities at the filter  3  and to arrange the second filter ribs  14  so as to form filter holes  15  uniform in size, achieving uniform filtering effect. And it can prevent that when the first filter ribs  13  and the second filter ribs  14  are arranged to cross each other vertically and horizontally, the filter holes  15  formed by the first filter ribs  13  and the second filter ribs  14  are different in size, resulting unstable filtering effect. The first filter ribs  13  along three directions respectively coordinate with different water guiding surfaces to guide water flow. 
     Generally, the bottom of the inner tank in dishwasher obliquely extends to the filter screen  1 . A common way is that four parts, divided by four edges of the bottom of the inner tank in dishwasher, obliquely extends to the filter screen  1  respectively. In this disclosure, the filter screen  1  coordinates with the bottom of the inner tank in dishwasher and is provided with at least two filter zones. Specifically, the direction of the first filter ribs  13  in each filter zone tends to guide water flow to the inner ring of the filter screen  1 . A preferable implementation is that the filter zone of the disclosure coordinates with corresponding inclined inner tank in dishwasher, and the whole slopes downwards and to the inner ring of the filter screen. In other words, the first filter zone arranged at two sides of the inner ring slopes along different directions, the second filter zones arranged at two sides of the first filter zone slope along different directions, and the first filter zone and the second filter zones also slope along different directions. 
     The filter screen  1  is recessed downwards from edge to the inner ring  12  and forms a funnel shape so as to make it easy for water flow to gather to the filter  3  at the inner ring and enter the filter  3  to be filtered. 
     An indicating arrow is provided on the filter screen, and the indicating arrow shows an installation direction of the filter screen. The indicating arrow points to the filter and also shows an approximate flowing direction of water flow. Preferably, the indicating arrow is integrally formed above the filter screen. 
     Embodiment 5 
     The embodiment herein discloses a dishwasher comprising the filter structure of a dishwasher described in above embodiments. The filter structure of a dishwasher comprises the filter screen  1  and a water tank under the filter screen  1 . The filter screen  1  is an integrally formed plastic filter screen. The filter screen  1  includes several first filter ribs  13  and several second filter ribs  14 , and the second filter ribs  14  and the first filter ribs  13  are arranged to cross each other so as to form a mesh structure. 
     Specifically, the water tank has a water inlet and a water outlet connected from up to down, and the filter screen  1  is arranged above the water inlet of the water tank. The filter screen  1  is an annular structure, and the filter  3  is installed in the inner ring  12 . The filter screen  1  is an integrally formed plastic filter screen, saving cost compared to metal filter screen. And the plastic filter screen can be integrally formed so that post-perforation is not require, which saves the forming cost. The filter screen  1  includes a mesh structure formed by the second filter ribs  14  and the first filter ribs  13  arranged to cross each other, the second filter ribs  14  and the first filter ribs  13  enhance the strength of the filter screen and the mesh structure avoids being blocked by washing impurities like the filter pores of the metal filter screen. Preferably, the second filter ribs  14  are arranged to cross the first filter ribs  13  and under the first filter ribs  13  so as to form the mesh structure. The first filter ribs  13  and the second filter ribs  14  are arranged to cross each other in two layers, which further enhances the strength of the filter screen  1  and prevents the filter screen  1  from being damaged. Also, two-layer crossed mesh structure has a larger effective filter area than metal filter screen with filter pores. And the two-layer crossed mesh structure intercept and filter water flow twice, which achieves better filtering effect and will not be blocked by washing impurities. In addition, the second filter ribs  14  and the first filter ribs  13  are arranged to cross each in two layers, which makes it easier to collect residue so that the residue is easy to remove, or makes it easy for the residue to enter a filter  3 . More preferably, the second filter ribs  14  and the first filter ribs  13  are arranged to cross each other vertically and horizontally. It avoids holes  15  of the filter screen being blocked by washing impurities and makes it easier for water flow passing through. And the holes  15  formed by the first filter ribs  13  and the second filter ribs  14  arranged to cross each other vertically and horizontally are uniform in size, which avoids being partial blocked and hard to remove. 
     The filter screen  1  is a flat filter screen of a dishwasher. The flat filter screen is not limited to a flat plate-shaped filter screen, it can also be a curved filter screen or an inclined filter screen. In this disclosure, the filter screen  1  is recessed downwards from the outer ring to the inner ring  12  and forms a funnel shape so as to make it easy for water flow to gather to the filter  3  at the inner ring and enter the filter  3  to be filtered. 
     Embodiment 6 
     On the basis of embodiment 5, the dishwasher also includes an inner tank. A bottom of the inner tank recessed downwards to form a groove  21 , and the filter screen  1  is installed in the groove  21 . The groove  21  is provided with an opening, and the water inlet of the water tank is connected with the groove  21  through the opening. The filter screen  1  is an annular structure, and the filter screen  1  is recessed from the outer ring  11  to the inner ring  12  and forms a funnel shape. Preferably, a side wall of the groove extends obliquely, and a side of an outer ring of the filter screen extends obliquely and is coordinated with the side wall of the groove. The side wall of the groove and the side of the outer ring have high compactness, resulting a small distance between the groove  21  and the outer ring of the filter screen, which further filters out washing impurities and prevents washing impurities from enter a space between the groove  21  and the outer ring  11  of the filter screen. Generally, the side wall of the groove  21  extends obliquely and the outer ring of the filter screen extends vertically. A distance between an upper end of the side wall of the groove  21  and the outer ring of the filter screen is larger than a lower end of the side wall of the groove  21  and the outer ring of the filter screen, so that a sealing part is required to seal the outer ring of the filter screen and the groove  21 . In contrast, according to the disclosure herein, the side of the outer ring  11  of the filter screen coordinates with the side wall of the groove  21  to extend obliquely. The side of the outer ring and the side wall of the groove are arranged similar in profile so as to achieve a high compactness. More preferably, the side wall of the groove  21  extends obliquely and downwards from the bottom of the inner tank  2  to a center of the groove  21  so as to make forming easy and make installation and disassembling convenient. 
     Embodiment 7 
     On the basis of above embodiments, a bottom of the outer ring  11  of the filter screen in this embodiment is in line contact with the bottom of the groove  21  of the inner tank, making coordination of the two more stable. It prevents large contact range when the two are in surface contact which results in large coordination range and then results in unstable installation. A bottom surface of the outer ring  11  of the filter screen, which is in contact with the groove  21  of the inner tank, is an arc surface protruding towards the groove of the inner tank. The arc surface is in line contact with the bottom of the groove  21  of the inner tank, making coordination of the two more stable and preventing unstable installation if the two were in surface contact. There are no sharp edges on the arc surface so as to prevent the groove  21  of the inner tank from being scratching by the sharp edges, avoiding scratching the groove  21  of the inner tank. 
     Embodiment 8 
     On the basis of above embodiments, in this embodiment, several outlets for water flow passing are provided between a bottom of the outer ring  11  of the filter screen and a bottom of the groove  21  of the inner tank, avoiding accumulation of water flow that enters from the space between a side of the outer ring  11  of the filter screen and a side of the groove  21 . Preferably, the bottom of the outer ring  11  of the filter screen comprises several interval arranged bulges  111 , and the recess between two adjacent bulges  111  forms the outlets for water flow passing. The interval arranged bulges  111  form a sawtooth shape, making the outflow of water flow easy and avoiding water flow accumulating between the groove  21  of the inner tank and the filter screen  1 . More preferably, an end surface of the bulge  111 , which is coordinated with the bottom of the groove  21  of the inner tank, is an arc surface protruding towards the bottom of groove of the inner tank. The arc surface is in line contact with the bottom of the groove  21  of the inner tank, making coordination of the two more stable and preventing unstable installation if the two were in surface contact. There are no sharp edges on the arc surface so as to prevent the groove  21  of the inner tank from being scratching by the sharp edges, avoiding scratching the groove  21  of the inner tank. 
     The above description is just used to illustrate some more practical embodiments of the disclosure but is not the limitation of the disclosure in any way. Although the disclosure has been enclosed as the above embodiments, they are not used to limit the disclosure. Within the technical scheme of the disclosure, any person skilled in the art should be able to make some changes or modifications based on the above techniques to obtain other embodiments with equal benefits. But any simple changes, equivalent changes or modifications, made to the above embodiments according to the technical substance within the technical scheme of the disclosure, still belong to the protection range of the disclosure.