Patent Publication Number: US-2005126634-A1

Title: Water level indicating device for a dishwasher

Description:
FIELD OF THE INVENTION  
      The present invention refers to a water level indicating device for a dishwasher, particularly to be applied in small and medium size dishwashers.  
     PRIOR ART  
      Dishwashers have a cabinet, which is usually parallelepipedic and closed by a vertical door, and inside which is mounted a washer tub designed to receive a determined quantity and type of dishes to be cleaned. For the washing operation, after closing the door and starting the washing operation, the washer tub is filled with water, up to a certain predetermined filling level, which, when achieved, is informed to a control unit that commands the interruption of water supply to the dishwasher.  
      The small and medium size dishwashers present, mounted inside the cabinet and adjacent and external to the washer tub, a level sensor in fluid communication with said washer tub through a duct arranged in a vessel communicating system. In the known constructions, the level sensor is mounted to a float provided inside a level duct in fluid communication with the washer tub and which is disposed substantially vertical, parallel and adjacent to a rear wall of said washer tub, said level duct having a lower end opened to a lower portion of the washer tub, in order to receive the filling water for the latter, and a vented upper end, through which is mounted the float with the level sensor.  
      In these constructions, the level sensor informs the control unit when a predetermined water level has been achieved inside the washer tub, allowing said control unit to start the washing operation. In such constructions, the level sensor may also, for example, inform the control unit about a minimum water level, indicating that either the washer tub has been drained, or, in a filling condition, that the minimum water level has not been achieved to allow the washing operation to start.  
      In these dishwashers, the grease of the dishes contained in the washing water inside the washer tub also reaches the level duct where the level sensor is located, impregnating in these elements and gradually interfering with the adequate operation of the level sensor, or even causing operational defects in the float that carries said level sensor.  
     SUMMARY OF THE INVENTION  
      Thus, it is an object of the present invention to provide a water level indicating device for a dishwasher, which minimizes the contact of the level sensor with the impurities existing in the washing liquid, particularly grease, thus preventing the inadequate operation of the float that carries said level sensor and consequently of said level sensor and said dishwasher.  
      A more specific object of the present invention is to provide a water level indicating device, such as that mentioned above which, in case of failure of its level sensor, prevents the dishwasher from working when the latter does not present effective operational conditions, for example, due to insufficient water therein.  
      These and other objectives are achieved by a water level indicating device for a dishwasher having a cabinet, inside which is provided a washer tub, and presenting a control unit, which determines the operational conditions of providing or interrupting the water supply to the inside of the washer tub, said device comprising: a first chamber, in fluid communication with the washer tub; a second chamber, having a lower portion maintained in fluid communication with a lower portion of the first chamber; and a level sensor, which is operatively associated with both the second chamber and the control unit, in order to inform said control unit about a water level detected inside said second chamber and corresponding to a desired filling level of the washer tub. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
      The following invention will be described below, with reference to the attached drawings, in which:  
       FIG. 1  illustrates a longitudinal sectional view of an embodiment of the water level indicating device for a dishwasher of the present invention, to be mounted inside the cabinet of the dishwasher, externally to the washer tub thereof and carrying two floats therewithin;  
       FIG. 2  is an upper view of the embodiment for the water level indicating device illustrated in  FIG. 1 , without the cover upper portion of said device;  
       FIG. 3  is a perspective view of the device of  FIG. 2 ;  
       FIG. 4  is a perspective view of a chamber divider of the device of the present invention;  
       FIG. 5  is a perspective view of the cover of the present device; and  
       FIGS. 6 and 7  illustrate a perspective view of each float with the respective level sensor of the device of the present invention. 
    
    
     DESCRIPTION OF THE ILLUSTRATED EMBODIMENT  
      The present invention will be described in relation to a small or medium size dishwasher of the type comprising, inside a non-illustrated cabinet, a washer tub  1 , which receives the dishes to be cleaned, and external and adjacent to said washer tub, and inside the cabinet, the water level device of the present invention.  
      The dishwasher further comprises a control unit, not illustrated, which determines the operational conditions for providing and interrupting the water supply to the inside of the washer tub  1 , based on the information received from a level sensor  2 , provided inside the present device, as described below and which indicates when the filling water of the dishwasher achieves a determined level in said water level indicating device corresponding to a certain water level within the washer tub  1 . Upon receiving this information from the level sensor  2 , the control unit commands the interruption of water supply to the washer tub  1  and the start of the washing operation. In a possible option, the level sensor  2  further informs the control unit when the water inside the device of the present invention achieves a minimum water level, indicating the washer tub  1  has been drained and that it may thus be refilled.  
      According to the present invention, the water level indicating device of the present invention comprises a first chamber  10  in fluid communication with the washer tub  1 , and a second chamber  20 , having a lower portion  21  maintained in fluid communication with a lower portion  11  of the first chamber  10  and to which are operatively associated the level sensor  2  and the control unit, so that the level sensor  2  detects and informs said control unit about at least one water level, which is previously defined and achieved by the water being supplied to the inside of said second chamber  20  corresponding to a respective and desired filling level of the washer tub  1 .  
      The level sensor  2  is displaceable inside the second chamber  20  between a first position and a second position, which are axially spaced form each other and respectively correspond to the conditions of presence of water inside the second chamber  20 , below and on a certain predetermined filling level of said second chamber  20 .  
      In the illustrated constructive option, the water level indicating device comprises a hollow body  40 , inside which are defined at least two, for example three chambers  10 ,  20 ,  30 , in fluid communication with each other and with the washer tub  1 , as described below, said hollow body  40  presenting a first end  41   a , opened to the washer tub  1  and providing fluid communication with the latter and with the first chamber  10 , and a second end  41   b , vented to the atmosphere and whereto is mounted the level sensor  2 . In the illustrated constructive option, the hollow body  40  is coupled to the washer tub  1  through its first end  41   a  and receives, through its second end  41   b , a first float  50 , which is displaceable inside the second chamber  20  and carries the level sensor  2 , and, through a third end  41   c , a second float  60  actuating inside the third chamber  30 , and a safety sensor  70  associated with said second float  60 . The safety sensor  70  is provided inside the third chamber  30  in a vertical higher position than that of the level sensor  2  in its position corresponding to a maximum filling condition of the washer tub  1 , so as to inform the control unit that a maximum filling limit of the washer tub  1  has been achieved.  
      Each float is made of plastic material, for example. The first float  50  carries a magnetic element, such as a magnet, which allows its movement in the respective chamber.  
      In the illustrated construction, the hollow body  40  is closed by a cover  43  carrying both the level sensor  2  and the safety sensor  70  and which is affixed to the hollow body  40 , closing the latter by fitting each of a plurality of ears  44  provided in a lower skirt portion of said cover  43 , into a corresponding tooth  45  provided in an upper portion of the hollow body  40 . In this construction, the cover  43  presents, from an external face thereof, first and second vented tubular projections  46 ,  47 , said first tubular projection  46  lodging the first float  50  and the level sensor  2  and said second tubular projection  47  lodging the safety sensor  70  and the second float  60 .  
      The first float  50  presents a buoy portion  51  and a rod portion  52  projecting from said buoy portion  51  and provided with grooves  53 , for example orthogonal to each other, a free end of said rod portion  52  presenting a magnet  54  and said second float  60  comprising a respective buoy  61  and an arm  62  projecting from an upper end edge of the respective buoy  61  and presenting, for example, a curved shape, particularly spacing away from said buoy  61 , said arm  62  being articulated by an end  63  to a portion of the second tubular projection  47 .  
      The first tubular projection  46  presents, internally along its length, at least one pair of longitudinal guides  48 , which are for example, continuous and opposite to each other, and which will receive respective grooves  53  of the rod portion of the first float  50 , in order to avoid that, when water is supplied to and drained from said chamber  20 , said first float  50  presents other movements than the vertical displacement to and from said first tubular projection  46 .  
      The safety sensor  70  is mounted to the vented portion of the second tubular projection  47  of the cover  43  and is actuated by a switch, whose operation is defined as a function of the movement of the second float  60  inside the third chamber  30 .  
      According to the illustrated constructive option, the hollow body  40  of the water level indicating device  10  of the present invention carries a divider  80 , for example in a single piece mounted inside said hollow body  40 , in order to define therein the first, the second and the third chambers  10 ,  20  and  30 , said first chamber  10  being positioned between the other chambers and having its lower portion opened to the first end  41   a  of the hollow body  40 . As a function of the construction of the divider  80 , the latter defines, for each chamber of the hollow body  40 , a respective lower opening on the same level inside the hollow body  40 .  
      The hollow body  40  presents, internally, in a lower portion of each lateral wall, internal projections  40   a , which define guides for the introduction and fixation of the divider  80 . In the illustrated construction, each lateral wall includes three internal projections  40   a , one of each being vertically longer and determining the support for the portion of the divider  80  that defines the third chamber  30 .  
      The hollow body  40  presents a bottom wall with a “V” profile, in order to allow water to be drained when said hollow body  40  is emptied. In the vertex region of said “V” profile is provided a lateral nozzle  49  located in the hollow body  40  and which is opened to the first end  41   a , for example being tooted and receiving a sealing ring, not illustrated, for mounting the present device to the washer tub  1 .  
      The divider  80  presents a flat central structure, from which upper contour project, to each side of said structure, flanges  81  provided with holes  82 , each hole for receiving a fitting end of an internal projection  40   a  provided in an internal lateral wall of the hollow body  40 .  
      In a way of carrying out the present invention, the level sensor  2  is a magnetic sensor and the safety sensor  70  is an electrical switch, said sensors being provided in order to, respectively, detect a minimum water level and a maximum water level in the dishwasher, and each sensor being mounted on a respective printed circuit board provided in the cover  43  of the hollow body  40  of the present device.  
      The safety sensor  70  operates independently of the level sensor  2 , preventing the water from flowing out of the dishwasher in case the level sensor  2  fails to detect the water level. After receiving the information from said safety sensor  70  that the water level has reached a predetermined maximum value and, therefore, indicating the operation of the level sensor  2  has failed, the control unit commands the deenergization of a water inlet valve and the energization of a drainage pump, for promoting the partial or total emptying of the washer tub  1 . In the illustrated construction, the water supply and water discharge in the hollow body  40  is made through the same opening, represented by the first end  41   a  of said hollow body  40 .  
      The device of the present invention minimizes reading errors of the water levels and reduces risks of water overflowing from said washer tub  1 .