Method for controlling a washing machine

Abstract

A washing machine is constructed with a special control unit and a conductance sensor in a washing liquid container for detecting a water level including whether there the water is above or below a given water level, and the presence of foam during a washing cycle. The control unit controls the operation of a pump, as well as the addition of fresh water, for eliminating excessive foam in the washing liquid container and in the drum. It is also possible to stop the pump from discharging this disturbing foam.

1 . A method for controlling operation of a washing machine, said washing machine having a control unit, a washing liquid container and a conductance sensor being located in a lower area of said washing liquid container, comprising the steps of:
 using a conductance sensor to measure a water level in said washing liquid container;   determining, by said control unit, said water level is lower than a position of said conductance sensor; and   stopping a pump pumping out the water in said washing liquid container.   
   
   
       2 . The method according to  claim 1 , wherein said pump is provided for said emptying of said washing liquid container and said stopping of said pump takes place within a few seconds delay after the water level has been detected to be lower than said position of said conductance sensor. 
   
   
       3 . The method according to  claim 2 , wherein said delay results in a water level further below said position of said conductance sensor without resulting in an intake of air in said pump. 
   
   
       4 . A method for controlling operation of a washing machine, said washing machine having a control unit, a washing liquid container and a conductance sensor being located in a lower area of said washing liquid container, comprising the steps of:
 determining a water level in said washing liquid container using said control unit;   determining using said control unit during a washing process that said sensor is surrounded by foam; and   adding fresh water into said washing liquid container for diluting said foam.   
   
   
       5 . The method according to  claim 4 , wherein sufficient fresh water is added to ensure that during said washing process or a rotation of said drum said conductance sensor is essentially surrounded by water. 
   
   
       6 . A method for controlling operation of a washing machine, said washing machine having a control unit, a washing liquid container and a conductance sensor located in a lower area of said washing liquid container comprising the steps of:
 measuring values of said conductance sensor by said control unit;   determining a surface tension of water in said washing liquid container by a detection of an ionic concentration of said water;   determining whether said surface tension exceeds a threshold limit associated with the ending of said washing cycle; and   determining a rinsing process based on said surface tension.   
   
   
       7 . A method for controlling operation of a washing machine, said washing machine having a control unit, a washing liquid container and a conductance sensor being located in a lower area of said washing liquid container, comprising the steps of:
 determining a value measured by said conductance sensor by said control unit; and   adjusting a drying speed so that said conductance sensor is surrounded by water.   
   
   
       8 . The method according to  claim 7 , further comprising:
 using a pump controlled by said control unit for emptying said water in said washing liquid container, wherein said pump runs continuously during said spin drying process.   
   
   
       9 . The method according to  claim 7 , wherein said spin drying speed is increased after a period of time when said conductance sensor is determined to be no longer surrounded by said water. 
   
   
       10 . The method according to  claim 9 , wherein said spin drying speed is slowly increased until said conductance sensor is again essentially surrounded by water. 
   
   
       11 . The method according to  claim 9 , wherein said period of time is a few minutes. 
   
   
       12 . The method according to  claim 11 , wherein said value measured by said conductance sensor is used by said control unit to control said pumping operation. 
   
   
       13 . The method according to  claim 12 , wherein on reaching a maximum of said spin drying speed said pump is switched off when said conductance sensor is no longer surrounded by said water and is switched on again when said conductance sensor is surrounded by said water. 
   
   
       14 . The method according to  claim 13 , wherein between a change of function at said conductance sensor and a switching on or off of said pump there is a time interval of a few seconds. 
   
   
       15 . A method for controlling operation of a washing machine, said washing machine having a control unit, a washing liquid container and a conductance sensor being located in a lower area of said washing liquid container, comprising the steps of:
 detecting a measured value of said conductance sensor;   providing said measured value to said control unit; and   determining by said control unit whether said conductance sensor is surrounded by water, foam, or air, whereupon detection of said foam a drying speed of said drum is reduced as a countermeasure for reduction of said foam.   
   
   
       16 . The method according to  claim 15 , further comprising the step of:
 establishing by said control unit using said conductance sensor whether said foam has already been adequately reduced or no longer surrounds said conductance sensor, wherein if said conductance sensor is not surrounded or has been adequately reduced, said drum is stopped.   
   
   
       17 . The method according to  claim 16 , comprising the further step of:
 detecting foam after said stopping of said drum;   waiting for a time of a few minutes; and   introducing fresh water into said drum for rinsing away said foam.   
   
   
       18 . A method for controlling operation of a washing machine, said washing machine having a control unit, a rotating drum controlled by said control unit, a washing liquid container and a conductance sensor being located in a lower area of said washing liquid container, comprising the steps of:
 interrupting a washing or rinsing process at a first time period of said washing machine wherein rotation of said drum is stopped;   measuring a first value of said conductance sensor when said drum is not rotating and supplying said first value to said control unit;   resuming said washing or rinsing process of said washing machine wherein said drum is rotating;   interrupting said washing or rinsing process at a second time period wherein said drum of said washing machine is stopped; and   measuring a second value of said conductance sensor when said drum is not rotating and supplying said second value to said control unit.