Patent Publication Number: US-8978186-B2

Title: Self-contained and wireless device for a washing machine

Description:
The invention relates to a monitoring device for use in a washing machine and a method to indicate shortage of detergent in said washing machine. 
     Advanced industrial dishwashers are nowadays equipped with automatic dosing systems to monitor the available detergent for the washing process and to refill detergent if required. These automatic dosing systems employ conductivity sensors to monitor the detergent concentration in washing liquid of said dishwashing machine. Such a system is disclosed in JP9-024016. 
     Another approach is disclosed in WO 01/07702, wherein a monitoring device for monitoring a washing process inside a washing apparatus comprises means for measuring physical and/or mechanical parameters of the washing process and means for recording the measured parameters. After the washing process is finished, the parameters are extracted from the monitoring device using an external device. The monitoring device can be positioned loosely inside the washing apparatus, e.g. on top of a conveyor belt of an industrial dish washer, and, as a result, may be used in a standard washing apparatus without the need of modifications. 
     It is an object of the present invention to provide a less complex and inexpensive monitoring device. Such a monitoring device is especially suitable for small dishwashing machines for which it is often not viable to install an automatic dosing system employing a conductivity sensor. Operators of these dishwashing machines who manually dose detergents often only estimate when to refill detergent, which is inefficient as this results in spillage or bad cleaning and may further result in calcification of machine components. 
     In an aspect of the invention, this object is accomplished by a self-contained and wireless monitoring device for use in a washing machine to indicate shortage of detergent in said washing machine, said monitoring device comprising a sensor arranged to monitor detergent concentration in washing liquid of said washing machine and to provide an alarm signal when said monitored detergent concentration is below a target value, wherein said monitoring device is capable of floating in said washing liquid and comprises signalling means for indicating said shortage of detergent in response to said alarm signal. 
     In another aspect of the invention, a method is disclosed for indicating shortage of detergent in a washing machine by a monitoring device capable of floating in washing liquid of said washing machine and comprising signalling means to indicate shortage of detergent for said washing machine, comprising the steps of:
         providing said monitoring device into said washing liquid of said washing machine, and   inspecting said signalling means in a floating state of said monitoring device to determine whether refilling of detergent is required.       

     The self-contained and wireless monitoring device is easily provided in any type of washing machine, whereas the floating character of the monitoring device allows easy inspection of the signalling means to verify whether refill of detergent is required. It is noted that the self-contained nature of the monitoring device implies that the monitoring device has an internal energy source, such as a (rechargeable) battery, a biobattery using e.g. enzymes or a galvanic element wherein e.g. two different metals are exposed to the washing liquid to charge a capacitor for powering the monitoring device. It should be appreciated that, although the monitoring device is preferrably for use in (small) dishwashing machines, other washing machines including laundry washing machines or bottle washing machines may use the monitoring device of the invention. 
     Further aspects and embodiments of the invention are defined in the dependent claims and will be elucidated in the detailed specification. 
    
    
     
       The invention will be further illustrated with reference to the attached drawings, which schematically show preferred embodiments according to the invention. It will be understood that the invention is not in any way restricted to these specific and preferred embodiments. 
       In the drawings: 
         FIG. 1  schematically illustrates a dishwashing machine provided with a monitoring device according to an embodiment of the invention; 
         FIG. 2  schematically illustrates a sensor according to an embodiment of the invention; 
         FIGS. 3A-3C  show cross-sections of a monitoring device according to an embodiment of the invention, and 
         FIGS. 4A-4C  show representation for an alternative body for the sensor of  FIG. 2 . 
     
    
    
       FIG. 1  schematically shows a dish washing machine  1  comprising a plurality of nozzles  2 ,  3  to clean dishes  4  by washing liquid  5  containing detergent. The washing liquid  5  is present in a tub  6 . The washing liquid  5  is circulated by a pump (not shown) from the tub  6  to nozzles  3  and subsequently over the dishes  4 . Clean rinsing water can be provided from the nozzles  2 . The dishes  4  are typically rinsed after each washing cycle with clean water which dilutes the washing liquid  5 . 
     A monitoring device  10  according to an embodiment of the invention is capable of floating in the washing liquid  5 . It is noted that washing liquid  5  typically remains within the tub  6  after completion of a washing cycle for several cycles. The monitoring device  10  comprises signalling means  11  to indicate shortage of detergent in the washing liquid  5  for the dishwashing machine  1 . Accordingly, the monitoring device  10  can be provided into the tub  6  before a washing cycle, simply by disposing it in the washing liquid  5 . After completion of the washing cycle, the signalling means  11  can be inspected, facilitated by the floating nature of the monitoring device  10 , to verify whether the washing liquid  5  still contains sufficient detergent. The monitoring device  10  is balanced to have said signalling means  11  in a substantially upright position in a floating state. 
     Preferably, the signalling means  11  comprises a lamp, e.g. a high power light emitting diode (LED). The light of the LED  11  may flash in order to allow easy inspection. Still further, the light of the LED  11  may change colour in case of shortage of detergent. For example, the LED  11  may provide a green flashing light if sufficient detergent is detected, whereas a red flashing light is emitted in case of shortage of detergent. In another example, no light is emitted when sufficient detergent is detected, whereas a red flashing light is emitted when is detergent deficit is detected. Alternatively or in addition, the signalling means  11  may provide audible signals, such as beeps. The frequency and/or loudness level of said beeps may vary. 
     In a more advanced embodiment, the signalling means  11  may wirelessly transmit a signal to a distant receiver  12 , indicated by the arrow W. The distant receiver may be integrated within the dishwashing machine  1  or be a separate unit as shown in  FIG. 1 . Alternatively, the distant receiver  12  may receive data via a unit (not shown) in the dishwashing machine  1  that communicates with the monitoring device  10 . In that case, the dishwashing machine  1  should be capable of performing such a function. 
     In order to monitor the detergent concentration in the washing liquid  5  to indicate the shortage of detergent, the monitoring device  10  employs a sensor  13  as shown in  FIG. 2 . The sensor  13  comprises a plurality of components and tracks provided on a circuit board  14 , including electrodes  15 , processing circuitry  16 , an internal battery  17  and, optionally, data storage means  18  and a temperature sensor  19 . Although hereinafter an electrical sensor will be described, the sensor may, in an embodiment of the invention, pertain to e.g. a chemical sensor for monitoring the detergent concentration in the washing liquid  5 . 
     The use of the circuit board  14  enables the sensor  13  to be executed as a micro device, i.e. a dedicated micro conductivity sensor. The dimensions of the circuit board  14  may preferably be in the range between 10 and 50 mm in both directions, such as 20×20 mm. 
     The electrodes  15  are arranged such that these may be exposed to the washing liquid  5  in order to monitor the detergent concentration. The electrodes  15  are provided on different positions on the circuit board  14  separated by a cut-out of said board  14 . The electrodes  15  may be flat plates accommodated in etched recess of the circuit board  14 . However, it should be appreciated that the electrodes  15  may have an alternative shape, including e.g. rods. To avoid monitoring inaccuracies by corrosion of the submerged electrodes  15 , these are provided with a coating comprising e.g. carbon, gold, tin or an alloy thereof. 
     The processing circuitry  16  may include various electrical components, such a resistors, capacitors and one or more integrated circuits suitably connected via wires or printed circuit tracks on said circuit board  14 . In the pre-sent embodiment, the function of these components is to measure the conductivity of the washing liquid  5  in order to determine the detergent concentration. It should be appreciated that these functions can be implemented on the circuit board  14  in various manners known per se. WO 02/086481 provides an example of how the measurement of the conductivity of the washing liquid  5  may be performed. 
     It is further noted that the conductivity of the washing liquid  5  may depend on the temperature of the washing liquid  5 . In order to avoid monitoring inaccuracies, the processing circuitry  16  preferably corrects for temperature effects, e.g. by determining the temperature of the washing liquid  5 . The temperature of the washing liquid can be measured by a temperature sensor  19 . The temperature sensor  19  may be fully accommodated within the body of the monitoring device  10 . If a quick measurement is required, the temperature sensor  19  preferably has measuring portions (not shown) directly exposed to the washing liquid  5 . 
     As the monitoring device  10  is a self-contained device, the sensor  13  has an internal energy source  17  in order to perform the monitoring function. A (rechargeable) battery may be used as well as a biobattery using e.g. enzymes or a galvanic element wherein e.g. two different metals are exposed to the washing liquid  5  to charge a capacitor for powering the monitoring device  10 . Consequently, the monitoring device  10  can be applied without the need to modify the dishwashing machine  1 . 
     The monitoring device  10  may comprise data storage means  18 . These data storage means may e.g. comprise a lookup table with correction values to correct for temperature effects on the conductivity vs. detergent concentration relationship. Further, the measured conductivity values and other data may be stored to enable subsequent analysis by reading stored data. The type of detergent used in the washing liquid  5  may also determine operation of the monitoring device  10 . The data storage means  18  allow programming of the monitoring device  10  for its intended purpose. 
     In operation, the electrodes  15  of the sensor  13  are submerged in the washing liquid  5 . The temperature sensor  19  measures the temperature of the washing liquid  5  and provides this information to the processing circuitry  16 . The processing circuitry  16  measures or derives the conductivity [and temperature] of the washing liquid  5  in a manner known per se in order to establish the detergent concentration. The established detergent concentration is compared with a target value preferably employing a correction value related to the measured temperature. This target value relates to the typically sufficient detergent concentration in the washing liquid  5 . A safety margin may be applied. In case the detergent concentration is below the target value, the processing circuitry  16  triggers an alarm signal A for the LED  11 . The LED  11  may flash in a particular colour as described above. Alternatively or in addition, the monitoring results may be stored in the storage means  18 . 
     The monitoring device  10  is further arranged to switch off when no washing liquid  5  is present between the electrodes  15 , i.e. the conductivity is low and the sensor  13  is in a sleeping mode. The alarm signal A is interrupted. Consequently, signalling by the signalling means  11  is avoided and the internal battery  17  is saved. As mentioned above, interruption of the alarm signal may also be performed when the monitored conductivity indicates the presence of sufficient detergent, such that no signals are emitted from the signalling means  11  in this case. 
     It is clear that the environmental conditions within the dishwashing machine  1  are harsh and the sensor  13  is to be protected against this environment. The monitoring device  10  may be waterproof, robust and chemically resistant against the detergent and other washing aids to allow the sensor  13  to function properly for a reasonable period of time. 
     In one embodiment, the sensor  13  may be partly embedded in a body of a material with a specific weight or gravity allowing the monitoring device  10  to float in the washing liquid  5 . Such a material may e.g. be a resin. The electrodes  15  and LED  11  protrude through the resin body to respectively allow conductivity measurements and inspection. The body should preferably be chemically resistant in an environment with pH&gt;12. 
       FIGS. 3A-3C  display an embodiment of a monitoring device  10  accommodated within a body  20 . 
     As can be observed from  FIG. 3A , the body  20  comprises shaped portions to form a receiving space  21  for the sensor  13 . Sidewalls  22  of the receiving space  21  widen on the side for the electrodes  15  of the sensor  13  to provide a larger volume at this location. The circuit board  14  is inserted in the receiving space  21  and the portions of the body  20  are welded to constitute air chambers  23 , making the monitoring device  10  capable of floating. The welds are preferably able to be substantially leakproof in a temperature range between 15-90° C. The receiving space  21  is filled with a filler material  24  to embed the sensor  13  partially, leaving the LED  11  and electrodes  15  free. The vulnerable parts of the sensor  13  are consequently protected from the harsh conditions within the dishwashing machine  1 . 
     The filler material  24  preferably is a resin. The resin  24  protects the vulnerable portions of the sensor  13  while it may simultaneously glue the portions of the body  20  to each other to form the monitoring device  10 . The density of the resin is preferably low, such as 0.7 g/ml, to facilitate floating of the monitoring device  10 . The resin  24  may e.g. comprise polyurethane, epoxy resin or silicone. 
     The widening sidewalls  22  ensure that the largest amount of filler material  24  is located near the electrodes  15 . Consequently, the centre of gravity is located near this position, such that the floating monitoring device  10  is always in an upright position, i.e. the LED  11  is above the surface of the washing liquid  5  (see  FIG. 1 ). 
     The body  20  is preferably made of plastic, such as polyethylene or polypropylene. The body  20  may have a spherical shape. The diameter of the body  20  may be in the range of 20-120 mm, preferably in the range of 40-90 mm, such as 60 mm. Preferably, the dimensions of the body  20  should be such that the monitoring device  10  is not washed with the washing liquid through the drain of the dish washing machine  1 . 
       FIGS. 4A-4C  show representations for an advantageous and preferred body  30  for the sensor of  FIG. 2 . It is noted that the sensor  13  is not shown in  FIGS. 4A-4C .  FIG. 4A  shows a three-dimensional representation of the body  30 , whereas  FIGS. 4B and 4C  show a side view and a bottom view respectively. 
     The body  30  comprises a receiving space  31  covered by a plate  32  with openings  33 . Further, the body  30  has wings  34  that are positioned at angles of 120° in the present embodiment. The plate further has an opening  35  located in the centre. The body  30  has a full height in the ranges of 50-60 mm, e.g. 56 mm, whereas the outer points of the wings  34  define a virtual circle with a diameter in the range of 80-100 mm, e.g. 85 mm. 
     The sensor  13  can be introduced from the bottom side of the body  30  into the receiving space  31 . The inner surface of the plate  32  may function as a stop while inserting the signalling means  11 , such as the LED, through the opening  35 . The dimensions of the circuit board  14  may be such that in this position, the electrodes  15  protrude from the receiving space  31 , such that they may be fully exposed to the washing liquid  5 . In order to isolate the rest of the sensor  13  from the washing liquid, the receiving space is filled with a filler material (not shown) such as the resin mentioned previously. 
     The body  30  in combination with the filler material in the receiving space  31  is dimensioned such that the LED  11  is in a substantially upright position in a floating state allowing easy inspection. 
     The openings  33  reduce fluid dragging of the monitoring device  10  by turbulent water during operation of the washing machine  1 . The wings  34  prevent the body  30  to block the drain or pump inlet of the washing machine  1  by their shape and/or dimensions. The openings  33  assist in passing of water when the body  30  is in front of a drain or pump inlet. Finally, the wings  34  have a curvature, such that in a non-floating state, the body  30  rests on the wings  34  with the electrodes  15  lifted from the bottom of the washing machine  1 . Accordingly, some remaining washing liquid  5 , e.g. in dents of the bottom, would not force the monitoring device  10  to continue functioning. 
     The monitoring device  10  is a simple, small and low cost device enabling said device to be included in a detergent package.