Classifications

• • A—HUMAN NECESSITIES
  • A47—FURNITURE; DOMESTIC ARTICLES OR APPLIANCES; COFFEE MILLS; SPICE MILLS; SUCTION CLEANERS IN GENERAL
  • A47L—DOMESTIC WASHING OR CLEANING; SUCTION CLEANERS IN GENERAL
  • A47L15/00—Washing or rinsing machines for crockery or tableware
  • A47L15/0018—Controlling processes, i.e. processes to control the operation of the machine characterised by the purpose or target of the control
  • A47L15/0049—Detection or prevention of malfunction, including accident prevention
• • A—HUMAN NECESSITIES
  • A47—FURNITURE; DOMESTIC ARTICLES OR APPLIANCES; COFFEE MILLS; SPICE MILLS; SUCTION CLEANERS IN GENERAL
  • A47L—DOMESTIC WASHING OR CLEANING; SUCTION CLEANERS IN GENERAL
  • A47L15/00—Washing or rinsing machines for crockery or tableware
  • A47L15/14—Washing or rinsing machines for crockery or tableware with stationary crockery baskets and spraying devices within the cleaning chamber
  • A47L15/18—Washing or rinsing machines for crockery or tableware with stationary crockery baskets and spraying devices within the cleaning chamber with movably-mounted spraying devices
  • A47L15/22—Rotary spraying devices
  • A47L15/23—Rotary spraying devices moved by means of the sprays
• • A—HUMAN NECESSITIES
  • A47—FURNITURE; DOMESTIC ARTICLES OR APPLIANCES; COFFEE MILLS; SPICE MILLS; SUCTION CLEANERS IN GENERAL
  • A47L—DOMESTIC WASHING OR CLEANING; SUCTION CLEANERS IN GENERAL
  • A47L15/00—Washing or rinsing machines for crockery or tableware
  • A47L15/42—Details
  • A47L15/4246—Details of the tub
• • A—HUMAN NECESSITIES
  • A47—FURNITURE; DOMESTIC ARTICLES OR APPLIANCES; COFFEE MILLS; SPICE MILLS; SUCTION CLEANERS IN GENERAL
  • A47L—DOMESTIC WASHING OR CLEANING; SUCTION CLEANERS IN GENERAL
  • A47L2401/00—Automatic detection in controlling methods of washing or rinsing machines for crockery or tableware, e.g. information provided by sensors entered into controlling devices
  • A47L2401/24—Spray arms status, e.g. detection of spray arm rotation
• • A—HUMAN NECESSITIES
  • A47—FURNITURE; DOMESTIC ARTICLES OR APPLIANCES; COFFEE MILLS; SPICE MILLS; SUCTION CLEANERS IN GENERAL
  • A47L—DOMESTIC WASHING OR CLEANING; SUCTION CLEANERS IN GENERAL
  • A47L2401/00—Automatic detection in controlling methods of washing or rinsing machines for crockery or tableware, e.g. information provided by sensors entered into controlling devices
  • A47L2401/30—Variation of electrical, magnetical or optical quantities
• • A—HUMAN NECESSITIES
  • A47—FURNITURE; DOMESTIC ARTICLES OR APPLIANCES; COFFEE MILLS; SPICE MILLS; SUCTION CLEANERS IN GENERAL
  • A47L—DOMESTIC WASHING OR CLEANING; SUCTION CLEANERS IN GENERAL
  • A47L2401/00—Automatic detection in controlling methods of washing or rinsing machines for crockery or tableware, e.g. information provided by sensors entered into controlling devices
  • A47L2401/32—Vibration or sound detection
• • A—HUMAN NECESSITIES
  • A47—FURNITURE; DOMESTIC ARTICLES OR APPLIANCES; COFFEE MILLS; SPICE MILLS; SUCTION CLEANERS IN GENERAL
  • A47L—DOMESTIC WASHING OR CLEANING; SUCTION CLEANERS IN GENERAL
  • A47L2501/00—Output in controlling method of washing or rinsing machines for crockery or tableware, i.e. quantities or components controlled, or actions performed by the controlling device executing the controlling method
  • A47L2501/22—Loading doors, e.g. door latches, inflatable door seals
• • A—HUMAN NECESSITIES
  • A47—FURNITURE; DOMESTIC ARTICLES OR APPLIANCES; COFFEE MILLS; SPICE MILLS; SUCTION CLEANERS IN GENERAL
  • A47L—DOMESTIC WASHING OR CLEANING; SUCTION CLEANERS IN GENERAL
  • A47L2501/00—Output in controlling method of washing or rinsing machines for crockery or tableware, i.e. quantities or components controlled, or actions performed by the controlling device executing the controlling method
  • A47L2501/26—Indication or alarm to the controlling device or to the user
• • A—HUMAN NECESSITIES
  • A47—FURNITURE; DOMESTIC ARTICLES OR APPLIANCES; COFFEE MILLS; SPICE MILLS; SUCTION CLEANERS IN GENERAL
  • A47L—DOMESTIC WASHING OR CLEANING; SUCTION CLEANERS IN GENERAL
  • A47L2501/00—Output in controlling method of washing or rinsing machines for crockery or tableware, i.e. quantities or components controlled, or actions performed by the controlling device executing the controlling method
  • A47L2501/32—Stopping or disabling machine operation, including disconnecting the machine from a network, e.g. from an electrical power supply

Definitions

• the present invention relates to a method for detecting rotation of a dishwasher spray arm and a dishwasher adapted to perform such a method.
• DE-A-40 100 66 there is described a dishwasher in which a microphone is used to detect the sound pattern created by the water jets emitted during operation of the dishwasher and wherein a frequency spectrum analysis of the signal generated by the microphone is performed.
• a plurality of bandpass filters is provided which are designed around specific predetermined frequency bands that are characteristic for the sound pattern caused by the rotating spray arms.
• a further method for monitoring proper operation of a dishwasher is described in DE-A-102 04 455 wherein it is suggested to record typical sound patterns that are created during operation of a dishwasher and to compare such sound patterns with a plurality of previously stored typical sound patterns which are recorded in advance for various components of the dishwasher, such as the drain pump, the circulation pump, the detergent dispenser and the spray arms. By determining whether an instantaneous sound pattern can be regarded as similar to any of the pre-stored sound patterns, it thus shall be possible to conclude whether the spray arms operate properly.
• the method suggested herein makes use of the fact that for any dishwasher the rotating speed of the unblocked spray arm is a design parameter which anyway is known or can be easily determined and which thus can be used as basis to predict the number of peaks in a vibration signal detected during operation of the dishwasher.
• dishwasher spray arms usually are driven by driving nozzles that direct a water jet at an angle to the axis of rotation of the spray arm, such as radially in the plane of rotation of the spray arm, the water jet emitted by such a driving nozzle will periodically hit the walls of the washing tub of the dishwasher, where due to the impact of the water jet vibrations will be generated which can be reliably detected by a vibration sensor.
• a vibration sensor that is located to pick up a vibration signal at one of the sidewalls of the tub can be expected to pick up a corresponding number of peaks that stand out from the vibratory signal level detected during the remainder of the revolution of the spray arm. In this manner the number of revolutions of the spray arm can be reliably detected. Should the count value of detected vibration peaks within a given period of time largely differ from a predetermined standard value, it thus can be determined that the spray arm is blocked or rotates at a speed that is outside the intended range.
• the rotation of the spray arm probably is blocked at a location that is remote from the sensor, so that the sensor does not pick up the vibration signal caused by the water jet of the non-rotating spray arm.
• the spray arm is blocked in a rotary orientation where a water jet emitted from one of the driving nozzles hits the dishwasher tub at a location where the vibrations caused by the impact of the water jet are constantly or repeatedly picked up by the sensor.
• the evaluation of the count value indicates that the count value is within a predetermined range that is higher than the predetermined target range for normal operation, then it can be determined that the spray arm rotates, however, at a speed that is higher than the design speed, which can be indicative for a blockage of the water feed to a different spray arm than that for which the evaluation of the count value is performed.
• the threshold In making the determination whether the level of the detected vibrations is above a predetermined threshold, the threshold should be set at a level that provides for a high confidentiality that the picked up signal is representative for a vibration peak caused by the passing water jet, such as by selecting for such threshold a signal level which corresponds to about half the expected maximum signal level.
• the predetermined period of time within which the count value is compared with a predetermined target range should not be set too short, so as to be able to provide for a statistically relevant evaluation of the comparison.
• a dishwasher spray arm typically rotates at speeds of about 25 to 45 rpm
• setting the predetermined period of time within which the count is made to one minute usually provides for reliable results.
• longer periods could be selected.
• a warning message such as an optic or acoustic signal, can be issued to alert the user of the washing machine, so that the user can check on the proper operation of the spray arm so as to avoid the washing cycle to be carried out inefficiently. Additionally or alternatively the respective washing cycle can be automatically interrupted or terminated to be continued only after intervention by the user.
• the method can be designed such that in step (b) the count value is increased only if the level of the detected vibrations exceeds the predetermined threshold for a predetermined duration of time, so as to avoid that incidental short term signal peaks which do not correlate with the rotation of the spray arm erroneously are interpreted to be indicative for a rotation of the spray arm.
• step (b) further can comprise, upon increasing the count value, waiting for a predetermined sampling period and then further increasing the count value if the level of the detected vibrations exceeds the predetermined threshold, wherein the sampling period preferably is determined based on a target frequency of rotation of the spray arm.
• the sampling period preferably is determined based on a target frequency of rotation of the spray arm.
• the method employs a vibration sensor which provides a voltage signal
• a vibration sensor which provides a voltage signal
• such signal can be converted into a logic signal, such as by an A D converter, which in preferred embodiments can be implemented by a transistor-transistor logic (TTL) which thus converts the voltage signal into a corresponding TTL signal, which then can be further processed in a microprocessor.
• TTL transistor-transistor logic
• a root mean square (RMS) value is determined from a plurality of measurements performed in step (a), wherein the thus obtained root mean square (RMS) value then is used in step (b) as level of the detected vibrations. In this manner, reliability of the detection of the spray arm rotation can be further increased.
• the present invention is a dishwasher adapted to cany out the above process, and in particular a dishwasher comprising a washing tub for accommodating articles to be cleaned, at least one spray arm arranged within the washing tub for directing a cleaning fluid to the articles to be cleaned, and a vibration sensor for detecting vibrations generated during operation of the dishwasher, wherein the dishwasher further comprises means for detecting rotation of the spray arm which means is adapted to carry out the process described above.
• the vibration sensor comprises a piezoelectric shock sensor.
• a piezoelectric shock sensor produces a voltage output signal that is substantially proportional to the acceleration of the sensor caused by a mechanical vibration of the sensor, i.e. an output signal that is substantially proportional to impacts or vibrations to which the sensor is exposed.
• the vibration sensor is attached to the exterior side of the tub so that the sensor is located outside the wet zone of the dishwasher. In this manner it is not necessary to take any specific precautions to avoid contact of electrically driven sensor components with the cleaning liquid that is circulated through the dishwasher tub.
• a preferred location for the vibration sensor is at a side wall of the tub.
• the vibration sensor preferably is attached to a side wall of the tub at about the level where the water jet emitted from the driving nozzle hits the side wall of the tub, so that the excitation of the vibration sensor by the passing water jet is at a maximum.
• the vibration sensor preferably is attached to the exterior side of the tub by a substantially rigid connection, such as by gluing the vibration sensor directly to the exterior side of the tub.
• the method described herein can be applied to detect rotation of any dishwasher spray arm, irrespective of whether such spray arm is part of a dishwasher having a single spray arm or is provided in a dishwasher having a plurality of spray arms. In case that rotation of more than one spray shall be monitored, this can be done by the use of a single vibration sensor, provided that measures are taken to assign the detected vibrations to the individual spray arms during evaluation of the signal.
• the processing of the sensor signals can be facilitated and at the same time made more reliable, if for each spray arm at least one individual vibration sensor is provided at a location where the respective spray arm causes vibrations at the tub, wherein additional measures can be taken to separate the vibration signals caused by the individual spray arms, such as by providing dampening elements at the exterior side of the tub so as to avoid that the vibration sensors pick up vibrations of comparative magnitude from more than one spray arm.
• the vibrations caused by the lower spray arm could be picked up at one of the side walls of the tub, for example at the left side wall, wherein in the upper part of such side wall there are provided dampening elements, such as additional fixations, so as to avoid or dampen any vibrations that are caused by the upper spray arm.
• rotation of the upper spray arm could be monitored by picking up vibrations caused by the upper spray arm at a different side wall of the tub, for example at the right tub wall, wherein dampening elements are provided in the lower part of such side wall, so as to avoid or dampen any vibrations that might be caused at the right tub wall due to water jets originating from the lower spray arm.
• FIG. 1 is a cross sectional view of a dishwasher in which a vibration sensor is provided to detect vibrations generated during operation of the dishwasher, and wherein means are provided to determine, based on the signal provided by the vibration sensor, whether the spray arm is in unblocked rotation;
• FIG. 2 shows the voltage signal provided by the vibration sensor of FIG. 1 during normal rotation of the spray arm
• FIG. 3 shows the signal of FIG. 1 when rectified
• FIG. 4 shows a counter trigger signal derived from the signal shown in FIG. 3;
• FIG. 5 shows the voltage signal provided by the vibration sensor of FIG. 1 when rotation of the spray arm is blocked close to the sensor, i.e. when the sensor constantly picks up a vibration signal;
• FIG. 6 shows a counter trigger signal derived from the signal shown in FIG. 5;
• FIG. 7 shows the voltage signal provided by the vibration sensor of FIG. 1 when rotation of the spray arm is blocked remote from the sensor, i.e. when the sensor does not pick up a strong vibration signal;
• FIG. 8 shows a counter trigger signal derived from the signal shown in FIG. 7;
• FIG. 9 shows the result of a root mean square (RMS) routine derived during normal rotation of the spray arm
• FIG. 10 shows the result of a root mean square (RMS) routine derived when rotation of the spray arm is blocked far from the sensor.
• RMS root mean square
• FIG. 1 1 shows the result of a root mean square (RMS) routine derived when rotation of the spray arm is blocked close to the sensor.
• RMS root mean square
• FIG. 1 there is shown a schematic cross-sectional view of the tub of a dishwasher 10 made in accordance with the teachings of the present invention.
• Dishwasher 10 comprises a tub 12 within which articles to be cleaned are accommodated during a washing cycle.
• a spray arm 16 having a plurality of spraying nozzles 18 via which a cleaning fluid can be sprayed upwardly towards the goods to be cleaned.
• spray arm 16 Towards its lateral ends spray arm 16 is provided with a driving nozzle 20 which is designed to eject a water jet at an angle to the axis 22 of rotation of the spray arm 16.
• a driving nozzle 20 which is designed to eject a water jet at an angle to the axis 22 of rotation of the spray arm 16.
• driving nozzle 20 is designed to eject a water jet radially from the spray arm 16 substantially in the plane of rotation of spray arm 16. Due to reaction forces of the water jet ejected from the driving nozzle 20 spray arm 16 is caused to rotate in FIG. 1 in the clockwise direction, as shown in FIG. 1 by an arrow of rotation indicated about axis 22.
• a vibration sensor 24 which is attached to the exterior side of the tub 12 and which in the embodiment shown in FIG. 1 is glued onto the exterior side of sidewall 26 at a level which corresponds to the level where the jet ejected from driving nozzle 20 impinges the sidewalls of tub 12.
• the vibration sensor need not be located exactly at the level of impingement. Rather, the vibration sensor 24 also can be placed offset from the level of impingement and/or from the center of the sidewalls, as it is shown in FIG. 1.
• FlG. 2 shows a typical example of a voltage signal generated by vibration sensor 24 during normal, unblocked rotation of the spray arm 16.
• the vibration sensor 24 outputs a signal having a distinct peak every time the water jet emitted from driving nozzle 20 hits the sidewall 26 of tub 12 at which the vibration sensor 24 is located.
• the spray arm 16 rotates at a speed of about 38 rpm, so that between each two adjacent peaks there is a time span of about 1.6 seconds.
• the output signal first is rectified, so that a signal curve is obtained as it is shown in FlG. 3.
• the target range determined during a one-minute period could be selected for example as 35 to 40, so as to take into account that spray arm 16 is driven with water that is circulated within the washing tub, i.e. with cleaning water which during a washing process is collected in the sump of the tub and which is fed via a circulation pump to spray arm 16. Since such water thus inevitably will contain dirt particles that have been washed off articles to be cleaned within the washing tub, the water fed to driving nozzle 20 will be subject to certain variations. Furthermore, rotation of the spray arm 16 can repeatedly be decelerated or accelerated by reaction forces caused by water jets that are emitted from any of the spray nozzles 18 and which impinge onto articles to be cleaned within the washing tub.
• FIG. 5 shows the voltage signal received from the output of vibration sensor 24 when the rotation of spray arm 16 is blocked, for example because one of the articles to be cleaned has been dislocated during the washing process and coincides with the path of rotation of the spray arm 16.
• FIG. 5 shows a situation where the spray arm 16 is blocked in an orientation in which the water jet ejected from driving nozzle 20 constantly impinges onto sidewall 26 where the vibration sensor 24 is attached, so that the vibration sensor 24 permanently generates a high output signal.
• FIG. 6 shows the corresponding counter trigger signal.
• a sampling period of 0.4 seconds has been selected, so that the count value of the counter is increased every 0.4 seconds.
• the system will determine that the spray arm apparently is blocked. Based upon this determination, an optic or acoustic warning message can be issued to the user to check on the status of the spray arm. Since for removal of an obstruction that impedes rotation of the spray arm the operation of the dishwasher has to be interrupted, the system also can be designed to automatically interrupt a washing cycle in case that it is determined that the spray arm does not rotate as intended.
• FIG. 7 there is shown a typical example of the output of vibration sensor 24 as recorded in a situation when rotation of the spray arm is blocked in an orientation in which the water jet emitted from driving nozzle 20 impinges onto the wall of tub 12 at a location that is remote from vibration sensor 24.
• the sensor will deliver an output signal that does not exhibit any clearly distinct peaks and which further constantly remains below the threshold voltage Vj. Therefore, the counter trigger signal will constantly remain at zero, as it is depicted in FiG. 8 so that within the predetermined time period the counter value will not reach the predetermined target range.
• the system will issue a warning message to the user and optionally will interrupt operation of the dishwasher, so as to give the user the opportunity to check on the state of the spray arm to then continue the washing process.
• the proper rotation of the spray arm thus can be reliably determined, basically by counting the peaks of the signal received from the vibration sensor and comparing the peak count with an expected value which is a design parameter for the specific dishwasher. While there may be situations wherein a signal peak is generated which is not directly associated to a rotation of the spray arm but which may be caused for example by an incidental impact of water jets that are reflected from articles within the dishwasher tub onto which a jet of cleaning liquid is sprayed, the predetermined target range for the count value should include some tolerance range which in the example referred to above wherein the spray arm rotates at a speed of 38 rpm may be selected as ⁇ 6 peak counts when measuring for a time period of one minute.
• the target range for the count value could be selected for example as the standard rotational speed ⁇ 2 rpm, wherein it is determined that the spray arm correctly rotates if the count value falls within such target range.
• the measuring cycle is repeated or a further more detailed evaluation routine is conducted. While a similar safety range could be provided at the lower end of the target range it of course is also possible to provide such a safety range in which the evaluation is repeated or altered only at one end of the target range.
• a particularly preferred embodiment of providing for a more sophisticated evaluation of the peak count is by employing a root mean square (RMS) routine in which sample values are obtained over a certain period of time and an average of the individual values is formed which average then is used as basis for a comparison with a predetermined target range.
• RMS root mean square
• the root mean square value RMS n would be In a preferred embodiment instead of calculating the above RMS value the average also could be calculated as
• the output signal of the vibration sensor during normal operation is a substantially regular signal comprising a plurality of subsequent adjacent maxima and minima
• the average of the detected maxima is determined for a certain period of time, the average of the minima detected over such period of time is determined and further the average of all the detected maxima and minima is determined, wherein in order to further rule out data errors each of the detected maxima and minima is compared with the preceding data point.
• FIG. 9 An example for a determination of the Av value for a normally rotating spray arm is shown in FIG. 9.
• FIG. 10 is a similar illustration which shows an Av chart when received when the spray arm is blocked in an orientation wherein the jet ejected from the driving nozzle impinges onto the wall of the tub remote from the vibration sensor.
• FIG. 1 1 shows an example of an Av chart obtained in a situation where the spray arm is blocked in an orientation wherein the jet from the driving nozzle hits the wall of the tub close to the sensor.
• the differentiation between a blockage of the rotation of the spray arm near or far from the sensor can be used to evaluate whether upon interruption of a washing cycle a delay should be triggered before releasing the lock of the dishwasher door so as to avoid that water is spilled to the exterior of the dishwasher when opening the dishwasher door in a situation where the spray arm is blocked in an orientation where the jet from the driving nozzle is directed towards the door of the dishwasher.

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Citations (7)

• 2012
  • 2012-01-10 EP EP12150555.6A patent/EP2614763B1/en active Active
  • 2012-01-10 PL PL12150555T patent/PL2614763T3/pl unknown
• 2013
  • 2013-01-10 WO PCT/EP2013/050378 patent/WO2013104700A1/en active Application Filing

Patent Citations (7)

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