Classifications

• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
  • G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
  • G01N21/17—Systems in which incident light is modified in accordance with the properties of the material investigated
  • G01N21/47—Scattering, i.e. diffuse reflection
  • G01N21/49—Scattering, i.e. diffuse reflection within a body or fluid
  • G01N21/53—Scattering, i.e. diffuse reflection within a body or fluid within a flowing fluid, e.g. smoke
  • G01N21/534—Scattering, i.e. diffuse reflection within a body or fluid within a flowing fluid, e.g. smoke by measuring transmission alone, i.e. determining opacity
• • 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
  • A47L15/4297—Arrangements for detecting or measuring the condition of the washing water, e.g. turbidity
• • D—TEXTILES; PAPER
  • D06—TREATMENT OF TEXTILES OR THE LIKE; LAUNDERING; FLEXIBLE MATERIALS NOT OTHERWISE PROVIDED FOR
  • D06F—LAUNDERING, DRYING, IRONING, PRESSING OR FOLDING TEXTILE ARTICLES
  • D06F34/00—Details of control systems for washing machines, washer-dryers or laundry dryers
  • D06F34/14—Arrangements for detecting or measuring specific parameters
  • D06F34/22—Condition of the washing liquid, e.g. turbidity

Definitions

• the present invention relates to a turbidity sensor for washing machines or dishwashers, adapted to detect the level of turbidity of a liquid during a wash cycle.
• Optical sensors adapted to detect the turbidity of a liquid in a washing machine or dishwasher are well known. These sensors typically comprise an optical transmitter which transmits light radiation through the washing liquid and an optical receiver which receives the optical radiation transmitted by the transmitter after the passage of the radiation through the washing liquid. By comparing the measurement of the optical radiation transmitted by the transmitter with the measurement of the optical radiation received by the receiver, the level of turbidity of the washing liquid can be determined.
• turbidity sensors depends on a number of factors, including the dispersion of the optical radiation transmitted by the transmitter.
• dispersion there is a known way of using transmitters which generate a beam having a small cross section in the direction of propagation.
• use is made, for example, of laser transmitters.
• transmitters of this type are costly.
• transmitters generating a beam with a small cross section must be aligned very precisely with the receiver .
• US-A-2007/0188763 describes a turbidity sensor comprising a diaphragm system placed between the transmitter and the receiver, enabling the precise alignment of the transmitter and receiver to be avoided.
• a turbidity sensor comprising a diaphragm system placed between the transmitter and the receiver, enabling the precise alignment of the transmitter and receiver to be avoided.
• the object of the present invention is to provide a simple and economical turbidity sensor, enabling a precise alignment to be established between the transmitter and receiver while using a smaller number of components than in the known solutions.
• this object is achieved with a turbidity sensor having the characteristics described in claim 1.
• FIG. 1 is an exploded perspective view of a turbidity sensor according to the present invention
• FIG. 1 is an exploded view in elevation in the direction of the arrow II in Figure 1
• FIG. 3 is an exploded cross section taken along the line III-III of Figure 2
• - Figure 4 is an axial section through the sensor of Figure 1
• FIG. 5 is a cross section taken along the line V-V of Figure 4.
• the number 10 indicates a turbidity sensor for washing machines or dishwashers.
• the sensor 10 comprises a hollow casing 12 of plastic material, having a longitudinal axis A.
• the casing 12 has a cylindrical lateral wall 14 having a circular aperture 16 at one of its ends.
• the hollow casing 12 has a bottom wall 18 and two hollow arms 20 extending beyond the bottom wall 18 in a direction parallel to the longitudinal axis A.
• the hollow arms 20 are made in one piece with the lateral wall 14, and have respective outer walls 21 and inner walls 22.
• the inner walls 22 face each other and are parallel to the longitudinal axis A.
• the sensor 10 comprises a printed circuit board 24 which carries an optical transmitter 26 and an optical receiver 28.
• the printed circuit board 24 also carries the components 30 of an electronic control circuit associated with the transmitter 26 and the receiver 28.
• the printed circuit board 24 also carries an electrical connector 32 for the electrical connection of the sensor 10 to an external circuit .
• the printed circuit board 24 has two opposing longitudinal edges 34 which are parallel to each other and are placed parallel to the longitudinal axis A.
• the printed circuit board 24 has two branches 36 spaced apart from each other in such a way that one end of the board 24 is substantially U-shaped.
• the transmitter 26 and the receiver 28 are fixed to the ends of the respective arms 36.
• the transmitter 26 can be, for example, an LED, while the receiver 28 can be, for example, a phototransistor, a photodiode or a solar cell.
• the hollow casing 12 is permeable to the optical radiation generated by the transmitter 26, at least on the inner walls 22. Preferably, the whole casing 12 is made from a single transparent plastic material.
• the transmitter 26 and the receiver 28 are fixed to the printed circuit board 24 by means of respective metal terminals 38 which are inserted and fixed into respective holes in the printed circuit board 24.
• the transmitter 26 and the receiver 28 are spaced at a certain distance from the surface of the front of the printed circuit board 24.
• the transmitter 26 and the receiver 28 are connected to, and project from, the front surface of the printed circuit board 24, by means of respective portions of the metal terminals 38.
• the metal terminals 38 have a degree of flexibility such that the transmitter 26 and the receiver 28 can be displaced to a small extent relative to the printed circuit board 24 by the elastic deformation of the portions of the terminals 38 which extend between the body of the transmitter 26 or of the receiver 28 and the front surface of the printed circuit board 24.
• the printed circuit board 24 is inserted into the hollow casing 12 by a movement in a direction parallel to the longitudinal axis A, as indicated by the arrow B in Figures 1, 2 and 3.
• the hollow arms 20 of the casing 12 have, on the inner surfaces of their walls 21, 22, respective guide formations 40, 42 which receive and guide the transmitter 26 and the receiver 28 in the course of the insertion of the printed circuit board 24 into the hollow casing 12 in the longitudinal direction A.
• Each of these guide formations is, for example, formed by two parallel ribs 40, 42 which extend parallel to the longitudinal axis A.
• the ribs 40, 42 are formed, respectively, on the inner surfaces of the walls 21, 22 of the arms 20.
• the ribs 40, 42 are located on opposite sides of a plane which lies parallel to the longitudinal axis A and which passes through the terminals 38 of the transmitter 26 and the receiver 28.
• the ribs 40, 42 are preferably spaced apart from each other in a direction perpendicular to the printed circuit board 24.
• the ribs 40, 42 come into contact with opposite sides of the transmitter 26 and the receiver 28, and form guides for the orientation of the transmitter 26 and the receiver 28 in such a way that the respective transmitting and receiving surfaces are correctly aligned with each other.
• the alignment of the transmitter 26 with the receiver 28 is made possible by the elastic yielding properties of the portions of the terminals 38 which connect the transmitter 26 and the receiver 28 to the printed circuit board 24. The alignment takes place automatically as a result of the insertion of the printed circuit board 24 into the hollow casing 12.
• the hollow casing 12 is provided with a further guide which receives the printed circuit board 24.
• This further guide is preferably formed by opposing grooves 44 which receive the opposing longitudinal edges 34 of the printed circuit board 24.
• the senor 10 is provided with a cover 46 which is fixed to the hollow casing 12 after the insertion of the printed circuit board 24.
• the cover 46 is preferably snap-fitted to the casing 12 by means of apertures 48 which engage with teeth 50 formed on the outer surface of the cylindrical wall 14 of the hollow casing 12.
• the cover 46 is also provided with a front aperture 52 facing the connector 32 of the printed circuit board 24.
• the solution according to the present invention enables the transmitter 26 and the receiver 28 to be aligned with each other by means of integral guides 40, 42 formed in the hollow casing 12.
• the alignment between the transmitter 26 and the receiver 28 is established in the course of the insertion of the printed circuit board 24 into the casing 12, without the need to perform any preliminary operation for aligning the transmitter 26 with the receiver 28.
• the present invention does not reguire diaphragms or other additional components for the optical alignment of the radiation transmitted by the transmitter 26.

Landscapes

• Engineering & Computer Science (AREA)
• Textile Engineering (AREA)
• Physics & Mathematics (AREA)
• Health & Medical Sciences (AREA)
• Life Sciences & Earth Sciences (AREA)
• Chemical & Material Sciences (AREA)
• Analytical Chemistry (AREA)
• Biochemistry (AREA)
• General Health & Medical Sciences (AREA)
• General Physics & Mathematics (AREA)
• Immunology (AREA)
• Pathology (AREA)
• Investigating Or Analysing Materials By Optical Means (AREA)
• Investigating Or Analyzing Materials By The Use Of Electric Means (AREA)
• Control Of Washing Machine And Dryer (AREA)
• Washing And Drying Of Tableware (AREA)

Applications Claiming Priority (2)

Publications (1)

Family

ID=43977518

Family Applications (1)

Country Status (2)

Cited By (4)

Citations (5)

• 2011
  • 2011-03-30 IT IT000286A patent/ITTO20110286A1/it unknown
• 2012
  • 2012-03-29 WO PCT/US2012/031149 patent/WO2012135457A1/en active Application Filing

Patent Citations (5)

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