Optical sensor for water-air detection

• US 9,861,248 B2
• Filed: 01/30/2015
• Issued: 01/09/2018
• Est. Priority Date: 01/30/2015
• Status: Active Grant

• Current Assignee: emz-Hanauer GmbH & Co. KGaA
• Original Assignee: emz-Hanauer GmbH & Co. KGaA
• Inventors: Schenkl, Johann, Signorino, Manfredi, Baumer, Johannes, Wilhelm, Georg
• Primary Examiner(s): Ko, Tony
• Application Number:
  US14/609,551
• Publication Number:
  US 20160223460A1
• Time in Patent Office: 1,075 Days
• CPC Class Codes: A47L 15/0018 Controlling processes, i.e. processes to control the operation of the machine characterised by the purpose or target of the control for control of water softening or water softener regeneration A47L15/4229; for control of water level A47L15/4244; for control of bad smells or odours A47L15/4276; for control of water temperature A47L15/4287; for control of water pressure A47L15/4289; for control of condition of crockery or tableware A47L15/4295; for control of condition of washing water A47L15/4297
• CPC Class Codes: A47L 15/4295 Arrangements for detecting or measuring the condition of the crockery or tableware, e.g. nature or quantity
• CPC Class Codes: A47L 2401/09 Water level
• CPC Class Codes: A47L 2401/10 Water cloudiness or dirtiness, e.g. turbidity, foaming or level of bacteria
• CPC Class Codes: D06F 2103/16 Washing liquid temperature
• CPC Class Codes: D06F 2103/18 Washing liquid level
• CPC Class Codes: D06F 2103/20 Washing liquid condition, e.g. turbidity
• CPC Class Codes: D06F 2105/58 Indications or alarms to the control system or to the user
• CPC Class Codes: D06F 33/30 Control of washing machines characterised by the purpose or target of the control controlling processes of washer-dryers D06F33/50
• CPC Class Codes: D06F 34/24 Liquid temperature
• CPC Class Codes: G01N 21/43 by measuring critical angle
• CPC Class Codes: G01N 21/534 by measuring transmission alone, i.e. determining opacity
• CPC Class Codes: G01N 21/552 Attenuated total reflection
• CPC Class Codes: G01N 2201/08 Optical fibres; light guides

Abstract

A sensor and a method of manufacture of a sensor includes a light interface portion comprising first and second walls, where a cavity is provided between the first and second walls, and where the first wall is configured such that at least a portion of light is totally reflected at the first wall when the sensor-external medium is water, and at least a portion of light is coupled out when the sensor-external medium is air, and a portion of light is coupled out and a further portion of light is totally reflected by the first wall when the sensor-external medium comprises foam. Light that is reflected by the first wall is directed toward a second wall, and reflected at the second wall to be directed to a light receiving element.

Claims

1. An optical sensor comprising:

a housing having a housing interior and a light interface portion;

a light emitting element disposed in the housing interior; and

a light receiving element disposed in the housing interior;

the light interface portion protruding from a base portion of the housing, the light interface portion comprising;

a first wall disposed to receive light emitted by the light emitting element;

a second wall disposed such that light reflected from the second wall is received by the light receiving element; and

a cavity formed between the first and second walls wherein each of the first and second walls comprises a wall inner surface and a wall outer surface, wherein the outer surface of the first wall defines an optical interface between a material of the wall and a sensor-external medium and is configured such that;

when the sensor-external medium is air, at least a portion of the light emitted by the light emitting element is totally reflected at the outer surface of the first wall and is directed from the first wall through the cavity to the second wall and from the second wall to the light receiving element; and

when the sensor-external medium is water, at least a portion of the light emitted by the light emitting element is coupled out into the sensor-external medium at the outer surface of the first wall.

2. The optical sensor of claim 1 wherein the first and second walls are disposed at an angle with respect to each other.

3. The optical sensor of claim 2 wherein the angle between the first and second walls is within a range from 60 to 120 degrees or 70 to 110 degrees or 80 to 100 degrees.

4. The optical sensor of claim 1 wherein the wall inner surface of at least one of the first and second walls has a stepped formation.

5. The optical sensor of claim 4 wherein a height and/or width of steps of the stepped formation have a dimension that is within a range of approximately 0.4 to 1.0 millimeters.

6. The optical sensor of claim 1 further comprising first and second light guides accommodated in the housing, the first light guide disposed to direct light from the light emitting element toward the first wall, the second light guide disposed to direct light from the second wall to the light receiving element.

7. The optical sensor of claim 6 wherein the first and second light guides are disposed adjacent to the cavity formed between the first and second walls.

8. The optical sensor of claim 6 wherein at least one of the first and second light guides comprises a converging lens at an end thereof proximal to the cavity.

9. The optical sensor of claim 6 wherein at least one of the first and second light guides has an angled or curved surface portion at an end thereof remote from the cavity to direct light to a light output port of the respective light guide by total reflection.

10. The optical sensor of claim 6 wherein the first and second light guides extend in parallel with each other.

11. The optical sensor of claim 6 wherein the first and second light guides extend substantially parallel to a printed circuit board carrying the light emitting element and the light receiving element.

12. The optical sensor of claim 6 wherein the light emitting element and the light receiving element are disposed on a printed circuit board, wherein the light emitting element has a main emission axis substantially perpendicular to the printed circuit board, wherein the light receiving element has a main reception axis substantially perpendicular to the printed circuit board, wherein the first light guide is configured to divert a light ray emitted from the light emitting element in the direction of the main emission axis to a direction substantially parallel to the printed circuit board, and wherein the second light guide is configured to divert a light ray travelling in the second light guide parallel to the printed circuit board to a direction substantially parallel to the main reception axis.

13. The optical sensor of claim 6 wherein the first and second light guides are provided on a light guide support that has a portion configured to conform to at least a portion of an inner surface of the base portion of the housing.

14. The optical sensor of claim 13 wherein the light guide support further comprises a substantially cylindrical portion configured to conform to an inner surface of a substantially cylindrical portion of the sensor housing.

15. The optical sensor of claim 1 wherein a ratio of the amount of light received by the light receiving element to the light emitted by the light emitting element is less than 20% when the sensor-external medium is water, more than 80% when the sensor-external medium is air, and between 20% and 80% when the sensor-external medium comprises foam.

16. The optical sensor of claim 1 wherein a material of the first and second walls includes polypropylene.

17. The optical sensor of claim 1 wherein the wall outer surface of at least one of the first and second walls is planar.

18. An electric home appliance comprising:

a cabinet including a wet compartment for receiving items to be washed;

an optical sensor comprising;

a housing having a housing interior and a light interface portion;

a light emitting element disposed in the housing interior; and

a light receiving element disposed in the housing interior;

the light interface portion protruding from a base portion of the housing, the light interface portion comprising;

a first wall disposed to receive light emitted by the light emitting element;

a second wall disposed such that light reflected from the second wall is received by the light receiving element; and

a cavity formed between the first and second walls wherein each of the first and second walls comprises a wall inner surface and a wall outer surface, wherein the outer surface of the first wall defines an optical interface between a material of the wall and a sensor-external medium and is configured such that;

when the sensor-external medium is air, at least a portion of the light emitted by the light emitting element is totally reflected at the outer surface of the first wall and is directed from the first wall through the cavity to the second wall and from the second wall to the light receiving element; and

when the sensor-external medium is water, at least a portion of the light emitted by the light emitting element is coupled out into the sensor-external medium at the outer surface of the first wall;

wherein the optical sensor is mounted in the cabinet to protrude with the first and second walls into the wet compartment; and

a control unit configured to receive a measurement signal based on light received by the light receiving element and control an operation of the appliance based on the measurement signal.