Abstract:
The sensor apparatus is intended to detect the level of a liquid, gel or powder substance contained in a receptacle and includes an emitter able to emit radiation and a receiver able to receive and convert into an electric signal radiation which is emitted by the emitter and the intensity of which is variable depending on the quantity or level of substance present in the receptacle. The emitter is designed to emit visible radiation and the apparatus also includes a visible optical indicator and an optical element able to couple optically the emitter to the optical indicator so that, when the quantity or level of the substance in the receptacle is lower than a predetermined threshold, a fraction of the radiation generated by the emitter is able to light up the optical indicator.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application is a National Stage of International Application No. PCT/IB2010/051278 filed Mar. 24, 2010, claiming priority based on Italian Patent Application No. T02009A000231 filed Mar. 26, 2009, the contents of all of which are incorporated herein by reference in their entirety. 
     FIELD OF INVENTION 
     The present invention relates to a sensor apparatus intended to detect the level of a liquid, gel or powder substance contained in a receptacle. 
     More specifically the present invention relates to a sensor apparatus according to the preamble of claim  1 . 
     BRIEF SUMMARY OF THE INVENTION 
     Apparatus for detecting the level of a substance present in a receptacle, particularly in sectors such as the household appliances sector, are known in the present state of the art. For example, these apparatus are widely used in dishwashing machines for the purpose of detecting the level of rinsing agent, or salt, present inside the receptacles associated with a dispensing device or a limescale-removal device. 
     The apparatus of the type specified above make use of the combined action of an emitter and a receiver which are associated with a receptacle containing a liquid, gel or powder substance. The emitter is designed to emit radiation. The receiver, usually a photodiode or a phototransistor, is able to receive and convert into an electric signal radiation which is emitted by the emitter and the intensity of which is variable depending on the quantity or level of substance present in the receptacle. 
     Usually these apparatus have the function of indicating the reserve level of the liquid depending on the intensity of the radiation received. An optical device intended to reflect and/or refract the radiation depending on the refraction index of the means present in the receptacle and facing the optical device is typically arranged between the emitter and the receiver. In the case where the liquid means exceeds a predetermined threshold value, its level is situated facing the optical device and the radiation is mainly refracted through the liquid means, being dispersed. In the opposite case, its level is below the optical element and therefore the light radiation is mainly reflected towards the receiver which is able to indicate to a control circuit that a reserve level has been reached. 
     Although this type of apparatus envisages an electrical system for performing signalling to the machine, it does not provide at the same time a visual indication relating to the level of the substance present in the receptacle. 
     One object of the present invention is to provide a sensor apparatus of the abovementioned type which is able to provide also a visual indication of the level of the substance present in the receptacle in a way which can be directly seen by the user, is operationally reliable and can be manufactured in a simple and low-cost manner. 
     This object, together with others, is achieved according to the present invention by means of a sensor apparatus defined by the characteristic features contained in the accompanying claim  1 . 
     As a result of these characteristic features the sensor apparatus is able to exploit fully the same visible radiation emitted by the emitter both for an electric signal and for an optical signal which can be seen by a user. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Further characteristic features and advantages of the present invention will become clear from the following detailed description provided purely by way of a non-limiting example, with reference to the accompanying drawings in which: 
         FIG. 1  is a perspective view of a dishwashing machine, the door of which includes a rinsing agent dispensing device provided with a receptacle which comprises a first example of embodiment of a sensor apparatus according to the present invention; 
         FIG. 2  is an enlarged and partly sectioned view along the line II-II of  FIG. 1  of the dispensing device in the configuration corresponding to the condition where the door is open; 
         FIG. 2   a  is a partial, schematic, cross-sectional view of the sensor apparatus along the line IIa-IIa of  FIG. 2 ; 
         FIG. 3  is a view which is similar to that of  FIG. 2 , but which shows the dispensing device in a second filling condition; 
         FIG. 3   a  is a partial, schematic, cross-sectional view of the sensor apparatus along the line IIIa-IIIa of  FIG. 3 ; 
         FIGS. 4 to 5  are partial schematic views which show two different variations of embodiment of the sensor apparatus according to the present invention; 
         FIG. 6  is a schematic cross-sectional view of a limescale-removal device with a receptacle which is provided with a second example of embodiment of a sensor apparatus according to the present invention and which is shown in a first filling condition; and 
         FIG. 7  is a view which is similar to that of  FIG. 6 , but which shows the receptacle in a second filling condition. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     In  FIG. 1 ,  10  denotes overall a dishwashing machine of the type known per se. 
     The machine  10  generally comprises a housing  12  which has a substantially parallelepiped shape and which defines internally a washing chamber  14  which can be accessed via an open front side  16  of the housing  12  with which a closing door  18  is associated. The door  18  is hinged on the structure of the machine  10  along a horizontal axis X-X in the vicinity of its bottom horizontal side. 
     The door  18  is therefore capable of assuming a vertical position (not shown) in which it closes off the washing chamber  14  and a lowered position, shown in  FIG. 1 , where it allows easy access to a device for dispensing washing agents, denoted overall by  20 . 
     In a manner known per se the dispensing device  20  is mounted on the inner side of the door  18  of the machine  10 . In this example of embodiment said dispensing device  20  is of the so-called integrated type, i.e. it comprises a single support structure or body  22  which contains both a device for dispensing a liquid or solid or powder washing agent and a device  26  for dispensing a rinsing or brightening agent. 
     The present invention is however not to be regarded as being limited to implementation in a device for dispensing washing agent integrated with an adjacent device for dispensing rinsing agent. In fact, as will become clear from the description below, the present invention may be applied to any receptacle intended to contain a liquid, gel or powder substance. 
     With reference to  FIG. 2 , this shows partly cross-sectioned the dispensing device  26  for the rinsing agent. 
     The inner walls of the dispensing device  26  form a receptacle  28  defining an inner chamber  30  which contains a quantity of rinsing agent which—as shown in FIG.  2 —lies above a reserve threshold level. Furthermore, the receptacle  28  comprises a sensor apparatus  100  according to the present invention. 
     The sensor apparatus  100  is arranged in a wall of the receptacle  28  and comprises a support plate  102  which carries an emitter  104  and a receiver  106 . 
     As can be seen more clearly in  FIG. 2   a , the sensor apparatus  100  also comprises an optical element, by way of example a triangular prism  108  preferably in the form of a right-angled triangle. Advantageously, the emitter  104  (for example an LED) and the receiver  106  are arranged facing the hypotenuse face or side  108   a  of said triangular prism  108 . Instead the cathetus faces or sides of this triangular prism  108  define, respectively, a first reflective face  108   b  and a second reflective face  108   c  which are directed towards the inner chamber  30  of the receptacle  28 . 
     The sensor apparatus comprises furthermore an optical waveguide, for example a semi-transparent rod  110 , which is fixed to a portion of the receptacle  28 . The semi-transparent rod  110  emerges inside the chamber  32  in a position at least partly facing the triangular prism  108 . The semi-transparent rod  110  has advantageously a reflective face  112  which is inclined for example at about 45° with respect to its longitudinal axis and which faces the triangular prism  28 . This semi-transparent rod  110  terminates at the top on the lid with its signalling end  114  directed outwards. 
     Preferably the rectangular edge of the triangular prism  108  (i.e. the edge where the two reflective faces  108   b  and  108   c  intersect each other) is parallel to the longitudinal axis of the rod  110 . 
     The triangular prism  108  is able to couple optically the emitter  104  and the signalling end  114  which acts as an optical indicator which is visible in the manner which is described hereinbelow. 
     In the condition shown in  FIGS. 2 and 2   a , the receptacle  28  has internally a level of rinsing agent above the signalling threshold of the apparatus  100 . The emitter  104  emits visible radiation L which is deviated so as to be reflected and refracted by the first reflective face  108   b  of the triangular prism  108  in a first reflected fraction L 1  and a second refracted fraction L 2 , respectively. In this case, the level of the rinsing agent is above the surface of the triangular prism  108 . Therefore, the refraction index, which is present inside the chamber  30  and is influenced by the presence of the rinsing agent, is such that the fraction L 1  which is reflected and then deviated by the second reflective face  108   c  has an intensity sufficient to activate the receiver  106  (advantageously a photodiode or a phototransistor). Furthermore the refracted fraction L 2  has a significant radiating intensity, but passing through the rinsing agent in liquid form is dispersed inside the chamber  30 , without managing to reach the semi-transparent rod  110  with an intensity sufficient to intercept the reflective face  112  so as to provide a visible indication at the signalling end  114 . 
     With reference to  FIGS. 3 and 3   a  (again relating to the horizontal position of the door  18 ), the receptacle  28  has internally a level of rinsing agent below the signalling threshold of the apparatus  100 . In this case, the level of the rinsing agent is below the surface of the triangular prism  108 . The refraction index of the prism  108  is therefore different from the previous index since there is no longer a liquid means which reaches the surface of the triangular prism  108 . Therefore the triangular prism  108  is formed so that—in this condition—the first reflected fraction L 1  has an intensity sufficient to activate the receiver  106  which sends to a control circuit (not shown) a signal indicating that the reserve level inside the receptacle  28  has been reached. At the same time, although the refracted fraction L 2  has a low intensity, it is however able to reach the reflective face  112  of the semi-transparent rod  110  which deviates the refracted fraction L 2  through it until it reaches the signalling end  114 . Therefore a visual signal which can be seen by a user looking at the receptacle  28  in the horizontal (or open) position of the door  18  is emitted. 
     Advantageously, the first reflective face  108   b  and the second reflective face  108   c  define planes which are perpendicular to each other. 
     With reference to  FIG. 4 , this shows a first variation of embodiment of the sensor apparatus according to the present invention. Parts which are similar to those of the previous embodiment are indicated by the same reference numbers and/or letters. 
     In contrast to the preceding embodiment, the right-angled edge of the triangular prism  108  is parallel with a straight line perpendicular to the longitudinal axis of the optical waveguide  110  (lowered position of the door  18 ). Furthermore the emitter  104  and the receiver  106  are preferably fixed on the hypotenuse face  108   a  of the triangular prism  108 . 
     With reference to  FIG. 5 , this shows a second variation of embodiment of the sensor apparatus according to the present invention. Parts which are similar to those of the previous embodiment shown in  FIGS. 1 to 3  are indicated by the same reference numbers and/or letters. 
     In contrast to the embodiment shown in  FIGS. 1 to 3 , the optical element is a prism  108  which has a cross-section which is in the form of an isosceles trapezium. The emitter  104  and the receiver  106  are advantageously fixed to the large-base face  108   a  of the prism  108 . Preferably the larger-base side of the prism  108  is parallel to the longitudinal axis of the optical waveguide  110 . The first reflective face  108   b  and the second reflective face  108   c  are defined by the oblique sides of the prism  108 . 
     Preferably, in the first and second variation of embodiment shown in  FIGS. 4 and 5 , only the first reflective face  108   b  is directed towards the inside of the container  28 . 
     Furthermore, the second reflective face  108   c  has preferably a coating  120  suitable for optimising reflection towards the receiver  106  and minimising the refraction of the radiation striking the aforementioned second reflective face. 
     With reference to  FIGS. 6 and 7 , these show a second embodiment of the sensor apparatus according to the present invention, denoted overall by  200 . 
     In this embodiment the sensor apparatus  100  is applied to a receptacle  300  of a limescale-removal device for dishwashing machines (details not shown). The sensor apparatus  200  comprises a first support plate  202  fixed onto a wall of the receptacle  300  and having an emitter  204  and a second support plate  203  fixed to the bottom of the receptacle  300  and having a receiver  206  directed towards the emitter  204 . 
     Furthermore, the apparatus has an optical waveguide, advantageously a semi-transparent rod  208  which is fixed in the region of the neck  302  of the container  300  by means of a plurality of radial spokes  304 . The semi-transparent rod  208  comprises a bottom reflective face  212  and a signalling end  214  which is directed towards the transparent lid  306  of the receptacle  300 . The semi-transparent rod  208  is arranged between the emitter  204  and the receiver  206  so that the radiation L′ emitted by the emitter  204  is directed towards the bottom reflective face  212 . 
     With reference to  FIG. 6 , the level of the powder material present in the receptacle  300  exceeds the signalling threshold of the apparatus  200  and covers the semi-transparent rod  208  so that it obstructs the radiation L′ which is unable to reach the bottom reflective face  212 . In this way no radiation reaches either the signalling end  214  of the semi-transparent rod  208  nor the receiving device  206 . 
     With reference to  FIG. 7 , the level of the powder material present in the receptacle  300  exceeds the signalling threshold of the apparatus  200 . In this condition, the level of powder material is below the bottom reflective face  212 . Consequently, the radiation L′, which is within the visible spectrum, is transmitted by the reflective face  212  in a first fraction L′, which continues its path towards the receiver  206 , and a second fraction L 2 ′. The reflected fraction L 2 ′ passes along the length of the semi-transparent rod  208  and lights up the signalling end  214 . The reflected fraction L 2 ′ is directed towards  206  and has an intensity such as to activate it so as to signal a reserve level of powder material to a control circuit (not shown). In this way the semi-transparent rod  208  acts not only as an optical waveguide for the signalling end  214 , but also as an optical element for selectively coupling this signalling end  214  to the emitter  204 . 
     Obviously, without affecting the principle of the invention, the embodiments and the constructional details may be greatly modified with respect to that described and illustrated purely by way of a non-limiting example, without thereby departing from the scope of the invention as defined in the accompanying claims.