Device and method for controlling the filling of a cup in a drinks vending machine such as a coffee machine

The invention applies also more particularly to products which produce froth by controlling the fill of the product including the layer of froth generated.

The invention will be better understood and further characteristics will emerge from the appended figures in which:

Figure 1 represents a coffee machine furnished with a device for controlling the filling of a cup according to a preferred mode of the invention;

Figure 2 shows a functional diagram of the device of Figure 1;

Figure 3 shows a detailed view of the principle of operation of the device according to the invention between a position of marking without liquid or froth and a position with a liquid or froth surface,

5 Figure 4 shows the example of an algorithm for determining the variables of the incident ray processed by the photoreceiver module, in particular, by the camera;

Figure 5 shows the example of an algorithm for control by the control system of the device on the basis of the variables determined by the algorithm of Figure 4;

Figure 6 represents, as an example, the differential value of the distribution of the intensity produced over a group of photodiodes corresponding to the light spot of the device of the invention (differential image vector);

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- 12Figure 7 represents in a diagrammatic view a coffee machine furnished with a control device according to a second embodiment;

Figure 8 shows a functional diagram of the device of Figure 7.

With reference to Figure 1, a coffee machine is illustrated bearing the reference 1 and equipped with an optoelectronic device 2 for monitoring the filling of a cup, which device is mounted rotatably about the horizontal axis I so as to allow orientation of the device so that the mark is aimed as a function of the height of the cups presented on the machine. As known per se, an exemplary coffee machine on which the device is associated comprises a body 10 including the essential elements for producing a drink of the coffee type or the like. Among these elements are generally found a flow duct 11, an extraction module for extracting a quantity of ingredient(s) contained in an (internal) capsule, an (internal) liquid pump for supplying the extraction module with liquid under pressure, an (internal) water heater for supplying the pump with heated liquid, a mechanism 12 for inserting the capsule into the extraction module, a cup holder and liquid collecting tray 13, and an electric current supply 14.

The control device 2 makes it possible to detect the level of drink in the cup 3 after it has flowed from the duct 11 and makes it possible to halt the filling of the cup by the drink, for example, by stopping the capsule extraction procedure; generally by shutting down the liquid pump which supplies the extraction module.

5 The control device comprises a module 20 for emitting a light ray at high intensity and a module for receiving the incident light ray 21. The emission module is preferably placed below the reception module so as to ensure a better angle of return of the signal even for receptacles of large size. The emission module 20 produces a light ray 40 focused, as by a collimator 22, capable of directing the ray onto the internal surface of the cup as a spot

41 of small size, for example of the order of from 1 to 2 mm or more. The size of the spot is also dependent on the capacity of the material of the receptacle to reflect light. For example, a white porcelain receptacle tends to form a more diffuse light spot than a black-coloured cup.

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- 13 A source of light intensity that is sufficient is preferably a laser or an emitter of light based on a lamp or some other optoelectronic component producing an emission of photons (for example an LED). The module also comprises a focusing means making it possible to reduce the light ray striking the receptacle to a relatively small spot. In the case of a laser, the laser is chosen to emit in a wavelength range that can be read by the reception module capable of detecting the incident ray 42 of the laser, in particular, in a visible light range of the order of 650 nm. A laser module that may be suitable for the device of the invention may be of the diode laser type with variable focal length marketed by Conrad Electronic under reference OLSH-703P.

The module for receiving the ray is preferably an electronic camera. It comprises a row 23 of photodiodes which is oriented in the same vertical plane as the emitted laser ray but angularly offset with respect to the emitted ray. Each photodiode is a semiconductor which produces an electric current when the incident light ray reaches it. The intensity of the current produced depends on the diffusion of the light ray over the row, the centre of the incident ray producing in principle on the photodiode hit a maximum intensity of current. The row of photodiodes 23 consists for example of at least 20, preferably at least 50, most preferably of 100 to 200 photodiodes, associated with an amplification circuit and a pixel data support function. The number, the spacing and the size of the pixels condition the accuracy of the camera and hence the accuracy of the tolerance on the detected movement of the incident ray. In general, the greater the number of pixels the better the resolution. The pixels are, for example, spaced around 80-85 microns apart from centre to centre. A camera that may be suitable for the device is marketed under the

5 reference TSL 1401R and under the brand TAOS, Plano, Texas, USA.

The camera 21 must be associated with an optical lens 24 placed in front of the camera so as to focus the angle of the camera onto the region of the light spot. A filter may also advantageously be associated in such a way as to allow through rays at certain wavelengths and prevent the passage of rays at undesired wavelengths. For example, very hot liquids may produce radiations close to infrared, hence invisible to the naked eye, which it may be necessary to filter out in order to avoid saturation of the camera and/or measurement errors. A filter impermeable to infrared therefore eliminates these

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- 14radiations and retains only those emitted by the light-emitting means.

As shown in Figure 2, the device comprises a control unit 5, generally a microcontroller which as is known per se is customarily furnished with a microprocessor, input and output sections (I/O), a program memory and a memory for variable data.

The input of the microcontroller is coupled to an operating button 60 of the pushbutton type or equivalent for receiving an input signal for starting up the filling cycle. According to an advantage of the invention, a single operating button is sufficient for starting a cycle for different sizes of cups, for example, 25, 40 and 110 mL, and different types of drinks. The microcontroller possesses an output of the MOS type to the laser emission module 20 for dispatching a signal in the form of a pulsed mode to the laser. The laser emission module thus produces light pulsations at a frequency of around 50 to 500 Hz. The pulsed mode is preferred since it makes it possible to improve the processing of the incident signal and to differentiate the useful parts of the signal from the parts disturbed by exterior conditions, for example, on account of the characteristics of the cups (colours, shapes, patterns), steam, ambient brightness, etc.

The reception module or camera 21 is connected to an input of the microcontroller 5.

The signal produced by the camera is of the analogue type, since it involves values of light intensity, and is then converted into digital mode by an A/D converter integrated into the circuit of the microcontroller. The signal produces a distribution of the electric intensity over the photodiodes, in the form of a peak of intensity produced by the incident ray striking the row of photodiodes. This signal is analysed by the microcontroller which determines the photodiode(s) or pixels which produce the maximum electrical intensity. In pulsed laser mode, the processing unit of the microcontroller calculates, at the given frequency, in differential mode so as to be able to determine the maximum intensity by differencing two intensity measurements; one performed when the laser is on, the other when the laser is off.

On another output of the microcontroller, of the MOS type, a signal is dispatched to a relay 7 which commands the electrical activation of the filling means, namely, for example, a piston pump 8. It should be noted that the filling means may comprise

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- 15 various means such as liquid transport, bypass and/or stopping means. It may be a pump, gate(s), valve(s) or a combination of these means. The pump may be a piston pump, a diaphragm pump, a peristaltic pump or some other pump.

The way in which the device works will be described in conjunction with Figures 2 and

3. The user positions his cup in a stable manner in the service zone; that is to say, placed on the surface of the support 13 below the duct 11. When the laser is turned on, the user can orient the laser ray in such a way as to mark the internal edge of the cup corresponding to the level of fill that he desires. The orientation of the laser ray may be done in various ways. A preferred way is to orient modules 20, 21 jointly in rotation about the axis I so as to raise or lower the ray vertically in the cup according to the level desired. The marking is manifested as a small light spot of high intensity inside the cup. Once the marking has been carried out, a press on the operating button 60 allows a new filling cycle to commence. The microcontroller then dispatches an activation signal to the relay 7 which turns on the pump 8. The procedure for preparing (e.g., extracting or brewing) the drink can then commence.

As shown in Figure 3, the ray emitted 40 produces a light spot on the internal surface 30 of the cup. The position of the light spot 41 on the internal surface 30 of the cup returns an incident ray 42 towards the reception module 21, in this instance, the linear camera. For example, the incident ray 42 and the emitted ray 40 make an angle A dependent on the geometry of the surface of reflection. The position of impact 41 of the incident ray 42 on the camera is then stored in the form of an image vector by the microcontroller. The microcontroller determines which of the photodiodes produces the maximum electrical intensity; for example, photodiode No. 64, of the row of photodiodes No. 1 to

No. 128. When the fill is reached in the cup, the light spot moves upwards and towards the inside of the cup 43. The spot 43 reflected by the surface 31 of liquid and/or of froth produces a new incident ray 44 at an angle B different from A. When froth is produced, it is the upper surface of the froth which serves as reflecting surface. The new incident ray 44 is sensed by the linear camera 21; this is manifested as a change of the photodiode or of the group of photodiodes producing the maximum electrical energy intensity; which change corresponds to a change in the image vector. For example, the adjacent photodiode No. 65 now produces the maximum electrical intensity; which

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-16intensity is measured and associated with this pixel number. Since all the photodiodes are measured in one and the same time span, a distribution of the intensity is obtained in the form of an image vector. When the tolerance on the position measurement exceeds a certain predetermined threshold, in this instance manifested as a change of one or more variables in the image vector, the microcontroller despatches a signal to open the relay; this deactivates the pump and halts the filling of the cup. The actual stopping of filling, that is the actual flow of the liquid into the cup, is dependent on various factors, namely, in particular, the tolerance determined by the microcontroller on the variable or variables of the image vector, and the volume of liquid finishing flowing into the capsule which contains the ingredients and into the flow duct. It may therefore be important to define the lowest possible tolerance so as to limit the difference between the moment at which the light spot is reflected by the surface of liquid or the froth and the moment at which no more liquid flows from the machine.

A preferred but nonlimiting principle of detection and analysis of the signal will now be described in greater detail with reference to Figures 4 to 6.

Figure 4 shows a repetitive cycle of an algorithm for acquiring the image vectors in differential mode and determining the relevant variables related to these image vectors.

This cycle is customarily implemented independently by the system of the camera itself. Each sample image is captured consecutively with, then without the light beam. In a first step 100, the integration time, necessary for the charging of the capacitors of the pixels of the camera, is adjusted automatically as a function of the mean value of all the pixels, respectively of the maximum detected. This time during which the pixels are permitted to receive the light flux is chosen in such a way that no pixel is saturated. This integration value is independent of the frequency at which the result of the conversion is read. The frequency of flashing of the ray also depends on the value of the integration time.

Two successive images are used to extract the useful information. A second step 200 therefore consists in acquiring an image vector when the laser is in on mode and an image vector when the laser is in off mode. The image vector is more precisely a table of intensity values, corresponding to a distribution of the intensity produced by the row of

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- 17pixels.

In the next step 300, the camera calculates the differential image vector corresponding to the difference between the two image vectors previously acquired. This is what yields the data necessary for detection.

An exemplary differential image vector is illustrated in Figure 6. Several intensity values are then determined from this vector. The first value determined is the position of the maximum intensity (or peak) 450 expressed as pixel numbers and determined in step

400. The latter corresponds to the centre of the reflected light spot which corresponds to one or more pixels. Next, in the following step 500 we determine a second value which is a quality factor expressed in the form of a slope 410. To do this, the camera searches for the pixel 440 below the mean value during a test 510. This mean is simply calculated by (max value-min value)/2. Once this pixel 440 has been detected, the camera determines the first pixel 450 situated above the mean value 430 in step 520. The slope 410 is then extracted by the camera in step 530 as being the junction line between the edges of the pixels 440 and 450 situated on either side of the line of mean value. Thereafter, a virtual pixel (or sub-pixel) 460 is interpolated in step 600 with the aid of this slope. This virtual intermediate pixel is also used in the level detection calculations;

this makes it possible to improve the accuracy of detection while retaining the same resolution. The cycle of determining the differential image vector and the relevant variables is updated and repeated in a loop by the camera.

Figure 5 shows the control cycle conducted by the control unit 5 on the basis of the data and variables established during the cycle of Figure 4 and transmitted by the camera to the control unit. The camera prepares the differential image vector permanently and the device is in standby mode (step 110). The button is then activated by the user (step 120) so as to commence the extraction cycle for a drink; stated otherwise, the pump 8 is activated and a test can confirm the starting or halt the extraction cycle in progress (steps

130-140). At the start of the detection procedure, the position of the pixels of maximum intensity, the sub-pixel and the slope are stored variables taken as reference (step 150). These variables are obtained in the cycle of data acquisition by the camera, as illustrated in Figure 4. During extraction, at regular intervals (for example every 50 ms) the system

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- 18performs a read of the information emanating from the camera (step 160) and performs tests of comparison with the references (step 170). The tests consist in calculating and supervising, for example, the position of the maximum, the alterations in the slope and the value of the sub-pixel. The control unit 5 then stops the extraction by acting on the relay 7 when the variation of one or more variables with respect to the references reaches or exceeds a predetermined threshold of tolerance (step 180).

It will therefore be understood that the accuracy is increased, for the same resolution, by controlling the variation of several parameters (position of the intensity maximum, sub10 pixel and slope) related to the alterations in the intensity distribution produced by the incident ray striking the row of photodiodes.

It will be appreciated that the method of detection may be simplified and may consist merely in measuring and comparing just the values of maximum intensity without interpolation of a sub-pixel nor slope calculation; the detection of the fill level then being done only when the maximum intensity changes from one diode to another.

Figures 7 and 8 illustrate a second possible mode of a device of the invention which works according to a principle of propagation of ultrasonic waves. The device 2B comprises an ultrasonic wave emitter 20B disposed vertically plumb with the zone of placement of the cup 3 so as to produce waves 40B heading towards the surface 31 of the liquid. An ultrasonic receiver 21B for receiving the reflected waves 42B coming from the surface of the liquid in the cup, is disposed vertically plumb with the zone of placement of the cup. The receiver is slightly offset horizontally with respect to the

5 emitter, for example, on the opposite side with respect to the flow duct 11. A mechanical marking system 9 is provided on the side of the placement zone and as near as possible to the cup so as to allow the user to mark the desired level with the aid of a visual marking cursor 90 displaceable vertically with respect to a ruler scale 91.

In contradistinction to the previous mode, the marking is done externally. It is of course understood that the mechanical marking may also be replaced with a marker or light pointer of the laser type or the like; to mark the inside or the outside of the cup surface.

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- 19Figure 8 shows the principle of operation in conjunction with a control unit 50. The cursor system 9 is associated with a variable resistor 92 which makes it possible to modify the voltage emitted by the controller which recovers a variable voltage measurement as a function of the position of the cursor on the ruler scale. By calibration, the voltage value corresponds to a predetermined theoretical distance between the surface of the liquid and the wave receiver. This theoretical distance itself corresponds to the visual level indicated by the visual marking cursor 90.

The wave emitter 20B is coupled with the control unit in output mode so as to receive a 10 signal therefrom when the pushbutton 60 is activated. In input mode, the wave receiver informs the control unit of the alterations in the actual distance separating it from the liquid surface. When the liquid reaches or exceeds the level corresponding to the theoretical distance value, the control unit outputs a signal for cutting the relay 7 so as to halt the supply to the pump 8.

The invention may comprise other variants and combinations within the scope of the person skilled in the art without thereby departing from the framework of the invention defined by the claims which follow.

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