Device for determining a fluid pressure

Abstract

A hot beverage preparation device for household purposes with a pump for conveying preparation water, with fluid lines (4) for supplying preparation units with preparation water and with a sensor unit (1; 10) on a fluid line (4) for detecting a pressure state in the fluid line (4) is further developed in that the fluid line (4) is enclosed on more than four sides in a radial plane in the region of the sensor unit (1; 10).

Description

The invention relates to a hot beverage preparation device, in particular for household purposes, having a fluid system comprising at least one pump for conveying preparation water, fluid lines for supplying preparation aggregates of the preparation device such as a heater or a brewing chamber with preparation water, and a sensor unit on at least one fluid line for detecting a change in a flow state in the fluid line.EP 2 628 421 B1 describes an apparatus for preparing a beverage containing milk, having a conveying device which is designed for conveying the milk and comprises a conveying channel. In and / or on the conveying channel, a detection unit with a sensor is formed, with which a change in the fill and / or flow state in the conveying channel can be detected. The conveying channel has a flexible section. The sensor as an electromechanical sensor, for example in the form of a piezoelectric sensor, as a Hall sensor or as a load cell, is positioned in such a way that a change in position, expansion, pressure and / or shape of the flexible section(s) can be measured therewith in order to detect the change in the state of filling and / or flow in the conveying channel.It is an object of the invention to provide a sensor unit for detecting a brewing pressure in a hot beverage preparation device which is sufficiently sensitive to provide accurate values.This object is achieved according to the invention in the case of the hot beverage preparation device mentioned at the beginning in that the fluid line is enclosed on more than quadrilaterals in the region of the sensor unit. The enclosure of the fluid conduit aims at its periphery. The enclosure is thus located in a radial plane of the fluid line. The invention thus differs from contacting the fluid line in the region of the sensor unit on multiple sides, but only on four sides at most, as occasionally occurs in medical technology. This is because with only a quadrilateral, tangential contact on the fluid line, four corners remain into which the fluid line can expand under the influence of pressure without the pressure which brings about the expansion being able to be detected by sensors.With each further tangential enclosing side, a further corner is formed, which, however, covers a significantly small proportion of the circumference of the fluid line and offers a significantly smaller expansion depth. An increasing number of enclosing sides thus reduces the circumferential portions that may undesirably deform, and thus increases the accuracy of the pressure values that the sensor unit can detect.According to an advantageous embodiment of the invention, the fluid line can be substantially completely surrounded on the circumference in the region of the sensor unit. According to the invention, the enclosure can ideally be of annular configuration, such that it acts substantially over the entire length of the circumference of the fluid line. The invention thus differs from contacting the fluid line in the region of the sensor unit only tangentially or in partial sections. Rather, it follows the principle of enclosing the circumference of the fluid line practically over the full circumference, which does not exclude small gaps between enclosing elements. The complete enclosure prevents the cross section of the fluid line from widening as well as completely, so that no deformation of the fluid line is "lost", but can be detected on the sensor side.With an enclosure substantially along the entire circumference of the fluid line, the detection accuracy of the sensor unit increases considerably. This is because, in the event of a pressure change, the fluid line or its jacket cannot yield to the pressure, for example by deformation, in those circumferential sections in which the fluid line or its jacket is not surrounded. The sensor unit can thus detect pressure changes significantly more accurately. It can therefore provide for example in the case of a linear pressure change substantially better characteristic values for a force-pressure characteristic curve, namely likewise substantially linearly running characteristic values. This is because conventionally determined force-pressure characteristic curves are regularly subject to a non-linearity which is not negligible and which has to be corrected by correction factors.The above construction according to the invention comprising the sensor device and the fluid line provides a significantly lower nonlinearity. It simplifies later corrections or can even make them unnecessary, which compensates for material changes of the fluid line over time or drifts (namely slow changes of the output variable, which are not related to the input variable) and fluctuations of the measuring device. In the simplest case, namely with particularly reliable sensor values, instead of a curve with changing gradient values, a gradient line of the force-pressure characteristic curve can be obtained, which can be determined exclusively by two points. Ascertained slope rates and, if appropriate, correction factors are stored in the preparation device. By means of a software algorithm, the corrections for compensating the material changes, drifts and fluctuations can then be readjusted at regular intervals. For readjustment, almost pressureless system states can be used in the preparation device or system states with known pressures.According to a further advantageous embodiment of the invention, the sensor unit can directly enclose and contact the fluid line. For this purpose, it can comprise two shell elements which surround the fluid line almost completely on the circumference in a radial plane. The shell elements can be formed in the form of two mutually opposite, one-dimensionally curved half shells, the curvature and inner radius of which is matched to the outer radius of the fluid line. This results in a large-surface contact of the shell elements on the jacket of the fluid line. The two half shells thus surround the fluid line almost completely. They can leave only a minimal gap at their joints in order to offer a minimal movement space relative to one another. A sensor unit designed in this way leads to a very precise force-pressure characteristic curve.The shell elements can be formed integrally with the sensor unit. For this purpose, the two half-shell-shaped shell elements can be formed in a body of the sensor unit where the sensor unit contacts the circumference of the fluid line. The integral construction of the damage elements and the sensor unit leads to a simple construction. Alternatively, the shell elements can be formed as separate components of the sensor unit. They can then be adapted more precisely to a diameter of the fluid line and are replaceable.The sensor unit is preferably located in a cold water region of the fully automatic coffee machine in order to keep temperature influences low. The cold water region is usually located between the pump and the heater.The principle of the invention is thus based on enclosing the circumference of the fluid line within the sensor device virtually over its full circumference, in order to prevent the fluid line from "yielding" due to deformation in the event of a pressure change. The obstruction of the deformation of the fluid line leads to the measured values of the sensor unit not being adulterated. According to an advantageous embodiment of the invention, the fluid line can also be protected in a protected section against radial deformation, in particular against radial widening, at least in a section upstream and / or downstream, that is to say outside or beyond the sensor unit. The invention is therefore to be thought of the realization that a deformation of the fluid line outside the sensor unit can also impair the measurement values inside the sensor unit.According to a further advantageous embodiment of the invention, the fluid line can be surrounded, at least in the protected section, by an non-deformable or pressure-resistant protective tube. For this purpose, the actual fluid system, in particular the existing fluid line, does not need to be varied or removed. Rather, the non-deformable protective tube can optionally also be attached subsequently to or on the fluid line. As a result, conventional fluid systems can be equipped according to the invention and hot beverage preparation devices can be retrofitted in a favorable manner.According to an alternative embodiment of the invention, the wall of the fluid line can contain an non-deformable material as a supporting structure or consist entirely thereof at least in the protected section. The fluid line itself can thus be designed to be pressure-resistant. In fluid lines whose jacket contains non-deformable material, the jacket consists of a material which is deformable per se, such as PVC or rubber, and contains a woven fabric or lattice or a spiral of plastic, glass or carbon fiber or of metal which is embedded therein and which can also be attached to the jacket on the outside. The jacket can also consist entirely of these materials or similar materials, but can then have a greater wall thickness or be less flexible. By using a pressure-resistant fluid line, manufacturing steps for the protected section can be reduced because a single fluid line according to the invention can be installed instead of two components, namely the fluid line on the one hand and a protective tube on the other hand. The reduction to a single component also leads to savings in space.According to a further advantageous embodiment of the invention, the fluid line in the protected section can be under a radial compressive prestress. This prevents the non-prestressed fluid line or its jacket from expanding under the action of pressure only up to its load limit, before the pressure is passed on to the sensor unit. Conversely, the fluid line can expand again in the event of a subsequent pressure drop. In both cases, the change in tension in the jacket of the fluid line can "swallow" portions of the change in pressure. A factory compressive prestress of the initially pressureless fluid line in the protected section can anticipate such a potential deformation in order to make the sensor unit more sensitive to pressure changes.The substantially complete enclosure of the fluid line according to the invention thus protects and supports the fluid line, at least in its section within the sensor device, against undesired radial widening. In a simple embodiment, the fluid line itself can be designed and installed without prestress. Alternatively, according to a further advantageous embodiment of the invention, the fluid line can also be prestressed within the sensor device. As a result, manufacturing-related tolerance fluctuations, for example with regard to the diameter or the wall thickness of the fluid line, can be compensated. In addition, influences from creep of the material of the fluid line can be eliminated by subjecting the fluid line to a suitable prestress before its installation, advantageously a prestress which corresponds to the later prestress in the installation state.According to a further advantageous embodiment of the invention, the fluid line can also be designed to be pressure-resistant within the sensor device. The wall of the prestressed fluid line can for this purpose contain pressure-resistant material. The wall of the fluid line may comprise a support structure as described above to render the fluid line pressure resistant. Under a compressive prestress, the supporting structure can be relieved, so that it does not absorb any compressive forces from the fluid line. The remaining material of the wall, on the other hand, can offer a certain expansion space under the pressure load to be sensed. The compressive prestress of the fluid line which is designed to be pressure-resistant per se virtually deactivates the supporting structure, with the result that it does not take over any compressive load components under a compressive load of the fluid line which could otherwise escape the detection by the sensor unit.If there are no deformation losses of the fluid line or of its jacket, the sensor unit according to the invention additionally generates significantly higher force values which are sensed. Higher force values are helpful for improved resolution of a force-pressure characteristic curve determined by means of the sensor unit.If the compressive prestress of the fluid line deactivates its supporting structure, a fluid line which is not designed to be pressure-stable could also be installed in the region of the sensor unit, that without prestress. However, it would require additional coupling points between fluid line sections which are designed to be pressure-stable and not pressure-stable. The combination of a pressure-resistant fluid line on the one hand and a compressive prestress of the fluid line within the sensor on the other hand makes it possible to install a fluid line of the same type throughout, namely a pressure-resistant design, both upstream and also within and optionally downstream of the sensor unit. The compressive prestress for deactivating the supporting structure therefore has, according to the invention, a completely different function than in the prior art.According to the invention, the sensor unit can be equipped with two mutually opposite one-dimensionally curved half shells, the curvature and inner radius of which is matched to the outer radius of the fluid line. In principle, they can correspond to one another. According to a further advantageous embodiment of the invention, the inner diameter of the shell elements can be adapted with respect to the outer radius of the fluid line insofar as it can be smaller than that or can be dimensioned smaller. The mounting of the fluid line in the sensor unit then leads to a constraint of the fluid line, which causes its compressive prestress. This makes it possible to simplify the application of the compressive prestress of the fluid line in the sensor device.The sensor unit can in principle be of relatively simple construction, namely of one piece construction, whereby the fluid line is drawn in for applying the prestress while overcoming a certain deformation resistance of its casing. To facilitate the mounting of the fluid line under prestress, the sensor unit can also be formed in two parts or in multiple parts in an alternative embodiment of the invention. The prestress can then be applied by mounting at least two parts of the sensor unit to one another with circumferential confinement of the fluid line in such a way that a constraint of the fluid line arises.The shell elements as contact points for the fluid line can likewise be formed integrally with the sensor unit and thus directly thereon. The sensor unit can thereby offer a small number of parts, which can simplify its handling. In an alternative embodiment of the invention, the shell elements can also be formed separately. They can be designed specifically for simple assembly and / or can be dimensioned more precisely with respect to the dimensions of the fluid line. The sensor unit can thus also be adapted more easily to different diameters of different fluid lines.The principle of the invention is explained in greater detail below by way of example with reference to a drawing. In the drawing, the following are shown: FIG. 1 : a first embodiment of a sensor unit according to the invention, FIG. 2 : a second embodiment of the sensor unit according to the invention, FIG. 3 : two pressure-force characteristic curves.The first embodiment of a sensor unit according to the invention according to FIG. 1 is designed as a force sensor and especially as a type of fork-shaped load cell 1 made of metal with two prongs 2, 3 running parallel to one another. In a straight-line gap 6 between the prongs 2, 3, which takes up approximately two thirds of the transverse extent of the load cell 1 and is shown larger than necessary structurally for clarity, the fluid line 4 of a beverage preparation device is arranged. The fluid line 4 has an outer radius A. As the pressure in the fluid line 4 increases, it expands, so that the prongs 2, 3 in the fluid line 4 are spread relative to one another.The lower tine 3 serves as a substantially rigid abutment. The upper tine 2 is shaped so as to constitute a spring body, the geometry of which changes or deforms slightly under the action of the spreading force of the fluid line 4. On the upper side of the tine 2, a strain gauge 5 is attached, which detects the elastic deformation of the tine 2 to convert it into an electrical signal.At their free ends 7, the prongs 2, 3 have at their mutually facing surfaces at the gap 6 two cut-outs in the form of one-dimensionally curved half-shells 8. The half shells 8 have a curvature or inner radius I and almost completely enclose the fluid line 4 mounted in the load cell 1 on the outside. Only in the region of the gap 6 do insignificantly small sections of the jacket of the fluid line 4 remain uncovered. Thus, the fluid line 4 can yield to an increasing pressure as well as not due to non-detected deformation. Rather, their pressure-induced deformation is almost completely absorbed by the half shells 8 and is detected as deformation of the tine 2.The fluid line 4 is composed of an inner silicone tube 9 and an outer textile sleeve 11, which are connected to one another in a materially bonded manner. The casing 11 consists of an unstretched glass fibre fabric as a supporting structure, so that the fluid line 4 is pressure-stable even outside the load cell 1, and in order that the casing 11 inside the load cell 1 cannot absorb any compressive forces which could escape the detection by the load cell 1, the fluid line 4 is pressure-prestressed.The compressive prestress of the fluid line 4 is generated during its mounting in the load cell 1. For this purpose, the curvature or inner radius I of the half shells 8 is formed slightly smaller than the outer radius A of the fluid line 4; the fluid line 4 therefore experiences a peripheral constraint during its mounting in the load cell 1 and by the load cell 1 itself, which constraint gives its jacket made of the silicone tube 10 and the jacket 11 the prestress according to the invention.The fluid hose 4 is mounted in the load cell 1 by drawing the fluid hose 4 into the half shells 8, which must be overcome by a certain resistance to deformation of the fluid hose 4 which corresponds largely to the prestressing force on the fluid hose 4 within the load cell 1.The load cell 10 according to FIG. 2 offers easier assembly of the pressure-prestressed fluid line 4 thanks to its two-part structure: for this purpose, the prongs 2, 3 are formed separately from one another or separately and are braced with one another in a flexurally rigid manner on a shank section 12. The mounting of the prongs 2, 3 on the shaft section 12 takes place only when the fluid line 4 is positioned in the half shells 8.After the load cell 1, 10 has been installed in a hot beverage preparation device at the factory, it is calibrated as a force measuring device and optionally adjusted. A calibration or a calibration of the load cell 1, 10 to the fluid line 4 takes place with a pressure adjustment, for example, at a final test stand in production. Pressure-force characteristic curves are determined.Ascertained gradient values of the pressure-force characteristic curves and correction factors are stored in a control unit of the preparation device. By means of a software algorithm, material changes can thus be readjusted at regular intervals, for example, on account of aging, in particular of the fluid line, over time or drifts and fluctuations of the measuring device, that is to say of the load cell 1, 10. Readjustment can be carried out in the case of largely pressureless states or in the case of states with known pressures in the preparation device.FIG. 2 shows two exemplary pressure-force characteristic curves a, b. The abscissa shows the values for an internal pressure in the fluid line 4 in the unit "bar", the ordinate shows the force caused thereby and determined by the load cell 1, 10 in the unit "Newton". The dotted line c shows linearity with respect to both characteristic curves a, b starting from a value of 1 bar.The characteristic curve a arises from a conventional load cell according to the prior art. It shows a pronounced nonlinearity resulting from a lateral deflection of the pressurized fluid line which rests on parallel planar surfaces of the prongs in a conventional load cell. The nonlinearity requires storing numerous individual values for mapping characteristic curve a or storing correction factors.The characteristic curve b, on the other hand, arises due to a load cell 1, 10 according to the invention. Due to the almost complete enclosure of the fluid line 4, the expected linear relationship arises between an internal pressure in the fluid line 4 and the force in the load cell 1, 10 resulting therefrom and detectable. In the simplest case, the characteristic curve b can be specified exclusively by two points, which significantly simplifies the calibration.Since the preceding load cells 1, 10 and the fluid line 4 described in detail are exemplary embodiments, they can be modified to a great extent by the person skilled in the art in the usual manner without departing from the scope of the invention. In particular, the specific embodiments of the half shells 8 can also be carried out in a different form than in the one described here, for example separately. The fluid hose 4 can likewise be designed in another shape if this is necessary for space reasons or design reasons. Furthermore, the use of the indefinite article "a" or "an" does not exclude that the features in question can also be present multiple or multiple times.List of reference characters1 Load cell 2 upper prongs 3 lower prongs 4 fluid line 5 strain gauges 6 gap 7 free end 8 half shell 9 tube 10 load cell 11 casing 12 shank portion A outer radius I inner radius a, b pressure-force characteristic curves c of linear courseReferences included in the specificationThis list of documents cited by the applicant has been produced in an automated manner and is only included for the better information of the reader. The list is not part of the German patent application or utility model application. The DPMA does not take any adhesion for any faults or omissions.Patent Literature citedEP 2 628 421 B1

[0002]

Claims

Hot beverage preparation device for domestic purposes with a pump for conveying preparation water, with fluid lines (4) for supplying preparation aggregates with preparation water and with a sensor unit (1; 10) on a fluid line (4) for detecting a pressure state in the fluid line (4), characterised in that the fluid line (4) is enclosed more than quadrilateral in a radial plane in the region of the sensor unit (1; 10).Hot beverage preparation device according to claim 1, characterised in that the fluid line (4) is completely surrounded on the circumference.Hot beverage preparation device according to one of claims 1 or 2, characterised in that the sensor unit (2) comprises two shell elements (8) which surround the fluid line (4) on the circumferential side almost completely in a radial plane.Hot beverage preparation device according to one of the above claims, characterised in that the fluid line (4) is protected against radial widening in a protected section at least in a section upstream and / or downstream of the sensor unit (1; 10).Hot beverage preparation device according to claim 4, characterised in that the fluid line (4) is surrounded in the protected section by an non-deformable protective tubeHot beverage preparation device according to claim 4, characterised in that the wall of the fluid line (4) contains or consists of an non-deformable material (11) in the protected section.Hot beverage preparation device according to one of the above claims, characterised in that the fluid line (4) is under a radial prestress in the region of the sensor unit (1; 10).Hot beverage preparation device according to one of the above claims, characterised in that the fluid line (4) is protected against radial widening at least in the section inside the sensor device (1; 10).Hot beverage preparation device according to claim 7 or 8, characterised in that the fluid line (4) is pressure-resistant within the sensor device (1; 10).Hot beverage preparation device according to one of claims 3 to 9, characterised byan inner diameter (I) of the shell elements (8) which is smaller than the outer diameter (A) of the fluid line (4).

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