CA2295624A1 - Method and device for indicating the price and designation of an article on stands for goods - Google Patents

Abstract

The invention concerns a method and a device for indicating prices, designation of an article or similar types of information on supports for goods in departmental stores or warehouses. The device is characterised by a graphic display system comprising bistable image cells requiring energy supply only when the image content is modified. The display of the article designation together with its price and other types of information simplifies the installation of the device by establishing a reference between the number of the article to be labelled, the electronic label identification number and an identification number for the site of the article on its support, whereto are added the designation and the price of the article stored in a control unit by means of a mobile data acquiring apparatus, the whole forming a data set for the article. The display device placed on the goods support has an image zone consisting of parallel display channels connected to non-visible overflow channels. At least two contrasting fluids are delivered into the display channels by micro-pumps operating alternately, on the basis of the image content to be produced, the required image quality being ensured by a phase-locking circuit wherein are integrated the micro-pumps and the sensors.

Description

Apparatus and Method for Displaying Prices and Article Designations on Article Carriers The present invention relates to a device and a method for displaying prices, article designations and similar information on article carriers in department stores and warehouses with the aid of display devices, which are mounted on the article carriers, in electronic labels that are functionally connected to an external control center such that the control center can address an individual electronic label and transmit information to said electronic label.
Printed labels for marking articles with prices or similar information are subject to changes at irregular intervals. The manual efforts are considerable, and that is why electronic price displaying devices have been suggested and are known which use display devices which can display the price and similar information and can be changed by a control center.
What is required is an information transmission from a control center to the respective electronic label, as well as a power supply for the display device and a control unit in the electronic label. Since devices have first become known in which the information is guided from a control center and the power supply via cable connections and conducting lines to the electronic label (GB 1544005, GB
2083673), patent specification US 531569 suggests as an electronic label an independent functional unit which contains display device, control unit and power supply and which is directly or indirectly connected to the control center.
The information regarding article numbers and article price are stored (see also EP
0228 377) in variable registers in the electronic label, the contents of said registers being compared by a microprocessor forming the control unit in the electronic label, with the information received from the control center, and being optionally changed and displayed. The address of the label is defined by the article number stored in a register and can thus be changed as well.
In the operative state, all of these devices demand a constant supply of energy for ensuring a display, be it in the form of an installed battery, a solar cell or a wire-bound power supply. As a result, there are considerable disadvantages for such devices.
For instance, the operator of such a price-marking device cannot accept that batteries are replaced during the service life of the electronic label. The available area of the electronic labels defines the size of the solar cells. Wire-bound power supplies considerably limit flexibility. Therefore, the design of the electronic label as an independent functional unit with a power supply of its own limits the practical design of the display device to an LCD type, with numerical values regarding article prices and quantities being displayed, but the representation of texts has to be dispensed within the known types because of the amount of energy required for the display device. As a result, the installation efforts for the price-marking device are correspondingly high, demanding great care from the operating personnel.
Finally, the electronic label must be arranged with a logic address which is derived from the article number, near the article in question. Such an arrangement must also be obvious to a potential buyer of the article to such an extent that there is no confusion.
Such a clear relationship between the label and the article in question is only possible without any further aids when the article carriers are clearly organized, as is for instance the case with shelves. To establish a clear relationship between article and electronic label for the customer in view of the great variety of article carriers, additional paper stickers are often applied to the electronic label, bearing the names of the associated articles. Such a measure further increases the installation efforts.
DE - 196 48 937 suggests a display type which does not need additional energy for upholding the article information shown. If one proceeds on the assumption that the text of the article designation is hardly changed, one will obtain a more favorable energy balance on the whole. A disadvantage is that the arrangement of pixel-based heating and field electrodes effects a high density of conductors and a great number of connections to the control unit. In addition, the dissipation of the heating heat via the substrate again deteriorates the energy balance. It is here still unsettled how the installation efforts can be reduced if one leaves out of consideration that no paper stickers are required on the electronic label.
It is the object of the present invention to provide a device and a method for electronic article labeling of the above-mentioned type which uses numeric, alphanumeric or also graphic article information, suited for article labeling, which can be changed by a control center, is flexible as to installation, clear for the customer, does not require any energy for the display information and avoids the above mentioned drawbacks. This object is achieved according to the invention in that the electronic label has a graphic display device the special feature of which consists in energetically bistable, contrast-producing picture cells. The electronic label contains a receiving communication module which contains a ROM with a fixedly set unique label identification number and an address comparator for comparing the label identification number with the address signals of the external control center. In case of correspondence the picture contents is transmitted via a gate to the graphic display device. A mobile data acquisition device with a reading head for bar codes senses, for the installation of the device, an identification number arranged on the article carrier, an identification number arranged on the electronic label and the article number arranged on the article, the numbers being expediently in the form of bar codes, and transmits said information to the external control center. The graphic display device is designed as a fluidic system in that, in accordance with the picture contents, at least two fluids that differ in contrast are conveyed in a meander-like channel, said meander consisting of vertical or horizontal viewing channels extending parallel and of overflow channels connecting the viewing channels. If a change in picture contents is needed, the old picture contents will be displaced by the new picture contents and pushed into a separator at the outputs of which the demixed fluids are again available to the respective micropumps. The fluidic system is thus closed. The two fluids can be demixed at different specific weights by the action of gravity. In another embodiment of the invention, a magnetically conductive fluid is used and demixing is carried out by the action of a magnetic field. The necessary precision of the dosage of the two fluids by the micropumps is achieved by providing a measurement channel which determines the flow rate of the fluid by optically acting sensors and controls the delivery rate of the micropumps with the result. Preferably, the whole control of the pumping capacity is performed as a phase-locked loop, with contrast changes which are provided for synchronising the pumping capacity with the transmission rate of the picture contents being inserted, at constant intervals, into the picture contents transmitted by the control center. The whole fluidic system is introduced into a basic body of 100-oriented silicon wafers by anisotropic etching. This leads to v-shaped channels having precise, reproducible cross-sections. The basic body with its channels is covered by an anodically bonded glass or silicon cover layer.
The two micropumps have rectangular pump chambers. The cover layer acts as a membrane which together with an adhesivily attached silicon plate forms a bimorph. In using different dynamic flow resistances in the inlet and outlet to the pump chamber, a resulting volume flow of the fluid is created upon a sawtooth-shaped control of the piezoelectric plates. Further sensors are provided in the outlets from the pump chamber to the mixer to prevent a back-flow of fluid into the pump which is inactive with respect to picture build-up, by way of a counter control. The whole fluidic system is filled through a special filling opening which expediently ends in the mixer for the different fluid flows. Electronic label, control center and the mobile data acquisition device are expediently connected by wireless transmission channels.
In an embodiment the fluidic system is accommodated in a basic body made of plastic material. At the same time the corresponding microstructures of the pump chambers and of the meander-shaped channels are worked into a plastic plate.
Thus the overflow channels of the meander as well as the inlet and outlet lines to the mixer and the measuring channel can be advantageously rounded off. By virtue of this the resistance to the flow of the fluid will be reduced. Moreover, channel transitions and channel connections having different cross-sections have narrowing or widening tapered constructions and also improve the flow conditions of the fluid.
The meander has horizontal viewing channels and accordingly requires a smaller number of channel transitions.

In a further embodiment the horizontal viewing channels are formed by two or more meander systems, which, however, are connected to a common depot or separator.
In the case of this embodiment separately adjustable multi-cell display fields can be realised. In case of changes, e.g. of only one line of the picture contents the picture contents of this meander only is changed, whereas the picture contents of the other lines is retained. Thus the energy required to change the picture contents can be reduced.
In an advantageous development of the device the viewing channels of the meander are covered with a screen. In this case the vertical webs of the screen cover the edge region of the visible sign pixel. With this screen, which appropriately is a metal screen, the residual inaccuracies of the positioned sign pixels are masked.
Consequently a picture or sign having a sharp contrast and contour is presented.
The screen takes care also of the guiding of the light exit of a rear reflection wall or of other light sources. If the base body is made of plastic material the screen also acts as a bimorph for the micropumps.
In a further development of the device behind the metal screen a reflection foil with fluorescent occlusions is provided, which emits the concentrated incident surrounding light on to the visible display surface and in this manner ensures an effective contrast-improving background lighting.
In a further construction instead of the reflection foil a light guiding body with diffusing centres made of fluorescent material is provided, which emits again the surrounding light falling on the front plate on to special optical surfaces and thus represents a background lighting without the supply of energy.
Furthermore, the object is achieved by using the above described device and a method in which the article number of the article which is read with the aid of a mobile data acquisition device is linked with the ID number of the electronic label, which is arranged in direct vicinity of the article, as an integrated system of article data that is transmitted to the control center and there supplemented with the price and the article designation. Derived from this centrally stored integrated system of article data is the picture contents for the display devices on the electronic labels, but also information for data cash registers or storeroom management in the sense of an integrated article management, which also includes the salesroom.
To explain the gist of the invention, it must be shown which integrated system of article data must be produced by linking various data so that an article management, including the salesroom, is possible.
It is assumed in the case of the known price-marking devices that in the control center there is an assignment of the article, characterised by an article number, to an article price and that such a link must be transmitted to the electronic label provided near the respective article. By the way, the same link is transmitted in salesrooms together with the article designation to electronic data cash registers and is available as so-called PLU (Price Look Up) table when during the selling operation the article is identified and the article price and article name are displayed for the customer or are printed. One of the advantages of such integrated article managing systems is that in the case of a centrally performed change, for instance, in the article price, the current price is identically displayed and charged both on the electronic label arranged near the article and at the customer display of the data cash register. The disadvantages of the known price-marking devices are that the automatic link only regards the article price with the article number; other links must be established manually and thus under efforts. This is, in particular, true when some transparency is to be guaranteed for the customer as to which electronic label is assigned to which article that is positioned nearby.
If one assumes that the control center already possesses a linked data set of article number, article designation and article price, it seems expedient to transmit the article designation also electronically to the electronic label and to display the same. The transparency required by the customer in assigning the article to the electronic label is thereby guaranteed without, for instance, an additional paper sticker having to be produced.

At the same time, such a procedure opens up an improved possibility of installing the price-marking device such that an electronic label is assigned to the article in question at the location of the article. It is here also necessary that after the electronic label has been assigned to the article the article designation should be represented as confirmation in plain text on the electronic label. This achieves a maximum degree of flexibility; mistakes made during installation are immediately corrected; the arrangement of the articles can also be optimised on site with respect to an optimum use of the available article carrier.
In the course of a further automatization of the article managing system, specifically also in the salesrooms, it will probably happen that the relatively expensive selling areas are also administered and managed. This means that the potential storage areas for articles on the article carriers must be encoded and described in a virtual salesroom. This increases the number of data to be linked by a further data group which describes the locations) of the articles. It seems expedient to enlarge the integrated system of article data by data regarding the location of the articles in the salesrooms.
Acquisition and reference formation of the individual data groups also pose a problem that can best be solved on site, i.e. at the place of the article, by entering a code on the article carrier which can be sensed with the same mobile data acquisition device.
The above-described organisational principles can only be realized with one type of display device in the electronic label that is novel in its technical implementation.
What is required is a combination of an at least alphanumeric, better also graphic display with a particularly low energy consumption. Standard display devices having a low energy consumption are LCD devices. Depending on the respective extent of the display, the power consumption is 50 ... 100 (W. When there is a restriction to numeric (7 segment) characters for displaying the article price and to a few special characters of a fixed structure, a power consumption of less than 20 (W can be expected. The power consumption of the microprocessor which is provided in the control device and is constantly needed for refreshing the displayed information is here not taken into account.
Statistically, a change in the price of an article is not needed more often than once a day. Hence, a minimum energy amount of 0.72 Ws is needed between two article price changes. Such an energy requirement is multiplied several times over when alphanumeric characters are to be displayed in a pixel structure with multiplex control. These facts show that there is a close connection between an improvement in the organisational structure of a price or article marking device and the availability of a display device which is optimally suited for such a purpose.
An important element of solution is the use of a display device which in the periods between changes to be expected in the displayed information does not require any energy supply for maintaining the information displayed, irrespective of whether the information is of a numeric, alphanumeric or graphic kind. To preserve the picture contents also independently of an external energy supply, visually analysable contrast values of picture cells must be established as an energetically stable state.
At least two different contrast values are required as energetically stable states, the transition from one state into the other state being achieved by a selective addition of energy. The necessity of supplying energy to pass from one state into the other one follows from the demand that over time there should be no drifting from one state into the other one; hence, the at least two energetically stable states of the picture cell must embody a low energy state.
Picture cells of such a type are known in many forms in the technical field, for instance, a leaf spring clamped at two sides and including a light deflection mirror which by the introduction of a force moves into a second stable position, or also materials which upon heating and the application of an electric field can be changed between two stages in their optical characteristics.
However, for a technical implementation of the principle, it should be borne in mind that a selective supply of energy for increasing the energy state of a picture cell also requires means for a selective energy supply. In view of the necessarily high number of picture cells, the means for the energy supply might have a complicated structure. This will become apparent from an example. For the representation of an article name on an electronic label within an article-marking device, 16 alphanumeric characters are at least needed. The readable representation of said characters in a so-called star-burst configuration (14 area elements per character) yield a total of 224 area elements to which energy must be supplied, for instance, via electric conductors. In addition, there is a further electrode structure, for instance, for the introduction of an electric field for changing the position of the optically active molecules. Even in the case of a matrix-like wiring of conductors and electrodes, one obtains an expensive structure that is difficult to produce. More advantageous is an increase in energy acting on all of the picture cells at the same time, for instance, by heating the whole device, and the mere selective introduction of the direction of the change in state. However, an increase in energy by heat seems to pose problems if one bears in mind that an undesired dissipation of heat is unavoidable and energy sources which are scarce at any rate are used.
In a consequent implementation of the above ideas, a display device which achieves the object of the present invention in an optimum manner is seen in that the energy level is increased by introducing a kinetic energy on all display volume elements which carry the area elements that are of relevance to the display.
The amount of such a kinetic energy can be small when these picture cells are equipped with minimum volumes or masses and when there are only slight frictional losses during their movement. An advantageous design consists in designing said volume elements as part of a liquid column which move in a closed channel arrangement.
The idea underlying the invention shall now be explained in the following description with reference to an embodiment which is illustrated in more detail in the drawings, in which:

Fig. 1 is a front view of a known electronic label;
Fig. 2 shows how an integrated system of article data is produced in known electronic price-marking devices;
Fig. 3 is a front view of the electronic label according to the invention;
Fig. 4 shows how an enlarged integrated system of article data is produced in the device of the invention for article labeling;
Fig. 5 is a simple block diagram showing the transmission channel between the control center and the electronic label;
Fig. 6 shows the structure of the data word transmitted to the electronic label, Fig. 7 shows the structure of the fluidic arrangement;
Fig. 8 is an enlarged view showing the structure of the display area of the display device;
Fig. 9 shows a scheme of the control circuit in the signal converter;
Fig. 10 shows the course of the communication signal;
Fig. 11a is a cross-section through the overflow channel according to Fig. 8;
Fig. 11 b is a cross-section through the viewing channel according to Fig. 8;
Fig. 12a is a cross-section through the micropump according to Fig. 7;
Fig. 12b is a top view on a pump chamber;

Fig. 13a is a schematic illustration of the mixer in the active state of pump P1;
Fig. 13b is a schematic illustration of the mixer in the active state of pump P2;
Fig. 14a is a top view showing the construction of the electronic label;
Fig. 14b shows the construction of the electronic label in section A-A.
Fig. 15 is a front view of a two-line electronic label according to Fig. 3;
Fig. 16 shows the structural construction of the device with a meander having horizontal viewing channels;
Fig. 16a shows the structural construction of the device with two meanders provided according to Fig. 16;
Fig. 17 is the cross-section according to Fig. 16;
Fig. 18 is the enlarged illustration of the device with a screen provided in the region of the viewing channels;
Fig. 19 is the enlarged illustration according to Fig. 18 with tapered channel transitions;
Fig. 20a is the enlarged illustration of the measuring channel according to Figs. 18 and 19;
Fig. 20b is the enlarged illustration of the measuring channel according to Figs. 18 and 19 with modified fluid columns;
Fig. 21 shows the cross-section in the region of the measuring channel according to Figs. 20a and 20b.

Known electronic labels 1, as are shown in Fig. 1, include a numeric display device 8 which displays the article price 23 with the aid of a plurality of 7-segment characters 88. The layout of the display device 8 may vary in accordance with the actual applications. For instance, there are known different numbers of digits and separate numerical display areas for quantity prices. The use of special flags 52 for representing information fixedly set by the masking of the display device 8 is also known and supports the organisation of the electronic price-marking device. In the example the electronic label 1 is supplied with power by a solar cell 17.
As shown in Fig. 2, the electronic label 1 is secured to the article carrier 4 near the article 42 to be labeled. As a rule, the article 42 is provided with a labeling tag 43 which normally contains at least one printed article number 45 for clearly identifying the article 42 as well as an "article" bar code 46 in modern article managing systems.
To change the price mark 88 upon a change in the article price 23 arising during article management, the electronic label 1 which is located near the article 42 on the article carrier 4 must be addressed. To this end, during an installation operation, each electronic label 1 is given an address which is stored in register 82.
This address is logically identical with the article number 24 so that a definite information transmission can be performed by the control center 20 via the transmitter antenna 29 to the receiver sensor 18. In the electronic label 1, the information received is supplied via a receiver amplifier 86 to comparison registers 83 and 85. A microprocessor 81 makes a comparison between the contents of the comparison registers 83 and 85 and upon a correct addressing of the respective electronic label 1 makes a change in the price mark 88 if the article price information 23 in register 85 differs from the article price information in register 84.
The article price 23 which is assigned to the article number 24 in the article management system 21 is logically imaged in the form of an image A2 into the register 84.
The efforts taken become apparent during installation. A reference R2 must be established between the label 1, which is per se neutral, and the article 42.
Such a reference is established in that the corresponding article number 24 of the article 42 is transmitted by the control center 20 into the register 82 for the article number. The article number 23 is logically imaged A1 from the article management system 21 into the register 82 of the electronic label 1. The electronic label 1 must subsequently be mounted on the article carrier 4 near the article 42, identified by the same article number 45 and bar code 46, respectively. For a customer who wishes to acquire an article 42 labeled in this manner and who takes the price mark 88 on the electronic label 1 as a reference, a clear relationship R1 must be established to avoid any misunderstandings. With the great number of articles 42 offered and the great number of possible article carriers 4, reference R1 cannot always be established in an unambiguous manner through a geometrical relationship. To establish a definite relationship R1, a name tag 7 must normally be arranged on the electronic label 1, the tag being produced by a special printer 6 and being secured to an assigned place on the electronic label 1. The contents of the name tag 7 is derived from the article designation 23' stored in the article management unit 21.
This process of printing and attaching the name tag 7 represents a further imaging A3 of a virtual image 27 of the real conditions on the article carrier 4 with its price-marked articles 42 in the article management unit 21.
A basic change in the logic of an electronic price-marking device is achieved by a type of electronic label 1 as is shown in Fig. 3. In contrast to the embodiment shown in Fig. 1, use is made of a display device 2 which with respect to the picture contents 5 to be represented is of a universal type for the article designation, i.e.
permits numeric, alphanumeric and also graphic information. Hence, the critical reference R1 according to Fig. 2 can be replaced by an automated relationship in that not only the article price 23, but also the article designation 22 is imaged from the article management unit 21 onto the display device 2 of the electronic label 1.
For the buyer of article 42 a clear relation is thereby established between the article 42 with the article designation tag 43 and the electronic label 1. It is assumed during installation of the electronic label 1 that the references R1 and R4 to be established (see Fig. 4) are meant to assign the article 42 to a specific electronic label 1 in the real salesroom on the article carrier 4. The person in charge of the installation will there get an optimum view of the real space available on the article carrier 4 and of the optimum arrangement of the articles 42, also under sales-promoting and esthetic aspects. To this end, there is provided a mobile data acquisition device 30 which establishes a reference between the unmistakable ID
number label 25 and the article 42 in question. This reference is stored in registers 34 and 35 and imaged in the article management unit 21. In principle, it is possible to extend this reference by another reference by adding the ID number 26 of the article carrier 4. To this end, the ID number of the article carrier 26 is read from the article carrier ID tag 41 with the aid of the mobile data acquisition device 30, is stored in the register 36 and transmitted together with the article number 24 from the register 34 and the ID number label 25 from the register 35 to the article management unit 21 via the transmitting module 37 and the transmitting antenna 38 provided on the mobile data acquisition device 30.
It is expedient when the ID number 26 is read on the article carrier 4 from an article carrier ID tag 41 as a bar code, similar to the article bar code 46, by the mobile data acquisition device 30 with the aid of the decoder bar code 32 and the reading head for bar code 39 to avoid different principles of recognition. In the same manner, the ID number label 25 can also be read in that a label ID tag 10 on which the ID
number label 25 is stored in the form of a bar code is provided on the electronic label 1. The ID number label 25 is also stored in an ID number ROM 11. Both numbers on the label ID tag 10 and in the ID number ROM 11 are memorized in an unmistakable and invariable manner within the manufacturing process of the electronic label 1.
In imaging A4 (Fig. 4) the reference between the article number 24 of the article 42 on the article carrier 4 with the ID number article carrier 26 and the ID
number label 25 into the article management unit 21, a further reference is established via the article number 24 with the article designation 22 and the article price 23, so that on the whole an integrated system 27 of article data is created with five linked references, with the system, so to speak, representing a virtual image of the situation prevailing in the salesroom. An imaging A5 into the display device 2 of the electronic label 1 just serves to inform the customer about article designation 22, article price 23 and possibly further facts displayed by special flags 52.
In contrast to the device illustrated in Figs. 1 and 2 and the comparison made there between register contents 82, 83 84, 85, no information is processed in the electronic labels 1 according to Figs. 3 and 4.
As shown in Fig. 5, upon receipt of the communication signal Salt) emitted by the control center 20 via antenna 29, a preamplification 14 and a demodulation 15 take place with the aid of sensor 18. The picture contents 5 is directly transmitted as a modulation (a(t) of a signal carrier. A gate 13 will be opened when the address signals contained in the transmitting signal of the control center 20 are identical with the ID number label 25, stored in the ID number ROM 11 of the corresponding electronic label 1. A signal converter 16 directly converts the communication signal Salt) and the picture contents function (a(t) respectively, of the control center 20 into the flow rate function (~ (t) and (2(t) as is needed for representing the picture contents on the display device 2. The modulation has the character of a pulse length modulation.
The electronic label 1 is addressed by an address information which is inserted at the beginning of the data flow between control center 20 and electronic label 1. This results in a data record structure as shown in Fig. 6. After an address preamble 100 received for synchronising the demodulator 15, the label address 101 is safely arranged with a CRC control sign 102. The synchronisation preamble 103 is subsequently transmitted for the channel structure of the display device 2, and then the picture contents function (a(t) 104 proper. The transmission is completed with a switch-off signal 105.
The display device 2 just needs energy for the period during which the picture contents function (a(t) is converted into the flow rate function (~(t) and (2(t), i.e. for the period when the picture contents 5 is transmitted.
The necessity of an energy supply in case that no new picture contents 5 is transmitted is reduced to the energy required by the communication module 19.
An embodiment of a display device 2 of the above-described type is schematically depicted in Fig. 7. Two micropumps 77 and 78 convey two different types of fluids 56 and 57 with different colors, e.g. black and white, in a meander-like channel arrangement 50. The two fluids 56 and 57 are alternately combined at mixer 70 and then pass via the inlet opening 49 into the meander 50. The meander 50 forms a matrix-like picture field 3, i.e. the picture contents 5 to be represented is formed by longitudinal modulation of the one fluid 56 over the other fluid 57. Contrast changes take place between the two fluids 56 and 57 in the direction from the contrast of fluid 56 to 57 or from 57 to 56. Upon change in the picture contents, the modulated types of fluids are pushed through the outlet 54 of the channel arrangement into a separator 55 in which the two types of fluids are separately supplied to the respective micropump 77 or 78. The device is energetically stable in this respect because a closed channel arrangement is here concerned in which, when the micropumps 77 and 78 are switched off, a pressure compensation takes place and a further movement of the fluids 56 and 57 is not possible.
The use of a longitudinal modulation for producing the picture contents 5 is also possible with the modulation of the communication signal Salt) from the control center 20 to the electronic label 1, so that, as shown in Fig. 5, one obtains a very simple structure of the control of the display device 2 which consists essentially of a communication module 19, a signal converter 16 and a picture field 3.
Character generators are implemented in the stationary control center 20; the flexibility of the picture contents 5 of the display device 2 is substantially defined by the achievable resolution of the channel density of the meander 50 and the steepness of the contrast change and the offset thereof between fluid 56 and fluid 57.

For achieving a representation of the picture contents 5 of the display device 2 in a suitable quality, it is important that the contrast changes 56 to 57 or 57 to 56 be shifted in a sufficiently accurate position into the meander 50.
Fig. 8 is a detailed view of the meander 50 shown under the special aspect of the accuracy to be achieved in the individual channels 51 and 53 of the meander 50. As shown in Figs. 11 a, 11 b and 12a, a '100'-oriented silicon wafer into which the channel structures 51, 53 are introduced by anisotropic etching and which is covered by a glass cover layer 66 is used as the basic body 65 for the meander 50.
The advantage is that the channels 51 and 53 can be produced with a very high accuracy by using said manufacturing method. In the embodiment, width bs of the viewing channels 51 is to be 0.4 mm. Due to the position of the crystal plane exposed by anisotropic etching, one obtains an area of the channel cross-section of the viewing channels 51 of AP = 0.057 mm2. By contrast, the distance as of the channels 51 from center to center is 0.5 mm, so that in this embodiment a resolution in x-direction with 2 lines/mm is obtained. By contrast, the resolution in y-direction follows from the accuracy of the dosage of the two differently colored fluids 56 and 57. The resulting lengths of the two fluids 56 and 57 in the meander 50 are described by the picture contents function (a(t) which, at the same time, is an expression of the picture contents 5. In the described embodiment, dosage accuracies of adjoining viewing channels 51 of (<0.02 mm are obtained. The picture cells 75 which are formed by pulse length control and which the picture contents (a(t) is composed of have a size of 0.4 * 0.5 mm2 in the case of a strictly matrix-like arrangement of the cells, these dimensions being determined on the basis of the width bs of the viewing channels 51 and the length Ip the control software in the control unit 20. Therefore, it is also possible for an improved picture quality to control the length IP of the picture cell 75 not in the multiple of the matrix distance aS, but analogously with a variable and freely selectable length Ip. The accuracy (< 0.02 mm is achieved by an exactly controlled dosage device as part of the signal converter 16. To this end, the flow rate of the fluid 55, 56 in the meander 50 is exactly controlled in the present embodiment to achieve a definite relation between the frequency of the communication signal Salt) and the length Ip of the picture cells 75.
The speed of the fluid 55, 56 is determined by determining the travel time tk in a measurement channel 48 from the sensor 73 to the sensor 74 for a specific contrast change 62 or 63 which exists between the two fluid types 55, 56. The measurement channel 48 may here be identical with the first viewing channel 51 of the meander 50. The sensors 73, 74 are preferably optical sensors which can register the contrast change 62, 63 between the two fluid types 56 and 57 because of their spectral sensitivity. The sensors 73 and 74 are mounted on the glass cover layer 66 and recognize the contrast changes 94, 95.
The corresponding sensor 74 is expediently arranged directly after the first viewing channel 51; the sensor 73 directly in front of the first viewing channel 51.
It is also expedient that the cross-section of the overflow channel 53 is smaller than the cross-section of the viewing channel 51. This results in a stronger resolution of an error (p of the picture cells 75 in adjacent viewing channels 51 in the overflow channels 53 during measurement of the synchronisation contrast changes 94 and 95, respectively, for the sensor 74; the control deviation thus becomes smaller on the whole.
When these overflow channels 53, for instance, are designed with a width of 0.05 mm and when a resolution of the optical sensors 73 and 74 of 0.125 mm is started from, this results in a measurement error of ((0 005 per viewing channel 51, which error may add up in an extreme case to an offset of 0.8 mm in the case of a total of 160 viewing channels 51 according to a length of 80 mm of the display range.
Such a value is acceptable.
The travel times tk which have been determined by the sensor 74 have an effect on a phase-locked loop, which is shown in Fig. 9. To achieve a coarse synchronisation of the power of the micropumps 77 and 78 with the communication signal Sa(t), the communication signal Salt) contains eight alternating synchronisation contrast changes 94 and 95 at a time interval which when the desired speed of the fluid 56, 57 is reached corresponds to the travel time tk between the sensor 73 and 74.
However, since the speed of the fluid 56 and 57 is very unlikely to be identical with the desired speed at the beginning of the renewal process of the picture contents -due to the delivery rate of the micropumps 77 and 78, one obtains a phase difference (a(t) of the synchronisation contrast change 94 or 95 as determined at the sensor 74, with respect to the corresponding flank of the communication signal.
Sa(t). In the easiest case this difference is obtained in a phase comparator 90 from the multiplication of the signal Salt) with the signal determined by sensor 74. The phase difference signal (a(t) is amplified, filtered with a low-pass filter 92 and influences the amplitude of the pump control pulses p ~ (t). The amplitude of the pump control pulses p~~(t) or p~2(t), in turn, influences the flow rates (~(t) and (2(t) in a manner that upon the next synchronization contrast change 94 and 95, respectively, the phase difference signal (a(t) becomes smaller, the signal being determined from the difference of the flanks of the communication signal Salt) with the signal S~4(t) registered by the sensor 74. In the manner of a phase-locked loop, the phase position is locked between the communication signal Salt) and the sensor signal S~4(t).
Since the pumping capacity of not only one, but of both micropumps 77 and 78 must be adjusted to the required flow rates (~ (t) and (2(t), the direction of the synchronization contrast change 94 or 95 is also evaluated and the amplitude of the micropump 77 or 78 is influenced.
Depending on the time constant of the low-pass filter 92, the operation is terminated after several, for instance, 8 synchronization contrast changes 94 and 95. Following a complete change in the picture contents of the display device, these synchronization contrast changes 94 and 95 are pushed into the separator 55, so that these contrast changes used for the initial synchronization of the pumping capacity of the micropumps 77 and 78 are not visible.
Upon completion of the starting synchronization operation, the real transmission of the picture contents function (a(t) is performed by the control center 20.
Further contrast changes 62 and 63 that carry the picture contents 5 are thus produced by the alternating control of the micropumps 77 and 78.
To obtain a sufficiently accurate synchronization of the pumping capacity for the whole duration of signal Sa(t), further synchronization contrast changes 94 or 95 of a specific direction are inserted into the communication signal Sa(t), the function of said changes solely consisting in ensuring a proper operation of the phase-locked loop shown in Fig. 9. Together with the synchronisation contrast changes 94 and 59 during the synchronisation operation, they form a quite specific, constant basic frequency in the communication signal Salt) to which the phase-locked loop is locked for the whole duration during which the picture contents or the picture contents function (a(t) is being changed. Upon completion of the process of changing the picture contents 5, the synchronisation contrast changes 94 and which are only needed for synchronisation are in the overflow channels 53 (Fig. 7) which are covered by a picture field cover 76 and are thus not visible. To provide a corresponding control range, the volume of the overflow channels 53 exactly corresponds to two picture cells 75. Hence, if one assumes that the picture cells 75 of a viewing channel 51 are filled within 1 sec in the embodiment, the admissible drift of the pumping capacity is 1 %/sec, a value which is achievable in a realistic manner.
Since the direction of the contrast changes 94 and 95 is derived in a predetermined manner from the synchronisation frequency fs = 1/TS, further so-called follow-up contrast changes 95, 97 must be inserted upon demand, depending on the color or fluid 56 or 57 with which the last picture cell 75 in the viewing channel 51 or the next picture cell 75 in the subsequent viewing channel 51 follows. If needed, these follow-up contrast changes 96, 97 are also in the overflow channels 53 when the change in picture contents 5 has been completed, and are thus covered.
A general view of the signal curves Salt) and (a(t) is shown in Fig. 10.
The mode of operation of the two micropumps 77 and 78 is explained in more detail in Figs. 12a and b. Expediently, the micropumps 77, 78, just like the viewing channels 51 and the overflow channels 53, are introduced by anisotropic etching into a 100-oriented silicon as the joint basic body 65. The feed channels 58 and the outlet channel 69 offer different dynamic flow resistances at an approximately identical total cross-section. The pump chamber 67 into which the feed channels 68 end and from which the outlet channel 69 extends has an approximately square surface. Together with the glass cover layer 66, one obtains a chamber 67 which is acted upon by a piezoelectric plate 64. The piezoelectric plate 64 is firmly connected to the glass cover layer 66 at one side, so that upon application of the pump control pulses p~ (t) to the electrodes of the piezoelectric plate 64 the piezoelectric plates 64 is curved together with the glass cover layer 66 in the manner of a bimorph.
As a result, a pressure pulse is generated in the pump chamber 67. When sawtooth-like pump control pulses p~(t) are used for the piezoelectric plate 64, the pressure pulse in the pump chamber 67 is also approximately sawtooth-shaped. Due to the different geometry of the feed channels 68 and the outlet channel 59, a transition of the laminar flow of the fluid 56, 57 into a turbulent flow is achieved at different times, so that a resulting volume flow of the fluid 56, 57 takes place in one preferred direction across the entire sawtooth-shaped pump control pulse p~~t). The delivery rate of the fluid 56, 57 is controlled via the amplitude (the frequency would also be possible) of the pump control pulse p~ (t).
The micropumps 77, 78 used in the embodiment produce a volume output (~(t) and (2~t) of 150 pl per control pulse; 150 (I are conveyed in a second. As follows from these values, a pump stroke effects a vertical offset of picture cell 75 in the viewing channel 51 of 0.01 mm. Hence, the resolution which can be achieved by pump strokes must be sufficiently great if one bears in mind that about 5 pump strokes are needed to control an offset of 0.05 mm between picture cells 75 of adjoining viewing channels 51. Another approach regards the time for changing the picture contents 5 of the entire display device 2. In the micropump 77, 78 of a supposedly identical capacity, 1.92 min are needed therefor, i.e. a time which is sufficient for the intended application.
Due to the type of the micropumps 77, 78 as are here described, the micropump 77, 78 just offers a slight resistance at low flow resistances of the fluid 56, 57 because of the absence of statically acting valves. An exact function of the alternating dosage of the two fluids 56, 57 presupposes that the fluid flow is absolutely blocked by the micropump 78 when, for instance, the micropump 77, is to convey fluid. On account of the errors to be observed, the use of static valves is not recommended. Two additional control circuits which are formed from the sensor 71 together with the micropump 77, and the sensor 72 and the micropump 78 are introduced as a substitute for static valves. In fact, when the micropump 77 conveys fluid, the fluid 56, as shown in Fig. 13a, is pressed not only in the direction of the meander 50, but also in the direction of the micropump 78. To avoid a situation where a great dosage error arises as a result thereof or the fluid 56 even passes into the micropump 78, the micropump 78 is activated as soon as a contrast change 62 has been registered by the sensor 72, until the contrast change 63 is measured at the sensor 72. This results in a control oscillation at the place of the sensor 72, which is triggered by the postcontrol of the micropump 78. The control oscillation can be kept small in a known manner by an optimum dimensioning of the control circuit, consisting of micropump 78, sensor 72 and signal amplifiers, so that this control circuit in the accuracy range considered, so to speak, operates like a precise static valve. Fig. 13 b shows a reversal of the function in case the micropump 78 has been ordered to proportion the fluid 57 for the meander 50. Upon switching of the one micropump 77, 78 to the other one, a small systematic error is created, which corresponds to the channel volume of the mixer region 70. The error can be kept sufficiently small or can be compensated by small cross-sections of the channels and by the insertion of a further sensor 73.

Upon completion of the process for inserting the two-colored fluid 56, 57 into the meander 50, the energy supply can be switched off for an arbitrarily long period of time. The fluidic system remains in an energetically stable state with constant pressure ratios at all points of the device.
Whenever a new picture contents 5 is desired, the old picture contents is pushed out in the manner of a shift register by the new information. For closing the circuit the two fluids 56, 57 must be separated from one another and supplied to separate supply containers. In the embodiment, a so-called separator 55 is used. The two fluids 56 and 57 are separated by exploiting a different physical characteristic, for instance the surface tension or the magnetic characteristics. In the present example, use is made of the different specific weights of the two fluids 56, 57. If the specific weights of the two fluids 56, 57 differ from one another by about 10%, the two fluids will be separated within a sufficiently short period of time provided that the influence of the surface tension can be kept small by the geometrical dimensioning of the separator 55. The inlet 54 is then expediently arranged at a middle level of the separator 55, the outlets 59 are at the highest point and the outlet 58 at the lowest point, if one presupposes that the fluid 57 has less weight than fluid 56. An artificial gravitational force is produced when a fluid, e.g. 56, is provided with magnetic characteristics. The separator 55 is, in principle, of the same structure, but an outer magnetic field of a permanent magnet acts on the lower part.
Independently of the separating process, the process of separating the two fluids 56, 57 can be supported by two liquids which hardly mix by nature, for instance oil and water.
The supply of fluid 56, 57 in the separator is at least twice the volume in the meander 50 and in the micropumps 77 and 78, because it must be assumed that the picture contents 5 can only have one color state. The meander 50, the micropumps 77 and 78 and all connection channels are filled via the filling opening 61, first with the fluid 56. The filling volume corresponds approximately to 50% of the total filling amount of both fluids. Subsequently, fluid 57 will be added until fluid exits at the overflow 60. The presence of air inclusions in the micropumps 77 and 78 and in the meander 50 and in the connection channels should be avoided because the function of the micropumps 77, 78 is greatly impaired thereby. It is expedient to start the filling operation with fluids at the branching point, mixer 50, to promote propagation into all of the channel junctions. After the filling process the overflow 60 and the filling opening 61 are sealed in an air-tight manner.
The design of the above-described display device leads to an independent functional unit which, independently of the control by a microprocessor and a power supply, can represent the information to be displayed over a long period of time. The micropumps 77, 78 are only activated in case of a change in the picture contents 5.
Fig. 14 illustrates the construction of the electronic label 1. The basic body 65 is received together with the glass cover layer 66 and the sensors 71 to 74 mounted thereon, the piezoelectric plate 64 as well as the solar cell 17 in a carrier member 9.
The carrier member 9 has disposed therein the separator 55 which together with the basic body 65 has four connection points for fluids 54, 58, 59, 61. All of the four connection points are sealed by an elastic O-ring 79. The carrier member 9 simultaneously receives the electronic plate 80 which contains all of the necessary electronic components for the construction of the communication module 19 and the signal converter 16 as well as an energy storage device for buffering the energy supplied by the solar cell 17.
It has already been described above that it is advantageous to construct the device with a multi-line execution.
Thus Fig. 15 shows the picture field 3 of the display 2 with a two-line execution. This two-line or multi-line execution can be realised both with a single closed meander 50 wherein in the case of a change of the picture contents the entire picture contents is changed (Fig. 16), and also with an arrangement of two or more meander systems (Figs. 16a and b) wherein the picture contents of each line can be changed individually.

This execution has the advantage that, when required, only one portion of the information, e.g. the price, is pumped out of the meander 50, whereas the other portion of the information, e.g. the description of the article, retains its status.
For this purpose the meanders 50 are appropriately horizontally structured, while they are connected to a common separator 55. Thus small amounts of energy are required to change the information, since no energy is required to change the data contents of unchanged lines.
In Fig. 16 the horizontally arranged meander 50 is covered by a metal screen 117, the webs of which are at right angle to the viewing channels 51 and mask the edge region of the visible display pixels. Thus the metal screen 117 contributes to the improvement of the contrast of the displayed information. The measuring channel 127 is arranged in front of the meander and will be described later on.
It can be seen in Fig. 16b, that the measuring channel has an s-shaped design, so that the fluid flow is detected twice by each of the sensors 122, 123 and 130, and consequently the system can be accurately calibrated in this manner.
In Figs. 15 to 21 an embodiment is illustrated, the basic body 65 of which is made from a plastic material. The structures for the channels and pump chambers are moulded into the basic body by a special process. Channel transitions, like the overflow channel 53 (Fig. 16), as well as outlets and inlets 56, 57, 54.1 to the pump chambers 67, separator 55 and in the mixer 70 are rounded off to reduce the resistance to the flow. For the purpose of a gradual transition, the changes of the cross-sections of the inlet channels 56; 57; 49 have narrowing or widening tapered constructions (Fig. 19) and thus form the lead sections 56a, 57a, 49 (Fig.
19).
Narrowings are provided appropriately and particularly at the measuring points on the mixer 70 and the s-shaped measuring channels 127 for the purpose of increasing the accuracy of the measurements. The flow conditions are improved particularly with the tapered channel transitions 56a; 57a.

At the same time in Figs. 18 and 19 the efficiency of the metal screen 117 to improve the contrast of the contents of the picture can be recognised.
It becomes clear from Fig. 17 that the metal screen 117 is provided below the meander cover, the glass cover layer 66, and thus it lets the light exiting from the reflection foil 118 through in such a manner that on the surface of the basic body 65 a masked well-contrasted display picture appears. The separator 55 for both fluidics 56, 57 is also situated below the glass cover layer 66 and the basic body 65 and is connected with the meander 50 via the opening 54.
In Figs. 20a and 20b shows a diagrammatic and enlarged illustration of the measuring channel 127. Two sensors 122, 123 each are provided above the s-shaped measuring channel 127, which perceive and measure the movement of the boundary surfaces between the two fluidics. For this purpose the different physical properties of the two fluids, like absorbing capacity, electric conductivity, magnetic properties and the like, are used.
In the example shown the various optical densities of the fluids in the visible range are made use for the measuring method. The time-dependent position of the boundary layer between the two fluids is measured, a) to control the "switching over"
between the two fluids on the mixer 70, and b) to adjust the throughput rate or the pump rate of the micropumps 64; 67 for both fluids.
For the detection of the boundary layer a pair of optical sensors 122, 123, preferably photo diodes with matched spectral sensitivity, are used. The ambient light strikes the sensor surface 122 passing through a screen 129. At the same time the sensors and screens are arranged in such a manner that only that light reaches the sensors 122, 123, which has passed through the fluid channel 56, 57. In the direction of flow the sensors 122, 123 are arranged one behind the other, so that by means of the less transparent fluid in the temporal progression a partial or complete covering of the effective sensor surface of one or both of a pair of sensor takes place. The change in time of the difference signal of both sensors 122, 123 is evaluated to compensate for the fluctuating intensity of the ambient light.
From the sensor signals information is obtained regarding the position of the boundary layer relative to the sensors 122, 123 with the aid of window discriminators. In this example the sensor 122 is used to control the exchange between the two fluids . In conjunction with the measuring channel 127 situated above it, the sensor 123 makes the determination of the flow rate feasible. The s-shaped channel below the sensors 122, 123 affects a compensation of asymmetries and adjustment errors in the actual construction, i.e. the deviations of the positions of the sensors relative to the measuring channel do not affect disadvantageously the measuring results.
A further advantageous, requiring little energy, background lighting takes place by a light guide body provided behind the display with fluorescent particles embedded in it, which light guide body can absorb the ambient light on its edge surfaces and lets the guiding of the light exit at desired places due to total reflection on the lateral walls almost loss-free on special output surfaces. The output of the light towards the display surface takes place in this case via the embedded scatter bodies, e.g. in an STP polymer with a chosen wave length range.
The invention has been described and illustrated above with reference to selected features. The invention is of course not limited to this illustration, but all features as such or in any combination can be used, also independently of their combination in the claims.

Claims (29)

claims

1. A device for displaying prices, article designations and similar information on article carriers in departmental stores or warehouses with the aid of display devices which are mounted on the article carriers, in electronic labels, this device being functionally connected to an external control center such that the control center addresses a single electronic label and can transmit information to said electronic label, characterised in that . the electronic label (1) includes a graphic display device (2) with energetically bistable contrast-producing picture cells (75), . in the electronic label (1) a receiving communication module (19) is present, which contains a ROM (11) with a firmly set unique label identification number (25) as well as an address comparator (12) to compare the label identification number (25) with the address signals (100) of the external control central (20) and a gate (13) to release the modulation of the signal carrier carrying the picture contents (111) to the graphic display device (2), . a mobile data acquisition (30) with a reading head for bar codes (39) to read the article carrier identification number (26), the label identification number (25) and the article number (24) and the mobile data acquisition device is communicating with the control center (20).

2. A device according to claim 1, characterised in that the graphic display device (2) consists of a fluidic system having a meander (50) and at least two fluids (56, 57) with different contrasts, while the meander (50) contains viewing channels (51 ) which extending parallel cover a picture field (3) in a matrix-like manner and which are interconnected by covered overflow channels (53) and that at least two micropumps (77) and (78) transport one fluid (56) or (57) each alternately via a mixer (70) and in accordance with the picture contents function (a(t) into the meander (50).

3. A device according to claim 2, characterised in that the meander (50) with its viewing channels (51) and overflow channels (53) has an inlet channel (49) which is connected with the mixer (70) and has an outlet (54) in a separator (55) in which a separation of the fluids (56, 57) is carried out due to their different physical properties, and the separator (55) has at least two openings (58; 59) for the separated fluids (56; 57) and that one outlet opening (58; 59) each is connected respectively with a micropump (77) or (78) via outlet channels (69) and that the micropumps (77; 78) are connected with the mixer (70) via further outlet channels (69) so that altogether a closed fluidic system is present.

4. A device according to claims 2 and 3, characterised in that the two fluids (56;
57) have different densities and that on the separator (55) an outlet (58) is provided for the fluid (56) and an outlet (59) for the fluid (57) at different levels.

5. A device according to claims 2 and 3, characterised in that one of the two fluids (56; 57) has magnetic properties and that the separator (55) is surrounded by a magnetic field separating the fluids (56; 57).

6. A device according to claims 2 and 3, characterised in that one or several measuring channels (48) are provided downstream from the micropumps which are connected with sensors (71, 72, 73, 74) to recognise contrast changes in the fluid flow.

7. A device according to claim 2, 3 and 6, characterised in that that measuring channel (48) which in the direction of the fluid flow is the first viewing channel (51) of the meander (50) and the sensors (73, 74) are arranged with the overflow channels (53) connected with the first viewing channel (51).

8. A device according to claim 2, 3, 6 and 7, characterised in that the cross-section of the overflow channels (53) between the viewing channels (51) is smaller than the cross-sections of the viewing channels (51)

9. A device according to claims 1 to 8, characterised in that in the picture contents function (a(t), which is transmitted from the control center (20) to the electronic label (1) as a modulation of a signal carrier S a(t), synchronisation contrast changes (94, 95) are inserted into the fluid flow at constant time intervals, the synchronisation contrast changes being provided for the control of the delivery rate of the micropumps (77, 78).

10. A device according to claims 1 to 9, characterised in that the sensors (73, 74) are provided at the beginning and the end of the measuring channel (48), which the synchronisation contrast changes (94, 95) inserted into the fluid flow the are as well [sic] as the other inlet of the phase comparator (90) is connected with the communication module (19), while the outlet of the phase comparator is connected with a pump control (93) thereby forming a phase-locked loop for the synchronisation of communication signals S a(t) transmitted by the control center (20) and the delivery rate of the micropumps (77, 78).

11. A device according to claims 2 to 10, characterised in that the viewing channels (51), the overflow channels (53), the inlet channels (68) and the outlet channels (69) between the micropumps (77) and (78) with the mixer (70) are constructed as V-shaped or trapezoidal channels and that the micropumps (77) and (78) have rectangular pumping chambers (67) into which the V-shaped or trapezoidal channels enter and that the basic body (65) is a 100-orientated silicon wafer into which the channels are introduced by anisotropic etching, and the basic body (65) is covered by a cover layer (66) made of glass or silicon and that piezo plates (64) are arranged on the cover layer (66) as drive for the pump chambers (67).

12. A device according to claims 2 to 11, characterised in that the inlet channel (68) is divided into several part-channels before its entry into the pump chamber (67), the total cross-sections of which is approximately that of the cross-section of the outlet channel (69) so that different dynamic flow resistances will occur and the pump control pulses p i(t) for the control of the piezo plate (64) on the pump chamber (67) have a steep rising flank and a more moderate falling flank.

13. A device according to claims 2 to 12, characterised in that the outlet channels (69) between the micropumps (77, 78) and the mixer (70) are connected with sensors (71, 72), which are in the position to register changes in the contrast (62, 63) and there is a counter-control device of the micropumps (77, 78) to prevent the micropump (77) or (78) which is active in the meander to build up the picture contents (5) to convey fluid (56) or (57) into the non-active micropump (78) or (77).

14. A device according to claims 2 to 14[sic], characterised in that the filling of the fluidic system is carried out through a special filling opening (61), an overflow (60) is present and that after filling the fluidic system is closed in an air-tight manner.

15. A device according to claims 2 to 15[sic], characterised in that the filling opening (61) is connected with the mixer (70) to ensure a uniform filling pressure on all channel branches of the fluidic system.

16. A device according to claims 1 to 3, characterised in that the communication between the electronic label (1) and the control center (20) is carried out in a wireless manner.

17. A device according to claims 1 to 3, characterised in that the communication between the mobile data acquisition device (30) and the control center (20) is carried out in a wireless manner.

18. A device according to claim 2, characterised in that the graphic display device (2) comprises a fluidic system with at least two fluidics (56; 57) having different contrasts, wherein the parallel viewing channels (51) are horizontally arranged.

19. A device according to claim 18, characterised in that the meanders (50) are connected only to a common separator (55) and form a closed system.

20. A device according to claim 8, characterised in that the measuring channel (127) has an s-shaped construction and is positioned in front of the meander (50) and its cross-section is less than the cross-section of the viewing channels (51).

21. A device according to claim 20, characterised in that in the region of the measuring channel (127) two sensors (122, 123) are provided, which record the movement of the boundary surfaces between the various fluidics and form an evaluable signal for the control of the micropumps (67; 64).

22. A device according to claim 2, 18 to 20, characterised in that the basic copy (65) carrying the structure is made of plastic material.

23. A device according to claim 12, characterised in that the transitions between the overflow channels (53) and the viewing channels (51) and the transitions (56a, 57) in the mixer (70) and the inlet in the meander (50) are tapered.

24. A device according to claims 2 to 22, characterised in that the viewing channels (51) of the meander (50) are covered by a metal screen (117) and the webs of the metal screen (117) are at right angle to the viewing channels (51).

25. A device according to claims 2 to 23, characterised in that behind the metal screen (117) a reflection foil (118) with fluorescent occlusions acting as contrastimproving background lighting is provided.

26. A device according to claims 2 to 23, characterised in that lighting takes place by a light guide body provided behind the meander (50) a light body with scatter centres from fluorescent material is arranged, which light body transmits with little loss the ambient light absorbed by its edge surfaces by virtue of total reflection to its lateral surfaces to special absorption surfaces facing the display area, while the absorption surfaces have embedded scatter bodies.

27. A device according to claim 26, characterised in that the light guiding body is an STP polymer.

28. A method for the management of articles in departmental stores and warehouses and for administering addresses of electronic labels with display devices which are mounted on article carriers and which communicate with a control center using the above mentioned device, characterised in that . an article number (24) provided on the article (42) on an article identification tag (43), article carrier identification numbers (26) which are provided with at least one article carrier identification tag (41) on the article carrier, . a label identification number (25) which is arranged on the electronic label (1) on a label identification tag (10) are sequentially read in with the aid of a mobile data acquisition device (30) and stored in the registers (34), (35) and (36) and that the related . article number (24) . article carrier identification number (26) label identification number (25) are linked in the mobile data acquisition device (30) as an integrated system (27) of article data and that this integrated system (27) of article data is transmitted to the control center (20) and that this integrated system (27) of article data is further complemented in the control center (20) with the article designation (22) and the article price (23).

29. A method according to claim 18, characterised in that the article carrier identification number (26), the label identification number (25) and the article number (24) all have the form of an optically readable bar code which is read by the same receiving means (28) of the mobile acquisition device (30).