Capacitive keyboard reading device for blind people

Abstract

The present invention relates to a capacitive keypad reader (1) comprising a one-piece front panel (2) made of dielectric material, wherein said front panel (2) comprises at least one recess (3) located on an outer surface of the front panel (2) and at least one groove (4) located on an inner surface of the front panel (2). The capacitive keypad reader (1) also comprises at least one array of electrodes located on the inner surface of the front panel (2), wherein each electrode array comprises at least one transmitting electrode (Tx) and one receiving electrode (Rx), facing the recess (3); wherein the groove (4) is positioned and oriented around the electrode array and the corresponding recess (3), occupying a space between the recess (3) and the electrode array; wherein the electrode array generates, when in operation, electric field lines between the transmitting electrode (Tx) and the receiving electrode (Rx); and wherein the groove (4) is configured and positioned to concentrate the electric field flux (FCE) lines of the electrode array in an area at the base of the corresponding recess (3) that it faces.

Description

[0001] DESCRIPTION

[0002] READER WITH CAPACITIVE KEYBOARD FOR THE BLIND

[0003] Object of the invention

[0004] The present invention consists of a reader with a capacitive keyboard whose configuration provides high reliability for use by blind or visually impaired people even in rainy and condensation conditions.

[0005] The present invention has application in the field of access control to rooms or areas by entering codes through keypads, specifically the adaptation of said keypads, such as those based on capacitive technology, for use by blind or partially sighted people.

[0006] Technical problem to be solved and background of the invention

[0007] Currently, in the field of access control systems for rooms or restricted access areas, there is a wide variety of systems and / or devices responsible for carrying out or allowing said access control and authorization, such as mechanical or electronic locks, different types of readers, as well as different types of keyboards.

[0008] The present invention is aimed at improving one of these devices: the reader with a keyboard based on capacitive technology adapted for people with no or reduced vision.

[0009] Capacitive keypads operate based on the capacitor effect and its variation when the user's finger is placed in the lines of electrical current generated. They operate by lightly touching the surface where the key is located to activate it. These capacitive keypads are very common in many access controls.

[0010] As shown in Figure 1A, the keys of the capacitive keyboard considered here base their operation on the mutual capacitance effect. For each key on the keyboard there is at least one set of electrodes comprising a transmitting electrode (Tx) and a receiving electrode (Rx), with an operation similar to that of a capacitor, such that a charge is applied to the transmitting electrode (Tx), generating an electric field flow (EFF) towards the receiving element (Rx). Said flow (EFF) travels in what would be the front panel of the keyboard, which consists of an element of dielectric material, a dielectric medium or simply a dielectric that comprises low electrical conductivity.In such materials, electrical charges do not flow through the material as they do in an electrical conductor, because they do not have loose or free electrons that can move through the material, but rather they are slightly displaced from their average equilibrium positions, causing dielectric polarization.

[0011] Using the electronics of the reading device, the intensities of the charges introduced into the transmitting electrode (Tx) are controlled and those received at the receiving electrode (Rx) are measured.

[0012] The operation consists in that, when the key of the keyboard is touched (for example, with a finger), the lines of the electric field flux (FCE) that protrude from the front panel are cut, the electronics detecting a drop in the charge that reaches the receiving element (Rx) and thus confirming that there is a contact on the capacitive keyboard key, as shown in figure 1 B.

[0013] That is, the capacitance between the electrodes (Tx, Rx), which forms a feedback path for an inverting amplifier, is reduced when the finger is applied to that surface. In fact, it can be configured to decrease more when detecting ridges and less when detecting the space between them, which is why these capacitive readers are also used in fingerprint reading devices.

[0014] One of the design parameters to consider when manufacturing the reader's capacitive keypad is the keypad's sensitivity, that is, how to distribute the electric field flux (EFF) lines to maximize touch sensitivity.

[0015] If the transmitting (Tx) and receiving (Rx) electrodes are positioned very close together, the electric field flux (EFF) lines do not protrude from the dielectric front panel and therefore do not recognize contact because they cannot be cut by the finger. That is, as shown in Figure 1C.

[0016] Conversely, if the transmitting electrode (Tx) and receiving electrode (Rx) are positioned too far apart from each other, as shown in Figures 1 D, the electric field flux (EFF) lines may protrude too far from the dielectric front panel, acting as a proximity detector instead of a reader, which may lead to errors in use.

[0017] Thus, it has been estimated that the usual optimal arrangement of the electrodes (Tx, Rx) is one that places them at a distance equal to half the thickness (d) of the dielectric (the keyboard face), for a range of intensities and materials commonly used for this type of device. With this ratio, the electric field flux (EFF) protrudes just enough from the dielectric face to ensure contact when the surface is touched.

[0018] Another relevant parameter, in addition to the operating ranges, the separation between transmitter (Tx) and receiver (Rx) and the dielectric material used on the front panel, is the one that manages to increase the density of electric flow lines (FCE) between the aforementioned “transmitter (Tx) and receiver (Rx)” thus increasing the sensitivity of the keys.

[0019] To this end, the electrode assemblies common in the sector comprise an “E” or comb-shaped geometry, with the receiving electrode (Rx) located inside the transmitting electrode (Tx) and separated by a distance equal to half the thickness (d) of the dielectric front panel, as shown in figures 2A and 2B.

[0020] Thanks to this separation between the electrodes (Tx, Rx), and their geometry, the sensitivity of the keyboard contact is maximized, achieving optimal performance of these capacitive keyboards. The problem arises when they must be used by users with reduced or no visual capacity.

[0021] These users must first make contact with the keyboard's front panel to locate the keys they wish to press. However, since sliding a finger across the keys on a capacitive keyboard activates them, using them is extremely complicated for these users. These capacitive keyboard readers include supports like the one shown in Figures 3A-3C.

[0022] There is currently a software solution on the market based on the time the finger must remain on the key. This means that for the system to consider contact to have occurred, the finger must remain touching the dielectric front panel for a predetermined number of seconds.

[0023] This solution, from a user perspective, can be cumbersome since it requires counting to ensure that a key is pressed correctly, even a combination of several keys, and therefore continues to generate errors.

[0024] To solve this problem and provide a capacitive-based keyboard that is easy to use by people with reduced or no vision, the following proposals have been made.

[0025] A first proposal is based on designing a plate-shaped accessory that fits over the front panel of a capacitive keyboard already on the market. This plate will have holes corresponding to the keyboard keys, allowing a blind person to position themselves over the accessory (and not directly on the keyboard) and then press the desired keys by inserting their finger into the hole.

[0026] This plate-shaped accessory poses two problems. First, there's a mounting issue, as the plate must be firmly glued to the reader's front panel to prevent air from entering between the two elements, as air deflects the electric field flow.

[0027] On the other hand, these readers may be installed outdoors, allowing water to enter between the board and the front panel, leading to deviations in the flow of the electric field that would affect the sensitivity and operation of the keys.

[0028] In a second proposal, a front panel is designed incorporating recesses. That is, a front panel manufactured by injection molding, in one piece, including recesses in the key area. This solved the problems associated with assembly, avoiding the need to glue any accessory to the reader and therefore avoiding the possibility of air infiltration. Furthermore, being a single piece, the problem of water entering between the accessory and the reader is avoided. However, this second embodiment maintains the problem with water, as it can accumulate inside the recess, affecting the flow of the electric field. This flow will tend to deviate toward the water, such that when touched by the user, it will generate a keystroke, even if not intended, as shown in Figure 4A.

[0029] In addition to the above, this configuration entails another, more important additional problem related to the electric field flux (EFF) lines. Since the dielectric front comprises the same material, but with different thicknesses, since the thickness in the recess area is less than in the rest of the panel, the distribution of the electric field flux (EFF) lines is not uniform and tends to deviate towards the thickest areas, as shown in Figures 4B and 8D. This is because the permittivity of the reader's dielectric front material is much higher than that of air, causing the electric field flux (EFF) to follow different trajectories than expected.

[0030] Just as with water accumulation within the recesses, in this case, the surface of the front panel between the recesses, outside the key areas, will become touch-sensitive, rendering it unusable for the blind.

[0031] Description of the invention

[0032] To solve the problems mentioned above, the present invention proposes a reader with a capacitive keyboard especially suitable for people with reduced or no visual capacity (blind people) that includes the following characteristics.

[0033] Said reader with a capacitive keypad comprises a single-piece front panel made of dielectric material. That is, a panel comprising only one part or body, without accessories in the form of plates or similar attached to a front surface, or assemblies of several parts, said panel being manufactured from a material with low electrical conductivity.

[0034] Said front panel comprises a flat structure with two opposing surfaces: an outer surface and an inner surface. That is, an outer surface that, when the capacitive keypad reader is in use, is accessible to the user to access its keys, and an inner surface that, also in use, conceals the electronic components of said capacitive keypad reader.

[0035] The front panel also comprises at least one recess located on the outer surface of the front panel and at least one groove arranged on the front panel, preferably open on the inner surface, it being understood that said panel may comprise more than one recess, these being arranged independently, as well as a series of grooves, without the number of recesses having to be the same as the number of grooves.

[0036] A recess is understood as a change in relief on an exterior surface that is substantially flat or regular. That is, a recess, open cavity, or opening, in the form of a valley or similar, preferably substantially circular, located on said exterior surface.

[0037] The reader with a capacitive keypad is configured so that said recess, or recesses, in case the front panel comprises more than one, correspond to or are assigned to be a key on the capacitive keypad.

[0038] In the main embodiment, the reader with capacitive keyboard comprises at least one set of electrodes located, preferably, in a keyboard circuit, adhered to the inner surface of the front panel, where said set of electrodes comprises at least one transmitting electrode and one receiving electrode, said set being facing each other and located under a recess in the front panel.

[0039] This electrode array generates, during operation of the capacitive keypad reader, electric field lines between the transmitting electrode and the receiving electrode. For the capacitive keypad to operate, each electrode array must be connected to an electric current that generates the electric field lines. If the capacitive keypad reader includes more than one electrode array, they may be located on a single keypad circuit.

[0040] The groove is located around the recess and the electrode assembly in such a way that it is sized and positioned to concentrate the electric field flux lines of each electrode assembly to an area within the base of the corresponding recess.

[0041] A groove is understood as a channel or slot, straight or curved, hollow, closed or open, through one of the surfaces of the front panel, which lacks the dielectric material of said panel. That is, a recess in said front panel.

[0042] The fact that the groove is located surrounding the recess and the electrode assembly does not imply that it surrounds it completely, but rather that it is located in a space of the front panel between the recess and the electrode assembly, without being in a straight path between the recess and the electrode assembly, being to one side of them, seen from a frontal projection of the front panel.

[0043] For example, in a preferred embodiment, the groove is located around a perimeter of the electrode assembly. That is, it is in a perimeter position, delimiting the exit of the electric field lines beyond the space defined by the recess and electrode assembly, acting as a dam or barrier for the electric field flow lines.

[0044] The fact that the electrode array is located on the inner surface of the front panel means that, for the capacitive keypad reader to function, or to be in the operating position, the electrode array, consisting of the transmitter and receiver, must be directly below the corresponding recess (from a frontal perspective) if there is more than one. For optimal operation, the electrode array must be glued to the inner surface of the front panel, avoiding the presence of air between the two parts, as air can affect the way in which the electric field flux lines generated between the electrodes propagate and decrease their intensity, significantly reducing the sensitivity of the keys.

[0045] Preferably, the groove(s) in the front panel may be filled with air, since this gas impedes the passage of electric field flux lines, as they do through the dielectric material of the front panel. The grooves may also be filled with any other fluid with low dielectric permeability, similar to that of a vacuum.

[0046] Since these grooves do not comprise a dielectric material similar to that of the front panel, the electric field flux is redirected and concentrated, so that said panel, with at least one recess and one groove, can function as a capacitive reader without recesses, as described in the background, that is, without dispersion of said lines. Thus, with the configuration described, the electric field flux lines protrude slightly, as necessary, above the base of the recess associated with the key and do not protrude from the rest of the front panel.

[0047] Thanks to this configuration, a blind person can slide their finger over the front panel and locate the recess assigned to a key, without actually activating it if they don't want to. Similarly, they can slide their finger along the base of the recess, which affects the electric field generated by the electrode array, activating the desired key.

[0048] Although the objective of the invention is to provide a reader with a capacitive keypad with a plurality of keys for entering an access code to spaces, both by blind and non-blind users, even in rainy and condensation conditions, the technical effect of the invention focuses on limiting or concentrating the lines of the electric field flow on the basis of a recess, so the main embodiment does not have to be limited to a plurality of recesses and keys, but to at least one, since with only one, the described configuration works correctly.

[0049] This implementation solves the problems described above, since, among other things, it does not require holding the finger on the key for a predetermined amount of time, as is the case with current systems used for the blind, which greatly facilitates its use, nor does it require installing an accessory to the panel that would affect the manufacturing and assembly process.

[0050] In one embodiment, the transmitting electrode and the receiving electrode of an electrode array are separated by a distance equal to half the thickness of the flat-shaped structure of the front panel, where the recess corresponding to the electrode array is located. While this separation distance between electrodes based on the thickness of the front panel is appropriate for the systems described above, this relationship has also been calculated with the presence of recesses and grooves, and is considered ideal for the correct operation of the keypad. In a preferred embodiment, the groove is open and located on the inner surface of the front panel.That is to say, the groove is an opening, slit or slot located on the inner surface of the flat-shaped structure of the front panel, since, being in this position facilitates its manufacture, and is sufficient to prevent a dispersion of the electric field flow lines to unwanted areas.

[0051] In one embodiment, the capacitive keypad reader comprises a plurality of grooves, located around a perimeter of the electrode array. That is, instead of just one, it may comprise as many as necessary to contain the electric field flux lines. The types of embodiments suitable for the number of grooves per recess, as well as their size, shape, and length, are highly variable. One of the most suitable embodiments would be short grooves, arranged in transverse and longitudinal directions, these being the directions in which the electrode array's electrodes are also oriented. Ideally, the volume of air contained in the grooves and the recesses should be the same, distributed equally between the recesses and the groove that surrounds them.

[0052] In one embodiment, the reader with a capacitive keypad comprises a plurality of recesses, preferably said recesses comprising the same shape and size, located on the exterior surface of the front panel, preferably also distributed regularly on said exterior surface. Similarly, the reader with a capacitive keypad also comprises the same plurality of electrode arrays, each of said electrode arrays being located beneath a corresponding recess in the front panel. In this way, each recess can act as a different key on the keypad, and said keypad can be used to enter a code with more than one different value or character.

[0053] In a dependent embodiment, the capacitive keypad reader comprises a plurality of grooves located in the front panel, arranged between each set of electrodes in each recess. These grooves act as boundaries or separation walls for the electric field flux lines of all the keys on the keypad. In this way, the number of grooves in the front panel can be reduced, and one of them can be used to limit or concentrate the electric field flux lines of two different sets of electrodes. In one embodiment, the capacitive keypad reader comprises a locating ring comprising a curved surface concentric to a recess. Said curved surface can be concave or convex and can be positioned on a recess located in a central position, relative to the plurality of recesses, to facilitate positioning a blind user relative to the front panel of the keypad.

[0054] In one embodiment, the groove is a straight channel oriented in the same direction as at least one of the electrodes in an electrode array. Typically, the electrodes used for capacitive readers have a flat, elongated shape, so for the invention to function properly, the grooves must be oriented in the same direction as the electrodes.

[0055] In one embodiment, at least one recess comprises a chamfered edge. With this chamfered edge or area, if any water droplets fall onto the outer surface of the front panel, the water droplets are substantially evacuated from the recess, and the electric field flow is not altered.

[0056] In one embodiment, the front panel is manufactured by injection molding.

[0057] In one embodiment, the front panel comprises two over-injected materials forming a single, single-piece body.

[0058] In a dependent embodiment of the previous one, one of the two over-injected materials forming a single, single-piece body is translucent; the reader with a capacitive keypad comprises at least one lighting element, preferably an LED, where said LED is located under a recess in the inner surface of the front panel.

[0059] With this implementation, the reader with a capacitive keypad can be configured so that, each time a key is activated, it lights up with a corresponding LED, either temporarily or remaining illuminated while the reader keypad is being used.

[0060] In addition to LED lighting elements, other types of lighting are possible, the configuration of which does not affect the operation of the electronic elements described in the main embodiment.

[0061] In one embodiment, the front panel comprises at least one Braille text comprising protrusions located on the outer surface of said front panel adjacent to a recess. With this embodiment, a blind person can pass their finger over the front panel and, by reading the Braille text, detect the key they wish to activate, without any risk of interference with the electric field flow of other keys, and therefore without the risk of incorrectly entering a key.

[0062] In one embodiment, at least one set of electrodes comprises an “E” shaped structure with the receiving electrode located inside the transmitting electrode.

[0063] In a more specific embodiment dependent on the above, the receiving electrode has a wire-like "E" shape and the transmitting electrode has an "E"-shaped recess; where a central leg of the receiving electrode is located between two central legs of the transmitting electrode, the latter being between two end legs of the receiving electrode.

[0064] With this arrangement of the electrodes, the grooves can be arranged parallel to the electrodes, to facilitate the containment of the electric field flux lines.

[0065] In one embodiment, the capacitive keypad reader comprises a keypad circuit comprising the electrode assemblies, wherein said circuit is located on the inner surface of the front panel.

[0066] In a more specific embodiment dependent on the previous one, the reader with a capacitive keypad comprises an adhesive sheet located between the keypad circuit and the interior surface of the front panel, where said adhesive sheet is configured to secure said keypad circuit to the front panel. This adhesive sheet prevents the presence of air between the interior surface of the front panel and the circuit, which could affect the flow of the electric field.

[0067] In one embodiment, the reader with a capacitive keypad comprises an electronic reader circuit, located next to the keypad circuit, on one side, opposite to where the adhesive sheet is located, and a perimeter seal configured to seal the keypad circuit, which prevents the entry of fluids into the interior of the keypad circuit and the electronic reader circuit.

[0068] Both the gasket and the reader's electronic circuit are inserted into the front of the reader and are "potted" (coated with a resin, thus isolating the reader's electronics).

[0069] Description of the figures

[0070] To complete the description and in order to help better understand the characteristics of the invention, this specification is accompanied, as an integral part thereof, by some figures in which, for illustrative and non-limiting purposes, the following have been represented:

[0071] • Figure 1A shows a section of the operating diagram of a capacitive keypad based on the principle of mutual capacitance. Said keypad comprises a transmitting electrode and a receiving electrode, which, in operation, generate an electric field flux represented by dashed lines over a dielectric material of low electrical conductivity.

[0072] • Figure 1 B shows the operating scheme of the capacitive keyboard shown in Figure 1A, where when the finger comes into contact with the dielectric, the electric field lines that protrude from it are interrupted, activating the button or key corresponding to the electrodes that generate said field.

[0073] • Figure 1C shows the operating scheme of the capacitive keyboard in Figure 1A where the electric field flow does not extend beyond the dielectric, so when the finger is brought close to said dielectric, the button or key is not activated because the flow lines are not interrupted.

[0074] • Figure 1 D shows the operating scheme of the capacitive keyboard in Figure 1A, where the electric field flow protrudes at an excessive distance from the dielectric, so that, when the finger approaches said dielectric, without touching it, it interrupts the flow lines and the button or key is activated.

[0075] • Figure 1 E shows a section of the operating diagram of a capacitive keypad with a receiver located between two transmitting electrodes, where the generated electric field is more regular and concentrated than that generated by a transmitting electrode and a receiving electrode, thereby increasing the sensitivity of the key. • Figure 2A shows an image of a keypad circuit comprising a plurality of electrode assemblies of a reader with a capacitive keypad, where each of said assemblies comprises a transmitting electrode and an “E” shaped receiving electrode.

[0076] • Figure 2B shows a schematic image of an electrode assembly comprising a transmitter electrode and an “E”-shaped receiver electrode, showing that the separation between transmitter and receiver is always the same. Half the thickness of the dielectric.

[0077] • Figures 3A-3C show a perspective, a front view and a profile view of a reader with a capacitive keyboard such as those currently on the market, where the buttons or keys do not include recesses or changes in plane on the outer surface of the front panel.

[0078] • Figure 4A shows a schematic view of a section of a front panel, comprising a recess without chamfer, of a mutual capacitance capacitive keypad, where the accumulation of water on the lower edge can be seen, when the front panel is in a vertical position, and how the distribution of the electric flow is altered by said water.

[0079] • Figure 4B shows a schematic view of a section of a front panel, comprising a recess without chamfer, of a mutual capacitance capacitive keypad, as shown in Figure 4A where the irregular distribution of the electric field flux lines can be seen due to the presence of the recess located on the outer surface.

[0080] • Figures 5A-5B show two perspective views, front and rear, of the capacitive keyboard reader of the invention, with recesses in the outer surface of the front panel.

[0081] • Figure 5C shows a rear perspective view of the front panel, where its grooves can be seen.

[0082] • Figure 6 shows an exploded perspective view of the reader with capacitive keyboard of the invention, where the front panel, the keyboard circuit, the adhesive sheet, located between the keyboard circuit and the inner surface of the front panel, an electronic circuit of the reader, located next to the keyboard circuit on one side opposite the adhesive sheet, and a perimeter seal configured to seal the keyboard circuit can be seen. • Figure 7A shows a front view of the front panel of the reader with capacitive keyboard, with a level of transparency sufficient to be able to appreciate both the recesses and the arrangement of the grooves with respect to said recesses.

[0083] • Figure 7B shows a section of Figure 7A marked with dot-dot lines, where the position, distribution and orientation of the recesses, electrode assemblies and grooves of the front panel can be seen.

[0084] • Figure 7C shows a detail of Figure 7B, allowing the position of the grooves relative to the recess and a set of electrodes to be seen more easily.

[0085] • Figure 7D shows a detail similar to that shown in Figure 7C, with the capacitive reader shown in operation, where the distribution of the electric field flow lines generated by the set of electrodes can be seen, and contained by the grooves at the base of the recess.

[0086] • Figure 8A shows a section similar to that shown in Figure 7B, where the front panel comprises two over-injected materials forming a single single-piece body, such that said panel comprises two different stripes for each of the materials.

[0087] • Figure 8B shows a detail of Figure 8A, similar to that shown in Figure 7C, where the front panel comprises two over-injected materials forming a single one-piece body.

[0088] • Figure 8C shows a detail similar to that shown in Figure 1 E, but with the front panel comprising two over-injected materials forming a single one-piece body.

[0089] • Figure 8D shows a detail similar to that shown in Figure 4B, but with the front panel comprising two over-injected materials forming a single, single-piece body.

[0090] • Figure 8E shows a detail similar to that shown in Figure 7D, but with the front panel comprising two over-injected materials forming a single, single-piece body.

[0091] List of numerical references shown in the figures:

[0092] Rx.- receiving electrode

[0093] Tx.- transmitting electrode

[0094] FCE.- Electric field flux d.- thickness of the front panel. 1 Reader with capacitive keypad;

[0095] 2.- front panel;

[0096] 3.- lowering;

[0097] 4.- groove;

[0098] 5.- protrusions;

[0099] 6.- Location ring;

[0100] 7.- keyboard circuit;

[0101] 8.- adhesive sheet;

[0102] 9.- electronic circuit of the reader;

[0103] 10.- perimeter joint; and

[0104] 11.- LED.

[0105] Preferred description of the invention

[0106] In the background of this document, the operation of capacitive keypads comprising an assembly formed by at least one transmitting electrode (Tx) and one receiving electrode (Rx), which can be in the shape of an “E” (as shown in figures 2A-2B), and which, in operation, generate electric field flow lines (EFF) that can be affected when a user's finger comes into contact with the dielectric surface of the front panel (2), has already been explained based on figures 1A-1E. Similarly, the readers with keypads based on the capacitive effect existing in the market, such as those shown in figures 3A-3C, have been shown, and the alternatives proposed to solve the problem of the use of this type of keypads by blind people have been detailed, such as the use of recesses without chamfer, shown in figures 4A and 4B, as well as the problems generated by said recesses.Therefore, all Figures 1A-1E, 2A-2B and 3A-3C show the prior art, while Figures 4A and 4B show the problems generated when trying to solve the described problems of the prior art.

[0107] The preferred invention is shown in Figures 5A-5C and 6, which represent a reader with a capacitive keyboard (1) specially designed or suitable for use by blind or visually impaired people.

[0108] The fundamental part of the invention of the reader with capacitive keyboard (1) is found in the single-piece front panel (2), made of dielectric material, as well as in the relationship of said front panel (2) with each set of electrodes comprising at least one transmitting electrode (Tx) and one receiving electrode (Rx).

[0109] In figure 5B you can see how the capacitive keyboard reader (1) comprises the front panel (2) which in turn comprises an exterior surface, accessible to the user and an interior surface where the keyboard electronics (1) are located.

[0110] On the outer surface are the buttons or keys of the reader with capacitive keyboard (1), in the form of recesses (3), made, in said outer surface of the front panel (2), during the injection of a dielectric material, to form said panel (2). Preferably, the invention is designed to provide a capacitive operation reader keyboard (1), so that blind people can enter an access code to a room or similar, that is, by typing different buttons or keys on the same front panel (2), whereby, preferably, the front panel (2) comprises a plurality of keys, in the form of recesses (3) that allow the introduction of a sequence of different digits. For example, in Figure 5B a front panel (2) with up to 12 keys is shown. However, said keyboard could be used for a different purpose, and could include a different number of keys in the form of recesses (3).

[0111] In Figure 5C it can be seen how, on the inner surface, opposite the outer surface, the front panel (2) comprises a plurality of grooves (4) open on said inner surface, arranged around the perimeters of each of the recesses. This distribution is easily appreciated in Figure 7A, where a front view of the front panel (2) appears, with transparency.

[0112] Figure 7B shows a sectioned, profile view of the reader with capacitive keyboard (1), shown in Figure 7A, in which the relationship between the sizes and position of the recesses (3) and the grooves (4) can be seen, the volume of the recesses (3) being similar to that of the grooves that surround them. In that same Figure 7B, the position of a keyboard circuit (7) comprising the electrode assemblies of said keyboard can also be seen, said keyboard circuit (7) being glued to the inner surface of the front panel (2). In fact, in Figure 7C, the relationship between a recess (3), two transverse grooves (4) and an electrode assembly formed by a transmitting electrode (Tx) surrounding a receiving electrode (Rx), which are located just below the recess (3) shown, can be seen in detail.

[0113] As indicated in the background, an electrode array must comprise, in order to generate electric field flux lines (EFF), at least one transmitting electrode (Tx) and one receiving electrode (Rx), and as shown in Figures 2A and 2B, an electrode array may comprise a complex shape that maximizes the functioning of the array, such as having an “E” shape.

[0114] The operation of the invention is explained from the diagram shown in Figure 7D, obtained from the diagram shown in Figure 7C, extracted from Figure 7B.

[0115] The electrode assembly shown generates, in operation, electric field lines between the transmitting electrode (Tx) and the receiving electrode (Rx), such that each groove (4) located in a position, with respect to the height, between the recess (3) and the electrode assembly, in this case, grooves (4) open on the inner surface, allow the electric field flow (EFF) lines of each electrode assembly to be concentrated in an area comprised in the base of the corresponding recess (3), unlike what happens without grooves (4), as shown in figure 4B.

[0116] In this way, if a finger approaches a recess (3), the button is not activated until it contacts the deepest base of said recess (3).

[0117] In order to ensure the correct functioning of the invention, the distance between the transmitting electrode (Tx) and the receiving electrode (Rx) of each set of electrodes is the same and is equal to half the thickness (d) of the flat-shaped structure of the front panel (2), where the recess (3) is located. Therefore, the relationship between the front panel (2) and the keypad circuit (7), which comprises the plurality of electrode sets, is not limited to the correct location between them, but also to the thickness (d) and shape of the panel (2) depending on the separation and size of the electrodes (Tx, Rx).

[0118] The grooves (4) can be of different shapes and sizes, and can be located in different positions with respect to the recesses (3) as long as: they are located at a height between the recess and the set of electrodes, seen from a side view as shown in Figures 7B-7D; they are between two sets of adjacent electrodes seen from a front view of the front panel (2), as shown in Figure 7A; they are surrounding a perimeter of a recess (3), seen from a front view of the front panel (2), as shown in Figure 7A; and their presence contains the electric field flux lines (EFF).

[0119] Preferably, these grooves are filled with air, since said medium prevents the propagation of the electric field flux lines (EFF) as does the dielectric material of the front panel (2), however, they could be filled with materials that have a similar conduction behavior, as well as other gases different from air.

[0120] In Figure 7A it can be seen how the recesses (3) assigned to the keys “2, 5, 6, 8 and 9” are surrounded by four grooves (4) arranged in longitudinal and transverse directions, while the rest of the recesses (3) are surrounded by two or three grooves (4) as they are in extreme positions and thus their manufacture is simpler. In alternative embodiments, the grooves (4) could be internal channels located in the front panel (2), they could be curved instead of straight, they could cover greater lengths to limit, a single groove, the electric field lines (EFL) of several recesses (3) and they could be the same number surrounding each recess.

[0121] Also in figure 7A it can be seen how the key marked with the number "5" comprises a location ring (6) that comprises a curved surface concentric to a recess (3). This surface allows the blind user to identify the position of all the recesses (3) as the central one is differentiated from the rest by a surface different from the others. Furthermore, to prevent fluid such as that generated in rain from accumulating in each recess (3), all the edges of the recesses (3) are chamfered or curved, solving the problem indicated from figure 4A.

[0122] On the other hand, in addition to the location ring (6), the front panel (2) also comprises a Braille text which comprises projections (5) located on the outer surface of said front panel (2) next to a recess (3), so that a blind user can know which key to press when passing his finger over it. An exploded image of the reader with capacitive keyboard (1) is shown in Figure 6, where the assembly order of each of the most important components of the keyboard can be easily seen. For example, the keyboard circuit (7) can be seen, which comprises all the electrode assemblies, located next to the inner surface of the front panel (2), fixed to it by means of an adhesive sheet (8). In the same way, an electronic circuit of the reader (9) can also be seen located next to the keyboard circuit (7) on one side opposite to where the adhesive sheet is located, and a perimeter seal (10) configured to seal the keyboard circuit (7).

[0123] In a main embodiment, the reader with capacitive keypad (1) is manufactured by injection in a single dielectric material, as shown in Figures 7B, 7C and 7D. Said material comprises only a grating when the front panel (2) is represented in a sectional view.

[0124] However, it is interesting to have a front panel (2) with two over-injected materials forming a single single-piece body, as shown in figures 8A to 8E, such that one of said materials is transparent or translucent to allow light to pass through, and the other material is opaque, to prevent viewing the electronics of the reader with capacitive keyboard (1).

[0125] This embodiment, where the front panel (2) comprises two single-piece dielectric materials, allows for the provision of a lighting system, such as a plurality of LEDs (11), in the keypad circuit (7), as shown in Figure 2A, which are activated based on the code entered. This embodiment of having two single-piece dielectric materials for the front panel (2) already exists on the market, but has not been applied to panels with recesses (3).

[0126] Alternatively, the capacitive keypad reader (1) may have sound generating elements, such as beeps or vibration, so that a blind user is aware of whether a key or a complete code has been typed correctly or incorrectly. Similarly, the capacitive keypad reader (1) may also comprise a screen or display where the typed code appears, or simply indicates, in some way, that a code has been typed.

Claims

CLAIMS 1.- Reader with capacitive keyboard (1) comprising a single-piece front panel (2) made of dielectric material, characterized in that said front panel (2) comprises: - a flat-shaped structure with two opposite surfaces: an outer surface and an inner surface; - at least one recess (3) located on the outer surface of the front panel (2); - at least one groove (4), arranged in the front panel (2), preferably on the inner surface; where the reader with capacitive keyboard (1) comprises at least one set of electrodes located on the inner surface of the front panel (2), where said set of electrodes comprises at least one transmitting electrode (Tx) and one receiving electrode (Rx), said set being located under a recess (3) of the front panel (2); where the set of electrodes generates, in operation, electric field lines between the transmitting electrode (Tx) and the receiving electrode (Rx); where each groove (4) is located between the recess (3) and the set of electrodes; and where the groove is positioned and configured to concentrate the electric field flux (EFF) lines of each set of electrodes to an area comprised at the base of the corresponding recess (3). 2.- Reader with capacitive keyboard (1), according to the previous claim, where the transmitting electrode (Tx) and the receiving electrode (Rx), of a set of electrodes, are separated from each other by a distance equal to half a thickness (d) of the flat-shaped structure of the front panel (2), where the recess (3) corresponding to the set of electrodes is located. 3.- Reader with capacitive keyboard (1), according to any of the previous claims, where the groove (4) is located surrounding a perimeter of the set of electrodes. 4.- Reader with capacitive keyboard (1), according to any of the previous claims, where the groove (4) is open and is located on the inner surface of the front panel (2). 5.- Reader with capacitive keyboard (1), according to any of the preceding claims, comprising a plurality of grooves (4), located surrounding a perimeter of the set of electrodes.

6. Reader with capacitive keyboard (1), according to any of the preceding claims, comprising a plurality of recesses (3) located on the outer surface of the front panel (2); and the reader with capacitive keyboard (1) comprises the same plurality of electrode sets, each of said electrode sets being located under a corresponding recess (3) of the front panel (2). 7.- Reader with capacitive keyboard (1), according to the previous claim, comprising a plurality of grooves (4), located on the front panel (2), arranged between each set of electrodes of each recess (3). 8.- Reader with capacitive keyboard (1), according to claim 6 or 7, comprising a location ring (6) comprising a curved surface concentric to a recess (3). 9.- Reader with capacitive keyboard (1), according to any of the previous claims, wherein the groove (4) is a straight channel oriented in the same direction as at least one of the electrodes of a set of electrodes. 10.- Reader with capacitive keyboard (1), according to any of the preceding claims, where each groove (4) is filled with air. 11.- Reader with capacitive keyboard (1), according to any of the preceding claims, wherein at least one recess (3) comprises a chamfered edge. 12.- Reader with capacitive keyboard (1), according to any of the previous claims, where the front panel (2) is manufactured by injection. 13.- Reader with capacitive keyboard (1), according to any of the preceding claims, wherein the front panel (2) comprises two over-injected materials forming a single one-piece body. 14.- Reader with capacitive keyboard (1), according to the previous claim, where one of the two over-injected materials that form a single single-piece body is translucent; where the reader with capacitive keyboard (1) comprises at least one lighting element, preferably an LED (11), where said LED (11) is located under a recess (3) of the front panel (2). 15.- Reader with capacitive keyboard (1), according to any of the previous claims, wherein the front panel (2) comprises at least one Braille text comprising protrusions (5) located on the outer surface of said front panel (2) next to a recess (3). 16.- Reader with capacitive keyboard (1), according to any of the previous claims, where at least one set of electrodes comprises an “E” shaped structure with the receiving electrode (Rx) located inside the transmitting electrode (Tx). 17.- Reader with capacitive keyboard (1), according to the previous claim, wherein the receiving electrode (Rx) has a wired “E” shape and the transmitting electrode (Tx) has an “E” shaped hollow; where a central leg of the receiving electrode (Rx) is located between two central legs of the transmitting electrode (Tx), these being between two extreme legs of the receiving electrode (Rx). 18.- Reader with capacitive keyboard (1), according to any of the preceding claims, comprising a keyboard circuit (7) comprising the electrode assemblies, where said keyboard circuit (7) is located on the inner surface of the front panel (2). 19.- Reader with capacitive keyboard (1), according to the previous claim, comprising an adhesive sheet (8) located between the keyboard circuit (7) and the inner surface of the front panel (2), where said adhesive sheet (8) is configured to fix said keyboard circuit (7) to the front panel (2). 20.- Reader with capacitive keyboard (1), according to the previous claim, comprising an electronic reader circuit (9) located next to the keyboard circuit (7) on one side opposite the adhesive sheet, and a perimeter seal (10) configured to seal the keyboard circuit (7).