Mechanical computer keyboard with analog input

Abstract

A mechanical computer keyboard including a plurality of keys and an input/output (i/o) interface for output of registration of pressing one or more of the plurality of keys. Each key includes a keycap, a key switch including a stem, a key registration unit for registering a keystroke, and a spring for forcing the keycap in a neutral release position and providing a perceptible increase in pressing force. The keyboard further includes an analog-to-digital converter and the keys include a distance sensor unit for determining a travel distance of the pushing-down of the keycap by measuring a complex electrical impedance corresponding to the travel distance of the pushing-down the keycap, wherein the analog-to-digital converter is configured to convert the complex electrical impedance to a digital input signal including a digitalized keystroke travel distance for outputting of the digital input signal by the i/o interface towards the computer.

Claims

1. A mechanical computer keyboard, for use as an input device of a computer, comprising: a plurality of keys; an input/output (i/o) interface for output of registration of pressing one or more of the plurality of keys; and an analog-to-digital converter; wherein each key comprises: a keycap for operating the key by pushing-down the keycap; a key switch comprising: a stem for connecting with the keycap; a key registration unit for registration of a keystroke upon the operating of the key; and a spring for forcing the keycap in a neutral release position and providing a perceptible increase in pressing force upon pushing-down the keycap; and a distance sensor unit for determining a travel distance of the pushing-down of the keycap by measuring a complex electrical impedance corresponding to the travel distance of the pushing-down the keycap; and wherein the analog-to-digital converter is configured to convert the complex electrical impedance to a digital input signal comprising a digitalized keystroke travel distance for outputting of said the input signal by the i/o interface towards the computer.

2. The mechanical computer keyboard according to claim 1, wherein: the key registration unit of the key switch further comprises a contact circuit for connecting and interrupting an electrical circuit for registration of the keystroke; and the key switch further comprises a slider for displacement of an element of the contact circuit for connecting and interrupting the electrical circuit in response to the keystroke.

3. The mechanical computer keyboard according to claim 1, further comprising a printed circuit board for receiving each of the plurality of keys and comprising leads for electrically connecting the key registration unit of the plurality of keys with the i/o interface, and wherein the distance sensor unit comprises a first electrically conductive element disposed between the printed circuit board and the key switch or on the printed circuit board, and a second electrically conductive element comprised of the spring of the key switch.

4. The mechanical computer keyboard according to claim 3, wherein the first electrically conductive element is integrated in the printed circuit board.

5. The mechanical computer keyboard according to claim 3, wherein the first electrically conductive element of the distance sensor unit comprises a coil for generating a variance in inductance in correspondence with compression of the spring of the key switch.

6. The mechanical computer keyboard according to claim 3, wherein the first electrically conductive element of the distance sensor unit comprises an electrically conductive surface forming a first electrical conductor of a capacitor and a second electrically conductive surface in the keyboard forming a second electrical conductor of the capacitor, wherein the spring of the key switch is disposed in between the first and the second electrical conductor for generating a variance in capacitance correspondence with compression of the spring of the key switch.

7. The mechanical computer keyboard according to claim 6, further comprising a metal plate for supporting the key switches, wherein the analog-to-digital converter comprises a shielding input terminal connected to the metal plate for receiving a background interference signal, and wherein the analog-to-digital converter increases the accuracy of the determined capacitance between the first and the second electrical conductor by subtraction by the shielding input.

8. The mechanical computer keyboard according to claim 6, wherein the distance sensor unit drives metal contacts of the key registration unit to obtain a high voltage potential over the contacts of the key registration unit for measuring a first capacitance and to obtain a low voltage potential over the contacts for measuring a second capacitance, and wherein the analog-to-digital converter is configured to obtain the complex electrical impedance by subtracting the measured first and second capacitances.

9. The mechanical computer keyboard according to claim 5, wherein the first electrically conductive element of the distance sensor unit and the analog-to-digital converter are disposed on a flexible printed circuit board disposed between the printed circuit board and at least one of the plurality of keys.

10. The mechanical computer keyboard according to claim 9, wherein the flexible printed circuit board comprises a plurality of first electrically conductive elements for the plurality of keys.

11. The mechanical computer keyboard according to claim 9, wherein the flexible printed circuit board comprises a flexible insulating substrate having a first and second surface side comprising a first and second segment of the coil, respectively, and wherein the first and second segments comprise a flat spiral shaped coil, interconnected by a through via through the flexible printed circuit board.

12. The mechanical computer keyboard according to claim 9, wherein the flexible printed circuit board is a multi-layer flexible printed circuit board, comprising a flexible insulating multi-layer substrate, each layer comprising a segment of the coil, and wherein each segment comprises a flat spiral shaped coil, interconnected by a through via through the layer of the flexible printed circuit board.

13. The mechanical computer keyboard according to claim 1, wherein the key switch is a linear, tactile and not-clicky or tactile and clicky key switch.

14. The mechanical computer keyboard according to claim 2, wherein the contact circuit is an electronic contact circuit and the slider is configured to displace an element of the electronic contact circuit to connect and interrupt the electronic circuit in response to the pushing-down and releasing of the keycap, or wherein the contact circuit comprises a light emitting element and an optical detecting element, and wherein the slider comprises an element for blocking or allowing light between the light emitting element and the optical element, for connecting and interrupting the electrical circuit in response to the pushing-down and releasing of the keycap.

15. The mechanical computer keyboard according to claim 1, wherein the key registration unit comprises a light emitting element, an optical detecting element, and a lens unit, and wherein the slider displaces the lens unit for registration of the keystroke by the optical detecting element in correspondence with the keystroke.

16. The mechanical computer keyboard according to claim 1, wherein the analog-to-digital converters of the keys are configured for simultaneous parallel conversion of the complex electrical impendences to the digitalized keystroke travel distances of a selection of the key switches.

17. The mechanical computer keyboard according to claim 16, wherein the selection is defined by a list of operated key switches, and wherein the operated key switches are determined by key registration units registering a keystroke of the key upon operation of the key.

18. A printed circuit board for a mechanical computer keyboard according to claim 1, the mechanical computer keyboard comprising a printed circuit board for receiving each of a plurality of keys and comprising leads for electrically connecting a key registration unit of the plurality of keys with the i/o interface, and the distance sensor unit comprises a first electrically conductive element disposed on the printed circuit board and a second electrically conductive element comprised of the spring of the key switch.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 shows, from a side view, an example of a key switch according to the prior art;

(2) FIG. 2 shows, the internal components of the key switch according to the prior art;

(3) FIG. 3 shows, the internal components of a key switch with a distance sensor in accordance with an aspect of the invention;

(4) FIG. 4 shows, the internal components of a key switch with a distance sensor in accordance with another aspect of the invention.

DETAILED DESCRIPTION

(5) FIG. 1 shows a key switch 100. The key switch is a mechanical key switch for a mechanical keyboard which consists of several individual key switches such as the key switch illustrated in FIG. 1. These key switches can be sold separately and sometimes, the computer keyboard is arranged for easy replacement of these keys through use of a key switch socket that is permanently fixed on the Printed Circuit Board, PCB, but which makes it possible to have the key switches removed and replaced without desoldering them from the PCB.

(6) The key switch shown in FIGS. 1 and 2, is a key switch known in the art and consists of several components such as a housing 120 and a stem 110. The stem is for receiving the key cap (not shown) and the housing houses the rest of the components of the key switch 100.

(7) These other components are shown in FIG. 2. The housing 120 of the key switch 100 keeps all the components together. However, the housing 120 is not a necessary element of the key switch and could consist of multiple separable parts. The components could also be configured in a different manner in which they are mutually connected without housing.

(8) The slider 130 is what eventually determines how tactile, clicky or linear the switch 100 is. In the example shown in the figures, the slider 130 and stem 110 are described as separate components. These could indeed be separate components, but can also be integrated into a single component.

(9) If the slider 130 is tactile, as shown in the figure, the pressing-down of the key will provide some tactile feedback. The slider could however also be shaped differently (e.g. linear) to provide less, non or more tactile feedback, or to make the pushing-down clicky or not-clicky. The point of actual registration of the keystroke can be defined by the slider as well. For example, the slider may have a first segment in which tactile feedback is giving upon pressing the key, and a second segment, which in time follows the first segment, that register the actual keystroke by moving the contact circuit of the key to either disconnect or connect an electrical circuit. These contacts 140a, 140b of the electrical contact circuit 140 can thus either be a standard or normally open or standard closed contact circuit. The spring 150 defines the level of force that has to be applied to the key in order to register the keystroke. The shape of the slider 130 however may also have some influence on the amount of force that has to be applied with the keystroke since for example tactile or clicky shaped sliders provide resistance as well.

(10) The key switch shown in FIGS. 1 and 2 are merely shown by way of example. These key switches consist of a few standard components such as the stem 110, contact circuit, slider, and spring. Since the present disclosure will provide a means for registering analog input with such a conventional key switch, the skilled person will appreciate that other, mechanical, key switches will work as well. For example, the way in which the keystroke is registered, e.g. by detecting a short or open circuit of the contact circuit 140, can also be performed in an electronic manner with an additional sensor. Examples thereof are also optical or photo electronic key switches. Key switches could be provided with an (infrared) light emitting element, e.g. an IR-LED. The light element emits a light beam and an optical element detects if the beam is still received or blocked. The stem of the key switch comprises an element that blocks or unblocks the light beam when the key is pressed-down. This way the keystroke can be registered without electronic circuit known from conventional mechanical keyboard. Accordingly, the present disclosure does not exclude such alternative mechanical key switches but can be used for such types as well. The slider of the present disclosure could therefor also be a slider for blocking or unblocking/allowing a light beam to be transmitted between a light emitting element such as a LED and an optical sensor. In this case, the light emitting element and the optical sensor form the contact circuit and the slider is arranged to block/unblock the light beam.

(11) In FIG. 3 the key switch 100 of FIGS. 1 and 2 is shown again but with additional components to provide for registration of an analog input of the key switch. In view of the present disclosure, analog input can be defined as the travel distance, travel time, travel speed, travel acceleration or jerk of the keystroke. This means that besides distance other physical quantities could be registered as well.

(12) The present disclosure provides means for registering these physical quantities such as distance and/or time. This registration is outputted to the device to which the keyboard is connected, for example a personal computer. Corresponding data may also be inputted into the keyboard and for example to a microprocessor inside the keyboard, e.g. for configuration of the sensor, the Analog-To-Digital converter, ADC 250, or the microprocessor itself and for example the way in which the keyboard simulates a known video game controller or other input peripheral.

(13) The standard use of the analog input data is to add an extra component to the input data. Whereas conventional keyboard data is binary, i.e. the key is pressed or not, the analog input data provides input at a high(er) resolution. The resolution corresponds to the level of accuracy of the sensor and can be increased by increasing the windings of the coil, and/or the shape of the coil (spiral, circular, rectangular, triangular, racetrack, etc.) upon inductance sensing or by removing interference signals upon capacitive sensing. In an example, the sensor is arranged for at least distinction of input at a resolution of approximately at least 5 discrete positions, more preferably at least 25 discrete positions, even more preferably at least 50 discrete positions, at least 100 discrete positions, more preferably approximately at least 500 discrete positions, even more preferably approximately at least 1000 discrete positions, or most preferably approximately at least 2000 discrete positions. In a preferred embodiment, the coil may have approximately at least 15 windings.

(14) Alternatively, or in another configuration modus, the keyboard according to an aspect of the invention may also be suitable for having a configurable actuation registration moment. This means, that conventional key switches have predefined actuation moments, which are defined by the slider and when the slider displaces the element of the contact circuit such that the circuit switches between short and open circuit. The present disclosure however may also bypass the slider and the contact circuit and use the distance sensor to determine if the key is pressed or not. Hence, in such a case, make swapping between key switches with different actuation moments superfluous. This is especially useful for persons who use the keyboard for different applications such as typewriting and playing video games. When typewriting, tactile feedback may have a higher priority that actuation speed. And thus, the moment of actuation only takes place when a certain threshold travel distance of the keystroke is exceeded, thereby preventing accidental keystroke registrations. When playing a video game, response time may be crucial. Hence, such a late keystroke registration may be undesirable and it may be preferred to have the key register the keystroke in the shortest time possible. Currently, such switching between these configurations requires replacement of the key switches. In some cases, these key switches may be placed on a key switch socket such that replacement is made very easy. In most cases however, these key switches are soldered to the PCB which makes replacement difficult and cumbersome.

(15) Such quick switching between different actuation registration configurations can be achieved by using the distance sensor instead of the stem, slider and contact circuit to register the keystroke, even in a binary input registration mode.

(16) The keyboard or the computer can be configured that for example binary input data is received from the keyboard but in which the actuation position of the key is different. On the other hand, the keyboard may also output digitalized analog input data. The computer can then decide to act upon receiving the first discrete step in the input data or upon a further, later discrete step, for example when the key is pressed already for 25% of the total allowable travel distance.

(17) To increase the accuracy of the registration of the input data in an analog input modus, the key switch or PCB is preferably modified to disconnect the conventional binary input registration circuit. This could be achieved by (temporary or permanently) disconnecting the contact circuit. As an alternative to such a hardware modification, this can also be achieved through a software modification in the microprocessor on the PCB of the keyboard. The keyboard works with a matrix for processing of each individual key by the microprocessor. In an example, the keyboard matrix could be provided with additional rows and/or columns for processing of the analog input data. This has the advantage that both the conventional binary input data as well as the (analog) input data from the distance sensors can be processed in parallel. This allows the microprocessor to use both input simultaneously, or to temporarily or permanently switch between analog and binary registration of the keystrokes of one, a group of, or all keys of the keyboard.

(18) Disabling the contact circuit can also be achieved by removing one of the slider elements 140a, 140b, or by interrupting one or more of the contacts of the key switch 100 that connect with the PCB. In the latter case, this could be achieved with a flexible printed circuit as well. The flexible printed circuit may have through holes to receive positioning or alignment pins for correct positioning of the key switch on the PCB, and interrupt other electrical connections between the contact circuit 140 in the key switch and the PCB 220 of the keyboard.

(19) The key switch 100 according to a first aspect of the present disclosure as shown in FIG. 3 is provided with an additional sensor element 210. This sensor element is a coil, and in particular a printed coil 210 on a flexible circuit board. This coil is preferably placed below the key switch 100 and above or on top of the PCB 220 of the keyboard, on which PCB the key switch may be disposed, soldered or fixed in any other known manner.

(20) The coil contains a certain number of windings and is connected to an ADC 250 that is arranged to convert an inductance in a digital signal as for further communication of this input data towards the computer or other device to which the keyboard is connected.

(21) The inductance of the coil 210 changes when a conductive object or element comes it the proximity of the coil 210. Conventional key switches may already be equipped with such a conductive element, i.e. the spring. The spring is most likely made from a conductive material such as iron or any other ferromagnetic material. In case the spring is made from a non-conductive material, the spring may also be replaced by conductive one.

(22) Since coil 210 is unshielded from the spring 150, the displacement of the spring influences the magnetic field of the coil and hence the inductance or energy stored in the magnetic field. Since level in which these two physical quantities change, i.e. the displacement of the spring 150 and the inductance of the coil 210, correlate to each other, the inductance is highly accurate value to determine the displacement of the spring, and hence, travel distance upon the keystroke.

(23) In FIG. 4 an alternative version of the sensor is shown. The key switch 100 in FIG. 4 is the same as in the previous FIG. 1, FIG. 2 and FIG. 3. However, as already indicated above with reference to the first example of the present disclosure, the key switch 100 used for the sensor according to the second example of the present disclosure may also consist of other components such as an electronic sensor version of the slider/contact circuit arrangement.

(24) The keystroke of the pressing-down of the key switch 100 as shown in FIG. 4 is registered through a change in capacitance of the capacitive distance sensor 230A. The capacitive distance sensor comprises a capacitor that is connected to an ADC for further communication towards the computer. A capacitor is a passive two-terminal electrical component that is able to store potential energy in an electric field between these two terminals. As such, the capacitor consists thus of two conductive terminals that have an isolating material in between to prevent depletion of the capacitor. These two terminals can differ and may be already present in the keyboard itself, e.g. by providing an electrical connection towards at least two different electrically conductive materials in the keyboard that are located close to each other but are not in direct, electrical, contact. Alternatively, and preferably, this is a combination of elements already present and elements added. This example is shown in FIG. 4, the PCB 220 or an additional (flexible or non-flexible) circuit board is provided with a conductive element such as a copper plate. This conductive element is the first terminal 230a of the capacitor and provided with a voltage potential. The second terminal 230b is provided by the metal plate to which the key switches 100 are mounted. This plate may be connected to ground. The plate may also be connected to the ADC 250 for noise or background reduction. By electronically connecting the plate to a shielding input of the ADC 250 the ADC can subtract the input signal obtained from the plate 230B from the input signal obtained from the capacitive sensor 230A such that a more accurate measurement can be achieved.

(25) Since these two terminals 230a, 230b are positioned at a certain distance from each other, they will function as a capacitance. The capacitance will however be influenced by any conductive element that is in or near the electrical field of the voltage potential between the two terminals. This could be the spring but also a conductive surface added to the key cap for example. When the spring 150 is compressed, it will influence this field in a corresponding manner. And thus, the level of compression of the spring, which represents the travel distance of the key upon the keystroke, may be determined by measuring the fluctuation in capacitance between the two terminals 14a, 14b of the distance sensor 140.

(26) Other variations to the disclosed examples can be understood and effected by those skilled in the art in practicing the claimed disclosure, from a study of the drawings, the disclosure and the appended claims. In the claims, the word “comprising” does not exclude other elements or steps and the indefinite article “a” or “an” does not exclude a plurality. A single processor or other unit may fulfil the functions of several items recited in the claims. The mere fact that certain measures are recited in mutually different dependent claims does not indicate that a combination of these measures cannot be used to advantage. A computer program may be stored/distributed on a suitable medium, such as optical storage medium or a solid-state medium supplied together with or as part of other hardware, but may also be distributed in other forms, such as via the internet or other wired or wireless telecommunication systems. Any reference signs in the claims should not construed as limiting scope thereof. Similar reference signs denote similar or equivalent functionality.

(27) The present disclosure is not limited to the examples as disclosed above, and can be modified and enhanced by those skilled in the art beyond the scope of the present disclosure as disclosed in the appended claims without having to apply inventive skills and for use in any data communication, data exchange and data processing environment, for example for use of the neuroprosthetic system for substituting auditory perception.