The present invention relates generally to text input devices for portable electronic devices and computers. More specifically, the present invention relates to a miniature keyboard having a magnetic proximity switch under each key. The keys are activated by a magnet.
Portable electronic devices such as cell phones, personal digital assistant devices (PDAs), portable email devices and the like often require text input. Text input is necessary for instant messaging and address entry on cell phones, and for portable email devices, for example. However, portable electronic devices are often too small for a practical, full function keyboard with 30, 40 or more keys. Very small keys are too small for the fingers. Also, keys that require pressure can cause repetitive stress injury in users that use the keyboard for hours a day.
Very small pressure sensitive keys can be activated by pressing with a stylus. However, forcefully pressing the keys with a stylus greatly slows text entry and is annoying for many users.
Pressure sensitive graphical pads with text recognition, optically projected keyboard images, and flexible keyboards that can be unrolled onto a flat surface have been proposed as solutions. However, all these methods are bulky, expensive, fragile or annoying to use.
What is needed is a simple, durable, inexpensive, fast and pleasant to use device for entering text into portable electronic devices. The text input device should require very little electrical power, employ simple detection circuitry, and be very small in size. Preferably, the text entry device would not require pressing of a stylus.
The present invention provides a keyboard having a plurality of keys, and a magnet-actuated switch disposed under each key. A stylus is provided with a stylus magnet at a tip of the stylus. The stylus magnet causes a magnet-actuated switch under a selected key to change state when the magnet is moved near the selected key. Electronic circuits are provided for sensing the state of each magnet-actuated key.
Each key can have a concave region disposed over each switch, for guiding the stylus tip and magnet.
The magnet-actuated switches can be reed switches or membrane switches, for example. The magnet-actuated switches can be microfabricated (i.e. by microlithographic patterning, thin film deposition and etching). The switches can comprise flexible ferromagnetic cantilevers that are pulled upwardly by the magnetic field from the stylus magnet. When pulled upward, each ferromagnetic cantilever makes electrical contact with an elevated electrode.
Preferably, the switches are normally-open switches that are closed by the presence of the stylus magnet.
Also preferably, the strength of the stylus magnet and sensitivity of the switches are selected such that only one switch changes state when the stylus magnet is disposed on a selected key. The stylus magnet is not strong enough to cause adjacent switches to close.
The keyboard of the present invention is particularly well suited for use in small portable electronic devices such as cell phones, PDAs and the like.
The present invention provides a magnet-actuated keyboard that can be incorporated into portable electronic devices such as PDAs and cell phones. Each key in the keyboard has an associated magnetic proximity switch (e.g. a magnetic reed switch). A user operates the keyboard with a stylus having a magnet at the tip. When the stylus magnet is moved close to a key, the corresponding proximity switch closes. A microprocessor detects which proximity switch in the keyboard is closed. The magnetic switches are passive magneto-mechanical devices and do not require bias current (e.g. unlike a Hall effect or magnetoresistive sensor). Accordingly, the present keyboard requires very little operating power, and is compatible with conventional keyboard switch detection electronics. Also, mechanical pressing with the stylus is not required to select a key. Hence, the switches are mechanically isolated from the stylus and the keyboard does not require movable mechanical elements built into the external shell of the electronic device. The present keyboard is small, simple to use and reliable.
Reed switch: a magnet-actuated switch having two closely-spaced, approximately parallel ferromagnetic cantilevers that make electrical contact when a magnetic field aligned with the cantilevers induces attractive magnetic moments in the cantilevers.
Magnetic membrane switch: a magnet-actuated switch having a ferromagnetic element supported by a flexible elastomeric membrane. When attracted by a magnet, the ferromagnetic element moves, causing electrodes to come into electrical contact.
Magnet-actuated switch: A mechanical electrical switch that can be opened or, more typically, closed by an applied magnetic field or magnet. Hall-effect devices, magnetoresistive (e.g. spin valve or spintronic) devices and other magnetic field sensors are not magnet-actuated switches as defined in the present specification, and are outside the scope of the appended claims.
The present text input device also includes a handheld stylus 26. In the present invention, the stylus includes a stylus magnet 28. The stylus magnet 28 is disposed in a tip of the stylus. The stylus 26 can be stored in a small hole or pocket (not shown) in the portable electronic device, as known in the art. The stylus magnet 28 can hold the stylus within the hole (not shown) by magnetic attraction to a complementary magnet inside the portable electronic device.
The stylus magnet 28 has an associated magnetic field 21 capable of triggering the proximity switches 50. Preferably, the magnet 28 is a high strength magnet comprising a rare earth alloy. A magnet with small size is preferred because this tends to localize the magnetic field. Preferably, the stylus magnet 28 is oriented so that the magnetic field lines 21 are approximately parallel with an axis 23 of the stylus 26 (as shown). The magnetic pole at the stylus tip can be north or south, which produce equivalent results in the present invention.
In operation, the stylus 26 is manipulated by hand to select keys representing desired text characters. Each proximity switch 50 closes (i.e. changes to a low-resistance state) when the magnet 28 is nearby. For example, switch 50a will close when magnet 28 is moved into concave region 24a. Pressing of the stylus 26 is not required. In order to trigger a switch and select a key, the magnet 28 merely needs to be moved close to the switch. Electronic circuitry (now shown) monitors the switches 50 for low resistance indicating presence of the magnet in close proximity to one of the switches 50. The electronic circuitry provides an output indicating the keys and text characters selected by a user.
It is noted that the concave regions 24 are optional in the invention. The keys can be flat or even convex. However, concave regions 24 are preferred in the invention because they help the user to align the magnet 28 with the switches 50.
Although the row conductor 34 is illustrated as being elevated above the circuitboard 51, it is noted that the row conductor 34 may be patterned on the circuitboard 51.
Preferably, the reed switches 50 are very small and are made using micromachining techniques (e.g. lithographic patterning, thin film deposition, chemical etching and plasma etching). The magnetic reed switches can be about 1×1 mm or 2×2 mm or smaller in size, for example.
In
In the present invention, it is important for the sensitivity of the magnetic reed switches 50a 50b 50c and magnetic field strength of the magnet 28 to be selected such that the magnet 28 triggers only the selected reed switch (i.e. reed switch 50a). The stylus magnet 28 is preferably not so large or powerful as to cause adjacent, unselected switches 50b 50c to close. This assures that only one key of the keyboard will be selected when the stylus magnet 28 is disposed in one of the concave regions 24.
The magnetic reed switches 50 can have a vertical orientation, or a horizontal orientation. Generally, the reed switches are most sensitive to magnetic fields oriented parallel with the cantilevers 52. Typically, then, the stylus magnet 28 should be oriented to provide a vertical magnetic field when the cantilevers are vertical, and a horizontal magnetic field when the cantilevers are horizontal.
The vertical embodiment of
As noted above, the sensitivity of the reed switches should be controlled such that nonselected keys adjacent to a selected key are not triggered by the stylus magnet 28. The reed switches can have sensitivity tuned in many ways. For example, the stiffness of the cantilevers 52 can be increased to make the switch less sensitive, or the permeability of the cantilevers can be reduced to make the switch less sensitive. Alternatively, the strength and size of the magnet can be adjusted.
The cantilever 60 can be made of micromachined single crystal silicon or polysilicon, for example. The ferromagnetic material 62 can comprise electrodeposited iron or iron-nickel alloy and the contacts 64 can be made of gold, for example. Methods of manufacturing micromachined reed switches are known in the art.
If normally closed reed switches are used (as illustrated in
In an alternative embodiment, elevated electrodes 55a 55b 55c comprise a conductive ink coating or metal film on the underside of the covering 27. The conductive ink coating can be applied in strips and can include carbon or silver particles for conductivity, as known in the art of conductive inks. Such conductive inks are commonly used in conventional keyboard membrane switches. Also, conductive inks or metal foils comprising the elevated electrodes can be disposed on a flexible circuit material (e.g., comprising polyimide film) adhered to the underside of the covering 27.
Preferably, the cantilevers 49 are made of a flexible and thin ferromagnetic material having a high permeability. These properties render the cantilevers easily bendable by the stylus magnet 28. For example, the flexible cantilevers can have a thickness of less than 0.001″, and a permeability of greater than 50,000.
In a preferred embodiment, the flexible cantilevers 49a 49b 49c are made of a metallic glass (i.e., a metal alloy with an amorphous crystal structure). Specifically, the cantilevers can comprise a metallic glass made of cobalt (75-90%), iron (7-13%), silicon (7-13%), boron (1-5%) and nickel (1-5%) (other ferromagnetic alloy compositions can also be used). With this material, the cantilevers can have a thickness of about 0.0004-0.0008 inches (or 0.0001-0.0015 inches), and a magnetic permeability in the range of about 100,000 to 1 million, or 250,000 to 1 million (in a DC field), or more. Cantilevers made of metallic glasses are preferred, but not essential, in the invention. Ferromagnetic metallic glasses can have high resiliency, high fatigue resistance, and high permeability, which are desirable properties for the flexible cantilevers. However, it is noted that nonamorphous (i.e. crystalline) ferromagnetic foils (e.g. mu-metal foil) can also be used. Also, the flexible cantilevers 49 can comprise non-ferromagnetic resilient material (e.g. such as a polymeric elastomer) with a conductive portion (e.g., conductive ink or metal foil) and a ferromagnetic portion (e.g., steel sphere) attached.
Also, it is noted that the metal foil strips 82, elevated electrodes 55 and other components can be gold plated to prevent the formation of insulating metal oxides.
Also, it is noted that the flexible cantilevers can be provided as separate parts for each switch (i.e., the cantilevers do not need to be part of a monolithic metal strip 82). For example, each switch can have a separate flexible cantilever that is glued, soldered or spot-welded to the circuitboard 51. The cantilevers do not need to be connected in a monolithic metal foil strip 82.
Also, it is noted that a weak return magnet (not shown) can be disposed within or underneath the circuit board 51. The return magnet pulls downwardly on the flexible cantilevers 49 and causes them to return to an unbent, open position when the stylus magnet 28 is removed.
In another aspect of the present invention, a selected key is detected by a change in capacitance. In this embodiment, the flexible cantilevers 49 and electrodes 55 do not need to form a low resistance contact. When a key is selected, the flexible cantilever 49 is moved very close to the corresponding electrode 55 (e.g. separated only by a very thin insulating film), resulting in a large increase in capacitive coupling.
In operation, the stylus magnet 28 is moved close to a selected switch (i.e. switch 70a). Ferromagnetic element 74a is attracted to the magnet 28, and moves upward until it contacts the conductors 3436. The ferromagnetic element 74a provides an electrical connection between the conductors 3436. In an alternative embodiment, the membranes 72 each have a conductive upper surface (e.g. coated with a carbon-containing paint), and the ferromagnetic element 74a presses the conductive upper surface against the conductors 3436. When the stylus magnet 28 is moved away from switch 70a, the membrane 72a returns to its former position, and the switch opens.
The ferromagnetic elements 74a can be magnets oriented such that they are attracted to the stylus magnet 28. The ferromagnetic elements can also be small steel or mu-metal objects, such as small steel spheres.
Preferably, the elastomer comprising the membranes 72a 72b 72c and sheet 75 is a very soft elastomer such as a soft silicone (e.g. having a hardness of Shore A 5, 10, 20, or 40). A soft, easily bendable elastomer is preferred in the invention because the stylus magnet 28 and ferromagnetic elements 74 will typically be very small (e.g. 1×1 mm or 2×2 mm), and hence will produce a small force on the ferromagnetic elements 74.
The magnetic membrane switches 70 are very similar to conventional membrane switches with the exception that the switches are actuated by an attractive magnetic force from a handheld magnet, instead of a compressive force from a users finger.
In the present invention, the reed switches of
The present keyboard device can be provided as a stand-alone keyboard module. The keyboard module can communicate wirelessly (e.g., via a Bluetooth link) with other electronic devices, or can have a conventional wired (e.g. USB or serial) connector for mating with other devices.
Magnetic field sensing devices such as Hall effect sensors and magnetoresistive sensors are not magnet-actuated switches as defined in the present specification and appended claims. These magnetic sensors are excluded from the scope of the claims. Hall effect sensors and magnetoresistive sensors require a power-draining bias current, and are therefore impractical for use in portable electronic devices.
The present invention provides a small size and low power keyboard that can be used in many alphanumeric input applications. The present invention is particularly well suited for use in portable electronic devices because of its small size, low power consumption, lack of mechanical moving parts. Also, the present invention provides the additional benefit of not requiring pressing of the stylus, which makes typing faster and reduces user fatigue and injury.
It will be clear to one skilled in the art that the above embodiment may be altered in many ways without departing from the scope of the invention. Accordingly, the scope of the invention should be determined by the following claims and their legal equivalents.
Number | Date | Country | Kind |
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PCT/US06/15029 | Apr 2006 | US | national |
The present application claims priority under 35 USC 120 from copending PCT application US2006/015029 filed on Apr. 21, 2006, and copending U.S. application Ser. No. 11/339,055, filed on Jan. 24, 2006.
Number | Date | Country | |
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Parent | 11339055 | Jan 2006 | US |
Child | 11705333 | Feb 2007 | US |