US 3129418 A
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Description (OCR text may contain errors)
April 14, 1964 R. B. DE LA TOUR ELECTRONIC KEYBOARD Filed Aug. 4, 1960 OSC.
\ JNVENTOR. BY ROGER BOY DE LATOUR wwf E pw ATTORNEYS M -l fio di f 'x KYSK Fle.
United States Patent O 3,129,418 ELECTRONIC KEYBOARD Roger Boy de la Tour, Los Angeles, Calif., assignor, by mesne assignments, to Teledyne, Inc., a corporation of California Filed Aug. 4, 1960, Ser. No. 47,456 4 Claims. (Cl. 340-345) This invention relates to keyboards for providing electrical signals in response to manual operation of various keys and more particularly to a novel contactless type keyboard in which such signals are provided without the necessity of any metal-to-metal switch contacts.
It is conventional practice to employ manually operated keyboards for -feeding information into computers and the like. Generally, such keyboards are designed to close switch contacts in an electrical circuit in response to depression of a key member. After prolonged use, the switch contacts tend to wear and corrode or become coated in such manner that electrical conduction therethrough -is greatly decreased. ln some instances, no conduction whatsoever may occur for a given period of time and .then in subsequent use the physical movement resulting in engagement and disengagement of the contacts may dislodge any impurity and thus cause conduction and proper operation lto follow.
There exists, accordingly, the possibility of errors in the information fed into a computer or other instrument by the keyboard. Further, such errors are extremely difficult to detect because of the possibility of the abovenoted type of intermittent failure of the physical contacts. The keyboard itself therefore represents one of the more serious problems in computer design. In fact, the reliability of a computer is often limited to the degree of reliability of ythe keyboard employed in conjunction with the Icomputer.
With the above in mind, it is a primary object of this invention -to provide a novel keyboard in which the `foregoing problems of complete or intermittent failure due to wear, corrosion, dirt, grit, and the like are wholly avoided.
More particularly, it is an object to provide a keyboard having a reliability approaching that of the computer itself to the end that greatly increased accuracy in the overall operation of computers or other instruments with which the keyboard is employed is insured.
Br-iefly, these and many other objects and advantages of this invention are attained by providing a nove-l keyboard which is entirely electronic in its switching operation. lIn other words, physically engaging metal-to-metal contacts are avoided. As a consequence, the possibilities of failure due to wear, corrosion, dirt, grit, or the like is eliminated.
rln -accordance with the preferred embodiment of the invention, there is provided a plurality of key members. Each key member has connected thereto a magnetic membe-r arranged to be moved upon actuation of the key between first and second positions. Cooperating with the magnetic member is an inductance preferably in the form of a toroidal ring of ferrite. A barrier physically separates the magnetic member from the inductance so that the inductance itself may be completely sealed against any dirt, grit, dust, or other contaminating influence. The inductance is physically positioned to be in iux coupling relationship with the magnetic member when the magnetic member is moved to its second position.
With the above arrangement, the inductance may be excited 'from a conventional A.C. oscillator and included in a simple ytransistor switching circuit such that the switching transistor is caused to conduct when a suliicient signal is present on its base. The magnitude of this 3,129,418 Patented Apr. 14, 1964 ICC signal in turn is controlled by the impedance of the inductance. The value `of this impedance will either be extremely high or extremely low depending upon Whether or not the magnetic member attached .to the key is moved to its first or second position. -By employing a switching transistor a-s part of the switching operation in the keyboard, the output D.-C. signal available is of a constant value; that is, there is either a constant signal present or no signal, there being no dependence upon lthe physical manner in which the magnetic member is caused to approach or recede from the inductance.
Also contemplated as a part of the overall combination with a plurality of key members and their associated magnetic members and inductances is a diode matrix which will effect all the desired `switching to provide D.C. outputs from various output terminals which heretofore have been achieved lby mechanical switches. The matrix itself may be designed in accordance With any given code so that depression of Iany one .key member will result in a particular type of coded signal at certain ones of the output terminals. All of .the electronic components may be potted or embedded in resin material for permanent protection. The only essential movable parts of the system constitute the key and magnetic members, and these may be made extremely rugged for long life.
A lbetter understanding of the invention, as Well as various further `features and advantages thereof, will be had by now referring to a preferred embodiment as illustrated in the accompanying drawings, in which:
FIGURE 1 is a cut-away perspective view partly exploded illustrating a part of a keyboard designed in accordance with the present invention;
-FlGURE 2 is a schematic circuit diagram representative of any one of the key member circuits which could be used in the embodiment of FIGURE l; and,
FIGURE 3 is another schematic diagram illustrating a diode matrix system incorporated in the keyboard in accordance with a particular operation for which the keyboard may be designe-d.
IReferring first to FIGURE 1, there is shown a base or cabinet structure 10 support-ing a plurality of manually operable key means including key members 11. As shown, the key members are numbered l-9 and positioned in rows of three in a symmetrical array. Also shown are a plurality of magnetic members 12 connected to the key members 11 for movement therewith respectively. In the particular example chosen for illustrative purposes, the magnetic members 12 constitute bar magnets and are arranged to be moved between first and second positions upon actuation of the corresponding key member. The magnets associated with adjacent keys are oriented at right ang-les with each other to minimize interference of their fields.
Also schematically illustrated in FIGURE 1 are a plurality of inductances in .the form of ferrite toroids stationarily secured and sealed within the base 10 in positions to be in flux coupling relationship with the respective magnets when the magnets are moved downwardly by depression of the corresponding keys to their second positions close Ito the toroids. Each of the inductances thus includes a magnetizable core so that the impedance of each inductance is decreased when :the magnets are moved into proximity thereto.
Referring now lto FIGURE 2, there is shown one illustrative circuit which could characterize any one of the keys depicted in `FIGURE l. Thus, the key 11 is shown as rigidly secured to a magnet 12 for movement between first and second positions, the second position being close to the inductance 13 so that the magnet 12 and inductance 1-3 are in flux coupling relationship. The first position results when the key 11 is moved up as by a return spring 14 so that the magnet 12 is physically spaced yfrom the inductance 11. As shown schematically, there is provided a lbarrier 15 which prevents actual physical contact between the magnetic member 12 and the inductance 13. The inductance 13 may thus be potted or sealed completely against dirt, grit, dust, and the like. The irnpedance of the inductance 13 Iis changed from a given high Value to a given low value when the magnet I12 is lowered to its second position close to the inductance 13 as a consequence of its magnetizable core. The ratio of the high value to the 10W value of impedance may be of the order of 100.
A D.C. input is supplied between a positive terminal 16 and ground 17 to an oscillator 18 including the inductance 13 and resistance 19 in its output circuit. The frequency of the oscillator may be from 16-20 kilocycles. As shown, the output across the resistance 19 passes through a rectifying means in the form of a diode 20. From the output of the diode, the signal passes through a lter network including resistances 21, 22, condenser 23, and resistor 24 to the base terminal 25 of a switching transistor 26. The collector and emitter terminals 27 and 28 of the transistor 26 in turn connect to an output circuit including a load 30. y
With the foregoing arrangement and the oscillator 18 energized, the coil 13 will be excited, but with key member 11 held in its up position by spring 14 its impedance will be sutiiciently high that the value of current at the base of the transistor vwill not be sufficient to switch the transistor to a conducting state. As a consequence, there will be no D.C. signal through the load 30.
When the key member 11 is depressed to move the magnet 12 close to the inductance 13, the impedance thereof can be decreased by a factor of the order of 1/100 of its original value so that sufficient current will be passed through the rectier 20 to the base of the transistor to switch the transistor to a conducting state. Current is then supplied through the load 30. Since the transistor is either conducting or non-conducting as a consequence of its sharp cut-olf characteristic, the output signal is either full yon or full off, and the manner or speed with which the magnet 12 is moved towards or away from the inductance 13 is immaterial. Generally, the input circuits for computers include switching transistors of this type so that all that is required at the output of the keyboard is a triggering signal.
Referring now to FIGURE 3, .there is illustrated a specic example of a keyboard which will provide DAC'. output signals at various ones of certain output terminals in response to depression of certain 'ones of the key members in accordance with a desired coding. For the sake of illustration, assume that it is desired to convert a decimal number system to a binary code so that depression of any one of the keys numbered one through nine will provide output D.C. signals representative of the binary code corresponding to the particular number associated with the depressed key member.
Towards this end, the schematic system illustrated in FIGURE 3 may be employed wherein for the key numbered l to the extreme left there is shown the magnet 12 and inductance 13 with the resistance 19 and diode rectifier means 20 all corresponding to the similarly numbered components in FIGURE 2. The remaining keys all include similar elements, but the corresponding rectifying means or diodes are arranged in a matrix designated generally by the numeral 31 All of the inductances may be energized by the same oscillator 13. The various outputs include the lter resistance 21 and condenser 23 and are designated respectively K1, K2, K3, and K4.
In the example of a binary output, various D.-C. signals at the output terminals Kl, K2, K3, and K4 are made to correspond to the binary representation of any of the digits,
one through nine on the corresponding keys 11. The necessary code is set forth in the following table:
Output Terminal Key K4 K3 K2 Ki From the foregoing, it will be seen that if the key number 1 is depressed, an output signal should appear on K1 and no output signal appear on Vany of the other outputs K2, K3, and K4. On the other hand, if key 3 is depressed, then an output signal should appear at the terminals K1 and K2 and no output signal at the terminals K3 and K4.
The diode matrix 31 is designed to provide a coded output as set forth in the above table. Thus, for example, if key 5, designated 32 in FIGURE 3, is depressed, the decrease in impedance in its corresponding inductance 33 will result in a signal passing through the diode 34 to the output K1 providing a D.C. signal on this output and will also result in the same signal passing through the diode 35 to the output K3. There is no passage of this signal to the outputs K2 or K4 and therefore the resulting code at the output will be 0 l 0 1 which is the binary designation for the numeral 5.
As a second example, assume that the key numbered 7 r is depressed, shown at 36 in FIGURE 3. In this case,
the'decrease in impedance of the corresponding inductance 37 will result in a signal passing through the diode 38 to output Kl, the same signal passing through diode 39 to output K2, and the same signal passing through the diode 40 to output K3. There will be no output at K4 so that the resulting coded signal is 0 1 1 1 which corresponds to the numeral 7.
From the above description, it will be evident that all of the switching involved is done entirely electronically. Thus, not only are the-key members, magnets, and coils, Vfree of any physical metal-to-metal contacts, but also the various switching taking place in the diode matrix is achieved without any metal-.to-metal contacts.V The reliability of the entire keyboard accordingly approaches that vof the computer itself and the problems heretofore encountered with mechanical contact type keyboards are wholly eliminated. Y
It should be understood, as mentioned heretofore, that the outputs K1, K2, K3, and K4 may be employed to trigger switching transistors such as 26 described in FIG- URE 2 so that the circuit including the emitter and co1- lector terminals of the transistor Will be subject to either an on or otf condition depending upon whether the transistor is rendered conductive or non-conductive. With this arrangement, the resulting signal will be a constant quantity regardless of the manner in which the magnet 12 is made to approach or recede from the inductance 13.
While only one particular embodiment of the invention has been shown and described for illustrative purposes, many changes that fall clearly within the scope and spirit of the invention will occur to those skilled in the art.v
The electronic keyboard is therefore not to be thought of as limited to the one example set forth.
What is claimed is:
1. An electronic -keyboard comprising, in combination: a plurality of manually operable key means, each key means including: `a key member; a magnet movable between irst and second positions in response to movement of said key member, an inductance including a magnetizable core stationarily positioned adjacent to said second position; barrier means disposed between said magnet and inductance preventing physical contact of said magnet with said inductance; and an electric circuit including means for generating an electric signal, and including said inductance, said circuit having an output, said inductance having its impedance reduced to a low value in response to movement of said magnet to said second position to pass said electrical signal to said output and having its impedance increased to a high value in response to movement of said magnet to said first position to substantial block said electrical signal from said output.
2. An electronic keyboard according to claim 1, in which said inductance comprises a toroid ring of ferrite including windings connected in said circuit, the ratio of said high value to said low value being greater than titty.
3. An electronic keyboard including a plurality of keys for providing output signals at output terminals in response to actuation of said keys, comprising, in combination: a plurality of magnetic members connected to said keys for movement upon actu-ation thereof respectively; a plurality of inductances each including a magnetizable core stationarily positioned to be in flux coupling relationship with said magnetic members respectively when said magnetic members are moved from a position spaced from to a given lposition in proximity to said inductances in response to actuation of said keys; barrier means physically sealing said inductances from said magnetic mem;l bers and an oscillator connected to excite said inductances whereby signals of a given magnitude are available at the output of said inductances when corresponding keys are actuated as a consequence of a `decrease in the irnpedances of said inductances resulting from the proximity of said magnets and whereby said signals are substantially attenuated at the output of said inductances when said corresponding keys have not been actuated as a consequence of the relatively high value of said impedances when said magnets are spaced therefrom.
4. An electronic keyboard `for providing constant =D.C. output signals at various output terminals, comprising, in combination: a plurality of manually operable key means,
each key means including: a key member; a magnetic member connected to said key member for movement therewith between first and second positions; an inductance including a magnetizable core stationarily positioned adjacent to said second position so as to be in flux coupling relationship with said magnetic member when in said second position and exhibit a low impedance relative to its impedance when said magnetic member is in said rst position; barrier means between said magnetic member and inductance to prevent physical contact therebetween; an oscillator connected to excite `said inductance; an output circuit including a switching transistor having base, emitter, and collector terminals, said emitter and collector terminals being connected in said circuit such that said D.C. output signal is provided when said switching transistor is switched to a conducting state; and rectifying means connected between said inductance and said base of said switch transistor whereby actuation of said magnetic member to said second position decreases the impedance of said inductance suiciently to provide a current value from said oscillator through said inductance and rectiiier to said base suicient to switch said transistor to a conducting state, the impedance of said inductance increasing to a value to decrease said current suiciently to switch olf said transistor when said magnetic member is moved to said lirst position.
References Cited in the file of this patent UNITED STATES PATENTS 2,520,935 Hubbell Sept. 5, 1950 2,521,723 Hubbell Sept. 12, 1950 2,665,336 Saykay Jan. 5, 1954 2,740,110 Trimble Mar. 27, 1956 2,781,503 Saunders Feb. 12, 1957 2,814,031 Davis Nov. 19, 1957 OTHER REFERENCES Publication: Proceedings of LRE., February 1949, Rectier Networks for Multiposition Switching, by Brown and Rochester, pages 139-147.