US3601534A - Alphanumeric keyboard - Google Patents

Alphanumeric keyboard Download PDF

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Publication number
US3601534A
US3601534A US795005*A US3601534DA US3601534A US 3601534 A US3601534 A US 3601534A US 3601534D A US3601534D A US 3601534DA US 3601534 A US3601534 A US 3601534A
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United States
Prior art keywords
tongue
key
core
contact
keyboard
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Expired - Lifetime
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US795005*A
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English (en)
Inventor
Alfredo Olivei
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Olivetti SpA
TIM SpA
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Olivetti SpA
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01H—ELECTRIC SWITCHES; RELAYS; SELECTORS; EMERGENCY PROTECTIVE DEVICES
    • H01H13/00—Switches having rectilinearly-movable operating part or parts adapted for pushing or pulling in one direction only, e.g. push-button switch
    • H01H13/70—Switches having rectilinearly-movable operating part or parts adapted for pushing or pulling in one direction only, e.g. push-button switch having a plurality of operating members associated with different sets of contacts, e.g. keyboard

Definitions

  • An output signal is thereby generated in output windings on the core, the output signal being so coded as to identify the key struck.
  • the present invention relates to an electronic keyboard for entering data in data priming, transmitting or processing equipment, having coded output signals in parallel on a plurality of lines and with coding obtained by means of ferromagnetic cores. More particularly, the invention relates to a keyboard of the type comprising a set of operating keys actuated by means of a manual mechanical movement and with each of which there is associated a bistable magnetic core which maybe saturated positively or negatively by input wires to produce in parallel on a'plurality of output wires a combination of binary signals representing the character of the corresponding operating key in a given code.
  • I represents a proportionality factor and a the average spread.
  • the keyboard according to the invention which provides an electronic keyboard comprising a set of manually operable keys, each of which bears on a metal changeover tongue which makes contact with one of two contacts in the unoperated and operated positions respectively of the key and thereby connects biasing wires differently to a voltage source, the biasing wires linking a bistable magnetic core associated with the key in an arrangement such that the core is saturated in its two different senses in the said unoperated and operated positions respectively and induces in output wires linking the core a combination of pulses representing the operated key in a given code.
  • FIG. I is a diagram which represents the probability of the time of offset in the striking of two keys operating consecutively
  • FIG. 2 shows the time diagrams of the input and output voltages for the magnetic cores used in the present invention
  • FIG. 3 shows one embodiment of the working principle of a keyboard embodying the invention
  • FIG 4 shows the hysteresis curve of a magnetic core used in the keyboard
  • FIG. 5 shows a particular form for the circuit for changing over the bias of the magnetic cores employed in the keyboard
  • FIG. 6 shows different waveforms of the output signals produced by the keyboard
  • FIG. 7 shows a constructional form of a keyboard embodying the invention.
  • FIG, 2 shown the diagrams of the variation in time of the feed voltage Vi on the input wire to the magnetic core and of the voltage Vu collected as output on the coding wires.
  • the time interval indicated by tpn represents the time necessary for the change from the connection to the positive source to the connection to the negative source (and vice versa), which is mechanical time necessary so that the changeover switch may be brought, from interruption of the contact with the positive pole, to initiate the contact with the negative pole; for good operation of the keyboard from the point of view of the mechanical speed of changeover, this interval must be less than 200 us.
  • connection between the input wires of the cores and the positive or negative source is insured in the illustrated embodiment by simple ohmic contacts actuated directly by the key.
  • FIG. 3 there appears a diagrammatic representation of the contacts a and b of the key 1 and of the changeover tongue 2.
  • a hump a present at one end 3 of the tongue 2 which is fixed at the other end 4, bears on'the negative contact a.
  • the tongue 2 comes to bear on the fulcrum f. This causes the tongue to bow so that the hump a is separated from the negative contact and another hump b present at the end 3 of the tongue 2 is brought into contact with the positive pole b.
  • the tongue 2 also serves as a spring for the key. In order to insure the sliding contact on contact a the fulcrum f is slightly spaced from the tongue in the inoperative position of the key.
  • the operator is able to bear resiliently on a key depressed into the end-of-stroke position or in the inoperative position without any risk of causing a signal on the output channel, since the core is able to supply a fresh signal only when the key has passed into the position opposite to that in which it is when the operator bears resiliently thereon.
  • sliding contacts show many fallings-off or drops in voltage, at times down to zero, during the establishment of the contact itself. In the present case, these fallings-off have no effect, because once the core has reversed its saturation it remains in the reversed state as long as the input wire is not placed in contact with the source of opposite sign again.
  • FIG. 3 illustrates the principle of operation for one key, it being understood that for each key there is a circuit identical to that show in the FIGURE, each with its code corresponding to the character represented by the respective operating key.
  • a bistable magnetic core 5 is shown diagrammatically by a thick straight line.
  • a winding on the core is indicated by a short line inclined to the left if the winding is in one sense termed direct and by a short line inclined to the right if the winding is in the inverse sense.
  • the magnetic core 5 with a rectangular hysteresis loop (FIG. 4), is provided with a winding with an input wire I constituted by a single turn wound in the direct sense, a winding with an input wire N constituted by a single turn wound in the inverse sense and the outgoing or output coding wires indicated by the references C1 to C7, which are wound in the direct sense.
  • a winding with an input wire I constituted by a single turn wound in the direct sense
  • a winding with an input wire N constituted by a single turn wound in the inverse sense
  • the outgoing or output coding wires indicated by the references C1 to C7 which are wound in the direct sense.
  • the wires land N are made of nickel-chromium.
  • the wire N is the biasing wire of the core and is connected from the positive pole of the source E through the current limiting resister R to earth and the wires indicated by the references C1 to C7 are the coding wires connected between earth and the respective outputs U1 to U7.
  • the resistance of the circuit through the wire N is larger than that through the wire I (either by use of a high resistance wire or by use of a limiting resistor in series with the wire N) so that the current in the wire N is only a small fraction of that flowing in the wire l.
  • Each core 5 therefore has a relatively small inverse magnetic biasing field by virtue of the current flowing through the biasing wire N.
  • the biasing field will be regarded as negative.
  • each core is also subjected to a relatively large inverse field due to the current flowing through the input wire indicated by the reference I which is connected to the negative pole of the source E through the tongue 2 and the contact a.
  • FIG. 4 shows the hysteresis curve of a core zero field being represented by point 9.
  • the core is saturated negatively by the combined effects of the currents in the wires I and N and its state is represented by the point 6 in FIG. 4.
  • the sign of the voltage is reversed and a relatively large forward current now flows through the wire I overcoming the reverse bias. It is well known that in the input wire I there occurs a counterelectromotive force equal to the voltage E applied and the current which is established will be such that these conditions are satisfied.
  • the counterelectromotive force is equal to df/dt, in which f is the flux and t is the time.
  • f the flux
  • t the time.
  • the working point on the hysteresis loop shifts from 6 to 7 and, at the same time, the saturation of the core is reversed, so that there is a change to the point 8 on the hysteresis loop, and the time T necessary for the reversal depends on the total variation 2F of the flux.
  • the two bias sources E and E shown in FIG. 3 can be reduced to a single source with a single sign, for example +E.
  • a single wire L linked both in direct manner and in inverse manner with the core 5 and a single voltage source E is sufficient to change over each core 5.
  • the wire L has an intermediate point F connected to earth and its ends connected to two contact positions A and B.
  • the changeover signal has the form and amplitude shown by curve Q in FIG. 6, while in the simplified arrangement of FIG. 5 the changeover signal has the course indicated by the curve S.
  • the simplified arrangement there is a decrease of approximately percent in the amplitude of the voltage of the changeover signal with respect to the optimum arrangement. That is, there is obtained a signal S which is reduced by the effect of the initial bias provided by the wire N in the arrangement illustrated in F IG. 3.
  • FIG. 4 illustrates the hysteresis curve developed preferably by the arrangement of FIG. 3.
  • the coding of the output signals may be most varied and other lines (for example an eighth line for timing), which may possibly be neces sary for the operation of storage devices for a plurality of characters, may be added to the seven lines for the lower case characters and the seven lines for the upper case characters.
  • lines for example an eighth line for timing
  • FIG. 7 A constructional form of a keyboard according to the invention is shown in FIG. 7.
  • a single wire L which may be of nickel chrome with a diameter of 0.3 mm. is wound in the manner indicated in FIG. 7 on a core 5 to effect the switching of the core.
  • the tongue 2 closes the circuit by means of the hump a through the contact A, so that the core is saturated negatively.
  • the contact A is opened and the contact B is closed via the hump b of the tongue 2.
  • each line C is connected to the primary P of a transformer which may have a primary of about a hundred turns, while the secondary S may be constituted by about a thousand turns, so that the signal at the output U is amplified 10 times.
  • a capacitor C of 1000 pF and a diode D which have the function of eliminating disturbances and suppressing the signals of a given sign, for example the negative signals.
  • a plastic plate 9 has through seats 10 in which the keys are simply inserted, the keys being formed in one piece, made of plastic and of parallelepipedal or cylindrical form and having at their base a flange 11 which prevents the keys becoming disengaged from the keyboard once they have been inserted into the plate 9 from below.
  • Each key is moreover extended and bears by means of a stem 12 directly on the changeover tongue 2, which may be made of beryllium bronze with a thickness of around 0.2 mm.
  • the tongue 2 bends and is lowered until it touches the fulcrum f, which is located 0.5 mm. from the tongue when the key is in the inoperative position. From the moment when the tongue touches the fulcrum f and only from this moment, the contact A opens and the key, continuing its stroke, bends the tongue further and the hump b of the tongue at the end 3 continues to rise until it closes the contact B.
  • the tongue 2 therefore performs a plurality of duties, that is of contact and springing and return of the key.
  • the contacts A and B may be formed as plane portions of a printed circuit by suitably metallizing the plates 9 and 13, as shown diagrammatically in FIG. 7.
  • the contact B is situated on a projection 14 of the plate 9, which could be formed at the same time as the plate 9 by moulding.
  • the changeover tongues 2 may form part of a single metal plate 15 cut so as to comprise as central body from which there extend arms or branches to form the tongues 2.
  • the central body of the plate 15 may be rivetted to a projection 16 of the lower plate 13.
  • the metal plate 15 is then connected to one pole (for example, the positive pole) of the voltage source E, the other pole being grounded.
  • An alphanumerical keyboard comprising:
  • a first and a second contact mounted proximate said other end of said tongue for making electrical contact respectively with one side of said tongue when said key is in an unoperated position and with the other side of said tongue after said key is operated and depressed beyond a predetermined amount
  • said first and second contacts being adapted to be connected to sources of electrical potential having opposite polarities with respect to a point of reference potential
  • said first and second winding linking the bistable magnetic core in opposed directions so that the core is saturated in two different statuses in the said unoperated and operated positions respectively
  • a keyboard as recited in claim 1 including a metal plate comprising a central body portion anchored to said fixed support and a plurality of resilient flexibly supported arms extending from said central body and wherein said plurality of resilient arms are adapted to serve as said plurality of flexible tongues.
  • a keyboard as recited in claim 2 including a stem intermediate each of said plurality of tongues and said corresponding key, said tongue operating through said stem to restore said corresponding key to its unoperated position when the key is manually released.
  • Analphanumerical keyboard comprising:
  • actuating means coupled to each of said keys, having a rest position and being movably mounted for depressing one side of said associated tongue at a point intermediate the ends when said key is actuated,
  • snap means mounted proximate the opposite side of said tongue intermediate said actuating means and the other end of said tongue for causing said other end of said tongue to swing in the opposite direction to said actuating means
  • first and second contact means mounted proximate said other end of said tongue when said actuating means is in its rest position and a second state of contact with said tongue when the key is actuated, respectively
  • plurality of magnetic cores each associated with one of said plurality of tongues each having a pair of opposite stable magnetic states
  • first and second biasing wires associated with each of said cores coupled between said first and second contact means and reference potential and linking said core in opposite senses, said wires causing said core to switch to the opposite state when said tongue is in said second state of contact, and
  • each output wire is connected to a stepup transformer having a capacitor and a diode in parallel with its output for absorbing disturbing signals and suppressing pulses of one sign.

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US795005*A 1968-02-13 1969-01-29 Alphanumeric keyboard Expired - Lifetime US3601534A (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
IT5049868 1968-02-13

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US3601534A true US3601534A (en) 1971-08-24

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US (1) US3601534A (enrdf_load_stackoverflow)
DE (1) DE1906720A1 (enrdf_load_stackoverflow)
FR (1) FR1594361A (enrdf_load_stackoverflow)

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS4831473A (enrdf_load_stackoverflow) * 1971-08-30 1973-04-25

Citations (11)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2505605A (en) * 1948-01-20 1950-04-25 Charles F Coake Snap switch
US2835741A (en) * 1956-11-01 1958-05-20 Bell Telephone Labor Inc Magnetic core signal generator
US2849539A (en) * 1956-12-13 1958-08-26 Bell Telephone Labor Inc Magnetic core circuits
US2904636A (en) * 1955-12-22 1959-09-15 Bell Telephone Labor Inc Telephone circuit using magnetic cores
US2997703A (en) * 1956-08-03 1961-08-22 Clary Corp Keyboard controlled circuitry
US3040304A (en) * 1958-07-03 1962-06-19 Int Standard Electric Corp Magnetic information storage arrangements
USRE25235E (en) * 1955-10-19 1962-09-04 Gener
US3255639A (en) * 1963-09-13 1966-06-14 Penn Controls Snap action switch
US3303290A (en) * 1964-01-02 1967-02-07 Automatic Elect Lab Signaling arrangements employing piezoelectric devices
US3487184A (en) * 1967-08-25 1969-12-30 Maxson Electronics Corp Overtravel mechanism for snap-action switch
US3495236A (en) * 1969-04-16 1970-02-10 Burroughs Corp Transducer

Patent Citations (11)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2505605A (en) * 1948-01-20 1950-04-25 Charles F Coake Snap switch
USRE25235E (en) * 1955-10-19 1962-09-04 Gener
US2904636A (en) * 1955-12-22 1959-09-15 Bell Telephone Labor Inc Telephone circuit using magnetic cores
US2997703A (en) * 1956-08-03 1961-08-22 Clary Corp Keyboard controlled circuitry
US2835741A (en) * 1956-11-01 1958-05-20 Bell Telephone Labor Inc Magnetic core signal generator
US2849539A (en) * 1956-12-13 1958-08-26 Bell Telephone Labor Inc Magnetic core circuits
US3040304A (en) * 1958-07-03 1962-06-19 Int Standard Electric Corp Magnetic information storage arrangements
US3255639A (en) * 1963-09-13 1966-06-14 Penn Controls Snap action switch
US3303290A (en) * 1964-01-02 1967-02-07 Automatic Elect Lab Signaling arrangements employing piezoelectric devices
US3487184A (en) * 1967-08-25 1969-12-30 Maxson Electronics Corp Overtravel mechanism for snap-action switch
US3495236A (en) * 1969-04-16 1970-02-10 Burroughs Corp Transducer

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DE1906720A1 (de) 1969-09-18
FR1594361A (enrdf_load_stackoverflow) 1970-06-01

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