Electronic digital displays

[57] ABSTRACT

A digital display device for displaying a plurality of alphanumeric characters from a single electronic display unit in which the single unit is reciprocated at a predetermined frequency through a given distance and the unit is energized to emit an alphanumeric character display at synchronized positions during its swing between extreme positions so that the complete display of alphanumeric characters appears without the eye being able to detect the motion of the single display unit.

Claims, 5 Drawing Figures

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PATENTED NOV 51974

3.846,784

SHEET 1 OF 4

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PATENTED NOV 51974

3.846J84

SHEET 2 OF 4

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PATENTEDNOV 51974 3,846.784

SHEET 3 OF 4

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SHEET 4 OF 4

PATENTED NOV 5 1974

3,846,784

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3,846,784

ELECTRONIC DIGITAL DISPLAYS

The present invention relates to electronic digital displays.

Equipment which displays information electronically is widely known and used, and there is a demand for electronic components which accept electrical signals and display either letters or numbers. An electronic calculator of known type contains eight such components each capable of displaying any of the digits from 0 to 9. Each display unit consists of a seven bar arrangement, the seven individual bars being separately illuminated and arranged in the shape of a square eight. With this arrangement the calculator is able to display any eight figure number. In addition, this type of display unit can be easily adapted to display letters as well as numbers.

However, the above described alphanumeric or numeric display devices are relatively expensive especially when one needs six or more in order to achieve the desired digital display.

It is therefore an object of the present invention to reduce this expense by utilizing only a single display device in order to obtain a display of a plurality of digits.

According to the present invention there is provided a digital display device capable of displaying a plurality of numbers and/or letters including a single electronic digital display unit, means for reciprocating said unit at a predetermined frequency through a given distance and means for causing a plurality of discrete electronic displays to be emitted from said display unit at precise positions in the swing of the unit from one extreme position to the other.

Preferably in one form the means for reciprocating said display unit includes a U-shaped piece of springy material to one extremity of which is attached an arm on the end of which the display device is mounted, and to the other extremity of which is attached adjustable counter weight means. Said counter weight means may comprise a threaded rod upon which a nut is threadably engaged such that it may be screwed in either direction along the threaded rod. Means may be provided for the aforesaid assembly to be lightly gripped in resilient pads at the base of the U and excited into oscillation in the manner of a tuning fork by the interaction of the field of an electro-magnet with a pole piece attached to one arm of the U.

Preferably in another form the means for reciprocating said display unit includes two lever arms pivotally attached one to the other at about their centres in the manner of a pair of scissors, the pivot point being fixedly attached to the casing of the display. The digital display device and the counterweight may be mounted on respective ends of the two lever arms. Between the other ends of the lever arms and the pivot point there may be mounted firstly a spring fixed at its outer ends to the two lever arms and at its centre to the instrument case and acting so as to maintain the adjacent lever arms at an appropriate angle one to another and secondly a solenoid associated with two pole pieces each being attached to one of the lever arms such that when the adjacent lever arms move closer to one another the pole pieces move further into, the solenoid.

Preferably the means for causing a plurality of discrete electronic displays to be emitted from said display unit at precise positions in the swing of the unit com2 prises a synchronizing circuit driven from a display oscillator and controlling the phase and frequency of the clock oscillator driving the calculator logic.

Preferably means are provided to speed up and slow down the clock oscillator by detection of the display digit position, this control ensuring even spacing of the displayed digits in spite of the sinusoidal variation of the digit velocity.

The present invention will now be described in greater detail by way of example with reference to the accompanying drawings, wherein:

FIG. 1 shows a front elevation of one preferred form of the mechanical arrangement of the display according to the present invention;

FIG. 2 is a section along the line I—I of FIG. 1;

FIG. 3 shows a front elevation of the mechanical arrangement of a second preferred form of the display according to the present invention;

FIG. 4 shows in functional block diagrammatic form the driving circuitry for the displays of FIGS. 1 to 3; and

FIG. 5 shows some of the waveforms relating to FIG. 4.

Referring to FIG. 1 the mechanical arrangement of a first form of the display according to the present invention comprises a one digit electronic display 21 mounted on the end of an arm 23, the arm 23 being mounted in the end of one arm of a U shaped spring metal component 24 in the other end of which is fixed a threaded rod 25 which carries an adjustable nut 26. The U-shaped component 24 is held between resilient pads 33 and 34, these pads being lightly held by blocks 31 and 32 which blocks are fixed in a mounting block 35 which in turn is fixed to the instrument casing (not shown). The mounting of the U-shaped component 24 is such as to retain it in position whilst permitting sufficient movement at the mounting point to enable a torque to be transmitted from one side of the mounting to the other thus enabling the assembly of the U component 24 in conjunction with the rod 25 carrying the nut 26 and the arm 23 carrying the digit display 21 to behave as a tuning fork.

The arm of the U-shaped component 24 which carries the arm 23 and the digit electronic display 21, has a pole piece 27 secured thereto near the extremity of said arm of the U-shaped component 24. A solenoid 29 is mounted on a block 30 which in turn is mounted on the instrument case (not shown). Associated with the solenoid 29 is a feedback coil 28 which is wound on the same former as the solenoid winding. The purpose of this feedback coil 28 will be explained in greater detail hereinafter.

The tuning fork arrangement discussed above is excited into oscillation at its resonant frequency by the attraction of the pole piece 27 by the solenoid 29 when energized, said solenoid being intermittently energized at the resonant frequency in order to maintain the oscillation of the digit display 21.

Fine gauge wires (not shown) which feed signals to the digit display 21 are attached to the arm 23 and are connected to the driving circuits via connection points (not shown) on the mounting block 35. Further connections are made to the driving solenoid 29 and the feedback coil 28. Adjustment of the nut 26 on the threaded rod 25 enables the two arms of the “tuning fork” to be balanced, i.e. the moment about the mounting point due to movement of the short heavy arm 25

3,846,784 is matched by the moment applied by the long fine arm 23 and display digit 21.

The sectional view of the assembly of FIG. 1 shown in FIG. 2 makes clear the arrangement whereby the U component 24 made of a flat strip of a springy metal is held by the resilient pads 33 and 34 which are clamped between the blocks 31 and 32.

The mechanical arrangement of a second preferred form of the display according to the present invention is shown in FIG. 3 wherein a resonant mechanical system is comprised by arms 41 and 44 in conjunction with a spring 45.

The arms 41 and 44 are coaxially pivoted on a pivot 42 which pivot is attached to the instrument casing (not shown). At one end of the arm 41 is mounted a display digit 40, the adjacent end of arm 44 bearing a counter weight 43. The arms 41 and 44 are held at a suitable mean angle one to the other by the spring 45 the centre of the spring 45 being located with respect to the instrument casing by a resilient peg 46.

The resonant assembly is excited into motion by a solenoid 48 attracting into it pole pieces 47 and 49 which are attached to the arms 41 and 44 respectively. The solenoid 48 has wound coaxially with it a position feedback coil 51 and is mounted on the instrument case by means of a mounting block 50. Fine gauge wires feed the required signals to the digit display 40 and are led along the arm 41 towards the pivot point 42 in the region of which they are terminated at suitable connection pins (now shown).

The operation of the display will now be explained with reference to the remaining figures of the accompanying drawings whereof FIG. 4 is a functional block diagram and FIG. 5 shows some of the waveforms appertaining to the blocks of FIG. 4.

In the following description the following components in the two embodiments of mechanical systems described above have the following general designation for the sake of simplicity.

The one digit displays 21 and 40 are designated 1.

The seven individual segments of the display 1 are designated 2.

The arms 23 and 41 are designated 3.

The pole pieces 27 and 47/49 are designated 4.

The position feedback coils 28 and 51 are designated 6.

The solenoids 29 and 46 are designated 7.

The digit display 1 is mounted at the end of the arm 3 and comprises seven segments 2 arranged in the form of a square eight, these segments being individually illuminated according to the output from the electronic circuit.

The display driving system of FIG. 4 comprises a display drive oscillator 8; a calculator oscillator 9; a synchronizing circuit 10; a flyback blanking circuit 11; a gate circuit 12; a monostable driver circuit 13; a calculator integrated circuit 14, hereinafter referred to as the calculator chip; a segment driver circuit 15 and a synchronization gate 16. Timing of circuit operations is controlled from the free running oscillator 8 which drives the solenoid 7 at the resonant frequency of the mechanical system of which the arm 3 is a part, setting the display digit 1 into oscillatory motion. The segments of the display digit 1 are driven according to the number to be displayed from the segment outputs of the calculator chip 14 via the segment driver 15. Whilst which segments are to be displayed is determined by the calculator output, illumination of the display is controlled by the state of the monostable driver 13 which switches the display on at appropriate instants.

The calculator clock oscillator 9 is synchronized in accordance with digit position by means of the synchronizer 10 which is fed the output signal of the driving oscillator 8 as well as a signal corresponding to output of the first display digit. The function of the synchronizer 10 is to compare the two aforesaid input signals and produce an output signal capable of controlling the oscillator 9 to synchronize the output of the first display digit from the calculator chip 14 with one end position of the display digit 1. A further control of the calculator clock oscillator 9 is provided by the digit position feedback winding 6 adjacent to the driving solenoid 7. The correction applied to the clock oscillator 9 by the output of the winding 6 serves to speed up and slow down the clock oscillator 9 to produce an even spacing of the displayed digits in a manner analogous to the S-correction employed in television receivers. When the display digit 1 is at the end of its swing it is moving slowly relative to its speed of movement at the centre of its swing and thus to produce an even spacing of the digits throughout the display digit’s swing the Stype correction applied by the winding 6 slows the clock oscillator 9 when the display digit approaches the end of its swing and speeds up the clock oscillator 9 when the display digit approaches the centre of its swing.

In order to stop the motion of the display digit 1 when a number is illuminated, i.e., to make the displayed number appear stationary, the display is lit for a short period only when a digit output from the calculator indicates the selection of segments corresponding to a number to be displayed has been made. The calculator digit outputs drive the short period monostable 13 via the gate 12 which gate prevents the monostable 13 from driving the display digit 1 when the flyback blanking circuit 11 driven by the oscillator 8 detects flyback of the display digit 1. Thus the display digit 1 displays on the appropriate segments 2 the calculator output during one half of its cycle of oscillation. The function of the gate 16 is to permit only the first displayed digit pulse to be fed to the synchronizer 10 so that it does not attempt to re-synchronize the clock oscillator 9 on receipt of each digit output.

The operation of the circuitry of FIG. 4 will now be further explained by reference to FIG. 5 wherein waveform (a) shows the square wave output of the flyback blanking circuit 11 of FIG. 4, the output level being “high” during the forward displaying stroke of the display digit and “low” during the return stroke of the display digit thus preventing the display from lighting up during the return stroke of the display digit. During the forward stroke of the display digit, the digit outputs from the calculator chip 14 pass via the gate 12 (opened by the output of the flyback blanking circuit 11 as described above) to the monostable driver 13 the output waveform of the gate 12 being illustrated in waveform (b) which shows the series of digit pulses. To provide the very short duration pulses required to “stop” the motion of the display digit the leading edge of each digit pulse triggers the monostable driver 13 this monostable having the required short pulse width and producing waveform (c).

The waveforms (a), (/;) and (c) of FIG. 5 are drawn to a timescale t which neglects the variation in clock

3,846,784 oscillator speed effected by S-correction. Taking this effect into account the display drive pulses are plotted against a real time axis T as shown in waveform (d). This waveform clearly shows their increased frequency towards the centre of the display, at which point the digit is moving at its maximum rate. When the display is driven by the waveform (d) of FIG. 5, the digits appear evenly spaced out.