US3707121A - Timing apparatus for high speed printer - Google Patents

Abstract

A high speed printer wherein print characters are disposed in rows about the periphery of a rotating drum, wherein the particular character opposite a print line along the direction of rotation of the drum is denoted by the state of a counter which is advanced as each character row passes the print line, and wherein the counter is reset when a predetermined point on the drum passes said print line.

Description

United States Patent Castoldi 51 Dec. 26, 1972 s41 TIMING APPARATUS FOR HIGH 3,001,469 9/1961 Davies et a1. ....101/93 0 SPEED PRINTER 3,024,723 3/1962 Wasserman ....101/93 C 3,117,514 1 1964 D ....l0l/93C 1 Invent: Fabml" Castoldl, Mllan, Italy 3,158,090 11/1964 ..101/93 c 3,220,343 11/1965 Wasserman ..10l/93 C [73] Ass'gnee S2122: 3$? s g g: 3,314,360 4/1967 Foster ..101/93 c x y 3,420,166 1/1969 Ellis ct a1. ..l0ll93 C luso (T urin), Italy [22] Filed: June 1, 1970 Primary Examiner-William 13. Penn Attorne Geor e V. Elt roth, Lewis P. Elbin er and [21] Appl' Frank Neuhaiser g g 52' us. c1. ..101/93 (2 ABSTRACT [51] Int. Cl. 1734 A hi h d g spec printer wherein prmt characters are [58] Filed of Search ..101/93 C, 340/149, disposed in rows aboutmtheggfiphml of imitating 1.724 drum, wherein the particular character opposite a print line along the direction of rotation of the drum is [56] References cued denoted by the state of a counter which is advanced as UNITED STATES PATENTS each character row passes the print line, and wherein 1 the counter is reset when a predetermined point on 2,757,605 8/1956 Dumey ..10l/93 C the drum passes said print line. 2,776,618 1/1957 Hartley... .101/93 C 2,906,200 9/1959 Pfleger ..101/93 C 7 Claims, 8 Drawing Figures COMPARISON AND CONTROL ClRCUlT PATENTEDnaczs I972 SHEET 1 BF 3 CONTROL CIRCUiT L COMPARISON AND CONTROL ClRCUlT.

Fabrl zl o CASTOLD/ INVENTOR.

ATTORNEY.

PATGNTED [15925 I973 3. 707 121 SHEET 3 [IF 3 w 33/ A 1 A 19 g L-' L, L 21 LJ 22," 25 B zzJ 5 COMPARISON COMPARISON AND CONTROL u AND CONTROL 23 CIRCUIT 23 c Rcu m7 Fig. 5 Fig.7

"a Fig. 8 x 36 u;::%x

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COMPARISON 1 AND CONTROL Fabr'm 23 CIRCUIT M17 CASTOLDI INVEXTOR.

ATTORNEY.

TIMING APPARATUS FOR HIGH SPEED PRINTER BACKGROUND OF THE INVENTION The present invention relates to high speed printers for use with digital data processing equipment and more particularly to timing devices and circuits for the same.

It is known, in the field of peripheral output devices for electronic computers, that high printing speeds may be obtained with serial, or preferably, parallel printers, by the principle known as printing on-the-fly. According to such principle, a type-carrying member is generally formed by a cylindrical ring on which the characters to be printed are provided in relief and arranged circumferentially, or of a drum on which'the characters are repeated on a number of parallel rings. Such a typecarrying member is caused to rotate at a constant speed in such a manner that all characters carried by said member pass a fixed generatrix of the drum or of the ring in a predetermined time interval.

Opposite to this fixed generatrix and in close proximity to the surface of the type-carrying member, a number of printing members, such as hammers, are arranged at fixed print positions, or, alternatively, one or more hammers may be moved along the generatrix in order to occupy successively different print positions.

An inking ribbon and a print receiving member, usually a paper sheet, are interposed between the typecarrying member and the printing members. When, a character required to be printed at a definite print position reaches, while rotating, the fixed generatrix and, therefore, is adjacent an associated hammer, the hammer is driven forward to press the print receiving member and the inking ribbon against such character, under the action of an electromagnet or similar device. Accordingly, the shape of the character is transferred to the print receiving member.

For such types of on-the-fly printers, and also for non-impact printers employing electrostatic, optical, and other techniques for transferring character images to print receiving members by on-the-fiy techniques, it is necessary that it be known when a predetermined character is in the proper position for printing, in order to be able to control the driving of one or more printing members at the proper moment.

Generally, the identification of a character and, accordingly, timing the driving of the printing members, is provided by using a code disc, secured to the typecarrying member and rotating therewith. This codedisc has reference indicia and timing means easily identifiable and radially arranged to correspond to the angular position of each character, or, if necessary, angularly displaced by a suitable angle relative to the angular positions of the characters.

For instance, if photoelectric cells are used for reading, or sensing, the timing and reference indicia, the code disc is opaque and the indicia are formed by arrangements of transparent windows through which the photo cells are suitably excited by a light source, thereby generating electrical pulses whose combinations correspond to the binary code combinations representing the different characters. The succession of these binary code combinations, which change continuously as different characters approach the printing position, is compared with the code combination representative of the character to be printed at each print position. When both combinations coincide for a particular print position, the printing member at such position is driven to carry out the print operation.

A simpler arrangement consists of generating a succession of pulses by means of indicia sensed by photoelectric cells or magnetic transducers, pick-ups, or equivalent means, each one of said pulses corresponding to a character position. These pulses advance a binary counter, whereby the code combinations appearing on the counters parallel outputs represent the characters approaching the print generatrix. In this case a reference signal must be generated at the beginning of each revolution to reset the counter to its initial state. For this purpose, an additional mark is used, which can be sensed by a second transducer, or by the same transducer used for the character pulses if proper discriminating circuits are provided. This arrangement is simple and economical, but has some drawbacks which limit, or even prevent its application in certain instances.

For example, if a magnetic transducer is used it must be associated-with a ferromagnetic wheel having teeth or notches, each tooth or notch corresponding to a character, and having an additional tooth or notch to denote the beginning of each revolution. This additional tooth or notch is necessarily interposed between two adjacent character teeth or notches, thereby preventing reduction below a. definite limit of the dimensions and, therefore, the inertia of the toothed wheel. Moreover, this additional tooth or notch disturbs the operation of the transducer, so that in correspondence with this tooth and the adjacent ones, it delivers electrical signals of considerable lower level, appreciably distorted, and having a frequency double the normal frequency. Thus, transducers of high sensitivity and having a greater frequency response are required.

Therefore, it is the object of this invention to provide an improved timing device for on-the-fly printers.

SUMMARY OF THE INVENTION The disadvantages and limitations of the prior art are overcome by the timing device of the instant invention, wherein the signalling of the beginning of every revolution is obtained by the detection of the absence of at least one tooth, or more generally, of one of the indicia in the normal succession of indicia carried by the timing disc.

The illustrative description following hereinafter, in order to more clearly explain the operation of the device and of the associated circuits, represents a preferred embodiment specifically employed in a highspeed drum printer. However, it is evident that the invention may be used in all instances wherein the angular position of bodies rotating at substantially constant angular speeds, or wherein the position reached by members repetitively carried along a closed path, must be identified; as, for example, in high-speed, on-the-fly printers of the serial type and in chain printers, ribbon printers, or the like.

BRIEF DESCRIPTION OF THE DRAWING The invention will be described with reference to the accompanying drawing, wherein:

FIG. 1 is a block diagram of the preferred embodiment of the invention;

circuit of FIG. 1;

FIG. 6 shows in detail the arrangement of the characters on the type-carrying member, as required by the variation of FIG. 5.

FIG. 7 is a block diagram of a second variation of the circuit of FIG. 1; and

FIG. 8 is a block diagram of another embodiment of the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT N In FIG. la type-carrying drum 1 is caused to rotate at a constant speed by amotor 2. A ferromagnetic timing disc 3 is secured to the shaft of drum 1 and rotates therewith. On the periphery of disc 3 are suitable reference notches 4, angularly spaced apart by the same angular pitch as the characters, FIG. 3, on the surface of drum 1.

Opposite to a fixed generatrix of the drum, and in close proximity to this generatrix, a suitable number of electromagnetically actuated hammers is provided. For simplicity, only one of these hammers is represented in the figure, indicated by the reference numeral 7. Hammer 7 is actuated by means of an electromagnet 8, controlled, in turn, by a control circuit 9. A print receiving member 5 and an inking ribbon 6 are interposed between the type-carrying drum and the hammer set.

An electromagnetic transducer, or pick-up, 10 is arranged proximate to the periphery of timing disc 3 at an appropriate angular position, and delivers on its output 11 avoltage pulse each time a notch 4 of the disc 3 passes by its reading, or sensing, head 12. The waveform (a), FIG. 4, of the pulses on output 11 constitutes a succession of approximately sinusoidal waves of normal period P. The pulses delivered by pick-up 10 are applied to the input of a square-pulse forming amplifier 13, which generates substantially square pulses with a normal repetition period P of constant amplitude and duration, waveform (b).

These square pulses are applied to input 14 of a oneshot 15, which responds to the negative trailing edge of each incoming pulse to generate a positive square pulse having a well-defined duration D, substantially shorter than repetition period P, waveform (c).

The output pulses of one-shot 15 are applied to input 16 of a comparison and control circuit 17, which also receives on input 23 code signal combinations representing the characters to be printed. The pulses on input 16 advance a binary counter, which thereby delivers code signal combinations corresponding to the characters arranged in succession on rings of the typecarrying drum. These code signal combinations are compared with the code signal combination of the character to be printed. When both code signal combinations are the same, a pulse is delivered on output 18, such pulse actuating electromagnet 8 of the hammer 7 associated with the print position at which such character must be printed. The instant at which this actuating pulse is transmitted depends solely on the timing of the pulses applied to input 16.

The arrangement thus far described is well known in the art.

The output pulses of one-shot 15 are termed character pulses. Such pulses are applied not only to comparison and control circuit 17, but also to the input of a rapid-recovery one-shot 19, which deliverspulses having awell-defined duration T. Such a circuit, known in the art, is characterized in that if the control pulses applied to its input follow each other by time intervals less than or equal to the time interval T, its output remains at a substantially constant high level. Only if the time interval between two successive received pulses is greater than the duration T of its output pulses, does the level of the output voltage fall to the rest level, where it remains until the receiptof the succeeding input pulse. This is shown in waveform (d), FIG. 4.

In the arrangement of FIG. 1, the operating time T of one-shot 19 is designed to be greater than the normal period P between successive character pulses delivered by one-shot 15, but less than twice the length of period P. Therefore, the output of one-shot 19 is normally at a high level, termed the work level.

If the interval between two consecutive character pulses becomes greater than T, the output 20 of oneshot 19 falls to the rest level; i.e., a negative voltage pulse is generated. This negative pulse is applied to the input of a one-shot 21, which has substantially the same characteristics as one-shot 15. Accordingly, a short positive pulse, waveform (e), is provided at output 22 of one-shot 21, in response to the negative leading edge of the pulse received from one-shot 19.

This output pulse of one-shot 21 occurs once for each revolution of drum 1 and disc 3 at a predetermined angular position of their rotation. Termed a turn pulse it is representative of the end of a revolution of the type-carrying drum. Accordingly, the turn pulse is applied to circuit 17 to restore the initial condition of the binary counter.

Assuming, now, by way of example, that the set of the characters required to be printed comprises the ten digits 0, l, 2 9. The surface of drum 1 is accordingly divided into eleven sectors of equal size, a different one of the 10 digits being located in each of 10 of these sectors. The unused sector is that between the sector carrying the last digit of the set, 9, and the sector carrying the first digit 0. FIG. 3 illustrates the developed surface of such a drum.

Corresponding to the exemplary drum organization of FIG. 3, timing disc 3 is divided in eleven equal sectors, each such sector being provided with a notch, except for the sector A, FIG. 2. Notches in adjacent sectors are equally spaced by a normal interval, whereas the interval between the notches in the sectors adjacent to sector A is double this normal interval. Waveform (a), derived from the disc of FIG. 2, demonstrates a periodic irregularity 29, FIG. 4. This irregularity corresponds to the absence of a pulse, as shown by the dashed line, and occurs concurrently with the passage of notch-less sector A by reading head 12.

Corresponding to irregularity 29, a square pulse is missing from the output waveform (b) of amplifier 13,

as shown by the dashed line 30. The corresponding pulse is missing in output waveform (c) of one-shot 15, as shown by dashed line 31.

Since the output signal of one-shot 19 is normally at work level, and falls to the rest level only when a pulse is missing in the regular succession of received pulses, the absence of a pulse in waveform due to the irregularity 29 in waveform (a), induces a rest pulse of duration 2P-T in the output of one-shot 19, waveform (d).

In response to this rest pulse, a turn pulse 32 is provided at the output of one-shot 21, as shown by waveform (e). This turn pulse represents the completion of a revolution.

In the example illustrated, the size of circular sector A has been considered to be equal to the size of each of the remaining sectors which contains a notch. It is evident that the size of sector A can be larger or smaller. By increasing sector A, a greater operating safety is obtained at the expense of a lesser utilization of the character-carrying surface of the drum if, as in the indicated arrangement, the sector of the drum corresponding to the sector A carries no print characters.

By reducing sector A, the utilization of the drum surface is increased, but a greater precision of the duration of operating time T of one-shot 19 is required. In addition, a more precise regulation of the speed of rotation of the drum is required to avoid the possibility of oneshot 19 failing to generate the rest pulse.

The apparatus of FIG. 1 may be modified to provide full utilization of the surface of the type-carrying drum. FIG. represents such a modification of the apparatus of FIG. 1. In FIG. 5, the timing pulses delivered by oneshot are applied to one input of a two-input OR-gate 24 and the output of one-shot 21 is applied to the other input of the OR gate. The output of OR-gate 24 is connected on input 25 of the comparison and control circuit 17 in lieu of input 16 of FIG. 1.

On input 25, both turn pulses and character pulses are present. The turn pulse on input 25 may be used to control the printing of an additional character located in the sector of the drum which in the embodiment of FIG. 1 had no character. Alternatively, the number of the sectors into which both the type-carrying member and the timing disc are divided may be reduced by one, the number ofcharacters remaining unchanged.

Waveform (f) of FIG. 4 represents the sequence of pulses provided on input 25 of FIG. 5. Turn pulse 32 is shown to be displaced relative to the normal time of occurrence of the character pulses, the interval between the preceding character pulse and the turn pulse being T+D, which is greater than P. Therefore, it is necessary to offset the position of the character whose printing is controlled by the turn pulse, relative to the position of the other characters. FIG. 6 shows the developed surface of a type-carrying wheel, or of a single ring of a type-carrying drum, suitable for use with the embodiment of FIG. 5. Character "O, which is located in the sector corresponding to the turn pulse, is offset by a distance x, corresponding to the time interval DTP, from the center of this sector.

This embodiment of FIG. 5 might possible cause difficulties if the offset character is too close to the following one. These difficulties would not arise if the characters on the wheel or drum were separated by a relative- 1y large distance, although such a solution could be employed only infrequently. These difficulties would be obviated if the sector allocated to the character corresponding to the turn pulse were somewhat larger than the other sectors, thus providing for the offset character to be sufficiently distant from the following one.

According to anothervariation, shown in FIG. 7, delay means may be introduced between the output of one-shot l5 and circuit 17. This delay means, comprising for example two one- shots 33 and 34, introduces a delay R for the character pulses, such delay R being determined so that turn pulse 32 occurs exactly midway between the last and the first character pulses, as indicated by waveform (g) of FIG. 4. In this instance the angular position of the timing disc relative to the type-carrying member must be suitably adjusted to accommodate this additional delay.

It is not essential to the operation of this invention that the drum rotate with a constant speed. The operating time of a one-shot depends, generally, on the charge or discharge time of a resistor-capacitor circuit. Therefore, by employing variable-parameter components, such as variable resistors or variable capacitors, in the one-shots, the operating time of the oneshots involved, such as rapid-recovery one-shot 19 and, in FIG. 7, one- shots 33 and 34, may be adjusted to accommodate to the speed of the drum. FIG. 8 illustrates such arrangement.

A tachometer 36 is coupled to motor 2 to provide an indication of the instantaneous rotation speed, for instance by delivering a voltage signal proportional to the speed. This voltage signal is applied to a control device 37, which operates to change the operating time of the one-shots involved; that is, in case of FIG. 1, of oneshot 19. Thus the duration T of the signal delivered by said one-shot 19 of FIG. 8 maintains a constant ratio relative to the period P of thecharacter pulses, for all possible rotational speeds of the type-carrying member.

Having described herein a preferred embodiment of the invention, and some variations of the same, with reference to specific application, it is apparent that other variations employing different and differently organized circuit elements may be devised without departing from the scope and spirit of the invention.

In the instant where the set of characters is repeated more than one time around the same ring, it is possible to identify the beginning or the end of each set by leaving an angular sector devoid of an identifying notch at the end of each set.

I claim:

1. In a device comprising movable members and means for identifying the position of said members during the motion thereof, means coupled to move with said movable members and provided with at least one ordered plurality of similar indicia regularly distributed, said plurality comprising a first indicium, a number of intermediate indicia, and a last indicium, each one of said intermediate indicia being located equal distance from the preceding indicium and from the following indicium, said first and last indicia being separated by a substantially greater interval single transducer, means responsive to such indicia for delivering signals representing said indicia, and means for detecting the interval between the signals corresponding to said last and first indicia, said interval being substantially larger than the intervals between the signals corresponding to said intermediate indicia.

2. ln apparatus for signalling the presence of a reference point on a cyclically movable member, said member having at least one intelligence-bearing element in each of selected ones of a plurality of contiguous sectors which measure the entire extent of said member along its direction of movement, the combination comprising: indicia-bearing means cyclically movable with said member, said indicia-bearing means having an indicium disposed in each of said sectors but a sector including said reference point, single transducer means disposed to sense said indicia along the path of their movement and to deliver an elementrepresenting signal each time an indicium passes said transducer, and means for receiving said elementrepresenting signals and responsive to the intervals between consecutive ones of said signals for generating an output signal when one of said intervals is greater than a predetermined duration, said predetermined duration being greater than the interval between consecutive element-representing signals delivered in response to indicia in adjacent sectors, but less than the interval between consecutive element-representing signals delivered in response to indicia in sectors spaced by a sector including said reference point.

3. In apparatus for signalling the presence of a reference point on a cyclically movable member, said member having a first plurality of intelligence-bearing elements uniformly spaced apart along the extent of said member in the direction of its movement, said member having a second plurality of intelligence-bearing elements uniformly spaced apart along said extent of said member, the spacing between said elements of said first plurality being the same as the spacing between said elements of said second plurality, the last element of said first plurality being spaced apart from the first element of said second plurality along said extent of said member by a distance greater than said uniform spacing, the combination comprising: indiciabearing means cyclically movable with said member, said indicia-bearing means having a first set of indicia uniformly spaced apart along the extent of said indiciabearing means in the direction of its movement, said indicia-bearing means having a second set of indicia uniformly spaced apart along said extent of said indicia-bearing means, the spacing between said indicia of said first set being the same as the spacing between said indicia of said second set, the number of indicia of said first set equal to the number of elements of said first plurality and the number of indicia of said second set being equal to the number of elements of said second plurality, the last indicium of said first set being spaced apart from the first indicium of said second set along said extent of said indicia-bearing means by a distance greater than said uniform spacing of said indicia, single transducer means disposed to sense said indicia along the path of their movement and to deliver an element-representing signal each time that an indicium passes said transducer, and means for receiving said element-representing signals and responsive to the intervals between consecutive ones of said signals for generating an output signal when one of said intervals is greater than a predetermined duration, said redetermrned duration being greater than the mterva between consecutive element-representing signals delivered in response to adjacent indicia of said first set, but less than the interval between the element-representing signals delivered in response to said last indicium of said first set and the first indicium of said second set,

4. The combination of claim 3 further including counting means responsive to each of said elementrepresenting signals to advance the count state represented thereby.

5. The combination of claim 4 further including means responsive to said output signal for resetting said counter.

6. The combination of claim 5 further including means for controlling the reproduction of a symbol corresponding to a respective one of said intelligencebearing elements each time one of said elementrepresenting signals is generated.

7. The'combination of claim 3 wherein said member and said indicia-bearing means revolve together at a substantially constant angular speed; wherein said spacing between said elements of said first plurality, said elements of said second plurality, said indicia of said first set, and said indicia of said second set is a single first angular value, and wherein said spacing between said last element of said first plurality and said first element of said second plurality and between said last indicium of said first set and said first indicium of said second set is a single second angular value.

Claims (7)

1. In a device comprising movable members and means for identifying the position of said members during the motion thereof, means coupled to move with said movable members and provided with at least one ordered plurality of similar indicia regularly distributed, said plurality comprising a first indicium, a number of intermediate indicia, and a last indicium, each one of said intermediate indicia being located equal distance from the preceding indicium and from the following indicium, said first and last indicia being separated by a substantially greater interval single transducer, means responsive to such indicia for delivering signals representing said indicia, and means for detecting the interval between the signals corresponding to said last and first indicia, said interval being substantially larger than the intervals between the signals corresponding to said intermediate indicia.

2. In apparatus for signalling the presence of a reference point on a cyclically movable member, said member having at least one intelligence-bearing element in each of selected ones of a plurality of contiguous sectors which measure the entire extent of said member along its direction of movement, the combination comprising: indicia-bearing means cyclically movable with said member, said indicia-bearing means having an indicium disposed in each of said sectors but a sector including said reference point, single transducer means disposed to sense said indicia along the path of their movement and to deliver an element-representing signal each time an indicium passes said transducer, and means for receiving said element-representing signals and responsive to the intervals between consecutive ones of said signals for generating an output signal when one of said intervals is greater than a predetermined duration, said predetermined duration being greater than the interval between consecutive element-representing signals delivered in response to indicia in adjacent sectors, but less than the interval between consecutive element-representing signals delivered in response to indicia in sectors spaced by a sector including said reference point.

3. In apparatus for signalling the presence of a reference point on a cyclically movable member, said member having a first plurality of intelligence-bearing elements uniformly spaced apart along the extent of said member in the direction of its movement, said member having a second plurality of intelligence-bearing elements uniformly spaced apart along said extent of said member, the spacing between said elements of said first plurality being the same as the spacing between said elements of said second plurality, the last element of said first plurality being spaced apart from the first element of said second plurality along said extent of said member by a distance greater than said uniform spacing, the combination comprising: indicia-bearing means cyclically movable with said member, said indicia-bearing means having a first set of indicia uniformly spaced apart along the extent of said indicia-bearing means in the direction of its movement, said indicia-bearing means having a second set of indicia uniformly spaced apart along said extent of said indicia-bearing means, the spacing between said indicia of said first set being the same as the spacing between said indicia of said second set, the number of indicia of said first set equal to the number of elements of said first plurality and the number of indicia of said second set being equal to the number of elements of said second pluraliTy, the last indicium of said first set being spaced apart from the first indicium of said second set along said extent of said indicia-bearing means by a distance greater than said uniform spacing of said indicia, single transducer means disposed to sense said indicia along the path of their movement and to deliver an element-representing signal each time that an indicium passes said transducer, and means for receiving said element-representing signals and responsive to the intervals between consecutive ones of said signals for generating an output signal when one of said intervals is greater than a predetermined duration, said predetermined duration being greater than the interval between consecutive element-representing signals delivered in response to adjacent indicia of said first set, but less than the interval between the element-representing signals delivered in response to said last indicium of said first set and the first indicium of said second set.

4. The combination of claim 3 further including counting means responsive to each of said element-representing signals to advance the count state represented thereby.

5. The combination of claim 4 further including means responsive to said output signal for resetting said counter.

6. The combination of claim 5 further including means for controlling the reproduction of a symbol corresponding to a respective one of said intelligence-bearing elements each time one of said element-representing signals is generated.

7. The combination of claim 3 wherein said member and said indicia-bearing means revolve together at a substantially constant angular speed; wherein said spacing between said elements of said first plurality, said elements of said second plurality, said indicia of said first set, and said indicia of said second set is a single first angular value, and wherein said spacing between said last element of said first plurality and said first element of said second plurality and between said last indicium of said first set and said first indicium of said second set is a single second angular value.

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