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Publication numberUS3813492 A
Publication typeGrant
Publication dateMay 28, 1974
Filing dateMay 25, 1972
Priority dateApr 23, 1971
Publication numberUS 3813492 A, US 3813492A, US-A-3813492, US3813492 A, US3813492A
InventorsPotter J
Original AssigneePotter Instrument Co Inc
Export CitationBiBTeX, EndNote, RefMan
External Links: USPTO, USPTO Assignment, Espacenet
Copier system
US 3813492 A
Abstract
An element responsive to the level of reflected light scans a document in consecutive parallel scan lines, producing an electrical output signal which is converted from analog to digital form. The digital output is entered into one of a pair of storage resistors. A copy of the document is produced by a multi-hammer helix printer which composes one line of dots at-a-time by printing plural line segments simultaneously. The hammers are energized so as to press against the helical bar in accordance with the outputs of corresponding digital-to-analog converters connected respectively to parallel output lines from the storage registers. A transfer switch control causes one register to be in the output mode operating the hammers while the other is in the input mode for serial data entry, and vice versa on alternate scan lines.
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Description  (OCR text may contain errors)

United States Patent 1191 Potter May 28, 1974 l l COPIER SYSTEM [75] Inventor: John T. Potter, Locust Valley, N.Y.

[73] Assignee: Potter Instrument Company Inc., Plainview, NY.

[22] Filed: May 25, 1972 [21] Appl. No.: 256,965

Related US. Application Data [63] Continuation-impart of Ser. No. 136,950, April 23,

[58] Field of Search 178/30, 71.13, 5,17, 17 D, 178/17 R, 17 S, 5.4 E, 5.4 ES, DIG. 27, 25, 7.1 E, 6.6 R, 7.1; 346/74 ES, 75

OTHER PUBLICATIONS Character Recognition, M. H. Glauberman, Electronic, pp. 132-136, Feb. 1956.

Character Selection for Mosaic Printer," J. Mako, 1MB, Vol. 4, No. 5, Oct. 1961, p. 6.

Primary Examiner-Thomas A. Robinson Attorney, Agent, or Firm-Laurence J. Marhocfer [57] ABSTRACT An element responsive to the level of reflected light scans a document in consecutive parallel scan lines, producing an electrical output signal which is converted from analog to digital form. The digital output is entered into one of a pair of storage resistors. A copy of the document is produced by a multi-hammer helix printer which composes one line of dots at-a- [56] References Cited time by printing plural line segments simultaneously. UNlTED STATES PATENTS The hammers are energized so as to press against the 2,618,702 11/1952 Thompson 178 71 E helical bar accordance with the outputs of 2,930,847 3/1960 Metzger 178/30 1 9 9 dlgltal'to'analog cPnveflers Connected 3,174,427 3/1965 Taylor 178/30 spectlvely to parallel Output 111168 from the Storage 3,233,037 2/1966 F611 178/5 s- A t ns er switch control causes one register to 3,465,360 9/1969 Hackley et a1. 346/74 ES be in the output mode operating the hammers while 3,512,158 6/1970 Scarbrough t 178/30 the other is in the input mode for serial data entry, 3,609,759 9/I97I Teske 6! 8|. I78/I7 and vice versa on alternate an line 3,622,701 11/1971 Gardner 178/30 3,723,646 3 1973 Behfllle 81 al. 346/74 ES 15 Claims, 3 Drawing Flgules /LOGIC UN1T8O FROM COPY LIMIT TRANSDUCER 88 92 FROM 84 COUNTER ZOOO PULSE IREV RESET TRANSDUCER 86 STORAGE UNIT 64 1 1 FROM A D 94 l l l l l l l l l l iiz'glNELvERLlNEs TO g-AR 7 PR E-AMR 1 seggon 2 68 f lllllllll 78 oi STORAGE UNIT 66 M FROM.

X E Z T PULSE/REV l swlTcH I FROM TRANSDUCER 9s QONTRQL lPULSE/REV.

TRANSDUCER 72 PATENIEBIIII 28 I974 3.813.492 SHEET 1 BF 2 FROM PRINTER I P/REV 0 38 PAPER FEEDB TRANSDUCER 72 FAST MOTOR 40 iBfis IE STEP Z GENERATOR Mom R 30 as Q50 "57 H 0728 p 12-34 COPY LI IT 36 SIGNAL TO 88 LOGIC UNIT so 8? [EL Is4- P/REV SCANIED COPY 90 N 5 HEL'X PR'NTER'Z' TO S.W.96 CLAM PED TO DRUM 9 86 5 M4 3 J 74 V m I-I- 2000 P/REV. I 72 TO LOGIC UNIT so ELI X 6/ \so 44{M0T0R 4 s2 46/ 52 4s HAMM E R c0I\ITR0I s6- FIRI- s 56 292? CIRCUIT FEED 54 56 l -5 DIGITAL T0 ANALOG D A 58 CONVERTER couv. cow CONV.

ROM STORAGE UNITS .66 VIA SWITCHES 94 PATENTEDIU 28 m4 SHEET 2 BF 2 fLOGI C UNIT 80 FROM COPY LIMIT o TRANSDUCER as 94 F/ 6. 2.

92 FROM a4 2000 PULSE /REV COUNTER HRESET TRANSDUCER as 60 STORAGE UNIT 64 76 I 78 94 FROM A D I 94 I I I I l I I I I, l TWELVE LINES To D-A SENSORPREAMP v ONVERTERS 58 F R 22 es ITITIITTI 78HAMMERS 4s I I im-rs I I STORAGE uNlTss I se FROM |54 I; PULSE/REV SWITCH I FROM TRANSDUCER 9a Q IPULSE/REV. TRANsDUcER 72 s'roRAeE UNIT 64 I [I02 I I I STAGE STAGE I I 1 #I2 I 7 l I I I I04 I FROM AD I I 16 corgv. 62I STAGE STAGE l I VIA 3 SWITCH ee #4 I I I -I L INPUT I |os I I I STAGE STAGE I I I I I2 I l I I I I O O FDR HAMMER|2 FOR HAMMER#I w I TO DA CONVERTERS 58 VIA SWITCHES 94 COPIER SYSTEM CROSS REFERENCE TO RELATED APPLICATION This application is a continuation-in-part of copending application Ser. No. 136,950, entitled Facsimile Printing System, filed on Apr. 23, 1971 by John T. Potter and assigned to the assignee of this application.

BACKGROUND OF THE INVENTION The invention relates generally to optical scanning and copier systems, and more particularly to improved systems for controlling the operation of an electromechanical printer in response to the output of an optical scanning system.

Unlike most photographic or xerographic copiers, the copier, or facsimile system of the instant invention first scans the original document with a light level sensor to produce electrical signals which drive a dot printer. The dot printer'reproduces the original, one narrow line at-a-time.

The mechanical and electrical elements of improved helical bar facsimile printer are disclosed in the aforementioned copending application Ser. No. 136,950. Briefly, that printer comprises a continuously rotating helical bar with a plurality of convolutions and a corresponding plurality of hammer blades aligned in parallel with the helix axis. Paper and inked ribbon are carried between the bar and hammer blades. Dots are printed by individually impelling the hammer blades against the bar. As the bar rotates the points where the helical bar and hammers intersect are continuously and repeatedly advanced along a line in each line segment. An entire line is thus composed by printing a plurality of line segments simultaneously.

While the multi-hammer helix printer operates at much higher speed than single-bladed, lawn mower type helix printers, scanning of the original document is complicated by the fact that the print line is divided into a plurality of simultaneously printed segments. In the past, special scanning systems were designed for scanning corresponding line segments of the original document simultaneously. In particular, in the aforementioned copending application, Ser. No. 136,950, the original document is scanned with a plurality of equally spaced photocells riding on a linear track. Each cell is simultaneously moved over a segment of the line corresponding to a particular hammer in the printer. In a copending application Ser. No. 178,211, filed Sept. 7, 1971, entitled "Optical Line Scanner and Facsimile System assigned to the same assignee as this application, a video tube scanning system is disclosed representing another technique for simultaneous scanning of plural line segments. Mechanical systems employing photocells do, however, have an advantage over video systems: photocells cost less, are inherently capable of higher resolution and have an output which is easier to transmit. However, if a single photocell is swept over an entire line, the electrical output is serial; that is, the output represents the light level point-by-point along the entire length of the scan line. The serial signals are therefore not in the proper form for operating a multihammer helix printer.

SUMMARY OF THE INVENTION Accordingly, the general purpose of the invention is to improve scanning systems and control circuits associated with multi-hammer, simultaneous line segment, facsimile printers. Another object of the invention is to enable the output of a single photosensor scanning system to drive a multi-hammer facsimile printer by reorganizing the output so that it corresponds with the line segments printed by each hammer. A further object of the invention is to employ digital techniques to enable a multi-hammer helix printer to print dots with a plurality of discrete levels of darkness representing the tonality of corresponding points in the original document.

These and other objects of the invention are achieved by employing a pair of alternated storage registers into which digital signals representing the analog output of a single photosensor are serially entered and then read out in parallel fashion to the hammer drive circuits of a multi-hammer helix printer. The original document is fastened to the surface of a continuously rotating scan drum. The photosensor is moved step-wise along a linear track extending parallel to the axis of the drum such that the document is scanned in consecutive, parallel sweeps. The helix printer includes a continuously rotating helical bar and a plurality of hammer blades aligned parallel to the axis of the bar such that each hammer blade corresponds to an adjacent helical convolution. Paper and ink ribbon are carried between the helical bar and the aligned hammer blades. The paper is advanced one line at a time in a direction perpendicular to the helix axis. The step-wise advancement of the photosensor corresponds to the movement of the paper in the printer. The output of the photosensor is digitized in an analog-to-digital converter. The converter output is alternately passed on corresponding cycles of the rotating helical bar to the serial input of either one of the pair of storage registers. The analog-to-digital converter and storage register are gated or clocked during input at a rate corresponding to the number of print positions along the entire print line. For example, in one embodiment the helix printer employs 12 hammers having 154 dot print positions for each hammer resulting in 1,848 print positions along the entire print line. Accordingly, the analog input to the converter is regularly sampled 1,848 times per cycle of the scan drum. Similarly, each storage register must provide 1,848 bits of storage per output bit of the analog-todigital converter.

Each storage register is tapped to provide a plurality of parallel output lines to the hammer drive circuits in the printer. In the above embodiment each storage register would provide 12 parallel output lines per converter output bit. After the digital information for one complete scanning cycle is stored in one of the registers, that register is switched to the output mode in which the stored bits corresponding to consecutive print positions are clocked past each of the hammer output lines at a rate corresponding to the number of dot print positions per hammer during each cycle of the helical bar. While one storage register is in the output mode the other storage register is in the input mode receiving digital information from the next scanning cycle. A digital-to-analog converter and hammer drive circuit are associated with each hammer in the helix printer. Corresponding output lines from the storage register in the output mode are connected to the digital-to-analog converters which cause the hammer blades to be fired with variable impact corresponding A BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic and block diagram illustrating the scanning apparatus and helix printer employed in the facsimile system according to the invention.

FIG. 2 is a block diagram illustrating the electronic circuitry which receives the output of the photosensitive element and reorganizes the input signals in digital form to provide outputs to drive the helix printer of FIG. I.

FIG. 3 is a block diagram illustrating one of the storage registers of FIG. 2 in more detail for an embodiment in which the converted analog output of the photosensitive element is coded in three bits.

DESCRIPTION or THE PREFERRED EMBODIMENT In FIG. 1 the scanning apparatus provides an electrical analog output representing the reflected light level of an original document along a pluralityof parallel'scan lines. A helix printer l2 reproduces the original document, that is, creates a facsimile thereof, in response to the electrical output of the scanning apparatus 10 by printing a plurality of dots of varying darkness along print lines which correspond to the scan lines along which the original document is read. The scanning apparatus 10 includes a rotatable cylindrical drum 14. The original document is affixed to the surface of the drum by means of suitable clamps (not shown). The clamp space occupies only a small portion of the circumference of the drum. A photosensor carriage assembly 16 is mounted for linear travel along a track 18 adjacent to the drum surface and extending parallel to the drum axis. The carriage assembly 16 houses a high intensity lamp 20 and a photosensor 22 which is optically aligned with a converging lens 24. The electrical output of the photosensor 22 represents the intensity of light reflected from the focal point of the lens 24 within the area illuminated by the lamp 20. The carriage 16 is movable along the track 18 by means of a taut cable 26 passing over a drive capstan 28 and a pulley 30 at opposite ends of the track 18. A stepping motor 32 drives the capstan 28 which imparts motion to the cable 26 and carriage 16. The capstan 28 may be mounted directly on the shaft of the stepping motor 32. When pulsed, the motor 32 provides an incremental, linear displacement or step of the carriage 16. The travel of the carriage 16 during one step should correspond to the motion of the paper in the printer 12, as explained below. A pair of limit switches 34 and 36 are located at opposite ends of the track 18. The switches 34 and 36 operate a switch 38 which alternately connects the stepping motor 32 to a source of paper feed pulses and a source of fast return pulses 40. For example, if the scanning proceeds from left to right as viewed in FIG. 1, when the carriage 16 engages the limit switch 34, the switch 38 will disconnect the stepping motor 32 from its normal pulse signal to the fast return pulse generator 40 so that the carriage I6 is quickly returned to its original position. After a series of closely spaced pulses from the fast return pulse generator 40, the carriage 16 engages the limit switch 36 which causes the switch 38 to return to its normal position for providing the stepping motor 32 with more widely spaced pulses during the next scanning operation.

The mechanical elements of the printer 12 are similar to those described in detail in the above-referenced copending application, Ser. No. 136,950. The printer 12 comprises a cylindrical drum 42 which is driven continuously at high speed by a motor 44 in close proximity to a row of hammers 46 aligned along a line parallel to the rotational axis of the drum 42. The motor 44 is also mechanically coupled to drive the drum 14 of the scanning apparatus 10 at the same speed, although interconnected scanning and printing drums are not essential as explained below. The embodiment of the printer 12 herein described has twelve hammers, although only four are shown in FIG. 1, for convenience of illustration. A helical bar 48 on the cylindrical surface of the drum 42 extends around the drum in one complete convolution for each hammer 46. Each hammer 46 comprises a blade 50 positioned so that its edge will strike the helical bar 48 when the hammer is actuated. Each blade 50 spans only one convolution of the helical bar 48 so that when the hammer is actuated, the blade will strike the bar 48 at only one point. Each of the hammers 46 includes a light weight electrical coil 52 affixed to each respective blade 50. The coils 52 are in a constant magnetic field provided by a permanent magnet field structure (not shown). To actuate each hammer 46, a firing pulse is applied to the coil 52 which drives the associated blade against the helical bar 48.

Paper on which the printing is carried'out and an ink or carbon ribbon (not shown) are positioned between the blades 50 and the drum 42 so that when an actuated hammer blade is impelled against the bar 48, a dot will be printed on the paper at the intersection of the blade and the helical bar. As the drum 42 rotates, the intersection of the bar 48 and each blade 50 will move repeatedly from left to right across the blade. As the intersection progresses in one pass by a blade 50, the hammer can be actuated repeatedly to print a selected pattern ofdots along the line corresponding to the edge of the hammer blade. This line, extended along all of the blade edges is referred to as the print line. It is important to note that corresponding intersections of the blades 50 and respective convolutions of the bar 48 occur simultaneously along the length of the drum 42. For example, if twelve spaced dots are to be printed by respective blades 50 at corresponding locations along each blade, the blades will all be fired at once.

The print paper is advanced perpendicularly to the drum axis as the printing is carried out so that parallel lines of dot patterns are printed. The print paper is advanced through the printer 12 by means of a paper feed motor 54. The motor 54 causes the paper to be advanced through the printer one line per revolution of the drums 42 and 14. The same pulses which activate the paper feed motor 54 also activate the stepping motor 32 so that the photosensor carriage 16 and the paper in the printer are advanced synchronously at the end of each complete revolution of the print drum 42 and scan drum 14.

Associated with each hammer blade assembly 46 is a hammer firing circuit 56 which produces the current pulses for the coil 52. Twelve digital-to-analog converters 58 provide respective outputs to the hammer firing circuits 56.

The inputs to the digital-to-analog converters 58 corresponding to the 12 hammer blades are produced by a signal processing system, as shown in FIG. 2, which is responsive to the output of the photosensor 22 of F IG. 1. The output of the photosensor 22 is passed via a pre-amplifier 60 to an analog-to-digital converter 62 which samples and converts the analog output of the pre-amplifier 60 at a pre-determined rate. A pair of identical storage units 64 and 66 are provided for storing the output of the analog-to-digital converter 62. Each storage unit 64, 66 is comprised of shift registers. The number of shift registers in each storage unit corresponds to the number of parallel output lines of the converter 62. The output of the converter 62 may be connected via a switch 68 to the serial data input of either storage unit 64 or 66. The switch 68 is operated by a transfer switch control 70 responsive to the output of a transducer 72 arranged adjacent to an index wheel 74 connected for rotation with the print drum 42. The transducer 72 provides one pulse per revolution of the print drum 42. The switch control 70 reverses the switch 68 once per revolution, causing the output of the converter 62 to be routed on one cycle to the storage unit 64 and on the subsequent cycle to the storage unit 66. The storage units 64 and 66 have clock pulse input terminals 76 and 78 respectively. A logic unit 80 provides a pulse output which gates the analog-todigital converter 62 and provides a clock pulse input to the storage units 64 and 66. The storage units 64 and 66 are alternated. While one storage unit is in the input mode, the other storage unit is in the output mode, and vice versa on alternate cycles of the drum 42. The clock pulses from the logic unit 80 are passed to either storage unit 64 or 66 via a switch 82 also controlled by the transfer switch control 70. Accordingly, during one cycle of the scan drum l4 and print drum 42, when the output of the converter 62 is connected via the switch 68 to the serial input of the storage unit 64, the clock pulses from the logic unit 80 are received at the terminal 76 via the switch 82. During this cycle, then, the output of the converter 62 will be entered serially into the storage unit 64. Serial entry of the output of the converter 62 into the other storage unit 66 is accomplished in a similar manner on the next cycle after the switches 68 and 82 have been thrown to their alternate positions by the switch control 70 between the two adjacent cycles.

The logic unit 80 includes a two-input AND gate 84. One input to gate 84 is from a transducer 86 arranged adjacent to an index wheel 87 connected for rotation with the scan drum 14. The transducer 86 provides 2,000 pulses per revolution of the scan drum 14. The other input to the AND gate 84 is from a copy limit transducer 88. The transducer 88 includes a fixed photocell arranged to receive light reflected from a narrow strip 90 about one end of the scan drums surface. The strip 90 has a darkened section corresponding to the clamp space on the scan drum. Accordingly, the output of the copy limit transducer 88 has two levels. The output of the transducer 88 will be a logic zero during the interval corresponding to the clamp space and a logic one during the remainder of the cycle. Thus, the output of the AND gate 84 in the logic unit 80 will be a pulse train interrupted once per cycle during the interval corresponding to the clamp space. The logic unit 80 has a second two input AND gate 92. One input to the AND gate 92 is the output of the AND gate 84. The other input to the gate 92 is provided by the output of a counter 94 responsive to the pulse output of the AND gate 84. The counter 94 is implemented to provide a logic one output until 1,848 pulses have been counted during one cycle, at which time the output of the counter 94 falls to the logic zero state. Accordingly, the output of the AND gate 92 will be a pulse train of 1,848 pulses per cycle of the scan drum 14. These 1.848 pulses from the logic unit 80 serve to gate the converter 62 and to shift the storage unit 64 or 66 during the input mode 1,848 times per cycle of the scan drum 14.

The logic unit 80 and analog-to-digital converter 62 cooperate to divide the scan line, that is one circular pass of the photosensor 22 over the circumference of the drum (except for the clamp space), into 1,848 points or units. In the helix printer 12, the print line consists of 1,848 dot positions. Each dot position corresponds to a point along the scan line at which the converter 62 sampled the analog output of the photosensor 22. The 1,848 dot positions are distributed over the 12 hammers 46. Each hammer must therefore be capable of printing 154 dots to compose a line segment. The 154 dot positions per hammer correspond to respective angular orientations of the print drum 42 because the angular position of the drum 42 determines the point of intersection of a convolution of the helical bar 48 and its corresponding hammer blade 50.

The storage units 64 and 66 provide twelve sets of parallel output lines each to the digital-to-analog converters S8 of the helix printer 12. The reason why the outputs of the storage units 64 and 66 are in parallel instead of serial form is because the helix printer 12 composes a print line in parallel or simultaneous line segments rather than in a series of dots from one end to the other of the entire print line. Although the helix printer 12 prints all 12 line segments simultaneously, the scanning apparatus 10 reads a scan line in a serial manner. Therefore, each storage unit 64, 66 must reorganize the digitized input signals originated by the photosensor 22 for operating the printer 12. A set of ganged switches 94, only three of which are shown for convenience of illustration, alternately connect the outputs of the two storage units 64 and 66 to respective digital-to-analog converters 58 of the helix printer 12. Each switch 94 is a symbolic representation of a plurality of switches, as each of the twelve sets of output lines ordinarily includes several individual leads corresponding to binary digits. In the condition illustrated in FIG. 2, the storage unit 66 is in the output mode in which its parallel output lines are connected to the converters 58 of the printer 12. At the same time, the storage unit 64 is in the input mode in which data from the converter 62 is loaded serially into the storage unit by means of the clock pulses from the logic unit 80. On the next cycle of the scan drum 14, the roles of the storage units 64 and 66 will be reversed; that is, the storage unit 64 will be in the output mode and the storage unit 66 will be in the input mode. Between cycles, all of the ganged switches 68, 82 and 94 will be thrown to their alternate positions by means of the switch control in response to the output of the one pulse per revolution transducer 72 associated with the printer 12.

When in the output mode, the storage unit 64 or 66 is clocked at the rate of 154 pulses per revolution of the print drum 42 by connecting the clock input 76 or 78 via a switch 96 to a transducer 98 arranged adjacent to an index wheel 100 connected for rotation with the print drum 42. The transducer 98 produces 154 output pulses per revolution. The switch 96 is operated by the switch control 70. When the switch control 70 is pulsed, the clock inputs to the storage units 64 and 66 are interchanged. For example, on the cycle following that depicted in FIG. 2, the output of the logic unit 80 will be connected to the terminal 78 and the output of the transducer 98 would be connected to terminal 76 of the storage unit 64.

In the input mode the storage units receive 1,848 clock pulses per drum cycle. The remaining 152 pulses from the transducer 86 correspond to the clamp space. That is, one line of the document is scanned in less time than it takes to complete one drum cycle. In the output mode, the storage units receive 154 clock pulses during a drum cycle. Therefore, the storage units are clocked at an average rate per drum cycle about 12 times faster during the input mode than during the output mode.

The analog-to-digital converter 62 may provide as many output bits as desired. If only one output bit is provided by the converter 62, the converter will operate as a threshold detector having a single binary output. In this case, each storage unit 64, 66 will comprise a single shift register of 1,848 bits. In the preferred embodiment, the converter 62 provides three parallel output bits. With three bits, the amplitude of the analog signal may be represented as any one of eight (2) discrete levels, that is from 000 to l l l, inclusive. Accordingly, each storage unit will include three synchroneously operated shift registers. The details of the storage unit 64 used with a three bit converter are shown in FIG. 3. The storage unit 66 is implemented in a similar manner. The three line output of the analogto-digital converter 62 is connected via the switch 68 (FIG. 2) to the serial inputs of three respective shift registers 102, 104 and 106 in the storage unit 64. Each shift register is divided into 12 states corresponding to the hammers 46 of the printer 12. Each stage of each register consists of 154 bits. In FIG. 3, only the first and twelfth stages of the shift registers are shown for convenience of illustration. The clock pulse inputs of the three shift registers 102, 104 and 106 are all connected in common to the terminal 76. During the input mode the clock pulse terminal 76 is connected to the logic unit 80, and the three line output of the converter 62 is passed in parallel to the inputs of the shift registers 102, 104 and 106 for serial data entry.

After 1,848 bits of information per shift register are stored during one complete cycle, the storage unit 64 is switched to the output mode by means of the switches operated by the transfer switch control 70. In the output mode, the serial data entry inputs of the shift registers are disconnected and the clock pulse output terminal 76 is connected to the transducer 98 associated with the printer 12. As shown in FIG. 3, only the last or 154th bit of each stage is tapped for output. The outputs from corresponding stages among the shift registers are grouped in threes corresponding to the respective hammers 46 of the printer 12. For example, the outputs from the 154th bit of the 12th stage in shift registers 102, 104 and 106 are passed to the digital analog converter 58 associated with the twelfth hammer 46. Likewise, the last bits of the first stages in the shift registers are passed to the digital-to-analog converter 58 associated with the first hammer 46.

The contents of each stage are shifted past the tapped bit synchronously with the occurrence of the corresponding dot positions along each hammer blade 50 in the printer 12. Following a given shift pulse, the three bit signal is applied to the respective digital-to-analog converter 58 which provides an analog output current through the coil 52 which fires the associated hammer blade 50 with sufficient impact to print a dot of corresponding darkness. After 154 bits have been shifted past each tapped output bit, the one pulse per revolution transducer 72 activates the switch control (FIG. 1) to return the storage unit 64 to the input mode in which data from the analog-to-digital converter 62 is again serially entered into the three shift registers 102, 104 and 106.

The dot printed by the printer 12 in each of the dot positions along the print line will have a darkness corresponding to one of eight discrete levels to represent the tonality of the corresponding point on the original copy scanned by the photosensor 22.

As shown in FIG. 1, the print drum 42 and scan drum 14 are mechanically coupled so that there is no requirement for electrically synchronizing their relative speed or phase. If it were desired to separate these drums for facsimile transmission, for example, several synchronization systems are available. In one system, a straightforward phased locked servo-mechanism can be used to control the speed and phase of the scanning drum through the input to its drive motor in response to a signal representing the speed and phase of the print drum 42. Other systems must be used if the two drum speeds are independent of each other. In one system, the scanning drum 14 would be run at more than twice the speed of the printing drum 42. This relationship would always allow enough time to read each line regardless of the phase relationship between the two drums. A scanning or reading cycle would be initiated after a given storage register was transferred back to the input mode, but not until the beginning of a copy limit signal appeared. Then, the 1,848 samples would be serially entered into the storage register and stored or held until the helical bar 48 returned to the start position. That is, samples would be held for whatever part of an incomplete helix revolution remained. In this system, the frequency response of the photosensor 22 would have to be doubled. Another system for non-phaselocked drums is similar to the foregoing system, except that the scanning drum speed would be increased only sufficiently to always exceed the speed of the printing drum 42. Instead of waiting for the copy limit signal the data from the photosensor 22 would start being entered into the available storage unit as soon as transfer occurred. Because the start of the scanning cycle would not usually correspond to the normal starting point of a scan line, that is, the end of the clamp space, additional logic would be required to shift the information in the storage registers to its proper position. This would require that each shift register be provided with a number of bits corresponding to 2,000 scanning points rather than 1,848. In addition, a loop would have to be provided to connect the last bit of the shift register to the first bit in order to run the bits in storage around until the 152 bits corresponding to the clamp space were located in the last bits of the storage register associated with a recognition circuit.

The use of the two alternating storage units 64 and 66 permits the serial output of the scanning apparatus to be reorganized in an efficient manner so that the information printed by the helix printer ]2 lags the information scanned by only one cycle. The multi-hammer helix printer [2 is thus operated as a facsimile printer without reorganizing the scan line into parallel segments at the scanning end of the operation. Moreover, the digital storage units facilitate digital representation of the tonality of the scanned points on the original document. As a result, the helix printer 12 is capable of faithfully reproducing a graphical representation having areas of varying darkness by printing dots of nonuniform density.

It will be understood that various changes in the details, materials, steps and arrangements of parts which have been herein described and illustrated in order to explain the nature of the invention, may be made by those skilled in the art within the principle and scope of the invention as expressed in the appended claims.

I claim:

1. A copier system for reproducing an original copy by composing a facsimile with a plurality of dots of variable darkness, comprising scanning means including photosensor means for producing an analog electrical output representing the reflected light level at points on said copy and means for causing said photosensor means to scan said copy in consecutive parallel scan lines, converter means operatively connected to receive the analog output of said scanning means for conversion thereof to a multi-bit digital output, means for storing said analog-to-digital converter means output, digital-to-analog converter means operatively connected to receive the output of said storing means, and multi-hammer printer means responsive to said digitalto-analog converter means output for simultaneously printing a plurality of line segments along a print line by printing dots of variable darkness corresponding to the tonality of respective points on said copy for composing a facsimile thereof.

2. The copier system of claim 1, wherein said storing means includes storage register means for serially receiving the output of said analog-to-digital converter means and for providing a plurality of parallel outputs corresponding to the hammers of said printer means, and said digital-to-analog converter means includes a plurality of digital-to-analog converters operatively associated with respective ones of said hammers for receiving corresponding ones of said parallel outputs from said storage register means.

3. The copier system of claim 2, wherein said printer means includes a helical bar having a plurality of convolutions, means for imparting continuous rotation to said bar about its axis, a corresponding plurality of hammer blades arranged in a line next to said helical bar and parallel to the axis thereof, and a plurality of firing circuits associated respectively with said hammer blades for selectively impelling individual ones of said hammer blades against said helical bar with variable impact in accordance with the respective outputs of said digital-to-analog converters.

4. A copier system for reproducing an original copy, comprising means for scanning said copy in consecutive parallel scans to produce an analog electrical output representing the level of reflected light from said copy, analog-to-digital conversion means connected to receive the output of said scanning means, a pair of digital storage units, means for alternately connecting said storage units in an input mode for serial entry of the output of said analog-to-digital conversion means on corresponding alternate scans, means for alternately connecting said storage units in an output mode for providing a plurality of parallel outputs from said storage units on corresponding alternate scans such that one unit is in the output mode while the other unit is in the input mode, and vice versa on alternate scans, a plurality of digital-to-analog conversion means connected to receive respective ones of said parallel outputs from said storage units, and printer means having a plurality of print hammers and respective hammer firing circuits for impelling said hammers with variable impact in accordance with the output of said digital-toanalog conversion means.

5. The copier system of claim 4, wherein said printer means further includes a helical bar having a plurality of convolutions corresponding to said hammers, means forimparting continuous rotation to said bar about its axis, said hammers being arranged in a line next to said helical bar and parallel to the axis thereof and being impelled against said corresponding helical convolutions when fired.

6. The copier system of claim 5, wherein said scanning means includes a single photosensitive element and means for causing said element to execute a plurality of consecutive parallel scans of said copy.-

7. The copier system of claim 6, wherein both said means for alternately connecting are responsive to the rotation of said helical bar for interchanging said storage units once per complete revolution.

8. A copier system, comprising: a scanning system including a drum upon which said original copy is fastened, means for imparting continuous rotation to said drum and a carriage having a light sensitive element mounted adjacent to the surface of said drum for linear travel in a direction parallel to the rotational axis of said drum such that said light sensitive element executes consecutive parallel scans of said copy; a helix printer including a helical bar with plural convolutions, means for imparting continuous rotation to said bar about its axis, a corresponding plurality of hammer blades arranged in a line next to said helical bar and parallel to the axis thereof for printing simultaneously a plurality of line segments along a print line, a plurality of digital-to-analog converters corresponding to said hammer blades, and a plurality of firing circuits associated respectively with said hammer blades for selectively impelling individual ones of said blades against said helical bar with variable impact in accordance with the output of respective ones of said digital-to-analog converters; and a data conversion system interposed between said scanning system and said helix printer including an analog-to-digital converter connected to receive the output of said light sensitive means, a pair of digital storage units each having a serial data entry terminal, a clock pulse terminal and a plurality of parallel output lines corresponding in number to said helix printer hammer blades, input switch means for alternately applying the output of said analog-to-digital converter to the serial input terminals of said storage units, output switch means for alternately connecting each set of parallel outputs associated with said storage units to the respective inputs of said digital-to-analog converters, clock pulse switch means for applying two different clock pulse rates alternately to the clock pulse input terminals of said storage units, one said clock pulse rate corresponding to the number of dot print positions occurring in an entire print line during one complete cycle of said helical bar, the other of said clock pulse rates corresponding to the number of dot print positions occurring within a line segment printed by one of said hammer blades during a complete cycle of said helical bar, and transfer switch control means operatively connected to said input, output and clock pulse input switch means for reciprocation thereof between respective alternate positions in response to each complete cycle of said helical bar, such that one of said storage units is in the input mode clocked at said one rate while the other storage unit is in the output mode clocked at said other rate, and vice versa on alternate cycles.

9. The copier system of claim 8, wherein saidanalogto-digital converter providesa plurality of parallel binary outputs and each said storage unit includes a plurality of shift registers corresponding in number to the outputs of said analog-to-digital converter.

10. The copier system of claim 9, wherein the number of said hammers in said helix printer is N and there are X dot print positions assigned to each hammer, each said shift register in each said storage unit being divided into N stages, each said stage having X bits of storage, said parallel output lines from each unit each including one output line associated with the last bit in each corresponding stage of said shift registers.

11. A method of producing a facsimile of an original 12 copy, comprising the steps of scanning said copy in consecutive parallel scan lines to produce an analog electrical output representing the level of light reflected from said copy. converting said electrical output to a digital signal, storing said digital signal, reconverting the stored digital signal to an analog signal, and printing dots of variable darkness simultaneously in a plurality of line segments along a print line in accordance with said analog signal.

12. The method of claim 11, further comprising the step of rearranging said stored signal in parallel form corresponding to said line segment before reconverting said stored digital signal to an analog signal.

13. The method of claim 12, wherein said scanning includes continuously rotating a scan drum on which said copy is fastened and moving a light sensitive element adjacent to said scan drum in a direction parallel to the rotational axis of said scan drum to produce said electrical analog output, and said printing is accomplished by continuously rotating a helical bar and selectively firing against said bar a plurality of hammers aligned in parallel adjacent to said bar.

14. The method of claim l3, wherein said bar and said scan drum are rotated at the same speed with predetermined relative phase.

15. The method of claim 14, wherein said scan drum is rotated at over twice the speed of said bar without a predetermined phase relationship.

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Referenced by
Citing PatentFiling datePublication dateApplicantTitle
US4400709 *Jul 14, 1980Aug 23, 1983Compagnie Industrielle Des Telecommunications Cit-AlcatelImage printer stylus bar, manufacturing method therefor and image printer device
DE2758139A1 *Dec 27, 1977Jul 13, 1978IbmSchaltung zur umordnung von bilddaten
DE3733265A1 *Oct 1, 1987Apr 20, 1989Cadtronic Computer Systeme GmbVerfahren zum erzeugen einer kopie von einem bild eines bildschirmes sowie vorrichtung zur durchfuehrung des verfahrens
EP0022704A1 *Jul 2, 1980Jan 21, 1981COMPAGNIE INDUSTRIELLE DES TELECOMMUNICATIONS CIT-ALCATEL S.A. dite:Image printing array, its manufacturing method and image printing device
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Classifications
U.S. Classification178/30, 358/303, 346/101
International ClassificationH04N1/191, H04N1/12, H04N1/16
Cooperative ClassificationH04N1/16, H04N1/1911, H04N1/1912
European ClassificationH04N1/191B, H04N1/16, H04N1/191B1