US3183830A - Print registration control means in high speed printers - Google Patents

Description

y 1965 D. M. FISHER ETAL 3,183,830

PRINT REGISTRATION CONTROL MEANS IN HIGH SPEED PRINTERS Filed Dec. 27, 1960 3 Sheets-Sheet 1 41-0 Q/mswrz 1,57 4

ma n 2550/5 60 y 18, 1965 D. M. FISHER ETAL 3,183,830

PRINT REGISTRATION CONTROL MEANS IN HIGH SPEED PRINTERS Filed Dec. 27, 1960 (Mm/a 1 9 9 5 Sheets-Sheet 2 m mi u F "A i5 7 W M) :L MW Q (L) VENTOR! y 18, 1955 D. M. FISHER ETAL PRINT REGISTRATION CONTROL MEANS IN HIGH SPEED PRINTERS 3 Sheets-Sheet 5 Filed Dec. 27, 1960 INVENTOR! Jam/u Mia/Vii mm": 4-, z/w/vm BY flat/VII United States Patent 3,133,330 PRINT REGISTRATION CONTRQL MEANS IN HIGH SPEED PRINTERS Donald M. Fisher, Gloucester, and James E. Linnell,

Haddonfield, N.J., assignors to Radio Corporation of America, a corporation of Delaware Filed Dec. 27, 196i), Scr. No. 78,370 3 Claims. (Cl. I0193) This invention relates to high speed printers and, more particularly, to means for and methods of accomplishing registration of printed characters in an electromechanical printer system, without affecting the print density of the individual printed characters.

Many of the high speed electromechanical printers used to print out information in modern information handling systems, digital computers for example, operate on-thefly. That is to say, the mechanisms bearing the type faces do not come to rest during a print cycle, but are struck selectively by hammers, with the paper or other Web interposed, while the type faces are moving, so as to produce impressions on the paper. The hammers generally are solenoid actuated.

Because of the electrical and mechanical tolerances of individual solenoid-hammer assemblies, no one set of uniform adjustments can be used on all assemblies to achieve registration of the printed characters in a line of output print. It has been suggested that print misregistration be corrected by individually adjusting the rest position of each hammer, in effect causing a particular hammer to travel a greater or lesser distance in printing, depending on the direction of adjustment. Such adjustments, however, affect the velocities with which the hammers strike the type faces, and differences in striking velocities among the various hammers cause uneven density of printing. Registration according to this technique, therefore, is accomplished at the expense of uniform print density.

It is an object of this invention to provide means for accomplishing registration of the printed output of a high speed printer.

It is another object of this invention to provide in an electromechanical printer system, means for accomplishing registration of the printed characters without affecting the density of print.

It is still another object of this invention to provide, in a printer of the type described, means for and methods of accomplishing registration of the characters in a line of print of uniform print density.

In accordance with these and other objects of the invention, the solenoid and hammer assemblies may be adjusted individually to achieve uniform print density. Misregistration resulting from these adjustments then is corrected according to the invention by delaying the individual signals applied to the respective solenoids. The amount of delay introduced in each channel is determined by the difference between the speed of response of the slowest acting solenoid-hammer assembly and the speed of response of the solenoid-hammer assembly in that channel.

In the accompanying drawing:

FIGURE 1 is a diagram of one type of solenoid-harnmer assembly, commonly used in high speed printers, and a typical operating environment therefor;

FIGURE 2 is an example of vertical misregistration in a line of output print;

FIGURE 3 is a set of curves of hammer travel distance versus time for different settings of the stop member in the FIGURE 1 solenoid-hammer assembly;

FIGURE 4 is a block diagram of an arrangement for supplying actuating signals to a printer solenoid, and including delay means according to the invention;

FIGURE 5 is a block diagram of a preferred arrangement for supplying solenoid actuating signals according to the invention;

FIGURE 6 is a schematic diagram of a portion of the FIGURE 5 arrangement; and

FIGURE 7 is a timing diagram useful in understanding the sequence of operation of the FIGURE 6 circuitry.

Two general types of on-the-fly printers are illustrated and described in a March 1953 publication of the American Institute of Electrical Engineers entitled Review of Input and Output Equipment Used in Computing Systems, at page 109. The first type of printer employs a plurality of continuously rotating type wheels, one for each character position in a line to be printed. The print or type wheels are mounted on a common shaft which is substantially parallel to the paper stock rollers. A hammer is actuated when the print wheel character corresponding to the character to be printed in that position is opposite that hammer.

The print Wheels may be arranged so the same character is moved into printing position by each print wheel at the same time. All characters of one type are printed at one time in selected positions by activating corresponding hammers, and a complete line of characters is printed during one revolution of the print wheels. Due to the aforementioned mechanical and electrical tolerances of the solenoid-hammer assemblies, however, different assemblies may have different speeds of response. The result is that some hammers strike their respective print wheels before the type face has moved fully into print position, while other hammers strike their respective print wheels after the type face has moved slightly out of print position. The end result is vertical misregistration of the characters in a line of output print. This condition is illustrated in FIGURE 2.

The second type of printer employs a single type or print wheel mounted on a continuously rotating shaft. The shaft is mounted transverse to the paper rollers. A separate solenoid-hammer assembly is provided for each character position in a line to be printed. For example, if a line of print is to contain printed characters, 120 solenoid-hammer assemblies are provided. In a printer of this type, mechanical and electrical tolerances giving rise to different speeds of response among different solenoid-hammer assemblies result in horizontal misregistration of the printed characters.

FIGURE 1 is a diagram of a solenoid-hammer assembly of a type commonly used in electromechanical printers. A solenoid it) includes an energizing coil 12 having input leads I4, 16 for receiving signals from a signal source 28. The coil mechanism is supported in a frame 18 which, in turn, is secured to a base member 20, or mounting plate. A solenoid arm 22 is pivotable about a pin 2-.- on the frame 18. A bias spring 26 urges the arm 22 in a counterclockwise direction, the counterclockwise rest position of the arm 22 being determined by the position of a stop member Tail. The stop member 30 may have the form, as illustrated, of an adjustable screw which is guided in a block 32 secured to the base 20.

A partial end view of the first type of printing mechanism, aforementioned, is illustrated above the stop member and arm A plurality of character print wheels, one id of which is illustrated in partial end view, is mounted on a continuously rotating shaft 42-. A separate print wheel ad is provided for each character position in a line to be printed on paper stock 44, and each print wheel dd has a separate hammer id, or striking member, and solenoid it? associated therewith. The striking portion of the hammer as is located at the upper end of a spring biased stein ed, and the stems are guided in a hammer block 52. A spring 56 urges the stem 48 in a downward direction away from the print wheel 46). The lower end of the stem 43 may or may not contact the arm 2-2 of its associated solenoid It) when the arm 22 is in the rest position, depending upon the setting of the stop member 39.

Type faces 56 for all printable characters are carried at the periphery of each of the rotating print wheels 49. A coded wheel (not shown) of known type may be mounted on one end of the shaft 42 to provide means for identifying the character which is in print position, that is to say, the particular type face which is opposite the hammer If it is desired to print this character on the paper 44, an energizing signal is sent from the signal source 28 to the coil 12. The magnetic force occasioned by coil 12 current attracts the arm 22 in a clockwise direction to reduce the air gap in the magnetic circuit. The hammer 46 is impelled in an upward direction as the arm 22 pivots, and the hammer 46 forces the paper 44 and inked ribbon 6t against the type face on the print Wheel 4t Several solenoids are energized substantially simultaneously when it is desired to print the same character at different positions in a line on the paper 44.

Vertical misregistration of the printed characters in a line of print occurs when various ones of the solenoidhammer assemblies have different response times. A line of print wherein the printed characters are vertically misaligned, or misregistered, is illustrated in FIGURE 2. It generally is not possible to achieve perfect registration of the printed characters by uniformly setting all of the stop members 3t Instead, it is necessary to adjust various ones of the stop members 36 different amounts in order to correct for misregistration, if such a method of correction is employed. This method of correcting misregistration, however, has the serious disadvantage that correction of the misregistration is accomplished at the expense of uniform print density, as may be seen by reference to FIGURE 3.

In FIGURE 3, hammer travel distance is plotted along the ordinate, and time is plotted along the abscissa. Curves es and 65 define travel distance to the hammer, as a function of time, for two different rest positions of the hammer 46 and solenoid arm 22 of the same solenoid-t hammer assembly. Time is measured from the instant that an energizing signal is applied to a solenoid coil 12. The velocity of the hammer at any time is equal to the slope of the defining curve at that time. It will be noted that the slope of a curve and, hence, the velocity of a hammer, varies as a function of time. Moreover, it will be noted that the two curves and 66 do not have the same slopes. That is to say, the curve 65 is not derived merely by translating curve 6 2- to the right a distance equal to T T The situation is further complicated by the fact that the response curves may be different for different solenoid-hammer assemblies having the same stop member adjustment.

It may be assumed for purposes of illustration that the curves 64 and 6% represent response conditions for the two different solenoid-hammer assemblies in which the stop members 3d are adjusted so that both hammers 46 strike the type face at a time T It may be seen from FIGURE 3, however, that the velocities of the two hammers, as measured by the slopes at points 68 and 7t respectively, are not the same at T Inasmuch as the density of print is a function of the velocity with which a hammer strikes the type face, nonuniform print density results in the different print positions when misregistration is accomplished according to the above technique.

Consider now the technique of correcting misregistration according to the present invention. Let the curve '74 represent the response of a particular hammer 4% as a function of time, measured from the instant an energizing signal is applied to the corresponding solenoid coil 12. Further, let the velocity at point 78, corresponding to time 1",, be equal to V, the velocity with which it is desired that all hammers strike their type faces to achieve uniform print density. If correction of misregistration dictates that an activated hammer strike its type face at a time T then, according to the invention, the energizing signal for this assembly is delayed for a period T T., before it is applied to the energizing coil 12. This delay has the effect of translating the curve 74 to the right an amount equal to T -T and the velocity of the hammer at T of the translated curve 74a is V, as measured by the slope of the curve 74a at point 3%). Note that for this condition, time along the abscissa is not measured from the instant the signal is applied to the energizing coil 12, but rather from the time that the energizing signal is applied to the delay means.

It is noted from the above description that the stop members 30 are not adjusted to correct misregistration of printing. Instead, the stop members 30 are adjusted so that each hammer 46 strikes its type face at the same velocity, to achieve uniform print density. Misregistration is then corrected by delaying the coil 12 energizing signals selected amounts. The amount of delay in each case may be determined by the worst case condition, as determined by the slowest responding solenoid-hammer assembly.

The problem of misregistration also is present in print mechanisms employing solenoids of other types than the one illustrated in FIGURE 1. The problem is also present in a printer of the second type aforementioned wherein horizontal misregistration results from solenoid-hammer assemblies having different response characteristics. It will be understood that the present invention also may be used to correct the misregistration in these cases, being not limited to the case described in detail.

FIGURE 4 is a block diagram of a solenoid energizing arrangement, including delay means according to the invention. Coils 12a and 1211 are the solenoid energizing coils for activating the hammers in the first and last, or nth, character positions. Coils for intermediate printing positions, and the circuitry therefor, are omitted for simplicity of drawing. It will be understood, however, that if 120 characters, for example, are to be printed in each line on the paper, then 120 coils I2 and associated circuitry are required.

The block 95) represents a storage device wherein are stored signals indicative of the characters to be printed. The storage device 9% may be, for example, a magnetic drum, tape, core memory, register or the like. In particular, the storage device may be a core memory having 12 rows and "m columns, where n, as before, is the number of character positions in a line of print and m is the number of printable characters, including alphabetical characters, numbers, special symbols, etc. The read out means (not shown) for the storage 99 is synchronized with the rotation of the character print wheels. For eX- ample, if it is desired to print the character A in a selected number of positions in a line, output signals are supplied from the storage device to the corresponding number of amplifiers 92a to 9211 when the letter A on the type wheels is in print position. A suitable storage device, and timing and synchronization signal means therefor, are described and illustrated in U.S. Patent No. 2,941,188 of D. Flechtner et al., issued June 14, 1960, for Printer Control System and assigned to the assignee of the present invention, and will not be described further.

The amplifiers 92a g2 are provided for amplifying the storage 9% outputs to a level suflicient to energize the 12a I212. The amplifiers 92a fin may include pulse shaping means. The amplifiers, of course, are unnecessary when the outputs of the storage device 90 are of sufiicient amplitude to drive the coils 12 a 1211 directly. The outputs of the amplifiers 2a 9211 are applied to variable delay devices 94a 94in, respectively, and the outputs of the delay devices are applied to respec tive ones of the energizing coils 12a 31212.

The delay devices 940 9411 may be any suitable type of variable delay devices, a preferred type of which is illustrated in FIGURE 6. In any event, the individual delays are adjusted, as described previously, to provide registration of the printed characters.

FIGURE 5 is a block diagram of a preferred arrangement for transferring signals from a storage device 94 to a solenoid energizing coil 12. The actual circuitry for the greater portion of this arrangement is illustrated in FIGURE 6. Similar circuitry is provided for each of the other energizing coils (not shown). Signals are read out of the storage device Ell to the amplifier 92 in synchronism with the rotation of the print wheels. The positive-going output hit of the amplifier is applied to one input of a two input not-and gate ltlt). A second input to the gate lltlti is a positive-going timing pulse 162.

A not-and gate may be defined as an and gate having an inverted output. In this case, the output of the not and gate is a negative-going pulse 164 when both of the inputs thereto are positive-going signals or pulses 98, 162. The not-and gates 10d and timing pulses Th2 are provided to staticize the outputs of the storage device for each like character to be printed.

The leading, negative-going edge of the output 1% of the gate 100 triggers a variable delay one-shot, or monostable multivibrator 106. The output of the one-shot 1th? is a negative-going pulse llilS, the time of occurrence of the trailing edge of which is determined by the setting of the variable delay one-shot 106. This positive-going trailing edge triggers a fixed delay one-shot lit! to provide a negative-going output pulse 112.

The output ill; of the fixed one-shot 118 is amplified and inverted in an amplifier 114. The solenoid energizing coil 12 has one end connected to the output of the power amplifier 1M and the other end connected to a biasing source, designated V. The output of the amplifier 114 normally is V volts, whereby no potential difference normally exists across the ends of the coil 12. The output 116 of the power amplifier lid rises in a positive direction to energize the coil 12 when a negative-going signal 112 is applied at the power amplifier 114 input.

The timing pulses 182 are applied simultaneously to the not-and gates tditl in all of the channels, only one of which is illustrated. Therefore, all of the not-and gates Tilt) which receive signal inputs 98 for printing a like character, provide negative outputs 104 at the same time. The variable delay one-shot 166 in each channel is adjusted so that all of the printed characters are properly aligned or registered. All of the outputs 112 of the fixed delay one-shots Elli) have the same width, whereby each coil 12 receives an energizing signal of the same width.

FIGURE 6 is a schematic diagram of preferred circuitry for implementing a portion of the FIGURE 5 arrangement. The positive pulse @3 output of the amplifier Q2 (FIGURE 5) is applied at one input terminal 130 of the not-and gate lltld. The timing pulses 1632 are applied at a second input terminal 132 of the gate 1%. The voltage at both of these input terminals 13%, T32 normally is 0 volt, and the voltage rises to +6.5 volts when an input pulse is applied. The terminals 136d, 1132 are connected by way or" resistor-capacitor networks 134, 136, respectively, to the base electrode of a PNP transistor M ll and to one end of a resistor M2. The other end of the resistor M2 is connected to a biasing source of +13 volts. The emitter electrode is returned directly to +6.5 volts, and the collector electrode is connected to -l9.5 volts through a resistor 14.4. A diode 146 prevents the voltage at the collector electrode from falling below ground potential, or 0 volt. The parameters of the notand gate tea are selected so that the transistor ldtl is on in full conduction, and the collector voltage is approximately +6.5 volts, until input pulses hr; and 1th"). are applied simultaneously at the input terminals 13%, 132, respectively. Simultaneously applied input pulses this bias the transistor oil, and the diode M6 then clamps the collector voltage at ground potential.

The collector electrode or" the transistor l ltl is con nected to the base electrode of a transistor 152 by way' of a parallel resistor-capacitor network 159. The collector electrode of another transistor 190, to be described, also is connected to the base electrode of the transistor 1523 by way of a parallel resistor-capacitor network 154. This base electrode is connected to a bias source of +13 volts by a resistor 156. The emitter electrode of the transistor T52 is returned directly to a source of +6.5 volts, and the collector electrode is connected to a bias source of +19.5 volts by a resistor 158. A diode 166 connected to the collector electrode prevents the voltage at the collector from falling below ground potential.

A pair of series-connected resistors 154, 166, one of which is variable, connects the collector electrode of the transistor 152 to the base electrode of an NPN transistor 168. A capacitor 170 is connected between the collector and base electrodes of the transistor 158, and the collector electrode is returned directly to a biasing source of +6.5 volts. The emitter electrode of the transistor 168 is connected to a source of -19.5 volts by a resistor, whereby the transistor 16S operates as an emitter follower.

A voltage divider comprising resistors 174, 176, serially connected between ground and +6.5 volts, supplies bias for the emitter electrode of a transistor 18%. The base electrode of this transistor T80 is directly connected to the emitter electrode of the emitter-follower transistor 168. The collector electrode of the transistor is connected (l) to a source of 19.5 volts by a load resistor 182, (2) to ground by Way of a clamping diode 184, and (3) to the base electrode of a transistor by way of a parallel resistor-capacitor network 188.

The base electrode of the transistor 1% also is connected by way of a parallel resistor-capacitor network 1% to the collector electrode of the transistor T52, and to a source of +13 volts by way of a resistor 194. The transistor 190 circuit operates as a not-and gate, as will be more fully apparent hereinafter. The emitter electrode of this transistor 190 is connected directly to a source of +6.5 volts, and the collector electrode is connected to a source of 19.5 volts by a resistor 196. A clamping diode 260 is connected between the collector electrode and ground.

The output at the collector electrode of the transistor 1% is coupled over a line 202 to the base electrode of the transistor 152 as feedback, and also is coupled to the base electrode of a transistor 208 by a coupling capacitor 2%. The transistor 208 circuit forms a part of the fixed delay one-shot 110. This transistor 233 is normally biased in the on condition by a pair of series resistors 210, 212 connected between the base electrode thereof and -19.5 volts. A capacitor 214 is connected between the junction of the resistors 21d and 214 and the collector electrode of a transistor 218. The collector electrodes of the transistors 2% and 218 are connected to 19.5 volts by resistors 216 and 220, respectively. The emitter electrode of the transistor Zllh is returned directly to +6.5 volts. The emitter electrode of the transistor 218 is connected to +6.5 volts by a resistor 222 and is connected directly to the base electrode of a transistor 23%.

The emitter electrode of the transistor 2% is connected to the 6.5 volt source through a resistor 232. This transistor 23d normally is biased off by virtue of the voltage at the emitter of the transistor 218. The voltage at the emitter of the transistor 2% is coupled directly to the base of a grounded emitter power transistor 2%, and normally is of such polarity as to bias the power transistor off. The collector electrode of the power transistor 234 is connected to the -l9.5 volt source by a resistor 23?. The solenoid energizing coil 12 is connected in parallel with this resistor 238, and a diode 24% is connected across the coil 12. inasmuch as the power transistor 234 is normally nonconductive, there is no potential difference across the ends of the coil 12, and the solenoid is de-energized. The voltage at the collector electrode rises in a positive direction when the power transistor 2% is turned on, and the voltage difference between the ends of coil 12 causes current to flow through the coil. The diode 240 provides a low resistance path for dissipating the energy stored in the coil 12 when the transistor 234 is again biased off, thereby preventing a large back from being developed across the coil 12 and possibly damaging the coil 12 and/ or the transistor 234.

Consider now the operation of the FIGURE 6 circuit with reference to the waveforms in FIGURE 7. These waveforms illustrate the voltages at various points in the FIGURE 6 circuit, the points being designated by the same alphabetic characters as are used in FIGURE 7.

At time T the inputs (A), (B) at the terminals 13% and 132, respectively, of the notand gate 1% are both volt. The transistor l t-ti is biased in the full on condition, and the output at the collector electrode thereof is approximately 6.5 volts. The output of the transistor 1% is also in the full on condition at this time, and the collector voltage (H) thereof is approximately +6.5 volts. The transistor 152 is biased in the oif condition because of the high inputs thereto and the Voltage (D) at the collector thereof is clamped at 0 volt. This voltage is coupled to the base of the transistor 196) to bias this transistor in the full on condition.

The transistor 168, connected as an emitter follower, is biased in a low conducting condition, relatively speaking, and the output (F) at the emitter thereof is some voltage less than 0 volt. This voltage is coupled directly to the transistor 189, the emitter of which is connected to a point of approximately volts. Accordingly, the transistor 18%) conducts heavily at this time and the output voltage (G) is approximately +5 volts.

A positive input pulse is applied at the input terminal at a time T This pulse alone is ineffective to turn off the transistor 140. At time T however, a timing pulse 102 is applied at the other input terminal 132. The voltage at the base electrode of the transistor Mt} rises above +6.5 volts and turns the transistor 140 off. The output (C) thereof falls to ground potential and turns on the transistor 152. The output (D) of the transistor 152 rises to approximately +6.5 volts, and has two effects. First, this voltage is coupled to the transistor 190, biasing this transistor oil. The output (H) thereof falls to ground potential and is fed back to the input of the transistor 152 to keep this transistor in the full on condition after the termination of the timing pulse 102. Second, the capacitor 17% in the base circuit of the transistor 168 disgins to discharge through a path including the Variable resistor 166. The setting of this resistor 166 determines the discharge time of the capacitor 172' As the voltage at the base electrode of the transistor 168 rises in a positive direction, due to the discharging of the capacitor 170, the transistor 16% conducts more heavily, and the voltage (F) at the emitter thereof increases in a positive direction. In general, the voltage at the emitter follows the voltage at the base as shown by the waveforms (E) and (F) of FIGURE 7.

The voltage (G) at the collector electrode of the transistor 18% decreases exponentially because of the exponentially rising voltage at the base electrode thereof. The collector voltage continues to fall as the capacitor 176i discharges until the transistor 18% cuts oil. Diode 134 prevents the collector voltage (G) from falling below 0 volt. This collector voltage is applied to one input of the transistor 1% and turns transistor 1% back on when the voltage (G) falls to 0 volt. The output (H) of the transistor 1% then rises to +6.5 volts and turns transistor 152 oif at T The capacitor ill-0 then begins to recharge toward +6.5 volts and the transistors 16% and 186i tend toward their normal, static conditions.

The rise in voltage (H) at T, at the collector electrode S of the transistor 1% is coupled to the base electrode of the transistor 2G8, and triggers this transistor off. The voltage (I) at the collector of transistor 2% falls to a low value and triggers transistor into heavy conduction. The rise in voltage at the collector electrode of the transistor 218 is coupled to the base electrode of the transistor 2% by capacitor 2% and completes the turn-off of transistor 2%. Transistor 2&3 remains in a nonconducting condition until the capacitor 214 has charged to such a value that the voltage drop across the resistor 212 is no longer sufficient to bias transistor 2%? below cutoii.

The voltage (I) at the emitter electrode of the transistor 2-13 decreases (becomes less positive) when the transistor 2155 is triggered into high conduction. The drop in voltage is suiiicient to bias the transistor 23% into conduction, and the voltage (K) at the emitter electrode fa ls below ground potential during the period in which the capacitor 214- is reverse-charging. The negative voltage developed across the resistor 232 biases the power transistor 23% into high conduction, whereby the solenoid coil 12 is energized for the duration of the fixed one-shot 11$ trigger period T -T To summarize the above operation, the fixed one-shot lllil is triggered by a positive-going pulse at time T The time T is determined by the rate of discharge of the capacitor 171? in the base circuit of the transistor 168. The discharging time of this capacitor 170, in turn, is determined by the setting of the variable resistor 166. The resistors are adjusted in all of the channels so that all of the printed characters in a line of print are in registration.

What is claimed is:

1. In an on-the-ily printer for printing a line of characters on a recording medium, the combination comprising: means providing a path for said recording medium; continuously moving type disposed on one side of said path; a plurality of hammers, one for each character position in said line, disposed on the opposite side of said path, each of said hammers having an adjustable rest position adjusted so that all of the characters printed in a said line have the same print density; a like plurality of signal responsive means each for impelling a different one of said hammers against said type; a storage device providing output signals over separate channels for said signal responsive means; adjustable delay means connected in each of said channels and being adjusted so that all of the characters printed in a said line are in registration; and a plurality of trigger circuits each connected to receive the output of a different one of said delay means, each trigger circuit providing, when triggered, a pulse of the same Width to a different one of said signal responsive means.

2. The combination as claimed in claim 1 wherein said signal responsive means are solenoids.

3. The combination as claimed in claim 2 including a plurality of pivotable solenoid arms each actuated by a different one of said solenoids for impelling a different one of said hammers.

References Cited by the Examiner UNITED STATES PATENTS 2,787,210 4/57 Shepard 101--93 2,947,916 8/60 Beck 317-1485 2,997,632 8/61 Shepard l0l93 X 3,085,935 10/61 Wood 3l7-l42 X 3,049,990 8/62 Brown et al 101-93 WILLIAM B. PENN, Primary Examiner.

RGBERT A. LEIGHEY, ROBERT E. PULFREY,

Examiners.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3,183,830 May 18, 1965 Donald M. Fisher et a1.

It is hereby certified that error appears in the above numbered patent requiring correction and that the said Letters Patent should read as corrected below.

COlJIIlIl 3, line 40, for "to" read of column 7, line 48, for "dis" read be- Signed and sealed this 2nd day of November 1965,

(SEAL) Attest:

ERNEST W. SWIDER EDWARD J. BRENNER Attesting Officer Commissioner of Patents

Claims (1)

1. IN AN "ON-THE-FLY" PRINTER FOR PRINTING A LINE OF CHARACTERS ON A RECORDING MEDIUM, THE COMBINATION COMPRISING: MEANS PROVIDING A PATH FOR SAID RECORDING MEDIUM; CONTINUOUSLY MOVING TYPE DISPOSED ON ONE SIDE OF SAID PATH; A PLURALITY OF HAMMERS, ONE FOR EACH CHARACTER POSITION IN SAID LINE, DISPOSED ON THE OPPOSITE SIDE OF SAID PATH, EACH OF SAID HAMMERS HAVING AN ADJUSTABLE REST POSITION ADJUSTED SO THAT ALL OF THE CHARACTERS PRINTED IN A SIGNAL LINE HAVE THE SAME PRINT DENSITY; A LIKE PLURALITY OF SIGNAL RESPONSIVE MEANS EACH FOR IMPELLING A DIFFERENT ONE OF SAID HAMMERS AGAINST SAID TYPE; A STORAGE DEVICE PROVIDING OUTPUT SIGNALS OVER SEPARATE CHAN-

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