US3835771A - Print train permitting accelerated printing speeds in a line printer - Google Patents

Abstract

A print train of predetermined length and comprised of a plurality of type carrying blocks is provided with an increased number of hammer impactable type characters to thereby enable the realization of significantly accelerated printing speeds, the type blocks being individually and alternately driven to advance a toothed belt to which the blocks are separately coupled around a pair of rotatable sprockets, said accelerated printing speeds being realized without an accompanying degradation of printing quality resulting from the closer spacing of the adjacent characters, means being provided to shield the characters adjacent to an impacted character against the striking force of the hammer associated with such impacted character.

Description

United States Patent Funk et al. Sept. 17, 1974 [5 PRINT TRAIN PERMITTING 3,633,500 1/1972 Edwards 101 111 ACCELERATED PRINTING SPEEDS IN A 3,633,501 l/l972 Edwards 101/111 LINE PRINTER Inventors: John W. Funk, Plymouth; Eugene L.

Merlino, Jr., Dearborn Heights; Stephen Barasch, Westland; Daniel J. Woods, Plymouth, all'of Mich.

Burroughs Corporation, Detroit, Mich.

Filed: May 2, 1973 Appl. No.: 356,393

Assignee:

US. Cl. 101/111, 101/93 C Int. Cl B41j 7/06 Field of Search 101/93 C, 111, 375, 269,

Ripple etal. 101/111 X Primary Examiner-Robert E. Pulfrey Assistant ExaminerEdward M. Coven Attorney, Agent, or Firm-Edwin W. Uren; Paul W. Fish; Charles S. Hall [5 7 ABSTRACT A print train of predetermined length and comprised of a plurality of type carrying blocks is provided with an increased number of hammer impactable type characters to thereby enable the realization of significantly accelerated printing speeds, the type blocks being individually and alternately driven to advance a toothed belt to which the blocks are separately coupled around a pair of rotatable sprockets, said accelerated printing speeds being realized without an accompanying degradation of printing quality resulting from the closer spacing of the adjacent characters, means being provided to shield the characters adjacent to an impacted character against the striking force of the hammer associated with such impacted character.

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PRINT TRAIN PERMITTING ACCELERATED PRINTING SPEEDS IN A LINE PRINTER BACKGROUND OF THE INVENTION Train printers of the type produced by Burroughs Corporation under style number B9247, and partially disclosed in U.S. Pat. No. 3,577,9l3 issued on May ll, 1971 to Herbert J. Hinze, may be characterized by the combination of a predetermined number of type characters on individual type carrying blocks, the blocks being removably couplable to an internally toothed belt to form a print train which is rotatably supported by a pair of spaced apart rotatable sprockets, the beltcoupled blocks not being otherwise interconnected. In train printers of this kind, rotation of the print train is accomplished by driving means cooperating alternately with coupling means disposed on the individual blocks, the alternate driving of the individual blocks serving to rotate the toothed belt around the rotatable sprockets and to abuttably push the downstream blocks in the direction of the sprockets, the blocks being separated from their abuttable relationship as they are pulled by the internal teeth of the belt around the peripheries of the sprockets. Train printers of this general character provide advantages over prior art chain printers wherein the individual type characters are fixed to a belt or band, the band being rotated by driving means which cooperates directly with at least one of the sprockets, the direct attachment of the type characters to the band and the direct driving of the band by cooperable driving means having been found to present various cost disadvantages in the areas of design and maintenance, and to present various operational disadvantages in the areas of type wear and band distortion.

A brief description of the construction and operation of the print train described in detail in the abovereferenced patent is hereinafter presented with refer ence to FIGS. 1 through 5. As shown in FIGS. 1 and 5, an endless belt 3 having internal teeth 5 is rotatably supported by a pair of rotatable and uprightly disposed sprockets 7 and 9, the lowermost portion of the belt representing an operative printing position thereof, and the uppermost portion representing an inoperative position, rotation fo the belt by hereinafter described means serving to advance the belt and particular areas thereof as between the operative and inoperative positions. A predetermined number of type carrying blocks 11, shown in detached form in FIG. 2, and in coupled relationship with the belt 3 in FIGS. 1 and 5, are each comprised of an apertured belt receiving member 13 for receiving the outside surface of the belt 3, and a plurality of offset and inwardly directed projections 15 for clampably receiving the inside surface of the belt and particularly the recesses formed by the internal teeth 5 thereof. Each of the type carrying blocks 11 is additionally comprised of a plurality of external teeth 17 extending outwardly from the belt receiving member 13, and an elongated type lug 19 normally disposed of the external'teeth l7 and the belt receiving member 13, the type lug 19 presenting a type character carrying surface 21 having a plurality of type characters 23 integrally formed thereon, the type lug 19 assuming a downwardly directed position when the block 11 is assembled on the belt 3 and is located in the operative position of the belt, as shown in FIG. 1. Each of the blocks 11 is also provided with spacing pads 25 disposed on opposite sides of the type lug 19, the function thereof being to abuttably advance the downstream blocks to the sprocket 7, and from the sprocket 7 to the sprocket 9 when a given block 11 is drivably advanced by hereinafter described means. The type carrying blocks llare assembled on the belt 3 as illustrated in FIG. 3, it being noted from FIG. 3 that the belt is wider than the sprockets 7 and 9, and that the offset and inwardly directed projections 15 of the blocks engage opposite portions of the belt which extend outwardly from the sprockets (as identified at 27 in FIG. 3), each block being coupled to the belt 3 with minimal linear play as permitted by the relative dimensions of the recesses between the teeth 5 of the belt and the projections 15 of the blocks.

With the plurality of type carrying blocks 11 coupled to the belt 3, the print train so formed is continuously rotatable about the sprockets 7 and 9 to thereby bring selected type characters 23 into impactreceiving relationship with a plurality of linearly arranged columnidentifying hammers 29, the print train being rotated in a counterclockwise direction (as viewed in FIG. 1) through the driving cooperation of a drive gear 31 fixed to a drive shaft 33 (as best illustrated in FIG. 4). Rotation of the drive gear 31 and the peripheral teeth 35 thereof is effective to alternately engage the external teeth 17 of the type carrying blocks 1 l to thereby alternately advance each block 11 in the direction of the downstream sprocket 7, the blocks 11 located between the driven block and the sprocket 7 being abuttably pushed to the sprocket through contact of the spacing pads 25 of the various blocks, movement of the driven blocks being transmitted to the belt by means of the hereinbefore described engagement of the projections 15 with the overhanging toothed portions 27 of the belt. Engagement of the drive gear 31 with the external teeth 17 of the individual blocks 11, and the pushing effect of the driven blocks on the downstream blocks can best be understood with reference to FIG. 4. FIG. 5 is illustrative of the manner in which the movement of the belt 3 serves to pull the blocks 11 around the sprockets 7 and 9, it being noted that the abutting relationship between the blocks is removed during such circular movement. It can be seen from FIG. 5 that the leading edges of the projections 15 of the blocks 11 that are being moved in the direction of the sprockets 7 and 9 are in contact with the trailing edges of the edges of the internal teeth 5 of the belt 3, the movement of such blocks serving to transmit rotational motion to the belt 3, whereas the trailing edges of the projections 15 of the blocks being moved around the sprockets 7 and 9 are in contacting relationship with the leading edges of the internal teeth 5, the moving belt 3 accordingly serving to pull the blocks 11 around the sprockets.

Known train printers of the type produced by Burroughs Corporation under style number B9247 have commonly provided or 132 linearly arranged impactable hammers 29, and 48 type carrying blocks 11 disposed along the print train, each of the blocks 11 being provided with four type characters 23, as shown in FIG. 2, presenting a total of 192 selectable type characters arranged along the belt 3. With a print train rotating speed of 170.66 inches per second, a printing throughput of from 440 to 1,200 lines per minute has been achieved, depending upon the character set employed, a 750 lines per minute throughput being achieved with a 48 character set, and with proportionately higher and lower throughput speeds with smaller and larger character sets, respectively. As is well known in the line printer art, increased printing throughput may be achieved with a given character set by increasing the total number of type characters disposed along the print train, or alternatively, through the employment of smaller character sets that permit increased repetition of the individual characters comprising the set.

With the increased processing speeds of present generation computers, continued attention is given to the development of ways and means of increasing the throughput speeds of input and output peripherals comprising data processing systems, and particularly to ways and means of increasing the throughput speeds of line printers. Since the employment of smaller character sets would present serious limitations to printing flexibility, attention has been focused on ways and means of increasing the total number of characters along the print train, as by increasing the number of type characters per block from 4 to 6, the total number of characters provided by the 48 type blocks being thus increased from 192 to 288. Early experimentation with this approach, in an effort to achieve a printing throughput of 1,000 lines per minute with a 48 character set, resulted in the ghost printing of type characters adjacent to the characters that were impacted by the hammers 29, as illustrated in FIG. 6 wherein the printed characters 37 on the media are accompanied by ghost characters 39. Investigation into the cause of such ghost printing revealed a tendency of a hammer 29 (FIG. 1 when impacted against a selected type carrier 23, to advance the media into light printing contact with the type characters adjacent to the selected character, the tendency being aggravated proportionally to an increase in the stiffness of the media and to a reduction in the space between the type characters on the blocks 11.

SUMMARY OF THE INVENTION It is accordingly an object of the present invention to significantly increase the printing throughput of train printers of the above characterized type, as from 750 lines per minute to 1,050 lines per minute in the case of the Burroughs train printer, such increase in speed to be achieved with a 48 character set.

It is a further object of the present invention to achieve this significant increase in printing throughput without altering the over-all dimensions of the printer, and without changing the number and size of the type carrying blocks that are disposed along the print train thereof.

It is yet a further important object of the present invention to provide for such significant increase in printing throughput without degrading the quality of the printed result, as by the entertainment of ghost printing of the kind illustrated in exaggerated form in FIG. 6.

Yet another object of the present invention is to provide a print train wherein the pitch distance between the type characters is significantly decreased, and wherein each type carrying block is provided with means effective for preventing a printing contact as between the media and the type characters adjacent a selected type character when the selected type character is impacted by its associated hammer.

BRIEF DESCRIPTION OF THE DRAWING The drawing figures accompanying the present specification, hereinafter described,are presented as an aid to understanding the general character of train printers, to comprehending the nature of the problem that is customarily encountered in attempting to achieve significantly increased throughput speeds therewith, and to conveying a lucid explanation of the solution to the problem as contemplated by the inventors.

FIG. 1 is a rear elevational view of a print train employed in line printers of the train type;

FIG. 2 is a front view of a type carrying block of the kind comprising the print train of FIG. 1, such block being provided with the conventional number of four type characters disposed on a type carrying surface thereof;

FIG. 3 is a sectional view of a type carrying block assembled on the belt and in engaged relationship with one of the sprockets;

FIG. 4 is a bottom view of the mechanism of FIG. 1;

FIG. 5 is a partial sectional view of the print train of FIG. 1 in association with one of the sprockets;

FIG. 6 is an enlarged and exaggerated sample of a printed result showing the ghost printing of characters on the media intermediate the intended printed characters;

FIG. 7 is an enlarged sample of the desired printed result on the media;

FIG. 8 is a front view of the inventive type carrying block showing six type characters arranged along the type carrying surface thereof and with barriers interposed between the characters; and

FIG. 9 is a perspective view of the type carrying surface of the inventive block of FIG. 8, showing the six type characters with barriers interposed therebetween.

DESCRIPTION OF THE PREFERRED EMBODIMENT The objective of increasing the printing throughput of the above referenced train printer from 750 to 1,050 lines per minute, based on a 48 character set, without altering the dimensions of the print train or the number or size of the type carrying blocks 11 carried by the belt 3, led to the development of the type carrying block 1 1' shown in FIG. 8, 48 of such blocks being arranged along the belt 3 with each block containing a total of six type characters 23, the type characters accordingly being spaced in closer proximity to one another. The effect of this increase of two type characters per block resulted in an increase in the total number of type characters in the print train from 192 to 288, such increased number of type characters permitting a multiplied repetition thereof along the belt 3 to thereby provide the desired increase in printing throughput. With the resultam decreased spacing between the type characters on the individual blocks 11', the inventive blocks were additionally provided with barriers 41 disposed between the type characters 23, such barriers, being of substantially equal height to the height of the type characters 23 extendiing outwardly from the type lugs 19, serving to support the media upon impacting of a hammer 29 against a selected type character 23 to thereby prevent the media from being moved into printable contact with the type character adjacent the selected character.

The barriers 41 may present a substantially flat raised surface between the type characters as illustrated in FIG. 9, or provided with a slightly radiused raised surface depending upon the relative stiffness of the media to be used and the corresponding adjacent characters.

What is claimed is:

1. An improved rotatably supported print train operatively associated with a plurality of linearly arranged selectively impactable hammers in a printing device and responsive to driving means of said printing device to bring selected type characters into printing position relative to said hammers for producing printed characters on printable media of varying rigidity, said print train comprising:

a. an endless toothed belt encompassing a pair of spaced-apart sprockets providing said rotatable support for said print train,

b. a predetermined plurality of type carrying blocks distributed along and removably coupled to said endless belt in engaged relationship relative to the teeth thereof, each of said blocks having a plurality of external teeth disposed on an edge thereof and in cooperable relationship relative to said driving means to be intermittently advanced thereby so as to rotate said belt around said sprockets, a type lug presenting a type carrying surface contiguous to and normally disposed of said external teeth, and a plurality of spaced-apart type characters arranged along said type carrying surface in close proximity to one another and effective for producing said printed characters on said printable media of said varying rigidity upon the impacting of selected hammers thereagainst, and media supporting means fixed to said type carrying surfaces of said type lugs and effective for preventing the printing of ghost characters on printable media of relatively greater rigidity such as would result from said close proximity of said type characters on said type carrying surfaces, said media supporting means comprising an elongated barrier fixed to and transversely disposed of said type carrying surface of each of said type lugs intermediate adjacent pairs of said type characters thereof, each of said barriers extending outwardly from the type lug to which it is fixed by a distance substantially equal to the extension of said adjacent type characters therefrom, whereby said printable media is held away from the type characters oppositely adjacent to a selected type character when activated into printable contact with said selected character upon impacting of the hammer associated therewith.

2. An improved printing mechanism for producing printed characters on printable media of varying rigidity comprising:

a. a media guideway,

b. means for advancing said media along said guidec. a plurality of selectively impactable hammers transversely disposed on one side of said media guideway,

d. a rotatably supported endless print train associated with driving means of said printing mechanism and transversely and normally disposed relative to said media guideway on the opposite side thereof from said plurality of hammers, said print train having a predetermined plurality of type character carrying blocks arranged therealong such that the rotation of said print train by said driving means is effective to transport said blocks as between an operative position thereof contiguous to said guideway and said hammers and an inoperative position thereof remote from said guideway and said hammers, each of said blocks including a plurality of external teeth disposed along an edge thereof and in cooperable relationship relative to said driving means to be intermittently advanced thereby so as to rotate said print train around said rotatable support thereof, a type lug presenting a type character carrying surface contiguous to and normally disposed of said external teeth, a plurality of spaced-apart type characters arranged along said type character carrying surface in close proximity to one another and effective for producing said printed characters on said printable media of said varying rigidity upon the impacting of selected hammers thereagainst, and

e. media supporting means fixed to said type character carrying surfaces of said type lugs and effective for preventing the printing of ghost characters on printable media of relatively greater rigidity such as would result from said close proximity of said type characters on said type carrying surfaces, said media supporting means comprising an elongated barrier fixed to and transversely disposed of said type character carrying surface of each of said type lugs intermediate adjacent pairs of said type characters thereof, each of said barriers extending outwardly from the type lug to which it is fixed by a distance substantially equal to the extension of said adjacent type characters therefrom, whereby said media is held away from the type characters oppositely adjacent to a selected type character when activated into printable contact with said selected character upon impacting of the hammer associated therewith.

3. An improved type character carrying block for use in a predetermined plurality in an endless rotatably mounted print train in a printing device for producing printed characters on printable media of varying rigidity, said print train having an endless toothed belt disposed in encompassing relationship with a pair of spaced-apart rotatable sprockets, said belt being effective for removably coupling said predetermined plurality of type character carrying blocks thereto relative to the teeth thereof, said printing device having media guiding and advancing means, a predetermined plurality of impactable hammers transversely arranged relative to the direction of advancement of the media, and print train driving means effective for rotating said belt and said blocks to thereby advance selected type characters into printable relationship with said hammers, said improved type carrying block comprising:

a. a plurality of external teeth disposed along an edge thereof and in cooperable relationship relative to said driving means to be intermittently advanced thereby so as to rotate said belt around said pair of sprockets,

b. a type lug presenting a type character carrying surface contiguous to and normally disposed of said external teeth,

0. a plurality of spaced-apart type characters arranged along said type character carrying surface in close proximity to one another and effective for producing said printed characters on said printable media of said varying rigidity upon the impacting of selected hammers thereagainst, and

d. media supporting means fixed to said type character carrying surface of said type lug and effective for preventing the printing of ghost characters on printable media of relatively greater rigidity such as would result from said close proximity of said characters on said type character carrying surface, said media supporting means comprising an elongated barrier fixed to and transversely disposed of said type character carrying surface of said type lug intermediate adjacent pairs of said type characters thereof, each of said barriers extending outwardly from the type lug by a distance substantially equal to the extension of said adjacent type characters therefrom, whereby said printable media is held away front the type characters oppositely adjacent to a selected type character when activated into printable contact with said selected character upon impacting of the hammer associated therewith.

4. An improved type carrying block for multiple use in association with a rotatably mounted and driven endless internally toothed belt to define a print train of a printing device having selectively impactable hammers, said printing device being effective for producing printed characters on printable media of varying rigidity, said block comprising:

a. an apertured belt receiving member presenting a flat orthogonal surface for receiving the outside surface of said belt, said member additionally presenting, within the framework of the aperture thereof, a plurality of oppositely'disposed offset and inwardly directed projections, said projections being effective for clampably receiving the inside surface of said belt and particularly for engageably receiving recesses formed by said internal teeth thereof, a

b. a plurality of external teeth substantially disposed in coplanar relationship with said belt receiving member, said external teeth being responsively effective for driving said belt and said print train,

'c. an elongated type lug parallelly disposed relative to said belt receiving member and normally disposed relative to said external teeth, said type lug presenting a type character carrying surface having a plurality of spaced-apart type characters integrally formed thereon in close proximity to one another, said type characters being effective for producing said printed characters on said printable media of said varying rigidity upon the impacting of selected hammers thereagainst, said type character carrying surface having also a plurality of elongated media supporting barriers transversely disposed relative thereto and intermediate adjacent pairs of said type characters, said barriers being effective for preventing the printing of ghost characters on printable media of relatively greater rigidity such as would result from said close proximity of said type characters on said type character carrying surface, each of said barriers extending outwardly from the type lug by a distance substantially equal to the extension of said adjacent type characters therefrom, whereby said printable media is held away from the type characters oppositely adjacent to a selected type character when activated into printable contact with said selected character upon impacting of the hammer associated therewith.

Claims (4)

1. An improved rotatably supported print train operatively associated with a plurality of linearly arranged selectively impactable hammers in a printing device and responsive to driving means of said printing device to bring selected type characters into printing position relative to said hammers for producing printed characters on printable media of varying rigidity, said print train comprising: a. an endless toothed belt encompassing a pair of spaced-apart sprockets providing said rotatable support for said print train, b. a predetermined plurality of type carrying blocks distributed along and removablY coupled to said endless belt in engaged relationship relative to the teeth thereof, each of said blocks having a plurality of external teeth disposed on an edge thereof and in cooperable relationship relative to said driving means to be intermittently advanced thereby so as to rotate said belt around said sprockets, a type lug presenting a type carrying surface contiguous to and normally disposed of said external teeth, and a plurality of spaced-apart type characters arranged along said type carrying surface in close proximity to one another and effective for producing said printed characters on said printable media of said varying rigidity upon the impacting of selected hammers thereagainst, and c. media supporting means fixed to said type carrying surfaces of said type lugs and effective for preventing the printing of ghost characters on printable media of relatively greater rigidity such as would result from said close proximity of said type characters on said type carrying surfaces, said media supporting means comprising an elongated barrier fixed to and transversely disposed of said type carrying surface of each of said type lugs intermediate adjacent pairs of said type characters thereof, each of said barriers extending outwardly from the type lug to which it is fixed by a distance substantially equal to the extension of said adjacent type characters therefrom, whereby said printable media is held away from the type characters oppositely adjacent to a selected type character when activated into printable contact with said selected character upon impacting of the hammer associated therewith.

2. An improved printing mechanism for producing printed characters on printable media of varying rigidity comprising: a. a media guideway, b. means for advancing said media along said guideway, c. a plurality of selectively impactable hammers transversely disposed on one side of said media guideway, d. a rotatably supported endless print train associated with driving means of said printing mechanism and transversely and normally disposed relative to said media guideway on the opposite side thereof from said plurality of hammers, said print train having a predetermined plurality of type character carrying blocks arranged therealong such that the rotation of said print train by said driving means is effective to transport said blocks as between an operative position thereof contiguous to said guideway and said hammers and an inoperative position thereof remote from said guideway and said hammers, each of said blocks including a plurality of external teeth disposed along an edge thereof and in cooperable relationship relative to said driving means to be intermittently advanced thereby so as to rotate said print train around said rotatable support thereof, a type lug presenting a type character carrying surface contiguous to and normally disposed of said external teeth, a plurality of spaced-apart type characters arranged along said type character carrying surface in close proximity to one another and effective for producing said printed characters on said printable media of said varying rigidity upon the impacting of selected hammers thereagainst, and e. media supporting means fixed to said type character carrying surfaces of said type lugs and effective for preventing the printing of ghost characters on printable media of relatively greater rigidity such as would result from said close proximity of said type characters on said type carrying surfaces, said media supporting means comprising an elongated barrier fixed to and transversely disposed of said type character carrying surface of each of said type lugs intermediate adjacent pairs of said type characters thereof, each of said barriers extending outwardly from the type lug to which it is fixed by a distance substantially equal to the extension of said adjacent type characters therefrom, whereby said media is held away from the type characters oppositely adjacent to a selected type character when Activated into printable contact with said selected character upon impacting of the hammer associated therewith.

3. An improved type character carrying block for use in a predetermined plurality in an endless rotatably mounted print train in a printing device for producing printed characters on printable media of varying rigidity, said print train having an endless toothed belt disposed in encompassing relationship with a pair of spaced-apart rotatable sprockets, said belt being effective for removably coupling said predetermined plurality of type character carrying blocks thereto relative to the teeth thereof, said printing device having media guiding and advancing means, a predetermined plurality of impactable hammers transversely arranged relative to the direction of advancement of the media, and print train driving means effective for rotating said belt and said blocks to thereby advance selected type characters into printable relationship with said hammers, said improved type carrying block comprising: a. a plurality of external teeth disposed along an edge thereof and in cooperable relationship relative to said driving means to be intermittently advanced thereby so as to rotate said belt around said pair of sprockets, b. a type lug presenting a type character carrying surface contiguous to and normally disposed of said external teeth, c. a plurality of spaced-apart type characters arranged along said type character carrying surface in close proximity to one another and effective for producing said printed characters on said printable media of said varying rigidity upon the impacting of selected hammers thereagainst, and d. media supporting means fixed to said type character carrying surface of said type lug and effective for preventing the printing of ghost characters on printable media of relatively greater rigidity such as would result from said close proximity of said characters on said type character carrying surface, said media supporting means comprising an elongated barrier fixed to and transversely disposed of said type character carrying surface of said type lug intermediate adjacent pairs of said type characters thereof, each of said barriers extending outwardly from the type lug by a distance substantially equal to the extension of said adjacent type characters therefrom, whereby said printable media is held away front the type characters oppositely adjacent to a selected type character when activated into printable contact with said selected character upon impacting of the hammer associated therewith.

4. An improved type carrying block for multiple use in association with a rotatably mounted and driven endless internally toothed belt to define a print train of a printing device having selectively impactable hammers, said printing device being effective for producing printed characters on printable media of varying rigidity, said block comprising: a. an apertured belt receiving member presenting a flat orthogonal surface for receiving the outside surface of said belt, said member additionally presenting, within the framework of the aperture thereof, a plurality of oppositely disposed offset and inwardly directed projections, said projections being effective for clampably receiving the inside surface of said belt and particularly for engageably receiving recesses formed by said internal teeth thereof, b. a plurality of external teeth substantially disposed in coplanar relationship with said belt receiving member, said external teeth being responsively effective for driving said belt and said print train, c. an elongated type lug parallelly disposed relative to said belt receiving member and normally disposed relative to said external teeth, said type lug presenting a type character carrying surface having a plurality of spaced-apart type characters integrally formed thereon in close proximity to one another, said type characters being effective for producing said printed characters on said printable media of said varyiNg rigidity upon the impacting of selected hammers thereagainst, said type character carrying surface having also a plurality of elongated media supporting barriers transversely disposed relative thereto and intermediate adjacent pairs of said type characters, said barriers being effective for preventing the printing of ghost characters on printable media of relatively greater rigidity such as would result from said close proximity of said type characters on said type character carrying surface, each of said barriers extending outwardly from the type lug by a distance substantially equal to the extension of said adjacent type characters therefrom, whereby said printable media is held away from the type characters oppositely adjacent to a selected type character when activated into printable contact with said selected character upon impacting of the hammer associated therewith.

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