CA1037776A - Force adjustment in impact printers - Google Patents

Abstract

FORCE ADJUSTMENT IN IMPACT PRINTERS
ABSTRACT OF THE DISCLOSURE

A plurality of self-restoring equally spaced apart print hammers selectively are driven lineally toward a printing position by continuously rotating impellers having equiangularly spaced radial impelling elements. Each impeller is effective through the agency of a rockable interponent, which is selectively elevated into the path of associated impelling elements upon latch-ing of the armature of an electromagnet, for transmitting impeller force to a corresponding print hammer. An elastomeric bumper, disposed in the path of the print hammers, dampens printing force on dies, which are conveyed past said hammers for printing, in equally spaced relationship different from the spacing of said hammers. Each die, when at a printing station, is aligned with a print hammer but spaced therefrom a distance inversely propor-tional to its printing area for producing copy of uniform intensity.

Description

Babler 5-A

This application is a division of application serial

2 nulriber 167,719, filed April 2, 19730

3 BACKGROUND OF THE INVENTION

4 The present invention relates ~o impact printers. More

5 particularly, the invention relates to means for adjusting printing

6 force in impact printers.

7 In printers of one class with which the present invention

8 is concerned, printing may be effected in response to signals, a ; 9 "line-at-a-time", on the fly, and at high speeds. In such printers, 10 character dies or type are conveyed on a continuously moving endless 11 carrier past print ha~ners which are actuated by a logic system 12 responsive to data to be reproduced.
13 Ideally suited for developing impact forces in said class 14 of printers, because of the high level of timing accuracy for print hammer control, are impelling means of the type disclosed in U.S.
16 Patent 2,927,960, issued to W. P. Byrnes, March 8, 1960. In my 17 copending Canadian application Serial No. 167,717 (Babler 3), filed 18 contemporaneously herewith, there is shown and described an improve-19 ment for adapting the disclosure of said patent for high speed printing.
21 Heretofore unknown for printers with such impelling 22 means are mechanisms for varying the printing forces such that 23 image density is substantially uniform from one print-out period 24 to another, regardless of the: (1) number of copies (within limits) simultaneously printed during each print-out period and (2) varia-26 tion in the masses of printing dies within a font.
27 The illustrated embodiment of the present invention 28 provides an improved impact printer, with adjustment of the 29 printing forces in accordance with the number of plies simultaneously ~ .

being printed, or according to the masses of the printing dies.
SUMMARY OF THE INVENTION
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In accordance with one aspect of the invention, in a printer of the type wherein printing is effected by driving an impacting means toward a selected one of a plurality of dies, each die having a printing surface area, a mechanism for increas-- ing the impact force of the impacting means on the selected die as the printing surface area of the selected die increases is provided.
The mechanism includes a carrier spaced from the impacting means and arranged for a relative movement therewith, and a plurality of die shanks mounted in and extending from the carrier for supporting the plurality of dies. The length of the die shanks are variable and set in accordance with the printing surface area of the die carried on each die shank. Means are pro~ided for decreasing the distance between the impacting means and the selected die as the printing surface area of the selected die increases so that the impact force on the selected die is increased as the printing surface area of the selected die increases.
In accordance with another aspectof the invention, in 20 a printer for impact printing on a record medium and having . a plurality of type character dies:

means for propelling a print hammer toward a selected one of the plurality of type character dies to effect a printing operation, said print hammer being propelled with the same initial velocity regardless of the type character to be printed; and means engagable with a portion of the print hammer as the print hammer is propelled toward the type character ` ~037776 die, for damping the velocity of the print hammer prior to impact with the type character die by varying amounts to reduce the printing energy by corresponding amounts as a function of the size of the printing surface area on the die of the selected type character ~o be printed with the velocity damped most and the least energy being exerted aga~nst dies having the least printing surface area.
BRIEF DESCRIPTION OF THE DRAWINGS
An embodiment of the invention will now be described, by way of example, with reference to the accompanying drawings in which:
FIGo 1 is a perspective view of an impact printer embodying one form of the invention, parts being broken away and parts omitted for the purpose of illustration;
FIG~ 2 is a vertical sec~ onal view of said printer according to the line 2--2 on FIG~ l;
FIG~ 3 is an enlarged elevational view of a print - hammer for said printer; and FIG~ 4 is a detailed view taken ina horizontal plane ; 20 according to the line 4--4 of FIGo 2, parts having been omitted for the purpose of illustration.
DETAILED DESCRIPTION of the EMBODIMENT
Referring now to FIG~ 1 of the drawings, the impact printer shown is generally designated 10. It has a pair of spaced apart pulleys 12 and 14 about which an endless carrier 16 is trained for translocating a plurality of pallets 18 by movement in a circuitous path. A plurality of dies 17 (FIGo 2) are carried on the front faces of the pallets, the latter being uniformly dimensioned and uniformly and equally spaced apart axially of the ;-ca~rier. When the dies comprise alphanumeric characters, two or more successive fonts axially of carrier 16 may enable longer line utput.

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Babler 5-A
,Q377q6 1 Carrier 16 and pallets 18, together with their mountings 2 may be substantially as shown and described in the copending 3 Canadian application of Franc~ E. Huntoon and James F. Kearney, 4 Serial No. 147,373, filed July 18, 1972, and assigned to the assignee of the present application. In accordance with said last 6 copending application, the plane in which parallel axes of pulleys 7 12 and 14 aredisposed and the vertical section 20 of web 22 on 8 which printing is about to occur are orthogonally disposed. Such

9 arrangement generates a loop in the carrier with an upper or print- -ing course 21 and a lower or return course 23 which are disposed in 11 a plane which is substantially parallel to web section 20.
12 In the exemplary printer 10, pulley 12 is an idler sheave 13 while pulley 14 is a drive sheave secured to a shaft 24. Driving 14 torque continuously is transmitted to said shaft from an operating prime mover means, herein shown as a motor 26, through a drive 16 train generally designated 28. The latter herein includes an 17 impeller shaft 30. This shaft is continuously driven in the 18 direction indicated by arrow 31 during printer operation.
19 A segment 32 of ribbon 34 is disposed in a plane substan-tially parallel to carrier course 21 between and spaced slightly 21 from face 36 of web section 20 and the pallets 18 supported from 22 said last course. The ribbon is trained about a plurality of ribbon 23 guides 38 which are spaced apart such that the ribbon assumes a 24 generally rectangular configuration in a horizontal plane. Opposed end portions of the ribbon are secured to a pair of adjoining 26 ribbon spools 40 and 42 which alternately function for ribbon 27 supply and accumulation. They alternately are driven in opposite 28 angular directions, by a spool control mechanism 44, the details 29 of construction of which form no part of the present .

~ ' Babler 5-A
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~0377 7~
1 invention. Mechanism 44 is connecte~ to motor 26 through a pulley 2 wheel 46, disposed in a common plane with spools 40 and 42, It is 3 secured on an end portion 47 of shaft 24 for driving the spool 4 control mechanism through a pulley belt 48.
A clutch 50, which may be conve~tional, is mounted for 6 releaseably securing the split shaft section 52 to the shaft 24 7 from which said section extends axially. Selective actuation of 8 the clutch may be effected through logic (not shown) which may be 9 conventional and the details of construction of which form no part of the invention. Thereupon, operating means, being a drive 11 train generally designated 54, advances web 22, in the direction 12 shown by arrow 56, a line at a time. Such advancement results from 13 incremental rotation of a worm gear 58 for driving a pulley belt 14 60 intermittently angularly to move a cylindrical roller 62.
Roller 62 is disposed transversely of and adjacent to the path of 16 web movement for frictionally engaging web 22 and in cooperation 17 with other components (not shown), intermitten ly drawing said -18 web from its s~pply source (not shown) about a guiding cylinder 64, 19 as said web is advanced.
Impelling means comprises an array of radially symmetri-21 cal impellers 66 (only representative ones of which are shown in 22 FIG. 1). The impelling means herein are substantially as shown and 23 described in my aforesaid copending Canadian application serial No.
24 167,717 (Babler 3) and in another copending Canadian application -serial No. 167,718 (Babler 4), also filed contemporaneously herewith.
26 Accordingly, each impeller is comprised of a plurality of radial 27 equiangularly spaced arms or impelling elements 68, the impellers 28 being concentrically secured to shaft 30 for rotation therewith 29 in the direction shown by arrow 70 (FIG. 2), in the e~emplary Babler 5-A

1 embodiment. The impellers are axially or horizontally spaced such 2 that each is disposed in substantially horizontal alignment with 3 a printing station on an imaginary line extending horizontally 4 acros~ web section 20. Opposed end portions of the shaft 30 are journalled in spaced apart vertical side members 72 (only one is 6 shown in FIGo 2) of the frame or chassis 74 of printer 10.
7 Impactor means for printing comprise a plurality o~
8 hammers 76 (only some of which are shown in FIG. 1) disposed behind 9 back face 78 (FIG~ 2) of web section 200 As shown in FIG~ 4, each hammer is aligned with the others in a horizontal array parallel to 11 the alignment of impellers 66. Each hammer also is aligned witb, 12 though spaced from, and disposed out of the path of movement of an 13 associated impeller by which it can be selectively driven in a 14 lineal path, perpendicularly to web section 20, between a normal or non-printing position (FIG~ 1) and a printing position (dashed 16 line of FIGo 4) against said back face 78 (FIGo 2).
17 The dies 17 on pallets 18 in course 21 and hammers 76 18 are disposed at a common horizontal level; and said pallets and 19 their dies when translocated move in a path parallel to the hammer array for printing. Thereby, each ~let 18 and groups thereof can 21 be moved successively into printing positions in horizontal align-22 ment with successive hammers 76 and groups thereof. The force 23 generated by each impeller 66 for urging web section 20, ribbon 24 segment 32 and any aligned dies 17 into contact is of sufficient magnitude for printing by forming an image of each such die on web 26 face 78. In the exemplary embodiment of the invention, the hammers 27 are associated with and reciprocatively arranged in chassis 74 by 28 means and in the manner disd osed in said copending application 29 Serial No. 167,717 (Babler 3).

Babler 5-A

- 1 A horizontal ~umper in the form of a rod 80 is disposed 2 parallel to shaft 30 has opposed end.s secured in the chassis 3 sides 72. Said rod extends through horizontally aligned slots 4 82 in the hammers 76 for limiting horizontal hammer movement~
A leaf spring 84 (FIGo 2) of gen~ral vertical orientation 6 and associated with each hammer 76, is included in hammer driving 7 means. It has a lower end portion which is rigidly secured to a 8 front chassis plate 86 and an upper end portion engaged in a down-9 wardly opening slot 88 in the printing head 77 of each hammer 76.

- 10 Each spring 84 has a slightly tensioned condition (FIGo 2) during

11 which its hammer is in its rearward or most remote non-printing

12 position, and a most tensioned condition (not shown) during print-.. ....

13 ing for urging or restoring its hammer to non-printing position.

14 Each impeller 66 is adapted to move a printingly asso-ciated and aligned hammer 76 through the agency of an interponent -16 90. In the preferred em~odiment of the invention, printing is 17 effected and the assemblies of the interponents as well as the 18 other parts of printer 10, including means for controlling and 19 liberating the interponents are, as shown and described in said ~ -last named copending application. In accordance therewith, the 21 interponents are disposed~n general horizontal alignement and 22 each has: (1) a first or upper position in which it is in a 23 projected condition, with its upper free end portion disposed in 24 the path of movement of associated impelling elements 68 for trans-mitting force from its impeller 66 to an aligned hammer 76 in 26 consequence of which printing occurs, and (2) a lower, non-pri~ ing 27 or second position in ~hich said interponent has fallen and is 28 removed from the impeller path.

Babler 5-A

1 As shown and described in said application Serial No.
2 167,717 (Babler 3), each interponent 90 intermittently is 3 controlled by an electromagnet assembly comprised of a 4 magnetically latchable armature 92 and an electromagnet 94 (FIG~ 2). Any suitable logic (not shown and forming no part of 6 the present invention) which may be conventional may be employed ` 7 for energizing each of sa~.d electromagnets 94 selectively. In - 8 consequence of energization of any electromagnet its armature will 9 be rocked, magnetomotively,against the restoring bias of its spring 96 clockwise from its position shown (FIG~ 2) to a latched position ;- 11 (not shown).
12 Correspondingly, an affected interponent will be thrust 13 upwardly (from its FIG~ 2 position) into its first position or 14 projected condition (not shown) between a pair of adjoining impel-~ 15 ling elements 68 against the lowering bias of an associated spring ; 16 98 which becomes tensioned upon upward movement of its interponent.
17 Ensuingly, the upwardly thrust interponent will be engaged by a 18 circuitously traveling impelling element 68 and rocked into engage-19 ment with an associated hammer 76 to effect momentum transfer and translation of impeller torque into a lineal force for printing.
21 In the e~emplary printer 10, both momentum transfer and restora-22 tion of an interponent to its second position (FIGo 2) following 23 momentum transfer, as well as the conditioning of interponents 90 24 for repeat cycles are as shown and described in said last named copending application.
26 In the printer 10, as illustrated (FIG. 4), the hammers 27 76 are equally spaced apart and the pallets 18 in a font in course 28 21 are also equally spaced apart. However, the spacing between 29 the centers of the hammers is not the same as the spacing between _ g _ ,' ,,: ~ , Babler 5-A

1 the centers of the pallets. Their spacing, as well as their 2 dimensions, mode and sequence of operations, and printing with 3 printer 10 are as shown and described in said copending applica-4 tion Serial Nos. 167,717 (Babler 3) and 167,718 (Babler 4).
As shown in said copending application Serial No. 147,373, 6 pallets 18 are mounted on the inner ends of shanks 100; and the 7 ~anks are disposed in a horizontal plane and are removably mounted 8 in carrier 16, extending transversely through its hammer prox~mate 9 side 102 and hammer distal side 104. In accordance with the present invention, for adjusting the impact of each hammer 76 ll upon printing according to the depth of material against which the 12 impact is applied, damping means is disposed in the path of hammer . .
13 movement. Herein, said last means comprises a resilient or a 14 viscous damper which may be an elastomer from which bumper 80 is -fabricated. Thereby, the hammers and said damping means are 16 arranged for relative movement. The disposition of the bumper 17 is such that it limits movement of each hammer in each of opposite 18 directions by engagement with front and rear sides 106 and 108 19 (FIG. 3) of slots 82.
The distance 110 between the rear wall 112 of bumper 8 21 and each rear side 108 of a slot 82, when its hammer 76 is in its 22 normal position (FIGo 3~ is such that, for the thickest number of 23 plies of sheets of paper intended to be accommodated in the hori- -24 zontal span 113, between the end face 114 of hammer head 77 and a die 16 aligned therewith for printing, side 108 will just come 26 into engagement with wall 112, when said hammer face reaches print-27 ing position. Accordingly, to the extent that the thickness of the 28 paper mass in span 113 is reduced from such ma~imum, each hammer 76 29 will move further ~o the right (relative to FIGS. 2 and 3), Ba~ler 5-A
, " ~037qq6 1 compressing the bumper 80 correspondingly, to reach printing 2 position, By fabricating bumper 80 of polyurethane material 3 having a durometer Shore hardness of 90A, printing of good 4 quality can be produced on as few as one sheet or on as many as 8i~ carbon copies, simultaneously without adjusting the distance 6 across span 1130 7 Additionally, the bumper 80 is proportioned such that 8 it serves to absorb rebound energy of the hammers 76 following - 9 printing as they are restored to normal positions (FIGo 1)~
For adjusting the spacing of hammers76 and pallets 18, 11 that is, for setting the distance across span 113, the pallets 12 are adjustable toward and away from the hammers. To that end a 13 back-up bar or stop member 116 is supported from a frame or 14 chassis member 118 along side 104 of carrier course 21. The back-up bar is engaged by the outer ends of shanks 100 in said upper 16 course and is adjustable in a horizontal plane toward and away from 17 carrier 16 within the limits of a slot 120 in said back-up bar.
18 Means forreleaseably securing the back-up bar in adjusted positions 19 may comprise a threaded pin 122 passed through slot 120 from member 118 for holding a clamping nut 124 against the back-up bar.
21 From another aspect, the impact upon printing is adjusted 22 according to the force transfer areas or sizes of the printing 23 surfaces of the printing dies. This adjustment is for minimizing 24 variation in copy intensity due to variation in the size of ` 25 characters of the dies. For that purpose, the lengths of shanks 26 100 are varied accordingly to the sizes of the printing surfaces 27 of dies 17. If it is impractical to vary the l~ngths according 28 to the size of the printing surface of each die, the variation may 29 be according to sizes within selected ranges. Herein, three pallet . .

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Babler 5-A

~- 1 groups, 18A, 18B and 18C are shown (FIG~ 4). Each group has a - 2 range of die sizes different from the size ranges of the others.
3 Pallets 18 having dies whose sizes or printing areas are within - -4 the smallest range have the shortest shanks lOOA. In an alpha-numeric font, punctuation marks such as a period, and a colon 6 belong in this last-named range. Dies whose printing areas are 7 within the greatest size range have the longest shanks lOOC.
8 Examples of alphanumeric characters in this last named range are 9 capitals M and W. Dies within the intermediate size range, such as many lower case letters, have shanks lOOB of intermediate 11 length.
12 Accordingly, a hammer 76 which is impelled toward a 13 pallet carried on a shank lOOA will travel the greatest distance 14 for printing. Such hammer will compact the greatest damping mass ; 15 in bumper 80. Consequently, when it strikes for printing, its 16 impact force will be less than the impact force when printing 17 with a die on a pallet carried on either a shank lOOB or lOOC;
18 and such force will be dissipated over an area in the smallest 19 range. On the otherhand, a hammer printing with a die on a shank lOOC will travel the least distance to printing position. Such 21 hammer encounters less damping mass in bumper 80 before reaching 22 printing position than a hammer printing with a die carried on 23 either a shank lOOA or lOOB. Such hammer will have the greatest 24 energy on impact; however, such force will be dissipated over a printing surface in the greatest range.
26 As many modifications in the described construction 27 could be conceived, and as many widely different embodiments 28 could be made without departing from the spirit and scope of the 29 claims, it is intended that all matter contained in the accompanying .' :

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Babler 5-A
10377~6 :~ 1 specifica~ion shall be consid~ed as illustrative only and not 2 in a limiting sense.

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Claims (7)

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. In a printer of the type wherein printing is effected by driving an impacting means toward a selected one of a plurality of dies, each die having a printing sur-face area, a mechanism for increasing the impact force of the impacting means on the selected die as the printing surface area of the selected die increases comprising:
a carrier spaced from the impacting means and arranged for a relative movement therewith; and a plurality of die shanks mounted in and extending from the carrier for supporting the plurality of dies, the length of the die shanks being variable and set in accordance with the printing surface area of the die car-ried on each die shank for decreasing the distance between the impacting means and the selected die as the printing surface area of the selected die increases so that the impact force on the selected die is increased as the print-ing surface area of the selected die increases.

2. In a printer for impact printing on a record medium and having a plurality of type character dies:
means for propelling a print hammer toward a selected one of the plurality of type character dies to effect a printing operation, said print hammer being propelled with the same initial velocity regardless of the type character to be printed; and means engagable with a portion of the print hammer as the print hammer is propelled toward the type character die, for damping the velocity of the print hammer prior to impact with the type character die by varying amounts to reduce the printing energy by corresponding amounts as a function of the size of the printing surface area on the die of the selected type character to be printed with the velocity damped most and the least energy being exerted against dies having the least printing surface area.

3. A printer as recited in claim 2, wherein the means for propelling includes:
means for initially positioning the hammer in the same position prior to propelling, regardless of the type character to be printed; and the means for damping includes a resilient bumper mounted in the printer for engaging a portion of the ham-mer prior to printing impact so as to absorb hammer energy and thus decelerate the hammer prior to printing and means for setting the distance between the type dies and the bumper in accordance with type face area so that the dies with the smallest printing area are positioned furthest from the bumper in the printing position.

4. A printer as recited in claim 3, wherein the type dies are formed at the inner ends of type support members, and further comprising:
a continuously traveling endless carrier mounted in the printer for advancement past the hammer, and carrying the type members so that the type dies face the hammer and continuously travel past the hammer in alignment there-with for printing; and wherein said means for setting the distance comprises a fixed back-up member mounted in the printer so that por-tions of the type support members travel along and engage the back-up member as they travel past the hammer, the type support members being formed of different lengths in accordance with type face area, so that the die faces are variably spaced from the bumper as they advance into the printing position aligned with the hammer.

5. A printer as recited in claim 4, wherein the type support members comprise elongated shanks mounted in the endless carrier; and wherein the back-up member comprises a fixed back-up bar mounted parallel to the bumper and engaging the outer ends of the shanks.

6. A printer as recited in claim 2, wherein the propelling means comprises:
means for mounting the hammer for free linear reciprocating movement along a line of flight toward and away from a type die in printing position, so that an inner printing end of the ham-mer faces the type die and an outer end extends away from the type die along the line of flight;
means for initially biasing the hammer to a fixed initial rest position spaced from the type die, in which the hammer occupies the same initial position regardless of the character to be printed; and means for striking the inner end of the hammer when it is desired to print a character, with a force sufficient to propel the hammer toward the type die to print the character.

7. A printer as recited in claim 6, further comprising:
an endless carrier for the type dies;
means for mounting a font of type dies on the carrier for continuous movement past the line of flight and in intermittent momentary alignment with the inner end of the hammer; and means for positioning the type dies on the carrier so that the faces of the dies are spaced variable distances from the hammer in the initial position, the spacing being set in accordance with the printing surface area of each die in the font so that those dies with the largest area are positioned closest to the hammer and those with the smallest area are spaced furthest from the hammer.