US2502133A

US2502133A - Ribbon inker in reciprocating printing machines

Info

Publication number: US2502133A
Application number: US566280A
Authority: US
Inventors: Harmon P Elliott
Original assignee: Individual
Current assignee: Individual
Priority date: 1944-12-02
Filing date: 1944-12-02
Publication date: 1950-03-28
Anticipated expiration: 1967-03-28

Description

H. P. ELLIOTT 2,502,133

March 28, 1950 RIBBON INKER IN RECIPROCATING PRINTING MACHINES" I I v Sheets-Sheet 2|.

Filed Dec. 2, 1944 INVENTOR.

and;

M 1950 v H. P. ELLKDTT 2,502,133

RIBBON INKER IN 'RECIPROCATING PRINTING MACHINES Q Y M March 28, 1950 H. P. EL LIOTT ,5

RIBBON INKER IN RECIPRQCATING PRINTING MACHINES Filed Dec. 2; 1944 a Sheets-Sheef 5 Patented Mar. 28, 1950 RIBBON INKER IN RECIPROCATING PRINTING MACHINES Harmon P. Elliott, Watertown, Mass.

Application December 2, 1944, Serial No. 566,280

9 Claims.

This invention relates to improvements in printing machines and especially addressing machines of the general type which employs a succession of address-bearing printing devices, such as stencils, for .coaction with printingmechanism at a stencil printing position. Frequently such machines, in. addition to printing datairom successive stencils ionisuccessive work sheets or in succession .ona'ccntinuous web, include :mechanism for printing .a date and .ior consecutively numbering the stencil-printed work sheets or associating the date and a number with each :stencil impression in the case of a continuous web. Ordinarily .thedating andnumbering mechanism is separate from the stencil printing mechanism although preferably operable simultaneously therewith, and itiis convenient to employ an ink ribbon fDIABGHCfiOIIIWlth type characters to efiect the dating. and numbering. .My present invention relates more particularly to means .for mount- .ing, feeding and reversing :the ink ribbon so that the feed of .the :ribbon and .its reversals may be entirely automatic :in response to .actuations .oi the printing mechanism.

It is among the objects of the invention to associate with conventional dating and numbering mechanism an ink ribbon having ex'ten-tbetween two spools into :coacting printing relation with date and number type characters with provision forautomatic step by step advance .of the ribbon in one.'direction inrresponse to .a predetermined substantial number of actuations oi the dating. and numbering imechanism, followed by automatic reversal of thedirection of feed of the ribbon for a similar. step .by step advance ofthe ribbon in .theopposite direction in response to a comparable substantial number of .actuations of said mechanism.

Another .object'is to provide an inkribbonfeeding means including .a cam and mechanism for automatic step :byzstep advance of theycam to effect a reversal of direction of :feed of the ink ribbon following a predetermined feed thereof in. one direction.

:Still another object .is to .mount an ink-ribbon and feeding and reversing 'meanstherefior on .a reciprocating printing mechanism including means whereby the ribbon feed and its .reversals are responsive to reciprocations of the printing mechanism.

It furtherobiec't 21's to associate an ink ribbon and feeding-and reversing means therefor with a reciprocating "printingimechanism, including means for automatic reversal of the direction of ribbon feed inresponse to a predetermined number of 'reciprocations of said mechanism.

It is, moreover, my purpose and object generally to improve rupon prior printing machines and more particularly printing machines em.- ploying an ink ribbon.

In the accompanying drawings:

Figure l is a .front elevation showing the stenoil printing mechanism and the dating and numbering mechanism of a well known type of addressing machine, the table being shown in longitudinal section, and the datingand numbering mechanism having features of my present invention associated therewith;

, Figure 2 is a cross-sectional view approximately on line 2-2 of Figure 1;

Figure 3 is a view similar to Figure 2 but .on a larger scale and showing the dating and numbering mechanismand the associated mechanism of the invention moved down .to a position .a-p- .proaching printing relation to the .coacting anvil which moves up from below;

Figure 4 is a top-plan view -.of the mechanism of Figure 3;

Figure 5 is a view similar to Figure .3 but with the dating and numbering mechanism in printing coaction with the anvil and showing the clutch mechanism and cam advanced counterclockwise one step;

Figure 6 is a sectional view on line 16-6 of Figure 4;

Figure 7 is a perspective of the ribbon feed reversing plate;

Figure 8 is an elevation, with parts in section, of the clutch and cam mechanism which controls ribbon feed reversals;

Figure 9 is a cross-sectional View on line 9-9 of Figure 8; and

Figure 10 is a sectional view through one of the ribbon spools and its support.

The invention is illustrated in connection with an addressing machine of the general type which prints names and addresses from a succession of printing devices, such as stencils, which advance step by step to a stencil printing position for coaction in succession with a printing mechanism operating intermittently at thestencil printing position.

The invention has .to .do with a dating and numbering mechanismlccated beside the stencil printing position and operable simultaneously with each stencil printing to associatea date and a number with each .nameand address on separate work sheets or on .a continuous web of paper or the like which subsequently maybe severed into separate sections or sheets. In particular the invention relates to mechanism for mounting an i l: ribbon in coacting relation to the dating and numbering mechanism .and for controlling and reversing its feed in response to operations of the printing mechanism.

Referring more particularly to Figs. 1 and .2 of the drawings, the machine herein represented has a generally horizontal table J0 mounting the tracks 62, I lalong whicha succession .of stencils l6 advance step by step from a stencil holder I8 at the right hand end of the machine to and through a stencil printing position. As each stencil moves out of stencil printing position, it engages in ejector means of a known type including a continuously rotating roller 20 which quickly moves the engaged stencil out of the Way of the dating and numbering mechanism, later to be described, so that the latter mechanism may operate between the stencil tracks I2, I4 to effect its printings on successive work sheets or on a web.

At the stencil printing position, an upper impression plate 22 coacts with a lower platen 24 to press the stencil which is in stencil printing position into printing engagement with a Work sheet or web. The face of plate 22 may be supplied with ink in any known manner, as by a wiper inking roll (not shown) which ordinarily sweeps across the impression face of plate 22 between operations of the latter, and then returns to rotational engagement with an ink distributor roll indicated at 20.

The stencils I may be intermittently advanced along tracks I2, I4 by mechanism including a pusher which engages the lowermost stencil in holder I8 and pushes it and stencils in advance of it on the tracks one stencil length forward thereby to bring the stencils in succession to stencil printing position. The pusher 28 may be intermittently operated by mechanism as disclosed in my United States Letters Patent No. 2,344,345, dated March 14, 1944, or by any comparable mechanism capable of advancing the stencils in timed relation to the operations of the printing mechanism at the stencil printing position.

The upper impression plate 22 is mounted at the forward ends of a pair of arms 30 projecting forwardly from a yoke member 32 which is pivotally mounted at 34 in a bracket 36 secured at 30 to the under side of table I0 as best seen in Fig. 2. Th yoke 32 has a depending arm 40 to the lower end of which is pivotally connected at 42 one end of a link 44 whose other end is pivotally connected at 46 to the depending arm 48 of a main operating lever 50 whose upper arm 52 is formed with a cam face 54. Lever 50 is pivotally mounted at 56 on a depending part of the bracket 36 and is adapted to be rocked intermittently on its pivot 56 by a connecting rod 58 which in turn ma be operated by any suitable power mechanism such as is disclosed in my said Patent No. 2,344,345.

The lower platen 24 is carried at one end of a pair of arms 00 which are pivotally mounted at their other ends at 02 on bracket 36, a roller 04 being mounted between the arms and below the platen for riding on the cam face 54 of arm 52 of the main operating lever 50. This lower platen 24 has substantial extent beyond the stencil printing position, to the left as seen in Fig. 1, for constituting an anvil 66 at a dateand-number printing position immediately adiacent to the stencil printing position. Preferably a resilient pad 68, of rubber or the like, is inset in the face of platen 24 for a purpose which later will appear.

A dating and numbering mechanism is indicated generally at I0, being a known type of available mechanism including an automatic counting device for printing numbers consecutively on successive work sheets which simultaneously receive a stencil impression at the stencil printing position, each work sheet having extent into both printing positions. The

mechanism I0 includes also a dating device which may be changed manually as occasion may require. Both the date characters and the number characters which at any time are to print on a work sheet, are exposed at the under side of the mechanism I0 for coaction with an ink ribbon I2 which overlies the characters and whose feed and reversal are controlled automatically by my improved mechanism to be described.

The numbering and dating mechanism I0 is mounted at the forward end of an arm I4 projecting forwardly from the yoke member 32, comparable with the arms 30 which carry upper impression plate 22. However, the arm I4 preferabl has a readily removable end part I6 on which the mechanism I0 is directly mounted, so that the mechanism I0 may be easily removed with the end part 76 of arm 14 to facilitate changing the date or to ffect any other needed changes or adjustments. For this purpose, the arm '14 has a screw I8 engaging in threaded hole 80 in the end part I6 for clamping the parts together by means of the wing head 82, there being pins 84 on part I6 projecting into holes 86 in arm I4 preventing relative rotation of parts I4 and it.

The numbering and dating mechanism I0 has ausual shank part 88 extending slidably through a hole 90 in the end of part IS, the shank having a head 92 limiting downward movement of mechanism I0, and a coil spring 94 around the shank intervenes between part I6 and the casing of mechanism '10 tending yieldingly to urge the mechanism I0 downward until the stud head 52 engages part I0 of arm I4. As a result, the mechanism I0 can yield in a usual manner when it is brought down into coacting relation with anvil 60 for a printing operation, and means 95 acts on each printing operation of mechanism I0 to advance the number in a well known manner.

According to my present invention, a pair of

ink ribbon spools

90, 98 are mounted on opposite sides of the numbering and dating mechanism l0, they being rotatably supported in bearings I00, I02 on a vertical plate part I04 of a bracket which has a horizontal plate part I05 secured as by screws I08 to the top of the mechanism 70. A hole in the plate part I00 permits free movement therethrough of the shank 88 of said mechanism. The vertical plate part I04 of the bracket depends as an apron in front of the mechanism I0, and the spools 9B, 98 are on its rear side so that the ink ribbon I2 can extend from one spool to the other in contact with the printing characters exposed at the under side of mechanism I0.

Each

spool

96, 98 may be of usual typewriter ribbon spool construction with tubular axle for slipping axially on a supporting shaft IIO which is rotatably mounted in a bearing I00 or I02 on the vertical bracket plate I04, as best seen in Fig. 10. Each spool axle has an interior key element I I2 for engaging a key way H4 in the shaft, thereby to prevent relative rotation of the spool and shaft but permitting the spool to be slipped from the shaft whenever desired. The shaft is reduced in size where it passes through a bearing I00 or I02 so that a shoulder IIB abuts against the bracket plate I04. A ratchet wheel H8 is fixed on the projecting reduced end of one spool shaft and a similar ratchet wheel I20 is fixed on the projecting reduced end of the other spool shaft, with a spring washer I22 between "c rca-res -the ratchet "wheel and. the bearing lflflxor .I02,

.unaintaining the shafts with :their respective :sh'oulders II 6 rotatablyqengaged'with the bracket .tplate I04.

.A laterally projecting "lug or boss I24 .onbracket plate I04 has a vertically .extendinginon-round lhole I26 therethrough. for receiving slidably the correspondingly non-round dependingshank I28 :of a pawl-carrying member I30. Shank I28 proelects a substantial amount :below the boss 1 24 .and has a collar I82 secured on its lower end. .A Lcoilspring I34 surrounds the projecting portion .ofthe .shank between the boss I24 and the col- --lar I32 and tends yieldingly to maintain the pawl- .carrying member :in its lowermost position where f.

itis in'engagement with boss I 24.

Pawl-carrying member I30 extends close up to the ratchet'wheel I I8:and h-asa groove I36 open toward the ratchet wheel within which is pivotally mounted at I 38a pawl 140. The pawl I 40 7" has an upstanding shank I42 extending loosely :through a hole 144 in a'reversing plate 146 which is'slidably mounted on the top of pawl-carrying member IJ30. Reversing plate I46 is shown in detail in Fig. I, it having a 'depending'rearxfiange I48 and two spaced apart from depending ears 1 50, I52. The plate rests on the top of pawlcarryi'ng member 180 with the said flange I48 and ears I50, I52 depending in guiding relation to member I30. itained on the member I30 by the head I54 of a screw I56 which'extends loosely through an elon- (gated opening I58 in the plate i and has threaded engagement .in the top of member I30, the head being out of clamping engagementwith the plate 6 so that it may slide relative to member I30. A pin I60 'upstands from the head I54 of the screw. and a coil spring I62 has one end connected "to this pin and its other end connected to the shank "I42 of pawl I40, tending always toswingthe pawl I 48 clockwise-about its pivot and into position for ratchet wheel engagement. However, :as shown in Fig. 6, this pawl I40 is held'out of ratchet wheel engaging position by the reversing plate I46.

A similar pawl 164 is pivotallymounted ina groove I66 at the opposite side of'member I30 "for coacticn with ratchet wheel I20, it having'an upstanding shank 468 extending through a hole I 10 in the reversing plate, and having'acoil spring "I12 constantly urging it into ratchet wheel engaging position. In Fig. 6 this pawl 164 is held by its spring I'I'Zin ratchet wheel engaging position, the reversing plate in this View being in its moved-to-the-left position. Amovement-of plate I46 to the-right, by mechanism to be described, releases pawl I40 for ratchet wheel engagement and swings pawl I64 clockwise and retains it out of ratchet wheel engaging position, as illustrated in Figs. 3 and 5.

The means for actuating reversing plate M6 to automatically, reversethe direction of feed-or ink ribbon 112 comprises a cam 'I 14 mounted rotatably on a stub shaft. I16 which is :fixedly'secured in the pawl-carrying-member 130 as -best-seen f inilFig. 9. The vcarn'has its high and low portions substantially equal in extent and these high and low edgeportions coact with 'a'roller I1 8 on'the depending'ear I 52 of the reversingp'late I46fthe-rear dependingfiange I48 of said plate havingia-pin I88 thereon to which one end of a coil spring I82 is connected. The opposite end .ofxspring I82 is connected to a fixed pin IB4'Qn 'the pawl-carryinjg body I30. Hence the spring I82 eonstantlyurges the reversing plate I46 to the right "to "keep roller Plate I46 is slidably relli 5H8 zpressed against the edge .IOf .cam I714 atall times. in Figs. 73 and'f5, the roller I18 is shown innengagement-with the low part of cam I 14 so tha't the reversing plate 146 is in its moved-to- "the-right position and pawl I40 is free 'for operative engagement with ratchet wheel II'B. .Hence, on reach

printing movementof arm

14, 16, the ratchet wheel H 8 will be advanced one tooth distance in :clockwisenirection to unwind a small amount of ribbon from spool '98 and wind substantially a like amount on spool 96, and this action will continue so long as roller I18 is in *engagementwith the low part of cam I14. However, the cam H4 is rotated counter-clockwise-a small fractional part of a revolution on each printing stroke of arm 1 4, -16, so that the high part of cam ultimately engages roller I18 to effect :a shift to'the left of reversin-gplate I46, thereby to "release pawl I64 tor-operative eoaction with its ratchet wheel I29, and pawl 1-49 simultaneously is put out of action.

0am 114 has :a cylindrical 'flange I86 projecting forwardly therefromandconcentric with stubshatt I16. Within this flange and rotatable on th'e'stub s'haft is a clutch member I88 having four 'equallydistributed cut-outs I98, as best seen in Fig. 8, within each of which is a spring pressed roller 3I9'2, each roller constantly urged by its spring I94 into wedging engagement with the flange I86 and-a wall of a cut-out I90. A cover plate I96 is secured to the member I88 and is rotatable with said member on stub-shaft I16, both "being retained on the stub-shaft by an arm I98 which is secured flatwise against the end of the stub-shaft by a, screw 200. Arm I98 depends and carries the arcuate brake band 202 having the'interior brake shoe 264, of leather or'the 'likeyas best seen in Fig. 8. The brake band extends around the lower side of flange I86 in spaced relation thereto, and brake shoe 204 is in thisspace in braking engagement with the fiange I86.

Cover plate I96 has a projecting ear 206 to which is connected one end of a coil spring 208 whose other end is-connected to depending arm 198, so that the spring constantly urges the cover plate I96 clockwise, and one end of the brake band 292' acts as a stop limiting its clockwise movement, as in Fig. 8. Cover plate I96 also has a projecting screw or pin 2I0 for slidably engaging in a slot 2I2 in a bar 2I4 pivotally mounted at 2I6 on a forwardly projecting part 218' of the bracket 'boss I24. Bar 2I4 extends substantiallyvertically but can swing a little to right or left. An adjustable stop screw 220 projects into the upper end of slot 2 I2 for a purpose which-"will appear.

When arm '14, 16 moves downwardly on a printing stroke, the lower end of depending shank I28 of the pawl-carrying'member I30 ultimately engages the anvil '66 and further movement .of

arm

14,16 downward compresses spring I34 thebossx'ifl'and all other'elements carried on thebracketplate I 04 continue downward while the'pawlmarrying-member I30 and elements car- :rie'cl thereon remain relatively stationary. The

slotted bar 214 being carried on the bracket plate I04 moves downward while screw 2I0 slidably engaging in slot 2I2 .is held stationary, where-by there is relative .movement of screw 2 I 0 toward-the upper-end of the slot. When screw '21 0 engages .stop screw 220 in'the slot, no further relative movementiof the screw 2I0 along the slotis permitted. Home the 'furtherand .final downward-

movementofarm

14, 16 carries screw 2H! down to produce a slight counter-clockwise rotational movement of cover plate I96 and clutch member I88. This movement wedges the clutch rollers I92 between member I88 and the cam flange I86 so that the cam moves with the clutch member the fractional part of a counter-clockwise rotation. On the up-stroke of arm 14, I6, the slotted bar 2M moves relatively to the screw am, moving stop pin 220 upward which permits spring 208 to return the cover plate I96 and clutch member I88 clockwise to their position of Fig. 8. However, on this clockwise return of the clutch member, its rollers I92 are freed from the cam flange I86 and the cam, aided by the brake shoe 204 remains in its advanced position. Hence, on each down-stroke of arms I4, I6 the cam is advanced a little counter-clockwise, and it will be obvious that during these intermittent advances of the cam, the ink ribbon I2 will feed in one direction when the low side of the cam is in engagement with roller MB of the reversing plate I46, and in the opposite direction when the high side of the cam is in engagement with roller I18.

It will be apparent from the foregoing description, in connection with the drawings, that I have provided an ink ribbon feeding and reversal control which is entirely automatic in conjunction with a printing mechanism, especially a printing mechanism acting in conjunction with the stencil printing mechanism of an addressing machine.

I claim as my invention:

1. In a printing mechanism having two coacting printing members at least one of which is pivotally mounted for reciprocating coaction with the other, one of said members having printing characters thereon, an ink ribbon mounted on said pivotally mounted printing member and having extent for coaction with said printing characters, a plunger carried on said pivotally mounted printing member and biased in general direction toward the other printing member, means on said other printing member for actuating the plunger against its said bias each time said pivotally mounted printing member approaches said other printing member, means responsive to each said actuation of the plunger for increment advance of said ink ribbon, and means for reversing the direction of advance of the ink ribbon, comprising an element which is slidably shiftable between two positions, a cam having a high part and a relatively low part for engaging said shiftable element and each determinative of one of the said positions of said shiftable reversing element, and means responsive to said actuations of the plunger for increment advance of the cam thereby to effect an ultimate sliding of the reversing element from one of its said positions to the other.

2. In a printing mechanism having two coacting printing members at least one of which is pivotally mounted for reciprocating coaction with the other, one of said members having printing characters thereon, an ink ribbon carried by said pivotally mounted member and having extent for coaction with said printing characters, a plunger carried on. said pivotally mounted member and biased in general direction toward the other member, means on said other member for actuating the plunger against its said bias each time the pivotally mounted member approaches said other member, means responsive to each actuation of the plunger for increment advance of the ink ribbon, and means responsive to a predetermined number of actuations of the plunger for reversing the direction of advance of the ink ribbon, the latter said means including a slidably mounted element and a cam coacting to effect a sliding movement of said element in one direction in response to a said predetermined number of actuations of said plunger.

3. In a printing machine having an anvil and a pivctally mounted reciprocating member carrying a printing head with printing characters exposed for coaction with the anvil, a pair of spools rotatably mounted on said printing head, an ink ribbon on the spools and having extent between the spools in coacting relation with said printing characters, spool feeding means mounted on the printing head and resiliently yieldable relative to the printing head and spools, and having a part projecting, in direction toward said anvil, beyond the plane of said printing characters whereby to engage the anvil prior to a printing coaction of the printing characters with the anvil and to cause yielding of said spool feeding means on each down-stroke of the reciprocating member, said spool feeding means recoiling on each up-stroke of the reciprocating member, a ratchet wheel rigid on each spool, a pair of pawls carried on said yieldable spool feeding means, means holding one pawl inactive while the other is active whereby one spool is rotated a fraction of a revolution in response to each cycle of yielding and recoiling of the spool feeding means thereby to feed the ink ribbon a predetermined amount in one direction, and means responsive to a predetermined number of cycles of yielding and recoiling of the spool feeding means for shifting said pawl holding means so that the pawl which had been active becomes inactive and the pawl which had been inactive becomes active, thereby to reverse the direction of feed of the ink ribbon.

4. In a printing machine having a pair of members relatively movable toward and away from each other at a printing position, an ink ribbon carried on one of said members with extent thereon for printing coaction between said members when the members move toward each other, a plunger mounted on the ribbon-carrying member and including a portion projecting beyond the latter said member toward the other member, means biasing the plunger in the direction of its said projection, means on the other member for actuating the plunger against its said bias each time the said members move relatively toward each other and prior to arrival of a said member at a limit of its movement, said biasing means restoring the plunger upon movement of said members away from each other, means responsive to each cycle of movement of the plunger for increment feed of said ink ribbon, and means responsive to a predetermined number of cycles of movement of the plunger for reversing the direction of said increment feed of the ink ribbon.

. 5. In a printing mechanism having a pair of coacting members of which one is movable toward and away from the other at a printing position, a pair of rotatable ink-ribbon spools carried on said movable member, a plunger mounted on said movable member and biased in general direction toward the other member, said plunger having a portion projecting beyond said movable member toward the other member, means on said other member for actuating the plunger against its said bias each time said movable member approaches said other member and prior to arrival of said movable member at the limit of its travel toward said other member, a ratchet wheel on each said spool, a pair of pawls carried on said plunger, each pawl adapted for coaction with a different one of said ratchet wheels, a shiftable member on said plunger engaging both pawls and shiftable between two positions in each of which it holds a different one of the pawls out of operative relation with its ratchet wheel while the other pawl is in operative relation with its ratchet wheel for increment rotation of one spool in response to each said actuation of the plunger, and means responsive to a predetermined number of actuations of the plunger for shifting said shiftable member from one of its said positions to the other.

6. In a printing mechanism having a pair of members of which one is movable toward and away from coacting relation to the other at a printing position, a pair of rotatable ink-ribbon spools carried on said movable member, a plunger mounted on said movable member and including a portion projecting beyond the movable member toward the other member, means biasing the plunger in general direction toward the other member, means on said other member for engaging and actuating said plunger against its said bias each time the movable member approaches said other member and prior to arrival of said movable member in coacting relation to the other member, means responsive to each said actuation of the plunger for increment advance of one of said spools in one direction under the urge of said biasing means when said movable member moves away from said other member, and means responsive to a predetermined number of actuations of the plunger for increment advance of the other of said spools in the opposite direction.

7. An ink-ribbon feed and reversing mechanism comprising a frame, a pair of ribbon spools rotatably mounted on the frame, a ratchet wheel fixed on each spool, a plunger mounted on said frame having means biasing it in one direction relative to said frame, a pair of pawls carried by said plunger, each pawl being arranged and adapted for coaction with a different one of said ratchet wheels, a shiftable element mounted on said plunger and engaging both of said pawls, said element being shiftable in one direction to hold one pawl out of coacting relation with its ratchet wheel and being shiftable in the opposite direction to hold the other pawl out of coacting relation with its ratchet wheel, means for actuating the plunger in opposition to its said biasing means thereby to set one pawl for increment advance of its ratchet wheel and spool by said biasing means following each said actuation of the plunger, and means responsive to a predetermined number of actuations of the plunger for shifting said shiftable element there;- by to hold a different pawl out of ratchet wheel engagement.

8. An ink-ribbon feed and reversing mechanism comprising a frame, a pair of ribbon spools rotatably mounted on the frame, a ratchet wheel fixed on each spool, a plunger mounted on said frame having means biasing it in one direction relative to said frame, a pair of pawls carried by said plunger, each pawl being arranged and adapted for coaction with a diflerent one of said ratchet wheels, a shiftable element mounted on said plunger and engaging both of said pawls,

said element being shiftable in one direction to hold one pawl out of coacting relation with its ratchet "wheel and being shiftable in the opposite direction to hold the other pawl out of coacting relation with its ratchet wheel, a cam rotatably mounted on said plunger, a spring constantly biasing said shiftable member into engagement with the cam, means for actuating the plunger against its said biasing means, and coacting means on said frame and plunger for increment advance of said cam in response to each actuation of the plunger, said cam being adapted to shift said shiftable element in one direction in response to a predetermined number of increment advances of the cam.

9. In a printing mechanism having a pair of members of which one is movable toward and away from coacting relation to the other at aprinting position, a pair of rotatable ink-ribbon spools carried on said movable member, a ratchet wheel fixed on each spool, a plunger mounted on said movable member and having a portion projecting beyond the movable member toward the other member, a pair of pawls pivoted on the plunger, one adjacent to each ratchet wheel,

shiftable means on the plunger engaging both pawls and shiftable between a position to hold one pawl inactive and a position to hold the other pawl inactive, means biasing the plunger in direction for increment advance of the particular spool whose ratchet wheel and pawl are in coacting relation, the other pawl passing idly by its ratchet wheel, means on said other member for actuating the plunger against its said bias each time the movable member approaches said other member and prior to arrival of the movable member in coacting relation to the other member thereby to position the active pawl in position for said increment advance of its spool upon recoil of the plunger by said biasing means, and means for shifting said pawl holding means in response to a predetermined number of actuations of the plunger whereby it holds a difierent pawl inactive, for increment advance of the other spool.

HARMON P. ELLIO'I'I'.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 446,886 Pusey Feb. 24, 1891 551,343 Ackley Dec. 10, 1895' 670,576 Adamson Mar. 26, 1901 832,260 Keeran Oct. 2, 1906 866,064 Pollock Sept. 17, 1907 1,007,691 Hansen Nov. 7, 1911 1,571,811 Smith Feb. 2, 1926.: 1,744,965 Hubbard et a1 Jan. 28, 1930 1,811,359 Kern June 23, 1931 1,937,144 Fassman Nov. 28, 1933 1,944,695 Phillips Jan. 23, 1934 1,982,380 Gollwitzer Nov. 27, 1934 2,015,552 Elliott Sept. 24, 1935 FOREIGN PATENTS Number Country Date 349,619 Great Britain June 1, 1931 10,228 Great Britain of 1905