US2978090A - Ribbon advancing and reversing mechanism for stamping devices, typewriters and the like - Google Patents

Description

APP!l 1961 HANS-ADO BRANDT 2,973,090

RIBBON ADVANCING AND REVERSING MECHANISM FOR STAMPING DEVICES, TYPEWRITERS AND THE LIKE Filed Aug. 25, 1959 2 Sheets-Sheet 1 IN V EN TOR.

HANS ADO BRANDT BY fi 1 f. $201242- April 1951 HANS-ADO BRANDT 2,978,090

' RIBBON ADVANCING AND REVERSING MECHANISM FDR STAMPING DEVICES, TYPEWRITERS AND THE LIKE Filed Aug. 25, 1959- 2 Sheets-Sheet 2 INVENTOR.

H'A'NSJADO BRANDT BY fiu'z/zmbl a Another objectof the invention is to Un ed tes P ti n RIBBON ADVANCING AND REVERSING MECHA- NISM FOR STAMPING DEVICES, TYPEWRITERS AND THE LIKE Hans-Ado Brandt, MuniclnGermany, assignor to Agfa Aktiengesellschaft, Leverkusen, Germany The present invention relates to a ribbon advancing and reversing mechanism for use in hand stamping devices, such as date stamps, registered or insured mail stamps and the like, as well as in typewritersand other impression-producing machines.

It is already known to utilize the tension of a typewriter or like ribbon to bring about a reversal in the direction in which the ribbon is advanced. According to one such conventional construction, each of the spools which alternately take up and pay out the ribbon is connected with a ratchet wheel, and the ratchet wheels are alternately advanced in opposing directions by one of a pair of interconnected pawls, one pawl'being always out of contact with its ratchet wheel while the other' pawl advances the second ratchet wheel whenever a typewriter or like key is depressed. The ribbon is led through the slots of two spaced fork-shaped switching or reversing members which are connected with each other and with the pawls by a system of levers and/or rods. The shifting members continuously deflect the ribbon in two bpposing directionsfrom a straight line'and, consequently,

when the ribbon is completely payed out by one of the spools and is tensioned upon subsequent depression of keys, the one or the other shifting member is caused by the tensioned ribbon to perform a movement which,

over a system of cams or bevel gears, is conveyed'to the respective pawl to cause the latters movement away from the teeth of its ratchet wheel while the otherpawl simultaneously engages the teeth of the second ratchet wheel. When a system of bevel gears is utilized, such gears are connected with each other by an axially movable shaft member and are moved back and forth in response to one or the other forked shifting member.

In hand and like stamping devices, the direction-in which the ribbon advances is customarily reversed by hand. A reversing mechanism of the type presently utilized in typewriters and like machines isimpractical because itoccupies too much space which is not available in hand stamping devices. In addition, the known ribbon reversing mechanisms comprise a large number of component parts and, consequently, their use in h'and stamping devices would greatly increase the cost of such apparatus. V r 5 An important object of the present invention is to'propressures generated by the tensioned ribbon upon the 'vide a very simple and reliable ribbon advancing and reversing mechanism which is 'sufliciently'compact to be mounted in hand stamping and like devices without un'-' duly increasing the "dimensions of such devices.

i provide an advancin'g and reversing mechanism for ribbons in hand stamping devices which may be installed between the spools to which the ends of the ribbon areconnected. A further object of. theinvention is to provide a system of braking springs which are so mounted as to pre-' vent undesired unwinding of the ribbon from. that spool which takes up the ribbon, but offer comparatively little resistance to the paying-out of the ribbon by the other a spool.

2,978,09d Patented Apr. 4, 1961 A concomitant object of the invention is to provide a ribbon advancing and reversing mechanism which is capable of advancing the ribbon in such a way that each zone'of the ribbon is subjected to equal wear andtear.

An additional object of the instant invention is to provide a mechanism of the above outlined characteristics in which the extent to which the ribbon is intermittently advanced may be varied within a wide range.

Still another object of the invention is to provide a ribbon advancing and reversing mechanism which may be readily installed in typewriters, calculating machines, stamping devices and the like without requiring any or only slight modifications in the construction and design 'of such apparatus.

' fully payed-out ribbon to reverse the direction in which i the ribbon should advance. However, instead of utilizing two individual pawls, or two sets of bevel gears, the novel mechanism comprises a double pawl which is rockably mounted on an oscillatable carrier plate and whose tips or pallets are alternately movable into engagement with the teeth of two ratchet wheels connected to the shafts on which the ribbon winding and unwinding spools are mounted. A very important advantage of such construction, as compared with the ribbon advancing and reversing mechanisms. of known design, is in that it requiresa very small number of component parts and in that itoccupiesvery little space. Thus, the entire assembly may be installed directly between the spools or reels to whose cores the ends of a ribbon are connected.

'. The carrier plate is pivoted to the frame member of a typewriter, hand stamping device or the like and is rockable between a pair of stops, the rocking movements toward and into abutment withone of the stops being caused by aconstantly acting spring which is connectedlo the carrier plate'and to the latters frame member. It is preferred to connect the double pawl with the carrier plate by means of an eccentrically biased rocker arm which swingably supports the pawl and, in turn, is swingably connected to the carrier plate. The pawl is constantly biased into engagement with the teeth of the one or the other ratchet wheel by a spring connected to the rocker arm,,and the latter is constantly biased into abutment with one of two arresting members mounted on the carrier plate by another spring which is anchored in the carrier plate. The pivot axis of the double pawl is capable of performing movements in a plane substantially parallel with the line connecting theshafts on which the ribbon spools are mounted.

Basically, the novel mechanism may operate without any specific reversing or shifting means for the pawl because the reaction force'between the pawl and the ratchet wheels can be directly utilized to bring about movements of the pivot axle about which the pawl is rocked as soon as the reaction force overcomes the resistance of the aforementioned spring. The pawl-biasing spring is mounted in such a way as to constantly urge the pawl into the one or the other extreme position, i.e. into engagement with the teeth of the one or the other ratchet wheel.

The axes about which the pawl, its rocker arm and the carrier member ,pivot are preferably parallel with the axis about which therratchet wheel and the spools gether with additional objects and advantages thereof, will be best understood from the following description of a specific embodiment when read in connection with the accompanying drawings, in which:

Fig. 1 is front elevational view of the ribbon advancing and reversing mechanism showing the double pawl and its supports in the left-hand end position and further illustrating one form of the ribbon advancing device; Fig. 2 is a similar view of the ribbon advancing and reversing mechanism with the pawl, its supports and the ribbon advancing device in an intermediate position;

Fig. 3 is a similar view of the mechanism with the pawl, its supports and the ribbon advancing device in the right-handend position; and

Fig. 4 illustrates a different form of the ribbon advancing device which simultaneously serves as a means for angularly moving a printing cylinder.

The ribbon advancing and reversing mechanism is mounted on a frame member or support F forming, for example, part of a hand stamping machine or the like,

preferably of the type in which the ribbon is automaticallly advanced when the stamping device is put to use.

Such stamping devices are well known and are frequently .utilized, among others, in various post offices for apply- .ing numbers to registered mail, insured mail, etc. For

the sake of simplicity, Figs. 1 to 3 which will be described first show a stamping device whose ribbon is advanced by a hand-actuated lever.

The frame member or support F rotatably supports a vpair of spaced parallel shafts 4, 5 for two supply spools or reels 1, 2,.respectively, to whose cores are fixed ,the ends of a ribbon or band 3. In the position of Fig. 1, the right-hand spool 2 pays out the ribbon 3 which latter is collected by and wound onto the lefthand spool ,1. It is assumed in Fig. 1 that the spools spools 1, 2 rotate with, but are separable from, their respective shafts 4, 5. The latter are rigidly connected with two ratchet wheels 6, 7 mounted thereon at the forward or front side of the frame member F. The

teeth of ratchet wheel .6 cooperate with the left-hand pallet or tip 8a of a double pawl 8 which is rotatably mounted on a pivot axle 9a and is permanentlybiased by an eccentrically mounted coil springlt) one end of which is connected to-a stud 80 carried by the pawl 8. The other endof spring 10 is affixed to the stud 9b mounted on a plate-like rocker arm 9 which latter also carries the aforementioned pivot axle 9a on which the double pawl 8 is rotatably mounted. The rocker arm 9 is rotatably mounted on the pivot pin or axle 11a supported by a carrier or wrist plate 11, and the latter is rotatably mounted on a pivot axle 11b fixed to the frame member F and isrockable or oscillatable about member 11b between and into'abutment with a pair of spaced stop pins 13, 14 mounted on the frame member F. Stop pins 13, 14 simultaneously serve as a means for limiting the rocking movements of pawl 8 in anticlockwise and clockwise directions, respectively. Thus, the positioningof pins 13, 14 determines the extent to which the ratchet wheels 6, 7 are angularly displaced by respective pallets 8a, 8b during each stroke orrocking motion of the double pawl 8. Carrier or wrist plate 11 mounts a'pair of arresting pins 11d, 11e whichlimit the oscillatory movements of rocker arm 9 about the latters pivot axle 11a. Double pawl 8 with its pallets 8a and 8b, the rocker arm 9, and the carrier plate 11 are disposed in parallel planes, and the palletssa, 8b are coplanar with the ratchet wheels 6, 7. It will be seen that the pawl 8 is rockably and eccentrically mounted with respect to the pivot axle 11a of rocker arm 9, and that the latter is rockablyand eccentrically mounted with respect to the pivot axis 11b of carrier plate 11. g

Member 11 carries a further studil'lc which is connected to one end of a coil spring 12; the other end of resilient member 12 isanchored in the stud 9b which latter, as mentioned hereinbefore, also serves as a means for holding an end of the spring 10. When the carrier plate 11 abuts against the stop pin 13, studs 9b and 110 are disposed at the opposing sides of and are out of alignment.withthepivot-axle11a of rocker-arm 9. -Thus,

--the.spring{10 tends to pivot thepawl Brim-anticlockwise direction about the pivot 9a, and thespring '12 simultaneously tends to rock the arm 10 in anticlockwise direction into abutment with the arresting pin file. A third coil spring 15, connected to the stud 11c and to a stud 15a carried by the frameor support member F, constantly urges the carrier plate 11 into abutment with the'stop-pin14. The pivot axes 9a, 11a and llb'are parallel with the axes of shafts 4 and 5.

When the stamping device of which the frame member -Fforms-a component part is put to use, the carrier plate v.11 is caused to rock about its pivot 11b from the posi- 'tion of Fig. 3 into the position of Fig. 1, i.e. into 'abut- -ment with the stop pin 13. The lever 23, articulately connected to the carrier-plate 11 by'a rivet 24, constitutes one form of means for rocking the member 11 against the action of spring 15. The free end of this 'lever carries a pin 25 which abuts against and is slidable along a flange Fa of'the frame member F. Themeans for rocking the'lever 23 and the carrier 11 against the action of the coil spring 15 comprises a handgrip member 26 fixed to the free end of the lever'and-adapted to be grasped by the fingers of an operator to advance the lever in a direction to the left, i.e. from the position ;of Fig. -3 into that shown in Fig. 1, whereby the carrierll moves from the right-hand stop pin 14 into abutment with the other stop pin 13. Upon release ofthe handgrip member 26, thespring 15 immediately returns the .carrier 11 into the position of Fig. .3. During the movement of carrier'plate 11 to'the left, i.e.in anticlockwise direction,the pallet 8a of double pawl 8 engages'witha selected tooth of the ratchet wheel 6 and rotates the latter .in anticlockwise direction to wind the ribbon 3 onto the spool 1. The magnitude of the angular movepawl 8 corresponds to the width of more than a single tooth on ratchet wheel 6, i.e. the length of ribbon 3 payed out by the right-hand spool 2 corresponds to a multiple of that unit length which would be payed out were the ratchet wheel rotated only a distance corresponding to the width of a single tooth thereof. When the spring 15 rocks the carrier plate 11 with members 8. 9 in clockwise direction, a resilient member in the form of a braking spring 16 prevents unwinding of the ribbon 3 from the left-hand spool 1. Thus, and as shown in Fig. 1, the braking spring 16 must resist the tendency ofshaft 4 to rotate in clockwise direction under the influence of the coil spring 10 which latter tends to urge the left-hand pallet 8a into firm engagement with the teeth of ratchet wheel 6.

The brake spring 16 preferably assumes the-shape of a spiral loop spring. also known as a spring band brake; its purpose is to brake the spool 1 only in a direction to prevent unwinding of the band 3 therefrom. The member '16 consists of a length" of resilient material, such as a metallic band or wire, which is wound spirally and under initial tension .onto the shaft 4. Due to such mounting, the brakingaction of the spring 16 in the direction'of its convolutions (clockwise in Figs. lto 3) is much greater than in the opposing (anticlockwise) direction.- Thus, when the spool 2 rotates clockwise to wind the ribbon 3 thereon, the spring 16 offers considerable resistance to such movement and maintains the ribbon under tension. On the other hand, when the .ribbon is payed outby the spool 2 and is wound onto the left-hand spool 1 in anticlockwise direction, the brake spring. 16 offers comparatively little resistance to such of the spring 16 thereon whereas an-antielockwise rotation of the shaft 4 tends to unwind. the spring and thus reduces its braking action. This brake spring simultaneously maintains the ribbon 3 under requisite tension and, as above stated, also prevents the pawl 8 from moving the ratchet wheel 6 in clockwise direction when the pawl is moved to the right by the coil spring 15. On the other hand, the resistance met by the pawl 8 in causing angular movements of the ratchet wheel 6 and spool 1 in anticlockwise direction is rather small because the braking action of spring 16 is felt solely in clockwise direction.

It will be readily understood that the lever 23 which 7 acts upon and rocks the carrier plate 11 toward the stop .pin 13 need not necessarily mo ve the carrier plate all the way into abutment with the member 13. Thus, if the carrier plate 11 is moved toward but not entirely into actual abutment with the stop pin 13, the pallet 8a will rotate the ratchet wheel 6 through a smaller angle. Consequently, by controlling the extent to which the carrier plate 11 is rocked, the extent of consecutive movements pcrformedby the ribbon 3 in the direction toward the reel 1 may be changed as desired. As soon as the stud 110 or another part connectedpto member 11 is released, springlS immediately returns the carrier plate into abutment with the stop pin 14. l

When the ribbon 3 is payed out by the right-hand spool 2, the ratchet wheel 6 is prevented from continuing its angular movements in anticlockwise direction, i.e. in the direction to wind the ribbon 3 onto the spool 1. During the subsequent stroke of rocker arm 11 into abutment with the left-hand stop pin 13, the pallet 8a of pawl 8 meets a substantial resistance, thus causing the pawl to pivot about member 9a in clockwise direction against the resistance of spring and simultaneously causing the rockerarm 9 to pivot about its axle 11a in clockwise direction against the action of coil spring 12. Such.

position of the rocker arm 9 is shown in Fig. 2. It will be noted that the tension to which spring 10 subjects the pawl 8 is smallest when the pawl 8 and rocker arm 9 assume the position of Fig. 2, i.e. the stud 8c is then closer to the stud 9b than in the positions of Figs. 1 and 3.

i -As the carrier plate 11 continues its advance toward the left-hand stop pin 13, the rocker arm 9' suddenly snaps over under the influence of spring 12 to move into abutment with the right-hand arresting pin 11d as is shown in Fig. 3. The stud 9b is then moved in clockwise direction about its pivot axle 11a and, consequently, the resilient element 10 acting between studs 80 and 912 now urges thejrigh-hand pallet 8b of double pawl ,8 into engagement with the teeth of ratchet wheel 7. Thus, the. movements of carrier plate 11 into abutment with the stop pin 14, after the carrier plate is acted upon by the lever '23 and returned by spring into abutment with member 14, bring about angular movements of ratchetwheel 7 in clockwise direction to wind the ribbon 3 onto the right-hand spool 2. Such angular movements of ratchet wheel 7 under the influence of spring 15 contime until the ribbon 3 is completely payed out by the spool 1, whereupon the ratchet wheel ,7 resists further rotation by the pallet 8b and the rocker arm 9 caused to snap over the'intermediate position of Fig. 2 back into the position of Fig. "1. Thus, the tension of ribbon 3 causes the spring 12 to rock the arm 9 between the arresting pins 110., He and the resilient member 10 thereupon alternately urges pallets 8a, 8b into engagement with the teethof ratchet wheels 6, ,7, respectively. The pivot axle 9a of double pawl 8 travels with respect to the carrier plate 11 in a path which is, substantially parallel with the line connecting the-axes of shafts 4 and 5. The springs 10, 12 alternately bias members 8, 9 in anticlock- .wise and clockwise directions, depending upon whether the pal1t-3a, ,engage s with the teeth ofiratchet wheel. 6 or the other pallet 8b engages with the teeth of ratchet wheel 7.

It will be noted that, to move the rocker arm 9 from the position of Fig. 1 into that of Fig. 3, an outside force is required only to such an extent as to rock the member 9 from the position of .Fig. 1 or 3 into that of Fig. 2 while the second half of rocking movement performed by the rocker arm 9 occurs under the influence permanently urges the pallet 8a or 8b into engagement with the teeth of ratchet wheel 6 or 7, respectively. Whether the spring 10 urges pallet 8a into engagement with ratchet wheel 6 or the pallet 8b into engagement with ratchet'wheel 7 depends upon the position of rocker arm .9. I

The magnitude of'the angle through which the ratchet wheels ,6, 7 are. advanced by the pawl 8 during each movement of the handgrip means 26in a direction to the left must be suflicient to insure that the rocker arm 9 snaps over when the ribbon 3 is under tension. In fact, the advance of the ribbon is actually excessive and, consequently, it could happen that only certain isolated zones of the ribbon would be used and that only such isolated ribbon zones would be put, to repeated use. Upon se'veral'reversals in the direction in which the ribbon 3 advances, certain zones of the latter would become worn out .while the zones therebetween would remain intact, i.e., such use of the ribbon would be very unecononiical. This is avoided by so positioning the stop pins 13, 14 that each movement of the carrier plate 11 thereagainst preferably brings about an angular movement of ratchet wheels 6, 7 equaling the width of three and one-half teeththereon. In such manner, the pallets 8a,- 8b advance the ribbon while continuously engaging with different teeth of ratchet wheels 6, 7, respectively. It can be readily calculated that such positioning of the stop pinstl3, 14 causes the pallets 8a, 8b to engage three difierent teeth on each of ratchet wheels 6, 7 during six subsequent reversals of the direction in which the ribbon 3 advances. This is due to the fact that, before the direction of the ribbon 3 is reversed, the ribbon is not fully payed out by the spool 1 or 2 but that there remains convoluted on the respective spool a length of ribbon corresponding to the angular movement of ratchet wheel 6 or 7 a distance equal to the width of one'or two teeth thereon; During the subsequent stroke of pawl 8, the ribbon is fully payed out by the respective spool and, in addition, the rocker arm 9 is moved partially away from its arresting pin 11d or 11 e, this being due to the fact that, as above described, the advance of the ratchet wheels 6, 7 during each stroke of double pawl 8 preferably corresponds to the width of three and onehalf teeth thereon. During the subsequent stroke of,

pawl 8, the rocker arm 9 is completely swung over the intermediate position of Fig. 2 into that shown in Fig. 1 or Fig. 3. Thus, the snapping-over or rocking of arm 9 is brought about during two subsequent strokes of the pawl 8 in response to two successive movements of carrier plate 11 into abutment with the stop pin 13 or 14.

.The right-hand shaft 5 is braked by a second spiral spring 17 in a manner. analogous to that of the aforementioned braking spring 16. Resilient members 16, 17 are not connected directly with the frame member F but are termed with resilient extensions or stems 16a, 17a, respectively, whose free ends form elongated loops or nooses slidably mounted on a pair of pins or studs18, 19, respectively,

'7 the comparatively'long stem of'that braking spring which controls the unwinding spool is slightly bentor arched Ito exert a moment of rotation or torque upon therespective shaft to in such a manner maintain'the ribbon .3 under requisite tension. While the pawl 8 moves between the ratchet wheels 6 and 7, e.g. whenthe pallet 8b moves away from its ratchet wheel 7, the long stem "16a of resilient member 16 maintainsthe ribbon under uniform tension. This is due to the fact that the stem 16a is slightly arched or bent while itresists unwinding of the ribbon off the spool 1. The formation of a loop at the free end of stem 16a allows for such deformation. The ribbon 3 communicates the tension to.the

,stem 17a of the other brake spring 17 when the pawl.8

moves from the ratchet wheel 6 toward the other ratchet wheel 7.

The ribbon advancing mechanisms ofpresently known design utilize braking springs whose action upon the spools is of equal magnitude regardless of whether the ribbon is wound onto or payed out by the spools. Thus,

the ribbon advancing mechanism must overcome substantial resistance of braking springs in order to cause the ribbon to advance from the one to the other spool.

"In contrast to such construction, the springs 16, 17 act as one-way braking means in that they resist unwinding of ribbon 3 from respective spools 1, 2 witha considerable force but offer comparatively little resistance tothe winding of the ribbon onto said spools. Consequently,

.the advance of ribbon 3 toward the spool 1.or 2 against the force of spring 16 or 17 requires a smaller force than in similar mechanisms of known design.

At its upper end, the frame member F is formed with an extension 20 carrying a pair of deflecting or guide rollers 21, '22 for the ribbon 3. The purpose of these whose periphery may carry a series of symbols, eg.

numerals, such as are utilized in date, hour or serial number stamps. Whenever the advancing arm 29 is swung in clockwise direction, a non-represented mech- 'anism of any known design advances the cylinder "31 through a given angle in order to move a dififerent symbol, e.g. a numeral, a letter, a series of numerals and/or a series'of letters, into a position adjacent to the ribbon 3 intermediate the deflecting rollers 21 and 22. A sheet of paper or any other material 32 on which an impression is to be imprinted is placed adjacent to the other side of the ribbon.

The flange Fa of the frame member F carries a bracket 33 which supports an electromagnet 34 inv a position of alignment with the sheet 32 and with the uppermost character or numerals on the printing cylinder 31. The core 35 of electromagnet 34 carries'at its lower end an impression plate 36 which, when the electromagnet 34 is energized and its core 35 moved in downward direction, strikes against the sheet 32 and moves the same against the ribbon 3 and the selected character or number on the cylinder 31 to produce a desired impression.

The stud 110 extends through an arcuate closed slot '37 formed in the frame member F into the path of the aforementioned bracket 30. Thus, whenever the advancing arm 29 is rocked to turnthe printingcylinder, the bracket 30 simultaneously swings the carrier plate fll'against the action of the spring 15 by acting upon the stud 110. The .handgrip member 26jthen merely constitutes an alternate .means for :advancing the :ribhon B on'the sheet 32, .ie. when the angular position of the printing cylinder .31 remains unchanged during a'series of consecutive energizations of the electromagnet .34.

It will be noted that the major part of theribbon advancing and reversing mechanism is installed directly between the spools 1 and 2; thus, the entire'mec'hanism occupies very little space and, in fact, does not increase :the dimensions ;of the stamping device since it is practicallyinevitable that a .space be formed intermediate the spools 1 and,2 because the ribbon must be flattened out between the spools a-distance sufiicient to permit the forming of impressions over a required area. For example, in the embodiment shown in Figs. 1 to 3, the

ribbon 3 may form impressions anywhere between the deflecting rollers 21 and 22. Thus, the space between the spools 1, 2 occupied by the ribbon advancing and reversing mechanism of my invention is not provided with a view to accommodate the novel assembly but is rather due to the necessity to provide for a flat length of ribbon 3 (between the rollers 21, 22) which forms impressions upon contact with the type and the surface to be imprinted. If the mechanism of Figs. 1 to 3 were installed in a typewriter or calculating machine, the spools 1 and 2 could be placed much closer to each other than in the presently utilized machines since the space between ratchet wheels 6, 7 must exceed only slightly the width of carrier plate 11.

Without further analysis, the foregoing will so fully reveal the gist of the present invention that others can, by applying current knowledge, readily adapt it for various applications without omitting features that, from the standpoint of prior art, fairly constitute essential characteristics of the generic and specific aspects of this invention and, therefore, such adaptations should and are intended to be comprehended within the meaning and range of equivalence of the following claims.

What is claimed as new and desired to be secured by Letters Patent is:

l. A ribbon advancing and reversing mechanism eomprising, in combination: support means; a pair of spaced parallel shafts rotatably mounted on said support means; a spool and a ratchet wheel fixed for rotation to each .shaft; carrier means rockably mounted on the support means between said shafts; a double pawl having two pallets; means rockably mounting the pawl on said carrier means for movements in a plane substantially parallel with the line connecting said shafts; stop means fixed to said support means for limiting the rocking movements of said carrier means and'for simultaneously limiting the rocking movements of said pawl between a pair of end positions in which one pallet engages with one of said ratchet Wheels and the other pallet engages with the other ratchet wheel, respectively; eccentrically mounted resilient means for alternately biasing said pawl into one of said end positions; and a ribbon having ends connected to said spools and adapted to prevent rotation of said ratchet wheels by the respective pallets when one spool fully pays out the ribbonwhereby the pawl is rocked against the action of said resilient-means.

2. A ribbon advancing and reversing mechanism comprising, in combination: support means; a pair of spaced parallel shafts rotatably mounted on said support means; a spool and a ratchet wheel fixed for rotation to each shaft; carrier means rockably mounted on the support means between said shafts; a rocker arm pivotably mounted on said carrier means; a double pawl having two pallets; means rockably mounting the pawl on said rocker arm for movements in a plane substantially parallel with the line connecting said shafts between a pair of end positions in which one pallet engages with one of said ratchet Wheels and the otherpallet engages with the other ratchet wheel, respectively; eccentrically mounted first resilient means for alternately biasing said pawl into one :of said'end positions; eecentrically mounted second re- }when aseriesaof.identicalimpressionstisstofbeimprinted 3T5 Bilientzmeansnperating between said carrier means and said rocker arm for constantly biasing the latter into a pair of spaced end positions with respect to said carrier means together with said pawl; and a ribbon having ends connected to saidjspools and adapted to prevent rotation of said ratchet wheels by the respective pallets when one spool fully pays out the ribbon whereby the pawl is rocked against the action of said first resilient means with respect to said rocker arm and the latter is pivoted with respect to said carrier means and against the action of said second resilient means. 7 a a ,3. A ribbon advancing and reversing mechanism comprising, in combination: support means; a pair of spaced parallel shafts rotatably mounted on said support means; a spool and a ratchet wheel fixed for rotationto each shaft; carrier means rockably mounted on the support means between and about an axis parallel with said shafts; a rocker arm pivotably mounted on said carrier means about an axis parallel with said shafts; a double pawl having two pallets; pivot means rockably mounting said pawl on said rocker arm for movements in a plane substantiallyparallel with the line connecting said shafts between a pair of end positions in which one pallet engages with one of said ratchet wheels and the other pallet engages with the other ratchet wheel, respectively; first eccentric resilientmeans operating between said pawl and the rocker arm for alternately biasing the pawl into one of said end positions; second eccentric resilient means operating between said rocker arm and said carrier means for alternately biasing the rocker arm into a pair of spaced end positions with respect to said carrier means together with said pawl; and a ribbon having ends connected to said spools and adapted to prevent rotation of said ratchet wheels by respective pallets when one spool fully pays out the ribbon whereby the pawl is rocked about said pivot means and the rocker arm is pivoted with respect to said carrier means against the action of said first and second resilient means, respectively, when the carrier means is rocked with respect to said support means. V

4.1 A ribbon advancing and reversing mechanism comprising, in combination: support means; a pair of spaced parallel shafts rotatably mounted on said support means; a spool and a ratchet wheel fixed for rotation to each shaft; carrier means rockably mounted on the support means between and about an axis parallel with said shafts; a rocker arm pivotably mounted on said carrier means about an axis parallel with said shafts; a double pawl having two pallets; pivot means rockably mounting said pawl on said rocker arm for movements in a plane substantially parallel with the line connecting said shafts between a pair of end positions in which one pallet engages with one of said ratchet wheels and the other pallet engages with the other ratchet wheel, respectively; first eccentric resilient means operating between said pawl and the rocker arm for alternately biasing the pawl into one of said end positions, over a median position in which said resilient means biases the pawlto an extent less than in each of said end .positions; second eccentric resilient means operating between said rocker arm and said carrier means for alternately biasing the rocker arm into a pair of spaced end positions with respect to said carrier means together with said pawl; and a ribbonhaving ends connected to said spools and adapted to prevent rotation of said ratchet wheels byirespective pallets when one spool fully pays out the ribbon whereby the pawl is rocked about said pivot means and the rocker arm is pivoted'withrespect to said carrier means against the action of said first and second resilient means, respectively, when the carriermeans is rocked with respect to said support means.

5. A ribbon advancing and reversing mechanism comprising, in combination: support means; a pair of spaced parallel shafts rotatably mounted on' said support means; a spool and a ratchet wheel fixed for rotation to each shaft; carrier means rockably mounted onthe support means between and about an axis parallel withsaid ithaftsta rocker arm pivotably mounted on said carrier 10 means about an axis parallelwith said shafts; a double pawl having two pallets; pivot means rockably mounting said pawl on said rocker arm for movements in a plane substantially parallel with the line connecting said shafts between a pair of end positions in which one pallet engages with one of said ratchet wheels and the other pallet engages with the other ratchet wheel, respectively; first eccentric resilient means operating between said pawl and the rocker arm for alternately biasing the pawl into one of said end positions by rocking the pawl about said pivot means in clockwise and counterclockwise directions, respectively; second eccentric resilient means operating between said rocker arm and said carrier means for alternately biasing the rocker arm into a pair of spaced end positions with respect to said carrier means together with said pawl; and a ribbon having ends connected to said spools and adapted to prevent rotation of said ratchet wheels by respective pallets when one spool fully pays out the ribbou'whereby the pawl .is rocked about said pivot means and the rocker arm is pivoted with respect to saidcarrier means against the action of said first and second resilient means, respectively, when the carrier means isv rocked with respect to said support means. i

6. Aribbon advancing and reversing mechanism comprising, in combination: support means; a pair of spaced parallel shafts rotatably mounted on said support means;

a spool and a ratchet wheel fixed for rotation to each shaft; carrier means rockably mounted on the support means between and about an axis parallel with said shafts; a rocker arm pivotably mounted on said carrier means about an axis parallel with said shafts; a double pawl having two pallets; pivot means rockably mounting said pawl on said rocker arm for movements in a plane substantially parallel with the line connecting said shafts between a pair of end positions in which one pallet engages with one of said ratchet wheels and the other pallet engages with the other ratchet wheel, respectively;

first eccentric resilient means operating between said pawl and the rocker arm for alternately biasing the pawl onto one of saidend positions; second eccentric resilient means operating between said rocker arm and said carrier means for alternately biasing the rocker arm into a pair of spaced end positions with respect to said carrier means together with said pawl; stud means mounted on said rocker arm and connected with one end of said first and said second resilient means; and a ribbon having ends connected to said spools and adapted to prevent rotation of said ratchet wheels by respective pallets when one spool fully pays out the ribbon whereby the pawl is ,rockedabout said pivot means and the rocker arm is pivoted with respect to said carrier means against the action of saidrfirst and second resilient means, respec-,

tively, when the carrier means is rocked with respect to said support means.

- 7. A ribbon advancing and reversing mechanism comprising,iin combination: support means; a pair of spaced parallel shafts rotatably mounted on said support means;

a spool and a ratchet wheel fixed for rotation to each shaft; a carrier plate rockably mounted on the support means between and about an axis parallel with said shafts; a plate-like rocker arm parallel with and pivotably mounted on said carrier plate about an axis parallel with said shafts; a plate-likedouble pawl having two pallets and parallel with said rocker arm; pivot means rockably mounting said pawl on said rocker arm for movements in a plane substantially parallel with the line connecting said shafts between a pair of end positions in which one pallet engages withone of said ratchet wheels and vthe other pallet engages with the other ratchet .wheel,.respectively; first eccentric resilient means operat ing betweensaid pawl and the rocker arm for alternately biasing'the pawl into one of. said end positions; second eccentric resilient means operating between said rocker arm and said,carrier platefcjr. alternately biasing the apnoea rocker arm into a pair of spaced 'end positions with respect to said carrier plate together with said pawl; and a ribbon having ends connected to'sai'd spools and adapted to prevent rotation ofsaid ratchet wheels by respective pallets when one spool fully pays out the ribbon whereby tho pawl is rocked about said pivot means and the rocker arm is pivoted with respect to said carrier plate against the action of said first and second resilient means, respectively, when the carrier plate is rocked with respect to said support means.

8. A ribbon advancing and reversing mechanism comprising, in combination: support means; apair of spaced parallel shafts rotatably mounted on said support means; a spool and a ratchet wheel fixed for rotation to each shaft; carrier means rockably mounted on the support means between and about an axis parallel with said shafts; a rocker arm pivotably mounted on said carrier means about an axis parallel with said shafts; a double pawl having two pallets; pivot means rockably mounting said pawl on said rocker arm for movements in a plane substantially parallel with the line connecting said shafts between a pair of end positions in which one pallet engages with one of said ratchet wheels and the other pallet engages with the other ratchet wheel, respectively; first eccentric resilient means operating between said pawl and the rocker arm for alternately biasing the pawl into one of said end positions; second eccentric resilient means operating between said rocker arm and said carrier means for alternately biasing the rocker arm into a pair of spaced end positions with respect to said carrier means together with said pawl; a pair of stop pins connected to the support means for limiting the rocking movements of said carrier means; a spring connected to the support means and to said carrier means for constantly biasing the latter into abutment with one of said stop pins; and a ribbon having ends connected to said spools and adapted to prevent rotation of said ratchet wheels by respective pallets when one spool fully pays out the ribbon whereby the pawl is rocked about said pivot means and the rocker arm is pivoted with respect to said carrier means against the action of said first and second resilient means, respectively, when the carrier means is rocked with respect to said support means.

9. A ribbon advancing and reversing mechanism comprising, in combination; support means; a pair of spaced parallel shafts rotatably mounted on said support means; a spool. and a ratchet wheel fixed for rotation to each shaft; carrier means rockably mounted on the support means between said shafts; a rocker arm pivotably mounted on said carrier means; a double pawl having two pallets; pivot means rockably mounting said pawl on said rocker arm for movements between a pair of end positions in which one pallet engages with one of said wheels and the other pallet engages with the other wheel, respectively; first eccentric resilient means operating between said pawl and the rocker arm for alternately biasing the pawl into one of said end positions; second eccentric resilient means operating between said rocker arm and said carrier means for alternately biasing the rocker arm into a pair of spaced end positions with respect to said carrier means together with said pawl; a pair of stop pins connected to the support means for limiting the rocking movements of said carrier means, said pawl abutting against one of said stop pins in each of its end positions; a spring connected to said support means and to said carrier means for constantly biasing the latter into abutment with one of said stop pins; and a ribbon having ends connected to said spools and adapted to prevent rotation of said ratchet wheels by the respective pallets when one spool fully pays out the ribbon, whereby the pawl is rocked about said pivot means and the rocker arm is pivoted with respect to said carrier means against the action of said first vand second resilient means, respectively, when ;the' carrier means -isrocfaed respect to :said :support" means.

, 12 v 10. A ribbon advancing-and reversing mechanism comprising, in combination: support means; a pair of spaced parallel shafts rotatably mounted on said support means;

a spool and a-ratchet wheel fixed for rotation to each shaft; carrier means rockably mounted on the support means between said shafts; a rocker Larm pivotably mounted on said carrier means; a double pawl having two pallets; ,pivot means rockably mounting said pawlton said rocker arm for movements between a pair of end positions in: which one pallet engages with one of said wheels and the other pallet engages with the other wheel, respectively; first eccentric resilient means operating between said pawl and the rocker arm for alternately biasing the pawl into one of said end positions; second eccentric resilient means operating between said rocker arm and said carrier means for alternately biasing the rocker arm into a pair of spaced end positions with re- 'spect to said carrier means together with said pawl; a pair of arresting pins mounted on said carrier means for limiting the rocking movements of said rocker arm in two opposing directions, the rocker arm abutting against one of said arresting pins in each of said last mentioned end positions; a pair of stop pins connected to the support means for limiting the rocking movements of said carrier means, said pawl abutting against one of said stop pins in each of its end positions; a spring connected to said support means and to said carrier means for constantly biasing the latter into abutment with one of said stop pins; and a ribbon having ends connected to said spools and adapted to prevent rotation of said ratchet wheels by the respective pallets when one spool fully pays out the ribbon whereby the pawl is rocked about said pivot means and the rocker arm is pivoted with respect to said carrier means against the action of said first and second resilient means, respectively, when the carrier means is rocked with respect to said support means.

11. A ribbon advancing and reversing mechanism comprising, in combination: support means; a pair of spaced parallel shafts rotatably mounted on said support means; a spool and a ratchet wheel fixed for rotation to each shaft; carrier means rockably mounted on the support means between said shafts; a rocker arm pivotably mounted on said carrier means; a double pawl having two pallets; pivot means rockably mounting said pawl on said rocker arm for movements between a pair of end positions in which one pallet engages with one of said wheels and the other pallet engages with the other wheel, respectively; first eccentric resilient means operating between said pawl and the rocker arm for alternately biasing the pawl into one of said end positions; second eccentric resilient means operating between said rocker arm and said carrier means for alternately biasingth'e rocker arm into a pair of spaced end positions with respect to said carrier means together with said pawl; a pair of stop pins connected to the support means for limiting the rocking movements of said carrier means, said pawl abutting against one of said stop pins in each of its end positions; a spring connected to said support means and to said carrier means for constantly biasing the latter into abutment with one of said I stop pins; a ribbon having ends connected to said spools and adapted to prevent rotation of said ratchet wheels by the respective pallets when one spool fully pays out the ribbon whereby the pawl is rocked about said pivot means and the rocker arm is pivoted with respect to said carrier means against the action of said first and second resilient means, respectively, when the carrier means is rocked with respect to the support means; and a braking spring operatively connected to each of said shafts and anchored in said support means for preventing unwinding of the ribbon off the respective spool when the pawl is idle.

12. A ribbon advancing and reversing mechanism comprising, in combination: support means; apair of spaced parallel shafts rotatably mounted on said support means; a spool and a ratchet wheel fixed for rotation to each shalt; carrier means rockably mounted on the support means between said shafts; a rocker arm pivotably mounted on said carrier means; a double pawl having two pallets; pivot means rockably mounting the pawl on said rocker arm for movements in a plane substantially parallel with the line connecting said shafts between a pair of end positions in which one pallet engages with one of said ratchet wheels and the other pallet engages with the other ratchet wheel, respectively; first eccentric resilient means operating between said pawl and the rocker arm for alternately biasing the pawl into one of said end positions; second eccentric resilient means operating between said rocker arm and said carrier means for alternately biasing the rocker arm into a pair of spaced end positions with respect to said carrier means together with said pawl; a ribbon having ends connected to said spools and adapted to prevent rotation of said ratchet wheels by the respective pallets when one spool pays out the ribbon whereby the pawl is rocked about said pivot means and the rocker arm is pivoted with respect to said carrier means against the action of said first and second resilient means, respectively, when the carrier means is rocked with respect to the support means; a braking spring connected to each of said shafts for preventing unwinding of the ribbon,

ofi the respective spool when the pawl is idle, each braking spring having a stem and a loop at the end of I the stem; and a pair of pins, each connected to said support means and each received in one of said loops for anchoring the respective braking spring to said sup port means. Y Y

13. A ribbon advancing and reversing mechanism comprising, in combination: support means; a pair of spaced parallel shafts rotatably mounted on said support means; a spool and a 'ratchetwheel fixed for rotation to each shaft; carrier means rockably mounted on the support means between said shafts; a rocker arm pivotably mounted on said carrier means; a double ,pawl' having two pallets; pivot means rockably mounting the pawl on said rocker arm for movements in a plane sub- 1 stantially parallel with the line connecting said shafts gages with one of said ratchet wheels and the other pallet engages with the other ratchet wheel, respectively;

' first eccentric resilient means operating between, said pawl and the rocker arm for alternatelybiasing the pawl 'into one of said end positions; second eccentricres'ilient: means operating between said rocker arm'and said. carrier means together with said pawl; aribbon having ends connected to said spools and ad'aptedto tpreventtrotation of said having two pallets; pivot means rockably mounting the pawl on said rocker arm for movements in aplane substantially parallel with the line connecting said shafts between a pair of end positions in which one pallet engages with one of said ratchet wheels and the other pallet engages with the other ratchet wheel, respectively; first eccentric resilient means operating between said pawl and the rocker arm for alternately biasing the pawl into one of said end positions; second eccentric resilient means operating between said rocker arm and said carrier means for alternately biasing the rocker arm into a pair of spaced end positions with respect to said carrier means together with said pawl; a ribbon having ends connected to said spools and adapted to prevent rotation of said ratchet wheels by the respective pallets when" one spool pays out the ribbon whereby the pawl is rocked about said pivot means and the rocker arm is pivoted with respect to said carrier means against the action of said first and second resilient means, respectively; when the carrier means is rocked with respect to the support means; a braking spring connected to each of said shafts for preventing unwinding of the 'ribbon off the respective spool when the pawl is idle,

comprising, in combination: support means; a pair of spaced parallel shafts rotatably mounted on said sup- 7 port means; a spool and'a ratchet wheel fixed for rotabetween a pair of end positions in which one pallet en- I ratchet wheels byrthe respective pallets when one spool,-

pays out the ribbon whereby the pawl is'rocked about :said pivot means and therocker arm is-pivoted with respect to said carriervmeans against the action of said 'first'and second resilient means, respectively, when the v carrier means is rocked with respect to the support 1 means; a braking spring connected to each of said shafts for preventing unwinding of the ribbon off the respective tion to each shaft; carrier means rockably mounted on the support means between said shafts; a pair of stop pins connected to the support means for limiting the movements of said carrier means in two opposing directions; a spring connected to said support means and to said carrier means for constantlyabiasing the latter into abutment with one of said stop pins; means for rocking thecarrier means against the action of said spring in a direction, toward the other stop pin; a rocker arm" pivotably mounted on said carrier means; a double pawl having two pallets; pivot means mounting the pawl on said rocker arm for movements in' a plane substantially parallel with the line connecting said shafts between a :pair of end positions in which one pallet engages with one of said ratchet wheels and the other pallet engages with the other ratchet wheel, respectively; ,first eccentric resilient means operating between said pawl and the rocker arm for alternately biasing the pawl'into one of said end positions; second eccentric resilient means operating between said rocker arm and said carrier means, for alternately biasing the rocker am into a pair of spaced end positions with respect to said carrier means I together with said pawl; a ribbon having ends connected to said spools and adapted to prevent rotation of said ratchet wheels by the respective pallets when one spool pays out the ribbon whereby the pawl is rocked about said pivot means and the rocker arm is pivoted with t respect to said carrier means against the action of said first and second resilient means respectively, when the carrier means is rocked with respect" to the support spo'ol when the pawlis idle,each brakin'grspring having a plurality of convolutions wound aboutthe respective {shaft and a stem formed witha loop at one end thereof; I and a'pair of pins,'each connected to said'supportmeans and each receivedin one of said,loops-for anchoring'the respectiverbraking spring to said support means.

, 14.;A ribbon advancing and reversing mechanism comprising, in combination: support means; a pair; of

i spaced parallel shafts rotatably-mounted, on-saidsupport means; aspool and a 'rat'chet-iwh'eel' fixed for'rotation to each shaft; carrier means rockably mounted on the support means between-"said shafts; means connected J tofthe. earrier'meanstfor;rocking 'same; a rocker arn pivotably mounted on said carrier meanna double pawl for preventing, unwinding of the ribbon off the irespec means; a braking spring connected to each of saidshafts 'r-tive' spoolgwhen the pawlis idle, each braking spring "having a stem andia loop atthe end-ofthe :stem; and

i-a'pair of pins', each connected to said support means and each received'in on'e of saidloops for anchoring the respective braking spring to said support means. e

References Cited i n mg file this patm NI E STATES PATENTS 1,198,585 Bishop etal.-- Mar. 31,1931 Dec. 22,4935

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