US2300755A - Ribbon-feed mechanism - Google Patents

Description

Nov. 1942. L. s. WILLIAMS RIBBON-FEED MECHANISM 4 Sheets-Sheet l Filgd July 25. 1941 Lqwrence 5. W/W/ams INVENTOR ATTORNEYS Nov. 3, 1942. 7L. s. WILLIAMS 2,300,755

RIBBON-FEED MECHANISM Filed July 25, 1941 4 Shee ts-Sheet 2 Lawrence J.- Mfl/ams INVENTOR I ATTORNEYS Nov. 3, 1942.

L. s. WILLIAMS RIBBON-FEED MECHANISM 4 Sheet-Sheet 3 Filed Jugy 25, 1941 2 a 4 3 9 n 79 v i 6 J 9 E: 0 Z 3 6w m y TV H: m a I Q Lawrence J. M/////am3 INVENTOR ATTORNEYS L. s. WILLIAMS ,300,755 RIBBON-FEED MECHANISM 'Nov. 3, 1942.

Filed July 25, 1941 4 Sheets-Sheet 4 I I LaW/"en'ce 5. [MW/007s E 1 INVENTOR zmwmfi Patented Nov. 3, 1942 l 2,300,755 RIBBON -FEED MECHANISM Lawrence S. Williams, Toledo, Ohio, assignor to Toledo Scale Company, Toledo, Ohio, a corporation of New Jersey Application July 25, 1941, Serial N0. 404,051

12 Claims. (Cl. 101-436) This invention relates to ribbon-feed mechanisms of the type which automatically reverse the direction of feed of the ribbon when it has been fed past the printing mechanism for substantially its full length, and more particularly to means for effecting such reversal of feeding direction.

Most ribbon-reversing mechanisms are constructed so that the direction of feed of the ribbon is changed by moving a feeding pawl, or a pair of feeding pawls, out of engagement with one ribbon spool and into engagement with the other at the time the reversal of direction of feed is desired.

The bodily shifting of the feeding pawl, or pawls, has a serious disadvantage if a mechanism operated in this way is to be used with any device which applies pressure to the ribbon, and the medium which is to receive the impression, from both sides. In a device of this type, the ribbon is held stationary at the moment of impression. If the feeding pawl shifts to the other spool and attempts to feed the ribbon during the impression, the ribbon is very likely to be torn. If this is prevented by having the ribbon less tightly held, then movement of the ribbon will cause a smeared impression. Since the ribbon is usually fed during the same cycle as when the impression is taken, the timing of the feeding and the impression taking must be very carefully adjusted to prevent either one of these two undesirable results.

Further diificulties arise in most ribbon-reversing mechanismsdue to the employment of a toggle-type over-center device to move the pawl from one spool to another and to hold it in engagement. Over-center devices of this type compress a spring as they approach dead center and must be carried past dead center by the force created by the shifting device operated by the ribbon so that the extension of the spring can be employed to shift the feeding pawls to change the direction of feed of the ribbon. If any friction exists in such an over-center device, since it is pulled only to dead center, it may very easily remain there and the mechanism will fail to feed in either direction. This failure to change over properly is the cause of most of the trouble encountered in ribbon feeding mechanisms using over-center devices to bodily move the feeding pawls from one ribbon spool to the other.

One type of ribbon-reversing mechanism often used is the so-called bulk type in which a rider wound on a spool and which rider, being pivoted, is swung away from the center of the spool by the increase in the bulk of the ribbon being accumulated on the spool. As the rider is swung away from the center of the spool, the toggle member is moved toward dead center, and when a sufficient bulk has accumulated on the spool, should snap over to the other side of center.

Operation, however, is often far from satisfactory, since the friction mentioned above may be aggravated by disadvantages peculiar to the bulk type of mechanism which include the softening of the mass of the ribbon as it winds on the spool and the wasting of some of the feeding stroke and the built-up tension in the irregularities and unevenness inthe subsequent feeding.

This unevenness of tension is particularly undesirable-where a reversing mechanism employing a toggle-like spring-actuated over-center device is used.

To overcome some of the disadvantages of the bulk type of mechanism, there is sometimes used the so-called eyelet type of mechanism.

In this device a small eyelet, clipped into the ribbon near its end, actuates the reversing mechanism as, or shortly after, it leaves the unwinding spool. As in the bulk type, though, if the usual spring-actuated toggle-like over-centerdevice is used, the ribbon tension must compress the spring in the toggle and, if friction exists, it may easily stick at dead center.

To eliminate some of these difficulties, mechanisms have been designed which areoperated in one direction only and which, when moving forward, coil a spring, the tension of which will return the ribbon after it has been fed its full length in one direction. This, however, causes rapid deterioration of the ribbon because of the high speed of return when the coiled spring'is released and so shortens the ribbon life as to make the total result less desirable than with the reversing type of feeding mechanism.

Because of these many diffic'ulties encountered is pressed against the surface of the ribbon being in the construction of ribbon-feeding andribbonreversing mechanisms, the usual one is quite complicated, subject to mechanical failure, uneven in operation and will not work satisfactorily where the feeding stroke and the return stroke of the feeding pawls are not substantially harmonic. Since many devices, incorporating ribbon-feeding and reversing mechanisms, do not have even feeding and returning strokes, the use of such mechanisms in such devices has been relatively unsatisfactory.

It is an object of this invention to provide a ribbon feeding and reversing mechanism, the operation of which is positive and which will not interfere with the necessity for holding the ribbon during aprinting cycle.

It is another object of this invention to provide a ribbon feeding and reversing mechanism which will not move the ribbon during-the time that an impression is being taken from it and will thus neither tear the ribbon nor smear the impression.

Another object of this i vention is to provide a ribbon mechanism which is relatively simple in construction and yet durable and not liable to get out of adjustment.

It is still another object of this invention to provide a ribbon mechanism which is fed in both directions by means of a pawl but which does not bodily move the pawl to change the direction of feeding.

It is yet another object of this invention to provide a ribbon feedingand reversing mechanism which changes the direction of feed of the ribbon by changing the path through which the feeding pawl may moverather than by changing the position of the feedin pawl itself and its subsequent motion. 7

It is still another object of this invention to provide an over-center device for changing the direction of feed of a ribbon mechanism which is actuated by the ribbon itself and held on one side or the other of center by magnetic means.

It is a more specific object of this invention to provide a magnetically detained over-center device for varying the path of movement of a feeding pawl to reverse the direction of feed of a ribbon mechanism.

Another more specific object of this invention is to provide a ribbon mechanism which can be used in connection with a printing disk and is adapted to feed the ribbon before the disk, the impression receiving medium and the ribbon are squeezed together to make an impression.

More specific objects and advantages are apparent from the description, in which reference is had to the accompanying drawings illustrating a preferred form of ribbon feed mechanism embodying the invention.

In the drawings:

Fig. I is a front elevation of a preferred embodiment of the invention as shown in connection with the type carrying wheel of a printing scale.

Fig. II is a View in vertical section on a larger scale, taken from the left side of the mechanism illustrated in Fig. I. n

Fig. III is a plan View on an enlarged scale of a ribbon mechanism embodying the invention.

Fig. IV is a vertical sectional view, taken on the line IV-IV of Fig. III.

Fig. V is a fragmentary vertical sectional View, taken on the line VV of Fig. III.

ing the mechanism in a different position in its operating cycle.

Fig. VIII is an enlarged fragmentary View in perspective of a portion of the mechanism illustrated in Fig. III.

Fig. IX is a schematic wiring diagram of a printing scale embodying the invention as illustrated in Fig. I.

These specific drawings and the specific description that follows merely disclose and illustrate the invention and are not intended to impose limitations upon the claims.

Mounted within a dial housing Ill (Fig. II), on a subframe I I, is an indicator shaft I2 having an indicator [3 attached to one end. Fixed on the shaft 12 is a pinion M, which is driven by a rack 15 attached to the load counterbalancing mechanism .(not shown). The indicator l3 sweeps over a dial IE to indicate the weights placed upon Fig. V1 is a still further enlarged fragmentary i Fig-VII is a view similar to Figure VI, show 75 the scale. Attached to the opposite end of the shaft [2, from the indicator I3, is a type bearing disk l1.

Mounted on a bracket [8 and supported bya secondary bracket l9, attached to the housing It (Fig. II), is a solenoid housin 20. A vertically movable core rod 2| is located within a solenoid 22 in the housing 26. The upper end of the core rod 2| has attached thereto a cross head 23. Pivoted on the cross head 23 are links 24 and 25. The links 24 are pivoted in a lower portion 26 of a horizontally slidable abutment 21 (Fig. IV). The abutment 2! slides on rods 28, which are fastened in the secondary bracket I9. A bearing ball 28a is held in the upper end of a support stud 29, which is screwed into the top of the solenoid housing 20, and serves to support the rear of the abutment 21. The link is similarly pivoted in the lower portion of a horizontally slidable platen 30.

When the solenoid 22 is energized, the core rod 2| is thrust upwardly pushing outwardly on the lower portions of the opposed abutment 27 and platen 30 and moving an inner face SI of the abutment 21 and an inner face 32, of the platen 30 towards each other.

The lower edge of the type bearing disk ll extends downwardly between the opposedgfaces 3i and 32 of the abutment 21 and the platen 39. Also interposed between the faces 3| and 32, and adjacent the periphery of the disk ll, is a metallic strip 33 bearing a character in the form of a pointer which is positioned to indicate the weight on the scale by pointing to the figure printed from the disk II.

The vertical portion of a ribbon mechanism support plate 34 is fastened to the platen 3E] and the plate has a horizontal shelf-like portion extending backward from the platen 30. A U shaped support member 35 (Fig. V) is resiliently attached, by means of a spring encircled bolt 36, to the vertical portion of the support plate 34 at one side of platen 30. A similar'U shaped supporting member 31 is mounted on the opposite end of the support plate 34. Metallic guides 38 are supported by the other arm of the U shaped supporting members 35 and 3'! and. extend between the platen 30 and printing disk I1 (Fig. IV). U clips 39 (Figures III and V) are fastened to the support plate 35 and have one bifurcated arm in the legs of which th U shaped support members 35 and 31 are horizontally slidable. The center of the metallic guides 38, that is those portions actually passing between the printing surfaces of the abutment-2'1 and platen 30, have apertures therein to permit the platen 39 to force a card 49 (Fig. II) or other impression receiving substance, into contact with a ribbon 4| also passing through the guides 38 and thus to print an impression ofthe type on the disk I! on the surface of the card. I

In order to secure a firm impression of the type on the disk 11, the abutment 21 and platen 39 are brought firmly towards each other. Since the guides 38 must be kept in relatively the same position to receive the card 49, andshould not move back and forth with the platen 39, because such movement would bend or crease the card, their connection through the U shaped support members 35 and 31 to thesupport plate 34, and thus to the platen 39, is through the spring encircled bolts 36 which, being resilient, permits movement on the part of the support plate 34 and still holds the guides as in position. The

clips 39 prevent any sagging of this resilient connection.

The ribbon 41 passes around out-rigger spools 42, and thence to ribbon feeding spools 43 and 44. The spools 43 and 44 are rotatable upon vertical axles 45 which are fastenedon the support plate 34. Springs 46 are chpped in the support plate 34 and pass around the peripheries of the spools 43 or 44. These springs 45 serve as tension brakes on the spools 43 and 44 to prevent back lash of the ribbon 4 l Also mounted on the axles 45, of spools 43 and 44, are ratchet wheels I 41 and 48 respectively.

A U shaped driving pawl 49 (Fig. IV) has one arm mounted in a bushing .59, which is slidable in a slot 51 in the support plate 34. The same arm of the pawl 49 passes through a clip 52, which is attached to the abutment 21 and which is adapted to slide the pawl 49 in the bushing 55 in a direction opposite to the movement of the platen 39 and the support plate 34. The lower portion of the pawl 49 is attached, by means of a spring 53, to a stud 54 attached to the underside or" the support plate 34. The other arm of the pawl 49 has a sharpened edge 55 extending part way up its length and a flattened portion 56 extending above the level of the support plate 34. The edges of the flattened portion 59 are adapted to engage the teeth of either the ratchet wheel 4! or the ratchet wheel 48. j a

A toggle member 51 is pivotally mounted on a finger 58, which extends upwardly through the support plate 34. A walking arm 59 (Figures III,

VIII) is mounted upon the arms of a vertical staple E0, the body of which passes through a horizontal hole 6| bored transversely through the toggle member 51. The walking arm 59 has upturned bifurcated ends through which the ribbon 4| passes. Mounted in small brackets 52; one on each side of the forward end of the toggle member 57 and with their faces in vertical planes converging on the pivot finger 58 of the toggle member 51, are small horseshoe magnets 63;

The end of the toggle member 57, which is opposite to that extending between the magnet 63, has mounted therein a downwardly extending stud 64, the forward edge of which is knifeshaped and opposed to the sharp edge of the pawl 49 (Fig. IV). Pivoted on a stud 65, which extends downwardl from the support plate 34, is a horizontally disposed guiding plate 65 (Figures IV and VI). The guiding plate 66 has an open center through which the arm of the pawl 49 extends which has the sharp edge 55 and the flattened surface 55. The guiding plate 66 has a in front of the spear point projection'tl. Pivotally mounted on the'guiding plate 63 are back pawls 68 and 69, which engage the ratchet wheels 41 and 48 respectively to prevent their being turned in the wrong direction. Springs 19 hold the back pawls 68 and 69 against the teeth of the ratchet wheels 41,-and 48-andagainst" limit studs H which project upwardlyfrom the guid ing plate 65. I

The lower end of thesolenoid core rod 2| II) has attached thereto a plate 12 and is surrounded by a spring 1 3 which,--'when the core rod is moved upwardly, upon energization of the solenoid 22, is compressed between the plate 12 and the solenoid housing 20.- When; the solenoid is de-energized, the spring 13 serves to return thesolenoid core'rod to its lower position. A vertical switch (actuating rod 14 is attached to the lower end of the core rod 2| and extends downwardly through a switchcontact 15'. The contact 75 is closed when the solenoidcore rod 2l approaches the limit of its upward stroke and is opened shortly after it has startedits return stroke.

In Figure IX, there is shown a wiring diagram of a printing scale embodying the invention;-

the solenoid operated contact 15.' Theopposite' side of the solenoid'ioperated Contact 151s connected to one side of a .normally'open contact 82' and through a resistance 83 to one side ofia relay coil 84, the other side of which is connected tothe lead 18. The push button 89 is' also connected to one side of the normally open contact 82 and through a normally closed contact 85, protected by a condenser '85, through a lead 87, to the other side of therectifier 19. 7

he operation of the ribbon feedinga'nd'ree versing meohanism, as usedfin connection with the printing scale illustrated in Figure I', will now be described. When the printing diskli has come to rest with the proper type character positioned over the platen 39, the operator closes the push button switch lw. .Current flows from the line through the switch 80, the normally closed contact to the rectifier I9 and thenito the solenoid 22. The solenoid core rod 2! (Fig. II) .is moved upwardly which, through the connections" on the cross head 23, moves the'faces of the platen'39 and the abutment 21 towards each other by means of the links 24 and 25. A card or slip 45, having been inserted between the platen'35 and. the printing disk [1, receives an impression of the ing type on the strip 33.

type on the disk i! positioned above the indicate.

Atthe same time, the movement of theiabut' ment 2! towards the rear of the mechanism has moved the clip 52, and through it, the pawl 49.

In Fig. VI, the mechanism .is shown with the. pawl 49 in the position which-it would ocoupyu just after the beginning of the upward stroke of.

the solenoid core rod 2!. The ribbon 4| is almost I entirely unwound from the ribbon spool '43 and an eyelet 88, clipped into the ribbon 4| near its end, has almost reached the end of the walking arm 59 throughwhiohthe ribbon ilpasses. The toggle member 51 is still located in" the downwardly extending stud 64, vmounted in' the toggle member 51, is positioned above andslightly From' the push position which it occupies when the ribbon mechanism is feeding onto the spool 44. Thus-the knife edge stud 64 is positioned above and slightly to the left of the spear point projection 61 on the guiding plate 66. The guiding-plate 66 is positioned normally with the point of the spear point projection 61 directly on the center line of travel of the pawl 49. As the pawl 49 is moved towards the rear, the knife edge 55, in its upturned end, approaches the point of the spear point projection 6'! but is guided to one side or the other of the spear point projection 61- by the knife edge stud 64 which depends from the toggle member 51. The toggle member 5! is, of course, positioned either to oneside or the other of the spear point projection 6'1 by being retained against one or the other of the magnets 63. As the knife edge 55 of the pawl 49 strikes the sides of the knife edge stud 64, it is guided to one side of the spear point projection 61. In Fig. VI, subsequent movement of the pawl will bring the two knife edges toward each other and their slanting faces will guide the pawl 49 to theright of the spear point projection 61. Since the clearance between the vertical edges of the spear point projection 6! and the teeth of the ratchet wheel 48 is not sufficient to permit the entry of the arm of the pawl 49, one edge of the flat portion 56 engages a tooth on the ratchet wheel 48 and the opposite edge acts as a cam to pivot the guiding plate 66 in a clockwise direction (Fig. VII). The pivoting of the plate 66 swings the limit stud H, fastened thereto, which disengages the back pawl 68 from the teeth of the ratchet wheel 41 to permit counterclockwise rotation of the ribbon spool 43 to allow the ribbon to be unwound from that spool. The pawl 49 has now approached the limit of its rearward stroke, and the spool 44 has wound on an additional amount of the ribbon 4|.

The back pawl, engaged in the teeth of the ratchet wheel 48, is snapped up by the teeth of the wheel 48 to permit the spool 44 to rotate in a counter-clockwise direction and wind on the ribbon.

The solenoid core rod 21 (Fig. IX), now having reached the upward limit of its stroke, closes the contact 15, which energizes the relay coil 84, and closes the normally open contact 82 and opens the normally closed contact 85. The circuit through the rectifier I9 is now open and the core rod 2| begins to descend. The resilient construction of the connection between the core rod 2| and the switch 15 holds the switch 15 closed for a short time during descent. Thus current passes through the solenoid coil 84 for a sufli I ciently additional length of time to prevent the switch 85 from reclosing until the operator releases the button 88 which he should do immediately upon the printing of the weight. If, however, the operator should fail to release the push button 89, current will continue to flow through the coil 84, the contact 82 and the push button 80, thus holding the contact 82 closed even after the contact 15 has been broken and preventing the contact 85 from closing which would start a second printing cycle. This is a safety circuit which prevents the repetition of printing cycles, no matter how long the button 88 is held closed. If the push button 88 is now released, the coil 84 is de-energized, the contact 82 snaps open and the contact 85 is closed to prepare the circuit for a subsequent printing operation.

When the solenoid core rod 2| starts its descending stroke, the platen 39 andthe abutment 21 are moved back to theiroriginal positions.

Thepawl 49, through'its connecting clip 52, is also returned to its original position. The guiding plate 66, under tension of the spring 10 connected to the back pawl 69 and working against the ratchet wheel 48, is swung in a counterclockwise direction back to the center position shown in Fig. VI.

If the feeding of the ribbon in the feeding stroke is suflicient to 'bring'the eyelet 88 into contact with the end of the walking arm 59 (the next stroke after that illustrated in Figures VI and VII), the tension on the ribbon 4| will pull the walking arm 59 bodily to the left. This movement, through the staple 60, will pivot the toggle member 51 on the finger 58 which will swing its forward end away from that one of the magnets 63, against which it is being held, and far enough towards'the other magnet 63 for the magnetic force to seize it and pull it against the other magnet 63. The toggle member 51 will thus be rotated in a counterclockwise direction on the finger 58 and positioned against the other magnet 63 than that against which it is shown positioned in Figures VI and VII. This will swing the knife edge stud 64 to the right (Fig. VI) and in subsequent strokes of the pawl 49, its edge 55 and flat portion 56 will travel on the lefthand side of the spear point projection 61 engaging the teeth in the ratchet wheel 41 to feed the ribbon on the spool 43 and in the opposite direction from that in which it is fed in the stroke illustrated in Figures VI and VII. The cycle of feeding will now be exactly the same as that described but the flat portion 56 of the pawl 49 will be moved through a different path.

Thus the reversing movement of the ribbon mechanism does not bodily move the pawl 49 out of engagement with one ribbon spool and into engagement with another, but rather changes the path through which the latching edge of the flat portion 56 of the pawl 49 moves to cause the pawl to engage the other ribbon spool and does not change the direction of stroke of the pawl actuating members. It is impossible for the toggle member 51 to be. moved to dead center and left there since if it were moved to dead center only a very slight force would be needed to break the balance between the magnetic pull of the two magnets 63 and such slight contact is always afforded on the return stroke of the pawl 49 and the return rocking motion of the guiding plate 66.

The embodiment of the invention that has been disclosed may be modified to meet various requirements.

Having described the invention, I claim:

1. In a ribbon feeding and reversing mechanism, in combination, a ribbon, a pair of alternately drivable spools on which said ribbon is adapted to be wound, spool driving mechanism, means for shifting said spool driving mechanism from driving relation with one of said spools to driving relation with the other of said spools and magnetic means for retaining said spool driving mechanism in driving relation with one of said spools until moved by said shifting means into driving relation with the second of said spools, said magnetic means then retaining said spool driving mechanism in driving relation with the second of said spools.

2. In a ribbon feeding and reversing mechanism, in combination, a ribbon, a pair of spools on each of which said ribbon is adapted to be wound, spool driving mechanism, means for conditioning said spool driving mechanism for driving oneof said spools, magnetic means for retaining said mechanism in condition to drive such spool and means operable when a definite portion of said ribbon is wound on'suchspool for causing said conditioningmeans .to condition said mechanism for driving the second of said spools, said magnetic means then operating for retaining said mechanism in condition to drive the second of said spools. V

3. In a ribbon feeding and reversing mechanism, in combination, a ribbon, a pair of spools on each of which said ribbon is adapted to be wound, spool driving mechanism, means for conditioning said spool driving mechanism for driving one of said spools, magnetic means for retaining said mechanism in condition to drive such spool and ribbon actuated shifting means for shifting said conditioning means to condition said mechanism for driving the second of said spools, said magnetic means then operating for retaining said mechanism in condition to drive the second of said spools.

4. In a ribbon feeding and reversing mechanism, in combination, a ribbon, a pair of spools on each of which said ribbon is adapted to be wound, spool driving mechanism, means for conditioning said spool driving mechanism for driving one of said spools, magnetic means for retaining said mechanism in condition to drive such spool and ribbon actuated shifting means operable when a predetermined amount of said ribbon is wound on such spool for shifting said conditioning means to condition said mechanism for driving the second of said spools, said magnetic means then operating for retaining said mechanism in condition to drive the second of said spools.

5. In a ribbon feeding and reversing mechanism, in combination, a ribbon, a pair of spools on each of which said ribbon is adapted to be wound, spool driving mechanism, alternately positionable guiding means for deflecting said driving mechanism into one of two paths, each leading to engagement with a different one of said spools and means operable when a definite portion of said ribbon is wound on such spool for moving said alternately positionable guiding means from one of its alternate positions to the other.

6. In a ribbon feeding and reversing mechanism, in combination, a ribbon, a pair of alternately drivable spools on which said ribbon is adapted to be wound, means for driving said spools, alternately positionable guiding means for guiding said driving means through either of two paths, each leading to engagement with a different one of said drivable spools, ribbon actuated means for shifting said guiding means and magnetic means for retaining said guiding means in one of its alternate positions until moved to the other by said ribbon actuated shifting means.

7. In a ribbon feeding and reversing mechanism, in combination, a ribbon, a pair of spools on each of which said ribbon is adapted to be wound, spool driving mechanism, alternately positionable guiding means for deflecting said driving mechanism from its path of movement through either of two alternate paths, each leading to engagement with a different one of said spools, means operable when a definite portion of said ribbon is wound on such spool for moving said alternately positionable guiding means from one of its alternate positions to the other and an over-center device for retaining said alternately positionable guiding means in either of its positions until moved to the other by said means operable when a definite portion of said ribbon is wound on such spooL- v 8,. 'Ina ribbon feeding and reversing mecha-. nism, in combination, a ribbon, a pair ofv spools on each of which said ribbon its adapted to be wound, spool driving mechanism, means for-conditioning saidspool driving mechanism forld'ri'v- 'ingone of said spools, a magnet for retaining said mechanism in condition to drive such spool,

actuating means operable when a definite portion of said ribbon is wound on such spool for causing said conditioning means to condition said mechanism for driving the second of said spools and a second magnet for retaining said mechanism in condition to drive such second spool, said first and second magnets in association with said conditioning means forming an over-center device for controlling said actuating means and said conditioning means.

9. In a ribbon feeding and reversing mechanism, in combination, a ribbon, a pair of spools on each of which said ribbon is adapted to be wound, spool driving mechanism, an alternately positionable guiding member adapted to be positioned to guide said spool driving mechanism into engagement with one or the other of said spools, ribbon actuated means for positioning said guiding member, and magnetic means for retaining said guiding member in one of its positions until moved to the other by said ribbon actuated means, said magnetic means then retaining said guiding member in the other of its positions.

10. In a ribbon feeding and reversing mechanism, in combination, a ribbon, a pair of spools on each of which said ribbon is adapted to be wound, spool driving mechanism, a guiding member having alternate pathways through which said mechanism is adapted to be moved, each of said pathways leading said mechanism to operative engagement with a different one of said spools, ribbon actuated means for conditioning said spool driving mechanism to follow one or the other of said paths and magnetic means for retaining said ribbon actuated means in position to condition said mechanism to drive one of said spools until said ribbon actuated means is moved to the other of their positions, said magnetic means then retaining said ribbon actuated means in its other position.

11. In a ribbon feeding and reversing mechanism, in combination, a ribbon, a pair of spools on each of which said ribbon is adapted to be wound, a spool driving pawl having a knife edge and a driving edge, an alternately positionable guiding bar having a knife edge adapted to be moved from one side to the other of the line of movement of the knife edge of said driving pawl whereby when said guiding arm is in one of its alternate positions such knife edges will guide said pawl through one path of movement and lead such driving edge into engagement with one of said spools and when said arm is in the other position such knife edges will guide said pawl through a second path of movement and lead such driving edge into engagement with the second of said spools and means for shifting the position of said guiding bar when a specified amount of ribbon is wound on such spool.

12. In a ribbon feeding and reversing mechanism, in combination, a ribbon, a pair of spools on each of which said ribbon isadapted to be wound, a spool driving pawl having a knife edge and a driving edge, an alternately positionable guiding bar having a knife eds adapted to be moved from one side to the other 01 the line of movement of the knife edge of said driving pawl whereby when said guiding arm is in one of its alternate positions such knife edges will guide 5 said pawl through one path of movement and lead such driving edge into engagement with one of said spools and when said arm is in the other position suchknife edges will guide said pawl through a second path of movement and lead 10 such drivin edge into engagement with the sec-- ond of said spools, means for shifting the position of said guiding bar when a specified amount of ribbon is wound on such spool and. magnetic meansfor retaining said guiding bar in one of, its positions until moved by said shifting means to its other position, said magnetic means then retaining said guide bar in its second position until reshifted by said shifting means.

LAWRENCE S. WILLIAMS.

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