US 3854670 A
A drive system for the automatic reversal of the motion of ink ribbons includes a driving gear which is mounted on a base plate through elastic return means, such as a flat spring. First and second driven gears are alternately engaged with a planentary gear meshed with the driving gear. When the driven gear engaged with the planetary gear is subjected to an increase in the resistant torque, deflection of the elastic return means causes relative displacement of the driving and driven gears to permit the planetary gear to rotate about the driving gear and engage the other driven gear.
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Description (OCR text may contain errors)
United States Patent [191 Bertolazzi Dec. 17, 1974 DEVICE FOR THE AUTOMATIC REVERSAL OF THE LENGTHWISE MOTION OF THE INK-RIBBON IN TYPEWRITERS AND PRINTERS  Inventor: Ugo Bertolazzi, Milano, Italy  Assignee: Honeywell Information Systems Italia, Caluso, Italy  Filed: Aug. 22, 1973  Appl. No.: 390,535
 Foreign Application Priority Data Sept. 1, 1972 Italy 28733/72 52 u.s.c1. ..242/67.4,74/354 s1 rm.c1 B65h 17/02 581 Field of Search 242/674, 191-,74/354  References Cited UNITED STATES PATENTS 2,583,385 l/l952 Miller 242/67.4 X
Smith.. 242 191 Mageoch 242/67.4
Primary Examiner-Donald E. Watkins Assistant ExaminerEdward J. McCarthy Attorney, Agent, or Firm-Fred Jacob  I ABSTRACT A drive system for the automatic reversal of the motion of ink ribbons includes a driving gear which is mounted on a base plate through elastic return means,
7 such as a flat spring. First and second driven gears are alternately engaged with a planentary gear meshed with the driving gear. When the driven gear engaged with the planetary gear is subjected to an increase in the'resistant torque, deflection of the elastic return means causes relative displacement of the driving and driven gears to permit the planetary gear to rotate about the driving gear and engage the other driven gear.
4 Claims, 4 Drawing Figures DEVICE FOR THE AUTOMATIC REVERSAL OF THE LENGTHWISE MOTION OF THE INK-RIBBON IN TYPEWRITERS AND PRINTERS BACKGROUND OF THE INVENTION The present invention relates to a device for the automatic reversal of the lengthwise motion of the ink ribbon in typewriters, teleprinters, and high speed printers as employed in data processing and related systems.
It is known that such printing devices usually comprise a single or two color ink ribbon, a finite length of which, wound on a spool, is made to unwind, in correspondance with the printing operation, and is wound up ona second take-up spool. Both spools are mounted on shafts, each one of which selectively controls the winding up of the ribbon on a corresponding spool. The shafts are usually driven, in the ordinary typewriter, by a ratchet device, associated with the printing bars; but in more sophisticated apparatus, they are preferably driven by an electrical motor energized during the printing operations. The ends of the ribbon are usually secured to the spools by suitable hooking devices.
When the ribbon has been completely unwound from a spool, the winding direction must be reversed by controlling the motion of the supporting shaft of the spool from which the ribbon has been unwound. Several motion-reversing devices have been built for this purpose, but most of them are rather unreliable in operation and somewhat complicated and therefore are not suitable for use with high speed printers, which require a peculiar ruggedness of all members and high operating reliability.
SUMMARY OF THE INVENTION The present invention provides a reversal device satisfying these requirements.
The device according to the invention comprises substantially a driving spur gear, a planetary gear driven by said driving gear, two driven gears for directly and indirectly driving the spools, selectively meshing with, said planet gear, and an elastic supporting memeber for said driving gear, for allowing a transverse displacement of said driving gear with respect to said driven gears, said displacement being normally prevented by the elastic reaction of the supporting member, and being effected as a consequence of the increase in the resisting torque developed by the driven wheel when the ribbon is entirely unwound from a spool. This transverse displacement of the driving gear causes the planet gear to disengage from the formerly engaged driven gear and to engage the formerly disengaged driven gear, thus causing the ribbon to be wound up in the reverse direction.
These and other features and advantages of the device and its operation will appear more clearly from the following detailed description, having exemplifying and not limiting purposes and from the attached drawings.
BRIEF DESCRIPTION OF THE DRAWINGS I FIG. 1 shows a perspective view of the preferred embodiment of the device.
FIG. 2 schematically shows a possible way of winding up and unwinding the ink ribbon.
FIG. 3 schematically shows a first alternative embodiment of the device using face gears.
FIG. 4 schematically shows a second alternative embodiment of the device.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows a perspective view of a preferred embodiment of the device according to the invention. A base plate 1 supports two driven shafts 2 and 3, rotatably journalled thereupon, and a pin 4. Two spur gears 5 and 6 are keyed respectively toshafts 2 and 3, and a third gear 7 is freely pivoted on pin 4 and in mesh with gear 6. The upper ends of shafts 2 and 3 are provided with support washers 8 and 9 and clutch keys l0 and 11 for receiving two take-up spools'l2 and 13 for the ink ribbon (R).
A supporting member 14 is elastically mounted on base plate 1 through elastic return means, for instance, a flat spring 15. A driving shaft 16' is rotatably journalled in supporting member 14, and a driving gear 17 is keyed to shaft 16. An electrical motor M drives shaft 16.
A planet gear 18, meshing withdriving gear 17, is secured by suitable means, for instance by a pair of brackets 19, to driving shaft 16. One bracket 19 is shown above gears 17 and 18, and the other is positioned directly below these gears in like position. Each of the brackets is provided with a hole near each end, one hole receiving shaft 16 and the other hole receiving a shaft for rotation of gear 18. Thus, gear 18 is free to planet gear 18, when the supporting member under the action of the return spring 15 is in the rest position.
The operation ofthe device will now be described. It is assumed that driving gear 17 is kept rotating in the direction shown by the arrow F, under the action of motor M. It is further assumed that the planet gear is in a random position, for instance the one shown by dashed lines 18, and is neither engaged by gear 5 nor by gear 7. Due to the friction between the teeth of wheels 18 and 17, planetary gear 18, instead of rotating on its axis, is driven in a planetary motion around gear 17, in the direction of rotation of the same, and arrives at the position represented in full line in the drawing, where it meshes with gear 5. At this moment, the contact reactions between planetary gear 18 and gears 5 and 17 prevent any further planetary motion and force gear 18 to turn on its axis in the direction indicated by the arrow F Therefore, gear 5 is forced to rotate in the direction shown by the arrow F The spool 12 inserted on shaft 2 winds up the ink ribbon. When the winding up is completed, the end of the ink ribbon, firmly fixed to the spool 13,,will exert a braking torque preventing any further rotation of the spool 12, and stopping the gear 5.
As the motor M goes on exerting the driving torque, the driving gear 17 and the planetary gear 18 go on rotating, the planetary gear 18 being forced to rotate around the center of rotation C corresponding to the contact generatrix between the pitch lines of the gears 5 and 18. This rotation generates a force on the driving shaft 16 and on the supporting member 14 which overcomes the action of the elastic return member and which therefore removes the shaft 16 from the shaft 2 by the distance needed for the planetary gear to pass between gear 17 and gear until it disengages from gear 5. Afterwards, the gear 18 continues its planetary motion until it meshes with the gear 7, assuming the position 18" indicated by dashed line. The gear 7 will therefore rotate in the sense indicated by the arrow F and will transmit the rotary motion to gear 6, which, in turn, rotating in the direction shown by the arrow F will wind up the ink ribbon on the spool 13.
It is clear that, when the ribbon is completely woundup on the spool 13, the motion reversal operation is repeated; that is, the planetary gear disengages from gear 7 and proceeds in its planetary motion in the direction of the arrow F, around the driving gear 17, until it meshes with the gear 5. The alternating operation of winding up alternately the ribbon on the one or the other of the spools goes one indefinitely without requiring any inversion of the motion of the motor M.
Having now disclosed a preferred embodiment of the invention, some modifications will now be considered. In first place, the use of a third gear 7 is not strictly needed for the invention. Its use depends only on the circumstance that it is required to drive alternately the two shafts 2 and 3 in opposed directions of rotation. However, the direction of rotation of the shafts may be the same, if the device is used for the motion reversal of the ink ribbon, or if used for different purposes as well. This is schematically illustrated for example in FIG. 2 which clearly shows how the ink ribbon may be wound up and unwound by two spools having the same direction of rotation.
It may also be noted that by the illustrated arrangement the times required for inverting the motion are different in the two cases: the case of the planetary gear disengaging from gear 5 and meshing with gear 7 and the case of the planetary gear disengaging from gear 7 and meshing with gear 5. If it is required that the reversal times be equal, or at least approximately equal, it is possible to arrange several planetary gears, or to locate the shaft 16 of the driving gear in a position intermediate between shaft 2 and pin 4, providing elastical return means which allows the shaft to move in both senses along the direction defined by the alignment of the shafts 2, l6 and 4. It may also be remarked that the toothed wheels may be replaced by friction wheels. In addition, whereas in the preferred embodiment all shafts are parallel and the gears are all spur gears, other arrangements may be provided, wherein some shafts are transversely located and the gears may be conical or face gears.
FIG. 3 shows, as an example and in schematic form, an arrangement employing spur and face gears and mutually orthogonal shafts. As shown by FIG. 3, two face gears 20 and 21, keyed respectively to shafts 22 and 23, are facing themselves at a suitable distance. The driving gear 24 and the associated planetary gear 25 are interposed between the face gears and have their axis perpendicular to the shafts 22 and 23. If the distance between each of face gears 20 and 21 and the driving gear 24 is smaller than the diameter of the planetary gear, the same conditions already described are obtained. Of course, the shaft of the driving gear should be provided with elastical return means which, by the action of a suitable thrust, allows the driving gear to move along the direction of the arrows F F Alternatively, the gears 20 and 21 may be maintained in the shown positionby axial springs, and be able to slide in the axial direction. It is clear that the essential condition for the operation of the device is that of a relative displacement between the driving gear and the driven gears, to allow the passage of the planetary gear.
The arrangement of FIG. 3 shows, in addition, that the driven gears 20 and 21 may be keyed to the same shaft: that means that by this device it is possible to drive alternately a single shaft in both opposed directions.
The same result may be obtained maintaining the parallel shaft layout, as shown by FIG. 4. In FIG. 4, the planetary gear 31 may mesh with one of the mutually engaged driven gears 33 and 34. Therefore, as the driving gear 36 rotates in the direction indicated by the arrow F and the planetary gear meshes with gear 33, and shaft 35 of this gear is made to rotate in the direction of the arrow F On the other hand, as the planetary gear meshes with gear 34, the direction of rotation of the shaft 36 is the one indicated by the arrow F It is thus possible to cause the alternating motion in both directions'of the shaft 35, the reversal of the motion being caused by a suitable increase of the resistant torque. The device according to the invention is therefore adapted not only for the reversal of the motion of an ink ribbon, but also for all cases wherein the alternating motion of a shaft in both directions of rotation, or an alternating and mutually exclusive motion of two shafts are required.
The invention claimed is:
1. A printing device, including a first take-up spool mounted on a first shaft; a second take-up spool mounted on a second shaft; a base plate supporting said shafts; an ink ribbon extending from one spool to the other spool and adapted to be wound on one spool and unwound from the other spool and vice versa; and drive means for alternately driving a first driven gear coupled to drive said first shaft and a second driven gear coupled to drive said second shaft, said drive means comprising;
a driving gear;
said first driven gear;
said second driven gear;
a planetary gear engaged with said driving gear and arranged for alternately engaging said first and said second driven gear by planetary rotation about said driving gear; and
elastic support means for supporting said driving gear on said base plate to permit relative displacement of said driving and driven gears in .response to an increase in resistant torque applied to one of the driven gears engaged by said planetary gear, whereby said planetary gear is permitted to disengage from one of said driven gears, rotate about said driving gear, and engage the other of said driven gears. .1
2. A printing device, including a first take-up spool mounted on a first shaft; a second take-up spool mounted on a second shaft; a base plate supporting said shafts; an ink ribbon extending from one spool to the other spool and adapted to be wound on one spool and unwound from the other spool and vice versa; and drive means for alternately driving a first driven gear coupled to drive said first shaft and a second driven gear coupled to drive said second shaft, in response to an increase in the resistant torque applied to the gear being driven, said drive means comprising:
a driving gear;
said first driven gear;
said second driven gear;
reverses the motion of said two driven gears, and wherein said first and said second driven gears are permanently mutually engaged. I
4. The device of claim 2, wherein said drive means reverses the motion of said ink ribbon and further comprises a third driven gear permanently engaged with said second driven gear, said first and said second shafts being respectively integral with said first and said third gear.