US 3889893 A
Drive and control apparatus utlizing a pair of gear motors alternating as drive and drag means for the ribbon wherein the drive motor has full voltage applied thereto for driving the ribbon, and the drag motor has reduced voltage applied for maintaining tension on the ribbon. The direction of drive is caused to be reversed by switching bars over which the ribbon travels, the bars being poles of a switch connected to the printer circuitry. The apparatus includes skew means to move the ribbon toward one or the other end of the spools and wherein a skew arm is swingably driven against either an upper or a lower stop by separate drive means caused to be actuated by ribbon sensing means at one end of the ribbon spools.
Description (OCR text may contain errors)
United States Patent Silverman et a1.
RIBBON DRIVE AND CONTROL SYSTEM Inventors: Ira Silverman. Chatsworth, Calif;
James M. Irvine, Lake Orion, Mich,
Computer Peripherals, lnc., Edina, Minn.
Filed: Jan. 14, 1974 Appl. No.: 432,819
US. Cl 242/57.I; 242/67.4 Int. Cl B65h 25/26; B65h 17/02 Field of Search 242/571, 67.4; 101/336;
References Cited UNITED STATES PATENTS Satas 242/57.l Mareggle 242/57.1
Primary Examiner-Edward J. McCarthy Attorney, Agent, or Firm-J. T. Cavender; Wilbert Hawk, Jr.; George J. Muckenthaler  ABSTRACT Drive and control apparatus utlizing a pair of gear motors alternating as drive and drag means for the ribbon wherein the drive motor has full voltage applied thereto for driving the ribbon, and the drag motor has reduced voltage applied for maintaining tension on the ribbon. The direction of drive is caused to be reversed by switching bars over which the ribbon travels, the bars being poles of a switch connected to the printer circuitry. The apparatus includes skew means to move the ribbon toward one or the other end of the spools and wherein a skew arm is swingably driven against either an upper or a lower stop by separate drive means caused to be actuated by ribbon sensing means at one end of the ribbon spools.
17 Claims, 10 Drawing Figures PATENTEDJUN 17 ms 31, 9, 93
saw 2 x FIG. 3
In? J 1 RIBBON DRIVE AND CONTROL SYSTEM BACKGROUND OF THE INVENTION In the field of high speed printing, driving and reversal of the inking ribbon is one of the basic requirements for continuous operation of the unit so as to obtain maximum output with minimum maintenance. Various ways and means have been devised to lower the cost of driving and reversing apparatus and to simplify the operation thereof in view of the higher printing speeds. Representative of one of such ways and means is disclosed in Pensavecchia et al. U.S. Pat. No. 3,185,083 wherein reversal of a ribbon drive mechanism is accomplished by drive means, drag springs, clutch coupling devices, and relay and switch means. Anderson U.S. Pat. No. 3,232,229 shows an ink ribbon feed and reverse mechanism using lever sensing means, a pawl and ratchet arrangement, and spring loading of the sensing lever. Another of such ink-ribbon feeding and reversing operations is an assembly having a pair of drive pawls and ratchets, means on the ribbon for actuating a sensing lever, in turn, operating an interposer, and a reversing switch control device, all as shown in Anderson U.S. Pat. No. 3,584,723. Gotschewski U.S. Pat. No. 3,621,969 discloses an ink ribbon feeding and reversing assembly having a drive train, a clutch device, a control member, and sensing levers mounted on the same axis. Another print ribbon drive and reversing system uses a cross threaded worm, a cooperating pivotal translator as a means of translating a unidirectionally driven ribbon drive shaft between its two driving directions, and resilient detent means to secure engagement of the drive members as disclosed in Bumgardner U.S. Pat. No. 3,633,841. Foley et al. U.S. Pat. No. 3,677,176 shows ribbon control apparatus for high speed printers wherein the ribbon is intermittently and reversibly driven between a pair of reels which are adjustably supported. The reels are driven by reciprocating pawls cooperating with ratchets, and sensing means is provided to select direction of ribbon wind and to re verse the feed direction of the pawls and ratchets. Satas et a]. U.S. Pat. No. 3,730,449 shows and describes ribbon rewinding apparatus having a pair of reels, reversible intermittent reel-driving means, and reelpositioning means for guiding the ribbon. Separate sensors detect the ribbon edge position and other sensors detect completion of ribbon winding and reversal of direction thereof. And, finally, Moneagle et al. U.S. Pat. No. 3,759,456 discloses a ribbon feed and correction device utilizing web axial position detection means, intermittent clutch means, and rotary-to-reciprocating motion conversion means.
SUMMARY OF THE INVENTION The present invention relates to high speed printers and, more particularly, to a ribbon drive and control system for such printers wherein the ribbon is driven in one direction of travel and then, at a desired point in such travel, the direction of travel of the ribbon is re versed to maintain continuous operation of the ribbon drive unit. Additionally, the ribbon is controlled in a manner so as to cause the ribbon to be skewed alternately right and left on the rollers or spools in relation to the line of printing.
A pair of gear motors, energized in a manner so as to be driven in the same direction, are connected to the ribbon spools with full voltage being applied to one motor for driving one of the spools and reduced voltage being applied to the other motor to impose a drag on the other spool for maintaining proper tension on the ribbon. The ribbon is in continuous contact with a pair of switching bars adjacent each spool during its travel in a path between the two spools and near the ends of the ribbon are conductive strips contactable with the switching bars and positioned to actuate reversing mechanism of which the switching bars comprise a part and parcel thereof. Upon reversal of the ribbon, the motor which was imposing drag on the one spool has full voltage applied to it and thereby becomes the driving motor, whereas the other motor receives the reduced voltage for spool drag. The two motors thus alternate between drive and drag action on the spools in the reversing arrangement for the ribbon.
In the skewing of the ribbon, a gear motor is connected to a skew arm which is swingably driven from one to another stop position depending upon presence or absence of one edge of the ribbon at a specified point on the ribbon spool. A sensing pawl is used to detect the presence or absence of ribbon at such point and rotation of the pawl allows its supporting lever to travel sufficiently along a path to bring a magnet mounted on the lever into the field of a Hall-effect switch to actuate the switch and to reverse the gear motor to swing the skew arm and thereby change the angle of the ribbon spools in relation to each other and in relation to the type line. In this manner, the ribbon is caused to be skewed in a rightward and leftward di rection on the spools and to utilize a greater area of the ribbon in the printing operation.
In view of the above discussion, the principal object of the present invention is to provide an improved drive and control system for driving and reversing a ribbon in a high speed printer.
Another object of the present invention is to provide a pair of motors for drive and drag on the ribbon spools for maintaining proper tension on the ribbon.
A further object of the present invention is to provide means for skewing the ribbon in a lateral direction during its travel between one spool and the other.
Additional objects and advantages will become apparent and fully understood from a reading of the following description taken together with the annexed drawings, in which:
FIG. 1 is a side elevational view of a portion of a high speed printer which utilizes the structure of the present invention;
FIG. 2 is a front elevational view of the ribbon apparatus and taken on the plane 2-2 of FIG. 1;
FIG. 3 is a side elevational view taken on the plane 33 of FIG. 2;
FIGS. 4A, B, and C are views of the several positions of the ribbon sensing apparatus; and
FIGS. 5A, B, C, and D are diagrammatic views of the several positions of the ribbon spools and the skew arm.
Referring now to the drawings, FIG. 1 shows a portion of a printer having a printing station for enabling high speed operation by means of the several components thereof. The printer utilizes a type character carrier in the form of a train-like member which is driven continuously in one direction, and a plurality of aligned hammers are selectively driven against the type characters, with the paper and the ribbon being positioned between the hammers and the type characters. The principal motivation for using the horizontal or train type of character carrier is for improved print alignment, and along with closely spaced characters, higher printing speeds are achieved. The trainlike member 12 is supported and driven on pulleys or sprockets (not shown), as the case may be, with the train member carrying a plurality of slugs 14 attached thereto on the outer periphery, and with each of the slugs having eight characters 16 on the face thereof in position to be impacted or struck by the hammers. Appropriate pulsing and firing of the hammers at pre-selected times against the type characters 16 thereby imparts desired printing on the paper 18, which paper is caused to be propelled along a path perpendicular to the path of the driven print hammers, there being a ribbon 20 adjacent the paper to imprint thereon upon striking of the hammers against the paper 18, the ribbon 20 and the type characters 16. A linefinder element 22 is provided adjacent the printing station to aid in positioning the paper 18 both horizontally and vertically in its path through the printing station, thereby accurately positioning the paper in relation to the moving characters 16, as well as to prevent the ribbon 20 from smudging the paper.
Each of the impact hammers 24 is carried on a pivot pin 26 and adapted to be swung thereabout by force from a push rod assembly 28, the hammer having an impact tip 30 engageable with the paper 18. A guide comb 32 is provided to maintain the hammers 24 in a prescribed path of flight and to control the travel and movement thereof, and a forms compressor 34 is positioned under the printing station to urge the paper 18 into proper condition prior to printing thereon. An impression pad 36 is provided for energy control of the hammers 24 in relation to the paper 18 and to accommodate for various forms thicknesses and number of copies, and a return spring mechanism 38 affords antirebound protection for the hammer.
The impact force for the hammers 24 is normally accomplished by means of an electromagnetic apparatus which is pulsed at desired intervals to obtain a high speed printing operation. In describing such apparatus, a supporting structure 40 carries a magnetic core 42 that is energized by a coil 44 to attract an armature 46 pivoted on a pin 48. The pin is held in place and supported by bearing plates 50 (only one of which is shown for each apparatus). The stroke of the armature 46 is limited and controlled by means of a stop 52 on which is mounted a small resilient pad 54, the stop 52 being secured to the core 42 by a screw 55. The entire assembly is rigidly attached to the structure by screws 56. Since it is necessary to provide for compact construction of the print hammers and their associated drive mechanism, the electromagnetic apparatuses are placed in decked and staggered manner, as shown with one apparatus above another, to properly actuate the respective push rods 28 for the impact hammers 24.
The ribbon 20 is caused to be driven from one reel or spool 60 to another reel or spool 62 in a path through the printing station, the reels being carried on and driven by shafts 64 and 66 on one side and supported by shafts 70 and 72 on the other side. The drive of such reels 60 and 62 is of a nature that one reel is driving the ribbon 20 while the other reel is imposing a drag on the ribbon to maintain proper tension thereon during the printing operation, as will be more fully explained. The ribbon carrying reels 60 and 62 are positioned in relation to the printing station so as to minimize the angle of wrap which reduces the amount of drive torque required. The angle of wrap is characterized as that all-inclusive angle from one spool 60 to the other spool 62 and includes the total angle of ribbon travel as it appears on top of spool 60 and below spool 62 and designated by incompleted showing of arrows as the angle 68.
In the front elevational view of FIG. 2, the reels 60 and 62 are shown supported from the shafts 64 and 66 on the driving or left hand side and from the shafts 70 and 72 on the right hand side. The shafts have mandrels 74, 76, 78 and connected thereto for carrying the ends of the reels, the mandrels 78 and 80 being spring loaded, as by coil springs 82 and 84, to effect easy removal and replacement of the reels when desired. The mandrels 74 and 76 are connected to the shafts 64 and 66, respectively, so as to be self-aligning in regard to mandrels 78 and 80 to compensate and allow for skewing of the spools 60 and 62.
The shafts 64 and 66 are journaled in a drive mount ing plate which carries motors 92 and 94 aligned with the shafts, the motors being of the A.C. induction type, wherein the speed can be varied by changing the voltage applied thereto, so as to drive one at full voltage and the other at reduced voltage to effect drive and drag, respectively, on the ribbon reels 60 and 62. The shafts 70 and 72 are journaled in a mounting plate 96 which is free to swing on a pivot 98 carried from a motor mounting plate 100, the arrangement and operation of such plate 96 and pivot 98, in relation to the spools 60, 62 and the plate 100 being more fully described hereinafter.
FIG. 3 shows in more detail the arrangement of additional parts connected with the operation of the ribbon drive and reversing system wherein the ribbon 20, during its travel, is subject to and engageable with a pair of upper bars 102, 104 and a pair of lower bars [06, 108 separated by insulating strips 110 and 112, respectively. The bars extend beyond the ends of the ribbon, as seen in FIG. 2, and are appropriately supported from strucutre in a manner that requires maintained contact of the ribbon 20 with the bars. Near each end of the ribbon is a conductive strip 114 (FIG. 3) extending thereacross and fastened to the ribbon on the bar side thereof and wherein, as the ribbon reaches the end of its travel, the strip 114 contacts the bars 102, 104 or bars 106, 108, as the case may be, spanning the bars and thereby completing a circuit to the printer circuitry, the bars being the two legs of a switch for reversing the direction of drive of the motors 92 and 94. Suffice it to say that these motors are 110 volt rated A.C. gear motors wherein the direction of drive is achieved by energizing one of the motors with full voltage and the other with a reduced voltage, the full voltage or drive motor being controlled by standard and appropriate bi-stable electronic circuitry. The value of the drag on each motor 92 or 94 is initially adjusted to a specifled torque range by means of respective rheostat-type potentiometers 91 and 93, (FIG. 2) the drag being selected to provide for correct ribbon tension during operation. As a matter of information, when the tension is too low, smudging of the printed matter can and does occur, and when the tension is too high, an increased drive torque is required and motor limitations can become a factor. The ribbon 20 is driven only during the printing operation so as to prevent unnecessary ink accumulation and smudging of the printed page. When the printing operation is discontinued for a short time,
there is provided circuitry in the printer controller which shuts off the drive to the ribbon motors 92, 94 but which maintains drag voltage on both motors to secure proper ribbon tension and thereby likewise pre vent smudging of the paper 18.
The ribbon skew sensing apparatus is provided to utilize a greater area of the ribbon in the printing operation, and by reason of the motion of the type carrier 12 tending to pull the ribbon in the same direction therewith so as to wind the ribbon on the spools 60 and 62 in uneven or skewed manner, the axes of the ribbon spools are shifted slightly with respect to the print line by changing the position of the plate 96. The plate 96 may assume one of two positions, either of which wili force the ribbon 20 to skew in one direction or the other, the direction of ribbon skew being determined by ribbon feed direction as well as the position of the ribbon along the spools and the position of the skew plate 96. As mentioned above, the plate 96 is free to swing a limited amount on a pivot 98 carried from the plate 100, the plate 96 being referred to as a skew mounting plate which is securely connected to a drive member 120 (FIG. 2) journaled through a bearing assembly 122 and connected by means of gear box mechanism 124 to a skew drive motor 126. The several positions taken by the skew mounting plate 96 along with the right hand reel shafts 70 and 72 are diagrammatically shown in FIGS. SA, B, C, and D and will be further described hereinafter. The gear box mechanism 124 (FIG. 2) is secured to a mounting bracket 130, in turn, carrying one end of a pin 132 extending toward the skew plate 96 and connected at the other end to a flexible shock member 134, the member 134 also being connected to a pin 135 carried in the mounting plate 100. The shock member 134 is provided in the skew arrangement to absorb any shock derived from swinging of the skew mounting plate 96 in its to-and-fro motion from one stop 136 to the other stop 138, as shown in FIGS. 2 and 3. Since the motion of skewing the ribbon spools 60 and 62 is of a rapid nature, the impact at either of the stops is sufficiently severe to cause shock and vibration at the end of such swinging travel, and the member 134 is of a material which reflects a twisting action therein to absorb the shock at either of the stops.
Mechanism for accomplishing the ribbon spool skewing motion is shown in FIGS. 2 and 4 wherein a ribbon sensing pawl 150 is rotatably carried on a shaft 152 supported from the drive mounting plate 90, such shaft also carrying a ribbon sensing arm 154 adjacent the pawl 150, and a cam follower arm 156 next to the plate 90, the cam follower arm being pivoted and rotatable on the shaft 152, and the ribbon sensing pawl being freely pivotable on a ribbon sensing pawl shaft 155. The arm 156 has a switch actuating magnet 158 attached at the upper end thereof which cooperates with a proximity switch 160 carried on a bracket 162 secured to one leg of the mounting plate 90. The mandrel or hub 76 for the lower reel 62 has a pair of roll pins 164 and 166 diametrically positioned thereon and extending from the left hand side thereof, which pins ro tate with the reel 62 and make contact with the cam follower arm 156 at the cam portion 168. The several positions of the arm 156 and of the sensing pawl 150 are shown in FIGS. 4A, B, and C wherein position 1 (FIG. 4A) indicates that one of the pins 166 is in contact with the cam portion or lobe 168 to rotate such arm. its bracket and the sensing pawl and its arm 154 in a counterclockwise direction, the pawl 150 being positioned to be engageable and non-engageable with the ribbon switching bars 106, 108 about which the ribbon 20 travels in its path between the reels 60 and 62. The ribbon sensing arm 154 is positioned in relation to the cam follower arm 156 so that when the arm 156 is activated by either of the pins 164, 166, the sensing pawl 150 moves away from the switch bars 106, 108.
Position 2 (FIG. 4B) shows the pin 166 having traveled past the cam portion 168 and with the sensing pawl 150 rotated counterclockwise, and position 3 (FIG. 4C) shows the pin 166 in a further rotation with pin 164 about to engage the cam portion 168. A rubber stop 170 is supported in position to be engageable by arm 156 and the support for switch is set to place the switch in close proximity with the magnet 158 to maintain a specified voltage to ground. It is thus seen that arm portion 168 is engaged twice for each revolution of the spool 62.
FIGS. 5A, B, C, and D show the several positions of the skew arm 96 with the right hand side of the reels 60, 62 following the travel of the arm to cause the ribbon 20 to skew to the right or left, depending upon the loca tion of the ribbon on the reels. The principle by which the ribbon skew is accomplished is based on the geometric fact that the ribbon in winding from one spool or reel to another seeks to wind onto the driving or wind-up spool so that the edges of the ribbon are perpendicular to the axis of the wind-up spool. The spool from which the ribbon is being unwound is not neces sarily maintained perpendicular to the line of print and therefore such spool, as Well as the ribbon, assumes an attitude in relation to the driving or take-up spool at that angle of skew depending upon the several factors mentioned above, the direction of ribbon drive, the position of the ribbon along the axis of the two spools, and the position of the skew arm. The ribbon is thus made to skew toward either end of the spool, the most important factor depending upon the skew angle between the axes of the two spools.
Presence or absence of contact of the ribbon sensing pawl 150 with the ribbon 20 at the edge thereof (as seen in FIG. 2) as the ribbon travels across the sensing bars 106, 108 (FIG. 3) determines whether or not to call for ribbon skew. As seen in such FIG. 2, the position of the left edge of the ribbon is detected by the upper portion of the sensing pawl 150 normally held in upright position by the counter balanced portion thereof against the reversal bars 106. 108. If the pawl 150 detects the ribbon 20, the motion of the ribbon moves the pawl out of vertical alignment in relation to its pivot 152. The ribbon skew motor 126 is always powered on in one direction or the other in printing mode wherein the skew arm 96 is in contact with either the upper 136 or lower 138 stop and when conditions call for switching position of the skew arm, the polarity of the drive voltage to the skew motor is reversed, and the motor then moves the skew arm to the alternate stop position with full voltage being maintained on the motor to hold the arm against the stop. As seen in FIG. 3, the stops 136, 138 are adjustable to provide the desired amount of skew for a given printer. In such printer wherein the type characters move in a horizontal plane, the dwell time of the print hammers 24 through the paper 18 and the ribbon 20 against the moving characters or font 16 causes the ribbon to experience a force in the direction of motion of the moving type. This force is proportional to the velocity of the font, the dwell time, and the frequency of the hammer impacts, so such force will be greater as the speed of printing is increased. The parameters of skew angle shift are therefore set out as the direction of ribbon drive, the position of the ribbon 20 along the axes of the spools 60, 62, and the position of the skew arm 96, as mentioned above.
Further to this, upon engagement of the pins 164, I66 with the cam follower arm portion 168 and causing swinging thereof, the sensing pawl 150 is moved away from the ribbon 20, it being seen that the pawl is counter balanced and free to swing on its pivot pin 152. When the sensing pawl 150 is not actuated by action of the roll pins 164, 166, the pawl is held against the ribbon switching bars 106, 108 by a spring 172 (FIG. 4). If the ribbon 20 is present, and moving between the sensing pawl 150 and the switching bars, the sensing pawl is tilted by action of the moving ribbon, allowing the spring 172 to move the cam follower arm 156 so that the magnet 158 moves sufficiently close to the proximity switch 160 to switch voltage levels in the proximity switching circuit. Thus, the ribbon sensing apparatus signals to the switching circuitry of presence or absence of the ribbon between the pawl 150 and the switching bars I06, I08.
Referring again to FIG. 5, skewing the several positions of the skew arm 96 and the skew of the spools 60, 62 in relation to direction of drive of the ribbon 20, FIG. A shows the ribbon being driven by and onto spool 62 is indicated by the arrow 180 and with the skew arm 96 rotated in a counterclockwise direction on pivot 98, as viewed from the left. The ribbon is being made to move in a leftward direction, as shown by the arrow 182. Continuing in the same direction of ribbon drive, as shown in FIG. 5B by arrow 184, the skew arm 96 has been rotated on its pivot 98 in a clockwise direction and the ribbon 20 is being made to move in a rightward direction, as shown by the arrow 186. The correction of ribbon position and skew is therefore accomplished between one or the other position of the skew arm 96, as shown in FIGS. 5A and B, for the direction of drive in the downward direction or onto spool 62.
FIG. 5C shows the ribbon being driven by and onto spool 60 as indicated by the arrow 188 and with the skew arm 96 rotated in a clockwise direction on pivot 98, as viewed from the left. The ribbon 20 is here being made to move in a leftward direction, as shown by the arrow 190, Again continuing in the same direction of ribbon travel or drive, as shown in FIG. SD by arrow 192, the skew arm 96 has been rotated on its pivot 98 in a counterclockwise direction and the ribbon is being made to move in a rightward direction, as shown by the arrow 194. Again, the correction of ribbon position and skew is accomplished between one or the other position of the skew arm 96, as shown in FIGS. 5C and D, for the direction of drive in the upward direction or onto spool 60.
Further to this and in view of the fact that the ribbon always seeks to wind onto the driving spool perpendicular to its axis, when the end of the ribbon is sensed by contact of the strip 114 with the switching bars 102, 104 or 106, 108, as the case may be, to cause reversal of the drive motors 92, 94, the motor that was driving now becomes the drag motor and vice versa. Thus, if
the position of the ribbon along the axis of the respective spool still requires the ribbon to be laterally moved therealong in the same direction for correction in winding onto the driving spool, as it was prior to reversal of the drive and drag motors, the skew arm 96 is rotated or swung on its pivot by action of the ribbon sensing pawl and its associated mechanism to maintain the same direction of ribbon skew.
It is thus seen that herein shown and described is a ribbon drive and control system which is substantially self contained in that no external sensing or switching is required. The apparatus for such system enables the accomplishment of the objects and advantages mentioned above, and while only one embodiment of the invention has been disclosed herein, certain variations may occur to those skilled in the art. It is contemplated that all such variations, not departing from the spirit and scope of the invention hereof, are to be construed in accordance with the following claims.
What is claimed is:
l. Ribbon drive and control mechanism comprising a pair of reels for carrying said ribbon in a path past a station for printing operations, said ribbon having conductive elements thereon, a
drive motor connected to each of said reels for driving thereof, potentiometer means connected with each of said drive motors for providing a predeter mined voltage thereto, each of said motors having different voltages applied thereto for providing driving of one reel in one direction while providing drag on the other reel and in the same direction, and
switching means including a pair of spaced members positioned adjacent each of said reels and contactable by said conductive elements on said ribbon near the ends thereof for actuating said switching means thereby reversing the direction of said drive motors to alternately provide for drive and for drag of the reels.
2. The mechanism of claim 1 wherein said spaced members comprise a pair of elongated bars extending in parallel relation with said reels.
3. The mechanism of claim 2 including a spacer connected between and separating each pair of said elongated bars to provide switch legs for actuating said switching means for reversing said drive motors upon contact by one of said conductive elements with said bars.
4. The mechanism of claim 1 wherein said spaced members extend beyond the edges of said ribbon and said conductive elements are elongated metallic strips secured to said ribbon and engageable with said spaced members.
5. The mechanism of claim 1 including arm means pivotally connected to one end of said reels and means for driving said arm means in swingable manner to effect skewing of said reels for axially moving said ribbon therealong.
6. The mechanism of claim 5 including ribbon-edge sensing means for actuating said arm means drive to swing said arm means from one to another predetermined position.
7. The mechanism of claim 6 wherein said ribbonedge sensing means comprises a sensing pawl for detecting absence of said ribbon for actuating said arm drive means.
8. The mechanism of claim including adjustable stops for limiting the swinging of said arm means by said drive means.
9. The mechanism of claim 7 including a cam follower arm pivotally connected in relation to one of said reels, said one reel having camming means thereon engageable with said follower arm. and switching means associated with said follower arm for reversing said arm means drive upon absence of ribbon contact by said sensing pawl.
10. In a high speed printer, mechanism for driving and controlling a ribbon, comprising a pair of reels operably positioned adjacent a printing station for carrying said ribbon in a path there through, means including a pair of motors for driv ing said reels in a manner whereby a driving force is imposed on one reel and a drag force is imposed on the other reel to maintain tension in said ribbon, and
means including a pair of spaced members positioned adjacent each of said reels and a conductive element secured to said ribbon near each end thereof engageable with a respective pair of spaced mem bers upon travel of said ribbon from one reel to the other for reversing the direction of drive of said ribbon to alternately drive and drag said reels.
11. The mechanism of claim 10 wherein said means for reversing includes a pair of elongated bars positioned adjacent said reels in parallel relation therewith and contactable by a respective conductive element for effecting reversal of the ribbon.
12. The mechanism of claim ll including a spacer connected between and separating each pair of elongated bars to effect switching legs and wherein said means for reversing includes switching means actuable by contact of said conductive element with said switching legs.
[3. The mechanism of claim 10 including arm means pivotally connected to one end of said reels and means including a motor for driving said arm means in swing able manner to effect skewing of the reels for axially moving said ribbon therealong.
14. The mechanism of claim 13 including ribbonedge sensing means for actuating said arm means drive motor to swing said arm means from one to another predetermined position.
15. The mechanism of claim 14 wherein said ribbonedge sensing means comprises a sensing pawl for tie tecting absence of said ribbon for actuating said arm drive means motor.
16. The mechanism of claim 13 including adjustable stops for limiting the swinging of said arm means by said drive means motor.
17. The mechanism of claim 15 including a cam follower arm pivotally connected in relation to one of said reels, said one reel having cumming pins thereon engageable with said follower arm, switching means including a proximity switch associated with said follower arm, the pivoting of said follower arm permitting said switching means to reverse said arm drive means motor for swinging of said arm means from one to the other