Abstract:
An apparatus for guiding a carbon ribbon from a supply reel to a take-up reel includes an adjusting member which is used for securing a guide rod around which the carbon ribbon passes to a fixed plate. A bolt passes through an off-center hole in the adjusting member and upon tightening of the bolt, one end of the rod is secured to the fixed plate. The other end of the rod is pivotably secured in a base plate. Therefore, by turning the adjustment member, the location of the off-center hole is changed and the inclination of the rod is adjusted. By suitable setting of the adjustment member, the orientation of the rod is adjusted so that a uniform tension is applied across the ribbon tape to thereby prevent wrinkling or misalignment thereof.

Description:
This is a continuation of application Ser. No. 774,295 filed on Sept. 10, 1985, now abandoned. 
    
    
     BACKGROUND OF THE INVENTION 
     The present invention relates to a transport guide device for guiding a carbon ribbon between a ribbon supply section and a ribbon take-up section, and more particularly to a carbon ribbon transport guide rod which is adjustable to apply a uniform tension across the width of the carbon ribbon. 
     Generally, carbon ribbon transport guide devices for use in thermal transfer or impact type printers include fixed guide rods, rotatable guide rods and guide plates which guide the ribbon from a supply section to a printing section and then to a ribbon take-up section. The ribbon is tensioned appropriately by mechanical loads applied to it both on the ribbon supply side and on the take-up side. 
     However, particularly with very wide ribbons, slight differences in tension develop across the width of the ribbon, causing wrinkling, misalignment and improper guidance of the ribbon. 
     Elimination of such wrinkling and misguidance of the ribbon requires delicate adjustment of the various ribbon guide rods of the ribbon supply and take-up sections. The adjustment is quite complex and considerable training is required for it. 
     SUMMARY OF THE INVENTION 
     It is an object of the present invention to provide a carbon ribbon transport guide device which permits easy adjustment of the tension at each side of the ribbon to prevent wrinkling and misguidance of the ribbon. 
     To attain the above object, the present invention comprises an adjusting member for adjusting the inclination of a ribbon guide rod across which the ribbon travels. Through inclination adjustments, the tension which the rod applies to the ribbon can be varied until a position is found at which the tension across the entire width of the ribbon becomes uniform. To this end, the adjusting member has an offset, i.e. eccentric fixing hole through which a retainer passes for securing one end of the ribbon guide rod to a fixed plate of the transport guide device. By rotating the adjusting member, the position of the eccentric hole with respect to the plate changes, for changing the inclination of the rod with respect to the plate. The tension at either end of the ribbon is thereby adjustable. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a plan view of a printer including an embodiment of a carbon ribbon transport device according to the present invention. 
     FIG. 2 is a cross-sectional view through line II--II in FIG. 1. 
     FIGS. 3 and 4 are plan views of the adjusting member of the device which show different positions thereof to facilitate understanding of the present invention. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     An embodiment of the carbon ribbon transport guide device according to the present invention is now described with reference to the drawings which show the invention in a non limiting embodiment of a thermal transfer type printer. 
     As illustrated in FIG. 1, a printer unit 1 is provided with a plate 2 on which a printing section 3, primarily comprising a platen 4 and heat sensitive head 10, is located. 
     The platen 4 of the printing section 3 is in the form of a roller that is rotatably supported on the plate 2 by means of its shaft 5. Platen 4 is rotated by a pulse motor PM, via a belt 6. Opposite the platen 4 is a head support 8, which is pivotally attached to the plate 2 by a pivot 7. A heat sensitive head 10 is attached to head support 8 via a strip spring 9. A compressed spring 11 disposed between the head support 8 and the heat sensitive head 10 urges the heating portion 10a of the heat sensitive head 10 into pressure contact with the platen 4. 
     Head support 8 is provided with a pair of symmetrically opposed, independently pivotable, support levers 12. The end of each lever 12 supports a rotatable follower roller 13. A pair of springs 15 are disposed between support levers 12 and a pair of pins 14 that are located on the head support 8. Springs 15 are tensioned to urge the follower roller 13 into pressure contact with the platen 4. Head support 8 may be turned clockwise, as shown by the arrow of FIG. 1, to facilitate the loading of a below-described label strip 16 and carbon ribbon 29 therethrough. During a printing operation, the head support 8 is fixed by a fixing mechanism, not shown, at an angle whereby the heat sensitive head 10 and the follower roller 13 are brought into pressure contact with the platen 4. 
     A label supply portion 20 is rotatably mounted on the plate 2 and is adapted to rotate while being subjected to a suitable mechanical load. Label supply portion 20 holds a reel of label strip 16 having the form of a printing paper which consists of a flexible support layer 17 to which a large number of contiguous labels 18 are temporarily adhered. After label strip 16 passes between the platen 4 and the heat sensitive head 10 and then past follower roller 13, a label separating pin 21 turns only the support 17 sharply through an approximately right-angle to separate the labels 18 from the support 17. The support 17 from which the labels 18 have been separated is reeled up by a support take-up portion 23 that is driven by the pulse motor via a belt 22. 
     The transported label strip 16 is suitably tensioned by a tension roller 25 which is rotatably mounted on a support arm 24. Support arm 24 is, in turn, pivotably attached to the plate 2, and a spring 26 urges the tension roller 25 against the label strip 16. A guide plate 27 guides the label strip 16 and provides a base on which a photoelectric detector 28 is disposed at one side thereof to detect each of the labels 18. 
     Plate 2 also supports a ribbon supply section 30 which is able to rotate while being mechanically loaded and which supports a reel of thermal transfer type carbon ribbon 29. The carbon ribbon 29 from the ribbon supply section 30 is guided to a superimposed position over the label strip 16 so that they pass together between the platen and both the heat sensitive head 10 and follower roller 13. Later, the carbon ribbon 29 is taken up on the ribbon take-up section 31. Ribbon take-up section 31 is rotatably mounted on the plate 2 and is also rotated by the pulse motor PM via a belt 32. 
     As the carbon ribbon 29 travels from the ribbon supply section 30 to the ribbon take-up section 31, it is guided along a guide plate 33 and around ribbon guide rods 34, 35, 36 and 37. The guide plate 33 includes an integrally formed fixing plate 38 which extends generally a predetermined distance away from and in parallel to the plate 2. Ribbon guide rods 34 and 37 are secured by screws between plate 2 and fixing plate 38 and provide supports therebetween. Ribbon guide rod 35 is also secured by a screw to retain its position with respect to head support 8. The rod 35 is located at a position where the carbon ribbon 29 and the label strip 16 meet and are superimposed over each other. 
     In a manner similar to rods 34 and 37, ribbon guide rod 36 is also fixed between plate 2 and fixing plate 38, except that it is also provided with means for adjusting the tension at the two edges of the carbon ribbon 29 which passes over it. The tension adjusting means are explained below with reference to FIGS. 2 to 4. 
     As shown in FIG. 2, the lower end of the rod 36 in that Figure is supported by a pillar-shaped bearing member 40 which has a threaded hole 40a formed along the lower part of its axis and a bearing inset 40b formed along the upper part of its axis. Bearing member 40 is fixed to the plate 2 by a bolt 41 which passes through the hole 2a formed in the plate 2 and which screws into threaded hole 40a. The rod 36 has a round-shaped engaging portion 36a formed integrally along its lower axis, and the portion 36a fits into the inset 40b of the bearing member 40. 
     An adjusting member 42 is provided at the top end of ribbon guide rod 36. The adjusting member 42 includes a hexagonal operating portion 42a at the top and a circular free-fit portion 42b therebelow which fits into a round fixing hole 38a provided in plate 38. Therefore, adjusting member 42 can be turned relative to the fixing plate 38. An axially eccentric through-hole 42c is located slightly off the center of the circular free-fit portion 42b. 
     A bolt 43 passes through the through-hole 42c of adjusting member 42 and screws into the threaded hole 36b located along the top of the central axis of rod 36. Bolt 43 secures ribbon guide rod 36, fixing plate 38 and adjusting member 42 to each other. 
     The rod 36 is supported between plate 2 and fixing plate 38. The inclination of the rod can be altered by the turning adjusting member 42, as explained below. 
     Operation of the pulse motor PM transports the label strip 16 and carbon ribbon 29 between the platen 4 and the follower roller 13. Thereafter, the support 17 of the label strip 16 is taken up by the support take-up portion 23, and the carbon ribbon 29 is taken up by the ribbon take-up section 31. While the label strip 16 and carbon ribbon 29 are being transported, the desired information is printed on the labels by the heating portion 10a of the heat sensitive head 10. 
     The carbon ribbon 29 is guided in part by ribbon guide rods 34, 35, 36 and 37. However, slight adjustment differences in the conditions of the supply, the guide, and the take-up means can cause variations in the tension that is applied across the width of the carbon ribbon 29 so that one side is tensioned more than the other. This may cause wrinkling of the section of the ribbon where less tension is applied, producing a crooked carbon ribbon 29. 
     However, in accordance with the present invention, by loosening the bolt 43, turning the adjusting member 42 to a desired degree and then retightening the bolt 43, the tension across the width of the carbon ribbon 29 can be equalized. This is enabled because through-hole 42c of the adjusting member 42 is located at an off-center position so that when adjusting member 42 is turned, through-hole 42c and the bolt 43 turn through a circular path A, as shown in FIGS. 3 and 4, which selectively alters the inclination of rod 36 with respect to the plate 2. Referring to FIG. 3, if for example the tension at the lower part A of the carbon ribbon 29 is higher than that at the upper part B thereof, through-hole 42c is rotated such that the rod 36, moves outwardly toward the ribbon 29. If the tension at the upper part is higher, adjusting member 42 is turned the other way to move the through-hole 42c away from the carbon ribbon 29 as shown in FIG. 4. 
     In the above embodiment, bolt 43 comprises the means for fixing the adjusting member 42 to the ribbon guide rod 36. As shown, bolt 43 is screwed into the threaded hole 36b in the ribbon guide rod 36. Alternately, a bolt may be formed integrally with the ribbon guide rod 36 along the upper axis thereof. The bolt has the form of a stud which passes through the hole 42c. A nut would then be provided for tightening the adjusting member 42. Further, instead of the bearing member 40 which is used as the support at the lower end of the ribbon guide rod 36, rod 36 may be bolted directly to the plate 2. In this case, the inner diameter of the hole 2a in the plate 2 would need to be somewhat larger than the diameter of the bolt to permit the rod 36 to tilt with respect to the plate 2. Finally, although the above embodiment shows the adjusting member 42 to be located at the top end of the ribbon guide rod 36, it is possible to form the device so that the adjustment is carried out at the lower part of the ribbon guide rod 36, or selectively at both the lower part and the upper part thereof. 
     As described above, in accordance with the invention, an adjusting member is provided which has an off-center fixing hole through which a bolt used as a fastening means passes. By rotating the adjustment altering member the inclination of the ribbon guide rod is altered, thus controlling the degree of tension on the two edges of the carbon ribbon. Consequently, ribbon wrinkling and improper guidance of the ribbon are prevented. 
     Although the present invention has been described by reference to specific embodiments thereof, many modifications, variations and other uses will now become apparent to those skilled in the art. It is preferred therefore that the present invention be limited not by the specific embodiments disclosed herein, but only by the appended claims.