PRINTER RIBBON DRIVE MECHANISM

Abstract: A ribbon (40) is driven past the printing station of a printer (12) only when a reciprocating print head (22) is moved in the right-to-left direction across the printer (12). An endless timing belt (46), which reciprocates together with the print head (22), causes rotation of a gear pulley (48) that is in mesh with an idler gear (66). The idler gear (66) is supported on a pair of projecting fingers (80, 82) of a plate (68) that is swingable on the spindle (56) supporting the gear pulley (48). The idler gear (66), being maintained in mesh with the gear pulley (48), is responsive to the direction of rotation of the gear pulley (48) through a drag effect of the ends (84, 86) of the projecting fingers (80, 82) on the bottom surface of the idler gear (66), to cause swinging movement of the plate (68) in accordance with the direction of rotation of the gear pulley (48), such that the idler gear (66) is in mesh with a ribbon drive gear (88) only when the print head (22) moves in a right-to-left direction across the printer (12).

Description: PRINTER RIBBON DRIVE MECHANISM Technical Field This invention relates to printers of the kind including print head drive means adapted to drive a print head in a reciprocating manner across the printer. Background Art In the wire matrix printer which is utilized for receipt and journal printing operation, the print head structure may be a multiple element type and may be horizontally disposed with the wire elements aligned in a vertical line and supported on a print head carriage which is caused to be moved or driven in a horizontal direction for printing in line manner across the receipt or journal paper and wherein the drive elements or transducers may be positioned in a circular configuration with the respective wires leading to the front tip of the print head. In such wire matrix printer which is utilized for business forms or like record media printing operation, the print head may be oriented in a manner wherein the nose is pointed downward for printing on the form, slip or like media while the carriage and print head are moved above and across the form or media in the horizontal direction. In printers of the kind specified, it is known to provide a mechanism for driving and inking ribbon. Disclosure of the Invention It is an object of the present invention to provide a printer of the kind specified having a simple, low-cost ribbon drive mechanism. Therefore, according to the present invention, there is provided a printer of the kind specified, characterized by: a gear pulley operably associated with said print head drive means and rotatable about a pivot in a clockwise or counterclockwise direction according to the direction of movement of said print head; an idler gear support member adapted to support an idler gear and swingably mounted on said pivot, said idler gear being maintained in mesh relationship with said gear pulley, and said support member including support projections engaging one surface of said idler gear so as to provide a drag effect thereon; and ribbon drive means including a ribbon drive gear, whereby said support member is adapted to swing in response to rotation of said gear pulley such that said idler gear is maintained either in or out of mesh relationship with said ribbon drive gear according to the direction of rotation of said gear pulley. Brief Description of the Drawings One embodiment of the invention will now be described by way of example, with reference to the accompanying drawings, in which: Fig. 1 is a perspective view of a printer incorporating the subject matter of the present invention; Fig. 2 is a view taken along the line 2-2 of Fig. 3, less a lower frame portion of the printer which supports the ribbon drive mechanism; Fig. 3 is a side elevational view of the ribbon drive mechanism; Fig. 4 is a view similar to Fig. 2 and showing certain parts in a disengaged position; Fig. 5 is a top view of the idler gear plate member; and Fig. 6 is a view showing two positions of the lower flange portion of the idler gear. Best Mode for Carrying Out the Invention Prior to describing the structure in detail, it should be noted that the printer of the present embodiment is a multi-function type that can accommodate a receipt, a journal and a slip or form which form consists of one or more parts. The printer can be set in one of five different modes of operation which include printing a journal only, printing a receipt only, printing a receipt and a journal, printing a slip or form only, or printing a slip or form and a journal. The journal and the receipt can accommodate 42 columns of printing and the slip or form can accommodate 46 columns of printing. Referring now to the drawing, Fig. 1 shows a perspective view of a printer 12 having a front portion 14, a right side 16, a left side 18, and a rear portion 20. A wire matrix print head 22 is moved in a side-to-side manner by suitable motor drive means (not shown), located at the right front corner of the printer 12. A journal station or module 24 is provided at the right hand side of the printer 12 and includes a supply roll 26 of journal paper that is guided past the journal print station platen 28 and is rewound on a take-up roller 30 by a step-type drive motor (not shown). A receipt station or module 32 is provided at the left hand side of the printer 12 and includes a supply roll 34 of receipt paper that is guided past the receipt print station platen 36 and is driven by a step-type drive motor (not shown) . The journal station 24 and the receipt station 32 are separated by six character spaces. A ribbon cassette 38 of the operator-changeable type is positioned to the rear of the print head 22 (toward the viewer of the illustration in Fig. 1) and the ribbon 40 is driven in one direction from right to left in a path between the front portion of the print head 22 and the record media (journal, receipt or slip). A slot 42 is provided at the left front side for insertion of the slip which can be inserted from the front of the printer, from the side thereof or from the top in a path in front of the receipt paper at the receipt station. Figs. 2 and 3 illustrate the ribbon drive mechanism of the present embodiment wherein a toothed endless timing belt 46 driven by the print head motor drive means (not shown) is trained around a toothed gear pulley generally designated as 48. The gear pulley 48 includes an upper gear portion 50 around which the timing belt 46 is in mesh, a flange portion 52 adjacent the upper gear portion 50, and a lower gear portion 54. A pin or stud 56 is molded into the frame 58 of the printer 12 and extends upwardly through the lower gear portion 54, the flange portion 52 and the upper gear portion 50. An E clip 60 is provided around the stud 56 and above a top flange 62 to hold the several parts in position. A ball bearing 64 is provided within the gear pulley 48 for journaling the upper gear portion 50 on the stud 56. An idler gear, generally designated as 66, is provided adjacent the gear pulley 48 to mesh with the lower gear portion 54 of the gear pulley 48. An idler gear plate 68 (see also Fig. 5) has a hub portion 70 for bearing on the stud 56 and has an extending or projecting central portion 72 which has an arcuate portion 74 for engaging with a middle portion 76 of the idler gear 66. The arcuate portion 74 extends about two-thirds around the circumference of the middle portion 76 of the idler gear 66. The frame 58 includes an opening 78 for a lower flange portion 79 of the idler gear 66. The opening 78 is of sufficient size to enable sideways movement of the lower flange portion 79 when the idler gear 66 is caused to be swung in a horizontal direction. The idler gear plate 68 includes two spring elements or fingers 80 and 82 extending in the same direction as the central portion 72 but bifurcated therefrom. The finger 80 has an upwardly extending, rounded projection 84 and the finger 82 has a like upwardly extending, rounded projection 86. The projections 84 and 86 are positioned on the centerline of and support the idler gear 66. A cassette drive gear, generally designated as 88, is mounted on a stud or pin 90 that is molded into the frame 58 of the printer 12. A drive spindle 92 is integral with the drive gear 88 and includes a drive portion 94 that extends upwardly to engage with a drive member (not shown) of the cassette 38. The frame 58 of the printer 12 has a ridge or raised portion 96 for supporting the drive gear 88 at the proper level to mesh with the idler gear 66. While Fig. 2 shows the ribbon drive mechanism in position for driving the ribbon 40, Fig. 4 is a similar view and is provided to show the mechanism in a ribbon non-driving position. Fig. 5 shows a top view of the idler gear plate member 68 and illustrates the spring fingers 80, 82 with the rounded projections 84, 86 at the ends of the fingers 80, 82. The rounded projections 84, 86 provide a support for the idler gear 66 and effect a drag on the idler gear 66 thereby causing the gear plate 68 to swing on the pivot stud 56 in response to rotation of the gear pulley 48, as will be explained more fully hereinafter. Fig. 5 also shows the slot 102 in the idler gear plate member 68 which enables and provides a spring effect for the arcuate portion 74 of the plate member 68 to partially surround the middle portion 76 of the idler gear 66. Fig. 6 is a view showing the aperture or opening 78 in the frame 58 of the printer 12 and the two positions of the lower flange portion 79 of the idler gear 66. The flange portion 79 is swung against one edge 98 of the opening 78 when the idler gear 66 is fully engaged with the cassette drive gear 88 and the flange portion 79 is swung against the opposite edge 100 of the opening 78 when the idler gear is disengaged from the drive gear 88. In the operation of the ribbon drive mechanism, when the print head 22 moves from right to left across the printer 12, the cassette drive gear 88 drives the ribbon 40. As illustrated in Fig. 2, which is looking in the direction of line 2-2 of Fig. 3 or from the bottom of the ribbon drive mechanism, the timing belt 46 causes clockwise rotation of the gear pulley 48 and counterclockwise rotation of the idler gear 66. The cassette drive gear 88 is driven in a clockwise direction by the idler gear 66 and the spindle 92 is driven in the same direction for driving or advancing the ribbon 40 past the printing station. The movement of the timing belt 46 and the clockwise rotation of the gear pulley 48 provides for and effects a drag on the idler gear 66 through the projections 84 and 86 supporting the idler gear 66. This drag effect causes the idler gear 66 to swing the gear plate 68 in a clockwise direction around the center of the gear pulley 48 on the stud 56 thereby bringing the idler gear 66 into mesh position with the drive gear 88, since the idler gear 66 is maintained in mesh with the lower gear portion 54 of the gear pulley 48. When the print head 22 moves from left to right across the printer 12, the cassette drive gear 88 is not driven and the ribbon 40 is stationary. As seen in Fig. 4, the timing belt 46 causes counterclockwise rotation of the gear pulley 48 and the idler gear 66 causes the gear plate 68 to swing in a counterclockwise direction around the center of the gear pulley 48 on the stud 56 by means of the drag effect through the projections 84 and 86 of the idler gear plate 68 with the bottom surface of the idler gear 66. The idler gear 66 thus moves out of mesh with the ribbon drive gear 88 with the result that the ribbon 40 is not driven when the print head 22 is moved from left to right. The swinging movement or amount of swing of the idler gear plate 68 is controlled or limited by the size of the circular recess or opening 78 relative to the lower flange portion 79 of the idler gear 66. Fig. 6 shows the opening 78 and the extent of travel of the lower flange portion 79 from one side or edge 98 of the opening 78 to the other side or edge 100. The opening 78 is sized to limit the travel of the idler gear 66 when it swings out of mesh with the ribbon drive gear 88 (Fig. 4) and also prevents overmesh or excessive mesh with the ribbon drive gear 88 (Fig. 2) during the cycle of ribbon feed or advance. The ribbon 40 is driven or advanced only when the print head 22 is driven from right to left and the ribbon 40 is stationary in the opposite direction of travel of the print head 22. It is thus seen that herein shown and described is a ribbon drive mechanism that is responsive to direction of travel of the print head and wherein the ribbon 40 is driven or advanced during only one direction of print head travel.

Claims: What is claimed is: 1. A printer including print head drive means adapted to drive a print head (22) in a reciprocating manner across said printer (12), characterized by: a gear pulley (48) operably associated with said print head drive means and rotatable about a pivot (56) in a clockwise or counterclockwise direction according to the direction of movement of said print head (22); an idler gear support member (68) adapted to support an idler gear (66) and swingably mounted on said pivot (56), said idler gear (66) being maintained in mesh relationship with said gear pulley (48), and said support member (68) including support projections (84, 86) engaging one surface of said idler gear (66) so as to provide a drag effect thereon; and ribbon drive means (88, 92, 94) including a ribbon drive gear (88), whereby said support member (68) is adapted to swing in response to rotation of said gear pulley (48) such that said idler gear (66) is maintained either in or out of mesh relationship with said ribbon drive gear (88) according to the direction of rotation of said gear pulley (48). 2. A printer according to claim 1, characterized in that said print head drive means includes a timing belt (46) adapted to be driven in a reciprocating manner in accordance with the direction of movement of said print head (22); and being adapted to drive said gear pulley (48). 3. A printer according to any one of the preceding claims, characterized in that said idler gear support member (68) includes a hub portion (70) mounted on said pivot (56) and in bearing engagement with said gear pulley (48), and an extended portion having spaced spring elements (80, 82) carrying said support projections (84, 86). 4. A printer according to claim 3, characterized in that said idler gear support member (68) includes an extending portion (72) having an arcuate portion (74) adapted to engage with a central portion (76) of said idler gear (66). 5. A printer according to claim 4, characterized in that said idler gear (66) includes a flange portion (79) adapted to move in an opening (78) provided in a frame portion (58) of said printer (12), thereby limiting the amount swing of said idler gear support member (68). 6. A printer according to any one of the preceding claims, characterized in that said ribbon drive means includes a spindle (92) integral with said ribbon drive gear (88) and adapted to engage with a drive member of a ribbon cassette associated with said printer (12) .

Inventors: BOSSACK THOMAS J, LEWIS BRADLEY W, WALKER ALAN H, BOSSACK, THOMAS, J., LEWIS, BRADLEY, W., WALKER, ALAN, H.
Applicants: NCR CO, NCR CORPORATION
Application year: 1989
Main classification: B41J33
IPC codes: B41J33