APPARATUS FOR FEEDING MEDIA

Abstract: An apparatus for feeding media (24) along a guide path including first and second feed roller means (50,74) respectively carried on first and second shafts (52,72) respectively having first and second gear means (56,78) mounted thereon. Drive means (98,100,108) is provided for moving the first feed roller means (50) relative to the guide path, and an arm (70) is pivotably supported on the second shaft (72) and biased for rotation in one direction about said second shaft (78). Cam means (43) is operably associated with the arm (70) whereby rotation of the arm (70) brings about rotation of the cam means (43). A cam surface engaging with a projection (114) on the arm (70) limits the rotation of the arm (70) in a direction opposite to said one direction.

Description: The present invention relates to an apparatus for feeding media and more particularly, but not exclusively, to an apparatus for feeding record media to a printing station in a printer. In a dot matrix printer which is used for receipt, slip and journal printing operations, the receipt paper from a supply roll thereof is driven through the receipt/slip printing station. The receipt/slip printing station is also used for printing on a slip or like business form. A known paper feed arrangement includes a supply roll for the receipt paper, a first feed roller and associated first pressure roller, and a second feed roller and associated second pressure roller. The conventional arrangement also includes a first gear, an intermediate gear and a second gear on associated shafts. When the first gear is driven in a counterclockwise direction, the first feed roller is rotated, with the help of the first pressure roller, to advance the receipt paper to the printing station. Rotation of the first gear rotates the intermediate gear and the second gear which drives the second feed roller for advancing the receipt paper from the supply roll. When the first gear is moved down and the first feed roller is separated from the first pressure roller to provide a port for the slip. An arm is pivoted on the shaft that carries the second feed roller, such arm being biased by a spring. When the first gear is moved down, the arm is rotated counterclockwise by the spring, so that engagement of the first gear and the intermediate gear on the arm is maintained. In the known arrangement the intermediate gear is pressed against the first gear only by the tensile force of the spring. When the first gear is rotated counterclockwise to feed the receipt paper, the first gear kicks the intermediate gear into rotation and a force is generated to cause the arm to rotate clockwise against the tensile force of the spring. The spring also tends to provide a force which will cause the arm to be biased in the counterclockwise direction and, by engagement of intermediate gear with the first gear, tends to move the first gear down and away from the first pressure roller. In a normal situation, these forces are balanced to correctly feed the receipt paper. However, in case of a force on the first gear that is greater than that of the spring acting on the arm, the gear may be moved down and the feed roller may not correctly advance the paper. For example, the supply roll may contact the side wall of the container thereof and increase the frictional force so that the arm tends to rotate against the tensile force of the spring. This may cause skipping of the teeth between the first gear and the intermediate gear, and cause problems in advancing or feeding of the receipt paper, as well as damage to the teeth of the gears. One of the objects of the present invention is to overcome the above disadvantages of the known paper feed arrangement. Accordingly, the present invention provides an apparatus for feeding media along a guide path including first and second feed roller means respectively carried on first and second shafts respectively having first and second gear means mounted thereon, drive means for moving said first feed roller means in a first direction from a first position to a second position against the action of biasing means, and intermediate gear means mounted on an arm in meshing engagement with said second gear means, said arm being pivotally supported on said second shaft and biased for rotation in a second direction about said second shaft so as to urge said intermediate gear means into meshing engagement with said first gear means, said arm being rotated in said second direction when said first feed roller means moved in said first direction, characterized by cam means having a fixed axis of rotation and operably associated with said arm whereby rotation of said arm brings about rotation of said cam means, said cam means having a cam surface engaging with said first shaft so as to limit movement of said first roller means in said first direction, and stop means arranged to engage with a projection on said arm for limiting the rotation of said arm in a direction opposite to said second direction, said stop means being operably associated with said drive means whereby said stop means is in engagement with said projection both when said feed roller means is in said first position and in said second position. An embodiment of the present 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 dot matrix printer incorporating the subject matter of the present invention; Fig. 2 is a right side elevational view in diagrammatic form showing the arrangement of certain elements of the printer; Fig. 3 is a left side elevational view in diagrammatic form showing the arrangement of such certain elements of the printer; Fig. 4 is a perspective view showing structure of a preferred embodiment of the present invention, certain of the parts being shown in exploded manner for clarity; Figs. 5A and 5B are side elevational views of the structure of Fig. 4 and illustrating the arrangement of the parts for driving two types of record media for printing operation; and Figs. 6A and 6B are similar views and showing drive mechanism in a conventional printer. Referring now to Fig. 1, a printer 10 is designed as a two station, receipt/slip and journal printer. The receipt/slip printing station occupies a front portion 12 and the journal printing station occupies a rearward portion 14 of the printer. A slip table 16 is provided along the left hand side of the printer 10. A front cover 17 swings toward the right to expose certain operating parts of the printer 10. Figs. 2 and 3 are right and left side elevational views and show certain elements of the printer 10 in diagrammatic form. The receipt/slip portion 12 and the journal portion 14 include individual print wire solenoids (not shown) along with a ribbon cassette 18 for the receipt/slip printing operation and a ribbon cassette 20 for the journal printing operation. A roll 22 of receipt paper is journaled at the front of the printer 10 and the receipt paper 24 is driven and guided by appropriate pairs of rollers, as 26, 28, 30 and 32 in a path past the receipt/slip printing station for printing operation and for issuance of a receipt 33 after cutting thereof from the receipt paper 24. A supply roll 34 of journal paper is positioned in a cradle at the rear of the printer 10 and the journal paper 36 is driven and guided by appropriate pairs of rollers, as 38 and 40, in a path from the supply roll 34, past the journal printing station, and onto a take-up roll 42. A timing plate 43 (Fig. 2) is provided at the receipt/slip printing station for positioning the receipt/slip feed rolls. Fig. 4 is a perspective view of the record media feed mechanism according to a preferred embodiment of the present invention. Prior to describing the invention in detail, it is convenient to mention certain aspects of a record media feed operation. In a printer for printing on receipt paper and on a slip at one printing station, the receipt paper and the slip are changed in accordance with the desired printing operation. When the slip is to be printed, the receipt paper is retracted from the printing station before the slip is inserted into the printer and the slip is then driven or advanced to the proper position for printing operation. A feature of the slip printing operation is the opening and closing of the feed rollers for enabling insertion and withdrawal of the slip at the printing station. When printing is to be performed on the receipt paper, the slip is removed from the printing station and the receipt paper is advanced to the proper position for printing operation. A plurality of feed rollers are provided for feeding the receipt paper and the slip and a gear train is used for rotating and driving the feed rollers by a single motor. Referring now to Fig. 4, the printer includes spaced, side plates 44 and 46 for supporting the various parts of the record media drive mechanism. The slip table 16 is shown at the left side and a slip 48 (shown in phantom line) occupies a position at the front of the printer for printing operation. A main feed roller 50 is carried on a shaft 52 that is supported in a platen assembly 54 between the side plates 44 and 46. The shaft 52 extends through an opening in the right side plate 44 and a gear 56 is secured on the shaft 52. The shaft 52 is coupled to a motor 58 which is swingably supported on a support bracket 60 that is journaled on a shaft 62 secured to the side plate 44. The motor 58 is swingable from the shaft 62 to move in accordance with movement of the main feed roller 50 when accommodating the receipt paper 24 and the form 48. A port 49 opens when feed roller 50 is moved down to enable insertion of the slip or form 48. A gear 64 is secured to a shaft 66 that is journaled in a bearing 68 in a plate 70 pivotally supported on a shaft 72 that carries a feed roller 74. The shaft 72 is journaled in a bearing 76 in the plate 70 and a gear 78 is secured to the shaft 72. The gear 64 operates as an intermediate or transmitting gear by reason of engaging with the gear 56 and with the gear 78 so as to transmit the drive from the gear 56 to the feed roller 74. A pressure roller 80 is carried on a shaft 82 suitably journaled in bearings 84 and 86 in the side plates 44 and 46 to cooperate with the main feed roller 50 on the shaft 52. A pressure roller 88 is carried on a shaft 90 suitably supported to cooperate with the feed roller 74 on the shaft 72. The platen assembly 54 includes a support structure 92 that carries the main feed roller 50 and a platen 94. The platen 94 is supported by a spring 96 at each end of the platen to maintain the platen in position at the printing station. The platen 94 is moved down against the action of the springs 96 by means of an arm 98 secured to a rotatable shaft 100. The shaft 100 is journaled in bearings 102 and 104 in the side plates 44 and 46 and extends a predetermined distance beyond the plate 44. A gear 106 is secured to the shaft 100 and a motor 108 has a threaded shaft 110 that meshes with gear 106 to rotate the shaft 100. Shaft 100 has a flat portion 112 outside the plate 44. The arm 70, in the form of an irregular plate, journals the shaft 66 with the gear 64 secured thereon. The shaft 72 is journaled in the arm 70 and has the gear 78 secured to the shaft 72 which provides a pivot means for the arm 70. A stud 114 is secured to the arm 70 at the other end thereof from the gear 64. The timing plate 43, in the form of a cam, is rotatably carried on a stud 116 secured to the right side plate 44. It should be noted that the shafts 52 and 82 for the drive roller 50 and the pressure roller 80 are supported in aligned manner and that the stud 116 is aligned with shafts 52 and 82. The arm 70 defines a wide slot 118 therein for the stud 116, the slot 118 being slightly arcuate to accommodate rotation of the plate 43 and travel of the stud 116 along the slot 118. The arm 70 also defines a narrow slot 120 therein for a pin 122 that is secured to the timing plate 43. A coil spring 124 is coupled to the stud 114 and to a frame portion (not shown) of the printer 10 to tend to rotate the arm 70 in a counterclockwise direction (Figs. 5A and 5B) so that the gear 64 is meshed with the gear 56. A stopper 126, in the form of an arm, is secured to the shaft 100 and is fitted on the flat portion 112 thereof. A portion of the stopper 126 engages with the stud 114 (Fig. 5A) upon rotation of the shaft 100 to prevent clockwise rotation of the arm 70 about the shaft 72. The motor 108 operates to rotate the shaft 100 through the gear 106 on the shaft 100 and the worm gear 110 on the shaft of the motor to control the downward movement of the platen assembly 54 with the drive roller 50 as a part of such assembly. In the operation of the drive roller 50 and its associated parts, reference is made to Figs. 5A and 5B. Fig. 5A shows the positions of the drive roller 50 and of the pressure roller 80 for holding the receipt paper 24 during advancement thereof. Fig. 5B shows the positions of the drive roller 50 and of the pressure roller 80 wherein the drive roller is lowered so as to permit entry and removal of the slip 48. Of course, the drive roller 50 is moved upward to advance the slip 48 to the correct printing location. When the motor 108 (Fig. 4) rotates in the direction of the arrow 130, the shaft 100 is rotated clockwise (Figs. 5A and 5B) through the warm gear 110 and the gear 106 and the platen assembly 54 is moved down by the action of the arm 98 on the shaft 100 which arm is engaged with the platen assembly 54. Since the drive roller 50 is a part of the platen assembly 54, the drive roller is moved down and away from the pressure roller 80 and the gear 56 is also moved down at the same time as the platen assembly. The arm 70 rotates counterclockwise on the shaft 72 as the gear 56 is moved down. It is seen that the gear 64 is moved with gear 78 engaged therewith to the position shown in Fig. 5B. When the arm 70 rotates counterclockwise, the pin 122 in the slot 120 of the timing plate 43 causes the timing plate to rotate at the same time to the position in Fig. 5B wherein the cam surface of the plate 43 prevents any further lowering of the shaft 52 of the gear 56. Since the shaft 52 is located directly above the stud 116 of the timing plate 43, any downwardly acting force applied from the shaft 52 will not cause the timing plate to rotate. When the gear 56 is rotated in the position shown in Fig. 5B, the shaft 52 of the gear is also rotated while in contact with the cam surface of the plate 43. Generation of friction between the shaft 52 and the surface of the cam plate 43 can be avoided by making the cam plate of oil-impregnated plastic or metal. It is also seen that when the platen assembly 54 is moved down by rotation of the shaft 100, the stopper 126 is rotated from the position wherein the end portion 128 is above the stud 114 on the arm 70 (Fig. 5A) to the position wherein the end portion 128 is engaged with the stud 114 (Fig. 5B). In this position of the parts, the arm 70 can not rotate in the clockwise direction. When the gear 56 is rotated clockwise, a force is acting in a direction to maintain engagement of the teeth of gear 56 with the teeth of gear 64. Figs. 6A and 6B show portions of a printer having a conventional arrangement of the drive rollers. Since many the parts of conventional arrangement are the same as the parts already described in Figs. 5A and 5B, the same reference numerals will be used for such parts. The conventional arrangement includes the supply roll 22 for the receipt paper 24, the drive roller 74 and associated pressure roller 88, and the drive roller 50 and associated pressure roller 80. The conventional arrangement also includes the gear 56, the intermediate gear 64 and the gear 78 on associated shafts 54, 66 and 72. Fig. 6A shows the position of the parts in a conventional gear mechanism wherein the gear 56 is in the normal receipt paper advancing position and the gear 56 is driven by a suitable motor (not shown). When the gear 56 is driven in a counterclockwise direction, the drive roller 50 is rotated, with the help of the pressure roller 80, to advance the receipt paper 24 toward the left in Fig. 6A. A receipt 33 is shown after printing on the receipt paper 24 and cutting thereof. Rotation of gear 56 rotates the intermediate gear 64 and the gear 78 which drives the feed roller 74 for advancing the receipt paper 24 from the supply roll 22. Fig. 6B shows the position of the parts in a conventional gear mechanism wherein the gear 56 has been moved down and the drive roller 50 is separated from the pressure roller 80 to provide the port 49 for the slip 48. An arm 132 is pivoted on the shaft 72 that carries the feed roller 74, such arm being biased by the spring 124. When the gear 56 is moved down, the arm 132 is rotated counterclockwise by the spring 124, so that engagement of the gear 56 and the gear 64 on the arm 132 is maintained. It is seen that the gear 64 is pressed against the gear 56 only by the tensile force of the spring 124. When the gear 56 is rotated counterclockwise to feed the receipt paper 24, the gear 56 kicks the gear 64 into rotation and a force is generated to cause the arm 132 to rotate clockwise against the tensile force of the spring 124. The spring 124 also tends to provide a force which will cause the arm 132 to be biased in the counterclockwise direction and, by engagement of gear 64 with gear 56, tends to move the gear 56 down and away from the pressure roller 80. In a normal situation, these forces are balanced to correctly feed the receipt paper 24. However, in case of a force on the gear 56 that is greater than that of the spring 124 acting on the arm 132, the gear 56 may be moved down and the feed roller 50 may not correctly advance the paper 24. For example, the supply roll 22 may contact the side wall of the container thereof (not shown) and increase the frictional force so that the arm 132 tends to rotate against the tensile force of the spring 124. This may cause skipping of the teeth between gears 56 and 64 and cause problems in advancing or feeding of the receipt paper 24. It is thus seen that herein shown and described is a compact dot matrix printer that includes a paper mechanism wherein a cam member is provided for limiting the movement of the feed roller and a stop member for avoiding rotation of an arm carrying a transmitting gear.

Claims: An apparatus for feeding media (24) along a guide path including first and second feed roller means (50,74) respectively carried on first and second shafts (52,72) respectively having first and second gear means (56,78) mounted thereon, drive means (98,100,108) for moving said first feed roller means (50) in a first direction from a first position to a second position against the action of biasing means (96), and intermediate gear means (64) mounted on an arm (70) in meshing engagement with said second gear means (78), said arm (70) being pivotally supported on said second shaft (72) and biased for rotation in a second direction about said second shaft (72) so as to urge said intermediate gear means (64) into meshing engagement with said first gear means (56), said arm (70) being rotated in said second direction when said first feed roller means (50) is moved in said first direction, characterized by cam means (43) having a fixed axis of rotation and operably associated with said arm (70) whereby rotation of said arm (70) brings about rotation of said cam means (43), said cam means (43) having a cam surface engaging with said first shaft (52) so as to limit movement of said first roller means (50) in said first direction, and stop means (126) arranged to engage with a projection (114) on said arm (70) for limiting the rotation of said arm (70) in a direction opposite to said second direction, said stop means (126) being operably associated with said drive means (98,100,108) whereby said stop means (126) is in engagement with said projection (114) both when said first feed roller means (50) is in said first position and in said second position. An apparatus according to claim 1, characterized in that said arm (70) includes a plate member (70) for journaling said second gear means (78) and said further gear means (64) at one end thereof. An apparatus according to claim 1 or claim 2, characterized by a motor (58) supported in pivoting manner for driving said first feed roller means (50) for feeding said media (24) along said guide path. An apparatus according to any one of claims 1 to 3, characterized in that said drive means (98,100,108) includes a shaft (100), an arm (98) secured to said shaft (100) and operably coupled to said first feed roller means (50), and a motor (108) for rotating said shaft (100). An apparatus according to any one of claims 1 to 4, characterized in that said arm (70) defines a first opening (118) therein and said cam means (43) comprises a plate member (43) having a first projection (116) operably associated with said first opening (118) permitting movement of said cam means (43) with said arm (70). An apparatus according to claim 5, characterized in that said arm (70) defines a second opening (120) therein and said cam means (43) has a second projection (122) operably associated with said second opening (120) for limiting rotation of said arm (70) relative to movement of said first feed roller means (50). An apparatus according to claim 5 or claim 6, characterized in that said first opening (118) comprises an arcuately-shaped slot (118). An apparatus according to claim 6, characterized in that said second opening (120) comprises a slot (120). An apparatus according to any one of claims 1 to 8, characterized by a first pressure roller means (80) and a second pressure roller means (88) operably associated with said first feed roller means (50) and with said second feed roller means (74), respectively. An apparatus according to claim 9, characterized in that said arm (70) is an irregularly-shaped plate member (70) adjacent one of a pair of spaced side frames (44,46) of a printer. An apparatus according to claim 10, characterized in that said arm (70) is biased for rotation by a coil spring (124) connected to said projection (114) on said arm (70). An apparatus according to claim 10 or claim 11, characterized in that said cam means (43) is positioned between one of said side frames (44,46) and said arm (70).

Inventors: JINGU, TOSHIHIRO, KUSAYANAGI, MASAO
Applicants: NCR INTERNATIONAL INC.
Application year: 1989
Main classification: B41J11
IPC codes: B41J11, B41J15, B41J13