IMPACT PRINTER

Abstract: An impact printer (10) in which the action of a rotatable cam assembly (50) positions a plurality of type racks (22), enables printing and indexes paper (12) prior to restoring the type racks to the home position. Teeth (54) on the cam assembly engage teeth (30) on the type racks for positioning thereof and an extended tooth (62) on the cam assembly causes impact of the racks against a platen (14) which is caused to be rotated by movement of the cam assembly to index the paper to the next print line.

Description: IMPACT PRINTER Technical Field This invention relates to an impact printer. Background Art In the field of impact printers, certain design goals have included the concepts of low cost production along with low power consumption and low cost operation. A number of the previous impact printers used electro¬ magnetic solenoids for moving certain parts of the printer such as the print hammers, however these solen¬ oids consumed energy in amounts considered larger than necessary or economically feasible if lower costs were to be maintained. Since impact printers commonly have included a type member with characters thereon for impact by the print hammers, the type member also required some type of drive means for positioning the type member for printing the proper characters at the exact instant in time. In the case of the very successful drum-type printer, the drum served as -a type member and required a drive mechanism to rotate the drum at the desired speed. Additionally, the paper or like record media needed to be advanced after the completion of a line of printing. Printers have also included type elements, such as type racks, carrying a plurality of type characters thereon and adapted to be positioned in one of a plural¬ ity of positions for printing. Type hammers impact the type elements against the paper and against a platen, and electromagnets are energized to attract and release the armatures for permitting movement of the type ele¬ ments. A printer having a plurality of type character bearing type racks is disclosed in the U.S. Patent No. 3,241,756. The type racks have rack teeth which are in mesh with the teeth of a respective pinion provided for each rack to move the latter until a selected type char¬ acter thereon is positioned for printing along a print line. Print hammers are provided for displacing the type racks into engagement with a ribbon and paper tape to imprint upon the latter an impression of the selected type character and a drive means is provided for rotating the platen to advance the paper. The disadvantage of this arrangement lies in its complexity. Disclosure of the Invention It is an object of the invention to provide a simple and efficient impact printer. Thus, according to the invention there is provided an impact printer including a platen and a plurality of type character bearing members positionable in relation to said platen for printing along a print line, characterized by actuating means arranged to per¬ form the multiple functions of moving selected ones of said type character bearing members from a home position into a printing position adjacent said platen for enabling printing along said print line, moving the selected type character bearing members towards said platen and into contact with a record medium, and causing said selected type character bearing members to be restored to the home position after printing. In the preferred embodiment of the invention, the actuating means is in the form of an elongated cam member which is mounted for rotation about a longi¬ tudinal axis thereof and which has shaped surfaces on the periphery thereof such that said cam member moves said selected type character bearing members into the printing position during a first part of its rotation, moves said selected type character bearing members into contact with said record medium during a second part of its rotation, and causes said selected type character bearing members to be restored to the home position during a third part of its rotation. o?.:? 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 view of a portion.of an impact printer according to the present invention; Fig. 2 is a side elevational view showing the type racks in the home position; Fig. 3 is a side elevational view showing the relationship of the type racks and a cam member at the start of a printing cycle; Fig. 4 is a side elevational view showing the cam member rotated into engagement with a released type rack; and Fig. 5 is a side elevational view showing the cam member rotated into position with a print tooth engaging the type rack and printing the desired type character. Best Mode for Carrying Out the Invention Referring now to Fig. 1 there is shown an isometric view of a portion of a printer generally designated as 10 wherein paper or like record media 12 is positioned in a path toward and trained around a platen 14. The paper 12 is caused to be moved or ad- vanced in the direction of the arrows. The platen 14 is supported from and pivotally carried on a shaft 16 journaled in suitable manner from side frames (not shown) so as to enable oscillation or limited rotary movement of the platen during a printing operation. Such platen 14 includes a printing surface 18 of material commonly used for impact printers of the type wherein type character impressions are made on the paper 12 as a result of impacting the type characters against the paper and against the platen. A plurality of type racks 22 are disposed generally in a vertical direction and positioned down¬ wardly and adjacent the platen 14. Such type racks 22 are supported from and pivotally carried on a pin or shaft 24 journaled in suitable manner from side frames (not shown) . The type racks 22 which may typically be ten or twelve in number are closely spaced on the pivot pin 24 but allow sufficient clearance between the racks and are spaced to permit freedom of movement of each of the racks in an up and down direction. Each of the racks 22 includes an elongated slot 26 therein for enabling travel along the pivot pin 24 as the racks are moved in an up and down direction during the printing operation. Each of the racks 22 also has a plurality of spaced type characters 28 on one face thereof adjacent the platen 14 and a plurality of teeth 30 on the opposite face thereof. Additionally, each of the racks 22 has an aperture 32 at the lower end thereof for connecting with one end of a spring 34- which has the other end thereof connected to a pin or rod 36 which is fixed or otherwise secured in suitable manner to the frame of the printer 10. Each of the type racks 22 also includes a permanent magnet 40 on the face opposite that face with the type characters 28, the magnet 40 being positioned near the lower portion of the slot 26. An electromagnet assembly comprising an electromagnet 42 for each of the type racks 22 is disposed adjacent the permanent magnet 40 of each type rack 22 for holding the respective rack in a home or latched position. An elongated actuating means or cam assembly generally designated as 50 is supported from and pivot- ally carried on a shaft 52 journaled in suitable manner from the side frames of the printer 10. Such cam as¬ sembly 50 has a plurality of teeth 54 extending across the width thereof and corresponding in size and shape to mesh with the teeth 30 on the type racks 22. The cam teeth 54 occupy more than half of the circumference of the cam assembly 50 while an extended radial portion or lobe 56 thereof is formed with circumferential surface O PI_ . wiPO portions 58 and 60 to meet with the teeth 54. The cam assembly 50 also includes one extended tooth 62 which is located as the second last tooth for engaging with the teeth 30 of the type racks 22 and for moving the racks 22 into engagement with the paper 12 and against the platen 14 for printing the respective characters 28 then positioned along the print line. The cam assembly 50 additionally carries a timing plate or wheel 66 having indicia thereon and a photo sensor 68 for initiating signals indicating the position of the cam assembly. The signals thus sensed are transmitted to appropriate control mechanism (not shown) . An ink pad 76 (Figs. 2-5) is secured to the frame of the printer 10 and is so disposed to be con¬ tacted by the type characters 28 for inking thereof when the type racks 22 are in the home or latched position (Fig. 2). During printer operation, the cam assembly 50 is effective to index each print rack 22 to the desired or proper print position, to apply printing force for printing the esired characters 28, to index the paper 12 by rotating the platen 14, to disengage the racks 22 to allow their return to the rest or home position by means of the springs 34 and to restore the type racks 22 to their latched position. Fig. 2 shows the type racks 22 in a home position after restoring by the cam assembly 50 and latched by reason of the attraction of the permanent magnets 40 to the electromagnets 42. At such time, the type racks 22 are seated on the pin 24 with the upper portion of each type rack being displaced from the platen 14 and with the radially-extending lobe portion 56 of the cam assembly 50 being in engagement with the upper teeth 30 of the type racks 22 and the type char¬ acters 28 being in contact with the ink pad 76. The beginning of a print cycle is shown in Fig. 3, wherein the electromagnet 42 of a type rack 22 selected for performing a printing function has been energized to repel the permanent magnet 40 and to allow the spring 34 to pivot the type rack 22 on the pin 24 in a counterclockwise direction for moving the type char- acters 28 thereof away from the ink pad 76 and for moving the teeth 30 thereof toward engagement with the teeth 54 of the cam assembly 50. The next portion of the print cycle is illustrated in Fig. 4, wherein the teeth 30 of the type rack 22 are engaged with teeth 54 of the cam assembly 50 during rotation of the cam assem¬ bly for driving the type rack 22 in the upward direction. The printing, portion of the print cycle is shown in Fig. 5, wherein the teeth 54 of the cam assembly 50 have been in engagement with teeth 30 of the type rack 22 to drive the type rack upward to position the desired or proper type character 28 on the rack adjacent the platen 14 and the cam assembly 50 has rotated suf¬ ficiently in a counterclockwise direction to cause the print tooth 62 thereof to engage the type rack 22 and force such rack clockwise' and against the paper 12 and the platen 14 for printing the aligned character 28. During the printing operation of the character on the paper, the upward movement of the type racks 22 rotates the platen 14 a predetermined amount to advance the paper 12 as shown by the angular rotation of the platen (Fig. 5), and as described hereinafter. In the operation of the printer 10, the type racks 22 are initially in the home or rest position and are latched by reason of the attraction between the electromagnet 42 and the permanent magnet 40 on each rack. A print cycle is initiated by selectively pulsing the electromagnets 42 to oppose the respective permanent magnets 40 on those print racks 22 selected for operation and thereby release such racks 22 to permit engagement of the teeth 30 thereon with the teeth 54 of the cam assembly 50 under the control or force of the associated springs 34. One or more of the type racks 22 associated with non-selected columns, of course, are not actuated and remain in the latched position for a particular printing cycle. The correct line of printing is set by first releasing the rack or racks 22 which must print the character which is farthest or most remote from the platen 14 in the latched position. The release of the respective print racks 22 is timed so that the teeth 30 on each print rack will engage the correct teeth 54 on the cam assembly 50 to cause the desired character 28 thereon to be moved into position at the face of the platen 14 at the precise instant that the print tooth 62 of the cam assembly 50 engages the rack 22 for impacting same against the paper 12 and the platen 14. The remaining racks 22 are thus released in time relationship to the first rack or racks released so that the correct character 28 for each rack and thereby for each column is aligned with the first character or column that was released. Since the type racks 22 are released in timed relationship, the selected characters 28 for all columns to be printed will be moved simul¬ taneously toward the platen 14 for printing these char¬ acters along a print line.. At this point in time, the print tooth 62 on the cam assembly 50 engages the type racks 22 and causes all the type racks selected for operation to pivot on the pin 24 and move against the platen 14 so that the paper 12 is compressed between the respective characters 28 aligned across the printing station and the platen 14 in the printing operation whereby the ink presented to the type characters 28 by the ink pad 76 is transferred from such characters 28 onto the paper 12. The assembly of type racks 22 continues to move when in contact with the paper on the platen 14 and such movement causes the platen 14 to pivot or rotate a precise amount in the clockwise direction (arrow of Fig. 5) to advance the paper 12 forward and upward an amount to index same the proper distance for printing on the next line. The paper is indexed the precise amount during the last portion of the printing operation and continued upward movement of the type racks 22 by engage¬ ment of the last tooth 54 with the particular tooth 30 on each rack. At the end of the printing portion of the print cycle, the last tooth 54 on the cam assembly 50 disengages from the teeth 30 on the print racks 22 and such racks are returned downwardly to home or rest position by the action of the springs 34. During such time, the cam assembly 50 is rotated from the last tooth 54 to the lobe portion 56 while the type racks 22 are returned to such home" position. Then the extended radial portion or lobe 56 of the cam assembly 50, upon reaching the proper position of counterclockwise rota¬ tion, becomes effective to drive the racks 22 to the latched position where the characters 28 on the racks again contact the ink pad 76 and the racks are held in place by the permanent magnets 40 being attracted to the electromagnets 42, as shown in Fig. 2. It is of course understood that the paper 12 may be indexed or advanced without printing of characters by means of a dummy character or index bump or the like being provided on the print rack 22 and of such config- uration or size to be not in position for inking thereof by the ink pad 76. For one example, the two end racks 22 can be utilized and engaged by the cam assembly 50 so that dummy character or index bumps thereon are driven to the line of printing to cause advancing of the paper 12 by a distance of one line without printing any char¬ acters. The printing can be advanced or indexed a plurality of lines by repeating the above cycle. Addi¬ tionally, during the printing cycle, if no character is to be printed in the end columns, the dummy characters can be used to prevent paper skew when printing occurs at only one end of the print line. Certain variations of the instant printer 10 may include the use of an ink roller in contact with the CI_? ~" type characters 28 rather than the ink pad 76. An ink ribbon may also be used, but if so done it is important that the dummy character or bumps on the type racks 22 contact the paper away from or off of the ribbon so as to accomplish paper feed without printing. The type racks 22 as described above are preferably made of a thermoplastic material by means of an injection molding process. Alternatively, such racks may be made of a non-ferrous metal. Another variation may include elimination of the ink pad 76 or like means altogether by making use of porous ink filled and re¬ placeable type strips which are secured to the type racks. The cam assembly 50 may be injection molded or extruded thermoplastic or it may even be made of pow¬ dered metal. The extruded plastic or the powdered metal cam assembly are not as susceptible to draft problems as may be the injection molded plastic. Additionally, while the described electromagnet structure 42 covers a single assembly of electromagnets to control the release of the print racks, dual assem¬ blies acting on alternate print racks may be more feasi¬ ble by reason of space limitation between the type racks. It is thus seen that herein shown and described is a low cost and energy impact printer allowing the use of a smaller power supply or even permit battery opera¬ tion. The printing is accomplished by means of cam action and the print elements are restored by spring and cam action with permanent magnets being utilized for latching the print elements in the home position.

Claims: CLAIMS : 1.. An impact printer (10) including a platen (14) and a plurality of type character bearing members (22) positionable in relation to said platen (14) for printing along a print line, characterized by actuating means (50) arranged to perform the multiple functions of moving selected ones of said type character bearing members (22) from a home position into a printing posi¬ tion adjacent said platen (14) for enabling printing along said print line, moving the selected type char¬ acter bearing members (22) towards said platen (14) and into contact with a record medium (12), and causing said selected type character bearing members (22) to be re¬ stored to the home position after printing. 2. A printer according to claim 1, charac¬ terized in that said actuating means (50) is in the form of an elongated cam member which is mounted for rotation about a longitudinal axis thereof and which has shaped surfaces on the periphery thereof such that said cam member (50) moves said selected type character bearing members (22) into the printing position during a first part of its rotation, moves said selected type character bearing members (22) into contact with said record medium (12) during a second part of its rotation, and causes said selected type character bearing members (22) to be restored to the home position during a third part of its rotation. 3. A printer according to claim 2, charac¬ terized in that said cam member (50) has a toothed por¬ tion (54) for engaging a toothed portion (30) of each of said selected type character bearing members (22) for movement thereof to the printing position. 4. A printer according to claim 3, charac¬ terized in that said cam member (50) has an extended 4 . ( concluded ) tooth (62) for moving said selected type character bear¬ ing members (22) into contact with said record medium (12). 5. A printer according to claim 2, character¬ ized in that said cam member (50) has an enlarged cam portion (56) engageable with said selected type charac¬ ter bearing members (22) for causing them to be restored to the home position. 6. A printer according to claim 1, charac¬ terized in that said type character bearing members are racks (22) each having an elongated slot (26) therein for enabling movement thereof along a common pivot pin (24) extending through the slots (26) in said racks (22). 7. A printer according to claim 6, charac¬ terized in that each of said racks (22) is independently pivotable about said pivot pin (24) for movement towards and away from said platen (14). ' 8. A printer according to claim 1, character¬ ized in that said platen (14) is elongated and pivotally mounted for rotation by the movement of the selected type character bearing members (22). 9. A printer according to any one of the preceding claims, characterized by magnetic means (40, 42) for latching said type character bearing members (22) in the home position and energizable to release selected ones of said type character bearing members (22) for movement by said actuating means (50). 10. A printer according to claim 9, character¬ ized in that said magnetic means include a permanent magnet (40) on each type character bearing member (22) 10. (concluded) and a respective electromagnet (42) disposed adjacent each permanent magnet (40) for holding said type char¬ acter bearing members (22) in the home position by reason of the attraction of the permanent magnet (40) to the electromagnets (42), said electromagnets (42) being selectively energizable to oppose the respective permanent magnets (40) and thereby release the associ¬ ated type character bearing members (22) for operation. -gUREΛ OMPI .- s--. W1PO ^NATl

Inventors: BRIGGS B, LAWTER R, SAMPSON E, WILLS D
Applicants: NCR CO, NCR CORP
Application year: 1980
Main classification: B41J1
IPC codes: B41J1, B41J7, B41J27