Printer

Abstract

A printer comprising a typewheel, typebar and position determining device. The typewheel is made with raised characters on its periphery and rotates at constant speed. The typebar is rockably supported on a shaft and has a portion for striking a selected character through paper, etc. in its printing position. The position determining device is associated with the typebar to swing it from the rest position to the driving position. The typebar in its driving position is impulsively rocked by engaging a hammer rotating in synchronism with the typewheel, and then returns to its rest position. The typebar in its rest position engages the position determining device without rocking so as to prevent double or repeated printing.

Claims

1. A printer comprising: a typewheel (2) having characters formed on its periphery and rotating at a substantially constant speed; a typebar (6) with a printing head (7) for printing a selected character on a material to be printed, such as paper, through an inked ribbon; a device for defining two different positions of the typebar (6), a rest position corresponding to when said printing head (7) is spaced from the periphery of the typewheel (2), and a driving position corresponding to when said printing head (7) is located beyond the rest position to a position where it may be impulsively driven towards said typewheel; a driving means (27-20) for impulsively driving said typebar (6) toward said typewheel (2) when said printing head (7) is in the driving position of the typebar so as to cause said printing head (7) to strike a selected character on the paper through an inked ribbon; characterized in that said position defining device comprises a first projection (9) formed on said typebar (6), a movable trigger lever (11) having first (12) and second (13) engaging portions respectively engageable with said first projection (9) in the driving (FIG. 2) and rest (FIG. 1) positions of the typebar (6), and said second engaging portion (13) including a recess into which said first projection (9) is selectively received after a printing operation to prevent said typebar (6) from moving toward said typewheel (2) and causing undesired double printing. 2. The printer according to claim 1 wherein said typebar (6) has a second projection (25) and said trigger lever (11) has a pressure arm (24) which selectively bears against said second projection (25) so as to cause the trigger lever (11) to contact the second projection (25) in the printing position and to move to another position when there is a change from the printing position to the rest position, said another position being one in which said first projection (9) is engaged in said second engaging portion (13). 3. The printer according to claim 2 wherein said trigger lever (11) has a free end portion (14) with said first and second engaging portions and said pressure arm (24) projects in a direction substantially perpendicular to the free end of the trigger lever (11). 4. The printer according to claim 1 wherein an adjustable eccentric stopper (30) is associated with said typebar (6) to adjust the angular position of said typebar (6) in the driving position of the typebar (6). 5. The printer according to claim 1 wherein said trigger lever (11) has a step (15) located adjacent to said second engaging portion (13), the first portion (12) being higher than the step (15) with respect to the bottom of the second engaging portion (13), the first projection (9) striking upon the step (15) when the typebar (6) is in its printing position. 6. The printer according to claim 1 wherein said first projection (9) is engaged in said second engaging portion (13) to prevent movement of said typebar (6), and wherein said position defining device includes means for disengaging said first projection (9) from said second engaging portion (13) for locating said typebar (6) in said driving position. 7. The printer according to claim 1 wherein said typewheel (2) has raised characters formed on its outer periphery. 8. The printer according to claim 1 including biasing means (8) for biasing said typebar (6) away from said typewheel (2). 9. The printer according to claim 1 comprising second biasing means (16) for biasing said trigger lever (11) toward an engagement position between said first projection (9) and said second engaging portion (13).
United States Patent [1 1 Ochiai [451' Dec. 4, 1973 PRINTER 3,266,419 8/1966 Erpel et a1. 197 49 'ux [75] Invento Tadashi Ochiai, Yokohama, Japan 3,670,647 6/1972 Funk et a1 197/49 X [73] Assignee: Tokyo Shibaura Electric C0., Ltd., Primary Examiner-Robert E. Pulfrey Kawasaki-shi, Japan Assistant Examiner-R. T. Rader Filed: g 1972 AttorneyRobert D. Flynn et a1. Appl. No 284,681 [30] Foreign Application Priority Data Aug. 31, 1971 Japan 46/78474 [52] US. Cl. 101/93 C, 197/49 [51] Int. Cl B41j 47/46 [58] Field of Search 197/49, 17; 101/93 C [5 6] References Cited UNITED STATES PATENTS 2,949,846 8/1960 Hoffman et a]. 101/93 C 2,796,966 6/1957 Toeppen......... 197/17 3,292,531 12/1966 Mutz 197/49 X 2,625,100 1/1953 Williams et a1. 197/49 X [57] ABSTRACT A printer comprising a typewheel, typebar and position determining device. The typewheel is made with raised characters on its periphery and rotates at constant speed. The typebar is rockably supported on a shaft and has a portion for striking a selected character through paper, etc. in its printing position. The position determining device is associated with the typebar to swing it from the rest position to the driving position. The typebar in its driving position is impulsively rocked by engaging a hammer rotating in synchronism with the typewheel, and then returns to its rest position. The typebar in its rest position engages the position determining device without rocking so as to prevent double or repeated printing. 9 Claims, 4 Drawing Figures PRINTER BACKGROUND OF THE INVENTION a normally rotating hammer which is interlocked; with a link or ratchet todrive the't-ypebar: There are,.however, the serious drawbacks in its complex construction, high manufacturing cost, double or. repeated printing, and low operational stability. Accordingly, an object of the present invention is to provide an improv'edprinter ofhigh reliability, low cost and simple construction. SUMMARY OF THE INVENTION This inventionprovidesa printer comprisinga type? wheel-made with raised characters onits periphery, and rotating at constant speed; atypebar withaxprintinghead forprinting a-selected character oniazmaterialto be printed, such.as paper, throughaninkedf ribboniadevice for determining two different positions of' the. typebar, arest position taken whenxsaid printing head is detached from the, periphery. of the.:typewheel; and a driving position occupiedwhen' saidr printing; head comes beyond the rest. position; a driving means for causing said printing head to strike the selected character on the paper through an inkedribbon byvimpul sively driving said typebar'when saidl'printinglieadis ine the driving position" of the typebar; characterized? in". thatisaid position-determining device has a fiistprojec tion formed on said typebar, a triggerlevenhas-t'irstand: second engaging portions respectively. engaging; said first projection'in the. rest and drivingxpositionsofzthe' typebar; said secondengaging portion =having a=recess into which said firstprojection 'isreceived. 1 i BRIEFDESCRIPTION OF THE DRAWING 'FIG. 1 is a side view of a printer in .the-restzposition of the typebar according to this'invention; - FIG. 2 is a side view showing -the.printer:of2FIG. lsin the driving position of the typebar; -'FIG.'3 is aside view illustrating the printenofiF-IG. 1 in the printing positionof the typebar; and FIG. 4 is va side view representing a :modifiedxprinter: otthe invention. DETAILED DESCRIPTION OF THEINVENTION In FIG. l'is shown a typewheel 2 -.which'is made with raised characters 1 on its periphery-and connected to a motor.(not shown) and rotated.counterclockwise:..at constant speed. Paper 3 or other material to; betprinted; and an inked ribbon 4 are disposed nearest the periph= cry of the typewheel-2. A-typebar 6tisisupportedito swing around a'shaft:5. A printing headflismounted ataone free. end of the typebars6-to strikea selected character on the-paper 3 through an inked ribbonx4: A spiral springB-isapplied to the .typeb'ar6-so asto normally exert forceto the typebar 6-clockwise around the shaft 5; A first projection 9 with: aarectangular .:head. is formed at the other end of thetypebar 6soas toengage the first and second engaging .portions ;-1 2i iand- 1350f 5a.. trigger lever l l which swings about a shaft 10. The pro jection 9 engages with the first portion 12 in the driving position of the typebar 6,-as shown in FIG. 2. It also engages with the second portion 13 in the rest position of the typebar 6, as shown in FIG. 1. The second-portion 13 has a recess somewhat wider than the head of the first projection 9. A step 15 is formed between the-second portion 13 and one free end 14 of the trigger lever 11. The'distance from the step 15 to the bottom of therecess of the second portion. '13 is somewhat shorter than the distance between the first and second engaging portions at bottom. A spiral spring 16 is used to normally swing the trigger lever 11 counterclockwise around the shaft 10. A predetermined swinging position is given to the trigger lever 11 so as to cause a stopper pin 17 to engage the third engaging portion 18 of the lever-11. in the rest position of the typebar .6, as shownin FIG. 1. A slit 19 is formed at one free end of thelever 11. The lever 11 is connected to the free end of-an armature 22 of a printing solenoid 21 through a link 20 one end of which isconnected to the slit 19. The-solenoid 21 is de-energized in the rest position of thetypebar 6 shown in FIG. 1. The armature 22 is sepa rated from a solenoidcore 23 by the action of the spring 16. I A pressure arm 24 projects almost perpendicular to thefree end portion 14 of the lever 11. Facing the arm 24, asecond projection 25 is formed in the typebar 6. This shape of the lever 1 l contributes much to the miniaturization of the printer. There is a certain spacing between the tip of the arm 24 and the projection 25 of the typebar 6 in its rest-position. The tip of the arm 24 slidably contacts the second projection 25 in the printing positionof the typebar 6 shown in FIG. 3. vAn impulse arm 26 projects on the opposite side of the typebar 6 with respect to the printing head 7. A rotating printhammer 27 is disposed near the tip of the arm 26. The hammer 27 is connected to the typewheel 2 through a gearing (not shown) and driven at constant 'speedcounterclockwise around a shaft 28 in synchronism with the typewheel 2 at a predetermined turning ratio. On the periphery of the hammer 27 are formed two strikingportions 29 which are symmetrical with respect to the shaft 28. When the typebar 6 is in the rest position, the hammer 27 rotates in nonco'ntactwith the arm 26. When the typebar 6 is in its driving position, the striking portion 29 strikes against the arm 26 and impulsively rocks the typebar 6 counterclockwisev against theaction of the spring 8. The hammer 27 is set at a half turn while the typewheel 2 rotates by one char-' acter. For example, when the typewheel 2 is made with l4 raised characters-on its periphery, the hammer 27 has seven rotations per rotation of the typewheel 2. Referring now to FIGS. 1 to 3, the operation of this embodiment is described in detail. When the typebar 6 is in its rest position shown in FIG. 1, a pulse-like printing signalis applied to the printing solenoid 21. As a re-' suit, the armature 22 is attracted by-the core 23 and its free end is rotated counterclockwise. The trigger lever within the striking range of the hammer 27 by one of the striking portions 29. Thus the typebar 6 is impulsively rocked counterclockwise against the action of the spring 8. As a result, the printing head 7 strikes a selected character through thepaper 3 and the inked ribbon 4, as shown in FIG. 3. The image of the selected character can thus be printed on the paper 3. The first projection 9 is positioned on the step 15 directly from the first engaging portion 12 without engaging the second portion 13 in the displacement from the driving position to the printing position of the typebar 6. In such a state, the tip of the pressure arm 24 of the lever 11 is in close contact with the second projection 25 of the typebar 6. After the printing head 7 strikes against the typewheel 2, the typebar 6 swings clockwise from its printing position shown in FIG. 3 by the reaction of the strike and under the tension of the spring 8. As a result, the first projection 9 securely inserts into the second portion or recess 13 by sliding along the step 15 because the first portion 12 is higher than the step 15 with respect to the bottom of the second position 13. At the same time, the pressure arm 24 which contacts the second projection 25 by sliding is forced to act so as to cause the trigger lever 11 to swing counterclockwise as the typebar rocks clockwise. The lever 1 1 is compelled to more counterclockwise in conjunction with the tension of the spring 16 even when a clockwise force is imparted to the lever 11 before the typebar 6 returns to its rest position by energizing the solenoid 21 due to the residual magnetic field and/or a misprint signal. The lever 11 swings one way (counterclockwise), thus preventing double or repeated printing. FIG. 4 illustrates a modified embodiment of the invention. For example, an eccentric stopper 30 is associated with the typebar 6 in its printing position (FIGS. 1 to 3) to adjust the angular position of the typebar 6 in its driving position, that is, the position taken when the striking portion 29 of the hammer 27 contacts the impulse arm 26 of the typebar 6 or an angle )8 between a line connecting a point of contact P between the striking portion 29 and arm 26 and the center of the shaft and a line connecting the point P and the center 0 of the shaft 28. The energy imparted to the typebar 6 by the rotating hammer 27 can thus be adjusted so as to regulate the printing strength of the head 7 per character. Especially when the printing speed is varied with varying rotating speeds of the hammer 27, the printing 1 strength is increased with increasing hammer rotation speed and decreased with decreasing hammer rotation speed, where the angular position of the typebar6 is fixed. The damage inflicted on paper 3, ambiguous printing, and misprints can thus be prevented by adjusting the printing strength. In FIG. 4, the velocity of the typebar 6 at the point P is v.cosB, where v is the velocity of the hammer 27 at P. If 0) denotes the angular velocity of the typebar 6 and FT), denotes the distance between P and Q, the following relationship exists: E30) vcosfl 3 cos ITLw/v With the value of B obtained from equation (2), the eccentricstopper 30 is adjusted so as to substantially fix the printing strength, respective of the printing (rotating) speed of the hammer 27, where the angular velocity to is practically constant. Throughout FIGS. 1 to 4, the same numerals designate the same parts. For the sake of brevity, the construction and operation of the printer shown in FIG. 4 are omitted here. What is claimed is: 1. A printer comprising: a typewheel (2) having characters formed on its pe riphery and rotating at a substantially constant speed; a typebar (6) with a printing head (7) for printing a selected character on a material to be printed, such as paper, through an inked ribbon; a device for defining two difierent positions of the typebar (6), a rest position corresponding to when said printing head (7) is spaced from the periphery of the typewheel (2), and a driving position corresponding to when said printing head (7) is located beyond the rest position to a position where it may 4 be impulsively driven towards said typewheel; a driving means (27-20) for impulsively driving said typebar (6) toward said typewheel (2) when said printing head (7) is in the driving position of the typebar so as to cause said printing head (7) to strike a selected character on the paper through an inked ribbon; characterized in that said position defining device comprises a first projection (9) fdrmed on said typebar (6), a movable trigger lever (11) having first (12) and second (13) engaging portions respectively engageable with said first projection (9) in the driving (FIG. 2) and rest (Fl 1) positions of the typebar (6), and said second engaging portion (13) including a recess into which said first projection (9) is selectively received after a printing operation to prevent said typebar (6) from moving toward said typewheel (2) arid causing undesired double printing. 2. The printer according to claim 1' wherein said typebar (6) has a second projection (25% ger lever (11) has a pressure arm (24) which selectively bears against said second projectioii 25) so as to cause the trigger lever (11) to contact e second projection (25) in the printing position and I move to another position when there is a change from the printing position to the rest position, said another ition being one in which said first projection (9) is e gaged in said second engaging portion (13). 3. The printer according to claim 2 wh rein said trigger lever (11) has a free end portion (14). with said first and second engaging portions and said pressure arm (24) projects in a direction substantially perpendicular to the free end of the trigger lever (11).f 4. The printer according to claim 1 wherein an adjustable eccentric stopper (30) is associated with said typebar (6) to adjust the angular position of said typebar (6) in the driving position of the typbbar (6). 5. The printer according to claim 1 wherein said trigger lever 11) has a step (15) located adjacent to said second engaging portion (13), the first l portion (12) being higher than the step (15) with respect to the bottom of the second engaging portion (13):, the first pro and said m g typewheel (2) has raised characters foi'med on its outer periphery. 8. The printer according to claim 1 including biasing means (8) for biasing said typebar (6) away from said typewheel (2). p 9. The printer according to claim 1 comprising second biasing means (16) for biasing said trigger lever 11) toward an engagement position between said first projection (9) and said second engaging portion (13).

Description

Topics

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