EP0502720A2 - Punktmatrixanschlagdruckkopf - Google Patents

Punktmatrixanschlagdruckkopf Download PDF

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Publication number
EP0502720A2
EP0502720A2 EP92301870A EP92301870A EP0502720A2 EP 0502720 A2 EP0502720 A2 EP 0502720A2 EP 92301870 A EP92301870 A EP 92301870A EP 92301870 A EP92301870 A EP 92301870A EP 0502720 A2 EP0502720 A2 EP 0502720A2
Authority
EP
European Patent Office
Prior art keywords
leaf spring
print head
print
piezoelectric element
dot matrix
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Withdrawn
Application number
EP92301870A
Other languages
English (en)
French (fr)
Other versions
EP0502720A3 (en
Inventor
Yoshiyuki c/o Brother Kogyo K. K. Ikezaki
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Brother Industries Ltd
Original Assignee
Brother Industries Ltd
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Brother Industries Ltd filed Critical Brother Industries Ltd
Publication of EP0502720A2 publication Critical patent/EP0502720A2/de
Publication of EP0502720A3 publication Critical patent/EP0502720A3/en
Withdrawn legal-status Critical Current

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Classifications

    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B41—PRINTING; LINING MACHINES; TYPEWRITERS; STAMPS
    • B41J—TYPEWRITERS; SELECTIVE PRINTING MECHANISMS, i.e. MECHANISMS PRINTING OTHERWISE THAN FROM A FORME; CORRECTION OF TYPOGRAPHICAL ERRORS
    • B41J2/00—Typewriters or selective printing mechanisms characterised by the printing or marking process for which they are designed
    • B41J2/22—Typewriters or selective printing mechanisms characterised by the printing or marking process for which they are designed characterised by selective application of impact or pressure on a printing material or impression-transfer material
    • B41J2/23—Typewriters or selective printing mechanisms characterised by the printing or marking process for which they are designed characterised by selective application of impact or pressure on a printing material or impression-transfer material using print wires
    • B41J2/27—Actuators for print wires
    • B41J2/295—Actuators for print wires using piezoelectric elements

Definitions

  • the present invention relates to a dot matrix impact print head device having a piezoelectric element which is expanded and contracted in response to the application of a voltage thereto and transmits expanding and contracting movement to a print wire that strikes a print medium such as a sheet of paper.
  • the device includes a print head having a head body, an arm, a motion transmitting mechanism, and a piezoelectric element.
  • the print head includes a print wire for striking a print medium.
  • the head body includes a nose, and a front end of the print wire can project forwardly from and be retracted back into the nose.
  • the arm has a distal end to which a proximal portion of the print wire is fixed.
  • the motion transmitting mechanism is mounted on the distal end of the arm, and the piezoelectric element is mounted on an end of the motion transmitting mechanism.
  • the piezoelectric element is expansible and contractible in response to the application of a voltage thereto.
  • the arm is moved through the motion transmitting mechanism, so that the print wire can be moved toward and away from the print sheet.
  • the disclosed print head includes a head body 1 substantially in the shape of a disk as viewed in plan, and a cylindrical cover 2 covering a back of the head body 1.
  • the head body 1 has a nose 3 projecting from a central portion thereof.
  • the head body 1 houses a plurality of radially arranged print units 4.
  • Each of the print units 4 includes a piezoelectric element 5, a support frame 6 supporting the piezoelectric element 5, a print wire 7 having a front end that can project forwardly from and be retracted back into the nose 3, an arm 8 to which a proximal end 7a of the print wire 7 is attached, and a motion transmitting mechanism 9 for amplifying the expanding and contracting movement of the piezoelectric element 5 and transmitting the amplified movement through the arm 8 to the print wire 7.
  • intermediate guide plates 42 are provided for guiding reciprocating movements of the print wires 7.
  • the motion transmitting mechanism 9 converts the expanding and contracting movement of the piezoelectric element 5 into angular movement of the arm 8 for amplifying projecting and retracting movement of the print wire 7 mounted on the distal end of the arm 8.
  • the motion transmitting mechanism 9 is in the form of an Eden's twin strips spring which has two parallel leaf springs 12, 13.
  • the leaf springs 12, 13 have ends joined to a rigid joint 10, providing a ⁇ shape as viewed in side elevation.
  • the first leaf spring 12 has a proximal end brazed to one side of the support frame 6.
  • the second leaf spring 13 has a proximal end brazed to a movable member 14 mounted on a front end of the piezoelectric element.
  • the first and second leaf springs 12, 13 extend in a direction parallel to the print wire 7. Further, the two leaf springs 12, 13 extend in a direction opposite the extending direction of the print wire 7.
  • the joint 10 interconnecting the ends of the leaf springs 12, 13 is angularly moved in the direction indicated by an arrow A into a two-dot-and-dash line position.
  • the arm 8 is angularly moved about an axis 15 that is located substantially intermediately between the parallel leaf springs 12, 13 and substantially at the center of the leaf springs 12, 13 in the longitudinal direction thereof.
  • the proximal end 7a of the print wire 7 is caused by the arm 8 to angularly move about the axis 15 along a curve having a radius R of curvature.
  • the proximal end 7a of the print wire 7 is disposed in a position closer to the nose 3 than a reference line 16 that extends from the axis 15 in a direction substantially parallel to the arm 8 and substantially perpendicular to direction in which the leaf springs 12, 13 extend, as shown in Fig. 7.
  • the position of the proximal end 7a is spaced perpendicularly from the reference line 16 toward the nose 3 by a distance Hl .
  • a line 17 interconnecting the axis 15 and the proximal end 7a along the radius R is angularly spaced from the reference line 16 by an angle ⁇ .
  • the angle by which the arm 8 angularly moves should preferably be converted into a maximum back-and-forth movement of the print wire 7.
  • a displacement X1 of the proximal end 7a along an-X-axis is greater as the angle ⁇ is larger.
  • the print wire 7 has an intermediate portion guided by the nose 3 so that the print wire 7 is slidably movable in the axial direction and limited against transverse movement. Consequently, if the transverse displacement of the proximal end 7a is large, then undue forces are imposed on the print wire 7, presenting a large resistance to the axial sliding movement of the print wire 7. Accordingly, a desired printing process cannot be carried out unless a large voltage is applied to the piezoelectric element 5. Stated otherwise, the electric power consumption of the disclosed print head is large, resulting in an energy loss in the performance of the print head.
  • the object of the invention is to provide large stroke of the printing wire in the back-and-forth direction yet providing a minimum displacement of the print wire in a lengthwise direction of the arm.
  • a dot matrix impact print head device for providing a dot matrix pattern on a print medium comprising a print head body having a nose portion, a print wire, an arm, a piezoelectric element, and a motion transmitting means.
  • the print wire has a distal end to strike on the print medium and has a proximal end. The distal end is projectable forwardly from and retractable back into the nose portion in a projecting/retracting direction.
  • the arm has a distal end portion to which the proximal end of the print wire is attached and has a proximal end portion.
  • the piezoelectric element is supported on the print head body. The piezoelectric element is expandable and shrinkable in a longitudinal direction thereof.
  • the motion transmitting means has a first resilient portion fixed to the print head body, a second resilient portion coupled to the piezoelectric element and a third portion joining together the first and the second resilient portions.
  • the third portion is coupled to the proximal end portion of the arm.
  • a pivotal center is defined in the motion transmitting means and resilient deformation of the first and second resilient portions provides a pivotal motion of the arm about the pivotal center.
  • a line connecting between the pivotal center and the proximal end of the print wire extends in a direction substantially perpendicular to the projecting/retracting direction.
  • a dot matrix type print head device according to a first embodiment of the present invention will be described with reference to Figs. 1, 2 and 8.
  • the device has a basic structure substantially the same as that of the print head device disclosed in the co-pending U. S. Patent Application Serial No. 07/760,479 such as shown in Fig. 7.
  • the dot matrix impact print head device generally includes a print head body 1 having a nose, and a print unit 4A.
  • the print unit 4A includes a print wire 7, an elongated piezoelectric element 5, a motion transmitting mechanism 20, and a support frame 6.
  • the piezoelectric element 5 is in the form of a stack of bonded piezoelectric ceramic segments.
  • the motion transmitting mechanism 20 is mounted on one end of the piezoelectric element 5 for amplifying and transmitting expanding and contracting movement of the piezoelectric element 5 to the print wire 7.
  • the support frame 6 extends from one side face of the print head body 1 and supporting the motion transmitting mechanism 20 and the piezoelectric element 5.
  • the support frame 6 is provided with a stop 30.
  • the support frame 6 is of an integral unitary structure having a U-shape cross-section.
  • the support frame 6 is composed of a main column 6a, an auxiliary column 6b, and an end portion (not shown), which jointly surround lengthwise sides and another end of the piezoelectric element 5.
  • the print wires 7 of the print units 4A can project forwardly from and be retracted back into the nose on the front surface of the print head body 1.
  • the piezoelectric element 5 When a voltage is applied, the piezoelectric element 5 is expanded and contracted along the stack thereof, i.e., in the longitudinal direction thereof.
  • a temperature compensation member (not shown) for correcting the dimensions of the piezoelectric element 5 which is contracted when the temperature increases, is interposed between the rear end of the support frame 6 and the rear end of the piezoelectric element 5.
  • the print wire 7 has a proximal end 7a brazed to an arm 22 which is of a substantially triangular shape as viewed in side elevation.
  • the motion transmitting mechanism 20 is coupled to a proximal end of the arm 22. Expanding and contracting movement of the piezoelectric element 5 is amplified and converted into back-and-forth movement of the print wire 7 by the motion transmitting mechanism 20 and the arm 22.
  • the arm 22 has one side provided with an abutment block 29 formed of a synthetic resin. The abutment block 29 is abutable on the stop 30 on the support frame 6.
  • the motion transmitting mechanism 20 includes a support leaf spring 24 and a drive leaf spring 25 extending rearwardly in the longitudinal direction of the main column 6a parallel to each other, and a rigid joint 26 interconnecting distal ends of the springs 24, 25.
  • the joint 26 is fitted in and fixed to the proximal end of the arm 22 as by spot-welding.
  • the support leaf spring 24 has a proximal end brazed to a side of the main column 6a.
  • the drive leaf spring 25 has a proximal end brazed to a side of a movable member 14 that is adhesively fixed to a front end of the piezoelectric element 5.
  • the piezoelectric element 5 When a voltage is applied, the piezoelectric element 5 is expanded and the movable member 14 is moved in the direction indicated by an arrow B (Fig. 1).
  • the joint 26 which interconnect the springs 24, 25 is angularly displaced in the direction indicated by an arrow A, and the angular displacement of the joint 26 is amplified by the arm 22 to cause the print wire 7 to project from the nose.
  • the arm 22 When the voltage application is stopped, the arm 22 is angularly moved back under the resiliency of the springs 24, 25 until the abutment block 29 mounted on the arm 22 abuts against and is stopped by the stop 30 mounted on the support frame 6.
  • Fig. 8 is a cross-sectional view taken along line VIII - VIII of Figs. 1 and 7.
  • a quadric link mechanism 27 is disposed astride of the other side of the movable member 14 and the auxiliary column 6b.
  • the quadric link mechanism 27 is in the form of a resilient member such as a leaf spring, and has a pair of wider side panels 27a each having a recess 28 that is substantially H-shaped as viewed in side elevation.
  • the wider side panels 27a are fixed to front and back sides of the auxiliary column 6b and also front and back sides of the movable member 14 by spot-welding at positions adjacent the drive leaf spring 25a and the stop 30.
  • the wider side panels 27a are elastically deformed into the shape of a parallelogram as viewed in side elevation, moving the movable member 14 in the longitudinal direction of and parallel to the auxiliary column 6b that is fixed in position with respect to the movable member 14.
  • the movable member 14 is movable in the longitudinal direction of and parallel to the auxiliary column 6b, i.e., linearly in the longitudinal direction of the piezoelectric element 5, no bending stresses are applied to the bonded surfaces of the stacked piezoelectric ceramic units, and hence the stacked piezoelectric ceramic units will not be peeled off accidentally along the bonded surfaces.
  • the arm 22 or the motion transmitting mechanism 20 is angularly moved about an axis 31.
  • a line 32 which interconnects the axis 31 and the proximal end 7a of the print wire 7 which is joined to the distal end of the arm 22 extends substantially perpendicularly to the direction in which the print wire 7 moves back and forth.
  • the direction of back-and-forth movement of the print wire 7 lies parallel to an axis 33 of the motion transmitting mechanism 20, along which the springs 24, 25 extend, the axis 33 passing through the axis 31.
  • the arm 22 has, on its lower side (Fig. 1), an integral protrusion 22a extending between the proximal end thereof to which the joint 26 is attached and the distal end thereof to which the proximal end 7a of the print wire 7 is fixed.
  • the protrusion 22a projects to the longitudinal intermediate portions of the springs 24, 25.
  • a recess 34 is formed at the proximal end of the arm 22, and the joint 6 is fixed to the recess 34.
  • the recess defines a depth in a direction toward the dot impacting direction of the printing wire 7, i.e., in the direction toward the back of the head body 1 (Fig. 1).
  • the proximal end 7a of the print wire 7 is spaced from the axis 31 by 50 mm, and that the axis of the print wire 7 extends perpendicularly to the line 32.
  • a dot matrix impact print head device is shown in Fig. 3.
  • a drive leaf spring 25 and a support leaf spring 24, which jointly serve as an Eden's twin strips spring, are positioned in an inverted relationship to those shown in Fig. 1.
  • the piezoelectric element 5 is contracted upon the application of a voltage, the print wire 7 projects from the nose for dot printing.
  • Fig. 4 shows a dot matrix impact printing device having a print unit 4C according to a third embodiment of the present invention.
  • a support leaf spring 24 and a drive leaf spring 25 are positioned on opposite sides of a joint 26 and extend respectively opposite directions parallel to each other.
  • the springs 24, 25 extend parallel to the direction of back-and-forth movement of the print wire 7.
  • the arm 22 is moved between an angle of - ( ⁇ /2) to an angle of ( ⁇ /2) with respect to a reference line (i.e., a line extending from the axis 31 perpendicularly to the direction of back-and-forth movement of the print wire 7).
  • a reference line i.e., a line extending from the axis 31 perpendicularly to the direction of back-and-forth movement of the print wire 7.
  • a dot matrix impact print head device having a print units 4D according to a fourth embodiment of this invention is shown in Fig. 5.
  • an arm 22 has a longitudinal direction thereof extending parallel to the direction in which the support and drive leaf springs 24, 25 extend, and a line 32 interconnecting the axis 31 and the proximal end 7a of the print wire 7 extends substantially perpendicularly to the direction in which the print wire 7 moves back and forth.
  • the line 32 interconnecting the pivotal center axis 31 and the proximal end 7a of the print wire 7 is selected in position to be substantially aligned with the reference line 16 in the conventional print head.
  • the line which interconnects the axis about which the arm is angularly movable upon elastic deformation of the support and drive leaf spring resulting from the expansion and contraction of the piezoelectric element and the position where the proximal end of the print wire is fixed to the distal end of the arm is selected in position to extend substantially perpendicularly across the direction in which the print wire 7 extends (i.e. moves back and forth).
  • any transverse displacement of the print wire 7 is greatly reduced while the angular displacement of the arm is selected to cause the print wire 7 to move back and forth over a minimum stroke necessary for dot printing.
  • the energy applied to energize the piezoelectric element can be reduced for effective back-and-forth movement of the print wire. Accordingly the dot matrix impact print head device according to the present invention can be relatively small in size and can exhibit improved printing performance.

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  • Impact Printers (AREA)
EP19920301870 1991-03-04 1992-03-04 Dot matrix impact print head device Withdrawn EP0502720A3 (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
JP1919691U JPH04109147U (ja) 1991-03-04 1991-03-04 ドツトインパクト印字ヘツド装置
JP19196/91 1991-03-04

Publications (2)

Publication Number Publication Date
EP0502720A2 true EP0502720A2 (de) 1992-09-09
EP0502720A3 EP0502720A3 (en) 1992-12-09

Family

ID=31905525

Family Applications (1)

Application Number Title Priority Date Filing Date
EP19920301870 Withdrawn EP0502720A3 (en) 1991-03-04 1992-03-04 Dot matrix impact print head device

Country Status (2)

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EP (1) EP0502720A3 (de)
JP (1) JPH04109147U (de)

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE4327326A1 (de) * 1992-08-18 1994-03-03 Fujitsu Ltd Elektromechanischer Betätiger, welcher in einem Matrix-Nadeldruckkopf verwendet wird

Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0333595A2 (de) * 1988-03-18 1989-09-20 Fujitsu Limited Druckkopf eines Nadelpunktanschlagdruckers
EP0352075A2 (de) * 1988-07-21 1990-01-24 Brother Kogyo Kabushiki Kaisha Vorrichtung zur Vergrösserung der Lageverschiebung eines piezoelektrischen Elementes
EP0452502A1 (de) * 1989-11-01 1991-10-23 Oki Electric Industry Company, Limited Drahtbetätigungsvorrichtung für drucker

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0333595A2 (de) * 1988-03-18 1989-09-20 Fujitsu Limited Druckkopf eines Nadelpunktanschlagdruckers
EP0352075A2 (de) * 1988-07-21 1990-01-24 Brother Kogyo Kabushiki Kaisha Vorrichtung zur Vergrösserung der Lageverschiebung eines piezoelektrischen Elementes
EP0452502A1 (de) * 1989-11-01 1991-10-23 Oki Electric Industry Company, Limited Drahtbetätigungsvorrichtung für drucker

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE4327326A1 (de) * 1992-08-18 1994-03-03 Fujitsu Ltd Elektromechanischer Betätiger, welcher in einem Matrix-Nadeldruckkopf verwendet wird
DE4327326C2 (de) * 1992-08-18 1999-08-12 Fujitsu Ltd Elektromechanische Betätigungseinrichtung für die Nadel eines Nadel-Matrixdruckers, sowie Druckkopf für einen Nadel-Matrixdrucker

Also Published As

Publication number Publication date
JPH04109147U (ja) 1992-09-21
EP0502720A3 (en) 1992-12-09

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