EP0252722B1 - Wire-dot print head and wire therefor - Google Patents

Wire-dot print head and wire therefor Download PDF

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Publication number
EP0252722B1
EP0252722B1 EP87306003A EP87306003A EP0252722B1 EP 0252722 B1 EP0252722 B1 EP 0252722B1 EP 87306003 A EP87306003 A EP 87306003A EP 87306003 A EP87306003 A EP 87306003A EP 0252722 B1 EP0252722 B1 EP 0252722B1
Authority
EP
European Patent Office
Prior art keywords
wire
chromium
alloy
print head
cobalt
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.)
Expired - Lifetime
Application number
EP87306003A
Other languages
German (de)
English (en)
French (fr)
Other versions
EP0252722A2 (en
EP0252722A3 (en
Inventor
Yasuo Oki Electric Industry Co. Ltd. Omori
Iwao Oki Electric Industry Co. Ltd. Hashimoto
Hirokazu Oki Electric Industry Co. Ltd. Andou
Masakazu Oki Electric Industry Co. Ltd. Shino
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.)
Oki Electric Industry Co Ltd
Original Assignee
Oki Electric Industry Co 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
Priority claimed from JP61300099A external-priority patent/JPS63147655A/ja
Application filed by Oki Electric Industry Co Ltd filed Critical Oki Electric Industry Co Ltd
Publication of EP0252722A2 publication Critical patent/EP0252722A2/en
Publication of EP0252722A3 publication Critical patent/EP0252722A3/en
Application granted granted Critical
Publication of EP0252722B1 publication Critical patent/EP0252722B1/en
Anticipated expiration legal-status Critical
Expired - Lifetime 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
    • B41J2/235—Print head assemblies
    • B41J2/25—Print wires
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C29/00—Alloys based on carbides, oxides, nitrides, borides, or silicides, e.g. cermets, or other metal compounds, e.g. oxynitrides, sulfides
    • C22C29/02—Alloys based on carbides, oxides, nitrides, borides, or silicides, e.g. cermets, or other metal compounds, e.g. oxynitrides, sulfides based on carbides or carbonitrides
    • C22C29/06—Alloys based on carbides, oxides, nitrides, borides, or silicides, e.g. cermets, or other metal compounds, e.g. oxynitrides, sulfides based on carbides or carbonitrides based on carbides, but not containing other metal compounds
    • C22C29/08—Alloys based on carbides, oxides, nitrides, borides, or silicides, e.g. cermets, or other metal compounds, e.g. oxynitrides, sulfides based on carbides or carbonitrides based on carbides, but not containing other metal compounds based on tungsten carbide

Definitions

  • This invention relates to a wire-dot or dot-matrix print head, in particular to a print head with an improved wire material and the wires therefor.
  • Laid Open Japanese Patent Application No. 56354/1983 has parts shown in cross-section in Figure including an armature 1, a first yoke 2, a magnetic spacer 3, a second yoke 4, a permanent magnet 5, a core 6, a demagnetizing coil 7, a bias spring 8, an armature supporter 9, a wire 10, an ink ribbon 11, a platen roll 12, and a recording media 13.
  • the demagnetizing coil 7 When the demagnetizing coil 7 is not excited, the magnetic flux from the permanent magnets is transmitted through the second yoke 4, the magnetic spacer 3, the first yoke 2, the armature and the core 6, producing a magnetic force that attracts the armature 1 to the core 6. The magnetic force overcomes the bias spring.
  • the flux from the demagnetizing coil 7 cancels the flux of the permanent magnet 5, releasing the spring 8, which drives the wire 10 attached to the tip of the armature 1 in the direction of the arrow so that the tip 10a of the wire 10 presses the ink ribbon 11 against the recording media 13 on the platen roll 12 to print on the media.
  • Laid-Open Japanese Patent No.79766/1984 discloses the use of a superhard alloy wire.
  • German Patent Application No.DE-A-1924753 discloses a hard metal composition containing from 0.1 to 2.5% by weight of chromium carbide, 9 to 20% by weight of cobalt and the balance substantially of tungsten carbide, and a method for making such a composition.
  • the chromium carbide is present as a dispersion of fine grains less than 0.2 microns in size and is preferably formed in situ.
  • the wires of the wire-dot print head are made of a superhard corrosion-resistant tungsten-carbide-cobalt (WC-Co) alloy in which the molar ratio of chromium to cobalt is from 0.004 to 0.2. This ratio will be referred to herein as the 'chromium concentration ratio'.
  • the wire portion exposed to ink at least is to be of the above indicated alloy.
  • m be the weight percentage of the cobalt component of the wire
  • n be the weight percentage of the chromium component of the wire
  • M be the atomic weight of the cobalt
  • N be the atomic weight of chromium
  • Points marked with X represent wire with a cobalt weight percentage of 30% and the symbols ⁇ , ⁇ , and ⁇ represent cobalt weight percentages of 25%, 20%, and 15% respectively.
  • the ink used in these tests had a dye content of 25%, and immersion temperature was 25°C.
  • Ink generally comprises a pigment, a dye, a dispersing agent, and an oil.
  • the pigment, the dispersing agent, and the oil were not observed to cause any corrosion.
  • Figure 4 shows the results of tests of the dye carried out as described above. The corrosion loss can be seen to vary in proportion to the percent of dye in the ink. When this percent is 0, the corrosion loss is 0. The conclusion reached was that the dye is the principal cause of the corrosion described above. The dye is, however, an essential component of the ink because it acts to complement the pigment colour.
  • the chromium concentration ratio is indicated on the horizontal axis and the corrosion loss (in milligrams) on the vertical axis.
  • the points marked with X represent wires with a cobalt weight percentage of 30% and the symbols ⁇ , ⁇ , and ⁇ represents cobalt weight percentages of 25%, 20% and 15% respectively.
  • the ink used in these tests had a dye content of 25% the immersion temperature was 95°C, and the immersion time was 100 hours.
  • FIG. 5 The results in Figure 5 indicated that at chromium concentration ratios above 0.004, the corrosion loss decreases and corrosion resistance improves markedly as the concentration ratio increases.
  • the mechanical strength of the wire which affects the print head performance is however influenced by the presence of chromium.
  • the mechanical strength of a superhard alloy is usually expressed in terms of transverse-rupture strength.
  • Figure 6 shows the relation between chromium concentration ratio and the transverse-rupture strength ratio.
  • the chromium concentration ratio is indicated on the horizontal axis.
  • the transverse-rupture strength ratio is indicated on the vertical axis.
  • the transverse-rupture strength ratio is defined as the transverse-rupture strength with no chromium added. The closer the ratio is to 1, the less is the degradation of transverse-rupture strength due to the addition of chromium.
  • the chromium concentration ratio should be selected to be from 0.004 to 0.2.
  • power of Cr was mixed in WC and Co.
  • powder of chromium carbide (Cr3C2) can be mixed in WC and Co and the mixture can be sintered. Similar alloys can be obtained by the use of chromium carbide.
  • Figures 7 and 8 show the results of similar trials using chromium carbide (Cr3C2) in place of chromium (Cr).
  • Figure 7 shows the relationship between the ratio of the quantity of moles of chromium carbide to the quantity in moles of cobalt (called the chromium-carbide concentration ratio below) and the amount of corrosion loss.
  • Figure 8 shows the relationship between the chromium-carbide concentration ratio and the transverse-rupture strength ratio. In both Figures 7 and 8 two scales are indicated on the horizontal axis, the lower one giving the chromium-carbide concentration ratio and the upper one giving the chromium carbide concentration ratio converted to a chromium-component (Cr) concentration ratio.
  • Cr chromium-component
  • the wire-dot print head of this invention uses a superheard, corrosion-resistant WC-Co alloy with a chromium concentration ratio of 0.004 to 0.2 which provides adequate mechanical strength and resistance to corrosion, gives long-term, stable printing service, and can therefore greatly improve the reliability of a printer in which it is employed.
  • Such benefits can of course be obtained not only in spring-charged wire-dot print heads but also in other types of print heads such as plunger-type and clapper-type heads.
  • a chromium concentration ratio of greater than 0.01 can give a very significant improvement and at a ratio of 0.05 a substantial amount of the total corrosion prevention effect can be obtained. At a ratio 0f 0.08 or in that region a substantial transverse rupture strength ratio is obtainable. Thus there is a region in which considerable improvements in corrosion resistance are possible at small or negligible losses in transverse rupture strength.
EP87306003A 1986-07-08 1987-07-07 Wire-dot print head and wire therefor Expired - Lifetime EP0252722B1 (en)

Applications Claiming Priority (4)

Application Number Priority Date Filing Date Title
JP158766/86 1986-07-08
JP15876686 1986-07-08
JP61300099A JPS63147655A (ja) 1986-07-08 1986-12-18 ワイヤドツト印字ヘツド
JP300099/86 1986-12-18

Publications (3)

Publication Number Publication Date
EP0252722A2 EP0252722A2 (en) 1988-01-13
EP0252722A3 EP0252722A3 (en) 1989-03-22
EP0252722B1 true EP0252722B1 (en) 1992-03-04

Family

ID=26485783

Family Applications (1)

Application Number Title Priority Date Filing Date
EP87306003A Expired - Lifetime EP0252722B1 (en) 1986-07-08 1987-07-07 Wire-dot print head and wire therefor

Country Status (2)

Country Link
EP (1) EP0252722B1 (un)
DE (1) DE3776994D1 (un)

Family Cites Families (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE751608C (de) * 1938-03-25 1952-11-24 Fried Krupp A G Verwendung von gesinterten Hartmetallegierungen
US3628921A (en) * 1969-08-18 1971-12-21 Parker Pen Co Corrosion resistant binder for tungsten carbide materials and titanium carbide materials
US4652157A (en) * 1983-12-21 1987-03-24 Kabushiki Kaisha Toshiba Printing wire

Also Published As

Publication number Publication date
EP0252722A2 (en) 1988-01-13
EP0252722A3 (en) 1989-03-22
DE3776994D1 (de) 1992-04-09

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