EP0322991A1 - Wire dot print head - Google Patents

Wire dot print head Download PDF

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Publication number
EP0322991A1
EP0322991A1 EP88300001A EP88300001A EP0322991A1 EP 0322991 A1 EP0322991 A1 EP 0322991A1 EP 88300001 A EP88300001 A EP 88300001A EP 88300001 A EP88300001 A EP 88300001A EP 0322991 A1 EP0322991 A1 EP 0322991A1
Authority
EP
European Patent Office
Prior art keywords
wire
print
wear
vanadium
strikes
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Withdrawn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
EP88300001A
Other languages
German (de)
English (en)
French (fr)
Inventor
Yasuo Ohmori
Hirokazu Andou
Iwao Hasihmoto
Masakazu 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
Application filed by Oki Electric Industry Co Ltd filed Critical Oki Electric Industry Co Ltd
Publication of EP0322991A1 publication Critical patent/EP0322991A1/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Withdrawn legal-status Critical Current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
    • B41J2/485—Typewriters or selective printing mechanisms characterised by the printing or marking process for which they are designed characterised by the process of building-up characters or image elements applicable to two or more kinds of printing or marking processes
    • B41J2/505—Typewriters or selective printing mechanisms characterised by the printing or marking process for which they are designed characterised by the process of building-up characters or image elements applicable to two or more kinds of printing or marking processes from an assembly of identical printing elements
    • 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

Definitions

  • This invention concerns the wire dot print head used in an impact printer, and in particular the print wires used in the print head.
  • Impact printers incorporating a print head that prints by driving print wires have the advantage of very low cost, and are able to print on various media at high speed. As a result, they are used as man-machine interfaces in peripheral terminals of data processing systems and a wide variety of other applications. But in recent years a strong need has emerged for higher printing speeds.
  • the print head should be highly reliable.
  • the print wires in particular, should not be liable to wear due to repeated impact or damage as a result of fatigue, so that the printer has a stable operation over long periods of time.
  • Fig. 8 is a view in profile of, for example, the wire dot print head shown in Japanese Patent Application Publication No. 56354/1983. In order to reveal the structure, the lower half of the print head is shown in section.
  • 1 is a print wire of which the base is fixed to the tip of armature 2.
  • the base of the armature 2 is supported by the end of biasing leaf spring 3, and the base of spring 3 is fixed to armature supporter 4.
  • 5 is a first yoke
  • 6 is a magnetic spacer
  • 7 is a second yoke
  • 8 is a permanent magnet
  • 9 is a base, these elements being layered in a specified order.
  • Said armature supporter 4 is fixed so that it is in contact with said first yoke 5, magnetic spacer 6 and second yoke 7.
  • a demagnetizing coil 11 is fitted to core 10.
  • the demagnetizing coil 11 when the demagnetizing coil 11 is not energizing, the flux of permanent 8 permeates second yoke 7, magnetic spacer 6, first yoke 5, armature 2, core 10 and base 9. Because of the magnetic attraction resulting then, the armature 2 is drawn to core 10 as it bends bias string 3.
  • Bias spring 3 then restores its shape.
  • printing wire 1 attached to armature 2 is driven in the direction shown by the arrow in the figure, and its tip strikes the recording medium on the platen roll (not shown in the figure) through the ink ribbon, and prints an ink dot as a pixel on the medium.
  • wire 1 begins to move in the reverse direction to the direction of said arrow, and when the excitation of said demagnetizing coil 11 stops, armature 2 is again pulled towards core 10 by the flux magnet 8. This completes one print cycle.
  • print wire 1 reciprocates a specified distance once.
  • a print head there are several sets of wires 1, armatures 2, bias springs 3, cores 10 and demagnetizing coils 11.
  • Each print wire 1 is driven selectively and by means of a printing action as described above. Characters consisting of dots are thereby recorded on the recording medium.
  • the wire dot print head traverses the specified distance back and forth once on each printing cycle. If the tip of the wire suffers wear and the wire becomes shorter, the distance traversed by the wire will be longer. As a result, the time from when the armature is released by the attractive force when it leaves the core until when the wire strikes the recording medium, and the time from when the print wire strikes the recording medium until when the armature is again attracted by the core, i.e. the return time, are longer, and so the time required by the print wire to travel both directions in order to complete one cycle is longer.
  • the wear of the print wire is a mechanical abrasion due to the ink ribbon.
  • This abrasive wear depends on the wire material, print force, amount of movement while the wire is in contact which depends on print speed, and the fractional coefficient between the contact surfaces of the wire and ink ribbon.
  • Typical frictional coefficients are given in "Transactions of the Institute of Electronics and Communication Engineers of Japan". Sept. 1984, Vol. J67-C, No. 9, p. 643 - p. 650.
  • the black ink used in the black ink ribbon in an impact printer is usually a composition containing carbon black as disclosed in Japanese Patent Application Publication No. 60956/1982.
  • This composition consists of carbon black and oil-soluble dyes or pigments added to a vegetable or mineral oil vehicle, with a further addition of dispersion and other agents.
  • Carbon black as disclosed in the "Kahbon Burakku Binran (Manual of Carbon Black)" (25 May, 1973), published by Tosho, p. 376 - p. 377, is an excellent pigment which has light resistance, heat resistance, alkali resistance, acid resistance and solvent resistance.
  • carbon black suffers very little structural disintegration under simple compression even up to 5400 kg/cm2.
  • the printing pressure on the print head (the printing pressure is the print force divided by the area of the wire contributing to printing, where the print force is the force applied during printing by the wire on the recording medium), is 1400 kg/cm2. It can thus be appreciated that since carbon black can withstand a pressure of 5400 kg/cm2, it must be regarded as consisting of very hard particles.
  • print wires consist of cemented carbide alloys
  • they have excellent wear resistance, but they contain 70 - 85% weight percent of tungsten carbide of density 13.5 - 14.5 g/cm3. It is therefore difficult to make the head lightweight, and to achieve high printing speeds.
  • the wire if the wire consists of ferrous metals such as high-speed steel, its density is then only 8 g/cm3. This makes lightweightness possible, which is favorable to high printing speeds, but as the hardness is much lower than in the case of cemented carbide alloys the wire lacks wear resistance, and there is a consequent shortening of lifetime and reliability.
  • the wire dot print head is composed of a large number or wires and armatures, so it is important that the print wire should be low cost.
  • An object of the invention is to provide a wire dot print head with excellent wear resistance which is also lightweight and low cost.
  • this invention offers a print wire made from powder of high-speed steel, to which no less than 4.0 weight percent of vanadium and no less than 14 equivalents of tungsten have been added to confer wear resistance and fatigue resistance.
  • the print wire composition of this invention described above is based on high-speed steel which is a ferrous metal, and it can therefore be made lightweight. At the same time, it contains no less than 4.0 weight percent of vanadium and 14 equivalents of tungsten which are homogeneously dispersed in the steel in powder form, so that wear resistance and fatigue resistance of the wire are improved.
  • the wire is therefore able to print at high speed in stable operations over a long period of time, giving improved reliability, and as it can be manufactured fairly easily, its cost is low.
  • the print wire consists of high-­speed steel with varying amounts of vanadium and equivalents of tungsten.
  • the wear resistance of metals can be improved by using as hard a material as possible, and increasing the hardness still further by heat treatment.
  • Methods for example as revealed in the article "Metal Wear and Countermeasures" (20 June, 1975), Yokendo, p. 3, of the grades of steel currently available, high-speed steel satisfies these requirements most closely.
  • molten mixture of steel, vanadium and tungsten is cooled by atomized water or nitrogen to solidify into minute particles of the size in the order of microns. This process is called atomization.
  • the particles are then sintered in vacuum at a temperature of about 1100 to 1250°C for about 60 minutes, and then pressed into block in argon (Ar) gas with a pressure of about 40MPa (408 kgf/cm2) at a temperature of about 1200°C for about 30 minutes.
  • Ar argon
  • high-speed steel a steel containing approx. 4 weight percent of chlorium with an equivalent weight of tungsten of about 10 - 30 and 1 - 5 weight percent of vanadium, and where in addition a high degree of secondary hardness is obtained by heat treatment such as quenching and tempering.
  • chromium mainly confers hardenability on the high-speed steel while vanadium, as a primary carbide in the steel, forms a vanadium carbide of great hardness (hardness Hv approx. 2500). These thereby confer wear resistance.
  • Tungsten and molybdenum as primary carbides in the steel, form tungsten carbide and molybdenum carbide of very great hardness (hardness Hv 1300 - 1800).
  • hardness Hv 1300 - 1800 hardness Hv 1300 - 1800.
  • secondary hardening a fine dispersion of secondary carbides is formed so as to give a tough matrix (secondary hardening), which together with the primary carbides confers high wear resistance on the high-speed steel.
  • the wire was manufactured by an elongation process which is economical and has excellent adaptibility to mass production techniques. For a content of 9 weight percent, however, the hardness of the high-speed steel is too great and the elongation process could not be used. It was in this case therefore manufactured by an extrusion process similar to that normally used for cemented carbide alloys, followed by sintering. Further, in order to remove decarbonizing and other defective layers on the wire surface, the cylindrical envelope of the wire was ground down.
  • Heat treatment such as quenching and tempering of high speed steel was also carried out under conditions for which the fatigue strength was greatest for each particular grade.
  • the ink ribbon was formed by taking 50 m of polyamide or polyester fiber, and winding it into a Mabius spool of width 13 mm and thickness 0.12 mm. The spool was evenly coated and impregnated with 20 g of ribbon ink containing 5, 10 and 15 weight percent of carbon black respectively.
  • Fig. 7 shows the progress of wear on the print wire, which is characterized by some very specific features. It is seen that for any content of vanadium, the reduction ⁇ h in the length of the wire on its central axis (referred to hereinafter as the amount of wear) is not in direct proportion to the number of print strikes, and until the tip of the wire assumes a definite shape, there is in fact practically no wear ⁇ h on the central axis.
  • position a in Fig. 7 corresponding to 30x104 strikes, b to 80x104, c to 140x104, d to 230x104 and e to 107.
  • position a in Fig. 7 corresponds to 70x104 strikes, b to 188x104, c to 329x104, d to 540x104, and e to 2370x104.
  • position a in Fig. 7 corresponds to 113x104 strikes, b to 355x104, c to 621x104, d to 1020x104, and e to 2255x104.
  • the number of print strikes until longitudinal wear of the wire begins is closely related to its vanadium content.
  • this number is 230x104; for a wire containing 5 weight percent of vanadium, the number is 540x104; while for a wire containing 7 weight percent of vanadium, the number 1020x104.
  • Fig. 1 shows the relation between the amount of wear of the wire as measured by this method and the number of print strikes, the number of strikes being shown on the horizontal axis, and the wear of the wire ⁇ h at a given number of strikes being shown on the horizontal axis.
  • the number of strikes at which wear ⁇ h begins to be observed depends on the vanadium content, and was found to be as follows.
  • Fig. 2 shows the correlation between the wear of the print wire at this time, and the vanadium content.
  • the vanadium content of the high-speed steel is on the horizontal axis, while the wear of the wire after 108 print strikes is shown on the vertical axis.
  • the vanadium content should be not less than 4 weight percent to improve the wear resistance of the print wire.
  • Fig. 3 shows the fatigue strength of the print wire in this experiment.
  • the horizontal axis is the amount of vanadium in the high-speed steel, while the vertical axis represents the average number of print strikes until a rupture occurred due to fatigue. At each measurement point, 10 samples were used.
  • the symbols correspond to pressures of 120 kg/mm2, 130 kg/mm2 and 140 kg/mm2, respectively. In every case, the fatigue strength tends to decrease depending on the vanadium content although the decrease is not very great.
  • the vanadium content should be no less than 4 weight percent in order to improve the wear resistance of the print wire without considerable loss of fatigue strength.
  • the vanadium content of the print wire should be no less than 4 weight percent in order to increase its wear resistance.
  • the wire was manufactured by the above elongation process.
  • wires with higher tungsten equivalents were very hard, however, they could not be manufactured by elongation. Instead, therefore, these latter wires were formed by extrusion as described above, followed by sintering and grinding.
  • Table 2 shows the detailed chemical composition of the wires used in this experiment.
  • the wires were formed by the same powder metallurgical techniques as in the previous experiments, and heat treatment was also carried out as previously under those conditions for which fatigue strength was greatest for the various grades of steel. In addition, all wear tests and fatigue tests performed on the wires were carried out under exactly the same conditions as in the previous experiments.
  • the amount of wear of the wire was investigated as a function of the number of print strikes using an ink ribbon wherein the ink contained 15 weight percent of carbon black.
  • Fig. 4 shows the relation between the amount of wear of the print wire and the number of print strikes at this time.
  • the horizontal axis in the figure is the number of print strikes mentioned above, and the vertical axis is the amount of wear of the wire for various numbers of print strikes.
  • the amount of wear ⁇ h increased in proportion to the number of strikes as in the previous experiment.
  • the amount of wear for 108 strikes of the print wire was then obtained.
  • Fig. 5 shows the relation between the wear of the wire and the equivalent tungsten content.
  • the horizontal axis is the equivalent tungsten content of the high-speed steel, while the vertical axis is the wear of the wire after 108 print strikes.
  • the amount of wear decreased with increasing equivalent tungsten content. Up to a tungsten content of 14, however, the wear increased sharply in comparison to other tungsten contents.
  • Fig. 6 shows the fatigue strength of the print wire in this experiment.
  • the horizontal axis is the equivalent tungsten content of the high-speed steel, while the vertical axis is the average number of print strikes until the wire ruptures due to fatigue.
  • 10 samples were used.
  • the symbols correspond to pressures of 120 kg/mm2, 130 kg/mm2 and 140 kg/mm2 respectively.
  • the fatigue strength of the wire tended to decrease with increasing equivalent tungsten content, although the decrease was not very great.
  • the equivalent tungsten content should be no less than 14 in order improve the wear resistance of the wire without any appreciable loss of fatigue strength.
  • the print wire in this invention consists of high speed steel containing no less than 4.0 weight percent of vanadium and having an equivalent tungsten content of no less than 14.
  • the wire is lightweight but also has sufficient mechanical strength and wear resistance. It can therefore be used for high speed print over long periods giving stable operation and improved reliability.
  • this wire based on high-speed steel can be manufactured more easily and at lower cost than in the case of a cemented carbide alloy.
  • This invention can of course not only be used in a spring-charged wire dot print head, but also offers the same advantages in a plunger or clapper type head.
EP88300001A 1987-01-09 1988-01-04 Wire dot print head Withdrawn EP0322991A1 (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
JP62001842A JPS63170042A (ja) 1987-01-09 1987-01-09 ワイヤドツト印字ヘツド
JP1842/87 1987-01-09

Publications (1)

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EP0322991A1 true EP0322991A1 (en) 1989-07-05

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EP88300001A Withdrawn EP0322991A1 (en) 1987-01-09 1988-01-04 Wire dot print head

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EP (1) EP0322991A1 (ja)
JP (1) JPS63170042A (ja)
KR (1) KR880008884A (ja)

Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3828908A (en) * 1972-01-11 1974-08-13 W Schneider Mosaic print head
JPS58112761A (ja) * 1981-12-26 1983-07-05 Hitachi Metals Ltd ドツトプリンタ用プリントワイヤ
JPS61199055A (ja) * 1985-02-28 1986-09-03 Hitachi Metals Ltd ドツトプリンタ用ワイヤ材
JPS62192574A (ja) * 1986-02-17 1987-08-24 Kobe Steel Ltd ドツトピン用窒化焼結高速度鋼の製造方法

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3828908A (en) * 1972-01-11 1974-08-13 W Schneider Mosaic print head
JPS58112761A (ja) * 1981-12-26 1983-07-05 Hitachi Metals Ltd ドツトプリンタ用プリントワイヤ
JPS61199055A (ja) * 1985-02-28 1986-09-03 Hitachi Metals Ltd ドツトプリンタ用ワイヤ材
JPS62192574A (ja) * 1986-02-17 1987-08-24 Kobe Steel Ltd ドツトピン用窒化焼結高速度鋼の製造方法

Non-Patent Citations (3)

* Cited by examiner, † Cited by third party
Title
Derwent Accession No. 83-732 685, Questele Telesystemes (WPIL) Derwent Publications Ltd., London * Abstract * & JP-A-58-112 761 (Hitachi) *
Derwent Accession No. 86-274 634, Questele Telesystemes (WPIL) Derwent Publications Ltd., London * Abstract * & JP-A-61-199 055 (Hitachi) *
Derwent Accession No. 87-274 871, Questele Telesystemes (WPIL) Derwent Publications Ltd., London * Abstract * & JP-A-62-192 574 (Kobe Steel) *

Also Published As

Publication number Publication date
KR880008884A (ko) 1988-09-13
JPS63170042A (ja) 1988-07-13

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