EP0067953B1 - Dispositif d'impression électrothermique - Google Patents

Dispositif d'impression électrothermique Download PDF

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Publication number
EP0067953B1
EP0067953B1 EP19820103987 EP82103987A EP0067953B1 EP 0067953 B1 EP0067953 B1 EP 0067953B1 EP 19820103987 EP19820103987 EP 19820103987 EP 82103987 A EP82103987 A EP 82103987A EP 0067953 B1 EP0067953 B1 EP 0067953B1
Authority
EP
European Patent Office
Prior art keywords
electrodes
print head
ribbon
print
contact
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
Application number
EP19820103987
Other languages
German (de)
English (en)
Other versions
EP0067953A2 (fr
EP0067953A3 (en
Inventor
Walter Crooks
Cameron Henry Hafer
William Joseph Weiche
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.)
International Business Machines Corp
Original Assignee
International Business Machines Corp
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 International Business Machines Corp filed Critical International Business Machines Corp
Publication of EP0067953A2 publication Critical patent/EP0067953A2/fr
Publication of EP0067953A3 publication Critical patent/EP0067953A3/en
Application granted granted Critical
Publication of EP0067953B1 publication Critical patent/EP0067953B1/fr
Expired 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
    • B41J2/315—Typewriters or selective printing mechanisms characterised by the printing or marking process for which they are designed characterised by selective application of heat to a heat sensitive printing or impression-transfer material
    • B41J2/32—Typewriters or selective printing mechanisms characterised by the printing or marking process for which they are designed characterised by selective application of heat to a heat sensitive printing or impression-transfer material using thermal heads
    • B41J2/335—Structure of thermal heads
    • B41J2/33555—Structure of thermal heads characterised by type
    • B41J2/3356—Corner type resistors
    • 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
    • B41J2/315—Typewriters or selective printing mechanisms characterised by the printing or marking process for which they are designed characterised by selective application of heat to a heat sensitive printing or impression-transfer material
    • B41J2/32—Typewriters or selective printing mechanisms characterised by the printing or marking process for which they are designed characterised by selective application of heat to a heat sensitive printing or impression-transfer material using thermal heads
    • B41J2/335—Structure of thermal heads
    • B41J2/33555—Structure of thermal heads characterised by type
    • B41J2/33565—Edge type resistors

Definitions

  • the invention relates to non-impact printers and, is more particularly concerned with electrothermal printers in which printing is effected by momentarily energising selected electrodes of an array of electrodes to cause discrete areas of a transfer ribbon to be resistance heated and release transfer material to a print medium to print characters and other indicia.
  • US Specification No. 2713822 (Newman) describes an early form of an electrothermal printer in which a three-layer resistive transfer ribbon is used in conjunction with a single stylus. By energising a circuit including the stylus facsimile images would be transferred to a receiving medium e.g. a paper sheet.
  • the Montanari electrothermal printer uses a resistive transfer ribbon and comprises a print head having a plurality of electrodes for electrically contacting the ribbon during printing.
  • the printer comprises a key board for applying an input to control coding device which selectively applies voltages between the electrodes and a common return electrode to effect printing of the keyed input.
  • the Montanari electrodes are L-shaped and the shorter legs extend down through a slot in a plate on which the electrodes are mounted by passing the lower legs through an upwardly projecting land on the plate. The ends of the shorter legs bear against the ribbon which contacts the underside of the plate.
  • the Montanari electrodes are sufficiently rigid to contact the transfer ribbon with the required contact pressure. To meet this standard of rigidity the electrodes have a cross- sectional area above a lower threshold cross- sectional area and this limits the resolution that can be obtained.
  • US 4,236,834 acknowledged in the preamble of claim 1 discloses an electrothermal print head comprising a line of wire electrodes and a support structure, approximately half of each electrode, remote from the ribbon, being embedded in the support structure and the remaining approximately half of each electrode, including the end in contact with the ribbon, being completely unsupported.
  • Each electrode is very fine which means that the contact pressure obtainable is low so that either the printing speed is low or the print produced is of poor quality.
  • EU 28,334 also discloses an electrothermal print head comprising a line of wire electrodes but in this case the return electrode is an integral part of the head and the electrode contact ends and the return electrode are arranged to be a mere 13 pm apart in an attempt to obtain high print resolution.
  • This head has no structural flexibility so if an irregularity in the print ribbon is encountered, the entire head is retracted and printing is temporarily lost.
  • the invention provides a print head for resistive ribbon printing using a ribbon of the type including an electrically conductive layer, said print head having an array of longitudinally extending wire electrodes each having an end for electrically contacting the ribbon at an acute angle during printing, the electrodes alone being insufficiently rigid resiliently to contact the ribbon with the required contact pressure, a support comprising insulating resilient material for supporting and stiffening each electrode over a substantial portion of its length while permitting limited lateral movement of individual electrodes with respect to other electrodes in the array and a relatively rigid mounting means for mounting said support, characterised in that:
  • the present invention solves all the problems posed by providing a resilient support extending effectively all the way to the contact tips of the electrodes but relieved in front of the electrodes and a rigid backing member extending along the back of the support to provide additional support for the electrodes at their contact ends.
  • This support supports the individual electrodes against excessive flexure, enabling them to withstand a much higher contact pressure, yet permits limited movement of any individual electrode away from adjacent electrodes without significantly affecting the adjacent electrodes.
  • the provision of a relief on the support ensures that the electrodes in the print head can contact the print ribbon at an acute angle and that the pressure between the print head and the ribbon is concentrated in the region of the support at which the electrode contact ends appear.
  • the support is formed of an elastomeric material. This has been found to be suitable since elastomeric materials can provide the rigidity, resilience and insulation required.
  • the electrodes are arranged in a single plane. This enables simple electrical driving circuits to be used and reduces the area of contact required between the print head and the print ribbon.
  • the backing member is a plate mounted parallel to the plane containing the electrodes, thereby providing a uniform pressure on the electrodes.
  • the backing plate is a sheet of spring steel.
  • the support is in the form of block which is relieved in front of the array of contacts by chamfer.
  • the backing plate is coextensive with a face of the block support on the opposife side of the block support from the chamfer.
  • the print head may be employed in an elec--trothermal printer including a print head as described above, a print head carrier for carrying said print head so that the electrodes are arranged to contact the ribbon at an acute angle during printing, means for moving said carrier and print head towards the ribbon during printing to produce a contact pressure between 1400 kPa and 7000 kPa and means for selectively energising the electrodes to effect printing.
  • the printing apparatus embodying the invention is shown illustratively associated with a typewriter-like printing apparatus 10 comprising a conventional keyboard 11.
  • the keyboard controls a print head 12 by means of a coding device of known type (not shown).
  • Print head 12 is mounted on a carrier 13 that is movable transversely of apparatus 10 but parallel to the feed path of a ribbon 14.
  • Print head 12 presses ribbon 14 against a record medium 15 that is backed up by a platen 16.
  • ribbon 14 is unwound from a supply reel 17 and wound onto a take-up reel 18, and record medium 15 is fed upwardly in a direction at right angles to the direction of movement of ribbon 14 and print head 12.
  • Print head 12 is mounted on carrier 13 by means to be described later which produces a predetermined overall pressure between the print head 12 and print ribbon 14.
  • Carrier 13 is driven by carrier drive means 20 (Fig. 2) to effect horizontal movement of the print head.
  • Carrier drive means 20 includes pulleys 21 and 22 about which is strung a cable 23 which connects to suitable clutch, drive shafts and the like 24.
  • Carrier 13 comprises a hollow rectangular member 25 which is mounted for movement on horizontal traverse members 26.
  • Print head mounting member 27 is mounted on traverse members 28 for movement toward the print medium for printing operations and away from the print medium for non-printing operations.
  • Traverse members 28 are fixed to hollow rectangular member 25 at a substantially right angle to horizontal traverse members 26.
  • Suitable control means 29 are actuated to move print head mounting member 27 relative to member 25 toward print ribbon 14 and record medium 15 to produce a predetermined pressure between print head 12 and print ribbon 14.
  • An adjustable stop 19 is provided to enable initial setting of the predetermined pressure.
  • control means 29 comprises a solenoid.
  • Print head 12 is fixed to print head mounting member 27 in a position so that the print electrodes form an angle with respect to platen member 16. This angle is not critical and an angle of about forty-five degrees has been found to be suitable.
  • print head 12 comprises an array of thin electrodes 30 arranged in a closely spaced row.
  • the electrodes are held in their equally closely spaced position by a support comprising a suitable electrically insulating resilient material 32.
  • a relatively rigid backing member 34 of a mounting means is fixed to the elctrode structure to permit the print electrode assembly to withstand the required pressure. This member 34 extends along the back of the resilient material 32 until the end thereof adjacent to the electrodes 30.
  • Print electrodes are electrically connected to a board member 31 which preferably has printed wiring patterns thereon.
  • a support board member 33 of said mounting means is provided through which contact pins 35 are passed between electrical connector 37 and board member 31 to provide an electrical circuit from each print electrode 30 to one of the contacts in connector 37.
  • a mounting block 38 is fixed into position between boards 31 and 33 to hold in a fixed position the end of backing member 34, which is away from the active ends of the print electrodes.
  • Connector 37 provides the electrical interface between print head 12 and the remainder of the printer, and suitable means such as a flex cable, for example, is provided to conduct signals to the print head.
  • the print head is fixed to a suitable mounting member 39 of said mounting means which provide the mechanical interface to the print head mounting member 27.
  • the active tip ends of the print electrodes 30 which normally contact the print ribbon 14 are shown in Fig. 4.
  • the electrodes 30 are held in an equally spaced line by electrically insulating resilient material 32 which maintains the electrodes spaced apart from mounting member 34.
  • Silicone rubber is a suitable insulating resilient material due to its ability to withstand the heat generated during operation of the print head.
  • the resilient material is formed with an angled relief portion or chamfered corner 36 on the side away from backing member 34 to enable better electrical contact between the print electrodes 30 and print ribbon 14.
  • the chamfered corner is obtained by removing a generally triangular-sectioned strip of the resilient material adjacent the contact ends of electrodes 30 so that the front side of said corner which faces the print ribbon 14 is confined by two parallel edges extending across the ribbon, the inner edge of which coinciding with the array of electrodes 30 embedded in the resilient material 32.
  • This construction also facilitates a limited movement of an individual print electrode out of alignment toward backing member 34 (Fig. 4) without arcing or other electrical interference. Should debris or a localised ribbon imperfection affect one or more of print electrodes 30, the print head construction described herein permits limited movement of individual electrodes without causing the print head 14 to move out of contact with the ribbon which causes either no printing or poor quality printing to occur.
  • the minimum resolution that produces printing with resolution approaching that of engraved type is about 100 dots per centimeter, i.e. 250 dots per inch, resolution.
  • the electrodes are limited to a diameter of 25.4 microns to 76.2 microns (0.001 inch to 0.003). This requirement presents a severe technical problem since electrodes of this size are not self-supporting, and to ensure excellent print quality, a pressure of several hundred pounds per square inch that is in excess of 1400 Kilo-Pascals, is required between the individual electrodes and the resistive substrate.
  • Electrodes of this size are necessary since 100 dots per centimeter resolution means dots or lines on 101.6 micron (0.004) centers, and the thermal spreading characteristics of available resistive ribbons limits the size of the electrodes to 25.4 microns to 76.2 microns (0.001 to 0.003 inch). Electrodes of this dimension are difficult to retain on 101.6 micron (0.004 inch) centers, particularly since the electrodes are not self-supporting.
  • the print head comprised 40 thin tungsten wire electrodes, each 38.1 microns (0:0015 inch) in diameter and held accurately equally spaced on 101.6 microns (0.004 inch) centers by a suitable resilient insulating material which, in that embodiment, comprised silicone rubber.
  • a suitable resilient insulating material which, in that embodiment, comprised silicone rubber.
  • One suitable silicone rubber is a high temperature RTV silicon rubber made by General Electric Company which withstands temperatures up to 500°C.
  • the electrode assembly was fixed to a relatively rigid mounting member which, in that embodiment, comprised spring steel 127 microns (0.005 inch)
  • Ribbon 14 comprises a resistive layer 50, a conductive layer 41, and an ink transfer layer 52.
  • the resistive layer 50 is in pressure contact with the print electrodes, and the ink transfer layer 52 is in contact with the record medium 15.
  • Appropriate control means 53 is provided to generate suitable signals to selectively energize print electrodes 30 according to the graphic or character data to be printed.
  • Element 54 is suitably connected to a reference potential such as ground.
  • the 1 2 R effect will cause heating of that portion of the layer 50 that extends from the tip end of the electrode 30 to the conductive layer 51.
  • This localized heating of the resistive layer 50 by the current-resistance effect causes melting of the thermally transferable material in the contiguous portion of the ink transfer layer 52.
  • the construction of the print head according to our invention permits printing to be accomplished in a reliable manner with excellent print quality even though the print electrodes are not self-supporting, and a pressure of several hundred pounds per square inch must be maintained between the individual print electrodes and the resistive ribbon.
  • a pressure of several hundred pounds per square inch must be maintained between the individual print electrodes and the resistive ribbon.
  • the entire print head would be moved out of position so that the required pressure could not be maintained between the individual print electrodes and the resistive ribbon. The result is either no printing at all or poor quality printing.
  • our print head includes the resilient electrically insulating which normally holds the print electrodes in a closely spaced row but has sufficient resiliency so that individual print electrodes can be moved out of position to a limited extent while maintaining the required pressure between the other print electrodes and the resistive ribbon.
  • the backing member cooperates with the electrode assembly to impart the needed stiffness to withstand the required pressure while maintaining a degree of resilience to the print electrode area due to the spring like nature of the backing member.

Claims (7)

1. Tête d'impression (12) pour impression par ruban électriquement résistant, utilisant un ruban (14) d'un type comportant une couche électriquement conductrice (51), ladite tête d'impression ayant une rangée d'électrodes (30) sous forme de fils s'étendant longitudinalement, chacune ayant une extrémité pour contacter électriquement le ruban sous un angle aigu pendant l'impression, les électrodes toutes seules étant insuffisamment rigides élastiquement pour venir en contact avec le ruban avec la pression de contact nécessaire, un support (32) comprenant un matériau élastique isolant pour supporter et raidir chaque électrode sur une partie substantielle de sa longueur, tout en permettant un mouvement latéral limité individuel des électrodes par rapport aux autres électrodes dans la rangée d'électrodes, et des moyens de montage relativement rigides (33, 34, 38,39) pour monter ledit support, caractérisée par le fait que le matériau élastique dudit support s'étend essentiellement sur toute la ligne des extrémités de contact des électrodes (30) et comporte un dégagement (36) en face de la rangée de contacts pour permettre à la rangée de contacts de venir en contact avec le ruban d'impression sous ledit angle aigu, et par le fait que lesdits moyens de montage, dans le but de fournir un support supplémentaire auxdites électrodes à leurs extrémités de contact, comportent une pièce de renforcement (34) relativement rigide s'étendant le long de l'arrière dudit matériau élastique jusqu'à l'extrémité de ce matériau élastique adjacent audites électrodes de contact.
2. Tête d'impression selon la revendication 1, dans laquelle ledit support (32) est formé d'un matériau élastomère.
3. Tête d'impression selon les revendications 1 ou 2, dans laquelle les électrodes (30) sont disposées dans un plan unique et dans laquelle la pièce de renforcement est une plaque (34) montée parallèlement au plan contenant les électrodes.
4. Tête d'impression selon la revendication 3, dans laquelle ladite pièce de renforcement (34) est une plaque d'acier à ressort.
5. Tête d'impression selon l'une quelconque des revendications précédentes, dans laquelle ledit support a la forme d'un bloc qui présente un dégagement en face de la rangée de contacts par un chanfrein (36).
6. Tête d'impression selon la revendication 5, et dépendant des revendications 3 ou 4, dans laquelle la plaque est de même étendue qu'un côté dudit bloc support sur le côté opposé dudit bloc support par rapport au chanfrein.
7. Imprimante électrothermique comportant une têté d'impression selon l'une quelconque des revendications précédentes, un chariot de tête d'impression pour déplacer ladite tête d'impression, de telle sorte que les électrodes soient disposées pour entrer un contact avec le ruban sous un angle aigu pendant l'impression, des moyens pour déplacer ledit chariot et la tête d'impression vers le ruban pendant l'impression, pour produire une pression de contact entre 1.400 et 7.000 kPa, et des moyens pour activer de façon sélective les électrodes afin d'effectuer l'impression.
EP19820103987 1981-06-22 1982-05-07 Dispositif d'impression électrothermique Expired EP0067953B1 (fr)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
US27631781A 1981-06-22 1981-06-22
US276317 1981-06-22

Publications (3)

Publication Number Publication Date
EP0067953A2 EP0067953A2 (fr) 1982-12-29
EP0067953A3 EP0067953A3 (en) 1985-04-17
EP0067953B1 true EP0067953B1 (fr) 1988-08-10

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Family Applications (1)

Application Number Title Priority Date Filing Date
EP19820103987 Expired EP0067953B1 (fr) 1981-06-22 1982-05-07 Dispositif d'impression électrothermique

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EP (1) EP0067953B1 (fr)
JP (1) JPS57212078A (fr)
CA (1) CA1181987A (fr)
DE (1) DE3278876D1 (fr)

Families Citing this family (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0443339A1 (fr) * 1990-02-21 1991-08-28 Lexmark International, Inc. Tête d'impression de transfert thermique et son procédé de fabrication
CZ81997A3 (en) * 1996-03-20 1997-10-15 Immuno Ag Pharmaceutical preparation for treating disorders connected with blood clotting, process of its preparation and use

Family Cites Families (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS537277B2 (fr) * 1973-07-11 1978-03-16
US3979966A (en) * 1974-08-08 1976-09-14 Kinoton Gmbh Clutch device for either intermittent or continuous driving of perforated film
US3978494A (en) * 1975-11-13 1976-08-31 Sperry Rand Corporation Stylus assembly
US4195937A (en) * 1977-09-19 1980-04-01 Termcom, Inc. Electroresistive printing apparatus
US4236834A (en) * 1978-09-28 1980-12-02 International Business Machines Corporation Electrothermal printing apparatus
EP0028334A3 (fr) * 1979-11-01 1982-12-29 International Business Machines Corporation Procédé et appareil pour marquer thermographiquement un support d'enregistrement

Also Published As

Publication number Publication date
EP0067953A2 (fr) 1982-12-29
EP0067953A3 (en) 1985-04-17
CA1181987A (fr) 1985-02-05
DE3278876D1 (en) 1988-09-15
JPS57212078A (en) 1982-12-27

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