EP0238926A1 - Druckkopf für einen Punktmatrixdrucker - Google Patents

Druckkopf für einen Punktmatrixdrucker Download PDF

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Publication number
EP0238926A1
EP0238926A1 EP87103348A EP87103348A EP0238926A1 EP 0238926 A1 EP0238926 A1 EP 0238926A1 EP 87103348 A EP87103348 A EP 87103348A EP 87103348 A EP87103348 A EP 87103348A EP 0238926 A1 EP0238926 A1 EP 0238926A1
Authority
EP
European Patent Office
Prior art keywords
needles
levers
electromagnets
printhead according
heads
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Withdrawn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
EP87103348A
Other languages
English (en)
French (fr)
Inventor
Claude-Michel Juvet
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.)
Comadur SA
Original Assignee
Comadur SA
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 Comadur SA filed Critical Comadur SA
Publication of EP0238926A1 publication Critical patent/EP0238926A1/de
Withdrawn legal-status Critical Current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
    • B41J2/235—Print head assemblies
    • B41J2/24—Print head assemblies serial printer type
    • 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
    • B41J2/275—Actuators for print wires of clapper type

Definitions

  • the subject of the present invention is a print head for a dot matrix printer.
  • needles are housed in a head which is moved step by step in the direction of the lines to be printed and which further comprises electromagnets for actuating them individually and several guide devices in which they pass successively and which have the role of concentrating the beam they form at the start and to ensure that the alignment of their ends is as perfect as possible.
  • the electromagnets which have a U-shaped yoke surrounded by a coil, are arranged around the upper part of the needles and each of these is fixed to the free end of a thin blade of magnetic material which extends radially in front of one of the poles of an electromagnet and which has its other end linked and magnetically coupled to the other pole of the latter.
  • the coil of an electromagnet is not energized, the magnetic strip associated with it is kept away from the pole to which it is not fixed, due to its own elasticity or under the action of 'a spring, and the corresponding needle remains in a withdrawal or rest position.
  • the blade comes to press against this pole and the needle is brought into printing position.
  • the needles only need to be slightly curved and they are almost all to the same degree. We can therefore dispense with passing them through tubes. In addition, these heads can be significantly smaller than the previous ones. Unfortunately, here again we can hardly exceed 1500 Hz and this for the following reason. Since the blades are made of magnetic material, they are relatively heavy and difficult to move and, in this sense, it is advantageous to reduce their dimensions as much as possible. However, the thinner and narrower they are, the more quickly they become saturated in magnetic flux when they are attracted to the electromagnets and the greater the iron losses in these, mainly due to the eddy currents. We are therefore obliged to be satisfied with a compromise which corresponds roughly to the value of the operating frequency which we have just indicated if we do not want the temperature of the heads in question to greatly exceed the 100 ° C.
  • the heads which are designed in this way make it possible to achieve a slightly higher working frequency, around 1800 Hz.
  • the electromagnets which are always arranged in a circle around the upper part of the needles, comprise each a yoke, a coil and a plunger core to which is fixed, by its central part, an elastic blade, one of the ends of which is made solid of the yoke, on the side opposite to that where the needles are located.
  • an elastic blade On the other hand, on this blade is molded a plastic stiffening piece which goes from the plunger core to the head of a needle which can be linked to it or simply kept in contact with it thanks to a spring acting on this needle.
  • the main object of the present invention is to provide a print head which can also work at a very high frequency and which does not have this drawback.
  • a printhead according to the invention which also includes a set of needles each having a first intended for printing and a second end, guide devices in which the needles are said to have their first ends aligned in at least one row, elastic means for making the needles normally occupy a first position, and a set of electromagnets arranged around the second ends of the needles and each comprising a yoke, a coil and a plunger core coupled to the second end of one of these needles to bring it into a second position when said coil is traversed by a current, the cores of the electromagnets are respectively coupled to the second ends of the needles by levers of non-magnetic material to which they are fixed.
  • levers can advantageously be made of a synthetic material which allows them to be light and, consequently, to be able to be moved very easily by the electromagnets.
  • the print head according to the invention has nine needles, which makes it possible to achieve a very good compromise between its volume and the graphic quality of the characters it is able to print.
  • this head comprises a main part 2 which would have the shape of a rectangular parallelepiped with a square base if its four lateral faces 4 were not slightly curved in the direction of their length and which is closed at its upper part by a cover 6, fixed by means of screws 8 arranged at its four corners.
  • this main part 2 At the front of this main part 2 is placed a rigid printed circuit board 10 which extends beyond the lower side face 4 in order to be able to carry a connection connector 12. Normally, this board is pierced with a number of holes and has conductive tracks on its front face but, for clarity of the drawing, neither these holes nor these tracks have been shown.
  • a nose 14 which includes a part 16 in the form of a pyramid trunk with rectangular section, a flange 20 located at the base thereof which allows this nose to be fixed to the part main 2 by means of two screws 22, the printed circuit board being taken between the two, and two wings 24 each pierced with an oblong hole 26, by which the head can be mounted on the printer for which it is intended, all these parts being made in one piece of plastic.
  • the pyramidal part has at its end a groove 28 in which is housed the last guide 30 in which the needles pass and which is the one which must ensure perfect alignment of their ends.
  • the nose 14 penetrates inside this opening 36 of the part 34, approximately to half the height of that -this, and forms a transverse wall 40 there, the upper face of which has nine countersinks 42 the utility of which will appear later, which are arranged in a circle around the center of the wall and the bottoms of which are pierced with respective holes 44, much smaller diameter, through which the needles pass 46.
  • This wall 40 therefore constitutes a first guide for the needles and, for this reason, it is necessary for the plastic material which constitutes the nose 14 to resist wear and temperature very well.
  • This material may for example be a polycarbonate loaded with carbon fibers.
  • first guide and the last 30 which has already been discussed and which is made up of a block of very hard and self-lubricating material such as synthetic ruby, pierced of closely spaced and perfectly aligned holes, there are two intermediate guides 48 and 50 mounted in slides formed by pairs of rectilinear and parallel bosses 52, respectively 54, that are present inside each of the walls of the nose 14 to which the fixing wings 24 (see figure 1).
  • the first of these intermediate guides that is to say the one, 48, which is closest to the transverse wall 40 consists of a plastic plate which is at least as resistant to wear and temperature as this wall and which is pierced with holes of diameter substantially equal to that of the needles.
  • These holes can be arranged in a smaller circle than that formed by the holes 44 in the first guide 40 or better in an ellipse whose major axis is parallel to the direction of alignment of those in the last guide 30.
  • the second intermediate guide 50 has only a slit of width equal to or barely greater than the diameter of the needles and parallel to the row of holes in the guide 30. It can be constituted for example by two bars of hard material, as the synthetic ruby, linked together by plastic plates fixed at their ends by glue which also penetrates between these two bars to define the length of the slot.
  • part 34 in addition to opening 36 it has nine cylindrical cavities 56 in which electromagnets 58 are housed and, like this part 34 its role is not only to carry these electromagnets but also to dissipate the heat they give off as best as possible, it is made of a material with good thermal conductivity, preferably cast aluminum.
  • its faces 32 have longitudinal grooves 60 that could already be seen in Figure 1 and which increase its contact surface with the ambient air.
  • each of these comprises a yoke 62, the bottom of which has a cylindrical internal boss 64, a coil 66 arranged around the latter and the wire 68 of which passes through holes 70, 72 and 74 drilled respectively in the bottom of the cylinder head, in the part 34 and in the printed circuit board, to have its ends fixed on conductive tracks not shown of the latter, a plunger core 76 placed above the boss 64 and a part of which comes out of the cavity in which the electromagnet is located, and a shunt 78 in the form of a washer situated above the coil and surrounding this core, all of these elements, except the coil, preferably being made of mild steel.
  • each needle 46 which is advantageously made of tungsten and which has a molded head of plastic material 80, is actuated by one end of a lever 82 of synthetic material, for example of P.O.M. (polyoxymethylene) loaded with glass fiber and Teflon (registered trademark), which has been molded onto a head 84 which has the plunger core 76 of the electromagnet associated with this needle and the other end of which has, on the side of the part 34, a hemispherical or semi-cylindrical boss 86 which bears on a metal flange 88, for example of brass, placed on this part and surrounding all the cores at a distance.
  • a lever 82 of synthetic material for example of P.O.M. (polyoxymethylene) loaded with glass fiber and Teflon (registered trademark)
  • an elastic blade 90 for example made of steel or a beryllium-copper alloy, which tends to lift it by pivoting it around an axis perpendicular to its longitudinal direction, which passes through the top of its boss 86 and under each needle head is provided a coil spring 92 which bears on the bottom of the countersink 42 of the wall 40 in which this needle passes and which permanently keeps this head pressed against the blade 90 of the lever which corresponds to it.
  • the blades 90 therefore have two roles here. The first is to ensure a correct position of the levers 82 relative to the needles and guide them so that they can only rotate around the axis that has been indicated. The second is to cooperate with the springs 92 to force the needles to normally occupy a withdrawal position when the coils of the electromagnets are not supplied with current or to bring them there when they move away from it.
  • this frame 94 is taken between the cover 6 and a spacer 98, for example made of brass, which rests on the flange 88 and whose thickness is substantially equal to the height of the bosses 86.
  • the ultrasonic welding technique can advantageously be used.
  • FIG. 2 shows the two levers, the two blades and the two needles which are in the broken section planes. Normally, we should see four more.
  • cover 6 its internal wall, the shape of which is adapted to that of the upper face of the levers, has two concentric circular grooves 100 and 102 in which rings of the "O-" type are placed.
  • ring “104, respectively 106 of a rubbery material.
  • the first, 104, of these rings which is located above the bosses 86 of the levers has the role of keeping these pressed against the flange 88.
  • the second, 106 larger, is placed above the heads of needles and serves as a stop for the ends of the levers and noise damper.
  • this cover is made of the same material as the part 34 and that it also has grooves (not shown) because thanks to this it can participate effectively in the evacuation of the heat of the head.
  • Tests carried out have shown that with a head of this kind it is easy to reach a frequency of 2500 Hz without exceeding an operating temperature of about 65 ° and that one could seek to go up to 3000 Hz.
  • this head fits in a cube of only four centimeters on the side and its structure lends itself very well to automated assembly. , which reduces its cost price.
  • the blades could be replaced by other means for positioning and guiding the levers, located for example in the head cover, and leaving the coil springs to maintain and return the needles to this position. In this case it would obviously be necessary to use stronger springs.

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  • Impact Printers (AREA)
EP87103348A 1986-03-27 1987-03-09 Druckkopf für einen Punktmatrixdrucker Withdrawn EP0238926A1 (de)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
FR8604668 1986-03-27
FR8604668A FR2596323A1 (fr) 1986-03-27 1986-03-27 Tete d'impression pour imprimante par matrice de points

Publications (1)

Publication Number Publication Date
EP0238926A1 true EP0238926A1 (de) 1987-09-30

Family

ID=9333779

Family Applications (1)

Application Number Title Priority Date Filing Date
EP87103348A Withdrawn EP0238926A1 (de) 1986-03-27 1987-03-09 Druckkopf für einen Punktmatrixdrucker

Country Status (3)

Country Link
EP (1) EP0238926A1 (de)
JP (1) JPS62236756A (de)
FR (1) FR2596323A1 (de)

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB2236078A (en) * 1989-08-26 1991-03-27 Citizen Watch Co Ltd Electrical connections and heat dissipation in dot matrix printers
EP0466286A1 (de) * 1990-06-20 1992-01-15 MANNESMANN Aktiengesellschaft Matrixnadeldruckkopf

Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0138779A2 (de) * 1983-10-14 1985-04-24 Ing. C. Olivetti & C., S.p.A. Matrixdrucker
EP0146751A1 (de) * 1983-11-23 1985-07-03 HONEYWELL BULL ITALIA S.p.A. Verfahren zur Herstellung einer Ankeranordnung für einen Mosaikdruckknopf
US4531848A (en) * 1982-10-27 1985-07-30 Royden C. Sanders, Jr. Dot matrix print head
US4555192A (en) * 1983-02-25 1985-11-26 Tokyo Electric Co., Ltd. Release type dot printer head
EP0162586A2 (de) * 1984-04-23 1985-11-27 BSR North America Ltd. Matrix-Nadeldruckkopf
US4575268A (en) * 1984-10-25 1986-03-11 Industrial Technology Research Institute Dot matrix printer head

Patent Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4531848A (en) * 1982-10-27 1985-07-30 Royden C. Sanders, Jr. Dot matrix print head
US4555192A (en) * 1983-02-25 1985-11-26 Tokyo Electric Co., Ltd. Release type dot printer head
EP0138779A2 (de) * 1983-10-14 1985-04-24 Ing. C. Olivetti & C., S.p.A. Matrixdrucker
EP0146751A1 (de) * 1983-11-23 1985-07-03 HONEYWELL BULL ITALIA S.p.A. Verfahren zur Herstellung einer Ankeranordnung für einen Mosaikdruckknopf
EP0162586A2 (de) * 1984-04-23 1985-11-27 BSR North America Ltd. Matrix-Nadeldruckkopf
US4575268A (en) * 1984-10-25 1986-03-11 Industrial Technology Research Institute Dot matrix printer head

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB2236078A (en) * 1989-08-26 1991-03-27 Citizen Watch Co Ltd Electrical connections and heat dissipation in dot matrix printers
GB2236078B (en) * 1989-08-26 1993-06-23 Citizen Watch Co Ltd Print head
EP0466286A1 (de) * 1990-06-20 1992-01-15 MANNESMANN Aktiengesellschaft Matrixnadeldruckkopf

Also Published As

Publication number Publication date
FR2596323A1 (fr) 1987-10-02
JPS62236756A (ja) 1987-10-16

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Inventor name: JUVET, CLAUDE-MICHEL