EP0156767A1 - Wire matrix printer - Google Patents

Wire matrix printer Download PDF

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Publication number
EP0156767A1
EP0156767A1 EP85810084A EP85810084A EP0156767A1 EP 0156767 A1 EP0156767 A1 EP 0156767A1 EP 85810084 A EP85810084 A EP 85810084A EP 85810084 A EP85810084 A EP 85810084A EP 0156767 A1 EP0156767 A1 EP 0156767A1
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EP
European Patent Office
Prior art keywords
needles
needle
plane
section
printer according
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.)
Granted
Application number
EP85810084A
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German (de)
French (fr)
Other versions
EP0156767B1 (en
Inventor
Jacques Vermot-Gaud
Didier Joyeux
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Battelle Memorial Institute Inc
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Battelle Memorial Institute Inc
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Priority to AT85810084T priority Critical patent/ATE39646T1/en
Publication of EP0156767A1 publication Critical patent/EP0156767A1/en
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Publication of EP0156767B1 publication Critical patent/EP0156767B1/en
Expired legal-status Critical Current

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    • 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
    • B41J1/00—Typewriters or selective printing mechanisms characterised by the mounting, arrangement or disposition of the types or dies
    • B41J1/22—Typewriters or selective printing mechanisms characterised by the mounting, arrangement or disposition of the types or dies with types or dies mounted on carriers rotatable for selection
    • 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
    • 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
    • B41J11/00—Devices or arrangements  of selective printing mechanisms, e.g. ink-jet printers or thermal printers, for supporting or handling copy material in sheet or web form
    • B41J11/22—Paper-carriage guides or races
    • 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

Definitions

  • the present invention relates to a needle printer comprising a set of needles, each of which is connected to a support and one end of which is free, members for guiding these needles and means for applying said respective free ends against a surface of the invention.
  • writing associated with pressure-sensitive marking means each needle being formed of an electrical conductor a portion of which deviates laterally from an axis connecting said guide means to the end integral with said support and which is connected, on either side of said portion, at the two respective poles of a current source a magnetic field generator being arranged to form a field which, in the presence of a current in said portion of the conductor, generates electrodynamic forces tending to reduce, respectively to move this portion away from said axis, in the direction of the current.
  • a loop is formed in the portion of the conductor spaced laterally from the needle guide axis. This loop is placed in a plane perpendicular to the plane containing the rest of the conductor and its laterally spaced portion.
  • a magnet pole is placed opposite said loop with its diverging flux oriented to penetrate this loop.
  • the object of the present invention is precisely to remedy this gap by a solution allowing the electrodynamic actuation not only of one needle, but of several needles forming a matrix printer.
  • the subject of this invention is a needle matrix printer according to claim 1.
  • the proposed solution is simple. It allows the stacking of all the needles of the printer in the air gap of the same magnet since only the needles fed by current pulses move. The size of such a printer can be greatly reduced due to the stacking of needles.
  • FIGS. 1 to 3 illustrates the principle of electrodynamic actuation of the needle printer object of the invention.
  • the head of this printer comprises a series of needles 1 of rectangular sections, stacked on one another with the interposition of an electrical insulating coating. These needles are fixed at their rear ends to a support 2 and pass through a guide 3 located near their front ends. These needles 1 have, between this support 2 and this guide 3, three inflection points 4, 5 and 6, so that the needles 1 form, with the straight line joining the inflection points 4 and 6, a very flat isosceles triangle. This portion of the needles 1 is disposed in the air gap of a permanent magnet 7. With respect to the front ends of the needles 1, a bundle comprising at least one ink carrier 17 and a sheet to be printed 18, is placed on a support 19.
  • Fig. 4 illustrates the electrical supply of the needles 1.
  • This includes a current pulse generator 8, a step-down transformer 9, a conductor 10, one end of which is connected to the needle 1 near its fixed support 2 and the other end of which is flexible and connected near the other end of the needle 1, so that the current I flows through the isosceles sides of the needle 1.
  • the electrical resistance of the electrical circuit including the needle portion and the secondary of the transformer is of the order of 0.01 to 0.1 ohm for example, so that the current is of the order of 1 to 20 A.
  • the iron section of the transformer must be approximately 0.3 cm 2 . They are therefore very small transformers which can be placed on the print head or outside of this head and remain stationary.
  • two symmetrical needles 11a and 11b are fixed to each other by forming a loop 12. Between the adjacent parts of the two needles, going from the support 13 to the first inflection point 14, an electrical insulator 15 separates the two needles. The isolated parts of these needles are connected respectively to the two ends of the secondary of the supply transformer 16. The current pulses thus pass through the loop 12 which is located in the magnetic field of a magnet 7 as described above. In this variant, the forces induced on the two needles 11a and 11b are opposite and the resulting force of the needles is therefore doubled.
  • the support 13 to which the rear end of this double needle 11a and 11b is fixed is, in this example, an ultrasonic transducer situated at a distance / / 4 from its nodal point of attachment 21 located equal ment at a distance ⁇ / 4 from the free end of the double needle lla, llb.
  • the needles 11a and 11b do not transmit ultrasound, the part of these needles situated behind the support 21 can be eliminated
  • the variant of fig. 6 illustrates a double needle 22, 23 the rear ends of which are fixed to an oscillator 24 formed by a ceramic 5 mm in diameter, for example located at the nodal fulcrum and fixed to the end of a steel rod 25
  • the oscillator intended to generate the ultrasonic vibrations is therefore integrated into the needle.
  • the magnet length can be reduced to:
  • the Samarium Cobalt is no longer necessary, the Ticonal 800 being sufficient.
  • the induction of the magnet can also be enhanced by concentrations of pure iron as will be shown later.
  • the needles can be stacked without having to concentrate their points, the stacking corresponding to the height of the characters to be printed.
  • the magnets also serve as guide elements.
  • the stacked needles can be isolated from each other by varnishes or fine ceramics, this insulation can also be used to isolate the needles from the magnets.
  • the point of the needles can also be isolated by a coating of glass or an equivalent material covering the end of the needle or the surface of the support 19 of the bundle formed of the ink support 17 and of the paper 18.
  • two wires 26 of stainless steel 50 ⁇ m in diameter can be taken and coated in the areas of greater rigidity and electrical conductivity with aluminum to form bars 27 which may have for example 0.15 mm d thickness and 2 mm in width, these bars being separated from each other by spaces of 4 mm.
  • the points of inflection are weakened by notches 28 made in the width of the strips 29 of rectangular section.
  • Fig. 9 illustrates an embodiment of such a needle.
  • This needle 30 is constituted by two strips of rectangular section 1 x 0.15 mm linked by their face 1 nm wide and fixed at their rear ends to an amplifier 31 connected to an ultrasonic transducer 32.
  • the total length of the needle is an integer multiple of ⁇ / 2 while the fulcrum of this needle is at a nodal point corresponding to ⁇ / 4.
  • the two rear portions of the blades of the needle 30 are electrically insulated by an insulating varnish and these blades are connected to a supply similar to those described above at their nodal fulcrum. In such a case, it is the major axis of the section of the lamellae of the needle 30 which defines the air gap of a permanent magnet 33.
  • the lamellae of the needle 30 are made of a metal combining sufficient elastic mechanical properties ( typically 40 kg / m 2 at least) with as low a resistivity as possible.
  • hard copper alloys CuAg to CuCd, bronze to phosphorus
  • pure metals such as molybdenum
  • composite materials such as silver with a precipitate of MgO or molybdenum or copper-coated steel.
  • the width of the slats exceeds 0.35 mm, it is always possible to produce a printhead by stacking the needles, but in this case it is necessary to provide for convergence of the tip of the needles.
  • FIG. 10 illustrates a variant of needle 34 in which the less rigid inflection zones 35 are produced by twisting the strips of rectangular section constituting the needle, by 90 ° around the longitudinal axis so that the width of these lamellae is perpendicular to the direction of the forces generated by the electrodynamic effect of the magnets 36 on the lamellae of the needle 34 traversed by an electric current.
  • the thickness of the strips which defines the air gap. The width of the slats being in the plane of the air gap, their rigidity in this portion is therefore greater with respect to the forces exerted than that of the inflection zones and the air gap is minimum.
  • Fig. 11 shows how a multi-needle printing head can be produced with such needles. Since such needles cannot be purely and simply stacked, the needles 34 can be stacked with the interposition of iron blades 37 intended to compensate for the difference. this between the width of the lamellae of the less rigid inflection zones 35 and the thickness of the lamellae of the more rigid parts connecting these inflection zones 35. These iron blades make it possible to strengthen the induction by playing the role of concentrators and d '' thus obtaining a weak air-gap effect. The ends of the needles 34 must then be brought close to each other on either side of the needle located in the center of the print head.
  • the needles can also be formed by round wires of uniform or stamped section in the areas with greater flexibility. Indeed, numerous tests have made it possible to verify the good behavior of the round wire.
  • An alternative is also to lightly laminate round wire so as to obtain a ribbon with a rounded edge in a thickness / width ratio of 2/3.

Landscapes

  • Printers Or Recording Devices Using Electromagnetic And Radiation Means (AREA)
  • Impact Printers (AREA)
  • Printing Plates And Materials Therefor (AREA)
  • Sewing Machines And Sewing (AREA)
  • Chair Legs, Seat Parts, And Backrests (AREA)
  • Electrostatic Charge, Transfer And Separation In Electrography (AREA)
  • Pens And Brushes (AREA)

Abstract

Les agiuilles (1) de cette imprimante sont alimentées par un conducteur électrique (10) associé au secondaire d'un transformateur abaisseur (9) connecté à un générateur d'impulsions de courant (8). L'aiguille 1 étant placée dans le champ magnétique d'un aimant permanent (7), le courant (I) qui traverse l'aiguille engendre des forces qui tendent à ramener cette aiguille sur une ligne droite joignant ses points d'appui et de guidage (2, 3) en dëplaçant l'extrémité libre contre un support d'écriture.The needles (1) of this printer are supplied by an electrical conductor (10) associated with the secondary of a step-down transformer (9) connected to a current pulse generator (8). The needle 1 being placed in the magnetic field of a permanent magnet (7), the current (I) which crosses the needle generates forces which tend to bring this needle on a straight line joining its points of support and guide (2, 3) by moving the free end against a writing medium.

Description

La présente invention se rapporte à une imprimante à aiguilles comprenant un jeu d'aiguilles dont chacune est reliée à un support et dont une extrémité est libre, des organes de guidage de ces aiguilles et des moyens pour appliquer lesdites extrémités libres respectives contre une surface d'écriture associée à des moyens de marquage sensibles à la pression chaque aiguille étant formée d'un conducteur électrique dont une portion s'écarte latéralement d'un axe reliant lesdits moyens de guidage à l'extrémité solidaire dudit support et qui est connecté, de part et d'autre de ladite portion, aux deux pôles respectifs d'une source de courant un générateur de champ magnétique étant disposé pour former un champ qui, en présence d'un courant dans ladite portion du conducteur, engendre des forces électrodynamiques tendant à ramener, respectivement à éloigner cette portion dudit axe, suivant le sens du courant.The present invention relates to a needle printer comprising a set of needles, each of which is connected to a support and one end of which is free, members for guiding these needles and means for applying said respective free ends against a surface of the invention. writing associated with pressure-sensitive marking means each needle being formed of an electrical conductor a portion of which deviates laterally from an axis connecting said guide means to the end integral with said support and which is connected, on either side of said portion, at the two respective poles of a current source a magnetic field generator being arranged to form a field which, in the presence of a current in said portion of the conductor, generates electrodynamic forces tending to reduce, respectively to move this portion away from said axis, in the direction of the current.

On a déjà proposé dans le GB-A-1.423.518 et en particulier dans la forme d'exécution de la fig. 4 de ce document un mode d'actionnement électrodynamique d'une aiguille d'imprimante. Selon cette forme d'exécution, une boucle est formée dans la portion du conducteur écartée latéralement de l'axe de guidage de l'aiguille. Cette boucle est placée dans un plan perpendiculaire au plan contenant le reste du conducteur et de sa portion écartée latéralement. un pôle d'aimant est placé vis-à-vis de ladite boucle avec son flux divergeant orienté pour pénétrer dans cette boucle. lorsqu'un courant parcourt la boucle du conducteur, celle-ci a tendance à enbras- ser le flux maximum. Comme celui-ci est divergeant et que le pôle de l'aimant est voisin de l'axe de guidage du conducteur, la boucle est donc attirée vers cet axe et l'extrémité libre de l'aiguille est poussée vers la surface d'impression.It has already been proposed in GB-A-1,423,518 and in particular in the embodiment of FIG. 4 of this document a mode of electrodynamic actuation of a printer needle. According to this embodiment, a loop is formed in the portion of the conductor spaced laterally from the needle guide axis. This loop is placed in a plane perpendicular to the plane containing the rest of the conductor and its laterally spaced portion. a magnet pole is placed opposite said loop with its diverging flux oriented to penetrate this loop. when a current flows through the conductor loop, it tends to obstruct the maximum flux. As the latter is divergent and the pole of the magnet is close to the guide axis of the conductor, the loop is therefore attracted towards this axis and the free end of the needle is pushed towards the printing surface. .

Etant donné que le plan du conducteur et celui de la boucle destinée à coopérer avec le chanp magnétique divergeant sont forcément perpendiculaires, une telle solution ne permet pas de former un enpilement de plusieurs aiguilles pour réaliser une imprimante matricielle. Il faut d'ailleurs remarquer que ce document reste muet sur la solution à adopter pour réaliser une telle inprimante à l'aide de cette forme d'exécution. Or, une seule aiguille ne constitue pas une imprimente, de sorte que l'on peut logiquement admettre que cette forme d'exécution ne constitue pas une solution industrielle dans la mesure où elle ne permet pas à l'homme de métier de réaliser sans autre une inprimante matricielle à aiguilles basée sur le principe décrit par la figure 4 du document susmentionné.Since the plane of the conductor and that of the loop intended to cooperate with the diverging magnetic edge are necessarily perpendicular, such a solution does not make it possible to form a stack of several needles to produce a matrix printer. It should also be noted that this document remains silent on the solution to be adopted in order to produce such an printer using this embodiment. However, a single needle does not does not constitute a print, so it can logically be admitted that this embodiment does not constitute an industrial solution insofar as it does not allow a person skilled in the art to produce without need a matrix based needle printer on the principle described by FIG. 4 of the above-mentioned document.

Le but de la présente invention est précisément de remédier à cette lacune par une solution permettant l'actionnement électrodynamique non seulement d'une aiguille, mais de plusieurs aiguilles formant une imprimante matricielle.The object of the present invention is precisely to remedy this gap by a solution allowing the electrodynamic actuation not only of one needle, but of several needles forming a matrix printer.

A cet effet, cette invention a pour objet une imprimante matricielle à aiguilles selon la revendication 1.To this end, the subject of this invention is a needle matrix printer according to claim 1.

La solution proposée est sinple. Elle permet l'empilement de toutes les aiguilles de l'imprimante dans l'entrefer du même aimant étant donné que seules les aiguilles alimentées par des inpulsions de courant se déplacent. L'encombrement d'une telle imprimante peut être fortement réduit en raison de l'empilement des aiguilles.The proposed solution is simple. It allows the stacking of all the needles of the printer in the air gap of the same magnet since only the needles fed by current pulses move. The size of such a printer can be greatly reduced due to the stacking of needles.

D'autres avantages de cette invention apparaîtront dans la des- cripticn qui va suivre et le dessin qui l'accompagne et illustre, schématiquement et à titre d'exemple, diverses variantes de l'imprimante matricielle à aiguilles objet de la présente invention.

  • La fig. 1 est une vue en élévation latérale d'une forme d'exécution de cette inprimante matricielle à aiguilles.
  • La fig. 2 est une vue selon la ligne II-II de la fig. l.
  • La fig. 3 est une vue selon la ligne III-III de la fig. 1.
  • La fig. 4 illustre un mode d'alimentation électrique de cette aiguille.
  • Les figs 5 et 6 illustrent deux variantes d'aiguilles.
  • La fig. 7 représente un mode de rigidification sélective d'une aiguille.
  • La fig. 8 représente une autre variante d'aiguille avec des zones de rigidité et de conductivité électrique différentes.
  • La fig. 9 est une vue en perspective d'une variante d'aiguille destinée à transmettre des ultrasons.
  • La fig. 10 est une vue en élévation d'une autre variante d'aiguille destinée à transmettre des ultrasons.
  • La fig. il est une vue en élévation d'une tête d'imprimante selon la variante de la fig. 10.
Other advantages of this invention will appear in the following description and the accompanying drawing, which illustrates, schematically and by way of example, various variants of the needle matrix printer object of the present invention.
  • Fig. 1 is a side elevational view of an embodiment of this needle matrix printer.
  • Fig. 2 is a view along line II-II of FIG. l.
  • Fig. 3 is a view along the line III-III of FIG. 1.
  • Fig. 4 illustrates a mode of electrical supply of this needle.
  • Figs 5 and 6 illustrate two variants of needles.
  • Fig. 7 shows a mode of selective stiffening of a needle.
  • Fig. 8 shows another variant of the needle with zones of different rigidity and electrical conductivity.
  • Fig. 9 is a perspective view of a variant needle intended for transmitting ultrasound.
  • Fig. 10 is an elevational view of another variant needle intended for transmitting ultrasound.
  • Fig. it's an elevation view of a printer head according to the variant of fig. 10.

La forme d'exécution des figs 1 à 3 illustre le principe d'actionnement électrodynamique de l'imprimante à aiguilles objet de l'invention. La tête de cette imprimante comporte une série d'aiguilles 1 de sections rectangulaires, empilées les unes sur les autres avec interposition d'un revêtement isolant électrique. Ces aiguilles sont fixées à leurs extrémités arrière à un support 2 et passent dans un guide 3 situé à proximité de leurs extrémités avant. Ces aiguilles 1 présentent entre ce support 2 et ce guide 3 trois points d'inflexion 4, 5 et 6, de sorte que les aiguilles 1 forment avec la ligne droite joignant les points d'inflexion 4 et 6 un triangle isocèle très aplati. Cette portion des aiguilles 1 est disposée dans l'entrefer d'un aimant permanent 7. Vis-à-vis des extrémités avant des aiguilles l, une liasse comprenant au moins un support encreur 17 et une feuille à imprimer 18, est placée sur un support 19.The embodiment of FIGS. 1 to 3 illustrates the principle of electrodynamic actuation of the needle printer object of the invention. The head of this printer comprises a series of needles 1 of rectangular sections, stacked on one another with the interposition of an electrical insulating coating. These needles are fixed at their rear ends to a support 2 and pass through a guide 3 located near their front ends. These needles 1 have, between this support 2 and this guide 3, three inflection points 4, 5 and 6, so that the needles 1 form, with the straight line joining the inflection points 4 and 6, a very flat isosceles triangle. This portion of the needles 1 is disposed in the air gap of a permanent magnet 7. With respect to the front ends of the needles 1, a bundle comprising at least one ink carrier 17 and a sheet to be printed 18, is placed on a support 19.

En faisant passer un courant.I dans une aiguille, des forces F s'exercent sur elle et tendent à la ramener sur la droite joignant les points d'inflexion 4 et 6.

Figure imgb0001
F en Newton B en Telsa I en Ampères L en mètresBy passing a current I through a needle, forces F are exerted on it and tend to bring it back to the right joining the inflection points 4 and 6.
Figure imgb0001
 F in Newton B in Telsa I in Amps L in meters

Si la longueur L est de 4 cm, le champ magnétique B de 1 Telsa, le courant I de 10 A, on a Σ F = 0,4 N, ce qui donne à l'extrémité de l'aiguille une force F2 de l'ordre de 2 N, le rapport F2/Fl étant fonction de la valeur de déplacement du point d'inflexion 5.If the length L is 4 cm, the magnetic field B of 1 Telsa, the current I of 10 A, we have Σ F = 0.4 N, which gives the end of the needle a force F 2 of on the order of 2 N, the ratio F 2 / F l being a function of the displacement value of the inflection point 5.

Cette solution présente des avantages importants. On peut noter que l'empilement des aiguilles 1 permet d'obtenir directement la hauteur des caractères à imprimer sans devoir concentrer les pointes d'aiguilles. L'application de forces F réparties sur toute la longueur des côtés isocèles du triangle provoque une rigidification naturelle de l'aiguille. Suivant le sens de l'impulsion de courant, l'action des forces F est positive, comme illustré, ou négative, ce qui permet de commander positivement le mouvement d'avance et de recul de la pointe des aiguilles 1.This solution has significant advantages. It can be noted that the stacking of the needles 1 makes it possible to directly obtain the height of the characters to be printed without having to concentrate the needle tips. The application of forces F distributed over the entire length of the isosceles sides of the triangle causes natural stiffening of the needle. According to the direction of the current pulse, the action of the forces F is positive, as illustrated, or negative, which makes it possible to positively control the movement of advance and retreat of the points of needles 1.

La fig. 4 illustre l'alimentation électrique des aiguilles 1. Celle-ci comporte un générateur d'impulsions de courant 8, un transformateur abaisseur 9, un conducteur 10 dont une extrémité est car nectée à l'aiguille 1 à proximité de son support fixe 2 et dont l'autre extrémité est souple et connectée à proximité de l'autre extrémité de l'aiguille 1, de sorte que le courant I parcourt les côtés isocèles de l'aiguille 1.Fig. 4 illustrates the electrical supply of the needles 1. This includes a current pulse generator 8, a step-down transformer 9, a conductor 10, one end of which is connected to the needle 1 near its fixed support 2 and the other end of which is flexible and connected near the other end of the needle 1, so that the current I flows through the isosceles sides of the needle 1.

La résistance électrique du circuit électrique englobant la portion d'aiguille et le secondaire du transformateur est de l'ordre de 0,01 à 0,1 ohm par exemple, de sorte que le courant est de l'ordre de 1 à 20 A.The electrical resistance of the electrical circuit including the needle portion and the secondary of the transformer is of the order of 0.01 to 0.1 ohm for example, so that the current is of the order of 1 to 20 A.

Pour fournir une telle impulsion de courant, on peut avantageusement avoir recours à un transformateur dont le primaire a 200 tours et le secondaire 10 tours. Dans ce cas, à 10 A au secondaire correspond 0,5 A au primaire. Si la résistance du circuit d'actionnement de l'aiguille est de 0,02 ohm, la tension au secondaire est de 0,2 volt et au primaire de 10 volt.To provide such a current pulse, it is advantageous to have recourse to a transformer whose primary has 200 turns and the secondary has 10 turns. In this case, 10 A in secondary corresponds to 0.5 A in primary. If the resistance of the needle actuation circuit is 0.02 ohm, the secondary voltage is 0.2 volts and the primary voltage is 10 volts.

Pour fournir une impulsion d'une durée totale de 0,5 ms, la section de fer du transformateur doit être de 0,3 cm2 environ. Il s'agit donc de très petits transformateurs qui peuvent être placés sur la tête d'impression ou à l'extérieur de cette tête et rester immobile.To provide a pulse with a total duration of 0.5 ms, the iron section of the transformer must be approximately 0.3 cm 2 . They are therefore very small transformers which can be placed on the print head or outside of this head and remain stationary.

Nous allons examiner maintenant le comportement dynamique d'une aiguille afin d'évaluer les limites de la vitesse d'inpression de la tête formée de telles aiguilles. Il y a lieu, à cet effet, de considérer l'aiguille comme une barre encastrée aux deux extrémités et d'en déterminer sa fréquence propre. Avec une barre de section rectangulaire, la fréquence fondamentale est:

Figure imgb0002

  • où k = densité en g/cm3.
  • E = module de Young en N/m2
  • h et 1 = épaisseur et longueur de l'aiguille en cm.
We will now examine the dynamic behavior of a needle in order to assess the limits of the speed of pressure of the head formed by such needles. For this purpose, it is necessary to consider the needle as a bar embedded at both ends and to determine its natural frequency. With a bar of rectangular section, the fundamental frequency is:
Figure imgb0002
  • where k = density in g / cm 3 .
  • E = Young's modulus in N / m 2
  • h and 1 = thickness and length of the needle in cm.

Pour une aiguille en alliage de cuivre k = 9 g/cm3, E = 12.10 N/m2, h = 1,5.10-2 cm, 1 = 2,5 cm.

Figure imgb0003
For a copper alloy needle k = 9 g / cm 3 , E = 12.10 N / m 2 , h = 1.5.10-2 cm, 1 = 2.5 cm.
Figure imgb0003

Pour une même aiguille en molybdène, k = 10,2 g/cm3, E = 35.1010 N/m2

Figure imgb0004
For the same molybdenum needle, k = 10.2 g / cm3, E = 35.1 0 10 N / m2
Figure imgb0004

De telles fréquences permettent d'envisager des vitesses d'impression de l'ordre de 1000 à 1500 points par seconde et même davantage en optimalisant les paramètres.Such frequencies make it possible to envisage printing speeds of the order of 1000 to 1500 dots per second and even more by optimizing the parameters.

Il est également possible d'utiliser les capacités d'auto-oscil- laticn de l'aiguille pour accroître l'énergie d'impression qui correspond à l'énergie cinétique de l'aiguille pendant son mouvement transversal. Pour le faire de la manière la plus favorable, il faut adopter un mode de commande de type "négatif-positif" consistant à envoyer d'abord dans l'aiguille une impulsion de courant "négative", provoquant le recul de la pointe de l'aiguille en écartant son articulation 5 de l'axe reliant le point d'encastrement au support 2 au palier de guidage 3, et amorçant ainsi une oscillation, puis en envoyant une inpulsion de courant "positive" dont l'effet s'ajoute au mouvement de retour naturel d'oscillation de l'aiguille.It is also possible to use the self-oscillation capacities of the needle to increase the printing energy which corresponds to the kinetic energy of the needle during its transverse movement. To do this in the most favorable way, it is necessary to adopt a "negative-positive" type of control mode consisting of first sending a "negative" current pulse into the needle, causing the tip of the tip to recede. needle by moving its articulation 5 away from the axis connecting the point of embedding to the support 2 to the guide bearing 3, and thus initiating an oscillation, then by sending a "positive" current pulse whose effect is added to the natural needle return swing movement.

Dans le cas des variantes des fig. 5 et 6 deux aiguilles symétriques lla et llb sont fixées l'une à l'autre en formant une boucle 12. Entre les parties adjacentes des deux aiguilles, allant du support 13 au premier point d'inflexion 14, un isolant électrique 15 sépare les deux aiguilles. Les parties isolées de ces aiguilles sont connectées respectivement aux deux extrémités du secondaire du transformateur 16 d'alimentation. Les impulsions de courant parcourent ainsi la boucle 12 qui se situe dans le champ magnétique d'un aimant 7 comme décrit précédemnent. Dans cette variante, les forces induites sur les deux aiguilles lla et llb sont opposées et la force résultante des aiguilles est donc doublée. Le support 13 auquel l'extrémité arrière de cette double aiguille lla et llb est fixée, est, dans cet exemple, un transducteur ultrasonique situé à une distance Â/4 de son point nodal de fixation 21 situé également à une distance λ/4 de l'extrémité libre de la double aiguille lla, llb. Dans le cas où les aiguilles lla et llb ne transmettent pas d'ultrasons, la partie de ces aiguilles située derrière le support 21 peut être suppriméeIn the case of variants of fig. 5 and 6 two symmetrical needles 11a and 11b are fixed to each other by forming a loop 12. Between the adjacent parts of the two needles, going from the support 13 to the first inflection point 14, an electrical insulator 15 separates the two needles. The isolated parts of these needles are connected respectively to the two ends of the secondary of the supply transformer 16. The current pulses thus pass through the loop 12 which is located in the magnetic field of a magnet 7 as described above. In this variant, the forces induced on the two needles 11a and 11b are opposite and the resulting force of the needles is therefore doubled. The support 13 to which the rear end of this double needle 11a and 11b is fixed, is, in this example, an ultrasonic transducer situated at a distance / / 4 from its nodal point of attachment 21 located equal ment at a distance λ / 4 from the free end of the double needle lla, llb. In the case where the needles 11a and 11b do not transmit ultrasound, the part of these needles situated behind the support 21 can be eliminated

La variante de la fig. 6 illustre une double aiguille 22, 23 dont les extrémités arrière sont fixées à un oscillateur 24 formé par une céramique de 5 mm de diamètre par exemple située au point d'appui nodal et fixée à l'extrémité d'une tige d'acier 25. Dans cette variante, l'oscillateur destiné à engendrer les vibrations ultrasoniques est donc intégré à l'aiguille.The variant of fig. 6 illustrates a double needle 22, 23 the rear ends of which are fixed to an oscillator 24 formed by a ceramic 5 mm in diameter, for example located at the nodal fulcrum and fixed to the end of a steel rod 25 In this variant, the oscillator intended to generate the ultrasonic vibrations is therefore integrated into the needle.

Il existe diverses solutions pour réaliser des aiguilles avec des points d'inflexion jouant le rôle d'articulations. Il faut cependant distinguer deux cas, celui ou l'aiguille constitue une fibre acoustique destinée à transmettre des vibrations ultrasoniques et celui où l'aiguille ne constitue pas une telle fibre, soit qu'elle est destinée à imprimer par un autre moyen, par exemple par la seule pression, soit que l'aiguille est destinée à appliquer une portion de la liasse comprenant le support encreur 17 et le papier 18, contre un support 19 constitué par une surface vibrante solidaire d'un transducteur ultrasonique 20 (fig. 7). Dans le cas où l'aiguille n'est pas une fibre acoustique, les contraintes sont limitées à la résistance électrique et à la masse qui doivent être le plus faible possible. Les points d'inflexion doivent être aussi souples que possible tout en n'augmentant aussi peu que possible la résistance électrique. L'épaisseur de l'aiguille dans l'entrefer de l'aimant permanent doit être le plus faible possible.There are various solutions for making needles with points of inflection acting as joints. A distinction must be made, however, between two cases, that in which the needle constitutes an acoustic fiber intended to transmit ultrasonic vibrations and that in which the needle does not constitute such a fiber, that is to say that it is intended to print by another means, for example by the only pressure, either that the needle is intended to apply a portion of the bundle comprising the ink support 17 and the paper 18, against a support 19 constituted by a vibrating surface secured to an ultrasonic transducer 20 (fig. 7) . In the case where the needle is not an acoustic fiber, the constraints are limited to the electrical resistance and to the mass which must be as low as possible. The inflection points should be as flexible as possible while not increasing the electrical resistance as little as possible. The thickness of the needle in the air gap of the permanent magnet should be as small as possible.

Si l'on admet par exemple un entrefer de 0,2 mm et une pente de la droite de recul dont la tangente est de 25, la longueur d'aimant peut être ramenée à:

Figure imgb0005
If we admit for example a gap of 0.2 mm and a slope of the recoil line whose tangent is 25, the magnet length can be reduced to:
Figure imgb0005

Dans un tel cas, le Samarium Cobalt n'est plus nécessaire, le Ticonal 800 étant suffisant.In such a case, the Samarium Cobalt is no longer necessary, the Ticonal 800 being sufficient.

L'induction de l'aimant peut également être renforcée par des concentrations de fer pur comme on le montrera par la suite.The induction of the magnet can also be enhanced by concentrations of pure iron as will be shown later.

Enfin, en réalisant une tête par empilement d'aiguilles comme illustré par les fig. 1 à 3, l'écartement des points étant de 2,6 mm/8 = 0,325 mm, on peut empiler les aiguilles sans devoir concentrer leurs pointes, l'enpilement correspondant à la hauteur des caractères à imprimer. En outre, en plus de l'autorigidification des aiguilles due à l'exercice de forces sur toute la portion d'aiguille située dans le champ magnétique, les aimants servent également d'éléments de guidage.Finally, by making a head by stacking com needles illustrated by figs. 1 to 3, the spacing of the points being 2.6 mm / 8 = 0.325 mm, the needles can be stacked without having to concentrate their points, the stacking corresponding to the height of the characters to be printed. In addition, in addition to the authentication of the needles due to the exertion of forces on the entire portion of the needle located in the magnetic field, the magnets also serve as guide elements.

Les aiguilles empilées peuvent être isolées les unes des autres par des vernis ou des céramiques fines, cette isolation peut également servir à isoler les aiguilles des aimants.The stacked needles can be isolated from each other by varnishes or fine ceramics, this insulation can also be used to isolate the needles from the magnets.

La pointe des aiguilles peut également être isolée par un revêtement de verre ou d'un matériau équivalent recouvrant l'extrémité de l'aiguille ou la surface du support 19 de la liasse formée du support encreur 17 et du papier 18.The point of the needles can also be isolated by a coating of glass or an equivalent material covering the end of the needle or the surface of the support 19 of the bundle formed of the ink support 17 and of the paper 18.

Il faut noter que, du fait de l'utilisation de transformateurs pour l'alimentation des aiguilles à actionnement électrodynamique, il n'est pas absolument nécessaire d'assurer l'isolement de la pointe des aiguilles. Au contraire, celle-ci peut être considérée comme étant au potentiel de référence.It should be noted that, due to the use of transformers for feeding needles with electrodynamic actuation, it is not absolutely necessary to ensure the isolation of the tip of the needles. On the contrary, it can be considered as being at the reference potential.

Il existe divers moyens pour réaliser des points d'inflexion moins rigides lorsque l'aiguille n'est pas destinée à transmettre des ultrasons. C'est ainsi que, comme illustré par la fig. 7, on peut prendre deux fils 26 d'acier inox de 50 µm de diamètre et les enrober dans les zones de plus grande rigidité et conductivité électrique avec de l'aluminium pour former des barreaux 27 qui peuvent avoir par exemple 0,15 mm d'épaisseur et 2 mm de largeur, ces barreaux étant séparés les uns des autres par des espaces de 4 mm.There are various ways to achieve less rigid inflection points when the needle is not intended to transmit ultrasound. Thus, as illustrated in FIG. 7, two wires 26 of stainless steel 50 μm in diameter can be taken and coated in the areas of greater rigidity and electrical conductivity with aluminum to form bars 27 which may have for example 0.15 mm d thickness and 2 mm in width, these bars being separated from each other by spaces of 4 mm.

Dans le cas de la variante de la fig. 8, les points d'inflexion sont affaiblis par des entailles 28 faites dans la largeur des lamelles 29 de section rectangulaire.In the case of the variant of FIG. 8, the points of inflection are weakened by notches 28 made in the width of the strips 29 of rectangular section.

Pour réaliser une aiguille d'impression constituant simulta- nénent une fibre acoustique destinée à transmettre des vibrations ultrasoniques, plusieurs conditions doivent être remplies en plus de la section constante de la fibre. La fig. 9 illustre un mode de réalisation d'une telle aiguille. Cette aiguille 30 est constituée par deux lamelles de section rectangulaire 1 x 0,15 mm liées par leur face de 1 nm de large et fixées à leurs extrémités arrière à un amplificateur 31 connecté à un transducteur ultrasonique 32. La longueur totale de l'aiguille est un multiple entier de λ/2 alors que le point d'appui de cette aiguille se trouve à un point nodal correspondant à λ/4. Les deux portions arrière des lamelles de l'aiguille 30 sont isolées électriquement par un vernis isolant et ces lamelles sont connectées à une alimentation semblable à celles décrites précédemment à leur point d'appui nodal. Dans un tel cas c'est le grand axe de la section des lamelles de l'aiguille 30 qui définit l'entrefer d'un aimant permanent 33. Les lamelles de l'aiguille 30 sont en un métal alliant des propriétés mécaniques élastiques suffisantes (typiquement 40 kg/m2 au moins) à une résistivité aussi faible que possible. A titre d'exemple, on peut citer des alliages de cuivre dur (CuAg au CuCd, bronze au phosphore); des métaux purs tels que le molybdène; des matériaux composites tels que l'argent avec un précipité de MgO ou du molybdène ou de l'acier recou- vert de cuivre.In order to produce a printing needle simultaneously constituting an acoustic fiber intended to transmit ultrasonic vibrations, several conditions must be fulfilled in addition to the constant section of the fiber. Fig. 9 illustrates an embodiment of such a needle. This needle 30 is constituted by two strips of rectangular section 1 x 0.15 mm linked by their face 1 nm wide and fixed at their rear ends to an amplifier 31 connected to an ultrasonic transducer 32. The total length of the needle is an integer multiple of λ / 2 while the fulcrum of this needle is at a nodal point corresponding to λ / 4. The two rear portions of the blades of the needle 30 are electrically insulated by an insulating varnish and these blades are connected to a supply similar to those described above at their nodal fulcrum. In such a case, it is the major axis of the section of the lamellae of the needle 30 which defines the air gap of a permanent magnet 33. The lamellae of the needle 30 are made of a metal combining sufficient elastic mechanical properties ( typically 40 kg / m 2 at least) with as low a resistivity as possible. By way of example, mention may be made of hard copper alloys (CuAg to CuCd, bronze to phosphorus); pure metals such as molybdenum; composite materials such as silver with a precipitate of MgO or molybdenum or copper-coated steel.

Si la largeur des lamelles dépasse 0,35 mm, il est toujours possible de réaliser une tête d'impression par enpilement des aiguilles mais il faut, dans ce cas, prévoir une convergence de la pointe des aiguilles.If the width of the slats exceeds 0.35 mm, it is always possible to produce a printhead by stacking the needles, but in this case it is necessary to provide for convergence of the tip of the needles.

La figure 10 illustre une variante d'aiguille 34 dans laquelle les zones d'inflexion moins rigides 35 sont réalisées en tordant les lamelles de section rectangulaire constituant l'aiguille, de 90° autour de l'axe longitudinal de manière que la largeur de ces lamelles soit perpendiculaire à la direction des forces engendrées par effet électrodynamique des aimants 36 sur les lamelles de l'aiguille 34 parcourues par un courant électrique. Par contre, entre les aimants 36 c'est l'épaisseur des lamelles qui définit l'entrefer. La largeur des lamelles étant dans le plan de l'entrefer, leur rigidité dans cette portion est donc plus grande vis-à-vis des forces exercées que celle des zones d'inflexion et l'entrefer est minimum.FIG. 10 illustrates a variant of needle 34 in which the less rigid inflection zones 35 are produced by twisting the strips of rectangular section constituting the needle, by 90 ° around the longitudinal axis so that the width of these lamellae is perpendicular to the direction of the forces generated by the electrodynamic effect of the magnets 36 on the lamellae of the needle 34 traversed by an electric current. On the other hand, between the magnets 36 it is the thickness of the strips which defines the air gap. The width of the slats being in the plane of the air gap, their rigidity in this portion is therefore greater with respect to the forces exerted than that of the inflection zones and the air gap is minimum.

La fig. 11 montre comment on peut réaliser avec de telles aiguilles une tête d'impression à aiguilles multiples. Etant donné que de telles aiguilles ne peuvent pas être purement et simplement enpilées, l'empilement des aiguilles 34 peut être réalisé avec interposition de lames de fer 37 destinées à compenser la différence entre la largeur des lamelles des zones d'inflexion moins rigides 35 et l'épaisseur des lamelles des parties plus rigides reliant ces zones d'inflexion 35. Ces lames de fer permettent de renforcer l'induction en jouant le rôle de concentrateurs et d'obtenir ainsi un effet d'entrefer faible. Les extrémités des aiguilles 34 doivent alors être rapprochées les unes des autres de part et d'autre de l'aiguille située au centre de la tête d'impression.Fig. 11 shows how a multi-needle printing head can be produced with such needles. Since such needles cannot be purely and simply stacked, the needles 34 can be stacked with the interposition of iron blades 37 intended to compensate for the difference. this between the width of the lamellae of the less rigid inflection zones 35 and the thickness of the lamellae of the more rigid parts connecting these inflection zones 35. These iron blades make it possible to strengthen the induction by playing the role of concentrators and d '' thus obtaining a weak air-gap effect. The ends of the needles 34 must then be brought close to each other on either side of the needle located in the center of the print head.

Il faut enfin noter que les aiguilles peuvent être également constituées par des fils ronds de section uniforme ou matricée dans les zones à plus grande flexibilité. En effet, de nombreux essais ont permis de vérifier le bon comportement du fil rond.Finally, it should be noted that the needles can also be formed by round wires of uniform or stamped section in the areas with greater flexibility. Indeed, numerous tests have made it possible to verify the good behavior of the round wire.

Une alternative consiste également à laminer légèrement du fil rond de façon à obtenir un ruban à bord arrondi dans un rapport épais- seur/largeur de 2/3.An alternative is also to lightly laminate round wire so as to obtain a ribbon with a rounded edge in a thickness / width ratio of 2/3.

Claims (9)

1. Imprimante matricielle à aiguilles conprenant un jeu d'aiguilles (1) dont chacune est reliée à un support (2) et dont une extrémité est libre, des organes de guidage (3) de ces aiguilles et des moyens pour appliquer lesdites extrémités libres respectives contre une surface d'écriture (18) associée à des moyens de marquage sensibles à la pression (17), chaque aiguille (1) étant formée d'un conducteur électrique dont une portion s'écarte latéralement d'un axe reliant lesdits moyens de guidage (3) à l'extrémité solidaire dudit support (2) et qui est connecté, de part et d'autre de ladite portion, aux deux pôles respectifs d'une source de courant (8,9; 16), un générateur de champ magnétique (7) étant disposé pour former un champ qui, en présence d'un courant dans ladite portion du conducteur engendre des forces électrodynamiques tendant à ramener, respectivement à éloigner cette portion dudit axe, suivant le sens du courant, caractérisé par le fait que ladite portion est comprise dans un plan commun au reste du conducteur électrique formant ladite aiguille (1) et que les pôles dudit générateur de champ magnétique (7) sont disposés de part et d'autre de ce plan pour former un champ homogène dont les lignes de force sont perpendiculaires audit plan.1. Needle matrix printer comprising a set of needles (1) each of which is connected to a support (2) and one end of which is free, guide members (3) of these needles and means for applying said free ends respective against a writing surface (18) associated with pressure-sensitive marking means (17), each needle (1) being formed of an electrical conductor, a portion of which deviates laterally from an axis connecting said means guide (3) at the integral end of said support (2) and which is connected, on either side of said portion, to the two respective poles of a current source (8,9; 16), a generator magnetic field (7) being arranged to form a field which, in the presence of a current in said portion of the conductor generates electrodynamic forces tending to bring back, respectively to move this portion of said axis, in the direction of the current, characterized by fact that said portion is included in u n plane common to the rest of the electrical conductor forming said needle (1) and that the poles of said magnetic field generator (7) are arranged on either side of this plane to form a homogeneous field whose lines of force are perpendicular to said plan. 2. Imprimante selon la revendication l, caractérisée par le fait que chaque aiguille (1) comporte deux parties symétriques (lla, llb, 12; 22, 23; 26) de part et d'autre d'un plan passant par la droite reliant le support aux moyens de guidage et perpendiculaire au plan contenant l'aiguille, les portions adjacentes de ces parties symétriques adjacentes au support étant isolées électriquement l'une de l'autre et connectées aux deux bornes de ladite source de courant (16), les portions adjacentes éloignées dudit support étant en contact électrique.2. Printer according to claim l, characterized in that each needle (1) has two symmetrical parts (lla, llb, 12; 22, 23; 26) on either side of a plane passing through the straight line connecting the support to the guide means and perpendicular to the plane containing the needle, the adjacent portions of these symmetrical parts adjacent to the support being electrically isolated from each other and connected to the two terminals of said current source (16), adjacent portions remote from said support being in electrical contact. 3. Imprimante selon la revendication 1, caractérisée par le fait que ladite source de courant (8,9; 16) comporte un générateur d'impulsion (8) relié au primaire d'un transformateur (9) dont le secondaire est connecté à l'une desdites aiguilles (1).3. Printer according to claim 1, characterized in that said current source (8,9; 16) comprises a pulse generator (8) connected to the primary of a transformer (9) whose secondary is connected to the 'one of said needles (1). 4. Imprimante selon la revendication 1, caractérisée par le fait que lesdits conducteurs formant lesdites aiguilles (1) sont de section rectangulaire avec le grand axe de la section situé dans le plan des aiguilles respectives, plusieurs aiguilles étant empilées dans l'entrefer d'un aimant permanent (7) générateur dudit champ magnétique avec interposition d'isolant électrique entre ces aiguilles, des portions moins rigides (4,5,6; 28) étant ménagées le long des aiguilles pour former des zones d'articulation.4. Printer according to claim 1, characterized by the fact that said conductors forming said needles (1) are of rectangular section with the major axis of the section located in the plane of the respective needles, several needles being stacked in the air gap of a permanent magnet (7) generating said magnetic field with interposition of electrical insulation between these needles, less rigid portions (4,5,6; 28) being provided along the needles to form articulation zones. 5. Inprimante selon la revendication 1, caractérisée par le fait qu'un transducteur ultrasonique (13, 20, 31) est associé aux aiguilles (1) ou à la surface d'écriture (18).5. Printer according to claim 1, characterized in that an ultrasonic transducer (13, 20, 31) is associated with the needles (1) or with the writing surface (18). 6. Imprimante selon l'une des revendications 1 ou 5, caractérisée par le fait que les conducteurs formant lesdites aiguilles (1) sont de section rectangulaire constante avec le grand axe de la section situé dans le plan des aiguilles respectives, des portions d'articulation moins rigides (35) étant ménagées le long des aiguilles en orientant le grand axe de la section rectangulaire des conducteurs respectifs perpendiculairement au plan des aiguilles, un empilement de ces aiguilles dans l'entrefer dudit aimant étant réalisé avec interposition de lames de fer (37) dans les portions des aiguilles où le grand axe de leur section est dans le plan des aiguilles pour compenser la plus faible hauteur occupée dans l'empilement par rapport auxdites portions d'articulation (35).6. Printer according to one of claims 1 or 5, characterized in that the conductors forming said needles (1) are of constant rectangular section with the major axis of the section located in the plane of the respective needles, portions of less rigid articulation (35) being formed along the needles by orienting the long axis of the rectangular section of the respective conductors perpendicular to the plane of the needles, a stack of these needles in the air gap of said magnet being produced with the interposition of iron blades ( 37) in the portions of the needles where the major axis of their section is in the plane of the needles to compensate for the smallest height occupied in the stack relative to said articulation portions (35). 7. Imprimante selon l'une des revendications 1 ou 5 dans laquelle le transducteur ultrasonique est associé à une extrémité de chacune desdites aiguilles (13, 31), caractérisée par le fait que la section du conducteur est rectangulaire et constante avec le grand axe de cette section parallèle au chanp magnétique dans l'entrefer de l'aimant (7, 33), que la longueur totale de l'aiguille correspond à un multiple entier de la demi longueur d'onde dudit transducteur alors qu'elle est reliée audit support à son point nodal situé à égale distance de ses deux extrémités.7. Printer according to one of claims 1 or 5 in which the ultrasonic transducer is associated with one end of each of said needles (13, 31), characterized in that the section of the conductor is rectangular and constant with the major axis of this section parallel to the magnetic edge in the air gap of the magnet (7, 33), that the total length of the needle corresponds to an integer multiple of the half wavelength of said transducer while it is connected to said support at its nodal point located equidistant from its two ends. 8. Imprimante selon l'une des revendications 1 et 2, caractérisée par le fait que lesdits conducteurs formant lesdites aiguilles sont de section circulaire.8. Printer according to one of claims 1 and 2, characterized in that said conductors forming said needles are of circular section. 9. Imprimante selon les revendications 4 et 8, caractérisée par le fait qu'une section sensiblement rectangulaire est obtenue consécutivement à un écrasement d'un fil de section circulaire.9. Printer according to claims 4 and 8, characterized in that a substantially rectangular section is obtained following the crushing of a wire of circular section.
EP85810084A 1984-03-07 1985-03-01 Wire matrix printer Expired EP0156767B1 (en)

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DE3813420A1 (en) * 1988-04-21 1989-11-02 Philips Patentverwaltung NEEDLE PRINTER

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ES8602492A1 (en) 1985-12-01
US4600322A (en) 1986-07-15
DK99885D0 (en) 1985-03-05
AU3953785A (en) 1985-09-12

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