EP0041126B1 - Mosaikdruckkopf mit Mitteln zur Verhinderung des Übersprechens - Google Patents

Mosaikdruckkopf mit Mitteln zur Verhinderung des Übersprechens Download PDF

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Publication number
EP0041126B1
EP0041126B1 EP81103083A EP81103083A EP0041126B1 EP 0041126 B1 EP0041126 B1 EP 0041126B1 EP 81103083 A EP81103083 A EP 81103083A EP 81103083 A EP81103083 A EP 81103083A EP 0041126 B1 EP0041126 B1 EP 0041126B1
Authority
EP
European Patent Office
Prior art keywords
magnetic
printing head
armature
pole piece
electromagnetic
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
EP81103083A
Other languages
English (en)
French (fr)
Other versions
EP0041126A2 (de
EP0041126A3 (en
Inventor
Angelo Gaboardi
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.)
Bull HN Information Systems Italia SpA
Original Assignee
Honeywell Information Systems Italia SpA
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 Honeywell Information Systems Italia SpA filed Critical Honeywell Information Systems Italia SpA
Publication of EP0041126A2 publication Critical patent/EP0041126A2/de
Publication of EP0041126A3 publication Critical patent/EP0041126A3/en
Application granted granted Critical
Publication of EP0041126B1 publication Critical patent/EP0041126B1/de
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
    • B41J2/22—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 present invention relates to a mosaic printing head with cross-talk preventing means in the electromagnetic structures of the printing head, the cross-talk limiting the printing speed.
  • a mosaic printing head generally comprises a needle guide assembly and a plurality of electromagnetic structures coupled to the guide assembly.
  • each structure includes a magnetic circuit formed by two pole pieces connected by a yoke and by a movable armature which completes the magnetic circuit. It further includes at least a coil wound around one of the two pole pieces.
  • each of the electromagnetic structures acts as an activator for one of the printing needles.
  • each movable armature is provided with at least one arm which protrudes externally to the electromagnetic structure and operates as an actuating arm for the associated needle.
  • the electromagnetic structures are radially arranged on the electromagnetic support preferably constituted by a ring member.
  • One of the two pole pieces of each magnetic circuit is arranged proximate to the internal periphery of the support ring, whilst the other is arranged in proximity to the external periphery of it (from now on the pole pieces will be named internal or external pole pieces).
  • the radial arrangement of the magnetic circuits involves that the internal pole pieces are closer together than the external pole pieces.
  • the internal pole piece is generally that one which attracts the free end of the armature: therefore an air gap exists at rest between such pole piece and the armature.
  • the magnetic field produced in the magnetic circuit has a leakage in correspondence of the initially open air gap: the more the ratio between the open air gap length and the adjacent pole piece distance increases, the more the flux lines tend to link with adjacent internal pole pieces.
  • the armature of the excited electromagnet is attracted as soon as the attraction force exerted on it by the magnetic field exceeds the value of the resisting force produced by a spring which determines at rest the opening of the magnetic circuit.
  • the attraction force on the movable armature is directly proportional to the value of the magnetic energy in the air gap, owing to the stealing of magnetic energy in the air gap from the adjacent magnetic circuits, the armature of the excited magnetic circuit is attracted with a certain delay compared with the ideal case when there is no leakage or stolen flux.
  • the actuation time of a printing needle changes according to whether the electromagnets near to the one associated to the needle are excited or not.
  • This problem limits the printing speed of the head as the upper limit of such speed is imposed by the maximum flying time of the needles. Besides that it causes misalignment in the printing operations due to the fact that such operations do not occur in steady printing head conditions but when the head is moving along the printing line. in fact, as the excitation command is given to the electromagnets when the printing head is in predetermined positions, the effective actuation of the several needles simultaneously excited occurs when a variable delay and therefore the resulting impression is variably offset as to the predetermined position, owing to such cross-talk.
  • a solution to reduce the above mentioned inconvenients could be the one of decreasing the diameter of the circular support of the electromagnetic structures, so that the open air gap width is much lesser than the distance between the internal pole pieces of two adjacent magnetic circuits.
  • a solution used for line printers involves the use of magnetic shields partially surrounding the excitation coils for the actuator electromagnets of the printing hammers, in order to avoid differences in hammer flying time.
  • Magnetic shields could be used for mosaic printing heads too, but such solution would however involve leakage fluxes and performance degradation.
  • cross-talk prevention means of the present invention which provide a "dynamic" shielding against the leakage fluxes instead of the static shielding achievable by means of the magnetic shields.
  • the critical portion of the magnetic circuit in a matrix printing head is, as already mentioned, the pole piece arranged in proximity to the internal periphery of the electromagnetic support, because of the air gap existing at rest between such pole piece and the armature. If such pole piece is shielded by conductive material, the magnetic flux of the magnetic circuit including such pole piece is prevented from linking to the internal pole pieces of the adjacent magnetic circuits. Therefore the conductor material shield confines the flux within the appropriate magnetic circuit.
  • the shield effect is accomplished by the well known eddy current phenomenon.
  • variable magnetic flux tending to cross the metallic shield during the electromagnet initial excitation phase induces eddy currents within it.
  • Such eddy currents generate a magnetic field opposing the inducing one as is e.g. described in the prior publication "Hand- buch für Hochfrequenz- und Elektrotechniker", 1965, Vol. 1, p. 406 and 407.
  • the non magnetic conducting shield surrounds the coil to be shielded.
  • Fig. 1 shows in side view an example of mosaic printing head structure.
  • the printing head of Fig. 1 comprises a needle guide assembly 2 and an electromagnetic assembly 3.
  • the needle guide assembly comprises a frame 4 having a bracket 6, fixed to the frame by a screw 5, which supports a guide for the printing ends of the needles generally formed by a pair of suitably-shaped ruby plates 7.
  • the needle guide assembly 2 is fixed to electromagnetic assembly 3 by means of two screws (in Fig. 1 the head 8 of one of such screws is visible) which locks two brackets formed on the sides of frame 4 against the electromagnetic assembly 3 (in Fig. 1 one of such two brackets, evidenced by 9, is visible).
  • the electromagnetic assembly 3 comprises a supporting disk 10, to which a suitable number of electromagnets, such as 12, 13, 14, ..., 18, are fixed, an internal bushing (11, Fig. 2) fixed by calking or shrinkage in a central opening of disk 10 (in alternative the bushing and the disk may form a unitary, sintered, casted, or molded body), an armature retainer 19 and a central cap 20.
  • the armature retainer 19 is fixed to the bushing (reference 11 in Fig. 2) by means of the central cap 20.
  • Central cap is provided in proximity of its external periphery with openings, each one receiving a screw (in Fig. 1 only two screws 21, 22 are visible).
  • Such screws insert into corresponding openings present in the armature retainer 19 and engage in corresponding threaded holes (references 23, 24, 25 in Fig. 2) of the bushing.
  • Fig. 1 also shows that the external surface of the ruby plates 7 is placed at a certain distance from a platen 26 of the printer.
  • a paper printing support 27 and an inked ribbon 28 are interposed between platen 26 and ruby plates 7.
  • FIG. 2 shows in exploded view some of the elements forming the electromagnetic assembly 3.
  • the supporting disk 10 in form of annular element having a central opening where the bushing 11 is engaged, has a suitable number of rectangular openings (in Fig. 2 nine openings 29, 30, ..., 37 are visible) intended to restrain an extension which each magnetic circuit is provided with.
  • These openings are radially arranged around the disk center and uniformly distributed near the disk periphery.
  • FIG. 2 shows a single electromagnetic structure as example of the plurality of electromagnetic structures generally included in the electromagnetic assembly 3.
  • Electromagnet 48 comprises a magnetic core 39 formed by a pack of U shaped magnetic sheets provided in correspondence of the yoke with an extension 40 for insertion in one of the rectangular openings of disk 10, for instance opening 30.
  • a coil 41 is wound around one of the two pole pieces of the core 39, and precisely around the one arranged in proximity of the external periphery of disk 10 (the external pole piece).
  • the internal pole piece of the magnetic core 39 not provided with an excitation coil, is partially surrounded by a conductive, non magnetic shield 42 (for instance copper) having C cross section.
  • the electromagnet 38 is completed by a movable armature 43 closing the magnetic circuit.
  • the armature 43 has an extended arm 44 which acts as an activator arm on the head 45 of a needle 46 associated to such armature.
  • the magnetic circuit formed by core 39 and armature 43 has an air gap in correspondence of the internal pole piece, owing to the action of a spring 47 on arm 44 of armature 43 through head 45.
  • the armature retainer 19 (Fig. 1) keeps the armature 43 in contact with the external pole piece of magnetic core 39.
  • the characteristic object of the present invention is the conductive non magnetic shield 42 which partially surrounds the internal pole piece of the magnetic core 39.
  • shield 42 does not cover the pole piece face leaning against bushing 11: the shielding effect on such face may be carried out by the same bushing, which can be made in aluminium. It is also to be noted that the shield 42 must not be in contact with bushing 11, if such last is of conductor material.
  • the open turn or C section of shield 42 is essential to avoid that such shield be linked with the main path of the magnetic flux, as it would occur in case of a closed ring.
  • the conductive non magnetic shields of the magnetic circuits in the electromagnetic structures of a mosaic printing head may clearly have shapes other than the described one, without departing from the scope of the invention.

Landscapes

  • Impact Printers (AREA)

Claims (2)

1. Mosaikdruckkopf mit Mitteln zur Verhinderung des Übersprechens, bei welchem eine Nadelführungseinrichtung für eine Vielzahl von Drecknadeln sowie eine Elektromagnetvorrichtung vorgesehen ist, die aus mehreren, sich radial erstreckenden, auf einem Tragring nebeneinander angeordneten Elektromagneten besteht, von denen jeder einen Magnetkern, bestehend aus einem inneren Polstück, einem von einer Erregerspule umgebenen äußeren Polstück, einem Joch und einem Anker aufweist, und wobei jeder Anker mit einem Hebelarm auf eine der Nadeln einwirkt, um diese gegen eine Druckplatte zu bewegen, dadurch gekennzeichnet, daß jeder der Elektromagnete gegenüber dem benachbarten Elektromagneten durch eine jeweils das innere Polstück teilweise umschließende nichtmagnetische aber elektrisch leitende Abschirmung magnetisch entkoppelt ist.
2. Mosaikdruckkopf nach Anspruch 1, dadurch gekennzeichnet, daß jede Abschirmung einen U-oder C-förmigen Querschnitt aufweist und eines der inneren Polstücke umgibt.
EP81103083A 1980-05-06 1981-04-24 Mosaikdruckkopf mit Mitteln zur Verhinderung des Übersprechens Expired EP0041126B1 (de)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
IT2181580 1980-05-06
IT21815/80A IT1131146B (it) 1980-05-06 1980-05-06 Mezzi di riduzione della diafonia in una testina stampante a mosaico

Publications (3)

Publication Number Publication Date
EP0041126A2 EP0041126A2 (de) 1981-12-09
EP0041126A3 EP0041126A3 (en) 1982-07-14
EP0041126B1 true EP0041126B1 (de) 1984-12-05

Family

ID=11187238

Family Applications (1)

Application Number Title Priority Date Filing Date
EP81103083A Expired EP0041126B1 (de) 1980-05-06 1981-04-24 Mosaikdruckkopf mit Mitteln zur Verhinderung des Übersprechens

Country Status (3)

Country Link
EP (1) EP0041126B1 (de)
DE (1) DE3167553D1 (de)
IT (1) IT1131146B (de)

Families Citing this family (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0312319A3 (de) * 1987-10-15 1989-09-06 Tokyo Electric Co., Ltd. Nach dem Auslöseprinzip arbeitender Punktdruckkopf und Verfahren zu seiner Herstellung
EP0341930A3 (de) * 1988-05-10 1990-01-10 Tokyo Electric Co., Ltd. Nach dem Auslöseprinzip arbeitender Punktdruckkopf
JPH01299053A (ja) * 1988-05-27 1989-12-01 Tokyo Electric Co Ltd 釈放型ドツトプリンタヘツド
ATE82721T1 (de) * 1989-03-01 1992-12-15 Mannesmann Ag Matrixdruckkopf mit einem elektromagnetspulentraeger.
JPH06270422A (ja) * 1993-03-17 1994-09-27 Fujitsu Ltd ワイヤドットプリンタの印字ヘッド用マグネットベースおよびその製造方法
CN114953738B (zh) * 2022-05-20 2023-05-23 合肥领迅喷码科技有限公司 一种喷码机

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
"Handbuch für Hochfrequenz- und Elektrotechniker" von C. Rint, Verlag für Radio-Foto-Kinotechnik GmbH, Berlin-Borsigwalde, Vol. 1, pages 406 and 407, edition 1965 *

Also Published As

Publication number Publication date
EP0041126A2 (de) 1981-12-09
DE3167553D1 (en) 1985-01-17
IT1131146B (it) 1986-06-18
IT8021815A0 (it) 1980-05-06
EP0041126A3 (en) 1982-07-14

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