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
  • B41J2/25—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
  • 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 subject of the present invention is a needle matrix printer comprising a set of needles, each of which is slidably mounted longitudinally and is associated with a flexible electrical conductor over at least part of its length, situated in a plane containing this needle, one of which portion is engaged with the middle part of this conductor, at least one segment thereof being located in the air gap of a permanent magnet with a homogeneous magnetic field perpendicular to said plane, a lateral force acting on this conductor when it is crossed by a current.
• this solution activates the needle by pushing it from its middle.
• this needle must be able to deform easily to allow the displacement of its free end towards the writing surface and, on the other hand, that it must be sufficiently rigid to resist compression, it is necessary to simultaneously satisfy two conflicting requirements.
• actuation mode moves the needle with a speed which tends towards zero and an increasing compressive force so that the kinetic energy also tends towards zero.
• This actuation mode is therefore not suitable for a printing mode in which the ink is transferred following an impact, from its support to the sheet to be printed.
• JP-A-58 145 467 describes a printer in which each needle is slidably mounted and its rear end bears against a segment of electrical conductor immersed in a homogeneous magnetic field. One end of this conductor is fixed, while its other end is mounted longitudinally sliding, so that when a current crosses this conductor, a lateral force is exerted on it. This force causes the lateral deformation of this conductor by longitudinal sliding of its end. This laterally deformed part of the conductor acts on the rear end of the needle and thus displaces it longitudinally.
• each plate has a length equivalent to the width of the writing surface. This implies a magnet of great length and sufficient rigidity of the plates, therefore a width and a thickness proportional to this length, hence a high mass which implies a large current to actuate the plate at high speed.
• the beé example indicating 40 watts, in can easily calculate that each plate must be supplied by a current of 70 A. This poses problems, given that such a current must be created in 1 millisecond and that the blade must be supplied with this high current. Indeed, the current having to pass through the elastic suspension elements where the passage section is reduced by the cutouts, the elastic tongues are liable to be deteriorated by an exaggerated heating.
• the object of the present invention is precisely to remedy at least in part the drawbacks of the above-mentioned solutions.
• the subject of this invention is a needle matrix printer according to claim 1.
• the solution proposed by this invention has several advantages.
• the electrodynamic actuation is dissociated from the needle so that one can have a rigid needle and an electrical conductor for flexible actuation.
• the flexible conductor works exclusively in traction.
• the needle receives kinetic energy capable of creating a pulse of sufficient force to effect a good transfer of ink from the ink carrier to the surface to be printed.
• the air gap of the magnet can be of the same order of magnitude as the transverse dimension of the conductor perpendicular to the plane of this air gap.
• This solution makes it possible to communicate large strokes on the hands, of the order of a millimeter with accelerations of the order of 6000 m / s 2 , which is much higher than existing solutions.
• the masses involved are also very small.
• the current flow section is constant so that there are no heating points of the conductor.
• the elasticity of the conductor is good and can be limited to certain parts of it without increasing either the mass or the cross-section of the current.
• the non-flexible parts can be made of aluminum increasing the electromechanical conversion efficiency.
• Fig. 1 is a perspective view of an embodiment.
• Fig. 2 is a perspective view of a variant of FIG. 1.
• Fig. 3 is a perspective view of another variant.
• Fig. 4 is a perspective view of yet another variant.
• Fig. 5 is a perspective view of a variant of FIG. 3
• Fig. 1 illustrates an embodiment in which a single needle 1 has been shown only for the sake of simplification. It is however obvious that several needles could be arranged in a stack for example. What is described here by way of example for a needle is obviously valid for each needle of a needle matrix printer.
• the needle 1 is guided by two bearings 2 and 3 in a direction perpendicular to a sheet to be printed 4 placed on a support roll 5, an ink ribbon 6 being called to pass between the front point of the needle 1 and the sheet to be printed 4, in a known manner.
• This needle 1 is connected by a stop 7 which is integral with it, to an electrical conductor 8 which, in this example, consists of a thin flexible copper tape, formed as a hairpin, fixed at its two ends with two elements of support 9 and 10 integral, like the bearings 2 and 3 of the needle 1, for example of a carriage (not shown), movable along an axis parallel to that of the roller 5.
• This same carriage is intended to carry a permanent magnet 11 in the air gap of which the electrical conductor 8 is located.
• the ends of this conductor are connected to the secondary of a transformer 12, the primary of which is connected to a source of current pulses 13.
• Tests have been carried out with such a needle structure using an electrical conductor 8 formed from a CuAg strip 50 ⁇ m thick and 0.7 mm wide.
• the length between the anchor points 9 and 10 and the hairpin loop is 3 cm, the needle 1 itself is made of a tungsten wire of 0.35 mm in diameter.
• the maximum spacing between the two strands of the electrical conductor 8 is of the order of 3 mm.
• the elongation e of needle 1 following the application of a current 1 A in conductor 8 with a magnetic cha ⁇ p of 0.5 Tesla is 100 to 200 ⁇ m. This is a static regime which does not correspond to reality since the needle is actuated according to a dynamic principle by brief current pulses. In this case, with pulses of 5 A during 0.5 ms, elongations e of needle 1 are measured from 200 to 400 ⁇ m.
• the strands of the conductor 8 at rest are slightly curved towards the outside rod illustrated in FIG. 1, position in which a spacing of the strands results in a greater elongation of the needle than from parallel and straight strands.
• FIG. 2 It essentially consists in spreading the anchor points 9 and 10 of the conductor 8 so that the deformation induced by the electromagnetic forces applied to the conductors 8 during the passage of a current I results in an elongation of the respective needles equal to the deflection of the conductor subjected to forces F.
• the configuration of fig. 2 is, from this point of view, optimal since the entire amplitude of the deformation of the conductor 8 is transmitted to the needle 1. Furthermore, this conductor 8 works in traction like that of FIG. 1.
• each pole N and S of the permanent magnet 11 can be shaped as a staircase 14, a milling 15 being intended to allow the passage of the needles 1.
• the complementary configuration of the pole S (not shown) of the magnet 11 makes it possible to provide a minimum air gap, substantially corresponding to the width of the section of each conductor 8 and thus ensure a high magnetic induction. This configuration with the conductors 8 parallel to the printing surface makes it possible to obtain a compact needle matrix printer head.
• the variant of fig. 3, which is directly applicable to the needle matrix print head of FIG. 2 makes it possible to avoid this triangulation effect by making the portion 8a of the conductor 8 which is disposed in the air gap of the permanent magnet 11 more rigid.
• the rigidity of the portion 8a can be obtained simply by twisting the ribbon 90 ° around its longitudinal axis so that its width is in the plane d 'application of the force F. Therefore, the portions 8b of the conductor provide the elastic suspensicn of the portion 8a which, it does not deform and allows to remove the triangulation effect resulting from a completely flexible conductor.
• the air gap of the magnet 11 can be further reduced.
• the portion of the conductor 8 located in the air gap of the magnet 11 could be made more rigid by increasing the thickness of this portion, for example by welding a segment of the same strip against this portion of the conductor.
• Tests by static supply of an electrical conductor 8 of the type illustrated in FIG. 2 were carried out to measure the elongation of the needle.
• the electrical conductor 8 is produced from an AgMgO wire with a diameter of 0.25 mm having a straight portion of 4 cm, the needle 1 being produced from a tungsten wire with a diameter of 0.35 mm and 35 mm long with a mass of 68 mg.
• the elongations measured are 0.06 mm for 0.2 A; 0.12 for 0.4 A; 0.17 for 0.6 A; 0.22 for 0.8 A; and 0.28 for 1 A.
• the tests were carried out with a mechanism similar to that illustrated in FIG. 3 with a needle identical to that used previously, ie a needle cut from an AgMgO wire of 0.25 min in diameter at a length of 25 min representing a mass 12.5 mg.
• the conductor 8 is produced from a CuAg ribbon 50 ⁇ m thick and 1.5 mm wide, representing a mass of approximately 0.60 mg / mm.
• the total length of the wire between the sup ports 9 and 10 is 75 mins.
• the length of the portion 8a located in the air gap of the arm is 50 mm.
• the electrical resistance R of conductor 8 is around 40 m ⁇ .
• the magnetic induction B in the air gap of the magnet is approximately 0.75 Tesla.
• the conductor 8 is supplied by an alternating positive and negative pulse train of 0.4 volts of 500 ⁇ s.
• the power dissipated in the useful part of approximately 60 mm in length is 2 watts.
• the acceleration is a
• the speed reached at the end of the 500 ⁇ s pulse is:
• the corresponding energy is:
• the positive pulse I accelerates the mass up to approximately 2.5 m / s at the time of impact against the surface to be printed which is located approximately 0.7 mm from the tip of the needle in rest position.
• the negative pulse decelerates the needle and is added to the rebound of the needle against the paper and its support to bring the needle back.
• it can still re be accelerated by shifting the negative pulse relative to the rebound following the impact against the surface to be printed and reducing the duration of this negative pulse accordingly. For example, you can offset this pulse by 0.2 ms and reduce it to 0.3 ms so that the needle does not move back beyond the rest position.
• the same speed and the same kinetic energy are obtained, but the dissipated power is then divided by 4, ie 0.5 watt. However, the frequency is reduced by 40%.
• the supply of the conductor 8 is preferably carried out using a transformer 12.
• the primary of this transformer which is connected to the pulse source 13 can be for example 50 turns and the secondary connected to the conductor 8 of 2 turns.
• a voltage of 10 V at the primary and a current of 0.4 A gives the secondary a voltage of 0.4 V and a current of 10 A.
• the supply of the conductor 8 can also be carried out, without transformer, by means of power transistors, preferably of transistors with weak field effect and resistance in the conductive state.
• the solution illustrated in fig. 4 is a variant of that of FIG. 3, in which the more rigid segment 8a is constituted by an aluminum strip which is welded at its respective ends to the bent portions 8b which are made of a strip or a wire of a CuAg alloy. Thanks to this solution, the fact of using an aluminum strip in the air gap of the magnet makes it possible to improve the electromechanical conversion efficiency. Indeed, this yield given by the formula:
• Fig. 5 shows another variant of FIG. 3 in which two conductors 8 and 8 ′ are arranged in parallel in the same plane and therefore in the same air gap of a magnet 11.
• the two conductors are in the plane of the air gap, which makes it possible to reduce the air gap occupied to the strict minimum, corresponding to the thickness of the only conductors 8 and 8 '.
• a transverse groove 11a is formed in a polar face of the magnet 11 to allow the passage of the needles 1 and the.
• the part of the needle l ' which passes under the conductor 8 and which is welded under the conductor 8' has a flat 11a to reduce its thickness.
• the needle matrix printer according to this invention makes it possible to produce a compact print head, of simple construction and giving an impression having good contrast.
• the type of electrodynamic actuator (a conductive element immersed in a magnetic induction) is particularly suitable for adjusting the impact force of the printing needle thanks to the fact that the driving force is proportional algebraically aware. It is therefore possible to reduce the impact force by using for example a negative current pulse following the positive pulse. This will significantly reduce the level of the source of acoustic noise. However, the printing force being reduced, this reduction can advantageously be offset by an additional supply of energy. It is indeed possible, for example, to replace the support roller 5 of FIG. 1 by an anvil formed by an ultrasonic transducer.

Landscapes

• Printers Or Recording Devices Using Electromagnetic And Radiation Means (AREA)
• Impact Printers (AREA)
• Electromagnets (AREA)

Priority Applications (1)

Applications Claiming Priority (2)

Publications (2)

Family

ID=4302972

Family Applications (1)

Country Status (8)

Cited By (1)

Families Citing this family (7)

Family Cites Families (7)

• 1984
  • 1984-12-19 CH CH6023/84A patent/CH661687A5/fr not_active IP Right Cessation
• 1985
  • 1985-12-16 EP EP86900039A patent/EP0209529B1/de not_active Expired
  • 1985-12-16 DE DE8686900039T patent/DE3568731D1/de not_active Expired
  • 1985-12-16 AU AU52338/86A patent/AU5233886A/en not_active Abandoned
  • 1985-12-16 US US06/905,386 patent/US4732498A/en not_active Expired - Fee Related
  • 1985-12-16 JP JP61500143A patent/JPS62501405A/ja active Pending
  • 1985-12-16 AT AT86900039T patent/ATE41362T1/de not_active IP Right Cessation
  • 1985-12-16 WO PCT/CH1985/000176 patent/WO1986003718A1/fr not_active Ceased

Non-Patent Citations (1)

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