EP0082742B1 - Verfahren und Vorrichtung zum magnetographischen Kopieren - Google Patents

Verfahren und Vorrichtung zum magnetographischen Kopieren Download PDF

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Publication number
EP0082742B1
EP0082742B1 EP82400425A EP82400425A EP0082742B1 EP 0082742 B1 EP0082742 B1 EP 0082742B1 EP 82400425 A EP82400425 A EP 82400425A EP 82400425 A EP82400425 A EP 82400425A EP 0082742 B1 EP0082742 B1 EP 0082742B1
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Prior art keywords
developer
dots
magnetic
magnetised
magnetic field
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EP82400425A
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English (en)
French (fr)
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EP0082742A3 (en
EP0082742A2 (de
Inventor
Jean-Jacques Eltgen
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Bull SAS
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CII Honeywell Bull
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Publication of EP0082742A3 publication Critical patent/EP0082742A3/fr
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    • G—PHYSICS
    • G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
    • G03G—ELECTROGRAPHY; ELECTROPHOTOGRAPHY; MAGNETOGRAPHY
    • G03G19/00—Processes using magnetic patterns; Apparatus therefor, i.e. magnetography

Definitions

  • the present invention relates to a magnetographic printing method which makes it possible to obtain images in two colors on a printing medium. It also relates to a machine for implementing this method.
  • Magnetic printing machines which, in response to signals received from a control unit, make it possible to form images, such as images of characters for example, on a printing medium also consisting of a strip. or a sheet of paper.
  • the printing of the images is carried out by first forming, from the signals received, a latent magnetic image on the surface of a magnetic recording element generally in the form of a rotating drum or an endless belt, this latent image consisting of a set of magnetized zones of very small dimensions .
  • This latent image is then developed by depositing on this surface a powdery developer containing magnetic particles which remain applied only to the magnetized areas of the recording element to form a powder image on the surface of this element. After which, this powder image is transferred to the print medium.
  • the image which is thus formed on the printing medium may appear in two different colors.
  • the printing of a color image on the printing medium is carried out by first forming on the recording element an image latent magnetic corresponding to the parts of the same color of the image to be printed, by developing this latent image by means of a developer having this color, by transferring the powder image thus obtained onto the printing medium, and by repeating this operation as many times as there are colors in the image to be printed.
  • a method has the drawback of requiring a particularly long time for its implementation.
  • the particles which have a determined size (and consequently a given color) are preferentially attracted by the elementary areas whose dimensions correspond to a given force of attraction, so that, after development, each elementary area is covered with particles whose color corresponds to the frequency that was used to form this elementary area.
  • the images or image portions whose hue corresponds to the areas elementary elements of large dimensions have a definition, that is to say a degree of finesse, less good than cells whose hue corresponds to elementary areas of small dimensions.
  • the elementary areas of small dimensions are capable, during development, of attracting only the smallest particles of the developer, it is impossible to prevent that the elementary areas of large dimensions attract not only the large particles. of the developer, but also the smaller particles, which naturally causes color change.
  • the present invention overcomes these drawbacks and proposes a magnetographic printing method as well as a machine using this method, which makes it possible to obtain on a printing medium, in a relatively short time, high quality two-color images, while requiring only two developers having the same particle size and the same magnetic characteristics.
  • FIG. 1A shows, in enlarged section, a magnetic recording element 10, of known type, which can be used for implementing the method of the invention.
  • this magnetic recording element is of a type analogous to that which has been described and represented in French patent No. 2,402,921 and that it comprises a support 11 formed of a material having a high magnetic permeability, such as iron or mild steel, this support being coated with a layer 12 of magnetic material with high coercivity such as, for example, the nickel-cobalt magnetic alloy.
  • this recording element 10 is magnetized transversely by means of one or more recording heads 13 of the type which has been represented in FIG. 3 Referring to FIG.
  • this recording head 13 comprises a magnetic core 14 on which is wound a winding E connected to an electrical excitation circuit which will be described a little later.
  • This magnetic core 14 has substantially the shape of a U and it is profiled so as to present at its ends a recording pole 15 and a flux closing pole 16. These two poles are arranged, as shown in FIG. 3 , near the surface of the magnetic layer 12, so that the magnetic core 14, the support 11 and the two regions 100 and 101 which are included between this core and this support and which are located directly above the poles 15 and 16 form a closed magnetic circuit. It should be noted here that, although in the case illustrated in Figure 3, the poles 15 and 16 are located near the surface of the magnetic layer 12, we could adopt another arrangement in which these two poles would be placed in contact of this surface.
  • FIG. 3 also shows that the width d of a recording pole 15 is very small compared to that D of the flux closing pole 16. Under these conditions, if an electric current is sent to winding E intensity
  • this current creates, inside the magnetic core 14, a magnetic flux whose line of average force is represented by the line of dashed lines 17.
  • the magnetic field is perpendicular to the surface of this layer 12, so that in this portion, the magnetization of the magnetic layer 12 takes place transversely.
  • the magnetic field created by the head 13 causes the appearance of a practically point magnetized zone usually called magnetized point, this magnetized zone remaining even when the winding E then ceases to be traversed by a current.
  • the magnetic layer 12 can be magnetized so that the magnetized zones thus formed constitute a latent magnetic image having a determined configuration, for example the configuration of a character.
  • FIG. 1 For example, FIG. 1
  • the spacing pitch P of the rows and columns of this matrix is at least equal to the transverse dimension L of a magnetized area. Under these conditions, it has been found that, even in the case where this pitch P was substantially equal to this dimension L, the magnetizations presented by two neighboring magnetized zones had practically no influence on each other. It will now be recalled that, in known methods, the image of the recording element is then developed by depositing on the surface of the magnetic layer 12 a powdery developer comprising finely divided particles each formed from an organic thermoplastic resin in which have incorporated a pigment and magnetic particles.
  • the surface of the magnetic layer 12 is subjected to a retouching operation which makes it possible to remove the developer particles which are in excess on this surface, so that, at the end of this operation, only the magnetized areas of this layer remains covered with a developer film, thus forming on the surface of layer 12 a powder image whose configuration corresponds to that of the magnetized zones.
  • This powder image is then transferred to a printing medium generally consisting of a strip of paper.
  • a printing medium generally consisting of a strip of paper.
  • the recording element 10 is magnetized so as to form on its surface magnetized zones which all have the same dimensions and which have magnetization intensities of different amplitudes and magnetic polarities opposite.
  • FIG. 1A only two of these zones, referenced A1 and A2, have been shown for reasons of simplification, but it is understood that the number of these magnetized zones can be absolutely arbitrary.
  • FIG. 1A also shows the north (N) and south (S) magnetic polarities, as well as the respective magnetizations J 1 and J 2 of the areas A1 and A2, each of these magnetizations being represented by an arrow whose length is proportional to the value of this magnetization. It can then be seen in FIG.
  • the magnetizations J 1 and J 2 of the zones A1 and A2 have different values and that they are oriented in opposite directions to each other, so that the magnetic polarity that presents zone A1 on the surface of the recording element 10, that is to say here a south polarity (S), is opposite to that which zone A2 has on this same surface, that is to say say here a north polarity (N). It can also be seen that, in the example illustrated in FIG. 1A, the magnetization J 1 of the zone A1 is greater than the magnetization J 2 of the zone A2.
  • the magnetized zones which are intended to form, on the printing medium, images or parts of images which must appear in one of the two colors chosen have magnetizations which all have the same value J 1 and which are all oriented in the same direction.
  • the magnetization of these zones is oriented in the opposite direction to the magnetizations of the other magnetized zones which are intended to form, on this support, images or image parts which must appear in the other color.
  • the magnetizations of these other zones all have the same value J 2 , J 2 being different from J 1 .
  • the areas A1 and A2 which have been shown in FIG. 1A and which have magnetizations of different values and of opposite directions, are intended to form on the printing paper two punctual spots of different colors.
  • the magnetized area A1 is intended to form a point spot of red color and that the magnetized area A2 is intended to form a point spot of black color.
  • the two magnetized zones A1 and A2 it is possible to use two identical recording heads, of the type which has been represented in FIG. 3, and to excite these two heads with currents of different intensities and such that the direction in which circulates the current in the winding of the first head is inverse to that in which the current flows in the winding of the second head.
  • the recording element 10 having been magnetized in the manner which has just been indicated, a first powdery developer is then deposited on the surface of this element, the tint of which is one of the two colors chosen. In the example described, it will be considered that this first, powdery developer is red in color.
  • This first developer which is brought into contact with the entire surface of the recording element 10, is however only attracted by the magnetized zones of this element, so that, if we manage to leave this revealing that on these areas magnetized, for example by arranging the recording element so that, when this developer is applied to this element, each developer particle is subjected, on the one hand to the action of the attraction force magnetic exerted by the magnetized zones, on the other hand to the action of a gravity force oriented in opposite direction to this magnetic attraction force, each of these magnetized zones is then coated, as shown in FIG. 1B, of a layer 18 of the first developer, the thickness of this layer being all the greater the higher the magnetic attraction force exerted by the magnetized zone on which this layer is deposited.
  • the force with which each of the developer particles which have been deposited on the same magnetized zone is attracted depends not only on the value of the magnetization J of this zone and on the distance h which separates each particle. of this zone, but also of the physical characteristics of this developer, such as the particle size state and the percentage of magnetic particles of this developer.
  • the magnetic force exerted on a developer particle which has been deposited on a magnetized area is all the greater the higher the value of the magnetization J of this area.
  • this magnetic attraction force is all the smaller the greater the distance h which separates this particle from this zone, the variations of this magnetic force Fm as a function of this distance h being illustrated by the curves which have have been shown in FIG. 6. In this FIG.
  • the dashed line curve 81 represents the variations, as a function of h, of the magnetic attraction force exerted by the magnetized zone A1, of magnetization J i .
  • the dashed line curve 82 represents the variations, as a function of h, of the magnetic attraction force exerted by the magnetized zone A2, of magnetization J 2 .
  • the value F G of the force of gravity mentioned above has also been shown, this force being exerted on each particle of developer during the application of this developer on the surface of the element. registration.
  • this recording element 10 is then subjected to a retouching operation intended, not only to remove the residual particles of first developer remaining outside the magnetized zones of this element, but also to remove all the particles of first developer on all the magnetized zones which, such as A2, have the smaller of the two magnetization values J 1 and J 2 .
  • a retouching operation which can be carried out by electrostatic or pneumatic means (suction or blowing of air) each particle of developer remaining on the surface of the recording element 10 is subjected to a constant force, of value F , which is exerted against the magnetic force F m which keeps each particle applied to the magnetized area on which it has been deposited.
  • a second powdery developer is then deposited on the surface of the recording element, the color of which is of the other of the two colors chosen, that is to say ie black in the example described.
  • the filing of this second developer is carried out under the same conditions as those which have been described for the deposition of the first developer, so that, when this deposition is completed, each of the magnetized zones of the recording element 10 is coated, as shown in the figure 1 D, a layer 19 of second developer. On the magnetized zones of stronger magnetization, such as the zone A1, this layer 19 is thus superimposed on the layer 18 of the first developer.
  • the recording element is subjected to a second retouching operation, similar to that described above, but the force of which, of constant value F 2 is less than the force F 1 of the first retouching operation.
  • This second retouching operation is carried out in the presence of a constant magnetic field, of value H, produced by a magnetic field generating device 56, (FIG. 1E) of known type.
  • the magnetic field H which is produced by this device 56 is oriented in the opposite direction to the direction of the larger of the two magnetizations of the magnetized zones, that is to say in the opposite direction to the direction of the magnetization J i .
  • the magnetization of the magnetized zones of greater magnetization is weakened, while that of the other magnetized zones, such as zone A2, is reinforced. This then results in a reduction in the magnetic attraction force exerted by each of the magnetized zones whose magnetization has been weakened, while the attraction force exerted by each of the magnetized zones whose magnetization has been strengthened is increased .
  • the value of the magnetic field H is chosen in such a way that the magnetic force exerted by each magnetized zone of weakened magnetization then becomes equal to that exerted, under the same conditions, by each magnetized zone of reinforced magnetization, the variations of this force magnetic, as a function of the distance h, being, on the diagram of FIG. 6, represented by the curve in solid lines 80.
  • immediate proximity is meant that the distance which separates the paper strip 20 from the surface of the recording element 10 is at most equal to one millimeter.
  • the magnetic field which is produced by the device 21 has the same amplitude H and the same direction as that which is produced by the device 56 so that, under the action of this field, the magnetic force exerted by each of the magnetized zones of the recording element 10 varies, as a function of the distance h, in the manner which, in the diagram of FIG. 6, is illustrated by the curve in solid lines 80.
  • the recording element 10 remains thus subjected to the action of the magnetic field produced by the device 21, the paper strip 20 is then brought into contact with this recording element, then each of the particles of one or the other developer which are found is subjected on this element to the action of a force, called transfer, which has the effect of urging each of these particles towards the paper strip and thus transferring almost all of these particles onto this strip.
  • This transfer operation can moreover be carried out either by pressing the strip of paper 20 on the recording element 10, or by using electrostatic means.
  • the transfer force used during this operation maintains a constant value F T.
  • F. of this force
  • the value FT of this transfer force is chosen so as to allow all or almost all of the particles on the element 10 to be transferred to the paper strip 20. It is of course possible to use a transfer force whose value F T is such that the line of ordinate F T is above the curve 80 and does not intersect this curve . Under these conditions, all of the developer particles are transferred onto the paper strip 20.
  • the value F T of the transfer force is chosen so that the ordinate line F T intersects the above-mentioned curve 80 at a point G whose abscissa e 3 is close to zero.
  • the abscissa e 3 of this point G is substantially equal to 3 ⁇ m. Under these conditions, almost all of the developer particles which were on the recording element 10 are transferred to the paper strip 20, so that at the end of the transfer operation, there remains, on each of the zones of the recording element 10, a layer of developer whose thickness e 3 is practically negligible.
  • the developer layers which have thus been transferred to the paper strip 20 are then subjected to a fixing operation intended to definitively fix these layers on the paper.
  • This operation is carried out at a temperature which makes it possible to bring the two developers constituting these layers, at least in the viscous state.
  • This temperature can be chosen, preferably, so as to cause the fusion of two developers, without however presenting the risk of ignition or carbonization of the paper.
  • the developers used can be of the type which have been described in the French patent application which was filed on March 20, 1980 by the Applicant and published under No. 2,478,839. These developers have the advantage of melting at a temperature below 140 ° C.
  • each of the heaps 34 forms on the paper a punctual spot having the shade of the second developer, that is to say black in the example described, while each of the heaps 35 forms on the paper a spot spot having the color of the first developer, that is to say red in the example described.
  • FIG. 2 shows a magnetographic printing machine which performs printing in two colors according to the printing process which has just been described.
  • the machine which is shown in this figure comprises a magnetic recording element in the form of a magnetic drum 10 similar to that which has been described and shown in the aforementioned French patent No. 2,402,921, this drum being driven in rotation, in the direction indicated by arrow R, by an electric motor 25.
  • the magnetization of the magnetic layer of this drum is ensured by a set of n magnetic heads 13-1 to 13-n arranged one next to the other , and aligned parallel to the axis of rotation of the drum, these heads being placed near the magnetic surface of this drum.
  • These heads which are of the type which has been shown in FIG. 3, are selectively excited by electrical pulses sent by a source of pulses 26 and applied to the windings of these heads via a calibration device and current inversion 27, the structure of which has been shown in detail in FIG. 4.
  • each of the respective windings E-1 to En of magnetic heads 13-1 to 13-n is connected, at one of its ends, to the movable contact blade of the '' a respective one of n first reversing contacts K-1 to Kn, and, at the other end, to the movable blade of one respective of n second reversing contacts L-1 to Ln, via one respective of n relay contacts CB-1 to CB-n.
  • Each of the relay contacts CB-1 to CB-n is controlled by a respective one of n relay coils B-1 to Bn.
  • FIG. 4 shows that each of the reversing contacts K-1 to Kn and L-1 to Ln has two positions designated by the numbers 1 and 2.
  • Position 1 of each of the reversing contacts K-1 to Kn is connected to the positive terminal (+) of a first current generator G1, while the position 1 of each of the change-over contacts L-1 to Ln is connected to the negative terminal (-) of this first generator G1.
  • Position 2 of each of the change-over contacts K-1 to Kn is connected to the negative (-) terminal of a second current generator G2, while position 2 of each of the change-over contacts L-1 to Ln is connected to the positive (+) terminal of this second generator G2.
  • FIG. 4 shows that the movable contact blades of the reversing contacts K-1 to Kn are mechanically coupled so that they can be placed simultaneously in the same position.
  • the relay coils B-1 to Bn can be excited by electrical pulses supplied on the outputs S1 to Sn of the pulse source 26, each of these coils B-1 to Bn being, in fact, connected to a respective one of the outputs S1 to Sn through the respective one of n conductors W1 to Wn.
  • the latent magnetic image necessary for the printing of a character is obtained by selectively exciting, on seven different occasions, five contiguous heads taken from among all of the magnetic heads 13-1 to 13-n, this excitation being carried out by means of pulses delivered at successive instants t 1 , t 2 , t 3 , t 4 , t s , t 6 and t 7 , on five corresponding outputs S1 to Sn of the pulse source 26.
  • the pulse source 26 delivered, at time t 1 a pulse on each of its outputs S2 to S4, at time t 2 a pulse on each of its outputs S1 to S5, at time t 3 a pulse on its output S5, at time t 4 a pulse on each of its outputs S1, S2, S3 and S5, at time t 5 a pulse on each of its outputs S1 to S5, at time t 6 a pulse on each of its outputs S1 to S5, and finally at time t, a pulse on each of its outputs S2 to S4.
  • the reversing contacts K-1 to Kn and L-1 to Ln and the current generators G1 and G2 are intended to determine the direction of orientation and the amplitude of the magnetizations of the magnetized zones on the drum 10; this direction and this amplitude conditioning the color of the spot which will be subsequently formed on the paper by each of these magnetized zones.
  • the first reversing contacts K-1 to Kn, the second reversing contacts L-1 to Ln, the relay contacts CB-1 to CB-n and the windings E-1 to En of magnetic heads are distributed, as as shown in FIG.
  • This current which has an intensity 1 2 lower than that I 1 of the current delivered by the generator G1, then flows in this winding in the direction which, in FIG. 4, is indicated by the arrow 1 2 .
  • the magnetization of the magnetized zone which is formed on the drum 10 by the head provided with this winding is oriented in the direction indicated by the arrow J 2 in FIG. 1A and has the same amplitude as that shown in this FIG. 1A.
  • the positioning of the reversing contacts K-1 to Kn and L-1 to Ln on one or the other of positions 1 and 2, can be carried out, either manually by the operator before any printing operation, or fully automatically, the changeover contacts K-1 to Kn and L-1 to Ln being, in the latter case, controlled by actuation means of known type, excited by the same control unit as that which controls the operation of the pulse source 26. It should also be noted that, depending on the case and applications , some of the reversing contacts K-1 to Kn and L-1 to Ln can be placed in position 2 while the other reversing contacts are placed in position 1, which allows, when printing a line of characters by example, to obtain characters printed in one of the two colors, while the other characters of this line are printed in the other color.
  • the current calibration and reversing device 27 which has been represented in FIG. 2 is constituted, in the example described, by the assembly comprising the generators G1 and G2, the reversing contacts K-1 to Kn and L-1 to Ln, the coils B-1 to Bn and the contacts CB-1 to CB-n, all these elements being connected together as illustrated in FIG. 4.
  • the printing machine produced according to the invention also comprises a first applicator device 40, of known type, which makes it possible to apply to the surface of the drum 10 particles of a first powdery developer contained in a reservoir 49. It will be considered, in the example described, that this first developer is red in color.
  • This first applicator device 40 is established for depositing on each of the magnetized zones of the drum 10 a layer of first developer, 1 thickness of which is, on the magnetization zones J 1 , close to 87 ⁇ m and, on the magnetization zones J 2 , close to 77 pm.
  • this applicator device 40 is of the type of cees which have been described and represented in French patents No.
  • this device comprising, on the one hand, a rotating magnetic element which brings the developer particles of the tank 49 to the vicinity of the surface of the drum 10, on the other hand a deflector interposed between this element and the drum to constitute a trough in which the particles collected by the deflector come to accumulate, this deflector leaving between it and the drum a very small opening of the order of 1 millimeter through which pass particles which have come to be applied against the surface of this drum.
  • the magnetized zones of the drum 10 which have thus been coated with a layer of first developer then pass in front of a retouching device 41 which on the one hand makes it possible to remove the particles of developer remaining on the drum 10 outside the magnetized zones, on the other hand to remove the first developer on the magnetized areas of magnetization J 2 .
  • the retouching device 41 which is used for this operation can be of the electrostatic or pneumatic type. It will be considered that, in the example described, this retouching device 41 is of the type which has been described and shown in French patent N ° 2,411,435 and that it is adjusted so as to leave subsist on each of the zones. magnetized with magnetization J 1 of the drum 10 a layer of first developer whose thickness is practically equal to 40 ⁇ m.
  • the magnetized zones of the drum 10 which have undergone this retouching operation then pass in front of a second applicator device 42, of a type similar to that of the first applicator device, this second applicator device 42 making it possible to deposit particles on the drum 10 of a second powder developer which, being black in the example described, is contained in a reservoir 50.
  • This second applicator device is established for, on the one hand, depositing on each of the magnetized magnetization zones J 2 of the drum 10 a layer second developer having a thickness substantially equal to 77 ⁇ m, on the other hand depositing on each of the already deposited layers of first developer a second layer of second developer, the thickness of this second layer being of the order of 50 ⁇ m.
  • the thickness of the layer of first developer is practically equal to 40 ⁇ m, the total thickness of the two layers is therefore of the order of 90 ⁇ m.
  • the magnetized zones of the drum 10 which are then coated with these layers of developers then pass in front of a magnetic field generating device 56 and in front of a second retouching device 43 similar to the retouching device 41.
  • the magnetic field generating device 56 is made up, in the example described, by a permanent magnet and it is arranged so that the magnetic field which it generates is oriented in the opposite direction to the magnetization J i . This device 56 is also established so that the amplitude H of this magnetic field meets the conditions which have been explained in detail above.
  • the second retouching device 43 in cooperation with this magnetic field generating device 56, makes it possible to reduce the thicknesses of the developer layers which are then located on the magnetized zones of the drum 10, and it is adjusted so that, after the the retouching operation carried out by this device 43, each of the magnetized zones of the drum is coated with a layer having a thickness practically equal to 35 ⁇ m, this layer then comprising only particles of first developer when it is on a zone d magnetization J 1 and only particles of second developer when it is on a magnetization zone J 2 .
  • the machine which has been shown in FIG. 2 comprises a transfer station which, in the example described, comprises a roller 45 over which the paper strip 20 passes.
  • the roller 45 is a pressure roller which makes it possible to apply the paper strip 20 to the drum 10 with a determined value force which in general does not exceed 600 newtons per linear meter. In the example described, this force has been adjusted by springs which have not been shown in the drawings, for reasons of simplification. In the more particularly advantageous embodiment which has been illustrated in FIG.
  • the transfer station further comprises a guide roller 44 which is disposed upstream of the roller 45 with respect to the direction of travel of the drum and the strip of paper, and which makes it possible to bring the paper strip 20 in the immediate vicinity of the surface of the drum 10, a little before this strip is applied against this surface.
  • FIG. 7 indeed shows that the point T where the strip 20 comes into contact with the drum 10 is located between the rollers 44 and 45.
  • the machine shown in FIG. 2 also has a second magnetic field generating device 21 which is arranged at the level of the transfer station, that is to say in the immediate vicinity of the roller 45.
  • this device 21 is constituted by a permanent magnet, but it should be noted however that this magnet could be replaced by any other equivalent device, for example by a magnetic induction coil excited by a direct current.
  • This second generator device 21 is established so that the magnetic field H that it produces is oriented in the same direction and the same amplitude as the magnetic field generated by the first magnetic field generator device 56.
  • the magnetization intensities of the magnetized zones subjected to the action of this magnetic field all take the same value, which makes it possible to transfer onto the paper strip 20, layers all having the same thickness.
  • the force with which the roller 45 presses the strip of paper 20 on the drum 10 is adjusted in such a way that the layers of first and second developers which were deposited on the magnetized zones of the drum 10 are transferred almost entirely on the strip of paper 20.
  • the second magnetic field generating device 21 is preferably placed between the guide roller 44 and the aforementioned point T, but close to this point T. It has in fact been found that this arrangement allows to improve the efficiency of the transfer and the quality of the image formed on the paper during this transfer.
  • the machine which has been shown in FIG. 2 also includes a developer fixing device 46 under which the paper strip 20 passes when the transfer operation which has just been described has been carried out.
  • This fixing device 46 which is constituted, in the example described, by an electrically heated element, is intended to permanently fix the developers which have been transferred, on the strip of paper 20. It should be noted here that this device fixing 46 is adjusted so that these developers undergo a clear melting without causing an ignition or even a deterioration of the paper strip 20, the melting temperature of these developers being, in the example described, lower than 140 ° C. . Under these conditions, each pile as 34 forms when it cools down on the paper a spot spot having the shade of the second developer, while each pile as 35 forms, when cooling on this paper, a point spot having the shade of the first developer.
  • the machine shown in Figure 2 further comprises a cleaning device which, consisting of a brush 47 in the example described, ensures the cleaning of the parts of the surface of the drum which have passed in front of the transfer station. After this cleaning, these parts pass in front of an erasing device 48, of the electromagnetic type, which erases the latent magnetic images carried by these parts, so that these parts are again able to be magnetized when they become then present in front of the set of magnetic heads 13-1 to 13-n.
  • a cleaning device consisting of a brush 47 in the example described, ensures the cleaning of the parts of the surface of the drum which have passed in front of the transfer station. After this cleaning, these parts pass in front of an erasing device 48, of the electromagnetic type, which erases the latent magnetic images carried by these parts, so that these parts are again able to be magnetized when they become then present in front of the set of magnetic heads 13-1 to 13-n.

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Claims (9)

1. Magnetographisches Druckverfahren, weiches darin besteht, daß die Oberfläche eines magnetischen Aufzeichnungselementes in einer Richtung senkrecht zu dieser Oberfläche magnetisiert wird, eine Menge von magnetisierten Punkten gebildet wird, die ein latentes magnetisches Bild darstellen, anschließend auf dieser Oberfläche ein pulverförmiger Entwickler aufgebracht wird, der so ausgelegt ist, daß er nur an den magnetisierten Punkten der genannten Oberfläche anhaftet und so ein Pulverbild erzeugt, und daß schließlich dieses Pulverbild auf einen Druckträger übertragen wird, wobei dieses Verfahren dadurch gekennzeichnet ist, daß zur Erzeugung eines Bildes auf diesem Träger in zwei zuvor ausgewählten Farben das Verfahren darin besteht, daß:
- zunächst die Oberfläche des Aufzeichnungselementes magnetisiert wird, um magnetisierte Punkte zu erzeugen, die unterschiedlich große Magnetisierungsstärken und entgegengesetzte Magnetpolung besitzen, wobei die Punkte zur Erzeugung derjenigen Bildteile, die auf dem Träger in einer der genannten Farben erscheinen sollen, jeweils dieselbe Magnetisierungsstärke J1 und dieselbe magnetische Polung aufweisen, wobei die magnetische Polung dieser Punkte entgegengesetzt zu der der anderen magnetisierten Punkte ist und wobei diese anderen magnetisierten Punkte jeweils dieselbe Magnetisierungsstärke J2 mit JZ<J, aufweisen,
- auf dieser Oberfläche ein ersten pulverförmiger Entwickler aufgebracht wird, dessen Färbung die einer ersten der genannten Farben ist,
- dieser erste Entwickler von dieser Oberfläche außer an denjenigen magnetisierten Punkten entfernt wird, wo die Magnetisierungsstärke gleich J1 ist,
- auf dieser Oberfläche ein zweiter pulverförmiger Entwickler aufgebracht wird, dessen Färbung die der zweiten Farbe ist, welche jedoch dieselben physikalischen Eigenschaften wie der erste Entwickler besitzt,
- dieser zweite Entwickler von dieser Oberfläche teilweise entfernt wird, wobei diese Oberfläche einem konstanten Magnetfeld ausgesetzt wird, welches entgegengesetzt zu der Magnetisierungsstärke J1 orientiert ist, wobei die Stärke dieses Magnetfeldes einen solchen Wert aufweist, daß die Magnetisierungsstärken der magnetisierten Punkte verändert werden und praktisch denselben Wert annehmen, so daß dieser zweite Entwickler von dieser Oberfläche außer an denjenigen magnetisierten Punkten entfernt wird, wo die Magnetisierungsstärke gleich J2 ist, wobei jeder dieser letztgenanten Punkte so mit einer einzigen Schicht des zweiten Entwicklers bedeckt ist, während jeder der anderen magnetisierten Punkte mit einer einzigen Schicht des ersten Entwicklers bedeckt ist,
- und daß schließlich eine Übertragung sämtlicher Entwicklerschichten auf den Druckträger vorgenommen wird.
2. Druckverfahren nach Anspruch 1, dadurch gekennzeichnet, daß die Übertragung der Entwicklerschichten auf den Druckträger in Anwesenheit eines zweiten Magnetfeldes durchgeführt wird, welches dieselbe Richtung und dieselbe Stärke wie das erste Magnetfeld bezitzt, das während des Vorganges der Beseitigung des zweiten Entwicklers ausgeübt wurde.
3. Magnetographische Druckmaschine zur Durchführung des Verfahrens nach Anspruch 1, mit einem Aufzeichnungselement (10), das mit einer magnetischen Aufzeichnungsoberfläche versehen ist, einer Mehrzahl von Magnetköpfen (13-1 bis 13-n), die durch elektrische Impulse angesteuert und derart ausgebildet sind, daß sie ansprechend auf diese Impulse die genannte Aufzeichnungsoberfläche senkrecht zu dieser magnetisieren, um auf dieser Oberfläche eine Menge von magnetisierten Punkten (A) zu erzeugen, welche ein latentes magnetisches Bild darstellen, Antriebsmitteln (25) zur Verursachung einer Relativbewegung zwischen dem Aufzeichnungselement und den Magnetköpfen, einer Impulsquelle (26) zum selektiven Anlegen von elektrischen Impulsen an die genannten Köpfe, einer Aufbringvorrichtung (40) zum Aufbringen eines pulverförmigen Entwicklers auf der genannten Aufzeichnungsoberfläche, wobei dieser Entwickler nur an den magnetisierten Punkten dieser Oberfläche anhaftet, um ein Pulverbild zu erzeugen, und mit einer Übertragungsstation (45) zur Übertragung des genannten Pulverbildes auf einen Druckträger (20), wobei die Maschine dadurch gekennzeichnet ist, daß der genannte Entwickler, der als erster Entwickler bezeichnet wird, Teilchen enthält, deren Färbung die von einer der zwei zuvor gewählten Farben ist, und die Maschine ferner umfaßt:
- Mittel (27) zur Strombemessung und -umkehrung, welche zwischen den Magnetköpfen (13-1 bis 13-n) und der Impulsquelle (26) angeordnet sind, um einerseits die Stromrichtung der von der Quelle abgegebenen Impulse selektiv zu invertieren und andererseits die selektive Einstellung jedes dieser Impulse auf einen von zwei vorbestimmten Amplitudenwerten zu gestatten und so auf der Aufzeichnungsoberfläche ein magnetisches latentes Bild zu erzeugen, dessen magnetisierte Punkte verschiedene Magnetisierungsstärken und entgegengesetzte magnetische Polungen aufweisen, wobei die magnetisierten Punkte zur Erzeugung derjenigen Bildteile, die auf dem Träger in einer der genannten Farben erscheinen sollen, jeweils Magnetisierungsstärken derselben Größe J1 und derselben Richtung aufweisen, wobei die magnetische Polung dieser Punkte entgegengesetzt zu der der anderen magnetisierten Punkte ist und diese anderen magnetisierten Punkte jeweils Magnetisierungsstärken derselben Größe J2 mit J2<J, besitzen,
-eine erste Retuschiervorrichtung (41), die bezüglich des Bewegungssinnes der Oberfläche hinter der Aufbringvorrichtung (40) angeordnet und derart ausgebildet ist, daß sie den ersten Entwickler von denjenigen magnetisierten Punkten entfernt, deren Magnetisierungsstärke kleiner als J1 ist,
-eine zweite Aufbringvorrichtung (42), die zwischen der Übertragungsstation (45) und der ersten Aufbringvorrichtung (40) angeordnet ist, um einen zweiten pulverförmigen Entwickler auf der genannten Aufzeichnungsoberfläche aufzubringen, wobei dieser zweite Entwickler Teilchen enthält, dessen Färbung die der anderen der genannten Farben ist, welcher jedoch dieselben physikalischen Eigenschaften wie der erste Entwickler besitzt, wobei der zweite Entwickler nur an den magnetisierten Punkten der genannten Oberfläche anhaftet,
- und eine zweite Retuschiervorrichtung (43), die bewegungsabwärts von der zweiten Aufbringvorrichtung (42) angeordnet ist und eine Vorrichtung (56) zur Erzeugung eines Magnetfeldes enthält, um ein konstantes Magnetfeld auf die Aufzeichungsoberfläche einwirken zu lassen, wobei die Stärke dieses Feldes derart gewählt ist, daß die Magnetisierungsstärken der magnetisierten Punkte verändert werden und diese praktisch gleich sind, wenn diese magnetisierten Punkte vor der zweiten Retuschiervorrichtung (43) vorbeigeführt werden, so daß nach diesem Durchgang jeder der magnetisierten Punkte, dessen Magnetisierungsstärke gleich J2 war, mit einer einzigen Schicht des zweiten Entwicklers bedeckt ist, während jeder der Magnetisierungspunkte, dessen Magnetisierungsstärke gleich J1 war, mit einer einzigen Schicht des ersten Entwicklers bedeckt ist, wobei diese zwei Entwickler so ein Pulverbild auf der Aufzeichnungsoberfläche in zwei Farben darstellen.
4. Druckmaschine nach Anspruch 3, dadurch gekennzeichnet, daß die Vorrichtung (56) zur Magnetfelderzeugung durch einen Permanentmagnet gebildet ist.
5. Druckmaschine nach Anspruch 3 oder 4, dadurch gekennzeichnet, daß jeder Magnetkopf eine Wicklung (E) aufweist, die um einen Kern (14) herum aufgebracht ist, und die Mittel (27) zur Strombemessung und Umkehrung enthalten:
- n Schaltungsteile (C1-, C-2, ... C-n), die jeweils einem der n Magnetköpfe (13-1, 13-2, ..., 13-n) zugeordnet sind und jeweils enthalten:
+ einen Relaiskontakt (wie CB-1), der in Reihe mit der Wicklung des zugeordneten Kopfes geschaltet ist und durch eine Spule (wie B-1) betätigt wird, welche selektiv durch die Impulse erregt wird, die von der Impulsquelle (26) abgegeben werden,
+ einen ersten Umschalter (wie K-1) mit zwei Schaltstellungen (1, 2) und einer beweglichen Kontaktzunge, die an eines der Enden der Gruppe angeschlossen ist, die durch die genannte Wicklung (E-1) in Reihe mit dem genannten Relaiskontakt (DB-1) gebildet ist, + und einen zweiten Umschalter (wie L-1) mit zwei Schaltstellungen (1, 2) und einer beweglichen Kontaktzunge, die mit dem anderen Ende der Gruppe verbunden ist, welche durch die genannte Wicklung (E-1) in Reihe mit dem Relaiskontakt (CB-1) gebildet ist, wobei dieser zweite Umschalter mit dem ersten Umschalter derart verbunden ist, daß die beweglichen Kontaktzungen dieser zwei Umschalter gleiche Stellungen einnehmen,
- und zwei Stromgeneratoren (G1, G2), wobei der erste (G1) dieser Stromgeneratoren mit seinem positiven Anschluß (+) an die erste (1) der zwei Schaltstellungen jedes der n ersten Umschalter (K-1 bis Kn) angeschlossen und an seinem negativen Anschluß (-) mit der ersten (1) der zwei Schaltstellungen jedes der n zweiten Umschalter (L-1 bis L-n) verbunden ist, wobei der zweite (G2) der genannten Stromgeneratoren an seinem positiven Anschluß (+) mit der zweiten (2) der zwei Schaltstellungen jedes der n zweiten Umschalter (L-1 bis L-n) und an seinem negativen Anschluß (-) mit der zweiten (2) der zwei Schaltstellungen jedes der n ersten Umschalter (K-1 bis K-n) verbunden ist, wobei jeder dieser beiden Generatoren derart ausgebildet ist, daß er, wenn die Relaiskontakte (CB-1 bis CB-n) selektiv ansprechend auf die von der Quelle (26) abgegebenen Impulse geschlossen sind, jeweils eine von zwei Stromstärken 11 und 12 abgeben, wobei diese Stromstärken 11 und 12 derart eingestellt sind, daß in dem Aufzeichnungselement magnetisierte Punkte mit der Magnetisierung J1 bzw. J2 erzeugt werden.
6. Druckmaschine nach einem der Ansprüche 3 bis 5, dadurch gekennzeichnet, daß sie ferner eine zweite Vorrichtung (21) zur Magnetfelderzeugung eine zweite Vorrichtung (21) zur Magnetfelderzeugung enthält, welche auf der Höhe der Übertragungsstation (45) angeordnet ist, um ein konstantes Magnetfeld auf die Aufzeichnungsoberfläche auszuüben, während diese vor dieser Übertragungsstation vorbeibewegt wird, wobei dieses Magnetfeld in derselben Richtung orientiert ist und dieselbe Stärke aufweist wie das Magnetfeld, welches von der ersten Vorrichtung (56) zur Magnetfelderzeugung erzeugt wird.
7. Druckmaschine nach Anspruch 6, dadurch gekennzeichnet, daß die zweite Vorrichtung (21) zur Magnetfelderzeugung ein Permanentmagnet ist.
8. Druckmaschine nach einem der Ansprüche 3 bis 7, dadurch gekennzeichnet, daß das Aufzeichungselement durch eine magnetische Trommel (10) gebildet ist und die Übertragungsstation einerseits eine Druckrolle (45) enthält, um den Druckträger (20) gegen diese Trommel anzulegen, und andererseits eine Führungsrolle (44) enthält, welche bewegungsaufwärts von der Druckrolle angeordnet ist, damit der genannte Träger in Berührung mit dieser Trommel an einem Punkt (T) gebracht werden kann, der zwischen diesen zwei Rollen liegt, und daß die zweite Vorrichtung (21) zur Magnetfelderzeugung im wesentlichen auf der Höhe dieses Punktes angeordnet ist.
EP82400425A 1981-12-23 1982-03-09 Verfahren und Vorrichtung zum magnetographischen Kopieren Expired EP0082742B1 (de)

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