EP0086683B1 - Device for the application of solid particles on the recording support of a printing machine - Google Patents

Description

The present application relates to an improvement to the device for applying solid particles to the recording medium of a non-impact printer, described in FR-A-2408462 in the name of the International Company for IT CII- HONEYWELL BULL.

It applies to the production of known printing machines, called non-impact or transfer without typing, in which the printing of the characters is carried out without for this calling upon the impact of types of relief printing on a receiving sheet of paper.

Printing machines of this kind generally comprise a recording medium, most often consisting of a rotary drum or an endless belt, on the surface of which it is possible to form, by electrostatic or magnetic means, sensitized zones also called latent images, which correspond to the characters or images to be printed. These latent images are then developed, that is to say made visible, with the aid of a powdery revealing pigment which, deposited on the recording medium, is only attracted by the sensitized zones of the latter. this. After which, the pigment particles which have thus been deposited on these latent images are transferred to a support sheet, such as a sheet of paper for example, on which they are permanently fixed.

In order to apply this pulverulent revealing pigment to the recording medium of a printing machine of this kind, various application devices have been used in the prior art. Thus, for example, a device was used which comprises a cylindrical casing containing the powdered pigment, this casing having an opening in front of which the recording medium passes, the inking of this medium being produced by a cylindrical brush which, rotating inside the casing, projects the pigment particles towards the surface of the support which passes in front of this opening. However, this device does not give complete satisfaction to the use of the fact that it causes, on the one hand the formation of a cloud of pigment particles which spreads outside the casing, which is particularly unpleasant for people who, being near the printer, are reached by this cloud, on the other hand, an undesirable electrification of the particles which, projected towards the support, can then remain on the non-sensitized zones of this one consequently of an electrostatic attraction.

The device which is described in the above-mentioned patent overcomes these drawbacks. It is a device for applying, on the recording medium of a non-impact printer, solid particles contained in a reservoir, this device comprising a transport element arranged to bring these particles to the vicinity of the surface of this support, said device being characterized in that it further comprises a deflector interposed between this support and this transport element for collecting the particles transported by this element, this deflector having one of its edges disposed in the immediate vicinity of said support for constitute with this support a trough, of substantially prismatic shape, in which the particles thus collected accumulate, this support being displaced in the direction where it entrains these particles towards the edge of said prism, the particles entrained beyond this edge remaining applied only to the sensitized areas of said recording medium.

However, the device described in the aforementioned patent has the drawback of requiring frequent filling of the reservoir with solid particles. Indeed, the transport element, consisting for example of a rotary cylinder, can no longer supply particles to the recording medium as soon as the level of particles in the reservoir falls below the lower end of the element transport.

To overcome this drawback, one can imagine having a first worm below the transport element to bring the solid particles to the latter, and a second worm arranged parallel to the first and not contrary to this to compensate for the lateral displacement of the particles caused by the first screw in case this first screw is the only one to function. This avoids local exhaustion of the tank, due to the mixing of particles, resulting from the movement of the two screws, and there is no longer any need to frequently fill this tank.

However, worms are expensive parts. In addition, they cannot be completely immersed in the pulverulent pigment because on the one hand, the mechanical power to be supplied for the rotation of these screws is then significant, on the other hand, in the case where the pulverulent pigment consists of particles coated with a thermoplastic resin, this pigment is subjected to crushing and rolling by the screws and the resin melts due to the friction which results therefrom, thus giving agglomerates of particles in the tank; in addition, particles are pushed against the various bearings provided in the walls of the tank to ensure the rotation of the screws and this results in jamming of the corresponding axes of rotation because there are no means that are both simple and suitable for sealing the bearings. Furthermore, the screws supply the transport element with particles in a discontinuous manner, which creates beads of particles on the transport element and, conversely, zones deprived of these particles, which are detrimental for the application of said particles. to the recording medium.

The object of the present invention is to remedy the drawback of a supply device comprising, according to the aforementioned patent, only one transport element (associated with a deflector), without however having the drawbacks of a worm device previously mentioned.

It relates to a device for applying, on the recording medium of a non-impact printer, solid particles according to claim 1 of the main patent, characterized in that it further comprises a shaped transport member cylindrical, designed to bring, by rotation about its axis, particles in the vicinity of the transport element, as well as another deflector interposed between this transport member and this transport element to allow the transfer of particles from the transport member to the transport element.

With this device, it avoids too rapid exhaustion of the tank. In addition, a cylindrical transport member is less expensive than a worm, can be completely immersed in the particle powder and allows this powder, due to the symmetry of this member, to arrive regularly. on the transport element, without seizing of bearings and without the formation of agglomerates of particles.

According to a particular characteristic of the device which is the subject of the invention, this device also comprises a means for mixing the particles in the reservoir. This stirring means causes a re-spreading of the powder in the reservoir, which avoids any local exhaustion thereof.

According to another particular characteristic, the device according to the invention further comprises at least one other transport member of cylindrical shape, provided for supplying, by rotation about its axis, said transport member with particles, by means of a deflector interposed between said member and said other transport member, so as to have a reserve of particles in the tank itself.

According to another particular characteristic, said other deflector extends over a length of the order of a centimeter, between said element and said transport member, and leaves between itself and this transport member a space at most equal to a millimeter and between itself and said transport element, a space of the order of 5 mm.

Finally, according to another particular characteristic, the solid particles being attracted by a magnet, said transport member and said transport element are magnetic on the surface.

• - la figure 1 est une vue schématique d'un mode de réalisation particulier du dispositif objet de l'invention dans le cas d'une imprimante magnétique,
• - la figure 2 est une vue schématique montrant le mouvement des particules d'une part, au voisinage du déflecteur interposé entre l'élément de transport et le support d'enregistrement, d'autre part, au voisinage de l'autre déflecteur interposé entre l'organe de transport et l'élément de transport,
• - la figure 3 est une vue schématique en coupe d'un mode de réalisation particulier d'un organe de transport de particules utilisé dans le dispositif de la figure 1, et
• - la figure 4 est une vue schématique d'un mode de réalisation particulier d'un moyen de brassage également utilisé dans le dispositif de la figure 1.

The invention will be better understood on reading the following description of exemplary embodiments given by way of non-limiting example with reference to the appended drawings in which:

• FIG. 1 is a schematic view of a particular embodiment of the device which is the subject of the invention in the case of a magnetic printer,
• - Figure 2 is a schematic view showing the movement of the particles on the one hand, in the vicinity of the deflector interposed between the transport element and the recording medium, on the other hand, in the vicinity of the other deflector interposed between the transport member and the transport element,
• FIG. 3 is a schematic sectional view of a particular embodiment of a particle transport member used in the device of FIG. 1, and
• - Figure 4 is a schematic view of a particular embodiment of a stirring means also used in the device of Figure 1.

In Figure 1, there is shown schematically a particular embodiment of the application device 5 object of the invention in the case of a magnetic printer. A part of this printer is schematically represented in FIG. 1. It comprises, as explained in the aforementioned patent, a recording medium constituted, in the example described, by a magnetic drum 2 driven in rotation, in the direction of arrow F _l , by an electric motor (not shown). The recording of information on this drum is carried out by a magnetic recording member 3. In the example described, this member 3 is formed by an assembly comprising several magnetic recording heads which, placed one beside the others, are aligned parallel to the axis of rotation A _i of the drum 2. Each of these heads generates, when it is excited repeatedly by an electric current, a variable magnetic field, which has the effect of creating domains magnetized 4, or "magnetic dots", on the surface of the drum which passes in front of the recording member 3, the instants of excitation of these heads being established in known manner, so as to obtain on this surface of the drum zones magnetized, which are sets of said domains 4, sets also called latent images and whose shape corresponds to that of the characters to be printed. The magnetized areas of the drum then pass in front of the application device 5 which is arranged below the drum 2 and which makes it possible to apply to the surface of the drum particles of a pulverulent pigment P contained in a reservoir 6. In the he example described, this pigment consists of magnetic particles coated with a resin which, by heating, is capable of melting and fixing on a paper on which it has been deposited. It should however be pointed out that the nature of this pigment is not specific to the invention and that, in the case of an electrostatic printer to which of course the invention applies, this pigment could very well consist of a known powder containing no magnetic particles.

The pigment mainly adheres to the magnetized areas 4, thus forming deposits 7 of particles (FIG. 2) on the surface of the drum 2. Touch-up means consisting of a rotating magnetic cylinder 8 disposed in the vicinity of the drum 2 are then provided for eliminate the particles having adhered elsewhere than on the magnetized domains 4 as well as the particles in excess on said domains. A small deflector 8b is arranged near the cylinder 8 retouching to cause the particles captured by this retouching cylinder to fall back into the tank 6. But this retouching 8 creates chains of particles which lie on the drum 2 and which one seeks to eliminate by means of another retouching by suction 9. After which, the particles are transferred to a support sheet such that 'a sheet of paper 10 applied against the drum by means of a transfer roller 11. Finally, the particles which remain on the drum are removed in a cleaning station 12 then the magnetic points are erased by an erasing module 13, at after which a new printing cycle can take place.

As can be seen in FIG. 1, the application device 5 comprises, on the one hand, a transport element 14, which removes particles of pigment from the reservoir 6, when the level of the particles is sufficient raised in this tank, to bring them near the surface of the drum 2, on the other hand, a fixed deflector 15 which is interposed between the transport element 14 and the drum 2 to collect the particles transported by this element 14 and apply them to the surface of the drum 2.

The transport element 14 consists for example of a magnetic cylinder whose axis of rotation A ₂ is parallel to the axis A, of the drum 2 and can rotate in two bearings not shown, which are respectively provided with the side faces of the reservoir 6. Only the rear side face 16 is shown in Figure 1, the front side face, located in front of Figure 1, not being shown.

The deflector 15, shown in FIG. 2, is a part fixed to the two lateral faces of the tank 6 and having a planar face 17 limited by a first and a second edge 18 and 19 parallel to the axes A, and A ₂ , the second edge 19 preferably forming a sharp edge to avoid an accumulation of particles on said edge. The deflector 15 is arranged so that its face 17 forms, with the plane defined by the axis A, of the drum and the axis A ₂ of the element, a dihedral whose edge is formed by the first edge 18 and is close to the transport element 14 and whose angle is less than 45 degrees. Furthermore, this deflector 15 is provided so that the sharp edge 19 is in the vicinity of the drum 2. By way of example, the deflector 15 is constituted by a semi-cylindrical rod arranged so that said flat face 17 (c ' i.e. the diametral plane defining this rod) contains the axes A, and A ₂ .

The transport element 14 has a direction of rotation, indicated by the arrow F ₂ in FIG. 2, intended to drive the particles towards this face 17. The space between the transport element and the first edge 18 of the deflector is chosen low enough so that the particles are mostly stopped in passing by the deflector 15 and then accumulate in a trough 20 delimited by the surface of the transport element 14 and by the face 17 of the deflector 15. The direction of rotation of the drum 2, indicated by the arrow F, in FIG. 2, is chosen so that the particles accumulated in the bucket 20 are entrained towards the sharp edge 19 of the deflector 15, so that part of between them can be applied to the magnetized areas of the drum 2. However, the particles thus entrained by the drum 2 are not stopped in passing by the deflector 15, owing to the fact that the latter does not touch the surface of the drum and which it therefore leaves, between the edge v ive 19 and the drum, an opening whose width is sufficient to allow the pigment particles entrained by the drum to exit from the bucket 20. The pigment particles which, applied to the magnetized zones of the drum, exit from the bucket 20, continue to adhere to these zones and thus make visible the characters which must be printed while those which leave the bucket 20 without being retained by the drum generally fall back into the tank 6.

According to the invention, the application device 5 (FIG. 1) further comprises, on the one hand, a transport member 21 which removes particles of pigment from the reservoir 6 to bring them in the vicinity of the surface of the transport element 14, on the other hand, another deflector 22 which is interposed between the transport member 21 and the transport element 14 to collect the particles transported by the transport member 21 and transfer them to the surface of the transport element 14. Said transport member 21 is disposed in the reservoir 6, below the transport element 14 and consists of a cylinder which is magnetic in the example described and whose axis A ₃ of rotation is parallel to the axes A, and A ₂ previously defined and can rotate in two bearings not shown, which are provided with the lateral faces of the reservoir 6.

The other deflector 22, shown in FIG. 2, is a part fixed to the two lateral faces. of the reservoir 6 and having a flat face 23 limited by a first and a second edge 24 and 25 parallel to the axis A ₂ of the transport element 14 and to the axis A ₃ of the transport member 21. The other deflector 22 is arranged so that its planar face 23 forms, with the plane defined by the axes A ₂ and A ₃ , a dihedral whose edge is formed by the first edge 24 and is close to the member 21 of transport and whose angle is less than 45 degrees. Furthermore, the other deflector 22 is provided so that its second edge 25 is in the vicinity of the transport element 14. By way of example, the other deflector 22 is constituted by a semi-cylindrical rod arranged so that its flat face 23 (that is to say the diametral plane defining this rod) contains the axes A ₂ and A _{3 ''}

The transport member 21 has a direction of rotation indicated by an arrow F ₃ in FIG. 2 and provided, as a function of the direction of rotation of the transport element 14, for driving the particles towards the flat face 23 of the deflector 22 , particles which are then entrained towards the transport element 14. In other words, the directions of rotation are such that an upward movement of parties is created. pigment cules. In the example shown in Figure 2, the seating faces 17 and 23 are turned to the left, the member 21 and the transport element 14 rotate clockwise and the drum 2, in the direction reverse. It can thus be seen that the roles played by the association of the transport member 21, of the other deflector 22 and of the transport element 14, association which results in a separation of the particles from the second edge 25 from the other deflector 22, and by the association of the transport element 14, of the deflector 15 and of the drum 2, association of which results, on the contrary, a bringing together of the particles of the edge 19 of the deflector 15, are different.

There is thus a supply of the drum 2 with particles as long as, in the tank 6, the level of the particles does not reach the bottom of the transport member 21, identified by a dashed line 33a therefore indicating a minimum level. When the level of the particles has dropped so as to reach the top of the transport member 21, the particles are always entrained towards the other deflector 22 but then accumulate in another trough 26 delimited by the surface of the member 21 transport and by the flat face 23 of the other deflector 22, before being driven by the transport element 14. The space existing between the first edge 24 of the other deflector 22 and the transport member 21 is chosen to be sufficiently small so that the particles are mostly stopped in passing by the other deflector 22.

With regard to the respective roles played by the deflectors 15 and 22, it should be noted that the deflector 15, which is interposed between the magnetic drum 2 and the transport element 14, is essentially intended to ensure proper application of pigment particles on this drum 2, while preventing the magnetized domains 4 which have been formed on this drum from being greatly altered at the moment when, passing in front of the transport element 14, they are subjected to the action of magnetic fluxes of dispersion generated by this element 14. On the contrary, the other deflector 22, which is interposed between the transport element 14 and the transport member 21, has essentially the purpose, when the level of particles in the tank 6 becomes lower than that of the top of the member 21, to ensure a consumable reserve of particles which makes it possible to regularly supply particles with the transport element 14 and provides a good distribution of the particles on the surface of this element Even if, as a result of slight variations in the driving speed of the transport member 21, for example, the arrival of the particles in this reserve becomes irregular.

To further improve the continuity and regularity of the supply of the transport element 14 (FIG. 1) with particles, a means 27 for mixing the pulverulent pigment is added to the reservoir 6. This mixing means 27 has an axis of rotation A ₄ parallel to that of the transport member 21 and carried by two bearings, not shown, placed on the lateral faces of the tank 6. In the latter, said mixing means 27 is by example placed at the same level as the transport member 21. We can also place this transport member 21 at the bottom of the tank 6, so that the maximum of particles of said tank is consumed.

A particular embodiment of the stirring means 27 is shown diagrammatically and in part in FIG. 4. It essentially comprises the axis A ₄ of rotation and two rods 27a and 27b taking the form of slots, made integral with said axis and arranged perpendicularly to each other. The rotation of the stirring means 27 is for example intended to take place in a direction, indicated by the arrow F, in FIG. 1, identical to that of the rotation of the transport member 21.

The capacity of the reservoir 6 can be further increased by increasing its depth, which is shown by dashed lines 6a in FIG. 1, and by placing in this reservoir another transport member 28, constituted by a magnetic cylinder and placed below said transport member 21. The axis of rotation A _s of this other member 28 is parallel to the axis A ₃ and carried by two bearings, not shown, placed in the lateral faces of the tank 6. A third deflector 29 is interposed between said member 21 and said other transport member 28. This other member 28 thus feeds the transport member 21 with particles, via the third deflector 29. This third deflector 29 is fixed to the lateral faces of the tank 6, is for example constituted like the other deflector 22, thus presents a flat face 30 and is disposed, between the other member 28 and the transport member 21, as is arranged the other deflector <22, between this transport member 21 and the transport element 14. The direction of rotation of said other member 28, represented by an arrow F _s in FIG. 1, is then chosen identical to that of said transport member 21. Qn can arrange the element 14, the member 21 and the other transport member 28 so that their respective axes of rotation are in the same plane and arrange the other deflector 22 and the third deflector 29 so that they have their respective flat faces 23 (Figure 2) and 30 (Figure 1) in said plane. Another means 31 of stirring can also be added in the reservoir 6, at the level of the other transport member 28.

In the tank 6, the particles can then pass from a maximum level 32 to a minimum level 33 corresponding to the bottom of the other transport member 28. At the start, the latter does not intervene, but it contributes to supplying the drum 2 with particles when the level of these particles has dropped sufficiently to be at the level of this other member 28.

There is thus a consumable reserve of particles in the tank 6 itself, which is more advantageous than an external lateral reserve, associated with a feed system with an endless magnetized belt or with buckets, a system which is difficult to master and requiring a great deal of drive and good prop chewiness to prevent ink, or pigment, from interposing between the drive rolls and the tape.

Of course, a level sensor could be provided to indicate to the users of the printer when the minimum level 33 is reached.

In Figure 3, there is shown schematically a particular embodiment of the transport member 21. It comprises a cylinder 21a of axis A ₃ , coated with a strip 21b which is permanently magnetized and which is formed, in the example described, by rubber in which metallic particles are permanently magnetized. FIG. 3 shows that this strip 21b has been magnetized so as to present on its external face 21c successive magnetized zones 21 whose polarity is such that any two consecutive magnetization zones have opposite magnetic polarities. In other words, the polarity of these successive magnetized zones is alternately north and south, the north and south poles being designated, in FIG. 3, respectively by the letters N and S. Under these conditions, part of the pigment particles found in the reservoir 6 (Figure 1) is attracted by the strip 21b. It should however be noted that the mode of magnetization of the strip 21b which has just been described is not exclusive of the invention and one could use any other mode of magnetization allowing the strip 21b to attract the pigment particles. The other transport member 28 and the transport element 14 can be produced in the same way.

In FIG. 1, the sliding cover 34 of the reservoir 6 is also seen, this cover being stopped by a stop 35 so as not to damage the drum 2. We also see, diagrammatically, a part of the pinions allowing the rotation of the retouching means 8 (pinion 8a), of the transport element 14 (pinion 14a), of the transport member 21 (pinion 21a) and of the threshing means 27 (pinion 27c). The pinion allowing the rotation of the other transport member 28, nor that which allows the rotation of the other threshing means 31 has not been shown. Also shown are some of the intermediate pinions 36 necessary to obtain suitable directions of rotation as well as the motor pinion 37 driven by a motor not shown and allowing the drive of all the other pinions. This set of pinions can be produced by a person skilled in the art and placed outside the tank 6, for example on the other side of the external face 16 in FIG. 1.

As an indication but not limiting, the deflector 22 and the other deflector 29 are made of a magnetic material, the distances D1, D2, D3, D4 (Figure 2) respectively between the drum 2 and the deflector 15, between the latter and the transport element 14, between the latter and the other deflector 22, between the latter and the other transport member 21, are respectively equal to 1 mm, 0.5 mm, 5 mm, 0.5 mm, the respective widths L1 and L2 of the faces 17 and 23 are of the order of 1 cm and the respective rotational speeds of the transport element 14 and of the transport member 21 are respectively of the order of 50 revolutions per minute and 30 revolutions per minute. It will also be noted, in FIG. 1, that, due to the small spaces existing on either side of the deflectors 22 and 29, these deflectors form with the element 14, the member 21 and the other member 28 of transport a sort of wall allowing the pigment P to be largely confined to one side of said wall (on the left in FIG. 1), so as not to hinder in particular the cylinder 8 for retouching.

Claims (5)

1. A device for the application on to the record carrier (2) of a non-impact printer, of solid particles of a pulverulent pigment contained in a reservoir (6) situated below this carrier, said device comprising a transport element (14) arranged to deliver these particles close to the surface of said carrier (2) and a deflector (15) interpositioned between this carrier (2) and the transport element (14) for collection of the particles transported by this element, said deflector (15) having one of its edges (19) positioned in the immediate proximity of the said carrier so as to form with this carrier a trough (20) of substantially prismatic shape, wherein are accumulated the particles thus collected, said carrier (2) being displaced in the direction (F,) such that it entrains these particles towards the edge of the said prism, the particles entrained beyond this edge remaining applied only to the sensitised areas (4) of the said record carrier (2), the said applicator device being characterised in that it also comprises a transport member (21) of cylindrical form, situated below the transport element (14) and so arranged that by rotation around its axis (A3) it delivers particles close to said transport element (14), as well as another deflector (22) interposed between said transport member (21) and said transport element (14) in such a manner as to have available a reserve of particles when the level of the particles in the container (6) drops lower than the upper level of the transport member (21).

2. Applicator device according to claim 1, characterised in that it also comprises a means (27) for stirring the particles within the container (6).

3. Applicator device according to either of claims 1 and 2, characterised in that it also comprises at least one other transport member (28) of cylindrical shape, arranged so that by rotation around its axis (A5) it feeds particles to the said transport member (21) via a deflector (29) interpositioned between the said member (21) and the said other transport member (28), in such a manner as to have a reserve of particles available in the container (6) itself.

4. Applicator device according to any one of claims 1 to 3, characterised in that the said other deflector (22) extends over a length of the order of one centimeter, between the said transport element (14) and the said transport member (21) and between itself and the transport member (21) leaves a gap equal to at most one millimeter and between itself and the said transport element (14), a gap of the order of 5 mms.

5. Applicator device according to any one of claims 1 to 4, characterised in that the solid particles being able to be attracted by a magnet, the said transport member (21) and the said transport element (14) are magnetic at the surface.

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