EP0371828B1 - Apparatus for separating and recovering solid toner particles transported by a gas flow - Google Patents

Abstract

The invention relates to an apparatus for separating and recovering solid particles transported by a gaseous flow. The apparatus includes a separation chamber (40), an admission conduit (43) by which the gaseous flow laden with particles arrives, an escape conduit (44) by which the flow leaves after having been relieved of its particles, a discharge conduit (47) toward which the particles separated from the gaseous flow are urged, a movable flap (49) making it possible with the discharge conduit to comprise a particle recovery box, and a helical device (52) placed in the discharge conduit to prevent the particles thus recovered from being re-aspirated by the rising flow that escapes via the escape conduit (44). The invention is applicable to magnetographic printing machines.

Description

The present invention relates to an apparatus for separating and recovering solid developer particles transported by a gas flow. Such a device finds more particularly, although not exclusively, its application in non-impact printing machines in which developer particles, after having been deposited in excess on the recording medium equipping these machines, are removed from the surface of this support by means of a suction device and collected in a recovery box for recycling.

The non-impact printing machines that are used in information processing equipment are now well known. These machines include a recording medium, most often consisting of a rotating 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 print. These latent images are then developed, that is to say made visible, using a powdery developer which, deposited on the recording medium, is only attracted by the sensitized areas thereof, thus forming a powder image on the surface of this support. After which, this recording medium is brought into contact with a sheet of paper in order to allow the developer particles constituting this powder image to be transferred onto this sheet to be definitively fixed there.

The application of developer particles on the recording medium of printing machines of this kind is carried out by applicators of known type, such as, for example, that which has been described in the United States patent. No. 4,246,588 (this patent corresponding to French patent No. 2,408,462). However, with these applicator devices, despite all the care taken in their construction, it is difficult to prevent developer particles from settling, not only in overabundance on the sensitized areas of the recording medium, but also, even in very small quantity outside these areas. This is why these printing machines are also provided with a retouching device which, disposed between the applicator device of particles and the station where these particles are transferred onto a sheet of paper, makes it possible to remove the developer particles which are in excess on the surface of the recording medium. Although retouching devices capable of retouching by magnetic attraction or by blowing air have been produced, preference is now given to retouching devices which operate by air suction and offer the advantage of being non-polluting and make it possible to remove the particles which are in excess on the surface of the recording medium, without this that these particles necessarily have magnetic properties. Thus, a retouching device has been produced which has been described in United States patent No. 3,680,528 and which comprises a suction duct provided, on the one hand with a slot or nozzle which extends near the surface of the recording medium, on the other hand, of an opening connected, by means of a pipe, to a suction turbine. In this device, the air which is sucked in through the slit of the suction duct entrains the excess particles which are found on the parts of the recording medium situated directly above this slit. The air which is thus charged with particles circulates in the pipeline, then, after passing through the turbine, is discharged towards an outlet conduit at the end of which has been fixed a recovery bag made of an air permeable material . The air which is discharged by the turbine can thus pass through the bag and be discharged into the atmosphere, while the developer particles which were transported by this air flow are stopped by the mesh of the bag and can therefore be recovered for be subsequently replaced in the applicator device. However, the fact that, in this retouching device, the air which passes through the suction turbine is necessarily charged with developer particles, there is, in the long run, fouling of the turbine, which makes maintenance of this particularly expensive retouching device.

In order to remedy this drawback, a retouching device has been proposed which has been described in United States patent No. 4,046,682 and in which an endless belt, made of a material permeable to air and thus playing the role of filter, crosses, during its journey, the pipe connecting the suction duct to the suction turbine. Under these conditions, the developer particles which are transported by the air sucked in by the turbine is stopped in passing by this endless band and therefore cannot pass through this turbine. However, this solution is not entirely satisfactory due to the fact that not only the recovery of the particles which have been captured by the strip is impractical and always incomplete, but the portion of the pipe which is located between this strip and the nozzle. suction ends up more or less clogging, which significantly reduces the efficiency of the suction turbine.

• une chambre de séparation (40) présentant un axe de révolution (45) disposé pratiquement verticalement, cette chambre étant pourvue, d'une part d'un conduit d'admission (43) agencé à sa partie supérieure de façon à créer un flux tourbillonnaire pour un flux gazeux qui, chargé de particules solides de révélateur, arrive dans cette chambre par ce conduit d'admission, d'autre part d'un conduit d'échappement (44) disposé axialement et s'étendant à l'intérieur de cette chambre pour permettre l'évacuation du flux gazeux qui a été débarrassé de ses particules, cette chambre étant pourvue en outre, à sa partie inférieure, d'un orifice de sortie (46) communiquant avec un conduit de décharge (47), les particules de révélateur étant, après s'être séparées dudit flux gazeux dans cette chambre, sollicitées par gravité vers ledit conduit de décharge,
• et un organe (52) pourvu d'au moins une ouverture, disposé dans ledit conduit de décharge (47) et à proximité dudit orifice de sortie (46), cet organe (52) étant formé d'une plaque très mince présentant au moins une ouverture dont l'inclinaison est orientée dans le même sens que celle du trajet hélicoïdal des particules solides afin d'empêcher que les particules qui arrivent dans le conduit de décharge ne soient à nouveau aspirées par le flux gazeux ascendant qui s'échappe par le conduit d'échappement

Ces cyclones permettent bien , lorsqu'ils sont traversés par un flux d'air contenant des substances pulvérulentes, telles que de la sciure de bois par exemple, d'éliminer la plus grande partie de ces substances avant que ce flux d'air ne soit rejeté dans l'atmosphère. Mais leur utilisation, dans une machine imprimante non-impact, poru sépare et récupérer pratiquement totues les particules de révélateur transportées par un flux d'air provenant d'un dispositif de retouche à aspiration, n'a jamais jusqu'ici été envisagée poru la raison que ces particules sont très fines et ont tendance à se disperser, lorsqu'elles tombent, en formant un nuage de particules difficiement récupérable. Dans ces condition, il serait pratiquement impossible avec ces cyclones de récupérer la quasi-totalité des particules de révélateur transportées par le flux d'air, ce qui est d'autant plus gênant que toutes ces particules n'ont pratiquement subi aucune altération et peuvent donc être recyclées, c'est-à-dire introduites à nouveau dans le réservoir du dispositif applicateur pour être réutilisées.The present invention overcomes the drawbacks of the prior art and proposes an apparatus which, when mounted in a pneumatic circuit in which a gas flow carrying solid particles circulates, such as a circuit comprising a touch-up device used in a machine non-impact printer for example, allows to separate and recover practically all the particles of this gas flow. The apparatus of the present invention comprises a device similar to those which, designated by the name of cyclones, are usually used to purify an air flow laden with solid particles, before discharging this air into the atmosphere. These cyclones, various embodiments of which have been described in United States patents No. 3,716,137 and 3,893,914, in Soviet Union patents No. 1,096,003 and 1,130,411, in British patent 686,966 and in German patent 849,950. In particular, German patent 849,950 describes an apparatus for separating and recovering solid particles transported by a gas flow comprising:

• a separation chamber (40) having an axis of revolution (45) disposed practically vertically, this chamber being provided, on the one hand with an intake duct (43) arranged at its upper part so as to create a vortex flow for a gas flow which, loaded with solid developer particles, arrives in this chamber via this intake duct, on the other hand an exhaust duct (44) arranged axially and extending inside this chamber to allow the evacuation of the gas flow which has been freed of its particles, this chamber being further provided, at its lower part, with an outlet orifice (46) communicating with a discharge conduit (47), the developer particles being, after being separated from said gas flow in this chamber, subjected to gravity towards said discharge conduit,
• and a member (52) provided with at least one opening, disposed in said discharge conduit (47) and close to said outlet orifice (46), this member (52) being formed from a very thin plate having at least an opening whose inclination is oriented in the same direction as that of the helical path of the solid particles in order to prevent the particles which arrive in the discharge conduit from being again sucked up by the ascending gas flow which escapes through the exhaust duct

These cyclones make it possible, when crossed by an air flow containing pulverulent substances, such as sawdust for example, to eliminate most of these substances before this air flow is released into the atmosphere. However, their use, in a non-impact printing machine, for separating and recovering practically all of the developer particles transported by an air flow coming from a vacuum retouching device, has never hitherto been envisaged for the This is because these particles are very fine and tend to disperse when they fall, forming a cloud of difficultly recoverable particles. Under these conditions, it would be practically impossible with these cyclones to recover almost all of the developer particles transported by the air flow, which is all the more annoying since all these particles have practically undergone no alteration and can therefore be recycled, that is to say introduced again into the reservoir of the applicator device to be reused.

Despite the dissuasive nature presented by these latter devices for recovering developer particles, the present invention relates more specifically to an apparatus of the type of the prior art for separating and recovering solid developer particles transported by a gas flow. , this device being characterized in that the opening of the exhaust duct (44) is situated at its upper part of the chamber (40), and in that the member (52) forms a helical surface (52) extending over a sector whose angle (A) is substantially equal to 360 °, and in that the helical edge (53) of the member (52) is in contact with the internal wall of said discharge conduit ( 47) and has, with respect to the horizontal, an inclination whose value (i) is between 3 ° and 10 °.

p représentant la valeur du pas de l'hélice de l'organe en hélice (52).According to another particular feature, the discharge conduit (47) has an internal radius whose value (R) is between two limit values R _m and R _M given by:

p representing the value of the pitch of the helix of the helical member (52).

According to another particular feature, the pitch p of the helix of the helical member (52) is greater than five millimeters.

According to another particular feature, the pitch p of the helix of the helical member (52) is less than twelve millimeters.

According to another particular feature, the exhaust duct (44) has an inside diameter of the same order of magnitude as the inside diameter of the discharge duct (47).

According to another particular feature, the internal diameter of the exhaust duct (44) is less than the internal diameter of the discharge duct (47) and its value does not differ by more than 15% from the value of the internal diameter of this last duct (47).

According to another particular feature, the separation chamber (40) being constituted - in a known manner - of a cylindrical upper portion (41) connected to a conical lower portion (42), the side wall of said conical portion forms with the axis of revolution (45) of this chamber an angle (J) at most equal to 15 °.

According to another feature, inside the separation chamber (40), the pressure - lower than atmospheric pressure - is adjusted to a fixed value between 760 and 900 hectopascals.

According to another particular feature, the discharge conduit (47) is closed at its lower end by a movable flap (49) to constitute a particle recovery box, in which the particles finally fall after their passage through the organ in propeller (52).

According to another particular feature, the opening of the exhaust duct (44) is located at a distance from the helical member (52), which is greater than the diameter of the discharge duct (47).

Another object is to propose a use of the device. This object is achieved by the fact that a non-impact printing machine includes a particle separation and recovery device according to the invention.

• . La figure 1 représente une vue schématique partielle d'une machine imprimante magnétographique munie d'un circuit pneumatique comprenant un dispositif de retouche et un appareil de séparation et de récupération de particules établi selon l'invention,
• . La figure 2 représente une vue en perspective, avec parties arrachées, montrant certains détails de réalisation de l'appareil de séparation et de récupération de particules qui équipe la machine représentée sur la figure 1.

The invention will be better understood and other objects and advantages thereof will appear better in the following description, given by way of nonlimiting example, and with reference to the appended drawings in which:

• . FIG. 1 represents a partial schematic view of a magnetographic printing machine provided with a pneumatic circuit comprising a retouching device and an apparatus for separating and recovering particles established according to the invention,
• . FIG. 2 represents a perspective view, with parts broken away, showing certain details of construction of the particle separation and recovery apparatus which equips the machine represented in FIG. 1.

The printing machine which has been shown diagrammatically in FIG. 1 comprises a recording medium which is constituted, in the example described, by a magnetic drum 10. This drum is mounted so as to be able to rotate around a horizontal axis 11 The rotation of this drum, in the direction indicated by the arrow F, is ensured by an electric motor (not shown). The recording of the information on this drum is carried out by a magnetic recording member 12 comprising several heads arranged one next to the other and aligned parallel to the axis of rotation 11 of the drum. Each of these heads generates, each time it is excited for a short time by an electric current, a variable magnetic field, which has the effect of creating magnetized zones 13, practically punctual, on the surface of the drum which passes in front the recording member 12, all of these areas constituting a latent magnetic image corresponding to an image to be printed. These magnetized zones 13 then pass in front of an application device 14 which is arranged practically below the drum 10 and which makes it possible to apply to the surface of the drum particles of a powdery developer contained in a reservoir 15. The particles of developer which are thus applied to the drum 10 do not adhere, in principle, that on the magnetized areas thereof, so that the magnetized areas which have passed in front of the application device 14 appear coated with a layer of developer, this layer forming, on the drum 10, the image of characters to be printed. In the example described, this developer consists of resin particles containing magnetic particles, these resin particles having a size of the order of twenty microns, this resin being capable of melting, when it is subjected to thermal radiation, and thus to be fixed on a paper on which it was deposited. It should however be noted that the nature of this developer is not specific to the invention and that, in the case of an electrostatic printer to which of course the invention applies, this developer could very well consist of a powder containing no magnetic particles. Likewise, for applying the developer to the drum 10, any conventional application device can be used. However, in a more particularly advantageous embodiment, the application device 14 which is shown in FIG. 1 is of the type which has been described and shown in the aforementioned United States patent No. 4,246. 588.

The developer, which adheres mainly to the magnetized areas 13, therefore forms deposits 16 of particles on the surface of the drum 10. These deposits 16 then pass in front of a retouching device 17 which has the role of removing the particles which have adhered elsewhere than on the magnetized zones 13, as well as the particles which are found in excess in these zones. After which, the developer particles which remain on the drum 10 are transferred, almost entirely, onto a sheet of paper 18 which is applied to the drum 10 by means of a pressure roller 19. The residual developer particles which, when this transfer is carried out, are still on the drum 10 are then removed by means of a cleaning device 20, of known type, for example with a brush. After which, the magnetized zones which have passed in front of the cleaning device 20 pass in front of an erasing device 21 where they are then erased, which allows the portions of the drum 10 which have thus been demagnetized to be able to be magnetized again when they then appear before the recording organ 11.

The retouching device 17 which has been shown in FIG. 1 is of the type which has been incidentally described in the patent of the United States of America No. 4,233,382. Without going into all the details of the constitution of this device, it will be indicated that the retouching device which is represented in FIG. 1 comprises a nozzle or suction duct 22 having practically the shape of a straight prism and having, at one of its ends, an air intake slot 23 which extends, near the surface of the drum 10, in a direction parallel to the axis of rotation 11 of this drum. This suction duct 22 communicates, at its other end, with a chamber 24, of cylindrical shape, arranged in such a way that the generators of this chamber extend parallel to the direction of elongation of the intake slot of air 23. One of the two circular walls of this chamber is provided with a suction opening provided with a pipe 25, the latter allowing this chamber 24 to be connected to a device for separating and recovering particles 26 which will be discussed later. This device 26 is itself connected, by means of another pipe 27 provided with a filtering element 28, to a suction turbine 29. It will then be understood that, when this turbine 29 is started, a vacuum is created inside the pneumatic device constituted by the retouching device 17, the pipe 25, the separation and recovery device 26, the pipe 27, the filter element 28 and the turbine 29. Consequently , the developer particles which have been deposited in excess on the surface of the drum 10 are entrained, when they pass in front of the slot 23 of the suction duct 22, by the air which is sucked in through this slot. This air, which is thus charged with developer particles, then forms an air flow which circulates, successively, in the suction duct 22, the chamber 24 and the pipe 25. This air is rid of its particles when it passes through the device 26, then, practically purified when it leaves this device, then circulates in the pipe 27 before passing through the filtering element 28 and being finally discharged into the atmosphere by the turbine 29. Given that, as will be seen below, practically all the particles which have been transported by this air flow are stopped by the device 26, the air which passes through the turbine 29 is not likely to cause fouling of the latter.

We will now describe, with reference to FIG. 2, the structure of the apparatus 26 which allows, not only to separate the particles from developer which have been transported by the air flow circulating in the pneumatic device, but also to recover practically all of these particles without these being able to be sucked in again by this air flow. The apparatus 26 which is shown in FIG. 2 comprises a separation chamber 40 consisting of an upper portion of chamber 41, of cylindrical shape, and of a lower portion of chamber 42, of conical shape. This chamber 40 is provided, at its upper part, on the one hand with an inlet duct 43 which is connected to the duct 25 through which the air charged with developer particles arrives, this inlet duct being arranged tangentially to the cylindrical wall of the portion 41, so as to create inside the chamber a swirling flow for the air which arrives in this chamber by this duct, on the other hand from an exhaust duct 44, of cylindrical shape, which is arranged along the vertical axis 45 of the chamber 40 and which extends inside the cylindrical portion 41 of this chamber in order to allow the evacuation of the air which has been rid of its particles in this room. This exhaust duct 44 is connected to the pipe 27 connecting the device 26 to the suction turbine 29. The separation chamber 40 is also provided, at its lower part, with an outlet orifice 46 which communicates with a discharge conduit 47, cylindrical in shape.

In a known manner, the vortex created by the air flow arriving in the chamber 40 by the intake duct 43 rotates rapidly in a direction which, in FIG. 2, is represented by the arrow 48. Under the effect of the centrifugal force, the developer particles whose specific mass is greater than that of air, separate from this air flow and form a swirling layer coming to contact the cylindrical wall of the portion 41 of the chamber. However, these particles are also subjected to a force of gravity, so that, while continuing to spin, they eventually descend into the portion 42 of the chamber and engage in the discharge conduit 47. In order to allow the recovery of these particles, the discharge duct 47 is normally closed, at its lower end, by a movable flap 49 which, as shown in FIG. 2, can slide, in a horizontal direction, in the slides of a fixed plate 50 secured to the machine frame. This flap 49, which is actuated in a known manner, manually for example, can occupy two positions, namely a closed position, illustrated in solid lines in FIG. 2, in which it completely closes the lower opening of the discharge conduit 47 and then forms with this conduit a box 51 in which the particles which accumulate have been separated from the air flow, and an open position, illustrated in phantom in this figure, in which it allows the particles thus accumulated to exit the discharge conduit 47 to be replaced in the reservoir 15 of the device application 14 shown in FIG. 1. This reintroduction of the particles can be carried out after these particles have been transported, either manually or using a transport device, from the box 51 to the reservoir 15. However, in a more particularly advantageous embodiment which has been shown in FIG. 1, the separation and recovery apparatus 26 is arranged just above above the reservoir 15, so that the particles collected in the box 51 are returned to this tank simply by bringing the flap 49 to the open position when this box is full, which has the effect of causing these particles in this tank. In an alternative embodiment, this flap 49 can also be advantageously replaced by a particle reintroduction device which has been described in a patent application filed on the same day by the Applicant.

As can be seen in FIG. 2, the separation and recovery apparatus 26 also comprises a helical member 52 which is arranged in the discharge conduit 47, near the outlet orifice 46. This member 52, which is formed of a very thin plate, has a surface limited by a helical edge 53 and it is dimensioned so that its helical edge 53 is in contact with the internal wall of the discharge conduit 47. This member 52 is centered along the vertical axis 45 of the chamber 40 and of the duct 47 and it extends all around this axis 45, over a sector whose angle A is substantially equal to 360 °. Under these conditions, the two ends of the helical edge 53 of this member are situated practically one below the other and are spaced apart by a distance p equal to the pitch of the propeller. FIG. 2 shows that the direction of the helix of the member 52 is the same as that of the helical path followed by the particles inside the separation chamber 40. In other words, the plate constituting this member has an inclination which is oriented in the same direction as that of the helical arrow 48. Under these conditions, the helical member 52 does not risk obstructing the developer particles which, after being separated from the air flow in the separation chamber 40, penetrate through the opening left between the two radial edges of this member to accumulate in the recovery box 51. In order to facilitate the passage of these particles through this opening and to prevent the particles accumulated in this box from being subjected to the action of the ascending air current which is exerted in the axial part of the chamber, it is preferable that the pitch p of the propeller of the member 52 is between five millimeters and twelve millimeters.

c'est-à-dire :

C'est ainsi, par exemple, que, dans le cas où le pas p de l'hélice est égal à cinq millimètres, le conduit de décharge 47 pourra avoir un rayon intérieur compris entre :

soit : $${\text{R}}_{\text{m}}{\text{≃ 4,5 mm et R}}_{\text{M}}\text{≃ 15 mm}$$

Dans ce cas, un conduit de décharge dont le diamètre intérieur est égal, par exemple, à deux centimètres conviendra parfaitement.It has also been observed that the best results are obtained by producing the helical member 52 so that its helical edge 53 has an inclination, relative to the horizontal, of value i between 3 ° and 10 °. Under these conditions, it is possible to determine the limit values which should be given to the internal radius R of the discharge conduit 47 in order to obtain the best results, these limit values being in fact given by the expressions:

that is to say :

Thus, for example, in the case where the pitch p of the propeller is equal to five millimeters, the discharge conduit 47 may have an internal radius between:

is : $${\text{R}}_{\text{m}}{\text{≃ 4.5 mm and R}}_{\text{M}}\text{≃ 15 mm}$$

In this case, a discharge conduit whose internal diameter is equal, for example, to two centimeters will be perfectly suitable.

soit : $${\text{R}}_{\text{m}}{\text{≃ 9 mm et : R}}_{\text{M}}\text{≃ 30 mm}$$

Dans ce cas, un conduit de décharge présentant un diamètre intérieur égal, par exemple, à quatre centimètres sera parfaitement convenable.Likewise, in the case where the pitch p of the propeller is equal to one centimeter, the discharge conduit may have an internal radius between:

is : $${\text{R}}_{\text{m}}{\text{≃ 9 mm and: R}}_{\text{M}}\text{≃ 30 mm}$$

In this case, a discharge conduit having an internal diameter equal, for example, to four centimeters will be perfectly suitable.

It should also be noted that, to allow the separation and recovery apparatus to function properly, the exhaust duct 44 has an internal diameter whose value is of the same order of magnitude as that of the internal diameter of the discharge duct 47 .

Thus, for example, in the case where the discharge conduit 47 has an internal diameter of four centimeters, the exhaust conduit 44 may have an internal diameter of thirty-five millimeters. Preferably, the inside diameter of the exhaust pipe is less than that of the discharge pipe and its value does not differ by more than 15% from that of the inside diameter of this latter pipe.

Furthermore, the conical part 42 of the separation chamber 40 is produced in such a way that its side wall forms with the axis of revolution 45 of this chamber, that is to say with the vertical, an angle J at most. equal to 15 °. Thanks to this arrangement, practically all of the developer particles which enter this chamber via the intake duct 43 are separated from the air flow which has previously entrained them.

à l'intérieur de cette chambre est maintenue à une valeur fixe comprise sensiblement entre 255 et 115 hectopascals.It should also be noted that the air flow rate of the suction turbine 29 is adjusted by known means (not shown) so that the air pressure inside the separation chamber 40 is maintained at a value fixed p₁, which is naturally lower than the p₀ value of atmospheric pressure and which is between 760 and 900 hectopascals. In other words, depression $\text{Δ p = p₀ - p₁}$

inside this chamber is maintained at a fixed value comprised substantially between 255 and 115 hectopascals.

By operating under the best conditions which have been indicated above, it has been possible to recover practically 99% of the developer particles which had been transported by the air flow coming from the retouching device.

Of course, the invention is in no way limited to the embodiments described and illustrated which have been given only by way of example. On the contrary, it includes all the means constituting technical equivalents of those described and illustrated, considered in isolation or in combination and implemented in the context of the claims which follow.

Claims (11)

1. An apparatus for separating and recovering solid particles of developer transported by a gaseous flow, comprising:

   - a separation chamber (40) having an axis of revolution (45) disposed practically vertically, this chamber being provided on the one hand with an inlet conduit (43) arranged in its upper portion so as to create an eddying flow for a gaseous flow which, loaded with solid particles of developer, arrives in this chamber through this inlet conduit, and on the other hand with an outflow conduit (44) disposed axially and extending inside this chamber so as to allow the removal of the gaseous flow that has been cleared of its particles, this chamber being further provided, in its lower portion, with an outlet orifice (46) communicating with a discharge conduit (47), the particles of developer, after being separated from said gaseous flow in this chamber, being attracted by gravity towards said discharge conduit,

   - and a component (52) provided with at least one aperture, disposed inside said discharge conduit (47) and close to said outlet orifice (46), this component (52) being formed of a very thin plate having at least one aperture, inclined in the same direction as that of the helical path of the solid particles in order to prevent the particles arriving in the discharge conduit from once more being drawn in by the rising gaseous flow which escapes through the outflow conduit, characterised in that the aperture of the outflow conduit (44) is located in its upper portion of the chamber (40), and in that the component (52) forms a helical surface (52) extending over a sector, the angle (A) of which is substantially equal to 360°, and in that the helical edge (53) of the component (52) is in contact with the inner wall of said discharge conduit (47) and has an inclination relative to the horizontal, the value (i) of which inclination is comprised between 3° and 10°.
2. An apparatus according to Claim 1, characterised in that the discharge conduit (47) has an internal radius, the value (R) of which is comprised between two limiting values R_m and R_M given by:

   

   p representing the value of the pitch of the helix of the helical component (52).
3. An apparatus according to any one of Claims 1 to 2, characterised in that the pitch p of the helix of the helical component (52) is greater than five millimetres.
4. An apparatus according to Claim 3, characterised in that the pitch p of the helix of the helical component (52) is less than twelve millimetres.
5. An apparatus according to any one of Claims 1 to 4, characterised in that the outflow conduit (44) has an inside diameter of the same order of magnitude as the inside diameter of the discharge conduit (47).
6. An apparatus according to Claim 5, characterised in that the inside diameter of the outflow conduit (44) is less than the inside diameter of the discharge conduit (47) and its value does not differ by more than 15% from the value of the inside diameter of this latter conduit (47).
7. An apparatus according to any one of Claims 1 to 6, characterised in that, the separation chamber (40) being constituted - in a known manner - of a cylindrical upper portion (41) connected to a conical lower portion (42), the side wall of said conical portion forms with the axis of rotation (45) of this chamber an angle (J) at most equal to 15°.
8. An apparatus according to any one of Claims 1 to 7, characterised in that, inside the separation chamber (40), the pressure - below atmospheric pressure

   - is adjusted to a fixed value comprised between 760 and 900 hectopascals.
9. An apparatus according to any one of Claims 1 to 8, characterised in that the discharge conduit (47) is closed at its lower end by a mobile valve (49) so as to constitute a particle recovery box, into which the particles finally fall after passing through the helical component (52).
10. An apparatus according to Claim 1, characterised in that the aperture of the outflow conduit (44) is located at a distance from the helical component (52), which is greater than the diameter of the discharge conduit (47).
11. A non-impact printing machine, characterised in that it comprises an apparatus for separating and recovering particles, according to any one of Claims 1 to 10.

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