EP0665966B1 - Pneumatic toner transport arrangement for an electrophotographic printing or copying machine - Google Patents

Abstract

A pneumatic toner transport arrangement for an electrophotographic printing or copying machine is useful for transporting toner and for removing toner and/or dirt particles from units of the machine, such as the developing station (10) and the cleaning station (28). The arrangement has a negative pressure generator (31) connected to the various units of the machine by a negative pressure duct system. A particle separator (24) designed as a cyclone filter for separating toner and dirt particles from a throughflowing air flow is associated with the duct system. The particle mixture is separated in a recycling arrangement into dirt particles and recyclable toner and the recyclable toner is once again supplied to the developing station. The dirt particles are collected in a fine filter (32) of the negative pressure generator (31). The toner recycling arrangement (25) is designed as an exchangeable module which can be exchanged for a collecting container.

Description

The invention relates to a pneumatic conveying device for an electrophotographic printing or copying device with a device for returning excess toner to the developer station.

In electrographic printing or copying machines that work on the principle of electrophotography, ionography or magnetography, a latent image is generated with the aid of a character-generating device on an intermediate carrier, which is colored with toner in a developer station. The toner image is then transferred to the recording medium in a transfer printing station and fixed in a fixing station. Before applying a new latent character image to the intermediate carrier, it is necessary to clean the intermediate carrier from adhering residual toner. This can be done using a brush and vacuum in a brush cleaning station. In the developer station, too, it may be necessary to extract residual toner dust and to remove it from the developer station.

This waste toner is usually collected in a collection container in the device and thrown away from time to time. A reuse of this waste toner was previously not intended, since only fresh toner can be processed in devices with high print quality requirements.

In electrophotographic printing devices, it is already known to suck off the waste or excess toner from the cleaning station and the developer station, separating it from the suction air in a cyclone separator and continuously feeding it back to the developer station via a conveyor. However, it has been found that such a simple return is not possible with high demands on the print quality. The waste toner contains dirt particles, used toner particles and other particles that interfere with the printing process, which have a negative effect on the print quality.

A pneumatic conveying device for an electrophotographic printing device for conveying toner and / or dirt particles from units of the device is known from US Pat. No. 3,439,630. The device has two vacuum-generating devices in the form of air pumps and two particle separators in the form of cyclone filters, via which the excess toner in the area of the transfer printing station and the toner located in the developer space of the developer station are sucked off and separated into dirt particles and reusable toner. The dirt particles are trapped in a filter box and the reusable toner is taken to the developer space, e.g. every time the printer is switched on.

Similar devices are also described in JP-A-61 100 783 and JP-A-59 143 180.

Another problem with recycling toner is that to develop the charge images in the developer station, the toner must be triboelectrically charged in a defined manner. Feeding the waste toner charged in an undefined way to the developer station can lead to disturbances in the charging behavior of the toner in the developer station, which in turn has a negative effect on the print quality.

The aim of the invention is therefore to provide a pneumatic conveying device for an electrographic printing or copying device with a toner return device in which waste toner arising in the units of the device can be easily returned to the developer station and reused without the print quality suffering.

Another object of the invention is to design the device so that the toner delivery can easily be adapted to different print quality requirements.

This goal is achieved in a pneumatic conveyor of the type mentioned in accordance with the features of the first claim. Another solution is given by the method according to claim 14.

Advantageous embodiments of the invention are characterized in the dependent claims.

If the toner is transported in printing or copying devices with the aid of a pneumatic conveying device, a toner recycling device can be arranged in the conveying device in a simple and functionally reliable manner, which separates the recyclable toner from the extracted waste or excess toner and supplies it to the developer station again. Dirt particles and other particles that negatively affect print quality are disposed of separately. This advantageously extends the operating time of the device with a predetermined toner supply, without this having to be renewed frequently. The amount of non-recyclable toner and dirt particles is reduced to a minimum.

The pneumatic conveying device can simultaneously be used to remove other particles which interfere with the printing operation, such as paper debris or punched particles from units required for paper transport, such as e.g. to remove and collect the paper brake. The pneumatic conveyance simplifies both the control of the supply of fresh toner and the control of the return of the cleaned toner to the developer station and is not susceptible to faults. Since there is constant negative pressure in the conveyor system, even in the event of leaks in the system, no toner dust can escape and contaminate the device. The entire toner handling is considerably simplified.

In an advantageous embodiment of the invention, the toner recycling device is designed as an independently replaceable structural unit. In the case of particularly high demands on the print quality, a collecting container for the waste toner can thus be arranged in a simple manner instead of the toner recycling device. The toner recycling facility can be arranged anywhere in the device. Since, in addition, the amount of residual toner accumulated is measured, the toner can be returned depending on the amount of residual toner.

The particle filter used for the separation is advantageously cleaned automatically without the filter having to be removed from the device. The pneumatic filter device serves both to supply fresh toner to the developer station and to return the toner. This means that an existing pneumatic conveying system for fresh toner can be expanded by a toner return device without substantial and complex design changes depending on the requirements of the device. The technical effort for a toner return system is significantly reduced. Since the developer station is supplied with toner controlled by a two-way valve on the one hand from a storage container for fresh toner and on the other hand from an intermediate container for recyclable toner corresponding to the fresh toner, the toner supply is buffered. The supply of fresh toner and the mixing in of recovered toner can thus be controlled depending on the operating state. A sudden toner depletion in the developer station due to high toner consumption can be easily compensated. The use of electrically conductive material for the line system prevents uncontrolled charging of the toner during transportation.

• Figur 1 ein schematisches Funktionsschaltbild einer pneumatischen Tonerfördereinrichtung für ein elektrografisches Druckgerät
• Figur 2 eine Schnittdarstellung einer in der pneumatischen Fördereinrichtung angeordneten Tonerrecycleeinrichtung mit zugeordnetem Tonerwegeventil
• Figur 3 eine Schnittdarstellung der Tonerrecycleeinrichtung im Normalzustand während des Druckbetriebes
• Figur 4 eine Schnittdarstellung der Tonerrecycleeinrichtung bei der Tonerrückführung während des Druckbetriebes
• Figur 5 eine Schnittdarstellung der Tonerrecycleeinrichtung im Reinigungsbetrieb
• Figur 6 eine schematische perspektivische Darstellung einer alternativen Anordnung einer Tonerrecycleeinrichtung oder eines Tonerauffangbehälters im Gerät
• Figur 7 und Figur 8 Explosionsdarstellungen der Tonerrecycleeinrichtung und
• Figur 9 eine Explosionsdarstellung eines Tonerregelventils.

Embodiments of the invention are shown in the drawings and are described in more detail below, for example. Show it

• Figure 1 is a schematic functional diagram of a pneumatic toner delivery device for an electrographic printing device
• FIG. 2 shows a sectional illustration of a toner recycling device arranged in the pneumatic conveying device with an associated toner directional control valve
• Figure 3 is a sectional view of the toner recycling device in the normal state during printing
• Figure 4 is a sectional view of the toner recycling device in the toner return during printing
• Figure 5 is a sectional view of the toner recycling device in the cleaning operation
• FIG. 6 shows a schematic perspective illustration of an alternative arrangement of a toner recycling device or a toner collecting container in the device
• FIG. 7 and FIG. 8 exploded views of the toner recycling device and
• Figure 9 is an exploded view of a toner control valve.

An electrophotographic printing device for printing on continuous paper contains a developer station 10 for coloring a charge image generated on a photoconductor drum with the aid of a developer mixture of toner particles and ferromagnetic carrier particles. The developer station 10 is divided into a developer station housing 11 for receiving application elements such as a magnetic brush, toner transport roller, etc. and a metering device 12 arranged above the developer station housing 11 for metered supply of toner 13 to the developer station housing 11. An emptying opening 14 for suction is located on the developer station housing 11 of the developer mixture from the developer station housing and a suction line 15 for sucking off the toner dust which arises during the developer process in the area of application elements. A toner box 16 assigned to the metering device 12 contains a filter space which serves as a buffer space for the toner and which is covered by a toner filter 17. The toner filter 17 is semicircular, with an air transport channel 18 located between the toner filter 17 and the walls of the toner box 16, which is led to a connection area on the toner box. In the air transport duct 18 there is an electrically controlled closure device in the form of a suction stroke valve 19 which, in an electrically controlled manner, interrupts or releases the air transport in the air transport duct 18. The filter chamber contains a doctor blade 21, which is driven by a motor 20, for mixing the toner 13, and a toner fill level sensor 22, which capacitively determines the toner fill level in the filter space, for example. Coupled to the filter space of the toner box is a toner delivery line 23 for supplying toner into the filter space by applying negative pressure to the air transport channel 18 when the suction cycle valve 19 is open. The toner 13 settles in the filter space and is mixed by the doctor blade 21, which Doctor blade 21 also brushes along the inside of the toner filter 17 and so keeps the filter clear. Below the filter space there is a feed device, not shown here, with a toner metering device, for example in the form of a foam roller lying against a wall, which feeds the toner to the developer station housing 11 in a metered manner.

The toner conveying device furthermore has a particle separator 24 in the form of a cyclone filter with a toner recycling device 25 arranged below the cyclone filter 24, the construction of which will be explained later. The cyclone filter 24 is coupled via the suction line 15 to the developer station housing 11, via a suction line 26 to the air transport channel 18 of the toner box and via a suction line 27 to a cleaning station 28 for the photoconductor drum, with an electrically adjustable cleaning brush 28 in the suction line 26 to the cleaning station 28 Throttle valve 29 is arranged. In throttle operation, the throttle valve 29 is in the 45 ° position shown, i.e. the partial vacuum present is reduced by partially closing the suction line 27. In cleaning operation, it is pivoted into a 90 ° position and thus the suction line 27 is opened. The vacuum is now fully applied to the cleaning station.

On the output side, the cyclone filter 24 is connected via a further suction line 30 to a device 31 generating negative pressure. This contains a particle fine filter 32 with an associated vacuum sensor 33 for detecting the vacuum in the device 31 as well as a drive motor 35 coupled to a turbine 34 and an air distributor 36 (FUMES).

A vacuum paper brake 37 arranged in the paper transport channel of the printing device is coupled to the suction line 30 via a further suction line 38. The negative pressure on the paper brake 37 is electrical adjustable throttle valve 39 and a solenoid valve 40 controlled.

A suction line 41, which connects the toner recycling device 25 to the toner delivery line 23, is used to supply the toner recovered via the toner recycling device 25 to the toner box 16 of the developer station. The toner delivery line 23 is also coupled via a suction line 42 to a toner reservoir 43 for fresh toner.

The toner reservoir 43 contains an exchangeably arranged toner bottle 44 and a suction tube 45 which can be inserted into the toner bottle 44. When negative pressure is applied to the suction line 42, ambient air is sucked in via the suction tube 45. This detects the toner particles 13 in the toner bottle 44 and transports them via the suction line 42 to the toner box 16. In order to be able to control the supply of either recycled toner from the toner recycling device 25 or fresh toner 13 from the toner storage container 43, there is a between the suction lines 41 and 42 Toner supply valve 46 arranged in the form of a two-way valve with which the suction lines 41 and 42 can alternatively be opened and closed. The structure of the toner supply valve 46 will be described later.

The toner delivery in the toner delivery system is controlled via a control arrangement 47, which can be part of the device control of the controller of the device. The controller is a conventional microprocessor-controlled controller which is connected to a control panel 48 of the device via a bus line. The operating parameters of the device, such as printing width, fusing temperature, printing operation, cleaning operation, etc., can be entered or set in a menu-controlled manner via the control panel 48. Coupled with the controller or part of the device control is a measured value acquisition and control arrangement 49, which serves to detect and convert the signals received by the various sensors of the toner conveying device and to control the toner conveyance via the negative pressure. In terms of hardware, it is constructed as a conventional microprocessor-controlled arrangement.

The toner conveyor is used to transport toner and particles in the printing device. Among other things, it enables fresh toner to be transported from the toner reservoir 43 into the developer station 10, to suck off a mixture of toner and dirt particles from the developer station 10 and the cleaning station 28, to separate the mixture from the air flow with the cyclone filter 24 in the toner recycling device 25 in recyclable toner and to separate them into dirt particles and to feed the separated recyclable toner to the developer station 10 again. Furthermore, it enables the separated dirt particles from developer station 10 and cleaning station 28 and from paper brake 37 to be collected in fine filter 32 of vacuum device 31. For all of these functions, function-dependent control is applied to the various aggregates, such as storage container 43, developer station 10, cleaning station 28, paper brake 37 and toner recycling device vacuum 25.

The different functions of the toner conveying device are now described in more detail using the units involved in the functions:

Toner recycling

An essential functional element for toner recycling is the toner recycling device 25, the basic structure of which is shown in FIG. 2. The detailed structure is shown in FIGS. 7 and 8. The toner recycling device contains a filter space 50 with an opening area 51 to the cyclone filter 24 and an outlet area 52. A particle sieve or particle filter 53 is arranged in the mouth area 51. A controllable closure flap 54 closes or opens the outlet area 52. The filter chamber 50 also has an air supply opening 55. Associated with the air supply opening 55 is an electrically actuable solenoid valve 56 which, if necessary, opens or closes the air supply opening 55 and thus connects the filter space 50 to the ambient air. Coupled to the filter space 50 via its outlet area 52 is a toner settling space 57. It also has an air supply opening 58 which can be opened and closed to the ambient air via a controllable closure flap 59. The toner settling space 57 is funnel-shaped and is coupled to the suction line 41 to the toner box 16 via an opening area 60. It also contains a toner sensor 61 for determining the toner fill level in the toner settling space 57 by capacitive measurement.

As can be seen from FIGS. 7 and 8, the filter space 50 and the toner settling space 57 are arranged in a housing 62 which accommodates the functional elements of the recycling device. These are: The particle sieve 53, e.g. from a wire mesh, which is interchangeably arranged in the mouth area 51 to the cyclone filter. The solenoid valve 56 for opening and closing the air supply opening 55. The controllable closure flaps 54 and 59 on the filter space 50 and on the toner settling space 57, as well as the associated drive elements for actuating the closure flaps 54 and 59.

The flaps 54, 59 are pivotally mounted on axes of rotation 63 which protrude from the housing 62 on one side (FIG. 7). Closing springs 64, which interact with actuating elements 65, are arranged on the outwardly projecting axes of rotation 63. The actuators 65 in turn are connected via connecting rods 66 to a drive element 67, which is coupled via a toothed belt 68 to a drive shaft 69 of a geared motor 70.

An axis 71 receiving the drive element 67 for the push rods 66 protrudes with its opposite axis end from the housing 62 (FIG. 8) on which a position transmitter 72 in the form of a magnet is arranged. This interacts with three position sensors (Hall sensors) H1, H2 and H3 fastened on a support plate 73. They serve to scan the position of the axis 71 and thus to scan the position of the flaps 54 and 59. The support plate 73 also receives a control module 74 in the form of a circuit which can be connected to the control arrangement 49 via connections 75. Furthermore, a differential pressure sensor 76 is arranged on the support plate 73, electrically coupled to the control module 74. Two pressure lines 77 of the differential pressure sensor 76 open below and above the particle sieve 53 into the mouth area 51 of the filter chamber 50. They detect the differential pressure on the particle sieve 53 via the differential pressure sensor 76 and thus the degree of contamination of the particle filter 53. If the differential pressure is high, the particle sieve 53 is contaminated and therefore impermeable. The particle sieve is permeable when the particle sieve is not contaminated.

If the axis 71 is rotated via the geared motor 70 and thus the push rods 66 are actuated, the flaps 59 and 54 close depending on the rotational position, the closing taking place against the spring force of the closing springs 64. With a corresponding further rotation of the axis 71, the flaps 54 and 59 open again automatically under the action of the closing springs 64.

Another essential functional element for toner recycling and fresh toner supply to the developer station is the toner supply valve 46 for opening and closing the suction lines 41 and 42 (Figure 1). As shown in FIG. 9 in connection with FIG. 1, the toner supply valve 46 consists of two silicone tubes 79 arranged in a carrier 78 with connecting pieces 80 for the suction lines 41 and 42. Between the silicone tubes 79 there is an eccentric roller 82 which can be rotated via a drive motor 81 that squeezes the silicone tubes 79 depending on their rotational position and thus closes or opens. Arranged on the eccentric roller 82 is a magnet 83 as a position transmitter which interacts with position sensors (Hall sensors) H4 and H5. These are permanently assigned to the carrier 78. Depending on the rotational position of the eccentric roller 82 and thus on the closed state of the silicone hoses 79, the position sensors H4 and H5 deliver a scanning signal to the control arrangement 49 of the controller 47.

Functional description of the toner recycling device

• Figur 3, Normalzustand während des Druckbetriebes
• Figur 4, Recyclezustand zur Tonerrückführung während des Druckbetriebs
• Figur 5, Reinigungszustand zum Reinigen des Partikelsiebs 53 und zur Rückführung der Schmutzpartikel in den Feinfilter 32 der Unterdruck erzeugenden Einrichtung 31 bei Bedarf, z.B. während einer Druckpause.

Depending on the control signals of the control arrangement 47, the toner recycling device 25 can be set in three operating states, which essentially differ in the different flap positions of the flaps 59 and 54 and the setting state of the toner valve 46. These are:

• Figure 3, normal state during printing
• Figure 4, Recycle condition for toner return during printing
• FIG. 5, cleaning state for cleaning the particle screen 53 and for returning the dirt particles into the fine filter 32 of the vacuum generating device 31, if necessary, for example during a printing break.

In the normal state (FIG. 3), the air valve 56 of the filter space 50 is closed, as is the air supply opening 58 of the toner settling space 57 via the flap 59. The flap 54 assigned to the outlet area 52 of the filter space 50 is open. The suction line 41 is hermetically sealed via the toner supply valve 46. The same pressure conditions prevail in the cyclone filter 54, in the filter chamber 50 and in the toner settling chamber 57, and the recyclable toner particles from the cyclone filter 24 fall through the particle sieve 53 into the toner settling chamber 57 and are collected there. Non-recyclable, large clumps of clumped toner or dirt particles 84 remain retained in the cyclone filter 24 by the particle sieve 53.

In order to be able to supply fresh toner from the toner reservoir 43 as required, the suction line 42 is opened. If fresh toner is requested as a function of the output signal of the toner fill level sensor 22, the suction cycle valve 19 is opened in a controlled manner by the control arrangement 49 and thus negative pressure is applied to the toner delivery line 23. The air flow thus generated in the suction tube 45 of the toner supply container 43 transports fresh toner from the toner bottle 44 into the toner box 16.

If a sufficient amount of recyclable toner has accumulated in the toner settling space 57, the filling state being sensed via the toner sensor 61, the recyclable toner is returned to the toner box 16 of the developer station during printing operation (FIG. 4). For this purpose, the flap 54 of the filter space 50 is closed and the flap 59 of the air supply opening 58 of the toner settling space 57 is opened via the control arrangement 49. The toner supply valve 46 releases the suction line 41 and closes the suction line 42 to the toner storage container 43. Controlled via the control arrangement 49, the suction cycle valve 19 opens, which results in negative pressure on the toner delivery line 23 and thus abuts the suction line 41. Ambient air is sucked in via the opened air supply openings 58, which flows through the toner settling space 57 and thus transports the recyclable toner accumulated in the toner settling space 57 via the suction line 41 and the toner conveying line 23 to the toner box 16.

If a correspondingly large number of dirt particles 84 have accumulated in the cyclone filter 24 and block the particle sieve 53, the differential pressure sensor 76 reports a corresponding differential pressure on the particle sieve 53 and, if necessary, e.g. during a print pause, the toner recycling device 25 is put into the cleaning state (FIG. 5). In this case, the suction line 41 is closed by the drive arrangement 49 via the toner supply valve 46. The flap 59 of the air supply opening 58 of the toner settling space 57 and the flap 54 of the filter space 50 are also closed. The solenoid valve 56 opens the air supply opening 55 of the filter space 50, as a result of which air flows through the air supply opening 55 via the particle filter 53 into the cyclone filter 24. The suction cycle valve 19 of the toner box 16 is closed. The air flow generated in this way transports the dirt particles 84 into the fine filter 32 of the vacuum-generating device 31, where they collect.

Description of a recycling process in detail:

In printing operation, the recycle device 25 is in the normal state shown in FIG. 3. Recyclable toner is accumulated in the toner settling space 57. After a toner fill level which can be predetermined by the position and the response threshold setting of the toner sensor 61 is reached, the toner sensor 61 responds and reports a corresponding fill level signal to the control arrangement 49. The control arrangement 49 starts the gear motor 70 for flap actuation as a function of the fill level signal. The geared motor 70 now runs until the magnet 72 of the position sensor reaches the area of the Hall sensor H2. The flap 54 of the filter chamber 50 is closed. After reaching the Hall sensor H2, the gear motor 70 stops. The Hall sensor H2 simultaneously starts the drive motor 81 of the toner supply valve 46. As a result, the eccentric roller 82 is pivoted into the position shown in FIG. 4, in which it clamps off the suction line 42 and the suction line 41 opens. The Hall sensor H5 stops the eccentric roller 82 in this position. Controlled by the output signal of the Hall sensor H5, the geared motor 70 starts again and opens the flap 59 of the air supply opening 58 of the toner sales space 57. After the position of the Hall sensor H3 has been reached, the geared motor 70 is stopped again. The Hall sensor H3 simultaneously triggers the suction process by actuating the suction clock valve 19 via the control arrangement 49 and switching on a time stage assigned to the control arrangement 49. During the suction process, the output signal of the toner sensor 61 drops again. The timer switches on the drive motor 81 of the toner supply valve 46 again after a presettable time of, for example, 2 seconds, as a result of which the eccentric roller 82 rotates again, the suction line 42 opens and the suction line 41 is pinched off. The output signal of the Hall sensor H4 ends the switchover and thus the suction process. At the same time, the suction clock valve 19 is closed via the output signal of the Hall sensor H4 and the geared motor 70 is started again. When the Hall sensor H1 is reached, the geared motor 70 stops again. This is the end of the recycling process. When rotating into the area of the Hall sensor H1, the flap 59 of the air supply opening 58 was closed again by the closing spring 64 and the flap 54 of the filter chamber 50 was opened again via the push rods 66. This is the starting position assigned to the normal state during printing reached again. Recyclable toner can accumulate again in the toner settling space 57.

A constant mixing ratio of recovered toner and fresh toner in the toner box 16 is maintained by the automatic sequence of the toner recycling process. E.g. consumes a lot of toner because e.g. large areas are colored, the fill level sensor 22 signals a corresponding need to the control arrangement 49. There is then an increased supply of fresh toner from the storage container 43. Due to the increased consumption of toner, in turn, a lot of residual toner accumulates at the cleaning station, from which in the recycling device 25 recyclable toner is obtained and the toner box 16 is supplied. Since the supply takes place as a function of the fill level in the toner settling space 57, the supply cycle increases. This restores the original mixing ratio. In the steady state, this amounts to approximately 30% recovered toner and 70% fresh toner. Regardless of the amount of toner used, a constant print quality is guaranteed.

In the exemplary embodiment described, the toner recycling process in printing operation takes place automatically as a function of the toner fill level in the toner settling space 57. However, it is also possible to start the toner recycling process selectively by calling up the control panel 48.

If the demands on print quality are very high, it can be beneficial to forego toner recycling. For this purpose and to facilitate any maintenance work on the device, the toner recycling device 25 is designed as an exchangeable structural unit in the form of a recycling insert, as shown in FIG. 6.

In the pressure device below the cyclone filter 24, an insertion opening 85 is arranged, which serves for the interchangeable reception of both the recycling insert (recycling device 25) and a catch box 86. The catch box 86 is a collecting container for collecting the particles separated by the cyclone filter 24. If a certain fill level is reached in the catch box 86, this is removed and the particles of toner particles and dirt particles accumulated therein are thrown away.

In order to enable this change between a catch box 86 and the recycling insert 25 in a simple manner, the insertion opening 85 contains guide rails 87 which are connected to corresponding guide elements 88, e.g. interact in the form of hooks on the catchbox 86 or the recycling insert 25. At the bottom of the insertion opening 85 there are electrical connection sockets 89 for receiving the connection plug 75 of the recycling insert 25 or a connection plug 90 of the catch box 86. The control arrangement 49 recognizes via the connections made whether the inserted collection container is the catch box 86 or a recycling insert 25 acts. The corresponding functions are switched depending on this.

The connections for the mouth area 60 and the electrical connections for the drive motor 70 of the recycling insert or the electrical connections 90 of the catch box 86 can be designed such that an automatic contact or an automatic connection between the mouth area 60 and Suction line 41 takes place. Furthermore, locking devices can be provided which only permit an exchange depending on the operating state of the device and which, for example, ensure that the suction line 41 is closed during the exchange.

Since the outlet area of the cyclone filter 24 is exposed when the inserts are exchanged, toner particles contained therein can fall into the insertion opening 85 and contaminate it. In order to prevent this, the inserts (catch box 86 or recycling insert 25) have a collecting tray 91 which, when exchanged, collects the residual particles contained in the cyclone filter 24. It is also possible to have a closure in the area of the exit opening of the cyclone filter 24, e.g. to be arranged in the form of a slide which, if necessary, closes the cyclone filter 24 during the exchange. Furthermore, it is possible to arrange this slide displaceably in the insertion opening 85 via guide rails and to provide it with fastening means for exchangeably fastening the inserts, be it the catch box 86 or the recycling insert 25.

As already described at the beginning, the toner particles are triboelectrically charged in the developer station in order to color the latent toner image on the photoconductor. So that this triboelectric charge or other charges do not interfere with the toner transport in the toner conveying device, the line system which receives the toner consists of electrically conductive material, e.g. made of metal or conductive plastic. The power system is grounded to discharge any charges. In order to enable this derivation, the inner surfaces of the line system that come into contact with the toner can be coated with a conductive layer or there are corresponding earth conductor tracks on the inner surface of the line system.

In the exemplary embodiment of the toner conveying device shown in FIG. 1, a cyclone filter is arranged as the particle separator 24. Instead of the cyclone filter, it is also possible to arrange other particle separators, for example sieves or the like. For this it is possible to put the flaps in the toner recycling device 25 to be replaced by corresponding other closures such as sliding elements or closure valves. As far as the formation of the toner supply valve 46 is concerned, it can be replaced by corresponding functionally equivalent valves which work with slides or other mechanical closure devices.

Reference list

10th

Developer station

11

Developer station housing

12th

Dosing device

13

toner

14

Emptying opening

15

Suction line

16

Toner box

17th

Toner filter

18th

Air transport channel

19th

Suction cycle valve, solenoid valve

20th

engine

21

Doctor blade, mixing device

22

Toner level sensor

23

Toner delivery line

24th

Particle separator, cyclone filter

25th

Toner recycling facility, recycling use

26, 27

Suction line

28

Cleaning station

29

Throttle valves

30th

Suction line

31

Vacuum generating device

32

Particle fine filter

33

Vacuum sensor

34

Turbine, blower

35

Drive motor

36

Air diffusers, fumes

37

Paper brake

38

Suction line

39

throttle

40

magnetic valve

41, 42

Suction line

43

Toner container for fresh toner

44

Toner bottle

45

Intake manifold

46

Toner supply valve

47

Controller, control arrangement

48

Control panel

49

Measured value, detection and control arrangement, control arrangement

50

Filter space

51

Mouth area

52

Exit area

53

Particle sieve, particle filter

54

Controllable shutter

55

Air supply opening

56

Solenoid valve, air valve

57

Toner deposition room

58

Air supply opening

59

controllable flap

60

Mouth area

61

Toner sensor

62

casing

63

Axes of rotation

64

Closing spring

65

Actuators, controls

66

Push rods

67

Drive element

68

Timing belt

69

drive shaft

70

Gear motor

71

axis

72

Position transmitter

H1, H2, H3

Hall sensors, position sensors

73

Support plate

74

Control module

75

Connections, plugs

76

Differential pressure sensor

77

Pressure line

78

carrier

79

Silicone hoses

80

Connecting piece

81

Drive motor

82

Eccentric role

83

Magnet, position transmitter

H4, H5

Position sensors, Hall sensors

84

Dirt particles

85

Slot

86

Catchbox, collecting container

87

Guide rails

88

Guide element, hook

89

Connection socket

90

Connector

91

Drip pan

Claims (14)

1. Pneumatic transport device for an electrographic printing or copying machine for transporting toner to and for removing toner and/or dirt particles from units of the machine, in particular the developer station and the cleaning station (28), having

   - a vacuum-producing device (31), which can be coupled to the units (10, 28, 37) of the machine via a duct system

   - a particle separator (24), which is assigned to the duct system and has means for separating toner and/or dirt particles from an airstream flowing through the particle separator (24)

   - a toner recycling device (25), which can be connected to the particle separator (24) via coupling means (87, 88) and has a toner separating device (53) with associated supply device (50, 57) for separating recyclable toner from the particle mixture separated by the particle separator (24) and for supplying the recyclable toner, via a recycled toner transport duct (41, 23), to a developer station (10) of the machine,

   - a toner metering device (12) which is assigned to the developer station (10), can be coupled to the toner recycling device (25) and a fresh toner container (43) and

   - means (46, 49, 61) for the controlled supply of recyclable toner and of fresh toner to the toner metering device (12) as a function of the accumulation of reusable toner.
2. Pneumatic transport device according to Claim 1, having a toner recycling device (25) which is designed as an independent, exchangeable constructional unit.
3. Pneumatic transport device according to Claim 2, having coupling means (87, 88) for the exchangeable accommodation of a particle mixture accommodation container (86) or of the toner recycling device (25).
4. Pneumatic transport device according to one of Claims 1 to 3, wherein the toner recycling device (25) has:

   - a filter space (50) having an opening region (51) towards the particle separator (24) accommodating a particle filter (53) and an exit region (52) accommodating a controllable closure element (54), and an air supply opening (55) having an associated controllable closure element (56)

   - a toner settling space (57), which is coupled to the filter space (50) via its exit region (52), and has an air supply opening (58) with associated controllable closure element (59) and an opening region (60) which can be coupled to the transport duct (41).
5. Pneumatic transport device according to Claim 4, having

   - a control device (49, 47), which is coupled to the closure elements (59, 54, 56) of the toner recycling device (25) and controls the closure elements (54, 59, 56) in such a way

   - that, for cleaning the particle filter (53) and for transporting away the dirt particles (84), the exit region (52) of the filter space (50) is closed and the air supply opening (53) of the filter space (50) is opened

   - that, for supplying the recyclable toner to the toner settling space (57) when vacuum supply to the transport duct (41) is interrupted, the exit region (52) of the filter space (50) is opened and the air supply opening (55) of the filter space (50) is closed

   - that, for supplying the recyclable toner to the developer station (10) when vacuum is applied to the transport duct (41), the exit region (52) of the filter space (50) is closed and the air supply opening (58) of the toner settling space (57) is opened.
6. Pneumatic transport device according to Claim 4 or 5, having a sensor device (61) which is assigned to the toner settling space (57) and detects the toner filling level in the toner settling space.
7. Pneumatic transport device according to one of Claims 1 to 6, having

   - a fresh toner transport duct (42) which couples the developer station (10) to the fresh toner supply container (43) and

   - a controllable closure device (46), which is coupled to the recycled toner transport duct (41) and the fresh toner transport duct (42), for the alternate closure of the ducts (41, 42).
8. Pneumatic transport device according to Claim 7, wherein the controllable closure device (46) is designed as a two-way valve having transport ducts (79), arranged on both sides of an eccentric roller (82) for the squeezing of the transport ducts (79) via the eccentric roller (82) as a function of its rotational position.
9. Pneumatic transport device according to one of Claims 1 to 8, wherein the toner metering device (12) has a buffer container (16), which can be coupled, on the one hand, to the toner recycling device (25) and/or the fresh toner container (43) and, on the other hand, via a controllable closure device (19), to the duct system of the vacuum-producing device (31).
10. Pneumatic transport device according to one of Claims 1 to 9, having a fine filter (32), which is assigned to the vacuum-producing device (31), for picking up the dirt particles (84).
11. Pneumatic transport device according to one of Claims 1 to 9, having a cyclone filter (24) as means for separating toner (13) and/or dirt particles (84).
12. Pneumatic transport device according to one of Claims 1 to 11, having a device (76) for determining the particle filter soiling by detecting the vacuum difference before and after the toner separating device (53) designed as a particle filter.
13. Pneumatic transport device according to one of Claims 1 to 12, having a duct system which has wall regions which contact the toner, dissipate charges and are made of electrically conductive material.
14. Process for the pneumatic transport of toner (13) and for the removal of toner and/or dirt particles (84) from units, in particular the developer station (10) and cleaning station (28), of an electrographic machine, having the following steps:

    - sucking up of toner (13) and/or dirt particles (84) from the units (10, 28, 37) of the machine by applying a vacuum to the units via a duct system

    - separating the sucked-up toner-dirt particle mixture in a toner recycling device (25) into non-reusable dirt particles (84) and reusable toner

    - mixing the reusable toner with fresh toner as a function of the accumulation of reusable toner in such a manner that a constant mixing ratio is obtained

    - supplying the mixed toner to the developer station (10)

    - collecting the dirt particles (84) in a catching device (32).

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