Abstract:
Methods of manufacturing toner for use in electrophotographic imaging members, such as photoreceptor structures. More particularly, embodiments pertain to an apparatus and process for separating toner from toner/carrier mixtures, such as reclaiming toner from waste toner, much more efficiently and with improved yields.

Description:
BACKGROUND 
       [0001]    Herein disclosed are embodiments pertaining to an apparatus and process for separating toner from a toner/carrier mixture, such as for example, waste toner containing carrier. The apparatus and process described herein operate much more efficiently to separate low density particles from larger, high density particles. 
         [0002]    Reclaiming toner from electrophotographic machines is a highly desirable alternative to depositing toner in landfills or subjecting toner to incineration. Reclaim of field returned waste toner through addition into an extruder is a known process for some existing toners. A conventional manner of producing such toner is disclosed in Laing et al., U.S. Pat. No. 5,888,691, which is herein all incorporated by reference. 
         [0003]    A problem that limits the efficiency of the reclaiming process, however, is that modern xerographic devices applies replenisher (toner plus some 5% to 40% fresh carrier) rather than only toner. Replenishers are used in order to keep the developer (carrier with up to 5% toner) in a steady-state aging condition. The equivalent amount of added fresh carrier leaves the developer through an overflow system and for some of these devices both waste toner and waste carrier are collected in the same waste bottle. 
         [0004]    For example, some waste toners are estimated to include about 40% to 50% carrier by weight of the total waste toner weight. At such high carrier to toner ratios, the conventional carrier separation process through direct turboscreening, for example, screening over 44 microns, is no longer feasible as frequent screen blinding will occur. In blinding, the screen apertures may become clogged or covered by the heavier and larger carrier particles and thus become inefficient in operation or cease to operate properly altogether. As a result, such waste toners is not available for reclaim into regular toner processing. 
         [0005]    Thus, there is a need for a more efficient separation process, and apparatus for performing such, to separate low density particles from a mixture of high and low density particles, including an apparatus and process for efficiently reclaiming waste toners, including those that have a high carrier content, to allow reclaim through regular toner processing. 
       SUMMARY 
       [0006]    According to embodiments illustrated herein, there is provided a way to separate a mixture of high and low density particles which can also be used to remove carrier particles from waste toner. 
         [0007]    In particular, an embodiment provides a process for separating toner from a toner/carrier mixture, comprising collecting waste toner containing a carrier, separating the carrier from the waste toner with a separating apparatus, the separating apparatus further comprising a cyclone separator covering a receiving vessel, a pressurized ring attached to the cyclone separator, an annular plenum defined by a tunnel, the tunnel being formed along an inner circumference of the pressurized ring, and a slit formed along an outer circumference of the tunnel, wherein pressurized air from the pressurized ring blows into the annular plenum through the slit to further separate the waste toner from the carrier such that the waste toner continues on a flow path along an inner circumferential of the annular plenum and the carrier continues along an outer circumferential of the annular plenum to exit into the receiving vessel, screening the waste toner in a screening device attached to the separating apparatus to remove extraneous debris to produce screened waste toner, and extruding the screened waste toner by itself and optionally with further raw materials in an extruder apparatus to produce a melt mixed product. 
         [0008]    Embodiments also provide an apparatus for separating toner from a toner/carrier mixture, comprising a cyclone separator covering a receiving vessel, a pressurized ring attached to an inside of the cover, an annular plenum defined by a tunnel, the tunnel being formed along an inner circumference of the pressurized ring, and a slit formed along an outer circumference of the tunnel, wherein pressurized air from the pressurized ring blows into the annular plenum through the slit to further separate a toner from a toner/carrier mixture such that the toner continues on a flow path along an inner circumferential of the annular plenum and the carrier continues along an outer circumferential of the annular plenum to exit into the receiving vessel. 
         [0009]    Further embodiments provide an apparatus for separating toner from a toner/carrier mixture, comprising a cyclone separator covering a receiving vessel, a pressurized ring attached to an inside of the cover, an annular plenum defined by a tunnel, the tunnel being formed along an inner circumference of the pressurized ring, and a slit formed along an outer circumference of the tunnel, the slit having a width of from about 0.1 mm to about 0.3 mm, wherein the cover further includes an entryway and an exitway and the exitway is in flow communication with a screening device adapted to screen toner, and wherein pressurized air from the pressurized ring blows into the annular plenum through the slit to further separate a toner from a toner/carrier mixture such that the toner continues on a flow path along an inner circumferential of the annular plenum and the carrier continues along an outer circumferential of the annular plenum to exit into the receiving vessel. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0010]    For a better understanding of the present invention, reference may be had to the accompanying figures. 
           [0011]      FIG. 1  is a perspective view of a separating apparatus according to an embodiment of the present disclosure; 
           [0012]      FIG. 2  is a perspective view of an underside of a separating apparatus according to another embodiment of the present disclosure; 
           [0013]      FIG. 3  is an alternative view of  FIG. 2  according to an embodiment of the present disclosure; and 
           [0014]      FIG. 4  is an alternative perspective view of a separating apparatus according to an embodiment of the present disclosure. 
       
    
    
     DETAILED DESCRIPTION 
       [0015]    In the following description, it is understood that other embodiments may be utilized and structural and operational changes may be made without departure from the scope of the present embodiments disclosed herein. 
         [0016]    The present embodiments relate to an apparatus and process for separating low density particles from larger, high density particles in a mixture of both low and high density particles. In embodiments, the apparatus and process is used to separate toner from a toner/carrier mixture, such as for example, waste toner containing carrier. The embodiments provide a much more efficient manner of reclaiming toner from such waste toner. 
         [0017]    Waste toner often comprises of a toner/carrier mixture which needs to be separated as the carrier will interfere with later processes to reclaim the waste toner for re-use. After subjecting the waste toner to the present embodiments as described herein, the waste toner contains very little or no carrier. 
         [0018]    According to the embodiments, the operating set points of a cyclone separator are tuned to separate toner from a toner/carrier mixture, such as for example, waste toner from carrier, rather than toner fines from toner, such that waste toner subjected to the centrifugal forces is separated from any carrier that is also contained in the waste toner. This step prevents screen blinding when the separated waste toner is subsequently sent into a turboscreener for screening. The reclaimed toner can then be used in extrusions of new toner. Without the use of the cyclone separator, the carrier will block the screening apertures and render the toner reclaim process very inefficient. 
         [0019]    In embodiments, there is provided an apparatus for separating toner from a toner/carrier mixture. As shown in  FIG. 1 , the separating apparatus  5  comprises a cyclone separator  10  being a cover for a receiving vessel or container  45 . A pressurized ring  15  may be welded to the outside of the lower part of cyclone  15  and forms part of the cover  20 . The pressurized ring  15  may apply an overpressure of from about 0.15 to about 0.25 bar. In  FIG. 2 , the cyclone separator is shown upside down for a clearer view. It can be seen that a tunnel  50 , located inside the cover  20 , is formed along an inner circumference of the ring  15 . The tunnel  50  defines an annular plenum  65  and, as shown in  FIG. 3 , has a slit  25  formed along the outer circumference of the tunnel  50 .  FIG. 3  is view of  FIG. 2 , rotated over 180° so that the inner wall of the pressurized ring  15  between the tunnel entrance  60  and tunnel exit  55  can be seen. The slit  25  provides an opening between the pressurized ring  15  and the tunnel  50 , thereby allowing airflow through the slit  25  from the pressurized ring  15  into the tunnel  50  at a perpendicular to the main airflow flowing through the tunnel  50 . The tunnel entrance  55  is connected to the cyclone entryway  30 , in the cover  20 , while exit  60  ends in the cyclone chamber. The cover  20  includes the entryway  30  and an exitway  35  where the exitway  35  is in flow communication with a screening device, such as a turboscreener, adapted to screen waste toner comprising a toner/carrier mixture. 
         [0020]    A toner/carrier mixture, such as for example, waste toner having carrier, is delivered into the separating apparatus  5  through the entryway  30  of the cover  20  and into the tunnel  50  (being a part of the cyclone). The toner/carrier mixture is subjected to centrifugal forces in the tunnel  50  which pushes the mass of the mixture to the outer part or outside of the tunnel  50 . The “outside” of the tunnel being defined as the portion of the tunnel being away from the center  40  of the cyclone separator  10 , and the “inside” of the tunnel being defined as the portion of the tunnel being closer to the center  40  of the cyclone separator  10 . Pressurized air from the pressurized ring  15  enters the tunnel  50  through the slit  25 , at a perpendicular direction to the main airflow traveling through the annular plenum.  65 , blowing toner off of the carrier particles. This “blow-off” airflow separates the toner from the carrier. 
         [0021]    While the heavier carrier particles remain at the outside of the tunnel  50  the lighter toner particles are blown toward the inner part or inside of the tunnel  50 . The mass leaving the tunnel exit  55  toward the outside of the tunnel  50  will be mostly carrier falling into the container  45 , such as for example, a barrel, below and connected to the cyclone cover  20 . The mass leaving the tunnel exit  55  toward the inside of the tunnel  50  will be mostly toner being carried by the main airflow which leaves the cyclone cover  20  through the exit  35  and continues into the screening device. Thus, the ring  15  acts as a carrier separation unit wherein the waste toner is circulated along the annular plenum  65  and the force of the pressurized air separates the toner from the carrier. 
         [0022]    In embodiments, the toner/carrier mixture has a toner to carrier ratio of from about 15:1 to about 1:2. These embodiments may be used to generally separate light density particles form high density particles, such as separating toner from waste toner containing carrier or toner from replenisher. 
         [0023]    The slit  25  may have a width of from about 0.1 mm to about 0.3 mm, or from about 0.2 mm to about 0.25 mm. In a particular embodiment, the slit  25  has a width of from about 0.1 mm to about 0.3 mm. In a particular embodiment, the slit is about 25 mm in width, and the pressure applied by the pressurized ring  15  is from about 0.15 to about 0.25 bar. 
         [0024]    Generally, a narrow slit is used to create a high speed blow-off airflow, which is more efficient in separating the particles than a wide slit with low speed blow-off air. The width of the slit and the overpressure from the pressurized ring is selected based on consideration of the size of cyclone cover and main airflow through the cyclone cover. The present embodiments create a high speed blow-off airflow that ensures substantially no toner will remain trapped in the carrier mass, but does not use such high overpressure that would create a speed that would blow both carrier and toner towards the inside of the tunnel and result in a high amount of carrier being moved with toner to the turboscreener. 
         [0025]    In further embodiments, shown in  FIG. 4 , the slit  25  further comprises a plurality of vertical slits  70  which may form a grating  75  over the entire circumferential of the pressurized ring. In the embodiment, the vertical slits  70  assure blow-off air to be present over the entire tunnel height. In embodiments, the slits  70  might be constructed such to have the pressurized air or blow-off airflow blown through the slits at a counter current direction to the flow path in the annular plenum. In other embodiments, the slits  70  might be constructed such to have the pressurized air or blow-off airflow blown through the slits  70  along the current direction of the flow path in the annular plenum. 
         [0026]    The waste toner may be passed through the tunnel  50  several times to ensure the optimal level of separation. In embodiments, the waste toner is passed through the tunnel from about 1 to about 5 times. Depending on the number of times the waste toner is passed through the apparatus  5 , up to about 100% toner can be reclaimed from the waste toner. In specific embodiments, from about 50% to about 70% toner is reclaimed from the waste toner. 
         [0027]    In yet other embodiments, there is provided a process for separating toner from a toner/carrier mixture. The waste toner may have a toner to carrier ratio of from about 15:1 to about 1:2. The process comprises collecting waste toner containing a carrier and subjecting the toner/carrier mixture to a separating step. In particular embodiments, this process can be used to effectively reclaim toner from any toner/carrier mixture. In embodiments, the carrier is separated from the waste toner comprising the carrier with a separating apparatus comprising a cyclone separator with a pressurized ring attached therewith. The pressurized ring has a tunnel formed along the inner circumference of the ring and the tunnel defines an annular plenum. The tunnel and the defined annular plenum, in embodiments, is formed over 270 degrees of the cyclone separator. In further embodiments, the tunnel length may be extended spiral-wise over several cyclone revolutions. The tunnel concentrates the full airflow over the entire length of the annular plenum before being able to escape into the return vortex. It appears that better separation is achieved from a longer annular plenum length and by spiraling the ring would allow the annular plenum to extend over several revolutions. 
         [0028]    A slit is formed along an entire outer circumference of the tunnel. As described above, the larger and heavier carrier particles continue to travel through the outside of the tunnel and is subsequently collected into a container below the cyclone cover. The separating step can be repeated to ensure that the separated waste toner contains no or very little carrier, for example, from about 1 to about 5 times. Once the toner and carrier is satisfactorily separated, the separated waste toner is subjected to screening to remove extraneous debris. The screening may be performed by a screening device, such as a turboscreener. The screened waste toner may be put into an extruder apparatus by itself or with other raw materials to produce a melt mixed product. In further embodiments, the process may also including grinding and classifying the melt mixed product produced providing re-manufactured toner particles. 
         [0029]    While the description above refers to particular embodiments, it will be understood that many modifications may be made without departing from the spirit thereof. The accompanying claims are intended to cover such modifications as would fall within the true scope and spirit of embodiments herein. 
         [0030]    The presently disclosed embodiments are, therefore, to be considered in all respects as illustrative and not restrictive, the scope of embodiments being indicated by the appended claims rather than the foregoing description. All changes that come within the meaning of and range of equivalency of the claims are intended to be embraced therein. 
       EXAMPLE 
       [0031]    The example set forth herein below and is illustrative of different compositions and conditions that can be used in practicing the present embodiments. All proportions are by weight unless otherwise indicated. It will be apparent, however, that the embodiments can be practiced with many types of compositions and can have many different uses in accordance with the disclosure above and as pointed out hereinafter. 
       Example I 
       [0032]    A modified cyclone separator cover was used fitting a 200 liter steel barrel. In the cyclone separator cover, an air-pressurized ring (0.25 bar) was installed. The ring had a 0.2 mm slit along the entire inner circumference of the ring. Next to the ring, over 270 degrees, a tunnel was mounted inside the cover and connected to the entryway to the cover. The cyclone separator was placed on a 200 liter steel barrel. The cyclone separator was connected to the toner feed line upfront of a Turboscreener (available from Sweco, Florence, Ky.). Airflow created by the downstream blower from the Turboscreener picked up the toner/carrier mixture at the feed rotary valve and sucked the mixture with the air through the cyclone separator cover where airflow from the pressurized ring entered into the annular plenum through the slit at a direction perpendicular to the main airflow in the tunnel (generated by the downstream turboscreener blower). The main airflow generated by the downstream blower was generated in an order of about 450 m 3 /hr (or about 25 m/sec) in comparison to what was generated by the pressurized airflow from the 0.2 mm slit at from about 0.1 to about 0.3 bar overpressure in the pressurized ring. 
         [0033]    The toner was blown-off from the carrier mass towards the inside of the tunnel. The carrier continued traveling along the outer side of the tunnel. Subsequently, the heavy carrier fell into the steel barrel while exiting from the outer side of the tunnel and the lighter toner particles continued with the main airflow and exited from the inside of the tunnel into the Turboscreener. 
         [0034]    Results 
         [0035]    The results of the separation testing demonstrated that about 70% of the available toner was reclaimed from the waste toner by the Turboscreener after being subjected to two passes through the cyclone separator. 
         [0036]    All the patents and applications referred to herein are hereby specifically, and totally incorporated herein by reference in their entirety in the instant specification. 
         [0037]    It will be appreciated that various of the above-disclosed and other features and functions, or alternatives thereof, may be desirably combined into many other different systems or applications. Also that various presently unforeseen or unanticipated alternatives, modifications, variations or improvements therein may be subsequently made by those skilled in the art which are also intended to be encompassed by the following claims. Unless specifically recited in a claim, steps or components of claims should not be implied or imported from the specification or any other claims as to any particular order, number, position, size, shape, angle, color, or material.