JP2005075542A - Sheet feeder and image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a sheet feeder, preventing inferior positioning accuracy, and surely feeding and separating sheets of various raw materials such as coated paper, OHP, art film and very thick paper, and an image forming apparatus including the feeder. <P>SOLUTION: In order to solve the problem, the sheet feeder of representative constitution of the invention includes: a sheet loading means loaded with a plurality of sheets; a feeding means for feeding the sheets placed on the sheet loading means; and a blowing means for blowing air current from the side of the sheets placed on the sheet loading means. A top plate is provided near the top face of the placed sheets, and bending of the sheets due to blown air current from the blowing means is restrained by the top plate. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a sheet feeding apparatus that separates and feeds sheets one by one from a sheet bundle stacked in a sheet storage unit, and an image forming apparatus using the sheet feeding apparatus, and particularly, separates and feeds sheets having high adhesion between sheets. The present invention relates to a sheet feeding apparatus and an image forming apparatus using the sheet feeding apparatus.

  Conventionally, in image forming apparatuses such as copiers and printers, cut sheets that can be continuously fed are usually limited to high-quality paper and plain paper designated by the copier manufacturer. In order to reliably separate and feed such sheets one by one, various separation methods have been conventionally employed. For example, the pickup roller is brought into contact with and pressed against the upper sheet of the sheet bundle to feed out the upper sheet, and a separation roller that is provided downstream of the sheet conveying direction and is driven in a direction opposite to the sheet conveying direction is fed with a predetermined torque. There is a retard separation system in which a roller is brought into contact with a predetermined pressure to prevent double feeding. There is also a Duplo system in which a friction member is brought into contact with the feed roller with a predetermined pressure to prevent double feeding. In order to reliably separate and feed the sheet by the above-described method, for example, in the case of the retard method, the return torque and the applied pressure are optimized in consideration of the frictional force of the sheet to be fed. It was possible to separate them one by one.

  On the other hand, in recent years, with the diversification of recording media, in addition to ultra-thick paper, OHP sheets, art films, etc., in order to obtain whiteness and gloss from the demands of colorization, coated paper, etc., whose surface is coated There is an increasing demand for image formation on sheets. However, in the case of ultra-thick paper, its own weight becomes a conveyance resistance and cannot be picked up and jammed. In addition, in the case of a sheet made of a resin material that is easily charged, such as an OHP sheet or an art film, the sheet surface is gradually charged by rubbing between sheets during a feeding operation in a low humidity environment, and the sheets are crushed by Coulomb force. Sticks, pickup is not possible, or double feeding occurs. Also, coated paper with paint applied on the surface of the paper has the property of adsorbing the sheets, especially when the sheets are stacked in a high humidity environment. There is a problem that there is no double feed. This is because the conventional separation method only considers the frictional force between the sheets. In the case of a special sheet as described above, the frictional force between the sheets itself is equal to or less than that of the above-mentioned plain paper, etc., but the adsorption by the frictional charging of the resin material sheet in a low humidity environment. Since the force and the adsorption force of the coated paper in a high humidity environment are adsorbed with a force much higher than the friction force between the sheets, there are cases where separation cannot be achieved by the conventional feeding separation system.

  In order to solve the extremely high adsorption as described above, air is blown from the side surface of the sheet bundle (hereinafter referred to as “auxiliary air blowing means”), the sheets are preliminarily blown and the adsorption between the sheets is eliminated. The printing industry and some copying machines adopt a feeding system that picks up one sheet at a time and separates the sheets one by one in a separation section provided downstream thereof. In the feeding method equipped with the auxiliary air blowing means, even in the case of a sheet having a high adsorbing force as described above, the sheet is rolled prior to feeding, compared with a generally used friction separation type device. Since the adsorption is released, feeding separation is possible.

  Many proposals related to a feeding system provided with such auxiliary air blowing means have been made. As an example, a feeding device 3155 shown in FIG. 6 includes a feeding tray 3059 for stacking sheets, a feeding unit for feeding sheets from the feeding tray 3059, and a side surface and a top surface of the stacked sheets. Air blowing means 3071 for blowing air from any direction and flow path moving means 3157 for moving the flow path of air blown from the air blowing means 3071 in the direction perpendicular to the sheet surface are provided. The flow path moving means 3157 includes a guide rail (not shown) that supports the air blowing means 3071 so as to be movable in the vertical direction, an electric motor 3121, and an output shaft of the electric motor 3121, which is fixed to the lower surface of the air blowing means 3071. And a cam plate 3123 for moving the air blowing means 3071 in contact therewith. Therefore, when the electric motor 3121 rotates and the cam plate 3123 rotates, the entire air blowing means 3071 moves in the vertical direction. In this feeding device 3155, the opening (air outlet) of the air blowing means 3071 has a constant opening area, and the entire air blowing means 3071 moves in the vertical direction, so that the air moves relative to the side surface of the seat 3057. Therefore, the sheet is moved in the direction perpendicular to the sheet surface. Further, at this time, the opening area of the opening portion of the air blowing means 3071 is constant, but the side surface of the sheet 3057 is opposed to the opening portion, so that the area of the opening portion is reduced and blown out from the opening portion. Thus, an air constricting portion for narrowing the air flow is formed. As a result, it is possible to lift the upper sheet 3057 and release the adsorption between all the sheets 3057 (see, for example, Patent Document 1).

  In addition, a technique for dehumidifying the sheet by heating the blown air with a heater and reducing the adsorptive power of the coated paper particularly in a high humidity environment is disclosed (for example, see Patent Document 2).

JP-A-11-005643 JP 2001-48366 A

  However, when the sheet is rolled by the auxiliary air blowing means, the sheet is fluttered and bent by the blown air, and the apparent paper width may be reduced due to the bending. Conventionally, the position of the sheet is regulated using a side regulating plate that regulates the width direction so as not to deviate from the normal position on the sheet stacking means, but the apparent paper width is reduced by bending as described above. As a result, a gap is formed between the seat and the side regulating plate. As a result, the gap causes the sheet to be displaced or swiveled, and the sheet is not fed and conveyed from the normal position. This causes a problem that the positional accuracy of the image formation is poor due to skew or lateral misregistration. The above problem is most likely to occur with small-sized thin paper that is largely bent by the air from the auxiliary air blowing means, and the positional accuracy is also increased.

  The present invention has been made in view of the above circumstances, and it is possible to reliably feed and separate sheets of various materials such as coated paper, OHP, art film, and ultra-thick paper while preventing poor positional accuracy. It is an object of the present invention to provide a sheet feeding apparatus and an image forming apparatus including the sheet feeding apparatus.

  In order to solve the above-described problems, a typical configuration of the present invention includes a sheet stacking unit that stacks a plurality of sheets, a feeding unit that feeds the sheets stacked on the sheet stacking unit, and a sheet stacking unit. A sheet feeding apparatus including a blowing unit that blows an air flow from a side of the stacked sheets, wherein a top plate is provided near the top surface of the stacked sheets, and the air is blown from the blowing unit by the top plate It is characterized by suppressing the bending of the sheet due to the flow.

  According to the present invention, by providing a top plate in the vicinity of the sheet upper surface of the sheet feeding apparatus, even if the auxiliary air blowing means is provided to separate the adsorbed sheet such as coated paper, The bending of the sheet can be prevented. Therefore, it is possible to prevent the positional deviation in the skew direction and the width direction (direction orthogonal to the conveyance direction), which is caused by the apparent reduction of the sheet width due to the bending. In addition, since the air path is restricted by the top plate, air leakage is reduced, and the wind effect is improved. As a result, it is possible to provide a highly reliable sheet feeding apparatus and image forming apparatus that can separate various sheets such as coated paper, ultra-thick paper, and OHP sheets one by one and convey them with high positional accuracy. .

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

(overall structure)
First, the overall configuration of the image forming apparatus will be described. FIG. 1 is a cross-sectional view of the image forming apparatus according to the present embodiment. A printer 1000 shown in FIG. 1 includes a printer main body 1001 and a scanner 2000 disposed on the upper surface of the printer main body 1001.

  The scanner 2000 reads an image on a document, and includes a scanning optical system light source 201, a platen glass 202, a document pressure plate 203 that opens and closes, a lens 204, a light receiving element 205 (photoelectric conversion), an image processing unit 206, and an image processing unit 206. And a memory unit 208 for storing the processed image processing signal. When reading the original, the original (not shown) placed on the platen glass 202 is read by irradiating light with the scanning optical system light source 201. Then, the read document image is processed by the image processing unit 206, converted into an electrically encoded electrical signal 207, and transmitted to the laser scanner 111. Note that the image information processed and encoded by the image processing unit 206 may be temporarily stored in the memory unit 208 and transmitted to the laser scanner 111 as necessary by a signal from the controller 120.

  The printer main body 1001 includes a sheet feeding device 1002 for feeding the sheet S, a sheet feeding device 1004 for feeding the sheet S fed by the sheet feeding device 1002 to an image forming unit 1005 as an example of an image forming unit, And a controller 120, which is a control means for controlling the printer 1000. Also, 1003 is a large capacity paper deck that is a detachable sheet feeding device as an option (the main structure of the paper deck 1003 is only symmetrical with the sheet feeding device 1002, and the mechanism and operation are the same. Detailed explanation will be omitted).

  Here, the sheet feeding device 1002 includes a cassette 100 as an example of a sheet stacking unit, a pickup roller 101 as an example of a feeding unit, a separation unit including a feed roller 102 and a retard roller 103, The sheets S in the cassette 100 are separated and fed one by one by the action of a pickup roller 101 that moves up and down / rotates at a predetermined timing and a separation unit. Further, a feeding sensor 104 is provided in the vicinity of the downstream side in the sheet conveying direction of the feed roller 102 and the retard roller 103, and is configured to detect the passage of the sheet S there.

  Further, each cassette 100 is partitioned by partition plates 106 and 107, and is sealed with a predetermined sealing degree. Each sealed space is provided with a temperature and humidity sensor 108 capable of detecting the temperature and humidity in the space, and the temperature and humidity in each space can be detected independently. In addition, the configuration of the feeding unit will be described in detail later.

  The sheet conveying device 1004 includes a conveying roller pair 105 and a registration roller unit including a pre-registration roller pair 130 and a registration roller pair 110, and the sheet S fed from the sheet feeding device 1002 is conveyed to the conveying roller pair 105. Thus, after passing through the sheet conveying path 109 constituted by the guide plate, it is guided by the guide plate, and thereafter guided to the registration roller pair 110. Thereafter, the sheet S is once abutted against the registration roller pair 110, corrected for skewing during sheet feeding and conveyance, and then conveyed to the image forming unit 1005.

  The image forming unit 1005 includes a photosensitive drum 112, a laser scanner 111, a developing unit 114, a transfer charging unit 115, a separation charging unit 116, and the like. During image formation, laser light from the laser scanner 111 is reflected by a mirror 113. 1 is applied to the exposure position 112a on the photosensitive drum 112 that is rotated in the clockwise direction in FIG. 1, thereby forming a latent image on the photosensitive drum 112. Further, the latent image formed on the photosensitive drum in this way is thereafter visualized as a toner image by the developing device 114.

  The toner image on the photosensitive drum 112 is then transferred to the sheet S by the transfer charger 115 in the transfer unit 112b. Further, the sheet S on which the toner image is transferred in this manner is electrostatically separated from the photosensitive drum 112 by the separation charger 116, and then conveyed to the fixing device 118 by the conveyance belt 117, and the toner image is fixed. Thereafter, the paper is discharged by the discharge roller 119. In addition, a discharge sensor 119a is provided in the conveyance path between the fixing device 118 and the discharge roller 119, and the passage of the sheet S there can be detected.

  In this embodiment, the printer main body 1001 and the scanner 2000 are separate, but the printer main body 1001 and the scanner 2000 may be integrated. In addition, the printer main body 1001 functions as a copying machine when a processing signal of the scanner 2000 is input to the laser scanner 111, and functions as a FAX when a FAX transmission signal is input. Furthermore, if an output signal of a personal computer is input, it functions as a printer. Conversely, if the processing signal of the image processing unit 206 of the scanner 2000 is transmitted to another FAX, it functions as a FAX. Further, in the scanner 2000, if an automatic document feeder 250 as shown by a two-dot chain line is attached instead of the pressure plate 203, the document can be automatically read.

  Next, the sheet feeding apparatus 1002 will be described in detail with reference to FIGS. 2 and 3 are plan views of the sheet feeding apparatus, FIG. 4 is a main sectional view of the sheet feeding apparatus, and FIG. 5 is a side sectional view for explaining the operation of the sheet feeding apparatus.

  In the cassette 100, a front side regulating plate 1 and a side regulating plate back 2 for regulating the position of the sheet S in the depth direction are provided. These are configured to be movable in a direction substantially perpendicular to the sheet conveying direction in the cassette 100 in accordance with the size of the sheet S in the depth direction. Further, a rear end regulating plate 3 for regulating the position of the sheet S in the sheet conveying direction is provided, and similarly, it is configured to be movable in the sheet conveying direction in the cassette 100 according to the size of the sheet S. . On the back side 2 of the side regulating plate, there are provided air blowing ports 2a, 2b, and ducts 9, 12 are provided in communication therewith. The ducts 9 and 12 are respectively provided with fans 4 and 5 as examples of the air blowing means, and the fans 4 and 5 can blow air to the sheet S through the air blowing ports 2a and 2b. ing. The fans 4 and 5 can be independently driven by a signal from the controller 120 by a fan driver circuit (not shown).

  Further, shutters 10 and 11 that can be moved up and down by a swing motor 13 (see FIG. 6) are provided between the fan and the air blowing ports 2a and 2b. By the action of the shutters 10 and 11, the air blown from the air blowing ports 2a and 2b can be swung to enhance the sheeting effect (the details are described in JP-A-11-005643, which is a conventional example, I'll omit the explanation).

  Further, the duct 9 is extended in the opposite direction to the air blowing port 2a of the fan 5, and an air heating means including a heater 6 and a heat sink 7 is provided therein to warm the air sucked from the air intake port 9a. It becomes the structure which can be blown out from 2a. A thermistor 8 is attached to the heat sink 7, and the temperature of the heat sink surface can be detected. Further, the detection signal is transmitted to the controller 120, whereby ON / OFF control of the heater 6 is possible, whereby the temperature of the hot air from the blower opening 2a can be controlled.

  As described above, the fans 4 and 5, the ducts 9 and 12, the heater 6 and the heat sink 7, the thermistor 8, and the shutters 10 and 11 are all attached to the back side 2 of the side regulating plate, as shown in FIG. Even if the sheet size changes from S to S2, the positional relationship with the end portion of the sheet S can be always maintained. Further, in the case of the size of the sheet S2 shown in FIG. 3, since the sheet end face is smaller than the position of the air blowing port 2b, the air blowing by the fan 4 is wasted. In this case, the sheet size signal from the sheet size detecting sensor 14 is used. The driving of the fan 4 can be stopped independently.

  As shown in FIG. 4, the cassette 100 can be pulled out along the rails 19 and 20 in the front-rear direction (substantially perpendicular to the sheet conveying direction) in the figure. It can be pulled out from the main body to the near side. As shown in FIG. 2, the cassette 100 is provided with a protrusion 100a, and a cassette attachment / detachment sensor 17 is provided at a position facing the apparatus main body. Then, by the action of the cassette attaching / detaching sensor 17, it is possible to detect whether the cassette 100 is attached to the apparatus or pulled out.

  A lifter base 16 for loading sheets is provided in the cassette 100 and can be moved up and down by a lifter motor (not shown). Then, when the cassette 100 is pulled out of the apparatus for the user to set the sheet, it is detected by the cassette attachment / detachment sensor 17, and the lifter motor acts so that the lifter base 16 is lowered to the lower limit position. Is lifted, the lifter base 16 is configured to rise. A paper surface position detection sensor 15 is provided above the cassette 100, and the lifter motor is controlled by a signal from the paper surface position detection sensor 15. That is, when the cassette 100 is housed, the lifter motor acts so that the lifter table 16 is raised, but when the proper paper surface height is detected by the paper surface position detection sensor 15, the lifter motor stops and the proper paper surface height is set. Can be maintained. As the sheet S is sequentially fed from the top along with the feeding operation, the paper surface height gradually decreases. When the paper surface position detection sensor 15 is turned off, the lifter motor 16 is raised again. It is configured to act in the direction and always control the paper surface height within a certain range.

(Configuration of the top plate)
A top plate 18 is provided above the stacked sheets S. As described above, the movement of the sheet S is restricted within a certain range in the lateral direction (in the direction parallel to the stacking surface), but the top plate 18 suppresses the bending of the sheet S due to the swing air blowing.

  The top plate 18 is composed of two flat plate-shaped members (hereinafter referred to as flat plates 18a and 18b). A rotation fulcrum member 21 is fixed to a flat plate 18a located beside the side regulating plate back 2, and is pivotally supported with respect to a hinge 22 provided at the side regulating plate back 2.

  The flat plate 18a is provided with a pinion gear 23, and the flat plate 18b having the rack 24 can slide relative to the flat plate 18a. Thereby, even if the sheet size changes from S to S2 shown in FIG. 3, the flat plate 18b can be slid relative to the flat plate 18a, and the flat plate 18a and the front side of the side regulating plate 1 regardless of the sheet size set on the lifter base 16. The gap between the flat plate 18b and the side regulating plate back 2 can be kept constant. That is, the top plate 18 is provided so as to be able to expand and contract in a direction orthogonal to the sheet conveying direction according to the sheet size to be fed, and the above-described pickup roller on the upper surface of the sheet S regardless of the sheet size set on the lifter table 16. It is arranged so as to cover almost the entire area other than the vicinity of 101.

(Operation of sheet feeding device)
Next, the operation of the sheet feeding apparatus according to the present invention will be described. Note that the sheet feeding apparatus according to the present embodiment has the air blowing means that swings as described above. However, in the case of plain paper, since the sheet is originally less adsorbed, the sheeting operation using air during the feeding operation is performed. Is not necessary. As described above, when it is not necessary, the air-spreading operation is not performed, thereby shortening the printing time for the first sheet (time from feeding the first sheet until printing is finished and discharging it: FCOT). This allows the user to use the printer comfortably.

  The following describes a mode in which a whirling operation with air during the feeding operation of coated paper or the like is performed. First, when the user pulls out the cassette 100 from the apparatus in order to set a sheet, it is detected by the cassette attachment / detachment detection sensor 17, and the lifter motor acts so that the lifter base 16 is lowered to the lower limit position. Next, as shown in FIG. 5, the user rotates the top plate 18 about 90 ° so as to open and close about the rotation fulcrum member 21 to expose the sheet stacking surface of the lifter table 16, and then sets the sheet S. To do.

  When the cassette 100 is stored in the apparatus after the sheet is set, the cassette attachment / detachment detection sensor 17 detects the cassette mounting and rotates the lifter motor in the direction in which the lifter base 16 is raised. Accordingly, the paper surface position gradually rises, and when the paper surface position detection sensor 15 detects the paper surface, the lifter motor is stopped. Here, the temperature / humidity inside the cassette 100 is measured by the temperature / humidity sensor 108, and the temperature control temperature of the heater 6 is obtained in light of a control table (not shown). And it waits until the temperature control of the heater 6 is completed, and when the temperature control of the heater 6 is completed, the fans 4 and 5 and the swing motor 13 are turned on. Thereby, air is blown onto the side surface of the sheet S from the air blowing ports 2a and 2b. When the blown air enters between the sheets, the adsorption between the sheets is released, and the air is sufficiently produced.

  During the air blowing operation, since the air blown as described above enters between the sheets, the sheet S tries to bend. However, since the top plate 18 is provided in the vicinity of the upper surface of the sheet S, the amount of bending of the sheet S can be suppressed to be equal to or less than the gap between the upper surface of the sheet S and the top plate 18. During this air blowing operation, the retard feeding mechanism including the pickup roller 101, the feed roller 102, and the retard roller 103 is operated to separate and convey the sheets S one by one.

  By configuring as described above, it is possible to provide a highly accurate sheet feeding apparatus with less skew of the sheet and positional deviation in the width direction (a direction orthogonal to the conveyance direction). Further, since the air path of the air blown by the top plate 18 is stabilized and the air leakage is reduced, the air blowing effect is improved. In order to obtain these effects, it has been experimentally obtained that the optimum distance (gap) between the top plate 18 and the upper surface of the sheet S is about 5 mm to 10 mm. Moreover, the distance between the top plate 18 and the upper surface of the sheet S may be appropriately set by making it possible to adjust the attachment position of the top plate 18 to the back side plate 2 in the vertical direction. As a result, more optimal sheet feeding can be performed.

  In this embodiment, the top plate 18 is rotatably attached to the back side of the side regulating plate 2. However, the top plate 18 is attached to the frame of the sheet feeding device, and a rotation fulcrum is provided in the vicinity of the rear end regulating plate 3 so as to be rotatable. However, the same effect as described above can be obtained without impairing the sheet setting property.

  The present invention can be used for a sheet feeding apparatus that separates and feeds a sheet bundle one by one from a sheet bundle stacked in a sheet storage unit, and an image forming apparatus including the sheet feeding apparatus.

1 is a cross-sectional view of an image forming apparatus according to an embodiment. It is a top view of a sheet feeding apparatus. It is a top view of a sheet feeding apparatus. It is a main sectional view of a sheet feeding device. FIG. 10 is a side cross-sectional view illustrating the operation of the sheet feeding device. It is a figure explaining the example of the conventional image forming apparatus.

Explanation of symbols

S ... Seat 1 ... Front side regulating plate 2 ... Back side regulating plate 2a, 2b ... Blower port 3 ... Rear end regulating plate 4, 5 ... Fan 6 ... Heater 7 ... Heat sink 8 ... Thermistor 9 ... Duct 9a ... Intake port
10, 11 ... Shutter
12 Duct
13… Swing motor
14… Sheet size detection sensor
15… paper position detection sensor
16… Lifter stand
17… Cassette attachment / detachment detection sensor
18… top plate
18a, 18b ... flat plate
19, 20… Rail
21… Rotating fulcrum member
22… Hinge
23… pinion gear
24 ... Rack
100… cassette
100a ... Projection
101… Pickup roller
102… Feed roller
103… retard roller
104… Feed sensor
105… Conveying roller pair
106, 107… partition plate
108… temperature / humidity sensor
109 ... Sheet transport path
110… Registration roller pair
111… Laser scanner
112… Photosensitive drum
112a ... exposure position
112b ... transfer section
113… Mirror
114… Developer
115… Transfer charger
116… Separate charger
117… Conveyor belt
118… Fixing device
119… Discharge roller
119a… discharge sensor
120… Controller
130… Roller pair before registration
201 ... Scanning optical system light source
202… Platen glass
203… Original platen
204… Lens
205. Light receiving element
206 ... Image processor
207… Electric signal
208… Memory section
250… Automatic document feeder
1000… Printer
1001 ... Printer body
1002 ... Sheet feeding device
1003… Paper deck
1004 ... Sheet conveying device
1005 ... Image forming section
2000… Scanner
3057… sheet
3059… Feeding tray
3071… Air spraying means
3121… Electric motor
3123… Cam plate
3155… Feeding device
3157… Flow path moving means

Claims (7)

A sheet stacking unit configured to stack a plurality of sheets; a feeding unit configured to send out the sheets stacked on the sheet stacking unit; and a blowing unit configured to blow an air flow from a side of the sheets stacked on the sheet stacking unit. Sheet feeding device,
A top plate is provided near the upper surface of the stacked sheets,
The sheet feeding device according to claim 1, wherein the sheet feeding device suppresses bending of the sheet caused by an air flow blown from the blowing unit by the top plate. 2. The sheet feeding apparatus according to claim 1, wherein the top plate covers substantially the entire area of the sheet bundle stacked on the sheet stacking unit. 3. The sheet feeding apparatus according to claim 1, wherein the top plate is composed of two flat plates and can be expanded and contracted according to the size of the sheets stacked on the sheet stacking means. 2. The sheet feeding apparatus according to claim 1, wherein the top plate is rotatably attached to the sheet stacking means, and is configured to expose a sheet stacking surface by rotating. The sheet feeding apparatus according to claim 1, wherein a gap between the top plate and the sheet upper surface can be changed. The gap between the top plate and the upper surface of the sheet can be changed by moving the top plate, and the distance between the top plate and the upper surface of the sheet is in a range of 5 mm to 10 mm. Sheet feeding device. The sheet feeding device according to any one of claims 1 to 6,
Conveying means for conveying the fed sheet;
An image forming apparatus comprising: an image forming unit that forms an image on a conveyed sheet.

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