Patent Application
20100209163
The present application is based on Japanese Patent Application No. 2009-031057 filed with Japanese Patent Office on Feb. 13, 2009, the entire content of which is hereby incorporated by reference.
1. Technical Field
The present invention relates to a sheet feeding device that is used for an image forming apparatus such as a copying machine, a printer, a facsimile machine, a printing machine and a multi-functional peripheral, and in particular, to a sheet feeding device wherein a single sheet is separated to be fed out from a sheet bundle through air-blowing, and to an image forming apparatus equipped with the sheet feeding device.
2. Background of the Invention
In recent years, uses for a copying machine and a printer have been expanded, and sheets of various types including coated paper have come to be used. Some of these sheets of various types show strong sticking power between respective sheets when they are stacked as a sheet bundle, whereby, an occasion where it is difficult to surely prevent multiple-sheet feeding tends to be caused, in a sheet feeding device that feeds out sheets one sheet by one sheet with a friction roller.
Therefore, there has been proposed a method wherein an air-blowing outlet is provided on a flank of the stacked sheet bundle in the sheet conveyance direction, and air is blown against plural sheets on the upper part of the stacked sheet bundle from this air-blowing outlet, so that air may pass between the sheets and plural sheets may be separated from the sheet bundle.
The sheet separated in this manner is sent to an image forming section one sheet by one sheet by a sheet-feeding roller, and in the case of image forming apparatuses such as printing machines, some of them employ a conveying method for the uppermost sheet on the stacked sheet bundle by using an adsorption belt, while attracting the sheet through suction. What is popular generally in this method is one having the structure wherein an air-blowing outlet that blows air against a sheet leading edge from the downstream side in the sheet conveyance direction is provided separately, and air is blown against a sheet leading edge from this air-blowing outlet to separate a single sheet only.
However, a sheet having high smoothness like coated paper has a characteristic to stick to each other strongly under the environmental condition of high humidity, and therefore, if a flow of air blown from the side to gaps of sheets is weak, it is impossible to separate sticking sheets from the sheet bundle and to cause the sheets to be lifted.
To solve this problem, air-blowing to lift the sheets may be made to be strong. However, if the air-blowing is made to be strong, there is generated air pressure that lifts up not only the sheet to be stuck on an adsorption belt but also plural sheets from the lower portion to press them against the adsorption belt. When air that lifts up sheets enters the gaps between sheets and plural sheets are lifted up, even if trying to separate and scrape off the useless sheet by blowing air from the front under the aforesaid condition, it is not possible to separate properly because of a collision between the aforesaid air and air to lift up, resulting in a cause for multiple-sheet feeding.
To solve this problem, Unexamined Japanese Patent Application Publication No. 2008-239312, for example, discloses a sheet feeding device wherein, when a sheet is stuck to an adsorption belt, air coming from the side is stopped to blow only air from the front side against the sheet, and thereby, to scrape off sheets other than the sheet that is stuck to the adsorption belt.
If this technology is employed, a collision between air from the front side and air from the flank side is not caused, and sheets other than the sheet that is stuck to the adsorption belt are scraped off properly.
However, even when the sheet feeding device disclosed in Unexamined Japanese Patent Application Publication No. 2008-239312 is used, it is difficult to cope with all sheets having various sheet types and various sizes (including thickness). In particular, in the case of a sheet that is small in size and is thin in thickness, there is a problem that plural sheets fly up to cause multiple-sheet feeding when air from the flank side is stopped and air from the front side is blown. For this problem, the inventors of the present invention found out through experiments that flying up of sheets can be inhibited by blowing air in a small air flow quantity from the flank side without stopping the air flow from the flank side when blowing air from the front side.
However, in the case of a sheet that is large in size and is thin in thickness, there still is a problem that sheets including the second sheet and thereafter are blown up and multiple-sheet feeding and sheet jamming are caused even when an air flow quantity is made to be small, if blowing of air from the side is continued even after the uppermost sheet in a sheet bundle is stuck on the adsorption belt.
An objective of the invention is to solve the aforesaid problems and to provide a sheet feeding device that is free from the problem of multiple-sheet feeding even for sheets having various sizes (including thickness), and has stable sheet conveyance properties.
The aforesaid objectives of the invention can be attained by the following constructions.
Item 1: A sheet feeding device including:
a sheet feeding tray on which a sheet bundle including a plurality of sheets is stacked;
a first air blowing section which blows air in a perpendicular direction to a sheet conveyance direction against a lateral side of the sheet bundle stacked on the sheet feeding tray;
a second air blowing section which blows air against a leading edge of the sheet bundle in a sheet conveyance direction from a downstream side in the sheet conveyance direction,
a sheet adsorption conveyance section which adsorbs by air suction and conveys sheets one by one from an uppermost sheet of the sheet bundle;
a sheet type information transmission section which transmits type information of the sheet to be used;
a shielding member which is arranged to be capable of opening and closing in a ventilating path of the first air blowing section to open or shield the ventilating path;
a shielding state switching section which switches a shielding state of the ventilating path by the shielding member to any one state of opening, partial shielding and overall shielding, wherein in the partial shielding state, less amount of air is allowed to pass than the amount of air in the opening state, and the air is totally shielded in the overall shielding state;
a sheet adsorption detecting section which detects that the uppermost sheet in the sheet bundle has been adsorbed, and transmits detection information to the sheet adsorption conveyance section, and
a control section which controls the shielding member and the shielding state switching section to operate and switch among the state of opening, partial shielding and overall shielding of the ventilating path, in accordance with the information from the sheet type information transmission section and the sheet adsorption detecting section.
Item 2: The sheet feeding device of Item 1, further including a sheet ejection detecting section which detects that the sheet adsorbed by the sheet adsorption conveyance section is ejected, and transmits the information of detection,
Wherein the control section controls the shielding member and the shielding state switching section to operate and switch among the state of opening, partial shielding and overall shielding of the ventilating path, in accordance with the information from the sheet type information transmission section and one of the information from the sheet adsorption detecting section or the sheet ejection detecting section.
These and other objects, advantages and features of the invention will become apparent from the following description thereof taken in conjunction with the accompanying drawings in which:
Each of
Each of
Each of
Each of
Referring to drawings, there will be explained, as follows, an embodiment of the invention, to which, however, the invention is not limited.
The embodiment of the invention will be explained as follows, referring to the drawings.
The illustrated image forming apparatus main body A is composed of an image forming section having therein photoconductor (image carrier) 1, charging unit 2, image-wise exposure unit 3, developing unit 4, transfer section 5 and cleaning section 6, fixing unit 7 and of a sheet conveyance system.
The sheet conveyance system is composed of sheet feed cassette 10, first sheet feeding section 11, second sheet feeding section 12, sheet ejection section 14, conveyance path switching section 15, circulation sheet re-feeding section 16 and of reversing sheet ejection section 17.
Document d placed on a document platen of the automatic document feeder DF is conveyed by a sheet feeding section, then, images on one side or both sides of document d are read out by an optical system of the image reading device SC, and are read in by image sensor CCD. Analog signals obtained through photoelectric conversion conducted by image sensor CCD undergo analog processing, A/D conversion, shading correction and image compression processing, in image processing section 20, and then, image signals are sent to image-wise exposure unit 3.
In the image forming section, there are conducted processes such as electrical charging, exposure, developing, transferring, separating and cleaning.
In the image forming section, electric charges (negative charging in the present embodiment) are given to photoconductor 1 by charging unit 2, and an electrostatic latent image is formed by irradiation of a laser beam coming from image-wise exposure unit 3, thus, the electrostatic latent image is visualized by the developing unit 4 to become a toner image (negative electric charge in the present embodiment). After that, sheet P loaded in the sheet feed cassette 10 is conveyed from the first sheet feeding section 11. The sheet P is conveyed after being synchronized with the toner image in the second sheet feed section 12 that is composed of registration roller. After that, the toner image is transferred onto the sheet P in the transfer section 5, and the toner image thus transferred is fixed by the fixing unit 7.
The sheet P subjected to fixing is ejected out of the apparatus by the sheet ejection section 14. On the other hand, toner remaining on the photoconductor 1 after the transfer processing is eliminated by cleaning section 6. Incidentally, in the case of duplex copying, sheet P on which an image has been formed on the first surface is fed into circulation sheet re-feeding section 16 to be reversed, and then, an image is formed again on the second surface in the image forming section, to be ejected out of the apparatus by the sheet ejection section 14. In the case of reversing and ejecting, the sheet P that has branched from a regular sheet ejection path is subjected to switchback in reversing sheet ejection section 17 to be reversed inside out, and then, is ejected out of the apparatus by the sheet ejection section 14.
Control section 80 is arranged inside image forming apparatus main body A to control operations of respective sections including the image forming apparatus main body A, image reading device SC, automatic document feeder DF and large capacity sheet feeding device LT.
The large capacity sheet feeding device LT connected to the image forming apparatus main body A has therein sheet feeding device main body 30, first air blowing section 40, second air blowing section 50 and sheet adsorption conveyance section (sheet feeding section) 60, and it houses large quantities of sheets P to feed them to the image forming apparatus main body A one sheet by one sheet.
The sheet feeding device main body 30 has therein sheet feeding tray 31, leading edge regulating member 32, trailing edge regulating member 33 and guide rail 34. The sheet feeding tray 31 is structured to be in three steps, and each sheet feeding tray 31 is structured to be capable of being drawn from the large capacity sheet feeding device LT by the guide rail 34.
In the drawings mentioned above, stacked plural sheets P are placed on the sheet feeding tray 31 as a sheet bundle which is housed by an unillustrated mechanism to be capable of going up and down. Side portion regulating member 41 is arranged to be movable freely in the direction (sheet width direction in the present example) that intersects the sheet conveyance direction for sheet P, and it regulates positions of both sides of the sheet bundle by pressing both sides of the sheet bundle lightly, for the sheet bundle. The leading edge regulating member 32 regulates a position of the leading edge of sheet P in the sheet conveyance direction, while, the trailing edge regulating member 33 is arranged to be movable freely in the sheet conveyance direction, and it regulates a position of the trailing edge of sheet P in the sheet conveyance direction.
Further, as shown in
For keeping the optimum height for air blowing and for adsorption of sheet P, for a sheet bundle stacked on the sheet feeding tray 31, the control section 80 drives an unillustrated motor for rise and fall based on the detection by the sheet height detection sensor PS3 shown in
As shown in
When the adsorption belt 63 is rotated while sucking sheet P on the uppermost layer of the sheet bundle stacked on the sheet feeding tray 31, the sheet P is conveyed in the direction of illustrated arrow X, and is fed into image forming apparatus main body A.
Sheet adsorption detecting sensor PS1 representing a sheet adsorption detecting section relating to the invention is arranged in the vicinity of an adsorption surface of the adsorption belt 63, and it detects that the upper surface of sheet P on the uppermost layer of the sheet bundle has been stuck, and transmits detection signals as sheet detection information.
Feed sensor PS2 serving as a sheet ejection detecting section relating to the invention is arranged in the vicinity of the adsorption belt 63 that is at the downstream side in the sheet conveyance direction of the sheet feeding tray 31, and it detects a passage of sheet P ejected from sheet adsorption conveyance section 60, to transmit signals serving as sheet detection information.
In the vicinity of the adsorption belt 63 that is at the downstream side in the sheet conveyance direction of the sheet feeding tray 31, second air blowing section 50 is fixed on sheet feeding device main body 30. The second air blowing section 50 is composed of an electric fan and others, and it blows air against the leading edge of the sheet bundle in the sheet conveyance direction from the downstream side in the sheet conveyance direction. Meanwhile, the second air blowing section 50 may also be in the construction wherein the second air blowing section 50 is attached on the sheet feeding device main body 30, and it blows air against the leading edge of the sheet bundle through a duct.
Electric fan 51 of the second air blowing section 50 is installed with its air-blowing outlet 53 facing upward. The air that is blown upward is changed in terms of direction by guide plate 52 to be blown out from the air-blowing outlet 53 upward obliquely, thus, air is blown against the vicinity of the adsorption belt 63 of sheet adsorption conveyance section 60.
A method of driving the second air blowing section 50 varies depending on types of sheet P. Namely, in the case of sheets including an OHP film, a tracing paper, a coated paper whose surface is smooth, a sheet subjected to processing of perforations and creasing, and a sheet on which powder is coated after offset printing, air is blown in a gap between sheets to ensure sheet separation.
As shown in
The first air blowing section 40 is arranged inside the side portion regulating member 41. The electric fan 42 is installed with its air-blowing outlet that faces upward. The air that is blown upward is changed in terms of direction by air-blowing guide 43 by 90 degrees, and is blown out of air-blowing outlet 41a in the horizontal direction. The air-blowing outlet 41a is opened in the vicinity of the upper end of the side surface where side portion regulating member 41 comes in contact with sheet P. A width of the air-blowing outlet 41a is almost the same as a width of a nozzle of the first air blowing section 40. Desirable positional relationship of sheet P on the uppermost layer is at almost the center between the upper end and the lower end of the air-blowing outlet 41a. Since the first air blowing section 40 is installed inside the side portion regulating member 41, the first air blowing section 40 can also be moved together by moving the side portion regulating member 41, even when a size of sheet P is changed. Meanwhile, though the first air blowing section 40 is provided on each of both sides of sheet P and the air-blowing outlet 41a are provided on each of both sides of sheet P in the present example, each of them can also be provided only on one side of sheet P.
When the first air blowing section 40 is driven, air is ejected from the air-blowing outlet 41a, and air is blown against several sheets positioned at an upper portion of the stacked sheets P. The air is blown from the end portion of sheets P on one side to the end portion on the other side through a gap between sheets. The air passes through gaps between sheets from the end portion on one side of sheet P and is blown against an end portion on the other side of sheet P. Owing to this, several sheets in the upper portion of sheets P are separated into individual sheets. The sheet adsorption conveyance section 60 takes out only the uppermost sheet from these separated sheets P, and sends it surely to the downstream side.
As shown in
a and 6b are sectional views showing a sheet adsorption conveyance process by the first air blowing section 40 and the second air blowing section 50.
a shows a sheet adsorption process. Sheets P in a small quantity in the upper layer of a sheet bundle stacked on sheet feeding tray 31 are lifted up defying their empty weight by the first air blowing V1 (illustrated outlined arrow) blown up by the first air blowing section 40, and are stuck by inspiration V3 (illustrated outlined arrow) by negative pressure of adsorption belt 63. The second air blow V2 (illustrated outlined arrow) blown up by the second air blowing section 50 blows against the vicinity of the front bottom portion of the adsorption belt 63. Sheet adsorption detecting sensor PS1 is arranged on an inner side of the adsorption belt 63, and it detects sheet P sticking to the adsorption belt 63 through a hole having a small diameter formed on the adsorption belt 63. The sheet adsorption detecting sensor PS1 that has detected adsorption of sheet P transmits the detection signals to control section 80.
b shows a process of sheet separation. When the sheet adsorption detecting sensor PS1 detects sheet P sticking to the adsorption belt 63, if the shielding member 45 shields an air intake of the first air blowing section 40 to stop the air blowing or to restrict the air blowing, the air blow by the second air blowing section 50 passes through a space between sheet P1 on the uppermost layer and a sheet of sheet P2 that is below the sheet P1. The sheet P1 on the uppermost layer is stuck by intake air V3 of the sheet adsorption conveyance section 60, and is separated from sheet P of the sheet bundle excluding the sheet P1 on the uppermost layer. Sheet P2 that is below the sheet P1 on the uppermost layer thus separated descends with its own weight in the direction of an arrow, to be received on sheet P.
When air blowing of the first air blowing section 40 and air blowing of the second air blowing section 50 are repeated in the aforesaid way, floating of several sheets P2 on the upper portion of the sheet bundle is spread on the most part of the entire surface of the air-blowing outlets 41a and 53, and respective gaps between sheets become identical roughly in terms of a space. Thus, air passes through this gap. Owing to this, separation of sheet P1 is improved, to make sheet P1 to be fed out easily. Thus, the foregoing solves the problems that floating of sheet P1 grows excessively great to damage sheets, and plural sheets floating together without being separated to make the sheet separation to be impossible.
After the separation of sheet P1 from sheet P2 comes to an end, an unillustrated drive section of the sheet adsorption conveyance section 60 starts its driving, and single sheet P1 sticking to the adsorption belt 63 is conveyed.
In
Cam CM serving as a stopper member representing a shielding state switching section relating to the invention is arranged inside the side portion regulating member 41, and it is held to be rotatable freely with rotation shaft KJ2 combined integrally that serves as a center of rotation. On the cam CM, there are formed first contact portion CMa located at the position to be farthest from rotation shaft KJ2, non-contact portion CMc located at the position close to the rotation shaft KJ2 and second contact portion CMb located at the position between the first contact portion CMa and the non-contact portion CMc. The rotation shaft KJ2 is connected with an unillustrated motor or the like, and is established so that shielding member 45 may stop at the position where the shielding member 45 touches the first contact portion CMa of cam CM or the second contact portion CMb, or the position where the shielding member 45 faces the non-contact portion CMc. As a motor to be connected with the rotation shaft KJ2, there is used a servo-motor or a stepping motor which is controlled to stop at the aforesaid position.
In
Though the rotatable cam CM serves as a stopper member in the present embodiment, the stopper member may also be a stopper member that is moved by a motor or the like in the direction perpendicular to air intake 41b.
By using a sheet feeding device having the structure relating to the present embodiment, it is possible to obtain, with a simple construction, an appropriate quantity of air blow corresponding to a sheet size, and to establish a set point of a air blow quantity easily to an optional value.
In
In
Incidentally, though the construction where the shielding member moves linearly is employed in the present embodiment, it is also possible to employ the construction wherein a shielding member having a shielding section and a partial shielding section rotates about a rotation axis, and to employ the construction wherein a shielding member having a shielding section, a partial shielding section and an opening section rotates.
In the present embodiment, a air flow quantity can be changed accurately by a simple structure, because a tolerance of dispersion for the stop position of the sliding shielding member 45 is broad.
In
In the present embodiment, a shielding state switching section is composed of cam CM and auxiliary shielding member 46. Operations of opening and closing shielding member 45 are carried out by operations of rotation about the rotation center by rotation shaft KJ2 of cam CM arranged inside the side portion regulating member 41, and cam CM is operated by solenoid SOL1.
The auxiliary shielding member 46 is held to be capable of rotating freely on rotation shaft KJ1 and is held to be capable of sliding freely on rotation shaft KJ1, similarly to the shielding member 45. The pressing spring SP1 is fixed on rotation shaft KJ1, and it presses auxiliary shielding member 46 against the shielding member 45, and urges the shielding member 45 in the direction for shielding the air intake 41b representing a ventilating path. Further, the auxiliary shielding member 46 is connected to solenoid SOL2 through connection plate 47 to be moved, by on-off of the solenoid SOL2, to any one of the first position where vent hole 45c and vent hole 46a agree with each other in terms of a phase, and the second position where the phases are deviated from each other. The connection plate 47 is engaged with the auxiliary shielding member 46 to be held on rotation shaft KJ1 to be slidable freely, and is connected to solenoid SOL2 to cause the auxiliary shielding member 46 to slide through on-off of the solenoid SOL2. Symbol SG represents a sliding guide that guides the sliding connection plate 47, while, symbol SP2 represents a returning spring that returns the auxiliary shielding member 46 to the first position from the second position through the connection plate 47 in the case of off of the solenoid SOL2. A size and the number of vent holes 45c and 46a are set to values with which an appropriate air flow quantity based on experiments are obtained depending on a type and a size (including a thickness) of the sheet to be used. Further, in the partial shielding state shown in
In
Incidentally, though there is employed the construction wherein the auxiliary shielding member moves linearly in the present embodiment, it is also possible to employ a construction wherein an auxiliary shielding member having a shielding section and a partial shielding section rotates about a rotation shaft.
In the present embodiment, an air flow quantity immediately after opening can be made to be large, because an air flow quantity can be changed with an accurate value in the simple structure, an amount of movement for each of shielding member 45 and auxiliary shielding member 46 can be made small, and a period of time from shielding to opening can be made short.
In
The sheet type information transmission section 70 relating to the invention is composed of an unillustrated operation section that inputs a size (including a thickness) of sheet P in advance, or of an unillustrated sheet size detecting sensor arranged inside large capacity sheet feeding device LT that detects information of longitudinal and lateral sizes of sheet P and transmits the information.
Further, although the sheet type information of sheets (sheet type information) coming from sheet type information transmission section 70 is made to be a sheet size (including a thickness), in the embodiment, information about coated paper, glossy paper or OHP film may also be made to be type information of sheets. Namely, it is a configuration where an optimum air flow quantity for the aforesaid sheets are inputted in the memory of control section 80 as a program in advance, and the air flow quantity is changed in accordance with a type of the sheet to be used.
Next, opening and closing operation timing of air intake 41b representing a ventilation path relating to the invention will be explained, referring to
In
Incidentally, though the shielding time of air intake 41b does not need to be exactly the same as the aforesaid timing, if it is limited to a moment of the start of feeding out of sheet P, a shielding time period becomes to be extremely short, sufficient effects for separation of sheet P cannot be obtained. Further, if the air intake 41b is on the state of continuous shielding when the sheet adsorption detecting sensor PS1 detects adsorption of sheet P, the sheet P is not stuck to adsorption belt 63 due to insufficient raising of the sheet p, and there is sometimes an occurrence of a problem of sheet feeding troubles. Namely, a problem of the sheet feeding troubles comes into existence, when a period of time for shielding is too long, and it is too short. As the best timing, the air intake 41b is closed before the start of sheet feeding, namely, when the sheet adsorption detecting sensor PS1 is in the state of on and when the feed sensor PS2 is in the state of off. In the case of sheet feeding, when the feed sensor PS2 is in the state of on, the air intake 41b is opened. The second sheet P2 is ejected, and the sheet adsorption detecting sensor PS1 is switched from the state of on to the state of off, then, the feed sensor PS2 is made to be in the state of off, and after a lapse of the designated time, the sheet adsorption detecting sensor PS1 is turned on again by the third sheet P3, thus, the air intake 41b is closed.
Based on experiments wherein sheet feeding devices equipped with the first-third shielding mechanisms are used, the inventors of the invention have confirmed that faborable sheet feeding can be practiced by changing an air flow quantity of air from the first air blowing section 40 that blows air against the side portion of sheets P, when a size (including a thickness) of sheet P is changed.
For example, in the case where sheet P is in a small size (for example, a sheet smaller than 35) and is thin (for example, a sheet with 45 kg or less), if the air intake 41b is made to be in the state of overall shielding after the first sheet P1 is stuck to adsorption belt 63, sheets P including the second sheet and thereafter are lifted up, resulting in a fear of occurrence of multiple-sheet feeding.
The sheet with 45 kg mentioned here is a sheet wherein a size is a 4×6 size (1091 mm in the longitudinal and 788 mm in the lateral direction) and a weight of 1000 sheets is 45 kg. When the air intake 41b is made to be in the state of overall shielding, there is a phenomenon that is caused when air coming from the first air blowing section 40 is intercepted, and only air coming from the second air blowing section 50 is blown against a small and thin sheet. For this problem, the inventors of the invention found out that excellent sheet feeding that is free from raising of sheets P for the second sheet and thereafter can be carried out, by making the air intake 41b to be in the state of partial shielding explained in the first-third shielding mechanisms without making the air intake 41b to be in the state of overall shielding, after sheet P1 is stuck to adsorption belt 63.
Further, in the case where sheet P is in a large size (for example, a sheet having a size of B4 or more) and is thin, if the air intake 41b is made to be in the state of partial shielding and gentle air is blown continuously after the first sheet P1 is stuck to adsorption belt 63, there is a fear that sheets P including the second sheet and thereafter are lifted up and multiple-sheet feeding is caused. In this case, therefore, the air intake 41b needs to be in the state of overall shielding. As explained above, it is necessary to change an air flow quantity of air to be blown against sheet P, depending on a size (including a thickness) of sheet P.
In
The sheet feeding device having the structure relating to the invention makes it possible to change easily an air flow quantity to be blown against sheet P depending on a size (including a thickness) of sheet P, which makes it possible to feed sheets stably, independently of sheet types.
Meanwhile, though the shielding member and the shielding state switching section both relating to the invention are provided on the side where air intake 41b side of the first air blowing section 40, in the present embodiment, they can also be provided inside of side portion regulating member 41, or in the vicinity of air-blowing outlet 41a.
Further, as the sheet feeding device of the invention, large capacity sheet feeding device LT connected to image forming apparatus main body A has been explained. However, the invention can be applied also to sheet feed cassette 10 arranged inside image forming apparatus main body A.
The aforesaid objectives of the invention can be attained by the following configurations of embodiments.
A sheet feeding device including: a sheet feeding tray on which a sheet bundle including a plurality of sheets is stacked; a first air blowing section which blows air in a perpendicular direction to a sheet conveyance direction against a lateral side of the sheet bundle stacked on the sheet feeding tray; a second air blowing section which blows air against a leading edge of the sheet bundle in a sheet conveyance direction from a downstream side in the sheet conveyance direction, a sheet adsorption conveyance section which adsorbs by air suction and conveys sheets one by one from an uppermost sheet of the sheet bundle; a sheet type information transmission section which transmits type information of the sheet to be used; a shielding member which is arranged to be capable of opening and closing in a ventilating path of the first air blowing section to open or shield the ventilating path; a shielding state switching section which switches a shielding state of the ventilating path by the shielding member to any one state of opening, partial shielding and overall shielding, wherein in the partial shielding state, less amount of air is allowed to pass than the amount of air in the opening state, and the air is totally shielded in the overall shielding state; a sheet adsorption detecting section which detects that the uppermost sheet in the sheet bundle has been adsorbed, and transmits detection information to the sheet adsorption conveyance section, and a control section which controls the shielding member and the shielding state switching section to operate and switch among the state of opening, partial shielding and overall shielding of the ventilating path, in accordance with the information from the sheet type information transmission section and the sheet adsorption detecting section.
The sheet feeding device of Item 1, further including a sheet ejection detecting section which detects that the sheet adsorbed by the sheet adsorption conveyance section is ejected, and transmits the information of detection, wherein the control section controls the shielding member and the shielding state switching section to operate and switch among the state of opening, partial shielding and overall shielding of the ventilating path, in accordance with the information from the sheet type information transmission section and one of the information from the sheet adsorption detecting section or the sheet ejection detecting section.
The sheet feeding device of Item 1 or 2, wherein the shielding member is urged in a direction to shield the ventilating path, and the shielding state switching section comprises a movable stopper member which contacts the shielding member, the stopper member having a first contact portion, a second contact portion and a non-contact portion, wherein the stopper is configured to move positions of the first, second and non-contact portions against the shielding member, such that: the ventilating path is in the state of opening when the first contact portion is at the position of contacting the shielding member; the ventilating path is in the state of partial shielding where the ventilating path is narrower than that in the state of opening when the second contact portion is at the position of contacting the shielding member; and the shielding member is separated from the non-contact portion and the ventilating path is in the state of overall shielding when the non-contact portion is at the position of facing to the shielding member,
wherein, the control section controls the stopper member to operate and switch among the state of opening, partial shielding and overall shielding of the ventilating path, in accordance with the information from the sheet type information transmission section and the sheet adsorption detecting section.
The sheet feeding device of Item 1 or 2, wherein the shielding member comprises a shielding section that makes the ventilating path to be in the state of overall shielding, and a partial shielding section that makes the ventilating path to be in the state of partial shielding, and the shielding member being capable of sliding to open and close the ventilating path, wherein the shielding state switching section comprises a shielding member drive section which drives to slide the shielding member, wherein control section operates the shielding member through the shielding member drive section to switch among the state of opening, partial shielding and overall shielding of the ventilating path, in accordance with the information coming from the sheet type information transmission section and the sheet adsorption detecting section.
The sheet feeding device of Item 1 or 2, wherein the shielding member is urged in a direction to shield the ventilating path, and has a first partial opening section that makes the ventilating path to be in the state of partial shielding in a case of shielding, wherein the shielding state switching section comprises a movable stopper member that contacts with the shielding member; an auxiliary shielding member arranged to be capable of sliding between a first position and a second position with respect to the shielding member; and an auxiliary shielding member drive section that drives the auxiliary shielding member, wherein the auxiliary shielding member has a second partial opening section, and the stopper member has a contact portion and a non-contact portion, wherein when the contact portion of the stopper member is at the position of contacting the shielding member the ventilating path is made to be in the open state; when the non-contact portion of the stopper member is at the position facing the shielding member, and the second partial opening section of the auxiliary shielding member is at the first position where the second partial opening section agrees in phase with the first partial opening section, the ventilating path is made to be in the partial shielding state; and when the non-contact portion of the stopper member is at the position facing the shielding member, and the second partial opening section of the auxiliary shielding member is at the second position where the second partial opening section is deviated in phase from the first partial opening section, the ventilating path is made to be in the state of overall shielding, wherein the control section controls the shielding member, the stopper member and the auxiliary shielding member to operate and switch among the state of opening, partial shielding and overall shielding of the ventilating path, in accordance with the information coming from the sheet type information transmission section and the sheet adsorption detecting section.
The sheet feeding device of any one of Items 1 to 5, wherein the sheet type information comprises information of a longitudinal size, a lateral size and a thickness of the sheet.
An image forming apparatus including: an image forming section for forming an image on an image carrier; a transfer section that transfers an image on the image carrier onto a sheet; and
a sheet feeding device which includes: a sheet feeding tray on which a sheet bundle including a plurality of sheets is stacked; a first air blowing section which blows air in a perpendicular direction to a sheet conveyance direction against a lateral side of the sheet bundle stacked on the sheet feeding tray; a second air blowing section which blows air against a leading edge of the sheet bundle in a sheet conveyance direction from a downstream side in the sheet conveyance direction, a sheet adsorption conveyance section which adsorbs by air suction and conveys sheets one by one from an uppermost sheet of the sheet bundle; a sheet type information transmission section which transmits type information of the sheet to be used; a shielding member which is arranged to be capable of opening and closing in a ventilating path of the first air blowing section to open or shield the ventilating path; a shielding state switching section which switches a shielding state of the ventilating path by the shielding member to any one state of opening, partial shielding and overall shielding, wherein in the partial shielding state, less amount of air is allowed to pass than the amount of air in the opening state, and the air is totally shielded in the overall shielding state; a sheet adsorption detecting section which detects that the uppermost sheet in the sheet bundle has been adsorbed, and transmits detection information to the sheet adsorption conveyance section, and a control section which controls the shielding member and the shielding state switching section to operate and switch among the state of opening, partial shielding and overall shielding of the ventilating path, in accordance with the information from the sheet type information transmission section and the sheet adsorption detecting section, wherein a transfer section transfers the image on the image carrier onto the sheet conveyed from the sheet feeding device.
By the use of the sheet feeding device having the structure in the invention, it is possible to offer a sheet feeding device that is free from the problem of multiple-sheet feeding even for sheets having various sizes (including thicknesses), especially for sheets which are small in size and thin in thickness, and has stable quality.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2009-031057 | Feb 2009 | JP | national |
