Patent Application
20080079216
Hereinafter, one embodiment of the present invention is described with reference to
First, with reference to
As shown in
Any desired image forming method of the image forming apparatus 2 can be selected from an electrophotographic method, an electrostatic recording method, an ink jet method and the like. For example, in the case of adopting the electrophotographic method, the image forming apparatus 2 is constructed to include a photoconductive drum, a charger, an exposing device, a developing device, a cleaner, a fixing device, etc.
The photoconductive drum is disposed rotatably about its shaft center and has an electrostatic latent image and a toner image formed on the outer circumferential surface thereof while being rotated. The toner image on this outer circumferential surface is transferred to the sheet P to form an image on the sheet P.
The charger uniformly charges the outer circumferential surface of the photoconductive drum. The exposing device irradiates the uniformly charged outer circumferential surface of the photoconductive drum with a beam based on image information of a document image read by an image reader, thereby forming an electrostatic latent image. The developing device forms a toner image by supplying toner particles to the electrostatic latent image formed on the outer circumferential surface of the photoconductive drum. The cleaner cleans the outer circumferential surface of the photoconductive drum by removing the toner residual on the outer circumferential surface of the photoconductive drum after an operation of transferring the toner image to the sheet. The fixing device fixes the toner image to the sheet having the toner image transferred from the outer circumferential surface of the photoconductive drum and includes, for example, a fixing roller internally provided with a heating element and a pressure roller whose outer circumferential surface is held in contact with the outer circumferential surface of the fixing roller.
The sheet feeder 1 includes slide rails 1a and casters 1b at the bottom and is movable along a direction shown by an outline arrow G (same in
A lid 1c is provided on the upper surface of the sheet feeder 1. A supporting point is provided in a direction normal to the plane of
Next, the construction of the sheet feeder 1 is described with reference to
As shown in
The width restricting guides 3a, 3b are formed by bending plate-like members, have a substantially L-shaped vertical cross section and restrict the sheets P in a direction parallel to the sheet feeding direction. The width restricting guides 3a, 3b are, for example, formed of a steel plate. It should be noted that holes 31 are formed near the upper ends of the width restricting guides 3a, 3b. Further, inserting portions 32 are provided at the bottom ends of the width restricting guides 3a, 3b (see
The width restricting guides 3a, 3b have slants 35 at upper ends 34 of contact surfaces 33 to be brought into contact with the sheets P. By having the slants 35, the user can place his hand holding the sheets P to be replenished on the slant 35 during the replenishment of sheets, thereby being able to ensure a hand placing space during the replenishment of sheets. Thus, an operation of replenishing the sheet feeder 1 with sheets can be easily performed. It should be noted that the angle of the slants 35 can be suitably set.
Further, each of the width restricting guides 3a, 3b is formed with two ribs 36 extending in an inserting direction of the sheets P from the contact surface 33 with the sheets P, to the slant 35 and to the upper ends of the width restricting guide 3a, 3b. As compared to the case where the upper ends of the contact surfaces 33 are at right angles, friction between the width restricting guides 3a, 3b and the sheets P becomes larger if the sheets P to be replenished are placed on the slants 35 during the replenishment of sheets. However, if one or more ribs 36 are provided, resistance resulting from such friction can be largely reduced.
The rear end guides 4a, 4b are for restricting the rear end position of the sheets P in the direction normal to the sheet feeding direction. Structurally, each rear end guide 4a, 4b is formed by bonding two members, i.e. an engaging member 41 to be fixed to the sheet feeder 1 and a rear-end guiding member 42 for restricting the position by coming into contact with the rear end of the sheets P.
Each engaging member 41 is formed with a plurality of holes 43 in order to be engaged with engaging portions 52 provided on the upper end of each opposite side plate 51 of the sheet accommodating portion 5 (see
Inserting portions 44 are provided at the bottom ends of the rear-end guiding members 42 (see
The elevating plate 10 is constructed to be movable in vertical direction. A construction for driving the elevating plate 10 is described in detail later. The sheets P are stacked on this elevating plate 10 (stacked position of the sheets P is shown in broken line in
In this embodiment, the elevating plate 10 is formed with four through holes 12 through which the width restricting guides 3a, 3b are inserted and six through holes 13 through which the rear end guides 4a, 4b are inserted. By such a construction, the width restricting guides 3a, 3b and rear end guides 4a, 4b can restrict the position of the stacked sheets P from the bottom to the top of the sheet feeder 1. Further, since a plurality of through holes 12, 13 are formed, supported positions of the width restricting guides 3a, 3b and rear end guides 4a, 4b can be switched. This enables sheets P of various sizes such as A4, A3, B5 and B4 to be stacked in the sheet feeder 1.
The decorative laminates 11 are so arranged as to cover the engaging portions 52 of the sheet accommodating portion 5 to be described later (see
Next, the internal construction of the sheet feeder 1 and the construction of the sheet accommodating portion 5 are described in detail with reference to
As shown in
The sheet accommodating portion 5 is comprised of a bottom plate 53, the side plates 51 arranged in parallel with the sheet feeding direction shown by the arrow F in
The bottom plate 53 is formed with a plurality of slits 55a, 55b used to insert the inserting portions 32, 44 provided at the bottom ends of the width restricting guide 3a and rear end guide 4a. These slits 55a, 55b are formed in conformity with the respective sizes of the sheets P. Specifically, there are formed a plurality of slits 55a, 55b that come in two kinds, i.e. the slits 55a used to insert the width restricting guides 3a, 3b in the direction parallel to the sheet feeding direction and the slits 55b used to insert the rear end guides 4a, 4b in the direction normal to the sheet feeding direction. The bottom ends of the width restricting guides 3a, 3b and rear end guides 4a, 4b are supported by inserting the inserting portions 32 of the width restricting guides 3a, 3b into the slits 55a and inserting the inserting portions 44 of the rear end guides 4a, 4b into the slits 55b.
As shown in
The front ends of the sheets P in the sheet feeding direction are held in contact with the front plate 54. The stacked sheets P are discharged toward the image forming apparatus 2 from the vicinity of the upper end of the front plate 54. Thus, the height of the front plate 54 is slightly lower than that of the side plates 51. The sheets P are fed through a section defined by this height difference. In other words, this section becomes the sheet discharge portion 56. The feeding unit 6 is arranged at the position of the sheet discharge port 56 although not shown in
Further, the aforementioned elevating plate 10 is arranged in the sheet accommodating portion 5. In
Next, the construction of the feeding unit 6 is described with reference to
The feeding unit 6 is arranged at an upper part of the sheet feeder 1 before the sheets P in the sheet feeding direction (direction of the arrow F in
First, the sensors provided in the sheet feeder 1 are described. These sensors are for detecting the stacked state of the sheets. As shown in
On the other hand, out of the two sensors disposed to the right of the pickup portion 61 in the transverse direction of
The light blocking member 67 is for blocking light emitted in the recess 63a. As shown in
Here, the pickup portion 61 is supported on the same supporting point 68 as the light blocking member 67. If the uppermost one of the stacked sheets P comes into contact with the pickup portion 61 upon an upward movement of the elevating plate 10 and the elevating plate 10 continues to move upward, the pickup portion 61 is lifted upward. If this pickup portion 61 is lifted up, the light blocking member 67 is simultaneously lifted up. It should be noted that this pivoting direction is shown by a broken-line arrow in
Then, the insertable piece 67a of the light blocking member 67 inserted in the recess 63a of the upper limit detection sensor 63 is lifted up to change a light receiving state of the sensor. By detecting this change, the uppermost position of the stacked sheets P is detected.
Here, a detecting member 54a (sheet detection switch 54aa) provided not in the sheet feeder 6, but at the front plate 54 is described in connection with the sensors.
As shown in
The sheet detection switch 54aa is comprised of an actuator portion 54ab projecting from the front plate 54 and a sensor portion (not shown) provided in the front plate 54. When the front ends of the sheets P come into contact, the actuator portion 54ab of the sheet detection switch 54aa is pushed into the inside of the front plate 54. On the other hand, when the front ends of the sheets P are not in contact, the actuator portion 54ab projects. The sensor portion detects whether the actuator portion 54ab is projecting or pushed in. For example, an optical sensor can be used as the sensor portion.
When the sheets P are placed on the elevating plate 10 or placed on the uppermost one of the stacked sheets P on the elevating plate 10 upon the replenishment of sheets, the elevating plate 10 is lowered by a specified amount.
If the front ends of the stacked sheets P come into contact with the front plate 54 by the replenishment of sheets and the actuator portion 54ab of the sheet detection switch 54aa is pushed in, the sheet detection switch 54aa is recognized to be on. If the elevating plate 10 is lowered to bring the front ends of the sheets P in the uppermost part of the sheet stack out of contact with the actuator portion 54ab and the actuator 54ab projects from the front plate 54, the sheet detection switch 54aa is recognized to be off. Accordingly, there can be executed such a control as to lower the elevating plate 10 if the sheets P are replenished and the sheet detection switch 54aa is turned on and to stop a downward movement of the elevating plate 10 if the sheet detection switch 54aa is turned off. In other words, the sheet detection switch 54aa is used to properly determine an amount of the downward movement of the elevating plate 10.
Although the contact switch is shown in the above, a noncontact sensor or switch for detecting, for example, a reflected light may be used as the detecting member 54a.
Next, with reference to
A pickup roller 69 is provided in the pickup portion 61. The pickup portion 61 is formed by mounting a cover 61a around the pickup roller 69. The pickup roller 69 picks the sheets P up one by one by coming into contact with the uppermost one of the stacked sheets P, and feeds the sheets P toward the image forming apparatus 2. Sheet feeding timings are controlled in accordance with control signals transmitted from the image forming apparatus 2 to the sheet feeder 1. The pickup roller 69 is driven to rotate in such a direction as to feed the sheets P by a driving mechanism (not shown).
The feed roller pairs 64, 65 are arranged downstream of the pickup roller 69 in the sheet feeding direction. Here, out of the feed roller pairs 64, 65, the one closer to the pickup roller 69 is the feed roller pair 64 and the one more distant is the feed roller pair 65.
The respective rollers in the feed roller pairs 64, 65 are driven to rotate in specified directions by the driving mechanism (not shown). The respective rollers of each feed roller pair 64, 65 form a nip therebetween, and the sheets P are conveyed through these nips. For example, in order to prevent the multiple feed of the sheets P, the lower one 64a of the rollers of the feed roller pair 64 can be rotated in a direction opposite to the sheet feeding direction.
Next, with reference to
First, with reference to
The motor M is controlled to be rotatable in forward and reverse directions, and has the rotating direction thereof controlled depending on whether the elevating plate 10 is elevated or lowered. The endless belt 71 is for transmitting the torque to a rotary shaft 72a of the worm 72, and mounted between a rotary shaft of the motor M and the rotary shaft 72a of the worm 72. The worm 72 transmits the torque to the worm wheel 73. The worm wheel 73 transmits the torque to the gear 74. The gear 74 transmits the torque to the take-up pulley 75. In this way, the torque is transmitted from the motor M to the take-up pulley 75.
One end of the wire 70 is connected to the take-up pulley 75, and the other end is connected to the securing member 78 disposed near the upper edge of the side plate 51. The wire 70 is mounted on the pulley 76 disposed adjacent to the securing member 78 and the first roller 77 secured to the elevating plate 10. The wire 70 is mounted in the order of the take-up pulley 75, pulley 76, first roller 77 and securing member 78. Here, the pulley 76 and securing member 78 are supported or rotatably supported on a fixture 79 and secured at an upper part of the side plate 51 and above an opening 81.
The opening 81 is vertically formed from the upper side to the lower side of the side plate 51 to guide upward and downward movements of the elevating plate 10. The first roller 77 and a second roller 82 to be described later, which are secured to the elevating plate 10, are fitted in this opening 81.
Although not shown in
When the motor M is rotated in such a direction that the take-up pulley 75 takes up the wire 70 and a drive force is transmitted, the take-up pulley 75 takes up the wire 70. Thus, the length of the mounted wire 70 becomes shorter and the elevating plate 10 is elevated. In order to lower the elevating plate 10 on the contrary, the motor M may be rotated in a direction opposite to the above direction.
Next, with reference to
The motor M, endless belt 71, worm 72, worm wheel 73 and gear 74 constructing the elevating mechanism 7 are so accommodated in a box 7a as to be supported or pivotally supported. By doing so, the adherence of dust to tooth surfaces of the worm 72, worm wheel 73 and gear 74 can be avoided and the sheet feeder 1 can be more easily assembled by unitization.
The inclining mechanism 8 includes inclination holding members 84 and the openings 81 formed in the side plates 51. The inclination holding member 84 is comprised of the first roller 77 and second roller 82 as an engaging member 84a, and a mounting member 84b supporting the engaging member 84a and secured to the elevating plate 10.
As described above, the opening 81 formed in the side plate 51 functions as a guide when the elevating plate 10 is elevated and lowered, and the wire 70 is mounted on the first roller 77. Thus, the inclining mechanism 8 constitutes a part of the elevating mechanism 7. Accordingly, it is not necessary to provide the inclining mechanism 8 extra in addition to the elevating mechanism 7 and the construction of the sheet feeder 1 is simplified, which is advantageous in terms of costs and productivity. It should be noted that the first roller 77 is formed with a groove 77a and the wire 70 is fitted into this groove 77a.
The first and second rollers 77, 82 as the engaging member 84a are rotatably supported on one mounting member 84b and arranged one above the other. The mounting member 84b is secured to the side surface of the elevating plate 10. The positional relationship of the first and second rollers 77, 82 are such that the first roller 77 is located vertically above the second roller 82. The mounting member 84b is so secured to the elevating plate 10 that the rotary shafts of the first and second rollers 77, 82 are fitted in a direction perpendicular to the side plate 51.
Each opening 81 is formed from the top side to the bottom side of the corresponding side plate 51. The first and second rollers 77, 82 as the engaging member 84a are fitted in this opening 81. Width W of the openings 81 in horizontal direction is wider than outer diameters R of the first and second rollers 77, 82. It should be noted that the outer diameters R of the first and second rollers 77, 82 shown in
In other words, the outer diameters R of the first and second rollers 77, 82 are shorter than the width W of the opening 81. By this length difference, the elevating plate 10 is inclined downward with respect to a direction parallel to the sheet feeding direction F. However, the outer circumferential surfaces of the first rollers 77 at one side come into contact with vertical first edges 81a forming the openings 81 and those of the second rollers 82 at a side opposite to the contact side of the first rollers 77 come into contact with second edges 81b of the openings 81 facing the first edges 81a, whereby the elevating plate 10 has the inclination thereof restricted so as not to be inclined beyond a specific angle.
Each opening 81 is so formed in the side plate 51 as to be located at a side B behind a center C of an entire length A of the elevating plate 10 in the sheet feeding direction (see
By forming the openings 81 at positions displaced toward the rear ends of the sheets from the center of gravity of the elevating plate 10 with respect to the sheet feeding direction, the front ends of the stacked sheets P are always inclined downward by the action of gravity even if the sheets P of various sizes are placed on the elevating plate 10. The angle of inclination can be adjusted by the positions and the outer diameters R of the first and second rollers 77, 82 and the width W of the opening 81 and can be suitable set. For example, it is considered not to set an excessively large angle of inclination since a sheet jam is likely to occur if the elevating plate 10 is excessively inclined. For example, the elevating plate 10 can be regulated to be inclined downward by about 1 to 5°.
It should be noted that each opening 81 may also be formed at the center C (center of gravity) of the entire length A of the elevating plate 10 with respect to the sheet feeding direction or at a side D located before the center C (center of gravity) with respect to the sheet feeding direction. In such a case, a mounting angle of the mounting member 84b rotatably supporting the first and second rollers 77, 82 may be, for example, adjusted such that a straight line extending from the center of the second roller 82 toward that of the first roller 77 is not vertical and the center of the second roller 82 is slightly shifted toward the rear ends of the sheets. By such a method, the front side of the elevating plate 10 with respect to the sheet feeding direction can be inclined downward.
The interference of the elevating plate 10 with the width restricting guides 3a, 3b and rear end guides 4a, 4b might hinder the movement of the elevating plate 10. Accordingly, sufficient widths are ensured for the through holes 12, 13 lest the elevating plate 10 and the width restricting guides 3a, 3b and rear end guides 4a, 4b should interfere with each other.
Since the front ends of the sheets P stacked on the elevating plate 10 are constantly inclined downward, the sheets P can be constantly stacked at a proper position without being displaced toward the rear ends of the sheets. When the elevating plate 10 is elevated to constantly bring the uppermost sheet P into contact with the pickup roller 69, the position of the pickup roller 69 becomes proper. In other words, the pickup roller 69 comes to be positioned such that the picked-up sheet P can be properly fed to the feed roller pair 64 and the sheet conveyance path 66. Accordingly, troubles such as sheet jams and sheet feeding timing errors during the sheet feeding can be solved. Further, since the uppermost part of the stacked sheets P can be precisely detected by the sheet detection switch 54aa, there is no likelihood of troubling the sheet replenishing operation due to an insufficient downward movement of the elevating plate 10 to stop at an undesired position on the way to the desired one.
To make doubly sure, although only one side plate 51 is shown in
Here, the operation of the sheet feeder 1 during the replenishment of sheets is described. As described above, the sheet feeder 1 according to this embodiment can accommodate about four thousands sheets P although it depends on the thickness of the sheets P. Generally, 500 copy sheets are packaged. Accordingly, the sheet feeder 1 according to this embodiment can accommodate eight packages of copy sheets.
When a user replenishes the sheets P, he or she first opens the lid 1c provided atop the sheet feeder 1. By doing so, a hollow part of the sheet feeder 1 is exposed to the above, so that the sheets P can be replenished into the sheet accommodating portion 5. Here, the elevating plate 10 is lowered in conformity with the remaining amount of the sheets P. Specifically, the motor M is rotated to determine an amount of downward movement of the elevating plate 10 during the lapse of several seconds after the sheet detection switch 54aa is turned off. Since a period during which the motor M is kept rotated after the sheet detection switch 54aa is turned off is determined by various factors such as the height at which the downward movement of the elevating plate 10 is tended to be stopped, the position of the sheet detection switch 54aa and a downward moving speed of the elevating plate 10, this period can be suitably set. Accordingly, the rotation of the motor M may also be stopped immediately after the sheet detection switch 54aa is turned off.
Here, since the sheet feeder 1 of this embodiment is capable of accommodating a great number of sheets, it is difficult to perform the sheet replenishing operation if the elevating plate 10 is lowered straight to the lower limit position. Accordingly, a state where the downward movement is stopped is a state where the height of the stacked sheets P or that of the elevating plate 10 is such a height at which the user can easily place the sheets P.
Since the user cannot replenish as many sheets as four thousands at once, he or she repeatedly replenish the sheets, for example, by replenishing five hundreds sheets each time. Accordingly, the sheet feeder 1 of this embodiment lowers the elevating plate 10 by a specified amount as the sheets P are replenished. The sheet detection switch 54aa is also used for the control of the motor M accompanying this downward movement. By the detection of this sheet detection switch 54aa, the rotation of the motor M is controlled such that the uppermost one of the already stacked sheets P is at such a height as to enable easy replenishment. In other words, the motor M is driven if the sheet detection switch 54aa is on, whereas the driving of the motor M is stopped upon the lapse of several seconds after the sheet detection switch 54aa is turned off. The replenishment of the sheets P can be repeated until the elevating plate 10 reaches a lowest permissible level.
When the user closes the lid 1c of the sheet feeder 1, the elevating plate 10 is elevated as much as necessary. Specifically speaking, the elevating plate 10 is elevated until the uppermost one of the stacked sheets P comes into contact with the pickup portion 61. The control of the motor M accompanying this upward movement of the elevating plate 10 is executed by the aforementioned upper limit detection sensor 63. In other words, the motor M is driven while the insertable piece 67a of the light blocking member 67 is blocking light, and the driving of the motor M is stopped when the light blocking member 67 is lifted up to lift the insertable piece 67a up from the recess 63a, thereby being no longer able to block light.
As described above, the sheet feeder 1 of this embodiment is attached to the image forming apparatus 2, is provided with the sheet accommodating portion 5 including the bottom plate 53 and a plurality of side plates 51 perpendicular to the bottom plate 53 in order to accommodate a plurality of sheets P, and successively feeds the sheets to the image forming apparatus 2 from the uppermost one of the accommodated sheets. In the sheet feeder 1, the elevating plate 10 movable upward and downward and adapted to carry the sheets is provided in the sheet accommodating portion 5, and the inclining mechanism 8 for inclining the elevating plate 10 is so provided that the front ends of the sheets P are inclined downward in the sheet feeding direction.
Since the front ends of the sheets P are inclined downward in the sheet feeding direction, the sheets P in the sheet feeder 1 can be constantly stacked at a proper position without being displaced toward the rear ends of the sheets due to the weight thereof unlike the prior art. Thus, the uppermost sheet P can be precisely picked up out of the sheets stacked in the sheet feeder 1, and there is no likelihood of sheet jam and the like.
The sheet accommodating portion 5 includes the front plate 54 which is provided perpendicular to the bottom plate and with which the front ends of the stacked sheets P in the sheet feeding direction are in touch. The sheet detection switch 54aa as the detecting member 54a for detecting whether or not the front ends of the sheets P in the uppermost part of the sheet stack with respect to the sheet feeding direction are in touch is provided on this front plate 54. Thus, the front ends of the stacked sheets P are inclined downward in the sheet feeding direction and the sheets P are not displaced toward the rear ends of the sheets. Therefore, the position of the uppermost part of the sheets P can be reliably detected. Accordingly, an insufficient downward movement can be prevented if the elevating plate 10 is lowered in accordance with a signal from the sheet detection switch 54aa.
The inclining mechanism 8 includes a pair of openings 81 vertically extending and formed in the both side plates 51 which are opposite to each other and extend in the direction parallel to the sheet feeding direction, and the inclination holding members 84 provided at the opposite side surfaces of the elevating plate 10 extending in the direction parallel to the sheet feeding direction and engageable with the openings 81. The openings 81 are formed at such positions located behind the center of gravity (assumed to be the center C in this embodiment) of the elevating plate 10 with respect to forward and backward directions, i.e. the sheet feeding direction. Each inclination holding member 84 is comprised of the engaging member 84a (first and second rollers 77, 82) fittable into the opening 81, and the mounting member 84b supporting the engaging member 84a and secured to the elevating plate 10. The width of the engaging member 84a is set narrower than the width W of the opening 81.
By having the above construction, the angle of inclination of the elevating plate 10 can be kept constant. Accordingly, there is even less likelihood of swinging the sheets P stacked in the sheet accommodating portion 5 and displacing the sheets P toward the rear ends of the sheets, wherefore the sheet feeder 1 free from a sheet jam and the like can be provided. Further, although it might be thought to fix the elevating plate 10 at a specified angle, there are cases where the suitable position or angle of inclination of the elevating plate 10 cannot be obtained due to a fabrication error and the like. Contrary to this, since the elevating plate 10 is inclined due to the weight thereof in the present invention, the above errors can be absorbed.
The engaging member 84a includes two rollers disposed one above the other, i.e. the first and second rollers 77, 82, wherein the wire 70 used to elevate and lower the elevating plate 10 is placed on the first roller 77. The openings 81 serve as guides upon moving the elevating plate 10 upward and downward, and the inclining mechanism 8 constitutes a part of the elevating mechanism 7. According to such a construction, since the inclining mechanism 8 doubles as the part of the elevating mechanism 7, it is not necessary to specially provide the inclining mechanism 8 in addition to the mechanism for elevating and lowering the elevating plate 10 and the construction of the sheet feeder 1 can be simplified. Therefore, this construction is advantageous in terms of costs and productivity.
Although the embodiment of the present invention is described above, the scope of the present invention is not limited to this and various changes can be made without departing from the gist of the present invention. For example, although the elevating mechanism 7 uses the wire 70, any construction will do provided that it functions as the elevating mechanism 7.
The specific embodiment described above mainly embraces inventions having the following constructions.
A sheet feeder according to one aspect of the present invention comprises a sheet accommodating portion including a bottom plate and a plurality of side plates provided perpendicular to the bottom plate, and being capable of accommodating a plurality of sheets, the accommodated sheets being successively fed to the outside from the uppermost one; an elevating plate provided to stack the sheets in the sheet accommodating portion and movable upward and downward; and an inclining mechanism for inclining the elevating plate such that the front ends of the sheets are inclined downward in a sheet feeding direction during sheet feeding.
An image forming apparatus according to another aspect of the present invention comprises an apparatus main body for performing an image forming operation to sheets; and a sheet feeder for feeding the sheets to the apparatus main body, wherein the sheet feeder has the construction of the above sheet feeder.
According to the above sheet feeder or image forming apparatus, there is no likelihood of displacing the stacked sheets toward the rear ends thereof due to the weight of the stacked sheets as in prior art sheet feeders since the front ends of the sheets with respect to the sheet feeding direction are inclined downward. In other words, the sheets are constantly stacked at a proper position. Therefore, there is no likelihood of a sheet jam and the like since the uppermost one of the sheets stacked in the sheet feeder is precisely picked up.
In the above construction, the elevating plate is preferably inclined downward in the sheet feeding direction within a range of 1 to 5° with respect to horizontal direction. Further, the elevating plate is preferably inclined downward by the weight of the stacked sheets.
In the above construction, the inclining mechanism preferably includes a support member for pivotally supporting the elevating plate on both sides thereof extending in a direction parallel to the sheet feeding direction, the support member being provided on the elevating plate at a position that is in the rear of a center of gravity of the elevating plate with respect to the sheet feeding direction. According to this construction, the elevating plate can be readily inclined merely by placing sheets on the elevating plate.
In the above construction, it is preferable to further comprise a front plate which is provided perpendicular to the bottom plate of the sheet accommodating portion and with which the front ends of the stacked sheets with respect to the sheet feeding direction are in touch, and a detecting member for detecting whether or not the front ends of the sheets in an uppermost part of the stacked sheets with respect to the sheet feeding direction are in touch with the front plate.
According to this construction, the sheets stacked on the elevating plate are not displaced toward the rear ends of the sheets with the front ends thereof with respect to the sheet feeding direction inclined downward, wherefore the position of the uppermost sheet can be reliably detected if the detecting member is so disposed as to be brought into contact with the front ends of the sheets. Therefore, an insufficient downward movement of the elevating plate can be prevented if the elevating plate is lowered in accordance with a signal from this detecting member.
In the above construction, it is preferable that the inclining mechanism includes openings extending vertically and formed in the side plates which are opposite to each other and extend in a direction parallel to the sheet feeding direction and inclination holding members provided at the opposite side surfaces of the elevating plate extending in the direction parallel to the sheet feeding direction and fittable into the openings; that each inclination holding member includes an engaging member engageable with the corresponding opening and a mounting member supporting the engaging member and securing the engaging member to the elevating plate and the width of the engaging members is narrower than that of the openings.
In this case, it is preferable that the openings are formed in the opposite side plates at positions that are in the rear of a center of gravity of the elevating plate with respect to the sheet feeding direction.
According to this construction, an angle of inclination of the elevating plate can be kept constant. Accordingly, there is even less likelihood of swinging the sheets stacked in the sheet accommodating portion and displacing the sheets toward the rear ends thereof, wherefore a sheet feeder free from a sheet jam and the like can be provided. Further, although it might be thought to fix the elevating plate at a specified angle, there are cases where a suitable position or angle of inclination of the elevating plate cannot be obtained due to a fabrication error and the like. Contrary to this, according to the present invention, since the elevating plate is inclined due to the weight thereof, the above errors can be absorbed.
In the above construction, it is preferable that each engaging member includes a first roller disposed at an upper position and a second roller disposed at a position vertically below the first roller; and that the elevating plate is inclined with the inclination thereof restricted by hoisting the first rollers by means of specified hoisting members to bring a part of the surface of each of the first rollers into contact with a first edge of the corresponding opening while bringing a part of the surface of each of the second rollers into contact with a second edge of the corresponding opening facing the first edge, the surface part of the second roller being on the opposite to the surface part of the first roller.
In this case, it is preferable that a wire used to elevate and lower the elevating plate is placed on the first roller; that the openings serve as guides upon elevating and lowering the elevating plate; and the inclining mechanism constitutes a part of the elevating mechanism for elevating and lowering the elevating plate.
According to this construction, since the inclining mechanism doubles as the part of the mechanism for elevating and lowering the elevating plate, it is not necessary to specially provide an inclining mechanism in addition to the mechanism for elevating and lowering the elevating plate and the construction of the sheet feeder can be simplified. Therefore, this construction is advantageous in terms of costs and productivity.
This application is based on patent application No. 2006-265781 filed in Japan, the contents of which are hereby incorporated by references.
As this invention may be embodied in several forms without departing from the spirit of essential characteristics thereof, the present embodiment is therefore illustrative and not restrictive, since the scope of the invention is defined by the appended claims rather than by the description preceding them, and all changes that fall within metes and bounds of the claims, or equivalence of such metes and bounds are therefore intended to embraced by the claims.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2006-265781 | Sep 2006 | JP | national |
