This application is based on and claims priority under 35 USC §119 from Japanese Patent Application No. 2011-052094 filed Mar. 9, 2011.
1. Technical Field
The present invention relates to an image forming apparatus and a transfer device.
2. Related Art
There is known an image forming apparatus or a transfer device in which a sheet is wrapped around a transfer unit to transfer a toner image onto the sheet. Further, there is an image forming apparatus or a transfer device including a gripper for holding a sheet to be wrapped around a transfer unit.
According to an aspect of the present invention, there is provided an image forming apparatus including: an image carrier that is rotatably arranged and carries an image on an outer circumferential surface thereof; a transfer member that is rotatably arranged to face the image carrier and transfers the image carried on the image carrier onto a sheet held between the transfer member and the image carrier; a leading edge gripping member that is secured to the transfer member and grips a leading edge side of the sheet in a transport direction thereof on an outer circumferential surface of the transfer member, the sheet being supplied toward the transfer member; and a trailing edge holding member that is arranged to be rotatable around the transfer member, holds a trailing edge side of the sheet in the transport direction thereof between the trailing edge holding member and the outer circumferential surface of the transfer member, the sheet being supplied toward the transfer member, and bends to release the trailing edge side of the sheet, which has been held, in the transport direction thereof.
An exemplary embodiment of the present invention will be described in detail based on the following figures, wherein:
The exemplary embodiment will be described in detail with reference to the accompanying drawings.
First, with reference to
As shown in
As shown in
The photoconductive drum 11 as an example of an image carrier includes a photoconductive layer 11A having negative charging polarity on the surface thereof, and is attached to rotate in the direction of arrow A. The charging device 12, the exposure device 13, the rotary developing device 14 and the cleaning device 15 are provided around the photoconductive drum 11 along the direction of arrow A in this order. Here, the outer diameter of the photoconductive drum 11 is, for example, 30 mm.
The charging device 12 is, in the exemplary embodiment, a discharge device of a contact roller type, and charges the photoconductive drum 11 while rotating with the photoconductive drum 11.
The exposure device 13 forms an electrostatic latent image by irradiating the charged surface of the photoconductive drum 11.
The rotary developing device 14 includes a rotational axis 14A and developing units 14Y, 14M, 14C and 14K for yellow (Y), magenta (M), cyan (C) and black (K), respectively, which are provided around the rotational axis 14A. The rotary developing device 14 is detachably attached to the housing 2. Further, the rotary developing device 14 rotates in the direction of arrow C around the rotational axis 14A.
The rotary developing device 14 is configured such that any one of the developing units 14Y, 14M, 14C and 14K stops at a developing position which faces the photoconductive drum 11. The rotary developing device 14 is also configured to develop the electrostatic latent image on the photoconductive drum 11, which has been formed by the exposure device 13, by use of toner. The outer diameter of the rotary developing device 14 is, for example, 100 mm. It should be noted that, in the case where only a monochrome image, not a multicolor image, is to be formed, the rotary developing device 14 may be replaced with a developing device (not shown) having only a developing unit of monochrome color (for example, a developing unit 14K for black (K) only).
In these developing units 14Y, 14M, 14C and 14K, single component developer using magnetic toner or non-magnetic toner alone is contained. Here, the single component developer is used in the exemplary embodiment; however, two component developer containing toner and carrier may also be used. It should be noted that, hereinafter, the single component developer will be simply referred to as developer.
The cleaning device 15 is configured to remove the developer or adhering materials other than the developer remaining on the surface of the photoconductive drum 11. The cleaning device 15 in the exemplary embodiment is a cleaner of a blade type.
Next, the transfer device 20 will be described. The transfer device 20 has a transfer drum 21 that transfers the toner image on the photoconductive drum 11 onto the sheet S. The transfer device 20 also includes a leading edge gripper 23 that grips a leading edge portion of the sheet S on the transfer drum 21 and a trailing edge gripper 27 that holds a trailing edge portion of the sheet S on the transfer drum 21. Further, the transfer device 20 includes a sheet detecting sensor 25 that detects passage of the sheet S.
The transfer drum 21, which is an example of a transfer member, is arranged to face the photoconductive drum 11 and to be rotatable around a rotational axis 21D. The transfer device 20 is detachably attached to the housing 2. Further, the transfer drum 21 includes a drum-shaped base portion 21A and an elastic layer 21B formed on an outer circumferential surface of the base portion 21A.
The elastic layer 21B is provided along the outer circumference of the drum-shaped base portion 21A from a leading edge of the elastic layer 21BL (a leading edge of the outer circumferential surface of the transfer member), which is a leading edge in the transport direction of the sheet S, to a trailing edge of the elastic layer 21BT, which is a trailing edge in the transport direction of the sheet S. Further, the elastic layer 21B has a clearance between the trailing edge of the elastic layer 21BT and the leading edge of the elastic layer 21BL, which serves as an exposure portion (a cutout portion) 21C where the base portion 21A is exposed.
The transfer drum 21 forms a nip portion (a transfer location Tr, which will be described later) with the photoconductive drum 11 by contacting the photoconductive drum 11 and causing the elastic layer 21B to be elastically deformed. The transfer drum 21 is provided to rotate in the direction of arrow B. Here, each of a rotational axis (not shown) of the photoconductive drum 11 and the rotational axis 21D of the transfer drum 21 is secured to the image forming apparatus 1. In other words, the photoconductive drum 11 and the transfer drum 21 are arranged so that a distance between the rotational axes of the photoconductive drum 11 and the transfer drum 21 is maintained. Further, the exposure portion 21C of the transfer drum 21 does not contact the photoconductive drum 11. Moreover, the outer diameter of the transfer drum 21 is larger than that of the photoconductive drum 11, which is 120 mm, for example.
The base portion 21A in the exemplary embodiment is a hollow tube having conductivity and is made of metal, for example. On the other hand, the elastic layer 21B is an elastic member having semi-conductivity and is made of rubber such as polyurethane, chlororprene, EPDM (ethylene propylene rubber) and NBR (nitrile-butadiene rubber), for example.
Here, a dielectric material such as a dielectric sheet is not provided on an outer circumferential surface of the elastic layer 21B. Further, the transfer drum 21 is not provided with a charger such as a corotron for performing electrostatic absorption of the sheet S. That is to say, the transfer drum 21 does not utilize so-called electrostatic absorption to hold the sheet S.
Further, the circumferential length of the transfer drum 21 (more specifically, the circumferential length of the elastic layer 21B) is longer than the maximum length of the image formed on the sheet S by the image forming apparatus 1 in the transport direction of the sheet S (maximum printing length).
A transfer bias, which is a voltage having an opposite polarity to toner, is applied from a high-voltage power supply (not shown) to the base portion 21A. This is a configuration in which toner constituting the toner image on the photoconductive drum 11 is transferred onto the sheet S on the elastic layer 21B at the transfer location Tr.
It should be noted that the transfer location Tr refers to a region where the toner image on the photoconductive drum 11 is transferred onto the sheet S on the elastic layer 21B, and a region where the elastic layer 21B (or the sheet S on the elastic layer 21B) contacts the transfer drum 21.
More specifically, as shown in
Further, as shown in
Then, in
The standby position of the trailing edge gripper 27 in the exemplary embodiment exists on the outer circumference of the transfer drum 21 and between a sheet supply position Pa and the transfer location Tr. As the standby position of the trailing edge gripper 27 comes closer to the transfer location Tr, misregistration of the image is suppressed.
Returning again to
The sheet detecting sensor 25 is arranged to face a supply path 51 (later described) and detects passage of the sheet S transported on the supply path 51. More specifically, the sheet detecting sensor 25 emits near infrared light toward the supply path 51. Then the sheet detecting sensor 25 receives reflected light (near infrared light) from the sheet S transported on the supply path 51.
Further, the sheet detecting sensor 25 detects a mark (not shown) provided on the transfer drum 21, thus measuring a phase of the rotating transfer drum 21.
The fixing device 30 includes a heat roll 31 that has a heat source (not shown) and is rotatably arranged and a pressure roll 32 that is brought into pressure contact with the heat roll 31.
The sheet supply unit 40 includes: a sheet container 41 that is provided at a lower part in the image forming apparatus 1, specifically, below the transfer drum 21, and contains sheets S inside thereof; a sheet size sensor (not shown) that is provided in the feed roll 42 and detects the size of the sheet S contained in the sheet container 41; the feed roll 42 that draws out the sheet S from the sheet container 41; a retard roll 43 that separates sheets S that are in intimate contact with each other; and transport rolls 44 that transport the sheet S.
The controller 100 receives an input of a signal via a user interface (not shown) that receives instructions from a user. The controller 100 also receives an input of an image signal from an image output instruction unit (not shown) provided inside or outside of the image forming apparatus 1. Further, the controller 100 receives an input of a signal indicating passage of the sheet S and a phase signal of the transfer drum 21 that are transmitted from the sheet detecting sensor 25.
The controller 100 is configured to output a control signal to each of the following components. That is, the controller 100 outputs a control signal to each of: a photoconductive drum driving unit (not shown) that rotationally drives the photoconductive drum 11; the charging device 12; the exposure device 13; a developing device driving unit (not shown) that rotates and stops the rotary developing device 14 to locate a target unit, which is one of the developing units 14Y, 14M, 14C and 14K, at the developing position facing the photoconductive drum 11; a developing bias setting unit (not shown) that sets a developing bias to be supplied to one of the developing units 14Y, 14M, 14C and 14K arranged at the developing position; a transfer drum driving unit (not shown) that rotationally drives the transfer drum 21; a trailing edge gripper driving unit (not shown) that rotationally drives the trailing edge gripper 27; a transfer bias setting unit (not shown) that sets a transfer bias to be supplied to the transfer drum 21; the leading edge gripper 23; the trailing edge gripper 27; the sheet supply unit 40; and the fixing device 30.
Here, the image forming apparatus 1 includes: the supply path 51 for supplying sheet S to the transfer location Tr from the sheet container 41; and an exit path 52 for outputting the sheet S onto which the toner image is transferred to the output sheet stacking unit 3 via the fixing device 30. Further, in the exemplary embodiment, the sheet S supplied toward the transfer drum 21 is rotated while being wrapped around the transfer drum 21 by the leading edge gripper 23 and the trailing edge gripper 27, and a path on which the sheet S passes is referred to as a rotation path 53.
Next, with reference to
First, each of the leading edge gripper 23 and the trailing edge gripper 27 is openable and closable. The leading edge gripper 23 and the trailing edge gripper 27 are rotatable with the transfer drum 21. Further, the leading edge gripper 23 and the trailing edge gripper 27 are configured to hold the sheet S on the transfer drum 21.
Specifically, as shown in
Here, the leading edge gripper 23 is secured to the transfer drum 21 (refer to
Hereinafter, configuration of each of the leading edge gripper 23 and the trailing edge gripper 27 will be described in this order.
First, as shown in
Moreover, the leading edge gripper 23 includes an outside member 23a that retains the sheet S from the outside with respect to the center of the rotation of the transfer drum 21 and an inside member 23b that retains the sheet S from the inside with respect to the center of the rotation of the transfer drum 21. The leading edge gripper 23 sandwiches the sheet S by the outside member 23a and the inside member 23b.
As shown in
Further, as shown in
The inside member 23b is a plate-like member, and is arranged to be along the outside member 23a.
The inside member 23b is secured to the transfer drum 21, and is arranged inside of the outside member 23a with respect to the center of the rotation of the transfer drum 21 in the state where the leading edge gripper 23 is closed.
Next, with reference to
As shown in
As shown in
<Sheet Restriction Unit 27a>
As shown in
Further, the sheet restriction unit 27a is made of a resin such as PET (polyethylene terephthalate), polyimide and fluorine, and is thus capable of being elastically deformed. The sheet restriction unit 27a has rigidity of the extent to which the sheet restriction unit 27a is able to bend by being pressed in the longitudinal direction thereof.
Here, since the sheet restriction unit 27a contacts the photoconductive drum 11 at the transfer location Tr (will be described later), the sheet restriction unit 27a causes damage to the photoconductive drum 11 in some cases depending on the shape of the sheet restriction unit 27a. In the exemplary embodiment, the sheet restriction unit 27a has a small thickness and chamfered edges.
It should be noted that the sheet restriction unit 27a in the exemplary embodiment is a plate-like member as described above; however, the sheet restriction unit 27a may be in the shape of a film, a wire, a circular cylinder or the like.
<Rotating Unit 27b>
As shown in
The first rotating unit 27b1 and the second rotating unit 27b2 are rotatable in synchronization with each other around the transfer drum 21. The first rotating unit 27b1 and the second rotating unit 27b2 in the exemplary embodiment are gears. The rotating unit 27b rotates upon receiving a driving force from a drive source not shown in the figure.
The first rotating unit 27b1 and the second rotating unit 27b2 hold respective both ends of the sheet restriction unit 27a. In the exemplary embodiment, one end portion of the sheet restriction unit 27a is connected to the first rotating unit 27b1, and the other end portion of the sheet restriction unit 27a is connected to the second rotating unit 27b2 via the operating piece 27c. Here, a through hole 29 into which the operating piece 27c is inserted is formed in the second rotating unit 27b2.
<Operating Piece 27c>
As shown in
Here, in the operating piece 27c, an end portion facing the inside of the transfer drum 21 (an end portion facing the elastic layer 21B) is referred to as an inside end portion 27c1. On the other hand, in the operating piece 27c, an end portion opposite to the inside end portion 27c1, namely, an end portion facing the outside of the transfer drum 21 is referred to as an outside end portion 27c2.
The inside end portion 27c1 is connected to the sheet restriction unit 27a. On the other hand, in the outside end portion 27c2, an inclination is provided by which the operating piece 27c is pressed toward the inside (refer to arrow E2) of the transfer drum 21 upon contacting a claw unit 49 (described later) with the rotation of the trailing edge gripper 27.
Though explanation is omitted in the above description, the image forming apparatus 1 (refer to
The claw unit 49 in the exemplary embodiment is secured to the housing 2. The claw unit 49 is provided at a position to be brought into contact with the operating piece 27c of the trailing edge gripper 27 rotating around the transfer drum 21.
To be further described, the claw unit 49 is provided at a position where the claw unit 49 is brought into contact with the outside end portion 27c2 of the operating piece 27c in the trailing edge gripper 27 when the trailing edge gripper 27 is arranged at the standby position. As described above, the inclination is provided on the outside end portion 27c2, and the operating piece 27c of the trailing edge gripper 27, which is in contact with the claw unit 49, comes into a state of being pressed toward the inside of the transfer drum 21 (refer to arrow E2) (a state of being hidden in the second rotating unit 27b2).
Here, with reference to
First, the closed state of the trailing edge gripper 27 will be described with reference to
Next, the opened state of the trailing edge gripper 27 will be described with reference to
Upon receiving the compressing force, as shown in
Here, in the longitudinal direction of the sheet restriction unit 27a, the length of the part of the sheet restriction unit 27a within a region where the elastic layer 21B exists (the length of the part of the sheet restriction unit 27a that exists above the elastic layer 21B in
As described above, in the closed trailing edge gripper 27 shown in
In the exemplary embodiment, the member that moves in the direction of the diameter (the vertical direction in
Next, with reference to
First, a coloring material reflective light image of a document read by a document reader (not shown) or coloring material image data formed by a personal computer (not shown) or the like is inputted to an image signal processing device (not shown) as each data of red (R), green (G) and blue (B) color components, for example, to undergo predetermined image processing. The image data subjected to the image processing is converted into coloring material gradation data of four color components of yellow (Y), magenta (M), cyan (C) and black (K), and outputted to the exposure device 13 (refer to
With the start of the recorded image forming operation, the photoconductive drum 11 and the transfer drum 21 (refer to
To be further described, at this time, the leading edge gripper 23 rotates with the transfer drum 21, whereas the trailing edge gripper 27 is at rest at the standby position (the circumferential speed is zero. Refer to arrow a in
Then, as shown in
On the other hand, in the rotary developing device 14, the developing unit containing toner of color component corresponding to the electrostatic latent image formed on the photoconductive drum 11 is rotated to be arranged at a position facing the photoconductive drum 11 and is stopped.
Then, the electrostatic latent image on the photoconductive drum 11 is developed by the developing unit 14Y, for example, to form the toner image on the photoconductive drum 11. With the rotation of the photoconductive drum 11, the toner image (here, the yellow toner image) is transported toward the transfer location Tr that faces the transfer device 20.
In response to the start of the recorded image forming operation, supply of the sheet S is also performed. Specifically, the sheet S is forwarded to the supply path 51 by use of the feed roll 42, the retard roll 43 and the transport rolls 44. Then the sheet detecting sensor 25 detects the passage of the leading edge in the transport direction of the sheet S (refer to arrow c in
In step with the arrival of the end portion of the sheet S on the leading edge side in the transport direction at the sheet supply position Pa, the leading edge gripper 23 shifts from the opened state to the closed state (refer to arrow d in
Thereafter, the leading edge gripper 23 gripping the sheet S passes between the sheet restriction unit 27a of the trailing edge gripper 27 at rest and the center of the rotation of the transfer drum 21 (passes the trailing edge gripper 27 at rest). The leading edge gripper 23 having passed between the trailing edge gripper 27 and the elastic layer 21B (refer to
The sheet S, which has passed through the transfer location Tr with being gripped by the leading edge gripper 23 (refer to allow f in
Then, after the electrostatic latent image of the first color (for example, yellow) according to the image information is formed by the exposure device 13, passage of the trailing edge in the transport direction of the sheet S is detected by the sheet detecting sensor 25 (refer to arrow e in
Here, the operation in which the trailing edge gripper 27 shifts from the opened state to the closed state will be specifically described. First, with the start to rotate, the trailing edge gripper 27 moves away from the claw unit 49. Then the operating piece 27c moves toward the outside of the transfer drum 21 (refer to arrow E1 in
Further, when the trailing edge gripper 27 is closed, the exposure device 13 has completed forming the electrostatic latent image of the first color (for example, yellow) and has not started yet to form the electrostatic latent image of the second color (for example, magenta). In short, when the electrostatic latent image is written (during exposure), operation of opening or closing of the trailing edge gripper 27 is not performed. Accordingly, disturbance of the electrostatic latent image due to opening or closing of the trailing edge gripper 27 is not caused.
The trailing edge gripper 27, which has started to rotate, rotates with the transfer drum 21 while holding the edge portion of the trailing edge side in the transport direction of the sheet S wrapped around the transfer drum 21. In other words, the sheet S rotates with the transfer drum 21 while the edge portion of the leading edge side in the transport direction thereof being gripped by the leading edge gripper 23 and the edge portion of the trailing edge side in the transport direction thereof being held by the trailing edge gripper 27 (refer to
It should be noted that, when passing through the transfer location Tr, the trailing edge gripper 27 holding the sheet S contacts the photoconductive drum 11, whereas the leading edge gripper 23 gripping the sheet S does not contact the photoconductive drum 11.
The toner image of the first color (for example, yellow) formed on the photoconductive drum 11 is transferred onto the sheet S on the transfer drum 21 at the transfer location Tr where the photoconductive drum 11 and the transfer drum 21 face each other. It should be noted that the toner remaining on the photoconductive drum 11 after transfer is removed by the cleaning device 15 (refer to
Then, the electrostatic latent image formation, development and transfer of the second color to the color (for example, magenta or cyan) preceding the final color (for example, black) are similarly repeated according to the above-described procedures. When the toner image of each color is formed, the rotary developing device 14 rotates to arrange the corresponding developing unit 14M or 14C at the stop position.
In the meantime, the sheet S is rotated and transported in the state of being wrapped around the transfer drum 21 by the leading edge gripper 23 and the trailing edge gripper 27, and the toner images of the second and subsequent colors are sequentially transferred to be superimposed each time the sheet S passes through the transfer location Tr. As a result, in the formation of a full-color image, for example, each of the toner images of yellow (Y), magenta (M) and cyan (C), except black (K), is multiply-transferred onto the sheet S on the transfer drum 21.
Then, in the case where the toner image of the final color is transferred, different from the case of transferring the toner image of any color preceding the final color (for example, black), the leading edge gripper 23 disengages (releases) gripping of the sheet S. That is to say, the leading edge gripper 23 shifts from the closed state to the opened state (refer to arrow h in
Thereafter, as the sheet S is transported, the trailing edge gripper 27 holding the trailing edge in the transport direction of the sheet S arrives at the above-described standby position. At the standby position, the claw unit 49 (refer to
It should be noted that, when the trailing edge gripper 27 shifts from the closed state to the opened state, the electrostatic latent image of the final color (for example, black) according to the image information has already been formed by the exposure device 13.
The trailing edge in the transport direction of the sheet S, which has been released from holding by the trailing edge gripper 27, is peeled from the transfer drum 21 and enters into the exit path 52 at the sheet exit position Pb.
The sheet S having entered into the exit path 52 is forwarded to the fixing device 30, and the toner image on the sheet S is fixed. The sheet S on which fixing has been finished is outputted to the outside of the image forming apparatus 1 by the transport rolls 44 and stacked in the output sheet stacking unit 3.
Here, with reference to
As shown in
As shown in
Further, the push-up unit 28 is provided to sandwich the elastic layer 21B at both ends thereof in the axial direction of the transfer drum 21. More specifically, the push-up unit 28 is provided outside the elastic layer 21B and inside the rotating unit 27b in the axial direction of the transfer drum 21.
Moreover, the push-up unit 28 is higher than the elastic layer 21B in the height from the base portion 21A toward the outer circumferential surface. For example, the push-up unit 28 is 1 mm to 2 mm higher than the elastic layer 21B.
The push-up unit 28 is made of rubber such as polyurethane, chlororprene, EPDM (ethylene propylene rubber) and NBR (nitrile-butadiene rubber), for example.
When the trailing edge gripper 27 arrives at the push-up unit 28 with the rotation around the transfer drum 21, the sheet restriction unit 27a of the trailing edge gripper 27 runs on an outer circumferential surface of the push-up unit 28 (refer to
If the trailing edge gripper 27 is opened in the state where the sheet restriction unit 27a is running on the outer circumferential surface of the push-up unit 28, the push-up unit 28 pushes up the sheet restriction unit 27a. That is, the push-up unit 28 holds the sheet restriction unit 27a so that the sheet restriction unit 27a bends in the direction away from the elastic layer 21B.
On the other hand, if the trailing edge gripper 27 is closed in the state where the sheet restriction unit 27a is running on the outer circumferential surface of the push-up unit 28, the sheet restriction unit 27a comes to a state of receiving a tension without bending, thereby compressing the push-up unit 28. Consequently, though in the state where the sheet restriction unit 27a of the trailing edge gripper 27 is running on the push-up unit 28, the trailing edge gripper 27 is closed to hold the sheet S with the elastic layer 21B.
In other words, the push-up unit 28 has elasticity to the extent that the trailing edge gripper 27 is closed to hold the sheet S with the elastic layer 21B though in the state where the sheet restriction unit 27a of the trailing edge gripper 27 is running on the push-up unit 28.
The push-up unit 28 pushes up the sheet restriction unit 27a in the direction away from the elastic layer 21B, thereby suppressing bending of the sheet restriction unit 27a in the direction approaching the elastic layer 21B when the trailing edge gripper 27 is opened. This suppresses damage to the sheet restriction unit 27a due to the contact with the sheet restriction unit 27a by the leading edge gripper 23 and the elastic layer 21B which move with the rotation of the transfer drum 21.
Here, in the modified example, there has been description that the push-up unit 28 is provided on both sides of the elastic layer 21B in the axial direction of the transfer drum 21 to sandwich the elastic layer 21B, but is not limited thereto. For example, the push-up unit 28 may be configured to be provided only on one side of the elastic layer 21B.
Further, there has also been description that the push-up unit 28 is provided in the part in the circumferential direction of the transfer drum 21 where the exposure portion 21C exists, but is not limited thereto. For example, as shown in
Here, with reference to
As a modified example of the exemplary embodiment, the configuration in which the push-up unit 28 is provided has been described. Here, if the trailing edge gripper 27 is configured to pass over the push-up unit 28, friction occurs between the trailing edge gripper 27 and the push-up unit 28. On the other hand, occurrence of the friction between the trailing edge gripper 27 and the push-up unit 28 may be avoided by operating the push-up unit 28 together with the trailing edge gripper 27. Hereinafter, a configuration example for achieving this will be described.
As shown in
Here, description will be given to a case where the push-up unit 28 is provided on the base portion 21A of the transfer drum 21, which is different from this modified example. In this case, if one of the transfer drum 21 and the trailing edge gripper 27 stops and the other rotates, the sheet restriction unit 27a of the trailing edge gripper 27 and the push-up unit 28 contact each other each time the one makes a single rotation. When the sheet restriction unit 27a and the push-up unit 28 are brought into contact, a load applied to the trailing edge gripper driving unit (not shown) that rotationally drives the trailing edge gripper 27 or the transfer drum driving unit (not shown) that rotationally drives the transfer drum 21 fluctuates (increases).
Next, description will be given to a case where the push-up unit 28 is configured to be provided to the trailing edge gripper holding member 282 to rotate around the transfer drum 21 with the trailing edge gripper 27, as in this modified example. In this case, the state of contact between the push-up unit 28 and the sheet restriction unit 27a does not change (the state where the push-up unit 28 and the sheet restriction unit 27a are in contact with each other is maintained) though one of the transfer drum 21 and the trailing edge gripper 27 stops and the other rotates. Accordingly, fluctuation in the load applied to the trailing edge gripper driving unit (not shown) or the transfer drum driving unit (not shown) is reduced compared to the case where the push-up unit 28 is provided to the base portion 21A of the transfer drum 21.
In the above-described example, the push-up unit 28 has been described to be the rectangular elastic member, but is not limited thereto. For example, as shown in
<Movement of Rotating Unit 27b>
In the exemplary embodiment, the sheet restriction unit 27a is configured to be bent by the movement of the operating piece 27c along the axial direction of the transfer drum 21, but is not limited thereto. For example, the sheet restriction unit 27a may be configured to be bent by moving forward or backward any one of the first rotating unit 27b1 and the second rotating unit 27b2 with respect to the other so as to increase or decrease the distance between the first rotating unit 27b1 and the second rotating unit 27b2, without providing the operating piece 27c. Or, the sheet restriction unit 27a may be configured to be bent by moving forward or backward both of the first rotating unit 27b1 and the second rotating unit 27b2.
The foregoing description of the exemplary embodiments of the present invention has been provided for the purposes of illustration and description. It is not intended to be exhaustive or to limit the invention to the precise forms disclosed. Obviously, many modifications and variations will be apparent to practitioners skilled in the art. The exemplary embodiments were chosen and described in order to best explain the principles of the invention and its practical applications, thereby enabling others skilled in the art to understand the invention for various embodiments and with the various modifications as are suited to the particular use contemplated. It is intended that the scope of the invention be defined by the following claims and their equivalents.
Number | Date | Country | Kind |
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2011-052094 | Mar 2011 | JP | national |