阅读说明：本技术 图像形成装置 (Image forming apparatus with a toner supply device ) 是由 田中健一 近藤惠太 井上优树 片野真吾 于 2021-05-14 设计创作，主要内容包括：一种图像形成装置包括定影装置和相对于片材进给方向设置在定影装置的下游侧的冷却装置。冷却装置包括：第一单元,所述第一单元包括第一带和第一辊；第二单元,所述第二单元包括用于与第一带协作以形成夹持部的第二带、散热器和第二辊；以及用于旋转第一辊和第二辊的驱动马达。第二单元能够在第一带和第二带彼此接触以形成夹持部的接触位置以及第一带和第二带彼此分离以释放夹持部的分离位置之间移动。(An image forming apparatus includes a fixing device and a cooling device disposed on a downstream side of the fixing device with respect to a sheet feeding direction. The cooling device includes: a first unit including a first belt and a first roller; a second unit including a second belt for cooperating with the first belt to form a nip, a heat sink, and a second roller; and a driving motor for rotating the first roller and the second roller. The second unit is movable between a contact position where the first and second belts contact each other to form the nip portion and a separation position where the first and second belts are separated from each other to release the nip portion.)

1. An image forming apparatus, comprising:

a fixing device configured to fix the toner image on the sheet by heating the sheet; and

a cooling device provided on a downstream side of the fixing device with respect to a sheet feeding direction, the cooling device including:

a first unit including a first belt and a first roller for stretching and rotating the first belt;

a second unit comprising: a second belt for cooperating with the first belt to form a nip that nips and feeds a sheet; a heat sink in contact with an inner peripheral surface of the second band; and a second roller for stretching and rotating the second belt, wherein the second unit is movable between a contact position where the first belt and the second belt are in contact with each other to form the nip and a separation position where the first belt and the second belt are separated from each other to release the nip; and

a drive motor configured to rotate the first roller and the second roller.

2. The image forming apparatus according to claim 1, wherein the second unit is rotatable relative to the first unit about a rotation axis extending in a sheet feeding direction of the cooling device, and

wherein the drive motor is disposed on the same side as a side on which a rotation center of the second unit is disposed with respect to a rotation axis direction of the first roller and rotates the first roller.

3. The image forming apparatus according to claim 1, further comprising:

a drive transmission portion including a plurality of gears and configured to transmit a rotational driving force of the driving motor to the first roller and the second roller by rotation of the gears.

4. The image forming apparatus according to claim 3, wherein the second unit is rotatable relative to the first unit about a rotation axis extending in a sheet feeding direction of the cooling device,

wherein the drive motor is disposed on the same side as a side on which a rotation center of the second roller is disposed with respect to a rotation axis direction of the first roller and rotates the first roller; and is

Wherein the drive transmission portion is provided to the first belt on a side opposite to a side where the drive motor is provided with respect to a rotational axis direction of the first roller.

5. The image forming apparatus according to claim 3, wherein the drive transmitting portion includes:

a first drive gear portion provided on the first unit and including a first gear to which a rotational drive force is transmitted from the drive motor and a first transmission gear to which a rotational drive force is transmitted from the first gear; and

a second drive gear portion provided on the second unit and including a second transmission gear from which a rotational drive force is transmitted to the second transmission gear by being engaged with the first transmission gear, and a second gear for transmitting the rotational drive force to the second roller.

6. An image forming apparatus according to claim 5, wherein said drive transmission portion further comprises a pushing portion for pushing said first drive gear portion so that said first transmission gear moves toward said second transmission gear; and is

Wherein when the second unit moves from the separation position to the contact position, the first drive gear portion is movable against the urging force of the urging portion by the urging of the second transmission gear against the first transmission gear.

7. An image forming apparatus according to claim 5, wherein in a state in which said second unit is moved to said contact position, in a case where said first transmission gear and said second transmission gear are not engaged with each other, said first drive gear portion is moved so that said first transmission gear is rotated by rotation of said first roller and is engaged with said second transmission gear.

8. An image forming apparatus according to claim 7, wherein said first drive gear portion is provided swingably about a rotation center of said first gear, and

wherein the first drive gear portion and the second drive gear portion are arranged such that: a straight line inclined from a tangent between the pitch circle of the first transfer gear and the pitch circle of the second transfer gear by a pressure angle of the first transfer gear passes closer to the second transfer gear side than a straight line connecting the rotation center of the first gear and a contact point between the pitch circle of the first transfer gear and the pitch circle of the second transfer gear.

9. An image forming apparatus according to claim 5, wherein said second drive gear portion includes a restricting member for restricting a center distance between said first transmission gear and said second transmission gear in a case where said second unit is moved to said contact position.

10. An image forming apparatus according to claim 5, wherein the number of teeth of said first gear and the number of teeth of said second gear are the same, and

wherein the number of teeth of the first transfer gear and the number of teeth of the second transfer gear are the same and greater than the number of teeth of the first gear and the number of teeth of the second gear.

11. An image forming apparatus according to claim 5, further comprising a drive switching portion configured to switch drive of the second roller such that the drive force of the first drive gear portion is not transmitted to the second drive gear portion in a case where a peripheral speed of the second roller is greater than a peripheral speed of the second gear, and such that the drive force of the first drive gear portion is transmitted to the second drive gear portion in a case where the peripheral speed of the second roller is not greater than the peripheral speed of the second gear.

12. The image forming apparatus according to claim 11, wherein the drive switching portion is a one-way clutch configured to interrupt transmission of drive from the second gear to the second roller in a case where the second roller and the second gear rotate in directions opposite to each other.

Technical Field

The present invention relates to an image forming apparatus including a sheet cooling device capable of clamping and feeding a recording material by a pair of belts that are in contact with each other and rotatable, and is suitable for an image forming apparatus such as a printer, a copying machine, a facsimile machine, or a multi-function machine.

Background

Conventionally, a belt type sheet feeding device is used in an image forming apparatus for forming an image on a recording material, in which the recording material (also referred to as a sheet) is nipped and fed by a pair of belts that contact and rotate with each other. In order to prevent adhesion between recording materials stacked on, for example, a discharge tray, a sheet feeding device is used in a recording material cooling device or the like for lowering the temperature of the recording material (japanese laid-open patent application 2009-181055). In this apparatus, in a case where the driving of a pair of belts is stopped in a state where a recording material is nipped between the belts (so-called jam) so as to allow a user to remove the recording material nipped by the belts, the belts are provided so as to be movable between a contact position where one belt is in contact with the other belt and a separation position where one belt is separated from the other belt.

Therefore, in the case of adopting a configuration in which one belt is movable between the contact position and the separation position with respect to the other belt, in general, a configuration in which a drive motor for driving one belt and a drive motor for driving the other belt are respectively provided on opposite sides will be considered.

With this configuration, the drive motor must be installed in each of the two belt units, resulting in an increase in cost. Therefore, a configuration in which the number of motors is reduced by driving the two belt units by a single driving motor will be considered, but a configuration in which both belt units are driven by a single motor in a cooling device in which one of the belt units is movable has not been proposed yet.

Disclosure of Invention

A primary object of the present invention is to provide an image forming apparatus including a cooling device using a configuration in which a pair of belt units are driven by a single motor.

According to an aspect of the present invention, there is provided an image forming apparatus including: a fixing device configured to fix the toner image on the sheet by heating the sheet; and a cooling device provided on a downstream side of the fixing device with respect to a sheet feeding direction, the cooling device including: a first unit including a first belt and a first roller for stretching and rotating the first belt; a second unit comprising: a second belt for cooperating with the first belt to form a nip that nips and feeds a sheet; a heat sink in contact with an inner peripheral surface of the second band; and a second roller for stretching and rotating the second belt, wherein the second unit is movable between a contact position where the first belt and the second belt are in contact with each other to form the nip and a separation position where the first belt and the second belt are separated from each other to release the nip; and a drive motor configured to rotate the first roller and the second roller.

Further features of the invention will become apparent from the following description of exemplary embodiments with reference to the attached drawings.

Drawings

Fig. 1 is a schematic view illustrating an image forming apparatus to which a sheet feeding apparatus according to an embodiment of the present invention can be applied.

Fig. 2 is a schematic view showing a recording material cooling device.

Fig. 3 is a perspective view showing the recording material cooling device with the belt in the contact position.

Fig. 4 is a perspective view of the recording material cooling device with the belt in the separated position.

Fig. 5 is an enlarged view showing a driving gear portion.

Fig. 6 is an enlarged view showing an inter-shaft (shaft) restriction member.

Fig. 7 is an exploded perspective view showing the one-way clutch.

Fig. 8 is a schematic diagram showing an example in which a recording material cooling device is provided outside the image forming apparatus.

Detailed Description

< image Forming apparatus >

Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. First, the structure of an image forming apparatus to which the sheet feeding apparatus of this embodiment can be applied will be described with reference to fig. 1. The image forming apparatus 100 shown in fig. 1 is a tandem type electrophotographic full-color printer. The image forming apparatus 100 includes image forming portions Pa, Pb, Pc, and Pd for forming yellow, magenta, cyan, and black images, respectively. The image forming apparatus 100 forms a toner image on a recording material S in accordance with image information from an original reading apparatus (not shown) connected to the apparatus main assembly 100A or from an external device (not shown) such as a personal computer communicably connected to the apparatus main assembly 100A. As the recording material S, various types of sheets including, for example: plain paper, thick paper, rough paper, embossed paper, and coated paper; a plastic film; and a cloth.

The recording material feeding process of the image forming apparatus 100 will be described. The recording material S is accommodated in a stacked form in the sheet feeding cassette 10, and is sent out from the sheet feeding cassette 10 by the sheet feeding roller 13 in synchronization with the image forming timing. The recording material S fed by the sheet feeding roller 13 is fed to the registration roller pair 12 provided in the middle portion of the feeding path 114. Then, the recording material S is subjected to skew movement correction and timing correction by the registration roller pair 12, and then sent to the secondary transfer portion T2. The secondary transfer portion T2 is a transfer nip formed by the inner secondary transfer roller 14 and the outer secondary transfer roller 11, and transfers the toner image onto the recording material S in response to application of a secondary transfer voltage to the outer secondary transfer roller 11.

In addition to the above-described feeding process of the recording material S to the secondary transfer portion T2, an image forming process of an image sent to the secondary transfer portion T2 at the same timing will be described. First, the image forming portions will be described, but the respective color image forming portions Pa, Pb, Pc, and Pd are substantially similar in configuration, differing only in that the colors of the toners used in the developing devices 1a, 1b, 1c, and 1d are yellow, magenta, cyan, and black, respectively. Therefore, hereinafter, the black image forming portion Pd is described as a representative example, and the description of the other image forming portions Pa, Pb, and Pc will be omitted.

The image forming portion Pd is mainly constituted by the developing device 1d, the charging device 2d, the photosensitive drum 3d, the photosensitive drum cleaner 4d, the exposure device 5d, and the like. In fig. 1, the surface of the photosensitive drum 3d rotating in the direction of the arrow R2 is uniformly charged in advance by the charging device 2d, and subsequently, an electrostatic latent image is formed by the exposure device 5d driven by a signal based on image information. Then, the electrostatic latent image formed on the photosensitive drum 3d is developed as a toner image with a developer by the developing device 1 d. Then, in response to application of a primary transfer voltage to a primary transfer roller 6d (which is disposed opposite to the image forming portion Pd through the intermediate transfer belt 20), the toner image formed on the photosensitive drum 3d is primarily transferred onto the intermediate transfer belt 20. The primary transfer residual toner remaining on the photosensitive drum 3d by a small amount is collected by the photosensitive drum cleaner 4d, and the image forming portion Pd is ready for the subsequent image forming process.

The intermediate transfer belt 20 is stretched by the inner secondary transfer roller 14, the tension roller 15, and the tension roller 16, and is driven in the direction of an arrow R2 in fig. 1. In the case of this embodiment, the tension roller 16 also functions as a driving roller for driving the intermediate transfer belt 20. The image forming processes of the respective colors performed in parallel by the image forming portions Pa to Pd are sequentially performed at the timing of superimposing the toner images on the toner images of the upstream colors primarily transferred onto the intermediate transfer belt 20. As a result, a full-color toner image is finally formed on the intermediate transfer belt 20 and fed to the secondary transfer portion T2. Incidentally, the secondary transfer residual toner passing through the secondary transfer portion T2 is collected by the transfer cleaner (device) 22.

As described above, by the above-described feeding process and image forming process, at the secondary transfer portion T2, the timing of the recording material S and the timing of the full-color toner image coincide with each other so that the secondary transfer is carried out. Subsequently, the recording material S is fed to a fixing device 30 in which a predetermined pressure and a predetermined heat are applied, thereby fixing the toner image on the recording material S. The fixing device 30 nips and feeds the recording material S on which the toner image is formed and thereby heats and pressurizes the fed recording material S, thereby fixing the toner image on the recording material S. That is, the toner for forming the full-color toner image on the recording material S is melted and mixed by heating and pressing, and is fixed as a full-color image on the recording material S. Thereby, the series of operations of the image forming process is ended. Incidentally, in the case of this embodiment, the recording material S on which the toner image is fixed is fed from the fixing device 30 toward the recording material cooling device 50, and then cooled. For example, the temperature of the recording material S is about 90 ℃ before the recording material cooling device 50, but is reduced to about 60 ℃ after the recording material S passes through the recording material cooling device 50.

In the case of single-sided image formation, the recording material S cooled by the recording material cooling device 50 is fed by a pair of discharge rollers 105 and is directly discharged onto a sheet discharge tray 120. On the other hand, in the case of double-sided image formation, the sheet feeding path is switched from a path continued toward the sheet discharge tray 120 to a path continued to the double-sided guide roller pair 111 by the switching member 110 (referred to as a flapper or the like), so that the recording material S nipped and fed by the discharge roller pair 105 is conveyed toward the double-sided guide roller pair 111. Subsequently, the leading end and the trailing end of the recording material S are interchanged by the pair of reverse rollers 112 and conveyed to the feeding path 114 again through the duplex path 113. Regarding the subsequent feeding process and the image forming process of the image on the back surface (second surface) of the recording material S, these processes are similar to the above-described processes, and therefore the description thereof will be omitted.

< recording Material Cooling apparatus >

Next, in the sheet feeding device of this embodiment, the recording material cooling device 50 will be described by using fig. 2 to 7 as an example. The recording material cooling device 50 described below is a cooling device of a belt cooling type. As shown in fig. 2, the recording material cooling device 50 includes an endless second belt 502 and an endless first belt 501, the first belt 501 being used to nip and feed the recording material S in cooperation with the second belt 502. For example, each of the second tape 502 and the first tape 501 is formed of a high-strength polyimide resin material, and is set to have a thickness of 100 μm and a circumference of 942 mm. Further, the recording material cooling device 50 includes a heat sink 503 as a cooling device for cooling the second belt 502. In the case of this embodiment, the heat radiator 503 contacts the second belt 502 (which can contact the recording material S) on the side where the toner image is fixed by the fixing device 30 (fig. 1). Incidentally, the cooling device is not limited to a cooling device for cooling the second belt 502 by the radiator 503. For example, the cooling device may be a belt fan that can cool the second belt 502 by blowing air to the second belt 502.

The first belt 501 is stretched around a plurality of first belt stretching rollers 501a to 501e, and one of the first belt stretching rollers 501a to 501e is rotated by a roller driving section 500 connected to a driving motor M. The roller driving portion 500 includes, for example, belt members and gear portions for transmitting the rotation (rotational force) of the drive motor M, and in the case of this embodiment, these belt members and gear portions are provided on one end side of the first belt stretching roller 501e with respect to the rotational axis direction. The roller driving section 500 is capable of rotating the first belt stretching roller 501e counterclockwise in fig. 2 in response to the rotation of the driving motor M. Thus, the first belt stretching roller 501e functions as a driving roller for driving the first belt 501.

Further, in this embodiment, the drive gear portion 510 is provided on the other end side with respect to the rotational axis direction of the second belt stretching roller 502e (second roller) and the first belt stretching roller 501e (first roller). As described later, the drive gear portion 510 is provided for rotating the second belt 502 by transmitting the rotational drive force of the first belt stretching roller 501e, which rotates in synchronization with the drive motor M, to the second belt stretching roller 502 e. The driving gear portion 510 will be described in detail below.

On the other hand, the second belt 502 is stretched around a plurality of second belt stretching rollers 502a to 502e and is contactable with the first belt 501. With this embodiment, the second belt stretching roller 502e is rotated in accordance with the rotational driving force transmitted by the driving gear portion 510, whereby the second belt 502 is rotated in the arrow B direction. That is, in response to the drive motor M as the same drive source, the second belt 502 and the first belt 501 rotate in the same direction in the cooling nip T4. Incidentally, in the case of this embodiment, the second belt stretching roller 502e and the first belt stretching roller 501e, which are connected to each other by the drive gear portion 510 to allow drive transmission therebetween, do not contribute to the formation of the cooling nip T4. That is, the second belt stretching roller 502e and the first belt stretching roller 501e are disposed outside the range of the cooling nip T4 with respect to the feeding direction of the recording material S, and the cooling nip T4 is not formed.

In this embodiment, the second belt stretching roller 502b and the first belt stretching roller 501b are turning rollers provided for controlling the displacement of the second belt 502 and the first belt 501, respectively. These steering rollers 502b and 501b press the second belt 502 and the first belt 501, respectively, from the inner peripheral surface side toward the outer side of the associated belt, so that the tension of each of the second belt 502 and the first belt 501 is, for example, about 39.2N (about 4 kgf). For this purpose, the second belt stretching roller 502b is urged by a spring 507a, and the first belt stretching roller 501b is urged by a spring 508 a. The steering rollers 502b and 501b are independently steered by the steering mechanism 400 so as to provide a steering angle with respect to the rotational axis direction (width direction) based on the center portion thereof as a rotation supporting portion, thereby controlling meandering of each of the second belt 502 and the first belt 501.

On the inner peripheral surface side of the first belt 501, pressure rollers 509a and 509b for pressing the first belt 501 toward the heat sink 503 of the second unit 502U are provided. The pressure rollers 509a and 509b as pressure members press the first belt 501 with a pressure of 9.8N (1 kgf). Thereby, the second tape 502 is pressed by the first tape 501 toward the heat sink 503 (specifically, toward the heat receiving portion 503a described later), so that the cooling nip T4 can be reliably formed.

The recording material S on which the toner image is fixed is nipped between the second belt 502 and the first belt 501, and is fed in the feeding direction (arrow D direction in the figure) by the rotation of these belts. During feeding, the recording material S passes through a cooling nip T4 formed by the second belt 502 and the first belt 501. In the case of this embodiment, the second belt 502 is cooled by a heat sink 503. In order to effectively cool the recording material S, the heat sink 503 is provided in contact with the inner peripheral surface of the second belt 502 at a portion where the cooling nip T4 is formed. When the recording material S passes through the cooling nip T4, the recording material S is cooled by the second belt 502. For example, in the case where the temperature of the recording material S is about 90 ℃ before the recording material S passes through the recording material cooling device 50, the recording material S is cooled so that the temperature thereof becomes about 60 ℃ after the recording material S passes through the recording material cooling device 50. As the recording material S cools, the toner on the recording material S is cooled and fixed on the recording material S.

The heat sink 503 is a heat sink (radiator) plate formed of metal such as aluminum. The heat sink 503 includes a heat receiving portion 503a for contacting the second belt 502 to absorb heat from the second belt 502, a heat dissipating (heat releasing) portion 503b for dissipating heat (releasing heat), and a heat sink base 503c for transferring heat from the heat receiving portion 503a to the heat dissipating portion 503 b. The heat dissipation portion 503b is formed with many fins in order to promote effective heat dissipation by increasing a contact area with air. For example, the thickness of the heat sink is set to 1mm, the height is set to 100mm, the pitch is set to 5mm, and the thickness of the heat sink base 503c is set to 10 mm. Further, in order to forcibly cool the radiator 503 itself, a cooling fan 513 that sends air to the radiator 503 (specifically, to the heat radiation portion 503b) is provided. The air flow rate of the cooling fan 513 is set to, for example, 2m³And/min. Incidentally, the cooling device for the radiator 503 is not limited to the cooling fan 513. Further, the cooling means is not limited to the radiator 503, but the first and second belts 501, 502 may also be cooled by using a belt cooling fan for blowing air toward the associated belt, or by using an air cooling unit in which a pipe or the like in which a cooling liquid circulates is in contact with the associated belt, or by using a similar device.

In such a recording material cooling device 50, an endless belt such as the second belt 502 or the first belt 501 is supported and rotated by a plurality of rollers, so that a meandering phenomenon can be generated such that the endless belt during rotation moves in the width direction. Therefore, one of the rollers for stretching each of the second belt 502 and the first belt 501 is inclined as a turning roller, and thereby these second belt 502 and first belt 501 move in the width direction, thereby suppressing the meandering phenomenon. To this end, a sensor portion 390 for detecting the position of the end of the associated belt is provided at one point of the rotational path of each of the second belt 502 and the first belt 501. Based on the detection signal of this sensor portion 390, the end position of each of the second belt 502 and the first belt 501 during rotation is detected. Then, based on the detected end position, the above-described steering mechanism 400 is operated, thereby adjusting the steering angle of the associated steering roller 502b or 501 b.

< contact and separation of tapes >

As shown in fig. 2 to 4, the recording material cooling device 50 is roughly divided into a first unit 501U and a second unit 502U. The first unit 501U includes the first belt 501, a drive motor M, first belt stretching rollers 501a to 501e, a first drive gear portion 510b, pressure rollers 509a and 509b, a sensor portion 390, and the like. On the other hand, the second unit 502U includes the second belt 502, second belt stretching rollers 502a to 502e, a second driving gear portion 510a, a radiator 503, a sensor portion 390, and the like. Further, in the case of this embodiment, by the rotation mechanism 550, the second unit 502U is provided so as to be movable relative to the first unit 501U between a contact position where the second belt 502 and the first belt 501 are in contact with each other and a separation position where the second belt 502 and the first belt 501 are separated from each other. As described above, the drive motor M is provided to the first unit 501U which is immovable with respect to the movable second unit 502U. Here, the stationary first unit 501U includes a structure that does not move when the sheet clamped in the cooling clamp T4 is removed, and also includes a structure that can slightly shake or move during maintenance of the first unit 501U. Thereby, the drive motor M is provided to the stationary first unit 501U, and therefore, a not-shown connecting line connecting the drive motor M and a control substrate or the like can be suppressed from being sandwiched between the first unit 501U and the second unit 501U during the rotation of the units.

The second unit 502U is provided to be rotatable with respect to the first unit 501U about a rotation axis (not shown) of the rotation mechanism 550 shown in fig. 4. The second unit 502U is movable between a contact position where the second belt 502 and the first belt 501 contact each other to form the cooling nip T4 and a separated position where the second belt 502 and the first belt 501 are separated from each other so as not to form the cooling nip T4. Fig. 3 shows a case where the second unit 502U is in the contact position, and fig. 4 shows a case where the second unit 502U is in the separation position. Incidentally, in this embodiment, a configuration may also be adopted in which the rotation center is provided at one end side of the second unit 502U with respect to the width direction, and the entirety of the second unit 502U can be moved with respect to the first unit 501U by using a slide mechanism or the like. Further, an example in which the second unit 502U is rotated upward with respect to the first unit 501U with respect to the direction of gravity is shown, but the present invention is not limited thereto. One end side of the first unit 501U with respect to the width direction may also swing downward with respect to the gravity direction with respect to the second unit 502U. In this case, the drive motor M may be provided to the second unit 502U that does not rotate.

< Driving gear portion >

In this embodiment, the rotation of the drive motor M for driving the first belt 501 is transmitted from the first belt stretching roller 501e to the second belt stretching roller 502e through the first drive gear portion 510, thereby rotating the second belt 502. As shown in fig. 3 and 4, the drive gear portion 510 is roughly divided into a second drive gear portion 510a provided on the second unit 502U and a first drive gear portion 510b provided on the first unit 501U. The drive gear portion 510 is separated into a second drive gear portion 510a and a first drive gear portion 510b in response to the swing of the second unit 502U, and is provided so as to be movable between a state in which a second transmission gear 504a and a first transmission gear 504b are engaged with each other and a state in which the second transmission gear 504a and the first transmission gear 504b are not engaged with each other, which will be described later. Therefore, a configuration is adopted in which the drive motor M is provided on one end side of the rotational shaft of the first belt stretching roller 501e (the same side as the side where the rotation mechanism 550 is provided), and the drive gear portion 510 is provided on the side opposite to the drive motor M side, and thereby in the case where the second unit 502U is rotated around the rotation mechanism 550, the engagement between the second drive gear portion 510a and the first drive gear portion 510b can be simply established and released. Incidentally, when the configuration is capable of establishing and releasing the engagement between the second drive gear portion 510a and the first drive gear portion 510b, it is also possible to adopt a configuration in which the second drive gear portion 510a and the first drive gear portion 510b are disposed on the same one end side as the drive motor M side with respect to the first belt stretching roller 502e, and thereby the drive is transmitted between the first unit 501U and the second unit 502U. With this configuration, by adopting a configuration in which the entirety of the second unit 502U can be moved upward relative to the first unit 501U by using the slide mechanism as described above, the engagement between the second drive gear portion 510a and the first drive gear portion 510b or the release of the engagement can be satisfactorily performed. Further, a configuration may also be adopted in which the drive motor M is provided on the other end side of the rotational axis of the first belt stretching roller 501e (the side opposite to the side where the rotation mechanism 550 is provided), and the second drive gear portion 510a and the first drive gear portion 510b are provided on one end side of the rotational axis of the first belt stretching roller 501e, and a configuration may also be adopted in which the drive motor M, the second drive gear portion 510a, and the first drive gear portion 510b are all provided on one end side of the rotational axis of the first belt stretching roller 501e, and drive is transmitted toward the first unit 501U and the second unit 502U.

The second drive gear portion 510a includes a second gear 506a and a second transfer gear 504 a. The second gear 506a is rotatably provided on the rotation shaft of the second belt stretching roller 501e through the one-way clutch 505. The second transfer gear 504a is rotatably provided on a second idler shaft 531 fixed to a side plate of the second unit 502U through a bearing (not shown). The second gear 506a and the second transmission gear 504a are always engaged with each other to transmit the driving force regardless of the swing of the first driving gear portion 510 b. The one-way clutch 505 will be described later.

The first drive gear portion 510b includes a first gear 506b and a first transfer gear 504 b. The rotation shaft of the first belt stretching roller 501e includes an end portion having a D-shape in cross section, and the first gear 506b has a shape engageable with the D-shape and is not rotatable about the rotation shaft of the first belt stretching roller 501 e. That is, the first gear 506b has a structure in which the first gear 506b can rotate integrally with the first belt stretching roller 501e and the rotation shaft thereof. The support member 522 is rotatably provided around the rotation axis of the first belt stretching roller 501e by a bearing (not shown). Thereby, the support member 522 can rotate around the rotation axis of the first belt stretching roller 501 e. The first transmission gear 504b is rotatably provided around an idler shaft 532 fixed to the support member 522 by a bearing (not shown). The support member 522 is urged to move the first transmission gear 504b toward the second transmission gear 504a by a spring member 521 fixed at one end thereof to a fixing portion (not shown) provided on a side plate of the first unit 501U (fig. 5). That is, the first drive gear portion 510b is swingably provided around a rotation shaft (also a rotation shaft of the first belt stretching roller 501 e) as a swing center of the first gear 506 b. The first gear 506b and the first transmission gear 504b are always engaged with each other so as to be able to transmit the driving force regardless of the swing of the first driving gear portion 510 b.

In this embodiment, the second gear 506a, the second transfer gear 504a, the first gear 506b, and the first transfer gear 504b described above are all formed to provide the same module. However, these gears are configured such that the number of teeth of the second transmission gear 504a and the first transmission gear 504b is larger than the number of teeth of the second gear 506a and the first gear 506 b. For example, the number of teeth of the second transfer gear 504a and the first transfer gear 504b is 24 teeth, and the number of teeth of the second gear 506a and the first gear 506b is 23 teeth. Thus, by making the numbers of teeth different from each other, the combination between the second gear 506a and the second transmission gear 504a, which are always engaged with each other so that the driving force can be transmitted, and the combination between the first gear 506b and the first transmission gear 504b, which are always engaged with each other so that the driving force can be transmitted, are prevented from being engaged at the same position (position). Further, in this embodiment, the second gear 506a, the second transfer gear 504a, the first gear 506b, and the first transfer gear 504b are all spur gears so as to facilitate engagement between the adjacent gears when the second unit 502U is moved from the separated state to the contact state with respect to the first unit 501U.

As shown in fig. 3, when the second belt 502 and the first belt 501 contact each other and form the cooling nip portion T4, the second transmission gear 504a of the second drive gear portion 510a and the first transmission gear 504b of the first drive gear portion 510b engage with each other, thereby forming a state capable of transmitting the driving force. On the other hand, as shown in fig. 4, when the second belt 502 and the first belt 501 do not contact each other and the cooling nip portion T4 is not formed, the second transmission gear 504a and the first transmission gear 504b are not engaged with each other, so that a state is formed in which the driving force is not transmittable.

As described above, in this embodiment, the first drive gear portion 510b is provided so as to be able to freely swing about the rotation axis of the first gear 506b as the swing center. Then, in the case where the second unit 502U is moved from the spaced-apart position (fig. 4) to the contact position (fig. 3), as shown in fig. 5, the first drive gear portion 510b is moved clockwise (arrow Q direction) against the urging of the spring member 521. This is because, with the movement of the second unit 502U, the second transmission gear 504a of the second drive gear portion 510a contacts and presses the first transmission gear 504b of the first drive gear portion 510 b.

Further, in the case where the second unit 502U is moved from the contact position (fig. 3) to the separation position (fig. 4), the first drive gear portion 510b is moved counterclockwise by the urging of the spring member 521. Here, in the case where the first drive gear portion 510b moves counterclockwise, the rotation restricting portion 523 formed on the support member 522 interferes with a protruding portion 524 (fig. 3 and 4) provided on a side plate of the first unit 501U, so that the rotation of the first drive gear portion 510b is restricted. Thereby, the first driving gear portion 510b and the second driving gear portion 510a are stopped at a predetermined angle. In the case of this embodiment, the predetermined angle is set so that the second transmission gear 504a and the first transmission gear 504b engage with each other and thus the driving force can be transmitted therebetween in the case where the second unit 502U is moved from the separated position to the contact position. In addition, each of the second drive gear portion 510a and the first drive gear portion 510b is provided such that when the first belt 501 is rotated by the drive motor M (fig. 2), the first transmission gear 504b is always rotated in a state where the first transmission gear 504b is pressed against the second transmission gear 504 a.

The arrangement of the second driving gear portion 510a and the first driving gear portion 510b will be described in detail. As shown in fig. 5, a straight line connecting the rotation center O of the second transmission gear 504a and the rotation center L of the first transmission gear 504b is referred to as a straight line OL. Further, a contact point at which the pitch circle of the second transmission gear 504a and the pitch circle of the first transmission gear 504b contact each other in a state (a state in which drive transmission is possible) in which a free end (top) of the teeth of the second transmission gear 504a and a free end (top) of the teeth of the first transmission gear 504b contact each other is referred to as a point K. Further, a straight line connecting the point K and the swing center J of the first drive gear portion 510b is referred to as a straight line JK. Further, a straight line perpendicular to the straight line LK passing through the rotation center L and the point K is referred to as a line segment KN. The line segment KN is a tangent between the second transfer gear 504a and the first transfer gear 504 b. The second transmission gear 504a and the first transmission gear 504a are capable of transmitting a driving force to each other. The transmission of the driving force acts in the direction of the line segment KN plus the pressure angle. In this embodiment, the pressure angle is set to 20 °.

The direction in which the drive force transmission is performed through the second transmission gear 504a and the first transmission gear 504b is indicated by a line segment SK that is inclined at the above-described pressure angle with respect to the line segment KN. The straight line JK and the line segment PK shown in fig. 5 are compared. In the case of this embodiment, the line segment PK indicating the driving force transmission direction of the second transmission gear 504a and the first transmission gear 504b is located on the upstream side of the straight line JK with respect to the rotational direction (arrow G direction) of the second transmission gear 504a and at a position where the first transmission gear 504b meshes into the second transmission gear 504a side, as compared with the case of the straight line JK. Thus, when the first belt 501 is rotated by the drive motor M, the first transmission gear 504b is operable to be meshed into the second transmission gear 504a by the force generated by the second transmission gear 504a and the first transmission gear 504 b.

Further, in a case where the second unit 502U is moved from the spaced-apart position to the contact position and the first and second transfer gears 504b and 504a are not engaged with each other, the tooth tops of the respective gears are in contact with each other, and therefore, the straight line OL becomes longer than the straight line OL when the second unit 502U is in the contact position. Further, when the second unit 502U is in the contact position shown in fig. 3 and the drive motor M does not rotate the first belt 501, the first transmission gear 504b is held in a state where the first transmission gear 504b is in contact with the first transmission gear 504a through the spring member 521 as urging means. Then, when the first belt 501 is rotated by the drive motor M, the first drive gear portion 510b is rotated clockwise, so that the second transmission gear 504a and the first transmission gear 504b are engaged.

That is, as the second unit 502U moves from the spaced-apart position to the contact position, when the tooth tips of the second transmission gear 504a abut against the tooth tips of the first transmission gear 504b, the first drive gear portion 510b moves against the urging force of the spring member 521 while maintaining the abutting state between the tooth tips. After the second unit 502U is moved to the contact position, when the first belt stretching roller 501E is rotated by the drive motor M (in the arrow E direction) in a state where the tooth tops are in contact with each other, the first transmission gear 504b is rotated clockwise (in the arrow F direction) by transmitting a driving force thereto. When the first transmission gear 504b rotates, the contact position between the teeth of the first transmission gear 504b and the associated teeth of the second transmission gear 504a, which abut against each other, is shifted. When the contact position is biased by the urging force of the spring member 521, the first drive gear portion 510b moves toward the second drive gear portion 510 a. Thereby, the first transmission gear 504b and the second transmission gear 504a are engaged with each other. To achieve such engagement, the second drive gear portion 510a and the first drive gear portion 510b are provided as described above.

Further, as described in this embodiment, in the case where the first drive gear portion 510b is made swingable, in the state where the first transmission gear 504b and the second transmission gear 504a are engaged with each other, the transmission of the driving force from the first transmission gear 504b to the second transmission gear 504a is liable to be hindered. This is because the first drive gear portion 510b is urged toward the second transmission gear 504a by the spring member 521, and therefore the first transmission gear 504b and the second transmission gear 504a are strongly engaged with each other by the urging force of the spring member 521. In view of this, in this embodiment, by ensuring the center distance between the second transmission gear 504a and the first drive gear portion 510b, the first transmission gear 504b and the second transmission gear 504a are engaged with each other by a force suitable for drive transmission without being affected by the urging force of the spring member 521. Specifically, as shown in fig. 6, an inter-shaft (center distance) restricting member 580 is provided so as to secure a center distance between the second transmission gear 504a and the first transmission gear 504 b. In fig. 2 to 5, the inter-shaft restricting member 580 is omitted from illustration. The inter-shaft restricting member 580 is provided on the rotation shaft of the second transmission gear 504a in the second unit 502U, and contacts the rotation shaft of the first transmission gear 504b when the second unit 502U is in the contact position. The inter-shaft restricting member 580 is formed in an arcuate shape at a portion thereof that contacts the rotation shaft of the first transmission gear 504 b. Thereby, when the inter-shaft restricting member 580 is in contact with the rotation shaft of the first transmission gear 504b, even if the abutment position is offset with respect to the feeding direction of the recording material S (arrow D direction of fig. 2), the center distance between the second transmission gear 504a and the first drive gear portion 510b can be ensured.

As described above, in this embodiment, in the case where the second unit 502U is moved from the separated position to the contact position, the second transmission gear 504a of the second drive gear portion 510a contacts the first transmission gear 504b of the first drive gear portion 510b, so that the first drive gear portion 510b swings. That is, during the movement of the second unit 503U to the contact position, even when the teeth of the second transmission gear 504a and the teeth of the first transmission gear 504b abut against each other, the first drive gear portion 510 moves to avoid the abutment, so that breakage is not easily generated between the teeth of the second transmission gear 504a and the teeth of the first transmission gear 504 b. Further, when the second unit 502U is moved to the contact position, even if the teeth of the second transmission gear 504 and the teeth of the first transmission gear 504b are not engaged with each other, these teeth are engaged with each other with the subsequent rotation of the first belt stretching roller 501 e. Also, at that time, it is possible to suppress excessive force from being exerted on the teeth, so that the teeth are not easily broken.

< one-way Clutch >

In order to cool the recording material S in the cooling nip portion T4, in the case where the recording material S is nipped and fed by the second belt 502 and the first belt 501, it is desirable to make the moving speed of the second belt 502 and the moving speed of the first belt 501 substantially equal to each other so as to stabilize the feeding of the recording material S. In the case of this embodiment, the moving speed of the first belt 501 rotated by the first belt stretching roller 501e directly driven by the drive motor M is a basic (reference) speed. For this reason, it is desirable to adopt a configuration in which the moving speed of the second belt 502 rotated by the second belt stretching roller 502e to which the drive of the drive motor M is indirectly transmitted through the drive gear portion 510 is equal to the moving speed of the first belt 501.

However, in the conventional configuration, the moving separation position of the second belt 502 and the moving speed of the first belt 501 do not coincide with each other in some cases. For example, in the case where the diameter of the second belt stretching roller 502e is formed smaller than that of the first belt stretching roller 501e due to the processing accuracy or in the like case, the moving speed of the second belt 502 is easily higher than that of the first belt 501. Therefore, in the case where the moving speed of the second belt becomes high due to the deviation in the diameter of the second belt stretching roller 502e or the like, the longer the rotation time of the second belt 502 is, the higher the moving speed of the second belt 502 is, so that the difference between the moving speed of itself and the moving speed of the first belt 501 becomes large. In this case, the feeding of the recording material S nipped and fed by the second belt 502 and the first belt 501 becomes unstable and is not preferable. Further, in the case of the configuration in which the first drive gear portion 510b is urged toward the second transmission gear 504a by the urging force of the spring member 521 as described above, when the moving speed of the second belt 502 becomes higher than the moving speed of the first belt 501, the rotation speed of the second transmission gear 504a becomes higher than the rotation speed of the first transmission gear 504 b. Then, the first transmission gear 504b rotated by the driving force of the drive motor M is repelled by the second transmission gear 504a, thereby releasing the engagement between the second transmission gear 504a and the first transmission gear 504b against the urging force of the spring member 521. Although the second transmission gear 504a and the first transmission gear 504b, which are disengaged from each other, can be engaged with each other again by the urging force of the spring member 521, as long as a difference in rotational speed occurs between the second transmission gear 504a and the first transmission gear 504b (between the second belt 502 and the first belt 501), release of the engagement between the transmission gears frequently occurs by repulsion of the first transmission gear 504 b. In this case, the driving force of the driving motor M is not transmitted to the second belt 502, and the operation of the second belt 502 is interrupted with respect to the first belt 501 (the driving force of the driving motor M is continuously transmitted to the first belt 501), and there is a possibility that defective sheet feeding or the like occurs.

In this embodiment, in order to suppress the occurrence of a difference in moving speed between the second belt 502 and the first belt 501, the drive gear portion 510 is provided with a one-way clutch 505. In the case where a speed difference is generated between the second belt 502 and the first belt 501, the transmission and interruption of the drive are automatically switched by the one-way clutch, so that the speed difference between the second belt 502 and the first belt 501 can be reduced. Hereinafter, the drive gear portion 501 provided with the one-way clutch will be described using fig. 7 while referring to fig. 2, 3, and 5.

As shown in fig. 5, in the case of this embodiment, a one-way clutch 505 as a drive switching portion is provided inside the second gear 506a so that the rotation center of the second gear 506a and the rotation center of the one-way clutch 505 coincide with each other. Specifically, as shown in fig. 7, the one-way clutch 505 is integrally attached to the second gear 506a, and the one-way clutch 505 can rotate on the rotation shaft 502ea of the second belt stretching roller 502e with the rotation shaft 502ea as a rotation center in a state where the one-way clutch 505 is press-fitted in the second gear 506 a. That is, the second gear 506a is supported by the rotary shaft 502ea via the one-way clutch 505. In the case where the second gear 506a rotates clockwise (in the arrow H direction) in fig. 5, the one-way clutch 505 rotates integrally with the rotation shaft 502a, and allows transmission of drive to the second belt stretching roller 502 e. In the case where the second gear 506a rotates counterclockwise (in the direction opposite to the arrow H direction) in fig. 5, the one-way clutch 505 idles with respect to the rotation shaft 502ea, and thus the transmission of drive from the second gear 506a to the second belt stretching roller 502e is interrupted.

For example, in the case where the driving of the drive motor M (fig. 2) is started to rotate the first belt 501, the first gear 506b of the first drive gear portion 510b starts to rotate counterclockwise (in the arrow E direction), so that the first transmission gear 504b rotates clockwise (in the arrow F direction). Then, the second transmission gear 504a of the second drive gear portion 510a to which drive (driving force) is transmitted rotates counterclockwise (in the arrow G direction), so that the second gear 506a rotates clockwise (in the arrow H direction).

When the second gear 506a rotates clockwise, the second gear 506a and the rotation shaft of the second belt stretching roller 502e are in a drive transmission state, so that the second belt stretching roller 502e rotates clockwise. Therefore, the second belt 502 is rotated clockwise (in the arrow B direction in fig. 2) by the clockwise rotation of the second belt stretching roller 502 e. At this time, the number of revolutions (number of revolutions) of the second gear 506a is the same as the number of revolutions of the second belt stretching roller 502 e. Then, in response to the number of rotations increasing to the predetermined number of rotations, the moving speed of the second belt 502 and the moving speed of the first belt 501 also increase. Here, when the diameter of the second belt stretching roller 502e and the diameter of the first belt stretching roller 501e are the same, the moving speed of the second belt 502 and the first belt 501 is the same. However, as described above, for example, when the diameter of the second belt stretching roller 502e is larger than the diameter of the first belt stretching roller 501e, a difference in moving speed may be generated between the second belt 502 and the first belt 501.

As described in this embodiment, by providing the drive gear portion 510 with the one-way clutch 505, a difference in moving speed between the second belt 502 and the first belt 501 can be suppressed. Here, in the case where the second belt stretching roller 502e and the second gear 506a are moved in opposite directions relative to each other, the one-way clutch 505 does not allow the transmission of the driving force to the rotation shaft 502ea of the second belt stretching roller 502e through the second gear 506 a. That is, when the moving speed of the second belt 502 becomes higher than the moving speed of the first belt 501, the second gear 506a and the rotation shaft 502ea of the second belt stretching roller 502e are placed in the drive interruption state by the one-way clutch 505. In this case, the second belt stretching roller 502e freely rotates (idles) with respect to the second gear 506 a. That is, the rotation of the second belt stretching roller 502e and the rotation of the second belt 502 are not related to the drive transmission of the drive gear portion 510.

Therefore, by providing the one-way clutch, in the case where the moving speed of the second belt 502 becomes higher than the moving speed of the first belt 501, the second gear 506a is rotated by receiving the driving force of the driving motor M via the first driving gear portion 510b, but the second belt-stretching roller 502e is rotated by receiving the rotation (rotational force) of the second belt 502. In this case, the second belt 502 is rotated only by the first belt 501 in contact therewith in the cooling nip T4, and the driving force of the driving motor M is not applied to the second belt 502. Accordingly, the moving speed of the second belt 502 follows the moving speed of the first belt 501, and thus gradually decreases to be equal to the moving speed of the first belt 501.

As described above, the moving speed of the second belt 502 follows the moving speed of the first belt 501, so that the peripheral speed of the second belt stretching roller 502e is reduced to be not more than the peripheral speed of the second gear 506a driven by the drive motor M. Then, the second gear 506a and the rotation shaft of the second belt stretching roller 502e are placed in the drive transmission state again by the one-way clutch 505. When the rotation shafts of the second gear 506a and the second belt stretching roller 502e are placed in a drive transmission state by the one-way clutch 505, the driving force is transmitted to the second belt stretching roller 502e through the driving gear portion 510, so that the second belt stretching roller 502e is rotated by the driving force. Then, as described above, when the moving speed of the second belt 502 becomes higher than the moving speed of the first belt 501 again, the drive interrupted state is formed by the one-way clutch 505.

Therefore, the one-way clutch 505 is provided to be able to change transmission and interruption of drive between the second gear 506a and the rotation shaft of the second belt stretching roller 502e with each other. Accordingly, in the case where a difference in moving speed is generated between the second belt 502 and the first belt 501, transmission and non-transmission of the driving force between the second gear 506a and the rotating shaft of the second belt stretching roller 502e are repeated by the one-way clutch. This can suppress the occurrence of a difference in the moving speed between the second belt 502 and the first belt 501.

< other examples >

In the above-described embodiment, the description was given taking as an example the case where the recording material cooling apparatus 50 is provided in the apparatus main assembly 100A of the image forming apparatus 100 (fig. 1), but the present invention is not limited thereto. For example, the recording material cooling apparatus 50 may also be provided outside the apparatus main assembly 100A. Fig. 8 shows an example in which the recording material cooling apparatus 50 is provided outside the apparatus main assembly 100A.

As shown in fig. 8, the external cooling device 101 is connected to the apparatus main assembly 100A. The external cooling device 101 is configured as an external apparatus (referred to as an optional unit or the like) that can be attached to the apparatus main assembly 100A so as to be connectable to the image forming apparatus 100 in order to expand the functions of the image forming apparatus 100. The external cooling device 101 is provided for reducing the temperature of the recording material S (which is high compared to the temperature before fixing) to a predetermined temperature by cooling the recording material S discharged through the discharge port. The external cooling device 101 includes the above-described recording material cooling device 50 for cooling the recording material S. In this embodiment, in the case where the external cooling device 101 is connected as an external apparatus to the image forming device 100 as shown in fig. 8, the image forming device 100 and the external cooling device 101 are collectively referred to as an image forming device. That is, in this embodiment, the entire apparatus related to the operation from the feeding of the sheet on which the image is to be formed to the discharging of the sheet to the outside of the image forming apparatus is referred to as the image forming apparatus. Further, in a case where a sheet processing apparatus for performing a binding process, a punching process, or the like on sheets is connected to the external cooling apparatus 101 on the downstream side of the external cooling apparatus 101, all configurations including the external cooling apparatus 101 and the sheet processing apparatus are collectively referred to as an image forming apparatus for forming an image on a sheet.

The recording material S cooled by the external cooling device 101 is discharged from the external cooling device 101 by a discharge roller pair 83, and is stacked on a sheet discharge tray 120. The sheet discharge tray 120 is provided to be attachable to and detachable from the external cooling apparatus 101 or the image forming apparatus 100. That is, in a case where the external cooling device 101 is not connected to the image forming apparatus 100, the sheet discharge tray 120 is mounted to the image forming apparatus 100 (fig. 1). Further, when the external cooling device 101 is connected to the image forming device 100, the sheet discharge tray 120 is detached from the image forming device 100 and then attached to the external cooling device 101.

Incidentally, as the peripheral machine, a plurality of external cooling devices 101 may also be connected. By increasing the number of external cooling devices 101 to be connected, the operator can easily improve the cooling capability of the recording material S in the image forming apparatus 100 that has been installed.

Incidentally, as described in the above-described embodiment, the present invention is not limited to the image forming apparatus applied to the recording material cooling apparatus 50, but may also be applied to a sheet feeding apparatus of a belt type, a fixing apparatus, or the like, in which the recording material S is nipped and fed by a pair of belts. That is, the present invention is applied in the case of a configuration in which the recording material S is nipped and fed through a nip portion formed by a pair of belts in contact with each other, so that it is possible to suppress the moving speed of one belt from becoming higher than the peripheral speed of the drive gear. Thereby, abrasion of the toner and wrinkle on the recording material S which is nip-fed due to the difference in the moving speed of the belt do not occur.

Incidentally, in the above-described embodiment, the configuration is described in which the drive transmission can be established between the first belt stretching roller 501e and the second belt stretching roller 502e by the first transmission gear 504b and the second transmission gear 504a, but the present invention is not limited thereto. For example, the drive transmission may also be established by direct engagement between the first belt stretching roller 501e and the second belt stretching roller 502e or by a larger number of transmission gears. Incidentally, in the case of the configuration in which the first belt stretching roller 501e and the second belt stretching roller 502e are directly engaged with each other, it is preferable that the tooth top of the first gear 506b and the tooth top of the second gear 506a are sharpened, and thus are easily engaged with each other.

Incidentally, in the above-described embodiment, the configuration in which the one-way clutch 505 is provided as the drive switching portion is described, but a similar effect can be obtained even in the configuration in which the torque limiter, the electromagnetic clutch, or the like is provided as the drive switching portion. Further, in the above-described embodiment, the configuration in which the one-way clutch 505 is provided on the rotation shaft of the second tape stretching roller 502e is described, but it may be required that only the one-way clutch 505 is provided on the gear shaft of any one of the second drive gear portion 510a and the first drive gear portion 510b constituting the drive transmission passage. For example, the first idler shaft 532 of the first transmission gear 504b serves as a rotatable shaft with respect to the support member 522, and the one-way clutch 505 may also be provided between the shaft and the first transmission gear 504 b. Further, a similar configuration may also be provided for the second idler shaft 531 of the second transfer gear 504 a.

According to the present invention, it is possible to provide an image forming apparatus including a cooling device capable of driving a pair of belt units by a single motor.

While the present invention has been described with reference to exemplary embodiments, it is to be understood that the invention is not limited to the disclosed exemplary embodiments. The scope of the following claims is to be accorded the broadest interpretation so as to encompass all such modifications and equivalent structures and functions.