Sheet feeding apparatus, and image forming apparatus and image reading apparatus respectively equipped with sheet feeding apparatus

A sheet feeding apparatus comprises a sheet stacking portion for stacking sheets thereon, a sheet feeding rotating member for feeding the sheet stacked on the sheet stacking portion, a stopper for regulating the sheet stacked on the sheet stacking portion, and a rotatable gear adapted to hold the stopper at the regulating position of regulating the sheet stacked on the sheet stacking portion, by engaging with the stopper. In this construction, the engagement of the gear and the stopper is released when the gear is rotated.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a sheet feeding apparatus, and an image forming apparatus and an image reading apparatus which are respectively equipped with the sheet feeding apparatus.

2. Related Background Art

Conventionally, an image forming apparatus such as a copying machine, a printer, a facsimile machine or the like, or an image reading apparatus such as a scanner or the like is equipped with a sheet feeding apparatus which feeds sheets to an image forming portion or an image reading portion. More specifically, in the sheet feeding apparatus like this, for example, the sheets stacked on a sheet stacking portion are fed to a sheet feeding means, the fed sheets are then separated one by one by a separating portion consisting of a separating roller and a separating pad, and the separated sheet is further conveyed to the image forming section or the image reading section.

Incidentally, as the conventional sheet feeding apparatus like this, there is an apparatus which is equipped with a stopper member rotating on, e.g., the upper point of a sheet conveying path so as to stop the sheets at a predetermined position when the sheets are stacked on the sheet staking portion. Thus, in this apparatus, the sheets are stacked when the stopper member is at the position to block up the sheet conveying path so that the stacked sheets abut against the stopper member, whereby the sheets are stopped at the predetermined position.

Here, in the case where the stopper member like this is provided, it is necessary to shift the stopper member to its initial position after ending the sheet conveying. In this context, as the construction for controlling the position of the stopper member, a construction for controlling the position of the stopper member without using a solenoid and an electromagnetic clutch being electrical actuators, and a mechanical spring clutch has been proposed (see Japanese Patent Application Laid-Open Nos. 2001-022137, H09-240862 and H09-058891).

In the above construction, for example, a driving source of a sheet conveying means is used as the driving source for controlling the position of the stopper member, and driving to the stopper member is transmitted through the sheet conveying means, whereby it is possible to prevent from transmitting excessive driving force. Thus, the above construction achieves the stopper member position controlling without using the electrical actuator and the spring clutch. Consequently, by not using the electrical actuator and the spring clutch as above, the above construction achieves space saving, cost reduction, and load reduction to a power supply substrate. Moreover, the above construction achieves achieve the high-reliability stopper member position controlling with extremely less number of parts.

However, in the conventional sheet feeding apparatus and the image forming and reading apparatuses respectively equipped with the conventional sheet feeding apparatus, after discharging all the sheets and before inserting a next sheet, it is necessary to execute an initialization operation to return the stopper member to its initial position preceding the stacking of the sheets so as to prepare a control function for the sheet leading edges. Here, to return the stopper member to its initial position, it is necessary to reverse a motor.

Incidentally, in Japanese Patent Application Laid-Open No. 2001-022137, when the stopper member is returned to its initial position and fixed, a large load is applied to the engaging arm portion of the stopper member, whereby it is necessary to sufficiently enlarge the stopper member (i.e., the engaging arm portion thereof) to maintain the intensity thereof. Moreover, there is a problem that the cost of the motor increases because large torque is necessary for the motor.

Further, in Japanese Patent Application Laid-Open No. H09-240862, it is necessary to surely reverse the motor as many as a predetermined rotation number to return the stopper member to its initial position. For this reason, there is a problem that the above controlling for the stopper member position is not applicable to the apparatus in which reverse rotation of the motor is executed for another use, that is, the use other than the return of the stopper member to its initial position.

Furthermore, in Japanese Patent Application Laid-Open No. H09-058891, the initial position of the stopper member is recognized by a sensor of primarily detecting whether an original (sheet) exists. However, in such a construction, turning on and off of the sensor are repeated intermittently even after a last original passed the stopper member, whereby interrupt processes of software frequently occur. Thus, the overall process might become heavy. Moreover, it is likely that the sensor is turned on because the position of the stopper member shifts due to opening and closing of an original guide. In this case, there is a problem that it is difficult on software to discriminate whether the original has been inserted or the stopper member is not on its initial position.

SUMMARY OF THE INVENTION

The present invention has been made in consideration of such present situations, and an object thereof is to provide a sheet feeding apparatus which can achieve space saving and cost reduction, and, when sheets are stacked thereon, can surely stop the sheets at a predetermined position, and to further provide an image forming apparatus and an image reading apparatus each of which is equipped with the sheet feeding apparatus.

The present invention is characterized by comprising a sheet stacking portion for stacking sheets thereon, a sheet feeding rotating member adapted to feed the sheet stacked on the sheet stacking portion, a stopper adapted to regulate the sheets stacked on the sheet stacking portion, and a rotatable gear adapted to hold the stopper at a regulating position of regulating the sheets stacked on said sheet stacking portion, by engaging with the stopper, and is further characterized in that the engagement of the gear and the stopper portion is released when the gear is rotated.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

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

FIG. 1is an exterior perspective diagram showing an MFP (multiple function peripheral) being an example of an image forming apparatus equipped with a sheet feeding apparatus according to the present invention, andFIG. 2is a cross section diagram of the MFP.

The MFP has four functions, i.e., a copy function, a facsimile function, a printer function for acting as a computer peripheral device, and an image scanner function for also acting as the computer peripheral device. Besides, the MFP consists of an apparatus main body100, a recording sheet feeding portion101, an electrophotographic image forming section102, an original reading section105, and an operation portion106.

Here, the recording sheet feeding portion101separates and feeds one by one recording sheets S stacked on a recording sheet cassette7by a separating means consisting of a not-shown separating pawl and a friction pad101b, and then supplies the recording sheet S to the image forming section102through a pair of registration rollers (hereinafter called registration roller pair)101c.

Incidentally, the recording sheet S is a paper, a resin sheet, and another material, and can use electrostatic dry recording toner as transferable toner. Besides, the recording sheet cassette7which can hold150standard-sized plain sheets (papers) can be drawn from the apparatus main body100in the near-side direction (i.e., direction B inFIG. 2). Thus, after the recording sheet cassette7was drawn from the apparatus main body100, the recording sheets S can be exchanged or refilled.

Moreover, inFIG. 2, numeral8denotes a front cover, and only one recording sheet can be inserted through an opening portion8aprovided on the front cover8. Then, the inserted recording sheet is interflowed by a sheet-passing bent path101dand the registration roller pair101cconnected to the recording sheet cassette7, and the interflowed recording sheet is further conveyed to a downstream transferring portion102a.

The image forming section102forms an image in an electrophotographic manner on the recording sheet S supplied from the recording sheet feeding portion101, in response to an image signal transmitted from another apparatus, an image signal transmitted from the later-described original reading section105or data output from a computer and the like. The image forming section102is held within a main body frame9, and consists of a laser scanner102b, a toner-incorporated cartridge102c, the transferring portion102a, a fixing portion102dand a discharging portion103.

Incidentally, the toner-incorporated cartridge102ccan be inserted into and removed from the opening portion which is opened by rotating the front cover8of the apparatus main body100in the direction indicated by an arrow C as shown inFIG. 3. Thus, when the toner-incorporated cartridge102cis loaded into the apparatus main body100and the front cover8is then closed, a not-shown recording portion driving means and the coupling of the rotating shaft of the toner-incorporated cartridge102care connected with each other, whereby driving is transmitted.

Moreover, the discharging portion103consists of a U-turn path103a, a pair of discharging rollers (hereinafter called discharging roller pair)103b, a recording sheet excessive stacking detecting portion103c, and a discharging tray103d. Further, a heat discharging duct10is provided between the discharging portion103and the original reading section105, whereby heat from the fixing portion102dis discharged forward and backward of the apparatus main body100.

The original reading section105converts reflection light obtained by illuminating light onto an original P into an electrical signal, executes a predetermined image process to the acquired electrical signal, and then transmits the processed signal to another apparatus or an own recording controlling portion104. Thus, the original feeding portion (sheet feeding device) is provided to feed an original being a sheet to the image reading section.

In addition, inFIG. 2, numeral11denotes a resin frame which supports the image reading section105, and a bottom face11aof the frame11also acts as the heat discharging duct together with the discharging portion103. Here, it should be noted that a hole is not made on the bottom face11aat all so that water vapor generated from the recording sheet S does not penetrate into the image reading portion at the fixing portion102d.

Numeral12denotes an original tray(sheet tray) which is equipped with original width regulating plates13aand13b, and the original tray12acts as the sheet stacking portion. Numeral14denotes an extension tray which is rotatable based on a fulcrum14a, numeral15denotes a pre-feeding roller, numeral16denotes a separating roller, numeral18denotes a detachable original discharging tray, numeral17denotes a photoelectric converting element which acts as the image reading portion, numeral20denotes a conveying roller, and numeral21denotes a discharging roller. Incidentally, in the present embodiment, a CIS (Contact Image Sensor) is used as the photoelectric converting element17to achieve downsizing.

Moreover, numeral1denotes an upper original guide in which an original presence/absence sensor2and an original edge sensor3each consisting of a photointerruptor and a resin actuator are provided. Numerals2aand3adenote wiring harnesses of the respective sensors2and3. The respective wiring harnesses2aand3aare led from the backside of the upper original guide1to the outside, and then connected to a connector4aprovided on an operation portion substrate4through a wiring harness holding portion1ashown inFIG. 4.

The reason why the wiring harnesses2aand3aof the respective sensors2and3are once led outside is to improve assembling performance. In other words, to dispose and connect the wiring harnesses2aand3awithin the area of the operation portion substrate4, it is necessary to lengthen these harnesses unnecessarily for wiring work and it is also necessary to provide a hole by which these harnesses and assembling tools are penetrated through the operation portion substrate4.

However, in the above former case, the redundant wiring harnesses2aand3acome into contact with the element legs, whereby there is a fear that these harnesses are damaged and/or short-circuited. In addition, in the above latter case, the unnecessary hole exists on the operation portion substrate4, whereby there is a fear that a degree of freedom of the layout of an operation key, which should attach importance to operability, is obstructed. Thus, in the present embodiment, to solve such problems, the wiring harnesses2aand3aare led outside the projection plane of the operation portion substrate4, the operation portion substrate4and an operation portion cover5shown inFIG. 2are assembled respectively, the assembled substrate and cover are attached to the upper original guide1, and then the wiring harnesses2aand3aare connected to the operation portion substrate4.

Moreover, as shown inFIG. 5, in the original guide1, backup rollers20aand21awhich are pressure contacted with the conveying roller20and the discharging roller21respectively by blade springs19aand19b, and a friction pad22which is urged toward the separating roller16by a spring22aare provided. Incidentally, numerals23aand23brespectively denote locking portions, and the upper original guide1is resiliently engaged with the resin frame11by means of the locking portions23aand23b.

Here, the upper original guide1is rotatably held based on a fulcrum14aby the frame11. Thus, when a jam occurs between a lower original guide12abeing the extension of the original tray12shown inFIG. 2and the upper original guide1, a jam process for releasing urging force of each roller is executed by rotating the upper original guide1in the direction indicated by an arrow A shown inFIG. 6.

Incidentally, metal parts, such as metal shafts20band21bof the respective backup rollers20aand21aofFIG. 5and the stainless blade springs19aand19bfor urging the metal shafts20band21b, which cause electrostatic noises are provided in the upper original guide1. Thus, an earth plate25which acts as a grounded means is provided for grounding these metal parts.

Moreover, in the original reading section105, a steel-plate original urging plate24(seeFIG. 2) urges the original P toward the CIS17by using a helical compression spring24a, and the bottom of the helical compression spring24ais in contact with the earth plate25through the hole provided on the resin wall of the upper original guide1. Furthermore, a charge eliminating brush (seeFIG. 2) made by conductive fabric is provided in the discharging portion103so that the brush is in contact with the earth plate25through an opening portion1cprovided on the upper original guide1.

Here, the earth plate25is fixed to the upper original guide1by screws together with the blade springs19aand19band an earth lead26consisting of a coated lead and a round terminal, and the earth lead26is connected to the frame ground through the opening portion1cprovided in the vicinity of a rotational supporting portion1bof the upper original guide1.

The operation portion106, which is used by a user to issue various indications to the apparatus with respect to the four functions such as the copy function and the like of the MFP, is provided on the upper portion (upper original guide1) of the original reading section105. Incidentally, the operation portion106is connected to a main body control substrate107as shown inFIG. 4by a flexible flat cable6through which power, a key matrix signal, an LCD signal and a sensor signal are transmitted.

Here, the position of the flexible flat cable6is fixed at the engaging portion provided on the frame11of the reading portion, and an elastic margin portion is provided between the engaging portion and the operation portion substrate4. Thus, when the upper original guide1is opened to deal with the jam of the original P, the elastic margin portion of the flexible flat cable6can absorb positional shifting of a flat cable connector4bon the operation portion substrate.

The main body control substrate107, which is provided on the side face of the main body, includes an image processing portion107c, a communication controlling portion107d, a CPU107e, a ROM107fand a RAM107g. Here, although not shown, a network connecting terminal, a telephone line connecting terminal, and a peripheral device connecting terminal (USB (Universal Serial Bus), IEEE (Institute of Electrical and Electronics Engineers) 1394 bus, a memory device, etc.) are provided on the communication controlling portion107d. Thus, the relevant apparatus can function as a standalone apparatus or can function as a network device or a computer peripheral device. Incidentally, the main body control substrate107is connected to a power supply104aand a recording control substrate104bprovided above the recording sheet cassette7through wiring harnesses107aand107b.

FIG. 7is a diagram showing the detail of the original feeding portion. As shown inFIG. 7andFIG. 5, the separating roller16acting as a sheet separating and conveying means to separate and convey the sheets one by one, a pre-feeding roller15acting as a sheet feeding rotation member (sheet feeding roller), a first idler gear28, a second idler gear29, the conveying roller20, the discharging roller21, the CIS17, and a motor40acting as a normally and reversely rotatable driving means are attached to the frame11.

Here, as shown inFIG. 8A, a resin collar30ais forcefully inserted by a separating roller shaft30to which the separating roller16is attached, whereby the resin collar30aalways rotates integrally with the separating roller shaft30. Moreover, as shown inFIG. 8B, a mechanical timer31is rotatably provided on the driving input side (i.e., motor side) being one end of the separating roller shaft30, and a separating driving gear32is inserted by the separating roller shaft30. Incidentally, in the present embodiment, the mechanical timer31and the separating driving gear32are provided at the end of the separating roller shaft30with appropriate slacks (lashes or plays) in the rotative direction so as to delay transmission of the driving.

Moreover, the separating roller16is rotatably attached to the separating roller shaft30on the side opposite to the separating driving gear32across the resin collar30a. Besides, an output gear33is fixed to the other end of the separating roller shaft30, whereby the output gear33rotates integrally with the separating roller shaft30.

FIG. 8Cshows the state that, after the mechanical timer31, the separating roller16and the like were attached to the separating roller shaft30, a clutch spring34is externally attached to the mechanical timer31, the resin collar30aand a sleeve16aof the separating roller16. Thus, the driving force of the separating driving gear32can be transmitted independently to each of the separating roller shaft30and the separating roller16.

Incidentally, the resin collar30aacts as a sheet feeding means driving force supplying portion which transmits the driving force from the motor40to the pre-feeding roller15through the clutch spring34, and the sleeve16aof the separating roller16acts as a sheet conveying means driving force supplying portion which transmits the driving force from the motor40to the separating roller16.

Here, in the present embodiment, the winding direction of the clutch spring34being a clutch means is, for example, the winding direction so as to transmit the power to the output gear33and the separating roller16through the resin collar30aand the sleeve16aof the separating roller16when the separating driving gear32being a driving force supplying portion for supplying the driving force from the motor40is rotated in the direction indicated by an arrow D shown inFIG. 7by the forward rotation of the motor4.

Moreover, in the case where the separating driving gear32is driving also in the direction indicated by the arrow D, when the original P reaches the conveying roller20of which conveying speed is higher than that of the separating roller16as described later, there is a possibility that the separating roller16rotates faster than the separating driving gear32because compelling force is applied to the separating roller16through the original P due to a difference in rotational speed between the separating roller16and the conveying roller20. In such a case, it is set that the clutch spring34loosens. Then, when the clutch spring34loosens, the driving force is not transmitted to the resin collar30a, whereby the output gear33does not rotate.

Incidentally, when the clutch spring34loosens as above, the clutch spring34rotates according to the sleeve16aof the separating roller16having the largest external diameter, and the mechanical timer31rotates according to the clutch spring34at rotational speed higher than that of the separating driving gear32due to loosening torque of the clutch spring34. Here, when the mechanical timer31rotates faster than the separating driving gear32as above, the slack provided between the mechanical timer31and the separating driving gear32shifts toward the one side of the rotational direction, that is, the slack becomes small gradually in the rotational direction.

Then, when the mechanical timer31further rotates, the slack completely shifts toward the one side of the rotational direction, that is, the slack disappears. After then, because the loosening torque of the clutch spring34is minute, the rotational speed of the mechanical timer31comes to be substantially the same as that of the separating driving gear32, and the state that the slack has shifted toward the one side of the rotational direction is maintained.

On one hand, after then, when the original P passed and thus the compelling force is not applied to the separating roller16, the driving force is not transmitted from the separating driving gear32through the clutch spring34until the separating driving gear32rotates by the slack amount even if the separating driving gear32rotates, because the slack provided between the mechanical timer31and the separating driving gear32shifts toward the one side. Incidentally, when the separating driving gear32rotates reversely in the opposite direction indicated by an arrow E, the clutch spring32loosens, whereby the driving force is not transmitted to the resin collar30a. For this reason, the driving force is not transmitted to the separating roller16and the output gear33.

Meanwhile, the pre-feeding roller15is formed of a section D-cut shape having a notch portion15A (seeFIG. 5) formed by partially cutting the circumference face of the roller, a gear43to which the driving force is transmitted from the output gear33through the second idler gear29is provided at one end of a pre-feeding roller shaft39, and a snaggletoothed gear37is provided at the other end thereof.

Here, it should be noted that the phase relation between the snaggletoothed portion of the snaggletoothed gear37and the notch portion15A of the pre-feeding roller15satisfies that, when the snaggletoothed portion of the snaggletoothed gear37is at the position facing a shock absorbing gear (or buffer gear)36, the notch portion15A of the pre-feeding roller15is at its initial position which faces the original P stacked on the original tray12and does not project from the original tray12.

When the rotation starts, the snaggletoothed gear37engages with the shock absorbing gear36being the intermediate gear. Here, the first tooth of the snaggletoothed gear37which first engages with the teeth of the shock absorbing gear36is made small so that the snaggletoothed gear37can easily engage with the shock absorbing gear36. More specifically, the height of the first tooth of the snaggletoothed gear37is made low and the heights of the following teeth are made gradually large. Moreover, for example, the ends of the first to fourth teeth of the snaggletoothed gear37are made arc so that the snaggletoothed gear37can easily engage with the shock absorbing gear36.

Furthermore, the ends of all the teeth of the shock absorbing gear36are made arc so that the shock absorbing gear36can easily engage with the snaggletoothed gear37. Incidentally, it should be noted that such arc shape may be formed to at least one of the snaggletoothed gear37and shock absorbing gear36.

The shock absorbing gear36and the first idler gear28being the transmitting gear engaging with the separating driving gear32are provided on the same shaft and thus constitute a train of gears as shown inFIG. 9A. Further, a delay portion is provided between the shock absorbing gear36and the first idler gear28, whereby the driving force from the first idler gear28is transmitted to the shock absorbing gear36after delay.

Incidentally, as shown inFIG. 9B, the delay portion consists of a shock absorbing spring35such as, e.g., a helical torsion spring, provided between the shock absorbing gear36and the first idler gear28, a hole36aprovided on the shock absorbing gear36, and an arc groove28aprovided on the first idler gear28.

Then, when the first idler gear28rotates without any load in the direction according to the rotational direction D of the separating driving gear32, that is, when the gears rotate in the state that the snaggletoothed gear37does not engage with the shock absorbing gear36, the first idler gear28rotates by a predetermined amount, and the driving force is then transmitted from the first idler gear28to the shock absorbing gear36through the shock absorbing spring35which generates torque when the relative phase between the first idler gear28and the shock absorbing gear36comes to be equal or lower than a predetermined amount. Incidentally, it should be noted that the shock absorbing gear36rotates in any direction with respect to the first idler gear28according to deflection of the shock absorbing spring35.

Moreover, the pre-feeding roller15is held at its initial position by a rotation controlling spring38being a holding means shown inFIG. 7. In the present embodiment, the rotation controlling spring38holds the roller by holding tight two planes39aprovided on the pre-feeding roller shaft39as shown inFIG. 10.

Incidentally, a stopper mechanism is provided in the original feeding portion to hold the original P at a predetermined position when the original P is inserted. As shown inFIG. 11, the stopper mechanism consists of a stopper member41acting as a stopper member of which upper end is rotatably supported based on a rotating shaft41das a fulcrum above the original tray12(original conveying face), and a pawl member42acting as a latch member (or locking member) which is rotatably provided based on a rotating center42das a fulcrum at the rotating end of the stopper member41. Here, it should be noted that the stopper member41and the pawl member42constitute the stopper of the present invention.

Here, the stopper member41is rotated or turned from an initial position41awhich is denoted by the dashed line inFIG. 12and restricted by a lower limit regulating portion1L provided on the upper original guide1before the original P is stacked on the original stacking board12to an upper limit position41bwhich is restricted by an upper regulating portion1kprovided on the upper original guide1, and the pawl member42is rotated or turned from an initial position42ato an upper limit position42bwith respect to the stopper member41.

Incidentally, when the original P is stacked and inserted to the original stacking board12by an operator and the stopper member41is pressed by the stacked and inserted originals P in the direction indicated by an arrow K as shown inFIG. 11, the stopper member41is rotated or turned from the initial position to the position where a latch pawl42gprovided on the pawl member42engages with the root of the teeth of the separating driving gear32being the rotating member. Thus, the stopper member41enters the fixed state, whereby the stopper member41regulates the positions of the originals P so that the leading edges of the originals P are aligned with others at a predetermined position.

That is, when the stopper member41is rotated or turned from the initial position to the regulating position for regulating the original P to the predetermined position by the pressing of the original P stacked by the operator on the original stacking board12, the stopper member41is held at the regulating position by a stopper holding means which consists of the pawl member42and the separating driving gear32, whereby the leading edges of the originals P can be aligned and held at the predetermined position.

Moreover, as above, when the stopper member41is pressed by the original P and thus shifted from the initial position to the regulating position, the stopper member41is held at the regulating position by the stopper holding means. Thus, even if the original P is strongly pressed, the original P can be surely stopped at the predetermined position.

Meanwhile, when the original P is fed, if the separating driving gear32rotates in the direction indicated by the arrow D as shown inFIG. 13A, the pawl member42rotates in the direction indicated by the arrow in accordance with the rotation of the separating driving gear32, whereby the latch state of the latch pawl42gof the pawl member42and the separating driving gear32is released. Thus, the stopper member41can freely rotate based on the rotating shaft41d.

Under the circumstances, the pre-feeding roller15rotates in the direction indicated by an arrow G according to the rotation of the separating driving gear32, and thus feeds the originals P from the lowest one on the original stacking board12. Then, as shown inFIG. 13B, the stopper member41is pressed in the direction indicated by an arrow M by the original P fed by the pre-feeding roller15, whereby the stopper member41rotates or turns to the position enabling to feed the original P. Incidentally, the fed original P advances in the arrow direction while pressing the stopper member41, and then the original P is separated and conveyed one by one in the downstream direction by the separating roller16and the friction pad22(seeFIG. 5).

Incidentally, as shown inFIG. 14, a barycenter41ewhich is acquired by synthesizing the stopper member41and the pawl member42is provided on the separating driving gear side (i.e., downstream side in feeding direction) with respect to the rotating shaft41dof the stopper member41. That is, because the barycenter41eacquired by the stopper member41and the pawl member42is provided on the downstream side in the feeding direction, when all the originals P are fed and thus there is no pressure by the original P, the stopper member41returns to the initial position41a(seeFIGS. 12 and 14) by the own weights of the stopper member41and the pawl member42. Here, it should be noted that, in the present embodiment, the weight of the pawl member42is set to ½ or less of the weights of the stopper member41.

In any case, after the stopper member41rotated or turned to the position which enables to feed the original P by the pressing of the fed original P, when the pressing by the original P is released, the stopper member41returns from the rotated position to the initial position, whereby it is possible to eliminate an initialization operation of the stopper member41. Moreover, by eliminating the initialization operation of the stopper member41as above, it is possible to omit an electrical actuator, a spring clutch and the like, whereby it is possible to achieve space saving and cost reduction.

Besides, a barycenter42eof the pawl member42is provided on the separating driving gear32side (i.e., downstream side in feeding direction) with respect to a rotating center42dof the pawl member42. Thus, the pawl member42can surely latch the latch pawl42gbetween the teeth of the separating driving gear32by its own weight.

Incidentally, the pawl member42is constructed to return by its own weight to the position where the latch pawl42is not latched between the teeth of the separating driving gear32in the case where the stopper member41returns to the initial position. Thus, by such a construction, when the stopper member41returns to the initial position41aor has returned to the initial position41a, it is possible to prevent that the latch pawl42gof the pawl member42engages with the separating driving gear32when the separating driving gear32rotates in the opposite direction (indicated by arrow N) to execute phase initialization of the pre-feeding roller15by the reverse rotation of the motor40as described later. As a result of this, it is possible to prevent that a load is applied from the pawl member42to the separating driving gear32, whereby it is possible to smoothly rotate the separating driving gear32.

Moreover, in a case where the upper original guide1is closed when the original P still remains on an original conveying path, the portions of the stopper member41and the pawl member42which first come into contact with the original P are set to be located on the downstream side of the rotating shaft41dof the stopper member41in the original conveying direction. Consequently, even when the upper original guide1is closed, the stopper member41smoothly rotates so that the original P is not damaged.

Subsequently, an original feeding operation in the original feeding portion of the original reading section105will be explained.

First, when the plural originals P are inserted in the direction indicated by an arrow F ofFIG. 2, the original presence/absence sensor2is turned on, and the leading edges of the inserted originals P then abut against the stopper member41as shown inFIG. 11.

Next, when a reading start indication is issued by the user from the operation portion106or from an external peripheral device, the motor40shown inFIG. 7rotates forwardly. According to such forward rotation of the motor40, the conveying roller20and the discharging roller21respectively rotate in the direction indicated by the arrow G and the separating driving gear32on the separating roller shaft30rotates in the direction indicated by the arrow D. Then, when the separating driving gear32rotates as above, the pawl member42of the stopper member41swings according to the rotation of the separating driving gear32as shown inFIG. 11, and the fixed (locking) state of the stopper member41is released, whereby the original P can advance toward the separating roller16.

Moreover, when the separating driving gear32rotates as above, the clutch spring34shrinks and the driving in the conveying direction (arrow G direction) is thus transmitted to the separating roller16, whereby the separating roller16rotates. At the same time, the driving is transmitted to the separating roller shaft30by the clutch spring34through the resin collar30a, whereby the separating roller shaft30rotates.

Then, when the separating roller shaft30rotates as above, the driving is transmitted to the input gear43acting as the roller shaft gear of the pre-feeding roller15through the output gear33and the second idler gear29acting as the transmitting gear, whereby the pre-feeding roller15rotates in the conveying direction (arrow G direction).

That is, when the motor40rotates forwardly, the rotation (driving force) of the motor40is transmitted to the pre-feeding roller15by a first driving transmitting portion consisting of the separating roller shaft30, the second idler gear29and the input gear43through the clutch spring34, whereby the pre-feeding roller15rotates in the direction for feeding the original P.

Next, when the pre-feeding roller15rotates by a predetermined amount, the pre-feeding roller15comes into contact with the original P and starts to convey the original P. Moreover, according to the rotation of the pre-feeding roller15, the snaggletoothed gear37engages with the shock absorbing gear36. In this case, even if the snaggletoothed gear37and the shock absorbing gear36are not in phase, these gears smoothly engage with each other due to the shapes of the teeth thereof as described above.

Moreover, the phase difference between the snaggletoothed gear37and the shock absorbing gear36is absorbed according as the shock absorbing gear36having a slack (lash or play) with respect to the first idler gear28in the rotational direction rotates with respect to the first idler gear28. Then, by constituting the snaggletoothed gear37, the shock absorbing gear36and the first idler gear28as above, the snaggletoothed gear37, the shock absorbing gear36and the first idler gear28can respectively rotate without preventing the separating driving gear from rotating even when the pre-feeding roller15rotates.

Next, the original P is fed by the rotation of the pre-feeding roller15as above, the fed original P is separated one by one by the separating roller16and the friction pad22, and the separated original P is then transported to the conveying roller20.

Incidentally, to prevent a jam and to make a gap between the current and subsequent originals P, the rotational speed of the conveying roller20is set higher than that of the separating roller16. For this reason, when the conveying roller20starts to convey the original P, the separating roller16rotates at speed higher than that of the rotational speed of the separating driving gear32according to the conveying of the original P.

Here, when the separating roller16rotates at the higher speed than that of the rotational speed of the separating driving gear32, the clutch spring34is loosened, whereby the shrinkage of the separating roller shaft30is released. Thus, the separating roller16rotates at the same speed as that of the conveying roller20without applying any load to the conveyed original P. Moreover, when the shrinkage of the separating roller shaft30by the clutch spring34is released, the driving force is hardly transmitted to the output gear33, whereby the driving force is hardly transmitted to the pre-feeding roller15through the second idler gar29.

Incidentally, even when the driving force is not transmitted through the second idler gear29, the snaggletoothed gear37and the first idler gear28engaging with the separating driving gear32and thus rotating engage with each other through the shock absorbing gear36, whereby the driving force is continuously transmitted to the pre-feeding roller15through these gears until the snaggletoothed portion of the snaggletoothed gear37comes to the position facing the shock absorbing gear36. As a result of this, the pre-feeding roller15rotates up to the initial position where the roller does not project from a lower original conveying path. In this case, when the pre-feeding roller15comes to the position nearby the initial position, the rotation controlling spring38holds it, whereby the pre-feeding roller15stops just at the initial position.

That is, even when the driving force is not transmitted through the second idler gear29, the rotation of the motor40is continuously transmitted to the pre-feeding roller15by a second driving transmitting portion consisting of the snaggletoothed gear37, the first idler gear28and the shock absorbing gear36. Thus, the pre-feeding roller15stops after it rotated up to the initial position.

Then, by stopping the pre-feeding roller15to the initial position as above, a released state is surely produced between the pre-feeding roller15and a pre-feeding pressing plate44when the original P is conveyed by the conveying roller20, whereby it is possible to convey the original P without loading it, and there is no fear that disturbance of image occurs.

Subsequently, when the original edge sensor3(FIG. 2) detects the leading edge of the original P, the image information reading by the CIS17starts at predetermined timing, and the original P of which reading ended is then discharged by the discharging roller21.

Incidentally, as described above, because the separating roller16rotates at high speed, the clutch spring34rotates according to the sleeve16aof the separating roller16. Thus, a slight idling torque occurs with respect to the resin collar30aeven when the pre-feeding roller15stops, whereby the slight driving is transmitted in practice to the pre-feeding roller15through the output gear33and the second idler gear29. However, because the relation of [“the holding force of the rotation controlling spring38” >>“the looseness torque of the clutch spring34”] is satisfied, the pre-feeding roller15does not rotate.

Moreover, when the separating roller16rotates according to the original P at the speed higher than that of the separating rotating gear32, the slack provided between the mechanical timer31and the separating driving gear32shifts toward the one side due to such a speed difference between the separating roller16and the separating driving gear32, and such a situation is maintained. In this case, it should be noted that the speed difference is set so that the slack can sufficiently shift toward the one side while one original is passing.

Meanwhile, when the trailing edge of the original P passes the separating roller16, the surrounding area of the separating roller16does not receive tensility. At that time, because the slack between the mechanical timer31and the separating driving gear32has shifted toward the one side, the separating roller16or the pre-feeding roller15does not rotate until the slack is consumed even when the separating driving gear32rotates in the D direction. Then, because a time of no sheet feeding is provided by inhibiting the pre-feeding roller15and the like from rotating, it is possible to control original reading intervals.

Subsequently, at the point that the slack provided between the separating gear32and the mechanical timer31is consumed, the clutch spring34again shrinks, whereby the separating roller16rotates based on the driving force transmitted from the separating driving gear32. At the same time, the driving is transmitted to the separating roller shaft30through the resin collar30a, and the driving is also transmitted again to the pre-feeding roller15.

Incidentally, at that time, because the holding force of the rotation controlling spring38is sufficiently small with respect to the driving force of the pre-feeding roller15to which the driving is transmitted when the clutch spring34shrinks, the pre-feeding roller15can surely rotate.

After then, when the original presence/absence sensor2detects the next original P, the above operation is repeated to sequentially execute the image reading. Meanwhile, when the original presence/absence sensor2does not detect the next original P and the original edge sensor3detects the passing of the original P, a not-shown controlling means judges that the reading and discharging of the originals P ended and thus the sequential image reading wholly ended.

Incidentally, when it is judged based on the outputs from the original presence/absence sensor2and the original edge sensor3that the sequential image reading wholly ended, the controlling means causes the motor40to rotate reversely as the initializing operation to return the pre-feeding roller15to its initial position.

Then, as shown inFIG. 8C, by rotating reversely the motor40as above, the separating driving gear32rotates in the direction indicated by the arrow E, and the clutch spring34is loosened according to the rotation of the separating driving gear32, whereby the transmission of the driving to the separating roller16and the separating roller shaft30is cut. As a result of this, the separating roller16does not rotate, and the transmission of the driving to the pre-feeding roller15through the second idler gear29is cut.

Here, when the pre-feeding roller15is not at the initial position, because the snaggletoothed gear37engages with the shock absorbing gear36as described above, the driving force is transmitted to the pre-feeding roller15through the first idler gear28, the shock absorbing gear36and the snaggletoothed gear37. As a result of this, the pre-feeding roller15rotates up to the position nearby the initial position, the rotation controlling spring38then holds it, whereby the pre-feeding roller15stops just at the initial position. Meanwhile, when the pre-feeding roller15is already at the initial position, the driving force is not transmitted to the pre-feeding roller15, whereby the pre-feeding roller15does not rotate.

By the above operation, it is possible to initialize the pre-feeding roller15, that is, to return the pre-feeding roller15to its initial position. By the way, the stopper member41automatically returns to its initial position due to its own weight when the original P on the stopper portion goes out of existence, whereby such an initializing operation as above is unnecessary.

As described above, when the motor40rotates forwardly, it is set to transmit the driving of the motor40to the pre-feeding roller15by using the clutch spring34through the first driving transmitting portion. On the other hand, when the motor40rotates reversely, it is set not to transmit the driving of the motor40to the pre-feeding roller15by using the clutch spring34, and it is further set to transmit the driving force to the pre-feeding roller15by the second driving transmitting portion to shift the pre-feeding roller15to the initial position. Thus, it is possible to execute the driving force transmission and the stop position controlling with respect to the pre-feeding roller15by using the one clutch spring34. Therefore, it is possible to achieve the driving force transmission and the stop position controlling of the pre-feeding roller15at low cost.

Subsequently, an interlock error preventing mechanism for the shock absorbing spring35provided between the shock absorbing gear36and the first idler gear28will be explained hereinafter.

As shown in above-describedFIG. 9B, both the ends of the shock absorbing spring35are bent. On this occasion, in case of interlocking the shock absorbing spring35, a shaft36bof the shock absorbing gear36is first inserted into the shock absorbing spring35, and one end35aof the shock absorbing spring35is then inserted into the hole36aprovided on the shock absorbing gear36. Subsequently, the shaft36bof the shock absorbing gear36is rotatably inserted into the hole provided on the first idler gear28, and the other end35bof the shock absorbing spring35is inserted into the arc groove28aprovided on the first idler gear28. Incidentally, it should be noted that the external diameter of the shock absorbing spring35is made smaller than the root circle of the gear so as to prevent teeth collision of the gear.

Here, in the present embodiment, the angle of the arc groove28aof the first idler gear28is made larger than the rotational angle necessary for the mechanical timer. Thus, by setting the angle of the arc groove28awithin such a range, the shock absorbing spring35can move without any load.

Moreover, if it is assumed that an angle θ made by the start point of the arc groove28aand the hole36aas shown inFIG. 15Aand an angle Ψ made by the two arms (i.e., both ends) of the shock absorbing spring35as shown inFIG. 15Bsatisfies θ<Ψ, there is a possibility that the shock absorbing spring35is assembled reversely. In this case, the mechanical timer31does not effectively operate. For this reason, it is set that the angle θ and the angle Ψ satisfies θ>Ψ so that the shock absorbing spring35is not interlocked reversely.

In addition, in the above-mentioned embodiments, the documents stacked on the document tray12are fed by the pre-feeding roller15, and then the documents fed by the pre-feeding roller15are separated by the separating roller16. However, it does not necessarily need not to provide pre-feeding roller15. That is to say, it is possible to form an apparatus in which the documents stacked on the document tray are fed and separated by a separating roller. Incidentally, the above explanation is directed to the case where the sheet feeding apparatus according to the present invention is applied to the original feeding portion which conveys the original P to the original reading section105. However, the present invention is not limited to this. That is, the present invention is also applicable to the recording sheet feeding portion101which supplies the recording sheet S to the image forming section102.

As explained above, according to the present invention, the stopper is held by the gear at the regulating position of regulating the sheets, and the holding state of the stopper by the gear is released when the driving is transmitted to the gear. Thus, even if the sheet is strongly pressed, it is possible to surely stop the sheet at the predetermined position, and it is further possible to achieve space saving and cost reduction.

This application claims priority from Japanese Patent Application No. 2004-028279 filed on Feb. 4, 2004, which is hereby incorporated by reference herein.