JP3204830B2 - Paper feeder double feed prevention mechanism - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a double feed preventing mechanism, and more particularly to a double feed preventing mechanism provided in a sheet feeding device for feeding supplied sheets one by one.

[0002]

2. Description of the Related Art An image forming apparatus such as a copying machine is provided with a sheet feeding device for supplying sheets to an image forming section.
This paper feeder is provided with a double feed prevention mechanism for sequentially feeding the paper fed from the paper feed cassette one by one, for example. The double feed prevention mechanism includes a paper feed roller, a friction pad pressed against the paper feed roller, and a spring for pressing the friction pad toward the paper feed roller. When two sheets of paper are conveyed, for example, since the friction coefficient between the paper feed rollers and the paper is higher than the friction coefficient between the papers, only the paper on the paper feed roller side is conveyed, and Side paper is not transported. In this way, even when sheets are multi-fed, they are sequentially fed one by one.

[0003]

In the double feed prevention mechanism, a guide sheet made of a resin film is provided to guide a sheet to a nip position between a sheet feeding roller and a friction pad. The guide sheet is mounted on a pad housing to which the friction pad is fixed, and the mounting position is very important. That is, if the guide sheet is brought too close to the nip portion between the feed roller and the friction pad, double feeding is likely to occur.

SUMMARY OF THE INVENTION It is an object of the present invention to reliably guide a sheet to a nip portion between a sheet feeding roller and a friction pad, and to suppress double feeding and curling of the leading edge of the sheet.

[0005]

The double feed prevention mechanism of the paper feeder according to the present invention is a mechanism for feeding supplied sheets one by one, and includes a feed member, a pad member, an urging member, and a guide. A sheet member. The feed member rotates in the paper feeding direction to feed the sheet in the paper feeding direction. The pad member is disposed to face the feed member, and can be pressed against the feed member via the sheet. The urging member is a member for bringing the feed member and the pad member into pressure contact with each other. The guide sheet member extends in the sheet width direction intersecting the sheet feeding direction, and the leading end in the sheet feeding direction forms a part of the pad member on the upstream side in the sheet conveying direction.
It is arranged to cover and the central part of the supplied sheet is
Sliding contact with the pad member before other parts
Is slower than the transport speed at both ends of the sheet.
A notch is provided at the center of the leading end to guide the supplied sheet to the press-contact portion between the feed member and the pad member.

[0006]

In the double feed prevention mechanism of the sheet feeding device according to the present invention, the sheet is guided by the guide sheet member to the press contact portion between the feed member and the pad member. The feed member and the pad member are pressed against each other by an urging member, and feed the sheet guided by the guide sheet member in the sheet feeding direction. At this time, for example, when two sheets are supplied in an overlapping manner, since the coefficient of friction between the feeding member and the sheet is larger than the coefficient of friction between the sheets, only the sheet that comes into contact with the feeding member is used. The paper is fed in the paper feeding direction to prevent double feeding.

Here, at the center of the leading edge of the guide sheet member, the center of the supplied sheet is located ahead of the other portions.
The sheet at the center of the sheet
Since the central end portion to be lower than the transport speed of the bets both ends are <br/> notch forming, the paper center portion is guided to remain nip with pulled by its opposite ends You. For this reason, it is possible to prevent the sheet from being turned up. Since the curl of the sheet tip is suppressed in this way,
The degree of freedom of the mounting position of the guide sheet member is increased, and the occurrence of double feeding can be easily suppressed.

[0008]

FIG. 1 shows a copying machine as an image forming apparatus employing a sheet feeding device according to an embodiment of the present invention. In FIG. 1, a document table 2 on which a document is placed is arranged on the upper surface of a copying machine main body 1. A document holder 3 is provided on the upper surface of the document table 2 so as to be openable and closable. Copying machine body 1
External paper feed units 4a and 4b are mounted on the bottom of the printer. On the left side of the copying machine body 1 in the figure, a paper discharge tray 5 for stacking discharged paper is mounted. Further, on the right side, a paper feed tray 6 for manual paper feed is mounted to be openable and closable.

A reading device 10 for reading image information of a document on the document table 2 is provided inside the copying machine body 1.
An image forming unit 11 arranged below the document reading device 10 for forming an image on a sheet and a paper feeding device 12 arranged below the image forming unit 11 for supplying a sheet to the image forming unit 11 are provided. Have been. Further, downstream of the image forming unit 11 in the sheet conveying direction, a sheet conveying device 13, a fixing device 14 for fixing an image formed on the sheet, and a discharging device for discharging the sheet to the discharge tray 5. Rollers 15 are provided in order.

The image forming section 11 has a photosensitive drum 16 on the surface of which an electrostatic latent image is formed.
6, a main charging device 17 for charging the photosensitive drum 16 with electric charge, a developing device 18 for developing the electrostatic latent image on the photosensitive drum 16, and a transfer for transferring the developed toner image to a sheet An apparatus 19, a separating apparatus 20 for separating paper from the photosensitive drum 16, and a cleaning apparatus 21 for removing residual toner on the photosensitive drum 16 are arranged.

The external paper feed units 4a and 4b each have a paper feed cassette, and each paper feed cassette can be pulled out to the front. As shown in FIG. 2, an opening 25 is provided below the manual paper feed tray 6 on the right side of the copying machine main body 1 as an external paper feed unit mounting portion.
When the external paper feed unit is not mounted, the mounting opening 25 is covered by the cover 26.

On the other hand, the external paper feed units 4a and 4b have
Attachment members 2 for attaching the paper feeding unit to the upper copying machine body 1 or the upper paper feeding unit 4a, respectively.
7 is fixed. An opening 28 having the same shape as the mounting opening 25 provided in the copying machine main body 1 is provided below the mounting member 27. The upper paper feed unit 4a has its mounting member 27 fixed to the mounting opening 25 of the copying machine body 1, and the lower paper feed unit 4b has its mounting member 27 mounted on the upper paper feed unit 4a.
Is attached to the mounting opening 28. Here, when the external sheet feeding units 4a and 4b are attached, the cover 2 covering the attachment opening 25 of the copying machine body 1 is used.
6 is a mounting opening 28 of the lowermost sheet feeding unit 4b.
It is designed to be attached to.

Here, the cover 26 covering the mounting opening 25 of the copying machine main body 1 can be used also as the cover of the sheet feeding unit 4, and the members can be used efficiently. Next, the sheet feeding device 12 will be described. The paper supply device 12 includes a paper supply cassette 30 for storing paper.
And a paper feed mechanism 31 for feeding paper from the paper feed cassette 30 to the image forming unit 11 side.

The paper feed cassette 30 is formed in a box shape as shown in FIGS. 1 and 3, and has a substantially rectangular parallelepiped case body 32 and a width adjusting mechanism 33 for adjusting the width of the stored sheets. And a press-contact mechanism 34 (see FIG. 4) for pressing the sheet against the paper feed mechanism 31. As shown in FIG. 5, the case main body 32 is movable in the front-rear direction along guide frames 35a and 35b on the copying machine main body side. A plurality of guide rollers 36 are rotatably provided on the guide frames 35a and 35b on the copying machine main body side. The lower surface of the bottom of the case body 32 is formed with guide grooves 32a and 32b (see FIG. 6) that fit into the guide rollers 36. Each guide groove 32a, 32b is formed at both ends of the case body 32 along the front-back direction. One guide groove 32a is formed in a concave shape so that the upper part of the guide roller 36 can be fitted therein. The other guide groove 32b can be fitted with the guide roller 36 in the same manner, but the outer side is open.

The guide grooves 32a, 32b having such a structure
Is formed on the case main body 32 so that the guide rollers 3
6 and the concave guide groove 32a can restrict the paper cassette from moving left and right when the paper cassette is pulled out.
It is possible to prevent the paper cassette from being pulled out smoothly by preventing the paper cassette from being caught at the time of drawing. FIG.
As is apparent from FIG.
In the side surface of the case body 32 on the side in contact with b, the back side and the front side protrude outward compared with the center part, and these protruding parts are the guide surfaces 32c and 32d abutting on the guide frame 35b. It has become. A space 32e between the guide surfaces 32c and 32d does not come into contact with the guide frame 35b.

As described above, the pair of guide surfaces 32
By forming the c and 32d, the contact area between the case main body 32 and the guide frame 35b is reduced, and in addition to the concave guide groove 32a described above, it is possible to suppress the displacement when the sheet cassette is pulled out and to supply the sheet. The paper cassette can be moved in and out more smoothly. Next, the width adjusting mechanism 33 will be described.

The width adjusting mechanism 33 provided in the paper feed cassette 30 has a pair of width adjusting guide members 40 as shown in FIGS. The width adjustment guide member 40 is formed in an L-shape, and a side wall 40a extending in the vertical direction abuts a side portion of the sheet to perform width adjustment. Paper cassette 3
0 on the bottom surface of the case body 32 along the width direction of the paper.
A pair of guide grooves 41 are formed. A rack 42 is arranged on the lower surface of the guide groove 41, and the rack 42 is connected to the bottom 40 b of the width adjusting guide member 40 through the guide groove 41. Therefore, the width adjusting guide member 40 and the rack 42 can move in the sheet width direction along the guide groove 41. As shown in FIG. 8, the rack 42 fixed to each of the pair of width adjustment guide members 40 has tooth portions 42a on the side surfaces facing each other. In addition, a pinion gear 43 is arranged on the lower surface of substantially the center of the case main body 32 of the paper feed cassette 30. The pinion gear 43 meshes with the teeth 42 a of the rack 42 fixed to each of the pair of width adjustment guide members 40. An adjusting plate 44 is arranged above the pinion gear 43 and on the upper surface of the bottom of the case body 32. A support shaft 45 is fixed to the lower surface of the central portion of the adjustment plate 44 so as to protrude downward.
The pinion gear 43 is rotatably supported by the support shaft 45. The hole 46 of the case main body 32 through which the support shaft 45 passes is an elongated hole as shown in FIGS. 8 and 9.
A screw 47 for fixing the adjustment plate 44 to the bottom of the case main body 32 passes through a long hole 44 a formed in the adjustment plate 44. Therefore, by loosening the screw 47, the pinion gear 43 can be moved in the width direction together with the adjustment plate 44.

Next, the paper feed mechanism 31 will be described. As shown in FIG. 4, the paper feed mechanism 31 is provided with a pre-feed roller 5 that abuts on the uppermost paper in the paper feed cassette 30 and feeds the paper.
0, a double feed prevention mechanism 51 provided downstream of the feed roller 50 in the sheet feeding direction, and a separation mechanism 53 for separating the feed roller 50 from the sheet in the sheet cassette 30.

The double feed prevention mechanism 51 has a paper feed roller 55 and a friction pad 56 pressed against the paper feed roller 55. The feed roller 55 is fixed to an intermediate portion of the feed shaft 57, and is rotated counterclockwise in FIG. 4 by a drive system (not shown). The paper feed shaft 57 is rotatably supported between the rear frame and the front frame 1a of the copying machine main body 1. The friction pad 56 is fixed to the upper surface of the pad housing 58, and the pad surface is located above the upper surface of the housing 58 (on the side of the paper feed roller 55). One end of the pad housing 58 is rotatably mounted on the case main body 32 of the paper feed cassette 30, and the upper end thereof is rotatable about a fulcrum P. A press-contact spring 59 is disposed between the pad housing 58 and the case main body 32, and the pad housing 58 always keeps the paper feed roller 5
It is urged to the 5th side.

As shown in FIGS. 10 and 11, the feed roller 55 includes a collar 55a fixed to the feed shaft 57 by a spring pin 61, and an elastic portion made of resin or the like fixed to the outer peripheral side of the collar 55a. 55b. One end of the paper feed shaft 57 on the front side of the apparatus is rotatably supported by a bearing 62 mounted on the front frame 1a of the copying machine main body 1. A notch 1c is formed in the front frame 1a from below, and the sheet feeding shaft 57 can be taken out through the notch 1c. A stop ring 63 is attached to the front end of the paper feed shaft 57, thereby restricting the movement of the paper feed shaft 57 in the front-rear direction. A pipe 64 as a paper feed guide is arranged between the collar 55a of the paper feed roller 55 and the front frame 1a. One end of the pipe 64 is fixed to the collar 55 a of the paper feed roller 55, and the other end is rotatably supported on the outer periphery of the bearing 62. The outer diameter of the pipe 64 is set smaller than the outer diameter of the paper feed roller 55. On the other hand, a temporary paper feed guide 57 a is fixed to the paper feed shaft 57 behind the paper feed roller 55. The outer diameter of the paper feed guide 57a is set to the same size as the outer diameter of the pipe 64.

In the pad housing 58, a guide sheet 60 for guiding the fed paper to the nip position between the paper feed roller 55 and the friction pad 56 is fixed on the upstream side of the friction pad 56 in the paper feeding direction. Have been. The guide sheet 60 is disposed so as to cover a portion of the friction pad 56 on the upstream side in the sheet transport direction from above. As shown in FIG. 12, a V-shaped notch 60a is formed at the center in the width direction of the friction pad 60.

One end of a support frame 65 is rotatably supported on the paper feed shaft 57. On the other end of the support frame 65, a drive shaft 66 for driving the forward feed roller 50 is supported. The paper feed shaft 57 and the drive shaft 66 are transmitted by a belt (not shown).
And the advance roller 50 are rotated in the same direction. In addition,
A protrusion 65a is provided at the front end of the support frame 65 on the forward feed roller side.
Are formed, and together with the photo-interrupter 67 fixed to the frame on the copying machine main body side, the vertical position of the forward feed roller 50 is detected.

The press-contact mechanism 34 has a placing plate 70 on which the front end of the sheet is placed, and a lift member 71 for lifting the leading end of the placing plate 70. The mounting plate 70 is shown in FIG.
As shown by a two-dot chain line in FIG. 2, the paper cassette 30 is placed on the paper feeding direction side of the paper feeding cassette 30, and the front end side is rotatable up and down around the rear end side. The lift member 71 is disposed below the front end of the mounting plate 70. The rear end of the lift member 71 is fixed to a lift shaft 72. As shown in FIG. 13, the lift shaft 72 protrudes further rearward from the rear wall of the case main body 32 of the paper feed cassette 30, and an engaging pin 73 is attached to a tip of the lift shaft 72. On the other hand, a joint 74 that engages with the engaging pin 73 is disposed on the copying machine main body side. The joint 74 is fixed to the tip of a drive shaft 75, and is rotated by a drive system (not shown). A spring 77 is arranged between the joint 74 and the rear frame 76 of the copying machine main body.

In such a configuration, the lift shaft 72 is rotated by the drive system via the joint 74 and the engagement pin 73, and the tip of the lift member 71 rotates counterclockwise in FIG. As a result, the mounting plate 70 moves upward, and the paper placed on the mounting plate 70 is
Pressed to zero. The amount of rotation of the lift member 71 is controlled by a detection signal from the photo interrupter 67.

Next, a mechanism 53 for separating the advance roller 50 from the sheet will be described. The separation mechanism 53 includes:
As shown in FIGS. 14 and 15, a support member 80 fixed to the rear side of the support frame 65 that supports the feed roller 50, and an interlocking mechanism 81 provided between the support member 80 and the sheet cassette 30. And The interlocking mechanism 81 is
It has a cam member 82 that can move in the front-rear direction of the apparatus and can contact the rear wall surface of the paper feed cassette 30, and an elevating member 83 provided between the cam member 82 and the support member 80.
The cam member 82 is accommodated in a case 85 fixed to the rear frame 1b of the copying machine main body. Similarly, the cam member 82 is urged toward the apparatus front side (paper feed cassette side) by a spring 84 arranged in the case 85. I have. Further, the cam member 82 includes a first cam surface 82a having a small lift amount and the first cam surface 82a.
A second cam surface 82b having a larger lift amount, and an inclined surface 8 formed between the first cam surface 82a and the second cam surface 82b.
2c. And the lower end of the elevating member 83
Each cam surface 82a, 82b abuts on the inclined surface 82c,
It moves up and down with the movement of the cam member 82.

Next, the paper transport path downstream from the paper feed roller 55 will be described. As shown in FIGS. 1 and 16, a return conveyance guide member 90 for changing the conveyance direction of the paper sent from the double feed prevention mechanism 51 is provided above the paper feed roller 55 and downstream in the paper conveyance direction. Are located. The return conveyance guide member 90 is provided to extend in the front-rear direction of the apparatus as shown in FIG. Further, it has a curved guide portion 91 for sending the sheet sent from below to the image forming portion side, and at both ends of the curved guide portion 91 for attaching the return conveyance guide member 90 to the frame 1c of the copying machine main body. It has a mounting portion 92. Curved surface guide 9
Reference numeral 1 denotes a sheet fed from a sheet feeding cassette in the copying machine main body 1 along with guide members 93 and 94 to an image forming section by a first conveying surface 91a on a side facing the sheet feeding roller 55, The sheet sent from the external sheet feeding units 4a and 4b is sent to the image forming unit side by the second conveying surface 91b opposite to the surface 91a. A long hole 92a long in the front-rear direction is formed in one of the mounting portions 92, and the return conveyance guide member 90 is mounted to the frame 1d via a minute gap by a screw 95 penetrating the long hole 92a. .

In such a configuration, when the return transport guide member 90 expands in the front-rear direction due to heat, the expanded portion is absorbed by the elongated holes 92a, so that the curved guide portion 91 is prevented from bending in the vertical direction. Can be prevented. Therefore, even if the return conveyance guide member 90 contracts due to heat, the gap between the curved surface guide portion 91 and the guide members 93 and 94 is maintained at a predetermined gap, and the conveyance of the sheet is not hindered.

As shown in FIG. 4, a light reflection type sensor 100 for detecting whether or not there is a sheet in the sheet cassette 30 is provided above the sheet cassette 30.
The reflection sensor 100 includes a light projecting unit 100a that irradiates light to the upper surface of a sheet, and a light receiving unit 100b that receives light reflected from the sheet. On the other hand, a notch 70a is formed in a portion of the mounting plate 70 where light from the light transmitting portion 100a is irradiated, as shown in FIG. An inclined portion 101 as shown in FIG. 18 is formed on the bottom surface of the case main body 32 below the notch 70a. A black paint is applied to the inclined portion 101 and its surroundings to absorb light from the light projecting portion 100a. The inclined portion 101 is inclined such that the front end side is located below the rear end side. Therefore, even when the light from the light projecting unit 100a is applied to the inclined unit 101 and a small amount of light is reflected, the reflected light is reflected by the reflection type sensor 1
No. 00 light receiving section 100b is not incident.

By providing such an inclined portion 101, even when the reflection type sensor 100 is made to have high sensitivity in order to enhance the detection accuracy of the presence or absence of a sheet, the case main body 3 is provided.
2 can be prevented from entering the light receiving portion, and erroneous detection of the presence or absence of paper can be avoided. Next, the operation will be described. When a document is placed on the document table 2 and the copy start key is pressed, an internal paper feed cassette 3 according to the document size is set.
0 or an appropriate size paper is selected from the external paper feed units 4a and 4b and supplied to the image forming unit 11 side.

Here, the operation when paper is supplied from the internal paper feed cassette 30 will be described. In a state where the sheet cassette 30 is set at the set position in the copying machine main body 1, as shown in FIG.
The paper on the mounting plate 70 is in contact with the forward feed roller 50. When the copy start key is pressed, the forward feed roller 50 rotates counterclockwise in FIG. 4, and the uppermost sheet is sent to the double feed mechanism 51 side. The sheet fed to the double feed mechanism 51 is guided by the guide sheet 60 and is guided to the nip position between the feed roller 55 and the friction pad 56. At this time, if two sheets are simultaneously supplied to the nip position between the paper feed roller 55 and the friction pad 56, the friction coefficient between the paper feed roller 55 and the paper overlaps between the supplied papers. Since the coefficient of friction is higher than the coefficient of friction, slippage occurs between the upper sheet and the lower sheet, and only the upper sheet is conveyed to the image forming unit 11 by the feed roller 55. In this way, double feeding of sheets is prevented.

Here, when the paper enters the double feed prevention mechanism 51, the friction pad 56 is disposed so as to protrude from the upper surface of the pad housing 58 toward the paper feed roller 55, and furthermore, the tip of the guide sheet 60 is The friction pad 56 is disposed so as to cover a part of the friction pad 56 on the upstream side in the sheet transport direction. For this reason, the occurrence of double feeding can be reduced and the tip of the sheet caused by the collision between the tip of the sheet and the friction pad 56 can be prevented from being turned up, as compared with the case where the friction pad 56 is embedded inside the pad housing 58.

Since the guide sheet 60 has a notch 60a at the center as shown in FIG. 12, when the leading end of the sheet passes through the leading end of the guide sheet 60, the center of the sheet comes first. Slidably contacts the friction pad 56. For this reason,
The transport speed S1 at the center of the sheet is slightly slower than the transport speed S2 at both ends. Therefore, the central portion of the sheet is guided to the nip position between the feed roller 55 and the friction pad 56 while being pulled on both sides thereof. Here, it is possible to reliably feed the paper while suppressing the double feed and preventing the tip of the paper from being turned up.

The paper fed from the paper feed cassette 30 as described above is transferred to the first transport guide member 90 by the first transport guide member 90.
The conveyance direction is changed along the conveyance surface 91a, and the conveyance direction is guided to the image forming unit 11 side by the guide members 93 and 94. In the image forming unit 11, a toner image corresponding to the image information of the document is transferred onto a sheet, and then conveyed to a fixing device 14 by a sheet conveying device 13. In the fixing device 14, the toner image on the sheet is fixed, and the sheet after the fixing process is discharged onto the discharge tray 5 by the discharge roller 15.

When the paper in the external paper feed units 4a and 4b is selected, the paper is sent out from the paper feed cassette in the same manner as described above, and the paper is fed along the second transport surface 91b of the return transport guide member 90. The transport direction can be changed. Thereafter, the same processing as described above is performed. Next, the paper feed cassette 3
The operation for removing 0 from the copying machine body 1 will be described.

When the paper cassette 30 is pulled out forward,
The lift member 71 is separated from the drive system on the copying machine main body side. That is, by pulling out the paper feed cassette 30 to the front side, the engagement pin 7 fixed to the tip of the lift shaft 72 is
3. The joint 74 comes off. Thereby, the lift shaft 7
2 is released, and the lift member 71 is released.
Is rotated clockwise in FIG. 4 by the weight of the mounting plate 70 and the like. As a result, the sheet is lowered together with the mounting plate 70 in the sheet cassette 30. At this time, the forward feed roller 50 is lowered by its own weight, but its lowering is restricted by a lowering restricting member (not shown).
The forward feed roller 50 separates from the upper surface of the sheet on the sheet No. 0.

When the paper cassette 30 is set at the set position in the copying machine main body, the interlocking mechanism 81
The cam member 82 is accommodated in a case 85 against the urging force of the spring 84, as shown by the one-dot chain line in FIG. In the state shown by the one-dot chain line, the elevating member 83 is in contact with the first cam surface 82a of the cam member 82. Therefore, the support member 80 is lowered, and the paper feed roller 50 can abut on the paper in the paper feed cassette 30 by its own weight.

On the other hand, when the sheet feeding cassette 30 is pulled out to the front side, the cam member 82 jumps out of the case 85 by the spring 84 to the front side. Then, the elevating member 83
From the first cam surface 80a of the cam member 82 to the inclined portion 82c.
And comes into contact with the second cam surface 82b having a high lift amount.
In this state, the elevating member 83 moves up and pushes the support member 80 upward. Then, the support frame 65 rotates clockwise around the paper feed shaft of the paper feed roller 55, and the forward feed roller 50 rises as shown by the solid line in FIG. For this reason,
The advance roller 50 is further separated from the sheet in the sheet cassette 30.

When the paper feed cassette 30 is pulled forward in such a state, the paper and the forward feed roller 50 are surely separated from each other.
It can be prevented from jumping out or even being damaged. Moreover, in this case, it is not necessary to lower the paper feed cassette 30 downward, so that the space in the vertical direction can be reduced.
It is possible to reduce the size of the entire device.

When the paper feed cassette 30 is pulled out, the support portions 32c and 32d on the front and rear of the case main body 32 of the paper feed cassette 30 are connected to the guide frame 35b on the copying machine main body side.
And the roller 36 on one side fits into the concave groove 32a of the case 32, so that the case body 32 can be pulled out smoothly while suppressing the rattling of the case body 32.

When the paper cassette 30 is set in the copying machine main body, when the paper cassette 30 is pushed into the copying machine main body 1 and moves near the set position, the rear wall of the case main body 32 is moved. Pushes the cam member 82 of the interlocking mechanism 81 toward the back of the apparatus. As a result, the cam member 82 moves rearward of the apparatus against the urging force of the spring 84. Then, the elevating member 8
3 comes into contact with the first cam surface 82a having a small lift amount from the second cam surface 82b through the inclined portion 82c. As a result, the elevating member 83 descends, and the support member 80 also descends to the position shown by the one-dot chain line in FIG. In this state, the support frame 65 and the forward feed roller 50 can abut on the paper in the paper feed cassette 30 by their own weight.

By setting the paper cassette 30 in the copying machine main body, the engagement pin 7 at the tip of the lift shaft 72 is provided.
3 engages the groove of the joint 74. Here, if the engagement between the groove of the joint 74 and the engagement pin 73 is not performed smoothly, the joint 74 is pushed backward. In this case, the spring 77 absorbs the movement of the joint 74. Since the groove of the joint 74 is formed to be inclined in the circumferential direction, when the joint member 74 is pushed forward by the urging force of the spring 77, the engaging pin 73 engages with the groove of the joint member 74.

Here, when the sheet cassette 30 is set at the set position, the mounting plate 70 is lowered. For this reason, the protrusion 65 a of the support frame 65 is located below the photointerrupter 67. In this case, the lift member 7 is controlled by the control unit of the copier main body via the lift shaft 72.
One is raised. As a result, the mounting plate 70 and the sheet are raised, and are brought into contact with the advance roller 50. Mounting plate 7
0 is raised by a predetermined amount and the protrusion 65 of the support frame 65 is
When a interrupts the light of the photointerrupter 67, the rotation of the lift member 71 is stopped by a signal from the control unit, and is maintained in this state.

Next, a description will be given of the width adjustment operation of the paper in the paper feed cassette 30 and the center alignment of the width adjustment mechanism. When adjusting the width of the paper, the width adjustment guide member 40 is moved along the guide groove 41. A rack 42 is fixed to the width adjustment guide member 40,
Since the rack 42 is engaged with the pinion gear 43,
By moving one width adjustment guide member 40, the other width adjustment guide member 40 is also moved inward or outward by the same amount, and the width adjustment can be performed according to the width of the sheet.

Further, in order to match the center of the image forming section 11 with the center position of the sheet stored in the sheet feeding cassette 30, the center of the width adjusting mechanism 33 must be adjusted.
In this case, the position adjusting plate 44 supporting the pinion gear 43 is moved by loosening the screw 47 and moving in the width direction. That is, by moving the adjustment plate 44 in the width direction, the meshing position between the pinion gear 43 and the rack 42 fixed to the width adjustment guide member 40 is changed, and the center position of the width adjustment guide mechanism 33 is adjusted.

In this case, the center of the width adjusting mechanism 33 can be adjusted only by moving the position adjusting plate 44, and the adjusting operation becomes very easy. In addition, since the structure is simple, the device is inexpensive. Next, the replacement operation of the paper feed roller 55 will be described. Since the paper feed roller 55 is a consumable item, it needs to be replaced when the paper feed roller 55 is worn out for a long period of use.
In this case, first, the stop ring 6 is provided from the front side of the device.
3 is removed, and the bearing 62 is pulled out of the front frame 1a. Next, the pipe 6 passes through the notch 1c of the front frame 1a.
4 is lowered to an opening provided below the front frame 1a, and is pulled out forward with its end face. Since the feed roller 55 is fixed to one end of the pipe 64, the pipe 6
By pulling out 4, the paper feed roller 55 can be pulled out at the same time.

In this case, the operator does not need to reach into the inside of the apparatus, and the paper feed roller 55 can be easily replaced. Further, since the paper feeding guide is formed by the pipe 64, the entire area of the paper can be guided, and the jam due to the turning of the paper can be suppressed. [Other Embodiments] (a) In the above embodiment, the mechanism for separating the forward feed roller 50 in conjunction with the pulling out of the paper feed cassette 30 is constituted by the separation mechanism 53 including the cam member 82 and the like. It may be configured to electrically detect that the 30 has been pulled out and raise the forward feed roller 50 by a solenoid or the like. (B) The notch at the center of the guide sheet 60 is not limited to the V-shape, and a U-shaped or rectangular notch may be formed as shown in FIGS. 19 and 20. (C) In the above embodiment, the pipe-shaped paper feed guide is provided only on the front side of the paper feed roller 55, but a similar pipe may be provided on the rear side.

[0047]

As described above, in the present invention, since the notch is formed at the center of the leading edge of the guide sheet member, the guide sheet member is pressed to the press contact portion between the feed member and the pad member while being pulled to both sides. Guided, the curl of the sheet tip is reduced. In addition, since the curving of the leading end of the sheet is reduced, the degree of freedom of the position where the guide sheet member is mounted is increased, and the occurrence of double feeding is easily suppressed.

[Brief description of the drawings]

FIG. 1 is a schematic cross-sectional view of a copying machine employing a sheet feeding device according to an embodiment of the present invention.

FIG. 2 is an exploded partial perspective view of the copying machine.

FIG. 3 is a plan view of a sheet feeding cassette.

FIG. 4 is a partial front view of the sheet feeding device.

FIG. 5 is a front view showing a support structure of the paper feed cassette.

FIG. 6 is an enlarged partial view of the structure shown in FIG. 5;

FIG. 7 is a partial perspective view of a width adjusting mechanism.

FIG. 8 is a partial bottom view of the width adjusting mechanism.

FIG. 9 is a sectional view taken along line IX-IX of FIG. 8;

FIG. 10 is a partial cross-sectional side view of a sheet feeding roller and a sheet feeding shaft.

FIG. 11 is a front view showing a mounting structure of a paper feed shaft.

FIG. 12 is a plan view of a friction pad and a guide sheet.

FIG. 13 is a plan view showing a drive system of the lift member 71.

FIG. 14 is a front view of the separation mechanism.

FIG. 15 is a sectional side view of the separation mechanism.

FIG. 16 is a front view of a return conveyance guide member of the sheet feeding device.

FIG. 17 is a partial perspective view of a return conveyance guide member.

FIG. 18 is a perspective view showing an inclined portion of a bottom portion of the sheet feeding cassette.

FIG. 19 is a plan view showing another embodiment of the guide sheet.

FIG. 20 is a plan view showing still another embodiment of the guide sheet.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 12 Paper feeder 31 Paper feed mechanism 51 Double feed prevention mechanism 55 Paper feed roller 56 Friction pad 59 Spring 60 Guide sheet 60a Notch

Claims (1)

(57) [Claims] 1. A double feed prevention mechanism of a paper feeder for feeding supplied sheets one by one, comprising: a feed member for rotating in a paper feed direction and feeding a sheet in a paper feed direction; A pad member disposed opposite to the feed member and capable of pressing against the feed member via a sheet, an urging member for pressing the feed member and the pad member against each other, and a sheet width intersecting the sheet feeding direction And the leading end in the sheet feeding direction is located on the upstream side of the pad member in the sheet conveying direction.
Arranged so as to cover part of the sheet that is supplied
The center part slides on the pad member before the other parts and seals.
The transport speed at the center of the sheet is higher than the transport speed at both ends of the sheet.
A guide sheet member having a notch at the center of the leading end so as to be delayed, and a guide sheet member for guiding a supplied sheet to a pressure contact portion between the feed member and the pad member;