Sheet inverting apparatus

A sheet inverting apparatus includes an inverting rotary member with a sheet clamping hole which clamps and inverts the sheet and is arranged orthogonal to a sheet carrying route of the apparatus.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The present invention is related to a sheet inverting apparatus, or to be 
more specific, an image forming apparatus equipped with an inverting roll 
to turn over the sheet on which the image is formed on the route of 
carrying the sheet. 
2. Related Background Art 
The conventional image forming apparatus is explained hereunder by taking a 
compact laser printer used for the output device of a data processing 
system as an example. 
As illustrated in FIG. 1, a laser printer is provided with a process 
cartridge 3 which is removably attached to the main body 2 of the 
apparatus, the said process cartridge 3 accommodating the conventional 
processing apparatus such as photosensitive drum 4, electric charger 5, 
developing apparatus 6, cleaner 7 etc. At the upper part of the main body 
2 of the apparatus is provided the scanner unit 8 and mirror 9 which 
irradiate a laser beam and execute scanning. A latent image corresponding 
to the specified image data is formed on the photosensitive drum 4 which 
is electrically charged by the charger 5 and the latent image is developed 
by the developing apparatus 6 to produce a toner image. 
At the lower part of the main body 2 of the apparatus is arranged a sheet 
feeding cassette 10 which holds many sheets S, a sheet feeding roll 11 is 
arranged at the sheet feeding cassette 10, and the sheets S housed in the 
sheet feeding cassette 10 are delivered sheet by sheet to the regist or 
registration roller 12 by the sheet feeding roller 11. The said regist 
roller 12 adjusts the timing to deliver the sheet to the point in between 
the photosensitive drum 4 and transfer charger 13 and there the toner 
image on the photosensitive drum 4 is transferred. The sheet S on which 
toner image is transferred is delivered to the fixing apparatus 15 by 
conveyor belt unit 14, the toner image is fixed thereon and the sheet is 
discharged to outside of the main body 2 of the apparatus. 
Laser printer 1 has two systems to discharge the sheet S, one being the 
system to discharge sheet S in face up posture i.e., the image plane 
facing upward, and discharge the sheet through the face up discharge 
roller 16 into the face up discharge tray 17, while the other being the 
system to discharge sheet S according to the order of the page in face 
down posture i.e., with the image plane facing down, wherein the sheet is 
turned over after being guided upward from the said face up discharge 
roller 16, via the sheet delivery direction change-over system such as 
flapper and sheet guide etc. and discharged through the face down 
discharge roller 18 into the face down discharge tray 19. 
Maintenance of the laser printer, i.e., prevention of jamming, exchange of 
process cartridge 3 etc. is executed as illustrated by two dotted lines in 
FIG. 1 by turning the upper part 2a of the main body 2 of the apparatus 
upward around the fulcrum shaft P as against the lower part 2b of the main 
body 2, thus opening the inside of the apparatus and introducing the hand 
from the direction of arrow A. 
In the case of the conventional double face copying machine as illustrated 
in FIG. 2, the image is transcribed by photosensitive drum 4 and fixed by 
fixing apparatus 15 on the 1st face of the sheet delivered from the sheet 
feeding cassette 10 and the sheet is delivered in S-letter shape by the 
rollers 16, 51 and 52. Then after inverting the sheet S at a pass 53, 
timing is adjusted by carrying rollers 54 and 55 at regist roller 12 and 
the image is formed on the 2nd face of the sheet S by photosensitive drum 
4. 
In the case of the rolled sheet discharge section of the conventional 
facsimile, rolled sheet 57 on which the image is formed by image forming 
section 56 is further carried forward and cut by the cutter 58. Thus cut 
sheet 57 droops down at the discharge outlet and the front end of the 
sheet 57 enters into the inverting hole 59 (FIG. 3A). Due to the bend of 
the sheet, loop 57a is formed (FIG. 3B), the roll is cut at the specified 
length (FIG. 3C) and discharged on the face down discharge tray 17 to be 
piled up. (FIG. 3D) 
With the conventional case as illustrated in FIG. 1, it was necessary to 
have two kinds of discharge systems i.e., a face up system and face down 
system and consequently it has the following drawbacks: 
(i) Since the apparatus has two discharge trays 17 and 19, it is necessary 
to have two kinds of discharge rollers, namely, face up discharge roller 
16 and face down discharge roller 18 and besides, discharge trays must be 
set at two places, namely face up tray 17 at one place and face down tray 
19 at another place. 
(ii) Since the discharging point differs between face up discharge and face 
down discharge, operability of the system is inferior. 
(iii) Sheet carrying route of the face down discharge is long and thus 
there is the higher probability of jamming and it also causes cost 
increase of the motor due to the increase of carrying torque and cost 
increased use due to the increase of guide plates. 
(iv) Because of the presence of face down carrying route (part surrounded 
by one point chain in FIG. 1), it is impossible to make the body compact 
and reduce the area occupied by the apparatus. 
The conventional apparatus as illustrated in FIG. 2 has such drawback that 
an extremely large space in S-letter shape is required at the part where 
sheet S turns over and thus it is difficult to make the equipment compact. 
The conventional apparatus as illustrated in FIG. 3 has such drawback that 
the system is effective for the rolled sheet 57 that is not so hard to 
bend but with a sheet having high hardness to bend such as cut sheet S, 
the front end of the sheet S does not enter into the inverting hole, and 
sufficient inverting performance is not obtained. 
SUMMARY OF THE INVENTION 
Now therefore, the objective of the present invention is to provide the 
image forming apparatus which can easily turn over and discharge the sheet 
by using an inverting roll with simple and low cost construction. 
The present invention is characterized by that, for example, as illustrated 
in FIGS. 5A and 7, an inverting roller having a sheet clamping hole which 
clamps the sheet in the direction right angle to the sheet carrying route 
of the image forming apparatus and turns over the sheet is provided in the 
freely rotatable manner. 
Based on the aforesaid composition, after carrying the sheet along the 
carrying route and forming an image thereon, the sheet is carried to the 
inverting roller and the front end of the sheet enters into the sheet 
clamping hole of the inverting roller. Then, by the resistance of the 
sheet against bending, the inverting roller is turned over and the sheet 
forms a loop to be inverted. 
According to the present invention, the inverting roller is turned over by 
the resisting force of the sheet against bending and thereby the sheet is 
also turned over and therefore no driving source is necessary for the 
inverting roller (use of driving source is also workable as stated later). 
Thus, the construction of the inverting mechanism is simpler and the 
manufacturing cost is lower. Since the construction is simple, it is 
possible to make the system as an optional system and it fits better to 
the user's convenience end, and besides, since the main body of the 
apparatus is compact, handling of the apparatus is easier. 
Since the sheet is clamped by the sheet clamping hole and the inverting 
roller is turned over by the resisting force of the sheet against bending 
as well as the friction force, no driving power source is required for the 
inverting mechanism, the construction is simplified and manufacturing cost 
is reduced. The inverting roller is turned over not only by utilizing the 
hardness of the sheet against bending but also by the friction force and 
therefore the inverting performance of the inverting roller is improved. 
Since the inverting roller can be made to retreat from the carrying route 
by the retreating means when necessary, it is possible for the user to 
freely select the timing of inverting of the sheet, thus providing a large 
freedom of operation for the users. 
The inverting roller does not require any driving source nor clutches but 
its posture can be controlled by keeping the front end of the sheet 
inserted into the sheet clamping hole by using a weight. Since the 
inverting roller is made into one unit with its shaft, its construction is 
particularly simple and thus it is made to be an optional device of the 
apparatus, which greatly contributes to the convenience of the user. 
Besides, by turning the rotating member by a driving source, the rotation 
is executed with certainty and inversion can be made with certainty. By 
providing a guide, the sheet is inserted into the rotating member with 
certainty.

DESCRIPTION OF THE PREFERRED EMBODIMENTS 
Hereunder are explained the preferred embodiments of the present invention 
in reference to the drawings. 
The 1st embodiment is explained in reference to FIGS. 4, 5A, FIG. 5B and 
FIGS. 6A-6H. 
The members having the same construction and performance with those of FIG. 
1 explained in the Related section are given the same symbols and their 
explanations are omitted. 
An inverting guide 20 is installed roughly horizontally somewhat below the 
discharge outlet of face up discharge roller 16, and adjacent thereto, an 
inverting roller 22 is supported by the shaft 21 which is installed 
horizontally outside the main body 2a. At the lower part of the inverting 
roller 22 is fixed a weight 22b such as a metallic plate and at the upper 
part is provided a bent sheet clamping hole 22a facing the upper surface 
of the inverting guide 20. The weight of the weight 22b is so adjusted 
that when the sheet S is inserted into the sheet clamping hole 22a and 
pushed forward, the inverting roller 22 turns counter-clockwise. The 
inverting roller 22 may be made into one unit with or be made separate 
from the inverting shaft 21 as long as it is freely rotatable. 
In reference to the FIGS. 6A-6H, the performance of the present embodiment 
is explained hereunder. 
Sheet S moves on the inverting guide 20 and is inserted into the sheet 
clamping hole 22a (FIGS. 6A-6B). When sheet S is delivered further by face 
up discharge roller 16, roller 22 is pushed due to the resistance of sheet 
S against bending and revolves counter-clockwise against the force given 
by the weight 22b (FIGS. 6C-6D). 
Then the sheet S rubs against B section of the roller 22 while forming a 
loop and its friction force further turns the roller 22 (FIGS. 6E and 6F). 
When the sheet S is kicked out, the upper part of the loop moves leftward 
and the sheet is piled up into the face up discharge tray 17 in a face 
down state. The roller 22 returns to the original position due to the 
force of weight 22b (FIGS. 6G and 6H). 
Next, in reference to FIG. 7, an embodiment where the present invention is 
applied to the double face copying type copying machine is explained. 
Sheet S is brought down from roller 16, carried rightward at the downstream 
of carrying roller 23 and by the action of the inverting roller 22 of the 
present invention which is rotatably attached to the carrying route at a 
point more than a sheet length apart from tray 24, the sheet is inverted 
on the tray 24 and carried again by carrying roller 54. 
By such mechanism as aforesaid, the height of the sheet inverting section 
of the double face copying machine may be made lower than the case when 
S-letter-shaped pass is formed as illustrated in FIG. 2. 
As explained above, only by rotatably attaching the inverting roller 22 at 
the discharge outlet of the sheet S, it is possible to easily invert the 
sheet. By employing the face down mechanism using such sheet inverting 
system, the main body 2 is made compact and measurable and cost reduction 
is also realized. 
This construction requires fewer elements, unit cost of parts is lower and 
the system requires no driving force and therefore it can be easily 
connected as an optional device to the conventional face up discharge 
apparatus which has no face down discharge outlet. Besides, since the 
sheet discharges outlets for face up and face down discharge are not 
different in type, the operability of the system for the users is superior 
to other systems. 
As aforesaid, when the present invention is practised, it is possible to 
invert the sheet S by a simple mechanism. 
In the case of the 1st embodiment as explained above, the sheet is inverted 
without employing a driving source, but as illustrated in FIGS. 8 and 9, 
the sheet may be inverted by attaching a drive force to the inverting 
shaft 21. 
At the inlet of sheet clamping hole 22a of sheet inverting roller 22 is the 
sheet passage sensor 25 (FIG. 9A) and when the sheet S tries to enter into 
the sheet clamping hole 22a, the sensor lever 27 which can rotate around 
the fulcrum shaft 26 is turned by sheet S to make the sheet passage sensor 
25 respond and turn ON the solenoid 28 (FIGS. 8 and 9B). On the inverting 
shaft 21 is provided a clutch mechanism such as spring clutch 29 and thus 
inverting shaft 21 starts to rotate. 
The inverting action of sheet S is the same as that of the aforesaid 1st 
embodiment and as soon as the inversion of sheet S completed, the actuator 
stopper 30 of the solenoid 28 turns until the stopper is caught by the 
stopper 31 of the one turn control hub of the spring clutch 29 and thereby 
the sheet clamping hole 22a waits for the sheet S at the specified 
position. 
Next, the 2nd embodiment is explained with reference to FIGS. 10-13. 
As illustrated in FIG. 10, by arranging the discharge guide 20 moderately 
inclined upward as against the sheet S to be discharged, the sheet S 
discharged from discharge roller 16 is smoothly guided into the sheet 
clamping hole 22 of the inverting roller 22 as the sheet is discharged in 
such manner that the front end of sheet S is always in contact with the 
inverting guide 20. 
In order to improve and make smooth the performance of inserting of sheet S 
into the sheet clamping hole 22, the shape of the sheet clamping hole 22a 
of FIG. 11A may be modified in such manner as illustrated in FIG. 11B. 
When it is constructed in such shape, the rear end of the sheet S does not 
separate from the sheet clamping hole 22a, when the sheet S forms a loop 
as it turns over. As shown in FIG. 11C, instead of attaching a weight 22b, 
the part where it is attached may be made larger and heavier. 
As illustrated in FIG. 12, instead of a one sheet clamping hole 22, two 
clamping holes may be provided (FIG. 12A) or the holes may be provided in 
plural number (FIG. 12B). By so doing, without attaching the weight 2b, 
the sheet S coming out of the discharge roller 16 can be properly clamped 
by the sheet clamping hole 22a while the inverting roller 22 holds its 
posture as the sheet S is discharged to the discharge tray 17 and it gives 
such an advantage that weight 22b becomes unnecessary. The inverting 
roller 22 with the shape as illustrated in FIG. 13A and its arrow mark X 
view (FIG. 13B), may be used instead and by properly expanding the inlet 
of the sheet clamping hole 22a upward and downward or also in right and 
left directions as illustrated in FIG. 13C and its Y view (FIG. 13D), it 
is possible to smoothly insert the sheet S which may be curled by the heat 
of fixing or sheet S with substantial thickness. 
To explain the weight of inverting roller 22, as illustrated in FIGS. 
6B-6E, the inverting roller 22 is turned by the torque of the stiffness of 
the sheet S. Since such torque is not large at all, the inertia moment of 
the inverting roller including the weight of the weight must be made 
small. Therefore, it is necessary to use plastic etc. with small specific 
gravity for the inverting roller 32 and the weight 22b must be of minimum 
weight necessary for restituting the posture to the original state. 
Next, the 3rd embodiment is explained in reference to FIG. 14. As shown in 
FIG. 6F, sheet S rubs the section B of inverting roller 22 while forming a 
loop. Therefore a friction member 22c having a large friction coefficient 
is attached to section B i.e., the periphery of the part roughly opposite 
to the sheet clamping hole 22a. By so doing, the inverting roller 22 may 
be turned not only by the resisting force to bending of sheet S but also 
by the friction force given by sheet S, thus the sheet inverting 
performance is improved. The said friction member 22c may be a rubber 
piece etc. attached to the surface or a material with large friction 
coefficient coated on the surface. Or alternatively, weight 22b made with 
material of a large friction coefficient may be attached at the periphery. 
Next, the 4th embodiment is explained in reference to FIGS. 15-22. 
When inverting roller 22 is always on the carrying route of sheet S, sheet 
S is always discharged in face down posture and it is impossible to 
discharge it in face up posture. 
In the present embodiment, the inverting roller 22 is made to retreat from 
the carrying route of sheet S so that the sheet S is discharged in face up 
posture or the roller 22 may not be made to retreat so that the sheet S is 
discharged in face down posture. 
In FIG. 15, fulcrum shaft 32 is fixed to the outer plane of the sheet 
discharge hole of main body 2, plates 33a and 33b are fixed to the said 
fulcrum shaft 32 to form one unit, the inverting shaft 21 is fixed to the 
side plates 33a and 33b and inverting roller 22 is rotatably fixed to the 
inverting shaft 21. 
As illustrated in FIG. 16, at the lower end of side plates 33a and 33b, the 
fulcrum arm 34 is supported centrally by the shaft 35 which is fixed to 
the main body 2. The compression spring 36, one end of which being fixed 
to the pin 36a which is fixed to the body 2, the other end being fixed to 
the front end of the fulcrum arm 34, pushes up or down the fulcrum arm 34 
from dead point. When the arm is pushed upward, it stops by pressing the 
fulcrum arm 34 against the fixed pin 37a, while when the arm is pushed 
down, it stops by pressing the fixed pin 37b. 
As illustrated in FIG. 17A, when the side plates 33a and 33b are located at 
the position indicated by solid lines in FIG. 16, the inverting roller 22 
orientates toward the sheet clamping hole 22a of inverting guide 20, while 
when the side plates 33a and 33b are located at the position indicated by 
the dotted line of FIG. 16 as illustrated in FIG. 17B, the inverting 
roller retreats to the position downside of inverting guide 20. 
When the operator turns the knob 32 at the end of the fulcrum shaft 32, 
sheet S is inverted and discharged in face down posture in the case of 
FIG. 17A and discharged in face up posture in the case of FIG. 17B. 
As illustrated in FIG. 18, when the inverting roller 22 is supported by the 
inverting shaft 21 provided at the outside plane of the sheet discharge 
hole of main body 2 and inverting guide 20 is fixed to and made into one 
unit with shaft 39 supported by the main body 2 and the operator turns the 
knob 39a at the end of shaft 39, the inverting guide 20 is supported at 
the upper or lower position by fulcrum arm 34 as illustrated in FIG. 19. 
As shown in FIG. 20A, when inverting guide 20 is orientated toward the 
sheet clamping hole 22a of inverting roller 22, sheet S is discharged in 
face down posture while if inverting guide 20 retreats to the position 
above the inverting roller 22 as illustrated in FIG. 20B, sheet S is 
discharged in face up posture. 
As illustrated in FIG. 21, inverting guide 20 and inverting shaft 21 are 
fixed to the main body and inverting roller 22 is attached to the 
inverting shaft 21 in the manner to allow sliding and free rotation, 
roller position restricting plate 40 is attached to both sides of roller 
22 below the inverting shaft 21 in the manner to allow free sliding, the 
restricting board 40 is attached to the upper part of wire 41, wire 41 is 
applied to pulleys 42a and 42b and pulleys 42a or 42b are driven by the 
driving power source (not shown). 
When pulley 42a or 42b is driven by the driving power source and inverting 
roller 22 retreats to the far side of the discharge hole of sheet S via 
the wire 41 and restricting plate 40, the sheet S is discharged in face up 
posture (FIG. 22B) and when inverting roller 22 is roughly at the center 
of the discharge hole, sheet S is discharged in face down posture. 
The present inventing may be utilized as a manuscript or original inverting 
apparatus. Instead of the roller, a disc-shaped rotary member may be used.