Fixing device for fixing images of an original document on plain paper copy sheets

A fixing device for fixing images of an original document on a copy material is provided for a plain paper copier. The fixing device comprises a pair of rollers for stressing under pressure the copy material carrying toner powder thereon. The toner powder is tightly adhered to the surface of the copy material to correspond to the images of the original document. In a preferred form, the toner powder is a pressure-fixable developing powder which consists of a wax component and a thermoplastic resin. A developing powder supplier is disposed within a developer powder reservoir for supplying developer powder to a magnet brush. A rotatable cylindrical magnet is provided within said developing powder supplier for generating a non-uniform magnetic field to stir the developer powder within the reservoir. A copy sheet stripping device is also provided which moves in synchronization with the approach of a copy sheet towards the fixing device and to move in synchronization with the separation of the copy sheet away from the fixing device.

BACKGROUND OF THE INVENTION 
The present invention relates generally to a fixing device for use in a 
copier and, more particularly, to a fixing device for fixing images of an 
original document on plain paper copy sheets for use in a plain paper 
copier (PPC). 
The plain paper copiers have been recently developed, wherein a 
heating-fixing device is provided for fixing the images of the original 
documents on plain paper copy sheets. However, it is required that the 
heating-fixing device be so large to facilitate the solution of a toner 
powder. The occurrence of a jam within the plain paper copier has a 
tendency to fire a plain paper copy sheet. Pre-heating for the 
heating-fixing device is further required to operate the fixing device in 
stable conditions for a predetermined period of time in response to the 
application of power energy for the plain paper copier for copy purposes. 
Therefore, it is desired that a fixing device shall not be preheated. On 
the other hand, non-heating fixing devices for fixing images of original 
documents on light-sensitive sheets of copy material are well known in the 
prior art. One such device is disclosed in J. Roteman et al., U.S. Pat. 
No. 3,846,151 entitled "FIXING DEVICE" issued on Nov. 5, 1974. However, it 
is commercially and practically impossible to realize the non-heating 
fixing device in the plain paper copier. 
OBJECTS AND SUMMARY OF THE INVENTION 
With the foregoing in mind, it is a primary object of the present invention 
to provide a new and improved fixing device for use in a plain paper 
copier. 
It is another object of the present invention to provide a new and improved 
fixing system for use in a plain paper copier to thereby facilitate fixing 
of images of an original document on a plain paper copy sheet for use in a 
plain paper copier. 
Other objects and further scope of applicability of the present invention 
will become apparent from the detailed description given hereinafter. It 
should be understood, however, that the detailed description and specific 
examples, while indicating preferred embodiments of the invention, are 
given by way of illustration only, since various changes and modifications 
within the spirit and scope of the invention will become apparent to those 
skilled in the art from this detailed description. 
To achieve the above objects, pursuant to an embodiment of the present 
invention, a fixing device is provided within a plain paper copier for 
fixing of images of an original document on a plain paper copy sheet. A 
developing powder is adhered to the surface of the plain paper copy sheet 
to correspond to an image of the original document. 
In a preferable form of the present invention, the developing powder 
comprises a wax component and a thermoplastic resin. This developing 
powder is flowable, pressure-fixable, and dry powder. An example of such 
developing powder is disclosed in the above U.S. Pat. No. 3,925,219. 
Preferably, the resistance value of the developing powder is selected in 
the order of 10.sup.13 -10.sup.14 .OMEGA./cm.

DESCRIPTION OF THE PREFERRED EMBODIMENT 
FIG. 1 shows a plain paper copier of the present invention, wherein a pair 
of fixing rollers 16 are provided for fixing under pressure images of an 
original document on a plain paper copy sheet 2. 
The plain paper copy sheet 2 passes through a paper feeding section, a 
transference section and a fixing section and the copied sheet 2 is 
discharged from a paper outlet as described hereinbelow. 
A plurality of the plain paper copy sheets 2 are stacked within a cassette 
1. A feed roller 3 is positioned on the plain paper copy sheets 2 to 
transfer the copy sheets 2 into the housing of the plain paper copier in 
response to a copy start signal applied thereto. 
The plain paper copy sheet 2 picked up by the feed roller 3 is transferred 
into a developing section as described below by a pair of feed rollers 4 
and other feed rollers 5. An image of an original document is produced on 
a light sensitive member 6 in the form of a toner powder pattern. The 
image is developed on the plain paper copy sheet 2 using a transference 
charger 7. The light sensitive member 6 comprises a master paper including 
a zinc oxide coating tightly adhered to a rotary drum. 
Around the light sensitive member 6 there are provided a charger 8 for 
charging the surface of the light sensitive member 6, an exposure section 
9 for projecting reflection light from the original document toward the 
drum and a developing section 10 for developing the reflection light 
images on the light sensitive member 6 by depositing toner powder 
corresponding to the reflection light images thereon. The reflection light 
image is formed by applying light from an illumination section 11 upon the 
original document. The original document is disposed on a transparent 
plate such as a glass plate. The reflection light passes an optical system 
12 to provide the reflection light images on the exposure part 9. A 
document plate 13 including the transparent plate is removed in accordance 
with the rotation of the drum to achieve slit exposure as is well known. 
The toner powder employed within the plain paper copier of the present 
invention is a flowable, pressure-fixable developing dry powder comprising 
wax and thermoplastic resin. Preferably, the resistance value of the toner 
powder is selected in the order of 10.sup.13 -10.sup.14 .OMEGA./cm. 
FIG. 2 shows the toner powder having the resistance value of 10.sup.13 
-10.sup.14 .OMEGA./cm in a cross-sectional view. The toner powder 20 
comprises, for example, 55.6% of magnetite powder 201, 7.4% of conductive 
carbon black 202 and 37% of low molecular weight polyethylene resin 203. 
The diameter of the toner powder grain is 15.mu.. 
The toner powder is transferred to the developing section 10 by the 
magnetically attractive force of a magnet roller within the developing 
section 10. In the developing section 10, the toner powder images formed 
on the light sensitive member 6 are developed on the plain paper copy 
sheet 2 through the transference charger 7. Assume now that the 
transference charger 7 is charged with polarity opposite to that of the 
charger 8. The plain paper copy sheet 2 is strictly adhered to the light 
sensitive member 6 for the transference purposes. 
A paper suction member 14 is provided for sucking the plain paper copy 
sheet 2 with air therein for removal from the light sensitive sheet 6. The 
plain paper copy sheet 2 is then placed on the travelling course of a belt 
14a while carrying the toner powder images thereon. A charge removal 
component 15 is disposed above the paper suction member 14 for removing 
the remaining charge on the plain paper copy sheet 2. 
When the plain paper copy sheet 2 reaches fixing rollers 16, the belt 14a 
presses the toner powder strongly on to the copy sheet 2 for adhesion 
purposes. The fixing rollers 16 can be implemented in a well known manner 
such as in U.S. Pat. No. 3,846,151 entitled "FIXING DEVICE" to J. Roteman 
et al. The toner powder images are strictly fixed on the plain paper copy 
sheet 2. After passing through the fixing rollers 16, the plain paper copy 
sheet 2 is sent to feed rollers 17 to be discharged out of the housing of 
the plain paper copier. 
A cleaner 18 is provided in the neighborhood of the drum for removing the 
remaining toner powder which has not been adhered to the plain paper copy 
sheet 2 from the surface of the light sensitive member 6 during the 
transference procedure. The cleaner 18 comprises a magnet roller 19 which 
magnetically attracts the toner powder in accordance with the rotation 
thereof such as the developing section 10. A cleaner brush can be employed 
instead of the magnet cleaner 18. 
Some advantages of the plain paper copier in accordance with the present 
invention are summarized as follows, which can not be expected in a prior 
art plain paper copier. 
(1) The fixing process of the present invention does not rely upon heat 
energy thereby overcoming the heat problems inherent with the fixing 
device. A pre-heating period is not required to speed up copying 
operation. 
(2) The present copier is free of danger such as firing the plain paper 
copy sheet 2 because of the absence of a heater. 
(3) The dry toner powder adapted to the present invention is useful for the 
fixing process, which toner powder comprises a wax component and a 
thermoplastic resin. Using the toner powder, carrier elements which are 
inevitably utilized in the prior art toner powder are omitted. Of course, 
the present invention needs replenishment of such carrier elements. 
(4) Using the plain paper copy sheet 2 enables a substantial reduction in 
copy cost and any character or mark can be written directly on the copy 
material 2 after copying. 
Many problems must be solved to realize the pressure fixing method in the 
plain paper copier of the present invention as described below. For the 
purpose of this invention "plain paper" means a paper having no 
light-sensitive coating as is well known in the art of copiers. 
(I) How to apply the developing powder comprising a wax component and 
thermoplastic to the plain paper copier of the present invention. 
When the conventional plain paper copier is activated using the 
conventional developing powder having resistance of 10.sup.7 -10.sup.8 
.OMEGA./cm, the copy produced might be damaged, especially, smeary or 
scattered copied images result during the transference procedure. The 
reasons therefor have not yet been revealed. 
To enhance the transference efficiency, the resistance value of the 
developing toner must amount to 10.sup.13 -10.sup.14 .OMEGA./cm, and 
simultaneously, the volume specific resistance of the plain paper is 
increased above 1.times.10.sup.12 .OMEGA./cm under relative humidity of 
10-90% at room temperature. To make a plain paper copy sheet adaptable to 
the purpose of the present invention it is desirable that a plain paper 
copy sheet be impregnated or coated with one or more of highly polymerized 
compound solutions such as acrylic ester resin, alkyd resin, epoxide 
resin, urethane resin, polyolefine resin, polystyrene resin, melamine 
resin, urea resin, and vinyl chloride resin. 
However, the developing efficiency is necessarily reduced because of the 
higher resistance value of the developing powder. Therefore, an 
improvement in the developing section is preferable for this reason as 
follows. 
(1) The outer diameter of the magnet roller in the developing section is 
enlarged. 
(2) A developer powder supply means in the developing section comprises a 
stationary sleeve and a rotatable cylindrical magnet enclosed by the 
stationary sleeve. The details of the stationary sleeve and the rotatable 
cylindrical magnet are described in the copending patent application Ser. 
No. 854,212 entitled "DEVELOPER POWDER SUPPLY IN MAGNET BRUSH DEVELOPMENT" 
filed Nov. 23, 1977, now U.S. Pat. No. 4,193,376. The corresponding West 
German Application was filed on Nov. 24, 1977 under No. P 27 52 561.7. 
Within such an arrangement a sleeve is stationary and the cylindrical 
magnet is rotatable unlike a conventional copier. In FIG. 3 a developer 
powder supply means 24 is disposed within a developer reservoir 26 for 
supplying developer powder 28 to a magnet brush developing roller 22 which 
is placed adjacent to a drum 21 carrying an electrostatic latent image 
formed on the surface thereof. 
The developer powder supply means 24 comprises a stationary sleeve 30 and a 
rotatable cylindrical magnet 32 enclosed by the stationary sleeve 30. The 
rotatable cylindrical magnet 32 includes a magnet shunt means or has an 
odd number of magnetic poles to produce distorted distribution of the 
magnetic field. The rotatable cylindrical magnet 32 generates a nonuniform 
magnetic field therearound and includes a surface portion which 
essentially does not have a magnetic field. The surface portion which 
essentially does not include a magnetic field is rotatable in response to 
the rotation of the cylindrical magnet for supplying the developer powder 
in a swinging movement causing the stirring of the developer powder within 
the reservoir 26. The stationary sleeve 30 has an extended portion which 
is placed above the rotatable cylindrical magnet 32, where the magnetic 
field established by the rotatable cylindrical magnet 32 does not effect 
the developer powder 28. 
Finally, with respect to the improvement in the developing section, to make 
the developing period much longer and enhance substantially the developing 
efficiency, the outer diameter of the stationary sleeve is selected in the 
order of 58-59 mm .phi., while the conventional sleeve has 51 mm .phi. at 
the same portion. 
(II) How to adapt the fixing device into the plain paper copier of the 
present invention. 
During operation of the fixing device static energy was inevitably caused 
on the plain paper and the developing toner, both having the higher 
resistance value as viewed in the prior art. A paper stripping member was 
provided within the fixing device for scrapping the plain paper copy 
sheet. The paper stripping member undesirably also stripped the developing 
toner which had been adhered to the fixing device, for example, a pair of 
fixing rollers. The stripped developing toner made the plain paper dirty 
because of an accumulation of toner on the plain paper in accordance with 
the static energy therebetween. 
Contrarily, according to the present invention, the paper stripping member 
is preferably movably secured adjacent to the fixing device. Such paper 
stripping member is disclosed in the copending U.S. patent application 
entitled "SHEET STRIPPING MEMBERS FOR FIXING DEVICE FOR FIXING IMAGES OF 
AN ORIGINAL DOCUMENT ON SHEETS OF COPY MATERIALS BY USING TWO ROLLERS IN 
PRESSURE ENGAGEMENT" Ser. No. 891,639 filed on Mar. 30, 1978 now U.S. Pat. 
No. 4,281,623. The corresponding West German patent application was filed 
on Mar. 30, 1978 under the Ser. No. P 28 13 777.1. As disclosed therein, 
in FIGS. 4 and 5 a couple of copy sheet stripping members 40 and 42 are 
provided for scraping away a copy sheet adhered strictly to one of two 
rollers 44 and 46 which are driven to fix images of an original document 
on a copy sheet 48 by pressure engagement. At least one of the copy sheet 
stripping members 40 and 42 is movably secured adjacent to the roller 44 
while the copy sheet 48 is not transferred out of the rollers 44 and 46. 
The copy sheet stripping member becomes pressed against the roller 44 when 
the copy sheet 48 is transferred to the roller and is detected by a 
forward sensing means. The copy sheet stripping member 42 is free of 
residue attached to the roller 44 because of the period of time whereby 
the roller 44 is engaged with the copy sheet stripping 42. The member 52 
can be further disposed to assure both the scraping of the copy sheet 48 
and the removal of the residue on the roller 44, the copy sheet stripping 
member 52 being continuously pressed against the roller 44. 
The operation of the copy sheet stripping member 42 is synchronized to move 
into engagement with the roller 44 when a first sensing means produces an 
output sensing the approach of a copy sheet 48 to scrape the copy sheet 48 
from the roller 44. The copy sheet stripping member 42 is synchronized to 
move out of engagement with the roller 44 when a second sensing means 50 
produces an output sensing the copy sheet 48 upon completion of the 
scraping of the copy sheet 48 from the roller 44. 
While only certain embodiments of the present invention have been 
described, it will be apparent to those skilled in the art that various 
changes and modifications may be made therein without departing from the 
spirit and scope of the invention as claimed.