Image forming device for electrostatic recording apparatus having a slidable replacement holding case

An image forming device for electrostatic recording apparatus which has a plurality of replacement units, and a case holding the replacement units and is integrally removable from the device body by sliding toward one direction, and in which each replacement unit is placed in operable position when the replacement unit holding case is set to a given position in the device body. In the replacement unit holding case, provided is a mechanism for automatically removing the position of each replacement unit further away from each other than the given setting position of each replacement unit, by pulling out the case from the device body.

FIELD OF THE INVENTION AND RELATED ART STATEMENT 
This invention relates to an image forming device for electrostatic 
recording apparatus. 
Recently as electrostatic recording apparatus such as the 
electrophotographic copying machine, facsimile (FAX) and electrostatic 
printer are widely spreading, the recording apparatus in which not only 
toner is supplied but also a photosensitive member and a cleaning unit are 
replaced by user's hands is becoming available. In particular, with 
printers, it is strongly requested that such replacement operation can be 
readily made by common users. Therefore, so far a method has been employed 
in which a photosensitive member, developing unit, cleaning unit and 
charger are integrated into an image forming unit that is to be replaced 
when it has been used up for a predetermined period of time. But, in this 
case, the cost per one sheet of print becomes expensive, because the parts 
cost for the integrated image forming unit is high. And, it is wasteful 
that even a photosensitive member still not exhausted must be replaced 
together with the other units to the shorter life of the cleaning unit or 
the shorter interval of toner supply. 
In this connection, to eliminate this kind of waste, another method has 
been commercially available in which a replacement cycle is set for each 
unit constituting the image forming unit and each unit is replaced 
independently. But, in this case, the replacement workability of each unit 
creates a problem. Particularly when replacing a photosensitive member, 
its surface isn't so hard that it may be finger imprinted or impaired due 
to contact or scratch with other parts, resulting in the deterioration of 
the function. And, there is a strong possibility of toner spill when 
replacing the developing unit and cleaning unit. 
Accordingly, to have a better operability, a piece of equipment has made 
its appearance in which each replacement unit such as a photosensitive 
drum, a developing unit and a cleaning unit is set in a case that can be 
integrally removed slidably out of the very equipment together with those 
units therein. And when replacing a unit, the case is drawn out of the 
equipment to replace the target unit. But, in this event, when removing 
the old unit and inserting a replacing unit, there are possibilities of 
the unit getting contact with the adjoining units or dropping on them, 
resulting in damage on units, thus introducing concern for making worse 
the quality of subsequent prints. 
OBJECT AND SUMMARY OF THE INVENTION 
The object of the invention is to provide an image forming device which has 
a plurality of replacement units, and a case holding the replacement units 
and integrally removable from the device body by sliding toward one 
direction, and in which each of the above replacement units is placed in 
operable position when the above replacement unit holding case is set to a 
given position in the device body, and in which the above case is pulled 
out to replace a given unit, which can prevent the given unit from getting 
contact with adjoining units or the toner from spilling out when the given 
unit is being replaced. 
To achieve the above object, an image forming device according to the 
invention adapted for an electrostatic recording apparatus having the 
above configuration is characterized in that: in the above replacement 
unit holding case is provided means for automatically displacing each of 
the above replacement units further away from each other, than the given 
setting position of each of the above replacement units. 
By using this configuration, each replacement unit disposed in a means for 
holding replacement units all together can be placed in a home position or 
a close-to-each-other position necessary for operation when the means is 
inserted into the device body, and can be removed from the home position 
so as to relatively separate away from each other when the means is pulled 
out of the device body. Therefore, gaps will be made between them, thus 
making the replacement of the units easier, eliminating possibilities of 
adjoining vulnerable units being damaged when replacing each unit, and 
further allowing each unit to be taken out without toner spilling out of 
the cleaning unit or the developing unit. 
These and other objects, novel features and advantages of the invention 
will be readily apparent from the following description taken in 
connection with the accompanying drawings.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENT 
FIG. 1 is a perspective view showing a first embodiment according to the 
invention, adapted for a laser printer. In FIG. 1, a drawer 2 supporting 
an image forming unit (including a unit to be replaced) has been pulled 
out of the laser printer body. FIG. 2 is a partially sectional view of the 
drawer 2 in FIG. 1. 
As shown in FIGS. 1 and 2, the drawer 2 in the laser printer according to 
the embodiment is slidably supported on a side of the body 1 by support 
guide rails 3 and 3'. 
In the drawer 2, an image forming unit consisting of a drum-shape 
photosensitive unit 4, a developing unit 5, a cleaning unit 6 and a toner 
cartridge 7 is removably housed. When the drawer 2 is pushed into the body 
1, each of these units is so properly installed as to keep their relative 
positions that the recording operation of the electrostatic photographic 
process is rightly performed, and also is so properly located as to keep a 
relative best position to an optical unit 21, an electro-charger 22, a 
charge-removing lamp 23 and resist rollers 25 which are installed on a 
side of the body 1. 
A handle 8 is installed on the front of the drawer 2 to pull out. Handles 
are attached respectively to the developing unit 5, the cleaning unit 6 
and the toner cartridge 7. But the handles are not shown in FIG. 2. 
In addition to the drawer 2 housing the above image forming unit and the 
optical unit 21 optically scanning over the photosensitive member, the 
body 1 is provided with a 1st feed paper cassette 11 and a 2nd feed paper 
cassette 12 supplying sheets of recording paper, as well as a fixing unit 
27 fixing, by heat and pressure toner image on recording paper developed 
by the image forming unit. On the top of the printer body 1, provided are 
a 1st discharge paper tray 15 and a 2nd discharge paper tray 16 receiving 
printed sheets of recording paper discharged through a transfer passage 
28. 
The printer body 1 is installed on an option unit 13 consisting of a 
separate mass feed paper unit 14 used, if required, as a so-called option, 
and of a reversing unit (not shown) to reverse sheets of paper recorded on 
a side discharged from the fixing unit 27 and to transfer them again to 
the image forming unit. 
A cover 10 is provided to prevent dust from flowing into the body 1 and to 
give a good appearance thereof, by raising the cover 10 to cover the side 
of the body 1 with the drawer 2 housed in. 
FIGS. 3 and 4 show a typical mechanism to remove the cleaning unit 6 away 
from the photosensitive unit 4 by pulling out the drawer 2. 
A pair of sliders 35 and 35', which respectively have sliding slots 31, a 
cleaning unit supporting notch 32, a spring latching protrusion (pin) 33 
and a cam plate 34, is provided on the front/back sides of the pulling 
direction of the drawer 2, and is fixed slidably to the drawer 2 by guide 
pins 36. And a spring 39 is secured between the spring latching protrusion 
33 on the slider 35 and a spring latching pin 38 fixed on the bottom of 
the drawer 2. 
An axis bar 40 is rotatably inserted into the front/back side plates of the 
drawer 2, a cam 41 is fixed on the bar 40 to a position facing the cam 
plate 34 on the slider 35, and a torsion spring 37 is fixed to the bar 40 
to rotate the bar 40 around its axis. Such kind of cam and spring is also 
provided on the slider 35' (not shown). To the back end portion of the bar 
40, a pin 42 is attached so as to engage with a cam 43 fixed to the body 
1. 
The cleaning unit 6 has four pieces of pins 44,44',45 and 45' at the front 
and back ends thereof, the two pins 44 and 44' are inserted into the 
notches 32 and 32' of the respective sliders 35 and 35' as shown in FIG. 4 
to be supported by the sliders 35 and 35', and the rest two pins 45 and 
45' are supported by pin support blocks 46 and 46' attached to the side 
walls of the body 1 as shown in FIG. 5. As shown in FIG. 6, the pin 
support blocks 46 and 46' have respectively pin sliding slots 47 to 
support the pins slidably in the sliding direction, and have openings 48 
above the slots to insert the pins thereinto. 
Of the drawer 2 housing the image forming unit having the above 
configuration, the pin 42 at the back end portion of the bar 40 is pressed 
against the back of the body-side cam 43 when the drawer 2 is pushed in 
position into the body 1, and the spring 37 does not permit the cam to 
rotate. As a result, only the elastic force of the spring 39 effectively 
works on the slides 35 and 35' to place the cleaning unit 6 supported by 
the slides 35 and 35' in proper operation position close to the 
photosensitive unit 4. In other words, the cleaning unit 6 is kept in 
position (home position) by being pulled to the right direction of FIG. 3 
by the spring 39. 
On the other hand, when the drawer 2 is pulled out, the pin 42 on the back 
end of the bar 40 extending over the length of the drawer 2 is going to 
work out of the body-side cam 43. As a result, the rotational (torsion) 
force of the spring 37 is going to move the cam 41 to press the plate 34 
on the sliders 35 and 35'. Because the spring 37 is designed to be 
stronger than the spring 39, the sliders 35 and 35' move toward the left 
side of FIG. 3, which results in the pins 44 and 44' on the cleaning unit 
6 moving to the left direction, thus removing the cleaning unit 6 away 
from the photosensitive unit 4. 
The above describes only the displacement of the cleaning unit 6, but the 
developing unit 5 also can be removed away from the photosensitive unit 4 
in the same way, when the drawer 2 is pulled out. 
In the above embodiment, in order to automatically remove each unit (set in 
the drawer 2) away from each other when the drawer 2 is pulled out of the 
body 1, a combination of a plurality of cam mechanisms makes the 
positional detection of the drawer 2, and also makes given units slide 
according to the detection. But, the invention is not limited to such a 
cam mechanism, but can use other means such as a combination of electrical 
detection of the drawer position and a electromagnetic mechanism driven 
thereby. 
In the above embodiment, when taking out any one of the units to replace, 
pulling the drawer 2 out of the body 1 automatically removes the 
developing unit 5 and the toner cartridge 7 together away from the 
photosensitive unit 4 toward the right side of FIG. 2, and the cleaning 
unit 6 toward the left side. Therefore, the replacing operation is so 
simple and there is no chance of the adjoining units being damaged. 
Next, the 2nd embodiment according to the invention will be described in 
detail referring to the drawings. 
FIG. 7 shows the 2nd embodiment of an image forming device according to the 
invention. A developing unit 101, a photosensitive drum 102 and a cleaning 
unit 103 are set in a case 104. They are set in the device body by loading 
these units and the case 104 integrally in the device body. Each of above 
units 101, 103 and 102 is located by inserting respectively positioning 
pins 105 and 107 as well as the boss (positioning pin) 106 of a bearing 
into U-shape openings of a positioning plate 108 attached to the front end 
of the case 104 with screws 109. 
As shown in FIG. 8, compression springs 121 and 122 are installed on the 
bottom plate of the case 104 respectively under the developing unit 101 
and the cleaning unit 103. The developing unit 101 and the cleaning unit 
103 are respectively energized by the springs 121 and 122 so as to rotate 
respectively around the pins 105 and 107 as if the photosensitive unit 
lifts up. As shown in FIG. 7, a stepped screw 110 is screwed into a 
threaded hole at the left end of the front portion of the case 104, 
through a left-end hole in a holding plate 111 and a left-end hole in the 
positioning plate 108, so that the holding plate 111 can be rotated around 
this screw 110. To set these plates, hold a lever 112 attached to the 
right end of the holding plate 111, and press bent pieces 111a against 
stoppers 103a and 101a respectively on the cleaning unit 103 and the 
developing unit 101 while pressing down the positioning pins 105 and 107, 
to press down each unit and to set each unit in a given position. These 
units are fixed by engaging a stopper 113 attached to the right end of the 
holding plate 111 by use of pin, with the bottom edge of the positioning 
plate 108. Each unit is set in position by inserting the case 104 
(together with each unit 101, 102 and 103 loaded therein) into the device 
body at this condition. 
To replace each unit, the case is pulled out of the device body, and the 
stopper 113 is removed from the positioning plate 108. The force of the 
springs 121 and 122 will permit the developing unit 101 and the cleaning 
unit 103 to rotate respectively around the pins 105 and 107 as if the 
photosensitive unit 102 lifts up, thus both removing away from the 
photosensitive unit 102. Therefore, when replacing either of the 
developing unit 101, the photosensitive unit 102 and the cleaning unit 
103, any unit can be removed without damaging any adjoining unit, thus 
preventing damage, finger prints attached, or toner spill due to contact. 
Because each unit cannot be taken out unless the holding plate 111 is 
removed, it is positively prevented that each unit is taken out without 
being separated from each other. 
Using the above configuration and pulling out the replacement unit holding 
case, can remove the developing unit and the cleaning unit away from the 
photosensitive drum. But, in replacing the photosensitive unit, since the 
surface of the photosensitive member is not so hard, there is a 
possibility of a deterioration of its functions due to attaching finger 
prints on and damaging the surface of the photosensitive member by getting 
contact with the surface or scratching the surface with other members. 
The above situation may necessitate a support mechanism of photosensitive 
member by which users can easily replace a photosensitive drum in an 
electrostatic recording apparatus without damaging the surface of the 
photosensitive member or getting contact with the surface. 
This photosensitive drum holding mechanism is particularly useful when used 
together with the invention described above. 
The photosensitive member holding mechanism consists of: 
an outer cylinder having a trunnion fitting into a bracket attached to the 
front plate of the replacement unit holding case being pulled out of the 
device body, rotatable around a horizontal axis lateral to the pulling-out 
direction of the above case; 
a socket fitting slidably into the above outer cylinder, being energized in 
a direction protruding toward the case insertion direction by a spring 
inserted between the bottom plate of the above case, and having an inner 
cylinder provided with a bottom plate and a means for prevention of 
working out from the above outer cylinder; and 
a journal portion fitting into the above socket slidable axially and 
rotatable around its axis, and constituting a cap of the above 
photosensitive member pressure fitted on one end of the shaft. 
As a 3rd embodiment according to the invention, an image forming device 
incorporating the photosensitive drum holding mechanism of the above 
configuration is described in detail referring to the drawings. 
FIG. 9 is a drawing showing an image forming device according to the 3rd 
embodiment. A photosensitive drum 201, a developing unit 202 and a 
cleaning unit 203 are housed in a case 200. In the figure, the case 200 
has been pulled out of a device body of a printer or the like. The unit 
case 200 is guided by guide rails 206 and 207. On a front plate 204 of the 
case, a handle 205 is attached. Using this handle, the unit case 200 can 
be readily pulled out, to set other units. On the upper portions of the 
both ends of the front plate 204, positioning holes 204a are opened. Using 
these holes, the unit case 200 is placed in position by inserting (into 
these holes) pins 208 and 209 screwed into the front plate of the device 
body 210, when the unit case 200 is housed in the device body. 
By pulling out the case, the developing unit and the cleaning unit are 
removed away from the photosensitive drum, and since the mechanism has 
been explained in the 1st and 2nd embodiments, this drawing omits its 
explanation. 
A mechanism for supporting a photosensitive drum in an image forming unit 
shown in FIG. 9 is explained referring to FIGS. 10 to 12. 
The shaft front end of the photosensitive drum 201 is supported by 
inserting the end into a socket 220 disposed in the front plate 204 on the 
unit case 200, and a flange 224 at the back end is supported by an opening 
in a unit case back plate 235 as shown in FIG. 12. When the unit is 
inserted into the device body, the photosensitive drum 201 is supported by 
fitting a cylinder 236 having a conical portion (on its center) cut with a 
number of grooves inside along slant lines, onto a driving shaft 211 of 
the device body having a conical end with mating grooves. 
The socket 220, as shown in FIGS. 10 and 11, consists of; an outer cylinder 
221 provided with projecting trunnions 234, fitting into openings 223a in 
a bracket 223 attached to the front plate 204, and rotatable around the 
horizontal axis lateral to the pulling-out direction of the unit case 200; 
an inner cylinder 233 provided inside the above outer cylinder and 
rotatable in the axial direction; a compression spring 231 disposed inside 
between the bottom plate of the outer cylinder 221 and the bottom plate of 
the inner cylinder 233 provided inside thereof at the middle portion; and 
a shaft fixed into the bottom plate of the inner cylinder 233, with the 
front end thereof penetrating through the bottom plate of the outer 
cylinder having a retaining ring for prevention of its working out. 
On the other hand, onto the front end shaft of the photosensitive drum 201, 
pressure fitted is the cap 222 slidable axially and rotatable around its 
axis in the inner cylinder 233 of the above socket 220, thus forming a 
journal for the inner cylinder 233. 
As a result, when loaded, the conical hole inside the backside flange of 
the photosensitive drum 201 comes into a pressure contact with the end 
conical portion of the driving shaft 211 of the device body, to transmit 
the driving force by engaging both grooves with each other, as well as the 
photosensitive drum 201 is supported by the inner cylinder 233 in the 
socket 220 at the front end and by the driving shaft of the device body at 
the back end. 
When replacing the photosensitive drum, the unit case is pulled out from 
the device body. The back end of the drum is removed away from the tip end 
of the driving shaft on the device body side, and the inner cylinder 233 
in the socket 220 is pushed out by the spring 231 as shown in FIG. 11 
until the retaining ring comes into contact with the outside face of the 
outer cylinder bottom plate. As the inner cylinder 233 is pushed out, the 
journal portion 222 of the photosensitive drum 201 extends out much longer 
than when it is loaded or operating. Then, as shown in FIG. 12, the 
journal portion 222 can be readily pulled out of the socket 220 to take 
out the photosensitive member, by raising the photosensitive drum 201 
around the trunnion 234 of the socket 220 while pressing the flange 224 of 
the drum 201 toward you, and by lifting up the both end faces of the 
photosensitive drum 201 with hands. 
Next, a new photosensitive drum can be loaded in the reverse order of the 
above, and supported by the socket 220 and the driving shaft 211 on the 
body side. It is desirable that a new photosensitive member be wrapped 
with protective paper to prevent the surface of the member from being 
spotted. 
The above photosensitive member holding mechanism can improve the 
workability during the replacement of the drum in an electrostatic 
recording apparatus such as printers, thus allowing users to easily 
replace the photosensitive member without causing damage.