Ozone filter unit for an electrophotographic apparatus

A filter case having open opposite ends is disposed with one of the open ends thereof facing an air exit formed in the side wall of the housing of an electrophotographic apparatus, and a filter element holding frame having an upper opening through which an ozone filter element is inserted therein is supported pivotally at its lower end on the lower portion of the filter case for turning about a substantially horizontal axis so as to be fitted in the filter case. In changing the ozone filter element, the cover is opened, the filter element holding frame is turned about the substantially horizontal axis to expose the upper opening thereof outside the filter case so that the ozone filter element can be taken out through the upper opening from the filter element holding frame. The wide, open upper space in the housing facilitates the filter element changing operation. Since the wide, open upper space in the housing is available for taking out the ozone filter element from and inserting the same in the filter element holding frame, the space between the inner surface of the side wall of the housing and the filter case may be relatively small and hence the size of the housing can be reduced accordingly.

FIELD OF THE INVENTION AND RELATED ART STATEMENT 
The present invention relates to an ozone filter unit for an 
electrophotographic apparatus. 
An electrophotographic apparatus charges a photoconductive body by a 
charger prior to forming an electrostatic latent image on the 
photoconductive body. In transferring a toner image formed on the 
photoconductive body to a recording sheet, an electric discharge is 
produced between a charger and the photoconductive body to charge the 
recording sheet. A discharge of negative polarity produces ozone injurious 
to human. Accordingly, an ozone filter unit is provided near a cooling 
exhaust blower to remove ozone from air containing ozone. FIG. 3 shows a 
conventional ozone filter unit for such a purpose. 
Referring to FIG. 3, an ozone filter element 17 provided on its upper side 
with a lug 25 is fitted in a filter case 24 having opposite open ends. A 
filter element holding frame 26 is provided integrally with hooks 27 on 
its right and left sides. The filter element holding frame 26 is joined to 
the filter case 24 with the hooks 27 elastically engaging openings 28 
formed in the opposite side walls of the filter case 24. Generally, the 
filter case 24 is disposed with its open end facing an air exit opening 
formed in the side wall of the housing of an electrophotographic 
apparatus, not shown. 
In changing the ozone filter element 17, the filter element holding frame 
26 is separated from the filter case 24, and then the ozone filter element 
17 is gripped by the lug 25 and is pulled out from the filter case 24. In 
removing the ozone filter element 17 from the filter case 24, the filter 
element holding frame 26 and the ozone filter element 17 must be pulled in 
the direction of flow of exhaust air. On the other hand, the filter case 
24 must be disposed with a narrow space between its open end and the inner 
surface of the housing to discharge exhaust air through the air exit of 
the housing of the electrophotographic apparatus. Therefore, only a narrow 
space is available for handling the ozone filter element 17 and the filter 
element holding frame 26, which makes operations for removing the ozone 
filter element 17 from and fitting the same in the filter case 24 very 
difficult. Increase in the space between the open end of the filter case 
24 and the inner surface of the housing to facilitate operations for 
removing the ozone filter element 17 from and fitting the same in the 
filter case 24 entails increase in size of the housing. 
OBJECT AND SUMMARY OF THE INVENTION 
Accordingly, it is a first object of the present invention to enable the 
housing of an electrophotographic apparatus to be formed in a relatively 
small size. 
A second object of the present invention is to facilitate operations for 
removing the ozone filter element from and fitting the same in the filter 
case. 
The present invention provides an ozone filter unit comprising: a housing 
containing an image forming unit and opening upward; a cover pivotally 
supported on the housing so as to cover the open upper space in the 
housing; a filter case having an open end facing an air exit formed in the 
housing and an opposite open end; an exhaust blower disposed within the 
filter case or near the open end of the same; and a filter element holding 
frame having an upper opening to receive an ozone filter element 
therethrough, and pivotally joined for turning about a substantially 
horizontal axis to the lower portion of the filter case so as to be fitted 
in the open end of the filter case on the side of the air exit. 
In changing the ozone filter element, the cover is opened and the filter 
element holding frame is turned on the substantially horizontal axis to 
place the upper portion of the filter element holding frame outside the 
filter case. A wide, open upper space in the housing available for 
changing the ozone filter element facilitates filter element changing 
operation. Since only the upper opening of the filter element holding 
frame needs to be placed outside the filter case for filter element 
changing operation, the filter element holding frame needs to be turned 
through a small angle and hence the space between the inner surface of the 
housing and the filter case may be relatively small, which enables the 
housing to be formed in a relatively small size.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
An ozone filter unit in a preferred embodiment according to the present 
invention will be described with reference to FIGS. 1 and 2. Referring to 
FIG. 2 showing the internal construction of an electrophotographic 
apparatus, there are shown a housing 1, and a cover 3 for covering an open 
upper portion 2 in the housing 1, pivotally supported on the housing 1 by 
pivots 4. An image forming unit 5 contained in the housing 1 comprises a 
photoconductive body 6, a charger, not shown, for charging the 
photoconductive body 6, an exposure unit 7 for irradiating the charged 
surface of the photoconductive body 6 by light signals corresponding to 
image signals to form an electrostatic latent image on the surface of the 
photoconductive body 6, a developing unit 8 for developing the 
electrostatic latent image in a visible image, a feed roller 9 for feeding 
a recording sheet delivered from a recording sheet cassette 10, a transfer 
charger 12 for transferring the visible image from the photoconductive 
body 6 of the recording sheet, a register roller 11 for inserting the 
recording sheet between the photoconductive body 6 and the transfer 
charger 12, fixing rollers 13 for pressing the recording sheet 
therebetween to fix the visible image on the recording sheet, and a 
delivery path 14 for delivering the recording sheet conveying the fixed 
visible image to a delivery tray 15 provided on the upper surface of the 
cover 3. An air exit, not shown, is formed near the fixing rollers 13 in 
the side wall of the housing 1, and a filter case 18 containing an exhaust 
blower 16 and an ozone filer element 17 is disposed inside the housing 1 
opposite to the air exit. 
As shown in FIG. 1, the filter case 18 has the shape of a box having 
opposite open ends. A filter element holding frame 19 having an upper 
opening is supported pivotally by pivots 20 on the lower portion of the 
filter case 18 at the open end on the side of the air exit of the housing 
1. The filter element holding frame 19 is provided with a lug 21 on its 
upper side, and projections 22 respectively on its opposite side surfaces. 
When the filter element holding frame 19 is put in place in the filter 
case 18, the projections 22 engage holes 23 formed in the opposite side 
walls of the filter case 18 to hold the filter element holding frame 19 in 
place. The ozone filter element 17 is inserted through the upper opening 
in the filter element holding frame 19. 
When the exhaust blower 16 is driven, air containing ozone produced around 
the photoconductive body 6 and hot air heated mostly by the heat generated 
by the fixing rollers 13 are sucked into the filter case 18 and are 
discharged outside through the air exit of the housing 1. Ozone contained 
in the air is filtered by the ozone filter element 17 while the air flows 
through the filter case 18. 
In replacing the ozone filter element 17 with a new one, the cover 3 is 
opened in a position shown in FIG. 2, and then the filter element holding 
frame 19 is turned outward on the pivots 20 so that the upper opening of 
the filter element holding frame 19 is exposed outside the filter case 18 
a shown in FIG. 1. The ozone filter element 17 can readily be taken out 
through the upper opening of the filter element holding frame 19 in the 
wide, open upper space 2 in the housing 1. The filter element holding 
frame 19 needs to be turned through a small angle in changing the ozone 
filter element 17 because only the upper opening of the filter element 
holding frame 19 needs to be exposed outside the filter case 18. 
Therefore, the space between the inner surface of the housing 1 and the 
filter case 18 may be relatively small and hence the size of the housing 1 
can be reduced accordingly. 
As stated above, the ozone filter unit of the present invention comprises: 
the housing containing the image forming unit and having the open upper 
space; the cover pivotally supported on the housing so as to cover the 
open space in the housing; the filter case having opposite open ends and 
disposed with one open end thereof facing the air exit formed in the 
housing; the exhaust blower provided within the filter case or near the 
open end and the filter element holding frame having the upper opening, 
detachably holding the ozone filter element, and pivotally supported at 
its lower end on the lower portion of the side walls of the filter case 
near the open end of the filter case on the side of the air exit of the 
housing so as to be turned about a substantially horizontal axis. In 
changing the ozone filter element the cover is opened and the filter 
element holding frame is turned about the substantially horizontal axis to 
expose the upper opening of the filter element holding frame outside the 
filter case. The wide, open upper space in the housing facilitates 
inserting the ozone filter element in and removing the same from the 
filter element holding frame through the upper opening of the filter 
element holding frame. Since only the upper opening of the filter element 
holding frame needs to be exposed outside the filter case in changing the 
ozone filter element, the filter element holding frame needs to be turned 
only through a small angle. Therefore, the space between the inner surface 
of the side wall of the housing and the filter case may be relatively 
small and hence the size of the housing can be reduced accordingly.