Screen photosensitive body for electrographic apparatus

A photosensitive body for electrographic apparatus is disclosed. The photosensitive body is composed of a mesh-shaped photosensitive body and spread under tension around a pair of spaced apart supporting discs. The mesh-shaped photosensitive body is provided near at its opposed end edges with an elongate solid member. At least one of the solid members is secured through a tension spring to the supporting disc.

BACKGROUND OF THE INVENTION 
This invention relates to a photosensitive body for electrographic 
apparatus. 
An electrographic apparatus which makes use of a mesh-shaped photosensitive 
body has heretofore been proposed. In such electrographic apparatus, the 
mesh-shaped photosensitive body is of four layer construction composed of 
an electrically conductive substrate having a number of openings, a 
photosensitive layer coated on one side of the substrate, an insulating 
layer coated on the other side of the substrate and an electrically 
conductive layer coated on the insulating layer. The mesh-shaped 
photosensitive body is uniformly charged and then exposed to a manuscript 
image so as to produce, on the mesh-shaped photosensitive body, a first 
electrostatic latent image corresponding to the manuscript image. 
Subsequently, a flow of corona ions is modulated on the basis of the first 
electrostatic latent image to produce, on an electrostatic record sheet, a 
second electrostatic latent image corresponding to the first electrostatic 
latent image. The second electrostatic latent image produced on the 
electrostatic record sheet is developed and fixed to obtain a visible 
image. 
In such electrographic apparatus, in the case of producing, on the 
electrostatic record sheet, the second electrostatic latent image, a 
corona discharge electrode for emitting a flow of corona ions must be 
opposed through the mesh-shaped photosensitive body to the electrostatic 
record sheet. For this purpose, the mesh-shaped photosensitive body is 
required to be held at its margin on the outside of an effective picture 
surface range, for example, to be held at its end edges. 
A drum-shaped photosensitive body has also been proposed in which a 
mesh-shaped photosensitive body is wound around a drum-shaped supporting 
frame and firmly secured thereto. 
In this case, however, since the photosensitive body is of a mesh-shaped 
one, it is difficult to handle it. In addition, in the case of winding the 
mesh-shaped photosensitive body around the drum-shaped supporting frame, 
at first the mesh-shaped photosensitive body must be temporarily fastened 
to the drum-shaped supporting frame and then the end edges of the 
mesh-shaped photosensitive body must be pulled under tension so as to 
remove wrinkles existing thereon and subsequently the mesh-shaped 
photosensitive body must be permanently secured to the drum-shaped 
supporting frame, thereby involving very troublesome operations for the 
purpose of securing the mesh-shaped photosensitive body to the drum-shaped 
supporting frame. 
It has also been proposed to secure a mesh-shaped photosensitive body to a 
drum-shaped supporting frame with the aid of a thin plate-shaped frame 
which is bonded with the end edge of the mesh-shaped photosensitive body 
and secured to the drum-shaped supporting frame by means of screws. 
An attempt has also be made to provide a drum-shaped supporting frame 
composed of a pair of spaced apart supporting discs and to provide between 
these supporting discs an intermediate disc which is arranged movably in 
the axial direction of the drum-shaped supporting discs. In this case, 
thin plates bonded to the end edges of the mesh-shaped photosensitive body 
are secured to both the outer periphery of the intermediate disc and the 
outer periphery of one of the pair of the supporting discs and then the 
intermediate disc is displaced toward the other supporting disc such that 
the drum-shaped photosensitive body becomes spread under tension around 
the discs. 
In all of these prior art mesh-shaped photosensitive bodies, the side edges 
or end edges of the mesh-shaped photosensitive body are bonded with the 
thin plate. As a result, if a bonding agent becomes irregular in thickness 
or if the mesh-shaped photosensitive body is not flat in the case of 
bonding the thin plate therewith, the photosensitive body tends to produce 
wrinkles when it is formed into a drum-shape, thus rendering the spreading 
operation very difficult. 
Another attempt has been made to provide a groove formed along the outer 
periphery of a pair of spaced apart supporting discs for constituting a 
drum-shaped supporting frame. The supporting discs are surrounded by a 
mesh-shaped photosensitive body and then against the groove is urged a 
resilient ring such that the mesh-shaped photosensitive body becomes 
spread under tension in a closely tight manner. In this case, an 
electrically conductive substrate of the mesh-shaped photosensitive body 
is composed of a wire mesh formed of a wire having a diameter of 30 to 
50.mu. or is composed of an etched foil having a thickness on the order of 
30 to 50.mu.. Such kind of wire mesh or etched foil has no flexibility 
which is sufficient to be deformed when it is spread under tension around 
the discs. As a result, it is impossible to spread under tension the 
photosensitive body around the supporting discs. 
The drum-shaped photosensitive body composed of the mesh-shaped 
photosensitive body secured directly or through the thin plate to the 
drum-shaped supporting frame by means of the screws requires a plenty of 
operating time in the case of replacing the mesh-shaped photosensitive 
body by a new one or in the case of assembling it. In addition, in the 
above described various kinds of drum-shaped photosensitive bodies, the 
mesh-shaped photosensitive body is directly or through the thin plate 
secured to the supporting discs for constituting the drum-shaped 
supporting frame, so that there is a risk of the mesh-shaped 
photosensitive being wrinkled by the difference between the thermal 
expansion of the mesh-shaped photosensitive body and that of the 
drum-shaped supporting frame due to change in the surrounding temperature. 
SUMMARY OF THE INVENTION 
An object of the invention, therefore, is to provide a photosensitive body 
composed of a mesh-shaped photosensitive body, which can eliminate the 
above described various drawbacks which have been encountered with the 
prior art techniques and which can improve the flatness of the mesh-shaped 
photosensitive body. 
A main feature of the invention is the provision of a photosensitive body 
for electrographic apparatus, comprising a mesh-shaped photosensitive body 
and an elongate solid member formed at near both end edges of said 
mesh-shaped photosensitive body and made integral therewith, said elongate 
solid member preventing said mesh-shaped photosensitive body from being 
deformed. 
The invention will now be described in greater detail with reference to the 
accompanying drawings.

DESCRIPTION OF THE PREFERRED EMBODIMENTS 
In FIG. 1 is shown one embodiment of a photosensitive body according to the 
present invention. A mesh-shaped photosensitive body 1 is composed of a 
mesh-shaped electrically conductive substrate having a number of openings, 
insulating layers coated on those both sides of the substrate which are 
located on an effective picture surface region 1a, a photosensitive layer 
coated on one of the insulating layers and an electrically conductive 
layer coated on the other insulating layer. To the marginal space located 
outside the effective picture surface range 1a of the mesh-shaped 
photosensitive body 1 and near the end edges thereof are secured 
bar-shaped solid members 2a, 2b made integral therewith and each having a 
length which is slightly longer than that of the end edge of the 
mesh-shaped photosensitive body 1. 
In the case of spreading under tension the photosensitive body 1 around a 
drum-shaped frame which will be described with reference to FIG. 6, one of 
the bar-shaped solid member 2a is secured through hooks 3a, 3b to the 
drum-shaped frame and the other bar-shaped solid member 2b is connected 
through tension springs 4a, 4b to the drum-shaped frame. The hooks 3a, 3b 
and tension springs 4a, 4b are connected to those portions of the 
bar-shaped solid members 2a, 2b which are projected out of the mesh-shaped 
photosensitive body 1. 
In FIG. 2 is shown another embodiment of a photosensitive body according to 
the invention. In the present embodiment, the length of the bar-shaped 
solid member 2b is made substantially equal to that of the end edge of the 
mesh-shaped photosensitive body 1. In addition, the mesh-shaped 
photosensitive body 1 is provided at that end edge to which is secured the 
bar-shaped member 2b with notches 5a and 5b spaced apart from each other 
and exposing two portions of the bar-shaped solid member 2b. With these 
exposed portions of the bar-shaped solid member 2b are engaged tension 
springs 4a, 4b, respectively. Similarly, the mesh-shaped photosensitive 
body 1 may be provided at that end edge to which is secured the bar-shaped 
solid member 2a with similar notches so as to expose two portions of the 
bar-shaped solid member 2a. The hooks 3a, 3b may then be engaged with 
these exposed portions of the bar-shaped solid member 2a. 
In the photosensitive body shown in FIGS. 1 and 2, if the centers of the 
bar-shaped solid members 2a, 2b are not aligned with the plane of the 
mesh-shaped photosensitive body 1, the end edges of the mesh-shaped 
photosensitive body 1 spread under tension by the hooks 3a, 3b and tension 
springs 4a, 4b tend to be turned up due to a torque subjected thereto and 
for bringing the centers of the bar-shaped solid members 2a, 3b into 
agreement with the plane of the mesh-shaped photosensitive body 1. In 
order to prevent such drawback, it is desirous to substantially align 
acting points and lines of the hooks 3 and tension springs 4 with the 
plane of the mesh-shaped photosensitive body 1. 
In FIG. 4a is shown one embodiment of a bar-shaped solid member which can 
prevent the above mentioned disagreement. In the present embodiment, that 
portion 6 of the bar-shaped solid member 2a, 2b which is not engaged with 
the hooks 3a, 3b and tension springs 4a, 4b and to which is secured the 
mesh-shaped photosensitive body 1 is made semicircular in section. 
In FIG. 4b is shown a modified embodiment of the bar-shaped solid member 
shown in FIG. 4a. In the present embodiment, the bar-shaped solid members 
2a, 2b are composed of a bar-shaped hollow cylinder and that portion 6 
thereof to which is secured the mesh-shaped photosensitive body 1 is also 
made semi-circular in section. 
As shown in FIG. 5, the use of the solid members 2a, 2b shown in FIGS. 4a, 
4b renders it possible to substantially align respective centers with the 
plane of the mesh-shaped photosensitive body 1 and provides the advantage 
that the mesh-shaped photosensitive body 1 can be made flat when it is 
spread under tension without inducing the above mentioned drawback. 
In FIG. 6 is shown a drum-shaped frame 7 adapted to spread under tension 
therearound the mesh-shaped photosensitive body into a drum-shaped one 
with its photosensitive layer faced outwardly. The drum-shaped frame 7 is 
composed of a pair of spaced apart insulating discs 8, 9 and a 
segment-shaped insulating connection member 10 for connecting opposed 
inner peripheral surfaces of the discs 8, 9 with each other. 
In FIGS. 7a and 7b is shown a drum-shaped photosensitive body formed by 
spreading under tension the mesh-shaped photosensitive body 1 around the 
drum-shaped frame 7 shown in FIG. 6. As shown in FIG. 7a, the disc 9 is 
provided along its periphery with two grooves 11, 12 distant apart from 
each other. Similarly, the disc 8 is also provided with two grooves 11', 
12' opposed to the grooves 11, 12, respectively. Into these grooves 11, 
11' is inserted the bar-shaped solid member 2a whose projected ends are 
secured to and made integral with the groove walls 11a, 11'a, 
respectively. Then, the mesh-shaped photosensitive body 1 is wound around 
both the discs 8 and 9 and the other bar-shaped solid member 2b is 
inserted into the grooves 12, 12'. One end of the bar-shaped solid member 
2b is connected through a tension spring 4b to a projection 13a of an 
electric supply ring 13 provided on the outside surface of the disc and 
the other end of the bar-shaped solid member 2b is connected through a 
tension spring 4a (not shown) to the disc 8. It is a matter of course that 
the grooves 12, 12' of the discs 9, 8 should be made slightly wider than 
the grooves 11, 11' of the discs 9, 8 for the purpose of permitting the 
tension springs 4b, 4a to effectively act upon the disc 9. In addition, 
the action lines of the tension springs 4a, 4b are possibly made aligned 
with the plane of the photosensitive body 1 in order to prevent the end 
edges of the photosensitive body 1 from being turned up as shown in FIG. 
3. Reference numeral 25 designates a corona discharge electrode arranged 
inside the mesh-shaped photosensitive body 1 and secured to that portion 
of a fixed shaft 19 which is located between the discs 8, 9. 
In the case of winding the mesh-shaped photosensitive body 1 around the 
discs 8, 9, care must be taken that the effective picture surface range 1a 
of the photosensitive body 1 should not cover the discs 8, 9. 
In FIG. 8 is shown the drum-shaped photosensitive body shown in FIGS. 7a 
and 7b and mounted on an electrographic apparatus. As shown in FIG. 8, 
both the discs 8 and 9 are provided along the periphery thereof with steps 
8a and 9a each having a width which is sufficient to allow displacement of 
the mesh-shaped photosensitive body 1 in its widthwise direction when it 
is thermally expanded. In addition, at least the tension spring 4b for 
connecting the bar-shaped solid member 2b to the disc 9 is made 
electrically condutive and is electrically connected to the electric 
supply ring 13 for the purpose of easily applying a voltage across the 
electrically conductive substrate and the electrically conductive layer of 
the mesh-shaped photosensitive body 1. For this purpose, a lead wire 14 
electrically connected to the electrically conductive layer is connected 
through an electrically conductive metal strip 15 embedded in the 
insulating disc 9 to a second electric supply ring 16 provided on the 
outside surface of the disc 9 as clearly shown in FIG. 7b. 
As shown in FIG. 8, the drum-shaped photosensitive body constructed as 
above described is rotatably mounted through bearings 17, 18 on the fixed 
shaft 19 having ends secured through brackets 20, 21 to side walls 22, 23 
of the electrographic apparatus. The disc 9 is provided at its outer 
periphery with a gear 24 which is geared with a driving gear (not shown) 
and makes it possible to rotate the drum-shaped photosensitive body 1 
about the fixed shaft 19. The electric supplying rings 13, 16 may be 
connected through slidable brushes (not shown) secured to the side wall 23 
to the electrically conductive substrate and electrically conductive layer 
of the mesh-shaped photosensitive body 1, respectively, thus enabling to 
apply a voltage therebetween. 
In FIG. 9 is shown a modified embodiment of the mesh-shaped photosensitive 
body shown in FIG. 7a. In the present embodiment, both ends of the 
bar-shaped solid member 2b are connected through the tension springs 4a, 
4b to the discs 8, 9 and one end of the bar-shaped solid member 2a is 
secured to the groove wall 11'a as shown in FIG. 7a, but the other end of 
the bar-shaped solid member 2a is connected through a third tension spring 
4c to the disc 9 as shown in FIG. 9. 
The mesh-shaped photosensitive body 1 shown in FIG. 9 is subjected to a 
reaction force acting in a radial direction as shown by an arrow R and to 
a tensile force acting in a circumferential direction as shown by an arrow 
T. But, both the end edges of the mesh-shaped photosensitive body 1 are 
made solid by the bar-shaped solid members 2a, 2b, so that the tensile 
force T acting along the overall width thereof becomes uniform. In 
addition, both the side edges 1b, 1c of the photosensitive body 1 are 
homogeneous with the center portion thereof, so that the reaction force R 
functions to spread the photosensitive body 1 under tension with a 
constant radius of curvature maintained with respect to the center axis 
thereof, thereby forming a uniform photosensitive surface. 
In addition, all of the ends of the bar-shaped solid members 2a, 2b except 
one end of the bar-shaped solid member 2a are resiliently movable, so that 
it is possible to prevent the mesh-shaped photosensitive body 1 from 
becoming unbalanced when it is spread under tension around the discs 8, 9. 
The use of the tension springs 4a, 4b, 4c ensures a good effect of 
absorbing unbalance of the internal stress of the mesh-shaped 
photosensitive body and hence of uniformly spreading under tension it 
around the discs 8, 9. Moreover, both the side edges 1b, 1c freely 
supported by the discs 8, 9 function to maintain the mesh-shaped 
photosensitive body 1 under uniform tension irrespective of the thermal 
expansion thereof and the exterior force subjected thereto. In the case of 
winding the mesh-shaped photosensitive body 1 around the discs 8, 9, care 
must be taken that the effective picture surface range 1a should not be 
superimposed about the connection member 10. It is a matter of course that 
the bar-shaped solid member 2b and the tension spring 4b should be made 
electrically conductive so as to connect them through the electric supply 
ring 13 to the electrically conductive substrate of the mesh-shaped 
photosensitive body 1. 
As stated hereinbefore, the mesh-shaped photosensitive body according to 
the invention comprises an elongate solid member formed at each end edge 
thereof and made integral therewith, so that it is possible to prevent the 
mesh-shaped photosensitive body from becoming easily deformed. In 
addition, in the case of winding the photosensitive body around the 
drum-shaped frame and securing the former through the elongate solid 
members to the latter, at least one of the elongate solid members is 
secured through a resilient member to the latter, and as a result, the 
mesh-shaped photosensitive body can be spread under tension around the 
drum-shaped frame. Even in the case of spreading under tension the 
photosensitive body around the drum-shaped frame, it is not necessary to 
secure the end edges of the photosensitive body to the outer periphery of 
the drum-shaped frames by means of screws. As a result, assembling of the 
drum-shaped photosensitive body and replacement of the mesh-shaped 
photosensitive body for a new one may easily be carried out. Since the 
photosensitive body is not firmly secured to the drum-shaped frame, the 
difference between the thermal expansion of the photosensitive body and 
that of the drum-shaped frame does not induce wrinkles in the 
photosensitive body. In addition, there is no risk of the photosensitive 
body being subjected to unreasonable internal stress. Moreover, the 
elongate solid member functions as an electrode for the electrically 
conductive substrate of the photosensitive body and hence provides a 
material decrease in number of parts. 
The invention is not limited to the embodiments described above and many 
alternations and modifications may be made. For example, the elongate 
solid member may be formed by coiling an end edge of the electrically 
conductive substrate of the mesh-shaped photosensitive body into several 
turns.