Cleaning blade for electrophotography

Disclosed are blades oriented in a trailing configuration for cleaning residual toner from the photosensitive drums of photocopying machines without marring the drum's surface. In one embodiment of the invention, the blade is constructed of layers of resilient material having different moduli of elasticity resulting in the blade's having greater resistance to transverse deformation than to deformation along the primary axis of the blade. In another embodiment, the blade comprises a mass of an elastic material having a partially hollow interior. The hollow interior results in a blade with differing moduli of elasticity in different directions.

BACKGROUND OF THE INVENTION 
This invention relates to blades for removing the residual toner from the 
surface of the photosensitive rotating drum of photocopiers, and, more 
particularly, to resilient blades in a trailing configuration. It is known 
to clean the surface of a photosensitive drum of a photocopier with 
resilient blades which are supported in either a leading or a trailing 
configuration. A trailing blade creates on the upstream side of the 
rotating drum an acute angle subtended by the tangent plane to the 
rotating drum through the line of blade contact and a plane corresponding 
to the primary axis of the blade, that is, an angle less than 90.degree.. 
With conventional trailing blades the resultant of the friction and normal 
forces on the blade allow toner or foreign matter relatively easily to 
lift the blade from the drum reducing thereby cleaning effectiveness. In 
addition, because of the relative ease with which a prior art trailing 
blade can be urged away from the surface of the drum, these trailing 
blades typically catch or trap small particles and are more likely to mar 
the photosensitive surface of the drum. 
An object of this invention, therefore, is a trailing cleaning blade which 
has excellent toner removing capability, while at the same time minimizing 
the trapping of toner and other particles between the blade and drum 
thereby causing scratching of the photosensitive surface. 
A further object of the invention is such a trailing blade which is not 
only highly effective, but also easily fabricated, reliable, and of 
uncomplicated mechanical construction. 
A still further object of the invention is an integral trailing blade and 
liquid dispensing means for lubricating the blade-drum surface interface. 
SUMMARY OF THE INVENTION 
In this disclosure, the cleaning blade, having a substantially rectangular 
cross section, is defined to have a primary blade axis parallel to the 
long axis of the operative portion of the blade cross section, and a 
transverse blade axis perpendicular to the primary blade axis. For a 
trailing configuration, therefore, the primary blade axis forms an acute 
angle with the tangent to the rotating drum as measured on the upstream 
side of the rotating drum. 
The apparatus for removing residual toner from the photosensitive surface 
of the rotating drum of a photocopying machine according to the present 
invention comprises a rotating drum having a photosensitive surface, an 
elastic cleaning blade having a cleaning edge, and holding means for 
disposing the cleaning edge of the blade for contact with the surface of 
the drum along the drum surface axial length as a trailing blade. The 
cleaning blade features at least one elastic material for providing the 
cleaning edge with a primary blade axis effective modulus of elasticity 
and a transverse blade axis effective modulus of elasticity, the primary 
blade axis effective modulus of elasticity being less than the transverse 
blade axis effective modulus of elasticity. 
The cleaning blade in one important embodiment of the present invention 
comprises a layer of a relatively lower elastic modulus material disposed 
between layers of a relatively higher elastic modulus material. These 
layers extend in a direction transverse to the primary blade axis, with 
one of the layers of the relatively higher elastic modulus material 
comprising the cleaning edge. This layered construction causes the blade 
to deform more readily in the direction along the primary blade axis than 
in the direction transverse to the primary blade axis. Thereby, a particle 
trapped between the blade and the drum surface can more easily be washed 
away than with conventional trailing blade structures. 
In another important embodiment, the cleaning blade comprises relatively 
high elastic modulus material having a partially hollow interior extending 
in a direction parallel to the rotation axis of the photosensitive drum. 
The hollow interior is defined by relatively thin side walls extending in 
the direction of the primary blade axis and connecting substantially 
transversely extending first and second layers of the elastic material. 
The partially hollow interior results in the blade's deforming more 
readily in the direction along the primary blade axis than along the 
transverse blade axis. In still another embodiment of the invention 
disclosed herein, the cleaning blade comprises a relatively high modulus 
of elasticity material having a partially hollow interior portion filled 
with a relatively low modulus of elasticity material. The blade thereby 
deforms more readily in the direction along the primary blade axis than in 
the direction along the transverse blade axis. 
It is preferred that the blade holding means further comprises means for 
pivoting the cleaning blade from an operative position contacting the drum 
surface to an inoperative position spaced away from the drum surface. In 
addition, the above described embodiments preferably comprise a rigid 
member closely spaced apart from the blade and adapted for limiting the 
deflection of the blade in the direction of the transverse blade axis when 
the blade is in the operative position. 
Yet another embodiment of the invention further comprises a cleaning roller 
in contact with the drum surface and dispensing means for applying 
lubricating liquid onto the drum surface and the cleaning roller. The 
blade holding means is further adapted for supporting the dispensing 
means. It is preferred that the lubricating liquid be developer solution.

DESCRIPTION OF PREFERRED EMBODIMENTS 
The cleaning blade disclosed herein is designed for use in particular with 
photocopying machines employing liquid development. In such a machine, a 
latent electrostatic image is formed on the surface of a rotating 
photosensitive drum. After latent image formation, the selectively charged 
drum is brought into contact with the liquid developer containing toner 
particles. The toner particles selectively adhere to the drum thereby 
developing the image. After such development, the image is then 
transferred to the copy material, usually ordinary paper. Because some 
residual toner remains on the photosensitive drum surface after image 
transfer, this surface must be cleaned before the next latent image is 
formed. 
In describing the various embodiments disclosed herein the same numbers 
will be used for corresponding parts throughout the figures. 
Referring first to FIG. 1, a rotating drum 9 is in contact with a trailing 
cleaning blade 11 so that as a photosensitive surface 10 rotates, any 
residual toner particles remaining on the surface after the transfer 
operation are wiped from the surface. Cleaning blade 11 is attached to a 
bracket 12, for example, by a plurality of screws spaced along its length 
parallel to the drum axis, and bracket 12 in turn is attached to a 
pivotable member 13. The member 13 is adapted to fit on a shaft (not 
shown) at a hole 14 which allows the blade assembly to pivot toward and 
away from photosensitive surface 10. An edge 16 of blade 11 contacts the 
photosensitive surface 10 and wipes residual developer therefrom. The 
blade assembly is located so that the edge 16 contacts photosensitive 
surface 10 at an angle .alpha. past the top position of photosensitive 
surface 10. A suitable value for the angle .alpha. is 24.degree.. 
In this embodiment, the illustrated blade 11 has a metal support surface M, 
such as aluminum, and three resilient layers: a soft layer (that is, a 
layer of a material having a relatively lower modulus of elasticity) S 
flanked by two layers H1 and H2 of a relatively harder material. Suitable 
materials for the layers S, H1 and H2 are elastic synthetic resins and 
rubbers which will not "poison" or be degraded by the developer solution. 
Typical materials can be composed of teflon, silicon rubber, polyester, 
polyethylene, polyurethane, etc. It is preferred that layers H1 and H2 be 
made of polyurethane having a hardness of 75-80 Durometer (Shore A) and 
that layer S be made of closed cell medium neoprene. A suitable material 
for layer H1 is Elastacast.RTM. polyurethane available from Acushnet 
Company. The bracket 12 can be made of chromic acid anodized or clear 
anodized aluminum. Blade 11 also has, at either end, vertical side members 
(not shown) which extend in a radial direction outside and below the 
surface of the drum. The side members can wipe against the drum edges for 
preventing liquid developer in front of the trailing blade from moving 
around the blade to the back side of the blade. 
Before the layers are assembled to create blade 11, the layer H1 
polyurethane is treated with Eccoprime. The layers are then bonded to one 
another and, in the illustrated embodiment, to metal layer M using 
semi-rigid formula Eccobond 45 (clear) adhesive and Catalyst-15 (clear). A 
suitable composition is one part adhesive to two parts catalyst by weight. 
These materials are available from Emerson and Cuming, Inc. of Canton, 
Massachusetts. The adhesive composition is cured for approximately 
forty-five minutes at a temperature of 160.degree. F. (71.degree. C.). In 
the embodiment of FIG. 1, layer H1 is approximately 3/8" thick, layer S, 
3/16" thick, and layer H2, 1/8" thick. The width of blade 11, that is, the 
dimension in the direction perpendicular to a primary blade axis 17, i.e., 
a transverse blade axis 18, is approximately 0.5". 
The blade structure described above resists transverse blade axis 
deformations relatively more than deformations along the longitudinal 
blade axis 17. The relatively high transverse stiffness of the blade 11 
enhances its toner removal capability, while at the same time the relative 
deformability along primary blade axis 17 prevents toner particles from 
becoming wedged in the space between the blade 11 and photosensitive 
surface 10, thereby reducing the likelihood that photosensitive surface 10 
will be scratched by toner or other particles. Illustrated blade 11 can 
also be reversed, in the preferred embodiment, so that blade edge 19 can 
also be used as a blade wiping edge in contact with the photosensitive 
surface. 
The illustrated blade 11 is oriented with respect to photosensitive surface 
10 so that it is a trailing blade, that is, the angle .theta. subtended by 
a tangent to the photosensitive surface 10 at the line of contact between 
the surface 10 and the blade 11 and the primary blade axis 17 is less that 
90.degree.. The preferred value for the angle .theta. is approximately 
56.degree.. Still referring to FIG. 1, the bracket 12, in addition to 
supporting the blade 11, can limit the amount of transverse deflection of 
the blade 11 to a predetermined maximum amount, for example, 1/16 ". 
Now referring to FIG. 2, a second illustrated embodiment of the invention, 
a trailing cleaning blade 20 is made of a relatively hard elastic material 
such as a hard polyurethane and has a cavity 21 created within the blade 
20 either in the forming process or by removing some of the blade material 
after the complete solid blade is formed. In this embodiment blade 20 is 
adhesively bonded to supporting bracket 12. The resulting blade 20, having 
thin side walls 22 of a hard, elastic material and defining in part the 
cavity 21 results in blade 20 having relatively high transverse stiffness 
for efficient cleaning with relatively low stiffness along the primary 
blade axis 17 to prevent drum surface scratching and the trapping of solid 
particulate. 
Yet another embodiment of the invention is shown in FIG. 3. An illustrated 
trailing cleaning blade 30 is made of a relatively hard elastic material 
which has a cavity filled with a relatively softer elastic material 31. 
The cavity can be created in the forming process, for example, or by 
removing material from the blade. As with the other embodiments described 
above, this arrangement of a relatively softer material embedded within a 
relatively harder material results in the blade 30 having relatively high 
stiffness transversely and relatively less stiffness along the primary 
blade axis 17. 
Referring now to FIG. 4, according to yet another embodiment of the 
invention, a trailing blade 40 is supported, for example, by an adhesive 
bond, by a pivoting bracket 41 arranged to pivot about a pivot line 42. A 
slot 43 in bracket 41 rides on a guiding pin 44 secured to the frame of 
the photocopying apparatus (not shown). The blade 40 of this embodiment is 
similar to the blade illustrated in FIG. 1, that is, the blade 40 is 
composed of three resilient layers: two hard layers H3 and H4 flanking a 
softer layer S1. It is to be understood that the blades described in FIGS. 
2 and 3 are also suitable for use in this embodiment. 
Bracket 41 pivotably supports a lubricant dispensing assembly 45 including 
a perforated tube 46. By conventional means (not shown), lubricating 
liquid, preferably developer liquid, is pumped into the tube 46. The tube 
46 extends the full length of drum 9. The fluid then travels through 
perforations 47 onto the surface of a cleaning roller 48. These 
perforations are preferably spaced apart along the length of the tube 46. 
The cleaning roller 48 rotates in the same sense as photosensitive drum 9 
so that the surface of roller 48 and photosensitive surface 10 are moving 
in opposite directions at their area of contact. Because the surfaces are 
moving in opposite directions, some of the lubricating fluid from the 
perforations 47 is squeezed from the roller 48 and flows by gravity and 
friction to the position where the blade 40 contacts the photosensitive 
surface 10. Such lubrication makes less likely the marring of the 
photosensitive surface 10 because of toner particles trapped between the 
photosensitive surface 10 and the blade 40. A bracket 49 is positioned to 
limit transverse deflection of the blade 40. 
SUMMARY OF ADVANTAGES AND UNOBVIOUSNESS OF THE INVENTION 
The trailing cleaning blade disclosed herein is highly effective for 
removing residual toner from the photosensitive drum surface of 
photocopying machines without marring the drum surface. This is so because 
of the unique blade construction combined with the blade's orientation as 
a trailing blade. 
The blade constructions disclosed herein result in different moduli of 
elasticity or resistance to deformation in different directions. In 
particular, these blades are stiffer in a transverse direction than in the 
direction parallel to the primary blade axis. The transverse stiffness 
assures good cleaning. The relative compliance along the blade minimizes 
the tendency for toner particles or other debris to become trapped between 
drum surface and blade. Such trapping can seriously damage the drum 
surface. 
Other efforts in the cleaning blade art neither anticipate nor suggest the 
unique blade construction disclosed herein; nor do they enjoy the 
advantages found in the present invention. By way of example, Komori et 
al, U.S. Pat. No. 3,927,936; Tanaka et al, U.S. Pat. No. Re. 29,632; and 
Katayama et al, U.S. Pat. No. 3,859,691 disclose resilient leading 
scraping blades; and in particular, Katayama et al teach away from the use 
of trailing blades. 
Additions, subtractions, deletions and other modifications of the blade 
construction disclosed herein will occur to those skilled in the art and 
are within the scope of the appended claims.