Electrophotography – Internal machine environment – Particle or contaminant control
Reexamination Certificate
2001-01-26
2002-10-01
Chen, Sophia S. (Department: 2852)
Electrophotography
Internal machine environment
Particle or contaminant control
C399S284000
Reexamination Certificate
active
06459867
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a developing apparatus that uses one-component toner, and more particularly to a developing apparatus for an image forming device, such as an electrophotographic copier.
2. Description of the Related Art
Numerous developing apparatuses that use one-component toner, such as an electrophotographic copier, perform development by forming toner used as a developing material into a uniform thin layer, by electrically charging the toner as necessary, and by attaching the charged toner to an electrostatic latent image on an image carrier.
The development method specifically described below is well known. In this method, toner is first supplied to a rotating cylindrical toner carrier, and a layer thickness controlling member extending in parallel with the toner carrier is made contact with the outer peripheral surface of the toner carrier to which the toner has been supplied, whereby the toner on the toner carrier is formed into a uniform thin layer. At the same time, the toner is electrically charged as necessary for development by friction charging, charge implantation or the like. After this, the charged toner layer is transferred to the contact portion wherein the image carrier makes contact with the toner carrier as the toner carrier rotates. The toner on the toner carrier is attached to an electrostatic latent image on an image carrier.
In the case of the above-mentioned development method, a method of controlling the thickness of the toner layer is carried out frequently in order to obtain excellent image quality. In this method, the surface or the edges of the layer thickness controlling member having the shape of a thin plate formed of a metal member, a high molecular resin member or a lamination of a metal member and a high molecular resin member are made contact with the toner carrier in order to control the thickness of the toner layer.
In this case, toner is not consumed in the vicinity of both end portions of the toner carrier corresponding to the non-image area of the electrostatic latent image. Furthermore, toner is moved to both end portions of the toner carrier by the dispersion action as the toner carrier rotates. Toner is thus oversupplied, resulting in toner scattering and leakage. This causes problems of contaminating the inside of the device, increasing the consumption of toner and the like.
The related art in accordance with Japanese Examined Patent Publication JP-B2 4-62391 (1992) discloses a method of preventing toner from moving to both end portions of the toner carrier, thereby preventing toner from scattering. The developing apparatus in accordance with this method is provided with elastic sealing members for covering both side portions of the end portion of the layer thickness controlling member formed of an elastic material in its longitudinal direction from the back side of its contact surface making contact with the toner carrier. Alternatively, the developing apparatus is provided with elastic sealing members for pressurizing both side portions in the longitudinal direction of the layer thickness controlling member from the back side of its contact surface making contact with the toner carrier inward in the radial direction of the toner carrier.
In the developing apparatus in accordance with the related art disclosed in JP-B2 4-62391 or the like, sealing member are provided on the surface of the layer thickness controlling member making contact with the toner carrier, on the rear surface or on both end side surfaces of the layer thickness controlling member in order to prevent toner leakage. However, slight gaps are apt to occur at both side end portions of the layer thickness controlling member and at the contact portion wherein the layer thickness controlling member makes contact with the toner carrier because of steps caused by the thickness of the layer thickness controlling member. This results in toner scattering and leakage, and causes problems of staining images, contaminating the inside of the device, increasing toner consumption and the like.
If the sealing pressure of the sealing members is raised in order to prevent improper sealing due to the gap at the contact portion wherein the toner carrier makes contact with the layer thickness controlling member, the contact pressure force exerted from the layer thickness controlling member to the toner carrier in the radial direction of the toner carrier increases. This increase of the contact pressure force prevents normal operation of the layer thickness controlling member, and disturbs the formation of the toner layer near both end portions of the layer thickness controlling member, wherein the sealing members are disposed. As a result, image quality may apt to lower at both end portions of an image region, and improper sealing may be apt to occur because of sliding abrasion between the toner carrier and the sealing members or between the toner carrier and the layer thickness controlling member. It is thus very difficult for the above-mentioned developing apparatus to prevent toner scattering and leakage.
SUMMARY OF THE INVENTION
An object of the invention is to provide a developing apparatus capable of supplying a uniform thin layer of toner and capable of preventing toner scattering and leakage.
The invention provides a developing apparatus which performs development by supplying a thin toner layer to an electrostatic latent image on an image carrier, comprising a cylindrical toner carrier for transferring supplied toner to a development position by rotation of the toner carrier, supply means for supplying toner to an outer peripheral surface of the toner carrier, a layer thickness controlling member for controlling thickness of the supplied toner to within a predetermined value while making slide contact with the outer peripheral surface of the toner carrier, and sealing means for holding the layer thickness controlling member and preventing toner leakage,
wherein the layer thickness controlling member is formed of an elastic plate extending in parallel with the toner carrier, and has a bent portion which is convex toward the toner carrier and makes elastic contact with the outer peripheral surface of the toner carrier over a nearly entire length thereof, one end of the layer thickness controlling member in a width direction thereof with respect to the bent portion outwardly extending in a radial direction of the toner carrier, a portion on the other side of the layer thickness controlling member in the width direction thereof extending in a peripheral direction of the toner carrier toward a downstream side of the rotation direction of the toner carrier, and
the sealing means consisting of an upstream side sealing member which makes contact with the one end of the layer thickness controlling member from an upstream side of the rotation direction of the toner carrier and a downstream side sealing member which makes contact with the one end of the layer thickness controlling member from a downstream side of the rotation direction of the toner carrier, the one end of the layer thickness controlling member being caught between the upstream side sealing member and the downstream side sealing member so that the layer thickness controlling member is held to be elastically displaceable in the radial direction of the toner carrier.
In accordance with the invention, since the convex bent portion of the layer thickness controlling member makes elastic contact with the outer surface of the toner carrier, no step is formed by the thickness of the layer thickness controlling member unlike the related art. As a result, toner leakage can be prevented, and the thickness of the toner layer formed on the toner carrier can be made uniform.
In addition, since the one end of the layer thickness controlling member extending outward in the radial direction of the toner carrier is caught between the upstream side and downstream side sealing members, it is possible to reduce the contact pressure force exerted by the sealing members
Inoue Atsushi
Ishii Hiroshi
Kido Eiichi
Masuda Jitsuo
Ohgoshi Toshihide
Chen Sophia S.
Sharp Kabushiki Kaisha
LandOfFree
Developing apparatus does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Developing apparatus, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Developing apparatus will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2998205