Developing apparatus for electrostatic image

Abstract

A developing device for electrophotography includes a developer supporter faced to an image bearing member with a constant space maintained therebetween at a developing station, a developer supply and an elastic developer limiting member maintained in predetermined pressure contact with the developer supporter between the developer supply and the developing station to limit the thickness of developer supported on the supporter to a value not causing contact of the developer with the non-imaged area on the image bearing member.

What we claim is: .[.1. A developing apparatus for developing with a powder developer, comprising: 
     
        .[.15.  A developing apparatus according to claim 14, wherein said first thickness limiting member is a rigid member..]. .[.16. A developing apparatus according to claim 14, including a magnet member for producing magnetic fields in the developing zone and in the regions of each of said thickness limiting members..]. .[.17. A developing apparatus according to claim 13, wherein said developer supporting means comprises a cylindrical sleeve, said supplying means being arranged to supply developer onto the peripheral surface of said sleeve..]. .[.18. A developing apparatus according to claim 17, wherein said sleeve is rotatable about its longitudinal axis to cause movement of the developer..]. .[.19. A developing apparatus according to claim 13, wherein said developer supporting means comprises an endless belt arranged to rotate about a plurality of rollers..]. .[.20. A developing apparatus according to claim 12, including means for producing a magnetic field at the developing zone..]. .[.21. A developing apparatus according to claim 12, including means for producing a magnetic field in the region of contact between said elastic thickness limiting member and said developer supporting means..]. .[.22. A developing apparatus according to claim 12, including a magnet member which produces a magnetic field at both the developing zone and in the region of contact between said elastic thickness limiting member and the developer support means..]. .[.23. A developing apparatus according to claim 22, wherein said magnet member is stationary so that said magnetic fields produced thereby are stationary..]. .[.24. A developing apparatus according to claim 22, wherein said magnet member is movable to cause movement of said magnetic fields..]. .[.25. A developing apparatus according to claim 12, wherein said elastic thickness limiting member is in the form of a resilient plate..]. .[.26. A developing apparatus according to claim 25, wherein said resilient plate is arranged with a gap between it and said developer supporting means tapering toward the region of pressure contact in the direction of movement of the developer..]. .[.27. A developing resilient plate is arranged with a gap between it and said developer supporting means tapering toward the region of pressure contact in a direction opposite to the direction of movement of the developer..]. .[.28. A developing apparatus according to claim 12, wherein said elastic thickness limiting member is a roller..]. .[.29. A developing apparatus according to claim 12, wherein at the developing zone the gap between said developer supporting means and the latent image carrying member is such as to avoid contact between the developer supported on said developer supporting means and the portion of the latent image on the latent image carrying member which is not to be developed..]. .[.30. A developing apparatus according to claim 12, including means for vibrating said elastic thickness limiting member to cause said thickness limiting member to oscillate in a direction transverse to the direction of movement of the developer, thereby to avoid the coagulation of developer between said developer supporting means and said thickness limiting member..]. 
     
     
        .Iadd.31.  A developing apparatus for developing with a powder developer, comprising: a movable developer supporting member provided in facing relationship with a image carrying means in a developing station for developing a latent image carried on the image carrying means, said supporting member being separated from the image carrying means by a predetermined distance;   means for supplying powder developer to said supporting member; and   an elastic developer limiting member having a free end upstream of the developing station, with respect to the direction of movement of the developer, which is maintained in predetermined pressure contact with said developer supporting member at a position between said developer supply means and the developing station to regulate a thickness of a layer of the developer particles supplied by said supplying means, wherein said limiting member includes an elastic plate having a surface including a contact portion which is in surface press-contact with said developer supporting member counter-directionally with respect to a movement direction of the developer supporting member, and an extension surface portion which extends toward the downstream direction from the contact portion and which is faced to said developer supporting member, wherein said plate and said developer supporting member cooperate to form a nip, in the contact portion, through which the developer particles are passed so that the thickness of the developer layer is regulated, and wherein the elastic plate has an end portion in the developer particles. .Iaddend. .Iadd.32. An apparatus according to claim 31, wherein the plate is press-contacted to said developer supporting member with a line pressure of 0.4-40 g/cm. .Iaddend. .Iadd.33. An apparatus according to claim 31 or 32, wherein the elastic plate is of a metal having elasticity. .Iaddend. .Iadd.34. An apparatus according to claim 31 or 32, wherein the elastic plate is of a rubber. .Iaddend. .Iadd.35. An apparatus according to claim 34, wherein the rubber has a hardness not more than 70 degrees. .Iaddend. .Iadd.36. An apparatus according to claim 31, wherein the elastic plate is of material which is positioned in the triboelectric series list such that it triboelectricially charges the developer particles to a predetermined polarity when it is rubbed with the developer particles. .Iaddend. .Iadd.37. An apparatus according to claim 31, wherein the elastic plate is of a laminated structure including two or more plates having different elasticities. .Iaddend. .Iadd.38. An apparatus according to claim 31, wherein the developer particles comprise nonmagnetic toner. .Iaddend.   
     
     
        .Iadd.39.  An apparatus according to claim 31, wherein a slit is formed between an end portion of said elastic plate and said developer supporting 
     
     
        member. .Iaddend. .Iadd.40.  A developing apparatus for developing with a powder developer, comprising: a movable developer supporting member provided in facing relationship with an image carrying means in a developing station for developing a latent image carried on the image carrying means, said supporting member being separated from the image carrying means by a predetermined distance;   means for supplying powder developer to said supporting member; and   an elastic developer limiting member having a free end upstream of the developing station, with respect to the direction of movement of the developer, which is maintained in predetermined pressure contact with said developer supporting member at a position between said developer supply means and the developing station to regulate the thickness of a layer of the developer particles supplied by said supplying means, wherein said limiting member includes a plate having rubber elasticity, wherein the plate has a surface including a contact portion which is in surface press-contact with said developer supporting member counter-directionally with respect to a movement direction of the developer supporting member, and an extension surface portion which extends toward the downstream direction from the contact portion and which is faced to said developer supporting member, and wherein said plate and said developer supporting member cooperate to form a nip, in the contact portion, through which the developer particles are passed so that the thickness of the developer layer is regulated. .Iaddend. .Iadd.41. An apparatus according to claim 40, wherein the developer particles comprise non-magnetic toner. .Iaddend. .Iadd.42. An apparatus according to claim 40, further comprising magnetic field generating means stationarily disposed behind said developer supporting member, wherein said developer supporting member is of non-magnetic material, and the developer particles are magnetic developer particles, and wherein the surface of the plate in the surface press-contact is convex, and wherein the nip is disposed within influence of a magnetic field generated by said magnetic field generating means. .Iaddend. .Iadd.43. An apparatus according to claim 40, wherein the plate is disposed to provide a convex surface in contact with the supporting member, and wherein the nip is placed at a position where said developer supporting member moves substantially upwardly. .Iaddend. .Iadd.44. An apparatus according to claim 43, further comprising magnetic field generating means stationarily disposed behind said developer supporting member, wherein said developer supporting member is of non-magnetic material, and the developer particles are magnetic developer particles, and wherein the nip is disposed within influence of a magnetic field generated by said magnetic field generating means. .Iaddend. .Iadd.45. A developing apparatus for developing with a powder developer, comprising:   a movable developer supporting member provided in facing relationship with an image carrying means in a developing station for developing a latent image carried on the image carrying means, said supporting member being separated from the image carrying means by a predetermined distance;   means for supplying powder developer to said supporting member; and   an elastic developer limiting member having a free end upstream of the developing station, with respect to the direction of movement of the developer, which is maintained in predetermined pressure contact with said developer supporting member at a position between said developer supply means and the developing station wherein said limiting member is an electrically conductive and elastic plate having a surface including a contact portion which is in surface press-contact with said developer supporting member co-directionally with respect to a movement direction of the developer supporting member, and an extension surface portion which extends toward the upstream direction from the contact portion and which is faced to said developer supporting member, and wherein said plate and said developer supporting member cooperate to form a nip, in the contact portion, through which the developer particles are passed so that the   
     
     
        thickness of the developer layer is regulated. .Iaddend. .Iadd.46.  A developing apparatus for developing with a powder developer, comprising: a movable developer supporting member provided in facing relationship with an image carrying means in a developing station for developing a latent image carried on the image carrying means, said supporting member being separated from the image carrying means, by a predetermined distance;   means for supplying powder developer to said supporting member; and   an elastic developer limiting member having a free end upstream of the developing station, with respect to the direction of movement of the developer, which is maintained in predetermined pressure contact with said developer supporting member at a position between said developer supply means and the developing station wherein said limiting member is an electrically conductive and elastic plate having a surface including a contact portion which is in surface press-contact with said developer supporting member counter-directionally with respect to a movement direction of the developer supporting member, and an extension surface portion which extends toward the downstream direction from the contact portion and which is faced to said developer supporting member, and wherein said plate and said developer supporting member cooperate to form a nip, in the contact portion, through which the developer particles are passed so that the thickness of the developer layer is regulated.   
     
     
        .Iaddend. .Iadd.47.  An apparatus according to claim 45 or 46, wherein the developer particles are non-magnetic toner. .Iaddend. .Iadd.48. An apparatus according to claim 45 or 46, further comprising magnetic field generating means stationarily disposed behind said developer supporting member, wherein said developer supporting member is of non-magnetic material, and the developer particles are magnetic developer particles, wherein the surface of the plate in the surface press-contact is convex, and wherein the nip is disposed within influence of a magnetic field generated by said magnetic field generating means. .Iaddend. .Iadd.49. An apparatus according to claim 45 or 46, wherein the surface of the plate in the surface press-contact is convex, and wherein the nip is placed at a position where said developer supporting member moves substantially upwardly. .Iaddend. .Iadd.50. An apparatus according to claim 49, further comprising magnetic field generating means stationarily disposed behind said developer supporting member wherein said developer supporting member is of non-magnetic material, and the developer particles are magnetic developer particles, and wherein the nip is disposed within influence of a magnetic field generated by said magnetic field generating means. .Iaddend.