DEVELOPING APPARATUS

• US 20170308005A1
• Filed: 03/24/2017
• Published: 10/26/2017
• Est. Priority Date: 04/22/2016
• Status: Active Grant

• Current Assignee: Canon Kabushiki Kaisha (Canon Inc.)
• Original Assignee: Canon Kabushiki Kaisha (Canon Inc.)
• Inventors: Ariizumi, Osamu
• Granted Patent: US 10,146,157 B2
• Time in Patent Office: Days
• CPC Class Codes: G03G 15/0822 Arrangements for preparing, mixing, supplying or dispensing developer
• CPC Class Codes: G03G 15/0889 for agitation or stirring
• CPC Class Codes: G03G 15/0891 for conveying or circulating developer, e.g. augers
• CPC Class Codes: G03G 15/0893 in a closed loop within the sump of the developing device

Abstract

An agitating screw at a first communication port delivering a developer from a collecting chamber to a developing chamber is formed to be a multiple-threaded screw. The use of the multiple-threaded screw makes it possible to increase a developer surface level at the first communication port. If the developer surface level becomes too high within the collecting chamber, an image defect caused by entrainment of the developer by the developing sleeve may occur. Then, an arrangement is made such that the developer surface level does not become so high that may cause the entrainment of the developer by accelerating delivery of the developer at the first communication port. Thus, the use of the multiple-threaded screw makes it possible to accelerate the delivery of the developer and to reduce an image defect otherwise caused by the entrainment of the developer.

Claims

1. A developing apparatus, comprising:

a developer bearing member configured to bear developer and to be rotatable;

a developing chamber configured to supply the developer to the developer bearing member;

a collecting chamber configured to collect the developer conveyed from the developer bearing member and to form a circulation path of the developer with the developing chamber;

a wall dividing the developing chamber from the collecting chamber and through which a first communication port for delivering the developer from the collecting chamber to the developing chamber and a second communication port for delivering the developer from the developing chamber to the collecting chamber are defined, the first communication port being disposed out of a developing area where the developer bearing member bears the developer in a rotation axial direction of the developer bearing member;

a first conveyance screw disposed within the developing chamber and conveying the developer in a first direction; and

a second conveyance screw disposed within the collecting chamber, comprising a first screw portion having at least one thread, configured to convey the developer in a second direction opposite to the first direction and provided in an area facing the developing area and second screw portion having a plurality of threads whose number is larger than that of the first screw portion, configured to convey the developer in the second direction opposite to the first direction, disposed in an area out of the developing area in the rotation axial direction and provided in an area facing the first communication port.

2. The developing apparatus according to claim 1, wherein the first and second conveyance screws are disposed such that the second conveyance screw is located higher than the first conveyance screw in a vertical direction and at least a part of the first conveyance screw overlaps with the second conveyance screw in a view from a horizontal direction.

3. The developing apparatus according to claim 1, wherein a diameter of a rotary shaft of the second screw portion is smaller than a diameter of a rotary shaft of the first screw portion.

4. The developing apparatus according to claim 1, further comprising a discharge port configured to discharge the developer, defined at a downstream end in the second direction of the collecting chamber such that a rotary shaft of the second conveyance screw penetrates through the discharge port and such that a gap is defined around an outer circumference of the rotary shaft;

wherein the second conveyance screw comprises a return portion disposed upstream of the discharge port and downstream of the second screw portion in the second direction and configured to convey the developer in the first direction.

5. The developing apparatus according to claim 4, further comprising a third screw portion disposed between the second screw portion and the return portion and having at least one thread whose number is less than that of the second screw portion.

6. The developing apparatus according to claim 1, wherein the first conveyance screw and the first screw portion are single-threaded screw.

7. The developing apparatus according to claim 1, wherein a lower end of the second conveyance screw is disposed above a lower end of the first conveyance screw in a view from a horizontal direction.