Toner cartridge

Abstract: A toner cartridge having no toner pump, with the toner adding roller (11) positioned horizontal to the developer roller (3), the toner chamber (9) located predominantly below the developer roller, the photoconductive drum (7) located 120 degrees from the top of the developer roller, and the doctor blade (5) located near the top.

Description: This invention relates to electrophotographic imaging and, more particularly, relates to a toner cartridge having no toner pump and associated structure. A toner pump is described in U.S. Patent No. 5,012,289 to Aldrich et al. It is a device which meters toner from a chamber above a developer station. The developer station employs a toner applying roller, which is at a predetermined electrical potential higher than that of the developer roller. The toner applying roller rotates in a bed of toner in contact with the developer roller and thereby applies toner onto the surface of the developer roller, the toner being charged primarily to the same electrical sign as that of both the toner applying roller and the developer roller. The developer roller then rotates past a doctor blade which is charged to a potential higher than the developer roller and rejects much toner having the other potential (termed wrong sign toner). However, such a system does not operate reliably under the pressures of a high column of toner which can reach the doctor blade-developer roller nip. Consequently a toner pump is employed to prevent the toner head reaching the doctor blade-developer roller nip. Elimination of the toner pump would reduce manufacturing and material costs and unwanted pressure variations during operation caused by the operation of the pump, which variations have previously been remedied by a vent between both sides of the toner pump and by close tolerances. A two phase toner pump has also been developed to remedy this effect and is the subject of U.S. Patent No. 5,101,237 to Molloy. Elimination of the toner pump would also reduce variations in torques, since the other rollers are driven off the same power source as the toner pump. Reduction in such fluctuations can reduce jitter or, alternatively, reduces costs in powering the system adequately to avoid jitter. US-A-5,086,728 to Kinoshita shows a toner applying roller horizontally aligned with a developer roller, but is not otherwise closely similar to this invention. Thus, it is known from US-A-5,086,728 to provide an electrophotographic imaging toner cartridge comprising a developer roller, a doctor blade in contact with said developer roller near the top of the developer roller, a toner applying roller in contact with the developer roller and located in substantially the same horizontal plane as the developer roller, and a chamber for electrophotographic toner positioned on the side of the toner applying roller away from the developer roller. In US-A-5 075 728 the toner chamber is substantially at the level of the developer roller. According to the present invention, however, the electrophotographic imaging toner cartridge is characterised in that the chamber for electrophotographic toner is positioned predominantly below the developer roller, the chamber extending downwardly below the top of the toner applying roller by more than twice the diameter of the toner applying roller. In a preferred toner cartridge of this invention the primary toner chamber is located lower than the developer station. This chamber has a paddle which rotates constantly during operation, as was true with a cartridge with a toner pump. In this cartridge, the paddle operation brings sufficient toner to the developing station even as the toner supply drops under the developing station. In a preferred embodiment a top half of the toner chamber exists to permit the paddle to smoothly rotate and to constrain airborne toner. However, the maximum filling of the toner chamber is roughly to the nip between the doctor blade and the developer roller. An embodiment of the invention will now be described by way of example and with reference to the accompanying drawing, in which the single figure is an illustrative, side-perspective, cross sectioned view of a toner cartridge in accordance with this invention. As seen in the drawing, the level of dry, powder toner 1 is not substantially above the nip of the developer roller 3 and the doctor blade 5. Doctor blade 5 contacts developer roller 3 substantially at the top of roller 3. In the drawing the loading of toner 1 is the maximum permitted in normal operation, and, of course, during use the amount of toner 1 will diminish. Developer roller 3 contacts photoconductive drum 7 at an angle of 30 degrees from the horizonal, which is 120 degrees from the location of contact of doctor blade 5 with roller 3. Since the toner chamber 9 occupies an area predominantly below roller 3, space is conserved by locating photoconductive drum 7 also predominantly below roller 3 (the foregoing cartridge with toner pump had a 13 degree angle). A toner applying roller 11 is located generally horizontally aligned with the developer roller 3 (i.e. with its nip control at 90 degree from the top of roller 3). This position blocks excess toner from the chamber 9, and is important for reliable operation. With toner applying roller 11 physically between developer roller 3 and chamber 9, chamber 9 extends downward more than twice the diameter of toner applying roller 11, as shown. Photoconductive drum 7 is located on the side of developer roller 3 opposite the location of toner applying roller 11. The bottom level of chamber 9 is determined by the toner volume requirements. The paper path 13 must be lowered to clear chamber 9. During operation, paddle 15 continually moves toner in chamber 9 by blades 17 at the outer periphery of chamber 9. The developer unit housing 19 defines chamber 9 and a corresponding upper chamber 21, to form a closed chamber of circular configuration in which paddle 15 turns freely. The upper chamber 21 is never filled with toner 1 and exists to capture flying toner. The lack of toner in this region is to prevent excessive toner pressure. Operation is inherent and characterized by a minimal number of operational parts in the cartridge. Paddle 15 rotates during all operation in a simple circle, and is therefore a minimal source of torque fluctuations. Toner applying roller 11 and developer roller 3 are electrically charged and rotate in the manner of the previous cartridge having a toner pump. Doctor blade 5 is preferably the low-cost, compliant doctor blade described in U.S. Patent No. 5,085,171 to Aulick et al. Doctor blade 5 is electrically charged but not rotated or otherwise moved directly. It will be understood that the elements described extend across the width of the cartridge, as shown in perspective in the drawing. It will also be understood that the photoconductive drum 7 is a part of the cartridge, the elements being enclosed in an outer housing 23, shown in phantom outline, as is now conventional. Toner is essentially the same as that in the cartridge with toner pump now widely distributed by the present applicant for the IBM LaserPrinters 4019 and 4029, and as summarized in the foregoing U.S. Patent No. 5,012,289.

Claims: An electrophotographic imaging toner cartridge comprising a developer roller (3), a doctor blade (5) in contact with said developer roller near the top of said developer roller, a toner applying roller (11) in contact with said developer roller and located in substantially the same horizontal plane as said developer roller, and a chamber (9) for electrophotographic toner (1) positioned on the side of said toner applying roller away from said developer roller, characterised in that said chamber (9) for electrophotographic toner (1) is positioned predominantly below said developer roller (3), said chamber (9) extending downwardly below the top of said toner applying roller (11) by more than twice the diameter of said toner applying roller. A toner cartridge as claimed in claim 1, also comprising a photoconductive roller (7) in contact with said developer roller (3), said photoconductive roller being positioned substantially below said developer roller. A toner cartridge as claimed in claim 2, wherein the location of contact between said toner applying roller (11) and said developer roller (3) is 90 degrees from the location of contact of said developer roller with said doctor blade (5), said photoconductive roller (7) is in nip relationship with said developer roller, and the location of said nip relationship is substantially 150 degrees from the location of contact between said toner applying roller and said developer roller on the side of said developer roller opposite the location of said toner applying roller. A toner cartridge as claimed in any of claims 1 to 3, containing dry toner (1) in an amount to fill said chamber (9) and up to no more than about the level of contact between said doctor blade (5) and said developer roller (3).

Inventors: BAKER RONALD WILLARD, BURDICK ROBERT LEONARD, DIGIROLAMO MARTIN VICTOR, HERRALL PAUL DOUGLAS, MERRIFIELD DAVID LEE, MOLLOY JAMES JOHN, WARD II EARL DAWSON, WILZBACH BERNARD LEE, BAKER, RONALD WILLARD, BURDICK, ROBERT LEONARD, DIGIROLAMO, MARTIN VICTOR, HERRALL, PAUL DOUGLAS, MERRIFIELD, DAVID LEE, MOLLOY, JAMES JOHN, WARD II, EARL DAWSON, WILZBACH, BERNARD LEE
Applicants: LEXMARK INT INC, LEXMARK INTERNATIONAL, INC.
Application year: 1993
Main classification: G03G15
IPC codes: G03G15