Metering roll assembly

Abstract: An end sealed metering apparatus comprises a cylindrical metering roll (10) mounted for rotation about a central longitudinal axis, a blade (11) aligned along an axis parallel to the longitudinal axis and contacting the metering roll (10), an elastomeric seal (30) supported against an end of the metering roll (10), a rigid plate (33) coupled with the elastomeric seal (30) for holding the elastomeric seal (30) stationary while the metering roll (10) rotates, and a spring (40) for urging the rigid plate (33) and elastomeric seal (30) against the end of the metering roll (10).

Description: The invention relates to a lubricant metering apparatus, including a metering roller and a metering blade and, more particularly, to a metering roll assembly for eliminating excessive oil concentrations transferred to a fuser roll. The basic xerographic process comprises exposing a charged photoconductive member to a light image of an original document. The irradiated areas of the pnotoconductive surface are discharged to record thereon an electrostatic latent image corresponding to the original document. A development system moves a developer mix of carrier granules and toner particles into contact with the photoconductor surface. The toner particles are attracted electrostatically from the carrier granules to the latent image, forming a toner powder image. The toner powder image is then transferred to a sheet of paper or other support material. This sheet of paper advances to a fuser roll which permanently affixes the toner powder image to the paper. In order to function properly, the rolling cylindrical or peripheral surface on the fuser requires application of a layer of lubricant for lubrication. Many copiers, such as the Model Nos. 1065 and 5090 copiers, manufactured by Xerox Corporation, contain a release agent management system for performing this function. The release agent management system generally includes a metering roll, a metering blade, a donor roll, and an oil applicator. The system operates by rotating the metering roll in conjunction with the donor roll so that as the metering roll rotates, the oil applicator applies oil to the peripheral surface of the metering roll where it is distributed evenly about peripheral surface by the metering blade. The peripheral surface of the metering roll contacts the surface of the donor roll to transfer oil from the metering roll to the peripheral surface of the donor roll. The donor roll also contacts the peripheral surface of the fuser roll to transfer oil to, and thus lubricate, the fuser roll. Such a system is disclosed in US-A-4 426 953. Due to insufficient space in the copier above the metering roll, the metering blade is generally positioned below the metering roll. As a result, when the metering roll stops rotating, any oil that is on the metering roll between the metering blade and the peripheral surface of the metering roll will flow to the top side of the blade due to gravity and create an excess oil accumulation. This excess oil accumulation is transferred to the fuser roll when the metering roll is subsequently rotated. The excess oil is then transferred to copies passing through the fuser assembly, creating undesirable marks on the copies. Undesirable marks on the copies are most pronounced on the sides of the copies due to excessive oil accumulation at the ends of the metering roll and the metering blade. This excess oil at the ends or the metering roll and metering blade is caused by two separate problems in the design or the metering roll assembly. First, as the metering roll rotates, there is a self-pumping action which forces oil to the ends and side edges of the metering roll. Since there is nothing to prevent this self-pumping action, when the metering roll stops rotating, the excess oil which has been pumped to the ends and side edges of the metering roll will accumulate on the ends of the metering blade, which is generally longer than the metering roll. Second, bending forces applied to the metering blade cause the ends of the metering blade to bend away from, and thus separate, from the surface of the metering roll. As a result, oil accumulating at the ends of the metering roll is not evenly distributed by the metering blade. This excess oil then accumulates on the metering blade when the metering roll stops rotating. The combination of the excess oil due to the self-pumping action of the metering roll and the separation of the ends of the metering blade from the metering roll forms an excess oil accumulation at the ends of the metering blade and roll which is subsequently passed to the fuser assembly and onto copies. As a result, an undesirable copy quality defect, known as a "oil wing", is formed on the copies as they pass through the nip between the fuser and the pressure roll. It is an object of the present invention to provide a metering apparatus which does not create copy quality defects on paper passing through the nip between a fuser roll and a pressure roll. Accordingly, the present invention provides a lubricant metering apparatus according to claim 1. Preferred embodiments of the invention are specified in the dependent claims. The metering apparatus prevents excess oil from accumulating on the metering blade, controls self-pumping action of oil toward the ends of a metering roll and eliminates excess oil from accumulating at the ends of a metering blade due to separation between the ends of the metering blade and a peripheral surface of a metering roll. The present invention will be described further, by way of example, with reference to the accompanying drawings, in which:- FIG. 1 is a largely schematic side elevation of a metering roll assembly embodied in an electrophotographic apparatus. FIG. 2 is a front view of the end sealed metering roll apparatus according to an embodiment of the present invention, FIG. 3 is an exploded perspective view of the end sealed metering roll apparatus of FIG. 2 and FIG. 4 is a side view of a force plate according to an embodiment of the present invention. FIG. 1 shows a metering roll assembly embodied in an electrophotographic apparatus, such as the Model No. 5775 copier manufactured by Xerox Corporation. A sheet of paper follows a paper path 1 along which a photoreceptor 2 affixes a toner powder image to the paper corresponding to an original document. The sheet of paper carrying the toner powder image then passes through a nip between a fuser roll 3 and a pressure roll 4 to permanently affix the toner powder image to the paper. To lubricate the fuser roll 3, an oil applicator 7 applies a layer of oil to a metering roll 10. The oil is evenly distributed on the peripheral surface of the metering roll 10 by a metering blade 11. The metering roll 10 then transfers the oil to the peripheral surface of a donor roll 5 which, in turn, transfers the oil to the peripheral surface of the fuser roll 3. Rotation of the metering roll 10 is controlled by the rotation of the fuser roll 3. A drive mechanism (not shown) is provided for rotating the fuser roll 3. Since the fuser roll 3 is in rolling contact with the peripheral surface of the donor roll 5, rotation of the fuser roll 3 also causes the donor roll 5 to rotate by friction. Similarly, since the donor roll is in rolling contact with the metering roll 10, friction between the peripheral surface of the metering roll 10 and the peripheral surface of the donor roll 5 causes the metering roll 10 to rotate with the donor roll 5 and fuser roll 3. FIG. 3 shows an exploded view of the metering roll assembly embodiment of the present invention. The metering roll comprises a hollow cylindrical shell 10 rotatable about a shaft 12 disposed within the hollow portion of the cylinder. Bearings 13 are mounted on the shaft within each end of the hollow cylinder and held in place by retaining clips 14. In the illustrated embodiment, the ends of the shaft are supported in non-circular openings 16 formed on support plates 15. A blade holder 20 is secured to the support plates 15 by screws 21. The blade holder 20 supports an edge of the metering blade 11 so that the opposite edge of the metering blade 11 is in contact with the peripheral surface of the metering roll 10. The metering blade 11 is typically longer than the metering roll and is made of an elastomeric material to reduce wear and better contact the surface of the metering roll 10. Referring to FIGS. 2 and 3, an end seal 30 having a hollow central portion 31 is mounted on the shaft 12 between each end of the metering roll 10 and the support plates 15. The end seal 30 is preferably disk-shaped and preferably having an outside diameter the same as the diameter of the metering roll shell 10. The end seal also has two diametrically spaced axial holes 32. The end seals 30 are made of an elastomeric material to slidably engage and seal with the ends of the metering roll shell 10 without causing wear. A preferred material is compound 65704 Fluorol B, ASTM No. D2000M7HK610 A1-10 B38 Z1. Rigid force plates 33 having a central circular opening 34 are disposed on the shaft 12 between the support plates 15 and the end seals 30. Each force plate 33 is preferably configured to have approximately the same dimensions as the end seal and is composed of a material of sufficient hardness to firmly hold the end seal 30 against the end of the metering roll 10. Such material may be a polycarbonate. Small protrusions 35 on the surface of the force plate 33 are designed to engage the small holes 32 of the end seal. As shown in FIG. 4, the force plate 33, which is preferably disk-shaped, has an engaging tang 36 formed on its peripheral surface to contact the blade holder 20. Since the blade holder is stationary, the tang 36 prevents the force plate 33 from rotating with the metering roll 10. Since the force plate 33 is coupled to the end seal 30 by the engagement of the protrusions 35 with the hollow portions 32, the end seal 30 is also prevented from rotating with the metering roll 10. A spring 40 is mounted on the shaft 12 between the support plate 15 and the force plate 33 to urge the force plate 33 and the end seal 30 against the end of the metering roll 10. A spring force of approximately 0.227 kg (0.5 lb) is generally sufficient to urge the end seal 30 in sealing contact with the end of the metering roll 10. The necessary force, however, may vary depending on the specific application. In the preferred embodiment of the invention, means are also provided for urging the ends of the metering blade 11 against the ends of the metering roll 10. The urging means preferably comprises two shims 50 or leaf springs secured to the blade holder 20 near the ends of the metering blade 10. The shims 50 force the ends of the metering blade 11 against the surface of the metering roll 10 to prevent separation between the metering blade 11 and the metering roll 10 at the ends of the metering roll 10. In operation, the metering apparatus of the present invention greatly reduces the accumulation of excess oil at the ends of the metering roll, thereby preventing copy quality defects from being formed on the paper copies. The elastomer end seals 30, which are held stationary against the side edges of the metering roll 10 while the metering roll 10 is rotating, prevent fluid dynamic forces from pumping fluid toward the ends and side edges of the metering roll 10 since there is no pumping action past the stationary end seals 30. Additionally, the shims 50 urge the ends of the metering blade 11 against the metering roll, thus preventing separation and deterring excess oil from flowing to the ends of the metering blade 11. Therefore, excess oil is prevented from accumulating on the top ends of the blade 11 and copy quality defects are greatly reduced. It will be apparent to those skilled in the art that various modifications and variations can be made in the present invention without departing from the scope of the claims.

Claims: A lubricant metering apparatus, including a cylindrical metering roll (10) supported for rotation about a central longitudinal axis having an outer cylindrical surface and two side edges; a metering blade (11) and support means (20) for supporting the blade (11) so that an edge of the blade (11) contacts said outer cylindrical surface of the metering roll (10), characterised by sealing means (30), held stationary against each side edge of the metering roll (10), for preventing excess lubricant from accumulating at the ends and side edges of the metering roll; and support means (15,33,40) for supporting the sealing means (30) against the side edges of the metering roll (10). A metering apparatus as claimed in claim 1, wherein the supporting means (15,33,40) holds the sealing means (30) stationary against the side edges of the metering roll (10) while the metering roll rotates. A metering apparatus as claimed in claim 1 or claim 2, wherein the sealing means (30) includes an elastomeric seal. A metering apparatus as claimed in any one of claims 1 to 3, wherein the supporting means (15,33,40) includes a rigid plate (33) coupled to the sealing means (30). A metering apparatus as claimed in claim 4, wherein the rigid plate (33) is disk-shaped and has a tang (36) formed on its peripheral surface to engage the blade supporting means (20) and prevent rotation of the sealing means (30). A metering apparatus as claimed in claims 4 or 5, wherein the supporting means (15,33,40) further comprises biassing means (40) for urging the rigid plate (33) against the sealing means (30) to force the sealing means (30) into sealing contact with the side edges of the metering roll (10). A metering apparatus as claimed in any one or claims 1 to 6, further comprising means (50) for urging the ends of the blade (20) against the outer cylindrical surface of the metering roll (10). A metering apparatus as claimed in claim 7, wherein two blade urging means (50) are provided, each disposed at a respective end of the blade support means (20), the blade urging means (50) comprising at least two springs or at least two shims.

Inventors: GARY ROBERT E, PAWLIK ROBERT S, GARY, ROBERT E., PAWLIK, ROBERT S.
Applicants: XEROX CORP, XEROX CORPORATION
Application year: 1993
Main classification: G03G15
IPC codes: G03G15, B05C1