Fuser member with reinforced slot

A fuser member includes a metallic core cylinder with an axially extending slot defined in an end region of the core cylinder. An integral flange is formed from material from the slot. The flange extends generally radially from the core cylinder adjacent the slot. A drive gear includes a key. The slot receives the key for rotation of the core cylinder.

BACKGROUND

The present exemplary embodiment relates generally to a fusing system for fusing marked media and more particularly to a fuser member with a reinforced slot for accepting a drive gear.

Fuser rolls used in electrographic imaging systems generally comprise a metal core cylinder coated with one or more elastomer layers. The fuser roll is heated, either internally or externally, to provide a heated exterior surface for fusing marking materials, such as toners, to paper or other marking media. Conventional fuser roll core cylinders are relatively thick-walled aluminum alloy cylinders. The thickness has been employed in order to provide strength and durability as the fuser roll presses against the adjacent compression roll in the nip region.

Typically, the fuser roll is allowed to cool between fusing operations to conserve energy and prolong the life of the fuser roll. The warm-up time of a fuser roll depends on its mass. It is desirable for the fuser roll to reach an operating temperature of about 150–200° C. within a relatively short period of time using conventional power sources. In order to save energy and shorten warm-up times, the fuser roll wall thickness has been progressively reduced. However, it has been found that the thinner cylinder walls are subject to weakness and cracking, particularly in the end region of the cylinder where a drive slot is punched out of the fuser core cylinder. The drive slot receives a key of a drive gear for rotation of the core cylinder. As the fuser roll rotates, the pressure placed on the fuser roll at the nip tends to cause the fuser roll to be slightly out of round. The slot acts as a stress raiser. Cracks may propagate from the slot, ultimately causing the failure of the fuser roll.

Various attempts have been made to strengthen the slot. In one method, a rib is mounted to the fuser roll in the region of the slot.

CROSS REFERENCE TO RELATED PATENTS AND APPLICATIONS

The following applications, the disclosures of which are incorporated herein in their entireties, are mentioned:

Published Application No. 2005/0129433 by Jaskowiak discloses a thin walled fuser roll with a radial slot at its terminus for redirecting axial stress in a radial direction.

Published Application No. 2005/0129435 by Jaskowiak discloses a thin walled fuser roll with a slotless keyway.

BRIEF DESCRIPTION

Aspects of the exemplary embodiment relate to a fuser member and to a method of forming a fuser member. The fuser member includes a metallic core cylinder including an axially extending slot defined in an end region of the core cylinder. An integral flange is formed from material from the slot which extends generally radially from the core cylinder adjacent the slot. A drive gear includes a key. The slot receives the key for rotation of the core cylinder.

In another aspect, the method for forming a fuser member includes forming a channel in an end region of a metallic core cylinder. A flange is formed from material of the core cylinder adjacent the channel to define an axially extending slot in the end region of the core cylinder. A drive gear is mounted to the core cylinder whereby the slot receives a key of the drive gear.

In another aspect, a fuser member includes a metallic core cylinder including a slot extending axially from an end of the core cylinder. A flange extends generally radially inward from the core cylinder along three sides of the slot to define opposed faces. A drive gear having an inside diameter sleeve for fitting over the core member includes a key. The slot receives the key for rotation of the core cylinder.

DETAILED DESCRIPTION

In aspects of the exemplary embodiment disclosed herein, a fuser member core cylinder includes an axial slot for receiving a key of a drive gear. The slot has a flange formed at its perimeter from material which would otherwise be thrown away when a slot is punched from the core cylinder. This material is used to define the perimeter of the slot by bending the material inward to define a lip having opposed engagement faces for engaging the key during rotation. The engagement faces extend radially inward and provide a reinforcement to the slot which resists cracking of the fuser member core during operation of the fuser member. The reinforcement enables an otherwise thin-walled core cylinder to be produced which provides energy efficiency and fast warm-up times while meeting or exceeding specifications for durability and imaging performance. A fusing system incorporating the core cylinder can have warm up times of less than one minute, for example, of about thirty seconds or less. The reinforcement provides strength to the core cylinder wall proximate to the slot sufficient to prevent cracking from repeated cyclic compression. The reinforced slot offers a more positive engagement for a plastic drive gear key than other known systems as it provides a face to take the torque loading that is at right angles to the direction of the torque.

The fusing system thus described may form a part of an imaging system, such as a printer or copier, or a multifunction device, such as a printer with print, copy, scan, and fax services. Such multifunctional printers are well known in the art and may comprise print engines based upon electrophotography, ink jet, or other imaging methods. In an electrographic (xerographic) process, a photoconductive insulating member is charged to a uniform potential and thereafter exposed to a light image of an original document to be reproduced. The exposure discharges the photoconductive insulating surface in exposed or background areas and creates an electrostatic latent image on the member, which corresponds to the image areas contained within the document. Subsequently, the electrostatic latent image on the photoconductive insulating surface is made visible by developing the image with a developing material. Generally, the developing material comprises toner particles adhering triboelectrically to carrier granules. The developed image is subsequently transferred to a print medium, such as a sheet of paper or other image support substrate. The fusing of the toner onto the paper is generally accomplished by applying heat to the toner with a heated roller and application of pressure. In the fusing process, the toner image is permanently affixed to the print medium for producing a reproduction of the original document. The fuser member of the exemplary embodiment is suited to use in such an electrographic apparatus for this process. In a final step in the process, the photoconductive surface layer of the photoreceptive member is cleaned to remove any residual developing material therefrom, in preparation for successive imaging cycles.

The above described electrographic reproduction process is well known and is useful for both digital copying and printing as well as for light lens copying from an original. In many of these applications, the process described above operates to form a latent image on an imaging member by discharge of the charge in locations in which photons from a lens, laser, or LED strike the photoreceptor. Electrographic imaging technology is described, for example, in U.S. Pat. No. 6,069,624 to Dash, et al. and U.S. Pat. No. 5,687,297 to Coonan et al., both of which are hereby incorporated herein by reference in their entireties.

With reference toFIG. 1, a fusing system includes a fuser member10and a pressure member12which define a nip14therebetween. Pressure is applied to the fuser member by the pressure member during passage of print media through the nip. The fuser member10includes a core cylinder16, such as a metallic core cylinder formed from aluminum, an alloy thereof, steel, or other suitable metal. The core cylinder has a wall thickness t, in the radial direction, of between about 0.5 millimeters and about 2.0 millimeters. In one specific embodiment, the wall thickness t is about 1.1. mm and the outside diameter of the core cylinder16is about 35.0 mm.

With reference also toFIG. 2, one or more slots18are formed in an end region20of the core member. In the embodiment ofFIG. 1, a single slot is shown, however more slots may be provided, such as two, four, or six slots. The slot18extends generally axially from a first open end22of the core cylinder to a terminus24, spaced from the end22. A perimeter26of the slot is defined by a flange or side wall28, which extends generally radially inward from the core cylinder16. As best shown inFIG. 3, where only a single slot is illustrated, the flange may extend along three sides of the slot, in a U-shape, to provide a lip to the core cylinder around the perimeter26of the slot18. The side wall28thus provides opposed engagement faces30,32joined by a terminal portion34with a radiused end surface adjacent the terminus24of the slot. The slot18thus provides a passage through the core cylinder16which is open adjacent interior and exterior surfaces of the core cylinder.

Since the side wall28is formed from the material which occupied the slot prior to formation of the slot (the “slot material”), the depth d of the flange28which extends beyond an interior surface35of the cylinder16can be up to about half the maximum width w of the slot (FIG. 1). This provides the core16cylinder with an increased thickness region of height (d+t) at the perimeter26of the slot without the need to add additional material. The depth d can be at least 1 mm, e.g., at least equal to the thickness t of the wall. For example, for a slot of width w of about 4–6 mm the depth d of the flange may be about 1.0–2.5 mm. This provides a face30,32having a height (d+t) of e.g., about 2.0–4 mm. In one embodiment, the height (d+t) is at least 2.2 mm. It will be appreciated that because of the curvature of the flange, its height (d+t) may be somewhat less than the theoretical height based on the dimensions of the slot material from which it is formed. The28flange may be radiused, as shown inFIGS. 1 and 3, such that the slot18decreases in width away from the cylinder wall16. The slot18may have an hourglass shape, i.e., the width increasing again towards a distal end36of the flange28. The convex shape of the flange28provides an efficient stress reducer when the core cylinder16is compressed by the pressure roll12.

The slot18provides a through passage into an interior38of the core cylinder16. The side wall28can be formed by bending the slot material without appreciable stretching of the slot material or the adjacent material of the core cylinder, resulting in the side wall having a wall thickness which is comparable to that of the average core cylinder wall thickness t in the end region.

The illustrated core cylinder16is heated by a heater40(FIG. 1), such as one or more halogen lamps located in the interior38of the core cylinder16. Alternative heaters are contemplated, such as external induction heaters or lamps, or the like. The core member16may be coated with one or more exterior conformable layers42(FIG. 2), such as a layer of silicone rubber and may be protected by an outer layer of Teflon™.

In operation, a drive gear50(FIG. 2) having an internal diameter sleeve52is fitted over the end region20of the core cylinder16such that a key54of the drive gear extends through the slot18. One or both of opposed side faces56,58of the key54engage one or both of the engagement faces30,32for forcing rotation of the core cylinder16. The key may have a depth D which is greater than the depth d of the slot and thus the key may extend radially inward of the side wall28, as shown inFIG. 1. The drive gear50may be formed from plastic or other suitable material. While an exterior drive gear50, as shown, conveniently allows the heating lamps to be inserted into the core cylinder16after mounting the drive gear to the core cylinder, the drive gear may alternatively be configured for slotting within the core cylinder with an exterior key protruding through the slot toward an exterior of the core cylinder.

Rotation of the fuser member10is effected by engagement of exterior teeth60of the drive gear50with a drive mechanism (not shown) that forces the gear50to turn. The sleeve52comprises the internal diameter of the gear50with the result that the sleeve52is also driven upon engagement of the teeth60. The key54engages the flange28of the slot18in order that the core cylinder16is driven by the drive gear50. As the fuser member10turns, print substrates are caught in the nip14between the core cylinder and the adjacent pressure roll12and are pulled and guided over and past the fuser member10. Since the fuser member is heated to fusing temperature, the result is fusing the toner to the copy substrate by at least partially melting the toner under pressure.

With reference toFIGS. 4 and 5, the slot or slots18can be formed in the core cylinder16by forming a channel70using a saw, laser cutting device, or the like. The channel70can be of any suitable width, depending on the width of the blade or other cutting member of the tool used to form the channel. For example the channel70may be about 1–2 mm, although laser cutting tools may result in a narrower channel. The channel70is narrower in width than the width w of the subsequently formed slot18, e.g., the width of the channel70is at least 2 mm less than that of the slot18and can be up to about 6 mm (or greater) less than the slot width w. For example, for a slot having a width w of 6 mm, the channel may be about 4–5 mm less e.g., about 1–2 mm. It is this difference in width that is used to form the flange28. The channel70has a length which is the approximate length of the slot, e.g., about 20 mm. A suitable tool74can be used to punch the wall of the core cylinder radially inward, around the edge of the channel70, to form the flange28.

While the flange is shown as extending on both sides of the slot18, in an alternative embodiment, the flange28is formed only or primarily on one side of the slot, that side being the one which lies in the direction of rotation of the core cylinder and which is engaged when the key54is inserted in the slot.

The fuser member thus described has a significantly longer lifetime than comparable fuser members formed without the flange. From tests on the fuser member, it is anticipated that a face height (d+t) of about 2.2 mm, or greater, is expected to provide a core cylinder which lasts for the useful life of other components of the fuser member.

Without intending to limit the scope of the exemplary embodiment, the following example demonstrates the effectiveness of the flange28in increasing the lifetime of a fuser member.

EXAMPLE

A fuser member was formed by milling four channels of about 1 mm in width, equally spaced around an aluminum core cylinder of wall thickness 1.1 mm. The material around the channels was bent inward to create four slots, each with a flange around the slot. The flange had a height (d+t) of about 2.5 mm. The core cylinder was fitted with a gear having four keys which were fitted into respective slots. The fuser member was installed in an imaging device and heated to an operating temperature of 188° C. The fuser roll was run constantly without cycling down the temperature. Fuser rolls formed with slots without a flange were tested under similar conditions. The number of revolutions of the fuser member until the first crack in the core cylinder appeared was determined and the number of revolutions to complete failure were also noted. Most of the conventional fuser rolls tested exhibited a first crack within 1,000,000 revs. The average time to the first crack of the conventional rolls was less than about 500,000 revs. Some of these fuser rolls exhibited a complete failure during the test (12,000,000 revs). In the case of the fuser member formed according to the exemplary embodiment, however, no cracks were observed prior to ending the test at 12,000,000 revs.