Belts having overlapping end sections

Details Belts having overlapping end sections Belts having overlapping end sections

2000-10-26

2002-08-20

Thomas, Alexander S. (Department: 1772)

Stock material or miscellaneous articles

Sheets or webs edge spliced or joined

Sheets or webs coplanar

C474S254000

Reexamination Certificate

active

06436502

ABSTRACT:

FIELD OF THE INVENTION
This invention relates to seamed belts.
BACKGROUND OF THE INVENTION
Cross reference is made to the following applications that were filed on Sep. 29, 2000 Ser. No. 09/675,189 entitled “SEAMED BELT HAVING BEVELED END SECTIONS”, Ser. No. 09/676,829 entitled “IMAGEABLE SEAM INTERMEDIATE TRANSFER BELT HAVING TONER PARTICLE SIZED KERF GAP”now U.S. Pat. No. 6,353,725, Ser. No. 09/676,122 entitled “SEAMED BELTS HAVING FILLED BACKSIDE NOTCHES”now U.S. Pat. No. 6,381,436, and Ser. No. 09/676,123 entitled “LASER MICRO-MACHINING OF SEAMED BELTS”.
Electrophotographic printing is a well-known and commonly used method of copying or printing documents. Electrophotographic printing is performed by exposing a light image representation of a desired document onto a substantially uniformly charged photoreceptor. In response to that light image the photoreceptor discharges, creating an electrostatic latent image of the desired document on the photoreceptor's surface. Toner is then deposited onto that latent image, forming a toner image. The toner image is then transferred from the photoreceptor onto a receiving substrate such as a sheet of paper. The transferred toner image is then fused with the substrate, usually using heat and/or pressure. The surface of the photoreceptor is then cleaned of residual developing material and recharged in preparation for the production of another image.
The foregoing generally describes black and white electrophotographic printing machines. Electrophotographic printing can also produce color images by repeating the above process for each color of toner that is used to make the color image. For example, the photoreceptive surface may be exposed to a light image that represents a first color, say black. The resultant electrostatic latent image can then be developed with black toner particles to produce a black toner layer that is subsequently transferred onto a receiving substrate. The process can then be repeated for a second color, say yellow, then for a third color, say magenta, and finally for a fourth color, say cyan. When the toner layers are placed in superimposed registration the desired composite color toner image is formed and fused on the receiving substrate.
The color printing process described above superimposes the color toner layers directly onto a substrate. Other electrophotographic printing systems use intermediate transfer belts. In such systems successive toner layers are electrostatically transferred in superimposed registration from the photoreceptor onto an intermediate transfer belt. Only after the composite toner image is formed on the intermediate transfer belt is that image transferred and fused onto the substrate. Indeed, some electrophotographic printing systems use multiple intermediate transfer belts, transferring toner to and from the belts as required to fulfill the requirements of the machine's overall architecture. Suitable toners include both dry toner and liquid toner.
In operation, an intermediate transfer belt is brought into contact with a toner image-bearing member such as a photoreceptor belt. In the contact zone an electrostatic field generating device such as a corotron, a bias transfer roller, a bias blade, or the like creates electrostatic fields that transfer toner onto the intermediate transfer belt. Subsequently, the intermediate transfer belt is brought into contact with a receiver. A similar electrostatic field generating device then transfers toner from the intermediate transfer belt to the receiver. Depending on the system, a receiver can be another intermediate transfer member or a substrate onto which the toner will eventually be fixed. In either case the control of the electrostatic fields in and near the transfer zone is a significant factor in toner transfer.
Intermediate transfer belts often take the form of seamed belts fabricated by fastening two ends of a web material together, such as by welding, sewing, wiring, stapling, or gluing. While seamless intermediate transfer belts are possible, they require manufacturing processes that make them much more expensive than similar seamed intermediate transfer belts. This is particularly true when the intermediate transfer belt is large, for example when the size of the belt is greater than about 500 to 1000 square inches in total surface area. While seamed intermediate transfer belts are relatively low in cost, the seam introduces a discontinuity that interferes with the electrical, thermal and mechanical properties of the belt. While it is possible to synchronize a printer's operation with the motion of the intermediate transfer belt so that toner is not electrostatically transferred onto the seam, such synchronization adds to the printer's expense and complexity, resulting in loss of productivity. Additionally, since high speed electrophotographic printers typically produce images on paper sheets that are cut from a paper “web,” if the seam is avoided the resulting unused portion of the paper web must be cut-out, producing waste. Furthermore, even with synchronization the mechanical problems related to the discontinuity, such as excessive cleaner wear and mechanical vibrations, still exist. Additionally, a discontinuity can act as a mechanically weak spot or region in the belt. However, because of the numerous difficulties with transferring toner onto and off of a seamed intermediate transfer belt in the prior art it was necessary to avoid toner transfer onto (and thus off of) a seam.
Acceptable intermediate transfer belts require sufficient seam strength to achieve a desired operating life. While that life depends on the specific application, typically it will be at least 100,000 operating cycles, but more preferably 1,000,000 or more cycles. Considering that a seamed intermediate transfer belt must endure mechanical stresses from belt tension, traveling over rollers, moving through transfer nips, and passing through cleaner and developer systems, achieving such a long operating life is not trivial. Thus, the conflicting constraints of long life and limited topographical size at the seam places a premium on adhesive strength and good seam construction.
A prior art “puzzle-cut” approach to seamed belts significantly improves the seam's mechanical strength. U.S. Pat. No. 5,514,436, issued May 7, 1996, entitled, “Puzzle Cut Seamed Belt;” U.S. Pat. No. 5,549,193 entitled “Endless Seamed Belt with Low Thickness Differential Between the Seam and the Rest of the Belt;” and U.S. Pat. No. 5,487,707, issued Jan. 30, 1996, entitled “Puzzle Cut Seamed Belt With Bonding Between Adjacent Surface By UV Cured Adhesive” teach the puzzle-cut approach. While the puzzle-cutstructures described in the forgoing patents beneficially improve the seam's strength, further improvements would also be beneficial. Furthermore, there are other difficulties when transferring toner onto and off of a seam of a seamed intermediate transfer belt.
For a seamed intermediate belt to be acceptable, the final image produced from across the seam must be comparable in quality to images formed across the remainder of the belt. This is a difficult task due to a number of interrelated factors. Some of those factors relate to the fact that the seam should not greatly impact the electrostatic fields used to transfer toner. However, electrostatic transfer fields are themselves dependent on the electrical properties of the intermediate transfer belt. While this dependency is complex, briefly there are conditions where transfer fields are very sensitive to the resistivity and thickness of the materials used for the various layers of the intermediate transfer belt. Under other conditions the electrostatic transfer fields are relatively insensitive to those factors. Similarly, there are conditions where the electrostatic transfer fields are very sensitive to the dielectric constants of the materials used for the layers of the intermediate transfer belt, and other conditions where the electrostatic transfer fields are insensitive to the dielectric constants.

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