Electricity: measuring and testing – A material property using electrostatic phenomenon
Reexamination Certificate
1998-11-16
2001-11-20
Brown, Glenn W. (Department: 2858)
Electricity: measuring and testing
A material property using electrostatic phenomenon
C324S459000
Reexamination Certificate
active
06320387
ABSTRACT:
This invention relates generally to an apparatus and a method for measuring charge, and more particularly concerns measuring the triboelectric charge on a flexible material.
Cross reference is made to the following application filed concurrently herewith: U.S. application Ser. No. 09/192,900, entitled “Charge Measuring Instrument”, by Dennis A. Abramsohn et al., the relevant portions thereof incorporated herein by reference.
The features of the present invention are useful in any machine which has concerns regarding the triboelectric charges within the machine. One such machine is a printing machine, for example electrophotographic printing machine.
In the process of electrophotographic printing, a photo-conductive surface is charged to a substantially uniform potential. The photoconductive surface is image wise exposed to record an electrostatic latent image corresponding to the informational areas of an original document being reproduced. This records an electrostatic latent image on the photoconductive surface corresponding to the informational areas contained within the original document. Thereafter, a marking material such as toner particles is transported into contact with the electrostatic latent image in a region known as the development zone. Toner particles are attracted from the magnetic roller to the latent image. The resultant toner powder image is then transferred from the photoconductive surface to a copy sheet and permanently affixed thereto. The foregoing generally describes a typical mono-color single component development electrophotographic copying machine.
Printing machines are widely used to print written material and documents of all types. The printing machines may be of many types including, but not limited to, gravature or offset type ink printing, thermal inkjet printing, bubble jet printing, direct electrostatic printing and electrostatographic or xerographic printing. Xerographic printing can be done with wet or dry marking materials.
The printing machines may utilize any type of substrate on which to print. Typically, printing machines use paper on which to print. The paper comes typically in two forms, that of a continuous roll and in single sheets. The sheets or rolls are typically fed by rollers and baffles through various parts of the printing or xerographic process. Static electricity causes many substrate handling problems and is particularly a problem with various papers. The static electricity is particularly a problem on sheet-type printing machines. The static electricity causes the sheets to adhere to each other and rather than feed seriatim or one at a time, the sheets feed in an overlapped basis because of the static electricity which causes adjacent sheets to be secured to each other. Such adherence of adjoining sheet leads to jams within the printing machine and resultant down time for the printing machine. Further, in operations in which collation or sorting of sheets occurs, the static electricity may cause for the undesired reordering of sheets which may make a printed copy inaccurate or include multiple or missing sheets.
Static electricity becomes even more of a problem in an electrostatographic or xerographic printing machine, or any machine in which static electricity is utilized for part of the printing process. Further, in xerographic and other types of electrostatographic printing, corona generating devices are included within the machine which may create additional static electricity within the machine.
Further, the mere existence of components which rub or contact the paper as it passes through the paper path within the printing machine may generate static electricity. The baffles, chutes and rollers within a printing machine may be made of any of a number of metal or plastic or synthetic rubber materials which may generate exceedingly large amounts of static electricity when in contact with, and rubbing against, paper. Coatings and additives to the copy sheets may further increase or decrease the static electricity generated through the rubbing process within the printing machine. Further adjacent sheets of paper, when in contact during the printing process, either while stacking or unstacking a set of sheets, may likewise generate static electricity.
These problems are exacerbated by the use of high speed printers. Xerographic and statiographic printers are now available at speeds of 200 copies per minute or greater. Offset gravature-type printing speeds can be many times greater than those. As the translational speed of paper through the printing machine becomes faster and faster, the levels of static electricity that can be generated likewise increase.
In attempt to alleviate these problems with static electricity in the printing process, paper has been selected to minimize static electricity. Further additives are added to the paper and coatings to the paper to minimize the static electricity build-up within the printing process. Paper can now be chosen by surface resistivity and charge acceptance. These characteristics of paper may assist the operator of the printing machine in the proper utilization of paper.
The attempts to categorize papers and to provide additives and coatings to paper to minimize the effect of static electricity has several problems. The current measuring systems of measuring surface resistivity and charge acceptance of a sheet of paper cannot accurately predict the severity or location of static buildup within the printing process. Different paper characteristics have different triboelectric behavior that is not predicted by surface resistivity measurements. A need therefore exists to reproducibly generate and measure static electricity and its effect on paper. If accurate measurements were able to be made of paper as it contacts various materials, machine designs could be improved by taking into account the interrelationship of various materials during the printing process.
Electrical properties of other materials and components in addition to flexible material such as sheets require exacting tolerances which are difficult to measure. For certain type of components used in the printing art, namely photoconductive drums, donor rolls such as those used in hybrid scavengeless development as disclosed in U.S. Pat. No. 4,868,600 to Hayes et al., the relevant portions thereof incorporated herein by reference and in rolls for direct electrostatic printing such as those disclosed in U.S. Pat. No. 4,755,837 to Schmidlin et al., the relevant portions thereof incorporated herein by reference the electrical properties of these components are critical.
Electrostatic printing rolls, donor rolls, and photoconductive drums require particularly specific electrical properties. In particular, electrostatic rolls and donor rolls may require a permittivity of a very narrow range for proper operation of the roll. Furthermore, donor rolls and electrostatic print rolls, due to the manufacturing processes involved in making the rolls, may have electrical properties including permittivity that vary widely within a particular roll compounding the difficulty in obtaining accurate electrical property measurements.
The following disclosures may be relevant to various aspects of the present invention:
U.S. Pat No. 5,805,961 discloses a charging member, which electrically charges an object to be charged by being placed in contact with the object to be charged and by being applied with a voltage. The charging member includes an electroconductive base and brush bristles to come into contact with the object to be charged and the brush bristles include at least one of etching fibers and divided fibers.
U.S. Pat. No. 5,795,990 discloses a tester having a horizontal base with a vertical column that supports vertical guides for guiding a carriage that supports a rotary drive mechanism for an upper specimen which is secured in a chuck and engages a lower specimen supported by an interchangeable bowl. The tester is also provided with a computerized measuring system for precisely measuring characteristics to be tested. The main dis
Abramsohn Dennis A.
Eckstrom Lois A.
Foley Diane M.
Brown Glenn W.
Kerveros J.
Ryan Andrew D.
Wagley John S.
Xerox Corporation
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