Sheet conveying roller and production method therefor

Abstract

The present invention provides a sheet conveying roller, which effectively reduces the amount of paper dust accumulated on its outer peripheral surface to thereby suppress sheet transportation failure. The sheet conveying roller includes a nonporous tubular elastic member (1). The elastic member (1) has a plurality of recesses (6) or a plurality of through-holes (8) equidistantly arranged in a center axis (L1) direction thereof and equidistantly arranged in a circumferential direction thereof, and each having an opening having a round plan shape in an outer peripheral surface (2) thereof, wherein the recesses (6) each have a constant depth as measured thicknesswise of the elastic member (1), wherein the through-holes (8) each extend thicknesswise through the elastic member (1). A production method includes forming the elastic member by vulcanizing a rubber composition in a vulcanization mold having projections corresponding to the recesses or the through-holes.

Description

TECHNICAL FIELD[0001]The present invention relates to a sheet conveying roller to be used for conveying sheets in electrostatic copying machines, various types of printers and the like, and to a production method for the sheet conveying roller.BACKGROUND ART[0002]Various types of sheet conveying rollers are incorporated in sheet conveying mechanisms provided, for example, in electrostatic copying machines, laser printers, plain paper facsimile machines, copier-printer-facsimile multifunction machines, inkjet printers, automatic teller machines (ATM) and the like.[0003]Examples of the sheet conveying rollers include sheet feed rollers, transport rollers, platen rollers and sheet output rollers, which are each adapted to be rotated in frictional contact with a sheet (the term “sheet” is herein defined to include a paper sheet, a plastic film and the like, and this definition is effective in the following description) to convey the sheet.[0004]Such a conventional sheet conveying roller...

AI Technical Summary

Benefits of technology

The present invention provides a sheet conveying roller that reduces paper dust and dirt accumulation to prevent sheet transportation failure. It is less likely to slip and maintains constant speed even when transporting sheets with high paper dust and dirt content. It is also less likely to change its outer diameter due to wear and compressive deformation, preventing sheet wrinkling or indentation even at higher contact pressure. The patent also provides efficient production methods for the sheet conveying roller, increasing productivity.

Problems solved by technology

However, paper dust and dirt generated from paper sheets are liable to adhere to the outer peripheral surface of the elastic member.

This reduces the contact area and the frictional coefficient of the elastic member with respect to a paper sheet, thereby causing sheet transportation failure at a relatively early stage.

The higher ash content paper sheets are more liable to generate paper dust and dirt, so that the accumulation of the paper dust and the dirt and the sheet transportation failure attributable to the accumulation are more liable to occur.

However, the knurled roller suffers from the following problem, because the grooves extend axially of the elastic member along the entire width of the elastic member.

This makes it impossible to maintain the transportation force at a constant level.

This makes it impossible to maintain the transportation speed at a constant level.

Where paper sheets having a greater amount of paper dust and dirt are occasionally transported, for example, the grooves extending along the entire width of the knurled roller simultaneously lose the scratching effect along their entire lengths, so that the sheets are liable to suffer from slippage.

Therefore, the knurled roller liable to suffer from the pulsation of the transportation speed and the slippage is not suitable for a use application requiring precise sheet feeding or for a use application requiring the control of the sheet feed amount for the sheet feeding.

In addition, a sheet contact pressure does not act on a groove portion of the knurled roller and, if the sheet contact pressure is set at a higher level, there is a great difference in contact pressure between the groove portion and portions of the knurled roller located at opposite sides of the groove portion, resulting in wrinkle or indentation of the sheet.

However, the porous elastic member has a smaller density, and is liable to be worn or suffer from a so-called permanent compressive deformation which is a phenomenon such that the elastic member is not restored to its original diameter after being compressed for a long period of time.

Therefore, the sheet conveying roller including the porous elastic member is more liable to suffer from the wear and the permanent compressive deformation and, hence, has a shorter product service life than a sheet conveying roller including a non-porous elastic member.

That is, the sheet feed amount is not constant, but constantly changed due to the wear and the permanent compressive deformation of the elastic member.

Therefore, the sheet conveying roller including the porous elastic member is not suitable for a use application requiring precise sheet feeding or for a use application requiring the control of the sheet feed amount for the sheet feeding.

If the number of the openings is locally reduced or the diameters of the individual openings are locally reduced in some region on the outer peripheral surface, for example, the openings in the region fail to sufficiently function as the pockets for trapping the paper dust and the dirt, thereby failing to sufficiently suppress the sheet transportation failure attributable to the accumulation of the paper dust and the dirt.

However, the grooves extending circumferentially of the outer peripheral surface fail to sufficiently function as pockets for trapping paper dust and dirt as compared with the aforementioned axial grooves and the openings of the porous cells.

However, the circumferential grooves extend generally parallel to the direction of the rotational force, thereby failing to efficiently convey and trap the paper dust and the dirt by the rotational force.

Therefore, the circumferential grooves fail to sufficiently function as the pockets for trapping the paper dust and the dirt.

In addition, a sheet contact pressure does not act on a groove portion of the sheet conveying roller and, if the sheet contact pressure is set at a higher level, there is a great difference in contact pressure between the groove portion and portions of the sheet conveying roller located at opposite sides of the groove portion, resulting in wrinkle and indentation of the sheet.

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