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Automatic document feeder/separator for copiers

  • US 4,750,726 A
  • Filed: 05/28/1987
  • Issued: 06/14/1988
  • Est. Priority Date: 05/28/1987
  • Status: Expired due to Fees
First Claim
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1. In a sheet feeder for a copier for the sequential separation and feeding of individual sheets sequentially from a stack of sheets in a sheet stacking tray by means of an impact type sheet feeder in which the top sheet of the stack to be fed is repeatedly impacted by overlying driven flexible frictional flapper blades adjacent a downstream end of the stack, which frictional flapper blades flex against the top sheet of the stack during impact therewith and feed the top sheet forward away from the downstream end of the stack;

  • the improvement comprising;

    repositioning means for automatically moving said sheet stacking tray with the stack of sheets thereon and said impact sheet feeder towards or away from one another;

    reference stop means for automatically limiting said movement of said sheet stacking tray towards said impact sheet feeder by said stack repositioning means to a maximum limit position of the top of the stack relative to said impact sheet feeder;

    said stack repositioning means having a first positioning mode for automatically repositioning said sheet stacking tray with the stack of sheets thereon into said maximum limit position of the top of the stack;

    said stack repositioning means having a second positioning mode for automatically slightly lowering said sheet stacking tray with the stack of sheets thereon into an optimum feeding position, in which optimum feeding position the top of the stack of the sheets is maintained at a substantially constant level position relative to said impact sheet feeder, which optimum feeding position is closely adjacent, but slightly spaced below, said maximum limit position of the top of the stack,said stack repositioning means automatically maintaining said repositioning of said sheet stacking tray as sheets are fed from the stack to maintain said optimum feeding position of the top of the stack to automatically compensate for the reduction in the height of the stack as sheets are fed therefrom;

    said stack repositioning means having a third positioning mode for automatically lowering said sheet stacking tray with the stack of sheets thereon into a retard position which is different from said optimum feeding position;

    take away feeding means spaced from said stack and said impact type sheet feeder for feeding a sheet away from said stack after it has been initially fed by said impact type sheet feeder;

    sheet feeding sensor means for detecting and providing signals as to whether a sheet has been successfully fed from said stack by said impact sheet feeder and acquired by said take away feeding means;

    said stack repositioning means being controlled to operate in said third positioning mode for automatically lowering the stack of sheets into said retard position in response to signals from said sheet feeding sensor means;

    and frictional sheet retard means for frictionally engaging the next underlying sheet of the stack to resist double sheet feeding in said retard position.

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