Cut-sheet feeder control method

Details Cut-sheet feeder control method Cut-sheet feeder control method

1990-06-21

1992-03-31

Eickholt, Eugene H.

Sheet feeding or delivering

Feeding

Separators

271110, 271270, 400624, 318696, B65H 330, B41J 1158

Patent

active

051001209

DESCRIPTION:

BRIEF SUMMARY
DESCRIPTION

1. Technical Field
The present invention relates to a method of controlling the sheet feeding operation of a cut-sheet feeder mounted on an impact printer to feed a cut-sheet to the printing unit of the impact printer and, more particularly, to a method of controlling the sheet feeding operation of a cut-sheet feeder so that the cut-sheet feeder will feed a cut-sheet at a feed speed equal to the sheet feeding speed of the associated printer.
2. Background Art
Conventional impact printers are classified generally into those which prints on a continuous forms paper and those which print on a cut sheet. Some impact printers using cut sheets require a hand-feed operation. Recently, a cut-sheet feeder for automatically feeding a cut sheet to the printing unit of a printer has been used.
The cut-sheet feeder comprises a hopper containing cut sheets to be supplied to a printer, a sheet feed mechanism for feeding the cut sheets contained in the hopper one at time to the printing unit of the printer, a motor for driving the sheet feed mechanism, a power transmission mechanism for transmitting the power of the motor to the sheet feed mechanism, and a control unit which exchanges control signals with the printer to control the cut-sheet feeding operation. The cut-sheet feeder is actuated by a sheet feed command signal given thereto by the printer.
The controller of the printer gives the sheet feed command signal to the control unit of the cut-sheet feeder in setting a cut sheet in the printing unit of the printer. Upon the reception of the sheet feed command signal, the control unit actuates the motor to drive the sheet feed mechanism so that a cut sheet is delivered from the hopper. Then, the cut sheet advances along a sheet passage formed in the cut-sheet feeder, the cut sheet enters the rear portion of the printing unit of the printer obliquely downward, and the leading edge of the cut sheet reaches the circumference of the platen of the printing unit. The platen backs up the cut sheet when an impact is applied to the cut sheet for printing and rotates to feed the cut sheet. When the cut sheet is delivered to the platen, the platen rotates by winding the cut sheet around its circumference and stops when the cut sheet is settled at a predetermined position, where the printer starts printing. Thus, the cut sheet is set in place in the printing unit by the cooperative feed actions of the sheet feed mechanism of the cut-sheet feeder and the sheet feed mechanism of the printer.
Incidentally, the sheet feed speed of the printer is fixed and the platen rotates at substantially the same peripheral speed as that of the sheet. The sheet feed mechanism of the cut-sheet feeder is set so that its sheet feeding speed coincides with the sheet feeding speed of the printer. However, the sheet feed speed it is slightly variable, and hence it is possible that the sheet feeding speed of the cut-sheet feeder may deviate from that of the printer. When the sheet feed speed of the cut-sheet feeder and that of the printer do not coincide exactly with each other, the cut sheet may be slackened or tightened excessively between the sheet feeder and the platen to jam the printer with the cut sheet or to cause the cut sheet to be torn.
The variation of the sheet feed speed of the cut-sheet feeder is attributable to variation in the frequency of a clock signal for timing the sheet feed control operation of the cut-sheet feeder. The cut-sheet feeder, in general, employs a stepping motor as its power source because the stepping motor is easy to control. The shaft of the stepping motor rotates at a rotating speed corresponding to the frequency of a driving signal given to the stepping motor by the control unit of the cut-sheet feeder. This driving signal is produced by the control unit according to the clock signal.
The control unit of the cut-sheet feeder comprises a microcomputer comprising a central processing unit (hereinafter, abbreviated to "CPU"), memories, an input-output port in order to communicate with the printer (hereinaf

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