CONTROL METHOD OF AUTOMATIC SHEET FEEDER

Abstract: The feeder supplies sheets (4, 5) selectively from hoppers (2, 3) to a printer (11). Hopper selection signals inputted from the control unit of the printer to the automatic sheet feeder and a sheet feed instruction signal are pulse signals having a short pulse width and a long pulse width with respect to a predetermined time width respectively, and are multiplexed and transferred as a control signal over a single signal line. The pulse of the multiplexed control signal is compared with the predetermined time width and these two kinds of signals are discriminated. Selection of the hoppers (2, 3) is made in accordance with the number of the inputted hopper selection signals and the feed of sheets is started by the sheet feed instruction signal. @(19pp Dwg.No.2/6)@

Description: The present invention relates to a method of controlling an automatic sheed feed installed on an impact printer and, more particularly, to a method of controlling an automatic sheet feed having a plurality of sheet hoppers to change the sheet hoppers automatically. BACKGROUND ART An automatic sheet feed installed on an impact printer feeds sheets one at a time to the impact printer. In changing sheets having a width for sheets having a different width on such an automatic sheet feed, the positions of sheet guides provided on a sheet hopper must be adjusted according to the width of the sheets. A recently developed automatic sheet feed is provided with a plurality of sheet hoppers respectively containing sheets of different widths to feed selected sheets from the sheet hoppers (see document US.A. 4 222 660). Fig. 6 is a time chart showing the operation of an automatic sheet feed provided with two sheet hoppers (hereinafter, referred to as "dual hopper automatic sheet feed") among conventional automatic sheet feeds provided with a plurality of sheet hoppers. The printer gives a sheet hopper select signal 51 to the automatic sheet feed in selecting either sheet hopper. A sheet delivery signal 62 commands the operation of a delivery roller, namely, a signal to drive a stepping motor provided in the automatic sheet feed. Upon the reception of the sheet delivery signal 52, the automatic sheet feed selects either sheet hopper corresponding to the hopper select signal 51, and drives the stepping motor to rotate the delivery roller for feeding a sheet from the selected sheet hopper to the printer. Upon the detection of the sheet by a detector, not shown, the printer gives a signal to stop sheet feeding operation to the automatic sheet feed, and then the automatic sheet feed stops the stepping motor to stop sheet feeding operation. Indicated at 53 is a line representing the sheet feeding speed of the automatic sheet feed. In case a sheet feed command is given in a state where the hopper select signal is not transmitted properly from the printer to the automatic sheet feed, the sheet hopper specified previously in the firmware stored in the automatic sheet feed is selected when the sheet feed command is given immediately after the automatic sheet feed has been connected to a power source or the sheet hopper selected by the preceding hopper select command becomes active when the sheet feed command is given during operation. This control method, however, requires a signal line for transmitting the hopper select signal 51 for selecting either sheet hopper, and signal line for transmitting a sheet delivery signal 52 requesting feeding a sheet. Once a host computer for controlling the printer has given a command for initial resetting, the printer is unable to send a new hopper select signal to the automatic sheet feed and, in some cases, the automatic sheet feed selects a wrong sheet hopper. The present invention provides a method of controlling a dual hopper automatic sheet feed, capable of solving problems resulting from the individual use of a signal line for sheet hopper selection and a signal line for starting sheet feed, and capable of controlling sheet feeding operation by using a single signal line. DISCLOSURE OF THE INVENTION The present invention provides a method of controlling an automatic sheet feed provided with a plurality of sheet hoppers which are used selectively to feed sheets to a printer, characterized in that a hopper select signal and a sheet delivery signal are given through a single signal line from the printer to the automatic sheet feed, the pulse width of the hopper select signal is smaller than that of the sheet delivery signal, the hopper select signal having a smaller pulse width is given to the automatic sheet feed to select the sheet hopper corresponding to the number of pulses of the hopper select signal, a stepping motor is driven to feed a sheet when the sheet delivery signal is given to the automatic sheet feed after the sheet hopper has been selected. Since the sheet hopper can be selected and sheet feed operation can be started by signals transmitted through a single signal line, the cost of control operation is reduced and the automatic sheet feed is inexpensive. Furthermore, in executing initial setting in response to a command given by a host computer for controlling the printer after the hopper select signal has been given to the automatic sheet feed, the sheet delivery signal can be cancelled by giving a hopper select signal for selecting a new sheet hopper from the printer to the automatic sheet feed, and hence selection of a wrong sheet hopper is obviated and correct operation can be expected. BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a perspective view of an automatic sheet feed embodying the present invention; Fig. 2 is a sectional view of an automatic sheet feed embodying the present invention; Fig. 3 is a block diagram of an automatic sheet feed embodying the present invention; Fig. 4 is a time chart of assistance in explaining a method of controlling an automatic sheet feed, embodying the present invention; Fig. 5 is a flow chart of a method of controlling an automatic sheet feed, embodying the present invention; and Fig. 6 is a time chart of assistance in explaining a conventional method of controlling an automatic sheet feed. BEST MODE FOR CARRYING OUT THE INVENTION Fig. 1 and 2 are a perspective view and a sectional view, respectively, of an automatic sheet feed emboding the present invention. Referring to Figs. 1 and 2, indicated at 1 are connecting lugs for connecting an automatic sheet feed to a printer, at 2 is a sheet hopper for holding a stack of sheets for printing, and at 3 is a sheet hopper similar to the sheet hopper 2. The sheet hoppers 2 and 3 hold the same kinds or different kinds of sheets. The sheet hoppers 2 and 3 are provided with delivery rollers 6 and 7 for feeding the sheets 4 and 5 held therein one sheet at a time, respectively. The delivery rollers 6 and 7 are interlocked through a one-way, not shown, with a stepping motor. Either the delivery roller 6 or 7, depending on the rotating direction of the stepping motor, is driven. The sheet 4 or 5 delivered from the sheet hopper 2 or 3 in response to a control signal given by the printer is held between a platen 8 and clamping rollers 9 and 10 pressed against the platen 8 and is fed as the platen 8 rotates. A print head 11 strikes, through an ink ribbon, the sheet 4 or 5 pressed against the platen 8 for printing. Then, the sheet 4 or 5 is delivered by rollers 12 and 13 pressed against each other to a stacker 14. Roller Δ 15 and 16 (17 and 18) which operate in synchronism with the rotation of the platen are provided to deliver the sheet 4 (5) delivered by the delivery roller 6 (7) to the platen in synchronism with the operation of the print head 11. The automatic sheet feed is provided with a hand feed slit 19 for manual sheet feed. Fig. 3 is a block diagram of an automatic sheet feed embodying the present invention. Referring to Fig. 3, the control unit 21 of the printer is connected to the control circuit 23 in the form of a one-chip microcontroller of the automatic sheet feed by an interface signal line 22. The control circuit 23 comprises a CPU 24, a ROM 25 storing programs, RAM 26 for storing data and results of intermediate calculations, an I/O port 27 for exchanging control signals therethrough with the printer, and an I/O port 28 for exchanging control signals therethrough with a stepping motor driving circuit 29. The stepping motor driving circuit 29 drives a stepping motor 30 for driving the delivery rollers 6 and 7 to deliver the sheets held by the sheet hoppers one by one. A method of controlling the automatic sheet feed, embodying the present invention will be described hereinafter with reference to a time chart shown in Fig.4 and a flow chart shown in Fig. 5. Referring to Figs. 4 and 5, indicated at 31 is a control signal given from the printer to the automatic sheet feed, and at 32 is a line representing sheet delivery speed at which the sheets 4 or 5 are delivered. T₁ and T ₂ are pulses of the control signal 31 given from the printer to the automatic sheet feed for sheet hopper selection. A pulse T₄ in the control signal 31 given from the printer to the automatic sheet feed commands the automatic sheet feed to deliver the sheets 4 or 5. On the line 32, T₃ is a delay time by which the actuation of the stepping motor 30 is delayed from a moment when the automatic sheet feed receives a control signal commanding the delivery of the sheet 4 or 5. Upon the reception of the control signal 31 and print data from the host computer, the printer gives the pulses T₁ and T₂ to the automatic sheet feed before giving a signal to the automatic sheet feed to deliver the sheet 4 or 5. The pulses T₁ and T₂ may have the least sufficient widths necessary only for sheet hopper selection and are far shorter than the delay time T₃. One of the sheet hoppers a (for example, the sheet hopper 2 in Fig. 1) and b (for example, the sheet hopper 3 in Fig. 1), for example, the sheet hopper a, is selected when only the pulse T₁ is applied to the automatic sheet feed, and the other sheet hopper b is selected when both the pulses T₁ and T₂ are applied to the automatic sheet feed. If the pulse T₄ requesting delivering a sheet is applied to the automatic sheet feed before applying neither pulse T₁ nor the pulse T₂ to the automatic sheet feed, the automatic sheet delivers the sheet held by the sheet hopper selected by the preceding hopper select command or either the sheet 4 held by the sheet hopper a or the sheet 5 held by the sheet hopper b, specified beforehand as an initial condition. The operation of the automatic sheet feed embodying the present invention will be described with reference to the flow chart shown in Fig. 5. Step 1: The CPU 24 selects the sheet hopper a as a default. Step 2: The automatic sheet feed stands waiting for control signals. Step 3: The automatic sheet feed measures the pulse width of the pulse T₁ upon the reception of the pulse T₁ from the printer. Step 4: The CPU 24 makes a query to see if the pulse width of the pulse T₁ is not longer than the delay time T₃. Step 5 is executed when the response is affirmative or the program jumps to Step 12 when the response is negative. Step 5: The sheet hopper a is selected. (The default is maintained.) Step 6: The automatic sheet feed stands waiting for the reception of the pulse T₂ through the signal line 22. Step 7: The pulse width of the pulse T₂ is measured. Step 8: The CPU 24 makes a query to see if the pulse width of the pulse T₂ is not longer than delay time T₃. Step 9 is executed when the response is affirmative or the program jumps to Step 12 when the response is negative. Step 9: The sheet hopper b is selected. Step 10: The automatic sheet feed stands waiting for the reception of the pulse T₄ through the signal line 22 from the printer. Step 11: The automatic sheet feed remains inoperative for the delay time T₃ after the reception of the pulse T₄. Step 12: The delivery roller of the selected sheet hopper is actuated to start feeding a sheet. Step 13: The stepping motor 30 is driven according to a predetermined profile of rotating speed during the duration of the pulse T₄. Step 14: The stepping motor 30 is stopped at the fall of the pulse T₄ to stop the delivery roller. The sheet drawn out from the sheet hopper by the delivery roller 6 (or 7) is delivered to the platen 8 by the rollers 15 and 16 (or 17 and 18) rotating in synchronism with the platen 8. Then, the print head 11 prints on the sheet. The sheet is delivered to the stacker 14 after the completion of printing on the sheet. For example, the present invention is applicable to controlling an-automatic sheet feed provided with three or more sheet hoppers. When the automatic sheet feed is provided with a plurality of sheet hoppers, pulse signals respectively each having a number of pulses representing each sheet hopper are used, and the selected sheet hopper is identified by the number of pulses included in the pulse signal. CAPABILITY OF EXPLOITATION IN INDUSTRY As is apparent from the foregoing description, a method of controlling an automatic sheet feed in accordance with the present invention uses a single signal line for selecting of a sheet hopper and for initiating the delivery of a sheet. Accordingly, the method curtails the number of signal lines of the system, simplifies the control of signals, and hence enables the use of an inexpensive automatic sheet feed.

Claims: A method of controlling an automatic-sheet feeder provided with a plurality of sheet hoppers (2, 3) which are used selectively for delivering sheets (4, 5) to a printer, characterized in that: a control signal including a hopper select signal and a sheet delivery signal is transmitted from the printer to the automatic sheet feed through a single signal line (31), the pulse width of pulses (T₁, T₂) of the hopper select signal is smaller than that of a pulse of the sheet delivery signal, and each selected sheet hopper (2, 3) is identified by the number of pulses (T₁, T₂) of the hopper select signal A method of controlling an automatic sheet feed according to Claim 1, wherein the hopper select signal is given to the automatic sheet feed before the sheet delivery signal. A method of controlling an automatic sheet feed provided with a plurality of sheet hoppers which are used selectively to feed sheets to a printer, characterized in that: a control signal including a hopper select signal and a sheet delivery signal is transmitted from the printer to the automatic sheet feed through a single signal line (31), the pulse width of pulses (T₁, T₂) of the hopper select signal is smaller than that of a pulse of the sheet delivery signal, the control signal is taken for the hopper select signal when the pulse width of the pulse or pulses (T₁, T₂) is smaller than a predetermined time T₃) or for a sheet delivery signal when the same is greater than the latter, the selected sheet hopper (2, 3) is identified for sheet hopper selection by the number of pulses of the hopper select signal, and the automatic sheet feed starts an operation to deliver the sheet (4, 5) after a delay corresponding to the predetermined time (T₃) from the reception of the sheet delivery signal.

Inventors: KIKUCHI, HIROSHI OKI ELECTRIC INDUSTRY CO., LTD., NAGUMO, AKIRA OKI ELECTRIC INDUSTRY CO., LTD., TANUMA, JIRO OKI ELECTRIC INDUSTRY CO., LTD., UCHIDA, TAKAO OKI ELECTRIC INDUSTRY CO., LTD.
Applicants: OKI ELECTRIC INDUSTRY COMPANY, LIMITED
Application year: 1989
Main classification: B65H3
IPC codes: B65H3, B41J13