METHOD AND DEVICE FOR SUPPLYING THE PAPER IN THE PRINTER

Abstract: To avoid paper sagging in a printer, especially occurring when fan fold paper is moved backward before and forward after an interrupt printing on cut sheet paper, a method for initially setting fan fold paper or for resetting fan fold paper after an intermediate cut sheet printing in a printer comprising a platen (1), a paper pressing member (5) having its tip resiliently contacting said platen (1) and a pushtractor (2) for feeding fan fold paper is suggested, wherein the fan fold paper (P) is first fed past the paper pressing member into a first position, is then reciprocated at least once between said first position and a second position where the front edge of the paper lies between said first position and said paper pressing member (5) near to the latter and is finally fed into a print start position. A device for supplying the paper in a printer to carry out this method is also disclosed.

Description: The present invention relates to a printer providing the possibility of selection between cut sheet paper and fan fold paper, and more specifically to the method and the device for feeding the paper. In a conventional printer adapted to process both, cut sheet paper and fan fold paper, in order to realize an interrupt printing, i.e. an interruption of printing on fan fold paper for temporarily printing on a cut sheet paper, the fan fold paper printing process is stopped and the fan fold paper moved away from the paper feeding path to allow the cut sheet printing. When the cut sheet printing has ended, the fan fold paper is returned to the position it had when the interrupt started, so that the printing of the fan fold paper can start again (JP-A-60-44379). However, the forward and backward movement of the fan fold paper causes a paper sagging within the paper feeding path, thereby also causing a print displacement. The document US-A-4,645,365 discloses a paper feed system in a printer including a platen for supporting a paper sheet, a paper feed drive motor and a transmission gear mechanism for transferring the rotation of the paper feed drive motor to the platen so as to conduct an automatic paper feed operation. The known paper feed system further allows a manual paper feed operation wherein the platen is manually rotated. A detection system is provided which detects the manual paper feed operation. If the manual paper feed operation has been conducted before the automatic paper feed operation, a compensating paper drive is first conducted when an automatic paper feed instruction is developed. In the compensating paper drive, the platen is first driven to rotate in the reverse direction by a predetermined amount and, then to rotate in the forward direction by the same amount, thereby compensating for the displacement of the paper sheet location caused by the backlash of the transmission gear mechanism during the manual paper feed operation. It is an object of the present invention to overcome the above stated problem of the prior art and to provide a method and a device for feeding fan fold paper in a printer, allowing an accurate repositioning of fan fold paper after an interrupt printing. This object is achieved with a method and a device, respectively, as claimed. By the repeated forward and backward feeding of the fan fold paper any paper sagging which may occur at the print start or the print restart after an interrupt printing is securely removed and a print displacement after a print restart can be prevented. This ensures a high quality printing. On way of carrying out the invention is described in detail below with reference to drawings which illustrate only one specific embodiment, and in which: Fig. 1 is a diagrammatic view of one embodiment of the invention, Fig. 2 is a block diagram of one embodiment of the control device, Fig. 3 is a flow chart for explaining the operation of the invention, and Fig. 4 is a view for explaining the reciprocation of the fan fold paper according to the invention. In Fig. 1 reference numeral 1 designates a platen, 2 a pushtractor for supplying fan fold paper, 3 a cut sheet feeder for supplying cut sheet paper, 4 a paper guide, 5 a paper pressing member, 6 a printing head and 7 a paper sensor. Tractor 2 and cut sheet feeder 3 are disposed on the upstream side of platen 1 with respect to the paper feeding direction A. Paper supplied by either tractor 2 or cut sheet feeder 3 is guided by paper guide 4 to the paper pressing member 5 to be fed to the printing area. Paper sensor 7 provided on the upstream side of platen 1 with respect to the paper feeding direction A serves to detect a reference position of the fan fold paper. Both, platen 1 and tractor 2, are driven by a common pulse motor 9 through a transmitting mechanism not shown. Pulse motor 9 is controlled by a motor driving circuit 10 which receives control signals from a control device 20 comprising a micro computer and from a host unit. A paper selecting switch 11 provided on an operation panel of the printer is used to select between cut sheet paper and fan fold paper. Fig. 2 shows one embodiment of the control device 20. In this embodiment the control device comprises a paper kind detector 21, a paper feeding amount detector 22, a memory 23, a coincidence detector 24, a reference position detector 25, a reciprocation amount setting means 26 and a reciprocation instruction means 27. The paper kind detector 21 detects which kind of paper has been selected by means of the paper selecting switch 11. The paper feeding amount detector 22 detects the paper feeding amount by counting the driving pulses supplied to pulse motor 9 from the time when the paper tip reaches a reference position, for example when the paper tip reaches the paper sensor 7. Depending on the direction of rotation of the pulse motor 9, the count value in the paper feeding amount detector 22 is increased or decreased. The memory 23 stores the contents of the paper feeding amount detector 22 at the time when during fan fold paper printing an interrupt printing is ordered and a corresponding signal output from the paper kind detector 21. The coincidence detector 24 compares the data stored in memory 23 with the contents of the paper feeding detector 22 and outputs a signal for stopping the pulse motor 9 when fan fold paper printing has to be restarted after the signal from the paper kind detector 21 indicated the end of an interrupt printing. The reference position detector 25 outputs a signal each time the fan fold paper passes the reference position. Using this signal, the fan fold paper is fed so that the paper tip projects a predetermined amount, for example 30 to 40 mm, from the paper pressing member 5, and the paper reciprocation between a paper bail 8 and the paper pressing member 5 can be performed. A stroke amount l′ within the above mentioned predetermined amount has been previously set in the reciprocation amount setting means 26. The pulse motor 9 is driven according to the preset stroke amount l′ by the reciprocation instruction means 27 to reciprocate several times, as will be explained in detail later. The operation of the above explained embodiment of the invention will next be explained in detail with reference to the flow chart of Fig. 3. When the process is started, it is decided in step (a) whether fan fold paper is selected by the paper selecting switch 11. If the answer is YES, pulse motor 9 is controlled to drive platen 1 and tractor 2 in such a manner that the circumferential speed of the platen 1 is slightly higher than that of the tractor 2. The fan fold paper is thus advanced and guided by the paper guide 4 from a refuge area (step (b)). During this feeding of the fan fold paper it is detected whether the tip of the paper passes the paper sensor 7 and a signal is output from the reference position detector 25 in step (c). Upon the signal from the reference position detector 25, the fan fold paper is further advanced by the reciprocation instruction means 27 until it projects for a predetermined amount l from the paper pressing member 5 (step (d)). This condition is shown in Fig. 4(I). After that the reciprocation instruction circuit 27 outputs a driving signal corresponding to the stroke amount l′ preset in the reciprocation amount setting means 26. In response to this driving signal, the motor driving circuit 10 drives the pulse motor 9 in the reverse direction to cause a backward feeding of the fan fold paper by tractor 2 (step (e)) (Fig. 4 (II)). Before the tip of the paper passes the paper pressing member 5 in the backward direction (opposite to arrow A in Fig. 1), the direction of rotation of pulse motor 9 is switched to forward rotation again (step (f)). Then the fan fold paper is again advanced towards the printing head 6 (step (g)) until it is detected in step (h) that the paper has been fed by the stroke amount l′. After this reciprocation of the fan fold paper has been repeated a predetermined number of times (step (i)), the paper is fed to the initial position (shown in Fig. 4 I) and maintained (step (j)). By the above mentioned reciprocation of the fan fold paper P tension is applied in the paper feeding direction by the sliding contact and, thus, any sagging of the paper is removed. When this initial setting is completed, a printing signal is input. Then, the printing head 6 is operated and transversely moved relative to the paper (step (k)). At the end of a printing line pulse motor 9 is activated to have the paper advanced to the next printing line by tractor 2 . The amount of this paper feeding is detected and kept by the paper feeding amount detector 22 (step (l)). During the printing operation, if printing of a cut sheet is required, cut sheet paper is selected by means of the paper selecting switch 11. The paper kind detector 21 detects the interrupt printing at step (m) and stops printing by stopping the pulse motor 9. At the same time the current content of the paper feeding amount detector 22 is stored in the memory 23 (step (o)). Pulse motor 9 is rotated in the reverse direction to cause the tractor 2 to retract the fan fold paper P back to the tractor side (step (o)). The amount of backward movement of the paper is subtracted from the feeding amount held by the paper feeding amount detector 22 when the printing was stopped, until the front edge of the paper passes the reference position. When the fan fold paper is retracted to a predetermined position (step (p)), clearing the way for the cut sheet printing, the reverse rotation of pulse motor 9 is stopped (step (q)). In this condition, the cut sheet is set to perform the interrupt printing. To end the interrupt printing, fan fold paper is again selected by the paper selecting switch 11, causing paper kind detector 21 to output a corresponding signal. When this is detected in step (r), the tractor 2 is driven to feed the fan fold paper P towards the platen 1. When during this process the tip of the fan fold paper passes the paper sensor 7, a signal is output to the reciprocation instruction means 27. Then the paper feeding is continued and reciprocation of the paper carried out in the same way as described above according to steps (b) to (i) in Fig. 3. After the paper has been reciprocated the predetermined number of times, the reciprocation instruction means 27 controls pulse motor 9 to feed the fan fold paper towards the printing head 6. During this feeding, the amount of paper feeding is detected by the paper feeding amount detector 22 until the detected paper feeding amount coincides with the data stored in memory 23 (steps (j) and (s)). At this moment, the paper has reattained the position where the interrupt printing started. The coincidence detector 24 outputs the coincidence signal to motor driving circuit 10 to stop the paper feeding. Thereby, the fan fold paper is set to exactly the same condition it had before refuging. At this time, the text to be printed is called to restart the printing, thereby continuing the printing from the position where it was stopped. In the above described embodiment, platen 1 and tractor 2 are driven by a common pulse motor 9. The invention may, however, also be realized with the platen and the tractor being driven by independent motors. Explanation to Fig. 3 (a) fan fold paper selected? (b) feed paper (c) reference position of fan fold paper detected? (d) feed paper by l and update the paper feeding amount detector 22 (e) retract paper and update the paper feeding amount detector 22 (f) paper retracted by l′? (g) feed paper and update the paper feeding amount detector 22 (h) paper fed by l′? (i) reciprocation performed a preset number of times? (j) count value of feeding amount detector 22 equal to value stored in memory 23? (k) print one line (l) advance paper by one line and update the paper feeding amount detector 22 (m) interrupt instruction? (n) store current value of feeding amount detector 22 in memory 23 (o) retract fan fold paper and update feeding amount detector 22 (p) fan fold paper back in refuge position? (q) stop motor (r) interrupt printing completed? (s) advance paper until the value of the feeding amount detector 22 equals that of memory 23 (t) everything printed?

Claims: A method for controlling the feeding of fan fold paper in a printer comprising a platen (1) and a pushtractor (2) for the feeding fan fold paper, said printer being adapted to selectively feed fan fold paper or cut sheet paper, wherein said method comprising the steps of: (1) selecting a fan fold paper mode, (2) feeding the fan fold paper (P) in a forward direction about the platen and detecting the amount of paper fed in the forward direction, (3) detecting whether an interrupt signal occurred indicating that a cut sheet mode has been selected, (4) feeding, in response to an interrupt signal, the fan fold paper in a reverse direction equal to said detected amount by which the fan fold paper was fed in the forward direction, and (5) feeding the fan fold paper upon the completion of the feeding of the cut sheet paper, in the forward direction by said detected amount, characterized in that step (5) comprises the substeps of (a) forward feeding the fan fold paper into a first position past a paper pressing member (5) resiliently contacting said platen (1), (b) backward feeding the fan fold paper by a predetermined distance into a second position where the front edge of the fan fold paper lies between said first position and said paper pressing member (5) near to the latter (c) forward feeding the fan fold paper by said predetermined distance, and (d) forward feeding the fan fold paper into a position corresponding to said detected amount. The method of claim 1, wherein substeps (b) and (c) are repeated a preset number of times before substep (d) is performed. A paper feeding device in a printer adapted to selectively feed fan fold paper or cut sheet paper, comprising a platen (1), a pushtractor (2) for feeding fan fold paper, said pushtractor being located on the upstream side of said platen (1) with respect to the forward feeding direction (A) of the fan fold paper, and control means (20) adapted to drive the push tractor in a reverse direction to remove the fan fold paper from the paper feeding path upon the feeding of cut sheet paper and to feed, upon completion of cut sheet paper feeding, the fan fold paper again in the forward direction for a length equal to the amount that the fan fold paper was fed in the reverse direction to return the fan fold paper to its previous printing position, characterized by a paper pressing member (5) resiliently contacting said platen (1), wherein said control means acts to feed, upon completion of cut sheet paper feeding, the fan fold paper past the paper pressing member (5) into a first position, to reciprocate the fan fold paper between this first position and a second position where the front edge of the fan fold paper (P) lies between said first position and said paper pressing member (5) near to the latter, at least once, and then to return the fan fold paper to its previous printing position. The device according to claim 3, wherein said control means (20) comprises: a reference position detector (25) for outputting a detection signal each time the fan fold paper passes a reference position, a reciprocation instruction means (27) for controlling the reciprocation of the fan fold paper, a feeding amount detector (22) for up- and down-counting the feeding amount of the fan fold paper depending on the feeding direction, a memory (23) for storing the content of said feeding amount detector (22) and a coincidence detector (24) for comparing the contents of the feeding amount detector (22) with that of the memory (23), wherein said reciprocation instruction means (27) causes said reciprocation of the fan fold paper upon a detection signal from the reference position detector (25), and said coincidence detector (24) controls the paper feeding into a print start position until coincidence between the content of the feeding amount detector (22) and that of the memory (23) is detected, and wherein upon an interruption instruction signal the current contents of the feeding amount detector (22) is stored in the memory (23) prior to removing the fan fold paper from the paper feeding path for interrupt printing of cut sheet paper. The device of claim 3 further comprising: switch means (11) for outputting an indication signal indicating that one of a cut sheet mode corresponding to feeding of cut sheet paper and a fan fold mode corresponding to feeding of fan fold paper has been selected, a paper detector (7) for detecting the presence of the leading edge of the fan fold paper at a predetermined position and a driving circuit (10) for driving the push tractor (2) in response to an output from the control means (20), the control means including: switch detector means (21) for detecting the indication signal and providing an interrupt signal when the indication signal indicates a cut sheet mode, paper feed detector means (22) for detecting the amount of fan fold paper fed by the push tractor prior to the producing of the interrupt detection signal and outputting the amount detected, memory means (23) for recording the amount detected by the paper feed in response to the interrupt signal, coincidence detector means (24) for producing a stop motor signal when the paper feed amount is equal to the amount stored in the memory means, the driving circuit causing the push tractor to stop feeding in response to the stop motor signal, a reference position detector (25) for outputting a reference position detect signal when the paper detector means (7) has detected the leading edge of the fan fold paper, reciprocation setting means (26) for storing a predetermined reciprocation distance and producing a distance output signal, and reciprocation instruction means (27) for receiving the reference position detect signal and the distance output signal and outputting a reciprocation instruction signal to cause the push tractor to feed said fan fold paper in a forward and backward manner in response thereto.

Inventors: KATO, TAKASHI, MURAYAMA, SUSUMU, OSHIMA, KEIICHI
Applicants: SEIKO EPSON CORPORATION
Application year: 1989
Main classification: B41J15
IPC codes: B41J15, B41J11