Printing apparatus, method of controlling it, and data storage medium storing a computer program realizing the method

Abstract: Printer control prevents a user from pulling printed roll paper before it is cut off the roll while still providing the printed paper quickly to the user. When the printing of the paper ends and before cutting the paper by a paper cutting mechanism (13) is completed, paper is ejected from an ejection opening (11) by driving ejection rollers (15, 16). When a paper sensor (17) detects the trailing end of paper, paper is held by ejection rollers (16) to hold the trailing end of the paper ejected from ejection opening (11) and wait for the user to remove the paper from the opening.

Description: The present invention relates to a printing apparatus for printing on roll paper and to a method of controlling it; more particularly, the invention relates to the structure for and the control of the advancement of the roll paper after printing. Printers used in ATM machines, for example, typically print on roll paper or other type of continuous printing medium; after a printing operation has been completed an appropriate length of paper including the printed part is cut off the roll paper by means of an automatic cutting mechanism. The cut-off sheet (referred to as "slip" hereinafter) is delivered as a receipt or for other purposes. Such printers are often installed in unattended locations, making it very important to minimize the potential for problems arising in conjunction with normal use. Controlling advancement of the paper must be carefully considered in this type of printer. If the leading end of the paper is gradually ejected through a paper exit as the roll paper is advanced step by step for printing and after printing is completed, there is the danger that the user pulls the end of the paper projecting from the paper exit before the paper is cut; if this happens, print defects or a paper jam can occur. To prevent such problems, it is known to temporarily stop paper advancement by a pair of ejection rollers provided near the paper exit so that the leading end of the paper does not project from the paper exit. Once cutting the paper is then completed, the ejection rollers eject the slip from the paper exit (JP-A-1-181659, US-A-5,649,776). A problem with this type of printer is that the user must wait to remove the slip because advancement of the slip does not start until after both printing and then cutting off the slip are finished. Another problem with such printers is that it is possible that a slip becomes too short when little information is printed on the paper, resulting in the paper being cut before the leading end has reached the ejection rollers near the paper exit. In such cases the slip may not be ejected from the paper exit and thus be left inside the printer. An object of the invention is to resolve the above noted problems of the prior art and to provide a printer and a method of controlling it that allow a printed slip to be given out to the user as soon as possible after printing is completed. A further object of our invention is to provide a printer and a printer control method that reliably eject a slip from the paper exit even when little content is printed on the printing medium. These objects are achieved with a printer as claimed in claim 1 and a method as claimed in claim 3. Preferred embodiments of the invention are subject-matter of the dependent claims. The invention prevents the user from pulling on the printing medium before it is cut and yet provides the slip to the user quickly after printing is completed. Furthermore, problems such as tearing and jamming that may occur as a result of the user pulling on the printing medium while it is being cut, and conflict between cutting and transport operations, can be avoided and prevented by cutting the printing medium before it is advanced, or by slowing the feed rate to the paper exit when there is no sufficient amount of slack formed by stopping ejection of the printing medium while printing is in progress. Moreover, a printer and printer control method according to the present invention can reliably eject the cut-off slip from the paper exit even when the printed area of the printing medium is small. Printer throughput can be improved by controlling the printer in this way because slip ejection starts without waiting for the cutting operation to finish. While ejection of the printing medium starts before the slip is completely cut off, prohibiting ejection of the printing medium while printing is in progress produces an accumulation of printing medium (slack) inside the printer between the cutting mechanism and the paper exit. Therefore, even if the leading end of the printing medium is exposed from the paper exit before its cutting is finished and the user pulls on the exposed leading end, this will not immediately cause a cutting defect or contribute to a medium jam. Further objects and advantages of the invention will be described in detail below with reference to preferred embodiments of the invention and the accompanying schematic drawings, in which Fig. 1 is a side view showing the internal structure of a printer according to a first embodiment of the present invention; Fig. 2 and Fig. 3 are side views of the paper ejection area at various stages of the paper ejection control process in the printer shown in Fig. 1; Fig. 4 is a flow chart of the paper ejection control process shown in Fig. 2 and Fig. 3; and Fig. 5 is a flow chart of the paper feed process performed as step 411 in Fig. 4; Fig. 6 is a block diagram of a control circuit in a printer according to an embodiment of the present invention; and Fig. 7 is a flow chart of the paper ejection control process according to an alternative embodiment of the present invention. Fig. 1 is a schematic lateral view showing the internal structure of a printer 10 according to a first embodiment of the invention. It should be noted that various controllers 3a to 3d are represented as functional blocks in Fig. 1 with arrows drawn from each controller to the respective controlled parts. Printer 10 may be installed in an ATM machine, for example, for printing transaction receipts. A roll of paper R is housed inside printer 10 as a supply of printing medium. It should be noted that the term "paper" is used in this text as representative of any suitable kind of printing medium that is capable of being printed and provided in the form of a roll or other form that requires cutting. As mentioned before, the term "slip" is used in this text to refer a sheet of paper (recording medium) that has been printed and cut off the rest (unprinted part) of the paper (recording medium). A paper path is formed between that part of the printer that houses the paper roll and a paper exit 11. Disposed along this paper path are a print head 12 and a feed roller 14, a cutting mechanism 13, and ejection rollers 15 and 16. Note that feed roller 14 and ejection rollers 15 and 16 are together referred to as transport rollers. Ejection rollers 15 and ejection rollers 16 each comprise a pair of rollers, namely a drive roller and a pinch roller resiliently pressed against each other with a certain roller pressure. In the present embodiment, a thermal line type of print head is used as the print head 12 and the feed roller 14 also acts as a platen for supporting the paper while it is being printed by the print head 12. Cutting mechanism 13 is disposed near the print head 12 on the downstream side thereof in the direction of paper transport and is used for cutting off the printed part from the unprinted rest of the roll paper R to form a slip of receipt. Feed roller 14 transports paper R printed by print head 12 toward paper exit 11. Ejection rollers 15 and 16 are controlled to either hold the paper R advanced thereto by feed roller 14 so that the leading end of the paper is not ejected from the paper exit 11, or to continue advancing the paper R to and through the paper exit 11. The transport rollers are driven appropriately according to a print command from a host device 1 shown in Fig. 6 to gradually advance the paper R drawn off the roll to and past print head 12. Print head 12 is driven in conjunction with the advancement of the paper R by feed roller 14 to print the desired text, symbols, or graphics on the paper R according to the print command. The printed part of the paper R is further advanced toward the paper exit 11 by feed roller 14 controlled by first transport controller 3a as printing progresses. When the trailing end of the printed part reaches a specific position, the paper is cut by cutting mechanism 13 controlled by cutting controller 3c so that a single slip can be presented from the paper exit 11 to the operator or customer. The preferred cutting mechanism 13 has a fixed blade and a movable blade disposed with the paper path therebetween. The movable blade is driven by a motor, for example, to cut the paper between the movable blade and fixed blade. Ejection rollers 15 and 16 are controlled by a second transport controller 3b to grab the leading end of the paper R advanced by feed roller 14, and guide the paper to paper exit 11. Ejection rollers 15 and 16 normally advance the paper R at the same speed as feed roller 14. This means that when feed roller 14 and ejection rollers 15 and 16 are driven, no tension is applied to the paper R between feed roller 14 and ejection rollers 15 and 16, and no excessive slack occurs. After being cut off, a slip starts being advanced by ejection rollers 15 and 16, and substantially all of the slip is ejected out of paper exit 11. Finally, ejection rollers 16, which are on the downstream side, in the paper transport direction, of the ejection rollers 15, keep holding the trailing end of the slip. Incidentally, the holding force applied by ejection rollers 16 to the paper is smaller than that exerted by the ejection rollers 15. This can be simply achieved by setting the roller pressure, e.g., the strength of a spring (not shown in the figure), in one roller pair different from that in the other roller pair so as to achieve the desired roller pressure relationship. As further described below, the trailing end of the slip is finally held by ejection rollers 16. The slip can then easily be pulled out from paper exit 11 by the user because it is weakly pinched between the ejection rollers 16. As regards the control method of an embodiment of the present invention, second transport controller 3b controls ejection rollers 15 and 16 and first transport controller 3a controls feed roller 14 such that ejection rollers 15, 16 and feed roller 14 are driven and stopped independently of each other. As will be appreciated by those skilled in the art, such independent roller drive can be easily realized by utilizing two independent drive sources such as DC motors, or by connecting the transport rollers to a common drive source via respective clutch mechanisms. Printer 10 further has a paper sensor 17 disposed between the two pairs of ejection rollers 15 and 16. Paper sensor 17 detects the leading end of the paper R as it is advanced past ejection rollers 15, and then detects the trailing end of the slip when it passes by. Paper sensor 17 outputs detection signals to first and second transport controllers 3a, 3b and cutting controller 3c, which use these detection signals to accomplish various control steps of an embodiment of the present invention. As is more fully described below, slack is created in the paper between feed roller 14 and ejection rollers 15 when second transport controller 3b stops ejection rollers 15, 16 while first transport controller 3a drives feed roller 14. The amount of slack, that is, the accumulation of paper between these rollers, is measured by a slack detector 3d. More specifically, when the second transport controller 3b stops rotation of the ejection rollers 15, 16 in response to detection of the leading end of paper by the paper sensor 17, the slack detector 3d resets a stack counter, and then starts the slack counter to count the amount of the paper transportation reported by the first transport controller 3a. Printer 10 also has a storage unit 20 for storing slips left in the paper exit 11. More specifically, when a slip is detected left in the paper exit 11 for a predetermined period, or a predetermined command is received from host device 1, ejection rollers 15 and 16 are driven in reverse to draw the slip back into printer 10. The retrieved slip is guided by a path switching mechanism not shown to storage path 21 and from there is deposited in storage tray 22. As shown in Fig. 6, printer 10 has a controller 3 comprising a CPU 31, a ROM 32, and a RAM 33. The printer CPU 31 executes a control program stored in ROM 32, and controls various electrical and mechanical components of the printer according to data such as control commands and print data received by way of interface circuit 4 from host device 1, which is typically a host computer. In the present embodiment, CPU 31 functions as the controllers 3a, 3b and 3c, as well as the above-noted slack detector 3d, in accordance with the control program stored in ROM 32. It will be obvious to one with ordinary skill in the art that the control program stored in ROM 32 can be changed by using an EEPROM or similar rewritable non-volatile memory device for ROM 32 and rewriting the control program as needed. In this case it is possible to download the control program to ROM 32 by way of interface circuit 4 from a hard disk drive or other storage device in host device 1, an external storage device connected to the host, or from a server connected to via a network or Internet connection. Referring to Fig. 2 (A) to (C), Fig. 3 (D) to (F) and Fig. 4 ejection control in a printer 10 according to an embodiment of the present invention is described below. When printer 10 receives data from the host device 1 by way of interface circuit 4, printer 10 stores the data temporarily in a receive buffer in RAM 33 of controller 3. A data interpreter implemented by CPU 31 and the control program then sequentially interprets the data from the buffer in a FIFO manner. If the received data is a print command, the CPU 31 drives feed roller 14 to advance paper R, and drives print head 12 to print the print data according to the print command on the paper (Fig. 2 (A)). The CPU 31 also drives ejection rollers 15 and 16 at this time synchronized to feed roller 14. Note that the direction of roller rotation at this time is indicated by the arrows in Figs. 2 and 3. Paper R is thus gradually advanced toward paper exit 11 in conjunction with this printing operation. When the leading end of the paper reaches ejection rollers 15, drive force from the ejection rollers 15 continues to advance the paper to the downstream side (Fig. 2 (B)). When the leading end of paper R passes ejection rollers 15, paper sensor 17 disposed on the downstream side of ejection rollers 15 detects the paper (step 401 in Fig. 4) and sends a detection signal to the CPU 31. When the CPU 31 detects this signal it pauses driving ejection rollers 15 and 16 (step 402). When ejection rollers 15 stop, the leading end of the paper R remains held therebetween. Printing by print head 12 continues, CPU 31 controls feed roller 14 to continue advancing paper R until printing according to the print command or print data has been completed. Because the leading end of the paper is stopped by ejection rollers 15 at this time, the paper gradually bends upward forming a loop or bulge (slack) between ejection rollers 15 and cutting mechanism 13 as shown in Fig. 2 (C). CPU 31 calculates how much paper has accumulated between feed roller 14 and ejection rollers 15. It should be noted that this can be easily calculated from the distance by which feed roller 14 advances the paper after ejection rollers 15 were stopped as explained above. The host device 1 sends a cut command instructing the printer 10 to cut the paper following the print data for one (slip) receipt. Note that this command is equivalent to a command terminating printing for one slip. When the data interpreter of the CPU detects a cut command (step 403, Fig. 4), the CPU starts the printing termination process. First, the length of paper advanced since ejection rollers 15 stopped, that is, the slack amount of paper between feed roller 14 and ejection rollers 15, is calculated (step 404). If the calculated slack amount is greater than a specific value (step 405), steps 406 and 407 are accomplished. If the calculated slack amount is equal to or less than this specific value, then steps 408 and 409 are executed. Fig. 3 (D) to (F) illustrate the result of steps 406 and 407 accomplished when the calculated slack amount is greater than the specific value. That is, when ejection rollers 15 and 16 are started to be driven (step 406) the leading end of the paper is passed to the outside through paper exit 11 as shown in Fig. 3 (D), and thus reduces the slack amount, that is, the bulge, of paper between feed roller 14 and ejection rollers 15. The cutting mechanism 13 is then driven (step 407) to cut the paper and thus separate the slip r from the rest of roll paper R (Fig. 3 (E)). It should be noted that paper is cut before the paper bulge is completely eliminated. It should further be noted that in this exemplary embodiment of the invention cutting paper in step 407 occurs after driving ejection rollers 15 and 16 starts in step 406, but the invention is not limited to this order. More specifically, as long as driving ejection rollers 15 and 16 starts before cutting of the paper is finished, it does not matter which occurs first, the start of driving ejection rollers 15 and 16 or the start of driving cutting mechanism 13. For example, the cutting operation can start immediately after the cutting command is detected, i.e., step 407 and steps 404 to 406 can be performed in parallel. This makes it possible to shorten the total processing time compared with starting to drive ejection rollers 15 and 16 after completion of cutting paper. In an exemplary embodiment of the invention, the specific paper slack amount is desirably 50 mm for a printer in which ejection rollers 15 advance paper at 100 mm/s and cutting mechanism 13 requires a maximum of 500 ms to cut the paper. As shown in Fig. 3 (F), the slip r severed from roll paper R by cutting mechanism 13 is advanced to the outside of the printer from paper exit 11 by ejection rollers 15 and 16. When paper sensor 17 detects that the trailing end of the slip r has passed, driving ejection rollers 15 and 16 stops. The trailing end of slip r is then held weakly by ejection rollers 16 as explained before, and the user can easily remove the slip r from the paper exit 11. If the slack amount of paper is less than the specific amount in step 405, cutting mechanism 13 is driven first to cut the paper (step 408), and after cutting is completed , ejection rollers 15 and 16 are driven to start ejecting the slip r from paper exit 11 (step 409). This control sequence prevents the paper from tearing at the cutting mechanism and also prevents paper from jamming when the ejection rollers 15 and 16 pull on the paper before cutting the paper is finished when the slack amount of paper is not sufficient. The control steps used when only a small amount of data is printed for one slip are described next. If a cut command is detected (step 410) before paper sensor 17 detects the leading end of paper R in step 401 (Fig. 4), and thus before ejection rollers 15 grasp the paper, control moves to a paper feed process (step 411). This process solves the problem of the slip being left inside the printer as a result of cutting mechanism 13 cutting the paper before ejection rollers 15 grasp paper. Fig. 5 is a flow chart of this paper feed process performed in step 411 of Fig. 4. The CPU 31 drives feed roller 14 and ejection rollers 15 and 16 to begin advancing paper R (step 501). When the leading end then passes ejection rollers 15 and is detected by paper sensor 17, paper sensor 17 sends a detection signal to the CPU 31 (step 502). When the CPU detects this paper detection signal, it stops driving feed roller 14 and ejection rollers 15 and 16 (step 503). This sequence of steps assures that the leading end of the paper R is held by ejection rollers 15 before the paper is cut. Control then passes to step 408 in Fig. 4 whereby the paper is cut. Ejection rollers 15 and 16 are then driven (step 409) to advance the slip r to and out of the paper exit 11. An alternative embodiment of the invention is described next below. This second embodiment differs from the above described first one only in the paper ejection process, or, more specifically, in the process used when the accumulated slack is less than the specific amount. Other aspects are the same in both embodiments. Only the ejection process of this second embodiment is therefore described below with reference to Fig. 7, in which like steps are identified with the same reference numerals as in Fig. 4, and further description thereof is omitted below. As noted above, CPU 31 measures the slack amount (step 404) and compares the measured slack amount with a specific value (step 405). If the slack amount is greater than the specific value, driving ejection rollers 15 and 16 starts (step 406). The ejection rollers are driven at this time at a first speed (or are accelerated to this first speed). Subsequent control steps are as shown in Fig. 4 and described above. However, if the slack amount is less than this specific value, driving ejection rollers 15 and 16 begins at a second speed (or is accelerated to this second speed) (step 412) the second speed being slower than the first speed. After driving ejection rollers 15 and 16 starts in step 412, paper R is cut (step 413). After cutting is finished, the drive speed of ejection rollers 15, 16 is changed to the first speed (or accelerated to the first speed) (step 414). It should be noted that completion of paper cutting can be detected using a movable blade position sensor (not shown in the figure). It is also possible for a timer implemented by the CPU to measure the maximum time required for the cutting mechanism 13 to cut the paper, and to issue a timer interrupt to control the timing at which the speed of the ejection rollers is to change in step 414. In an exemplary embodiment the specific value to which the measured slack amount is compared is 50 mm and the second speed at which the ejection rollers are driven in step 412 is 20 mm/s when the maximum time required for the cutting mechanism 13 to cut the paper is 500 ms and the first transportation speed in step 406 is 100 mm/s. In this case the minimum amount of slack is 10 mm by design, and tearing at the paper cut tends to occur when the paper slack is less than 10 mm. Furthermore, while cutting the paper begins after the start of driving ejection rollers 15 and 16 in step 406 or 412, the invention is not limited to this sequence. That is, regardless of how much slack there is, cutting the paper can start at any time after the cut command is detected in step 403 as long as ejection rollers 15 and 16 start transporting paper before cutting the paper ends. Paper jams, tearing, and other problems caused by conflict between cutting and transporting the paper can be avoided by thus lowering the paper transportation speed when the slack amount is not sufficient. Furthermore, the slack is compared with a single specific value, and the paper transportation speed is set to one of two speeds based on the comparison result in this embodiment, but the invention is not limited to these numbers. More specifically, paper slack can be compared with a plurality of specific values to select the transportation speed from among three or more speeds. In this case a table defining the relationship between slack amount ranges and transportation speeds is preferably used. Although the present invention has been described in connection with preferred embodiments thereof with reference to the accompanying drawings, it is to be noted that various changes and modifications will be apparent to those skilled in the art. For example, an embodiment of the present invention is described above using two pairs of ejection rollers but it will be obviously possible to achieve the present invention using only one pair of ejection rollers. Such changes and modifications are to be understood as included within the scope of the present invention as defined by the appended claims.

Claims: A printing apparatus comprising: a print head (12) for printing on a printing medium (R, r); an ejection opening (11) through which the printing medium (R, r) printed by the print head (12) is ejected; a cutting mechanism (13) disposed downstream of the print head (12) for cutting the printing medium (R, r) and separating a printed part of the printing medium from an unprinted part of the printing medium; first transport roller means (14) and second transport roller means (15, 16) for transporting the printing medium (R, r) printed by the print head (12) toward the ejection opening (11), the second transport roller means being disposed downstream of said first transport roller means in the direction in which the printing medium is transported; detection means (31) for detecting completion of printing on the printing medium (R, r); and cutting control means (3c, 31) responsive to said detection means (31) for controlling the cutting mechanism (13) to cut the printing medium (R, r); transport control means (3b, 31) adapted to control said second transport roller means (15, 16) such that the second transport roller means (15, 16) stop transporting said printing medium to hold the leading end of the printing medium at a predetermined position before said ejection opening (11), the transport control means (3b, 31) being responsive to said detection means (31) for controlling said second transport roller means (15, 16) to release the printing medium (R, r) and restart transporting the printing medium to and through the ejection opening (11); characterized in that said transport control means (3b, 31) is adapted to control said second transport roller means (15, 16) to release the printing medium (R, r) and begin transporting the printing medium to the ejection opening (11) before the cutting mechanism (13) completes cutting the printing medium (R, r). The apparatus according to claim 1, characterized by further comprising a slack detector (3d, 31) for measuring an amount of slack in the printing medium (R, r), wherein the transport control means (3b, 31) is adapted to control said second transport roller means (15, 16) to transport the printing medium to said ejection opening (11) at a first speed when the amount of slack is greater than a specific amount, and at a second speed, slower than the first speed, when the amount of slack is less than the specific amount. A method of controlling the printing apparatus as defined in claim 1 comprising the steps of: (a) printing on a printing medium (R, r); (b) transporting the printing medium (R, r) printed in step (a) toward an ejection opening (11); (c) holding the leading end of the printing medium (R, r) at a predetermined position before the ejection opening (11) so as to produce slack in the printing medium (R, r) transported in step (b); (d) cutting the printing medium (R, r) to separate the part of the printing medium printed in step (a) from an unprinted part of the printing medium; and (e) resuming transport of the printing medium (R, r) toward the ejection opening (11); characterized in that step (e) is performed before step (d) is completed. A method according to claim 3, wherein step (e) comprises the steps of: (e1) measuring an amount of slack produced in the printing medium (R, r); (e2) comparing the amount of slack measured in step (e1) with a specific value; (e3) starting transportation of the printing medium toward the ejection opening (11) at a first speed if the amount of slack measured in step (e1) is exceeds the specific value, and at a second speed, slower than said first speed, if the amount of slack measured in step (e1) is less than the specific value. A method according to claim 4, further comprising the step of: (e4) when transportation in step (e3) started with said second speed, changing upon completion of step (d) the transportation speed of the printing medium to said first speed. A method according to any one of claims 3 to 5, wherein: step (c) comprises stopping the printing medium (R, r) by stopping rotation of ejection roller means (15, 16) disposed before said ejection opening (11), and step (e) comprises starting transportation of the printing medium (R, r) by starting rotation of said ejection roller means. A computer-readable data storage medium storing a computer program implementing the method as defined in any one of claims 3 to 6.

Inventors: OGUCHI ASAHIRO, TAKAMIZAWA YUJI, YAMAJI ATSUSHI, OGUCHI, ASAHIRO, TAKAMIZAWA, YUJI, YAMAJI, ATSUSHI
Applicants: SEIKO EPSON CORP, SEIKO EPSON CORPORATION
Application year: 2000
Main classification: B41J11
IPC codes: B41J15, B41J11, B41J13, B41J2