Printer and method of controlling it

Abstract: A printer and control method therefor improve the operability of loading paper to the printer, and specifically enable paper to be loaded reliably and easily with a simple operation. Opening of a release lever that is operated to load paper to the printer is detected to automatically start a paper feed operation. When closing of the release lever is then detected, paper transportation is stopped and the paper loading process is terminated. A paper detector can also be provided to detect the presence of paper, and the paper transport amount is then controlled based on paper detector output. When a predetermined amount of paper is transported through the printer, paper transportation is stopped and loading the paper is completed.

Description: The invention relates to a printer of the type that prints on a recording medium located in a recording medium path such as between a print head and a platen. The invention further relates to a method of controlling such printer. In printers in which the gap between the print head and the platen is narrow, the medium (which is simply be referred to as "paper" in the following) can easily be caught between the print head and the platen when it is loaded into the printer. A release lever is typically provided to prevent this by increasing the distance between the print head and the platen when paper is loaded, thereby making it easier to insert the paper. In line thermal printers in particular, the print head touches the platen, thus effectively closing the paper path in this area and making it difficult to feed the paper that is being loaded to the printing region between the print head and the platen. It is therefore necessary to separate the print head from the platen, i.e. to open the paper path, before inserting the paper. FIG. 6 shows the printer mechanism of a line thermal printer. In the mechanism shown in FIG. 6 the release lever 2 operates in conjunction with the print head 6. During printing print head 6 is resiliently pressed against platen 4 with the paper (not shown) disposed therebetween, by means of a coil spring or other means. This assures tight contact between the paper and print head 6, and enables the effective transfer of heat from the print elements in print head 6 to the paper. When paper must be loaded, release lever 2 is operated to lift print head 6 from platen 4, thereby forming a gap between them through which the paper can be easily passed. Note that this operation is referred to below as "opening" the release lever. Thepaper is then inserted into the gap between platen 4 and feed roller 5, which is embedded in paper guide 9, and paper feed knob 3 linked to platen 4 is manually turned to advance the paper pinched between platen 4 and feed roller 5. To load the paper it is, thus, necessary for the operator to hold and insert the paper with one hand while turning feed knob 3 with the other hand. After the paper has been advanced by the required length, release lever 2 is again operated to close the gap between print head 6 and platen 4 and complete the paper loading process. Note that this last operation of release lever 2 to close the gap is also referred to below as "closing" the release lever. Printers such as those described above have become a widely used peripheral device connected to personal computers (PC) and other information processing devices, and people that have never before operated such printers are increasingly exposed to the need and opportunity to use such printers. This widespread use of printers has increased the demand for greater ease of use, particularly in the frequently performed, trouble-prone procedure of paper loading or paper setting. Paper is one of the most common printer consumables, and the roll paper that is used in printers for POS and ECR stations must be replaced right at the checkout counter. Because the paper must often be replenished, i.e., loaded, while customers are waiting, it is necessary to complete the loading quickly and reliably in order to minimize the customer waiting time. The conventional method of loading paper as described above is, however, both complicated and time-consuming. The fact that feed knob 3 shown in FIG. 6 must also be turned with the fingers is also not intuitively understood, and it is therefore necessary to educate and train people in how to properly load or install the paper. It can also be difficult to hold and insert the paper with one hand, making sure the paper stays straight, while turning the feed knob with the other hand to advance the paper. The object of the present invention is to solve the aforementioned problems and to provide a printer and method for easily inserting and loading the paper to the printer. These objects are achieved with a printer as claimed in claim 1 and a method as claimed in claim 10, respectively. Preferred embodiments are subject-matter of the dependent claims. At least part of the recording medium or paper path in the printer is defined by printing means usually formed by a print head and a platen arranged opposite to each other. When the print head and the platen are in a closed condition, i.e, in contact with each other or, via a small gap, opposite to each other the paper path in between the print head and the platen is closed. To allow insertion of paper, this paper path must be opened by creating or increasing the gap between the print head and the platen. In a preferred embodiment of the invention a release lever is provided to open and close the paper path. When paper is to be loaded the release lever is operated, i.e. opened, to open the paper path. According to the invention a detector is arranged to detect whether the release lever is open or closed. When the detector detects the open condition of the release lever and, thus, the paper path, a paper feed operation is automatically executed. It is, therefore, no longer necessary to manually turn a paper feed knob or the like to advance the paper for loading it into the printer because the paper feed operation is automatically executed whenever paper is loaded because the release lever must be operated to insert and load the paper. Because the inserted paper is automatically advanced, the operator has both of his hands free to hold and insert the paper to the insertion opening. This makes insertion and loading of paper simple and reliable. A paper detector can be additionally provided to detect whether paper has been inserted during the automatic paper feed operation. If presence of paper is detected the length by which (or the time during which) the paper is advanced may be measured. This also makes it possible to automatically advance the paper by a known required length, thereby eliminating problems caused by insufficiently advancing the paper. Furthermore, it is preferable to measure the time during which the automatic paper feed operation is executed in case the paper path has been opened but no paper inserted. If a certain time period has passed and still no paper is detected the paper feed operation can be automatically stopped. This avoids a continued needless operation of the paper transport means, a wasteful consumption of electricity, and needless heating and wear of mechanical parts. Instead of directly measuring the time the transport amount by which paper if it were present would have been transported, the number of transport unit steps or any other magnitude representative of the time may be measured. Preferred embodiments of the present invention are described below with reference to the accompanying figures. FIG. 1 is a simplified view of a printer mechanism according to a first embodiment of the invention. FIG. 2 is a simplified lateral cross sectional view of the printer mechanism of FIG. 1 additionally including elements of a second embodiment of the invention. FIG. 3 is a flow chart of the paper loading operation executed by the printer according to the first embodiment. FIG. 4 is a flow chart of the paper loading operation executed by the printer according to the second embodiment. FIG. 5 is an external view of a printer according to the present invention. FIG. 6 is a simplified view of a printer mechanism according to the prior art. FIG. 1 shows a printer mechanism 1 according to a first embodiment of the invention. Although not shown, the printer mechanism will normally be accommodated in a housing like that of printer 18 shown in FIG. 5. Print head 6 and release lever 2 are a linked assembly and open and close together. More specifically, when release lever 2 is moved in the direction of arrow A (i.e. is "opened") to open the gap between print head 6 and platen 4, print head 6 is lifted off platen 4. When release lever 2 is moved in the direction opposite arrow A (i.e. is "closed") to close the gap, print head 6 is pressed against platen 4 once again. This closed position is shown in FIG. 2. To put the printer mechanism in a condition for paper loading, release lever 2 is opened and, thereby, print head 6 lifted off platen 4. To print, release lever 2 is closed again allowing print head 6 to be pressed against platen 4. To detect the position of release lever 2 a sensor 10 is provided. When release lever 2 is closed, sensor 10 is ON, and when release lever 2 is open, sensor 10 is OFF. It is, therefore, possible to determine whether release lever 2 is open or closed by reading the state of sensor 10. Sensor 10 may be a microswitch or one of a variety of other sensors, including a photointerrupter. Stepping motor 7 is provided for driving platen 4 through transfer gear set 8. Paper 14 pulled off paper roll 13, is held between platen 4 and feed roller 5, and is advanced when stepping motor 7 rotates platen 4 in the direction of arrow B in FIG. 2. As is also shown in FIG. 2, in the second embodiment of the invention the printer mechanism additionally comprises an automatic paper cutter 12 and a paper detector 11. Feed roller 5 and paper detector 11 are provided in paper guide 9 facing the paper path. Paper detector 11 may be a common photoreflector that detects the existence or absence of paper in the passage between paper detector 11 and platen 4 from the difference in the reflectance of paper 14 and platen 4. Once paper has been detected by paper detector 11, the length by which the paper has been advanced relative to the position of the paper detector, i.e., the paper transportation amount, can be calculated from the number of steps stepping motor 7 is driven. Paper cutter 12 is mounted above print head 6, and controlled to automatically cut the excess end of paper 15 fed out from the printer by the paper feed operation. The process for loading paper into the printer of the first embodiment is described below with reference to the flow chart in FIG. 3. This process starts (S1) when the power is turned on. It is then immediately determined whether release lever 2 is open by checking the on/off state of sensor 10 (S2). If release lever 2 is not open, the procedure continues to loop through this step (S2). Other necessary printer control processes can be executed during this standby period. When the operator opens release lever 2, this opening is detected by sensor 10 (S2), and control passes to the start of the paper feed operation. In step S3 the paper is fed by a unit amount in response to stepping motor 7 rotating platen 4. Once the paper feed operation has started it is determined whether release lever 2 is closed again by checking the on/off state of sensor 10 (S4). The process loops through steps S3 and S4 until release lever 2 is closed again. If the operator inserts paper between paper feed roller 5 and platen 4 while platen 4 is rotated in this way, the paper is automatically fed into the printer because platen 4 rotates in the direction advancing the paper towards the printing region between print head 6 and platen 4. Thus, according to the invention, it is not necessary to manually rotate a paper feed knob to insert the paper, and the operator can, therefore, hold the paper with both hands to assure that it is inserted in the correct orientation. After the paper is inserted and advanced a sufficient length, the operator closes release lever 2. When the printer detects this closing by means of sensor 10 (S4) driving of stepping motor 7 is stopped, and, thus the paper feed operation (S5) is stopped and the process terminates (S6). With the printer according to the first embodiment of the invention it is, thus, possible to quickly and reliably load paper by simply operating a release lever 2 and inserting the paper, and it is not necessary to manually turn a paper feed knob. The paper can be simply and reliably inserted because it can be held with both hands. The operation of a printer according to the second embodiment is described next with reference to the flow chart in FIG. 4. As has been mentioned above, the second embodiment comprises paper detector 11, and the condition for initiating the process shown in FIG. 4 is that paper 14 is not detected by paper detector 11. The purpose of this is to allow a distinction between the paper replenishing or loading process and the normal printing process. More specifically, even during normal printing it is often necessary to operate release lever 2 to lift the print head from the platen in order to clean the print head or remove foreign matter or jammed paper. When the release lever is opend in such a situation the state of paper detector 11 indicates there is paper. On the other hand when the paper loading process is to be started, there is no paper to be detected by the paper detector. Therefore, the process shown in FIG. 4 is only executed when paper detector 11 detects that there is no paper in the printer. When the process starts (S11) it is determined whether release lever 2 is open by checking the on/off state of sensor 10 (S12). If release lever 2 is not open, the procedure continues to loop through this step (S12). The paper feed operation starts when sensor 10 detects that release lever 2 has been opened. In step S13 stepping motor 7 is driven by one step and the paper is advanced by a corresponding unit length. In step S14 it is checked whether paper detector 11 indicates presence of paper. If so, the process proceeds to step S15 while otherwise it branches to step S21. If paper is detected in step S14, the paper has been transported from the insertion opening, i.e., from paper feed roller 5 and platen 4, up to paper detector 11. In step S15 a counter is incremented. The counter measures the length the paper is advanced from where it is first detected by paper detector 11, i.e., the paper transportation amount. This is accomplished by counting the number of drive steps of stepping motor 7. It is next determined whether the paper transport amount as represented by the count value of the counter has reached a predetermined value (S16). If not, the paper is again fed by the unit length (S13) until this predetermined value is reached. More specifically, the paper is automatically advanced through the printer when the operator inserts the paper, and the paper feed operation is continued until the paper transportation amount in the paper-present state reaches a predetermined value. The paper feed operation is then stopped automatically (S17). The process then waits until release lever 2 is closed as indicated by the state of sensor 10 (S18). Once release lever 2 is closed, paper cutter 12 is operated (S19) to automatically cut off the excess paper 15 fed out from the printer, and the process terminates (S20). While this automatic paper cutting operation is preferably executed with the paper held firmly between print head 6 and platen 4, it is also possible to cut the paper by cutter 12 before release lever 2 is closed. Note that because the paper feed operation is stopped automatically it is not necessary for the operator to manually confirm that the paper has been advanced an appropriate length and then close release lever 2 to stop the feed operation. Furthermore, the need for the operator to manually cut off any excess paper with scissors or other means can be eliminated by automatically operating paper cutter 12. In this case the operator only needs to remove the cut paper end. If step S14 reveals that no paper is present, a counter is incremented in step S21. It is then determined whether the count value has reached a predetermined value (S22). If it has not, the process loops back to step S13. If the operator does not insert paper and the count value of the counter incremented in step S21 reaches a predetermined value (S22), the feed operation is automatically stopped (S23). This prevents the feed operation from continuing endlessly when the operator fails to insert paper. On the one hand, the loop of steps S13, S14, S21 and S22 allows for some time for the operator to insert paper. On the other hand, if she or he fails to insert paper, the loop stops the feed operation at some point, thereby preventing unnecessary shortening of the printer life, and reducing power consumption. It is to be noted that the counters incremented in step S15 and step S21, respectively, count unit amounts of transportation (this unit amount may correspond to one step of stepping motor 7). Since for the purposes of the present invention the transport speed may be considered constant, the count values of the counters virtually represent the time duration of the paper feed operation. Counting the number of drive pulses to the stepping motor may , therefore, be considered as a simple way of time measurement not excluding other ways of time measurement. As shown in FIG. 5 printer 18 preferably comprises an LED 16 and a paper feed switch 17. When the paper feed operation is stopped automatically (S23), LED 16 flashes (S24) to notify the operator that paper could not be loaded because no paper has been inserted. It should be noted that a buzzer or other indication means may be used in addition to or as an alternative to the LED 16. It will also be understood that if the printer is connected to a host device, other commonly used means such as sending a status signal to the host device to notify the user can be used. In the present example the LED 16 continues flashing until paper feed switch 17 is pressed (S25) or the printer turned off. If the operator notices that the paper was not loaded and wishes to retry loading the paper, she or he can simply press paper feed switch 17. This causes LED 16 to turn off (S26), returns control to the main routine, i.e., step S13, and restarts the paper loading process. With the control process described above the same process that is executed in response to release lever 2 being opened is executed when the printer could not load the paper and the operator then presses paper feed switch 17. Note that instead of switching off LED 16 in step S26 its flashing may also be stopped after the paper loading process is completed, i.e., immediately before or somewhere after step S15 as indicated by step S26_ shown in broken lines in FIG. 4. In the embodiment illustrated in FIG. 4, the paper loading process can be repeated by operating the paper feed switch 17 without the need to close and then re-open release lever 2 and the process loops through step S25 until the paper feed switch is pressed. In an alternative embodiment step S25 may be replaced by a step which waits for release lever 2 being closed like step S18. Then, if closing of the relase lever is detected, the process loops back to step S12. In this case the flashing of LED 16 is preferably stopped immediately before or somewhere after step S15. Thus, in this alternative embodiment it is not the paper feed switch 17 but the release lever 2 that is used for repeating the loading process. In other words the paper feed operation can be repeated by simply closing and then re-opening release lever 2. The invention has been described with reference to a line thermal printer. It is to be noted, however, that the invention is not limited to line thermal printers . From the content of the above disclosure it will be obvious to those skilled in the art that the invention can be applied to all printers in which part of the paper path is opened and closed for loading the paper. The invention is, furthermore, not limited to using paper supplied in roll form, but can also be used with printers using cut sheet forms and fan-fold paper in which latter cases the paper cutter of the second embodiment may not be necessary.

Claims: A printer having printing means (4, 6), a recording medium path for transporting a recording medium (14) past the printing means, opening/closing means (2, 6) switchable between a closed condition in which the recording medium (14) is held in the recording medium path and an open condition in which the recording medium is released, transport means (4, 5, 7, 8) for transporting the recording medium along the recording medium path, first detection means (10) for detecting whether the opening/closing means is in its open or closed condition, and transport control means responsive to the first detection means (10) for controlling the transport means to start transporting the recording medium when the first detection means detects the open condition of the opening/closing means. The printer of claim 1, wherein said printing means comprises a print head (6) and a platen (4) disposed opposite the print head, the region between the print head and the platen forming part of said recording medium path, and the print head and the platen being arranged such that in the closed condition of said opening/closing means (2, 6) the print head faces the platen with a first or no distance formed between them, while in the open condition of said opening/closing means the print head faces the platen with a second distance formed between them, the second distance being substantially greater than the first distance. The printer according to claim 1 or claim 2 wherein the transport control means is adapted to stop operation of the transportation means (4, 5, 7 ,8) when the first detection means (10) detects the closed condition of the opening/closing means (2, 6). The printer according to claim 1 or 2 further comprising second detection means (11) for detecting presence/absence of a recording medium (14) in the recording medium path, and first measuring means responsive to said second detection means for measuring, when presence of a recording medium is detected, the length by which the recording medium is transported by the transport means, wherein the transport control means is adapted to stop the transport means in response to the first measuring means having measured a first predetermined value. The printer according to claim 4 further comprising second measuring means responsive to the second detection means for measuring, when absence of a recording medium (14) is detected, a transportation amount of the transport means, wherein the transport control means is adapted to stop the transport means in response to the second measuring means having measured a second predetermined value. The printer according to claim 5 further comprising a stop state indication means (16) for indicating that the transport means has been stopped in response to the second measuring means having measured said second predetermined value. The printer according to claim 5 or 6 further comprising a restart command means (17) for causing the transport control means to restart the transport means after the transport means has been stopped in response to the second measuring means having measured said second predetermined value. The printer according to any one of claims 4 to 7, further comprising cutting means (12) for cutting the recording medium (14), and cutting control means for driving the cutting means to cut the recording medium after the paper transport means has been stopped in response to the first measuring means having measured said first predetermined value. The printer according to claim 8 wherein the cutting control means is adapted to drive the cutting means after the first detection means (10) detects the open condition of the opening/closing means (2, 6). A method of controlling a printer having a recording paper path through which a recording medium (14) is transported past printing means (4, 6), wherein the recording medium path is either in an open or a closed condition, the method comprising the steps of: a) detecting that the recording medium path is in its open condition, and b) starting to transport the recording medium along the recording medium path in response to step a). The method according to claim 10 further comprising the steps of: c) detecting the presence or absence of a recording medium in the recording medium path, d) measuring the amount of transport of the recording medium, and e) stopping the transport if absence of a recording medium is detected in step c), and the amount measured in step d) is a first predetermined amount. The method according to claim 11 further comprising the step of: f) stopping the transport if presence of a recording medium is detected in step c), and the amount measured in step d) is a second predetermined amount. The method according to claim 11 or 12 further comprising the steps of; g) notifying, in response to step e), that the transport has been stopped, and h) waiting for a command to restart transport. The method according to claim 10 further comprising the steps of; c) detecting the presence of a recording medium in the recording medium path, d) measuring the amount of transport of the recording medium, and e) stopping the transport in response to presence of a recording medium being detected in step c), a predetermined amount having been measured in step d).

Inventors: TSUKADA TOSHIHIRO, TSUKADA, TOSHIHIRO
Applicants: SEIKO EPSON CORP, SEIKO EPSON CORPORATION
Application year: 1997
Main classification: B41J11
IPC codes: B41J11, B41J13, B41J25, B41J29