GB2228448A

GB2228448A - Paper feeding device

Info

Publication number: GB2228448A
Application number: GB8929134A
Authority: GB
Inventors: Takeshi Tashiro
Original assignee: Tokyo Electric Co Ltd
Current assignee: Toshiba TEC Corp
Priority date: 1988-12-27
Filing date: 1989-12-22
Publication date: 1990-08-29
Anticipated expiration: 2009-12-22
Also published as: KR930008444B1; GB8929134D0; JPH02175170A; KR900009292A; GB2228448B

Abstract

A paper feeding device includes a paper feeding path (PT), a stepping motor (6), a platen (2) driven by the stepping motor (6) to feed the paper along the paper feeding path (PT), and a control circuit for rotating the stepping motor (6) to feed the paper in the reverse direction from a cutter position (3) toward the printing head position on the paper feeding path (PT) so as to set a printing starting portion of the paper at the printing position. The paper feeding device further includes an optical sensor (4) disposed between the cutter position and the printing head position, for detecting the front end of the paper fed back from the cutting position towards the printing head position, and the control circuit further rotates the stepping motor (6) by an angle necessary for moving the printing starting portion of the paper to the printing position when the optical sensor (4) has detected the front end of the paper. <IMAGE>

Description

"PAPER FEEDING DEVICE" This invention relates to a paper feeding device for a printer, and more particularly to a paper feeding device capable of feeding paper in a reverse direction to set the same at the printing starting position.

Conventionally, there is provided a label printer for printing label data on a continuous sheet of paper, separating the printed portion from the remaining portion and issuing the same as a sheet of label. In this type of label printer, a printing head is used to print label data on the paper and a cutter is used to cut apart the paper fed from the printing head so as to separate the printed portion from the remaining portion as a sheet of label. When the printing paper is cut off, the front end of the remaining portion of the paper is located at the cutter position. Therefore, when a distance between the printing head and the cutter is relatively large, the label printer feeds the paper in a reverse direction in order to make ready for the next printing operation after the paper is cut off.As a result, the printing paper is so set that the printing head can be set to face an internal portion of the paper which is slightly apart from the front end thereof.

The paper feeding operation is explained in more detail with reference to Figs. 1A to 1F. As shown in Fig. 1A, the paper first passes the printing head position and is set so that the front end thereof may be set to project from the cutter position. When the cutter cuts off the paper as shown in Fig. 1B, the remaining portion of the paper is fed back from the cutter position by a distance X1 which is slightly smaller than a distance D between the cutter and the printing head. As a result, the paper is set at the printing starting position so that the printing head can be set to face an internal portion of the paper which is separated from the front end thereof by a distance (D-X1) as shown in Fig. 1C.After this, the paper is again fed in a forward direction from the printing starting position and is subjected to the printing operation by the printing head while the paper is being fed by a distance X2 corresponding to the printing line number. When the printing operation is completed, the paper is further fed in a forward direction by a distance (X1+P-X2) (P is a label length). As a result, the paper is set at the paper cut-off position so that the cutter can be set to face a portion of the paper corresponding to the rear end of the label. After the cutter has cut off the paper, the remaining paper is fed back from the cutter position by the distance X1 and set at the printing starting position as shown in Fig. 1F.

The printing paper is fed in a forward or reverse direction by means of a platen which is driven by a stepping motor. The rotation angle and rotation direction of the stepping motor are controlled by numeral data determined according to the traveling distance and the traveling direction of the paper. In a case where the paper is fed back in order to make ready for the printing operation, there is a possibility that the paper cannot be fed by the distance X1 even if the stepping motor is correctly driven. This is because a slippage occurs between the paper and the platen.

Particularly, the slippage easily occurs when the platen begins to rotate. As a result, the paper may be often set at a position deviated from the printing starting position. The deviation in the printing starting position accumulatively increases as the paper feeding back operation is repeatedly effected to issue a large number of labels. That is, the paper feeding operation of the conventional label printer cannot be controlled with a sufficiently high precision.

An object of this invention is to provide a paper feeding device in which error in the feeding distance can be suppressed to a minimum.

The above object can be attained by a paper feeding device comprising a paper feeding path; a stepping motor; a paper feeding mechanism driven by the stepping motor to feed the paper along the paper feeding path; a paper sensor disposed between first and second preset positions on the paper feeding path, for detecting the front end of the paper fed back from the first preset position towards the second preset position; and a control circuit for rotating the stepping motor to feed back the paper and further rotating the stepping motor by a predetermined angle when the sensor has detected the front end of the paper, thereby to move a desired portion of the paper to the second preset position.

With the above paper feeding device, when the paper sensor has detected the front end of the paper while it is being fed back from the first preset position towards the second preset position, the control circuit rotates the stepping motor by a predetermined angle necessary for moving the desired portion of the paper to the second preset position. Since the sensor is set nearer to the second preset position than to the first preset position, the rotation angle of the stepping motor can be set to be smaller when it is determined with the sensor position set as the reference position than when it is determined with the first preset position set as the reference position. Therefore, the desired portion of the paper can be set at the second preset position at higher precision.

This invention can be more fully understood from the following detailed description when taken in conjunction with the accompanying drawings, in which: Figs. 1A to 1F are diagrams for illustrating the positions of paper to be fed in the conventional label printer; Fig. 2 is a diagram showing the construction of a label printer according to one embodiment of this invention; Fig. 3 is a circuit diagram of a control circuit of the label printer shown in Fig. 2; Figs. 4 and 5 are flowcharts for illustrating the operation of the label printer shown in Fig. 2; and Figs. 6A to 6F are diagrams for illustrating the positions of paper to be fed in the label printer shown in Fig. 2.

There will now be described a label printer according to one embodiment of this invention with reference to Figs. 2 to 6F. The label printer prints label data on a continuous sheet of label paper, cuts off the printed portion from the remaining label paper, and issues the same as a sheet of label. In a case where sheets of label paper are removably attached to base paper, the label printer prints label data on a sheet of label paper, peels off the printed sheet of label paper, and issues the same as a sheet of label.

Fig. 2 shows the construction of the label printer.

The label printer includes a printing head 1, a platen 2, a cutter 3, an optical sensor 4, a peel-off plate 5 and a stepping motor 6. The printing head 1 is disposed in opposition to the platen 2 and has a plurality of printing elements arranged in a row along the axis of the platen 2 so as to print label data on the label paper for each printing line. For example, when thermosensible paper is used as label paper, the printing head 1 is constructed by a thermal head. The label paper is initially supplied to the printing head 1 and is fed by a preset distance each time data of one line is printed. The platen 2 is driven by means of the stepping motor 6 to feed the label paper along a path PT indicated by broken lines in Fig. 2.The label paper is fed in a forward direction when the stepping motor 6 is rotated in a counterclockwise direction, and is fed in a reverse direction when the stepping motor 6 is rotated in a clockwise direction. The cutter 3 is disposed at a relatively distant position from the printing head 1, and functions to cut the label paper which is supplied after printed by means of the printing head 1 so as to separate a printed portion of the label paper from the remaining portion thereof as a sheet of label. The optical sensor 4 and the peel-off plate 5 are disposed between the printing head 1 and the cutter 3. The peeloff plate 5 is used to peel off the label paper from the base paper in the case where the label paper is removably attached to the base paper. The optical sensor 4 is used to detect the front end of the label paper which is cut by means of the cutter 3 and then fed in a reverse direction to make ready for the next label data printing operation. The optical sensor 4 is also used to detect the front end of the label paper peeled off from the base paper in the case where the label paper is removably attached to the base paper. The optical sensor 4 shown in Fig. 2 is a light transmission type sensor having a light emitting unit and a light reception unit. In this case, the light emitting unit and light reception unit are disposed to face each other on both sides of the path PT. The construction of the light sensor 4 may be modified according to the type of label paper, and for example, it can be constructed by a light reflection type sensor.

Fig. 3 shows a control circuit of the label printer. The control circuit includes a CPU 10, ROM 11, RAM 12 and I/O interface 13 which are connected to one another via a bus line BS. The I/O interface 13 is connected to a driver 20 for the printing head 1, a driver 21 for the cutter 3, a driver 22 for the stepping motor 6, an input unit 23 and the optical sensor 4. For example, the CPU 10 controls various operations such as the label data printing operation, the label paper feeding operation and the label paper cutting operation.

The ROM 11 stores a control program for the CPU 10 and other fixed data, and the RAM 12 temporarily stores input/output data of the CPU 10. The printing head driver 20 receives label data supplied from the CPU 10 via the I/O interface 13 and supplies the label data to the printing head 1 for each printing line so as to selectively drive the printing elements of the printing head 1 according to the respective label data of one printing line. The driving circuit 21 receives a paper cut-off signal supplied from the CPU 10 via the I/O interface 13 to drive the cutter 3. The driving circuit 22 receives, as control data, numeral data from the CPU 10 via the I/O interface 13 to drive the stepping motor 6 by an angle and in a direction determined by the numeral data.The rotation angle of the stepping motor 6 is designated by the number of driving pulses which should be supplied from the driver 20 to the printing head. The stepping motor 6 rotates by one step or a preset angle, in response to each driving pulse supplied from driver 20. The optical sensor 4 generates a detection signal when detecting the front end of the paper.

The detection signal is supplied from the optical sensor 4 to the CPU 10 via the I/O interface 13. The input unit 23 includes various input keys and a connector portion for an external computer which are used for inputting the label issuing starting instruction and data necessary for formation of label data and input signals generated from the various keys and external computer are supplied to the CPU 10 via the I/O interface 13.

Now, the operation of the label printer is explained with reference to Figs. 4 and 5.

When the power source switch of the label printer is turned on, the CPU 10 starts the operation shown in Fig. 4 according to the control program stored in the ROM 11. When the above operation is started, circuit elements such as RAM 12 and I/O interface 13 are initialized in the step S1 and then it is checked in the next step S2 whether or not a label issuing starting instruction is input from the input unit 23. When it is detected that the label issuing starting instruction is not input, another processing is effected in the step S3 and then the step S2 is again effected. For example, label data creating process and label issuing process using the label paper removably attached to the base paper may be effected as the other processing in the step S3.

When it is detected that the label issuing starting instruction is input, label data of one line is printed on label paper whose front end is set in the position ST shown in Fig. 2 in the step S4, and it is checked in the step S5 whether or not all the label data corresponding to one sheet of label has been printed. When it is detected that all the label data has not been printed, the paper is fed by a distance corresponding to one printing line space in the step S6 and then label data of one line is printed on the paper.The steps S5, S6 and S4 are repeatedly effected, and when the operation of printing all the label data for one sheet of label is completed, the paper is further fed in the step S7 so that a portion of the paper corresponding to the rear end of the label can be set at the position of the cutter 3. After this, the paper is cut off by means of the cutter 3 in the step S8 so that the printed portion of the paper can be separated from the remaining portion thereof and issued as a sheet of label. At this time, the front end of the remaining paper is located at the position of the cutter 3.In the next step S9, the paper is fed in a reverse direction so as to be set at the printing starting position, whereby the front end of the paper is located at the position ST and the printing starting portion of the paper positioned slightly inwardly from the front end thereof is located at the position of the printing head 1. In this operation, the stepping motor 6 is rotated in such a direction as to move the front end of the paper in a reverse direction from the position of the cutter 3 to a position beyond the position of sensor 4.In this case, when the front end of the paper has reached the position of the sensor 4, the stepping motor 6 is further rotated by an angle necessary for moving the printing starting portion of the paper to the position of the printing head 1 (more precisely, the position of the printing elements) with the position of the sensor 4 set as a reference position. When the paper is set at the printing starting position to make ready for the operation of printing a label to be subsequently issued, it is checked in the step S10 whether or not all the necessary number of labels have been issued. If it is detected that all the necessary number of labels have been issued, the step S2 is again effected.In contrast, if all the necessary number of labels have not been issued, the steps S4 to S10 are effected again to issue the remaining labels.

Fig. 5 shows the printing preparation process shown in the step S9 in detail. In this process, first numeral data is set into the motor driver 22 in the step S20. The first numeral data is determined to specify a rotation angle and a rotation direction of the stepping motor 6 which are required to feed the paper in the reverse direction by a distance longer than the distance between the position of the cutter 3 and the position of the sensor 4. When the stepping motor 6 is rotated according to the first numeral data set into the motor driver 22, the platen 2 is driven to feed the paper in the reverse direction. It is checked in the step S21 whether or not the front end of the paper fed in the reverse direction is detected by means of the optical sensor 4. The step S21 is repeatedly effected until the front end of the paper is detected by the sensor. When the front end of the paper has reached the position of the optical sensor 4, the front end is detected by the sensor in the step S21 and then the step 22 is effected.

In the step S22, the first numeral data which has been set is cancelled and second numeral data is set into the motor driver 22 instead of the first numeral data. The second numeral data is determined to specify a rotation angle and a rotation direction of the stepping motor 6 which are required to feed the paper in the reverse direction by a distance equal to the distance between the position of the sensor 4 and the position ST. In this case, if a period delay time from the time when the front end of the paper has reached the position of the sensor 4 until the second numeral data is set into the motor driver 22 cannot be neglected, the rotation angle specified by the second numeral data is reduced according to a distance by which the paper is fed during the delay time.When the stepping motor 6 is further rotated by the angle corresponding to the second numeral data set into the motor driver 22, the paper is fed in the reverse direction to the printing starting position.

At this time, the front end of the paper is set at the position ST and the printing starting portion of the paper which is slightly apart from the front end is set at the position of the printing head 1.

Figs. 6A to 6F are diagrams showing the positions of the paper to be fed in the label printer shown in Fig. 2. When the label issuing starting instruction is input and the label data printing operation is started, the paper is fed in the forward direction from the printing starting position, which allows the front end of the paper to be set at the position ST separated from the position of the cutter 3 by the distance X1 as shown in Fig. 6A. The paper is fed in the forward direction by the distance X2 during the label data printing operation and reaches the position shown in Fig. 6B when the printing operation is completed. After this, the paper is fed in the forward direction by a distance (X1+P-X2) as shown in Fig. 6C to set a portion of the paper corresponding to the rear end of a sheet of label to the cutter position.Then, the cutter 3 cuts off the paper as shown in Fig. 6D and therefore the front end of the remaining portion of the paper is located at the position of the cutter 3. After this, the paper is fed in the reverse direction for the next printing operation.

When the paper is fed in the reverse direction by a distance X3 equal to a distance between the cutter 3 and the sensor 4 as shown in Fig. 6E, the front end of the paper is detected by means of the sensor 4. Then, the stepping motor 6 is further rotated by a predetermined angle to further feed the paper in the reverse direction by a distance (X1-X3) as shown in Fig. 6F to set the same at the printing starting position.

In this way, in the above embodiment, the paper is fed in the reverse direction by the preset distance (X1+P-X2) after the operation of printing label data on the paper, and then the cutter 3 is driven to cut the paper and the printed portion of the paper is issued as a sheet of label. After this, the paper is fed in the reverse direction and when the front end of the paper is detected by the sensor 4, the paper is further fed in the reverse direction by the distance (X1-X3) according to the numeral data to set the paper at the printing starting position.

Therefore, the distance (X1-X3) which is determined by the numeral data and by which the paper is fed in the reverse direction after the front end of the paper is detected by the sensor 4 until the paper is set at the printing starting position can be set to an extremely small value by setting the distance X3 between the cutter 3 and the sensor 4 to a relatively large value.

As described above, since the distance by which the paper is fed in the reverse direction according. to the numeral data can be set to a small value, the printing operation can be correctly effected by the printing head 1 without making a significant deviation even if the paper is fed with a slight difference in the feeding distance. Further, the feeding distance to the position of the sensor 4 in the reverse direction is mechanically determined by the setting position of the sensor 4.

Therefore, a difference occurring in the feeding distance (X1-X3) in the reverse feeding operation and a difference occurring in the feeding distance by which the paper is fed to make ready for the cutting operation will not be accumulated each time the label is issued even if a difference occurs in the feeding distance in the operation of feeding the paper to the cutting position. That is, the deviation of the printing starting position is a small deviation caused by a single feeding operation effected in the reverse direction based on the numeral data determined with the position of the sensor 4 set as a reference position. Therefore, when a plurality of labels are issued, the label data printing area can be prevented from being deviated from the preset position for each label.

The above embodiment is explained as an example in which this invention is applied to a label printer, but this invention is not limited to the label printer.

This invention can be applied to any type of printer in which the paper is fed in the reverse direction to the printing starting position. For example, there is a color printer which repeatedly performs a printing operation using a multi-colored ribbon. In this printer, the paper is fed back to a printing starting position each time the printing operation for a specified color is completed. This invention can be applied to the color printer.

Further, in the embodiment described above, the first and second numeral data are set into the printing head driver 20 in the printing preparation process.

However, the first numeral data is not required in the case where a printing head driver is provided which sequentially supplies driving pulses to the stepping motor 6 when the second numeral data is set in place of the first numeral data, counts the number of the driving pulses after the optical sensor 4 detects the front end of the paper, and stops the supply of the driving pulse when it is detected that the count has reached a value determined by the second numeral data.

Claims

Claims:

1. A paper feeding device comprising: a paper feeding path a stepping motor; a paper feeding mechanism driven by said stepping motor to feed the paper along said paper feeding path; paper sensing means disposed between first and second preset positions on said paper feeding path, for detecting the front end of the paper fed back from the first preset position towards the second preset position; and control means for rotating said stepping motor to feed back the paper and further rotating said stepping motor by a predetermined angle when said paper sensing means has detected the front end of the paper, thereby to move a desired portion of the paper to the second preset position.

2. A paper feeding device according to claim 1, wherein said second preset position is a printing position at which the paper is subject to a printing operation.

3. A paper feeding device according to claim 2, wherein said first preset position is a paper cut-off position at which the paper is cut-off to separate a printed portion thereof from the remaining portion.

4. A paper feeding device according to claim 3, wherein said paper sensing means is disposed closer to said second preset position than to said first preset position.

5. A paper feeding device according to claim 4, wherein said control means includes motor driving means for driving said stepping motor in accordance with data determined by the distance between the second preset position and the position at which the desired portion of the paper is located when the paper sensing means has detected the front end of the paper.

6. A paper feeding device according to claim 5, wherein said paper sensing means includes a sensor disposed between first and second preset positions on said paper feeding path, for detecting the front end of the paper fed back from the first preset position towards the second preset position, and for detecting the front end of a paper of a different type fed from a third preset position towards said second preset position, said third preset position being located between said second preset position and the position of said paper sensing means.

7. A paper feeding device according to claim 6, wherein said paper of a different type is constituted by sheets of label paper removably attached to base paper, and said third preset position is a paper peeloff position at which a sheet of said label paper is peeled off from said base paper.

8. A paper feeding device according to claim 1, wherein said paper sensing means is disposed closer to said second preset position than to said first preset position.

9. A paper feeding device according to claim 1, wherein said control means includes motor driving means for driving said stepping motor in accordance with data determined by the distance between the second preset position and the position at which the desired portion of the paper is located when the paper sensing means has detected the front end of the paper.

10. A paper feeding device according to claim 1, wherein said paper sensing means includes a sensor disposed between first and second preset positions on said paper feeding path, for detecting the front end of the paper fed back from the first preset position towards the second preset position, and for detecting the front end of paper of a different type fed from a third preset position towards said second preset position, said third preset position being located between said second preset position and the position of said paper sensing means.

11. A paper feeding device according to claim 10, wherein said paper of a different type is constituted by sheets of label paper removably attached to base paper, and said third preset position is a paper peeloff position at which a sheet of said label paper is peeled off from said base paper.

12. A paper feeding device, substantially as hereinbefore described with reference to Figs. 2 to 6F of the accompanying drawings.