Method and apparatus for sequentially feeding media

Description

CROSS-REFERENCE TO RELATED PATENT APPLICATION

This application claims the benefit under 35 U.S.C. § 119(a) of Korean Patent Application No. 10-2004-0117933, filed on Dec. 31, 2004, in the Korean Intellectual Property Office, the entire disclosure of which is hereby incorporated by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an image printing method and apparatus. More particularly, the present invention relates to a method and apparatus for calculating a conveying distance of a second medium for picking up a third medium based on the length of the media and the gap between a first medium and a second medium and correcting a pickup time from the third medium based on the conveying distance to sequentially feed the media.

2. Description of the Related Art

In an image printing apparatus, such as a laser printer, an inkjet printer or a facsimile, it is important that the relative timing between a point of media feeding time and a point of image printing time is controlled. Particularly, in a process for sequentially printing predetermined images to the media, it is important that the pickup time of the media is controlled such that the media are rapidly and sequentially fed.

FIG. 1 schematically shows an apparatus for sequentially feeding media in the image printing apparatus. While the medium loaded in a feeding tray 110 is picked up by a pickup roller 120 to be conveyed along a conveying path, the rear end of the medium is sensed by a sensing unit 130. The sensing unit 130 includes a light emitting unit (not shown) and a light receiving unit (not shown). The light emitting unit emits light, such as white light, to the medium conveyed along the conveying path. The light receiving unit senses the medium by the strength of the light reflected from the medium.

When the rear end of the medium is sensed by a sensor unit 130, the pickup roller 120 picks up the next medium and the medium that is currently being conveyed is conveyed to a printing engine unit 150 by a conveying roller 140 so that a predetermined image is printed on the medium.

The next medium is picked up and is sequentially fed when the rear end of the medium is sensed to sequentially feed the medium. However, since the next medium can be fed when the rear end of the previous medium passes through the pickup roller, a loss is caused in the feeding speed by the distance between the location that the medium is picked up and the location that the medium is conveyed to the sensor unit.

Accordingly, a need exists for an image printing apparatus and method thereof that facilitates sequential feeding of media through the image printing apparatus to substantially prevent loss of printing speed.

SUMMARY OF THE INVENTION

The present invention provides a method for calculating a conveying distance of a second medium for picking up a third medium based on the length of the media and the gap between a first medium and a second medium and correcting a pickup time from the third medium based on the conveying distance to sequentially feed the media.

The present invention also provides an apparatus for calculating a conveying distance of a second medium for picking up a third medium based on the length of the media and the gap between a first medium and a second medium and correcting a pickup time from the third medium based on the conveying distance to sequentially feed the media.

According to an aspect of the present invention, a method of sequentially feeding media includes (a) sensing the front end and the rear end of a first medium and calculating the length L1 of the first medium; (b) sensing the front end of a second medium that is fed next to the first medium and calculating the gap G1 between the rear end of the first medium and the front end of the second medium; (c) calculating a conveying distance P1 of the second medium for picking up a third medium after the front end of the second medium is sensed; and (d) sequentially picking up and feeding the media using the conveying distance P1.

The operation (a) may include sensing the front end and the rear end of the first medium; and measuring the conveying distance between a time that the front end of the first medium is sensed and a time that the rear end of the first medium is sensed, and calculating the length L1 of the first medium.

The operation (b) may include sensing the front end of the second medium; and measuring the conveying distance between the time that the rear end of the first medium is sensed and a time that the front end of the second medium is sensed and calculating the gap G1 between the rear end of the first medium, and the front end of the second medium.

The conveying distance P1 may be calculated by P1=L1−(G1−Gs), where Gs is a spacing gap between the media.

According to another aspect of the present invention, an apparatus for sequentially feeding media includes a sensing unit sensing the front end and the rear end of the media; a counter unit measuring the conveying distance of the media; a calculating unit calculating the length L1 of a first medium and the gap G1 between the rear end of the first medium and the front end of a second medium that is fed after the first medium; and a controlling unit picking up a third medium using the length L1 of the first medium and the gap G1.

The controlling unit may include a third calculating unit calculating a conveying distance P1 of the second medium for picking up the third medium after the front end of the second medium is sensed based on the length L1 of the first medium and the gap G1; and a pickup time correcting unit correcting a pickup time of the media such that the third medium is picked up when the second medium is conveyed the conveying distance P1.

Other objects, advantages and salient features of the invention will become apparent from the following detailed description, which, taken in conjunction with the annexed drawings, discloses preferred embodiments of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other features and advantages of the present invention will become more apparent by describing in detail exemplary embodiments thereof with reference to the attached drawings, in which:

FIG. 1 schematically shows a conventional apparatus for sequentially feeding media in an image printing apparatus;

FIG. 2 is a functional block diagram of a media feeding apparatus according to an exemplary embodiment of the present invention;

FIG. 3 is a perspective view of a counter unit according to an exemplary embodiment of the present invention;

FIG. 4 schematically illustrates a conveying distance P1 according to an exemplary embodiment of the present invention;

FIG. 5 is a graphical representation of the speed of a pickup roller and a conveying roller versus time;

FIG. 6 schematically illustrates the location of the medium positioned in a feeding tray and the location of the pickup roller; and

FIG. 7 is a flowchart of a media feeding method according to an exemplary embodiment of the present invention.

Throughout the drawings, like reference numerals will be understood to refer to like parts, components and structures.

DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS

The media feeding method and apparatus according to the present invention will now be described more fully with reference to the accompanying drawings.

FIG. 2 is a functional block diagram of a media feeding apparatus according to an exemplary embodiment of the present invention. The media feeding apparatus includes a sensing unit 210, a counter 220, a calculating unit 230 and a controlling unit 240.

The medium picked up by the pickup roller (not shown) is conveyed along a conveying path and the front end and the rear end of the medium are sensed by the sensing unit 210 located in the conveying path. The counter unit 220 measures the conveying distance between the front end and the rear end of the medium sensed by the sensing unit 210.

FIG. 3 shows the structure of the counter unit 230 according to an exemplary embodiment of the present invention. An encoder 360 attached to a registration roller 310 has a plurality of disc-shaped slits 350. An encoder sensor 320 senses the rotation of the registration roller 310 by sensing when light passes through one of the encoder slits 350 and when light is not sensed. The encoder sensor 320 generates an electrical signal corresponding to the state of the sensed light. For example, when the light passing through the encoder slit 350 is sensed, a high signal is generated, and, when the light is not sensed, a low signal is generated. Since the encoder slits 350 are arranged at a certain interval, the low and high signals are counted such that the conveying distance of the medium may be measured.

Referring back to FIG. 2, the calculating unit 230 includes a first calculating unit 232 and a second calculating 234, and calculates the length L1 of a first medium and the gap G1 between the rear end of the first medium and the front end of the second medium that is fed after the first medium with the sensing unit 210 and the counter unit 220. The first calculating unit 232 calculates the distance L1 between the front end and the rear end of the first medium that is first conveyed by the pickup roller and the conveying roller according to an image printing command. When the front end of the first medium is sensed by the sensing unit 210, the first calculating unit 232 begins to count the low and high signals with the counter unit 220. When the rear end of the first medium is sensed by the sensing unit 210, the counter unit 220 finishes the count. The distance L1 of the first medium is calculated by the number of the high and low signals counted between the time that the front end of the first medium is sensed and the time that the rear end of the first medium is sensed.

The second calculating unit 234 calculates the gap G1 between the rear end of the first medium and the front end of the second medium that is fed after the first medium. When the rear end of the first medium is sensed by the sensing unit 210, the second calculating unit 234 begins to count the low and high signals with the counter unit 220, and, when the front end of the second medium is sensed by the sensing unit 210, the counter unit 220 finishes the count. The gap G1 between the first medium and the second medium is calculated by the number of the high and low signals counted between the time that the rear end of the first medium is sensed and the time that the front end of the second medium is sensed. The first calculating unit 232 and the second calculating unit 234 may be integrated into one calculating unit according to the field for which the present invention may be applied, and this is included in the scope of the present invention.

The controlling unit 240 includes a third calculating unit 242 and a pickup time correcting unit 244, and determines the pickup time of a third medium based on the length L1 of the first medium calculated in the first calculating unit 232 and the gap G1 between the rear end of the first medium and the front end of the second medium calculated in the second calculating unit 234. The third calculating unit 242 calculates the conveying distance P1 of the second medium for picking up the third medium after sensing the front end of the second medium, which is based on the length L1 of the first medium and the gap G1. The pickup time correcting unit 244 corrects the pickup time of the pickup roller (not shown), such that the third medium is picked up when the second medium is conveyed the conveying distance P1. The conveying distance P1 is calculated such that the media are sequentially fed at a predetermined spacing gap Gs from the third medium. That is, the pickup time is corrected such that the third medium is picked up when the second medium is conveyed the conveying distance P1, and the pickup roller (not shown) is controlled such that the media is picked up at the corrected pickup time from the third medium.

The feeding speed of the medium is calculated during a predetermined period of time, for example, 1 minute, according to the conveying distance P1 calculated by the third calculating unit 242 and the feeding speed may be classified into a certain feeding mode. For example, the feeding mode of the medium may be classified into a high speed mode, a middle speed mode, and a low speed mode. Preferably, the feeding speed or the feeding mode of the medium may be displayed to a user by a display unit 250 and the user may set the feeding speed or the feeding mode of the medium according to the type of medium.

FIG. 4 schematically illustrates a conveying distance P1 according to an exemplary embodiment of the present invention. The first medium 410 and the second medium 420 are picked up and conveyed according to the printing command of the user. When the first medium is conveyed to the sensing unit 210, the front end (a) of the first medium is sensed by the sensing unit 210. When the front end of the first medium 410 is sensed, the counter unit 220 starts the count and, when the rear end (b) of the first medium 410 is sensed by the sensing unit 210, the counter unit 220 finishes the count. Based on the counted value, the first calculating unit 232 calculates the length L1 of the first medium. After the rear end (b) of the first medium 410 is sensed, the front end (c) of the second medium 420 that is picked up and fed after the first medium 410 is sensed by the sensing unit 210. The counter unit 220 starts the count again when the rear end (b) of the first medium 410 is sensed and finishes the count when the front end (c) of the second medium 420 is sensed. The second calculating unit 234 calculates the gap between the rear end (b) of the first medium 410 and the front end (c) of the second medium 420 based on the counted value. The lengths of the media are equal to the calculated length L1 of the first medium 410.

The third calculating unit 242 calculates the conveying distance P1 for picking up the third medium 430 when the second medium 420 is conveyed a predetermined distance. The conveying distance P1 is calculated such that the media are fed and conveyed at a predetermined spacing gap Gs from the third medium, and is preferably calculated by Equation 1.
P1=L1−G1+Gs  [Equation 1]

When the second medium 420 is conveyed the conveying distance P1, that is, when the second medium 420 is conveyed to the location (d) after the sensing unit 210 senses the front end (c) of the second medium 420, the third medium 430 is picked up and fed. From the third medium 430, the pickup time is determined based on the calculated conveying distance P1 and the media are sequentially picked up and fed. Accordingly, the media may be sequentially fed at the spacing gap Gs. Preferably, the feeding speed of the media will be maximized by minimizing the spacing gap Gs. Hereinafter, a minimum spacing gap Gs_min is described.

The pickup roller operates only when picking up the medium and stops after the medium is picked up. The conveying roller conveys the media at a predetermined speed. Accordingly, the medium is picked up and fed at an acceleration speed and the picked-up medium is conveyed by the conveying roller at a predetermined speed. Accordingly, if the rear end of the first medium 410 has not completely passed through the pickup roller although the first medium 410 has been conveyed the conveying distance P1, the pickup roller presses both the front end (c) of the second medium 420 and the rear end (b) of the first medium 410 to generate double conveyance. Accordingly, the spacing interval Gs must be calculated to a minimum spacing gap Gs_min to substantially prevent double conveyance.

FIG. 5 is a graphical representation of the speed of the pickup roller and the conveying roller versus time. The conveying roller operates at a certain speed 510. The pickup roller may operate at different speeds 520, 530 and 540 depending on the speed of the motor (not shown) for driving the pickup roller, and picks up and conveys the medium at a predetermined acceleration. The spacing S between the media is generated by the distances corresponding to the region S1 through the region S3 according to the speed difference between the pickup roller and the conveying roller. As shown in FIG. 6, the media precede the pickup roller 620 by a predetermined distance D in the feeding tray 610. Accordingly, the start location of the second medium precedes the first medium 410 by the predetermined distance D. Accordingly, the minimum spacing gap Gs_min to substantially prevent double conveyance is calculated by Equation 2.
Gs_min=S−D  [Equation 2]

By setting the minimum spacing gap Gs_min to be close to 0, the media may be rapidly and sequentially fed. Also, by adjusting the spacing S, the feeding speed of the medium may be controlled. That is, by setting the spacing gap Gs between the media to a value greater than the minimum spacing gap Gs_min, the feeding speed of the media may be controlled.

FIG. 7 is a flowchart showing a medium feeding method according to an exemplary embodiment of the present invention. The pickup roller picks up the first medium from the feeding tray and conveys it according to the printing command of the user. The first medium is conveyed along the conveying path and the locations of the front end and the rear end of the first medium are sensed by the sensing unit positioned in the conveying path (operation 710). The counter unit counts predetermined low and high signals from the time that the front end of the first medium is sensed to the time that the rear end of the first medium is sensed, and the first calculating unit calculates the length L1 of the first medium based on the counted value (operation 720). The second medium, which is picked up after the first medium, is conveyed along the conveying path and the front end of the second medium is sensed by the sensing unit (operation 730). The counter unit starts the count at the time that the rear end of the first medium is sensed and counts the low and high signals from the time that the rear end of the first medium is sensed to the time that the front end of the second medium is sensed. The second calculating unit calculates the gap G1 between the rear end of the first medium and the front end of the second medium based on the counted value (operation 740). From the third medium, the spacing gap Gs of the media is set (operation 750). The spacing gap Gs may be previously set and controlled by the user. Preferably, the spacing gap Gs is set to the minimum spacing gap that substantially prevents double conveyance of the media, which is preferably based on the speed difference between the pickup roller and the conveying roller and the difference between the pickup location of the second medium and the front end location of the second medium.

The conveying distance P1 of the second medium for picking up the third medium is calculated based on the length L1 of the first medium, the gap G1 between the rear end of the first medium and the front end of the second medium, and the set spacing gap Gs (operation 760). From the third medium, the pickup time for picking up the media is determined based on the conveying distance P1 (operation 770). At the determined pickup time, that is, when the second medium is conveyed the conveying distance P1, the third medium is picked up and fed.

The exemplary embodiments of the present invention may be written as computer programs and may be implemented in general-use digital computers that execute the programs using a computer readable recording medium. Examples of the computer readable recording medium include magnetic storage media (for example, ROM, floppy disks, hard disks, and other similar storage media), optical recording media (for example, CD-ROMs, or DVDs), and storage media such as carrier waves (for example, transmission through the Internet).

The media feeding method and apparatus according to exemplary embodiments of the present invention may correct the pickup time from the third medium based on the length L1 of the media measured from the first medium and the second medium and the gap G1 between the first medium and the second medium. By picking up and feeding the media based on the corrected pickup time, the feeding speed may be improved. Also, the minimum spacing gap Gs is set to substantially prevent double conveyance, and the feeding pattern of the media may be optimized based on the speed difference between the pickup roller and the conveying roller.

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it will be understood by those of ordinary skill in the art that various changes in form and details may be made therein without departing from the spirit and scope of the present invention as defined by the following claims.