Patent Description:
Recently, with the rapid development of enterprises, security measures against document leakage of enterprises have been devised. In recent years, as security measures against document leakage, a document security technology employing security paper has been developed. Security paper refers to paper printed by inserting a special material therein or by using a special material, which generates a signal for distinguishing between characteristics of materials by resonating to a specific frequency using an amorphous or similar non-crystalline magnetic material (alloy), a metal wire in nanoscale, and a material having magnetic resonance characteristics.

Such security paper is detected by an electromagnetic (EM) sensor. That is, when a soft magnetic material in the security paper approaches an alternating current (AC) magnetic field generated by the sensor, the AC magnetic field changes, and a high frequency spectrum generated due to the change is detected to detect the security paper. The sensor may include a transmission coil generating an AC magnetic field, a reception coil detecting a change in the AC magnetic field generated by the transmission coil, and an electronic system controlling the AC magnetic field generated by the transmission coil and processing a signal received from the reception coil.

Alternatively, security paper may include a plurality of conductive fine metal pieces irregularly distributed throughout the paper. The fine metal piece may be any type of metal as long as it has conductivity and generates an induced current in a magnetic field. For example, the metal piece contained in the paper may have a fine size so that it is not easily identified by the naked eyes of a user. For example, the metal piece may be a metal piece having a thickness of <NUM> to <NUM>, a length of <NUM> to <NUM>, and a width of <NUM> to <NUM>. As such, with the security paper in which the conductive fine metal pieces are scattered, a primary magnetic field generated by an inductive sensor induces an eddy current in the fine metal pieces of a fed paper, and a magnetic field secondarily generated by the eddy current affects the primary magnetic field generated by the inductive sensor to change intensity thereof. Accordingly, the inductive sensor transmits a security paper detection signal to a control device to be described later according to whether intensity of the magnetic field generated by the inductive sensor itself changes.

<FIG> and <FIG> are diagrams illustrating a background art of the present disclosure regarding a belt transfer type multi-function device that may be applied to a multi-function device for security paper. A general process of printing paper in a belt transfer type multi-function device will be described with reference to <FIG> and <FIG>. Once printing starts, a laser scanner unit (LSU) <NUM> irradiates a laser to an OPC drum <NUM> according to an image to be printed, to form an image on the OPC drum <NUM>, the OPC drum <NUM> on which the image is formed comes into contact with a roller to which a toner is attached, and the toner is attached only to a portion of the OPC drum <NUM> in which the image is formed due to a potential difference between voltages applied to the roller and the drum. The OPC drum <NUM> to which the toner is attached comes into contact with a transfer belt <NUM> so that the toner attached to the OPC drum <NUM> is moved to the transfer belt <NUM> due to a potential difference applied between the OPC drum <NUM> and the transfer belt <NUM>. For example, in the case of a color printer, each color toner is moved to the transfer belt <NUM> in order of yellow (Y), magenta (M), cyan (C), and black (K). For reference, the order of the colors may differ depending on a multi-function device maker. The toner moved to the transfer belt <NUM> meets the paper lifted from a feeding device between the transfer belt <NUM> and a transfer roller <NUM> according to a rotational motion of the transfer belt <NUM>, and as the toner of the transfer belt <NUM> is moved to a paper <NUM> according to a potential difference between the transfer belt <NUM> and the transfer roller <NUM>, an image is formed on the paper <NUM>. As the paper <NUM> on which the image has been formed by the toner passes through a fuser unit <NUM>, the toner is fused to the paper <NUM> by heat, thereby finishing a final printing process.

In the printing process of the belt transfer type multi-function device described above, printing is first performed (image is formed) on the transfer belt <NUM> before the paper <NUM> is picked up by a pickup roller <NUM> in a paper tray <NUM>, and in both a case in which the security paper detection sensor <NUM> is installed in the paper tray <NUM> and a case in which the security paper detection sensor <NUM> is installed on a transfer path of the paper <NUM> as shown in <FIG>, whether the paper <NUM> is a security paper or a plain paper may be detected only when the paper <NUM> is picked up and the picked-up paper is moved from the transfer path. Here, there is no particular problem when the security paper is detected, but when the plain paper is detected, there is a problem in that the image formed on the transfer belt <NUM> is already transferred to the plain paper and printed, before being detected.

For example, <CIT> discloses that a printer control unit controls a pressure roller/heating means of the fusing unit so that the toner may not settle on the printed plain paper after printing.

According to the present disclosure, in a case in which an image transferred to a transfer belt should not be printed on paper (next paper or plain paper) immediately before being caught between the transfer roller and a belt roller in a belt transfer type multi-function device in any event, it is possible to normally perform printing on paper (or security paper) caught between the transfer roller and the belt roller and to eject the next paper or plain paper as blank paper without being printed.

As described above, a multi-function device in the present disclosure includes not only a multi-function device incorporating functions of a printer, a fax machine, a copier, and a scanner but also a device that implements only individual functions of a printer, a fax machine, a copier, and a scanner. In general, a multi-function device refers to a device capable of implementing all the functions of a printer, a fax machine, a copier, and a scanner; however, in the present disclosure, as can be noted from the following descriptions, whether fed paper is plain paper or security paper is determined and a printing operation is performed accordingly, and thus, the multi-function device in the present disclosure may also be understood as indicating a printer, a fax machine, or a copier, not a multi-function device. That is, although a device functions only as a printer or only as a copier, if the functions described below in the present disclosure are implemented according to paper to be fed, the device will fall within the scope of the present disclosure. Alternatively, a related art multi-function device implementing all of the above functions will naturally fall within the scope of the present disclosure.

Hereinafter, an example in which security paper or plain paper is determined by a security paper detection sensor and printing is normally performed on security paper and is not performed on plain paper will be described, but the present disclosure is not limited thereto and may also be applied to a case in which an image already transferred to a transfer belt should not be printed on paper (hereinafter, referred to as "next paper" or "plain paper") immediately before being caught between a transfer roller and a belt roller in a belt transfer type multi-function device in any event. That is, printing may be normally performed on paper (which may be "security paper" according to an embodiment of the present disclosure) caught between the transfer roller and the belt roller, and next paper or plain paper, on which printing is not performed, is ejected as blank paper. In other words, the present disclosure may be applied to a case in which printing is normally performed on paper already caught between the transfer roller and the belt roller, while an image already transferred to the transfer belt should not be printed on next paper. Therefore, the scope of the present disclosure should not be limited by the description of the embodiments below but will be defined only by the claims described below.

<FIG> is a view illustrating a paper transfer path and plain paper ejection operation in the belt transfer type multi-function device according to an embodiment of the present disclosure. <FIG> is a block diagram illustrating an operation of ejecting plain paper in a belt transfer type multi-function device according to an embodiment of the present disclosure. <FIG> is a flowchart illustrating an operation of ejecting plain paper in of a belt transfer type multi-function device according to an embodiment of the present disclosure.

Referring to <FIG>, a belt transfer type multi-function device <NUM> according to the present disclosure includes a security paper detection sensor <NUM> installed on a transfer path of a paper <NUM> and a control device <NUM> determining whether the paper <NUM> is security paper or plain paper according to a detection value from the security paper detection sensor <NUM>. When the paper <NUM> is recognized as plain paper, the belt transfer type multi-function device <NUM> turns off a feed roller clutch <NUM> , and after the lapse of a predetermined time, the belt transfer type multi-function device <NUM> turns on the feed roller clutch <NUM> so that the paper <NUM> is output as blank paper. Hereinafter, the belt transfer type multi-function device <NUM> according to the present disclosure will be described in detail with reference to the accompanying drawings.

When the paper <NUM> is picked up by a pickup roller <NUM> from a paper tray <NUM> and transferred along a transfer path (indicating a path along which the paper, starting from the paper tray, is fed, printed and ejected from the inside of the multi-function device), the security paper detection sensor <NUM> located on the transfer path transmits a detection value to the control device <NUM> and the control device <NUM> compares the detection value from the security paper detection sensor <NUM> with a predetermined reference value to determine whether the paper <NUM> is security paper. According to an embodiment of the present disclosure, the control device <NUM> compares a first detection value detected by the security paper detection sensor <NUM> at a time point at which the corresponding paper <NUM> is not present near the security paper detection sensor <NUM> in the process in which the paper <NUM> to be determined is transferred on the transfer path with at least one second detection value detected by the security paper detection sensor <NUM> for the paper <NUM> to be determined on the transfer path, and if a comparison value is equal to or greater than the predetermined reference value, the control device <NUM> determines that the paper <NUM> is security paper, whereas if the comparison value is less than the predetermined reference, the control device <NUM> determines that the paper <NUM> is plain paper.

In some cases, the security paper detection sensor <NUM> may be provided in a predetermined position inside the paper tray <NUM> to detect whether the paper, included in the paper tray <NUM> and starting to be fed, is security paper or plain paper.

When the control device <NUM> recognizes the paper <NUM> as a plain paper, a feed roller clutch <NUM> may be turned off by firmware or the control device <NUM> of the belt transfer type multi-function device <NUM> to forcibly stop rotation of the feed roller <NUM>. When rotation of the feed roller <NUM> is stopped, the transfer belt <NUM> continues to rotate with no paper <NUM> between the transfer roller <NUM> and the belt roller <NUM> so that the image already transferred to the transfer belt <NUM> may be automatically erased by a belt cleaner <NUM>, while security paper (paper already caught between the transfer roller and the belt roller) in front of plain paper on the transfer path is normally printed and ejected.

In general, in a method of stopping transfer of the paper <NUM>, if a jam signal is generated by controlling a feed sensor <NUM> of the belt transfer type multi-function device <NUM> or by processing a signal thereof or by controlling a door open sensor <NUM> or by processing a signal thereof, all operations of the belt transfer type multi-function device <NUM> may be stopped, and in this case, the front security paper, which has been normally printed, may also be stopped and damaged by heat of a fusing device (or an image printed on the security paper may be damaged). Therefore, in the present disclosure, when the firmware or the control device <NUM> recognizes (determines) the next paper <NUM>, immediately before being caught between the transfer roller <NUM> and the belt roller <NUM>, as plain paper, an OFF signal is forcibly generated by controlling a feed roller clutch <NUM> by the firmware or the control device <NUM> of the belt transfer type multi-function device <NUM> according to the present disclosure to thereby prevent a printer engine controller <NUM> of the belt transfer type multi-function device <NUM> from recognizing that the next paper <NUM> or plain paper is stopped, and thus, a normal printing process may be completed on the security paper (already caught between the transfer roller and the belt roller) in front of plain paper on the transfer path.

Thereafter, when a printer engine controller <NUM> recognizes that the door <NUM> is opened and then closed by controlling the door open sensor <NUM> (or by processing a signal thereof) (in the present disclosure, controlling a sensor includes processing a signal from the sensor) by the firmware or the control device <NUM> of the belt transfer type multi-function device <NUM> according to the present disclosure, the belt transfer type multi-function device <NUM> according to the present disclosure performs an initiation operation by the printer engine controller <NUM>. Here, the printer engine controller <NUM> recognizes that there is no paper by controlling sensors (or by processing or controlling signals thereof) including the feed sensor <NUM> on the paper transfer path by the firmware or the control device <NUM> of the belt transfer type multi-function device <NUM> according to the present disclosure, and here, plain paper is normally ejected when the belt transfer type multi-function device <NUM> performs the initiation operation by turning on the feed roller clutch <NUM> by the firmware or the control device <NUM> of the belt transfer type multi-function device <NUM>.

Here, in order to enable the belt transfer type multi-function device <NUM> according to the present disclosure to maintain the initial operation, the feed sensor <NUM>, an exit sensor <NUM>, a bin full sensor <NUM> through which plain paper passes are controlled by the firmware or the control device <NUM> of the belt transfer type multi-function device <NUM> according to the present disclosure so that the printer engine controller <NUM> may recognize that paper does not pass (there is no paper on the transfer path) until plain paper is ejected (alternatively, controlled by processing signals from the corresponding sensors). Details thereof will be described hereinbelow with reference to <FIG> and <FIG>.

In addition, in an embodiment of the present disclosure, a second feed clutch switch <NUM> connected to the feed roller clutch <NUM> and a printer feed clutch switch <NUM> and a first feed clutch switch <NUM> connected to the second feed clutch switch <NUM> are provided, and ON/OFF of the first feed clutch switch <NUM> and the second feed clutch switch <NUM> are controlled by the firmware or the control device <NUM> of the security multi-function device <NUM>. Details thereof will be described hereinbelow with reference to <FIG> and <FIG>. The printer feed clutch switch <NUM> is controlled by the printer engine controller <NUM>.

<FIG> is a view illustrating switching control for an operation of ejecting plain paper in a belt transfer type multi-function device according to an embodiment of the present disclosure, and <FIG> is a timing chart illustrating switching control for an operation of ejecting plain paper in a belt transfer type multi-function device according to an embodiment of the present disclosure.

An operation of controlling ON/OFF of the feed roller clutch and each sensor in the belt transfer type multi-function device <NUM> according to the present disclosure will be described in detail by a the timing chart with reference to <FIG> and <FIG>. In the timing chart of <FIG>, in a section ①, the printer feed clutch switch <NUM> is controlled by a feed clutch signal from the printer engine controller <NUM> and is turned on (ON). When paper is recognized as plain paper, a second feed clutch switch control (C) is formed low by the firmware or the control device <NUM> of the security multi-function device <NUM>, so that the second feed clutch switch <NUM> is blocked, an operation of the feed roller clutch <NUM> is turned off, the feed roller <NUM> does not rotate, and thus, paper is stopped on the transfer path.

Here, in a section of ②, when the door open sensor switch control is turned off and then turned on by the firmware or the control device <NUM> of the security multi-function device <NUM>, door open OUT transferred to the printer engine controller <NUM> is dropped to low and then returned to high although there is no change (closed) actually in the door <NUM> like a state of door open IN, so that the printer engine controller <NUM> recognizes that the door <NUM> is opened and then closed, the belt transfer type multi-function device <NUM> starts an initialization operation (motors inside the belt transfer type multi-function device <NUM> are all rotated to erase the remaining image of the transfer belt <NUM> and the initialization operation is performed).

Here, as in the section of ③, when outputs of all sensors (feed sensor <NUM>, exit sensor <NUM>, and bin full sensor <NUM>) on the paper transfer path are turned off by feed sensor switch control, exit sensor switch control, bin full sensor switch control by the firmware or the control device <NUM> of the security multi-function device <NUM> from a time point at which door open sensor switch control is dropped to low to a time point at which the initialization operation is finished, the printer engine controller <NUM> determines that there is no paper in spite of the presence of paper in the belt transfer type multi-function device <NUM> and continuously performs the initialization operation.

Here, since all the motors of the belt transfer type multi-function device <NUM> rotate, when a first feed clutch switch control (B) is made high by the firmware or the control device <NUM> of the security multi-function device <NUM> to turn on the first feed clutch switch <NUM> as in a section ④, the feed roller <NUM> rotates to transfer the paper <NUM> inside the belt transfer type multi-function device <NUM> to eject the paper <NUM> to the outside.

In the above case, all the driving motors required for transfer of the paper rotate during the initialization operation, but in some cases, some of the motors required for transfer of the paper may not rotate during the initialization operation depending on types of multi-function devices. In this case, plain paper may be ejected by transferring paper by rotating a motor which does not rotate during the initialization operation. Motors currently used in multi-function devices are mostly classified into two types of step motors and blushless DC (BLDC) motors, and the same controlling may be performed by controlling drivers thereof. Specifically, the control in the sections ① to ④ above may be followed as is, and if a motor does not rotate, a multi-function device side motor control signal may be interrupted by turning on P/S switch control, the motor may be rotated by connecting a sensor side motor control signal, whereby paper may be ejected to the outside.

The present disclosure is not limited to the specific embodiments described above and may be variously modified by a person skilled in the art.

Claim 1:
A control device (<NUM>) for a belt transfer type multi-function device (<NUM>) printing an image transferred on a belt (<NUM>) to paper moving between a transfer roller (<NUM>) and a belt roller (<NUM>),
wherein the control device (<NUM>) determines whether corresponding paper is security paper according to a detection value from a security paper detection sensor (<NUM>) installed on a transfer path of paper starting from a paper tray (<NUM>) of the belt transfer type multi-function device (<NUM>), and performs control such that security paper is normally printed and plain paper is ejected as blank paper,
wherein the control device (<NUM>) performs controlling such that an image to be printed on paper (<NUM>) already caught between the transfer roller (<NUM>) and the belt roller (<NUM>) is printed as it is, and if the control device (<NUM>) determines that next paper along a movement direction of paper is plain paper, the control device (<NUM>) performs controlling the belt transfer type multi-function device by ON/OFF switching such that movement of the next paper is stopped on the transfer path of paper before the next paper is positioned between the transfer roller (<NUM>) and the belt roller (<NUM>), the image already transferred on the transfer belt (<NUM>) is deleted in a state in which the next paper is maintained to be stopped on the transfer path of paper, and the next paper in a stopped state is ejected as a blank paper through an ejection port of printed paper along the transfer path of paper, with the image already transferred to the transfer belt (<NUM>), which is to be printed on the next paper along the movement direction of paper, being not printed on the next paper.