Patent Description:
Conventional portable printers have a box shape and are relatively large, and are carried in a bag or the like. Portable printers are preferably small, light, and easy to carry. For portable printers, a sheet cassette for storing recording sheets may be used. See, for example, <CIT> and <CIT>. An exemplary portable printer according to the preamble of the independent claim <NUM> is shown in <CIT>.

Portable printers contain a battery and are driven with electric power stored in the battery. To make portable printers as small as possible, small, low-capacity batteries are used.

While high-speed printing is not performable with small, low-capacity batteries, small portable printers that can perform high-speed printing are desired.

According to an aspect of the present invention, a sheet cassette comprises the features of claim <NUM>.

According to an aspect of the present invention, a sheet cassette is connected to a portable printer to enable the portable printer to perform high-speed printing.

Embodiments of the present invention are described below with reference to the accompanying drawings. In the following, the same members or the like are referred to using the same reference numeral, and duplicate description thereof is omitted. Furthermore, the embodiments are described using an XYZ coordinate system as defined as illustrated in the drawings. A direction along the X-axis is referred to as "X direction. " A direction along the Y-axis is referred to as "Y direction. " A direction along the Z-axis is referred to as "Z direction. " The X direction, the Y direction, and the Z direction are orthogonal to one another.

A portable printer <NUM> to which a sheet cassette according to an embodiment is attachable is described with reference to <FIG>. The cylindrical printer <NUM> is also referred to as a pen-type printer. <FIG> are a perspective view and a cross-sectional view, respectively, of the printer <NUM>. The printer <NUM> is an Internet of Things (IoT) device including a printing function and a radio communication function.

The printer <NUM> includes a print head <NUM> such as a thermal head, a platen roller <NUM>, a feed roller <NUM>, a sheet guide <NUM>, a spring, a control board <NUM>, an insertion opening sensor <NUM>, an inner cover <NUM>, and an outer cover <NUM>. The print head <NUM> is pressed against the platen roller <NUM> by the spring. A recording sheet is fed by the feed roller <NUM> to move into the printer <NUM> along the sheet guide <NUM>. The recording sheet is conveyed by the platen roller <NUM> while being held between the print head <NUM> and the platen roller <NUM>, and is thereafter discharged. An electronic circuit and electronic components that control the printer <NUM> are mounted on the control board <NUM>.

The cylindrical inner cover <NUM> is accommodated in the cylindrical outer cover <NUM>. The inner cover <NUM> includes an insertion opening <NUM> and a discharge opening <NUM> that are open along the generatrix of the inner cover <NUM>. The outer cover <NUM> includes an insertion opening <NUM> and a discharge opening <NUM> that are open along the generatrix of the outer cover <NUM>. The outer cover <NUM> is rotatable relative to the inner cover <NUM>.

When the printer <NUM> performs printing, the opening <NUM> and the opening <NUM> are aligned to be open, and the opening <NUM> and the opening <NUM> are aligned to be open. A recording sheet enters the printer <NUM> through the openings <NUM> and <NUM>, and is discharged through the openings <NUM> and <NUM>. A sheet cassette <NUM> can be connected to the opening <NUM> with the openings <NUM> and <NUM> being open.

Print data are transmitted from an information terminal to the printer <NUM> through radio communications using, for example, Bluetooth Low Energy (BLE). The printer <NUM> receives the print data and performs printing on a recording sheet. The printer <NUM> contains a built-in antenna for performing radio communications.

The printer <NUM> includes a power supply <NUM> storing a lithium-ion battery, which is a rechargeable battery, and can be driven with electric power supplied from the lithium-ion battery. The printer <NUM> includes a built-in connector for charging a rechargeable battery. In this specification, the battery contained in the printer <NUM> may be referred to as "printer battery.

The printer <NUM>, which is approximately <NUM> in diameter and approximately <NUM> to <NUM> in length, can be carried around without feeling stress. The printer <NUM> includes a hook <NUM> which allows the printer <NUM> to be put in the chest pocket of clothes to be carried around just like a pen.

The cassette <NUM> according to this embodiment is attached to the printer <NUM>. <FIG> is a phantom perspective view of a housing <NUM> of the cassette <NUM>. <FIG> is a perspective view of the cassette <NUM> from another angle. <FIG> is a front view of the cassette <NUM>.

The cassette <NUM> can store recording sheets <NUM> in the housing <NUM>, and includes two rechargeable batteries 120a and 120b, a motor <NUM>, a feed roller <NUM>, an assist roller <NUM>, a control board <NUM>, and a coil <NUM> for power transmission. The control board <NUM> is provided with a universal serial bus (USB) connector <NUM>.

Sheet guides <NUM> are so provided in the housing <NUM> as to extend on three sides of the recording sheets <NUM> to control the position of the recording sheets <NUM>, so that the recording sheets <NUM> are placed inside the sheet guides <NUM> as illustrated in <FIG>. In this specification, a section for storing recording sheets defined by the sheet guides <NUM> may be referred to as "storage part," and the batteries 120a and 120b may be collectively referred to as "battery <NUM>.

A spring <NUM> is provided at the bottom of the storage part to press the stacked recording sheets <NUM> upward in the Z1 direction.

The batteries 120a and 120b are connected in series. The printer battery is a single-cell rechargeable battery whose nominal voltage is approximately <NUM> V, while the series-connected batteries 120a and 120b supply electric power of approximately <NUM> V, which is twice the nominal voltage of the printer battery. The electric power of the batteries 120a and 120b is supplied to the motor <NUM>, the control board <NUM>, and the coil <NUM>, and may also be supplied to the printer <NUM>.

The motor <NUM> rotates the feed roller <NUM>. A gear <NUM> and a gear <NUM> are attached to the shaft of the motor <NUM> and the shaft of the feed roller <NUM>, respectively. A gear <NUM> is provided between the gears <NUM> and <NUM>.

In a view from the X2 side, when the motor <NUM> rotates clockwise, the gear <NUM> also rotates clockwise, so that the gear <NUM> meshing with the gear <NUM> rotates counterclockwise. When the gear <NUM> rotates counterclockwise, the gear <NUM> meshing with the gear <NUM> rotates clockwise, so that the feed roller <NUM> also rotates clockwise. The feed roller <NUM> is in contact with the topmost recording sheet <NUM>. As the feed roller <NUM> rotates clockwise, the recording sheets <NUM> contacting the feed roller <NUM> are conveyed one by one to the Y2 side to be fed to the printer <NUM>.

Two claws <NUM> for attaching the cassette <NUM> to the printer <NUM> are provided at the Y2 end of the cassette <NUM>. The cassette <NUM> can be attached to the printer <NUM> by hooking the claws <NUM> over the shaft of the feed roller <NUM>.

The assist roller <NUM> rotates independent of the feed roller <NUM>. As described below, when the cassette <NUM> is attached to the printer <NUM>, the assist roller <NUM> rotates in tandem with the rotating feed roller <NUM> to assist feeding of the recording sheets <NUM> to the printer <NUM>.

On a Y2 surface of the cassette <NUM>, which is a surface to be attached to the printer <NUM>, two magnets <NUM> for magnetically attracting the printer <NUM>, electrode terminals 115a and 115b for supplying electric power from the battery <NUM> to the printer <NUM>, and communication terminals <NUM> for communicating information with the printer <NUM> are provided.

Referring to <FIG>, which is a front view of the printer <NUM>, the printer <NUM> includes connection parts 31a and 31b, electrode terminals 32a and 32b, and communication terminals <NUM>, which are exposed in the openings <NUM> and <NUM>. The connection parts 31a and 31b are positioned one at each end of the openings <NUM> and <NUM>.

The connection parts 31a and 31b, which are formed of a magnetic material such as a metal material including iron, cobalt, or nickel, are magnetically attracted to the magnets <NUM>. The electrode terminals 32a and 32b are connected to the electrode terminals 115a and 115b to supply electric power from the cassette <NUM> to the printer <NUM>. The communication terminals <NUM> are connected to the communication terminals <NUM> to perform serial data information communications between the printer <NUM> and the cassette <NUM>.

When the printer <NUM> is magnetically attracted and connected to the cassette <NUM> by the magnets <NUM>, the electrode terminals 115a and 115b contact the electrode terminals 32a and 32b, respectively, so that the electric power of the battery <NUM> can be supplied from the cassette <NUM> to the printer <NUM>. Furthermore, the communication terminals <NUM> contact the communication terminals <NUM>, so that the cassette <NUM> and the printer <NUM> can perform communications.

The electrode terminals 115a and 115b are provided one at each end of the Y2 surface of the cassette <NUM>. Therefore, when the cassette <NUM> is not connected normally to the printer <NUM>, such as when the cassette <NUM> is attached at an angle to the printer <NUM>, at least one of the electrode terminals 115a and 115b is not connected to a corresponding one of the electrode terminals 32a and 32b, so that no electric power is supplied from the cassette <NUM> to the printer <NUM>. This makes it possible to prevent a recording sheet jam or damage to gears due to an operation under loose connection. One of the electrode terminals 115a and 115b is positive and the other is negative.

The printer <NUM> and the cassette <NUM> perform bidirectional communications via the communication terminals <NUM> and <NUM>. Therefore, it is possible to control an operation of the cassette <NUM>, such as driving of the motor <NUM>, from the printer <NUM>.

A control integrated circuit (IC) is mounted on the control board <NUM> to control various operations in the cassette <NUM>, such as the rotation of the motor <NUM>. The coil <NUM> is provided to wirelessly charge the printer battery. The printer <NUM> is placed on part of the cassette <NUM> where the coil <NUM> is provided, and a power-receiving coil provided in the printer <NUM> receives electromagnetic waves radiated from the power-transmitting coil <NUM>. Thus, the printer battery can be wirelessly charged.

Next, a connection of the cassette <NUM> and the printer <NUM> is described. As described above, the cassette <NUM> is attached and connected to the printer <NUM> by hooking the claws <NUM> over the shaft of the feed roller <NUM>. <FIG> are a top-side perspective view and a bottom-side perspective view, respectively, of the printer <NUM> to which the cassette <NUM> is attached.

A Z1 surface of the housing <NUM> includes a placement area <NUM> for placing a portable terminal <NUM> such as a smartphone. The portable terminal <NUM> to which a cover <NUM> is attached may be placed on the placement area <NUM> as illustrated in <FIG> are a top-side perspective view and a bottom-side perspective view, respectively, of the cassette <NUM> to which the printer <NUM> and the portable terminal <NUM> are attached.

<FIG> is a sectional view of the cassette <NUM> to which the printer <NUM> and the portable terminal <NUM> are attached. With the cassette <NUM> attached to the printer <NUM>, gears 13a of the feed roller <NUM> meshes with gears <NUM> of the assist roller <NUM>. Therefore, the assist roller <NUM> rotates in tandem with the rotating feed roller <NUM> to assist feeding of the recording sheets <NUM> to the printer <NUM>. Specifically, to perform printing on the recording sheet <NUM> in the state illustrated in <FIG>, the gears 13a are rotated clockwise by a motor of the printer <NUM> to rotate the feed roller <NUM> clockwise, thereby conveying the recording sheet <NUM> from the cassette <NUM> toward the print head <NUM>. When the gears 13a rotate clockwise, the gears <NUM> meshing with the gears 13a rotate counterclockwise, so that the assist roller <NUM> rotates counterclockwise.

In the cassette <NUM>, when viewed from the X2 side, the feed roller <NUM> is rotated clockwise by the motor <NUM> to convey the recording sheet <NUM> to the Y2 side. When the recording sheet <NUM> enters the nip between the feed roller <NUM> and the assist roller <NUM>, the recording sheet <NUM> is conveyed into the printer <NUM> by the feed roller <NUM> and the assist roller <NUM>.

The feed roller <NUM> rotates independent of the feed roller <NUM>. The conveying speed of the feed roller <NUM> is higher than the conveying speed of the feed roller <NUM> to prevent the slack in the recording sheet <NUM>. During the conveyance of the recording sheet <NUM> by the feed roller <NUM>, to prevent an adverse effect on printing, the feed roller <NUM> is freely rotated by the recording sheet <NUM> conveyed by the feed roller <NUM>. The motor <NUM> stops when the leading edge of the recording sheet <NUM> is detected by the sensor <NUM> illustrated in <FIG>. As a result, no recording sheet <NUM> is conveyed from the cassette <NUM>. Therefore, it is possible to prevent the next recording sheet <NUM> from being fed from the cassette <NUM> after the end of printing on the recording sheet <NUM>.

To attach the portable terminal <NUM> to the cassette <NUM>, an attachment plate <NUM> for attaching the portable terminal <NUM> may be used as illustrated in <FIG>. <FIG> are a top-side perspective view and a bottom-side perspective view, respectively, of the cassette <NUM> to which the portable terminal <NUM> is attached using the attachment plate <NUM>. <FIG> is a perspective view of the portable terminal <NUM> with the cover <NUM>, the attachment plate <NUM>, the printer <NUM>, and the cassette <NUM>. <FIG> illustrates the process of attaching the attachment plate <NUM> to the printer <NUM> using a fixing band <NUM>.

Referring to <FIG>, the attachment plate <NUM> is provided with the fixing band <NUM> for fixing the printer <NUM>, and is fixed to the printer <NUM> by covering the power supply <NUM> with the fixing band <NUM>. The attachment plate <NUM> and the cover <NUM> may be bonded together or magnetically attracted to each other with, for example, a magnet.

With the portable terminal <NUM> being accommodated in the cover <NUM> attached to the attachment plate <NUM> and being fixed to the printer <NUM> through the fixing band <NUM>, the attachment plate <NUM> is placed on and attached to the placement area <NUM>.

The supply of electric power to the printer <NUM> is described with reference to <FIG> and <FIG>. <FIG> and <FIG> are block diagrams illustrating a circuit configuration of the printer <NUM>. The printer <NUM> includes the USB connector <NUM>, a charging circuit <NUM>, a rechargeable battery <NUM>, a knock switch <NUM>, diodes <NUM> and <NUM>, a first gate circuit <NUM>, a second gate circuit <NUM>, an OR circuit <NUM>, a DC-DC converter <NUM>, a controller <NUM> including a central processing unit (CPU), a state-of-charge (SOC) detector <NUM>, and an on-off switch <NUM>. The switch <NUM> turns on and off in accordance with the state of connection of the cassette <NUM> to the printer <NUM>. When the cassette <NUM> is connected to the printer <NUM>, the switch <NUM> is pressed by the housing <NUM> to turn off. The switch <NUM> turns on when the cassette <NUM> is not connected to the printer <NUM>. The switch <NUM> forms a short circuit when not pressed, and is so positioned in the printer <NUM> as to be pressed by the housing <NUM> when the cassette <NUM> is connected to the opening <NUM>. The battery <NUM> is housed in the power supply <NUM>. The DC-DC converter <NUM> converts DC voltage. When a <NUM> V DC voltage is input to the DC-DC converter <NUM>, the DC-DC converter <NUM> outputs a <NUM> V DC voltage that is a logic voltage.

The controller <NUM> includes a detector <NUM> that detects applied voltage. A <NUM> V voltage is applied from the battery <NUM>, while a <NUM> V voltage is applied from the battery <NUM>. Therefore, the controller <NUM> can control the printer <NUM> differently between the time of application of drive voltage with the battery <NUM> and the time of application of drive voltage with the battery <NUM> in accordance with the voltage detected by the detector <NUM>. A threshold for distinguishing between driving with the battery <NUM> and driving with the battery <NUM> may be set to, for example, <NUM> V.

Driving of the printer <NUM> using the battery <NUM> is described with reference to <FIG>. Referring to <FIG>, because the cassette <NUM> is not attached to the printer <NUM>, the switch <NUM> is closed to form a circuit to supply electric power from the battery <NUM>. Because of the closure of the switch <NUM>, an electric current from the battery <NUM> bypasses the diode <NUM>. Thus, when the switch <NUM> is closed, the voltage of the battery <NUM> is applied to the knock switch <NUM>, the first gate circuit <NUM>, and the second gate circuit <NUM> via the switch <NUM>. When the knock switch <NUM> is depressed in this state, a power-on request signal is output to the first gate circuit <NUM>. In response to receiving this signal, the first gate circuit <NUM> outputs "HIGH" to the OR circuit <NUM>. The OR circuit <NUM> outputs "HIGH" to the subsequent DC-DC converter <NUM>. The DC-DC converter <NUM> outputs a logic voltage VDD. As a result, the controller <NUM> is activated to output a lock signal to the second gate circuit <NUM>. At this point, because the controller <NUM> continues outputting the lock signal, this state continues even after the knock switch <NUM> is released. The voltage of the battery <NUM> is applied to the controller <NUM> via the switch <NUM>. The controller <NUM> includes a driver for driving the print head <NUM> and a driver for driving a motor for rotating the platen roller <NUM>, and the electric power of the battery <NUM> is supplied to these drivers. The detector <NUM> detects supply voltage applied to the print head <NUM>, the motor, etc., and the controller <NUM> performs energy control and print speed control in accordance with the detected voltage.

When driving with the battery <NUM>, the applied voltage is less than <NUM> V. Therefore, the controller <NUM> executes a process according to the detected voltage, such as low-speed printing control with the battery <NUM>.

Attaching the cassette <NUM> to the printer <NUM> and driving the printer <NUM> with the battery <NUM> is described with reference to <FIG>. When driving the printer <NUM> with the battery <NUM>, unless the battery <NUM> is disconnected, an excess current flows from the battery <NUM> of higher voltage to the battery <NUM> to cause a trouble. According to this embodiment, an excess current is prevented from flowing to the battery <NUM>.

Referring to <FIG>, because the cassette <NUM> is attached to the printer <NUM>, the switch <NUM> is open. The voltage of the battery <NUM> is applied to the controller <NUM>, the knock switch <NUM>, the first gate circuit <NUM>, and the second gate circuit <NUM>. The voltage of the battery <NUM> is higher than the voltage of the battery <NUM>. Therefore, when the cassette <NUM> is connected to the printer <NUM>, electric current is prevented from flowing to the battery <NUM> by the diode <NUM>, and electric power is supplied from the battery <NUM> to the controller <NUM>, etc. At the same time, the battery <NUM> is disconnected. When the voltage of the battery <NUM> is applied to the controller <NUM>, the controller <NUM> can execute a process according to the applied voltage, such as a high-speed printing process.

When the cassette <NUM> is attached to the printer <NUM>, the printer <NUM> can be driven with the battery <NUM>. In parallel with driving with the battery <NUM>, it is possible to charge the battery <NUM>, specifically by supplying electric power, fed through the USB connector <NUM>, from the charging circuit <NUM> to the battery <NUM> via the diode <NUM>. When a USB charger is inserted into the USB connector <NUM>, a voltage applied to the charging circuit <NUM> is at most approximately <NUM> V. Therefore, the applied voltage is separated from the subsequent circuit by the diode <NUM> and no electric power is supplied to the controller <NUM>, etc. Therefore, charging is normally performed.

At this point, the output of the charging circuit <NUM> is also input to the SOC detector <NUM>, and the SOC detector <NUM> outputs a signal indicating that the battery <NUM> is being charged to the controller <NUM>. In response to this signal, the controller <NUM> transmits an unlock signal to the second gate circuit <NUM> in order to ensure the charging of the battery <NUM> and stop a printing operation.

When the cassette <NUM> is detached from the printer <NUM> during the charging of the battery <NUM>, the detector <NUM> detects a voltage lower than or equal to a threshold. At this point, the controller <NUM> checks a connection with the cassette <NUM>. When there is no response from the cassette <NUM>, the controller <NUM> determines that the cassette <NUM> is detached from the printer <NUM>. When the cassette <NUM> returns an acknowledgment, the controller <NUM> determines the occurrence of an abnormality in the battery <NUM>. In this case, the controller <NUM> determines whether the battery <NUM> is being charged. If the battery <NUM> is being charged and the printer <NUM> is not performing printing, the controller <NUM> turns off the printer <NUM>.

When the cassette <NUM> is attached to the printer <NUM> during driving the printer <NUM> with the battery <NUM>, the detector <NUM> detects an applied voltage exceeding a threshold. At this point, the controller <NUM> sends a connection check signal to the cassette <NUM>. When the cassette <NUM> returns an acknowledgment, the controller <NUM> determines that the cassette <NUM> is connected, and switches control to high-speed printing control on an as-needed basis. When no acknowledgment from the cassette <NUM> is detected, the controller <NUM> determines the occurrence of an abnormality, and displays an error indicator and stops the operation of the printer <NUM>.

The diode <NUM> is a backup diode in the case of switching between the battery <NUM> and the battery <NUM>. When the battery <NUM> is connected, the diode <NUM> prevents electric current from flowing from the battery <NUM> to the battery <NUM>. Furthermore, because the voltage of the battery <NUM> is higher than the voltage of the battery <NUM>, the diode <NUM> is reversely biased, so that it is possible to drive the printer <NUM> with the battery <NUM> independent of charging the battery <NUM>, and it is possible to prevent chattering of the switch <NUM> when the cassette <NUM> is detached.

A sheet cassette <NUM> according to a second embodiment is described below with reference to <FIG>. <FIG> is a phantom side view of the cassette <NUM>, seeing through a housing <NUM>. <FIG> are sectional views of the cassette <NUM> attached to the printer <NUM>, taken along different planes. According to the cassette <NUM>, no motor for rotating a feed roller <NUM> is provided, and the gears <NUM> mesh with gears <NUM> provided on the feed roller <NUM>.

By attaching the cassette <NUM> to the printer <NUM>, the gears 13a mesh with the gears <NUM>.

Accordingly, when the printer <NUM> performs printing, the feed roller <NUM> rotates clockwise to rotate the gears 13a clockwise, so that the gears <NUM> rotate counterclockwise to rotate the assist roller <NUM> counterclockwise. Furthermore, as the gears <NUM> rotate counterclockwise, the gears <NUM> rotate clockwise to rotate the feed roller <NUM> clockwise. As a result of this operation, the recording sheet <NUM> contacting the feed roller <NUM> is conveyed toward and fed into the printer <NUM>.

According to this embodiment because no motor for conveying a recording sheet is necessary, it is possible to save power.

In other respects than those described above, the second embodiment may be the same as the first embodiment.

A sheet cassette <NUM> according to a third embodiment is described below with reference to <FIG>. The cassette <NUM> is compatible with fanfold paper. <FIG> are perspective views of the cassette <NUM>. <FIG> is a diagram illustrating the non-claimed inside of the cassette <NUM>. <FIG> is a sectional view of the cassette <NUM> attached to the printer <NUM>.

The cassette <NUM> includes a housing <NUM>, in which folded fanfold paper <NUM> is placed below on the Z2 side of a partition plate <NUM>. That is the partition plate <NUM> defines a storage part below the partition plate <NUM> in the housing <NUM>. A spring <NUM> is attached to the Z1 surface of the partition plate <NUM>. Furthermore, in order to smoothly convey the fanfold paper <NUM>, ribs <NUM> protruding in the Z1 direction and extending along the Y direction are provided on the Z1 surface of the partition plate <NUM>. An opening <NUM> for pulling out the fanfold paper <NUM> from the lower side to the upper side of the partition plate <NUM> is provided on the Y1 side of the partition plate <NUM>, specifically between a Y1 edge 360a of the partition plate <NUM> and an inner wall surface 310a of the housing <NUM> as illustrated in <FIG>. This allows part of the fanfold paper <NUM> placed below the partition plate <NUM> to be placed onto the spring <NUM> on the upper side of the partition plate <NUM> through the opening <NUM>. The spring <NUM> lifts the fanfold paper <NUM> upward in order to facilitate feeding of the fanfold paper <NUM> to the printer <NUM>.

As illustrated in <FIG>, when the cassette <NUM> is not connected to the printer <NUM>, the claws <NUM>, the magnets <NUM>, the electrode terminals 115a and 115b, the communication terminals <NUM>, and the assist roller <NUM> on the front side of the cassette <NUM> are exposed. Therefore, as illustrated in <FIG>, a front cover <NUM> may be attached to the front side of the cassette <NUM> so as to make it possible to carry the cassette <NUM> even when the cassette <NUM> is disconnected from the printer <NUM>.

Use of the cassette <NUM> makes it possible to perform printing on the fanfold paper <NUM> using the printer <NUM>.

In other respects than those described above, the third embodiment may be the same as the first embodiment.

Claim 1:
A sheet cassette (<NUM>, <NUM>, <NUM>) attachable to a portable printer (<NUM>), the sheet cassette (<NUM>, <NUM>, <NUM>) comprising:
a storage part configured to store a recording sheet (<NUM>); and
a battery (<NUM>, 120a, 120b);
characterized by:
two electrode terminals (115a, 115b) configured to be connected to electrode terminals (32a, 32b) of the portable printer (<NUM>) such that electric power of the battery (<NUM>, 120a, 120b) is supplied to the portable printer (<NUM>) through the two electrode terminals (115a, 115b) when the sheet cassette (<NUM>, <NUM>, <NUM>) is attached to the portable printer (<NUM>), the two electrode terminals (115a, 115b) being provided one at each of ends of a surface of the sheet cassette (<NUM>, <NUM>, <NUM>), the surface being configured to be attached to the portable printer (<NUM>).