Patent Description:
When a trouble occurs in printing dots in a printer having a thermal head, the thermal head needs to be replaced. Therefore, conventionally, a variety of structures have been suggested in order to facilitate replacement of a thermal head. Japanese Unexamined Patent Application Publication No. <CIT>- <CIT>, for example, discloses a printer. In order to replace a thermal head in this printer, screws are released first to remove a head support member from a pressure plate. Then, a locking piece of the head support member is removed from an opening part by rotating the head support member forward around a shaft. After the head support member is removed from the pressure plate, the thermal head can be replaced. Document <CIT> relates to a press mechanism of a thermal head and printer using the same. In a state where a platen is detached from a head press mechanism part, a printing head into which a head support shaft is inserted under pressure is inserted in a support groove part opened at its upper part and a head press plate is moved along a guide rail part to be attached to a support groove part to energize press force to the printing head. A head support part is opened on the side reverse to the platen and a spring receiving part is provided to the rear surface of the printing head at the position between the support shaft and the contact position of the platen with the printing head. Document <CIT> relates to a printer equipped with a support plate, having a printing head provided thereon, support plate guide pins provided to both side surfaces of the support plate, a platen roller and a frame having a platen roller attaching guide and a support plate attaching guide formed thereto. The support plate guide pins are fitted in and attached to the support plate attaching guide and the platen roller is attached to the platen roller attaching guide to align the printing part of the printing head with the center part of the platen roller. The frame is fixed to base of the thermal printer with screws. Furthermore, the structure comprises a plate spring fixed to the base <NUM> with screws, which presses the print head against the platen
Document <CIT> relates to a printer having a separation unit attached to a support board. The separation unit includes a guide rail hole to engage with a shaft so as to slide and swing with respect to the support board. The separation unit moves to a continuous ejection position in which one end of the guide rail hole comes in contact with the shaft, swings in a first rotation direction about the shaft in contact with the other end side of the guide rail hole so as to move away from a thermal head to a swing end position in which the separation unit on the forward end side is within a swing trajectory of the opening and closing cover, and swings from the swing end position in a second rotation direction while engaging on the forward end side with the opening and closing cover moving to the closed position so as to be located at a separation ejection position where the separation roller is adjacent to the feed roller when the opening and closing cover is located at the closed position.

However, tools are required to remove the head support first to replace the thermal head in the conventional printer noted above. Thus, with this printer, workability in replacing the thermal head is not very good.

In view of the above, an object of the present invention is to improve workability in replacing a thermal head.

This object is solved by a printer according to claim <NUM> and a method for replacing a print head according to claim <NUM>.

The embodiment of the present invention improves workability in replacing a thermal head.

A printer <NUM> according to one embodiment of the present invention is a label printer in which continuous issuing and peeling issuing can be switched. Hereinafter, the printer <NUM> will be described in detail with reference to the attached drawings.

It is noted that directions of up (UP), down (DN), left (LH), right (RH), front (FR), and rear (RR) are defined in each drawing, for example, as illustrated in the perspective views of <FIG>, but these definitions of directions are made mainly for convenience of explanation of drawings and are not intended to limit an in-use position of the printer of the present invention.

In these definitions of directions, a "printer front-rear direction" means a front-rear direction of the printer <NUM>. A "printer width direction" means a right-left direction or a lateral direction of the printer <NUM>.

Each of <FIG>, and <FIG> is a perspective view of the printer <NUM> of this embodiment. <FIG> shows a case in which a printer cover <NUM> is in a closed state. <FIG> and <FIG> show cases in which the printer cover <NUM> is in an open state. <FIG> shows a state in which a paper roll "R" is set. <FIG> illustrates a paper roll "R" and shows a state of the printer <NUM> before the paper roll "R" is set.

As shown in <FIG>, the printer <NUM> has a body case <NUM> and the printer cover <NUM> that protect internal functional components. The printer <NUM> has an upper surface provided with an ejection part <NUM> for ejecting labels.

It is possible to use the printer <NUM> with the ejection part <NUM> facing upward (in a horizontally placed state); however, the printer <NUM> can also be used with the ejection part <NUM> facing a horizontal direction (in a vertically held state), such as by hanging a belt hook (not shown) provided on a bottom of the printer <NUM>, on a belt of an operator, or by attaching a shoulder strap (not shown) to the printer <NUM> and putting it on a shoulder of an operator.

A display panel <NUM> is provided on a front side of the ejection part <NUM> in the body case <NUM>. The display panel <NUM> may have a touch panel input mechanism for receiving an operation input from an operator. The display panel <NUM> is connected to a circuit board inside the printer <NUM> and outputs an image of a user interface related to, for example, an operating state of the printer <NUM> or operation of the printer <NUM>, based on a display signal supplied from the circuit board.

Although not shown, an internal frame for supporting or holding various functional components is disposed in the inside of the printer <NUM>, which is surrounded by the body case <NUM> and the printer cover <NUM>. The internal frame, the body case <NUM>, and the printer cover <NUM> correspond to a printer body.

The printer cover <NUM> is able to swing between an open position for exposing the inside of the printer <NUM> and a closed position for covering the inside of the printer <NUM>.

In response to operation to a cover open button 51b that is provided to the body case <NUM>, the printer cover <NUM> opens as shown in <FIG>. Opening the printer cover <NUM> exposes a paper roll-containing chamber <NUM>. The paper roll-containing chamber <NUM> forms space for containing a paper roll "R" (an example of a roll body).

As shown in <FIG>, the paper roll "R" has a roll shape into which a strip continuous paper "P" is wound. The continuous paper "P" includes a strip liner PM and a plurality of labels PL that are temporarily attached on the liner PM at predetermined intervals. A label adherend surface of the liner PM is coated with a release agent, such as silicone, in order to easily peel off labels PL. In addition, position detection marks "M" that indicate reference positions of labels PL are formed at predetermined intervals on a back surface of the label adherend surface of the liner PM.

A front side of the label PL is a printing surface to be printed with information, and it is formed with a thermal color developing layer that develops a specific color when reaching a predetermined temperature region. A back side of the printing surface is an adhesive surface coated with an adhesive. The adhesive surface is attached to the label adherend surface of the liner PM, whereby the label PL is temporarily attached on the liner PM.

A pair of paper roll guides 6a are placed in the paper roll-containing chamber <NUM>. The pair of paper roll guides 6a are members that rotatably support the paper roll "R" while being in contact with both side surfaces of the paper roll "R" and that guide feeding the continuous paper pulled out of the paper roll "R. " The paper roll guides 6a are preferably movable along a width direction of the paper roll "R" in order to vary their positions in accordance with the width of the paper roll "R.

As shown in <FIG>, the printer cover <NUM> is axially supported to the body case <NUM> by a hinge <NUM> so as to swing relative to the body case <NUM> between the open position and the closed position. The hinge <NUM> has a hinge shaft <NUM> that is provided with a torsion spring (not shown) for biasing the printer cover <NUM> in a direction from the closed position to the open position.

As shown in <FIG>, a platen roller <NUM> (an example of a feed roller) is axially supported in a manner rotatable in forward and reverse directions, at an end of the printer cover <NUM>. The platen roller <NUM> is a feeding unit for feeding the continuous paper "P" pulled out of the paper roll "R" and is formed in such a manner as to extend along the width direction of the continuous paper "P. " A gear 10b is coupled to an end of a platen shaft 10a of the platen roller <NUM>. When the printer cover <NUM> is at the closed position, the gear 10b engages with a gear 22b that is disposed in the body case <NUM>, and it is mechanically connected via the gear 22b to a roller-driving stepping motor (not shown) or the like.

As shown in <FIG>, a peeling bar <NUM> is placed along and in the vicinity of the platen roller <NUM>, in the printer cover <NUM>. The peeling bar <NUM> is a peeling member for peeling labels PL from the liner PM and is fixed to both side walls of the printer cover <NUM> at both ends. The peeling bar <NUM> may be fixed to both ends of the platen shaft 10a.

In an embodiment, the cross section of the peeling bar <NUM> has a substantially triangle shape; however, it is not limited thereto, and it may have a spherical shape or an elliptical shape.

The body case <NUM> is provided with a platen-holding bracket <NUM> for holding the platen shaft 10a of the platen roller <NUM> when the printer cover <NUM> is closed. A thermal head <NUM> is disposed in front of the platen-holding bracket <NUM>.

The thermal head <NUM> (an example of a print head) is a print unit for printing information such as characters, symbols, figures, or bar codes, on labels PL, which are temporarily attached on the liner PM fed out of the paper roll "R. " The thermal head <NUM> is provided so as to face the platen roller <NUM> when the printer cover <NUM> is in the closed state.

As described later, a flexible cable that is connected to the circuit board (not shown) is detachably attached to the thermal head <NUM>. The thermal head <NUM> includes a plurality of heating elements (heating resistors) that are arranged along the width direction of the continuous paper "P. " The thermal head <NUM> performs printing by selectively energizing the plurality of heating elements based on a signal transmitted from the circuit board.

As shown in <FIG>, coil springs <NUM> (an example of a biasing member) are disposed in front of the thermal head <NUM>. The coil spring <NUM> is in contact with the thermal head <NUM> at a rear end and is also in contact with the internal frame at a front end (also refer to <FIG>). The coil spring <NUM> biases the thermal head <NUM> to the platen roller <NUM> in printing, whereby the thermal head <NUM> is pressed against the platen roller <NUM> by an optimum pressure for printing.

The printer <NUM> includes a peeling unit <NUM> and performs continuous issuing and peeling issuing in accordance with the peeling unit <NUM> moved between a continuous issuing position and a peeling issuing position. As shown in <FIG>, a peeling unit open button 52b is exposed when the printer cover <NUM> is at the open position. The peeling unit <NUM> is moved by operating the peeling unit open button 52b. <FIG> shows a state of the peeling unit <NUM> when the peeling unit open button 52b is operated.

As described later, the peeling unit open button 52b is operated by an operator, in order to switch from continuous issuing to peeling issuing.

As shown in <FIG>, the peeling unit <NUM> includes a peeling roller cover <NUM> and a peeling roller holder <NUM> that holds a peeling roller <NUM>. The peeling roller cover <NUM> covers the peeling roller holder <NUM> in continuous issuing. The peeling roller cover <NUM> is axially supported by the internal frame in the body case <NUM> and swings from a closed position to an open position (state shown in <FIG>) in accordance with operation to the peeling unit open button 52b.

The peeling roller holder <NUM> is axially supported by the peeling roller cover <NUM>. In continuous issuing, the peeling roller holder <NUM> is contained in such a manner as to be folded under a back surface of the peeling roller cover <NUM>.

The peeling unit <NUM> will be detailed later.

The printer cover <NUM> is provided with a sensor <NUM>. The sensor <NUM> is disposed in a feeding path of the continuous paper "P", along which the continuous paper "P" pulled out of the paper roll "R" reaches the platen roller <NUM>. The sensor <NUM> detects positions of labels PL, when the printer cover <NUM> is in the closed state. It is preferable to control a feeding amount of the continuous paper "P" based on results detected by the sensor <NUM>.

Although not shown, it is preferable to provide a cutter for cutting the liner PM of the continuous paper "P" that has been continuously issued. In the case of providing a cutter, the cutter is placed at the ejection part <NUM> so as to extend along the width direction of the continuous paper "P. " Alternatively, the function of the cutter may be imparted to the peeling bar <NUM>.

Next, continuous issuing and peeling issuing of the printer <NUM> will be described with reference to <FIG>.

The printer <NUM> is configured to allow switching between peeling issuing and continuous issuing. Peeling issuing is issuing labels after peeling them from a liner of a continuous paper, while continuous issuing is issuing labels without peeling them from the liner.

For continuous issuing, a liner that is attached with a necessary amount of labels is prepared, and the labels can be affixed by peeling them from the liner in a working site. Thus, continuous issuing is appropriate for a situation that a target on which a label is to be affixed is distant from the printer <NUM>. In order to perform continuous issuing, the peeling unit <NUM>, which is mounted to the printer <NUM>, is set to the continuous issuing position.

On the other hand, in the case of peeling issuing, labels are ejected one by one in a state of being peeled from a liner. Thus, peeling issuing is appropriate for a situation that a target on which a label is to be affixed is close to an operator. In order to perform peeling issuing, the peeling unit <NUM>, which is mounted to the printer <NUM>, is set to the peeling issuing position. In this state, as a continuous paper is fed by rotating the platen roller <NUM> in order to perform printing, while a liner is fed in a state of being nipped between the peeling roller <NUM> and the platen roller <NUM>, printed labels are individually peeled from the liner and are then ejected to the outside of the printer <NUM>.

<FIG> shows schematic partial sectional views showing positional relationships between the peeling unit <NUM>, the platen roller <NUM>, the peeling bar <NUM>, and the thermal head <NUM> in continuous issuing and in peeling issuing. The peeling roller cover <NUM> and the peeling roller holder <NUM> of the peeling unit <NUM> are represented only by outlines in <FIG>. The outline of the peeling roller cover <NUM> is shown by a dotted line.

In addition, the position of the peeling roller holder <NUM> differs between continuous issuing and peeling issuing, and therefore, only the peeling roller holder <NUM> is shown by hatching.

The position of the peeling unit <NUM> in continuous issuing corresponds to the continuous issuing position, whereas the position of the peeling unit <NUM> in peeling issuing corresponds to the peeling issuing position.

As shown in <FIG>, in continuous issuing, the peeling roller holder <NUM> is contained under the peeling roller cover <NUM>, and the peeling roller <NUM> is thereby at a position spaced apart the platen roller <NUM> and thus does not interrupt ejection of the continuous paper "P. " The continuous paper "P" that has been pulled out of the paper roll "R" is nipped between the platen roller <NUM> and the thermal head <NUM>, and labels on the continuous paper "P" are printed.

In order to switch from continuous issuing to peeling issuing, the peeling roller holder <NUM> is swung around a shaft 42a to a position shown in <FIG>. As shown in <FIG>, in peeling issuing, the peeling roller <NUM> is disposed at a position facing the platen roller <NUM>. Also, in peeling issuing, the continuous paper "P" that has been pulled out of the paper roll "R" is nipped between the platen roller <NUM> and the thermal head <NUM>, and labels on the continuous paper "P" are printed. This movement is the same as in continuous issuing. In peeling issuing, the liner PM of the continuous paper "P" that has been pulled out of the paper roll "R" is quickly turned by the peeling bar <NUM> and is nipped between the platen roller <NUM> and the peeling roller <NUM> to be ejected. In accordance with quick turning of the liner PM at the peeling bar <NUM>, a label PL is peeled from the liner PM and ejected.

Next, opening movement of the printer cover <NUM> will be described with reference to <FIG> and <FIG>. In addition, a cover open lever <NUM> and a peeling unit open lever <NUM> will also be described.

<FIG> shows side views of the cover open lever <NUM>, the peeling unit open lever <NUM>, the platen-holding bracket <NUM> (an example of a locking member), and the peeling unit <NUM> when the printer cover is closed and when the cover open button is operated. <FIG> shows an exemplary situation in which the peeling unit <NUM> is at the continuous issuing position.

As shown in <FIG>, in a side view, the cover open lever <NUM> and the peeling unit open lever <NUM> are disposed to face in the front-rear direction, while extending in the front-rear direction at mutually different heights, resulting in space-efficient arrangement.

<FIG> is a perspective rear view of the cover open lever <NUM>, the peeling unit open lever <NUM>, the platen-holding bracket <NUM>, and the peeling unit <NUM> when the printer cover is closed. <FIG> omits illustration of the peeling unit <NUM>.

The cover open lever <NUM> has the cover open button 51b that is exposed to the outside, as shown in <FIG>. The cover open lever <NUM> is formed with a shaft insertion hole 51a, and a shaft part <NUM> (not shown in <FIG>) that is provided to the internal frame is inserted in the shaft insertion hole 51a. This makes the cover open lever <NUM> be able to swing around the shaft part <NUM>. As shown in <FIG>, the cover open lever <NUM> has a protrusion 51c that protrudes inward.

As shown in <FIG>, the platen-holding bracket <NUM> has a shaft 27a. One end of the shaft 27a is inserted in a boss 52a that is provided to the peeling unit open lever <NUM>, whereas the other end of the shaft 27a is inserted in a boss that is provided to the internal frame (not shown). This makes the platen-holding bracket <NUM> be able to swing around the shaft 27a.

In addition, the peeling unit open lever <NUM> has an engaging protrusion <NUM> (refer to <FIG>) that protrudes inward, although the engaging protrusion <NUM> is not seen in <FIG>. As described later, the engaging protrusion <NUM> engages with the peeling roller cover <NUM> of the peeling unit <NUM>.

The platen-holding bracket <NUM> has a hole 27c that is formed in a side wall, and the protrusion 51c of the cover open lever <NUM> is inserted in the hole 27c. Herein, the hole 27c is formed greater than the protrusion 51c in a side view (that is, the hole 27c has play), whereby the platen-holding bracket <NUM> is able to swing. The platen-holding bracket <NUM> swings around the shaft 27a, whereas the cover open lever <NUM> swings around the shaft part <NUM> (refer to <FIG>), and therefore, they have different swing axes. In consideration of this, the hole 27c is provided with play so as to absorb the difference in trajectory between the hole 27c and the protrusion 51c due to the different swing axes.

The peeling unit open lever <NUM> is able to turn (or swing) around the shaft 27a, which is inserted in the boss 52a. That is, the platen-holding bracket <NUM> and the peeling unit open lever <NUM> share the single swing shaft 27a, which eliminates a need to provide another swing shaft for the peeling unit open lever <NUM>, resulting in contribution to reduction in space and cost. Nevertheless, the structure is not limited thereto, and in another embodiment, an individual swing shaft may be set to each of the platen-holding bracket <NUM> and the peeling unit open lever <NUM>.

A coil spring <NUM> is interposed between the peeling unit open lever <NUM> and the internal frame (not shown), at a position immediately below the peeling unit open button 52b. Upon being pressed (operated) down against a restoring force of the coil spring <NUM>, the peeling unit open lever <NUM> swings around the shaft 27a (swings in a clockwise direction in <FIG>). As described later, in accordance with swinging of the peeling unit open lever <NUM>, the peeling unit <NUM> swings via the engaging protrusion <NUM> and moves from the closed position to the open position.

When the force for pressing down the peeling unit open button 52b is released, the peeling unit open lever <NUM> returns (swings) to the position where it is disposed before being pressed down, by the restoring force of the coil spring <NUM>.

The platen-holding bracket <NUM> is biased by a pair of coil springs <NUM>. In <FIG>, one end of each of the coil springs <NUM> is hooked to the platen-holding bracket <NUM>, whereas the other end of each of the coil springs <NUM> is hooked to the internal frame (not shown).

Unless an external force is applied to the platen-holding bracket <NUM>, the platen-holding bracket <NUM> is in the position at the time the printer cover is closed, as shown in <FIG>, and it holds the platen shaft 10a in a groove 27b. This position is a locking position for locking the printer cover <NUM> coupled to the platen shaft 10a, at the closed position.

In this state, in response to the cover open button 51b being pressed (operated) down, the cover open lever <NUM> swings around the shaft part <NUM> (swings in a counterclockwise direction in <FIG>). In accordance with swinging of the cover open lever <NUM>, the protrusion 51c presses a rim of the hole 27c of the platen-holding bracket <NUM> to swing the platen-holding bracket <NUM> around the shaft 27a (in the clockwise direction in <FIG>) against the restoring force of the coil spring <NUM>.

As described above, the printer cover <NUM>, which is mounted with the platen shaft 10a, is biased in the direction from the closed position to the open position. Thus, the printer cover <NUM> moves to the open position when the platen shaft 10a comes off from the groove 27b due to swinging of the platen-holding bracket <NUM>. The position of the platen-holding bracket <NUM> at this time is an unlocking position for unlocking the printer cover <NUM> at the closed position.

Conversely, in closing the printer cover <NUM>, a pressing down force of an operator closing the printer cover <NUM> makes the platen shaft 10a, which is mounted to the printer cover <NUM>, press down an inclined top part of the platen-holding bracket <NUM> against the restoring force of the coil spring <NUM>. In response to this, the platen-holding bracket <NUM> is swung in the clockwise direction in <FIG>, and the platen shaft 10a is inserted in the groove 27b of the platen-holding bracket <NUM>. In the state in which the platen shaft 10a is inserted in the groove 27b, the platen-holding bracket <NUM> returns to the locking position at the time the printer cover is closed, as shown in <FIG>, by the restoring force of the coil spring <NUM>.

Next, the peeling unit <NUM> will be described with reference to <FIG>.

<FIG> shows perspective views of the peeling unit <NUM> when open and when closed. The peeling unit <NUM> when closed, which is shown in <FIG>, is at the continuous issuing position.

The open position of the peeling unit <NUM> is a position when the peeling roller cover <NUM> is opened in accordance with operation to the peeling unit open button 52b. That is, the open position of the peeling unit <NUM> corresponds to the open position of the peeling roller cover <NUM>.

The open position of the peeling roller cover <NUM> is a position for exposing at least a part of the inside of the printer <NUM> or at least a part of the inside of the body case <NUM>, as shown in <FIG>. In one example, as shown in <FIG>, when the peeling roller cover <NUM> is at the open position, the coil springs <NUM>, a flexible cable <NUM> (refer to <FIG>) connected to the thermal head <NUM>, and so on, inside the body case <NUM>, are exposed. From another point of view, the open position of the peeling roller cover <NUM> may be defined as a position for exposing the thermal head <NUM> inside the body case <NUM>. From yet another point of view, the open position of the peeling roller cover <NUM> may be also defined as a position for allowing opening the peeling roller cover <NUM> at the corresponding position when the peeling roller holder <NUM> is at a position facing the back surface of the peeling roller cover <NUM>. As shown in <FIG>, when the peeling roller cover <NUM> is at the open position (is open), the peeling roller holder <NUM> protrudes upward (in a protruding state).

The closed position of the peeling unit <NUM> is a position when the peeling roller cover <NUM> is closed. That is, the closed position of the peeling unit <NUM> corresponds to the closed position of the peeling roller cover <NUM>.

The closed position of the peeling roller cover <NUM> is a position for covering at least a part of the inside of the printer <NUM> or at least a part of the inside of the body case <NUM>, which is exposed when the peeling roller cover <NUM> is at the open position. In one example, as shown in <FIG>, when the peeling roller cover <NUM> is at the closed position, the coil springs <NUM>, the flexible cable <NUM>, and so on, are not visible from the outside and are covered. From another point of view, the closed position of the peeling roller cover <NUM> may be defined as a position for covering at least a part of the thermal head <NUM> inside the body case <NUM>. From yet another point of view, the closed position of the peeling roller cover <NUM> may be also defined as a position for retaining the peeling roller cover <NUM> at the corresponding position instead of opening it, when the peeling roller holder <NUM> is at the position facing the back surface of the peeling roller cover <NUM>. When the peeling roller cover <NUM> is at the closed position, the position of the peeling roller holder <NUM> differs between for continuous issuing and for peeling issuing.

As shown in <FIG>, when the peeling roller cover <NUM> is at the closed position in continuous issuing, the peeling roller holder <NUM> is contained under the peeling roller cover <NUM> (in a contained state).

With reference to <FIG>, the peeling roller cover <NUM> is a swing member that has a pair of shafts 41a and is thereby able to swing around the shafts 41a. The shaft 41a has a circular cross section and is inserted in a tubular part (not shown), which is provided to the internal frame, so as to be rotatable. The tubular part is preferably formed with, for example, an elongated hole in the printer front-rear direction so that the shaft 41a can be slightly displaced in the printer front-rear direction thereinside. The elongated hole provides play in the printer front-rear direction to the shaft 41a that is inserted in the tubular part, and it improves resistance to impact of falling, etc., of the printer <NUM>.

The direction of the elongated hole that is formed in the tubular part is not limited to the printer front-rear direction, and for example, it can be set to any direction such as the upper-lower direction of the printer <NUM>, in a plane perpendicular to the right-left direction of the printer <NUM>.

The peeling roller cover <NUM> extends in the same direction as the extending direction of the platen roller <NUM>. The peeling roller cover <NUM> has a surface <NUM> and a back surface <NUM>. The surface <NUM> is a surface that is exposed when the peeling roller cover <NUM> is at the closed position. The back surface <NUM> is formed with a recess so as to contain the peeling roller holder <NUM>. Conversely, the surface <NUM> has a swollen shape at the center in the front-rear direction, which is convenient to cut a liner when a cutter is provided to the ejection part <NUM>.

The peeling roller cover <NUM> is formed with an engaging hole <NUM> in the vicinity of the shaft 41a. As described later, the engaging protrusion <NUM> of the peeling unit open lever <NUM> is inserted in the engaging hole <NUM>.

The peeling roller cover <NUM> may be provided at the side with a pair of U-shaped grooves <NUM>. The U-shaped groove <NUM> abuts on a protrusion <NUM> (refer to <FIG>) that is formed to the internal frame, when the shaft 41a is at the closed position. The U-shaped groove <NUM> functions as a part for positioning in the upper-lower direction of the peeling unit <NUM> by abutting on the protrusion <NUM>. The U-shaped groove <NUM> in the state of abutting on the protrusion <NUM> provides a predetermined gap between the peeling unit <NUM> and the thermal head <NUM>. Thus, it is possible to reliably prevent interference between the peeling unit <NUM> and the thermal head <NUM>.

As described above, the shaft 41a of the peeling unit <NUM> is preferably inserted in the elongated hole in the printer front-rear direction, which is formed in the tubular part of the internal frame, whereby play is provided in the printer front-rear direction. Under these conditions, the U-shaped groove <NUM> in the state of abutting and being engaged with the protrusion <NUM> (refer to <FIG>) prevents positional deviation in the printer front-rear direction of the peeling unit <NUM> (peeling roller cover <NUM>) due to play of the shaft 41a inserted in the elongated hole (that is, functions as a part for positioning in the printer front-rear direction of the peeling unit <NUM>).

However, the U-shaped groove <NUM> and the protrusion <NUM> are not necessarily provided. The abutting parts of a part of the peeling unit <NUM> and the internal frame can be formed into any shape as appropriate, in the condition in which they can abut on each other while ensuring the gap between the peeling unit <NUM> and the thermal head <NUM>. Instead of such an abutting structure, the position in the upper-lower direction of the peeling unit <NUM> can be determined by, for example, limiting the movable range of the shaft 41a of the peeling roller cover <NUM>.

The surface <NUM> of the peeling roller cover <NUM> is disposed with a peeling sensor <NUM>. The peeling sensor <NUM> is an optical reflective sensor that detects presence or absence of a label peeled in peeling issuing. With reference to <FIG>, a label PL that is peeled by the peeling bar <NUM> is controlled so that its part on a feeding direction upstream side will be fed and stop in the vicinity of the peeling bar <NUM>, and the peeled label PL thereby remains at the peeling bar <NUM> by its adhesive strength. The peeling sensor <NUM> detects presence or absence of this label PL. When the peeled label is picked up by an operator, the peeling sensor <NUM> detects absence of the label PL, and control is performed to issue a next label.

With reference to <FIG>, the peeling roller holder <NUM> is a member that holds the peeling roller <NUM>.

The peeling roller holder <NUM> extends in the same direction as the extending direction of the platen roller <NUM>, as in the case of the peeling roller cover <NUM>. The peeling roller holder <NUM> is configured to be contained under the back surface <NUM> of the peeling roller cover <NUM>. For this purpose, a pair of shafts 42a are disposed inward of the pair of shafts 41a of the peeling roller cover <NUM>, and the width of the peeling roller holder <NUM> is made smaller than that of the peeling roller cover <NUM>.

The peeling roller holder <NUM> is a swing member that has the pair of shafts 42a and is thereby able to swing around the shafts 42a. The pair of shafts 42a are axially supported by the peeling roller cover <NUM>, at positions separated from the shafts 41a. The peeling roller <NUM> is disposed to distal ends of arms <NUM> extending from the shafts 42a. Thus, as shown in <FIG>, the peeling roller <NUM> largely protrudes upward based on the shafts 41a, when the peeling unit <NUM> is open.

That is, the peeling roller holder <NUM> is able to swing between a contained position when the peeling roller <NUM> is contained under the peeling roller cover <NUM>, and a protruding position when the peeling roller <NUM> is not covered with the peeling roller cover <NUM>. The protruding position is a position when the peeling roller cover <NUM> is open, as shown in <FIG>. The contained position of the peeling roller holder <NUM> is also a position for facing the back surface <NUM> of the peeling roller cover <NUM> as well as a position for being covered with the peeling roller cover <NUM>.

In order to contain the peeling roller holder <NUM>, the peeling roller holder <NUM> is swung around the shaft 42a to the back surface <NUM> of the peeling roller cover <NUM>, and moreover, the whole peeling roller cover <NUM> and peeling roller holder <NUM> are swung around the shaft 41a. As a result, the peeling roller holder <NUM> is compactly contained under the peeling roller cover <NUM> in such a manner as to be folded down.

On the other hand, when the peeling roller cover <NUM> is at the open position, the peeling roller holder <NUM> is able to swing between the contained position and the protruding position. As described later, the peeling roller holder <NUM> is biased in a direction from the contained position to the protruding position by a coil spring <NUM>. Thus, immediately after the peeling roller cover <NUM> moves from the closed position to the open position, the peeling roller holder <NUM> moves in such a manner as to spring out from the contained position to the protruding position. This structure enables an operator to quickly switch from continuous issuing to peeling issuing.

When the peeling roller holder <NUM> is at the protruding position, the peeling roller <NUM> is highly protruded. This enables moving the peeling roller <NUM> to a distant position in setting the peeling unit <NUM> to the peeling issuing position.

A pair of arms <NUM> extend from the pair of shafts 42a. A shaft 45a for rotating the peeling roller <NUM> and auxiliary rollers <NUM> is disposed at the distal ends of the pair of arms <NUM>. Each of the auxiliary rollers <NUM> has a diameter smaller than that of the peeling roller <NUM>. Providing the auxiliary rollers <NUM> on both sides of the peeling roller <NUM> enables smoothly ejecting a wide liner in peeling issuing of a wide label. If the auxiliary rollers <NUM> were not provided, a wide liner would be able to move in the width direction (right-left direction); but providing the auxiliary rollers <NUM> enables stably feeding a wide liner.

However, the auxiliary rollers <NUM> are not necessarily provided. In the case of not using the auxiliary rollers <NUM>, peeling issuing can be executed in the condition in which the peeling roller <NUM> is provided.

Each of the arms <NUM> is formed with a protrusion <NUM> that protrudes outward. As described later, the protrusion <NUM> is provided so as to engage the peeling unit <NUM> with the printer cover <NUM> in peeling issuing.

As shown in <FIG>, a pair of coil springs <NUM> are provided in the vicinity of the pair of shafts 42a of the peeling roller holder <NUM>. Although not shown, the coil spring <NUM> is coupled to the peeling roller holder <NUM> at one end and is also coupled to the peeling roller cover <NUM> at the other end, and it thereby biases the peeling roller holder <NUM> in the direction for swinging from the contained position to the protruding position. With this structure, when the peeling roller cover <NUM> is at the open position (that is, the peeling unit <NUM> is at the open position), the peeling roller holder <NUM> is at the protruding position at any time.

<FIG> is a perspective view of the peeling unit <NUM> when open, as seen from a viewpoint different from that of <FIG>. In the state in which the peeling roller holder <NUM> is at the protruding position, the arms <NUM> of the peeling roller holder <NUM> partially abut on the surface <NUM> of the peeling roller cover <NUM>. In other words, the surface <NUM> of the peeling roller cover <NUM> functions as a stopper for the peeling roller holder <NUM> that is swung by the coil spring <NUM>.

Next, movements in making the peeling unit <NUM> be at the open position from the state in continuous issuing, will be described with reference to <FIG> and <FIG>.

<FIG> and <FIG> sequentially show side views of the peeling unit open lever <NUM> and the peeling unit <NUM>, from states S1 to S3.

The state S1 shows a state in which the printer cover <NUM> is open in continuous issuing. The state S2 shows a state of continuously operating the peeling unit open button. The state S3 shows a state of releasing operation of the peeling unit open button.

The peeling unit open lever <NUM> and the peeling unit <NUM> are engaged with each other by inserting the engaging protrusion <NUM> of the peeling unit open lever <NUM> in an engaging hole <NUM> of the peeling roller cover <NUM>, from the inside. The peeling unit open lever <NUM> swings so as to move the peeling roller cover <NUM> between the closed position and the open position.

The engaging hole <NUM> has, for example, a heart shape, and it allows the engaging protrusion <NUM> to move therein.

As shown by the state S1 in <FIG>, when the printer cover <NUM> is open in continuous issuing, the engaging protrusion <NUM> is positioned on a lower side in the engaging hole <NUM>. In this state, the peeling roller holder <NUM> is at the contained position under the back surface <NUM> (refer to <FIG>) of the peeling roller cover <NUM>.

When the peeling unit open button 52b is pressed (operated) down, the peeling unit open lever <NUM> swings around the shaft 27a in a clockwise direction in <FIG>. In response to this, the engaging protrusion <NUM> of the peeling unit open lever <NUM> moves upward in the engaging hole <NUM> and upwardly presses the peeling roller cover <NUM>, at an upper rim of the engaging hole <NUM>. The peeling roller cover <NUM> is thereby swung around the shaft 41a to the open position in a counterclockwise direction in <FIG>. As described above, the peeling roller holder <NUM> is biased in the direction for swinging from the contained position to the protruding position, by the coil spring <NUM> (refer to <FIG>). Thus, as the peeling roller cover <NUM> swings to the open position, a position restriction of the peeling roller holder <NUM> due to a second stopper <NUM> is released to form space in which the peeling roller holder <NUM> is able to swing. As a result, the peeling roller holder <NUM> swings to the protruding position, as shown by the state S2 in <FIG>. The second stopper <NUM> will be described later.

As shown by the state S2 in <FIG>, the position of the shaft 42a is higher when the peeling roller cover <NUM> is at the open position than when the peeling roller cover <NUM> is at the closed position. In addition, as described above, in the printer <NUM>, space is formed in which the peeling roller holder <NUM> is able to swing from the contained position to the protruding position, when the peeling roller cover <NUM> is at the open position. Thus, the peeling roller holder <NUM> springs up by the biasing force of the coil spring <NUM>.

When pressing down of the peeling unit open button 52b is released from the state shown by the state S2, the peeling unit open lever <NUM> swings around the shaft 27a in the counterclockwise direction in <FIG>, with the restoring force of the coil spring <NUM>. The peeling unit open lever <NUM> and the peeling roller cover <NUM> thereby return to the positions in the state S1. Meanwhile, the peeling roller holder <NUM>, which swings to the protruding position once, remains at the protruding position, instead of returning to the contained position. As a result, the peeling unit <NUM> is in the condition shown by the state S3 in <FIG>.

In the printer <NUM>, the peeling unit <NUM> is set to the peeling issuing position while the printer cover <NUM> and the peeling unit <NUM> are engaged with each other, by swinging the printer cover <NUM> from the open position to the closed position in the state S3 in <FIG>.

Hereinafter, engagement between the peeling unit <NUM> and the printer cover <NUM> in peeling issuing will be described with reference to <FIG>, and <FIG>.

First, the structure of the printer cover <NUM> for engaging with the peeling unit <NUM> will be described with reference to <FIG> is a plane view of the printer cover <NUM>, and <FIG> is an enlarged view of an A-A cross section in <FIG>.

As shown in <FIG>, the printer cover <NUM> has a pair of peeling unit-receiving parts <NUM> at front ends. The peeling unit-receiving part <NUM> is provided in the vicinity of the position at which the platen roller <NUM> and the peeling bar <NUM> are supported.

As shown in <FIG>, the peeling unit-receiving part <NUM> is formed with a guide groove 31p that opens forward. The guide groove 31p is a groove that opens only to the inside along a direction from the front end to a rear end of the printer cover <NUM>. The guide groove 31p receives the protrusion <NUM> (refer to <FIG>) of the peeling unit <NUM> that is positioned on a front side, in the process of closing the printer cover <NUM>.

A roller-pressing mechanism <NUM> is provided in the guide groove 31p. As described later, the roller-pressing mechanism <NUM> presses the peeling roller <NUM> to the platen roller <NUM> to generate a nip pressure for nipping a liner between the peeling roller <NUM> and the platen roller <NUM>, when the printer cover <NUM> is at the closed position.

The roller-pressing mechanism <NUM> includes an abutting part <NUM> that is disposed in the guide groove 31p and also includes a coil spring <NUM> that is disposed behind the abutting part <NUM>. In accordance with the printer cover <NUM> being moved to the closed position, the protrusion <NUM> of the peeling unit <NUM> is guided to the abutting part <NUM>.

When operation to move the printer cover <NUM> from the open position to the closed position is performed in the state S3 in <FIG>, the protrusion <NUM> of the peeling unit <NUM> enters the guide groove 31p of the peeling unit-receiving part <NUM> during the process of moving the printer cover <NUM>. As the printer cover <NUM> swings to the closed position, the protrusion <NUM> advances toward the rear of the printer cover <NUM> along the guide groove 31p and abuts on the abutting part <NUM>. In this manner, the printer cover <NUM> engages with the peeling unit <NUM>. When the printer cover <NUM> reaches the closed position, the peeling roller <NUM> of the peeling unit <NUM> engaging with the printer cover <NUM> is at a position facing the platen roller <NUM>.

Thus, it is possible for an operator to engage the printer cover <NUM> with the peeling unit <NUM> while moving the peeling unit <NUM> to the peeling issuing position, only by operation to close the printer cover <NUM>.

<FIG> is an enlarged sectional view showing a part in the vicinity of the platen roller <NUM> when the printer cover <NUM> is completely closed and the peeling unit <NUM> is set to the peeling issuing position.

As shown in <FIG>, when the printer cover <NUM> is at the closed position, the peeling roller <NUM> of the peeling unit <NUM> is disposed at a position facing the platen roller <NUM>. In this state, the protrusion <NUM> of the peeling unit <NUM> abuts on the abutting part <NUM> of the peeling unit-receiving part <NUM> of the printer cover <NUM> to compress the coil spring <NUM> behind the abutting part <NUM>. A restoring force of the coil spring <NUM> acts on the peeling roller <NUM> via the protrusion <NUM> and thereby makes the peeling roller <NUM> press the platen roller <NUM>, resulting in generation of a nip pressure for nipping a liner. With this structure, a force in a rotation direction around the shaft 42a of the peeling roller holder <NUM> (F5c in <FIG>) is converted into a nip pressure between the peeling roller <NUM> and the platen roller <NUM>.

In an embodiment, a normal line direction of an abutting surface of the abutting part <NUM> abutted with the protrusion <NUM> (direction denoted by a reference symbol "F5b"), and a direction from the center of the peeling roller <NUM> to the center of the platen roller <NUM>, may be the same in a side view, as shown in <FIG>. However, the direction of the force F5 varies depending on the abutting angle between the protrusion <NUM> and the abutting part <NUM>, and therefore, these directions may not be the same. As shown in <FIG>, a component force F5b being a normal component with respect to the abutting surface, of a reaction force F5 of the abutting part <NUM> acting on the protrusion <NUM>, causes the peeling roller <NUM> to press the platen roller <NUM>, whereby a nip pressure for nipping a liner is more effectively generated.

Next, movement for moving the peeling roller holder <NUM> at the protruding position to contain it under the peeling roller cover <NUM> and setting the peeling unit <NUM> to the continuous issuing position, will be described with reference to <FIG> and <FIG>.

In order to switch from peeling issuing to continuous issuing, the cover open button 51b is pressed down to open the printer cover <NUM>, and the peeling unit open button 52b is then pressed down. In response to this, as shown by the state S2 in <FIG>, the peeling roller cover <NUM> swings to the open position, and the peeling roller holder <NUM> swings to the protruding position. In this state, operation to fold down the peeling roller holder <NUM> to contain it under the peeling roller cover <NUM> (folding operation) is performed by an operator, whereby the peeling unit <NUM> is set to the continuous issuing position.

<FIG> and <FIG> sequentially show perspective views of the peeling unit open lever <NUM> and the peeling unit <NUM> when an operator performs the folding operation of the peeling unit <NUM>, from states S5 to S9.

As shown in <FIG>, the peeling unit open lever <NUM> has a first stopper <NUM> and a second stopper <NUM> that protrude inward. The first stopper <NUM> and the second stopper <NUM> are disposed separately in the front-rear direction and are provided so as to abut on the arm <NUM> of the peeling roller holder <NUM> and thereby restrict swinging of the arm <NUM>.

The state S5 in <FIG> is a state in which the peeling roller cover <NUM> is at the open position and the peeling roller holder <NUM> is at the protruding position, which corresponds to the state S2 in <FIG>. An operator can maintain this state by continuously pressing down the peeling unit open button 52b.

In the state S5, an operator may rotate (or swing) the peeling roller holder <NUM> around the shaft 42a and move it to the contained position under the back surface <NUM> of the peeling roller cover <NUM>. Thus, the state is changed to the state S6. At this time, a part most distant from the shaft 42a of the arm <NUM> crosses over the first stopper <NUM> by the operating force of the operator. This makes the arm <NUM> abut on the first stopper <NUM> to restrict swinging of the peeling roller holder <NUM>, against the restoring force of the coil spring <NUM> (refer to <FIG>). That is, when the peeling roller holder <NUM> is in the contained position and the peeling roller cover <NUM> is at the open position, the first stopper <NUM> abuts on the arm <NUM> to restrict swinging of the peeling roller holder <NUM>.

In the state in which the first stopper <NUM> restricts swinging of the peeling roller holder <NUM>, it is easy to move the peeling roller cover <NUM> to the closed position while retaining the peeling roller holder <NUM> at the contained position. If the first stopper <NUM> were not provided, an operator would need to move the peeling roller cover <NUM> to the closed position by releasing pressing down the peeling unit open button 52b while holding the peeling roller holder <NUM> by hand so as to prevent it from swinging from the contained position. Thus, providing the first stopper <NUM> improves operability.

When the operator releases pressing down the peeling unit open button 52b in the state in which the peeling roller holder <NUM> is locked at the contained position by the first stopper <NUM>, the peeling roller cover <NUM> starts moving to the closed position. The state S7 shows a state while the peeling roller cover <NUM> is moving to the closed position.

In the process in which the peeling roller cover <NUM> moves to the closed position, restriction of swinging of the arm <NUM> by the first stopper <NUM> is released in accordance with swinging of the peeling roller cover <NUM>. Specifically, an outer edge of the arm <NUM> is formed so that restriction of swinging of the arm <NUM> will be released at the time the peeling roller cover <NUM> is closed to a predetermined angle.

The state S8 in <FIG> is a state at the time the operator further closes the peeling roller cover <NUM> from the state S7. The peeling roller holder <NUM>, in which restriction of swinging by the first stopper <NUM> is released, is swung by the restoring force of the coil spring <NUM>, but it is again restricted from swinging by the second stopper <NUM>, which is on a rear side of the first stopper <NUM>. That is, the second stopper <NUM> comes into contact with the arm <NUM> while the peeling roller holder <NUM> moves from the open position to the closed position, whereby it restricts the peeling roller holder <NUM> from swinging between the contained position and the protruding position. The state S9 is a state in which the peeling roller cover <NUM> is at the closed position and the peeling unit <NUM> is at the continuous issuing position.

Providing the second stopper <NUM> prevents the peeling roller holder <NUM> from swinging while the peeling roller cover <NUM> moves from the open position to the closed position. Moreover, the second stopper <NUM> is positioned rearward of the first stopper <NUM>, and thus, when the peeling unit open button 52b is operated in the state in which the peeling unit <NUM> is at the continuous issuing position as shown by the state S9, the peeling roller holder <NUM> smoothly swings to the protruding position.

The first stopper <NUM> and the second stopper <NUM> are not necessarily provided. Providing even only one of the stoppers can contribute to improving operability. It is also possible to perform the folding operation of the peeling unit <NUM>, even when both of the first stopper <NUM> and the second stopper <NUM> are not provided. Specifically, it is possible for an operator to contain the peeling roller holder <NUM> under the peeling roller cover <NUM> by carefully moving the peeling roller cover <NUM> to the closed position while holding the peeling roller holder <NUM> at the contained position by hand.

Next, movement to switch between continuous issuing and peeling issuing of the printer <NUM> will be described with reference to <FIG> and <FIG>.

<FIG> and <FIG> sequentially show side views of a main part of the printer <NUM> at the time of switching from continuous issuing to peeling issuing, from states S10 to S15. <FIG> omits illustration of the platen-holding bracket <NUM>.

The state S10 in <FIG> shows a state of the printer <NUM> in continuous issuing. In this state, the platen shaft 10a of the platen roller <NUM>, which is axially supported by the printer cover <NUM>, is fitted in the groove 27b of the platen-holding bracket <NUM>, whereby the printer cover <NUM> is held. In the state S10, the peeling unit <NUM> is set to the continuous issuing position.

When an operator presses down the cover open button 51b in the state S10, holding of the platen shaft 10a by the platen-holding bracket <NUM> is released. Then, as shown by the state S11, the printer cover <NUM> is moved to the open position by the biasing force of the torsion spring provided to the hinge <NUM> (refer to <FIG>).

Subsequently, when the operator presses down the peeling unit open button 52b, the peeling roller cover <NUM> swings from the closed position to the open position, and the peeling roller holder <NUM> swings from the contained position to the protruding position, as shown by the state S12. Then, when the operator releases pressing down of the peeling unit open button 52b, the peeling roller cover <NUM> returns to the closed position, but the peeling roller holder <NUM> remains at the protruding position with the biasing force of the coil spring <NUM> (refer to <FIG>), as shown by the state S13 in <FIG>.

Next, in accordance with the printer cover <NUM> being closed by the operator, the protrusion <NUM> of the peeling roller holder <NUM> at the protruding position is inserted in the guide groove 31p (refer to <FIG>) of the printer cover <NUM> and is guided therealong, whereby the printer cover <NUM> and the peeling unit <NUM> engage with each other, as shown by the state S14.

As shown by the state S15, when the printer cover <NUM> reaches the closed position, the platen shaft 10a of the platen roller <NUM> is held by the platen-holding bracket <NUM>, and the peeling unit <NUM> is set to the peeling issuing position. That is, the peeling roller <NUM> of the peeling unit <NUM> is disposed at the position facing the platen roller <NUM> to nip the liner PM with the platen roller <NUM>. In this state, as described above, the protrusion <NUM> that is engaged with the printer cover <NUM> is pressed by the coil spring <NUM> (refer to <FIG>), whereby an appropriate nip pressure against the platen roller <NUM> is generated in the peeling roller <NUM>.

In peeling issuing, a label PL that is printed by the thermal head <NUM> is peeled from the liner PM, due to the liner PM being quickly turned by the peeling bar <NUM>. The peeling roller <NUM> is driven to rotate in accordance with rotation of the platen roller <NUM> and ejects the liner PM.

In order to switch from peeling issuing to continuous issuing, the cover open button 51b is pressed down to open the printer cover <NUM>, and the peeling unit open button 52b is then pressed down. This causes the peeling roller cover <NUM> of the peeling unit <NUM> to swing to the open position and also causes the peeling roller holder <NUM> to swing to the protruding position. Thereafter, as described with reference to <FIG> and <FIG>, the folding operation of the peeling unit <NUM> is performed to set the peeling unit <NUM> to the continuous issuing position.

As described above, the printer <NUM> of the embodiment includes the peeling unit <NUM> that is movable between the continuous issuing position and the peeling issuing position. When the peeling unit <NUM> is at the continuous issuing position, the peeling roller holder <NUM> holding the peeling roller <NUM> is compactly contained at the contained position under the back surface of the peeling roller cover <NUM>.

Switching from continuous issuing to peeling issuing is performed by a simple operation as follows: opening the printer cover <NUM>; operating the peeling unit open button 52b to move the peeling roller holder <NUM> to the protruding position; and closing the printer cover <NUM>. That is, switching can be performed by a simple action of these easy three steps, and operability is excellent. In addition, when the printer cover <NUM> is at the closed position, the peeling roller <NUM> is pressed against the platen roller <NUM> by the roller-pressing mechanism <NUM> of the printer cover <NUM>, resulting in generation of an appropriate nip pressure.

Conversely, switching from peeling issuing to continuous issuing is performed as follows: opening the printer cover <NUM>; operating the peeling unit open button 52b to move the peeling roller holder <NUM> to the protruding position; performing the folding operation to move the peeling roller holder <NUM> to the contained position; and closing the printer cover <NUM>. Also in this case, the operation is simple.

Next, a method of mounting and removing the thermal head <NUM> to and from the printer <NUM> will be described with reference to <FIG>.

<FIG> shows a front side (an example of a first side) biased by the coil spring <NUM>, which is one of both surfaces of the thermal head <NUM>, and <FIG> shows a rear side (an example of a second side) of the thermal head <NUM>. The rear side of the thermal head <NUM> faces the platen roller <NUM>. <FIG> shows enlarged sectional views of an A-A cross section and a B-B cross section in <FIG>.

As shown in <FIG> and <FIG>, the thermal head <NUM> has a structure in which a board <NUM> is attached to a heat dissipation plate <NUM> (an example of a base) that has a substantially rectangular shape in a plane view. The heat dissipation plate <NUM> is made of a metal material having a high thermal conductivity, such as aluminum. The A-A cross section in <FIG> shows that the board <NUM> is attached to the heat dissipation plate <NUM> in such a manner as to extend from a surface 281a of the heat dissipation plate <NUM> to a back surface 281b on a side opposite to the surface 281a, via a first end part 281e1 interposed therebetween. The board <NUM> is, for example, a ceramic board.

As shown in <FIG> and by the B-B cross section in <FIG>, a cutout 283c is provided at a substantially center position in a longitudinal direction (lateral direction) of the surface 281a of the thermal head <NUM>. The cutout 283c does not have the board <NUM> and exposes the surface 281a of the heat dissipation plate <NUM>. As described later, the cutout 283c is configured to be in contact with a protrusion <NUM> (refer to <FIG>) for allowing the thermal head <NUM> to swing.

As shown in <FIG> and by the A-A cross section in <FIG>, the board <NUM> that is attached to the back surface 281b of the heat dissipation plate <NUM> is mounted with, but not limited to, surface-mount devices (SMDs) such as a connector <NUM>, an EEPROM <NUM>, and a diode <NUM>. In the state in which the thermal head <NUM> is mounted to the printer <NUM>, the flexible cable <NUM> is connected to the connector <NUM>. The flexible cable <NUM> transmits a signal from the circuit board (not shown) of the printer <NUM> to the thermal head <NUM>.

In the state in which the thermal head <NUM> is mounted to the printer <NUM>, the relatively tall surface-mount devices (e.g., the connector <NUM>, the EEPROM <NUM>, and the diode <NUM> in <FIG>), which are mounted on the back surface 281b of the heat dissipation plate <NUM>, face the front side of the printer <NUM>. This configuration protects these surface-mount devices from water, etc., which may enter from the ejection part <NUM> on a rear side of the thermal head <NUM>. A driver IC (not shown) is mounted in the vicinity of a heat generating part <NUM> on the rear side of the thermal head <NUM> facing the ejection part <NUM> (on a side on which the surface 281a of the heat dissipation plate <NUM> is provided). Due to the driver IC with low height, the driver IC and wiring are protected together with the heat generating part <NUM> by a protective layer or a coating layer, whereby they are unlikely to be damaged by water entering from the ejection part <NUM>.

As shown in <FIG>, the tall surface-mount devices, such as the connector, are not disposed on the rear side of the thermal head <NUM> (on the side disposed with the heat generating part <NUM>). Thus, a feed angle of a label PL relative to the heat generating part <NUM> can be small (in other words, it can be an angle approximately perpendicular to the heat generating part <NUM> in a side view) (refer to <FIG>). Here, good print quality is obtained due to the following reasons.

The heat generating part <NUM> includes a glaze layer (partial graze) generally having a protrusion shape, and it thereby has a protrusion shape as a whole. If tall surface-mount devices are disposed on the rear side of the thermal head <NUM>, the feeding angle of a label PL relative to the heat generating part <NUM> is made large in order to avoid the tall surface-mount devices. In this case, due to the heat generating part <NUM> having a protrusion shape and to stiffness (resilience) of a label PL, the label PL tends to rise from the heat generating part <NUM> at the position thereof, and it is difficult to apply an appropriate printing pressure to the label PL between the heat generating part <NUM> and the platen roller <NUM>. In contrast, for a small feeding angle of a label PL relative to the heat generating part <NUM>, although having a protrusion shape, the heat generating part <NUM> pinches a label PL with the platen roller <NUM> by applying an appropriate printing pressure, in the vicinity of a top of the heat generating part <NUM>. Thus, good print quality is obtained.

A pair of shafts 28a that extend outward are coupled to both end surfaces of the heat dissipation plate <NUM>. As described later, the pair of shafts 28a are provided in order to mount the thermal head <NUM> to the internal frame of the printer <NUM>. As shown in <FIG>, the shaft 28a has a large-diameter part joined to the heat dissipation plate <NUM> and has a small-diameter part extending outward from the large-diameter part, and it thereby has a high strength. The small-diameter part of the shaft 28a is inserted in a shaft-receiving groove <NUM>, which will be described later.

<FIG> is a partial sectional view of the printer <NUM> in a plane perpendicular to the right-left direction, in the state in which the peeling unit open button 52b is continuously pressed down to make the peeling roller cover <NUM> be at the open position and to make the peeling roller holder <NUM> be at the protruding position. <FIG> does not show the thermal head <NUM> and the coil spring <NUM>, in order to make the shaft-receiving groove <NUM>, into which the shaft 28a of the thermal head <NUM> is inserted, clearly visible.

As shown in <FIG>, the internal frame of the printer <NUM> is formed with the shaft-receiving groove <NUM> having a substantially L-shape. Although <FIG> shows only a shaft-receiving groove <NUM> that receives one of the pair of shafts 28a of the thermal head <NUM>, another shaft-receiving groove <NUM> that receives the other shaft 28a is also formed in the same manner.

As shown by the enlarged drawing in <FIG>, the shaft-receiving groove <NUM> has a first groove <NUM> and a second groove <NUM>. Herein, each of positions P1 and P2 shows a position where the shaft 28a can be in the shaft-receiving groove <NUM>, in a virtual manner. In this disclosure, the state in which the shaft 28a is at the position P1 may be referred to as a state in which the thermal head <NUM> is at the position P1; the state in which the shaft 28a is at the position P2 may be referred to as a state in which the thermal head <NUM> is at the position P2.

The first groove <NUM> extends in a direction in which the thermal head <NUM> moves to and away from the position P1 (an example of a first position of a print head). The second groove <NUM> extends from the position P1 to the position P2 (an example of a second position of a print head) in a direction in which the coil spring <NUM> in front of the thermal head <NUM> biases the thermal head <NUM> (that is, in a rear direction; an example of a first direction). The shaft-receiving groove <NUM> is an L-shaped groove composed of the first groove <NUM> and the second groove <NUM>, and therefore, the position of the thermal head <NUM> can be switched between two positions P1, P2 by this relatively simple shape. Herein, the position P2 is a position at which the thermal head <NUM> cannot be removed by moving it upward, while the position P1 is a position at which the thermal head <NUM> can be removed by moving it upward.

The thermal head <NUM> is movable between the positions P1 and P2 in the direction of being biased by the coil spring <NUM>. Thus, in mounting the thermal head <NUM>, the thermal head <NUM> can be easily set to the position P2 due to the biasing force of the coil spring <NUM>, simply by inserting the shaft 28a to the position P1 along the first groove <NUM>.

Next, a method of replacing the thermal head <NUM> will be described with reference to <FIG>.

<FIG> illustrates a method of replacing the thermal head <NUM> and shows partial side views of a replacement-target thermal head <NUM> in states S20 and S21.

Normally, the replacement-target thermal head <NUM>, which is mounted to the printer <NUM>, is disposed at the position P2 of the shaft-receiving groove <NUM>, as shown by the state S20. In this state, the whole thermal head <NUM> is biased to the platen roller <NUM> (not shown in <FIG>) (that is, in the rear direction) by the biasing force of the coil spring <NUM>, and the shaft 28a of the thermal head <NUM> is thereby stably positioned at the position P2.

In order to remove the replacement-target thermal head <NUM>, it is moved from the position P2 to the position P1 in a direction opposite to a first direction, against the biasing force of the coil spring <NUM>, as shown by the state S21. The first direction is a direction in which the coil spring <NUM> biases the thermal head <NUM>, and the direction opposite to the first direction is a front direction. Subsequently, the replacement-target thermal head <NUM> is moved upward (an example of a second direction) from the position P1, and the shaft 28a of the replacement-target thermal head <NUM> is removed from the shaft-receiving groove <NUM>, whereby the replacement-target thermal head <NUM> is removed. At this time, the flexible cable <NUM> is connected to the connector <NUM> of the replacement-target thermal head <NUM> (refer to <FIG>). Thus, the flexible cable <NUM> is disconnected from the connector <NUM> of the replacement-target thermal head <NUM>.

After the replacement-target thermal head <NUM> is detached from the flexible cable <NUM>, a new thermal head <NUM> may be mounted to the printer <NUM> in a procedure reverse to the procedure of taking out the thermal head <NUM>.

Specifically, the disconnected flexible cable <NUM> is first connected to the connector <NUM> of a new thermal head <NUM> (refer to <FIG>). The new thermal head <NUM> is then inserted into the position P1 and is moved from the position P1 to the position P2 by the biasing force of the coil spring <NUM>. In more detail, the new thermal head <NUM> is moved downward (an example of an opposite direction to a second direction), and the shaft 28a of the new thermal head <NUM> is inserted into the shaft-receiving groove <NUM> from the first groove <NUM> (refer to <FIG>). At this time, insertion is performed while the end of the coil spring <NUM> (rear end of the coil spring <NUM>) is pressed forward (in the direction against the biasing force of the coil spring <NUM>) by the back surface 281b (surface facing forward of the printer <NUM>) of the new thermal head <NUM>. Upon reaching the position P1, the shaft 28a of the new thermal head <NUM> is moved to the position P2 by the biasing force of the coil spring <NUM>, without requiring an operating force of an operator.

Thus, the thermal head <NUM> is replaced as described above.

The thermal head <NUM> is not disposed with the surface-mount devices, such as the connector, on the rear side (on the side disposed with the heat generating part <NUM>), as shown in <FIG>, and it is thereby easy to replace. Also, in consideration of the coil spring <NUM> biasing the thermal head <NUM> rearward, if the thermal head <NUM> did not have a flat rear side, it would interfere with the internal frame on a rear side (e.g., a wall surface <NUM>; refer to <FIG>) and would be difficult to smoothly insert into the shaft-receiving groove <NUM>. In contrast, due to the thermal head <NUM> having a flat rear side, the new thermal head <NUM> can be smoothly inserted into the shaft-receiving groove <NUM>, although biased by the coil spring <NUM>.

Mounting and removing of the thermal head <NUM> are performed when the peeling unit <NUM> is at the open position. In more detail, the peeling unit <NUM> at the closed position covers at least a part of the thermal head <NUM>, whereas the peeling unit <NUM> at the open position does not cover the thermal head <NUM>, as shown in <FIG>. In view of this, mounting and removing of the thermal head <NUM> are performed when the peeling unit <NUM> is at the open position.

When the peeling unit <NUM> is at the closed position, none of other member is interposed between the peeling unit <NUM> and the thermal head <NUM>, and the peeling unit <NUM> directly covers at least a part of the thermal head <NUM>.

With reference again to <FIG>, in the state in which the peeling roller cover <NUM> is at the open position (that is, the peeling unit <NUM> is at the open position), space for allowing mounting and removing the thermal head <NUM> having the shaft 28a at the position P1, is formed. Thus, an operator can remove the thermal head <NUM> from the printer <NUM> in accordance with merely the following operation process: opening the printer cover <NUM>; continuously pressing down the peeling unit open button 52b to make the peeling unit <NUM> be in the state shown in <FIG>; as described above, sliding the shaft 28a of the thermal head <NUM> from the position P2 to the position P1 against the biasing force of the coil spring <NUM>; and pulling up the thermal head <NUM>.

In addition, in the printer <NUM> of this embodiment, at least a part of the rear side of the thermal head <NUM> is exposed to the paper roll-containing chamber <NUM>, as shown in <FIG>. With this structure, working space for taking out the thermal head <NUM> is ensured by temporarily removing the paper roll "R," which enables more easily taking out the thermal head <NUM>. Specifically, in sliding the shaft 28a of the thermal head <NUM> from the position P2 to the position P1, an operator needs to apply an operating force to the thermal head <NUM> from a rear side to a front side, but the operating force is easily applied due to the space behind the thermal head <NUM>. Moreover, in pulling up the thermal head <NUM>, the space behind the thermal head <NUM> helps an operator in putting a hand therein and pulling up.

In mounting the thermal head <NUM> to the printer <NUM>, an operation is performed in the order reverse to the operation in taking out the thermal head <NUM> from the printer <NUM>. As in the case described above, the peeling unit <NUM> is set to the state shown in <FIG>. Then, the shaft 28a of the thermal head <NUM> is inserted into the position P1 from the first groove <NUM> of the shaft-receiving groove <NUM> while the end of the coil spring <NUM> (rear end of the coil spring <NUM>) is pressed forward (in the direction against the biasing force of the coil spring <NUM>) by the back surface 281b (surface facing forward of the printer <NUM>) of the thermal head <NUM>. The thermal head <NUM> is then moved to the position P2 by the biasing force of the coil spring <NUM>.

Thus, the thermal head <NUM> can be easily replaced without using tools.

In another embodiment, the shaft-receiving groove may have another shape, instead of the L-shape. The shaft-receiving groove may have, for example, a groove extending obliquely forward or extending obliquely rearward from the position P1, as long as the thermal head <NUM> can be attached and removed from the position P1. Alternatively, the shaft-receiving groove may have a U-shaped groove path between the positions P1 and P2 in such a manner that the position P2 is provided at a position that the path reaches after starting from the position P1 in <FIG>, extending forward, extending slightly downward, and then extending rearward, although this structure causes mounting and removing the thermal head <NUM> to be a little difficult. In this case, an operator can remove the shaft 28a of the thermal head <NUM> by moving it from the position P2 to the position P1 along the U-shaped groove.

Next, a support structure of the thermal head <NUM> will be described with reference to <FIG>, <FIG>.

First, a structure of the internal frame on a rear side of the thermal head <NUM> will be described with reference to <FIG> is a perspective view of a part of the internal frame along with components attached to the internal frame, a part of which is enlarged. <FIG> does not show the thermal head <NUM>.

As shown in <FIG>, the internal frame has a wall surface <NUM> that is configured to face the rear surface of the thermal head <NUM>, behind an area to be disposed with the thermal head <NUM> (on a paper roll-containing chamber <NUM> side). The wall surface <NUM> is formed with a protrusion <NUM>. The protrusion <NUM> abuts on the rear surface of the thermal head <NUM> that is mounted. As shown in <FIG>, the abutting surface of the protrusion <NUM> is preferably curved so as to be convex toward the rear surface of the thermal head <NUM>.

<FIG> both illustrate forces that act on the thermal head <NUM> in the printer <NUM> of this embodiment; <FIG> shows a cross section in a plane perpendicular to the upper-lower direction, and <FIG> shows a cross section in a plane perpendicular to the right-left direction. <FIG> have scales different from each other.

As shown in <FIG>, the protrusion <NUM> is provided at a position at which it abuts on a substantially center part in the right-left direction of the thermal head <NUM> that is mounted. In addition, the protrusion <NUM> is provided at a position at which it abuts on a substantially center position in the right-left direction between the pair of coil springs <NUM>, of the rear side of the thermal head <NUM>.

The cutout 283c (refer to <FIG>) is provided at the approximate center in the right-left direction of the thermal head <NUM>, as described above, and the protrusion <NUM> abuts on the thermal head <NUM> at the cutout 283c. The cutout 283c is not covered with the board <NUM> and exposes the heat dissipation plate <NUM> of the thermal head <NUM>, whereby the thermal head <NUM> is more stably supported.

It should be noted that the cutout 283c is not necessarily provided. The protrusion <NUM> may support the thermal head <NUM> at an area of the board <NUM>, without the cutout 283c provided.

The rear surface of the thermal head <NUM> is preferably provided with a recess having a shape corresponding to the protrusion <NUM>, at the position for abutting on the protrusion <NUM>. This causes the thermal head <NUM> to hardly deviate from the position for abutting on the protrusion <NUM> and to be more stably supported.

In an embodiment, a recess may be provided in the wall surface <NUM> of the internal frame, whereas the rear surface of the thermal head <NUM> may be provided with a protrusion having a shape corresponding to the recess of the wall surface <NUM>. In this case, the thermal head <NUM> is also able to swing, but it is stably supported.

The shape of the protrusion <NUM> shown in <FIG> is merely an example, and it can be another shape that swingably supports the thermal head <NUM>. For example, the outer shape of the protrusion <NUM> may be a part of a spherical surface, instead of the shape shown in <FIG>.

As shown in <FIG>, in a plane view of the printer <NUM>, rearward restoring forces F1 and F2 of the pair of coil springs <NUM> act on the front side of the thermal head <NUM>, whereas a reaction force F3 acts from the protrusion <NUM> abutting on the rear side of the thermal head <NUM>. Herein, the protrusion <NUM> is at the approximate center position in a top view of the printer <NUM>, and thus, the thermal head <NUM> is able to swing around a fulcrum at the protrusion <NUM>, in a clockwise direction and a counterclockwise direction in <FIG>.

As shown in <FIG>, in a side view of the printer <NUM>, the rearward restoring forces F1 and F2 (restoring force F2 is not visible in <FIG>) of the pair of coil springs <NUM> act on the front side of the thermal head <NUM>. A reaction force F4 from the platen roller <NUM> acts on the rear side of the thermal head <NUM>, above the points of application of the restoring forces F1 and F2. The reaction force F3 from the protrusion <NUM> acts on the rear side of the thermal head <NUM>, under the points of application of the restoring forces F1 and F2. Thus, the thermal head <NUM> is able to swing around a fulcrum at the protrusion <NUM>, in a clockwise direction and a counterclockwise direction in <FIG>.

In addition, in a side view of the printer <NUM>, the points of applying the biasing forces of the coil springs <NUM> to the thermal head <NUM> are between the position at which the thermal head <NUM> receives the reaction force from the platen roller <NUM> and the position at which the protrusion <NUM> supports the rear side of the thermal head <NUM>. With this structure, the biasing forces of the coil springs <NUM> are received at an upper part and a lower part, whereby the thermal head <NUM> is supported with good balance.

In <FIG>, the surface on which the protrusion <NUM> abuts (that is, the surface on which the heat dissipation plate <NUM> is exposed by the cutout 283c), and the surface corresponding to the heat generating part <NUM>, are preferably in the same reference plane on the rear side of the thermal head <NUM>. This enables pressing the heating elements of the thermal head <NUM> against the platen roller <NUM> at an appropriate angle.

As shown in <FIG>, the thermal head <NUM> is able to swing around a fulcrum at the protrusion <NUM> in a clockwise swinging direction and a counterclockwise swinging direction in a side view of the printer <NUM>. The thermal head <NUM> is also able to swing around a fulcrum at the protrusion <NUM> in a clockwise swinging direction and a counterclockwise swinging direction in a plane view of the printer <NUM>. Thus, the thermal head <NUM> uniformly applies pressure to the platen roller <NUM> in printing. The reason of this is as follows.

In a printer having an existing thermal head, the thermal head is fixed, for example, at two points, by using screws, shafts, brackets, or the like, so as to be mounted to an internal frame or a housing of the printer. In such a case, due to deviation of the mounted position, the pressure of the thermal head abutting on a platen roller may not be uniform in an axial direction of the platen roller, which may cause degradation in print quality.

On the other hand, in this embodiment, the thermal head <NUM> is able to swing around a fulcrum at the protrusion <NUM> in a side view and in a plane view of the printer <NUM>. With this structure, the thermal head <NUM> can follow and maintain uniform pressure on the platen roller <NUM>, for example, even when there is a mounting error of the platen roller <NUM>, circular runout of the platen roller <NUM> is large in rotating, or a rugged surface label is temporarily attached on a liner.

Moreover, the thermal head <NUM> is movable between the positions P1 and P2 (refer to <FIG>) in the direction of being biased by the coil spring <NUM>, and thus, the thermal head <NUM> is not prevented from swinging around a fulcrum at the protrusion <NUM>.

In some printers having an existing thermal head, a fulcrum shaft is provided at a lower part of the thermal head, and this shaft is fixed to a printer body to enable the thermal head to swing in a side view. However, unlike the printer <NUM>, this thermal head cannot be replaced without using tools. On the other hand, the printer <NUM> is superior to existing ones in that the thermal head <NUM> can be replaced without using tools while enabling to swing in a side view and in a plane view of the printer <NUM>.

In another embodiment, protrusions <NUM> may be provided at two positions separated in the right-left direction on the wall surface <NUM> shown in <FIG>. Also in this case, the thermal head <NUM> is able to swing around fulcrums at the protrusions <NUM> in a side view of the printer <NUM>. Even in the case in which the thermal head <NUM> is able to swing only in a side view of the printer <NUM>, degradation in print quality is prevented.

In another embodiment, protrusions <NUM> may be provided at two positions separated in the upper-lower direction on the wall surface <NUM> shown in <FIG>. Also in this case, the thermal head <NUM> is able to swing around fulcrums at the protrusions <NUM> in a plane view of the printer <NUM>. Even in the case in which the thermal head <NUM> is able to swing only in a plane view of the printer <NUM>, degradation in print quality is prevented.

As shown in <FIG>, the flexible cable <NUM> is detachably connected to the thermal head <NUM>. The flexible cable <NUM> is connected from the connector <NUM> of the thermal head <NUM> that is mounted to the printer <NUM>, to the circuit board (not shown) at a front part of the printer <NUM>, as shown in <FIG>. The flexible cable <NUM> is fixed at a fixing position 24a on an upper surface of a bracket <NUM> in front of the thermal head <NUM>, for example, by screwing or adhesive.

A cable-containing chamber <NUM> for containing the flexible cable <NUM> is formed between the thermal head <NUM> and the circuit board. The cable-containing chamber <NUM> is configured to contain the relatively long flexible cable <NUM> between the connector of the thermal head <NUM> and the fixing position 24a. With this structure, when removed, the thermal head <NUM> can be moved to a position sufficiently higher than the printer <NUM> based on the fixed position 24a. This makes it easy to remove the flexible cable <NUM> from the connector of the thermal head <NUM> and to replace with a new thermal head <NUM>.

However, the cable-containing chamber <NUM> is not necessarily formed. Even in this case, although the cable length from the connector <NUM> of the thermal head <NUM> to the fixing position 24a is reduced, it is possible to remove the flexible cable <NUM> from the connector <NUM> and to replace the thermal head <NUM>.

As shown in <FIG>, the cable-containing chamber <NUM> is formed in space between the platen-holding bracket <NUM> and the thermal head <NUM>. Thus, the space that is formed by the platen-holding bracket <NUM> having a U-shape in a plane view is efficiently used.

The cable-containing chamber <NUM> may not be formed as the space between the platen-holding bracket <NUM> and the thermal head <NUM>. In one example, the flexible cable <NUM> extending from the connector of the thermal head <NUM> may be passed under the platen-holding bracket <NUM>, and a containing chamber may be provided on a front side of the platen-holding bracket <NUM>.

As described above, in the printer <NUM>, the surface-mount devices are not mounted on the rear surface of the thermal head <NUM> and are thereby protected from water, etc., which may enter from the ejection part <NUM>.

In the printer <NUM>, space for allowing mounting and removing the thermal head <NUM> is formed when the peeling unit <NUM> is at the open position not covering the thermal head <NUM>, which improves the workability in replacing the thermal head <NUM>. Moreover, the thermal head <NUM> is biased rearward (in a direction to the platen roller <NUM>) and is movable along this direction between the first position for allowing mounting and removing the thermal head <NUM> and the second position for restricting mounting and removing of the thermal head <NUM>. Thus, the thermal head <NUM> can be removed only by moving it from the second position to the first position, and tools and the like are not necessary.

In the printer <NUM>, the thermal head <NUM> is able to swing around a fulcrum at the protrusion <NUM> in a clockwise swinging direction and a counterclockwise swinging direction in a side view of the printer <NUM>, and the thermal head <NUM> is also able to swing around a fulcrum at the protrusion <NUM> in a clockwise swinging direction and a counterclockwise swinging direction in a plane view of the printer <NUM>. Thus, the thermal head <NUM> uniformly applies pressure to the platen roller <NUM> in printing, and it is possible to prevent degradation in print quality due to the method of mounting the thermal head.

Next, a thermal head 28A according to another embodiment will be described with reference to <FIG>.

<FIG> is a perspective front view of the thermal head 28A, and <FIG> is a perspective rear view of the thermal head 28A. <FIG> is a perspective view of a plate member included in the thermal head 28A. <FIG> is a perspective view of the thermal head 28A, as seen from a viewpoint different from those of <FIG>.

It is clear from a comparison between <FIG> and <FIG> that the thermal head 28A differs from the thermal head <NUM> in having a plate member <NUM>.

The plate member <NUM>, which is a member formed of a metal material such as stainless steel, is fastened to the heat dissipation plate <NUM> with screws. As shown in <FIG>, the plate member <NUM> has a base <NUM>, projecting pieces <NUM> and 72R, and a projecting plate <NUM>.

The projecting pieces <NUM> and 72R project from both ends of the base <NUM> in a direction perpendicular to a main surface of the base <NUM> (that is, in a direction perpendicular to the surface 281a when they are attached to the heat dissipation plate <NUM>). In the state in which the plate member <NUM> is attached to the heat dissipation plate <NUM>, the projecting pieces <NUM> and 72R project on a side mounted with the heat generating part <NUM>, as shown in <FIG>. The projecting pieces <NUM> and 72R have edge parts <NUM> and 721R at ends.

The projecting piece <NUM> is formed with a hole 72a, whereas the projecting piece 72R is formed with a U-shaped groove 72b. As shown in <FIG> and 28B, one of the pair of shafts 28a is inserted in the hole 72a, and the other shaft 28a is inserted in the U-shaped groove 72b. One of the edge parts <NUM> and 721R is formed with a hole, and the other is formed with a U-shaped groove. This facilitates attaching the plate member <NUM> to the heat dissipation plate <NUM>.

In the state in which the plate member <NUM> is attached to the heat dissipation plate <NUM>, the projecting plate <NUM> projects on a side mounted with the relatively tall surface-mount devices (e.g., the connector <NUM>, the EEPROM <NUM>, and the diode <NUM>), as shown in <FIG>.

The projecting plate <NUM> is provided between the projecting pieces <NUM> and 72R over the longitudinal direction of the base <NUM> and projects from the base <NUM> in a direction opposite to the projecting pieces <NUM> and 72R.

The base <NUM> is formed with two holes 71a for allowing screws to pass in mounting the plate member <NUM> to the heat dissipation plate <NUM>. The base <NUM> has two projections <NUM>. As shown in <FIG>, the projections <NUM> are disposed so as to not interfere with the surface-mount devices when the plate member <NUM> is attached to the heat dissipation plate <NUM>.

Hereinafter, effects of the thermal head 28A having the plate member <NUM> will be described with reference to <FIG> is a side view showing a positional relationship between the thermal head 28A and the platen-holding bracket <NUM>.

As described above, when the printer cover <NUM> is at the closed position, the platen shaft 10a of the platen roller <NUM>, which is attached to the printer cover <NUM>, is fitted in the groove 27b of the platen-holding bracket <NUM>, whereby the printer cover <NUM> is held. In a case of the thermal head <NUM> that does not have the plate member <NUM>, when an operator presses the printer cover <NUM> from above, for closing the printer cover <NUM> for example, the platen roller <NUM> may deviate downward from a designed position at which the platen roller <NUM> and the thermal head <NUM> abut on each other. This causes variations in density of printing. Further, the thermal head <NUM> is fitted to the shaft-receiving groove <NUM> (refer to <FIG>), which is provided in the internal frame. The one end of the shaft 27a of the platen-holding bracket <NUM> is inserted in the boss 52a of the peeling unit open lever <NUM>, whereas the other end of the shaft 27a is inserted in the boss provided to the internal frame (refer to <FIG>). Thus, the position at which the platen roller <NUM> and the thermal head <NUM> abut on each other is susceptible to accumulated errors in assembling components and tends to deviate from the designed position.

The drawback of the thermal head <NUM> noted above is overcome by the thermal head 28A.

As shown by an enlarged drawing in <FIG>, in the case in which the thermal head 28A is mounted to the printer <NUM>, instead of the thermal head <NUM>, upper ends of the edge parts <NUM> and 721R of the plate member <NUM> of the thermal head 28A are disposed at positions higher than rims that form the grooves 27b of the platen-holding bracket <NUM>. Thus, the platen shaft 10a that is fitted in the platen-holding bracket <NUM> is in contact with the edge parts <NUM> and 721R in the grooves 27b. This makes it difficult for the platen roller <NUM> to deviate downward from the designed position at which the platen roller <NUM> and the thermal head <NUM> abut on each other, even when an operator presses the printer cover <NUM> from above. This is because the plate member <NUM> is integrally coupled to the heat dissipation plate <NUM> mounted with the heat generating part <NUM>, whereby a relative positional relationship between the platen roller <NUM> and the heat generating part <NUM> is unlikely to be affected even when the platen shaft 10a presses down the edge parts <NUM> and 721R.

With reference again to <FIG>, in the state in which the thermal head 28A is mounted to the printer <NUM>, the projecting plate <NUM> of the plate member <NUM> projects toward the front side of the printer <NUM>. Thus, an upper part of the cable-containing chamber <NUM>, which is formed in front of the thermal head 28A, is covered with the projecting plate <NUM>. This structure prevents dust from entering the printer <NUM> from the outside, resulting in preventing dust from adhering to upper surface portions of the surface-mount devices disposed on the front side of the thermal head 28A. That is, the projecting plate <NUM> functions as a hood. In particular, as shown in <FIG>, replacement of the paper roll "R" is performed while the printer cover <NUM> is maintained at the open position, and dust tends to enter the printer <NUM>. However, in this situation, it is also possible to protect the surface-mount devices of the thermal head 28A from dust.

From another point of view, providing the projecting plate <NUM> improves strength of the plate member <NUM>.

For example, the structures and the mounting and removing methods of the thermal heads <NUM> and 28A are not technically related to the structure of the peeling unit <NUM> and the method of switching the issue modes, and therefore, they may be employed in a printer without the peeling unit <NUM>. Conversely, the structure of the peeling unit <NUM> and the method of switching the issue modes may be employed in a printer that uses a structure and an mounting and removing method of a thermal head different from those of the thermal heads <NUM> and 28A.

A case in which some parts (e.g., shafts and ends of springs) of components inside the printer <NUM> are coupled to the internal frame is described here; but the structure is not limited thereto, and these parts may be coupled to the body case <NUM>.

Although a case of using a print medium that is a continuous paper having a plurality of labels temporarily attached on a liner is described in the foregoing embodiments, the print medium is not limited thereto. For continuous issuing or for a printer not provided with a peeling unit, for example, a continuous label having an adhesive surface on one side (label without a liner), a continuous sheet without an adhesive surface (continuous sheet), or a material other than papers such as a film, which is printable by a thermal head, may also be used as a print medium. In addition, in a case of feeding a label having an exposed adhesive due to no liner, a feeding path may be coated with a non-adhesive material, and a non-adhesive roller containing silicone or the like may be provided as a platen roller.

Claim 1:
A printer (<NUM>) comprising:
a feed roller (<NUM>) configured to feed a print medium (P);
a print head (<NUM>, 28A) configured to pinch the print medium (P) with the feed roller (<NUM>) and to print on the print medium (P); and
a biasing member (<NUM>) configured to bias the print head (<NUM>, 28A) in a first direction toward the feed roller (<NUM>),
wherein the print head (<NUM>, 28A) is movable in the first direction between a first position (P1) and a second position (P2), the first position being a position at which the print head (<NUM>, 28A) can be removed when moved in a second direction, the second position being a position at which the print head (<NUM>, 28A) cannot be removed when moved in the second direction,
wherein
the print head (<NUM>, 28A) comprises: a base (<NUM>) on which heating elements are mounted;
and a pair of shafts (28a) that extend outward from both ends of the base (<NUM>),
the printer (<NUM>) further comprises a pair of grooves (<NUM>) that receives the pair of shafts (28a), the pair of grooves (<NUM>) including a first groove (<NUM>) and a second groove (<NUM>), the first groove extending in the second direction from the first position, the second groove extending in the first direction from the first position to the second position, characterized in that the print medium (P) includes a liner (PM) and labels (PL) releasably attached on the liner, peeling issuing and continuous issuing can be switched in the printer (<NUM>), peeling issuing allowing the labels to be issued after being peeled from the liner of the print medium, continuous issuing allowing the labels to be issued without being peeled from the liner,
the printer (<NUM>) further comprises a peeling unit (<NUM>) configured to hold a peeling roller (<NUM>) that faces the feed roller (<NUM>) in peeling issuing, the peeling unit (<NUM>) being movable between a closed position and an open position, the closed position being a position at which the peeling unit (<NUM>) at least partly covers the print head (<NUM>, 28A), the open position being a position at which the peeling unit (<NUM>) does not cover the print head (<NUM>, 28A), and
when the peeling unit (<NUM>) is at the open position and the pair of shafts (28a) is at the first position, space for allowing mounting and removing the print head (<NUM>, 28A) is formed.