Patent Publication Number: US-11040549-B2

Title: Portable printer

Description:
RELATED APPLICATIONS 
     This application claims priority to Japanese Patent Application No. 2018-203473, filed on Oct. 30, 2018, the entire content of which is incorporated herein by reference. 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a portable printer. 
     2. Description of the Related Art 
     There have been known portable printers configured to output (print) information, which is input to a host device (for example, personal digital assistant (PDA)), at visiting places or the like. The portable printer is sometimes used under an environment such as outdoors in which drip-proof performance is required. The portable printer includes a casing, and a movable component such as a button provided on the casing (for example, an eject button to be operated to open an open/close cover). For example, under the environment in which drip-proof performance is required, there is a fear in that rainwater during outdoor work, or liquid such as water adhering to a hand of a user flows into the printer through a boundary portion between the casing and the movable component, and adheres to, for example, a roll sheet or a board. Adhesion of the liquid to, for example, the roll sheet or the board causes printing failure or a malfunction of an electronic component. Therefore, the portable printer is required to have the structure capable of preventing inflow of the liquid into the printer. As such a printer, there has been known a printer having a configuration that makes it difficult for water to flow into a housing through a gap between the eject button and the housing. In the printer having this configuration, a waterproof intimate-contact surface is formed at a peripheral edge portion of the eject button, and the eject button can be urged so that the waterproof intimate-contact surface is held in intimate contact with an inner wall surface of the housing. 
     However, in the printer having the above-mentioned configuration, the eject button is assembled from an inner side of the housing, and hence a water-drop sometimes remains on a step between the housing and the eject button. Further, in the printer having the above-mentioned configuration, the eject button cannot overlap the housing. Thus, it is difficult for the eject button to function as an umbrella configured to prevent inflow of the waterdrop. There is a risk in that the water remaining on the step may flow into the housing when the eject button is pushed. 
     Therefore, in this type of field, it has been desired a portable printer capable of suppressing inflow of liquid into the printer from an outside. 
     SUMMARY OF THE INVENTION 
     According to one embodiment of the present invention, there is provided a portable printer, including: a casing configured to receive a recording medium; a head configured to perform printing on the recording medium; a platen roller, which is arranged so as to be opposed to the head, and is configured to convey the recording medium while sandwiching the recording medium together with the head; a button, which is provided on the casing, and is configured to perform operation of separating the head and the platen roller from each other; and a stepped portion, which is formed on the casing along a peripheral edge of the button, and protrudes so that an inner side of the casing is higher than an outer side of the casing. 
     In the above-mentioned portable printer according to the one embodiment, wherein in an assumed carriage posture in which a depression surface of the button is positioned beside a front wall of the casing, the stepped portion is formed at least at a lowermost portion of an edge portion of the casing along a vertical direction of the button. 
     In the above-mentioned portable printer according to the one embodiment, wherein in the assumed carriage posture, the stepped portion is formed across the entire edge portion along the vertical direction of the button. 
     In the above-mentioned portable printer according to the one embodiment, wherein in the assumed carriage posture, the button is provided in a boundary portion between the front wall and a side wall of the casing. 
     In the above-mentioned portable printer according to the one embodiment, wherein the stepped portion includes: a landing adjacent to an outer surface of the casing; and a protruding wall protruding from the landing. 
     In the above-mentioned portable printer according to the one embodiment, wherein a height of the protruding wall is larger than a width of the landing. 
     In the above-mentioned portable printer according to the one embodiment, wherein a width of the protruding wall is larger than a width of the landing. 
     In the above-mentioned portable printer according to the one embodiment, wherein a gap is defined between the protruding wall and the button, and wherein the width of the landing is larger than a width of the gap. 
     In the above-mentioned portable printer according to the one embodiment, wherein an angle formed between the landing and the protruding wall is an obtuse angle. 
     The above-mentioned portable printer according to the one embodiment, further including: a cover configured to support the platen roller in a freely rotatable manner; and a lock mechanism, which is provided in the casing, and is configured to lock the platen roller, wherein the casing supports the head, and wherein the button is capable of undoing locking of the lock mechanism. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a perspective view of a portable printer according to an embodiment of the present invention under a state in which a cover takes a closing position. 
         FIG. 2  is a side view of  FIG. 1 . 
         FIG. 3  is a side view of the portable printer according to the embodiment under a state in which the cover takes an opening position. 
         FIG. 4  is an exploded perspective view of the portable printer according to the embodiment from which the cover is removed. 
         FIG. 5  is a side view of a button of the portable printer according to the embodiment. 
         FIG. 6  is a perspective view for illustrating a state in which the button is removed from the portable printer according to the embodiment. 
         FIG. 7  is a perspective view including a cross section taken along the line VII-VII of  FIG. 6 . 
         FIG. 8  is an explanatory view of a stepped portion in the embodiment including a cross section taken along the line VIII-VIII of  FIG. 5 . 
         FIG. 9  is an explanatory view of a peripheral edge portion of a button in a comparative example. 
         FIG. 10  is an explanatory view of a stepped portion in a modification example of the embodiment. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Now, an embodiment of the present invention is described with reference to the drawings. In the following embodiment, as a portable printer, there is exemplified a thermal printer capable of being carried by a user. In the drawings to be referred to in the following description, in order to illustrate each component with a recognizable size, a contraction scale of each component is changed as appropriate. In the drawings, FR, LH, and UP represent a front side, a left side, and an upper side of the portable printer, respectively. In the following embodiment, a posture of the thermal printer assumed during carrying of the thermal printer, which has front-and-rear, up-and-down, and right-and-left directions as illustrated in  FIG. 1 , is referred to as “an assumed carriage posture”, and description is made of the thermal printer in the assumed carriage posture. 
     As illustrated in  FIG. 1 , a thermal printer  1  includes a casing  2 , a cover  3 , a printing unit  4  (see  FIG. 3 ), and a button  5 . The thermal printer  1  is configured to print information on a recording sheet P being a recording medium (see  FIG. 4 ), and to deliver the recording sheet P through a delivery port  24 . 
     For example, the casing  2  is made of a resin material such as polycarbonate, or a metal material. An upper portion of the casing  2  is formed into a rectangular parallelepiped shape to include a front wall  10  and side walls  14 . A lower portion of the casing  2  is formed into a box-like shape to have an opening portion  9  (see  FIG. 4 ) opens forward. 
     An operation unit  11  is provided in an upper portion of the front wall  10  of the casing  2 . The operation unit  11  is configured to perform various operations on the thermal printer  1 . The operation unit  11  includes various function switches  12  such as a power switch and a FEED switch, and various lamps  13  such as a POWER lamp configured to inform ON/OFF information of the power switch, and an ERROR lamp configured to inform, for example, an error of the thermal printer  1 . 
     As illustrated in  FIG. 4 , a roll sheet receiving portion  21  is defined in the lower portion of the casing  2 . A roll sheet R is received in the roll sheet receiving portion  21  through the opening portion  9 . The roll sheet receiving portion  21  includes a guide plate  22  configured to hold the roll sheet R. An inner surface of the guide plate  22  and an inner surface of the cover  3  (see  FIG. 1 ) hold the roll sheet R so as to cover the roll sheet R. The guide plate  22  has an arc-shaped cross section when seen from the right-and-left direction. The guide plate  22  holds the roll sheet R under a state in which an outer peripheral surface of the roll sheet R is held in contact with an arc-shaped inner peripheral surface of the guide plate  22 . The guide plate  22  is configured to guide the recording sheet P, which is drawn out from the roll sheet R, to the printing unit  4 . 
     In the embodiment, the recording sheet P is heat-sensitive sheet. For example, the recording sheet P is suitably used for printing of various labels, receipts, and tickets. The recording sheet P is wound into a roll shape to form the roll sheet R having a hollow hole. 
     As illustrated in  FIG. 1 , the cover  3  forms a lower front surface of the thermal printer  1 . For example, the cover  3  is made of a resin material such as polycarbonate. The cover  3  is a covering portion (sheet cover) configured to open and close the opening portion  9  (see  FIG. 4 ). The cover  3  is supported on the casing  2  so as to be pivotable. As illustrated in  FIG. 3 , owing to a hinge structure  15  provided below the cover  3 , the cover  3  is pivotable with respect to the casing  2 . The hinge structure  15  is formed by coupling hinge plates  16  (see  FIG. 4 ) and a hinge shaft  17  in a pivotable manner. The hinge plates  16  are formed on the casing  2 , and a hinge shaft  17  is provided to the cover  3 . 
     An upper end of the cover  3  is lockable to the casing  2  through intermediation of a platen unit  32 . A platen roller  36  is supported on the cover  3  so as to be freely rotatable. At a closed position of the cover  3 , a gap defined between an upper edge of the cover  3  and a lower edge of the front wall  10  of the casing  2  forms the delivery port  24  through which the recording sheet P subjected to printing by the printing unit  4  is delivered (see  FIG. 1 ). 
     As illustrated in  FIG. 1 , cutting blades  25  are provided at opening edges of the delivery port  24 . The cutting blades  25  are configured to cut the recording sheet P delivered through the delivery port  24 . The cutting blades  25  are integrally formed at the lower edge of the front wall  10  of the casing  2  (or an upper opening edge portion among the opening edges), and the upper edge of the cover  3 , respectively. For example, the recording sheet P is cut by pulling down the recording sheet P toward the cutting blades  25 . 
     As illustrated in  FIG. 2 , a hook  19  is provided on a back-side upper portion of the casing  2 . For example, a strap or a belt is mountable to the hook  19 . For example, when a user carries the thermal printer  1 , it is assumed that the user often carries the thermal printer  1  under a state in which a strap slung across a shoulder or a waist belt is mounted to the hook  19 . Accordingly, the state of the thermal printer  1  having the front-and-rear, up-and-down, and right-and-left directions as illustrated in  FIG. 1  corresponds to an assumed carriage state of the thermal printer  1 . 
     As illustrated in  FIG. 3 , the printing unit  4  is received in the casing  2 . The printing unit  4  includes a head unit  31  and the platen unit  32 . The printing unit  4  performs printing on a portion of the recording sheet P drawn out from the roll sheet R (see  FIG. 4 ). 
     The head unit  31  is provided at a lower end portion of the front wall  10  of the casing  2 . The head unit  31  includes a thermal head  33  including a plurality of heating elements. The thermal head  33  is connected to, for example, a control unit through a flexible board (not shown). In the thermal head  33 , a driver IC (not shown) installed on the thermal head  33  controls generation of heat of the heating elements based on a signal from the control unit. Then, when the recording sheet P passes through the heating elements, printing is performed on the recording sheet P. 
     The platen unit  32  is provided at an upper end portion (distal end portion) of the cover  3 . The platen unit  32  is combined with the head unit  31  so as to be attachable and detachable through opening and closing operation of the cover  3 . The platen unit  32  includes a platen frame (not shown) and the platen roller  36 . The platen frame is mounted to the cover  3 . The platen roller  36  is supported on the platen frame so as to be rotatable. 
     Under a state in which the cover  3  is closed, the platen roller  36  is arranged so as to be opposed to the thermal head  33 . The platen roller  36  is configured to convey the recording sheet P while sandwiching the recording sheet P together with the thermal head  33 . 
     The platen roller  36  includes a platen shaft  37  and a roller main body  38 . The platen shaft  37  extends along the right-and-left direction. The roller main body  38  is made of, for example, rubber that is externally fitted to the platen shaft  37 . Bearings (not shown) are externally fitted to both end portions of the platen shaft  37 , respectively. The bearings are configured to support the platen shaft  37  in a rotatable manner. The platen roller  36  is supported on the platen frame through intermediation of the bearings (not shown) so as to be rotatable. 
     For example, a platen gear (not shown) is mounted to a right end portion of the platen shaft  37 . The head unit  31  includes a train mechanism and a motor. The train mechanism is meshed with the platen gear (not shown). The motor is connected to the train mechanism. When the platen unit  32  and the head unit  31  are combined with each other, the platen gear is meshed with the train mechanism provided on the head unit  31  side, thereby transmitting a rotational drive force of the motor to the platen roller  36 . When the platen unit  32  and the head unit  31  are combined with each other, the thermal head  33  of the head unit  31  is brought into press-contact with the outer peripheral surface of the platen roller  36 . 
     As illustrated in  FIG. 1 , the button  5  is provided in a boundary portion between the front wall  10  and the side wall  14  of the casing  2 . The button  5  includes a depression surface  40  on a front surface thereof. The button  5  is an operation portion configured to perform operation of separating the thermal head  33  and the platen roller  36  from each other. The button  5  is an operation portion configured to unlock between the casing  2  and the cover  3 , to thereby release the opening portion  9  of the casing  2  (see  FIG. 4 ). 
     For example, when the button  5  is depressed (pushed rearward in the assumed carriage posture), the locking between the casing  2  and the cover  3  is undone. Thus, the cover  3  is pivoted from the closed position illustrated in  FIG. 2  to the opened position illustrated in  FIG. 3 . 
     As illustrated in  FIG. 6 , a receiving portion  45  is formed in the casing  2 , and is configured to receive the button  5  (see  FIG. 5 ). The receiving portion  45  has an edge portion  46  extending along an outer peripheral edge of a base portion  41  (see  FIG. 5 ) of the button  5 . The receiving portion  45  is hollow so as to link an internal mechanism (not shown) by the button  5 . The receiving portion  45  communicates with the inside of the casing  2 . A control board (not shown) having, for example, a printer mechanism and an electronic component mounted thereon is provided inside the casing  2 . The control board is arranged behind the front wall  10  of the casing  2  (for example, behind the operation unit  11  illustrated in  FIG. 1 ). In  FIG. 6 , reference symbol  42  denotes a guide pin configured to guide the base portion  41  (see  FIG. 5 ) of the button  5  in the front-and-rear direction. 
     As illustrated in  FIG. 3 , a lock mechanism  47  is provided in the casing  2 , and is configured to lock the platen roller  36 . The lock mechanism  47  includes a lock arm  48  configured to hold the platen roller  36  inserted in a roller insertion groove  49 . For example, when the button  5  is depressed, the lock arm  48  is pivoted in a direction indicated by the arrow Q  1  against an urging member (not shown). Then, the lock arm  48  is disengaged from the bearing (not shown) of the platen shaft  37  so that the platen roller  36  is disengaged from the roller insertion groove  49 . Thus, the cover  3  can be opened. 
     As illustrated in  FIG. 5 , a stepped portion  50  is formed on the casing  2  along a peripheral edge of the button  5 , and protrudes so that an inner side of the casing  2  is higher than an outer side of the casing  2 . The stepped portion  50  protrudes forward on the inner side (left side) with respect to the side wall  14  (outer surface) of the casing  2 . The stepped portion  50  is formed at least at a lowermost portion of the edge portion  46  along a vertical direction of the button  5 . The stepped portion  50  is formed across the entire edge portion  46  along the vertical direction of the button  5 . 
     As illustrated in  FIG. 7 , the stepped portion  50  includes a landing  51  and a protruding wall  52 . The landing  51  is adjacent to the outer surface (side wall  14 ) of the casing  2 . The landing  51  extends across the entire edge portion  46  along the vertical direction of the button  5  (see  FIG. 6 ). The landing  51  has a flat surface substantially parallel to the right-and-left direction (see  FIG. 8 ). 
     The protruding wall  52  is a projecting portion protruding forward from the landing  51 . The protruding wall  52  extends across the entire edge portion  46  along the vertical direction of the button  5  (see  FIG. 6 ). The protruding wall  52  and the landing  51  are integrally formed of the same member. In a sectional view of  FIG. 8 , the protruding wall  52  and the landing  51  form an L shape together. 
     As illustrated in  FIG. 8 , a gap  53  is defined between the protruding wall  52  and the base portion  41  of the button  5 . The gap  53  communicates with the inside of the casing. The gap  53  opens a space between the protruding wall  52  and the base portion  41  of the button  5  forward. For example, the gap  53  (or a width W 3  of the gap  53 ) has a size large enough to allow a depressing operation of the button  5  (movement in the assumed carriage posture during position change in the front-and-rear direction) to be performed smoothly. 
     In the embodiment, a height H 1  of the protruding wall  52  is larger than a width W 2  of the landing  51  (H 1 &gt;W 2 ). Here, the height H 1  of the protruding wall  52  refers to a protruding amount of the protruding wall  52  protruding forward from the landing  51  under the assumed carriage posture. The width W 2  of the landing  51  refers to a length of the flat surface of the landing  51  in the right-and-left direction under the assumed carriage posture. 
     In the embodiment, a width W 1  of the protruding wall  52  is larger than a width W 2  of the landing  51  (W 1 &gt;W 2 ). Here, the width W 1  of the protruding wall  52  refers to a length (thickness) of the protruding wall  52  in the right-and-left direction under the assumed carriage posture. 
     In the embodiment, the width W 2  of the landing  51  is larger than the width W 3  of the gap  53  (W 2 &gt;W 3 ). Here, the width W 3  of gap  53  refers to a distance in the right-and-left direction between the protruding wall  52  and the base portion  41  of the button  5  under the assumed carriage posture. 
     In the embodiment, an angle A 1  formed between the landing  51  and the protruding wall  52  is a substantially right angle (A 1 ≈90°). Here, the angle A 1  refers to an angle formed between a flat surface of the landing  51  and an outer surface of the protruding wall  52  under the assumed carriage posture. 
     Next, actions of the stepped portion  50  are described together with a comparative example.  FIG. 9  is an explanatory view of a peripheral edge portion of the button in the comparative example. In the comparative example, the stepped portion  50  (see  FIG. 8 ) in the embodiment is not provided. For example, rainwater during outdoor work, or liquid (a waterdrop  60 X) such as water adhering to a hand of a user may sometimes remain in a boundary portion between a casing  2 X and a button  5 X. In the comparative example, the waterdrop  60 X is held in contact with the casing  2 X and the button  5 X. Due to surface tension, the waterdrop  60 X maintains a spherical shape while being held in contact with the casing  2 X and the button  5 X. There is a risk in that the waterdrop  60 X remaining in the boundary portion between the casing  2 X and the button  5 X flows into the casing  2 X through a gap  53 X between the casing  2 X and the button  5 X. 
       FIG. 8  is an explanatory view of the stepped portion  50  in the embodiment. In the embodiment, the stepped portion  50  includes the landing  51  adjacent to the outer surface (side wall  14 ) of the casing  2 , and the protruding wall  52  protruding forward from the landing  51 . Accordingly, the rainwater accompanied during outdoor work, or the liquid (a waterdrop  60 ) such as water adhering to a hand of a user tends to remain in a boundary portion between the landing  51  and the protruding wall  52 . In the embodiment, the waterdrop  60  is not held in contact with the button  5 , but is held in contact with the landing  51  and the protruding wall  52 . The waterdrop  60  remaining in the boundary portion between the landing  51  and the protruding wall  52  flows downward along the landing  51 . Thus, a risk of inflow of the waterdrop  60  into the gap  53  between the protruding wall  52  and the button  5  (risk of inflow into the casing  2 ) is low. 
     As described above, a thermal printer  1  of this embodiment includes a casing  2  configured to receive a recording sheet; a thermal head  33  configured to perform printing on the recording sheet; a platen roller  36 , which is arranged so as to be opposed to the thermal head  33 , and is configured to convey the recording sheet while sandwiching the recording sheet together with the thermal head  33 ; a button  5 , which is provided on the casing  2 , and is configured to perform operation of separating the thermal head  33  and the platen roller  36  from each other; and a stepped portion  50 , which is formed on the casing  2  along a peripheral edge of the button  5 , and protrudes so that an inner side of the casing  2  is higher than an outer side of the casing  2 . 
     According to the embodiment, the stepped portion  50  is formed on the casing  2  along the peripheral edge of the button  5 , and protrudes so that the inner side of the casing  2  is higher than the outer side of the casing  2 . Thus, inflow of the liquid into the casing  2  from an outside can be blocked. Therefore, inflow of the liquid into the printer from the outside can be suppressed. In addition, as compared to a case of using, for example, a waterproof cover or a water-repellent oil, drip-proof performance can be enhanced at low cost. Moreover, as compared to a case of using the water-repellent oil, prevention effects are not degraded due to degradation over time, and hence the present invention is preferred. 
     Further, in this embodiment, in an assumed carriage posture in which a depression surface  40  of the button  5  is positioned beside a front wall  10  of the casing  2 , the stepped portion  50  is formed at least at a lowermost portion of an edge portion  46  of the casing  2  along a vertical direction of the button  5 . 
     According to the embodiment of the present invention, the stepped portion  50  is formed at least at the lowermost portion of the edge portion  46  along the vertical direction of the button  5 . Thus, at a portion at which the liquid is liable to remain the most due to an action of gravity, inflow of the liquid into the casing  2  from the outside can be blocked. Therefore, inflow of the liquid into the printer from the outside can be suppressed further effectively. 
     Further, in this embodiment, the assumed carriage posture, the stepped portion  50  is formed across the entire edge portion  46  along the vertical direction of the button  5 . 
     According to the embodiment of the present invention, as compared to a case in which the stepped portion  50  is formed at only part of the edge portion  46  along the vertical direction of the button  5 , inflow of the liquid into the casing  2  from the outside can be blocked further effectively. 
     Further, in this embodiment, in the assumed carriage posture, the button  5  is provided in a boundary portion between the front wall  10  and a side wall  14  of the casing  2 . 
     According to the embodiment of the present invention, even when the liquid flows toward the button  5  along the front wall  10  or the side wall  14  of the casing  2 , the stepped portion  50  can block inflow of the liquid into the casing  2 . In addition, as compared to a case in which the button  5  is provided on any one of the front wall  10  and the side wall  14  of the casing  2 , the present invention contributes to improvement in usability of the button  5 . Moreover, as compared to a case in which the button  5  is provided only on the front wall  10  of the casing  2 , the present invention contributes to an improvement in delivering performance for the recording sheet. 
     Further, in this embodiment, the stepped portion  50  includes a landing  51  adjacent to an outer surface of the casing  2 ; and a protruding wall  52  protruding from the landing  51 . 
     According to the embodiment of the present invention, with a simple configuration in which the stepped portion  50  includes the landing  51  and the protruding wall  52 , inflow of the liquid into the casing  2  from the outside can be blocked. 
     Further, in this embodiment, a height H 1  of the protruding wall  52  is larger than a width W 2  of the landing  51   
     According to the embodiment of the present invention, as compared to a case in which the height H 1  of the protruding wall  52  is equal to or smaller than the width W 2  of the landing  51 , the liquid is less liable to flow beyond the protruding wall  52 . The liquid is liable to overflow from the landing  51  before flowing beyond the protruding wall  52 , and hence inflow of the liquid into the casing  2  from the outside can be blocked further effectively. 
     Further, in this embodiment, a width W 1  of the protruding wall  52  is larger than a width W 2  of the landing  51 . 
     According to the embodiment of the present invention, as compared to a case in which the width W 1  of the protruding wall  52  is equal to or smaller than the width W 2  of the landing  51 , the liquid is less liable to flow beyond the protruding wall  52 . The liquid is liable to overflow from the landing  51  before flowing beyond the protruding wall  52 , and hence inflow of the liquid into the casing  2  from the outside can be blocked further effectively. 
     Further, in this embodiment, a gap  53  is defined between the protruding wall  52  and the button  5 , and wherein the width W 2  of the landing  51  is larger than a width W 3  of the gap  53 . 
     According to the embodiment of the present invention, as compared to a case in which the width W 2  of the landing  51  is equal to or smaller than the width W 3  of the gap  53 , the liquid is less liable to flow into the gap  53 . The liquid is liable to overflow from the landing  51  before flowing into the gap  53 , and hence inflow of the liquid into the casing  2  from the outside can be blocked further effectively. 
     Further, in this embodiment, the portable printer further includes a cover  3  configured to support the platen roller  36  in a freely rotatable manner; and a lock mechanism  47 , which is provided in the casing  2 , and is configured to lock the platen roller  36 , wherein the casing  2  supports the thermal head  33 , and wherein the button  5  is capable of undoing locking of the lock mechanism  47 . 
     With this configuration, in the configuration in which the thermal head  33  and the platen roller  36  are separable from each other along with opening and closing of the cover  3 , inflow of the liquid into the printer from the outside can be suppressed. 
     Modification Example 
     Note that, the technical scope of the present invention is not limited to the above-mentioned embodiment, but various modifications may be made without departing from the gist of the present invention. 
     In the embodiment described above, description is made of the configuration in which the angle A 1  formed between the landing  51  and the protruding wall  52  is the right angle, but the present invention is not limited thereto. For example, as illustrated in  FIG. 10 , the angle A 1  formed between a landing  151  and the protruding wall  52  may be an obtuse angle. The landing  151  may be inclined in a sectional view so that a left end of the landing  151  (flat surface) is located on the front side and a right end of the landing  151  (flat surface) is located on the rear side. With this configuration, the water-drop  60  easily flow along the inclination of the landing  151 . 
     In this modification example, an angle A 1  formed between the landing  151  and the protruding wall  52  is an obtuse angle. 
     According to the modification example of the present invention, as compared to a case in which the angle A 1  formed between the landing  51  and the protruding wall  52  is an acute angle, the liquid is less liable to remain on the landing  151 . The liquid easily flow along the inclination of the landing  151 , and hence inflow of the liquid into the casing  2  from the outside can be blocked further effectively. 
     In the embodiment described above, description is made of the configuration in which the stepped portion  50  is formed across the entire edge portion  46  along the vertical direction of the button  5  under the assumed carriage posture, but the present invention is not limited thereto. For example, the stepped portion  50  may be formed only at the lowermost portion of the edge portion  46  along the vertical direction of the button  5 . In addition, the stepped portion  50  may be formed on at least one of an upper edge portion and a lower edge portion of the peripheral edge portion of the button  5  along a horizontal direction of the button  5 . 
     In the embodiment described above, description is made of the configuration in which the width W 1  of the protruding wall  52  is larger than the width W 2  of the landing  51  (W 1 &gt;W 2 ), but the present invention is not limited thereto. For example, the width W 1  of the protruding wall  52  may be equal to or smaller than the width W 2  of the landing  51  (W 1 ≤W 2 ). 
     In the embodiment described above, description is made of the configuration in which the stepped portion  50  includes one protruding wall  52  protruding from the landing  51  (configuration in which only single stepped portion  50  is formed), but the present invention is not limited thereto. For example, the stepped portion may include a plurality of protruding walls protruding from the landing. That is, the stepped portion may have the stepwise structure. 
     In the embodiment described above, description is made of the configuration in which the protruding wall  52  and the landing  51  are integrally formed of the same member, but the present invention is not limited thereto. For example, the protruding wall  52  and the landing  51  may be formed of different members and integrated with each other. 
     In the embodiment described above, description is made of the case in which the thermal printer is used as an example of the portable printer, but the present invention is not limited thereto. For example, the portable printer may be applied to various printers other than a thermal printer of a dot impact type. 
     Besides the above, the components in the above-mentioned embodiments may be replaced by well-known components as appropriate without departing from the gist of the present invention.