Patent Publication Number: US-11046095-B2

Title: Printer

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application is based upon and claims the benefit of priority from Japanese Patent Application No. 2018-239616, filed on Dec. 21, 2018, the entire contents of which are incorporated herein by reference. 
     FIELD 
     Embodiments described herein relate generally to a printer that conveys an image receiving medium pulled out of, for example, a roll body obtained by winding an elongated image receiving medium in a roll shape and performs printing on the conveyed image receiving medium. 
     BACKGROUND 
     A conventional printer conveys an image receiving medium pulled out of a roll body obtained by winding an elongated image receiving medium in a roll shape and performs printing on the conveyed image receiving medium. Such a type of printer has a tension applying mechanism for absorbing impact at the start of conveying the image receiving medium by applying tension to the image receiving medium on an upstream side of a print head to stabilize a print quality. 
    
    
     
       DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a perspective view of a printer according to an embodiment; 
         FIG. 2  is a sectional view schematically illustrating the printer in  FIG. 1 ; 
         FIG. 3  is a perspective view illustrating a buffer device according to the embodiment incorporated into the printer in  FIG. 1 ; 
         FIG. 4  is a perspective view illustrating a first damper of the buffer device in  FIG. 3 ; 
         FIG. 5  is a perspective view illustrating the first damper in  FIG. 4  as viewed from a back surface side; 
         FIG. 6  is a perspective view illustrating a second damper of the buffer device in  FIG. 3  as viewed from the back surface side; 
         FIG. 7  is an enlarged sectional view illustrating a state of the buffer device when a diameter of a roll body in  FIG. 2  is reduced; and 
         FIG. 8  is a partially enlarged sectional view illustrating main portions in  FIG. 7 . 
     
    
    
     DETAILED DESCRIPTION 
     In accordance with an embodiment, a printer comprises a housing section configured to accommodate a roll body obtained by winding an elongated image receiving medium in a roll shape; a conveyance section configured to pull out the image receiving medium from the roll body to convey it; a printing section configured to perform printing on the image receiving medium pulled out of the roll body by the conveyance section; and a buffer device arranged at the bottom of the housing section on an upstream side of the conveyance section along a direction in which the image receiving medium is pulled out by the conveyance direction so as to apply a pressing force in a direction towards the roll body to the image receiving medium pulled out of the roll body. 
     Hereinafter, an embodiment is described in detail with reference to the accompanying drawings. 
       FIG. 1  is a perspective view illustrating a state in which a printer  100  according to the embodiment is placed on a predetermined horizontal plane. As shown in  FIG. 1 , the printer  100  according to the embodiment includes a housing  110  having a substantially rectangular box shape with an opening formed on an upper surface side thereof. The printer  100  also has a cover body  120  that covers the upper surface side of the housing  110 . The cover body  120  is connected in the vicinity of one end (a right end in  FIG. 1 ) in a longitudinal direction of the housing  110  via a hinge (not shown), and opens and closes the opening on the upper surface side of the housing  110 . For convenience of description, the one end side where the hinge of the printer  100  is provided is referred to as a rear side, and the opposite side thereof is referred to as a front side.  FIG. 1  shows a state in which the cover body  120  is fully opened with respect to the housing  110 . 
     As shown in  FIG. 2 , the housing  110  has a space communicating with the above-described opening. A bottom wall  112  positioned on the rear side below the space is formed in a substantially arcuate shape that curves from a rear side end of the opening towards a front side end thereof. A space between the bottom wall  112  and the above-described opening has a semi-cylindrical shape like a lower half of a cylinder horizontally laid down. In this space, a roll body R obtained by winding an elongated recording paper T (i.e., the image receiving medium) with a predetermined width in a roll shape is accommodated in a freely rotatable state. A lower portion of the roll body R is fit in the semi-cylindrical space when the roll body R is horizontally laid down. An outer circumferential surface of the roll body R that fits in the space extends along the arc of the bottom wall  112 . A curvature radius of the bottom wall  112  is slightly greater than that of the unused roll body R with the maximum diameter. This is because the outer shape of the roll body R gradually decreases as the recording paper T is pulled away from the outer circumference of the roll body R. A size in a width direction of the bottom wall  112  is slightly greater than a width in an axial direction of the roll body R. The width direction of the bottom wall  112  is parallel to the axial direction of the above-described hinge. 
     The outer side of the housing  110  has four side walls  110   a ,  110   b ,  110   c  and  110   d  ( FIG. 1 ) extending in a vertical direction. The side wall  110   a  on the rear side of the housing  110  is lower in the vertical direction than the other side walls  110   b ,  110   c  and  110   d . A part of the bottom wall  112  protrudes outward from an upper end of the side wall  110   a . In other words, the bottom wall  112  includes a portion that protrudes from the upper end of the side wall  110   a  to the outside of the side wall  110   a  and a portion that extends to the inside of the side wall  110   a , which are continuous to each other. 
     The bottom wall  112  has a shape in which the lowermost end thereof is bent into an obtuse V shape, and a bent portion  112   a  thereof is positioned at the inside of the side wall  110   a . A portion of the bottom wall  112  on the front side of the bent portion  112   a  is inclined upward to extend substantially straight. The printer  100  includes a buffer device  10  described below at the portion of the bottom wall  112  extending substantially straight. 
     The bottom wall  112  has a plurality of rotatable support rollers  111 . The plurality of support rollers  111  is provided at symmetrical positions with the bent portion  112   a  as a center. Each of the support rollers  111  includes two roller portions coaxially arranged in a mutually separated manner. Each of the support rollers  111  is attached to the bottom wall  112  with an outer circumferential surface thereof slightly protruding upward from the inner surface of the bottom wall  112  of the housing  110 . In the present embodiment, two support rollers  111  separated from each other in the width direction of the roll body R are provided on the rear side of the bent portion  112   a , and two support rollers  111  separated from each other in the width direction of the roll body R are provided on the front side of the bent portion  112   a . Specifically, in the present embodiment, a total of four support rollers  111  are provided, two on the left side and two on the right side with the bent portion  112   a  sandwiched therebetween. 
     A rotating shaft (not shown) of each of the support rollers  111  is provided in parallel with a rotating shaft of the roll body R. An outer circumferential surface of the roll body R placed in the space above the bottom wall  112  is supported by contacting the outer circumferential surfaces of the four support rollers  111 , and hardly contacts an inner surface of the bottom wall  112 . For this reason, if the recording paper T is pulled out of the roll body R, the roll body R rotates and a plurality of support rollers  111  is rotated correspondingly. Regardless of the diameter of the roll body R, a central shaft of the roll body R is always positioned above the bent portion  112   a  of the bottom wall  112 . 
     The cover body  120  includes a top wall  122  bent in an arcuate shape to cover the roll body R from above in the state in  FIG. 2  in which the opening of the housing  110  is closed. The recording paper T pulled out of the roll body R is discharged from the printer  100  along the outer surface of the top wall  122 , as described below. The top wall  122  has a size and shape at which the top wall  122  does not contact the outer circumferential surface of the unused roll body R with the maximum diameter supported by a plurality of support rollers  111  in the state in  FIG. 2 . A curvature radius of the top wall  122  is slightly greater than that of the bottom wall  112 . Therefore, if the cover body  120  is pivoted to the fully open position in  FIG. 1 , a part of the top wall  122  overlaps with the outer side of the bottom wall  112 . 
     The cover body  120  has two side walls  120   a  and  120   b  ( FIG. 1 ) extending in parallel with each other in a longitudinal direction thereof. As shown in  FIG. 2 , in a state in which the cover body  120  is closed, an edge of the side wall  120   a  separated from the top wall  122  abuts against an edge of the side wall  110   c  of the housing  110 , and an edge of the side wall  120   b  separated from the top wall  122  abuts against an edge of the side wall  110   d  of the housing  110 . Thus, in a state in which the cover body  120  is closed, a housing section S serving as a space for accommodating the roll body R is formed between the housing  110  and the cover body  120 . The housing section S has a substantially cylindrical shape horizontally laid down. 
     The printer  100  includes the buffer device  10 , a printing and conveyance device  20  and a cutter  30 . 
     The buffer device  10  applies tension to the recording paper T pulled out of the roll body R. The recording paper T pulled out of the roll body R is wound around a platen roller  22  described below. The buffer device  10  applies a pressing force in a direction towards the roll body R to the recording paper T between the roll body R and the platen roller  22  to change a conveyance path of the recording paper T, and meanwhile applies tension to the recording paper T. The buffer device  10  applies a braking force to the roll body R to brake the rotation of the roll body R only for a predetermined period until the diameter of the roll body R reaches a certain diameter from the start of use of the roll body R having the maximum diameter. The detailed structure and function of the buffer device  10  are described in detail below. 
     The printing and conveyance device  20  includes the platen roller  22  and a print head  24 . The platen roller  22  rotates while sandwiching the wound recording paper T between the platen roller  22  and the print head  24  to apply a conveyance force to the recording paper T. In other words, the recording paper T is energized against the platen roller  22  by the print head  24  to obtain the conveyance force from the rotating platen roller  22 . The platen roller  22  is provided at an end on the front side of the cover body  120 . The print head  24  is provided on the front side of the opening of the housing  110 . If the cover body  120  is closed with respect to the housing  110  in the state shown in  FIG. 2 , the platen roller  22  and the print head  24  are pressed against each other across the recording paper T at a predetermined pressure to sandwich the recording paper T to be capable of conveying the recording paper T. 
     The platen roller  22  is connected to a rotating shaft of a motor  23  via a plurality of gears (not shown) in the state in  FIG. 2  in which the cover body  120  is closed with respect to the housing  110 . The motor  23  is provided in the housing  110  and is driven based on a control signal from a control section (not shown). By rotating the motor  23 , the platen roller  22  rotates to convey the recording paper T sandwiched between the print head  24  and the platen roller  22 . The platen roller  22  and the print head  24  function as a conveyance section that pulls out the recording paper T from the roll body R to convey the recording paper T pulled out. 
     The print head  24  is, for example, a thermal head, and prints predetermined characters or images on the recording paper T conveyed between the outer circumferential surface of the platen roller  22  and the print head  24  based on a print signal transmitted from the control section (not shown). The print head  24  is pressed against the outer circumferential surface of the platen roller  22  via a spring  25 . The print head  24  functions as a printing section. 
     A cutter  30  is arranged on a conveyance downstream side of the printing and conveyance device  20  in the conveyance path in which the recording paper T pulled out of the roll body R is conveyed. The cutter  30  includes a fixed blade  32  and a movable blade  34 . The fixed blade  32  is arranged on the front side of the housing  110 , as with the print head  24 . The movable blade  34  is provided on the front side of the cover body  120 , as with the platen roller  22 . The movable blade  34  faces the fixed blade  32  across the conveyance path of the recording paper T in a state in which the cover body  120  is closed with respect to the housing  110  (i.e., the state in  FIG. 2 ). In this state, by driving the movable blade  34 , the recording paper T is cut between the movable blade  34  and the fixed blade  32 . The recording paper T on which characters and the like are printed by the print head  24  is cut to a predetermined length by the cutter  30 . After passing between the fixed blade  32  and the movable blade  34  and being cut to a predetermined length, the recording paper T is discharged from a discharge port  121  provided on the front side of the cover body  120  onto an outer surface of the top wall  122  of the cover body  120 . 
     Below, the structure of the buffer device  10  is described in detail with reference to  FIG. 3  to  FIG. 6 .  FIG. 3  is a perspective view illustrating main portions of the buffer device  10  as viewed from the roll body R (not shown here) side.  FIG. 4  is a perspective view illustrating a state in which a second damper  60  is removed from the structure shown in  FIG. 3 .  FIG. 5  is a perspective view illustrating a swinging member  42  of a first damper  40  as viewed from the back surface side.  FIG. 6  is a perspective view illustrating a swinging member  62  of the second damper  60  as viewed from the first damper  40  side on the back surface side. 
     The buffer device  10  includes the first damper  40  and the second damper  60 . The buffer device  10  of the present embodiment is a double damper in which the first damper  40  that generates a relatively stronger pressing force and the second damper  60  that generates a relatively weaker pressing force cooperate with each other. The first damper  40  includes the swinging member  42  (i.e., a first swinging member) shown in  FIG. 3  to  FIG. 5 , and three tension springs  44  (i.e., first energization members) shown in  FIG. 2  (only one is shown in  FIG. 2 ). The second damper  60  includes the swinging member  62  (i.e., a second swinging member) shown in  FIG. 3  and  FIG. 6 , and two compression springs  64  (i.e., second energization members) shown in  FIG. 2  (only one is shown in  FIG. 2 ). 
     The swinging member  42  of the first damper  40  includes two pivot shafts  41  (i.e., first pivot shafts) protruding in mutually separated directions from both ends in a longitudinal direction of the swinging member  42 . The two pivot shafts  41  are arranged at positions closer to one end side (i.e., a swinging base end side) of the swinging member  42  in a lateral direction, and are arranged coaxially with each other. The bottom wall  112  of the housing  110  includes support portions (not shown) that support the two pivot shafts  41  of the swinging member  42  in a pivotable manner at two positions separated in the axial direction of the roll body R. Specifically, the support portions of the housing  110  support the two pivot shafts  41  of the swinging member  42  in a direction parallel to the shaft of the roll body R. The swinging member  42  is arranged along the bottom wall  112  in such a posture that a surface  42   a  thereof faces the roll body R and the pivot shaft  41  is arranged on a side close to the bent portion  112   a  of the bottom wall  112 . The swinging member  42  is mounted on the bottom wall  112  in a swingable manner in such a posture that a longitudinal direction of the swinging member  42  is parallel to the axial direction of the roll body R. 
     The swinging member  42  integrally includes three hooks  45  protruding from a back surface side thereof in a direction substantially orthogonal to the back surface. The three hooks  45  are provided on the back surface side to protrude from a position closer to one end of the swinging member  42  in the lateral direction. Specifically, the base ends of the three hooks  45  are close to the pivot shaft  41 . The three hooks  45  are arranged separated from each other in the longitudinal direction of the swinging member  42 . One end of each tension spring  44  is hooked on the tip of each hook  45 . 
     The other ends of the three tension springs  44  are respectively hooked on three hooks  114  ( FIG. 2 ) protruding from the back surface side of the bottom wall  112  of the housing  110 . The three hooks  114  on the bottom wall  112  side are respectively provided at positions facing in a mutually separated manner the front side of the three hooks  45  of the swinging member  42 . 
     Each of the tension springs  44  is stretched between the hook  45  of the swinging member  42  and the hook  114  on the housing  110  side in a slightly stretched state. For this reason, a swinging tip of the swinging member  42  is always energized in a pivot direction (clockwise direction in  FIG. 2 ) towards the roll body R by a restoring force of the three tension springs  44 . 
     The swinging member  42  of the first damper  40  has a step portion  42   b  engaged with an edge  112   b  ( FIG. 2 ) of the bottom wall  112  of the housing  110  at the tip of the pivot. As described above, the swinging member  42  is energized in the direction towards the roll body R by the three tension springs  44 , and further pivot thereof is restricted by engaging the step portion  42   b  with the edge  112   b  (regulating member) of the bottom wall  112 . In the state in  FIG. 2  in which the step portion  42   b  of the swinging member  42  is engaged with the edge  112   b  of the bottom wall  112 , the both ends of each of the three tension springs  44  are slightly stretched, and at least the restoring force is applied. 
     Specifically, a pivotable range of the swinging member  42  of the first damper  40  is between a position shown in  FIG. 2  at which the step portion  42   b  of the swinging member  42  is engaged with the edge  112   b  of the bottom wall  112  and a position at which a part of the swinging member  42  abuts against a tip of a stopper  112   c  (regulating member) arranged integrally with the bottom wall  112  of the housing  110 . The swinging member  42  is energized in a clockwise direction in  FIG. 2  around the pivot shaft  41  by the restoring force of the tension spring  44  at any pivot position within the pivotable range described above. 
     The swinging member  42  of the first damper  40  has two pivot shafts  46  (i.e., second pivot shafts) for supporting the swinging member  62  of the second damper  60  in a swingable manner. The two pivot shafts  46  are arranged at separated positions from the pivot shafts  41  of the first damper  40  described above to the swinging tip of the swinging member  42  along the lateral direction of the swinging member  42 . The two pivot shafts  46  are coaxially extended in mutually separated directions from both ends of the swinging member  42  in the longitudinal direction. The swinging member  62  of the second damper  60  is superposed on the swinging member  42  in a direction in which the back surface thereof faces the surface of the swinging member  42  of the first damper  40 . Specifically, the swinging member  62  of the second damper  60  is arranged between the swinging member  42  of the first damper  40  and the roll body R as shown in  FIG. 2 . 
     The swinging member  62  of the second damper  60  has plate-like support arms  66  at both ends in the longitudinal direction thereof. The both support arms  66  extend along the lateral direction of the swinging member  62  in a mutually parallel posture. The swinging member  62  has two shaft holes  61  that receive the pivot shaft  46  of the swinging member  42  at the base end of the pivot of each support arm  66 . The two shaft holes  61  are provided coaxially along the longitudinal direction of the swinging member  62 . 
     The swinging member  62  of the second damper  60  includes two engaging claws  68  ( FIG. 6 ) on the back surface side thereof at positions separated from the shaft holes  61  described above in the lateral direction thereof. The two engaging claws  68  protrude in a direction substantially orthogonal to the back surface of the swinging member  62  in an integrated manner. The two engaging claws  68  are arranged separated from each other in the longitudinal direction of the swinging member  62 . On the other hand, the swinging member  42  of the first damper  40  includes two engaging holes  47  ( FIG. 4 ) at positions respectively facing the two engaging claws  68  of the swinging member  62  of the second damper  60 . If the swinging member  62  of the second damper  60  pivots about the pivot shaft  46  and the two engaging claws  68  are inserted to the engaging holes  47  of the swinging member  42  of the first damper  40 , the engaging claws  68  are elastically deformed to be hooked on edges  47   a  of the engaging holes  47 . 
     The swinging member  42  of the first damper  40  has two recesses  48  on a surface thereof each for receiving one end of each of two compression springs  64  (second energization members). The two recesses  48  are respectively provided on the outer sides in the longitudinal direction of the two engaging holes  47  described above at the swinging tip side of the swinging member  42  that is separated from the pivot shaft  41  in the lateral direction. Each recess  48  has a protrusion  49  inserted into one end of the compression spring  64 . On the other hand, the swinging member  62  of the second damper  60  has two circular recesses  69  ( FIG. 6 ) on a back surface thereof each for receiving the other end of each of the two compression springs  64 . The two recesses  69  are provided on the outer sides in the longitudinal direction of the two engaging claws  68  described above at positions facing the two recesses  48  of the swinging member  42  of the first damper  40 , respectively. 
     The two compression springs  64  are respectively attached between the recesses  48  of the swinging member  42  of the first damper  40  and the recesses  69  provided on the back surface of the second damper  60 . As shown in  FIG. 7 , in a state in which the compression spring  64  is arranged between the swinging member  42  and the swinging member  62 , if the engaging claw  68  of the swinging member  62  is hooked on the edge  47   a  of the engaging hole  47  of the swinging member  42 , the compression spring  64  is compressed. In this state, the swinging member  62  of the second damper  60  is energized in a direction towards the roll body R (clockwise direction in  FIG. 7 ) around the pivot shaft  46  with respect to the swinging member  42  of the first damper  40 . In the state in  FIG. 7  in which the engaging claw  68  is hooked on the edge  47   a  of the engaging hole  47 , the swinging of the swinging member  62  of the second damper  60  in the direction towards the roll body R is restricted. 
     The pivotable range of the swinging member  62  of the second damper  60  relative to the swinging member  42  is between a position (shown in  FIG. 7 ) at which the engaging claw  68  of the swinging member  62  is hooked on the edge  47   a  of the engaging hole  47  of the swinging member  42  and a position (not shown) at which a back surface of the swinging member  62  contacts the surface  42   a  of the swinging member  42 . The swinging member  42  is energized in the clockwise direction in  FIG. 2  around the pivot shaft  46  by the restoring force of the compression spring  64  at any pivot position within the pivotable range. When viewed from a fixed system of the printer  100 , the pivotable range of the second damper  60  is a combination of a pivotable range relative to the first damper  40  and a pivotable range of the first damper  40 . 
     As shown in  FIG. 3 , the second damper  60  has two sets of pivotable pressing rollers  70  (pressing members) on the swinging tip side of the swinging member  62  pivoting around the pivot shaft  46 , i.e., on a surface  62   a  side of the swinging member  62 . The two sets of pressing rollers  70 , each of which includes a plurality of roller portions arranged coaxially in a mutually separated manner, are arranged separated from each other in the longitudinal direction of the swinging member  62 . The two sets of pressing rollers  70  press the recording paper T (wound around the roll body R) pulled out of the roll body R towards the roll body R at two positions separated from each other in a width direction of the recording paper T. 
     Below, a function of the buffer device  10  described above is described mainly with reference to  FIG. 2 ,  FIG. 7 , and  FIG. 8 .  FIG. 7  shows a state in which the housing section S accommodates a roll body R′ being used after the recording paper T is pulled out of the unused roll body R with the maximum diameter to some extent. In  FIG. 7 , an outer circumferential surface of the roll body R with the maximum diameter is indicated by a broken line for comparison.  FIG. 8  is an enlarged sectional view illustrating main portions in  FIG. 7 . 
     As shown in  FIG. 2 , in a state in which the unused roll body R with the maximum diameter is accommodated in the housing section S, and the recording paper T is pulled out of the roll body R and passes between the platen roller  22  and the print head  24 , the pressing roller  70  of the buffer device  10  is in contact with the outer circumferential surface of the roll body R. Specifically, in this state, almost no tension is applied to the recording paper T pulled out of the roll body R, and therefore the recording paper T is pressed against the roll body R by the pressing roller  70 . 
     In other words, in this state, the engaging claw  68  of the swinging member  62  of the second damper  60  is not engaged with the edge  47   a  of the engaging hole  47  of the swinging member  42  of the first damper  40 . Specifically, the swinging member  62  is positioned within the pivotable range. For this reason, in this state, the two sets of pressing rollers  70  are pressed against the outer circumferential surface of the roll body R by the restoring force of the two compression springs  64 . Specifically, in the present embodiment, the buffer device  10  is positioned so as to approach the roll body R until a position at which the two sets of pressing rollers  70  are at least pressed against the outer circumferential surface of the roll body R in a state in which the roll body R with the maximum diameter is accommodated in the housing section S. 
     On the other hand, in the state shown in  FIG. 2 , the step portion  42   b  of the swinging member  42  of the first damper  40  is engaged with the edge  112   b  of the bottom wall  112  of the housing  110 , thereby restricting the swinging of the swinging member  42  in a direction towards the roll body R. Specifically, in this state, the restoring force of the three tension springs  44  does not act on the pressing roller  70 , and thus, a relatively weak pressing force acts on the recording paper T. 
     From this state, if the motor  23  is energized to rotate the platen roller  22  in a predetermined direction (clockwise direction in the drawing), a conveyance force is applied to the recording paper T by the platen roller  22 , and in this way, the recording paper T is pulled out of the roll body R. At this time, since the roll body R attempts to keep stopping due to its inertia, a relatively large tension acts on the recording paper T between the roller body R and the platen roller  22  immediately after an operation of pulling out the recording paper T is started (until the roll body R starts to rotate). At this time, the tension applied to the recording paper T increases as the mass (i.e., the diameter) of the roll body R becomes large. 
     For this reason, immediately after the start of the rotation of the platen roller  22 , the pressing roller  70  of the buffer device  10  is pushed back in a direction away from the roll body R by the tension of the recording paper T. At this time, first, the swinging member  62  of the second damper  60  provided with the pressing roller  70  swings in a counterclockwise direction in the drawing as the two compression springs  64  are compressed. Furthermore, after the back surface of the swinging member  62  of the second damper  60  contacts the surface  42   a  of the swinging member  42  of the first damper  40 , as the three tension springs  44  are extended, the swinging member  42  of the first damper  40  swings in the counterclockwise direction in the drawing. 
     As described above, according to the buffer device  10  of the present embodiment, even if a large tension is applied to the recording paper T immediately after the conveyance of the recording paper T is started, an impact on the recording paper T can be absorbed, and problems such as cut of the recording paper T or an unstable conveyance speed of the recording paper T can be prevented. When the roll body R starts rotating after the start of the conveyance of the recording paper T, the pressing roller  70  of the buffer device  10  moves within the pivotable range in accordance with the change in the tension of the recording paper T, and the recording paper T can be conveyed stably. 
     On the other hand, when the printer  100  finishes a printing operation and the control section stops energization to the motor  23  to stop the platen roller  22 , the roll body R being rotating in the housing section S attempts to continue rotating due to its inertia. At this time, an inertial force by which the roll body R attempts to continue rotating increases as the mass of the roll body R becomes large. As described above, if the roll body R continues rotating after the platen roller  22  is stopped, the recording paper T becomes slack between the roll body R and the platen roller  22 . If the recording paper T is slack, there is a possibility that the recording paper T is stained or jammed. For this reason, it is desirable to stop the roll body R rapidly after the platen roller  22  is stopped. 
     In the present embodiment, as shown in  FIG. 7 , the buffer device  10  is positioned at a position at which the pressing roller  70  overlaps the roll body R beyond an imaginary outer circumferential surface of the roll body R with the maximum diameter (indicated by the broken line in  FIG. 7 ) in a state in which the pressing roller  70  is positioned at one end of the pivotable range that protrudes towards the housing section S most. For this reason, according to the present embodiment, the pressing roller  70  can contact the outer circumferential surface of the roll body R in a state in which no tension is applied to the recording paper T in a certain period from the start of the use of the unused roll body R with the maximum diameter (until the outer circumferential surface is separated from the pressing roller  70  protruding most, like the roll body R′ being used and provided with the outer circumferential surface indicated by a solid line in  FIG. 7 ). 
     Specifically, according to the buffer device  10  of the present embodiment, immediately after the platen roller  22  is stopped and no tension acts on the recording paper T, the pressing roller  70  can be pressed against the outer circumferential surface of the roll body R at a predetermined pressure. For this reason, a certain braking force can be applied to the roll body R that attempts to continue rotating after the printing operation is finished, and in this way, the rotation of the roll body R can be rapidly stopped. Therefore, according to the present embodiment, the stain or a conveyance jam caused by the slack of the recording paper T can be prevented. 
     During a predetermined period from the start of use of the roll body R with the maximum diameter (i.e., until the pressing roller  70  does not contact the roll body R), the buffer device  10  can apply the braking force to the roll body R as described above. However, after the diameter of the roll body R is decreased to such an extent that the pressing roller  70  does not contact the roll body R, the buffer device  10  cannot apply the braking force to the roll body R. As described above, the inertial force of the inertia by which the roll body R attempts to continue rotating is increased as the mass of the roll body R becomes large. Specifically, since the problem such as the slack of the recording paper T is difficult to occur even if no braking force is applied to the roll body R′ whose mass is reduced to some extent, as in the present embodiment, it is effective to apply the braking force at the beginning of the use of the roll body R with the maximum diameter. 
     According to the present embodiment, since the buffer device  10  is mounted on the bottom wall  112  of the housing  110 , the printer  100  can be downsized. However, if the buffer device  10  is mounted on the bottom wall  112  of the housing section S for accommodating the roll body R as in the present embodiment, there is a concern that a buffer performance is reduced due to narrowing of the pivotable range of the pressing roller  70  for applying the tension to the recording paper T. As a countermeasure, in the present embodiment, the buffer device  10  is mounted at a position at which the roll body R with the maximum diameter and the pivotable range of the pressing roller  70  partially overlap. 
     Therefore, in the buffer device  10  of the present embodiment, the pivotable range of the pressing roller  70  is maximized at a time point at which the diameter of the roll body R becomes equal to that of the roll body R′ that is indicated by the solid line in  FIG. 7 . Specifically, according to the present embodiment, a sufficient pivotable range of the pressing roller  70  can be ensured while the device configuration is downsized, and undesired slack of the recording paper T can be prevented. 
     In the buffer device  10  of the present embodiment, the tension spring  44  is used as the first energization member for energizing the swinging member  42  of the first damper  40 , and the compression spring  64  is used as the second energization member for energizing the swinging member  62  of the second damper  60 . This combination is suitable for relatively increasing the pressing force by the first damper  40  and relatively decreasing the pressing force by the second damper  60 . In the present embodiment, the tension spring  44  is provided in a space between the swinging member  42  of the first damper  40  and the housing  110 , and the compression spring  64  is provided in a space between the swinging member  42  of the first damper  40  and the swinging member  62  of the second damper  60 , thereby downsizing the device configuration. 
     According to the printer  100  of the embodiment described above, since the buffer device  10  is mounted on the bottom wall  112  of the housing  110 , the device configuration can be downsized. According to the buffer device  10  of the present embodiment, the pressing roller  70  is energized in the direction of pressing against the roll body R. For this reason, the slack of the recording paper T can be suppressed by applying the braking force to the roll body R with the maximum diameter. In this way, the recording paper T can be prevented from being stained or jammed. According to the present embodiment, the buffer device  10  is arranged in such a manner that a part of the pivotable range of the pressing roller  70  overlaps with the outer circumferential surface of the roll body R with the maximum diameter. In this way, at a time point at which the diameter of the roll body R′ being used is reduced to some extent, the pivotable range of the pressing roller  70  can be maximized, and the buffer performance can be maintained. 
     While certain embodiments have been described, these embodiments have been presented by way of example only, and are not intended to limit the scope of the invention. Indeed, the novel embodiments described herein may be embodied in a variety of other forms; furthermore, various omissions, substitutions and changes in the form of the embodiments described herein may be made without departing from the spirit of the invention. The accompanying claims and their equivalents are intended to cover such forms or modifications as would fall within the scope and spirit of the invention. 
     For example, in the above-described embodiment, the recording paper is used as the image receiving medium; however, it is not limited thereto, and a medium other than the paper may be used. In the above-described embodiment, the platen roller  22  and the print head  24  are used as the conveyance section; however, it is not limited thereto, and another conveyance device that applies a conveyance force to the recording paper T may be provided separately.