Medium supply apparatus

Abstract

A medium supply apparatus supplying a rolled medium includes a tension member contacts to the medium to apply a tension to the medium, a state switching part that switches states of the tension member between first and second states, and a control unit. The tension member is swingable between a first position at which a first corner angle (θ1) and a second position at which a second corner angle (θ2) is formed, the second corner angle (θ2) being greater than the first corner angle (θ1). The control unit causes the state switching part to switch the state of the tension member to the fixed state in the first position when the medium is supplied, the control unit causes the state switching part to switch the state of the tension member to the releasing state in the first position when the control unit does not receive an image forming start signal for a predetermined period, and the control unit causes the state switching part to switch the state of the tension member to the fixed state when the tension member reaches the second position.

What is claimed is: 
     
         1 . A medium supply apparatus, comprising:
 a holder that is configured to rotatably support a medium, which is wound in a rolled shape and to be rotated by a drive part,   a conveyance part that conveys the medium in a conveyance direction, and is disposed in a downstream side with respect to the holder in the conveyance direction,   a tension member that is disposed between the holder and the conveyance part, and contacts to the medium, which is positioned between the holder and the conveyance part, to apply a tension to the medium,   a state switching part that has a detection sensor that detects a position of the tension member and switches states of the tension member between two states in correspondence with a detection result by the detection sensor, one state being a fixed state where the tension member is locked such that the tension member is not movable, and the other state being releasing state where the tension members is not locked such that the tension member is movable,   a control unit that controls the drive part for the holder, conveyance part, and the state switching part, wherein   the tension member is swingable between a first position at which a first corner angle (θ1) is formed and a second position at which a second corner angle (θ2) is formed, the first and second corner angles being determined with two tangent lines formed on the tension member which are seen from a rotational axis view of the holder, one tangent line being at an upstream contact point (UCP) where the medium comes in first contact with the tension member, and the other tangent line being at a downstream contact point (DCP) where the medium, which curves around an outer peripheral of the tension member, departs from the outer peripheral of the tension member, the second corner angle (θ2) being greater than the first corner angle (θ1),   the control unit causes the state switching part to switch the state of the tension member to the fixed state in the first position when the medium is supplied, and   the control unit causes the state switching part to switch the state of the tension member to the releasing state in the first position when the control unit does not receive an image forming start signal, which is a signal to start an image forming process, for a predetermined period after the conveyance part stops conveying the medium so that the tension medium is moved to the second position as the drive part drives the holder to rotate in an opposite direction to the conveyance direction, and   the control unit causes the state switching part to switch the state of the tension member to the fixed state when the tension member reaches the second position.   
     
     
         2 . The medium supply apparatus according to  claim 1 , wherein
 the control unit causes the state switching part to switch the state of the tension member to the releasing state in the second position when the control unit does not receive the image forming start signal, which is the signal to start an image forming process, for another predetermined period after the conveyance part stops conveying the medium.   
     
     
         3 . The medium supply apparatus according to  claim 1 , wherein
 a conveyance length of the medium that is determined between the holder and the conveyance part through the tension member when the tension member is at the first position is longer than another conveyance length of the medium when the tension member is at the second position.   
     
     
         4 . The medium supply apparatus according to  claim 3 , wherein
 the second position of the tension member is determined to cause the conveyance length to be the shortest.   
     
     
         5 . The medium supply apparatus according to  claim 1 , wherein
 the second corner angle ranges from 150° to 180°.   
     
     
         6 . The medium supply apparatus according to  claim 1 , wherein
 the second corner angle ranges from 170° to 180°.   
     
     
         7 . The medium supply apparatus according to  claim 1 , wherein
 the drive part conveys the medium in the conveyance direction by rotating the rolled medium in a first direction, and   the drive part winds up the medium, which was once supplied, around the holder by rotating the rolled medium in a second direction that is opposite to the first direction.   
     
     
         8 . The medium supply apparatus according to  claim 7 , wherein
 the drive part moves the tension member from the second position to the first position by rotating the medium in the first direction, and   the drive part moves the tension member, which is in the releasing state, from the first position to the second position by rotating the medium in the second direction.   
     
     
         9 . The medium supply apparatus according to  claim 1 , further comprising:
 a first position sensor that detects the first position of the tension member, and   a second position sensor that detects the second position of the tension member, wherein   when the first position sensor detects the first position, the control unit causes the state switching part to switch the state of the tension member from the releasing state to the fixed state,   when the second position sensor detects the second position, the control unit causes the state switching part to switch the state of the tension member from the releasing state to the fixed state.   
     
     
         10 . The medium supply apparatus according to  claim 1 , wherein
 the conveyance part is configured with a pair of rollers sandwiching the medium.   
     
     
         11 . The medium supply apparatus according to  claim 1 , wherein
 the tension member includes a contact portion that contacts to the medium, a supporting member that supports the contact part and a supporting shaft that is provided in an apparatus body and rotatably supports the supporting member, and   the contact portion swings between the first position and the second position by the supporting member rotating around the support shaft.   
     
     
         12 . The medium supply apparatus according to  claim 11 , wherein
 the contact portion includes a roller that is rotatably disposed at a tip of the support member.   
     
     
         13 . A medium supply apparatus, comprising:
 a holder that is configured to rotatably support a medium, which is wound in a rolled shape and to be rotated by a drive part,   a conveyance part that conveys the medium in a conveyance direction, and is disposed in a downstream side with respect to the holder in the conveyance direction,   a medium guide part that has a curved portion, is disposed in a upstream side with the conveyance part in the conveyance direction,   a tension member that is disposed between the holder and the medium guide part along the conveyance path and applies a tension to the medium by contacting, the tension member being swingable between a first position and a second position,
 when the tension member is at the first position, the medium being curved by the curved portion of the medium guide part so that the medium is in a curved shape, seen from a side view of the medium being conveyed, the side view being perpendicular to the conveyance direction and to flat surfaces of the medium, 
 when the tension member is at the second position, the medium not contacting to the curved portion of the medium guide part so that the medium is in a linear shape, seen from the side view of the medium, 
 the tension applied by the tension member being oriented from the second position to the first position, 
   a state switching part that has a detection sensor that detects a position of the tension member and switches states of the tension member between two states in correspondence with a detection result by the detection sensor, one state being a fixed state where the tension member is locked such that the tension member is not movable, and the other state being releasing state where the tension members is not locked such that the tension member is movable,   a control unit that controls the drive part for the holder, conveyance part, and the state switching part, wherein   the control unit causes the state switching part to switch the state of the tension member to the fixed state in the first position when the medium is conveyed to the downstream side for an image forming process, and   the control unit causes the state switching part to switch the state of the tension member to the releasing state in the first position when the control unit does not receive print data for the image forming process for a predetermined period after the conveyance part stops conveying the medium so that the tension medium is moved to the second position as the drive part drives the holder to rotate in an opposite direction to the conveyance direction, and   the control unit causes the state switching part to switch the state of the tension member to the fixed state when the tension member reaches the second position.   
     
     
         14 . The medium supply apparatus according to  claim 13 , wherein
 the tension member is configured to be biased by a spring, which consistently pushes the tension member toward the first position,   when the state switching part switches the state of the tension member, which is in the second position, from the fixed state to the releasing state, the tension member is moved toward the first position due to the spring, and   the control unit causes the state switching part to switch the state of the tension member to the fixed state when the tension member reaches the first position.