A sheet supply apparatus for sequentially unwinding a first sheet from a first roll and a second sheet from a second roll, the sheet supply apparatus comprising:
- a first support shaft configured to rotatably support the first roll at a center position thereof;
- a second support shaft configured to rotatably support the second roll at a center position thereof;
- a joining mechanism configured to join the first sheet and the second sheet to each other by a pressing operation of pressing the first sheet to an adhesive on an outer peripheral surface of the second roll;
- and
- a controller configured to control a rotation of the first support shaft and a rotation of the second support shaft such that a target joining portion of the first sheet is joined to the adhesive on the outer peripheral surface of the second roll due to the pressing operation by the joining mechanism when a residual length of the first sheet reaches a target residual wound length,
- wherein the controller includes:
- a residual length calculation section configured to calculate:
- (i) a radius of the first roll that changes in accordance with a sheet supply from the first roll based on a running speed of the first sheet and a rotational speed of the first support shaft;
- (ii) a sheet thickness of the first sheet in accordance with a reduction in the radius of the first roll for each rotation of the first roll;
- and (iii) the residual length of the first sheet from a result of calculation of the radius of the first roll and the sheet thickness of the first sheet;
- a residual length monitoring section configured to monitor the residual length of the first sheet that has been calculated by the residual length calculation section, and output a control instructive signal when the residual length of the first sheet reaches a watch length that is a sum of a predetermined length and the target residual wound length;
- a first shaft control section configured to control the rotation of the first support shaft in response to the control instructive signal such that the first sheet is unwound at a predetermined running speed;
- and
- a second shaft control section configured to control the rotation of the second support shaft in response to the control instructive signal, and
- wherein the second shaft control section is configured to execute:
- a first rotation control of regulating a rotational speed of the second support shaft such that a peripheral speed of the second roll coincides with the predetermined running speed of the first sheet;
- and
- a second rotation control of regulating the rotational speed of the second support shaft such that the rotation of the second support shaft is accelerated or decelerated in accordance with a distance between the adhesive and a pressing position where the joining mechanism performs the pressing operation in a rotational direction of the second roll after the first rotation control, and subsequently, such that the peripheral speed of the second roll is restored to and maintained at the predetermined running speed of the first sheet when the adhesive on the outer peripheral surface of the second roll arrives at the pressing position while the target joining portion of the first sheet meets the pressing position.