Sheet member positioning device

A sheet member positioning device includes a plate on which a sheet member is loaded; a reference member provided at a side, in a first direction, of the plate, the sheet member being able to abut the reference member; a conveying member provided at a side, in a second direction, of the plate, and due to the conveying member being moved toward the side in the first direction and conveying the sheet member, the conveying member makes the sheet member abut the reference member so as to determine a position of the sheet member in the first direction; and a detecting mechanism which, at a time when the position of the sheet member in the first direction is determined, detects a distance between the reference member and the conveying member, and detects a size of the sheet member on the basis of the detected distance.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a sheet member positioning device which positions a sheet member.

2. Description of the Related Art

Printing plate exposure devices have been developed which expose (record) an image directly by a laser beam or the like onto an image forming layer (photosensitive layer, emulsion surface) on a support of a sheet-shaped printing plate (for example, a so-called photopolymer plate or a thermal plate).

In such a printing plate exposure device, the printing plate which is loaded on a flat-plate-shaped plate is, as needed, conveyed to a punching section, and is subjected to punching processing (a processing for forming punch holes) at the punching section. Further, the printing plate, which is loaded on the plate, is conveyed to an exposure section, and exposure processing of the printing plate is carried out at the exposure section.

In order to improve the accuracy of the punching processing and the exposure processing, the printing plate must be positioned at a predetermined printing plate positioning device before the punching processing in the punching section and the exposure processing in the exposure section.

Here, if the size of the printing plate can be detected simultaneously with the positioning of the printing plate by using the printing plate positioning device, there is no need for a separate mechanism for detecting the size of the printing plate, and costs can therefore be reduced. Further, because there is no need for a separate period of time for detecting the size of the printing plate, it is possible to prevent the productivity from deteriorating.

SUMMARY OF THE INVENTION

In view of the aforementioned, an object of the present invention is to provide a sheet member positioning device which aims for lower costs and prevention of deterioration in productivity.

A sheet member positioning device relating to a first aspect of the present invention comprises: a plate on which a sheet member is loaded; a reference member provided at a side, in a first direction, of the plate, the sheet member being able to abut the reference member; a conveying member provided at a side, in a second direction, of the plate, and due to the conveying member being moved toward the side in the first direction and conveying the sheet member, the conveying member makes the sheet member abut the reference member so as to determine a position of the sheet member in the first direction; and a detecting mechanism which, at a time when the position of the sheet member in the first direction is determined, detects a distance between the reference member and the conveying member, and detects a size of the sheet member on the basis of the detected distance.

In the sheet member positioning device, the conveying member is moved toward the side in the first direction, and conveys the sheet member on the plate. In this way, the sheet member abuts the reference member, and the position of the sheet member in the first direction is determined.

Here, at the time when the position of the sheet member in the first direction is determined, the detecting mechanism detects the distance between the reference member and the conveying member, and detects the size of the sheet member on the basis of the detected distance. Accordingly, the size of the sheet member can be detected by using the sheet member positioning device. The size of the sheet member can be detected simultaneously with the determining of the position of the sheet member in the first direction. There is no need to separately detect the size of the sheet member. In this way, there is no need for a separate mechanism for detecting the size of the sheet member, and costs can be reduced. Moreover, because there is no need for a separate period of time for detecting the size of the sheet member, it is possible to prevent deterioration in productivity.

Further, another aspect of the present invention is a method of positioning a sheet member in a sheet member positioning device which includes a reference member and a conveying member which are set apart from one another by a predetermined distance, a plate, and a detecting mechanism, the method comprising the steps of: (a) supplying a sheet member to the plate; (b) abutting the sheet member, which is supplied to the plate, against the reference member, which is provided at a side in a first direction of the plate, by the conveying member; (c) detecting a distance between the reference member and the conveying member by the detecting mechanism; and (d) detecting a size of the sheet member on the basis of the detected distance.

DESCRIPTION OF THE PREFERRED EMBODIMENT

FIG. 2shows an automatic printing plate exposure device10relating to the present embodiment, and structured such that the sheet member positioning device of the present invention is applied thereto.

The automatic printing plate exposure device10relating to the present embodiment is a device which exposes (records) an image onto an image forming layer (a photosensitive layer, an emulsion surface) on a support of a sheet-shaped printing plate12such as a photopolymer plate, a thermal plate, or the like. The automatic printing plate exposure device10is divided into a conveying guide unit14, a punching section16, and an exposure section18. The punching section16and the exposure section18are disposed ahead of the conveying guide unit14, and the exposure section18is disposed beneath the punching section16.

The conveying guide unit14includes a plate supplying guide20which serves as a plate and is a substantially rectangular flat-plate shape, and a plate discharging guide22which is a substantially rectangular flat-plate shape. The relative positional relationship of the plate supplying guide20and the plate discharging guide22is such that the guides20,22are disposed to form a sideways V-shape. The conveying guide unit14rotates a predetermined angle around a vicinity of the center ofFIG. 2. Due to this rotation, the conveying guide unit14can make the plate supplying guide20and the plate discharging guide22selectively correspond to the punching section16or the exposure section18. The printing plate12is supplied to and loaded on the plate supplying guide20, and the size of the printing plate12is inputted in advance to the automatic printing plate exposure device10.

As shown inFIG. 1, a conveying roller24is rotatably provided at the front side region of the plate supplying guide20. The conveying roller24is a skewer-like structure in which a plurality of cylindrical roller portions24A formed of silicon rubber are aligned at a rotating central shaft24B which is parallel to the left-right direction. The conveying roller24projects above the top surface of the plate supplying guide20. Due to the conveying roller24being driven to rotate in a state in which the bottom surface of the printing plate12is contacting the conveying roller24, the printing plate12is conveyed forward.

A predetermined number of ribs26, which are formed in trapezoidal column shapes, are provided on the plate supplying guide20. The ribs26are disposed parallel to the front-back direction. The height by which the ribs26project out above the top surface of the plate supplying guide20is slightly lower than that of the conveying roller24. A predetermined number of cylindrical rotating rollers28are provided on the plate supplying guide20so as to be freely rotatable. The rotating rollers28are disposed parallel to the left-right direction. The height by which the rotating rollers28project out above the top surface of the plate supplying guide20is substantially the same as that of the conveying roller24. Here, due to the supporting of the printing plate12on the ribs26and the rotation of the rotating rollers28which accompanies the conveying of the printing plate12, the frictional force at the time of conveying the printing plate12can be reduced.

A pair of positioning pins30are provided at the front end of the plate supplying guide20parallel to the left-right direction. The positioning pins30are formed as cylinders, are freely rotatable around central shafts, and project out with respect to the top surface of the plate supplying guide20. Further, the pair of positioning pins30can be lowered from the top surface of the plate supplying guide20. When the printing plate12is conveyed forward due to the rotation of the conveying roller24as described above, the front end of the printing plate abuts the pair of positioning pins30. In this way, the position of the printing plate12in the front-back direction is determined. Next, the pair of positioning pins30are lowered from the top surface of the plate supplying guide20. Due to the rotation of the conveying roller24, the printing plate12is conveyed forward so as to cross over the front end of the plate supplying guide20.

A slit32is formed in the right side region of the plate supplying guide20in a vicinity behind the conveying roller24. The slit32is disposed parallel to the left-right direction, and a supporting shaft34passes through the interior thereof. As shown inFIG. 4, the supporting shaft34is supported on a supporting stand68which is beneath the plate supplying guide20. A male screw70which is a ball screw is screwed together with the supporting stand68, and the supporting stand68stands upright with respect to the male screw70. The male screw70is disposed parallel to the left-right direction directly beneath the slit32. The male screw70is connected to a driving shaft of a pulse motor72which forms a detecting mechanism. The pulse motor72is connected to a control device74which forms the detecting mechanism. Due to the pulse motor72being driven, the male screw70is rotated, and the supporting stand68moves in the left-right direction while the state in which the supporting stand68stands upright with respect to the male screw70is maintained.

A cylindrical reference pin36, which serves as a reference member, is supported at the top portion of the supporting shaft34so as to be freely rotatable around the supporting shaft34. The reference pin36projects further upward than the top surface of the plate supplying guide20, and can abut the printing plate12on the plate supplying guide20. The right end portion of the plate supplying guide20is the base position of the reference pin36. Due to the movement of the supporting stand68due to the driving of the pulse motor72, the supporting shaft34is moved along the slit32. Due to the reference pin36being moved toward the left (a second direction), the reference pin36is positioned at a predetermined position in accordance with the size of the printing plate12which is inputted to the automatic printing plate exposure device10as described above. Further, on the basis of the number of driving pulses of the pulse motor72from the start of movement of the reference pin36from its base position to the time when the reference pin36is positioned at the aforementioned predetermined position, a control device74computes a distance M which the reference pin36has moved toward the left from its base position until it is positioned at the aforementioned predetermined position.

A reference sensor76, which forms the detecting mechanism, is provided at a side of the supporting shaft34(in the present embodiment, at the front side of the supporting shaft34) at the top surface of the supporting stand68. Due to the reference sensor76sensing the right edge of the printing plate12, it can be detected that the printing plate12has abutted the reference pin36as will be described later. The reference sensor76is connected to the control device74.

As shown inFIG. 1, a slit38is formed in the left side region of the plate supplying guide20in a vicinity behind the conveying roller24. The slit38is disposed parallel to the left-right direction, and a supporting shaft40passes through the interior thereof. As shown inFIG. 4, the supporting shaft40is supported on a supporting stand78which is beneath the plate supplying guide20. A male screw80which is a ball screw is screwed together with the supporting stand78, and the supporting stand78stands upright with respect to the male screw80. The male screw80is disposed parallel to the left-right direction directly beneath the slit38. The male screw80is connected to a driving shaft of a pulse motor82which forms the detecting mechanism. The pulse motor82is connected to the control device74. Due to the pulse motor82being driven, the male screw80is rotated, and the supporting stand78moves in the left-right direction while the state in which the supporting stand78stands upright with respect to the male screw80is maintained.

A cylindrical conveying pin42, which serves as a conveying member, is supported at the top portion of the supporting shaft40so as to be freely rotatable around the supporting shaft40. The conveying pin42projects further upward than the top surface of the plate supplying guide20, and opposes the reference pin36in the left-right direction. The left end portion of the plate supplying guide20is the base position of the conveying pin42. The conveying pin42, which is disposed at its base position, and the reference pin36, which is disposed at its base position, are separated in the left-right direction by a distance L. Here, as described above, when the printing plate12abuts the pair of positioning pins30and the position of the printing plate12in the front-back direction is determined, due to the movement of the supporting stand78due to the driving of the pulse motor82, the supporting shaft40is moved along the slit38and the conveying pin42is moved toward the right (a first direction). The conveying pin42thereby pushes the printing plate12so as to convey the printing plate12toward the right. The movement of the conveying pin42stops after the printing plate12has abutted the reference pin36. In this way, the position of the printing plate12in the right direction is determined, and as shown inFIG. 3, the printing plate12is temporarily positioned. Note that buckling deformation of the printing plate12due to the pushing force of the conveying pin42can be prevented by structuring the supporting shaft40so as to be able to move in a state in which a predetermined elastic force is applied toward the reference pin36side.

A conveying sensor84, which forms the detecting mechanism, is provided at a side of the supporting shaft40(in the present embodiment, at the front side of the supporting shaft40) at the top surface of the supporting stand78. The conveying sensor84is connected to the conveying pin42either directly or indirectly. The conveying sensor84senses that a load of a predetermined amount has been applied to the conveying pin42due to the printing plate12, which is being conveying by the conveying pin42, abutting the reference pin36. The conveying sensor84is connected to the control device74. The control device74computes a distance N, which the conveying pin42moves from its base position to the right until the printing plate12abuts the reference pin36, on the basis of the number of driving pulses of the pulse motor82from the start of movement of the conveying pin42from its base position, to the time the reference sensor76detects that the printing plate12has abutted the reference pin36and the conveying sensor84detects that a load of the predetermined amount has been applied to the conveying pin42.

The reference pin36, which is disposed at its base position, and the conveying pin42, which is disposed at its base position, are separated in the left-right direction by the distance L. Further, the distance M, which the reference pin36moves toward the left from its base position to being disposed at the aforementioned predetermined position, is computed. Moreover, the distance N, which the conveying pin42moves toward the right from its base position until the printing plate12abuts the reference pin36, is computed. Thus, due to the control device74computing the value L-M-N (which is equal to a distance W of separation in the left-right direction between the reference pin36and the conveying pin42at the time when the position of the printing plate12in the right direction is determined), an actual length W of the printing plate12in the left-right direction is detected (computed).

Further, the control device74computes the difference between the actual length W in the left-right direction of the printing plate12, and a length in the left-right direction of the printing plate12which is determined from the size of the printing plate12inputted in advance to the automatic printing plate exposure device10. If this difference is greater than or equal to a given amount (e.g., ±5 mm), error processing is carried out. Examples of this error processing are processing for stopping the automatic printing plate exposure device10, processing for discharging the printing plate12from the plate supplying guide20by rotation of the conveying guide unit14, and the like.

As shown inFIG. 1, the punching section16has a flat-plate-shaped supporting plate44. A predetermined number of punching devices46are supported on the supporting plate44. (In the present embodiment, a pair of punching devices46is provided at each of the left and the right, for a total of four punching devices46.) Here, the conveying guide unit14is rotated such that the plate supplying guide20corresponds to the punching section16(opposes the punching devices46), and the pair of positioning pins30are lowered from the top surface of the plate supplying guide20. In this way, the front end portion of the printing plate12can be conveyed by the rotation of the conveying roller24from the plate supplying guide20into the punching devices46.

A positioning pin48is provided between the two punching devices46of each pair of punching devices46. This pair of positioning pins48is disposed parallel to the left-right direction. Each positioning pin48is cylindrical, and rotates freely around a central shaft. The front end of the printing plate12conveyed into the punching devices46abuts the pair of positioning pins48. In this way, the position of the printing plate12in the front-back direction is determined. Moreover, in this state, the conveying pin42is moved and conveys the printing plate12to the right, and after the printing plate12has abutted the reference pin36, movement of the conveying pin42is stopped. The position of the printing plate12in the right direction is thereby determined. In this way, as shown inFIG. 3, the printing plate12is actually positioned in the punching section16. Further, the left-right direction central line of the printing plate12which is actually positioned coincides with the left-right direction central line of the pair of positioning pins48and the two pairs of punching devices46.

A predetermined number of punch holes (not shown), which are, for example, round holes or elongated holes or the like, are formed by the punching devices46in the front end portion of the printing plate12which is actually positioned. As will be described later, the predetermined number of punch holes serve as a reference for winding the printing plate12onto a plate cylinder of a rotary press of a printing device (not shown) on which the printing plate12is conveyed, and are used in positioning the printing plate12for the printing processing at the printing device.

When the processing at the punching devices46is completed, by rotating the conveying roller24reversely, the printing plate12is returned onto the plate supplying guide20. The pair of positioning pins30are projected from the top surface of the plate supplying guide20, and the printing plate12is again temporarily positioned as described above.

The exposure section18is equipped with a cylindrical rotating drum50. The rotating drum50is disposed parallel to the left-right direction, and can rotate in the direction of arrow A and the direction of arrow B inFIG. 2. Here, when the printing plate12, which has returned onto the plate supplying guide20from the punching section16, is temporarily positioned as mentioned above, the conveying guide unit14is rotated such that the plate supplying guide20corresponds to the exposure section18(opposes the rotating drum50in a direction tangent to the rotating drum50), and the pair of positioning pins30are lowered from the top surface of the plate supplying guide20. In this way, the front end of the printing plate12is conveyed by the conveying roller24onto the outer periphery of the rotating drum50.

A pair of positioning pins52are provided at the outer periphery of the rotating drum50. The pair of positioning pins52is disposed parallel to the left-right direction. Each positioning pin52is cylindrical, and rotates freely around a central shaft. The front end of the printing plate12conveyed onto the outer periphery of the rotating drum50abuts the pair of positioning pins52. In this way, the position of the printing plate12in the front-back direction is determined. Moreover, in this state, the conveying pin42is moved and conveys the printing plate12toward the right. Movement of the conveying pin42stops after the printing plate12has abutted the reference pin36. The position of the printing plate12in the right direction is thereby determined. In this way, as shown inFIG. 3, the printing plate12is actually positioned in the exposure section18.

As shown inFIG. 2, a plate-shaped front end chuck54is provided, in a vicinity of the pair of positioning pins52, at the outer periphery of the rotating drum50. The substantial central portion of the front end chuck54in the front-back direction is pivotably supported at the rotating drum50. Elastic force, in a direction of moving away from the outer periphery of the rotating drum50, is applied to the front side of the front end chuck54.

An attaching cam56is provided above the front end chuck54. Due to the attaching cam56pushing the front side of the front end chuck54, the rear side of the front end chuck54moves apart from the outer periphery of the rotating drum50. In this way, the front end of the printing plate12, which is conveyed onto the outer periphery of the rotating drum50from the plate supplying guide20as described above, is inserted between the rear side of the front end chuck54and the outer periphery of the rotating drum50, and in this state, the above-described actual positioning of the printing plate12is carried out. Further, after the above-described actual positioning of the printing plate12has been completed, the attaching cam56is rotated and the pushing of the front side of the front end chuck54is cancelled. When the pushing of the front side of the front end chuck54is cancelled, the front end chuck54rotates due to the aforementioned elastic force which is applied to the front side of the front end chuck54, and the rear side of the front end chuck54presses the front end of the printing plate12. In this way, the front end of the printing plate12is held at the outer periphery of the rotating drum50. When the front end of the printing plate12is held at the outer periphery of the rotating drum50, the rotating drum50is rotated in the direction of arrow A inFIG. 2, and the printing plate12is taken up onto the outer periphery of the rotating drum50.

A squeeze roller58is disposed in a vicinity of the outer periphery of the rotating drum50, at the arrow A direction side (inFIG. 2) of the attaching cam56. The printing plate12wound on the rotating drum50is rotated while being pressed toward the rotating drum50due to the squeeze roller58being moved toward the rotating drum50, and the printing plate12is closely contacted with the outer periphery of the rotating drum50.

A rear end chuck attaching/removing unit60is disposed between the attaching cam56and the squeeze roller58in a vicinity of the outer periphery of the rotating drum50. The rear end chuck attaching/removing unit60has a shaft62. The shaft62is movable toward the rotating drum50. A rear end chuck64is mounted to the distal end of the shaft62. When the rear end of the printing plate12wound on the rotating drum50opposes the rear end chuck attaching/removing unit60, the shaft62moves the rear end chuck64toward the rotating drum50, and attaches the rear end chuck64to a predetermined position of the rotating drum50. Simultaneously, the rear end chuck64separates from the shaft62. In this way, the rear end chuck64presses the rear end of the printing plate12such that the rear end of the printing plate12is held on the outer periphery of the rotating drum50.

When the front end and the rear end of the printing plate12are held at the rotating drum50by the front end chuck54and the rear end chuck64, the squeeze roller58moves away from the rotating drum50. After the squeeze roller58moves away from the rotating drum50, the rotating drum50is rotated at high speed at a predetermined rotational speed.

A recording head portion66is disposed in a vicinity of the outer periphery of the rotating drum50. Synchronously with the rotation of the rotating drum50which is being rotated at high speed, the recording head portion66irradiates a laser beam which has been modulated on the basis of read image data. The printing plate12is thereby exposed on the basis of the image data. This exposure processing is so-called scanning-exposure in which, while the rotating drum50is rotating at high speed (while main scanning is carried out), the recording head portion66is moved in the axial direction of the rotating drum50(subscanning is carried out).

When the scan-exposure of the printing plate12is completed, the rotating drum50is temporarily stopped at the position where the rear end chuck64opposes the shaft62. Then, the rear end chuck64is removed from the rotating drum50by the shaft62(the rear end chuck64is attached to the shaft62), and the pressing of the rear end of the printing plate12by the rear end chuck64is released. Moreover, after the conveying guide unit14is rotated such that the plate discharging guide22corresponds to the exposure section18, i.e., after the conveying guide unit14is rotated such that the plate discharging guide22opposes the rotating drum50in a direction tangential to the rotating drum50, the rotating drum50is rotated in the direction of arrow B inFIG. 2. The printing plate12is thereby conveyed backward from the rear end side thereof, and is discharged to the plate discharging guide22. At this time, due to the attaching cam56being rotated and pushing the front side of the front end chuck54, the pressing of the front end of the printing plate12by the rear side of the front end chuck54is released. Further, when the printing plate12is sent to the plate discharging guide22, the conveying guide unit14is pivoted, and the printing plate12is discharged from the plate discharging guide22. The printing plate12is thereby conveyed to a developing device or a printing device (both not shown) which is the subsequent process adjacent the automatic printing plate exposure device10.

Next, operation of the present embodiment will be described.

First, the printing plate12is loaded on the plate supplying guide20. At this time, the printing plate12may be fed-in by so-called manual feeding, or may be fed-in by an automatic plate feeding device or the like.

The printing plate12on the plate supplying guide20is loaded in a state in which the loaded position and the inclination and the like of the printing plate12with respect to the plate supplying guide20are relatively rough. In this state, the printing plate12is conveyed forward by the rotation of the conveying roller24such that the front end of the printing plate12abuts the pair of positioning pins30. After the front end of the printing plate12abuts the positioning pins, the printing plate12is conveyed toward the right by the conveying pin42, and abuts the reference pin36. The printing plate12is thereby temporarily positioned.

When the printing plate12is in this temporarily positioned state, the conveying guide unit14is pivoted such that the plate supplying guide20is made to correspond to the punching section16. Simultaneously, the pair of positioning pins30are lowered from the top surface of the plate supplying guide20, the printing plate12is conveyed forward by the rotation of the conveying roller24, and the front end of the printing plate12abuts the pair of positioning pins48. Next, the printing plate12is conveyed toward the right by the conveying pin42, and abuts the reference pin36. In this way, the printing plate12is actually positioned at the punching section16. A predetermined number of punch holes are formed by the punching devices46in the front end portion of the printing plate12which has been actually positioned. Then, due to the conveying roller24rotating reversely, the printing plate12is returned onto the plate supplying guide20. The pair of positioning pins30are made to project from the top surface of the plate supplying guide20, and the printing plate12is again temporarily positioned in the same way as described above.

In this state in which the printing plate12has been temporarily positioned again, the conveying guide unit14is pivoted such that the plate supplying guide20corresponds to the exposure section18. When, simultaneously therewith, the pair of positioning pins30are lowered from the top surface of the plate supplying guide20, the printing plate12is conveyed forward by the rotation of the conveying roller24, and the front end of the printing plate12abuts the pair of positioning pins52of the rotating drum50. Then, the printing plate12is conveyed toward the right by the conveying pin42and abuts the reference pin36. In this way, the printing plate12is actually positioned at the exposure section18. The front end and the rear end of the printing plate12, which has been actually positioned, are held on the outer periphery of the rotating drum50by the front end chuck54and the rear end chuck64, respectively. Further, while the printing plate12is made to fit tightly to the outer periphery of the rotating drum50by the squeeze roller58, the printing plate12is wound onto the outer periphery of the rotating drum50. Thereafter, the rotating drum50is rotated at high speed, and exposure processing of the printing plate12by the recording head portion66is carried out.

When exposure processing is completed, the conveying guide unit14is pivoted such that the plate discharging guide22corresponds to the rotating drum50. While the holding of the printing plate12on the outer periphery of the rotating drum50by the front end chuck54and the rear end chuck64is released, the printing plate12is discharged from the rotating drum50to the plate discharging guide22. Thereafter, the conveying guide unit14is pivoted, and the printing plate12is conveyed from the plate discharging guide22to a developing device or a printing device.

Here, as shown inFIG. 4, at the automatic printing plate exposure device10, the reference pin36, which is disposed at its base position, and the conveying pin42, which is disposed at its base position, are separated by the distance L in the left-right direction. Further, on the basis of the number of driving pulses of the pulse motor72from the start of movement of the reference pin36from its base position to the time when the reference pin36is positioned at the aforementioned predetermined position, the control device74computes the distance M which the reference pin36has moved toward the left from its base position until it is disposed at the aforementioned predetermined position. Moreover, the control device74computes a distance N, which the conveying pin42moves from its base position toward the right until the printing plate12abuts the reference pin36, on the basis of the number of driving pulses of the pulse motor82from the start of movement of the conveying pin42from its base position, to the time the reference sensor76detects that the printing plate12has abutted the reference pin36and the conveying sensor84detects that a load of the predetermined amount has been applied to the conveying pin42due to the printing plate12abutting the reference pin36.

Thus, due to the control device74computing the value L-M-N, the distance W by which the reference pin36and the conveying pin42are separated in the left-right direction at the time when the position of the printing plate12in the right direction is determined, is detected. Namely, the actual size of the printing plate12(the actual length W of the printing plate12in the left-right direction) is detected on the basis of the computed distance W. Accordingly, the size of the printing plate12can be detected by using the reference pin36and the conveying pin42and the like which position the printing plate12, and the size of the printing plate12can be detected simultaneously with the determination of the position of the printing plate12in the right direction. Thus, there is no need to detect the size of the printing plate12separately. In this way, there is no need for a separate mechanism for detecting the size of the printing plate12, and costs can be reduced. Moreover, because a separate period of time for detecting the size of the printing plate12is unneeded, it is possible to prevent a deterioration in productivity.

Further, not only can it be detected that the printing plate12has abutted the reference pin36by the conveying sensor84detecting that a load of a predetermined amount has been applied to the conveying pin42, but also, it can be detected that the printing plate12has abutted the reference pin36by the reference sensor76as well. Accordingly, it can reliably be detected that the printing plate12has abutted the reference pin36.

The present embodiment is a structure in which the conveying sensor84and the reference sensor76are provided. However, it suffices to provide only the conveying sensor84. In this case as well, due to the conveying sensor84detecting that a load of a predetermined amount has been applied to the conveying pin42, it can be detected that the printing plate12has abutted the reference pin36.

Moreover, in the present embodiment, the actual length W of the printing plate12in the left-right direction is detected at the time the printing plate12is temporarily positioned before punching processing. However, the actual length W of the printing plate12in the left-right direction (the actual size of the printing plate12) can be detected at the time the printing plate12is actually positioned in the punching section16, or at the time when the printing plate12is temporarily positioned before exposure processing, or at the time the printing plate12is actually positioned in the exposure section18.

Further, the present embodiment may utilize a structure in which the conveying pin42is not moved at the time the printing plate12is temporarily positioned. In this case as well, when the printing plate12is actually positioned in the punching section16and the exposure section18, the printing plate12can be made to abut the reference pin36by the conveying pin42, and the actual length W of the printing plate12in the left-right direction (the actual size of the printing plate12) can be detected.

In the present embodiment, the pairs of positioning pins30,48,52are disposed parallel to the left-right direction. However, a structure may be utilized in which the pairs of positioning pins are not disposed parallel to the left-right direction (the axial direction of the rotating drum).

In place of the pairs of positioning pins30,48,52in the present embodiment, flat-plate-shaped positioning plates can be used.

In the sheet member positioning device having the above structure, the detecting mechanism detects the distance between the reference member and the conveying member at the time the position of the sheet member in the first direction is determined. Further, because the size of the sheet member is detected on the basis of this detected distance, the size of the sheet member can be detected simultaneously with the determining of the position of the sheet member in the first direction. Accordingly, costs can be reduced, and a deterioration in productivity can be prevented.