1. Field of the Invention
The present invention relates to a sheet processor for the sorting, binding, and loading of sheets discharged from an image forming apparatus after formation of an image thereon, and, more particularly, to a sheet processor with a punching means for punching out a hole in a sheet. The present invention also relates to an image forming apparatus including such a sheet processor.
2. Description of the Related Art
A conventional sheet processor performs post-processing operations (such as sorting, binding, loading, and punching operations) on sheets to be discharged from an image forming apparatus after formation of an image thereon.
In such a sheet processor, a known punching method for punching out a hole in a sheet is used. In this punching method, holes are punched in a batch of sheets on a processing tray. However, because holes are formed in a batch of sheets, the next sheet cannot be transported during a punching operation. In addition, depending on the capacity of the punching means, it may be necessary to temporarily stop the sheets from being transported from an image forming apparatus and perform punching operations separately a number of times, making it difficult to increase processing speed.
To overcome the above-described problems, two known methods have been used. In the first method, a hole is formed in the sheets one sheet at a time, as the sheets are continuously discharged at predetermined intervals from an image forming apparatus. In the second method, a punching means comprising a punch and a die is disposed in a sheet transporting path. The transportation of sheets and punching operations are synchronized, so that punching operations can be performed without temporarily stopping sheet transportation. Therefore, sheet processing time is not increased by punching operations.
In the above-described conventional example, two methods of adjusting punching positions are used. In the first method, the front edge or the back edge of a sheet being transported in a sheet transporting direction is detected, and, based on the detection results, the timing of punching a hole is changed to adjust the punching position. In the second method, in a direction transverse to the sheet transporting direction (i.e., the sheet width direction), an edge of a sheet being transported is detected, and, based on the detection results, the punching means is moved in the transverse direction to adjust the punching position.
In such a sheet processor in which sheets are transported and punching operations are performed in synchronism without temporarily stopping sheet transportation, when the punching position is adjusted with respect to the sheet width (transverse) direction, the edge portion of the next sheet is detected after the driving of the punch motor is completed. In order to detect the edge of the next sheet, the sheet edge detecting means starts to move to a sheet edge detection standby position. Therefore, time is required to perform operations on the next sheet being transported. Consequently, compared to sheet processors in which the punching position is not adjusted in the sheet width direction, this method has lower sheet processing capacity.
Accordingly, in view of the above-described problems, it is an object of the present invention to provide a sheet processor which allows a punching means to be set at the punching position more precisely, and which can perform a larger number of punching operations.
To this end, according to a first aspect of the invention, there is provided a sheet processor comprising:
a sheet transportation path for transporting sheets in a sheet transportation direction;
punching means provided in the sheet transportation path for performing a punching operation on the sheets, the punching means comprising a punch slide having a punch mechanism thereon;
moving means for moving the punch slide from a sheet punching operation position to a punch slide home position in a direction transverse to the sheet transportation direction; and
detecting means for detecting completion of the punching operation by the punching means;
wherein when the detecting means detects the completion of the punching operation, the moving means moves the punch slide to the punch slide home position.
According to a second aspect of the present invention, there is provided a sheet processor comprising:
a sheet transportation path for transporting sheets in a sheet transportation direction;
punching means provided in the sheet transportation path for performing a punching operation on the sheets, as a result of rotation of the punching mechanism;
moving means for moving the punch slide from a sheet punching operation position to a punch slide home position in a direction transverse to the sheet transportation direction;
detecting means for detecting completion of the punching operation, before the punch mechanism rotates back to a punching operation home position; and
movement controlling means for starting movement of the punch slide by the moving means when the detecting means detects completion of the punching operation.
According to a third aspect of the present invention, there is provided a sheet processor comprising:
a sheet transportation path for transporting sheets in a sheet transportation direction;
punching means for performing a punching operation on the sheets;
moving means for moving the punch slide between a sheet punching operation position and a punch slide home position in a direction transverse to the sheet transportation direction;
edge detecting means for detecting an edge, in the sheet transporting direction, of each of the sheets; and
punching operation completion detecting means for detecting that the punching means has completed the punching operation;
wherein when the edge of each of the sheets is detected by the edge detecting means, the moving means causes the punch slide to move to the sheet punching operation position; and
wherein when the punching operation completion detecting means detects the completion of the punching operation, the moving means causes the punch slide to move to the punch slide home position.
According to a fourth aspect of the present invention, there is provided a sheet processor comprising:
a sheet transportation path for transporting sheets in a sheet transportation direction;
punching means for performing a punching operation on the sheets, as a result of rotation of the punch mechanism;
punch moving means for moving the punch slide between a sheet punching operation position and a punch slide home position in a direction transverse to the sheet transportation direction;
edge detecting means for detecting an edge, in the sheet transporting direction, of each of the sheets;
punching operation completion detecting means for detecting completion of the punching operation, before the punch mechanism rotates back to the punching operation home position; and
movement controlling means which causes the punch moving means to move the punch slide to the sheet punching operation position when the edge of each of the sheets is detected by the edge detecting means, the movement controlling means causing the punch moving means to move the punch slide to the punch slide home position when the completion detecting means detects completion of the punching operation performed on each of the sheets.
According to a fifth aspect of the present invention, there is provided an image forming apparatus including any one of the above-described sheet processors.
By virtue of the above-described structures, the punch moving means causes the punch slide to move from home position HP, in a direction transverse to the sheet transporting direction, to a predetermined position in order to punch a hole in the back end portion of the sheet. When a detecting means detects that the punch mechanism has completed a punching operation on the sheet, the punch mechanism rotates back to a punching operation home position HP, while simultaneously moving the punch slide to the punch slide home position HP in a direction transverse to the sheet transporting direction, that is, to a standby position. This shortens the time required to punch a hole in a sheet.