Image forming system, image forming apparatus, finisher and method of controlling image forming system

An image forming system is described which is capable of assembling an output product which consists of sheets having uniform sheet widths by appropriately performing a trimming process even if the output product is made from a plurality of paper types. The image forming system consists of an image forming apparatus configured to form an image on a sheet; a finisher provided with a slit unit for trimming edges of sheets and capable of assembling an output product by joining the trimmed sheets, and a control unit for controlling the image forming apparatus and the finisher. When a book cover (standard paper type sheet) is supplied, the control unit trims the paper edges by a designated trimming width. Conversely, when a book body (non-standard paper type sheet) is supplied, the control unit trims the paper edges by a designated trimming width to which an offset amount is added.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application claims priority under 35 U.S.C. §119 to Japanese Patent Application No. 2013-179558, filed on Aug. 30, 2013. The contents of this application are herein incorporated by reference in their entirety.

FIELD OF INVENTION

The present invention relates to an image forming system, an image forming apparatus, a finisher and a method of controlling the image forming system.

DESCRIPTION OF RELATED ART

Conventionally, in an image forming apparatus, a finisher or an image forming system including such an apparatus and a finisher, a plurality of sheets are bound together to provide an output product such as a saddle-stitched booklet or a single-side binding booklet. This kind of apparatus is provided with a slit unit for cutting off (i.e., trimming) the edges of sheets. When sheets are supplied from a sheet source, the apparatus trims the edges (for example, top and bottom edges) of the sheets one after another in succession with the slit unit and binds together the trimmed sheets to provide an output product. It is therefore possible to make up a good-looking high quality output product which consists of sheets having uniform sheet widths.

For example, Japanese Patent Published Application No. 2003-323272 discloses a printing apparatus provided with a cutter for successively cutting continuous form paper supplied from a paper roll into separate sheets. This printing apparatus can use a variety of paper types such as cloth, vinyl and the like materials in addition to usual paper materials, and thereby a transmission unit supplies the printing apparatus with the setting data relating to the trimming process suitable for trimming each material with the cutter as well as print data. By this configuration, users need not designate the suitable trimming process by operating the printing apparatus so that there is a little possibility of damaging the cutter and sheets due to operation errors.

Also, for example, Japanese Patent Published Application No. 2003-260833 discloses a recording apparatus provided with a cutter device for cutting off recording media. When transferring paper from a paper roll to a cutter blade by a conveyance roller, a slip occurs between the paper and the conveyance roller, and the amount of slip varies depending upon the type of paper. The control unit of the recording apparatus thereby transfers a cut line printed on the paper to the cutter blade by adding a correction value to the rotational amount of the conveyance roller required for transferring the paper from the paper roll to the cutter blade. The correction value is specifically determined in correspondence with the type of paper. It is said that the paper can be cut off at an accurate position.

However, in the case where a plurality of paper types are handled to provide an output product as has been discussed above, the cutting positions can be misaligned between different paper types, and therefore there is a problem that the output product consists of sheets having uneven widths. While paper sheets are cut off one by one for making up an output product, the cutting operation is sometimes performed with a sheet being warped by its own weight. The warp amounts differ between the paper types, and the differential warp amount results in the misalignment of cutting positions between different types.

The present invention has been made in order to solve the problems as described above. It is an object of the present invention therefore to provide a system capable of assembling an output product which consists of sheets having uniform sheet widths by appropriately performing a trimming process even if the output product is made from a plurality of paper types.

SUMMARY OF THE INVENTION

To achieve at least one of the abovementioned objects, an image forming system reflecting one aspect of the present invention comprises: an image forming apparatus configured to form an image on a sheet; a finisher provided with a slit unit for trimming edges of sheets which are successively supplied from the image forming apparatus, and configured to assemble an output product by joining the trimmed sheets; and a control unit configured to control each of the image forming apparatus and the finisher. Particularly, the finisher can assemble the output product with sheets of a plurality of paper types including a standard paper type and a non-standard paper type which is different from the standard paper type, and the control unit comprises: a paper type notification unit configured to notify which of the standard paper type and non-standard paper type is supplied to the finisher from the image forming apparatus; a finisher control unit configured to control the operation of the slit unit in accordance with the paper type of sheets supplied to the finisher; and an offset amount designation unit configured to designate an offset amount corresponding to the displacement of the sheet width of the non-standard paper type in relation to the sheet width of the standard paper type. In this case, when the paper type notification unit notifies that the non-standard paper type is supplied, the finisher control unit trims the edge of a sheet on the basis of the offset amount designated by the offset amount designation unit.

In accordance with the present invention as described above, it is preferred that the control unit further comprising a base trimming width designation unit which designates a trimming width of the edge of a sheet for assembling the output product, and wherein when the paper type notification unit notifies that the standard paper type is supplied, the finisher control unit trims the edge of a sheet in accordance with the trimming width designated by the base trimming width designation unit, and when the paper type notification unit notifies that the non-standard paper type is supplied, the edge of a sheet is trimmed in accordance with a corrected trimming width calculated by adding the offset amount designated by the offset amount designation unit to the trimming width designated by the base trimming width designation unit.

Also, it is preferred that the output product consists of a book cover and a book body which is made from sheets of one or more paper type different from that of the book cover, and wherein the paper type notification unit notifies, when the supplied sheet is used as a book cover, that the standard paper type is supplied, and notifies, when the supplied sheet is used as a book body, that the non-standard paper type is supplied.

Furthermore, it is preferred that the image forming system further comprises an input unit through which a user can perform input operation. In this case, the offset amount designation unit designates the offset amount on the basis of the amount designated by the user through the input unit.

Still further, it is preferred that the image forming system further comprises a storing device configured to store a table in which is defined an offset amount of the non-standard paper type in relation to the standard paper type corresponding to a variety of combinations of the non-standard paper type and the standard paper type. In this case, the offset amount designation unit designates the offset amount with reference to the table stored in the storing device.

Still further, it is preferred that the offset amount designation unit designates the offset amount on the basis of the size of the supplied sheet.

Still further, it is preferred that when the corrected trimming width exceeds the maximum trimming width which can be trimmed by the slit unit, the finisher control unit replaces the corrected trimming width by the maximum trimming width, and trims the edge of a sheet in accordance with the trimming width after replacement.

Still further, it is preferred that the image forming system further comprises a notification unit configured to notify a user of information. In this case, when the corrected trimming width exceeds the maximum trimming width which can be trimmed by the slit unit, the finisher notifies that the corrected trimming width exceeds the maximum trimming width through the notification unit.

Still further, it is preferred that after trimming the paper edges of sheets by the slit unit, the finisher performs a predetermined post-printing process on the trimmed sheets to provide the output product.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

FIG. 1is an explanatory view for schematically showing the overall configuration of the image forming system in accordance with this first embodiment of the present invention. This image forming system consists mainly of an image forming apparatus10, an intermediate conveyance unit20and a finisher30. The image forming apparatus10, the intermediate conveyance unit20and the finisher30are connected in series from the upstream to the downstream with respect to the direction of conveying sheets.

The image forming apparatus10is an apparatus which forms an image on a sheet P on the basis of image data. The image forming apparatus10consists mainly of an original reading unit11, an image forming unit12, a fixing unit13, a paper feed unit14and a manipulation display15.

The original reading unit11is located on the top of the housing of the image forming apparatus10, and provided with an automatic document feeder for automatically taking and feeding originals to this feeder when reading images thereof. This original reading unit11reads an image from an original and outputs a predetermined image signal. The output image signal is converted into image data by performing necessary processes such as AD conversion.

The image forming unit12is for example an electrophotographic image forming unit. Around a photoreceptor unit in the form of a drum, not shown in the figure, there are arranged a charging unit, an exposure unit, a developing unit, a transfer unit, a separation unit, and a cleaning unit in the image forming unit12. These units forming the image forming unit12cooperates with each other to form an image (toner image) on the photoreceptor unit by charging, exposing and developing, and then form an image on a sheet P by transferring the image.

The fixing unit13is provided with a heat roller and a pressure roller to fix an image onto a sheet P by heating and pressing the sheet P on which the image has been formed by the image forming unit12.

The paper feed unit14includes a plurality of paper feed trays. Each paper feed tray is used to store sheets P. Different paper feed trays may be used to store sheets P having different types and/or sizes. When sheets are supplied, one paper feed tray is selected of the paper feed unit14to feed the sheet P from the selected paper feed tray.

The manipulation display15is for example a touch panel (input unit) through which users can input setting information with reference to the information displayed on the panel. Through this manipulation display15, users can designate the specifications of a job, for example, the mode of single/double-side printing, the density and reduce/enlarge ratio of images, the use of saddle-stitching, the paper types used for forming a book cover and a book body respectively, whether to trim (cut) off sheets at top and bottom edges, the number of pages to be trimmed and the cutting amounts (trimming widths) thereof, and so forth. On the other hand, the manipulation display15can notify a user of predetermined information by displaying the information on the display (as a notification unit)

The intermediate conveyance unit20is located in the downstream side of the image forming apparatus10, and conveys sheets P discharged from the image forming apparatus10to the finisher30. This intermediate conveyance unit20is provided with a sheet reversing unit21which is used to reverse the front and back sides of a sheet P if necessary.

The finisher30is an apparatus for processing sheets P successively supplied from the image forming apparatus10as a paper source to join a plurality of sheets P and provide one output product. The finisher30of the present embodiment is a saddle-stitching apparatus which joins a plurality of sheets P together and saddle-stitches the joined sheets to assemble a booklet (saddle-stitched booklet). In this case, the finisher can form a booklet consisting of a book cover and a book body. The book cover and the book body can be made from different materials, for example, a cardboard for the book cover and a thin sheet for the book body.

The finisher30is provided with a reversing stack unit31, a slit unit32, a creasing unit33, a saddle-stitching unit34, an SQF (SQuare Fold) unit35and a fore edge trimming unit36.

The reversing stack unit31receives a sheet P supplied from the image forming apparatus10, and makes the sheet P enter a predetermined reversing stack route and be put on standby. Namely, each time a sheet P is supplied from the image forming apparatus10, the reversing stack unit31repeats the entering/standby action of the sheet P to join a plurality of sheets P together. The reversing stack unit31then sends out the joined sheets P (sheet stack) by switchback operation to supply the joined sheets to the downstream side of the conveying route.

The slit unit32has the function of trimming the edges of a sheet P, i.e., opposite edges corresponding to the top and bottom edges of the sheet in the case of the present embodiment. This slit unit32is located in the middle of the reversing stack route to perform the edge trimming operation of each sheet P supplied from the image forming apparatus10one after another when the sheet P is transferred to the stand-by position of the reversing stack unit31.

The creasing unit33has the function of making a folding line on a sheet P. The creasing unit33can make a folding line on a sheet stack formed by the reversing stack unit31in the center position of the sheet stack.

The saddle-stitching unit34performs a saddle-stitching operation on the sheet stack which is sent out from the reversing stack unit31, and provided with a folding unit (not shown in the figure) and saddle-stitching staple units (not shown in the figure). The folding unit consists of a sheet pushing unit, folding rollers, a transfer belt, a pressure roller and so forth. The folding unit upward obliquely moves a pushing plate of the sheet pushing unit, and pushes upward the center portion of the sheet stack such that the folding rollers are pushed upward, pivoted and separated from each other at the nip portion therebetween by the sheet stack. After the tip portion of the pushing plate is passed through the nip portion, the pushing plate is retracted from the nip portion so that the center portion of the sheet stack is gripped by the folding rollers to form a folding line. The saddle-stitching staple units are arranged in a pair in the direction perpendicular to the paper conveying direction, and capable of moving by a driving means (not shown in the figure) in the direction perpendicular to the paper conveying direction. After transferring the sheet stack, which is center folded by the folding unit, to a predetermined position, the saddle-stitching staple units fasten the sheet stack with staples (U-shaped wire pieces) in two positions distant from the center in the width direction.

The SQF unit35performs a square folding process on the sheet stack which is center folded by the saddle-stitching unit34. The SQF unit35includes a roller which is used to press and flatten the folded portion (backbone) of the sheet stack in the form of a square shape.

The fore edge trimming unit36consists of an upper trimming blade, a lower trimming blade, movable plates, a pressure roller, a driving means and so forth. The fore edge trimming unit36trims the fore edge of the sheet stack folded by the saddle-stitching unit34in the form of a booklet to make the fore edge flat.

FIG. 2is a block diagram showing the control configuration of the image forming system in accordance with the present embodiment. The image forming system includes a control unit which consists of a main control unit16, an intermediate transfer control unit22and a finisher control unit37. These control units serve to individually control the apparatuses10,20and30respectively. Specifically speaking, the main control unit16controls the image forming apparatus10, and the intermediate transfer control unit22controls the intermediate conveyance unit20. Also, the finisher control unit37controls the finisher30.

The main control unit16is designed to communicate with the intermediate transfer control unit22and the finisher control unit37to integrally control the operation of the image forming system in operative association with these control units22and37.

In accordance with the present embodiment, when assembling a booklet with a plurality of paper types, the main control unit16(as a paper type notification unit) of the image forming system notifies the finisher control unit37of the paper type of a sheet P supplied from the image forming apparatus10to the finisher30, i.e., which of a standard paper type and a non-standard paper type which is different from the standard paper type. In the present embodiment using different paper types for a book cover and a book body respectively, it is notified that the book cover is of a standard paper type and that the book body is of a non-standard paper type.

On the other hand, as shown inFIG. 3, the main control unit16(as a base trimming width designation unit) designates the trimming width of paper edges, that is, in the case of the present embodiment, the trimming widths of the opposite edges corresponding to the top and bottom of a booklet on the basis of the information designated by a user through the manipulation display15. This trimming width can be selected as a predetermined value within a range from zero to a maximum trimming width which can be cut off by the slit unit32. Different trimming widths can be selected between one edge and the other edge.

The main control unit16(as an offset amount designation unit) designates an offset amount corresponding to the displacement of the sheet width of a book body from the sheet width of a book cover. In accordance with the present embodiment, the main control unit16designates the offset amount on the basis of the value designated by a user through the manipulation display15. The designated offset amount is output to the finisher control unit37.

When the main control unit16notifies that the sheet is supplied as the book cover, the finisher control unit37trims paper edges with the trimming width designated by the main control unit16. On the other hand, when the main control unit16notifies that the sheet is supplied as the book body, the finisher control unit37trims paper edges on the basis of the offset amount designated by the main control unit16. More specifically, the finisher control unit37trims the paper edges with the corrected trimming width calculated by adding the offset amount to the trimming width designated by the main control unit16.

Next is a description of a series of steps which are to be taken for assembling a booklet consisting of a book cover and a book body made from different paper types by using the image forming system of the present embodiment.FIG. 4is a flow chart for showing the procedure of setting an offset amount by a user himself required for performing the job of preparing a booklet by the image forming system. In this case, the paper type of a book cover and the paper type of a book body are designated respectively through the manipulation display15by the user and acquired by the main control unit16.

First, in step10(S10), the user inputs the trimming widths of the opposite ends of a sheet P through the manipulation display15. The amount input by the user is acquired and designated as trimming widths by the main control unit16.

In step11(S11), the user instructs outputting a sample through the manipulation display15. The main control unit16receives the instruction of outputting a sample, and starts feeding a book cover (for example, a cardboard) from the paper feed unit14. Then, the main control unit16supplies the fed sheet P to the finisher30from the image forming apparatus10, and notifies the finisher control unit37of the designated trimming width and that this sheet P is used as a book cover. Since it is notified that the sheet P is supplied from the image forming apparatus10as a book cover, the finisher control unit37trims the paper edges in accordance with the trimming width which is designated for this sheet P (as a book cover) by the main control unit16. After trimming the paper edge, the sheet P is discharged, for example, to a catch tray as it is without any processing.

Also, after trimming the paper edges of the book cover, the main control unit16feeds a book body (for example, thin sheets) from the paper feed unit14. Then, while supplying the fed sheets P to the finisher30from the image forming apparatus10, the main control unit16notifies the finisher control unit37of the designated trimming width and that this sheet P is used to form a book body. Since it is notified that the sheet P is supplied from the image forming apparatus10as a book body (of a different paper type than the book cover), the finisher control unit37trims the paper edges in accordance with the corrected trimming width calculated by adding the offset amount designated in step15as described below to the trimming width designated by the main control unit16.

Incidentally, since the offset amount has not been designated yet just after starting up, the finisher control unit37uses an offset amount of zero.

In step12(S12), the user confirms the output results of the book cover and the book body.

In step13(S13), the user determines whether or not the book cover and the book body match in sheet width. If the determination is in the affirmative in step13, i.e., if the book cover and the book body match in sheet width, the process proceeds to step16(S16) to be described below. Conversely, if the determination is in the negative in step13, i.e., if the book cover and the book body are not aligned in sheet width, the process proceeds to step14(14).

In step14, the user measures the difference between the book cover and the book body.

In step15, the user sets an offset amount through the manipulation display15. In this case, the user can set the offset amount to the measured difference. Then, the procedure is repeated from step11.

In step16, the user switches the operation mode through the manipulation display15to a mode of outputting a booklet for actual use (refer toFIG. 5to be described below).

FIG. 5is a flow chart showing the procedure of assembling a booklet in a series of control steps in the image forming system. The procedure shown in the flow chart is done when performing a job of outputting a booklet for actual use. In advance of performing this job, the user designates, through the manipulation display15, the paper types used for forming a book cover and a book body respectively, whether to trim sheets at top and bottom edges thereof, the number of pages to be trimmed and the trimming width thereof, the offset amounts and so forth. The parameters designated by the procedure shown inFIG. 4may be used in this case.

In step20(S20), the main control unit16determines whether or not the opposite edges of sheets are to be trimmed for preparing a booklet. If the determination is in the affirmative in step20, i.e., if the opposite edges of sheets are to be trimmed, the process proceeds to step21(S21). Conversely, if the determination is in the negative in step20, i.e., if the opposite edges of sheets are not to be trimmed, this routine returns control.

In step21(S21), the main control unit16determines whether or not all the pages of the booklet are to be trimmed for preparing a booklet. If the determination is in the affirmative in step21, i.e., if all the pages of the booklet are to be trimmed, the process proceeds to step22(S22). Conversely, if the determination is in the negative in step21, i.e., if all the pages of the booklet are not to be trimmed, this routine returns control.

In step22, the main control unit16determines whether or not a book cover is supplied. If the determination is in the affirmative in step22, i.e., if a book cover is supplied, the process proceeds to step23(S23). In this case, the main control unit16feeds a sheet P (for example, a cardboard) corresponding to the book cover from the paper feed unit14. Then, the main control unit16supplies the fed sheet P to the finisher30from the image forming apparatus10, and notifies the finisher control unit37of the trimming width and that this sheet P is used as a book cover. The trimming width notified to the finisher control unit37can be designated by the main control unit16on the basis of the amount designated by the user.

In step23, since it is notified that the sheet P is supplied from the image forming apparatus10as a book cover, the finisher control unit37trims the paper edges in accordance with the trimming width which is designated for this sheet P (as a book cover) by the main control unit16.

Conversely, if the determination is in the negative in step22, i.e., if a book body is supplied, the process proceeds to step24(S24). In this case, the main control unit16feeds a sheet P (for example, a thin sheet) corresponding to the book body from the paper feed unit14. Then, while supplying the fed sheet P to the finisher30from the image forming apparatus10, the main control unit16notifies the finisher control unit37of the designated trimming width and that this sheet P is used to form a book body.

In step24, since it is notified that the sheet P is supplied from the image forming apparatus10as a book body (of a different paper type than the book cover), the finisher control unit37corrects the trimming width on the basis of the offset amount designated by the main control unit16. More specifically, the finisher control unit37sets the trimming width to a corrected trimming width which is calculated by adding the offset amount to the designated trimming width.

In step25(S25), the finisher control unit37determines whether or not the corrected trimming width falls within a maximum trimming width which can be cut off by the slit unit32. This maximum trimming width is predetermined on the basis of the mechanical constraints of the slit unit32and so forth. If the determination is in the affirmative in step25, i.e., the corrected trimming width falls within the maximum trimming width, the process proceeds to step26(S26). Conversely, if the determination is in the negative in step25, i.e., the corrected trimming width exceeds the maximum trimming width, the process proceeds to step27(S27).

In step26, the finisher control unit37trims the paper edges of a sheet P (book body) supplied from the image forming apparatus10in accordance with the corrected trimming width.

In step27, the finisher control unit37replaces the corrected trimming width by the maximum trimming width, and trims the paper edges of a sheet P (book body) supplied from the image forming apparatus10in accordance with the trimming width after replacement.

In step28(S28), the main control unit16determines whether or not all the sheets P have completely been processed. If the determination is in the affirmative in step28, this routine returns control. Conversely, if the determination is in the negative in step28, the process returns to step22.

As has been discussed above, in the image forming system of the present embodiment, when the main control unit16notifies that the sheet P is supplied from the image forming apparatus10as a book cover (standard paper type sheet P), the finisher control unit37trims the paper edges by the trimming width designated by the main control unit16. On the other hand, when the main control unit16notifies that the sheet P is supplied from the image forming apparatus10as a book body (non-standard paper type sheet P), the finisher control unit37trims the paper edges by the corrected trimming width calculated by adding the offset amount to the trimming width designated by the main control unit16.

By this configuration, the book body is trimmed by taking into consideration the offset amount corresponding to the displacement of the sheet width of the book body in relation to the sheet width of the book cover. With such an offset amount, the trimming width of the book body can be adjusted in agreement with the sheet width of the book cover even if the book cover and the book body are made from different paper types. The sheet widths of the book cover and the book body thereby match after trimming to assemble a high quality booklet as an output product.

Also, in accordance with the present embodiment, the trimming widths are corrected only with respect to relative differences among different paper types as the offset amount of a book body (non-standard paper type sheet P), rather than individually corrected for each paper type. Because of this, while to lighten the burden of determining the offset amount for each paper type, a booklet can be formed with uniform sheet widths.

In addition, the main control unit16of the present embodiment designates the offset amount on the basis of the amount designated by the user through the manipulation display15(as an offset amount designation unit).

The offset amount can therefore be designated corresponding to a preference desired by a user. It is therefore possible to provide a user-friendly image forming apparatus.

Also, when the corrected trimming width exceeds the maximum trimming width which can be cut off by the slit unit32, the finisher control unit37of the present embodiment replaces the corrected trimming width by the maximum trimming width, and trims the paper edges in accordance with the trimming width after replacement.

By this configuration, even if the corrected trimming width exceeds the mechanical constraints, the slit unit32need not stop operation but can continue trimming within an operable range. It is therefore possible to inhibit the deterioration of productivity.

As has been discussed above, in accordance with the present embodiment, if the corrected trimming width exceeds the maximum trimming width, the trimming operation continues after the corrected trimming width is set to the maximum trimming width in accordance with the present embodiment. However, in such a case, it is possible to halt the operation of the image forming system and issue a warning through the manipulation display15.

In what follows, a series of steps for assembling a booklet by an image forming system of the second embodiment will be explained. The procedure of the second embodiment differs from the procedure of the first embodiment as described above in that the offset amount is automatically set. The second embodiment will be explained below mainly with respect to the differences from the first embodiment without repeating redundant description.

FIG. 6is a flow chart showing the procedure of assembling a booklet in a series of control steps conducted in the image forming system. The procedure shown in the flow chart is done when performing a job of outputting a booklet for actual use. In advance of performing this job, the user designates, through the manipulation display15, the paper types used for forming a book cover and a book body respectively, whether to trim sheets at top and bottom edges thereof, the number of pages to be trimmed and the trimming width thereof, and so forth.

In step30(S30), the main control unit16determines whether or not the opposite edges of sheets are to be trimmed for preparing a booklet. If the determination is in the affirmative in step30, the process proceeds to step31(S31). Conversely, if the determination is in the negative in step30, i.e., if the opposite edges of sheets are not to be trimmed, this routine returns control.

In step31(S31), the main control unit16determines whether or not all the pages of the booklet are to be trimmed for preparing a booklet. If the determination is in the affirmative in step31, the process proceeds to step32(S32). Conversely, if the determination is in the negative in step31, this routine returns control.

In step32, the main control unit16determines whether or not a book cover is supplied. If the determination is in the affirmative in step32, the process proceeds to step33(S33). In this case, the main control unit16feeds a sheet P (for example, a cardboard) corresponding to the book cover from the paper feed unit14. Then, the main control unit16supplies the fed sheet P to the finisher30from the image forming apparatus10, and notifies the finisher control unit37of the trimming width and that this sheet P is used as a book cover.

In step33, since it is notified that the sheet P is supplied from the image forming apparatus10C as a book cover, the finisher control unit37trims the paper edges in accordance with the trimming width which is designated for this sheet P (as a book cover) by the main control unit16.

Conversely, if the determination is in the negative in step32, i.e., if a book body is supplied, the process proceeds to step34(S34).

In step34, the main control unit16determines whether or not the book body is to be made from a different paper type than the book cover. If the determination is in the negative in step34, i.e., if the book body and the book cover are to be made from the same paper type, the process proceeds to step33as described above. At this time, the main control unit16feeds a sheet P (for example, a cardboard) corresponding to the book body from the paper feed unit14. Then, the main control unit16supplies the fed sheet P to the finisher30from the image forming apparatus10, and notifies the finisher control unit37of the trimming width and that this sheet P is used as a book body. In step33, since it is notified that the sheet P is supplied from the image forming apparatus10as a book body (of the same paper type as the book cover), the finisher control unit37trims the paper edges in accordance with the trimming width which is designated for this sheet P (as a book body) by the main control unit16.

Conversely, if the determination is in the affirmative in step34, i.e., if the book body and the book cover are of different paper types, the process proceeds to step35(S35). In step35, the main control unit16designates an offset amount. The main control unit16includes a storing device (for example, a ROM) for storing a table as shown inFIG. 7in which are defined offset amounts of non-standard paper types in relation to standard paper types respectively corresponding to a variety of combinations. In this step35, the main control unit16refers to the paper types of the book cover and book body, and designates an offset amount on the basis of the table stored in the storing device.

Also, the main control unit16feeds a sheet P (for example, a thin sheet) corresponding to the book body from the paper feed unit14. Then, while supplying the fed sheet P to the finisher30from the image forming apparatus10, the main control unit16notifies the finisher control unit37of the trimming width, the offset amount and that this sheet P is used to form a book body.

In step36, since it is notified that the sheet P is supplied from the image forming apparatus10as a book body (of a different paper type than the book cover), the finisher control unit37corrects the trimming width on the basis of the offset amount designated by the main control unit16. More specifically, the finisher control unit37sets the trimming width to a corrected trimming width which is calculated by adding the offset amount which is designated in step35to the designated trimming width.

In step37(S37), the finisher control unit37determines whether or not the corrected trimming width falls within a maximum trimming width which can be cut off by the slit unit32. If the determination is in the affirmative in step37, i.e., the corrected trimming width falls within the maximum trimming width, the process proceeds to step38(S38). Conversely, if the determination is in the negative in step37, i.e., the corrected trimming width exceeds the maximum trimming width, the process proceeds to step39(S39).

In step38, the finisher control unit37trims the paper edges of the sheet P (book body) supplied from the image forming apparatus10in accordance with the corrected trimming width.

In step39, the finisher control unit37replaces the corrected trimming width by the maximum trimming width, and trims the paper edges of the sheet P (book body) supplied from the image forming apparatus10in accordance with the trimming width after replacement.

As has been discussed above, the main control unit16of the present embodiment designates an offset amount on the basis of the table stored in the storing device.

By this configuration, the offset amount can be automatically adjusted in accordance with each of different paper types. The user need therefore not operate the system so that a user-friendly image forming apparatus can be realized.

In accordance with the present embodiment as described above, the offset amount is automatically determined by taking only the paper types into consideration. However, even if considering only the same paper type, the warp amount tends to increase as the size increase. The main control unit16as an offset amount designation unit can therefore designate the offset amount by further taking the size of a sheet P into consideration. For example, the offset amount determined in accordance with a paper type may be increased by a correction value which is set to a larger value as the size of a sheet P increases. This scheme can be applied also to the calculation of the offset amount in accordance with the first embodiment in the same manner.

Meanwhile, the booklet provided as an output product by each of the first and second embodiments as described above includes two paper types for a book cover and a book body. However, the booklet as an output product can include three or more paper types, e.g., one for a book cover and two or more for a book body.

Also, in the case where there are three or more paper types, any paper type can be used as a standard paper type. However, it is preferred to use the paper type of a book cover as a standard paper type and the other paper types of a book body as a non-standard paper type. In such a case, the paper types of the book body positioned inside the book cover are given offset amounts respectively which are set up relative to the book cover P. While the trimming error between the book cover and the book body can be corrected by the offset amount, there may be some relative trimming error between different paper types of the book body. Appearance after making up the booklet determines the quality of the output product. Even if there occurs some relative trimming error among sheets of the book body, it is avoided that the edge of the book body protrudes from the book cover which is used as a reference of trimming the book body. It is therefore possible to inhibit the appearance of an output product from being degraded.

Also, while the finisher30of the first or second embodiment of the present invention is used to assemble a saddle-stitched booklet as an output product, the present, invention is not limited thereto. The finisher30may be any type of a finisher capable of processing a plurality of sheets P successively supplied from the image forming apparatus10to bind the sheets P together as one output product. The output product may for example be a book assembled by case binding, a booklet assembled by binding sheets together at edges with staples, a simple stack of a plurality of sheets or the like.

For example, the image forming system in accordance with the above embodiments includes an image forming apparatus and a finisher. However, the present invention can be considered to relate also to the image forming apparatus itself comprises: (1) an image forming unit configured to form an image on a sheet; (2) a finisher unit provided with a slit unit for trimming edges of sheets which are successively supplied from the image forming unit, and configured to assemble an output product by joining the trimmed sheets; and (3) a control unit configured to control each of the image forming unit and the finisher unit, wherein the finisher unit can assemble the output product with sheets of a plurality of paper types including a standard paper type and a non-standard paper type which is different from the standard paper type. In this case, the control unit (3) comprises: (3-1) a paper type notification unit configured to notify which of the standard paper type and non-standard paper type is supplied to the finisher unit from the image forming unit; (3-2) a finisher unit configured to control the operation of the slit unit in accordance with the paper type of sheets supplied to the finisher unit; and (3-3) an offset amount designation unit configured to designate an offset amount corresponding to the displacement of the sheet width of the non-standard paper type in relation to the sheet width of the standard paper type, wherein when the paper type notification unit notifies that the non-standard paper type is supplied, the finisher control unit trims the edge of a sheet on the basis of the offset amount designated by the offset amount designation unit.

Also, the present invention can be considered to relate also to the finisher itself including the above mentioned “paper type notification unit”, “finisher control unit” and “offset amount designation unit”. In this case, the image forming apparatus is not necessarily provided as a sheet source, but the finisher may be of an offline-typo.

In accordance with the image forming system, the image forming apparatus or the finisher as described above a non-standard paper type sheet is trimmed by taking into consideration the offset amount corresponding to the displacement of the sheet width of the non-standard paper type sheet in relation to the sheet width of a standard paper type sheet. With such an offset amount, the trimming width of the non-standard paper type sheet can be adjusted in agreement with the sheet width of the standard paper type sheet. The standard paper type sheet and the non-standard paper type sheet therefore can match in sheet width after trimming to provide a high quality output product.

Furthermore, the present invention can be considered to relate also to the control method for assembling output products in accordance with the above embodiments. This control method can be applied to any of the image forming system, the image forming apparatus and the finisher in accordance with the present invention.

Still further, while the operation of the image forming system is controlled by the control units which are provided for the respective apparatuses, a dedicated control unit can be provided for performing the above-mentioned process of assembling output products as a separate unit from the control units for controlling the image forming apparatus and the finisher. For example, the image forming apparatus can be connected through a network to a personal computer in which a server application and a printer driver are installed to monitor the behavior of the image forming apparatus or the like and conduct the control method for assembling output products.