Sheet feeding apparatus and recording apparatus

A sheet feeding apparatus to which a cassette accommodating a sheet is detachably mountable includes supplying means for supplying the sheet from the cassette; a reference member having a reference surface for regulating a position of a lateral edge of the sheet being fed in a predetermined feeding direction by the supplying means; feeding means for feeding the sheet in a direction inclined relative to the feeding direction toward the reference surface to abut the lateral edge of the sheet to the reference surface; and moving means for selectively moving the reference member in response to mounting of the cassette such that reference member is placed at a position corresponding to a width of the sheet accommodated in the cassette.

FIELD OF THE INVENTION

The present invention relates to a sheet feeding apparatus for feeding a recording sheet fed from a cassette in an image recording apparatus such as a printer, a copying machine, a facsimile machine, and a recording apparatus using the sheet feeding apparatus.

RELATED ART

In a recording apparatus having a function of a printer, a copying machine, a facsimile machine or the like, an image (including letters, sign or the like) is recorded on the recording sheet on the basis of image information by a recording head. The recording material (recording sheet) may be paper, textile, plastic resin material sheet or OHP sheet or the like. The recording system of such a recording apparatus is either one of a serial type and a line type. In a serial type, a main-scanning operation moving the recording head along the recording material and a sub-scan operation feeding the recording material are alternately repeated. In a line type, on the other hand, a long recording head extending in a widthwise direction of the recording material is used wherein the recording is effected at once on a line, and the recording material fed, thus the scanning operation is effected only in one direction.

The recording apparatus is provided with a sheet feeding apparatus for picking the recording sheet one by one up from the cassette or the like and for feeding the recording sheet to the image forming station. In such a sheet feeding apparatus, the recording sheet may be fed obliquely due to insufficient sheet feeding accuracy or the like. Such an oblique feeding may be a cause of sheet jamming and/or deterioration of the recorded image quality. Japanese Laid-open Patent Application Hei and Japanese Laid-open Patent Application Hei, for example, disclose an inclination correcting mechanism for rectifying the feeding operation.FIG. 20is a substantial top plan view of an example of conventional inclination correcting mechanisms. InFIG. 17, designated by502is a feeding roller for feeding the recording sheet in the direction indicated by an arrow T. Designated by503is an inclination roller disposed inclined relative to the feeding direction T and opposed to the feeding roller502.

The recording sheet504is nipped between the inclination roller503and the feeding roller502and is fed by rotation of the feeding roller. Designated by501is a reference member provided at a side of a feeding surface. Reference member501is provided with a reference surface501awhich is parallel with the feeding direction T and which is perpendicular to the feeding surface. The reference surface is effective to position the recording sheet504in the direction perpendicular to the feeding direction and functions as a guide for feeding the recording sheet in the feeding direction T. The reference member501comprises a wall member or projection member so that lateral edge of the recording sheet assuredly abuts the reference surface501a.

Referring toFIG. 20, the description will be made as to inclination correction of recording sheet feeding using the reference member501. When the recording sheet504is fed obliquely, the leading end of the recording sheet is inclined in the counterclockwise direction in the Figure by an inclined roller503, and the lateral edge of the recording sheet is brought into contact to the reference surface501a.By this, the movement of the recording sheet is corrected such that lateral edge thereof moves along the reference surface while the lateral edge is in contact with the reference surface. Thus, the inclination of the recording sheet504is corrected, and the recording sheet504is correctly positioned with respect to the direction parallel to the feeding direction T of the recording sheet on the feeding surface. The reference surface501ais also called “contact or abutment surface” since the recording sheet is contacted or abutted to it. Such an inclination correction method can be implemented with a relatively simple structure.

However, with such an inclination correcting mechanism, when the recording sheets having different widths, it is impossible to feed such sheets with the center thereof aligned with a reference line, although one lateral ends of the sheets may be aligned with a reference line.FIG. 21is a schematic top plan view of such a state. InFIG. 21, the oblique feeding of the recording sheet6is by abutting to the reference member601. In the inclination correcting mechanism ofFIG. 21, the fixed reference member601functions to position the sheets with respect to the direction perpendicular to the feeding direction. Therefore, the inclination correction for the recording sheets is based on the abutment surface601airrespective of the widths of the sheets.

For this reason, the recording sheet having a width smaller than the maximum width is laterally shifted (off-set) toward the reference member601as compared with the recording sheet having the maximum width.

Here, the advantages of center line alignment of feeding will be described. In most cases of sheet feeding apparatuses, the parts such as rollers on the feeding surface are disposed symmetrically with respect to the center line of the feeding surface. In the case that recording sheet is fed the lateral edge alignment, the position or the width of the nip varies depending on the widths of the sheets. Therefore, the feeding force distribution with respect to the widthwise direction is not symmetrical with the result of tendency of unbalanced feeding force distribution.

When the center line of the feeding surface and the center line of the recording sheet are aligned with each other, the feeding force distribution is symmetrical, so that sheet can be fed stably with uniform feeding force distribution.

FIG. 22is a substantial top plan view of a conventional example with which the inclination correction is possible with the center line alignment. As will be understood fromFIG. 22, there are provided two reference members701,702to effect the inclination correction with the center line alignment. With the use of the reference member having two reference surfaces701a,702a,the inclination correction is possible for both of the large width recording sheet7aand the small width recording sheet7b.The lateral edges of the recording sheets are abutted to the corresponding one of the reference surfaces. However, with such a method, when the inclination correction is carried out for a large width recording sheet by the reference member701, the reference member702for the small width recording sheet interferes with the recording sheet.

Japanese Laid-open Patent Application Hei 4-72252 and Japanese Laid-open Patent Application Hei 4-235847 disclose an inclination correction mechanism which uses two reference members and in which one of the reference member are selectively movable.

However, the conventional inclination correcting mechanisms as disclosed in the prior art requires a complicated mechanism for moving the reference member from the contact position where the recording sheet abuts it to the contactable position where the recording sheet does not abut it. This makes assembling of the sheet feeding apparatus difficult and makes the reliability of the feeding performance poor.

SUMMARY OF THE INVENTION

It is a principal object of the present invention to provide a sheet feeding apparatus having an inclination correcting mechanism which is simple in the structure and which is good in assembling property, the inclination correcting mechanism being capable of feeding the sheets with the center line alignment and with inclination correction for recording sheets widths.

According to an aspect of the present invention, there is provided a sheet feeding apparatus to which a cassette accommodating a sheet is detachably mountable, said sheet feeding device comprising supplying means for supplying the sheet from said cassette; a reference member having a reference surface for regulating a position of a lateral edge of the sheet being fed in a predetermined feeding direction by said supplying means; feeding means for feeding the sheet in a direction inclined relative to the feeding direction toward the reference surface to abut the lateral edge of the sheet to the reference surface; and moving means for selectively moving said reference member in response to mounting of said cassette such that reference member is placed at a position corresponding to a width of the sheet accommodated in said cassette.

According to another aspect of the present invention, there is provided a A sheet feeding apparatus to which a cassette accommodating a sheet is detachably mountable, said sheet feeding device comprising supplying means for supplying the sheet from said cassette; a reference member having a reference surface for regulating a position of a lateral edge of the sheet being fed in a predetermined feeding direction by said supplying means; feeding means for feeding the sheet such that lateral edge of the sheet abuts the reference surface; and moving means for selectively moving said reference member in response to mounting of said cassette.

According to the present invention, there is provided a sheet feeding apparatus having an inclination correcting mechanism which is simple in the structure and which is good in assembling property, the inclination correcting mechanism being capable of feeding the sheets with the center line alignment and with inclination correction for recording sheets widths.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Hereinafter, the preferred embodiments of the present invention will be concretely described with reference to the appended drawings. Incidentally, if an item in a given drawing is the same in reference symbol in another item in the given drawing or another drawing, the two items are identical or correspond to each other.FIG. 1is a vertical sectional view of a preferable example of a recording apparatus, to which a sheet feeding apparatus, that is, a sheet conveying apparatus in accordance with the present invention is applicable. It shows a recording apparatus of the thermal transfer type, which records an image by transferring the ink on an ink ribbon onto a sheet of recording medium with the use of a thermal head. Referring toFIG. 1, a cassette2in which recording sheets1are stored is removably mountable in the main assembly of a recording apparatus100. Located in the space below the cassette2are an ink ribbon chamber101, from which an ink ribbon113is unwound, and an ink ribbon chamber102, into which the ink ribbon113is wound. As a ribbon winding shaft115is rotationally driven, the ribbon113on a ribbon shaft114in the ink ribbon chamber101is wound out from the ink ribbon chamber101and is wound up onto the shaft115in the ink ribbon chamber102.

The image forming operation carried out by this image forming apparatus is as follows: A single sheet of recording medium is fed into a U-turn sheet conveyance passage122provided with a sheet feeding roller120as a sheet feeding means, while being separated from the rest of sheets in the cassette2, and is conveyed through the U-turn passage122. Then, the recording sheet1is conveyed to an image forming portion123which is between a recording head118(thermal head) and a platen roller119. A sheet conveying apparatus150in accordance with the present invention is between the U-turn sheet conveyance passage122and image forming portion123in terms of the recording sheet conveyance direction. The recording sheet1is conveyed, together with the ribbon113, through the image forming portion123, while remaining pinched between the recording head118and platen roller119, by a pair of conveyance rollers117. While the recording sheet1and ink ribbon113are conveyed through the image forming portion123in the state described above, an image is formed by thermally transferring (melting and transferring) the ink coated on the ink ribbon113, onto the recording sheet1by the heating member with which the recording head118is provided. When forming a full-color image, a ribbon for recording in full-color is used. A full-color recording ribbon has multiple sections which repeat in terms of the lengthwise direction of the ribbon, and each section has multiple subsections coated with inks different in color, for example, yellow, magenta, cyan, etc., one for one. Thus, when forming a multicolor or full-color image, the recording sheet1is conveyed through the image forming portion123, in a reciprocating manner, by the number of times equal to the number of colors in which the image is to be formed, so that the inks different in color are transferred in layers onto the recording sheet1.

FIG. 2is a perspective view of the cassette2in which one or more of the recording sheets1are stored.FIG. 3is a sectional view of the cassette2shown inFIG. 2, at a plane parallel to the front panel of the image forming apparatus, as seen from the direction indicated by an arrow mark V1inFIG. 2,FIGS. 3(a) showing a cassette for holding one or more recording sheets of a first width, that is, narrower recording sheets, andFIG. 3(b) showing a cassette for holding one or more recording sheets of a second width, that is, wider recording sheets.FIG. 4is a schematic, phantom, and perspective view of the cassette2in the recording apparatus100, showing the direction in which the recording sheet1is fed into the main assembly of the recording apparatus100. Referring toFIG. 2, multiple recording sheets1are stacked into the cassette2. This embodiment of the present invention will be described with reference to a case in which two kinds of recording sheets in terms of width, more specifically, recording sheets1aand1b,which are different in width, are used. The recording sheet1a,or the narrower sheet, is stored in the cassette2a,whereas the recording sheet1b,or the wider sheet, is stored in the cassette2b.

Shown inFIG. 3are the cassettes2aand2b,which are different in the width of the recording sheet stored therein. As will be evident fromFIG. 3, the two cassettes2aand2bare differentiated in shape according to the width of the recording sheet1therein.

The first cassette2ashown inFIG. 3(a) is the cassette which stores the recording sheets1a,or the sheets with the first width. Designated by reference characters201aand202aare regulating portions, which are for regulating the positioning of the lateral edges of the recording sheet1a,one for one. The second cassette2bshown inFIG. 3(b) is the cassette which stores the recording sheets1b,or the sheets with the second width which is greater than the first width. Designated by reference characters201band202bare regulating portions, which are for regulating the positions of the lateral edges of the recording sheet1b,one for one.

Referring toFIG. 4, it is in the direction indicated by an arrow mark A that the recording sheet1is fed into the main assembly of the recording apparatus100from the cassette2in the recording apparatus100, and is conveyed to the image forming portion123, by the feeding-and-conveying roller120. After being sent out of the cassette2, the recording sheet1is made to U-turn in the direction indicated by an arrow mark B following the U-turn conveyance passage122. Then, the recording sheet1is conveyed to the image forming portion123through the sheet conveying apparatus150, which is located on the sheet conveyance surface5(FIG. 5) which is located in the area below the cassette2.

FIG. 5is a schematic plan view of the sheet conveying apparatus150in the first embodiment of the present invention.FIG. 6(a) is a sectional view of the sheet conveying apparatus150, at a line D-D inFIG. 5, above which the cassette2is not present, andFIG. 6(b) is a sectional view of the sheet conveying apparatus, at the line D-D inFIG. 5, above which the cassette2acontaining the recording sheets1a,or the cassette containing the recording sheets with the smaller width, are present.FIG. 7is a schematic plan view of the sheet conveying apparatus150in the first embodiment of the present invention, which is in the process of straightening the recording sheet1a,or the positioned recording sheet with the narrower width, which is being obliquely conveyed.FIG. 8(a) is a sectional view of the sheet conveying apparatus150, at the line D-D inFIG. 5, above which the cassette2is not present, andFIG. 8(b) is a sectional view of the sheet conveying apparatus150, at the line D-D inFIG. 5, above which the cassette2bcontaining the recording sheets1b,or the recording sheets with the larger width, are present.FIG. 9is a schematic plan view of the sheet conveying apparatus150in the first embodiment of the present invention, which is in the process of straightening the recording sheet1b,or the recording sheet with the larger width, which is being obliquely conveyed.

Referring toFIG. 5, located on the center area of the sheet conveyance surface5is a sheet feeding or conveyance roller3(inclined or slant roller), as a sheet conveying means, which is inclined or slanted so that it generates sheet conveyance force in a direction inclined relative to the normal sheet conveyance direction T. Located on one of the lateral areas of sheet conveyance surface5is a positional reference member4, which has a reference surface4awith which the lateral edge of a recording sheet is placed in contact in order to regulate the position of the recording sheet.

Referring toFIG. 6, the reference member4is attached to the frame7of the recording apparatus so that it is movable in the direction (for example, direction indicated by arrow mark U) perpendicular to the normal sheet conveyance direction T. Designated by a reference character4cis a guide for guiding the reference member4when the reference member4is moved in the direction of the arrow mark U. Designated by a reference character4bis a protrusion which is fitted in a guide4c.The reference member4is kept pressured inward of the sheet conveyance surface5, in terms of the width direction of the sheet conveyance surface5, by a spring4d,and is held in the home position (initial position), shown inFIGS. 5-7, by a stopper.

Next, referring toFIGS. 6-9, the operation of the sheet conveying apparatus150in the first embodiment of the present invention will be described. The cassette2is inserted into the recording apparatus150from the direction indicated by an arrow mark F, and is moved into its preset operational position in the recording apparatus150. Designated by a reference number205is a cassette guide for guiding the cassette2into the abovementioned preset operational position in the recording apparatus. Located in the area above the left end portion of the sheet conveyance surface5is a cassette positioning member8(which hereafter will be referred to simply as positioning member8) for regulating the position of the cassette2when the cassette2is mounted into the recording apparatus. First, the case in which the cassette2a,or the cassette in which recording sheets1a,or the recording sheets with the smaller width, is mounted into the recording apparatus, will be described. When the sheet conveying apparatus is in the state shown inFIG. 6(a), that is, before the cassette2ais mounted into the recording apparatus, the reference member4is held in the home position (initial position). As the cassette2ais moved into the abovementioned operational position in the recording apparatus, the cassette positioning surface203aof the cassette2acomes into contact with, and remains in contact, with the cassette positioning surface8aof the positioning member8, and therefore, the cassette2ais correctly placed, and kept, in the operational position. That is, when the cassette2a,or the cassette in which the recording sheets1aof the smaller width are stored, is mounted, the reference member4is not pressed by the cassette2a;the reference member4remains held in its home position, as shown inFIG. 6(b). Therefore, as the recording sheet1a,which is being obliquely conveyed, reaches the sheet conveying apparatus, it is straightened by the sheet conveying apparatus, with the reference member4remaining held in its home position, as shown inFIG. 7(correction of oblique feeding).

More specifically, referring toFIG. 7, as the recording sheet1a,or the sheet with the smaller width, which is being conveyed askew, reaches the sheet conveying apparatus150, it begins to be conveyed in the direction which is slightly deviant leftward from the normal sheet conveyance direction T in the drawing, by the sheet conveyance roller3, which is positioned at the abovementioned angle, and one of the lateral edges of the recording sheet1ais placed in contact with the reference surface4aof the reference member4. Thus, the recording sheet1ais conveyed through the sheet conveying apparatus150while remaining in contact with the reference surface4awhich is in its home position. As a result, not only is the recording sheet1a,which has obliquely arrived at the sheet conveying apparatus150, is straightened by the reference surface4a,but also, it is correctly position in terms of its width direction by the reference surface4a.

Next, the case in which the cassette2b,or the cassette in which the recording sheets1b,or the recording sheets with the second width, which is larger than the first width, are stored, are mounted, will be described. When the sheet conveying apparatus is in the state shown inFIG. 8(a), that is, before the cassette2bis mounted into the recording apparatus, the reference member4remains held in the home position. As the cassette2bis inserted into the recording apparatus from the direction of the arrow mark F, and is moved into the operational position in the recording apparatus, the cassette positioning surface203bof the cassette2bcomes into contact with, and remains in contact, with the cassette positioning surface8aof the positioning member8, and therefore, the cassette2bis correctly placed, and kept, in the operational position, as shown inFIG. 8(a). That is, when the cassette2b,or the cassette in which the recording sheets of the second width are stored, is mounted, the reference surface4aof the reference member4comes into contact with the reference member pressing surface204b(reference member moving means) of the cassette2b,and is pressed leftward of the drawing by the cassette2b.As a result, the reference member4is moved leftward of the drawing against the pressure application spring4d;in this embodiment, the reference member4is moved from its home position in the direction indicated by an arrow mark G, into a position X, which is closer to the lateral edge of the sheet conveyance surface5than the home position of the reference member4. Then, as the recording sheet1b,which is being obliquely conveyed, reaches the sheet conveying apparatus150, it begins to be conveyed in the direction which is slightly deviant leftward from the normal sheet conveyance direction T in the drawing, by the conveyance roller3, which is slanted, and one of the lateral edges of the recording sheet1bis placed in contact with the reference surface4aof the reference member4which is in the position X. Thus, the recording sheet1bis conveyed through the sheet conveying apparatus150while remaining in contact with the reference surface4awhich is in the position X. As a result, not only is the recording sheet1b,which has obliquely arrived at the sheet conveying apparatus150, is straightened (correction of oblique feeding), but also, it is correctly position in terms of its width direction, as shown inFIG. 9.

If the abovementioned recording sheet1aor recording sheet1b,which are different in width, is obliquely conveyed, the recording sheet1a,or the recording sheet with the smaller width, is straightened by the reference surface4aof the reference member4while the reference member4is in its home position, whereas the recording sheet1b,or the recording sheet with the larger width, is straightened by the reference surface4aof the reference member4in the position X, into which the reference member4was moved by the cassette2b.Further, the sheet conveying apparatus is structured so that the path of the center of the recording sheet1a,or the recording sheet with the smaller width coincides with the path of the center of the recording sheet1b,or the recording sheet with the larger width (so that centers of two kinds of sheets in terms of width direction coincide). This structural arrangement can be realized by setting the distance by which the reference member4is to be moved, according to the width of the recording sheet which is being conveyed. With the reference member4placed in the position X into which the reference member4is moved by the distance which corresponds to the width of the recording sheet which is being conveyed, not only is the recording medium, which is being obliquely conveyed, straightened, but also, it is positioned so that the path of its center roughly aligns with the path of the centers of the other recording sheets, when two kinds of recording sheets in terms of width are conveyed through the sheet conveying apparatus150. Incidentally, the sheet conveying apparatus150is structured so that when the recording sheet1in the sheet conveying apparatus150is correct in its attitude and position, its center roughly aligns with the center line of the sheet conveyance surface5, in terms of the width direction of the recording sheet.

More specifically, in the first embodiment described above, as the recording sheet1is conveyed to the sheet conveying apparatus150, the recording sheet1is conveyed by the conveyance roller3, which is slanted, in the direction which is deviant toward the reference member4, regardless of whether or not the recording sheet1is obliquely positioned. As the recording sheet1is conveyed in the deviant direction, one of its lateral edges comes into contact with the reference surface4aof the reference member4which is movable in the width direction of the recording sheet1. The position in which the reference member4is held is determined by the shape and measurement of the cassette2, which correspond to the width of the recording sheet1which is being conveyed. The sheet conveying apparatus150is structured so that the reference member4is moved into, and held in, the position in which it regulates the position of the recording sheet1so that after the recording sheet1, which has obliquely reached the sheet conveying apparatus150, is straightened, the path of the center of the recording sheets1through the sheet conveying apparatus150coincides with the paths of the centers of the other recording sheets1through the sheet conveying apparatus150, in terms of the width direction of the recording sheet1. In other words, as the cassette2is mounted into the recording apparatus, the reference member4is moved by the cassette2. Therefore, even if the recording sheet1is obliquely fed, not only is the recording sheet1is straightened, but also, it is positioned so that the path of its center, in terms of its width direction, through the sheet conveying apparatus150, coincides with those of the other recording sheets1, regardless of the width of the recording sheets1.

One of the positions indicated by a solid line inFIG. 9is the position of the recording sheet1bprior to the correction of its attitude, and the other is the position of the recording sheet1bafter the correction of its attitude. One of the positions indicated by a dotted line inFIG. 9is the position of the recording sheet1aprior to the correction of its attitude, and the other is the position of the recording sheet1aafter the correction of its attitude. As will be evident from the comparison between the positions indicated by the solid line and the positions indicated by the dotted line, the sheet conveying apparatus150in this embodiment does not align the lateral edges of two kinds of recording sheets against a reference surface. Rather, it aligns them so that the paths of their centers coincide. That is, the sheet conveying apparatus150in this embodiment is simple in structure, and yet, not only can it straighten in attitude the recording sheet1, while being obliquely conveyed, but also, it can position all the recording sheets so that the paths of their center lines, in terms of their width direction, coincide, while the recording sheets1are conveyed through the sheet conveying apparatus150. Moreover, the sheet conveying apparatus150in this embodiment is easier to assemble than a sheet conveying apparatus in accordance with the prior art, and its mechanism for straightening an obliquely conveyed recording sheet is more reliable, than that of a sheet conveying apparatus in accordance with the prior art.

Incidentally, in this embodiment, the reference member4is moved with the use of an electrical driving force source, such as an electric motor, an electrical plunger, or the like. The width of the recording sheet1is determined by identifying the type of the cassette2with the use of an electrical element (sensor). The sheet conveying apparatus150is structured so that as the recording sheets1are conveyed through the sheet conveying apparatus150, not only are they straightened in attitude if they are oblique, but also, they are correctly positioned in terms of their width direction, by placing the reference member4in one of the abovementioned two positions. It should be specifically noted, however, that the sheet conveying apparatus150in this embodiment can be modified in structure so that the reference member4can be moved into three or more positions to enable the apparatus to correctly position three or more kinds (in terms of width) of recording sheets, in terms of their width direction, while correcting them in their attitude. More specifically, multiple cassettes which correspond in size and shape to the width of the recording sheets they store, are prepared, and the reference member4is moved by the pressing surface of the selected cassette, to the position which corresponds to the size of the recording sheets therein. In other words, the structural arrangement which makes a sheet conveying apparatus capable of straightening three or more kinds (in terms of width) of recording sheets is included in the scope of the present invention.

FIG. 10is a schematic plan view of the sheet conveying apparatus, in the second embodiment of the present invention, in which the cassette2is not present.FIG. 11is a sectional view of the sheet conveying apparatus shown inFIG. 10, at a line D-D inFIG. 10.FIG. 12is a schematic plan view of the sheet conveying apparatus in the second embodiment of the present invention, in which an oblique recording sheet with the smaller width is being straightened.FIG. 13is a sectional view, at a line D-D inFIG. 12, of the sheet conveying apparatus in the second embodiment of the present invention, which is in the state shown inFIG. 12.FIGS. 14,15, and16are schematic plan views of the sheet conveying apparatus in the second embodiment of the present invention, which show how a recording sheet of the first width (smaller width) having obliquely reached the sheet conveying apparatus is straightened.FIG. 17is a sectional view of the sheet conveying apparatus shown inFIG. 12, at the line D-D inFIG. 12.FIG. 18is a schematic plan view of the sheet conveying apparatus in the second embodiment of the present invention, which shows how a recording sheet of the second width (which is larger than the first width) having obliquely reached the sheet conveying apparatus is straightened.FIG. 19is a schematic perspective view of the means for rotating clockwise or counterclockwise a recording sheet having reached the sheet conveying apparatus,FIG. 19(a) showing the recording sheet being rotated, andFIG. 19(b) showing the recording sheet being moved in the direction parallel to the normal recording sheet conveyance direction. Hereafter, the sheet conveying apparatus in the second embodiment, which employs two reference members401and402, will be described regarding its structural arrangement.

The sheet conveying apparatus in the second embodiment of the present invention, which is shown inFIGS. 10-18, is similar to the above described sheet conveying apparatus in the first embodiment, in that both sheet conveying apparatuses straighten an oblique recording sheet regardless of the width of the recording sheet. Also in the second embodiment, the sheet conveying apparatus is structured so that two kinds of cassettes in terms of the width of the recording sheet they store can be removably mounted. The second embodiment is different from the first embodiment in that the sheet conveying apparatus in the second embodiment is provided with multiple (two) reference members401and402, a slider403as a means for moving one of the reference members, and a means capable of rotating a recording sheet clockwise or counterclockwise, and also, in that, unlike the conveyance roller3in the first embodiment, the conveyance roller3in the second embodiment is not slanted; it is perpendicularly positioned to the normal recording sheet conveyance direction so that when a recording sheet is conveyed, the lateral edges of the recording sheet remains parallel to the normal recording sheet conveyance direction.

Referring toFIGS. 10-18, the reference members401and402are located near the lateral edges of the sheet conveyance surface5, one for one. The inwardly facing side of the reference member401(first reference member) is provided with a reference surface401afor accurately positioning a recording sheet1a,or the recording sheet with the first width, while straightening the recording sheet1a,or the recording sheet with the first width, by regulating the position of one of the lateral edges of the recording sheet1aafter the recording sheet1ais obliquely positioned. The inwardly facing side of the other reference member, or the reference member402(second reference member), is provided with a reference surface402afor accurately positioning a recording sheet1b,or the recording sheet with the second width which is greater than the first width, while straightening the recording sheet with the second width, by regulating the position of one of the lateral edges of the recording sheet1b(including oblique recording sheet1b) after the recording sheet1ais obliquely positioned. These reference members401and402are kept under the pressure generated by a pair of compression springs401cand402c,one for one, in the direction to keep the reference members401and402in their bottom positions (in which reference members401and402are in contact with the sheet conveyance surface5). The sheet conveyance roller3for conveying a recording sheet is disposed in contact with the sheet conveyance surface5, and is located roughly at the mid point between the two reference surfaces. The sheet conveyance roller3is arranged perpendicular to the lateral edges of the sheet conveyance surface5to convey a recording sheet so that while the recording sheet is conveyed by the sheet conveyance roller3, the lateral edges of the recording sheet remain parallel to the normal recording sheet conveyance direction. Further, the sheet conveying apparatus is provided with a recording sheet rotating means (attitude controlling means) made of two pairs6of recording sheet rotating rollers. The recording sheet rotating means is on the upstream side of the reference members401and402on the sheet conveyance surface5, in terms of the recording sheet conveyance direction.

The reference member401, which is for a recording sheet with the smaller width, is also provided with a slanted surface401b,which also faces inward like the reference surface401aand is located so that it does not interferes with the function of the reference surface401a.The aforementioned slider403(movable means), which is for lifting the reference member401against the force generated by the resiliency of the spring401c,is located in the inward adjacencies of the abovementioned slanted surface401b.The slider403is kept pressured by the elastic force4B (springy force) in the direction to move away from the slanted surface401b.As a cassette404bwhich contains the recording sheets1b,or the sheets with the greater width, is mounted, the slider403is moved by this cassette404btoward the slanted surface401bagainst the force4B, as will be described later. As the slider403is changed in position as described above, the reference member401is lifted into its retreat (FIG. 15) against the force4A generated by the spring401c.On the other hand, as the cassette404bis removed, the slider403and reference member401are moved back into their home positions (initial positions), shown inFIG. 11, by the force4B, and the force4A generated by the spring401c,respectively. However, when a cassette404a,which stores the recording sheets of the smaller width, is mounted, the slider403and reference member401remain in their home positions (initial positions).

At this time, referring toFIG. 19, the structure and operation of the recording sheet rotating means made up of the two pairs6of recording sheet rotating rollers will be described. The two pairs6of recording sheet rotating rollers are aligned in the direction perpendicular to the normal recording sheet conveyance direction, with the provision of a preset distance between the two pairs6. Each of the pair6of recording sheet rotating rollers (which correspond to pair of rollers6and6inFIG. 10) is made up of a driving roller6aand following roller6b.A recording sheet is conveyed through both of the nips between the two pairs6of recording sheet rotating rollers (6aand6b). Referring toFIG. 19(a), as the driving roller6aof one of the two pairs6of recording sheet rotating rollers is rotated in the direction opposite to the direction in which the driving roller6aof the other pair6is rotated, as shown by two arrow marks, the recording sheet is subjected to the torque generated by the friction between the recording sheet and one of the pairs6of sheet rotating rollers and the friction between the recording sheet and the other pair6. Thus, the recording sheet is rotated by this torque about an axis perpendicular to the surface of the recording sheet, in the direction indicated by an arrow mark6c.Incidentally, the recording sheet can be rotated in the direction opposite to the direction indicated by the arrow mark6c, by rotating the two driving rollers6aand6ain the directions opposite to the abovementioned directions indicated by the two arrow marks. On the other hand, as the two driving rollers6aand6aare rotationally driven in the same direction as shown inFIG. 19(b), the recording sheet is subjected to two parallel forces which are generated by the two pairs6of recording sheet rotating rollers, one for one. Thus, the recording sheet is conveyed in the direction indicated by an arrow mark6D, which is parallel to the normal recording sheet conveyance direction T.

Next, referring toFIGS. 10-19, the relationship between the width of the recording sheet1, which is being conveyed, and the operation of the sheet conveying apparatus150, will be described.FIGS. 12 and 13, which correspond toFIGS. 10 and 11, respectively, show the state of the sheet conveying apparatus150after the mounting of the cassette404acontaining the recording sheets1a,or the recording sheet with the first width (smaller width), into the recording apparatus100.FIG. 17, which corresponds toFIGS. 10 and 11, shows the state of the sheet conveying apparatus150after the mounting of the cassette404bcontaining the recording sheet1b,or the recording sheet with the second width, which is greater than the first width, into the recording apparatus100.

The reference surfaces401aand402aof the reference members401and402, respectively, are parallel to the normal recording sheet conveyance direction T, and are perpendicular to the sheet conveying surface5. An oblique recording sheet1a,or an oblique recording sheet with the first width, straightens while it is conveyed through the sheet conveying apparatus, with one of its lateral edges (left edge in drawing) placed in contact with the reference surface401a.On the other hand, an oblique recording sheet1b,or an oblique recording sheet with the second width, straightens while it is conveyed through the sheet conveying apparatus, with one of its lateral edges (right edge in drawing) placed in contact with the reference surface402a.The reference surfaces401aand402aare positioned so that once the oblique recording sheet with the smaller width and the oblique recording sheet with the greater width are straightened, their centers in terms of their width direction coincide (so that they will be centered relative to sheet conveyance surface5in terms of their width direction).

FIGS. 12 and 13show the state of the sheet conveying apparatus150after the mounting of the cassette404a,or the cassette containing the recording sheets1a,or the recording sheets with first width (smaller width), into the main assembly of the recording apparatus100. Referring toFIG. 12, the two areas contoured by broken lines101aand102aare where the ink ribbon chambers, from which the ink ribbon is wound out, and the ink ribbon chamber, into which the ink ribbon is wound up, are located below the cassette404a.The ink ribbon chamber101a,from which the ink ribbon is wound out, is provided with a recess103afor preventing the interference (contact) between the ink ribbon chamber101aand slider403. Referring toFIG. 13, when the cassette404a,which is for the recording sheet of the smaller width, is mounted into, or in, the main assembly of the recording apparatus100, it does not contacts the slider403; it does not press the slider403. Therefore, even when the cassette404ais in the main assembly, the reference member401remains held in the home position (contact position) in which it allows the recording sheet1ato come into contact therewith.

Referring toFIG. 14, as the recording sheet1afed from the cassette404ainto the apparatus main assembly is conveyed to the sheet conveying apparatus150, the sheet conveying apparatus150rotates the recording sheet1aby the pairs6of sheet rotating rollers as sheet rotating means, on the upstream side of the reference members401and402in terms of the recording sheet conveyance direction, so that the recording sheet1aslants rightward in the drawing. After rotating (slanting) the recording sheet1aso that the trailing portion of the recording sheet1a,that is, the upstream portion of the recording sheet1a,in terms of the normal recording sheet conveyance direction T, is deviated toward the lateral edge of the sheet conveyance surface5on the reference surface401aside, relative to the leading portion, or the downstream portion, of the recording sheet1a,the sheet conveying apparatus150moves the recording sheet1ain the direction parallel to the normal recording sheet conveyance direction T by the two pairs6of sheet rotating rollers. As a result, the left lateral edge of the recording sheet1ais placed in contact with the reference surface401aof the reference member401, as shown inFIG. 15. Thus, as the slanted recording sheet1ais conveyed by the sheet conveyance roller3, it is straightened by the reference surface401a.More specifically, the recording sheet1ais slanted so that its trailing portion is deviated toward the lateral edge of the sheet conveyance path5on the reference surface401aside. Thus, as the recording sheet1ais conveyed through the sheet conveying apparatus150, the upstream end portion of the left lateral edge of the recording sheet1acome into contact with the reference surface401a,and then, is further conveyed in the direction parallel to the normal recording sheet conveyance direction T while being gradually straightened. In this case, the recording sheet1ais straightened while it is conveyed between the left and right reference members401and402. Therefore, it does not occur that the right reference member402interferes with the straightening of the recording sheet1a(FIG. 16). Further, at the same time as the slanted recording sheet1ais straightened, it is correctly positioned (centered) by the reference surface401arelative to the image forming portion in terms of the direction perpendicular to the normal direction in which the recording sheet1a,or the recording sheet with the smaller width, is conveyed.

FIGS. 17 and 18show the state of the sheet conveying apparatus150after the mounting of the cassette404b,or the cassette containing the recording sheets1b,or the recording sheets with second width, into the main assembly of the recording apparatus100. Referring toFIG. 18, the two areas contoured by broken lines101band102bare where the ink ribbon chamber, from which the ink ribbon is unwound, and the ink ribbon chamber, into which the ink ribbon is wound up are located, respectively, below the cassette404b.The ink ribbon chamber101b,from which the ink ribbon is unwound, is provided with a recess103b,which is provided with a pressing surface103cfor moving the slider403leftward as the cassette404bis inserted into the main assembly of the recording apparatus100. More specifically, as the cassette404bcontaining the recording sheets1b,or the recording sheets with the larger width, is inserted into the recording apparatus main assembly, the slider403is pressed by the pressing surface103c,being thereby moved leftward against the force4B generated by the spring. As the slider403is moved leftward, the surface403aof the slider403comes into contact with the slanted surface401bof the reference member401, and lifts the reference member401while remaining in contact with the reference member401. By the time the cassette404bis set in its operational position in the recording apparatus main assembly, the reference member401is lifted into the retreat position, shown inFIG. 17, in which the reference member401does not regulate the position of the lateral edge of the recording sheet1b.As a result, a gap which is large enough for the recording sheet1bto freely pass is created below the reference member401. In other words, the reference member401remains held in the position in which it does not interfere even if an oblique recording sheet1b,or an oblique recording sheet with the second width (larger width), is conveyed while being straightened, through the sheet conveying apparatus.

As the recording sheet1bis fed from the cassette404ainto the apparatus main assembly and is conveyed to the sheet conveying apparatus150, which is in the state shown inFIGS. 17 and 18, the sheet conveying apparatus150rotates the recording sheet1bby the pairs6of sheet rotating rollers, on the upstream side of the reference members401and402, in terms of the recording sheet conveyance direction, so that the recording sheet1bslants leftward in the drawing. After rotating (slanting) the recording sheet1bso that the downstream portion of the recording sheet1b,in terms of the normal recording sheet conveyance direction T, is moved away from the reference surface402a,the sheet conveying apparatus150moves the recording sheet1bin the direction parallel to the normal recording sheet conveyance direction T by the pairs6of sheet rotating rollers. As a result, the right lateral edge of the recording sheet1bis placed in contact with the reference surface402aof the reference member402. Then, the obliquely positioned recording sheet1bis straightened by the reference surface402awhile being conveyed by the recording sheet conveyance roller3, remaining in contact with the reference surface402a,in the direction parallel to the normal recording sheet conveyance direction T. Since the recording sheet1bis obliquely positioned so that its trailing portion is deviated toward the lateral edge of the sheet conveyance surface5on the reference surface402aside, the recording sheet1bis conveyed, with the upstream portion of the recording sheet1bremaining in contact with the reference surface402a.Therefore, it is conveyed in the direction parallel to the normal recording sheet conveyance direction T, while being subjected to the pressure generated in the direction to straighten the recording sheet1b.In this case, the recording sheet1bis straightened while it is conveyed below the reference member401which is in the retreat position. Therefore, it does not occur that the reference member401interferes with the straightening of the recording sheet1b(FIG. 16). Further, at the same time as the obliquely positioned recording sheet1bis straightened, it is correctly positioned by the reference surface402arelative to the image forming portion123, in terms of the direction perpendicular to the normal direction T in which the recording sheet1bis conveyed. Incidentally, as the cassette404b,or the cassette for the recording sheet of the larger width, is removed, the slider403is returned to the home position (initial position), and the reference member401is returned by the spring401cto the position in which the reference member401remains in contact with the sheet conveyance surface5. That is, the reference surface401ais returned to the position, shown inFIGS. 11 and 13, in which it comes into contact with a recording sheet1a.

With the employment of the sheet conveying apparatus which is structured and operates as described above, it does not occur that the reference member401, or the reference member for the recording sheet with the smaller width, interferes when conveying the obliquely positioned recording sheet with the larger width while straightening it, and therefore, not only is it possible to straighten an obliquely positioned recording sheet, but also, correctly position the recording sheet, in terms of the width direction of the recording sheet, regardless of recording sheet width. The positions of the left and right reference members401and402, respectively, are selected so that, in terms of the width direction of the recording sheet, the path of the center of the recording sheet1awhich moves along the reference surface401acoincides with the path of the center of the recording sheet1b,which is different in width from the recording sheet1aand moves along the reference surface402a.Therefore, not only can the two kinds of recording sheets in terms of width be straightened (if they are obliquely positioned), by these reference members, but also, they can be positioned so that their centers in terms of the width direction coincide.

The second embodiment of the present invention described above with reference toFIGS. 10-19also makes it possible to provide a sheet conveying apparatus having a mechanism for straightening an oblique recording sheet, which is simple in structure, is capable of conveying multiple kinds of recording sheets in terms of width, while straightening (if they are obliquely positioned) and positioning the recording sheets so that the paths of the centers of the recording sheets coincide, is easy to assemble, and is highly reliable. Further, in the second embodiment, the sheet conveying apparatus is structured so that the positions of the reference members201and202are automatically and mechanically set by the cassette404, the shape and size of which corresponds to the width of the recording sheet1. Therefore, the second embodiment is superior in terms of mechanical simplicity and ease of assembly to the above described first embodiment, in which the sheet conveying apparatus was structured so that the recording sheet width is identified with the use of a sensor or the like, and the reference member4was moved with the use of an electrical driving power source. Moreover, the second embodiment is superior to the first embodiment in terms of reliability.

Incidentally, in the second embodiment described above, the sheet conveying apparatus was structured so that the two kinds of recording sheets in terms of width were correctly positioned in terms of the width direction of the recording sheets, while being straightened (if they were obliquely positioned), by two reference members, one of which is movable to a retreat position. Incidentally, this embodiment can be modified to employ three of more reference members so that the reference members other than the reference member for the recording sheet of the largest width can be moved to their retreats. With such a modification, the sheet conveying apparatus can be structured so that three or more kinds of recording sheets in terms of width can be straightened (if they are obliquely positioned) and correctly positioned in terms of their width direction (for example, they can be positioned so that the paths of their centers coincide). In other words, the present invention includes in its scope the structural arrangement capable of straightening three or more kinds of recording sheets in terms of width (if they are obliquely positioned).

In the preceding embodiments of the present invention, the present invention was described with reference to only the recording apparatus of the thermal transfer type, which employed the sheet conveying apparatus. However, the present invention is also applicable to other recording apparatuses than the recording apparatus of the thermal transfer type, for example, an ink jet recording apparatus, a laser beam recording apparatus, a thermal recording apparatus, a wire-dot recording apparatus, etc., which employ the sheet conveying apparatus. Further, the present invention is applicable to various recording apparatuses which employ the sheet conveying apparatus, regardless of the number of recording heads, the positioning of recording heads, and the structure of recording heads.

This application claims priority from Japanese Patent Application No. 032448/2006 filed Feb. 9, 2006 which is hereby incorporated by reference.