Title:
Sheet separating/conveying mechanism and sheet conveying apparatus therewith
Kind Code:
A1


Abstract:
A sheet separating/conveying mechanism 30 has an upper unit 30a in which a paper feed roller 31 and other components are arranged and a lower unit 30b in which a separating roller 32, an arm member 36, and other components are arranged. The arm member 36 is U-shaped as seen in a plan view by being composed of a left and a right movable lever 36a that are mutually parallel and that make contact with both ends of a center shaft 23b and a pivot shaft 36b that supports the movable levers 36a so that they are rotatable in a direction indicated by arrow BB′. The movable levers 36a have locking holes 39 formed at the tip ends thereof, and the lower ends of tension springs 38 are locked in those locking holes 39. The lower unit 30b is fitted with an applied force adjusting member 45 on which locking portions 42a and 42b are formed to protrude therefrom leftward and rightward that permit adjustment of the positions at which the upper ends of the tension springs 38 are locked.



Inventors:
Okada, Takehiko (Osaka-shi, JP)
Yoshinaga, Shinji (Osaka-shi, JP)
Satoh, Masaki (Osaka-shi, JP)
Yamamura, Kazuyoshi (Osaka-shi, JP)
Hanano, Susumu (Osaka-shi, JP)
Fuchi, Masami (Osaka-shi, JP)
Nishioka, Nobuhiro (Osaka-shi, JP)
Daigo, Hironori (Osaka-shi, JP)
Application Number:
11/432486
Publication Date:
11/16/2006
Filing Date:
05/12/2006
Assignee:
KYOCERA MITA CORPORATION
Primary Class:
International Classes:
B65H3/52
View Patent Images:



Primary Examiner:
CICCHINO, PATRICK D
Attorney, Agent or Firm:
SMITH, GAMBRELL & RUSSELL, LLP (WASHINGTON, DC, US)
Claims:
What is claimed is:

1. A sheet separating/conveying mechanism comprising: a paper feed roller for feeding a sheet in a sheet conveying direction; a separating member pressed onto a lower part of said paper feed roller or taken away therefrom in a direction approximately perpendicular to the sheet conveying direction; and force applying means for pressing said separating member onto said paper feed roller, said force applying means permitting an applied force to be adjusted independently at both sides of said separating member in an axial direction thereof, wherein said sheet separating/conveying mechanism separates and conveys only a topmost sheet from a stack of sheets.

2. The sheet separating/conveying mechanism of claim 1, wherein said force applying means includes: two tension springs that apply the force to both sides of said separating member in the axial direction thereof; and an applied force adjusting member provided with, one at each of left and right sides thereof, locking portions for locking one ends of the tension springs, wherein said locking portions each have a plurality of engagement grooves formed therein at different positions in a direction of expansion/contraction of said tension springs.

3. The sheet separating/conveying mechanism of claim 2, wherein said engagement grooves are formed stepwise along upper edges of said locking portions, and a flexible sheet member is attached above said locking portions so as to close open ends of said engagement grooves, said sheet member being retractable to a position where said sheet member leaves open the open ends.

4. The sheet separating/conveying mechanism of claim 2, wherein, on said applied force adjusting member, for each of said locking portions, as many marking symbols as said engagement grooves formed therein are provided.

5. The sheet separating/conveying mechanism of claim 3, wherein, on said applied force adjusting member, for each of said locking portions, as many marking symbols as said engagement grooves formed therein are provided.

6. The sheet separating/conveying mechanism of claim 4, wherein said marking symbols are provided to correspond to arrangement of said engagement grooves.

7. The sheet separating/conveying mechanism of claim 5, wherein said marking symbols are provided to correspond to arrangement of said engagement grooves.

8. The sheet separating/conveying mechanism of claim 1, wherein said separating member is a separating roller composed of a roller body formed of an elastic material and a center shaft that penetrates a center of rotation of the roller body.

9. The sheet separating/conveying mechanism of claim 8, wherein said separating roller is provided with a torque limiter that permits said roller body to rotate only when a driving force stronger than a predetermined level is applied.

10. The sheet separating/conveying mechanism of claim 8, wherein, in said locking portions, mutually corresponding ones of said engagement grooves are formed, with consideration given to arrangement of said roller body in an axial direction thereof and a position of a center of gravity of said separating roller, in such positions that the force applied by the tension springs acts equally at left and right sides of said roller body.

11. The sheet separating/conveying mechanism of claim 9, wherein, in said locking portions, mutually corresponding ones of said engagement grooves are formed, with consideration given to arrangement of said roller body in an axial direction thereof and a position of a center of gravity of said separating roller, in such positions that the force applied by the tension springs acts equally at left and right sides of said roller body.

12. The sheet separating/conveying mechanism of claim 1, wherein said force applying means has movable levers that are rotatably supported at one ends thereof and that have said tension springs coupled to the other ends thereof, so that said movable levers apply the force applied by the tension springs to said separating member by making contact therewith, and rotary follower members are provided in parts of said separating member where said separating member makes contact with said movable levers.

13. The sheet separating/conveying mechanism of claim 12, wherein said separating member is a separating roller composed of a roller body formed of an elastic material and a center shaft that penetrates a center of rotation of the roller body, and said rotary follower members are fitted at both ends of said center shaft.

14. The sheet separating/conveying mechanism of claim 13, wherein said rotary follower members are bearings.

15. A sheet conveying apparatus comprising the sheet separating/conveying mechanism of claim 1.

Description:

This application is based on Japanese Patent Applications Nos. 2005-141572 and 2005-141592, both filed on May 13, 2005, the contents of which are hereby incorporated by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a sheet conveying apparatus that is used in an image forming apparatus such as a digital copier or laser printer to convey sheets of copying paper or sheets of an original document. More particularly, the present invention relates to a sheet separating/conveying mechanism that separates and then conveys one sheet after another from a stack of sheets.

2. Description of Related Art

The construction of a conventional image forming apparatus is shown in FIG. 9. In the image forming apparatus (for example, printer) 1, to form an image, a photoconductor drum 5 that rotates clockwise in the figure is uniformly charged by a charger unit 4, then an electrostatic latent image is formed on the photoconductor drum 5 by a laser beam from an exposure unit (such as a laser scanning unit) 7 according to an original document image data, and then a developer agent (hereinafter “toner”) is adhered to the electrostatic latent image by a developer unit 8 to form a toner image.

The toner is supplied to the developer unit 8 from a toner container 9. The image data is transmitted from a personal computer (unillustrated) or the like. In addition, a charge eliminating unit (unillustrated) for eliminating the residual charge on the surface of the photoconductor drum 5 is provided on the downstream side of the cleaning unit 18.

Toward the photoconductor drum 5 having the toner image formed thereon as described above, a sheet is conveyed from a paper feed cassette 10 via a sheet conveying passage 11 and a pair of resist rollers 12, so that the toner image formed on the surface of the photoconductor drum 5 is transferred to the sheet by a transfer roller 13 (an image transfer unit). The sheet having the toner image transferred thereto is then separated from the photoconductor drum 5, and is then conveyed to a fixing unit 14 having a pair of fixing rollers 14a, where the toner image is fixed. The sheet having passed through the fixing unit 14 is conveyed to an upper part of the apparatus via a sheet conveying passage 15, and is then ejected into an ejected paper tray 17 by a pair of ejecting rollers 16.

Next, the construction of the paper feed cassette will be described. FIG. 10 is a side sectional view of the paper feed cassette 10. Sheets 26 set in a cassette base 25 of the paper feed cassette 10 are pressed onto a pickup roller 29, which is provided in the main body of the apparatus, with a predetermined pressure exerted by a sheet mount plate 28, which is loaded with an upward acting force applied by a conical compression spring 27. When a copy start button of the image forming apparatus is operated, the pickup roller 29 and a paper feed roller 31 are driven to rotate in the directions indicated by arrows in FIG. 9.

Usually, one or a plurality of sheets among those located in a top part of the sheets 26 set on the sheet mount plate 28 are fed by the pickup roller 29 to a sheet separating/conveying mechanism 30, which has the paper feed roller 31 and a separating roller 32. If a plurality of sheets are fed to the nip between the paper feed roller 31 and the separating roller 32, only the topmost one of the sheets is separated by the separating roller 32 so as to be conveyed toward the sheet conveying passage 11. Here, the rotation of the separating roller 32 is controlled by a torque limiter (see FIG. 12) so that the separating roller 32 either remains at rest or rotates in the same direction as the paper feed roller 31. A rear-edge cursor 33 for truing up the rear edges of the sheets 26 is provided so as to be movable in the sheet conveying direction (left/right direction).

FIG. 11 is an enlarged view of the sheet separating/conveying mechanism 30 shown in FIG. 10, and FIG. 12 is a front view as seen from the direction indicated by arrow C in FIG. 11. The sheet separating/conveying mechanism 30 is composed of: an upper unit 30a in which the paper feed roller 31 and other components are arranged and that forms an upper guide for the conveyed sheet; and a lower unit 30b in which the separating roller 32, an arm member 36, and other components are arranged and that forms a lower guide for the conveyed sheet.

The separating roller 32 is composed of: a roller body 32a formed of an elastic material; and a center shaft 32b that penetrates the center of rotation of the roller body 32a. At each end of the center shaft 32b in the axial direction thereof, a bracket 34 is fixed, and a guide groove 35 that engages with the bracket 34 is formed in the cassette base 25 (see FIG. 10). Thus, the separating roller 32 is supported so as to be slidable along the guide groove 35 in the directions indicated by arrows AA′. Moreover, the separating roller 32 is fitted with a torque limiter 41 so that the roller body 32a rotates only when it receives a driving force stronger than a predetermined level.

The arm member 36 is formed in a substantially rectangular shape by being composed of: two mutually parallel movable levers 36a each making contact with one end of the center shaft 32b; and a pivot shaft 36b and a linking portion 36c that link together the movable levers 36a. The arm member 36 is supported by the pivot shaft 36b so as to be rotatable in the directions indicated by arrows BB′. It should be noted that, in FIG. 11, only the movable lever 36a on one side is shown. In a middle part of the linking portion 36c in the length direction thereof, a locking hole 39 is formed in which one end of a tension spring 38 is locked. The other end of the tension spring 38 is locked to a locking portion (unillustrated) of the lower unit 30b. Thus, the arm member 36 is loaded by the tension spring 38 with a force acting in the direction indicated by arrow B so that, in a middle part of the movable levers 36a, the arm member 36 applies to the center shaft 32b a pressure acting in the direction indicated by arrow B.

A retraction projection 43 is formed on the pivot shaft 36b of the arm member 36. When the paper feed cassette 10 (see FIG. 10) is pulled out in the direction (indicated by arrow D) perpendicular to the sheet conveying direction, the retraction projection 43 rides on an elevation 44 formed on the floor face of the apparatus to rotate the arm member 36 in the direction indicated by arrow B′. That is, at the same time that the paper feed cassette 10 is pulled out of the main body of the apparatus, the separating roller 32 moves apart from the paper feed roller 31. Thus, even if a sheet is caught in the nip between the paper feed roller 31 and the separating roller 32, the sheet is prevented from breaking.

In the sheet separating/conveying mechanism described above, to ensure that a single sheet is separated without fail even if more than one sheet is fed simultaneously, as disclosed in JP-A-2004-026479, the separating roller 32 is pressed onto the paper feed roller 31 with a predetermined pressure by force applying means such as the tension spring 38. Here, the pressure with which the separating roller 32 is optimally pressed onto the paper feed roller 31 varies with the thickness of the sheet actually used and other factors. Thus, for example, if the pressure is too strong, a plurality of sheets are fed simultaneously and, of the pressure is too weak, no sheet at all is fed, in either case resulting in a paper feed error. On the other hand, if the pressure is uneven at the left and right sides of the separating roller 32 in the axial direction thereof, the sheet is conveyed obliquely or otherwise in an undesired way.

Under these circumstances, there have been proposed various methods for adjusting the pressure with which a separating member such as a separating roller is pressed onto a paper feed roller. For example, JP-A-2001-031275 discloses a sheet separating/conveying mechanism provided with pressing force adjusting means for adjusting the pressing force with which pressing means (a spring) presses a separating roller onto a paper feed roller wherein the pressing force with which the separating roller is pressed can be adjusted by varying the length of a spring with a tool such as a screwdriver.

However, in the construction shown in FIG. 11, whereas the separating roller 32 slides linearly in the direction (indicated by arrows AA′) perpendicular to the sheet conveying direction, the movable levers 36a, which presses the separating roller 32, moves circularly about the pivot shaft 36b. That is, the direction in which the pressing force from the movable levers 36a is transmitted does not coincide with the direction in which the separating roller 32 slides, and thus friction occurs at the contact between the center shaft 32b and the movable levers 36a and between the center shaft 32b and the side walls of the guide groove 35. This hampers smooth transmission of the force applied by the tension spring 38 to the separating roller 32.

On the other hand, JP-A-H10-207141, which is directed to a paper post-processing apparatus that nips and conveys one sheet of recording material after another at the nip formed between two rollers kept in contact with each other while “de-curling” (flattening) curled sheets, discloses a method for adjusting the intensity of de-curling stepwise by varying the axis-to-axis distance between the rollers stepwise.

Moreover, JP-A-2002-302324, which is directed to an original document feeding apparatus that conveys one sheet after another by the use of a separating roller and a separating belt, discloses a method for adjusting the pressure without replacement of components but instead by manipulating a positioning member for adjusting the distance between the separating roller and the separating belt by the use of an adjustment scale provided along the displacement direction of the positioning member. Inconveniently, however, with the methods disclosed in JP-A-H10-207141 and JP-A-2002-302324, it is difficult to recognize at a first glance in which direction to adjust. This may lead to an unduly long time required in the assembly of the apparatus and in readjustment by a serviceperson, and to adjustment errors.

Moreover, in a case where, as shown in FIG. 12, the roller body 32a is arranged not in the middle of the center shaft 32b but slightly leftward, the force applied at the left and right sides of the roller body 32a needs to be made even by applying a stronger force at the left side, where the distance from the roller body 32a to the end of the center shaft 32b is shorter, than at the right side by exploiting the principle of a lever. On the other hand, in a case where the torque limiter 41 is arranged on the right side of the roller body 32a, the center of gravity of the separating roller 32 is located not in the middle thereof but slightly rightward. This requires that the force be applied so much more at the right side as the center of gravity is displaced. In this way, it is necessary to adjust the force applied at the left and right sides in the axial direction separately with consideration given to the arrangement of the separating roller 32 and the displacement of the center of gravity attributable to the torque limiter 41.

Inconveniently, however, with the construction shown in FIG. 12, since the tension spring 38 is linked to one location in a middle part of the separating roller 32 in the axial direction, it is impossible to adjust the force applied at the left and right sides independently. Incidentally, although the above description deals with a paper feed cassette incorporated in an image forming apparatus to serve as a sheet paper feeding source, the same inconveniences are experienced in an original document conveying apparatus (ADF—automatic document feeder) that automatically conveys sheets of an original document or a paper feeding apparatus that is used as an interleaf paper feeding source.

SUMMARY OF THE INVENTION

In view of the conventionally experienced inconveniences mentioned above, it is an object of the present invention to provide a sheet separating/conveying mechanism that permits the force with which a separating member such as a separating roller is pressed to be adjusted easily and independently at the left and right sides thereof in the axial direction, and to provide a sheet conveying apparatus provided with such a sheet separating/conveying mechanism. It is another object of the present invention to easily and inexpensively provide a sheet separating/conveying mechanism that permits smooth transmission of a force from force applying means so that a separating member such as a separating roller is pressed with a stable pressure, and to provide a sheet conveying apparatus provided with such a sheet separating/conveying mechanism.

To achieve the above objects, according to one aspect of the present invention, a sheet separating/conveying mechanism that is provided with a paper feed roller for feeding a sheet in the sheet conveying direction, a separating member pressed onto a lower part of the paper feed roller or taken away therefrom in the direction approximately perpendicular to the sheet conveying direction, and force applying means for pressing the separating member onto the paper feed roller and that separates and conveys only the topmost sheet from a stack of sheets is characterized in that the force applying means permits the applied force to be adjusted independently at both sides of the separating member in the axial direction thereof.

With this construction, the pressure with which the separating member is pressed onto the paper feed roller can be adjusted separately at the left and right sides in the axial direction. This permits the separating member to be pressed more evenly at the left and right sides than is conventionally possible. Thus, it is possible to effectively reduce oblique sheet feeding and improper paper feeding.

According to the present invention, in the sheet separating/conveying mechanism constructed as described above, the force applying means includes two tension springs that apply the force to both sides of the separating member in the axial direction thereof and an applied force adjusting member that is provided with, one at each of the left and right sides thereof, locking portions for locking one ends of the tension springs. Here, the locking portions each have a plurality of engagement grooves formed therein at different positions in the direction of expansion/contraction of the tension springs.

With this construction, the applied force can be easily adjusted by changing the engagement positions of the tension springs according to the displacement of the center of gravity of the separating member, the thickness of sheets actually used, and other factors.

According to the present invention, in the sheet separating/conveying mechanism constructed as described above, the engagement grooves are formed stepwise along the upper edges of the locking portions, and a flexible sheet member is attached above the locking portions so as to close the open ends of the engagement grooves. The sheet member is retractable to a position where it leaves open the open ends.

With this construction, there is no risk of the tension springs disengaging from the engagement grooves while a sheet is being conveyed. On the other hand, when the applied force is readjusted, the sheet member can be bent to leave open the open ends of the engagement grooves, so that the engagement positions of the tension springs can be easily adjusted.

According to the present invention, in the sheet separating/conveying mechanism constructed as described above, on the applied force adjusting member, for each of the locking portions, as many marking symbols as the engagement grooves formed therein are provided.

With this construction, by previously marking the marking symbols that correspond to the initially adjusted positions of the tension springs, it is possible to enhance work efficiency in the assembly and readjustment of the apparatus, and also to reduce adjustment errors.

According to the present invention, in the sheet separating/conveying mechanism constructed as described above, the marking symbols are provided to correspond to the arrangement of the engagement grooves.

With this construction, the adjusted positions of the tension springs can be grasped at a glance in the assembly and readjustment of the apparatus.

According to the present invention, in the sheet separating/conveying mechanism constructed as described above, the separating member is a separating roller composed of a roller body formed of an elastic material and a center shaft that penetrates the center of rotation of the roller body.

With this construction, the force applied to the separating roller can be adjusted separately at the left and right sides so that the pressure with which the separating roller is pressed onto the paper feed roller is even in the axial direction.

According to the present invention, in the sheet separating/conveying mechanism constructed as described above, the separating roller is provided with a torque limiter that permits the roller body to rotate only when a driving force stronger than a predetermined level is applied.

With this construction, by controlling the rotation of the separating roller with the torque limiter, it is possible to further enhance the sheet separation performance, and thereby to reduce paper feed errors such as multiple sheets being fed simultaneously or no sheet being fed at all.

According to the present invention, in the sheet separating/conveying mechanism constructed as described above, in the locking portions, mutually corresponding ones of the engagement grooves are formed, with consideration given to the arrangement of the roller body in the axial direction thereof and the position of the center of gravity of the separating roller, in such positions that the force applied by the tension springs acts equally at the left and right sides of the roller body.

With this construction, simply by engaging the left and right tension springs with the engagement grooves located to correspond to each other, it is possible to make the applied force act evenly at the left and right sides of the roller body irrespective of the arrangement of the roller body or the position of the center of gravity of the separating roller.

According to the present invention, in the sheet separating/conveying mechanism constructed as described above, the force applying means has movable levers that are rotatably supported at one ends thereof and that have the tension springs coupled to the other ends thereof, so that the movable levers apply the force applied by the tension springs to the separating member by making contact therewith, and rotary follower members are provided in the parts of the separating member where it makes contact with the movable levers.

With this construction, it is possible to reduce friction in the parts of the separating member and the movable levers where they make contact with each other. Thus, it is possible to press the separating member onto and take it away from the paper feed roller smoothly.

According to the present invention, in the sheet separating/conveying mechanism constructed as described above, the separating member is a separating roller composed of a roller body formed of an elastic material and a center shaft that penetrates the center of rotation of the roller body, and the rotary follower members are fitted at both ends of the center shaft.

With this construction, it is possible to reduce friction at both ends of the separating roller. Thus, it is possible to apply the applied force to the separating roller smoothly, and to make even the force with which the separating roller is pressed onto the paper feed roller in the axial direction.

According to the present invention, in the sheet separating/conveying mechanism constructed as described above, the rotary follower members are bearings.

With this construction, it is possible to more effectively reduce friction between the separating member and the movable levers, and thereby to press the separating member onto and take it away from the paper feed roller more smoothly.

According to another aspect of the present invention, a sheet conveying apparatus is provided with the sheet separating/conveying mechanism constructed as described above.

With this construction, it is possible to easily and inexpensively realize a sheet conveying apparatus in which a force is applied to the separating member evenly in the axial direction thereof to permit the separating member to be pressed onto and taken away from the paper feed roller smoothly so as to reduce oblique sheet feeding and improper paper feeding and to permit easy adjustment of the applied force.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a front view showing the construction of the sheet separating/conveying mechanism of a first embodiment of the present invention;

FIG. 2 is a perspective view of the lower unit of the sheet separating/conveying mechanism of the first embodiment, as seen from where the applied force adjusting member is located;

FIG. 3 is a perspective view of the applied force adjusting member used in the sheet separating/conveying mechanism of the first embodiment;

FIG. 4 is an enlarged view of a part around a locking portion of the applied force adjusting member;

FIG. 5 is an enlarged view showing another construction around the locking portion;

FIG. 6 is a side view showing the construction of the sheet separating/conveying mechanism of a second embodiment of the present invention;

FIG. 7 is a front view showing the construction of the sheet separating/conveying mechanism of the second embodiment;

FIGS. 8a and 8b are side views illustrating how a force is applied to the separating roller via the movable levers in the sheet separating/conveying mechanism of the second embodiment;

FIG. 9 is a sectional view showing an outline of the overall construction of a conventional image forming apparatus;

FIG. 10 is a side sectional view showing the construction of a conventional paper feed cassette;

FIG. 11 is a side view showing a conventional sheet separating/conveying mechanism, and

FIG. 12 is a front view showing the conventional sheet separating/conveying mechanism.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. FIG. 1 is a front view showing the construction of a sheet separating/conveying mechanism of a first embodiment of the present invention. Such parts as are found also in the conventional example shown in FIG. 12 are identified with common reference numerals, and no description thereof will be repeated. In this embodiment, the arm member 36 is U-shaped as seen in a plan view by being composed of two mutually parallel movable levers 36a that make contact with both ends of the center shaft 32b and a pivot shaft 36b that links together the movable levers 36a.

The left and right movable levers 36a have locking holes 39 formed at the tip ends thereof, and the lower ends of tension springs 38 are locked in those locking holes 39. The upper ends of the tension springs 38 are locked on locking portions 42a and 42b, respectively, of an applied force adjusting member (described later) fitted to the lower unit 30b (see FIG. 11).

With this construction, the pressure with which the separating roller 32 is pressed onto the paper feed roller 31 can be adjusted separately at the left and right sides in the direction of the center shaft 32b. Thus, as compared with the conventional construction in which a force is applied with a single tension spring 38, a force can be applied to the roller body 32a more evenly at the left and right sides. This helps effectively reduce oblique sheet feeding and improper paper feeding.

FIG. 2 is a perspective view of the lower unit 30b as seen from the bottom of FIG. 1. Reference numeral 45 represents an applied force adjusting member that permits adjustment of the force applied by the left and right tension springs 38. The applied force adjusting member 45 is fixed to the lower unit 30b with screws. At the left and right ends of the applied force adjusting member 45, locking portions 42a and 42b are formed to protrude therefrom. The locking portions 42a and 42b permit adjustment of the locking positions of the tension springs 38.

The structure of the applied force adjusting member 45 is shown in FIG. 3. The applied force adjusting member 45 is a metal plate that has a vertical surface 45a and a horizontal surface 45b and that is substantially L-shaped in a cross section thereof. The locking portions 42a and 42b are formed to protrude obliquely upward from the left and right ends of the vertical surface 45a. In the horizontal surface 45b, screw holes 46 are formed that permit the applied force adjusting member 45 to be fixed to the lower unit 30b (see FIG. 2).

Moreover, on the vertical surface 45a, as many marking symbols 47 (here, seven at each of the left and right sides) are impressed as there are formed engagement grooves (described later) in the locking portions 42a and 42b. By previously marking the marking symbols 47 that correspond to the initial adjustment positions of the tension springs 38, the adjustment positions of the tension springs 38 can be grasped at a glance in the assembly of the apparatus. This helps enhance work efficiency and reduce adjustment errors.

The optimal value of the force applied by the tension springs 38 varies according to the thickness of the sheet actually used. In the assembly of the apparatus, the applied force is set at an optimal value that corresponds to the thickness of standard sheets. However, in a case where frequently used sheets are not standard sheets, a user or serviceperson readjusts the applied force to suit the thickness of those sheets. Even in this case, the marking positions of the marking symbols 47 can be referred to to move, by the desired positions, the locking positions of the tension springs 38 from the initial adjustment positions. This makes readjustment easy.

FIG. 4 is an enlarged view of a part around the locking portion 42b (the part inside circle S shown in FIG. 3). The locking portion 42b has seven engagement grooves 48 formed therein stepwise at different positions in the direction of the expansion/contraction of the tension springs 38 (in the up/down direction of the figure). For example, in a case where the fourth marking symbol 47 (see FIG. 3) is marked as the initial adjustment position, as shown in FIG. 4, the tension spring 38 is locked in the fourth engagement groove 48 as counted from inside.

The locking portion 42a is similarly structured, and therefore no separate description will be given thereof. It should be noted, however, that the locking portions 42a and 42b are not symmetrical, but are so designed that even a pair of engagement grooves 48 located at mutually corresponding positions makes the tension springs 38 expand to different lengths, that is, make them exert different forces. As shown in FIG. 1, the roller body 32a of the separating roller 32 is arranged not in the middle of the center shaft 32b but slightly leftward. Thus, to make the force applied to the left and right sides of the roller body 32a even, it is necessary, by the principle of a lever, to apply a stronger force at the left side, where the distance from the roller body 32a to the end of the center shaft 32b is shorter, than at the right side.

On the other hand, since the torque limiter 41 is arranged on the right side of the separating roller 32, the center of gravity of the separating roller 32 is located not in the middle thereof in the axial direction but slightly rightward. Thus, the force applied at the right side needs to be made so much stronger as the center of gravity is displaced. Accordingly, the left and right locking portions 42a and 42b have their engagement grooves 48 formed in positions determined with consideration given to the arrangement of the separating roller 32 and the displacement of the center of gravity attributable to the torque limiter 41. Thus, when the tension springs 38 are locked in a pair of engagement grooves 48 at mutually corresponding positions in the locking portions 42a and 42b, the applied force acts evenly at the left and right sides of the roller body 32a.

In a case where the engagement grooves 48 are formed stepwise as shown in FIG. 4, when the paper feed cassette 10 is removed and inserted, a swinging movement of the movable levers 36a may cause the tension springs 38 to disengage from the engagement grooves 48. To prevent this, as shown in FIG. 5, flexible sheet members 50 are attached above the locking portions 42a and 42b, with only a fixing portion 50a of the sheet member 50 fixed with adhesive, so that a flexible portion 50b thereof, at the bottom edge thereof, closes the open ends of the engagement grooves 48. This prevents a swinging movement of the movable levers 36a from causing the tension springs 38 to disengage from the engagement grooves 48. Moreover, when the applied force is readjusted, by bending the flexible portion 50b toward the face of sheets to open the open ends of the engagement grooves 48, it is possible to easily adjust the engagement positions of the tension springs 38.

The sheet member 50 may be formed of any material so long as it is formed as a flexible sheet of synthetic resin or the like. It is, however, preferable that the sheet be so strong as to keep the tension springs 38 engaged. A preferred example of the sheet is a sheet (Lumilar sheet) of polyethylene terephthalate (PET).

The shapes and arrangement of the applied force adjusting member 45, the locking portions 42a and 42b, and the engagement grooves 48 specifically described above are merely an example thereof, and may be modified as necessary to suit the specifications of the sheet separating/conveying mechanism 30. For example, instead of the locking portions 42a and 42b being formed to protrude, the engagement grooves 48 may be formed along the left and right edges of the vertical surface 45a. In this case, forming the engagement grooves 48 hook-shaped prevents the tension springs 38 from disengaging therefrom even without the provision of the sheet member 50.

FIG. 6 is a side view showing the construction of the sheet separating/conveying mechanism of a second embodiment of the present invention, and FIG. 7 is a front view thereof as seen from the direction indicated by arrow C in FIG. 6. Such parts as are found also in FIG. 11 or in FIG. 1, which shows the first embodiment, are identified with common reference numerals, and no description thereof will be repeated. In this embodiment, at both ends of the center shaft 32b of the separating roller 32, bearings 40 are fitted. The separating roller 32 is so built as to make contact with the movable levers 36a via the bearings 40. In FIG. 7, the tension spring 38 at the right side is omitted.

Thus, in a state where the separating roller 32 is located apart from the paper feed roller 31, when the arm member 36 rotates in the direction indicated by arrow B under the force applied thereto by the tension springs 38, as shown in FIG. 8a, the movable levers 36a gives the center shaft 32b a pressing force that acts in the direction indicated by arrow B. Here, the bearings 40 fitted around the center shaft 32b rotate in the direction indicated by arrow C, and thus the center shaft 32b slides in the direction indicated by arrow A along the guide grooves 35 (see FIG. 6).

On the other hand, in a state where the separating roller 32 is pressed onto the paper feed roller 31, when the arm member 36 rotates in the direction indicated by arrow B′ against the force applied by the tension springs 38, as shown in FIG. 8b, the bearings 40 rotate in the direction indicated by arrow C′ to follow the movable levers 36a retracting in the direction indicated by arrow B′, and thus the center shaft 32b slides in the direction indicated by arrow A′. Accordingly, no friction occurs at the contact between the center shaft 32b and the movable levers 36a or between the center shaft 32b and the guide grooves 35. Thus, with the movable levers 36a, the separating roller 32 can be slid smoothly in the direction indicated by arrows AA′.

In this embodiment, the bearings 40 are fitted on the center shaft 32b to permit the separating roller 32 to slide smoothly. Instead of the bearings 40, any other rotary follower members such as rollers may be fitted that can freely rotate relative to the center shaft 32b. The rotary follower members may be formed of metal, resin, or any other material.

In any other aspects, the present invention may be carried out in any other manners than specifically described above, and many modifications and variations are possible within the spirit of the present invention. For example, in the embodiments described above, instead of using the substantially U-shaped arm member 36 to give the separating roller 32 its pressing force, the pivot shaft 36b may be provided one at each of the left and right sides independently so that the movable levers 36a are supported separately. Instead of the tension springs 38, any other type of spring member may be used, such as compression springs, torsion springs, or plate springs.

The embodiments described above deal with a sheet separating/conveying mechanism that prevents multiple feeding of sheets by pressing a separating roller 32 onto a paper feed roller 31. These constructions, however, are equally applicable to a sheet separating/conveying mechanism in which, instead of the separating roller 32, a separating pad or separating belt formed of an elastic material is pressed onto the paper feed roller 31.

The embodiments described above deal with examples in which a sheet separating/conveying mechanism is incorporated in a paper feed cassette 10 that is incorporated as a sheet paper feeding source in an image forming apparatus. The sheet separating/conveying mechanism, however, may also be applied to an ADF that automatically conveys sheets of an original document or a paper feeding apparatus that is used as an interleaf paper feeding source.

According to the present invention, it is possible to adjust the force applied to a separating member separately at the left and right sides in the axial direction. Thus, it is possible to realize a sheet separating/conveying mechanism that can press a separating member onto a paper feed roller with a pressure more even at the left and right sides than is conventionally possible and that can thus effectively prevent oblique sheet feeding and improper paper feeding.

Moreover, force applying means is used that includes two tension springs and an applied force adjusting member having locking portions formed at two, left and right, locations, each locking portion having a plurality of engagement grooves, with which the tension springs are to be engaged, formed at different positions in the direction of the expansion/contraction of the springs. Thus, it is possible to easily adjust the force applied by the tension springs to suit the displacement of the center of gravity of the separating member, the thickness of the sheet actually used, and other factors.

Moreover, the engagement grooves are formed stepwise along the upper edges of the locking portions, and, above the locking portions, a flexible sheet member is attached to close the open ends of the engagement grooves. This prevents, when a sheet is being conveyed, the tension springs from disengaging from the engagement grooves. When the applied force is readjusted, the sheet member is bent so as to be retracted to a position where it leaves open the open ends of the engagement grooves. This permits easy adjustment of the engagement positions of the tension springs.

Moreover, for each locking portion, as many marking symbols are provided in the applied force adjusting member as there are formed engagement grooves. Thus, by previously marking the marking symbols corresponding to the initial adjustment positions of the tension springs, it is possible to enhance work efficiency and reduce adjustment errors in the assembly or the readjustment of the apparatus. Furthermore, by making the arrangement of the marking symbols correspond to the arrangement of the engagement grooves, it is possible to grasp the adjustment positions of the tension springs at a glance.

Moreover, the separating member is built as a separating roller composed of a roller body and a center shaft, and the engagement grooves are formed in the locking portions with consideration given to the arrangement of the roller body in the axial direction and the position of the center of gravity of the separating roller. Thus, simply by engaging the tension springs with a pair of engagement grooves located at corresponding positions at the left and right sides, it is possible to apply a force to the roller body evenly at the left and right sides.

Moreover, in a case where the force is applied via the movable levers to the separating member, providing rotary follower members at the contact between the separating member and the movable levers helps, as a result of the rotary follower members rotating, prevent friction at the contact between the movable levers and the separating member. Thus, through the rotation of the movable levers, the force applied to the separating member is converted into a force acting in the direction in which the separating member slides, and thereby permits the separating member to slide smoothly.

Moreover, by incorporating a sheet separating/conveying mechanism according to the present invention in a sheet conveying apparatus such as a paper feed cassette or original document conveying apparatus, it is possible to realize a sheet conveying apparatus in which the force applied to a separating member is made even in the axial direction to reduce oblique sheet feeding and improper paper feeding and to permit easy adjustment of the applied force.