Patent Application
20120117814
This application is based on Japanese Patent Application No. 2010-252466 filed on Nov. 11, 2010 and Japanese Patent Application No. 2011-23475 filed on Feb. 7, 2011, the contents of both of which are hereby incorporated by reference.
1. Field of the Invention
The present invention relates to a paper size detecting mechanism for detecting the size of paper (sheets of paper) stacked in a paper feed cassette unloadably loaded in an image forming apparatus, and to an image forming apparatus provided with such a paper size detecting mechanism. More particularly, the present invention relates to a paper size detecting mechanism that has a simple structure, that requires a reduced installation space, and that can prevent erroneous detection.
2. Description of Related Art
Image forming apparatus such as copiers, printers, facsimile machines, and the like are unloadably loaded with paper feed cassettes in which paper of different sizes can be appropriately stacked. An image forming apparatus loaded with such paper feed cassettes is designed to be capable of automatically detecting the size of the stacked paper.
In one typical example of a known paper size detecting mechanism, there is provided a switch that detects the position of a pressing member that, when paper is stacked in a paper feed cassette, is pressed against an edge of the paper to detect its position. Inconveniently, however, this detection mechanism requires as many switches as there are different sizes of paper and thus requires an increased number of components. Moreover, providing many switches requires an accordingly large space. This hampers the miniaturization of image forming apparatus.
As a solution to the above problem, there is known, for example, a paper size detecting mechanism that uses less switches and instead detects the paper size based on the combination of the on and off states of those switches. This improved paper size detecting mechanism is provided with—in the cabinet of an image forming apparatus—three push switches and—on a paper feed cassette—a segment gear which rotates in concert with a pressing member, and has cogs formed at its circumferential edge; an idle gear which is rotated by the segment gear; and a partly cut member which has a rack meshing with the idle gear, moves as the segment gear rotates, and has a recess and a protrusion that, when the paper feed cassette is loaded in the image forming apparatus, selectively press the switches to turn them on or off.
Inconveniently, however, the above paper size detecting mechanism requires gears, such as a segment gear, an idle gear, and a rack, and in addition a plurality of (three) independent switches. Thus, the mechanism is complicated and costly.
In another known paper size detecting mechanism, there are provided—on a paper feed cassette—a movable pressing member which is pressed against stacked paper; and a following member which swings in concert with the pressing member, and has one or more protrusions in a tip-end portion thereof in the loading direction of the paper feed cassette, and—in an image forming apparatus—a detecting member which has a detecting plate that elastically deforms when any of the protrusions on the following member makes contact with it; and a multiple switch which is operated by the action of the detecting plate. With this design, the use of a single multiple switch, which is compact and inexpensive, instead of a plurality of independent switches and the provision of a detecting member of an elastic material between the paper feed cassette and the switch helps simplify the mechanism and thus helps achieve space saving and cost reduction.
Inconveniently, however, with the above design, the detecting member is a plate-shaped member made of resin, and the elasticity of the resin is exploited to restore the plate-shaped member from the position (on position) where it presses a contact of the multiple switch to the position (off position) where it ceases to do so.
Thus, depending on the degree and frequency of deformation, the detecting member may go beyond the limit within which it can restore from elastic deformation and undergo creep deformation (plastic deformation). The detecting member then fails to completely restore from the on position to the off position and causes erroneous detection.
To overcome the inconveniences mentioned above, an object of the present invention is to provide a paper size detecting mechanism that can effectively prevent erroneous detection of paper size through suppression of creep deformation of a detecting member, and to provide an image forming apparatus provided with such a paper size detecting mechanism.
To achieve the above object, according to one aspect of the present invention, a paper size detecting mechanism is provided with: a restricting member which is reciprocably provided on the inside of the bottom of a paper feed cassette unloadably loaded in the cabinet of an image forming apparatus and which restricts an edge of paper accommodated in the paper feed cassette; a following member including a following arm portion of which one end is coupled to the restricting member and an arc-shaped portion which is continuous with the other end of the following arm portion and which has formed thereon at least one protrusion protruding in the radial direction, the following member being provided swingable in concert with the movement of the restricting member; a detecting member which is arranged in the cabinet of the image forming apparatus at a position facing the arc-shaped portion and which has a plurality of detecting plates elastically deformable by contact with the protrusion, the detecting plates each including a base-end portion of which one end is supported on the main portion of the detecting member and a swing portion which is located on the tip-end side of the base-end portion and with which the protrusion makes contact, the base-end portion in at least one of the detecting plates having a wider elastically deformable range than the swing portion; a multiple switch which is provided on the rear side of the detecting member and which has a plurality of contacts switchable between an on state and an off state by elastic deformation of the plurality of detecting plates; and a prop which is provided horizontally over the multiple switch and which is kept in contact with the reverse side of the detecting plates, at the base-end portion thereof, to serve as a fulcrum of swinging, the paper size detecting mechanism detecting the size of the paper accommodated in the paper feed cassette.
The further objects of the present invention, and the specific benefits of the present invention, will be clear from the following description of embodiments of the present invention.
Hereinafter, an embodiment of the present invention will be described with reference to the accompanying drawings.
In the image forming sections Pa, Pb, Pc, and Pd, photoconductive drums 1a, 1b, 1c, and 1d are respectively arranged which carry visible images (toner images) of the different colors. In addition, an intermediary transfer belt 8 which is rotated counter-clockwise in
Paper 26 onto which the toner images are to be transferred is accommodated in a paper feed cassette 10 in a lower part of the apparatus. The paper 26 is stacked on a paper stack plate 28 in the paper feed cassette 10. Pressing a pick-up roller 29 against the top face of the paper 26 under a predetermined pressure and rotating the pick-up roller 29 starts the feeding of the paper 26. A pair of paper feed rollers 27 separates the topmost sheet out of the plurality of sheets of paper 26 and transports it toward a paper transport passage 11. Having passed through the paper transport passage 11, the paper 26 reaches a pair of resist rollers 14, and is transported, with proper timing for image formation, to the nip between a secondary transfer roller 9 and a driver roller 13 of the intermediary transfer belt 8, which will be described later.
As the intermediary transfer belt 8, a sheet of a dielectric resin is used; used here is an endless belt formed by bonding together opposite ends of such a sheet with an overlap, or a seamless belt with no seam. On the downstream side of the secondary transfer roller 9 with respect to the movement direction of the intermediary transfer belt 8, there is arranged a cleaning blade 17 for removing the toner remaining on the surface of the intermediary transfer belt 8.
An image reading section 20 is composed of (though none of these is illustrated): a scanning optical system including a scanner lamp which illuminates a document during its copying and a mirror which changes the optical path of the light reflected from the document; a condenser lens which condenses and thereby focuses the light reflected from the document; a CCD sensor which converts the focused image light into an electrical signal; etc. The image reading section 20 reads an image of the document and converts it into image data.
Next, the image forming sections Pa to Pd will be described. Around and under the photoconductive drums 1a to 1d which are rotatably arranged, there are arranged: chargers 2a, 2b, 2c, and 2d for electrically charging the photoconductive drums 1a to 1d; an exposure unit 4 for exposing the photoconductive drums 1a to 1d to light conveying image information; developing units 3a, 3b, 3c, and 3d for forming toner images on the photoconductive drums la to 1d; and cleaning devices 5a, 5b, 5c, and 5d for removing the developer (toner) remaining on the photoconductive drums 1a to 1d.
When image data is fed in from the image reading section 20, first, the chargers 2a to 2d electrically charge the surfaces of the photoconductive drums 1a to 1d uniformly; next, the exposure unit 4 emits a light beam according to image data to form electrostatic latent images on the photoconductive drums 1a to 1d according to the image data from the image reading section 20. The developing units 3a to 3d are provided with developing rollers (developer carrying members) arranged opposite the photoconductive drums 1a to 1d, and are filled with predetermined amounts of two-component developer containing cyan, magenta, yellow, and black toner respectively. By the developing rollers of the developing units 3a to 3d, the toner is supplied onto the photoconductive drums 1a to 1d so as to electrostatically adhere thereto, thus forming toner images according to the electrostatic latent images formed through exposure to light from the exposure unit 4.
Then, primary transfer rollers 6a to 6d apply an electric field with a predetermined transfer voltage between the primary transfer rollers 6a to 6d and the photoconductive drums 1a to 1d, and thereby the cyan, magenta, yellow, and black toner images on the photoconductive drums 1a to 1d are primarily transferred onto the intermediary transfer belt 8. These images of four colors are formed in a predetermined positional relationship prescribed for formation of a predetermined full-color image. Thereafter, in preparation for formation of new electrostatic latent images to be formed subsequently, the toner remaining on the surfaces of the photoconductive drums 1a to 1d is removed by the cleaning devices 5a to 5d.
The intermediary transfer belt 8 is wound around and between a follow roller 12 and a drive roller 13. When a belt driving motor (not illustrated) starts to rotate the drive roller 13, the intermediary transfer belt 8 starts to rotate counter-clockwise. The paper 26 is then transported from the pair of resist rollers 14 to the nip portion (secondary transfer nip portion) between the intermediary transfer belt 8 and the secondary transfer roller 9 arranged adjacent thereto with predetermined timing, so that, at the nip portion, the full-color toner image is transferred onto the paper 26. Having the toner images transferred onto it, the paper 26 is then transported to the fixing unit 7.
The paper 26 transported to the fixing unit 7 then, while passing through the nip (fixing nip portion) of a pair of fixing rollers 15, has heat and pressure applied to it so that the toner images are fixed on the surface of the paper 26 and thus the predetermined full-color image is formed. Having the full-color image formed thereon, the paper 26 is then directed into a desired transport direction by a transport guide member 21 arranged at a branching portion in a paper transport passage 19. The paper 26 is then, as it is (or after having been transported into a reversing transport passage 23 and subjected to double-side copying), ejected into an ejection tray 18 through a pair of ejection rollers 24.
Specifically, on the downstream side of the fixing rollers 15, the paper transport passage 19 branches into two, left and right, passages, one passage (the one branching to the left in
Next, the paper size detecting mechanism will be described.
Except for the paper size detecting mechanism 30, the paper feed cassette 10 involves no novel feature of the present invention; thus, the paper feed cassette 10 itself may be of any known design. Accordingly, no description will be given except for the paper size detecting mechanism 30. In a known paper feed cassette 10, paper 26 of a selected size is stacked in a state positioned by a pair of movably provided width restricting members 39a and 39b and the above-mentioned trailing edge restricting member 31.
At the outer circumferential portion 33a of the arc-shaped portion 40, a pair of radially protruding protrusions 43a and 43b are formed, with a recess 43c between them. The positions of the protrusions 43a and 43b and the recess 43c are determined according to the relationship between the position, depending on paper size, of the trailing edge restricting member 31 on the paper feed cassette 10 and the detecting member 35 with which the protrusions 43a and/or 43b makes contact when the paper feed cassette 10 is loaded. The contact relationship between the protrusions 43a and 43b and the detecting member 35 will be described later.
In a tip-end portion of the following arm portion 41, a guide hole 41a is formed which has an elongate shape extending radially from the swing center 32. In the guide hole 41a, a rod 31a provided on the trailing edge restricting member 31 is movably fitted. Thus, by moving the trailing edge restricting member 31 between the position (position A in
Specifically, as the trailing edge restricting member 31 is moved in the direction from position A to position E, the following member 33 swings clockwise; reversely, as the trailing edge restricting member 31 is moved in the direction from position E to position A, the following member 33 swings counter-clockwise.
The detecting plates 51a to 51c are, in upper-end portions thereof, integrally coupled to and supported on the main portion 50, are arranged side by side on the same plane as the main portion 50, and extend downward like cantilevers. The detecting plates 51a to 51c have, at a position a distance L1 away from their upper ends, projections T1, T2, and T3 formed respectively which project away from the loading direction X of the paper feed cassette 10.
Moreover, at a position a distance of L2 away from the upper ends of approximately one-half of the distance L1, on the reverse side of the faces where the projections T1, T2, and T3 are provided respectively, juts T4, T5, and T6 are formed respectively with which contacts S1 to S3 (see
Moreover, in a region from the lower ends of the detecting plates 51a to 51c to a position a distance L3 away therefrom which is approximately one-half of the distance L2, ribs 53 are formed. In the following description, a region from the upper ends of the detecting plates 51a to 51c respectively to the position the distance L3 away therefrom is referred to as a base-end portion R1, and a region from that position the distance L3 away to the lower ends of the detecting plates 51a to 51c respectively is referred to as a swing portion R2.
The ribs 53 formed in the swing portions R2 of the detecting plates 51a and 51c are composed of frame portions which are formed to surround the swing portions R2, and diagonal portions of which a plurality are formed inside those the frame portions. The ribs 53 formed in the detecting plate 51b are composed of a frame portion which is formed to surround the swing portion R2 and a vertical portion which vertically divides the frame portion into two parts. Thus, the ribs 53 are formed so as to be continuous in the lengthwise direction of the swing portions R2 or overlap as seen from an end parallel to the lengthwise direction, and the swing portions R2 of the detecting plates 51a to 51c are thicker than their base-end portions R1 by the thickness of the ribs 53.
Moreover, in the base-end portions R1 of the detecting plates 51a and 51c, two slits 55 are formed. The detecting member 35 has a plurality of (five) hook-shaped fitting legs 50a formed integrally therewith, and is fitted in place with those fitting legs 50a fitted in fitting holes 61 (see
When the contact 51 is pressed to the on position, an electrical signal is output via a connector CN-1. Likewise, when the contact S2 is pressed to the on position, an electrical signal is output via a connector CN-3, and when the contact S3 is pressed to the on position, an electrical signal is output via a connector CN-4. What is referred to as a multiple switch in the present specification is not limited to a single switch having a plurality of (here, three) contacts as shown in
In the cabinet of the image forming apparatus 100, to which the detecting member 35 is fitted, the multiple switch 37 is provided which has three contacts S1 to S3. Over the multiple switch 37, a prop 60 is horizontally provided which makes contact with the reverse side (the face where the juts T4 to T6 are formed) of the detecting member 35. The prop 60 is arranged to face a position on the detecting plates 51a to 51c slightly higher than the position of the distance L3.
When the paper feed cassette 10 is loaded into the cabinet of the image forming apparatus 100 and any of the detecting plates 51a to 51c deforms as a result of the corresponding one of the projections T1 to T3 being pressed by the protrusion 43a or 43b on the following member 33, the amount of deformation, that is, the movement stroke in the cassette loading direction X, is reduced to about one-half of L2/L1 and the result is transmitted via the juts T4 to T6 to the contacts S1 to S3 respectively.
Though not illustrated, in a case where a paper size smaller than that handled with the trailing edge restricting member 31 at position A is handled, the protrusions 43a and 43b are swung further counter-clockwise from their positions in
Likewise, in a case where a paper size larger than that handled with the trailing edge restricting member 31 at position E is handled, the protrusions 43a and 43b are swung further clockwise from their positions in
As described above, different paper sizes cause the trailing edge restricting member 31 to be located at different positions, and thereby cause the multiple switch 37 to output electric signals in different combinations. These electric signals from the connectors CN-1, CN-3, and CN-4 of the multiple switch 37 are fed to a controller (not illustrated) provided in the image forming apparatus 100 so that, by reading the combination of the electrical signals, the size of the paper in the paper feed cassette 10 is detected.
In this way, by use of a compact, inexpensive single multiple switch instead of a plurality of independent switches as conventionally used, by use of a following member 33 using no gears instead of a segment gear, an idle gear, a rack, etc. as conventionally used, and by use of a detecting member 35 made of an elastic material, it is possible to simplify the mechanism. It is also possible to achieve space saving. In particular, providing the detecting member 35 with detecting plates 51a to 51c formed as plate-shaped members like cantilevers makes it possible to read the loading stroke of the paper feed cassette 10 in smaller detection steps, and this helps make the multiple switch 37 compact. By use of the following member 33 using no gears and the multiple switch 37 that is inexpensive and can be made compact, it is possible to make the paper size detecting mechanism less costly.
In the first embodiment, the paper size detecting mechanism 30 is characterized in that slits 55 are formed in the base-end portions R1—which make contact with the prop 60—of the detecting plates 51a to 51c—which move into and out of contact with the contact S1 to S3, respectively, of the multiple switch 37—of the detecting member 35, and that ribs 53 are formed in the swing portions R2—which are located downward of the base-end portions R1—of the detecting plates 51a to 51c.
In the construction according to the first embodiment, the swing portions R2—on which the projections T1 to T3 and the juts T4 to T6 are formed—have parts thereof formed, with ribs 53, into thicker portions which are continuous in the lengthwise direction or overlap as seen from an end parallel to the lengthwise direction. This gives the swing portions R2 increased rigidity and makes them less easy to deform elastically. Consequently, the deformation of the detecting plates 51a to 51c resulting from contact with the protrusions 43a and 43b on the following member 33 concentrates in the base-end portions R1, and this makes the swing portions R2 less likely to undergo creep deformation.
On the other hand, the slits 55 reduce the rigidity of the base-end portions R1, and make their elastically deformable range wider (make them easier to elastically deform) than that of the swing portions R2. Even so, since their deformation is restricted by contact with the prop 60, the base-end portions R1 are unlikely to undergo creep deformation beyond the limit within which it can restore from elastic deformation. Moreover, owing to the reduced rigidity of the base-end portions R1, even when the base-end portions R1 undergo creep deformation, the detecting plates 51a to 51c return to their positions before contact under the restoring force of the contacts S1 to S3 of the multiple switch 37. Thus, it is possible, with a simple construction, to make the elastically deformable range of the base-end portions R1 wider than that of the swing portions R2. This improves the response of the detecting plates 51a to 51c to the movement of the protrusions 43a and 43b into and out of contact with them, and thus helps effectively prevent erroneous detection of paper size.
In general, with most materials, deforming them slightly (within the elastic range) does not disable them from restoring their original shape. Deformation within a range in which a material retains elasticity is called elastic deformation. When deformation goes out of that range, that is, beyond a certain limit (yield point), it no longer is in a range of elastic deformation but is in a range of creep deformation from where the original shape cannot be restored. In the present specification, “elastically deformable range” denotes the range of deformation between the original shape to the yield point.
Moreover, in the detecting plates 51a and 51c, giving the base-end portions R1 smaller widths than the swing portions R2 makes the base-end portions R1 easier to deform. Although, here, slits 55 are formed only in the base-end portions R1 of the detecting plates 51a and 51c, similar slits 55 may also be formed in the base-end portion R1 of the detecting plate 51b. Alternatively, ribs 53 and slits 55 may be formed only, of the detecting plates 51a to 51c, the one (for example, the detecting plate 51a) which is pressed by the outer circumferential portion 33a of the arc-shaped portion 40 when the following member 33 is located at the position corresponding to the most frequently used paper size. Moreover, forming a plurality of slits 55 parallel to the lengthwise direction of the detecting plates 51a and 51c, as compared with forming slits perpendicularly to the lengthwise direction, helps effectively reduce the rigidity of the swing portions R2 while maintaining the durability of the base-end portions R1.
The sheet of metal 70 has a plurality of through holes formed therein; bosses 53 formed on the main portion 50 and the swing portions R2 are put through those through holes and formed into fused portions 71, so that the base-end portions R1 and the main portion 50, and also the base-end portions R1 and the swing portions R2, are fixed together. As in the first embodiment, ribs 53 are formed in the swing portions R2. The structures of the components other than the paper size detecting mechanism, such as the following member 33 and the multiple switch 37, and the relationship between the following member 33 and the detecting member 35 to handle different paper sizes, are similar to those in first embodiment, and therefore no overlapping description will be repeated.
In the paper size detecting mechanism 30 according to the second embodiment, forming the base-end portions R1 out of an elastic sheet of metal 70 makes the elastically deformable range of the base-end portions R1 wider than that of the swing portion R2, and also increases the strength of the base-end portions R1 against heat creep and their fatigue limit against repeated elastic deformation. Thus, it is possible to more effectively suppress creep deformation of the detecting plates 51a to 51c during transport or storage of the image forming apparatus 100 in high-temperature environments, and thereby to surely prevent erroneous detection of paper size. Suitable examples of the sheet of metal 70 of which the base-end portions R1 are formed include a sheet of stainless (SUS) with a high limit of elasticity and a sheet of stainless steel for springs (SUS304CSP).
Instead of putting the bosses 53 on the main portion 50 and the swing portions R2 through the through holes in the base-end portions R1 and forming them into the fused portions 71, it is possible, when the main portion 50 and the swing portions R2, which are formed of resin, are molded, to place a sheet of metal 70 to serve as the base-end portions R1 inside the mold and form, at the same time that the main portion 50 and the swing portion R2 are molded, the fused portions 71, so as to thereby form the base-end portions R1 integrally with the main portion 50 and the swing portions R2. This helps reduce the number of steps to produce the detecting member 35. On the other hand, fusing and fixing the base-end portions R1 to the main portion 50 and the swing portions R2 after the molding of the main portion 50 and the swing portions R2, which are made of resin, helps simplify the structure of the mold used to mold the main portion 50 and the swing portion R2.
Although, here, the base-end portions R1 of the detecting plates 51a to 51c are all formed of a sheet of metal 70, it is possible to form, out of a sheet of metal 70, not all of the detecting plates 51a to 51c but only the one (for example, the detecting plate 51a) which is pressed by the outer circumferential portion 33a of the arc-shaped portion 40 when the following member 33 is located at the position corresponding to the most frequently used paper size.
It should be understood that the present invention is not limited by the embodiments specifically described above, and that many variations and modifications are possible without departing from the spirit of the present invention. For example, although, in the embodiments described above, two protrusions 43a and 43b are provided in the outer circumferential portion 33a of the following member 33, any number of, namely one or two or more, protrusions may be provided depending on the number of different paper sizes to be detected.
Although, in the first embodiment described above, ribs 53 are formed on the swing portions R2 to increase the rigidity of the swing portions R2, instead, for example, part or the whole of the swing portions R2 may be made thicker than the base-end portions R1 continuously in the lengthwise direction or so as to overlap in the direction perpendicular to the lengthwise direction, in order to increase the rigidity of the swing portions R2. Forming a rib-like thicker portion as in the first embodiment, as compared with making the entire swing portions R2 thicker, helps reduce the amount of resin constituting the detecting member 35.
Although, in the embodiments described above, an auto-recovery multiple switch 37 is used, it is also possible to couple the contacts S1 to S3 of the multiple switch 37 to the detecting plates 51a to 51c of the detecting member 35 by an appropriate means and use a simpler switch of a non-auto-recovery type.
An embodiment of the present invention can be used in a paper size detecting mechanism mounted on a paper feed cassette unloadably loaded in an image forming apparatus. By use of the present invention, it is possible to realize, easily and inexpensively, a paper size detecting mechanism that can effectively prevent erroneous detection of paper size due to creep deformation of a detecting member.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2010-252466 | Nov 2010 | JP | national |
| 2011-023475 | Feb 2011 | JP | national |
