Image reading apparatus

An image reading apparatus incudes a guiding shaft extending in an axial direction; a reading portion supported by the shaft so as to be movable in the axial direction; a casing accommodating the reading portion, the casing including a first supporting portion supporting an end portion of the shaft and a second supporting portion supporting the other end portion of the shaft; and an elastically deformable bonding portion bonding the casing and the shaft with each other, the bonding portion being provided between the first supporting portion and the second supporting portion in the axial direction and between the casing and the shaft in a diametrical direction perpendicular to the axial direction. The shaft is supported by the first supporting portion, the second supporting portion and the bonding portion, without contact to the casing except for the first supporting portion and the second supporting portion.

FIELD OF THE INVENTION AND RELATED ART

The present invention relates to an image reading apparatus which reads an image on a sheet of recording medium.

There has been proposed an image reading apparatus having: a casing; a guide rail supported by the casing; and an image reading unit which moves in the secondary scan direction while being guided by the guide rail (Japanese Laid-open Patent Application No. 2015-119421). The casing is provided with a pair of positioning ribs, and ribs for adhesive. The guide rail is supported by the pair of positioning ribs from their underside. Further, the ribs for adhesive are positioned between the pair of positioning ribs, and the top surface of each rib for adhesive is coated with adhesive, with which the guide rails are adhered.

The casing and pair of positioning ribs disclosed in Japanese Laid-open Patent Application No. 2015-119421 are parts of a monolithic component. Therefore, it sometimes occurs that as the casing deforms, the pair of positioning ribs displaces toward the guide rail.

The guide rail is directly in contact with the pair of positioning ribs. Therefore, it is possible that the displacement of the pair of positioning ribs will be transmitted to the guide rail, and cause the guide rail to deform. If the guide rail deforms, it becomes impossible for the image reading unit, which is guided by the guide rail, to accurately read the image on a sheet of recording medium.

SUMMARY OF THE INVENTION

An object of the present invention is to provide an image reading apparatus which can more accurately read an image on a sheet of recording medium than any conventional image reading apparatus.

According to an aspect of the present invention, there is provided an image reading apparatus comprising: a guiding shaft extending in an axial direction; a reading portion supported by said guiding shaft so as to be movable in the axial direction; a casing accommodating said reading portion, said casing including a first supporting portion supporting an end portion of said guiding shaft and a second supporting portion supporting the other end portion of said guiding shaft; and an elastically deformable bonding portion bonding said casing and said guiding shaft with each other, the bonding portion being provided between said first supporting portion and said second supporting portion in the axial direction and between said casing and said guiding shaft in a diametrical direction perpendicular to the axial direction, wherein said guiding shaft is supported by said first supporting portion, said second supporting portion and said bonding portion, without contact to said casing except for said first supporting portion and said second supporting portion.

DESCRIPTION OF THE EMBODIMENTS

The present invention is described, with reference to the image forming apparatus A in one of the preferred embodiments of the present invention, and appended drawings. By the way, the image reading apparatus in this embodiment is described as a stand-alone image reading apparatus. However, not only is the present invention applicable to a stand-alone image reading apparatus as an image scanner, but also, an image reading apparatus which is an integral part of such an image forming apparatus as a copying machine, a printing machine, a facsimileing machine, or a multifunction machine capable of functioning as one or more of the preceding machines.

Further, in this embodiment, an “original” includes not only an image formed on a sheet of ordinary paper, but also, an image formed on a special paper such as a coated paper, an image formed on recording media such as an envelop and a sheet of index paper, which are specific in shape, an image formed on a sheet of plastic for an overhead projector, and an image formed on fabric. In addition, an original includes a sheet of white paper, a sheet of recording medium having an image on one of its two surfaces, a sheet of recording medium having an image on both of its surfaces.

Referring toFIGS. 1 and 2, the image reading apparatus101has: a casing1; and a glass platen2for an original, which is in the top portion of the casing1. The casing1is in the form of a box having an internal space. It is formed of a metallic material such as a sheet of metallic plate. It functions as the frame of the image reading apparatus101.

Disposed in the internal space of the casing1are: a guide shaft5, which extends in the shaft direction AD, which is parallel to the secondary scan direction; a gear pulley7; a pair of pulleys8aand8b; a drive belt9which is wrapped around the combination of the gear pulley7and pulleys8aand8b; and a reading portion3. The gear pulley7is driven by a motor4supported by the casing1. As the gear pulley7is driven by the motor4, the drive belt9rotationally moves.

Not only is the reading portion3supported by the drive belt9and guide shaft5, but also, guided by the guide shaft5in the shaft direction AD. Further, also disposed in the internal space of the casing1is an unshown detecting portion which detects whether or not the reading portion3is in its standby position in which it is to be when it is not reading an image.

In this embodiment, the standby position of the reading portion3coincides with the left end of the internal space of the casing1inFIGS. 1 and 2. When the reading portion3is in its standby position, it reads (detects) the edge of the original on the glass platen2for an original. When the reading portion3is on standby before a job for reading the image of an original is inputted, it remains on standby in its standby position.

The reading portion3has: an unshown carriage which holds an image sensor and other internal components; an unshown light source for casting light on an original. The image sensor has electrical connection to an unshown control portion through an unshown FFC (flexible flat cable) which is in the form of a belt. The information obtained by the reading of an original by the image sensor is transmitted to the control portion.

As an original is set on the glass platen2, and a scan job is started, the drive belt9is driven by the motor4. As the drive belt9is driven, the reading portion3which is supported by the drive belt9, is moved from its standby position in the shaft direction AD along the guide shaft5. During this movement of the reading portion3, the original on the glass platen2is scanned (original is read) by the reading portion3.

As the reading portion3moves to a preset position which corresponds to the size of the original, the motor4begins to be driven in reverse. As a result, the drive belt9begins to rotate in reverse. Thus, the reading portion3returns to its standby position, ending the reading operation.

[Structure for Supporting Guide Shaft]

Next, the structural arrangement for supporting the guide shaft5is described in detail.FIG. 3is a perspective view of one51(or other52) of the lengthwise end portions of the guide shaft5, and its adjacencies, in terms of the shaft direction AD. The lengthwise end portions51and52are similar in the structural arrangement by which they are supported.

FIG. 4is a sectional view of the end portion of the guide shaft, and its adjacencies, shown inFIG. 3, at a plane A-A inFIG. 3.FIG. 5is a sectional view of the reading apparatus, at a plane B-B inFIG. 2. Referring toFIGS. 3 and 4, a lateral wall1a, which is one of the lateral walls of the casing1in terms of the shaft direction AD, is provided with a hole61, in which the end portion51of the guide shaft5is fitted to be supported by the lateral wall1a. Similarly, the other lateral wall1bof the casing1, in terms of the shaft direction AD, is provided with a hole62, as the second supporting portion, in which the other end portion of the guide shaft5is fitted to be supported by the lateral wall1b.

The end portions51and52of the guide shaft5are prevented by a pair of fixing members, such as E-shaped locking rings, from coming out of the holes61and62of the lateral walls, respectively, that is, from becoming disengaged from the lateral walls. By the way, all that is necessary is that at least one of the end portions51and52is kept locked to the corresponding lateral wall of the casing1by a fixing member. As described above, the guide shaft5is precisely positioned relative to the casing1, in terms of the shaft direction AD, and also, the radius direction of the guide shaft5, which is perpendicular to the shaft direction AD.

On the other hand, referring toFIGS. 1 and 2, the bottom wall1cof the casing1, which is below the guide shaft5, is provided with multiple (three, in this embodiment) protrusive portions16,17, and18, which protrude upward toward the guide shaft5. The protrusive portions16,17, and18are formed by crimping, for example. They are positioned directly below, being aligned in the shaft direction AD, with the provision of a preset amount of interval between the adjacent two. Further, in terms of the shaft direction AD, the protrusive portions16,17, and18are positioned between the holes61and62, in such a manner that they divide the portion of the guide shaft5, which is between the holes61and62, into four sections, which are equal in length.

The top surface (16a, for example, inFIG. 5) of each of the protrusive portions16,17and18is provided with a preset amount of adhesive (19,20or21), which makes up an adhesive portion25. The adhesives19,20and21also are positioned directly below the guide shaft5, like the protrusive portions16,17and18, being aligned in the shaft direction AD with the provision of a preset amount of gap between the adjacent two. For example, in terms of the shaft direction AD, the adhesive20, as the second adhesive, is positioned a preset distance from the adhesive19as the first adhesive. Also, in terms of the shaft direction AD, the adhesives19,20and21are positioned between the holes61and62, in such a manner that they divide the length of the portion of the guide shaft5between the holes61and62, into four sections which are roughly equal in length.

In terms of the direction which is parallel to the radial direction of the guide shaft5, which is perpendicular to the shaft direction AD, as well as the vertical direction, the adhesives19,20and21are positioned between the protrusive portions16,17and18, which are integral parts of the casing1, and the guide shaft5, in such a manner that they hold the protrusive portions16,17and18and guide shaft5together, while remaining elastic. The adhesives19,20and21have only to be elastically deformable after they harden. That is, the adhesives19,20and21do not need to be controlled in material, and the ingredients thereof, as long as they remain elastically deformable after they harden. For example, ordinary adhesive which hardens in the air, UV adhesive which is curable with UV light, thermoplastic adhesive, etc., are usable as the adhesives19,20and21.

By the way, in this embodiment, the number of the protrusive portions16,17and18and that of the adhesives19,20and21are both three. This embodiment, however, is not intended to limit the present invention in scope in terms of the number of the protrusive portions and that of the adhesives. They may be one, two, or four or more.

As described above, the guide shaft5is supported by the adhesive portion25. Therefore, it is not in direct connection to the casing1, except for the portions which correspond in position to the portions of the casing1, which have the holes61and62, one for one. In other words, the guide shaft5is directly supported by only the portions of the casing1, which correspond in position to the holes61and62. By the way, the image reading apparatus101may be structured so that the guide shaft5is supported by something other than the casing1. For example, the image reading apparatus may be structured so that the guide shaft5is supported by springs or sponges.

By the way, there are various types thinkable for the reading portion3depending on the specifications of an apparatus in which the reading portion3is mounted, and also, what kind of optical system employed by the reading portion3, for example, a reduction optical system or a contact optical system. The reading portion of a reduction optical system has: multiple optical mirrors, optical lenses, an imaging element, and an illuminating apparatus having multiple light sources. The reading portion of a contact optical system is smaller than a reduction optical system. It has a lens assembly, an imaging element, an illuminating apparatus, and a small casing in which preceding components are mounted. That is, an apparatus for which the reading portion3is employed is variable in the size of each components of the apparatus, and component count, depending on its specification. Therefore, the reading portion3is variable in size and weight depending on the specifications of an apparatus.

Referring toFIG. 5, the reading portion3has a holding portion10, which is supported by the guide shaft5in such a manner that it is movable in the shaft direction AD. The holding portion10is loosely fitted around the guide shaft5. Therefore, the level of accuracy at which an image is read by the reading portion3is affected by how straight the guide shaft5is. In other words, as the guide shaft5deforms, the reading portion3reduces in the level of accuracy at which it can reads an image.

A reading portion varies in size and weight depending on its type. As a scanning job is started, the reading portion3moves in the shaft direction AD. Thus, the guide shaft5is subjected to a certain amount of load, which is attributable to the vibrations caused by the moment which occurs as the reading portion3moves, and the weight of the reading portion3itself. Referring toFIGS. 1-5, the load to which the guide shaft5is subjected is caught by the adhesives19,20and21, which are between the holes61and62. Thus, the guide shaft5is prevented from bowing downward. Therefore, the reading portion3is prevented from reducing in the level of accuracy at which it reads an image.

Further, even if the bottom wall1cof the casing1deforms, and/or a user gives vibrations or the like to the casing1, the adhesives19,20and21, which are formed so that they can elastically deform, absorb these deformations and vibrations. For example, if the bottom wall1cof the casing1deforms in such a manner that its center portion displaces upward, the protrusive portions16,17and18, with which the casing1is provided, move upward toward the guide shaft5. However, the adhesives19,20and21, which are provided between the protrusive portions16,17and18and guide shaft5absorb the displacement of the protrusive portions16,17and18. Therefore, the guide shaft5is prevented from deforming. Therefore, the reading portion3is prevented from being reduced in its reading performance.

In this embodiment, the adhesives19,20and21have lengths L1, L2and L3, respectively, in terms of the shaft direction AD. Further, the lengths L1, L2and L3of the adhesives19,20and21, respectively, are set so that a sum (L1+L2+L3) of the lengths of the adhesives19,20and21becomes no more than ⅓ of the length L4(FIG. 2) of the guide shaft5.

Therefore, it is possible to provide the image reading apparatus100with areas R1, R2, R3and R4, which are between the holes61and62, and in which the guide shaft5is directly supported by the adhesives19,20and21. In these areas R1, R2, R3and R4, the guide shaft5does not catch the deformation and/or vibrations of the casing1. Therefore, it is possible to effectively prevent the deformation of the guide shaft5to prevent the reading portion3from reducing in its reading performance.

Further, in terms of the vertical direction VD, the adhesives19,20and21have a thickness of 0.5 mm-3.0 mm. It is preferable that in terms of the vertical direction VD, the adhesives19,20and21have a thickness of 1.0 mm-2.5 mm. In this embodiment, they have a thickness of 1.7 mm. Further, the adhesives19,20and21are lower in rigidity than the casing1formed of a metallic material. Therefore, the adhesives19,20and21can effectively absorb the displacement of the protrusive portions16,17and18. Therefore, this embodiment can prevent the reading portion3from reducing in image reading performance.

As described above, not only is the downward deformation of the guide shaft5, which is attributable to the weight and vibrations of the reading portion3itself prevented by the adhesives19,20and21, but also, the upward displacement of the protrusive portions16,17and18, which is attributable to the deformation and vibrations of the casing1is absorbed by the adhesives19,20and21. Therefore, the guide shaft5is prevented from deforming, and the reading portion3is prevented from reducing its reading performance.

Further, all that is necessary to embody the present invention is to fit the guide shaft5into the holes61and62after the application of adhesives19,20and21to the protrusive portions16,17and18, respectively. That is, this embodiment can improve a reading portion in the efficiency with which it can be assembled. Further, this embodiment can reduce the guide shaft5in the amount of deformation, without requiring other elastic members, such as leaf springs and sponges, than the adhesives19,20and21, to be placed between the guide shaft5and bottom wall1cof the casing1. Thus, this embodiment can reduce a reading portion in cost and size.

In this embodiment, the casing1was formed of a metallic material. This embodiment, however, is not intended to limit the present invention in scope in terms of the material for the casing1. For example, the present invention is compatible with a casing formed of a resinous material. Further, in this embodiment, the guide shaft5was cylindrical. This embodiment, however, is not intended to limit the present invention in scope in terms of the shape of the guide shaft5. That is, the present invention is also compatible with a guide shaft which is oval or polygonal, in cross-section.

This application claims the benefit of Japanese Patent Application No. 2019-216152 filed on Nov. 29, 2019, which is hereby incorporated by reference herein in its entirety.