Development device

A development device includes a first frame and a second frame. The second frame is configured to be combined with the first frame by fixing first, second and third walls of the first frame to the second frame. The first and second walls are disposed opposite to each other, and the third wall is configured to connect the first and second walls. An opening is formed by the combined first and second frames. The first frame includes first and second engageable portions, and the second frame includes third and fourth engageable portions, such that engagement of the first and second engageable portions with the third and fourth engageable portions brings the first and second frames into alignment. The first and second engageable portions are disposed between the first wall and the second wall.

CROSS-REFERENCE TO RELATED APPLICATION(S)

This application claims priority from Japanese Patent Application No. 2011-186879 filed on Aug. 30, 2011, the disclosure of which is incorporated herein by reference in its entirety.

FIELD

Apparatuses consistent with one or more aspects of the present invention relate to a development device comprising two frames fixed together.

BACKGROUND

A development device such as a development cartridge for use in an image forming apparatus may be configured to comprise a lower frame and an upper frame wherein the lower frame includes right and left sidewalls, and bottom and rear walls which connect the right and left sidewalls. When the upper frame is welded on an upper surface of the lower frame (i.e., upper surfaces of the right and left sidewalls and the rear wall), an opening and a toner reservoir are formed therein.

In such a development device, a boss and a corresponding boss hole may be formed on an upper surface of each sidewall of the lower frame and in the upper frame, respectively, so that the boss and the boss hole are engaged with each other to place the upper and lower frames in alignment.

In order to provide sufficient areas of faying surfaces of the both frames, it may be preferable that the boss or like structures formed on the upper surface (i.e., faying surface) of the lower frame be dispensed with. Sufficient areas of faying surfaces could be made on the upper surface of the lower frame by thickening part of the sidewalls of the lower frame; however, this would disadvantageously increase the size of the development device.

There is a need to provide a developing device in which the size of the device can be reduced while ensuring that sufficient areas of the faying surfaces are provided.

SUMMARY

It is one aspect to provide a development device in which the aforementioned need is satisfied.

More specifically, according to one or more embodiments of the present invention, a development device which comprises a first frame and a second frame is provided. The first frame includes a first wall, a second wall, a third wall, a first engageable portion and a second engageable portion. The second wall is disposed opposite to the first wall. The third wall is configured to connect the first wall and the second wall. The second frame is configured to be combined with the first frame by fixing the first wall, the second wall and the third wall of the first frame to the second frame. An opening is formed by the combined first and second frames. The second frame includes a third engageable portion and a fourth engageable portion, such that engagement of the first engageable portion with the third engageable portion and engagement of the second engageable portion with the fourth engageable portion brings the first frame and the second frame into alignment. The first engageable portion and the second engageable portion are disposed between the first wall and the second wall.

DESCRIPTION OF EMBODIMENTS

A detailed description will be given of an illustrative embodiment of the present invention with reference to the drawings. In the following description, a general setup of a laser printer1(image forming apparatus) in which a development cartridge7as an example of a development device configured according to the present embodiment is installed will be described at the outset, and then features relating to the development cartridge7will be described in detail.

Hereinbelow, the direction is designated as from the viewpoint of a user who is using (operating) the laser printer1. To be more specific, inFIG. 1, the right-hand side of the drawing sheet corresponds to the “front” side of the printer, the left-hand side of the drawing sheet corresponds to the “rear” side of the printer, the front side of the drawing sheet corresponds to the “left” side of the printer, and the back side of the drawing sheet corresponds to the “right” side of the printer. Similarly, the direction of a line extending from top to bottom of the drawing sheet corresponds to the “vertical” or “up/down (upper/lower or top/bottom)” direction of the printer.

<General Setup of Laser Printer>

As shown inFIG. 1, the laser printer1comprises a body casing2, and several components housed within the body casing2which principally include a sheet feeder unit3configured to feed a sheet S (e.g., of paper), an exposure device4, a process cartridge5configured to transfer a toner image (developer image) onto the sheet S, and a fixing device8configured to thermally fix the toner image on the sheet S.

The sheet feeder unit3is provided in a lower space within the body casing2, and principally includes a sheet feed tray31, a sheet pressure plate32, a sheet feed mechanism33and a registration roller34. Sheets S stored in the sheet feed tray31are pushed up by the sheet pressure plate32, and one sheet S separated from the others is fed by the sheet feed mechanism33toward the process cartridge5, and passes through the registration roller34in which the sheet S is aligned in registration and gets ready to be conveyed into an interface between a photoconductor drum61and a transfer roller63in a photoconductor cartridge6.

The exposure device4is provided in an upper space within the body casing2, and principally includes a laser beam emitter (not shown), a polygon mirror, lenses and reflecting mirrors (shown in part, but indication with reference characters omitted). The exposure device4is configured to cause a laser beam produced based upon image data by the laser beam emitter to travel along a path indicated by alternate long and short dashed lines, so that a peripheral surface of the photoconductor drum61is rapidly scanned and illuminated consecutively with the laser beam.

The process cartridge5is disposed below the exposure device4within the body casing2, and configured to be installable in and removable from the body casing2through an opening formed when a front cover21provided at the body casing2is swung open. The process cartridge5includes a photoconductor cartridge6and a development cartridge7.

The photoconductor cartridge6principally includes a photoconductor drum61, a charger62and a transfer roller63.

The development cartridge7is configured to be detachably attachable to the photoconductor cartridge6, and thus is removably installable together with the photoconductor cartridge6(i.e., as a part of the process cartridge5) in the body casing2. The development cartridge7principally includes a development roller71, a supply roller72, a doctor blade73, a toner reservoir74which is configured to store toner (as an example of developer) therein, and an agitator75.

In the process cartridge5, the peripheral surface of the photoconductor drum61is uniformly charged by the charger62, and then exposed to a rapidly sweeping laser beam from the exposure device4so that an electrostatic latent image formulated based upon image data is formed on the photoconductor drum61. Meanwhile, toner in the toner reservoir74is being agitated by the agitator75, and is supplied first to the supply roller72and then from the supply roller72to the development roller71. As the development roller72rotates, the toner goes through between the development roller71and the doctor blade73so that a thin layer of toner having a predetermined thickness is carried on the development roller71.

The toner carried on the development roller71is supplied from the development roller71to the electrostatic latent image formed on the photoconductor drum61. Accordingly, the electrostatic latent image is visualized and a toner image is formed on the photoconductor drum61. Thereafter, while a sheet S is conveyed through between the photoconductor drum61and the transfer roller63, the toner image on the photoconductor drum61is transferred onto the sheet S.

The fixing device8is disposed rearwardly of the process cartridge5. The fixing device8principally includes a heating unit81and a pressure roller82. The heating unit81includes a halogen heater, a fixing belt, a nip plate and other components which are shown but of which indication with reference characters is omitted. The pressure roller82is disposed opposite to the nip plate of the heating unit81and configured to be pressed against the nip plate so that the fixing belt of the heating unit81is nipped between the pressure roller82and the nip plate of the heating unit81. In the fixing device8, a sheet S with a toner image transferred thereon is conveyed through between the pressure roller82and the heated fixing belt of the heating unit81, so that the toner image is thermally fixed on the sheet S. The sheet S with the toner image thermally fixed thereon is ejected by a sheet ejection roller23onto a sheet output tray22.

<Detailed Structure of Development Cartridge>

As shown inFIG. 2, the development cartridge7includes, in addition to the aforementioned components71-75, a lower frame100as an example of a first frame, an upper frame as an example of a second frame, a left extension portion300L as an example of a first extension portion, and a right extension portion300R as a second extension portion (see alsoFIG. 3).

As shown inFIG. 3, the lower frame100principally includes a left sidewall110as an example of a first wall, a right sidewall120as an example of a second wall, and a bottom wall130and a front wall140as an example of a third wall.

The left sidewall110and the right sidewall120are disposed opposite to each other, facing in a leftward-and-rightward direction (the direction of an axis of rotation of the development roller71). Lower ends of the left and right sidewalls110,120are connected by the bottom wall130, and front sides of the left and right sidewalls110,120are connected by the front wall140. Upper surfaces111,121,141of the left sidewall110, the right sidewall120and the front wall140are continuously configured as a single flat surface shaped generally like a letter U as viewed in plan view, so as to provide a weld surface W as an example of a faying surface to be fixed to a faying surface of the upper frame200which will be described later in detail.

The left sidewall110includes a left mount portion150L as an example of a first mount portion, and the right sidewall120includes a right mount portion150R as an example of a second mount portion. The left and right mount portions150L,150R are portions to which the doctor blade73(blade assembly400) is fixed. The left mount portion150L is formed to protrude upward from a rear end portion of the upper surface111(weld surface W) of the left sidewall110, and the right mount portion150R is formed to protrude upward from a rear end portion of the upper surface121(weld surface W) of the right sidewall120.

Each of the left mount portion150L and the right mount portion150R has a screw hole152provided in a rear surface151(surface facing to a side on which the development roller71is to be provided) thereof, so that the blade assembly400will be fixed to the left and right mount portions150L,150R by screws B, as shown inFIG. 4.

As shown inFIG. 5, the blade assembly400principally includes a doctor blade73, a blade holder420, and a blade reinforcing plate430.

The doctor blade73includes a plate member73A made of a metal plate shaped substantially like a rectangle, and a pressing member73B made of rubber. The pressing member73B is provided on a rear side of a lower-end portion of the plate member73A, and configured to bulge rearwardly (toward the development roller71). The pressing member73B of the doctor blade73in operation is brought into contact with the development roller71being caused to rotate, and the thickness of toner on the peripheral surface of the development roller71is regulated while the peripheral surface of the rotating development roller is sliding on the doctor blade73.

The blade holder420is formed by bending a metal plate substantially into the shape of a letter L as seen in side view, and principally includes a holding portion421extending in the upward-and-downward direction ofFIG. 5, a connecting portion422extending in the leftward-and-rightward direction ofFIG. 5, and a pair of attachment portions423extending upward from the left and right ends of the holding portion421(see alsoFIG. 4). The blade reinforcing member430is formed by bending a metal plate substantially into the shape of a letter L as seen in side view, and principally includes a holding portion431extending in the upward-and-downward direction ofFIG. 5, and a connecting portion432extending in the leftward-and-rightward direction ofFIG. 5.

The blade assembly400is an assembly made by holding an upper-end portion of the doctor blade73(the plate member73A thereof) by the holding portions421,431and fastening the connecting portions422,432together by screws440. The blade assembly400is fixed to the lower frame100by screws B applied to the left and right attachment portions423of the blade holder420positioned in alignment with the left and right mount portions150L,150R, respectively, of the lower frame100.

In the present embodiment, the doctor blade43can be fixed on a surface substantially parallel to a tangent plane which contains a line of contact of the doctor blade with the peripheral surface of the development roller71, that is, on a plane PL substantially parallel to the direction of extension of the plate member73A on which the pressing member73B is provided.

An alternative arrangement of the doctor blade is known in which a plate member is shaped, by bending, substantially like a letter L in side view such that the plate member includes a first portion having a surface to which a pressing member is attached and a second portion having a surface at which the doctor blade is fixed to a frame, the second portion extending in a direction different from a direction of extension of the first portion. However, such a bent-plate configuration of the doctor plate would, in some instances, lead to undesirable variations in the contact pressure of the doctor blade against the development roller due to tolerances involved in the bending process during manufacturing. In contrast, in the present embodiment, the plate member73A is not bent, and thus such variations in the contact pressure as derived from the tolerances involved in the bending process are eliminated.

In the present embodiment, each of the left and right mount portions150L,150R has a protruding portion that protrudes upward from the weld surface W; therefore, a distance between the lower-end portion of the doctor blade73(plate member73A) and each attachment portion423can be increased, so that deformation of the doctor blade73, particularly of a portion thereof at or around the lower-end portion of the plate member73A, which would be caused by tightening the screws B can be suppressed. Accordingly, undesirable variations in the contact pressure of the doctor blade73against the peripheral surface of the development roller71can be reduced.

As shown inFIG. 3, the left extension portion300L is disposed to extend from a rear end of a surface, facing inward in the leftward-and-rightward direction (i.e., right side; inner side), of the left sidewall110inwardly toward the right sidewall120, and the right extension portion300R is disposed to extend from a rear end of a surface, facing inward in the leftward-and-rightward direction (i.e., left side; inner side), of the right sidewall120inwardly toward the left sidewall110. To be more specific, the left extension portion300L is disposed adjacent to, and inward (in the leftward-and-rightward direction) of, the left mount portion150L, and the right extension portion300R is disposed adjacent to, and inward (in the leftward-and-rightward direction) of, the right mount portion150R.

Each of the left extension portion300L and the right extension portion300R principally includes an upper wall310and a plurality of first ribs320.

An upper surface311of the upper wall310is contiguous and flush with upper surfaces111,121(weld surfaces W) of the left sidewall110and the right sidewall120.

A left boss330L, as an example of a first engageable portion configured as a projection, which is shaped generally like a circular cylinder protruding upward is provided on the upper surface311of the upper wall310of the left extension portion300L. A right boss330R, as an example of a second engageable portion configured as a projection, which is shaped generally like a circular cylinder protruding upward is provided on the upper surface311of the upper wall310of the right extension portion300R.

In other words, the left boss330L and the right boss330R are disposed between the left sidewall110and the right sidewall120, and between the left mount portion150L and the right mount portion150R (i.e., disposed inward, in the leftward-and-rightward direction, of the left and right mount portions150L,150R).

As shown inFIG. 5, the first ribs320are configured to protrude from the undersurface of the upper wall310downward and to extend in the leftward-and-rightward direction. To be more specific, each of the first ribs320is disposed to extend downward when the development cartridge7is operational. The term “operational” used herein refers to the state in which the device is able to function or be used. In this embodiment, it is understood that the development cartridge7is operational when the development cartridge7is installed in the body casing2of the laser printer1(seeFIG. 1).

The first ribs320serves to reinforce the extension portions300L,300R (upper walls310thereof). Also, the arrangement and configuration of the first ribs320as described above serve to reduce the possibility that developer fed into a space under each extension portion300L,300R would get retained or accumulated between the ribs320.

As shown inFIG. 3, the upper frame200comprises a main body210shaped substantially like a plate, and several portions provided in or on the main body210which include a left boss hole220L as an example of a third engageable portion, a right boss hole220R as an example of a fourth engageable portion, a beam-like portion230, a weld rib240(seeFIG. 6), and a second rib250.

The upper frame200is configured to be combined with the lower frame100by welding the left sidewall110, the right sidewall120and the front wall140of the lower frame100to the lower frame100, and an opening A through which toner is to be supplied to the development roller71, and a toner reservoir74are formed by the combined lower and upper frames100,200, as shown inFIG. 4. The development roller71is disposed opposite to the opening A formed by the lower frame100and the upper frame200(seeFIG. 4).

Referring again toFIG. 3, the main body210has cutaways211formed by cutting off left and right corners at a rear side thereof. The cutaways211are so shaped as to allow the left mount portion150L and the right mount portion150R to be fitted in the left and right cutaways211, respectively, when the upper frame200is combined with the lower frame100(seeFIG. 4).

The left boss hole220L is a through hole engageable with the left boss330L provided in the lower frame100, and is disposed on the right side (inward, in the leftward-and-rightward direction) of the left cutaway211. The right boss hole220R is a through hole engageable with the right boss330R provided in the lower frame100, and is disposed on the left side (inwardly, in the leftward-and-rightward direction) of the right cutaway211.

The beam-like portion230is a portion protruding downward from the rear side of the main body210between the left boss hole220L and the right boss hole220R (inward thereof in the leftward-and-rightward direction). As shown inFIG. 4, the beam-like portion230has left and right sides which come in contact with inner surfaces, in the leftward-and-rightward direction, of the extension portions300L,300R, respectively, when the upper frame200is combined with the lower frame100, so that the opening A is formed by the beam-like portion230, the extension portions300L,300R, the left sidewall110, the right sidewall120and the bottom wall130.

As shown inFIG. 6, the weld rib240is formed on the underside of the upper frame200, and extends on a rear side of the main body210from a spot located between the left boss hole220L and the beam-like portion230, running along the edges (the left side, the front side and the right side) of the main body210, to a spot located between the right boss hole220R and the beam-like portion230. The weld rib240provides a surface to be welded to the weld surface W of the lower frame100.

As shown inFIG. 3, the second rib250is formed on the top side of the main body210, protruding upward, extending along the rear side of the main body210in the leftward-and-rightward direction. In other words, the second rib250extends in the leftward-and-rightward direction along one end401of the doctor blade73(more precisely, of the blade assembly400) opposite to another end of the blade assembly400which is disposed to come in contact with the development roller71(i.e., the lower end of the doctor blade73).

The second rib250serves to reinforce the upper frame200. Also, the arrangement and configuration of the second rib250as described above serve to prevent a user from inadvertently touching the end401of the blade assembly400.

A brief description will now be given of a method of manufacturing a development cartridge7as described above.

First of all, the agitator75(seeFIG. 2) is mounted in the lower frame100. Next, as shown inFIG. 3, the left boss hole220L of the upper frame200is fitted on the left boss330L of the lower frame100, and the right boss hole220R of the upper frame200is fitted on the right boss330R of the upper frame200, so that the upper frame200is aligned and combined with the lower frame100, as shown inFIG. 4.

Thereafter, the weld surface W of the lower frame100and the weld rib240of the upper frame200are welded to each other, for example, using a known ultrasonic welding machine, so that the lower frame100and the upper frame200are fixed together. Subsequently, the supply roller72(not shown inFIG. 4), the doctor blade73(the blade assembly400), the development roller71and other components are mounted, and consequently, assembly of the development cartridge7is completed.

According to the present embodiment described above, the following advantageous effects can be achieved.

Since the left boss330L and the right boss330R of the lower frame100are disposed between the left sidewall110and the right sidewall120in the present embodiment, the development cartridge7can be designed to be compact in size and light in weight, in comparison with an alternative configuration in which the left sidewall110and the right sidewall120are designed to be thicker to provide positioning bosses on their upper surfaces (weld surface W), or such positioning bosses are disposed outside the left sidewall110and the right sidewall120. Furthermore, since the positioning bosses are not disposed on the weld surface W in this embodiment, a sufficient area can be provided for the weld surface W without making the left sidewall110and the right sidewall120thicker.

Moreover, since the left boss330L is provided at the left extension portion300L extending from the left sidewall110toward the right sidewall120, and the right boss330R is provided at the right extension portion300R extending from the right sidewall120toward the left sidewall110in the present embodiment, the so-called “inward tilt” of the left sidewall110and the right sidewall120can be corrected by the upper frame200when the upper frame200is combined with, and fixed to, the lower frame100. As a result, distortions which would take place in the lower frame are corrected, and thus the dimensional accuracy of the frames of the development cartridge7can be improved.

Furthermore, since the left boss330L is disposed inward of the left mount portion150L and the right boss330R is disposed inward of the right mount portion150R in the present embodiment, the development cartridge7can be miniaturized particularly in the frontward-and-rearward direction, in comparison with an alternative configuration in which, the left boss330L and the left mount portion150L, as well as the right boss330R and the right mount portion150R, are arranged in the frontward-and-rearward direction.

Since the bosses330L,330R are disposed between the protruding portions of the left mount portion150L and the right mount portion150R which protrude from the weld surface W in the present embodiment, the inward tilt of the left sidewall110and the right sidewall120due to shrinkage in the molding process during manufacturing can be suppressed because the upper frame200is disposed between the left and right mount portions150L,150R when the lower frame100and the upper frame200are combined and fixed together.

In the present embodiment, the blade assembly400can be mounted and fixed, correctly into place, to the left and right mount portions150L,150R with increased ease, so that the mounting of the blade assembly400can be performed easily. Furthermore, the suppression of the inward tilt of the left sidewall110and the right sidewall120, and associated correction of distortion of the development cartridge7, make it possible to achieve improved positioning accuracy of the blade assembly400and the frames.

Although an illustrative embodiment of the present invention has been described above, the present invention is not limited to the above-described embodiment. Various modifications and changes may be made to the specific structures and arrangement without departing from the scope of the present invention.

In the above-described embodiment, the left boss330L (first engageable portion) is disposed inward of the left mount portion150L (first mount portion), and the right boss330R (second engageable portion) is disposed inward of the right mount portion150R (second mount portion), but the present invention is not limited to this specific configuration. For example, the engageable portions (the extension portions300L,300R, as inFIG. 3, on which the bosses330L,330R are formed) may be disposed approximately at midpoints, in the frontward-and-rearward direction, of the left and right sidewalls110,120.

In the above-described embodiment, the left and right bosses330L,330R (first and second engageable portions) are disposed at the extension portions300L,300R, respectively, but the present invention is not limited to this specific configuration. For example, columnar portions protruding upward from the bottom wall130ofFIG. 3may be provided and the engageable portions may be provided at upper end portions of the protruding columnar portions.

In the present embodiment, the first engageable portion and the second engageable portion are configured as projections (the left boss330L and the right boss330R), and the third engageable portion and the fourth engageable portion are configured as holes (the left boss hole220L and the right boss hole220R), but the present invention is not limited to this specific configuration. For example, alternative equivalent configurations may include: (1) the first engageable portion and the second engageable portion are configured as holes, whereas the third engageable portion and the fourth engageable portion are configured as projections; (2) the first engageable portion and the fourth engageable portion are configured as projections, whereas the second engageable portion and the third engageable portion are configured as holes; and (3) the first engageable portion and the fourth engageable portion are configured as holes, whereas the second engageable portion and the third engageable portion are configured as projections.

The left and right bosses330L,330R in the illustrative embodiment shown inFIG. 3may have diameters different from each other, and the left and right boss holes220L,220R which are shaped and dimensioned so as to be engageable with the left and right bosses330L,330R, respectively, may also have diameters different from each other, accordingly. To be specific, in one example, the left boss330L may have larger diameter than the right boss330R. In this configuration, the left boss hole220L may have larger diameter than the right boss hole220R so that the left boss330L and right boss330R can fit the left boss hole220L and the right boss hole220R, respectively. In another example, the right boss330R may have larger diameter than the left boss330L. In this configuration, the right boss hole220R may have larger diameter than the left boss hole220L so that the right boss330R and left boss330L can fit the right boss hole220R and the left boss hole220L, respectively.

In the above-described embodiment, the lower frame100(the first frame) and the upper frame200(the second frame) are fixed by welding by way of example, but the method of fixing the first frame and the second frame to each other, which is practically consistent with the present invention is not limited to this illustrated method. For example, the first frame and the second frame may be fixed by an adhesive.

In the present embodiment, the doctor blade73is fixed to the lower frame100at the attachment portions423aligned with the plane PL extending substantially in the upward-and-downward direction that is the plane with which the plate member73is aligned, but the present invention is not limited to this specific configuration. For example, the doctor blade73(blade assembly400) as shown inFIG. 5may be fixed to at least one of the upper frame200and the lower frame100on the plane with which the connecting portions422,432are aligned.

The first ribs320of the present embodiment are illustrated by way of example, and the present invention is not limited to the specific illustrative configuration of the first ribs320. In other words, the shape and the number of the first rib(s) consistent with the present invention may be selected arbitrarily without limitation as long as developer will not be retained or accumulated under the extension portion. For example, the first ribs320ofFIG. 5may be modified into an alternative configuration such that the total two first ribs320are provided at left and right ends (inFIG. 5) of the upper wall310or that only one first rib320is provided at the center in the leftward-and-rightward direction (inFIG. 5) of the upper wall310.

In the above-described embodiment, the development cartridge7is illustrated as an example of a development device, but the present invention is not limited to this specific configuration. For example, a process cartridge in which a photoconductor cartridge6and a development cartridge7as in the above-described embodiment are provided inseparably in an integrated unit may be configured as a development device in accordance with the present invention.

In the above-described embodiment, the present invention is applied to a development device for use in the laser printer1for forming a monochrome image, but the present invention is not limited thereto; for example, a color printer for forming a multicolor image may be configured in accordance with one or more of the embodiments of the present invention. Also, any other image forming apparatus such as a photocopier, a multifunction peripheral and the like which includes a document scanning device (e.g., flat bed scanner) may be configured in accordance with one or more of the embodiments of the present invention.