Information
-
Patent Grant
-
6522851
-
Patent Number
6,522,851
-
Date Filed
Tuesday, February 20, 200123 years ago
-
Date Issued
Tuesday, February 18, 200321 years ago
-
Inventors
-
Original Assignees
-
Examiners
Agents
-
CPC
-
US Classifications
Field of Search
US
- 399 115
- 399 123
- 399 110
- 399 107
- 399 174
- 399 176
- 399 350
- 399 351
- 399 349
-
International Classifications
-
Abstract
A bracket to mount a charge roller and a blade against a photoconductive drum within an image forming apparatus. Bracket may include a pair of guides that extend outward to receive the ends of the charge roller. A biasing device may be positioned to bias the charge roller against the photoconductive drum. The guides may include an opening sized to allow the charge roller to move and maintain contact with the photoconductive drum. A mounting surface may be positioned on the bracket for receiving adhesive to mount the blade. In one embodiment, the bracket is constructed of a molded thermoplastic polymer.
Description
BACKGROUND OF THE INVENTION
Image forming devices including copiers, laser printers, facsimile machines, and the like, include a photoconductive drum (hereinafter referred to as a drum) having a rigid cylindrical surface that is coated along a defined length of its outer surface. The surface of the drum is charged to a uniform electrical potential and then selectively exposed to light in a pattern corresponding to an original image. Those areas of the photoconductive surface exposed to light are discharged thus forming a latent electrostatic image on the photoconductive surface. A developer material, such as toner, having an electrical charge such that the toner is attracted to the photoconductive surface is brought into contact with the drum's photoconductive surface. A recording sheet, such as a blank sheet of paper or a transfer belt, is then brought into contact with the photoconductive surface and the toner thereon is transferred to the recording sheet in the form of the latent electrostatic image. The recording sheet is then heated thereby permanently fusing the toner to it.
In preparation for the next image forming cycle, the photoconductive surface is optionally discharged and cleaned of residual toner. A cleaner blade is positioned adjacent to the drum for removing the residual toner that has not been transferred during the printing process. Removal of the residual toner is necessary prior to preparing the drum to receive a new image.
Conventional cleaner blades are manufactured by stamping and forming a bracket from a sheet metal stock, then molding or adhering a flexible elastomer member to the bracket. This assembly is attached to the printer in proximity to the drum such that the flexible member is deflected and pressed against the surface of the drum. There are often manufacturing difficulties in these conventional designs resulting from variations in the properties of the steel such as the thickness and temper. These variations cause deviations from the desired form resulting in inconsistent removal of the residual toner across the length of the drum.
It is further desirable for the image forming apparatus to have the smallest dimensions possible. This is a key selling point to consumers who desire the small dimensions because the apparatus is easier to manipulate and move, and occupies a minimal amount of desk space in a workstation where available space is often at a premium. As a result of the smaller sizes, these internal elements of the image forming apparatus are located in a very compact space. Element designs used in physically larger printers may not be applicable to the smaller-sized apparatus because of the large dimensions. Thus, it is necessary to reduce the physical size of the elements.
SUMMARY OF THE INVENTION
The invention comprises a multi-function cleaner blade bracket sized to mount both a cleaner blade and charge roller. The bracket includes a mounting surface for fixedly attaching the cleaner blade and guides for positioning the charge roller. The bracket may further contain at least one biasing element to force the charge roller against the photoconductive drum.
Another aspect of the invention is that the bracket is molded and reinforced through a plastic polymer rather than the conventional stamping and forming from sheet metal stock. Molding allows for incorporating reinforcing ribs into the bracket design that helps to resist deflection due to pressing the flexible scraper blade against the photoconductive drum. The mounting surface for the flexible scraper member can be contoured to compensate for this deflection resulting in a more uniform pressure of the cleaning edge across the entire width of the blade. Molding also provides for additional features to be incorporated into the bracket such as the guides.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1
is a side view illustrating a color laser printer constructed according to one embodiment of the present invention;
FIG. 2
is a partial perspective front view illustrating a first end of the bracket with a charge roller attached therein;
FIG. 3
is a partial perspective back view illustrating the bracket and charge roller positioned against a drum; and
FIG. 4
is a partial perspective front view illustrating a second end of the bracket with a charge roller attached therein and mounted against the drum.
DETAILED DESCRIPTION OF THE INVENTION
FIG. 1
illustrates the basic elements of an image forming device and is incorporated for an understanding of the overall electrophotographic image forming process. A color laser printer is illustrated as
100
, however, one skilled in the art will understand that the present invention is applicable to other types of image forming devices. The image forming apparatus, generally designated
100
, includes a plurality of similar toner cartridges
110
,
210
,
310
, and
410
. Each toner cartridge has similar construction but is distinguished by the toner color contained therein. In one embodiment, the device includes a black cartridge
110
, a magenta cartridge
210
, a cyan cartridge
310
, and a yellow cartridge
410
. The different color toners form individual images of a single color that are combined in layered fashion to create the final multicolored image. As the cartridges are respectively identical except for the toner color, the cartridge and elements for forming black images will be described, with the other color image forming units being omitted for simplification.
Drum
14
is generally cylindrically-shaped with one end having a means for coupling with the image forming device drive gears to provide for rotational movement. The drum
14
has a smooth surface for receiving an electrostatic charge over the surface as the drum
14
rotates past charge roller
26
. The drum
14
continuously and uniformly rotates past a laser scanning assembly
120
that directs a laser beam
121
onto selected portions of the drum surface forming an electrostatic latent image representing the image to be printed. The drum
14
is rotated at a constant speed as the laser beam
121
is scanned across its length. This process continues as the entire image is formed on the drum surface.
After receiving the latent image, the drum
14
rotates past a toner area having a toner bin
122
for housing the toner and a developer roller
124
for uniformly transferring toner to the drum
14
. The toner may also be charged to assist in the transfer to the paper. The toner is a fine powder usually composed of plastic granules that are attracted and cling to the electrostatic latent image formed on the drum surface by the laser scanning assembly
120
.
The drum
14
next rotates past an adjacently-positioned intermediate transfer medium belt
500
(hereinafter, ITM belt) to which the toner is transferred from drum
14
. As illustrated in
FIG. 1
, the ITM belt
500
is endless and extends around a series of rollers adjacent to the drums. The ITM belt
500
and the image on each drum
14
,
214
,
314
,
414
are synchronized providing for the toner from each drum to precisely align on the ITM belt
500
during a single pass. By way of example as viewed in
FIG. 1
, the yellow (Y) toner will be placed on the ITM belt, followed by cyan (C), magenta (M), and black (K). After depositing the toner on the ITM belt
500
, the drum
14
rotates through a cleaning area where residual toner is removed from the surface via a cleaning or scraper blade, hereinafter blade
40
.
As the drums are being charged and gathering toner, a recording sheet, such as blank sheet of paper, is being routed to intercept the ITM belt
500
. The paper may be placed in one of the lower trays
510
, or introduced into the image forming device
100
through a side track tray
520
. A series of rollers and/or belts transports the paper to point Z where the sheet contacts the ITM belt
500
and receives the toner. Preferably, voltage is applied to the roller that pushes the sheet of paper against the ITM belt
500
at point Z to pull the charged toner away from the belt
500
and onto the paper. The sheet and attached toner next travel through a fuser
530
having a pair of rollers and a heating element that heats and fuses the toner to the sheet. The paper with fused image is then transported out of the image forming apparatus.
FIG. 2
illustrates a bracket
30
for mounting the charge roller
26
and cleaner blade
40
against the drum
14
. The drum
14
has been omitted from
FIG. 2
for clarity in illustrating the blade
40
and bracket
30
but is included in
FIGS. 3 and 4
. Guides
31
extend out to mount the charge roller
26
and a biasing device
62
biases the charge roller
26
against the drum
14
. Blade
40
is attached to a mounting surface
50
(
FIG. 3
) on the bracket
30
and extends outward to contact the drum
14
. Bracket
30
does not contact the drum
14
, but is positioned such that charge roller
26
and blade
40
are maintained in contact with the drum
14
. As the drum
14
rotates as indicated by arrow A in
FIG. 3
, blade
40
removes the residual toner that remains from the previous printing cycle. Drum
14
then rotates against charge roller
26
to be charged in preparation for the next printing cycle.
Bracket
30
may have a variety of orientations to mount and position the charge roller
26
and blade
40
against the drum
14
. In the embodiment illustrated, bracket
30
comprises a unitary piece having first and second sections
32
,
34
connected together along one edge. Sections
32
,
34
may extend outward in a variety of angles including between about 90-130 degrees depending upon the dimensions and spacing of the charge roller
26
and blade
40
relative to the drum
14
, and the size of the drum
14
. In another embodiment, bracket
30
has a curved orientation that roughly corresponds to the curvature of the drum
14
to maintain the blade
40
and charge roller
26
seated on the drum surface. One skilled in the art will recognize that bracket
30
may have a variety of orientations and/or configurations.
An adhesive bonds the blade
40
to the bracket
30
. A variety of adhesives may be used that provide an adequate bonding strength, and do not deteriorate the blade
40
or the bracket
30
. Adhesive is applied across the length of the blade
40
to firmly bond the blade
40
to the bracket
30
, and also form a seal to prevent toner from escaping between the blade
40
and bracket
30
.
Bracket
30
may include a mounting surface
50
having a plurality of raised surfaces and channels or waffle pattern as illustrated in FIG.
3
. Adhesive applied to the mounting surface
50
is distributed about the surfaces and excess adhesive flows into the channels to effectively bond the blade
40
to the bracket
30
and locate the blade
40
properly with respect to the bracket
30
. Channels may be recessed below the outer surface of the bracket
30
forming lateral edges
52
and a top edge
54
. A barrier
55
, such as a sponge pad, may be placed along the lateral and/or top edges of the blade
40
to further prevent toner escape. In another embodiment, mounting surface
50
is a substantially flat surface.
A bottom edge
56
of the mounting surface
50
establishes a flexural pivot of the blade
40
and affects the amount of force applied and therefore the cleaning properties. Blade
40
is constructed of a elastic material having a bowed configuration when placed against the drum
14
as illustrated in
FIGS. 3 and 4
. The resiliency of the blade
40
and the length of the blade
40
extending beyond the bottom edge
56
factor into the amount of force applied to the drum
14
by the blade
40
.
Guides
31
extend outward from each end of the bracket
30
to position the charge roller
26
against the drum
14
. Placement of the guides
31
at the bracket ends allows the charge roller axle
28
to be positioned within the guides
31
and the surface of the charge roller
26
to maintain contact across the surface of the drum
14
. In one embodiment, guides
31
extend outward from the bracket
30
and comprise an opening
35
having an inner edge
37
and stops
33
. A bearing
60
that extends around a portion of the charge roller axle
28
is positioned within the opening
35
. Bearing
60
is sized to move between the inner edge
37
and stops
33
in the direction indicated by arrow B in FIG.
2
. Bearing
60
may further include an end cap
64
that extends across at least a portion of the charge roller axle
28
. Various other embodiments are also contemplated for mounting the charge roller
26
within the guides
31
such as the charge roller axle
28
mounting directly within the guides
31
. In this embodiment, opening
35
is sized to directly contact the axle
28
and maintain the positioning of the charge roller
26
.
A biasing device
62
is positioned between the bracket
30
and the charge roller
26
to bias the charge roller
26
against the drum
14
. A variety of different mechanisms may be used as the biasing device
62
including mechanical devices such as a leaf or coil spring, or a material having resilient properties that bias the charge roller
26
against the drum
14
. In the embodiment illustrated in
FIG. 2
, a spring
62
is positioned between the bracket
30
and the carriage
60
. Grooves
36
may be positioned within the bracket
30
to position the biasing device
62
and prevent it from moving along the length of the bracket
30
. The force of the biasing device
62
is adequate for the charge roller surface to maintain contact with the drum surface across the entire length of the charge roller
26
. Likewise, the force is adequate such that the rotation of the drum
14
is imparted to the charge roller
26
. The force is not excessive such that the charge roller
26
binds or otherwise hinders the rotation of the drum
14
.
In one embodiment, charge roller
26
is movably positioned within the bearing
60
and buttresses
39
extend outward from the bracket
30
on the outside edge of one or both guides
31
to limit the lateral movement of the charge roller
26
. The ends of the charge roller axle
28
contact the buttress
39
to limit this movement. Buttresses
39
further provide protection for the charge roller
26
in the event the bracket
30
and/or image forming device
100
are dropped as they may prevent the charge roller
26
from falling out of the guides
31
and becoming damaged.
Electrical connections
80
contact the charge roller
26
to charge the charge roller
26
. In one embodiment, electrical connections
80
comprise contact fingers
82
that contact one end of the charge roller
26
. The contact fingers
82
may apply an axial force to the charge roller
26
that pushes it against the opposite buttress
39
and maintains the electrical contact. In one embodiment, end cap
64
is constructed of a conductive plastic material. The contact fingers
82
contact the end cap
64
, which in turn transfers the charge to the charge roller
26
. This embodiment minimizes noise that may be caused by the contact fingers
82
directly contacting the rotating charge roller axle
28
.
Blade
40
extends from the bracket
30
to contact the drum
14
and remove residual toner remaining from the previous printing cycle. Blade
40
has a generally rectangular configuration that extends beyond the mounting surface
50
. Blade
40
is constructed of a resilient material, such as urethane, that can be bent to apply additional force against the surface of the drum
14
.
Charge roller
26
applies a uniform electrical charge to the drum
14
in preparation for receiving the image via the laser scanning assembly
120
. Charge roller
26
comprises an outer surface that contacts the drum
14
and an axle
28
about which the roller rotates. The charge roller
26
is substantially cylindrical, and may have a slightly larger circumference about a mid-point to ensure contact is maintained across the entire length of the drum
14
.
In one embodiment, bracket
30
is constructed via a molding process that allows for easier inclusion of elements such as guides
31
and the reinforcing ribs
38
and provides for reduced cost and increased dimensional accuracy. Reinforcing ribs
38
may be incorporated to prevent the bracket
30
from deflecting due to the force of applying the blade
40
against the drum
14
. Additionally, bracket
30
may be contoured to compensate for the deflection thus resulting in a more uniform pressure of the blade working edge
44
against the drum
14
. In one embodiment, bracket
30
is constructed of a reinforced thermoplastic polymer, although one skilled in the art will understand that the bracket
30
can be molded from a variety of materials.
A toner removal tray
70
may be positioned adjacent to the cleaner blade
40
as illustrated in
FIGS. 3 and 4
. Tray
70
includes a channel
79
to capture the residual toner that is removed from the drum
14
. Channel
79
may be sized to hold the toner, or may include an auger (not illustrated) or other like device for directing the toner along the channel
79
for storage in a reservoir
76
. Supports
74
may further extend from the tray
60
to assist in maintaining the blade
40
positioned against the drum
14
. Additional stiffening ribs
73
prevent deflection of the toner removal tray
70
.
The present invention may be carried out in other specific ways than those herein set forth without departing from the scope and essential characteristics of the invention. The embodiment illustrated in
FIG. 1
comprises separate cartridges for each different color. The present invention is not limited to this type of printer, but is also applicable in various other printer embodiments that feature a photoconductive drum. Additionally, bracket
30
may be positioned within a cartridge that is removably positioned within the image forming device
100
, or may be permanently mounted within the device. Fasteners
72
that extend through apertures in the bracket
30
are used for attachment. The present embodiments are, therefore, to be considered in all respects as illustrative and not restrictive, and all changes coming within the meaning and equivalency range of the appended claims are intended to be embraced therein.
Claims
- 1. A device for cleaning and charging a photoconductive drum within an image forming apparatus, said device comprising:a. a bracket being of a unitary molded construction comprising first and second guides and a mounting surface, said first guide being positioned adjacent to a first end of said bracket and said second guide being positioned adjacent to a second end of said bracket; b. a cleaner blade attached to said mounting surface and extending outward therefrom to contact the photoconductive drum; c. a charge roller mounted to said first and second guides and being positioned against the photoconductive drum and d. a biasing device to bias the charge roller against the photoconductive drum.
- 2. The device of claim 1, further comprising a bearing positioned within each of said guides to receive said charge roller.
- 3. The device of claim 1, wherein the biasing device is mounted on said bracket to bias said charge roller against the photoconductive drum.
- 4. The device of claim 2, wherein the biasing device is operatively mounted to said bearing to bias said charge roller against the photoconductive drum.
- 5. The device of claim 1, wherein said charger roller is attached to a first side of said bracket and said blade is attached to a second side of said bracket.
- 6. The device of claim 5, wherein said bracket comprises first and second sections positioned at an angle between them within the range of 90-130 degrees.
- 7. The device of claim 1, wherein said bracket is constructed of a molded thermoplastic polymer.
- 8. A device for cleaning and charging a photoconductive drum, said device comprising:a. an elongated bracket extending along at least a length of the photoconductive drum; b. first and second guides extending outward from a first side of said bracket, said first guide being positioned adjacent to a first end of said bracket and said second guide being positioned adjacent to a second end of said bracket, said bracket and said guides being of a unitary, molded construction; c. a bearing movably positioned within each of said guides; d. a charge roller mounted within said bearings; e. a biasing device operatively connected to at least one of said bearings and said bracket, said biasing device applying a force to maintain said charge roller positioned against the photoconductive drum; and f. a blade connected to said bracket and extending outward therefrom to contact the photoconductive drum.
- 9. The device of claim 8, further comprising a mounting surface positioned on a second side of said bracket, said mounting surface having a waffle pattern and said blade is bonded to said waffle pattern by an adhesive.
- 10. The device of claim 8, wherein said bracket comprises first and second sections connected together along a common edge, said first and second sections being angled apart between about 90 and 130 degrees.
- 11. An image forming device comprising:a. a photoconductive drum; b. a charge roller to apply a charge to said photoconductive drum; c. a laser assembly to create an image on said photoconductive drum; d. a developer roller to transfer toner to said photoconductive drum; e. a cleaner blade to remove the toner from said photoconductive drum; f. a bracket to mount said cleaner blade and said charge roller against said photoconductive drum, said bracket being of a unitary molded construction and comprising first and second guides each comprising an opening adapted to receive said charge roller and a mounting surface adapted to receive said cleaner blade; and g. a biasing device positioned between said bracket and said charge roller to bias said charge roller against said photoconductive drum.
- 12. The device of claim 11, wherein said bracket is constructed of a thermoplastic polymer.
- 13. The device of claim 11, further comprising at least one contact finger extending from the device and being operatively connected to said charge roller to supply a charge to said charge roller.
- 14. The device of claim 13, further comprising a conductive end cap attached to an end of said charge roller, said contact finger contacting said conductive end cap to supply the charge to said charge roller.
- 15. The device of claim 11, further comprising at least one buttress extending outward from said bracket and being adjacent to one of said guides to limit lateral movement of said charge roller relative to said bracket.
- 16. The device of claim 11, wherein said biasing device applies a force to press said charge roller against said drum, said force being adequate such that rotation of said drum causes rotation of said charge roller.
- 17. The device of claim 11, wherein said bracket, charge roller, and cleaner blade are mounted within a cartridge that is removably positioned within the image forming device.
- 18. A device for cleaning and charging a photoconductive drum within an image forming apparatus, said device comprising:a. a bracket extending along the photoconductive drum, the bracket comprising a pair of guides extending outward from a first side and a mounting surface positioned on a second side; b. a cleaner blade attached to said mounting surface and extending outward therefrom to contact the photoconductive drum, the cleaner blade being constructed of a flexible material and having a bowed orientation when contacting the photoconductive drum to remove residual toner; c. a charge roller mounted within said guides; and d. a pair of springs to bias said charge roller against the photoconductive drum, a first spring positioned adjacent to a first guide and a second spring positioned adjacent to a second guide to contact a surface of the charge roller against the photoconductive drum.
- 19. A method of assembling a cleaner blade assembly within an image forming apparatus, the method comprising the steps of:a. providing a molded thermoplastic bracket; b. attaching a charge roller to the bracket and biasing the charge roller against a photoconductive drum; c. attaching a cleaner blade to the bracket; and d. positioning the bracket within the image forming apparatus such that the charge roller and the cleaner blade are positioned against the photoconductive drum with the cleaner blade having a bowed orientation to apply pressure against the drum and operatively connecting a first end of the charge roller to electrical contacts extending from the image forming apparatus to charge the charge roller.
US Referenced Citations (19)
Foreign Referenced Citations (2)
Number |
Date |
Country |
9-305088 |
Nov 1997 |
JP |
1997409305088 |
Nov 1997 |
JP |