Patent Application
20110158714
1. Field of the Invention
The present invention relates generally to a fuser assembly including a rotatable backup member and a translatable heater member and, more particularly to a fuser assembly having a single biasing member for biasing the translatable heater member against the rotatable backup member.
2. Description of the Related Art
An image forming apparatus, such as a color printer typically includes four units associated with four colors, black, magenta, cyan, and yellow. Each unit includes a laser printhead that is used to provide a latent image on the charged surface of a photoconductive unit. The latent image on each photoconductive unit is developed with the appropriate color toner and is then transferred to either an intermediate transfer medium or directly to a media (such as paper) that travels past the photoconductive units.
The un-fused toner on the media is then fused to the media by application of heat and pressure in a fuser assembly. The fuser assembly includes a rotatable backup member and a translatable heater member disposed adjacent the rotatable backup member to form a nip through which the media passes for fusing the toner to the media.
Due to space constraints in the image forming apparatus the spring 24, in the prior system, was relatively short with a high spring rate. The tolerance of this short spring 24 positioned on each end frame 16 accounted for 20% difference in force applied by the spring 24 positioned on end frame 16 disposed at one end of the fuser assembly 10 with respect to the force applied by the spring 24 positioned on end frame 16 disposed at the other end of the fuser assembly 10. This difference in force applied by the spring 24 resulted in an inconsistent and unequal loading of the rotatable backup member 12 against the translatable heater member 14.
Further, using two springs 24 magnifies geometrical differences between the ends of the fuser assembly 10 causing uneven loading of the rotatable backup member 12 against the translatable heater member 14. The uneven loading of the rotatable backup member 12 against the translatable heater member 14 results in several disadvantages such as treeing, worming, tail flip, and light print.
Therefore, it would be advantageous to have a fuser assembly that has the translatable heater member substantially evenly loaded against the rotatable backup member.
Disclosed herein is a fuser assembly including a rotatable backup member, a translatable heater member positioned adjacent the rotatable backup member, a biasing member positioned adjacent and parallel to the translatable heater member, the biasing member having a first end and a second end, and a support structure positioned at the ends of the biasing member for supporting the biasing member, the biasing member applying a force on at least a portion of the translatable heater member through at least a portion of the support structure in a direction towards the rotatable backup member to bias the translatable heater member against the rotatable backup member.
In some embodiments, a first end frame and a second end frame are disposed on the ends of the fuser assembly with the first end of the biasing member extending through the first end frame and the second end of the biasing member extending through the second end frame. The support structure includes a first bracket member mounted on the first end frame, a second bracket member mounted on the second end frame, a first bell crank member pivotally mounted on the first bracket member, and a second bell crank member pivotally mounted on the second bracket member. Each bell crank member includes a pivot post mounted on the bracket members, an extension at one end of the bell crank member, and a hook portion at other end of the bell crank member, the hook portion having a curved surface that engages an end of the biasing member which applies a force on the hook portion to move the bell crank member such that the extension of the bell crank members applies a force on at least the portion of the second support structure towards the first support structure.
In some embodiments, the translatable heater member includes a heater housing, a heater element located in the heater housing, and a first end cap and a second end cap positioned at the ends of the translatable heater member for supporting the translatable heater member, the first end cap mounted within the first end frame and the second end cap mounted within the second frame. In this way, the bell cranks apply a force on the portion of the heater housing extending through the end frames. This force results in a substantially evenly distributed force on the translatable heater member against the rotatable backup member.
Additional features and advantages of the invention will be set forth in the detailed description which follows, and in part will be readily apparent to those skilled in the art from that description or recognized by practicing the invention as described herein, including the detailed description, which follows, the claims, as well as the appended drawings.
It is to be understood that both the foregoing general description and the following detailed description of the present embodiments of the invention are intended to provide an overview or framework for understanding the nature and character of the invention as it is claimed. The accompanying drawings are included to provide a further understanding of the invention and are incorporated into and constitute a part of this specification. The drawings illustrate various embodiments of the invention and together with the description serve to explain the principles and operation of the invention.
The above-mentioned and other features and advantages of the various embodiments of the invention, and the manner of attaining them, will become more apparent will be better understood by reference to the accompanying drawings, wherein:
It is to be understood that the invention is not limited in its application to the details of construction and the arrangements of components set forth in the following description or illustrated in the drawings. The invention is capable of other embodiments and of being practiced or of being carried out in various ways. Also, it is to be understood that the phraseology and terminology used herein is for the purpose of description and should not be regarded as limiting. The use of “including,” “comprising,” or “having” and variations thereof herein is meant to encompass the items listed thereafter and equivalents thereof as well as additional items. Unless limited otherwise, the terms “connected,” “coupled,” and “mounted,” and variations thereof are used broadly and encompass direct and indirect connections, couplings and mountings. In addition, the terms “connected” and “coupled” and variations thereof are not restricted to physical or mechanical connections or couplings.
Reference will now be made in detail to the exemplary embodiment(s) of the invention, as illustrated in the accompanying drawings. Whenever possible, the same reference numerals will be used throughout the drawings to refer to the same or like parts.
As illustrated in
An imaging device 48 forms an electrical charge on a photoconductive unit within the image forming units 46 as part of the image formation process. Various imaging devices may be used such as a laser printhead or a LED printhead.
Media with un-fused toner from one or more image forming units 46 is then moved by the media transport belt to a fuser assembly 50. The fuser assembly 50 includes a translatable heater member 52 and a rotatable backup member 54. The fuser assembly 50 applies heat and pressure to the media to fuse the un-fused toner to the media. Exit rollers 56 rotate in a forward or reverse direction to move the media with the fused image from the fuser assembly 50 to an output tray 58 or a duplex path 60.
The image forming apparatus 30 also includes a processor 62 and a memory 64. The processor 62 controls the transfer of the toner image on to the media, as well as movement of the media through the media path 38 and the duplex path 60.
The rotatable backup member 54 includes a rotatable backup roll 76 positioned adjacent the translatable heater member 52. Pressure is applied between the translatable heater member 52 and the rotatable backup member 54 to forms a nip 78 through which the media with the un-fused toner is passed. As media enters the nip 78, energy is passed from the heating element 72 through the translatable heat transfer member 74 to the media, such that the un-fused toner on the media is fused to the media due to the applied heat and pressure between the translatable heater member 52 and the rotatable backup member 54.
The translatable heater member 52 includes a first end cap 88a positioned at end 90a of the translatable heater member 52 and a second end cap 88b positioned at end 90b of the translatable heater member 52. As shown in
The fuser assembly 50 further includes a biasing member 92 positioned adjacent and parallel to the translatable heater member 52. The biasing member 92 has a first end 94a extending through the first end frame 80a and a second end 94b extending through the second end frame 80b. The biasing member 92 in the present embodiment is an extension spring.
The fuser assembly 50 includes support structure 96a and 96b to which the ends 94a and 94b of the biasing member 92 are coupled. With reference to
The support structure 96a further includes a first bell crank member 100a and the support structure 96b further includes a second bell crank member 100b. The first bell crank member 100a includes a pivot post 102a for pivotally mounting the first bell crank member 100a on the first bracket member 98a. The first bell crank member 100a is free to rotate around the pivot post 102a of the first bell crank member 100a. The second bell crank member 100b includes a pivot post 102b for pivotally mounting the second bell crank member 100b on the second bracket member 98b. The second bell crank member 100b is free to rotate around the pivot post 102b of the second bell crank member 100b.
The first bell crank member 100a and the second bell crank member 100b include extensions 104a and 104b, respectively, positioned adjacent the portion of the heater housing 70 extending through the end frames 80a and 80b. The first bell crank member 100a has a hook portion 106a and the second bell crank member 100b has a hook portion 106b. Hook portion 106a is positioned on the opposite side of pivot post 102a from extension 104a, and hook 106b is positioned on the opposite side of pivot post 102b from extension 104b. As shown in
As shown, the first end 94a of the biasing member 92 is engaged with the hook portion 106a which pulls the first bell crank member 100a in a generally horizontal direction X towards the biasing member 92 and bell crank 100b. This bias force causes the first bell crank member 100a to pivot about the pivot post 102a in a generally counter-clockwise direction such that the extension 104a of the first bell crank member 100a is displaced in a generally upward direction Y which pushes the portion of the heater housing 70 extending through the first end frame 80a generally upwardly towards the bearing 84a mounted within the first end frame 80a.
Similarly, the second end 94b of the biasing member 92 similarly pulls the second bell crank member 100b to pivot the second bell crank member 100b in a clockwise direction about pivot post 102b. The extension 104b of the second bell crank member 100b moves generally upwardly which pushes the portion of the heater housing 70 extending through the second end frame 80b towards the bearing 84b mounted within the second end frame 80b.
The upward force applied by the extensions 104a and 104b of the bell crank members 100a and 100b on the heater housing 70 biases the translatable heater member 52 against the rotatable backup member 54 such that a substantially constant and uniform pressure is applied between the translatable heater member 52 and the rotatable backup member 54.
As a single biasing member 92 is used for loading both ends 82a and 82b of the fuser assembly 50, a substantially consistent and substantially equal load is applied across fuser assembly 50. Further, as there are less space constraints along the length of the fuser assembly 50 than along its lateral dimension, a much longer biasing member 92 is used in the present invention, resulting in a lower spring rate. The lower spring rate reduces the effects of geometric differences between the ends 82a and 82b of the fuser assembly 50. Using a single biasing member 92 also eliminates the shortcoming of having different spring tolerances from two springs that result in uneven loading of the fuser assembly of prior systems, like the fuser assembly of
Additionally, with the single biasing member 92 the pressure between the translatable heater member 52 and the rotatable backup member 54 can be changed with a single adjustment of the biasing member 92 without changing the relationship between forces applied by the biasing member 92 to the support structure 96a and support structure 96b.
As shown in
This force applied by the bell crank members 116 to the portion of heater housing 70 extending through the end frames 80, towards the pivots 84a and 84b mounted within the end frames 80 biases the translatable heater member 52 against the rotatable backup member 54 such that a substantially constant pressure is applied between the translatable heater member 52 and the rotatable backup member 54. As a single biasing member 110 is used for loading both ends 82 of the end frames 80 a substantially consistent load is applied along the fuser assembly 50.
It will be apparent to those skilled in the art that various modifications and variations can be made to the present invention without departing from the spirit and scope of the invention. Thus it is intended that the present invention cover the modifications and variations of this invention provided they come within the scope of the appended claims and their equivalents.
