Metal deforming – By use of tool acting during relative rotation between tool... – During rotation of work
Reexamination Certificate
2000-12-01
2003-05-13
Tolan, Ed (Department: 3725)
Metal deforming
By use of tool acting during relative rotation between tool...
During rotation of work
C072S084000, C072S370140, C072S370250
Reexamination Certificate
active
06561001
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to a thin-walled circular-shaped metal structure and a method of fabricating the same, and more particularly to such a metal structure usable as a photosensitive drum or a fixing roller in an electrophotographic printer or copier, and a method of fabricating the same.
2. Description of the Related Art
For instance, in accordance with Japanese Unexamined Patent Publication No. 10-10893, a film of which a photosensitive drum or a fixing drum used in a conventional electrophotographic printer and copier is fabricated is composed generally of organic material such as polyimide or a metal as inorganic material, such as iron, aluminum, stainless steel and nickel.
The above-mentioned film is required to have a thickness in the range of 0.03 to 0.20 mm as a practical thickness. However, such a thickness can be accomplished only by a film composed of polyimide or nickel. For instance, a nickel film having such a thickness can be fabricated by electrocasting.
It is generally said that a fixation section consumes about 80% of power to be totally consumed in an electrophotographic printer or copier. In addition, power consumption depends greatly on a material of which a fixing roller or a fixing film is composed.
For instance, if a fixing roller or film is composed of polyimide, an organic material, having a thermal conductivity {fraction (1/510)} to {fraction (1/40)} smaller than a thermal conductivity of the above-mentioned iron, aluminum, stainless steel or nickel, it would be necessary to heat a fixing roller or film much time until the fixing roller or film become workable. A period of time in which a fixing roller or film is heated is a time in which a user has to wait after a printer or copier has been turned on until the printer or copier becomes workable. Since a user usually desires a printer or copier to become workable as soon as possible, a fixing roller or film has to be heated even when the printer or copier is not in use, resulting in an increase in power consumption.
On the other hand, if a fixing roller or film is composed of nickel having a thermal conductivity 210 times greater than that of polyimide, it would be necessary to heat a fixing roller or film less time than a time during which a polyimide film has to be heated, until the fixing roller or film become workable. As a result, it is no longer necessary to heat a fixing roller or film to heat in advance, and hence, a printer or copier including the fixing roller or film composed of nickel becomes workable immediately when the printer or copier is turned on.
As mentioned above, power consumption in a printer or copier can be reduced by using a nickel film as a fixing film. However, a conventional method of fabricating a nickel film is accompanied with problems as follows.
As mentioned earlier, a nickel film having a thickness of 0.03 to 0.20 mm is fabricated by electrocasting. That is, such a nickel film is fabricated by precipitating nickel ions by electrolysis. Hence, the thus fabricated nickel film has such a columnar crystal structure as illustrated in
FIG. 7
, and resultingly, has a shortcoming that the nickel film is weak to a mechanical repeated stress.
In addition, in accordance with a fatigue test, the nickel film has a lifetime in the range of a couple of tens thousand rotation to a couple of millions rotation. There is much dispersion in a lifetime of a nickel film.
In particular, a nickel film fabricated by electrocasting shows remarkable thermal embrittlement when heated to a temperature over 200 degrees centigrade. Hence, a nickel film fabricated by electrocasting is not suitable as a fixing film.
Though ions can be readily precipitated out of a pure metal by electrocasting, it is almost impossible to precipitate ions out of an alloy such as a stainless steel.
As another method of fabricating a metal cylindrical film, there has been suggested a method including the steps of rounding a thin film having a thickness in the range of 0.03 to 0.20 mm, and welding the thus rounded film into a cylinder-shaped film. According to this method, any metal may be used for fabricating a metal cylindrical film.
However, this method is accompanied with such a problem of shortage in a mechanical strength and non-uniformity in a shape of a cylinder, due to a bead treatment at a welded portion, and further due to a defect in a welded portion with respect to a metal structure. In addition, since a metal cylindrical film is fabricated in the method by splicing thin films to each other, a skill is required and it takes much time to do so, resulting in an increase in cost and absence of mass-productivity. Hence, the method is not put to practical use yet.
SUMMARY OF THE INVENTION
In view of the above-mentioned problems in the conventional method of fabricating a metal cylinder film, it is an object of the present invention to provide a circular-shaped metal structure such as a metal cylinder film which has a sufficient mechanical strength and lifetime, and is suitable for mass-production.
It is also an object of the present invention to provide a method of fabricating such a circular-shaped metal structure.
It is further an object of the present invention to provide an apparatus of fabricating such a circular-shaped metal structure.
In one aspect of the present invention, there is provided a circular-shaped metal structure fabricated by plastic working and having a thickness equal to or smaller than 0.09 mm.
In the specification, the term “circular-shaped metal structure” covers a structure composed of a metal, having a closed cross-section in a direction perpendicular to an axis thereof, and being in the form of a loop. For instance, a typical circular-shaped metal structure is a metal cylinder. A belt, a sleeve, a pipe and the like are all included in a circular-shaped metal structure.
The circular-shaped metal structure may include a seam extending in an axis-wise direction thereof. However, it is preferable that the circular-shaped metal structure includes no seams extending in an axis-wise direction thereof.
In the above-mentioned circular-shaped metal structure, a reduction rate of a thickness of the circular-shaped metal structure after plastic-worked to a thickness of the circular-shaped metal structure before plastic-worked is equal to or greater than 40%.
It is preferable that the circular-shaped metal structure has a Vickers hardness Hv equal to or greater than 380 after plastic-worked.
It is preferable that the circular-shaped metal structure has a Vickers hardness Hv in the range of 100 to 250 both inclusive after plastic-worked and then annealed.
For instance, the above-mentioned circular-shaped metal structure is fabricated by spinning working. However, the circular-shaped metal structure can be fabricated by plastic working other than spinning.
In another aspect of the present invention, there is provided a method of fabricating a circular-shaped metal structure, including the steps of (a) rotating a pipe around an axis thereof, the pipe being composed of a plastic-workable metal, and (b) applying drawing to an outer wall of the pipe with the pipe being kept rotated, to reduce a wall thickness of the pipe and lengthen a wall of the pipe.
In accordance with the method, it is possible to fabricate a circular-shaped metal structure which may be used as a photosensitive drum or a fixing roll by applying spinning working to a pipe. Herein a pipe includes a pipe having a bottom and a pipe having no bottom. A pipe having a bottom can be fabricated by warm or cold drawing, and a pipe having no bottom can be fabricated by rounding a film and welding the film at opposite ends. The pipe is annealed to control a hardness thereof, if necessary, and then, is subject to spinning to have a thickness in the range of 0.03 to 0.20 mm both inclusive. Then, if necessary, the pipe is annealed again at a low temperature. The resultant circular-shaped metal structure is stiff, has a high resistance to fatigue and a high thermal conductivity, and is superi
Ito Youji
Sakuma Masaru
Hayes & Soloway P.C.
K.K. Endo Seisakusho
Tolan Ed
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