Abrading – Abrading process
Reexamination Certificate
1998-09-02
2001-08-14
Eley, Timothy V. (Department: 3723)
Abrading
Abrading process
C451S056000, C451S178000, C451S231000
Reexamination Certificate
active
06273785
ABSTRACT:
The present invention relates to machining of cylindrical parts. More specifically, the invention relates to a process and apparatus for machining long slender shafts.
Cross-reference is made to the following application filed concurrently herewith: U.S. Application Ser. No. 09/145,813, entitled “Grinding Wheel With Geometrical Pattern”, by Timothy R. Jaskowiak et al.
Components for machines and mechanical apparatuses are typically machined to obtain precision tolerances and accurate surface conditions. Machining of the precision surfaces are typically machined by presenting a cutting tool or a grinding wheel against the precision surface.
During machining common precision parts include cylindrical parts. Cylindrical parts or workpieces are rotated about centers found at the ends thereof or supported on the periphery of the workpiece. Cylindrical parts which are relatively soft, having a hardness of Rockwell “C” scale (R
c
) of 40 or less and which have medium tolerance requirements, for example ±0.002 inches in diameter tolerance, are typically turned on a turning machine with a cutting tool.
A lathe, for example, a numerically controlled lathe, is typically used to manufacture this type of workpiece. The workpiece may be rotated about its centers by pressing in with centers on the lathe or, preferably, a portion of the outer periphery of the workpiece is clamped to provide sufficient torque required for the turning process.
More accurate or precision machining, i.e. for parts requiring a tolerance of less than ±0.002 inches and/or for grinding materials having a hardness greater than, for example,
40
R
c
is typically performed on a grinding machine utilizing a grinding wheel. Grinding of precision workpieces is accomplished by rotating the workpiece simultaneously with rotating a cylindrical grinding wheel in contact with the outer periphery of the workpiece. The workpiece is typically rotated about centers found at the end of the workpiece on a machine called a center-type grinder or may be supported on the periphery of the workpiece by a regulating wheel and a rest blade. Such peripheral support for a workpiece is performed on centerless-type grinders.
Long slender shafts requiring precision surfaces that may require a turning or a grinding to be performed thereon are used extensively in machines that pass a substrate through the machine. The long slender shafts are utilized to guide and direct the paper substrate through the machine and/or for performing operations on the substrate. For example, copying machines and printing machines have large substrates in the form typically of paper. The substrate may be in the form of a roll of paper or in the form of cut sheets.
Long shafts and, in particular, long, slender shafts such as those made from durable materials such as steel, deflect under the grinding or cutting of the workpiece. The deflection of the shafts affects the quality of the shafts and the precision requirements required for such shafts may be very difficult to obtain.
Attempts have been made to improve the quality of long thin shafts, which are turned or ground by reducing the deflection of the shaft during machining. The most common tool utilized in reducing the deflection of long thin workpieces is a work support or steady rest. The part deflection due to the force of the grinding wheel or cutting tool or simply due to the mass or weight of the workpiece is counteracted by the support from the steady rest. A further function of the steady rest is to prevent workpiece vibration and thereby to eliminate or reduce chatter.
An understanding of the use of steady rest is more thoroughly described in
Modern Grinding Technology
by Salmon, the relevant portions thereof incorporated herein by reference.
Referring now to
FIG. 8
, a prior art mechanically contacting steady rest is shown in FIG.
8
. The standard steady rest is typically a 2 or 3 point contact tool that holds the part rigidly in place. For example, the steady rest
1
includes three fingers
2
which include contact points
3
which are equally spaced about roll
4
. The fingers
3
are in contact with periphery
5
of the roll
4
and serve to support the roll
4
as it rotates about longitudinal axis
6
. The work support
1
is secured to machine base
7
.
In the well-known process of electrophotographic printing, a charge retentive surface, typically known as a photoreceptor, is electrostatically charged, and then exposed to a light pattern of an original image to selectively discharge the surface in accordance therewith. The resulting pattern of charged and discharged areas on the photoreceptor form an electrostatic charge pattern, known as a latent image, conforming to the original image. The latent image is developed by contacting it with a finely divided electrostatically attractable powder known as “toner.” Toner is held on the image areas by the electrostatic charge on the photoreceptor surface.
Thus, a toner image is produced in conformity with a light image of the original being reproduced. The toner image may then be transferred to a substrate or support member (e.g., paper), and the image affixed thereto to form a permanent record of the image to be reproduced. Subsequent to development, excess toner left on the charge retentive surface is cleaned from the surface. The process is useful for light lens copying from an original or printing electronically generated or stored originals such as with a raster output scanner (ROS), where a charged surface may be imagewise discharged in a variety of ways.
While shafts in electrophotographic printing for guiding substrates require accurate tolerances and may be long and slender, exasperating the accurate tolerance problems, the difficulties encountered in providing accurate donor rolls for scavengeless development systems is particularly acute.
In a scavengeless development system, toner is detached from the donor roll by applying AC electric field to self-spaced electrode structures, commonly in the form of wires positioned in the nip between a donor roll and photoreceptor in the case of hybrid scavengeless development or by applying the AC electrical field directly to the donor roll in the case of hybrid jumping development. This forms a toner powder cloud in the nip and the latent image attracts toner from the powder cloud thereto. Because there is no physical contact between the development apparatus and the photoreceptor, scavengeless development is useful for devices in which different types of toner are supplied onto the same photoreceptor such as in “tri-level”; “recharge, expose and develop”; “highlight”; or “image on image” color xerography.
Since hybrid scavengeless development relies on a continuous, steady toner powder cloud at the nip between the latent image and the donor roller, the speeds at which the rollers operate are significantly higher and the accuracy requirements are much more precise.
The purpose and function of scavengeless development are described more fully in, for example, U.S. Pat. No. 4,868,600 to Hays et al., U.S. Pat. No. 4,984,019 to Folkins, U.S. Pat. No. 5,010,367 to Hays, or U.S. Pat. No. 5,063,875 to Folkins et al. U.S. Pat. No. 4,868,600 is incorporated herein by reference.
For proper operation of a donor roll in a hybrid scavengeless development, the diameter tolerance, runout and surface finish requirements of the donor roll are very critical and require very precise dimensions. Furthermore, donor rolls typically have a long length and a small diameter. For example, donor rolls may have a length of, for example, 18 to 24 inches and a diameter from 1 to 1 ½ inches. When machining donor rolls with such a length to diameter ratio of 20 to 1 or greater, the rolls tend to deflect during the machining process. To complicate the situation, donor rolls may be made of a hard ceramic material which is difficult to machine. Because of the high tolerances and hard material, the donor rolls are often ground rather than turned. The grinding forces are typically higher than turning forces, thus
DiGravio Thomas L.
Mulroy Grethel K.
Sippel Steven M.
Berry Jr. Willie
Eley Timothy V.
Ryan Andrew D.
Xerox Corporation
LandOfFree
Non-contact support for cyclindrical machining does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Non-contact support for cyclindrical machining, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Non-contact support for cyclindrical machining will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2499695