Grinding body for on-line roll grinding

Details Grinding body for on-line roll grinding Grinding body for on-line roll grinding

1999-08-03

2001-04-24

Morgan, Eileen P. (Department: 3723)

Abrading

Rigid tool

Rotary disk

C451S541000, C451S359000, C451S259000, C451S178000

Reexamination Certificate

active

06220949

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a grinding body for an on-line roll grinding device which is mounted and used on a rolling mill.
2. Description of the Related Art
When on-line roll grinding is performed, it is common practice, as shown in
FIG. 16
, that a plurality of on-line roll grinding devices
20
are placed to face a roll
21
to be ground, each of the on-line roll grinding devices
20
having a grinding body
22
capable of reciprocating in an axial direction of the roll
21
and rotatable along the axial direction, and the grinding body
22
is pressed against a surface of the roll
21
, which is rotating, to grind the surface of the roll
21
. A shaft center
20
a
of the grinding device
20
is set at the same height as an axis
21
a
of the roll
21
, or at a height displaced upward or downward (an offset height H) by a certain distance from the axis
21
a
. The shaft center
20
a
of the grinding device
20
is also set to be horizontally inclined at an angle of &agr; (e.g., 0.5°) from a line
20
b
perpendicular to the axis
21
a
of the roll
21
. This angle of inclination, &agr;, is called a grindstone pressing angle.
Such grinding of the roll
21
with the grinding device
20
is known to pose the following problems: The offset height H and the grindstone pressing angle &agr; that have been set vary because of wear of the roll
21
by rolling, or owing to adjustment of a gap between the upper and lower rolls
21
and
21
. Thus, the grindstone contacts the surface of the roll
21
unevenly, forming a spiral mark and deteriorating the roll surface. Eventually, the roll becomes unusable. Furthermore, roughening of the surface of the roll
21
, and vibrations of the roll
21
due to an increased gap between the roll surface and the grinding body
22
, cause the vibration of the grinding body
22
, thereby forming a pitching surface mark
23
with a streaked pattern, as shown in
FIG. 17
, on the surface of the roll
21
to be ground. Rotary grinding bodies for preventing the formation of the pitching surface mark
23
or the spiral mark were proposed by {circle around (1)} Japanese Unexamined Patent Publication No. 6-47654 (hereinafter referred to as the earlier technology I) {circle around (2)} Japanese Unexamined Patent Publication No. 9-1463 (hereinafter referred to as the earlier technology II), and {circle around (3)} Japanese Unexamined Utility Model Publication No. 62-95867 (hereinafter referred to as the earlier technology III).
The earlier technology I, as shown in
FIGS. 18
to
19
, tries to prevent the formation of the pitching surface mark
23
by securing a thin grindstone
32
onto a flexible, thin, circular base plate
31
having a central portion rotatably supported to constitute a low-rigidity grinding body
22
, and absorbing vibrations of the roll
21
, during grinding, by local warpage of the thin, circular base plate
31
of the grinding body
22
pressed against the roll
21
.
FIG. 20
shows a state in which only an outer edge of the grindstone
32
contacts the roll
21
, so that the thin, circular base plate
31
warps, thus bringing the entire width of the grindstone into contact with the roll
21
.
FIG. 21
shows a state in which only an inner edge of the grindstone
32
contacts the roll
21
.
The earlier technology II focuses on the fact that when the grinding body of the earlier technology I contacts the roll
21
at a circumferential portion of the thin grindstone
32
, as shown in
FIG. 21
, only the warpage of the thin circular base plate
31
is not enough to resolve the uneven contact. In light of this fact, the earlier technology II, as shown in
FIGS. 22
to
25
, secures a cup-shaped grindstone
42
onto a circular base plate
41
having an inward groove
43
defined by a circumferential portion of the circular base plate
41
bent on a surface side, thereby constituting a grinding body. Making use of the groove
43
, the earlier technology II attempts to resolve the contact of only the outer edge or the inner edge of the cup-shaped grindstone
42
with the roll surface, thereby preventing the formation of the spiral mark.
The earlier technology III, as shown in
FIGS. 26
to
27
, tries to prevent the formation of the pitching surface mark by fixing a cup-shaped grindstone
52
having a bottom plate to a circular base plate
51
by means of a nut
55
, with the bottom plate being sandwiched between rubber plates
53
and
54
(FIG.
26
), or fixing a bottom plate of a cup-shaped grindstone
52
to a circular base plate
51
by means of a nut
55
, with a rubber plate
53
being sandwiched therebetween (FIG.
27
), so that vibrations of the roll
21
will be absorbed by the rubber plate
53
(
54
).
With the grinding body of the earlier technology I, the pitching surface mark
23
has been assumed to occur because of vibrations of the roll
21
during on-line grinding. As a countermeasure, the circular base plate has been thinned to impart low rigidity to the grinding body. However, the thinning of an abrasive grain layer and a support portion (collectively called a grindstone) to impart low rigidity because of emphasis on flexibility involves the following problems:
(1) Vibrations occurring in the grinding body
22
during grinding include resonance vibrations associated with vibrations of the roll
21
, and self-excited vibrations associated with stick-slips at the interface between the grindstone and the roll
21
in contact with each other. The self-excited vibrations occur because of the low dynamic stiffness of the support member for the grindstone, i.e., the circular base plate. The self-excited vibrations lead to the formation of the pitching surface mark
23
.
(2) Since the support member for the grindstone is a flexible, thin, circular base plate, uneven contact of the grindstone with the roll is liable to occur, under a high grinding force, according to changes in roll setting. Thus, the oscillating speed and the grinding force are restricted, so that the grinding power declines.
(3) If the thickness of the abrasive grain layer secured to the thin circular base plate differs, the rigidity of the grindstone also varies.
FIG. 13
is a graph showing the relationship between the thickness of a grindstone and the rigidity of the grindstone. As a one-dot chain line in the drawing indicates, decreases in the grindstone thickness result in rapid decreases in the grindstone rigidity. Thus, the accuracy of grinding lowers according to changes in the rigidity of the grindstone.
To retain the grindstone rigidity, the abrasive grain layer can be thickened only up to a predetermined thickness. Thus, the life of the grindstone shortens.
(4) When the grindstone supported on the flexible thin circular base plate is pressed against the roll with a predetermined pressing force, local warpage occurs, and the stress of the grindstone at the site of warpage increases. Thus, the pressing force is limited to a level at which the imposed stress is below the allowable grindstone stress. Consequently, the grinding power is restricted.
FIG. 14
is a graph showing the relationship between the grindstone pressing force and the grindstone stress. As indicated by a one-dot chain line in the drawing, the imposed stress exceeds the allowable grindstone stress when the pressing force is about 50 kgf or more.
(5) To reduce the weight of the rotary movable portion, the abrasive grain layer needs to be thinned. Since the thickness of the abrasive grain layer is thus restricted, the life of the grindstone becomes short.
With the earlier technology II, special deformation of the grooved circular base plate
41
has resolved uneven contact of the grindstone with the roll. However, the pitching surface mark associated with self-excited vibrations, the problem with the earlier technology I, has not been resolved.
According to the earlier technology III, the pitching surface mark has considerably been diminished because of the effect of the rubber plate. However, its diminution has not been complete

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