Patent Publication Number: US-6220949-B1

Title: Grinding body for on-line roll grinding

Description:
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 α (e.g., 0.5°) from a line  20   b  perpendicular to the axis  21   a  of the roll  21 . This angle of inclination, α, 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 α 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. The reason is that the inserted rubber plates  53  and  54  are exposed to the outside, so that the damping effect of rubber has not been fully exhibited owing to the penetration of foreign matter or the deterioration of rubber. 
     SUMMARY OF THE INVENTION 
     The present invention has been accomplished in view of the above-described problems. It is an object of the invention to provide a grinding body for on-line roll grinding, which can effectively prevent the formation of a spiral mark and a pitching surface mark, which can improve the grinding power and grinding accuracy, and which can prolong the life of a grindstone. 
     To attain the above object, an aspect of the present invention claims a grinding body for on-line roll grinding, comprising a grindstone mounted in a cup shape on a surface portion, and near a peripheral edge, of a circular support base plate, wherein: 
     a peripheral edge portion of the circular support base plate has on a surface side thereof a two-layer structure including a flat ring-shaped portion jutting toward an inner periphery so as to define a transverse groove-like gap opening inward; 
     the grindstone is mounted on the flat ring-shaped portion; and 
     a damping material is filled and mounted into the transverse groove-like gap. 
     According to this aspect of the invention, the uneven contact of the grindstone with the roll is resolved during roll grinding, the formation of a spiral mark on the roll surface is resolved, the oscillating speed of the grinding body can be increased, the grinding force is not restricted, and the grinding power can be improved. Vibration energy generated in the grindstone is mostly absorbed to the damping material filled into the groove, and transmitted to the circular support base plate. As a result, self-excited vibrations in the grinding body associated with stick-slips at the interface between the grindstone and the roll in contact with each other are markedly reduced, and the formation of a pitching surface mark on the roll surface due to the self-excited vibrations is resolved. 
     Preferably, an opening of the transverse groove-like gap filled and mounted with the damping material is sealed with a waterproof joint filler. This sealing can prevent the penetration of foreign matter, and protect the damping material, thus preventing the deterioration of the grinding body. 
     Another aspect of the invention is a grinding body for on-line roll grinding, comprising a grindstone mounted in a cup shape on a surface portion, and near a peripheral edge, of a circular support base plate, wherein: 
     a peripheral edge portion of the circular support base plate has on a surface side thereof a two-layer structure including a flat ring-shaped portion jutting toward an inner periphery so as to define a transverse groove-like gap opening inward; 
     a plate thickness, c, of the flat ring-shaped portion as one of two layers of the two-layer structure, and a plate thickness, b, of the other layer of the two-layer structure, with the transverse groove-like gap being sandwiched between the two layers, is in a relation, b&lt;c; 
     the grindstone is mounted on the flat ring-shaped portion with the plate thickness c; and 
     a damping material is filled and mounted into the transverse groove-like gap. 
     According to this aspect of the invention, the flat ring-shaped portion with a large thickness minimally deforms during roll grinding, and excessive stress does not occur in the grindstone (including its mating surface). Thus, an increase in the grindstone pressing force can enhance the grinding power. Furthermore, even if the thickness of the grindstone varies, the rigidity of the grindstone minimally changes, and the grinding accuracy can be retained. In addition, the abrasive grain layer can be thickened to prolong the life span of the grindstone until its replacement. 
     Preferably, an opening of the transverse groove-like gap filled and mounted with the damping material is sealed with a waterproof joint filler. This sealing can prevent the penetration of foreign matter, and protect the damping material, thus preventing the deterioration of the grinding body. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The present invention will become more fully understood from the detailed description given hereinbelow and the accompanying drawings which are given by way of illustration only, and thus are not limitative of the present invention, and wherein: 
     FIG. 1 is a vertical sectional side view of a grinding body according to a first embodiment of the present invention; 
     FIG. 2 is a view taken on line II—II of FIG. 1; 
     FIG. 3 is a partly enlarged view of FIG. 1; 
     FIG. 4 is a sectional view showing a state of contact of only an outer portion of a cup-shaped grindstone with a roll; 
     FIG. 5 is a sectional view showing a state of contact of only an inner portion of a cup-shaped grindstone with a roll; 
     FIGS.  6 ( a ) and  6 ( b ) are graphs for comparing the vibration waveform of a grindstone in the present invention with that in the earlier technology; 
     FIGS.  7 ( a ) and  7 ( b ) are graphs for comparing the dynamic stiffness (compliance) of a grindstone in the present invention with that in the earlier technology; 
     FIGS.  8 ( a ) and  8 ( b ) are graphs for comparing the status of a pitching surface mark in the present invention with that in the earlier technology; 
     FIG. 9 is a vertical sectional side view of a grinding body according to a second embodiment of the present invention; 
     FIG. 10 is a partly enlarged view of FIG. 9; 
     FIG. 11 is an explanation drawing showing the state of warpage of a circular support base plate of the grinding body as the second embodiment of the present invention; 
     FIG. 12 is an explanation drawing showing the state of warpage of a circular support base plate of a grinding body according to the earlier technology I; 
     FIG. 13 is a graph showing the relationship between the thickness and rigidity of a grindstone in each of the present invention and the earlier technology I; 
     FIG. 14 is a graph showing the relationship between the pressing force and stress of a grindstone in each of the present invention and the earlier technology I; 
     FIGS.  15 ( a ) and  15 ( b ) are graphs showing the relationship between the pressing force of a grindstone and grinding power in each of the present invention and the earlier technology I; 
     FIG. 16 is a perspective view showing the situation of on-line roll grinding; 
     FIG. 17 is a side view of a roll; 
     FIG. 18 is a side sectional view of a conventional grinding body; 
     FIG. 19 is a front view of the conventional grinding body; 
     FIG. 20 is a view showing an operating state of the conventional grinding body; 
     FIG. 21 is a view showing a different operating state of the conventional grinding body; 
     FIG. 22 is a side sectional view of a different conventional grinding body; 
     FIG. 23 is a front view of the different conventional grinding body; 
     FIG. 24 is a view showing an operating state of the different conventional grinding body; 
     FIG. 25 is a view showing a different operating state of the different conventional grinding body; 
     FIG. 26 is a sectional plan view of a further different conventional grinding body; and 
     FIG. 27 is a sectional plan view of a modified conventional grinding body. 
    
    
     PREFERRED EMBODIMENTS OF THE INVENTION 
     A grinding body for on-line roll grinding according to the present invention will now be described in detail by way of the following Embodiments with reference to the accompanying drawings, but it should be understood that the invention is not restricted thereby. 
     [First Embodiment] 
     Constitution 
     In FIGS. 1 to  3 , the reference numeral  12  denotes a grinding body having a central portion and a peripheral edge portion rotatably supported by a support shaft  10  and a bearing  11  of an on-line roll grinding device  20 . The grinding body  12  is composed of a circular support base plate  13  of a metal, such as SUS, constructed in a two-layer structure from a horizontal jutting portion  13   b  and a flat ring-shaped portion  13   c , the horizontal jutting portion  13   b  jutting outward from a short tubular portion  13   a , and the flat ring-shaped portion  13   c  extending upward and then toward a central side from an outer peripheral edge portion of the horizontal jutting portion  13   b  in such a manner as to be opposed to the horizontal jutting portion  13   b  while defining a transverse groove  14  opening toward the central side; a damping material  15  filled into the groove  14 ; and an integral, cup-shaped grindstone  16  secured onto a surface of the flat ring-shaped portion  13   c . The reference numeral  17  denotes a joint filler, such as a waterproof silicone material, provided to seal an opening of the groove  14  when the damping material  15  is not waterproof. As the damping material  15 , a vibration absorbing rubber member, such as a sand-containing one, or a damper is used. 
     Actions and Effects 
     When only an outer end of the cup-shaped grindstone  16  of the grinding body  12  contacts a surface of a roll  21 , and is pressed against it, as shown in FIG. 4, the horizontal jutting portion  13   b  below the groove  14  in the circular support base plate  13  warps outwardly downwardly. Thus, the entire width of the cup-shaped grindstone  16  contacts the surface of the roll  21 . In this state, the grinding body  12  rotates. 
     When only an inner end of the cup-shaped grindstone  16  of the grinding body  12  contacts the surface of the roll  21 , and is pressed against it, as shown in FIG. 5, the flat ring-shaped portion  13   c  above the groove  14  in the circular support base plate  13  warps inwardly downwardly. Thus, the entire width of the cup-shaped grindstone  16  contacts the surface of the roll  21 . In this state, the grinding body  12  rotates. 
     Under these actions, the uneven contact of the grindstone  16  with the surface of the roll  21  is resolved. Thus, the formation of a spiral mark on the roll surface is resolved, the oscillating speed of the grinding body can be increased, the grinding force is not restricted, and the grinding power can be enhanced. 
     In this state, vibration energy occurring in the cup-shaped grindstone  16  is mostly absorbed to the damping material  15  filled into the groove  14 , and transmitted to the circular support base plate  13 . As a result, self-excited vibrations in the grinding body  12  associated with stick-slips at the interface between the cut-shaped grindstone  16  and the roll  21  in contact with each other are markedly reduced, and the formation of a pitching surface mark  23  on the surface of the roll  21  due to the self-excited vibrations is resolved. 
     FIGS.  6 ( a ) and  6 ( b ) show the results of a hammering test conducted to compare a vibration waveform occurring in the grinding body (a) when the damping material  15  is provided in the groove  14  as in the present invention, and (b) when the damping material  15  is absent as in the earlier technology II, but with the same constitution provided. In these drawings, the vertical axis represents the amplitude relative to a reference line 0, while the horizontal axis represents the passage of time in seconds. In the absence of the damping material  15 ( b ), vibrations under an external force continue at the same amplitude. In the presence of the damping material  15 ( a ), it is clear that the amplitude is rapidly attenuated. 
     FIGS.  7 ( a ) and  7 ( b ) show the results of a hammering test conducted to compare displacement under unit load (compliance) which occurs for each vibration frequency, i.e., dynamic stiffness, in the circular support base plate  13  (grinding body), (a) when the damping material  15  is used, and (b) when the damping material  15  is not used. In these drawings, the vertical axis represents the vibration frequency in Hz, while the horizontal axis represents the displacement of the circular support base plate in μm/kgf at a major ratio (b)/(a)=100/1. In the absence of the damping material  15 ( b ), displacement of about 230 μm/kgf appears at maximum resonance. In the presence of the damping material  15 ( a ), displacement at maximum resonance is about 1.6 μm/kgf. Thus, the dynamic stiffness of the circular support base plate increases under the action of the damping material  15 , and the displacement of the circular support base plate markedly decreases to about {fraction (1/100)} of the value obtained for (b). Thus, a damping effect can be obtained. 
     Furthermore, an opening of the groove  14  mounted with the damping material  15  is sealed with the joint filler  17 . This sealing can prevent the penetration of foreign matter, and protect the damping material  15 , thus preventing the deterioration of the grinding body. 
     FIGS.  8 ( a ) and  8 ( b ) show the results of investigation into the status of a pitching surface mark under on-line grinding conditions (a) when the damping material  15  is used, and (b) when the damping material  15  is not used. In these drawings, the horizontal axis represents the peripheral speed of the roll (m/min), while the vertical axis represents the grindstone pressing linear pressure (kgf/mm). In experiments, on-line grinding operation was performed for a constant period of time at roll peripheral speeds of 600 m/min, 900 m/min, 1200 m/min and 1500 m/min under a grindstone pressing linear pressure varied from 0.5 kgf/mm to 3 kgf/mm with a pitch of 0.5 kgf/mm. The status of a pitching surface mark was evaluated visually under the following criteria: 
     No pitching surface mark occurred=“Satisfactory” ∘ 
     A faint pitching surface mark occurred=“Allowable” Δ 
     A clear pitching surface mark occurred=“Poor”  
     The results of FIGS.  8 ( a ) and  8 ( b ) demonstrate that the constitution of the present invention combined with the damping material  15  resolves the formation of a pitching surface mark which has occurred with the earlier technologies. 
     [Second Embodiment] 
     Constitution 
     This embodiment is the preceding First Embodiment, but with the constitution of the circular support base plate  13  being partially changed such that the plate thickness b of the horizontal jutting portion  13   b  and the plate thickness c of the flat ring-shaped portion  13   c  will be in the relationship b&lt;c. The same members as in the First Embodiment are assigned the same numerals, and their detailed explanations are omitted. 
     In FIGS. 9 to  10 , dimensions for the plate thickness in the circular support base plate  13  are set such that the plate thickness c of the flat ring-shaped portion  13   c  is greater than the plate thickness b of the horizontal jutting portion  13   b , i.e., b&lt;c. Along with this configuration, the thickness of the cup-shaped grindstone  16  can be made greater than before, e.g., can be increased to about 20 to 30 mm. Other constituent features of the grinding body are nearly the same as in the First Embodiment, and their explanations are omitted. 
     Actions and Effects 
     The surface of the grindstone  16  secured to the flat ring-shaped portion  13   c  grinds the surface of the roll  21  while rotating in contact with the roll  21 . During this grinding, the force, with which the grindstone is pressed against the roll, imposes a warping, deforming force on the circular support base plate  13 . As stated above, the plate thickness b of the horizontal jutting portion  13   b  and the plate thickness c of the flat ring-shaped portion  13   c  are set in the relation b&lt;c. Thus, the flat ring-shaped portion  13   c  given a great plate thickness minimally deforms, while only the horizontal jutting portion  13   b  with a small plate thickness warps and deforms. 
     FIG. 11 illustrates these situations found by FEM analysis. When an external force is exerted on a grinding surface of the grindstone  16  (its upper surface in the drawing), the circular support base plate  13  warps and deforms from a state indicated by a solid line to a state indicated by a one-dot chain line. As this deformation shows, deformation at a site B is predominant, and there is no local deformation at a site C. Thus, no overstress occurs in the grindstone  16  (including its mating surface). With the earlier technology I shown in FIG. 12, by contrast, excessive stress may occur in the boundary line A between the circular base plate  31  and the grindstone  32 , damaging the grindstone  32 . 
     FIG.  15 ( a ) shows the results of experiments for measuring the grinding power per unit time versus the grindstone pressing force for the present invention (solid line) and the earlier technology I (one-dot chain line). FIG.  15 ( b ) is an enlarged view of FIG.  15 ( a ) for the earlier technology I (one-dot chain line) In these experiments, grinding was performed, using a roll of nickel grains and a grindstone of CBN, at a roll peripheral speed of 600 m/min and an oscillating speed of a grinding device of 30 m/sec to 80 m/sec. The amount of grinding per unit time was measured at a plurality of points with different magnitudes of the grindstone pressing force. In the case of the earlier technology I indicated by the one-dot chain line in the drawings, experiments were performed under the same conditions, with the grindstone pressing force restricted to a practical range of 40 kgf or less. Similarly, the amount of grinding per unit time was measured at a plurality of points with different magnitudes of the grindstone pressing force. 
     According to the present invention, even when the grindstone pressing force is rendered high as shown by a solid line in FIG. 14, the stress of the grindstone remains within the grindstone allowable stress (indicated by a dashed line in the drawing). Thus, the grinding power can be enhanced by increasing the grindstone pressing force, as indicated by the solid line in FIG.  15 ( a ). Furthermore, deformation at the site B in FIG. 11 is predominant, and there is no local deformation at the site C. As shown by the solid line in FIG. 13, therefore, even when the thickness of the grindstone varies, the rigidity of the grindstone minimally changes. Consequently, the grinding accuracy can be maintained. Besides, the absence of location deformation at the site C makes it possible to thicken the abrasive grain layer, thus prolonging the life span of the grindstone  16  until replacement. 
     This invention being thus described, it will be obvious that the same may be varied in many ways. Such variations are not to be regarded as a departure from the spirit and scope of the invention, and all such modifications as would be obvious to one skilled in the art are intended to be included within the scope of the following claims.