NUMERICALLY CONTROLLED CHAMFERING APPARATUS FOR GLASS PLATES

Abstract: This invention relates to a numerically controlled chamfering apparatus used to chamfer and grind the peripheral portions of a glass plate, such as a window glass for an automobile. An object of this invention is to chamfer a glass plate at a predetermined rate at all times in accordance with the variations in the grinding capacity of a chamfering wheel used for chamfering a corner portion of a glass plate. This invention is directed to a numerically controlled chamfering apparatus for glass plates, consisting of a mechanism for transferring a chamfering head (58) with chains (42), (62) on a horizontal plane in the direction of X-axis and the direction of Y-axis which crosses the direction of X-axis at right angles thereto, a swing mechanism composed of a rotary disc provided in the chamfering head, a pressure applying mechanism slidingly supporting the chamfering wheel in the direction of a normal to a periphery of the glass plate with respect to the disc, and adapted to move the chamfering wheel forward and backward, and a control unit for regulating the quantity of the forward and backward movements of the chamfering wheel. This apparatus is capable of chamfering a glass plate at a predetermined rate even when the shape of the glass plate and the diameter of the chamfering wheel vary.

Description: The present invention relates to a numerically controlled chamfering apparatus for a glass plate in accordance with the preamble of Claim 1. Such a device is known from EP-A-0 114 141. BACKGROUND TECHNIQUE Heretofore, there has been known as a numerically controlled chamfering apparatus for a glass plate of this kind a chamfering apparatus disclosed in Japanese Unexamined Patent Publication 37040/1984. The numerically controlled chamfering apparatus for a glass plate comprises a fitting holder for setting a glass plate having a desired shape horizontally and a chamfering wheel provided at the upper side of the fitting holder so as to be movable to a desired position by two driving systems having an X axis and a Y axis intersecting the X axis perpendicularly, wherein the chamfering wheel comprises a Z axis system which horizontally turns an arm supporting the chamfering wheel by a servo motor, and the arm has the same center axis as that for turning horizontally in the horizontally turning mechanism, the arm having a degree of freedom around the central axis as a supporting point. As the arm has such degree of freedom, problems of an error in shape of a glass plate, an error in position of the glass plate and so on can be eliminated. In the numerically controlled chamfering apparatus for a glass plate disclosed in Japanese Unexamined Patent Publication No. 37040/1984, however, there were problems that because a point for driving by the X and Y driving systems did not coincide with a point for grinding the glass plate, (1) it was unavoidable that a speed of grinding at a corner portion greatly decreased in comparison with that at a linear portion, and (2) a centrifugal force was produced at a swing arm and a wheel spindle at the corner portion, however, there was no back-up system. As a result, it was difficult to uniformly chamfer the peripheral edge of a glass plate. Further, since the shape of glass plates to be supplied are slightly different from each other. The diameter of the chamfering wheel becomes small due to wearing. In a case of the replacement of a chamfering wheel, the function of grinding of a fresh chamfering wheel is different from that of the chamfering wheel which has been replaced. In such cases, the conventional numerically controlled chamfering apparatus for a glass plate could not cope enough with a change of the function of grinding of the chamfering wheel or another change, and there were a disadvantage that a quantity of chamfering varies for products. SUMMARY OF THE INVENTION In view of the above-mentioned circumstances, it is an object of the present invention to provide a numerically controlled chamfering apparatus for a glass plate capable of machining at a constant quantity of chamfering even when a change in the function of grinding of a chamfering wheel takes place. The foregoing and other objects of the present invention have been attained by providing a numerically controlled chamfering apparatus for a glass plate in accordance with Claim 1. In the present invention, a constant quantity of chamfering can always be obtained even when an error in shape of a glass plate, an error in diameter of a chamfering wheel and so on take place. BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 is a plane view of a numerically controlled chamfering apparatus for a glass plate according to the present invention; Figure 2 is a side view of the numerically controlled chamfering apparatus for a glass plate taken along a line II-II in Figure 1; Figure 3 is a side view of the numerically controlled chamfering apparatus for a glass plate taken along a line III-III in Figure 1; Figure 4 is a plane view of a chamfering head for the numerically controlled chamfering apparatus for a glass plate according to the present invention; and Figure 5 is a side view of the chamfering head. BEST MODE OF AN EMBODIMENT OF THE PRESENT INVENTION Preferred embodiments of the numerically controlled chamfering apparatus for a glass plate of the present invention will be described in detail with reference to the drawings. As shown in the drawings, leg portions 14, 15 are provided at the central portion of a base frame 12 of a numerically controlled chamfering apparatus for a glass plate 10, and a table 6 is attached to the top of the leg portions. A plurality of attracting pads 18, 18, ... are arranged in a same level on the table 16 so that a glass plate 20 can be attracted and fixed in a horizontal plane. At four corners of the base frame 12, leg portions 22, 22, 22, 22 are set up. A pair of X axis fixed frames 24, 24 are provided on the leg portions 22 in the direction of right and left in Figure 1, and further, X axis guides 26, 26 are respectively provided at the X axis fixed frames 24, 24 in the direction of right and left. Between the paired X axis guides 26, 26, a Y axis movable frame 28 is extended in the longitudinal direction in Figure 1 so that the Y axis movable frame 28 can run in the right and left direction (the X axis direction) in Figure 1 by the X axis guides 26, 26 through a bearing 30 which is shown in Figure 2. An X axis driving servo motor 34 is attached through a bracket 32 to the leg portion 22 located at the lower left corner in Figure 1, and the output shaft 36 of the servo motor 34 is directly connected to an X axis driving shaft 38 in the longitudinal direction in Figure 1. Sprockets 39, 39 are respectively provided at both ends of the X axis driving shaft 38, and sprockets 40, 40 (only one is shown) are respectively provided at the X axis fixed frames 24, 24 so as to correspond to the respective sprockets 39, 39. Chains 42, 42 are respectively extended between the sprockets 39 and 40, and the Y axis movable frame 28 is attached to the chains 42, 42 by the aid of fitting pieces 44, 44 (only one is shown). Accordingly, when the servo motor 34 is actuated to rotate, the Y axis movable frame 28 is moved in the X axis direction (in the direction of right and left in Figure 1). A Y axis driving servo motor 48 is attached to the X axis fixed frame 24 through a bracket 46, and a spline shaft 50 is connected to the output shaft of the servo motor 48. A spline nut 52 is attached to the spline shaft 50 so as to be slidable in its axial direction. On the other hand, Y axis guides 54, 54 are attached to the upper part of the Y axis movable frame 28 in the longitudinal direction in Figure 1, and a chamfering head 58 which will be described hereinafter supported by the X axis guides 54 so as to be movable in the longitudinal direction (the direction of Y axis) in Figure 1 through a bearing 56 shown in Figure 3. On the other hand, a sprocket is formed at the outer circumference of the spline nut 52, and a sprocket 60 is pivottally supported by the Y axis movable frame 28 in correspondence to the spline nut 52. Further, a chain 62 is extended between the spline nut 52 and the sprocket 60, and the chain 62 is connected to the chamfering head 58 through a fitting piece 64. Accordingly, when the servo motor 48 is actuated to rotate, the chamfering head 58 is moved in the Y axis direction (in the longitudinal direction in Figure 1). Figure 4 is a plane view of the chamfering head 58, and Figure 5 is a side view of the chamfering head 58. As shown in Figure 5, a circular plate 70 is rotatably supported on and by a frame 66 for the chamfering head 58 through a bearing 68, and a gear 72 is formed at the circumference of the circular plate 70. On the other hand, a motor 74 is attached to the frame 66, and a gear 78 is fixed to the output shaft 76 of the motor 74 so that the gear 78 is interlocked with the gear 72 of the circular plate 70. Accordingly, when the motor 74 is actuated to rotate, the circular plate 70 is actuated to rotate. A spindle housing 80 is attached to the circular plate 70 so as to be movable in the right and left direction in Figures 4 and 5. Namely, a guide bar 82 attached to the spindle housing 80 is guided between a pair of guide rollers 84, 86 which are arranged keeping a predetermined space therebetween so as to be movable in the direction of right and left in Figures 4 and 5. On the other hand, a servo motor 88 is provided on the circular plate 70 as shown in Figure 4; a gear 90 is formed at the output shaft of the servo motor 88; and the gear 90 is interlocked with a rack 96 through idle gears 92, 94, which is formed at a side surface of the spindle housing 80. Accordingly, when the motor 88 is rotated, the spindle housing 80 is guided by the guide rollers 84, 86 so that it is moved in the direction of right and left in Figures 4 and 5. A spindle 9 is supported in a rotatable manner in the spindle housing 80, and a chamfering wheel 102 is attached to the lower portion 100 of the spindle 98. The chamfering wheel 102 is so adapted as to come in contact with the peripheral edge of a glass plate 20 to grind the peripheral edge of the glass plate 20 to thereby perform the chamfering operations as described hereinafter. The spindle 98 is rotated by a motor 106 through a transmission mechanism which will be described hereinafter. Namely, a pulley 110 is provided at the output shaft 108 of the motor 106, and a timing belt 116 is extended between the pulley 110 and a pulley 114 for an intermediate shaft 112 supported by an arm 107 which is provided integrally with the motor 106. Further, a timing belt 112 is extended between a pulley 118 of the intermediate shaft 112 and a pulley 120 of a spindle 98. Thus, a rotational force from the motor 106 is transferred to the chamfering wheel 102 attached to the lower portion of the spindle 98. The embodiment of the present invention having the above-mentioned structure functions as follows. First of all, a glass plate 20 is fixed onto the table 16 through the attracting pads 18, 18, .... The chamfering wheel 12 is rotated by driving the motor 106. In these state, the X axis driving motor 34, the Y axis driving motor 48, the horizontally turning motor 74 and the pushing motor 88 are actuated to be rotated so that the point of grinding 124 of the chamfering wheel 102 is moved along the peripheral edge of the glass plate 20. In this case, it is necessary for the chamfering wheel 102 that the direction of pushing of the wheel 102 is vertical to the peripheral edge of the glass plate 20. This can be accomplished by controlling the turning motion of the chamfering wheel so as to have an angle of 90° to a composite vector of the X axis and the Y axis during the grinding operations. On the other hand, it is sometimes difficult to keep the composite speed of the X and Y axes constant during the grinding due to the shape of the glass plate 20. Accordingly, a torque of the wheel 102 is controlled by a pushing force on the basis of the composite speed. Namely, the pushing force is controlled to generate a wheel torque which corresponds to the composite speed on real time basis in accordance with a previously a determined composite speed or a wheel torque curve. There is a case that the same quantity of grinding can not be obtained even by producing the same wheel torque depending on the ability of grinding of chamfering wheels 102 because the ability of the chamfering wheels 102 varies as they operate for a large number of glass plates. Accordingly, it is necessary to control the ability of grinding the wheels 102. By controlling the ability of grinding the wheels 102, the quantity of grinding to be required can be kept constant. The ability of grinding of the chamfering wheels 102 is generally in proportion to a ratio of the pushing force to the wheel torque. Namely, when the ratio of is large , the ability of grinding of the wheel is low. On the other hand, when it is small, the ability is high. By utilizing the above-mentioned relation, the wheel torque for every composite speed during the grinding is determined by using the following equation, and the pushing force of the chamfering wheel 102 is controlled to produce a torque as a target value. where pushing force measured at the last time: the average value of values obtained by sampling data of pushing force when chamfering operations are carried out, wheel torque measured at the last time: the average value of values obtained by sampling data of wheel torque when chamfering operations are carried out at the last time, coefficient: a constant (the quantity of grinding can be changed by changing it), K: a constant (obtained by experience). Thus, by using the pushing force and the wheel torque of the chamfering wheel 102 measured at the last time chamfering operations, the target value of the wheel at this time is determined, and the pushing force of the chamfering wheel 102 is controlled so that the target value of the torque is produced. In this case, however, since there is no data to be learned for the first time after replacement of wheel and wheel dressing, an estimated value which has been previously obtained by experience is used as the ability of grinding of the wheel. The glass plate processed first after the replacement of wheel and after wheel dressing is also controlled to produce a requisite quantity of grinding. By using the above-mentioned controlling system, it is possible that the same quantity of grinding can be obtained for an in-curved portion, an out-curved portion and a linear portion. A quantity of grinding can be maintained constant by self-determining the ability of grinding of the wheel and without relying on the ability of grinding of the wheel. To transfer the glass plate 20 having subjected to the chamfering operations to the outside of the chamfering operation system is as follows. For instance, a V-belt driving type glass plate transferring conveyor 130 as shown in Figure 3 is arranged between the attracting pads 18, 18, ...; the entirety of the conveyor 130 is raised as soon as the glass plate 20 is released from the attracting pads 18, 18, ... so that the glass plate 20 is raised to a level higher than the upper plane of the pads 18, and the glass plate is transferred out of the system. The above-mentioned embodiment provides the following effect. (1) It is possible to control as desired a quantity of grinding by detecting and controlling a torque for grinding. For instance, uniform chamfering of the peripheral edge of a single glass plate is possible. Further, it is possible to form chamfering and polishing portion at a part of a glass plate and a thin chamfering portion at the other part of it. (2) Since a change of the sharpness of the chamfering wheel can be detected, a timing of the dressing and a timing of the replacement of the wheel can be foreseen. (3) Since the point used by the X and Y driving systems coincides with the point of grinding of a glass plate, and the pushing force applying means is provided, a speed of processing a corner portion of the glass plate can be increased. As described above, in accordance with the numerically controlled chamfering apparatus for a glass plate according to the present invention, the pushing force applying means for controlling a torque of grinding by causing advance and retreat movements of the chamfering wheel along the direction of the normal line of the peripheral edge of the glass plate in addition to the X axis and Y axis driving systems and the horizontally turning driving system for driving the chamfering wheel. Accordingly, it is possible to process at a constant quantity of chamfering even when the shape of glass plates and the diameter of the chamfering wheel vary.

Claims: A numerically controlled chamfering apparatus for a glass plate (20) wherein a numerical instruction indicating a shape resembling the shape of the peripheral edge of a glass plate (20) is previously given, and a chamfering wheel (102) is moved along the peripheral edge of the glass plate (20) on the basis of the numerical instruction to grind the peripheral edge of the glass plate (20) to thereby perform chamfering, said numerical controlled chamfering apparatus comprising: a base (12); a fitting holder (18) provided on the base (12) to hold the glass plate (20); an x-axis moving means (24,26,34,39,40,42,54) for moving a chamfering wheel (102) on the base (12) in the direction of an x-axis; a y-axis moving means (28,48,54,52,60,62) for moving the chamfering wheel (102) on the base (12) in the direction of a y-axis which intersects the x-axis at a right angle; a turning means for turning the chamfering wheel on the base (12); a pushing force applying means (88) which slidably supports the chamfering wheel (102) on the base (12) in the direction of the normal line of the peripheral edge of the glass plate (20) so as to cause advance and retreat movements of the chamfering wheel (102) relative to the peripheral edge of the glass plate (20), characterized in that , said numerically controlled chamfering apparatus further comprises a control section including means for measuring the pushing force and the wheel torque of the chamfering wheel (102) in the chamfering operation at the last time, said control section adjusting a quantity of the advance or retreat movement of the chamfering wheel (102) in the next chamfering operation by controlling the pushing force applying means (88) on the basis of the grinding ability of the chamfering wheel (102) which is determined by the ratio of the pushing force and the wheel torque. The chamfering apparatus according to claim 1, wherein a circular plate (70) is rotatably supported by a flame (66) in a chamfering head (58), and the circular plate (70) is rotated by a motor (74) whereby the chamfering wheel (102) mounted on the circular plate (70) is turned. The chamfering apparatus according to claim 1, wherein a spindle housing (80) is attached to a circular plate (70) rotatably mounted on a frame (66) in a chamfering head (58) so as to be movable horizontally in any direction; the turning means is adapted to coincide the moving direction of the spindle housing (80) with the direction of the normal line of the peripheral edge of the glass plate (20); the spindle housing (80) is moved toward the glass plate (20) in this state and the chamfering wheel (102) mounted on the spindle housing (80) is pushed to the peripheral edge of the glass plate (20).

Inventors: KANAMARU SHIGEYUKI, NAKAI KOUICHIROU, KANAMARU, SHIGEYUKI, NAKAI, KOUICHIROU
Applicants: ASAHI GLASS CO LTD, ASAHI GLASS COMPANY LTD.
Application year: 1988
Main classification: B24B9
IPC codes: B24B9, B24B7