| 摘要 |
Machine for grinding of optical glass comprises a set (T) of grinders fixed on a shaft (2), and a blank holding unit that brings the blank into contact with the grinders. Also provided are a supplementary, freely-rotating grinder (9) mounted on a support (10, 19), and a device for activating the support in order to move the supplementary grinder from a retracted position to an active position in which the supplementary grinder is spaced from the drive disc. In the active position, the axis of rotation of this grinder (9) is parallel to the axis of the shaft (2). The supplementary grinder (9), whose periphery has magnetic poles (P2), is contactlessly driven by a drive disc (17) which is locked to the grinder set (T), and which is also provided with magnetic poles (P1) at its periphery. The poles (P1) of the drive disc (17) have the same polarity, and the poles (P2) of the supplementary grinder have opposite polarity to those of the drive disc (17). Further devices are included for bringing the blank into contact with the supplementary grinder (9) when the latter is in the active position. Preferably, the supplementary grinder comprises a cylindrical section provided with magnetic poles (P2). In the active position, the periphery of the supplementary grinder (9) is located in the immediate vicinity of that of the drive disc (17). The drive disc (17) can be an additional disc added to the stack of grinders (14A, 14B, 15, 16) of the main set (T) of grinders, or can constitute a section of a grinder of the main set (T). The external diameter of the supplementary grinder (9) is distinctly less than that of the grinders of the main set. The supplementary grinder (9) is preferably a counter-beveling grinder that has two opposed active surfaces and that has truncated cone form. The support (10, 19) comprises a crank pivotally mounted on an axis parallel to the axis of the shaft (2). The support (19) can hold a second supplementary grinder (34) that forms a scoring grinder, and that is axially spaced from, and integrated with, the first supplementary grinder (9). The second supplementary grinder (34) is axially set back from the first supplementary grinder (9).
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