1. Field of the Invention
This invention relates to an apparatus for exchanging abrasive disc or stones in a vertical-spindle grinding machine.
2. Prior Art
Conventionally, when exchanging an abrasive disc in a vertical-spindle double-head grinding machine, the abrasive disc lifted by a crane can not be brought directly into and out from a space between the opposed spindle housing. Therefore, when exchanging the abrasive disc, feed guide members, such as carriers for feeding a workpiece and/or through-feed blades, are removed. Then, a guide member for sliding contact with a face plate (by which the abrasive disc is fixed to the spindle housing) or one side (end face) of the abrasive disc is inserted into and supported by the machine frame. For example, the guide member comprises a guide plate 61 (FIG. 12) or parallel guide bars 62 (FIG. 13). The upper spindle housing is moved downward to place the upper abrasive disc 5U on the lower abrasive disc 5L, and the upper abrasive disc 5U is removed from the spindle and is placed on the guide member. Then, the upper abrasive disc 5U is slidingly moved over the guide member exteriorly of the machine frame, and is lifted by a crane. Then, the guide member is removed from the machine frame, and the lower abrasive disc 5L is moved upward and is disconnected from the spindle. Then, the guide member is inserted into and fixed to the machine frame, and the lower abrasive disc is placed on the guide member. Then, the lower abrasive disc 5L is slidingly moved over the guide member exteriorly of the machine frame, and is lifted by the crane. Next, for exchanging the lower abrasive disc 5L for a new one, the new abrasive disc 5L is caused to descend so that a face plate of the abrasive disc 5L is brought into contact with that portion of the guide member extending outwardly from the machine frame. Then, a abrasive disc-lifting member of the crane is released from the abrasive disc 5L, and the abrasive disc 5L is slidingly moved over the guide member toward the space between the two spindle housings. Then, the lower abrasive disc is mounted on the lower spindle housing. Then, the guide member is withdrawn or removed from the machine frame, and the lower spindle housing is moved downward. Then, the guide member is again inserted into and fixed to the machine frame, and similarly a new upper abrasive disc 5U is caused to descend by the crane and is placed on the guide member. Then, the upper abrasive disc 5U is slidingly moved over the guide member to come between the two spindle housings, so that the upper abrasive disc 5U is placed over the lower abrasive disc 5L, already mounted on the lower spindle housing, in overlapping relation thereto. Then, the guide member is removed from the machine frame, the upper spindle housing is moved downward toward the upper abrasive disc 5U, and the upper abrasive disc is attached to the upper spindle housing. Thereafter, the feed guide members for feeding the workpiece are again mounted on the machine.
The above prior art has the following problems:
(1) Since the abrasive discs of a heavy weight are caused to slide over the guide member, their face plate or the end face are damaged. PA1 (2) Since the upper abrasive disc is placed over the lower abrasive disc in registry therewith and is slidingly moved relative thereto, there is a risk that the two abrasive discs are damaged, even if an interposing member is interposed between the two abrasive discs. Such an interposing member is made of wood or the like, and therefore it is very difficult to slide the abrasive disc over the interposing member. PA1 (3) Since the guide member is merely inserted into the machine frame, it is difficult to preposition the abrasive disc with respect to the spindle housing when attaching the abrasive disc to the spindle housing. Therefore, much time is required in this respect, and at this time the face plate or the end face of the abrasive disc slides over the guide member or the lower abrasive disc back and forth and right and left, so that the face plate or the end face of the abrasive disc may be further damaged. PA1 (4) Since the upper abrasive disc is placed over the lower abrasive disc, the abrasive disc can not be attached to the spindle housing if the feed guide member for feeding the workpiece is not removed from the machine. PA1 (5) The attachment of the upper abrasive disc is cumbersome because it must be placed over the lower abrasive disc, and besides the upper and lower abrasive discs can not be replaced independently of each other. PA1 (6) Since the abrasive disc is placed directly on the guide member and is pushed into the space between the two spindle housings, there is encountered a large resistance to the sliding movement of the abrasive disc over the guide member. PA1 (7) The abrasive disc is merely placed on the guide member, and hence can be moved freely on the guide member. Therefore, care must be taken to prevent the abrasive disc from becoming disengaged from the guide member. PA1 (8) The above-mentioned problem lowers the operability, and it is rather difficult to arrange the procedure of the operation. PA1 (a) a cover member surrounding the upper and lower abrasive discs and having an opening disposed in a radial direction of the upper and lower abrasive discs for the passage of the abrasive discs therethrough, the cover member having a lid for closing the opening, and the lid being movable into an open position where the lid opens the opening; PA1 (b) a guide rail; PA1 (c) guide rail accommodating means for accommodating the guide rail; PA1 (d) support means for holding the guide rail horizontally so as to allow the guide rail to extend toward a space between the upper and lower spindle housings when the lid is moved to its open position; and PA1 (e) a abrasive disc-carrying slide capable of carrying each of the upper and lower abrasive discs, the slide being engageable with the guide rail for movement therealong into and out of the space between the upper and lower spindle housings when the guide rail is disposed horizontally, and the slide having a pair of first and second positioning portions provided respectively at opposite ends thereof for holding the peripheral surfaces of the upper and lower abrasive discs respectively in first and second predetermined positions. PA1 (a) a cover member surrounding the abrasive disc and having an opening disposed in a radial direction of the abrasive disc for the passage of the abrasive disc therethrough, the cover member having a lid for closing the opening, and the lid being movable into an open position where the lid opens the opening; PA1 (b) a guide rail; PA1 (c) guide rail accommodating means for accommodating the guide rail; PA1 (d) support means for holding the guide rail in a horizontal position so as to allow the guide rail to extend toward the spindle housing when the lid is moved to its open position; and PA1 (e) an abrasive disc-carrying slide capable of carrying the abrasive disc, the slide being engageable with the guide rail for movement therealong toward and away from the spindle housing when the guide rail is disposed horizontally, and the slide having a positioning portion provided at one end thereof for holding the peripheral surface of the abrasive disc in a predetermined position.
The above problems (1), (3), (6), (7) and (8) are also encountered with a vertical-spindle single-head grinding machine.