Stamper plate attaching/detaching device of an injection mold for forming an optical disc substrate

A stamper plate attaching/detaching device of an injection mold for forming an optical disc substrate, said device having a longitudinal axis, comprising:

• a fixed disc cavity plate having a plurality of first holes in a surface thereof, said first holes being equally spaced along a first circle having a center on said longitudinal axis and a given diameter;
• a movable disc cavity plate having a plurality of second holes in a surface thereof, said second holes being equally spaced along a second circle having a center on said longitudinal axis and said given diameter, said plurality of second holes being angularly displaced about said longitudinal axis with respect to said plurality of first holes;
• a cavity ring interposed between said fixed and movable cavity plates, said cavity ring, fixed cavity plate and movable cavity plate defining a cavity wherein a stamper plate is supported, said cavity ring having a plurality of magnets therein spaced along a third circle having a center on said longitudinal axis and said given diameter;
• means for rotating said cavity ring about said longitudinal axis between a first angular position and a second angular position with respect to said fixed and movable cavity plates;
• and
• an attractive force generating means, said means generating when said cavity ring is in said first angular position an attractive force between said plurality of magnets and said fixed disc cavity plate and not generating an attractive force between said plurality of magnets and said movable disc cavity plate;
• and when said cavity ring is in said second angular position not generating an attractive force between said plurality of magnets and said fixed disc cavity plate and generating an attractive force between said plurality of magnets and said movable disc cavity plate.

A stamper plate attaching/detaching device of an injection mold for forming an optical disc substrate, said device having a longitudinal axis, comprising:

• a fixed disc cavity plate having a plurality of first magnets buried in a surface thereof, said first magnets being equally spaced along a first circle having a center on said longitudinal axis and a given diameter;
• a movable disc cavity plate having a plurality of second magnets buried in a surface thereof, said second magnets being equally spaced along a second circle having a center on said longitudinal axis and said given diameter, said plurality of second magnets being angularly displaced about said longitudinal axis with respect to said plurality of first magnets;
• a cavity ring interposed between said fixed and movable cavity plates, said cavity ring, fixed cavity plate and movable cavity plate defining a cavity wherein a stamper plate is supported, said cavity ring having a plurality of holes therein spaced along a third circle having a center on said longitudinal axis and said given diameter, and
• means for rotating said cavity ring about said longitudinal axis between a first angular position and a second angular position with respect to said fixed and movable cavity plates, the holes in said cavity ring not being in alignment with said plurality of first magnets and in alignment with said plurality of second magnets when said cavity ring is in said first angular position, whereby said cavity ring is attracted to said fixed disc cavity plate;
• and the holes in said cavity ring not being in alignment with said plurality of second magnets and in alignment with said plurality of first magnets when said cavity ring is in said second angular position, whereby said cavity ring is attracted to said movable disc cavity plate.

A stamper plate attaching/detaching device of an injection mold for forming an optical disc substrate, said device having a longitudinal axis, comprising:

• a fixed disc cavity plate having a plurality of first holes in a surface thereof, said first holes being equally spaced along a first circle having a center on said longitudinal axis and a given diameter;
• a movable disc cavity plate having a plurality of second holes in a surface thereof, said second holes being equally spaced along a second circle having a center on said longitudinal axis and said given diameter, said plurality of second holes being angularly displaced about said longitudinal axis with respect to said plurality of first holes;
• a cavity ring interposed between said fixed and movable cavity plates, said cavity ring, fixed cavity plate and movable cavity plate defining a cavity wherein a stamper plate is supported, said cavity ring having a plurality of magnets therein spaced along a third circle having a center on said longitudinal axis and said given diameter;
• and
• means for rotating said cavity ring about said longitudinal axis between a first angular position and a second angular position with respect to said fixed and movable cavity plates, the magnets in said cavity ring not being in alignment with said plurality of first holes and in alignment with said plurality of second holes when said cavity ring is in said first angular position, whereby said cavity ring is attracted to said fixed disc cavity plate;
• and the magnets in said cavity ring not being in alignment with said plurality of second holes and in alignment with said plurality of first holes when said cavity ring is in said second angular position, whereby said cavity ring is attracted to said movable disc cavity plate.