Spindle unit
A sealing portion on a lower end of a cover portion of a spindle cover has an upper side surface and a lower side surface that are inclined toward an outer circumferential surface of a spindle. A larger-diameter disk and the outer circumferential surface of the spindle define therebetween a second gap that is narrower than a first gap defined between the spindle and the cover portion. The second gap is effective to prevent a processing waste liquid from entering between the spindle and the spindle cover to prevent a solid waste contained in the processing waste liquid from sticking to the spindle. The spindle is thus prevented from becoming less liable to rotate smoothly due to solid waste deposits.
1. A spindle unit comprising:
a spindle having a distal end coupled to a mount for mounting a processing tool;
a casing surrounding an outer circumferential surface of the spindle, the spindle being rotatably supported by an air bearing in the casing; and
a spindle cover surrounding the spindle between a lower end of the casing and the mount, wherein the spindle cover includes:
a cover portion having an inner circumferential surface facing the outer circumferential surface of the spindle, the inner circumferential surface of the cover portion and the outer circumferential surface of the spindle defining a first gap therebetween, and
a sealing portion integrally formed with the cover portion at a lower end of the cover portion and having a first inner oblique surface inclined toward the outer circumferential surface of the spindle, and
the sealing portion and the outer circumferential surface of the spindle define therebetween a second gap that is narrower than the first gap for preventing a solid waste from being dried and deposited on the outer circumferential surface of the spindle, wherein a clearance between the spindle on the one side and the casing and the spindle cover on the other side forms a channel filled exclusively with air from the air bearing which discharges partially through the second gap, wherein the channel includes both the first gap and the second gap.
2. The spindle unit of claim 1 , wherein the first inner oblique surface forms a lower side surface of the sealing portion, such that the lower side surface is non-perpendicular with the outer circumferential portion of the spindle.
3. The spindle unit of claim 1 , wherein the first inner oblique surface forms a lower side surface of the sealing portion, such that the lower side surface is oblique with respect to an axis of rotation of the spindle.
4. The spindle unit of claim 1 , wherein the sealing portion further comprises a second inner oblique surface and a vertex where the first inner oblique surface and the second inner oblique surface join, wherein the first inner oblique surface and the second inner oblique surface are inclined in opposite directions.