The present invention generally relates to disk chucks that center and clamp disks, such as rigid and flexible magnetic media, optical data storage media and the like, and in particular to disk chucks for releasably securing a disk for high speed rotation.
During the manufacture of magnetic or optical recording media, such as floppy disks, hard disks, CD ROM disks, magneto-optical disks, and the like, many process steps require that the disk be releasably mounted to a rotatable arbor. Such process steps may include application of surface coatings, as well as cleaning, polishing, burnishing, and testing.
There are known in the prior art various forms of rotating disk chucks for releasably mounting a disk. Data disks must conform to extremely close tolerances for planarity, surface finish, and coating integrity, which requires that the chuck securing a disk during processing must grip the disk with a high degree of concentricity and planarity, and cannot impart any curvature or warping to the disk. Moreover, the chuck must grip the disk only at portions that will not be used for data recording. An improved disk chuck is desired.
In accordance with an embodiment of the present invention, a chuck holds a disk by the inside diameter with a plurality of contact surfaces at the end of fingers. Axial motion of an actuator is translated into outward radial movement of the fingers to place the contact surfaces in contact with the inside diameter of the disk. The force that is applied to the disk is limited to reduce or eliminate warping or curvature of the disk. In one embodiment, a sleeve that surrounds the fingers of the collet can be used as a hard stop to physically limit the range of outward radial movement of the fingers.
The chuck 100 includes an expander element, such as expander cap 104, that is used to radially expand the collet 112 to contact and hold a disk. As illustrated in
The expander element, e.g., expander cap 104, is coupled to an actuator 120 via a piston rod 106, which may be, e.g., threadedly coupled to both the expander cap 104 and the actuator 120. The actuator 120 pulls the piston rod 106 axially towards the base 110, which pulls the expander cap 104 into the collet 112. The rounded fillet 105 on the expander cap 104 and beveled surfaces on the inside surfaces of the collet 112 translate the axial motion of the expander cap 104 into radial expansion of the collet 112. In this manner, the collet 112 can be expanded to contact the inside diameter of a disk. The sleeve 102, however, limits the radial expansion of the collet 112, thereby limiting the force that is applied on the collet 112 to the disk 101. It should be understood that if desired, the expander cap 104 may have a beveled surface and the collet have the rounded fillet. Alternatively, both the collet and the expander cap may have beveled surfaces, but this will increase friction when attempting to expand the collet 112.
The actuator 120 is mounted in a cavity 116 within the base 110. The actuator 120 may be a vacuum activated piston, as illustrated in
The sleeve 102, expander cap 104 and the collet 112 (and, thus, the base 110 and shaft 111, which are integrally formed) are manufactured from non-magnetic materials, such as stainless steel, aluminum and possible plastic may be used, particularly for the expander cap. Additionally, the materials used for the collet 112 and the expander cap 104 should be dissimilar.
As shown in
Moreover, because the fingers 142 impart an outward force on the inside diameter 101ID of the disk 101, as opposed to a downward clamping force, the fingers 142 generate little or no curvature or warping of the disk 101. It should be noted that it may be desirable for the contact surface 148 of the projections 146 to be slightly beveled downward, e.g., approximately 1° or less, to impart a small downward force on the disk 101 to help maintain the position of the disk 101 against the end of the sleeve 102. Nevertheless, even with a beveled contact surface 148, most of the force provided by the fingers 142 on the disk 101 is outward and, thus, there is little or no curvature or warping of the disk 101. Further, collet 112 provides a large approximately continuous area of contact on the inside diameter of the disk 101, which further assists in limiting the curvature or warping of the disk 101. During manufacturing, it may be desirable to machine and/or polish the contact surfaces 148 of the fingers with the chuck 100 in a closed position, i.e., with the fingers 142 pushed outward, so that the position of the contact surfaces 148 are as accurate as possible when the chuck 100 is holding a disk.
In one embodiment, the fingers 142 are manufactured to provide a spring force to bias the chuck 100 in an open position. The spring force of the fingers 142 should be less than the force applied by the actuator 120, which is, e.g., approximately 3 to 3.5 pounds, but sufficient to open the chuck to release a disk when the vacuum is released. The fingers 142 may be manufactured with an appropriate spring force by one of ordinary skill in the art in light of the present disclosure and taking into considerations such as the number, thickness and material of fingers as well as the vacuum force applied by the spindle and friction coefficient between the collet 112 and the expander cap 104. In another embodiment, a spring inside the central bore 113, e.g., between the expander cap 104 and the bearing mount 134, may be used to produce the desired open bias force. Alternatively, the spindle may apply a vacuum to close the chuck 100 and air pressure to open the chuck 100. In yet another embodiment, the chuck 100 may be biased closed, e.g., with a spring inside the central bore 113, e.g., between the bearing mount 134 and/or the base 110 and the actuator 120, may be used to produce the desired closed bias force. The spindle would apply air pressure to the actuator 120 to overcome the spring bias to open the chuck 100.
Chuck 200 includes cantilevered collet 240 that is formed separately from and is coupled to the base 210. A sleeve 202 is mounted to the base 210 and in one embodiment is integrally formed with the base 210 as an axially extending shaft. As with sleeve 102 in
As with the collet 112 in
In operation, the actuator 120 pulls the piston rod 206 axially towards the base 210, which pulls the expander cap 204 into the collet 240 thereby producing radial movement of the fingers 242. The amount of outward movement of the fingers 242 and, thus, the static force applied to a disk 101, is controlled by the actuator 120 and the vacuum or air pressure supplied by the spindle (not shown) to which the chuck 200 is attached. The sleeve 202 may serve as a hard stop to limit the radial movement of the fingers 242 as described in reference to chuck 100.
The chuck 200 may be bias closed using spring 262 and opened using air pressure supplied from the spindle to the actuator 120. Alternatively, the chuck 200 may be biased open using spring 264, illustrated with dotted lines, and closed using a vacuum supplied from the spindle to the actuator 120. In yet another embodiment, the spring force supplied by the fingers 242 may bias the chuck 200 open, as discussed above.
Although the present invention is illustrated in connection with specific embodiments for instructional purposes, the present invention is not limited thereto. Various adaptations and modifications may be made without departing from the scope of the invention. Therefore, the spirit and scope of the appended claims should not be limited to the foregoing description.
Number | Name | Date | Kind |
---|---|---|---|
2398278 | Bailey | Apr 1946 | A |
2507686 | Altmayer | May 1950 | A |
3360276 | Peffer | Dec 1967 | A |
3495844 | Dee | Feb 1970 | A |
3583714 | Weltzer et al. | Jun 1971 | A |
3587371 | Sherwood | Jun 1971 | A |
3734513 | Kanebako et al. | May 1973 | A |
3768815 | Mathurin | Oct 1973 | A |
4755981 | Ekhoff | Jul 1988 | A |
4958839 | Guzik et al. | Sep 1990 | A |
5048005 | Ekhoff | Sep 1991 | A |
5056082 | Ekhoff | Oct 1991 | A |
5275424 | Watanabe | Jan 1994 | A |
5560624 | Williams et al. | Oct 1996 | A |
5644564 | Peters | Jul 1997 | A |
5785324 | Williams et al. | Jul 1998 | A |
6954330 | Yeom | Oct 2005 | B2 |