Work holders – Relatively movable jaws – Means to actuate jaw
Reexamination Certificate
2001-11-30
2004-02-03
Hail, III, Joseph J. (Department: 3723)
Work holders
Relatively movable jaws
Means to actuate jaw
C269S073000, C269S021000, C324S262000
Reexamination Certificate
active
06685179
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention pertains to an object positioning device, and in particular, to a three-dimensional positioning device and a positioning method that are used for measuring instruments and are of high accuracy in terms of ideal positioning and low cost.
2. Discussion of the Background Art
There are many opportunities for positioning probes for transmitting and receiving electric signals in cases of circuits to be tested and for heads for recording data or reading data from recording media, etc., with measuring instruments. Furthermore, in recent years there has been a demand for miniature, high-density circuits and recording media, and as a result, higher positioning accuracy. In order to facilitate understanding of the present invention, the latter will be described below in the present Specification using as an example magnetic recording media, particularly, the testing device for magnetic heads that read-write data onto a hard disk. The device and method that will be explained belong to the ideal field of use of the present invention, but the field of use of the present invention is not restricted to that described herein.
The magnetic head positioning device simulates the actual read-write operation of a magnetic head and therefore, has movable carriages with which approximate positioning is performed and a precision positioning stage with which precision positioning is performed. The stage for precision positioning, onto which a magnetic head is loaded and this magnetic head is driven and positioned by a piezo element, is anchored on a movable carriages and operates as one unit with the movable carriage. Although the accuracy of the approximate positioning is inferior to the accuracy of the precision positioning, its stability must be high enough to guarantee the accuracy that is realized with the precision positioning. The positioning range of the stage for precision positioning is 10 &mgr;m and resolution is from several nm to several ten nm, and the movable carriage has a range of movement from 100 mm to 150 mm, in typical positioning devices. Unless otherwise described in the Specification of the present invention, the magnetic head and precision positioning stage and related circuits, etc., are referred to simply as “head”.
It is necessary, for instance, to perform positioning in a horizontal direction and positioning in a vertical direction in order to produce a more exact approximate positioning of the head. Therefore, a stationary plate that provides a reference horizontal surface or a mechanism equivalent to this stationary plate, etc., is set up and the head is positioned at a predetermined position on this reference horizontal surface and at a predetermined height from this reference horizontal surface.
Positioning device
10
of a first prior art design is shown in FIG.
1
. By means of positioning device
10
, a pair of linear guides
12
A and B, which are set up parallel to one another on stationary plate
11
, guide movable carriage
13
traveling along these linear guides
12
A and B. Head
16
is anchored to movable carriage
13
. Servo motor
15
is anchored to one end of linear guides
12
A and B and the axis of this servo motor
15
engages and drives nut
17
, which is attached to movable carriage
13
via ball screw
14
, to drive movable carriage
13
. Ball screw
14
is turned when the axis of servo motor
15
rotates and movable carriage
13
moves forward or backward along linear guides
12
A and B. Movable carriage
13
moves back to the side of servo motor
15
and head
16
is replaced, adjusted, etc. Then movable carriage
13
is moved forward away from the side of servo motor
15
and is stopped at a predetermined position, where the head is tested, etc. The height of linear guides
12
A and B and movable carriage
13
is selected so that the height of head
16
from the surface of the stationary plate is a predetermined height.
Positioning device
20
of a second prior art design is shown in FIG.
2
. By means of positioning device
20
, tilt base
24
is attached so that it can turn as needed to tilt axis of rotation
23
anchored to a pair of bearings
22
A and B set up parallel to one another on stationary plate
21
. Tilt base
24
holds pedestal
25
, to which head
26
is anchored at the end opposite tilt axis of rotation
23
, and performs a tilt operation (inclination operation) in the direction of arrow T in the figure in order to position head
26
using an actuator, such as an air cylinder, etc., that is not shown. Head
26
is positioned away from stationary plate
21
by the actuator and the head is replaced, adjusted, etc., then tilt base
24
is lowered toward stationary plate
21
and re-positioned by the actuator, and tests, etc., are performed on head
26
and the media.
In the above-mentioned example, tilt axis of rotation
23
was parallel to the top surface of stationary plate
21
, but a structure wherein it is perpendicular is also possible. In this case, tilt base
24
engages with and is driven by tilt axis of rotation
23
and the head is moved up and down parallel with the top surface of stationary plate
21
.
Positioning device
30
of a third prior art design is shown in FIG.
3
. By means of positioning device
30
, movable carriage
34
moves along a pair of guides
32
A and B set up parallel to one another on stationary plate
31
. The stators of linear motor
36
are attached to guide
32
B and movable carriage
34
functions as a runner of linear motor
36
. Moreover, linear scale
37
is attached to guide
32
A along the direction in which the movable carriage moves and gives the position of movable carriage
34
.
In addition, by means of the technology disclosed in International Patent Application WO 99/66498 (Dec. 23, 1999) in which the above-mentioned design was modified, movable carriage
34
in
FIG. 3
is moved by being floated up from around the outside by air bearings. On the other hand, movable carriage
34
is firmly vacuum suctioned onto stationary plate
31
when it stops so that it is positioned with stability. Movable carriage
34
is pre-vacuum suctioned at the vacuum suction opening and when running, is floated up by the compressed air that is introduced from the air release hole. This technological solution is very stable with high-speed designs, reaching a stability of ±10 nm within 50 ms after the carriage moves.
The positioning devices of the above-mentioned first and second designs of the prior art are relatively inexpensive. However, the accuracy and stability of the resting position of moving tubes and the accuracy and stability of the posture of the movable carriages are insufficient. The movable carriages are held by ball screws and axes of rotation, both when driven and when resting, and therefore, the accuracy and stability of the base position are poor because of restrictions in terms of backlash and rigidity of the ball screws, the rigidity of the axis of rotation, and the holding power of the servo motor and actuator. When viewed in terms of resting convergence speed, the vibration amplitude increases as rigidity decreases and speed is relatively slow. Moreover, it is difficult to always keep the suctioning surface and anchoring surface (top surface of the stationary plate) for the movable carriages parallel to one another and therefore, efficient vacuum suctioning for stable anchoring of the resting carriage position is not possible.
By means of the positioning device of the above-mentioned third design of the prior art, the connection with the drive mechanism is cut when the moving carriage is resting and the position is maintained with stability by vacuum suctioning. However, there is a demand for a very high finishing accuracy of the compressed-air release opening and flotation surface in order to produce stable flotation in particular. Therefore, the finishing cost of the movable carriage increases. Moreover, because the amount by which the movable carriage floats has a strong effect on positioning accurac
Agilent Technologie,s Inc.
Hail III Joseph J.
Shanley Daniel
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