Abrading – Machine – Rotary tool
Reexamination Certificate
1999-06-08
2001-04-17
Young, Lee (Department: 3729)
Abrading
Machine
Rotary tool
C451S005000, C451S028000, C451S494000, C029S603160, C029S603170
Reexamination Certificate
active
06217425
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates an apparatus and a method for lapping magnetic heads, and in particular to an apparatus and a method for lapping a workpiece provided with a plurality of magnetic heads.
2. Description of the Related Art
Conventionally, a thin film magnetic head, which is used in a disc drive in a computer, is manufactured in a batch process. In this process, a workpiece, provided with a ceramic bar (thereafter being divided into sliders) on which a row of transducers including a plurality of thin film magnetic heads are arranged, is lapped such that throat heights in gaps of the respective transducers are adjusted to have desired values at which optimum data signal processing can be realized.
A problem that exists in lapping such magnetic heads so as to obtain desired throat heights is that the ceramic bar or the workpiece is stressed and/or has an undesirable curvature or bow. Namely, when the ceramic bar is stressed and/or has an undesirable curvature or bow, a lapping apparatus can not uniformly lap the ceramic bar. For example, even if the throat heights of the magnetic heads on a center of the ceramic bar have optimum values, the throat heights of the magnetic heads on both ends of the ceramic bar might be too low or too high to have optimum values.
An apparatus for lapping magnetic heads, which can solve such problem, is disclosed in U.S. Pat. No. 5,620,356. The apparatus adjusts throat heights of thin film magnetic heads arranged on a ceramic bar to be optimum by correcting the curvature of the ceramic bar and lapping the corrected ceramic bar while measuring resistances whose values are changed by the throat heights.
In the lapping apparatus disclosed in the U.S. Patent, a workpiece, which is provided with a ceramic bar on which a row of transducers including a plurality of magnetic thin films are arranged, is adhered to a bottom of a tool which likes a long thin plate, and the tool is attached to a back plate of the apparatus. However, the conventional apparatus has a problem that an attitude of the back plate to which the tool is adhered is not based on the abrasive surface of a rotary lapping table. For example, let us assume a case that the back plate is set vertically based on the abrasive surface of the rotary lapping table which is set horizontally. In this case, if the abrasive surface of the lapping table is not set horizontally, the workpiece can not be lapped with accuracy, or flatness of the lapped workpiece is decreased. As a result, the throat heights of the magnetic heads become uneven.
Further, the conventional lapping apparatus is provided with three magnetic actuators which are used to correct the curvature or bow of the ceramic bar. However, since the magnetic actuators are operated to rotate arms and to supply operating forces to the workpiece through the pivotal movements of the arms, thrust characteristics of the magnetic actuators for rotating the arm are undesirably decreased.
SUMMARY OF THE INVENTION
It is therefore an object of the present invention to provide an apparatus and method for lapping magnetic heads which can decrease unevenness of throat heights of a plurality of magnetic heads arranged on a workpiece by increasing a flatness of the workpiece on a basis that the attitude of the workpiece is controllable based on an abrasive surface of a rotary lapping table.
It is another object of the present invention to provide an apparatus and method for lapping magnetic heads which can improve thrust characteristics of magnetic actuators for correcting a curvature or bow of a workpiece.
It is still another object of the present invention to provide an apparatus and method for lapping magnetic heads which can correct with accuracy the bow of the workpiece.
The above object is achieved according to the present invention by providing an apparatus for lapping a workpiece including a plurality of magnetic heads supported by a tool, the apparatus comprising a rotary lapping table having an abrasive surface, lapping head attachment means provided so as to be movable with respect to the lapping table, an adjuster ring resiliently supported by the lapping head attachment means so as to contact with the abrasive surface, a lapping head attached to the adjuster ring, the attitude of the lapping head being controlled by the adjuster ring, a tilting assembly attached to the lapping head so as to tilt around a tilt shaft parallel with the abrasive surface, tilting assembly drive means for tilting the tilting assembly with respect to the abrasive surface, a lift assembly movable up and down with respect to the tilting assembly, a back plate pivotally attached to the lower portion of the lift assembly, said tool being attached to the back plate, first actuator means for correcting balance by applying forces on right and left sides of the pivotal point of the back plate, and second actuator means for correcting bow of the workpiece by applying operating forces on a plurality of predetermined locations of the tool so that the moving directions of movable parts of the second actuator means are substantially parallel with the directions of the operating forces.
In a preferred embodiment of the present invention, the first actuator means is provided so that the moving directions of movable parts of the first actuator means are substantially parallel with the directions of the forces.
In another embodiment of the present invention, the second actuator means includes a plurality of second magnetic actuators.
In still another embodiment of the present invention, the second actuator means includes a plurality of low-friction type cylinders.
The above object is also achieved according to the present invention by providing a method for lapping a workpiece including a plurality of magnetic heads, the method comprising the steps of providing a tool for supporting the workpiece, a rotary lapping table having an abrasive surface, an adjuster ring contacting with the abrasive surface, a lapping head attached to the adjuster ring, a tilting assembly attached to the lapping head, a lift assembly movable up and down with respect to the tilting assembly, a back plate pivotally attached to the lower portion of the lift assembly, first actuator means for correcting balance by applying forces on the back plate, and second actuator means for correcting bow of the workpiece by applying operating forces on the tool so that the moving directions of movable parts of the second actuator means are substantially parallel with the directions of the operating forces, attaching the tool to the back plate, controlling the attitude of the lapping head by the adjuster ring, lapping the plurality of magnetic heads of the workpiece under the condition that the first actuator means applies forces on right and left sides of the pivotal point of the back plate and the second actuator means applies operating forces on a plurality of predetermined locations of the tool while the tool is supported by the lift assembly, and lapping the bottom surface of the workpiece under the condition that the tool is tilted with respect to the vertical plane to the abrasive surface of the lapping table by the tilting assembly being tilted with respect to the lapping head.
In a preferred embodiment of the present invention, the method further comprises the step of continuously rotating or oscillating in a predetermined angle the lapping head.
In another embodiment of the present invention, the method further comprises the step of rotating the adjuster ring.
In still another embodiment of the present invention, the method further comprises the step of reciprocating the lapping head and the adjuster ring.
The above and other objects and features of the present invention will be apparent from the following description by taking reference with accompanying drawings employed for preferred embodiments of the present invention.
REFERENCES:
patent: 4104099 (1978-08-01), Scherrer
patent: 4186480 (1980-02-01), Binder Kriegelstein
patent: 4272924 (1981-06-01),
Abe Tetsuo
Hasebe Tsugihiro
Ogawa Akio
Shindou Hiroshi
Frishauf, Holtz Goodman, Langer & Chick, P.C.
TDK Corporation
Trinh Minh
Young Lee
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