Test fixture for air bearing magnetic head suspension assembly

A fixture (10) for testing a head/gimbal assembly (11) before installion into a disk file functions to load and unload the assembly onto and from a rotating disk (12). The fixture comprises a mounting block (15) for attaching the fixture to a stationary frame (16) to position the fixture in a predetermined position relative to a rotating disk and to permit adjustment of the fixture to selected vertical positions relative to the disk surface. A platform (25) which carries a head/gimbal clamping device (30) is pivotally attached to the mounting block to move a clamped head/gimbal assembly in an arc in a plane normal to the disk surface during loading and unloading. The clamping device comprises a base (31) having a surface which mates with the surface of the head/gimbal and is clamped by a spring-biased element (32) having tooth-type extensions (37) for clamping the head/gimbal against the mating surface of the base. The spring biased element is mounted for pivotal movement relative to the platform and a thumb lever (33) is provided for the operator to release the clamp to readily replace the assembly. The external loading/unloading force is applied directly to the platform and not the assembly.

FIELD OF THE INVENTION 
This invention relates in general to test fixtures for air bearing type 
magnetic recording head/gimbal assemblies and in particular to a fixture 
for loading and unloading a head suspension assembly relative to a 
rotating disk surface. 
DESCRIPTION OF PRIOR ART 
Air bearing type magnetic recording transducer assemblies are used 
extensively in magnetic disk files that are employed to store information 
for use by information processing systems. These devices are referred to 
in the art as head/gimbal assemblies which comprise an arm member that is 
adapted at one end to be attached to an actuator and a head suspension 
that supports an air bearing slider at the other end. Current technology 
employs a thin film magnetic transducer which is carried by the slider in 
a closely spaced noncontact relationship with a recording disk. The slider 
rides on a film of air next to the disk surface as the disk is rotated at 
relatively high revolutions per minute (RPM)s. In practice, an actuator is 
used to position the recording gap of the transducer over one of a large 
number of concentric recording tracks that have been defined on the disk 
surface. The specific track is designated by a track address that is 
supplied to the actuator by a servosystem. 
Because the mechanical and electrical interfaces between the rotating disk 
and the head assembly are relatively delicate, it is important to test 
each manufactured head assembly with a known standard disk prior to 
installing the head in a disk file. To a lesser degree, it is also 
important to test each disk with a known standard head assembly but since 
the magnetic surface of the disk must be checked for imperfections and 
also formatted, those operations generally also suffice for establishing 
the fitness of the mechanical interface. 
In most files, the head is loaded onto the disk after the disk has reached 
its normal operating speed. The head is unloaded from the disk prior to 
the disk stopping if the drive is turned off. The loading and unloading 
operations are the most critical in that it is during these periods that 
the tendency of the head to crash into the disk is the greatest. 
Prior art testing fixtures generally have employed the same technical 
concepts that have been used in the actual files to load and unload the 
head. This concept involves providing a thin lifting blade under the head 
suspension and lifting the suspension slightly to raise the head from the 
disk. Since the lifting blade comes in contact with the suspension there 
is a possibility that this contact could affect the loading 
characteristics of the suspension. Also, as disk drives become smaller, 
the head assemblies also must be reduced in size. Since most drives employ 
one head assembly per disk surface, with the heads being mounted on 
suspensions at opposite surfaces of the disk, the distance between the 
pair of suspensions has become quite small, which complicates the 
insertion of two lifting blades to perform the loading and unloading 
operations. 
Another problem with existing test fixtures is that the test operator is 
required to spend considerable time fixedly positioning each head assembly 
into the test fixture. In one known fixture the operator must attach the 
head/gimbal assembly to the fixture by screws. A further problem is 
encountered when the fixture is required to test head assemblies having 
different design parameters, such as being mounted at a different heights 
(Z-distance) above the disk. Adjusting the Z-distance of prior art 
fixtures involves significant time and requires special shims. In 
addition, most prior art fixtures were designed to test a specific 
head/gimbal assembly. When a new head/gimbal design was adopted a new test 
fixture had to be built. The present invention provides an improved 
fixture for testing head/gimbal assemblies that avoids the above-mentioned 
problems. 
SUMMARY OF INVENTION 
An object of the present invention is to provide an improved test fixture 
for head/gimbal assemblies in which the force for loading/unloading the 
head from the disk is not applied directly to the head suspension. 
Another object of the present invention is to provide a test fixture for 
head suspension assemblies in which the assembly is easily clamped to the 
fixture prior to testing by action of an operator. 
A further object of the invention is to provide a test fixture in which the 
device for clamping the head/gimbal assembly to the fixture includes a 
base member which is replaceable so that differently designed assemblies 
may be clamped merely by changing the base member. 
In accordance with the present invention, a test fixture comprises a 
mounting block which is attachable to a stationary frame member of the 
test fixture by means of a Z-axis lead screw disposed normal to the plane 
of a rotating disk on which the head is to be loaded. The function of the 
mounting block is to permit control by the operator of vertical movement 
of a pivotally attached loading platform to which a head/gimbal assembly 
is clamped and to support the loading platform for a pivoting motion about 
a horizontal axis disposed at one end of the platform. The other end of 
the loading platform is provided with a horizontally positioned U-shaped 
recess into which a head/gimbal assembly clamping device is mounted. 
The clamping device functions to rigidly clamp the distal end of the 
suspension portion of the head/gimbal assembly to the loading platform so 
that the head is loaded and unloaded as a result of the pivoting motion of 
the platform. The clamping device includes three major components. The 
first component is a clamp base which is removably attached to the 
mounting platform. The clamp base is tailored to the particular 
head/gimbal assembly in that its bottom horizontal surface is designed to 
mate with the flat surface of the head suspension. The second component of 
the clamp is a pivotally mounted jaw element which functions to clamp the 
distal end of the head suspension against the horizontal mating surface of 
the clamp base. The jaw element is replaceable to accommodate head/gimbal 
assemblies with differently designed distal ends. 
The third component of the clamping device is the thumb lever which the 
operator uses to open the clamp prior to inserting a new head/gimbal 
assembly for test. The thumb lever is a vertically disposed yoke shaped 
member to which the upper end of the jaw element is attached for pivotal 
movement about an axis parallel to the pivotal axis of the platform. The 
jaw element is attached to the platform by a horizontally disposed axle 
mounted in the platform and therefore pivots about a second axis 
positioned between the thumb lever and the end of the element which clamps 
the head/gimbal assembly. The axle is also parallel to the pivotal axis of 
the platform. 
The actual loading and unloading force for the improved fixture is applied 
to the underside of the platform as contrasted to the prior art 
arrangement where the force is applied directly to the head/gimbal 
assembly.

DESCRIPTION OF THE PREFERRED EMBODIMENT 
FIG. 1 illustrates a test fixture designated generally by reference 
character 10, for loading a head/gimbal assembly 11, shown 
diagrammatically in FIG. 1, loaded against a rotating disk 12. 
The test fixture 10, as shown in an exploded view in FIG. 2, comprises a 
mounting block 15, which is mounted under a stationary frame member 16. 
The mounting block 15 is provided with an guide shaft 17, that extends 
through an opening 18 in the frame member 16. A guide bushing 19 screws 
onto the threaded end of the guide shaft 17 and is prevented from being 
released from the lead screw by a washer 20 and adjusting nut 21. A set of 
coil springs 22 are sandwiched between the top of block 15 and the bottom 
of frame member 16. A guide pin 23 disposed normal to the top surface of 
block 15 keeps the movement of block 15 parallel to the axis of the guide 
shaft 17. 
The fixture further comprises a loading platform 25 which is pivotally 
attached to the block 15 by means of the shaft 26 which is mounted in the 
openings 27. The axis 26a of shaft 26 is horizontal and generally 90 
degrees to the longitudinal axis of the head/gimbal assembly 11. The other 
end of the platform is provided with a square U-shaped opening 27 which 
functions to mount a head/gimbal clamping device designated generally by 
reference character 30. 
Device 30 as assembled is shown diagrammatically in FIG. 3 and comprises a 
clamp base 31, a clamp jaw element 32 and a thumb lever 33. The bottom 
surface 34 of the block 31 is designed to mate with the head/gimbal so 
that as the top portion of the element 32 is biased to the left the bottom 
portion is rotated about the axis 35 to the right to clamp the head/gimbal 
11. In the preferred embodiment, the jaw element is provided with a pair 
of teeth 37 for gripping the head/gimbal 11. Pin 36 which defines the 
pivotal axis 35 is mounted horizontally in sides 38 and 39 defining the 
U-shaped opening 27 in platform 25. 
The thumb lever 33 is pivotally attached to the upper end 40 of the jaw 
element 32 by the pin 42. As shown in FIG. 2, a spring 43 is disposed 
between the thumb lever 33 and the upward extension 44 of the block 31 
maintains the clamping force on the head/gimbal 11. In effect there are 
two orthogonal forces applied against the baseplate or block 31 pressing 
the thumb lever to the left as shown in FIG. 3 releases the clamp and 
allows the insertion of a new head/gimbal assembly. 
In operation, after the head/gimbal assembly is attached to the fixture, a 
vertical force F as shown in FIG. 1 is applied to the platform 10 to load 
and unload the head/gimbal 11 relative to the disk 12. Since the force F 
is not applied directly to the head/gimbal 11 there is no possibility of 
damaging the assembly as a result of the testing operation. It will also 
be apparent that attaching the head/gimbal 11 to the fixture by means of 
the clamping device is considerably more efficient than arrangements 
suggested by the prior art. 
While the invention has been particularly shown and described with relation 
to a preferred embodiment thereof, it will be apparent to those persons 
skilled in the art that various changes and modifications may be made 
therein without departing from the spirit of the invention and the scope 
of the appended claims.