Low mass sectioned load beam of head gimbal assembly having increased high first torsion frequency mode

A load beam of a head suspension assembly includes a base plate attachment segment, and an intermediate region that extends integrally from the base plate attachment segment. A bend region extends integrally from the intermediate region for providing the load beam with a predetermined preload spring force and for increasing the lateral stiffness of the load beam. A forward section extends from the bend region, so that the center of gravity of the bend region and forward section is shifted toward the base plate attachment in order to improve the shock performance of the load beam, and so that a moment arm of the bend region and the forward section is shortened. In a preferred embodiment the intermediate region is wider than the base plate attachment segment.

FIELD OF THE INVENTION 
This invention relates to disk drive head suspension assemblies and in 
particular to a load beam of a head gimbal assembly. 
DESCRIPTION OF THE PRIOR ART 
A typical disk drive includes one or more head suspension assemblies (HSAs) 
formed of load beams and head gimbal assemblies (HGAs). Each HGA includes 
a slider that is pivotally attached to a flexure. A magnetic transducer is 
disposed on the slider for interaction with a magnetic disk or medium 
during operation of the disk drive. 
During operation, the load beam is subject to oscillation and vibration, 
particularly at the structural resonance frequencies, and is also subject 
to bending and twisting forces and sway or lateral displacement. During 
the seek mode, when the magnetic head accesses the data tracks and is 
moved radially between selected data tracks, the load beam may experience 
undue vibration at resonance frequencies. Also, the HGA can experience an 
external mechanical shock, typically in a nonoperating mode, which may 
result in mechanical failure of the head, the disk, or both. 
One objective in load beam designs is the reduction of the rail height for 
minimizing the profile of the HGA. However, rail height is limited by 
several factors such as disk drive overall dynamic performance, integrity 
and stiffness. 
Therefore, there is still a need for a load beam design that increases the 
high first torsion frequency mode and possibly the second torsion 
frequency mode for improved positioning performance in high areal density 
applications. The desired load beam should be able to sustain a high shock 
excitation with minimal separation of the head from the disk, which may 
occur, particularly in laptop computers. 
SUMMARY OF THE INVENTION 
An object of the present invention is to provide a low mass load beam of a 
head suspension assembly that optimizes at least the first and second 
torsion frequency modes, while sustaining a high shock excitation with 
minimal separation of the head from the disk. 
According to this invention, the load beam includes a base plate attachment 
segment, and an intermediate region that extends integrally from the base 
plate attachment segment. A bend region extends integrally from the 
intermediate region for providing the load beam with a predetermined 
preload spring force and for increasing the lateral stiffness of the load 
beam. A forward section extends from the bend region, so that the center 
of gravity of the bend region and forward section is shifted toward the 
base plate attachment in order to improve the shock performance of the 
load beam, and so that a moment arm of the bend region and the forward 
section is shortened. In a preferred embodiment the intermediate region is 
wider than the base plate attachment segment.

DETAILED DESCRIPTION OF THE INVENTION 
In FIG. 1, a load beam 10 comprises a square-shaped base plate attachment 
segment 12 which extends to a bend region 14 and projects forward to a 
forward section 16. The load beam 10 is typically etched as a single piece 
from stainless steel sheet stock or another suitable material. 
The base plate attachment segment 12 has a circular central opening 19 for 
receiving a boss 21 of a base plate 23, as shown in FIG. 3. The base plate 
attachment segment 12 is defined by a rearward edge 25, and a forward edge 
27 parallel to the rearward edge 25 and delineated by a hypothetical line 
QQ shown in dashed lines. Two side edges 29, 31 that join the rearward 
edge 25 and the forward edge 27 are located symmetrically relative to the 
central axis B--B. In another embodiment, these side edges may be 
positioned at an angle relative to the central axis B--B. 
FIG. 3 illustrates an HGA 33 incorporating the load beam 10. The bend 
region 14 provides the load beam 10 with the desirable spring force for 
preloading the HGA 33 and opposes the air bearing force generated by the 
floating action of the head or slider 36 over a rotating magnetic disk. In 
the present embodiment the bend region 14 increases the in-plane or 
lateral, stiffness of the load beam 10, along the X-Y plane direction, in 
order to improve the dynamic performance of the HGA 33. As a result, the 
in-plane resonance frequency improves the HGA 33 positioning in high areal 
density disk drive applications. 
The bend region 14 includes a window 40 that assists in adjusting the 
out-of-plane (i.e., the Z direction which is normal to the lateral plane) 
spring force of the load beam 10, so that appropriate load may be applied 
to the slider 36 while flying over the rotating magnetic disk. The window 
40 is shown to be trapezoidally shaped, but it can assume any other 
polygon or arcuate shape. Alternatively, multiple windows may be 
distributed throughout the bend region 14. The window 40 may be eliminated 
partially or completely. The thickness of the bend region 14 may be 
reduced by etching it to a desired thickness, in order to obtain the 
desirable spring force for each specific application. In the present 
illustration the window 40 is symmetrically disposed relative to the load 
beam central axis B--B. 
Another feature of the bend region 14 is to shift the center of gravity of 
the load beam 10 from the forward edge 27 of the base plate attachment 
segment 12 to a distal tip 43 toward the rearward edge 25 along the 
central axis B--B. The rearward shift of the center of gravity will 
improve the overall shock performance of the HGA 33. The window 40 is 
sized and positioned in the bend region 14, so as to relocate the center 
of gravity to a more desirable rearward position, and further to provide 
an appropriate spring force to the load beam 10. 
The desired lateral stiffness of the load beam 10 is achieved by the novel 
shape and geometric configuration of the bend region 14. The bend region 
14 is wider than the base plate attachment segment 12, in order to 
increase the stiffness of the load beam 10 in the in-plane (X-Y plane) 
direction. 
The bend region is formed at an angle relative to the surface of the base 
plate attachment segment 12. The bend region 14 is defined by the forward 
edge 27 of the base plate attachment segment 12, two side edges 44, 46, 
and a forward edge 48 delineated by a hypothetical line SS. 
The side edges 44 and 46 are symmetrical relative to the central axis B--B 
of the load beam 10, and therefore only one side edge, i.e., side edge 44, 
will be described in detail. The side edge 44 is formed of two segments: a 
first segment QR and a second segment RS. However, it should be clear that 
the side edge 44 may alternatively include a different number of segments 
or shapes, provided it is wider than the base plate attachment segment 12. 
For instance, the side edge 44 may be arcuately shaped. 
In the example illustrated in FIG. 2, segment QR of side edge 44 is 
straight, and defines an angle "a" with the central axis B--B. Angle "a" 
may range between 3.5 degrees and 7 degrees; however, other values may 
alternatively be adapted. The length of segment QR may vary with the 
specific applications. Segment RS may be straight or have an arcuate 
shape. 
The position of points R, and the value of angle "a" may be adjusted in 
conjunction with the size, dimensions and position of the window 40, in 
order to optimize the static and dynamic performance of the HGA, and 
further to shift the center of gravity of the load beam 10 rearward, while 
minimizing its mass. 
The forward section 16 extends from the bend region 14, and from the 
forward edge 48 (dashed line S--S) to the narrower distal or forwardmost 
tip 43. The forward section 16 is formed of a tapered forward section 
plate 50; two side rails 52, 54; a central channel 55; tooling holes 58, 
60; two sets of side openings 62, 64; and a dimple 66. 
An objective of the novel design is to increase the first torsion frequency 
mode and possibly the second torsion frequency mode by minimizing the mass 
of the forward section 16, while still maintaining a high stiffness to 
mass ratio. This objective is achieved in part, by providing the forward 
section 16 with two curved sections 70 and 72 that are symmetrical 
relative to the central axis B--B. Each curved section 70, 72 extends 
between two points S and T, with a curvature corresponding to that of the 
adjacent curved segment RS. The radius of curvature of each segment RT may 
vary between 0.35 inch and 0.65 inch. An exemplary curvature is 0.5 inch. 
As a result of this design, the torsional frequency of the load beam 10 is 
increased to satisfy a desirable objective of the present invention. 
In a preferred embodiment of the present invention, it is desirable to 
remove an optimum amount of mass from the forward section 16, by 
minimizing its width, particularly at the distal end U--U. However, the 
width of the distal end U--U is limited by the dimension of the dimple 66. 
In an implementation of the invention, the dimple 66 is approximately 15 
mils (0.015 inch) in diameter. The shape of the forward section 16 
contributes to a reduction in the overall mass of the load beam 10, thus 
increasing the resonant frequency of the first torsion resonant mode. The 
tapered forward section 16 is also significant for increasing the resonant 
frequency of the second torsion resonant mode. 
The length of the forward section 16 varies with respect to the total 
length of the load beam 10. A shorter forward section 16 can be employed, 
thereby further reducing the mass of the load beam 10. Such a design may 
require that the actuator arm (not shown), to which the boss 21 is swaged, 
be extended for a given disk drive design. An advantage in increased 
resonant frequencies is obtained with the present invention over prior art 
head suspension assemblies using load beams. 
The side rails 52, 54 are stiffening flanges that run substantially the 
length of the forward section 16. The side rails 52, 54 serve to stiffen 
the load beam 10 so that all bending in the out-of-plane direction is 
essentially at the bend regions with minimal deformation at the distal end 
U--U. By using the design of the present invention, the height of the side 
rails 52, 54 can be decreased, and still achieve equal or higher resonant 
frequencies than prior art devices. For example, in known prior art load 
beams, the height of such side rails or flanges would be 0.014 inch. With 
the present design, for load beams used in a comparable environment, the 
flange heights are made to be from 0.008-0.0095 inch (a 40-32 percent 
decrease in height). This is advantageous because it permits closer 
spacing between disks platters in a disk drive, resulting in a more 
compact drive or a drive having a greater number of disks. When used in 
combination with a flexure 81 (FIG. 3) and the slider 36, a substantial 
reduction in disk head assembly height can be achieved, resulting in even 
more compact drives or drives having a greater number of disks. 
With reference to FIG. 4, the central channel 55 helps to increase the 
overall stiffness of the load beam 10, and more particularly the stiffness 
in the out-of-plane or Z bending direction and in the torsion direction 
(turning motion around the major axis of the load beam 10). Another 
feature of the central channel 55 is to help in locating the center of 
gravity of the HGA 33 in proximity to or on the plane of the load beam 10, 
in order to reduce the excitation in the torsion modes of the load beam 
10. 
Generally, the center of gravity of a conventional HGA is not necessarily 
located within the plane of the load beam, but is offset in the 
out-of-plane direction. An important feature of the present invention is 
that the center of gravity of the HGA 33 may be positioned within the 
plane of the load beam 10. 
The central channel 55 is formed of a single continuous straight trough 
that extends along the central or major axis B--B of the load beam 10. The 
central channel 55 may be located at any position along the major axis or 
central axis B--B, between the edge of the window 40 in the bend region 14 
and the circular tooling hole 60. The channel 55 is located in the nodal 
area of the first torsion vibration mode of the load beam 10, which is an 
area of the load beam 10 that does not move much in the first torsion mode 
of vibration. 
In one embodiment, the channel 55 tapers as it progresses toward the 
tooling hole 60. For instance, the width of the rearward end of the 
channel 55 may vary from 0.010 inch to 0.025 inch, with the forward end 
varying between 0.005 inch and 0.020 inch. In another embodiment the 
channel 55 is uniform along its entire axial length. The depth (in the 
out-of-plane direction of the load beam) may vary between 0.002 inch and 
0.010 inch depending on the thickness of the material used to form the 
load beam 10. 
While the central channel 55 is shown to be formed of a single continuous 
trough, it should be clear that in an alternative embodiment the central 
channel 55 may be formed of a series of adjacent troughs. In yet another 
alternative, the central channel 55 is not a trough or a depression, but 
is rather embossed or raised. In still another embodiment, the central 
channel 55 may be formed of a combination of a series of adjacent or 
alternating troughs and raised sections. Some or all of these troughs 
and/or raised sections may be collinear with the major axis of the load 
beam 10, or alternatively, they may be offset relative thereto. 
The side openings 62, 64 are symmetrical relative to the central axis B--B 
of the load beam 10. The openings 62, 64 may have any desired shape even 
though they are illustrated in FIGS. 1 and 2 as being a square-shaped 
section. In a preferred embodiment, the openings 62, 64 are located 
outside the nodal area of the first torsion vibration mode of the load 
beam 10. A typical size of a single opening is approximately 0.010 inch by 
0.010 inch. While seven openings 62, 64 are illustrated on each side of 
the forward section 16, it should be clear that a different number of 
openings may be alternatively selected. 
These side openings 62, 64 assist in reducing the overall mass of the HGA 
33 and in positioning the center of gravity of the HGA 33 along the 
central axis of the load beam 10, closer to the base plate attachment 
segment 12. Generally, the reduction in the overall mass is beneficial to 
increase the frequencies of all vibration modes, and in particular the 
first torsion frequency, it being understood that the vibration 
frequencies are inversely proportional to mass and directly proportional 
to stiffness. The side openings 62, 64 are specifically located where the 
ratio of stiffness to mass is low for the vibration modes of interest, 
including the first torsion mode of load beam 10. Another advantage of 
having the center of gravity of the HGA 33 located as far rearward as 
possible is to render the HGA 33 more shock resistant, that is, to 
increase the amount of shock force required to separate the magnetic head 
from the disk, which improves disk drive performance. 
FIGS. 5 and 6 illustrate a load beam 100 comprising a base plate attachment 
segment 112 which extends to a bend region 114 and which projects forward 
to a forward section 116. The load beam 100 is typically formed as a 
single piece from stainless steel sheet stock or another suitable 
material. 
The base plate attachment segment 112 has a circular central opening 119 
for receiving a boss 121 of a base plate 123, as shown in FIG. 7. The base 
plate attachment segment 112 is defined by a rearward edge 125, and a 
forward edge 127 parallel to the rearward edge 125, and delineated by a 
hypothetical line QQ shown in a dashed line. Two side edges 129, 131 that 
join the rearward edge 125 and the forward edge 127 are located 
symmetrically relative to the central axis B--B. In another embodiment, 
the side edges 129, 131 may be positioned at an angle relative to the 
central axis B--B. 
FIG. 7 illustrates an HGA 133 incorporating the load beam 100. The bend 
region 114 provides the load beam 100 with the desirable spring force for 
preloading the HGA 133 and opposes the air bearing force generated by the 
floating action of the head or slider 136 over a rotating magnetic disk. 
In the present embodiment an intermediate region 137 extends integrally 
from the base plate attachment segment 112, and is disposed between the 
base plate attachment segment 112 and the bend region 114 as delineated by 
the hypothetical line PP shown in a dashed line in FIG. 6. The 
intermediate region 137 increases the in-plane or lateral, stiffness of 
the load beam 100, along the X-Y plane direction, in order to improve the 
dynamic performance of the HGA 133. As a result, the in-plane resonance 
frequency improves the HGA 133 positioning in high areal density disk 
drive applications. 
The intermediate region 137 includes two symmetrical and substantially 
identical side flanges 144, 145 (see FIG. 5), each of which extends from a 
rear point or edge V to a forward point or edge P. Flanges 144, 145 
increase the stiffness of the load beam 100 in the out-of-plane bending 
mode, and further increase the stiffness of the load beam 100 in torsion. 
The height of each flange 144, 145 ranges between approximately 7 to 10 
milli-inches; however, other values may also be used. The height of 
flanges 144, 145 does not exceed the thickness of the slider 136. 
Another feature of the intermediate region 137 is to shift the center of 
gravity of the load beam 100, from the forward edge 127 of the base plate 
attachment segment 112 to a distal tip 143 (FIG. 6), rearward, toward the 
edge 125, along the central axis B--B. The rearward shift of the center of 
gravity will improve the overall shock performance of the HGA 133. While 
the effective moment arm in a conventional load beam 100 is determined by 
the distance between the tip 143 and forward edge 127 of the base plate 
attachment segment 112, an object of the present invention is to reduce 
the moment arm by the length of the intermediate region 137. In the 
present example the length of the intermediate region 137 is defined as 
the distance between lines PP and QQ along the central axis B--B. The 
shortening of the moment arm enables the achievement of improved dynamic 
performance characteristics of the load beam 100 in the in-plane, 
out-of-plane, and torsion directions. 
The desired lateral stiffness of the load beam 100 is achieved by the novel 
shape and geometric configuration of the intermediate region 137. The 
width of the intermediate region 137, that is the distance between the two 
flanges 144, 145, gradually increases from line QQ to line PP, in order to 
increase the stiffness of the load beam 100 in the in-plane (X-Y plane) 
direction. 
The intermediate region 137 is preferably co-planar with the surface of the 
base plate attachment segment 112. The intermediate region 137 is defined 
by QQ, that is the forward edge 127 of the base plate attachment segment 
112, two segments QP, and line PP. Segments QP are symmetrical relative to 
the central axis B--B of the load beam 100, and therefore only one segment 
QP will be described in detail. Segment QP is formed of 31 two segments: a 
first segment QV and a second segment VP. The first segment QV does not 
include a flange in order to provide a clearance between the flange 144 
and the base plate attachment segment 112. The flange 144 is formed along 
the second segment VP. It should be clear that segment QP may 
alternatively include a different number of segments or shapes, provided 
it is wider than the base plate attachment segment 112. For instance, 
segment QP may be arcuately shaped. 
In the example illustrated in FIG. 5, segment QV is straight, and defines 
an angle "b" with the central axis B--B. Angle "b" may range between 3.5 
degrees and 8 degrees; however, other values may alternatively be used. 
The length of segment QV may vary with specific applications. Segment VP 
may be straight or may have an arctuate shape. The position of points P, 
and the value of angle "b" may be adjusted in order to optimize the static 
and dynamic performance of the HGA 133, and further to shift the center of 
gravity of the load beam 100 rearward, while minimizing its mass. 
The bend region 114 includes a window 140 that assists in adjusting the 
out-of-plane (i.e., the Z direction which is normal to the lateral plane) 
spring force of the load beam 100, so that appropriate load may be applied 
to the slider 136 while flying over a rotating magnetic disk. The window 
140 is shown to be trapezoidally shaped, but it can assume any other 
polygon or arcuate shape. Alternatively, multiple windows may be 
distributed throughout the bend region 114. The window 140 may be 
eliminated partially or completely. The thickness of the bend region 114 
may be reduced by etching it to a desired thickness, in order to obtain 
the desirable spring force for each specific application. In the present 
illustration the window 140 is symmetrically disposed relative to the load 
beam central axis B--B. 
An objective of the present novel design is to increase the first torsion 
frequency mode and possibly the second torsion frequency mode by 
minimizing the mass of both the bend region 114 and the forward section 
116, while still maintaining a high stiffness to mass ratio. This 
objective is achieved in part, by providing the bend region 114 with two 
curved sections 170 and 172 that are symmetrical relative to the central 
axis B--B. Each curved section 170, 172 extends between two points P and 
W. The radius of curvature of each segment PW may vary between 0.35 inch 
and 0.65 inch. An exemplary curvature is 0.5 inch. As a result, the 
torsional frequency of the load beam 100 is increased to satisfy a 
desirable objective of the present invention. 
The forward section 116 extends from a forward edge 148 (defined by a 
hypothetical dashed line WW) of the bend region 114 to the distal or 
forwardmost tip 143. The forward section 116 is formed of a tapered 
forward section plate 150; two side rails 152, 154; cooling holes 158, 
160; and a dimple 166. 
In a preferred embodiment of the present invention, it is desirable to 
remove an optimum amount of mass from the forward section 116, by 
minimizing its width, particularly at the distal end U--U. However, the 
width of the distal end U--U is limited by the dimension of the dimple 
166. In an implementation of the invention, the dimple 166 is 
approximately 15 mils (0.015 inch) in diameter. The shape of the forward 
section 116 contributes to a reduction in the overall mass of the load 
beam 100, thus increasing the resonant frequency of the first torsion 
resonant mode. The tapered forward section 116 is also significant for 
increasing the resonant frequency of the second torsion resonant mode. 
The length of the forward section 116 varies with respect to the total 
length of the load beam 100. A shorter forward section 116 can be 
employed, thereby further reducing the mass of the load beam 100. Such a 
design may require that the actuator arm (not shown), to which the boss 
121 is swaged, be extended for a given disk drive design. An advantage in 
increased resonant frequencies is obtained with the present invention over 
prior art head suspension assemblies using load beams. 
The side rails 152, 154 are stiffening flanges that run substantially the 
length of the forward section 116. The side rails 152, 154 serve to 
stiffen the load beam 100 so that all bending in the out-of-plane 
direction is essentially at the bend regions with minimal deformation at 
the distal end U--U. By using the design of the present invention, the 
height of the side rails 152, 154 can be decreased, and still achieve 
equal or higher resonant frequencies than prior art devices. For example, 
in known prior art load beams, the height of such side rails or flanges 
would be 0.014 inch. With the present design, for load beams used in a 
comparable environment, the flange heights are made to be from 
0.008-0.0095 inch (a 40-32 percent decrease in height). This is 
advantageous because it permits closer spacing between disks platters in a 
disk drive, resulting in a more compact drive or a drive having a greater 
number of disks. When used in combination with a flexure 181 (FIG. 7) and 
the slider 136, a substantial reduction in disk head assembly height can 
be achieved, resulting in even more compact drives or drives having a 
greater number of disks. 
FIG. 8 shows another load beam 200 which is generally similar to the load 
beam 100 of FIG. 6, with similar numerals referring to similar components. 
The load beam 200 includes an intermediate region 237 which is defined by 
the hypothetical lines PP and Q"'Q"'. In addition, the load beam 200 
includes two triangular anchoring regions 221, 222 defined by the vertices 
Q"'QQ'. The anchoring regions 221, 222 are symmetrically disposed relative 
to the central axis B--B. In this embodiment, two rear flanges 243, 244 
extend alongside part of the intermediate region 237 from point P to point 
V. In another embodiment the rear flanges 243, 244 may extend from point P 
to point Q', or to any point therebetween. The embodiment illustrated in 
FIG. 8 further improves the out-of-plane, lateral, and torsional load beam 
stiffness values. 
FIG. 9 shows another load beam 300 which is generally similar to the load 
beam 100 of FIG. 5, with similar numerals referring to similar components. 
The load beam 300 includes an intermediate region 314 which is similar to 
the intermediate region 114, in which one or more windows are formed. In 
this particular illustration four windows 331, 332, 333, 334 are formed 
within the intermediate region 314 in order to provide means for adjusting 
stiffness. To this end, each of these windows 331-334, includes two 
stiffening flanges, such as flanges 341 (for window 331) and 343, 344 (for 
window 334). These flanges may have the same orientation, such that all of 
these flanges 331-334 may be directed either upwardly or downwardly. 
Alternatively, some of the flanges may be oriented upwardly and others may 
be oriented downwardly. In the specific illustration shown in FIG. 9 the 
flanges have alternating orientations. 
FIG. 10 shows another load beam 400 which is generally similar to the load 
beam 10 of FIG. 2, with similar numerals referring to similar components. 
The load beam 400 includes a bend region 414 is defined by the 
hypothetical line QQ', two side edges 444, 446, and a forward edge 48 
delineated by a hypothetical line SS. 
The side edges 444 and 446 are symmetrical relative to the central axis 
B--B of the load beam 400, and therefore only one side edge, i.e., side 
edge 444, will be described in detail. The side edge 444 is formed of two 
segments: a first segment RG and a second segment RQ'. However, it should 
be clear that the side edge 444 may alternatively include a different 
number of segments or shapes, provided it is wider than the base plate 
attachment segment 12. The length of segment RG may vary with specific 
applications. In addition, the load beam 400 includes two triangular 
anchoring regions 461, 462 defined by the vertices QQ'G. The anchoring 
regions 461, 462 are symmetrically disposed relative to the central axis 
B--B, and improve the out-of-plane, lateral, and torsional load beam 
stiffness values. 
There has been described herein a load beam which has low profile side 
rails, a low effective mass, and a low mass moment of inertia. The present 
design may be used to reduce disk spacing in disk drives. 
It should be understood that the geometry and dimensions described herein 
may be modified within the scope of the invention. For example, the widths 
and lengths of the various components of the load beam 100 may be modified 
depending upon the disk drive operating characteristics. Other 
modifications may be made when implementing the invention for a particular 
application. Furthermore, the present invention can be used with different 
types of sliders and having different sizes. The present inventive concept 
may also be used in conjunction with optical and magneto-optical disk 
drives.