Lead screw/transducer aligning mechanism for disk drive apparatus

A bidirectional stepper motor having a lead screw coupled thereto is mounted to a sliding base which has two right-angular contact surfaces for sliding contact with two right-angular reference surfaces formed on a fixed platform of the machine. Fixedly mounted to the platform and extending parallel to both reference surfaces, a guide rod has a transducer carriage slidably mounted thereto for guiding the same in a radial direction of a flexible magnetic disk or like record media. The transducer carriage is mated with the lead screw for linearly transporting the transducer from track to track on the disk upon incremental rotation of the stepper motor. The sliding base is sprung against one of the two reference surfaces and is fastened to the other reference surface by screws inserted in and through clearance holes in the sliding base. Before fully tightening the screw, the sliding base may be moved by a suitable tool back and forth along the two reference surfaces, within the limits determined by the clearance with which the screws pass through the clearance holes in the sliding base, for fine adjustment of the longitudinal position of the lead screw with respect to the radial position of the transducer on the magnetic disk.

BACKGROUND OF THE INVENTION 
My invention relates generally to apparatus having a transducer such as a 
magnetic read/write head for data transfer with a disklike record medium 
such as a flexible magnetic disk, with the transducer transported radially 
of the record medium by a positioning mechanism including a lead screw. 
More specifically, my invention pertains to improved means in such data 
transfer apparatus for easy, precise adjustment, at the time of the 
assemblage of the apparatus, of the longitudinal position of the lead 
screw with respect to the radial position of the transducer on the record 
medium. 
In apparatus for data transfer (writing and/or reading) with flexible 
magnetic disks, a head positioning mechanism is employed for moving the 
magnetic head radially of the magnetic disk across a series of concentric 
storage tracks thereon. Typically, the head positioning mechanism 
comprises a stepper motor and a mechanism for translating the 
bidirectional, incremental rotation of the stepper motor into the linear, 
stepwise travel of a carriage carrying the magnetic head. While a variety 
of motion translating mechanisms have been suggested and used, perhaps the 
most widely accepted in the art is a lead screw which is coupled directly 
to the stepper motor and which is matingly engaged with the head carriage 
either directly or via suitable means mounted to the carriage. U.S. Pat. 
No. 4,030,137 to Dalziel suggests an example of lead screw for use in the 
head positioning art. 
One of the problems heretofore encountered in the use of lead screws for 
head positioning is how to obtain exact alignment, at the time of the 
manufacture or assemblage of the apparatus, between the longitudinal 
position of the lead screw relative to the head carriage and the position 
of the magnetic head on a preassigned track on the magnetic disk. The 
longitudinal position of the lead screw must be determined relative to the 
head carriage with the rotor of the stepping motor, and therefore of the 
lead screw itself, held in a prescribed start position, in order that the 
magnetic head may move to a desired track position on the magnetic disk 
upon stepping of the motor a required number of times. 
Usually, the longitudinal position of the lead screw is adjusted with 
respect to the radial position of the magnetic head on the magnetic disk 
by manually moving the assembly of the lead screw and the stepping motor 
back and forth relative to the head carriage before the 
motor-and-lead-screw assembly is screwed fast to the framework of the data 
transfer apparatus. However, no matter how precisely such manual 
adjustment is made, misalignment has been prone to occur upon full 
tightening of the screws because of the resulting possible displacement of 
the motor-and-lead-screw assembly with respect to the framework. 
SUMMARY OF THE INVENTION 
I have briefly invented how to easily establish precise alignment between 
the longitudinal position of the lead screw relative to the head carriage 
and the position of the magnetic head on a preassigned track on the 
magnetic disk. 
My invention may be summarized as a lead screw/transducer aligning 
mechanism for an apparatus for data transfer with a disklike record 
medium. The alignment mechanism comprises a stationary support structure 
having two planar reference surfaces formed thereon in right-angular 
relation to each other. A carriage carrying a transducer such as a 
magnetic read/write head is movable along a guide rod immovably mounted to 
the support structure and extending parallel to the first and second 
reference surfaces thereon. In order to be driven along the guide rod for 
transporting the transducer radially of the record medium, the carriage is 
mated with a lead screw which is coupled to a head positioning motor and 
which extends parallel to the guide rod. The motor with the lead screw is 
rigidly mounted to a sliding base to make up a motor-and-lead-screw 
assembly. The sliding base has two right-angular contact surfaces for 
sliding contact with the two reference surfaces of the support structure. 
A spring or like resilient means urges the sliding base against one of the 
reference surfaces. Also included are screws or like fastener means for 
fastening the sliding base to the support structure. 
As will be understood from the foregoing summary, the longitudinal position 
of the lead screw is adjustable relative to the carriage, and hence to the 
transducer being held on a prescribed track position on the record medium, 
by manually moving the sliding base back and forth along the two 
right-angular reference surfaces of the support structure before fully 
tightening the screws on the sliding base. Being sprung against one of the 
reference surfaces, the sliding base will be hardly displaced over the 
support structure when the screws are tightened after the adjustment of 
the lead screw position with respect to the transducer position on the 
record medium. 
An additional advantage of my invention is that the lead screw can be laid 
exactly parallel to the guide rod, the latter being immovably mounted to 
the support structure in parallel relation to the two fixed reference 
surfaces. All that is required for the establishment of such exactly 
parallel relation between lead screw and guide rod is to maintain the 
sliding base in contact with the two reference surfaces. 
The above and other features and advantages of my invention and the manner 
of realizing them will become better understood, and the invention itself 
will best be understood, from a study of the following description and 
appended claims, with reference had to the attached drawings showing a 
preferred embodiment of my invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT 
I will now describe in detail the lead screw/transducer aligning mechanism 
of my invention as adapted for use with a head positioning mechanism of a 
flexible magnetic disk drive. Although in FIG. 1 I have illustrated the 
disk drive fragmentarily and insofar as is necessary for a full 
understanding of my invention, it will nevertheless be seen that it has a 
flexible magnetic disk 10 mounted in position on a turntable 12 for 
rotation therewith in a horizontal plane. The turntable 12 is coupled 
directly to a disk drive motor 14 thereby to be driven. 
The transducer for data transfer with the magnetic disk 10 is shown as a 
magnetic read/write head 16 conventionally mounted on a carriage 18 of 
rigid plastic material via a flexure seat 20. This head is for data 
transfer contact with the lower side of the magnetic disk 10. Another 
similar head, not shown, may be suitably mounted on the carriage 18 for 
data transfer contact with the upper side of the magnetic disk 10. 
As shown also in FIG. 2, the carriage 18 has a hole 22 extending 
therethrough to slidably receive a guide rod 24. This guide rod is 
immovably mounted to the framework of the disk drive herein shown as a 
fixed metal-made platform 26. The platform 26 has a main surface 28 laid 
parallel to the plane of rotation of the magnetic disk 10. The guide rod 
24 is mounted on this main surface 28 of the platform 26 in parallel 
spaced relation thereto. The orientation of the guide rod 24 with respect 
to the magnetic disk 10 is such that the magnetic head or heads 16 are 
movable radially of the disk across a series of concentric data storage 
tracks 30 thereon as the carriage 18 slides back and forth along the guide 
rod. 
With reference to all of FIGS. 1-3 the platform 26 is formed to include a 
relatively thin first ridge 32 and a wider second ridge 34, both extending 
parallel to the guide rod 24. Taller than the second ridge 34, the first 
ridge 32 provides a first planar reference surface 36 which is directed 
away from the guide rod 24 and which is at a right angle with the main 
surface 28 of the platform 26. The second ridge 34 is disposed on that 
side of the first ridge 32 which is opposite to the side where the guide 
rod 24 is disposed. This second ridge 34 provides a second planar 
reference surface 38 parallel to the main surface 28 of the platform 26. 
It is thus seen that the first and second reference surfaces 36 and 38 are 
in right-anglular relation to each other, with the guide rod 24 laid 
parallel to the extensions of both reference surfaces. 
Movable back and forth in sliding contact with both reference surfaces 36 
and 38 is a metal-made sliding base 40 shown also in FIGS. 1-3. As best 
illustrated in FIG. 1, the sliding base 40 has rigidly mounted thereon a 
head positioning motor 42 of the electric stepping type, generally known 
as a stepper motor, having a lead screw 44 coupled directly thereto for 
driving the same. The lead screw 44 extends exactly parallel to the guide 
rod 24, provided that the sliding base 40 in contact with both reference 
surfaces 36 and 38. The sliding base 40 has two upstanding webs 46 and 48 
formed in one piece therewith both for rigidly supporting the stepper 
motor 42 and for rotatably supporting the lead screw 44. 
As shown in FIG. 1 and more clearly in FIG. 2, the lead screw 44 is 
matingly engaged with the carriage 18, as via a pin 49 mounted fast to an 
arm 51 extending laterally from the carriage. The lead screw 44 and pin 49 
make up a known motion translating mechanism, operating to translate the 
bidirectional, incremental rotation of the stepper motor 42 into the 
bidirectional, linear, stepwise travel of the carriage 18 along the guide 
rod 24, and hence of the magnetic head or heads 16 thereon from track to 
track on the magnetic disk 10. 
The sliding base 40, stepper motor 42 and lead screw 44 constitute in 
combination a motor-and-lead-screw assembly generally labeled 50. The 
complete motor-and-lead-screw assembly 50 is slidable along the two 
right-angular reference surfaces 36 and 38 for fine adjustment of the 
longitudinal position of the lead screw 44 to the radial position of the 
head or heads 16 on the magnetic disk 10. As indicated in both FIGS. 2 and 
3, the sliding base 40 has a first contact surface 52 for sliding contact 
with the first reference surface 36, and a second contact surface 54 for 
sliding contact with the second reference surface 38. As the two reference 
surfaces 36 and 38 are at a right angle to each other, so, of course, are 
the two contact surfaces 52 and 54 of the sliding base 40. 
FIG. 1 shows that the sliding base 40 is fastened to the platform 26 by two 
threaded fasteners herein shown as screws 56 extending perpendicular to 
the second reference surface 38 and hence to the main surface 28 of the 
platform. As will be noted from FIG. 2, each screw 56 extends with 
clearance through a hole 58 in the sliding base 40 and is engaged in a 
tapped hole 60 in the second ridge 34 and platform 26. A washer 62, 
preferably a spring washer, is mounted underneath the head of each screw 
56 not only to improve tightness but for an additional purpose to which I 
will refer presently. 
As shown at 64 in FIGS. 1 and 2, a torsion spring is coiled about an 
upstanding pin 66 on the main surface 28 of the platform 26. An arm 70 of 
the torsion spring 64 is held against a lateral projection 72 of the 
sliding base 40, urging the sliding base against the first reference 
surface 36, as indicated by the arrow 74 in FIG. 1. 
As seen in both FIGS. 1 and 3, the first ridge 32 of the platform 26 and 
the sliding base 40 has a pair of aligning recesses 76 and 78 formed 
contiguously therein. These recesses are to receive a suitable aligning 
tool such as a screwdriver 80 whereby the sliding base 40 is to be 
adjustably moved back and forth along the first and second reference 
surfaces 36 and 38, as will be explained in more detail in the course of 
the following description of operation. 
OPERATION 
The incremental rotation of the stepper motor 42 with the lead screw 44 
correspondingly steps the carriage 18, and hence the magnetic head or 
heads 16, radially of the magnetic disk 10 from one track to another. The 
pitch of the threads on the lead screw 44 must be so determined that the 
magnetic head or heads 16 move a unit pitch distance of the magnetic disk 
tracks 30 upon rotation of the stepper motor 42 through a predetermined 
increment. In order to enable the stepper motor 42 to access the head or 
heads 16 to a desired track in response to an appropriate seek signal, 
exact correspondence must be established, at the time of the assemblage of 
the disk drive of the above described construction, between the angular 
position of the rotor, not shown, of the stepper motor and the radial 
position of the head or heads on the magnetic disk 10. Further, for the 
same objective, the longitudinal position of the lead screw 44 must be 
adjusted relative to the carriage 18 so that the magnetic head or heads 16 
thereon will be in a preassigned track position when the rotor of the 
stepper motor 42 is in a preassigned angular position. My invention is 
designed to expedite this adjustment of the longitudinal position of the 
lead screw 44 with respect to the carriage 18. 
Preparatory to the commencement of such adjustment, the screws 56 may be 
inserted in and through the clearance holes 58 in the sliding base 40 and 
engaged in the tapped holes 60 in the platform 26, only to such an extent 
that the sliding base is movable back and forth along the two 
right-angular reference surfaces 36 and 38 within the limits determined by 
the clearance with which the screws 56 extend through the clearance holes 
58. 
Then, as illustrated in FIG. 3, the end of a screwdriver 80 may be inserted 
in the pair of aligning recesses 76 and 78. The screwdriver 80 may be 
turned in either direction. Fulcrumed by the stationary edges of the 
recess 76 in the first ridge 32, the screwdriver 80 will pivot to move the 
sliding base 40, and therefore the complete motor-and-lead screw assembly 
50, back and forth along the reference surfaces 36 and 38, as indicated by 
the double-headed arrow 82 in FIG. 3. 
It should be appreciated that, while being so moved back and forth, the 
sliding base 40 is forced against the first reference surface 36 by the 
torsion spring 64, as indicated by the arrow 74 in FIG. 1, and against the 
second reference surface 38 by the spring washers 62 underlying the heads 
of the screws 56, as indicated by the arrow 84 in FIG. 2. Consequently, 
the sliding base 40 will move infallibly in sliding contact with both 
reference surfaces 36 and 38, and only to the extent desired by the 
operator. 
The screws 56 may be fully tightened following the establishment of 
alignment between the longitudinal position of the lead screw 44 with 
respect to the carriage 18 and the radial position of the magnetic head or 
heads 16 on the magnetic disk 10. The full tightening of the screws 56 
will invite no displacement of the sliding base 40, and of the lead screw 
44, because the sliding base is being forced as aforesaid against the two 
right-angular reference surfaces 36 and 38. Thus, unlike the case 
heretofore experienced, no misalignment will take place upon full 
tightening of the screws. It is also noteworthy that the lead screw 44 can 
be mounted exactly parallel to the fixed guide rod 24 as the sliding base 
40 is constantly sprung against the first reference surface 36. 
Notwithstanding the foregoing detailed disclosure, I do not wish my 
invention to be limited by the exact details of the illustrated embodiment 
since a variety of modifications thereof will readily occur to one skilled 
in the art within the broad teaching hereof. The following is a brief list 
of such possible modifications: 
1. The second ridge 34 with the second reference surface 38 is dispensible 
if the sliding base 40 is placed directly on the main surface 28 of the 
platform 26. In this case the main surface of the platform will serve as 
the second reference surface at a right angle to the first reference 
surface 36. 
2. The sliding base 40 may be urged against the second reference surface 38 
not by the spring washers 62 but by other springs or like resilient means 
provided in any convenient locations. 
3. Not only the spring washers 62 but any other resilient means may not be 
provided for biasing the sliding base 40 against the second reference 
surface 38, the motor-and-lead-screw assembly 50 being urged against the 
second reference surface under its own weight if the disk drive is laid 
horizontally, that is, with its disk drive motor 14 in an upstanding 
attitude. 
4. The lead screw 44 may be mated with the carriage 18 via a ball or balls 
or other engagement means, instead of via the pin 49, or may be engaged 
with internal threads formed directly on the carriage. 
5. The invention may be adapted for optical disk apparatus wherein a 
transducer in the form of an optical head is fed radially of an optical 
disk for data transfer therewith.