Apparatus for centering and clamping a flexible magnetic recording disc

Apparatus for centering and clamping a flexible magnetic recording disc in a disc drive comprises a spindle having on its outer end a face for supporting the associated recording disc and also has a recess within that face and a disc clamping element which cooperates with the spindle and includes a plurality of resiliently deflectable fingers extending in a direction both angularly outwardly of the axis and toward the spindle with means for deflecting the fingers radially outwardly for centering the associated recording disc with respect to the center of the spindle, and means for selectively moving the clamping element toward and away from the spindle and into and out of releasable engagement with the recording disc and spindle.

BACKGROUND OF THE INVENTION 
This invention relates to apparatus for clamping and centering a flexible 
magnetic recording disc in a disc drive. 
Disc drive units incorporating inexpensive, flexible, removable magnetic 
recording discs have become very popular in the field of data processing. 
These drives and their associated discs provide for a relatively 
inexpensive means for storing data, diagnostic codes, or programs for 
computers and other types of equipment. Because of the low cost recording 
media used therein and its replaceability, these devices have provided for 
an inexpensive means of providing such stored information in a wide 
variety of equipment. A number of manufacturers are now producing 
generally similar disc drives of this nature, with one relatively new and 
increasingly popular such drive being the Memorex Model 550, within which 
the subject matter of the present invention may be incorporated. The 
recording media generally used in such disc drives is in the form of a 
relatively thin and flexible plastic disc coated with a magnetic recording 
material and enclosed within an envelope providing for limited access to 
the recording surface of the disc and access to a central, circular 
aperture which is used for centering and clamping the disc to the disc 
drive. 
Various types of disc centering and clamping structures have been 
incorporated and disclosed in the prior art. Typical of such clamping 
apparatus has been that disclosed in U.S. Pat. No. 3,678,481 and that 
disclosed in U.S. Pat. No. 3,768,815. Among the requirements for such a 
disc centering and clamping structure have been the ability to effectively 
and positively center the disc with respect to the axis of rotation of the 
drive spindle prior to clamping it immovably in place on that spindle, 
reliability of operation, and simplicity and low cost of manufacture and 
assembly. The various prior art clamping devices have, in general, been 
unnecessarily complex and frequently lacking in the ability to center a 
disc effectively prior to clamping it firmly against the drive spindle. 
This failure to center properly can result in damage to the material 
surrounding the central aperture of the disc as well as an eccentric 
recording and substantial compromises in the ability of the disc and drive 
combination to reproduce accurately data previously recorded thereupon. 
The inability of many of the prior are devices to center the disc 
adequately prior to clamping has become a particularly acute problem with 
respect to the more recently developed disc drives in which the recording 
density has been substantially increased and the distance between adjacent 
recording tracks has been substantially decreased. 
SUMMARY OF THE INVENTION 
It is the object of this invention to provide a centering and clamping 
apparatus for use in a flexible magnetic recording disc drive which 
effectively centers the recording disc with respect to the center of 
rotation of the drive spindle and then clamps the recording disc firmly 
against the drive spindle for rotational drive by that spindle. It is also 
an object of the invention to provide such a centering and clamping 
apparatus which is both effective in operation and reliable in service. It 
is yet another object of this invention to provide such a centering and 
clamping apparatus which is economical to manufacture and assemble. It is 
a further object of this invention to provide such a centering and 
clamping apparatus in which the clamping element is a single unitary 
element formed of a generally rigid synthetic resin. 
The centering and clamping apparatus of this invention comprises a spindle 
mounted to the end of a rotatable drive shaft and having at its outer end 
a face for supporting the associated recording disc, a disc clamping 
element rotatable about an axis and selectively movable toward and away 
from the spindle, and means for selectively moving the clamping element 
toward and away from the spindle and into and out of releasable engagement 
with the recording disc and spindle. The spindle includes a recess within 
the face which is concentric with the drive shaft and is defined by an 
inner wall. The disc clamping element includes a plurality of resiliently 
deflectable fingers extending in a direction both angularly outwardly of 
the axis of rotation and toward the spindle and drive shaft, the outermost 
portions of the fingers including means for deflecting those fingers 
radially outwardly for centering the associated recording disc with 
respect to the center of the spindle and drive shaft and for clamping the 
disc against the spindle face when the clamping element is brought into 
engagement with the disc and spindle.

DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT 
A particularly preferred embodiment of the flexible magnetic disc centering 
and clamping apparatus of this invention is illustrated in FIGS. 1 through 
3. In FIG. 1 the centering and clamping apparatus of this invention is 
illustrated mounted within a suitable magnetic disc drive, such as the 
well known Memorex Model 550. The portions of this disc drive which form 
no part of the invention are shown in phantom. The basic components of 
this centering and clamping apparatus include the spindle 2 which is 
mounted and driven for rotational movement on the chassis of the disc 
drive shown in phantom, the clamping element 4 and the hinged panel 6 or 
other suitable means for selectively moving the clamping element toward 
and away from the spindle. For purposes of illustration in FIG. 1 the 
panel 6, hinged to the chassis of the disc drive shown in phantom, is 
shown pivoted well open, far more open than is necessary or would likely 
be the case in an operational disc drive. 
In FIG. 2 and in the sectional views of FIGS. 3A through 3C the principal 
components of the apparatus of this invention are represented at a larger 
scale to illustrate more clearly the principles of the invention. The 
spindle 2, formed of a suitable material such as steel, is mounted at the 
end of a rotatable drive shaft 8, which may be mounted by suitable 
bearings to the chassis of the disc drive (not shown). The drive shaft 
conventionally may be provided at its opposite end with a drive pulley 10 
(shown in phantom) driven by a suitable belt 12 (shown in phantom) from a 
suitable drive motor (not shown). At its outer end the spindle has a flat 
face 14 for receiving and supporting the recording disc 16 (shown in 
phantom in FIG. 2). Additionally, the outer end of the spindle 2 includes 
a recess 18 within the face 14, defined by inner wall 20. This recess 18 
is circular, preferably in the form of a truncated cylinder and is 
concentric with drive shaft 8. 
The disc clamping element 4 is suitably formed as a unitary molding of a 
generally rigid synthetic resin, such as nylon or the like. This clamping 
element 4 is rotatably mounted by means of a bearing 22 to a shaft 24, 
which in turn is attached to the plate 6 pivotally mounted to the disc 
drive chassis. The shaft 24, suitably in the form of a bolt or other 
threaded member, defines the axis of rotation of the clamping element 4 
and is slidably attached to the plate 6 so that, when the clamping element 
4 is brought into engagement with the spindle 2 as illustrated in FIGS. 3A 
through 3C, the axes of rotation of both the spindle and the clamping 
element 4 will be collinear. 
Clamping element 4 includes the bearing-receiving central body 26 with a 
plurality of resiliently deflectable fingers 28 extending both angularly 
outwardly of the central body 26 and thus shaft 24 and also toward the 
spindle 2 and drive shaft 8. Thus, in the orientation illustrated in FIGS. 
2 and 3A through 3C the resiliently deflectable fingers 28 angle 
downwardly toward the spindle 2 and outwardly of the axis of rotation of 
the clamping element 4 in a generally conical fashion. The outermost 
portions of the fingers 28 include both generally radially extending tabs 
30 and portions 32 extending generally axially outwardly (downwardly in 
FIGS. 2 and 3A through 3C) of the clamping member 4. Axially extending 
portions 32 suitably define sectors of a circle which, when the fingers 
are in their undeflected state (FIGS. 2, 3A and 3B), has a diameter which 
is smaller than the diameter of the spindle recess 18, for purposes to be 
described below. The generally radially outwardly extending tabs 30 
suitably define sectors of an annular figure which generally corresponds 
to the size of the face 14 of the spindle. 
In this preferred embodiment the clamping element shaft 24 preferably is 
mounted to the pivotal plate 6 by means providing for a predetermined 
amount of movement of the clamping element 4 toward and away from and a 
limited amount of movement transversely of the plate 6. Conveniently this 
mounting may be effected by a bushing 34 in the plate 6 having a central 
aperture slightly larger than shaft 24, through which the shaft 24 
projects, with stopping means such as lock nuts 36 retaining the shaft 
against further movement of the clamping element 4 away from plate 6. 
Resilient biasing means, such as compression spring 38 preferably are 
provided between the plate 6 and the clamping element bearing 22 for 
resiliently urging the clamping element 4 away from the plate 6. 
By virtue of the structure described above, the method of centering and 
clamping a flexible disc 16 may be seen with respect to FIGS. 3A through 
3C. FIG. 3A represents the configuration of the spindle and clamping 
element when the disc drive is in its open, disc receiving configuration. 
In this configuration a cartridge 17 containing flexible disc 16 may be 
inserted into the disc drive and, by suitable mechanical stops and guides 
(not shown) is positioned such that the central aperture 40 of the disc is 
generally concentric with the spindle 2 and clamping element 4. The 
diameter of the circular central aperture 40 of the flexible recording 
disc 16 is standardized throughout the industry, and the diameter of the 
recess 18 within the spindle is dimensioned to be substantially the same 
as the diameter of the disc aperture 40. Since the axially projecting 
portions 32 of the clamping element 4 define sectors of a circle which, 
when the fingers 28 are in their undeflected configuration, has a diameter 
smaller than the diameter of the spindle recess 18 and thus the disc 
aperture 40, these axially extending portions 32 may be introduced without 
binding through the disc aperture 40 and into the spindle recess 18, as 
indicated in FIGS. 3A and 3B. The introduction of the clamping element 4 
through the disc aperture 40 and into the spindle recess 18 is 
accomplished by closing the pivotally mounted panel 6 and thus moving the 
clamping element toward the spindle. The ready insertion of the 
projections 32 of the clamping element 4 is further facilitated by the 
generally conically inward taper provided on those projections 32 and 
illustrated in the sectional views of FIGS. 3A through 3C. 
As illustrated in FIG. 3B, continued advancement of the clamping member 
toward the disc 16 and spindle 2, as the panel 6 is further closed, brings 
the generally radially projecting tabs 30 into engagements with the disc 
16 immediately adjacent the aperture 40 and urges that disc into 
engagement with the face 14 of the spindle 2. Since, at this point, the 
disc has been only approximately centered with respect to the axis of 
rotation defined by shaft 8, it is important that the disc be more 
accurately centered before it is rigidly clamped against the spindle 2. 
This function is achieved by the configuration of the clamping element 4 
in the following manner. As the generally radially extending tabs 30 more 
fully engage the disc 16, as the body 26 of the clamping element 4 is 
further advanced toward the spindle, these tabs 30 themselves may no 
longer advance axially along with the body 26 of the clamping element 4. 
Thus, the configuration of the clamping element fingers 28, extending 
angularly outwardly and axially toward the spindle 2 and drive shaft 8, 
and their engagement with the disc 16 and spindle 2 cause the fingers 28 
to flex radially outwardly, thus spreading the axially extending portions 
32 from their undeflected positions, as shown in FIG. 3C. As long as this 
radial spreading continues, the disc 16 is not rigidly clamped against the 
face 14 of the spindle 2 by the clamping element 4 and may be repositioned 
slightly as necessary to center the disc. By virtue of the plurality of 
the generally axially extending finger portions 32 defining sectors of a 
circle, the radial spreading of these portions 32 will continue until they 
firmly engage the wall 20 defining the spindle recess 18. Since this 
recess is dimensioned to be of substantially the same diameter as the 
standardized central aperture 40 of the disc 16, the expansion of the 
clamping element axial finger portions 32 against the spindle recess wall 
20 will force the central aperture of disc 16 into substantial 
concentricity with the spindle recess 18 and thus with the axis of 
rotation of the spindle 2. 
Provision of the compression spring 38 urging the clamping element 4 away 
from the pivotally mounted plate 6 enables the plate 6 to be brought 
further toward the spindle 2 and locked in place, with the compression of 
spring 38 providing for resilient engagement between the clamping element 
4 and the disc 16 and spindle 2 in order to maintain satisfactory level of 
engagement between these elements despite minor variations in the 
positioning of the pivotal plate 6. 
Upon movement of the plate 6 away from its position shown in FIG. 3C and 
toward the position shown in FIG. 3A, the clamping engagement between the 
clamping element 4 and the disc 16 and spindle 2 is released, thus 
permitting removal and replacement of the disc 16 with another suitable 
disc. Upon the reinsertion of another disc, the same procedure illustrated 
in FIGS. 3A through 3C may be repeated to center and clamp the disc in 
place for use. 
From the foregoing it may be seen that this invention provides for an 
exceptionally simple and economical, as well as positive, means for 
centering and clamping a flexible magnetic recording disc to a disc drive. 
While the foregoing description describes a particularly preferred 
embodiment of the invention, it is to be recognized that such description 
is for purposes of illustration only and is not to be considered 
limitative of the principles of the invention. Thus, since numerous 
variations and modifications of structure, all within the scope of this 
invention, will readily occur to those skilled in the art, the invention 
is not to be limited by the foregoing description but solely by the claims 
appended hereto.