Mechanism to clamp magnetic disk against cartridge shell

A data storage cartridge has a recording medium and a door covering an opening in the shell. The door is opened when the cartridge is inserted into the drive and closed when the cartridge is removed from the drive. A movable member rotates in cooperation with a stationary member by an actuating arm that is coupled to the door. Preferably, a screw/nut mechanism is operated by the opening and closing of the door to actuate a clamping mechanism which clamps the recording against a planar wall of the shell when the cartridge is removed from the drive.

FIELD OF THE INVENTION
 This invention relates to data storage drives and more particularly, to a
 removable cartridge for magnetic disk drives.
 BACKGROUND
 Magnetic disk drives which write and read digital data from flexible
 magnetic disks have been extensively used. "Floppy disk drives" have been
 extensively used for small, so-called microcomputer systems, for
 word-processing applications and the like. The flexible disk cartridge
 includes a relatively thin, flexible jacket which is inserted into the
 floppy disk drive.
 Rigid disk drives, such as the IBM 3350, usually have a fixed rigid
 magnetic media. The magnetic heads do not contact the magnetic surface,
 but ride on a thin film of air. Because of this, and other features, these
 disk drives are capable of extremely precise and high speed operation.
 This type of disk drive is commonly referred to as a "Winchester" drive.
 Rigid disks enclosed in a rigid, removable cartridge, or shell have also
 been used. U.S. Pat. No. 4,864,452--Thompson et al is an example of such a
 drive. "Bernoulli" disk drives having performance characteristics similar
 to that of Winchester drives, but with removable cartridges, have been
 developed. A flexible magnetic disk is enclosed in a rigid box which is
 normally completely closed. U.S. Pat. No. 4,400,748--Bauck, et al and
 related patents to the common assignee show such drives using Bernoulli
 stabilized flexible disks. U.S. Pat. No. 4,901,173--Jones et al and
 related patents to the common assignee, show improvements which relate to
 so-called "half height" drives.
 The cartridges for these drives have a door which closes the cartridge when
 it is removed from the drive. This prevents debris from contaminating the
 magnetic recording medium when the cartridge is not in the drive. When the
 cartridge is inserted into the drive, this door slides to an open position
 to provide access for the magnetic recording heads to engage the recording
 medium.
 When the cartridge is removed from the drive, it is often subject to rough
 handling. During handling, physical contact of the disk with the shell may
 damage the disk, particularly if the disk and cartridge shell are subject
 to excessive "rattling".
 U.S. Pat. No. 5,444,586, Iftikar, et al. discloses a mechanism for clamping
 the cartridge against the cartridge shell when the cartridge is removed
 from the drive and releasing the clamping mechanism when the cartridge is
 inserted into the drive. In the Iftikar, et al patent a nut and screw
 mechanism is actuated by a tang which is rotated as the cartridge is
 inserted into the drive. Unfortunately, such a design requires added
 complexity of the drive because the mechanism to actuate the tang is
 disposed within the drive, as distinguished from within the cartridge.
 U.S. Pat. No. 5,650,899 Schick, et al. discloses a cam mechanism which
 clamps the hub against the cartridge shell as the access door of the
 cartridge is opened and closed when the cartridge is inserted into or
 ejected from the drive.
 It is a goal of the present invention to provide an advantageous clamping
 mechanism which is actuated by the opening and closing of the cartridge
 door as it is inserted into and ejected from the drive, which optimizes
 head space, which reduces the number of moving parts, and which diminishes
 rattling of the cartridge while the cartridge is outside of the drive.
 SUMMARY OF THE INVENTION
 In accordance with the present invention, a clamping mechanism in a data
 storage cartridge includes a movable member and a stationary member. The
 mechanism is actuated by the door of the cartridge which is opened when
 the cartridge is inserted into the drive and is closed when the cartridge
 is removed from the drive. The mechanism of the present invention
 restrains the recording medium to prevent rattling when the cartridge is
 removed from the drive, i.e. when the door is closed. The clamping
 mechanism is disposed on the same axis as the rotatable recording medium.
 When the door is closed the clamping mechanism translates the motion of the
 door closing into a surface that clamps the hub on which the recording
 medium is mounted against a rear wall of the cartridge. Preferably, the
 clamping mechanism is at least partially located in a cavity formed in the
 hub while the clamping mechanism is in the clamped position, although such
 location is not necessary. The clamping mechanism comprises a stationary
 member and a movable member. The stationary member is affixed to the
 planar surface of the cartridge. The movable member is operationally
 coupled to the door via an actuating arm, and movably coupled to the
 stationary member such that as the door opens and closes, the movable
 member is rotated on the stationary member. The door movement, thus,
 causes axial motion of the clamping mechanism which is disposed in a
 cavity in the hub. A surface of the clamping mechanism bears against the
 disk hub to clamp the disk hub against the planar wall of the cartridge.
 Four embodiments of the present invention are provided, each of which
 provides an actuating arm that is coupled to the cartridge door, a
 stationary member that is rigidly connected to the cartridge shell, and a
 movable member that is coupled to the stationary member. The actuating arm
 rotates the movable member, which is coupled to the stationary member such
 that rotation of the movable member produces axial translation of the
 movable member. The movable member translates toward the recording medium
 housed within the cartridge while the cartridge is removed from the drive
 so as to clamp the recording medium between a contact surface of the
 movable member and the cartridge shell.
 In the first two embodiments, a spring that is coiled around the axis of
 rotation provides torsion to the movable member, which are a nut and a
 screw, respectively, to bias the movable member toward the camped
 position. In the third embodiment, a helical spring is disposed near the
 periphery of the movable member, which is a screw, to bias the movable
 member toward the clamped position. The fourth embodiment lacks a spring
 to bias the movable member, which is a spiral spring and plate assembly.
 Therefore, the clamping mechanism of the fourth embodiment may either be
 actuated entirely by the door, or may be biased by a spring coupled to the
 actuating arm.
 The present invention produces the advantage that the mechanism for
 actuating the clamping mechanism is disposed within the cartridge shell,
 preferably within a cavity in the disk hub, which saves vertical space
 within the drive and reduces complexity. Further, providing a clamping
 mechanism that has only one moving part (in addition to the door and the
 actuating arm) within the cartridge produces less debris, which is an
 important and growing consideration with increasing areal density of the
 magnetic information.
 The present invention encompasses any clamping mechanism that is
 operatively coupled to the cartridge door and that includes a movable
 member that is coupled to a stationary member such that rotation or
 pivoting of the movable member results in axial translation. For example,
 the present invention encompasses a screw/nut combination regardless of
 whether the movable member clamps the recording medium against the top or
 the bottom of the cartridge shell, or whether the screw or the nut
 comprises the movable member Further, in addition to a nut and screw
 arrangement, the present invention encompasses a protrusion (for example,
 a pin) that slides within a helical or inclined groove, and also a helix
 or helically oriented members that slide within a helical
 groove--regardless of whether the grooves are disposed in the stationary
 or movable member. Further, the terms "screw" and "nut" are broadly used
 herein to comprise threads of any type on either or both the movable
 member and stationary member.
 The foregoing and other objects, features and advantages of the invention
 will be better understood from the following more detailed description and
 appended claims.

DESCRIPTION OF PREFERRED EMBODIMENTS
 FIGS. 1A and 1B show a cartridge having two half shells 11 and 12 joined
 together at 13. The cartridges has a front 14, a back 15, and two sides 16
 and 17. Between the two sides are two substantially flat, planar surfaces:
 shell first planar surface 18 and shell second planar surface 19, which
 have four edges that connect to the front 14, back 15, and sides 16 and
 17. An opening 20 in the front of the cartridge provides access by the
 read/write heads to the recording medium disposed within the cartridge. A
 flexible door 23 covers the opening 20 when the cartridge is removed or is
 outside of the drive. Door 23 sides in tracks 28 disposed in the planar
 surfaces 18 and 19. A spindle motor aperture 21, best shown in FIG. 3A, is
 disposed in surface 19.
 When a cartridge, such as the cartridge of FIGS. 1A and 1B is not in use
 (e.g., outside of a disk drive), it is desirable to fix the recording
 medium into place such that it cannot "rattle" inside of the cartridge
 shell. The following discussion uses reference numerals with corresponding
 letters to refer generally to parts of the invention. Description of
 particular embodiments below use these reference numerals consistently,
 and add a letter designation to distinguish embodiments. FIG. 2A and 2B
 illustrates the operation of a clamping mechanism of the invention that
 prevents the recording medium from rattling within the cartridge. The
 cartridge further comprises a recording medium 70, including a platter 72
 that is fixed to a hub 74, a clamping mechanism 10, and an arm 58.
 Clamping mechanism 10 is disposed within a center hollow 77 of hub 74, and
 arm 58 is coupled between door 23 and clamping mechanism 10. As a result
 of the coupling of arm 58 to door 23, when door 23 moves in the direction
 indicated by arrow 202, the arm 58 moves concurrently. This movement of
 door 23 and arm 58 actuates clamping mechanism 10 between positions A
 (shown in phantom) to clamp medium 72 against cartridge shell 12 or B to
 release recording medium 72.
 Clamping mechanism 10 generally comprises two members 36, 42--one
 stationary and another movable. The present invention contemplates two
 configurations for clamping mechanism 10. In the first configuration
 member 36 is stationary, e.g., fixed to shell 11, and member 42 rotates
 around stationary member 36. Alternatively, in another configuration,
 member 42 is stationary (e.g., fixed to shell 11) and movable member 36
 rotates within stationary member 42. Exemplary embodiments of these two
 configurations, as well as others, are provided herein below. In either
 configuration, the movable member is coupled to door 23 via arm 58. The
 movable member translates the motion of door 23 into a rotary motion about
 the other member so that the movable member is thereby translated axially.
 The axial motion provides a force within hub 74 to clamp against shell 12.
 As shown in the figures, arm 58 (including specific embodiments 58a,b,c,d)
 preferably is able to flex so that an end that is coupled to the movable
 member may easily move axially with the movable member. Further, arm 58 is
 operationally coupled to door 23, which includes a catch (not shown). The
 drive engages the catch as the cartridge enters the drive so as to pull
 the door along the side of the cartridge. Preferably the catch is pulled
 along the outside of the cartridge. The present invention encompasses
 doors having a catch formed integrally thereon and doors having a catch
 that are attached thereon as a separate member or strap, and encompasses
 doors that travel along the inside wall of the cartridge and that travel
 along the outside wall when the door is proximate its fully open position.
 As will be described fully below, screw 36a, nut 42b, nut 42c, post 108,
 and stationary member 36a' are provided as examples of stationary members
 according to the present invention. Nut 42a, screw 36b, screw 36c, the
 assembly comprising coil 96 and plate 102, and movable member 42a' are
 provided as examples of movable members according to the present
 invention. Other embodiments of stationary and movable members within the
 scope of the present invention will be apparent to those generally
 familiar with cartridges.
 Referring to FIGS. 3A, 3B, 4 and 5 to illustrate a first embodiment of the
 present invention, a clamping mechanism 10a is actuated as the door 23 is
 opened and closed. Mechanism 10a, which is rotatable on the same axis 56
 on which a recording medium rotates, comprises a screw 36a, a nut 42a, and
 a coil spring 46a, and is coupled to an actuating arm 58a.
 Screw 36a comprises a post 40a and screw threads 38a. Preferably, post 40a
 is rigidly connected to planar surface 18 opposite spindle motor aperture
 21 disposed in planar surface 19. Post 40a may be integrally molded into
 planar surface 18 in one piece, or may be formed as a separate piece and
 connected to surface 18 by welding or gluing, or by a screw through
 surface 18 and into post 40a. Screw threads 38a, preferably three or four,
 are disposed on post 40a, preferably in a helical pattern. Post 40a has a
 post slot 52 disposed therein that may be formed as a recess or slotted
 hole. FIG. 4 shows screw 36a with exemplary threads 38a and slot 52a in
 greater detail.
 Nut 42a, which is preferably shaped as a hollow cylinder with and open end
 and a closed, comprises nut threads 44a, a clamping surface 43a, and a nut
 slot 54. Nut threads 44a preferably are disposed on the inside surface of
 nut 42a. Clamping surface 43a is disposed on nut 42a proximate the
 recording medium 70, as will be described below. FIG. 5 shows an enlarged
 view of the nut slot 54.
 Actuating arm 58a, which is also shown in FIG. 12, includes a door end 60a
 for coupling arm 58a to door 23, and a clamp mechanism end 62a.
 Coil spring 46a is preferably a helical spring, preferably having several
 turns, that has a first end 48a and a second end 50a, each of which are
 bent substantially radially from the coil. Spring 46a is disposed around
 post 40a, preferably proximate shell surface 18. Spring end 48a is
 disposed in post slot 52 and spring end 50a is disposed in nut slot 54.
 Spring 46a provides torsion (the direction of which depends on the
 orientation of threads 38a and 44a) so as to rotate nut 42a in a direction
 that translates nut 42a away from shell surface 18 and into contact with
 recording medium 70.
 FIG. 3A shows the clamping mechanism 10a in a retracted position
 corresponding to the cartridge door 23 in an open position. Nut 42a is
 threaded onto screw 36a such that nut 42a is in its fully retracted
 position, and closest to shell planar surface 18. Coil spring 46a is
 urging nut 42a to unscrew from screw 36a, but is unable to produce motion
 because door 23 is held open by a mechanism within the drive (not shown).
 Recording medium 70 is unencumbered from both clamping mechanism 10a and
 shell surfaces 18 and 19 so that a drive spindle motor (not shown), which
 accesses a disk hub 74 at surface 76b through aperture 21, may spin
 recording medium 70.
 When the cartridge is to be removed from the drive, spring 46a urges nut
 42a to screw away from planar surface 18 and to clamp against recording
 medium 70. Spring 46a may provide sufficient torsion to drive nut 42a and
 to drive door 23 from its open to its closed position, or a mechanism
 within the drive may help drive the door closed, and therefore augment the
 torsion of spring 46a. FIG. 3B shows clamping mechanism 10a in an expanded
 position corresponding to cartridge door 23 in a fully closed position.
 Nut 42a has been fully rotated by door 23 such that nut 42a has translated
 axially away from surface 18. Clamping surface 43a urges against hub
 contact surface 76a to force hub 74 against shell surface 19 so as to
 clamp recording medium 70 against the shell half 12.
 Referring to FIGS. 6A and 6B to illustrate a second embodiment of the
 present invention, a clamping mechanism 10b is similar to first embodiment
 clamping mechanism 10a in that there is one stationary threaded part and
 one movable threaded part. Clamping mechanism 10b comprises a screw 36b, a
 nut 42b, and a coil spring (which is similar to spring 46a shown in FIGS.
 3A and 3B, but which is omitted from FIGS. 6A and 6B for clarity), and is
 coupled to an actuating arm 58b. Unlike mechanism 10a, nut 42b is
 stationary and screw 36b rotates and translates on nut 42b.
 Nut 42b comprises nut threads 44b and a door slot 45. Nut 42b is preferably
 shaped as a hollow, short cylinder with and open end and another end that
 is rigidly connected to planar surface 18 opposite spindle motor aperture
 21. Nut 42b may be integrally molded into planar surface 18 in one piece,
 or may be formed as a separate piece and connected to surface 18 by
 welding or gluing, or by several screws (not shown) through surface 18 and
 into nut 42b. Door slot 45 provides an open portion on the side of nut 42b
 to provide access to screw 36b by arm 58b. Nut threads 44b preferably are
 disposed on the inside surface of nut 42b. FIG. 7 shows an enlarged view
 of nut 42b.
 Screw 36b comprises a post 40b, screw threads 38b, and movable clamping
 surface 43b. Screw threads 38b, preferably three or four, are disposed on
 post 40a, preferably in a helical pattern. Screw threads 38b are shown
 schematically in FIG. 6A to illustrate that the present invention
 encompasses a groove (generally located similar to threads 38b) that
 receives a protruding thread 44b as shown in FIG. 7. Post 40a has a post
 slot 52 (not shown for clarity) disposed therein that may be formed as a
 recess or slotted hole. Screw 36b interacts with nut 42b by screwing nut
 threads 38b in mesh with threads 44b. Clamping surface 43b is disposed on
 screw 36b proximate the recording medium 70, as will be described below.
 Actuating arm 58b, which is also shown in FIG. 12, includes a door end 60b
 for coupling arm 58b to door 23, and a clamp mechanism end 62b. The coil
 spring (not shown) is disposed substantially between screw 36b and nut
 42b, and provides torsion to rotate screw 36b away from planar surface 18.
 FIG. 6A shows the clamping mechanism 10b in a retracted position
 corresponding to the cartridge door 23 in an open position. Screw 36b is
 threaded into nut 42b such that screw 36b is in its fully retracted
 position, and closest to shell planar surface 18. The coil (not shown) is
 urging screw 36b to unscrew from nut 42b, but is unable to produce motion
 because door 23 is held open by a mechanism within the drive (not shown).
 Recording medium 70 is unencumbered in this position and may spin freely,
 as described above.
 When the cartridge is to be removed from the drive, the spring (not shown)
 urges screw 36b to screw away from planar surface 18 and to clamp against
 recording medium 70. The spring (not shown) may provide sufficient torsion
 to drive screw 36b and to drive door 23 from its open to its closed
 position, or a mechanism within the drive may help drive the door closed,
 and therefore augment the torsion of the spring (not shown). FIG. 6B shows
 clamping mechanism 10b in an expanded position corresponding to cartridge
 door 23 in a fully closed position. Screw 36b has been full rotated by
 door 23 such that screw 36b has translated axially away from surface 18.
 Clamping surface 43b urges against hub contact surface 76a to force hub 74
 against shell surface 19 so as to clamp recording medium 70 against the
 shell half 12.
 Referring to FIGS. 8A, 8B, and 9 to illustrate a third embodiment of the
 present invention, a clamping mechanism 10c comprises a screw 36c, a nut
 42c, and a helical spring 90, and is coupled to an actuating arm 58c.
 Screw 36c comprises a cylindrical portion 80, an internal flange 82, a
 contact shoulder 43c, screwthreads 38c, and a screw spring anchor 86
 (shown in FIG. 9). Screw 38c is preferably open at both ends of
 cylindrical portion 80, and has an internal flange 82 disposed on the
 spindle motor side of cylindrical portion 80. Contact shoulder 43c is
 formed on the interior upper surface of flange 82. Threads 38c are sized
 to mesh with nut threads 44c. The interior upper corners of flange 82 and
 the corresponding corners of disk hub 74 may be beveled (not shown) to
 provide self-alignment during clamping. Referring specifically to FIG. 9,
 spring anchor 86 comprises a radial tab on the exterior portion of
 cylindrical portion 80. Alternatively, spring anchor 86 may be formed on
 arm 58c.
 Nut 44c, which preferably is formed on the rim of second surface 19 formed
 by aperture 21, comprises nut threads 44c. The invention also encompasses
 providing a shell having a thickened portion in the rim region in the
 direction of axis of rotation 56 to provide greater depth for threads 44c.
 Further, nut threads 44c may be finer and more numerous than corresponding
 threads 44a and 44b because of the comparatively lesser depth.
 Helical spring 90 is disposed between an anchor 84 (shown in FIG. 9), which
 is fixed to surface 19, and anchor 86, and biases screw 36c toward the
 clamped, upward direction. Proximate one point on the circumference of nut
 42c, an arcuate spring retainer 92 is formed to prevent spring 90 from
 bowing in the radial direction, although spring 90 may be designed such
 that it is under constant tension. Preferably, retainer 92 comprises an
 arcuate wall and a recessed portion 91 of surface 19 that provides a space
 to house spring 90. Because spring 90 is partially within recessed portion
 91, the retainer 92 is shorter and the vertical dimension of spring 90
 over surface 19 is diminished.
 FIG. 8A shows the clamping mechanism 10c in a retracted position
 corresponding to the cartridge door 23 in an open position. Screw 36c is
 threaded into nut 42c such that nut 42c is in its fully retracted
 position, and farthest from shell planar surface 18.
 Helical spring 90 biases screw 36c to rotate and translate toward the
 clamped position. Spring 90 may provide sufficient torsion to drive nut
 42c and to drive door 23 from its open to its closed position, or a
 mechanism within the drive may help drive the door closed, and therefore
 augment the torsion of spring 90.
 FIG. 8B shows clamping mechanism 10c in a clamped position corresponding to
 cartridge door 23 in a fully closed position. Screw 36c has been fully
 rotated by door 23 such that screw 36c has translated axially toward
 recording medium 70. Contact surface 70 urges against hub contact surface
 76a to force hub 74 against shell surface 18 so as to clamp recording
 medium 70 against the shell half 11.
 Referring to FIGS. 10A, 10B, and 11 to illustrate a fourth embodiment of
 the present invention, clamping mechanism 10d comprises a helical coil 96,
 a contact plate 102, and a post 108, and is coupled to actuating arm 58d.
 Post 108 is fixed to the surface 18 concentric with axis 56, and may be
 integrally molded into planar surface 18 in one piece, or may be formed as
 a separate piece and connected to surface 18 by welding or gluing, or by
 several screws (not shown) through surface 18 and into post 108. Post 108
 has a longitudinal keyway 110 formed therein that is disposed on its end
 opposite its fixed end.
 Helical coil 96, which is substantially concentrically disposed around the
 axis of rotation 56, comprises a first end 98 that is coupled to actuating
 arm 58d at a central circular potion 61 proximate surface 18, and a second
 end 100 that is coupled to plate 102.
 Plate 102 is preferably a circular disk that is rigidly coupled to the
 second end 100 of coil 96, and has center cutout portion 103 and a key
 portion 106 that protrudes into center cutout 103 and that is insertable
 into keyway 110 in the post 108. Key 106 may slide freely longitudinally
 within keyway 110, and plate 102 preferably is perpendicular to axis 56.
 Plate 102 has a contact surface 43d disposed on its side facing recording
 medium 70.
 Actuating arm 58d, which is also shown in FIG. 12, includes a door end 60d
 for coupling arm 58d to door 23, a circular portion disposed substantially
 concentric with post 108, and a clamp mechanism end 62d. Arm 58d is
 movably fixed to shell surface 18 in a way that enables arm 58d to rotate
 or pivot, but which keeps arm 58d substantially flat against surface 18.
 For example, multiple retainer clamps 63, shown in relief in FIG. 10A may
 be used at points around the circumference of the circular portion of arm
 58d to prevent arm 58 from moving away from surface 18 yet enable arm 58
 to rotate or pivot around post 108.
 FIG. 10A shows the clamping mechanism 10d in a retracted position
 corresponding to the cartridge door 23 in an open position. Plate 102 is
 in its closest position to surface 18 with coil 96 connected between arm
 58d and plate 102. Plate 102 is at rest on top of coil 96 with key 106
 disposed in keyway 110. Recording medium 70 is unencumbered in this
 position and may spin freely, as described above.
 When the cartridge is to be removed from the drive, arm 58d rotates or
 pivots around axis 56 in response to the door moving in a closing
 direction. FIG.10B shows clamping mechanism 10d in an expanded position
 corresponding to cartridge door 23 in a fully closed position. As door 23
 closes, movement of arm 58d results in rotation of coil 96 in a direction
 that urges plate 102 to translate toward recording medium 70 along post
 108. Plate 102 translation occurs in response to coil 96 rotation because
 plate 102 is prevented from rotating by key 106. Plate 102 moves toward
 recording medium 70 until contact surface 43d on plate 102 contacts a hub
 contact surface 105, which may be disposed on a hollow, longitudinally
 protruding portion 107 of hub 74. A shown in FIG. 10A, post 108 may be
 disposed within the hollow portion of protruding portion 107 while the
 cartridge is in the unclamped position. Therefore, adequate clearance
 between post 108 and the interior of protruding portion 107 so as to
 enable recording medium 70 to rotate freely during drive operation. When
 the door is in its fully closed position, contact surface urges against
 surface 105 and hub contact surface 76b urges against shell surface 19 so
 as to clamp recording medium 70. Although clamp mechanism 10d is
 illustrated using a disk hub having a protruding portion, clamp mechanism
 10d according to the present invention may also be employed with disk hubs
 having a cavity, as shown in the first two embodiments.
 Although the first three embodiments have been described using threads on
 both the stationary and movable members, the present invention encompasses
 using other designs to translate the movable member in response to
 rotation by the actuating arm. FIGS. 13, 14, and 15 illustrate an
 alternate assembly that is similar to the first embodiment shown in FIGS.
 3A and 3B, and that may be used to form the movable and stationary members
 according to the present invention Specifically, a clamping mechanism 10a'
 may be used in place of screw 36a and nut 42a shown in FIGS. 3A and 3B.
 Recording medium 70, spring 46a, and surface 19 have been omitted from
 FIG. 13 for clarity.
 Clamping mechanism 10a' comprises a stationary member 36a', a movable
 member 42a', and is coupled to door 58a'. Stationary member 36a' comprises
 a post 40a' that is rigidly fixed to surface 18 and plural pins 114
 extending substantially radially from post 40a'. Movable member 42a'
 comprises a hollow cylinder with a helical groove 116 formed on the inside
 surface capable of receiving pins 114.
 In response to movement of door 23, movable member 42a' rides on pins 114
 to translate relative to stationary member 36s', similar to as described
 with respect to the first embodiment.
 Nuts 42a,b,c interact with screws 36a,b,c by screwing nut threads 44a,b,c
 in mesh with screw threads 38a,b,c with adequate clearance therebetween
 such that threads 38a,b,c and 44a,b,c do not deform. Such a clearance
 enables nut 42a, screw 36b, and nut 42c to rotate and translate on screw
 36a, nut 42b, and screw 36c with a minimum amount of rotational force
 applied thereto.
 Actuating arm 58a,b,c,d may include a telescoping wire 64 disposed in a
 recess opening 62a,b,c,d, in arm 58a,b,c,d, as more fully described in
 U.S. Pat. No. 5, 560, 899-Schick et al. to the present assignee, which is
 incorporated herein by reference in its entirety.
 Although the present invention has been described with reference to a
 cartridge in which a flexible door travels along a radius of curvature
 that changes by angular position (that is, as shown in FIG. 1A), the
 present invention encompasses a cartridge in which a rigid door travels
 along an arc of constant radius. In the latter design, the door may be
 formed of rigid plastic or metal in a circular arc that travels in the
 circular track, and the actuating arm may span the entire arcuate segment
 of the door to form substantially a radial portion of a circle.
 The terms "axial" and "axially" as used herein refer to an axis of rotation
 of the recording medium. The term "longitudinal" when used herein to any
 part of the clamping mechanism, refers to a direction or orientation
 substantially parallel to the axis of rotation of the recording medium.
 While a particular embodiment has been shown and described various
 modifications may be made. The appended claims are, therefore, intended to
 cover all such modifications within the true spirit and scope of the
 invention.