Computer slot security adaptor

A security device for securing portable equipment having a security slot in the chassis of the equipment, comprising an attachment having a slot-mating head and an axially movable head locking member which is inserted into the slot after the head to prevent rotation and removal of the head from the slot.

TECHNICAL FIELD
 The invention relates to security devices for portable equipment. More
 specifically, the invention relates to devices used to prevent theft of
 computers and other office equipment.
 BACKGROUND OF THE INVENTION
 Theft of portable equipment such as personal computers and other office
 equipment is widespread and imposes significant costs on individuals and
 businesses. Developing a common security solution to prevent theft of
 portable equipment has proven challenging, because portable equipment
 varies so much in terms of size, shape and construction. Accordingly,
 previous attempts to provide a common, inexpensive and secure method to
 protect even a single class of portable equipment, such as personal
 computers, have been largely unsuccessful.
 One particular type of security device for portable equipment uses
 interlocking plates to affix the underside of an office equipment unit to
 a work surface. U.S. Pat. No. 4,655,429 to Gaensle et al. (1987) discloses
 fixture with plates and a bonding method to secure them. Other methods
 have the user drill holes in the work surface to bolt the interlocking
 plates together from underneath.
 These methods are satisfactory for certain applications, but are generally
 unacceptable because they make movement of the equipment time consuming
 and difficult when offices are relocated, sometimes forcing permanent
 modifications to be made to the equipment or anchoring surface, and do not
 allow the user the option of repositioning the equipment once it has been
 installed. In addition, many of these devices must be manufactured to fit
 the specific geometry of the machines they secure, making them expensive
 to manufacture and purchase.
 Another class of devices that share many of these same drawbacks encase the
 equipment to be protected in a protective housing using various methods to
 anchor the housing to a secure location. Several types of these devices
 have been disclosed. For example, U.S. Pat. No. 4,123,922 to Kuenstler
 (1978) describes various means to lock equipment inside a protective
 housing. U.S. Pat. No. 4,252,007 to Kerley (1981) discloses a protective
 housing of similar intent but different design. Although appropriate for
 certain applications, these devices must be designed to house a particular
 size and shape of equipment, making them expensive to manufacture and
 purchase. In addition, they have the drawback of dramatically altering the
 appearance of the office equipment.
 To overcome these objections consumers have resorted to security devices
 that have more flexible anchoring methods. Many of these devices utilize
 steel cable, sometimes referred to as "wire rope", to tether personal
 computers and other office equipment in place. Some steel cable devices
 use existing screws to secure the cable to the office equipment. First, a
 bracket is mounted to the equipment using an existing screw. Then the
 steel cable is passed through the bracket, blocking removal of the screw.
 These devices can be used on a broad variety of computers, are inexpensive
 to manufacture and can be removed when no longer desired. However, these
 screw attached devices have some disadvantages. First, the security
 provided by this method is based on the strength of the screw arrangement
 which anchors the bracket. Most personal computers have relatively small,
 frail screws. Additionally, the surfaces that they screw into are
 generally thin and easily stripped by wrenching forces on the cable and
 screw. Consequently, a thief, depending on the personal computer, could
 dislodge the bracket with a good quick tug. Another disadvantage is the
 difficulty that users encounter mounting these devices. Many users have a
 difficult time visualizing how these devices are utilized and installed.
 Another steel cable device uses a tether to anchor a housing that encases
 the equipment. This approach has the same drawbacks as the other
 protective housing approaches mentioned above. They are expensive and
 dramatically alter the appearance of the equipment they are protecting.
 Still other office equipment steel cable devices, as disclosed in U.S. Pat.
 No. 3,785,183 to Sander (1974), U.S. Pat. No. 3,859,826 to Singer et. al.
 (1975), U.S. Pat. No. 3,990,292 to Shontz (1992) and U.S. Pat. No.
 4,310,371, to Herwick et. al. (1981), focus on elaborate keylock
 assemblies. These devices are expensive and fail to provide a simple and
 widely applicable method to attach the steel cable to a personal computer
 or other office equipment. For attaching the cable to equipment to be
 secured, Sanders suggests making a hole in the equipment to take advantage
 of the disclosed lock and back plate assemblies. Most users find this
 unacceptable because they do not wish to drill into the equipment for fear
 of violating the warranty or damaging the equipment. Singer et. al.
 suggests using tamper proof screws to attach to the equipment to take
 advantage of the disclosed locking assembly. This assumes that there are
 suitable screw mounting sites that are in the necessary location to mate
 with the particular security plate for the equipment. Additionally,
 security screws are only suitable as long as a thief does not have the
 correct screwdriver. Shontz suggests drilling a hole in the office
 equipment, finding a suitably located and sized hole, or adapting a plate
 to fit existing nuts and bolts to mount the cable. This approach has many
 of the same disadvantages that are apparent in the Sander disclosure.
 A more satisfactory means for securing portable equipment has been
 developed which takes advantage of existing plates or fittings on the
 equipment to provide anchoring attachments for security fittings. Such
 security devices replace the plate or fitting with a security fixture
 which is designed to be securely mounted in the original location of the
 plate or fitting. Ideally, such devices are mounted without exposed screws
 or bolts which may be removed by unauthorized persons. One such security
 device specifically designed for personal computers is a mechanical
 security fixture which mounts to a standard expansion slot opening in the
 personal computer chassis. This security fixture can be used on a broad
 range of personal computers, can be securely mounted without exposed
 screws or bolts, and takes advantage of the integrity of the computer
 chassis to provide a strong mounting location for the security fixture.
 A recent development in the field of security devices for portable
 equipment has been the use of security fixtures which are specifically
 designed to mate with standardized openings manufactured into the chassis
 of the equipment. One such chassis mating fixture commonly used in
 personal computers and other portable office equipment is a lockable
 mating fixture manufactured by Kensington, Inc., San Mateo, Calif.,
 adapted to mate with standardized, oval shaped security slots manufactured
 into the chassis of the equipment. Such security slots are now routinely
 provided for a range of portable computers, such as laptop and notebook
 computers sold under the Macintosh.RTM. trademark (Apple Computers, Inc.,
 Cupertino, Calif.), as well as manufactured by Dell.RTM. (Austin, Tex.),
 AST.RTM. (Irvine, Calif.), and Toshiba USA.RTM. (Irvine, Calif.), among
 others. The slots are designed to lockably engage a t-shaped head
 connected by a rotatable shaft to the security fixture which is in turn
 anchored to a stationary object by an anchoring tether.
 To attach the Kensington fixture to the portable equipment, the head is
 inserted into the slot through the wall of the chassis of the equipment
 and the shaft is then rotated by insertion and rotation of a key into the
 device. This rotates the head out of line with a longitudinal axis of the
 slot into an engaged position, so that removal of the head is blocked by
 an interior wall of the chassis surrounding the slot. Removal of the head
 can then only be accomplished if the head is further rotated or
 counter-rotated to realign the head with the longitudinal axis of the
 slot.
 To prevent counter-rotation and removal of the head once it is engaged, the
 Kensington device provides an elaborate head locking system. The system
 includes a head locking mechanism consisting of two pins mounted on either
 side of the shaft in line with an insertion plane defined by the head and
 shaft when the head is in the non-engaged position. The length of a
 horizontal, slot-mating portion of the head, and the spacing between the
 locking pins, approximates the length of the slot so as to enable
 simultaneous insertion of the head and pins into the slot. once the head
 and pins are inserted into the slot, the shaft and head are rotated about
 the shaft axis, while the pins remain stationary in the slot. Once the key
 is removed, the head becomes locked in the engaged position and cannot be
 independently angularly rotated about the longitudinal axis of the shaft
 relative to the pins, which themselves cannot be angularly rotated with
 respect to the shaft axis because such action is blocked by sidewalls of
 the slot.
 While the Kensington device features a number of advantages over
 alternative security devices for portable equipment, it also features a
 number of disadvantages. Primary among these disadvantages is the complex
 head locking system which imposes extensive manufacturing costs. In
 addition, use of the Kensington device is limited to portable equipment
 manufactured to include a security slot opening in the chassis, making the
 device incompatible with a wide range of portable equipment.
 Accordingly, a need exists in the art for a security fixture for securing
 portable equipment having a security slot opening in the chassis of the
 equipment, which is simple in design and inexpensive to manufacture. In
 addition, there is a need in the art for a means of adapting portable
 equipment which has not been manufactured to include a slot opening to
 make such equipment securable by slot-mating security fixtures.
 SUMMARY OF THE INVENTION
 It is therefore an object of the present invention to provide a slot-mating
 security device which is simple in design and inexpensive to manufacture.
 It is a further object of the invention to provide a method and device for
 modifying portable equipment which does not have a security slot opening
 to make the equipment compatible for use with slot-mating security
 fixtures.
 The invention achieves these objects and other objects and advantages which
 will become apparent from the description which follows by providing a
 slot-mating security fixture which has a slot-mating head including a
 transverse limb attached by a shaft to a main body, and an elongated,
 axially moveable head locking member to prevent counter-rotation of the
 head out of an engaged position.
 In the preferred embodiment, the head includes two transverse limbs so that
 the head and shaft make up a t-shaped extension from the body. The body
 defines a main axis and has a head locking aperture for permitting axial
 movement of an elongated head locking member. The head locking member is
 independently axially moveable with respect to the head to allow for
 independent insertion of the head locking member into the slot after the
 head has been inserted and rotated in the slot to an engaged position.
 After the head is engaged, the head locking member is axially advanced
 through the aperture into the slot, thereby preventing rotation or
 counter-rotation of the head so that the head is locked in the engaged
 position. In addition, the invention provides a mechanism for concealing
 the head locking member after it has been advanced through the aperture
 into the slot, so that the head locking member cannot be retracted from
 the slot. The security device can also be attached to an anchoring tether.
 In alternate embodiments, the security fixture compensates for different
 slot wall thicknesses, and is provided with alternative cable locking
 mechanisms.
 The design of the body, head and head locking member is simple, yet
 obviates the need for an elaborate head locking system requiring
 independent angular adjustability and lockability between the head
 relative to the head locking mechanism.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
 A security device employing the principles of the present invention is
 generally indicated at reference numeral 10 in FIG. 1. The device is about
 to be mounted into a standard security slot 12 of a chassis 14 of a
 portable equipment unit. The device includes a main body 16 defining a
 central axis 18, a mounting end 20 and a terminal end 22. As shown in
 FIGS. 3 and 4, the body further defines a head locking bore 24 and a
 threaded head locking aperture 25 for engaging a head locking member, or
 screw 26.
 Referring to FIGS. 1 and 3, the security device 10 also features a
 slot-mating head 27 including a transverse limb 28 sized for insertion
 into the security slot 12. The head is supported on a perpendicular shaft
 29 attached to the mounting end 20. The preferred head has two transverse
 limbs, 28, 28' so that the head and shaft form a t-shaped extension from
 the body, and has an overall length 30 of approximately 7-8 mm, and a
 width 31 of approximately 3 mm. A head axis 32 and a shaft axis 33 (see
 FIG. 2) define an insertion plane which, in order for proper functioning
 of the security device, must be substantially parallel to, but not
 include, longitudinal axes of the bore 24 and aperture 25 which are
 coincident with the main axis 18.
 In addition to these features, the security device 10 also includes a pair
 of diametrically opposed, transverse holes 34, 35 in the terminal end 22
 of the body 16 for accepting an anchoring tether 36, as shown in FIGS. 1,
 3-5, 8 and 9.
 The security device 10 of the present invention can be mounted to any
 portable equipment which has an elongated security slot 12 in the chassis
 14. As represented in FIGS. 1 and 3, the device is mounted by inserting
 the head 27 into the slot in the direction of the insertion arrow 40 while
 the insertion plane includes a longitudinal axis 50 of the slot opening
 12. The head is advanced until it has passed beyond an inner wall 52 of
 the chassis 14. At this point during mounting, the device 10 is rotated
 angularly with respect to the shaft axis 33 until the screw 26 is aligned
 with the slot (compare FIGS. 3 and 4). In the engaged position, shown in
 FIG. 4, the head 27 cannot be removed from the slot opening 12 without
 being further rotated or counter-rotated, because removal of the head in a
 direction opposite to the insertion arrow 40 is blocked by contact between
 the transverse limb 28 of the head and the inner wall 52 of the chassis.
 Although a single limb is sufficient to prevent rearward removal of the
 head, two limbs 28, 28' provide better anchorage against the inner chassis
 wall and are therefore preferred.
 At this point during mounting, the head locking screw 26 can be advanced
 through the bore 24 and aperture 25 in the direction of the insertion
 arrow 40 so that the screw passes through the aperture into the slot
 opening 12 to a head locking position 54. The screw is advanced by
 inserting a screwdriver into a blockable, longitudinally directed access
 opening 56 defined by the terminal end 22 of the body 16, and thereafter
 causing the screwdriver to turn a head 58 of the screw to advance the
 screw within the bore 24 and aperture 25. The screw must be advanced
 sufficiently far into the slot opening so that it remains in the slot
 opening if the security device is pulled away from the chassis 14 in the
 direction of the arrow 59 shown in FIG. 4 so that the transverse limbs 28,
 28' of the head 27 are drawn against the inner chassis wall 52. Contact
 between the head limbs and inner wall prevents further withdrawal of the
 device away from the chassis so that the head locking member remains
 engaged in the slot opening in the head locking position.
 Advancement of the screw 26 into the head locking position 54 prevents
 further rotation or counter-rotation of the head 27, so that the head
 cannot be removed from the slot 12. This is because a separation distance
 60 between the screw and head shaft 29 is at least slightly wider than a
 width 62 of the slot opening (see FIG. 1). The separation distance between
 the screw and shaft is fixed, such that rotation of the head is prevented
 by contact of the screw and shaft 29 with side-walls 64 of the slot
 opening 12. This relationship prevents realignment of the head axis 32
 with the slot axis 50 to allow removal of the head from the slot.
 The invention also provides mechanisms for axially adjusting the head 27
 relative to the body 16, to accommodate variations in thicknesses 66 (see
 FIGS. 3 and 4) of slot side-walls 64 among different portable equipment
 designs. Axial adjustability of the head is desirable because a greater
 degree of security is provided if the head 27 and mounting end 20 are
 separated by a seating distance 68 (see FIG. 3) which closely approximates
 the thickness of the sidewalls 64 of a particular slot opening. If the
 seating distance is nearly the same as the sidewall thickness, the device
 can be mounted with a snugger fit; i.e. after insertion and rotation of
 the head 27, a rear surface 70 of the head limbs 28, 28' preferably seats
 against the inner wall 52 of the chassis 14, while a front surface 72 of
 the mounting end snugs against an outer wall 74 of the chassis (see FIG.
 3). The closer the match between the sidewall thickness 66 and seating
 distance 68, the less play there is for manipulating the device after
 mounting. This reduces the risk that a thief may be able to joggle the
 device in the slot to put force on the chassis walls 52, 74 and perhaps
 break the head free from the slot by disrupting the integrity of the
 chassis walls. In addition, the more snugly the device fits, the more
 appealing is the aesthetic appearance of the portable equipment after the
 device is mounted.
 Axial adjustability of the head 27 is provided by a spring-mounted, axially
 adjustable head support 80 to which the shaft 29 and head are attached
 (see FIGS. 3 and 4). To accommodate the adjustable head support, the body
 has a hollow cavity 82 defined by the mounting end 20, and a transverse
 retaining wall 84 intermediate the mounting end and terminal end 22. The
 head support 80 seats like a piston within the cavity 82 and rides on a
 compression spring 86 mounted between the head support and retaining wall.
 The head locking bore 24 passes through the retaining wall 84 and is in
 registration with the threaded aperture 25 defined by the head support 80.
 The head locking screw 26 is cooperatively threaded with the aperture and
 is movably mounted through the bore and aperture.
 In operation, the invention employs a dually functional head locking screw
 26, which not only prevents rotation of the head 27 when the head and
 screw are engaged in the slot 12, but also controls axial adjustment of
 the head. To accomplish both functions, the screw 26 is advanced in the
 direction of the insertion arrow 40 (see FIG. 3) so that the screw passes
 into the slot opening 12 to the head locking position 54, as described
 above. When the screw is partially advanced, the screw head 58 comes into
 contact with a rear surface 90 of the retaining wall 84. The bore 24 is
 not threaded, allowing the screw to continue turning in the bore and
 threading through the aperture 25 after the screw head 58 contacts the
 rear surface of the retaining wall. This causes the head support 80 and
 head 27 to move axially toward the retaining wall simultaneous with
 advancement of the screw into the slot opening 12 toward the head locking
 position 54. As the screw approaches the head locking position, the
 seating distance 68 diminishes until it is approximately the same as the
 sidewall thickness 66. At this point the rear surface 70 of the head limbs
 28, 28' are brought into contact with the inner chassis wall 52, and the
 front surface 72 of the mounting end is brought into contact with the
 outer chassis wall 74 to snugly mount the device. The spring 86, which
 need not be present, functions to resist axial movement of the head
 support 25, maintaining the head support in an extended position, as shown
 in FIG. 4, for easier mounting of the device.
 Once the device 10 of FIG. 1 has been mounted, (i.e. once the head is
 engaged, the screw 26 is advanced to the head locking position 54, and the
 head is axially adjusted), the anchoring tether 36 is threaded through the
 anchoring holes 34, 35, as depicted in FIG. 5. A preferred type of
 anchoring tether is a standard anchoring cable (not shown) made of braided
 steel or other material resistant to cutting, having bulbous attachments
 at each end. After the tether is threaded through the access openings 34,
 35 and an opening in a furniture frame or other relatively immovable
 structure, the tether is locked in a closed configuration by standard
 attachments which engage the bulbous enlargements and are designed to be
 padlocked together.
 After the anchoring tether 36 is secured it also blocks access to the head
 locking screw 26 via the access opening 56 in the terminal end 22. The
 tether effectively conceals the screw head 58 so that a screwdriver cannot
 be used to unseat the screw and allow rotation and removal of the screw 26
 from the head locking position 54.
 To accommodate anchoring restrictions imposed by the stiffness of the
 tether 36 and the need to link the tether between the device 10 and
 immobile anchoring structures (eg. a table or desk frame), the invention
 provides a mechanism for angular rotation of the body 16 about the central
 axis relative to the head 27. This allows the body to be independently and
 selectively angularly positioned with respect to the head, the engaged
 position of which is dictated by the equipment and slot position, so that
 the anchoring holes 34, 35 can be approximately aligned with the
 restricted tether path.
 Selective rotation between the head and body is accomplished by providing
 multiple keyways 94, 94', 94" within the hollow cavity 82 for mating with
 a key 96 on the head support 80 (see FIGS. 2 and 3. Using this arrangement
 the body 16 can be selectively rotated relative to the head support, by
 removing the head support from the hollow cavity and disengaging the key
 96 from a first keyway 94, rotating the head support or body to align the
 key with a second keyway 94', 94", and then reinserting the head support
 into the cavity so that the second keyway engages the key. The body can
 thereby be oriented with the anchoring holes 34, 35 aligned with the
 restricted path of the tether 36. This allows for freer positioning and
 movement of the equipment, while preserving the ability to angularly fix
 the position of the head relative to the body for easier mounting.
 Other embodiments of the invention are provided which avoid the use of a
 padlock and are thus advantageously designed for securing smaller portable
 equipment, such as laptop and notebook computers and calculators, which
 are frequently transported between locations. With such equipment it is
 desirable to employ a security device which may be rapidly and easily
 detached from the equipment. In a first alternate embodiment 10', shown in
 FIG. 6, One end of the anchoring tether 36 is provided with a male lock
 fitting 100 which is lockably interconnectable with a combination lock
 housing 102 which makes up the main body of the device (see FIGS. 6 and
 7). The lock fitting has a slot-engaging pin 104 which functions to
 prevent rotation of the head 27 in the slot 12 in a similar manner as the
 head locking screw 26 operates in the previously described embodiments.
 This embodiment provides an alternate mechanism for axial adjustability of
 the head 27', as shown in FIG. 6a. The head is mounted on a threaded shaft
 29' which may be adjustably advanced or retracted within a cooperatively
 threaded shaft opening 105 defined by the mounting end 20'. Axial
 adjustment of the head in this manner serves to decrease or increase the
 seating distance 68 to adjust for variations in slot side-wall thickness
 66.
 A second, padlock-free alternate embodiment is shown in FIG. 7, in which
 the anchoring tether 36 is provided with a keyed male lock fitting 100'
 which is lockably interconnectable with the lock housing 102'.
 To mount the embodiments 10', 10" shown in FIGS. 6 and 7, the head 27 is
 inserted into the slot 12 and rotated in the same manner as described for
 the previous embodiments. Next, the male lock fitting 100, 100' is
 inserted into a lock fitting receptacle 106 (see FIG. 7) defined by the
 lock housing 102, 102'. Upon insertion of the lock fitting into the
 receptacle, the pin 104 passes through the head locking aperture 25 in the
 mounting end 22 and into the slot opening 12 to prevent rotation of the
 head from the engaged position. When the lock fitting is fully inserted
 into the receptacle, the housing lockably engages the fitting by way of
 conventional locking mechanisms, such as fixed or retractable teeth 108,
 108' on the male lock fitting and teeth engaging notches 110 within the
 receptacle for engaging the teeth, so that the pin is secured in the head
 locking position.
 A principal advantage of these embodiments 10', 10" designed for small
 equipment is that the tether 36 is not attached directly to the housing
 102, 102' of the security device. Rather, the tether is attached to the
 male lock fitting 100, 100'. Accordingly, the tether can be removed from
 the housing merely by dialing the appropriate combination or turning the
 key to disengage the fitting from the housing. This action retracts the
 slot-engaging pin 104 from the slot 12, allowing rotation and removal of
 the head 27 from the slot. This detaches the security device and frees the
 equipment for transportation more quickly and easily than can be
 accomplished with the previously described embodiments, which require that
 the padlock be removed from the tether locking attachments and the tether
 be unthreaded through the anchoring holes 34, 35, in addition to
 unscrewing the head locking screw 26, before the security device can be
 disengaged from the equipment.
 A number of simplified embodiments are also provided by the present
 invention, including the embodiments 10'", 10"" shown in FIGS. 9 and 10.
 The first simplified embodiment 10'", shown in FIG. 9, principally
 resembles the embodiment of FIGS. 3 and 4, but lacks a compression spring
 to regulate axial movement of the head support 80'. The body 16' is freely
 rotatable about the central axis 18 with respect to the head support. The
 cavity 82' defined by the mounting end 20' has a head support retaining
 rim 111 and a transverse retaining wall 84' for retaining the head
 support. The mounting end is made of a compressible material to
 accommodate different side wall thicknesses among security slots. The head
 support has a screw seating collar 112 through which the threaded head
 locking aperture 25' and cooperatively threaded head locking screw 26
 extend. The collar is engageable within a collar opening 113 defined by
 the retaining wall. Importantly, a length 114 of the collar is greater
 than a length 115 of the collar opening, so that when the head locking
 screw is advanced through the aperture into the slot opening to the head
 locking position, as depicted in FIG. 9, the screw head 58 seats on a
 screw locking rim 116 of the collar. This arrangement differs from the
 screw head seating arrangement provided by the embodiment of FIGS. 3 and
 4, wherein the screw head seats against the rear surface 90 of the
 retaining wall 84. The latter arrangement could create difficulties if the
 body 16 and head support of the embodiment of FIGS. 3 and 4 were not
 angularly fixed with respect to one another after mounting, due to the
 engagement of the head support key 96 by one of the keyways 94, 94', 94".
 If such angular fixation between the head and body were not provided, a
 thief could conceivably unscrew the screw out of the head locking position
 54 by pulling the body away from the chassis 14 and rotating the body so
 that friction between the screw head and rear surface of the retaining
 wall caused the screw to become unthreaded from the head locking aperture
 25 and disengaged from the slot opening 12. This potential problem is
 avoided by the collar seating arrangement provided in the embodiment of
 FIG. 9. Although this embodiment features free angular rotatability
 between the body and head support, the seating of the screw head against
 the screw locking rim 116 of the collar 112 prevents the application of
 friction to unthread the screw by rotation of the body.
 In another simplified embodiment of the invention, shown in FIG. 10, the
 body 16 is unitarily constructed, and the head 27 and shaft 29 are
 directly connected to the body. The retaining rim 111' of the cavity 80"
 is designed for retaining the compression spring 86', which regulates
 axial movement of an engagement piston 117. The head locking member is a
 pin 118 connected to the engagement piston. To mount this embodiment, the
 head is inserted and rotated in the slot opening 12, as described
 previously, and as shown in FIG. 9. Next, the pin is advanced through the
 head locking aperture 25 into the slot opening by using a thumb to apply
 force to the engagement piston to compress the spring and drive the piston
 axially toward the chassis 14, so that the pin is advanced into the head
 locking position 54. The piston has a transverse, piston locking channel
 119 which is alignable with the anchoring holes 34, 35 when the piston has
 been advanced sufficiently to drive the pin into the head locking
 position. The piston locking channel may be a transverse notch or bore in
 the piston, and its function is to secure the head locking pin in the head
 locking position. This is accomplished by threading the anchoring tether
 36 through both the anchoring holes, and simultaneously through the piston
 locking channel, whereafter the piston cannot be axially repositioned to
 allow disengagement of the pin from the slot opening.
 For optimal manufacturing and performance purposes, it is desirable to
 build the security device so that the longitudinal axes of the head
 locking aperture 25 and head locking member, eg. screw 26 or pin 104, 118,
 are collinear with the central axis 18 of the body 16, and so that the
 head shaft 29 is parallel to the central axis. This is due in part to size
 constraints on the device imposed by aesthetics and by the particular
 design of certain types of portable equipment. In general, it is
 aesthetically desirable to limit the size of the device, because a bulky
 fitting may appear ungainly attached to a streamlined or sophisticated
 portable equipment unit such as a computer. In addition, many portable
 equipment units are manufactured with the slot opening 12 located in a
 circular well, or mounting depression 120, in the chassis (see FIG. 4). To
 be mounted properly, a maximum width 121 of the mounting end 20 of the
 device must be the same as, or smaller than, a minimum diameter 122 of the
 mounting depression. Otherwise the mounting end will not seat snugly
 against the outer chassis wall 74 surrounding the slot opening 12. A
 standard minimum diameter for a mounting depression in a personal computer
 chassis is approximately 26 mm. Accordingly, a security device for use
 with such equipment should have a maximum mounting end width of equal or
 lesser size.
 These size constraints impose an additional constraint in terms of location
 of the head locking screw 26 or pin 104, 118. The maximum width 121 of the
 mounting end 20 must be less than or equal to the diameter 122 of the
 mounting depression 120, so it is preferable to have the longitudinal axes
 of the screw or pin collinear with the central axis 18. This is because
 the screw or pin is necessarily bulky, so to place them eccentrically
 would require increased width of the mounting end. In addition, collinear
 placement of the screw axis provides for smoother angular rotation of the
 body relative to the head support 80, because the central axis 18 is
 collinear with the aperture 25 and bore 24 through which the screw 26
 passes.
 If the screw 26 axis is placed collinear with the central axis, it then
 becomes necessary to make the mounting end width 121 somewhat smaller than
 the diameter 122 of the mounting depression 120. This is because the
 central axis of the screw and male lock fittings must be outside of the
 insertion plane defined by the head 27 and shaft 29 for proper functioning
 of the device. Accordingly, the shaft is preferably located eccentrically
 relative to the central axis 18. However, when the head is inserted into
 the slot opening 12, the shaft must be positioned at the midpoint of the
 slot, which is also the center of the depression. This means that the body
 cannot be centered relative to the depression during mounting. At the same
 time, the mounting end 20 must be positioned very close to the outer
 chassis wall 74 to allow the head to be inserted in the slot opening.
 Unless the mounting end width is somewhat smaller than the diameter of the
 depression, part of the mounting end will contact a lip 124 of the
 depression during mounting, and proper mounting will be prevented.
 Accordingly, the device is preferably designed so that a maximum clearance
 distance 126 between the head shaft 29 and an outer edge 128 of the
 mounting end 20 is less than or equal to one-half of the mounting
 depression diameter 122, i.e. about 13 mm in the case of a standard
 computer mounting depression.
 In yet another embodiment of the invention, a security device and method
 for using the device is provided for use with portable equipment which
 does not have a pre-fabricated security slot opening 12 in the chassis 14.
 The device includes any of the embodiments of the invention described
 above, in combination with a slot opening adapter plate 130, shown in FIG.
 8. The adaptor plate features a raised portion 132 having a slot opening
 12' for receiving the slot-mating head 27. The adaptor plate is secured to
 the chassis 14 of a portable equipment unit by peeling back an adhesive
 protective sheet 134 to expose an adhesive backing 136 on the plate, and
 affixing the adhesive backing to the chassis. The raised portion of the
 slot adaptor must provide a depression 138 beneath and surrounding an
 inner wall 140 of the raised portion to provide sufficient clearance for
 the head, i.e. the depression must be at least as deep as a height
 dimension 142 of the head.
 The body 16 and other parts of the security device 1010', 10'", 10"" can be
 constructed from any material having suitable hardness to resist breakage
 or cutting, such as steel, aluminum, other metals or hardened plastics.
 Similarly, the body and other parts of the invention can be manufactured
 by any of a variety of production process, such as casting, milling or
 molding.
 In view of the above, the invention is not to be limited to the above
 description but should be determined in scope by the claims which follow.