Automobile anti-theft device

An anti-theft device surrounds the plastic housing for the ignition switch, the protruding plastic lock barrel and the exposed end of the lock cylinder with hardened steel. The device consists of (i) a hardened steel bracket which attaches directly to the housing and the steering column with screws, (ii) a cup-like cover which attaches to the bracket, covering the housing, the screws and the protruding lock barrel with hardened steel, and (iii) a torque-sensitive end cap which is rotateably supported by the cover. The torque-sensitive cap consists of an outer sleeve and a center disk press fit into the sleeve. The disk includes a key slot for access to the lock cylinder. The disk is the same size as an opening in the cover, which accommodates key access to the lock cylinder. The sleeve is rigid and larger in diameter than the opening. An indentation in the cap sleeve engages a boss on the lock cylinder to align the slot in the disk with the lock cylinder keyhole and operate the lock. If a thief attempts to insert a screwdriver through the slot to rotate the cap and force the rotation of the lock cylinder, the disk alone rotates without operating the lock cylinder.

FIELD OF INVENTION 
The invention relates generally to automobile anti-theft devices and more 
particularly to an anti-theft device for preventing unauthorized access to 
an automobile ignition switch. 
BACKGROUND 
One manufacturer has redesigned an automobile ignition switch mechanism and 
enclosed it and the ignition lock in a plastic housing. The housing 
includes a protruding lock barrel which surrounds the ignition lock 
cylinder. An opening in the housing, at one end of the lock barrel, 
exposes the keyhole end of the lock cylinder. A driver inserts a key into 
the keyhole to unlock the ignition lock and operate the ignition switch. 
A thief must enter the housing to gain access to the switch. Unfortunately, 
the plastic housing is not tamper-proof and a thief can gain access to the 
ignition switch either by forceably removing the lock cylinder from the 
housing through the opening and thereby freeing the switch, or by 
inserting a screwdriver into the exposed keyhole and forceably rotating 
the cylinder to unlock and operate the switch. 
Various devices have been designed to prevent unauthorized access to the 
lock cylinder. One such device is described in U.S. Pat. No. 5,063,765 to 
Squire et al. It comprises a lock barrel protector, having an end cap 
which fits over the otherwise exposed keyhole end of the cylinder and 
provides a guarded passageway for the ignition key. A "retaining means," 
such as a set screw, holds the protector in place. The device slides over 
and attaches to the lock barrel which surrounds the lock cylinder, with 
the set screw embedded in the lock barrel to prevent removal of the 
device. 
The Squire et al. device works well with locks having metallic barrels. It 
does not work well with locks which have plastic barrels, such as the 
locks described above. To defeat this lock protection device, a thief can 
puncture the plastic barrel to disable or detach the set screw, and remove 
the device. The thief then has direct access to the lock cylinder and, 
ultimately, to the ignition switch. 
SUMMARY OF THE INVENTION 
The invention is an anti-theft device which surrounds the plastic housing 
for the ignition switch, the protruding plastic lock barrel and the 
exposed end of the lock cylinder with hardened steel, rendering the 
housing and lock virtually inaccessible except to the ignition key. This 
anti-theft device consists of (i) a bracket which attaches directly to the 
housing and the steering column with screws, (ii) a cup-like cover which 
attaches to the bracket, covering the housing, the screws which attach the 
bracket and the housing to the steering column and the protruding lock 
barrel with hardened steel, and (iii) a novel torque-sensitive end cap 
which is rotateably supported by the cover and which shields the otherwise 
exposed end of the lock cylinder. To gain access to the ignition switch 
without the ignition key, a thief must detach the cover from the bracket, 
while the cover is in place on the steering column. If break-away, or 
one-way, screws are used to secure the cover to the bracket, access to the 
ignition switch cannot be gained without drilling out the screws. The 
removal of the device thus takes too much time and effort to interest a 
thief. 
The torque-sensitive cap, which can be manufactured relatively easily and 
inexpensively, consists of a center disk, which includes a key-sized slot, 
and an outer sleeve. The center disk is press fit into the sleeve to form 
the cap. The disk is the same size as an opening in the cover, which 
accommodates key access to the lock cylinder. The sleeve is larger in 
diameter than the opening and rigid, and thus, the cap cannot be re-shaped 
and forceably pulled through the opening when the cover is in place on the 
housing. 
An indentation in the cap sleeve engages a boss on the lock cylinder to 
align the slot in the disk with the lock cylinder keyhole. The aligned 
slot thus forms a passageway to accommodate the ignition key. The cap and 
the lock cylinder then operate together, to unlock the lock and operate 
the ignition switch, when a torque is applied to the key and/or a 
protective bezel attached to the cap. 
The disk is relatively thick, and thus, the end of the slot into which a 
key is inserted is separated from the lock cylinder. The slot in the cap 
is no wider than necessary to accommodate the ignition key. Accordingly, a 
conventional screw driver inserted into the slot may not extend far enough 
through the slot to reach the lock cylinder. An instrument which is more 
slender than a screwdriver may reach the lock cylinder, however, this 
instrument will break rather than overpower the lock cylinder. 
If a thief attempts to insert a screwdriver through the slot to rotate the 
cap and force the rotation of the lock cylinder, the disk alone rotates 
without operating the lock cylinder. The thief is thus prevented from 
unlocking the ignition switch.

DETAILED DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS 
FIG. 1 depicts a steering column 10 which supports a steering wheel 12. The 
column 10 supports a plastic housing 14 (depicted by dotted lines) which 
encloses an ignition switch and an ignition switch lock. The housing 
includes a protruding plastic lock barrel 16, which surrounds a lock 
cylinder and leaves the keyhole end of the cylinder exposed and accessible 
to the ignition key. A bezel 18, with a passageway 20 for the ignition 
key, covers the exposed end of the lock cylinder and engages a boss 23 
(FIG. 6) on the cylinder. The bezel 18 both facilitates the unlocking of 
the ignition lock with the key and protects the key against over-rotation. 
A plastic shroud 22 with a cut-out for the protruding lock barrel covers 
the steering column 10 and the housing 14. 
A thief may gain access to the ignition switch mechanism by inserting an 
instrument such as a screwdriver into the bezel passageway 20 and down 
into the lock cylinder, and forceably rotating the cylinder to unlock the 
ignition switch. Alternatively, he may pry the lock cylinder from the 
barrel 16 and insert an instrument through the barrel and directly into 
the housing to operate the switch. 
Referring to FIG. 2, to prevent unauthorized access to the ignition switch 
mechanism, a hardened steel anti-theft device 30 attaches to and shields 
the housing 14 and the lock barrel 16. The anti-theft device 30 includes a 
cup-like cover 34, which fits over the housing 14 and the lock barrel 16, 
and brackets 32-33 which secure the cover 34 to the housing 14. The cover 
34 includes an opening 35 for insertion of the ignition key into the lock 
cylinder 21. 
A torque-limiting cap 50 with a slot 54 for the ignition key (shown in more 
detail in FIGS. 3 and 4) fills the opening 35, providing a guarded 
passageway for the ignition key and preventing other instruments from 
gaining access to the lock cylinder 21. A bezel 36 which includes a key 
passageway 38, attaches to the cap with screws 37. The key passageway 38 
in the bezel 36 aligns with the slot 54 in the end cap 50 to extend the 
key passage way to the lock cylinder. This passageway accommodates the 
ignition key, but is too narrow to permit the full insertion of a 
conventional screwdriver. 
The brackets 32-33 attach directly to the housing 14 with screws 35, which 
are inserted through mounting holes 37 in the housing and are threaded 
into the steering column. The cup-like cover 34 then attaches to the 
brackets with break-away, or one-way, screws which are inserted through 
clearance holes 40 and threaded into holes 42 in the brackets. When the 
cover 34 is attached to the brackets, it prevents access to the screws 35, 
which prevents removal of the brackets from the steering column 10 (FIG. 
1). 
The anti-theft device 30 may also include a translucent ring 44, for 
illuminating of the key passageway 38. This ring is lit by a light bulb 
(not shown), which is powered through the steering column and inserted 
behind the ring. The ring 44 corresponds to a ring provided by the 
automobile manufacturer and may be included as part of the anti-theft 
device to match the appearance of exposed portion of the device to that of 
the original lock mechanism. 
The underside of the cover 34 is depicted in FIG. 3. One end of the section 
34b of the cover which shields the lock barrel 16 (FIG. 2) is permanently 
attached, shown here as welded, to the underside of the top section 34a of 
the cover. The end cap 50 fits into the opening 35 at the opposite end of 
the section 34b, and the bezel 36 (FIG. 2) is attached to the side of the 
cap which is hidden from view with screws 37. 
The cap 50, which is depicted in more detail in FIG. 4, includes a disk 52 
with a key slot 54 and a larger diameter sleeve 56. The disk 52 is press 
fit into the sleeve 56 such that a portion of the disk extends out, past 
the end of the sleeve. The disk 52 is sized to fit the opening 35 (FIG. 
4), while the sleeve 56, with its larger diameter, prevents the cap from 
being forced through the opening 35. The disk 52 and the sleeve 56 are 
both rigid, so that a thief can not forceably deform either of them in an 
attempt to fit the cap through the opening 35. 
The sleeve 56 includes an indentation 58, which mates with the boss 23 on 
the lock cylinder 21 (FIG. 2) to align the key slot 54 and the keyhole in 
the lock cylinder 21 to accommodate the ignition key. The cap 50 and the 
lock cylinder then operate together. 
As discussed above with reference to FIG. 2, the slot 54 is narrow such 
that while it accommodates the ignition key, it does not fully accommodate 
instruments such as screwdrivers. Further, since the disk is relatively 
thick, the slot is deep and the accessible end of the slot is separated 
from the lock cylinder keyhole. Accordingly, the tip of a conventional 
screwdriver inserted into slot does not reach the lock cylinder keyhole. 
If a thief inserts the tip of a screwdriver into the slot 54 and attempts 
to force the rotation of cap 50, and thus, the lock cylinder 21 (FIG. 2), 
by applying a sufficiently large torque, the disk 52 turns within the 
sleeve 56, without turning the lock cylinder. If a thief inserts an 
instrument which is more slender than the screwdriver into the slot the 
instrument reaches the lock cylinder, however, the instrument is so 
slender it will break rather than overpower the lock cylinder, when a 
large torque is applied. 
FIG. 5 depicts the ant-theft device 30 with an alternative cap 51. The cap 
51 is similar in shape to the cap 50 depicted in FIGS. 2 and 4, except 
that it includes two indentations 60 and 62, which are shaped and 
positioned to engage two flanges (not shown) which are part of an 
alternative lock cylinder design. The cap 51 includes the same disk 52, 
which rotates inside the sleeve 56 a torque sufficiently larger than that 
required to operate the lock with the key is applied to the cap 51. 
Referring to FIGS. 2 and 6, to install the anti-theft device 30, a user 
removes the housing 14 from steering column 10 (FIG. 1) and attaches the 
brackets 32 and 33 to the housing with screws 35. The screws 35 feed 
through the clearance holes 46 in the brackets, the mounting holes 37 in 
the housing and into threaded mounting holes (not shown) in the steering 
column. The user then slides the cover 34 over the housing 14, such that 
the screws 35, the top and sides of the housing 14 and the length of the 
lock barrel 16 are thus covered with hardened steel. The cap 50 and bezel 
36 which are supported by the cover 34 fit over separated from the lock 
cylinder keyhole. Accordingly, the tip of a conventional screwdriver 
inserted into slot does not reach the lock cylinder keyhole. If a thief 
inserts the tip of a screwdriver into the slot 54 and attempts to force 
the rotation of cap 50, and thus, the lock cylinder 21 (FIG. 2), by 
applying a sufficiently large torque, the disk 52 turns within the sleeve 
56, without turning the lock cylinder. If a thief inserts an instrument 
which is more slender than the screwdriver into the slot the instrument 
reaches the lock cylinder, however, the instrument is so slender it will 
break rather than overpower the lock cylinder, when a large torque is 
applied. 
FIG. 5 depicts the ant-theft device 30 with an alternative cap 51. The cap 
51 is similar in shape to the cap 50 depicted in FIGS. 2 and 4, except 
that it includes two indentations 60 and 62, which are shaped and 
positioned to engage two flanges (not shown) which are part of an 
alternative lock cylinder design. The cap 51 includes the same disk 52, 
which rotates inside the sleeve 56 a torque sufficiently larger than that 
required to operate the lock with the key is applied to the cap 51. 
Referring to FIGS. 2 and 6, to install the anti-theft device 30, a user 
removes the housing 14 from steering column 10 (FIG. 1) and attaches the 
brackets 32 and 33 to the housing with screws 35. The screws 35 feed 
through the clearance holes 46 in the brackets, the mounting holes 37 in 
the housing and into threaded mounting holes (not shown) in the steering 
column. The user then slides the cover 34 over the housing 14, such that 
the screws 35, the top and sides of the housing 14 and the length of the 
lock barrel 16 are thus covered with hardened steel. The cap 50 and bezel 
36 which are supported by the cover 34 fit over the end of the lock 
cylinder 21 to provide a secured passageway for the ignition key. 
Clearance holes 40 in the cover align with threaded holes 42 in brackets 32 
and 33. Break-away screws 39 are inserted through the holes 40 and 
tightened into the holes 42 until the heads 39a of the screws twist off 
the bodies 39b. Flanges on the screw bodies 39b are larger than the holes 
40. These flanges ensure that the cover 34 is held in place by the screws 
39. These headless screws can not be extracted from the holes 40, without 
drilling. 
When the shroud 22 is reassembled around the steering column, covering the 
anti-theft device, the column resembles the steering column 10 of FIG. 1, 
with the exception of the differences in appearance between the bezel 18 
and the bezel 36. 
The anti-theft device 30, with an included torque-sensitive cap 50 or 51, 
renders the ignition switch inaccessible to all but the ignition key. 
Known devices which include different end caps are not as successful in 
rendering the lock cylinder inaccessible, because the end caps can be 
forceably removed. 
The foregoing description has been limited to two specific embodiments of 
this invention. It will be apparent, however, that variations and 
modifications may be made to the invention, with the attainment of some or 
all of its advantages. Therefore, it is the object of the appended claims 
to cover all such variations and modifications as come within the true 
spirit and scope of the invention.