Sidebar ignition lock

A sidebar ignition lock is provided with improved anti-tampering features. The ignition lock includes a cylinder extending along a longitudinal axis and rotatably supported within a sleeve. The tumblers are maintained entirely within the diameter of the cylinder to prevent possible picking of the lock. A knob is provided to prevent access to the area between the outer surface of the cylinder and the inner surface of the sleeve. When the cylinder is received within the sleeve, the knob is maintained on the cylinder head by a retaining member extending from the sleeve. The sidebar ignition lock further includes a roller ball detent to prevent over rotation of the cylinder with respect to the sleeve.

BACKGROUND OF THE INVENTION 
This invention relates to a mechanical lock, and in particular, to a 
sidebar ignition lock for a motor vehicle. 
A mechanical key lock includes a cylinder rotatably supported within a 
sleeve. When the mated key is inserted in the cylinder, the key and the 
cylinder may be rotated within the sleeve. 
In order to prevent rotation of the cylinder without a mated key, a sidebar 
is utilized. The sidebar is placed within a slot in the cylinder and 
aligned with a groove in the sleeve. The sidebar is biased away from the 
sleeve toward the interior of the cylinder by a spring. When the mated key 
is not present in the cylinder, tumblers, supported within the cylinder, 
maintain a portion of the sidebar within the groove in the sleeve. This, 
in turn, prevents the cylinder from being rotated relative to the sleeve. 
Each tumbler includes a notched portion such that when the mated key is 
inserted in the cylinder, the notch in each tumbler is aligned with the 
sidebar. As a result, the biased sidebar is urged toward the notches in 
the tumblers by action of the springs. If the tumblers have been properly 
set by the mated key, the sidebar will enter the notches in the tumblers, 
and exit the groove in the sleeve. As a result, the cylinder is free to be 
rotated within the sleeve. 
In an ignition lock, when a mated key inserted in the cylinder, the 
cylinder is free to rotate within the sleeve from a locked position to an 
unlocked or fully rotated position. A stop may be provided to prevent over 
rotation of the cylinder within the sleeve. Over rotation of the cylinder 
may result in damage to the column or other components of the motor 
vehicle. 
Further, over the last several years, it is become increasingly desirable 
to improve the anti-tampering features of lock and key sets. This is 
particularly true with respect to automobile ignition systems where auto 
theft has almost developed into an art form. Typically, the key and 
cylinder lock for engaging and energizing the ignition system is either 
bypassed or pulled out from the sleeve in order to facilitate theft. 
Therefore, it is a primary object and feature of the present invention to 
provide a sidebar ignition lock for a motor vehicle which incorporates 
features to prevent theft of the motor vehicle. 
It is a further object and feature of the present to provide a sidebar 
ignition lock wherein the cylinder is prevented from over rotating in the 
sleeve. 
SUMMARY OF THE PRESENT INVENTION 
In accordance with the present invention, a sidebar ignition lock is 
provided. The ignition lock includes a cylinder rotatably receivable 
within a sleeve. The cylinder defines an external cylinder surface, a 
longitudinal axis and a key way disposed along the axis for slidably 
receiving a key therein. The cylinder further includes a sidebar slot 
extending radially with respect to the axis, a detent slot extending 
radially with respect to the axis, and a tumbler ward extending radially 
from the axis at a location angularly spaced from the sidebar slot. The 
sidebar slot has an opened inner end which opens into the tumbler ward, 
and an opened outer end which opens to the external cylindrical surface. 
A sidebar is slidably mounted within the sidebar slot for radial movement 
therein. The sidebar includes a tongue at its inner end and a radially 
outer end. The sidebar is movable between a first cylinder locking 
position wherein the outer end of the sidebar projects from the cylinder, 
and the second cylinder unlocking position wherein the outer end of the 
sidebar is retracted within the cylinder. Means are provided for biasing 
the sidebar radially inward toward the unlocking position. 
A tumbler is disposed in the tumbler ward for sliding movement radially 
with respect to the axis between a non-aligned position with the sidebar 
whereby the tumbler holds the sidebar in its cylinder locking position, 
and an aligned position with the sidebar whereby the sidebar is permitted 
to move to its cylinder unlocking position. The entire tumbler is 
retracted within the tumbler ward in the cylinder when the tumbler in its 
non-aligned position and when the tumbler is in its aligned position. 
A roller ball detent is rotatably mounted within the detent slot for radial 
movement therein. The roller ball detent is movable between a first 
position wherein in a portion of the roller ball detent projects from the 
outer surface of the cylinder, and a second position wherein the roller 
ball detent is retracted within the detent slot. 
A knob is provided having a plurality of tangs projecting therefrom. The 
tangs define a cylinder head receipt cavity for receiving a portion of the 
cylinder therein. The tangs are movable between a first locking position 
wherein a portion of the cylinder may not be removed from the cavity, and 
a second unlocking position wherein the portion of the cylinder may be 
removed from the cavity. 
Finally, a retaining member is provided. The retaining member extends from 
the sleeve and maintains the tangs in the locking position when the 
cylinder is received within the sleeve.

BRIEF DESCRIPTION OF THE PREFERRED EMBODIMENT 
Referring to FIG. 1, the sidebar ignition lock of the present invention is 
generally designated by the reference numeral 10. The ignition lock 10 
includes a cylinder 12 extending along a longitudinal axis 13, and which 
is rotatably supported within a sleeve 14. 
Cylinder 12 is in the form of a cylindrical, substantially hollow housing, 
which defines a central longitudinal axis 13 about which cylinder 10 is 
rotated. Cylinder 12 includes a center key way 15 disposed along axis 13 
for receiving a key (not shown) in the conventional manner to permit 
rotation of cylinder 12. As is conventional, key way 15 opens at its front 
end to the front face of cylinder 12 is blind or closed at the opposite 
end of cylinder 12. 
Cylinder 12 is rotatable in sleeve 14 between a first locked position and a 
second fully rotated position. A mated key is used in normal circumstances 
for unlocking the sidebar ignition lock 10 so as to allow cylinder 12 to 
rotate within sleeve 14. When a mated key is not present in the cylinder 
12, cylinder 12 cannot be rotated. However, when a mated key is inserted 
in the cylinder 12, the key and the cylinder 12 may be rotated from the 
locked position to the start position so as to start the motor vehicle in 
the known manner. 
In order to prevent rotation of the cylinder 12 without a mated key, a 
sidebar 16, FIG. 5, is utilized. The sidebar 16 is placed within a slot 18 
in cylinder 12 and aligned with groove 20 in the sleeve 14. The sidebar is 
biased away from the sleeve 14 toward the interior of the cylinder 12 by a 
pair of springs 15 (one shown in phantom). 
A plurality of tumblers 22 are slidably mounted within a corresponding 
number of tumblers slots or wards 25 contained within cylinder 12. Each 
ward 25, and therefore tumblers 22, are oriented transversely in a plane 
passing perpendicularly through axis 13. Each ward 25 extends 90.degree. 
with respect to slot 18, and as is conventional, each tumbler is slidably 
mounted to engage sidebar 16. As best shown in FIG. 5, a ward or slot 25 
is defined by opposing walls 27 and 29 in cylinder 12 which guide tumbler 
22 and its sliding movement. 
When a mated key is not present in the cylinder 12, tumbler engaging 
surface 23 on the tongue of sidebar 16 engages the outer surface 24 of 
tumbler 22 such that a portion of sidebar 16 is positioned within groove 
20 and sleeve 14. Hence, sidebar 16 will engage the sidewalls 21 of groove 
20 if a user attempts to rotate cylinder 12 without a mated key. 
Each tumbler 22 also includes a corresponding spring 31 extending between a 
seat 33 formed in the interior side portion of cylinder 12 in wall 29 and 
a boss 19 projecting from tumbler 22. Thus, spring 31 urges tumbler 22 in 
a radial direction from axis 13 and thus, biases tumbler 22. It is 
important to note that the normal spring force of springs 31 acting on 
tumbler 22 is greater than the normal spring force of the sidebar springs 
acting on sidebar 16. This permits tumblers 22 to slide with respect to 
sidebar 16 even though the tumbler engaging surface 23 of sidebar 16 
engages notch 27 of tumblers 22. 
As best seen in FIG. 5, in accordance with the present invention, each 
tumbler 22 is maintained entirely within the diameter of cylinder 12. 
Since no portion of each tumbler 22 extends beyond the outer surface 33 of 
cylinder 12 when a mated key is not present in the cylinder 12, the lock 
10 becomes more difficult to pick. As herein after described, cylinder 12 
is allowed to rotate within sleeve 14 when notches 27 in each tumbler 22 
are in alignment. It has been found that if tumbler 22 extends beyond the 
outer surface 26 of cylinder 12, it is easier for the thief to insert a 
tool between cylinder 12 and sleeve 14 so as to align the tumblers and 
unlock lock 10 without a mated key. 
As previously described, each tumbler 22 includes a notch 27 where the 
tumbler diameter is reduced. When the mated key is inserted into cylinder 
12, the notches 27 in each tumbler 22 aligned with tumbler engaging 
surface 23 of sidebar 16. As previously described, sidebar 16 is urged 
toward the interior of cylinder 12 such that when a mated key is inserted 
in cylinder 12, a portion of tumbler engaging surface 23 will enter 
notches 27. Consequently, sidebar 16 will exit groove 20 so as to allow 
cylinder 12 to rotate freely with respect to sleeve 14. 
Referring to FIGS. 2-3, and 6, in order to further deter theft of the motor 
vehicle, sidebar ignition lock 10 incorporates an anti-tampering knob 28. 
Knob 28 includes a plurality of resilient tangs 30 which extend from knob 
28 toward sleeve 14 when mechanical lock 10 is assembled. Each tang 30 
includes a rib portion 32 directed toward longitudinal axis 13. 
Knob 28 is mounted to cylinder 12 by press-fitting knob 30 over cylinder 
head 34 such that tangs 30 are urged radially outward. Cylinder head 34 is 
positioned in cavity 35 defined by tangs 30 such that ribs 32 fit over 
shoulder 36 of cylinder head 34. As resilient tangs 30 return to their 
original position, cylinder head 34 is prevented from being removed from 
knob 28 without urging tangs 30 radially outward again. 
In order to defeat a motor vehicle lock, automobile thieves are known to 
grab the head of the cylinder 12 of the lock and forcibly rotate the 
cylinder to its start position so as to actuate the ignition switch. As a 
prerequisite to grabbing cylinder head 34, the automobile thief must 
remove knob 28. To combat a thief, sleeve 14 includes a plurality of 
retaining members 38 which act to prevent the urging of tangs 30 radially 
outward when cylinder 12 is rotatably supported in sleeve 14. The 
retaining members 38 prevent the outward radial movement of tangs 30 such 
that rib portion 32 cannot pass over the diameter of cylinder head 34. As 
a result, knob 28 cannot be removed from ignition lock 10 without breaking 
knob 28 into pieces. The delay in requiring the automobile thief to break 
off knob 28 from cylinder 12 increases the amount of time it takes to 
steal the motor vehicle. In many cases, this delay may be sufficient to 
foil a theft attempt. 
Further, in order to defeat a motor vehicle ignition lock, automobile 
thieves are known to attempt to manipulate each tumbler 22 in cylinder 12 
so as to align notches 27 with tumbler engaging surface 23 of sidebar 16. 
As previously described, when notches 27 are aligned, sidebar 16 may exit 
groove 20 so as to allow cylinder 12 to rotate freely with respect to 
sleeve 14. Knob 28 in conjunction with step 37, FIG. 2, along inner 
surface 46 of sleeve 14 prevent the automobile thief from gaining access 
to the tumblers through the area between the cylinder 12 and sleeve 14 by 
blocking access to the area. As previously explained, knob 28 cannot be 
removed from cylinder head 34 without breaking knob 28. As previously 
described, the delay caused by requiring the automobile thief to break off 
knob 28 from cylinder 12 and manipulate a tool past step 37 in sleeve 14 
may be sufficient to foil a theft attempt. 
In order to prevent rotation of cylinder 12 beyond the fully rotated 
position, a detent mechanism is provided in cylinder 12 by forming a 
radially extending slot or bore 40 for receiving a spring 42 and a ball 
44. Spring 42 urges ball 44 toward the interior surface 46 of sleeve 14. 
The interior surface 46 of sleeve 14 is provided with a groove 48. Groove 
48 includes a first end 50 having a notch 52 therein, and a second end 54 
also having a notch 56 therein. 
Referring to FIG. 4b, notch 52 corresponds to the locked position of 
cylinder 12. When cylinder 12 is rotated to the locked position, a portion 
of ball 44 is received within notch 52 in groove 48. Notch 52 gives the 
user notice, by feel, of when the ignition lock 10 is in the locked 
position. In addition, ball 44 in notch 52 prevents undesired 
counterclockwise rotation of cylinder 12 from the locked position to the 
accessory position, as is conventional. If the user attempts to rotate 
cylinder 12 counterclockwise from the locked position, the portion of ball 
44 in notch 52 will engage contact 53 of notch 52 thereby hindering, but 
not preventing, further rotation of cylinder 12. 
Referring to FIG. 4a, when a user inserts a mated key in the cylinder and 
turns the cylinder 12 and key clockwise, ball 44 rotates along sidewall 55 
of groove 48 until cylinder 12 reaches the fully rotated position for the 
ignition switch. The fully rotated position for the ignition lock 10 
corresponds to notch 56 on the second end 54 of groove 48. When a portion 
of ball 44 enters into notch 56, cylinder 12 may no longer be rotated 
clockwise because any attempt to turn cylinder 12 clockwise results in the 
portion of ball 44 in notch 56 abutting against shoulder 58 along the 
inner surface 46 of sleeve 14. This prevents the user from over rotating 
the cylinder 12 which may, as previously described, cause damage to the 
motor vehicle. 
In order to remove cylinder 12 from sleeve 14, the mated key and cylinder 
12 must be rotated from the locked position to the fully rotated position 
such that a portion of ball 44 is partially received within notch 56 in 
sleeve 14. An aperture 60 is provided in the side wall of sleeve 14 so as 
to allow access to the interior of sleeve 14. In order to remove cylinder 
12 from sleeve 14, a user may insert a tool such as a pin or the like into 
aperture 60 so as to urge ball 44 against the compression of spring 42 
into bore 40 such that no portion of ball 44 extends into notch 56 in 
sleeve 14. Ball 44 will no longer abut notch 56 in sleeve 14 when the user 
attempts to slide cylinder 12 longitudinally out of the sleeve 14. 
Various modes of carrying out the invention are contemplated as being 
within the scope of the following claims, particularly pointing out and 
distinctly claiming the subject matter which is regarded as the invention.