Barrel lock

A barrel lock has a cylindrical barrel with an axial bore. A compression spring and a center pin are coaxially mounted in the bore. A pair of locking balls mounted for limited movement in radially extending passageways are held radially outward in a locking position by the compression spring. When a key for locking and unlocking the lock is fully inserted into the lock and the key handle is operated, the compression spring is drawn rearwardly and the locking balls are permitted to move radially inward to an unlocking position.

BACKGROUND OF THE INVENTION 
Prior art barrel locks and keys are shown in U.S. Pat. Nos. 1,923,025; 
3,002,368; 3,835,674; and 4,040,279. The disclosures of these patents are 
incorporated herein by reference and made a part of the present 
disclosure. These prior art locks and keys have become increasingly less 
secure with the passage of time because of the relatively wide, albeit 
substantially controlled, distribution and use of the keys by a large 
number of people. Assignee's copending U.S. Pat. No. 4,441,343, the 
disclosure of which is incorporated herein by reference, described one 
approach to overcoming this problem. 
It is the object of this invention to provide a barrel lock which cannot be 
opened with a conventional key or with picks or nails. 
SUMMARY OF THE INVENTION 
The barrel lock of this invention is similar in many respects to the prior 
art locks. However, in the present invention, a compression spring and a 
center pin are coaxially mounted within an axial bore in the lock barrel. 
A pair of locking balls mounted for limited movement in radially extending 
passageways are held radially outward in a locking position by the 
compression spring. 
The key described herein is specifically designed to open the barrel lock 
of this invention and is similar to the prior art keys. The key is 
inserted into the lock of this invention whose locking balls are normally 
in the locking position. When the key handle is operated, the compression 
spring is retracted by the outward and rearward movement of the key's 
expanding fingers. This action permits the locking balls to move radially 
inward to their unlocking position and the unlocked lock can then be 
withdrawn entirely.

DESCRIPTION OF THE PREFERRED EMBODIMENTS 
FIG. 1 shows a barrel lock 14 of the invention in its locked condition 
wherein its two locking members 16, for example locking balls, have been 
forced radially outward so that they engage a groove in a front end cap 
18. Thus, when barrel lock 14 is in its FIGS. 1 and 2 locked condition, it 
cannot be longitudinally removed from front end cap 18. 
Barrel lock 14 can be used in many situations to lock two elements against 
various types of relative movement. Front end cap 18 illustrates but one 
locking situation of the type wherein two unshown apertured flat panels 
have the lock inserted through and both the two flat panels are prevented 
from separating by the large rear end cap 20 of the lock on one side and 
the large front end cap 18 on the other side. There are many other 
situations in which barrel lock 14 is useful. 
Barrel lock 14 has a hollow cylindrical lock barrel 22 which has a closed 
front end 24 and an open rear end 26. Rear end cap 20 is fitted over and 
fixed to open rear end 26 enlarging its effective outer diameter and 
creating an apertured rear end 28 with a selected aperture size. A 
transverse passage 30 is also provided to accommodate a conventional "tell 
tale" or lead seal used to signal tampering. 
The barrel lock barrel 22 has a stepped axially extending bore 32 including 
a front small diameter bore 34 and a rear large diameter bore 36. The 
diameters are small and large relative to each other. The front bore 34 is 
joined to the rear bore 36 by an annular shoulder 38, the surface of which 
extends at an angle to the axis of the barrel bore 32. 
The lock barrel 22 also has two radially extending passageways 40 which run 
from the exterior surface 42 of the barrel to the front bore 34 of the 
lock barrel. The locking balls 16, for example steel locking balls, are 
movably mounted in the passageways 40 and are free to move radially within 
the passageways. At the outer aperture of each passageway, a very small 
inwardly extending peripheral rim is provided which prevents the locking 
balls 16 from completely escaping outwardly. However, almost half of the 
locking ball can project outwardly from the passageway as can be seen from 
FIGS. 1 and 2. 
A compression spring 44 having a narrow forward neck portion 46 and an 
enlarged rear body portion 48, is sized, shaped and mounted to reciprocate 
within the stepped barrel bore 32. The front narrow neck portion 46 of 
compression spring 44 slidably fits within the front bore 34 of the barrel 
22, and the rear enlarged body portion 48 slidably fits within the rear 
bore 36 of the barrel 22. The rear body portion 48 has a compressible open 
coiled rear end 50 and a noncompressible close coiled central portion 52, 
the neck portion 46 being close coiled as shown at 54. 
A lock center pin 56 is sized, shaped and mounted to be able to move 
axially within the stepped barrel bore 32 and the narrow neck portion 46 
of the compression spring 44. The lock center pin 56 has an enlarged head 
58 at its front end and a rearwardly extending shaft 60 that terminates in 
a point 62 at its rear end. The outer diameter of the enlarged head 58 is 
slightly less than the inner diameter of front bore 34. The enlarged head 
58 is sized, shaped and mounted to have a sliding fit within front barrel 
bore 34. The center pin shaft 60 extends rearwardly through the narrow 
neck portion 46. The outer diameter of center pin shaft 60 is just 
slightly less than the inner diameter of narrow neck portion 46 so that 
there is a sliding fit therebetween. 
In the illustrated embodiment, a friction producing compound is placed in 
the front bore 34 of barrel 22. In the fully locked position shown in FIG. 
1, the center pin enlarged head 58 is frictionally held by the friction 
producing compound in the front bore 34. Therefore, axial movement of the 
lock center pin 56 within the bore 32 is yieldingly resisted by the 
friction producing compound. 
The friction producing compound prevents axial movement of the center pin 
56 in the barrel bore 32 under all conditions except when the axial force 
exerted on the center pin is in excess of the frictional retaining force 
provided by the friction producing compound. Excessive force on the center 
pin 56 will cause it to move axially in the plunger bore. When an 
authorized key is used to unlock the barrel lock 22, the friction 
producing compound exerts sufficient frictional retaining force to prevent 
axial movement of center pin 56 and to prevent its enlarged head 58 from 
moving across passageways 40 during authorized unlocking of the lock. When 
an unauthorized device is forced into bore 32 in an attempt to retract 
spring 44 and to unlock the barrel lock, the unauthorized device contacts 
and becomes affixed to the sharply pointed center pin 56. Then, when the 
unauthorized device retracts compression spring 44, it also retracts 
center pin 56. This causes the enlarged head 58, in its rearward position, 
to hold the locking balls 16 radially outward in passageways 40, and to 
maintain the barrel lock in its locked condition. 
As shown in FIGS. 1 and 2, the front exterior portion of neck portion 46 of 
the compression spring 44 is positioned across and closes the inner 
apertures of both locking ball passageways 40 when the lock is in its 
normally locked condition. The compression spring 44 forces both locking 
balls 16 radially outward to their locking position whenever the 
compression spring covers the locking ball passageways 40. The combined 
axial length of the uncompressed compression spring 44 and the enlarged 
head 58 is greater than the axial length of barrel bore 32 so that the 
compression spring is in a partially compressed state within barrel bore 
32. As shown in FIG. 3, when the compression spring 44 is further 
compressed by operation of a key 72, its neck portion 46 moves rearwardly 
and uncovers the passageways 40, and the locking balls move radially 
inward towards the front barrel bore 34. 
FIGS. 1-3 show the sequence of the unlocking steps produced by movement of 
the key handle 122. FIG. 1 shows the key 72 fully inserted through the 
apertured rear end 28 of the lock barrel 22. Compression spring 44, in its 
expanded position, forces the locking balls 16 radially outwardly to their 
locking position. In FIG. 1, the key handle is in its first position. 
FIG. 2 shows the key handle 122 rotated to its second position. The 
compression spring 44 has not moved at all, but the key expander 102 has 
moved rearwardly and the key fingers 80 have radially expanded to grip the 
inner surface of the central portion 52 of the compression spring 44. 
FIG. 3 shows the key handle 122 rotated to its third position. The 
compression spring 44 has now been fully compressed and fully retracted to 
its rearward position, and the lock center pin 56 remains stationary in 
its forward position because of the friction producing compound. At this 
point, the lock becomes unlocked because the compression spring front 
exterior neck portion 46 has cleared the inner apertures of passageways 40 
and the locking balls 16 are free to move inwardly in the passageways 
until they contact the shaft 60 of the lock center pin 56. The lock shown 
in FIG. 3 has been unlocked and removed from the front end cap 18. 
It will be understood from the drawings that if a prior art key or a pick 
or a nail were inserted in an improper attempt to unlock barrel lock 14 by 
compressing and retracting the compression spring 44, the lock center pin 
56 would be pulled by the unauthorized device to its rearward position 
along with the compression spring as the compression spring is retracted. 
Therefore, when the front exterior neck portion 46 cleared the inner 
apertures of passageways 40, the enlarged head 58 of the lock center pin 
56 would close the inner apertures of passageway 40 and continue to 
maintain locking balls 16 in their locking position and the barrel lock 
would remain locked. 
The above description obviously suggests many possible variations and 
modifications of this invention which would not depart from its spirit and 
scope. It should be understood, therefore, that the invention is not 
limited in its application to the details of structure specifically 
described or illustrated and that, within the scope of the appended 
claims, it may be practiced otherwise than as specifically described or 
illustrated.