King pin lock

A trailer king pin lock for preventing theft of a trailer by negating connection of a trailer king pin with a tractor fifth wheel coupling. A sleeve is provided that is receivable about the trailer king pin. A locking unit housing, which extends radially relative to the sleeve, is attached to the sleeve and carries a locking cylinder for sliding movement therein. A bore is provided in the sleeve and is enclosed by the housing. The locking cylinder passes through the bore for insertion into an annular groove typically found in a trailer king pin. A radially extending locking cylinder retaining pin is carried by the locking cylinder and is outwardly extendable upon the turning of a key inserted into the locking cylinder. The outward extension of the locking cylinder retaining pin prevents extraction of the locking cylinder from the annular groove through the bore, thereby fixing the locking cylinder within the annular groove and retaining the king pin lock on the king pin against unauthorized attempts at removal therefrom.

BACKGROUND OF THE INVENTION 
The present invention relates to a locking device for preventing 
unauthorized insertion of a trailer king pin into a tractor fifth wheel 
coupling. 
The conventional tractor-trailer hitch or coupling structure has been 
standardized so that practically any tractor can be coupled to any 
trailer. The conventional coupling structure includes a fifth wheel 
attached to the tractor and a downwardly extending king pin carried on the 
underside of the trailer, adjacent the front of the trailer. The fifth 
wheel is provided with a skid plate having an opening in which the king 
pin of the trailer is carried. The king pin has an annular groove which is 
engaged by movable jaws of the fifth wheel. The jaws on the fifth wheel 
engage the annular groove on the king pin of the trailer to pivotally 
secure the trailer to the tractor. When the king pin is locked into 
engagement with the fifth wheel, the trailer can be hauled by the tractor. 
Often, when the destination of the trailer is reached, the trailer is 
uncoupled from the tractor to await unloading of its contents, reloading, 
storage or the like. There are thus many occasions when the trailers are 
left unattended. It is thus relatively simple for thieves to merely couple 
their own tractor to any unattended trailer and haul the trailer and its 
contents away. Such hijacking of trailers occurs frequently. Various 
locking means have been devised to prevent theft of trailers. For example, 
U.S. Pat. No. 2,554,306 granted to Mack for a "Theft Prevention Device for 
Tractor Drawn Trailers" discloses a king pin cover which is held to the 
king pin by the latch arm of a locking unit. U.S. Pat. No. 2,641,124 
granted to Gallagher et al. for a "Lock for Fifth Wheel King Pins" 
discloses a king pin cover which is held to the king pin by a conventional 
padlock. U.S. Pat. No. 3,269,159 granted to Young for a "Theft Prevention 
Device for Trailers" discloses a hinged king pin cover having two ends 
which lock together. 
Prior king pin locks, including those disclosed above have several 
disadvantages. Particularly, prior lock collar designs are generally not 
strong enough to resist a heavy blow from a sledge, for example, without 
being broken and thus, rendered useless. Other designs have required 
costly parts or are expensive to manufacture. Still other collar designs 
are difficult to install and remove by the user. 
SUMMARY OF THE INVENTION 
It is an object of the present invention to provide a device for preventing 
unauthorized insertion of a shaft into a receiving coupling, more 
specificaly, the insertion of a trailer king pin into a tractor fifth 
wheel. 
Another object of the present invention is to provide a device for 
preventing unauthorized insertion of a trailer king pin into a tractor 
fifth wheel which is resistant to forceful external blows. 
Still another object of the present invention is to provide an improved 
device for preventing unauthorized insertion of a king pin into a tractor 
fifth wheel. 
Yet another object of the present invention is to provide a device for 
preventing unauthorized insertion of a trailer king pin into a tractor 
fifth wheel which is easy to install and remove by the user. 
Generally, the present invention includes a locking device receivable about 
an annularly extending groove defined in a cylindrical trailer king pin 
for preventing insertion of the trailer king pin into a tractor fifth 
wheel coupling, comprising a housing defining a king pin-receiving opening 
therethrough; and locking means associated with said housing for movement 
into and out of said king pin-receiving opening; said locking means having 
lock-retaining means associated therewith; said lock-retaining means being 
movable to a retaining position when said locking means is located within 
said king pin-receiving opening to preclude the retraction of said locking 
means therefrom; so that when said king pin-receiving opening of said 
housing is received about the trailer king pin, said lock-retaining means 
is adjacent said annularly extending groove defined in the trailer king 
pin, said locking means being movable into the annularly extending groove 
and retainable therein by said lock-retaining means. 
More specifically, the locking device of the present invention includes a 
cylindrical sleeve which is receivable about the king pin. A radially 
extending housing is located about the circumference of the sleeve at a 
location which is adjacent the annular groove of the king pin when the 
sleeve is placed thereon. A locking cylinder is received within the 
radially extending housing and is movable inwardly with respect to the 
housing for insertion into the annular groove of the king pin. When the 
locking cylinder is within the annular groove, a key received in the 
rearward end of the locking cylinder may be turned to force a locking pin 
out of the forward end of a locking cylinder into contact with the inside 
surface of the sleeve. The locking pin prevents removal of the forward end 
of the locking cylinder from the interior of the sleeve, thereby locking 
the locking cylinder within the annular groove of the king pin. A 
protective rubber casing may be provided to enclose the sleeve and the 
housing for added protection against heavy blows delivered thereto during 
an attempted theft of the trailer. 
In the preferred embodiment of the present invention, a triangular support 
web, spanning between the housing and the side wall of the sleeve, is 
provided to discourage attempts at prying the king pin lock from the king 
pin by the use of a pry bar against the housing. In another embodiment, 
the housing is in the shape of a truncated cone or frustum to also 
discourage attempts at prying the king pin lock from the king pin through 
contact of a pry bar with the locking cylinder housing. Still another 
embodiment of the present invention includes a sleeve of sufficient 
thickness such that the need for the locking cylinder housing is 
eliminated. When the locking cylinder is inserted into the annular groove 
of the king pin, the rearward end of the locking cylinder becomes flush 
with, or slightly indented relative to, the side wall of the sleeve.

DESCRIPTION OF THE INVENTION 
Referring to the drawings in detail, wherein like reference characters 
represent like elements throughout the various views, the king pin lock of 
the present invention is designated generally by the reference character 
10. King pin lock 10 includes a cylindrical sleeve 12, a cylindrical 
housing 14 radially disposed about cylindrical sleeve 12, a cylindrical 
locking cylinder or unit 16 carried for sliding movement within housing 14 
and a triangular support web 18 extending between housing 14 and the side 
wall 20 of cylindrical sleeve 12. 
FIG. 1 illustrates a preferred embodiment of the present king pin lock 10 
and is shown encompassing a stardard-sized trailer king pin 22. The inner 
diameter of cylindrical sleeve 12 is such that cylindrical sleeve 12 may 
be placed around trailer king pin 22. Cylindrical sleeve 12 is preferably 
made from a strong, damage-resistant material such as steel. A radially 
extending bore 24 is provided in side wall 20 of cylindrical sleeve 12 for 
receipt of locking unit 16. Cylindrical housing 14 encircles bore 24 and 
is attached to cylindrical sleeve 12 by suitable means such as by welding. 
Housing 14 carries locking unit 16 within for sliding movement. 
An endcap 26 is provided at the extreme end of housing 14 opposite where 
housing 14 attaches to side wall 20 of cylindrical sleeve 12. Endcap 26 
completely covers the cylindrical opening of housing 14, except for a 
small keyhole 28 through which a conventional key 30 is inserted into 
locking unit key slot 31 to actuate locking unit 16. A retaining bolt or 
screw 32 is carried by housing 14 which extends into the interior of 
housing 14 and serves to retain locking unit 16 within housing 14 through 
sliding interaction with the interior of a longitudinally extending groove 
34 provided in locking unit 16. Removal of retaining screw 32 allows 
expedient removal and replacement of locking unit 16. 
Locking unit 16 is of conventional design and is generally cylindrical in 
shape. The interaction of retaining screw 32 within longitudinally 
extending groove 34 allows locking unit 16 to be slidingly advanced within 
housing 14 to and from trailer king pin 22 when cylindrical sleeve 12 is 
placed around trailer king pin 22. The interaction of retaining screw 32 
in longitudinally extending groove 34 also prevents locking unit 16 from 
rotating within housing 14 when key 30 is turned within keyhole 28 to 
actuate a retaining pin 36 carried in locking unit 16. 
Retaining pin 36 is carried completely within locking unit 16 when locking 
unit 16 is fully retracted in housing 14. The retraction of locking unit 
16 within housing 14 allows for cylindrical sleeve 12 to be placed over 
trailer king pin 22. 
FIG. 2 illustrates locking unit 16 being in an advanced position, inserted 
into annular groove 38 of trailer king pin 22, which is supported by 
mounting plate 40 on the underside of a trailer. FIG. 3 illustrates 
locking unit 16 in a retracted position within housing 14. 
Upon placement of cylindrical sleeve 12 over trailer king pin 22, key 30 is 
used to advance locking unit 16 into a standard-sized annular groove 38 
typically found in a trailer king pin 22. Upon insertion of locking unit 
16 into annular groove 38, key 30 is turned to actuate retaining pin 36, 
causing retaining pin 36 to extend radially outward from locking unit 16. 
Key 30 is then removed from locking unit 16, thereby securing king pin 
lock 10 to the trailer king pin 22. The outward radial extension of 
retaining pin 36 from locking unit 16, caused by the turning of key 30 
within key slot 31 of locking unit 16, prevents locking unit 16 from being 
extracted through bore 24 rearwardly into housing 14. The locking unit 16 
thus prevents unauthorized removal of cylindrical sleeve 12 from trailer 
king pin 22 through the insertion thereof into annular groove 38. 
The advancement of locking unit 16 inwardly into the annular groove 38 of 
trailer king pin 22 lessens the likelihood of the locking unit 16 being 
susceptible to heavy blows delivered to cylindrical sleeve 12 in an 
unauthorized attempt to remove king pin lock 10 from trailer king pin 22. 
The maintaining of cylindrical sleeve 12 on trailer king pin 22 allows 
king pin lock 10 to provide trailer king pin 22 with an additional 
diameter dimension which creates sufficient interference between king pin 
lock 22 and a tractor fifth wheel coupling (not shown) to negate insertion 
of trailer king pin 22 into the tractor fifth wheel coupling. 
FIG. 2 illustrates the present king pin lock 10 provided with a protective 
casing 42. The casing 42 serves to dampen or absorb the forces delivered 
to king pin lock 10 by heavy external blows during an attempted theft of a 
trailer. Casing 42 can be made from rubber or another similar-type 
force-absorbent material such as plastic. 
An alternate embodiment of the present king pin lock 10 is illustrated in 
FIG. 3 where instead of providing a cylindrical exterior for housing 14, a 
housing 44 is provided having a truncated cone-shaped, or frustum-shaped, 
exterior. The frustum shape of the housing 44 deters the use of a pry bar 
against housing 44 in attempts to destroy king pin lock 10. 
FIG. 4 illustrates an alternate embodiment of the present invention, king 
pin lock 110. King pin lock 110 has a thicker cylindrical sleeve 112 than 
does king pin lock 10. Because of the thicker cylindrical sleeve 112, the 
necessity of a locking unit housing is eliminated. Locking unit 16 is 
simply advanced to and from annular groove 38 within a radially extending 
bore 124. When locking unit 16 is fully inserted in annular groove 38, the 
rear end of locking unit 16 is flush with or even slightly indented from 
side wall 120 of cylindrical sleeve 112, thereby reducing the 
susceptibility of locking unit 16 from external blows delivered to king 
pin lock 110. Instead of having a thick cylindrical sleeve 112, nesting 
concentric cylindrical sleeves (not shown) could be provided which when 
combined have approximately the same outer diameter and inner diameter as 
sleeve 112. 
A retaining bolt or screw 32 could be provided in the bore 124 of king pin 
lock 110, as is provided in housing 14 of king pin lock 10, to prevent 
locking unit 16 from rotating upon the insertion and turning of key 30 
therein. Retaining bolt or screw 32 in king pin locks 10 and 110 allows, 
upon removal, for the locking unit 16 to be removed and replaced. 
Alternate embodiment king pin lock 110 illustrated in FIG. 4 performs in 
the same manner as does king pin lock 10 to prevent unauthorized insertion 
of a trailer king pin into a fifth wheel coupling. 
While a preferred embodiment of the invention has been described using 
specific terms, such description is for illustrative purposes only, and it 
is to be understood that changes and variations may be made without 
departing from the spirit or scope of the following claims.