Modified fifth wheel trailer hitch and trailer tongue construction

A fifth wheel trailer hitch assembly mounted under and attached to a vehicle frame comprising a cradle and king pin adaptor. The trailer hitch assembly attaches to the trailer with the goose-necked trailer tongue king pin adaptors. The king pin of such assembly engages a fifth wheel trailer hitch mounted in the cradle mounted under the towing vehicle. The trailer tongue king pin adaptor may also be hinged to facilitate storage of the adaptor when the trailer is parked.

FIELD OF THE INVENTION 
The invention relates to a fifth wheel trailer hitch assembly. More 
particularly, the invention relates to a fifth wheel trailer hitch 
assembly that is mounted under and attached to the frame of the towing 
vehicle. The trailer hitch assembly couples to the trailer with the 
invention's goose-necked trailer tongue assembly's king pin. 
BACKGROUND OF THE INVENTION 
The utilization of a fifth wheel trailer hitch for pulling various towed 
vehicles, especially recreational trailers, has been suggested in the 
past. This method has been used on a variety of towing vehicles and is 
commonly attached to a pick-up truck inside the bed of such vehicle, as 
disclosed in the U.S. Pat. No. 4,960,288. The major disadvantage of such a 
method of trailer coupling is that the bed of the pick-up truck cannot be 
used to its fullest capacity because of the fifth wheel assembly and the 
space needed to allow the trailer free pivot clearances. Another 
disadvantage of such prior methodology is that the trailer hitch and 
trailer tongue must be raised a sufficient distance to couple with the 
fifth wheel assembly in the truck bed. Such raising usually requires a 
jack or lift of some kind. 
A fifth wheel trailer hitch has also been mounted on the bed of a pick-up 
truck or on such truck's bumper as shown in U.S. Pat. No. 3,941,407. Other 
fifth wheel trailer hitch assemblies use a separate dolly between the 
towing vehicle and the towed vehicle as shown in U.S. Pat. No. 3,865,405 
and 3,829,129. The disadvantages of such arrangements are the trailer 
balance points are harder to equalize, many parts in the assemblies, 
turning radii are reduced, and multiple-pivot points in the towing axis. 
SUMMARY OF THE INVENTION 
The general object of the present invention is to maximize the use of the 
pick-up truck bed while providing the benefits of a fifth wheel trailer 
hitch. 
A cradle constructed of suitable material, such as angle or channel iron, 
is mounted to the frame of the towing vehicle, typically a pick-up truck 
but can also be a van or recreational vehicle. The cradle is mounted as 
close to the drive train differential as possible. The cradle is 
adjustable as to width between the vehicle frame as well adjustable as to 
height above the travel surface. 
The cradle engages and supports a typical fifth wheel trailer hitch of the 
type that engages a king pin. The principle benefit of this type of 
trailer hitch is the safety inherent in the method. 
One important aspect of the invention is that the truck bed of the usual 
towing vehicle is entirely open to use and not involved with the trailer 
hitch assembly. 
Another important aspect of the invention is that in usual operation only 
one person is needed to couple and uncouple the trailer hitch. 
Another aspect of the invention is that a low center of gravity is 
established with the cradle and king pin assembly being mounted and 
engaged under the towing vehicle frame. 
Another aspect of the invention is that sway of the towed vehicle is 
greatly minimized by the king pin hitch assembly and yet allows a full 90 
degree turning radius left or right in either the forward or backward 
direction. 
Another aspect of the invention is that it can be used with existing 
straight or A-frame trailer tongues or can be built with the trailer 
during initial manufacturing. 
Another aspect of the invention is that it can be attached to the towing 
and towed vehicles in such a manner as to allow complete removal of the 
cradle and king pin adaptor. 
Another aspect of the invention is that the king pin adaptor assembly may 
be hinged in front of the trailer ball attachment to allow a retracted 
position of the king pin extension portion of the hitch rails when the 
towed vehicle is in a parked condition and an extended position when the 
towed vehicle is being towed. In either position the hinge assembly 
provides a locking means to lock the king pin extension portion in the 
desired position. 
These and other features, aspects, advantages and objects of the invention 
will become apparent to those of ordinary skill in the art upon review of 
the following description reference being made to the appended drawings.

Before explaining at least two embodiments of the invention in detail it is 
to be understood that the invention is not limited in its application to 
the details of construction and arrangement of the components set forth in 
the following description or illustrated in the drawings. The invention is 
capable of other embodiments or being practiced or carried out in various 
ways. Also it is to be understood that the phraseology and terminology 
employed herein is for the purpose of description and should not be 
regarded as limiting. 
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT OF THE INVENTION 
Shown in the various figures is a fifth wheel trailer hitch with the fifth 
wheel being mounted in a cradle attached to the frame of a towing vehicle 
and engaged by a King pin mounted on a King pin adaptor assembly attached 
to the tongue of a towed vehicle. 
CRADLE ASSEMBLY 
As can be seen in FIGS. 1, 2, and 3, the fifth wheel trailer hitch cradle 
includes a left (1) and right (2) top channel irons in spaced apart 
relationship, each providing a plurality of mounting holes (11). Said 
channel irons are mounted to a vehicle frame (15) by means well known in 
the art such as welding. The preferred method of mounting is to attach the 
top channel irons to the vehicle frame with mounting bolts through the 
mounting holes provided in the top channel irons. Such method of mounting 
facilitates later removal of the cradle assembly at such time as the 
towing vehicle is to be disposed of by the owner. The top channel iron 
members are maintained in spaced apart relationship by means of width 
adjusting plates (6) mounted to the top channel irons, said plates being 
provided with adjustment holes (10). The width adjustment plates provide 
traverse bracing between the top channel irons with the adjustment holes 
providing a means to accommodate various distances between vehicle frames 
to which the cradle may be mounted. 
Attached to each top channel iron (1) and (2) are an upper adjuster plate 
(3) and a lower adjuster plate (4), each of which is provided with a 
plurality of holes (10). The upper and lower adjusting plates provides a 
means for raising or lowering the fifth wheel coupling device (not shown). 
Attached to each lower adjusting plate, at a right angle thereto and 
parallel to the top channels, are channel irons (12) and (13) adapted to 
mount the fifth wheel trailer hitch using a pivot saddle (7), lock pin (8) 
and cotter pin (9) assembly on each such channel irons. The fifth wheel 
trailer hitch assembly and the mounting assembly are well known in the 
art. A steel plate (14) is mounted to each of the left and right side of 
the cradle at the inside adjuster plate (5) and the upper (3) and lower 
(4) adjuster plates. The cradle assembly provides and defines an opening 
(16) adapted to receive the fifth wheel trailer hitch. 
In operation the cradle assembly is mounted to a towing vehicle, preferably 
behind the rear axle of such vehicle, along and parallel to the vehicle's 
frame rails. The height of the fifth wheel trailer hitch, above the 
ground, is adjusted to provide maximum clearance under the circumstances 
of the terrain to be traveled. The fifth wheel trailer hitch is mounted in 
the cradle so as to be spaced below the towing vehicle and positioned to 
accept the king pin adaptor, yet to be described, which is attached to the 
trailer tongue of the vehicle to be towed. 
KING PIN ADAPTOR 
The king pin adaptor, as illustrated in FIGS. 4, 5, 6A and 6B, and 7, is 
attached to the trailer tongue of a vehicle to be towed. The king pin 
adaptor comprises two formed iron hitch rails (19) maintained in spaced, 
parallel relationship by the ball plate adjuster (22) and the king pin 
plate extension (18). The king pin plate extension is mounted to one end 
each of two channel extension irons (21); the other end of which is welded 
to one end of each formed iron hitch rail. The channel extension iron (21) 
and the angle iron hitch rail is joined in a goose neck configuration as 
shown in FIG. 5 and braced at said junction by a brace member (20) welded 
to each piece. A king pin (17) is mounted in the center of the king pin 
plate extension as shown in FIGS. 4, 5, and 7. 
The ball plate adjuster (22) having a plurality of mounting holes is bolted 
to the formed iron hitch rails at a location to facilitate the attachment 
of the trailer tongue of the towed vehicle. A trailer ball (23) is mounted 
on the ball plate adjuster. 
The king pin adaptor is attached to the trailer tongue of a towed vehicle 
at the ends of the two formed iron hitch rails, opposite the king pin 
plate extension, clamping the trailer tongue (27) between two end cap 
locking brackets (24) using a plurality of bolts (26) and angle brackets 
(25) if the trailer tongue is of the A-frame construction or by clamping 
the trailer tongue using an end cap locking bracket (24A) and a plurality 
of bolts (26) if the trailer tongue is of the straight tongue construction 
(28). 
In use, the king pin adaptor is attached to a trailer tongue of a vehicle 
to be towed by mounting the trailer ball locking assembly of the towed 
vehicle on the trailer ball (23) mounted on the king pin adaptor and 
clamping the king pin adaptor to the trailer tongue thereby forming a 
three-point attachment configuration. The king pin adaptor is mounted to 
the towing vehicle by engaging the fifth wheel trailer hitch mounted in 
the cradle fixed to the towing vehicle with the king pin fixed to the king 
pin adaptor thus completing the towing vehicle/towed vehicle arrangement. 
A second embodiment of the invention provides a hinge 40 and means for 
locking 41 the hinge in each of the formed iron hitch rails 21 between the 
ball plate adjustor 22 and the king pin plate extension 18. Such 
embodiment allows the king pin adaptor to be pivoted to a stowed position, 
about the hinge, and locked when the king pin adaptor is not being used, 
such as when the towed vehicle is parked. When in use, the king pin 
adaptor is locked into the extended position by the means for locking the 
hinge. 
Thus it should be apparent that there has been provided in accordance with 
the present invention a fifth wheel trailer hitch assembly comprising a 
cradle and king pin adaptor adapted for attachment to and under a towing 
vehicle which trailer hitch assembly attaches to the trailer with the 
invention's goose-necked trailer tongue king pin adaptor's king pin by 
engaging the fifth wheel trailer hitch mounted in the invention's cradle. 
Although the invention has been described in conjunction with the specific 
embodiments thereof, it is evident that many alternatives, modifications 
and variations will be apparent to those skilled in the art. Accordingly, 
it is intended to embrace all such alternatives, modifications, and 
variations that fall within the spirit and broad scope of the appended 
claims.