 |
Description  |
|
|
BACKGROUND OF THE INVENTION
The field of the invention is tractor trailer running gears and the
invention relates more specifically to trailer connecting dollies of the
type commonly used to connect a second trailer to a first tractor-drawn
trailer. This first tractor drawn trailer is commonly attached to the
tractor by a fifth wheel. It is often desirable to attach a second trailer
to the first trailer, and this is commonly accomplished by the use of a
dolly which carries a fifth wheel, and is attached to the rear of the
first trailer by an "I" bolt or pinnel hook and pin. In several states it
is now permissible for a third trailer to be attached, and this likewise
has, in the past, been connected to the second trailer through a second
dolly.
A major difficulty with the use of such dollies results from the plurality
of pivot points which exist at each fifth wheel and also at each "I" bolt
and pin. The existence of such pivot points increases the hazard of
fishtailing or jack knifing. They further essentially preclude the
accurate backing of a multiple trailer rig for any significant distance.
A detachable dolly is shown in U.S. Pat. No. 2,590,962, although a less
complex dolly is in more common use. The use of unitized shipping
containers has given rise to a detachable wheel bogey and dolly, an
example of which is shown in U.S. Pat. No. 3,066,953. When the bogey or
dolly is moved to its forward position, however, the rear of the trailer
is not properly supported. Other patents relating to tractor trailer
attachments are U.S. Pat. Nos. 2,195,636; 3,070,386 and 3,933,374.
There is thus a need for a trailer-connecting dolly which provides improved
control for the attachment of two or more trailers to a tractor. This need
is especially acute for the attachment of three trailers to a tractor.
SUMMARY OF THE INVENTION
The present invention is for an improved trailer connecting running gear
for tractor-drawn trailers, recreational vehicles and the like. The
running gear is of the type having at least two axles resiliently attached
to a frame and a fifth wheel affixed near the rearward part of the
running-gear frame. The improvement of the present invention is a trailer
gear frame attached to the under side of a trailer body which frame
extends to about the rear of the trailer body. A running gear member
including wheels is attached to the trailer gear frame in a manner to
permit the longitudinal sliding of the running gear member with respect to
the trailer gear frame. Locking means comprising a double fifth wheel hold
the member and frame together in one forward position and one rearward
position. The running gear holding means prohibits the rotational or
turning movement of the running gear with respect to the trailer gear
frame. Preferably the trailer has a pair of rails affixed along its under
surface and the running gear has a mating pair of rails which support and
slide along the tractor gear frame rails. The rails are preferably
positioned inboard of the wheels of the running gear.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a side elevation of a tractor having three trailers attached by
the use of the running gear of the present invention.
FIG. 2 is an enlarged side elevation of the trailer gear frame and running
gear of the present invention.
FIG. 3 is a cross-sectional elevation taken along line 3--3 of FIG. 2.
FIG. 4 is a perspective view of the trailer gear frame and running gear
frame of the present invention.
FIG. 5 is a cross-sectional view taken along line 5--5 of FIG. 4.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
A tractor 10 is attached to trailers 11, 12 and 13. While double tractor
trailer combinations are widely permitted, there is an increasing trend
toward the use of triple trailers, and such trailers are presently allowed
in several Western United States. With the increasing importance of energy
conservation, the continuation of this trend is anticipated.
Tractor 10 has a conventional fifth wheel 14, which is pivotally held to a
king pin 15 in a conventional manner. Likewise, the landing gear 16 of
trailer 11 is conventional.
A trailer running gear support frame 17 is permanently affixed to the
underside of trailer 11. While trailer 11 is shown as a conventional box,
the present invention is also useful for a flatbed trailer, a tanker, or
even a bottom dump trailer. A running gear of the present invention is
indicated generally by reference character 20 and has axles 21 and 22,
each of which support four wheels 23 through 30. As shown more clearly in
FIG. 2, the wheels are resiliently supported in a conventional manner by
resilient means such as leaf springs 31, and a trunion apparatus of a
relatively conventional nature is useful with the running gear of the
present invention. A fifth wheel 32 is attached to the running gear frame
33. Frame 33 is slidingly attached to trailer running gear support frame
17, which permits the running gear frame to be moved from its rearward
position as shown in FIG. 2 to its forward position as shown in phantom
lines in FIG. 2.
As shown most clearly in FIGS. 3 and 4, the running gear support frame 17
which is attached to trailer 11 is slidably affixed to running gear frame
33 by a pair of channel members 34 and 35. Similarly, a second running
gear support frame 36 is affixed to the underside of trailer 11 and is
slidably held to a second running gear frame 37 by a pair of channel
members 38 and 39. These channel members are welded or otherwise held to
the running gear frame members 33 and 37 and should be held closely enough
to permit sliding of the members, and yet not permit any appreciable
lateral movement which would allow rotation or pivoting about the vertical
axis of the running gear. In other words, the running gear of the present
invention is unlike the prior art trailer dolly which is free to turn or
pivot about its vertical axis. This feature of the present invention
enables a rig utilizing the invention to be much safer against jack
knifing and to be far more stable in hazardous situations such as curves
when a portion of the truck runs off the shoulder of a highway, or is in a
strong crosswind.
Another important feature of the firm support provided by channel members
34, 35, 38 and 39 is that the running gear is not allowed to tip with
respect to the trailer. The conventional running gear being attached by a
pin and "I" member will permit some turning movement of the dolly along
the longitudinal axis of the trailer. It is therefore more likely that the
end trailer will turn over in a hazardous situation such as running off
the shoulder of the road or a strong crosswind, or both, because the prior
art dolly does not prevent this movement. The running gear of the present
invention, however, being firmly held to the forward trailer, is capable
of preventing some turning over by virtue of the support provided by the
tractor and forward trailer or trailers.
Turning now to FIG. 4, a double fifth wheel 40 has a pair of jaws 41 and
42, and a double latch and release member 43. One of the jaws faces
forward and is connectable to a forward kingpin and the other jaw faces
rearwardly and is connectable to a rearward kingpin. Latch 43 functions as
the kingpin release member and has an arm 44 which is attached to a handle
45. Arm 44 passes through running gear frame 33 and allows the release and
attachment of the kingpins which are affixed to the underside of trailer
11.
A forward kingpin 50 is affixed to the underside of trailer 11 as shown in
FIG. 2, and a rear kingpin 51 is likewise affixed to the underside of
trailer 11. When the running gear is in its rearward position, jaws 42 of
double fifth wheel 40 are held to rear kingpin 51. When the running gear
is in its forward position, jaws 41 are held to forward kingpin 50.
It is important that the running gear support frame which is affixed to the
trailer and the running gear frame which is affixed to the running gear be
firmly and slidably attached to one another. The channel member method
shown in the drawings is one effective way of making such an attachment.
The channel members 34, 35, 38 and 39 should be long enough so that the
stress created along the two frames is spread over a wide area. It is
believed that a length of about six feet is ideal. It would, of course, be
possible to devise other support methods and a simple single extrusion
could be used to achieve the same structure as the "I" beam and channel
members shown, for instance, in FIG. 5.
In operation, the driver may move the running gear from its rearward
position as shown in FIG. 2 to its forward position in the following
manner. First, he would leave the cab, setting the brakes on all trailers.
Secondly, he would lower the landing gear on the rearward trailer and pull
the release on fifth wheel 32, unhooking the air hose and lights between
trailer 12 and the running gear 20 of the trailer 11. He would then
re-enter the cab and drive forward a distance of about 15 feet. He would
then again set the brakes on running gear 20 and pull handle 45, releasing
jaws 42 from rear kingpin 51. He would then back up until jaws 41 grasp
forward kingpin 50. The running gear would then be securely held in the
forward position as shown in phantom lines in FIG. 2.
An important feature of the present invention is the support which the
running gear frame gives to the running gear support frame 17, along
substantially the entire overlapping positions of the two frames. Thus,
when the running gear is in its forward position, the running gear frame
33 supports the trailer running gear support frame along the entire length
of running gear frame 33. When the running gear is in its rearward
position running gear frame 33 supports frame 17 along the entire
overlapping portion. This overlapping portion is approximately equal to
the length of channel members 34, 35, 38 and 39. This support provides an
important practical result related to weight distribution. A comparison of
weight distribution by the use of the running gear of the present
invention as compared to the use of a conventional dolly is as follows. If
the rig of FIG. 1 contained a net weight of 20,000 pounds in trailer 11,
trailer 12 was empty and trailer 13 contained 20,000 pounds of net weight
the following portions of the net weight would be carried approximately as
follows: 10,000 pounds on axle 53, 10,000 pounds distributed approximately
equally between axles 54 and 55 and 10,000 pounds on axle 56. In contrast,
if running gear 20 were replaced with a conventional dolly, the axle of
the dolly would carry none of the net weight of the rig, since there would
be no way of transferring the load weight of trailer 11 to a dolly which
would be connected to trailer 11 through a pin and "I" hitch. The dolly
which replaces running gear 52 would, of course, contain approximately
half of the load of trailer 13. This imbalance of weight distribution
creates a safety hazard in the event of a sudden stop because of the lack
of load on the dolly which supports the front of trailer 12. The result
could be jack knifing. It is for that reason that it is common practice to
keep the empty trailer at the rear of the rig, but this has frequently
resulted in the rear trailer turning over in a strong wind combined with
either running off the shoulder of the road, or swinging as a result of a
passing truck combined with an attempt to correct the swinging by the
driver.
A still further advantage of the present invention is a decreased tendency
to "cheat" when the rig is turning a sharp corner. As can readily be
pictured from FIG. 1, in a turning situation the kingpin of trailer 12
will more accurately follow trailer 11 with the running gear of the
present invention as compared to a dolly which is connected through a pin
and clevis attachment at the end of trailer 11. The improved control on
backing between the running gear of the present invention and the
conventional dolly is even more evident, particularly in the three-trailer
situation such as shown in FIG. 1.
The running gear frame indicated generally by reference character 52 is
attached to trailer 12 in a manner analogous to that described above and a
further description is not believed necessary for an understanding of the
present invention. Trailer 13 is shown as a conventional single axle
trailer. It would, of course, be possible to use the same moveable running
gear on trailer 13 as is shown on trailers 11 and 12.
The running gear of the present invention although shown on a tractor and
trailer combination is useful in various other applications such as
recreational vehicles. The secure attachment of the running gear to the
trailer greatly increases safety as compared to the conventional dolly
which has a pair of pivot points, one at the end of the forward trailer
and the second at the kingpin. This elimination of one pivot point at each
dolly especially improves handling in those situations where the third
trailer 13 is loaded and the second trailer 12 is not.
The present embodiments of this invention are thus to be considered in all
respects as illustrative and not restrictive, the scope of the invention
being indicated by the appended claims rather than by the foregoing
description. All changes which come within the meaning and range of
equivalency of the claims therefore are intended to be embraced therein.
* * * * *
|
|
 |
|
 |
Description |
|
