Note: Descriptions are shown in the official language in which they were submitted.
CA 02334436 2001-02-06
FIFTH WHEEL LOCK RELEASE
BACKGROUND OF THE INVENTION
This invention relates to a fifth wheel hitch and particularly to the hitch
release
actuation mechanism.
Fifth wheel hitches employing a jaw-straddling yoke to hold hitch jaws around
a
kingpin are set forth in L1.S. Patents 4,428,595; 4,106,793; 3,013,815;
3,485,513;
3,640,549; and 2,982,566.
This type of hitch has been found to be reliable in operation. One difficulty
experienced, however, is the amount of manual pulling force required to
release the
hitch. Most persons have little or no difficulty, but if the driver is small
or of less
robust build, pulling the release could be troublesome. As will be noted from
the above
cited prior patents, the cam plate for the hitch release mechanism is
typically formed to
have an inner cam track that has primary and secondary pockets or notches for
engagement by the roller-type camp follower. These are designated in Patent
3,013,815
as the forwardly directed pocket 4'7 and the rearwardly directed pocket 48.
Forwardly
directed pocket 47 engages the care follower 42 when the yoke 33 is in the
unlock
position of the kingpin-engagement jaws 24, while rearwardly directed pocket
48
engages the cam follower 42 when. the yoke 33 is in the lock position of the
jaws.
SUMMARY OF THE INVENTION
The present fifth wheel hitch structure provides a novel fifth wheel release
mechanism that enables the operator to effectively pull the release handle
with
considerably less effort than previously required, even up to a 40 % reduction
in handle
pull effort. The cam mechanism is specially designed to enable a novel cam
abutment
pin on the yoke to engage a configurated outer surface of the cam, in addition
to the
usual cam follower on the inside c;~m surface, to thereby permit a novel
inside cam
surface geometry which enables beater leverage for manually pulling the
release handle.
The novel hitch release mechanism has the added cam abutment pin on the yoke
spaced from the conventional cam follower on the yoke, and cooperable with the
cam
plate outer surface to inhibit the yoke from prematurely moving to its release
position.
Therefore, the inner cam track of t:he cam plate can be reconfigured to
increase the
leverage of the cam on the cam follower which retracts the yoke to thereby
release the
hitch jaws.
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These and other features, advantages and objects of the present invention will
be
further understood and appreciated by those skilled in the art by reference to
the
following specification, claims and appended drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
In the drawings:
Fig. 1 is a top view of a fifth wheel hitch constructed in accordance with the
present invention; and
Fig. 2 is a partial cross section of the fifth wheel hitch taken along lines 2-
2' in
Fig. 1.
Figs. 3-8 depict the under side of the novel fifth wheel hitch arrangement,
showing sequential stages of the hitch mechanism in cooperation with a
conventional
kingpin. For purposes of clarity, Figs. 3P-8P depict the prior art hitch
mechanism in
corresponding sequential stages during cooperation with the conventional
kingpin, to
clearly demonstrate the difference;s of the novel construction. Figs. 9 and 10
illustrate
different conditions that may occur during operation of the novel fifth wheel
hitch
arrangement. Figs. 9P and lOP illustrate different conditions that may occur
during
operation of the conventional fifth wheel hitch arrangement. In Figs. 3-10 and
3P-lOP:
Fig. 3 is the bottom view of the novel fifth wheel hitch assembly showing the
yoke in a nominal position with both the added cam engager pin and an
auxiliary lock
capturing the yoke;
Fig. 3P is the bottom view of the conventional fifth wheel hitch assembly
showing the yoke in a nominal position with both the added cam engager pin and
an
auxiliary lock capturing the yoke;
Fig. 4 is the bottom view of the novel fifth wheel hitch assembly with the
release
handle at approximately 50% of its travel when pulled, and the auxiliary lock
released;
Fig. 4P is the bottom view of the conventional fifth wheel hitch assembly with
the release handle at approximate:iy 50 %o of its travel when pulled, and the
auxiliary lock
released;
Fig. 5 is the bottom view of the novel fifth wheel hitch assembly with the
yoke
releasing the lock jaws near the rr~aximum point of manual pull effort on the
release rod;
Fig. SP is the bottom view of the conventional fifth wheel hitch assembly with
the yoke releasing the lock jaws near the maximum point of manual pull effort
on the
release rod;
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Fig. 6 is the bottom view of the novel fifth wheel hitch assembly with the
hitch
jaws in a unlocked position so thc: kingpin can exit the lock;
Fig. 6P is the bottom view of the conventional fifth wheel hitch assembly with
the hitch jaws in a unlocked position so the kingpin can exit the lock;
Fig. 7 is the bottom view of the novel fifth wheel hitch assembly wherein the
kingpin has exited the lock, forcing the yoke tips into the lock jaw recesses,
and the cam
is free to move to the "ready to couple" position;
Fig. 7P is the bottom vievr of the conventional fifth wheel hitch assembly
wherein the kingpin has exited the lock, forcing the yoke tips into the lock
jaw recesses,
and the cam is free to move to the "ready to couple" position;
Fig. 8 is a bottom view of the novel fifth wheel hitch assembly with the cam
in
the "ready to couple" position so that a kingpin entering the hitch hits the
rear of the
lock, forcing the lock jaws to close, whereupon the yoke compression spring
moves the
yoke down into a locked position and the release handle spring forces the cam
to rotate
into a locked position as in Fig. 3;
Fig. 8P is a bottom view of the conventional fifth wheel hitch assembly with
the
cam in the "ready to couple" position so that a kingpin entering the hitch
hits the rear of
the lock, forcing the lock jaws to close, whereupon the yoke compression
spring moves
the yoke down into a locked position and the release handle spring forces the
cam to
rotate into a locked position as in Fig. 3P;
Fig. 9 is a bottom view of the novel fifth wheel hitch assembly showing the
kingpin locking position such that: if the yoke is inadvertently forced
forwardly after
coupling, it is fully secured by the mechanism;
Fig. 9P is a bottom view of the conventional fifth wheel hitch assembly
showing
the kingpin locking position such that if the yoke is inadvertently forced
forwardly after
coupling, it is fully secured by the mechanism;
Fig. 10 is a fragmentary bottom view of the novel fifth wheel hitch assembly
showing the yoke at full adjustment, near the end of the hitch jaw design
life; and
Fig. lOP is a fragmentary bottom view of the conventional fifth wheel hitch
assembly showing the yoke at fully adjustment, near the end of the hitch jaw
design life.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENT
In the description to follow, the terms forward and rearward have reference to
the forward and rearward portions of the hitch when mounted on a conventional
truck
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tractor. Details of the truck tractor, a trailer and conventional depending
kingpin, and
standard fifth wheel hitch mounting components are not depicted in order to
maximize
clarity of the hitch features which are unique to this invention.
The fifth wheel assembly 1 basically comprises a hitch 2 which has a
conventional fifth wheel hitch plate 16 with a bifurcated rear portion
straddling a hitch
throat 18 and mouth 5 in conventional fashion as depicted in detail in Fig. 1.
Hitch 2
comprises a kingpin locking mechanism having a pair of pivotal locking jaws 4
which
form the socket or mouth 5 in which a kingpin of conventional type, such as
that:
depicted in Patent 4,428,595, is retained. The fifth wheel hitch is to be
attached on a
truck tractor frame in a conventional manner utilizing a pair of trunnions 15
which
pivotally connect the fifth wheel plate to the frame of the tractor, as in
Patent 3,640,549,
so the fifth wheel plate can tilt rearwardly-downwardly. The bifurcated
structure
includes a pair of sloping rearward projecting ramps 17, which straddle and
define the
tapered, rearwardly oriented kingpin receiving throat 18 and the blind mouth 5
about
which the jaws 4 close or open to retain or release the kingpin.
As illustrated in Fig. 3, locking jaws 4 are positioned on the left and right
sides
of the mouth as viewed, these having a substantially identical but mirror
image
construction. The jaws are adapted to mate with the smaller diameter portion,
i.e.,
neck, of a kingpin. These jaws are pivotally mounted on the fifth wheel
assembly on
vertical pivot pins 41 which extend through jaw apertures 25 and have their
upper ends
mounted in the fifth wheel hitch plate 16. This hitch plate has downwardly
projecting
ribs 19 astraddle and at controlled spacing from both jaws. These ribs have
conventional
apertures formed therein such that, in the unlocked hitch position, jaws 4 can
pivot out
through these apertures (Figs. 7 and 8).
A conventional U-shaped ;yoke 44 is slidingly mounted between rearwardly-
inwardly tapered ribs 19. Yoke 44 includes a cross leg 44a and a pair of
generally
parallel legs 44b extending from i:he ends of cross leg 44a and having wedge-
shaped
ends 44c to engage contact surfaces 32 on outwardly projecting jaw ears 30, to
thereby
retain the jaws in the closed position. The forward surfaces of jaw ears 30
are concave
in conventional fashion to act upon wedge-shaped ends 44c, as explained below.
A
conventional adjustment device can be connected to yoke 44 to move the same
forwardly
and rearwardly to thereby adjust t:he closed position of the jaws and insure
close mating
contact with a kingpin. Yoke 44 has a yoke shaft 44d projecting forwardly from
the
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center of cross leg 44a of yoke 44, and through a front rib 21 of fifth wheel
plate 16.
Yoke 44 is biased toward its rearward locking position by a compression coil
spring 54
provided around shaft 44d and captured between front rib 21 of fifth wheel
plate 16 and
cross leg 44a of L1-shaped yoke 44.
As shown in Fig. 2, an L-shaped bracket 45 is mounted to cross leg 44a of yoke
44 so as to provide a pin mounting portion 45a that extends parallel to, and
below, yoke
shaft 44d and compression spring 54. Projecting through and downwardly from
pin
mounting portion 45a is a vertical pin 60 on which is preferably a cam
follower roller
62. Also projecting downwardly, spaced from pin 60, is a second vertical cam
abutment pin 64. As shown in Fi.g. 3, cam follower roller 62 engages an
internal cam
track 70a in a novel cam plate 70 while second pin 64 cooperates with an
external cam
track surface 70b on cam plate 7C1. Cam plate 70 is pivotally mounted to fifth
wheel
hitch plate 16 by a pin 74 so as to pivot thereabout and cooperatively engage
cam
follower roller 62 and second pin 64.
As illustrated in Fig. 3, cam plate 70 can be forcefully rotated by means of a
pull
rod 78 and its pull-type release handle 78a. Release pull rod 78 has one end
78'
pivotally mounted in cam plate 70 at a spaced distance from the axis of
rotation of cam
plate 70 at pin 74, and has its opposite end extending through fifth wheel
plate 16 at one
lateral side thereof and terminating in handle 78a. Pull rod 78 is biased to a
locked
position by a compression coil spring 80 that has one end trapped at a
location along the
pull rod and the other end trapped against an internal rib near the outside
edge of fifth
wheel plate 16.
Referring back to Fig. 2, pins 60 and 64 extend through apertures in an oblong
washer 47. Washer 47 thus retains a portion 70c of cam plate 70 between pin
mounting
portion 45a of bracket 45, pins 60 and 64, and an upper surface of oblong
washer 47.
By retaining a portion of cam plai;e 70 in this fashion, cam plate 70 is more
likely to
rotate in a plane that is parallel to hitch plate 16 and yoke shaft 44d. In
the past, the
cam plates have tended to get manipulated by the various forces acting on it,
to rotate in
a non-parallel plane, which may result in increased effort to pull release
handle 78a and
thus unlock the hitch.
By providing bracket 45 a:nd positioning pin 60 (and pin 64) on the bracket
below
yoke shaft 44d, instead of mounting pin 60 directly on the yoke shaft as was
done in the
past, the distance between pin 60 and pin 74 may be reduced without requiring
a
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CA 02334436 2001-02-06
reduction in the length of compression spring 54. In fact, the length of
compression
spring 54 may be increased to extend all the way to bracket 45 mounted
adjacent to cross
leg 44a of yoke 44. This allows compression spring 54 to either apply a
greater biasing
force to yoke 44 or allows a spring having less force per unit length to be
used. By
decreasing the distance between pins 74 and 60, more leverage force may be
applied by
cam plate 70 to move yoke 44 from the locked position when release handle 78a
is
pulled. As apparent from a comFrarison of Figs. 3 and 3P, not only has the
distance
between cam follower 62 and pin 74 been decreased, but also the distance
between pin
74 and end 78' of release pull rod 78 has been increased. This increased
leverage
significantly reduces the force reduired to pull handle 78a and hence unlock
the locking
mechanism. Additional reductions in the pull handle force can be realized by
changes to
spring 54 permitted by the additional length as described above.
The function of the apparatus is depicted in sequential form in the drawing
figures, particularly Figs. 3-8. Fig. 3 shows the hitch mechanism in the fully
locked
condition, in the form of a relatively newly manufactured hitch with little or
no wear.
As shown, lock jaws 4 extend around a kingpin thereby retaining the kingpin
within the
socket or mouth 5. Jaws 4 are locked in place by yoke 44 whose tapered tips
44c
prevent jaw ears 30 from moving into the respective apertures formed in ribs
19 as they
would move when releasing the kingpin. Yoke 44 is retained in this locking
position by
the biasing force of compression spring 54 and by an auxiliary lock 33, which
is
pivotally mounted to hitch plate 16 and is biased to pivot against cross leg
44a of yoke
44. Cam plate 70 is maintained in;~ the position shown in Fig. 3 by the force
of release
handle spring 80. When in the illustrated position, cam plate 70 does not
apply any
significant forward or rearward force on yoke 44.
Fig. 4 illustrates the movement and position of the hitch elements when
release
handle 78a is in the process of being pulled to release the hitch lock, and
has traveled
approximately 50 % of its full travel, with cam plate 70 being pivoted about
pin 74. As
pull rod 78 is pulled as shown in :Fig. 4 compressing handle spring 80, a cam
follower
pin 31 on auxiliary lock 33 is deflected laterally by the outer surface of cam
plate 70 to
pivot auxiliary lock 33 about its pivotal mounting point 35 in fifth wheel
plate 16 so the
end which is opposite the pivotally mounted end will move out of alignment
with cross
leg 44a of the yoke 44 and not prf:vent the yoke from being forced forward. As
shown,
when cam plate 70 is forcefully rotated by pull rod 78, inside cam track 70a
of cam plate
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70 moves into contact with cam follower 62 and cam plate 70 thus forces cam
follower
62 and hence yoke 44 forward and out of the locked position. Fig. 5
illustrates the
positioning of the lock elements just prior to a time when release rod 78 has
reached full
extension.
When release rod 78 is at its full extension as depicted in Fig. 6, cam plate
70,
and particularly the inner cam surface 70a thereof, has forced cam follower
62, and
hence yoke 44 (and yoke shaft 44d to which cam follower 62 is attached)
forwardly
against the bias of compression coil spring 54, thereby retracting the yoke
from astraddle
projecting ears 30 of jaws 4. Concurrently, cam follower 62 moves into a notch
70a'
formed in inside cam track 70a. The compressive force of spring 54 pushes cam
follower 62 hard against the rearward portion of notch 70a' such that the
compressive
force of handle spring 80 is insufficient to move cam follower 62 laterally
from notch
70a' when handle 78a is released.. In this manner, the operator may release
handle 78a
and yoke 44 is maintained in a retracted unlocked position. When yoke 44 is in
the
retracted unlocked position shown in Fig. 6, a spring (not shown) pivots jaws
4 slightly
open until a tapered forward surf;~ce portion 30a thereof contacts yoke tips
44c. When
the pull rod 78 is fully extended, as in Fig. 6, auxiliary lock 33 is out of
the way of
cross leg 44a of yoke 44.
Having released pull handle 78a, the operator is now free to enter the truck
cab
and pull the truck forward. The iForward movement of the truck moves the hitch
forward relative to the stationary kingpin. This forward movement of the hitch
causes
the kingpin to push open jaws 4 ;as depicted in Fig. 7, under the influence of
the
withdrawing kingpin. As the jaws pivot, the tapered forward surface portions
30a of
jaw ears 30 force yoke 44 further forward against the force of compression
spring 54.
As shown in Fig. 7, this additional forward movement of yoke 44 results in a
corresponding forward movement of cam follower 62 and second pin 64, which
removes
cam follower 62 from notch 70a' while bringing second pin 64 into contact with
outside
cam track 70b. Once cam follower 62 has moved from notch 70a' in cam track
70a,
cam plate 70 is released from the force of compression spring 54 and is free
to rotate.
Consequently, the compressive force of handle spring 80 retracts pull rod 78
and thus
pivots cam plate 70. Cam plate TO stops pivoting when second pin 64 moves into
a
second notch 70b' that is part of outside cam track 74b of cam plate 70, as
shown in Fig.
8. At this point, jaws 4 have opened sufficiently to allow the kingpin to exit
the hitch
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lock and the trailer is therefore uncoupled. The forced opening of jaws 4 by
the kingpin
results in yoke tips 44c being positioned within a concave forward surface
portion 30b of
jaw ears 30. This relative positioning keeps yoke 44 in a forward position
while holding
jaws 4 open. Following this uncoupling operation, the hitch is in a ready-to-
couple state
without requiring any further manipulation by the operator. Thus, Fig. 8 also
represents
the position of the locking elements when in the ready-to-couple position. The
hitch in
Fig. 8 is thus ready to receive a kingpin.
During a coupling operation, the truck is backed up toward a stationary
trailer,
and thus, the stationary kingpin enters throat 18 and eventually mouth 5 of
the hitch. As
the kingpin fully enters the hitch mouth, it pushes against the forward end of
the inner
surfaces of jaws 4 thereby causing jaws 4 to pivot fully closed to the
position illustrated
in Fig. 3. As a result of the closing of jaws 4, compression coil spring 54
forces yoke 44
rearwardly to cause yoke tips 44c to extend beyond, straddle and engage ears
30 of jaws
4, as shown in Fig. 3. In this condition, abutment pin 64 moves out of
engagement with
notch 70b' on outer cam track 70b thereby allowing handle spring 80 to rotate
cam plate
70 and retract pull rod 78 back to their starting positions as shown in Fig.
3. Once cam
plate 70 has returned to its starting position, auxiliary lock 33 is no longer
prevented
from pivoting under force of a spring (not shown) into the locked position.
The
sequence illustrated in Figs. 3-8 is thus repeated each time the hitch is
uncoupled and
recoupled to the trailer kingpin.
Fig. 9 illustrates a potential condition resulting from excessive drawbar
force
resulting from the kingpin entering and striking jaws 4 at an excessive speed.
When this
occurs, the kingpin bounces rearward pushing jaws 4 open possibly before yoke
44 has
fully extended rearward. The qui~,ck movement of jaws 4 from an open to a
closed
position may also cause a bouncing effect on cam plate 70 and spring 80 such
that cam
plate 70 rotates toward an unlocked position whereby the outer surface of cam
plate 70
would engage pin 31 on auxiliary lock 33 and push it out of the locked
position. T'o
prevent cam plate 70 from rotating that far and disengaging auxiliary lock 33,
a
protrusion 70b" is provided on outside cam track 70b to catch second pin 64
and serve
as a supplemental lock. In this manner, pin 64 and cam plate 70 prevent yoke
44 from
moving further forward. Thus, second pin 64 permits the notch A (Figs. 8P and
9P)
provided in the inside cam track of the prior art cam plate to be eliminated.
As a result,
the inside cam track 70a may be designed in a manner that reduces pull handle
effort.
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Fig. 10 illustrates another potential condition where yoke 44 is at the full
adjustment near the end of the hitch jaw design life, i.e., locking jaws 4
have worn
sufficiently that yoke 44 can extend fully rearward of the mechanism.
The above description is considered that of the preferred embodiment only.
Modifications of the invention will occur to those skilled in the art and to
those who
make or use the invention. Therf:fore, it is understood that the embodiment
shown in the
drawings and described above is merely for illustrative purposes and not
intended to
limit the scope of the invention, which is defined by the following claims as
interpreted
according to the principles of patent law, including the doctrine of
equivalents.
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