Note: Descriptions are shown in the official language in which they were submitted.
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This invention relates to an improved fifth wheel
structure. In particular it relates to fifth wheel pads in
the form of at least one self-lubricating slip pad and
preferably three, four or five such pads, secured to a
fifth wheel.
The trucking industry utilizes automotive vehicles,
commonly referred to as truck rigs consisting of a
motorized tractor and one or more trailers connected in
tracking relation thereto for the transportation of heavy
loads over great distances. It is well known that in order
to achieve the maximum economic benefit from the use of
such equipment it is desirable to maintain it in as nearly
continuous use as possible. Unfortunately such equipment
requires a substantial amount of maintenance to keep it in
operating condition and to avoid breakdowns enroute.
Such vehicles commonly employ a coupling device known
as a fifth wheel in order releasably to couple the trailer
to the tractor. A fifth wheel is used pivotally to couple
a semi-trailer to a tractor. It generally includes an
upper bearing face, front and opposite side marginal edge
portions and a rearwardly opening slot. Such fifth wheel
is adapted to be used in conjunction with a kingpin plate
of the type which includes a lower bearing face downwardly
from which a kingpin projects. The fifth wheel plate is
adapted to have the kingpin plate disposed thereover with
the faces in contact with each other and with the kingpin
rotatably and captively disposed in the inner forward end
of the slot.
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Such fifth wheels provide releasably engaged bearing
surfaces, one being mounted on the underside of the forward
portion of the trailer. The bearing surface of the tractor
supports the weight of the trailer resting against it and
acts as a surface against which the bearing surface of the
trailer rotates as necessary during towing operations.
Lubrication of the engaged bearing surfaces has normally
been provided by the application of a lubricant, usually
grease, to the bearing surface of the tractor. Because of
long hours of use and the rather rapid dissipation of the
lubricant, frequent disconnection of the trailer from the
tractor for reapplication of the lubricant was required in
order to maintain the equipment in optimum working
condition. This reapplication process, when done
correctly, requires recleaning of the bearing surfaces to
remove residue and accumulated dirt prior to the
reapplication of the lubricant. Since nearly continuous
operation is economically desirable and since the task is
onerous and time consuming, such maintenance is often not
performed as frequently as would be desirable. This
results in aggravated wearing of the bearing surfaces and
progressively worse handling characteristics for the truck
rig. This is costly to the trucking business, and annoying
to the operator of the vehicle. Further, when the bearing
surfaces become worn, they must be replaced. This
necessitates removal and replacement of the fifth wheels,
a time consuming and expensive undertaking.
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It has also been found that the presence of dirt and
moisture between the upper surface of a fifth wheel plate
and the opposing undersurface of a kingpin plate of an
associated trailer results in excessive wear of the
opposing bearing surfaces defined by the fifth wheel plate
and the kingpin plate with the result that the pivot
connection established between the fifth wheel and the
fifth wheel pin or kingpin becomes sloppy and thus enables
greater shock loads to be transmitted from the associated
tractor to-the semi-trailer.
Fifth wheel lubrication heretofore has been difficult
to maintain. Rocking and turning action between a trailer
and fifth wheel squeezes the grease off the fifth wheel
surface and renders the steering progressively more
difficult as the break away friction between the fifth
wheel and the trailer bed plate increases. Steering tires
deflect laterally during steering maneuvers and this
deflection and relative force increase in proportion to the
fifth wheel friction. As the static friction breaks loose,
the laterally deflected tires rebound re~uiring an
immediate steering correction. The result is trailer swing
and vehicle yawing.
one attempt to improve the lubrication on the bearing
surface has been the use of a TEFLONTM plate attached to the
bearing surface on the underside of the trailer so that the
TEFLONTM provides lubrication for the fifth wheel unit.
Such a plate avoids the necessity of grease or other types
of lubricant as the TEFLONTM itself has lubrication
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properties. It has been found, however, that~if a TEFLONTM
disc is placed on the trailer, then one requires far more
discs because there are more trailers than there are
tractors. TEF10NTM is an expensive material and as the
trailer can sit for days without moving, the use of this
TEFLONTM disc on the traller is an expensive item.
Another approach to improve the lubrication on the
bearing surface was by the ~d'dition of a sheet of a low
friction plastic covering, e.g., coverings of certain ultra
high molecular weight polyethylenes and polypropylenes.
Such coverings were particularly preferred due to their
exceptionally low coefficient of friction and durability.
These plastic coverings were commonly held in place on the
fifth wheel bearing surface by screws,- rivets and/or
adhesives. Such a sheet improved the lubrication between
the two bearing surfaces of the fifth wheel attachment.
Unfortunately, the sheet was often damaged when the tractor
was coupled to the trailer because of the impact occurring
when the tractor is backed up to the trailer. This impact
can often rip off a portion of the sheet, and, in some
instances, can rip off the entire sheet.
To protect these plastic coverings, it was proposed to
provide two protective "riser bars" on the outsidé
peripheral edges of the fifth wheel bearing plate of the
tractor and its associated sloped flanges. Such riser bars
were substantially flush with the surface of the plastic
covering and extended from the forward edge of the sloped
flanges backwards along the circular portion of the bearing
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plate to a point at which the bearing plate was pivotally
mounted to the tractor body. The riser bars were
positioned in cutout portions of the plastic covering to
allow replacement of the covering without disturbing the
riser bars. Such peripherally located riser bars were
intended both to guide and to pivot the fifth wheel
attachment of the tractor so that it was at the correct
alignment and location with respect to the trailer during
coupling.
In utilizing fifth wheel assemblies having protective
riser bars of the type described above, it had been
observed that the riser bars, owing to their location,
thickness and shape, eventually wore arcuate grooves in the
mating bearing surface (commonly known as the "bolster"
plate) of the trailer. Moreover, it had been observed
perhaps as a result of the bolster plate wearing unevenly
and the fact that the riser bars did not extend rearwards
beyond the bearing plate pivot axis, that there was a
tendency for the bolster plate to gouge and tear the
protective plastic covering on the fifth wheel bearing
plate of the tractor. Being located along the outer edge
of the substantially circular portion of the bearing plate
of the tractor, and being flush with the upper surface of
the plastic covering of the bearing plate, the riser bars
frequently contacted the bolster plate of the trailer at
times other than tractor/trailer coupling. For example,
normal rocking of the trailer about a hori~ontal axis
extending parallel to the trailer length caused the riser
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bars repeatedly to impact against the bolster plate. Also,
as the tractor turned relative to the trailer to follow
curves in the road, the risers bars rubbed against, and
thereby scraped, the bolster plate of the trailer. This
action was believed to give rise to the observed arcuate
grooves in the bolster plate. Further, since the riser
bars did not extend beyond the pivot axis, they afforded no
protection from the bolster plate of the trailer after the
bearing plate of the trailer tipped (pivotal) to a
horizontal seating position during tractor/trailer
coupling.
To overcome the above-described difficulties, many
proposals have been made in the patent literature.
U.S. Patent No. 3,511,523 patented May 12, 1970 by L.
T. Fuller purported to provide one solution to this problem
by means of a seal-forming attachment for the fifth wheel.
The attachment included an elongated resilient seal
structure adapted to be secured about, and to extend
slightly above, the forward and opposite side marginal edge
portions of a fifth wheel. This was alleged to provide
fluid-tight sealed engagement with the under-surface of the
king pin plate on the associated semi-trailer as the
tractor was advanced rearwardly beneath the forward end of
the semi-trailer.
U.S. Patent No. 3,704,924 patented December 5, 1972 by
R. W. Lowry purported to provide another solution to this
problem by means of a replaceable wear plate for the fifth
wheels. The wear plate was a substantially flat sheet of
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disposable material having a low coefficient of friction
which was releasably secured in fixed position on one of
the bearing surfaces for engagement with the other bearing
surface and was removable from its respective surface for
replacement.
U.S. Patent No. 3,801,136 patented April 2, 1974 by J.
J. Cunha purported to provide another solution to this
problem by means of an impervious trough surrounding a
portion of the periphery of a fifth wheel. The trough was
V-shaped, one side being formed by the edge surface of the
fifth wheel, the other side being formed by a band fastened
to the edge surface. The band resided at an angle to the
edge surface of about 45~ to facilitate cleaning the
trough. The upper edge of the band resided below the
bearing surface of the fifth wheel to avoid interference
therewith.
U.S. Patent No. 3,924,909 patented December 9, 1975 by
J. A. Kent et al purported to provide yet another solution
to this problem by means of a cover plate which was adapted
to fit over the upper surface of a fifth wheel and
substantially to conform to the shape of the fifth wheel.
Interposed between the upper surface of the fifth wheel and
the lower surface of the cover plate was a low friction
material. The cover plate and low friction material were
allowed to rotate about the kingpin centre through an angle
of approximately 5~ each side of centre. When turns were
negotiated which required greater than 5~ of rotation, the
trailer pivoting continued between the upper surface of the
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cover plate and the trailer bed plate. A pivot centre was
provided to attach the cover plate to the fifth wheel and
to hold it secure when a trailer was not attached.
U.S. Patent No. 4,169,635 patented October 2, 1979 by
F. Szalay et al purported to provide still another solution
to this problem by means of a bearing plate cover for the
fifth wheel of a vehicle engaging the entire bearing and
non-bearing surfaces thereof. The bearing plate cover was
composed of a flat sheet plastic material having a low
friction coefficient and high deflection characteristics so
as to provide a wear-resistant slippery surface for contact
with another bearing surface.
U.S. Patent No. 4,542,912 patented September 24, 1985
by A. St.-Louis purported to provide a further solution to
this problem by means of a fifth wheel bearing attachment
for mounting on a tractor to avoid the necessity of
providing oil or grease to lubricate the attachment. The
improvement to the attachment included an antifriction
polyolefin plastic sheet covering to fit over a circular
fifth wheel metal bearing plate and over two-sloped flanges
of the fifth wheel attachment. The plastic sheet was
attached to the bearing plate and the flanges. Two
protective riser bars located on the outside of the two-
sloped flanges acted as protection for the sheet when the
tractor was coupled to the trailer.
U.S. Patent No. 4,752,081 patented June 21, 1988 by
D.C. Reeners et al purported to provide another solution to
this problem by means of protection from damage of a low-
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friction plastic covering on the fifth wheel bearing plate
of a tractor by a pair of elongated metal "skip" plates.
Such plates were preferably rectangular in shape and were
positioned in the interior region of the plastic covering,
one on each side of a tapered slot adapted to receive the
kingpin of a fifth wheel tongue attachment of the trailer.
The size, shape and position of such skip plates were said
to minimize wear on the bolster plate of the trailer, and
to minimize any tendency for tearing of the plastic
covering during tractor/trailer coupling and normal use of
the tractor-trailer.
U.S. Patent No. 5,165,713 patented November 24, 1992
by G. N. Picard purported to provide still another solution
to this problem by means of a fifth wheel cover comprising
a substantially sheet-like member having a circular portion
and a pair of tail portions extending from one side'of the
circular portion for covering the bearing plate and sloped
flanges of a fifth wheel of a tractor. It also had a
central kingpin opening between the tail portions. A cup
portion was provided at the end of each tail portion for
receiving the rear ends of the sloped flanges therein. At
least one hook formation on the side of the circular
portion opposite the tail portions was provided for
engaging with the rim of the fifth wheel, in order to
secure the cover on the fifth wheel. The circular and tail
portions and the cup and hook formations were integrally
moulded from an anti-friction synthetic plastic material.
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U.S. Patent No. 5,165,714 patented November 24, 1992 by J. W. Kaim
~u~ul~ed to provide yet another solution to this problem by means of a fifth wheel
assembly which had a bearing plate with a lubricating plate. A peripheral wall was
provided with ~i~metrically-opposed notches extending above the bearing plate
Ss~ ce. A non-met~llic lubri~ting wear liner was provided with diametrically-
opposed ears notchable with the notches to resist rotational motion by the liner. The
liner extended above the peripheral wall and was secured against the bearing plate as
a lubrir~ting liner but was retained within the bearing plate cavity against radially
outward displacement by the peripheral wall.
10It has been found that these purported solutions were not entirely successful.In view of the foregoing, it is an object of one aspect of this invention to minimi7e
the above-noted wear on a fifth wheel bearing surface of the trailer and the ~tten~l~nt
deterioration of the fifth wheel bearing surface of the tractor.
An object of another aspect of the present invention is to provide a fifth wheel15attachment assembly having sufficient lubrication properties to avoid the necessity of
providing grease or other lubrication to the fifth wheel attachment.
An object of yet another aspect of the present invention is to provide an
improved fifth wheel construction whicfi mitig~tes the above-mentioned difficulties.
The present invention provides an improved fifth wheel structure fûr a fifth
20wheel of the type including a fifth wheel plate having an upper bearing face and a
rearwardly opening slot having a closed fo~ rd end for use in conjunction with akingpin plate of the type including a lower bearing face from which a kingpin projects
downwardly, the fifth wheel plate being adapted to have the kingpin plate disposed
thereover with the respective bearing faces in contact with each other and with the
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kingpin rotatingly and captively disposed in the forward end of the slot, the
improvement, in combination with the fifth wheel plate, comprising: a plurality of
self-lubri~ting slip pads, each slip pad being formed of a self-lubricating plastic
selected from the group con~isting of polytetrafluoroethylene and ultra-high molecular
5 weight polyethylene, each slip pad being substantially rectangular in shape with four
rounded corners and having only its peripheral edges tapered or rounded to be lower
than its central region j each slip pad having a plurality of circular counterbored holes
therein each circular counterbored hole termin~ting in a circular hole; and each slip
pad being secured into its respective rectangular counterbored hole within the upper
bearing face of the fifth wheel plate, by means of an associated one of a plurality of
weld washers, each of which has been placed in its respective circular counterbored
hole in its associated slip plate and then welded to the fifth wheel plate.
Optimally, by a pl~fell~d variant thereof, three such pads are provided which
are secured within associated recesses in the fifth wheel by means of three weld
washers. Four or five slip pads can also be provided. By a variant thereof, each slip
pad is 0.280" thick and wherein each the recess is 0.125" thick.
In the acco~l~panying drawings,
Fig. 1 is a perspective view of the fifth wheel modified according to one
embodiment of the present invention;
Fig. 2 is a perspective view of one embodiment of a slip pad; and
Fig. 3 is a perspective view of the assembled improved fifth wheel structure
of one embodiment of this invention; and
Fig. 4 is an enlarged section along the line IV-IV of Fig. 3.
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As seen in Fig. 1, the fifth wheel plate 10 is of the usual shape, having a
curved rear portion 11, and a pair of arms 12 defining a slot 13 therebetween.
A plurality, in this case three, recesses 14, 15, and 16 are provided on the
upper face 17 of the fifth wheel plate 10. Each of the recesses 14, 15, 16 in this
5embodiment is provided with locating apertures 18, 19, 20 for the weld washers (not
shown) used to secure the slip pad 30 the fifth wheel plate 10.
As seen in Fig. 2, the slip pad 30 is rectangular, but is provided with rounded
corners 31 to facilitate the engagement of the tractor into the fifth wheel 10. The
upper surface 32 of each slip pad 30 is provided with three countersunk bores, 33,
1034, 35, terrnin~ting in bores 36, 37, 38 to enable securement by the weld washers,
(see Fig. 3 and Fig. 4).
Fig. 3 and Fig. 4 show the assembled fifth wheel structure. Each slip pad 30
is secured into its respective recess 14, 15, 16 by means of weld washers 40, which
are placed in the countersunk bores 33, 34, 35 and then welded to the fifth wheel
15plate 10 by conventional welding means, e.g., welds 43, 44, 45 in bores 36, 37, 38.
This embodiment of the invention shows the attachment of the slip pads by weld
washers.
As described for this embodiment, the weld washer securement technique
involves a drilling a counterbored hole in the slip pad, placing a washer on top in the
20counterbored hole and welding the washer to the fifth wheel plate by welding means.
Thus, the present invention provides an improved fifth wheel structure by
including three or more self-lubricating slip pads which are firmly secured within
sized recesses on the fifth wheel. Such slip pads are substantially-grease-free sliding
plates forrned of a self-lubricating plastic, e.g., ultra-high molecular weight
.
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polyethylene or polytetrafluoroethylene (TEFLONTM). Such m~teri~l wears longer
than steel and requires no grease or other lubrication and remains slippery even in
extremely cold weather.
Present coverings for fifth wheels are of approximately 0.280" thick which is
appa,ently an absolute maximum having regard to the manufacturers concerns giventhe standardized dimensions prevalent in conventional/pin fifth wheel arrangements.
It is, of course, not desired to be restricted to any particular dimension. However,
to provide one useful example, in one specific embodiment, the recesses provided in
the fifth wheel each are 0.125" thick. The slip plate itself is 0.280" thick, giving
0.155" of clearance. The slip pad is preferably tapered or rounded at its extremities
to f~cilit~te the engagement of a tractor onto the wheel (i.e. to prevent damage).
A further feature of the present invention is that the slip pad is of a single
"size" so that it becomes universal. Its particular shape may vary to being square,
round, rectangular or curved on one side. The recess may be configured such thatthe configuration in combination with the slip pad could present a mechanical
gripping locking mech~nicm.
Three or more slip pads are believed to be required to cover the respective
main areas of the fifth wheel.
Among the many advantages to this invention are the ability to do a "quick
fix" on the highway involving the unhooking of the trailer, using a chisel to remove
a worn slip pad to be replaced by a new slip pad. Additionally, this particular system
for a slip pad would elimin~te any damage caused by impact damage during coupling
and uncoupling of trailers by tractor drivers. Another feature in the invention
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includes a method of adapting existing fifth wheel plates by providing recesses therein
to accommodate the slip pads disclosed herein.
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